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DULUTH, MINNESOTA
INNESOTA
MAY 8-13,1979
MAY
8-13, 1979
•e
25th ANNUAL
ANNUAL
INSTITUTE ON
ON
LAKE SUPERIOR
SUPERIOR GEOLOGY
GEOLOGY
___;_• ,.
�TECHNICAL SESSIONS
and
ABSTRACTS
for the
the
25th
ANNUAL
25
th AJ.\lNUAL
INSTITUTE ON
ON LAKE
LAKE SUPERIOR
SUPERIORGEOLOGY
GEOLOGY
Sponsored by
Sponsored
UNIVERSITY OF
OF MINNESOTA,
MINNESOTA, DULUTH
DULUTH
held at
DULUTH, MINNESOTA
Joint Session with the
in Joint
the North Central
Central Section
Section
Geological Society of America
May 8 —- 12, 1979
Donald M.
M. Davidson,
Davidson, Jr.,
Jr., Program Chairman
Chairman
David G.
G. Darby,
Darby, Field Trip Chairman
Moss, Technical Editor
Carol Moss,
Editor
�TABLE OF CONTENTS
Page
Page No.
No.
INSTITUTE DIRECTORS AND LOCAL COMMITTEE
1
1
PROGRAM
22
ABSTRACTS OF
OF TECHNICAL
TECHNICAL SESSIONS
SESSIONS
8
8
**
COVER DRAWING:
large anticline.
anticline. View from the
the east
east bank of
of the
the
The large
St.
bridge,
St. Louis
Louis River,
River, just south of the highway bridge,
looking west. Thomson Dam Area, near
near Thomson,
Thomson, Minnesota.
Minnesota.
W. Wilson,
Wilson, May 30,
W.
30, 1968
�-1—1—
25th Annual
INSTITUTE ON LAKE SUPERIOR GEOLOGY
Sponsored by
University of
of Minnesota, Duluth
Duluth
at
at
Duluth, Minnesota
Duluth,
May 8 —- 12, 1979
1979
INSTITUTE BOARD OF DIRECTORS
DIRECTORS
Donald M.
M. Davidson,
Davidson, Jr.,
Jr., Department of
of Geology,
Geology, University
University of
of Minnesota,
Minnesota,
Duluth,
Duluth, Duluth,
Duluth, Minnesota*
Minnesota*
J.
J. D.
D. Hughes,
Hughes, Department of
of Geography,
Geography, Earth
Earth Science
Science and
and Conservation,
Conservation,
Northern Michigan,
Michigan, Marquette,
Marquette, Michigan
M. F.
M.
F. Kehlenbeck,
Keh1enbeck, Department of
of Geology,
Geology, Lakehead
Lakehead University,
University, Thunder
Thunder
Bay,
Bay, Ontario
G.
G. Mursky,
Mursky, Department of Geological Sciences,
Sciences, University of
of Wisconsin,
Wisconsin,
Milwaukee,
Milwaukee, Milwaukee, Wisconsin
Wisconsin
R. C.
C. Reed,
Reed, Geological
Geological Survey Division,
Division, Department of
R.
of Natural Resources,
Resources,
Lansing,
Lansing, Michigan
M. Walton,
M.
Walton, Minnesota Geological Survey, University of
of Minnesota, Minneanolis,
Minneapolis,
Minnesota
*Present address:
address:
Department of Geological Sciences,
Sciences, University of
of Texas,
Texas,
El Paso,
Paso, El Paso,
Paso, Texas
Texas
�—2—
-2-
PROGRAM
Tuesday, May 8,
8, 1979
8 a.m.
Field Trip 1 leaves Hotel Radisson Duluth
Duluth
Wednesday, May 9,
Wednesday,
9, 1979
8 a.m.
a.m.
Field Trip 2 leaves Hotel Radisson
Radisson Duluth
Duluth
12 noon
opens, Superior
Superior Foyer,
Foyer, Hotel
Hotel
Registration opens,
Radisson Duluth
p.m.
5 p.m.
return Hotel Radisson
Radisson Duluth
Duluth
Field Trips 1 and 22 return
7-10
p.m.
7—10 p.m.
Smoker poolside,
poolside, Hotel Radisson Duluth
Duluth
Thursday, May 10,
Thursday,
10, 1979
7:30 —12 a.m.
Registration,
Registration, Superior Foyer, Hotel
Hotel Radisson
Radisson
Duluth
�—3—
SESSION 1
Morning
Thursday, May 10, 1979
Early Precambrian
Co—chairmen;
Manf red Kehienbeck, Paul Meyers
8:45
D. H. Davidson, Jr.
Opening Remarks
9:00
John Klasner and
Paul Sims
Geologic Interpretation of Gravity Data in
the Marinesco, Thayer and Watersmeet Quadrangles, Michigan
9:20
K. Howard Poulsen
Polyphase Deformation of Archean Rocks at
Rainy Lake, Ontario
9:40
Elizabeth Palmer
and Donald Davidson
Paleostrain Analysis - Across a Shear Zone,
Northwestern Marathon County, Wisconsin
10:00
Stephanie Wurdinger
Structural Geology of Amphiboliric Gneisses,
Northeast Chippewa County, Wisconsin
10:20
Coffee Break
10:40
Hanfred Kehienbeck
Structural Interpretations in the }Iazelwood
Lake Area, Thunder Bay, Ontario
11:00
Paul Sims and
David Southwick
New evidence on the stratigraphy and structure
of the Soudan area, Western Vermilion district, Minnesota
11:20
Bruce Brown
Deformational History of Arehean Creenstone
Terrane, Eastern Lake of the Woods, Ontario
11:40
Thomas Waggoner
and Thomas Mroz
Palmer Gneiss Update
12:00
Noon. Adjourn for Lunch
Luncheon Meeting of Board of Directors —
location
to be announced.
�—4—
SE S SI ON
2
Afternoon
Thursday, May 10, 1979
Middle Precambrian
Co—chairmi:
Ralph W. Marsden, Glen Morey
2:00
David Larue and
F. William Cambray
Cross folding in the eastern part of the
Marquette Trough, Michigan
2:20
Roy Shegelskl.
Stratigraphy of the Cunflint Formation,
Kakabeka Falls Area, Ontario
2:40
Karen Kimball
Coexisting Ainphiboles in the metamorphic
iron formation, Jackson County, Iron Mine,
Wisconsin
3:00
Mike Cutmnings
Phase relations of oxide—free iron formation
in the Amphibolite Facie
3:20
Coffee Break
3:40
Mark Kirstein
Contact Metamorphism of iihe Virginia Fonna—
tion in the Minnamax Deposit, St. Louis
County, Minnesota
4:00
Jesse Dann
Comparative najor element variations within
the Emperor Igneous Complex, and the Hemlock
and Badwater Volcanic Formations, northern
Michigan
4:20
C. Bennett and
0. C. Innes
Stratigraphy and Petrochernistry of Huronian
Volcanies, North Shore of Lake Huron, Ontario
4:40
Discussion Session
5:00
Adjourn
****
****** ***
Even ln&
7:30
Banquet with North Central Section GSA —
Speaker:
Dr. Vincent McK'lvey
For"ie r Di e I:
t
United States Geological Survey
Hot1
Normandy
�—5—
-5-
SE
ON 33
S E S SSI
ION
Morning
Friday, May
Friday,
~fuy 11, 1979
Late Precambrian
Late
Co—chairmen:
Co-chairmen:
Foos
Stan Watowich, Mike Foos
9:00
William Matlack
Geology of
of the
Duluth Complex-Virginia
Complex—Virginia FormaFormaGeology
the Duluth
tion Contact,
Contact, Minnamax Deposit, Minnesota
tion
9:20
George Lehman and
and
Donald Davidson
Petrology Aspects of the
the Troctolite—Olivine
Troctolite-Olivine
Gabbro Series,
Series, Duluth
Duluth Gabbro
Gabbro Complex (Late
Gabbro
(Late
Precambrian), Northeast Cramer
Cramer Quadrangle,
Quadrangle,
Minnesota
9:40
James Hahnenberg
James
Petrology and
a~d Geochemistry of Keweenawan
Diabase Dikes in Michigan's Western Upper
Peninsula
10:00
Coffee Break
Coffee
10:20
John Green
Green
Bedrock Geology of the Milepost 7 Area,
Area, Silver
Bay,
Bay, Minnesota
10:40
Stephen Cuggenheim,
Guggenheim,
Peter Wilkes and
S. hT.
W. Bailey
S.
The Nature of Greenalite
Greenalite
11
:00
11:00
Discussion Session
11:20
Adjourn for Lunch
�—F.—
SESSION
4
Afternoon
Friday, Nay 11, 1979
Ceneral Session
Co—chairmen:
Cedric Iverson, Mike Mudrey
1:40
Business Meeting of the Institute
2:00
William Cannon and
Dennis Kostick
Ronchi Filtering — an easy, inexpensive tech—
nique for linear enhancement of many kinds of
Geologic Data
2:20
Elizabeth King
and William Cannon
Results of a Truck Magnetometer Survey of the
Southwestern Quarter of the Iron River 20 sheet
2:40
Jim Trow
DOE-Bendix—Michigan Geological Survey Diamond—
Drilling for
and
Geologic Information in Marquette
Iron Counties
3:00
Coffee Break
3:20
Maurice Brock,
Jo Kalliokoski and
Richard Ojakangas
Status of USGS Uranium Studies in Michigan's
Upper Peninrula
3:40
Tom Evsns
State Legislation Affecting Mineral Development
in Wisconsin
4:00
End of Technical Session
Saturday, May 12, 1979
Field Trips 3, 4, 5, 7, 8 Depart
Leave 0800
Normandy Inn
�—7—
-7-
POSTER PAPERS
Morning
Friday,
Friday, May 11, 1979
1979
9:00 to
to 12:00*
12:00*
Room, Radisson Duluth
Duluth Hotel
Hotel
Explorer Room,
Glenn R.
R. Bruck
Glenn
A
for the Origin of the Horse
A new Proposal for
Creek Channel,
Channel, in
in Polk
Polk && St.
St. Croix
Croix Counties,
Counties,
Wisconsin
Jeff Greenberg
and Bruce Brown
Preliminary Geologic
Geologic Interpretation
lnterpretation of the
the
Northeastern Wisconsin 1:250,000 Geologic
Geologic Map
Frank Karner
and
and John T.
T. Ray
The Precambrian Basement
Basement of
of North Dakota
M. P.
M.
P. McKenna
and L.
L. W.
W. Gladen
and
and Mineral Potential of Cook
Mineral Survey and
County, Minnesota
County,
Nancy Scofield
and David B.
B. Jorgenson
Pink and
Green Albite Phenocrysts from the
the
and Green
Mohawk Mine,
Mine, Michigan--Indicators
Michigan——Indicators of Changes
in Hydrothermal Fluids
D. tv.
N. Snider
D.
and B.
B. K.
K. Parker
copper—sulfide potential of several igneous
The copper-sulfide
plugs in Michigan's Keweenaw Peninsula
G.
G. Bennett
and D.
D. G.
G. Innes
Innes
Huronian Volcanic
Volcanic Rocks,
Rocks, North Shore of Lake
Huron, Ontario
Huron,
*Authors
to 12:00
*Authors will
will be
be present
present 11:00 to
�—8--8-
HURONIAI'TVOLCANIC
VOLCANIC ROCKS, NORTH SHORE
HURONIAN
SHORE OF
OF LAKE HURON,
ONTARIO
HURON, ONTARIO
G. Bennett
G. Innes
Bennett andand
D. G.D.
Innes
Ontario Ministry
of Natural
Ontario
Ministry
ofResources
Natural Resources
ABSTRACT
distribution, petrochemical and
The distribution,
and stratigraphic
stratigraphic relationships
relationships
of volcanic and
and clastic
clastic formations
formations at
at or
or near
near the
the base
base of
of the
the Huronian
Huronian
of
Supergroup of the
the Southern Structural
Structural Province
Province of
of Ontario
Ontario permits
permits the
the
following
following reconstruction of
of Middle Precambrian
Precambrian events
events in
in terms
terms of
of
rift tectonics.
tectonics.
1.
1.
Sands
Sands and gravels of the
the Livingstone Creek
Creek Formation
Formation
are deposited on
on Archean
Archean basement.
basement.
2.
2.
Thermotectonic uplift centered east
east of
of the
the present
present Elliot
Elliot
Lake area (probably
(probably in the
the Sudbury
Sudbury area)
area) causes
causes an
an easteastward erosional
erosional beveling
beveling of
of the
the Livingstone
Livingstone Creek
Creek Formation.
Formation.
3.
3.
The andesitic member of the
The
the Thessalon Formation
Formation erupts
erupts
from central vents and fissures in
in aa subsiding
subsiding basin
basin or
or
graben. The study of
of 110
110 chemical
chemical analyses
analyses indicates
indicates
that
that in spite of local spilitization, these
these oldest
oldest vol—
volcanics included (tholeiitic)
canics
(tholeiitic) basaltic andesite,
andesite, icelandite,
icelandite,
rhyolite;
rhyolite; and (mildly
(mildly alkalic)
alkalic) hawaiite, mugearite
mugearite and
and
ankaramitic flows.
flows.
4.
4.
The
of compositionally uniform
uniform tholeiitic
tholeiitic flood
flood
The eruption of
basalt forms
the
upper
(basaltic)
member
of
the
Thessalon
forms the
(basaltic)
Formation.
5.
5.
Reoccurrence of
of uplift in
in the
the Sudbury
Sudbury area
area results
results in
in
of the upper member of the
erosion of
the Thessalon
Thessalon Formation
Formation
east of
of Thessalon and its complete removal
east
removal east
east of
of the
the
Elliot Lake area.
area.
6.
6.
In
the Sudbury area the
the thick
thick accumulations
accumulations of
of tholeiitic
tholeiitic
In the
basalt (Elsie
erupt from
(Elsie Mountain and Stobie Formations)
Formations) erupt
fissures
basin or
or graben.
graben. Increasing subsubfissures in a subsiding basin
sidence and/or waning volcanism causes
causes much intercalated
intercalated
Formation; while in
wacke and conglomerate in the Stobie Formation;
the
Massey area (80
the Massey
(80 km to the
the west),
west), basalt to
to rhyolite
rhyolite of
of
the
the Salmay Lake Formation is
is erupted on
on aa surface
surface in
in part
part
of exhumed,
exhumed, layered gabbro—anorthosite
of
gabbro-anorthosite which was probably
probably
emplaced during the Thessalon volcanic event.
event.
Coarse
Coarse sands
sands and
and uraniferous gravels of the
the Matinenda
Matinenda
Formation are
on the
the eroded
surface of
of the
are laid
laid down
down on
eroded surface
the
Thessalon
Formationinin the
the Elliot
Thessalon Formation
ElliotLake
Lake area
areaand
andwestward;
westward;
but
in the
but are
are intercalated
intercalated with
with the
the younger
younger volcanics
volcanics in
the
Massey and Sudbury areas
areas to
to the
the east.
east.
7.
7.
The eruption of the
the predominantly
predominantly rhyolitic
rhyolitic Copper
Copper Cliff
Cliff
the Sudbury area marks
the final
Formation of
of the
marks the
final Huronian
Huronian
volcanic episode.
episode.
8.
8.
Cessation of volcanism in
in the
the Sudbury—Massey
Sudbury-Massey area
area is
is folfoland the deposition of the
lowed
the
lowed by
by prolonged subsidence and
thick
thick turbidite
turbidite sequence of the
the McKim Formation.
�-9—9—
STATUS OF USGS URANIUM STUDIES IN MICHIGAN'S UPPER PENINSULA
U.S. Geological
Geological Survey,
Survey, Denver,
Denver, Colorado
Colorado 80225,
80225, Richard
Richard
Maurice Brock, U.S.
W. Ojakangas,
Ojakangas, University of Minnesota, Duluth,
Duluth, Duluth,
Duluth, Minnesota
Minnesota 55812
55812
W.
and
Survey, and J.
J. Kalliokoski, Michigan
~1ichigan Technological
Technological
and U.S.
U.S. Geological Survey,
University, Houghtor,
Houghton, Michigan 49931
49931 and
and U.S.
U.S. Geological
Geological Survey
Survey
University,
ABSTRACT
The U.
U. S.
S. Geological Survey is
is conducting work
work related
related to
to uranium
uranium
Lower, Middle,
Middle, and Upper Precambrian
Precambrian rock
rock units.
units. Randomly
potential of Lower,
selected samples from all units are being
being analyzed
analyzed for
for uranium
uranium content.
content.
In
knowledge is
is
In general,
general, base-level
base—level data
data are being generated where such knowledge
lacking.
Possible enrichment
enrichment of shear zones
zones is
is one focus
focus of
of the
the study.
study.
Mylonitic shear zones containing radioactive biotite
biotite and
and chlorite
chlorite pods
pods
cut granitic rocks;
rocks; some
Some of these
these porphyritic or
or porphyroblastic
porphyroblastic rocks
rocks
A number of primary
are 3—5
3-5 times
times more radioactive than
than other granites.
granites.
A
radioactive occurrences are present in
in the
the granitic
granitic terrane
terrane (see
(see Kallio—
Kalliokoski,
1976).
koski, 1976).
All the
the major Middle and
and Upper Precambrian
Precambrian sedimentary
sedimentary units
units of
of the
the
Cogebic Range in Michigan and
Wisconsin, and other units
Cogebic
and Wisconsin,
units to
to the
the east,
east, are
are
in the
the process of being
being studied.
studied. Paleocurrent patterns have been
been determined
determined
(largely
on cross--bedding)
cross—bedding) for
for the
the Sunday
Sunday Quartzite (72
(largely on
(72 readings——bimodal
readings--bimodal
WNW
I~l and ESE),
ESE), the
the Palms Formation
Formation (102
(102 readings——bimodal
ceadings--bimodal W~ and
and E),
E), the
the
Bessemer
ENE and
and W),
W), and
and the
the Jacobsville
Jacobsville
Bessemer Sandstone
Sandstone (105
(105 readings—--biniodal
readings--bimodal ENE
Formation (150
(150 readings——local
readings--local variability).
variability~ Field data are of primary
importance, but
but drill
drill core
core samples
importance,
samples of the
the Jacobsville are also being studied.
studied.
Paleogeographic—depositional
Paleogeographic-depositional models are
are being
being constructed;
constructed; these
these should
should be
be
of value in determining sources and
and transport
transport directions
directions of
of radioactive
radioactive
However, to date abnormal radioactivity
mineral grains
grains and/or
and/or solutions.
solutions. However,
radioactivity
has only been found
has
found in detrital monazite of
of the
the Goodrich
Goodrich Quartzite
Quartzite (Vickers,
(Vickers,
1956)
in phosphatic zones
zones of
of the
the Michigaimni
Michigammi Formation
(Cannon and
1956) and in
Formation (Cannon
Kiasner, 1976).
Klasner,
1976). There are a number of minor radioactive
radioactive occurrences
occurrences which
which
may be related to the sub—Jacobsville
sub-Jacobsville unconformity
unconformity (Kalliokoski,
(Kalliokoski, Langford
Langford
and Ojakangas, 1978).
1978).
References
Cannon, W.
W. F.
Klasner, J.
Cannon,
F. and Klasner,
J. S.,
S., 1976, Phosphorite and
and other
other apatite—
apatitebearing sedimentary rocks
rocks in
in the
the Precambrian
Precambrian of
of Northern
Northern Michigan:
Michigan:
U.S. Geological
Geological Survey
Survey Circular
Circular 746,
746, 66 p.
p.
U.S.
Kalliokoski,
Kalliokoski, J.,
J., (with
(with C.
C. Johnson), 1976,
1976, Uranium
Uranium and
and thorium
thorium occurrences
occurrences
in Precambrian rocks,
rocks, Upper
Upper Peninsula of Michigan and northern
in
Wisconsin, with thoughts
Wisconsin,
thoughts on other possible
possible settings:
settings: U.S. ERDA,
ERDA,
Grand Junction, BJX—48(76),
BJX-48(76), 294
294 p.
�-10-
Kalliokoski, J.,
J., Langford, F.
F. F.,
F., and
and Ojakangas,
Ojakangas, R.
R. W.,
W., 1978,
1978, Critera
Critera
Kalliokoski,
guides to
to
for uranium cccurrences
occurrences in Saskatchewan and Australia as
for
as guides
favorability for
for similar deposits
deposits in the United States:
fsvorability
States: U.S. D.O.E.,
D.O.E.,
Grand Junction,
Junction, CJBX—1l4(78),
Grand
CJBX-114(78), 480
480 p.
p.
Vickers, 1956,
1956, Geology and monazite content
content of
of the
the Goodrich
Goodrich Quartzite,
Quartzite,
Vickers,
Palmer area,
area, Marquette County,
County, Michigan in
in Contributions
Contributions to
to the
the
U.S. Geological Survey Bulletin
geology of uranium, 1955:
1955: U.S.
Bulletin 1030,
1030,
p.
p. 171-185.
�-11-·
—11.-DEFORMATIONAL HISTORY OF AN ARCHEAN
ARCHEAN GREENSTONE
GREENSTONE TERRANE:
TERRANE:
EASTERN LAKE OF THE WOODS,
WOODS, ONTARIO
ONTARIO
A. Brown*
Bruce A.
Department of Earth Sciences
University of
of Manitoba, Winnipeg
Winnipeg
ABSTRACT
ABSTRACT
A
A structural and stratigraphic study
study has
has been
been completed
completed in
in the
the east—
eastcentral part of the
the Lake
Lake of
of the
the Woods
Woods region.
region. The rocks of this
this area
area conconstitute aa typical greenstone assemblage of volcanic and
stitute
and sedimentary
sedimentary litho—
lithologies. The greenstones occupy an east—to—west
east-to-west trending
trending belt
belt bounded
bounded on
on
the
the north,
north, south,
south, and east by granitic batholiths in
in the
the study
study area.
area. The
results
this study indicate that
that the
the greenstones have
have undergone
undergone aa comcomresults of
of this
can be
be related
related to
to the
the diapiric
diapiric emplacement
emplacement
plex deformational history which can
of the
large bordering plutons
of
the large
plutons and several smaller stocks
stocks within the
the belt.
belt.
features of
of the
the area
area are
are aa series
series of
of major
major
The earliest structural features
east-west
trending isoclinal folds
folds (F1)
(F I ) with horizontal to
to shallow
shallow plunging
plunging
east—west trending
axes.
F1 folds
FI
folds have an associated axial
axial planar
planar foliation
foliation and
and are
are well
well
defined by top
defined
top reversals
reversals within the
the volcanic—sedimentary
volcanic-sedimentary section.
section. These
folds are
are aa regional
folds
regional feature
feature and can be traced
traced beyond the
the area
area of
of study.
study.
facies distribution
distribution as
as well
well as
as structure
structure supports
supports
Evidence from sedimentary facies
their early
early origin.
origin.
Deformation which accompanied emplacement
emplacement of
of the
the granitic
granitic plutons
plutons
produced folds
folds (F2)
(F 2 ) and aa complex
complex pattern
pattern of
of faults
faults and
and shear
shear zones.
zones. Axial
planar cleavages,
cleavages, penetrative mineral lineation,
lineation, and
and aa complex
complex set
set of
of
F2
folds
and
related
fabrics
crenulations are associated
associated with
with the
the F2
F2 folds.
folds. F
folds
fabrics
2
show a consistent style throughout
throughout the
the area,
area, but
but their
their orientation
orientation and
and
degree of development is
is variable depending
depending on
on their
their location
location relative
relative to
to
the deformational
deformational and
and metamorphic regime surrounding the
the
the plutons.
plutons.
Where pluton contacts parallel the
the structural
structural grain
grain of
of the
the greenstones,
greenstones,
F1
FI folds
folds were tightened
tightened and
and flattened,
flattened, and
and shear
shear zones
zones developed
developed along
along litho—
lithologic boundaries. Vertical displacement occurred
occurred along
along these
these zones,
zones, causing
causing
repetition of section and development
development of
of cataclastic
cataclastic textures.
textures. Where the
the
structural grain met a pluton contact
contact at
at aa high
high angle,
angle, shear
shear zones
zones acted
acted as
as
detachment faults
faults to
to accommodate flexural
flexural folding
folding of
of bedding
bedding and
and F1
F I axial
axial
planes around steeply
steeply plunging
plunging F2
F 2 axes.
axes.
In
In the late stages of deformation,
deformation, a set
set of
of northwest—
northwest- and
and northeast—
northeasttrending kink
kink bands
bands was
was overprinted on rocks
trending
rocks with strong planar fabrics.
fabrics.
Kinks grade into crenulation cleavage
Kinks
cleavage in
in fine
fine grained
grained pelitic
pelitic rocks
rocks and
and fine
fine
grained cataclastic
cataclastic rocks.
rocks.
The latest
latest structures are a series of northwest—trending
northwest-trending faults
faults into
into
diabase dikes
dikes were intruded
intruded in
in Late
Late Proterozoic
Proterozoic time.
time.
which diabase
*Present address:
address:
Wisconsin Geological and Natural History Survey,
Survey,
Madison, WI 53706
Madison,
�—12—
-12-
A PROPOSED SOUTHERN
SOUTHERN SPILLWAY
SPILLWAY FOR
FOR GLACIAL
GLACIAL LAKE
LAKE GRANTSBURG
GRANTSBURG
A
Glenn R.
R. Bruck
and Earth
Earth Science
Science
Department of Plant and
The University of Wisconsin—River
Wisconsin-River Falls
Falls
54022
River Falls, WI 54022
ABSTRACT
In 1935 W.
W. S.
S. Cooper described Glacial Lake Grantsburg
Grantsburg which
which was
was
formed when the Mississippi and St.
St. Croix
Croix Rivers
Rivers were dammed
dammed by
by the
the
glacial advance of
of the
the Grantsburg
Grantsburg Sublobe.
Sublobe. Lacustrine sediments
sediments indiindicate that the lake occupied an area of
of approximately
approximately 11,500
11,500 km2
km 2
mi 2 ). The estimated geographic center
center of
of this
this body
body of
of water
water
(4,500 mi2).
lies within Burnett County,
County, Wisconsin.
Wisconsin. Lacustrine sediments also indiindicate that the lake maintained a level
level between 305
305 mm (1002
(1002 ft)
ft) and
and 325
325 mm
(1070 ft)
a possible maximum
maximum at
at 335
335 mm (1100
(1100 ft).
ft).
(1070
ft) with
with a
Cooper's
the lake includes
includes aa southern
southern limb
limb of
of water
water
Cooper's description of the
This limb was
extending to the vicinity of St.
St. Croix
Croix Falls,
Falls, Wisconsin. This
confined on the west by the
the Grantsburg Sublobe
Sublobe and
and on
on the
the east
east by
by the
the
St. Croix Moraine,
Moraine, which was deposited about
St.
about 1,300
1,300 years
years earlier
earlier by
by the
the
Superior Lobe.
Lobe. The present investigation
investigation suggests
suggests that
that the
the lake's
lake's
southern extension terminated near St.
St. Croix
Croix Falls
Falls and
and Dresser,
Dresser, Wisconsin;
Wisconsin;
this
this location being determined by evidence
evidence indicating
indicating that
that the
the Grantsburg
Grantsburg
was pinned against the
Sublobe was
the St.
St. Croix Moraine in
in this
this area.
area.
Although Cooper's
most detailed
of the
the
Cooper's study is
is the most
detailed investigation
investigation of
lake to date,
date, he was unable to
to find aa drainage
drainage spiliway
spillway associated
associated with
with
its highest
highest level.
level. As a result,
result, he hypothesized that
that the
the lake,
lake, at
at its
its
highest stand,
stand, might have drained over
over the
the Grantsburg
Grantsburg Sublobe.
Sublobe.
A
A topographic
topographic examination
examination of
of the
the St.
St. Croix
Croix Moraine
Moraine near
near Dresser,
Dresser,
Wisconsin, reveals
reveals a gap that lies
lies at
at the 304
304 m
(1,000 ft)
level, fully
Wisconsin,
m (1,000
ft) level,
fully
(180 ft)
ft) below the
the morainal ridge
ridge it
it divides.
divides. During the
the glaciation,
55 m
m (180
this gap
gap was
was low enough
enough so
so that
this
that it was penetrated by outwash
outwash from
from the
the
marks the
beginning of
of a
42 km
nearby Grantsburg Sublobe.
Sublobe. The gap also
also marks
the beginning
a 42
(26 mi)
is clearly defined by the
the 304
304 m
m (1,000
(1,000 ft)
ft) contour.
contour.
(26
mi) channel
channel which
which is
The channel trends
trends southward and
and merges with the
the Apple
Apple River
River near
near HuntingHuntington, Wisconsin. From here it follows
ton,
follows the Apple River to
to a
a point
point 6.5
6.5 km
(4
it finally
the St.
St. Croix
(4 mi)
mi) WNW
WNW of
of Sommerset,
Sommerset, Wisconsin,
Wisconsin, where
where it
finally joins the
River.
This route describes a course which bypasses aa 26
This
26 km
km (16
(16 mi)
mi)
stretch of the
the St.
St. Croix
Croix River.
River. The present study suggests
suggests that
that this
this bybypass represents a southern spillway
spillway for
for Glacial
Glacial Lake
Lake Grantsburg
Grantsburg which
which
facilitated the
the lake's
lake's drainage
drainage during
during the
the maximum
maximum advance
advance of
of the
theGrants-'
Grants~
burg Sublobe.
Sublobe.
Evidence in support of this
this hypothesis consists
consists of
of two
two major
major observaobservations: First,
the altitude
altitude of
of the
the channel
channel
First, the close correlation between the
and the
level of
of Glacial Lake Grantsburg;
and
the level
Grantsburg; and
and secondly,
secondly, the
the outwash
outwash from
from
the
the gap
gap at
at Dresser
Dresser indicates
indicates that
that
the Grantsburg
Grantsburg Sublobe found east of the
from the
the ice
ice flowed
flowed through
through the
the gap.
gap.
drainage from
�—13—
-13-
RONCHI FILTERING--A
FILTERING——A RAPID INEXPENSIVE TECHNIQUE TO AID IN THE
DETECTION OF LINEATIONS
LINEATIONS IN PHOTOGRAPHS,
PHOTOGRAPHS, MAPS,
MAPS, ROCKS,
ROCKS, AND THIN SECTIONS
F. Cannon and Dennis Kostick
William F.
U.S. Geological Survey
U.S.
Survey
Reston, Virginia 22092
Reston,
22092
ABSTRACT
Ronchi filtering
filtering is
is a simple visual technique that
that can aid in
identifying
linear trends
trends in
in Landsat
Landsat images,
images, aerial
aerial photographs,
photographs, geologic
geologic
identifying linear
maps, aeromagnetic and gravity maps,
maps, and topographic maps;
maps; it can also be
maps,
It may
used to
to detect subtle
subtle linear
linear features
features in
in rocks
rocks and
and thin
thin sections.
sections. It
sometimes be
be an
an adequate
adequate substitute for
for more
more expensive
expensive and
and time—consuming
sometimes
time-consuming
computer enhancement
enhancement of
of data.
data.
A
A Ronchi
parallel thin
thin
width of each
parent area.
area.
filter is a type
type of linear diffraction
opaque stripes
stripes are
are arranged
arranged on
on aa clear
opaque
opaque stripe is equal to
to the
the width of
The filter used in our work contains
contains 88
grating in
in which
so that
plastic so
that the
the
the adjacent
adjacent transtransstripes
stripes per
per millimeter.
millimeter.
filter is
held about
about 10-30
10—30 cm in front
front of
of the eye,
The filter
is held
eye, and the object
to be studied,
studied, for
for example, aa Landsat
Landsat image,
image, is
is viewed
viewed through
through the
the filter.
filter.
when viewed
viewed in this
way is
Any small object when
this way
is seen as
as multiple images
images aligned
to the
the direction
direction of
of stripes
stripes on
on the
the filter.
filter. For example,
example, aa
perpendicular to
dot
dot appears as a line
line of
of several
several individual
individual but
but closely
closely spaced
spaced dots.
dots. This
property can be used to
to enhance
enhance subtle
subtle linear
linear trends.
trends. For example,
example, by
viewing aa Landsat image
image through
through the
the filter
filter and
and slowly
slowly rotating
rotating the
the filter
filter
0 , a
through 180
1800,
a user
user performs
performs aa rapid
rapid linear
linear enhancement
enhancement in
in all
all possible
possible
through
directions.
Subtle linear trends,
not easily visible to the untrends, commonly not
aided eye,
eye, may become readily visible through the filter when it is
is
stripes on the grating is
is perpendicular
oriented so that the direction of
of stripes
to the
to
the trend on the
the image
image or
or object.
object.
This technique has
has been useful in regional tectonic studies in the
the
Lake Superior region by helping us
us to identify linear trends
trends in Landsat
images,
maps.
images, aeromagnetic,
aeromagnetic, and gravity maps.
�—14—
-14FOR~ATION IN THE AMPHIBOLITE FACIES
FACIES
PHASE RELATIONS OF OXIDE-FREE IRON FORMATION
M. L.
M.
L. Cummings
Department of Geology
University of
of Wisconsin
Eau Claire,
Claire, Wisconsin 54701
54701
ABSTRACT
Iron
Iron formation
formation units,
units, up
up to
to 50
50 m
m thick,
thick, occur
occur in
in the
the Precambrian
Precambrian
Quinnesec Formation,
Formation, west central
central Marinette
Marinette County,
County, Wisconsin.
Wisconsin. The iron
formations
metasediments and
formations are associated with basalt flows,
flows, graphitic metasediments
and
sub-economic
sub—economic massive sulfide.
sulfide.
The iron formation
well—bedded gray quartz and iron silicate
formation contains
contains well-bedded
Locally,
are
Locally, quartz beds
beds are fractured
fractured and in some cases
cases fragments
fragments are
separated by thin septa of iron silicates. Some sections are charactercharacterized by
by rounded,
ized
rounded, 1 to
to 2 cm,
em, quartz nodules.
nodules. Oxides and/or sulfides are
are
disseminated in iron silicate beds
with
beds or occur as
as thin layers
layers interbedded
interbedded with
iron silicates. Ilmenite
is the oxide phase,
phase, but magnetite is
is locally
locally
Ilmenite is
abundant.
Monoclinic pyrrhotite is
is the
the main
main opaque
opaque phase.
phase. Sphalerite
grains interstitial to
to iron silicates or associated
associated with
occurs as isolated grains
with
pyrrhotite.
only in
in pyrrhotite—bearing
pyrrhotite-bearing beds.
beds.
Chalcopyrite occurs only
beds.
sequences can be determined by the
the
The metamorphic grade of
of volcanic sequences
iron silicate assemblages in oxide—free
iron
oxide-free iron
iron formation.
formation. Iron silicate
assemblages in oxide—free
oxide-free samples
samples from
from the Quinnesec Formation include
include
grunerite/quartz, grunerite/stilpnomelane/quartz,
grunerite/stilpnomelane/quartz, grunerite/ferro—hornblende/
grunerite/ferro-hornblende/
stilpnomelane/quartz, grunerite/garnet/ferro—hornblende/quartz,
grunerite/garnet/ferro-hornblende/quartz, grunerite/
grunerite/
ferro—actinolite
ferro-actinolite ±
± ferro—hornblende/quartz.
ferro-hornblende/quartz. Calcite is a common accessory
accessory
mineral. Stilpnomelane,
Stilpnomelane, restricted
restricted to
to grunerite
grunerite and
and grunerite/ferro—
grunerite/ferrohornblende assemblages,
assemblages, is
is more
more iron—rich
iron-rich than
than associated
associated amphiboles.
amphiboles.
grunerite in garnet-free
garnet—free
Manganese is preferentially partitioned into grunerite
samples.
samples. Magnesium is
is preferentially partitioned into
into ferro—actinolite
ferro-actinolite in
in
Ferro—hornblende is
grunerite/ferro—actinolite
grunerite/ferro-actinolite assemblages.
assemblages. Ferro-hornblende
is the
the silicate
phase containing
containing the
the highest
highest concentration
concentration of
of titanium.
titanium.
The iron silicates can be represented in the simplified system FeOFeO—
A1203—CaO—Si02—H20.
Na2O in stilpnomelane,
MgO, MnO
MnO and
and Ti0
TiO2
A1203-CaO-Si02-H20. K2O
K20 and Na20
stilpnomelane, MgO,
in
2 in
amphiboles remove
remove the
the system
system from
from the
the ideal
ideal simplified
simplified system.
system. Iron silicate assemblages
assemblages in the Quinnesec Formation indicate that
that the
the assemblage
assemblage
hornblende/grunerite/quartz is
approxiis stable under metamorphic conditions,
conditions, approximated from associated
associated metasediments,
metasediments, at
at 5200
520 0 CC and
and 1.5
1.5 to
to 3.5
3.5 kb.
kb. Actinolite/
high—manganese bulk
garnet/quartz is
is stable at
at higher temperatures
temperatures or in
in high-manganese
compositions.
�—15—
-15-
MAJOR-ELEMENT VARIATION WITHIN THE EMPEROR IGNEOUS COMPLEX
AND THE HEMLOCK AND BADWATER
BADWATER VOLCANIC FORMATIONS
FORMATIONS
Jesse C.
C. Dann
Department of Geology && Geological Engineering
Engineering
Michigan Technological University
Houghton,
Houghton, Michigan
Michigan 49931
49931
ABSTRACT
Major—element variations
variations within the Emperor Igneous
Major-element
Igneous Complex,
Complex, and
the
the Hemlock and Badwater volcanic formations
formations of
of the
the Lower
Lower Proterozoic
Proterozoic
of northern Michigan were studied
studied to
to determine
determine the
the magma
magma series
series type.
type.
Fifty-two
Fifty—two new
new analyses
analyses indicate
indicate that
that continental
continental tholeiite
tholeiite dominates
dominates
and that
most of
of the
the less
less abundant
abundant calcalkaline
calcalkaline rocks
rocks are
are not
not really
really
and
that most
distinguishable from
from those
those associated
associated with
with aa Lower
Lower Proterozoic
Proterozoic Cu-Zn
Cu—Zn
distinguishable
massive sulfide deposit in
in Wisconsin.
The Emperor
Emperor Igneous
Igneous Complex
Complex in
in the
the East
East Gogebic
Gogebic Range
Range consists
consists of
of
The
two
two distinct suites:
suites: calcalkaline volcanic rocks and
and tholeiitic
tholeiitic sills.
sills.
The
the Ironwood
The volcanic
volcanic rocks,
rocks, interbedded
interbedded with
with the
Ironwood Iron-formation,
Iron—formation, consist
consist
mostly of andesite breccia with minor lava flows;
flows; they
they are interpreted to
to
S1O2
increases
upward
from
represent a subaqueous volcanic apron.
apron. Si0
increases
upward
from
2
54 to
to 62
62 percent with FeO remaining
remaining at
at 99 to
to 11
11 percent.
percent. The sill comcomintruded the
iron—formation in
in three
stages which
which show aa FeO
FeO increase
increase
plex intruded
the iron-formation
three stages
from 12 to
to 19
19 percent.
percent.
Formation north
north of
of Crystal Falls
Falls displays
displays tremendous
The Hemlock Formation
tremendous
Rhyolite lava
lithologic and geochemical variety.
variety. Rhyolite
lava and/or volcaniclastic
deposits occur at
three horizons
the formation
formation which
is dominated
deposits
at three
horizons within
within the
which is
and volcaniclastic sediments
sediments (pillow
breccia, flow
by basaltic lavas
lavas and
(pillow breccia,
breccia,
hyaloclastite, and
and turbidites).
turbidites). The lowermost basalts, deposited
deposited
breccia, hyaloclastite,
about
b.y. ago,
ago, are
are poorly
poorly differentiated oceanic basalts,
basalts, perhaps
about 2 b.y.
perhaps
in aa fault—bound
fault-bound basin;
ironerupted in
basin; these are
are overlain by slate and iron—
formation.
continental tholeiite
The succeeding lavas,
lavas, composed
composed of.
of. continental
basalt,
subcycles of
of FeO
FeO and
and Ti02
Ti0 2 enrichment.
enrichment. The upperbasalt, display several subcycles
high-iron basalt (up
(up to
to 25
25 percent
percent FeO)
FeO) is
is
most unit of extraordinarily high—iron
immediately overlain by
by iron—formation.
iron-formation. The rhyolites do
do not
not occur
occur at
at
the top
the
top of volcanic cycles.
cycles.
The Badwater Greenstone outcropping along the north margin of the
Iron
Iron River-Crystal
River—Crystal Falls
Falls basin
basin consists
consists of
of several
several different
different sequences
sequences of
of
dominantly tholeiitic
tholeiitic volcanic
volcanic rocks.
rocks. Exposures on the south limb of the
basin exhibit a close relationship between high iron tholeiite basalts and
iron-rich
iron—rich sediments;
sediments; these
these rocks
rocks are
are interpreted
interpreted to
to belong
belong to
to the
the Hemlock
Hemlock
Formation.
It is
is clear
clear that
that lavas
lavas associated
associated with
with the
the Ironwood
Ironwood Iron-formation
Iron—formation
It
are not
not enriched in
are
in iron.
iron. However,
is some evidence which leads one
However, there is
to suspect
to
suspect aa relationship
relationship between
between iron-rich
iron—rich lavas
lavas of
of the
the Hemlock
Hemlock Formation
Formation
and the
and
the overlying Amasa Iron—formation.
Iron-formation.
�—16—
-16-
STATE LEGISLATION AFFECTING
AFFECTING MINERAL
MINERAL DEVELOPMENT IN
IN WISCONSIN
WISCONSIN
Thomas J.
J. Evans
Evans
Geological and Natural History Survey
Survey
University of
of Wisconsin
Wisconsin —- Extension
1815 University
University Avenue
1815
Madison, Wisconsin
Wisconsin 53706
53706
ABSTRACT
development in Wisconsin has
has stimulated
stimulated
Proposed metallic mineral development
wide—ranging
wide-ranging legislative
legislative activity
activity by
by the
the State
State of
of Wisconsin.
Wisconsin. The new
legislation,
1977 and
and 1978,
1978, also
also has
has impact
existlegislation, passed in 1977
impact on the
the two
two existing
metal
mines
in
Wisconsin.
ing metal
in
to
Metal mining operations are subject to
new laws concerning
concerning (1)
(1) taxation
taxation of
of mineral
mineral revenues
revenues (Chapters
(Chapters 31,
31,
185, and
(2) controls
controls on
on operating
operating procedures
procedures and environmental
185,
and 423),
423), (2)
impacts from
from the exploration (drilling)
impacts
(drilling) phase
phase through
through actual
actual mine
mine propro(Chapters 377,
377, 420,
420, and
and 421),
421), (3)
(3) controls
controls on
on metallic
metallic mineral
mineral
duction (Chapters
exploration lease terms
procedures (Chapter
and
terms and
and recording
recording procedures
(Chapter 253),
253), and
(4) submittal
submittal of
of metallic
metallic mineral
mineral exploration information of
(4)
of geologic
geologic
interest to the
the State
State (Chapter
(Chapter 422).
422).
Some of
will be
be
of the background leading to
to the
the recent
recent legislation will
reviewed with
with aa brief discussion of the
reviewed
the current
current status
status of
of each
each law,
law, its
its
impact
the mining industry,
industry, and subsequent regulatory
regulatory activity.
activity.
impact on the
Potential modifications of
of the
the laws
laws will
will also
also be
be noted.
noted.
Proposed legislation in the
the 1979
long1979 legislative sessions
sessions concerns
concerns long—
term
of mining companies and
and registration
registration of
of severed
severed mineral
mineral
term liability of
interests. Prospects
for and ramifications
ramifications of
this additional
Prospects for
of this
additional legislative
legislative
addition, the
activity will
will be
be examined.
examined. In addition,
the work of
of the
the Legislative
Legislative Council
Council
Mining Committee's
Committee's Subcommittee
Subcommittee on
on Reclamation of Nonmetallic Mining will be
reviewed.
�—17—
-17-
BEDROCK GEOLOGY
AREA, SILVER BAY,
BAY, MINNESOTA
GEOLOGY OF
OF THE MILEPOST 7 AREA,
C. Green
Green
John C.
Geology Department
University of Minnesota
Duluth,
Duluth, Minnesota 55812
55812
ABSTRACT
tailings disposal
disposal area
area lies
lies in
in the
the
Reserve Mining Company's new tailings
broad valley of the
the Thirty—nine
Thirty-nine Creek
Creek tributary
tributary to
to the
the West
'vast Branch
Branch of
of
the Beaver River about five
the
five miles
miles west
west of
of Silver
Silver Bay.
Bay. The basin
basin is
is
underlain by lavas of the
the North Shore
Shore Volcanic Group
Group whereas
whereas the
the high
high
the southeast side is
is held up
up by
by diabase
diabase of
of the
the Beaver
Beaver Bay
Bay
ridge along the
complex. The
the northwest flank
flank is
is also
also underunderThe more
more gradual slope on the
by mafic
mafic intrusive
intrusive rocks.
rocks. All of
of the
the bedrock
bedrock is
is of
of
lain predominantly by
Keweenawan (Late
(Late Precambrian)
Precambrian) age.
age. During the summer of 1978 the
the bedrock geology of the
the area was studied by field
field mapping and
and examination
examination
of
of drill cores obtained
obtained for
for dam
dam foundation
foundation testing.
testing.
The lavas
The
lavas in the basin and along strike to
to the
the south
south can
can be assigned
assigned
to
of Green
Green (1942).
(1942). They dip gently (about
(about
to the
the Gooseberry River basalts of
90)
9 0 ) to
to the southeast,
southeast, and consist of roughly
roughly 700
700 feet
feet of
of intergranular
intergranu1ar
andesites
andesites and basaltic andesites overlain by about
about 850
850 feet
feet of
of ophitic
ophitic
olivine basalts.
basalts. The later tend
tend to
to hold up low
low hills within the
the southsoutheast part of
of the
the basin.
basin.
The high ridge along the
the east
east side
side is
is made predominantly
predominantly of
of ophitic
ophitic
olivine diabase,
diabase, but
but a
olivine
a few anorthosite xenoliths and
and thick
thick screens
screens and
and
blocks of basaltic hornfels are
are also
also present
present as
as well
well as
as minor
minor interflow
interflow
volcanic sandstone
sandstone and
and breccia.
breccia. The main diabase intrusion
intrusion appears
appears to
to
have been localized
localized along
along aa major NNE—trending
NNE-trendin8 fault
fault which
which also
also divides
divides
the
lava succession into two
the lava
two separate structural and stratigraphic blocks;
blocks;
the
flows east
east of
of the ridge
the flows
ridge strike WNW and dip south whereas those
those to
to the
the
west strike NE
NE and
and dip
dip SE.
SE.
Some
also occurred
occurred since
since intrusion,
intrusion,
Some faulting
faulting has also
producing breccias and topographic
topographic cross—valleys
cross-valleys and
and juxtaposing
juxtaposing unmeta—
unmetamorphosed sediments
sediments next
next to
to diabase.
diabase.
morphosed
The intrusive rocks
rocks of the
the western flank
flank are
are more diverse
diverse and
and are
are
probably interdigitated with lavas
lavas but exposures
exposures are
are too
too poor
poor to
to show
show
contact relations.
relations. The uppermost unit is
is aa ridge—forming,
ridge-forming, fine—grained,
fine-grained,
iron—rich trachybasalt
iron-rich
trachybasa1t sill,
sill, probably
probably with
with two
two branches.
branches. The other major
units
the west side of the
the area are
are mostly ophitic
ophitic olivine
olivine diabase
diabase
units along the
and gabbro of various types;
types; some have highly zeolitized
zeo1itized roof
roof zones.
zones.
This
the Minnesota Geological Survey
Survey with
This project was
was supported by the
the cooperation
cooperation of
of Reserve
Reserve Mining
Mining Company and Klohn Leonoff Consultants,
the
Consultants,
Ltd.
�—18—
-18-
INITIAL PROGRESS AND INTERPRETATION OF
GEOLOGICAL MAPPING IN
IN NORTHEASTERN
NORTHEASTERN WISCONSIN
WISCONSIN
J.K.
J.K. Greenberg and B.A.
B.A. Brown
Brown
and Natural
Natural History
History Survey
Survey
Wisconsin Geological and
Madison, Wisconsin
Madison,
ABSTRACT
Initial results
Initial
results from reconnaissance—scale
reconnaissance-scale bedrock geological
geological mapping
mapping
in
(an area bound by 45°N,
45 0 N, 90°W
90 0 W and the
the state
state border)
border)
in northeastern
northeastern Wisconsin
Wisconsin (an
suggest the presence of four distinct tectonic
tectonic regions
regions separated
separated by
by three
three
structures which
which are
are best
best defined
defined by
by their
their geophysical
geophysical signasignamajor boundary structures
tures. Available age data
data indicate
indicate that
that most,
most, if
if not
not all,
all, of
of the
the observed
observed
rock units are Middle Precambrian.
Precambrian.
The three
The
three boundaries extend approximately east
east to
to west across
across the
the map
map
area. The northern one is
is nearly parallel with and
and just
just north
north of
of the
the
of Vilas County and just
just south
south of
of the
the Wisconsin—Michigan
Wisconsin-Michigan
southern border of
border in Forest and Florence Counties.
Counties. The central boundary extends from
from
the northern border of Lincoln County
County in
in the
the west,
west, across
across central
central Forest
Forest
The southern boundary
County, and through Amberg in
in eastern Marinette County.
County. The
County,
continues from northern Marathon County
County east—northeast
east-northeast through
through Merrill
Merrill and
and
across southern Forest County before swinging
across
swinging to
to the
the south
south along
along the
the eastern
eastern
border of Oconto County.
County.
The northernmost tectonic
tectonic region
region consists
consists of
of Michigamme
Michigamme and
and equivalent
equivalent
sedimentary rocks including iron
iron formation
formation and
and small
small volumes
volumes of
of volcanic
volcanic
rocks,
rocks, all of
of aa wide range
range in
in metamorphic
metamorphic grade.
grade. The next region to
to the
the
is separated from
from these
these rocks
rocks by
by the
the northern
northern boundary,
boundary, aa complex
complex
south is
series of
of fault
fault zones.
zones. This region is
is characterized
characterized by
by isolated
isolated areas
areas of
of
migmatitic gneisses
gneisses associated
associated with
with foliated
foliated granitic
granitic intrusions.
intrusions. These
areas
areas of
of felsic
felsic rocks are surrounded on
on the
the north
north and
and east
east by
by predominantly
predominantly
mafic volcanic
volcanic rocks,
including the
the Quinnesec
Quinnesec Formation,
Formation, and
and are
are apparently
apparently
mafic
rocks, including
However, late
truncated on
on the
truncated
the south by the central geologic boundary.
boundary. However,
late to
to
post—kinematic
post-kinematic plutons,
plutons, ranging
ranging in
in composition
composition from
from gabbro
gabbro to
to granite,
granite,
the regions to
to the
the north
north and
and south
south of
of the
the boundary.
boundary. Much of
of
intrude both the
the
immediately to
to the
the south
south is
is typical
typical ofofa at!greenstonelt
"greenstone" terrane
the region immediately
terrane composed of metavolcanic and
and metasedimentary rocks
rocks which
which are
are the
the hosts
hosts for
for major
major
massive sulfide
sulfide mineralization.
mineralization. The southern boundary between
between the
the greenstone
greenstone
terrane and
and rocks
rocks including the McCaslin Mountain Quartzite
terrane
Quartzite and
and Wolf
Wolf River
River
intrusives to
to the
the south
south is
is expressed,
expressed, at
at least
least in
in part,
part, as
as aa major
major
Batholith intrusives
shear zone.
zone. All of
of the tectonic
tectonic features in
in the
the map area
area will
will be
be better
better
understood as future
future work extends
extends mapping
mapping coverage
coverage to
to the
the west
west and
and south.
south.
�—19—
-19-
THE NATURE OF
OF GREENALITE
GREENALITE
Stephen Guggenheim,
Guggenheim~ Department of Geology,
Geo1ogy~ University of
of Illinois
Illinois at
at
Peter Wilkes,
Wi1kes~ Department of
of Metallurgical
Metallurgical and
and Mineral
Mineral
Engineering, University of Wisconsin—Madison,
Engineering~
Wisconsin-Madison~ and
and S.
S. W.
w. Bailey,
Bai1ey~ DepartDepartment of Geology
Geology and
and Geophysics,
Geophysics~ University
University of
of Wisconsin—Madison,
Wisconsin-Madison~Madison,
Madison~
Wisconsin
Chicago, Illinois,
Chicago~
I11inois~
ABSTRACT
Pure samples of greenalite,
greena1ite~ including
including aa single
single crystal,
crysta1~ have
have made
m&de
detailed structural
structural characterization
characterization than
than before.
before. All
possible a more detailed
samples studied consist of an intimate lntergrowth
samples
intergrowth of
of aa predominant
predominant
trigonal
trigonal phase and
and a
a minor monoclinic phase,
phase~ even
even down
down to
to the
the smallest
smallest
in the
the electron
electron microscope.
microscope. Specific polytypes cannot
cannot
particles visible in
3n reflections,
be assigned because of absence
absence of
of the
the diagnostic
diagnostic kl I 3~
ref1ections~
but the mode of layer
layer stacking
stacking differs
differs in
in the
the two
two phases.
phases. The single
crystal allows
allows the
crystal
the sense of the axes to
to be established and
and leads
leads to
to the
the
conclusion that
that the monoclinic phase is
is in
in a fixed
fixed orientation
orientation relative
relative
to
the trigonal
trigonal host~
layers. Tetrahedral inversion
inversion
to the
host, but
but with inverted layers.
is
for relief of the
the lateral misfit anticipated
anticipated due
due
is aa known
known mechanism for
2+-rich octahedral
to
Si—rich tetrahedral
tetrahedral sheet
sheet and
and aa Fe
Fe2—rich
to aa Si-ric~'
octahedral sheet.
sheet. As in
in
antigorite,
antigorite~ it
it causes elimination
elimination of
of octahedral
octahedral cations
cations and
and surface
surface OH
OH
groups at
at the
groups
the inversion loci,
loci~ thus
thus simulating an excess
excess of
of Si
Si upon
upon con—
conventional allocation of chemical
chemical analyses
analyses assuming
assuming aa full
full complement
complement of
of
anions.
Hexagonal arrays of satellite spots
spots around
around sharp
sharp kl I 3n
3~
spectra on hkO
hkO electron diffraction nets are interpreted
spectra
interpreted as
as due
due to
to
multiple diffraction caused by the
the coherent
coherent intergrowth
intergrowth of
of the
the mono—
monoclinic phase scattered as islands
islands throughout
throughout the
the matrix
matrix of
of the
the trigonal
trigonal
2+-rich and
Mn2+_rich
host.
and its
its abundance
abundance increases
The
is Mn
Thc monoclinic phase is
with
fromgreenalite
greenalitethrough
through the
the species
species tosalite
tosalite to
to caryc—
carycwith Mn2+
Mn2+ cont
conttntfrom
pilite,
pilite~ the
the Mn
~ill or-analogue
grecnalite~ where the
the monoclinic phase
phase is
is
—analogue of
of greenalite,
predominant and the
the trigonal
trigonal phase
phase is
is minor.
minor.
predominant
2
�—20—
-20-
PETROLOGY AND GEOCHEMISTRY OF KEWEENAWAN DIABASE DIKES
ONTONAGON,
ONTONAGON, GOGEBIC,
GOGEBIC, IRON AND DICKINSON COUNTIES,
COUNTIES, MICHIGAN
James J.
J. Hahnenberg
Hahnenberg
Department of
of Geology
Geology
Western Michigan University
Kalamazoo,
Kalamazoo, Michigan 49008
Keweenawan diabase dikes in Michigan's Upper Peninsula
Peninsula are
are being
being
trace element
element (Rb,
(Rb, Sr,
Sr, Ba)
Ba) concenconcenanalyzed for major and selected trace
trations
compositions. Specifically, techniques
techniques
trations and bulk mineral compositions.
microscope, x—ray
using the
the petrographic microscope,
x-ray fluorescence,
fluorescence, atomic
atomic absorption
absorption
spectrographic analysis
analysis and
and the
spectrographic
the magnetometer are being used to
to
accurately define mineralogical and
and chemical
chemical trends
trends and
and magnetic
magnetic
Sample distribution is
character of the
the dikes.
dikes. Sample
is spaced as uniformly as
possible on a trend
trend roughly perpendicular to
to the
the Keweenawan
Keweenawan "rift
"rift
trend". The dikes
dikes will be compared to
to other Keweenawan igneous
igneous units,
units,
in the
the region
region (the
(the Powdermill
Powdermill
specifically lower Keweenawan flows in
Group, formerly the
Group,
the South
South Trap
Trap Range).
Range). Correlation with chemical
trends in more recent
trends
recent rift
rift systems
systems will
will be
be attempted.
attempted.
The larger dikes are composed of subophitic
subophitic plagioclase
plagioclase and
and
pyroxene (augite
(augite and
and pigeonite).
pigeonite). Opaque minerals are a minor,
minor, but
minerals are orthoclase and
ubiquitous, constituent.
constituent. Interstitial minerals
quartz which occur locally
locally as micropegmatitic intergrowths
intergrowths associated
associated
with needles of
of apatite.
apatite. Some
altered, being
Some dikes
dikes are only slightly altered,
uralitized and chioritized,
chloritized, while others
others consist
consist of
of 15—25%
15-25% secondary
secondary
minerals. In
In small
small dikes,
dikes, mineral grains are microcrystalline to
to
cryptocrystalline. The
dike~ have narrow chilled margins
The larger dikes
abruptly changing to
to phaneritic texture
texture toward
toward their
their centers.
centers.
�—21—
-21-
INTERPRETATIONS IN THE HAZELWOOD
STRUCTURAL INTERPRETATIONS
AREA, THUNDER
THUNDER BAY, ONTARIO
ONTARIO
LAKE AREA,
M.M. Keh1enbeck
Kehienbeck
M.M.
Department
Department of Geology
Geology
Lakehead University
University
Lakehead
Bay, Ontario
Ontario P7B
P7B SB1
5l
Thunder Bay,
ABSTRACT
The Hazelwood
is underlain by
Hazeiwood Lake area is
by Archean stratified sedimentary rocks
rocks and
and fragmental
fragmental volcanic
volcanic rocks.
rocks.
Primary structures,
structures, particularly graded bedding,
bedding, are well
in most
most outcrops.
outcrops. Pillow lava
lava flows
flows occur
occur sporadisporadipreserved in
cally interlayered
inter1ayered with agglomerates and
and tuffaceous
tuffaceous units.
units.
All rocks possess a well developed cleavage which appears
parallel to
axial surface
surface of
of observed
observed minor
minor folds
folds in
parallel
to the
the axial
in the
the
sedimentary sequence.
sequence.
Applying the
the technique
technique of structural facing to
to the
the rocks
rocks
gives the
sense of
of younging
younging of
of the
folded stratigraphic
stratigraphic
gives
the sense
the folded
succession.
Results from
from Hazelwood
Hazelwood Lake
Lake indicate
Results
indicate that
that a
a significant
the stratigraphic sequence
down prior to
to
portion of
of the
sequence was
was upside
upside down
the last
last folding event
the
event in
in the
the area.
area.
�—22—
-22-
COEXISTING AMPHIBOLES
ANPHIBOLES AT
AT BLACK RIVER FALLS,
FALLS, WISCONSIN
WISCONSIN
Karen Kimball
Department of Geology and
and Geophysics
University of Wisconsin
Madison, Wisconsin
Madison,
Wisconsin 53706
S3706
ABSTRACT
Extensive outcrops
outcrops of
of iron
iron formation
formation are
are present
present seven
seven miles
miles west
west of
of
Extensive
Black River Falls,
Falls, Wisconsin.
Wisconsin.
The dominant mineral assemblages in
The
in the
the iron
iron
formation are:
are:
1)
1)
magnetite—quartz-.grunerite—ferroactinolite
magnetite-quartz-grunerite-ferroactinolite
2)
magnetite—quartz—cummingtonite—biotite
magnetite-quartz-cummingtonite-biotite
3)
3)
magnetite—quartz—garnet—hornblende—ferroactinolite—grunerite
magnetite-quartz-garnet-hornblende-ferroactinolite-grunerite
The amphiboles
amphiboles in
in the
iron formation
formation are
are products
products of
of aa metamorphic
metamorphic event
event
The
the iron
which reached
reached lower
lower amphibolite
amphibolite facies.
facies.
Coexisting amphiboles
amphiboles occur
occur as
as disdis-
grains in
in contact
contact with
with each
each other,
other, as
as coarse
coarse intergrowths,
intergrowths, or
or occaoccacrete grains
sionally as
as 20—25
20-2S micron blebs of
of one
one amphibole
amphibole in
in another.
another.
are not
are
not altered and
and not
not exsolved.
exsolved.
The amphiboles
Individual amphibole grains are
are homogeneous.
homogeneous.
Multiple electron microprobe analyses show that
that compositional variations are
less than
than two
two percent.
percent.
The amphibole assemblage hornblende—ferroactinolite—grunerite
hornblende-ferroactinolite-grunerite is
is the only
three amphibole assemblage found
found in
in the
the iron
iron formation.
formation.
three
quartz this assemblage
quartz
assemblage is
is invariant.
invariant.
In the
In
the presence of
of
The chemical formulas
formulas for
for these
these amphi—
amphi-
boles
are (Na,K)
2Ca9(Mg,Fe,Al)5Si75023 for
9Mg1 4Fe4
boles are
(Na,K) .2Ca.g(Mg,Fe,Al)SSi7.S023
for the
the hornblende,
hornblende, Ca1
Cal.9Xgl.4Fe4
Si7 . 8023
for the ferroactinolite and
7Si7 7023 for
Si
and (Mg,Fe)6
(Mg,Fe)6.7Si7.7023
for the
the grunerite.
grunerite.
7 8 0 23 for
are abundant
abundant and
and include:
include:
Amphibole pairs are
(Na,K)1Ca19Mg3Fe11Al29Si5023
grunerite—hornblende
Mg14Fe57Si77023 —- (Na,K)lCal.gMg3Fel.lAlZ.gSiSOZ3
grunerite-hornblende Mgl.4FeS.7Si7.7023
grunerite—ferroactinolite
Mg18Fe57Si79023 —- Ca19Mg14Fe39Si78023
grunerite-ferroactinolite Mgl.8FeS.7Si7.9023
Cal.gMgl.4Fe3.9Si7.8023
cummingtonite—gedriteMg4.SFe2.lSi7.SAl.4023
Mg48Fe21S178A14023 —- Mg12Fe47A12Si56A115023
cummingtonite-gedrite
Mgl.2Fe4.7A12SiS.6All.S023
cummingtonite—actinoliteMg3.7Fe3.8Si7.9023
Mg37Fe38Si79023 —
cummingtonite-actinolite
- Ca19Mg32Fe15Si8O23
Cal.gMg3.2Fel.SSiS023
�—23—
-23-
Ferroactinolite coexisting with
with grunerite
grunerite has
has higher
higher Mg/Mg+Fe
Ng/Mg+Fe and
and
Ferroactinolite
Ca/Mg+Fe
ratios than
ferroactinolite coexisting with
with grunerite
grunerite and
and hornhorn—
Ca/Mg+Fe ratios
than ferroactinolite
blende.
Grunerite
Gruncrite in the two
two phase assemblage
assemblage has
has lower
lower MgIMg+Fe
Mg/Mg+Fe ratios
ratios
and higher Ca/Mg±Fe
Ca!Mg+Fe ratios than
than in
in the
the three
three phase
phase assemblage.
assemblage.
Cumming—
Cumming-
tonite
with gedrite
gedrite has
has higher
higher Mg!Mg+Fe
Mg/Mg±Fe and
and lower
lower Ca/Mg+Fe
tcnite coexisting
coexisting with
ratios
ratios than cummingtonite
cucrmingtonite coexisting
coexisting with
with actinolite.
actinolite.
The
the chemistry
the
The composition
composition of
of the
the amphiboles
amphiboics is
is related
related to
to the
chemistry of
of the
rocks.
The
in magnetite
sections of
the
The Fe-rich
Fe—rich amphiboles
amphiboles occur
occur in
magnetite deficient
deficient sections
of the
iron formation.
formation.
The
magnetite.
The Fe-poor
Fe—poor amphiboles occur with magnetite.
The !1g-rich
Mg—rich
The
amphiboics occur in a transition
amphiboles
transition zone
zone surrounding
surrounding aa talc
talc schist.
schist.
�—24—
-24-
PRELIMINARY RESULTS OF A
A TRUCK-MOUNTED MAGNETOMETER
SURVEY
OF THE
THE
SURVEY OF THE SOUTHWEST QUARTER OF
IRON
QUADRANGLE, MICHIGAN AND
AND WISCONSIN
WISCONSIN
IRON RIVER 10x2°
l°x2° QUADRANGLE,
R. King and
and William
William F.
F. Cannon
Cannon
Elizabeth R.
U.S. Geological Survey
U.S.
Survey
Reston, Virginia 22092
22092
Reston,
ABSTRACT
In August
August of
of 1978,
1978, the U.S.
U.S. Geological Survey
In
Survey made
made aa survey
survey of
of the
the
southwest quarter of the
southwest
the Iron River l°x2°
10x2° quadrangle,
quadrangle, Mich.—Wis.,
Mich.-Wis., using
using
a truck—mounted
This work,
work, which is part
truck-mounted magnetometer.
magnetometer. This
part of
of aa mapping
resource-evaluation program in
in the
the Iron
Iron River
and resource—evaluation
River quadrangle,
quadrangle, was
was done
done
over poorly exposed Proterozojc
Proterozoic and
and Archean
Archean terrane,
terrane, which
which is
is covered
covered
by a thick
thick layer
layer of glacial alluvium.
alluvium.
The survey consisted of
470 miles
traverses generally
of nearly 470
miles of
of traverses
generally
The traverses
in aa north—south
north-south direction.
direction. The
traverses were done over
over
oriented in
selected unpaved forest
forest roads
roads to
to minimize
minimize the
the effects
effects of
of heavy
heavy traffic
traffic
and of steel in
in the
the roadbed.
roadbed. The system used a fluxgate
fluxgate magnetometer
magnetometer
on aa boom on the
the top
top of the
the truck,
truck, and the
the variations in the
the
mounted on
total
field were recorded in
in both analog
analog and
and digital
digital form.
form.
total magnetic
magnetic field
The purpose of the
the survey
survey was to
to augment
augment existing
existing aeromagnetic
aeromagnetic
coverage, which
which was
was flown
coverage,
flown at a 1/2—mile
1/2-mile line
line spacing
spacing and
and at
at an
an elevation
elevation
of 500 ft.
above the
surface, with
with ground-level
ground—level magnetic
magnetic data
data to
aid in
in
of
ft. above
the surface,
to aid
detailed geologic
geologic interpretations.
interpretations. A
A number of domal
domal uplifts
uplifts have
have been
been
both mapped and inferred
inferred from
from sharp
sharp linear
linear magnetic
magnetic anomalies
anomalies that
that outoutline them.
them. The Archean Precambrian gneisses in
in the
the cores
cores of
of these
these domes
domes
have relatively low magnetic relief,
relief, as
as do
do the
the metasedimentary
metasedimentary rocks
rocks of
of
the overlying
overlying Michigamme
Michigamme Formation,
the
Formation, and are not readily
readily distinguishable
distinguishable
on the aeromagnetic
aeromagnetic map.
map. However,
However, there
there are subtle differences
differences in the
magnetic signatures between the
Michi—
the almost magnetically featureless
featureless Michigamme
rocks. These differences
gainme slates
slates and
and the
the more
more variable
variable gneissic rocks.
can be observed on the
the detailed
detailed ground
ground magnetic
magnetic profiles
profiles and
and permit
permit more
more
accurate interpretation of the
the aeromagnetic
aeromagnetic map.
map.
complex system
system of
of faults
faults having
having predominant
predominant
The
The area has
has been cut by a complex
northwest and northeast trends,
trends, some
some with considerable horizontal
horizontal and
and
vertical displacements,
of
displacements, which are apparent from the magnetic pattern of
the
the contoured
contoured aeromagnetic data and the
the ground profiles.
profiles. The magnetic
profiles also
also detect
detect relatively
relatively low amplitude,
amplitude, sharp
sharp negative
negative magnetic
magnetic
profiles
anomalies
anomalies associated with a series
series of
of reversely
reversely magnetized
magnetized Keweenawan
Keweenawan
diabase dikes
djabase
dikes striking approximately east.
east.
�~25-
FORMATION
CONTACT METAMORPHISM OF THE VIRGINIA FORMATION
MINNAMAX DEPOSIT, ST.
ST. LOUIS
LOUIS CO.,
CO., MINNESOTA
Mark Kirstein
Department of Geclogy
Geology
University of Minnesota—Duluth
Minnesota-Duluth
Duluth, Minnesota 55812
Duluth,
55812
ABSTRACT
Calc-silicate
Calc—silicate bodies occur in the Virginia Formation
Formation and
and as
ns xenoliths
xenoliths
in metadiabase dikes near the contact with the
the base of
of the
the Duluth
Duluth Complex
Complex
in the Minnamax Deposit,
Deposit, St.
St. Louis County,
County, Minnesota. The rocks of
of the
the
footwall
footwall have been matamorphosed to
to the
the pyroxene
pyroxene hornfels
hornfels facies.
facies. Later
sulfide mineralization is present in
in all metamorphic rocks.
rocks.
The calc—silicate
calc-silicate bodies are
are ellipsoidal
ellipsoidal to
to spherical
spherical and
and range
range in
in
length from 4 inches to
to 44 feet.
feet. They are generally
generally light
light gray
gray and
and are
are
fine to
fine
to medium grained
grained granofels.
granofels. There are
are three
three types
types of
of bodies:
bodies: (a)
(a)
homogenous, (b)
(b) layered,
layered, with alternating
alternating layers
layers of
of leucoxene
leucoxene or
or diopside,
diopside,
homogenous,
and
(c) concentric'
two distinct mineral layers.
layers. The most
and Cc)
concentric showing at
at least two
common
mineral
assemblages
are
diopside
and
wallastonite
with
either
common mineral assemblages
either
grossularite or
or anorthite.
anorthite. Accessory minerals include
include ilmenite,
ilmenite, sphene,
sphene,
and leucoxene. Later sulfide replacement occurs with chalcopyrite,
and
chalcopyrite, exsolved
exsolvcd
cubanite, and
Associated with
cubanite,
a~d minor magnetite.
with the
the sulfide
sulfide mineralization
mineralization
is the
the development
development of
of poikiloblastic quartz,
is
quartz, calcite, and
and apophyllite
apophyllite with
minor anhydrite,
and laumontite.
laumontite.
minor
anhydrite, fluorite,
fluorite, humite,
humte, and
The Virginia Formation,
Formation, a pelitic hornfels,
hornfels, and
and later
later metadiabase
metadiabase
dikes look almost identical in
in hand sample.
sample. They are fine
fine grained,
grained, massive,
massive,
and dark
dark gray.
gray. Relict bedding,
bedding, when seen
seen in
in the
the hornfels,
hornfels, is
is highly
highly concontorted and discontinuous. The hornfels consists dominatly
torted
dominntly of
of equigranular
equigranular
plagioclase, cordierite, and hypersthcne
hypersthene with
with minor
minor quartz,
quartz,
untwinned plagioclase,
apatite, and
and graphite.
graphite. Biotite and orthoclase
orthoclase occur
occur locally.
locally. Black
"reacticn"
"reaction" rims
rims exist for
for 3 inches into
into the
the hornfels when in
in contact
contact with
with
calc—silicate bodies.
calc-silicate
bodies. The rima
rims consist of plagioclase,
plagioclase, hypersthene, and
and
poikiloblastic augite.
augite. The metadiabase dikes
dikes consist
consist primarily
primarily of
of lathy
lathy
interstitial hypersthene
hypersthene and
and augite.
augite. Ilmenite, quartz,
quartz,
labradorite with interstitial
and apatite occur as accessory
accessory minerals.
minerals. Sulfides in the
the hornfels consist
consist
of pyrrhotite with exsolved pentlandite,
pentlandite, chalcopyrite,
chalcopyrite, and
and minor
minor magnetite
magnetite
and ilmenite.
ilmenite. Sulfides
Sulfides in the metadiabase are restricted
restricted to
to fractures
fractures and
and
are dominatly composed of
are
of pyrrhotite.
pyrrhotite.
The calc—silicate
calc-silicate bodies show metasomatic effects
effects with aa gain
gain of
of
aluminum and
and aa loss
loss of
of calcium.
calcium. This is responsible for
for the
the formation
formation of
of
the "reaction" rims.
the
rims. Some
the bodies may bc
the top
top of the
the
Some of
of the
be from the
that were brought up
up by
by the
the intrusion
intrusion of
of the
the Duluth
Duluth
Biwabik Iron Formation that
Complex.
The
to have originated as concretions in
in the
the
The majority appear to
Virginia Formation.
Formation. The sulfides and associated silicates
silicates are
are related
related to
to
a
a later retrograde
retrograde metamorphic
metamorphic event.
event.
�—26—
-26-
GEOLOGIC INTERPRETATION OF GRAVITY DATA
DATA IN
IN THE
THE
MARENISCO-WATERSMEET AREA,
AREA, NORTHERN MIGHIGAN
J.
S. Kiasner,
Klasner, U.
U. S.
University,
J. S.
S. Geological
Geological Survey
Survey and
and Western Illinois University,
S. Geological Survey,
Macomb, Illinois
Illinois 61455,
61455, P.
P. K.
K. Sims,
Sims, U.
U. S.
Survey, Denver,
Denver,
Macomb,
Colorado,
Colorado, 80225,
80225, and S.
S. A.
A. Jankowski,
Jankowski, Department of
of Geology,
Geology, Western
Western
Illinois
61455
Illinois University,
University, Macomb,
Macomb, Illinois
Illinois 61455
ABSTRACT
Geophysical studies have been conducted in
in the
the western part
part of
of
northern Michigan to aid in determining the
the geology
geology of
of the
the tectonic
tectonic zone
zone
marking the
the boundary between
between two
two Archean
Archean terranes
terranes recognized
recognized in
in the
the Lake
Lake
Superior region;.a
region;. a greenstone—granite
greenstone-granite terrane
terrane on
on the
the north
north and
and aa gneiss
gneiss
terrane on the
the south.
south. A
the area having aa 22 milligal
milligal contour
contour
A gravity map of the
interval
stations. The map
interval was
was prepared
prepared using
using data
data from approximately 310 stations.
includes gravity readings obtained
includes
obtained along
along 33 profiles
profiles with
with 300
300 in
m station
station
spacing to
to aid in
in interpretation
interpretation of
of the
the data.
data.
The gravity anomalies generally are in
The
in good agreement
agreement with the
the mapped
mapped
geology. Pronounced lows coincide
coincide with the
the large
large pluton
pluton of
of Archean
Archean
Puritan Quartz Monzonite west of Lake Gogebic and
and the
the Archean
Archean gneiss
gneiss dome
dome
Small positive anomalies
anomalies coincide with synclinal basins
near Watersmeet. Small
of the lower Proterozoic
Formations and
and with magnetic
of
Proterozoic Copps
Copps and
and Michiganmie
Michigamme Formations
anomalies interpreted as being caused
anomalies
caused by lean
lean iron—formation
iron-formation and
and associated
associated
rocks.
Amphibolitic layers
layers in
in both the
the quartz
quartz monzonite
monzonite and
and the
the gneiss
gneiss
also have positive gravity
gravity anomalies.
anomalies. A
A relatively steep
steep (approximately
(approximately
5 milligals per km)
km) north—sloping
north-sloping gradient coincides
coincides with the
the inferred
inferred
position of
of the
the boundary zone
zone between the
the Archean greenstone
greenstone and
and gneiss
gneiss
terranes.
A two—dimensional
A
two-dimensional gravity model consistent
consistent with mapped geologic
geologic units
units
and measured rock densities suggests that
that the
the synclinal
synclinal basin
basin within
within the
the
greenstone terrane which involves
involves the
the Copps
Copps Formation
Formation is
is about
about 2.0
2.0 km
km deep,
deep,
whereas the
gneiss terrane
which includes
Michigamme
the basin within the gneiss
terrane which
includes the
the Michigamme
Formation may be approximately 33 km deep.
deep.
A north-sloping
north—sloping regional gravity gradient extrapolated
A
extrapolated from
from data
data outoutside the study area corresponds with the
the boundary zone
zone between
between the
the two
two
basement terranes and reflects an increase
increase in
in density
density from
from north
north to
to south
south
rocks of the
the upper crust and perhaps also
also in
in the
the lower
lower crust
crust and/or
and/or
in rocks
upper mantle.
�—27—
-27-
CROSS FOLDING IN THE PRECAMBRIAN
CROSS
PRECAMBRIAN X STRATA
STRATA
OF
OF THE
THE EASTERN
EASTERN MARQUETTE
MARQUETTE TROUGH,
TROUGH, MICHIGAN
MICHIGAN
D.
D. K.
K. Larue
Larue
F.
F. W.
W. Cambray
Cambray
Michigan
State University
Michigan State
Northwestern University
Evanston, Illinois 60201
East Lansing,
Lansing, Michigan 48824
ABSTRACT
X Chocolay and Menominee Group strata
The Precambrian X
strata in
in the
the
eastern Marquette trough
trough of Michigan show evidence
evidence of
of two
two episodes
episodes of
of
deformation. The first and major
nlajor deformation
deformation CD1)
(Dl) folded
folded the
the strata
strata
E-W slaty
slaty cleavage
cleavage (S1).
(Sl). The second,
second, less
less intense
intense
and formed vertical E—W
deformation (D2)
(D2) locally formed cross
cross folds of
of bedding
bedding and
and folded
folded
cleavage.
The major synclinal fold
fold in the
the trough,
trough, termed
termed the
the Marquette syn—
synclinorium, was
Dl deformation. Macroscopic D1
Dl folds
folds are
are
clinoriuni,
was formed
formed by
by the D1
confined to the
the hinge region of this
this synclinorium (e.g.,
(~.£., Harvey
Harvey Quarry,
Quarry,
Marquette). Minor Dl fold axes plunge gently
gently to
to the
the EE or
or WW in
in vertical
vertical
E—W
E-W axial planes.
planes.
At
localities, the Enchantment Lake Formation along
along U.S.
U.S. 41
41 in
in
At two localities,
Negaunee and the Kona Formation in Sec.
Sec. 32, T48N,
T48N, R26W,
R26W, Negaunee,
Negaunee, the
the
quartzose beds
beds exhibit minor folds
folds with steeply plunging
plunging axes,
axes, F2,
F2, and
and aa
vertical NW—SE
NW-SE axial
axial plane,
plane, S2.
S2. These minor folds
folds have an
an S—shaped
S-shaped profile
profile
and can be shown to
to deform
deform Sl.
Sl. Similar features
features of minor folds
folds can be
(northeast shore of
of Teal Lake),
Lake), in
in the Mesnard
observed in the Siamo Slate (northeast
Marquette), and in
Quartzite (shore
(shore of Lake Superior,
Superior, Marquette),
in the
the Negaunee
Negaunee Iron
Iron
Formation (New
(New Richmond Mine,
Palmer, and on Jasper Knob,
Knob, Negaunee).
Negaunee). These
Mine, Palmer,
lithologies rarely develop cleavage so it
it is
is not possible to
to determine
determine the
the
sequence of folding directly.
directly. However,
However, minor folds
folds showing
showing steeply
steeply plunging
plunging
fold axes
fold
axes are thought to have been superimposed on the
the already
already steeply
steeply dipdipping limbs of
In addition,
addition, small intrafolial
of the
the Marquette
Marquette synclinorium.
synclinorium. In
folds in bedding with an E—W
folds
E-W axial surface and steep plunge can
can be seen
seen on
on
an island in Teal Lake and are attributed to
to the
the D2 episode.
episode.
folds in the Marquette synclinorium exhibit aa somewhat
The major folds
variable fold—axis
fold-axis orientation
orientation from
from south
south of
of west
west to
to north
north of
of west,
west, as
as
exhibited by the Goose Lake syncline and the
the folds
folds associated with the
the
Isabella syncline in
in the
the Palmer
Palmer area.
area. These major folds
folds may be either
refolded D1
Dl folds or
or both
both D1
Dl and
and D2
D2 folds.
folds. Absence of a pervasive slaty
cleavage makes assignment
assignment difficult.
difficult.
The sequence of events is
is consistent
consistent with aa north—south
north-south compression
compression to
to
D1 structures,
structures, followed by a NE—SW
produce Dl
NE-SW compression to
to form
form the
the D2
D2
structures. The NE—SW
NE-SW compression could
could be induced
induced by aa left—lateral
left-lateral strike—
strikeslip movement on the Marquette trough in the
the late
late stages of
of D1
Dl compression.
compression.
Such displacement
shortening
displacement would
would be expected if the regional directions of shortening
during Dl
D1 were
were not
not precisely orthogonal to
during
to the
the trough.
trough.
It
is interesting
interesting to
note that
It is
to note
that the
the regional
regional shortening represented by
D2 has a similar orientation to
to that
that represented
represented by the
the folds
folds in
in the
the
Republic trough.
trough.
�—28--28-
PETROLOGY OF THE TROCTOLITE—OLIVINE
TROCTOLITE-OLIVINE GABBRO SERIES,
SERIES, DULUTH
DULUTH GABBRO
GABBRO COMPLEX
COMPLEX (LATE
(LATE
PRECAMBRIAN) NORTHEASTERN
NORTHEASTERN CRAMER
CRAMER QUADRANGLE,
LAKE AND
AND COOK
COOK COUNTIES,
QUADRANGLE, LAKE
COUNTIES, MINNESOTA
MINNESOTA
George Lehman
Dames and Moore Co.
Co.
Lakewood, Colorado
Colorado 80401
and
Donald
M. Davidson,
Davidson, Jr.
Jr.
Donald ~.
Dept.
Dept. Geological Sciences
Sciences
University of Texas,
Texas, El Paso
El Paso,
Paso, Texas
Texas 79968
in the
the northeast quarter
quarter of
of the
the Cramer
Cramer quadrangle,
quadrangle, MinneMinneAs observed in
sota,
textures, the orientation of igneous
igneous laminations,
laminations, systematic
systematic
sota, rock textures,
in modal abundances
abundances of
of minerals as
as well
well as
as the
the chemical
chemical comcomvariations in
of major minerals Indicate
position of
indicate that
that the
the troctolite—olivine
troctolite-olivine gabbro
gabbro series
series
in the Duluth Gabbro Complex
(Keweenawan) differentiated
differentiated in situ
situ as
Complex (Keweenawan)
as a
a
result of crystal
crystal settling.
settling. Here,
Here, the
the troctolite—olivine
troctolite-olivine gabbro
gabbro series
series is
is
exposed as
as a
southwest—northeast trending band of outcrops approximately
exposed
a southwest-northeast
approximately two
two
km in
in width which lies
lies between two
two distinct
distinct terrains.
terrains. The area to
to the
the
northwest is
is dominated by rocks
rocks of
of the
the anorthosite
anorthosite and
and felsic
felsic series
series while
while
the
area to
southeast contains flow units of the
the area
to the
the southeast
the North
North Shore
Shore Volcanic
Volcanic
Group.
The general orientation of igneous
igneous laminations
laminations (N6OE,
(N60E, 15SE)
lSSE) within
within the
the
troctolite—olivine gabbro
gabbro series
troctolite-olivine
series is interpreted to
to be
be the
the result
result of
of gravity
gravity
settling, suggesting that
that the
the unit has
has tilted
tilted approximately
approximately 15
IS degrees
degrees toward
toward
settling,
the southeast since solidification. The general strike of
the
of the
the troctolite
troctolite
unit is parallel to
to a well defined
defined lineament
lineament which
which occurs
occurs along
along the
the northnorthwestern contact
contact of
of the
the unit.
unit.
Textures
Textures of
of the troctolitic
troctolitic and
and gabbroic
gabbroic rocks
rocks indicate
indicate that,
that, in
in general,
general,
plagioclase and olivine are
are cummulate,
cummulate, while pyroxenes
pyroxenes and
and oxides
oxides are
are interinterstitial.
stitial. Modal analyses show that rocks
rocks of troctolitic
troctolitic affinity
affinity (P1
(PI -— 70%;
Cpyx —- 10%; 01 —
- 16%) are
the northwest boundary (base?)
(base?)
are abundant
abundant along the
is the
the most abundant
while olivine gabbro (P1
(PI —- 68%; Cpyx —- 22%; 01 —- 8%) is
lithology along
along the
the southeastern
southeastern contact
contact (top?).
(top?). Interstitial ilmenite is
is
the major
major oxide
oxide component and occurs as 1—1.5%
the
1-1.5% of the
the rock
rock unit.
unit.
Electron microscope analyses of
of plagioclase,
plagioclase, olivine,
olivine, and
and pyroxene
pyroxene
mineral grains from rocks of the troctolite series vary
vary nearly continuously
and systematically in
in composition
composition upward
upward through
through the
the column.
column. These compositional variations are:
are: An77 to
to An58
AnS8 (plag),
(plaf,), Fo70
Fo 70 to
to Fo50
FoSO (01),
(01), and
and
Wo41
En45
Fs14
to
Wo38
En36
Fs26
(Cpyx).
W0 4l En4S FS 1 4 to W038 En36 FS 26 (Cpyx).
the troctolite—olivine
troctolite-olivine gabbro
gabbro series
series as
as calculated
calculated
The bulk composition of the
from modal abundance data
data and
and individual
individual mineral
mineral compositions
compositions suggests
suggests that
that
the
could have been derived from aa magma with aa composition
composition identical
identical
the series
series could
to
that of
the chilled margin of the
the Pigeon Point
Point sill.
sill. The results of
of this
this
to that
of the
investigajion support the
investigation
the model proposed by Weiblen which indicates
indicates that
that units
units
the Duluth Complex
Complex (other
(other than
than the
the anorthosite
anorthosite and
and felsic
felsic series)
series) have
have
of the
been derived from
from aa late
late stage,
stage, high—Al
high-Al magma,
magma, the
the composition
composition of
of which
which is
is
compatable with the
the Pigeon
Pigeon Point
Point sill.
sill.
�—29—
-Z9-
GEOLOGY OF THE DULUTH COMPLEX-VIRGINIA FORMATION CONTACT
MINNAMAX DEPOSIT,
MINNAN.AX
DEPOSIT, MINNESOTA
MINNESOTA
William Matlack
Department of Geology
University of Minnesota-Duluth
Minnesota—Duluth
Duluth, Minnesota 55812
Duluth,
5581Z
Deposit, near Babbitt,
Babbitt, Minnesota, is
is aa large,
large, low—
lowThe Minnarnax
Minnamax Deposit,
sulfides at
at the
of the
grade deposit
deposit of
of iron—copper—nickel
iron-capper-nickel sulfides
the contact
contact of
the
and the
the Virginia Formation.
Formation. Mineralization is
is primarily
Duluth Complex and
disseminated
disseminated in
in troctolitic
troctolitic rocks
rocks of
of the
the Duluth
Duluth Complex,
Complex, and
and is
is locally
locally
massive at the
the contact and in the immediately adjacent Virginia Formation.
tion.
°
In
In the
the Minnamax test shaft area,
area, the
the contact
contact dips
dips 0 to
to 35
35 degrees
degrees
is highly irregular.
irregular. Apophyses
Apophyses of the
the Duluth Complex intrude
SE and is
the
Formation and
and xenoliths
xenoliths of
of the
the Virginia
Virginia Forrna—
Formathe underlying Virginia Formation
tion,
feet in dimension,
dimension, occur
occur in
in the
the complex.
complex.
tion, ranging
ranging upwards
upwards of
of 150 feet
primarily of
of argillic
argillic hornfels
hornfels with
with
The Virginia Formation consists
consists primarily
calc-silicate concretions.
concretions. Minor lithologies include
include graphite
abundant calc—silicate
Bedding,
schist,
schist, and calcareous argillic
argillic hornfels.
hornfels. Bedding,
schist, biotite schist,
where visible,
for a
a few feet
feet and
is locally
locally conconvisible, can only be traced for
and is
torted;
concretions appear randomly oriented.
oriented. Metadiabase dikes
dikes and
and
torted; concretions
sills, metamorphosed
metamorphosed by
by the
the Duluth
Duluth Complex,
Complex, occur
occur in
in the
the Virginia
Virginia
sills,
Formation.
The Duluth Complex consists primarily of a mineralized
phase which is characteristically troctolitic.
troctolitic. Near the
the contact
contact it
it is
is
commonly noritic. Here it contains cumulus
cumulus plagioclase and intercumulus
hypersthene, olivine,
olivine, and
and augite,
augite, and
and is
is highly
highly variable
variable in
in composition,
composition,
hypersthene,
texture,
Sulfides are primarily interstitial
texture, and sulfide
sulfirle content.
content. Sulfides
interstitial to
to
Xenoliths of
of an
an unmineralized
unmineralized phase,
phase, ranging
ranging upwards
upwards of
of 100
100
silicates. Xenoliths
feet in dimension,
dimension, occur in
in the
the mineralized
mineralized phase.
phase. These xenoliths
feet
range
from olivine
olivine gabbro
gabbro to
feldspathic peridotite,
peridotite, and
and
range in composition
composition from
to feldspathic
Fractures
and
cumulus olivine
olivine and
and plagioclase.
plagioclase.
are characterized by cumulus
breccia zones,
zones, both in
in the
the Virginia
Virginia Formation
Formation and
and the
the Duluth
Duluth Complex,
Complex,
commonly contain
ides and
and granitic
granitic veins
veins and veinlets.
contain massive
massive sulf
sulfides
Sulf
ides locally
locally replace
replace hornfels,
hornfels, particularly
particularly at
at the Duluth Complex
Sulfides
Complex
contact.
Field
relationships and
and petrography
petrograhy indicate
Field relationships
indicate that
that the
the Virginia
Virginia
and metamorphosed
to pyroxene hornfels
Formation was
was highly
highly deformed
deformed and
metamorphosed to
hornfels
facies
facies by the
the Duluth
Duluth Complex.
Complex. The common
cornmon pelitic mineral assemblage
assemblage of
of
plagioclase—hypersthene—cordierite
plagioclase-hypersthene-cordierite suggests
suggests substantial
substantial loss
loss of
of Si02,
SiOZ,
Na20,
from the
the Virginia
Virginia Formation
Formation (Bonnichsen,
NaZO, K20,
KZO, and
and 1120
HZO from
(Bonnichsen, 1971).
1971). These
constituents
constituents contaminated
contaminated the
the base
base of
of the
the mineralized
mineralized phase
phase of
of the
the comcomplex.
formed from a residual fluid of
Granitic vein material may have formed
the
the mineralized
mineralized phase,
phase, or
or by
by direct
direct partial
partial melting
melting of
of the
the Virginia
Virginia
Formation.
of unmineralized metadiabase dikes and sills in
Recognition of
the Virginia Formation explains many complexities
complexities in
in the
the petrology,
petrology,
the
structure,
of the
the contact
contact zone.
zone. Massive sulfides
sulfides
structure, and mineralization of
appear to
to have formed
formed by:
by: 1)
1) migration of a sulfide—rich
sulfide-rich fluid into
into
and along fractures,
and
fractures, and
and 2)
Z) local
the Virginia Formation.
Formation.
local replacement of the
�-30MINERAL SURVEY
MINERAL
SURVEY AND MINERAL POTENTIAL
OF COOK COUNTY,
COUNTY, MINNESOTA
M.P.
and D.G.
M.P. McKenna,
McKenna, L.W.
L.W. Gladen,
Gladen, M.K.
M.K. Vadis,
Vadis, and
D.G. Meineke
Resources, Division
Division of
of Minerals
Minerals
Department of Natural Resources,
P.O.
567
P.O. Box 567
Hibbing,
55746
Hibbing, Minnesota 55746
ABSTRACT
ABSTRACT
This
This study was
was conducted to
to obtain and compile information on
on the
the
mineral potential
potential of
of Cook
Cook County,
County, Minnesota.
Minnesota. This
This information will be used
to
the Minnesota Department of Natural Resources
Resources (MDNR)
(MDNR) in
in making
making
to assist
assist the
decisions in
in relation to
to mineral
lands it
land management
management decisions
mineral lands
it administers
administers and
and
to
to provide
provide information which may lead to
to further
further leasing
leasing and
and exploration
exploration of
of
MDNR administered
administered lands.
lands.
The study included
included various
various informatfon
information gathering
gathering activities.
activities. Initially,
aa literature survey was conducted to
to determine
determine the
the existence
existence and
and location
location of
of
reported economic mineral occurrences. This was followed by
reported
by aa field
field examinexamination, during
during which
which outcrop
outcrop samples
samples were
were collected
collected for
for assay
assay and
and microscopic
microscopic
ation,
study
study in
in order
order to
to determine
determine the
the nature
nature and
and extent
extent of
of mineralization
mineralization and
and the
the
host rock
rock geology.
geology. A
A compendium was prepared on past mineral exploration
activity in
in Cook
Cook County;
County; it
it includes
includes available
available drill
drill logs
logs and
and assays,
assays, geologic,
geologic,
geophysical, and geochemical
In some
some cases,
cases, where drill logs and assays
geophysical,
geochemical data.
data. In
were not available, the
the cores
cores were
were logged
logged and
and assayed.
assayed. An organic'-rich
organic--rich lake
sediment e~~loration
exploration geochemical reconnaissance
sediment
reconnaissance survey
survey was
was conducted
conducted concurconcurthe field
field examination
examination of
of mineral
mineral occurrences.
occurrences.
rently with the
A report
will contain all
derived
A
report is
is in preparation which will
all information derived
from this study.
study. It
It also describes the
the various models
models which
which were
were used
used in
in
models are
are based
based on
the mineral potential
potential of
of the
the area.
area. These models
determining the
economic
mineral occurrences
occurrences found
Minnesota and
and in similar
environ—
economic mineral
found in Minnesota
similar geologic
geologic environments in other parts of
ments
of the
the world.
Results
Results of
of this
this study indicate
indicate that
that significant
significant vanadium concentrations
concentrations
exist in titaniferous magnetlte
magnetite deposits
deposits occurring
occurring within
within the
the Duluth
Duluth Complex.
Complex.
Disseminated low grade
grade Cu-Ni
in the
the more
Cu—Ni mineralization also
also occurs
occurs in
more mafic
mafic
units of the
the Duluth
Duluth Complex.
Complex. Ag—Cu—Zn
Ag-Cu-Zn fissure—vein
fissure-vein mineralization occurs in
the Rove Formation where the
the Rove
Rove is
is intruded
intruded by
by Logan
Logan sills.
sills. The lake
lake sedisedithe
ment geochemical
geochemical survey
survey indicates
indicates anomalous values in
in certain areas which have
potential for
for economic
economic mineralization.
mineralization.
survey did
did not
not include
include the
the Boundary
Boundary Waters
Waters Canoe
Canoe Area
Area (BWCA);
(BWCA);
This survey
however,
however, some
some of the
the highest mineral potential areas in Cook County were
added
added to
to the BWCA after the
the field
field surveys
surveys were
were completed.
completed.
�—31—
-31-
PALEOSTRAIN ANALYSIS ACROSS AA "SHEAR
"SHEAR ZONE",
ZONE",
NORTHWESTERN MARATHON COUNTY,
COUNTY, WISCONSIN
Elizabeth Palmer
Department of Geology
University of Minnesota
Duluth, Minnesota
Duluth~
and
N. Davidson, Jr.
Donald M.
Jr.
Department of
of Geological
Geological Sciences
Sciences
University of
of Texas
Texas
El Paso,
Paso, Texas
Texas
ABS
TRACT
ABSTRACT
The boundary between
two major
trending Precambrian
terranes
between two
major northeast
northeast trending
Precambrian terranes
(superbelts?) is
is structurally
structurally concordant
concordant with geological units which
(superbelts?)
which trend
trend
approximately 750
approximately
75 0 through Athens,
Athens, Wisconsin
vTisconsin in
in northwestern
northwestern Marathon
Marathon County.
County.
This
0.75 to
width, generally,
generally, though
not
This belt or "shear"
"shear" zone,
zone, 0.75
to 4 km in width,
though not
uniquely,
gneissic amphibolites
amphibolites of
of the
uniquely, separates
separates gneissic
the Chippewa Amphibolite ComCom(Archean?) to
to the north
from volcano-plutonic
(greenstone-granite
plex (Archean?)
north from
volcano—plutonic (greenstone—granite
units (PG
(P8 x?) on
on the
the south.
south.
Foliations within the host
host rock strike 50_700
50-70 0 and dip
dip 50—75°
50-75 0 N
N while
0
0
lineations trend
trend 230_2500,
230-250 , and
and plunge
plunge 65—75°.
65-75 . The zone itself has gradational
gradational
boundaries and is
is composed of
of cataclasized equivalent greenstone and amphibo—
amphibolite
units showing
showing mortar
mortar texture,
texture, feldspathic
feldspathic porphyroclasts,
porphyroclasts, comminution
comminution
lite units
and
structure, and varying degrees
degrees of
of recrystallization.
recrystallization. Discrete
and fluxion
fluxion structure,
fault
fault planes have also been recognized
recognized within
within the
the zone.
zone.
Paleostrain
Paleostrain analysis
analysis was
was carried
carried out
out on
on samples
samples from
from each
each host
host unit
unit at
at
distances up
up to
km from
from the
the shear
shear zone
zone as
as well
well as
as on
on samples
samples located
located
distances
to 99 km
within the
the zone
zone itself.
itself. At least 50 strain indicators,
indicators, usually deformed
fragments, were measured from 3 sets of orthogonal
mineral grains or volcanic fragments,
faces
cut on
to the
the principal
faces cut
on each
each sample
sample as
as well
well as
as the
the angle
angle relative
relative to
principal
directions
directions (foliation,
(foliation, lineation
lineation and
and right
right angles
angles to
to both)
both) in
in the
the rock
parallel to
to which cuts
cuts were
were made.
made. Strain was
the methods of
of
was analyzed using the
Ramsay (Rf/Q),
Ramsay
(Rf/8), Elliott's polar
polar plot
plot and
and the
the Hsu
Hsu plot.
plot. A
fit strain
A best
best fit
for each
each sample
sample using
using the
the Pase
Pase 55 program
program of
of Siddans.
Siddans.
ellipsoid was
was calculated for
Error
the best
Error limits
limits on
on the
the dimension
dimension and
and orientation
orientation of
of the
best fit
fit strain ellipsoid
and its
its orientation
orientation were
were calculated
calculated at
at less
less than
percent for
for each
each
soid and
than 2 percent
sample.
Results
indicate that
that both
the gneiss
Results indicate
both the
gneiss and
and volcano-plutonic
volcano—plutonic regimes
regimes are
characterized by
fabric (V=+O.16,
(V=+0.16, 0.19,
characterized
by aa flattened
flattened fabric
0.19, 0.3;
0.3; K=0.4)
K=O.4) with
with
generally low strain values (G5=O.75,
(8 s =0.75, 1.29,
1.29, 0.5).
0.5). As the
the shear
shear zone
zone is
is
approached,
(V=-0.5; K=2.4)
is
approached, aa strong
strong linear
linear fabric
fabric (V=—O.5;
K=2.4) is
is developed
developed which is
generally one order of magnitude greater
greater in
in €s value than
than is
is flattening
flattening in
in
the host
host rocks.
the
rocks. This
This linear
linear fabric
fabric cannot
cannot have
have developed
developed from simple shear
alone.
alorre. The
lineation appears
to have
as aa result
The lineation
appears to
have developed
developed as
result of
of ductile
deformation
along the
the
deformation which,
which, though
though regional
regional in
in scope,
scope, appears
appears localized
localized along
zone.
zone. A
consistent with the strain
A strong
strong vertical
vertical stress
stress component
component appears
appears consistent
pattern.
�—32—
-32-
POLYPHASE DEFORMATION
DEFORMATION OF
OF ARCHEAN
ARCHEAN ROCKS
ROCKS
POLYPHASE
AT
AT RAINY
RAINY LAKE,
LAKE, ONTARIO
ONTARIO
K.
K. Howard
Howard Poulsen
Department of Geology
Geology
Lakehead University
Thunder Bay,
Bay, Ontario
ABSTRACT
The Archean geology
geology of
of the
the Rainy
Rainy Lake
Lake area
area has
has been
been the
the subject
subject of
of
considerable study
study for
considerable
for nearly a
a century.
century. A.C.
A.C. Lawson
Lawson mapped
mapped the
the region
region
(1888, 1913)
1913) and
and interpreted the
(1888,
the stratigraphy.
stratigraphy. He placed aa sequence
sequence of
of
metasedimentary
metasedimentary biotite schists
schists (the
(the Coutchiching Group)
Group) beneath
beneath aa sequence
sequence
He further
of metavolcanic schists
schists (the
(the Keewatin
Keewatin Group).
Group). He
further recognized a
second sequence of
metasedimentary rocks (the
of largely
largely congloineratic
conglomeratic metasedimentary
(the Seine
Seine
Group) which he placed unconformably above
Group)
above the
the Keewatin.
Keewatin. Various workers
re-studied the
the area applying the
the techniques
techniques of a
a number of geological
have re—studied
subdisciplines.
Some
of the
the Coutchiching
Coutchiching Group
Group
Some have
have disputed the existence of
and have placed it above the
and
the Keewatin as
as aa lateral
lateral equivalant
equivalant of
of the
the Seine
Seine
Group.
Others have
have upheld
upheld Lawson's
Lawson's original
original interpretation
interpretation and
and the
the conconOthers
flicting points
the Seine-·Coutchiching
flicting
points of
of view
view have
have become
become referred
referred to
to as
as the
Seine-Coutchiching
problem.
proble~.
present study re—examines
re-examines the
the significance of the Keewatin—
KeewatinThe present
boundary in
in light
light of
of detailed
detailed structural
structural investigation
investigation of
of two
two
Coutchiching boundary
type localities.
At Rice Bay,
and geometric
analysis of
of fabric
At
Bay, lithological mapping and
geometric analysis
fabric
reveals the
the presence
presence of
of aa major
major antiform
antiform with
with moderate
moderate plunge.
plunge.
elements reveals
Observed younging information (graded
(graded bedding and
and pillow shapes)
shapes) does
does not
not
to this
this simple
simple interpretation
interpretation and
and part
part of
of the
the sequence
sequence is
is recognized
recognized
conform to
as having a downward structural
structural facing
facing with
with respect
respect to
to the
the major
major fold
fold closure.
closu~e.
This implies that
that the
the sequence
sequence was
was overturned
overturned by
by an
an episode
episode of
of folding
folding (F1)
(F l )
predated the
the development
development of
of the
the major
major closure
closure (F2).
(F 2 ).
which predated
At Bear Passage,
Passage, structural
structural elements
elements similar
similar to
at Rice
Rice Bay
Bay are
are
At
to those
those at
Fold axes
axes (F2)
axial surfaces
surfaces (S2)
no longer
have systematic
systematic
exposed.
(F2) and
and axial
(S2) no
longer have
orientations, however,
however, and
and appear
appear to
be complexly
due to
orientations,
to be
complexly redistributed
redistributed due
to the
the
intrusion of a quartz monzonite pluton.
The crest of this pluton conforms
pluton. The
conforms to
to
a
a broadly antiformal
antiformal structure
structure (F3).
(F 3 ). The rocks
rocks of
of the
the Bear
Bear Passage
Passage area
area are
are
transected by
by aa penetrative crenulation cleavage S4
transected
S4 which
which is
is axial
axial planar
planar to
to
minor folds
folds (F4).
(F4). While simple stratigraphic interpretations
interpretations are precluded
precluded
by this
this polyphase deformation,
deformation, a
a key exposure at
at the
the Keewatin—Coutchiching
Keewatin-Coutchiching
contact reveals the
contact
the presence of
of structurally
structurally overturned
overturned strata.
strata. These strata
appear to
appear
to have a
a downward structural
structural facing
facing with
with respect
respect to
to each
each of
of the
the
observed fold
observed
fold phases and hence overturning
overturning is
is assigned
assigned to
to F1.
Fl.
The documentation of polyphase deformation
The
deformation in
in the
the Rainy
Rainy Lake
Lake area
area makes
makes
clear the
clear
the reason for
for previous conflicting
conflicting stratigraphic
stratigraphic interpretations.
interpretations. The
of structurally overturned strata
recognition of
strata favours
favours the
the stratigraphic
stratigraphic supersuper"
Fold nappes (F1)
position of the
the Coutchiching
Coutchiching upon
upon the
the Keewatin.
Keewatin.
(FI) may have
responsible for
for inverting
inverting part
part of
of the
the sequence.
sequence. It
It is not clear
clear whether
whether
been responsible
this
and subsequent deformations were unique
this and
unique events
events or
or merely
merely progressive
progressive
episodes in
in a
a continuous
continuous sequence
sequence of
of deformation.
deformation.
�—33
-33-
THE PRECAMBRIAN
PRECf~BRIAN BASEMENT OF NORTH DAKOTA
John T.
T. Ray
Ray and
John
and Frank R.
R. Karner
North Dakota Geological
Geological Survey
Survey and
and
University of North Dakota
Grand
Grand Forks,
Forks, North Dakota
Dakota 58202
58202
ABSTRACT
Information on
on the
Information
the Precambrian basement of
of North
North Dakota
Dakota is
is based
based on
on
cores and
and cuttings
cuttings from 132 drilling tests
cores
tests (Lidiak,
(Lidiak, unpublished;
unpublished; Muehiberger
Muehlberger
and
others, 1967;
Moore, unpublished),
unpublished), 11 age
age determinations
determinations (Peterman
and
and ethers,
1967; Moore,
(Peterman and
Hedge,
data and
and correlation
correlation with
with surrounding areas
areas of
of
Hedge, 1964),
1964), geophysical
geophysical data
exposure.
The North
North Dakota
Dakota Precambrian
Precambrian consists
consists of
of several
several types
of Archean
Archean
The
types of
Superior Province
Province and
and possibly younger terranes
Superior
terranes in
in the
the east,
east, often
often with
with deep
deep
profiles, and
and much
much less
less well
well known
known terranes
in the
west, including
weathering profiles,
terranes in
the west,
younger rocks,
rocks, possibly aa southern
southern extension
extension of
of the
the Churchill
Churchill Province.
Province. The
Williston basin,
basin, centered
centered in
northwestern ~orth
North Dakota,
Dakota, is
is the
dominant strucstrucWilliston
in northwestern
the dominant
tural
that determines
the depth to
to the
the Precambrian.
Precambrian. From aa depth of
tural feature
feature that
determines the
approximately
200 m
the Precambrian
approximately 200
m in
in eastern
eastern North
North Dakota,
Dakota, the
Precambrian surface
surface slopes
slopes
The distribution of
3 rn/kin
m/km totoa adepth
of radiometric
radiometric age
age
S
depthof
of 5100
5100 m
m in
in the west.
dates and
dates
and a pronounced break in
in the
the trend
trend of
of geophysical
geophysical features
features suggests
suggests
that the
the Superior/Churchill
Superior/Churchill Provincial boundary transects
that
transects central
central North
North
Dakota.
The Precambrian
Precambrian basement
basement of
of east2rn
eastern North
North Dakota
Dakota has
has been
been divided
divided into
into
The
five terranes
terranes based
based on
on predominant
predominant petrographic character
five
character and
and r2gional
regional gravity
gravity
features
(Lidiak, unpublished). Amphibole
Amphibole schist
schist terrane is characterized by
features (Lidiak,
belts of
belts
of low and medium grade
grade metamorphic rocks
rocks with
with associated
associated gravity
gravity highs.
highs.
The predominant
predominant rock
rock types
types are
arc actinolite
actinolite and
and hornblende
hornblende schists
schists with
with occuroccurThe
rences
rences of
of retrogressive quartz—biotite—feldspar
quartz-biotitc-feldspar gneiss,
gneiss, serpentinite,
serpentinite, stretched
stretched
lithic lapilli tuff,
lithic
tuff, massive and porphyritic
porphyritic basalt
basalt and
and banded
banded iron
iron iron
iron formaformaThe Ramsey
Ramsey gneiss
tion. The
gneiss tërrane
terrane consists of
of silicic
silicic to
to intermediate
intermediate rocks
rocks
with aa persistent
The characteristic lithology
persistent gneissic
gneissic fabric.
fabric. The
lithology is
is layered
layered
gneiss metamorphosed
metamorphosed to amphibolite facies
gneiss
facies and
and fine—
fine- to
to medium—grained
medium-grained gneiss
gneiss
with subordinate foliated
foliated plutonic
plutonic rocks.
rocks. The
three terranes
terranes are
are
The remaining three
characterized by silicic
silicic to
to intermediate
intermediate massive
massive plutonic
plutonic rocks
rocks with
with associated
associated
gravity
gradient and are
are distinguished by
by location.
location. The Grand
Grand
gravity lows
lOWS of
of gentle gradient
terrane (east—central),
(east-central), McIntosh
~1cIntosh granite
granite terranc
terrane (southeast),
(southeast),
Forks plutonic terrane
and Towner
terrane (north—central)
(north~central) all
and
Towner granite
granite terrane
all contain
contain occurrences
occurrences of
of amphiamphi—
bolite facies
faci2s gneiss.
gneiss. The generalized pattern of large
l3rgc plutonic
plutonic areas
ureas within
gneissic terranes
terranes and intervening
intervening greenstone
greenstone belts
belts is
is consistent
consistent with
with the
the
gneissic
exposed
2XpOSeG Archean rocks
rocks to
to the
the northeast.
northeost.
~ew information
infor~ation on the Precambrian of eastern North Dakota
Dakota was
New
was added
added by
the
Red River
River Valley
Valley drilling
drilling program
program of
of 1977
1977 (Moore,
(Moore, unpublished)
unpublished) which
which propro
the Red
vided 26
26 cores.
ceres. Preliminary petrographic results
results suggest
suggest that
that the
the concept
concept
of the
amphibole schist
schist terrane
terrane be
be ret&ined
retained and
and the
the distinction
distinction of
of the
the remainremainof
the amphibole
ing tcrranes
on the
ing
terranes on
the basis of rock fabric
fabric ha
b2 abandoned.
abandoned. Amphibole schist
schist
tcrrane
terrane is
is characterized
charactGrized by
ty low
low to
to medium
mediu~ grade
grade metasedimentary
~et3sedimentaryand
and tnetavolcanic
metavolcanic
rocks
sever. cores which included
included the
the following
following rock
rock types;
types;
rocks and
and was
was penetrated
penetrated by seven
pillowed basalt,
basalt, porphyritic
porphyritic basalt,
basalt, stretched
stretched lithic
lithic lapilli
l&pilli tuff,
tuff, mica
mica schist,
schist,
talc-chlorite schist,
(with graded
graded beds),
beds), and
and meta—graywacke.
meta-graywacke. The
talc—chlorite
schist, phyllite (with
remaining cores
cores pen2trated
penetrated fine—
re~aining
fine- to
to coarse—grained
coarse-grained igneous
igneous rocks,
rcck8, gneiss,
gneiss, and
and
�—34—
-34-
banded gneiss.
gneiss. The intcrpretation
interpretation of the
the dominant igneous
igneous character of
banded
the Grand
Grand Forks
Forks plutonic
plutonic terrane
terrane is
is revised
revised by the
occurrence of
of rocks
the
the occurrence
rocks
with aa gneissic-migmatitic
gneissic-migmatitic fabric
fabric in
in six
six of
of seven
seven cores.
cores. Accordingly,
the distinction of the
the remaining terranes
terranes by predominant fabric
fabric may be
misleading and will be
be eliminated.
eliminated. Subdivision of these
these gneissic
gneissic and
and
the basis of rock
rock chemistry and
plutonic terranes is being attempted on the
petrographic character.
character.
Lidiak,
E. G.,
G., Buried Precambrian Rocks of North Dakota:
Dakota: unpublished
Lidiak, E.
manuscript.
Moore, W.
W. L., 1978, AA Preliminary
Preliminary Report
Report on
on the
the Geology
Geology of
of the
the Red
Red River
River
Valley Drilling Project,
Project, Eastern North Dakota and Northwestern
Minnesota: unpublished manuscript.
manuscript.
Muehlbergcr,
Muehlberger, W.
W. R.,
R., R.
R. E.
E. Denison,
Denison, E.
E. G.
G. Lidiak,
Lidiak, 1967,
1967, Basement Rocks in
in
Interior of
of United
United States:
States: AAPG Bull. v. 51,
51, no.
no. 12,
12,
Continental Interior
p.
2351-2380.
p. 2351—2380.
Peterman, Z.
Peterman,
Z. E.,
E., and
and C.
C. E.
E. Hedge,
Hedge, 1964,
1964, Age of Basement Rocks from the
the
Basin of
of North
North Dakota
Dakota and
and Adjacent
Adjacent Areas:
Areas: USGS Prof.
Prof.
Williston Basin
Paper, 475—D,
Paper,
475-D, p.
p. Dl00—D104.
DlOO-Dl04.
�—.
-I —
-35-
PINK AND GREEN ALBITE PHENOCRYSTS FROM THE MOHAWK
MINE,
- INDICATORS OF CHANGES IN
IN HYDROTHERMAL
HYDROTHERMAL FLUIDS
FLUIDS
MINE, MICHIGAN -
Nancy Scofield
Institute of
Institute
of Mineral Research and
and
Department of Geology and
and
Geological Engineering
Michigan Technological University
Houghton,
Houghton, Michigan 49931
49931
B. Jorgenson
David B.
Department of
of Geology
Geology
Central Michigan University
Mount Pleasant,
Pleasant, Michigan 48859
ABSTRACT
Albite phenocrysts
phenocrysts with
with green
green rims
and pink interiors
Albite
rims and
interiors are
are present in
samples
of altered
altered basalt
basalt taken
from the
and known to be presamples of
taken from
the Mohawk mine and
In the
#3 and
and #4
#4 mines.
mines. In
the collected samples,
samples, phenocrysts are
sent in Ahmeek #3
5-20 rom
long and
and 1—10
1-10 mm
mm wide.
wide. Some
the smaller phenocrysts are green
5—20
mm long
Some of
of the
only.
Microscopically, the
green portion consists
Microscopically,
the green
consists primarily of
of pumpellyite
with some white to
to light
light green
green remnant
remnant albite.
albite. Some of the
the pumpellyite
pumpellyite
extends into
into the
the pink
pink interiors
interiors which
which are
are predominantly
predominantly albite
albite with
with an
an
extends
abundance of
of sericite as an alteration product.
abundance
product. Under high power,
power, small
amounts of
of red
red iron
iron oxide
oxide are
are apparent
apparent in
in the
the phenocryst
phenocryst interior,
interior, appearappearamounts
ing as
as clouds
clouds or clots of dust—like
ing
dust-like particles.
particles. Albite twin lamellae
lamellae are
are
continuous through
through the
the green
green and
and pink
pink portions
portions of
of the
the phenocrysts
phenocrysts although
continuous
masked by alteration in
in the
the pink
pink portion.
portion. Flat stage extinction angle
measurements on albite
albite twins
twins suggest
suggest a composition of about An5.
AnS.
X—ray
X-ray diffraction analysis
analysis of the phenocrysts verifies the
the mixture of
of
albite and
and pumpellyite
pumpellyite in
in the
the green
green rims,
rims, with
with albite
albite showing
showing up
up as
as the only
albite
Structural differences
differences between
between the pink and
phase of
of the
the pink
pink interiors.
interiors. Structural
green albite were not
not detected.
detected.
Electron microprobe
microprobe analyses
analyses show pumpellyite compositions
Electron
compositions in green and
pink portions
portions to
to be identical
identical with total
total iron,
iron, calculated
calculated as
as FeO,
FeO, about
about 5%.
5%.
in major element
element compocompoAlbite compositions are near AnO with no difference in
sition between
the exception of
of a range of K
K
between pink
pink and
and green
green albite
albite with
with the
(0—3%
in pink albite.
(0-3% 1(20)
K20) in
albite. The
suggests its
its presence in
The distribution
distribution of
of K
K suggests
alternation products.
products. Measurement of minor Mg and Fe concentrations
concentrations in
in
albite revealed that
that incipient
incipient pumpellyitization
pumpe11yitization is
is common.
common. But only pink
pink
albite showed
showed minor
minor Fe
Fe (up
0.7% Fe203)
Fe203) unaccompanied by Mg,
Mg, consistent
albite
(up to
to 0.7%
with the
the red
red iron oxide microscopically observed as
as aa possible
possible source
source of
of the
the
pink coloring.
coloring.
Because
cross-cuts albite,
to be
Because pumpellyite
pumpellyite cross—cuts
albite, pumpellyite is assumed to
paragenetically
paragenetica11y later
later than
than albite.
albite. The
of sericite suggests
The distribution of
control by the original calcic
calcic interior
interior of
of plagioclase.
plagioclase. But whether
sericitization preceded
preceded or
contemporaneous with albitization is
is unclear.
unclear.
sericitization
or was
was contemporaneous
At
least two
two stages
fluids of
of different comAt least
stages of
of alteration
alteration by
by hydrothermal
hydrothermal fluids
comare inferred.
inferred.
position and/or conditions are
�—36—
-36-
AREA, ONTARIO
STRATIGRAPHY OF THE GUNFLINT FORMATION,
FORMATION, KAKABEKA FALLS AREA,
J. Shegeiski
R. J.
Shegelski
Lakehead University
Thunder Bay,
Bay, Ontario
ABSTRACT
total of
ten stratigraphic
stratigraphic sections
sections of
the Gunflint
For.mation
A total
of ten
of the
Gunflint Formation
have been measured
measured over a
distance of
a lateral distance
of 3.6
3.6 kilometers
kilometers in the
the
From the
m
Kaministikwia River
River gorge.
gorge.
the study,
study, a
a composite section 57
57 m
Kaministikwia
thick was
was found
found to
to contain six distinct
distinct lithostratigraphic
lithostratigraphic members.
members.
These members
members are,
These
are, in ascending order:
order: 1.
(3 meters)
1. basal
basal member (3
composed of
of conglomerate,
composed
conglomerate, quartzite,
quartzite, stromatolites,
stromatolites, taconite
taconite or
or pyritic,
pyritic,
black chert—carbonate;
meters) composed of
chert-carbonate; 2.
2. lower shale member (7
(7 meters)
of
fissile carbonaceous shale;
fissile
shale; 3.
3. lapilli
lapilli member
member (4
(4 meters)
meters) composed
composed of
of
felsic quartz—feldspar
felsic
quartz-feldspar lapilli—tuffs;
lapilli-tuffs; 4.
4. middle
middle shale
shale member
member (22
(22 meters)
meters)
composed of
of fissile
fissile carbonaceous
carbonaceous shale;
shale; 5.
5. chert-carbonate
chert—carbonate member
member (11
composed
(11
meters)
meters) composed
composed of
of alternating
alternating layers
layers and
and lenses
lenses of
of chert
chert and
and siderite;
siderite;
6.
(at least
least 10
10 meters; top
top not
not exposed)
exposed) composed
composed of
of
6. upper shale member (at
fissile carbonaceous shale.
shale. The composite section
section therefore
therefore contains
contains
70% fissile
70%
fissile carbonaceous shale, 20%
20% chert—carbonate,
chert-carbonate, 7%
7% lapilli—tuff
lapilli-tuff
and
3% diverse lithologies of
of the
the basal
basal member.
member.
and 3%
Primary
in the
the various
Primary sedimentary
sedimentary structures
structures are
are well
well preserved
preserved in
various
strata. Well rounded,
rounded, well sorted
sorted sand
sand grains
grains in
in the
the basal
basal quartzites,
quartzites,
in association with taconites
taconites and
and stromatolite
stromatolite mounds
mounds suggest
suggest aa shallow,
shallow,
littoral environment.
environment. The presence
presence of
of accretionary
accretionary mudball
mudball lapilli,
lapilli,
graded ash-fall
ash—fall tuffs
and large
large scale
scale crossbedding
crossbedding in
in the
lapilli—tuffs
graded
tuffs and
the lapilli-tuffs
indicate subaerial derivation and
and shallow
shallow water
water reworking
reworking and
and deposition.
deposition.
Dessication
Dessication features
features and
and soft
soft sediment
sediment slumpage
slumpage and
and brecciation
brecciation occur
occur
within chert
chert carbonate
carbonate layers
layers and
and lenses.
lenses.
The
The lenticular geometry of
of
chert
chert carbonate beds as well as
as their
their intimate
intimate interlayered
interlayered relationrelationships with
with ripple-marked,
ripple—marked, and
and mud-cracked
mud—cracked carbonaceous
carbonaceous shales
shales suggest
suggest aa
ships
The entire strati—
shallow water origin for
for both
both of
of these
these lithologies.
lithologies.
The
stratigraphic
is therefore
therefore considered
to have
in aa
graphic section
section is
considered to
have been
been deposited
deposited in
shallow water environment
environment at
at the
the margin
margin of
of aa large
large restricted
restricted basin.
basin.
�—37.-37-
NEW EVIDENCE ON THE STRATICRA2HY
STRATIGRAPHY AND
AND STRUCTURE
STRUCTURE OF
OF THE SOUDAN AREA,
AREA,
WESTERN VERMILION
MINNESOTA
VEmlILION DISTRICT,
DISTRICT, MI~mESOTA
P.
P. K.
K. Sims
Sims
U.S. Geological Survey
U.S.
Survey
Denver, Colorado 80225
80225
Denver,
and
D.
D. L.
L. Southwick
Minnesota Geological Survey
Survey
St.
St. Paul,
Paul, Minnesota
~innesota 55108
55108
ABSTRACT
southeast of
of Soudan,
Soudan, Minnesota at scale
Recent geologic mapping southeast
1:24,000 has
has further
further clarified
clarified the
the stratigraphy
stratigraphy and
and structure
structure of
of the
1:24,000
the
western Vermilion
Vermilion district.
district. Numerous top—indicators
top-indicators confirm the
the major
structure
the area
to be
structure of
of the
area to
be aa broad,
broad, steep-limbed,
steep—limbed, southward-overturned
southward—overturned
anticlinorium,
the axial trace
trace of
of which trends
trends about
about N.70°
N.70 o W.
W. The core
core
anticlinorium, the
of the
anticlinorium is
is metabasalt
metabasalt belonging
belonging to
of the
of
the anticlinorium
to the
the lower member of
the
Ely Greenstone. On the
the upright north limb of the fold,
fold, the
the stratigraphic
succession
succession above
above the
the lower
lower member
member is
is as
as follows:
follows: Soudan
Soudan Iron—formation
Iron-formation
Member of Ely Greenstone,
Greenstone, upper member of Ely Greenstone,
Greenstone, and
and Lake Vermilion
Formation. Although the
the Soudan Member is
is characterized
characterized by the
the presence of
of
cherty iron—formation,
stratigraphy is
iron-formation, its
its internal.
internal stratigraphy
is complex and
and more
more than
than
half of it is composed
half
composed of
of volcanic and
and volcaniclastic
volcaniclastic rocks.
rocks. Felsic volcanic and
and volcanogenic
rocks of
of the
the Lake
rest
volcanogenic sedimentary
sedimentary rocks
Lake Vermilion Formation rest
directly
Soudan Member in the
directly on the
the Soudan
the Soudan quadrangle,
quadrangle, but pinch out
out
toward the
east beneath a tongue
toward
the east
tongue of pillow
pillow breccia,
breccia, mafic
mafic aquagene
aquagene tuff,
tuff,
iron—formation, and
and pillowed
pillowed metabasalt
metabasalt belonging
belonging to
to the
the upper
upper member
member of
of the
the
iron-formation,
Ely Greenstone. The iron—formation
iron-formation at
at Jasper Peak is a lenticular body
member; it
within the
the lower Ely member;
it is
is stratigraphically beneath the Soudan
Iron—formation Member.
Iron-formation
The stratigraphy of
of the overturned south limb of the
the anticlinorium is
as
as follows:
follows: lower
lower member
member of
of Ely
Ely Greenstone,
Greenstone, member
member of
of Ely
Ely Greenstone
Greenstone near
near
Two Rivers,
Rivers, upper member of
of Ely
Ely Greenstone,
Greenstone, and
and Lake
Lake Vermilion
Vermilion Formation.
Formation.
The member near Two
Two Rivers
Rivers is
is aa heterogeneous
heterogeneous sequence
sequence of
of pillowed
pillowed basalt,
basalt,
tuff, felsic
felsic porphyry,
porphyry, felsic tuff,
tuff, and cherty iron—formation
iron-formation that
that
basalt tuff,
appears to
be slightly
slightly below the
stratigraphic position
position of
of the
appears
to be
the stratigraphic
the Soudan Iron—
Ironformation
connect with
with it.
it.
formation Member and does not connect
lower and upper members of the
the Ely Greenstone are distinct in
in terms
terms
The lower
of
of primary structures,
structures, textures,
textures, and
and bulk
bulk chemical
chemical compositions
compositions (Schulz,
(Schulz,
1977). The
lower member
the form
The lower
member consists
consists chiefly
chiefly of
of calc-alkaline
caic—alkaline basalt
basalt in the
of massive
massive and
and pillowed
pillowed flows;
flows; the
pillows typically
of
the pillows
typically are irregular
irregular in size
and
shape and
are highly
highly amygdaloida1,
amygdaloidal, indicating
and shape
and are
indicating deposition in shallow
water.
The
tholeiitic basalt
the form of
of pillowed
The upper
upper member
member is
is chiefly
chiefly tholeiitic
basalt in the
flows. The
The pillows
pillows are
are regular
regular in
in size
size and
and shape and
and are generally non—
nonamygdaloida1,
indicating deposition
deposition in
in deep
deep water.
water.
amygdaloidal, indicating
The stratigraphic
record clearly
clearly indicates
indicates a
a highly mobile vo1canostratigraphic record
volcano—
tectonic environment
that may
a smaller scale to
to the
tectonic
environment that
may have been
been analogous
analogous on a
modern volcanic arc
arc and
and back—arc
back-arc basin.
basin.
REFERENCE
Schulz, K.J.,
K.J., 1977,
Schulz,
1977, The petrology
petrology and
and geochemistry
geochemistry of
of Archean
Archean volcanics,
volcanics,
district, northeastern Minnesota:
Minnesota: Unpublished Ph.D.
Ph.D.
western Vermilion district,
Dissertation,
p.
Dissertation, University
University of
of Minnesota,
Minnesota, 349 p.
�-38—38—
GEOCHEMICAL AND GEOPHYSICAL ANOMALIES
ASSOCIATED WITH THE BEAR LAKE INTRUSIVE,
INTRUSIVE,
SECTIONS 24
24 AND
AND 25,
25, T56N,
T56N, R34W,
R34W, HOUGHTON COUNTY,
SECTIONS
COUNTY, MIGHIGAN
D.
D. W.
W. Snider and
and B.
B. K.
K. Parker
Michigan Geological Survey
Survey
Geology and Minerals Research
Research Unit
Unit
Lansing,
Lansing, Michigan
Michigan
ABSTRACT
The Bear Lake Intrusive
Intrusive is
is aa nearly circular
circular felsic
felsic igneous
igneous body
body
which appears to
to have intruded
intruded the
the Freda
Freda Sandstone.
SQndstone. The
The body is roughly
1.3 km
km in diameter and is
1.3
is located about 11.2 km (7
(7 miles)
miles) north
north of
of the
the
city of
of Hancock, Michigan.
Michigan.
The work at the
the Bear Lake body was part
part of
of aa larger
larger investigation
investigation
that
was designed to
that was
to test
test a
a model based upon the
the copper
copper sulfide
sulfide mineralimineralization at
at Mt.
Mt. Bohemia (Section
zation
(Section 29,
29, T58N,
T58N, R29W,
R29W, Keweenaw Co.,
Co., Michigan).
Michigan).
Basically,
Basically, the
the model
model suggests
suggests that
that several,
several, isolated
isolated intrusive/extrusive
intrusive/extrusive
bodies of Keweenawan age distributed throughout
throughout the
the Keweenaw
Keweenaw Peninsula
Peninsula
may represent exploration targets
targets for
for copper
copper sulfide
sulfide mineralization.
mineralization. Both
the
soil geochemistry and
the soil
and the ground geophysics tend
tend to
to support
support this
this idea
idea
at the Bear Lake body.
at
body.
The results of the
the field mapping,
mapping, geochemistry
geochemistry and
and geophysics
geophysics indiindicate the following:
following:
1.
1.
The predominantly felsic body displays
displays an
an easily
easily recognizable
recognizable
magnetic signature.
signature.
2.
2.
There are two
two relatively strong conductors
conductors (VFL—EM)
(VFL-EM) associated
associated
with the
the body.
body.
3.
The body has
has potassic rock
rock chemistry,
chemistry, averaging
averaging 6.43%
6.43% K20,
K20, with
with
a high K20
Na20
0 ratio averaging 3.4.
K2 0 : Na
3.4.
2
Trace element analyses indicate
indicate that
that the
the copper
copper values
values for
for the
the
felsic
felsic body average 190 ppm
ppm which is
is anomalous
anomalous when
when compared
compared
to
for that
that rock type
type (15—3Oppm).
(15-30ppm).
to the
the published
published averages
averages for
:
4.
4.
5.
5.
The results
results of a soil geochemistry survey
survey indicate
indicate aa pattern
pattern of
of
anomalous copper values that
that appears
appears to
to be
be associated
associated with
with the
the
anomalous
location of
of the VLF—EM
VLF-EM conductors.
conductors.
development of
of aa model
model or
or "type"
"type" deposit
deposit based
based upon
upon the
the
Although the
the development
Mt. Bohdmia
sulfide mineralization
mineralization is
is still
still in
in its
its early
early stages,
stages, we
we
Mt.
Bohemia copper sulfide
hope that
chemistry studies
studies as
as well
well as
as geophysical
geophysical and
and case
case
that further
further rock
rock chemistry
history studies
studies from
history
from several
several other
other known
known areas
areas of
of similar
similar copper
copper sulfide
sulfide
the idea that Michigan's Copper
mineralization will confirm or refute the
Country may
may have
have another type
Country
type of
of mineralization for
for which to
to explore
explore in
in
addition to
addition
to the
the native copper and White Pine—type
Pine-type copper
copper settings.
settings.
�—39--39-
DOE-BENDIX-MICHIGAN
GEOLOGICAL
SURVEY DIAMOND-DRILLING
DIAMOND-DRILLING
DOE-BENDIX-MI
CHIGAN GEOLOG
ICAL SURVEY
INFORMATION IN MARQUETTE AND IRON COUNTIES,
FOR GEOLOGIC
FOR
GEOLOGIC INFORMATION
COUNTIES, MICHIGAN
James Trow
Department of Geology
Michigan State University
East Lansing,
Lansing, Michigan
Michigan 48824
East
ABSTRACT
Many Precambrian XX argillites
argillites and
and slates
slates are
are carbonaceous
carbonaceous and
and
pyritic,
and
some
contain
pyrrhotite,
chalcopyrite,
pyritic,
chalcopyrite, sphalerite,
sphalerite, and
and
galena.
PrecambrianW metabasalt
Precambrian.W
metabasalt (1059—1148')
(1059-1148') at
at DL—5
DL-5 contains
contains
strata—bound
ides with
with 130-2010
130—2010 ppm Cu and 20—50
strata-bound suif
sulfides
20-50 ppb
ppb Au.
Au. Maximum
uranium content in holes occurs in
a
2"—thick
conglomerate
in a 2"-thick conglomerate at
at 3011'
3011'
at
DL—4, with 130 ppm U
U (nitric/perchloric)
at DL-4,
(nitric/perchloric) or
or 260
260 ppm
ppm UU (hydro—
(hydroW metarhyolite
fluoric/nitric/perchloric acid
acid digestion).
digestion). Precambrian W
fluoric/nitric/perchioric
at DL-S
(997-1059') with 72—76
72-76 ppm U
U is
is aa possible
possible source
source rock
rock for
for
at
DL—5 (997—1059')
uranium in
in Precambrian
Precambrian XX strata.
strata.
In Marquette County,
County, age Y
dikes and minor gravity
gravity faults
faults
In
Y diabase dikes
appear in
E-.W, vertical,
vertical, and
and 2)
2) parallel
parallel to
in two
two orientations:
orientations: 1)
1) E-W,
to SW—
SWE—W vertical faults
Precambrian XX slaty
slaty cleavage.
cleavage. Such E-W
faults at
at DL—1
DL-l
dipping Precambrian
and
DL—7 have downthrown north sides;
and DL-7
sides; SW—dipping
SW-dipping faults
faults at
at DL—3,
DL-3, DL—5,
DL-5,
and DL-4
DL—4 have downthrown SW sides,
and
sides, suggesting the
the possibility
possibility of
of age
age YY
horst and graben structure in
horst
in the
the region,
region, in
in harmony with Cannon's
Cannon's
north—south tension enunciated at 1978 Institute
north-south
Institute on
on Lake Superior
Superior
Geology. Epigenetic
X rocks
Epigenetic sulfide remobilization in Precambrian X
appears
to be structurally related to
to the
the post—Penokean
post-Penokean faulting,
faulting, which
appears to
drags
drags slaty cleavage
cleavage as
as well
well as
as bedding.
bedding. Lower dip of Penokean slaty
cleavage at
DL—5 is
at DL-5
is thought
thought to
to reflect post—Penokean
post-Penokean rotation
rotation of
of Clark
Clark
Creek block.
block.
�I
DL—l:
DL-l:
DL—3:
DL-3:
DL—7:
DL-7 :
DL—5:
DL-5:
DL—4:
DL-4:
DL—6:
DL-6:
NWk-4,
NW¼,
SW~,
Sw¼,
NW~, NW¼,
NW~,
NW¼,
SW!t;,
NE~,
SW¼, NE¼,
NW~,
SE~,
NW¼, SE¼,
NWk-4, NE¼,
NE~,
NW¼,
28W,
Section 5,
5, TT 50N,
50N, RR 28W,
29W,
14, TT 50N,
Section 14,
50N, RR 29\01,
Section 4,
T SON,
50N, RR 28W,
4, T
27W,
Section 16,
16, TT 49N,
49N, RR 27\01,
2, TT 48W,
48N, RR 28W,
Section 2,
30, TT 46N,
46N, RR 33W,
NE~,
NE~, Section 30,
NE¼, NE¼,
Hole number
--
DL—l
DL-l
2148'
Terminal depthdepth.
............
Terminal
2148'
Maximum deviation
deviation
56~0
from vertical ............ 56½0
Overburden ................ 0—71'
0-71'
Age Y
Y diabase
diabase ............. --X strata
Age X
Dip of bedding ........... 30°SE—
30 0 SE3 0 m'1
Dip of cleavage
cleavage .......... 37°—65°SW
37 0 -65 0 SW
(Argillite,
(Argillite, slate
slate, ...... 71—2148'
71-2148 '
(turbidite, marble,
marble,
(algal stromatolite
(algal
Cherty carbonate,...)
carbonate, ... )
--))
clastics, algal
clastics,
))
stromatolite,
stromatolite,
))
"iron—formation"
"iron-formation"
(Argillite
(Argillite and .......
--(g r aywacke
(graywacke
Quartzite ............... --Age W
W basement ............ ---
O
I
0
--r
I
Shallowest phosphate ......
---
I
I
East Baraga Basin, Marquette County
East Baraga Basin, Marquette County
East Baraga Basin, Marquette County
Clark Creek Basin, Marquette County
Dead River Basin, Marquette County
NW of
of P.masa
Amasa Oval, Iron County
DL-3
DL—7
DL-7
DL—5
DL-5
DL—4
DL-4
DL-6
1634'
697'
697'
1148'
3176'
1093'
1 4½0
l41P
0—243'
0-243'
0
330
0-320'
0—3 20'
523—602'
523-602'
12°
0-76'
0—76'
2286—2358'
2286-2358'
2825-2827'
2825—2827'
41.,,,0
4½0
2
0-236'
0—2 36'
0
SW1
55°—70°
-70 0 S1'
0
l5
-45 0 S\-7
l5°—45°SW
O -40 0 NE
55°—40°NE
55°
S—
55 S-
0 -65 0 SW
37°—65°SW
37
243—569'
243-569'
20°—40°SW
20 0 -40 0 sw
320-523'
320—523'
0 -6S o SW
3 5°—6.5°SW
35
76—2966'
76-2966'
569—659'
569-659'
660—714'
660-714'
2966-3019'
2966—3019'
440
44 0
0—163'
0-163'
1545—15
51'
1545-1551'
20 0°NE—
NE0 SW 0.T.
60°SW
60
O.T.
40 0-55 0 SW
40°—55°SW
163—1634'
163-1634'
---
---
0
vertical
0
65
65 °NN
?
---
---
714-884'
714—884'
-----
---
884—997'
884-997'
997—1059'
997-1059'
metarhyolite
1059—1148'
1059-1148'
metameta—
basalt
514'
514'
---
)
)
236-1903'
?
---
659—697'
659-697'
granite
490'
3019—3119''
3019-3119
3119—3176'
3119-3176'
tonalite
2810'
421'
421'
�—41—
-41-
PALMER GNEISS UPDATE
Thomas Waggoner and Thomas Mroz
Thomas
Cleveland-Cliffs
Cleveland—Cliffs Iron Company
Ishpeming,
Ishpeming, Michigan
Michigan 49849
49849
ABSTRACT
The Palmer
Palmer Gneiss
Gneiss is
The
is somewhat of a misnomer for
for an
an Early
Early Precambrian
Precambrian
formational unit composed primarily of quartz
quartz chiorite—sericite
chlorite-sericite schists.
schists.
The unit
unit contains
The
contains thin beds of orthoquartzite and
and slate,
slate, along
along with
with aa typical
typical
Archean magnetite/pyrite chert iron—formation.
iron-formation. The gneiss has been intruded
intruded
by granite with small
small amounts
amounts of
of calcite,
calcite, ankerite,
ankerite, pyrite
pyrite and
and chalcopyrite.
chalcopyrite.
The preference of the intrusive granites for
for foliation
foliation planes
planes indicates
indicates
deformation prior
prior to
to the
the granitic
granitic episode.
episode.
In Sections
Sections 25,
In
25, 26 and 27,
27, T47N,
T47N, R27W,
R27W, the
the northern limit
limit of
of the
the Palmer
Palmer
0
Gneiss
the east-west
to
Gneiss is
is the
east—west Palmer
Palmer Fault
Fault that
that dips
dips fairly
fairly uniformly
uniformly at
at 58
580
to
the north.
north. The gneiss is
is in
in direct
direct contact
contact with
with the
the middle
middle and
and upper
upper portions
portions
of the Negaunee Iron—Formation.
of
Iron-Formation. Both the Palmer Gneiss and
and the
the Negaunee
Negaunee Iron—
IronFormation have been offset by northwest—trending
northwest-trending near—vertical
near-vertical faults.
faults. The
terminus of the Palmer Gneiss is
is gradational
gradational into
into the
the pegmatitic
pegmatitic
southern terminus
granite. Assimilation of
of the Palmer Gneiss into
into granite
granite has
has produced
produced comcomthat make determination
determination of
of the
the original
original rock
rock extremely
extremely
positional variations that
difficult.
The Palmer Gneiss contains numerous east—west
The
east-west vertical
vertical faults
faults that
that
further confuse the
further
the lithologic
lithologic sequence.
sequence.
The foliation trends N
N 700_800
70 0 -80 0 W
W with northerly
northerly attitudes
attitudes varying
varying between
between
Where bedding was observed,
was N
N 720
W with a
observed, the trending was
72 0 W
a
northeasterly dip
dip of
of 610.
61 0 •
3500
35 to 85°.
85 0 •
The Palmer Gneiss is
is a Lower Precambrian
Precambrian meta—sedimentary
meta-sedimentary sequence
sequence that
that
has
by Lower
Lower Precambrian
Precambrian pegmatitic
pegmatitic granite
granite whose
whose abundance
abundance
has been intruded by
increases to
to the
the south.
south. Assimilations and
and post—intrusion
post-intrusion
progressively increases
shearing have caused extensive silicification,
shearing
silicification, carbonization
carbonization and
and sericitization.
sericitization.
�—42--42-
STRUCTURAL GEOLOGY OF
OF AMPHIBOLITIC
AMPHIBOLITIC GNEISSES,
GNEISSES,
NORTHEAST CHIPPEWA
CHIPPEWA COUNTY,
COUNTY, WISCONSIN
WISCONSIN
Stephanie Wurdinger
Wurdinger
Department of Geology
University of Minnesota
Duluth,
Duluth, Minnesota,
55812
ABSTRACT
ABSTRACT
Precambrian amphibolites,
amphibolites, hornblende schists and
and intrusive
intrusive units
units
are exposed along the
the Chippewa and Fisher rivers
rivers near
near Holcombe,
Holcombe, Wisconsin.
Wisconsin.
the northern boundary of
of the
the Chippewa
Chippewa
These rock formations occur near the
Amphibolite Complex and are judged
judged to
to be Archean
Archean (?)
(?) in
in age. Exposures
of
in order
order to
to determine
determine the
the stages
stages of
of
of the rocks were investigated in
deformation and
and their
their relative
relative ages.
ages.
The major rock units
units in the
the area are quartz—biotite
quartz-biotite amphibolite
amphibolite at
at
Holcombe dam,
dam, and interbanded amphibolite gneiss
gneiss and
and tonalite
tonalite along
along the
the
Fisher River.
River.
Intrusives into
into the quartz-biotite
include
Intrusives
quartz—biotite amphibolite include
dikes, and
and aa hypabyssal
hypabyssal
coarse grained granodiorite and associated dikes,
andesite intrusive.
intrusive. The two
two amphibolite units are
are separated
separated by
by aa zone
zone
of mylonite
mylonite at
at least
least 300
300in
m wide.
Banded gneiss
gneiss along the
the Fisher River displays
displays three
three periods
periods of
of
An early phase of
folding.
of deformation,
deformation, Fi,
Fl, produced
produced isoclinal
isoclinal folds
folds in
in
A
tonalite banding
banding and
and aa mineral
mineral lineation in zones of amphibolite.
tonalite
amphibolite. A
penetrative axial planar foliation,
foliation, S1,
Sl, trending
trending east—west
east-west was
was also
also
During FI
F1 deformation,
deformation, ptygmatic folds
During
folds formed in
in response
response to
to
produced.
the
closely spaced
spaced S1
Sl foliation.
foliation. During aa later
later deformadeformathe development of closely
tion, F2,
F2, large
large folds,
folds, possibly
possibly isoclinal,
isoclinal, refolded earlier mineral
tion,
lineations and
along aa great
great circle
circle distribution.
distribution.
and minor
minor fold
fold axis
axis lirieations
lineations along
The axial planes of F1
Fl and F2 are believed to
to be
be coplanar.
coplanar. A
A third
third fold
fold
deformation, F3,
deformation,
F3' produced broad,
broad, open
open folds
folds with north—south
north-south axial
axial planes
planes
at a
a high angle
angle to
to earlier
earlier fold
fold axes.
axes.
At Holcombe dam the
the first and third
third fold
fold deformations
deformations can
can be
be
Late synkinematic granitic
in the
the quartz—biotite
quartz-biotite amphibolite.
amphibolite. Late
observed in
intrusives
foliation parallel
parallel to
to S1.
Sl. The hypabyssal andesite
andesite
intrusives show a faint foliation
intrusive
faint
intrusive exhibits
exhibits aa strong,
strong, steeply-plunging
steeply—plunging lineation and a faint
foliation which also
also parallels
parallels S1.
Sl.
The quartz—biotite
quartz-biotite amphibolite was later
later converted
converted to
to hornblende
hornblende
A
schist along a shear zone
zone which is
is exposed
exposed along
along the
the Chippewa
Chippewa River.
River.
A
penetrative lineation plunges
plunges moderately to
to the
the west.
west. Late movements
along
the zone
zone formed
formed small pods
pods of
of brecciated mylonite along
along foliation
foliation
along the
planes.
the rocks in
in the
the area
area were crosscut
crosscut by
by aa series
series of
of closely—spaced,
closely-spaced,
All the
steeply-dipping
faults.
Strike separation along the
the faults
faults is
is dominantly
steeply—dipping faults.
right lateral,
right
lateral, and offset
offset does
does not
not exceed
exceed ten
ten feet.
feet.
�
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7ce48d615fb442ba698f3fd3d1fd53cb
PDF Text
Text
u.a.eX
UNIVERSITY OF WISCONSIN-EXTENSION
GEOLOGICAL AND NATURAL HISTORY SURVEY
Meredith E. Ostrom, State Geologist and Director
MIDDLE PRECAMBRIAN GEOLOGY
OF NORTHERN WISCONSIN
Prepared for:
TWENTY-FIFTH ANNUAL MEETING
INSTITUTE ON LAKE SUPERIOR GEOLOGY
UNIVERSITY OF MINNESOTA-DULUTH
DULUTH, MINNESOTA
MAY 8-13,1979
FIELD TRIP
GUIDE BOOK
NUMBER 4
1979
�-{ffr
_____
Tuesday May 8 Route
..........
Wednesday May 9 Route
5
I "
0
" I
10
I
I
miles
20
I
I
�Field Trip Guidebook
Number 4
University of Wisconsin-Extension
GEOLOGICAL AND NATURAL HISTORY SURVEY
Meredith E. Ostrom, State Geologist and Director
MIDDLE PRECAMBRIAN GEOLOGY OF NORTHERN WISCONSIN
Road Log and Geological Stop Descriptions
Gene L. LaBerge and M.G. Mudrey, Jr.
Edited by
M.G. Mudrey, Jr.
Geological and Natural History Survey
Prepared for
Twenty-Fifth Annual Meeting
INSTITUTE ON LAKE SUPERIOR GEOLOGY
University of Minnesota-Duluth
Duluth, Minnesota
May 8 - 13, 1979
(meeting concurrently with the Thirteenth Annual Meeting,
North-Central Section, Geological Society of America)
David G. Darby, Chairman, Field Trip Committee
University of Minnesota-Duluth
Available from the Wisconsin Geological and Natural History Survey,
University of Wisconsin-Extension, 1815 University Avenue, Madison,
Wisc.onsin 53706.
1979
�CONTENTS
INTRODUCTION by M.G. Mudrey, Jr. ........................................................................
1
TUESDAY, May 8, 1979
Geologic Road Log for Ashland, Bayfield, Iron, and Vilas Counties ....
6
WEDNESDAY, May 9, 1979
Geologic Road Log for Oneida, Price, and Sawyer Counties .......•.....
9
GEOLOGICAL STOP DESCRIPTIONS
Stop 1 - Grand View Quarry by G.L. LaBerge ..•••.•.•.....••..•.......
Stop 2 - Mount l~itt1esey by G.L. LaBerge
.
Stop 3 - Pence by G. L. LaBerge ....•....••...........................
Stop 4 - Hurley Overpass by G.L. LaBerge ...•.........•.•............
Stop 5 - Bear River by G.L. LaBerge .............•...................
Stop 6 - Monico East by M.G. Mudrey, Jr
.
Stop 7 - Monico Gravel Pits by M.G. Mudrey, Jr . .....•...............
Stop 8 - Witte Farm by M.G. Mudrey, Jr
.
Stop 9 - Monico West by M.G. Mudrey, Jr ...•.........................
Stop 10 - Beck Tower Wayside Park by M.G. Mudrey, Jr
.
Stop 11 - Jump River at Big Falls County Park by G.L. LaBerge ......•.
Stop 12 - Arpin Dam in Radisson by M.G. Mudrey, Jr
.
12
15
20
23
27
30
32
34
36
38
40
43
ILLUSTRATIONS
Figure 1.
Figure 2.
Table 1.
Map of northern Wisconsin showing distribution of various
lithologies in the Middle Precambrian ................•....
Schematic cross sections showing inferred lithologic -structural relations during the "Penokean event of
Middle Precambrian age ........•......................•....
Time-stratigraphic framework of Precambrian rocks in
Wisconsin ............•..•.................................
Highway map showing route of excursion
5
2
inside front cover
SPECIAL EVENT
TUESDAY, May 8, 1979 - Evening
Field trip banquet at Holiday Acres, Rhinelander, t..Jisconsin
After dinner addresses:
Discussion of Massive Sulfide Deposits by J.M. Franklin
Discussion of the Crandon Deposit by E.R. May and Paul G. Schmidt
i
4
�INTRODUCTION
M.G. Mudrey, Jr. l
Northern Wisconsin is blessed with an abundance of sand and gravel
resources deposited by the last major glacial advance. This is a mixed
blessing, in that bedrock exposures are few and far between. A fair average
would be about one small outcrop per township. Since the 1920's and extensive
exploration for iron deposits, bedrock studies in northern Wisconsin have been
few. In the late 1960's, Gene LaBerge and Paul Myers working for the
Geological and Natural History Survey initiated detailed-reconnaissance mapping
in the central part of the state. Renewed interest in the Precambrian geology
of northern Wisconsin was spurred in 1968 with the discovery near Ladysmith in
Rusk County of a small, but rich massive sulfide ore body. Additional discoveries since then include the Pelican River deposit near Rhinelander in Oneida
County, and the Crandon deposit in Forest County. In addition, numerous
theses and dissertations have studied the various Precambrian and Pleistocene
units. Although present detailed coverage is sparse (less than five percent of
Wisconsin is mapped in any detail), the general framework and distribution is
known or can be inferred from geophysical studies.
This trip is designed to show the lithologies which illustrate changing
environments in the Middle Precambrian, with predominantly sedimentary rocks
in the north, and extrusive and intrusive igneous rocks in the south. Classical localities of Middle Precambrian iron-formation, conglomerates within the
Middle Precambrian, the environment of volcanogenic massive sulfide accumulation and granitic plutons will be visited in road cuts, quarries, and natural
exposures. To cover the terrane, we must travel over 500 miles. Some of the
exposures are well studied, whereas others are having been identified in the
past few years.
Because of the non-ferrous base-metal interest in northern Wisconsin,
several of the stops will concentrate on the general rock types infue
volcanic pile, and their relation to known ore deposits. In addition, at the
field trip banquet Tuesday evening in Rhinelander Jim Franklin of the
Geological Survey of Canada will give a general summary on Precambrian massive
sulfide deposits and their enclosing rocks and Ed May and Paul Schmidt of
Exxon, U.S.A., will present their observations on the largest zinc-copper find
to date in Wisconsin, the Crandon deposit near Little Sand Lake in Forest
County.
The weather this time of year can be nasty, but usually is crisp and
invigorating. Stops will not be particularly strenuous. We will assemble
for prompt 8:00 a.m. departure on Tuesday, ~fuy 8, 1979, and proceed with field
stops to Rhinelander, Wisconsin, for an overnight stop, and journey back to
Duluth with field stops the next day. We plan on returning to Duluth about
6:00 p.m. on Wednesday, in time for you to join the activities of the
Twenty-Fifth Annual Institute on Lake Superior Geology and the Thirteenth
Annual North-Central Section of the Geological Society of America.
Monday evening, before the trip, an informal technical/social gathering is
scheduled in Duluth. The geologic framework will be discussed, and all
participants will have the opportunity to get acquainted before the Tuesday
morning departure.
WELCOME TO BADGER LAND!
1
�Table 1.
Era
System
Paleozoic
Time-Stratigraphic Framework of Precambrian Rocks in lVisconsin
Stratigraphic Units
Intrusive Rocks
Approximate Age
-----------------------------::-:::7':::-~::::_::_;:_"i:'_:;;:_~::::1;'~------------------66O:T:"iiDO-;;~;_:_
semimature at base grading
600-1,100 m.y.
Bayfield Group
upward to mature clastic
rocks deposited mainly in
shallow water
Oronto Group
immature clastic rocks deposited mainly in shallow
water
Upper Keweenawan
·--disconformity--
Middle Keweenawan
c
co
N
Lithology and Depositional
Environment
...
.0
E
co
t)
Q)
...
0-
Lower Keweenawan
Portage Lake and
Powder Mill volcanics
south of Lake Superior
and Chengwatana volcanics in northwest and
along St. Croix River
--disconformity-Bessemer Quartzite along
Gogebic Range
mafic and intermediate
lavas and interbedded
sedimentary rocks
600-1,100 m.y.
gabbroic and granophyric complexes near
Mellen and Mineral Lake
south of Lake ~uperior
immature clastic rocks deposited mainly in shallow
water
1,120 m.y.
1,200 m.y.
Q)
+-'
rapakivi massif and associated granite, syenite
and anorthosite in northeast (Wolf River area)
co
....J
--unconformity?-Quartzite at Baraboo,
Barron and as isolated
outliers in north
--unconformity--
clastic rocks deposited
mainly in shallow water
rhyolite inliers in south
subaerial tuffs and
breccias
--regional unconformity--
1,500 m.y.
1,765 m.y.
epizonal, Dost-tectonic
granite in south and isolated plugs in north
1,765 m.y.
epizonal to mesozonal,
syntectonic granites
1,880-1,820 m.y.
1,800 m.y.
�positions uncertain - - - - - - - - - - - - - - - - - - - - - - - - - - - - - basaltic to felsic
volcanic and volcaniclastic rocks in north
c
eo
.....
..a
E
eo
submarine flows, tuffs,
and volcanic sediments
model lead ages from massive sulfide
deposits are l,830 m.y. Physical
correlation with other units is difficult
at best. May correlate with Tyler Formation
in north.
metamorphic studies suggest 685 0 C at
7.5 RDars. This area has been correlated
with the Gogebic Range.
kyanite-staurolitegarnet bearing schists
and associated
quartzo-feldspathic
gneiss near Park Falls
to Mercer (including
Powell kyanite locality)
u
Q)
.....
a.
~
"'C
"'C
~
basaltic to felsic
volcanic and volcaniclastic rocks in extreme northeast
(Florence area)
submarine flows, tuffs,
and volcanic sediments
uranium-lead ages on zircon from gneisses
are around l,850-l,900 m.y. Some volcanic
rocks (Quinnesec) have been correlated with
the Lower Precambrian and with the Middle
Precambrian. Stratigraphic relations in
this area are not clear.
Tyler Formation on
Gogebic Range
clastic rocks deposited
mainly in deep water
(=Baraga
v.>
~roup
of Michigan)
0.
:l
>.
I:
0,....
l-i <1l
c.:J .u
--local unconformity?--
(1)
.....
Ironwood Iron-formation
on Gogebic Range
iron formation
Palms Formation on
Gogebic Range
immature clastic rocks
deposited in shallow water
(=Menominee Group of Michigan)
1.1'\
00
(1)
..::< e
..... e
S .....
."<1lC ,..,I
<t<.u
(1)0
."e ::;::
II
.......
0
~
.uo
~I.I'\
U
~
eN
:l
>.
(1)""
--regional unconformity?-Bad River Dolomite on
Gogebic Range
o
o
(/J
cc..o
stromatolitic dolomite
C1l
(=Chocolay Group of Michigan)
<1l
..0
---------::~~::~::~.::::~----------------~
--regional unconformity--
2,600 m. y.
c
eo
..a
E
eo
u
volcanics and associated
sediments south of
Gogebic Range
submarine flows, tuffs
and agglomerates
.....
>-
.....
eo
L.LJ
epizonal granite south
of Hurley
2,710m.y.
--unconformity?--
Q)
a.
gneiss, migmatite and
amphibolite in south
and western end of
Gogebic Range
o
l-i
0.
high-grade migmatites
2,800 m.y.+
�---------~---~-~~-
MIDDLE PRECAMBRIAN ROCKS
IN WISCONSIN
Geology modified from Sims 11976)
Figure 1.
IX'ii'l
Granitic Rocks
Ii>!
Metasedimentary Rocks
[:,/:',:::':]
Metavolcanic Rocks
Map of northern Wisconsin showing distribution of various lithologies in the Middle Precambrian. Metasedimentary rocks include
slates, conglomerates, iron-formations, and carbonates. These
rocks are least deformed and metamorphosed in the extreme northwest.
To the south, these rocks contain kyanite and various other higher
metamorphic grade minerals. The metavolcanic rocks include mafic
to felsic lavas and associated pyroclastic and epiclastic materials. The granitic rocks include epizonal granodiorite to granitic
plutons, and alkali-rich post-tectonic granites.
4
�WAUSAU
. ..
".
"
1900 m·y·
LAKE
SUPERIOR
m.y.
... .'. ...
tsJ
B
MIDDLE
GLL
PRECAMBRIAN
GRANITIC ROCKS
SEDIMENTARY ROCKS
EARLY PRECAMBRIAN
~
15?:1
~
~I"GREENSTONE"
~ VOLCANIC ROCKS
~ DOLOMITE, ETC.
Figure 2.
GRANITIC ROCKS
Schematic cross sections showing inferred lithologic -- structural
relations during the "Penokean" event of Middle Precambrian age.
The upper diagram illustrates a north (right-side) -- south (leftside) section from Lake Superior to central Wisconsin near
Wausau during the Middle Precambrian about 1,900 m.y. ago. To the
north, platform sediments including carbonates and iron-formation
were deposited, while to the south, deeper water sediments and
volcanics were accumulating. The lower diagram illustrates the
cross-section after cessation of tectonism about 1,800 m.y. ago.
To the north the sequence is little deformed, whereas to the south
the sequence is folded, and in the extreme south the sequence was
moved to shallow structural levels along major faults or shear
zones in an apparent host-graben arrangement.
5
�Tuesday, May 8, 1979
Geologic Road Log for Ashland, Bayfield, Iron, and Vilas Counties
This leg of the trip visits the dominantly sedimentary part of the
Middle Precambrian. The first stop is about two hours after starting.
Lunch will be at Stop 2 on Mt. Whittesey. The last stop will be about
4:00 with a 90 minute deadhead trip to Holiday Acres in Rhinelander.
Mileages
63
Follow U.S. 2 from Superior to the intersection with
U.S. 63 turn right (south) on U.S. 63.
14
Proceed on U.S. 63 to intersection with Bayfield County D
in Grand View. Turn left (south) on County D. Note: There
are several approaches to stop 1. Directions are given for
the best route, however roads may be closed by washouts.
The alternate direction given below is longer, but is
generally a better maintained road.
3.2
Proceed on County D to intersection with U.S. Forest Rd. 377
at Chequamegon National Forest Sign. Turn left (east) on
Forest 377.
2.6
Proceed on Forest 377 to intersection with Forest 378.
right (south) on 378.
3.1
Proceed on Forest 378 intersection Forest 198 (straight
ahead) and 202 (cross road). Continue straight ahead (east)
on Forest 198.
1.3
Proceed on Forest 198, crossing Marengo River and then
turning right onto unmarked road parallel to Forest 198.
0.2
Proceed on unmarked road to bridge with gate over Marengo
River. Park vehicles in area left (north) of road.
1900
ft.
Cross bridge on foot, entering private land. Follow quarry
road, keeping to right at branches of road, into quarry.
Stop 1.
10.4
Turn
Grand View Quarry -- Bad River Dolomite
Return to Grand View.
6
�Alternate Route From Grand View to Stop 1
4.8
Proceed on County D to intersection with Forest 201 (Atkins
Lake Road). Turn left (east) on Forest 201.
4.0
Proceed on Forest 201 to intersection with Forest 202.
left (north) toward Marengo Lake on Forest 202.
1.5
Proceed on Forest 202 to intersection with ~orest 198 (right)
and 378 (left). Turn right (east) on Forest 198.
1.3
Proceed on Forest 198, crossing Marengo River and then
turning right onto unmarked road parallel to Forest 198.
0.2
Proceed on unmarked road to bridge with gate over Marengo
River. Park vehicles in area left (north) of road.
1900
ft.
Cross Bridge on foot, entering private land. Follow quarry
road, keeping to right at branches of road, into quarry.
Stop 1.
11.8
Turn
Grand View Quarry -- Bad River Dolomite
Return to Grand View.
4.8
Follow U.S. 63 north from Grand View to intersection with
County E. Turn right (east) on County E.
7.4
Proceed on County E to intersection with Ashland County C
(E turns left). Continue straight ahead on County C.
1.3
Proceed south on County C to crossroad intersection with
Midway Road. Turn left (east) on Midway Road.
2.3
Proceed east on Midway Road and rejoin County C.
straight ahead (east) on County C.
2.4
Proceed east on County C to intersection with State 13.
Turn right (south) on State 13.
9.9
Proceed south on State 13 to intersection with State 77 in
Mellen south of railroad tracks. Turn left (east) on
State 77.
0.4
Proceed east on State 77 to intersection with County P
(Lake Drive). State 77 turns left (north) over railroad
tracks. Continue straight ahead on County P (Lake Drive).
1.6
Proceed on Lake Drive. Road jogs left. Stay on Lake Drive.
Road jogs left. Stay on Lake Drive towards Camp Galike.
Turn left on third dirt road to left (east). This may be
marked "Mellen Fire Tower Road."
7
Continue
�1.5
Proceed on dirt road to flagged area. Hike 100 yards north
of road into cleaning. Note: There is a locked gate on the
Fire Tower Road. The key is available from the Head Ranger,
Copper Falls State Park, about 3 miles northeast of Mellen
on State 169.
Stop 2.
Mt. Wittlesey.
Ironwood Iron formation
Afternoon, May 8
3.1
21
Return to County P and State 77 in Mellen.
Follow State 77 east from Mellen to Pence (mileage that
follows is calculated from sign on west city limits of Pence.
0.4
Proceed into Pence on State 77 to intersection with Spruce St.
Proceed south one block, and park on Whiteside Street. Out
crop is located on south side of Whiteside Street, at the
intersection with Spruce Street, under a large tree.
5.1
Return to State 77, and continue east towards Hurley. Enter
Hurley. Stop sign at intersection of State 77 and Fifth Ave.
Turn left (north) onto Fifth Avenue.
0.5
Follow Fifth Avenue to intersection with U.S. 51.
(west) onto U.S. 51.
1.1
Follow U.S. 51 northbound, taking overpass towards U.S. 2
westbound. Stop at large outcrop on right (east) side of
road immediately after crossing the overpass.
2.5
Return to southbound U.S. 51 by taking U.S. 2 westbound to
cross-over (about 0.5 miles) and reverse direction to eastbound U.S. 2, and taking the exit ramp to southbound U.S. 51.
Next leg of trip mileage is measured from intersection of
U.S. 51 and State 77 in Hurley.
26.6
Turn left
Proceed south on U.S. 51 to intersection of U.S. 51 and
State 47 in Manitowish. Turn right (south) on State 47.
3.9
Follow State 47 to intersection with State 182.
(west) on State 182.
1.2
Follow State 182 to large outcrops on both sides of road.
Stop 5.
1.2
50
Turn right
Bear River - Powell Kyanite
Return to State 47.
Turn right (south) on State 47.
Follow State 47 southbound towards Rhinelander and intersection U.S. 10.
8
�Wednesday, May 9, 1979
Geologic Road Log For Oneida, Price and Sawyer Counties
This leg of the trip visits the dominantly volcanogenic part of the
Middle Precambrian basin near Monico in Oneida County, with incidental
stops at granite localities. We will start with a short trip to Monico
and examine volcanic rocks, and spend the last half of the morning
deadheading to our lunch stop in Price County. One afternoon stop will
be made in Sawyer County. We plan on arriving in Duluth - Superior
around 6:00 p.m.
Morning, May 9
Mileages
14
1.0
Follow U.S. 8 east from Rhinelander to the intersection with
U.S. 45 and U.S. 47 south in Monico.
Continue east on U.S. 8, crossing on bridge over Chicago and
Northwestern Railroad tracks and U.S. 45 to north. About
0.2 miles east of intersection of U.S. 45 to north, take.
County V to the right, and park. Outcrop is located at
intersection of U.S. 45 and County V.
Stop 6.
Monico East - Mafic Pillow Basalt.
0.2
Return westbound on U.S. 8 to intersection with U.S. 45 north.
Turn right (north) on U.S. 45.
0.5
Proceed to Lake Road, and turn left (west) onto Lake Road.
0.6
Proceed on Lake Road, crossing Baade Road and stopping
behind house on left (south).
Stop 7. Monico Gravel Pits (Baade and Lake Roads)--Intermediate to felsic pillow lavas.
0.6
Return to U.S. 45 and turn left (north) on U.S. 45.
0.9
Proceed to small, abandoned farm on right (east) side of road.
Stop 8.
Witte Farm - Coarse Felsic Agglomerate.
1.4
Return south to U.S. 8.
2.4
Proceed west on U.S. 8 to intersection with old U.S. 8 and
Leith Road. Proceed on old U.S. 8.
0.7
Proceed to flagged area.
road.
Stop 9.
0.7
Turn right (west) on U.S. 8.
Small outcrops on both sides of
Monico West -- Section 26 - pyritic tuff.
Return to U.S. 8 and proceed east on U.S. 8.
9
�1.6
Proceed east on U.S. 8 to intersection U.S. 45 (southbound).
Turn right (south) on U.S. 45.
2.5
Proceed to Wayside on west (right) side of highway.
in wayside.
Stop 10.
2.5
Outcrop
Beck Tower Wayside Park - Late red granite.
Return north to U.S. 8.
Turn left (west).
14
Proceed on U.S. 8 west to Rhinelander.
44
Continue west on U.S. 8 to Prentice.
18
Continue west on U.S. 8 to junction with Price County N near
Kennan. Turn left (south) on County N.
10.2
Proceed on County N to junction with road to Big Falls County
Park road. Turn right (west).
1.0
Proceed on park road to park entrance and turn left (south)
into park.
0.2
Proceed to pavillion.
Outcrops in river west of pavillion.
Stop 11. Big Falls County Park on the Jump River, Price
County - Granite and Pyritic tuff.
Afternoon, May 9
11.9
0.9
Return to Kennan and junction of County J and N.
(west) on County J.
Follow County J to U.S. 8.
Ladysmith.
Turn left
Turn left (west) on U.S. 8 to
27
Follow U.S. 8 through Ladysmith to intersection with State 77.
Turn right (north) on State 27.
23
Follow State 27 to Ojibwa to intersection with State 70.
Turn left (west) on State 70.
4.4
Follow State 27 and 70 west.
road.
0.7
Proceed on gravel road.
cross bridge.
0.4
Proceed to junction with Swede Road.
Turn right.
0.25
Proceed to junction with Birch Lane.
Turn right.
0.6
Follow Birch Lane. Turn right crossing bridge and park.
Walk 350 feet along trail to river.
Stop 12.
Turn left (south) on gravel
Turn left (east) on asphalt road,
Arpin Darn in Radisson - Late Porphyritic Granite.
10
�1. 25
Return to intersection
1
Continue west on asphalt road into Radisson and intersection
with State 40. Turn right (north) to intersection with
State 70 and 27.
with asphalt road.
29
Follow State 27 to Hayward.
77
Follow State 77 to Minong and U.S. 53 to Duluth.
540.2
mi.
End of Log
GEOLOGICAL STOP DESCRIPTIONS
Page
Stop
1 - Grand View Quarry - Bad River Dolomite ..........•......... 12
Stop
2 - Mount Whittlesey - Ironwood Iron-formation ...........•.... 15
Stop
3 - Pence - Basal Palms Formation ........•.................... 20
Stop
4 - Hurley Overpass - Tyler Formation
Stop
5 - Bear River - Powell Kyanite •.............................. 27
Stop
6 - Monico East - Mafic Pillow Basalt
30
Stop
7 - Monico Gravel Pits - Andesite Pillow Lava
32
Stop
8 - Witte Farm - Coarse Felsic Agglomerate
34
Stop
9 - Monico West - Section 26 Pyritic Tuff
36
Stop 10 - Beck Tower Wayside Park - Jennings Granite
23
,
38
Stop 11 - Jump River at Big Falls County Park - Granite
40
Stop 12 - Arpin Dam in Radisson - Late Porphyritic Granite
43
11
�BA 44/5W/22
Title:
Grand View Quarry -- Bad River Dolomite
Location:
Johnson & Johnson Quarry, Grand View. NW~, NW~, NW~, Sec. 22,
T.44N., R.5W., Bayfield County. (Chequamegon National Forest,
1 mile, 1968)
~ inch
o
Author:
Gene L. LaBerge (1978)
Description: This quarry provides one of the largest and most excessible
exposures of the Bad River Dolomite in IVisconsin. The formation was named by
Van Rise and Leith (1911) from exposures along the Bad River at Penokee Gap
southwest of Mellen. According to Aldrich (1929), it unconformably overlies
the Lower Precambrian greenstones and granites to the south. In the eastern
part of the Gogebic Range the Sunday Lake Quartzite conformably underlies the
dolomite, but both the dolomite and quartzite are missing in the central part
of the district, presumably due to erosion prior to deposition of the overlying
Palms Formation (Irving and Van Rise, 1892). Thus, there appears to have been
gentle folding or arching along a north-south axis causing erosion of the
Bad River Dolomite and Sunday Lake Quartzite prior to deposition of the Palms
Formation, the basal unit of the Animikie Series (James, 1958) in this area.
12
�BA 44!5W!22 (2)
The exposures in the quarry are fairly typical of the formation. The
bedding dips 35 0 - 75 0 north, along with all other Middle Precambrian units on
the Gogebic Range in Wisconsin. Komatar (1972) estimates a minimum thickness
of 550 feet in this area, thinning to about 310 feet eight miles to the east.
Aldrich (1929) reports that the lower part of the formation is mainly a
dolomitic limestone with a much more siliceous upper part. The silica occurs
as lenses of sandy dolomite or cross-bedded sandstone (now quartzite), and
as beds, pods and irregular masses of chert (Komatar, 1972). The chert ranges
in color from light gray to black, presumably due to included organic matter.
Algal structures up to nearly 1 meter in diameter, some with black chert
layers alternating with dolomite, are present in the formation (Figure 1).
Figure 1. Algal structures in the Bad River Dolomite. Photo is of
a large glacial erratic near Clam Lake, about 10 miles southeast of
Grandview.
Several mafic dikes striking N.80oE. and dipping 84°S. are exposed in the
quarry (Komatar, 1972). These are presumably Keweenawan diabase dikes.
Mineralogically, the formation consists of medium-grained granular
carbonate with lenses, pods and patches of quartz. A reaction rim of pale
green tremolite typically occurs between the quartz and carbonate. The
tremolite is also present in layers of massive, randomly oriented crystals
and as radial aggregates several inches in diameter.
The mineral assemblage in the Bad River Dolomite and associated Palms and
Tyler Formation indicate that the area was metamorphosed to greenschist facies
during the Penokean orogeny about 1700 m.y. ago (Komatar, 1972). He reports that
the metamorphic grade increases from quartz-albite-muscovite-chlorite subfacies
on the east to quartz-a1bite-epidote-almandine subfacies in the Grandview area.
This metamorphism was associated with only slight deformation.
13
�BA 44/5W/22 (3)
Intrusion of the Mellen gabbro produced widespread contact metamorphism
superimposed on the earlier regional metamorphism. K/Ar ages (Komatar, 1972)
date this event at 1050±40 m.y.
Discussion: The Bad River Dolomite was deposited on an erosion surface of
Lower Precambrian greenstones and granites. The presence of algal structures,
sandy dolomite and interbedded layers of sand indicate deposition in a shallow
marine environment. The increase in sand content upward in the formation
suggests either a shallowing of the basin or a change in source area providing
more coarse clastics to the basin. The unit is similar in all respects to the
Kona and Randvi11e dolomites in the Marquette and ~1enominee districts of
Michigan respectively, with which it is generally correlated.
The absence of the Bad River Dolomite in the central part of the Gogebic
suggests a gentle upwarp in that area resulting in erosion of the formation
prior to deposition of the overlying Palms Formation. Gentle folding and
greenschist facies metamorphism occurred during the Penokean orogeny.
The major northward tilting of the units and contact metamorphism
associated with emplacement of the Mellen gabbro occurred during Late Precambrian time.
References Citied:
Aldrich, H.R., 1929, The geology of the Gogebic Iron Range of Wisconsin:
Wisconsin Geological and Natural History Survey, Bulletin 71, 279 p.
Irving, R.D., and Van Rise, C.R., 1892, The Penokee Iron-bearing Series of
Michigan and Wisconsin: U.S. Geo1goical Survey Monograph 19, 534 p.
James, R.L., 1958, Stratigraphy of Pre-Keweenawan rocks in parts of northern
Michigan: U.S. Geological Survey Professional Paper 314-C, p. 27-44.
Komatar, F.D., 1972, Geology of the Animikian metasedimentary rocks, Mellen
Granite, and Mineral Lake Gabbro west of Mellen, Wisconsin: Unpub.
M.S. Thesis, University of Wisconsin-Madison, 70 p.
Van Rise, C.R., and Leith, C.K., 1911, The geology of the Lake Superior
Region: U.S. Geological Survey Monograph 52, 641 p.
14
�AS 44/2H/9B
Title:
Mount Hhittlesey - Ironwood Iron-formation
Location:
Author:
Berkshire Mine, SH\, SW\, sE\, Sec. 9, T.44N, R.2W., Ashland County.
(Mt. Hhittlesey 7~-minute topographic quadrangle. 1967) (Get key
from Ranger at Copper Falls State Park)
Gene L. LaBerge (1978)
Description: The Ironwood Iron-formation ranges from about 450-950 feet in
thickness and extends for approximately 60 miles across Michigan and Hisconsin
in a west-southwesterly direction from west of Lake Gogebic, Michigan, to west
of Mineral Lake in Wisconsin. It lies conformably between the Palms Formation
and the Tyler Formation. The prominent hill here (Mt. Whittlesey) results from
the resistant nature of the exposed metamorphosed iron-formation. The lowlands
west and east of the hill are the result of cross-faults of Late Precambrian
age that offset the Middle and Upper Precambrian strata (Aldrich, 1929).
The iron-formation exposed here shows the bedding characteristics typical
of Middle Precambrian iron-formations of the Lake Superior region. Two basic
styles of bedding are readily apparent -- one is a laminated rock consisting of
alternating layers about 1 cm thick of recrystallized chert and iron oxides.
This is commonly referred to as "banded" or "even-bedded" or "slaty" ironformation. The other bedding type present is a thick and irregularly-bedded
variety with beds up to 15 cm or more thick. The thicker beds are cherty with
abundant sand-size clasts (granules or oolites) of chert in a chert matrix.
The clasts commonly are somewhat ferruginous, whereas the matrix is more pure
15
�AS 44/2W/9B (2)
:oj
~
..,
<1J
.
0
o
o
~.
o
o
.... ..,
_
.
- ,
-
6
-
-
--l
-
-~
-
Volcanics along Powder Mill Creek
Intermediate to felsic lava flows
unco!Or1Ol1 basdlt flows;except in I
Lower 5000 ft thin basalt flows
with a few intermediatG flows .
Pillow lavas at base
~
N
.n a.
S a.
~
:l
0'-'
..,:.J
o
o
0..
Bessemer Sandstone of Seaman (1944)
Quartz arenite with abundant matrix;
congLunLeratic at base
'"
C1l
~~_---.-f-..-~/'-r---u-"1""-':"';;"~~~"--~~--+------------------------1
f-.-
a.
£i
:l
0
..,
-.-;
Cl
><
:l
E
C1l
-
C1l
If)
(:Q
- -- -
S
C1l
00
C1l
..,
-
0
0
-
-
a-.
-
-
-
---- -
Tyler formation
Light - to dark - gray pl&gioclaserich fine-grained sandstone, argillaceous siltstone, and argillite.
--Lowermost 1000 [t is partly
ferruginous and has len~es of lean
cherty iron-formation
-
~~=
0.
:l
X
C
..,0
C1l
..-4
r--.
<lJ
Cl
-<
.n
"0
«>
..,
E
C1l
u
..,<lJ
0..
"U
-.-;
E
'-'
~
C
-aor,
a-.
-a
I
If)
~
-.-;
E
0
c
<lJ
?-:
0.
:l
..,o
Cl
I
-0
0alf)
',-..'-_ Anv il"M~~be~ ..:::.:;--\ Ironwood Iron-Formation
.....-
--
-_...:.---.;..
==-=:=-'?ence Membcl- ~-'--:'~MostlY thin-bedded cherty carbonate
~ ;:-" - -_- ::.. -, "." -.. =,-;;
i.ron- forma t ion
--::'-Norr ie Member ~ ~
~~":>l" fj er---I
~-':
Mostly thick wavy bedded cherty iron----.a
.: ..---.-- - -e - r'Cr1
- .. " '. ~ ,,"'~'
forma tion
:- ~ym-;:;uth M~m:,~r ./
Palms Formation
Sericitic argillite; red-brown
'"~ ~-~~.*~~~~~~
quartzite at top
Bad River Dolomite
/
Gray to buff dolomite and cherty doloo
mite. Stromatolitic structures common.
a
in both east and west parts of
Found
'"
Gogebic district, absent in center
':-~-=- - ~
'--
-=---- ---
>.
C1l
--i
o
u
o
..c:
u
a
If)
rl
....
Sunday Quartzite
Mainly white, gray, and red vitreous
quartzite, and conglomerate at the
base. Known only in the eastern
Gogebic
Precambrian W(lower)complex
Sedimentary-volcanic ("greenstone")
sequence, partly metamorphosed to
foliated hornblende gneiss,
intruded by quartz monzonite
and pegma t i te
Figure 1.
Generalized stratigraphic section in central and western Gogebic
Range (from Schmidt and Hubbard, 1972, p. A3).
16
�AS 44/2W/9B (3)
chert. These cherty units are highly irregular in shape and are separated by
layers composed mainly of iron oxides. Intra-formational conglomerates are
relatively common in the "wavy" or "irregularly" bedded or "cherty" ironformation.
These different bedding styles represent different intensities of wave
action in the basin during iron-formation deposition. Or alternatively, they
represent alternately shallow and deep water conditions, with the thin-bedded
variety representing deep (quiet) waters and the wavy bedded units indicating
shallow (agitated) waters.
These bedding differences were used by Hotchkiss (1919) as a basis of
subdividing the formation into five members based on the dominant bedding style.
He recognized three units with dominantly wavy bedding (Plymouth, Norrie, and
Anvil) separated by two units of mainly thin-bedded iron-formation (the Yale
and Pence). These units can be recognized over much of the 60-mile length of
the range, and are roughly correlative with the lower cherty, lower slaty,
upper cherty and upper slaty members of Biwabik Iron-formation in Minnesota.
The iron-formation here has been metamorphosed to grunerite grade, and
consists of quartz, grunerite, magnetite and minor hematite and garnet, with
minor dolomite, ankerite and siderite co-existing with the grunerite (Laybourn,
1979). Minnesotaite is the stable iron-silicate present in the iron-formation
east of Ballou Creek (about 2 miles east of here), and iron-rich pyroxenes
(ferrohypersthene and ferroaugite) appear from Mellen westward (Laybourn, 1979).
The metamorphic facies are produced by contact metamorphism related to the
Mellen and Mineral Lake gabbro complexes.
Economic Geology: Iron ore was discovered on the Gogebic Range at Bessemer,
Michigan in 1873, and over 300 million tons of natural ore was mined before
operations ceased in 1966 (Schmidt and Hubbard, 1972). Most of the mining
operations were done ,between Hurley, Wisconsin, and Wakefield, Michigan, on
the eastern part of the range. Natural ores that are economically exploitable
have been worked out.
Marsden (1978) reports that major reserves of taconite ore in the Ironwood
Iron-formation remain on the western end of the Gogebic range where the rocks
have been more highly metamorphosed. The intensity of metamorphism increases
progressively westward from biotite grade to pyroxene grade (Marsden, 1978).
The area of interest for development of magnetite taconite extends from near
Upson southwestward for 21~ miles to just west of Mineral Lake. Outcrop
width of the iron-formation is 1000-1500 feet over much of this length, but
folding in the }1t. vfuittlesey area produce an outcrop width of 2500 feet
locally (Marsden, 1978).
Marsden (1978) estimates the total reserves of magnetic taconite in
Wisconsin to be 4,171,000,000 metric tons, of which 3,711,000,000 metric tons
are in the Ironwood Iron-formation of the Gogebic Range. The other taconite
reserves are the Agenda deposit (Sec. 22, 23, 24, T.42N., R.IE.), 160,000,000
tons; the Butternut deposit (Sec. 20, 21, 28, 29, T.49N, R.1W), 48,000,000
tons; and the Pine Lake deposit (Sec. 21, 22, 23, 26, 27, 28, T.44N, R.3E.),
184,000,000 tons. The latter three deposits are not in the Ironwood Ironformation, but appear to be in lateral equivalents (Allen and Barrett, 1914).
17
�AS 44/2W/9B (4)
Thus, the Middle Precambrian of northern Wisconsin contains one of the
largest undeveloped taconite reserves in North America.
Discussion: Mineralogically, the iron-formation is generally referred to as
"oxide facies," implying that it was deposited as oxides with the chert.
LaBerge (1964) showed that the magnetite is almost entirely secondary.
Dimroth (1975) points out that the mineral facies are diagenetic (or metamorphic)
and do not reflect the depositional environment. Thus, unless we can prove that
the present mineralogy is the original mineralogy, there is no basis for
interpreting the depositional environment from the mineralogy. The Facies
concept of James (1954) should be restricted to a descriptive rather than
interpretative concept. The present mineralogy of iron-formations is the
product of the depositional, diagenetic, metamorphic, and in many cases, the
weathering environment; it should not be assumed that the present mineralogy is
the original mineralogy.
The subdivision of the Ironwood into members based on the dominance of
granular (cherty) or laminated (slaty) iron-formation (Hotchkiss, 1919) works
well in the eastern two-thirds of the Gogebic. However, subdivision of the
formation into the various members in the western third of the district is
difficult. In part, this may be due to the highe~ metamorphic grade in the
western end of the district, but there seems to be a real change in the
stratigraphy as well. Morey (1972, p. 209) shows a similar relationship for
the western Mesabi, where subdivision into the cherty and slaty members is
difficult. This may suggest a change in the Animikie Basin to the southwest.
The presence of a thicker succession, interbedded clastics and volcanic rocks
in iron formation in the Cuyuna district (Marsden, 1972) may indicate a change
from platform to deeper basin to the southwest.
References Cited:
Aldrich, H.R., 1929, The Geology of the Gogebic Iron Range of Wisconsin:
Wisconsin Geological and Natural History Survey, Bulletin 71, 279 p.
Allen, R.C., and Barrett, L.P., 1915, Contribution to the pre-Cambrian geology
of northern Michigan and Wisconsin: Michigan Geological Survey Publication 18, Geologic Series 15, p. 13-164.
Dimroth, E. 1975, Paleo-environment of iron-rich sedimentary rocks:
Geologischen Rundschau, v. 64, p. 751-767.
Hotchkiss, W.O., 1919, Geology of the Gogebic Range and its relation to
recent mining developments: Engineering/Mining Journal, v. 108,
p. 443-452, 501-507, 537-541, 577-582.
James, H.L., 1954, Sedimentary facies of iron-formation:
v. 49, p. 235-293.
Economic Geology,
LaBerge, G.L., 1964, Development of magnetite in iron-formations of the
Lake Superior Region: Economic Geology, v. 59, p. 1313-1342.
Laybourn, D.P. 1979, Geology and metamorphism of the Ironwood Iron-formation,
Gogebic Range, Wisconsin: Unpub. M.S. Thesis, University of MinnesotaDuluth, 223 p.
, s:l
�AS 44/2W/9B (5)
Marsden, R.W., 1972, Cuyuna District: in P.K. Sims and G.B. Morey, editors,
The Geology of Minnesota (G.M. Schwartz Volume): Minnesota Geological
Survey, p. 227-239.
Marsden, R.W., 1978, Iron ore reserves of Wisconsin -- A Minerals Availability
Systems Report: in Proceedings of the 51st Annual Meeting, Minnesota
Section AIME and 39th Annual Minnesota Mining Symposium, p. 24-1 -- 24-28.
Morey, G.B., 1972, Mesabi Range: in P.K. Sims and G.B. Morey, editors,
The Geology of Minnesota (G.M-.-Schwartz Volume): Minnesota Geological
Survey, p. 204-217.
Schmidt, R.G. and Hubbard, H.A., 1972, Penokean Orogeny in the central and
western Gogebic Region, Michigan and Wisconsin: Field Trip A, 18th Annual
Institute on Lake Superior Geology (Roughton, Michigan).
19
�Ir 46/2E/32
Title:
Pence--Basal Palms Formation
Location:
Author:
Intersection of ~~iteside Street and Spruce Street in Pence, Wisconsin.
SE~, SW~, Sec. 32, T.46N., R.2E., Iron County.
(Iron Belt 7~-minute
topographic quadrangle, 1956).
Gene L. LaBerge (1978)
Description: The Palms Formation is the basal unit of the Middle Precambrian
Animikie Group (James, 1958), and unconformably overlies the Bad River Dolomite
and Sunday Lake Quartzite of the Chocolay Group (Cannon and Gair, 1970).
According to Aldrich (1929), the Palms is continuous throughout the Gogebic range,
averages about 450 feet in thickness, and contains a basal conglomerate, a
"quartz-slate" unit, and an upper quartzite unit.
At this locality the basal Palms rests on Lower Precambrian granite, the
older Bad River Dolomite and Sunday Lake Quartzite evidently having been
removed by post-Bad River - pre-Palms erosion. Both west and east of here the
Bad River Dolomite and Sunday Lake Quartzite are present between the Palms and
the underlying Early Precambrian granite and greenstone. The following generalized description is taken mainly from Aldrich (1929).
The basal conglomerate of the Palms is up to about six feet thick and appears
to be derived mainly from the immediately underlying rock types (Aldrich, 1929).
It was deposited on an uneven erosion surface, and thus varies in thickness
locally. The larger clasts are well rounded at some localities, and very angular
20
�Ir 46/2E/32 (2)
at others according to Aldrich (1929). Here the clasts consist of quartz, chert,
granite, and felsic and melfic volcanics, are moderately well rounded and range
up to about 8 cm in ~iameter. The outc~op is slightly phosphatic.
Overlying the basal conglom~rate~ and comprising about 400 feet of the
formation is the thin-bedded "quartz-slate" unit characteristic of the Palms.
It consists of alternating quartz-rich and argillaceous beds 1-3 cm thick with
ripple marks, cross-bedding and scour-and-fill features common. The quartz-rich
beds are composed mainly of quartz, although some are quite feldspathic. 0uartz
grains range from angular to well rounded, with the larger grains generally the
most rounded (Aldrich, 1929). Argillaceous layers consist mainly of fine
sericite, chert, ~hlorite and magnetite. A general coarsening of grain size of
argillaceous materials and the appearance of octahedra of magnetite west of the
Tyler Forks River is evidently due to contact metamorphism produced by the
Upper Precambrian Mellen Gabbro.
The uppermost 50 feet of the Palms consists of a vitreous quartzite
composed of medium-grain, well-rounded quartz. Minor mica is present on bedding
planes. The quartzite varies from white, green, brown to red (Aldrich, 1929).
The Palms is overlain conformably by the Ironwood Iron-formation. This
represents an abrupt transition from clastic sedimentation in the Palms to
chemical sedimentation (with virtually no clastics) in the Ironwood. A similar
abrupt transition is present throughout most -- but not all -- of the
Lake Superior region.
Discussion: The Palms Formation is an important part of understanding the
geometry of the Animikie Basin. It is genetally correlated with the Pokegama
and Kakabeka Formations of the Mesabi and Gunflint districts respectively on
the north shore of Lake Superior, and the Siamo and Ajibik Formations of the
Marquette district (Cannon and Gair, 1970). The Kakabeka Formation is mainly
a conglomerate and generally only a few feet thick (Goodwin, 1954). The
Pokegama is mainly a quartzite and up to 167 feet thick (Morey, 1972). These
formations underlie the iron-formation in their respective districts. The
general thickening of the clastic sequence beneath the iron-formation suggests
a deeper (or older) basin to the south, or alternately that the sea was
transgressing northward onto the craton at the onset of iron-formatin deposition.
In the ~1arquette district, the Siamo Slate and Ajibik Quartzite are 1,000 feet
thick in the Neguanee area, but thin markedly to only about 100 feet near
Michigamme at the western end of the district (Boyum, 1970).
Thus, the nature and thickness of the formations underlying the major
iron-formation differs from place to place within the basin and must reflect
local differences in the pre-iron-formation history of the Animikie basin.
In the Gogebic district, the Palms has some features typical of shallow water
deposition, and some (the quartz-slate) which appears to have similarities to
deeper water deposition, perhaps transitional into a graywacke-type environment
farther south.
References Citied:
Aldrich, H.R., 1929, The geology of the Gogebic Iron Range of Wisconsin:
Wisconsin Geological and Natural History Survey, Bulletin 71, 279 p.
Boyum, B.H., 1970, the Marquette Mineral Range, Michigan: Geological Society of
America, Field Trip to Marquette Iron Range, }1ichigan, 21 p.
21
�Ir 46/2E/32 (3)
Cannon, W.F., and Gair, J.E., 1970, A reVlSlon of stratigraphic nomenclature for
Middle Precambrian rocks in northern Michigan: Geological Society of America,
Bulletin, v. 81, p. 2843-2846.
Goodwin, A.M., 1954, Facies relations in the r,unflint Iron-formation:
Geology, v. 51, p. 565-595.
Economic
James, H.L., 1958, Stratigraphy of pre-Keweenawan rocks of northern Michigan:
U.S. Geological Survey Professional Paper 3l4-C, p. 27-44.
Morey, G.B., 1972, Mesabi Range: in P.K. Sims and G.B. Morey, editors,
The Geology of Minnesota (G.M. Schwartz Volume): Minnesota Geological
Survey, p. 204-217.
22
�IR 46/2E/14B
Title:
Hurley Overpass.
Location:
Tyler Formation.
Junction U.S. Highway 2 and U.S. Highway 51 north of Hurley, Wisconsin.
SE~, SE~, NE~, Sec. 14, T.46N., R.2E., Iron County.
(Ironwood
7~-minute topographic quadrangle, 1975)
77
Author:
Gene L. LaBerge, 1978
Description: This exposure is characteristic of most of the Tyler Formation which
conformably overlies the Ironwood Iron-formation, and is the youngest Middle ~re
cambrian unit recognized on the Gogebic Range. The unit is generally referred to
as the Tyler "slate," although Alwyn (1976) reports that the formation is about
one-third slate and two-thirds graywacke sandstone. Alwyn (1976) reports that the
Tyler formation is approximately 7,000 feet thick in this area, but increases in
thickness westward to about 12,000 feet near Mellen. Schmidt and Hubbard (1972)
report that the Tyler has been completely removed by pre-Keweenawan erosion to the
east. Because of its stratigraphic relations, the Tyler is generally correlated
with the Virginia and Rove formations in Minnesota and with the Michigamme formation in Michigan (Leith, Lund, and Leith, 1935; James, 1960).
Sedimentological studies led Alwyn (1976) to conclude that the Tyler formation
was derived mainly from a granitic terrane and that sediment transport was northward into the Animikie basin. Thus, he postulates a granitic landmass south of
the Gogebic range shedding abundant clastics. The presence of probable Middle
Precambrian submarine volcanics near Mercer approximately 20 miles to the south
23
�IR 46/2E/14B (2)
PREeM"R IAN Y
ROCKS
r-
I
PRECAMflRIAN X ROCKS
SOUTH
+
2000 FEET
+
+
+
+
+
+
+
+
+
+
2000 FEET
+
+
...
...
+
+
+
...
+
...
+
+
+
+
+
...
...
+
+
+
+
+
+
+
+
+-
+
++
...
+
+
+
...
+
+
+
+
+
+
+
+
+
+
PRECAMBRIAN W ROCKS
Generalized diagram of the relationship of Precambrian
rocks in the central Gogebic district
EROSION SURFACE
NORTH
SOUTH
+
1-
+
+
+
+
1-
+.
+
+
...
+
<-
+
1-
+-
+
+.
+
...
+
++
t-
+
+
+
...
+
+
+
+-
+
+.
+
+
+
+
+
+
+
+
+
+
+
+
+
t
++
+
Hypothetical post-Penokean pre-Keweenawan cross-section on
same surface as front of block diagram above
24
+
+
�IR 46/2E/14B
(3)
(Allen and Barrett, 1914; Dutton and Bradley, 1970) suggest that the granitic
landmass must have been narrow. Assuming that the volcanics near Mercer are
correlative with those in the Ironwood Iron-formation in the eastern Gogebic range
(Aldrich, 1929), limits on the size of the landmass would suggest that it must
have been tectonically uplifted to continue to provide the source of sediments for
the Tyler Formation.
The dip of the Tyler Formation at this location is 70 0 N\~. Graded beds and
other primary structures indicate that the beds are right-side up (Schmidt and
Hubbard, 1972). Cleavage in the shaly layers dips less steeply than the bedding
(about 30 0 NW). According to Schmidt and Hubbard (1972), this cannot be a
Keweenawan axial plane cleavage because that cleavage would dip more steeply than
the bedding. If this is an axial plane cleavage, it must have formed during an
earlier deformation, presumably the Penokean Orogeny.
Discussion: Schmidt and Hubbard (1972) point out that the basal Keweenawan dips
more steeply northward than the Middle Precambrian Tyler and Ironwood Formations,
suggesting that the Middle Precambrian was dipping south'during early Keweenawan
time. The cleavage to bedding relationship at this stop also suggests that the
Tyler Formation was dipping south at the time the cleavage formed. Thus, the
present orientation of the units is a result of subsidence of the Lake Superior
syncline during Keweenawan time, as shown for most of the Gogebic range, suggesting
that a block approximately 60 miles long and perhaps 10-15 miles wide rotated
northward nearly 90 0 with no obvious internal deformation.
The tilting of this block occurred after deposition of the Oronto Group (of
early Late Keweenawan time (Craddock, 1972)) because of the Freda sandstone dips
near vertically along the Montreal River on the Michigan-Wisconsin border. This
suggests that the Tyler and other Middle Precambrian rocks were buried beneath
at least 12 miles (20 kms) of Keweenawan basalts and sandstones during the Late
Precambrian. However, the low metamorphic grade of the Tyler at this locality is
difficult to reconcile with the interpretation of having been buried to a depth
of 12 miles. Either an unusually low geothermal gradient of burial was too short
to affect much recrystallization, or heretofore unrecognized structures in the
Keweenawan sequence give an exaggerated apparent depth of burial. The last
alternative seems most likely. Most recognized faults (and the most obvious ones)
on the Gogebic are cross-faults; however, mine mapping (Hotchkiss, 1919) has
demonstrated the presence of bedding faults and strike faults in the Ironwood
Iron-formation. The strike faults duplicate the section in places. I suggest
that strike faults (or perhaps thrust faults) exist in the Keweenawan duplicating
the section to give an exaggerated thickness of Late Precambrian rocks and
therefore an exaggerated apparent depth of burial for the Tyler Formation in
this area. Perhaps the question should be raised whether the cleavage may be
related to these postulated thrust faults, and therefore of Keweenawan age.
Resolution of this problem is pertinent to an understanding of both the Middle
and Late Precambrian geology of the Lake Superior region.
References Cited:
Aldrich, H.R., 1929, The geology of the Gogebic Iron Range of Wisconsin:
Wisconsin Geological and Natural History Survey Bulletin 71, 279 p.
25
�IR 46/2E/14B (4)
Allen, R.C., and Barrett, L.P., 1915, Contributions to the pre-Cambrian geology
of northern Michigan and Wisconsin: Michigan Geological and Biological
Survey, Publication 18, p. 65-129.
Alwyn, B.W., 1976, Sedimentation of the Middle Precambrian Tyler Formation of
north-central Wisconsin and northwestern Michigan: Unpub. M.S. Thesis,
University of Minnesota-Duluth, 175 p.
Craddock, C., 1972, Late Precambrian - Regional geologic setting: in P.K. Sims
and C.B. Morey, editors, The Geology of Minnesota (C.M. Schwartz Volume):
Minnesota Geological Survey, p. 281-291.
Dutton, C.E., and Bradley, R.E., 1970, Lithologic, geophysical and mineral
commodity maps of Precambrian rocks of Wisconsin: U.S. Geological Survey
Miscellaneous Geological Investigation Map 1-631, 1:500,000, 6 sheets,
separate text.
Hotchkiss, W.O., 1919, Geology of the Gogebic Range and its relation to recent
mining developments: Engineering/Mining Journal, v. 108, p. 443-452, 501-507,
537-541, 577-582.
James, H.L., 1960, Problems of stratigraphy and correlation of Precambrian rocks
with particular reference to the Lake Superior Region: American Journal of
Science, v. 258-A, p. 104-114.
Leith, C.K., Lund, P.J., and Leith, A., 1935, Precambrian rocks of the Lake
Superior Region: U.S. Geological Survey Professional Paper 184, 34 p.
Schmidt, R.G., and Hubbard, H.A., 1972, Penokean Orogeny in the central and western
Gogebic Region, Michigan and Wisconsin: Field Trip A, 18th Annual Institute
on Lake Superior Geology (Houghton, Michigan).
26
�IR 42/4E/28B
Title:
Bear River-Powell Kyanite
Location:
On State Hwy. 182 approximately 1 mile west of State Hwy. 47.
SE\, SW\, Sec. 28, T.42N., R.4E. (Wilson Lake, 7Yz-Minute
Topographic Quadrangle, Vilas County).
47
Author:
Gene L. LaBerge (1978)
Description: This exposure is part of a sequence of upper amphibolite facies
gneisses and schists that occur as widely scattered outcrops along the
Flambeau River flowage. Magnetic surveys and diamond drilling suggest that this
sequence of rocks continues eastward into northern Michigan, and the occurrence
of iron-formation, pellitic rocks and volcanics has served as a basis for
correlating these rocks with the much lower-grade rocks on the Gogebic range
(Allen and Barrett, 1915). James (1955) includes this area in the core of his
"Watersmeet node," an elongate area of high-grade regional metamorphism, and
Dutton and Bradley (1970) show that metamorphic intensity decreases in
directions from this high-grade center.
l1ain lithologies present include amphibolites, quartzo-feldspathic gneisses
and schists, some of which contain staurolite and kyanite ±sillimanite
(Black, 1977). Exposures here are mainly garnet-staurolite-kyanite-bearing
schists, although sillimanite is present in small amounts. The sillimanite
occurs as incipient crystal clusters in the kyanite. Black (1977) concluded that
27
�IR 42/4E/28B (2)
the mineral assemblage kyanite-staurolite-muscovite + sillimanite suggests
metamorphism at 685 0 C and a pressure of about 7.5 Kb. This indicates that
the rocks were metamorphosed at a depth of 25 kilometers and at temperatures
at or near minimum melting range (Black, 1977).
The rocks have been intensely folded about an east-northeast trending
fold axis with a prominent east-northeast foliation. Quartz boudins, intrafolial
folds, disconnected fold hinges and limbs, and augen and other features of
transposed bedding are common and obliterate most primary features of the rocks
(Black, 1977). The sequence probably represents a highly deformed and metamorphosed pile of mafic to felsic volcanic rocks and graywackes.
The high-grade rocks are bounded on the north by a sequence of less deformed,
and less metamorphosed mafic-intermediate volcanics, iron-formation and slate
(Allen and Barrett, 1915; Black, 1977). The boundary between these sequences
contains a prominent zone of electrical conductivity called the flambeau Anomaly
(Sternberg and Clay, 1977). The anomaly is evidently produced mainly by highly
graphitic rocks that extend a minimum of 17 kilometers into the crust. The
conductive zone extends west-southwesterly more than 100 km to near Couderay in
Sawyer County.
Discussion: Allan and Barrett (1915) interpreted the boundary between the
greenstones on the north and the high-grade rocks on the south as an unconformity. Black (1977) interprets the boundary as a major fault with the south
side uplifted. The proposed fault may correlate with Sims' (1976) postulated
boundary between a 2650-2700 m.y. old granite-greenstone terrane to the north
and an older gneiss terrane to the south (Black, 1977). The Flambeau Anomaly
appears to be in-folded or in-faulted along the boundary between the greenstones
(of unknown age) and high-grade metamorphic rocks (also of unknown age).
Thus, the more recent interpretations of the geology in this area raise
the question of whether the high-grade metamorphic rocks exposed here are really
correlative with the Tyler Formation of the Gogebic. The stratigraphic position
of the greenstones to the north is also debatable. Alwyn's (1976) interpretation
of a granitic landmass south of the Gogebic as a source area for the Tyler
coupled with the recent recognition of major faults and the Flambeau Anomaly
suggests that the geology may be far more complex than heretofore recognized.
References Citied:
Allen, R.C., and Barrett, L.P., 1915, Contributions to the pre-Cambrian geology
of northern Michigan and Wisconsin: Michigan Geological and Biological
Survey, Publication 18, p. 65-129.
Alwyn, B.W., 1976, Sedimentation of the Middle Precambrian Tyler Formation of
north central Wisconsin and northwestern Michigan: Unpub. M.S. Thesis,
University of Minnesota-Duluth, 175 p.
Black, F.M., 1977, The geology of the Turtle-Flambeau area: Iron and Ashland
Counties, Wisconsin: Unpub. M.S. Thesis, University of Wisconsin-Madison,
150 p.
28
�IR 42/4E/28B (3)
Dutton, C.E., and Bradley, R.E., 1970, Lithologic, geophysical and mineral
commodity maps of the Precambrian of ~~isconsin: U.S. Geological Survey
Miscellaneous Geologic Investigation }1ap 1-631, 1:500,000, 6 sheets,
separate text.
James, H.L., 1955, Zones of regional metamorphism in the Precambrian of northern
Michigan: Geological Society of America Bulletin, v. 66, p. 1455-1487.
Sims, P.K., 1976, Presidential address - Precambrian tectonics and mineral
deposits, Lake Superior Region: Economic Geology, v. 71, no. 6, p. 1092-1118.
Sternberg, B.K., and Clay, C.S., 1977, Flambeau Anomaly: Ahigh-conductivity
anomaly in the southern extension of the Canadian Shield: in J.G. Heacock,
editor, The Earth's Crust: American Geophysical Union Monograph 20,
p. 501-530.
29
�ON 36/llE/29
Title:
Monico East - Mafic Pillow Basalt
Location: Intersection of U.S. 8 and County V, center of Sec. 29, T.36N.,
R.llE., Oneida County (Monico 7Yz-minute topographic quadrangle, 1965).
45
8
&
8
47
Author:
M.G. Mudrey, Jr. (1978)
Description: A large outcrop is in the southwest corner of the intersection. The
rock consists predominantly of sulfide-bearing, gray-green, chloritic pillow
basalt trending N. 85 0 E., and dipping 80 0 SE. The two-foot thick by three-foot
long pillows are slightly stretched and top to the south. Original pyroxene has
altered to hornblende and chlorite. Plagioclase is extensively altered. The
southeast edge of the outcrop is a ten-foot thick massive flow or sill. Diabasic
texture in this unit is well developed.
Discussion: Two supracrustal sequences characterize the Middle Precambrian
succession in northern Wisconsin and Michigan, a dominantly sedimentary unit
including iron formations to the north, and a dominantly volcanic sequence including
massive sulfide deposits to the south. Inasmuch as bedrock exposures are poor south
of the Gogebic Range area, geologic maps of northern Wisconsin are based dominantly
on geophysical interpretation. Units defined in the few areas of outcrop are
extrapolated into the poorly exposed areas. The belt of rocks from Ladysmith on
the west to Pembine on the east appears to be dominantly volcanic, with few
intrusives. The volcanics in the Monico area are among the least deformed and better
exposed in this belt. Pillows and other indicators of subaqueous deposition are
evident in the volcanic rocks exposed in the Monico area. These features are well
preserved because of the low metamorphic grade. The sequence around Monico appears
30
�ON 36/llE/29 (2)
to young to the south, and the sequence is known to be repeated by faulting that
trends east-northeast. This particular outcrop appears to lie stratigraphically
above the massive sulfide deposit at Pelican River to the west, and possibly
above the Crandon deposit to the east. It is representative of the basaltic
rocks in the Monico area.
�ON 36/llE/30
Title:
Monico Gravel Pits - Andesite Pillow Lava
Location: Exposures are at the top of the hill behind houses on Baade and Lake
Roads, and on the north side of the gravel pit to the west, NE~, NE~, Sec. 30,
T.36N., R.llE., Oneida County (Monico 7~-minute topographic quadrangle, 1965).
Author:
M.G. Mudrey, Jr. (1978)
Description: The outcrops consist of pillowed. fine grained. light gray andesite
with sparse to abundant quartz and plagioclase phenocrysts. The pillows appear
to top south. Schriver (1973, p. 25) describes the rocks as amygdaliodal basalt.
In the gravel pit, the amygdule fillings have weathered out, leaving a pockmarked vesicle texture. Amygdules constitute up to three percent of the rock.
range in size up to three mm, and have a ~lobular shape, but are generally
undeformed. A chlorite rim encloses the amygdule filling of epidote or epidote and
quartz. The groundmass consists predominantly of epidote and actinolite less than
0.05 mm in size. Plagioclase phenocrysts are largely altered to epidote and
calcite and appear to be around AnZ5-30'
Schriver (1973, p. SO, no. 16) reports the following chemical data:
SiO Z
TiOZ
Al Z0 3
FeO T
MuO
53.5
0.7
14.0
9.3
0.1
Molecular Norm (Irvine-Baragar)
Q
ZO.5
Or
0.3
Ab
10.1
An
15.3
Ho
12.9
3Z
�On 36/llE/30 (2)
MgO
CaO
Na20
K20
6.9
10.6
2.1
0.1
Total
97.3
En
Fs
Mt
II
25.5
12.0
2.1
1.3
Other analyses of this unit several miles to the southwest contain more
silica and potassium, and might more properly be termed dacite.
Other outcrops of this unit may be found on the hills to the southwest and
to the northeast. Mapping in 1978 by Mudrey suggests that this unit can be traced
along an east-northeast strike about 3/4 mile. Mapping also suggests that this
unit overlies the tuffaceous agglomerate unit to the east and south.
Discussion: Intermediate to felsic Middle Precambrian volcanism characterizes the
northern Wisconsin volcanic belt. May (1977) describes the host rocks associated
with the Flambeau deposit near Ladysmith, and Schmidt and others (1978) describe
similar rocks associated with the Crandon deposit. Recently, Bowden (1978)
described a similar sequence of rocks at the Pelican River deposit. Present mapping and geophysics suggest that the sequence of volcanic rocks immediately
around Monico are close to the same stratigraphic position as the rocks at
Pelican River. This exposure probably lies stratigraphically beneath the Pelican
ore body, although definitive mapping has not been completed.
References Cited:
Bowden, D.R., 1978, Volcanic rocks of the Pelican River massive sulfide deposit,
Rhinelander, Wisconsin: A study in wallrock alteration: Unpub. M.S. Thesis,
Michigan Technological University, 62 p.
May, E.R., 1977, Flambeau - A Precambrian supergene enriched massive sulfide
deposit: Geoscience Wisconsin Vol. 1, p. 1-26.
Schmidt, P.G., Dolence, J.D., Lluria, M.R., and Parsons, G., III, 1978, Geology
of the Crandon massive sulfide deposit in Wisconsin: Skillings' Mining
Review, v. 67, no. 18, p. 1, 8-11.
Schriver, G.H., 1973, Petrochemistry of Precambrian greenstones and granodiorites in southeastern Oneida County, Wisconsin: Unpub. M.S. Thesis,
University of Wisconsin-Milwaukee, 83 p.
33
�(00
Title:
Witte Farm - Coarse Felsic Agglomerate
/""
ON 36/11E/2l
"'~
Location: 1.4 miles north of intersection of U.S. 8 and U.S. 45. Outcrop located
400 feet east of highway behind abandoned house. SE~, NW~, Sec. 21, T.36N.,
R.llE., Oneida County (Monico 7~-minute topographic quadrangle, 1965).
Author:
M.G. Mudrey, Jr. (1979)
Description: Three-foot long, angular, dacite clasts range in size from inches to
several feet are set in an amphibole-bearing tuff or graywacke. Within the clasts,
sparse euhedral plagioclase phenocrysts (An20) up to 1.8 mm in maximum dimension
are set in a flow banded matrix which wraps around the crystals. The rock is
intensively altered, and sericite extensively replaces plagioclase. The groundmass
consists predominantly of quartz, muscovite, and calcite. Blood red hematite is
present, along with local concentrations of epidote and chlorite.
The matrix for the clasts consists of altered mineral grains 0.3 to 0.4 rnrn in
size. A few relict (? pyroxene (?) and amphibole crystals remain, but the grains
in the matrix consist predominantly of epidote-chlorite-muscovite-quartz granules.
Calcite occurs abundantly as granules and in veins. Blood red hematite is sparse,
and reflict glass shards can be seen in thin sections.
The trend of bedding is N. 70 0 -75 0 W. and dips 85 0 SW. About 700 feet to the
northeast, intermediate pillow lavas appear to top south, however the bedding
trend at this locality is N. 60 0 W. This is the only area of the quadrangle in
which folding has been suggested.
34
)
�ON 36/llE/2l (2)
A small body of intrusive granodiorite can be found about one thousand feet
north.
Discussion: Sangster (1972) noted the close spatial association between felsic
agglomerates (or coarse pyroclastics) and massive sulfide ores, and that these
agglomerates were a characteristic feature of many mining regions. Sangster
(1972, p. 3) remarks that "the author L-Sangster=/ once remarked to his colleagues
that whenever he stood on the outcrop containing the largest fragments of acid
pyroclastic in any given mining camp, he could invariably hear the mine mill
nearby. His colleagues immediately dubbed this distinctive lithology 'millrock'
and since then, 'millrock' has been observed close by most massive sulfide
deposits in Precambrian volcanic rocks." The interpretation of this distinctive
lithology is still open. Millrock is generally found in, or close to volcanic
units in which the massive sulfides occur. The belt of rocks from the Pelican
deposit, about 7 miles west, to several miles east of this locality has been
extensively explored since the early 1970's. Although only the Pelican deposit
has been announced as a possible massive sulfide deposit, the intensity of
exploration attests to the favorable terrane.
References Cited:
Sangster, D.F., 1972, Precambrian volcanogenic massive sulfide deposits in Canada:
A review: Geological Survey of Canada Paper 72-22, 44 p.
35
�ON 36/10E/26
Title:
Monico West - Section 26 Pyritic Tuff
Location: Old U.S. 8 west of Monico, SE~, NW~, Sec. 26, T.36N., R.IOE.,
Oneida County (Monico 7~-minute topographic quadrangle, 1965).
8
&
47
8&47
Author:
M.G. Mudrey, Jr. (1978)
Description: The low outcrop on the north side of the road is a fine, light-gray,
pyritic, indistinctly bedded lithic-crystal tuff which trends N. 60 0 -70 0 E. and
dips vertically. The crystals consist of millimeter-sized, sericitized plagioclase.
Most of the crystals are euhedral and embayed and corroded. Less altered lithic
fragments contain minor amphibole. Actinolite, chlorite, and epidote are the
dominant alteration minerals. Prehnite (?) and hematite are sparse.
The low ledge on the south side of the road consists of beds of gray, finegrained, chloritic crystal tuff and bedded, light gray, aphanitic ash. The tuff
is similar to the tuff on the north side, but matrix is more abundant, and the
crystals sparser. Chlorite in the ash is berlin blue in thin section. This
volcaniclastic unit varies considerably from fine tuffs and ashes to lapilli tuff.
The unit is 3,000 to 4,000 feet thick and can be traced along strike at least
three miles.
Discussion: Massive sulfide are bodies consist mainly of sulfide-rich tuff, and
grade distally into pyritic tuffs. These lithologies usually do not crop out
because the sulfides weather readily. Therefore, the sulfide-rich outcrop here
is unusual. It illustrates the general lithology and composition of the distal
ends of a massive sulfide are body. Some outcrops in the area contain more
36
�ON 36/l0E/26 (2)
sulfide than this One. A recent road cut in Sec. 21, T.36N., R.llE. contains
abundant sulfidic and sericitic schists, and may represent the lateral equivalent
of the mineralized zones at Little Sand Lake. The trend of bedding at this
locality and at the Crandon deposit near Little Sand Lake in Forest County is
slightly north of due west, and on projection this locality could be essentially
the same stratigraphic horizon as that at Little Sand Lake. Intervening between
the two, however, is the granite body at Jennings (exposed at Beck Tower Wayside).
Wisconsin aeromagnetic data suggest a northwest-trending fault immediately west
of the Little Sand Lake deposit, therefore, this particular exposure probably is
not directly correlatible with Little Sand Lake, but does illustrate many of the
rock types spatially associated with the host rocks for the massive sulfide
deposit.
37
�On 35/llE/6
Title:
Beck Tower Wayside Park - Jennings Granite
Location: 2~ miles south of Monico on U.S. 45 and State 47 S\V~ SEY. Sec 6
T.35N., R.llE., Oneida County (Monico 7~-minute topographic'qua~;ang;~, 1965)~
Author:
M.G. Mudrey, Jr.
Description: This outcrop is a coarse, red, biotite granite and exhibits
spheroidal weathering. Another outcrop is present 500 feet to the northeast in
a railroad cut. Fresher outcrops of the same granite are found near Jennings,
about 6 miles east. According to Venditti (1973, p. 46), the rock contains
euhedral orthoclase, microcline and microperthite (40 percent), subhedral to
euhedral oligoclase (An27, 23 percent), anhedral quartz (31 percent), and minor
amounts of interstitial biotite (3 percent). The biotite is pleochroic and
light brown to dark brown, is sagenitic, and altered to chlorite. The grain size
is 4-5 mm and shows no cataclastic textures at this outcrop, although outcrops
near Jennings show narrow, well developed mylonitic zones.
Venditti (1973, p. 90, no. 24) reports the following analysis:
73.1
tr
15.5
1.5
tr
tr
Si02
Ti02
A1 2 0 3
FeaT
MnO
MgO
38
�On 35/llE/6 (2)
CaO
Na 2 0
1.5
3.0
4.3
Total
98.9
K2 0
Van Schmus and others (1975, p. 1259, no. D1356) report a Rb-Sr age of
1,580 m.y. from this locality. Van Schmus (in press) reports a U-Pb zircon age
of 1,765± 10 m.y. from this locality.
Discussion: The potassic granitic intrusives in the Middle Precambrian of northern
Wisconsin are all post-tectonic, and their ages cluster around 1,765 m.y. The
younger 1,600 m.y. Rb-Sr age represents a wide-spread alteration of Rb-Sr ages
that is not fully understood.
Van Schmus (in press) has divided the Middle Precambrian igneous activity
into two pulses. The older one began with mafic to felsic volcanism 1,850~ 20 m.y.
ago, and was followed immediately by tonalitic to granitic plutonism 1,840 1,820 m.y. ago. Structural studies by Maas (1977) indicate that these rocks were
emplaced during the main phase of the Middle Precambrian thermotectonic event.
The second pulse consisted predominantly of phyolitic and granophyric granite and
occurred about 1,765± 10 m.y. ago. No plutonic units have been found so far with
zircon ages in excess of 1,850, nor have any been found with ages on the order of
1,615 - 1,630 m.y., the time of widespread alteration of the Rb-Sr isotopic
systems in the region.
After emplacement of the late granites, major faulting occurred (LaBerge
and Myers, 1976 and LaBerge, 1977), and has been recently studied to the south
in Marathon County. Late faulting is recognized in north-central Wisconsin as
seen in the mylonitic samples from Jennings. Extent and magnitude of the faulting
in north-central Wisconsin is not known.
References Cited:
LaBerge, G.L., 1977, Major structural features in central Wisconsin and their
implications to the Animikie Basin (abs.): 23rd Annual Institute on
Lake Superior Geology (Thunder Bay, Ontario).
LaBerge, G.L., and Myers, P.E., 1976, The Central Wisconsin Batholith (abs.):
22nd Annual Institute on Lake Superior Geology (St. Paul, Minnesota).
Maas, R.S., 1977, Structure and petrology of an Early and ~iddle Precambrian
gneiss terrane between Stevens Point and Wisconsin Rapids, Wisconsin:
Unpub. M.S. Thesis, University of Wisconsln-Madison, 128 p.
Van Schmus, W.R., in press, Chronology of igneous rocks associated with the
Penokean orogeny in Wisconsin: Geological Society of America Memoir.
Van Schmus, W.R., Thurman, E.M., and Peterman, Z.E., 1975, Geology and Rb-Sr
chronology of Middle Precambrian rocks in eastern and central ~visconsin:
Geological Society of America Bulletin, V. 86, p. 1255-1265.
Venditti, A.R., 1973, Petrochemistry of Precambrian rocks in southeastern
Oneida County, Wisconsin: Unpub. M.S. Thesis, University of WisconsinMilwaukee, 93 p.
39
�Pr 34/2W/20
Title:
Jump River at Big Falls County Park
Location: Along the Jump River in NE~, NE~, Sec. 29, and SE~, Sec. 20, T.34N.,
(Jump River Fire Tower, Topographic Quadrangle,
R.2W., Price County.
1970).
N
N
Author:
Gene L. LaBerge
Description: The main rock type exposed here is a weakly foliated quartz
monzonite of presumed Middle Precambrian age. Foliation strikes approximately
east-west and dips vertically. Late stage aplite dikes along with minor
pegmatite and vein quartz cut the main quartz monzonite body.
DO\Vllstream from the main park area the rock has been extensively sheared to
f1aser gneiss and mylonite. The main catac1astic foliation is oriented approximately east-west with a vertical dip and is about one-half mile wide. Within
the catac1astic zone are smaller mylonitic zones that strike N.30 o E. and about
40 o SE.
Pyritic tuffaceous andesitic(?) greenstone crops out at the major bend in the
river approximately three-quarters of a mile downstream from the park. ~ood
preservation of primary textures suggests the rocks have undergone only greenschist
or lower amphibolite facies metamorphism. A number of exposures of mafic rocks
are present along the river between the tuffaceous greenstone and quartz monzonite.
They appear to be somewhat metamorphosed and sheared.
40
�Pr 34/2W/20 (2)
Discussion: This exposure is along a major structural feature in Wisconsin, the
"Jump River lineament" (Myers, 1974). The lineament is expressed topographically
and on both the Bouguer anomaly gravity map (Ervin and Hammer, 1974), and the
aeromagnetic map (Zietz, Karl, and Ostrom, 1978). Where exposed, the lineament
consists of cataclastic rocks. North of the lineament of the rocks are dominantly
volcanic rocks in the greenschist and/or lower amphibole facies with numerous
more or less foliated granitic plutons. This forms a major east-west volcanic
belt of Middle Precambrian rocks across Wisconsin from the Michigan border westward to the Keweenawan overlap (Sims, Cannon, and Mudrey, 1978). (Note that the
"Jump River Fault" of Sims, Cannon, and Mudrey (1978) does not coincide with the
"Jump River lineament" of Myers (1974).)
South of the lineament, gneisses, amphibol~tes, schists and migmatites are
the predominant rock types for nearly 30 miles. Relatively unmetamorphosed
volcanic and plutonic rocks are common in Marathon County and are in fault
contact with the gneisses (LaBerge, 1977). Little or no work has been done on
the high-grade rocks; however, they appear to be mainly amphibolite grade with
few, if any, primary features preserved. Cummings and Myers (1978) and Myers
(1977) have studied similar rocks in the Eau Claire area that are evidently part
of this terrane, and they concluded that the rocks are at least in part Early
Precambrian. Probable Middle Precambrian granitic rocks intrude the highergrade rocks, and isolated patches of low-grade metavolcanic and metasedimentary
rocks are present in places (Myers, 1978a, b). The low grade metamorphic rocks
are probably Middle Precambrian in age, but no age determinations are available
on the higher grade rocks. Thus, we do not know whether the high-grade rocks
represent an Early Precambrian basement on which simply more highly metamorphosed
Middle Precambrian rocks. The "horst-graben" pattern in Central Wisconsin is
suggestive of basin and range structure. The implications of this structure, as
well as its timing, has important bearing on our interpretation of the tectonic
development of the Animikie Basin. As indicated here, the emplacement of at
least some of the granitic plutons occurred prior to final displacement along the
fault zones. If this is a Penokean age pluton, the faulting must be either late
Penokean or post-Penokean in age.
References Citied:
Cummings, M.L., and Myers, P.E., 1974, Eau Claire River at Big Falls:
Wisconsin Geological and Natural History Survey, Geology of Wisconsin Outcrop Description EC 27/8W/13, 10 p.
Evin, C.P., and Hammer, S., 1974, Bouguer anomaly gravity Map of T..visconsin:
Wisconsin Geological and Natural History Survey, scale 1:500,000, 2 sheets,
separate text.
LaBerge, G.L., 1977, Major structural features in central Wisconsin and their
implications on the Animikie Basin (Abs.): 23rd Annual Institute on
Lake Superior Geology (Thunder Bay, Ontario), p. 23.
Myers, P.E., 1977, Eau Claire River at Little Falls: Wisconsin Geological and
Natural History Survey, Geology of Wisconsin Outcrop Description
EC 27/8W/19, 6 p.
Myers, P.E., 1978a, North Fork of the Eau Claire River at Knight Pool: lJisconsin
Geological and Natural History Survey, Geology of Wisconsin Outcrop
Description EC 26/5W/lO, 2 p.
41
�Pr 34/2W/20 (3)
Myers, P.E., 1978b, Eau Claire River at Confluence of North and South Forks:
Wisconsin Geological and Natural History Survey, Geology of Wisconsin
Outcrop Description EC 26/5W/29, 2 p.
Sims, P.K., 1976, Presidential address - Precambrian tectonics and mineral
deposits, Lake Superior Region: Economic Geology, v. 71, no. 6,
p. 1092-1118.
Sims, P.K., Cannon, W.F., and Mudrey, M.G., Jr., 1978, Preliminary geologic
map of Precambrian rocks in part of northern Wisconsin: U.S. Geological
Survey Open-file Report 78-318, scale 1:250,000, 2 sheets.
Zietz, I., Karl, J.H., and Ostrom, M.E., 1978, Preliminary aeromagnetic map
covering most of the exposed Precambrian terrane in Wisconsin: U.S. Geological Survey Miscellaneous Field Study MF-888, scale 1:250,000.
42
�SW 38/7W/23
Title:
Arpin Dam in Radisson - Late Porphyritic Granite
Location: River channel downstream from Arpin Dam, one mile southeast of Radisson,
NW\, SE\, Sec. 23, T.38N., R.7W., Sawyer County (Radisson 7~-minute topographic
quadrangle, 1972)
Author:
M.G. Mudrey, Jr. (1978)
Description: Outcrops are reasonably abundant in the vicinity of Radisson. The
bedrock consists of a coarse, hornblende-granodiorite with inch-sized microcline
megacrysts generally aligned N. 50o~E. Medium-granied aplite dikes up to onefoot wide trend N. 15 0 -35 0 E. The granodiorite consists of subhedral to euhedral
microcline set in a groundmass of sutured quartz grains, subhedral plagioclase
(An 15-20),
minor brown biotite slightly altered to chlorite, and green
hornblende with trace amounts of apatite, epidote and zircon are found. The
aplite dikes consist of equal amounts of subhedral plagioclase (An 20), microcline,
and anhedral quartz. Trace quantities of muscovite, chlorite and zircon are
present. Van Schmus (in press) reports an U-Pb zircon age of 1,765 10 m.y. for a
sample from Grimh Flowage, about 0.6 miles west of this locality.
Discussion: This granodiorite, the Jennings granite, other alkalic granites,
and the rhyolites of south-central Wisconsin are all late Penokean and yield ages
around 1,765 m.y. For the most part, the granitic rocks are little deformed,
but all yield Rb-Sr ages around 1,600 m.y. The 1,600 m.y. age is widespread.
However, there appears to be no rock units or major structures related to this
resetting in northern Wisconsin. Smith (1978) has determined that the Baraboo
43
�SW 38/7W/23 (2)
Quartzite and the rhyolites of southern Wisconsin were metamorphosed and deformed
about this time. The 1,600 m.y. age is pre-Wolf River and associated rapakivi
granites, syenites and anorthosites. Some of the faulting in the area may be
related to this 1,600 m.y. thermal event.
The Radisson granodiorite is similar to the Rockville Granite of Minnesota,
both in petrography and in age (Keighin and others, 1972, p. 240).
References Cited:
Keighin, C.W., Morey, G.B., and Goldich, S.S., 1972, East-Central Minnesota:
in P.K. Sims and G.B. Morey, editors, The Geology of Minnesota
(C.M. Schwartz Volume): Minnesota Geological Survey, p. 240-255.
Smith, E.I. 1978, Precambrian rhyolites and granite in south-central Wisconsin:
Field Relations and geochemistry: Geological Society of American Bulletin,
v. 89, p. 875-890.
Van Schmus, W.R., in press, Chronology of igneous rocks associated with the
Penokean orogeny in Wisconsin: Geological Society of American Memoir.
44
600-3 J 9T025-79
�
https://digitalcollections.lakeheadu.ca/files/original/eec5ad95f486276a3fc18dd307239f9b.pdf
8d0703cdf8c8bf578aa79690dfd9c0ec
PDF Text
Text
DEPARTMENT OF GEOLOGY, UNIVERSITY OF MINNESOTA
AT DULUTH
QUATERNARY GEOLOGY OF
THE DULUTH AREA
BY
CAROL M. MOSS, RANDEE
J,
ZARTH
CHARLES L. MATSCH
AND
---------
I
PREPARED FOR FIELD TRIP N0.3 OF
GEOLOGICAL
THE
NORTH-CE:·!TRA.L SECTIO~!
SOCIETY OF AMERICA 13TH ANNUAL MEETING AND
INSTITUTE
OF
LAKE SI.IPERIOR
GEOLOGY
MAY 3-12, 1979
DULUTH, MINNESOTA
MAY 12, 1979
25TH i'1EETING
THE
�DEPARTMENT OF GEOLOGY, UNIVERSITY OF MINNESOTA
AT DULUTH
QUATERNARY GEOLOGY OF
THE DULUTH AREA
BY
CAROL M. MOSS, RANDEE
J,
ZARTH
AND
C!1ARLES L. MATSCH
CHARLES L. MATSCH, FIELD TRIP LEADER
PREPARED FOR FIELD TRIP N0.3 OF THE NORTH-CENTRAL SECTION
GEOLOGICAL SOCIETY OF AMERICA 13TH ANNUAL MEETING AND THE
INSTITUTE OF LAKE SUPERIOR GEOLOGY 25TH MEETING
MAY 12, 1979
��1
PHASES OF GLACIAL
¾;
ACTIVITY IN
NNESOTA
.,_
1
1-------,;i;_
·--·T-.i..,
!
\. j
r,.c\i>-
i
·-·-
""o
--
4ss,~
---=-
· lae•c" ~_,_.__.,,,__,
~•-T£.-~,·
~
4o
I,
,s..
r· . ,.
•
•
!
I
--
LAKE
'----·-·-\
~
:-=-===
,. .--;ro~
, . b
--
R
LAKE DULUTH
LEGEND
AGE OF ICE
•Dc~rOldHI
□
~
I]
•
■
~
-
SCALE
,o
v......,.
,.
-WUN
Source: Geology of Minnesola: A Cen1t,nn1 ■ f Volume
Frontispiece drafted by Mark Zwaschka; reproduced through the courtesy of
the Department of Geography, UMD.
��QUATERNARY GEOLOGY OF THE HEAD OF LAKE SUPERIOR REGION
Regional Setting
Bedrock
The northwestern shore of Lake Superior lies generally parallel to
the strike of a southeastward dipping sequence of lava flows and mafic
intrusive rocks emplaced about 1.2 b.y. ago (Fig. 1).
This Keweenawan
volcanic pile called the North Shore Volcanic Group is composed mainly
of basalt, but includes significant volumes of rhyolite and lavas of
Fig. 1.
General geologic map of Minnesota and
adjacent states.
1
�intermediate composition.
The flows are estimated to be over 20,000
feet thick (Green, 1972).
The largest of the associated intrusive
bodies is the Duluth Complex, a meld of mafic material, mainly gabbro
and anorthosite, but including the felsic rock granophyre.
Smaller
intrusions in the form of dikes and sills lace the entire section.
Geophysically, rocks of similar density are traceable as a gravity
high southwestward as far as Kansas,
region (Fig. 2).
and elsewhere in the Great Lakes
The belted configuration as well as the composition of
the rocks suggests that the entire sequence represents an episode of
crustal rifting and insipient sea-floor spreading.
That the process
aborted is indicated by the insignificant width of the mafic rock belt.
0
0
Miles
250
Kilometers
400
Minnesota
\
Wisconsin
Nebraska
Fig. 2.
The mid-continent gravity high outlines the
distribution of basaltic rocks emplaced during
a rifting event about 1. 1 b. y. ago.
2
�Following the cessation of volcanic activity, the last to occur in
this part of the earth's crust, subsidence of the area resulted in the
tilting of the entire sequence gently eastward.
sediments accumulated in the subsiding basin.
A thick wedge of elastic
These Late Precambrian
sediments include the arkosi.c Fond du Lac Formation and the Hinckley
Sandstone.
Paleozoic marine transgressions either did not reach the western
Lake Superior region, or the sedimentary record of such activity has
been completely removed by erosion since deposition.
Atop the Precam-
brian, and separated from it by a profound unconformity, is the Quaternary
System.
Quaternary Geology
The structure and differential erosion of the Precambrian bedrock
in the Lake Superior region
resulted in the development of a pre-glacial
lowland which had a direct effect on ice movement in northeastern
Minnesota.
The lowland channeled ice from the Laurentide Ice Sheet
into individual lobes which periodically invaded the western Lake
Superior region from the north and northeast.
Multiple glaciation of ~he region is evident from stratigraphic,
geomorphic, and
lithologic relations.
The Superior Lobe generally
moved southwest along the axis of the Lake Superior basin and west onto
the upland, transporting sediment derived from the North Shore Volcanics,
Duluth Complex, and Precambrian sandstones.
Another ice mass, the Rainy
Lobe, invaded from the north-northeast and deposited fragments of Precambrian crystalline rock (granite, gneiss, and gabbro), meta-sedimentary
rocks, and iron formation.
3
�Four main advances during the Wisconsin Glaciation are recognized
and shown in Figure 3 (Wright, 1972).
The earliest, or St. Croix Phase,
involved concurrent movement of the Rainy and Superior Lobes in a southwesterly direction, with deposition of a sandy-matrixed till and formation of the St. Croix moraine in south-central Minnesota.
The formation
of the Toimi Drumlins in northeastern Minnesota, composed of gray to brown
sandy till with a large percentage of gabbroic fragments, is attributed
to this phase of the Rainy Lobe.
A period of glacial retreat followed,
and a vast system of tunnel valleys was eroded in the glacial drift by
subglacial streams flowing in a southwesterly direction.
100 Miles
0
100 Kilometers
0
A
Silver Say
I
St. Croix Phase
'
·..... •·
'\
Automba Phase
.
Split Rock Phase
\
@ Nickerson
\
'
Fig. 3.
Phase
''
.
Minneapolis~.···.
' , ...... .
.
Outline of ice margins during successive phases of
the Superior Lobe during Late Wisconsin glaciation.
(From Wright, 1973.)
4
�The second, or Automba Phase, brought a readvance of the Superior
Lobe out of the basin, this time in a more westerly direction.
Movement
continued as far west as the Mille Lacs Moraine, which borders the west
and south sides of Mille Lacs Lake.
The Automba drumlin field in western
Carlton County is associated with this advance, as is the Highland moraine,
which marks the northernmost extent of the lobe as it moved laterally out
of the basin.
The Rainy Lobe again advanced across the upland from north-
east to southwest, forming the Vermilion moraine.
After this phase, the
Superior Lobe retreated far enough into the Lake Superior Basin to allow
proglacial lakes to form around its margins.
These lakes were sufficiently
deep to allow deposition of silt and clay which was incorporated into
glacial till during the next advance, or Split Rock Phase.
The third, or Split Rock Phase of Wright (1969) is marked by the
advance of a small tongue of ice which moved southwestward in the Denham
area, depositing a discontinuous-layer of red clay-rich till on some of
the eskers and tunnel valleys associated with earlier phases.
A small
field of drumlins was also formed in the Split_ Rock River Valley near
Barnum.
Late-glacial and early postglacial activity- is represented by extensive glaciolacustrine deposits and shoreline features at various
levels, which developed during successive glacial lake stages as the
Superior Basin was uncovered by melting of the Laurentide Ice Sheet.
Winchell (1901) distinguished three lake levels in the western Lake
Superior region:
(1) "Glacial Lake St. Louis" at 345 m, (2) a lower,
but more distinct level,
Glacial Lake Nemadji (324 m), and (3) Glacial
Lake Duluth 4 m lower than Glacial Lake Nemadji.
5
Glacial Lake Nemadji
�was recognized from lacustrine clays, beach features, and a channel at
roughly 321 m, which drained by way of the Kettle and St. Croix River
systems.
In Winchell's view, Glacial Lake Duluth covered approximately
the same area as Glacial Lake Nemadji but had an outlet at 316 m and
drained by way of the Brule-St. Croix River system.
Leverett (1929) in addition to mapping Superior Lobe moraines, discussed the development of proglacial lakes.
In his view, Glacial Lake
2
Nemadji was a small lake, covering a maximum area of 130 km, at an
elevation of 321 m.
It was bound on the northwest by the Thomson moraine
and by the ice margin as it stood at the Fond du Lac moraine (Leverett,
1929).
With further ice retreat, Lake Nemadji merged with several other
small, proglacial lakes and eventually stabilized as Glacial Lake Duluth.
Beach elevations at the western part of this lower lake range from 305 m
to 318 m (Leverett, 1929).
G. M. Schwartz (1949)
delineated strandline features of Glacial
Lake Duluth at elevations of 325 m.
He also noted the extensive clay
and silt deposits associated with the lake plain, especially the varves
found at the Wrenshall clay pits.
W. R. Farrand (1960) integrated much of the earlier shoreline data
and added new observations in an attempt to correlate strandlines basinwide.
His results are shown in Table 1.
Farrand considered the shorelines
of Glacial Lake Nemadji, as described by Leverett, to be associated with
Glacial Lake Duluth.
The term Glacial Lake Duluth was modified
" ... to include all those major water bodies which occupied
the southwestern part of the Lake Superior basin and which
discharged into the St. Croix River system via either the
Moose Lake outlet or the Brule-St. Croix outlet or both."
(Farrand, 1960).
6
�TABLE 1--LAKE STAGES. (after Farrand,· 1960).
LAKE STAGE
ELEVATION
AGE
OUTLET
(B.P,)
(ft)
Sault
Lake Superior
Sub-Sault
Sault Beach
1000
2000
602
602
602
St. Marys River
St. Marys River
St. Marys River
Algoma
3200
595-596
St. Marys Strait
Ni pissing
Great Lakes
4100
605-607
St. Marys StTait
Houghton Low
Stage
8500
360
Post-Minong
series
90008500
?
Minong
Post-Duluth
Beaver Bay
Manitou
Washburn
9200
proto St. Marys R.
St •. Marys Str,:lit
:
I
St. Marys Strait
&Au Train-Whitefish Strait
.
420?
470?
I
650
765
850
Au Train-Whitefish
I Strait?
Marquette
Marquette
10,000
'
870
Moquah
Highbridge
Sub-Duluth
Duluth
Epi-Duluth
10,220
920
955
1007
Marquette
Huron Mts.
Huron Mts.
1035
1060
1070
1085
Brule-St. Croix R.
1100
10, 700. 10,500
Moose Lake and
Brule-St. Croix
Moose Lake;
Brule-St. Croix
Recent work by H. E. Wright has contributed to working out stratigraphic sequences and relationships among ice lobes.
In his interpre-
tation of the development of glacial lakes following ice wastage, Wright
supported the sequence proposed by Leverett:
(1) the highest lake level
of Glacial Lake Nemadji (318 m) and (2) the lower level of Glacial Lake
Duluth near 305 m (Wright, 1972).
7
�Quaternary Stratigraphy, Sedimentology and Geomorphic Features
Introduction
Surficial sediments in the western Lake Superior region can be broadly
grouped into three types: those deposited during advances of the Superior
Lobe, those resulting from retreat and stagnation of the glacial ice, and
and sediments associated with the formation of Glacial Lake Duluth.
Lodge-
ment till, deposited by actively advancing glacial ice is exposed in, or
underlies, most of the region.
In a generally NE/SW-trending belt
roughly parallel to- Lake Superior, ice disintegration features of till
and interbedded or associated sands and gravels predominate.
A similarly
trending belt of ground moraine parallels the present shoreline along the
southern edge of the stagnant ice features.
Lake clays with varying
amounts of pebbles and boulders cover much of the remaining southern parts
of the region.
Tills
Two tills of different ages, representing· separate advances of the
Superior Lobe are extensively exposed along the Lake Superior shoreline
and in some of the deeper stream valleys.
Visually and texturally, the
tills are very similar, and unless seen in their stratigraphic sequence,
it is difficult to distinguish the two.
The contact between the ~Jo
tills is generally sharp and commonly a stone line or a gravelly or
sandy layer separates them.
Lower Till
The lower till is generally dark reddish-brown, silt-rich, stony
and very compact.
Fissility is developed locally.
8
Although texture
�varies, most of the samples analyzed fall into the loam category (U.S.
Department of Agriculture Soil Classification).
Analysis of 9 samples
from exposures northeast of Duluth averaged 36% sand, 46% silt, and 18%
clay.
Basalt fragments comprise greater than 50% of the 1-2 nnn sand
fraction, with gabbro and "red rock" fragments being the only other rock
types of significance.
boulder size.
Up to 25% of the clasts by volume are cobble or
This till is correlated with the St. Croix phase of the
Superior Lobe as described by Wright (1969).
Upper Till
The upper till is the predominant surface material in upland areas
away from the lake plain, including the Highland moraine.
Its color is
similar·to the lower till, although in many exposures it appears to be
more red-brown.
Compactness varies among localities; in places, the
sediment is as highly compacted as the lower till, while in other areas,
the material is easily disaggregated by the fingers.
Although the same
Lake Superior region rock fragments are present (basalt, gabbro, "red
rock" sandstone, etc.) and in the same general percentages as in the
lower till, this till varies considerably in the amount of pebbles,
cobbles and boulders which are present from locality to locality; some
sections are extremely stone-poor.
Although variable in texture, the younger till is generally somewhat siltier than the lower till.
Analysis of 28 samples from the
Duluth vicinity shows an average composition of 30% sand, 50% silt and
20% clay (Fig. 4).
Clasts of cobble or boulder size comprise at most
20% of the volume of the sediment.
The textural variability may be due
in part to the position of this till in the stratigraphic section; it
9
�CLAY
Figure 4
Grain Size
Disf ribuf ion
in Tills
I
I
\
@
Upper till
average
...
Lower f i II
average
0
\
A
I \
clay
I
("'\
silty
clay
I
I-'
0
sandy
clay
sandy clay
\
\
\
\tlty clay loam
clay loam O
("\ a._O
mcf' ?o
I
/~
loam 6. J.
sandy 1oam
I
\
~
~
0
e
-
0
0
0
silty
loam
00
00
I
I).
I
SAND
0
A
I
0
.I
s i It
0
SILT
�was probably partially derived from the various sediments left by the preceding glacial advance.
Thus, reworked older drift of varying composition
may comprise most of this till rather than material eroded directly from
bedrock sources.
Th_is till has been attributed to advance of the Superior
Lobe during the Automba phase (Wright, 1969).
Stratigraphic Type Sections
Although the two tills can be seen superimposed at many locations,
probably the two best exposures are on McQuade Road in the French River
quadrangle and in the City of Duluth along the shoreline at Leif Erikson
Park (Stop No. 1 on the road log).
At Leif Erikson Park the lower till is a sandy, dark brown to dark
red-brown, fissile sediment with abundant boulders.
the Superior Lobe are present.
Clasts typical of
The upper till is more red-brown in color,
more silt-rich, and at this location more cohesive than the lower till.
A discontinuous boulder line marks the generally sharp contact between
the two tills.
This may represent an erosional surface developed between
glacial advances.
At this location the textural difference between the
two tills is easily distinguished.
Along McQuade Road at the Sucker River, the same sequence is again
exposed, although less textural difference is apparent between the two
tills.
The lower till at this location lacks the fissility of that at
the Leif Erikson exposure; both tills at the McQuade location are compact
and stony.
Fabric Studies
Orientation of the long axis and dip of elongated stones were measured
for both tills at the McQuade Road location (Fig. 5).
11
The majority of
�oo
00
f--'
N
0
A.
1so
FIGURE 5:
B.
1so 0
Orientations of longest axes of elongated stones in McQuade Road exposure. Each
circle equals one stone. A) Upper till, B) Lower till; average regional striation
direction associated with the deposition of this till is approximately N65°E.
�elongated stones dip in an upglacier direction.
In general, the long axes
of stones in the lower till tend to lie approximately 45° from the direction
of ice flow as inferred from the regional striation pattern.
In the upper
till, a similar pattern is evident, with a large concentration of stones
lying nearly transverse to ice flow as inferred from regional features
such as the Highland flutes.
Both tills also show a slight concentration
of elongated stones in the direction parallel to inferred direction of ice
flow.
Clast Composition
At both the Leif Erikson Park and McQuade Road exposures, grain
counts of three size ranges were studied: clasts larger than 2 mm (up
to and including roughly 4 cm), the 1-2 mm fraction, and the fraction
less than 1 mm (Figure 6).
Basalt is the predominant rock type in the
1-2 mm fraction as well as in the greater than 2 mm fraction.
This is
due in part to the abundance of basalt as the predominant bedrock type at
and upglacier from the sample site.
rock are also important.
Physical characteristics of the bed-
The abundance of joints and vesicles makes the
basalt flows more susceptible to breakdown by abrasion, plucking and
grinding during a glacial advance.
The gabbro and diabase with their
more widely-spaced joints and fractures are more resistant to plucking
and crushing.
abundant.
The less than 1 mm fractions show quartz to be extremely
Granite from sources still farther northeast as well as sand-
stone from within the Lake Superior Basin are probably the source.
little sandstone in the larger size range is an indication of its
"crushability."
13
Very
�80
BO
LE 2
60
60
i/
40
40
20
20
I
:~:=::
/
,/{
/f~-,
R,G
B
LE 6
GB
0
Q,F
R,G
B
GB
0
I-'
+'
80
60
'
40
1\}::
!
80
N25-1
N25-2
60
::::::
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204:::
20
••••••••
B
.-.·.·
It?
1-:-:-:-:
R,G
GB
Q,F
ss
0
FIGURE 6: Percent composition of sand fractions in
lower (LE 2, N25-l) and upper (LE 6, N25-2) tills.
B=basalt, R,G= red rock or granite, GB=gabbro, QF=
quartz or feldspar, SS=sandstone, O=other.
B
□
< l mm
R,G
GB
□
1-2 mm
ss
Q,F
[ill
'
'
> 2 mm
0
�Ice Disintegration Features
In the areas west of the broad band of lacustrine clays, most of the
topography reflects ice-marginal deposition of material from active as
well as stagnant ice.
A distinctive geomorphic feature, the Highland
moraine, marks the northernmost edge of the Superior Lobe at its maximum
advance during the Automba phase, and the Thomson moraine developed in
the later Nickerson phase.
Both features display great variability in
sediment types over very short distances, and the landforms also indicate
varying environments of deposition.
The following studies of a part of the Thomson moraine near Wrenshall,
Minnesota are presented as an introduction to terrains originating from
ice disintegration.
The moraine is a hulIDllocky complex of kames, kettles,
disintegration ridges, and eskers.
to 20 m.
Local relief is varied but may be up
These features are typical of an ice-disintegration environment.
Ice-disintegration describes the processes involved in the break-up of
a stagnant, wasting glacier.
Ice-disintegration features are of two maj.or types: (1) controlled
ice-disintegration and (2) uncontrolled ice-disintegration (Gravenor and
Kupsch, 1959).
Uncontrolled ice-disintegration results from equal forces
acting in all directions forming unoriented features, such as kames,
kettles, and general hummocky terrain.
Controlled ice-disintegration
occurs when there is break-up along fractures in the ice and when deposition
is localized to form linear disintegration ridges and eskers.
Uncontrolled Ice-disintegration Features
Karnes
Kames are conical hills or mounds of any size consisting of stratified sand and gravel.
Kames are abundant in the northwest portion of
15
�the Wrenshall quadrangle and are associated with the Thomson moraine.
There they are generally small, reaching maximum dimensions of up to
0.5 km in length and 20 min elevation.
They have flat to rounded tops
and varying slopes according to the texture of the underlying material.
The kames are found to occur both as single, isolated hills and as composite hills which merge to produce ridge-like landforms.
Texturally,
these kames consist of poorly to moderately sorted, stratified sand and
gravel, with boulders.
The sand and gravel is in some places capped with
fine sand to silt.
Kettles
Kettles are small basins created by the ablation of buried ice.
Kettles found in the Thomson moraine area vary in size but are generally
small, less than 1 km in diameter.
Some display irregular shapes but most
kettles tend to approach circularity.
Kettles that are associated with
kames tend to give a "pitted" appearance to the landscape and this "kettle
and kame" topography is characteristic of ice-disintegration complexes.
F. G. Driscoll (1976) in a study of moraine lakes at the Klutlan
Glacier, Yukon Territory, suggests lake development may be the result of
(1) the melt-out of ice containing differing amounts of debris, resulting
in an irregular depositional surface; or (2) uneven surface debris accumulations due to topographic reversals, resulting from slumping of sediment.
Superglacial lake development on a stagnant debris-covered surge lobe
proceeds in five distinct stages as the buried ice melts (Driscoll, 1976):
(1) accumulation of meltwater in low areas on the moraine; (2) expansion
of the lake basin by both lateral and vertical melting, and the establishment of inlet and outlet streams; (3) accumulation of melt-out debris along
lake perimeter, vegetation cover, and mass-wasting along steep shore areas;
16
�(4) stabilized slopes, rounded lake bottom, areal expansion ceases, significant life in lake; (5) reduction in enclosing slopes, heavy vegetation
on periphery, decrease in lake depth and areal extent, final melt-out of
buried ice, increase in biomass.
Controlled Ice-disintegration Features
Linear Disintegration Ridges
The term linear disintegration ridge pertains to a ridge that originates during ice stagnation (Gravenor and Kupsch, 1959).
Ridges of varying
sizes, up to 12 min height and several kilometers in length, are found
within the Thomson nroraine.
Although these ridges are related to controlled
disintegration, they appear gradational with uncontrolled features and are
found with kettles and kames.
The linear ridges vary in composition from medium and fine sand to
sandy gravels, although the latter is predominant.
The stratified nature
of the drift contained in these ridges suggests that they were open crevasses in the stagnating ice which provided a site for the accumulation
of stratified sediments.
Sedimentology
The sediments associated with ice-disintegration in the Duluth area
exhibit a wide variety of textural characteristics, geometries, and
sedimentary structures.
The sediments are generally poorly to moder-
ately sorted, stratified sand and gravel.
The geometry of the units
varies from sheet deposits to pods and lenses.
The grain size distri-
bution shows abrupt changes and an extreme range of sizes from boulders
to clay.
The sediments are thin to thickly bedded, with some cross-
bedding, faults, current and gravity structures.
17
The clasts,generally
�surrounded, are composed of Precambrian sandstone, basalt, rhyolite,
gabbro, granite, gneiss, iron formation, slate, and graywacke.
The
sediments can be divided into five units based on their internal and
external characteristics.
These are (1) gravel, (2) horizontally-
bedded sand, (3) cross-bedded sand, (4) silt and clay, and (5) diamicton.
A gravel pit along West Alcohol Road, SW½, SE½, Sec. 19, T48N, RJ.6W,
(Stop
in road log) reveals good exposures of these sedimentary units and
their structures.
The exposures generally show abrupt vertical changes
with an overall fining upward sequence in most sections.
One locality in the pit near the entrance shows fine to medium sand
overlain by very coarse sand, gravel, and boulders, occasionally with
mudballs.
These units are overlain by laminated silt and clay which show
discontinuous beds that are gently contorted in the lower 0.5 m.
Lobes
of overlying fine sand protrude downward into the silt and clay unit.
The fine sand shows small scale cross-laminations with sets 2 cm in
thickness.
The sand is overlain by another silt and clay unit which
shows load structures into an overlying medium to fine sand.
Another location, approximately 75 m to the northwest, shows the
gravel to be the predominant sediment with lesser amounts of crossbedded sand, horizontally-bedded sand, and diamicton.
gravel occurs in the basal 4.5 m of the section.
The
The unit shows crude
cross-bedding with sets to 0.5 min thickness and often containing interstratified sand, less than 0. 3 min thickness. Overlying the gravel are
'
the horizontally-bedded
and cross-bedded sand units.
bedded with gravel-boulder lenses.
These are inter-
Horizontally-bedded sand has bed
thicknesses from 2-3 cm to 2 mm and the cross-bed sets are up to 0.5 m
18
�thick.
The sand exhibits scour and fill features in some localities, in
addition to normal faults.
Cross-bedding measurements, from both the cross-bedded sand and the
gravel unit, show that paleocurrent directions (n=l2) for the WestAlcohol Road Gravel Pit are generally to the northwest, but there is a
considerable amount of scatter in the orientations.
Depositional Environment
The ice-disintegration complex west of Wrenshall is characterized
by hummocky, kettle-kame topography, consisting of a wide range of
sediment types and structures.
The extreme range of grain size along
with abrupt changes in texture and slump structures indicate that these
• sediments were deposited in close contact with stagnant ice (Flint, 1971).
Sediment supplied to the complex originated from the stagnating ice mass.
The abundance of granite and iron formation clasts (typical of Rainy Lobe
sediment) suggests that there has been reworking of the older, underlying
drift.
The depositional environment of the sediment was one of large
velocity fluctuations of the meltwater, which must have varied considerably as indicated by the rapid change in grain size.
In the west central portion of the Wrenshall quadrangle, the very
hummocky terrain was the result of deposition in ice-walled basins and
later wastage of the sediment-covered ice.
There was abundant meltwater
available which allowed the sorting and stratification of the sand and
gravel.
An esker depositional environment is also observed.
The esker was
probably formed in a tunnel in the stagnant ice as evidenced by a single,
steep-sided ridge containing longitudinally continuous sedimentary units
19
�(Banerjee and McDonald, 1975).
Current flow appears to have been to the
southeast with the esker terminating in a delta in a lacustrine environment.
The sediments of the West Alcohol Road gravel pit may have been
deposited in an ice-walled, fluvial environment, possibly by braided
streams.
The fining upward sequence, sand and gravel lenses, apparent
channeling, scour and fill features, and floodplain silt and clay tend
to support this hypothesis.
Paleocurrents indicate major flow N60W
with some directional variations which would be expected in a braided
stream environment.
Another possibility is that the sediments were deposited in a large
ice-walled basin.
The predominance of gravel and boulders indicates the
need for a proximal source of sediment.
Slump structures, faults, and
a diamicton support an ice-contact origin.
The laminated silt and clay
would have been deposited in a quiet water pool or lake, with an increase
in current velocity or loading from overlying material causing convolutions.
In general, these sediments were deposited on, against, or under
stagnant, wasting ice, and according to R. F. Flint (1971):
"In such a place (ice-contact environment) anything can
happen and it often does."
20
�GLACIOLACUSTRINE ENVIRONMENT
The western tip of the Lake Superior Basin contains geomorphic
features and sediments associated with a glaciolacustrine environment.
The morphology, stratigraphy, and spatial occurrence of various sedimentary facies are ascribed to the activities of Glacial Lake Duluth, which
had a high-stand above 1100 feet.
Geomorphic features and sedimentary
deposits of Glacial Lake Duluth are well-displayed in the Wrenshall and
Frogner 7-1/2 minute quadrangles, and the following discussion is largely
concerned with that area.
Geomorphology
The lacustrine environment in the Wrenshall and Frogner quadrangles
is characterized by well-developed beach landforms and extensive lake
plains.
These features may be compared to the marine shoreline profile
typical of sandy, mainland coasts.
Coastal areas are
divided into three morphologic zones: (1) mainland, (2) nearshore, and
(3) offshore.
The mainland area consists of older features, such as ancient strandplains, alluvial plains, lagoons (or shallow, restricted bodies of water),
or bedrock.
Dunes are common, as a result of a large supply of loose sand,
and are found bordering the beach.
The nearshore area, in a marine environment, extends seaward from
the mainland and consists of two main zones: (1) backshore and (2) shoreface.
The backshore is the area which is subjected to wave action only
during extreme high water, usually generated by storms.
ward, the profile shows the shoreface zone.
21
Continuing sea-
The shoreface is defined as
�a submerged zone which extends to a depth where sand size material is not
moved by normal currents (Harms and others, 1975).
It is the shoreface
that is affected by swash and backwash, breakers, and longshore currents,
which transport sand across the entire zone.
The offshore area is not affected by normal wave action.
Coarse
sediment is transported into the offshore zone only under extraordinary
conditions, such as storms or density currents (Harms and others, 1975).
The lacustrine complex in Wrenshall and Frogner quadrangles is
divided into two main morphologic groups: (1) nearshore and (2) offshore,
which are separated by a narrow transition zone.
shows two zones, the backshore and the shoreface.
usually less than 120 min width.
The nearshore profile
The backshore is narrow,
This merges with the hummocky terrain
of the ice-disintegration complex previously discussed.
The backshore
is relatively flat, but in some places is marked by small discontinuous
beach ridges.
The shoreface in these quadrangles is expressed as a north-
east trending belt, approximately 1.8 km in width.
The shoreface here is
basically a surface of no relief, sloping gently, 3 to 8 degrees, to the
southeast and east.
The shoreface zone is influenced by current action which is reflected
in the presence of beach scarps, spits, an offshore bar, and a delta at
elevations near 330 m.
Wave-cut beach scarps in the shoreface dip 5 to 8
degrees to the southeast and are underlain by medium to fine sand with
boulders and gravel concentrated at the base of the slope.
The largest
spit trends north-south and is located at the center of Sec. 1, T47N,
Rl7W.
It is 1.3 km in length and 0.5 km in width with side slopes of
3 degrees.
The spit curves to the southwest indicating longshore currents
flowing to the southwest.
Several smaller spits are located in section 2.
22
�An offshore bar, with up to 6 m of relief is found in SW¼, Sec. 11, and
W½, Sec. 4, T47N, Rl7W.
It generally lies parallel to the former shore-
line, 0.8 km lakeward, and extends for 2.4 km.
Paleocurrent directions
(four measurements) to the northwest indicate shoreward growth of the
bar.
A fan-shaped form, located in Sec. 31, T48N, Rl6W, is interpreted
to be a delta.
It is roughly 2.6 km
2
in area, relatively flat-surfaced
in the north portion, with a foreset slope of 4 degrees to the southeast.
A
former ice tunnel, now containing an esker found to the northwest in
the ice-disintegration complex, appears to have supplied the delta with
meltwater.
Lakeward of the nearshore area
nearshore and offshore environments.
is a transition zone which separates
The transition zone occurs as a
northeast trending scarp between 300 and 309 min elevation which slopes
3 degrees to the southeast.
The sediments of this zone are transitional
in nature between the nearshore sands and the offshore clays, with the
sands and clays interfingering.
This feature was misinterpreted by
Leverett, Farrand, and Wright to be a strandline feature of Glacial Lake
Duluth.
It appears instead to be a depositional feature associated with
the higher (330 m) elevation of Glacial Lake Duluth.
The offshore environment is represented by an extensive lake plain
that covers the southeast quarter of the Wrenshall quadrangle and most
of the Frogner quadrangle.
southeast
A profile of the offshore from northwest to
shows it to be gently dipping to the east-southeast at less
than 3 degrees.
Two weak scarps are seen on the profile at elevations
of 288 and 264 m, which may represent lower lake levels of the Highbridge
and Washburn stages respectively (Farrand, 1960).
23
The offshore area has
�been deeply dissected by the Nemadji River and the Red River, a tributary
of the St. Louis River.
These streams have downcut as much as 42 m into
the offshore sediments.
Extensive slumping is very common along the
stream valleys, indicating the instability of the underlying material.
Sedimentary Units
The sediments of the glaciolacustrine environment may be divided
into four units: (1) horizontally-bedded sand, (2) cross-bedded sand,
(3) laminated silt and clay with dropstones, and (4) massive clay with
dropstones.
Horizontally-bedded Sand
This sand occurs widely throughout the nearshore zone as a sheetlike deposit, with a minimum thickness of 6 m.
The grain size distri-
bution shows moderately sorted sand with gravel and a mean grain size
of 20 (O.25 mm, medium-fine sand).
Sedimentary structures are not abun-
dant in the horizontally-bedded sand.
nated to medium bedded.
The sand varies from finely lami-
The bedding planes are faint and difficult to
recognize, giving a massive appearance to the sand.
Heavy mineral
laminae are present and help to distinguish bedding planes.
Slightly
inclined bedding at one locality gives a general paleocurrent direction
to the south-southwest.
The only other direction indicator available
is a general fining of the sand on the shoreface from medium to very
fine sand, suggesting currents flowing to the south.
The presence of a plane bed structure associated with the medium to
fine grained, horizontally-bedded sand indicates an upper flow regime
(Reineck and Singh, 1973).
In the upper flow regime the main mode of
24
�sediment transport is via continuous rolling of grains in sheets several
grains thick (Reineck and Singh, 1973).
Accordingly, the sediment trans-
port is large.
Cross-bedded Sand
The cross-bedded sand occurs as ribbon type deposits.
These deposits
are generally small, less than 1.5 km in length and 0.5 km in width.
The grain size distribution for cross-bedded sand shows that this is
moderately sorted.
The mean grain size is 1.50 (0.35 mm, medium sand),
although there is locally coarse sand and gravel.
sedimentary structures found in this unit.
Cross-beds are the main
These occur as planar or tabu-
lar forms with sets up to 0.5 min thickness.
The cross-beds show good
topset, foreset (inclined 25 degrees), and bottomset beds with laminae
comprised of gravel, fine sand, or heavy minerals.
Paleocurrent directions indicate (1) current flow to the east-southeast
(lakeward) and (2) current flow to the northwest (shoreward).
The shore-
ward current direction is observed in the area of the offshore bar and
indicates a shoreward growth of the bar.
Bedforms of small ripples and mega-ripples associated with the crossbedded sand indicate transport and deposition in the lower flow regime
(Reineck and Singh, 1973).
The cross-bedding developed as a result of
the migration of small current ripples and megaripples.
In the lower
flow regime, the resistance to flow is large and the sediment transport
is small.
Laminated Silt and Clay
The laminated silt and clay occurs as extensive sheet-like deposits
which are also associated with massive clay.
nated silt and clay varies from 0.5 to 15 m.
25
The thicknesses of the lami-
�Texturally, two distinct populations are observed: high silt content
and high clay content.
The silt layer is moderately sorted with a mean
grain size of 5.80 (0.02 mm, medium silt).
The unit is pale brown
(Munsell color: 10 YR 6/3, dry) and consists of greater than 55 percent
silt. The clay layer is reddish brown (Munsell color: 5 YR 4/4, dry)
is
ang_/composed of greater than 75 percent clay, with silt generally less
than 10 percent and sand Oto 2 percent.
In a few locations, carbonate
concretions are found within the clay layers.
The sedimentary structures associated with the silt and clay are very
thin to thin bedding, discontinuous and distorted bedding.
The silt and
clay beds vary from several millimeters to several centimeters in thickness,
and change considerably within a stratigraphic section.
Discontinuous
bedding is contorted, showing small scale recumbent folds and lenses of
silt.
The laminated silt and clay are rhythmites, alternating layers of
different compositions, which may be varves if each couplet represents
a single year of deposition (Reineck and Singh, 1973).
These appear to
have been deposited in the quiet water, deep portion of the basin.
The
abundance of clay indicates that the main mode of deposition was from
the falling out of fine particles from suspension.
The presence of silt
would indicate more competent currents or turbulence, possibly during
the summer thaw, which would periodically transport and deposit the silt.
Massive Clay
The massive clay, with the laminated silt and clay, comprises the
major portion of the lake basin.
Massive clay appears as a thick, sheet-
like deposit which has lateral continuity.
26
The exposed thickness of the
�clay is up to 20 m.
Texturally the clay content is greater than 75 per-
cent with several samples showing greater than 90 percent.
prises the remaining 10 to 25 percent of the sediment.
Silt com-
The clays are
reddish brown (Munsell color: 5YR 4/4, dry) to dark reddish gray (Munsell
color: 5YR 4/2) where unoxidized and have a general massive appearance.
There are no visible laminae of coarser or different colored
material, however in some exposures, the clay does show minor fissility,
indicating an internal structure.
The presence of massive clay suggests
quiet, deep water deposition without apparent current activity.
Drops tones
Scattered within the massive clay and laminated silt and clay are
individual clasts up to 10 cm or more in length.
These stones are thought
to have originated as ice-rafted material as evidenced by their sporadic
occurrence, in addition to their large size which would otherwise require
a competent current for transport.
Clay Mineralogy
Four samples from the laminated silt and clay and massive clay were
analyzed by x-ray diffraction.
These include a red clay lamina, a gray
silt lamina, reddish gray massive clay, and reddish brown massive clay.
There is little difference in composition, other than peak intensities,
among these samples.
The samples contain (1) quartz, (2) calcite,
(3) dolomite, (4) plagioclase, (5) k-feldspar, (6) montmorillonite-illite
mixed layer, (7) chlorite, and (8) possible hematite.
This mineral group
is consistent with those determined by Mengel and Brown (1976) for other
clay samples in the Wisconsin portion of the lake basin.
27
�These minerals were derived from the underlying weathered bedrock and
older glacial sediments.
The abundance of calcite and dolomite indicates
a source in the drift of the St. Louis Sublobe to the northwest of the
study area.
Calcite is commonly found as vein fillings and amygdules in
the flows of the North Shore Volcanics and could have been incorporated
into the drift of the Superior Lobe.
Another possible source for the
carbonates is the Hudson Bay area with glacial transport of the sediment
into the Wrenshall and Frogner area (Mengel and Brown, 1976).
Stratigraphy
Exposures along roadcuts and stream valleys in the lacustrine complex allow the stratigraphic relationships of the sedimentary units to
be worked out.
Subsurface data are available only for the area near
Wrenshall and show the drift to be up to 115 m thick.
Various sections
are summarized in a schematic north-south cross-section (Figure 7 ).
The section shows the basal unit as older drift or bedrock.
These older
units are overlain by (1) moderately sorted, probable nearshore sand,
(2) massive clay with laminated silt and clay, and including dropstones,
and (3) moderately sorted, fine to medium grained, horizontally- and
I
cross-bedded sand.
The presence of shallow water sand over deepwater silt
and clay suggests progradation resulting in nearshore facies over offshore
facies.
Depositional Environment
As shown on a surface plot of the sediments (Fig.
8 ), the mean grain
size distribution changes depending on the distance from the shoreline.
The nearshore facies is shown to be composed primarily of medium sand.
The sand consists of both horizontally-bedded and cross-bedded units.
Shoreface activity includes upper and lower flow regimes, as indicated by
28
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�bedforms.
The current directions to the southwest parallel the shoreline,
causing the formation of spits (Figure 9 ).
The offshore bar formed sub-
aqueously and paleocurrents show a shoreward growth, possibly due to
storm waves.
The north-central portion of the study area has very fine
sand and silt relatively close to the shoreline, suggesting lower current
strength.
Deltaic sedimentation shows an upper surface of sand, with very fine
sand and silt on the prodelta slope.
and west from the feeding esker.
Two narrow valleys radiate south
These may represent remnant distributary
channels cut into the delta, with the silt and fine sand as floodplain
deposits, as suggested by their standard deviations (Folk and Ward, 1957).
-There is an abrupt grain size change in the lake basin from predominantly sand to predominately silt and clay (Fig.
8).
This boundary, which
can be traced laterally, occurs between 300 and 309 min elevation and is
represented by a northeast trending scarp,
The zone shows
varying textures with interfingering sand, silt, and clay.
The variety
in sediment type reflects the changes in current strength.
This abrupt
change in slope and sediment type is here interpreted to represent the
depositional front of a coarse grained shelf of Glacial Lake Duluth.
The offshore facies occurs south and east of the transition zone
(Fig.
8).
It is composed of laminated silt and clay, massive clay, and
dropstone deposits.
These sediments were derived from the wasting ice
lobe and meltwater streams draining the ice-disintegration complex.
Offshore sedimentation must have occurred primarily as the settling of
sediment from suspension as evidenced by massive appearing clays.
32
�The rhythmite couplets (silt and clay layer) are not gradational
but occur as distinct layers.
This would suggest deposition by two
sedimentation pulses and modes of deposition (Ashley, 1975).
The normal
suspension sedimentation may have been periodically interrupted by density
currents as underflows, interflows, and overflows.
These flows result
from the high suspended sediment content of meltwater streams from the
ice-disintegration complex and ice lobe entering the lake.
These flows
have been described in present day Glacial Lake Malaspina, Alaska, by
Gustavson (1975).
These currents provide a mechanism for the deposition
of the silt layers of the rhythmites during the summer months.
This
would result in clay being deposited continuously in areas not reached
by current flows, and massive clays would form (Gustavson, 1975).
In add~tion, offshore occurrence of dropstone deposits, interbedded
with silt and clay, suggest ice rafting of sediments as a depositional
mechanism.
The ice dammed Glacial Lake Duluth,with calving of the ice
front,would produce massive icebergs which would release sediment over
the lake basin as the ice would melt.
Vegetational History
Cores from bogs and lakes contain a history of plant succession
in the form of pollen and macro-fossils, including seeds, woody fragments, and leaves.
Studying quantitatively the contents of such cores
at a particular site allows the determination of the time of arrival
of plant migrants, as well as the reconstruction of the fabric of the
plant communities at different times.
All of these studies lead to the
fuller view of the vegetational history within the time represented by
the sediment core.
As a data proxy for climate, the pollen record is
33
�then transcribed into a history of climatic change.
Sampling along the
proper traverses allows the monitoring of the march of vegetation in
the wake of retreating glaciers.
Most ponds and lakes in glaciated terranes deep enough to accumulate a significant sediment record originated as kettles on ice-cored
end moraines.
The vagaries of down-wasting of buried stagnant ice decree
a complex natural history for the surface features of such a terrane.
Topographic reversals are common because the hillslopes are extremely
unstable: debris flows and slumps denude sediment-mantled slopes, fill
depressions with colluvium, and thereby redistribute the insulation on
the stagnant ice surface.
slopes and hilltops.
Melting proceeds more rapidly on the bared
Differential melting transforms ice-cored hills
into holes, and vice versa.
In such an unstable environment lakes and ponds are ephemeral.
Sediment, including pollen and plant macro-fossils is not collected into
a continuous and permanent record until a stable basin is formed, generally near the demise of the ice core.
Melting to that point in the
moraine's history may take thousands of years.
Therefore, radiocarbon
dates on bottom sediments in such lakes can be significantly younger
than dates obtained from beneath basal till in the same moraine.
For
the same reason, cores contain an incomplete record of revegetation-generally the earliest part is missing.
It follows that the best lakes
for pollen studies are those that formed early in the history of deglaciation and that continued as stable catchments to the present.
In broad outline, the pattern of plant succession in Minnesota
during the Late Wisconsin and post glacial is similar to that of the
34
�entire Great Lakes region (Wright, 1976).
Minnesota (see Fig.
Wolf Creek in central
for location WC) and Weber Lake in northeastern
Minnesota are two sites that have been especially useful to reconstructing
the vegetational history •
.
·1.
i
r..
,,
ti
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..
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0
KILOMETERS
Figure 10. Major phases in the Wisconsin glaciation in M:lnnesota.
Approx1rrate dates 1n thousands of yeal's. Note the
non-synchronous maxima of the SL1perior and ~s 1·-:0ines
lobes. Locations of Wolf Cr~~k .:ind Weber I,'1.lw al.'c
sho~m.
The oldest pollen zone at Wolf Creek represents an herb tundra,
which prevailed from 20,500 yr BP until about 14,700 years ago.
was followed by shrub tundra and forest tundra.
This
Spruce expanded into
the area about 13,600 years ago and was the dominant species for about
35
�4,000 years.
Then, spruce was replaced by pine about 10,500 years ago.
Cores from Weber Lake, situated farther northeast in the Toimi drumlin
field, indicate that herb tundra persisted there until about 11,000 yr
BP, with a rapid transition to shrub tundra and then spruce and finally
pine.
A summary of the changes in major vegetation types and their relationships to glacial phases is shown in Figure
NORTH
2000
RAINY
20
0
!:J
Stagnant ice
Figure 11.
40
♦
LOBE
SUPERIOR
LOBE
60
,co
80
,20
Ro.c.iacarbon do.le, wit!\ one <10.nd<1t"d c!ev1<11ion
14()
160
180
ZOOmdtt
• Rejected r<1d10c<1rbon d.<11e
Transect from north to south in eastern Minnesota, showing
times and areas of ice-lobe advance, as well as the changes
in major vegetation types since glaciation, as inferred from
pollen and seed analyses of lake sediment cores. (Courtesy.
H. E. Wright).
36
�Glacial Materials and Soil Profiles
by
Royce Lewis, Soil Conservation Service
The kind of soil horizons and their sequence formed on well drained
sites in the Duluth area generally can be correlated with the kind of
glacial materials.
as examples.
The Ahmeek, Duluth and Ontonagon soils may be used
See Figures 1 through 6 for some physical and chemical
properties of these soils.
The Ahmeek soils are formed in noncalcareous, reddish brown, sandy
loam till.
Their sequence of horizons may be interpreted as A , A ,
2
1
Bhir, B, and C.
X
X
The Duluth soils are formed in noncalcareous, reddish
brown, loam till and have a sequence of horizons of A , A , Bhir, A , BT,
2
2
1
and C.
The Ontonagon soils are formed in calcareous reddish brown, lacus-
trine sediment and have a sequence of horizons of A , A , BT and CCA'
2
1
The A horizons of these soils have higher accumulation of organic
1
carbon, lower bulk density and higher porosity than other horizons in the
pedon (area of about l square meter).
They are higher also in available
water capacity (1/3 minus 15 bar water).
They generally are higher in
base saturation and pH than the horizons immediately below.
They cotmnonly
are black.
The A2 horizons generally are discontinuous within a pedon of
Ahmeek and Duluth soils and are continuous in the Ontonagon soils.
They are horizons of maximum removal of clay, iron or aluminum, which
results in a concentration of quartz or other resistant minerals in
the sand and silt size.
They are lighter in color than the underlying
B horizons.
The Bhir horizons have significant accumulations of organic carbon,
iron and aluminum coatings on sand and silt particles.
37
They are low in
�bulk density, base saturation and pH.
They have also a higher cation
exchange capacity per unit of clay than the underlying horizons.
They
are commonly reddish brown.
The BT horizons have appreciable accumulations of translocated
silicate clay particles as contrasted to the B horizons (in the Ahmeek
X
soils); however they have higher bulk density and lower porosity than BT
horizons.
The base saturation of the B horizons, and content of clay
range widely among these soils.
They seem to be a mark of the kind of
glacial materials along with the properties of the C horizons.
The C horizons are presumed to be relatively little affected by
biological activity and include accumulation of calcium and magnesium
carbonate (CCA horizons) and high bulk density (Cx horizons).
38
�.&IIKEEJ:l'ElXJ11'
J'art:l.oJ.. Siu Dutz:1.bution ('6)
2
l)optb
so
ail1:
l'vtiolA Sue D1atr..bution ('6)
2S
50
75
l!ue S&turation
JO
50
Co)
70
pf! (~0)
6,6
7.0
.4
2S
Sill:
Clq
so
lllJLll'm PEllOI
hrt:l.olA Siu ll1atribut1on (1')
2
0
7,
..
l)optb
2S
so
olq
1111:
llua· S&tun.tian (1')
10
50
70
pf! (CaCl)
.4
�REFERENCES CITED
Ashley, G.M., 1975, Rhythmic sedimentation in Glacial Lake Hitchcock,
Massachusetts-Connecticut, in Glaciofluvial and Glaciolacustrine
Sedimentation, A.V. Jopling and B.C. McDonald, eds.: SEPM Special
Pub. 23, Tulsa, p. 304-320.
Banerjee, I. and McDonald, B.C., 1975, Nature of esker sedimentation, in
Glaciofluvial and Glaciolacustrine Sedimentation, A.V. Jopling and
B.C. McDonald, eds., SEPM Special Pub. 23, Tulsa, p. 132-154.
Driscoll, F.G., 1976, Formation and wastage of neoglacial surge moraines
of the Klutlan Glacier, Yukon Territory, Canada, Unpub. PhD Thesis,
U of Minnesota, 309 p.
Farrand, W.R., 1960, Former shorelines in western and northern Lake
Superior Basin, Unpub. PhD Thesis, U. of Michigan,. Ann Arbor, 226 p.
Flint, R.F., 1957, Glacial and Pleistocene Geology, Wiley and Sons:
New York, 553 p.
Folk, R.L., and Ward, W.C., 1957, Brazos River bar: a study in the significance of grain size parameters, Jour. Sed. Pet., Vol. 27, p. 3-26.
Gravenor, C.P., and Kupsch, W.O., 1959, Ice-disintegration features in
western Canada, Jour. Geol., Vol. 67, p. 48-64.
Green, J.C., 1972, General geology, northeastern Minnesota and North Shore
Volcanic group: in Geology of Minnesota: A Centennial Volume, Minnesota
Geological Survey, p. 291-332.
Gustavson, T.C., 1975, Sedimentation and physical limnology in proglacial
Malaspina Lake, southeastern Alaska, in Glaciofluvial and Glaciolacustrine Sedimentation, A.V. Jopling and B.C. McDonald, eds., SEPM
Special Pub. 23, Tulsa, p. 249-263.
Harms, J.C., Southard, J.B., Spearing, D.R., and Walker, R.G., 1975,
Depositional environments as interpreted from primary sedimentary
structures and stratification sequences, Short Course #2, SEPM,
Dallas, 161 p.
Leverett, F., 1929, Moraines and shorelines of the Lake Superior basin,
U.S. Geol. Survey, Prof. Paper 154-A, 72 p.
Mengel, J.T., and Brown, B.E., 1976, Final report: red clay slope stability
factors, Little Balsam Creek drainage, Douglas County, NW Wisconsin,
U.S. E.P.A. and Red Clay Project# G-005140-01.
Moss, C.M., 1977, The Surficial and Environmental Geology of the French
River Quadrangle, St. Louis County, Minnesota: unpub. MS Thesis,
University of Minnesota, Duluth, 69 p.
40
�Reineck, H.E., and Singh, I.B., 1973, Depositional Sedimentary Environments, Springer-Verlag: New York, 439 p.
Schwartz, G.M., 1949, The geology of the Duluth metropolitan area,
Minn. Geol. Survey Bull. 33, 136 p.
Winchell, N.H., 1901, Glacial lakes of Minnesota, Geol. Soc. Amer.
Bull., Vol. 12, p. 109-128.
Wright, H.E., Jr., and Watts, W.A., 1969, Glacial and vegetational history
of northeastern Minnesota: Minnesota Geological Survey, Spec. Publ.
SP-11, p. 1-23.
_ _ _ _ _ , 1972, Quaternary history of Minnesota, in The Geology of
Minnesota: A Centennial Volume, P.K. Sims and G.B. Morey, eds.,
Minn. Geol. Survey, p. 515-547.
Ice retreat and revegetation
- - -Area,
- - , in1976,
Quaternary Stratigraphy of North
in the Western Great Lakes
America, W.C. Mahaney,
Editor: Dowden, Hutchinson, and Ross, Inc., Stroudsburg, Pa.
Zarth, R.J., 1977, The Quaternary geology of the Wrenshall and Frogner
quadrangles, northeastern Minnesota: unpublished M.S. thesis,
University of Minnesota, Duluth, 93 p.
41
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10 MILES
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INDEX
TO
QUADRANGLES
:,A STERN MINNESOTA SHo,vING l\'IAJOR GEOIVIORPHIC FEATURES
From:
Wright, H.E., Jr., and Watts, W.A., 1969, Glacial and
Vegetational History of Northeastern Minnesota, Minn.
Geol. Survey Special Publication No. 11, 59 p.
43
STUDIED
�ROAD LOG AND STOP DESCRIPTIONS
Mileage
o.o
0.0
Start. Normandy Village, Superior St., Downtown
Duluth. Proceed to 3rd Ave. W., turn right. Proceed 2 blocks to 2nd St. W. Turn right. Proceed
to 10th Ave. E. Turn right and continue to London
Rd. Turn left and proceed to Viking ship at Leif
Erikson Park on Lake Superior.
1.5
1.5
STOP 1. Leif Erikson Park. Exposures along the waveeroded shoreline of Lake Superior show two different
tills atop the striated and polished Keweenawan lava
flows and interflow sediments. The unconformity
between the Precambrian and Quaternary Systems encompasses over one billion years.
Continue east on London Road
4.7
6.2
Lester River. Rocks are lava flows. A wellstriated whaleback is exposed at the mouth of the
stream. The river is popular with smelt and steelhead fishermen.
0.5
6.7
Turn right onto Lake Superior Scenic Drive. Many
miles of shoreline were given to the City of Duluth
by the Congdon family to be developed as public
recreational areas. Notice the effects of recent
wave erosion.
2.3
9.0
City of Duluth Water Supply Plant. On the left is
the newly constructed filtration plant necessitated
by the high amounts of fine-textured fibrous amphiboles suspended in the lake water. Source of the
minerals is a taconite (low grade iron ore) processing plant at Silver Bay, which disposes of tailings
into Lake Superior.
0.5
9.5
STOP 2. Turn right into scenic pull-out near Duluth
Tent and Trailer Camp. Proceed along path to Lake
Shore. A variety of glacial sediments, including
tills and possibly glaciolacustrine sediments, is
exposed along the shore, resting atop lava flows
of the North Shore Volcanics.
Continue east on Scenic Drive
1.7
11.2
Turn left onto McQuade Rd. (St. Louis Co. Rd. 33)
44
�0.6
11.8
Intersection with Hwy 61 Expressway. Continue
north on McQuade Rd. Exposures along the route
are pebbly mud deposited in Glacial Lake Duluth.
The road transects several flat benches that may
be shoreline features.
2.9
14.7
Junction with Lismore Rd.
McQuade Rd.
0.7
15.4
Continue north on
STOP 3. Gravel pit on the right exposes a complex
of cross-bedded outwash interpreted to be a delta
constructed by a meltwater stream at its junction
with Glacial Lake Duluth's highest stand in the
area. Thin diamictons may be debris flows from
high-standing ice-cored topography near the shoreline.
Continue north on McQuade Rd.
0.9
16.3
STOP 4. Sucker River. Two tills exposed in the stream
bank correlate with those along the Lake Shore. Here
the upper, fine-textured till is far above the level
of Lake Duluth, eliminating the possibility that it
is of glaciolacustrine origin. Both tills contain a
fabric resulting from the preferred orientation of
elongate clasts. See general text for details.
Make a U-turn carefully and return south on
McQuade Rd.
3.5
19.8
Turn right onto Lismore Rd.
2.9
22.7
Outcrop on right is a coarse-textured felsic intrusive called "granophyre". In one view this rock
type, which is common in the Duluth Complex, is a
late-stage magmatic differentiate derived from
basaltic magma during the crystallization of the
Duluth gabbro.
3.4
26.1
Turn left onto Jean Duluth Rd.
5.2
31.3
Large outcrop of granophyre on right.
1.3
32.6
Intersection with Glenwood Ave.
Duluth Rd. and Skyline Pkwy.
1.0
33.6
Turn left onto Woodland Ave.
0.1
33.7
Turn right onto Arrowhead Rd.
1.5
35.2
Turn left onto Kenwood Ave.
45
Continue on Jean
�1.1
36.3
0.7
37.0
Turn right onto Skyline Pkwy.
STOP 5. Turn left into parking lot of First Methodist
Church. View of Duluth-Superior harbor. The
outer natural barrier at the head of Lake Superior,
called Minnesota and Wisconsin Point, is the largest
fresh water bar in the world. Sand derived from
till bluffs to the east along the south shore is
moved to the lakehead by beach drifting. It began
to form about 3,000 years ago. Segments of an
inner bar are also visible. This feature was constructed during the slightly higher Nipissing level
of the lake about 4,000 years ago.
Continue west on Skyline Pkwy to Hwy 2.
Numerous outcrops of gabbro along the route.
8.3
45.3
0.3
45.6
Junction Hwy 2. Proceed through intersection to
Thompson Hill Information and Rest Area. Gabbro
bedrock along Hwy 2 is abraded and plucked into
whaleback forms.
STOP 6. Thompson Hill Rest Area and lunch stop. Good
views of the estuary of the St. Louis River. Very
accessible are outcrops of the so-called layered
series of the Duluth Complex, the result of episodic
crystallization of different minerals in the magma
chamber. Remember Bowen's reaction series?
Exit on northeast side to Hwy 2 and Interstate 35 North.
2.1
47.7
Exit right onto Central Ave and Hwy 2.
0.2
47.9
Turn right onto Central Ave.
0.3
48.2
Stop sign.
Turn right onto Raleigh St.
0.6
48.8
Stop sign.
Turn left onto Grand Ave, and Hwy 23
8.0
56.8
Fond du Lac village limit. French fur traders were
the first white men to see the "head of the lakes"
region, about 1659. Twenty years later Daniel de
Greysolon Sieur de Lhut raised the French flag on
the shores of Lake Superior. In 1817 John Jacob
Astor established one of his fur trading posts on
the banks of the St. Louis River at Fond du Lac.
0.5
57.3
Junction Hwy 210.
0.5
57.8
Excavation on right exposes glaciolacustrine sediments associated with Glacial Lake Duluth.
46
Keep left on Hwy 23.
�2.3
60.1
STOP 7. Turn right into scenic overlook. The St.
Louis River and its tributaries have entrenched
deep valleys into the sediments of Glacial Lake
Duluth. Mass-wasting of the fine-grained sediments results in a distinctive rounded topography. Watch for bald eagles--an active aerie
is a few miles upstream.
Continue south on Hwy 23.
(Following road log is approximated from topographic maps.)
1.7
61.8
Turn right onto Carlton Co. Rd 18 to Wrenshall.
The route crosses the nearshore "continental
shelf" of Lake Duluth.
2.2
64.0
Turn right into Wrenshall.
0.5
64.5
Turn left onto West Alcohol Rd. The route will
climb gradually across nearshore glaciolacustrine
sediments onto a hurmnocky bounding stagnation
moraine, a part of the Thomson moraine.
1.3
65.8
STOP 8. West Alcohol Rd. gravel pit. Exposures
show the sedimentary complexities of a moraine
resulting from the stagnation and melting of
dirty glacier ice.
Return to Wrenshall
1.3
67.1
Turn left to Carlton. The lake plain narrows to
a long embayment. Outcrops are Thomson Formation,
a Middle Precambrian metasiltstone-slate.
4.2
71.3
Carlton. Continue north on Hwy 45. Numerous outcrops of Thomson Formation striking generally
east-west in the form of miniature hogbacks (piggy
backs?).
2.4
73.7
Junction Hwy 45 and I-35.
Hwy 45.
0.3
74.0
Stop sign.
Continue to Scanlon on
Turn left on Hwy 45 toward Cloquet.
Prepare for sharp left turn
0.3
74.3
Turn left onto Washington Ave. (Carlton Co. Rd. 16)
1.4
75.7
Junction Hwy 33.
lane.
47
Turn right and proceed into left
�0.3
76.0
Turn left onto service road fronting National
Guard Armory, then right toward Armory entrance.
0.1
76.1
Stop sign.
0.4
76.5
Turn left into City of Cloquet Public Works
Dept. gravel pit.
0.1
76.6
STOP 9. Cloquet esker. Gravel pit exposes the
internal structure of the highest esker in
Minnesota. See the Wrenshall Quadrangle topographic map. Mixed bedrock lithology suggests
erosion of older tills before final deposition
of esker gravel.
Turn left to Pine Valley Park.
Retrace route to Armory
0.5
77 .1
Turn left to Hwy 33 via service road to Pizza Hut.
0.2
77 .3
Turn left (north) onto Hwy 33.
0.7
78.0
Junction Hwy 33 and Hwy 45.
Hwy 33.
0.1
78.1
St. Louis River.
0.9
79.0
Turn right onto North Rd (Carlton Co. Rd. 2)
1.7
80.7
STOP 10. Pit on left exposes the southeast end of
a drumlin-like landform ascribed to the Automba
phase of the Superior Lobe. Reworked clay displays slickensides produced by "drumlin-forming
processes."
Continue north on
Continue east on County Rd 2
7.0
87.7
Junction Midway Rd (St. Louis Co. Rd 13).
right to I-35.
1.9
89.6
Junction I-35. Turn left to I-35 northbound to
Duluth. Rock outcrops are lava flows near the
bottom of the North Shore Volcanics, of Late
Precambrian age.
9.9
99.5
Exit from I-35 onto Superior St. in Duluth.
0.6
100.1
Normandy Inn.
End of field trip.
48
Turn
�DIAGRAM SUPPLEMENT TO ROAD LOG
8·12"
LAKE CLAY
6• 10'
UPPER
LE t3
LE 5
TILL
LC 4
LE 3
5-s'
LOWER
TILL
LE 2
LE 1
lava flows
Stratigraphic section at Leif Erickson Park; Duluth,Minnesota. S]%, S\'l¼, Sec. 23, T5ON, Rl4W.
Textural composition of samples: LE 1, 34% sand, 45%
silt, 21% clay; LE 2, 49% sand, 42% silt, 9% clay;
LE 3, 39% sand, 43% silt, 18% clay; LE 4, 23% sand,
74% silt, 3% clay; LE 5, 20% sand, 65% silt, 15% clay;
LE 6, 24% sand, 47% silt, 29% clay. c~ M., Moss, 1977
HIGHLAND
MORAINE
1400'
f
ICI DISINTIOaAr I O N - - - - - - .
flATUUS
LAKI
SUPERIOR
------? ---UPPU TIU
LACUSUINI
7
Dll'OSITS
,===----------
?
=-----'
DIAGRAMMATIC CROSS SECTION
LOWU JILL
IIDaOCIC
•
49
FRENCH RIVER QUADRANGLE
1200'
? --
1000'
aoo'
ooo'
£LIV.
C. M. Moss, 1977
�O lacustrine clay
or silt
Figure 12
• average, 22 samples
Cl ccmpaci, pebbly clay
Grain Si%e
Oistri but ion in
Lacustrine
Deposits
0
0
□
□
Cl
(C. M. Moss, 1977)
0
LO
1.1
1.2
0
1.3
A
0
0
Cl
0
C
A
A
A
A
A
1. 4
1.5
l. 6
1.7
1.8
1.9
2.0
Bulk Density; g/cc
FIGURE 14:
Comparisons of bulk den3ities of glacial sediments:
□ = pebbly, compact clay
O= laminated or massive pebble-free clays
A= sand- or silt-rich. till
(C.M. Moss, 1977)
50
�INLAND
AREAS
L. SUPERIOR
BASIN
GLACIAL LAKE
DULUTH
PEBBLE•FREE CLAY
DEPOSITION
ICEBERGS
-0- -- ------...
, •o " a·· .. _ .- -
RETREATING
ICE
'
DROPSTONES
DEBRIS WASHED OR
SLUMPED FROM
ICE
A
M I XE D P £ 8 BL E • f REE CLAY &
DROPS TONE DEPOSITS
I
RETREATING
ICE
DEBRIS SLUM PED
,FROM ICE
.t
B
Model for deposition of clay facies in Glacial Lake Duluth. (A) earliest stages of
deposition with material supplied from icebergs and retreating ice. Clays are carried
away from the ice and are deposited in deeper water. (B) later stages of deposition;
pebble-free clays continue to settle over slumped debris and icebergs drop coarser
material over scattered areas.
(Moss, C.M., 1977)
51
�FIGURE 15: Composite stratigraphic section for locations
below 115or in French River quadrangle.
{C.
M;
Moss, 1977)
0
360
I
0
270-
Measurements of planar cross bedding in deltaic
sands and gravels. Section 31; 'I'52N, Rl2W; 24
observations.
(C. M. Moss, 1977)
52
�N25-2
N2S-1
Stratigraphic section, McQuade Road at Sucker River;
SW 1/4, NW 1/4, Sec. 30, T 52 N, R 12 W ~d SE 1/4,
NE 1/4, Sec. 25, T 52 N, R 13 W. Textural composition of samples: N 25-1, 32% sand, 44% silt, 24%
clay; N 25-2, 26% sand, 46% silt, 28% clay. (C. M. Moss, 1977)
·"·
. BAY-HEAD. BARS IN LAKE -SL'PERIOR
Tilll
La ke
Superior
DULUTH
Aerial oblique map of the Duluth-Superior Harbor (From Loy, W. G., 1963,
The Evolution of Bay-head Bars in Western Lake Superior, Publ. No. 10,
Great Lakes Research Di¥ision, Univ. of Michigan)
53
�29? 1:1
295 m
SILT-FINE SANO
290 m
CLAY
SILTY CLAY WITH SILT LAYERS
285
nt
CLAY, MASSIVE
280 m
CLAY WITH SILT LAYERS
275 m
SANDY GRAVEL
GRAVELY CLAY
SANO
270
CLAY WITH PEBBLES
Ill
SANO, i-lEDIUM
265 m
SILT-;INE SAND WITH CLAY LAMINAE
260 m
f,AMINATEO CLAY AND SILT
~55
m
HNE SAND
250 m
-----------------------------------------------------
CLAYEY SILT
SILTY CLAY WITH PEBBLES
Wayside Rest, Esko Quadrangle, SW 1/4, SW 1/4, Sec. 13,
T 48 N, R 16 W. (Zarth, R. J., 1977)
\
'
I
~
\'-----.
..___
Striated bedrock
from I-35 Thomson
Fm outcrop. Sketc- =C
from photograph.
North is towards to~
of figure; scale ~s
approx. 1.5.
---
J
~fi / ) Y,1
1
(A. Norton)
�
Dublin Core
The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/.
Title
A name given to the resource
Institute on Lake Superior Geology
Dublin Core
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Title
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Institute on Lake Superior Geology: Proceedings, 1979
Description
An account of the resource
Institute on Lake Superior Geology. University of Minnesota, Duluth, Minnesota. May 8-12, 1979.
Creator
An entity primarily responsible for making the resource
Institute on Lake Superior Geology
Date
A point or period of time associated with an event in the lifecycle of the resource
1979
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PDF
Language
A language of the resource
English
-
https://digitalcollections.lakeheadu.ca/files/original/4d5f21876dae8187655f5bdd3788714d.pdf
68bc6e24596e10eeea5abbcd8bbaf56f
PDF Text
Text
I INNESOTA
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THREE SYMONS
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STANDARD CONE
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OPERATING AT
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TRANSVAAL, REPUBLIC
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TRANSVAALJ
REPUBLIC OF
OF SOUTH
SOUTH AFRICA.
2,
2.
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SHOVELS J BUILT
BUILT ININMILWAUKEE
MILWAUKEE BY
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HARNISCHFEGER J HAVE
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ADAMSMINE
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KIRKLAND LAKE
LAKE,
J ONTARIO,
CANADA
SINCE IT
IT BEGAN
IN 1964k
CANADA SINCE
BEGAN OPERATIONS
OPERATIONS IN
1964.
3.
3,
ROTARY KILN
KILN COMPLETES
INDURATION OF
OF IRON
ROTARY
COMPLETES INDURATION
IRON ORE
ORE
PELLETS AT
AT 2400°F
2'400°F IN
PELLETS
INTHIS
THISGRATE—KILN
~ PELLETIZING
PELLETIZING
PLANT IN
PLANT
IN MINNESOTA.
MINNESOTA.
I
�PROCEEDINGS
Twenty Fourth
Twenty
Fourth Annual
Annual Meeting
Meeting
INSTITUTE ON LAKE
INSTITUTE
LAKE SUPERIOR
SUPERIOR GEOLOGY
HELD AT
HELD
AT THE
THE
PFISTER HOTEL
PFISTER
HOTEL
MILWAUKEE
r~IlH,~UKEE
WISCONS IN
WISCONSm
MAY9-14
9-1I4 1978
MAY
1978
J
SPONSORED BY
BY THE
SPONSORED
THE
DEPARTMENTOF
OF GEOLOGiCAL
GEOLOGICAL SCIENCES
DEPARTMENT
SCIENCES
UNIVERSITY OF
UNIVERSITY
OF WISCONSIN-MILWAUKEE
WISCONSIN-MILWAUKEE
53201
MIlWP\UKEE WISCONSIN
\JI SCo;~S IN 53201
MILWAUKEE,
G,
MURSKY C,A,
SAlOTTI AND
ANDW1H.
W,H,SCHRAMM
SCHRAMM
G1 MURSKY)
C.A1 SALOTTIJ
GEiJERAl
IT Ji"{S
GENERAL ED
EDITJRS
J
J
J
I
�1
I
I
I
I
I
1
I
I
I
I
I
SALES
I
Department of Geological Sciences,
Please order from:
from: Department
Sciences, Univer—
University of
of Wisconsin-Milwaukee,
Wisconsin—Milwaukee, Milwaukee,
Milwaukee, Wisconsin,
Wisconsin, 53201.
sity
53201. Price
Make checks
checks payable
payable to
to Institute
on Lake
Lake Superior
Superior
$5.00
(U.S.A.). Make
Institute on
$5.00 (U.S.A.).
Geology,
Wisconsin.
Geology, Milwaukee, Wisconsin.
I
I
I
I
I
�TABLE OF
OF CONTENTS
CONTENTS
GENERAL INFORMATION
GENERAL
INFORMATION .
.
.
.
.
.
.
.
.
.
.
.
.
.
vv
INSTITUTE BOARD OF DIRECTORS .
INSTITUTE
.
.
.
.
.
.
.
.
.
.
.
.
v
.
LOCAL COMMITTEE .
.
.
.
.
.
.
FIELD TRIP COMMITTEE
COMMITTEE .
SESSIONS CHAIRMEN .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
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.
.
.
.
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.
.
.
.
. ..
vi
vii
vii
ANNUAL BANQUET KEYNOTE SPEAKER . . . . . . . . . . .
ix
ACKNOWLEDGEMENTS . . . .
ix
.
.
.
.
.
.
.
.
.
.
CALENDAR OF EVENTS AND PROGRAM . . . . . . . . . . . . . .
POSTER SESSION .
. ..
xv
ABSTRACTS OF
OF PAPERS
PAPERS . . . . . . . . . . . . . . . . . . .
1
1
FIELD TRIPS .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
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.
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.
.
.
.
INDEX OF
OF AUTHORS
AUTHORS . . . . . . . . . . . . . . . . .
.
x
.
. ..
43
49
�GENERAL INFORMATION
INFORMATION
24
TH
214TH
ANNUAL
ANNUAL
INSTITUTE ON
INSTITUTE
ON LAKE
LAKESUPERIOR
SUPERIORGEOLOGY
GEOLOGY
PFISTER HOTEL
PFISTER
HOTEL
MILWAUKEE,
MILWAUKEE) WISCflNSIN
WIsrn~SIN
MAY 9-1
9-14LL 1978
~1AY
SPONSORED BY
BY THE
SPONSORED
THE
DEPARTMENT OF
OF GEOLOGICAL
DEPARTMENT
GEOLOGICAL SCIENCES
SCIENCES
UNIVERSITY OF
UNIVERSITY
OF WISCONSIN-MILWAUKEE
WISCONSIN-MILWAUKEE
MILWAUKEE,
MILWAUKEE) WISCONSIN
WISCO:~SIN
INSTITUTE BOARD OF DIRECTORS
Giblin, Ontario Division of Mines,
P.E. Giblin,
Mines, Ministry of
of Natural
Natural
Resources,
Ontario.
Resources, Sault Ste. Marie, Ontario.
J.D.
J.D. Hughes,
Hughes, Department of Geography,
Geography, Earth Science and
Conservation, Northern Michigan University,
Conservation,
University,
Marquette, Michigan.
Marquette,
M.M.
Kehienbeck, Department
Department of
of Geology,
Geology, Lakohead
Lakhead UniverM.M. Kehlenbeck,
University, Thunder
sify,
Thunder Bay,.
Bay" Ontario.
G. Mursky,
Mursky, Department
Department of
of Geological
Geological Sciences,
Sciences, University
University
G.
of'Wisconsin-Milwaukee,
Milwaukee, Wisconsin.
Wisconsin.
of Wisconsin—Milwaukee, Milwaukee,
R.C. Reed (Secretary-Treasurer),
R.C.
(Secretary-Treasurer), Geological Survey
Survey Division,
Division,
Department of Natural
Natural Resources,
Resources, Lansing,
Lansing, Michigan.
Michigan.
M.S.
M.S. Walton,
Walton, Minnesota Geological Survey,
Survey, University of
Minnesota, Minneapolis,
Minnesota,
Minneapolis, Minnesota.
Minnesota.
v
b
�LOCAL COMMITTEE
Conference Chairman
Gregory Mursky,
Mursky, Department
Department of
of Geological
Geological Sciences,
Sciences, University
University
of Wisconsin—Milwaukee,
Wisconsin-Milwaukee, Milwaukee,
Milwaukee, Wisconsin.
Wisconsin.
Organizing Committee
Committee
Richard Bains,
Corporation, Milwaukee,
Milwaukee, Wisconsin.
Bains, Rexnord.
Rexnord Corporation,
Frank J.
Qf Geological
Geological Sciences,
J. Charnon,
Charnon, Department Of
Sciences, University
of Wisconsin—Milwaukee,
Wisconsin-Milwaukee, Milwaukee,
Milwaukee, Wisconsin.
Wisconsin.
John Erb,
Milwaukee, Wisconsin
Erb, Allis-Chalmers Corporation,
Co~po+ation, Milwaukee,
Robert E.
E. Gernant,
Gernant, Department of Geological Sciences,
Sciences, University
of Wisconsin-Milwaukee, Milwaukee,
Milwaukee, Wisconsin.
Wisconsin.
Donna McElroy,
McElroy, Department of
of Geological
Geological Sciences,
Sciences, University
University
of Wisconsin-Milwaukee,
Wisconsin—Milwaukee, Mill·'aukee,
Milaukee, Wisconsin.
of
Wisconsin.
Katherine G.
G. Nelson,
Nelson, Department of Geological
Geological Sciences,
Sciences,
Milwaukee, Wisconsin.
Wisconsin.
University of
of Wisconsin,
Wisconin, Milwaukee,
Mervin Nelson,
Nelson, Mervin Nelson
Nelson and
and Associates,
Associates, Milwaukee,
Milwaukee, Wisconsin.
Wisconsin.
A. Paull,
Richard A.
Paull, Department of Geological Sciences,
Sciences, University
University
Wisconsin-Milwaukee, Milwaukee, Wisconsin.
of Wisconsin-Milwaukee,
Wisconsin.
Gordon R.
R. Pirie,
Pine, Department
Gordon
Department of
of Geological
Geological Sciences,
Sciences, University
University
Qf Wisconsin-Milwauk~e,
Wisconsin-Milwaukee, Milwaukee,
of
Mi~waukee, Wisconsin.
Wisconsin.
Charlene Ryder,
Ryder, Harnisch~eger
Harnischeger Corporation,
Charlene
Corporation, Milwaukee,
Milwaukee, Wisconsin.
Wisconsin.
Charles A.
A. Salotti,
Salotti, Department
Department of
of Geological
Geological Sciences,
Sciences, University
University
Charles
Wisconsin—Milwaukee, Milwaukee, Wisconsin.
of Wisconsin-Milwaukee,
Wisconsin.
Department of of
Geological
Sciences,
University University
William
B. Schramm, Department
Geological
Sciences,
William }.
of
Wisconsin-Milwaukee,
Milwaukee,
Wisconsin.
of Wisconsin—Milwaukee,
Milwaukee,
Wisconsin.
Robert W.
W. Taylor,
Taylor, Department
Department of
of Geological
Geological Sciences,
Sciences, University
Robert
Wisconsin'.
of ~visconsin-Milwaukee,
Wisconsin—Milwaukee, Milwaukee, Wisconsin.
Carol Taylor, Cedarburg,
Cedarburg, Wisconsin.
David E.
E. Willis,
Willis, Department
Department of
of Geological
Geological Sciences,
Sciences, University
of Wisconsin—Milwaukee,
Wisconsin-Milwaukee, Milwaukee, Wisconsin.
Wisconsin.
vi
�FIELD TRIPS
Chairman, R.A.
Chairman,
R.A. Paull,
Paull, Department of
of Geological
Geological Sciences,
Sciences, UniverUniverof Wisconsin-Milwaukee,
Wisconsin-Milwaukee, Milwaukee,
sity of
I1ilwaukee, Wisconsin.
Trip II -- Southwestern
Southwestern Wisconsin Zinc
Zinc —
- Lead District
W.A. Broughton,
W.A.
Broughton, University of Wisconsin-Platteville, Platteville,
Platteville,
Wisconsin.
A.V.
A.V. Heyl,
Heyl, U.S.
U.S. Geological
Geological Survey,
Survey, Reston,
Reston, Virginia.
Virginia.
M.G.
M.G. Mudrey,
Mudrey, Jr.,
Jr., Wisconsin Geological
Geological and
and Natural
Natural History
History Survey,
Survey,
Madison, Wisconsin.
Madison,
Wisconsin.
W.S. West,
West, U.S.
W.S.
U.S. Geological Survey, Platteville,
Platteville, Wisconsin.
Wisconsin.
Trip II
Mineral Extraction and Processing
II -- Mineral
Equipment Manufacturers in the Greater
Equipment
Milwaukee Area
C.A. Salotti,
C.A.
Salotti, Department of Geological Sciences,
Sciences, University
University of
of
Wisconsin—Milwaukee,
Milwaukee
Wisconsin.
Wisconsin-Milwaukee,
Trip III -- Precambrian Rhyolite and
and Granite
Granite
Inliers in South—Central
Inliers
South-Central Wisconsin.
E.I. Smith,
Wisconsin—Parkside,
E.I.
Smith, Division rf
nf Science, University of Wisconsin-Parkside,
Kenosha,
Kenosha, Wisconsin.
SESSIONS CHAIRMEN
A.T.
A.T. Broderick,
Broderick, Manager,
I1anager, Mineral
Mineral Development,
Development, Inland
Inland Steel
Steel Company,
Company,
Ishpeming, Michigan.
Ishpeming,
J.D. Hughes,
J.D.
Hughes, Chairman,
Chairman, Department of
~f Geography, Earth
Earth Science
Science
and Conservation,
Conservation, Northern Michigan University,
University, Marquette,
Marquette,
Michigan.
J.O. Kalliokoski,
Kalliokoski, Chairman,
Chairman, Department
Department of
of Geology,
Geology, Michigan
Michigan
J.O.
Technological University, Houghton,
Houghton, Michigan.
Michigan.
vii
�M.M.
M.M. Kehienbeck,
Kehlenbeck, Chairman,
Chairman, Department of Geology,
Geology, Lakehead
University, Thunder
Thunder Bay,
Bay, Ontario.
Ontario.
E.R.
May, Senior Geologist,
E.R. May,
Geologist, Exxon
Exxon Company U.S.A.,
U.S.A., Rhinelander,
Rhinelander,
Wisconsin.
Rachel
Rachel K.
K. Paull,
Panll, Department of Geology
of Wisconsin-Madison, Madison,
Madison,
and
and Geophysics,
Geophysics, University
University
Wisconsin.
Wisconsin.
P.K.
P.K. Sims,
Sims, U.S.
U.S. Geological Survey, Denver,
Denver, Colorado.
Colorado.
M.S.
M.S. Walton,
Walton, Director,
~irector, Minnesota
Minnesota Geological
Geological Survey,
Survey, Minneapolis,
Minneapolis,
Minnesota.
viii
�ANNUAL BANQUET
BANQUET KEYNOTE
KEYNOTE SPEAKER
SPEAKER
Congressman James
James Santini,
Santini, House
House of
of Representatives,
Representatives, Washington,
Washington,
Member,
D.C.
Member, Committee
Committee on
on Interior
Interior and
and Insular
Insular
D.C.
Affairs;
Affairs; Subcommittee
Subcommittee on
on Oversight
Oversight of
of Public
Public Lands
Mines
Mines and
and Mining.
Mining.
ACKNOWLEDGEMENTS
ACKNOWLEDGEMENTS
The organizing committee for
for the
the 24th
24th Annual
Annual Meeting
Meeting on
on Lake
Lake
Superior Geology gratefully
gratefully acknowledges
acknowledges the
the support
support of
of the
the followfollowing corporations in
in the
the Milwaukee
Milwaukee area:
area:
Allis-Chalmers Corporation
Corporation
Harnischfeger Corporation
Rexnord Corporation
Ix
ix
�CALENDER OF EVENTS
CALENDER
AND PROGRAM
Tuesday
Tuesday
9,
9, 1978
1978
May
~lay
Pre—Institute Field Trip I
Pre-Institute
I —
- Southwestern
Wisconsin Zinc-Lead
District,
departs
Zinc-Lead
departs
from
Madison,
Wisconsin
to
Platteville,
from Madison,
to Platteville,
Wisconsin at 12:30
12:30 P.M.,
P.M., and
and return
return to
to
Milwaukee,
Wednesday
May
10,
1978
Milwaukee,
10, 1978 about
about
6:00 P.M.
P.M.
Wednesday
May 10,
10, 1978
1978
Pre—Institute
Mineral
Pre-Institute Field Trip
Trip II
II —- Mineral
Extraction and Processing
Equipment
Processing Equipment Manufacturers in the
facturers
the Greater Milwaukee
Milwaukee Area,
Area,
departs from
from the
the Pfister
Pfister Hotel
Hotel about
about
8:30
A.M., and return
8:30 A.M.,
return about
about 4.30
4:30 P.M.
P.M.
1:00 -- 3:30
3:30 P.M.
and
6:00 —9:00
-9:00 P.M.
P.M.
Early Registration,
Registration, near the
the Imperial
Imperial
Ballroom, Pfister Hotel
Ballroom,
Hotel
7:30 -- 10:00 P.M.
Conference 'Smoker",
"Smoker", Henry
Henry && Louis
Louis Room,
Room,
Pfister Hotel.
Hotel.
Thursday
May
Hay 11, 1978
1978
7:00 —- 8:00 A.M.
7:00
Early Registration near
near the
the Imperial
Imperial Ballroom,
Ballroom,
Pfister
Pfister Hotel.
Hotel.
8:00—11:55
8:00-11:55 A.M.
A.M.
Morning Session,
Session, Imperial
Imperial Ballroom,
Ballroom, Pfister
Hotel.
Hotel.
9:00 A.M.
A.M. -- 4:50 P.M.
Poster Session,
Session, Henry and Louis Room,
Room, Pfister
Hotel
1:30 —- 4:50 P.M.
Afternoon Session,
Session, Imperial
Imperial Ballroom,
Ballroom, Pfister
Hotel.
6:00 P.M.
P.M.
Cocktail Hour
Hour (cash
(cash bar),
bar), Henry
Henry and
and Louis
Louis
Room,
Room, Pfister
Pfister Hotel.
Hotel.
7:00 P.M.
P.M.
Annual Banquet,
Banquet, Imperial
Imperial Ballroom,
Ballroom, Pfister
Pfister
Hotel. Keynote speaker:
Congressman James
speaker: Congressman
James Santini.
Santini.
xx
�Friday
Friday
12, 1978
1978
May 12,
8:10 A.M.
A.H. —- 12:10
12:10 P.M.
P.M. Morning
Morning Session,
Session, Imperial
Imperial Ballroom,
Ballroom,
8:10
Pfister
Pfister Hotel.
Hotel.
4:10 P.M.
P.r-!.
1:30 —- 4:10
Afternoon
Afternoon Session,
Session, Imperial
Imperial Ballroom,
Ballroom,
Pfister
Pfister Hotel.
Hotel.
6:30 P.M.
P.M.
6:30
Post—Institute
Post-Institute field
field trip
trip III
III —Precambrian
Precambrian Rhyolite
Rhyolite and
and Granite
Granite Inliers
Inliers
in
in South-Central Wisconsin departs from
from
the Pfister Hotel,
Hotel, for
for Oshkosh,
Oshkosh, Wisconsin.
Wisconsin.
This field
field trip
trip will
will return
return to
to Milwaukee,
Milwaukee,
Saturday, May 13,
13, 1978
1978 about
about 6:30
6:30 P.M.
P.M.
xi
xi
�TECHNICAL PROGRAMS
A.M.
8:00 —- 11:55
11:55 A.M.
Thursday, May 11,
11, 1978
1978
Morning Session
Session -- Co-Chairmen:
Rachel
Rachel K.
K. Paull
Paull and
and Paul
Paul K.
K. Sims
Sims
8:00
8:00
Opening Remarks
Remarks
8:15
8:15
Smith, E.I.
E.I.
A
A New Precambrian Surface Contour Map for
for
South-Central
South-Central Wisconsin.
Wisconsin.
8:35
Zietz, I.
I.
A
A New Detailed
Detailed Aeromagnetic Map Covering
Most of
of the
the Precambrian
Precambrian Shield
Shield in
in Wisconsin.
Wisconsin.
8:55
Sims, P.K.
P.K.
Peterman, Z.E.
Z.E.
Precambrian Geologic Framework of Northern
Wisconsin.
Wisconsin.
9:15
Cannon, W.F.
W.F.
A
A Middle
Middle and
and Late
Late Precambrian
Precambrian Fault System
System
in Northern Wisconsin and Northern Michigan.
9:35
Jones, D.G.
D.G.
Geology of the Iron Formation and Associated
Rocks of the
the Jackson
Jackson County
County Iron
Iron Mine,
Mine,
Jackson
Jackson County, Wisconsin.
Wisconsin.
9:55 -- 10:15
COFFEE BREAK
10:15
Van Schnius,
Schmus, W.R.
Woronick, R.E.
R.E.
Egger, N.L.
N.L.
Geochronologic Relationships
Relationships in
in the
the Carney
Geochronologic
Lake Gneiss
Gneiss and other Basement Gneisses
Gneisses in
in
Dickinson County,
County, Upper Michigan.
10:35
DuBois, J.F.
J.F.
Van Schxnus,
Schmus, W.R.
Petrology and Geochronology of Archean
Gneiss in the Lake Arbutus Area,
Area, West-Central
West-Central
Wisconsin.
10:55
R.D.
Hammond, R.D.
Van Schmus, W.R.
W.R.
Geochronology of Archean Rocks
Rocks in
Marquette County,
County, Upper Michigan.
Michigan.
11:15
Peltonen, D.R.
D.R.
Salotti, C.A.
Salotti,
Taylor,
R.W.
Taylor, R.W.
Relations Between Soil Geo9hemistry
Geochemistry and
Bedrock Geology, Iron
Iron County,
County, Wisconsin.
Wisconsin.
11:35
11:35
Cummings, M.L.
M.L.
Myers, P.E.
P.E.
Petrology and Geochemistry of Amphibolites,
River, Eau Claire County, Wisconsin.
Eau Claire River,
Wisconsin.
11:55 —
- 1:30
LUNCH
xii
�1:30
1:30 —- 4:50
4:50 P.M.
P.M.
Thursday,
Thursday, May
May 11,
11, 1978
1978
Afternoon Session
Session -- Co-Chairmen:
Co-Chairmen:
A.T.
A.T. Broderick
Broderick and
and J.
J. Kalliokoski
Kalliokoski
1:30
1:30
Ojakangas, R.W.
R.W.
Criteria
Criteria for
for Alligator
Alligator River
River Type
Type
Uranium
Uranium Deposits
Deposits in
in the
the United
United States.
States.
1:50
1:50
Kalliokoski, J.
J.
Kalliokoski,
The Unconformity-Type
Unconformity-Type Proterozoic
Proterozoic
Pitchblende Ore Body Model and
and Its
Its
Application to
to Northern
Northern Michigan.
Michigan.
2:10
2:10
Peterman, Z.E.
Z.E.
Peterman,
P.K.
Sims, P.K.
Baseline Uranium and Thorium in Archean
and Lower
Lower Proterozoic
Proterozoic Rocks
Rocks of
of the
the
Marenisco—Watersmeet
Marenisco-Watersmeet Area,
Area, Michigan.
Michigan.
2:30
2:30
D.G.
Meineke, D.G.
M.K.
Vadis, M.K.
Klaysmat, A.W.
A.W.
Pilot Exploration Geochemical Survey of
Uranium
Uranium in
in Organic-Rich
Organic-Rich Lake
Lake Sediments,
Sediments,
Northeastern
Northeastern Minnesota.
Minnesota.
2:50
J.
Trow, J.
Possibilities
possibilities for
for Uranium-Gold
Uranium-Gold QuartzQuartzPebble Ores in the
the Lake Superior Region
in the Light of a New Model for
for Elliot
Elliot
Lake—Witwatersrand
Lake-Witwatersrand Genesis.
Genesis.
3:10"3:l0 - 3:30
COFFEE BREAK
3:30
W.S.
Meddaugh, W.S.
Salotti, C.A.
Mursky, G.
G.
The Distribution of Uranium and Thorium in
the Wolf
Wolf River
River Batholith,
Batholith, Northeastern
the
Wisconsin.
3:50
Heinrich, E.W.
E.W.
Industrial Sand and Sandstone Resources of
of
Michigan.
4:10
Nebrija, E.L.
Welkie,
Welkie, C,J.
CJ.
Meyer,
Meyer, R.P.
Gere,
Jr.
Gere, M.A. Jr.
Offshore Sand and
and Gravel
Gravel Exploration
Exploration
Offshore
in Western Lake Michigan.
4:30
4:30
Economic Mineral
Mineral Production in
in Michigan
Michigan
Economic
Past and Present.
Present.
xiii
xiii
�8:10
8:10 —- 12:10
12:10 A.M.
A.M.
Friday,
Friday, May
May 12,
12, 1978
1978
Morning
Morning Session
Session -- Co-Chairmen:
Co-Chairmen:
M.M.
M.M. Kehienbeck
Kehlenbeck and M.S.
M.S. Walton
8:10
Molling,
MoIling, P.A.
P.A.
Tyson,
Tyson, R.M.
R.M.
Chang, I..L.Y.
L.L.Y.
Chang,
A
iA Petrographic
Petrographic Guide
Guide for
for Unit
Unit Identif
Identification
River Troctolite,
cation of
of the
the Partridge River
Duluth
Duluth Complex,
Complex, Minnesota.
Minnesota.
8:30
8:30
Foose, M.P.
M.P.
Cooper, R.W.
R. W.
Faulting in
in Part
Part of
of the
the Duluth
Duluth Complex,
Complex,
Northeastern
Northeastern Minnesota.
Minnesota.
8:50
8:50
Bauer,
Bauer, R.L.
R.L.
Polyphase Deformation
Deformation in
in Archean
Archean Schists
Schists
of the
the Western Lake
Lake Vermilion
Vermilion Area,
Area,
Minnesota.
Minnesota.
9:10
9:10
Cambray,
Cambray, F.W.
F.W.
Plate Tectonics
Tectonics as
as aa Model
Model for
for the
the EnviEnvironment of
of Sedimentation
Sedimentation the
the Marquette
Marquette
Super
group and the Subsequent
Supergroup
Subsequent Deformation
Deformation
and Metamorphism
Metamorphism Associated
Associated with
with the
the
Penokean Orogeny.
Orogeny.
9:30
Larue, D.K.
D.K.
Problems in
in Paleogeographic
Paleogeographic ReconstrucReconstruction of the Chocolay and
and Lower
Lower Menominee
Menominee
Group Sedimentation, Marquette Range
Range
Supergroup , Lake Superior Region.
Supergroup,
Region.
9:50 -- 10:10
COFFEE BREAK
10:10
Massey, N.W.D.
N.W.D.
The Geochemistry of Keweenawan
Keweenawan Lavas
Lavas of
of
the Mamainse Point Formation,
Formation, Ontario.
Ontario.
10:30
Jirsa, M.A.
M.A.
The Petrology and Tectonic
Tectonic Significance
Significance
of the Interf
low Sediments
Sediments in
in the KeweeInterflow
nawan North Shore Volcanic Group of
Northeastern
Northeastern Minnesota.
Minnesota.
10:50
10:50
West
john, D.
D.
Westjohn,
Cambray, F.W.
Cambray,
F.W.
Finite Strain in the Precambrian Kona
Formation
Formation of
of the
the Marquette
Marquette Synclinoriuxn.
Synclinorium.
11:10
11:10
Strakele, A.E.
A.E.
The Geology and
and Petrology
Petrology of
of the
the Wine
wine
Lake Intrusion,
Lake
Intrusion, Cook County,
County, Minnesota.
11:30
11:30
Cambray, F.W.
The Origin and Timing of Cleavage FormaThe
Formathe Siamo
Siamo Slate
Slate of
of Precambrian
Precambrian
tion in the
X
X Age, Marquette County,
County, Michigan.
Michigan.
11:50
11:50
Hughes, J.D.
Hughes,
J.D.
A
A Post Two Creeks Buried Forest in
in
Michigan's Northern Peninsula.
12:10 —
- 1:30
LUNCH
xiv
�1:30 —- 4:10 P.M.
Friday, May 12,
Friday,
12, 1978
Afternoon Session
Session -- Co-Chairmen:
J.D.
J.D. Hughes and E.R.
E.R. May
May
1:30
Banaszak, K.J.
K.J.
The pH of Ore
Ore Fluids of
of Mississippi
Mississippi
Valley Type
Deposits.
Type Deposits.
1:50
Cummings, M.L.
M.L.
Stratigraphy and Mineralization,
Mineralization,
Quinnesec Formation, Northeastern
Northeastern
Wisconsin.
2:10
Aaquist, B.E.
B.E.
Hodder, R.w.
R.W.
Microstylolites—An
Microstylolites-An Indicator
Indicator for an
Early Stage of Native Copper Deposition
in a
Phyolite Tuff,
a Rhyolite
Tuff, Keweenaw Peninsula,
Peninsula,
Michigan.
Michigan.
2:30
Scofield, N.
N.
Native Copper Deposits Derived from
from
Keweenawan Basalt by
by Combined
Nearby Keweenawan
Igneous,
Igneous, Deuteric,
Deuteric, and Metamorphic
Processes.
3:10
2:50 -- 3:10
COFFEE BREAK
3:10
Johnson, A.
A.
Scofield, N.
N.
Doane, V.
V.
Geology and Mineralogy of Northern
Michigan Phosphorites.
Phosphorites.
3:30
Shanabrook, D.
D.
Precambrian X
X Paleopoles from the Upper
Peninsula and a
a New Method for Remanent
Vector Determination.
Determination.
3:50
Luther, F.R.
F.R.
The Geology of
of the
the Gore
Gore Mountain
Mountain Garnet
The
Deposit, Southeastern Adirondacks,
Deposit,
Warren County,
County, New
New York.
York.
END OF TECHNICAL SESSIONS
SESSIONS
POSTER SESSION
Thursday, May ii,
Thursday,
11, 1978
4:50 P.M.
8:00 A.M.
A.M. -- 4:50
M.G.
Mudrey, M.G.
Aereomagnetic Map
Map of
of Northern
Northern Wisconsin.
Wisconsin.
Sims, P.K.
Sims,
Cannon, W.F.
W.F.
Mudrey, M.G.
M.G.
Preliminary Geologic Map of Northern
Wisconsin
Wisconsin.
Shaffer, N.
N.
Possibility of Mississippi Valley-Type
Ore Deposits in
in Indiana.
Indiana.
xv
�h
I
�MICROSTYLOLITES-AN
MICROSTYLOLITES-AN INDICATOR
INDICATOR FOR
FOR AN EARLY STAGE
STAGE OF
NATIVE
NATIVE COPPER
COPPER DEPOSITION
DEPOSITION IN
IN AA RHYOLITE
RHYOLITE TUFF,
TUFF,
KEWEENAW
KEWEENAW PENINSULA,
PENINSULA, MICHIGAN
MICHIGAN
B.E.
B.E. Aaquist,
Aaquist, American
American Copper
Copper && Nickel
Nickel Co.,
Co., Milwaukee,
Milwaukee,
Wi,
Wi, 53226
53226 and
and R.W.
R.W. Hodder,
Hodder, University
University of
of Western
Western Ontario9
Ontario p
London,
London, Ont.
Onto N6A
N6A 5B7
5B7
ABSTRACT
Microstylolites
Microstylolites are
are contact
contact surfaces
surfaces between
between clasts
clasts in
in aa
rhyolite
rhyolite tuff
tuff hosting
hosting native
native copper
copper in
in the
the Kingston
Kingston mine.
mine.
The microstylolites conform
conform to
to Pettijohn's
Pettijohn's (1949)
(1949) definition:
definition:
"a stylolite seam
seam is
is aa surface
surface of
of contact
contact marked
marked by
by interlockinterlockor mutual
mutual interpenetration
interpenetrationof'
of the two sides.
sides. The teethteething or
like projections
projections of
of one
one side
side fit
fit into
into the
the sockets
sockets of
of like
like
on the
the other."
other." The microstylolites are
are mostly
mostly
dimensions on
chlorite grains
grains with
with their
their long
long axis
axis parallel
parallel to
to the
the contact
contact
surface. Some fine
fine grained
grained hematite
hematite is
is also
also present3
present. Quartz
and feldspar phenocrysts terminated
terminated by
by aa microstylolite
microstylolite are
are
Fluid
inclusions
in
neither
neither fractured,
fractured p nor
nor stressed.
stressed.
in pheno—
phenocrysts are similarly
similarly terminated
terminated by
by microstylolites.
microstylolites.
Depth of burial is the
the single
single most important factor
factor in
microstylolite development.
development. In sandstones,
sandstones p microstylolites
microstylolite
have been
been recorded
recorded at
at depths
depths of'
of burial
burial of
of 1250
1250 to
to 1650
1650 meters
meters
(Trurnit
1968). Tuft
Tuff in the Kingston mine is overlain
overlain by
by
(Trurnit,p 1968).
about 1700
1700 meters of
of lavas
lavas and
and sedimentary
sedimentary rocks
rocks of
of the
the Portage
Portage
Lake Lava Series,
Series, sufficient
sufficient weight to induce
induce formation of
microstylolites.
micro stylolites.
native copper
copper is common in white
white rims
rims on
In the
the tuff,
tuff p native
These rims are white where potash
rhyolite clasts.
clasts. These
reddish rhyolite
feldspar grains in clasts
clasts are
are clear
clear and
and lack
lack disseminated
disseminated
hematite of
of reddish
reddish grain
grain interiors.
interiors. Microstylolites terminate
terminate
This suggests deposition of
the white,
white p copper-bearing
copper-bearing rims.
rims. This
the
native copper and whiting of the
rims of clasts
clasts prior
prior to
to
native
the rims
microstylolite formation and,
and, hence,
hence, before
before lithification of
microstylolite
the tuff'.
tuff.
the
References
Pettijohn,
F.J. (1949);
(1949); Sedimentary
Sedimentary rocks:
rocks:
Pettijohn, F.J.
Brothers,p New
and Brothers
New York,
York, 526
526 p.
p.
Publ. by Harber
Publ.
(1968); Pressure
Pressure solution phenomena
phenomena in detrital
Trurnit, P.
p. (1968);
Sed, Geol.,
Geol., vol.
rocks:
vol. 2,
2, p.
p. 89—114.
89-114.
rocks Sed.
—3—
-3-
�The pH of Ore Fluids of Mississippi Valley
Valley Type
Type Deposits
Deposits
by
Konrad J.
J. Banaszak
Department of Geology
Indiana/Purdue University at
at Indianapolis
Indianapolis
925
W. Michigan
Michigan,t Indianapolis,
925 w.
Indianapo1is t Indiana
Indiana 46202
of the
solutions responsible
responsible for
for Mississippi
Mississippi Valley
The pH of
the ore solutions
type
deposits is
critical chemical
chemical variable
variable in the
the discussion
type ore deposits
is aa critical
musthave
havebeen
been acid,
acid, based
based
of the origin of
of these
these deposits.
deposits. This p1-I
pH must
curves,t equilibrium relations
relations with
with silicate
on zinc
zinc dispersion curves
minerals of "modern
"modern ore fluids",
fluids", and the absence of magnesium
silicates in the paragenetic sequences
sequences of
of the
the deposits.
deposits. Zinc
and
dispersion curves were recreated
recreated in the
the laboratory by Lavery and
Barnes (1971)
buffered to
to aa pH of
of 6 at
at
(1971) with model ore solutions
solutions buffered
0
basic did
did not
not reproduce
100 C.
C. The model ore solutions that
that were basic
the curves.
have both aa low partial
curves. Modern "ore fluids"
fluids" appear to
to have
acidic pH,
pH, and are probably in
pressure of carbon dioxide and an acidic
equilibrium
equilibrium with
with silicate
silicate rocks.
rocks. The composition of fluid
fluid inclusions
inclusions
in an assumed equilibrium with K-spar,
K—spar, albite,
albite, quartz,
quartz, muscovite,
muscovite, and
0
montmorillinite indicates
of 5 for
at 150
150°
montmori11inite
indicates an approximate pH of
for brines at
to 200°C.
minerals in the
200 0 C. Other evidence is
is the
the absence of silicate minerals
the
paragenetic sequence
sequence (See
(See Drever,
Drever, 1974.).
1974.). In Mississippi Valley
type deposits,
deposits, the
the absence of sepiolite,
sepio1ite t an easily crystallized
others,t 1973)t
1973), especially restricts
restricts the
phase (Christ
(Christ and others
the pH of the
ore solution to acidic values. In the presence of a silica
silica phase,
phase t
quartz or opa11ine
opalline silica,
and at
at the
the magnesium activities
either quartz
si1ica t and
of the
ore fluid
must have been
indicated by fluid
fluid inclusions,
inc1usions t the
the pH of
the ore
fluid must
no greater
greater than
than 66 at
at 100°C
1000 C and
and 55 at
at 150°C.
1500 C.
Christ, C.
C. L.
L.,t Hostet1er
Hostetler,t P.
P. B.
B.,t and
and Siebert
Siebert,t R.
R. M.
M.,t 1973
1973,t Studies
Christ,
Studies
in the system MgO —- Si02 -— C02 -— H20 (III): The activity
product of sepiolite:
sepiolite: Amer.
Amer. Jour.
Jour. Sci.,
Sci. t v.
v. 273,
273 t p.
p. 65—83.
65-83.
Drever,t J.
J. I.,
1974,t Geochemical
Geochemical model
model for
of Precambrian
Drever
I., 1974
for the origin of
Bull. Geol.
banded iron
iron formations:
formations: Bull.
Geo1. Soc.
Soc. Amer.,
Amer. t v.
v. 85,
85 t p.
p.
1099—1106.
1099-1106.
Lavery, N.
N. G.,
G., and
and Barnes,
Barnes, H.
H. L'
L.,
1971, Zinc
Zinc dispersion'in
dispersionin the
LaverYt
the
t 1971,
Econ. Geol.,
Wisconsin zinc—lead
zinc-lead district:
district: Econ.
Geo1., v.
v. 66,
66 t p.
p. 226—242.
226-242.
Wisconsin
—4—
-4-
�POLYPHASE DEFORMATION IN
POLYPHASE
IN ARCHEAN SCHISTS
SCHISTS OF THE
THE WESTERN
WESTERN
LAKE VERMILION
VERMILION AREA, MINNESOTA*
MINNESOTA *
Bauer, Department
Robert L.
Robert
L. Bauer,
Department of
of Geology
Geology and
and Geophysics,
Geophysics, University
University of
of
Minneapolis, Minnesota
Minnesota, Minneapolis,
Minnesota 55455,
55455, and Department of Geology,
Macalester College,
College, St.
St.Paul,
Paul,Minnesota
Minnesota55105
55105
ABSTRACT
A
and structural
structural study
study has
has been
been initiated
detailed petrologic
petrologic and
initiated in
in the
the
A detailed
Norwegian
Bayquadrangle
quadrangleand
andparts
partsof
of adjacent
adjacent quadrangles
quadrangles in
in the western
Norwegian Bay
western
Lake
The rock
Lake Vermilion
Vermilion area. The
rock exposures
exposures consist
consist of
of Archean
Archean schists
schists and
and
lamprophyres metamorphosed
metamorphosedto
to the
the middle
middle amphibolite
amphibolite facies
facies and
and intruded by
lamprophyres
quartz monzonite
monzonite stock
stock(Wakemup
(Wakemup Bay
Bay stock).
stock). The
The stock and
and adjacent
adjacent
aa quartz
schists
are bounded
on the
the north
north by
by the
the Vermilion
fault, on
on the southeast
schists are
bounded on
Vermilion fault,
southeast by
by
the Frazer
the
Frazer Bay
Bay fault,
fault, and
and on
on the
the south
south by
by the
the Haley
Haley fault.
fault. The
The structural
studies
reported on
on here
studies reported
here indicate the
the schists
schists have
have undergone
undergone four periods
periods of
deformation
The
most evident
evident structural
structural feature in
The most
in the
the area
areaisisaaprominent
prominent foliation
foliation
which
wraps around
around the
the Wakemup
WakemupBay
Baystock.
stock. This
This foliation
foliation (S
(si)
which wraps
1) is axial planar
planar
parallel to
to bedding
to rare
rare isoclinal
isoclinal F1
F 1 folds
folds and
and is
is parallel
bedding (S(Sj
r in
in the
the schist.
schist.
Numerous thin
Numerous
thin lamprophyre and granitic veins cutting 0 the schist are
boudinaged
or folded
folded by
by the
the flattening
flattening normal
boudinaged or
normal to S
5l'
F2
F 2 folds
folds are
are the
the most
mostcommon
common minor
minor structures
structures preserved
preserved and
and are
are
commonly accompanied
accompaniedbybyaa weak
weak to
to strong
commonly
strong axial
axial plane
plane foliation
foliation (S,).
(S). The
distribution of
of minor
distribution
minor F2
F 2 folds
folds indicates
indicates the
thepresence
presenceofofa amajor
majorsou'Thwestsou1hwestaxes of
plunging FF,2 antiform
south of
of the
plunging
antiform partially
partially exposed
exposed south
the stock.
stock. The
The axes
of the
the
minor
F, 'Tolds
show aa systematic
variation inin orientation
orientation to
to the
minor F
lolds show
systematic variation
the west,
west,
northwest and
olding (F.)
northwes~
and north of the
the intrusion
intrusion as
as aa result
result of
ofref
refolding
(F 3) of
of the
the major
major
F, structure
stoc1. Despite
F2
structure around
around the
the western
western end
end of
of the
theWakemup
Wakemup Bay
Bay stOCK.
Despite the
la1ge-sca1e
F3folding
foldingaround
aroundthe
thestock,
stock,minor
minorF'3
F folds
large-scale F3
folds are
are rare
rare and
and occur
occur only
only
Th'se folds
along
the western margin
of the
along the
margin of
the intrusion.
intrusion. The-se
folds are
are open,
open, westwardwestwardplunging
warpsof
ofthe
the foliation
foliation with
with near
near vertical axial
plunging warps
axial planes.
planes.
The shallow
shallowdips
dipsofofthe
the schist
schist near
near the
the contacts
contacts of
of the stock
The
stock and
and the
presence of a flat-lying roof pendant of
of schist and
lamprophyrenear
near the
the center
center
and lamprophyre
of the stock's
stock's exposure,
exposure, suggest
suggest the surface
surface exposures
exposures are very
very near the
the top
top of
of
the stock.
stock.
Evidence for
for an
an Fh
is restricted to
Evidence
F 11. deformation
deformation is
to kink
kink bands,
bands, up
up to 55 cm
cm
wide, which
whichdeform
deformthe
theS2
2 foliation.
wide,
A similar
similar sequence
sequence of
of structural
structural events has been recognized
north of
of the
A
recognized north
Vermilion
fault. Further study
lead to the
Vermilion fault.
study of the
the area
area isis in
in progress
progress which
which may
may lead
of major
correlation of
major structural features across
across the
the fault.
fault.
*Research supported by
by the
the Minnesota
Minnesota Geological
Geological Survey
Survey
-5-
—5—
�PLATE TECTONICS
PLATE
TECTONICS AS
AS AAMODEL
MODEL FOR
FOR THE
THE ENVIRONMENT
ENVIRONMENT OF
OF SEDIMENTATION
SEDIMENTATION
THE
AND THE SUBSEQUENT
THE MARQUETTE
MARQUETTE SUPERGROUP
SUPERGROUP AND
SUBSEQUENT DEFORMATION
DEFORMATION AND
AND
METAMORPHISMASSOCIATED
ASSOCIATED WITH THE
METAMORPHISM
THEPENOKEAN
PENOKEANOROGENY
OROGENY
CAMBRAY,
William,Department
Departmentofof Geology,
Geology, Michigan
Michigan State
CAMBRAY,
F. F.
William,
University, East
University,
East Lansing,
Lansing, Michigan
Michigan 48824
The
Marquette Supergroup
Supergroupof
of Precambrian
Xage
agehas
hasbeen
beendivided
divided into
into
The Marquette
Precambrian X
three groups.
This sequence
can be
be compared
comparedtoto the
the one
one which
which forms
forms on
on
groups. This
sequence can
plate margin
suchasasthe
theAtlantic.
Atlantic. The
aa passive
passive plate
margin such
The Chocolay
Chocolay Group
Group
represents
anepicontinental
epicontinentalshallow
shallowsea
seafollowed
followedbybythetheinitiation
initiation of
represents an
rifting
thethe
beginning
of of
Menominee
riftingatat
beginning
Menominee times.
times. The
The doming
doming associated
with rifting
would
thethe
unconformity
rifting
wouldaccount
accountforfor
unconformitybetween
between the
thetwo
twogroups
groups
and the
the separate
separate basins
basins in
in which
the banded
iron formations
formations and
andturbidites
turbidites
and
which the
banded iron
were
depositedformed
formedasasa aresult
resultof
of rifting
rifting producing
were deposited
producing local
localdepressions
depressions
such
as the
the Marquette,
Republic and
andIron
Iron River/Crystal
River/Crystal Falls
such as
Marquette, Republic
FallsTroughs.
Troughs.
This extensional
wasaccompanied
accompanied
intrusionofoftholeiite
tholeiite dykes
This
extensional phase
phase was
by by
intrusion
dykes
parallel to
Troughand
and
intrusion
sills into
parallel
to the
the Marquette
Marquette Trough
by by
thethe
intrusion
ofofsills
the sediments
within the
Subsequently the area
the
sediments within
the troughs.
troughs. Subsequently
area underwent
underwent
subsidence
and accumulated
accumulatedthe
the large
large thickness
subsidence and
thickness ofofBaraga
BaragaGroup
Group sediments
sediments
which compare
comparefavourably
favourablywith
withthe
the turbidites
turbidites which
which
which formed
formed on
on the
the subsubshelf edge
edge of
ofthe
themodern
modern Atlantic
AtlanticOcean.
Ocean.
siding shelf
In this interpretation
proposed
In
interpretation ititis is
proposed that
thatthe
theIron
IronRiver/Crystal
River/Crystal
which includes
includes the
the Riverton
Riverton Iron Formation,
Falls area
area succession,
succession, which
Formation, is
contemporaneous
with the
the Menominee
Groupofof the
the Marquette
and that
contemporaneous with
Menominee Group
Marquette Range
Range and
Greenstonesrepresent
representsubmarine
submarine
extrusionsrelated
related to
to the
the Badwater
Badwater Greenstones
extrusions
the
of the
the troughs
troughs referred
referred to
rifting which
at this time.
rifting
which isisproposed
proposed at
time. Each
Each of
are
which are
are found
found today
today on
on constructive plate
plate margins.
margins.
are likened
likened to
to those
those which
Subsequent
to deposition
was
Subsequent to
depositionthe
thearea
area
wascompressed
compressedand
andmetamorphosed
metamorphosed
It isisproposed
Orogeny(1.85
(1.85- - 1.9
1.9 Ga
B.P.). It
in the
the Penokean
Penokean Orogeny
Ga B.P.).
proposed that
that during
during
this episode
Archean
this
episode deformation
deformation ofofthe
theunderlying
underlying
ArcheanBasement
Basement occurred
occurred by
by
particularly the
ductile shears
shears along
along pre-existing weaknesses,
weaknesses, particularly
the mafic
mafic
dykesreferred
referred to
to above,
producingeast-west
east-westfolding
folding in
in the
dykes
above, producing
the overlying
overlying
Marquette Supergroup.
During this phase
Marquette
Supergroup. During
phase troughs
troughs are thought
thought to
to have
have
beenthe
the locii
locii ofofgreater
andand
that
weaknesses
been
greaterstrain
strain
that
weaknessesdeveloped
developed during
during
the
were
utilised
to narrow
them
andandproduce
the earlier
earlierrifting
rifting
were
utilised
to narrow
them
producea amore
more
intense folding. The
seeminglyanomalous
anomalous
orientationsofoffolds
folds in the
intense
The seemingly
orientations
the
troughs
as the
the Republic
are thought
thought to have
controlled
troughs such
such as
Republic Trough
Trough are
have been
been controlled
by
the stress
stress distribution
distribution across
troughswith
withvariable
initial orientaby the
across troughs
variable initial
orientations.
history of the
The deformation
deformation was
The
was accompanied
accompanied by
by metamorphism.
metamorphism. The
The history
the
region has
manyfeatures
featuresinin commonwithaplate
commonwithaplatetectonic
tectonic cycle
cycle involving
region
has many
followed
byby
subsidence
aa continental
continental rift
rift
followed
subsidenceatatthe
themargin
marginof,ofananexpanding
expanding
ocean followed
followed by
movement,
ocean
by reversal
reversal ofofplate
plate
movement, subduction,
subduction,compression
compression
and metamorphism.
Thefact
fact that
that all the
cited is situated
and
metamorphism. The
the evidence
evidence cited
situated on
on
crust does
older Archean
Archean crust
does not negate
negate the hypothesis.
hypothesis. All the
themore
more recent
recent
examplessuch
suchasas the
the Appalachian
Appalachian and
andAlpine
Alpine Orogeny
are underlain
underlain by
examples
Orogeny are
by
continental crust. All this
thethe
supposed
continental
thismeans
means isisthat
that
supposedocean
oceanwas
was comcompletely
andcontinental
continentalcollision
collision resulted.
The suture zone
pletely subducted
subducted and
resulted. The
zone
associated with
with this
weare
are left
left totodebate
associated
this event
event has
has not
not been
been located
located and
and we
debate
whether
whether itit is
is present
present but
but cryptic
cryptic ororthat
thatProterozoic
Proterozoictectonics
tectonicswas
was
similar in
in all
allother
otherrespects
respects to
to plate
plate tectonics.
tectonics.
—6—
-6-
�THE
IN THE
THE ORIGIN
ORIGIN AND
AND TIMING
TIMINGOF
OFCLEAVAGE
CLEAVAGE FORMATION
FORMATION IN
THE SIAMO
SIAMO SLATE
SLATE OF
OF
PRECAMBRIAN
X AGE, MARQUETTE
PRECAMBRIAN X
MARQUETTE COUNTY,
COUNTY, MICHIGAN
MICHIGAN
CAMBRAY,
William, Department
Departmentof
of Geology,
Geology, Michigan
CAMBRAY, F. F.William,
Michigan State
State
University,
University,East
EastLansing,
Lansing,Michigan
Michigan 48824
48824
In the
the previous
previous work
work (Powell,
(Powell, C.
C. McA;
McA; 1969,
1969, Bull.
Bull.Geol.
Geol.Soc.
Soc.America)
America)
itithas
cleavage
formed
hasbeen
beensuggested
suggested that
thatthethe
cleavage
formedpenecontemporaneously
penecontemporaneously
with the
of sandstone
sandstonedikes
dikes and
andthe
the origin
origin of
theemplacement
emplacement of
ofboth
bothwas
was
ascribed
ascribed to
to dewatering
dewatering during
during late
latediagenesis
diagenesisororlow
lowgrade
grademetamormetamorphism.
In the
the outcrop
outcrop referred
referredtotobybyPowell
Powellthe
thedikes
dikescan
canbebeshown
shown to
tohave
have
been
emplacedbefore
beforedeformation
deformation and
and to
to have
undergonerotation
rotation as
been emplaced
have undergone
as
rigid
rigid bodies
bodies prior
priortotothe
theformation
formationofofthe
thecleavage.
cleavage. The
The cleavage
cleavage cuts
cuts
acros
thedikes
dikesand
andthe
thehost
hostsediment,
sediment,and
anditit is
across the
theboundary
boundary between
between the
not deformed
folds in
in the bedding
whichare
arerelated
related to
to the
the rotation
deformed bybyfolds
bedding which
The
sense
of
this
rotation
is
consistent
with
of the
the dikes.
dikes. The sense of this rotation is consistent with the
the shear
shear
magnitude however
couple
on the
the limbs
limbs of
of the
couple on
the major
major fold. The
The magnitude
however is
greater than
one
than that
thatpredicted
predictedif if
oneassumes
assumes the
the dikes
dikes originated
originatednormal
normal
to bedding
and
were
deformed
by
flexural
slip
or
flexural
flow folding.
bedding and were deformed by flexural slip or flexural flow
This can
can be
introducing aa flattening
This
beexplained
explainedbyby"additional
"additionalstrain"
strain" introducing
flattening can
across
as the
across the bedding
bedding as
the fold
fold develops.
develops. The
The flattening
canbebedemondemonstrated
strated by
by the
the variation ininbed
bed thickness
thickness as
as a function
function of
of distance
distance
from
the rigid
from the
rigidsandstone
sandstone dikes.
dikes.
The
cleavageisisdefined
definedbybythin
thin laminae
laminaeofofoptically
optically irresolvable
The cleavage
material
areascontaining
containing quartz,
quartz, chlorite,
material separated
separated by
by broader
broader areas
chlorite,muscomuscoquartz, chlorite
vite and
and aa carbonate.
carbonate. The
The quartz,
chloriteand
andmuscovite
muscovite show
show features
features
vite
which
suggestthe
thecleavage
cleavageoriginated
originatedbybyrecrystallisation,
recrystallisation, possibly
which suggest
possibly
in conjunction
conjunction with
with pressure
pressure solution.
solution.
All the
theevidence
evidence points
points totocleavage
cleavage forming
forming late
late inina asequence
sequence of
of
deformation and
metamorphism
which
involvedrotation
rotation of the
deformation
and metamorphism
which
involved
thesandstone
sandstone
dikes, flattening and
and rec~ystallisation.
dikes,
recrystallisation.
—7—
-7-
�middle and
and late
late Precambrian
fault system
A middle
Precambrian fault
system
and northern Michigan
in northern Wisconsin
Wisconsin and
by
W. F. Cannon
W.
U. S. Geological Survey
Survey
Reston, Virginia 22092
Reston,
22092
Interpretation
Interpretationofofaeromagnetic
aeromagneticand
and gravity
gravitymaps
mapsof
ofnorthern
northernWisconsin
Wisconsin and
and
northern Michigan
that major regional faults
Michigan suggests
suggests that
faults are
are much
much more
more abundant
abundant
than previously
previously believed.
believed. The
newly identified
identified faults
abrupt linear
than
The newly
faults appear
appear as
as abrupt
scale aeroaerotruncations of aeromagnetic
aeromagnetic patterns
patterns on
on aa newly
newly compiled
compiled 1:250
1:250 000
000 scale
(U.S.G.S.map
mapMF
MF888).
888). Some
Somefaults
faults also
also coincide
coincide with
with steep
magnetic map
map (U.S.G.S.
gravity
gravity gradients.
gradients. Many
Manyfaults
faultsproduce
producelateral
lateraloffset
offset(some
(someasasmuch
muchas
as 20
20 km)
km)
of magnetic
magnetic anomalies
anomalies caused
caused by
by middle
middle Precambrian
Precambriansupracrustal
supracrustaland
andPenokean
Penokean
indicates that
that large-scale
large-scale lateral adjustment
intrusive rocks;
rocks; this evidence
evidence indicates
adjustment took
took
place
orogeny(-1,800
(-1,800m.y.
m.y.ago).
ago). Other
Other faults,
faults,
place in the area
area after the
the Penokean
Penokean orogeny
especially in northern Michigan,
hadlarge
large vertical
vertical displaceMichigan, are known
known to have
have had
ments during
during the
the Penokean
Penokeanorogeny.
orogeny.Some
Somefaults
faultscut
cutrocks
rocksofofthe
the Wolf
Wolf River
River
ments
batholith
intrusive and
and flow
flow rocks (-1,100
('1,100
batholith 4-1,500
~1,500 m.y.
m.y. old)
old) and
and Keweenawan
Keweenawan intrusive
m.y. old).
old). Some
m.y.
Some east-trending faults and
and fractures
fractures contain
contain lower
lower Keweenawan
Keweenawan
diabase
diabase dikes.
Although the
the age
age at
at which
which it
it began
is unknown,
unknown,the
the faulting
faulting is at least
Although
began is
least as
as old
as
orogeny,and
anditit continued
continued until
until at least
as the Penokean
Penokean orogeny,
least 1,100
1,100 m
m y.
y. ago,
ago, probably
probably
episodically. Some,
most, lateral
Some, and
and perhaps
perhaps most,
lateral movement
movement isis of
ofKeweenawan
Keweenawan age.
age.
Much of
of the
the map
map pattern
pattern in
in northern
northern Wlsconsin
Wisconsinreflects
reflectsmajor
majorlateral
lateral fault
fault moveMuch
movements;
ments; it may
may be
be aa reflection of
of intraplate
intraplatetectonics
tectonicsduring
duringthe
theopening
opening of
of the
the
Keweenawan
rift, as
Keweenawan rift,
as the
the older
older Precambrian
Precambrian rocks
rocks ininMichigan
Michiganand
and Wisconsin
Wisconsin
were caught between the somewhat opposed
opposedopening
openingdirections
directions of
of the midconwere
tinent
arms of
of the
the rift
rift system.
tinent and
and mid-Michigan
mid-Michigan arms
system. AApre-Keweenawan
pre-Keweenawan fault
fault and
and
fracture
fracture system
system probably
probably controlled the
the location
location and
and orientation
orientation of
of the
the KeweenKeweellawan
rift and
of pre-existing
awan rift
and associated
associated transform faults,
faults, so
so that
that some
some segments
segments of
faults behaved
as transform
transform faults during rifting,
behaved as
rifting,whereas
whereas other
other segments
segments shifted
so
as to
to alter the
the Wisconsin-Michigan
Wisconsin-Michigan plate
plate as
as it
it moved
so as
the shape
shape Of
of the
moved generally
southward.
Regardless
of its
its origin
origin and
and history,
history, the
the fault system
Regardless of
system is important
important geologically
geologically
because
its control
control on
on the
the regional
regional map
mappattern.
pattern. Additional faults
because ofofits
faults having
having
displacements
displacements too small to resolve
resolve by
by means
means of existing
existing aeromagnetic
aeromagnetic data
data probably
probably
are also
also abundant
abundantand
andwill
willbe
beimportant
important in
in interpreting
interpreting the map
map pattern on a
a
larger scale.
scale.
—8—
-8-
�I
Petrology and
and Geochemistry of Amphibolites,
Amphibolites, Eau
Petrology
Eau Claire
Claire River,
River,
Eau Claire
Claire County,
County, Wisconsin
Wisconsin
Eau
M. L.
L. Cummings,
Cummings, Dept.
M.
Dept. of
of Geology
Geology and
and Geophysics,
Geophysics, LJW
UW -- Madison
P.
E. Myers,
Myers, Dept.
Dept. of
of Geology,
Geology, UW Claire
- Eau Claire
P. E.
Precambrian amphibolites,
amphibolites, mica schists,
Precambrian
schists, and intrusives
intrusives crop
crop out
out for
for
12 km
km along
along the
the Eau
Eau Claire
Claire River
River in
north—central Eau Claire
12
in north-central
Claire County.
County.
Massive
Massive and
and banded.
banded. mafic
mafic amphibolites,
amphibolites, with
with more
more than
than 40
40 percent
percent
hornblende
local mineral
mineral assemblages: hornblende-garnet--plagiohornblende,
have local
hornblende-garnet-plagioclase-quartz, and
and hornblende-cummingtonite-garnet-plagioclase-quartz
clase-quartz,
hornblende-cummingtonite-garnet-plagioclase-quartz
with accessory apatite,
and opaques
opaques as
as sulfides
and
with
apatite, sphene,
sphene, biotite,
biotite, and
sulfides and
oxides.
amphibolites,
oxides.
Feldspathic amphibol
ites, with 10
10 to
to 25
25 percent
percent hornblende,
hornblende, are
are
characterized by dominant plagioclase.
characterized
plagioclase. Accessory epidote, quartz,
quartz,
sphene, and
and garnet
garnet show
show variable
variable abundance.
abundance. Banding
Banding and
and hornblende
hornblende 1inunsphene,
eation are
Hornblende analyses
analyses from
from amphibolites
amphibolites show
show
eation
are indistinct.
indistinct. Hornblende
Al203
15.7 weight
weight percent with
in 1.05
1.05 to
to 1.81
between 9.8
Al 203 between
9.8 and 15.7
with Al
Al in
1.81 tetrahedral sites.
100 Mg/(Mg
Mg/(Mg + Fe) vary from
hedral
sites. 100
from 20
20 to 70
70 with
values below
with values
50 dominant.
50
dominant.
,
Mica schists
schists with assemblages:
assemblages: biotite-hornblende—epidote-plagioclasebiotite-hornblende-epidote-plagioclasequartz,
and subordinquartz, and muscovite-biotite-epidote—plagioclase-quartz
muscovite-biotite-epidote-plagioclase-quartz and
subordinate amphibolite layers
layers composed
composed of hornblende,
hornblende, biotite,
biotite, plagioclase and
quartz underlie the
100 Mg/(Mg + Fe) of
quartz
the eastern half
half of
of the
the area.
area. 100
of hornhornthese amphibolites
amphibolites ranges
ranges from
from 47
47 to
to 52.
52. Epidote in
blende in.
in. these
in both
both
assemblages contains
contains 11.5
11.5 to
to 13.0
13.0 weight
weight percent
percent Fe203.
Fe203'
An intrusion
intrusion breccia 0.75 km south of Big Falls
Falls contains amphibolite
xenoliths in
in strongly foliated
foliated granodiorite(?)
granodiorite(?) composed of biotite,
biotite, muscovite, epidote,
epidote, plagioclase,
plagioclase, and
and quartz.
quartz. AA second intrusion
intrusion breccia
breccia at
at
county highway
highway KK 1.5
1.5 km
km east of Big
Big Falls
Falls contains mafic amphibolite
xenoliths
corase—grained, flow-laminated
flow-laminated tonalite(?)
tonalite(?) matrix.
matrix. The
xenol iths in
in a,
a corase-grained,
The
rocks
rocks described above are cut
cut by
by granite
granite pegmatite
pegmatite and
and diabase
diabase dikes.
dikes.
The following,
following, tentative
tentative chronology
chronology is
is based
based on
on petrochemistry,
petrochemistry,
structure,
structure, and
and regional
regional geology.
geology. The oldest rocks
rocks -- mica schists
schists and
and
amphibolites
amphibolites -- representing volcanic sediments
sediments and mafic flows(?)
flows(?) were
intruded
by aa gabbro which differentiated into
intruded by
into mafic
mafic and
and anorthositic
anorthositic
layers.
layers. Metamorphism of these
these rocks
rocks to
to garnet amphibolite
amphibolite grade
grade accomaccompanied intrusion
intrusion of tonalite,
tonalite, trondhjemite
trondhjemite and adamellite north
north of the
the
panied
area.
area. AA second
second metamorphism produced
produced coarse
coarse hornblende
hornblende and
and plagioclase
plagioclase
in
in the
the amphibolites
amp~ibolites , while
while compositional
compositional layering
layering was
~as transposed
transposed by
by
strong
strong compressional
compressional stresses.
stresses. Synkinematic
Synkinematic intrusion
intrusion of tonalite
tonalite (1850
(1850
++ 50
m.y.) produced
produced the
the breccias
breccias east
east and
and west
west of
of Big
Big Falls,
Falls, and
and was
was
50 m.y.)
followed by
by postkinematic
postkinematic intrusion
intrusion of
of granite
granite pegmatite
pegmatite dikes.
dikes. ShearShearing
ing with contemporaneous
contemporaneous formation
formation of
of epidote
epidote and
and chlorite
chlorite was
was followed
followed
by
by prolonged
prolonged erosion
erosion after
after which east—northeast-trending
east-northeast-trending olivine
01 ivine diabase
diabase
dikes
dikes were intruded
intruded (1100-900
(1100-900 m.y.).
m.y.). Weathering and
and erosion
erosion continued
continued
until
until marine
marine deposition
deposition of
of Upper
Upper Cambrian
Cambrian sandstones.
sandstones.
,
This chronology
chronology implies
implies an
an Archean
Archean age
age for
for the
the mica
mica schists
schists and
and
This
layered
layered gabbro
gabbro sequence.
sequence.
—9—
-9-
�Stratigraphy
Stratigraphy and
and Mineralization,
Mineralization, Quinnesec Formation,
Formation, Northeastern
Wisconsin
Wis
cons in
M.
M. L.
L. Cummings,
Cummings, Dept.
Dept. of
of Geology
Geology and
and Geophysics,
Geophysics, 13W
UW —- Madison
Madison
Volcanogenic semi—massive
semi-massive to
to massive sulfide zones
zones occur at several
stratigraphic
stratigraphic levels
levels in
in the
the Quinnesec
Quinnesec Formation
Formation in
in Narinette
Marinette County,
County,
Northeastern
Northeastern Wisconsin.
Wisconsin. The Quinnesec
Quinnesec Formation
Formation includes
includes basic
basic to
to felsic
felsic
flows,
flows, tuffs,
tuffs, iron
iron formation
formation and
and clastic
clastic sediments,
sediments, that
that were
were intruded
intruded by
by
quartz diorite to
to quartz
quartz monzonite
monzonite at
at about
about 1850—1900
1850-1900 m.y.
m.y.
Two
Two types
types of
of conformable
conformable massive sulfide
sulfide deposits occur
occur in
in the
the
Quinnesec Formation.
Formation. 1)
1) 2 to 10 cm
cm beds with up
up to
to 70%
70% sulfide
sulfide in
in iron
iron
Quinnesec
formation,
formation, and
and 2)
2) 33 to
to 20
20 meter
meter sulfide
sulfide zones
zones characterized
characterized by
by subangular
subangular
quartz clasts
clasts and
and rounded
rounded graphitic
graphitic muscovite—chlorite
muscovite-chlorite clasts
clasts supported
supported
in aa sulfide
sulfide matrix.
matrix. Two
Two main zones
zones have been defined at
at stratigraphic
stratigraphic
in
levels
levels separated by approximately
approximately 300
300 meters
meters of
of basalt
basalt flow,
flow, tuffs
tuffs and
and
iron formation.
formation. The lower deposit overlies
overlies graphitic,
graphitic, sulfide—bearing
sulfide-bearing
felsic
felsic tuff and is overlain by garnetiferous
garnetiferous iron
iron formation
formation and
and biotite—
biotiteThe
upper
deposit
overlies
a
30
to
60
meter
amphibole metasediments.
overlies a 30 to 60 meter
iron formation and is capped
capped by thinly
thinly laminated,
laminated, graphitic,
graphitic, siliceous
siliceous
sediments that grade upward into
into fine
fine grained,
grained, well—bedded
well-bedded siltstones.
siltstones.
Both main sulfide
sulfide deposits
deposits overlie
overlie and
and are
are interbedded
interbedded at
at the
the base
base with
with
tremolite and anthophyllite—bearing
assemblages,
possibly
representing
anthophyllite-bearing assemblages, possibly representing
alteration zones.
zones. The sulfide mineralogy of
of the
the massive
massive sulfide
sulfide deposits
deposits
alteration
Sphalerite
and
is simple,
simple, with monoclinic pyrrhotite
pyrrhotite predominant.
predominant.
is
chalcopyrite occur throughout
throughout the
the deposits
deposits with
with sphalerite
sphalerite forming
forming loloPyrite
is
generally
secondary,
associated
with fracthin beds.
beds.
is generally secondary, associated with
fraccalized thin
tures, however,
however, some pyrite may be part of the
tures,
the metamorphic
metamorphic sulfide
sulfide
Highest Zn and
and Cu concentrations
concentrations are
are 1.0%
1.0% and
and 0.1%
0.1% respecrespecHighest
assemblage.
tively.
Iron formation
formation is
is represented by the assemblage
Iron
assemblage grunerite—quartz,
grunerite-quartz,
grunerite—ferro—actinolite—quartz,
grunerite—ferro—hornblende—ferro—
grunerite-ferro-actinolite-quartz, grunerite-ferro-hornblende-ferroactinolite—quartz,
and gruneritegrunerite—
actinolite-quartz, grunerite—ferro—hornblende—garnet—quartz
grunerite-ferro-hornblende-garnet-quartz and
Grunerite—
All
assemblages
can
contain
calcite.
stilpnomelane-quartz.
contain calcite. Gruneritestilpnomelane—quartz.
ferro—actinolite—garnet—quartz occurs in
ferro-actinolite-garnet-quartz
in high Mn bulk
bulk compositions.
compositions.
phase with
with magnetite
magnetite and
and ilmenite locally
Pyrrhotite is
is the main opaque phase
locally
Sphalerite
occurs
either
or
pyrrhotite,
abundant.
Sphalerite
occurs
with
magnetite
or
pyrrhotite,
abundant.
chalcopyrite tends
tends to be restricted to
to pyrrhotite—bearing
pyrrhotite-bearing samples.
samples. The
formation that
that underlies the upper main massive sulfide
iron formation
sulfide zone
zone is
is
divided into
into upper
upper and
and lower
lower units
units separated
separated by
by aa sulfide
sulfide rich
rich zone
zone
divided
unit is
containing 0.5% Cu and
and 0.5%
0.5% Zn.
Zn. The lower unit
is characterized by
The
upper
unit
numerous
sulfide-rich beds.
beds.
upper unit is
is characterized by
numerous thin sulfide—rich
Base metal ions
garnetiferous beds,
beds, some of which are
garnetiferous
are highly graphitic.
graphitic. Base
were available periodically during iron formation deposition with precipitation controlled
controlled by
by local
local Eh-pH
Eh—pH conditions
conditions and
and intensity
intensity of
of hydrothermal
hydrothermal
pitation
activity.
Metamorphic conditions
conditions were
were in
in the
the epidote
epidote amphibolite
amphibolite facies
facies of
of
Metamorphic
Primary
textures
are
well
preserved
with
penetrative
amphibolite
facies. Primary textures are well preserved with penetrative
amphibolite facies.
deformational features
features weakly
weakly developed.
deformational
developed.
—10--10-
�PETROLOGY AND GEOCHRONOLOGY OF
OF ARCHEAN
ARCHEAN GNEISS
GNEISS IN
THE LAKE ARBUTUS AREA,
AREA, WEST-CENTRAL
WEST—CENTRAL WISCONSIN
THE
James F.
F. DuBois
DuBois and W.
W. R.
James
R. Van Schmus
Department of Geology
University of Kansas
Lawrence, Kansas 66045
Lawrence,
66045
The
gneiss of
of central
out along the Black
central Wisconsin crops out
The basal gneiss
River in
in Clark
Clark and
and Jackson
Jackson counties
counties and
and is
is particularly
particularly amenable
amenable to
to
River
detailed study at
at a
detailed
a series of exposures below
below Arbutus
Arbutus Dam
Dam near
near Hatfield,
Hatfield,
gneiss has
has aa heterogeneous
heterogeneous composition,
composition, ranging from
Wisconsin. The gneiss
granite to
granite
to tonalite,
tonalite, and contains interlayered
inter layered amphibolite
amphibolite units.
units.
There is considerable
considerable scatter
scatter of
of the
the Rb—Sr
Rb-Sr geochronologic
geochronologic data,
data,
but an upper age limit
limit can
can be
be defined
defined by
by aa 2.8
2.8 b.y.
b.y. isochron.
isochron. This
age presumably dates the time of upper amphibolite to granulite facies
metamorphism. Later open system conditions are probably due either
to
Rb metasomatism or to loss of
to Rb
of radiogenic
radiogenic Sr.
Sr. The former
former may be
be
explained as an
an effect
effect from
from intrustion
intrustion of
of Penokean
Penokean granite
granite (1830
(1830 m.y.
m.y.
old)
old) 33 k.m.
k.m. north of
of the
the study
study area.
area. Two models are proposed for the
structural relationships between
between the
the gneiss
gneiss and
and granite.
granite. The granite
may be a small body intruding continuous and extensive gneissic terrane,
terrane,
or the gneiss may be present as a
a roof pendant within a large Penokean
batholithic
batholithic complex.
complex. Due to limited exposure it may be difficult to
prove either
either model.
model.
U—Pb
U-Pb data on zircon from the
the gneiss yield a concordia intercept
intercept
corresponding to
The lower concordia
to an
an age
age of
of 2.9
2.9 b.y.
b.y.
concordia intercept
intercept
of 1.0 b.y.
b.y. is too high to be interpreted by a simple diffusion model.
model.
It may,
may, however,
however, be explained by U
U and Pb diffusion affected by a second
second
metamorphic
metamorphic event
event about
about 1.8
1.8 b.y.
b.y. ago.
ago.
—11—
-11-
�FAULTING IN
PART OF
OF THE
THE DULUTH
DULUTH COMPLEX,
COMPLEX, NORTHEASTERN
NORTHEASTERN MINNESOTA
MINNESOTA
FAULTING
IN PART
FOOSE, Michael
S. Geological
Geological Survey,
Survey, Reston,
FOOSE,
Michael P.,
P., U.
U. S.
Reston, Va.
Va. 22092, and
and
COOPER, Roger W.,
W., Minnesota Geological
COOPER,
Geological Survey,
Survey, University
University of
of
Minnesota,
Minnesota, St.
St. Paul,
Paul, Minn.
Minn. 55108
55108
faulting and
and fracturing
Intense faulting
fracturing in
in part
part of the
the Duluth
Duluth Complex,
Complex, northnortheastern Minnesota,
Minnesota, has
eastern
has been documented by
by detailed
detailed field
field mapping.
mapping.
Faulting is
Faulting
is recognized principally by
by the
the displacement
displacement of
of mappable,
mappable,
mineral graded layers
mineral
layers that
that were
were probably
probably formed
formed in
in aa manner
manner analagous
analagous
to that
to
that of
of sedimentary
sedimentary turbidites.
turbidites. Recognition of the
the faulting,
faulting,
fracturing, and depositional
fracturing,
depositional environment establishes
establishes aa basic
basic geologic
geologic
style that
that may have significant regional
regional implications.
implications.
The area mapped
in Lake
Lake County,
County, approximately
approximately 23
23 km southeast
mapped is
is in
of Ely,
Ely, Minn.,
Minn., near
near the
the basal
basal part
part of
of the
the Duluth
Duluth Complex.
Complex. It
It is
is
between Birch Lake,
between
Lake, the
the Tomahawk Road,
Road, and
and Minnesota
Minnesota Highway
Highway 1.
1. Two
distinct rock sequences were identified.
distinct
identified. The lower
lower sequence is
is prepremedium—grained troctolites
10 percent
dominantly medium-grained
troctolites that
that contain
contain 33 to 10
intercumulus
pyroxenes and/or oxides;
oxides; the
intercumulus pyroxenes
the upper sequence
sequence is
is mediummediumto
to fine-grained
fine-grained troctolites
troctolites that
that contain
contain little
little or
or no
no intercumulus
intercumulus
pyroxenes or
or oxides.
oxides. Well-defined and mappable layering
layering is
is best
best
developed in
in these
these upper
upper troctolites.
troctolites. Most common are layers
layers that
that have
have
abundant cumulus
cumulus olivine
olivine at
at the
the base
base and
and decreasing
decreasing amounts
amounts of
of olivine
olivine
abundant
upward.
Contacts of layers
layers are sharp,
sharp, but
but inclusions
inclusions of
of olivine-poor
olivine-poor
clasts
clasts occur within the
the olivine-rich basal
basal part
part of
of overlying
overlying layers.
layers.
The olivine-poor top
of
one
layer
is
approximately
10
m
thick
top
layer is approximately 10 m thick and
and
provides
a
distinctive
marker
horizon
provides
horizon that
that can
can be
be traced
traced through
through much
much
of the
the study
study area.
area. Layers
Layers appear to
to have been
been formed
formed by
by density
density
currents
currents carrying olivine and
and plagioclase
plagioclase grains.
grains.
Faults
and
fractures
are
the
Faults
fractures
the most abundant
abundant and
and important
important strucstructures
recognized
in
the
area.
They
are
identified
principally
tures
in the area.
identified principally by
by the
the
off—setting
off-setting of mappable layers,
layers, but also by variations in
in the
the orientation
mineral laminations,
occurrence of
of gouge,
gouge, and
and the
tation of mineral
laminations, the
the occurrence
the presence
of marked topographic
the study area are three
topographic lineaments.
lineaments. In
In the
three major
major
directions of faulting.
direction trends
trends N30-40E,
N3O—OE, and
faulting. The principal
principal direction
and
less
prominent faults
less prominent
faults are usually oriented N-S
N-S and
and N35W.
N35W. However,
However,
virtually any direction of
of faulting
faulting may
may be
be observed
observed locally.
locally. Rarely,
minor folds
folds are
are observed
observed in
in association
association with
with some
some major
major faults.
faults.
Previously,
Previously, only a few
few faults
faults have
have been
been identified
identified by
by groundgroundcontrolled
mapping, largely
owing to
great difficulty
difficulty of
of detailed
detailed
controlled mapping,
largely owing
to the great
field
field mapping in
in the
the Duluth
Duluth Complex.
Complex. However,
However, the
the intense
intense faulting
faulting
documented
area defines
defines aa structural
structural style that
may be
documented in
in this
this small
small area
that may
common to
to much of
of the
the region.
region. Certainly,
Certainly, the
the possibility
possibility of
of intense
intense
faulting and fracturing
fracturing must
must be
be considered
considered in
in any
any further
further work
work and
and
interpretation of the
the Duluth
Duluth Complex.
Complex.
—12—
-12-
�ECONOMIC
MINERAL PRODUCTION
ECONOMIC MINERAL
PRODUCTION IN MICHIGAN
MICHIGAN
PAST
PAST AND
AND PRESENT
PRESENT
Milton
Milton A.
A. Gere,
Gere, Jr.
Geological
Geological Survey
Survey Division
Michigan
Michigan Department
Department of Natural
Natural Resources
Resources
Box
30028, Lansing, Michigan
Box 30028,
Michigan 48909
48909
ABSTRACT
ABSTRACT
Michigan's
mineral production
production statistics
statistics have
compiledeither
either in
Michigan's mineral
have been
been compiled
whole
or in part
whole or
part from
from 1845
1845 to the
the present.
present. In 1877
1877 Act
Act 99was
was passed
passed
which
created the
the position of
MineralStatistics.
Statistics. The
which created
of Commissioner
Commissioner ofofMineral
The
duty of
wastoto give
give the
of the
theCommissioner
Commissioner was
the governor
governor an
an annual
annual report
report
about
the yearly mineral
about the
mineral production
production statistics
statisticsand
andthe
thedevelopment
development of
of
the
smelting industries.
industries. Part
the mining
mining and
and smelting
Part of Act
Act 99 required
required all
all mining
mining
companies
submittheir
their production
companies toto submit
production figures
figurestotothe
theCommissioner.
Commissioner. In
1911
the duties
duties of
weretransferred
transferred to
to the
1911 the
of the
theCommissioner
Commissioner were
the Geological
Geological
Survey,
Survey, now
now aa Division of
ofthe
theMichigan
MichiganDepartment
Department of
of Natural
Natural Resources.
Resources.
Presently,
receives most
mostof
of the
the yearly mineral
mineral
Presently, the
the Geological
Geological Survey
Survey receives
production
statistics, exclusive
production statistics,
exclusiveofofpetroleum
petroleum and
and natural
natural gas,
gas, through
through
understandingwith
withthe
the U.S.
U.S. Bureau
a memorandum
memorandum of ofunderstanding
Bureau of Mines.
Mines. Company
data
submittedto
to the
the U.S.B.M.
sent on
on to
to the
data submitted
U.S.B.M. isis sent
the State.
State. Oil and
and gas
gas
silver
production
is collected by
directly. Copper,
production is
by the
the State
State Survey
Survey directly.
Copper, silver
and iron
iron ore
ore figures
figures are
for taxation
and
are also
also received
received separately
separately for
taxation as
as well
well
as
through the
the U.S.B.M.
U.S.B.M.
as through
Tabulationsof
of the
the value
value of
of nonmetallic,
Tabulations
nonmetallic, metallic,
metallic, and
and fuel
fuel minerals
minerals
from
1910toto present
present show
showthat
thatuntil
until 1977,
from 1910
1977, the
the fuel
fuel minerals
mineralswere
were
always the
the smallest
smallest group
group with
with the metallics
always
metallics and
and nonmetallics
nonmetallics switching
switching
leading
leading places
places several
several times.
times. In 1977
1977 the
the fuels
fuels formed
formed the
the middle
middle group
group
for the
first time.
the first
time.
Michigan's 1977
mineral production
production value,
value, according
1977 mineral
according to the
the U.S.B.M.
U.S.B.M.
Michigan's
1976total
total value
annual, preliminary
preliminary report,
report, was
$1.51billion.
billion. The
annual,
was $1.51
The 1976
value
it was
million.
record at $1,543.5
$1,543.5 million.
1910 it
was $80.5
$80.5 million~
set a record
million. In 1910
Everyone
the8383counties
countiesininthe
theState
Statecontribute
contribute to
to the
the total mineral
Everyone ofofthe
mineral
However,all
all of the
value. However,
the metallic
metallicminerals
minerals and
and aa large
large amount
amount of the
the
high value
high
value for nonmetallic
nonmetallic minerals
minerals isisproduced
produced ininthe
theUpper
Upper Peninsula.
Peninsula.
The balance
balanceofofthe
the nonmetallics
nonmetallicsand
andall
all of
of the
The
the fuel
fuel minerals
minerals are
are derived
derived
from the
the Lower
Lower Peninsula.
Peninsula.
from
—13—
-13-
�GEOCHRONOLOGY
GEOCHRONOLOGYOFOFARCHEAN
ARCHEANROCKS
ROCKSIN
IN
MARQUETTE COUNTY,
COUNTY, UPPER MICHIGAN
MICHIGAN
Roger D.
D. Hammond
Hammond and
and W.
W. R.
R. Van Schmus
Roger
Department of Geology
University of Kansas
Lawrence,
66045
Lawrence, Kansas 66045
According to
Morey and
and Sims
Sims (1976)
the Archean
Archean basement
basement of
of the
Lake
According
to Morey
(1976) the
the Lake
is composed
of two
two different
different terranes,
gneiss terrane
Superior region is
composed of
terranes, aa gneiss
terrane
dnd aa granite-greenstone
granite—greenstone terrane,
terrane, which
which differ
differ in age,
and
type, strucstrucage, rock type,
tural
style,
and
metamorphic
grade.
tural style, and metamorphic grade. They extend the boundary between
these two
two terranes
these
terranes through the central part of
of Marquette
Marquette County,
County, Michigan,
Michigan,
beneath the middle Precambrian rocks
of
the
Marquette
Range
rocks of the Marquette Range Supergroup.
Supergroup.
Locally, the
north of the
boundary, which
which are
are part
part of the
Locally,
the Archean rocks
rocks north
the boundary,
the
granite—greenstone terrane,
are known as
as the
and those
granite-greenstone
terrane, are
the Northern Complex and
those
south
boundary, which
which are
are part
of the
gneiss terrane,
are known
south of the boundary,
part of
the gneiss
terrane, are
as
as the Southern
Southern Complex.
Complex. If Morey and Sims'
Sims' model is
is correct,
correct, rocks
rocks
m.y. should be present in the gneiss
older than 3,000 m.y.
gneiss terrane,
terrane, and the
rocks of
of the
the granite-greenstone
granite—greenstone terrane
terrane should
should not
not be
be older
older than
than about
about
rocks
2,800
A geochronologic study was
was done
2,800 m.y.
m.y. A
done on the
the rocks of
of the Northern
and on
on aa granite
granite body
body of
of the
the Southern
Southern Complex
Complex which
which had
had yielded
yielded
Complex and
anomalous Rb—Sr
Rb-Sr age
age systematics
systematics with
with one
one sample
sample giving
giving aa 3,200
3,200 m.y.
m.y.
Woolsey, 1975),
1975), to
model age (Van
(Van Schmus and Woolsey,
to verify or revise Morey and
Sims'
Sims' model.
The Northern Complex
Complex consists
consists of
of granitic
granitic to
to tonalitic
tona1itic gneisses,
gneisses,
with lesser
lesser amounts
amounts of
of granites,
granites, amphibolites,
amphibo1ites, and
and volcanics,
volcanics, that
that extend
extend
approximately 80
80 kilometers
kilometers east—west
east-west and
and 40
40 kilometers
kilometers north—south.
north-south.
The eastern part
part of
of the
the Complex
Complex includes
includes aa greenstone
greenstone belt.
belt. U—Pb
U-Pb isotope
isotope
studies on zircons from samples of the gneisses and volcanics do not
indicate an age any greater than 2,750 m.y.
m.y. for rocks of the Northern
Complex.
Complex.
The rocks of the Southern Complex are primarily granitic gneisses
with lesser
lesser amounts
amounts of granites,
granites, mafic gneisses,
gneisses, and
and amphibolites,
amphibo1ites, which
extend approximately 75
75 kilometers east—west
east-west and 50 kilometers north—
northsouth.
body, 1.5 by 4 kilometers in size,
south. One granite body,
size, was mapped about
8 kilometers south
south of
of Ishpeming.
Ishpeming. It is a medium-grained
medium—grained granite which
appears gray
gray in
in outcrop
outcrop in
in the
the western half
half and
and red
red in
in the
the eastern
eastern half.
half.
Parts of
of the
the granite
granite body are
are quite
quite porphyritic
porphyritic with
with aligned
aligned feldspar
feldspar
phenocrysts.
phenocrysts. Although
Although no
no direct
direct contacts
contacts were observed,
observed, the
the presence
presence
of gneissic inclusions suggest that the granite was intruded
intruded into
into the
the
surrounding
surrounding gneiss.
gneiss. Rb—Sr
Rb-Sr isotope
isotope data
data on
on wholerock
wholerock samples
samples from
from the
the
granite define a 2,400 m.y.
m.y. isochron with a Sr87/Sr86
Sr 87 /Sr 86 intercept
intercept of
0.7200.
U—Pb
V-Pb isotope studies on zircon
Zircon from
from the
the granite do
do not indicate
indicate
an
an age
age any
any greater
greater than
than 2,600—2,700
2,600-2,700 m.y.
m.y. The
The granite
granite is
is possibly
possibly remobil—
remobilized crustal
crustal material
material as
as indicated
indicat~d by
by the
the high
high initial
initial Sr87/Sr86
Sr 87 /Sr 86 ratio.
ratio.
Ages
Ages of
of the
the rocks
rocks studied
studied from
from both
both these
these complexes
complexes conform
conform with
with
Morey
Morey and 5j?
Sims'model,
model,even
eventhough
thoughprimary
primaryages
agesininexcess
excessofof2,800
2,800 m.y.
m.y.
have
have yet
yet to
to be
be found
found from
from the
the Southern
Southern Complex.
Complex.
—14—
-14-
�INDUSTRIAL
INDUSTRIAL SAND
SAND AND
AND SANI)STONE
SANDSTONE
RESOURCES
RESOURCES OF
OF MICHIGAN
MICHIGAN
E.
E. Wm. Heinrich
Heinrich
Dept.
Dept. Geology and Mineralogy
The
The University
University of
of Michigan
Michigan
Ann Arbor, MI
48109
MI
48109
Michigan's silica,
silica, sand
sand and
and sandstone
sandstone deposits,
deposits, which range
range in
in age
from Middle Precambrian to
to Quaternary,
Quaternary, embrace a considerable diversity
of geological types
types and have a remarkable diversity of technological
applications.
applications.
Historically,
Historically, Michigan sandstones were famous for
for two
two pur-
poses:
poses: 1)
1) the
the Jacobsville sandstone (Cambrian)
(Cambrian) used as a colorful dimension
stone in the construction of
of larger
larger buildings
buildings (churches,
(churches, courthouses,
courthouses,
breweries),
breweries), mainly in
in the
the Upper Peninsula and 2)
2) the
the Marshall sandstone
(Devonian),
(Devonian), utilized in the last half of the
the 19th
19th century
century for
for abrasive
abrasive
(Grind Stone
Stone City,
City, Huron
Huron Co.).
Co.).
wheels (Grind
The spectrum of deposits and
and poten—
poten-
tial deposits,
deposits, by formation,
tial
formation, age and application, includes:
includes:
1.
1.
Sunday, Sturgeon,
Middle Precambrian quartzites:
quartzites: Sunday,
Mesnard, Ajibik,
Ajibik, and Goodrich
Mesnard,
Goodrich quartzites:
quartzites: aggregate;
the Ajibik
Ajibik may be of potential value for
the
for ferrosilicon.
ferrosilicon.
2.
2.
Munising sandstone (Late
(Late Cambrian):
Cambrian):
3.
3.
Sylvania sandstone (Lower
(Lower Devonian): presently exploited
glass—sands of the
near Rockwood as one of the premier glass-sands
United States;
States; also
also abrasive
abrasive sand
sand and
and silica
silica flour.
flour.
4.
4.
Napoleon sandstone (uppermost
Napoleon
(uppermost Devonian): quarried near
Jackson for
for flagging,
flagging, riprap
riprap and
and sandstone-bituminous
sandstone—bituminous
Jackson
hot
hot mix for pavement.
5.
5.
Pleistocene till,
till, glaciofluvial deposits,
deposits, and
and lakebeds:
lakebeds:
fill
fill sands
sands and aggregate.
6.
6.
Dune sands in southwestern Michigan
Michigan (Quaternary):
(Quaternary): active
mining for
for molding
molding sands
sands (considered
mining
(considered the industry
industry standard
for such
such sands);
sands); also
also evaluated as glass—sand.
for
glass-sand.
—15—
-15-
glass—sand potential.
glass-sand
potential.
�A POST
POST TWO
TWO CREEKS
CREEKS BURIED FOREST
A
IN MICHIGAN'S
MICHIGAN'S NORTHERN PENINSULA
IN
John D.
D. Hughes,
Hughes, Department
Department of
of Geography,
Geography, Earth
Earth Science
Science and
and
John
Conservation, Northern
Northern Michigan University,
Conservation,
University, Marquette, MI
MI 49855
9855
ABSTRACT
In 1976-77,
1976—77, spruce
spruce and
and tamarack
tamarack trees
trees in
in growth
growth position
position
In
were exposed
exposed between six and eleven
meters below the
were
eleven meters
the surface
surface
during construction
construction of the
tailings basin for
during
the Gribben
Gribben tailings
for the
the
Cleveland—Cliffs Iron
Cleveland-Cliffs
Iron Company.
Company. The
The site,
site, located sixteen
kilometers southwest
southwest of Marquette,
Marquette, Michigan,
Michigan, lies
kilometers
lies within the
the
outwash apron of the outer Marquette
Marquette moraine.
moraine.
Throughout
the excavation,
excavation, there
there is
no evidence
that glacial
glacial override
the
is ~o
evidence that
override
occurred following
following the
the period of growth such as
presence
occurred
as the
the presence
of distorted strata,
strata, sheared
sheared trees,
trees, or
or intercalated
intercalated till.
till.
+
1he outer parts
parts of two trees
yere dated at
+
14he
treesl~ere
at 9780
.
—250 C.y.a.,
C.y.a., W3904
W3901 and
and 98509850± 300
300]C.y.a.,
-250
C.y.a., W3866
W3866 (N.
(M. Rubin).
Rubln).
Spruce needles
needles from the
Spruce
the upper pars
part of the
the buried A0
Ao soil
horizon were dated
dated at
at 10,230±3001
10,230~3001 C.y.a.,
C.y.a., W3896
W3896 (M.
(M. Rubin).
Rubin).
The largest
tree
collected
has
a
diameter
of
sixty
centimeters
largest
has
sixty centimeters
and 150 growth rings.
and
rings. Most trees
trees suffered a severely
severely reretarded growth
growth rate
rate during their final
tarded
final thirty
thirty or forty
forty years
years
of growth,
growth, a
a condition that is
is attributed to climatic
climatic deterideterioration accompanying
accompanying the
the glacier's
glacier's return.
return.
Evidence in
in the Gribben
Gribben tailings
tailings basin indicated
indicated aa
minimum period of
of plant
plant growth
growth of
of 150
150 years
years following
following
recession of the Valders (Great
(Great Lakean)
Lakean) Stadial.
Stadial. Tree
growth in the
the basin was terminated by local
local ice-marginal
ice-marginal
ponding caused by glacial
glacial readvance
readvance into
into the
the area.
area.
Deposition of lacustrine sediment capped
capped by outwash gravel
gravel and
and
sand occurred during building of the Marquette-Munising
moraine
Similar dates have
moraine system.
system.
have been obtained from
from
detrital
detrital spruce and hemlock found
found in red till and
and red
red clay
clay
till in Michigan's westernmost
westernmost county
county and
and near
near Ashland,
Ashland,
Wisconsin
at elevations
elevations 400
00 to
Wisconsin at
to 600
600 feet
feet above
above present
present Lake
Lake
Superior.
Superior.
It
It appears that a
a glacial
glacial advance
advance climaxed
climaxed slightly
slightly
less
less than 10,000 years
years ago,
ago, and
and at
at that
that time,
time, almost
almost all,
all,
if not
not all,
all, of the Lake Superior
Superior basin was occupied
occupied by
by
glacial
It
glacial ice.
ice.
It is
is proposed that the name Marquette Stadial
Stadial
be adopted
adopted for
for the
the period
period of
of glacial
glacial advance
advance and
and Gribben
Gribben
Interstadial for
for the
the preceding
preceding time
time of
of retreat.
retreat.
—16—
-16-
�THE
THE PETROLOGY
PETROLOGY AND
AND TECTONIC
TECTONIC SIGNIFICANCE
SIGNIFICANCE OF
OF THE
THE INTERFLOW
INTERFLOW SEDIMENTS
SEDIMENTS IN
IN THE
THE
KEWEENAWAN
KEWEENAWAN NORTH
NORTH SHORE
SHORE VOLCANIC
VOLCANIC GROUP
GROUP OF
OF NORTHEASTERN
NORTHEASTERN MINNESOTA
MINNESOTA
Mark
Mark A.
A. Jirsa
Jirsa
University
University of
of Minnesota—Duluth
Minnesota-Duluth
Duluth,
Duluth, Minnesota
Minnesota 55812
55812
Interfiow
Interflow sediments
sediments occur
occur as
as lenticular
lenticular bodies
bodies between
between and.
and crevice
cre~ce
fillings,
fillings, within, lavas
lavas of
of the
the North
North Shore
Shore Volcanic
Volcanic Group.
Group. Their
Their structure,
structure,
texture,
texture, and composition
composition offer evidence of the
the depositional/erosional relrelationships
ationships between
between the
the volcanic
volcanic and
and sedimentary
sedimentary accumulations
accumulations and
and the
the
borderland during
during Keweenawan
Keweenawan rifting.
rifting.
surrounding borderland
The
The majority
majority of
of the
the 380
380 (total)
(total) of
of interflow
interflow sediments
sediments occur
occur as
as bedded
bedded
interflow
interflow sandstones,
sandstones, conglomerates,
conglomerates, and
and minor
minor shaly
shaly sediments.
sediments. Tabular
Tabular and
and
trough
trough cross—bedding,
cross-bedding, planar bedding and lamination,
lamination, and ripple marks are the
the
most
most prevalent
prevalent primary
primary structures.
structures. Other deposits include
include sediment—filled
sediment-filled
flow—top
flow-top breccias, clastic
clastic dikes,
dikes, and
and sedimentary/volcanic
sedimentary/volcanic breccias.
breccias. Nearly
Nearly
Most
clastic
all interflow
interflow beds
beds lie
lie on
on uneroded
uneroded flow
flow tops.
tops. Most clastic dikes
dikes are
are the
the
result
result of sediment filling
filling fractures in upper lava surfaces;
surfaces; however,
however, some
were
were filled
filled by
by sediment
sediment injected
injected into
into lava
lava fractures
fractures from
from underlying
underlying clastic.
clastic.
Mud
cracks,
slump
structures,
and
convolute
laminations
occur in
cracks,
structures,
in
deposits.
most types
types of
of deposits.
deposits.
most
These volcanogenic arkosic sediments are reddish—brown
reddish-brown to
to buff,
buff, and consist of predominantly fine—to
well—sorted grains
fine-to medium—grained,
medium-grained, subrounded,
subrounded, well-sorted
of plagioclase, clinopyroxene,
clinopyroxene, magnetite,
magnetite, and
and various
various rock
rock fragments.
fragments. The
The
dominant rock fragments
fragments are volcanic;
volcanic; however,
however, agate,
agate, chert,
chert, shale,
shale, and glass
Minor constituents
shards also occur.
occur. Actual tuff
tuff beds
beds are
are rare.
rare. Minor
constituents are
are potpotGrains
are
fresh
assium feldspar,
quartz,
and
accessory
heavy
minerals.
feldspar, quartz, and accessory heavy minerals. Grains are fresh to
to
altered, and in many cases,
altered,
cases, replaced
replaced by
by various
various zeolites,
zeolites, chlorite,
chlorite, calcite,
calcite,
and potassium
feldspar. In
In addition to silica and hematite, these
these minerals
minerals
potassium feldspar.
form the major chemical
chemical cements.
cements.
Paleocurrent indicators show predominant current flow sourhward and
southeastward towards the
the present Lake
Lake Superior
Superior Basin.
Basin. These data imply
imply a
a
fluvial
environment
of
deposition,
and
sedimentary
structures
support
this
fluvial environment of deposition, and sedimentary structures support this
Several deposits
deposits may
may reflect
reflect influences
influences of
of fluvio-lacustrine
fluvio—lacustrine
implication. Several
and eolian environments.
The response
response of
of the
the Keweenawan
Keweenawan terrain
terrain to
to rifting
rifting and
and basinal
basinal developdevelopThe
and
ment is interpreted from a combination of sedimentological,
sedimentological, petrographic,
petrographic, and
In
general,
sediment
bodies
are
thicker
clastic dike orientation
orientation analyses.
analyses. In general, sediment bodies are thicker
and more
more variable
variable in
in lithology
lithology in the
the area
area from
from Tofte
Tofte to
to Grand
Grand Portage
Portage than
than
and
This
may
suggest
more
ponding
and/or
longer
in the area from Duluth
Duluth to
to Tofte.
Tofte. This may suggest more ponding and/or longer
periods of
of volcanic
volcanic quiescence
quiescence in
in the
the northeasternly
northeasternly portions
portions of
of the
the basin.
basin.
periods
Petrology indicates
indicates predominantly
predominantly local
local (Keweenawan)
sources for
for sediments;
sediments;
Petrology
(Keweenawan) sources
however, several
several deposits
deposits had
had variable
variable sources
sources which
which may
may include
include some
some prepre—
however,
The
presence
of
agate
fragments
some
Keweenawan sediments and intrusions.
intrusions. The presence of agate fragments in some
deposits implies
implies mineralization
mineralization of
of lava
lava prior
prior to
to erosion,
erosion, and
and thus
earlier
deposits
thus an earlier
Data obtained
obtained from
from
cycle of
of volcanism,
volcanism, burial, and uplift
cycle
uplift in
in the
the source
source area.
area. Data
clastic dike
dike orientations
orientations is
is significant
significant because
because sediment
sediment filling
filling (by
whatclastic
(by whatdating the
the stress
stress
ever process)
process) occured
occured near
near the
the time
time of
of lava
lava deposition,
deposition, thus
thus dating
ever
Although
many
of
these
orientations
are
scattered
and
patterns
at
that
time.
Although
many
of
these
orientations
are
scattered
and
patterns at
time.
reflect cooling
cooling fractures
fractures filled
filled with
with sediment,
sediment, some
some conjugate
conjugate orientations
orientations
reflect
occur
stresses.
occur which
which may
may reflect
reflect regional stresses.
This study
study was
was partially funded
This
funded by the Minnesota Geological
Geological Survey.
Survey.
—17—
-17-
�Geology and
and Mineralogy
Mineralogy of
of Northern
Geology
Northern Michigan
Michigan Phosphorites
Phosphorites
Scofield and
Allan Johnson,
Johnson, Nancy
Nancy Scofield
and Virginia
VirginiaDoane
Doane
Institute ofofMineral
Institute
MineralResearch
Research
Michigan Technological
Technological University
University
Michigan
Houghton, Michigan 49931
Houghton,
Widespreadoccurrences
occurrencesofof Middle
Middle Precambrian
Precambrianphosphate-bearing
phosphate-bearingstrata
strata in
Widespread
in
the
werefirst
first reported
the central part
partofofthe
theUpper
Upper Peninsula
Peninsula of Michigan
Michigan were
reported by
by
Cannonand
andKlasner
Klasner (1976). Surface
Surface exposures
Cannon
exposures of the
the bedded
bedded phosphorites
phosphorites were
were
found
of several
basins near
near the
the contact
contact with
with older
found at margins
margins of
several sedimentary
sedimentary basins
older
Archean
crystalline rocks.
The thickest
thickest known
phosphorite section
section (100
Archean crystalline
rocks. The
known phosphorite
(100 m)
m) is
the eastern
eastern margin
margin of
of the
in Section
Section 15,
15,T49N
T49N R28W,
R28W, ononthe
the Dead
Dead River
River Basin
Basin 17
17
miles northwest
The rocks
rocks here
here strike
strike NS
miles
northwest of
of Ishperning,
Ishpeming, Michigan.
Michigan. The
NS and
and dip
steeply to the
Early in 1977,
wascollected
collected for
steeply
the west.
west. Early
1977, aa bulk
bulk surface
surface sample
sample was
mineralogical study
studyand
andpreliminary
preliminarybeneficiation
beneficiationtests
testsbybythe
theInstitute
Institute of
mineralogical
Mineral Research
During the
the summer
1977,the
theupper,
upper,richest
richest section
Research (IMR).
(IMR). During
summer ofof1977,
was
diamonddrilled
drilled by
in cooperation
was diamond
by IMR
IMR in
cooperation with the
theMichigan
Michigan and
and U.S.
U.S. Geological
Geological
Surveys.
Results
the apatite to
thiswork
work showed
showed the
to be
be present
present as
as pebbles,
pebbles, oöids
ooids
Results of this
andasasfine
finecrystallites
crystallites in aa quartzitic
the apatite
apatite is
is in
and
quartzitic matrix.
matrix. Most
Most ofof the
in length. Aphanitic apatite
dark, elongate
elongate pebbles
pebbles 1-30
1-30 mm
mm in
apatitecomprises
comprises75-80%
75-80%
Submicrongraphite,
graphite, pyrite
pyrite euhedra,
of the
the pebbles.
pebbles. Submicron
euhedra, quartz
quartz and
and stilpnomelane
stilpnomelane
are also present.
This apatite has
identified by
francolite, the
are
present. This
has been
been identified
by XRD
XRD asasfrancolite,
the
carbonatefluorapatite.
fluorapatite.
carbonate
Someofofthe
the rich surface
P205,but
but the
the bulk
Some
surfacebeds
beds contained
contained as
as much
much as
as 15%
15% P205,
However,
the drill
drill core
However, ininthe
coreapatite
apatitedecreased
decreased
zones
with depth,
depth, although
although intermittent
intermittentricher
richer
zoneswere
wereencountered.
encountered. Calcite
Calcite was
was
observed
with depth
replaced some
apatite.
observed to be
be more
more abundant
abundant with
depth and
and may
may have
have replaced
some apatite.
Several pyrite-rich
pyrite-rich zones
Several
zoneswere
were encountered,
encountered, but
but surface
surface weathering
weathering had
had oxidized
The conglomerate
conglomeratecontaining
containing the
the apatite
muchofof the
the pyrite
pyrite in
much
inthe
theupper
upper 55meters.
meters. The
pebbles appears
appearsto
to have
shale-pebble origin
origin and
pebbles
have aa shale-pebble
and the
theoccurrence
occurrencemay
may be
be aa channel
channel
deposit.
surface
6.95% P205.
P205.
surface sample
sample averaged
averaged 6.95%
The
bestresults
resultsofof initial
initial beneficiation
fatty acid
The best
beneficiationtests
testsusing
using aa standard
standard fatty
acid
float produced
float
produced aa27%
27% grade
grade P205
P205 at 60%
60% recovery.
Reference
F. and
Kiasner, J.
J. S.
ApatiteCannon, W.
W. F.
and Klasner,
S. (1976),
(1976), Phosphorite
Phosphorite and
and Other
Other ApatiteBearing
Rocksinin the Precambrian
of Northern
Bearing Sedimentary
Sedimentary Rocks
Precambrian of
Northern Michigan,
Michigan, U.S.G.S.
U.S.G.S.
Circular 746,
746, 66 p.
p.
—18—
-18-
�GEOLOGY OF
OF THE
THE IRON
IRON FORHATION
FORMATION AND ASSOCIATED ROCKS
GEOLOGY
OF THE
THE JACKSON
JACKSON COUNTY
COUNTY IRON
IRON MINE,
MINE, JACKSON COUNTY,
OF
COUNTY, WISCONSIN
WISCONSIN
David G.
C. Jones,
Jones, Department
Department of
of Geology
Geology and Geophysics,
David
Geophysics, University
University of
Wisconsin, Madison,
Madison, Wisconsin
Wisconsin 53706
53706
Wisconsin,
AB STRACT
ABSTRACT
Precambrian
Precambrian magnetite
magnetite iron
iron formation
formation crops
crops out
out as
as low
low hills
hills in
in
Jackson County,
Jackson
County, Wisconsin.
Wisconsin.
The
pit
The Jackson
Jackson County Iron Company's open pit
taconite mine
mine was
was opened
opened in
in the
taconite
the largest of the
the hills.
hills. The
The ore
ore body
body mined
mined
strikes northwest
northwest and
and dips
dips 70—80
degrees southwest.
strikes
70-80 degrees
southwest.
The
The ore
ore body
body is
is aa
lens 915
915 meters
meters in length and 150 meters in
lens
in width.
It
It averages
averages about
about 35%
magnetite.
magnetite. Dominant
the iron
iron formation
formation are:
Dominant mineral
mineral assemblages within the
are:
1. magnetite-quartz-grunerite-ferroactinolite
magnetite—quartz—grunerite—ferroactjnolite
1.
2. magnetite-quartz-cummingtonite-biotite
magnetite—quartz—cummingtonjte_bjotite
2.
3. magnetite-quartz-garnet-Ca-rich
magnetite—quartz-.garnet—Ca—rich hornblende-ferroactinolite-grunerite
hornblende—ferroactinolite—gruneritc
3.
Amphiboles commonly contain visible exsoiution
Amphiboles
exsolution features.
features.
Ca-rich
Ca—rich hornblende
(hastingsite) replaces garnet.
(hastingsite)
garnet.
Southwest of
Southwest
of the
the iron formation
formation is
is aa highly
highly weathered
weathered siliceous
siliceous schist
schist
as the
of quartz,
and
mapped as
the hangingwall
hangingwall schist.
schist. It
It is composed of
quartz, biotite,
biotite, and
sericite.
Weathering decreases
sericite.
decreases with depth.
depth. The
schist, northeast
The footwall
footwall schist,
of the
ore body,
of
the ore
body, is
is identical
identical to
to the
the unweathered
unweathered hangingwall
hangingwall schist.
schist.
Both
are composed mainly of three
are
three assemblages:
assemblages:
1. quartz-chlorite-muscovite-andalusite
quartz—chlorite—muscovite—andalusje
1.
2.
quartz—biotite—chlorite_stauroljte_garnet_andalusjtemuscovite
2. quartz-biotite-chlorite-staurolite-garnet-andalusite-muscovite
3. quartz-biotite-oligoclase-muscovite
quartz—biotite--oligoclase—muscovite
3.
Phase relations
relations suggest
suggest that
rocks attained
attained chemical
chemical equilibrium at
at
Phase
that the
the rocks
staurolite—grade metamorphism.
staurolite-grade
metamorphism. Texturally the
the footwall
footwall schist ranges from
from
a
a highly foliated
foliated coarse—grained
coarse-grained schist
schist to
to aa nearly
nearly granular
granular schist.
schist.
Interlayered
with the
pelitic schist
schist are
are zones
of grunerite-garnet-quartz
grunerite—garnet—quartz
Interlayered with
the pelitic
zones of
iron
iron formation and poorly foliated,
foliated, dark
dark green
green amphibolite.
amphibolite.
A
A lenticular zone
zone of talc
talc schist about 350 meters long and 40 meters
wide is
is situated within the
the iron
iron formation
formation in
in the
the eastern portion of the
the mine.
mine.
The assemblages taic-garnet—andalusite,
talc-garnet-andalusite, talc—biotite,
talc-biotite, and talc—cummingtonite
talc-cummingtonite
are locally
locally present.
present.
the
Compositional banding of quartz and magnetite is prominant within the
iron
iron formation
formation and
and provides
provides the
the contrast
contrast necessary
necessary for
for viewing
viewing minor
minor structure.
structure.
The rocks
rocks have been isoclinally
isoclinally folded
folded around nearly vertical axes and
and
sheared
sheared into
into boudins.
boudins. Features
Features observed
observed include:
include: 1)
1) small
small boudins
boudins and
and
isolated
isolated and
and rotated
rotated fold
fold hinges
hinges of
of minor
minor isoclinal
isoclinal folds,
folds, 2)transposed,
2)transposed,
bedding, 3)
3) prominent
prominent lineation
lineation of
of amphiboles
amphiboles developed in
in the
the plane
plane
parallel bedding,
of compositional
compositional banding,
banding, and
and 4)
4) distinct thickening
thickening and
and thinning
thinning of
of iron
iron
formation
formation along
along strike.
strike.
Upper
Upper Cambrian
Cambrian Mount
Mount Simon
Simon Sandstone
Sandstone unconformably
unconformably overlies
overlies the
the PrePrecambrian
cambrian terrane.
terrane. Within
Within the
the Mount
Mount Simon
Simon aa basal
basal conglomerate
conglomerate containing
containing
clasts
clasts of
of angular
angular hematitic
hematitic iron
iron formation
formation is
is well
well developed.
developed. The
The congloconglomerate
merate grades
grades rapidly
rapidly upward
upward into
into well
well sorted,
sorted, poorly
poorly indurated
indurated sandstone.
sandstone.
The
The deposit
deposit has
has not
not been
been dated,
dated, but
but structural
structural and
and metamorphic
metamorphic style
style
indicate
indicate that
that it
it may
may be
be Archean.
Archean.
—19—
-19-
�U
The
The Unconformity-Type
Unconformity-Type Proterozoic
Proterozoic Pitchblende
Pitchblende Ore
Ore Body
Body Model
Model
And
And Its
Its Application
Application to
to Northern
Northern Michigan
Michigan
J.
J. Kalliokoski
Kalliokoski
Michigan
Michigan Technological
Technological University
University
Houghton,
Houghton, Michigan
Michigan 49931
49931
Previous
Previous studies
studies establish
establish that
that this
this class
class of
ofore
orebodies
bodieshasP
has aa characcharacteristic setting:
setting: aa short
short distance
distance below
below an
an unconformity,
unconformity, in
in almost
almost any
any
teristic
kind
kind of
of host
host rocks
rocks that
that have developed
developed permeability through either physical
or chemical
chemical ground
ground preparation
preparation (or
(or both).
both). This
This chemical
chemical ground
ground preparapreparaor
tion
tion is
is represented
represented in
in the
the viscinity
viscinity of the
the ore
ore body also
also by various types
of
of low
low temperature
temperature alteration,
alteration, none of which need to
to be a
a direct
direct effect or
the deposition
deposition of
of the
the pitebblende.
pitchblende. The
The quantity
quantity and
and intensity
intensity
cause of the
of
of alteration
alteration cannot
cannot be related
related to
to the
the size
size of
of the
the pitchblende deposits.
deposits.
In
In a similar
similar coincidental
coincidental fashion,
fashion, pitcbblende
pitchblende ore
ore bodies
bodies can
can adjoin
adjoin
also economic concentrations
concentrations of
of nickel—cobalt
nickel-cobalt arsenides
arsenides and
and gold.
gold. By
By
contrast, graphite
graphite and
and pyrite
pyrite are
are interpreted
interpreted to
to be
be related
related more
more directly
directly
the ore
ore body
body and
and to
to the
the mineralization
mineralization process.
process.
to the
An evaluation of the geochemical system indicates
indicates there to be
be adequate
adequate
major outstanding
sources and
and uranium
uranium transport
transport mechanisms.
mechanisms. The
The major
outstanding
uranium sources
problem concerns the locus
locus and manner in which uranium is deposited
deposited as
as
pitchblende. There is some indirect geological evidence to suggest that
uraniferous fluids
the precipitation results
results from
the mixing
mixing of
of oxidized
oxidized uraniferous
the
from the
fluids
methane and
with those containing
containing large quantities of such reducants as methane
and
within
are capable
capable of precipitating
precipitating pitchblende
pitchblende within
H2S,
These substances
substances are
H2S.
remaining of
of their
low
little evidence remaining
their
low temperature systems,
systems, with very little
previous existence.
existence.
thick
the model
model to
to northern
northern Michigan
Michigan one
one can note
note that
that aa very
very thick
Applying the
sandstone
body of young Precambrian continental
rests
continental redbed
redbed Jacobsville
Jacobsville sandstone rests
Thus,
unconformably on a
a floor
floor of middle and
and lower
lower Precambrian
Precambrian rocks.
rocks.
Thus,
oxidized system
the first
first requirement
requirement of
of the
the model
model is
is met,
met, that
that of
of an
an oxidized
the
system
The
basement
is
cut
by aa series
series of
of
situated
a more reduced
reduced one.
one. The basement is cut by
situated above a
These
provide
the
easterly
faults and diabase dikes.
dikes. These provide the
easterly trending
trending major faults
The
second requirement,
requirement, that of secondary permeability
second
permeability in
in the
the basement.
basement. The
Jacobsville
grade metasedimentary
metasedimentary rocks
rocks below the
the Jacobsville
middle Precambrian low grade
It is
is proposed
proposed that because of their
are
are quite
quite carbonaceous and pyritic. It
the gaseous
gaseous hydrohydrolow
low metamorphic
metamorphic grade
grade these
these rocks
rocks could
could have
have provided
provided the
precipitate
carbons
carbons or
or possibly
possibly HH2S
that are
are required
required by
by the
the model
model to
to precipitate
2 S that
pitchblende
zones of
of mixing.
mixing.
pitchblende in and along the permeable zones
—20—
-20-
�Problems in
in Paleogeographic Reconstruction of the
the Chocolay and lower
lower
Menominee Group Sedimentation,
Sedimentation, Marquette Range Supergroup,
Supergroup, Lake Superior
region
Larue, D.
D. Knight,
Knight, Northwestern University,
University, Evanston,
Evanston, Il.
Larue,
II. 60201
60201
Due to
structural complications
and few outcrops,
outcrops, little is
to structural
complications and
is known
about
the
regional
sedimentary
facies
and
source
areas
of
the
Chocolay
about
facies and
areas of
and Menominee Groups
and their
Groups of the Marquette Range Supergroup and
their
Animikian equivalents. In structurally deformed areas
isopachous
areas isopachous and
and
paleocurrent data are equivocal (Ramsay,
1961, 1966),
1966), but have
have been used
used
(Ramsay, 1961,
Trends
in
in previous
previous reconstructions (Taylor,
in
(Taylor, 1972, Sims,
Sims, 1976).
1976).
regional mineralogy are
are employed
employed by
by others
others (Morey,
(Morey, 1973,
1973, Gair,
Gair, 1975).
1975).
Data bearing on paleogeographic reconstructions
reconstructions of the
the Chocolay
1) an increase in feldspar and grain size
Group include:
include: 1)
size in
in basal
basal
quartzites toward
toward the
the Lake
Lake Mary
Mary Quadrangle
Quadrangle (Bayley,
1959, Gair
Gair and
and
quartzites
(Bayley, 1959,
to weakly
weakly unimodal NE —
Weir, 1956);
Weir,
1956); 2)
2) strongly unimodal NW —
- SE to
- SW
orientations of
of symmetric—ripple
symmetric-ripple mark crests
crests in
in quartzites;
quartzites; 3)
3) regional
regional
decrease in basal quartzite thickness toward the west (excluding
(excluding the
poorly understood
understood Trout
Trout Lake
Lake Formation)
Formation) (Sims,
(Sims, 1976); 4)
4) local
local westerly
westerly
thinning
of quartzite
quartzite in the
the Gogebic
Gogebic Range;
Range; 5)
5) restriction
restriction of
of large
large
thinning of
domal stromatolites
stromatolites to
Kona Dolomite
Dolomite (Marquette
area); 6)
6) greater
greater
domal
to the
the Kona
(Marquette area);
volume of intercalated clastic silica in the
the Kona Dolomite than
than strati—
stratigraphic equivalents;
equivalents; 7)
7) presence
presence of
of subrounded
subrounded quartzite
quartzite and
and chert
chert
graphic
Symmetric—
pebbles in channel deposits of
of the
the Randville
Randville Dolomite.
Dolomite. Symmetricripple spacing in quartzite indicates
indicates short
short period
period waves.
waves. Evaporite
casts (Taylor,
1972) with mud
mud cracks
cracks in dolomitic
dolomitic units
units indicate
indicate
mineral casts
(Taylor, 1972)
aa semi—arid
semi-arid to
to arid environment with
with periods
periods of
of subaerial
subaerial exposure.
exposure.
facies transition in
North —
- south facies
in the
the lower
lower Menominee
Menominee Group
Group
continues into Iron
Iron Formation
Formation sedimentation
sedimentation (Gair,
(Gair, 1975).
1975). Available
of the
paleocurrent data suggest flow parallel to
to the
the trend
trend of
the transition
(E -— W).
(E
data, though obviously scant,
scant, support the interThese available data,
pretation of aa shallow basin deepening gently to
to the south,
south, with aa
major detrital source
source to
to the
the north,
north, and a local source for feldspar
feldspar
and subrounded pebbles
pebbles near
near the
the Lake
Lake Mary
Mary Quadrangle.
Quadrangle. Shorelines
possibly extended NW
NW —- SE during deposition of Chocolay
Chocolay sediments.
sediments.
Water depth varied from intertidal (possibly
(possibly supratidal)
supratidal) to
to shallow
subtidal for
for the entire area,
area, thus
thus the significance of the term
"shoreline" for
for the dolomitic units is
is questionable.
questionable. The Wewe Slate
may represent aa still deeper—water
deeper-water phase of sedimentation (Puffett,
(Puffett,
1974, Gair and Thaden, 1968).
1974,
1968). Lower Menominee Group
Group sedimentation was
similarly influenced
influenced by
by aa northern
northern source
source (Morey,
1973) and
and by
by mean
mean
similarly
(Morey, 1973)
water depths increasing southward,
southward, but the contribution of local
faulted uplifts is indicated
faulted
indicated (Gair,
(Gair, 1975,
1975, James,
James, 1954).
1954).
—21—
-21-
�THE GEOLOGY
OF THE
GARNETDEPOSIT,
DEPOSIT,
THE
GEOLOGY OF
THE GORE
GORE MOUNTAIN
MOUNTAIN GARNET
SOUTHEASTERNADIRONDACKS,
ADIRONDACKS, WARREN
WARREN COUNTY,
COUNT!, NEW
SOUTHEASTERN
NF.W YORK
YORK
Frank R.
Luther, Department of
Geological Sciences,
Sciences, Lehigh
University,
Frank
R. Luther,
of Geological
Lehigh University,
Bethlehem, Pa.
Pa. (now
University of
Bethlehem,
(now at Department
Department of Geography-Geology,
Geography-Geology, University
Wisconsin -- Whitewater, Whitewater, Wis.)
Wisconsin
deposit, aa garnet amphibolite,
amphibolite, is
The garnet deposit,
is located on the north
slope of Gore Mountain
Mountain in
slope
in the
the southeastern
southeastern Adirondack
Adirondack Highlands.
Highlands. The
1) rocks
rocks of
of charnockitic affinity, 2)
major rocks
rocks of
of the
the area
area are:
are: 1)
2) ananorthosite,
gabbro; all of these rocks are
orthosite, and 3)corona-bearing olivine gabbro;
metamorphosed to the
the upper amphibolite or hornblende granulite facies.
facies.
The garnet amphibolite contains euhedral to anhedral garnet porphyroblasts which
which are
are commonly
commonly 10-20
10-20 cm in
in diameter
diameter (some
range up
up to
to 30
30
roblasts
(some range
cm).
These
garnets
are
surrounded
oy
a
surrounded by
1-2 mm
~u rim of plagioclase (an52)
(an52)
em).
and biotite,
biotite, a thick (up
(up to
to 10 cm)
em) shell of hornblende,
hornblende, and often a pressure shadow of plagioclase (an40)
and orthopyroxene
sure
(an 40 ) and
orthopyroxene (en67).
(en67). Electron
microprobe analyses show the composition of
microprooe
of the garnets to be remarkably
uniform for
for garnets of this
this size.
size. To the north,
north, the garnet amphibolite
grades through a 2 m
m transition
transition zone into aa layered
layered gabbro containing
igneous olivine,
olivine, pyroxenes,
pyroxenes, and
and plagioclase
plagioclase and
and corona
corona structures
structures of
of
igneous
metamorphic pyroxenes,
pyroxenes, garnet,
garnet, and
and plagioclase.
plagioclase. This contact is
is charcharacterized by major changes in mineral proportions and texture
texture while the
the
3 /Fe+ Z
change
Fe+3/Fe+2
Change in bulk chemistry is small (an
(an increase in H2O
HZO and Fe+
toward
toward the
the garnet amphibolite).
amphibolite). Electron microprobe analyses show that
that
compositional
compOSitional variations between minerals occurring in the
the garnet ampnibolite and gabbro are very small;
small; compositions are:
are: plagioclase (p1)-an39,
(pl)-an39,
garnet
-ai47py40gr1sp1, orttiopyroxene
garnet (g)
(g)-a147PY40grl2sPl,
orthopyroxene (opx)-en68,
(opx)-en b8' norublende
hornlJlende (h)(h)paragasite, clinopyroxene
clinopyroxene (cpx)—augite,
(cpx)-augite, and
and magnetite
magnetite (mt).
(mt). These two
two
rocks are surrounded
surrounded by
by anorthosite
anorthosite on
on the
the west,
west, north,
north, and
and east.
east. Tne
gabbro contains
contains xenoliths
xenolithS of
of deformed
deformed anorthosite.
anorthosite. To the
the south,
south, there
there
is
with syenitic granulite
granulite (mangerite);
patches of ananis aa sharp contact with
(mangerite); patches
orthosite up
up to
to 55 mm thick
thick occur
occur along
along this
this contact.
contact.
The following
A hot dry gabbrolc
follOWing geologic
geologic history
history is
is proposed.
proposed. A
gabbroic magma
was intruded
intruded along the
the contact of already deformed mangerite and anorthoanorthosite. The magma crystallized slowly
slowly without tectonic
tectonic disturbance to
to proproduce the
was absorbed
absorbed by
the layered
layered gabbro.
gabbro. Water from
from an external source was
by
the
of the
the margin of
the gabbro during subsolidus
subsolidus cooling causing aa transformation
from gabbro to
trom
to garnet
garnet arnphibolite
amphibolite following
tollowing tne
the reaction:
reaction:
19
p1++ S8 cpx+
opx+4
mt+
- 66 h+
19 pi
cpx +1.0
10 0px
+ 4 oi+
01 + I.
l rot
+ 66H20
HZO ~
h + 9Y p1+4
pi -:- 4 g+
g +1 1opx.
opx.
A
A petrogenetic
petrogenetic grid
grid suggests
suggests that
that aa temperature
temperature of
of about
about 800°C
BOUoC and
and aa load
load
pressure of
of large
large garof 77-~kb
kb isisconsistent
consistent with
with this
this reaction.
reaction. Growth
Growth of
nets consumed
piagioclase yielding aa hornblende shell around
around each garnet.
consumed plagioclase
garnet.
Later detormation produced pressure shadows
garnets and
shadows around the
the.garnets
and aa weak
weak
toliation
foliation through
through the
the garnet
garnet amphibolite.
amphibQlite.
Reference
Luther, Frank R., 1976,
1976, The petrological evolution
evolution of
ot tue
the garnet
garnet deposit
deposit
at
at Gore Mountain, Warren
Warren County,
County, New
New York; unpublished
unpublished dissertation,
dissertation,
Lehigh
Lehigh University.
University.
—22—
-22-
�THE GEOCHEMISTRY
GEOCHEMISTRY OF KEWEENAWAN LAVAS
LAVAS OF
OF THE
THE MAMAINSE
MAMAINSE POINT
POINT
THE
FORMATION, ONTARIO
FORMATION,
N.W.D.
N.W.D. Massey,
Massey, Dept.
Dept. Geology,
Geology, McMaster
McMaster Univ.,
Univ., Hamilton,
Hamilton, Ont.
Onto
The Mamainse Point Formation
Formation outcrops
outcrops at
at Mamainse
Mamainse Point,
Point,
about 80
about
80 km north of Sault Ste.
Ste. Marie, Ontario.
Ontario.
It consists
of tholeiitic flood
flood basalts with rhyolites
rhyolites and conglomeratic
sediments, and
and spans
spans the
the palaeomagnetic
palaeomagnetic reversal
reversal normally
normally
sediments,
regarded as the boundary between Lower
Lower and
and Middle
Middle Keweenawan.
Keweenawan.
The
The flows
flows consist of olivine-phyric melaphyres
melaphyres at
at the
the base
base
which pass up
up into
into feldspar-phyric
feldspar-phyric melaphyres
melaphyres and
and ophites.
ophites.
The
Alona Bay
Bay sequence is
is also
also olivine-phyric
olivine-phyric and
The thin Alona
with the
basal section of the
Mamainse
probably correlative with
the basal
the Mamainse
Point sequence.
sequence.
Low—grade, burial
burial metamorphism has
has caused zeolite—grade
Low-grade,
zeolite-grade
secondary minerals
minerals to
develop, both
both within
within the
to develop,
the rock
rock and in
veins and vesicles.
vesicles. Although laumontite occurs throughout,
throughout,
a
a crude metamorphic zoning
zoning is
is developed
developed with
with epidote
epidote occuroccurring mainly
mainly in
in the
the basal
basal section
section and
and stilbite
stilbite in
in the
the upper
upper
ring
Heterogeneity, with the development of
parts.
Heterogeneity,
of epidote-,
epidote-,
chlorite—
chlorite- and albite—rich—metadomains,
albite-rich-metadomains, is
is restricted
restricted to
to
feldspar-phyric melaphyres in lower
feldspar-phyric
lower parts of
of the
the section.
section.
The metamorphism was
was accompanied by increases in
The
in Na,
Na, K,
K, Rb,
Rb,
Li,
Li, Ba,
Ba, Fea/Fe2,
Fe3/Fe2, H2O+
H20+ and
and C02,
C02, and
and increases
increases or
or decreases
decreases
in Ca,
Ca, Sr and
in
and Cu.
Cu. Al,
AI, EFe,
~Fe, Ti,
Ti, P,
P, Y,
Y, Zr,
Zr, Nb,
Nb, ?FeOT/MgO
?FeOT/MgO
and ?MgO appear to be immobile or little
and
little affected
affected by
by the
the
The immobile trace elements confirm
the
tholeialteration. The
confirm the tholeiitic nature of the
itic
the lavas and suggest an
an ocean—floor
ocean-floor to
to
within-plate
character.
within-plate character.
The occurrence of a suite of
of flows
flows of
of distinctive
distinctive chemchemical
type
beneath
the
"Great
Conglomerate",
but
ical type
the "Great
but not
not repeatrepeated above,
above, would suggest the triple
triple reversal
reversal in the
the palaeo1
magnetic stratigraphy of Mamainse Point'
is
real
and not
Point
due to strike
strike fault
fault repetition.
repetition.
(1970) Paleomagnetism
Paleomagnetism and
and correlation
correlation of
of some
Ipalmer,
H.C. (1970)
'Palmer, H.C.
Can.
Jour.
Middle Keweenawan rocks,
rocks, Lake
Lake Superior.
Superior.
Can. Jour.
Earth Sci., 7,
I, 1410—1436.
1410-1436.
—23—
-23-
�THE DISTRIBUTION
DISTRIBUTION OF
OF URANIUM
URANIUM AND THORIUM
IN THE
THE WOLF
WOLF RIVER
RIVER BATHOLITH,
IN
BATHOLITH, NORTHEASTERN WISCONSIN
Meddaugh,
t-leddaugh, W.
\.J. S.;
S.; Salotti,
Salotti, C. A.; and
and Mursky,
Mursky, G.
G.
Department of Geological
Geological Sciences
Sciences
University of Wisconsin —- Milwaukee
Milwaukee,
Milwaukee, Wisconsin 53201
53201
Measurements of outcrop radioactivity
radioactivity at
at over
over 175
175 locations
locations and
and wholewholerock
and thorium analyses
rock uranium and
analyses by gamma spectroscopy have
have revealed
revealed
significant differences
differences in
in the
the radioactive
radioactive character
character and
and radloelement
radioelement
distribution of several
several of the
the lithologic
lithologic units
units that
that comprise
comprise the
the Wolf
Wolf
River Batholith.
is aa large
Batholith. The batholith,
batholith, dated about
about 1500
1500 m.y., is
large
epizonal anorogenic composite pluton consisting
epizonal
consisting mainly of
of quartz
quartz mon—
monzonite and
and granite
granite with much lesser
lesser amounts
amounts of
of monzonite,
monzonite, syenite,
syenite, and
and
rhyolite.
For the
the purposes
purposes of
of this
For
this study the
the batholith has
has been
been arbiarbitrarily divided
trarily
divided into
into a southern section and
and aa northern
northern Section.
section.
In the
the southern
southern section,
section, the
the Red
monzonite, the
In
Red River quartz monzonite,
the most radioradioactive unit
of the entire batholith,
active
unit of
batholith, is
is considerably
considerably more
more radioactive
radioactive
than
than either the Wolf River quartz monzonite or
or the
the Waupaca
Waupaca quartz
quartz mon—
monzonite. Two somewhat
some~"hat anomalous
anomalous areas,
areas, one
one east
east of
of Tigerton
Tigerton and
and the
the
other near
near Big
Big Falls,
Falls, have
have been
been located
located within
within the
the more
more radioactive
radioactive
interior region
of the
monzonite. Preliminary analyses
interior
region of
the Red
Red River quartz monzonite.
analyses
of typical
yield average
values of
oF
typical samples
samples of Red River quartz
quartz monzonite yield
average values
37
and 10
10 ppm
ppm UU (Tb/U
(Th/U == 3.7)
3.7) while
while samples of mafic—rich
mafic-rich material
material
37 ppm Th and
yield individual
individual values
values as
as high
high as
as 150
150 ppm
ppm Tb
Th and
and 190
190 ppm
ppm U.
U. Peripheral
areas of the
areas
the Wolf River quartz monzonite, particularly
particularly near
near its
its contact
contact
with the
the Tigerton anorthosite,
anorthosite, are
are more
more radioactive
radioactive than
than central
central areas.
areas.
The \1aupaca
Waupaca quartz monzonite and
The
and the
the Wolf River
River quartz
quartz monzonite
monzonite have
have
similar average outcrop radioactivities.
radioactivities.
The Belongia
Wolf River
Belongia granite,
granite, slightly more radioactive
radioactive than the Wolf
is the
the most
most radioactive
quartz monzonite, is
radioactive unit
unit in
in the northern section
of the
the batholith.
batholith. Marginal
l-larginal regions
regions of
of the
the granite
granite tend
tend to
to be
be more
more
radioactive than inner
inner areas.
areas. Typical
Typical samples of Belongia
Belongia granite
granite yield
yield
preliminary average values of 27
27 ppm
ppm Th
Th and
and 6.3
6.3 ppm UU (Th/U
(Th/U == 4.3).
Average outcrop radioactivity
radioactivity of
of the
the Hager
Hager rhyolite
rhyolite is
is slightly
slightly less
less
than
than that of the
the Belongia
Belongia granite.
granite. Samples of the
the Peshtigo
Peshtigo monzonite,
monzonite,
the least
least radioactive
radioactive unit
unit of the
the entire
entire batholith,
batholith, yield
yield preliminary
preliminary
the
5.14). ftverage
114ppm
ppm Th
Tb and
and 2.6
2.6 ppm
ppm U
U (Th/U
/verage outcrop radio—
values of
of 14
(Th/U == 5.4).
radioactivities
activities of
of the Hager feldspar
feldspar porphyry
porphyry and
and the
the Hager
Hager syenite
syenite are
are
intermediate between that
that of the
the Belongia
Belongia granite
granite and
and Peshtigo
Peshtigo monzonite.
monzonite.
intermediate
—24—
-24-
�PILOT EXPLORATION GEOCHEMICAL SURVEY OF URANIUM IN
ORGANIC—RICH
ORGANIC-RICH LAKE SEDIMENTS, NORTHEASTERN MINNESOTA
D.G.
Meineke, M.K.
M.K. Vadis and A.W.
A.W. K1aysmat,
Klaysmat, Minnesota Department of
D.G. Meineke,
of
Natural Resources,
Minerals, Hibbing,
Hibbing, Minnesota 55746
Resources, Division of Minerals,
ABSTRACT
As part of the National Uranium Resource Evaluation Program (NURE
(NURE
Program)
Carbide—Nuclear
Program) of the
the U.
U. S.
S. Department of Energy (DOE),
(DOE), Union Carbide-Nuclear
Division,
Division, the DOE contractor responsible for
for geochemical exploration
surveys, decided to
surveys,
to investigate
investigate the
the use
use of
of organic—rich
organic-rich lake
lake sediments
sediments
for
for the NURE Program
Program in
in Minnesota.
Minnesota. This study was done in conjunction
NDNR
with the
the Minnesota
Minnesota Department
Department of
of Natural
Natural Resources
Resources (MDNR).
(MDNR). The MDNR
had previously applied organic—rich
sediment to various areas of
organic-rich lake
1ake'sediment
northern Minnesota for
for the
the evaluation
evaluation of
of base
base metal
metal potential.
potential. The
observations and
and conclusions
conclusions described
described here
here are
are those
those of
of the
the MDNR
MDNR and
and
observations
do not necessarily represent those
those of
of Union
Union Carbide—Nuclear
Carbide-Nuclear Division.
Division.
Organic—rich lake
sediment samples
samples were
were selected
selected to
to represent
represent five
five
Organic-rich
lake sediment
major geologic
geologic formations
formations from
from previous sediment surveys conducted by
the MDNR in the
the Western Vermilion
Vermilion District
District of
of northeastern
northeastern Minnesota.
Minnesota.
The objectives of
of this
this study
study were: 1)
1) to determine whether or not
uranium in the various
various rocks
is reflected
reflected in the
sediment, and
and 2)
2) to
to
rocks is
the sediment,
determine if
of the raw data was
was necessary in order
order to
to
if any treatment
treatment of
use this information for
for evaluation
evaluation of
of uranium
uranium potential.
potential.
of the bedrock is
Results indicate that the uranium content
content of
is
reflected in
in the
the sediment.
sediment. The uranium concentrations in
in sediments
sediments
over the Vermilion Massif
Massif are about twice those over
over other rocks;
rocks; which
compares with
with the
the difference
difference in
in relative
relative radioactivity
radioactivity levels
levels of
of the
the
compares
same rocks
rocks as reported by Ojakangas (1976).
(1976).
Examination of the data suggests that uranium may be concentrated
in the inorganic fraction of the
the sediment.
sediment. Although the reflection of
the uranium content
content of
of the
the bedrock is
is discernible
discernible by
by basing
basing the
the uranium
the unignited
unignited (total)
sample weight,
weight, the
the distribution
distribution
concentration on the
(total) sample
of uranium based on
on the
the ignited
ignited sample
sample weight
weight (inorganic
fraction) more
more
of
(inorganic fraction)
reflects the bedrock
bedrock geology
geology because
because of
of loss-on-ignition
loss—on—ignition varivariclearly reflects
ation between samples.
samples. No significant relationships were observed for
for
or manganese,
manganese, which
which would
would suggest
suggest that
that uranium is
is not
not
uranium and iron or
preferentially
preferentially adsorbed
adsorbed by
by iron—manganese
iron-manganese hydroxides
hydroxides and,
and, therefore,
therefore,
does not create elevated uranium
uranium values
values unrelated
unrelated to
to the
the bedrock
bedrock geology.
geology.
REFERENCE
Potential ininPrecambrian
1976, Uranium Potential
Ojakangas, R.W.,
R.W., 1976,
Precambrian Rocks
Rocks of
of
Report to U.
Minnesota: Report
U. S.
S. Energy Research and Development
Administration, Contract
ContractAT(O5—l)—1652,
AT(05-1)-1652, 259
259 pages.
—25—
-25-
�A PETROGRAPHIC
PETROGRAPHIC GUIDE
GUIDE FOR UNIT
UNIT IDENTIFICATION
OF THE
THE PARTRIA
IDENTIFICATION OF
DGE RIVER TROCTOLITE,
TROCTOLITE, DULUTH COMPLEX,
COMPLEX, MINNESOTA
MINNESOTA
DGE
Molling, Philip
Philip A.,
A., Tyson,
Tyson, R.
R. Michael,
Michael, and
and Chang,
Chang, Luke
Luke
Molling,
L. Y.,
Y., Department of Geology,
Geology, Miami University,
L.
University,
Oxford, Ohio 45056
Oxford,
The partridge
Partridge River
River Troctolite
Troctolite (PRT)
has aa lithology
lithology simisimiThe
(PRT) has
lar to
to that
that exhibited
exhibited by
by the
the south
South Kawishiwi
Kawishiwi Intrusion
Intrusion
lar
However, the
the units
units recognized
recognized in
the SKI
SKI do
do not
not
(SKI). However,
in the
extend into
extend
into the PRT (Bonnichsen
(Bonnichsen and Tyson,
Tyson, 1975).
1975). The
The PRT
does exhibit
exhibit aa cryptic-like
cryptic—like layering
layering as
as it
it becomes
becomes more
more
does
However, there is
no distinct
distinct variabimafic with depth.
depth. However,
is no
lity in the mafic mineral species which thus
thus provides
provides
aid in the definition of correlatable units.
little aid
units. This
study of one drill core has concentrated on
on the
the silicate
silicate
and oxide mineralogy and their
their relationships
relationships with
with depth.
depth.
Five specific petrographic relationships
relationships used in conjunction have been determined as indicators
indicators of units:
units: (1)
(1) Some
This epitaxial bio—
biotite grows epitaxially
epitaxially to
to augite.
augite. This
biotite is
is characteristic of the lower
lower portion of
of the
the drill
drill
(2) Inclusions
Inclusions of
of biotite
biotite aligned
aligned in
core studied.
(2)
in paralin the
the upper
upper half
half of
lel arrays
arrays within
within augite
augite are
arecommon
cornmon in
of
is believed
believed to
to be aa rethe drill core. This
This occurrence
occurrence is
(3) Oxide
Oxide inclusions,
inclusions, reddish—brown
placement texture.
texture.
(3)
reddish-brown
rutile and
and opaque
opaque ilmenite,
appearing in
in augit
augit as
as minute
minute
rutile
ilmenite, appearing
blebs and rods are arranged in rows,
rows, locally throughout the
drill core and may represent gradational contact
contact zones.
zones.
(4)
The texture
texture and
and amount
amount of
of exsolved
exsolved oxide inclusions in
(4) The
in
the plagioclase crystals varies consistently with depth and
is believed
believed to
to be
be the
the most
most diagnostic
diagnostic feature
of differenis
feature of
tiation.
(5)
wormy, symplectitic
symplectitic intergrowth Gf
of plagio(5) AA wormy,
clase and orthopyroxene similar to Taylor's (1964)
(1964) mymer—
mymerkite is
is evident.
evident. This
This fine
fine grained
grained symplectite
symplectite appears
appears to
to
have
set up
have set
up its
itsown
own plagioclase
plagioclasedomain
domain wherein
wherein the
the opx
opx
blebs
blebs exist. Another symplectite,
symplectite, coarser
coarser in
in grain
grain size,
size,
appears as an earlier phase relative to the fine grained
symplectite and does
does not
not exhibit
exhibit aa separate
separate domain.
domain.
Of the
the petrographic relationships
relationships used,
used, only two
two appear
to be representative
representative of
of the
the primary
primary conditions
conditions of
of the
the magma;
magma;
the oxide inclusions
inclusions in
in augite
augite and
and in
in plagioclase.
plagioclase. The
The
others appear
appear to
to be due
due to
to later
later stages
stages of
of crystallization
crystallization
or deuteric
deuteric alteration.
alteration. The use of these
these relationships
relationships
will allow
allow for
for the
the definition
definition of
of crystallization
crystallization units
units
which heretofore
heretofore have
have not
not been described
described for
for the
the Partridge
Partridge
River
River Troctolite.
Troctolite.
the drill core.
—26—
-26-
�AEROMAGNETIC MAP
MAP OF
OF NORTHERN
NORTHERN WISCONSIN
WISCONSIN
AEROMAGNETIC
(Poster Session)
Session)
(Poster
M. G.
G. Mudrey,
Mudrey, Jr.,
Jr., Geological
Geological and
and Natural
Natural History
History Survey,
Survey, University
University of
M.
of
Wisconsin—Extension,
1815
University
Avenue,
Madison,
Wisconsin
Wisconsin-Extension, 1815 University Avenue, Madison, Wisconsin 53706,
53706,
and J.
J, H,
H, Karl,
Karl, Department
Department of
of Physics,
Physics, University of Wisconsin—Oshkosh,
and
Wisconsin-Oshkosh,
Oshkosh,
Wisconsin
54901
Oshkosh, Wisconsin 54901
ABSTRACT
In 1973,
In
1973, the
the Geological
Geological and
and Natural
Natural History
History Survey
Survey and
and the
the Department
of
Physics,
University
of
Wisconsjn—Oshkosh,
initiated aa detailed
of Physics, University of Wisconsin-Oshkosh, initiated
detailed aeroaero—
magnetic survey
survey of
of northern
northern Wisconsin
Wisconsin with
with primary
primary funding
funding from
from the
the Upper
Upper
magnetic
Great Lakes
Lakes Regional
Great
Regional Commission.
Commission. The
is a
a color compilaThe map
map on display is
tion at
at 1:250,000
1:250,000 by Zeitz,
Zeitz, Karl
tion
Karl and
and Ostrom (1977)
(1977) published
published as
U, S.
as U,
Geological Survey
Survey Open-file
Open—file Report
Report 77-598,
77—598, and
and is
is available
available in
in black
black and
Geological
white as
white
as U.
U. S.
S. Geological Survey Miscellaneous
Miscellaneous Field
Field Study
Study MF—888.
MF-888.
The map is derived by photographic
The
reduction of 86 aeromagnetic
aeromagnetic survey
survey
maps published at a scale of 1:62,500
maps
1:62,500
by the Geological and
and Natural
Natural History
History
Survey with a
a standard line
line spacing
spacing of
of
0,8 kilometers flown
flown north—south
north-south at
at an
an
elevation of 150 meters (48,000
(48,000 square
square
kilometers of
of coverage),
coverage). The process
of construction of the
the maps
maps consisted
consisted
of removing the
the regional
regional magnetic
magnetic varivariation of the
the earth's total
total magnetic
magnetic
field
field as determined by
by Fabiano
Fabiano and
and
Peddie (1969),
(1969), and
and contouring
contouring the
the reresidual at
at 20
20 gammas.
gammas. If the regional
regional
variation is
is not
not removed,
removed, aa severe
severe
banding
banding effect,
effect, which
which •is
.is not related
related
to the geology,
geology, subdues
subdues the
the magnetic
magnetic
pattern caused by
by the
the geology,
geology. An
additional 3,400 square
square kilometers
kilometers
were
were flown
flown in
in 1977.
1977.
An obvious
obvious correlation
correlation when the
the map
map is
is compared
compared to
to a
a geological map
map
(Sims,
(Sims, Cannon and Mudrey,
Mudrey, 1978, and
and presented
presented at
at this
this Institute
Institute on
on Lake
Lake
Superior
Superior Geology
Geology meeting)
meeting) in
in addition
addition to
to the
the parallelism
parallelism of
of magnetic
magnetic and
and
geological
geological trends
trends is
is that
that the
the broad
broad magnetic
magnetic "low"
"low" areas
areas coincide
coincide very
very
well
well with
with regions
regions of
of predominantly
predominantly metasedimentary
metasedimentary and
and metavolcanic
metavolcanic rocks,
rocks,
and
and their
their gneissic
gneissic equivalents.
equivalents. The
The magnetically
magnetically "high"
"high" areas,
areas, on
on the
the
other
other hand,
hand, correlate
correlate well
well with
with more
more extensively
extensively granitized
granitized terranes,
terranes.
The
The Gogebic
Gogebic Iron
Iron Range,
Range, other
other iron
iron formations,
formations, and
and Middle
Middle and
and Late
Late PrePrecambrian
cambrian gabbroic
gabbroic plugs
plugs are
are readily
readily discerned
discerned as
as magnetic
magnetic highs
highs of
of over
over
7,000
7,000 gammas.
gammas.
—27—
-27-
�OFFSHORE
IN
SAND AND GRAVEL EXPLORATION
EXPLORATION
WESTERN LAKE MICHIGAN
Edgardo L.
L. Nebrija,
Nebrija, Carol
Carol J.
J. Welkie,
Welkie, and
and Robert
Robert P.
P. Meyer
Meyer
Geophysical and Polar Research
Research Center
Center
Lewis Weeks
Weeks Hall,
Hall, University
University of
of Wisconsin
Lewis
1215 W.
W. Dayton
Dayton St.,
St.,
Madison,
Madison, Wisconsin
Wisconsin 53706
53706
Offshore sand and gravel
deposits are
are potentially
potentially important
resourgravel deposits
important resources,
near high-use
high—use urban centers
centers which
which usually
usually lack nearby
nearby
ces, especially near
land sources and,
of this
low—cost, high-bulk
high—bulk
and, thus,
thus, require transport
transport of
this low-cost,
commodity from aa distance.
Conventional acoustic
acoustic profiling and
and coring
coring
distance. Conventional
of these deposits
however, because
because the
high acoustic
acoustic imdeposits is
is difficult,
difficult, however,
the high
impedance of sands and
and gravels
and because
because concongravels inhibits
inhibits sound penetration and
ventional coring is
is generally
generally inapplicable.
inapplicable.
off Kewaunee,
At three
three test
test areas in
in Western
Western Lake
Lake Michigan
Michigan —- off
Kewaunee, Mani—
Manitowoc, and Rawley Point
towoc,
Point —- experiments
experiments to
to determine the lateral extent
extent
and thicknesses of sands
and gravels
were conducted
conducted using
using combined
combined
sands and
gravels were
acoustic and Schlumberger
resistivity profiling,
profiling,resistivity
Schlumberger resistivity
resistivity sounding
from the
the water
water surface,
surface, and selective surficial
surficial sediment
sediment sampling.
sampling. PrePrevious detailed sediment sampling by other workers
workers showed
showed temporally
temporally
changing sediment patterns off Kewaunee,
Kewaunee, and
and laterally
laterally uniform,
uniform, well—
wellsorted, fine
sorted,
fine sands off Rawley Point.
Point. Knowledge of
of the
the apparent
apparent resisti—
resistivities obtained over these sediments
was used
used to
offshore exsediments was
to determine offshore
extensions of
of known onshore gravels at Manitowoc.
tensions
Initial
testing of
of this
this integrated
integrated geological-geophysical
geological—geophysical approach
approach
Initial testing
shows that:
that:
(1) Where
Where surficial
surficial sediments
sediments are thin,
(1)
thin, there is
is low
low correlation
correlation
between the
and the sediment type inferred
the observed apparent
apparent resistivity and
inferred
from acoustic profiles or physical samples.
samples. Instead,
Instead, the
the contours
contours of
of
apparent resistivity
resistivity reflect
reflect the
the trends
trends in
in the
the till
till and
and glaciolacustrine
glaciolacustrine
apparent
clays beneath
beneath the
the thin
thin sediments
sediments and
and point
point to
to prospective
prospective areas,
areas, such
such as
as
clays
probable buried channels
channels or
or ancient
ancient shorelines.
shorelines.
(2) In
In areas
areas where
where acoustic
acoustic profiles show thick
the ob(2)
thick sediments, .the
observed apparent resistivity is correlatable
served
correIa table with
with the
the type
type and
and distribudistribution of
of the
tion
the sediment.
sediment. The lateral uniformity of
of the
the acoustically—impenetacoustically-impenetrable sands
sands off
off Rawley
Rawley Point,
Point, for
for example,
example, is
is reflected
reflected in
in the
the relativerelativerable
ly constant apparent resistivity over most of
ly
of the
the area.
area.
(3) Given
Given the
the water
water depth
depth from acoustic profiles,
(3)
profiles, the
the water resisresistivity
from independent
independent specific-conductance
specific—conductance measurements,
measurements, and
and the
the
tivity from
resistivity ranges
ranges of the sands
sands and underlying till
till from resistivity
profiling elsewhere,
yields aa resistivity—
elsewhere, then,
then, resistivity sounding yields
resistivitydepth structure
structure which
which is
is helpful
helpful in
in estimating
estimating thicknesses.
thicknesses. The
The electrielectridepth
cal pseudo-section
pseudo—section also
also aids
aids in
in interpreting
interpreting the
the lateral
lateral changes
changes in
in sand
sand
cal
thickness.
(4)
gravel deposits
deposits
(4) The
The offshore
offshore extensions
extensions of
of the thick
thick onshore gravel
are mappable
mappable on
on the
the basis
basis of
of their
their relatively
relatively high
high resistivity
resistivity and
and potenpotenare
tial
tial subsurface deposits undetectable from
from surficial
surficial samples
samples are
are inferinferred from the resistivity
red
resistivity data.
data.
—28—
-28-
�CRITERIA
CRITERIA FOR
FOR ALLIGATOR
ALLIGATOR RIVER
RIVER TYPE
TYPE
URANIUM
URANIUM DEPOSITS
DEPOSITS IN
IN THE
THE UNITED
UNITED STATES
STATES
Richard
Richard W.
W. Ojakangas
Ojakangas
Department
Department of
of Geology,
Geology, University
University of
of Minnesota, Duluth, Minnesota
55812
55812
Three
Three geologically
geologically similar
similar uranium
uranium subprovinces—-Rum
subprovinces--Rum Jungle,
Jungle, South
South AlliAlligator River Valley,
Valley, and Alligator Rivers——are
Rivers--are present in the top end of
the Northern Territory
Territory of
of Australia.
Australia. Pitchblende
Pitchblende deposits,
deposits, with
with minor
minor
secondary minerals,
minerals, are found in a specific,
specific, generally carbonaceous
carbonaceous and
chloritic horizon of
of Lower
Lower Proterozoic
Proterozoic metasedimentary
metasedimentary rocks.
rocks. This
This horihorizon consists of the presumably equivalent Golden Dyke,
Dyke, Koolpin,
Koolpin, and Cahill
Formations
Formations in
in the
the three
three respective
respective subprovinces.
subprovinces. In the Rum Jungle and
Alligator Rivers
Rivers subprovinces,
subprovinces, Archean
Archean basement
basement rocks
rocks are
are also
also exposed.
exposed.
The
The ore
ore bodies generally
generally occur
occur at relatively
relatively shallow
shallow depths,
depths, and most
intersect the
the eroded Lower
Lower Proterozoic
Proterozoic surface.
surface. The grade
grade of
of ore
ore genergenerally
ally ranges
ranges from
from 0.25
0.25 to
to 0.40
0.40 percent U308, with short
short lengths
lengths of
of core
core
as 72
72 percent.
percent. Structural preparation of
of the host rocks
rocks is
is evias rich as
dent
dent in
in each
each deposit.
deposit. Remnants of
of aa hematite—quartz
hematite-quartz breccia are associassociated with many ore
ore deposits,
deposits, and
and may
may represent
represent aa Proterozoic
Proterozoic regolith.
regolith.
Throughout the eastern part of
of the region,
region, the Middle Proterozoic (1500
(1500
m.y.?) Kombolgie Formation
Formation of conglomerates,
conglomerates, quartzose
quartzose sandstones
sandstones and
and
volcanics, overlies
overlies the
the Lower proterozoic metasedimentary rocks
rocks with
Rivers subpro—
unconformity. All ore bodies in the Alligator Rivers
subproangular unconformity.
vince occur near this
this unconformity.
unconformity. In the South Alligator River
River Valley
Valley
subprovince,
Volcanics and the overlying Kombolgie Formasubprovince, the Edith River Volcanics
deposits occur
tion overlie the
the Lower Proterozoic rocks,
rocks, and all ore
ore deposits
In the
the Rum Jungle
Jungle subprovince,
subprovince, the
the Depot
Depot Creek
near this
this unconformity.
unconformity. In
m.y.) may
may have had essentially
Sandstone of Upper Proterozoic
Proterozoic age
age (<1400
~1400 m.y.)
the same
same relationship
relationship to
to the
the Lower
Lower Proterozoic
Proterozoic and
and to
to the
the ore
ore deposits
deposits
the
as do the Kombolgie and
and Edith
Edith River
River Volcanics
Volcanics in
in the
the other
other subprovinces.
subprovinces.
Evidence can be amassed for
for both
both syngenetic
syngenetic and
and supergene
supergene origins.
origins. Most
workers seem to prefer a
Australian workers
a syngenetic origin with initial deposition of uranium in Lower Proterozoic geosynclinal rocks
rocks during sedimentation. Additional enrichment is
is attributed to anatexis and metamorphism, with later
morphism,
later local
local supergene
supergene enrichment.
enrichment. The original sources
sources
of the uranium are generally
generally thought
thought to
to be
be the
the Archean
Archean complexes.
complexes. Some
River Volcanics
Volcanics as
as the source rock in the
workers suggest the Edith River
Alternatively, a
South Alligator subprovince. Alternatively,
a strong case can be made
for aa dominant
dominant supergene
supergene origin,
origin, with
with oxidizing
oxidizing waters
waters having
having carried
carried
for
eroded Lower Proterozoic surface either before,
before, during
uranium along the eroded
or after
after deposition of the overlying rock
or
rock units.
units.
What is the
What
the applicability of these criteria to exploration in the United
Regardless of
of the hypothesis
hypothesis of
of origin,
origin, the major field
States? Regardless
field criteria
The presence
presence of
of aa major
major unconformity
unconformity is
is of
of
remain essentially the
the same.
same. The
primary importance,
importance, as
as is
is the
the reducing nature of the structurally preThe significance
significance of
of the
the relative
relative ages
ages of
of the
the rock
rock units
units
pared
rocks. The
pared host rocks.
beneath and above the
the unconformity
unconformity is
is not
not clear.
clear.
—29—
-29-
�Relations Between
Between Soil
Soil Geochemistry and Bedrock Geology,
Relations
Geology,
Iron County,
County, Wisconsin
Iron
Peltonen, D.R.,
D.R., Salotti,
Peltonen,
Salotti, C.A.,
C.A., and
and Taylor,
Taylor, R.W.
R.W.
Department of Geological Sciences
Wisconsin—Milwaukee
University of Wisconsin-Milwaukee
Milwaukee,
Milwaukee, Wisconsin 53201
heavy metal
metal geochemical
geochemical soil
soil (B
horizon) and
and biogeochemical
biogeochemical (aspen
A heavy
(B horizon)
(aspen
twigs) survey
survey was
was completed
completed over
over approximately
approximately 100
100 square
square miles
miles directly
directly
twigs)
south of the
the Gogebic
Gogebic Range
Range in
in aa granite-greenstone
granite—greenstone terrain
terrain in
in Iron
Iron
south
County, Wisconsin.
County,
Soil samples
samples were
were dry
dry sieved,
sieved, the
the -80
—80 mesh
mesh fraction
fraction
Soil
and taken
taken into
into solution
solution using aa lithium metaborate
metaborate fusion
fusion
collected and
technique.
The twigs
The
twigs were ashed and dissolved in
in 2M
2M HC1.
HCl.
3000
Nearly 3000
elemental analyses were made using
using atomic
atomic absorption
absorption spectrophotometry.
spectrophotometry.
These results
were processed by
by computer
computer and statisttcal
statistjcal parameters
parameters
These
results were
assigned to
to all anomalous
anomalous values.
values.
indicates there
there is
is communication between the
the B
Geochemical data indicates
soil horizon in
in the
the glacial
glacial till
till and
and the
the underlying
underlying bedrock.
bedrock.
Nickel and
and
copper are distinctly lower
lower in
in soils
soils overlying
overlying "granites"
"granites" than
than in
in soils
soils
the underlying rock
rock types
be disdisoverlying greenstones,
greenstones, and allow the
types to be
tinguished with greater than
than aa 97.5%
97.5% confidence
confidence level.
level.
In two areas
where Zn
Zn concentrations are known to be greater than 0.1% in parts of
the bedrock,
bedrock, anomalous values
values of
of Zn
Zn in
in the
the overlying
overlying soil
soil samples
samples occur.
occur.
—30—
-30-
�BASELINE URANIUM
URANIUM AND
AND THORIUM
THORIUM ININARCHEAN
ARCHEANAND
ANDLOWER
LOWER PROTEROZOIC
PROTEROZOIC
ROCKS OF
OF THE
AREA, MICHIGAN
ROCKS
THE MARENISCO-WATERSMEET
MARENISCO-WATERSMEET AREA,
MICHIGAN
E. Peterman
K. Sims
Z. E.
Peterman and
and P.
P. K.
Sims
U.S. Geological
U.S.
Geological Survey,
Survey, Denver,
Denver, Colorado
Colorado 80225
80225
Radiometric dating in
area, northern
Radiometric
inthe
theMarenisco-Watersmeet
Marenisco-Watersmeet area,
Michigan, has
Michigan,
has delineated
delineated aalower
lowerArchean
Archean (Precambrian
(Precambrian W)
W) gneiss
gneiss
terrane at least
terrane
least 3,400
3,400 m.y.
m.y. old
old adjacent
adjacent to
to and
and south
south of aa greengreenstone-granite terrane
terrane (2,600
to 2,700
m.y. old).
old). Both
stone-granite
(2,600 to
2,700 m.y.
Both terranes
formed
the basement
basementfor
for the
the lower
formed the
lower Proterozoic
Proterozoic (Precambrian
(Precambrian X)
X) sedsedimentary
Marquette
imentary and
and volcanic
volcanic rocks
rocks ofofthe
the
MarquetteRange
RangeSupergroup.
Supergroup.
The
gneisses were
were involved
involved in folding
during the
The gneisses
foldingand
andmetamorphism
metamorphism during
Periokeanorogeny
orogeny
(1,750
m.y.ininthis
this area). Analyses
Analyses of UU
Penokean
(1,750
++
5050
m.y.
and Th
Thin
in samples
samplescollected
collectedfor
for radiometric
and
radiometric dating
dating provide
provide basebaseline data
line
data for
forevaluating
evaluatingradioelement
radioelement mobility,
mobility, and
and possibly
possibly enenrichment, during
richment,
during reactivation
reactivation ofofthe
theancient
ancientbasement
basement rocks.
rocks. The
lower Archean
gneiss at Watersmeet
contains 1.4 to
lower
Archean gneiss
Watersmeet contains
to1414ppm
ppm UUand
and 99
The available
available data
to 35
35 ppm
ppm Th.
Th. The
data suggest
suggest UUand
and Th
Th enrichment
enrichment in
in
more
highly cataclasized
cataclasizedfacies
fades of the
more highly
the gneiss.
gneiss. A leucogranite
dike in the
dike
the gneiss,
gneiss, provisionally
provisionally related
related totothe
thelate
lateArchean
Archean
event, contains
and6868ppm
ppm
fieldscintillometer
scintillometer
event,
contains 18
18 ppm
ppm UUand
Th,Th,
andand
field
measurements
suggestthat
that these
these high
high values
in the
measurements suggest
values are
are common
common in
granite near
nearThayer
ThayerofofFritts
Fritts (1969),
dikes. The
The granite
(1969), also thought
thought to
be reactivated Archean
gneiss, has
has U
Uand
andThThcontents
contentssimilar
similar to
be
Archean gneiss,
those of the
leucocratic phase
of this
those
the gneiss
gneiss atatWatersmeet.
Watersmeet. A leucocratic
phase of
The Puritan
Puritan Quartz
rock contains
contains2121ppm
ppm UUand
and 29
29 ppm
ppm Th.
Th. The
Quartz MonzoMonzonite, aalate
nite,
lateArchean
Archean intrusion
intrusion ininthe
thegreenstone-granite
greenstone-granite terrane,
terrane,
is higher
Th/U ratio.
ratio. Uranium
higher than
than average
average in Th
Th content
content and
and Th/U
ranges from
from 2.5 to
ranges
to 88ppm
ppm and
and Th
Th from
from 17
17 to
to 62
62ppm.
ppm. In
In all the
the
crystalline rocks,
crystalline
rocks,K Kand
and UUvary
vary independently,
independently, aa feature
feature suggestsuggestof the
ing post-crystallization
movement
post-crystallization
movement of
of U.
U. Metagraywackes
Metagraywackes of
Marquette Range
RangeSupergroup
Supergroup
consistentlylow
low in
in both
Marquette
areare
consistently
both UU and
and Th,
Th,
These values
values are
are simiwith averages
averages of
of2.6
2.6ppm
ppmUUand
and 6.6
6.6ppm
ppm Th.
Th. These
with
lar
mayreflect
reflect a
lar totothose
thoseofofother
othergraywackes
graywackes and
and may
a high
high volcanic
volcanic
componentininthe
thedetritus.
detritus.
component
—31—
-31-
�NATIVE COPPER
COPPER DEPOSITS
DEPOSITS DERIVED
DERIVEDFROM
FROM NEARBY
NEARBY
KEWEENAWANBASALT
BASALTBY
BY COMBINED
COMBINED IGNEOUS,
KEWEENAWAN
DEUTERIC,
DEUTERIC, AND
ANDMETAMORPHIC
METAMORPHICPROCESSES
PROCESSES
NancyScofield,
Scofield, Institute
Mineral
Research
Nancy
Instituteof of
Mineral
Researchand
andDepartment
Department ofofGeology
Geology and
and
Geological Engineering,
Technological University,
University, Houghton,
Geological
Engineering, Michigan
Michigan Technological
Houghton, Michigan,
Michigan,
49931
ABSTRACT
flow) from
A thick (60
(60 m)
m) basalt
basalt flow
flow (Scales
(Scales Creek
Creek flow)
from the
the middle
middle of the
the
Portage
LakeVolcanics
Volcanicswas
wasintensively
intensivelystudied
studiedpetrographically
petrographically and
and its
its conPortage Lake
conIn the
stituent minerals
stituent
mineralsanalyzed
analyzed by
by electron
electronmicroprobe
microprobe techniques.
techniques. In
the interior
chemically:
1) 1)
whole
rock
CuCuabundance
of the
the flow,
flow,which
whichisisnearly
nearlyunaltered
unaltered
chemically:
whole
rock
abundance
is 110-150
ppm;2)2) microscopically-visible
microscopically-visible native
110-150 ppm;
native Cu
Cu isispresent
presentwithin
withinpseudopseudomorphsafter
after olivine;
olivine; and
morphs
and 3)
3) Cu
Cu concentrations
concentrations in oxidized
oxidized titanomagnetite
titanomagnetite
(2-3 modal
modal %)
%) are
are2000-2500
2000-2500ppm.
ppm. With
With increasing degree
degree of deuteric
deutericand
and metametamorphic alteration,
alteration, Cu
morphic
Cu was
was released
released from
from primary
primary minerals,
minerals, disseminated,
disseminated, and
and
mechanismsofof Cu
Cuconcentration
concentration
incorporated into
incorporated
into secondary
secondary minerals. Dominant
Dominant mechanisms
1) igneous
differentiation by
transfer within
after extrusion
extrusion are:
are: 1)
igneous differentiation
by gaseous
gaseous transfer
the flow, 2)
the
2) release
release of
ofnative
nativeCu
Cu during
during deuteric
deuteric oxidation
oxidation of
ofFe-Ti
Fe-Ti oxides
oxides
and Fe-Mg
Fe-Mg
silicates, and
and3)3)mobilization
mobilization and
andredistribution
redistribution by
and
silicates,
by later
latermetametamorphic
fluids.
morphic fluids.
Extrusion of the
Extrusion
the flow
flowonto
ontoaawet
wetsurface
surfaceproduced
produced aa basal
basal zone
zone of high
high
oxygenand
andvolatile
volatile activity,
accompanied
oxygen
activity,
accompaniedbybygaseous
gaseous transfer
transferdownward
downward of
of Cu,
Cu,
This zone,
Cu by
by this
this gaseous
transfer, was
Fe, and
and Ti. This
zone, enriched
enriched to
to 420
420 ppm
ppm Cu
gaseous transfer,
was
Fe,
immediately
abovethe
thevesicular
vesiculartop
top of
of the
immediately above
the underlying
underlying flow,
flow, and
and provided
provided aa
source
of Cu
Cufor
for later
later circulating
source of
circulatingmetamorphic
metamorphic fluids which
which followed
followed the
the perperIf this
within
meable flow-top
flow-top channeiways.
meable
channe1ways. If
thisprocess
processwas
was repeated
repeated elsewhere
elsewhere within
the volcanic pile,
belowthe
the basal
basal zones
zonesofof thick
thick flows
the
pile,channelways
channe1ways below
flows may,
may, in
some
cases, have
haveunusually
unusually high
high Cu
some cases,
Cu concentrations.
—32—
-32-
�POSSIBILITY OF
OF MISSISSIPPI
MISSISSIPPI VALLEY-TYPE
VALLEY-TYPE ORE
ORE DEPOSITS
DEPOSITS IN
IN INDIANA
INDIANA
POSSIBILITY
Shaffer, Nelson
Nelson R.,
R., Indiana
Indiana Geological
Geological Survey,
Survey, Bloomington,
Bloomington, Indiana
Indiana
Shaffer,
The midwestern
midwestern United
United States
States is
is recognized
recognized as
as aa lead-zinc
lead—zinc metallmetall—
The
ogenic
province
due
to
the
occurrence
there
of
low—temperature
ogenic province due to the occurrence there of low-temperature
ore deposits
deposits of the
the Mississippi Valley-type.
ore
Valley-type.
Such
Such deposits
deposits
commonly
rocks on
on the
the flanks
flanks
commonly occur within
within Paleozoic dolomite host rocks
of structurally high areas
of
areas far from
from regions
regions of
of igneous
igneous activity.
activity.
They are
are characterized by simple mineral suites,
They
suites, usually
usually sphalerite,
sphalerite,
fluorite, galena,
galena, or
or barite,
barite, that
that are
are believed
believed to
to have
have formed
formed
fluorite,
at moderate
moderate temperatures
temperatures from strong brines.
at
brines. One
One explanation
of
the
origin
and characteristics
characteristics of
of Mississippi
Mississippi Valley-type
Valley—type
of the origin and
deposits
suggests
that
they
formed
as
a
natural
consequence
of
deposits suggests
they formed as a natural consequence of
when sedimentary
sedimentary connate
connate waters,
waters, the
the metalmetalbasin development when
brines, migrated
migrated updip from
the basin
basin and precipitated
bearing brines,
from the
ore minerals upon encountering
encountering sources
sources of
of reduced
reduced sulfur.
sulfur.
Indiana lies
lies near
near this
Indiana
this general province and
and contains
contains many
many geologic
geologic
features
that
appear
suitable
for
the
development
of
Mississippi
features
development of Mississippi
Valley-type deposits.
A structurally high
high region collectively
deposits.
known as
the
Cincinnati
and
Kankakee
Arches,
crosses Indiana and
as the
Kankakee Arches, crosses
separates
the
Michigan
and
Illinois
Basins.
separates the
Paleozoic carbonates
occur in the Knox Dolomite (Cambrian
Ordovician); Black River
(Cambrian and Ordovician);
and Trenton Limestones
Limestones (Ordovician);
Salamonie, Louisville,
Louisville, and
(Ordovician); Salamonie,
Wabash Formation (Silurian);
Muscatatuck
Group
(Devonian);
(Silurian);
(Devonian); and
Salem,
St.
Louis,
and
Ste.
Genevieve
Limestones
Salem, St.
and Ste. Genevieve Limestones (Mississippian).
(Mississippian).
Unconformities
Knox, Trenton,
Trenton, and Wabash
Unconformities exist at the
the tops
tops of Knox,
Formations.
Numerous occurrences of
of sphalerite,
sphalerite, fluorite,
fluorite, barite,
barite,
and galena
galena have
have been
been noted
noted in
in Indiana
Indiana in
in the
the past,
past, and
and more
more than
than
and
60 new but generally minor occurrences have been found
found during
this recent
recent study,
study, many
many in
in the
the Black
Black River—Trenton
River-Trenton section,
section,
especially in northern Indiana where extensive dolomitization has
occurred.
occurred. The dolomitized reef facies
facies of the Wabash Formation
had many mineral occurrences in northern Indiana as did the overlying
lying Devonian
Devonian limestones.
limestones. Limestones of the
the Salem
Salem and
and Ste.
Ste.
Genevieve also had occurrences of sphalerite and fluorite
fluorite in
southern
southern and
and southwestern
southwestern Indiana.
Indiana.
Limited information
information from
from fluid
fluid inclusions
inclusions in
in sphalerite,
sphalerite, barite,
barite,
and fluorite
fluorite indicates
indicates that
that some
some samples
samples have
have formed
formed from
from brines
brines
in the range of temperatures reported from Mississippi Valleytype deposits.
deposits. Minor elements in 80 sphalerite specimens from
Indiana
Indiana included
included cadmium
cadmium (.03
(.03 to
to 6.9
6.9 percent),
percent), iron
iron (.01
(.01 to
to .61
.61
percent),
percent), and lesser amounts of gallium,
gallium, germanium,
germanium, copper,
copper, and
manganese.
Silver was not
not detected
detected in
in sphalerite
sphalerite samples.
samples.
Due to favorable
favorable geology,
geology, occurrence of minor amounts of ore
minerals, arid
tentative
evidence that
that fluids
fluids of the ore—forming
and tentative evidence
ore-forming
type passed through suitable host rocks,
rocks, a real possibility
exists
exists that
that undiscovered
undiscovered Mississippi
Mississippi Valley-type
Valley-type ore
ore deposits
deposits
may occur
in
Indiana.
occur in Indiana.
—33—
-33-
�PRECAMBRIAN
X PALEOPOLES
THE UPPER
PRECAMBRIAN X
PALEOPOLES FROM
FROM THE
UPPER PENINSULA
PENINSULA AND
AND AANEW
NEWMETHOD
METHOD
FOR REMANENT
VECTOR DETERMINATION
FOR
REMANENT VECTOR
DETERMINATION
SHANABROOK,
David,
Department
Geology,Michigan
Michigan State
State
SHANABROOK,
David,
Department
ofofGeology,
University,
University, East
EastLansing,
Lansing, Michigan
Michigan 48824
A method
methodwill
will be
which makes
makesitit possible
possible to use
be described
described which
use the
the
three-dimensional
modelingprogram
programofofWhitehill
Whitehill modified
three-dimensional magnetic
magnetic modeling
modified so
so
as
magneticvector
vectorinto
intoaccount
account
thatitit is
as to take
take the
the remanent
remanent magnetic
soso
that
possible
the declination
declination and
inclination of
possible to determine
determine the
and inclination
ofaabody's
body's
remanentvector
vector directly
directly from
remanent
fromobserved
observed magnetic
magnetic data. This
This is
is done
done
by
SHALOCI
writtenbybyWilliam
William Ciolek,
Ciolek,
by using
using aacomputer
computer program
program named
named SHALOCI
written
Mark
Locher,and
andthe
theauthor
authortotocalculate
calculate the
the induced
field due
Mark Locher,
induced field
due to
to
This induced
field isisthen
the body.
body. This
induced field
thensubtracted
subtractedfrom
fromthe
theobserved
observed
data
data to yield
yieldthe
themagnetic
magnetic field
fielddue
due totothe
thebody's
body'sremanent
remanent vector.
vector.
SHALOCI
thenused
used
againtotocalculate
calculate the
the magnetic
magneticfields
fields due
SHALOCI is isthen
again
due to
to
various vectors
various
vectors in
inorder
ordertotomatch
matchthe
theobserved
observed anomalie.
anomalie. This method
method
is accurate
of the
the vector's
vector's true
accurate to within
within 10
10 degrees
degrees of
true declination
declination
and44degrees
degreesofofits
its inclination.
inclination. Because
this, the
the results
results of
and
Because ofofthis,
are often
often useful
this method
method are
useful in
in determining
determining the
the age
age of aa body
body which
which is
very
very helpful ininPrecambrian
Precambrian shield areas
areas like
likethe
theUpper
Upper Peninsula
Peninsula of
of
Michiganwhere
wherethere
thereare
aremagnetic
magneticbodies
bodiesofofdifferent
different ages.
Michigan
ages. At
Present, this computer-oriented
approachisislimited
limited to bodies
present,
computer-oriented approach
bodies with
fairly strong
fairly
strongremanent
remanentmagnetic
magnetic vectors
vectorsand
and which
which have
have not
not been
been
metamorphosed
very
severely,but
butfuture
futurework
workmay
maybebeable
abletotoalleviate
alleviate
metamorphosed very
severely,
these problems.
problems.
Paleomagnetic
work done
done on
on samples
samplesfrom
from aa metadiabase
metadiabase dyke
dyke of
of
Paleomagnetic work
PrecambrianXXage
ageinin connection
connection with the
of supposed
supposed Precambrian
themagnetic-modeling
magnetic-modeling
described
hasyielded
yieldedsome
some
interestingresults.
results. Thermal
described above
above has
interesting
Thermal dedemagnetization
hasestablished
establishedaapaleopole
paleopolethat
that falls
falls on
magnetization has
on the
the apparent
apparent
polar wandering
curvefor
for North
Americaeither
either at 2.04
wandering curve
North America
2.04 bybp
bybp or 1.84
1.84
bybp depending
dependingononwhether
whetheritit is
is normal
bybp
normal or reversed.
reversed. Further work
work
is being
undertaken
clarifythe
thesituation,
situation,but
butitit is
is clear
being undertaken
to to
clarify
clear that
the
the long
long held
held idea
idea that
thatthe
themany
many positive
positivemagnetic
magnetic anomalies
anomalies in the
the
Upper
Peninsula of
of Michigan
were due
due to
to "normally"
Upper Peninsula
Michigan were
"normally" magnetized
magnetized PrePrecambrian
metadiabases
have
revised
lightofof the
the fact
cambrian XXmetadiabases
willwill
have
to to
be be
revised
in in
light
that they
Southern
they yield
yieldnorth-seeking
north-seekingpaleopoles
paleopolesininthethe
SouthernHemisphere.
Hemisphere.
—34—
-34-
�Precambrian geologic
geologic framework
framework of northern Wisconsin
by
P. K. Sims
Sims and
and Z.
Z. E.
E. Peterman
U.S.
u.S. Geological
Geological Survey,
Survey, Denver, Colorado
Colorado 80225
80225
Northern Wisconsin contains rocks belonging to each of the three
major
major subdivisions
subdivisions of
of the
the Precambrian.
Precambrian. Lower Precambrian
Precambrian (Archean
(Archean or
or
Precambrian W) rocks
rocks constitute
constitute the
the basement.
basement. Except for the
the Gogebic
Gogebic
Range and vicinity,
vicinity, which is underlain by 2,700—m.y.—old
2,700-m.y.-old greenstone—
greenstonegranite complexes,
complexes, the
the basement rocks are dominantly gneisses and
amphibolite.
m.y. have
amphibolite. Minimum ages for the
the gneisses of 2,800—3,000
2,800-3,000 m.y.
been obtained at a few localities in central Wisconsin (by
W. R.
(by W.
R. Van
Schmus)
Schmus) and near Morse, south
south of
of Nellen.
Mellen. Middle Precambrian
Precambrian
(Precambrian
(Precambrian x)
X) supracrustal rocks occur on the
the Gogebic Range,
Range, in
in a
75—km—wide
belt across
across northern Wisconsin,
Wisconsin, and
and in
75-km-wide east—trending
east-trending belt
Marathon
Marathon County
County and
and vicinity
vicinity in
in central
central Wisconsin.
Wisconsin. The proportion
proportion
of volcanic rocks
rocks Increases
that of
of sedimentary
increases southward relative to
to that
rocks;
rocks; these volcanic rocks contain the valuable massive sulfide
deposits known at
at Crandon,
Crandon, Ladysmith,
Ladysmith, and
and Pelican
Pelican River,
River. near
near Monico.
Monico.
Abundant granitic
m.y. old)
granitic rocks (1,800—1,850
(1,800-1,850 m.y.
old) intrude
intrude the
the volcanic
rocks. As known previously, the
the youngest rocks are local platform
quartzite deposits
m.y. old,
l,500—m.y.—
deposits more than 1,500 m.y.
old, the large 1,500-m.y.old Wolf River batholith and associated syenite,
syenite, and the approximately
l,l00—m.y.—old
1,100-m.y.-old (Keweenawan)
(Keweenawan) volcanic
volcanic and
and sedimentary
sedimentary rocks
rocks related
related to
to
the midcontinent rift
the
rift system.
system.
The middle Precambrian rocks that overlie Archean gneisses,
gneisses, together
basement, were folded
m.y. ago,
with the basement,
folded and metamorphosed about 1,800 m.y.
ago,
and were cataclastically
cataclastically deformed
deformed locally
locally about
about 1,600
1,600 m.y.
m.y. ago.
ago. In
In
contrast, strata overlying
overlying the
the greenstone-granite
greenstone—granite basement
basement on the
the Gogebic
Gogebic
contrast,
Range were not deformed
deformed during
during this
this interval.
interval.
At least three
three major high—angle
high-angle fault
fault sets
sets have
have been
been recognized.
recognized.
The youngest, related
related to
to the
the midcontinent
midcontinent rift
rift system,
system, consists
consists of
of N.
N.
50—55 E.
E. faults
faults that
that were
were formed
formed in
in late
late Keweenawan
Keweenawan time;
time; they
they probably
probably
50-55
produced most of
of the
the northward
northward tilting
tilting of
of strata
strata on
on the
the Gogebic
Gogebic Range.
Range.
North—northeast—trending
North-northeast-trending faults
faults that had repeated movements and that
that
typically have wide
wide zones
zones of
of mylonite
mylonite bound
bound the
the middle
middle Precambrian rocks
rocks
in the Marathon County area, as
as described
described earlier
earlier by
by G.
G. L.
L. LaBerge.
LaBerge.
Probably the
the oldest set consists of long,
long, northwest—trending
northwest-trending faults
that
reactivated and
and have
have apparent
apparent right-lateral
right—lateral movemovethat were repeatedly reactivated
f—
ments; the
the major fault,
fault, the
the Mineral
Mineral Lake
Lake fault,
fault, is
is interpreted
interpreted to
to of
offset Archean rocks about 160
160 km
km and
and middle
middle Precambrian
Precambrian rocks,
rocks, 10—15
10-15 km.
km.
—35—
-35-
�A NEW PRECAMBRIAN
PRECMIBRIAN SURFACE
SURFACE CONTOUR
CONTOUR MAP
MAP FOR SOUTH-CENTRAL
WISCONSIN,
Eugene I.
I. Smith,
Smith, Division
Division of
of Science,
Science, Univ.
Univ. of
of
Eugene
Wisconsin-Parkside, Kenosha,
Wisconsin-Parkside,
Kenosha, WI 53141
A new surface
su~face contour map for
for the
the buried Precambrian
Precambrian
basement of south-central Wisconsin was constructed
constructed using
using
data from
from 200
200 deep water
water and oil test wells,
wells, geophysical
data
studies, and
and previously published Precambrian surface
studies,
contour maps of
of Wisconsin. The new map shows that
that (1)
(1) the
the
Precambrian surface
Precambrian
surface slopes
slopes gently to the
the east,
east, southeast
southeast
and south off the
and
the Wisconsin arch.
arch. Standing above this
this
surface are
are numerous
numerous ridges
ridges and knobs of resistant rhyolite,
surface
granite and quartzite,
quartzite, many of which protrude through
granite
through the
the
Paleozoic and Pleistocene cover as inliers (e.g.,
(e.g., at Waterloo, in
in the
loo,
the Fox River Valley, and
and at
at Baraboo).
Baraboo). Buried
knobs of Precambrian rock occur
occur at
at Ripon
Ripon (granite),
(granite), BrotherBrothertown (quartzite),
Waupun (quartzite),
town
(quartzite), Waupun
(quartzite), Whitewater (quartz(quartzite)
ite) and Rosendale (rock
(rock type
type unknown)
unknown) . Both the
the exposed
knobs rise abruptly from
and buried knobs
from the
the peneplained
peneplained PrePrecambrian surface;
surface; for
for example,
example, the
the rhyolite knob at
at Berlin
stands
stands over 600 feet
feet above this
this surface,
surface, and that
that at
at
Marcellon, 470
470 feet.
feet. The change in
in elevation
elevation in
in both
both cases
cases
occurs
occurs over a
a lateral
lateral distance of less
less than
than 11 mile. Other
knobs have
The eastward plunging
have similar
similar relief.
relief. (2)
(2) The
Waterloo syncline
syncline is
is revealed
revealed by
by an
an arcuate
arcuate ridge
ridge that
that in
in
places stands 700
700 feet
feet above the
the level
level of
of the
the surrounding
surrounding
Precambrian surface.
surface. This ridge
ridge is
is only
only exposed
exposed in
in the
the
area to
the
east
of
Waterloo,
near
Portland.
to the east of Waterloo, near Portland. The nose of
of
the Waterloo
Waterloo fold is
the
is in
in the
the Portland
Portland area.
area. The north limb
limb
extends as a ridge from
from Portland
Portland to
to near Hartford
Hartford in
in WashWashington County, aa distance
distance of
of 30
30 miles.
miles. The south
south limb
limb
extends as aa continuous
continuous (?)
(?) ridge as far as Fort Atkinson
and then
then continues as a series
series of
of quartzite
quartzite knobs
knobs into
into
central Walworth County, aa distance
distance of
of 45
45 miles
miles (( a buried
quartzite knob is
is located
located at
at Whitewater, and
and quartzite
quartzite is
is
found
Delavan). (3)
found beneath Delavan).
(3) The subsurface
subsurface data
data is
is supsupportive
portive of a northeast trending
trending fault
fault extending
extending from
from near
near
Sheboygan to
to central
central Walworth
Walworth County
County (( as shown
shown on
onmaps
mapsby by
Thwaites, and Dutton and
and Bradley), but
but the
the presence
presence of
of
other
other faults
faults in
in the
the Precambrian
Precambrian basement
basement of
of south-central
south-central
Wisconsin
Wisconsin is
is uncertain.
uncertain.
.
—36—
-36-
�THE GEOLOGY AND PETROLOGY OF
OF THE
THE WINE
WINE LAKE
LAKE INTRUSION,
INTRUSION, COOK
COOK COUNTY,
COUNTY,
MINNESOTA
by
Andrew E.
E. Strakele,
Strakele, Jr.
Jr.
University of Minnesota, Duluth
Duluth,
Duluth, MN 55812
Exposures of
of granophyric
granite and associated
associated felsic
felsic intrusive
rocks
Exposures
granophyric granite
intrusive rocks
of the
eastern part
part of the
Duluth Complex form
form an east-west
east—west trending
belt
of
the eastern
the Duluth
trending belt
which parallels the
the northern or basal contact of the North Shore Volcanic
Group in Cook County,
County, Minnesota.
Minnesota. Along the western limit
limit of
of this
this belt,
belt,
where it begins to
to trend
trend southwestward near the county line,
line, there
there exist
several bodies of medium—grained
medium-grained diorite
diorite and
and quartz
quartz diorite.
diorite. The largest
body of these
bodies, together with
these dioritic rocks and some smaller satellite bodies,
an adjacent
adjacent unit
unit of recrystallized
recrystallized rhyolite
rhyolite and
and granite
granite have
have been
been informally
informally
an
designated as
as the Wine Lake Intrusion
Intrusion by Grout,
Grout, Sharp,
Sharp, and
and Schwartz
Schwartz in
in 1959.
1959.
Coarse—grained gabbroic
gabbroic anorthosite
anorthosite underlies
underlies this
this general
general area to
to the
Coarse-grained
the
north and west,
west, being locally overlain by a fine
medium—grained gabbro.
fine to medium-grained
gabbro.
dioritic rocks
rocks also
also occur above
above the
the gabbroic
gabbroic anorthosite
anorthosite as
as bodies
bodies of
of 1
The dioritic
to
to 5 km2
km 2 in
in area.
area. Both gradational and intrusive contacts appear to exist
between these
these three
three rock
rock units.
units. The rhyolite and granite unit of the Wine
Lake Intrusion has an outcrop pattern
pattern suggestive
suggestive of
of aa subhorizontal
subhorizontal sheet.
sheet.
locally contains
contains both
both irregular cuspate
cuspate and
and sometimes
sometimes angular
The granite
granite locally
inclusions
inclusions of fine—grained
fine-grained quartz
quartz diorite
diorite near
near the
the granite—diorite
granite-diorite contact.
contact.
Large xenoliths
xenoliths of amygdaloidal
amygdaloidal basalt
basalt and
and some
some late-stage
late—stage basaltic
basaltic dikes
dikes
Large
have also
also been observed
observed in
in the
the Wine
Wine Lake
Lake area.
area.
Field relationships,
relationships, petrography,
petrography, chemistry,
chemistry, and modelling of chemical
trends by
by aa least
least squares
squares approximation
approximation program for
for crystal
crystal fractionation
fractionation
trends
and
magma
mixing
support
the
derivation
of
gabbro
by
fractionation
of
and
support the derivation
gabbro by fractionation of
plagioclase from
gabbroic
anorthosite.
The
gabbro
was
apparently
altered
from gabbroic anorthosite. The
altered
by the addition of the components of albite,
albite, quartz,
quartz, orthoclase,
orthoclase, and H2O
H20
to produce the diorite and quartz
to
quartz diorite
diorite phases.
phases. The evidence also suggests
that the
components were
were derived
derived from the
the remelting of
of
that
the granitic
granitic mineral components
xenoliths of
of rhyolite
rhyolite composition.
composition. This model is in conflict with the
the model
of Weiblen and Morey (1975)
(1975) which states that the
the felsic
felsic series rocks
rocks were
the differentiation
differentiation of
of gabbroic
gabbroic anorthosite.
anorthosite.
produced by the
—37—
-37-
�POSSIBILITIES
POSSIBILITIESFOR
FORURANIUM-GOLD
URANIUM-GOLD QUARTZ-PEBBLE
QUARTZ-PEBBLE ORES
ORES IN
IN THE
THE LAKE
LAKE SUPERIOR
SUPERIOR
REGION IN
IN THE
REGION
THE LIGHT OF AANEW
NEW MODEL
~lODEL FOR ELLIOT IAKE-WITWATERSRAND
lAKE-WITWATERSRAND GENESIS
James Trow,
Thow, Department of Geology, Michigan
Michigan State
State University,
University,
East
Lansing,Michigan
Michigan 48824
L882
East Lansing,
Gibbs free-energy calculations support
support a new model for the
the formation of quartz-pebble
tion
quartz-pebble oresg
oresl 1)
1) a typically granitic,
granitic, alkaline,
alkaline, or metamorphic source area was exposed to
to 2)
2) oxygenated atmospheres during mamorphic
jar
C02—impoverished episodes
jor glacial C02-impoverished
episodes since
zince the
the Early
Early Precambrian.
Precambrian. Lower PC02
P002 and related higher pH
pH of rain
rain and
and runoff
runoff inhibited the
the dissolvdissolvirig
oxidizeduranium
uraniumasasU020~,
UO20},U0
UO2CO°,
UO2(CO3)2(H2O)
to
ing ofofoxidized
C0
0,
and
U02(C01)2(H20)2
to propro2 3
duce some
some clastic
clastic hydrated
hydrated uranyl
uranyl oxide
oxide pseudomorphs
seudomorphs arter
duce
after uraninite,
uraninite,
some
water-soluble U02(HP04)i
u02(HP0) complex
some water-soluble
complexions,
ions, and
and possibly
possibly (if
(if not
not exposed
exposed
too long)
long) some uraninite clasts 3)
3) which were transported by streams
along with
with magnetite
magnetite and
and hematite
hematite clasts,
clasts, ferric
ferric hydroxide
hrdroxide hydrosols,
hydrosols,
nuggets, and
and ilmenite
ilmenite clasts,
clasts, among
among others.
others. 4)
) These materials were
gold nuggets,
where hydrated uranyl
uranyl oxide
oxide clasts
clasts were
were
carried to aa steep Eh gradient where
re-reduced to
to uraninite
uraninite pseudomorphs,
pseudomorphs, where
whereU02(HP04)Z
UO2(HPO) complex
complex ions
ions were
were
reduced to interstitial uraninite,
uraninite, where
where magnetite and hematite
hematite clasts
were reduced to pyrite "clasts",
"Clasts", where
where ferric
ferric hydroxide hydrosols were
were
reduced to interstitial pyrite,
lost their
their clastk
clastc
pyrite, and where gold nuggets lost
Au5 (to
precipitate much
much later as
as non-clas~
non-clastt
character by dissolving as AuS(to precipitate
gold),
gold), all by reactions paradoxically requiring 02 as well as anticiHS, the
pated H2S or HS-,
the latter
latter two
two from
from interbedded
interbedded and
and underlying
underlying sulfidic
sulfi~
from the
the reaction of botanic
botanic sugars
sugars upon
upon S04.
SOC. Quartz
quartz pebbles
pebbles
basalts or from
indicate the
the sedimentary environment and
and imply the
the availavailindicate
the vigor of the
ability
elastic ilmenite resulted in
ability of
of reactant
reactant air.
air. Sulfurization of clastic
iron sulfide
sulfide (later to
to become
become pyrrhotite)
pyrrhotite) and
and Ti021
T102; the
the latter
latter then
then
endure as ore,
joined U02 to form brannerite. 5) To endure
ore, the reduced system
from renewed
renewed oxidation under
under post-glacial highhighwas sealed and preserved from
A 55,000-miles
er PC02 climates,
climates. A
55,OOO-miles Jeep reconnaissance
reconnaissance in the Basin and
Range,
Mountains, and the
Range, the Rocky Mountains,
the Appalachians has discovered five
five
of further
Late
Precambrian
targets worthy
worthy of
further study,
study,ofof
Late
Precambrianand
andEocambrian
Eocambrian ages.
ages.
Additional glacially-related
glacially—related terranes
terranes to be
Additional
be reconnoitered
reconnoitered include
include Late
Late
and Pliocene-Pleistocene.
Pliocene-Fleistocene.
Ordovician-Early Silurian, Permocarboniferous, and
Late Precambrian possibilities in the Lake Superior region inviting examination include i)
Mt. McCaslin
NcCaslin (Wis1) the parent ledge
ledge from which the Nt.
(Wisconsin)
consin) pyritic-quartz-pebble conglomerate boulder was wrenched during
the Pleistocene,
Pleistocene, 2)
2) conglomerates
conglomerates at
at the
the base
base of
of the
the Keweenawan,
Keweenawan, ininthe
cluding the
the Bessemer
Bessemer Conglomerate
Conglomerate (Wisconsin),
(Wisconsin),Nopeming
Nopemingand
andPuckwunge
Puckwunge
Conglomerates
(Minnesota),and
andcorrelatives
correlativesalong
alongthe
the northern
northern and
and easteastConglomerates (Minnesota),
ern shores of
of Lake Superior
Superior (Ontario),
(Ontario), and
and 3)
3) the southwestward continuation of the pyritic quartz-pebble conglomerate
conglomerate at
at the
the base
base of
of the
the
Fond du Lac
Lac Formation (Minnesota)
(Minnesota) particularly where it overlies the
St. Cloud Granite,
Granite, and the
St.
the correlative top of the
the Copper Harbor Conglomerate (Michigan).
(Michigan). AA Pleistocene possibility
possibility beneath
beneath lake—bottom
lake-bottom
U
ppb
Ste. Marie (Michigan),
(l'iichigan), suggested by 37
37
U in
in well
well
clays near Sault Ste.
source
as
Elliot
Lake
ores.
water,
may
have
been
derived
from
the
same
source
as
Elliot
Lake
ores.
water, may have been derived from the same
—38—
-38-
�GEOCHRONOLOGIC RELATIONSHIPS
RELATIONSHIPS IN
GEOCHRONOLOGIC
THE
IN THE
CARMEYLAKE
LAJCEGNEISS
GNEISS AND
AND OTHER
CARNEY
OTHER BASEMENT
BASEMENT GNEISSES
GNEISSES
IN DICKINSON
DICKINSON COUNTY,
COUNTY, UPPER MICHIGAN
IN
W. R.
R. Van
Van Schmus,
Schmus, R.
R. E.
E. Woronick,
Woronick, and N.
W.
N. L.
L. Egger
Egger
Department
of
Geology
Department of
of Kansas
University of
Lawrence, Kansas
Kansas 66045
66045
Lawrence,
The Carney
Carney Lake
Lake Gneiss
Gneiss and
and other
other granitic
granitic gneisses
gneisses exposed
exposed in
The
in the
the
Feich trough
trough region,
region, Dickinson
Dickinson County,
County, have
have generally
generally been
been assumed
Felch
to
assumed to
be Archean
Archean (Lower
be
(Lower Precambrian)
Precambrian) in
in age.
age. According
According to
to the
the model
model of
of Morey
Morey
and Sims
Sims (1976),
gneisses belong
belong to
to aa terrane
and
(1976), these
these gneisses
terrane that is in
in part
older than
older
than 3.0
3.0 b.y.
b.y. We are carrying out total—rock
total-rock Rb—Sr
Rb-Sr and zircon
U—Pb analyses
analyses from
from these
rocks in
in order
order to
to determine
determine their
primary age
U-Pb
these rocks
their primary
age
and to
to evaluate effects of post—Archean
and
post-Archean metamorphic
metamorphic events.
events.
for the
Carney Lake
Lake Gneiss
Gneiss indicate
indicate that
that this
unit has
has aa
Data for
the Carney
this unit
of about
about 2.8
2.8 b.y.
b.y. and
and has
has undergone
undergone extensive
extensive redistribution
primary age of
of Rb
Rb and Sr
of
Sr during
during aa metamorphic
metamorphic event
event about
about 1.8
1.8 b.y.
b.y. ago. This event
event
was probably regional metamorphism associated with emplacement of the
the
during the
the Penokean Orogeny
northeastern Wisconsin plutonic complex during
about
Orogeny about
1.83 b.y.
1.83
b.y. ago.
ago.
Feich Trough region continue to
reflect the
Data from the
the Felch
to reflect
the complex
geochronologic relationships
relationships reported on previously by Banks and Van
Schmus (1971,
Schmus
(1971, 1972).
1972). There is
is clear
clear evidence for
for a major event 2.1
2.1
b.y. ago that
that caused
caused extensive Rb—Sr
Rb-Sr re—equilibration
re-equilibration in
in the
the basement
gneisses.
gneisses. Our preferred interpretation
interpretation is
is that
that the
the event was high—grade
high-grade
metamorphism, perhaps with minor anatexis, affecting 2.8
2.8 b.y.
b.y. old
old
gneisses.
gneisses. Alternatively,
Alternatively, it
it is
is possible that
that much of the
the gneiss has
has
primary
primary ages of about
about 2.l
2.1 b.y.,
b.y., but have
have incorporated
incorporated substantial
substantial amounts
amounts
of
of older
older radiogenic
radiogenic Sr87.
Sr 87 •
Finally,
Finally, even
even though
though the
the age
age systematics
systematics are quite
quite complex,
complex, there
there
is
is no clear
clear evidence
evidence that
that any
any of
of the
the units
units studied
studied to
to date
date are
are older
older than
than
2.8
2.8 b.y.
b.y.
—39—
-39-
�FINITE
THETHE
PRECAMBRIAN
FINITESTRAIN
STRAININ IN
PRECAMBRIANKONA
KONAFORMATION
FORMATIONOFOFTHE
THEMARQUETTE
MARQUETTE
SYNCLI
SYNCLINORIUM
NORIUM
WESTJOHN,
Davidand
andCAMBRAY,
CAMBRAY,
William,Department
Department of
of Geology,
WESTJOHN, David
F. F.
William,
Geology,
Michigan
State University,
Michigan State
University, East
EastLansing,
Lansing, Michigan
Michigan 48824
Slates ininthe
thePrecambrian
Precambrian Kona
Kona Formation
Formation of the
the Marquette
Marquette SuperSupergroup
contain
ellipsoidal
reduction
spots
and
deformed
group contain ellipsoidal reduction spots and deformed veins.
veins. Each
Each
feature has
independently in other
has been
been used
used independently
other areas
areas as
as aameans
means of
measuring
finite strain
measuring finite
straininduced
induced in
in rocks
rocks during
during tectonic
tectonicdeformation.
deformation.
However,
the
strain
values
obtained
from
either
However, the strain values obtained from either of these
these indicators
are open
open to questions
questions because
because the
the following
followingassumptions
assumptionsmust
mustbebemade;
made;
the
werepredeformational
predeformationaland
and
initially spherical,
the reduction
reduction spots
spots were
initially
spherical,
and
the veins
veins were
were predeformational
predeformationaland
andinitially
initially had
and the
had aa wide
wide range
range of
presenceofof these
these features
features in
planar
planar orientations.
orientations. The
The presence
in the
thesame
same
lithology provided
an opportunity
opportunitytoto test
test the
the validity
validity ofofsuch
provided an
such
assumptions. Both
Both indicators occur
occur ininthe
thesame
same strain
straindomain,
domain, and
and
should show
showthe
thesame
same
strainstate
stateif
if the
are valid.
valid.
should
strain
the assumptions
assumptions are
In this
and
thisstudy,
study,reduction
reductionspots
spots
anddeformed
deformedveins
veinsfrom
fromthe
thesame
same
strain domain
are used
to determine
the orientation
strain
domain are
used to
determine the
orientation and
and dimensions
dimensions of
the
minimum
finitestrain
strain ellipsoid.
ellipsoid.
the minimum
finite
In
using
the
two
methods
it is
possible
test
is valid to
In using the two methods it is
possible
to to
test
if ifitit is
to
use
them
independently
as
a
measure
of
finite
strain.
use them independently as a measure of finite strain.
Preliminary
suggests that
that there are
differences which
Preliminary work
work suggests
are some
some differences
which indicate that
the
veins
may
have
developed
after
some
increment
strain
that the veins may have developed after some increment ofof strain
and
that
they
record
only
part
of
the
strain
history
and
that
the
and that they record only part of the strain
and that the rereduction spots
provide
a
more
complete
record.
spots provide a more complete
If this
may
If
thisisisthe
thecase
caseit it
maybe
be possible
possible to
to plot
plotpart
partofofthe
theincremental
incremental
strain history
of
the
region
and
to
record
both
magnitude
and
history of the region and to record both magnitude and orientation
orientation
of strain
thethe
Penokean
strainatatseparate
separatetimes
timesduring
during
PenokeanOrogeny.
Orogeny.
The
reduction
spots
indicate
a
minimum
finite strain ininwhich
The reduction spots indicate a minimum finite
which
Orientations
Orientations of
Principle
Axial Ratios
Ratios k value
value Extensions
Principle Axes
Axes
V
Z
(a-i/b—i)
V
X
Z
X : YY :: ZZ
(a
-1/ b-l) XX
Y
Z XX
Y
Z
Reduction
+58% +7% -43% 82°/O93° 8°/273° 10/0030
1.5:1.1:0.6
0.50
Spots
:
—40—
-40-
�—
AA new
new detailed
detailed aeromagnetic
aeromagnetic map
map covering
covering
most
most of
of the
the Precambrian
Precambrian shield
shield in
in Wisconsin
Wisconsin
by
by
Isidore
Isidore Zietz
Zietz
U.S.
U.S. Geological
Geological Survey,
Survey, National
National Center,
Center, Reston,
Reston, Virginia
22092
22092
ABSTRACT
ABSTRACT
A
A detailed aeromagnetic survey,
survey, having a flight
flight separation of ½
~
flight altitude of 500 feet,
feet, has been made over most of
mile and a flight
the Precambrian shield
shield in
in Wisconsin.
Wisconsin.
The survey
survey was under
under the
the
direction ofofJohn
direction
John1-1.
H. Karl
Karl of the University of
of Wisconsin
Wisconsin at
at Oshkosh.
Oshkosh.
An aeromagnetic
aeromagnetic map,
map, published
published by
by the
the U.S.
U.S. Geological
Geological Survey
Survey in
in 1977,
1977,
was prepared at
was
at a scale of 1:250,000 by photographically reducing and
compiling 86
maps that
that cover
cover areas
areas shown on standard
86 aeronlagnetic
aeromagnetic maps
standard U.S.
U.S.
Geological Survey 15'
IS' quadrangles.
quadrangles.
In addition,
addition, a colored
colored aeromagnetic
aeromagnetic
and at
the same
has been
map of the
the same area and
at the
same scale (1:250,000)
(1:250,000) has
prepared and placed on
on open-file
open-file by
by the
the U.S.
U.S. Geological
Geological Survey.
Survey.
By using
using these
these two
two aeromagnetic
aeromagnetic maps,
maps, together
together with
with the
the existing
existing
By
regional gravity data,
regional
data, available
available outcrops,
outcrops, and
and existing
existing isolated,
isolated,
sparse geologic
geologic mapping,
mapping, Paul
Paul Sims
Sims and
and William
William Cannon
Cannon have
have prepared
prepared
sparse
aa regional
regional geologic map.
In the
the main,
main, the
In
the uncolored aeromagnetic map was
was used
used for
for
structural analysis,
analysis, whereas
whereas the
the colored
colored version
version of
of the
the map
map on
on which
which
structural
the differences
differences of magnetic
magnetic intensity
intensity are
are conspicuous
conspicuous was
was used
used for
for
the
inferring
inferring lithologic variations.
—41—
-41-
�— — — — —;
———
I-
m
-Fl
—
�FIELD
FIELD TRIP
TRIP II
SOUTHWESTERN
SOUTHWESTERN WISCONSIN
WISCONSIN ZINC-LEAD
ZINC-LEAD DISTRICT
DISTRICT
LEADERS:
LEADERS:
M.G.
M.G. Mudrey,
Mudrey, Jr., Wisconsin Geological and
and Natural
Natural History
Survey,
Survey, W.A.
W.A. Broughton,
Broughton, University
University of
of Wisconsin-Platteville,
Wisconsin-Platteville,
Walter
Walter S.
S. West,
West, U.S.
U.S. Geological
Geological Survey,
Survey, and
and Allen
Allen V.
V. Heyl,
Heyl,
U.S.
U.S. Geological
Geological Survey.
Survey.
DATE:
DATE:
1978.
May 99 —- 10, 1978.
This trip will visit the Wisconsin part of the historic Upper Mississippi
Mississippi
Valley
Valley Zinc-Lead
Zinc-Lead District.
District. Stops
Stops at
at quarries and
and roadcuts
roadcuts will provide
a
a background on the ore—bearing
ore-bearing Paleozoic rocks before going underground
at a historic mining site,
site, and
and aa producing
producing zinc-lead
zinc-lead mine.
mine.
1.
1.
Assemble in
in Madison, Wisconsin,
Wisconsin, at
at 12:30
12:30 p.m.
p.m. on
on Tuesday,
Tuesday, May
May 9,
9,
1978, and proceed to
to Platteville,
Platteville, Wisconsin
Wisconsin for
for overnight
overnight lodging.
lodging.
Tour southwest
southwest Wisconsin, and
and journey
journey to
to Milwaukee
Milwaukee on
on Wednesday,
Wednesday,
May 10,
10, for
for the
the evening
evening festivities.
festivities.
2.
2.
The cost is
is $40.00
$40.00 and
and includes:
includes:
a)
a)
b)
b)
c)
c)
d)
d)
Overnight accommodations
accommodations (double
(double occupancy)
occupancy) at
at Platteville.
Platteville.
Bus transportation from Madison to Platteville with a
a
return trip
trip to
to Milwaukee.
Milwaukee.
An evening banquet in Platteville on Tuesday,
Tuesday, May 9,
9, and
lunch on Wednesday, May
May 10.
10.
Guidebook.
3.
3.
participants.
Limited to a
a maximum of
of 36 participants.
4.
4.
The guide materials designed for
for this
this field
field trip
trip are:
are:
a)
a)
b)
b)
c)
c)
d)
d)
Geology of Upper Mississippi Valley Zinc-Lead
Zinc-Lead District,
District,
Information Circular Number 16,
16, 1970.
1970.
($3.00)
Upper Mississippi
Mississippi Valley
Valley Base
Base Metal
Metal District,
District, Field Trip
Trip
Upper
Guidebook Number
Number 1.
1.
($4.00)
If purchased
purchased together,
together, the cost is $6.00.
If
$6.00.
Available from:
from:
Natural History Survey
Wisconsin Geological and Natural
1815 University
University Avenue
Avenue
1815
Madison,
Madison, Wisconsin 53706
608-262-1705
608—262—1705
—45—
-45-
�FIELD
TRIP II
II
FIELD TRIP
MINERAL
MINERAL EXTRACTION
EXTRACTION AND
AND PROCESSING
PROCESSING EQUIPMENT
EQUIPMENT MANUFACTURERS
MANUFACTURERS IN
THE GREATER
GREATER MILWAUKEE
MILWAUKEE AREA
AREA
LEADER:
LEADER:
Charles
Charles
DATE:
DATE:
May 10,
10, 1978
1978
A.
A. Salotti,
Salotti, University
University of
of Wisconsin-Milwaukee.
Wisconsin-Milwaukee.
This tour will visit a number of major manufacturing plants where
mineral and
and solid
solid fuel
fuel extraction and processing equipment is fabrifabricated. Milwaukee is
is a world center
center for
for this activity,
activity, and much of the
equipment used in the
the Lake Superior Region originated in southeastern
Increased
coal utilization,
utilization, coupled with rapidly changing
Wisconsin.
Wisconsin.
technologies
processing, are
are reflected in
technologies in mineral and solid fuel
fuel processing,
the dynamic character
character of this
this industry.
industry.
1.
1.
Depart from the
the Pfister Hotel,
Hotel, downtown
downtown Milwaukee,
Milwaukee, on Wednesday
morning about
about 9:00
9:00 a.m.,
a.m., May
May 10,
10, 1978.
1978.
Return to the Pfister Hotel
Hotel about
about 4:00
4:00 p.m.
p.m.
2.
2.
There is no guidebook for
for this
this trip.
trip.
—46—
-46-
�FIELD
FIELD TRIP
TRIP III
III
I
PRECAMBRIAN
PRECAMBRIAN RHYOLITh,
RHYOLITE, GRANITE,
GRANITE, AND QUARTZITE INLIERS
INLIERS IN
IN
SOUTH-CENTRAL
IN
SOUTH-CENTRAL WISCONS
WISCONSIN
LEADER:
LEADER:
Eugene
Eugene I.
I. Smith,
Smith, University
University of
of Wisconsin—Parkside.
Wisconsin-Parkside.
DATE:
DATE:
May
May 12
12 -- 13,
13, 1978
1978
This field trip will visit rhyolite ash—flow
ash-flow tuff and granite of Middle
Precambrian age
age (1765
(1765 +
~ 20
20 m.y.), which are
are inliers
inliers on the
the southern
southern
margin of
of the
the Precambrian
Precambrian shield.
shield. These rocks are younger than
than granite
granite
margin
and rhyolite in the Wausau area of central Wisconsin (1900
m.y.), and
(1900 m.y.),
older than the
Wolf River
River batholith
batholith of
of northeastern
northeastern Wisconsin
Wisconsin (1500
(1500 m.y.).
m.yJ.
the Wolf
Stops are
are designed
designed to
to illustrate
illustrate stratigraphic
stratigraphic and
and structural
structural relations
relations
interesting province.
province.
in this interesting
1.
1.
Depart Milwaukee on Friday evening,
evening, May 12,
12, 1978,
1978, at
at 6:30
6:30 p.m.,
p.m.,
and proceed to Oshkosh,
and
Oshkosh, Wisconsin for
for overnight
overnight lodging.
lodging. Tour
south—central
south-central Wisconsin on Saturday, May
May 13,
13, and
and return
return to
to
Milwaukee
Milwaukee about
about 6:30
6:30 p.m.
p.m.
2.
2.
The cost is $35.00
$35.00 and includes:
includes:
a)
a)
b)
b)
c)
c)
d)
Overnight accommodations
accommodations (double
occupancy) at
at The
The Pioneer
Pioneer
Overnight
(double occupancy)
in Oshkosh,
Oshkosh, Wisconsin.
Bus transportation from
Milwaukee to
to Oshkosh
Oshkosh and
and return
return
Bus
from Milwaukee
to Milwaukee.
Lunch on May
May 13.
13.
Guidebook.
3.
3.
No limit on number of participants.
No
4.
4.
The guide materials designed for
for this
this trip
trip are:
are:
a)
a)
b)
b)
c)
c)
d)
d)
Introduction,
Introduction, Geochronology, and
and Engineering
Engineering Geology
Geology of
of
Precambrian Rocks
Rocks in South-Central
South-Central Wisconsin,
Wisconsin, Geosciences
Geosciences
Precambrian
Wisconsin
Number 2.
2. ($4.00).
($4.00).
Wisconsin Number
Wisconsin, Field
Precambrian Inliers
Inliers of South-Central Wisconsin,
Trip Guidebook
Guidebook Number
Number 2.
2. ($5.00).
($5.00).
If purchased
purchased together,
together, the cost is
If
is $8.00.
$8.00.
Available from:
from:
Natural History Survey
Wisconsin Geological and Natural
1815
1815 University Avenue
Madison,
Madison, Wisconsin
Wisconsin 53706
608-262-1705
608—262—1705
—47—
-47-
�U
INDEX OF AUTHORS
AUTHOR
PAGE
• • • • 3
Aaquist, B.
B. E.
E.
Banaszak, K.
K. J.
J.
· 44
• • • • • • • • • 55
Bauer, R.
R. L.
L.
6,
6, 7, 40
40
Caxnbray, F.
F. W.
Carnbray,
.
Cannon, W.
Cannon,
W. F.
F.
. 8
26
• 26
Chang, L.
L. L.
L. Y.
Y.
Cooper, R.
R. W.
W.
. . . 12
Cummings, M.
M. L.
L.
.
.
9, 10
. 9,
Doane, v.
V.
18
DuBois,
DuBois, J.
J. F.
Egger,
.
.
.
. 11
11
L.
39
Foose, N.
Foose,
M. P.
P.
12
· 12
Gere,
N.
13
M. A., Jr.
M.
Jr.
Hammond, R.
R. D.
D.
.
. .
• . 14
Heinrich, E.
E. W.
W.
.
.
.
.
. 15
15
3
Hodder, R.
R. W.
W.
.
Hughes, J.
J. D.
D.
.
.
.
.
.
.
.
.
. 16
17
· 17
Jirsa, M.
Jirsa,
M. A.
A.
Jonnson, A.
A.
18
Jones, D.
D. G.
G.
19
19
• • • . 20
J.
Kalliokoski, J.
Klaysmat,
Klaysrnat,
25
A. W.
W.
A.
21
Larue, D.
K.
D. K.
•
R.
F. R.
Luther, F.
W. D.
D.
N. W.
Massey, N.
W. S.
S.
Meddaugh, W.
e.
•
•
•
•
•
•
•
•
•
•
•
•
• 22
· 23
23
• • • • • • • • • • • • • • • • 24
-49-49-
�AUTHOR
PAGE
Meineke, D.
D. G.
G.
25
· 25
Meyer, R.
R. P.
P.
28
Molling,
MoIling, P.
P. A.
A.
. . . . . . . . . . . . .
26
Mudrey,
Mudrey, M.
M. G.,
G., Jr
Jr.
27
• 27
Mursky, G.
G.
24
Myers, P.
P. E.
E.
9
Nebrija, E.
E. L.
L.
28
Ojakangas, R.
R. W.
W.
29
Peltonen, D.
D. R.
R.
30
Peterman, Z.
Z. E.
E.
31,
31, 35
35
Salotti, C.
C. A.
A.
24,
24, 30
30
Scofield, N.
N.
18, 32
32
Shaffer, N.
N.
33
Shariabrook, D.
Shanabrook,
D.
34
Sims, P.
Sims,
P. K.
K.
· 31,
31, 35
35
Smith, E.
E. I.
I.
• .
Strakele, A.
A. S.,
Strakele,
E., Jr
Jr.
.
.
.
.
• • .
.
.
• 36
37
• 37
Taylor, R.
R. W.
W.
30
Trow, J.
J.
38
• 38
Tyson, R.
R. M.
M.
26
Vadis, M.
M. K.
K.
25
Van
Van Schmus,
Schmus,
W. R.
W.
R.
14, 39
11, 14,
39
Welkie, C.
C. J.
J.
28
Westjohn,
West
john, D.
D.
• • 40
Woronick, R.
R. E.
E.
39
· 39
Zietz, I.
I.
41
—50—
-50-
�TWENTY—SEVENFIRMS
FIRMS IN
IN THE
TWENTY-SEVEN
THE GREATER
GREATER
MILWAUKEE
MILWAUKEE AREA
AREA EITHER
EITHERMANUFACTURE
MANUFACTURE
OR SUPPLY
FOR MINERAL
OR
SUPPLY COMPONENTS
COMPONENTS FOR
EXTRACTION
EXTRACTION AND
AND PROCESSING
PROCESSING MACHINERYI
MACHINERY,
THEIR
SALES IN
IN 1977
THEIR AGGREGATE
AGGREGATE SALES
1977WAS
WAS
9.5 BILLION
9,5
BILLIONDOLLARS.
DOLLARS,
�2,51O,000'E
§+
OZAUKEE CO.
OZAUKEE CO.
'7
LEGEND
2,590,00~E
2.5+00'
+§
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.
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TOTAL FOR COUNTY
DEPARTMENT OF TRANSPORTATION ')
DIVISION OF HIGHWAYS
STATE OFFICE BUILDING
Madison, Wisconsin
o
I
,
SCALE ~:::::::J MILES
MILES OF HIGHWAY
asofJan.I,1975
STATE
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LOCAL ROADS
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.... 2615
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Compiled frcrn U.S.G.S. Quad/angles
Based on Aerial Photographs
MILWAUKEE 40·9
�
https://digitalcollections.lakeheadu.ca/files/original/cdb7e5f2759e322eb662e91633befa43.pdf
8b8cb45be09f5be9ace0f0580c35e58a
PDF Text
Text
UNIVERSITY OF WISCONSIN-EXTENSION
GEOLOGICAL AND NATURAL HISTORY SURVEY
Meredith E. Ostrom, State Geologist and Director
UPPER MISSISSIPPI VALLEY
BASE-METAL DISTRICT
Prepared for:
TWENTY-FOURTH ANNUAL MEETING
INSTITUTE ON LAKE SUPERIOR GEOLOGY
UNIVERSITY OF WISCONSIN-MILWAUKEE
MILWAUKEE, WISCONSIN
MAY 9—14, 1978
FIELD TRIP
GUIDE BOOK
NUMBER 1
1978
�Field Trip Guide Book
Book
Number
Number 11
University
University of
of Wisconsin—Extension
Wisconsin-Extension
GEOLOGICAL
GEOLOGICAL AND NATURAL HISTORY SURVEY
Meredith
Meredith E. Ostrom,
Ostrom, State Geologist and
and Director
UPPER MISSISSIPPI
MISSISSIPPI VALLEY BASE-METAL DISTRICT
DISTRICT
(companion volume
to Information
volume to
Information Circular
CircularNumber
Number 16)
16)
With contributions
contributions by
With
by
W. A.
A. Broughton, A.
A. V.
V. Heyl,
Heyl~ M.
M. G.
G. Mudrey,
Mudrey, Jr.,
Jr., M.
M. E.
E. Ostrom,
Ostrom,
Rachel K.
A. Paull,
W. S.
K. Paull,
paull, Richard A.
Paull, and W.
S. West
Edited by
M.
M. G.
G. Mudrey,
Mudrey, Jr.
Jr.
Natural History Survey
Geological and Natural
Prepared for
Annual Meeting
Twenty-Fourth Annual
INSTITUTE ON
ON LAKE
LAKE SUPERIOR
SUPERIORGEOLOGY
GEOLOGY
University
University of
ofWisconsin,
Wisconsin,Milwaukee
Milwaukee
Milwaukee,
Milwaukee, Wisconsin
May 9-14,
9-14, 1978
Richard A.
A. Paull,
Chairman, Field Trip Committee
PaUll, Chairman,
University of Wisconsin-Milwaukee
Available from the
the Wisconsin
Wisconsin Geological
Geological and
and Natural
Natural History
History Survey,
Survey,
of Wisconsin-Extension,
Wisconsin—Extension, 1815
University of
1815 University
University Avenue,
Avenue, Madison,
Madison,
Wisconsin 53706
53706
1978
�CONTENTS
OONTENTS
Page
INTRODUCTION
INTRODUCTION by
by M. G.
G. Mudrey,
Mudrey, Jr
Jr. • • • • • • • . • • • • • • . • • • • •
1
TUESDAY, MAY
MAY 9,
9, 1978
1978
TUESDAY,
Geologic Road
Road Log
Log for
for U.
U. S.
S. 151
151 from
from Madison,
Madison, Wisconsin
Wisconsin (U.
(U. S.
S. 12
12 and
and
14 junction)
junction) to
to Platteville,
Platteville, Wisconsin
Wisconsin (Wisconsin
(Wisconsin 80
80 and
and 81
81
junction)
junction) by
by Richard
Richard A. Paull
Paull and
and Rachel
Rachel K.
K. Paull
Paull
• • • • • 77
• Geologic Road
Road Log
Log for
for Grant
Grant County
County by
by M.
M. G.
G. Mudrey,
Mudrey, Jr.,
Jr., W.
W. A.
A.
14
Broughton,
Broughton, A. V.
V. Heyl,
Heyl, and
and W.
W. S.
S. West
West • • • • • • • •
WEDNESDAY, MAY
MAY 10,
10, 1978
1978
WEDNESDAY,
Geologic Road
Road Log
Log for
for Lafayette
Lafayette County
County by
by M.
M. G.
G. Mudrey,
Mudrey, Jr.,
Jr., W.
W. A.
A.
Broughton,
Broughton, A. V.
V. Heyl,
Heyl, and
and W.
W. S.
S. West
West . • • • • • • • • • • • • • • 16
16
Geologic Road Log for
for Madison Beltline,
Beltline, 1—90,
1-90, and
and 1—94
1-94 from
from Madison,
Madison,
Wisconsin
Wisconsin (U.
(U. S.
S. 12
12 and
and 14
14 junction
junction with
with U.
U. S.
S. 18
18 and
and 151)
151) to
to
Milwaukee,
Milwaukee, Wisconsin
Wisconsin (1—94
(1-94 junction
junction with
with 1—43
1-43 and
and 1-794)
1-794) by
by
Rachel
Rachel K.
K. Paull and
and Richard
Richard A. Paull
Paull • • • . • • • . • • • • • • • • 17
17
SlOP DESCRIPTIONS
GFXHl>GICAL S1UP
DESCRIPTIONS
GEX)LOGICAL
Stop 11
Stop
Stop
Stop
Stop
Stop
22
33
44
55
—
——-—-
...3228
M. E.
Hoadley Hill by M.
E. Ostrom • • • • •
Section 22 Quarry by M.
Section
M. G.
G. Mudrey,
Mudrey, Jr
Jr .•
Hill by M.
M. E.
E. Ostrom
Ostrom. • . • • •
Potosi Hill
St. John Mine by M.
St.
M. G.
G. Mudrey,
Mudrey, Jr
Jr . • •
Industries
Shullsburg Mine by
Shullsburg
by Staff,
Staff, Eagle—Picher
Eagle-Picher Industries
(not
(not attached to road
road log)
log)
.
.
.
28
32
33
37
37
ILLUSTRATIONS
Figure 1.
1.
Figure 2.
2.
Figure 3.
3.
4.
Figure 4.
Map of main part of Upper Mississippi Valley
Valley zinc—lead
zinc-lead
district
district.
. . . . .
. . . . . . . . . . . . . . .
Highway map showing route
route of
of field
field trip
trip • • . • • • • •
Detailed stratigraphic column
column of
of Platteville,
Platteville, Decorah,
Decorah, and
and
Galena formations in
in zinc—lead
zinc-lead district
district • . • • • • • • • • •
Simplified stratigraphic column
column showing
showing relative
relative quantitative
quantitative
.
stratigraphic distribution of zinc and lead in Wisconsin.
stratigraphic
Stalactites in Cave
Cave of the
the Mounds
Mounds near
near Blue
Blue Mounds
Mounds. •
Cross section through Blue Mounds
Cross
Mounds from west to east • •
Blue Mound viewed
viewed from
from west • • • • • • • • • • . • • • • • •
. . •.
of glacial
glacial deposits
Photograph of
deposits of southeast Wisconsin
polished Precambrian Waterloo Quartzite . •
Glacially polished
•
Intensively farmed
Intensively
farmed drumlin near Sullivan • • . • . • • • • • •
Scenic overview of the southern Kettle Interlobate
Scenic
Interlobate Moraine.
Moraine • •
.
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
5.
5.
6.
6.
7.
7.
8.
8.
9.
9.
10.
10.
11.
.
.
i
:i.
22
3
4
5
9
10
11
18
20
22
23
�I NTRODUCT ION
INTRODUCTION
M. G.
G. Mudrey, Jr.'
M.
Jr.1
The zinc
zinc and
and lead
mines of
of southwestern Wisconsin
Wisconsin are
are part
part of
of the
the oldest
oldest
The
lead mines
producing zinc-lead
zinc-lead mining district
district in the
the United
United States,
States, the
continuously producing
The largest
and most
most productive parts
Upper Mississippi Valley District. The
largest and
parts of
of
this district
district extend
extend across
across five
five Wisconsin
Wisconsin counties
counties and
and into
into small
small areas
areas in
in
this
Illinois and
and Iowa (Fig.
Over 1.2
1.2 million
million tons
tons of
of zinc
zinc and
and nearly 100,000
Illinois
(Fig. 1).
1). Over
tons of
of lead
lead have
have been
been recovered
recovered from
from the Wisconsin portion of
tons
of the
the Upper
Upper MissMississippi Valley
Valley district
district from 1910 to
issippi
to 1974,
1974, with
with aa combined
combined value
value in
in excess
excess of
of
Heyl and
and others
others (1959)
suggest that an
an additional
additional 250,000 tons
$267 million. Heyl
(1959) suggest
tons
of zinc
zinc and
and 350,000 to 400,000 tons
of lead
were produced
produced in the
Wisconsin part
of
tons of
lead were
the Wisconsin
of
of the district in
in the
the period
period following
following 1800.
1800. The text that accompanies this
this
field trip (Heyl
and others,
others, 1970)
1970) covers
covers the
of the
region, and
field
(Heyl and
the early history of
the region,
the
the geologic controls on ore
ore mineralization.
mineralization.
In
(1976)
In addition,
addition, West
West and Weeks (1976)
provide additional information
information on
on the
the district
district and
and its
its production.
production.
The field
field trip commences
commences in Madison,
Madison, proceeds
The
proceeds to Platteville for
for an overnight stop,
examines the
formations directly related
related to the
horizons, and
night
stop, examines
the formations
the ore horizons,
visits an historic lead
Mine) and
and an operating zinc-lead mine
visits
lead mine (St.
(St. John Mine)
near Shullsburg
Shullsburg (Fig.
(Fig. 2).
2). The
returns to Madison where private
The field
field trip returns
vehicles can be picked up,
up, and
vehicles
and terminates
terminates in downtown Milwaukee prior to the
25th Annual Institute
Institute on
on Lake
Lake Superior
Superior Geology.
Geology.
Potosi and Shullsburg 7.5Geologic stops will be in
in the
the Dickeyville,
Potosi
In addition,
addition, the
the route leads through
minute topographic quadrangles.
In
through the
the
Platteville,
Platteville, Cuba City, and
and New
New Diggings
Diggings 7.5-minute
7.5-minute topographic
topographic quadrangles.
quadrangles.
Geologic
(1963); Dickeyville,
Geologic quadrangle references
references are Cuba City,
City, Agnew (1963);
Dickeyville, Whitlow
and West (l966a);
Diggings, Mullens
Mullens (1964);
Potosi, Whitlow and West (l966b);
(1966a); New Diggings,
(1964); Potosi,
(1966b);
Shullsburg, Mullens (1964).
and Shullsburg,
(1964).
cuts and a
The trip starts with two road cuts
a quarry that include units of the
the
The first
Sinnipee Group (Figs.
(Figs. 33 and
and 4).
4). The
first day ends
ends with a
a visit to an early
lead mine (St.
(St. John Mine),
Mine), that
that may well have been the
the first operating mine in
in
Wisconsin. The second day the
the Shullsburg Mine
Mine of
of Eagle
Eagle Picher
Picher Industries,
Industries, Inc.
Inc.
will be
be visited.
visited. After a lunch
lunch stop
stop in
in Shullsburg,
Shullsburg, the
the route leads
leads back to
to
cultural tour along back roads,
roads, and
and then returns
Platteville via aa cultural
returns to Madison
and Milwaukee.
This year marks the
the 125th
l25th anniversary
anniversary of the
the first Wisconsin geological
survey.
Under an act of
of the Legislature approved March 25,
25, 1853,
1853, a
a State
Geological Survey was created,
created, with an annual
annual appropriation
appropriation of
of $2,500 per
per year
year
for four years.
years. Edward Daniels was appointed
appointed State Geologist by Governor
Leonard J.
J. Farwell. Daniels'
Daniels' instructions
instructions were to
to "complete his
his survey
survey of
of that
that
of the state known as
mines' before commencing the survey of
portion of
as the 'lead
'lead mines'
the remainder of
of the
the state."
state."
We welcome you
you to
to the
the Zinc-Lead
Zinc-Lead District, and
and hope that
that you
you find
find the
the geology,
geology,
companionship, and
and tour
tour rewarding!
rewarding!
1 Wisconsin
Wisconsin Geological
Geological and
and Natural History Survey,
Survey, Madison
Madison
1
1
�Pb
\
"'" "ALLAMAKEE
Cu
)
RICHLAND
*
Pb*
CRAWFORD
/
*
COLUMBIA
SAUK
Pb* Cu
(
River
Pb*
I'
Pb Madison
*
*
DANE
Zn *Pb
o
Pb
Zn
*
0
Pb
CLAYTON
--
Belmont
•
·Calamine
.Darlington
Platteville _
IOW4 "\
LAFAYETTE
~
Dubuque
• Shullsburg
~
Pb
--~bO---
"ol'ol' .
'-"ol'ol'/
DELAWARE
~O
WISCONSIN
-ILLINOiS - -
.,~-.- - ~.o....
DUBUQUE
•
Galena
STEPHENSON
Cu Zn
PbOAu
Freepo·rt
-Opb
~...t..
-..!?....-...-.-
JONES
--I-_=-----,:---------j
JACKSON
Pb
A.
CARROLL
o
Pb
0o
10
I
I
I
I
Pb
Lead
Zn
Zinc
Cu
Copper
Au
Silver
Silver
0o
Miles
20 Miles
I
I
I
EXPLANATION
OGLE
I
I
I
io
10
20
Kilometres
*
*
Mine or
or prospect
prospect inin dolomite
dolomite of
Mine
Silurian age
age
o
Mine or prospect
Mine·or
prospect in
in Galena,
Galena, DecoDecorah, and
and Platteville
Platt~ville formations
formations
A
prospect in
in Prairie
Prairie du
du
Mine or prospect
Chien group
Boundaryof
of main
main part
part of
of district
Boundary
Figure 1.
1.
Figure
Map of main part of the
the Upper
Upper Mississippi Valley
Valley zinc—lead
zinc-lead district,
district.
2
�Route from Madison t. Platteville
and return via U.S. Hwy 151
(69 miles)
iH?E
HHHr
\
P
iiNL
-
'I
lmH fl0
1HRRI
-
i-t
)JTF
F- -I
\ (ELMON
LAIi
_=i__
,
S -4=4
--S
'
I
/11/
\V F
TN
'
:
)Jf
—
r
(Ii
1
k
1ff
S—f—
-7L
ij
I•
Figure 2.
2.
hul Isburg
1k
WHITEII
F-
RI-N
STATE OF
STATE
OF ILLINOIS
ILUNOIS
----
j
/
)SHUL/UR
j MON
R-2•W
........
I
k-2
O(
Jj 7L
oi
-
ENONç
L
—
—
T'1JL/ ,/
I
'-
ELKVE
1-
-
/
-
/L J
17
'—
t
R.2E
Tuesday May
May 99 Route
Route
Tuesday
Wednesday May
Route
Wednesday
May 10
10 Route
Scheduled Stops
Scheduled
Stops
Highway map
map showing
showing route
route of
of field
field excursion.
excursion.
3
3
Of TRANSPORTATION
TRANSPORTATIClH
DEPARTMENT OF
D1VI~0t4
.
SCALE?
SCALE
O' MIG"",AYS
,
.1Lf:S
MILES
�System
System
Series
Group
Upper
Unner
Devonian
Devonian
Member
Kenwood
Kenwood (55')
(55' \
Milwaukee (80')
(80')
Thiensville
Thiensville (65')
(65')
Lake
Lake Church
Church (35')
(35' )
Middle
Cayugan
Silurian
Formation
Waubakee (30')
(30')
Racine
Racine (100')
(100' )
Manistique
Manistique (150')
(l50' )
I1endricks
Hendricks)
(110'))
(1l0'
Byron
Bvron
Mayville (175')
(175' )
Niagaran
Alexandrian
Alexandrian
Cincinnatian
Sinnipee
Sinnipee
Champlainiao
Champlainian
Ordovician
Neda (55')
(55')
Maquoketa (240')
(240' )
Galena
230'
Galena (230')
(25')
Decorah
Decorah (25')
Platteville (100')
(lOO' )
St.
St. Peter
Glenwood (13')
(13' )
Tonti
)
Tonti
332'))
(332'
Readst
own
Readstown
Shakopee
Canadian
Prairie
du
Chien
Chien
Willow
Willow River
River (50')
(50' )
New Richmond
Richmond (25')
(25')
Oneota (200')
(200' )
Jordan
Trempealeau
Trempealeau
Cambrian
St. Lawrence
St.
(50 ))
(50'
St. Croixan
St.
.
Tunnel City
City
(200'
(200'))
Lone Rock
Lone
Mazomanie
Maz~
Wonewoc (100')
(100' )
Sunset Point
Point
Van Oser
Oser)
Norwalk j (60')
.Black
Black
Loch
Lodi
< -. Earth
Earth
<
Reno
Tomah
Birkmose
Ironton (40')
Ironton
(40')
Galesville
Bonneterre (20')
(20')
~onneterre
Elk Mound
(250')Eau Claire (250')
Mt.
Mt. Simon (500')
(500')
Figure 3.
Detailed stratigraphic column of Platteville,
Detailed
Platteville, Decorah,
Decorah, and
and
Galena formations
Galena
formations in the Upper Mississippi Valley
Valley zinc—lead
zinc-lead
district.
4
�I
Known]ECIl
relative
Quantities
-1:<;0
•
•
I
~
t;,
Q)
_-'-';~- i~I' ~
'
G roup or
formation
In
Dolomite, buH, cherty; Ptllt4mtru, at lop,
~~; I
~ ~~~
0(
~
Average
thickness.
Description
90
fLjP-=A--o-o,-om-,-..-.-"-11-.-oh-'-ff'-;-'-"-i1-,,-,,-o,-,-n-.-,,-,-,-,.---t-- -jO 200
II
DolomIte. yellowlsh·buff. thln·bedded, snaly_
I
Dolomite. yellowlsh.buff, thiCk. bedded :.Rt. f!ptucullt1!S
In middle
225
105
Dolomite. drab to butt: cherty; Rrclpta.cutiU.
near base
limestone and doIOI'T"te. brown and grayish: green,
sandy shale and phosphatic nO(lules at base
DISCONFORMITY
40
80
Galena dolomite
St. Peter sandstone
I
I
108=l
Shale, blue. dolomitiC: phosphatic depauperate
fauna <1t base
Maquoketa shale
I
feet_I
55 75
40 ~
Sandstone. quartz, coarse. rounded
. , f - - - - - - - D1SCONF'ORMITV------f---I
280-
-f".
Dolomite, Iight·buff, cherty; sandy near base and
Prairie du ChIen group
~:~ .~:, ~:".~".~.~.'
lundifferentlated)
Trempealeau
formation
FranconIa sandstone
Sandstone and Siltstone. glaucoroitlc
Dresbach sandstone
Sandstone
f.------l';;:±8-----------Eau Clai,e sandstone
Siltstone and sandstone
0-
I
320
I
---~
110· 140
~o
l
70
330
1050
I
700
I
I
Mount Simon
sandstone
Figure
Figure 4.
4.
Sandstone
440
780
I
__J
Simplified stratigraphic
stratigraphic column
column shOWing
showing relative
relative quantitative
quantitative
Simplified
stratigraphic distribution
distribution of
of zinc
zinc and
and lead
lead in
in the
the Wisconsin
Wisconsin
stratigraphic
district.
district.
55
�References Cited
Agnew,
Agnew, A.F., 1963,
1963, Geology
Geology of
of the
the Platteville
Platteville quadrangle
quadrangle Wisconsin:
Wisconsin:
U.S.
U.S. Geol.
Geol. Survey Bull. l123—E,
1123-E, p.
p. 245—277.
245-277.
Heyl,
A.V., Jr.,
Heyl, A.V.,
Jr., Agnew,
Agnew, A.F., Lyons,
Lyons, E.J.,
E.J., and
and Behre,
Behre, C.H.,
C.H., Jr.,
Jr., 1959,
1959,
The Geology of the
the Upper
Upper Mississippi Valley
valley Zinc—Lead
Zinc-Lead District:
District:
U.S.
U.S. Geol.
Geol. Survey Prof. Paper 309,
309, 310
310 p.
p.
Heyl, A.V.,
Ay., Jr.,
Heyl,
Jr., Broughton,
Broughton, W.A.,
W.A., and
andWest,
West, W.S.,,
W.S., 1970,
1970, Guidebook
Guidebook to
to the
the
Upper Mississippi Valley
Geol. and
valley base
base metal
metal district:
district: Wisconsin Geol.
Nat.
Nat. History Survey Inf.
Inf. Circ. No.
No. 16,
16, 49
49 p.
p.
Mullens, T.E.,
City, New
New Diggings,
Diggings, and
and Shullsburg
Shullsburg
Mullens,
T.E., 1964,
1964, Geology of
of the Cuba City,
quadrangles, Wisconsin
U.S. Geol.
Geol. Survey
Wisconsin and
and Illinois:
Illinois:
U.S.
Survey Bull. 1123-H,
1123-H,
p.
437-531.
p. 437—531.
West, W.S.
West,
W.S. and
and Weeks, R.A.,
R.A., 1976,
1976, Zinc
Zinc and
and Lead
Lead in
in C.E.
C.E. Dutton,
Dutton, ed.,
ed.,
Report prepared by the
Mineral and
and Water Resources
Resources of
of Wisconsin:
Wisconsin: Report
U.S. Geol.
Geol. Survey in
U.S.
in collaboration with the
the Wisconsin
Wisconsin Geol.
Geol. and
and Nat.
Nat.
History Survey for the Committee on Interior
Interior and
and Insular
Insular Affairs,
Affairs,
United States Senate, p.
p. 132—145.
132-145.
Whitlow, J.W.,
West, W.S.,
W.S., l966a,
Geologic map of
of the
Dickeyville
Whitlow,
J.W., and West,
1966a, Geologic
the Dickeyville
quadrangle, Grant County,
quadrangle,
County, Wisconsin:
Wisconsin: U.S.
U.S. Geol.
Geol. Survey
Survey Map
Map GQ-488.
GQ-488.
Whitlow,
Whitlow, J.W.,
J.W., and
and West, W.S.,
W.S., 1966b,
1966b, Geology
Geology of
of the
the Potosi
Potosi quadrangle,
quadrangle,
County, Wisconsin,
Wisconsin, and Dubuque County, Iowa:
U.S. Geol.
Geol. Survey
Grant County,
Iowa:
U.S.
1123-1, p.
p. 533—571.
533-571.
I
Bull. 1123—I,
6
�Tuesday,
Tuesday, May 9,
9, 1978
1978
for U.S.
U.S. 151
151 from
from Madison,
Madison, Wisconsin
Wisconsin (U.S.
(U.S. 12
12 and
an 14
Geologic Road
Road Log for
Geologic
14 junction)
junction)
to
Platteville, Wisconsin (Wisconsin
to platteville,
(Wisconsin 80
80 and
and 81
81 junction)
jUnction)*
A. Paull
Richard A.
11
and Rachel K.
K. Paull
and
2
2
U.S.
U.S. 151 from Madison to
to Verona traverses
traverses aa recently
recently glaciated
glaciated (Woodfordian)
(Woodfordian)
part of the Eastern Ridges and
and Lowlands
Lowlands physical
physical province.
province. Since the
the drift in
in
this area was
was deposited
deposited near
near the
the ice
margin, it
it is
and the
the
this
ice margin,
is generally thin,
thin, and
exerts considerable
considerable influence
on the
the character of
of the
landunderlying bedrock exerts
influence on
the landFrom the
scape.
the western edge of the
the Wisconsinan (Woodfordian)
(Woodfordian) terminal moraine
just west
west of
of Vernoa to the
River, the
route crosses
crosses aa thin sliver of
of older
the Sugar River,
the route
(Illinoian) drift.
drift. The remainder of the route lies within the
the classic Driftless
Area of
of the
the Western
Western Uplands
Uplands physical
physical province.
province.
and Mt.
Mt. Horeb,
Horeb, rock exposures
exposures along
along the
Between Madison and
the highway are mainly
dolomite assigned to
to the
the Lower Ordovician
Ordovician Prairie
Prairie du
du Chien
Chien Group.
Group. However,
The bedrock from Mt.
some younger rocks are
are also
also present.
present. The
Mt. Horeb to
to Platteville
Plattevil1e
is predominantly Middle Ordovician limestone
is
limestone and
and dolomite
dolomite of
of the
the Platteville,
Platteville,
Decorah, and Galena formations,
formations, although the
the Middle
Middle Ordovician St.
St. Peter Sandstone
Decorah,
is also exposed along
along the
the highway
highway in
in aa few
few places.
places. Several isolated mounds
(outliers)
of Upper
Upper Ordovician
Ordovician Maquoketa
Maquoketa Shale
Shale capped
capped by
by resistant,
resistant, Silurian
Silurian
(outliers) of
dolomite are present near U.S.
of Blue Mounds
Mounds and
Platteville.
U.S. 151 in the vicinity of
and Platteville.
Mileages
0
o
(69)
U.S. 12 and 14 on the southwest
Junction U.S.
U.S. 151 and 18 with U.S.
The road
road log
edge of Madison,
Madison, Wisconsin. Note: The
log from
from Madison
Madison
to Milwaukee
Milwaukee provided
provided for
for Wednesday
Wednesday May
May 10,
10, 1978
1978 also
also begins
begins
to
at this
this intersection.
intersection.
1.5
(67.5)
Gravel pits
pits to the southeast
southeast are in glacial outwash that fills
fills
aa preglacial bedrock
bedrock valley.
valley.
2.5
(66.5)
Rock exposures
exposures along the valley sides
sides are red and yellow
St. Peter Sandstone capped by Middle Ordovician
weathering St.
Platteville-Galena dolomite.
8
(61)
Verona, Wisconsin and
Verona,
and junction
junction with
with Wisconsin
Wisconsin 69.
69. The thin
thin
drift cover here was deposited near the margin of
Wood—
of the Woodfordian ice.
ice.
9
(60)
Moraine, the terminal moraine of Wisconsinan
Cross the Johnstown Moraine,
(Woodfordian) glaciation in
(Woodfordian)
in this
this area.
area.
*This road
road log is
is published
pUblished with permission
permission of
of Kendall/Hunt
Kendall/Hunt Publishing
Publishing Co.,
Co.,
Dubuque, Iowa and it should not
not be
be duplicated
duplicated by
by any means
means without
without written
Dubuque,
permission.
11 The University of WisconsIn—Milwaukee
Wisconsin-Milwaukee
Alverno College,
22 The
The University
University of
of Wisconsin-Madison
and Alverno
College, Milwaukee
Milwaukee
Wisconsin-Madison and
7
�Mileages
Mileages
10
10
(59)
(59)
Cross the
the Sugar River.
River. The
of the Sugar River,
The upper
upper course of
which flows
flows south and
which
and southeast to
to join the
the Rock River,
developed along
along the
developed
the western margin of the
the Woodfordian glacier.
glacier.
This broad,
broad, terraced
terraced valley once carried great quantities
This
quantities of
of
meltwater and outwash southward
southward from
from the
the wasting
wasting ice
ice front,
front,
which lay immediately east of
of here.
The Sugar River defines the
the edge of
of the
the Driftiess
Driftless Area
Area here.
here.
The outer edge
edge of
of the
the Woodfordian
Woodfordian terminal
terminal moraine
moraine forms
forms the
the
The
partially wooded
wooded ridge
ridge on the east side of the
partially
the valley. The
deposits between the
Sugar River
River and
and the
the terminal
terminal moraine
moraine
deposits
the Sugar
probably include
include aa thin strip of Illinolan
probably
Illinoian glacial deposits.
deposits.
River, the
the route
route gradually
gradually ascends
ascends toward
toward aa
From the
the Sugar River,
ridge
crest which marks
marks the
the edge
edge of
of the
the Middle
Middle Ordovician
Ordovician
ridge crest
Platteville-Galena upland
Platteville-Galena
upland surface.
surface.
15
(54)
Junction County
County P.
P. Friable St.
St. Peter Sandstone is
is quarried
quarried
just north of
of here
here at
at Kievenville.
Klevenville. A thin layer of overlying
Middle
Middle Ordovician Platteville
Platteville Dolomite
Dolomite is
is stripped
stripped away,
away, and
and
the poorly
poorly consolidated
consolidated quartz sandstone below is
the
is mined for
for
foundry and
and refractory
refractory sand.
sand.
18
(51)
Mt.
Mt. Horeb, Wisconsin
Wisconsin occupies
occupies aa ridge
ridge top.
top. Originally settled
settled
Swiss farmers,
farmers, its
its heritage
heritage is
recalled by
by
by Norwegian and
and Swiss
is recalled
commercial establishments along
along the
the route.
route.
20.5
(48.5)
(48.5)
Junction with
with County
County JG.
JG. This steep,
steep, wooded road
road descends
descends one
one
mile north to
to Little Norway,
Norway, a
a restored Norwegian pioneer
homestead. The side
ttV?i
side road
road follows
follows a anarrow,
narrow,deeply—cut,
deeply-cut,
"V"shaped valley that is
is typical
typical of
of the
the upper
upper reaches
reaches of
of drainages
drainages
in the Driftless Area. The Tyrol Ski Basin, 22 miles
miles north
north of
of
Little Norway,
Norway, takes
takes advantage
advantage of
of these
these steep
steep valley
valley walls.
walls.
20.8
(48.2)
Entrance to
to Cave
Cave of
of the
the Mounds
Mounds is
is north
north of
of the
the highway,
highway, off
off
County
County F.
F. This cave is developed in the
the Middle Ordovician
Galena
had no
no natural entrance,
Galena Dolomite.
Dolomite. It
It had
entrance, and was accidently
accidently
discovered by
by quarry
quarry blasting
blasting in
in 1939.
1939. The cave,
cave, which
which features
features
aa variety
variety of
of intricate
intricate dripstone
dripstone deposits,
deposits, is
is open
open for
for tours
tours
during the
the summer
summer months
months (Fig.
(Fig. 5).
5). Brigham
Brigham County
County Park,
Park, on
on
East Blue Mound, is
is aa short
short distance
distance beyond
beyond the
the cave
cave on
on County
County F.
F.
21
21
(48)
(48)
The wayside park
park north
north of
of the
the highway
highway is
is developed
developed in
in an
an old
old
quarry
quarry in
in the
the Galena
Galena Formation.
Formation.
88
�Figure 5.
5.
Dripping
Dripping stalactites
stalactites hang
hang from
from the
the ceiling
ceiling of
of this
this
narrow passageway in
in Cave of the
the Mounds near
near Blue
Blue
Mounds, Wisconsin. Photo courtesy of Cave of
of the
the
Mounds.
Mileages
22.7
(46.3)
village of
Mounds, nestled beneath
Village
of Blue Mounds,
beneath the
the west
west and
and east
east
summits of
of the Blue Mounds (Fig.
summits
(Fig. 6).
6).
The summits
summits of East and West Blue Mounds are
The
are about
about 1.6
1.6 miles
miles
apart (Fig.
(Fig. 6).
6). The East Mound,
Mound, site of Brigham
Brigham County
County Park,
Park,
has aa broad flat
has
flat top
top developed on the
the Upper
Upper Ordovician
Ordovician
led Silurian
Silurian
Maquoketa Shale. However a
a few blocks
blocks of
of silicif
silicified
9
�Mileages
dolomite are
are found
found on the crest and flanks.
dolomite
flanks. The
The elevation of
the West
West Mound
Mound is
the
is 1716 feet,
feet, some 230 feet higher
higher than
than its
its
neighbor to the
east.
This mound has a
the
This
a smaller,
smaller, more rounded
rounded
led Silurian
Silurian
summit area,
area, and it
it is
is capped
capped by
by 85
85 feet
feet of
of silicif
silicified
dolomite. Thus,
Thus, West Mound is
is an outlier of
of the
the Silurian
escarpment, which has
has retreated about 50 miles to
escarpment,
to the
the southwest
southwest
as aa result of downdip
as
downdip erosion.
erosion.
Iowa Co.
Dane Co.
EAST
WEST
W MOUND
Silurian dolomite
O~I--------il
o
1.6
Mil.
Km
E. MOUND
U. Ord. Maquoketa Shale
M. Ord. Plalteville-Goleno dolomites
Figure
Figure 6.
6.
section through
through Blue
Blue Mounds
Mounds from
from west
west to
to east.
east.
Cross section
Elevation in
in feet is indicated along the
the right
margin. After Black, 1970.
1970.
Blue Mounds State Park,
Park, on West Blue Mound,
Mound, is
is reached by a
well—marked
well-marked road
road that
that goes
goes north
north through
through the
the village.
village. At the
the
mound top,
top, observation towers
towers are located
located at both the
the east and
and
west ends
ends of
of an
an old
old racetrack.
racetrack. The towers
towers provide an opporthe Driftless
tunity to view the
Driftless Area
Area to
to the
the west,
west, the
the glaciated
Madison, and
and the
the Precambrian Baraboo
Baraboo Range
Range
countryside toward
toward Madison,
to the north.
Indians
reportedly used
used the
mound top as
as an
an
north.
Indians reportedly
the mound
led cap rock into
observation post,
post, and
and fashioned
fashioned the
the silicif
silicified
projectile points.
points. They attributed the blue haze,
haze, which often
veils these wooded mounds when viewed from below,
below, to the
the pipe
smoke of Wakanda, the
the Earth—maker.
Earth-maker.
The Upper Ordovician Maquoketa Shale,
Shale, which makes up East Mound
the Silurian on West Mound,
forms the
the upper part
and underlies the
Mound, forms
of the
the gently sloping
sloping sides
sides of
of these
these wooded
wooded mounds
mounds (Fig.
(Fig. 6).
6).
The Platteville—Galena
Platteville-Galena formations
formations are the basal foundation for
both mounds,
mounds, which are perched
perched on the edge of the
the Middle
Ordoviclan
Ordovician cuesta
cuesta called
called Military
Military Ridge.
Ridge. To the north,
north, steep
drainages flow toward
toward the
the Wisconsin River valley,
valley, about 11.5
away. The headwaters of one of these north-flowing
miles away.
streams forms the separation
separation between
between the
the two
two mounds.
mounds.
22.9
22.9
(46.1)
(46.1)
Dane/Iowa County
County line.
line. Enter Iowa
Iowa County in
in an
an area where
Dane/Iowa
roadcuts expose thin—bedded,
thin-bedded, nodular
nodular Middle
Middle Orcovician
Orcovician dolomite.
dolomite.
Several small quarries
quarries along the highway between here and
Barneveld also
also provide
provide exposures of
of the
the Middle Ordovician
Platteville—Galena
Platteville-Galena formations.
formations.
10
10
�Mileages
26
(43)
Barneveld, Wisconsin.
Wisconsin. The Blue Mounds, the
the most northeasterly
northeasterly
of
of the Silurian outliers,
outliers, are
are visible
visible to
to the
the east
east (Fig.
(Fig. 7).
7).
Figure 7.
Figure
7.
A
A view east
east to
to the
the gently—sloped,
gently-sloped, wooded
wooded Blue
Blue Mound,
Mound,
from a
a quarry developed in
in the
the Middle Ordovician
Ordovician
Galena Dolomite.
The route westward from Barneveld to
to Ridgeway
Ridgeway passes
passes numerous
numerous
roadcuts in the Middle Ordovician
Ordovician Platteville-Galena
Platteville-Galena formations
formations
as
as it traverses Military
Military Ridge.
Ridge.
31
31
(38)
Ridgeway, named for the
Town of Ridgeway,
the Middle Ordovician
Ordovician cuesta
cuesta of
of
Military Ridge,
Ridge, upon
upon which
which it
it is
is perched.
perched.
35
35
(34)
Wayside to
for
to north of the
the highway has a
a historical marker for
Military Road".
Road". This road was completed in 1835 to link
"Old Military
Fort Howard
Howard at
at Green
Green Bay
Bay to
to Fort
Fort Crawford
Crawford at
at Prairie
Prairie du
du Chien.
Chien.
In this
this area,
area, the
the route
route followed
followed the well-defined,
well-defined, broad,
In
treeless ridge crest at the
the northern edge
edge of
of the
the Middle
Middle Ordovician
Ordovician
Platteville-Galena cuesta.
Platteville-Galena
cuesta. Since this
this ridge forms the
the drainage
divide between the
the Wisconsin River to
to the
the north
north and
and the
the Platte,
Platte,
Galena, and Pecatonica rivers
Galena,
rivers to
to the
the south,
south, it
it is
is not
not dissected
dissected
by streams. This aided
aided road
road construction
construction by
by eliminating
eliminating the
the
need for bridges.
bridges.
Besides army traffic,
thousands of
of pioneers
pioneers passed
passed this
this way
way to
to
Besides
traffic, thousands
the booming
booming lead
lead mining area,
the
area, the early territorial
territorial capitol of
of
Wisconsin, and
and the
the thriving
thriving port
port cities
cities on
on the
the Mississippi
Mississippi River.
River.
This same route was utilized
utilized later
later by
by the
the Chicago
Chicago and
and NorthNorthwestern Railroad.
11
�Mileages
Mileages
39
39
(30)
(30)
Junction with
with U.S.
U.S. 18
18 and
and State
State 23.
23. U.S.
Junction
U.S. 18,
18, west
west from
from here,
here,
continues
continues along
along the
the route
route of
of the
the historic
historic army
army road
road along
along
Military Ridge.
Ridge.
Military
Governor
Park, located 3 miles north
north of
of this
this
Governor Dodge
Dodge State Park,
intersection
intersection along
along Wisconsin
Wisconsin 23,
23, embraces
embraces two
two lakes
lakes formed
formed by
by
impounding Mill
Mill Creek,
Creek, aa tributary to
impounding
to the
the Wisconsin River.
Bedrock exposures
exposures in
in the
the park
park include
include roadcuts
roadcuts through
through the
the
Bedrock
Platteville-Galena
Platteville—Galena upland
upland surface,
surface, and
and scenic,
scenic, natural
natural outcropoutcrop—
pings
pings of
of the
the underlying
underlying Middle
Middle Ordovician
Ordovician St.
St. Peter
Peter Sandstone
Sandstone
along the floor of the
the valleys.
valleys.
Turn south on U.S.
U.S. 151 into Dodgeville, Wisconsin. U.S.
Turn
U.s. 151,
from here
here to Platteville,
Platteville, generally follows an
from
an historic
historic cutoff
cutoff
from the
the Military
Military Road to the lead mines,
from
mines, and
and the
the river
river ports
ports
along the Mississippi.
395
39.5
(29.5)
(29.5)
Dodgeville, Wisconsin. The
The city was
was named
named for
for Henry Dodge,
Dodge, an
early lead miner and Indian
Indian fighter
fighter in
in this
this district.
district. Since
avid supporter of
of President Andrew
he was well-liked and an avid
Jackson, he
he was
was appointed
appointed as
as the
the first
first territorial
territorial governor
governor
Jackson,
of Wisconsin in
in 1836.
1836.
43
43
(26)
(26)
Silurian outliers
of Belmont
outliers of
Belmont Mound
Mound and
and Platte
Platte Mound are
are visible
to the
the southwest,
southwest, as
as the
the highway
highway crosses
crosses the
the rolling,
rolling, partiallypartiallyto
dissected, Middle Ordovician
dissected,
Ordovician upland
upland surface.
surface. Roadcuts provide
of Middle Ordovician dolomites
this part of
of the
exposures of
dolomites along this
route.
47
47
(22)
(22)
of the
commemorates the
The historical marker north of
the highway commemorates
early days of
of Mineral
Mineral Point.
Point.
48
48
(21)
(21)
Mineral Point,
Point, Wisconsin. This part of the
the zinc—lead
zinc-lead district
was settled
settled in
in the
the l820t5
1820's and 1830's by miners from other mining
regions in the U.S.,
U.S., and
and by
by Cornish
Cornish immigrants.
immigrants. A
A short
short side
side
trip into this historic town,
town, with
with its
its narrow,
narrow, steep
steep streets,
streets,
is interesting. Here,
Here, on Shake
Shake Rag
Rag Street,
Street, the
the Cornish
Cornish miners
miners
their small
small homes from local
local dolomite along the side
side of
of
built their
aa narrow
narrow valley
valley across
across from
from the
the mines.
mines. The street
street received
received
its name because the
the miners'
miners' wives waved
waved dish
dish rags
rags to
to call
call the
the
menfolk
menfolk home
home when
when dinner
dinner was
was ready.
ready. As aa carry—over
carry-over from
from these
these
days, local
local restaurants and bakeries still make pasties
pas ties (meat
(meat
days,
pies),
pies), the
the traditional,
traditional, hearty
hearty lunch
lunch of
of the
the Cornish
Cornish miner.
miner.
Part of Shake Rag Street contains a
a complex of
of restored Cornish
Cornish
cottages
cottages from
from the
the 1830's
1830's and
and 1840's,
1840's, that
that includes
includes Pendarvis
Pendarvis
House.
House. This
This site
site is
is operated
operated by
by the
the Wisconsin
Wisconsin Historical
Historical
Society
Society for
for the
the public.
public. The
The Mineral
Mineral Point
Point Historical
Historical Society
Society
has
has aa museum at
at Pine
Pine and
and Davis streets that contains excellent
mineral
mineral samples
samples from
from local
local mines.
mines.
49
49
(20)
(20)
The
The highway
highway south
south of
of Mineral
Mineral Point
Point follows
follows aa narrow
narrow ridge
ridge that
that
forms
forms aa drainage
drainage divide
divide overlooking
overlooking numerous,
numerous, small,
small, steep—sided
steep-sided
valleys
valleys on
on either
either side.
side.
12
12
�Mileages
Mileages
52
52
(17)
(17)
The
The wayside
wayside park
park north
north of
of the
the road
road provides
provides another
another view
view of
of
Platte and
and Belmont Mounds, as
as the
the route
route traverses
traverses the
the dissected
dissected
Middle
Middle Ordovician
Ordovician highland
highland surface.
surface.
54
54
(15)
(15)
Iowa/Lafayette
Iowa/Lafayette county
county line.
line. Enter
Enter Lafayette
Lafayette County.
County. Within
Within
one mile
mile the
the highway has
has crossed
crossed Mineral Point
Point Branch
Branch and
and the
the
upper
upper reaches
reaches of
of the
the Pecatonica
Pecatonica River.
River. The valleys
valleys formed
formed by
by
these
these drainages
drainages cut
cut through
through the
the Middle
Middle Ordovician
Ordovician PlattevillePlattevilleGalena formations into
into the
the underlying
underlying Middle
Middle Ordovician
Ordovician St.
St. Peter
Peter
Sandstone. The contact between
between these
these formations
formations is
is exposed
exposed west
west
Sandstone.
of the
the highway
highway near
near the
the county
county line.
line.
61
61
(8)
(8)
Belmont, Wisconsin.
Wisconsin.
Enter Belmont,
dolomite.
61.5
(7.5)
Junction
Junction with
with County
County GG in
in Belmont.
Belmont. A
A short
short side
side trip
trip along
along this
this
highway
highway provides
provides access
access to
to two
two interesting
interesting state
state parks.
parks. Three
Three
miles northwest
northwest on
on County
County GG (and
(and B)
B) is
is First
First Capitol
Capitol State
State Park,
Park,
the restored site of the
the first Wisconsin Territorial
Territorial Capitol
Capitol in
in
This apparently remote
1836.
remote location
location was
was in
in the
the booming
booming lead
lead
1836.
mining district,
district, and
and consequently
consequently at
at the
the population
population center
center of
of
this
this territory when Governor Henry Dodge called
called the
the Territorial
Territorial
Legislature to
to order.
order. They met here for 46
46 days in
in 1836
1836 to
to
Madison, then essentially
develop aa constitution. Eventually Madison,
uninhabited and undeveloped,
undeveloped, was selected
selected as
as the
the permanent
permanent
capitol.
Roadcuts
Roadcuts expose
expose Middle
Middle Ordovician
Ordovician
Less than aa mile
mile east
east of
of First
First Capitol
Capitol State
State Park
Park on
on County
County G
G
Less
Here,
a
scenic
parking
area
is
is Belmont Mound State
State Park.
Park. Here, a
parking area is
is
This is another Silurian
located on the
the south
south side
side of
of the
the mound.
mound. This
outlier, as evidenced by abandoned
outlier,
abandoned quarry
quarry exposures
exposures of
of thin—
thinbedded Lower Silurian
Silurian dolomite.
dolomite. An observation
observation tower
tower affords
affords
a
a panoramic view that includes
includes numerous
numerous mounds, and
and the
the distant
distant
edge of
of the Silurian escarpment to
to the
the south
south and
and southwest.
southwest.
Both the mounds and the
the escarpment are
are capped
capped with
with resistant
resistant
dolomite, and
and once
once were
were part
part of
of aa continuous
continuous bedrock
bedrock
Silurian dolomite,
surface that
that sloped
sloped gently to the southwest.
surface
southwest. There are several
old lead and zinc mines in
old
in this
this area.
area.
U.S. 151 turns west here.
U.S.
here.
62
(7)
Junction of Wisconsin 126
126 in
in Belmont.
Belmont.
66
(3)
Platte Mound,
Mound, north of
of the
highway, rises to an elevation
Platte
the highway,
elevation of
of
Locally, this
1430 feet.
feet.
Locally,
this wooded hill is
is called "M"
"M" Mound, because
because
of the
the letter
letter formed
formed of
of white
white painted stones that is
of
is maintained
annually by
by mining
mining engineering students from the University
annually
University of
of
This feature,
feature, and Little Platte Mound to
Wisconsin-Platteville.
to
Wisconsin—Platteville. This
the east,
east, are
are capped
capped by resistant,
the
resistant, cherty Lower Silurian
Silurian dolomite.
dolomite.
The nonresistant
nonresistant Upper Ordovician Maquoketa Shale underlies
The
underlies the
the
Silurian (cap rock),
rock), and forms
forms the gradual slopes that
Silurian
that rise
rise
These isolated
isolated
upward
upward from
from the
the Middle
Middle Ordovician Galena surface. These
hills are
are remnants
remnants (outliers)
(outliers) of
of an
an extensive
extensive Silurian upland
hills
The edge of
of this
surface, which
which eroded downdip to
surface,
to the
the southwest.
southwest. The
highland is
is low
low located
located in
in northwestern
northwestern Illinois
highland
Illinois and east—central
east-central
Iowa.
Iowa.
13
13
�Mileages
67
(2)
(2)
Lafayette/Grant county line.
line.
69
69
(0)
Enter Platteville and pass a
a large quarry developed in
in the
the
Middle Ordovician Galena
Galena Dolomite
Dolomite to
to the
the north of
of the
highway.
Middle
the highway.
Wisconsin 80
Junction U.S.
U.S. 151 with Wisconsin
80 and
and 81.
81.
Enter Grant County.
The University
University of
of Wisconsin-Platteville,
Wisconsin—Platteville, with its
The
its long history
of training
engineers and
and geologists,
geologists, is
located in this
of
training mining engineers
is located
this
The Mining
Mining Museum,
Museum, on
on Main
Main Street
Street in
in Platteville,
Platteville, provides
city. The
provides
an opportunity for
for tourists
tourists to
to tour
tour uiilerground
underground in the historic
Bevan lead mine,
mine, and to
to view relics from the
the early days of the
the
lead rush.
rush.
MADISON—PLATTEVILLE LOG
END OF U.S.
U.S. 151 MADISON-PLATTEVILLE
Geologic Road Log
for Grant County
3
l , W.A.
W.A. Broughton1'2,
M.G. Mudrey,
Broughton l ,2, A.V.
A.V. Heyl3,
Hey13, W.S.
W.S. West3
west
M.G.
Mudrey, Jr.
Jr.,
Continuation of Tuesday, May
May 99
Continuation
This leg of
of the
visits four
four localities
localities that
Middle
This
the trip visits
that illustrate the
the Middle
Ordovician succession of southwestern Wisconsin,
Wisconsin, and a
a tour of a vintage 1830
lead mine now operated as
as aa tourist
tourist attraction.
attraction. After the
the visit
visit to
to the
the mine,
mine,
we will return
return to
to Platteville
Platteville for
for the
the evening.
evening. Lodging and dinner this
this evening
follow the
the
Individual stop descriptions follow
are covered by
by the
the field
field trip
trip fee.
fee.
road logs.
logs.
Mileages
1
2
33
0.0
Governor
Governor Dodge
Dodge Motel.
Motel.
on U.S.
U.S. 151
and proceed
proceed right
right (southwest)
(southwest)
Leave motel and
6.1
Stop
Stop 11 —- Hoadley Hill.
Hill. Excellent exposure
exposure of
of St.
St. Peter,
Peter,
Platteville, and Decorah formations. Continue west on
Platteville,
on U.S.
U.S. 151.
151.
7.4
Right turn
turn onto
onto Church
Church Road
Road (gravel).
(gravel).
7.8
Bear left,
left, at
at YY in
in road.
road.
8.1
2 quarry in upper part
part of
of Platteville Formation
Stop 2 -- Section 2
stop
and Decorah Formation. Quimbys
Quimbys Mill
Mill Member of
of Decorah
Decorah Formation
is especially
especially well
well exposed.
exposed. Middle Ordovician
Ordovician fossil
fossil locality.
locality.
Turn around
around at
at top
top of
of hill,
hill, and
and return
return to
to U.S.
U.S. 151.
151. Continue
Continue
west on
on U.S.
U.S. 151.
151.
Wisconsin
Wisconsin Geological and
and Natural
Natural History
History Survey
Dept.
of
Geology,
IJW—Platteville
Dept. of Geology, UW-Platteville
U.S.
U.S. Geological Survey
Survey
14
14
�Mileages
11.7
11.
7
Enter Dickeyville.
Enter
12.0
12.0
Right turn (north)
Right
(north) onto U.S.
U.S. 61 and State 35.
35.
15.9
15.9
Cross Platte River.
Cross
River.
16.1
16.1
Base of
of Potosi
Potosi Hill
Hill roadcut.
roadcut.
16.6
Stop 3 Potosi Hill. Excellent exposure of upper part
stop
- Potosi
part of
of
Platteville Formation,
Shale,an.d
lower part
part of
of the
the
Formation, Decorah Shale,
axd lower
Galena Formation. Continue north on U.S.
U.S. 61 and
and State 35.
35.
18.5
Enter Tennyson.
19.1
Turn left
left (west)
(west) on
on County
County 0.
O.
19.7
Enter Potosi.
Potosi.
20.3
sign. Proceed straight ahead (south)
Stop sign.
(south) on State 133.
133.
20.5
Stop 4 -- St.
St. John's Mine.
Mine. Old lead
lead mine from the
the 1830's.
1830's.
Retrace route to
to intersection
intersection State
State 133
133 and
and County
County 0.
O.
21.9
Intersection with U.S.
U.S. 61
61 and
and State
State 35.
35.
County
County 0.
O.
27.6
Enter Cornelia.
31.5
Junction with
with U.S.
U.S. 151.
151.
34.7
Governor Dodge
Dodge Motel.
Motel.
Turn left
left (north)
(north) toward
toward Platteville.
Platteville.
END OF LOG
15
15
Continue east on
�Wednesday May 10, 1978
1978
Geologic Road
Road Log
Log
for
for Lafayette County
Hey13, W.S.
1 , W••
A Broug
h ton 1,2 , A.V.
Broughton1'2,
d rey, Jr.
M.G. Mu
Mudrey,
Jr.',
LA.
M.G.
A.V. Heyl3,
W.S. West3
West 3
of the trip visits the Shullsburg Mine of
of Eagle-Picher Industries,
This leg of
Industries,
the only
only operating
operating zinc-lead
zinc—lead mine
mine complex
complex in
in the
the Upper
Upper Mississippi
Mississippi Valley
Valley base
base
the
metal district. Participants are
are reminded
reminded to
to wear
wear appropriate
appropriate safety
safety equipment;
equipment;
including hard hat,
hat, light,
light, self—rescuer,
self-rescuer, safety
safety boots
boots and
and glasses.
glasses.
In
the afternoon
afternoon we
we will
will return
return to
to Platteville,
Platteville, Madison
Madison (where
private
In the
(where private
automobiles can be
be picked
picked up),
up), and
and Milwaukee.
Milwaukee. Historical and cultural
cultural stops
stops
may be made en
en route.
route. We plan
plan to
to arrive
arrive in
in Milwaukee
Milwaukee about
about 6:00
6:00 P.M.
P.M.
Morning,
Morning, May 10
10
Mileages
11
2
3
0.0
Leave Governor Dodge Motel and
and proceed
proceed left
left (east)
(east) on
on U.S.
U.S. 151.
151.
0.2
Turn right (south)
(south) on
on State
State 80
80 and
and State
State 81.
81.
6.8
Buildings and tailings pond of
of abandoned New Jersey Zinc
Company's Elmo Mine can
can be
be seen
seen in
in left
left distance.
distance.
9.4
Enter Cuba
Cuba City.
City.
9.7
Turn left
on County
County H (best route).
left (east)
(eas~on
10.9
Junction with County
County J.
J.
Turn right,
right, proceed
proceed south
south on
on County
County J.
J.
11.9
Vinegar Hill Acid Plant,
Plant, closed in 1948,
1948, was located south of
road.
13.6
Enter Benton.
14.0
14.0
Join State 11.
11. Turn left
left (east).
(east).
are along this
this road.
road.
21.8
Shullsburg.
Enter Shullsburg.
23.1
Right turn (south)
(south) on County 0.
o.
24.7
Tailings area of
of Eagle-Picher Industries,
Mine
Tailings
Industries, Inc.
Inc. Shullsburg Mine
on left.
left.
25.1
Left turn
turn (east)
(east) on
on County
County W.
W.
Numerous abnadoned
abnadoned mines
mines
Wisconsin Geological and Natural History Survey
Dept. of
of Geology,
Geology, TJW—Platteville
UW-Platteville
U.S. Geological Survey
U.S.
16
�Mileages
Mileages
25.8
Left
Left
Stop
Stop
hat,
hat,
mine
mine
29.8
About noon;
noon; return to
to Shullsburg
Shullsburg for
for box
box lunch.
lunch.
turn (north).
(north). Entry to Eagle-Picher property.
property.
Shullsburg Mine. You
55 -— Shullsburg
You are
are reminded
reminded to
to have
have on hard
light, self-rescuer,
self—rescuer, safety boots,
light,
boots, and
and glasses. Tour
complex with company geologists.
geologists.
Afternoon,
Afternoon, May
May 10
Scenic return to
Scenic
to Platteville. Historical sights en route via
via
W, include
County W,
include towns
towns of
of New
New Diggings, and
and Hazel
Hazel Green.
Green. Right
turn (north)
turn
(north) on State 80 and 11 to
to Cuba City and
and Platteville.
Platteville.
57.1
Enter Platteville. Return to Madison. Stop to pick up private
Bus will
will continue
continue to
Milwaukee, arriving
arriving about
about
automobiles. Bus
to Milwaukee,
6:00 P.M.
Geologic Road
Road Log for
Geologic
for Madison
Madison Beitline,
Beltline, 1—90,
1-90, and
and 1-94
1-94 from
from Madison,
Madison,
Wisconsin
Wisconsin (Junction
(Junction U.S.
U.S. 12
12 and
and 14
14 with
with U.S.
U.S. 18
18 and
and 151)
151) to
to Milwaukee,
Milwaukee,
Wisconsin (Junction
(Junction 1—94
1-94 with 1—43
1-43 and
and I_794)*.
1-794)*.
2
Rachel K.
K. Paull'
paull l and
and Richard A. Paull2
paul1
Milwaukee is
within the
Eastern
This route from Madison to Milwaukee
is entirely within
the Eastern
Ridges and
at right
right angles
angles to
to the
the
Ridges
and Lowlands physical province,
province, and
and it
it trends
trends at
general strike of the
the Paleozoic
Paleozoic formations.
formations. Consequently,
Consequently, the
the bedrock along
the route,
route, although largely obscured by Woodfordian
the
Woodfordian glacial
glacial deposits,
deposits, ranges
ranges
from Upper
Upper Cambrian
Cambrian formations
formations on
on the
the west
west to
to Silurian
Silurian dolomite
dolomite on
on the
the east.
east.
The glacial geology encountered
encountered along
along 1—94
1-94 is
is spectacular.
spectacular. As shown
shown in
in
Figure 8,
8, the
the interstate
interstate cuts most of these
these glacial features
features essentially at
right angles.
angles. From
From west to
to east,
east, these
these include
include well-developed
well-developed drumlin
drumlin fields,
fields,
outwash plains,
plains, the
the Kettle
Kettle Interlobate
Interlobate Moraine with numerous scenic lakes,
lakes, and
recessional moraines of
of the
the Lake
Lake Border
Border morainic
morainic system.
system. Other significant
significant
attractions along this
this route
route include:
include: the Lapham Peak
Peak overlook
overlook high
high in
in the
the
Kettle Moraine and the
the subcontinental
subcontinental divide
divide that
that separates
separates drainage
drainage destined
destined
for the
the North
North Atlantic
Atlantic via
via the
the St.
St. Lawrence
Lawrence from
from that
that which
which reaches
reaches the
the Gulf
Gulf
of Mexico
Mexico via
via the
the Mississippi.
Mississippi.
*This
*This road
road log
log is
is published
pUblished with
with permission
permission of
of Kendall/Hunt
Kendall/Hunt Publishing
Publishing Company,
Company,
Dubuque, Iowa,
means without written
Iowa, and
and it
it should
should not be duplicated by any means
permission.
permission.
1
1 University
University of
of Wisconsin—Madison
Wisconsin-Madison && Alverno
Alverno College,
College, Milwaukee
Milwaukee
22 University
of
Wisconsin-Milwaukee
University of Wisconsin-Milwaukee
17
17
�1/ f 1\ .........-
I
/I
; ' l c•• 3m.1
I
"I
I II
I II
,I
II
'pm. ~ GLACIAL LAKE DEPOSITS
I
,\ \
~----<16km ~
~VALDERAN DRIFT
I
i-T7@;--.---\fij.+:.w
1._......
I
I
I
II"
UE££E1!..S~
Whit_atr-
G>
~
I
WALWORTH
I
I
I
I
R.cine
r - -++·~4)H+.:f>{
I
i--- .....
I
I
(WOODFORDIAN)
IT] RECESSIONAL MORAINE
'i
~
L..nG_.....
Figure 8.
Figure
8.
::......
;:.
I
I I
1·...:·.. :·:1 LAKE BORDER MORAINE
rn
D
TERMINAL MORAINE
WOODFORDIAN DRIFT
[l] INTER LOBATE MORAINE
[Z[] DRUMLIN TRENDS
•
AL TONIAN DRIFT
KENOSHA
Glacial deposits
deposits of
Wisconsin, including
of southeast Wisconsin,
glacial lake
lake deposits, the
the Kettle
Kettle Interlobate
Interlobate Moraine,
Moraine,
drumlin patterns,
patterns, and
and the
the Lake
Lake Border
Border morainic
morainic system.
system.
The Altonian drift shown
shown in
in Rock
Rock and
and Walworth
Walworth counties,
counties,
Wisconsin
Wisconsin also
also includes
includes drift that
that is
is older than
than
Interstates 94,
43, and 90 are also
Wisconsinan.
Interstates
94, 43,
also
indicated. Generalized from numerous
numerous sources,
sources,
including Thwaites, 1956.
1956.
Mileages
Mileages
o
0
(83)
Intersection of U.S.
U.S. 12 and 14
14 with U.S.
U.S. 18
18 and
and 151
151 on
on the
the
southeast edge of
of Madison, Wisconsin.
Wisconsin. Turn east on the Madison
Beltline (U.S.
(U.S. 12,
12, 14,
14, 18,
18, and
and 151).
151). Note: This was the
the
starting point
point for
for the
the U.S.
U.S. 151
151 Madison
Madison to
to Platteville
Platteville roadguide
roadguide
starting
provided for Tuesday May 9,
9, 1978.
1978.
11
(82)
The wooded tracts on both sides of the highway are parts of the
1,240 acre University of Wisconsin Arboretum. Although primarily
aa research and study area,
area, hikers are
are permitted
permitted on
on 24
24 miles
miles of
of
extends north from here to
foot trails.
trails. This nature preserve extends
the south shore of
of Lake
Lake Wingra.
Wingra.
3
3
(80)
Intersection of
of U.S.
U.s. 12 and
and 18 with U.S.
Intersection
U.S. 14 and
and 151.
151.
east on U.S.
U.S. 12
12 and
and 18.
18.
4.5
(78.5)
Monona, north of the
Lake Monona,
the highway,
highway, is
is the
the second
second largest
largest of
of
Madison's four
four lakes.
lakes. These lakes are the result of Pleistocene
erosion and deposition along the
the Yahara
Yahara River
River drainage.
drainage.
5.5
(77.5)
wooded, irregular
ridge visible
visible to the
the south over
over the
the flat
flat
The wooded,
irregular ridge
part of
of the
Woodfordian Johnstown-Milton
outwash surface
surface is
is part
the Woodfordian
terminal moraine system.
terminal
6.2
(76.8)
Cross the
the Yahara River,
River, which
which connects
connects Madison's
Madison's four
four lakes.
lakes.
flows southeasterly to
to join the
the Rock River north
The Yahara flows
The relatively flat
flat land surface
of Janesville,
Janesville, Wisconsin. The
of
south of
of the
the highway
highway is
is probably
probably an
an outwash
outwash deposit
deposit (valley
south
(valley
train) formed
formed during the complex Pleistocene history
train)
history of
of the
the
Yahara River.
18
18
Continue
�—
Mileages
7.5
(75.5)
of U.S.
Junction of
U.S. 12,
12, 18,
18, and U.S.
U.S. 51.
12 and 18.
18.
east on
on U.S.
U.S.
Continue east
9.2
(73.8)
and 18 with 1—90.
Junction of
of U.s.
U.S. 12 and
1-90.
Turn north (left)
(left) on
on 1—90.
1-90.
12.
12.
(71)
Interstate 90
90 traverses
traverses rolling,
rolling, morainal countryside.
Interstate
13.7
(69.3)
Junction of 1—90
1-90 with
with 1—94.
1-94.
Turn east on 1—94
1-94 to
to Milwaukee.
Southeast of
of this
this intersection,
intersection, crushed
crushed stone
stone is
is produced
produced from
from
theMiddle Ordovician Platteville Formation. The underlying
St. Peter Sandstone is also exposed in
St.
in this
this quarry.
quarry.
18
(65)
(65)
Exit County NN to
to Sun
Sun Prairie
Prairie and
and Cottage
Cottage Grove.
Grove. Well-developed
drumlins, trending southwesterly, rise
drumlins,
rise above
above rolling
rolling ground
ground
moraine,
moraine, and
and are
are cut by
by the
the interstate.
interstate. The irregular,
irregular, hilly
ridge on the skyline to the
the south is
is the
the Woodfordian
Woodfordian MiltonMiltonJohnstown terminal moraine system of the
the Green Bay
Bay lobe.
lobe.
21
(62)
Area of poorly
poorly drained,
drained, peaty
peaty soil
soil in
in an
an interdrumlin
interdrumlin area.
area.
A commercial sod
sod and mint farm is
is north of the
the highway.
highway.
This region is drained by Koshkonong Creek, which crosses
This
crosses
This stream flows into
beneath the interstate at Baxter Road. This
into
Lake Koshkonong to the south,
Lake
south, after draining aa vast,
vast, marshy
marshy area.
area.
24
(59)
Exit Wisconsin 73
Southwest—trending
73 to
to Marshall and
and Deerfield.
Deerfield. Southwest-trending
drumlins form islands between swamps within the
drumlins
the rolling
rolling countryside.
countryside.
Just east of this junction,
junction, a
a large
large number
number of
of glacial
glacial erratics
erratics
are present. These are part of
of the
the boulder
boulder train
train derived
derived from
from
exposures of
exposures
of the Precambrian Waterloo Quartzite northeast
northeast of
of here.
here.
27
(56)
Goose Lake
Lake and the swamp to the
Goose
the south
south are
are remnants
remnants of
of aa much
much
larger shallow lake that once existed between
between drumlins
drumlins in
in this
this
area. Much of the
the land
land here
here has
has been
been ditched
ditched for
for drainage,
drainage, but
but
drumlins still rise as wooded islands
some drumlins
islands surrounded
surrounded by
by swamps.
swamps.
Fossil remains of
of aa mastodon
mastodon and
and aa giant
giant beaver
beaver dated
dated at
at 9,000
9,000
to 10,000 years
years B.P.
B.P. were found in
to
in shallow peat
peat deposits
deposits nearby.
nearby.
28
(55)
Dane/Jefferson county
county line.
line. Enter Jefferson
Jefferson County, and
and aa specspectacular array of drumlins. An excellent swarm
swarm occurs
occurs where
where
County 0 crosses
crosses the
the interstate.
interstate. The extensively tiered
tiered roadcut
roadcut
at the
at
the county line provides a
a transverse section
section through
through aa
drumlin.
Erratic boulders are common in
in the
the drift
drift in
in this
this area.
area.
33
(50)
Exit Wisconsin 89 to
to Lake
Lake Mills and
and Waterloo. The rough country
immediately west of
of here consists of pitted
pitted outwash
outwash between
between
patches of
of the Lake Mills recessional moraine system.
patches
system. Rock Lake,
Lake,
.25 mile
mile to
to the
the southwest,
southwest, occupies
occupies aa very large kettle.
.25
kettle. There
are also many small ice stagnation features in
are
in this
this area.
area. Most
of these are
are sandy deposits,
of
deposits, some of which lap
lap onto
onto the
the margins
margins
of drumlins.
of
19
�Mileages
Exposures of Precambrian quartzite exist north and east of
Waterloo, where they form low hills
waterloo,
hills and ledges which protrude
through thin
thin glacial
glacial drift
drift (Fig.
(Fig. 9).
9). Most of these
these outcrops
outcrops
are polished and striated by glaciation.
are
Figure 9.
9.
Exposures of glacially polished,
polished, gently eastwarddipping, Precambrian Waterloo
Waterloo Quartzite
Quartzite near
near
dipping,
Hubbleton, Wisconsin. Milwaukee Public Museum
Hubbleton,
Museum photo.
photo.
This quartzite
quartzite is
similar to
to that
exposed in the
the BarabooBarabooThis
is similar
that exposed
Devil's Lake
Lake area.
area. A basal conglomerate is
is present between
the quartzite
quartzite and
and the
the
the overlying Paleozoic sandstone.
sandstone. Small
Small
potholes
are scoured
scoured on
on some
some quartzite
quartzite surfaces,
surfaces, and
and bedding
bedding
potholes are
planes are occasionally ripple marked.
planes
The main outcroppings of
of Waterloo Quartzite are about a
a mile
east of Portland,
of Waterloo Creek and
Portland, and at the junction of
the Crawfish
Crawfish River.
River. These exposures occur
occur on
on the
the borders
borders of
of
connect4d series
series of
of marshes,
marshes, which
which mark
mark aa preglacial
preglacial valley
valley
aa connect4d
that was
was a
that
a tributary to
to the
the Rock
Rock River.
River.
35
(48)
Eastbound rest area in
in an
an area
area of
of rolling
rolling ground
ground moraine.
moraine.
37
(46)
1-94 crosses
crosses the
1-94
the Crawfish River,
River, a tributary
tributary to
to the
the Rock.
Rock.
miles south on the
west bank of
of this
Aztalan State Park is
is 1.5
1.5 miles
the west
this
river.
In
Late Woodland Indian
In addition to Late
Indian effigy mounds,
mounds,
this park
park contains
contains aa two-tiered
two-tiered pyramidal
pyramidal mound,
mound, and
and aa partly
partly
this
restored stockaded
led with
with the
the Middle
Middle Mississippi
stockaded village
village identif
identified
culture. When the
the site was first described in
in 1837,
1837, it
it was
named Aztalan in the hope
hope that the cultural
cultural remains
remains preserved
here were
were those
here
those of
of the Mexican Aztecs.
Aztecs. To reach the
the park,
park, use
use
the Lake
Lake Mills
Mills exit and then turn
the
turn east on
on County
County B.
B.
38
(45)
Westbound rest area,
area, in
in an area of ground moraine and low—lying
low-lying
drumlinoid hills.
hills.
20
�Mileages
Mileages
39
39
(44)
(44)
1-94 crosses
crosses the
the Rock
Rock River.
River. The
The Rock
Rock marks
marks aa general
general
1-94
vegetation
vegetation divide
divide between
between native
native hardwood
hardwood forests
forests to
to the
the east,
east,
and
and oak
oak savannas
savannas and
and prairies
prairies to
to the
the west.
west. Some
Some think
think the
the
river
river formed
formed a
a barrier to
to prairie
prairie fires,
fires, thus
thus preserving
preserving the
the
on the
the east.
east.
forests on
Jefferson,
Jefferson, 6.5
6.5 miles to
to the
the south at the
the junction
junction of
of the
the Crawfish
Crawfish
and
and Rock
Rock rivers,
rivers, experienced
experienced aa short—lived,
short-lived, geology-related,
geology-related,
land boom
boom about
about 1840.
1840. A
A federally-assisted
federally-assisted project
project was
was planned
planned
land
to
to construct a
a canal from Lake Michigan at Milwaukee to
to the
the
Rock River
River near
near Jefferson.
Jefferson. Some
Some construction
construction was
was actually
actually
Rock
accomplished
accomplished before
before the
the million—dollar
million-dollar project
project was
was abandoned.
abandoned.
Meanwhile,
Meanwhile, land
land values
values had
had sky—rocketed
sky-rocketed in
in Jefferson
Jefferson as
as the
the
prospect
prospect of
of a
a connection between the
the Mississippi River and
and
Lakes seemed
seemed imminent.
imminent. Land promoters
promoters arrived,
arrived, and
and
the Great Lakes
a
a steamboat made it
it up
up the
the Rock
Rock River
River from
from St.
St. Louis.
Louis. Tracts
Tracts
of
of swampland
swampland were bought
bought by local
local residents
residents and
and newcomers
newcomers at
at
inflated prices,
prices, in the hope that great profits would result
when· the
the canal
canal was
was completed.
completed. The land
land promoters
promoters left
left town
town
when
with well—laden
well-laden carpetbags,
carpetbags, before
before news
news of
of the
the abandonment
abandonment of
of
reached southern
southern Wisconsin.
Wisconsin.
the canal plans reached
40
40
(43)
(43)
Exit Wisconsin 26
26 to
to Watertown,
watertown, Johnson
Johnson Creek, and
and Jefferson,
Jefferson,
within the
the Jefferson
Jefferson County
County drumlin
drumlin field.
field. Where the
the interstate
interstate
within
drumlin, the roadcuts
cuts through a
a drumlin,
roadcuts have been carefully sodded
over to conceal the internal character of the sandy and clayey
till. However,
However, at the
the northwest
northwest corner
corner of
of this
this intersection,
intersection,
behind the service station and restaurant,
restaurant, an excavated drumlin
is
exposeq.
is exposed.
46
46
(37)
Irregular ground
ground moraine
moraine assumes
assumes symmetry
symmetry and
and order
order as
as the
Irregular
the
highway traverses
traverses aa classical
classical drumlin
drumlin field,
field, produced
produced by
by the
the
highway
Green Bay lobe
lobe of the
the Woodfordian
Woodfordian ice
ice advance
advance (Fig.
(Fig. 10).
10). These
drumlins trend
essentially north-south
north—south in
in this
area, but
but nearer
nearer
drumlins
trend essentially
this area,
to Madison
Madison the orientation was southwesterly.
to
southwesterly.
Poorly drained
drained areas
areas and
and tamarack
tamarack swamps
swamps flank
flank many
many of
of the
Poorly
the
drumlins
this area.
area.
drumlins in this
50
50
(33)
(33)
Wisconsin 135 exit.
52
52
(31)
(31)
Enter Waukesha
Waukesha County.
County. The
Jefferson/Waukesha county line.
Jefferson/Waukesha
line. Enter
drainage
in
this
rolling
countryside
is
poor,
and
farm fields
fields
drainage in this rolling countryside is poor, and farm
Numerous
tamarack
swamps
with
red
osier
must
must be ditched.
ditched. Numerous tamarack swamps with red osier
dogwood are
are lingering
lingering evidence
evidence of
of the
the boreal
boreal climate
climate of
of the
the
dogwood
Pleistocene.
Pleistocene.
21
21
�Figure 10.
10.
An intensively—farmed,
intensively-farmed, north—south
north-south trending drumlin
Sullivan, in Jefferson County, Wisconsin. In
near Sullivan,
this
this area,
area, these streamlined hills
hills are
are so
so numerous
numerous
that they are termed a
a drumlin swarm
swarm or
or field.
field.
Milwaukee Public
Public Museum
Museum photo.
photo.
Mileages
55
(28)
(28)
Wisconsin
Wisconsin 67
67 exit
exit to
to Oconomowoc
Oconomowoc and
and Dousman.
Dousman. The interstate
interstate
now traverses outwash and proglacial lake
lake sediments
sediments in
in an
an area
area
once occupied by the
the Green Bay lobe during the
the Woodfordian
Woodfordian ice
ice
advance. To the
the east,
east, the
the view
view of
of the
the Interlobate
Interlobate Moraine
Moraine
looming above the flat outwash surface
surface is
is impressive.
impressive. A
A few
overgrown kettles are adjacent to
to the
the highway on
on the
the south
south side.
side.
To the
the north,
north, rising
rising above
above the
the flat
flat outwash
outwash plain,
plain, is
is an
an inconincongruous
gruous landform that
that resembles the
the classic moulin
moulin kames
kames of
of the
the
northern
northern Kettle
Kettle Moraine.
Moraine. This is
is an
an artificially—created
artificially-created ski
ski
hill near Oconomowoc.
59
(24)
(24)
provides a
a side trip to
to view the
the Kettle
An exit on County CC provides
Kettle
Interlobate Moraine from the
the observation
observation tower
tower on
on Lapham
Lapham Peak
Peak
(Fig.
This tower
(Fig. 11).
11).
tower provides
provides an
an excellent
excellent overview
overview from
from the
the
highest vantage
vantage point
point in
in the
the southern
southern Kettle
Kettle Interlobate
Interlobate Moraine.
Moraine.
To the
the west
west is
i~ Genesee
Genesee Flat.
Flat. To the
the east is
is the
the glacial spill—
spillway described
described at
at Mile
Mile 61.
61. Several scenic
scenic glacial
glacial lakes
lakes are
are
also visible.
visible.
22
22
�Figure 11.
11.
Kettle Interlobate
A scenic overview of
of the southern Kettle
Interlobate
Moraine from the
the observation tower
tower on
on Lapham
Lapham Peak.
Peak.
Photo by Professor R.F. Black, University
of
University of
Connecticut.
To reach Lapham Peak,
To
Peak, go south on County CC (Kettle
(Kettle Moraine
Moraine
Scenic Drive)
Drive) about 1.8 miles to a crossroad.
Scenic
crossroad. Turn left (east)
(east)
onto Government Hill
Hill Road.
Road. Continue about 0.7 mile to
to a
a small
small
The tower
park that
that includes
includes the
the Lapham Peak observation tower.
park
tower. The
A marker at 1233
for state station WHAD is also located
for
located here. A
feet of
of elevation,
elevation, on a
feet
a glacial erratic boulder
boulder in
in the
the park,
park, is
is
dedicated to one of Wisconsin's earliest geologists
dedicated
geologists and
and
"Increase A.
A. Lapham,
Lapham, Eminent scientist and
naturalists:
and useful
naturalists: "Increase
citizen".
citizentt.
The route ahead crosses a
a region of pitted
pitted (kettled)
(kettled) outwash
outwash
Nagawicka
deposits, and
and many
many kettle
kettle lakes
dot the
deposits,
lakes dot
the landscape.
landscape. Nagawicka
Other
Lake, immediately
immediately north of
of the
highway, is such a
Lake,
the highway,
a lake.
lake. Other
examples are
are Upper
Upper and
and Lower Nemahbin lakes,
examples
lakes, which sandwich the
the
23
23
�Mileages
interstate about 1 mile west
west of
of here.
here. The
The ice
ice blocks
blocks which
formed these
lake basins
basins were
were derived
derived from
from the
formed
these lake
the Green Bay lobe
lobe
along the
the western
western edge of
of the Interlobate Moraine.
along
60
(23)
The interstate approaches the
The
the crest
crest of
of the
the Interlobate
Interlobate Moraine.
Moraine.
A small ski area south of the highway utilizes part of this
this
slope. From the crest of this
this ridge,
ridge, the radio tower
tower and
observation tower on Lapham Peak
Peak are
are visible
visible south
south of
of the
the highway.
highway.
The Kettle
Kettle Interlobate
Moraine, whi.ch
which trends
trends northeasterly
northeasterly across
across
The
Interlobate Moraine,
miles, from Walworth to
Wisconsin for about 130 miles,
to Kewaunee counties
is the premier glacial feature in
is
in Wisconsin.
It
It is
is probable
that the
the resistant Silurian
that
the position
Silurian dolomite
dolomite influenced
influenced the
of the
deposits in
in this
area, by
by retarding
retarding the
of
the interlobate
interlobate deposits
this area,
the
spread of the
the Green
Green Bay
Bay lobe.
lobe.
Within this
this morainal complex,
complex, the country is rolling and rugged,
rugged,
with abundant
abundant knobs
knobs and
and kettles.
kettles. This feature formed during the
the
Woodfordian glacial advance by a
a juxtapositioning of the
the terminal
terminal
moraines of
of the
the Green
Green Bay
Bay and
and Lake
Lake Michigan
Michigan lobes.
lobes. Between
these
icy walls,
walls, complex
complex drainageways
drainageways developed,
developed, and
and meltwaters
meitwaters
these icy
reworked some of the morainal materials. The resultant
resultant deposits
deposits
are a
a mixture of
of sand,
sand, gravel,
gravel, boulders,
boulders, and
and clayey
clayey till.
till. Much
of the coarser material was derived from
of
from the
the Silurian
Silurian dolomite,
dolomite,
but igneous
and metamorphic
metamorphic rock
rock types
from far
far to
to the
the north
but
igneous and
types from
are also present.
present.
61
(22)
Wisconsin 83
Wisconsin
83 exit.
exit. This'highway
This/highway follows
follows low ground along an
agandoned drainage
drainage channel
channel which
which carried
carried the
the last
last meltwater
meltwater
agandoned
that
drained southward
southward through
through this
this part
part of
of the
the Kettle
Kettle Inter—
that drained
Interlobate Moraine. Water drained
drained down
down this
this .25
.25 mile
mile wide
wide valley
valley
until it
reached Wales,
Wales, about
about 33 miles
miles to
to the
the south,
south, where
where it
until
it reached
cut through the Interlobate
Interlobate Moraine to
to flow
flow west.
west. Gravel
flank this
this drainage,
drainage, and
and aa remnant
remnant of
of aa high
outwash terraces
terraces flank
terrace is
is visible on the
the east side
side of
of this
this valley.
valley.
62
62
(21)
Pewaukee Lake
Lake lies
lies to
to the
the north.
north. The church at Holy Hill,
Hill, a
kame
high on
on the
the Interlobate
Interlobate Moraine,
Moraine, is
is also
also visible
visible
kame perched
perched high
to the north on aa clear
clear day.
day. Pewaukee Lake occupies a
a pre—
preglacial river valley which was scoured into the Upper Ordovician
Maquoketa Shale.
Shale. This ancient valley was
Maquoketa
was blocked by morainal
debris deposited along its eastern margins by the
the Lake Michigan
lobe during the Woodfordian ice
ice advance.
advance.
63
63
(20)
Ground moraine deposits
deposits in
in this
this area
area are
are thin.
thin. North of the
the
highway on the
west edge
edge of
of the
golf course,
course, there
the west
the Tumblebrook golf
there
is
is a
a small quarry
quarry in
in Silurian
Silurian dolomite.
dolomite. Glacial striae
striae on
on bedbedrock in this area indicate
indicate that
that ice
ice movement
movement was
was west—southwest.
west-southwest.
South of the
the
Valley), and
and
character of
road,
names of
of aa subdivision (Pebble
road, the
the names
a farm (Stoney
(Stoney Hill),
Hill), bear testimony
testimony to
to the
the
the
morainal
material.
the
24
�Mileages
65
(18)
Exit County GG to
to Pewaukee.
Pewaukee. A
A drumlin field lies
lies south of the
the
highway for the
the next
next several
several miles.
miles. These east-west trending
trending
drumlins
abundant
drumlins are composed of
of sandy clay till
till that
that contains
contains abundant
boulders.
68
(15)
Exit County
County F.
F. West of
of this
this intersection,
intersection, the
the route
route crossed
the Pewaukee River,
River, which is
the
is tributary
tributary to
to the
the Fox. This valley
valley
is paralleled by outwash terraces,
is
terraces, which are
are commercial
commercial sources
sources
of sand
sand and
and gravel
gravel in
in this
this area.
area.
69
(14)
Exit Wisconsin 164
164 to
to Sussex
Sussex and
and Waukesha.
Waukesha. East—west
East-west trending
trending
drumlins are north and
and south
south of
of the
the highway.
highway.
Dunbar, while visiting Waukesha in 1869,
Colonel Dunbar,
1869, drank from
from
some of
of the springs which issue
some
issue from the
the glacial
glacial drift
drift in
in this
this
area with high amounts of dissolved calcium
area
calcium magnesium
magnesium bicarbonate.
bicarbonate.
Upon deciding that the local
Upon
local mineral waters had
had eliminated
eliminated his
his
!tincurable ailments",
ailments", he
he began
began to
to advertise
advertise his
his cure
cure nationwide,
nationwide,
"incurable
and Waukesha
Waukesha soon became a
and
a fashionable health
health spa.
spa. Although
this
fad waned after about 30
this fad
30 years,
years, bottled
bottled spring
spring water
water is
is
still a Waukesha product.
product.
Waukesha is
is located
located on
on the
the Fox
Fox River.
River. Outwash terraces
terraces along
along
this
this river are important commercial sources
sources for
for sand
sand and
and gravel.
gravel.
Since the glacial drift
drift is quite thin in this
this region,
region, Silurian
dolomite is extensively quarried along the
the valley oC
of the
the Fox
from the
from
the Waukesha area northward to
to Sussex,
Sussex, Lannon,
Lannon, and
and
Menomonee Falls.
Falls.
71
(12)
Road) to Waukesha and Wisconsin State
Exit U.S.
U.S. 18 (Blue
(Blue Mound Road)
Patrol headquarters.
headquarters.
74
(9)
Moorland Road.
Road. The flat terrain here is
is poorly
poorly drained,
drained,
Exit Moorland
clay—rich ground moraine. Ditching and
clay-rich
and channelization
channelization were
required for
for the extensive development of
required
of the
the land
land north
north of
of
the highway. The golf course to
to the
the south
south represents
represents aa more
more
intelligent land
land use.
use. A
A few
few isolated
isolated patches
patches of
of moraine,
moraine, and
and
east—west trending drumlins rise
several east-west
rise above
above the
the generally
generally
swampy ground.
The route ahead
ahead descends
descends aa prominent
prominent ridge,
ridge, which
which is
is part
part of
of
the Woodfordian
Woodfordian Lake Border recessional
the
recessional moraine system.
system. Sunny
Slope Road traverses this
forms the drainage
drainage divide
divide
this crest,
crest, which forms
between Lake Michigan
Michigan and
and the
the drainage
drainage basin
basin of
of the
the Fox
Fox River.
River.
The Fox flows southward
southward parallel
parallel to
to the
the Woodfordian
Woodfordian moraines
moraines
to
to reach the Illinois River,
River, and
and ultimately
ultimately the
the Gulf
Gulf of
of Mexico
Mexico
via the Mississippi.
76
(7)
Milwaukee/Waukesha county
county line.
line.
78
(5)
Exit 1—894
45 north to
1-894 (U.S.
(U.S. 45)
45) south to Chicago and
and U.S.
U.S. 45
du Lac.
Lac. The Milwaukee County Zoo
Zoo is
is northwest
northwest of
of this
this
Fond du
intersection.
25
Enter Milwaukee County.
County.
�Mileages
79
79
(4)
(4)
Wisconsin State
Exit
Exit Wisconsin
Wisconsin 181
181 (84th
(84th Street).
Street). The Wisconsin
State Fair
Fair
Park grounds
and an Olympic-size
Olympic—size outdoor
outdoor ice
are southeast
grounds and
ice rink are
of
of this
this junction.
junction. The interstate traverses
traverses Wisconsinan
(Woodfordian)
ground moraine and recessional moraines of
(Woodfordian) ground
of the
the
Border system.
system. The highway here is essentially parallel
Lake Border
to the
east—west direction of
of ice
movement, and
and consequently
the east-west
ice movement,
the inorainic
ridges trend north-south. About 100
morainic ridges
100 feet
feet of
of glacial
glacial
deposits,
deposits, primarily
primarily a boulder clay till,
till, overlie Silurian
dolomite in
in this
this area.
area.
81
(2)
U.S.
u.S. 41 exit (north
(north and
and south).
south). Milwaukee
Milwaukee County
County Stadium,
Stadium, home
home
of the
the Milwaukee Brewers and also the
the site of the
the Milwaukee
games of the
the Green Bay Packers,
Packers, is
is just
just west
west of
of this
this junction.
junction.
The large
large hill southwest of the
the stadium is a Silurian dolomite
of the
Veterans Administration
exposure on the
the grounds
grounds of
the U.S.
U.S. Veterans
Hospital.
82
(1)
Route parallels
parallels the
the industrial
industrial complex
complex along the
the east—west
east-west
Menomonee River
River valley.
valley. Three large,
large, glass
glass domes in
in
trending Menomonee
Mitchell Park
Park are
are visible
visible to
to the
the south.
south. One contains aa display
of vegetation native to a
desert environment,
environment, another features
features
a desert
tropical
houses local
flora and is often
tropical plants,
plants, and the last houses
local flora
used for special
special flower
flower shows.
shows.
83
(0)
Junction 1—94
1-94 with
with 1—43
1-43 (U.S.
(U.S. 141)
141) and
and 1—794.
1-794. The Milwaukee
Harbor is
is to
to the
the woutheast, toward
toward the
the high—rise
high-rise Harbor
Freeway bridge along
along the
the lakeshore.
lakeshore.
Three rivers
rivers merge at the Milwaukee Harbor,
Harbor, the Menomonee
west, the Milwaukee River comes
River flows
flows from the
the north and west,
from the
the north,
north, and the Kinnickinnic
Kinnickinnic River originates to the
west and
and south.
south.
Milwaukee grew from three settlements that were originally
separated by these
these rivers.
rivers. Walker's Point,
Point, east
east of
of the
the
Kinnickinnic River,
River, is now dominated by the towering
towering clock of
the Allen Bradley Company.
Company. The Milwaukee River flowed between
Kilbourntown on the west and Juneautown
Juneautown to
to the
the east.
east.
The high smokestack to the
the east is part of
of the Jones Island
Island
Here, sewage sludge is dried and
Sewage Plant.
Plant. Here,
and
Metropolitan Sewage
Milorganite, aa commercial
converted to Milorganite,
commercial fertilizer.
fertilizer.
Jones Island,
Jones
Island, an artificially breached
breached peninsula,
peninsula, also
also contains
contains
aa tanker pier,
pier, cargo terminals
terminals and
and aa heavylift
heavylift wharf,
wharf, and
and is
is
headquarters for the
the Port of
of Milwaukee. Milwaukee's inner
harbor was
was developed
developed by
by an enlargement
enlargement of
of the
lower Kinnickinnic
Kinnickinnic
the lower
River, and it serves
serves as
as the
and wintering
wintering area for
for part
River,
the service
service and
part
of U.S.
U.S. Steel's
Steel's iron ore carrier fleet.
of
fleet.
END OF LOG
through downtown Milwaukee to the Pfister
Proceed through
Pfister Hotel;
Hotel; headheadquarters for
for the
the 24th
24th annual
annual meeting
meeting of
of the
the Institute
Institute on
on Lake
Lake
quarters
Superior Geology.
We hope you enjoy
enjoy your
your stay
stay in
in Milwaukee!
Milwaukee!
26
�—
GX)LOGICAL
GIDLOGICAL STOP
SIDP DESCRIPTIONS
DESCRIPTIONS
Page
Stop
Stop
1I —-
Hoadley Hill
Hill
Hoadley
28
28
Upper
Upper part
part of
of the
the St.
St. Peter
Peter Sandstone,
Sandstone, the
the Glenwood
Glenwood
Formation,
Formation, aa complete
complete section
section of
of the
the Platteville
Platteville
Formation,
Formation, and the
the lower
lower part
part of the
the Decorah Formation
Stop 22 —- Section
Section 22 Quarry
Quarry
Stop
32
32
QUimby's Mill
Mill (upper
(upper part
part of
of the
the Platteville
Platteville
Quimby's
Formation)
Formation)
Stop 33 —- Potosi.
Potosi Hill
Hill
Stop
33
33
Upper part of the Platteville Formation,
Formation, the Decorah
Formation,
Formation, and the lower part of the Galena
Galena Formation
(Snake Cave)
Cave)
Stop 44 —- St. John Mine (Snake
Dunleith Member (cherty
(cherty
(non-cherty
upper
(non—cherty upper unit)
unit)
37
37
lower unit) and
and Wise Lake
Lake
lower
of the Galena Formation
Formation
27
27
�Title:
Title:
Hoadley Hill
Hill
Hoadley
Location:
Exposure
Exposure in
in roadcut
roadcut at
at north
north side
side of
of U.
U. S.
S. Highway
Highway 151
151 about
about 6.5
6.5
miles southwest of
of Platteville
Platteville in
in the
the NW!,
NW, NWI, Sec.
Sec. 12,
12, T.2N.,
T.2N., R.2W.,
R.2W., Grant
Grant
County (Dlckeyville
(Dickeyville 7.5—minute
7.5-minute topographic
topographic quadrangle,
quadrangle, 1972),
1972).
Author:
NWt,
M.
M. E.
E. Ostrom (modified
(modified from Agnew et. al.,
al., 1956)
1956)
section for
for the
the Platteville
Platteville Formation.
Formation.
Description: This is the reference section
exposed qere
lere are
are the
the upper
upper part
part of
of the
the St.
St. Peter
Peter Sandstone,
Sandstone, the
the
The strata4
strat~exposed
Formation, a
Formation, and the
Glenwood Formation,
a complete section of
of the Platteville Formation,
the
lower
et. al,,
al., (1956)
(1956)
lower part
part of
of the Decorah Formation. Description from Agnew et.
is:
ORDOVICIAN SYSTEM
Decorah Formation
Spechts Ferry Shale Member
Member (+1.0
(+1.0 feet)
feet)
62.9'
- 63.4'
62,9' —
0.5'+
Shale, bluish—green.
Shale,
bluish-green.
62.7' —
62.7'
- 62.9'
0.2'
Bentonite, white;
Bentonite,
white; weathers
weathers orange
orange brown.
brown.
62.7'
62.5' —
62.5'
- 62.7'
0.2'
Shale, yellowish-green
yellowish—green above
above to bluish-green below.
below.
Shale,
28
�62.4' —- 62.5'
62.5'
62.4'
0.1'
001'
Shale,
Shale, brown
brown and
and olive,
olive, soft.
soft.
Platteville
Platteville Formation
Formation (54.3
(54.3 feet)
feet)
Quimbys
Quimbys Mill
Mill Member
Member (0.3
(0.3 —- 0.5
0.5 feet)
feet)
62.0' —- 62.4'
62.4'
62.0'
0.4'+
0.4'±
Limestone,
Limestone,
conchoidal
conchoidal
dark—brown
dark-brown
parting
parting at
at
dark
dark purple,
purple, fine—crystalline,
fine-crystalline, dense,
dense,
fracture;
fracture; very
very wavy
wavy upper
upper surface;
surface; thin,
thin,
to
to black,
black, fossiliferous
fossiliferous platy
platy shale
shale
base.
base.
McGregor
McGregor Limestone
Limestone Member
Member (30.9
(30.9 feet)
feet)
61.1' —- 62.0'
62.0'
0.9'
0.9'
Limestone,
Limestone, light—gray,
light-gray, very fine
fine crystalline,
crystalline, very
very
dense,
dense, conchoidal fracture like
like "glass rock"
rock" above,
above,
fairly massive,
massive, very
very fossiliferous;
fossiliferous; wavy upper
upper
surface.
surface.
60.4' —- 61.1'
61. l'
60,4'
0.7'
0.7'
Limestone as next above
above but less
less dense, medium—
mediumbedded above to
to thinthin- bedded below, fossiliferous;
fossiliferous;
wavy upper surface.
surface.
58.8' —- 60.4'
1.6'
Dolomite, light
Dolomite,
light olive drab,
drab, fine
fine crystalline,
crystalline,
"sugary", argillaceous,
argillaceous, very
very thin—bedded;
thin-bedded; molular,
molular.
55.8' —- 58.8'
3.0'
Dolomite as above
above but thick—bedded;
thick-bedded; calcite
calcite near
near
middle.
55.2' —- 55.8'
55.2'
2.6'
Limestone, thin—bedded
Limestone,
thin-bedded yet stands massively as one
unit; light greenish
unit;
greenish gray
gray brown;
brown; weathers
weathers brown,
brown,
with a
a few argillaceous streaks;
streaks; sparingly fossiliferous,
ferous, but with fossils
fossils and
and fucoids
fucoids on
on top
top surface.
surface.
51.8' —
- 55.2'
55.2'
51.8'
3.4'
Limestone,
Limestone, thin—bedded
thin-bedded as above but the
the beds are
a~e
distinct; modular beds and shaly partings;
distinct;
partings; argillaceous is
is upper 0.3 feet,
ceous
feet, which
which is
is very
very fossiliferous,
fossiliferous.
48.2'
- 51.8'
51.8'
48,2' —
3.6'
3,6'
Limestone, light buff
ish gray,
gray, in
in medium
medium to
to thick
Limestone,
buffish
beds; in places
beds;
places gradational
gradational into
into above
above unit,
unit.
44.3'
- 48.2'
48.2'
44,3' —
3.9'
3,9'
Limestone, light
light greenish to
to bluish gray,
gray, in massive
Limestone,
beds but
but composed
composed of
of thin
thin beds
beds which are
are not sepabeds
rated; ample
ample shaly
shaly material
material in
in wavy
wavy bands;
bands; fairly
fairly
rated;
fossiliferous, argillaceous;
argillaceous; aa peculiar mottled
fossiliferous,
light gray
gray and
and darker
darker gray 0,1-foot
light
O.l-foot zone,
zone, 11 foot
foot
below top,
top.
40.3'
44,3'
40.3' -— 44.3'
4.0'
4,0'
Limestone, light
light gray,
gray, very
very fine
fine crystalline,
crystalline, very
very
Limestone,
dense, sublithographic,
sublithographic, in.
in extremely
extremely thin
thin and
and modumodudense,
lar beds
beds with
with thin
thin calcareous
calcareous shaly
shaly partings
partings which
which
lar
become thinner
thinner below;
below; the
the shale
shale beds
beds are
are light
light
become
grayish blue,mottled,
blue,mottled, very
very fossiliferous;
fossiliferous; weathers
weathers
grayish
slightly recessed.
recessed,
slightly
29
29
�36.7' —- 40.3'
40.3'
36.7'
3.6'
3.6'
Limestone,
Limestone, as
as above,
above, but
but beds
beds are
are not
not quite
quite as
as
thin;
thin; fossiliferous;
fossiliferous; poor
poor gastropod
gastropod zone
zone 1.7
1.7 feet
feet
above
above base;
base; shaly
shaly zone
zone at
at base,
base.
33.1' —- 36.7'
36.7'
33.1'
3.6'
3.6'
Limestone,
Limestone~ dolomite,
dolomite, light—gray,
light-gray, fine
fine crystalline,
crystalline,
very
very slightly
slightly argillaceous,
argillaceous, very
very fossiliferous,
fossiliferous,
medium—bedded;
medium-bedded; Indistinct
indistinct argillaceous
argillaceous partings,
partings,
not
not wavy;
wavy; calcite
calcite and
and limonite,
limonite, especially
especially In
in
basal
basal 0.6
0.6 feet.
feet.
Pecatonica
Pecatonica Dolomite
Dolomite Member
Member (21.5
(21.5 feet)
feet)
28.3' —- 33.1'
33.1'
28.3'
4.8'
4.8'
Dolomite,
Dolomite, light
light grayish
grayish brown,
brown, very
very coarse
coarse crystalcrystalline and vuggy,
vuggy, upper 2 feet a mixture of
of lithology
lithology
and a somewhat argillaceous fine crystalline "sugary"
"sugary"
laminated dolomite;
dolomite; a 1-foot
I-foot bed of very
very vuggy
vuggy
dolomite
dolomite from
from 1.8
1.8 to
to 2.8
2.8 feet
feet above
above base;
base; shaly
shaly
in lower part;
part; stylolitic partings 1 foot above
above
base.
base.
21.4' —- 28.3'
21.4'
6.9'
DolomIte,
gray, laminated,
laminated, somewhat argil—
Dolomite, mediuin
medium-gray,
argillaceous,
laceous, fine—crystalline
fine-crystalline "sugary",
"sugary", fossiliferous,
fossiliferous,
especially in lower 0.9 feet;
feet; medium—
medium- to
to thick—
thickbedded; shaly at top;
bedded;
top; weathers brownish in
in lower
lower
2.5 feet.
17.8' —- 21.4'
3.6'
Dolomite, medium
medium gray,
gray, laminated,
laminated, argillaceous;
argillaceous;
very fossiliferous partings.
partings.
16.4'
17.8'
16.4' —- 17.8'
1.4'
1.4'
Dolomite, light
light grayish
grayish brown,
brown, very
very coarse
coarse crystalcrystalline and
and vuggy;
vuggy; thin
thin brownish gritty dolomitic
line
and platy shaly parting at top.
and
top.
13.6'
16.4'
13.6' -— 16.4'
2.8'
2.8'
Dolomite, medium gray,
Dolomite,
gray, laminated,
laminated, somewhat argillaceous, fine crystalline.
laceous,
H.6'
13.6'
11,6' -— 13.6'
2.0'
2.0'
Dolomite, medium gray,
Dolomite,
gray, laminated,
laminated, argillaceous,
argillaceous,
silty and
and sandy
sandy with
with fine
fine to
to coarse
coarse quartz
quartz grains
grains
silty
similar to
to those
those of
of the
the St.
St. Peter
Peter Sandstone,
Sandstone, phossimilar
phate nodules
nodules abundant (especially
phate
(especially in
in two
two zones,
zones,
one at
at base,
base, the
the other 1 foot above
one
above base).
base).
Glenwood Formation (1.5
(1.5 feet)
feet)
11.2'
11.6'
11.2' -— 11.6'
0.4'
0.4'
Shale, sandy with rounded quartz grains,
Shale,
grains, khaki to
to
drab, soft;
drab,
soft; phosphate nodules.
H.O'
11.2'
11.0' -— 11.2'
0.2'
0.2'
Shale, sandy,
sandy, olive
olive to
to grayish
grayish brown;
brown; mottled
mottled
Shale,
yellowish brown,
brown, friable.
friable.
yellowish
10.4'
11,0'
10.4' -— H.O'
0.6'
0.6'
blocky,
Shale, sandy,
sandy, mediummedium— to dark—gray,
Shale,
dark-gray, olive,
olive, blocky,
very hard,
very
hard.
30
30
�10.1' —
10.1'
- 10.4'
0.3'
Shale, medium-gray,
medium-gray, blocky;
blocky, hard,
Shale,
hard, sandy;
sandy; streak
of carbonaceous material at
at top.
top.
St. Peter Sandstone Formation
St.
Formation (÷10,2
(+10.2 feet)
feet)
10.0' — 10.1'
10.0'
-
0.1'
Sandstone, red and white;
white; rounded;
Sandstone,
rounded; frosted,
frosted, coarse
to medium-grained.
medium—grained.
9,8'
9.8' —- 10.0'
0.2'
Sandstone, gray,
Sandstone,
gray, pinkish,
pinkish, very
very friable.
friable.
9.7'
9.7' —-
9.8'
0,1'
0.1'
Sandstone, brown,
Sandstone,
brown, iron—stained,
iron-stained, hard.
hard.
8.4' —
8.4'
9.7'
9.7'
1.3'
1.
3'
Sandstone, yellow to gray,
Sandstone,
gray, very friable,
friable, with irreirregular lower
lower surface.
surface.
8.3' —
8.3'
-
8.4'
8.4'
0,1'
0.1'
Sandstone, light—gray,
Sandstone,
light-gray, very
very friable.
friable.
8,1' —
8.1'
-
8,3'
8.3'
0.2'
Sandstone, yellow to
Sandstone,
to dark—brown,
dark-brown, laminated,
laminated, hard,
hard.
7.0'
7.0' —-
8.1'
8.1'
1.1'
1.1 '
Sandstone, gray and yellow;
Sandstone,
yellow; hard irregular lower
lower
surface.
-
7,0'
7.0'
7.0'+
Sandstone as above,
above, but
but medium—
medium- to
to fine-grained;
fine-grained;
spoils.
0.0'
0.0' —
EXPOSURE
BASE OF EXPOS
URE
Significance: This is the reference section
section for
for the
the Platteville
Platteville Formation.
Formation.
The contact relationships and lithologies of the St.
St. Peter,
Peter, Glenwood,
Glenwood, Platte—
Platteville,
and Decorah Formations can be examined.
yule, and
Note the lithology,
mineralogy, and structure of the St.
Formation,
lithology, mineralogy,
St. Peter Formation.
What direction did it
it come from? Does it contain evidence of life? How do
for its mineral homegeniety? What was the
you account for
the environment
environment of
of deposideposiit change toward
toward the
the top?
top? What is
is the
the significance
significance of
of no
no change?
change?
tion? Does it
of
of change? What is
is the
the relationship of
of the
the St. Peter
Peter to
to the
the Glenwood?
Glenwood? Note
the various beds
beds of
of the
the Glenwood,
Glenwood. What is
is their
their significance?
significance? If
If they could
for long distances
distances of
of several hundred miles,
miles, what would be the signibe traced for
ficance? What is
is the
the nature and
and significance
significance of
of the
the Glenwood/Platteville conconlithology, i.e.
i.e. phosphate nodule beds,
beds,
tact? Note the variable Platteville lithology,
fossil
etc. What is
is their
their significance?
significance? What would be
be the
the
fossil beds,
beds, sandy beds, etc.
significance if
if they could be
be traced several.hundred
several. hundred miles?
References: Dapples,
Dapples, 1955;
1955; Agnew et.
et. al.,
al., 1956;
1956; Templeton
Templeton and
and Willman, 1963;
1963;
Ostrom, 1964 and
Ostrom,
and 1970.
1970.
31
�Title:
Title:
Section 2 Quarry
Section
Location: Abandoned
Abandoned quarry on west side of gravel road
Location:
road about
about 0.7
0.7 miles
miles north
north
of
U.
S.
Highway
151
about
0.3
miles
west
of
Piddington
Cementary
in the
the SW!,
SW,
of U. S. Highway 151 about 0.3 miles west of Piddington Cementary in
SW,
SE,
Sec.
2,
T.
2
N.,
R.
2
W.,
Grant
County
(Dickeyville
7.5—minute
SW!, SE!, Sec. 2, T. 2 N., R. 2 W., Grant County (Dickeyville 7.S-minute
topographic quadrangle,
quadrangle, 1972). Map location
location on Hoadley Hill
Hill description.
topographic
description.
See Hoadley Hill
Hill description.
description. QUimby's
Quimby's Mill
Mill Member of Decorah
Description:
See
,Formation is
is well
well exposed. Excellent
Excellent Middle
Middle Ordovician
Ordovician fossil
fossil locality.
"Formation
locality.
32
32
�Title:
Title:
Potosi Hill
Hill
Potosi
at east
east side
side of
of U.
U. S.
S. Highway
Highway 61
61 in
inthe
theSW!,
SW, NW!,
NW, Sec.
Location:
Location: Roadcut
Roadcut at
Sec. 7,
7,
R.2W., Grant
Grant County.
County. (Potosi
(Potosi 7.5-minute topographic
topographic quadrangle,
quadrangle, 1972),
1972).
T.2N., R.2W,,
Author:
M. E.
E. Ostrom
Ostrom (modified
from Cline
dine et
M.
(modified from
et al,
aI, 1956,
1956, Kruse,
Kruse, 1970).
1970).
in
Description: The lower part of the section exposed here can be examined in
The major
major emphasis
emphasis here
here is
is focused
focused
closer detail at the
the Hoadley Hill
Hill Stop.
Stop. The
uppör part wh~ch
which includes
Ferry, Guttenberg,
Guttenberg, and Ion
on the
the upper
includes the Spechts Ferry,
Ion Members of
of the
bers
the Decorah Shale Formation and
and the
the lower part of the Galena Dolomite
The Quimbys
Quimbys Mill
Mill Member consists
consists of purplish gray-brown,
Formation. The
gray-brown, sublitho—
sublithographic, thick-bedded,
thick—bedded, conchoidally fractured
fractured limestone
graphic,
lilnestone with uneven upper surIt is
is called
called the
the "Glass
"Glass Rock"
Rock" locally
locally because
because
face
base. It
face and
and shale at its base.
when broken,
broken, and
and when broken pieces
pieces are
are shaken together,
when
together, it sounds like broken
glass.
The Quimbys
Quimbys Mill
Mill is
is overlain
overlain by
by the
the Spechts
Spechts Ferry
Ferry Member
Member which
which consists
consists
The
of fossiliferous,
fossiliferous, gray-brown
gray—brown limestone
limestone with
with green
green shale
shale interbeds.
interbeds. At this
of
this
Metabentonite
exposure two thin beds of "metabentonite" occur near its
its base,
base. Metabentonite
The metametais
of volcanic
volcanic ash
ash dust.
dust. The
is believed
believed to
to be
be the product of alteration of
bentonites are
are orange
orange to
to light
light reddish brown and about 2 inches thick.
bentonites
thick.
The
The Spechts
Spechts Ferry
Ferry is
is overlain
overlain by
by the
the Guttenberg
Guttenberg Limestone
Limestone Member
Member which
which
33
�consists of
of hard,
hard, finely
consists
fossiliferous, light
light brown,
brown,
finely crystalline,
crystalline, thin-bedded,
thin—bedded, fossiliferous,
limestone with
with brown
brown carbonaceous shale interbeds,
limestone
interbeds. The
The presence
presence of
of these
these
interbeds has
has led
led to
to the
the member
member being
being referred
referred to
to as
as the
the "Oil
"Oil Rock"
Rock" in
in the
interbeds
the
southwest Wisconsin
Wisconsin zinc-lead
zinc—lead mineral district,
southwest
district.
The Ion Dolomite
Dolomite Member overlies the
The
the Guttenberg.
Guttenberg. It
It is
is aa gray
gray to
to blue
dolomite, medium-crystalline,
medium—crystalline, and
and medium-to
medium—to thick-bedded
thick—bedded with
with green
dolomite,
green shale
shale
interbeds, It
It is
is locally called
interbeds.
called the
the "Bluet'.
"Blue".
The Galena Dolomite Formation overlies the
The
the Ion,
Ion. It
It is
is aa light
light buff
buff to
drab, cherty,
cherty, thick-bedded,
thick—bedded, vuggy
vuggy dolomite
dolomite with
with medium
medium to
drab,
grains.
to coarse
coarse sugary grains,
The basal
basal contact is gradational.
gradational. A zone of
of Prasopora insular
The
is Ulrich marks
insularis
marks
the top
top of
of the Ion Member in some areas.
the
areas. It
It is
is absent here.
here,
Good fossil hunting in
in the
the Spechts
Spechts Ferry
Ferry and
and Guttenberg
Guttenberg Members.
Members.
Near the north end of
of the roadcut there is
is a
a quarry in which can be seen
seen
an example of
is the main site of
of zinc and
of "pitch-and-flat"
"pitch—and—flat" structure which is
lead mineralization
mineralization in the district,
lead
district. Here
Here there
there is
is no mineralization.
mineralization,
Description of outcrop follows:
follows:
ORDOVICIAN SYSTEM
Galena Dolomite Formation
Cherty Unit
45.8' —
45.8'
- 65.8'
65.8'
20.0'
Dolomite, yellowish-buff,
yellowish-buff, medium—to
medium-to coarse—grained,
coarse-grained,
Dolomite,
vuggy,
chert in
in upper
upper 10',
10'.
vuggy, abundant white chert
Decorah
Decorah Formation
Formation (43,8
(43.8 feet)
feet)
Ion Dolomite Member
Member (19,5
(19.5 feet)
feet)
(Gray unit)
38
3' —- 45
8'
38.3'
45.8'
7,0'
7.0'
buff, thick-to
thick-to massive—bedded,
massive-bedded, vuggy,
vuggy,
Dolomite, buff,
green shale
shale partings throughout,
throughout, sparry
sparry calcite
calcite
present.
present.
33,8'
33.8' —- 38.3'
38.3'
5.0'
5.0'
Covered
Covered interval,
interval.
32,8'
32.8' —- 33.8'
33.8'
1.5'
Dolomite, buff,
buff, medium—grained,
medium-grained, medium—bedded,
medium-bedded,
with
with green
green shale
shale partings,
partings.
(Blue unit)
unit)
27.2'
27.2' —- 32.3'
32.3'
5.1'
5.1'
Dolomite, purplish
purplish gray,
gray, medium—grained,
medium-grained, slightly
slightly
Dolomite,
fossiliferous.
fossiliferous. Green
Green shale
shale present
present as
as partings,
partings,
and as
as a 05'
0.5' bed
bed 0.8'
0.8' below
below the
the top
top of
of the
the interinterand
val,
val, calcite
calcite present.
present.
26.3'
26.3' —- 27,2'
27.2'
0,9'
0.9'
Shale, green.
green.
Shale,
of
of interval,
interval.
0.3 green
green dolomitic
dolomitic shale
shale in
in middle
middle
0.3
Guttenberg
Guttenberg Limestone
Limestone Member
Member (15.3'
(15.3' feet)
feet)
34
34
�21.7'
21.7' —- 26.3'
4.6'
Limestone,
Limestone, purplish brown,
brown, fine-grained to
to sublithosublithographic,
graphic, fossiliferous,
fossiliferous, upper 1'
l' fine—to
fine-to medium—
mediumgrained,
grained, brown shale
shale present as
as partings,
partings, calcite
calcite
and limonite after iron
iron sulfide
sulfide present
present in
in small
small
amounts.
21.6' —- 21.7'
21.6'
0.1'
Metabentonite, brownish
brownish orange,
orange, crumbly,
crumbly, sticky
sticky
when
when wet.
wet.
12.0' -- 21.6'
9.6'
9.6'
Limestone,
Limestone, purplish brown,
brown, sublithographic,
sUblithographic, thinthinwavey—bedded,
wavey-bedded, fossiliferous,
fossiliferous, brown
brown carbonaceous
carbonaceous
shale present as thin
thin beds and partings,
partings, calcite
calcite
and limonite
limonite present.
present.
11.0'
- 12.0'
12.0'
11.0' —
1.0'
1.0'
Limestone,
Limestone, brown—gray,
brown-gray, Line—grained,
fine-grained, thick-bedded.
thick-bedded.
Spechts Ferry Shale
Shale Member
Member (9.0
(9.0 feet)
feet)
11.0'
10.2' —- 11.0'
0.8'
Shale,
Shale, orange—gray,
orange-gray, calcareous,
calcareous, and
and limestone,
limestone, tan—
tangray,
gray; fine—grained,
fine-grained, limestone
limestone 0.4'
0.4' to
to 0.7'
0.7' from
from
base of
of unit.
unit.
9.6' —- 10.2'
9.6'
0.6'
Limestone, gray,
gray, fine—grained,
fine-grained, thin-bedded.
thin-bedded.
6.4'
6.4' —- 9.6'
9.6'
3.2'
3.2'
Shale,
Shale, gray,
gray, green,
green, brown,
brown, fissle,
fissle, some
some beds
beds fossi—
fossiliferous, limestone
limestone present as thin lenses near
liferous,
middle of
of the
the interval.
interval.
5.6'
5.6' —- 6.4'
08'
0.8'
Limestone,
Limestone, tan,
tan, with iron
iron oxide mottlings, finefinegrained, thin—bedded.
thin-bedded.
3.9'
3.9' —- 5.6'
5.6'
1.7'
Shale, gray-green—brown.
gray-green-brown. Fissle, with
with thin
thin lenses
lenses
Shale,
of gray fine-grained
fine—grained limestone.
of
limestone.
3.2'
3.2' —- 3.9'
0.7'
Limestone,
Limestone, dark to light gray,
gray, thin-bedded,
thin-bedded, fossilfossilif erous.
iferous.
2.7' —- 3.2'
2.7'
3.2'
0.5'
Shale,
Shale, brown—green-orange—gray,
brown-green-orange-gray, brown carbonaceous
carbonaceous
shale parting at top,
top, metabentonite
metabentonite near
near middle.
middle.
2.2' —- 2.7'
2.2'
2.7'
0.5'
Limestone,
Limestone, purplish-brown,
purplish-brown, fine-grained,
fine-grained, thin—
thinbedded,
bedded, very fossiliferous,
fossiliferous, fucoids at
at base.
2.2'
2.0' —- 2.2'
2.0'
0.2'
Metabentonite, orange,
Metabentonite,
orange, sticky when wet,
wet, with
with brown
brown
shale partings.
Platteville Formation
Quimbys Mill Member
Member (1.2
(1.2 feet)
feet)
2.0'
0.8' —
0.8'
- 2.0'
1.2'
Limestone, purplish gray-brown,
gray-brown, sublithographic,
Limestone,
sUblithographic,
thick—bedded, conchoidal fracture,
fracture, irregular upper
thick-bedded,
surface, shale at
surface,
at base.
base.
35
�McGregor Limestone
Limestone Member
Member (0.8
(O8 feet)
feet)
0.' -- 0.8'
0.8'
0.'
0.8'
O8'
Limestone, purplish gray-brown,
medium—
Limestone,
gray-brown, fine—to
fine-to mediumgrained, thick-bedded.
grained,
thick-bedded.
Spechts Ferry and Metabentonite beds
beds are
Significance: The Spechts
are not present everywhere.
In addition,
addition, in
in the
the district
district mineralization
mineralization it
it quite
quite often
often occurs
occurs
In
where the
the Spechts
Spechts Ferry
Ferry is
is thickest0
thickest.
could one
one account
account for
for the
the local
absence of
of the
How could
local absence
the Spechts Ferry Member?
one account for
for the
the thickening of
of the
The metabentonite beds? How could one
Spechts Ferry Shale coincident
coincident with mineralization? for
Spechts
for the location and
mineralization
minerali'zation of "pitch—and—flat"
"pi tch-and-flat" structures?
References:
Cline et al,,
Wiliman, 1963;
al., 1956;
1956; Templeton and Willman,
1963; Kruse,
Kruse, 1970.
1970.
36
�Title:
Title:
St. John
John Mine
Mine (Snake
(Snake Cave)
Cave)
St.
Location: Opening
Opening is
is in
in valley
valley wall
wall on
on the
the north
north side
side of
of State
State Highway
Highway 133
133
Location:
about
about 0.2
0.2 miles
miles south
south of
of intersection
intersection of
of County
County Highway
Highway "0"
"0" and
and State
State
Highway
in Potosi
Potosi in
in the
the swi,
SW, NW, SW,
Highway 133
133 in
swi,Sec.
Sec.34,
34,T.T.3 3N.,
N., R.R. 2 2 E,,
E.,
Grant County
County (Potosi
(Potosi 7.5—minute
7.S-minute topographic
topographic quadrangle,
quadrangle, 1972),
1972).
Grant
NW!,
M. G.
G. Mudrey,
Mudrey, Jr.,
Jr., (Modified
St. John Mine brochure,
Author: M.
(Modified from St.
brochure, L.C.
L.C. Ihm,
Ibm,
owner,
1966).
owner, and
and Whitlow
Whitlow and West,
West, 1966).
This mine
mine is
is aa natural
natural cave
cave that
that was
was extensively exploited for
Description:
Description: This
By 1843,
1843, it
it had
had yielded
yielded 2S0,000
250,000 pounds of lead,
lead
1870. By
lead. The
lead prior to 1870,
Potosi sub-district
sub—district produced
produced 21,300
21,300 tons
tons of
of 80 percent lead from 1862 to
Potosi
to 1876,
1876.
The vein strikes
Galena
joints. The
Galena occurs
occurs in
in gash
gash veins
veins and
and openings
openings along minor joints,
N.
its length and
N. 6So
65° W.,
W., and
and is
is noted
noted for
for its
and continuity.
continuity.
Host rock
rock is
is Ordovician
Ordovician Galena Dolomite,
Dolomite, with Maquoketa Shale on the
Host
the
ridge
ridge to the west.
37
37
�The floor
floor of
of the
the cave
cave is
is in the Dunleith Member (cherty
The
(cherty lower
iower unit)
unit) of
of
the
Galena
Dolomite.
In most
most outcrops,
outcrops, it
it is
is aa pale-yellowish-brown
pale—yellowish-brown to
the Galena
In
light-olive—gray and
and grayish-orange finefine- to medium~grained
medium—grained vuggy
light-olive-gray
vuggy fossiliferous
fossiliferous
dolomite containing abundant chert as nodules or
or as
as nearly
nearly continuous
continuous layers.
layers.
Chert in the Dunleith Member is nodular and
and distributed parallel
parallel to
to the
the bedding.
bedding.
Near mineralized
mineralized zones
zones chert is
Near
is selectively mineralized and contains microscopic
microscopic
grains of
of disseminated
disseminated iron
iron sulfide
sulfide that
that color
color it
it bluish
bluish gray
gray and
and locally
locally very
very
grains
dark gray.
gray.
The top of the cherty unit is
is marked by
by two
two discontinuous
discontinuous layers
layers of
of chert
chert
odulea
separated
from
the
main
cherty
section
by
6—9
feet
of
non—cherty
odulesnseparated
section by 6-9 feet of non-cherty
dolomite.,
dolomite.
The roof of the cave is in
in the Wise Lake Member (non—cherty
(non-cherty upper
upper unit)
unit)
of
the
Galena
Dolomite.
The
strata
of
the
non-cherty
unit
are
pale—yellowish—
of
The
of
pale-yellowishbrown to yellowish—
yellowish- and grayish-orange fine—grained
fine-grained porous
porous fossiliferous
fossiliferous
dolomite.
The minerals
minerals of
of the
zinc and
and lead
lead deposits
deposits in
in the
the Potosi
Potosi quadrangle
quadrangle are
are
the zinc
mostly simple
suif
ides,
carbonates,
and
sulfates,
simple sulfides, carbonates,
sulfates. The primary sulfide
sulfide minerals
are sphalerite,
sphalerite, galena,
galena, pyrite,
pyrite, marcasite,
marcasite, chalcopyrite,
chalcopyrite, and
and digenite.
digenite. Galena
is fairly
fairly stable and persists
the others
others are
are commonly
is
persists above
above the
the water
water table.;
table.; the
altered.
These include smithsonite,
smithsonite, cerussite, limonite,
limonite, melanterite,
melanterite, malachite,
malachite,
azurite,
azurite, and erythrite,
erythrite.
Mine, originally a natural cave,
History: St.
St. John Mine,
cave, was first
first named
named LaSalle
LaSalle
Cave,
de La Salle,
Salle, an
an early
early French
French explorer
explorer in
in
Cave, after Robert Cavelier Sieur de
North America,
America, who traveled with his company on
on an
an expedition
expedition through
through the
the upper
upper
Mississippi River Valley
Valley in
in 1679
1679 and
and again
again in
in 1687
1687 after
after King
King Louis
Louis XIV
XIV names
names
him Viceroy of North
North America. LaSalle is
is the man who claimed and
and named
named"
Louisiana Province
Province for
for the
the French
French king.
king.
St. John Min~
Mine was worked by the
St.
the Indians
Indians many years
years before
before white
white pioneers
pioneers
arrived in the
the 1827
1827 "lead
"lead rush".
rush". Drifts of
of the
the old
old mine follow
follow the
the natural
natural
crevices filled with
with stalactites.
stalactites.
The foxes who used
used it
it for
for dens
dens are
are said
said to
to have
have uncovered
uncovered the
the rich
rich lead
lead
deposits near
near the
the entrance
entrance by
by digging
digging and
and running
running in
in and
and out
out the
the natural
natural cave
cave
crevice. The Indians mined galena for barter but
but it
it was left
left to
to the
the white
white
men to
to extensively develop
develop these
these diggings,
diggings.
The first white man
John Mine
man known
known to
to have
have worked
worked St.
St. ·John
Mine and
and who
who gave
gave it
it
the
the name it still bears was Willis St.
St. John,
John, who made aa small
small fortune
fortune from
from this
this
mine between
between 1828
1828 and
and 1870.
1870.
In the Upper Mississippi Valley,
valley, lead
lead seems
seems to
to have
have been
been discovered
discovered about
about
noted in
in 1700
1700 by
by LeSueur,
LeSueur, who
who
1692 by Nicholas
Nicholas Perrott.
Perrott. This metal was als,o
als.o noted
took lead out of a place which we believe from the
the description
description must
must have
have been
been
Snake Hollow,
Hollow, now
now Potosi,
Potosi, Wisconsin,
Wisconsin. In 1766 John Carver brought to
to St. Louis
Louis
aa 500 pound hunk of lead
lead he had received from barter
barter with
with the
the Indians
Indians who
who mined
mined
a
a cave on the eastern Mississippi bank somewhere
somewhere between
between the
the mouth
mouth of
of the
the Grant
Grant
and Platte
Platte Rivers.
Rivers. This 500 pound
pound piece of lead
lead may have
have been
been taken
taken from
from St.
St.
John Mine,
Mine, which
which points
points to
to the
the importance
importance St.
St. John
John Mine
Mine played
played in
in bringing
bringing
settlers to
to the
the lead
lead region.
region.
38
38
�With
With the
the arrival
arrival of
of permanent
permanent settlers
settlers in
in 1825,
1825, the
the Winnebago Peace Treaty
and
and "lead
"lead rush
rush of
of 1827",
1827", the
the convening
convening of
of the
the first
first Wisconsin
Wisconsin Territorial
Territorial
Legislature in
in 1836,
1836, Potosi
Potosi and
and its
its suburbs
suburbs (La
(La Fayette,
Fayette, Van
Van Buren,
Buren, Dutch
Dutch Hollow,
Hollow,
British Hollow,
Hollow, Buena
Buena Vista,
Vista, and
and Rockville)
Rockville) flourished.
flourished. Potosi
Potosi in
in 1838
1838 was
was
British
hoping
hoping to
to become
become the
the capital
capital of
of Wisconsin; first
first state
state capitol
capitol was
was Belmont,
Belmont,
but Madison
Madison won
won out.
out. The
The Mexican
Mexican War
War of
of 1847;
1847; the
the Gold
Gold Rush
Rush of
of '49
'49 and
and the
the
but
cholera
cholera epidemic
epidemic in
in 1854
1854 depleted
depleted its
its citizens
citizens for
for aa few
few years;
years; but
but by
by 1859
1859
when the
the Civil War broke
broke out,
out, production
production of
of lead,
lead, and
and with
with it
it the
the growth
growth of
of the
the
village of
of Potosi,
Potosi, was
was on
on an
an upswing.
upswing.
village
Well
Well over
over two—thirds
two-thirds of
of all
all lead
lead for the
the North was supplied during the
. Civil War by
by the
the Galena,
Galena, Benton,
Benton, New
New Diggings,
Diggings, Shullsburg,
Shullsburg, Mineral
Mineral Point
Point and
and
mines. The
The remainder
remainder was
was furnished
furnished by
by mining
mining towns
towns called
called Platteville,
Platteville,
Potosi mines.
Hardscrabble,
Hardscrabble, Yuba,
Yuba, and
and Meeker's Grove,
Grove, all
all in
in the
the southwestern
southwes~ern Wisconsin
Wisconsin
zinc-lead region.
region.
zinc—lead
W. S.,
References: Whitlow,
Whitlow, J.
J. W.,
W., and
and West,
west, W.
S., 1966,
1966, Geology of the Potosi
References:
quadrangle, Grant
Wisconsin, and Dubuque County,
Grant County,
Count~ Wisconsin,
County, Iowa:
Iowa: U.S. Geol.
Geo!.
Bull. 1123—I,
1123-1, p.
p. 533—571.
533-571.
Survey Bull,
Heyl,
Heyl, A.
A. V.,
V., Jr.,
Jr., Agnew,
Agnew, A.
A. F., Lyons,
Lyons, E.
E. J.,
J., and
and Behre,
Behre, C.
C. H.,
H., Jr.,
Jr.,
1959,
Zinc-Lead District: U.S.
1959, The
The Geology of
of the Upper Mississippi Valley Zinc—Lead
Geol. Survey
Survey Prof.
Prof. Paper
P~per 309,
309, 310
310 p.
p.
Geol.
Ibm, L.
undated, St.
Brochure, Potosi, Wisconsin.
Ihm,
L. C.,
C., undated,
St. John Mine Brochure,
It
N
I
Flowstone
ST.
MINE MAP
ST. JOHN
JOHN MINE
Grant County,
County, WI.
WI.
March,
March, 1967
By
By Norm
Norm Frater,
Frater, Mike
Mike Wopat,
Dome to Surface
and
Priscilla Wilson
Wilson
and Priscilla
Length,
Length, 1050
1050 ft.
ft.
o0
,
25
I
50
50
I
39
39
500-3J8T026-78
500-3J8T026-78
�
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LU~
UN
IVERSITY OF
UNIVERSITY
OFWWISCONSIN-EXTENSION
IS CO NS IN -E XT EN
SI ON
GE OL OG
IC AL AN
D NA
GEOLOGICAL
AND
NATURAL
HISTORY
SURVEY
TU RA L HI
ST
OR Y SU RV EY
M er ed ith E. Os
tro m I St
Meredith E. Ostrom,
State
and
Director
at e Geologist
Ge ol og ist an
d Di re ct or
PRECAMBRIAN INLIERS
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INliERS IN
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M AY9—14,
MAY
1978
9_ 14 ,1
97 8
FI
ELD TR
IP
FIELD
TRIP
GU
ID
E
BO
OK
GUIDE BOOK
NU
M BE R 22
NUMBER
19
78
1978
�Field Trip
Trip Guide
Guide Book
Book
Number
Number 22
University of Wisconsin-Extension
Wisconsin—Extension
GEOLOGICAL
GEOLOGICAL AND
AND NATURAL
NATURAL HISTORY
HISTORY SURVEY
SURVEY
Meredith E. Ostrom,
Ostrom, State Geologist
Geologist and
and Director
Director
PRECAMBRIAN
PRECAMBRIAN INLIERS
INLIERS IN
IN SOUTH-CENTRAL
SOUTH-CENTRAL WISCONSIN
WISCONSIN
(companion volume
volume to Geoscience Wisconsin
Wisconsin Volume
Volume 2)
2)
With
With contributions
contributions by
by
Rachel K.
A. Paull,
K. Paull,
Paull, Richard A.
Paull, and Eugene I.
I. Smith
Edited by
by
Eugene I.
I. Smith,
Smith, University of Wisconsin-Parkside
of of
Wisconsin-Milwaukee
A. Paull,
Paull,University
University
Wisconsin-Milwaukee
Richard A.
G. Mudrey,
Mudrey, Jr.,
Jr., Geological and Natural History Survey
M. G.
for
Prepared for
Twenty—Fourth
Twenty-Fourth Annual Meeting
INSTITUTE ON LAKE SUPERIOR
SUPERIOR GEOLOGY
GEOLOGY
University of Wisconsin, Milwaukee
Milwaukee
Milwaukee,
Milwaukee, Wisconsin
May 9—14,
9-14:, 1978
A. Paull,
Paull, Chairman,
Chairman, Field Trip Committee
Richard A.
University of Wisconsin—Milwaukee
Wisconsin-Milwaukee
Available from the Wisconsin Geological and Natural History Survey,
Survey,
of Wisconsin—Extension,
1815 University
University Avenue,
University of
Wisconsin-Extension, 1815
Avenue, Madison,
Madison,
Wisconsin 53706
1978
�CONTE
NrS
CONTENTS
Page
Page
INTRODUCTION by Eugene I.
I. Smith
Smith. • • • • • • • • • • • • • • • • • • • • •
11
FRIDAY,
FRIDAY, MAY
MAY 12,
12, 1978
1978
Geologic
Geologic Road
Road Log
Log for
for U.S.
U.S. 41
41 from
from the
the Intersection
Intersection of
of Wisconsin
Wisconsin 74
74
Menomonee
Menomonee Falls
Falls at
at the
the North
North Edge
Edge of
of Waukesha
Waukesha County
County to
to Oshkosh,
Oshkosh,
Wisconsin
Wisconsin (junction
(junction Wisconsin
Wisconsin 21)
21) by
by Richard
Richard A.
A. Paull
Paull and
and Rachel
Rachel
K. Paull
Paull
K •
. .
.
.
.
.
. .
• • • . . • • . .
• .
.
.
.
.
5
.
SATURDAY, MAY 13,
13, 1978
1978
SATURDAY,
to Precambrian Rhyolite and
and
Geologic Road Log for aa Field Excursion to
Granite Inliers
Inliers of South—Central
South-Central Wisconsin by Rachel K.
K. Paull
Paull
A. Paull • • •
• • • • • • • • • •
and Richard A.
11
11
GEOLOGICAL STOP
STOP DESCRIPTIONS by Eugene I.
I. Smith
Stop 11 —- Granite
Granite at Flynn's Quarry
Quarry County Park.
Park • • •
Stop
Stop 2 —- Rhyolite
Rhyolite at Observatory Hill
Stop 33 —- Rhyolite at Marcellon
Marcellon.• • • • •
Stop 4 -- Rhyolite at Marquette • • • • •
.
. •
. •
• •
. ••
Supplemental Stop —- Rhyolite
•
Rhyolite at Ingall's Knob •
Stop 5 —- Quartzite
Portland.
Quartzite at Portland
.
•
.
33
49
49
57
68
76
83
88
REFERENCES
REFERENCESCITED.
CITED. • •• .
.
ILLUSTRATIONS
Figure 1.
1.
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
2.
2.
3.
3.
4.
4.
5.
5.
6.
6.
7.
7.
8.
8.
9.
9.
10.
10.
11.
11.
12.
12.
13.
13.
14.
14.
15.
15.
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
16.
16.
17.
17.
18.
18.
19.
for the Lake Superior Institute field
Route for
field trip to the south—
southcentral Wisconsin Precambrian rhyolite and granite inliers •.
•
Flynn's Quarry County Park • •
compass map of
of Flynn's
Pace and compass
Contact between granite porphyry dike and granite • •
•
Metabasalt dike cutting
cutting granite.
granite. • • • • • • • • •
Route map from Redgranite to
to Montello.
Montello. ~ • •. •. • . . • • .
Elemental concentrations for
for rhyolite
rhyolite groupings
groupings • •
•
Geologic map of Observatory
Observatory Hill
Hill • •. • • • • • • •
•
sandstone outcrops on Observatory Hill.
Cambrian sandstone
Hill. • . . . •
•
in Cambrian
Cambrian sandstone
Conglomerate in
sandstone • • • • • • • • • • . .
.
Contact between rhyolite dike and rhyolite
•
of contact of
Close-up
of rhyolite dike and
and rhyolite.
rhyolite.
Close—up of
•
Route map for
for traverses on the Marcellon exposures • • • • •
Geologic map
map of
of the
the Marcellon
Marcellon inlier
inlier • • • • • • •
Geologic
Photomicrograph of
of Marcellon
Marcellon rhyolite
rhyolite ash-flow
ash—flow tuff
tuff • • • • • • •
Photomicrograph
Stratigraphic variation in
in elemental
elemental concentrations
concentrations for
for
Stratigraphic
the Marcellon
Marcellon rhyolite
rhyolite • • • • • • • • • • • • • • • • • •
the
• •
. •. •• . ..
Weathered spherulites in the Marcellon rhyolite.
rhyolite • •
of spherulitic
spherulitic texture
texture in Marcellon
Marcellon rhyolite
Photomicrograph of
of spheroid
spheroid with
with concentric
concentric bands
bands • • • • •
Photomicrograph of
Photomicrograph of
of spheroid
spheroid with
with aa core
core of
of coarse
coarse quartz
quartz
Photomicrograph
and epidote.
and
•
.
.
.
.
.
.
•
•
.
•
.
.
•
.
•
.
.
.
• . . .
epidote.
•
•.
•
.
•
.
.
•
•
i1
22
32
32
33
35
35
36
37
48
49
49
50
50
53
53
56
56
58
58
59
59
59
59
60
62
62
62
63
63
�Page
Figure 20.
20. Pumice
Pumice and
and shard
shard fragments
fragments in Marcellon
Marcellon rhyolite
rhyolite • •
Figure
Figure 21.
21. Lineation formed
formed by
by stretched
stretched pumice
pumice in
in the
the Tertiary A.
A. L.
L.
Figure
Tuff, San
San Mateo
Mateo Mountains,
Mountains, New
New Mexico
Mexico • •
. •
. •
Peak Tuff,
. •••••••
Figure 22.
22. Folds in the Marcellon rhyolite
rhyolite. • • • • • • • • • •
• •••
Figure 23.
23. Sketches
Sketches of
of folds
folds in the
the Marcellon
Marcellon rhyolite
rhyolite• • • • • •
. •
. •. •
Figure
Figure 24.
24. Route
Route map
map for
for traverses
traverses at
at the
the Marquette
Marquette exposures
exposures • •. •. •. •
Figure
Figure 25.
25. Geologic map of the Marquette inlier • • • • • • • •
Figure 26.
26. Rb/Sr-Na
Rb/Sr—Na20/K20
plot for
for Marquette
Marquette rhyolite
rhyolite • • •
.
•
. . •
Figure
0/K 0 plot
2
2
Figure 27.
27. Photomicrograph
Photomicrograph of
of shards
shards in
in Marquette
Marquette rhyolite
rhyolite • •
Figure
.
Figure 28.
28. Photomicrograph of shards in Marquette rhyolite.
rhyolite • • • • • • •
Figure 29.
29. Sketch map of breccia on Ingall's
Ingall's Knob • •
.
. •••
Figure 30.
30. Detailed map of
of the Portland quartzite quarries.
quarries • • . . . . . . .
Figure 31.
31. Photomicrograph of
of the Waterloo Quartzite • • • • •
Figure 32.
32. Detailed route map through the Waterloo Quartzite area
area.
Figure 33.
33. View of phyllite layer in quartzite
quartzite. • • • •
• •••
Close—up of foliated
Figure 34.
34. Close-up
foliated Waterloo Quartzite • • • • • • • •.
.
.
.
.
65
65
66
67
68
6969
70
76
77
79
82
84
85
87
87
TABLES
TABLES
Table 1.
Table
1.
for Central Wisconsin inliers and igneous
Chemical analyses
analyses for
rocks in
in the
the Baraboo area
area. • • • • • • • • • • • • • • • • •
39
�INTRODUCT
ION
INTRODUCTION
Eugene I.
Smith1l
Eugene
I. Smith
v
years very little attention has
has been paid to the
For the
the past seventy years
At the
well known
igneous rock in
in the
the Fox
Fox River
River Valley.
Valley. At
the turn of the
the century well
geologists
Chamberlin, Weidman.
Weidman. Leith and
Hobbs described
geologists such as
as Irving,
Irving, Chamberlin,
and Hobbs
these isolated
these
isolated exposures of Precambrian rock.
rock. Between 1907 and 1972 few
The last
geological studies
studies were
were initiated.
initiated. The
last major field
field trip to visit these
was conducted by A.
A. Leith in 1935 for
Precambrian rocks
rocks was
for the
the Kansas
Kansas Geological
While the
will be
be shown to you on this
Society. While
the geology that
that will
this Lake Superior
Institute
field trip is based for
Institute field
for the
the most part
part on
on geological
geological studies
studies comcom1972, descriptions
descriptions of the
Hill rhyolite
pleted since 1972,
the Observatory Hill
rhyolite and
and the
Waterloo
This field trip
Waterloo Quartzite
Quartzite rely
rely considerably
considerably on
on the
the earlier
earlier work.
work.
This
trip
is intended
intended to
to introduce
introduce you
you to
to the
the rock
rock types
types and
and the
the rock
rock fabric
fabric formed
formed
is
post—Penokean igneous
event (1765
m.y. ago)
ago) and
during a
a major post-Penokean
igneous event
(1765 m.y.
and to demonstrate
the structural
structural style of a post—Penokian
The
the
post-Penokian deformation
deformation (1650
(1650 m.y.
m.y. ago?).
ago?).
field trip stops
oldest to youngest
field
stops are
are arranged
arranged in stratigraphic
stratigraphic order from
from oldest
youngest
(fig. 1).
1). Since the
the exposures are
are on
on the
the flank
flank of
of the
the Wisconsin
Wisconsin Arch,
Arch,
(fig.
travelling to the
travelling
the southeast off the
the crest of
of the
the arch
arch conveniently
conveniently exposes
exposes
younger units.
units.
Here fine—grained
The first
first stop is
is at
at the
the Flynn's Granite
Granite Quarry.
Quarry. Here
fine-grained
granophyric granite is
is cut
cut by
by granite
granite porphyry
porphyry and
and metabasalt
metabasalt dikes.
dikes. The
granite probably is the
equivalent of
of the
rhyolites to be
the subvolcanic
subvolcanic equivalent
the rhyolites
3, and
viewed at
at stops
stops 2,
2, 3,
and 4.
4.
Hill (stop
by a
sequence of
of steeply dipping
Observatory Hill
(stop 2)
2) is
is formed
formed by
a sequence
porphyritic rhyolite
which erupted
erupted from
from source
source chambers
chambers now
porphyritic
rhyolite ash—flow
ash-flow tuffs
tuffs which
represented by granite cropping out to
represented
to the
the northwest
northwest (Flynn's
(Flynn's Quarry,
Quarry,
The rhyolite
rhyolite is
cut by
by finefine— and
coarse—grained
Montello and
and Redgranite).
Redgranite). The
is cut
and coarse-grained
rhyolite dikes and
and is
is surrounded
surrounded by
by exposures
exposures of
of Cambrian
Cambrian sandstone.
sandstone.
Stops 33 and
Marcellon and
and Marquette
Marquette rhyolites)
rhyolites) display the
fabric
Stops
and 44 (The
(The Marcellon
the fabric
and
and mineralogy of the
the texturally
texturally variable
variable rhyolites.
rhyolites.
In
In the
the volcanic
volcanic section
sparsely-porphyritic
sparsely—porphyritic plagioclase-bearing
plagioclase—bearing rhyolite
rhyolite commonly alternates
alternates with
with
quartz, plagioclase,
porphyritic quartz,
plagioclase, alkali
alkali feldspar
feldspar rhyolite.
rhyolite. The rocks
rocks show
show
fabrics common
common to ash-flow
ash—flow tuffs
have undergone
undergone compaction,
compaction, welding
welding and
and
fabrics
tuffs that
that have
late—stage primary laminar
flowage (eutaxitic
and spheruloidal
spheruloidal textures
late-stage
laminar flowage
(eutaxitic and
textures and
and
large flow folds).
folds).
The Waterloo Quartzite
Quartzite (stop
5), the
youngest exposed
exposed Precambrian
Precambrian rock
The
(stop 5),
the youngest
in south-central
south—central Wisconsin,
Wisconsin, is
is folded
folded into
into a
broad eastward
eastward plunging synsyn—
a broad
dine. The
The nose
nose of
of the
structure lies
lies in
the Portland
Portland area
area near
near the
quarry
cline.
the structure
in the
the quarry
visited during Stop
stop 5.
5.
1'Division
Division of
of Science,
Science, University
University of
of Wisconsin—Parkside,
Wisconsin-Parkside, Kenosha,
Kenosha, Wisconsin
Wisconsin
53141
53141
1
1
�Red granite
Redgranite
S TO p'1)!e!.---.oE::-----I
CD
Flynn's
Quarry
County Park
STOP
Du Lac
@) Marquette
Rhyolife
Rhyolite
Hill
Marcellon
R hy o life
/
z
C,
Waterloo
Quart zite
I
\
'::')"""----~+--~I
Mllwaukee\
o
o
0
10
20
30
30
C-)
w
uJ
~
<t
-J
...J
40 MIles
40
Miles
SCALE
Figure 1.
1.
Route for
the Lake
Lake Superior
Superior Institute
the south—
Route
for the
Institute field
field trip to
to the
southcentral
Wisconsin
Precambrian
rhyolite
and
granite
inliers.
central
rhyolite and granite inliers.
2
�I
thank Pattie
Pattie Fields-Troha
Fields—Troha for
for typing
typing draft
draft copies
copies of
I thank
of these
these stop descriptions and Jill Ann Hartnell for
for drafting
drafting the
the figures.
figures.
Diane Pyper made
many useful
editorial corrections
corrections that
that helped
helped smooth
smooth out
out the rough spots.
many
useful editorial
spots.
also thank
thank Frank
Frank Luthur
Luthur (University
(University of
of Wisconsin-Whitewater)
Wisconsin—Whitewater) for
for an
an
II also
informative discussion on
on the
the metamorphic
metamorphic rocks
rocks from
from Waterloo.
Waterloo.
Participants on this trip
will traverse
Participants
trip will
traverse the
the scenic,
scenic, glaciated countryside
side of southeastern and
and south—central
south-central Wisconsin to study isolated exposures
of Precambrian granite,
granite, rhyolite,
quartzite that
rhyolite, and
and quartzite
that project through a cover
of Paleozoic rocks
of
rocks and Pleistocene drift (Fig.
(Fig. 1).
1).
Board bus at 6:30 P.M.
P.M. sharp on Friday May 12,
12, 1978 in
in the front of the
the
Pfister Hotel (Headquarters
(Headquarters for
for the
the 24th
24th Annual
Annual Lake
Lake Superior
Superior Institute).
Institute).
of travel
will follow U.S.
Our route
route of
travel will
U.S. 41
41 to
to Oshkosh,
Oshkosh, Wisconsin.
Wisconsin. A
A geological
roadguide for
for this
this part
part of
of the
the trip
trip is
is provided.
provided. Overnight accommodations
accommodations
will
will be at
at the Pioneer Inn,
Inn, on the west shore of Lake Winnebago in
in Oshkosh
8:00
trip
This
6:30
On Saturday
Saturday May
May 13,
13, 1978,
1978, board
board the
the bus
bus in
front of
of the
the Pioneer
Pioneer at
at
On
in front
A.M.
A.M. sharp.
sharp. The guidebook includes
includes a
a geologic roadguide for the field
field
route,
route, as well as
as detailed information
information on
on each
each of
of the
the geologic
geologic stops.
stops.
field
field excursion will terminate at the Pfister Hotel in
in Milwaukee about
about
P.M.
P.M.
A companion volume to this Geoscience Wisconsin Volume 2,
2, contains papers
papers
by Smith (1978c),
Van Schmus (1978)
(1978c), Van
(1978) and Haimson (1978)
(1978) on the
the geology,
geology, ages,
ages,
and
and engineering properties of
of the
the granites,
granites, rhyolites
rhyolites and
and quartzites.
quartzites.
3
�Friday,
Friday, May
May 12,
12, 1978
1978
Geologic
Geologic Road
Road Log
Log for
for U. S.
S. 41
41 from
from the
the Intersection
Intersection of
of Wisconsin
Wisconsin 74
74
Menomonee
Menomonee Falls
Falls at
at the
the North
North Edge
Edge of
of Waukesha
Waukesha County
County
to
to
Oshkosh,
Oshkosh, Wisconsin
Wisconsin (junction
(junction Wisconsin
Wisconsin 21)
21)
1
2
Richard
Richard A.
A. Paull1
Paull and
and Rachel
Rachel K.
K. Paull2
Paull
U.
U. S.
S. 41
41 trends
trends north—northwesterly
north-northwesterly through
through the
the glaciated
glaciated Eastern
Eastern Ridges
Ridges
and Lowlands
Lowlands Province
Province of
of Wisconsin.
Wisconsin. The
The orientation of this
this route
route is
is such
such
and
that
that it
it cuts
cuts obliquely
obliquely across
across the
the strike
strike of
of the
the Paleozoic
Paleozoic formations.
formations. From
From
south—southeast
south-southeast to
to the
the north—northwest,
north-northwest, these
these units
units include
include Silurian
Silurian dolomite,
dolomite,
Tipper
Ordovician Maquoketa
Maquoketa Shale,
Shale, and
and the Middle Ordovician
Upper Ordovician
Ordovician Platteville—
PlattevilleGalena formations.
formations. However,
However, the
the bedrock
bedrock along
along the
the highway
highway is
is largely
largely obobGalena
scured
scured by
by Wisconsinan (Woodfordian
(Woodfordian and
and the
the younger
younger Valderan)
Valderan) glacial
glacial deposits.
deposits.
exception exists
exists along
along the
the crest
crest of
of the
the prominent
prominent Niagaran
Niagaran (Silurian)
(Silurian)
An exception
escarpment, where
where glacial
glacial deposits
deposits are
are thin.
thin.
escarpment,
Included
Woodfordian glacial
glacial features
features are
are well—displayed
well-displayed along
along U.
U. S.
S. 41.
41.
Included
are a
a recessional moraine related to retreat of the Lake Michigan lobe,
lobe, kames
kames
and kettles
kettles associated with the spectacular Kettle Interlobate
Interlobate Moraine,
Moraine, and
and
well—formed
well-formed drumlins
drumlins within the area occupied by the
the Green Bay lobe.
lobe. Deposits
Deposits
that accumulated
accumulated in
in Glacial
Glacial Lake
Lake Oshkosh
Oshkosh when
when retreat
retreat of
of the
that
the last
last Wisconsinan
(Valderan) ice
ice tongue
tongue blocked northeastward drainage
(Valderan)
drainage into
into Green
Green Bay
Bay are
are also
also
traversed.
Details on the
the geology
geology encountered
encountered along
along U.
U. S.
S. 41
are provided
provided in the
Details
41 are
the
geologic road log that
that follows.
follows. We hope this
this will help to make your
your
enjoyable. Mileages in
in the
the road
road log
log are
are cumulative,
cumulative, with
journey more enjoyable.
mileage increments between each
each entry
entry included
included in
in brackets.
brackets.
Mileages
o
0
(2.0)
(2.0)
Con—
74 exit
exit from U.
U. S.
S. 41
Wisconsin 74
41 to
to downtown Menomonee Falls.
Falls.
Continue
northwest on U.
U. S.
S. 41
Oshkosh, the
tinue northwest
41 and
and 45 toward
toward Oshkosh,
the location of
tt
our "watering
our
watering hole"
hole " for
for this
this evening.
evening.
Lime Kiln Village
Village Park is
mile west
west in the
Lime
is about
about one mile
the heart
heart of
Here,
the
the business
business district
district of Menomonee Falls.
the
Falls. Here, the Silurian
Dolomite
dolomite
forms
a
small
falls
on
the
dolomite forms a small falls
the Menomonee River.
River.
was
quarried
here
for
lime
production
as
early
as
the
1850's,
was quarried
for lime
as
as the 1850's, and
Glacial
three historic
historic kilns
three
kilns are preserved within the
the park.
park.
striae on
on the
the Silurian bedrock in
striae
in the
the vicinity
vicinity of
of the
the kilns
kilns
establish an
an east-west
east—west flow
flow direction
direction for
for advance
advance of
of the
the Lake
Lake
establish
Michigan glacial
glacial lobe during the
Michigan
the Woodfordian.
2.0
2.0
(5.0)
(5.0)
Enter Washington
Washington county
county in an
Waukesha/Washington county line.
Waukesha/Washington
line.
Enter
area of
of foIling
folling countryside,
countryside, on
on the
the northwestern
northwestern edge
edge of
of the
the intensely
intensely
area
lThe
1The University
University of
of Wisconsin-Milwaukee,
Wisconsin—Milwaukee, Milwaukee,
Milwaukee, Wisconsin
Wisconsin
University of
of Wisconsin-Madison,
Wisconsin—Madison, Madison,
22The
The University
Madison, Wisconsin;
Wisconsin; and
and Alverno
Alverno College,
College,
Milwaukee,
Milwaukee, Wisconsin
Wisconsin
55
�Mileages
Mileages
urbanized, greater
greater Milwaukee
Milwaukee area.
area. This
urbanized,
This region
region was
was last
last glaciated
glaciated
during the
the Woodfordian
Woodfordian by
by the
the advance
advance of
of the
the Lake
during
Michigan
Lake Michigan lobe.
lobe.
The outermost
outermost (oldest)
(oldest) of
of a a series
series of
of three,
three, major
major ridgeridge—
The
forming recessional
recessional moraines
moraines (Lake
Border Moraines),
Moraines), which
forming
(Lake Border
which parallel
parallel
the
shore
of
Lake
Michigan
in
the
Milwaukee
the shore of Lake Michigan in the Milwaukee area,
area, trends
trends through
through
this area.
area.
this
To the
the west,
west, one
one catches
catches glimpses
glimpses of
of the
the irregular
irregular hills
To
hills of
of the
the
Woodfordian
interlobate
moraine
that
developed
Woodfordian interlobate moraine that developed between
between the
the Lake
Lake
Michigan lobe
lobe on
on the
the east
east and
and the
the Green
Green Bay
Michigan
Bay lobe
lobe on the west. This
This
is
the
Kettle
Interlobate
Moraine,
which trends
is the Kettle Interlobate Moraine, which
trends north-northeast
from Walworth
Walworth County
County to
to Kewaunee
Kewaunee County
County to
from
to form
form the
the glacial
glacial backbone
of
eastern
Wisconsin.
bone of eastern Wisconsin. Northwest-trending
Northwest—trending u.s.
U.s. 41
41 is
is on
on aa
collision course
course with
with this
this prominent
prominent topographic
topographic feature.
collision
feature.
7.0
7.0
(1.0)
(1.
0)
8.0
8.0
Wisconsin 167
167 (Holy
Hill Road)
Road) exit;
exit; continue
continue on
Wisconsin
(Holy Hill
and 45.
45.
on u.s.
U.S. 41
41 and
Holy
Hill,
aprominentkame
topped
by
Holy Hill, a prominent kame
by aa picturesque
picturesque church,
church, is
located about
about 77 miles
miles west
west of
of here
here within
within the
the heart of the Kettle
located
Interlobate Moraine.
U.S.
u.s.
45 exit
exit to
to West
West Bend;
Bend; continue
continue north
north on U.S.
45
u.s. 41.
41.
(4.0)
(4.0)
12.0
12.0
(1.0)
(1.
0)
13.0
13.0
(lO)
(1. 0)
14.0
14.0
(0.4)
(0.4)
14.4
14.4
(0.9)
(0.9)
The highway
highway ascends
ascends the
the eastern
eastern edge
edge of the
the Kettle
The
Kettle Interlobate
Moraine,
and
leaves
the
lowland
occupied
by the Lake Michigan lobe
Moraine,
during the Woodfordian advance.
advance. This
This country is
is higher and more
more
irregular,with
with kettles
kettles and
and abundant
abundant locally
locally derived
derived erratics
irregular,
of
erratics of
light—colored Silurian
light-colored
Silurian dolomite.
dolomite.
Wisconsin 60 exit to Slinger and Hartford within the Kettle Inter—
Interlobate Moraine.
Moraine ..
The Hilltop Restaurant on the west side of the highway is
is well
well
named,
named, for
for it
it occupies
occupies the
the crest
crest of
of the
the Kettle
Kettle Interlobate
Interlobate Moraine.
Moraine.
The
The scenic
scenic kettle
kettle and
and kame
kame topography
topography that
that characterizes
characterizes this
this region
region
formed
formed when the Green Bay and Lake Michigan glacial lobes
lobes stagnated
stagnated
along
along their
their junction
junction during
during the
the Woodfordian.
Woodfordian. As
As the
the ice
ice at
at the
the
melting edges
edges of
of these
these juxtaposed
juxtaposed lobes
lobes began
began to
to thin,
thin, sedimentsedimentladen meltwater
meltwater •flowed
flowed down
in the
the ice
ice to
to provide
provide
laden
down cracks
cracks and holes in
aa source
source for
for subglacial
subglacial streams.
streams. Meltwater
Meltwater also
also cascaded
cascaded over
over the
the
ice
ice surface
surface into
into the
the widening abyss
abyss between the
the tongues.
tongues. Here,
Here,
large
large chunks
chunks of
of ice
ice were buried in
in the
the outwash
outwash sands
sands and
and gravels.
gravels.
The
The resulting
resulting maze
maze of
of crevasse
crevasse fills,
fills, moulin
moulin kames,
kames, eskers,
eskers, outwash
outwash
fans,
fans, and
and kettles
kettles is
is superimposed
superimposed on
on aa dual
dual complex
complex of
of ridges
ridges which
which had
had
previously
previously formed
formed as
as lateral
lateral moraines.
moraines.
Little Switzerland
Switzerland Ski
Ski Hill,
Hill, to
to the
the west
west of
of the
the highway
highway at
at the
the edge
edge
Little
of
of Slinger,
Slinger, utilizes
utilizes aa prominent
prominent moulin
moulin kame.
kame. The
The internal
internal makeup
makeup
of
of aa similar
similar kame
kame is
is revealed
revealed in
in an
an abandoned
abandoned sand
sand and
and gravel
gravel
operation
operation about
about 0.1
0.1 mile
mile north
north of
of the
the ski
ski hill.
hill. The
The gravel
gravel in
in this
this
kame
kame is
is well—stratified,
well-stratified, and
and it
it includes
includes an
an abundance
abundance of
of lightlightcolored Silurian
Silurian dolomite
dolomite cobbles
cobbles and
and aa few
few large
large boulders.
boulders. Other
Other
colored
well-formed
well-formed kames
kames are
are present
present east
east of
of the
the highway.
highway.
66
�Mileages
Mileages
15.3
15.3
Junction
Junction U.S.
u.s. 41
41 and
and Wisconsin
Wisconsin 144.
144.
Continue
Continue north
north on
on U.S.
u.s. 41.
41.
(1.7)
(1.7)
17.0
17.0
(0.8)
(0.8)
17.8
17.8
(3.5)
(3.5)
Junction
Junction U.S.
u.s. 41
41 and
and County
County K.
K. The
The highway
highway descends
descends from
from the
the
Interlobate
Interlobate Moraine toward
toward the
the lowland
lowland area
area occupied
occupied by
by the
the Green
Green
Bay lobe
lobe during
during the
the Woodfordian
Woodfordian ice
ice advance.
advance.
Bay
The sand
sand and
and gravel
gravel pit
pit west of
of the
the highway
highway is
is on
on the
the northnorthwestern
western edge
edge of
of the
the Kettle
Kettle Interlobate
Interlobate Moraine.
Moraine. This
This is
is one
one of
of
many
many such
such operations
operations that
that exploit
exploit the
the abundant
abundant resource
resource of
of waterwaterwashed
washed sand
sand and
and gravel
gravel within
within this
this unique
unique morainal
morainal complex.
complex.
The route
poorly—drained ground
route ahead
ahead traverses
traverses gently
gently rolling,,
rolling, poorly-drained
moraine. Tamaracks
Tamaracks flourish
flourish in
in some
some of
of the
the wetter
wetter areas.
areas.
moraine.
21.3
21.3
(1.7)
(1.7)
23.0
23.0
Junction
Junction U.S.
u.s. 41
41 and
and Wisconsin 33;
33; continue
continue north
north on
on U.S.
u.s. 41.
41. The
The
route
route crosses
crosses aa recessional
recessional moraine that
that formed
formed as
as the
the Woodfordian
Woodfordian
Green Bay
Bay lobe
lobe paused
paused during
during its
its retreat.
retreat.
Green
Wayside east
east of
of the
the highway is
is in
in an
an area
area of
of swampy,
swampy, rolling
rolling ground
ground
(4.0)
(4.0)
moraine.
moraine.
27.0
27.0
(2.5)
(2.5)
This high area provides an excellent overview of scenic,
scenic, irregular
irregular
abundance of
of erratics
erratics in
in the
the till
till here
here is
is documented
documented
countryside. An abundance
by
by stone
stone fences
fences that
that line
line some
some fields,
fields, and
and by
by rock
rock piles
piles in
in others.
others.
29.5
(0.6)
(0.6)
u.s. 41
41 and
and Wisconsin
Wisconsin 28.
28.
Junction U.S.
30.1
(1.9)
(1.9)
county line.
line. Enter Dodge County in
in an
an area
area dominated
dominated
Dodge/Washington county
large, well—formed
well-formed druinlins.
drumlins. Erratics in
in fence
fence rows
rows and
and farmyards
farmyards
by large,
the stony
stony nature
nature of
of this
this till.
till.
testify to the
32.0
(0.4)
(0.4)
Wayside east of
of the
the highway.
highway.
32.4
(1.6)
(1.6)
Wayside west of
of the
the highway.
highway.
34.0
34.0
(2.4)
(2.4)
The
Junction
67.
Continue north on U.S.
u.s. 41.
41.
The
Junction u.s.
U.S. 41 and Wisconsin 67.
route ahead
ahead gradually
gradually climbs
climbs the
the gentle
gentle (2°-5°),
route
(2°-5°), easterly dipslope
However, the
the bedrock in this
of
resistant Silurian
Silurian dolomite.
dolomite.
However,
of the
theresistant
region is
is covered
covered by
by aa swarm of broad,
broad, low drumlins
drumlins that create
region
aa gently
gently rolling landscape.
36.4
36.4
(1.0)
(1.0)
Junction
49.
Junction u.s.
U.S. 41
41 and
and Wisconsin 49.
37.4
37.4
(1.4)
(1.4)
Fond
line.
Fond du
du Lac/Dodge
Lac/Dodge county line.
38.8
38.8
(0.5)
(0.5)
highway utilize
utilize a
Sand and
and gravel
gravel operations
operations on
on both
both sides
sides of
of the
the highway
Sand
a
local
local area
area of outwash deposits.
39.3
39.3
(2.7)
(2.7)
Roadcut on
on the
the west
west side
side of
of the
the highway
highway exposes
exposes Silurian
Silurian dolomite
dolomite
Roadcut
The proximity
proximity of
of bedrock
bedrock to
to the
the
where
thin.
The
where glacial
glacial deposits
deposits are thin.
77
Continue north
north on
on U.S.
u.s. 41.
41.
Continue north
north on
on U.S.
Continue
u.s. 41.
41.
Enter Fond du
du Lac County.
Enter
County.
�Mileages
Mileages
surface has
has facilitated
facilitated the
the development
development of
of numerous
numerous dolomite quarries
surface
in this
this general area.
This rock
rock is
is an excellent dimension
in
area.
This
dimension stone,
stone,
but most
most of it
it is
is crushed for
but
for agricultural lime and road building.
building.
However, some
some is
is kilned to produce chemical
However,
chemical lime.
lime.
This high
high point
point provides
provides aa good
good view
view of
of the
the north-northeasterly
This
trending Kettle
Kettle Interlobate
Interlobate Moraine
Moraine along
along the
the skyline
skyline to
to the
the east.
east.
trending
A lowland region,
nonresistant Middle
Middle
region, developed on relatively nonresistant
and Upper
Upper Ordovician rocks,
and
rocks, lies
lies to
to the
the west.
west.
42.0
42.0
(0.6)
42.6
42.6
(2.0)
Large
Large quarries
quarries in
in Silurian dolomite are located east and west of
U.s. 41.
U.S.
41.
This is
is the
the edge of the
the Silurian (Niagaran)
This
(Niagaran) escarpment,
escarpment, and it
provides
a
fine
view
of
the
Ordovician
lowland
ahead.
provides a fine
the
ahead.
This excarpment (or
ment
(or cuesta)
cuesta) is the
the most significant bedrock feature in eastern
Wisconsin. It
It emerges
emerges from
from aa thick
thick cover
cover of
of glacial
glacial deposits
deposits aa
few miles
miles northeast
northeast of
of Milwaukee,
Milwaukee, and
and trends
trends north-northeast
north—northeast as
few
as aa
prominent cliff along the
the east side of Horicon Marsh and Lake
Winnebago.
From here,
here, the
the escarpment persists northeastward to
form the
the rocky
rocky spine of the Door Peninsula. It continues across
form
Lake Michigan as
as a
Lake
a string of bedrock islands before it rises
rises as the
the
rugged Garden Peninsula of
of Upper
Upper Michigan.
Michigan.
The route
descends toward the Ordovician lowland through
route ahead descends
through an
an
area of gently rolling
ground
moraine.
rolling ground moraine.
44.6
44.6
(0.6)
The highway in this vicinity crosses the ill—defined
The
ill-defined terminal
terminal moraine
of the latest Wisconsinan (Valderan)
(Valderan) ice advance of the
the Green Bay
Bay
lobe.
The wooded edge of the Silurian escarpment is
is visible
visible along
along the
the skyskyline to
to the
the east.
east.
45.2
(1.8)
Junction U.S.
U.S. 41 and Wisconsin 175 to Fond du Lac,
Lac, at
at the
the south
south end
end
of Lake Winnebago.
Winnebago. Continue northwest
northwest on
on U.S.
U.S. 41.
41.
Lake Winnebago,
Winnebago, with a surface area of 215
215 square
square miles and
and aa
maximum
maximum depth
depth of
of 21
21 feet,
feet, is
is the
the largest
largest inland
inland lake
lake in
in Wisconsin.
Wisconsin.
It sprawls for
for 28
28 miles along the west edge of the
the Silurian
Silurian
escarpment,
escarpment, and is situated in an area underlain by relatively
relatively
nonresistant Middle
Middle and
and Upper
Upper Ordovician
Ordovician rocks.
rocks. This lowland
lowland extends
extends
from
from Green Bay southwestward through
through Lake Winnebago, Horicon
Horicon Marsh,
Marsh,
and over a
a low
low drainage divide into
into the
the broad valley
valley now
now occupied
occupied
by
by the
the Rock
Rock River.
River. During the
the Pleistocene, the
the Green
Green Bay
Bay lobe
lobe
advanced and
and retreated
retreated along
along this
this route
route numerous
numerous times.
times. The ice,
ice,
in part confined by the
the resistant
resistant Silurian
Silurian escarpment,
escarpment, scoured
scoured the
the
Ordovician bedrock and deposited aa variety
variety of
of glacial
glacial landforms.
landforms.
During northeastward regressions
regressions of
of the
the Woodfordian
Woodfordian and
and Valderan
Valderan glaciers,
glaciers,
drainage along
along the
the lowland
lowland into
into Green
Green Bay
Bay was temporarily
temporarily blocked
blocked
by
by the
the retreating
retreating wall
wall of
of ice.
ice. A
A vast
vast lake,
lake, termed
termed Glacial
Glacial Lake
Lake
Oshkosh, formed
impounded behind
behind the
the youngest
youngest
formed from
from the
the meltwaters
meltwatersimpounded
(Valderan)
(Valderan) of
of these
these icy
icy dams.
dams. At
At this
this time,
time, the
the site
site of
of Fond
Fond du
du Lac
Lac
was
was under
under 40
40 to
to 60
60 feet
feet of
of water.
water. Eventually
Eventually Green
Green Bay
Bay became
became ice
ice
free,
free, and Glacial Lake Oshkosh drained into Lake Michigan via
via the
the
88
�Mileages
Mileages
Winnebago
remnantofofthis
this feature,
feature, surviving
Fox River.
River. Lake
Lake Winnebago
is isa aremnant
surviving
Fox
in a shallow irregularity on the floor
floor of
of this
this ancient
ancient water
water body.
body.
in a shallow irregularity on the
Cross
Cross east
east branch
branch of
of Fond
Fond du
du Lac
Lac River.
River.
47.0
47.0
(1.8)
(1.8)
48.8
48.8
(4.2)
(4.2)
Junction
Junction U.S.
U.S. 41
41 and
and U_S.
U.S. 151.
151. Continue
Continue north
north on
on U.S.
U.S. 41.
41. The
The
route
route ahead
ahead traverses
traverses aa relatively
relatively subdued
subdued area
area underlain
underlain by
by
sediments
sediments deposited
deposited in
in Glacial
Glacial Lake
Lake Oshkosh.
Oshkosh.
Junction U.S.
U.S. 41
41 and
and Wisconsin
Wisconsin 23.
23.
Junction
Continue
Continue northwest
northwest on
on U.S.
U.S. 41.
41.
The
The wooded
wooded Silurian
Silurian escarpment
escarpment continues
continues to
to dominate
dominate the
the horizon
horizon to
to
the east.
east.
the
53.0
53.0
Wayside
Wayside west
west of
of the
the highway,
highway, as
as U.S.
U.S. 41
41 curves
curves northward.
northward.
(4.0)
(4.0)
57.0
(1.7)
(1.7)
58.7
58.7
(3.2)
(3.2)
ascends to
to reddish,
reddish, rolling
rolling Valderan
Valderan ground
ground moraine
moraine at
at
Highway ascends
the western
western edge
edge of
of Glacial
Glacial Lake
Lake Oshkosh.
Oshkosh.
the
Winnebago County
Fond du
du Lac/Winnebago
Lac/Winnebago county
county line.
line. Enter
Enter Winnebago
County in
in an
an area
area
Fond
rolling ground
ground moraine.
moraine. There is a good view to
to the
the east
east of
of the
the
of rolling
Silurian escarpment
escarpment along
along the
the far
far shore
shore of
of Lake
Lake Winnebago.
Winnebago. The
The
sediments deposited
deposited
route from here to Oshkosh traverses reddish sediments
Lake Oshkosh.
Oshkosh.
in Glacial Lake
61.9
61.9
(0.7)
(0.7)
of the
the highway.
highway.
Wayside east of
62.6
62.6
(2.7)
(2.7)
U.S. 41
Junction U.S.
U.S. 41 and Wisconsin
Wisconsin 26.
26. Continue north on U.S.
through aa subdued
subdued area underlain by flat-lying glacial lake
through
deposits.
65.3
65.3
(2.9)
(2.9)
Continue north
north
Junction U.S.
U.S. 41 and Wisconsin 26
26 and
and 44
44 to
to Oshkosh.
Oshkosh. Continue
Oshkosh, on
on the west shore
Winnebago, is
on U.S.
U.S. 41.
41. Oshkosh,
shore of Lake Winnebago,
developed on the ancient floor
floor of
of Glacial
Glacial Lake
Lake Oshkosh.
Oshkosh.
68.2
68.2
The geologic
geologic roadguide
roadguide for
Junction U.S.
U.S. 41 and Wisconsin 21.
21. The
for
intersection,
the Precambrian
Precambrian inliers
inliers field
field trip
trip begins
begins at
at this
this intersection,
the
and
21.
and continues
continues westward on State 21.
A PLEASANT
PLEASANT EVENING:
EVENING
HAVE A
END
- HAVE
END OF
OF LOG -
99
�__________
__________
Saturday,
Saturday, May
May 13,
13, 1978
1978
Geologic
Geologic Road
Road Log
Log for
for aa Field
Field Excursion
Excursion to
to Precambrian
Precambrian Rhyolite
Rhyolite and
and Granite
Granite
Inliers
Inliers of
of South—Central
South-Central Wisconsin
Wisconsin
l
2
Rachel
Rachel K.
K. Paull'
Paull and
and Richard
Richard A.
A. Paull2
Paul1
This
This road
road log
log starts
starts at
at the
the intersection
intersection of U.
U. S.
S. 41
41 and
and Wisconsin 21
21 on
on
the
the northwestern
northwestern edge
edge of
of Oshkosh,
Oshkosh, Wisconsin,
Wisconsin, and
and terminates
terminates in
in Milwaukee,
Milwaukee,
'Wisconsin
"Wisconsin at
at the
the junction
junction of 1—94
1-94 with 1—43
1-43 (U.
(U. S. 141) and
and 1—794
1-794 (see
(see
Fig. i).
1).
Fig.
The
The route
route of travel
travel on this
this trip
trip is
is due
due west from
from Oshkosh for
for 26
26 miles
miles
to Redgranite,
Redgranite, and then
then south—southwest
south-southwest nearly
nearly to
to Portage
Portage (Marcellon
(Marcellon inlier).
inlier).
to
Since
Since we detour to
to look
look at
at two
two Precambrian
Precambrian inliers,
inliers, this
this leg
leg involves
involves about
about 50
50
we proceed northeast
miles of
of travel.
travel. From here,
here, we
northeast to
to a
a rhyolite inlier near
miles
Marquette; aa distance
distance of
of 20
20 miles
miles by
by road.
road. After
After aa 5 mile segment
segment to
to the
the east,
east,
Marquette;
our route
route trends
trends south
south for
for 40
40 miles.
miles. From immediately
immediately north
north of
of Waterloo,
Waterloo,
our
we travel
travel eastward
eastward for
for 7
7 miles
miles to
to the
the Waterloo
Waterloo Quartzite,
Quartzite, and
and then
then south
south for
for
we
to reach
reach Interstate
Interstate 94
94 at
at Lake
Lake Mills.
Mills. After aa fast
fast 50—mile
50-mile run
run to
to
8 miles to
In all,
all, we
we will
will cover 206
east, we are
are back
back in
in Milwaukee.
Milwaukee.
206 miles,
miles, make
make
the east,
5 geologic
stops, and even stop
stop for
for lunch
lunch (Fig.
(Fig. 1).
1). It will be
be aa busy
busy day
day:
5
geologic stops,
This odyssey through east—central
east-central Wisconsin traverses
traverses parts of two
two of
However,
the four
four major physical provinces
provinces recognized
recognized in
in Wisconsin.
Wisconsin.
However, in
in the
the
the
provinces are
area
the features
are
area covered
covered by
by this
this field
field excursion,
excursion, the
features of
of both
both provinces
The Eastern Ridges and
by young
young glacial
glacial deposits.
deposits. The
and Lowlands
Lowlands parallels
parallels
masked by
This province
province contains
contains aa sequence
sequence of
of generally
generally north—south
north-south
Lake Michigan. This
striking, Ordovician
Ordovician through
through Devonian formations,
formations, with
with the
older rocks
striking,
the older
rocks to
to the
the
Differences in
in resistance
resistance of
of these
units result
west. Differences
these units
result in broad,
broad, subdued
subdued
ridges alternating with lower
lower areas.
areas.
The Central Plain is
is aa lowland
lowland region,
region,
ridges
developed on Upper
Upper Cambrian sandstones,
sandstones, that
west of
of the
developed
that lies
lies to
to the
the west
the Eastern
Ridges and Lowlands.
Lowlands~
Ridges
Within the
the general region of the
the Central
Central Plain covered by this
this trip,
trip,
there are
are ten localities
localities where
where Precambrian granite
granite and
and rhyolite
there
rhyolite project
project
through
through aa cover
cover of
of Lower
Lower Paleozoic
Paleozoic rocks
rocks and
and unconsolidated
unconsolidated Pleistocene
Pleistocene
The igneous
igneous rocks
rocks in these inliers
deposits.
The
inliers are dated
dated at
at 1765
1765 m.y.
m.y. old,
old,
and they
they probably
probably formed
and
formed during the waning stages
stages of
of the
the Penokean
Penokean orogeny.
orogeny.
Although
Granite inliers
inliers lie
lie northwest
Granite
northwest of the
the area
area where rhyolite
rhyolite is
is exposed.
exposed. Although
the field
field relations
relations are
are not
not established
established at
at present,
present, the
the rhyolite
rhyolite and
and granite
granite
the
If so,
so, the
the granite
granite is
are
comagmatic. If
is a
a subvolcanic
are generally
generally believed
believed to be comagmatic.
equivalent
of
the
extrusive
rhyolite.
equivalent of the
rhyolite.
After accumulation of
of the
sequence of
of Precambrian quartz
After
the rhyolite,
rhyolite, a
a thick sequence
After
deposition, these
sandstone
deposited. After deposition,
sandstone and
and other
other sedimentary rocks was deposited.
rocks and
and the
the underlying
underlying rhyolite
rhyolite were
were subjected
subjected to
to an
an intensive
intensive episode
episode of
of
rocks
Detailed information
information on
on the
the Precambrian
Precambrian
folding,
m.y. ago.
ago.
Detailed
folding, possibly
possibly 1650 m.y.
history of
of this
this region
region is
is provided
provided by
by Eugene
Eugene I.
I. Smith
Smith in
in the
the next
next section
section of
of
history
this
this guidebook.
guidebook.
The five
five stops
stops on
on this
this field
field excursion
excursion provide
provide an
an opportunity
opportunity to
to examine
examine
The
However, rhyolite
rhyolite
each
types described above.
above.
However,
each of
of the
the major
major Precambrian rock types
receives the
the most
most emphasis,
emphasis, with
with three
three stops
stops devoted
devoted to
to an
an examination
examination of
of this
this
receives
diverse
diverse rock
rock type.
type.
11
11
1
1University
of Wisconsin—Madison,
Madison, Madison,
Wisconsin; and
Alverno College,
University
of Wisconsin-Madison,
Wisconsin;
and Alverno College,
Milwaukee,
Wisconsin
Milwaukee, Wisconsin
2University of
of Wisconsin-Milwaukee,
Wisconsin—Milwaukee, Milwaukee,
Milwaukee, Wisconsin
Wisconsin
2University
�The glacial
glacial geology
geology of
of east-central
east—central Wisconsin
Wiscctisin is
is also
also spectacular,
spectacular, and
and
The
quite
varied.
The trip
trip begins
begins in
in an
an area
area occupied
occupied by
by the
the youngest
youngest Wisconsinan
Wisconsinan
quite varied.
The
(Vanderan) ice
ice advance,
advance, and
and by
by lakes
lakes which
which formed
formed during
during the
the retreat
retreat of
of this
this
(Vanderan)
ice. However,
However, most
most of
of the
the route
route traversed
traversed is
within the
ice.
is within
the region covered by
an older
older Wisconsinan
Wisconsinan (Woodfordian)
an
(Woodfordian) advance of
of the
the Green
Green Bay
Bay lobe.
lobe. Deposits
Deposits
formed by
by this
this icy
icy tongue
tongue include large expanses of
formed
of glacial
glacial lake
lake sediments,
sediments,
recessional moraines
moraines related
related to
to the
the retreat
retreat of
of this
this lobe,
lobe, outwash
outwash sands
sands and
and
recessional
gravels, scenic
scenic kettle
kettle lakes,
lakes, and
and some
some of
of the
the best
best drumlin
drumlin swarms
swarms in
in the
the
gravels,
world. All
All of
of these
these features
features combine
combine to make
make this
this region
region a
glacial showworld.
a glacial
case, and a
most pleasant
place to
case,
a most
pleasant,place
to spend
spend aa field
field day.
day.
We hope
hope the
the geologic
geologic roadguide
roadguide that
that follows
follows makes
makes your trip more
We
enjoyable. Mileages
Mileages are
are cumulative,
cumulative, with
with mileage
mileage increments
enjoyable.
increments between each
entry provided in
in brackets.
brackets. Detailed
for each stop is
Detailed geologic
geologic information for
provided by Eugene I.
provided
I. Smith in
in the
the next
next section
section of
of this
this guidebook.
guidebook.
It
It would
would
be beneficial
beneficial if
if you
you would
would read
read the
the detailed
detailed descriptions
descriptions of
be
of each area
area before
we stop.
we
stop.
Mileages
Mileages
o0
(2.2)
(2.2)
Start of
of Geologic
Geologic Road
Road Log
Log at
at intersection
intersection of
of V.. S. 41
Start
41 and
Wisconsin 21 at the
the northwestern edge of
of Oshkosh,
Oshkosh, Wisconsin.
Wisconsin.
west on State Highway
Proceed west
Highway 21.
21.
is located
located on
on the
west shore
shore of
of Lake
Lake Winnebago,
Winnebago, the largest
Oshkosh is
the west
inland lake in
in Wisconsin. This shallow lake
lake is
is aa remnant
remnant of
of Glacial
Glacial Lake
Lake
Oshkosh,
Oshkosh, a much larger
larger Pleistocene water body formed
formed when the
the retreating
retreating
Valderan ice
blocked northeastward
northeastward drainage
drainage along
Valderan
ice blocked
along the
the Green Bay lowland
into
into Lake
Lake Michigan.
Michigan. The route ahead traverses lacustrine
lacustrine sediments that
that
accumulated in
in Glacial
Glacial Lake
Lake Oshkosh.
Oshkosh.
2.2
2.2
(2.6)
Enter an
an area
area of
of higher,
higher, gently
gently rolling
rolling countryside.
countryside. This
is
ground moraine
moraine and
is a
a Valderan ground
and outwash complex that
that
once stood
stood as
as an
an island
island in
in Glacial
Glacial Lake
Lake Oshkosh.
Oshkosh.
4.8
4.8
(2.2)
(2.2)
the flat floor of
of
Descend from the morainal "island" onto the
Glacial
Glacial Lake
Lake Oshkosh.
Oshkosh. Here,
Here, the
the lake
lake sediments
sediments are
are
well-drained to
to be
be intensively
intensively farmed.
farmed.
sufficiently well—drained
7.0
7.0
(0.7)
(0.7)
This
This subdued
subdued ridge
ridge is
is the
the western
western edge
edge of
of the
the gentle,
gentle,
east—dipping,
east-dipping, Middle Ordovician
Ordovician (Platteville—Galena
(Platteville-Galena
formations)
formations) cuesta.
cuesta. The route
route ahead
ahead descends
descends through
through the
the
Ordovician St.
St. Peter
Peter Sandstone
Sandstone onto
onto aa relatively
relatively
Middle Ordovician
flat surface
surface developed
developed on
on dolomites
dolomites of
of the
the Lower
Lower Ordovician
Ordovician
flat
Prairie
Prairie du
du Chien
Chien Group.
Group. However,
However, the
the bedrock
bedrock in
in this
this area
area
is
is obscured
obscured by
by glacial
glacial deposits.
deposits.
7.7
(0.3)
Enter
Enter Omro
Omro on
on the
the Fox
Fox River.
River. The
The Fox
Fox flows
flows northeasterly
northeasterly to
to
join the
the southeasterly
southeasterly flowing
flowing Wolf River
River drainage
drainage in
in Lake
Lake
join
Butte
Butte des
des Morts.
Morts. This
This shallow
shallow lake
lake is
is another
another remnant
remnant of
of
Glacial
Glacial Lake
Lake Oshkosh,
Oshkosh, and
and it
it drains
drains into
into Lake
Lake Winnebago
Winnebago at
at
Oshkosh.
Oshkosh.
12
12
�Mileages
Mileages
The
The Middle
Middle Ordovician
Ordovician St.
St. Peter
Peter Sandstone
Sandstone is
is quarried
quarried for
for foundry
foundry
This
sand
sand
a
few
miles
south
of
here
near
Waukau.
sand a few miles south of here near Waukau.
This sand is
is trucked
trucked
to
to Berlin
Berlin for
for processing,
processing, but
but from
from 1870-1878,
1870-1878, the
the St.
St. Peter
Peter in
in this
this
area supplied aa glass
factory
in
Omro.
glass factory in Ornro.
8.0
8.0
(0.5)
(0.5)
The
The park
park on
on the
the south
south bank
bank of
of the
the Fox
Fox River
River represents
represents
Unfortunately,
use
use of
of the
the flood
flood plain.
plain. Unfortunately, such
such foresight
foresight
exercised
exercised when
when downtown
downtown Omro
Omro was
was developed.
developed.
intelligent
intelligent
was
was not
not
8.5
8.5
(2.5)
(2.5)
Junction
Junction Wisconsin 21
21 and
and 116
116 at
at the
the west
west edge
edge of
of Omro.
Ornro. Continue
Continue
on
on State
State 21,
21, and
and cross
cross the
the Fox
Fox River.
River. The route ahead
ahead parallels
the north side of the swampy Fox River valley for
for the
the next
next few
few miles.
miles.
11.0
11.0
(2.8)
(2.8)
Another
Another area
area of
of rolling
rolling Valderan
Valderan moraine
moraine that
that once
once stood
stood as
as an
an island
island
in Glacial
Glacial Lake
Lake Oshkosh.
Oshkosh.
13.8
13.8
(2.0)
(2.0)
Intersection Wisconsin
Wisconsin 21
21 and
and County
County K.
K. The gentle
gentle ridge
ridge just
just east
east
of this intersection is the easterly—dipping,
western
edge
of
the
easterly-dipping,
edge of the
Lower Ordovician
Ordovician Prairie
Prairie du
du Chien
Chien escarpment.
escarpment. As such,
such, it
it serves
serves
to define the boundary between the Eastern Ridges
Ridges and
and Lowlands
Lowlands and
and
Central Plain.
Plain.
the Central
The bedrock underlying the
the Central Plain is
is predominantly
predominantly sandstone
sandstone
Late Cambrian
Cambrian age.
age. However, the
the bedrock in
in this
this vicinity
vicinity is
is
of Late
covered by glacial lake
lake sediments.
sediments.
A
A quarry developed
developed in
in the
the Prairie
Prairie du
du Chien
Chien dolomite
dolomite is
is immediately
immediately
intersection. The glacial deposits here are
are thin
thin
southeast of this intersection.
edge of
of the
the cuesta.
cuesta.
along the edge
15.8
15.8
Waushara/Winnebago
WausharajWinnebago county
county line.
line.
Enter Waushara
Waushara County.
County.
(1.3)
(1.3)
17.1
(2.0)
(2.0)
19.1
(1.8)
(1.8)
bogs, like the one north of the highway,
Tamarack bogs,
highway, are common
common in
in poorly—
poorlydrained localities throughout
throughout this
this region.
region.
The truck-farming area south of the road was a former
The
former tamarack
tamarack bog.
When drained by ditching,
ditching, the peaty bog soils are highly productive.
A remnant of the former habitat still exists along the west edge
edge of
of
the tilled
tilled land.
land.
The prominent line of northeasterly trending ridges about
about 33 miles
here is
northwest of here
is part
part of
of the
the Woodfordian
Woodfordian morainal
morainal complex.
complex.
These ridges,
ridges, which
which mark
mark the
the western
western edge
edge of Glacial Lake Oshkosh,
These
Oshkosh,
are older
older than
than the
the patches
patches of Valderan
Valderan till previously traversed.
are
traversed.
Continue west
west on
on 21.
21.
20.9
(0.3)
(0.3)
Junction of Wisconsin 21
21 with 49.
49.
21.2
21.2
(5.2)
(5.2)
Good view
view to
to the
the northwest of the hilly Woodfordian
Good
Woodfordian drift.
drift.
The
soils adjacent
adjacent to the road are lacustrine sediments
pinkish to red soils
Poor drainage
drainage and
that accumulated in Glacial Lake Oshkosh.
that
Oshkosh. Poor
numerous tamarack
tamarack swamps
swamps are
are characteristic
characteristic of
of this
this lowland area.
numerous
area.
13
13
�Mileages
Mileages
26.4
26.4
(1.3)
(1.
3)
Enter Redgranite
Redgranite and
and Junction
Junction with
with County N.
N.
Enter
County NN toward
toward Lohrville.
Lohrville.
County
Proceed
Proceed west
west on
on
Redgranite was
was once
once the
the site
site of
of aa thriving
thriving quarry
quarry operation
operation and
and
Redgranite
pickle factory.
factory. The
aa pickle
The pickle
pickle factory
factory might
might prosper
prosper again,
again, but
but
the quarry
quarry is
is permanently
permanently abandoned.
abandoned. Now
the
Now flooded,
flooded, it
it is
is the
the focus
focus
of aa city
city park.
park.
of
This
This quarry,
quarry, adjacent
adjacent to
to Wisconsin
Wisconsin 21
21 aa few
few blocks
blocks northwest
northwest of
of
here, employed
employed about
about 260
260 workers
workers in
in 1909
1909 to
to produce
produce hand-trimmed
here,
granite paving
paving blocks
blocks for
for aa few cents apiece.
granite
apiece. With
With the
the average
average
trimmer producing
producing up
up to
to 300
300 blocks
blocks per
per day,
day, four
four trains
trains were
trimmer
were
required
required to
to haul
haul the
the daily
daily output
output southward
southward to
to the
the booming
booming towns
towns of
of
Milwaukee, Chicago,
Chicago, and St.
Milwaukee,
St. Louis. Quarrying
Quarrying declined
declined rapidly
rapidly
after 1915,
1915, when
when concrete
concrete became
became the
the preferred road building
after
material. However,
material.
a more modest
However, other
other uses
uses of granite
granite allowed a
operation to continue until the
the pit
pit was
was closed
closed in
in 1931.
1931. By this
time, the
the quarry
quarry occupied
occupied 77 acres
acres and extended downward to aa depth
time,
depth
of 200
of
200 feet.
feet.
As the name of the town indicates,
indicates, the rock
rock exposed here is a
reddish granite.
reddish
granite. It is
and granophyric
granophyric in
in texture,
texture,
is fine-grained and
and leucocratic
leucocratic in
in composition,
composition, with quartz
quartz and alkali feldspar
and
feldspar
comprising 90% to 98% of the
the rock.
rock. Subordinate minerals include
biotite (altered
(altered to
to chlorite),
chlorite), sphene,
muscovite, and
sphene, hornblende,
hornblende, muscovite,
zircon.
zircon. This granite,
granite, like others exposed in
in this
this general
general area,
area, is
is
dated
dated at
at 1765
1765 m.y.
m.y. old.
old. A
A well-exposed,
well-exposed, greenish-black, vertical
vertical
dike of fine—grained
fine-grained metabasalt trends
trends northeasterly across
across the
the lake.
lake.
This dike is about 5 feet
feet wide,
wide, and it
it has sharp
sharp contacts
contacts with
with the
the
granite.
granite.
The Precani1rian
bedrock at
at this locality
Precambrian bedrock
locality was polished
polished and
and striated
striated
by
by westerly
westerly moving
moving Woodfordian
Woodfordian ice.
ice.
27.7
27.7
(0.3)
(0.3)
28.0
28.0
(0.1)
(0.1)
28.1
28.1
(0.1)
(0.1)
28.2
28.2
(0.1)
(0.1)
28.3
28.3
Enter
Enter the
the village
village limits
limits of
of Lohrville,
Lohrville, once aa thriving
thriving center
center for
for
granite
granite quarrying.
quarrying. County NN turns
turns south.
south.
County
County NN turns
turns west.
west. An
An abandoned,
abandoned, small
small quarry
quarry north
north of
of the
the road
road
exposes
exposes aa medium—to
medium-to coarse—grained,
coarse-grained, reddish
reddish granite.
granite.
The
The Lohrville
Lohrville Stone
Stone Company
Company north
north of
of the
the highway
highway occupies
occupies aa building
building
constructed
constructed from
from local
local granite.
granite. The
The piles
piles of
of glacial
glacial erratics
erratics
gathered
gathered together
together by
by this
this firm
firm suggest
suggest that
that these
these are
are aa more
more
important
important commodity
commodity today
today than
than the
the local
local bedrock.
bedrock.
County
County NN turns
turns south.
south. The
The large,
large, glacially-smoothed
glacially-smoothed knob
knob of
of granite
granite
north
of
the
highway
establishes
that
Pleistocene
deposits
north of the highway establishes that Pleistocene deposits are
are thin
thin
in
in this
this area.
area.
Depart
Depart Lohrville
Lohrville as
as County
County NNturns
turns westward.
westward.
(0.8)
(0.8)
14
14
�Mileages
Mileages
29.1
29.1
(0.6)
(0.6)
STOP
STOP 11 at
at Flynn's
Flynn's Quarry
Quarry County
County Park
Park south
south of
of the
the highway.
highway. This
This
park,
park, like
like the
the one
one at
at Redgranite,
Redgranite, is
is developed
developed around
around aa flooded
flooded
granite quarry.
quarry. The
The park
park road
road is
is an
an old
old quarry
quarry road,
road, which
which loops
loops
granite
around
around the
the lake
lake before
before returning
returning to
to County
County Highway
Highway N.
N.
Details
Details on
on the
the geology
geology at this stop are described by Eugene Smith
Smith
in
in the
the next
next section
section of
of this
this guidebook.
guidebook. Unfortunately,
Unfortunately, only
only
30
30 minutes is
is available
available to
to examine
examine this
this interesting
interesting locality:
locality~
After
After stopping,
stopping, continue
continue westward
westward on
on County
County N.
N. The
The route
route ahead
ahead
passes
passes through
through aa low
low area
area occupied
occupied by
by tamarack
tamarack bogs
bogs before
before ascending
ascending
to
to higher, better-drained,
better-drained, Woodfordian
Woodfordian ground
ground moraine.
moraine.
29.7
29.7
(0.5)
(0.5)
County
County N
N turns
turns southward
southward along
along an
an irregular,
irregular, rolling
rolling morainal
morainal ridge.
ridge.
The
The till
till is
is studded
studded with large,
large, locally—derived
locally-derived granitic
granitic erratics.
erratics.
30.2
30.2
(0.2)
(0.2)
Enter community
community of
of Spring
Spring Lake.
Lake.
Enter
30.4
30.4
(0.3)
(0.3)
Junction County
County NNand
in Spring
Spring Lake.
Lake.
Junction
and FF in
30.7
30.7
(4.1)
(4.1)
County NN turns
turns west.
west.
Turn northward
northward on
on N.
N.
County NNand
Z. Turn southwesterly on N
N and
and leave
leave Spring
Spring
Junction County
and Z.
Lake,
Lake, through an area of rolling sandy till
till within the
the Woodfordian
complex. Large glacial erratics of
of local
local derivation
derivation are
are
morainal complex.
common in the fields
fields adjacent to the highway,
highway, and
and several
several kettle
kettle
lakes
general area.
area.
lakes are present in this general
The attractive countryside between here and
and Neshkoro is
is part of
of
As
such,
Green Lake
Lake recessional
recessional moraine.
moraine. As such, it
it has
the Woodfordian Green
little value
value for
agriculture, but
but it is
little
for agriculture,
is highly prized as recreational
land
for
city
dwellers
who
want
to
be
land for city dwellers who want to be weekend "tree farmers."
farmers." The
The
pine plantations that enhance this landscape are
the
are the result
result of
of their
their
endeavors.
34.8
(0.5)
(0.5)
Pine Bluff
Bluff
Enter Marquette County. Pine
Waushara/Marquette county
county line.
line.
This
prominent
landmark
is located about 33 miles west of
is
of here.
here.
landmark is
is
a
glacially-smoothed,
elliptical
knob
of
coarse-grained,
a glacially-smoothed, elliptical knob
coarse-grained, gray to
pinkish granite
granite that
that rises
rises more
more than
than 100 feet
above the swampy
pinkish
feet above
The granite of this
lowlands
River. The
this inlier is lithlowlands along the White River.
related
to
the
granites
exposed in
in the
the
ologically and genetically
genetically related to the granites exposed
Redgranite-Lohrville and Montello areas.
Redgranite-Lohrville
areas.
Glacial striations
striations on
on the
the bedrock
bedrock at
at this
this locality
locality trend
trend about
about
Glacial
N65°W.
35.3
35.3
(0.7)
(0.7)
in an
an area
area
Turn west
west on
on County
County Nand
N and E in
Junction
Nand
E. Turn
Junction County N
and E.
where sand
sand dunes
dunes formed
where
formed on top of the
the sandy Woodfordian drift.
drift.
36.0
36.0
(0.5)
(0.5)
Junction County
County Nand
N and E with Wisconsin 73.
Junction
73.
and
E.
and County
County E.
36.5
36.5
(0.7)
(0.7)
Cemeteries on
on both
both sides
sides of
of the
the highway
highway provide
provide ample
ample evidence
evidence of
Cemeteries
the monument-quality
monument-quality of central Wisconsin granites.
the
granites.
15
15
Turn south
south on
on State
State 73
73
Turn
�Mileages
Mileages
37.2
37.2
Cross White
White River in downtown Neshkoro.
Cross
(0.4)
(0.4)
37.6
37.6
(1.3)
(1.
3)
38.9
38.9
Junction Wisconsin 73,
Junction
73, and County E
E and
and N.
N. Turn west on EE and
and N.
N.
The route
route ahead
ahead leaves
leaves the
the lowland
lowland occupied
occupied by
by the
the White
White River and
The
traverses aa scenic,
scenic, rolling
rolling upland
upland within
within the
the Woodfordian
Woodfordian morainal
traverses
complex.
complex.
and E.
Junction County
County NNand
E.
Continue west on E.
Continue
E.
(1.6)
(1.
6)
40.5
40.5
(2.6)
There are
are several kettle lakes
There
lakes of various sizes developed nearby in
in
sandy, glacial outwash. This
This is
is another
another region
region with
with low agriculagriculsandy,
tural potential,
potential, which
which is
is rapidly
rapidly being
being converted to
to recreational
tural
recreational
!Ifarms
"farms."
43.1
43.1
(0.4)
Junction County E and
and Wisconsin
Wisconsin 22.
22.
43.5
43.5
(0.6)
Wisconsin granite
granite headstones
headstones dominate the cemetery east of
Central Wisconsin
the highway.
44.1
44.1
(0.3)
Junction County E and Wisconsin
Wisconsin 22. Continue south
south on
on 22.
22. The
route ahead
ahead traverses
traverses sandy,
sandy, rolling,
route
rolling, Woodfordian ground moraine.
moraine.
44.4
44.4
(4.0)
(4.
0)
48.4
(2.9)
(2.9)
51.33
51.
(1.6)
(1. 6)
52.9
52.9
Turn
22.
Turn south on E and 22.
Cross Mecan River,
River, one of many fine
fine trout
trout streams
streams in
in central
central
Wisconsin.
Peat swamps along the highway were drained and
and developed
developed as
as muck
muck
farms.
The route
traverses a
The
route ahead traverses
a stony till formed into broad,
broad,
low drumlins with aa general
general east—west
east-west orientation.
orientation. This better—
betterdrained land
supports aa growth of pine and
land supports
and cedar.
cedar.
The sand and gravel pit east of the
the road
road is
is developed
developed in
in Woodfordian
Woodfordian
outwash.
outwash. Kettles are
are also
also present
present in
in this
this area.
area.
Enter the
the city
city of
of Montello.
Montello.
(0.5)
(0.5)
53.4
53.4
(0.3)
(0.3)
53.7
53.7
(0.1)
(0 .1)
Junction of
of Wisconsin
Wisconsin 22
22 with
with 23
23 in
in Montello.
Montello.
22
22 and
and 23.
23.
Turn west on Wisconsin
Quarries north of the
the highway exploited aa ridge
ridge of
of finefine- to
to mediummediumgrained,
red
to
grayish—red
granite
to
produce
monument
stone,
grained, red to grayish-red granite to produce monument stone,
paving
paving blocks,
blocks, building
building stone,
stone, and
and crushed
crushed rock.
rock. When
When this
this granite
granite
was
was selected
selected for
for the
the tomb
tomb of
of U.S.
u.s. Grant
Grant in
in New
New York
York City,
City, business
business
boomed.
activity peaked,
peaked, with
with some
some 200 workers employed.
boomed. By 1910,
1910, activity
employed. In
In
later
later years,
years, business declined until the
the last
last quarry
quarry closed
closed in
in 1976,
1976,
after nearly
nearly 100
100 years
years of
of operation.
operation. The
The longevity
longevity of
of operations
operations at
at
this locality
locality was facilitated
facilitated by well—developed
well-developed vertical
vertical joints
joints that
that
allowed the
the rock
rock to
to be
be removed
removed in
in large
large "precut"
"precut" blocks.
blocks.
The granite of this
this inlier is granophyric and leucocratic like
area and
and at
at Pine
Pine Bluff.
Bluff. It
It
those
those exposed in
in the
the Redgranite-Lohrville
Redgranite-Lohrville area
is
is also
also of
of the
the same
same age
age (1765
(1765 m.y.
m.y. old).
old). Several
Several near-vertical
near-vertical dikes
dikes
16
16
�Mileaqe
of
of greenish-black,
greenish-black, fine-grained
fine-grained metabasalt
metabasalt up
up to
to 55 feet
feet thick
thick cut
cut
the
the granite,
granite, and
and are
are well
well exposed
exposed in
in the
the quarries.
quarries.
Well
monadnock
Well drilling
drilling adjacent
adjacent to
to the
the granite
granite ridge
ridge discloses
discloses that
that this
thismonadnock
stood
stood more
more than
than 200
200 feet
feet above
above the
the general
general level
level of
of the
the Precambrian
Precambrian
surface
surface prior
prior to
to transgression
transgression of
of the
the Late
Late Cambrian
Cambrian sea
sea (see
(see article
article
by
by Eugene
Eugene I.
I. Smith
Smith in
in this
this guidebook).
guidebook).
Glacial
Glacial striae
striae on
on the
the bedrock
bedrock surface
surface indicate
indicate
ice moved westerly
westerly across
across this
this area.
area.
ice
53.8
53.8
(0.5)
(0.5)
54.3
54.3
(0.4)
(0.4)
Junction Wisconsin
Wisconsin 22
22 and
and 23.
23.
Junction
that
that the
the Woodfordian
Woodfordian
Turn
Turn south
south on
on State
State 22.
22.
Cross the
the Fox
Fox River
River once
once
Cross
again.
again. The
The Fox flows
flows northeasterly
northeasterly to
to reach
reach
Lake Winnebago,
Winnebago, and
and ultimately Lake
Lake Michigan at
at Green
Green Bay.
Bay. We
We first
first
crossed it
it about
about 46
46 miles
miles ago,
ago, at
at Omro.
Omro.
The Fox was part of the historic canoe
canoe highway
highway across
across Wisconsin.
Wisconsin.
Although used
used by
by Indians
Indians for
for centuries,
centuries, it
it was
was "popularized"
"popularize& by
Marquette and
and Joliet on their
their historic journey
journey from
from Lake
Lake Michigan
Michigan
A
flood
of
explorers,
missionaries,
trappers,
Mississippi. A flood
trappers,
to the Mississippi.
The Fox is dammed just
and traders
traders soon
soon paddled
paddled after
after them.
them.
just upstream
and
and enlarge
enlarge Buffalo
Buffalo Lake.
Lake. Thelocks
The locks visible from
from here to deepen and
the highway were part of
of a
a navigation scheme
scheme originally
originally designed
designed
to link the
the North Atlantic (via
the
Great
Lakes)
with
the
Gulf of
(via
Lakes)
Shifting
Mexico (via
the
Wisconsin
River
and
the
Mississippi).
(via the Wisconsin River and the Mississippi).
Shifting sandsandbars along the
shallow
Wisconsin
River
ruled
against
this
the
River ruled against this plan
plan from
from
the beginning.
1.5
A canal at
Portage, Wisconsin was started in 1838 to eliminate the
at Portage,
the 1.5
mile land bridge between the headwaters of the Fox and the Wisconsin
mile
This project was finally completed in 1876,
River.
1876, but the cost of
maintaining a
a channel in the Wisconsin River proved prohibitive,
prohibitive, and
and
soon abandoned.
abandoned.
the project was soon
54.7
(1.
8)
(1.8)
56.5
(1.
7)
(1.7)
58.2
58.2
(1.
5)
(1.5)
into an
an
Leave Montello and
Leave
and the
the lowland
lowland along
along the
the Fox
Fox River,
River, and proceed
proceed into
area
ground moraine.
moraine.
area of rolling,
rolling, Woodfordian ground
The prominent,
prominent, wooded
wooded hill
hill about
about 44 miles
miles to
to the
the southwest
southwest is
is
The
Observatory Hill,
Hill, the highest point in
with an
an
Observatory
in Marquette
Marquette County,
County, with
This will
will be the locale of our
elevation
feet.
This
our second
second stop.
stop.
elevation of 1080 feet.
deposited in
The
in aa
The truck
truck farms
farms in
in this
this flat
flat area
area utilize
utilize fertile
fertile soils
soils deposited
glacial lake,
lake, which
which formed
formed when
when northeasterly
northeasterly drainage
drainage was
was blocked
glacial
by
ice.
by the
the retreating Woodfordian ice.
59.7
59.7
(0.2)
(0.2)
We will
will return
return to this
Junction
B. We
this interJunction Wisconsin 22 and County B.
loop.
section in
in aa few
few hours,
hours, and
and go
go east
east on
on BB after
after making
making aa large
large loop.
section
outwash.
Continue south
south on
on State
State 22
22 in
in an
an area
area of
of pitted
pitted sandy
sandy outwash.
Continue
purity of
of
Gravel
Gravel pits
pits in
in this
this area
area are
are testimony
testimony to
to the
the water-washed
water-washed purity
these
these deposits.
deposits.
59.9
59.9
(0.9)
(0.9)
Our
Turn east on Gem Road.
Junction
22. Turn
Road. Our
Junction Gem
Gem Road
Road and Wisconsin 22.
southwest
immediate destination
destination is
is Observatory
Observatory Hill,
Hill, about
about 22 miles
miles southwest
immediate
17
17
�Mileages
Mileages
of here.
here. To
To
of
and
approach
and approach
reach our
our objective,
objective, we
we must
must circle
circle this
this promontory,
promontory,
reach
from the
the west.
west.
A small
small kettle is located northwest
northwest of
of the
the highway.
highway.
60.8
60.8
(1.4)
(1.4)
Large glacial
glacial erratics
erratics of
of local
local derivation
derivation litter the field north of
Large
the road.
the
road.
62.2
62.2
(0.2)
Junction 14th Road and Gem Road.
Junction
Road.
62.4
62.4
(1.0)
Junction 14th Road and 13th Road. Turn
Junction
(left) on 13th Road
Turn south (left)
in an
an area of rolling ground moraine. At long last,
in
last, we are closing
in on Observatory
Observatory Hill!
in
Hill~
63.4
63.4
(0.5)
An irrigation well west of the road encountered Precambrian
Precambrian porphyritic rhyolite,
rhyolite, lithologically identical to
to exposures
exposures on
on
Observatory Hill,
Hill, at a
a depth of
of 300
300 feet.
feet.
63.9
63.9
(0.4)
(0.4)
64.3
64.3
(1.1)
(1.1)
Turn
(left) on 14th Road.
Road.
Turn west
west (left)
-
Junction 13th Road and Gillette Ave.
Ave. Proceed southeasterly (straight
(straight
ahead) on
on Gillette
Gillette Ave.
Ave. and ascend the
ahead)
the flank
flank of Observatory Hill.
Hill.
STOP 22 for
for Observatory
Observatory Hill rhyolite.
STOP
rhyolite. This bedrock hill,
hill, which rises
rises
about 250
above the
level of the surrounding landscape,
about
250 feet
feet above
the level
landscape, has aa
core of resistant
core
resistant rhyolite
rhyolite flanked by medium—to
medium-to coarse—grained,
coarse-grained,
friable,
friable, iron-stained Upper
Upper Cambrian
Cambrian sandstone.
sandstone. Locally,
Locally, this sandgrades into a
stone grades
a conglomerate that contains clasts derived from
from
the Precambrian bedrock.
the
bedrock.
Glacial striae on the rhyolite vary from N45W to N74W,
Glacial
N74W, and record
record
the movement of ice over and around this resistant knob.
the
knob.
A
A detailed description of the
the rocks
rocks at
at this
this locality
locality is
is provided
provided by
by
Eugene Smith
Smith in
in the
the next
next section
section of
of this
this guidebook.
guidebook. Since only 60
60
minutes is
is allocated for
for this
this stop,
stop, we should
should proceed
proceed with
with
enthusiasm:
enthusiasm~
NOTE:
Since this road dead ends
ends about
about 0.4 mile ahead, backtrack northwesterly to
to the
the intersection
intersection of
of Gillette
Gillette Road
Road and
and 13th
13th Road.
Road. The
logged mileage that follows
follows' assumes a turn—around
turn-around at the
the dead end
end
of Gillette
Gillette Road
Road after
after this
this stop.
stop.
a
65.4
65.4
(0.7)
(0.7)
66.1
66.1
(0.2)
(0.2)
66.3
66.3
(0.4)
(0.4)
66.7
66.7
(1.5)
(1.5)
Intersection of Gillette Road
Road and
and 13th
13th Road.
Road. The bedrock
bedrock of
of the
the high,
high,
wooded hill west of
of this
this intersection
intersection is
is Upper Cambrian
Cambrian sandstone
sandstone
with no
no rhyolite
rhyolite exposed.
exposed. Turn south
south on
on 13th
13th Road.
Road.
13th
13th Road
Road turns
turns sharply
sharply to
to the
the west
west in
in an
an area
area of
of rolling
rolling countryside
countryside
formed by aa Woodfordian
Woodfordian recessional
recessional moraine.
moraine Pine plantations, cedars,
cedars,
and oaks accentuate
accentuate the
the beauty
beauty of
of this
this glacial
glacial landscape.
landscape.
Junction
Junction 13th
13th Road
Road and
and Gillette
Gillette Drive.
Drive. Continue
Continue west
west on
on Gillette.
Gillette.
NOTE:
NOTE: It
It seems
seems that
that the
the Gillettes
Gillettes are
are important
important in
in this
this country!
country~
AA low
low bedrock
bedrock ridge
ridge north
north of
of the
the road
road is
is the
the Taylor
Taylor Farm
Farm rhyolite
rhyolite
locality.
porphyritic rhyolite exposed here
locality. The
The well-jointed,
well-jointed, porphyritic
here is
is
18
18
�Mileages
Mileages
similar
similar to
to that
that found
found on
on Observatory
ObservatoryHill.
Hill. However,
However, the
the high
high bedbedrock
rock hill
hill of
of sandstone
sandstone northeast
northeast of
of here
here separates
separates these
these two
two
localities. Glacial
Glacial striae
striae on
on this
this rhyolite
rhyolite document
document aa general
general
localities.
N70W
N70W direction
direction of
of ice
ice flow
flow for
for the
the Green
Green Bay
Bay lobe
lobe of
of Woodfordian
Woodfordian
ice at
at this
this locality.
locality.
ice
Turn
Turn south
south on
on County
County F.
F.
68.2
68.2
(0.2)
(0.2)
Junction
Junction Gillette
Gillette Drive
Drive and
and County
County F.
F.
" 68.4
68.4
LUNCH STOP
STOP at
at John
John Muir
Muir County
County Park
Park on
on Ennis
Ennis Lake.
Lake.
LUNCH
(1. 4)
(1.4)
John
John Muir,
Muir, aa distinguished
distinguished naturalist
naturalist and
and aa prime
prime mover
mover in
in the
the
establishment
establishment of
of our
our national
national park
park system
system in
in 1890,
1890, was
was born
born in
in
His
family
came
to
Wisconsin
to
farm
the
land
Scotland
in
1838.
His
family
came
to
Wisconsin
to
farm
the
land
Scotland in 1838.
he
was
only
a
boy
of
across
the
lake
from
this
memorial
park
when
he
was
only
a
boy
of
across the lake from this memorial park when
Fountain
Lake
11.
He
grew
up
on
this
beautiful
kettle
lake
(called
Fountain
Lake
He grew up on this beautiful kettle lake (called
11.
ingredient
in
the
in
those
days),
and
it
proved
to
be
a
significant
ingredient
in
the
in those days), and it proved to be a significant
development
of
his
love
of
nature.
development of his love of nature.
The
The importance
importance of
of this
this lake
lake to
to Muir
Muir is
is well
well documented
documented on
on page
page 96
96
Youth"
(University
of his autobiography,
autobiography, "The
"The Story of My Boyhood
Boyhood and
and Youth" (University
Press, 1965).
1965).
of Wisconsin Press,
"Our beautiful
beautiful lake,
lake, named Fountain Lake by father,
father, but Muir's
Muir's Lake
Lake
lakes
by the neighbors,
neighbors, is one of the many small
small glacier
glacier lakes that
that adorn
adorn
It is
Wisconsin landscapes.
landscapes.
is fed by twenty or thirty meadow
the Wisconsin
surrounded by
by
springs, is
is about
about half a
mile long,
wide, and surrounded
springs,
a mile
long, half as wide,
meadows
low finely-modeled
hills
dotted
with
oak
and
hickory,
and
finely-modeled hills
hickory,
meadows
and ferns.
full of grasses
ferns.
full
grasses and
and sedges
sedges and many beautiful orchids and
First there
a zone
rushes, and just
just beyond
beyond the
the
there is
is a
zone of green,
green, shining rushes,
fifty or
or sixty
rushes
sixty feet
feet
rushes aa zone
zone of
of white
white and orange
orange water-lilies fifty
On bright days,
forming aa magnificent
magnificent border.
border.
days, when the lake
wide forming
sun—spangles
danced together
together
breeze, the lilies
lilies and
and sun-spangles danced
was rippled by a breeze,
between
in radiant
radiant beauty,
beauty, and
and it
it became
became difficult
difficult to
to discriminate
discriminate between
in
them.
them.
and Bible-lessons,
Bible—lessons,
On
chores and sermons and
On Sundays,
Sundays, after or before
before chores
especially
in
lily time,
we
the lake
lake for
for hours,
hours, especially in lily
time,
we drifted about on the
ducks,
getting finest
finest lessons
lessons and
and sermons
sermons from
from the
the water
water and flowers,
getting
flowers, ducks,
In particular
particular we
we took
took Christ's
Christ's advice
advice and
and
fishes,
fishes, and
and muskrats.
muskrats. In
they grow
grow up
up in
in beauty
beauty out
out
how they
devoutly
devoutly "considered the lilies" -- how
ideglOri0USlY
among
the
breezy
sun-spangles."
of
of gray
gray lime
lime mud,
mud, and
and ride gloriously among the breezy sun-spangles."
of rolling,
rolling,
After lunch,
lunch, continue
continue south
south on
on County
County FF through
through an
an area of
After
Immediately to
to the
the west,
west, the
the north-flowing
north-flowing Fox
Fox River
River
sandy
sandy drift.
drift. Immediately
parallels
parallels the
the highway.
highway.
69.8
69.8
(1.
7)
(1.7)
The rolling,
rolling, sandy,
sandy,
Turn east
east on
on County 0.
Junction
O. Turn
o. The
Junction County
County F and 0.
Differences
ground moraine
moraine contains
contains large
large erratics
erratics scattered about.
ground
about. Differences
with tamaracks
tamaracks
in
in drainage
drainage are
are clearly
clearly reflected
reflected in
in the vegetation,
vegetation, with
the
higher,
well—
in
in swampy
swampyplaces,
places,and
andoaks
oaksand
andplantation
plantation pines
pines on
on the higher, welldrained
drained soils.
soils.
19
19
�Mileages
Mileages
71.5
71.
5
(1.4)
(1.
4)
72.9
72.9
Junction County
County 00 and
and 13th
13th Road.
Road.
Junction
Turn
Road.
Turn south
south on
on 13th Road.
Knights Lake,
Lake, on
on the
the east
east side
side of
of the
the road,
road, occupies
occupies aa small
Knights
small kettle.
kettle.
(0.7)
(0.7)
73.6
73.6
(0.4)
(0.4)
Junction 13th Road and 14th Road.
Junction
Road. Turn
(right) on 14th Road.
Road.
Turn south
south (right)
This road
road curves
curves eastward immediately ahead.
This
ahead.
74.0
74.0
(0.9)
(0.9)
Junction 14th
14th Road
Road and
and Dalton
Dalton Road
Junction
Road at
at the
the Marquette/Columbia
Marquette/Columbia county
line.
Turn south
south (right)
on Dalton
Dalton Road
Road and
and enter
enter Columbia County,
County,
line.
Turn
(right) on
through rolling
rolling country
country with
with some
some land
land suitable
suitable for
agriculture.
through
for agriculture.
74.9
74.9
(0.2)
(0.2)
Junction Dalton
County CM.
CM.
Junction
Dalton Road
Road arid
and County
Turn
(right)
Turn southwesterly (right)
County CM
CM in
in an
an area with abundant erratics.
County
erratics. We
will
backtrack
We will
this intersection after Stop 3.
this
3.
75.1
75.1
(0.4)
(0.4)
well on
on the
the A.
A. Uchtung farm on the right side of the road reached
A well
Precambrian rhyolite at
at aa depth
depth of
of 390
390 feet.
feet. Drilling continued 170
feet
into
the
rhyolite.
feet into the rhyolite.
75.5
75.5
(0.6)
(0.6)
76.1
76.1
(0.1)
(0.1)
76.2
76.2
(0.7)
(0.7)
Junction County CM and
and Monthey
Monthey Road.
Road.
Road.
Road.
on
to
Turn south (left)
(left) on Monthey
Exposure
road.
Exposure of Middle
Middle Precambrian Marcellon rhyolite east of the road.
This is
is one
one of four
This
four isolated exposures of rhyolite in this immediate
immediate
area.
area.
STOP 33
at Marcellon rhyolite locality.
STOP
locality. This scenic exposure is
is aa
70 feet
feet above
above
glacially rounded and polished knob that rises nearly 70
the surrounding
surrounding countryside.
countryside. Glacial striae indicate aa westerly
direction for
for Woodfordian
Woodfordian ice
ice flow
flow at
at this
this locality.
locality.
A
A detailed description of
of the geology
geology to
to be
be observed
observed here
is
is supplied
supplied by Eugene Smith
Smith in
in the
the next
next section
section of
of this
this guidebook.
guidebook.
only 45
45 minutes for
for an
an examination
examination of
of this
this
Unfortunately, we have only
interesting
interesting exposure.
exposure.
After studying
studying the
the rock
rock here, turn
turn around
around and
and backtrack
backtrack northward
northward
along
along Monthey
Monthey Road.
Road.
76.9
76.9
Junction
Junction Monthey
Monthey Road
Road and
and County
County CM.
CM.
Turn northeast
northeast (right)
(right) on
on CM.
CM.
Turn
(0.6)
(0.6)
77.5
77.5
(2.7)
(2. 7)
80.2
80.2
(0.6)
(0.6)
80.8
80.8
(0.2)
(0.2)
Junction
Junction CM
CM and
and Dalton
Dalton Road.
Road. Continue
Continue northeastward
northeastward on
on CM
CM through
through
rolling,
rolling, glacial
glacial countryside.
countryside.
Junction
Junction County
County CM
CM and
and Wisconsin
Wisconsin 22.
22. Turn
.=T:.. :u:.::r:..:.n=-.north
. :n.:.:o::..:r=.t.=.h:..:. . .(left)
--'(.=1:.. :e:.. :f::..:t"-'):.. .-o::.on
.:n:..:. . . =State
S:.. :t:..:.a::..:t::..:e::.. . .22
. :2::..:2=.
and
and cross
cross Columbia/Marquette
Columbia/Marquette county
county line.
line. Enter
Enter Marquette
Marquette County
County
once
once again.
again.
State
State Historical
Historical Marker
Marker on
on the
the east
east side
side of
of the
the highway
highway is
is entitled
entitled
"John
"John Muir
Muir Country,"
Country," and
and it
it describes
describes his
his sojourn
sojourn in
in this
this area.
area. It
It
also
also includes
includes this
this meaningful
meaningful quote
quote of
of Muir's:
Muir's:
20
20
�Mileages
Mileages
"Everybody needs beauty as well as
as bread;
bread;
places to
play
in
and
places
to
pray
to
in and
to pray in,
in,
where nature may heal
heal and
and cheer,
cheer, and
and give
give
strength to body and
and soul
soul alike."
alike."
81.0
(1.
2)
(1.2)
The house
house west of the
fieldstone, the trade
82.2
(3.6)
Wisconsin 22
22 climbs
climbs onto a
a highland littered
littered with
with glacial
glacial erratics.
erratics.
85.8
(3.5)
road
name
is a
a showplace for samples of Wisconsin
for
for glacial
glacial erratics.
erratics.
Junction Wisconsin
Wisconsin 22
22 and
and County
County B.
B. Turn east on County B, in
in a
a
region of sandy outwash
outwash occupied
occupied by
by gravel
gravel pits.
pits. The route ahead is
is
numerous swamps,
characterized by numerous
swamps, some of which are drained for muck
farming. Higher areas support
support pine
pine plantations.
plantations.
89.3
(0.7)
Marquette/Green
Marquette/Green Lake
Lake county
county line.
line.
Enter Green Lake
Lake County.
County.
90.0
(3.1)
(3.1)
The poorly drained lowland
lowland north of
of the
the road
road is
is part
part of
of the
the extenextensive Grand River Wildlife Area.
Area. When the retreating Woodfordian ice
dammed the
the northeastward flowing
flowing drainage
drainage of
of the
the Fox
Fox and
and Grand
Grand rivers,
rivers,
In time,
time, it filled with meltaa glacial lake formed
formed in
in this
this area.
area. In
water,
westward into
water, and overflowed westward
into the
the Wisconsin River.
River. However,
continued retreat of the Green Bay lobe
lobe of the Woodfordian ice redrainage, and this lake was emptied.
However, Lake
stored northeasterly drainage,
emptied. However,
Puckaway and
and Buffalo Lake
Lake exist
exist as
as remnants
remnants of
of this
this ancient
ancient water
water body.
body.
93.1
Junction County
and H..
Junction
County BBand
H.
Continue northeasterly (left)
(left) on
on BBand
H.
and H.
(0.3)
93.4
(2.4)
95.8
(0.5)
(0.5)
96.3
(0.3)
and H.
Junction County B
Band
H. Turn north
north on
on County
County H.
H. The high,
high, wooded
hill to the northeast of this
this intersection
intersection is
is Bartholomew
Bartholomew Bluff.
Bluff. It
It
is a
is
a bedrock feature
feature composed of Upper Cambrian formations
formations capped
by resistant Lower Ordovician dolomite
dolomite of
of the
the Prairie
Prairie du
du Chien
Chien Group.
Group.
The route ahead traverses the
the east
east edge
edge of
of an area of
of poorly—drained,
poorly-drained,
glacial lake
deposits now occupied by the Grand River Marsh.
glacial
lake deposits
Marsh.
The bedrock hill immediately northwest of the
the road
road is
is one of several
isolated rhyolite exposures,
exposures, which trend northwestward from
from here for
for
about
one
mile.
about one mile. In
In all,
all, there
there are
are seven rhyolite knobs
knobs in this general
area.
area. These features
features stood several hundred feet
feet above
above the
the general
general Precambrian erosional level as monadnocks,prior to transgression of
of the
the
Upper Cambrian sea (see
(see article by Eugene I.
I. Smith in this guidebook).
guidebook).
STOP 4
STOP
4 at an exposure of the
the Marquette
Marquette rhyolite.
rhyolite. The cedar-covered,
cedar-covered,
glacially-smoothed, bedrock
bedrock knob west of the highway rises about
glacially-smoothed,
100 feet
above poorly-drained tamarack swamps to the north.
100
feet above
north. A
A similar
exposure lies immediately east
east of
of the
the road.
road.
Glacial striations and chatter marks on the bedrock indicate
indicate that
that the
the
Woodfordian ice generally moved westward at this locality.
locality. However,
measurements vary
vary from
from N57W
N57W to
to N86W.
N86W.
analysis of
of the
the rhyolite
rhyolite at
at this
this stop
stop is
is provided
provided by
by Eugene
Eugene Smith
An analysis
in the next section
section of
of this
this guidebook.
guidebook. About 60
60 minutes are available
to study the
the exposures
exposures at
at this
this locality.
locality.
21
�Mileages
After examining the rhyolite,
rhyolite, continue northeasterly on County H.
H.
96.6
(1.0)
(1.
0)
97.6
(3.8)
KK. Turn
Turn east (right)
and KK.
Junction County H
H and
and KK.
(right) on H
Hand
KK. The route
ahead traverses
traverses rolling
rolling ground
ground moraine
moraine studded with
with numerous
numerous erratics.
erratics.
ahead
The shape of the east—west
east-west trending drumlin south of the road
road estab—
establishes that ice movement in this area
lishes
area was
was to
to the
the west.
west.
Junction County H,
Continue straight ahead (east)
H, KK,
KK, and
and B.
B. Continue
(east) on
County H. The route ahead traverses scenic,
County
scenic, glacial countryside
countryside with
some agricultural potential.
some
potential. Lake
Lake Puckaway,
Puckaway, an
an enlargement of the
Fox River,
River, is occasionally
occasionally visible
visible to
to the
the north.
north.
101.4
(2.1)
Junction County HH and
Wisconsin 73. Turn south (right)
and Wisconsin
(right) on State
State 73.
73.
The route ahead traverses
traverses rolling
rolling agricultural
agricultural land.
land.
103.5
(0.3)
Junction Wisconsin 73
73 and
and 44.
44.
103.8
(0.6)
Enter Manchester,
Manchester, a
a hilltop community astride the
the Green Lake
Lake recessional
recessional
moraine. This prominent glacial feature,
feature, which trends
trends north-northwestnorth-northwestward and south—southeastward
south-southeastward from
from here,
here, formed
formed as
as the
the Green Bay
Bay lobe
lobe
of the Woodfordian ice paused
paused during
during retreat.
retreat.
104.4
104.4
(0.4)
Leave Manchester in an
an easterly
easterly direction.
direction. The boundary between two
major physical provinces trends
trends northeast—southwest
northeast-southwest through
through this
this area.
area.
The Central Plain,
Plain, to the
northwest, is a
The
the northwest,
a subdued region characterized
by Upper
Upper Canibrian
Cambrian bedrock.
The Eastern Ridges and Lowlands,
Lowlands, with
younger bedrock, occupies the
the region
region to
to the
the east
east and
and southeast.
southeast.
However, this
However,
this division is ill—defined
ill-defined here because of the thick cover
cover
of young glacial
glacial deposits.
deposits.
104.8
(0.4)
(0.4)
Junction Wisconsin 73
73 and
and 44.
44.
rolling agricultural
agricultural land.
land.
105.2
105.2
Cross Grand River.
River.
Continue south on 73
73 and
and 44.
44.
Turn south on State 73 in an area
area of
(1.6)
(1. 6)
106.8
106.8
(0.7)
(0.7)
The highway intersects
intersects aa drumlin
drumlin that
that trends
trends east-west.
east-west. The blunter,
east—facing
east-facing nose of this drumlin indicates westerly ice
ice movement in
in
this area.
area.
107.5
107.5
Lake Maria,
Maria, east of the highway,
highway, lies
lies along the trend of the
the Green
Lake recessional moraine.
moraine.
(1.8)
(1. 8)
109.3
(0.6)
(0.6)
Green Lake/Columbia
Lake/Columbia county
county line.
line. Enter Columbia County in
in an
an area
area
where intensively farmed
farmed drumlins stand
stand above
above flat,
flat, low
low areas
areas that
that
are poorly
poorly drained.
drained. When drained,
drained, these lowlands
lowlands are
are productive
muck farms.
farms.
109.9
109.9
(2.9)
(2.9)
Several roadcuts
the next 0.5 mile expose thin-to medium-bedded
roadcuts in the
Lower Ordovician
Ordovician dolomite
dolomite of
of the
the Prairiedu
Prairie du Chien
Chien Group.
Group. Some of
of
these bedrock exposures form
form the
the cores
cores of
of drumlins.
drumlins.
112.8
112.8
(2.0)
(2.0)
The high-voltage power lines crossing the highway come
come from
from aa large,
large,
coal-fired power plant
plant at
at Portage.
Portage. This facility
facility utilizes Wisconsin
River water
water as
as aa coolant.
coolant.
22
22
�Mileages
Mileages
114.8
114.8
(0.5)
(0.5)
Junction
Junction Wisconsin
Wisconsin 73
73 and
and 33.
33.
115.3
115.3
(1.0)
(1.0)
Enter Randolph.
Randolph.
Enter
116.3
116.3
(0.2)
(0.2)
Leave
Leave Randolph.
Randolph.
'116.5
ll6.5
(13.0)
(13.0)
Continue
Continue south
south on
on 73.
73.
Cross
Cross Columbia/Dodge
Columbia/Dodge county
county line,
line, as
as Wisconsin
Wisconsin 73
73 turns
turns east,
east, and
and
then south.
south. Enter
Enter Dodge
Dodge County.
County. The route
route ahead
ahead traverses
traverses rich
rich
agricultural land
land developed on a swarm
swarm of broad, well—formed,
well-formed, southsouthwesterly-trending drumlins.
drumlins.
westerly-trending
129.5
129.5
(1.3)
(1.3)
Junction Wisconsin 73
73 and
and U.S.
u.s. 151.
151.
130.8
130.8
(0.9)
(0.9)
Dodge/Columbia
Dodge/Columbia county
county line.
line. Enter Columbia County and
and the
the city
city of
of
Cross
southeasterly
flowing
Crayfish
River.
Columbus.
southeasterly
flowing
Crayfish
River.
Columbus.
131.7
131.7
(0.6)
(0.6)
Junction Wisconsin
Wisconsin 73
73 and
and 89
89 in
in Columbus.
Columbus.
Wisconsin
89.
Wisconsin 89.
132.3
132.3
(3.0)
(3.0)
Leave Columbus.
Columbus. The route
route ahead
ahead traverses
traverses intensively
intensively farmed,
farmed, rolling,
rolling,
glacial countryside.
countryside.
135.3
135.3
(4.8)
(4.8)
Columbia/Dane county
county line.
line. Enter Dane County.
County.
drumlins here trend
trend southwesterly.
southwesterly.
140.1
(1.4)
(1.4)
Dane/Dodge county
county line.
line.
drumlins.
141.5
(0.7)
(0.7)
Stop sign at junction
junction of
of Wisconsin
Wisconsin 89
89 and
and County
County T.
T.
(east) on
on Dalman
Dalman Road.
Road.
ahead (east)
142.2
(1.0)
(1.0)
Junction Dalman Road
Road and
and County
County I.
I.
143.2
(1.0)
(1.0)
village of Portland and junction with Wisconsin 19.
Village
19.
19, and
and leave
leave Portland.
Portland.
on State 19,
144.2
(0.3)
(0.3)
Cross Maunesha
Maunesha River.
River.
144.5
(0.1)
(0.1)
Knobs of
of glacially-smoothed,
glacially-smoothed, Middle
Middle Precambrian
Precambrian Waterloo Quartzite
Knobs
These exposures
exposures are
are two of
lie
lie north
north and south of the highway. These
about aa dozen
dozen quartzite
quartzite knobs
knobs that
that protrude
protrude through the
the glacial drift
about
All of the
the exposures
exposures are
are smoothed by glacial
in
area. All
in this general area.
action, and
and some
some have
have small potholes developed
action,
developed on
on the
the upper
upper surfaces.
surfaces.
This quartzite
quartzite is
is quite
quite
This
Baraboo syncline,
syncline, about
Quartzite, ripple
ripple marks
marks
Quartzite,
also present
present within
within the
also
Continue south
south on
on State
State 73.
73.
Turn south
south (left)
(left) on
on
Broad,
Broad, well-shaped
Enter Dodge County in an area with occasional
Proceed straight
Turn south (right)
(right) on County
County I.
I.
Turn northeast
to that
that exposed in the well-known
similar to
Like the
the Baraboo
35
35 miles to
to the
the northwest.
northwest. Like
cross
bedding, and conglomeratic beds are
cross bedding,
thick quartzite sequence
sequence in
in this
this area.
area.
23
23
�Mileages
The structure here is an easterly plunging
The
plunging syncline.
syncline.
as at
at Baraboo,
Baraboo, may have occurred 1650
as
1650 m.y.
m.y. ago.
ago.
This folding,
folding,
Measurements of glacial striae indicate that the ice flowed
Measurements
flowed about
S2OW at
at this locality.
S20W
locality.
144.6
(0.3)
STOP 5 at
at the
the abandoned
abandoned John
John O'Laughlin
O'Laughlin quarries
quarries in
in the
the Waterloo
Waterloo
STOP
Quartzite.
The quartzite
quartzite at
this stop is described by Eugene Smith in the next
The
at this
minutes Is
section of this
this guidebook.
guidebook. About 30
30 minutes
is allotted to
assimilate the geology at
at this
this locale.
locale.
144.9
144.9
(1.7)
Junction Wisconsin 99
99 and
and Hubbleton
Hubbleton Road.
Road.
19.
Proceed east on Wisconsin
About 1 mile north along
along Hubbleton Road,
Road, in
in the
the ditch
ditch along
along the
the
eastern edge
edge of the
the road,
eastern
road, an isolated exposure of Paleozoic conglomThis conglomerate,
erate is
is present.
present. This
conglomerate, which contains rounded Waterloo
Quartzite boulders
boulders up to 66 feet
across, is probably a
Quartzite
feet across,
a local facies
facies
of the Middle Ordovician St.
St. Peter
Peter Sandstone.
Sandstone.
It is
is also one of the
few Paleozoic exposures in
in this
this general
general area.
area.
About 0.5
0.5 mile
mile straight north of the St.
About
St. Peter conglomerate locality,
locality,
at the
at
the junction of Maunesha Creek and the Crawfish River,
River, is
is Stony
Stony
Island.
This is
This
is another glacially rounded mass of Waterloo Quartzite.
Here, several pegmatite dikes
dikes up to 3.2 feet thick intruded the
Here,
quartzite after
after folding.
folding.
These dikes were dated by L.T.
L.T. Aldrich and
and
others in 1959 as
as 1444
1444 m.y. old.
old.
The route
more drumlin county,
The
route ahead traverses
traverses more
county, although the agricultural potential is
not
as
good
as
it
was
is
as good as it was east
east of
of Portland.
Portland.
146.4
146.4
(0.4)
Easterly dipping
Middle Precambrian Waterloo Quartzite adds
dipping ledge
ledge of Middle
adds
interest to
Interto the lawn of the
the farmhouse
farmhouse south of the highway.
highway.
mittent exposures indicate
indicate that
that this
this ledge
ledge persists
persists southward
southward along
along
strike for
almost
a
mile.
for almost a mile.
147.0
(0.3)
(0.3)
Another exposure of Waterloo Quartzite is
is visible
visible about
about 100
100 yards
yards north
north
of the
highway.
the highway.
147.3
(0.5)
(0.5)
Junction Wisconsin
Wisconsin 19
19 and
and County
County GG (north).
(north).
Continue east
east on
on 19.
19.
Exposures of brecciated Waterloo Quartzite cemented
cemented by
by milky
milky quartz
quartz
are located about 0.75
0.75 mile to
to the
the north.
north. Additional exposures of
quartzite are present in
in the
the vicinity
vicinity of
of Mud
Mud Lake,
Lake, about
about 55 miles
miles
north—northeast
north-northeast of
of here
here along
along County
County G.
G.
147.8
147.8
(0.5)
Dodge/Jefferson
Dodge/Jefferson county
county line.
line.
Enter Jefferson County.
County.
148.3
148.3
(2.4)
Hubbleton
Hubbleton and
and junction
junction Wisconsin
Wisconsin 19
19 and
and County
County G.
G. Turn south
south (right)
(right)
on GG in a
a broad area of flat,
flat, poorly-drained muck soils
soils located
located
between
between intensively
intensively farmed drumlins.
drumlins. Where
~ihere ditched,
ditched, the muck soils
soils
are also
also cultivated.
cultivated.
24
24
�Mileages
Mileages
150.7
150.7
(2.1)
(2.1)
County
county GG continues
continues southward
southward through
through drumlin
drumlin country.
country.
152.8
152.8
(1.4)
(1.4)
The
The low
low ridge
ridge of
of Waterloo Quartzite
Quartzite in
in the
the field
field about
about 150
150 yards
yards
east
of
the
highway
is
sometimes
referred
to
as
the
Lake
east of the
is sometimes referred to as the Lake Mills
Mills
here is
is light
light blue
blue to gray in
exposure.
exposure. The
The quartzi-te
quartzite here
in color,
color, and
and
it
is
composed
almost
entirely
of
coarse,
interlocking
quartz
it is composed almost entirely of coarse, interlocking quartz
grains
grains with
with rare
rare mica.
mica. Primary
Primary foliation
foliation (bedding)
(bedding) strikes
strikes
N.
500
W.
and
dips
70°
northeast
on
the
south
N. 50° W. and dips 70° northeast on the south limb
limb of
of the
the
Waterloo syncline.
syncline.
Waterloo
154.2
154.2
(2.0)
(2.0)
Junction
Junction County
County GG and
and Wisconsin
Wisconsin 89.
89.
through good
good drumlin
drumlin country.
country.
through
156.2
156.2
(1.8)
(1.8)
Junction
Junction Wisconsin
Wisconsin 89
89 and
and Interstate
Interstate 94.
94.
Milwaukee. 1
Milwaukee.1
Turn south on Wisconsin 89
89
Turn east on 1-94
I-94 toward
toward
The 1-94
I-94 route from
from the Lake Mills-Waterloo interchange
interchange to
to Milwaukee
is entirely within the Eastern Ridges and
and Lowlands physical province,
and the highway trends at right angles to the
the general
general strike
strike of
of the
the
Paleozoic
Paleozoic formations.
formations. Consequently,
Consequently, the bedrock along
along the
the route
route
ranges from
from Middle Ordovician formations
formations on the
the west to
to Silurian
Silurian
on the
the east.
east. However,
However, these rocks
rocks are
are largely
largely obscured
obscured
dolomite on
glacial deposits.
deposits.
by Woodfordian glacial
The glacial geology encountered along
along 1-94
I-94 between here and
and Milwaukee
Milwaukee
spectacular. The orientation of the
the route
route is
is such
such that
that the
the interinteris spectacular.
state cuts
cuts most glacial
glacial features
state
features essentially at right angles.
angles. From
west to east,
east, these include well—developed
well-developed drumlin
drumlin fields,
fields, outwash
outwash
plains,
plains, the Kettle Interlobate
Interlobate Moraine with numerous scenic
scenic lakes,
lakes,
and recessional
recessional moraines
moraines of the
the Lake
Lake Border morainic system.
and
system. Other
significant attractions along
along this
this route
route include:
include: the Lapham Peak
overlook high in the Kettle Moraine,
Moraine, and
and the subcontinental
subcontinental divide,
divide,
which separates drainage destined for
for the North Atlantic via
via the
the
St. Lawrence
Lawrence from that
that which flows
to the
St.
flows to
the Gulf of Mexico via the
Mississippi.
158.0
(2.0)
(2.0)
Eastbound rest area in
in an area
area of rolling
rolling ground
ground moraine.
moraine.
160.0
(1.0)
(1.0)
1-94 crosses the Crawfish River,
I-94
River, aa tributary
tributary to
to the
the Rock.
Rock. Aztalan
In
State Park is
is 1.5 miles
miles south on the west bank of this river.
State
river.
In
addition to
to Late
Late Woodland
Woodland Indian
Indian effigy
effigy mounds,
mounds, this
this park
park contains
contains
addition
two—tiered pyramidal mound,
mound, and a
aa two-tiered
a partly restored stockaded
village identified with the
the Middle
Middle Mississippi
Mississippi culture.
culture. When the
site was
was first
first described
described in
in 1837,
1837, it
it was
was named
named Aztalan
Aztalan in the
the hope
hope
site
that the
the cultural
cultural remains
remainspreserved
here were
were those
those of Mexican
Mexican Aztecs.
Aztecs.
that
preserved here
To reach
reach the
the park,
park, use
use the
the Lake
Lake Mills
Mills exit
exit and
and then
then turn
turn east on
To
County
B.
County B.
161.0
161.0
(1.0)
Westhound rest
rest area,
area, in
in an
an area
area of ground
ground moraine
moraine and low—lying
Westbound
low-lying
drumlinoid
drumlinoid hills.
this geologic
guide
published
with with
permission
ofofKendall/
1ndof
The remainder
of this road
geologic
roadis
guide
is published
permission
Kendall/
be duplicated
duplicated by
by any
any means
means
Hunt Publishing Company,
Company, Dubuque,
Dubuque, Iowa,
Iowa, and
and it should not
not be
Hunt
without
25
without written permission.
permission.
25
�Mileages
Mileages
162.0
162.0
(1.0)
(1.0)
1—94 crosses the Rock
The Rock
Rock marks
marks aa general
general vegetation
I-94
Rock River.
River.
The
divide between
between native
native hardwood
hardwood forests
forests to
to the
the east,
east, and
and oak
oak
divide
savannas and prairies to the west.
Some think
think the
the river
river formed
savannas
west.
Some
formed
barrier to
to prairie
prairie fires,
fires, thus
thus preserving
preserving the
the forests
forests to
to the
the
aa barrier
east.
east.
Jefferson, 6.5 miles
miles to
Jefferson,
to the south at the junction of the Crawfish
and Rock
Rock rivers,
rivers, experienced
experienced aa short-lived,
short—lived, geology-related,
geology—related, land
and
boom about
about 1840.
1840. A federally—assisted
federally-assisted project was planned to
to
construct aa canal
canal from
from Lake
Lake Michigan
Michigan at
at Milwaukee
Milwaukee to
to the
the Rock River
construct
Some construction
construction was
was actually
actually accomplished before
near Jefferson.
Jefferson.
Some
the million-dollar
million—dollar project was
was abandoned.
abandoned. Meanwhile,
Meanwhile, land
land values
had sky—rocketed
sky-rocketed in Jefferson as
as the prospect of a connection
the Mississippi
Mississippi River
River and
and the
the Great
Great Lakes
Lakes seemed
seemed imminent.
iminent.
between the
Land promoters arrived,
arrived, and a
a steamboat made it up the Rock River
River
from St.
St. Louis. Tracts of swampland were bought by local residents
residents
and newcomers
newcomers at
at inflated
inflated prices,
prices, in
in the
the hope
hope that
that great profits
profits
and
would result when the
the canal
canal was
was completed.
completed.
The
The land promoters
left town
town with
with well-laden
well—laden carpetbags
carpetbags before
before news
news of the
the abandonabandonleft
ment of the canal plans
plans reached
reached southern
southern Wisconsin.
Wisconsin.
163.0
(6.0)
Watertown, Johnson Creek,
Exit Wisconsin 26 to Watertown,
Creek, and Jefferson,
Jefferson,
within the Jefferson County
County drumlin
drumlin field.
field. Where the interstate
interstate
cuts through a
a drumlin,
drumlin, the roadcuts have been carefully sodded
sodded
over to conceal the internal character of the sandy and
and clayey
clayey till.
till.
However,
However, at the northwest corner of this intersection, behind the
the
service station and restaurant,
restaurant, an excavated drumlin is
is exposed.
exposed.
169.0
(4.0)
moraine assumes
assumes symmetry and order as
Irregular ground moraine
as the highway
traverses a classic drumlin field,
field, produced by the
the Green
Green Bay
Bay lobe
lobe
drumlins trend essentially
of the Woodfordian ice
ice advance.
advance. These drumlins
north—south,
north-south, but nearer to Madison the
the orientation is southwesterly.
Poorly drained areas and tamarack
tamarack swamps
swamps flank
flank many of
of the
the drumlins.
drumlins.
173.0
(2.0)
Wisconsin
Wisconsin 135
135 exit.
exit.
175.0
(3.0)
Jefferson/Waukesha
Jefferson/Waukesha county
county line.
line. Enter
Enter Waukesha
Waukesha County.
County. The
The
drainage in this rolling
rolling countryside
countryside is
is poor, and
and farm
farm fields
fields must
must
be ditched.
ditched. Numerous tamarack
tamarack swamps
swamps with red
red osier
osier dogwood
dogwood are
are
lingering evidence of the
the boreal
boreal climate
climate of
of the
the Pleistocene.
Pleistocene.
178.0
(4.0)
Wisconsin 67
67 exit
exit to
to Oconomowoc
Oconomowoc and
and Dousman.
Dousman. The interstate now
traverses
traverses outwash and proglacial lake sediments in an area once
occupied by the
the Green Bay
Bay lobe
lobe during the
the Woodfordian
Woodfordian ice
ice advance.
advance.
To
To the
the east, the
the view of the
the Interlobate
Interlobate Moraine
Moraine looming
looming above
above the
the
flat
flat outwash surface
surface is
is impressive.
impressive. A
A few
few overgrown kettles are
are
adjacent to
to the
the highway
highway on
on the
the south
south side.
side. To the north,
north, rising
rising
above the flat
flat outwash plain,
plain, an incongruous landform
landform resembles
resembles
the classic moulin kames
kames of
of the
the northern
northern Kettle
Kettle Moraine.
Moraine. This is
is
the artifically—created
artifically-created ski
ski hill
hill near
near Oconomowoc.
Oconomowoc.
182.0
182.0
(1.0)
(1.0)
An
An exit
exit on
on County
County CC
CC provides
provides aa side
side trip
trip to
to view
view the
the Kettle
Kettle
26
26
�Mileages
Mileages
Interlobate Moraine
Moraine from
from the
the observation
observation tower
tower on
on Lapham
Lapham Peak.
Peak.
This
This tower
tower provides
provides an
an excellent
excellent overview
overview from
from the
the highest
highest
vantage
vantage point
point in
in the
the southern
southern Kettle
Kettle Interlobate
Interlobate Moraine.
Moraine. To
To
the
the west
west is
is Genesee
Genesee Flat.
Flat. To the east is
is the
the glacial
glacial spillway
spillway
described
described at
at mile
mile 184.
184. Several scenic,
scenic, glacial
glacial lakes
lakes are
are also
also
visible.
visible.
To reach Lapham Peak,
Peak, go south
south on County CC (Kettle
(Kettle Moraine Scenic
Scenic
Turn
left
(east)
onto
Drive)
about
1.8
miles
to
a
crossroad.
Drive) about 1.8 miles to a crossroad.
left (east) onto
Government
Government Hill
Hill Road.
Road. Continue about 0.7
0.7 mile to
to aa small
small park
that includes
includes the
the Lapham
Lapham Peak
Peak observation
observation tower.
tower. The
The tower
tower for
for
state station
station WHAD
WHAD is
is also
also located
located here.
here. A
A marker at
at 1233
1233 feet
feet
of elevation,
elevation, on a
a glacial erratic boulder in
in the
the park,
park, is
is dedicated
dedicated
to one of
of Wisconsin's earliest
earliest geologists
geologists and
and naturalists:
naturalists:
"Increase A.
A. Lapham,
Lapham, Eminent scientist
scientist and
and useful
useful citizen."
citizen."
The route
route ahead
ahead crosses
crosses a
a region
region of
of pitted (kettled)
(kettled) outwash
outwash
deposits, and
and many
many kettle
kettle lakes
lakes dot
dot the
the landscape.
landscape. Nagawicka
Nagawicka Lake,
Lake,
immediately
immediately north
north of
of the
the highway,
highway, is
is such
such aa lake.
lake. Other examples
examples
are
are Upper and Lower Nemahbin lakes,
lakes, which sandwich the interstate
west of
of here.
here. The ice blocks which formed
formed these lake
lake
about 1 mile west
basins were derived from
from the
the Green
Green Bay
Bay lobe
lobe along
along the
the western
western edge
edge
of the Interlobate
Interlobate Moraine.
Moraine.
183.0
183.0
(1. 0)
(1.0)
The interstate approaches the crest of the Interlobate
Interlobate Moraine.
Moraine.
A
small
ski
area
south
of
the
highway
utilizes
A small ski area south of the highway utilizes part
part of
of this
this slope.
slope.
From the crest of this ridge,
ridge, the radio tower and
and observation tower
tower
on Lapham
Lapham Peak are
are visible
visible south
south of
of the
the highway.
highway.
The Kettle Interlobate Moraine,
Moraine, which trends northeasterly across
across
Wisconsin for
for about 130 miles,
miles, from
from Walworth to
to Kewaunee
Kewaunee counties,
counties,
It is
is probable that the
is the
the premier glacial feature
is
feature in
in Wisconsin.
Wisconsin.
It
resistant Silurian
Silurian dolomite
dolomite influenced the
the position of the inter—
resistant
interlobate deposits
deposits in
in this
this area,
area, by retarding the spread of the Green
lobate
Bay lobe.
lobe.
Within this morainal complex,
complex, the country
country is
is rolling
rolling and
and rugged,
rugged,
This feature formed
with abundant knobs
knobs and
and kettles.
kettles.
formed during the
Woodfordian glacial advance by a
a juxtapositioning
juxtapositioning of
of the
the terminal
terminal
inoraines
of the
the Green
Green Bay
Bay and
and Lake
Lake Michigan
Michigan lobes. Between these
moraines of
walls, complex drainageways
drainageways developed,
developed, and meltwaters reworked
icy walls,
some
a
some of the morainal materials. The resultant deposits are a
Much of the
mixture of sand,
mixture
sand, gravel, boulders, and
and clayey
clayey till.
till.
material was
was derived from the Silurian dolomite,
coarser material
dolomite, but
igneous and
and metamorphic
metamorphic rock
rock types
types from
from far
far to
to the
the north
north are
are also
also
igneous
present.
184.0
184.0
(1.
0)
(1.0)
This highway
highway follows
an
Wisconsin 83
83 exit.
exit. This
follows low ground along an
abandoned drainage
drainage channel
channel which
which carried the
the last meltwater that
abandoned
drained southward
southward through
through this
this part
part of the
the Kettle
Kettle Interlobate
drained
Water drained
drained down
down this
this .25
mile wide
wide valley
valley until
until it
Moraine.
.25 mile
Moraine. Water
reached Wales,
Wales, about
about 33 miles
miles to
to the
the south,
south, where
where it
it cut
cut through
through the
the
reached
Gravel outwash
outwash terraces
terraces flank
flank
Interlobate
Interlobate Moraine
Moraine to
to flow west.
west. Gravel
this drainage,
drainage, and
and aa remnant
remnant of aa high terrace
terrace is
this
is visible on the
east
east side
side of this valley.
27
27
�Mileages
185.0
(1.0)
(1.
0)
Pewaukee Lake
Lake lies
lies to
to the
the north.
north. The church at
at Holy
Holy Hill,
Hill, on
on aa kame
kame
perched high on the Interlobate
Moraine,
is
also
visible
to
the
north
Interlobate
is also visible to the north
on aa clear
clear day.
day. Pewaukee Lake occupies aa preglacial river
river valley
valley which
which
was scoured into the Upper Ordovician Maquoketa Shale.
This
Shale. This ancient
valley was blocked by morainal debris deposited along
along its
its eastern
eastern
margins by the Lake Michigan lobe
during
the
Woodfordian
ice
lobe
the
ice advance.
advance.
186.0
(2.0)
Ground moraine deposits in
in this
this area
area are
are thin.
thin. North of the highway
on the west edge of the Tumblebrook golf
golf course,
course, there
there is
is aa small
small
quarry in
Silurian
dolomite.
Glacial
striae
on
bedrock
in this
in Silurian dolomite.
area indicate that ice
ice movement was
was west—southwest.
west-southwest.
the road,
road, the
the names
names of a
South of the
a subdivision (Pebble
(Pebble Valley),
Valley), and
Hill), bear testimony to the character of the
aa farm (Stoney
(Stoney Hill),
the
morainal material.
material.
188.0
(3.0)
Exit County GG to
the highway
to Pewaukee.
Pewaukee. A drumlin field lies south of the
for the next several
several miles.
miles. These east—west
east-west trending drumlins are
composed of sandy clay till
till that contains abundant boulders.
boulders.
191.0
(1. 0)
(1.0)
Exit County
County F.
F. West of this intersection,
intersection, the
the route
route crossed
crossed the
the
Pewaukee River,
River, which
which is
is tributary
tributary to
to the
the Fox.
Fox. This valley is
is
paralleled by outwash terraces,
terraces, which are commercial
commercial sources
sources of
of sand
sand
and gravel
gravel in
in this
this area.
area.
192.0
(2.0)
Exit Wisconsin 164
164 to
to Sussex
Sussex and
and Waukesha.
Waukesha.
lins are ,north
north and
and south
south of
of the
the highway.
highway.
East-west trending drum-
Colonel Dunbar,
Dunbar, while visiting Waukesha in 1869, drank
drank from
from some
some of
of
the springs
the
springs which issue from the glacial drift,
drift, with high amounts
amounts of
of
dissolved calcium
calcium magnesium
magnesium bicarbonate.
bicarbonate. Upon deciding that the
local
local mineral waters had eliminated his "incurable
"incurable ailments,"
ailments," he
he
began to
to advertise
advertise his cure
cure nationwide,
nationwide, and
and Waukesha
Waukesha soon
soon became
became aa
fashionable health spa.
fashionable
spa. Although this fad
fad waned after about
about 30
30 years,
years,
bottled spring
water
is
still
a
Waukesha
product.
spring
is still a Waukesha product.
Waukesha
Waukesha is
is located
located on
on the
the Fox
Fox River.
River. Outwash terraces along
along this
this
river are important commercial sources for
for sand and
and gravel.
gravel. Since
the glacial drift is quite thin in this region,
the
region, Silurian dolomite
is
is extensively quarried along the valley of the Fox from
from the
the
Waukesha area
area northward to
to Sussex,
Sussex, Lannon
Lannon and
and Menomonee
Menomonee Falls.
Falls.
194.0
(3.0)
U.S. 18 (Blue
Exit U.S.
(Blue Mound Road)
Road) to Waukesha and WiscOnsin
Wisconsin State
Patrol Headquarters.
197.0
(2.0)
Exit Moorland
Moorland Road.
Road. The flat terrain here is
is poorly drained, clayclayground moraine.
moraine. Ditching and channelization were required
required for
for
rich ground
the extensive development
development of
of the
the land
land north
north of
of the
the highway.
highway.
The golf course to the south represents a more intelligent
intelligent land
land use.
use.
A few
few isolated patches of moraine,
moraine, and several east—west
east-west trending
trending
drumlins rise
rise above
above the
the generally
generally swampy
swampy ground.
ground.
The route
route ahead
descends aa prominent ridge,
The
ahead descends
ridge, which is part of the
28
�Mileages
Mileages
Woodfordian
Woodfordian Lake
Lake Border
Border recessional
recessional moraine
moraine system.
system. Sunny
Sunny Slope
Slope
Road
Road traverses
traverses this
this ridge
ridge crest,
crest, which
which forms
forms the
the drainage
drainage divide
divide
between
between Lake
Lake Michigan
Michigan and
and the
the drainage
drainage basin
basin of
of the
the Fox
Fox River.
River.
The
The Fox
Fox flows
flows southward
southward parallel
parallel to
to the
the Woodfordian
Woodfordian moraines
moraines to
to
reach
reach the
the Illinois
Illinois River,
River, and
and ultimately
ultimately the
the Gulf
Gulf of
of Mexico
Mexico via
via
the Mississippi.
Mississippi.
the
199.0
199.0
(2.0)
(2.0)
Milwaukee/Waukesha
Milwaukee/Waukesha county
county line.
line. Enter Milwaukee
Milwaukee County.
County. Exit
Exit 1-894
1-894
(U.S.
45) south
south to Chicago and U.S.
(U.S. 45)
U.S. 45
45 north
north to
to Fond
Fond du
du Lac.
Lac. The
The
Milwaukee
Milwaukee County
County Zoo
Zoo is
is northwest
northwest of
of this
this intersection.
intersection.
202.0
202.0
(2.0)
(2.0)
Exit Wisconsin
Wisconsin 181
181 (84th
(84th Street).
Street). The
The Wisconsin State
State Fair
Fair Park
Park
Exit
grounds and an Olympic-size outdoor ice
ice rink
rink are
are southeast
southeast of
of this
this
Wisconsinan (Woodfordian)
junction.
junction. The interstate traverses
traverses Wisconsinan
(Woodfordian) ground
moraine
moraine and
and recessional
recessional moraines
moraines of
of the
the Lake
Lake Border
Border system.
system. The
The
highway
highway here
here is
is essentially
essentially parallel
parallel to
to the
the east-west
east-west direction
direction
of ice
ice movement,
movement, and
and consequently
consequently the
the morainic ridges
ridges trend
trend north—
northsouth. About 100
100 feet
feet of glacial
glacial deposits,
deposits, primarily
primarily aa boulder
boulder
south.
clay
clay till,
till, overlie
overlie Silurian
Silurian dolomite
dolomite in
in this
this area.
area.
204.0
(1.0)
(1.0)
U.S.
U.S. 41
41 exit
exit (north
(north and
and south).
south). Milwaukee County
County Stadium,
Stadium, home
home of
of
the Milwaukee Brewers and
also
the
site
of
the
Milwaukee
games
and also the site of the Milwaukee games of
of
the Green
Green Bay
Bay Packers,
Packers, is
is just
just west
west of
of this
this junction.
junction. The large
large
hill southwest of the stadium
is
a
Silurian
dolomite
stadium is a Silurian dolomite exposure
exposure on
on
the grounds of the
the
the U.S.
U.S. Veterans
Veterans Administration
Administration Hospital.
Hospital.
205.0
(1.0)
(1.0)
Route parallels the
the industrial
industrial complex
complex along
along the
the east-west
east-west trending
trending
Three
large,
glass
domes
in Mitchell Park
River valley.
valley.
large,
Menomonee River
are
to the
the south.
south. One contains a
a display of vegetation
are visible to
native to a desert environment,
another
features
environment, another features tropical
tropical plants,
plants,
and the
the last houses
houses local flora and is used for special flower shows.
shows.
206.0
Junction 1—94
1-94 with
with 1-43
1-43 (U.S.
(U.S. 141)
141) and
and 1—794.
1-794. The Milwaukee Harbor
is
to
the
southeast,
toward
the
highrise
Harbor Freeway bridge along
is to the southeast,
the
the lakeshore.
Three rivers merge at
at the
the Milwaukee
Milwaukee Harbor.
Harbor.
flows from
from the
the north
north and
and west,
west, the
the Milwaukee
Milwaukee
flows
north, and the
north,
the Kinnickinnic River originates
The Menomonee
Menomonee River
The
River comes
comes from the
the
to the west and south.
south.
Milwaukee grew from three settlements that were originally separated
Walker's Point,
by these rivers.
rivers. Walker's
Point, east of the Kinnickinnic River,
River,
is now
now dominated
dominated by
by the
the towering
towering clock
clock of
of the
the Allen
Allen Bradley Company.
Company.
is
The Milwaukee River flowed between Kilbourntown on the west and
The
Juneautown to
to the
the east.
east.
The high
high smokestack
smokestack to
to the
the east
east is
is part
part of the
the Jones
Jones Island
The
Here, sewage
sewage sludge
sludge is
is dried and
Metropolitan Sewage Plant.
Metropolitan
Plant. Here,
converted to Milorganite,
Milorganite, aa commercial
converted
commercial fertilizer.
fertilizer.
Jones Island,
Island, an
an artificially
artificially breached
breached peninsula,
peninsula, also contains
Jones
contains
tanker pier,
pier, cargo
cargo terminals
terminals and
and aa heavylift
heavylift wharf,
wharf, and is
aa tanker
is
Milwaukee's inner harbor
headquarters for the Port of Milwaukee. Milwaukee's
headquarters
29
�was developed by an enlargement of the lower Kinnickinnic River,
was
River,
and it
it serves
serves as
as the
the service
service and
and wintering area for
and
for part of
U.S. Steel's iron ore carrier fleet.
u.s.
fleet.
END OF
OF LOG
END
Proceed through downtown Milwaukee to
Proceed
to the
the Pfister
Pfister Hotel.
Hotel.
30
30
�,/
*
N
I
o0
NE
NE
QUARRY
QUARRY
A
A
,,-
\\ \I
/ '\
'\
rn
1!
200 FEET
FEET
Flynn's
SW
QUARRY
QUAR RY
QUARRY
--
—
\
/ , , / -:.- \I I " \
"'/ ,"- '\,
[J
I
"
-V,-.
\
\
/
.:::
N
~
A'
\
\
./
E
X P L A N AT I 0 N
EXPLANATION
METABASALT
METABASALT DIKE
DIKE
STRUCTURE RELATED
RELATED TO
TO
I• STRUCTURE
QUARRY OPERATION
OPERATION
QUARRY
J
o DEBRIS
DEBRIS PILE
PILE
D
[Tj
GRANITE
PORPHYRY
r,o "0)
GRANITE
PORPHYRY DIKE
DIKE
l'v I GRANITE
GRANITE AT
AT REDGRANITE
REDGRANITE
Figure
Figure 2.
2.
!
y'
1'
QUARRY WALL
OR STEEP
STEEP
QUARRY
WALL OR
SLOPE
SLOPE
Pace
Pace and
and compass
compass map
map of
of Flynn's
Flynn's Quarry
Quarry County
County Park,
Park, Waushara
Waushara County.
County.
32
32
�Geologic
Geologic Stop
Stop Descriptions
Descriptions
. 11
Eugene
Eugene I.
I. Smith
Smlth
STOP 11 -- GRANITE
GRANITE AND
AND RELATED
RELATED INTRUSIONS
INTRUSIONS AT
AT FLYNN'S
FLYNN'S QUARRY
QUARRY COUNTY
COUNTY PARK
PARK
STOP
Location: All
All exposures
exposures at
at this
this stop
stop are
are reached
reached by
by an
an easy
easy walk
walk from
from the
the ParkParkLocation:
ing area
area (Fig.
(Fig. 2).
2).
ing
Description:
Description:
Granite
Granite
Fine—to
Fine-to medium—grained
medium-grained red
red (granophyric)
(granophyric) granite with micropegmatitic
micropegmatitic and
and
myrmeketic texture
texture is
is exposed in
in three
three quarries within the
the boundaries
boundaries of
of Flynn's
Flynn's
County Park
Park (Fig.
(Fig. 2).
2). Quartz and
and alkali
alkali feldspar
feldspar compose
compose 90
90 to
to 98
98 perperQuarry County
cent
cent of
of the
the rock,
rock, with biotite
biotite (partially
(partially or
or wholly altered
altered to
to chlorite),
chlorite), sphene,
sphene,
muscovite and
and zircon
zircon as
as subordinate
subordinate minerals.
minerals. The granite for
for the
the
hornblende, muscovite
most part
part is
is texturally
texturally homogeneous.
homogeneous. Locally
Locally however,
however, grain
grain alignments
alignments and
and fine—
fineThe mineralogy and texture of the granite
grained bands (dikes?)
(dikes?) are
are observed.
observed.
(especially
the intergrowths
intergrowths of
of quartz
quartz and
and alkali
alkali feldspar)
feldspar) suggest
suggest that
that it
(especially the
it is
is a
a
shallow
intrusion.
shallow intrusion.
Granite Porphyry Dike
Dike
In
northeast quarry,
quarry, the
the granite
granite is
is cut
cut by
by aa 200
200 m wide
wide east
east trending
In the
the northeast
granite porphyry dike
dike (strike
(strike east—west,
east-west, dip
dip 75°
75° to
to the
the south).
south). The dike rock
rock
is
characterized by
by large
large (5
mm) alkali
alkali feldspar
feldspar phenocrysts
phenocrysts set
set in
in aa fine—
is characterized
(5 mm)
fineof quartz,
quartz, biotite
biotite and
and chlorite.
chlorite. The finely disseminated chlorite
grained matrix of
gives the matrix of the
the dike rock a
a green color,
color, thus
thus making it easily distinguishable from
from the
the red
red granite.
granite. The contact between granite and dike rock is
is
clearly visible
visible on
on aa ledge
ledge on
on the
the north
north wall
wall of
of the
the northeast
northeast quarry
quarry (Fig.
(Fig. 3).
3).
In
detail, the
the contact
contact bends
bends in
in and
and out,
out, suggesting
suggesting some
some assimilation
assimilation of
granite
In detail,
of granite
during intrusion.
intrusion. Fragments (xenoliths)
(xenoliths) of
of granite are found
found within the
the dike
near the
the contact;
contact; also
also feldspar
feldspar phenocrysts
phenocrysts are
are concentrated
concentrated and
and weakly
weakly aligned
aligned
near
in
the granite mornhvrv
porphyry dike at
at the
the contact.
contact.
in the
Figure 3.
Figure
View of
of the
the contact
contact between
between the
the granite
granite porphyry
porphyry dike
dike and
and granite
granite
View
Note
in Flynn's
Flynn's Quarry
Quarry County
County Park (dashed
in
(dashed line traces
traces contact).
contact).
that the
the feldspar
feldspar phenocrysts
phenocrysts are
are concentrated
concentrated and
and weakly
weakly aligned
aligned
that
in the
the dike
dike rock near the
in
the contact.
contact.
of Science,
Science, University
University of
of Wisconsin-Parks
Wisconsin—Parkside,
lDivision
ide , Kenosha,
Kenosha, Wisconsin
Wisconsin 53141.
53141.
Division of
33
33
�Chemically, the
the dike
dike is
is aa less
less differentiated
differentiated phase
phase of
of the
granite. It
It is
Chemically,
the granite.
lower in SiO , and K
K20
and higher
higher in
in Al
A1203,
Fe20
and CaO when
when compared to
lower
0 and
0 , FeO + Fe
0 and
2
3
uarry granite
1, an~lyses
analyses 18
18 and
and 31).
3).
In terms
terms of trace
the Flynn's auarry
g~anite (Table
(Table 1,
In
elements the
the dike
dike is
is higher
higher in
in Ba,
Ba, and
and has
has aa lower
lower Rb/Sr
Rb/Sr ratio than the
granite.
elements
the granite.
,
Metabasalt Dike
Dike
On the
the north
north wall
wall of
of the
the main
main quarry,
quarry, the
the granite
granite is
cut by a
m wide)
wide)
On
is cut
a thin (2
(2 m
0
metabasalt dike striking
striking N.
N. 80
80 E.
E. and
and dipping
dipping 700
70 to
to the south (Fig.
(Fig. 2).
2).
The dike
rock is
is fine
fine grained
grained and
and has
has aa distinctive
distinctive green color
color on both weathered and fresh
~ock
fresh
surfaces.
In
thin
section,
the
metabasalt
displays
intergranular
texture
with
In thin section, the metabasalt displays intcrgranular texture with
laths of
of plagioclase enclosing mats of
laths
of epidote,
epidote, clinozoisite
clinozoisite and
and iron
iron oxide.
oxide.
The
contact
between
the
metabasalt
and
granite
is
clearly
observed
on
a
contact between the metabasalt and granite is
observed
a ledge just
above
Here lenses
lenses of
of granite
granite are
above water level
level (Fig.
(Fig. 4).
4). Here
are completely enclosed by
stringers of metabasalt. Except for these lenses,
no
granite fragments
lenses,
fragments were
noticed within dike rock.
These
contact
relationships
suggest
that
rock.
that the
the meta—
metabasalt intruded
primarily
by
the
dilation
of
country
rock.
intruded primarily by the dilation of country rock.
Comparison of
of Flynn's
Flynn's Quarry
Quarry Granite
Granite to
to Granite
Granite in
in Nearby
Nearby Areas:
Areas:
Redgranite to
to Pine Bluff—
Bluff- Granites and Dikes
Granites similar in
Granites
in mineralogy and
and texture
texture to that
that at
at Flynn's
Flynn's Quarry are
exposed in discontinuous
discontinuous outcrops
Redgranite to Pine Bluff
exposed
outcrops from
from the
the city of
of Redgranite
(Fig.
(Fig. 5).
5). Dikes of
of metabasalt trending east—west
east-west and
and approximately
approximately N.
N. 45E.
45E. cut
cut
the
One of the
most easily visited of
the granite in
in many
many localities.
localities.
One
the most
of these dikes
forms
distinct ridge
ridge jutting into the
forms aa distinct
the quarry lake
lake north of S.T.H.
S.T.H. 22 in
downtown Redgranite
Redgranite (just
(just north
north of
of Griffs'
Griffs' Cafe).
Cafe). A
A coarse—grained
coarse-grained diorite
dike cuts granite in
in a small
small quarry in
in the
the N
N 1/2,
1/2, Sec.
Sec. 27,
27, T.18 N.
N. R.
R. 11
11 E.
E.
(Fig.
5). The
The dike
dike is about 5 m
(Fig. 5).
m thick
thick and
and trends
trends N.
N. 40
40 E.
E. (dip vertical).
In
thin section,
section, flow—aligned
flow-aligned plagioclase
plagioclase laths
laths surround
surround clots
clots of
of chlorite
chlorite and
and epidote.
epidote.
Montello Granite
Granite
Another granite similar in
in lithology to
to that
that at
at Flynn's Quarry and
and at
at Red
Red
Granite is located in
the
city
of
Montello
(Buckley,
1898).
in the city of Montello (Buckley, 1898). There is
is also
also an
an
exposure to the
the east of Montello in
in the
the SE
SE 1/4,
1/4, Sec.
Sec. 9,
9, T.
T. 15
15 N.,
N., R.
R. 10
10 E.
E.
This granite
granite was
was extensively
extensively quarried
quarried from
from 1880
1880 to
to 1976.
1976. President Grant's
sarcophagus in
in New York City is
is carved
carved from
from Montello
Montello Granite.
Granite. The rock in
in the
the
Montello quarry is
is a
a red granite composed of
of intergrown
intergrown quartz and
and alkali
alkali feldfeldspar crystals (myrmeketic
(myrmeketic and
and micropegmatitic textures
textures are common)
common) with chlorite,
chlorite,
biotite,
biotite, and
and euhedral
euhedral zircon
zircon as
as accessory
accessory minerals.
minerals. Attempts to
to date this
this rock
rock
by the
the fission—track
fission-track technique
technique failed because an
an insufficient
insufficient number of
of zircon
zircon
grains were separated
separated and
and most
most of
of the
the separated
separated zircons
zircons were
were metamict.
metamict. The
Montello granite is
is cut by thin
thin metabasalt dikes (plagioclase
(plagioclase and
and sausserite
sausserite as
as
dominant minerals)
Quarry
minerals) which
which trend
trend northeast,
northeast, north—south
north-south and
and northwest.
northwest.
faces
faces at Montello are
are commonly
commonly bounded
bounded by
by these
these dikes.
dikes. The metabasalt
metabasalt dikes
dikes
are closely sheared at
at their
their margins;
margins; several
several dikes
dikes are
are sheared
sheared throughout.
throughout. The
granite commonly shows
shows aa dark red
red bake zone
zone extending 22 to
to 5
5 cm
em inward
inward from
from the
the
intrusive contacts,
contacts, also small
more common in granite near
small grains
grains of
of pyrite are more
metabasalt
metabasalt than
than farther
farther away
away from
from the
the granite—dike
granite-dike contacts.
contacts.
34
34
�Figure
Figure 4A.
4A.
View of a
a thin metabasalt
metabasalt dike that
that
The
dike
in
this
view
County
Park.
County Park.
in this view
dips about
southern
southern contact
contact (left)
(left) dips
about
Granite (G)
to
the
north of
line).
(G)
in the dike rock
rock (D).
(D).
Figure
4B.
Figure 4B.
Close—up of the contact between the
Close-up
the metabasalt dike
dike and
and granite.
granite.
Basalt intruded granite along
Basalt
along closely
closely spaced
spaced joints.
joints.
35
cuts
cuts granite in Flynn's Quarry
is
is 22 meters
mete~s thick.
thick. The
10° to the north
north (dashed
the dike appears
appears as
as a window
�Lohrville
Lohrville
Quarries
Redg ranj.t(f~~---/'
.c-"~edgranite Quarry
—2'FIynns
Spring Lake,
Lake"",
/_Jf\.
Flynn's Quarry (STOP
(STOP I)
I)
Spring
Quarri es
Quarries
I"
WAUSHARA COUNT
COUNTY
WAUSHARA
-MARQUETTE COUI
COU
.YY
;,.' -
Quarry
Quarry with
with Diorite Dike
Dike
—
T;--
GREEN
GREEN LAKE
LAKE COUNTY
COUNTY
00 Berlin
Gran ite
Berlin
Pine
Pine Bluff Granite
I
I
I
o
I
I
"--1
~
Granite
Montello Granite
Buffalo
Lake
Figure 5.
5.
3:iiii~
2 3 4 5 Miles
0
.Oiii32• 3iE!
Mil es
SCALE
SCALE
I
I
Princeton
EXPLANATION
...
C.J
Granite
Exposures
~
Quarry
00
City
Field Trip
Trip
~ Field
Route
Route
Detailed route
route map
map from
from Redgranite
Redgranite to
to Montello
Montello showing
showing granite
granite
Detailed
exposures and
and locations
locations of important quarries.
exposures
quarries.
36
36
�_____________ _________
Chemical Comparisons:
The granite at
at Redgranite (and
(and presumably Flynn's Quarry)
Quarry) is
is similar in
in
chemistry, mineralogy and age to that
chemistry,
that at Montello,
Montello, except for noticably higher
higher
amounts of
of Cu and Cr in
amounts
in the
the Montello
Montello Granite,
Granite, (Table
(Table 1,
1, analyses
analyses 14
14 and
and 18).
18).
These similarities indicate that the granites are comagmatic and
and that
that they
they
formed during the same intrusive
formed
intrusive event.
event.
Studies of cuttings from
from deep
deep wells
wells
show that
that granite lithologically similar to
to that
that exposed at
at Redgranite and
and
Montello occurs in the basement over a
a large area of south—central
south-central Wisconsin.
Wisconsin.
These rocks
rocks probably
probably form
form aa large
large late—Penokean
late-Penokean or
or post—Penokean
post-Penokean (1765
(1765 m.y.
m.y. old)
old)
composite batholith which is exposed only in
in the
the Redgranite area
area and
and at
at Montello
(Smith, 1978c).
(Smith,
The similarity of the
the granites at Montello and
and Redgranite was noted
noted long
long
ago by Weidman (1904)
who
labelled
these
rocks
the
Waushara
Granite.
(1904)
labelled these rocks the Waushara Granite. Emmons
(1940) also
also suggested the presence of aa large
(1940)
large batholith
batholith in
in central
central Wisconsin.
Wisconsin.
However,
he
did
not
distinguish
between
the
older
Penokean
aged
granites
However,
the
aged granites in
in
central Wisconsin (Wausau area)
area) and
and the
younger granites
granites in south—central
central
the younger
south-central
Wisconsin.
-
44
--
3
--
-
--
-
--
-
-
2
-- -
0.
Co
:::J
0
(I
o
I
I
I
I
I
I
o0200500400500600
200 300 400 500 600
0
10
Zr
20
-
-
-
•
~I
I
I
3040
30 40 50
50
I
0
50
I
I
10015020
100
150 20 3040
30 40
Cu
Cr
I
--I
0)
50
Pb
I
I
100150200250
100
150 200 25 o
Zn
Zn
4—
4
3 -3
2
0.
Co
:::J
0
o1
~I
I
0
o
000
1000
500
Ba
Ba
ao
2.0
I
I
50
50
00
100
I
I
150
150 00
200
Sr
La
tOO 150
50 200
100
200
Rb
10
10
30
50
I
I
I
70
70
90
90
ItO
110
V
Y
(ppm)
Figure
6
6.
chemical groups
groups (from
Some elemental
concentrations for
for the four
four chemical
(from
elemental concentrations
for
Smith, l978a).
1978a). Bars indicate
indicate the
the range
range of
of values
values for each
each chemical
chemi~al
Smith,
group.
Dot indicates that
data point is
is based
based on
on one
one analysis.
analysls.
that the
the data
Dot
group.
37
�Relationship of Granites to
to Rhyolite:
Rhyolite:
The Redgranite
Redgranite and
and Montello
Montello Granites
Granites are
are similar
similar in
in major
major 8nd
cnd mino~
minor element
element
The
chemistry and
and age
age to
to the
the rhyolites
rhyolites exposed
exposed to
to the
the south
south (stop
for example)
example)
chemistry
(stop 22 for
(see table
analyses 4-29;
4—29; and
and Fig.
Fig. 6;
6; and Smith,
(see
table 11 , analyses
Smith, 1978c by Van
Van Schmus,
Schmus, 1978.
1978.
These similarities
similarities strongly
strongly suggest
suggest that
that the
the granites
granites and
and rhyolites
rhyolites are
are comagThese
comag—
matic.
In other
other words,
words, the
the granites
granites may
may represent
represent the
the magma
magma chambers
chambers from
from
matico
In
which the
which
the rhyolite ash—flow
ash-flow tuffs
tuffs were erupted.
erupted. Later,
its
Later, granite intruded its
own volcanic
volcanic cover engulfing much of
9wn
of the
the rhyolite.
rhyolite. Surviving
Surviving rhyolite exists
as roof
roof pendants within
as
within the
the granite.
granite.
,
38
38
�Table 1.
1.
NEW CHEMICAL ANALYSES FOR CENTRAL WISCONSIN INLIERS AND IGNEOUS ROCKS
ROCKS IN THE BARABOO
BARA~OO AREA
AREA
11
2
2
3
3
4
4
5
5
6
6
w
CA,
°t.O BB
Ba
Ba
Co
Co
Cr
Cr
Cu
La
La
Mo
Ni
Ni
V
Y
Y
Zr
Pb
Pb
Rb
Sr
Zn
Zn
Sc
Sc
20
20
1300
1300
33
32
32
30
30
49
10
10
12
12
77
32
32
320
28
165
165
210
210
55
70.61
0.37
14.29
0.92
2.03
0.34
1.61
4.45
3.78
0.92
0.04
0.08
99.55
70.26
0.30
14.10
0.86
2.66
0.10
1.02
1.48
4.29
3.69
1.32
1.
32
0.04
0.17
100.29
71.79
71. 79
0.28
14.46
1.40
0.86
0.07
0.30
1.34
3.48
4.63
1.25
1.
25
0.09
0.08
100.03
24
1350
33
15
20
55
10
10
10
33
38
440
22
22
154
212
190
55
25
1200
33
25
50
31
31
10
10
66
15
15
320
22
22
120
324
110
55
28
690
33
55
120
35
10
10
66
30
200
40
40
152
105
130
0.11
O.ll
8
8
99
10
GROUP 22
GROUP 11
69.28
Si02
0.42
Ti02
TiO2
A1203 13.90
Fe203
1.37
2.89
FeO
0.14
MnO
0.90
MgO
CaO
1.68
Na20
4.17
K20
4.33
H20+
0.92
0.07
H20H20—
0.18
P205
P205
TOTAL 100.25
7
7
71.81
71. 81
0.26
14.29
1.57
1.
57
0.90
0.06
0.20
1.15
4.14
4.54
1.09
0.05
0.09
100.15
33
650
33
10
55
40
10
10
88
22
230
30
125
97
70
72.95
0.25
13.77
13.77
1.69
0.72
0.06
0.26
0.91
3.88
4.46
0.73
0.04
0.04
99.76
71.11
71.11
0.28
14.68
1.67
0.84
0.06
0.26
1.11
4.00
4.35
1.21
1.
21
0.06
0.09
99.72
20
590
33
11
60
35
10
10
99
28
210
45
137
97
145
20
650
33
10
45
45
10
10
10
30
240
30
134
137
105
73.07
0.28
14.65
1.60
0.69
0.06
0.06
0.13
0.94
3.78
4.21
0.78
0.06
0.05
100.30
28
690
33
11
II
55
47
10
10
6
30
210
40
138
95
105
72.85
72.85
0.27
0.27
13.88
1.13
1.09
1.
09
0.05
0.05
0.27
0.27
1.09
1.09
3.58
3.58
4.53
0.96
0.05
0.05
0.10
99.85
71.85
71. 85
0.29
14.32
14.32
0.68
0.68
1.82
1.
82
0.09
0.09
0.26
0.26
1.25
1.
25
3.68
3.68
4.52
4.52
0.78
0.78
0.08
0.08
99.70
99.70
22
630
33
10
55
40
10
10
88
22
230
35
35
130
130
130
130
70
70
20
20
720
33
12
12
45
42
10
10
10
10
55
30
200
200
45
116
116
150
150
115
115
�Table 1.
1. (Continued)
(Continued)
11
11
12
12
13
13
14
14
15
15
16
16
17
17
GROUP 22 Continued)
GROUP
(Continued)
Si02
Si02
Ti02
A1203
A12O3
Fe203
FeO
MnO
MgO
CaO
GaO
Na20
K20
H20+
H20P205
71.22
0.24
0.24
14.15
14.15
1.53
0.70
0.12
0.12
0.15
0.15
2.03
2.03
3.14
4.66
1.94
0.05
0.07
TOTAL 100.00
71.64
71.64
0.28
14.36
14.36
1.84
1.84
0.65
0.07
0.28
1.37
1.
37
4.07
3.74
1.50
0.09
0.10
99.99
18
18
19
19
20
20
GROUP 33
72.27
72 .27
0.30
13.83
13.83
1.51
1. 51
1.08
1.08
0.08
0.24
1.61
1. 61
3.87
3.72
1.51
1. 51
0.07
0.09
72.33
72 .33
0.28
13.62
1.94
1.94
0.68
0.07
0.29
1.27
4.70
3.73
1.16
0.05
0.10
75.83
0.21
11.92
11.
92
1.08
0.98
0.07
0.06
0.53
3.43
5.45
0.54
0.01
0.01
75.09
0.21
12.33
12.33
1.08
1.12
0.08
0.04
0.39
3.76
5.58
0.49
0.00
0.01
100.18
100.22
100.12
100.18
25
25
20
73.73
0.29
12.09
12.09
1.83
1.83
1.34
0.11
0.04
0.36
3.50
6.03
0.36
0.01
0.01
0.00
99.69
76.14
0.24
11.79
11. 79
1.10
1.10
0.88
0.02
0.09
0.45
3.16
5.65
0.58
0.01
0.01
0.01
0.01
100.12
75.30
0.19
0.19
12.04
12.04
1.04
1.04
1.04
1. 04
0.06
0.06
0.04
0.04
0.33
0.33
4.65
4.65
4.63
4.63
0.33
0.33
0.03
0.03
0.00
0.00
99.68
99.68
75.60
75.60
0.17
0.17
12.59
12.59
0.99
0.99
0.71
0.71
0.03
0.03
0.04
0.04
0.13
0.13
4.46
4.46
4.95
4.95
0.47
0.47
0.02
0.02
0.00
0.00
100.16
100.16
A
o
B
B
Ba
Co
Co
Cr
Cu
La
La
Mo
Ni
Ni
V
yy
Zr
Pb
Pb
Rb
Rb
Sr
Zn
Zn
Sc
Sc
29
29
730
33
11
11
55
55
45
10
10
10
10
77
27
27
190
50
50
155
155
126
120
26
26
26
26
20
20
630
3
3
9
9
55
55
35
35
10
10
10
12
12
28
200
40
116
126
126
115
750
33
88
72
37
37
10
10
10
10
12
12
22
22
210
40
102
102
135
135
85
-
-
-
650
3
3
77
50
37
37
10
10
10
10
10
27
270
35
75
106
106
120
120
-
440
3
3
38
23
78
10
10
10
10
5
5
70
420
22
190
190
25
55
55
33
410
3
3
23
22
90
10
10
10
5
5
71
590
23
152
152
31
125
125
33
20
20
390
33
27
26
120
10
10
55
85
550
22
152
11
115
33
20
20
390
33
88
9
95
10
10
10
55
65
590
28
202
21
65
3
22
22
22
22
115
115
545
545
3
13
13
22
22
72
10
10
10
10
55
49
450
19
19
117
117
55
105
105
33
33
16
16
25
25
65
10
10
10
10
55
49
480
480
28
120
120
28
28
95
95
33
�Table
Table 1.
1. (Continued)
(Continued)
21
21
22
22
23
25
25
24
24
26
26
27
27
28
28
MARCELLON
Si02
Si02
Ti02
Ti02
A1203
A1203
Fe203
Fe203
FeO
FeO
MnO
MnO
MgO
MgO
CaO
CaO
Na20
Na20
K20
K20
H20+
H20+
H20H20P205
P205
TOTAL
TOTAL
B
B
oJ:>. Ba
,.... Co
Cr
Cr
Cu
Cu
La
La
Mo
Mo
Ni
Ni
Co
V
V
Y
Y
Zr
Zr
Pb
Pb
Rb
Rb
Sr
Sr
Zn
Zn
Sc
Sc
75.68
75.68
0.12
0.12
12.46
12.46
0.68
0.68
1.09
1.09
0.13
0.13
0.12
0.12
0.36
0.36
3.66
3.66
5.00
5.00
0.57
0.57
0.04
0.04
0.07
0.07
99.98
99.98
78.25
78.25
0.11
0.11
11.05
11.05
0.95
0.95
0.84
0.84
0.07
0.07
0.16
0.16
0.29
0.29
3.66
3.66
3.72
3.72
0.70
0.70
0.09
0.09
0.09
99.98
75.55
75.55
0.14
0.14
12.21
12.21
0.42
0.42
1.71
1.71
0.17
0.17
0.29
0.29
0.45
0.45
2.82
2.82
5.16
0.85
0.04
0.06
99.87
76.63
0.12
11.38
11.38
0.97
0.97
1.13
0.12
0.12
0.13
0.62
3.16
4.66
0.59
0.01
0.06
99.58
40
40
240
240
33
54
54
95
95
47
47
10
10
55
55
50
50
200
200
22
22
131
131
72
72
100
100
55
25
25
160
160
33
44
44
115
115
35
35
10
10
11
11
55
42
42
180
180
19
19
108
108
61
61
130
130
55
20
20
180
33
62
62
160
160
50
50
10
10
55
55
52
52
200
180
180
165
165
61
61
105
105
55
35
35
240
33
41
80
45
45
10
10
55
55
50
50
190
190
14
14
130
130
46
110
55
,
29
29
BARABOO
BARABOO
71.99
71. 99
0.26
0.26
13.57
1.93
1.
93
0.88
0.11
0.37
1.10
4.34
4.91
1.20
1.
20
0.08
0.03
100.77
.
30
970
5
5
15
15
40
90
10
10
55
88
60
150
22
102
95
95
102
102
77
71.80
0.32
13.74
1.30
1.72
0.11
0.58
0.85
4.43
4.49
0.60
0.04
0.13
100.11
100.11
20
1050
3
3
58
105
52
10
55
55
35
220
18
110
176
135
135
77
73.77
0.14
0.14
12.35
1.01
1.81
1.
81
0.13
0.13
0.39
0.94
3.26
4.92
1.25
0.04
0.07
100.08
100.08
22
22
410
3
3
58
58
110
42
10
55
55
38
160
19
108
82
82
110
55
73.83
73.83
0.16
0.16
13.33
13.33
0.96
0.96
1.21
1. 21
0.07
0.07
0.31
0.31
0.43
0.43
2.51
2.51
5.28
5.28
1.43
1.43
0.05
0.05
0.08
0.08
99.65
99.65
27
1100
1100
3
3
25
25
42
42
49
49
10
10
10
33
31
240
55
205
110
110
35
35
55
72.76
72.76
0.22
0.22
13.34
13.34
1.77
1.77
0.72
0.72
0.12
0.12
0.18
0.18
0.45
0.45
4.39
4.39
5.25
5.25
0.77
0.77
0.08
0.08
0.01
0.01
100.06
100.06
35
35
950
950
5
5
22
22
45
45
80
80
10
10
55
55
33
33
140
140
25
25
115
115
62
62
115
115
77
I
�Table 1.
1. (Continued)
Table
(Continued)
30
31
32
33
34
35
35
36
36
37
37
DIKES
Si02
Ti02
A1203
Fe203
FeO
MnO
MgO
CaO
CaO
Na20
1(20
K20
H20÷
H20+
H20—
H20P205
P205
TOTAL
>l:>
t'V
B
B
Ba
Ba
Co
Co
Cr
Cr
Cu
La
La
Mo
Mo
Ni
Ni
V
V
Y
Zr
Zr
Pb
Pb
Rb
Sr
Zn
Sc
63.92
0.94
0.94
15.65
15.65
1.92
1.
92
4.38
0.20
1.40
1.40
1.58
1.58
4.71
4.71
3.34
3.34
1.51
0.11
0.11
0.31
0.31
99.97
99.97
72.10
0.30
12.74
1.06
2.21
0.12
0.09
1.08
3.12
6.12
0.73
0.03
0.04
99.74
20
20
20
1050
1050
1170
3
3
3
3
12
12
65
65
26
16
16
88
88
10
10
10
10
5
5
63
590
19
180
56
110
33
40
10
10
10
10
15
15
25
25
200
30
30
113
218
218
75
75
-
60.59
0.93
16.47
1.61
1.61
4.50
0.18
1.77
3.86
4.27
3.27
1.50
0.11
0.48
99.54
50
1200
4
4
16
70
68
10
10
6
6
92
28
28
220
25
25
105
514
180
20
48.94
0.99
17.84
2.21
6.56
0.19
6.57
9.59
3.25
1.11
2.97
0.12
0.31
100.29
25
660
24
42
50
10
10
10
24
24
240
11
11
75
75
28
28
38
642
180
27
49.47
0.94
14.77
1.46
7.42
0.19
7.05
6.54
4.59
1.09
5.57
0.18
0.36
99.63
52.02
1.27
15.84
2.66
7.72
0.21
4.78
7.87
3.23
1.66
1.96
0.10
0.34
99.66
15
680
20
155
77
21
10
19
240
14
86
15
15
55
55
270
170
25
25
33
950
20
27
27
75
75
29
10
10
270
31
31
180
180
20
20
154
154
419
190
24
24
60.72
0.99
15.72
1.13
5.86
0.19·
0.19
1.89
1.
89
3,94
3.94
3.90
3.31
1.43
0.10
0.46
99.64
56.21
1.33
1.33
13.20
13.20
1.95
1.
95
6.66
6.66
0.14
0.14
5.10
6.01
3.09
2.56
2.34
0.14
0.98
99.71
22
22
1250
77
20
32
32
33
33
10
16
55
55
32
32
240
22
22
155
155
420
220
16
16
70
70
1100
37
150
80
95
95
10
10
51
51
260
260
45
620
21
21
75
75
625
160
160
23
23
I
�Table 1.
1. (Continued)
(Continued)
Si02
Si02
Ti02
Ti02
A1203
A1203
Fe203
Fe203
FeO
FeO
MnO
MnO
MgO
MgO
CaO
Na20
Na20
K20
K20
H20+
H20+
H20H20P205
P205
TOTAL
TOTAL
..,.
w
B
B
Ba
Ba
Co
Co
Cr
Cr
Cu
Cu
La
La
Mo
Mo
Ni
Ni
V
V
yY
Zr
Zr
Pb
Pb
Rb
Rb
Sr
Sr
Zn
Zn
Sc
Sc
38
38
39
39
40
40
69.76
69.76
0.37
0.37
13.77
13.77
0.76
0.76
2.25
2.25
68.44
68.44
0.50
0.50
14.20
14.20
1.46
1.46
2.99
2.99
0.17
0.17
0.62
0.62
2.02
4.78
4.78
3.06
1.11
1.11
0.04
0.13
99.52
70.22
70.22
0.35
14.26
14.26
0.94
2.47
2.47
0.19
0.34
0.34
1.30
4.48
3.76
1.07
0.06
0.09
99.53
17
17
990
990
33
28
28
135
135
40
40
20
20
10
10
55
22
22
280
280
25
25
105
105
205
205
97
97
20
20
1250
1250
55
15
15
110
110
29
29
20
20
55
22
22
29
29
260
260
20
20
1400
55
25
25
90
40
20
55
55
30
270
-----
-----
---
10
55
0.13
0.43
0.43
2.30
2.30
. 3.95
3.95
3.55
3.55
2.12
2.12
0.03
0.03
0.11
0.11
99.53
99.53
-----
-----
72
72
420
84
84
275
275
41
41
42
43
43
71.20
71.20
0.47
0.47
14.90
1.72
1.60
67.60
67.60
0.44
0.44
15.10
1.75
1.
75
2.24
2.24
76.17
76.17
0.17
0.17
12.05
0.96
0.96
1.00
0.03
0.11
0.26
3.76
4.27
0.63
0.07
0.06
99.53
-----
---
0.72
0.71
0.71
1.70
1.
70
5.98
0.70
0.40
1.10
2.10
1.95
1.95
4.95
1.60
0.90
100.38
100.62
-----
18
550
33
45
410
33
20
10
10
40
20
220
220
10
190
190
26
110
66
---
25
25
450
25
17
370
35
20
17
35
20
220
40
40
180
79
205
66
16
16
165
165
33
45
45
155
55
20
10
17
26
340
16
95
26
120
55
�Table 1.
1.
Number
Sample
Number
Explanation
Description.
Description
1.
1.
179
Coarse-grained rhyolite dike on Observatory
Hill.
2.
2.
180
Contact zone of coarse-grained rhyolite dike
on Observatory Hill.
on
Hill.
3.
3.
183
Baxter Hollow
Hollow Granite.
Granite.
4.
89
5.
5.
102
Marquette rhyolite
rhyolite (unit
(unit G).
G).
6.
6.
106
Marquette rhyolite
rhyolite (unit
(unit G).
G).
7.
7.
101
Marquette rhyolite
rhyolite (unit
(unit F).
F).
8.
8.
100
Marquette rhyolite
rhyolite (unit
(unit E).
E).
9.
9.
103
Marquette rhyolite
rhyolite (unit
(unit D).
D).
10.
104
Marquette rhyolite
rhyolite (unit
(unit D,
D, massive
massive phase).
phase).
11.
91
Marquette rhyolite
rhyolite (unit
(unit C).
C).
12.
92
Marquette rhyolite
rhyolite (unit
(unit B).
B).
13.
98
Marquette rhyolite
rhyolite (unit
(unit B).
B).
14.
99
99
Marquette rhyolite
rhyolite (unit
(unit B).
B).
15.
15.
107
Montello Granite.
Granite.
16.
16.
108
Observatory Hill
Hill rhyolite.
rhyolite.
17.
17.
109
Endeavor rhyolite.
rhyolite.
18.
110
Granite at Redgranite collected
collected in
in Flynn's
Flynn's
Quarry.
19.
19.
112
Berlin rhyolite.
rhyolite.
Marquette rhyolite (unit
(unit C)
G) from
from Noble's
Quarry. Samples 4-14 are
are keyed
keyed to
to figure
figure 45.
45.
44
�Table
Table 1.
1.
Explanation
Explanation (Continued)
(Continued)
20.
20.
114
114
Utley
Utley rhyolite.
rhyolite.
21.
21.
173
173
Marcellon
Marcellon rhyolite
rhyolite (unit
(unit A).
A). Sample
Sample
numbers
21-27
are
keyed
to
figure
numbers 21-27 are keyed to figure 33.
33.
22.
22.
176
176
Marcellon
Marcellon rhyolite
rhyolite (unit
(unit A).
A).
23.
23.
174
174
Marcellon
Marcellon rhyolite
rhyolite (unit
(unit B).
B).
24.
24.
161
161
Marcellon rhyolite
rhyolite (unit
(unit B).
B).
25.
25.
145
Marcellon rhyolite
rhyolite (unit
(unit C).
C).
26.
26.
175
175
Marcellon
Marcellon rhyolite
rhyolite (unit
(unit C).
C).
27.
27.
178
178
Marcellon rhyolite
rhyolite (unit
(unit D).
D).
28.
28.
182
182
Caledonia Church rhyolite
rhyolite (south
(south limb
limb
of the
the Baraboo Syncline).
Syncline).
29.
29.
147
Baraboo rhyolite
from the
the NE
NE ~,
, sec. 23,
rhyolite from
T. 12
T.
12 N.,
N., R.
R. 7 E.
30.
30.
105
Marquette andesite
andesite dike
dike (figure
(figure 45).
45).
31.
31.
111
111
Granite porphyry dike from
from Flynn's Quarry
County Park.
Park.
32.
32.
148
Marcellon andesite
andesite dike
dike (figure
(figure 33).
33).
33.
33.
177
Marcellon basalt dike
dike (figure
(figure 33).
33).
34.
34.
153
Netabasalt dike
Metabasalt
dike at Montello (collected
(collected from
from
23).
quarry just north
north of
of S.H.
S.H. 23).
35.
35.
154
154
Metabasalt dike at Redgranite (from
(from quarry
city of Redgranite).
36.
36.
155
dike from
granite quarry near
Diorite dike
from granite
11 E.).
E.).
27, T.
T. 18 N., R.
Spring Green
Green (NE
(NE ~,, sec. 27,
Spring
R. 11
37.
37.
184
Denzer diorite
45
45
�Pable 1.
1.
Table
Explanation (Continued)
(Continued)
Explanation
38.
38.
192
192
Dacite dike
dike at
at Marquette
Marquette (figure
Dacite
(figure 45).
45) .
39.
39.
190
190
Dacite dike
dike at
at Marquette
Marquette (figure
Dacite
(figure 45).
45) .
40.
40.
191
191
Dacite
Dacite dike
dike at
at Marquette
Marquette (figure
(figure 45).
45) .
41.
41.
210
210
Dacite
Dacite dike
dike in
in the
the Utley Quarry.
Quarry.
42.
42.
211
211
Andesite
Andesite dike
dike in
in the
the Utley Quarry.
Quarry.
43.
43.
193
193
Taylor Farm rhyolite.
Taylor
rhyolite.
major element
element analyses
analyses on
on Table
Table 6 (except
All major
#41 and
(except 'ft4l
and 42)
42)
were made
made using conventional wet-chemical methods
were
methods (K.
(K. Aoki,
Aoki,
analyst). Major element analyses 41 and 42 were
analyst).
were done
done by
0. Joensuu.
Joensuu. Trace element analyses (Rb,
O.
(Rb, Sr,
Sr, Pb
Pb and
and Zn)
Zn)
by atomic absorption spectrometry (0.
(0. Joensuu, analyst).
analyst).
All other trace
trace elements by optical emission spectrography
spectrography
(0. Joerisuu,
analyst).
(0.
Joensuu, analyst).
The
for Zr
Zr are
are accurate
accurate to
to
The result~
result for
±
107g.
Sr
and
Rb
are
accurate
to
± 10%. Sr and Rb are
to -- 5%
the amount present
present
5% of
of the
xcept for
~xcept
for low
low Sr
Sr (less
(less than
than 20
20 ppm)
ppm) which
which is
is accurate
accurate to
to
1070 of
-- 10%
of the
the amount
amount present.
present.
46
46
�')
(
.5 MILES
0
zz
<{
a::
CD
EXPLANATION
rn
:E
<{
containing rounded
Friable quartz sandstone, locally containing
rounded
rhyolite fragments
C)
u
zz
<{
a::
CD
:E
<{
C)
u
Ui
lLI
a::
LII
E3
t"(\/]
0
~
I
Fine-grained
Fine - grained rhyolite dike
Coarse-grained
rhyolite dike
Coarse-grained rhyolite
rhyolite
Hill rhyolite
Observatory Hill
Q.
a-
Location of
Location
-+-
Figure 7.
Figure
7.
field
fi eld trip stops
Quarry
Vertical banding
Geologic
Hill adapted
adapted from
from Hobbs
Hobbs and
and Leith
Leith (1907).
(1907).
Geologic map of Observatory Hill
Approximate locations of field
field trip Stops
stops are superimposed.
Contour
interval 20
20 feet
feet between
between 800
800 and
and 960
960 feet;
feet; above
above 960
960 feet
feet the
the interinterinterval
val is
val
is 10 feet.
feet.
Contour
Contour lines
lines between
between 900
900 and
and 960
960 feet
feet are
are approxapproximately located.
located.
48
�STOP 22 -- RHYOLITE
RHYOLITE AT
AT OBSERVATORY
OBSERVATORY HILL
HILL
STOP
Location:
Location:
Observatory
Observatory Hill
Hill (Hobbs
(Hobbs and
and Leith,
Leith, 1907)
1907) is
is one
one of
of five
five porphyritic
porphyritic
rhyolite inliers
inliers in
in south—central
south-central Wisconsin
Wisconsin (others
(others are
are at
at Endeavor,
Endeavor, Taylor
Taylor
rhyolite
Farm, Utley
Utley and
and Berlin).
Berlin). The
The hill
hill is
is formed
formed by
by steeply
steeply dipping
dipping flows
flows of
of
Farm,
quartz—and
quartz-and alkali
alkali feldspar—bearing
feldspar-bearing rhyolite
rhyolite tuffs,
tuffs, cut
cut by
by coarse—grained
coarse-grained and
and
fine-grained rhyolite
rhyolite dikes.
dikes. Observatory
Observatory Hill
Hill is
is surrounded
surrounded by
by outcrops
outcrops of
of
fine—grained
Upper Cambrian
Cambrian sandstone
sandstone and
and conglomerate
conglomerate (Fig.
(Fig. 7).
7).
Upper
The traverse
traverse to
to the
the summit
summit of
of Observatory
Observatory Hill
Hill will
will follow
follow an
an easy
easy but
but
The
It
is
Please
stay
together
during
the
climb.
sometimes
indistinct
trail.
Please
stay
together
during
the
climb.
It
is
sometimes indistinct trail.
Observatory
Hill.
quite
easy
to
become
lost
on
the
slopes
surrounding
Observatory
Hill.
quite easy to become lost on the slopes surrounding
Description:
Description:
Stop 2A
2A
Stop
The climb
climb to
to the
the summit
summit of
of Observatory
Observatory Hill
Hill begins
begins at
at exposures
exposures of
of Cambrian
Cambrian
The
sandstone just
just to
to the
the east
east of
of the
the bend
bend in
in Gillette
Gillette Road
Road (north
(north side
side of
of road)
road)
sandstone
of
rhyolite
The
outcrop
at
this
stop
is
about
300
m
to
the
south
(Fig.
7).
outcrop
at
this
stop
is
about
m
to
the
south
of
rhyolite
(Fig. 7).
outcrops on Observatory Hill and
and is
is composed
composed of aa friable
friable reddish—brown
reddish-brown quartz
quartz
No
fragments
of
rhyolite
are
found
here;
they
are
quite
common,
sandstone.
fragments
of
rhyolite
are
found
here;
they
are
quite
common,
sandstone.
however, in
in sandstone
sandstone exposures
exposures closer
closer to
to the
the rhyolite ledges.
ledges.
however,
Stop 2B
2B
Stop
Walk from
from stop
stop 2A
2A to
to the
the northwest over
over the
the low
low rise
rise to
to the
the first
first northnorththe
outcrops
of
sandstone
and
east
trending
valley
(Fig.
7).
Note
the
outcrops
Cambrian
east
valley (Fig. 7).
A conglomerate
conglomerate on the southeast side
side of
of the
the valley
valley (Fig. 8).
8). A
conglomerate
thick and
and contains
contains rhyolite
bed in this exposure is approximately 40 cm thick
cropping
m to
fragments
to rhyolite
rhyolite cropping out
out 200
200 m
to the
the north.
north.
fragments lithologically similar to
rounded
and
reach
10
cm
in
size
The
fragments
within
the
conglomerate
are
rounded
and
reach
10
cm
in
size
The fragments
are
pebbles in
Occasionally, quartzite
quartzite is
is found
found as
as small
small rounded
rounded pebbles
(Fig.
9). OCcasionally,
in the
the
(Fig. 9).
of
quartz—
The
source
of
these
clasts
may
be
in
the
large
area
conglomerate.
The
source
of
these
clasts
may
be
in
the
large
area
of
quartzconglomerate.
(Smith, 1978c)
1978c) or
or from
from vein
vein quartz
quartz
ite
ite to
to the
the northeast
northeast of
of Observatory Hill (Smith,
within the rhyolite.
Figure
Figure 8.
8.
View of
of Cambrian
Cambrian sandstone
sandstone outcrops
outcrops at
at stop
stop 2B
2B on
on the
the south
south flank
flank
View
of
49
of Observatory
Observatory Hill.
HIll.
�Figure 9A.
Figure
9A.
Figure
Figure 9B.
9B.
Close—up of
of aa conglomerate
conglomerate layer
layer interbedded
interbedded with
with Cambrian sandClose-up
stone at stop
stop 2B.
2B.
In
fragments are angular (compare
(compare
In these
these bands,
bands, fragments
with Fig.
with
Fig. 9B).
9B). Most
Most of the fragments
fragments are
are porphyritic
porphyritic rhyolites
rhyolites
similar to
to those cropping out on Observatory
Observatory Hill.
Hill.
View
View of
of large
large rhyolite
rhyolite fragments
fragments (up
(up to
to 10
10 cm
cm in
in size)
size) in
in aa conconglomerate
glomerate layer
layer at
at stop
stop 2B.
2B. In
In this
this band,
band, fragments
fragments are
are rounded
rounded
(compare
(compare with
with Fig.
Fig. 9A).
9A).
50
50
�o
On
On Observatory
Observatory Hill
Hill exposures
exposures of
of conglomerate
conglomerate containing
containing rhyolite
rhyolite pebbles
pebbles are
are
usually
usually restricted
restricted in
in occurrence
occurrence to
to aa zone
zone 55 to
to 20
20 mm wide
wide about
about the
the rhyolite
rhyolite
ledges. The
The conglomerate
conglomerate layer
layer at
at Stop
Stop 2B
2B is
is located
located an
an unusually
unusually large
large distance
distance
ledges.
from
from rhyolite
rhyolite exposures
exposures (200
(200 m),
m), and
and its
its deposition
deposition probably
probably reflects
reflects aa relatively
relatively
short lived
lived and
and highly
highly energetic
energetic event.
event. In
In the
the Baraboo
Baraboo region
region Dott
Dott and
and Dalziel
Dalziel
short
(1970)
(1970) reported large
large boulders of
of Baraboo Quartzite entrapped within Cambrian
sandstone. They
They envisaged
envisaged transport
transport of
of cobbles
cobbles and
and boulders
boulders by
by waves
waves and
and strong
strong
sandstone.
currents
currents generated
generated by
by violent
violent tropical
tropical storms
storms that
that pounded
pounded the
the Baraboo
Baraboo islands
islands
during Cambrian
Cambrian time.
time. Observatory
Observatory Hill
Hill probably
probably existed
existed as
as aa small
small island
island in
in
during
Strong
late
Cambrian
time
and
was
probably
also
hit
by
violent
tropical
storms.
late Cambrian time and was probably also hit by violent tropical storms.
Strong
currents
currents generated
generated during
during these
these storms
storms are
are probably
probably responsible
respon$ible for
for the
the transtransport
port of
of rhyolite
rhyolite fragments
fragments away
away from
from the
the Observatory
Observatory Hill
Hill island,
island, thus
thus forming
forming
the
conglomerate
band
observed
at
Stop
2B.
the conglomerate band observed at Stop 2B.
Stop 2C
2C
Stop
From Stop
Stop 2B
2B climb
climb the
the ridge
ridge above
above the
the sandstone
sandstone exposure
exposure and
and join
join aa trail
trail
Follow
this
trail
to
where
it
running along
along the
the crest
crest of
of the
the ridge.
ridge.
Follow this trail to where it joins
joins the
the
running
main
main trail
trail and
and then
then continue
continue up
up the
the hill on
on the
the main trail
trail (Fig.
(Fig. 7).
7).
Note the
the first
first outcrops
outcrops of
of rhyolite
rhyolite to
to your
your left
left and
and straight
straight ahead.
ahead. There
There
vicinity
is at least 500 feet
feet of relief on the Precambrian surface in
in the
the vicinity of
of
is
Observatory Hill.
Hill. Just ahead rhyolite exposures are
are at an elevation of
of 1080
1080
Observatory
northwest of
of Observatory
Observatory Hill,
Hill, rhyolite
rhyolite was
was enfeet. About
About 1200
1200inm to the
the northwest
feet.
countered in
in an irrigation
irrigation well at a depth of 300 feet
feet (480
(480 feet above
above sea
sea
level).
level).
Cross into
into the
the rhyolite exposures and
and continue to
to the
the trail
trail junction.
junction.
the trail
trail to
to the
the right
right (south).
(south). The fork to the
the left
left (north)
(north) goes
goes to
to
Follow the
1920's
the summit
summit where
where aa lookout
tower was
was once
once located
located in the
the
lookout tower
the early 1920's
The ruins
ruins of
of the
the tower
can still
still be
be observed
observed along
along the
(Fig.
7).
The
tower can
the inscriptions
(Fig. 7).
carved into the
rhyolite by
by several
several of
of the
the workers
workers who manned
manned the
carved
the rhyolite
the tower.
tower.
Follow the
trail (south)
to aa large
large area
area of
of bare
bare rock
rock which forms
Follow
the trail
(south) to
forms the
bluff).
sharp
the south bluff).
sharp southern
southern edge
edge of
of Observatory Hill
Hill (hereafter called
called the
rhyolite exposures
exposures (20
From the south bluff
bluff the
the Marcelloii
Marcellon rhyolite
(20 km to
to the
the south)
clear
and the
the Baraboo
Baraboo Hills
Hills (30
(30 km
km to
to the
the southwest)
southwest) can
can be
be easily
easily seen
seen on
on aa clear
and
At this
stop, we
we will
will examine
examine the
Hill rhyolite
rhyolite and a
day.
At
this stop,
the Observatory Hill
a
day.
coarse-grained
dike.
coarse—grained rhyolite dike.
Observatory
Observatory Hill
Hill Rhyolite
Rhyolite
rhyolites exposed
exposed
The Observatory
Observatory Hill
Hill rhyolite
rhyolite is
is typical
typical of
of porphritic
porphritic rhyolites
The
It contains
contains phenocrysts
phenocrysts of
of quartz
quartz (<
1 mm in
in
(~l
in size
size
in south-central
south—central Wisconsin.
Wisconsin. It
in size)
size) set
set in
and
in a
a
and rounded)
rounded) and
and pink
pink to
to white
white alkali
alkali feldspar
feldspar (1
(1 to
to 55 mm
mm in
On close
close examination,
examination, the
the matrix
matrix of
of the
the rhyolite
rhyolite
dark
dark gray to black matrix. On
and pumice
pumice fragments.
fragments.
shows
shows faint
faint flow
flow structure
structure formed
formed by flattened shards and
o
50°E.
The rhyolite
rhyolite is
In
E. The
is an
an
In general,
general, these
these bands
bands dip
dip steeply
steeply and
and strike
strike N.
N. 50
the entire
entire hill.
ash-flow
hill.
ash—flow tuff
tuff and
and is
is remarkably
remarkably texturally
texturally homogenous
homogenous over
over the
pheno—crysts
Petrographic studies
studies indicate
indicate that
that the
the rhyolite
rhyolite is
is composed
composed of
of pheno-crysts
Petrographic
The
devitrified ground-mass.
ground—mass. The
of
of quartz
quartz and
and alkali
alkali feldspar
feldspar set
set in
in aa coarsely
coarsely devitrified
51
51
�quartz is
is anhedral
anhedral and
quartz
and is
is usually
usually strained
strained (7%).
(7%). Some
Some of
of the
the quartz
quartz is
is deeply
deeply
embayed. Alkali
Alkali feldspar
feldspar (23%)
(23%) is
is probably
probably orthoclase
orthoclase and
and may
may display
display carlscarlsembayed.
bad twinning.
twinning. Accessory
Accessory minerals
minerals are
are chlorite,
chlorite, biotite
biotite (?),
bad
epidote, iron
(?), epidote,
iron
oxide and
and zircon.
The matrix
matrix commonly
commonly contains
contains aligned
aligned and
and flattened
flattened Y
Y shaped
shaped
oxide
zircon. The
and cuspate
cuspate shards.
and
shards.
o
In terms
terms of
of major
major and
and minor
minor element
element chemistry,
chemistry, the
the rhyolite
rhyolite belongs
belongs to
to
In
chemical group
group 33 (Table
1, analysis
analysis 16;
16; Fig.
Fig. 6),
6), of
of Smith
Smith (1978a)
and is
chemical
(Table 1,
(1978a) and
is
therefore similar
similar in
in chemistry
chemistry to
to granophyric
granophyric granites
granites and
and porphyritic
porphyritic rhyorhyo—
therefore
lites in the Fox River Valley.
The group
group 33 rhyolites
rhyolites and
and granites
granites are
are
lites
Valley. The
distinguished
,
distinguished from
from other
other south-central
south—central Wisconsin
Wisconsin igneous
igneous rocks
rocks by
by high
high Si0
Si02,
2
K20/Na20,
La,
Zr,
Y
and
Rb/Sr;
and
low
CaO,
A1203
and
Ba
(Table
1).
K 0/Na 0, La, Zr, Y
Rb/Sr; and low CaO, A1 0 and Ba (Table 1).
2
2 3
2
Coarse—Grained Rhyolite
Coarse-Grained
Rhyolite Dike
coarse—grained rhyolite
dike strikes north south across Observatory
A coarse-grained
rhyolite dike
(Fig. 7).
The dike is about
m wide
wide at
(Fig.
7). The
about 70 m
at the south bluff but pinches out to
to
the north.
m thick)
dike of similar coarse—grained
the
north. A thin (15
(15 m
thick) dike
coarse-grained rhyolite
strikes N.
N. 50 E.
E. across the
strikes
the southeast
southeast slopes
slopes of
of Observatory
Observatory Hill.
Hill. These
dikes were
were originally identified by Hobbs and Leith (1907)
dikes
(1907) who referred
referred to
to
them as
as granite dikes.
them
The contact between the
the dike and the Observatory Hill rhyolite is well
displayed on the
east
edge
the
edge of
of the
the south
south bluff.
bluff. The contact shows complex
interfingering of
of dike
dike rock
rock into
into Observatory
Observatory Hill
Hill rhyolite
rhyolite (Fig.
10) and
and in
interfingering
(Fig. 10)
in
locality a
a rhyolite zenolith is
is found
found in
in dike
dike rock
rock close
close to
to the
the contact.
contact.
Locally the
Hill rhyolite is intensely fractured near the
the Observatory Hill
the contact
contact
(Fig.
11).
Also, quartz veins are concentrated on either side of the
(Fig. 11). Also,
the contact.
contact.
Extending 55 to
to 10
10 m
m into
into the
the dike from
from the
the intrusive
intrusive contact
contact is
is aa fine—
finegrained
contact
zone
(chill
zone?).
grained contact zone
zone?). The rock in this zone is
is gray—green
gray-green in
in
color and
and contains large
large plagioclase
plagioclase phenocrysts.
phenocrysts.
Petrographic
Petrographic studies
studies of
of the
the dike rock
rock of
of the
the contact zone
zone reveal
reveal sub—
subhedral
hedrHl zoned
zoned plagioclase phenocrysts (30%)
(30%) with cores altered to
to sausserite
sausserite
and unaltered
unaltered rims,
rims, subhedral alkali feldspar
feldspar (5%),
(5%), fractured and broken
quartz (3%)
(3%) and
and small
small subhedral
subhedral feather—like
feather-like grains
grains of
of biotite (1%).
(1%). The
matrix is
a
microbreccia
containing
fragments
of
fine—grained
is a
fragments of fine-grained rhyolite,
rhyolite,
basalt and
and eutaxitic
eutaxitic rhyolite.
rhyolite.
At this
this locality
locality also
also notice
notice the
the glacial
glacial polish
polish and
and grooving.
grooving.
glacial
striations
trend
N.
70°
W.
glacial striations trend N. 70° W.
Here
Here
Walk
Walk to
to the
the east
east of
of the
the south
south bluff
bluff to
to the
the first
first major
major outcrop.
outcrop. Here
Here
rhyolite
in
the
central
part
of
the
dike
is
well
exposed.
rhyolite in the central part of the dike is well exposed. This
This rhylite
rhylite is
is
similar
similar in
in mineralogy to
to that
that of
of the
the contact zone,
zone, but differs by
by having
having aa
coarser—grained
coarser-grained matrix
matrix than
than the
the contact—zone
contact-zone rock.
rock. Also,
Also, it
it is
is pink
pink to
to red
red
in
in color
color in
in outcrop,
outcrop, not
not green
green in
in color
color like
like the
the contact—zone
contact-zone rock.
rock. Petro—
Petrographic
graphic examination
examination indicates
indicates that
that plagioclase is
is the
the dominant phenocryst
phenocryst
(46%).
(46%). Alkali
Alkali feldspar
feldspar is
is present
present in
in micropegmatitic
micropegmatitic intergrowths
intergrowths with
with
quartz
quartz (21%).
(21%). Quartz,
Quartz, in
in addition
addition to
to its
its occurrence
occurrence in
in alkali
alkali feldspar—quartz
feldspar-quartz
52
52
�Figure 10.
10.
Figure
View of the contact between the coarse—grained
coarse-grained rhyolite dike (below),
(below),
Hill rhyolite
rhyolite (above).
(above). Note
Note the
the fingers
fingers of
of
and the Observatory Hill
coarse—grained rhyolite
rhyolite extending
extending into
into the
the Observatory
Observatory Hill
coarse-grained
Hill rhyolite
rhyolite
Also
noteworthy
are
the
numerous
veins
of
quartz
(dashed line).
line).
veins
that
the contact.
contact.
that roughly parallel the
Figure
Figure 11.
11.
Close—up view
view of
of the
the shattering
shattering of
of the
the Observatory
Observatory Hill
Hill rhyolite
rhyolite
Close-up
at
dike.
at the
the contact
contact with
with the
the coarse-grained
coarse—grained rhyolite dike.
53
53
�intergrowths,
intergrowths,
(10%) include
include
(10%)
oxide.
These
oxide.
These
is present
present as
as small
small anhedral
anhedral phenocrysts
is
phenocrysts (2%).
(2%). Accessory
Accessory minerals
minerals
chlorite in
in irregular
irregular clots,
clots, epidote,
epidote, clinozoisite,
clinozoisite, and
chlorite
and iron
iron
minerals are set
led groundmass
groundmass (21%).
set in
in aa finely
finely devitrif
devitrified
(21%).
This dike
dike and
and aa fine-grained
fine—grained granite at
This
at Baxter Hollow
Hollow (Gates,
(Gates, 1942)
1942) are
are
similar
in
chemistry,
and
form
chemical
group
1
of
Smith
(1978a)
similar in chemistry,
group 1 of Smith (1978a) (Table
(Table 1,
1,
analyses 11 and
The rocks
rocks are
are distinguished
distinguished from
from the
the other
other
analyses
and 2;
2; and
and Fig.
Fig. 6).
6). The
granites
and
rhyolites
in the
the Fox
Fox River
River Valley
Valley and
and Baraboo
Baraboo area
area by
by higher
higher
granites and rhyolites in
Ti02,, CaO,
CaO, Ba,
Ti0
Ba, V
V and Sr
Sr and
and by
by lower
lower Si02
Si0 and
and Rb.Sr
Rb.Sr ratio.
ratio.
Both
Both the
the ObserObser—
2
2
vatory Hill
Fox
ovatory
Hill rhyolite
rhyolite and
and the
the Baxter
Baxter Hollow
Hollow Granite are younger than the
the Fox
River Valley
Valley and
and Baraboo
Baraboo rhyolites.
Baxter Hollow
Hollow Granite
Granite intrudes
rhyolite
River
rhyolites. Baxter
intrudes rhyolite
(Gates, 1942)
1942) but
but its
its relationship
relationship to the overlying Baraboo
(Gates,
Baraboo Quartzite
Quartzite is
is
unclear (Dott
Daiziel, 1972).
unclear
(Dott and
and Dalziel,
1972). This
This stratigraphic
stratigraphic and
and chemical
chemical evidence
evidence
suggests that
that the
the intrusion
intrusion of
of the
the Baxter
Baxter Hollow
Hollow Granite
Granite and
and the
the Observatory
Observatory
suggests
Hill rhyolite
rhyolite was
was a
discrete igneous
event that
occurred after the
emplacement
Hill
a discrete
igneous event
that occurred
the emplacement
and folding
folding of
of the
the widespread rhyolite ash—flow
and
ash-flow sheets.
sheets.
The
for aa short
short time
time at
at the turn
The coarse-grained
coarse—grained rhyolite
rhyolite dike
dike was
was quarried
quarried for
of the
the century.
century. This
This opera~ion
operation is
evidenced by
by aa large
of
is evidenced
large area
area of broken dike
rock located just
just below and
and to
to the
the east
east of
of the
the south
south bluff.
bluff.
Labradorite Porphyry Dike
Dike
Hobbs and
east—trending "labradorite porphyry"
Hobbs
and Leith (1907)
(1907) reported
reported an east-trending
porphyry"
dike just to
to the
the north
north of
of the
the south
south bluff.
bluff. A
for this
this dike
dike
A careful search for
revealed an east-trending
east—trending fine—grained
quartz—feldspar rhyolite dike about
fine-grained quartz-feldspar
5
5 m
m in
in width.
width. This
This dike is
is truncated by the north—trending
north-trending coarse—grained
coarse-grained
rhyolite
rhyolite dike as
as is the "labradorite porphyry"
porphyry" dike described by Hobbs and
Leith.
In terms
terms of
of location,
location, orientation
orientation and
and stratigraphy,
stratigraphy, it
almost
Leith.
In
it is
is almost
certainly the
the same
same dike
dike mapped
mapped by
by them.
them.
In
In thin
thin section,
section, this rock contains
rounded
rounded and embayed quartz phenocrysts
phenocrysts (2%)
(2%) and alkali feldspar with perthitic
texture (altered
(altered to
to sericite
sericite and
and dusted
dusted with
with iron
iron oxide)
oxide) (3%).
(3%). These minerals
occupy a
a fine—grained
fine-grained matrix (devitrified)
(devitrified) with iron oxide accentuating a
a
crude
evidence of
crude banding
banding (95%).
(95%). The only evidence
of metabasalt on Observatory Hill is
found
found on
on the
the south
south bluff.
bluff. Here aa green metabasalt that
that occurs
occurs in
in an
an outcrop
outcrop
only 3 m
m long
long and
and 0.3
0.3 mm wide
wide may
may intrude
intrude rhyolite.
rhyolite.
Other
Other Exposures
Exposures of
of Porphyritic
Porphyritic Rhyolite:
Rhyolite:
Other
Other exposures of
of porphyritic
porphyritic rhyolite
rhyolite (Endeavor,
(Endeavor, Utley,
Utley, Berlin,
Berlin, and
and
Taylor Farm)
Farm) are
are mineralogically,
mineralogically, texturally,
texturally, and
and chemically similar
similar to
to the
the
rhyolite
rhyolite at
at Observatory
Observatory Hill.
Hill. However,
However, common
common in
in the
the Utley rhyolite
rhyolite are
are zones
zones
of
of spherulites
spherulites and
and lithophysae,
lithophysae, also
also disk—shaped
disk-shaped coarse—grained
coarse-grained inclusions
inclusions
may
may represent
represent recrystallized
recrystallized collapsed
collapsed pumice.
pumice. Rhyolite is
is locally
locally sheared
sheared at
at
Berlin (Weidman,
(Weidman, 1898)
1898) and
and slickensided
slickensided surfaces
surfaces are
are found
found at
at Utley
Utley (Gram,
(Gram,
1947).
1947). Rhyolite at
at Utley
Utley is
is intruded
intruded by
by rhyolite,
rhyolite, dacite
dacite and
and metabasalt
metabasalt dikes.
dikes.
54
54
�1/
/
o
/
CC
~_
~ I ~~v'1'\:Y
N
t4
/'
.>..
~
t
J
~ (
--- -/
) /
(A/
(AI
J
~<
~4
~
/' EXPOSURES
EXPOSURES
/OF WELL
BANDED
WELL BANDED
?/ UNIT C
---- "---.,,,
~
--
~
UW DEEP HOLE
HOLE
)
WAYNE
/
BUSH
FARM
BUSH FARM
SPHEROIDS) I / f
~/u,,~ /
(~~~~
----
,..-
L BOX - PARK HERE
WELL
BANDED
UNIT B
QUARTZ
VEINS
EXPLANATION
---
-o
O
..
200
200 400
400FEET
FEET
I
4
4-
CONTACT
STRIKE AND
AND DIP
DIP OF
OF
STRIKE
FLOW BANDING
BANDING
FLOW
PLUNGING ANTICLINE
ANTICLINE
PLUNGING
PLUNGING SYNCLINE
SYNCLINE
PLUNGING
FIELD TRIP
TRIP ROUTE
ROUTE
,,~;~ FIELD
I''
-+-+-+- FENCE
FENCE
Figure
Figure 12,
12.
Route
Route map
map for
for traverses
traverses at
at the
the Marcellon
Marcellon rhyolite
rhyolite exposures,
exposures.
Letters
Letters A,
A, B,
B, CC refer
refer to
to Marcellon
Marcellon rhyolite
rhyolite unit
unit numbers
numbers (see
(see
text
text and
and Fig,
Fig. 13).
13).
56
56
�STOP 33 -- THE
THE MARCELLON
MARCELLON RHYOLITE-SPHEROIDAL
RHYOLITE-SPHEROIDAL TEXTURES
TEXTURES
STOP
Location:
Location:
To
To reach
reach the
the outcrops
outcrops of
of spheroidal
spheroidal rhyolite
rhyolite we
we will
will walk
walk into
into the
the woods
woods
at
at the
the mail
mail box
box located
located across
across Monthey
Monthey Road
Road from
from the
the Wayne
Wayne Bush
Bush Farm.
Farm.
This
This traverse
traverse requires
requires aa bit
bit of
of climbing
climbing on
on bare
bare rock
rock that
that becomes
becomes quite
quite
slippery during
during wet
wet weather.
weather. Wear
Wear proper
proper field
field boots
boots and
and take
take considerable
considerable
slippery
care while
while on
on this
this traverse.
traverse.
care
(west)
(west)
This
This stop
stop will
will illustrate
illustrate several
several of
of the
the textural
textural types
types of
of rhyolite
rhyolite in
in the
the
Marcellon inlier.
inlier. See Figure
Figure 12
12 for
for the
the traverse
traverse route.
route. The
The rhyolite
rhyolite exposures
exposures
Marcellon
to
to the
the east of
of Monthey
Monthey Road
Road are
are described
described in
in aa supplemental
supplemental stop.
stop.
Introduction to the
the Marcellon Rhyolite:
Rhyolite: The
The Marcellon
Marcellon inlier
inlier (Hobbs
(Hobbs and
and Leith,
Leith,
1907;
1907; Smith,
Smith, 1978a)
1978a) is
is composed of texturally
texturally variable rhyolites
rhyolites similar
similar in
in
chemistry and
and lithology
lithology to
to rhyolites at the
the Marquette exposure (Stop
(Stop 4),
4), and
and
in the Baraboo
Baraboo area.
area. The Marcellon inlier
inlier is
is formed by four
four mineralogically and
and
chemically distinct ash—flow
ash-flow tuffs
tuffs folded into
into aa northeast striking
striking asymmetric
asymmetric
(and possibly overturned)
overturned) antiform
antiform (Fig.
(Fig. 13).
13). The western limb
limb of
of the
the antiform
antiform
(and
N. 500
50° E.
E. and
and dips
dips 50—85°
50-85° to
to the
the northwest.
northwest. The eastern limb
limb also
also
strikes N.
strikes
strikes N.
N. 50°
50° E.
E. but dips
dips steeply
steeply (80°
(80° to
to vertical)
vertical) to
to the
the southeast.
southeast. The
The
rhyolite
are cut
cut by a
northeast trending andesite dike and by an east
rhyolite flows
flows are
a northeast
(Table 1,
1, analyses
analyses 32
32 and
and 33).
33). The andesite
andesite dike
dike cuts
cuts
trending basalt dike (Table
and is
is therefore
therefore younger.
younger.
the basalt dike and
The structurally highest
A) at Marcellon
Marcêllon is a
The
highest unit
unit (unit
(unit A)
a sparsely porphy—
porphyritic
ritic plagioclase (1%),
(1%), quartz (2%),
(2%), alkali feldspar
feldspar (2%)
(2%) rhyolite characterized
diameter) composed of radiating
by abundant
abundant large spherulites
spherulites (up
(up to 15 cm in diameter)
On
the
fibers
of
alkali
feldspar
and
quartz.
On
the
eastern flank of the
the fold,
fold,
fibers
alkali feldspar and quartz.
spherulites are
are less
less distinct and
and smaller,
smaller, but
but still
still conspicuous.
conspicuous. Structurally
below unit
unit A is
is a
a rhyolite (unit
(unit B)
(6%), alkali
B) which contains sparse quartz (6%),
feldspar (4%)
feldspar
(4%) and plagioclase (1%)
(1%) phenocrysts in a
a banded matrix with
Several samples
samples show
show perlitic
perlitic cracks
cracks in
occasional
occasional faint
faint spherulitic growths. Several
characteristically
well
banded
and
contains
plagioclase
the
Unit
Unit C is
the matrix.
Bnnding in unit
as
(14-18%). B~nding
unit C is
is continuous and
as the
the dominant phenocryst (14—18%).
0
relatively
consistent
in
orientation
(N.
50°E.)
but
locally
broad westward
westward
relatively consistent in orient~tion (N. 50 E.) but locally broad
Several
lenses
of
spherulitic
rhyolite
plunging
exposed. Several lenses of spherulitic rhyolite lie
lie
plunging flow folds
folds are exposed.
Unit C
parallel
sharp contacts
contacts with
with nonspherulitic
nonspherulitic rock.
rock.
C
parallel to banding and have sharp
mineralogy to rock on
on the
on
the
on the
the eastern
eastern flank
flank of
of the
the fold
fold is
is similar
similar in
in mineralogy
The core
core of the antiform is
western flank,
flank, but it
it lacks
lacks conspicuous
conspicuous banding.
banding. The
is
(2%),
formed
(unit D)
formed by
by aa rhyolite
rhyolite (unit
D) which
which contains
contains phenocrysts
phenocrysts of
of quartz
quartz (2%),
plagioclase (15%)
and alkali
alkali feldspar
feldspar (2%)
in aa fine-grained
fine—grained devitrified
devitrified
plagioclase
(15%) and
(2%) in
groundmass
with
numerous
shards,
flattened
pumice
and
perlitic
fractures
groundmass with numerous shards, flattened pumice and perlitic fractures
All
units
at
are
interpreted
as
ash—flow
tuffs.
(Fig.
14).
All
Marcellon
ash-flow
tuffs.
(Fig. 14).
Marcellon includes:
Evidence
at Marcel10n
includes:
Evidence for
for the
the northeast
northeast striking
striking antiform at
(b)
geologic
map (Fig.
(a)
(Fig. 13);
13); (b)
(a) the
the symmetric
symmetric pattern
pattern of
of lithologies on the geologic map
rhyolite)
which
indicates
structural
(orientation of
structural data
data (orientation
of banding
banding within
within the
the rhyolite) which indicates
50° E.
E. and
and dips
dips to
to the
the
that
N. 50°
that the
the western
western part
part of
of the
the structure strikes N.
but
dips
steeply
to the
the
northwest;
the eastern part also
also strikes northeast,
northeast, but dips steeply to
northwest; the
rhyolite
The chemical
chemical correlation
correlation of
of lithologically
lithologically similar
similar rhyolite
southeast.
(c)
The
(c)
southeast.
Similarities in
structure. Similarities
from
the eastern flank of
of the
the structure.
in
from the
the western
western flank
flank to the
57
57
�o0
250 500
1000
250
500 750
750 1000
2000 FEET
250
250
o0
500 METERS
N
1
:j
':·1
~
l:{:.
Basalt DIke
Baaalt
Dike
'f",$#!)
Quartz
Plagloclase
Alkali Feldspar
Quartz·- Plavlacla
.. -- Alkali
Feldapar Rhyolite
Rhyolite
.'
I, .......,/
:j176
YII76
::.::::rr-——,
....~';T
,.::.
:':.:::.)
)•_•
,,,
....~:.y
EXPLANATION
':6~
'/
Andesite
grained And..lte
Andesite Dike
And..lte Dike
Dike,• Coarse
Caar.. -—vralned
Dike
I,
'-
Unit
Unit D
D
Plagloclase
Plav1acla.. RhyolIte
Rhyolite
banded
and flaw
flow folded
banded and
folded
Unit
Unit C
C
Quartz—
Plagloclese
Alkali Feldlper
Feldiper Rhyollte
Quartz
- Plavlacla
.. • -Alkali
Rhyolite
Unit
Unit B
8
Spheruiitlc
Spherulllic Rhyellte
Rhyeille
U,dt
Utit AA
45
Strike
Strike and
and Dip
Dip .f
efBanding
Bandlnv
~+-
Vertical
Vertical Banding
BandlllV
-_
..
+-
~+-
Contect,
whereInferred,
lnf.rred, dotted
Contact, dashed
daahed where
dotted where
where
I4
burled
burled
Flow
Flow Foldln
Faldln,
Trace of
of axIal
axial Diane
,lane of
orrow indicates
Indlcat ..
Trace
of anticline,
enticllne, arrow
direction
direction of
ofplunge
plunve
Trece of
axialplane
plane of
of syncline,
Iyncllne, arrow
arrow indicates
Indlcat..
Trace
of xlal
direction
direction of
of plunge
plunve
Sample Location
Location
Sample
Antlcllne,
trace of
Anticline, showing
Ihowlnv trace
of azlal
axial plane
plane
Figure
Figure 13.
13.
Geologic
Geologic map
map of
of the
the Marcellon
Marcellon inhier
inlier (adapted
(adapted from
from Smith,
Smith, 1978a).
1978a).
58
58
�Figure 14.
14.
Figure
Photomicrograph
Photomicrograph of cuspate and Y—shaped
Y-shaped shards
shards in
in the
the Marcellon
rhyolite ash—flow
ash-flow tuff
tuff (unit
(unit D).
D). Bar scale
scale is
is 11 mm
mm long.
long.
rhyolite
the
ratios of
of lithologically
lithologically similar
similar units
units (Table
(Table 1,
1, analyses
analyses 21—27)
21-27)
the Rb-Sr
Rb—Sr ratios
For
example,
both
spheru—
s.tratigraphically
suggest
that
they
are
&tratigraphically
equivalent.
For
example,
both
spherusuggest that they are
Similar
groupexposures (unit
(unit A)
A) show similar Rb/Sr
Rb/Sr values.
values.
Similar grouplitic rhyolite exposures
Unit D
D (Quartz_plagioclaSe—alkali
ings
for units
units B
Band
(Quartz-plagioclase-alkali feldfeldings are apparent for
and C. Unit
quartz—bearing rhyolites
by a
spar) can be distinguished from
from the
the other
other quartz-bearing
rhyolites by
a lower
lower
spar)
(2.82% as
as compared
compared with
with a
Fe20
Rb/Sr
and higher
0
(2.82%
a
Rb/Sr ratio and
higher Ba,
Ba, CaO,
CaO, and
and FeO ++ Fe
2 he other rhyolites by having a
1.77-2.13
%).
Also,
C
from
~he
other
rhyolites
by
having
a
unit
is
different
from
1.77—2.13 %).
higher
Ba content
content (Fig.
(Fig. 15).
15).
higher Ba
Bt-
DtD-
•
•
•
S
•
•
•
S
•
CtC
Bha. B
o0
Cf>
A CD
:>
I
100
100
~oo
500
Ba
Ba
Figure
Figure 15.
15.
1000
30 40 50
~o 60708090
60 70 80 90 00
0003040
La
La
I
~o
50
100
00
50
I~O
Sr
Sr
HI
00
100
ISO
I~O
Rb
Rb
2000
1.00
2.0
2.0
Rb/Sr
Rb/Sr
0)
0.5
O.~
1.0
1.0
CoO
CaO
.20
I.~O
0.5
Stratigraphic variation
variation in
in elemental
elemental concentrations
concentrations for
for the
the MarMar—
Stratigraphic
Ba, La,
La, Sr
Sr and
and Rb
Rb are
are in
in ppm;
ppm; CaO
CaO and
and MgO
MgO are
are
cellon
cellon rhyolite.
rhyolite. Ba,
For
comparison,
elemental
concentrations
for
in
in weight
weight percent.
percent. For comparison, elemental concentrations for
(from
Smith,
1978a).
the
Baraboo
rhyolites
(B)
are
also
plotted
the Baraboo rhyolites (B) are also plotted (from Smith, 1978a).
59
59
O.~
MO
MgO
�Marcellon Traverse:
Walk into
into the
the woods
woods to the
the west
west
Marcellon
Traverse: Walk
Monthey
Road
from
the
Wayne
Bush
Farm.
See
Figure
12
Monthey Road from the Wayne Bush Farm. See Figure 12
at the
the mailbox located
at
located across
across
for
the traverse
traverse route.
for the
route.
Unit B
B
Unit
Note the
the well-banded
well—banded unit
unit BB rhyolite
rhyolite to
to your
your right
right in
in the
exposure just
Note
the exposure
just
to
the
west
of
Monthey
Road
(Fig.
12).
The bands
bands are
are discontinuous
discontinuous and
to the west of Monthey Road (Fig. 12). The
and are
are
formed by
by collapsed pumice fragments and
formed
and shards.
shards. At
At this
this exposure,
exposure, bands
bands
strike N.
N. 50°
500 E.
E. and
and dip
dip to
to the
the northwest
northwest at
at 50°
50° to
to 70°;
70°; thus
thus indicating
indicating the
the
strike
orientation of
orientation
of the
the west limb of the
the Marcellon
Marcellon antiform.
antiform. Band
is
Band orientation
orientation is
remarkably consistent
consistent in
in this
this area,
area, but
but several
several broad
broad folds
folds interrupt
this
remarkably
interrupt this
pattern.
In several
several places unit B is
pattern.
In
is spherulitic.
spherulitic.
Walk to the southwest along
along the
the margin
margin of
of the
the bluff.
bluff. Cross
Cross the barbedbarbed—
wire fence and
wire
and climb to
to the
the crest
crest of
of the
the bluff
bluff (Fig.
(Fig. 12).
12). As
ascend,
As you ascend,
note the
grooves in differentially weathered unit B rhyolite
note
the lichen
lichen growing in grooves
(the grooves
grooves are
are parallel
parallel to
(the
to the
the banding described
desc~ibed above).
above).
At
the crest of
At the
the bluff
bluff notice
notice the
the glacially
glacially polished
polished and
and striated
striated surface
surface (striations
the
(striations trend
trend
N. 70°
of milky quartz on the
N.
70° W.).
W.).
Also noteworthy are
are the
the large
large veins
veins of
south flank of
of the
the bluff.
bluff.
One
is 20 cm wide and
and over
over 66 mm long.
long.
One quartz
quartz vein is
Cross the
the summit
the hill
hill and descend
descend to its base (you
Cross
summit of
of the
(you should now be
on the
the west
west side
on
side of the hill and almost at
at its
its end)
end) (Fig.
(Fig. 12).
12). Notice that
that
as
hill is
east to west
west the
as the
the hill
is traversed
traversed from east
the banding so common in
in unit B
disappears and
and that
the rock becomes
becomes highly charged
charged with spheroids (characterdisappears
that the
(characteristic
istic of
of unit
unit A).
A). This
the contact between
between unit
unit BB and
and unit
unit A.
A.
This change marks the
Spheroidal
Spheroidal Texture
Texture
Unit A is a
a poorly—banded
poorly-banded ash—flow
ash-flow tuff with a
a spheroidal texture
texture
(Figure
(Figure 16).
16). Banding trends
trends N.
N. 20°E.
20 0 E. to
to N.
N. 30°
30° W.
W. and
and may
may swirl
swirl about
about
spheroids or may be truncated
truncated by
by them.
them. Three important types of spheroids
are
are present
present in
in this
this exposure.
exposure.
Figure
Figure 16.
16.
View
Vi~w of
of weathered
weathered spherulites
spherulites in
in the
the Marcellon
Marcellon rhyolite
rhyolite (unit
(unit C).
C).
These
These spheruljtes
spherulites are
are identical
identical to
to those
those observed
observed in
in unit
unit A.
A.
60
60
�Spherulites
Spherulites composed
composed of
of radiating
radiating fibers
fibers of
of quartz
quartz and
and alkali
alkali feldspar
feldspar
A
small
alkali
feldspar
crystal
may
be
present
in
the
(Fig.
17).
A
small
alkali
feldspar
crystal
may
be
present
in
the core
core of
of the
the
(Fig. 17).
Spherulites
In
outcrop
they
appear
massive
and
may
be
broken.
spheroid.
In outcrop they appear massive and may be broken. Spherulites
spheroid.
commonly
commonly form
form by
by the
the devitrification
devitrification of
of volcanic
volcanic glass,
glass, and
and commonly
commonly occur
occur in
in
the
densely
welded
vitric
basal
zone
of
an
ash—flow
cooling
unit.
the densely welded vitric basal zone of an ash-flow cooling unit.
(1)
(1)
Spherulites
Spherulites are
are also
also quite
quite common
common in
in felsic
felsic lava
lava flows.
flows.
Spheroids with
with concentric
concentric bands.
bands. In thin section they
they are
are composed
composed of
of
Spheroids
alternating
led glass
alternating concentric
concentric bands
bands of
of coarsely
coarselyand
and finely
finelydevitrif
devitrified
glass (Fig.l8).
(Fig.18).
"Thesespheroids
spheroids may
may be
be concretionary
concretionary lapilli
lapilli (??).
(??).
These
(2)
(2)
(3) Lithophysae
Lithophysae with
with hollow
hollow cores
cores and
and in
in many
many cases
cases with
with drusy
drusy quartz
quartz lining
lining
(3)
In thin
the cavity
cavity wall.
wall. These
These spheroids
spheroids may
may not
not have
have aa central
central cavity.
cavity.
thin
the
section many of
of them
them have aa core
core of
of epidote,
epidote, and/or
and/or quartz
quartz (Fig.
(Fig. 19).
19).
The
The spheroids
spheroids have
have cross sections
sections that
that are
are nearly
nearly circular
circular (average
(average ratio
ratio
± 0.11).
of minor to
to major
major axis
axis == 0.71
0.71 ~
0.11). The cross sections of
of these
these
of length of
spheroids may be regarded as strain ellipses,
ellipses, and their
their nearly circular
suggests that
that these
these rhyolites
rhyolites were
were not
not strongly
strongly deformed.
deformed. Also
Also supportsupportshape suggests
ing this
this suggestion is
is the
the overall freshness of the
the rhyolites
rhyolites (there
(there is
is little
little
evidence for medium—
medium- or high—grade
high-grade metamorphism,
metamorphism, and
and original textures
textures are
are
in the
the matrix).
matrix). Also considering
considering their
their age,
age, these
these rocks
rocks are
are
preserved in
remarkably fresh
fresh in
in terms
terms of
of their
their chemistry
chemistry (Smith,
(Smith, l978a).
1978a).
Deep Well:
Well: Return
Return to
to Monthey
Monthey Road.
Road. Walk from
from the
the Bush Farm
Farm to
to the
the tree
tree
Deep
covered hill just to
to the
the north
north of
of the
the farm
farm (Fig.
(Fig. 12).
12).
The outcrop of well—
wellbanded unit
at the
base of
of the
hill was
was the
banded
unit C at
the base
the hill
the site of a
a deep hole drilled by
B. Haimson and students
students from the
the University of
of Wisconsin—Madison.
Wisconsin-Madison. Two
B.
ninety—seven feet
of core
core was
was recovered
hundred
and ninety-seven
feet of
recovered before drilling had to
hundred and
The
1978).
be stopped because of
of the
the extreme
extreme hardness
hardness of
of the
the rock
rock (Haimson,
(Haimson, 1978).
The
hole penetrated banded
banded unit
C. and
hole
unit C.
and then
then entered a
a poorly banded rhyolite
C. This
This poorly banded
banded rock is most probably
mineralogically identical
identical to unit
unit C.
separate ash-flow
ash—flow cooling
aa textural
textural variant
variant of
of unit
unit C.
C. and
and may
may represent
represent aa separate
Also, a
1 m thick
dike trending
trending N.
N. 26°E.
26°E. was
was intersected
intersected
unit.
Also,
aIm
thick inetabasalt
metabasalt dike
unit.
at
feet in
in the
the hole.
hole.
at aa depth of 132 feet
61
61
�Figure 17.
Figure
17.
Figure
Figure 18.
18.
Photomicrograph of spherulitic texture in the Marcellon rhyolite
unit
These spherulites
spheruljtes are
are composed
composed of
of radiating
radiating fibers
fibers of
of
unit A.
A. These
quartz and
and alkali
alkali feldspar.
feldspar. Bar scale in
in 11 mm
mm long.
long.
Photomicrograph
Photomicrograph of
of aa spheroid
spheroid with
with concentric
concentric bands.
bands. Core
Core is
is
composed
composed of
of coarse—grained
coarse-grained quartz and
and alkali
alkali feldspar;
feldspar; rim
rim is
is
formed
formed by
by fine—grained
fine-grained quartz
quartz and
and alkali
alkali feldspar.
feldspar. Several
Several
spheroids
spheroids show
show alternating
alternating bands
bands of
of coarse—
coarse- and
and fine—grained
fine-grained
material.
material. Bar
Bar scale
scale is
is 11 mm
mm long.
long.
62
62
�Figure
Figure 19.
19.
and
Photomicrograph of
of aa spheroid
spheroid with
with aa core
core of
of coarse
coarse quartz
quartz and
Photomicrograph
Quartz grains
grains are
are interlocking
interlocking and
and probably
probably grew
grew in
in aa
epidote.
epidote. Quartz
surrounded
The core
core is
is off-center
off—center within
within the
the spheroid
spheroid and
and is surrounded
cavity.
cavity. The
Many
of the
the
by aa band
band of
of fine-grained
fine—grained quartz
quartz and
and alkali
alkali feldspar.
by
feldspar. Many of
fine—
and
spheroids are
are more
more intricate
intricate and
and have
have alternating
alternating bands
bands of
of fine- and
spheroids
These
coarse—grained alkali
alkali feldspar
feldspar and
and quartz
quartz about
about the core. These
coarse-grained
Bar scale
scale is
is 11 mm
mm long.
long.
structures
structures may
may be
be lithophysae.
lithophysae. Bar
63
63
�Supplemental Stop
Stop -— Flow
Flow Structures
Structures in
in the
the Marcellon
Marcellon Rhyolite:
Rhyolite:
Supplemental
This stop
stop illustrates
illustrates structures
structures and
and textures
textures in
in unit
unit C.
This
From
C.
From the
the Bush
Bush
Farm walk
walk to
to the
the north
north on
on Monthey
Monthey Road
Road to
to the
the tree
tree covered
covered knob
Farm
(Fig.
knob (Fig. 12).
12).
Turn right
right (east)
on the
dirt road
road (just
Turn
(east) on
the dirt
(just south
south of
of the
the hill).
hill). Walk
the
Walk~st
st the
drilling site
site (described
(described in
in Stop
Stop 3)
3) and
and continue
continue walking
walking for
for about
drilling
70
m
about 70 m
(Figure 12).
12). Turn
Turn left
left (north)
(north) into
into the
the trees
trees and
and follow
follow the
the "canyon"
"canyon" to
(Figure
to the
the
bare steep
steep exposure
exposure on
on the
the right
right (a
(a distance
distance of
of about
about 50
50 m,
bare
on
the
way,
m, on the way, you
you
should pass
pass aa large
large red
red granite
granite erratic).
erratic). The
should
The textures
textures described
described below
below are
are
located on
on this
this exposure.
exposure.
located
Unit CC is
is aa well-banded
well—banded rhyolite
rhyolite containing
containing plagioclase
plagioclase (15-25
(15—25 %)
Unit
as the
the
%) as
dominant phenocryst.
The unit
unit strikes
strikes N.
N. 30°
E. and dips steeply
dominant
phenocryst. The
30° E.
steeply 500
50° to
to 80°
80°
to the
the northwest
northwest (this
exposure is
to
(this exposure
is on the west limb
limb of
of the
the Marcellon
antiform).
Marcellon antiform).
Bands
are
discontinuous
and
are
in
general
lighter—colored
Bands are discontinuous and are in general lighter-colored than
than the
the matrix
matrix
(Fig. 20).
20). Many
Many bands
bands have
have aa dark
dark medial
medial line,
line, and
and in
in places
places they
they are
(Fig.
are observed
to bend
bend about
about phenocrysts.
phenocrysts. The
to
The bands
bands were
were formed
formed during
during primary
primary flowage
flowage and
and
compaction
of
an ash-flow
ash—flow tuff
tuff by
by shearing
shearing and
and compaction
compaction of
compaction of an
shards.
of pumice and shards.
Banded ash-flow
ash—flow tuffs
tuffs similar
similar to
to those
those observed
observed here
here are
Banded
in
are quite
quite common in
outflow
deposits
about
Tertiary
volcanic
centers
(Schmincke
outflow deposits about Tertiary volcanic centers (Schmincke and Swanson,
1967; Deal
Deal and
1967;
and Rhodes,
Rhodes, 1976).
1976). When viewed perpendicular to the foliation
plane,
these
Tertiary
ash—flow tuffs
tuffs display
display strong
strong lineation formed
plane, these Tertiary ash-flow
formed by
flattened
pumice
(Fig.
21).
flattened pumice (Fig. 21). The
be 20
20 to
to 11 on
the
The axial
axial ratio of pumice may be
on the
flow plane,
plane, and
flow
and as
as high
high as
as 200
200 to
to 1
1 on
to the
the flow
flow surface
surface
on the
the plane normal to
and parallel
parallel to
and
to the
the direction
direction of
of flow.
flow.
Where pumice shows a
a high degree of
stretching and
flattening
the
rock
and
the rock may
may resemble
resemble aa flow-banded
lava, but the
the
flow—banded lava,
presence of glass shards
shards and the discontinuous nature of the bands suggests
suggests
instead that
that the
the rock
rock is
highly foliated
foliated ash-flow
ash—flow tuff
instead
is aa highly
(Smith, 1978b).
1978b).
tuff (Smith,
The banding at this locality is
is folded
folded into aa series
anticlines
series of broad anticlines
and synclines that
plunge
steeply
(50°
that plunge steeply (50° to
to 80°)
80°) to the
the west.
west. Fold amplitudes
amplitudes
are as great as
as 30
30 mm and
and wavelengths
wavelengths vary
vary up
up to
to 10
10 m.
m.
In most
most cases where aa
fold
nose
is
observed,
the
plunge
of
the
fold
fold
is observed, the plunge of the fold axis parallels the
the dip
dip of
of unit
unit
C
C as
as aa whole.
whole. Fold
Fold limbs
limbs are
are themselves
themselves folded
folded into antiforms and synforms
synforms
that plunge steeply
steeply to
to the
the west
west (Fig.
(Fig. 22).
22). These minor
minor folds
folds have amplitudes
amplitudes
of
up
to
10
m
and
wavelengths
that
of up to 10 m and wavelengths that vary
vary from
from several
several centimeters
centimeters to
to several
several
meters.
meters. Flow
Flow bands
bands on
on fold
fold limbs
limbs may
may truncate
truncate each
each other,
other, also fold crests may
may
not
not completely
completely close,
close, forming
forming fanning
fanning patterns
patterns (Fig.
(Fig. 23).
23).
The
ae interpreted
The folds
folds:re
interpreted as
as ramp
ramp structures
structures formed
formed during
during the
the flowage
flowage of
of an
an
ash—flow
tuff.
ash-flow tuff. In
In detail
detail they
they are
are formed
formed by
by compressional
compressional buckling
buckling and
and thrustthrusting
ing of
of the
the upper
upper part
part of
of an
an ash—flow
ash-flow cooling
cooling unit
unit over
over aa more
more fluidal
fluidal interior
interior
(Smith,
1978b).
In
Tertiary
ash—flow
(Smith, 1978b).
In Tertiary ash-flow tuffs
tuffs ramp
ramp structures
structures are
are broad
broad warps
warps in
in
the
the flow
flow foliation
foliation that
that resemble
resemble large
large folds
folds in
in felsic
felsic lavas.
lavas. Amplitudes
Amplitudes are
are
up
up to
to 50
50 mm and
and wavelengths
wavelengths vary
vary from
from several
several meters
meters to
to tens
tens of
of meters.
meters. Many
Many
are
asymmetric
with
gentle
limbs
dipping
10°
to
30°
sourceward,
are asymmetric with gentle limbs dipping 10° to 30° sourceward, and
and are
are convex
convex
upward
upward (Schminke
(Schminke and
and Swanson,l967).
Swanson,1967).
64
f14
�20.
Figure 20.
Highly flattened
and sheared
sheared pumice
pumice and
and shard
shard fragments
flattened and
fragments forming
forming a
a
pronounced lineation
lineation in
in the
the Marcellon
Marcellon rhyolite
rhyolite (unit
(unit C).
C). The
The bands
bands
colored than
are discontinuous and
and are
are in
in general
general lighter
lighter colored
than the
the matrix.
matrix.
Note that
that several bands
bands trend
trend to
to form
form about
about cavities
cavities and
and phenocrysts.
phenocrysts.
Figure
Figure 21.
21.
Close—up of
of lineation
lineation formed
formed by
by highly
highly flattened
flattened and
and stretched
stretched
Close-up
pumice in
in the
the Tertiary
Tertiary A.
A. L.
L. Peak
Peak Tuff,
Puff, San
San Mateo
Mateo Mountains,
Mountains, New
New
pumice
The
strong
lineation
formed
during
the
late—stage
laminar
Mexico.
The
strong
lineation
formed
during
the
late-stage
laminar
Mexico.
Also note
note the
the numerous
numerous rotated inclusions.
flowage
flow. Also
inclusions.
flowage of
of the
the ash flow.
65
65
�Figure
Figure 22A.
22A.
A large steeply plunging flow fold
fold in the Marcellon rhyolite
The fold
fold axis
axis strikes
strikes N.
N. 50°
5Ø0 W.
W• and
and plunges
plunges 8So
85° to
to
(unit C).
C). The
The plunge of the fold axis
the west. The
axis parallels
parallels the
the dip
dip of
of unit
unit
as aa whole.
Dashed line traces
C as
Dashed
traces the limbs
limbs of
of the
the fold.
fold.
Figure
Figure 22B.
22B.
AA small
small fold
fold in
in the
the Marcellon
Marcellon rhyolite
rhyolite (unit
(unit C).
C). This
This structure
structure
probably
probably formed
formed during
during primary
primary flowage
flowage of
of the
the ash—flow
ash-flow tuff.
tuff. Its
Its
axis
axis strikes
strikes east—west
east-west and
and plunges
plunges 60°
60° to
to the
the west.
west.
66
66
�I
23A.
Figure 23A.
I foot
Sketch of a fold
fold in
in the Marcellon rhyolite unit C
C where
does not
completely
close
producing
a
fanning
pattern.
not completely close producing a fanning pattern.
truncation of
of banding.
banding.
fold
fold
Also
Also
crest
crest
note
note
O.5m
0.5 m
Figure
23B.
Figure 23B.
Sketch of
of aa large
large fold
Sketch
fold in Marcellon rhyolite
rhyolite unit
unit C.
C.
steeply
(left).
steeply to
to the
the west
west (left).
67
67
Fold plunges
Fold
plunges
�STOP 44 -- THE
THE MARQUETTE
MARQUETTE RHYOLITE
RHYOLITE(NORTH
(NORTh OF
OF COUNTY
COUNTY HIGHWAY
STOP
HIGHWAYH)
H)
Location: The
The stratigraphy
stratigraphy and
and fabric
fabric of
of the
the Marquette
Marquette rhyolite
rhyolite to
Location:
to the
the north
north of
of
County
Highway
H
will
be
examined
at
this
stop.
County Highway H will be examined at this stop. AA supplemental
supplemental stop
stop views
views
banding, pumice
pumice lenses
lenses and
and aa block-flow
block—flow breccia
breccia in
in exposures
banding,
exposures to
to the
the south
south of
of
County HH on
on Ingall's
Ingall's knob.
knob. See
See Figure
Figure 24
24 for
for traverse
traverse routes.
routes.
County
EE
--
r
N
t4
STOP
400 FEET
400
FEET
=
/)
I
z-
UNIT B
—,
' — FIAMME
BR EC CIA
EXPLANATION
CEJ
GEOLOGIC
GEOLOGIC UNIT
UNIT
.---
CONTACT
CONTACT
_——--
~
Figure
Figure 24.
24.
-+--t-+-
see
see text
text for
for
xpI
an at ion
'3xplanation
PLUNGING
PLUNGING ANTICLINE
ANTICLINE
—-----. ' -
GATE
GATE
~
TRAIL
TRAIL
--:yo
PLUNGING
PLUNGING SYNCLINE
SYNCLINE
FENCE
FENCE
FIELD TRIP
FIELD
TRIP ROUTE
ROUTE
Route
Route map
map for
for traverses
traverses at
at the
the Marquette
Marquette rhyolite
rhyolite exposure.
exposure.
Introduction
Introduction to
to the
the Geology
Geology of
of the
the Marquette
Marquette Exposure:
Exposure:
The
The rhyolite
rhyolite at
at Marquette
Marquette (Pretts,
(Pretts, 1895;
1895; Hobbs
Hobbs and
and Leith,
Leith, 1907;
1907; Smith
Smith and
and
Hartlaub,
Hartlaub, 1974;
1974; Smith
Smith l978a)
1978a) occupies
occupies seven
seven small
small hills
hills surrounded
surrounded by
by PleisPleistocene
tocene sediments
sediments and
and Paleozoic
Paleozoic sedimentary
sedimentary rocks
rocks (Fig.
(Fig. 25).
25). The
The extensive
extensive
cover
cover prevents
prevents reliable
reliable field
field correlation
correlation of
of units
units from
from hill
hill to
to hill,
hill, and
and
since
most
contacts
are
obscured,
relative
since most contacts are obscured, relative age
age of
of the
the Marquette
Marquette units
units can
can only
only
be
be inferred
inferred by
by noting
noting their
their stratigraphic
stratigraphic position
position within
within major
major folds.
folds. CorreCorrelations
lations depicted
depicted on
on the
the geologic
geologic map
map (Fig.
(Fig. 25)
25) are
are based
based primarily
primarily on
on chemical
chemical
68
68
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fool·
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fool·
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CD
'"i
Plagioclose Rhyollte
Plagioclase
Rhyolite
Volts EE and
Units
and C
C
V.~~;ij
Breccia
Breccia
ILI'/-
E$KtFJ
C.
Strike and
dip of
of contact
Strike
and dip
contact
Normal fault,
fault, dashed
Normal'
dashed where
where
,~
approximately
located,
approximately
located, UUD
.... ""U
upthrown
upthrown side,
side, D-downthrown
D-downthrawn
,,""
Antlcllne,
trace of
Anticline, showing
showing trace
of
axIal plane
directIon
axial
plane and
and direction
)'7
,,""
Syncline,
trace of
Syncline, showing
showing trace
of
axial
dIrection
axial plane
plane and
and direction
of plunge
of
plunge
Overturned Anticline,
Overturned
Anticline,showing
showing
trace
trace of
of axial
axial plane
plane and
and
direction of
direction
of plunge
plunge
c' Overturned
",""
Overturned Syncline,
Syncline,
l'
showingtrace
trace of
of axial
showing
axial
plane and
and direction
direction of
plane
of
plunge
plu n g e
)
I
I
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— Sample
SampleLocation
Location
I
I
I
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Andeslte C?)
Andesite
(f) Dikes
Dikes
Fine- Gralned Rhyolite
Rhyollte Dike
Fine-Grained
Dike
8
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ll>
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C.
"0
Vertical
Vertlcol banding
bonding
of plunge
of
plunge
Very fine-grained rhyolite.
coarsely porphyritic rhyolite
H>
~
StrIke and
Strike
and dip
dip of
of banding
bonding
s
side
side
[2]
L Very fine—gralned rhyollte,
rn
coarsely porphyritic rhyollte
0
CD
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Quar
t z- Plagloclase
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AI ka II
Feldspar
Feldspar Rhyollte
Rhyolite
,'/ '
1/oils B,O,F
8,O,F and
Units
and A
A
(J'q
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fool·
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Porphyritic Quartz-Alkali
Porphyritic
Quartz-Alkali FeldFeldspar
Rhyollte with
spar Rhyolite
with interbedded
Interbedded
flne-gralned
rhyollte flow
fine-grained rhyolite
flow
(Jolt 6
Unit
G
D
0
0
I-.
0
::r
Contact,
dashed where
where InInContact. dashed
(erred,
ferred, dotted
dolled where
where burled
burled
-.
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EXPLANATION
t:
I
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and petrographic
petrographic similarities.
and
similarities.
The inlier
inlier is
is formed
formed by
by seven
seven mineralogically
mineralogically and
and chemically
chemically distinct
distinct
The
volcanic
flows,
ash—flow
tuffs,
and
breccias.
volcanic flows, ash-flow tuffs,
The
The units
units lettered
lettered A
A to
to G from
from
southeast to
to northwest
northwest are
are broadly
broadly folded
folded into
into aa series
series of
of normal
normal and
and oversoutheast
overturned anticlines
anticlines and
and synclines
synclines with
with an
an average
average wavelength
wavelength of
of 300
300 m.
turned
The
m.
The
fold axes
axes strike
strike N.
N. 200
N. 400
fold
20° to N.
40° E.
E. and plunge
plunge to
to the
the northeast.
northeast.
These
These
folded rhyolite
rhyolite units
units are
are cut
cut by
by aa 100
100 m
m thick
thick andesite
andesite dike
dike (Table
1, analysis
analysis
folded
(Table 1,
30)
which
was
intruded
along
a
northeast
trending
normal
fault.
30) which was intruded
a
trending normal fault.
The
The fault
fault
is downthrown
downthrown to
to the
the north,
north, and
and the
the displacement,
displacement, calculated
calculated by
by estimating
estimating the
is
the
amount of
of structural
structural shortening,
shortening, probably
probably does
does not
not exceed
exceed 600
600 m.
amount
The
m.
The structures
structures
to the
the north
north of
of the
the fault
fault have
have aa one
one to
to one
one correspondence
correspondence to
to those
those to
to the
the
to
south, except
except that
south,
that they are displaced to
to the
the southwest.
southwest. While the
the map
shows
map shows
simpler structural
structural patterns
patterns to
to the
the north
north of
of the
the fault
fault then
then to
to the
the south,
south, this
this
simpler
difference is
probably due
due to poor
poor structural
structural control
control to
difference
is probably
to the
the north of the
fault.
fault.
The youngest
youngest rock in
northeast trending fine—grained
The
in the
the inlier
inlier is
is aa northeast
fine-grained
massive dacite
dacite dike,
dike, 35
35 m
m thick,
which cuts
cuts the
fault and
dike
massive
thick, which
the fault
and the
the andesite
andesite dike
(Table 1,
1, analyses 39
The dike
dike is
unit C in lithology
(Table
39 and
and 40).
40).
The
is similar to unit
(fine—grained with
with plagioclase
plagioclase as
as the dominant phenocryst),
(fine-grained
phenocryst), but
but it
it is
is disdistinguished from unit
unit C
C on
on chemical
chemical grounds
grounds (Fig.
(Fig. 26).
26).
89 "ioo
G—.-•\
\106\
'I98 !1194
—II
10
10
i'92.—B
I
/
'
9
Rb!
Rbi
/Sr
I Sr
97 'I
—
jP5
!e'P5
191
(i ', ,
191 (.......
Rhyolite
Rhyolite
dike
dike
,
\ \ "Andesite"
\ \ dOk
..... ....
\ \ \dike
I e
~ \
190' \ \
.....
I9O \,
\
,
~.J 189
189
0
0
l.a
1.8
Na20/K20
Figure
Figure
26.
26.
°
Rb/Sr—Na20/K
Rb/Sr-Na 2 0/K 0 plot
plot for
for Marquette
Marquette inlier
inlier samples.
samples. This
This plot
plot de~
de
monstrates
monstrates tat
t5at mineralogically
mineralogically similar
similar rhyolites
rhyolites can
can be
be distindistinguished
guished on
on the
the basis
basis of
of Rb/Sr
Rb/Sr and
and Na20/K20
Na O/K
ratios. Also
Also note
note the
the
ratios.
cyclic
cyclic change
change in
in Rb/Sr
Rb/Sr ratio.
ratio. Plagioclase_bearing
Plagi~cla~e-bearingrhyolites
rhyolites (unit
(unit
CC and
and E)
E) have
have Rb/Sr
Rb/Sr greater
greater than
than 1,
1, whereas
whereas quartz—plagioclase_
quartz-plagioclasealkali
alkali feldspar
feldspar rhyolites
rhyolites (units
(units B,
B, D,
D, and
and F)
F) have
have Rb/Sr
Rb/Sr less
less than
than
1.
1. Unit
Unit GG is
is the
the quartz—alkali
quartz-alkali feldspar—plagioclase
feldspar-plagioclase rhyolite
rhyolite
(from
(from Smith,
Smith, l978a).
1978a).
°
70
70
�unit GG is
is aa thick
thick (1000
(1000 m)
m) quartz
quartz (10
(10 %),
%), alkali
alkali feldspar
feldspar (commonly
(commonly perth—
perthUnit
Except
for
minor
porphyry.
rhyolite
thitic)
(16
%)
and
plagioclase
(7
%)
rhyolite
porphyry.
Except
for
minor
plagioclase
(7
%)
and
thitic) (16 %)
variations
variations in
in phenocryst
phenocryst abundance
abundance and
and faint
faint banding,
banding, the
the unit
unit is
is texturally
texturally
Shard—like
forms
were
observed
in
the
matrix
of
unit
G,
homogeneous.
Shard-like
forms
were
observed
in
the
matrix
of
unit
G, indicating
indicating
homogeneous.
it is
is an
an ash—flow
ash-flow tuff.
tuff. AA fine—grained
fine-grained rhyolite
rhyolite is
is interbedded
interbedded with
with
that it
unit
unit G,
G, and
and crops
crops out
out near
near the
the south
south end
end of
of the
the unit
unit GGexposure.
exposure.
The
The 66 units
units lying
lying to
to the
the southeast
southeast of
of unit
unit GG are
are texturally
texturally variable,
variable, with
with
banded,
banded, fine—grained
fine-grained and
and porphyritic
porphyritic varieties
varieties common.
common. Most of
of the
the units
units show
show
evidence
~vidence of
of brecciation
brecciation and
and micro—brecciation.
micro-brecciation. Coarse
Coarse breccia
breccia is
is found
found on
on the
the
southeast
southeast margin of Ingall's
Ingall's Knob where clasts of
of porphyritic
porphyritic and
and fine—grained
fine-grained
red to
to black
black rhyolite
rhyolite exceed
exceed 10
10 mm in
in size.
size. Unit D
D on
on Cluppert's Hill is
is also
also
Eutaxitic
texture
is
well
displayed
in
several
of
extensively brecciated.
brecciated.
texture is
displayed in several of the
the
extensively
units.
units.
Each unit
unit in
in the
the Marquette inlier
inlier has distinguishing chemical
chemical and
and
mineralogical characteristics which are
used
to
correlate
units
between
are used to correlate units between
(Fig. 46,
46, Table
Table 1,
1, analyses
analyses 4—14).
4-14). Units
Units A,
A, B,
B, D,
D, and
and FF are
are porphy—
porphyexposures (Fig.
ritic
ritic plagioclase (18
(18 to
to 27%),
27%), quartz (2
(2 to
to 8%),
8%), and
and alkali
alkali feldspar
feldspar (1
(1 %)
%)
20 to
to 36
36 %
% total
total phenocrysts.
phenocrysts. Unit B is
is distinguished from
from
rhyolites with 20
the other quartz bearing rhyolites by Na
Na20/K20
0/K 0 greater than 1.0 and
and low
low Rb/Sr
2
2
0.92). Unit D
D and Unit F
P are similar in
in both major and
and minor element
(0.64 —- 0.92).
however, contains in its upper part aa 100 m
D, however,
m thick
thick massive
chemistry. Unit D,
phase;
similar massive
masive rock
phase; aa similar
rock is
is not
not associated
associated with
with unit
unit F.
F. To date,
date, no
Units
C
and
E
are
I
ine--grained
been made
made on
on unit
unit A.
A.
Units C and E are fine-grained
chemical studies have been
(10 to 15
15 %% phenocrysts) with plagioclase
plagioclase as
as the
the dominant
dominant phenocryst.
phenocryst. Unit E
(10
is
C by lower
lower CaO.
CaO.
is distinguished
distinguished from unit C
Noteworthy is the cyclic change from phenocryst—poor
phenocryst-poor plagioclase
rhyolite (units
E) to phenocryst—rich
(units C and E)
phenocryst-rich three—mineral
three-mineral rhyolite (units
(units B,
B,
D,
and F).
F). This cyclic variation in mineralogy is
is also reflected in
in trace
trace
D, and
element chemistry (Table
(Table 1,
1, analyses 4—14);
4-14); for example,
example, Rb/Sr ratios
ratios vary
vary
from 1.45
1.45 to
to 1.23
1.23 for
for units
units EE and
and C and
and from
from 0.71
0.71 to 1.0 for
from
for units
units F,
F, D,
D, and
B (Fig.
(Fig. 26).
26).
Chemical and flow direction data (Smith,
(Smith, 1978a)
1978a) show that
that all
all of
of the
the
Marquette units are comagmatic and that all flows
flows erupted from
from aa source
source to
to
This evidence
evidence suggests
the
outcrops. This
suggests that
that cyclic
the northwest of the present outcrops.
variation in
chemistry, mineralogy,
mineralogy, and
texture reflect
reflect eruption from a
variation
in chemistry,
and texture
a
differentiating source.
source. Fine—grained
Fine-grained units probably represent eruption
eruption from
from
On the
the other
other hand,
hand, more
more highly porphyritic
fractionated
crystal-poor magma. On
fractionated crystal—poor
varieties may
may represent
represent eruption from
from zones
zones of
of crystal
crystal accumulation within
varieties
The lower
lower Rb/Sr
Rb/Sr ratios
ratios in phenocryst
phenocryst and
the source chamber.
chamber. The
and feldspar rich
units (F,
and B)
B) may
may be
be explained
explained by aa model
model where
where Sr is
units
(F, D and
is concentrated into
As a
the crystallizing feldspar and
the
and Rb
Rb is
is enriched
enriched in
in the
the liquid
liquid phase.
phase. As
a
consequence phenocryst
phenocryst and
rich units
would have
have lower Rb/Sr than the
consequence
and feldspar
feldspar rich
units would
the
fine—grained, feldspar-poor
feldspar—poor varieties
varieties (units
(units C
C and
and E)
E) which
which formed
formed from
from
fine-grained,
fractionated,
crystal- and
and feldspar—poor
feldspar-poor magma.
magma.
fractionated, crystal—
Alternately, fine—grained
Alternately,
fine-grained and
and phenocryst—rich
phenocryst-rich pairs
pairs may represent
compositionally zoned
zoned ash-flow
ash—flow sheets
sheets with
with the
the phenocryst-rich
phenocryst—rich unit
unit at
at the
compositionally
the
Zoned ash-flow
ash-flow tuffs
tuffs commonly
commonly
top
at the
the base.
base.
Zoned
top and
and the
the fine-grained unit at
show an
an upward
upward increase
increase in
in MgO,
MgO, CaO,
CaO, A1
Al203,
TiO2 and
and Sr/Rb
Sr/Rb and
and may
may vary
vary in
0 , Ti0
show
2 3
2
71
71
�from quartz
quartz latite
latite at
at the
top to rhyolite
rhyolite at
composition from
the top
at the
the base (for
(for example
see Smith,
Smith, 1960;
1960; Ratte
Ratte and
and Steven,
Steven, 1964;
1964; Smith
Smith and
and Bailey,
Bailey, 1966;
1966; Noble
Noble and
and
see
Hedge, 1969;
1969; and
Phenocryst abundance,
abundance, and
and xenolith
xenolith abundance
abundance
Hedge,
and Rhodes,
Rhodes, 1976).
1976). Phenocryst
and size
size usually
usually increase
increase upward,
upward, with
with pumice
pumice commonly
commonly showing
showing reverse
reverse zonation
zonation
and
(Sparks, 1976).
ash—flow sheet
sheet the
(Sparks,
1976). Within one
one ash-flow
the transition from phenocryst—poor
phenocryst-poor
to phenocryst-rich
phenocryst—rich tuff
tuff can
can be
be abrupt
abrupt (Noble,
1970). Marquette
Marquette units
units FF and
and EE
to
(Noble, 1970).
may
together
represent
a
single
compositionally
zoned
ash—flow
sheet
with
unit
may together represent a single compositionally zoned ash-flow sheet with unit
B
the
differentiated
fine—grained
base
and
unit
F
the
less
differentiated
pheno—
E the differentiated fine-grained base and unit
the less
phenocryst-rich top.
Grouping of
of units
units D
D and
and C
C is
is doubtful
doubtful since
since they
they are
are separated
separated
cryst-rich
top. Grouping
. by a
a fault
fault and by an
an andesite
andesite dike.
dike. More
More detailed
detailed field
field and
and chemical
chemical data must
be
obtained
before
this
be
this model
model can
can be
be properly
properly evaluated.
evaluated.
The Marquette Rhyolite Traverse:
The
Stop 4A —
Unit CC
Stop
- Unit
Walk due
then
turn to
to
then turn
north from the
the locked
locked gate on
the
woods
(east)
the woods (east) to the
the first
first
the
the north side
side of County Highway H,
H,
exposure
(see
exposure (see Fig.
Fig. 24
24 for
for the
the route).
route).
This exposure
exposure is
formed by
by a
plagioclase—bearing rhyolite
rhyolite ash—flow
This
is formed
a plagioclase-bearing
ash-flow tuff
tuff
(unit C).
It contains
contains small
small (up
to 55 mm
mm in
in size)
size) anhedral
anhedral to
to subhedral
subhedral plagioplagio—
C).
It
(up to
clase laths
set in a
fine—grained matrix
matrix that
brown.
clase
laths set
a black fine-grained
that is
is streaked reddish brown.
Unit C is
well banded,
banded, and
and may
may also
also display spherulitic and
Unit
is commonly well
and brecciated
texture.
texture.
At this
this locality,
locality, bands stand out prominently due to
to differential
erosion. The bands form the
erosion.
the reddish—brown
reddish-brown streaks,
streaks, and
and under
under careful scrutiny
scrutiny
they
are observed
observed to be
be composed
composed of
discontinuous lenses
lenses of collapsed pumice
they are
o£ discontinuous
and shard fragments.
fragments. The banding trends
trends N.
N. 60 E.
E. and dips 85° south
south or
or is
is
vertical.
Since this
exposure is
on the
flank of
of a
northeast plunging
vertical.
Since
this exposure
is on
the south flank
a northeast
syncline,
syncline, aadip
dip to
to the
the north
north is
is expected.
expected. This
is probably due
This deviation is
due to
flow folding
folding in the
ash—flow tuff
supplemental stop at
flow
the ash-flow
tuff (see
(see the
the supplemental
at the Marcellon
rhyolite for
for further
further discussion
discussion of
of flow
flow folding).
folding).
Stop 4B
4B —- Unit
Unit B
B
This stop is
is just to
to the
the west of an old stone fence (Fig.
(Fig. 24)
24) constructed
about 1900 as
about
as part of
of the
the old
old Driblow
Driblow farm.
farm.
Unit B is
is a
a porphyritic quartz,
quartz, plagioclase,
plagioclase, alkali feldspar—bearing
feldspar-bearing rhyo—
rhyolite with aa reddish—brown
reddish-brown to
to black
black matrix.
matrix. Quartz is
is rounded and
and clear and
and
may
may be
be up
up to
to 33 mm
mm in
in size.
size. Plagioclase is
is pink to
to white in
in color and
and occurs
in
in laths up
up to
to 66 mm
mm in
in size;
size; some
some grains
grains show
show prominent
prominent albite
albite twinning.
twinning.
Alkali
Alkali is
is difficult
difficult to
to identify
identify in
in hand
hand specimen.
specimen. On weathered surfaces
surfaces faint
faint
banding
banding and
and minor
minor brecciation
brecciation are
are observed.
observed. This quartz—bearing
quartz-bearing rock is
is distinguished from other quartz—bearing
quartz-bearing rhyolites in
in the
the Marquette inlier
inlier by its
its
higher
ratio.
higher Na20/K20
Na 0/K
ratio. Unit B is
is the
the only sodic rhyolite in
in the
the inlier
inlier
2
(Fig.
(Fig. 26).
26). Unit
ufiit B changes in
in lithology
lithology laterally.
laterally. On Ingalls
Ingalls Knob
Knob (south
(south of
of
Highway
Highway H)
H) quartz
quartz is
is small
small and
and rarely
rarely observed
observed in
in outcrop
outcrop whereas quartz
quartz is
is
large and
and easily identified
identified in
in unit
unit BB exposures
exposures to
to the
the north
north of
of HighwayH.
HighwayH.
°
The
The contact
contact between
between unit
unit BB and
and unit
unit C
C trends
trends No.
No. 10°
10° W. and
and passes
passes to
to the
the
south
south and
and east
east of
of this
this stop.
stop. Many
Many of
of the
the large
large blocks
blocks observed
observed just
just to
to the
the
south of our present position are breccias with an assortment of fragment
fragment types.
types.
It
It is
is doubtful,
doubtful, however,
however, whether
whether these
these blocks
blocks are
are in
in place.
place.
72
72
�Stop 4C
4C —- Small
Small Andesite Dike Intruding
Intruding Unit C
C Rhyolite
Stop
Traverse due north
north from
from Stop
Stop 4B to
to the
the low
low outcrops
outcrops across
across the
the field
field in
in
the trees (just
(just to
to the
the north
north of
of ihe
the Bee
Bee Hives)
Hives) (Fig.
(Fig. 24).
24). At this
this stop
stop aa
fine—grained
unit C is
fine-grained variety of unit
is cut by a
a thin andesite dike (an
(an off—shoot
off-shoot
trending dike).
dike). The andesite
andesite and
and rhyolite
rhyolite are
are at
at first
first
of the main northeast trending
difficult
The following
difficult to
to distinguish
distinguish from
from one
one another
another in
in the
the field.
field.
following
characteristics will aid
aid in
in their
their identification.
identification. Unit C
C rhyolite
rhyolite breaks
breaks
irregularly
irregularly with
with aa splintery
splintery surface.
surface. Sparse small plagioclase laths
laths are
are the
the
dominant phenocryst.
,dominant
phenocryst. Jointing produces straight breaks and angular
angular corners
rock. The andesite contains small plagioclase laths (1/2
(1/2 mm)
mm) set in
in a
a
in the rock.
fine—grained
fine-grained matrix with
with aa characteristic
characteristic greenish
greenish hue.
hue. Jointing
Jointing produces
produces
irregular breaks and
and rounded corners
corners in
in the
the dike
dike rock.
rock. A
A fresh
fresh surface
surface of
of
the rhyolite reflects
when
reflects light
light from
from numerous
numerous planes,
planes, and
and thus
thus "twinkles't
"twinkles" when
rotated in
in direct
direct sunlight.
sunlight. Partially
Partially separated
separated splinters
splinters of
of rock
rock are
are lighter
lighter
in color than unbroken rock
rock and
and form
form grooves
grooves on
on the
the broken
broken surface.
surface. In concontrast,
trast, the andesite has aa smooth
smooth and
and dull
dull freshly
freshly exposed
exposed surface.
surface.
In several
several places,
places, aa very fine
fine banding is
observed in the
is observed
the andesite and
(N. 450
45° E.) obliquely to
to the
the strike
strike of
of the
the dike.
dike. These bands may
may be
be
trends (N.
flow bands sheared into
into this
this orientation
orientation after
after dike
dike emplacement.
emplacement. Alternately
they may reflect aa rock
rock cleavage
cleavage formed
formed during
during the
the folding
folding of
of these
these rocks.
rocks.
Stop 4D (Optional)
(Optional) —
- The Contact Between the
the Andesite Dike and
and Unit
Unit C
C
Rhyol
ite
Rhyolite
Since the
exposure is
small, it
will not
not be
be visited on the
the size of this
this exposure
is small,
it will
It is
is of
of considerable
considerable interest,
interest, however,
however, because
because it
it displays
displays one
one
field trip.
trip.
It
of the few exposed contacts
contaots in
in the
the inlier.
inlier.
east across
From Stop 2C walk to the east
across the
the field
field to the
the gap in the north—
northThe exposure
exposure (piled
trending fence
fence (Fig.
(Fig. 24).
24). The
(piled with rock)
rock) encountered on the
way is composed of
of unit
unit C
C rhyolite
rhyolite cut
cut by
by numerous
numerous quartz
quartz veins.
veins. After passpassing through
through the
ing
the gap in the fence proceed through
through the
the forest
forest (bearing
(bearing N.
N. 10
10 E.)
E.)
The contact
contact between rhyolite
rhyolite and
to the
the first
first rock
rock ledge.
ledge. The
and andesite is
is exposed
on top of
has toppled exposof this
this ledge where a
a juniper tree
tree with shallow roots
roots has
ing aa fresh
fresh rock
roák surface
surface (the
tree was
was uprooted
uprooted during
during aa major
major ice
ice storm
storm in
in
ing
(the tree
April, 1976).
1976). The intrusive contact trends
trends N.
N. 87°
87° E.
E. and
and dips
dips 60°
60° to
to the
the north.
north.
This dip
dip probably reflects
reflects the
northeast—trending normal
This
the inclination of
of a
a northeast-trending
normal
fault
fault (later
(later intruded
intruded by the
the dike)
dike) (Fig.
(Fig. 25).
25). The difference between rock
rock
types
types is subtle (see
(see discussion
discussion under
under Stop
Stop 4C).
4C). The contact is
is sharp;
sharp; no
no
are found
dike and
and no contact
contact effects
effects are
xenoliths of
of rhyolite
rhyolite are
found within the
the dike
in the
the rhyolite.
rhyolite. This dike is
is fine—grained
fine-grained and
and shows
shows little
little change
observed in
In thin
thin section,
section, the
in grain size from ôontact
in
contact to
to center.
center.
In
the texture of the
the
dike rock is intergranular to ophitic
of sausseritized plagio—
dike
ophitic with aa framework
framework of
plagioclase laths
clots set in aa patchy matrix of
epidote—clino—
clase
laths and clots
of iron oxide
oxide and
and epidote-clinozoisite. Both andesite and
and rhyolite
rhyolite are
are jointed
jointed with
with N.
N. 60°
60° E.
E. and
and N.
N. 40°
40° W.
W.
as
as important directions.
displays the contact
contact between the
dike and
Another exposure that displays
the andesite dike
unit C rhyolite can be reached by walking through the
the trees
trees from Stop 4C
(bearing N.
N. 10°
10° W.)
W.) to
to an
an exposure piled with rock (Fig.
(bearing
(Fig. 24).
24). The contact
here trends N.
N. 80 E. and
and dips
dips 65°
65° to
to the
the north.
north. Piled on top of the
the exposure
exposure
73
...,
�are rocks
rocks moved
moved to
to this
this location
location from
from the
the cleared
cleared field
field to
to the
the north.
north. Most
Most of
of the
are
the
blocks
are
massive
unit
D
rhyolite.
This rock is similar in outward appearance
blocks
unit D rhyolite. This
to unit
unit C,
C, but
but it
it can
can be
be distinguished
distinguished quickly in the
field from the other fine—
to
the field
finegrained units
grained
units by the bell-like sound
sound emitted
emitted when
when hit
hit by
by aa hammer.
hammer.
Also the
rock breaks with aa distinctive "breaking
"breaking glass"
glass" sound.
sound.
Stop 4E —
Massive Unit
Unit D,
D, and Unit E
- Massive
See Figure 24 for directions from
See
from Stop
Stop 4D
4D to
to this
this locality.
locality.
at point 4E*
4E* (see
Fig. 24)
For orientation stand at
(see Fig.
24) and
and look to the northwest;
northwest;
the contact
contact between
between unit
unit D
D and
and unit
unit EE trends
trends N.
N. 30°
300 E.
E. through
through the
the grassgrass—
the
Unit E lies on the
covered depression before you.
you. Unit
the rock
rock ledge
ledge to
to the
the northwest.
northwest.
Massive unit
rhyolite is
fine grained near
near its
Massive
unit D rhyolite
is very fine
its contact with unit E,
E,
but becomes noticeably coarser in
in grain size to
to the
the south.
south. Plagioclase
altered to sausserite
sausserite occurs
occurs in glomeroporphyritic
glomeroporphyritic clots and
altered
and is the
the dominant
dominant
Phenocrysts are
set in a
devitrified matrix that
phenocryst. Phenocrysts
are set
a devitrified
that contains coarser—
coarsergrained pod—shaped
pod-shaped areas
areas (pumice
(pumice fragments?).
fragments?).
Broken spherulites are also
Unit D locally displays
displays fine
fine striations that
observed in
in the
the matrix.
matrix.
Unit
that are
similar to those in
in the
the andesite
andesite dike
dike (see
(see description
description of
of Stop
Stop 4D).
4D).
These
0
striations strike (N.
30°E.)
contact between units D
striations
(N. 30
E.) parallel
parallel to the
the contact
D and E but
dip obliquely to it
striations as
dip
it (80°
(80° south for
for the
the striations
as compared to 60°
60° north
for the
the contact).
Unit D at
at this
Unit
this location is
is similar in lithology to the
the fine—grained
fine-grained
variety of
of unit
unit C observed at
Stop 4C;
4C; it
however, splinters like glass
glass.when
at Stop
it however,
.. when
This fine-grained
broken and commonly rings
rings like
like aa bell
bell when
when hit
hit by
by aa hammer.
hammer.
has chemical
chemical characteristics
characteristics that
rock has
that distinguish it
it from other fine—grained
fine-grained
Marquette rhyolites (Fig.
(Fig. 26).
26).
Walk across
across the
the grass covered depression to
to the
the low
low rock
rock ledge
ledge of
of banded
banded
unit E rhyolite.
rhyolite. The contact between unit
unit D
D and unit
unit E trends
trends northeast
northeast
through this
this depression.
depression. Banding in
in unit
unit E is
is formed
formed by discontinuous white
to pink streaks
pumice fragments
fragments and
streaks that
that represent
represent pumice
and shards sheared and compressed during late—stage
late-stage primary flowage and
and during post—depositional
post-depositional compaction
compaction
and welding. Bands may be up to
to 50 cm long,
long, but are
are usually
usually less
less than
than 55 mm
mm in
in
width. Commonly they
they bend
bend about
about phenocrysts.
phenocrysts. Bands strike N.
N. 53°E.
53°E. and
and dip
47° to
to the
the west.
west.
On the
southwest corner of
of the
near the
On
the southwest
the outcrop near
the base of the
the unit,
unit, unit E
grades into
into aa spherulitic
spherulitic rhyolite.
rhyolite. Spheruites
Spherulites are
are as
as large
large as
as 33 cm
cm in
in
diameter.
diameter.
To the
the west,
west, the
the outcrops are
are covered by aa drumlin elongated in
in an
an east—
eastwest direction.
direction. This orientation reflects the
the movement of the
the Green Bay
Bay Lobe
Lobe
(Woodfordian)
(Woodfordian) from east
east to
to west
west in
in this
this area.
area.
Stop 4F
4F (Optional)
(Optional) —- Porphyritic
Porphyritic Unit DD
From
From Stop 4E walk north
north to
to the
the east—trending
east-trending fence,
fence, then
then follow
follow the
the fence
fence
eastward (300
(300 m)
m) to
to the
the north—south
north-south fence
fence (Fig.
(Fig. 24).
24). Outcrops encountered to
to
the
east—trending fence
fence are
are of
of unit
the north
north of the
the east-trending
unit E rhyolite,
rhyolite, blocks in the field
field
74
74
�to
to the
the south
south are
are fine—grained
fine-grained unit
unit DD rhyolite.
rhyolite. Continue
Continue walking
walking
Note
the
angular
blocks
fence to
to the
the first
first exposure.
exposure. Note the angular blocks of
of rock
rock to
to
fence
of the
the fence.
fence. Here aa wide
wide assortment
assortment of
of rhyolite
rhyolite lithologies
lithologies is
is
of
blocks
blocks were
were probably
probably transported
transported by
by ice
ice aa short
short distance.
distance.
along
along the
the
the
the north
north
found.
found. These
These
Unit
Unit DD is
is gray
gray on
on weathered
weathered surfaces
surfaces but
but pink
pink on
on freshly
freshly broken
broken fractures.
fractures.
In
In hand specimen abundant
abundant phenocrysts of rounded quartz up
up to
to 3
3 mm in
in size
size and
and
subhedral feldspar (plagioclase
and
alkali
feldspar)
up
to
5
mm
in
length
(plagioclase
feldspar) up to
in length are
are
-easily identified.
identified. In
In thin section the rock contains large
large rounded
rounded and
and embayembayeasi1y
ed quartz (10%),
(10%), subhedral grains of sausseritized plagioclase (8%),
(8%), and
and ortho—
orthoperthitic texture
texture (14%).
(14%). Banding in
in unit D
D at
at this
this locality
locality is
is
clase with perthitic
faint;
faint; band trends
trends vary
vary from
from N.
N. 7°
7° E.,
E., 70°
70° east
east to
to N.
N. 500
50° E,
E, 85°
85° southeast
southeast
(deviation due to
to flow
flow folding?).
folding?).
(deviation
Unit D
D is
is easily distinquished from unit B,
B, particularly by differences
in Na20/K20 ratio (the
greater than 11 for
for unit
(the ratio is
is greater
unit B and
and less
less than 1 for
unit D).
D). Also,
Also, unit D
D contains a 100 m
m thick
thick massive phase (stop
(stop 4E);
4E); aa
unit
similar
similar massive phase
phase is
is not
not associated
associated with
with unit
unit BB (or
(or in
in fact
fact with
with unit
unit F,
F,
the other quartz,
plagioclase, alkali
alkali feldspar—bearing
feldspar-bearing rhyolite
rhyolite unit).
unit).
the
quartz, plagioclase,
75
75
�SUPPLEMENTAL STOP
STOP -- MARQUETTE
MARQUETTE RHYOLITE
RHYOLITE ON
ON INGALL'S
KNOB
SUPPLEMENTAL
INGALL'S KNOB
Highlights of
of this
this stop
stop include
include the
the well-banded
well—banded unit
unit C,
C, and
and pumice
pumice
Highlights
lenses and
and breccia in
lenses
in unit
unit A.
A.
Unit C —
Banding: Park
Park at
at the
the entrance
entrance to
to the
the Ingall's
Knob gravel
gravel pit
pit (see
Unit
- Banding:
Ingall's Knob
(see
Fig. 24).
Walk along
along the
the dirt
dirt road
road toward
toward the
the gravel
gravel pit
pit and
and then
then bear
bear right
right
Fig.
24). Walk
(south) to
to the
the outcrops
outcrops of
of dark rhyolite clearly visible
(south)
visible on
on the
the flanks
flanks of
of
Ingall's Knob. These
These outcrops
outcrops are
are composed
composed of
of well
well banded
banded unit
unit C
C rhyolite
rhyolite
Ingall's
(Fig. 27) •
(Fig.
Figure
Figure 27.
27.
Photomicrograph of highly
highly flattened
flattened and
and crenulated
crenulated shards
shards in
in the.
the.
Marquette rhyolite
rhyolite (unit
(unit C).
C). Flattening probably occurred during
during
primary movement of the
Folding may have occurred during
the ash
ash flow.
flow.
during
flowage or during
during later
later deformation.
deformation. Bar scale
scale is
is 11 mm
mm long.
long.
The bands are discontinuous and are formed by sheared and collapsed pumice
fragments.
Banding strikes
strikes N.
N. 50°E.
50 0 E. and dips 700
70° to
to 800
80° to the
the south;
south; bands
are locally
folded.
The
rock
in
this
locality
also
contains
lenses
of breccia
locally folded.
in this
and spherulitic
spherulitic rhyolite.
rhyolite.
Unit AA —- Fiamme
Fiamme (Pumice Lenses):
Lenses): Walk
Walk to
to the
the end
end of
of Ingall's
Ingall's Knob
Knob (see
(see Fig.
Fig.
24)
24) and
and climb directly
directly up
up the
the rock
rock face.
face. The
The rock
rock forming
forming the
the bluff
bluff on
on the
the
southeast end of Ingall's
Knob
is
a
porphyritic
quartz,
orthoclase,
plagio—
Ingall's
is
quartz, orthoclase, plagioclase—bearing
ash—flow tuff
tuff showing
showing nicely
nicely developed
developed fiamme
fiamme (the
black
clase-bearing rhyolite
rhyolite ash-flow
(the black
lens—like
features
in
the
rock).
The
fiamme
are
collapsed
pumice
fragments
lens-like features in the rock). The fiamme are collapsed pumice fragments
and
and are
are elongated
elongated parallel
parallel to
to the
the strike
strike of
of unit
unit AA (N.
(N. 50°E.).
50 0 E.). They
They have
have an
an
average
average axial
axial ratio
ratio of
of 12
12 ++ 8/1
8/1 (based
(based on
on the
the measurement
measurement of
of 50
50 fiamme).
fiamme).
In thin section,
section, unit A
A rhyolite
rhyolite contains
contains rounded
rounded and
and embayed
embayed quartz
quartz
(10%),
alkali
feldspar
with
perthitic
(10%),
feldspar
perthitic texture
texture (8%),
(8%), partially
partially sausseritized
sausseritized
76
76
�plagioclase
and iron
plagioclase (5%),
(5%)"and
iron oxide
oxide (tr).
(tr). The
The matrix
matrix is
is finely
finely devitrified
devitrified but
but
contains bands
bands that
that are
are more
more coarsely
coarsely recrystallized.
recrystallized. Flow
Flow texture
texture is
is common
common
contains
with
with shard—like
shard-like forms
forms aligned
aligned and
and locally
locally bent
bent about
about phenocrysts
phenocrysts of
of quartz
quartz
Ic xenolith
xenolith was
was identified in
and feldspar
feldspar (Fig.
(Fig. 28).
28). One
One small
small maf
mafic
in thin
thin
and
sections.
sections.
Figure 28.
28.
Figure
flattened shards
shards in the Marquette rhyolite
Photomicrograph of flattened
rhyolite
ash-flow tuff
tuff (unit
(unit A).
A). Shards are
are aligned and locally
ash—flow
locally bent
bent about
about
quartz and
and feldspar.
feldspar. Bar scale is
phenocrysts of quartz
is 11 mm
mm long.
long.
The change in slope above the rock face
face marks the contact
Unit A
A —- Breccia: The
between the top of unit
unit A ash—flow
ash-flow tuff
tuff (below)
(below) and
and the base of unit A
A breccia
o
contact
varies
in
orientation
between
N.
40°E.
and
N.
30°W.,
(above).
This
in
orientation
between
N.
40
E.
and
N.
30 o W.,
(above).
o
The wavy nature of this
trends N.
N. 50°E.
50 E. The
this contact suggests that
that
but in general trends
it
is
an
unconformity.
it is
It is
Unit
is poorly sorted and
and is
is approximately
approximately 50
50 mm thick.
thick.
It
is
Unit A breccia is
o
50°E.
banded with large clasts and
crudely banded
and matrix
matrix fragments
fragments elongated
elongated in
in aa N.
N. 50
E.
Along the
the route of this
direction
(parallel to the
the strike of
of unit
unit A).
A). Along
this traverse,
traverse,
direction (parallel
concentrated toward
toward the
aa crude
is observed with large fragments concentrated
the
crude size
size sorting
sorting is
This size
size sorting,
sorting, however,
however, is
is not
not characteristic
characteristic of
of
upper part of the
the unit.
unit. This
In
other
locations,
large
of
rhyolite
are
the
unit
as
a
whole.
In
other
locations,
large
fragments
rhyolite
are
the unit
On our
our route,
route, breccia
breccia near
near the
the base
base of
of the
the unit
unit
found
the unit.
unit.
On
found throughout the
contains
(less than
contains small
small (less
than 30
30 cm
cm in
in size)
size) dark-colored
dark—colored porphyritic
porphyritic rhyolite
rhyolite
Toward
fragments.
are quartz—bearing
quartz-bearing rhyolites.
rhyolites. Toward
Only aa few
few of
of the
the fragments
fragments are
fragments. Only
the top
top of
of the
the unit
unit the
the fragments
fragments become
become huge;
huge; one
one block
block is
is 33
33 m
m long
long in
in aa
the
o
Most of
of the
the larger
larger fragments
fragments are
E. direction and is
is 12 m
m wide. Most
are similar
N.
N. 50
50°E.
However,
three
in
lithology
to
the
quartz-bearing
unit
A
ash-flow
tuff.
However,
three other
in lithology to the quartz—bearing unit
ash—flow tuff.
rock types
types are
are present;l)banded
present;.l)banded rhyolite
rhyolite with
with small
small white
white feldspar,
feldspar, 2)
2) banded
banded
rock
rhyolite with
with large
large (5mm)
(5mm) white
white feldspar,
feldspar, and
and 3)
3) massive
massive rhyolite
rhyolite with
with small
small
rhyolite
The matrix
matrix of
of the
the breccia
breccia is
is gray
gray in
in
quartz
phenocrysts. The
quartz and
and alkali
alkali feldspar
feldspar phenocrysts.
77
77
------------------------------------------...,
�color on
on weathered
weathered
color
with
crystal,
rock
with crystal, rock
surfaces.
In thin
thin section
section the
the matrix
matrix is
is microbrecciated
microbreccjated
surfaces.
In
o
and angular
angular shard
shard fragments
fragments aligned
aligned in
in the
the N.
and
E. direction.
N. 50
50°E.
direction.
Breccia Exposure
Exposure at
at the
the Summit
Summit of
of Ingall's
Knob: Details
Breccia
Ingall's Knob:
Details of
of the
the relationship
relationship
between
fragments
and
matrix
are
revealed
in
an exposure
between fragments and matrix are revealed in an
exposure at
at the
the summit
summit of
of
Ingall's Knob
Knob (Fig.
The largest
largest fragment
fragment at
at this
this location
location is
is aa porphyporphy—
Ingall's
(Fig. 29).
29). The
ritic (black
(black in
in color)
color) rhyolite
rhyolite composed
composed of
of quartz
quartz and
and alkali
alkali feldspar
feldspar phenoritic
pheno—
o
crysts.
It
is
5
in
wide
and over
over 10
10 m
m long
long in
in the
the N.
N. 50
50°E.
direction. Contacts
crysts.
It is 5 m wide and
E. direction.
Contacts
between it
it and
and the
the breccia matrix (gray
between
(gray in
in color) are
are sharp.
sharp. Note
Note the
the smaller
fragments of
of black
black rhyolite
rhyolite in
in the
the matrix
matrix on
on both
both sides
sides of
of the
the larger
fragments
larger blackblack—
colored rhyolite
rhyolite fragment.
colored
fragment.
These
These fragments
fragments probably
probably are
are pieces
pieces of
of rhyolite
rhyolite
that broke
broke off
off the
the larger
larger fragment
fragment during
during transport.
that
transport.
Just
Just to
to the
the north
north there
is
a
large
red
fragment
impregnated
is a large red fragment impregnated with quartz veins.
veins. The
fragThe size
size of
of this
this fragment is
is difficult
difficult to estimate because of extensive cover.
ment
cover. Notice
Notice the
the smaller
smaller
red—colored fragments
fragments in
in the
the matrix
matrix just
just to
to the
the south
south of
of the
the red
red-colored
red clast.
clast. The
The
red fragment
fragment is
is aa porphyritic
porphyritic rhyolite
rhyolite similar
similar in
in mineralogy
mineralogy to
red
to the
the black
black
fragments. Both
Both fragment
fragment types
are similar
similar in mineralogy to
to the
unit A ashfragments.
types are
the unit
ash—
flow tuff.
flow
tuff.
Origin of
Origin
of the
the Breccia:
Breccia:
In
this breccia in
in the
the
In order
order to
to explain
explain the origin of this
following observations
observations must be accounted for:
following
for:
1.
The matrix
matrix of
of the
the breccia
breccia may
may show a
crude layering that
1.
The
a crude
that resembles
resembles
a
flowage
a flowage texture.
texture. Smaller
and shards
aligned in the
the
Smaller fragments,
fragments, crystals
crystals and
shards are
are aligned
N. 50°E.
N.
50 o E. direction.
direction.
Many of
of the
the larger clasts have unequal dimensions in
in section
and have
have
section and
their long axes oriented in
in the
the N.
N. 50°E.
50 o E. direction.
direction.
2.
2.
There are
are aa wide variety
variety of
of clast
clast types.
types. Many of the
the larger
larger fragfragments are
are similar in
in lithology to
to the unit A
A ash—flow
ash-flow tuff.
tuff.
3.
3.
4.
4.
There is
is only a
a slight suggestion of size sorting in
in the
the deposit.
deposit.
5.
5.
Many of
of the
the fragments
fragments are
are very
very large
large (up
(up to
to 33
33 mm long).
long).
The unit
unit is
is similar
similar in
in overall
overall fabric
fabric to
to mud—flow
mud-flow breccias or
or lahars
lahars
commonly
tuffs and lavas in
commonly interbedded
interbedded with
with ash—fLow
ash-flow tuffs
in Tertiary
Tertiary and
and Holocene
Holocene
volcanic
volcanic piles,
piles, in
in terms
terms of
of poor
poor sorting
sorting and
and fragment
fragment size
size (Parsons,
(Parsons, 1968;
1968;
Smith,
Smith, 197Gb).
1976b). However,
However, mud—flow
mud-flow breccias
breccias usually
usually do
do not
not contain
contain elongated
elongated
or
or oriented
oriented fragments,
fragments, and
and the
the matrix does not show
show flow
flow structure.
structure. The
The
unit
unit may
may instead
instead represent
represent aa pyroclastic—flow
pyroclastic-flow breccia
breccia (that
(that is,
is, aa block
block avalavalanche
anche or
or block—flow
block-flow deposit).
deposit). Modern
Modern examples
examples of
of this
this type
type of
of deposit
deposit are
are
described
described by
by Aramaki
Aramaki (1963)
(1963) and
and Parsons
Parsons (1968)
(1968) from
from Asama
Asama Volcano
Volcano in
in Japan.
Japan.
Modern
Modern block—flow
block-flow deposits
deposits may
may erupt
erupt initially
initially as
as ash
ash flows
flows and
and then
then during
during
emplacement
emplacement may
may pick
pick up
up large
large fragments
fragments from
from the
the surface
surface over
over which
which they
they
travel.
travel. Also,
Also, fragments
fragments from
from the
the walls
walls of
of the
the vent
vent and
and cognate
cognate pumice
pumice are
are
often
often incorporated.
incorporated. The
The matrix
matrix of
of the
the Holocene
Holocene block—flow
block-flow deposits
deposits around
around
Asama
Asama Volcano
Volcano may
may be
be crudely
crudely banded
banded and
and is
is commonly
commonly composed
composed of
of fine
fine ash
ash and
and
dust.
dust. These
These breccia
breccia units
units extend
extend as
as far
far as
as 18
18 km
km from
from Asama
Asama Volcano
Volcano and
and vary
vary
in
in thickness
thickness from
from 40
40 cm
cm to
to 10
10 mm (Parsons,
(Parsons, 1968).
1968).
There
There are
are many
many similarities
similarities between
between the
the Holocene
Holocene pyroclastic—flow
pyroclastic-flow breccias
breccias
about
about Asama
Asama Volcano
Volcano and
and the
the unit
unit AA breccia;
breccia; consequently,
consequently, II suggest
suggest that
that the
the
78
78
�Matrix
Matrix
NN
0
:
o
\/
I—
Ii
Cover
Cover
quartz veins
veins
quartz
k~~v~:'~>:"?
_
~~
~
\N?
.
/"
'.
. ~/
. .,; 0
—
o()
oO
00
o
"" \
"
-
0
0
-
/
"",
?...
'"
.......""
",......... ---/
00
—7-Matrix oo~
~ 7
7- --~/
Matrix
\
"
I
- /
\ '
./ ./,r-.
-~/~.
/. -=- /.
.........
-::: . :
\ -
/
.r
-.
?
•
~
?:;:~/- \
~
°/....-- / ......
•
?/
/
C/.
ct:1/.· .
7/ '
/
110
T
Tree
Tree
feet _I
00
0
00
00
.
?"- - ? /1' / ..
• _ . Tree
?"2?
ree 7' ..
Matrix
Matrix
Stump
EXPLANATION
fH
Black
r::I
Red
Red rhyolite
rhyolite
rhyolite
Small
of rrhyolite
Sma
II ffragments
rag men t s of
hy 0 lit e
in
matr ix
in matrix
o11
Figure
Figure 29.
29.
Matrix,
microbreccia
Matrix, microbreccia
Sketch map
map of
of an
an exposure
exposure of
of unit
unit A breccia
Sketch
breccia on Ingall's
Ingall's Knob.
Knob.
79
79
�unit A
A breccia
breccia is
is aa pyroclasticpyroclastic— or
or block-flow
block—flow breccia
breccia and
and not
not aa mud-flow
mud—flow
unit
deposit.
deposit.
Unit A-Unit
A—Unit B Contact
Unit
The contact
contact between
between unit
unit A
A and
and unit
unit B
B on
on Ingall's
Ingall's Knob
Knob is
is gradational.
gradational.
The
The basal
basal part
part of
of unit
unit B
B contains
contains numerous
numerous beds
beds and
and lenses
lenses of
of breccia
breccia that
that
The
grade into unit A
Just to
to the
the northwest
northwest of
of the
the outcrop
outcrop of
of unit
unit A
grade
A breccia. Just
detail above)
good exposure
exposure of brecciated unit
breccia (described
(described in detail
above) is
is a
a good
This lens
of breccia is
separated from
from massive
massive unit B by a
B (Fig.
(Fig. 24).
24). This
lens of
is separated
a thin
(2 m
m wide)
wide) sheared zone.
Unit B breccia at
(2
zone.
Unit
at this
this exposure is
is monomictic.
monomictic.
This is
contrast to other
other unit
lenses, and
This
is in contrast
unit B breccia lenses,
and the
the unit A breccias
that are
are polymictic.
that
80
80
�N
WATE RTOWN
WATERTOWN
t+
IUNCTION
TO
WATERLOO
STOP 5 -
POLISHED
EXPOSURE
NORTH
QUARRY
SOUTH QUARRY
SOUTH
QUARRY
UW
DRILLIN
DRILLING
SITE
.5 MILES
0
CONTOUR INTERVAL
CONTOUR
INTERVAL
10 FEET
10
FEET
EXPLANATION
—
====ROAD
ROAD
•
BUILDING
BUILDING
QUARRYWALL
WALL
JVQUARRY
Figure
Figure 30.
30.
Detailed map of the Portland
Portland Quarries.
Quarries. Field trip Stop 55 is
is in
in the
the
north quarry.
quarry. South quarry should
should be
be entered
entered from
from the
the east.
east.
82
82
�QUARTZ ITE NEAR
NEAR PORTLAND
PORTLAND
STOP 5 -- WATERLOO QUARTZITE
This stop illustrates
quartzite, the
This
illustrates the
the lithology of the
the Waterloo quartzite,
the youngest major Precambrian rock
est
rock unit
unit in
in south—central
south-central Wisconsin.
Wisconsin. These outcrops
are at
at the
the extreme
extreme southeastern
southeastern edge
edge of
of the
the exposed
exposed Precambrian
Precambrian shield
shield in
in
are
Wisconsin.
gate on the
19, walk south
Location:
From the
the locked gate
the south side
side of
of S.T.H.
S.T.H. 19,
toward
~oward the
the John
John O'Laughlin
O'Laughlin Quarries
Quarries (this
(this area
areaisis-a
-a Department
Department of
of Natural
Natural
Resources hunting
hunting preserve).
preserve). At the
the road
road junction
junction take
take the
the left
left fork.
fork. The
right
of the
Wisconsin's two deep drill
drill
right fork leads
leads to the
the site
site of
the University of Wisconsin's
holes, about 900 feet of
holes,
of core
core was
was obtained
obtained from
from one
one of
of them.
them. Drilling was
terminated
before intersecting the
base of
quartzite (see
Haimson, guide
terminated before
the base
of the
the quartzite
(see Haimson,
Walk
past
the
large
corrugated
iron
building
and
then
turn
1978).
the large
iron
and then turn west (right)
(right)
1978).
and walk
walk about
about 70 m
m through the
and
the trees
trees to
to the
the quarry
quarry (see
(see Fig.
Fig. 30
30 for
for route).
route).
The Waterloo Quartzite is
Introduction:
The
is probably stratigraphically equivalent
to the
the Baraboo
Baraboo and
and Barron
Barron Quartzites
Quartzites in
in Wisconsin
Wisconsin and
and to
to the
the Sioux
Sioux Quartzite
Quartzite
to
In
south—central
in Minnesota
Minnesota and South Dakota (Dott
in
(Dott and
and Dalziel,
Dalziel, 1972).
1972).
In south-central
Wisconsin the quartzite
quartzite sheet lies
lies stratigraphically above late—Penokean
late-Penokean
aged rhyolites
rhyolites and
and granites
granites and
and is
is mainly
mainly preserved
preserved as
as infolds
infolds into the
aged
the igneigneThe absolute age
ous basement.
basement. The
age of the quartzite can only be determined by
indirect means. At Baraboo
Baraboo the
the quartzite overlies
overlies rhyolites
rhyolites that
that are
are similar
similar
in
chemistry
to
those
rocks
in
the
Fox
River
Valley
dated
at
1765
m.y.
in
in the Fox River Valley dated at 1765 m.y. old.
old.
This date is
This
is the
the maximum
maximum age
age of
of the
the quartzite.
quartzite. Both the rhyolite and overlying quartzite
quartzite were
were deformed
deformed during an event suggested by Smith (1978a)
(1978a) to
to
Rb—Sr apparent age of the
have occurred 1650
1650 m.y. ago.
ago. This date is the Rb-Sr
the Fox
River Valley igneous
igneous rocks
rocks (Van
(Van Schmus
Schmus and
and others,
others, 1975).
1975). These data suggest
suggest
that
Baraboo—Waterloo Quartzite was
was deposited on an eroded rhyolite—granite
that the
the Baraboo-Waterloo
rhyolite-granite
basement between 1765
1765 and
and 1650
1650 m.y.
m.y. ago.
ago. A pegmatite dike with
with coarse
coarse quartz,
quartz,
feldspar and
muscovite crystals
crystals that
feldspar
and muscovite
that cuts the Waterloo Quartzite (on
(on Rocky
T. 9N.,
R. l3E.)
has been dated at 1440 m.y.
Island —- NW
Sec. 27,
27, T.
9N., R.
l3E.) has
m.y. old by
the
Rb—Sr method (Aldrich
Also, muscovite from a phyllite
the Rb-Sr
(Aldrich and
and others,
others, 1959).
1959). Also,
bed in the
Quartzite has
has been dated
dated at
m.y. old by the K—Ar
bed
the Waterloo Quartzite
at 1410 m.y.
K-Ar
technique (Goldich
dates place a
(Goldich and
and others,
others, 1966).
1966). These dates
a minimum age on the
the
deposition of
of the
the quartzite.
quartzite.
,
t,
At Waterloo,
Waterloo, the
the dominant rock
rock is a
a red to
to gray vitreous
vitreous quartzite comcomposed
of
75
to
98%
Si02.
Quartz
is
present
as
interlocking
posed
to 98% Si02'
is
interlocking and
and strained
strained
sand—sized grains (Fig.
sand-sized
(Fig. 31).
31). Muscovite in
in the
the matrix of the
the quartzite commoncommonly displays
displays lepidoblastic
lepidoblastic texture,
with increasing amounts
ly
texture, and
and with
amounts of mica the
Occasionally, thin phyllite layers
rock may grade into aa foliated
foliated quartzite.
quartzite.
Occasionally,
are found
found interbedded with the
Bands of
are
the quartzite.
quartzite. Bands
of andalusite
andalusite schist were
identified
in core
core recovered
recovered from
from the
the deep
deep well
well drilled
drilled just to the
identified in
the east of
the quarries
quarries (Haiinson,
(Haimson, 1978). The andalusite is
is partially
partially altered
altered to
to sericite.
sericite.
The assemblage andalusite—muscovite—quartz
andalusite-muscovite-quartz suggests that
that the
the quartzite was
locally, if
not regionally,
regionally, metamorphosed
metamorphosed to the
part of the
locally,
if not
the upper
upper part
the greenschist
facies. An amphibolite dike was also encountered in
in the
the well (Haimson,
(Haimson, 1978).
1978).
In the
the Waterloo
Waterloo area
area the
the quartzite
quartzite forms
forms aa broad
broad east-plunging
east—plunging syncline
syncline
In
(Buell, 1892,
1892, Warner,
Warner, 1904,
1904, Sumner,
Sumner, 1956)
1956) which
which is
is almost
almost entirely
entirely buried
buried
(Buell,
by Ordovician and
and Cambrian sedimentary
sedimentary rocks
rocks (Fig.
(Fig. 32).
32). Outcrops to
to the
the
north of
-h-, Sec. 25,
T. 8N.,
8N., R.
R. l3E.)
define the
north
of Lake
LakeMills
Mills(NE(NE
25, T.
l3E.) define
the south limb
of the structure.
structure. Here bedding dips
dips to
to the
the north
north at
at 500.
50°. The apparent nose
t,
83
�of the
of
the fold
fold is in the Portland area
area (the
(the area
area of
of Stop
Stop 5).
5). Here the strike
o
of
bedding
changes
from
N.
30°W.
(in the
the south)
south) to N.
N. 30°E.
of bedding
from N. 30 W.
(in
30 o E. (in
(in the
the north)
north)
defining a
a broad concave eastward arc;
arc; the
the nose
nose of
of the
the syncline.
syncline.
Strike
and dip
dip measurements
measurements are
are a
bit erratic
erratic in this
area suggesting that
and
a bit
this area
that the
the
structure in the nose of
the
syncline
is
complex.
The north limb of
of the syncline is complex. The
of the
the syn—
syndine is
cline
is exposed
exposed near
near Mud
Mud Lake
Lake where
where quartzite
quartzite strikes
strikes N.
N. 80°E.
80 o E. and
and dips
dips
The north
north limb
limb may
may extend
extend as
as far
far to the
east as
steeply to the
the south.
south. The
the east
as Hartford in Washington County (Sumner,
ford
(Sumner, 1956).
1956).
Figure
Figure 31.
31.
Photomicrograph of
of the
the Waterloo
Waterloo Quartzite
Quartzite from
from the
Photomicrograph
the Portland Quarry.
Quarry.
Interlocking and strained quartz grains
grains are
are interrupted
interrupted by aligned
laths of
laths
of muscovite.
muscovite. With increasing
increasing amounts of muscovite the
the rock
rock
grades into
into aa foliated
foliated quartzite
quartzite and
and finally
finally aa phyllite or schist.
grades
Bar scale
scale is
is 11 mm
mm long.
long.
The quartzite at
at Waterloo is well jointed
jointed with N.
N. 40°E.
40 o E. and N.
N. 80°E.
80 o E.
o
directions common (also
(also N.
N. 70°W.
70 W. as
as aa minor
minor direction).
direction). However no
no detailed
studies of
of the rock fabric in
studies
in the
the Waterloo
Waterloo area
area have
have been
been undertaken.
undertaken. Thick
Thick
layers of
of phyllite,
layers
phyllite, so common in
in the
the upper
upper part
part of
of the
the Baraboo
Baraboo Quartzite,
Quartzite,
are lacking in the Waterloo Quartzite. Phyllite beds at Waterloo are thin
are
thin
(rarely thicker
thicker than
than 25
25 cm)
cm) and
and commonly
commonly pinch
pinch out
out over
over aa lateral
lateral distance
distance
(rarely
of 10 to
to 20
20 m.
m. Primary structures such as bedding planes,
planes, cross bedding and
and
conglomerate beds are common,
common, and ripple marks are occasionally observed.
observed.
The unravelling of the structural history of the Waterloo Quartzite is
is crucial
to the understanding
understanding of
of the
the 1650
1650 m.y.
m.y. old
old event.
event.
The Waterloo
Waterloo Quartzite
Quartzite is
is overlain
overlain by
by Cambrian
Cambrian sandstones
sandstones that
that locally
locally
contain large
large rounded
rounded boulders
boulders of
of quartzite.
quartzite. About 3 km north
north of
of Stop
Stop 55 (Fig.
(Fig.
32),
32), blocks of quartzite 1 meter in size are embedded in Cambrian sandstone
sandstone
close to the quartzite exposures;
exposures; the size of the
the clasts decreases rapidly
until just 700 m
m from the
the sandstone—quartzite
sandstone-quartzite contact the
the Cambrian sandstone
is
fine grained and friable and
is fine
and contains
contains no
no quartzite
quartzite fragments
fragments (Buell,
(Buell, 1892).
1892).
84
84
�PORTLA D
SHIELDS
19} - . . - - - - - - l
1
WATERTOWN
o
2 MILES
WATERLOO
N
MILFORD
t
EXPLANATION
E X P L A N AT I ON
o0
QUARTZITE
QUARTZITE
EXPOSURE
EXPOSURE
DIP OF
OF BEDDING
AND DIP
BEDDING
STRIKE
STRIKE AND
-®—i--— f
-.-...;:)~
H.R.
H.R.
ROAD
ROAD
RAILROAD
TRACK
RAILROAD TRACK
FIELD
ROUTE
TRIP ROUTE
FIELD TRIP
HUBBLE
TON
HUBBLETON
ROAD
ROAD
Stop 55
Figure
Detailed route
route map
map through
through the
the Waterloo
Waterloo Quartzite
Quartzite area.
area. Stop
Figure 32.
32. Detailed
Map adapted
adapted from
from Buell
Buell (1892).
(1892).
is
is at
at the
the Portland
Portland Quarries.
Quarries. Map
85
85
�If the
the Paleozoic
Paleozoic sedimentary
sedimentary rocks
rocks and
and the
the Pleistocene
Pleistocene sediments
If
sediments were
were
stripped
from
the
Waterloo
area,
the
quartzite
would
stripped from the Waterloo area, the quartzite would stand
stand as
as an
an arcuate
arcuate
ridge (concave
(concave to
to the
the east)
east) 500
500 to
to 900
900 feet
feet above
above the
ridge
the surrounding
surrounding Precambrian
Precambrian
surface.
For
example,
to
the
north
of
the
city
of Waterloo,
Waterloo, quartzite
surface. For example, to the north of the
quartzite is
is
intersected in
in deep
deep wells
wells at
at 135
135 feet
feet above
above sea
intersected
sea level.
level. Just
Just 22 miles
miles to
to the
the
east, quartzite
quartzite is
is exposed
exposed at
at the
the Portland
Portland quarries
quarries at
east,
at an
an elevation
elevation of
of 860
860
feet (see
(see Smith,
Smith, 1978c).
l978c).
feet
Only one
one deep
deep well
well has
has penetrated
penetrated quartzite.
quartzite. This
Only
This well
well located
located near
near
Reesville
in
western
Dodge
County
penetrated
500 feet
feet of
of quartzite
Reesville in western Dodge County penetrated 500
quartzite before
before
entering aa mica-rich
mica—rich rock described by Thwaites (1940)
entering
(1940) as
as aa gneiss
gneiss or
or aa
schistose
quartzite.
schistose quartzite.
Studies of
of well
well cuttings
cuttings show
show that
that the
the Waterloo
Waterloo Quartzite
Quartzite is
Studies
is part
part of
of aa
large
area
of
quartzite
extending
from
Waterloo
to
Milwaukee
large area of quartzite extending from Waterloo to Milwaukee and
and north
north to
to
Fond du
du Lac
Lac (Smith,
Fond
(Smith, l978c).
1978c). Thwaites
Thwaites (1940)
(1940) reported
reported iron-bearing
iron—bearing shale
shale
interbedded
with
this large quartzite sheet.
interbedded with this
sheet.
Stop Description:
Description: After
Stop
its steep south
wall.
After entering
entering the
the quarry,
quarry, walk to its
south wall.
The
rock
this quarry
quarry is
typical of
of Waterloo
Waterloo Quartzite
Quartzite in
The rock in
in this
is typical
area.
in the
the Portland area.
It is
is coarsely
coarsely recrystallized and is
It
is rich in
in muscovite.
muscovite. Bands
Bands of conglomerate
are common and
and contain quartzite
quartzite fragments
fragments up
up to
to 33 cm in
are
in size.
size. Conglomerate
Conglomerate
bands
strike
N.
35°E.
and
dip
42°
to
the
south.
bands
N. 35°E. and
42° to the south.
On the western part of
of the
the
quarry wall a 25 cm thick
thick phyllite
phyllite lens
lens is
is exposed
exposed (Fig.
(Fig. 33).
33). The
phyllite
The phyllite
thins
thins to
to 3
3 cm
cm and
and eventually
eventually pinches
pinches out
out to
to the
the west. Color banding that
that
represents
primary
bedding
parallels
conglomerate
represents
parallels conglomerate layers.
layers. Cross
is
Cross bedding
bedding is
observed just above the
the phyllite lens
lens (Fig.
(Fig. 33).
33). Dott and Dalziel (1972)
(1972)
report
report a
a mean current direction of
of 165
165 degrees
degrees (S.
(S. l5°E.)
15°E.) for
for the Waterloo
Quartzite
based
on
measurements
of
38
Quartzite based on measurements of 38 cross sets.
sets. This compares with aa
direction of 171 degrees measured for the Baraboo Quartzite
Quartzite (Dott
(Dott and
and Dalziel,
Dalziel,
1972).
1972). Common current directions for these two quartzites strongly
strongly suggest
suggest
that
that the
the Baraboo
Baraboo and
and Waterloo
Waterloo Quartzites
Quartzites are correlative.
correlative.
In
In outcrops just to the
the south
south of
of the
the quarry,
quarry, foliated
foliated quartzite
quartzite is
is
highly
polished
and
grooved
(due
to
highly polished and grooved (due to glaciation).
glaciation). Grooves
Grooves trend
trend N.
N. 20°E.
20 o E.
Foliation
Foliation and
and cross
cross bedding
bedding (?)
(?) impart
impart aa swirl—like
swirl-like pattern
pattern to
to the
the outcrop.
outcrop.
In
places
the
foliatedquartzite
In places the foliated quartzite has
has weathered
weathered out in
in aa series
series of
of low
low ridges
ridges
each
each about
about 11 cm
cm high
high (Fig.
(Fig. 34).
34).
86
86
�Figure 33.
33.
Figure
View of aa thin
thin phyllite
phyllite layer
layer (between
(between arrows)
arrows) interbedded
interbedded with
with
quartzite at
at the
the Portland
Portland Quarry
Quarry (Stop
(Stop 5).
5). Note
Note the
the crossbedding
crossbedding
in the quartzite just
just above
above the
the phyllite
phyllite bed.
bed.
Figure
Figure 34.
34.
located just
just to
to the
the
Close-up
Close—up view
view of
of foliated
foliated Waterloo
Waterloo Quartzite
Quartzite located
Foliation planes
planes are
are
south
south of
of the
the quarry
quarry visited
visited at
at Stop
Stop 5.
5. Foliation
each about
about 11 cm
cm high.
high.
weathering out
out here
here into
into aa series
series of
of low
low steps
steps each
weathering
87
87
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89
1 000-3K8T007-78
1000-3K8T007
-78
�OMISSIONS
OMISSIONS
South-Central Wisconsin
Wisconsin
Precambrian Inliers
Field
Field Trip
Trip Guide
Guide Book
Book Number
Number 22 -- Precambrian
Inliers in
in South-Central
off the
bar scales
In preparation
publication, the
the bar
scales were
were inadvertently
inadvertently left
left off the
In
preparation for
for publication,
following figures.
figures.
Figure 14
14 (p.
(p. 59)
59)
Photomicrograph
Marcellon rhyolite
Photomicrograph of
of Marcel10n
ash-flow tuff.
tuff.
Marcellon
rhyolite ash-flow
Horizontal
dimension,
3.3
mm.
Horizontal dimension, 3.3 rom.
Figure 17
17 (p.
(p. 62)
62)
Photomicrograph of
Marcellon rhyolite
Photomicrograph
of Marce1lon
rhyolite spherulitic
spherulitic texture0
Marcellon
texture.
Horizontal
dimension,
6.4
mm.
Horizontal dimension, 6.4 rom.
62)
Figure 18
18 (p.
(p. 62)
bands.
Photoinicrograph of
of aa spheroid
spheroid with
with concentric
concentric bands.
Photomicrograph
Horizontal dimension,
Horizontal
dimension, 6.4
6.4 mm.
rom.
Figure 19
19 (p.
63)
(po 63)
(p.
and
Photornicrograph of
of aa spheroid
spheroid with
with aa core
core of
of quartz
Photomicrograph
quartz and
Vertical
dimension,
11.2
mm.
epidote. Vertical dimension, 11.2 rom.
epidote.
Figure 27
27 (p.
76)
(p. 76)
in the
Photomicrograph
crenulated shards
Photomicrograph of
of flattened
flattened and
and crenulated
crenu1ated
shards in the
Marquette rhyolite.
dimension, 6.6
Marquette
rhyolite. Horizontal
Horizontal dimension,
6.6 mm.
rom.
Figure 28
77)
28 (p.
(p. 77)
Photomicrograph of
of flattened
Marquette
in the
Photomicrograph
flattened shards
shards in
the Marquette
Horizontal
dimension,
rhyolite ash-flow
rhyolite
ash-flow tuff.
tuff. Horizontal dimension, 6.6
6.6nun0
rom.
(p. 84)
Figure 31
31 (p.
84)
Photomicrograph
Quartzite.
Photomicrograph of
of the
the Waterloo
Waterloo Quartzite.
Horizontal
dimension,
6.6
Horizontal dimension, 6.6nun.
rom.
Figure 33
33 (p.
(p. 87)
87)
View
em thick.
View of
of thin
thin phyllite
phyllite layer,
layer, about
about 40
40 cm
cm
thick.
in middle
middle of
in
of layer.
layer.
Pen lies
Pen lies
�
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Institute on Lake Superior Geology
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Institute on Lake Superior Geology: Proceedings, 1978
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Institute on Lake Superior Geology. Milwaukee, Wisconsin. May 9-14, 1978.
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Institute on Lake Superior Geology
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1978
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Aaquist, B. E.
Banaszak, K. J.
Bauer, R. L.
Carnbray, F. W.
Cannon, W. F.
Chang, L. L. Y.
Cooper, R. W.
Cummings, M. L.
Doane, v.
DuBois, J. F.
Egger, N. L.
Foose, M. P.
Gere, M. A., Jr.
Hammond, R. D.
Heinrich, E. W.
Hodder, R. W.
Hughes, J. D.
Jirsa, M. A.
Jonnson, A.
Jones, D. G.
Kalliokoski, J.
Klaysrnat, A. W.
Larue, D. K.
Luther, F. R.
Massey, N. W. D.
Meddaugh, W. S.
Meineke, D. G.
Meyer, R. P.
MoIling, P. A.
Mudrey, M. G., Jr.
Mursky, G.
Myers, P. E.
Nebrija, E. L.
Ojakangas, R. W.
Peltonen, D. R.
Peterman, Z. E.
Salotti, C. A.
Scofield, N.
Shaffer, N.
Shanabrook, D.
Sims, P. K.
Smith, E. I.
Strakele, A. E., Jr.
Taylor, R. W.
Trow, J.
Tyson, R. M.
Vadis, M. K.
Van Schmus, W. R.
Welkie, C. J.
Westjohn, D.
Woronick, R. E.
Zietz, I.
-
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luoty !big
Aoooal
Meetio
Institute on Lake
Ihooder
Hay, Ootariu
Superior Geology
�PROCEEDINGS
tWENTY - THIRD ANNUAL
INSTITUTE ON LAKE SUPERIOR GEOLOGY
HELD AT THE
AIRLANE MOTOR HOTEL
THUNDER BAY
ONTARIO
MAY 2 — 8,
1977
SPONSORED BY THE
ONTARIO DIVISION OF MINES
AND LAKEHEAD UNIVERSITY
THUNDER BAY.. ONTARIO
M.M. Keh1enbeck,:S.A.
Kissin, R.H.
General Editors
Mi t che 11
�This page intentionally left blank
�TABLE OF CONTENTS
GENERAL INFORMATION
.
INSTITUTE EOARD OF DIRECTORS
LQCAL COMMITTEE
Vi
.
SESSIONS CHAIRMEN
.
.
ANNUAL BANQUET SPEAKER.
ACKNOWLEDGEMENTS
V
.
,..
...
.
.
.
.
Vii
Viii
.
ix
CALENDAR OF EVENTSAND. PROGRAM
ABSTRACTS
FIELD TRIPS
.
.
51
A.
COLDWELL COMPLEX, MARATHON, ONTARIO.
51
B.
PROTEROZOIC ROCKS OF THE THUNDER
BAY AREA
52
MATTABI, IGNACE, ONTARTO
53
C.
iii
�L
GENERAL INFORMATION
23rd
"ANNUAL
INSTITUTE. ON. LAKE SUPERIOR GEOLOGY
AIRLANE MOTOR HOTEL
THUNDER BAY
MAY 2.
-: 8,
1977:
SPONSORED BY THE
ONTARIO DIVISION OF MINES
AND LAKEHEAD UNIVERSITY
THUNDER,. BA, 'ONTARIO
INSTITUTE BOARD OF DIRECTORS
P.E.
Giblin, Ontario Division of Mines, Ministry
Resources,. Sault Ste. Marie, Ontario.
of Natural
J.D. Hughes, Department of Geography., Earth .Science,and
Conservation, 'Northern Michigan University, Marquette,
Michigan.
.
M.M.
$
Kehlenbeck, Department of Geology, L.akehead',Iiniversity,
Thunder Bay, Ontario.
R.C. Reed'
(Secretary-Treasurer), Geological Survey Division,
Department of Natural Resources, Lansing, Michigan.
M.S. Walton, Minnesota Geological Survey, University of Minnesota,
St. Paul, Minnesota.
v
�Trip C -
Mattabi
James M Franklin, Geological Survey of Canada,
Ottawa, Ontario.
WallyGibb, Mattabi Mines Ltd, Ignacé, Ontario.
Howard Poulsen, Department of Geology, Läkehead
University, Thunder Bay, Ontario.
Paul Severin, Sturgeon Lake Mines Ltd. ,
Ontario.
Adel Tammán, Mattabj Mines Ltd. ,
Ignace,
Ignace, Ontario.
Banquet Chairman
John S. Mothersill, Dean of S,cience, Lakehead
University, Thunder Bay, Ontario.
Session Chairmen
S.S. Goldich1, Department of Geology, University
of Northern Illinois, DeKalb, Illinois.
H.C. Halls, Dgpartment of Geology, University
of Toronto, Toronto, Ontario.
Bram Janse, Selco Mining Corp., Tpronto, Ontario.
R.H. McNutt, Department of Geology, •McMaster
University, Hamilton, Ontario.
G.B. Morey, lvlinnesota Geologidal Survey, University
of Minnesota, St.: Paul, Minnesota.
R.W. Ojakangas, Department of Geology, University
of Minnesota, Duluth, Minnesota.
H. Walton, Minnesota Geo'ogical Survey, University
of Minnesota, St. PaUl, Minnesota.
G.M. Young, Department of Geology,. University of
Western Ontario, London., Ontario.
vii
�LOCAL COMMITTEE
General Chairman
Hanf red M. Kehlenbeck, Department of Geology,
Lakehead University, Thunder Bay, Ontario.
Technical' Program
Stephen A. Kissin, Department of'Geoiogy,
Lakehead University,, Thunder Bay, Ontario.
Roger H. Mitchell,' Department of Geology,
Lakehead University, Thunder Bay, Ontarip;
Field Trips
Trip A -
Coldwell
Complex
Roger H., Mitchell, Department of Geology,
Lakehead University, Thunder Bay, Ontario.
R. Garth Platt, Department of Geology,
Lakehead University, Thunder Bay, Ontario.
Trip B -
Proterozoic
Rocks of the Thunder. Bay Area
Kenneth G. Fenwick, Ontario Division of Mines.,
Thunder Bay, Ontario.
Clarence R.. Kustra,: Ontario Division of Mines,
Toronto, Ontario.
William
"
'
H. Mcllwaine, Petrologic 'Ltd. ,,thunder' Bay,
Ontario.
John F. Scott, Ontario Division Of Mines,
Thunder Bay, Ontario.
vi
�Annual Banquet Guest Speaker
Dr. J. Tuzo Wilson, Department of Physibs Geophysics Division, University of Toronto)
Toronto, Ontario
Acknowledgements
The organizing committee for the 23rd Annual Meeting
of the Institute on Lake Superior Geology gratefully
acknowledges the work of Wendy Bons and Cathy LeBrun for
typing the final, manuscripts of the field trip guidebooks
and proceedings volume.
Special thanks to Sam Spivak wh prepared the many
figures, maps, and cover illustrations'.
viii
�CALENDER OF EVENTS
AND PROGRAM
MONDAY,
MAY 2, 1977
1:00 p.m.- 330 p.m.
Early Registration
.AirianeMotor Hotel-Lobby
4O0 p.m.
Pre—Institute field trip ACoidwell Complex departs from
the Airlane parking lot for
Marathon, Ontario:
8:00 p.m.—10:00 p.m.
Early Registration
Airlane Motor Hotel-Lobby
TUESDAY, MAY 3, 1977
7:00 a.m.- 8:00a.m.
8:00 a.m.
5:00 p.m.
Early RegiStration
Airlane Motor Botel-Lobby
:pre....Institute fièldtrip B—
(part 1)—Proterozoic Rocks of the
Thunder Bay area departs from the
Airlane parking lot.
Field trip B (part 1) returns
to Airlane Motor Hotel.
ix
�WEDNESDAY, MAY 4, 1977
Pre—Institute field trip B
(part 2)—Proterozoic rocks
8:00 a.m.
of
the Thund'ei Bay area.
departs Airlane parking lot.
5:00 p.m.— 9: 00 p.m.
Registration
5:00 p.m.
Pre—Institute
Airlane Motor Hotel—Lobby
field trip B
returns to Airlane
(part 2)
Motor Hotel.
5:00 p.m.
Pre—Institute field trip A
returns from Marathon to
Airlane Motor Hotel.
8:00 p.m.
Conference Smoker (cash bar)
Tiberio Room - Airlane Motor
Hotel
THURSDAY, MAY
7:30
5, 1977
Registration
Airlane Motor Hotel-Lobby
a.rn.— 9:30 a.m.
8:30 a.m..-12:00 a.m.
Technical Session 1
(see page xii)
1:30 p.m.-' 6:00 p.m.
Technica' Session 2
(see page xiii)
7:00 p.m.— 8:00
p.m.
Cocktail Hour (cash bar)
Tiberio 1oom - Airlane Motor
Hotel
Annual Banquet -
8:00 p.m.
x
Tiberio
Room
�-
FRIDAY, NAY 6, 1977
-
8:30 a.m.—12:;00 noon
Technical Session 3
(seepage. xiv)
l:30 p-.m.— 5:40 p.m.
Technical Session 4
(see page xv)
.1
6: 30 p.m.
Post—Institute field trip C—
Mattabi. departs Airlane
parking lot for Ignace. Trip
C will return on Sunday, May
8,1977 by 1:00 p.m. to
Airlane Motor Hotel.
8:00 p.m.
Northwoods MOtel, Ignace
Informal discussion period
in preparation for field trip..
xi
�$7SSZON
2
1Morning'
Thursday, May 5th, 2977
8.20
Opening Remarks
8.30
Meineke, D.G.,
Valdis, M.K. &
Klaysmat.
A.W.
-
8:30
-
22:00
a.m.
Organic-rich lake sediment exploration
geochemical survey of eastern Lake
Verraillion-Ely
Minnesota.
area, Northeastern
8.50
Beard, R.C..
Urani'vM deposits of the Kenora area.
9.10
0jakanas, R.W.
Proterozoic pitchblende vein potential
in Minnesota: Theory and Speculation.
9.36
Cannon,
Two-hi 1 lion-year-old sedimentary
phosphorite deposits in •the precambrian
of northern Michigan.
IV. F.
9. 50. -
10.00
t4ôrey, G.B..
Preliminary manganese resource
for the Cuyuna District:
approach.
Mudrey, M.G.,
Massive sulphide deposits
Beltrarne, R.J.,
I-Ioltzman,
10.20
£offe_ByLeak
C.
estimates
A statistical
in Wisconsin.
Ostrom,
M.E.
Reinke, G.
10.40
Booy, E.
Engineering problems in glacial soils
near the Canadian-United States border.
11.00
Morey, G.B.
Stratigraphic and tectonic history of
lower and middle precambrian rocks in
east-centra7 Minnesota.
LaBerge, GIL.
Major structural fsatures in Central
Wisconsin and their implications on the
11.20
$
Animike Basin.
11.40
Davidson, D.M.
12.00 -.
Paleostrain
i.30
Lunch
jj
S
analyvis: That, How and Why?
�SESSION
2
'A Lt erno on"
Thursday,
l30
Ma_yb 5th, 19??
Birk, D.
McNutt, R .H.
-
1.30 - 6.00 p.m1
Rb/Sr geochronolo,yof Wabigoon Belt
Granitoids, Northwestern Ontario.
Rare earth element geochemistry of
'Archean anrphiboli tes, tona lites, granites
and paragneisses in the eastern Lac Seul
area, Ontario.
1.50
thou, C.L.
2.10
Mcbennan, S.M.,
Fryer, B.J. '
An estimate of the rare earth element''
distribution in Post-Kenoran upper crust,
Young,
north
2.30
G.M.
of Lake Huron.
The occurénce" and some nobel metal
concentrations in selected komatiitic'
ultramafic volcanic rocks from Munro
McCrae, W.E. &
Crocket, J.H.
Township, Ontario.
2.50 3.00
3.90 goffe_Bea&
Geochemistry of early proterozoic
of Lake Huron, Ontario.
Fryer, B.J.
north
3.20
Longstaffe,
F.J.,,
180/160 results for Archean plutonic rocks,
Lake Despair 'area, Northwestern Ontario.
Schwarcz,H:P.
3.40
4.00
'
4.20
Review of Occygen isotope geochemistry of
Ahinad, SN
Perry, E.G. Jr.
some precambrian
Mitchell, R.H
Platt, R.G.'
CoQper,
'
Mafic
iron formations.
mineralogy of ferroaugite syenite from
the coldwell Complex, Marathon, Ontario.
'
Weiblen, P.W.
paleosols
Shape, sixe, cznd cooling history of
trochtolitic—gabbroic rocks in the Duluth
E,
R.W.
complex.
4.40
McMaster,
B.,
1'icNutt, R.H.
Archean volcanism Washeigamaga' Lake area,
Wabigoon Subprovince, Northwest Ontario.
5.00
Blackburn, G.E.,
Identification
5.20
Pilatzke, R.H.,
Petrology and trend curface,analjgsis of two
lake-stage gra'nodioritic plutons, Northern
.
Er
Karner,
F.R. Er
Peterson, W.M.
'5.40
Morris, W.J., E
Wilband,
J.T,
of archean calc-alkaline
volcanid centres in the Ma'nitou Lakes, area,
Northwestern Ontario
Lake of
the'Woods region, Ontario.
Geochemistry of the Yellow Dog Plains.,
Marquette County, Michigan.
peridotite,
xiii
�SESSION
3
'Morning,'
Friday, May ôf/j,
8.30
Weber, R.E.
1977
—
8.30
-
12.00
a.rn.
The petrology and sedimentation of the
upper precambrian sioux quartzite. of
Minnesota South Dakota, and Iowa.
8.50
Morey, G.B
Schulz, K.J.
9.10
Young, G.M.,
Long, D.G.F
Petrographic and chemical attributes of
some lower and middle precambrian gray-wacke-shale sequences in northern
Minnesota.
Deltaid deposits in tlze upper Pecors,
Espanola and Gowanda formations (Huronian).
McLennan, S.M.
9.30
Mancuso, J.J.,
Seavoy, R.E.
Lougheed, M.S.
Strati graphy of tle Baraga Basin metasediment, Michigan;
9.50 - 10.00. Coffle Break
Lougheed, M.S. f
Mancuso, J.J.
Fossil collectibles from the Gunf lint
10.20
Shegeiski, R.J.
Evidence fbr archean turbidite and submarine fan sedimentation from the Savant
Lake greenstene terrain, N.W. Ontario.
10;40
Frost, B.R.
Some comment; on the metamorphism of
iron-formati 'n$.
11.00
Gower, C.F.
Clifford, P.M.
Metamorphism in the English River
Feixzn, W.C.
The stratigraphy and petrology of the
archean volcanic rocks at Jasper Lake,
eastern Vermilion District, Cook County,
Minnesota.
Maas, R.S.,
Medaris, L.G. El
VanSchmus, W.R.
Penokean structures and
10.00
Jl.20
11.40
12.00 -
formatiiin.
sub-
province near Kenora, Northwest Ontario.
Wisconsin.
1.30
Lunch
xiv
plutpnic
rocks iv
�SESSION
4
'Afternoon
1.30
Friday, May 6th, 1977 '
-
5.40
p.m.
1,30
Eyerson.C,I,
Drift lithology in relation to bedrothk
geology, Long Is land Lake Quadrangle,
Cook County, Minnesota.
1.50
Zarth, R.
Sedimentary facies associated with late
2.10
2.30
Wisconsin Glacial Lake. Duluth, Wrenshall
'areas Minnesota.
Welke, C.J.,
Nebriga, E.t.
Meyer, R.P.
Swrficial
Green, J.C.
Environmental
sediment analyse,s offshore of
the copper-bearing provinc of Keweenaw
Point,
geotogy 'of the North Shore'a
coastal zone management project.
Lso - 3,00
43.00
Upper Michigan.
Mothersill, j.s.
Coffiae Break
Post-glacial
Canadian
3.20
the
The application of linear topographic
features
a glaciated precainbiian terráine in
Cooper, R.W. e
Morey, G.B.
t.o structural interpretation of
northeas tern
3.40
sediment 'distribution ih
of Lake. SuperiorS
portion
Minnesota.
Geophysical' studies of peridotite dikes,
Yellow Dog Plains, Northern Michigan.
Snider, D.W,,
Kiasner, J.S,
Quam, S.,
Lilienthal, R.
Geraci, P. G
Grosz, A.
4.00
4.20
Dugan, J.P. Jr.
Ervin, C.P.
Geophysical study 'of a gabbroic' intrusion,
Klasñer,' J.S.,
Bouguer gravity anomaly map of northern
peninsula of Michigan, Lake Superior, and
Hinze, W.J.,Bacon,
L.0.
4.40
E O'Hara, N.W.
Chandler, v.w.,
Hinze, w.j.
Braile, L.W.
'
'
5.00
5.20
environs.
Analytical'correlation
magnetic
data in
of gravity and
the North American
Midcontinent.
studies of a regional'gravity
model
anomaly in norther'n'Michigan and Wisconsin,
.extent.of anomaly, and its relationship to
near surfac geology.
D.'
Pesonén, LJ .
Halls, 4Ij.C.
Lake, Wisconsin.
Crustal
Klasner, J.s.
Bomke,
Clam
"
PaleomagnetidAtiñdpaleointensity
studies of
normal and reversed keweenawan 'rocks -
implications
North
xv
for the polar wander path of
America.
�Str
cts
�This page intentionally left blank
�REVIEW OF OXYGEN ISOTOPE GEOCHEMISTRY
OF SOME PRECAMBRIAN IRON FORMATIONS
S.N. Ahmad
and
E.C. Perry, Jr.
ABSTRACT
A review of published values for oxygen isotope data for
quartz and magnetite from the Hamersley Iron Formation and the
eastern portion of the Biwabik Iron Formation indicates that
consistent trend lines appear if ol8o of quartz and magnetite
are plotted v5AQM. This implies that during metamorphism
these iron fprmations behaved as closed systems on same scale
and that the system as a whole records isotopic information
not present iii any one sample.
The Hamersley and Biwabik
trend lines intersect one another at a olSo
for quartz of
about 24.0 0/00., a value close to that observed for pure chert
horizons in the Hamersley Iron Formation and the Gunflint Iron
Formation (correlative with the Biwabik).
Subject to certain assumptions, the intersectiônof the
Hamersley and Biwabik oxygen isotope trend lines permits us
to estimate that the temperature oX precipitation or diagenesis
of these iron formations was about 22°C.
A continuing study of
other iron formations of low metamorphic grade may show whether
this temperature estimate is reliable.
It may also permit
evaluation of reactions proposed by several authors for conversion of iron carbonate to magnetite during diagenesis and
metamorphism.
3
�URANIUM DEPOSITS O,F'TH:IENORP AREA
R. C. Beard, Ont. Div. of Mines, MNR, Kenora, Ontario
Uranium deposits were first recognized in the Kenora
area in 1949 and exploration has been carried out on these
occurrences during two periods, 1952-57 and 1965-67. Recent
increases in the price of uranium have stimulated a new cycle
of exploration in the area, and numerous programs, both
detailed examinations of previously known occurrences and
grassroots exploration for new deposits, are currently under
way.
Past work on the various properties consisted of tren—
ching, geophysical surveys, and diamcnd.drilling.
An exception, the flew Campbell Island Mining and Exploration Ltd.
deposit in MacNicol Twp., has been explored by underground
development on two levels.
Over thirty deposits have been documented in the KenoraDryden area; there is evidence to suggest that many more have
been discovered which have not yet found their way into the
public record.
They tend to be concentrated in two general
areas:
a) near Vermilion Bay, 40 miles east of Kenora,
associated with a narrow "greenstone" belt and, b) north of
Kenora within the English ,River Gneiss Belt.
The uranium occurrences are (typibally) asociated with
pegmatitic phases of anatectically—derived, rather than plutonic, granitoid rocks. Supracrustal rocks of Archean age,
exhibiting remelting and assimilation features to varying
degrees, are associated with almost all deposits. These are
quartz-biotite paragneisses of sedimentary derivation although
some deposits are associated with amphibolitized mafic volcanic rocks.
'Uranium occurs as fine grains of uraninite disseminated
in the granitoid rocks which are usually, but not always,
It js frequently associated with one
pegmatitic in texture.
of the following accessory minerals:
biotite, magnetite,
sulphides, or apatite. Minor leaching and redeposition as
uranophane along near surface fractures is common to many of
Grab sample assays from radioactive zones range
the deposits.
from 0.5 or less to 1.5 'lbs. U 08 per ton; with occasional
grab samples assaying over 10 bs. per ton.
It is suggested that the urahiferous pegmatites of the
area are, to a certain extent, stratigráphically controlled,:
having been anatectically derived from supracrustal rocks
which contained ahomalous amounts of uranium. Study should
be directed toward the identification of these "source beds",
so that exploration may then be directed to these more favorable areas. Reconnaissance mapping by the Ontario Div. of
Mines (Breaks et al, 1975) suggests one such area near Umfre—
ville Lake, north of Kenora.
4
�PRELIMINARY MANGANESE RESOURCE ESTIMATES OR THE
CUYUNA DISTRICT: .A STATISTICAL APPROACH
R.3. Beltrame, Richard C.' Holtzman, and G.B. Morey, Minnesota Geologiëal Survey,
University of Minnesota, St. Paul, Minnesota.
The Cuyuna range in east-central Minnesota has produced over 105 million tons
of iron ore and manganiferous-iron ore during the past 62 years. Although iron ore
reserves are nearly exhausted and all mining activity, has ceased, significant amounts
of manganese beating materials are presently available.
The occurtence of high-grade rnanganiferous material (>5 weight % Mn) is
generally limited to the Emily iron-formation member of the Rabbit Lake Formation
and more commonly to the Trommald Formation. In both iron-rich units the
manganese is present in both the original protolithic iron-formation (10-30% Fe) and
the so-called secondarily enriched "natural ores" (40-60% Fe). In the Trommald
Formation of the North range,most of the manganese occurs in the transistion zone
between the thick-bedded (granule chert layers 1-100 cm thick) and thin-bedded
(laminae ci cm thick) facies rocks. Due to the complexity of the stratigraphic and
structural relations and because of the enormous amount of available drill hole data,
preliminary manganese resource estimates were statistically calculated for 69 uniquely
defined deposits. A deposit was defined, for statistical reasons, as a legal land section.
The location coordinates, collar elevations, and chemical assay data for 5,045
drill holes were entered into a computerized storage and retrival system. Statistical
methods involved calculating an area of influence for each given Mn assay value for
each drill hole. These areas of influence were calculated based on the spatial
distribution of drill holes in each deposit and the location of the drill hole relative to
the section boundaries. Computer-generated data location and drift thickness maps
were produced as were grade-quantity estimates of manganese resources.
Manganese quantity resource estimates were calculated for five gcade classes (13%, 3-5%, 5-10%, 10-15%,and >15%) for each of five depth intervals (<30, <60, <90,
<120, and < 150 meters below the surface) for each of the 69 deposits.' Resource
estimates for three deposits in the Emily district, 39 deposits in the North range, and
27 deposits in the South range accounted for 6%, 77%, and 17% of the total Cuyuna
district resource estimate respectively.
A total of 22.4 billion metric tons of manganiferous material (>1% Mn) was
talculated 'to a depth of 150 meters for the entire Cuyuna district. More realistic
values are 2.3 billion metric tons at>5% Mn, and 887 million metric tons at >10%
Mn, calculated to a depth of 60 meters.
5
�Rb/Sr GEOCHRONOLOGY OF WABIGOON BELT GRANITOIDS, NORTHWESTERN ONTARIO
DIETER BIRK and POI3ERT H. McNUTT
Department of Geology, McMaster University.
Hamilton, Ontario L8S 4M1
granitoid
ThirtyLóne whole rocksamples from five
piutons, intrusive intomet-
volcanics- of the Wabigoon Greenstone Belt, generate a composite Rb/Sr errorchro
(MSWD =
2,34):
Age = 2621 ± 42 m.y'.
(2°)
k0 = :7007 ± 4
(2e)
Linear regression of togenetic samples generate Rb/Sr isochrons sensustricto for each
pluton as follows:
Pluton (No. Of
Samples Analysed)
Age in m.y.
Lithology
(±
2a)
-
Initial
Location
Ratio (± 2a)
(NTS)
Burditt Lake (9)
granodiorite
2598
± 45
.7009 ± 6
52C/13
Esox Lake (4)
quartz-feldspar porphyry
2572 ± 42
•.7003 ± S
-52F/3
Flora Lake (5)
granite-monzodiorite
2636 ± 63
.7017 ±
52F/S
Taylor Lake (5)
granodiori'te-monzonite
2640 ± 31
.7005 ± 3
52F/7E-
Ryckman Lake (7)
granodiorite-.mónzodiorite
2609 ± 63
:7001 ±
52C/lS
2230 ± 55
Ryckman Lake (5)
For the Ryckman Lake Stock, the lower
S
.7012 ± 2-
52C/1S
age, is fro'm a "pseudoisochron" caused- by the
fortuitous alignment of five data points beyond that expected from known analytical
error.
The seven point isochron represents a wider range of rock chemtstry a-nd more
meaningful age and-intercept.
Isochron data must be tested by several linear regression
techniques to expose such "pseudoisochrons'1.
i
These Wabigoon granitoid isochrons, when compared with published isochrons from the
Rainy Lake area, suggest juvenescence of granitoid plutonism from north to south.
This
may relate genetically to the presence of the Quetico-Wabigoon Belt interface near Rainy
Lake.
The low 875r/86Sr ratios for all the late-kinematic granitoids implies a source
region of low Rb/Sr.
Partial melting of upper mantle rather than older sialic material
is indicated,
6
�IDENTIFICATION OF ARCHEANS CALC-ALKALINE VOLCANIC
CENTRES IN THE MANITOU LAKES AREA,. NORTHWESTERN ONTARIO
C.
E. BLACKBURN
Ontario Division o: Mifles, Queen Park, Toronto
A B S T R A C T
Centres of felsic to intermediate vo1Oanisn within Archean
volcanic-sedimentary belts have long remained enigmatic.
In
their detection reliance has frequently been made upon
physical parameters in pyroclastic rocks (eg. coarsening
towards vents), without special attention to overall volcanic
and subvolcanic stratigraphy.
In the Manitou Lakes area
detailed geological mapping has pinpointed a number of vent
areas, both simple and compOund.
Within the study area a thick submarine basaltic flow sequence
of tholeiitic affinity was built up, followed by eruption of
a caic—alkaline sequence composed predominantly oE dacitic to
andesitic coarse pyroclastics.
The tholeiitic baa1t sequence was intruded by quartz-feldspar
porphyry plugs, at Sunshine Lake and at Thundercloud and
Washeibemaga. Lakes (McMaster and McNutt, this volume).
The
plug at Sunshine Lake is the subvolcanic equivalent of rhyolitic
flows that occur within the pyroclastic sequence.
This plug
was in turn intruded by irregular lamprophyric dikes and sills
that are subvolcanic equivalents of a calc-alkaline to alkaline
mafic flow that terminated volcanism in this part of the area.
Southwest of Cane Lake, elongate to lenticular quartz-feldspar
porphyry bodies within the pyroclastic sequence variously have
subvolcanic and volcanic characteristics, suggesting theY.
location of a felsic vent in this vicinity.
A mafic sill
correlatable with the late mafic phase at Sunshine Lake occurs
in close spatial association with these porphyries.
None of these vents has been directly identified as supplying
dacitic to andesitic pyroclastic debris. However, one vent
that did supply such coarse pyroclastic material has been
identified at Frenchman Island, Upper Manitou Lake, where a.
subvolcanic porphyritic to inequigranular plug intrudes
coarse pyroclastics of comparable chemical and.. mineralogical
composition.
7
�ENGINEERING PROBLEMS IN GLACIAL SOILS NEAR TILE
CANADIAN-UNITED STATES BORDER
Emmy Booy
Department of Geology ar3d Geological Engineering
Michigan Technological University
Houghton Michigan 49931
ABSTRACT
The borderlands of the United States and Canada ranging from Lake
Superior eastward to the Gulf of St. Lawrence are characterized
by the presence of glacial deposits which cause problems in safe
utilization of the land. At various locations, but particularly
along the valley of the St. Lawrence River and its tributaries
and along the southern margin of Lake Superior, slope failures
have caused expensive losses in property and hazards to human life.
Because glacial clays in northern climates have been .known for cén—
tunes to be prone to failure, they have been studied by engineers
and geologists to determine the causes of their failures and means
for controlling them.
Most of these investigations have concentrated on the so—called "quick clays", glacial clays laid down in marine
environments.
There have been relatively few studies of fresh—water
glacial deposits and their relationship, if any,,to the marine and
estuarine deposits.
At the present state of knowledge, there is no definitive explanation for the sudden outflows of clay which are characterized as
quick clay failures.
It should be noted that a variety of types
of failures are observad in all the glacial deposits. Many of them
appear to be a result f excess hydrostatjc pressure in the coarser
strata of varved deposits. These occur in both the fresh water and
marine deposits.
Classic slump failures have, also been described in
both fresh and salt—water deposits.
The only major difference in slope stability between the more easterly marine deposits of glacial soils and those deposited in the
fresh water predecessors of Lake Superior, is the apparent lack of
quick clay flows in the latter. These flows have been reported from
Scandinavia, Alaska, and eastern Canada as occurring suddenlyon
slopes as low as a few degrees.
The failed material has an extremely
low viscosity and may require hours to regain significant shear
strength.
There has been a significant lack of reports in the literature of similar failures in freh—water glacial deposits.
It appears likely that there is a significant difference in material
between those soils which fail as quick clays and those which do. not.
It is generally agreed that there is a major rearrangement of soil
fabric during quick clay failure which is held responsible for the
variation in shear strength between failed and unfailed portions- of
a deposit.
Itis equally possible that the "cement" which is alleged
to give quick clays their original shear strength is significantly
different i-n marine and fresh water glacial deposits.
S
�Two—billion—year—old sedimentary phosphorite deposits
in the Precambrian of northern Michigan 1/
by
W. F. Cannon
S. Geological Survey
Reston, Virginia 22092
U.
Abstract
Phosphate—rich beds have recently been found at five localities in 2—billion—.
year—old metasedimentary rocks of the t4arquette Range Supergroup in northern
Michigan (Cannon and Klasner, 1976).
All occurrences are near the
unconformable base of the supergroup within 100 meters stratigraphically
above older gneisè. Four occurrences are in the Michigamme Formation, part
of the Baraga Group; the fifth is in the older Ajibik Quartzite, part of
the Menominee Group.
as
The phosphatic minerals occur in two ways:
1)
thin beds of apatite, mostly associated with lean carbonate iron—formation,
and 2) as pebbles of apatite in conglomerate.
Two thin—bedded occurrences
in the Michigannne Formation, first reported by Mancuso and others (1975),
have not been evaluated for grade and extent.
Of the three new occurrences
reported by Cannon and Kiasner (1976), two are low grade and consist of
scattered pebbles of apatite in basal Michigamme and Ajibik conglomerates,
and a few thin beds of apatite generally less than 1 cm thick.
The third
contains thick conglomerate beds, including a bed about 15 m thick that
averages about 15% P205, and many thinner beds of comparable grade.
Because outcrops are very limited in *the area, the grade and extent of the
deposits are impossible to determine without subsurface data, but the
economic potential of these deposits warrants further evaluation. 'The area
has never been systematically explored for phosphate minerals. The five
known occurrences were found by only a cursory examination of field notes
and hand specimens; none of these rather cryptic deposits was identified
in the field.
Precambrian sedimentary rocks have not been considered a likely host for'
economic phosphate deposits in the United States, and these deposits are
the richest so far known in the Precambrian of this country.
Because five
localities have been found without a thorough field search in an area that
has very sparse outcrops, a good possibility exists for undiscovered
phosphate deposits in the region.
-
References
cannon, W. F., and Klasner, J. 5., 1976, Phosphorite and other apatite—bearing
sedimentary rocks in the Precambrian of northern Michigan: U. S.
Geol. Survey Circ. 746, 6 p.
Mancuso, J. J., Lougheed, M. 5;, and Shaw, R., 1975, Carbonate—apatite in
Precambrian cherty iron—formation, Baraga County, Michigan: Econ.
Geology, v. 70, no. 3, p. 583—586.
1/
Prepared in cooperation with •the Geological Survey Division, Michigan
Department of Natural Resources
9
�ANALYTICAL CORRELATION OF GRAVITY AND. MAGNETIC DATA
IN THE NORTH AMERICAN NIDCONTCNtNT
V.W. Chandlr, W.J. Hinze and L.W. raile
Department of Geosciences
Purdue University.
West Lafayette, Indiana 47907
The correlation of gravity ane mágñetic data isone of
the most commonly used geophysical techniques in basement.
This usage is especially vital in the
geological studies.
Midcontinent area of North America where direct observation
of the basement complex is essentially prohibited by a
In the past the àorrelation
blanket of Phanerozoic strata.
of.gravity and magnetic data has usually been carried out
by purely visual method:; or by restricted applications of
Visual
theoretical methods such as Poisson's theorem.
methods are hampered by their subjectie nature wherea the
classical application of Poisson's theorem is often voided
Recent studies have
by necessary theoretical assumptions.
investigated several computerized apprc'aches to the correlaOne of these recently
tion of gravity and magnetic data.
developed techniques, internal correspondence, has been
investigated through model studies and has been shown to be
a potentially valuable supplement to ccmbined gravity and
magnetic interpretation. The technique '3 involves a moving
window analysis Df anotalies of the fir;t vertical derivative
A least squares
of gravity and iragnetics reduced to the pole.
linear regression is conducted between the two data sets
for each window position with a subsequent creation of three
Considregression coefficient arrays over the data space.
eratic:n of Poisson's theorem shows that the slope coefficient
array is equivalent to a continuous estimate of magnetization-density ratios for anomalous sources. The intercept
coefficient array yields valuable information regarding
The correlation coefficient array
anomaly base levels.
expresses the significance of the linear fit for each
window position. Analysis of gravity and riagnetic data from.
the Midcontinent region of North America demonstrate that
the internal correspondence approach yieldE useful constraints
in local as well as regional geophysical irterpretation of
the basennnt complex.
-
10
�RARE EARTH ELEMENT GEOCHEMISTRY OF ARCHEAN AMPHIBOLITES, TONALITES,
GRANITES AND PARAGNEISSES IN TIlE EASTERN LAC SElL AREA, ONTARIO
C.—L. Chou, Department of Geology and Erindale College, University
of Toronto, Mississauga, Ontario, Canada LSL1C6
ABSTRACT
Using neutron activation techniques twenty samples from the
eastern Lac Seul area of the English River gneiss belt have been
analyzed for twenty—eight major and 'trace elements (A12O3, total Fe,
MgO, CaO, Na2O, K2O, T1O2, MnO, Sc, V, Cr,
Co, Zn,'Rb, Zr,. Ba, La,
Nd, Sm, Eu, Tb, Dy, Yb, Lu, Hf, Ta and Th). Variations of Mn,
Sc, Co and Cr are related to total Fe content, their concentrations
decrease in the order of amphibolites, tonalites
paragneisses,
leucosome, trondhjemite, granites, muscovite granites, and peginatite.
Distinct rare earth element (REE) patterns are found for. various
rock types.
Two amphibolites have flat REE patterns and total REE
contents about l0—l2X chondritic abundances, similar to Archean
basalts. A third amphibolite (T91) is enriched in La and Ce relative
to other amphibolites, probably due to metamorphism.
Six tonalites
can be separated into two groups based on their REE patterns.
Type—A tonalites (4 samples) have smooth and steep—sloped REE
patterns with remarkable enrichment of lIght REE and depletion of
Ce,
heavy REE (LaE
F
=71—135 and YbE F
3—11).
Type—B tonalites
(two samples) have higher total REE contents than type—A, negative
anomalies and flat heavy REE abundances (LaEF = 106—112 and
Type—A tonalites may have derived from garnet
= 22—39) .
eclogites, with garnet as a residual phase during partial melting,
Eu
whereas type—B tonalites are probably derived from dioritic source
with amphibole and plagioclase as residual phases.
Granites have
smooth and steep—sloped REE patterns. Muscovite granites have
lower light REE contents than granites and negative Eu anomalies.
Both granites and muscovite granites may have originated from
sedimentary rocks by crustalanatexis. The REE patterns of garnet
paragneiss and biotite paragneiss are. similar to type—A tonalites,
suggesting that tonalitic rocks are the dominant source of meta—
sediments.
'I
�THE APPLICATION OF LINEAR TOPOGRAPHIC I'EATURES TO STRUCTURAL
INTERPRETATION OF A GLACIATED PRECAMBRIAN TERRANE
IN NORTHEASTERN MINNESOTA
R.W. Cooper and G.l3. Morey, Minnesota Geological Survey, tiniMersity of Minnesota,
St. Paul, Mjnnesota
The application of linear topographic features to various kinds of structural
interpretations has become increasingly popular since the advent of spacecraft and
high-altitude imagery. Although many types of lineaments can be recognized in
Minnesota, a major question remains as to their usefulness in structural studies,
particularly in areas where glacial activity has obscured many fundamental bedrock
attributes. We have analyzed in detail an area of 3600 sq. km. in parts of northern St.
any, exists
Louis and Cook Counties. Minnesota to determine what correlatAu,
between the bedrock geology and topographic linearrients.
The bedrock geology of our study area may be divided into four strato-tectonic
units:
(1) Lower Precambrian metavolcanic and metasedirnentary rocks of Jhe
Vernlion distct having a &redeminance of Saults trending approximately N.20 E.,
(2) Lower Precambrian "granitig"
N.33 E., N.55 -6o°E;, N.70 -75 E. and N.85 E.;
rocks of the Vermilion massif and Giants Range batholith having faults trending N.20 40 E.; (3) Middle Precambrian sedimentary rocks of the Animikie Group having a few
northwest- and north-northeast- trending faults; and (4) various kinds of Upper
Precambrian mafic rocks assignable to the Duluth Complex. lm\ addition, the northern
part of the study area is covered by thin (c6 meters), discontinuous patches of
Quaternary materials, 'whereas a thick, more- or less continuous mantle of these
materials obscures bedrock relationships in the southern part of the area.
The southern part of ths stu0dy area is characterized by numerous topographic
lineãments trending in a N.35 -40 E. direction; a direction parallel to movement of
the Rainy lobe in this area. In contrast, lineaments in the northern part of the study
area exhibit a number of divora !irect½r.a. ".r.tn alysis o these lineaments indicates
that bedrock structural features exerted a profound influence on 8resent-y lend
forms. or eample, an excellent correlation exists between N.20 E., N.35 -40 F_..
N.55 -60 E. and N.85 E. trending lineaments and ground-mapped faults in areas
underlain by Lower Precambrian metavolcanic and etaedimentary rocks. Similarly
there is a marked correspondence between N.25 -40 E. trending lineaments and
ground-mapped faults in areas underlain by the Lower Precambrian Vermilion massif
and Giant's Range batholith. FUrthermore faulting or fracturing in a northeast
direction may be much more prevalent in the "granitic" rocks than present mapping
indicates 'ecause of many codirectional lineaments that are not ssociated with areas
of known faulting.
Previous mapping has documented only a few northeast- and northwest-trending
faults in the Duluth Complex. However this part of the study area is characterized by
nhim,rn,,c northeast-trending topographic lineaments. Thus an area of approximately
20 sq. km. was mapped in detail to determine if the lineaments could be related to any
strtktural features in the bedrock. As a result of this mapping several faults having
unknown amounts of displacement were recognized that correspond to major lineament
trends.
Subsequently it was recognized that many topographic lineaments also
coihcide with northeast-trending aeromagnet ic lineaments and with disrupted struc-
tural elements such as contacts between, and o1Lsiü .. n vnap units.
This
suggests that faulting in a northeast direction was a majar tectonic process during and
after.intrusion of the Duluth Complex.
A few northwest-trending faults have been inferred, primarily on the basis of
subsurface inforrnaiiui, tn nit the western margin of the Duluth Complex. In places
these faults correspond to mapped faults in the Middle Precambrian Animikie Group,
whereas in other places they correspond to well-defined northwest-trending aeromagnetic gradients. However other magnetic gradients have no known geologic expression.
We infer from these data that northwest-trending faults may he more numerous than
present mapping indicates.
The results of our lineament analysis suggest that any pre-glacial topographic
expression of the. northwest-trending faults was eliminated by the. southward flow of
glatial ice which at the same time enhanced the topographic expression of the
northeast-trending bedrock structures. Thus although topographic lineaments are a
useful adjunct to structural studies in nqrthern Minnesota, they must be carefully
interpreted in terms of the glacial history.
�PALEOSTRAIN ANALYSIS:
WHAT, HOW AND WHY?
Donald M. Davidson, Jr., Geology Department, University of Minnesota,. Duluth, 55812
ABSTRACT
WHAT?
Several excellent techniquest for 3lantitatively'analyzing natural strain
(paleostrain) in deformed rock units have appeared in the geological literature
within the past decade.
HOW?
Samples are collected and slabbed along orthoganal planes ot photographs
taken of the unit viewing three such planes. Deformed structures within rocks,
such as fossils, oolites, concretions, phenocrysts, or reduction spots, often
The major and minor axes of these ellipses may be
have elliptical shapes.
measured along with angular relationship of the axes (0) to some fundamental
directional property in the rock (bedding, cleavage, foliation, lineation).
The particular method used in treating the data is dependent upon certain
assumptions fundamental to the mathematical techniques employed, although virtually
Other
all methods assume that deformation involved finite, homogeneous strain.
assumptions relate to.knbwledge of the initial shape of the deformed object
(circular or otherwise) tr knowledge of the orientation of primary planar features
such as bedding ,within the deformed unit.
The procedures of Ramsay, Elliott, Dunnet, Hsu and Matthews and a new method
currently being developed at the.University of Toronto will be reviewed,
WHY?
Paleostrain techniques are powerful tools in direcdy analyzing strain
history in rocks and shear zones, in preferentially.discriminating between defor—
mational models or in treating sedimentary fabrics.. These methods warrant' serious.
consideration by geologists working in the Lake Superior region.
REFERENCES
Barr, M. and Coward, M. P., 1974, A method for the, measurement of volume
change, Ceol. Nag., v. 111, p. 293—296.
Boulter, C. A., 1976, Sedimentary fabrics and their relation to strain—
analysis methods: Geology, v. 4, p. 141—146.
Coward, M. P., 1976, Strain within ductile shear zones? Tectonophysics,
v. 34', p. 181—197.
Coward, N. 1?. and James, P.. R. 1974, The deformation of two' Archaean greenstone
belts in Rhodesia and Botswana: Precambrian Res., v. 1, p. 235—258.
Dunnet, D. and Siddans, A.W.B., 1971, Non—random sedimentary fabrics and their
Tectonophysics, v. 12, p. 307-325.
modification by strain:
Elliott, D.,' 1970, DeterminatiOn of finite strain and' initial shape from deformed
elliptical objects: Geol. Soc. Amer. Bull: v. 81, p. 2221—2236.
Hobbs, B. E. and Talbot,' J. 1., 1966, The analysis of strain in deformed rocks.
Jour. Ceol: v. 74, p.'. 500—512.
Matthews, P. E., Bond, R.A.B; and Van Den Berg, J. J., 1974, An algebraic
method of strain analysis using elliptical markers: Tectonophysics,
v. 24, p. 31—67.
Owens, W. H., 1974, Representation of finite ,strain state by three—axis planar
diagrams: G.S.A. Bull., v. 85, p. 307—310.
Ramsay, J. G., 1967, Folding and fracturing of rocks: McGraw—Hill, New 'York,
p. 103—120, 134—142, 200—221.
Talbot, C. J., 1969, The minimum strain ellipsoid using deformed quartz veins:
Tectonophysics, v. 9, p. 47—76.
Tobisch, 0. T., et al., 1977, Strain' in metamorphosed volcaniclastic rocks and
its bearing on the evolutiQn of 'orogenic belts: G.S.'A.B., v. 88, p. 23—40.
'
,
1.3
.
'
�GEOPHYSICAL STUDY OF A GABBROIC INTRUSION,
CLAM LAKE, WISCONSIN
Joseph Patrick Dugan, Jr., and C. Patrick Erviri, Dept. of Geology,Northerrt
Illinois University, DeKalb, IllinOis
60115
ABSTRACt
Aeromagnetic maps recently released by the &Wisconsin Geologiàal àhd
Natural History Survey contain a sharp, 7000 gamma magnetic anomaly near
the town of Clam Lake, Ashland County, in the northwestern part of the
state. The anomaly has a wavelength of only 5.5 km, suggesting a shallow
source. A coincident, but less well-defined, Bouguer gravity anomaly of
15-20 mgals is also present.
Inland Steel Company drilled a 104 m hole in the center of the anomaly
using a diamond drill. The lithologic log shows 29 meters of drift overlying
a fresh, unaltered gabbroic sequence with zones containing up to 60% magnetite and ilmenite.
Preliminary analysis of the potential field anomalies suggests that
the source is a vertical body that is circular-to-elliptical in horizontal
section. Since the Mellen Gabbro Complex lies only about 8 •km to the
north, the Clam Lake Anomaly may be caused by an intrusive offshoot at
depth..
14
�DRIFT LIThOLOGY IN RELATION TO BEDROCK GEOLOGY,
LONG ISLAND LAKE QUADRANGLE, COOK COUNTY, MINNESOTA
Curtis I. Everson, Department of Geology, University of .Minnesota, Duluth
Lithologic studies in northeastern Minnesota suggest that drift
prospecting is a useful tool for mappIng drift—covered bedrock. A detailed
study of till clasts composition in the Long Island Lake quadrangle revealed
a significant relationship between drift lithology and bedrock geology.
The Long Island Lake quadrangle. is a suitable area for this study for
1) outcrops are numerous enough to have allowed
the following reasons:
the construction of a detailed geologic map, 2) the area contains eight
3) the local bedrock experiended glacial erosion,.
distinctive rock unit,
indicated by the existence of glacially abraded and quarrIed outcrops.
The distribution of glacial sediments, mainly till and outwash,&were
mapped,. and one hundred and one samples of drift were collected along
traverses parallel to ice flow (perpendicular to strike of the bedrock).
Both till and outwash contain a large quantity of local bedrock clasts in
the size ranges greater than 2 mm in diameter. Clasts smaller than 2 mm
are mainly the mineral quartz, and therefore not so diagnostic of local
As a test, boulders greater than 1 meter in diameter were used
bedrock.
in the field for inferring bedrock contacts. These contacts were found
to be within ± 60 meters (200 ft.) of cQntacts placed by outcrop mapping..
tack of local bedrock clasts in the smaller size fractions indicate
either high resistance of local bedrock to crushing, or lack of opportunity
for crushing because of short residence .time in the glacial system (short
distance transport). In either case, the fine—grained fraction therefore
represents a eontribution to the glacial load from more distance sources.
15
�THE STRATIGRAPHY AND PETROLOGY OF THE ARCHEAN
VOLCANIC ROCKS AT JASPER LAKE, EASTERN VERMILION
DISTRICT, COOK COUNTY, MINNESOTA
William C. Feirn, Geology Department, University of Minnesota,
55812
Duluth, Minnesota
ABSTRACT
The Jasper Lake area, located within the eastern Vermilion
district in Cook County, northeastern Minnesota, represents the
basal portion of a thick metavolcanic-metasedimentary sequence.
Gruner (1941) found the area to contain threedominantly.ign'eoas
units: a greenstone unit, an "agglomerate-conglomerate" unit,
and an "andesite intrusive" unit., These rocks were shown t&
have been complexly faulted and isoclinally folded. All units
have been metamorphosed to greenschist facies.
The oldest unit consists of predominantly massive metavolcanics (including basalt, diabase, andesite, and lesser dacite)
and is herein referred to as the Jasper Lake greenstone. Du'e
to the presence of pillow structures and quench textures observed
at several localities, thse rocks are interpreted, as subaqueous
The unit is linear in outline, 1000—1500 meters thick
flows.
(exposed), and trends east-west, and is probably continuous with
the Chub Lake Volcanic Complex of Morey, Weiblen, and others (1971)
to the east. The SaganaEa tonalite intruded the greenstone unit
along its northern margin, locally metamorphosing it to amphibolite
n'ade along a 30-60 meter wide zone.
The "agglomerate-conglomerate", herein referred to as the
Jasper Lake pyroclastic unit, and the associated "andesite intrusive" conformably overlie the greenstone. The pyroclastip
unit consists mainly of volcanic breccias, tuffs, and lesser
amounts of epiclastic volcanic breccias, conglomerates,, and metaClasts range from 0.1 mm to 1.2 meters in diameter
graywacke.
and are composed of dominantly porphyritic andesite with very
minor amounts of basalt, dacite, and tuff. Some of the basaltic
clasts may have been derived from the older greenstone unit.
The Jasper Lake andesite unit (Gruner's "andesite intrusive")
is composed of predominantly porphyritic augite andesite with
lesser amounts of massive, porphyritic hornblende andesite-dacite.
The rock is typically fine-grained to aphanitic, and vesicular
to amygdaloidal, thereby representing a shallow hypabyssal intrusion which may have reached the surface locally.
These rocks are conformably overlain by a well-bedded,
graded graywacke-slate unit, greater than 1.6 kilometers thick.
Detailed study in the area shows that the volcanic rocks
at Jasper Lake represent the oldest portion of the regional
volcanic pile. They trend west-northwest and are faulted off
to the west by northeast-trending units which are clearly
younger, as they contain clasts of the Saganaga tonalite, which
intrudes the greenstone.
�SOME COMMENTS ON THE METAMORPHISM OF IRON—FORMATIONS
B. Ronald Frost, Department of Geology, University of Minnesota, Duluth, Mn. 55812
ABSTRACT
Preliminary work on the metamorphism of iron—formations shows that the rocks
can be modeled by the system Fe—Si—O—C—H. In the typical assemblage of Fe—silicate--
quartz—magnetite, the fluid composition is controlled by a reaction of the form:
Fe—silicate
+ 02 =
magnetite
t quartz ± H2Q
When fayalite i present the oxygen fugacity is controlled by the QFM' buffet1
and
it deviates increasingly from the buffer when it is controlled by increasingly
lower—temperature Fe—silicates.
It is conceivable that at very low temperatures,
of the range of diagenesis, the oxygen fugacity buffered by the greenalite +
those
quartz + Fe—oxide assemblage is high enough to make the coexisting Fe—oxide hematite.
The presence of siderite requires the consideration of carbon in the fluid
Fortunately, the oxygen fugacities of an Fe—silicate—quartz—magnetite rock
seem to be high enough to allow CO2 to exist as the major carbon—bearing component
in the fluid instead of CH4. Under such conditions siderite will.break down to
magnetite by the reaction:
phase.
6 siderite 1- 0.2: = 2 magnetite
Siderite
+ 6. CO2
will also react to form an Fe—silicate by the reaction:
siderite + quartz +H20 =
Fe—silicate
Simple topological calculations show that the assemblage siderite ± magnetite +
Fe—silicate + quartz will be isobarically, isothermally invariant, indicating
that at fixed T and P the fugacities of O2 H2O, and CO2 will be fixed.. Furthermore,
the same diagrams show that the breakdown of siderite to magnetite canoccur at
constant f0 if there is a gradient of H20 present;
2
model can be used to explain the origin of magnetite in siderite—bearing
taconite formations. If the rock originally consisted of alternating layers rich
This
in
siderite with those containing iron—silicate + quartz, each layer would be
Equilibration of the fluids across the
layers would cause the chemical potential of CO2 in the siderite layer to decrease,
and induce the formation of magnetite without introduction of oxygen from outside
buffered to a.different. fluid co:mposition.
the system.
.
.
11
.
,.
�Geochemistry of Early Proterozoic PaleosoU;
North ofLakeHuron,bntir±o
B. J, Fryer, Department of Geology
University of Western Ontario
London, Ontario, Canada
The contact between the reHuroniàrI and Hurbniañ tôcks, north pt
Lake Huron, Ontario, is often marked byresidual weathering products
or paleosols. These -are characterized by extensive leaching of Na, Ca,
Mg, Fe, Mn and Si inthOir upper parts and conctmtration of K, Al and Ti.
Even-when developed on mafic volcanics, these paleosOls approach a
sériciteatitanium dioxide mineralogy. With increasing depth in the
páleosois a very iroa—rich chlorite abruptly jOins the sericite and
titanium oxide assemblage. This transitionpossIbly represents the
permanent paleowater table.
The behavior of the rare earth eleMents in these plebsols indicates
that the ground waters responsible for these weathered deposits were of
significantly higher pH (greater than 8) than at present. A direct
consequence of this,is that the-high K contents of these paleosols are
almost certainly original features produced during weathering and not
a result of later metasomatism. This is substantiated by the behavior of
Rh and Ba.
The behavior of all elements, whether major or trace, appears to be
dominated by the reducing and high pH nature of the ground waters. These
results suggest that element solubilities and hence concentrations during
Early
Proterozoic
surficial prOcesses nay have been considerably different:
thn previously assumed
18
�?ETAM0PPHISM IN THE ENGLISH rv:u
Gower, C.F.
ançi
SUBPROVINCE NEAP KENORA-,. NOPtHWT ONTAPTO
Cliffqrd1 P4M., Dept.
of Geplo, MoMaster University, Hamilton,
Ontario
Detailed petrograpitic investigations on 300 thift sections of gneissic
and associated rocks from 200 6q.km. of the EnglIsh River Subprovince near
Kenora have enabled two metemorphic episodes to be. defined.
N1 metamorphism attained uppermost amphibolite facies and, using mineral
assefnbiages together with whole rock chemistry in calcic pods, amphibolites and
metasedimgnts, it is estimated that the P-P conditions were 5.25 ±0.75 kb and
650 ± 40 C.
Prograde reactions during this metamorphism generated garnet from
hornblende and biotite in amphibolite and tonalitic gneisses respectively.
The
distribution of garnets can be closely correlated with U) alkali feldspar mega-cryst distribution, (ii) lowest Fe20 /FeO bulk composition ratios in amphibolite
and tonalitic gneisses, (iii) deepes structural level. The garnets are .undeform—
ed and show no correlation with F? fold trends suggesting that the earliet recognizable metamorphism is late or pOst-f2.
The N9 metamorphism is retrograde and, using mineral assemblages in amphi—
bolites and metasediments, appears to have taken place under greenschist facies
conditions.
P—T conditions cannot be closely0defined from petrographic evidence
but are estimated as 2.25 ± 1 kb and 400 ± 50 C.
Potassium has behaved as a mobil,! component during both phases of metamorphism and is extensively involved in (i) asa reactant with hornblende to give
biotite and epidote/clinozoisite, (ii) as a product, together with magnetite,
from the oxidation of biotite, (iii) as a roduct from the reaction of biotite to
give garnet.
The presence of megacrysts in both gneisses and granitoid rocks is
suggested as an expression of this mobility.
19
�ENVIRONMENTAL GEOLOGY OF THE NORTH SHORE
A COASTAL ZONE MANAGEMENT PROJECT
by
John C. Gren, Gedlogy Department, TJniversity-df Minnesota, Duluth
ABSTRACT
During the jast two years the Minnesota Geblogicàl -Survey, on contrac
-from the State Planning Agency, has undertaken a study of the environmental
geology of the state's Lake Superior shore as an element of the Federal
Coastal Zone Management Program.
Two field seasons were devoted to mapping,
with sample analysis, literature research, map development,, and report
writing during the academic year.
Besides the author, two graduate students
(C. Moss and M. Jirsa) and five undergraduates (C. Baker, M. Gasser, K. Husby,
and K. Peterson) were involved.
The products, are a set of 13 maps,' covering
the entire shore at a scale of 1:24,000, of each of 5 types (Bedrock geology,
Surf icial geology, Depth t' bedrock, Landforms, and Economic Geology), plus
a report which includes interpretations. Geologic processes currently active!
geologic hazards, opportunities and resources offered, and land—use constraints
are treated for the major surf icial material types and landform units.
In this aréa the major geology—basèd lthid—use constraints are imposed by
(a) geologic processes such as wave processes-and stream erosion and flooding,
(b) soil suitability related to clayey glacial lake deposits and to shallow
and exposed bedrock, and (c) economic resource protection, particularly gravel.
in abandoned deltas of higher lake levels.
20
�CRUSTAL MODEL STUDIES OFA REGIONAL GRAVITY ANOMALY
IN NORTHERN MICHIGAN AND WISCONSIN, EXTENT OF ANOMALY,
AND ITS RELATIONSHIP TO NEAR SURFACE GEOLOGY
J. S. Kl'asner and D'. Bbmke, Department of Geology,
Western Illinois University, Macomb, Illinois
61455
The Bouguer gravity anomaly map oP northern Michigan •and Wisconsin has a broad,
long wavelength gravity maximum that extends in an east—west direction for about 800
km from near the eastern end of the northern peninsula of Michigan into north-central
Wisconsin. This anomaly may be part of a generally continuous gravity maximum that
extends along the Southern Province of the Canadian Shield, except where it is
overprinted by the gravity expression of the midcontinent gravity high.. It is
truncated in South Dakota by a gravity maximum of similar width and amplitude that
extends 'around the western and northern edge of the' Superior province. It is
truncated on the eastern end by the gravity expression o'f the Grenville..orogenic
belt.
Two dimensional gravity models were constructed over the' regional anomaly in
The models consider mass variations within the upper 20 km
Michigan and Wisconsin.
of the crust and consist of primarily two layers with a density of 2.80 gm/cc for the
upper layer and 2.94 gm/cc for the lower layer. Th'ey show that the upper layer is
thinnest beneath the middle Precambrian (X) basins and troughs such as the Marquette
Trough and it reaches a thickness of about 16 km in central Wisconsin.
In Michigan and Wisconsin several important geologic and economic features are
associated with the regional gravity anomaly. For example, middle Precambrian (X)
basins and troughs, which cause relatively short (a few kilometers or less) wavelength
gravity anomalies, are located over the regional anomaly. Middle Precambrian (X)
volcanic accumulations are generally located along the edge of the regional anomaly
or within the middle Precambrian (X) basins. The recently discovered boundary between
gneiss and greenstone terrane (Sims, 1976) is located roughly near the northern edge
of the regional gravity anomaly. Regional metamorphic zones are generally located
near the edge of the gravity anomaly, or, where superimposed upon the anomaly, cause
gravity minima within the regional anomaly. The recently discovered massive sulfide
deposits in Wisconsin seem to occur ajong the edge of the regional gravity anomaly
or along prominent gravity features that cut the regional anomaly.
The above data suggest a genetic relationship between the thinning of the uppermost (2.81) gm/cc) crustal layer and the formation of the middle Precambrian (Xe) basins
and troughs, the accumulation of volcanic deposits, the formation of regional
metamorphic zones, and possibly the accumulation of the sulfide deposits in northern
Wisconsin. Perhaps the v,olcanic deposits, the sulfide deposits, and the igneous
intrusions that supplied the heat for the formation of the metamorphic zones are all
differentiates of the lower (2.94 gm/cc) crustal layer. They were intruded and
extruded through fracture zones that formed in the 'uppermost layer during the Penokean
orogeny. Sims (1976) has suggested that the middle Precambrian (X) basins were
developed over, and approximately parallel to, the boundary between gneiss and
greenstone terranes. The regional gravity maxima lie within the eugeosynclinal zone
that Sims has postulated for this area'.
Sims, P. K. 1976, Precambrian Tectonics and MineràT Deposits, Lake Superior Region,
Presidential Address:
Econ. Geol. V.
.71
, M6, p. 1092-1110.
21
�BOUGIJER GRAVITY ANOMALY MAP OF,
NORTHERN PENINSULA OF MICHIGAN,
LAKE SUPERIOR, AND ENVIRONS
J.
S. Klasner, U.S. Geological $urvey and Western Illinois University, "acomb,
61455, William J. Hinze, Purdue University, Lafayette, Indiana 47907,
.L. 0. Bacon, Michigan Technological University, Houghton, Michigan 49931, arid
N. W. OtHara, Florida Institute 'of Technology, Melbourne, Florida 32901
Illinois
ABSTRACT
A prepublicatin version of the Boug1uer gravity anomaly map of the northern
peninsula of Michigin, Lake Superior, and adjacent parts of Michigan, Lake Huron
and Lake Michigan, Ls presented for discussion purposes.
The map, which is at,
1:500,000 scale and has a 5-mga. contour interval, is a compilation of data
collected since 1951 f±om several sources.
Personnel from the U.S. Geological
Survey tied each of the individual surveys to the 1971 base reference datum
and made additional observations in areas that lacked gravity coverage. Data
were reduced and compiled on digital tape by the Defense Mapping Agency, Aerospaae Center, St. Louis, Missouri, using the 1967 international gravity formula,
sea-level datum and a 2.67-gm/cc reduction density.
Terrain corrections were
applied to selected sections in the Porcupine Mountain area only.
Because of
high station density in the western part of northern Michigan, the Bouguer
gravity data were contoured using values selected frpm 1-minute quadrilaterals.
On most of the map, station spacing is broader than the 1-minute interval, so
that all stations are represented.
Although the geologic implications' of many of the individual anomalies on
the map h:tve been discussed in the literature, this map provides a comprehensive
integrated view of the gravity field, which can be used in geologic and strutural anaLysis.
The geologic Fources of a few of the gravity anomalies are
discussed in this context. Over the Keweenawan-Lake Superior basin, a pronowiced g .'avity low is found along the center of the lake, and gravity maxima
parallel ;he shoreline and join together at both ends of the lake to connect
the midcontinent gravity high with the mid-Michigan gravity
maxima.
In general
the gravity maxima reflect near-surface accumulations of relatively dense mafic
volcanic and plutonic rock and the gravity mnima reflect thick less dense
clastic rock.
In northern Michigan, middle Frecambrian (x) basins and troughs
such as the Marquette trough have east-trending positive anomalies. Lower
Precambrian (W) granitic terranes commonly have gravity minima.
A broad
gravity maximum extends east across the northern peninsula.
It has no
apparent surficial origin and is believed to be caused by deep crustal or
upper mantle mass variations..
22
�Major Structural Features in Central Wisconsin
and Their Implications on the Animikie Basin
by Gene L. LaBerge
university of Wisconsin—Oshkosh, Oshkósh, WI, 54901
EXPLANATION
Abstract
PRECAMBRIAN
Paleotoic
Niddle Precambrian batholith comprising numerous
in composition from quartz diorite to granite intrusive
sedimentary pile in Central Wisconsin has been outlined
LaBerge and Myers.
This batholith lies on the southern
west trending sedimentary-volcanic (Animikie) basin.
-
IN)
C.s.)
A
epizonal plutons ranging
into a complex volcanicby recent mapping by
margin of the large east—
WISCONSIN
LATE PREcAMBRIAN
I
Broad steeply dipping cataclastic zones separate the composite batholith
and its greenschist facies roof pendants from upper amphibolite gneisses,
migmatites and amphibolites that flank the batholith on the north and south.
The scale of cataclasis, presence of ultramafic bodies along the zones, and the
marked difference in metamorphic grade across the shear zones indicates deformation
on a crustal scale. The gneissic areas appear to be horsts, and the batholith
a graben-like structure.
Field relations along comparable shear zones within
the batholith indicate a long and complex history of cataclasis during emplacement
of the batholith, and, by inference, during the history of the Animikie Basin.
of
[
::::::::::::
Bayf
ld Group
Oronto Group
I! :::: :::::
Wetf
RiVer aatholith
Qqartslte
MIDDLE P}EECLMBRIAN
The present distribution of Precambrian rocks in Wisconsin is one of east—
west trending belts of Middle Precambrian sedimentary-volcanic-plutonic rocks
alternating with Early Precambrian(?) gneissic rocks. This has disrupted the
basin into a series of horst-like and graben-like blocks. Field relations in
Central Wisconsin indicate that at least part of this deformation occurred
during the. tectonic history of the basin, and is consistent with Cannon's (1973)
interpretation in the Marquette District. This suggests that the Animikie
Basin was characterized by vertically moving blocks, which may have provided
local sediment sources within the basin and also produced local strongly
reducing troughs, one of which may have resulted in the highly graphitic
"Flambeau Anomaly."
Granitic Ro49
Iron-Formation
Dominantly Matasedimeckary Rocks
1Ta
tlyMt
1
Rok
EARLY PREcAMBRIAN
Granitic
Reeks
Metavolcanic
Rocks
GneisSic Rocks
(Modified from Sims, 1976)
Gee Eases
Creenschtst
Gneisses
kigeaEttas
)taa,rphism
Pligeatitea
MiphtkCliteI
Episenal Plutats
Asphibolita
-
Greenschist
Matarerphisa
Gneisses
Pligmatitis
Asphibolltss
�18
0/ 15 0
Results for Archean Plutonic Rocks,
Lake Despair Area, Northwestern Ontario
F. J. Longstaffe
and
R. H. McNutt, H. P. Schwarcz
Department of Geology, McMaster University, Hamilton, Ontario
An oxygen isotope study of the Jackfish Lake nlutonic complex and the
Burditt Lake stock, (Ivabigoon granite-greenstone belt), has indicated the
importance of nagmatic-autometasomatic fluid activity and/or hydrothermalmeteoric water interaction in their crystallization and alteration.
o18o values of the main phase of the Burditt Lake granodiorite are
relatively constant across the stock (8.00 ± 0.33 0/00); microcline megacryst
hearing phases, as well as late stage anlitic rocks have higher 6180 values
(8.95 ± 0.35 0/00); Depletion in lo occurs in t e volcaniclastic county
rocks as the granodiorite contact is approached (11.35 to 8.00 0/00).
The
movement of mac'matic water unward from hotter, deeper portions of the stock
through the roof zone into the country rocks can cause such isotopic variations.
The high water/rock ratios required at the contact by such a model
appear reasonable, as considerable chemical modifications of the country
rock has occurred in the vicinity of the contact.
The Jackfish Lake Complex. as exnosed in the Lake Despair area, is
composed nrelominantly of diorite and monzodiorite, with lesser volumes of
quartz diorite, miaocline megacryst hearing granodierite and soda syenite.
The samnles Thich preserve the highest and the most concordant oxygen
isotopic terneratures are located within 50 meters of the contact with the
mafic amphibnlite country rock (which itself has been enriched in 18o from
5.7 to 8.0 otoo).
Apnarently, the oxygen isotopes have been quenched more
rapidly and nore comnletely in the outer margins of the body. Elsewhere
in the Complex, discordant oxygen isotope mineral-pair temperatures indicate
varying degrees of isotopi disequilibrium. Th"se disturbances can he
largely attributed
to late stage deuterir alteration and continuing subIn snite of such pe'turhations, some primary
solidus isotonic exchange.
isotopic trends are still discernible; 6180 values of cluartz, plagioclase,
hornhlende and hiotite decrease gradually with increa;ing degree of differentiation of the rock type. This hehavinur nrohahly reflects the relative
imnoverishment of the remaining melt in ISO as Iarc'e amounts of 180-rich
mineral rhases begin to crystallize during the formation of the late stac'e
srnll volume granodiorite. The preservntion of citch trends. as ''ll as the
nrrnnl a18o enrichnont pattnn from diorite tO granodiorite observed in
rock samples swgests cln.scl system isotonic exchange in these rocks.
The
southern boundary of the Jackfish Lake Complex is formed by a major
fault. Cranodiorite located near the shear zone is altered, showing Fe
staining arid large scale saussuritization of felclspars. Chemically, such
samples are enriched in lirht rare earths, Zr, Ni, Fe. Ti, P, K and Rh, and
denleted in Na, Sr and Ha. These rocks are also denleted in 18o (5.41 O/oo
The depleted
750 meters from the fault;
7.80 °/oo 2400 meters distant).
rocks contain minRral phases which are grossly out of isotopic equilibrium
and depleted in 1o0 relative to "unaltered" granodiorites from the Complex.
Such behaviour is best explained by hydrot'iermal-meteoric water interaction
ir anisotopically
open system.
24
�FOSSIL COLLECTIBLES FROM THE GUNFLIN'P FO1MATION
S. Lougheed and J. J. Mancuso, Department
of Geology, Bowling Green State University,
Bowling Green, Ohio 43403
P4.
ABSTRACT
Iron—formation to be. of economic value is dependent upon a
succession of processes that transform the initial biogenic particulate material, produced on a gently sloping marine shelf zone
There are five great fossil collectibles
into iron-rich, minerals.
of initial material bccurring in the Gunf lint; they are, siliceous
and carbonate shells, blue—green algae, greenaloid and bacterial
framboidal pyrite. Two outstanding areas for collecting fossil
materials occur at Kakabeka Falls and in the vicinity of Schreiber.
Excellent specimens of ooids are found at the falls, but more remarkably, many chalcedonic chert laminae contain totally or almost
completely dissolved ooids so that only the nuclei remain. The
nuclei are varied in their structural pattern but commonly appear
as ellipsoids, spheres, or as spheres with concentric laminae.
The structures are small, generally less than thirty microns in
diameter. The ellipsoid structures and probably some of the spherical structures are siliceous shells of microorganisms. Some, if
not most, of the spherical nuclei are silicified shells of calcar—
Both siliceous and calcareous shells are
eous microorgansisms.
fairly common in organically pigmented chalcedonic chert.
Although bacterial carbonate, is common in specimens from Kakabeka
Falls particularly those specimens rich in pyrite, the best specimens are found in the Schreiber area, where the micron sized
carbonate crystals occur in the cortex of oncolites. The; carbonate
bacteria produce ammonia as a by-product from their metabolism of
expired algal laminae in the cortex, and carbonate is therefore
precipitated in the microdomain of high alkalinity., The columnar
stromatolites in the Sbhreiber area are noted for the fidelity of
preservation of the filimentous and coccoid algae in a siliceous
matrix and therefore are not associated with bacterial carbonate.
We find the best specimens of bacterial carbonate produced in
columnar stromatolites occurring in the Biwabic iron—formation,
however good specimens 'may be found in the road cut at the junction
of highways 590 and 17-11 near Kakabeka Falls. Greenaloid, the
gel-like material composed of silica, and sapropel complexed with
ferrous iron, is best collebted as matrix material in laminae of
ooids or as matrix material occurring with tuffball laminae at
Many specimens show transitional steps in the'
Kakabeka Falls,.
oxidation of greenaloid to greenalite and/or magnetite and less
commonly to hematite.
2.5
�PENOKEAN STRUCTURES AND PLUTONIC ROCKS IN WISCONSIN
K. S. Maass'and L. G. Nedaris, Jr.,' DepartmerIt'of Geology and Geophysics,
University of Wisconsin, Madison 53706
W. R. Van Schmus, Department of Geology, University of Kansas, Lawrence,
Kansas 66044
ABSTRACT
Last •year we reported on the occurrence of Penokean structures and
plutonic rocks in early Precambrian gneiss in Portage and Wood Counties,
Wisconsin. We now have completed more detail3d structural and isotopic
studies on these occurrences and have extende tour investigations westward about 100 miles to include localities in Clark, Jackson, and Chip—
pewa Counties.
The Early Precambrian gneiss, formed about 2.8 by. ago (Van Schmüs
and Anderson, 1977) and domposed of quartzofeldspathic gneiss, amphibo—
lite, and migtnatite, contains three sets of folds:
first, penetrative
isoclinal folds; second, non—penetrative S-- and Z—folds; and third, non—
penetrative broad, open folds.
The axial surfaces of the second and
third fold sets are discordant -to those of the first set, but the fold
axes of all three are colinear,
Well developed lineations, defined by
the dimensional orientation of elongate minerals and trains of mineral
In all the localities examined so
grains, are parallel to fold axes.
far, fold axes and lineations plunge steeply, from 45° to 900.
•
The gneiss has been intruded by two different tonalites: an earlier
medium—grained tonalite, which contains a strong foliation and lineation,
and a later fine—grained tonalite, which contains a weak foliation and
strong lineation. Lineations in both tonalites are colinear with those
in the gneiss. The tonalites as well as the gneiss have been recrystal—
1ied under middle—grade metamorphic conditions.
Petrofabric analyses have been completed for samples along the Wisconsin River, including three samples of quartzofeldspathic gneiss, one
Measure—,
-of medium—grained tonalite,- and two of fine—grained tonalite.
ments of [0001] in quartz have given a similar pattern for all five
samples:
a girdle normal to the h fabric axis.- Thus, the tonalites contain structural elements in common with some of those in the gneiss, on
both mesoscopic and microscopic scales.
-
U—Pb analyses of zircofl'have yielded ages of 2800'm.y. 'for the
gneiss, 1850 ± 25m.y.- for the medium—grained tonalite, and 1800 ± 25 m.y.
for the fine—grained tonalite. We believe that the zircon ages for the
tonalites represent their times of emplacement and, consequently, that
the structures within them and some of the structures within the gneiss
were produced during the Penokean orogeny.
-Further investigations of this type shouli give a 'more complete un— -
derstancling of the Penokean orogeny in Wisconsin and provide a basis for
comparison between gneisses of Early Precambrian age in Wisconsin and
'those of the Minnesota River Valley terrane.
26
�THE OCCURENCE AND SOME NOBLE METAL CONCENTRATIONS IN SELECTED
KOMATIITIC ULTRAMAFIC VOLCANIC ROCKS FROM MUNRO TOWNSHIP,
ONTARIO.
'
MacRae, William E., and Crocket, James I-I., Department of
Geology, McMaster University, Hamilton, Ontarjo.
Munro township, situated in 'the Abitibi volcariic belt,
Is the location of a sequence of well documented komatiitic
ultramafic voldanics. The rocks are well exposed and the area
has been subjected to only very low' grade metamorphism. The
Jcomatiitic volcanic rocksrange from peçidotitic through pyroxenitic to basaltic in composition'.
Samples taken from peridotitic flows at the base of Centre,
Hill have been'analysed for gold, platinum, palladium, and
iridium by neutron activation analysis. Four lithologic units
were sampled from two flows. The results pf the analysis are
summarized below:
Lithologic Unit
Au 'Pt"
Pd
Ir
1.6
2.5
8.9
1.1
Spinifex zoné(3)
2.1'
14.3*
10.7'
0.8
Foliated zone(1)
3.3
'—
'7.5
0.4
Cumulate zone(4)
3.6
ll,.l.
6.3
1.5.
'
(Flow)
Chilled marins(3)
'
,
(ppb)
*(3) Number of samples for zone.
There appears to be a slight enrichment of'gold in the'
cumulate zone as well as'iridium relative to the spinifex zone.
This is probably due to the settling of immiscible sulphides as
well as olivine before the formation of the spinifex. Platinum
and palladium increase in the spinifex zone and were possibly
enriched in the molten silicate phase. The average of the cumulate and the spinifex zone for palladium and iridium are the"
same as the chilled zone, while the 'values: fr gold and platinum
are lower. The latter values are possibly due to seawater leaching.
The average concentration of gold (2.7 ppb) is not significantly higher in peridotitic komatiites 'than' in other major
rock types and do not appear to contain enough gold to make
them a source 'rock for 'gold deposits.
27
�Stratigraph of the Dar1aga'
Bain
Metasédiments; Michigan
J• J. Mncu'èo, R.- E. éavoy, M. S. Louc4heed
Bowling Green State University
Bowling Green, Dhio 43403
ABSTRACT
The BaragaBasin is located- in eastern Baraga and northern
Marquette Counties, Michigan. It is 30 miles long by 8 miles
wide and is filled with approximately 1400 feet of mildly deformed Middle Precambrian metasediments.
Lower Precambrian basement. rocks ecposed around the perimeter of the basin are crystalline
granites and gneisses which unbonformably underly the metasediments.
The lowermost Middle Precambrian unit in the basin is a
white vitreous quartzite which appears to be limited to the western and central portibn of the basin. A basal quartz-pebble
conglomerate is exposed at Pikes Peak in sec. 11, T. 51 .N., R.
32 W.
Overlying the quartzite is a chert-carbonate iron-formation and a volcaniclastic sequence. Recent phosphate discoveries
occur within this unit (Mancuso, Lougheed, Shaw, 1975; Cannon and
Klasner, 1976). More than 1100 feet of graphitic slates and a
thick meta-arkose make up the rest of the section. Flat lying
Cambrian(?) Jacobsville Sandstone unconformably overlies the Precambrian rock section.
.
-The white basal quartzite -is correlated with the Goodrich
Formation while the iron-formation, volcaniclastic. sequence, the.
black slates and the meta—arkose are correlative with the Greenwood Iron-formation Member, the çlArksburg Volcanics Member, and
the Lower Slate member of theMichigarnme1ormationin.the.western
part
of the
.
Marquette Basn,.
.
.
References, Cited.
Mancuso, J. •J., Lougheed, M. S., and Shaw,R., l975,Carbonate
apatite in Precambrian cherty iron-formation, Baraga County,
Michigan:
Econ. Geology, v. 70, no. 3, p. 583-586.
Cannon, W. F., and Klasner, 3. 5., 1976, •Phosphorite and other
apatite bearing sedimentary •rocks in the Precambrian of
Northern Michigan:
U.S. Geol.. Survey Circular 746, 6 p.
28
�AN ESTIMATE OF THE RARE EARTH ELEMENT DISTRIBUTION
IN POST-KENORAN UPPER CRUST, NORTH OF LAKE HURON
McLenrian,. Scott M., Fryer,B.J.., and Young,. Grant 1W.,
Department' of ceology, University of Western
Ontario., London, .Qntario., N6A 5.B7.
Rare earth analyses havë been made on'.sampls
of tillite matrix from the Gowganda' Formation, north
of Lake Huron.
Agrandmean based on averages.from
the. Cobalt, Quirke Lake and Esp-anola'-
SudburSr Areas
is
considered to berepresentative of upper cnistal
abundances for a large area. northof Lake Huron.
The
three districts were given equal weight in the estimate.
The ovtrall abundances are('ih ppm):
La,
24,;' 'Ce, 55
Nd, 23; Sm, 43; Eu, 1.2; Gd, 3.8; Dy,. 31 Er, 2.0.
These data are compatible with analyses of granitic
and volcanic rocks typical of the surrounding areas.
Values are also in line with estimate's 'pf Canadian
Precambrian crust and post-Arch'ean crustal abundance.s
in Australia, though relative distributions have
significant 'dirferenoes.
Analyses of Gowganda argillites and sandy argillites
intimately associated with the tillites have- similar
patterns tji those of the tillites.
Absolute magnitudes,
however, are consistentlyhigher(by. a factor of about
1.3) than the tillites. A possible explanation for
this could be concentration of clay minerals in the
argillites.
This may suggest that other estimates of
crustal abundances which are based, in part, 'on analyses
of fine grained sedimentary rocks are systematically
high by a similar proportion.
29
�Archean Volcanism Washeibamaga Lake Area, Wabigoon -ubprovinc?, Northwest Ontario.
G.E. McMaster
and
Departmento
R.!J. McNutt
Geology, McMaster 'University.
The Washeibamaga-Thind'rcloüdtâkes area' )f the Wabigoon
Subprovince, can be subdivided into three faàies;
I)
The Lower volcanic sequence of metabaèalts (lower greenschist
facies) is preserved. as a:-stenly-dipping, north-facing- homoclinal
volcanic -pile six kilometres thick
Nb, rr, Ni,-Ba .Pb, Sri',
They show trace, element (Y,
geochemical. similrities tomoderxi
ocear. --floor. tholeiitic basalts.
2)
The Thundercloud Lake Quartz-Porphyry intrudes the lower
sequence-and is helieved-to..represent a vent-plug filling a
late-stage felsic volcano.
Accompanying explosive vojcanism
produced 'a threekilometre. thick sequence of coarse pyroclastic
rocks an&-tuffs..
Associated dacitic and autobrecciated.
rhyolltic flows have calc .alkaline affinties and are chemically
'distinct from both volcanic sequences and appear not to be a
differentiated product but to have originated as a seperate
magma.
3)
The Upper volcanic sequence of metabasalts is composed of
tightly folded, massive to pii.lowed flows.
The contact with
t le unde: 'lying epiclastic and pyroclastic rocks is at ah angle
c' thirt-- degrees-, implying either profound angular unconformity
or a fau'±t dont ct.
-The upper sequence is chemically distinct
from the lower sequence.
K,-Rb-, Sr, Ba, abundances suggest
similariie with rirodern Island Arc'tho3eiites
30
�ORGANIC-RICH 'lAKE SEDIMI4T EXPLORATION GEOCHEMICAL SURVEY
OF EASTERN LAKE VERMILION—ELY AREA, NORTIIEASTERN MINNESOTA
D. G. Meineke, M. K. Vadis and A. W. Klaysmat
Minerals Exploration Section, Division of Minerals,
Minnespta Department of Natural Resources,
Hibbing, Minnesota 55746
ABSTRACT
An organic rich (gyttja) lake sediment geochemical survey was conducted over Lower Precambrian volcanic and associated rocks in northeastern
Minnesota for the purpose of determining the applicability of this method
for evaluation of mineral resource potential and, reconnaissance exploration.
Two hundred and seventy samples were collected from 75 lakes over an area
of 200 square miles (520 sq. km.).
A weak aqua regia leach on unignited gyttja produced the best contrast over background.
Statistical analysis of the data indicates that
trace element distributions are greatly dependent upon the limnological
environment of each lake; trace elements tend to be concentrated in the
organic and/or inorganic fractions of the gyttja; and, of all parameters
considered, LOl (loss on ignitipn) is the best single 'indicator of limno—
logical environment.
Due to the variations in lake environments and trace eLement
accumulation inthe gyttja, parameters other than the element concentrations
were considered.
However, the study indicated, even though a perfect datum
for comparing lakes was not possible, •the element concentrations for arsenic,
cobalt, copper, nickel,'lead and zinc provided the best datum for comparing
all 75 lakes.
Several significant anomalieth were located by the survey. Anomalous
copper was found in a lake near an interesting copper prospect.
Copper,
lead, titanium and zinc appear to reflect bedrock composition; chromium,
magnesium and nickel reflect bth bedrock domposition ,and glacial dispersion.
31
�MAFIC MINERALOGY OF FERROAUGITE SYENITE PROM THE COLDWELJ1 ALKALINE COMPLEX
ROGER H. MITCHELL and R. GARTH PLATT
DEPT. OF GEOLOGY
LAKEHEAD UNIVERSItY ,. THUNDR BAY ,ONTARIO
Plutonic Center 1 of the Coldwell alkaline complex
is dominantely ferroaugite syenite associated with minor
A c. 2000 m.
amounts of earlier hypersthene gabbro.
section of ferroaugite syenite exposed on the lake shore
between Marathon and the eastern margins of the complex
exhibits well defined igneous layering in the eastern
portion of the sequence. The layered syenites grade
into syenites with poorly defined diffuse turbulent
layering and thSe in turn into coarse syenites conCryptic layering
taining patch and sheet pegmatites.
is well developed in the sequence and indicates this
portion of Center 1 ferroaugite syenite is a small
intrusion in which crystallization occurred simultaneously
Olivines range in composition from
at the roof and base.
Fa3 to Fa03. Pyroxenes initially belong to the diopside—
hedenbergiCe series (Di42HdagAc3.to Di10Hd85Ac5 and grade
into members of thp acmie-hedenbergite series (Di10H95
Ac5-Di5Hd45Ac0) Pyroxene c npostional trends are
similar to tháse observed in peralkaline igneous rocks
and in particular to those of the undersaturated
Fivegroups of amphiboles are
Ilimaussaq intrusion.
present; 1 — ferroedenite-hastingsite; 2 — sub-aluminousr
ferroedenite; 3 - aluminous ferrorichterite - ferrorichterite;
Amphibole compositional
4 — arfvedsonite; 5 - ferroactinolite.
trends parallel those of the pyroxene in showing dcreasing
Al and Ca with increasing Na and extreme iron enrichment.
Oxides minerals in the earliest stages of crystallization
were Fe—Ti oxides and baddeleyite, these were replaced as.
liquidus phase by aenigmatite and zircon respectively as
Residual liquids, as represented by
the magam evolved.
the pegmatites crystallized ferrorichterite, feldspar,
zircon and quartz. The ferroaugite syenite magma evolved
along an oversaturated peralkaline trend characterized
by extreme iron enrichment under conditions pf low oxygen
fugacity at high silica activity.
32.
�STRATIGRAPHIC AND TECTONIC HISTORY OF LOWER AND MIDDLE
PRECAMBRIAN ROCKS IN EAST-CENTRAL MINNESOTA
G.B. Morey, Minnesota Geological Survey, University of Minnesota, St. Paul, Minnesota
It has been recognized for nearly 70 years +that a great diversity of Precambrian
rock types crop out in east-central Minnesota. However the rocks are poorly exposed
and an understanding of their geologic history has been hampered by a lack of
definitive geologic data from which age and spatial relationships can be deduced.
Nonetheless, recent geologic studies utilizing conventional mapping techniques in
conjunction with subsurface, magnetic, and recently acquired gravity data have more
precisely defined the spatial relationships of various rock units and have led to a more
complete understanding of their stratigraphic and tectonic histories.
The Lower and Middle Precambrian rocks in east-central Minnesota are divisible
into three distinct terranes: (I) a diverse Lower Precambrian terrane; (2) overlain on
the north by a thick sequence of folded and metamorphosed Middle Precambrian
stratified rocks; and (3) intruded on the south by a variety of Middle Precambrian
plutonic rocks. All of these rocks are overlain by generally flat-lying sedimentary
rocks of Late Precambrian, Cambrian and Cretaceous age.
Two presumably high_angle, east-trending faults of Early Precambrian age divide
the Lower Precambrian terrane into three lithotectonic segments. The southernmost
segment consists dominantly of quartzófeldspathic gneisses metamorphosed to the
'upper. amphibolite or granulite grade. Granite and lesser a,mounts of rnetasedimentary
and metavolcanic rocks assignable to the greenstone-granite belts of northern
Minnesota comprie the northern mast segment. Substantive data bearing on the lithic
attributes in the middle segment are lacking, The segment may consist of either
cataclasized gneissic rocks or metagraywacke and slate similar to that in northernmost
segment. However, regardlessof their original age and character, the rocks in the
middle segmen't forrrt a discrete zbne separating two considerably different Lower
Precambrian lithotectonic units.
The Middle Precambrian strt-ified 'rocks occur within an intracratonic baih
centered over and approximately parallel to the boundary zone between the Lower
Precambrian gneissic 'and greenstone-granite segments.
The stratified rocks are
divisible into two 'groups separated by an unconformity. The older group consists
dominantly of quartzose rocks of clastic and perhaps volcanogenic origin. Mappable
ynits of metabasalt, mafic 'tuft, oxide- to carbon,ate-facies iron-formation and
carbonaceoui mudstone are abundant near the base, whereas carbonate rocks occur as
mappable beds near 'the top of the group. The younger group is similar to, an,d
correlative with, the well-known Animikie Group of northern'Minnesota and Ontario.
Sedimentation was either terminated or cldsely followed by a period of regional
deformation and metamorphism assignable to the Penokean orogeny. The dominant
Penokean structure is an eastward-plunging synchnorium bounded on the north, west,
and.south by"Lower Precambrian rocks. However the extent to which the rocks were'
deformed varies from place to place ,within the synclinorium and the style of
deformation is attributable to the tectonic behavior of contrasting kinds of Lower
Precambrian rocks. Where they overlie granitic basement rocks, the stratified rocks
dip gently southward and the basal contact is relatively undisturbed.' ln contrast,
where they overlie gneissic or metasedimentarv basement rocks, the stratified rocks
are complexly infolded into a number of large anticlines and synclines having numerous
coaxial. second- and third-order folds on their limbs.
The metamorphic grade of the stratified rocks increases from north' to south. To
the north, argillaceous rocks contain minerals indicative of high-grade diagenesis or
zeolite-facies metamorphism, whereas to, the south they contain minerals indicative of
the lower atnphibolite facies. Metamorphic mineral isograds conform in a general way
to the fold geometry, but in detail they transect fold axes implying that deformation
'
nd metamorphism were discrete events.
-
Teètonic instability during the Penokean orogeny was manifested principally by
vertical uplift of the gneissic basement rocks and the development of a mantled gneiss
dome along the south edge of the Penokean synclinorium. The virtual coincidence of
bedding in the stratified rocks that surround the gneiss dome with cataclastic
foliations within the gneiss dome suggests that folding and uplift occurred contemporaneously. In addition, the spatial coincidence of high-grade metamorphic rocks
along, the flanks of the gneiss dome suggests that the gneissic terrane' was
characterized by relatively high heat flow during deformation.
The Middle Precambrian plutonic rocks are confined to that part of east-central
Minnesota underlain by gneissic rocks. Most' of the plutonic rocks are post-tectonic in.
age as evidenced by cross-cutting relationships with the mantled gneiss dome,' and by
their relatively homogeneous and undeformed nature. Igneous activity of calc-alkaline
affinity began with the emplacement of dike-like bodies of quartz diorite. This was
followed by the emplacement of small, to large plutons of granodiorite and quartz
monzonite, which in turn was follOwed by the emplacement of various sized plutons.of
granite. Quartz monzonitic rocks having rapakivi-like textures occur locally as border
phases to some of the granite plutons.
.
'
Erosion, following uplift along major northwest-trending faults, exposed the
5gneissic and' plutonic rocks prior' to the deppsition of Upper Precambrian sedimentary
-rocks.
'
-
-
�PETROGRAPHIC AND CHEMICAL ATTRIBUTES OF SOME LOWER
AND MIDDLE PRECAMBRIAN GRAY WACK E-SH ALE SEQUENCES
tN NORTHERN MINNESOTA
G.B. Morey and NI Schulz, Minnesbta Geological ,$UrVey, University of Minnesota, Si.
Paul, Minhesota.
Graywacke-shale sequences comprise a significant proportion of the Lower and
Middle Precambrian rock record in northern Minnesota. Although the petrographfc
character of these rocks has been evaluated in detail, little use has been made oftheir
bulk chemical compositions, particularly in classification and provenance studies. We
suggest however that the chemical data, when used with petrographic data, provide
useful new insights regarding the sedimeritological history of these rocks.
According to the classification scheme of Crook (1974), which considers only th
framework grains, the Lower Precambrian graywackes are quartz-poor to quartzintermediate in composition and are indicative of a tectonically active island-arc
environment. They contain 2 5-50 percent dacitic to rhyodacitic rock fragments, 10-36
percent sodic plagioclase, trace amounts to 12 percent volcanic quartz, and as much as
22 percent labile components such as hornblende. In contrast, the Middle Precambrian
graywackes are quartz-intermediate to quartz-rich in composition and are indicative
of deposition under tectonically stable conditions. They contain: 15-90 percent plutonic
quartz, 1-36 percent feldspar, and as, much as 7 percent rock fragments of mostly
granitic composition.
The bulk chemistry of the two sequences emphasizes the fact that they are
different chemical entities. The_Middle Precambrian graywackes contain more silica
(X= 75% vs. 62%) and less K20 (X=l.43% vs. 1.90%) and Na 0 (X=2.42% vs. 4.06) than
do the Lower Precambrian graywackes. The former also Jhibit a narrower range of
Na2O/K.,O values (1:2'to 2:1) than do the latter (1:1 to 13:1). These differences can be
related 'to the, mineralogy of the framework grains. Quartz is the dominant
mineralogic variable in the Middle Precambrian gçaywackes, and its abundance exerts
a major influence on the amount of Si02 in the analyzed samples. In contrast, dacitiç
to rhyodacitic rock fragments dominate the framework grains of ' the! Lower
Precambrian graywackes 'and exert a strong influence on the. Na20/K20 ratios.
Very little is known about the petrography of intercalated shale units iri either
sequence. However the bulk chemical data suggest that the tower Precambrian shales
are fine-grained equivalents of the graywackés, whereas the Middle Precambrian
shales are discrete chemical entities not related to graywackes simply ,by the relative
abundances of framework grains.
The bulk chemistry of the Lower Precambrian graywackes suggests that they
were derived from: a dacitic to rhyodacitic source with little attendent chemical
alteration.
Thus these rocks were not 'markedly affected by .post-depositiona
.
processes; the framework grains reflect the comp'osition of the source area. However
neither the Middle Precambrian graywackes nor their' intercalated shales can be
derived chemically. from a simple granitic source; chemical-mixing calculations
indicate a complex source of consisting of quartz monzqnitic, rhyodacitic, and basaltic1
rocks. The mixing calculations'also imply that the Middle 'Precambrian sediments were,
derived from a considerably weathered terrane and subjected to post-depositional
processes which considerably modified the original framework mineralogy.
3.4
�-GEOCHEMISTRY OF THE YELLOW DOG PLAINS PERIDOTITE,
MARQUETTE COUNTY, MICHIGAN
W. J. Norris and J. T. Wilband, Geology Department, Michigan State
University, East Lansing, NI 48824; P. W. Snider, Geological
Survey Division, Michigan Department of Natural Resources, Lansing,
MI. 48909
.
A relatively fresh, previously undescribed,.peridotite body outcrops
in an area locally known as the Yellow Dog Plains, adjacent to county road
MA in the Champion quadrangle, Marquette County, Michigan. A small exposure
south of the road and a roughly oval shaped "plug", 120 meters wide by 190
meters long, intrude the Precambrian X Michigaimne Slate which underlies most
of the Yellow Dog Plains.
The larger outcrop stands 15 meters above the plain
at its highest point.
Recent paleomagnetic data indiqate the, intrusive is of
lower Keweenawan (Precambrian Y) age (K. Books, U.S.G.S., personal 'communication, 1977).
The fact that the Yellow Dog Plains peridotite is located in an
extensive east—west trending magnetic belt suggests it maybe' genetically
related to the exposed east—west,trending Keweenawap diabase dikes to the
south -which-haye been saippied and analyzed for comparisons.
The peridotite contains up to. 50 percent olivine, as much as 30- percent
pyroxene (both clino— and orthopyroxene), approximately 10 percent plagioclase,
and less than 10 percent opaque minerals. A dark red pleochroic biotite
(Cl percent) is common in most specimens.
Preliminary microprbbe analysis of
unserpentinized olivine and plagioclase give Fo80 and An8.65, respectively.
The sulfide minerals pyrite, pyrrhotite, chalcopyrite, cubanite (?), pentlandite,
and bornite are present in small amounts mostly associated wit-h magnetite.
Major oxides, Cu, Ni, Cr, Zp,. Co, and several rare earth elements were
analyzed from 22 specimens. The average values for the oxides are as follows:
5i02 = 42.46%,' A1203
4.24%, Fé203 = 5.65%, FeO = 8.71%, MgO = 26.19%,
CaO = 4.40%, Na20 = 0.49%, K20 = 0.24%, 1120 = 6.72%, Ti02 = 0.71%, P.20s 0.10%,
MnO = 0.18%.
Samples from a 30'meter vertical drill core in the large exposure
show a continuous increase in Ni with depth.
MgO, FeO, and Cr have the
same trend as Ni., A break' in. the alkali values, which otherwise consistently
decrease with depth, suggests. the intrusion maybe layered. Layering has not
been confirmed by modal data.
-
35
�Post-Glacial Sediment Distribution in the Canadian
Portion. of .-Läkë SupérioJ
J. S. Mothersill, Lakehead Univerity
The Canadian portion of Lake Superior covers an area
•of approximately 29,882 km2 -of a -total lake area of 82,375 km2.
The drainage area of the Canadian portion of the lake,
excluding the lake and the Lake--Nipigon drainage basin, is
approximately72,,000 km2. The drainage basin which was covered
.by a virgin forest up:until a century ago, is'still mainly
covered by boreal forest. Based on radiocarbon dating of the
lake-sediments, glacial retreat from the-northern part- of Lake
Superior occurred about 11,600 yrs. B.P.
Since the time of
glacial retreat, approximately 12,545x106 m3 of sediment have
been deposited in the lake proper and adjacent -bay areas.
The post-glacial sediments tendto have been deposited in
topographic basins with the thickest sequences occurring in
Thunder Bay, Nipigon Bay and Black Bay where up to 12 m, 12 m
and 14 m respectively have been deposited in topographic
basins.
In the lake proper, the. maximum thickness of post—
glacial sediments is only in the -order of S m. The average
rate of sediment reaching the. lake since glacial retreat has
been about l.08x106m3/yr. The sediments consist ofquartzarenite to arkosic.sandswhich occüradjacent to the shore and
the islands-and a silty clay, sequence that occurs in the
topographic basins.
The bulk of the sediments (>99% percent)
are formed of silty- clay'-.which'is comprised of major amounts
of quartz, K—feldspar and plagioclase, subordinate amounts
of chlorite, ililte and kaolin añd minor amounts of amphibole
and an interbedding 'Of vermiculite artdsmectite. - The average
sediment yield fromthe drainaqebasin was about 15 m3/km2/yr.
or a total-of l74;000 m3/km Sinde- glacial retreat'.
3-
�MSSIVE SULFllTh 1)E1OSITh IN WISO0N4TN
M. G. Mudres', Jr., K. K. Ostrom, Wiscons in Geological and Na Lu,-a I Ill s)ot'y
Survey, l815 University Avenue, Madison, Wisrons in 5371)6, antI Gordon
Reinke, Wisconsin Department of Natural Resources, 4610 University Avenue,
Madison, Wisconsin 53702.
ABS TRACT
Since 1968 with tile discovery near Ladysmith in Husk County of n
massive sulfide ore body, over three dozen mining conpanies have at one
time or another explored for non—ferrous massive sulfide deposits in the
Precambrian of northern Wisconsin. The most significant find to date is
by the Exxon Company, U. 5. A., of a 60-million ton deposit of zinc and
copper south of Crandon in Forest County. Exploration activity has precipitated numerous studies by the state, including geological, geophysical
and hydrotogical surveys, review of legislation, and social and economic
,.impact analysis.
Exploration has been concentrated in a 100—km wide hand from Ladysmith
in the west, through the ghinelander-Crandon area to the Pembine area in
the east, a distance of 350 kilometers. Available outcrop data, gravity
compilations, and state—acquired aeromagnetic data, coupled with isotopic
studies by the U. S. -Geological Survey and the University of Kansas,
suggest that this terrane is a middle Precambrian volcanic belt surrounded
by early Precambrian gneisses,
Detailed geology is known only for the Ladysmith deposit.
This deposit, owned by the Kennecott Copper Qorporat ion, is essentially a verti—
cally—oriented, lens-shaped pod 15 m wide, 720 m long, and 240 m deep.
Country rock consists of intermediate to felsic volcanic rocks of anda—
lusite metamorphic grade.
Economic minerals found within a pyritized
quartz—serieite schist are a supergene enriched blanket of chalcocite and
bornite of pre—Late Cambrian age, overlying primary chalcopyrite. The
6-million ton body averages three and one-half to Tour percent copper.
Favorable terrane was identified by an INPUT survey in 1967, and follow—up
drilling in 1969—1970.
sulfidc ore hodics in North A:aerjca.
Wisconsin environmental laws are administered by the state Department of Natural Resources. Present regulations require an:environme,ntal
impact assessment of all proposed mining operations. Experience has
shown that for significant new mines this assessment will invariably result in preparation if an Environmental Impact Stateaent by the Department.
New mines are also required to obtain a mining permit which in—
Mine operators
cludes a reclamation plan approved by the Department.
are required to post a bond to cover the cost of reclamation, Uining
&mmpanies must also obtain other permits required by thc Department for
the protection of the environment.
-
Several pieces of legislation that were introduced in the spring 1977
legislative session would: (I) replice present mineral taxes with a
graduated severance tax on net proceeds; (2) require the registrótion Cf
exploration companies in Wisconsin with the additional requirement that
some kinds of company—acquired geologic data be turned over to the state
after exploration; (3) require the registration of severed mineral rights
and ultimate aquisition of orphan mineral rights; (4) set limits on the
duration of mineral exploration leases; (5) set a cooling—off peiod
during which n exploration lease could be broken; and (6) eliminate the
mine'al depletion atlowande.
-
It
is reasonable to expect that more deposits of massive sulfide ore
will be identified in future years in Wisconsin. Whether or not the deposits are developed depends on cots, mctal prices,- environmental constraints at each individual prospect, the tax climate, and the mineral
policy of the state.
-
Tn 1974, Noranda Exploration, Ihc. announced the discovery of a small
zinc—copper body on 'the Pelican River east of Rhinelander in Oneida County,
The deposit consists of three zones. The total deposit consists of 2.3
million tons at an average grade of one percent copper and four and one—
half percent zinc.
The deposit is 300 a long, 15 m wide and 203 m deep.
It was identified by combined geologic and INPiJI' surveys. The generally
small- size and uncertain mine development climate, preclude the immediate
develop'nent of the property.
Noranda is continuing exploration activities
in the area.
In May 1976, the Exxon-company-U. S. A., announced the discovery of
a zinc-copper body south of Crandon. The body appears to be slightly less
than 2 km long, at least 480 m deep, and about 69 a wide, Preiiminarv
drilling suggests 60—million tops of ore sveraging six and one—half percent
zinc and one percent copper, making this nnc of the five largest massive
-
�PROTEROZOIC PITCHBLENDE flIN POTENTIAL IN
MINNESOTA::
THEORY 4ND SPECULATION
Richard W. Ojakangas, Department of Geology,.University of Minnesota, Duluth
ABSTRACT
Several major Proterozbic unconformitie-s are present within the rock
column of Minnesota.
(1) The MPG Animikian formations (the Pokegama Quartzite
and older units) rest upon LPG granitic and volcanic rocks.
(2) The UPG Sioux
Quartzite overlies LPG rocks in southwestern Minnesota and adjacent South Dakota
and Iowa.
(3) The UPG Puckwunge Formation overlies the MPG Rove Formation in
northeastern Minnesota, and in adjacent Ontario the correlative Sibley Formation
overlies the Rove and older Anits.
(4) The UPG "Nopeming Quartzite" overlies
the MPG Thomson Formation near Duluth.
(5) The UPG Fond du Lac Formation rests
upon the MPG Thomson Formation in east—central Minnesota.
In addition, Upper
Cambrian rocks of southeastern Minnesota unconformably overlie LPG, MPG, and
UPG units and Cretaceous deposits overlie LPG, MPG and UPG rock units over
the westernhalf of the state.
Two localities which have abnormal total radioactivity may be related tc
nearby unconformities. One is in the LPG McGrath Gneiss, nearly adjacent to
moderately dipping unnamed MPG roék units. The second is in a probable shear
zone in the MPG Thomson Formation, a few miles from the UPG Fond du Lac
Formation.
-
At Beaverlodge, Northern Saskatchewan, the MPG Martin Formation overlies
crystalline basement rocks; pitchblende veins in the area may be related to
this unconformity (e.g., Langford, 1977).
Further south, the UPG Athabasca
Sandstone unconformably overlies a similar basement and uranium mineralization
appears to be related to the unconformity. Discoveries in northern Australia
are of a similar nature.
No promising uranium shows have as yet been discovered in Minnesota.
However, the stratigraphic—structural relationships, coupled with the supergene
pitchblende vein model, callsforcIetailed exploration along the cited uncon—
*
formities.
Refer en
a e
Langford, F. F., 1977, Surficial origin of North American pitchbiende and
related uranium deposits: American Assoc. Petroleum Geologists Bull.,
v. 61, p. 28—42.
38
�PALEOMAGNETIC AND PALLOINTENSITY STUDIES OF NORMAL AND REVERSED KEWEENAWAN ROCKS IMPLICATIONS FOR THE' POLAR WANDER PATH OF NORTH AMERICA
Lauri J.
PeAOnen
and Henry C. Halls
Department of Geology, Erindale College
University of Toronto, TOronto, Ontario
KB S TRA c
t
Paleomagnetic' studies on Keweenawan rocks (1200 - 1000 my) have revealed a
well—defined magnetic stratigraphy composed of units with both normal and 'reversed
polarity.
There are at least two polarity changes in the Keweenawan sequence of
which the younger One (from reversed to normal polarity) has been detected
throughout the Lake Superior region. A characteristic feature of this reversal
is its asymmetry: the reversed magnetization always has a much steeper (upward),
inclination than the normal (downward) one; resulting'in a difference of 300 in
their paleopoles. Of particular concern in the interpretation of Keweenawan
paleomagnetism is whether this asymmetry in reversal is caused by ,a secondary
remagnetization component or whether it is the signature of apparent polar wander
during Keweenawan igneous activity.
,
'
,
-
Detailed
thermal and alternating field demagnetizaticin "studies On both igneous and baked Keweenawan rocks do not, however, reveal any systematic secondary
component but rather the difference in inclination between reversed and normal rocks
A possibility
remains throughout the blocking temperature and coercivity spectra.
exists that these demagnetization techniques are unable to detect the secondary component.
If a 'non—removable' secondary component indeed is present in all
Keweenawan rock units", it would result in a lower Thellier-type paleointensity
still
determination for the reversed rocks compared to that predicted for the normal
ones.
On the other hand, if the apparent polar wander 'interpretation is correct,
and the Earth's magnetic field was dipolar during the Keweenawan, an enhanced paleo—
field'value would be obtained for the reversed rocks because they have a significantly
higher paleolatitude than do the normal ones. In order to test the credibility 'of
the above models, we have conducted about luo Thellier—Thellier paleointensity
measurements on Keweenawan intrusives of both polarities, and adjacent baked contact
rocks from the Sibley and Rove formations. These results suggest a higher paleo—
field for the reversed epoch compared to that for the normal one.
Moreover if the
paleofield data are reduced to the paleoequator, this difference in paleointensity
between reversed and normal rocks disappears. Both paleomagnetic and paleointensity
data therefore cast doubt on the hypothesis that a secondary component has caused
the Keweenawan asymmetric reversal.
The results, however, are 'consistent with
apparent polar wander during Keweenawan tin'e.
39
�PETROLOGY AND TREND SURFACE ANALYSIS OF TWO LATE-STAGE GRANODIORITIC PLUTONS,
NORTHERN LAKE OF THE WOODS REGION, ONTARIO
Pilatzke, Richard H.; Karner, Frank R.; and Peterson, William M., Geolc5gy
Department, University of North Dakota, Grand Forks, North Dakota 58202
Trend Surface analysis of modal data for two small plutons in the Keno±a
block of the Superior Province show similar concentric patterns of mineral
abundance.
Alkali feldspa ith concentrated at the margins of the plutons
and oligoclase in the cores.
The Indian Reserve pluton Outcrops about one km northeast of Kejick at the
north end of Shoal Lake at latitude 49°38'N and longitude 95°04'W.
the area
of exposure is about 6 km2 and has an elliptical shape about 4.0 km by 1.6 km
with the major axis trending E-W. •Field study at 60 locations and point-count
analysis of 30 thin sections shows that the rock is typically a pink, mediuiñgrained, hypidiomorphic granular granodiorite with minor oligoclase phenocrysts
and scattered, small, greenstone xenoliths. The average composition is 50%
oligoclase, 26% quartz, 13% slightly perthitic microcline, 4% biotite, 3%
sericite, 2% epidote and minor opaque minerals, sphene and apatite. The
oligoclase typically contains two or three, thin, euhedral.to subhedral, in€eLrnal
alteration zones marked by a concentration of fine—grained sericite and epidot.e.
The Dogtooth pluton. outcrops about 16 km east of Kenora at latitude 49°l''N
The area studied is 4 km2 and is irregular in shape
and longitude 94°l3'W.
with its long axis oriented NE—SW. It appears to be a texturally distinct
lobe of a larger granodioritic pluton to the east.. Field study at 115 locations
and point-count analysis of 86 thin sections indicates that the rock is
typically a pink, medium-grained, hypidiomorphic granular granodiorite
characterized by polycrystalline quarta aggregates, protoclastically deformed
oligoclase, and ve;y low total mafic mineral content. The average composition
is 47% oligoclase, 26% quartz, 20% slightly perthitic microcline, 1% biotite
and 4% epidote, sericite, chlorite, opaque minerals and accessories.
In these rock?s oligoclase typically varies from 40% to 60% and microcline
Trend surface analysis of mineral distributions shows similar
from. 5% to 25%.
NE-SW trends for first and second—order surfaces for oligoclase and alkali
feldspar with oligoclase increasing to the SE and inward and alkali feldspar
Higher degree surfaces show increasingly
increasing to the NW and outward.
complex, concentric patterns. Quartz surfaces show mpre irregular patterns
with higher order surfaces showing marginal, alternating highs and lows.
Biotite surfaces for the Indian Reserve pluton follow the pattern of. alkali
feldspar surfaces.
We interpret the striking concentric patterns of the feldspar distributions
to be related to the cooling and crystallization histories of the plutons.
The linear trends for lower order surfaces and the axes of elongation of the
The. southeastward
concentric patterns ref léct regional structural trends.
increase of oligoèlase and the northwestward increase of alkali feldspar
shown on lower order surfaces may reflect a fundamental assymmetry of the
plutons or their regional tectonic framework relative to the present erosional
Both plutons nay be on the, southern lint of major synclinal features.
surface.
40
�.EVIDENCE FOR ARCHEAN TURBIDITE AND SUBMARINE FAN SEDIMENTATION
FROM THE SAVANT LM GREENSIONE TERRAIN, N. W. ONTARIO
R.J. SHEGELISKI
LSKEHEAD UNIVERSfl'Y
Results from an investigation of vertithliy dipping Archeah netaseditrnts
in the Savant area have outlined the presence of four basic sedimentary facies:
•
1.
2.
3.
4.
Graded-stratified cohglomerates of submarine fan association.
Graded greywacke—siltstone beds of turbidite association.
Stratified-laminated mudstones of pelitic association.
Laminated oxide iron formati6i of chemical association.
The graded—stratified conglomerates are corrnDnly associated wfth graded
greywacke—siltstone beds and form a coarse-grained l.—2. facies group. The
oxide iron formation and mudstones re also associated with greywacke—siltstone
sequences and form a finer—grained 2.-3.-4. facies group. The sequence of
deposition of metasediments in the north arm of Savant Lake is that of coarse—
grained l.—2. facies group overlain by the finer grained 2.—3.—4. facies group,
thereby forming a mega—fining upward cycle.
Facies Group l.—2.
Detailed field mapping of this conglomerate—rich group reveals major
fining—upward cycles within the group. Such features nay be indicative of
fan—channel abandonment. A predominanbe of well—rounded clasts within the
conglomerate suggest efficient abrasion of clasts in a shallow—water, highenergy environment, prior to final deposition, via turbid flow, in a deepwater environment. The l.-2. facies group is therefore considered to represent
a portion of a submarine fan systen composed of residimented conglomeratçs and
inter layered turbidites.
*
Facies Group 2.-3.-4.
Detailed mapping indicates that the overlying greywacke—silstone and
mudstone
facies contain several sedimentary structures and textures of the
deep—water turbidite association. The presence of interlayered iron—rich
and chemical iron formation indicate extrenely quiet periods between
mudstones
turbidite deposition. This facies group is therefore considered to represent
elastic and chemical accumulation in a portion of a restricted, deep—water
turbidite basin.
The interpretation that the clastic metasec.iments are coexisting
proximal coarse—grained submarine fan facies and dist al finer—grained turbidite
basin facies requires a deep—water environment for tIe acccmulat ion of oxide
iron formation as well. This interpretation sheds dcubt upon the ccrmnn belief
that Archean oxide facies iron formations are products of shallow water
deposition.
41
�GEOPHYSICAL STUDIES OF PERID0TITE DIKES,
YELLOW DOG PLAINS, NORThERN MICHIGAN
W. Snider, Michigan Dept. of Natural Resources, Lansing, Michigan 48926,
3. S. Klasner, U.S. Geological Survey and Western Illinois University, Macomb,
61455, S. Quam, Western Illinois University, Macomb, Illinois 61455,
R. Lilienthal, Michigan Dept. of Natural Resources, Lansing, Michigan 48926,
and P. Geraci and A. Grosz, U.S. Geological Survey, Reston, Virginia 22092
D.
Illinois
ABSTRACT
Very low frequency electromagnetic, gravity, and ground magnetic studies
indicate that peridotite exposed in two outcrops within the Pleistocene outwash of the Yellow Dog Plains is part of a dike swarm that extends in a westnorthwest direction for about 20 km beneath the Pleistocene drift cover. Rocks
at the two outcrops contain small quantities of copper— and nickel-bearing
sulfide minerals and have slightly anomalous copper content. Paleomagnetic
studies by Kenneth Books of the U.S. Geological Survey show that the perido-
.tite
has a remnant pole position typical of lower Keweenawan rocks from
throughout the region.
Analyses of the three types of geophysical data in sec. 11 and 12, T. 50
N., R. 29 W., where the peridotite crops out, indicate that several dikes are
present.
The dikes are intruded into middle Precambrian (x) metasedimentary
rocks within a structural trough in lower Precambrian (W) rocks.
Gravity
data suggest that a steep, west-trending fault with the downdropped side to
the south lies beneath the southernmost dike in secs. 11 and 12.
The fault
offsets the contact between lower and middle Precambrian rocks and may have
been a channelway for intrusion of the dikes. Northwest-trending faults offset both the dikes and the west-trending fault.
Filtered VLF-EM data combined with ground magnetic data suggest the
presence of two different types of dikes. Negative VLF-EM anomalies and
associated large-magnitude positive magnetic anomalies occur at the peridotite
outcrops.
In addition, positive VLF-EM anomalies cannot be attributed to nearsurface conductors or fault zones, and therefore suggest the presence of subsurface conductors. Gravity studies indicate the presence of dikes in the NW)
1W* sec. 12 and NW NW sec. 11, T. 50 N., R. 29 W. but no magnetic anomalies
were found.
Two positive VLF-flt anomalies were also found there. We believe
that these are attractive exploration targets for sulfide mineralization and
warrant further study.
42
�TIlE PETROLOGY AND SEDIMENTATION OF THE UPPER PRECAMBRIAN
SIOUX QUARTZITE OF MINNESOTA, SOUTH DAKOTA, AND IOWA
Richard E. Weber, Department of Geology, University of Minnesota, Duluth,
Duluth, Minnesota 55812
ABSTRACT
The Upper Precambrian Sioux Quartzite.is exposed at
along
several locations
an east—west trend 175 miles long and 30 miles wide between Mitchell,
South Dakota and New Ulm, Minnesota.
It rests unconformably on Lower Precambrian rocks and is overlain by Cretáceous sediments and Pleistocene
drift.
The formation consists of over 1600 meters of orthoquartzite sandThe conglomerates
stone with minor interbedded conglomerates and mudstones.
are present in the lower two—thirds of the section and mipor thin mudstones
occur in the upper third. The pebbles of the conglomerates consist of vein
A coarse basal conquartz, hematitic chert, iron formation and quartzite.
glomerate is exposed at New Ulth, Minnesota where it crops out 110 meters
from the underlying granite.
The mature orthoquartzite is composed almost exëlusively of well
rounded, moderately sorted, monocrystalline quartz.
Detrital chert and
jasper are common in some samp1e. Grains are coated with a thin film of
iron oxide and cemented by quartz overgrowths that are locally partially
replaced by secondary diaspore and sericite. Rounded zircon and tourmaline.
are the only common nonopaque detrital heavy minerals.
Measurements of. 856 cross—beds and 491 ripple marks show paleocurrent
directions to the south and southeast; no major vertical or lateral changes
in trends were observed.
Paleocurrent patterns are unimodal throughout most
of the unit but some bimodal patterns occur in the upper part of the section.
The crossbedding consists predominantly, of narrow troughs 60 to 140 cm wide
and 15 to 30 cm thick.
Asymmetric current ripple marks are common, but both
small— and large—scale symmetrical ripple marks are also present.
The abundance of crossbedding and current ripple marks indicates vigorous current action. Mudcracks and mudchip conglomerates suggest periodic
exposure and fluctuating current strength. These structures may suggest in
part a fluvial origin but herring—bone cross—beds and reactivation surfaces,
structures commonly associated with tidal deposits, are present in a few
areas in the upper third of the section.
It is intruded by diabase at
The Sioux Quartzite is gently folded.
Corson, South Dakota. A rhyolite interbedded with the quartzite in a well
at Hull, Iowa has been dated at 1470±. 50 m.y. (Lidiak, 1971).
REFERENCES
Lidiak, E. G., 1971, Buried Precambrian rocks of: South Dakota: Ceol. Spc.
America Bull., v. 82, p. 1411—1420.
43
�SHAPE, SIZE, AND;COOLING HISTORY OF TROCTOLITIC-GABBROIC ROCKS
IN THE DULUTH COMPLEX
by PW. Weiblen and R.W. Cooper
Data on mineral proportions and chemistry have been obtained on randomly
oriented thin sections of troctolitic-gabbroic rocks along a 10 km traverse normal
to the contact in the central part of the Duluth Complex in N.E. Minnesota. The
data provide, new insights into the shape, size, and cooling history of individual
intrusions.
The spread in data at - any locality on olivine (fig. I), plagioclase, and to a
lesser extent clinopyroxene may be correlated with degree of layering in the rocks.
The data suggest a regular increase in mineral layering away from the contact.
Data on biotite (fig. 2) sulfides, iron oxides and orthopyroxene show an
expontential decrease away from the contact. These data suggest a diffusion
controlled equilibration of basaltic magma with pelitic country rocks and
introduction of K, H20, and S into the magma.
The above data combined with geological and geophysical data on textural
relations, faulting, and aeromagnetic anomalies suggest the shape and size of
individual troctilitic-gabbroic intrusions as shown in fig. 3. These intrusions are
distinctly asymetric and show a continuous variation betweçn. flow (region A fig. 2)
and gravity (region B, fig. 2) layered rocks.
HIGHWAY
HIGHWAY
TRAVERSE
I
TRAVERSE
!!
+\
;L_•
:i
-
Fig.
Di%1.r. FaOI C1RC1tVM;
I
'•'
4+
OSTPtLC( FRO CONTPCT IKM
1. Olivine vs distance.
Fig. 2.
Biotite
-
-
-
vs distance.
Inclusions
A
Curved lines - Flow pattern
Blaèk areas
5 KK
Fault shown is normal to the
probable transform fault direction in the kidcontinent Rift..
IN
Fig.
3. Three dimensional view qf proposed magma chamber for
troctolitic—gabbroic intrusions in the Duluth Complex.
44-
�Surf icial Sediment Analyses Offshore of the Copper—Bearing Province of Keweenaw
Point, Upper Michigan
C. J. Welkie, E. L. Nebrija, R. P. Meyer, Geophysical and Polar Research Center,
Department of Geology & Geophysics, University of Wisconsin, Madison, WI 53706
Surficial bottom samples collected in 1974 and 1975 around Keweenaw Point were
analyzed for selected trace elements and textural parameters as indicators of
depositional processes following the methods of Moore and Welkie (1976).
The distribution of the concentrations of Cu, Zn, Ni, Co, Mn and Fe were compared for Five
Mile Point (north of the peninsula) and Bete Grise bay (south). The test of log—
normality was applied (Ahrens, 1954) and the number of statistical geochemical
populations for each element determined.
For Cu, three statistical populations
were found in both sites. Regression curves were drawn for all possible pairs of
trace elements and a least—squares fit determined. The slopes of the regression
lines support the contention of Smith and Moore (1972) that the sediments north of the
Keweenaw represent a separate grouping of popuiations from those to the south.
The contours fo copper distribution off Five Mile Point generally parallel the
shore, with three areas of high concentration (295 to 175 ppm) which are uncorrelated
to bathymetry.
In Bete Grise, six samples containing anomalous values were found
(145 to 175 ppm) and these clustered in two areas, both occurring in an elongate
bathymetric low corresponding to a postulated ancient channel of the Montreal River
Thus, the samples are anomalous
which drains copper—bearing rocks (Goodden, 1974).
according to the criteria established by Bolviken (1971), i.e., values exceeding two
standard deviations from the arithmetic mean over all samples.
After correlation of copper content with all other variables, multiple linear—
regression analysis showed 91% of the variation in Cu at Five Mile Point could be
and
explained by the variables Zn, Ni, Fe, Mn, by percent 3.5 , percent 4.0
At Bete Grise, only 72% of the variation
percent 4:5 $ grain size, and by bathymetry.
in the copper concentrations could be explained by these variables; either the
relationships between these parameters are nonlinear, or other vari4bles as yet
undetermined enter into the linear model.
3.5 Kc seismic profiles and towed electrical resistivity profiling and sounding
failed to correlate with the areal extent of the placer deposits as determined from
physical sampling in Bete Grise, implying that the anomalous values do not continue
to depth or that these geophysical techniques as applied had insufficient resolution.
References:
Ahrens, L. H., 1954, The lognormal distribution of the elements, Geochim. Cosmochim.
Açta, 5, 49—73.
Bolviken, B., 1971, A statistical approach to the problem of interpretation in
geochemical prospecting, Geochemical Exploration (Boyle, Tech. Ed.),Special
Vol. No. 11, Canadian Institute of Mining and Metallurgy, 564—567.
Goodden, J.J., 1974, Sedimentological aspects of underwater copper exploration in
Lake Superior, M.S. Thesis, University of Wisconsin, Madison, Wisconsin.
Moore, J. R., and C. J. Welkie, 1976, Metal—bearing sediments of economic interest,
coastal Bering Sea, Symposium Proc., Alaska Geol. Society, Recent & Ancient
Sed. Envir. in Alaska, pp. K—l to K—17.
Smith, P. A., and J. R. Moore, 1972, The distribution of trace metals in the surficial
sediments surrounding Keweenaw Point, Upper Michigan, Sea Grant College Reprint,
WIS—SG—73—341, 383—393.
45
�DELTAIC DEPOSIPS IN TITLE UPPER PECORS,ESPANOLA AND GOWGANDA
FORMATIONS (HIJRONIAN)
G. IC Young, D.
G. F. Long. ad S. N. NcLennan
Dept. of Geology, -University of Western Ontario, London, Ont.
The cyclical repetitibn of mixtite, siltstone, sandstone
is the hall-mark of much of the Huronian succession. Little
attention has been given to the finer grained units (Pecors,
Espanola and upper Gowganda Formations). This report deals
mainly with the upper parts. of these units in the southern
part of the Huronian outcrop belt.
The upper parts of the Pecors and Gowganda Formations
constitute complex coarsening upward sequences with many of the
attributes of the classical prograding deltaic sequence. Both
units are composed mainly of muddy and silty argillite. The
prodelta deposits consist of laminated, in some cases graded
siltstone-mudstone couplets, some of which may be varves. The
delta slope is represented by finely interbedded mudstonés and
wavy, laminated and cross laminated,siltstones. Slope instability
is evidenced by The presence of abundant asymmetrical flame, and
ball and pillow structures. Thin—to—thick massive units of siltstone-fine sandstone.with rip-up clasts and erosive bases are
considered to have been resedimented by downslope mass movement.
Clastic dykes are present in the Pecors Formation. The delta
slope deposits pass rapidly upwards into fluvial(?) sandstones
of the Nississagi and Lorrain Formations which appear to have
been derived predominantly from the northwest.
The upper Espanola Formation differs from the other two
units in containing much more sandstone3 anc carbonate-rich
units.In some areas the upper Espanola Formation contains
abundant fining upward sequences(one to seeral metres thick)
like those of both fluvial and tidal channel deposits. The
interpretation is favoured because of the presence oL
bimodal-bipolar(NW-SE oriented) cross bedding distributions
in some units. This interpretation is important because it
implies a tide-dominated and therefore marine environment
in the upper Espanola Formation. This unit passes upward
into the fluvial (part eolian?) sandstones of the Serpent
Formation.
The Pecors and upper Gowganda Formations are interpreted
as prograding muddy delta deposits whereas the upper Espanola
appears to have accumulated in a higher energy, tide-dominated
delta platform. The reasons for this difference are not understood, but might have been caused.by greater rates of subsidence
or fluvial advance in the Pecors and Gowganda than in the case.
of the Espanola Formation.
latter
o oO
00
46
�SEDIMENTARY FACIES ASSOCIATED WITH LATE WISCONSIN
GLACIAL LAKE DULUTH, WRENSI-LALL AREA, MINNESOtA.
Randee Zarth, Geology Dept., University of Minnesota, Duluth, Mn, 55812
ABSTRACT
Study of Late Wisconin glacial deposits southwest of Duluth
suests a revised model for the late'- and postglacial history of
the area. Two major sedimentary environments, are distinguishedi
(1) an ice-disintegration environment and (2) a glaciolacustrine
environment associated with Glacial Lake Duluth.
Sediments produced by ice-disintegration are stratified, 'moderately- to poorly-sorted sand, and gravel, with clasts predominately
Of Precambrian. sandstone, volcanics, gr'anite, and slate; and minor
bodies of'laminated silt and clay.. Topographically, these sediments
comprise a wide belt of 'kettles, kames, disintegration ridges; and
outwash plains that are dissected locally by meltwater channels and'
tunnel valleys, some of which contain eskers.
The lacustrine environment contains the following facies:
(1) thick, flat-bedded sands, (2) cross—bedded sands, (3) parallel
laminated silt and clay, (k), massive clay, and (5) massive' and
stratified drop stone deposits. In the nearshore environment. are
found moderately—sorted and well-rounded sand grains (0.25 mm) with
boulders at' the shoreline. At 305 to 31k meters in elevätion,,the
sand grades rather abruptly to massive clay. The sand facies overlies
the silts and clays indidating progradation into Glacial Laket Duluth
by nearshóre currents.
The highest strandline features occur 'at elevations near 335
meters. They are expressed primarily as beach scarps and other welldeveloped shoreline features, such as several spits and a delta. A
prominent linear, northeast trending scarp between 305 and 31k meters
previously considered to be a strandline, is here interpreted, to be
the depositional front of. a coarse-grained shelf deposited into
Glacial Lake Duluth as it stood near its highest stage (335 meters).
This indicates what wa previously considered to be two stages
Glacial Lake Nemadji and Glacial Lake Duluth is actually a single
stage of Glacial Lake Duluth,
The following, late- ard early postglacial history is" indcateds
(1) Ice from the last advance of the Superior Lobe stagnated along
the margin of the Lake Superior Basin, resulting in the development
of an ice-disintegration complex and stratified glacial deposits.
(2) Meltwater from the disintegrating ice, the retreating Superior
Lobe in the basin, and from more distant upland sources, along with
runoff from the hydrologic cycle, were ponded in fron.t of the
retreating ice to form Glacial Lake Duluth. (3) A lake level rise
to 335 meters is represented by a transgressive sequence of sediments.
(k) The lake stabilized long enough to develop strong beach features.
Sediment supplied, to the lake at this stage appears to have been
mainly derived from the ice-disintegration complex with minor
contributions 'from ice rafting, (5) Progradation of the shallbw water
facies over the deep water facies was the result of sediment laden
streams, meltwater, and, other runoff enterinE the lake. '(6) The
lack of a regressive facies indicates a rapid drop in the lake level
as a lower outlet was uncovered by the retreating ice front..
47"
�!field
rs
Copies of the guidebooks
Department
of
may be
obtained frOm:
Geology
Lakehead University
Thunder Bay, Ontario
PTh 5E1
Price
$5.90 Canadian.
Make checks payable to Lake SUperiOr Institute.
�FIELD TRIP A
'COLDWELL COMPLEX
LEADERS:
R.H. Mitchell and R.G. Platt
DATE:
May 2 -4,
1977.
The Coldwell Complex is a large Proterozoic alkaline
igneous complex containing saturated, oversaturated, and
under-saturated syenites. Visits will be made to
exposures of all the major rock types found within the
complex and to areas which illustrate the relationships
between the magma types and the mechanisms of intrusion
of the. complex.
1.
Depart Thunder Bay on Monday May 2 at4:00 p.m.
Return Thunder Bay Wednesday May 4 by 5:00p.m.
All 'day Tuesday May .3 and the morning of. Wednesday
May 4 will be spent examining the complex.
2.
The cost is $7O.O0. and includes:
a) 2 nights accomodation (double) at Marathon.
b) Transportation to and from Thunder Bay and
during the. excursion.
c) Guidebook.
Maximum costs for meals
Cost does not include meals.
in Marathon are about $12.00 per day,.
3.
Accomodation will be in rñotels in Marathon (with
restaurants).
Costs are based upon double occupancy
of motel units.
Persons requiring single occupancy
must notify the organizers in advance and be prepared
to pay $10.00 extra.
4.
Limited to a maximum of 45 persons.
51
�FIELD TRIP
PROTEROZOIC ROCKS OF THE THUNDER BAY AREA
LEADERS:
K.G. Fenwick, C.R. Kustra, W.H. Mcllwalne,
J.F. Scott.
DATE:
May 3: and 4,
1977.
A two day field trip will cover the Proterozoic (Middle
to Lake Precambrian) rocks of the Thunder Bay area. Day
one will cover selected stratigraphic units of lower and
upper members of the Gunflint Formation and the overlying
Rove Formation.
On the second day, outcrops of the Sibley
Group will be examined. The stops are designed to
illustrate the stratigraphic relationships of the three
fold division of the Sibley Group into formations.
Side
trips to Ouimet Canyon and the Thunder Bay Amethyst Mine
are also planned.
leave the Airlane Motor Hotel,
Thunder Bay, on Tuesday May 3rd and on Wednesday
May 4th at 8:00 a.m.
The bus will return each
day by late afternoon.
1.
Field Trip B will,
2.
The costs for participants is $4O.OQper person.
This fee includes bus transportaion, lunch each
day, literature, and guide to field stops1.
It
does not include lodging.
3.
Limited to a maximum of 45persons.
52
�FIEL,D TRIP C
STURGEON. LAKE
LEADERS:
W. Gibh, P. Severin, A. Tarnman, H. Poulsen,
J. Franklin.
DATE:
May 6 - 8, 1977.
A one ay field trip to the Sturgeon Lake area will
include the examination Qf two open-pit mines (Mattabi
and Sturgeon Lake Mines Ltd.) and outcrops representative
of the volcanic stratigraphy of the lower portion of the
pile..
The Mattabi and Sturgeon Lake Mines are typical
volcanogenic massive sulphide deposits. Tour stops
within the mines will include an examination of both
massive and stringer ore and various types of alteration
The
associated with the footwall stringer suiphides.
regional stops will examine a variety of felsic and
mafic pyroclastic, flow,, and epiqlastic rocks,. and two
subvolcanic intrusive bodies.
1.
Participants will depart by bus from Thunder Bay at
A
approximately.6:30 p.rp. on Friday, May 6.
discussion period, will be held in Ignace that
evening.
As the tour will be rather lengthy,
participants will stay in Ignacethe evening of
Saturday, May 7.
Buses will reach Thunder Bay
and Dryden on Sunday, 'May 8 in order to connect
with mid-day planes.
2..
A fee of $75.00 will include transportation,
accomodatjon,, meals, and guidebook.
3.
Limited to a maximum of 45 persons.
53
�
https://digitalcollections.lakeheadu.ca/files/original/b2bf913cd5f79f3b89a1b7891165c6b1.pdf
c40ef197359f1bb47e247efcc376edec
PDF Text
Text
a
I*eHty
Third
Alinoal
MeeliHg
Thunder
ilay, Ontario
Ii
r
Institute on Lake
Superior Geology
S
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P.!
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COLD WELL TRIP
COLDWELL
U
�r
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FIELD GUIDE
GUIDE TO
TO ASPECTS
ASPECTS OF
OF THE
THE
FIELD
I
GEOLOGY OF
OF THE
THE COLOWELL
COLDWELL ALKALINE
ALKALINE COMPLEX
COMPLEX
GEOLOGY
I
I
ROGER
ROGER
H. MITCHELL AND R. GARTH PLATT
H. MITCHELL AND R. GARTH PLATT
I
I
Department of Geology
Lakehead University
Thunder Bay
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Twenty Third
Third Annual
Annual Meeting,
Meeting, Institute
Institute on Lake
Twenty
on Lake
Superior Geology, Marathon, May 1977
Superior
Geology, Marathon, May 1977
�THE
COLDWELL ALKALINE CuwLEX
COMPLEX
na LULIDWELL
".
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The Coldwell complex
located
1 o - y is
410c-~-d on the north shore
shore
Superior between the Pie
of Lake Superior
Pic and
and Little
Little Pie
Pic Rivers.
Rivers.
The community
The
community of Marathon
rathon is
is located
located on the
the eastern
eastern side
side
of the
the complex.
complex. This circular complex with a diameter
of 25
25 km.
of
km. is the largest alkaline
alkaline intrusion
intrusion in
in North
North
America and is
is unusual in that oversaturated,
oversaturated, under—
undersaturated and saturated magmatism
magmatism is
saturated
is present.
present.
The alkaline
(1000 m.y.
)
The
alkaline rocks
rocks are
areof
ofNeohelikian
Neohelikianage.
age(1000
m.y.)
are emplaced
in Archean
rocks of
the Superior
Province
and are
emplaced
in Archean
rocks
of the
Superior Province
of
Canadian Shield,
f the Canadian
Shield, which in this area form
form an
north—
essentially
east—west trending
ssentially east-west
trending greenstone
greenstone belt.
belt. A northeasterly
bifurcation of this belt originates
originates in the
easterly
Marathon area
area and it is
is at this
this point that the
the alkaline
alkaline
rocks have
have been
The Archean rocks,
rocks, which
rocks
been emplaced.
emplaced. The
include basic and acidic volcanics and greywackes have
been metamorphosed to greenschist and amphibolite
amphibolite grade,
grad
been
subjected to at least two periods of folding and intruded by Archean granites
Little is
granites and
and syenites.
syenites. Little
is
known of the
the Archean geology although
although some
some information
information
known
can be found in Puskas
Puskas (1967)
(1967) Milne
Milne (1967),
(1967), Walker
Walker (1967),
(1967).,
Ayres et al. (1970),
(1970), Thompson
Thompson (1931),
(1931), and Einarsson (1972).
(1972).
A general geological map of the complex,
complex, together
together
with an aeromagnetic map is
figures lA
with
is given
given in
infigures
1A and
and lB.
IB.
The geological
(1967),
geological map is
is based on the
the work of Puskas
Puskas (1967),
together with our own observations
observations and re—interpretation
together
re-interpretation
of the sequence
sequence of igneous
It should
should be
be noted
igneous events.
events. It
that
simplication of the geology of
hat figure 1A is an over simplication
the area.
area.
In detail,
detail, relationships
relationships are
the
are extremely
extremely
mapping, coupled with
complicated and very detailed mapping,
extensive mineralogical
mineralogical studies,
is required
required before
before
studiesis
extensive
anything
approaching an accurate geological map can be
nything appr
produced.
reduced.
S-
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The structure
The
structure of
of the
the complex
complex is
is poorly
poorly known because
of insufficient
insufficient geophysical
geophysical and
and structural
structural observations.
observations.
Puskas
Puskas (1967) believed that the
the complex
complex was
was aa lopolith
lopolith
but our recent work does
does not support this
this concept of a
single
differentiated intrusion.
single differentiated
intrusion. Lilley (1964)
(1964) considers
conside
that the bulk of the intrusion
intrusion is a funnel
funnel shaped
shaped body
of gabbro
gabhro and ferroaugite
of
ferroaugite syenite
syenite which has been intruded
intruded
by nepheline
nepheline syenites.
syenites. Our recent studies
studies indicate
indicate that
that
several
present, and that an
several centers
centers of intrusion
intrusion may be present,
an
area
Pic River,
area bounded by the
the Little
Little Pic
River, Redsucker Cove
Cove
and Geordie
Geordie Lake
Lake may be
be aa downfaulted
downfaulted block.
block. Rocks
Rocks within
within
this area are characterized
characterized by
by the occurrenceof
occurrerueof multiple
this
breccias
breccias and
and metasomatism
metasomatism and
and may represent
represent rocks
rocks which
which
were
were originally
originally close
close to
to the
the roof
roof of
of the
the complex.
complex. Rocks
Rocks
of the
the eastern
eastern portion of the
the intrusion
intrusion are
are in
in contrast
contrast
less
ss complex
complex and
and relatively
relatively xenolith
xenolith free.
free.
Petrologically we have
Petrologically
have recognized
recognized three
three distinct
distinct
intrusive
magmatic episodes,
episodes, each being characterized
trusive magmatic
characterized
by
In order
differentiationtrend.
by a distinct differentiationtrend.
order of
of^
intrusion
these are:
intrusion these
are:
CENTER 11
CENTER
-— Saturated
Saturated
rocks with peralkaline
alkaline rocks
peralkaline
oversaturated
residua.
oversaturated residua.
CENTER
Miascitic alkaline
alkaline rocks
rocks with
with under—
un
CENTER 22 -- Miascitic
saturated
saturated residua.
residua.
CENTER 3 - Alkaline rocks with oversaturated
rsaturate
residua.
-
.
.,
Gabbro,, ferroaugite
ferroaugite syenite
I
CENTER
CENTER 1 -
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The
The oldest unit of the
the complex
comulex is
is represented
represented by
by
eastern border
These rocks
the eastern
border gabbros
gabbros (figure
(figure lÀ).
1A). These
rocks
are
Igneous layering
layering
are intruded
intruded by ferroaugite
ferroaugite syenites.
syenites. Igneous
Several centers
is characteristic
characteristic of
of both
both units.
units. Several
centers of
o
intrusion may be present in
in the
the ferroaugite
ferroaugite syenites
syenite
,
.
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which typically
typically exhibit
exhibit extreme
extreme iron
iron enrichment
enrichment and
and
,
Characteristic
differentiate to quartz
differentiate
quartz bearing
bearing residua.
residua. Characteristic
minerals of
minerals
of the
the ferroaugite
ferroaugite syenite
syenite are
are fayalite,
fayalite,
ferroaugite,
ferroaugite, ferrorichterite,
ferrorichterite, ferroedenite
ferroedenite and
aenigmatite.
aenigmatite.
CENTER 2
Biotite gabbro,
gabbro, nepheline and natrolite syenites
2 —- Biotite
syenites
CENTER
outcrops is an arcuate
Alkaline biotite gabbro outcrops
arcuate ring
pattern on the Coldwell Penninsula
Penninsula and we believe
believe that this
this
together with nepheline syenite
syenite defines
defines an undersaturated
undersaturated
nepheline
intrusive center
center (figure
(figure lA).
1A). AA second intrusion
intrusion of ne~heline
Nepheline syenites
syenite may be located
syenite
located on
on Pic
Pic Island.
Island. Nepheline
syenites are
are
characterised by
characterised
by moderate
moderate iron
iron enrichment,
enrichment,alurninous
aluminous amphiholes
amphiboles
and acmitic
acmitic pyroxenes.
pyroxenes. Titanium in these rocks enters
amphibole and pyroxenes rather than forming
forming aenigmatite
aenigmatite as
in Center
Center 1.
1.
of Centers
Centers 11 and
and
The distinctly differentiation
differentiation trends
trends of
2 are well illustrated
illustrated by the trends
trends in pyroxene compositions
compositions
Platt, 1977)
illustrated below.
illustrated
below. (Mitchell and Platt,
1977)
ACM ITE
ACMITE
DIOPSIDE
HEDENBERGITE
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Figure
-
lÀ - Geological
Geological map of thq
the Coldwll
Coidwell alkaline
Department of
complex based upon Ontario Department
Preliminary Map P114
Mines Preliminary
P114 (Puskas
(Puskas 1967)
1967)
together
ogether with our own observations and
re—interpretation of the sequence of
re-interpretation
igneous events.
igneous
events.
1
'
1
Figure
alkaline
Based upon Ontario
Department of Mines Aeromagnetic Maps
2146G, 2147G, 2156G, 2157G.
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-
lB - Magnetic
Magnetic expression of the Coldwell
r
complex.
�+
0
z
In
-4
C-)
+
�GEOLOGICAL
S—
MAP
—a
I
2
4
I
3
6
4
6
Gabbro
Ferroaugite Syenite
Biotite-Gabbro
+-LIIIJ Acid Metavolcanics & Metasediments
LZ1II Basic Vojcanjcs & Metcisediments
[±IEI Ultrabasjc Intrusives
LII1 Granite Gneisses
1IIIJ Basic Xenoljths (metavolcanics)
PAA
Nepheline Syenite
Syenite - Syenodiorife
2
MILES
8 KILQMETRES
5
++ Granite ,Quartz - Syerüte, Hybrid Syenites
I
2
LEGEND
o
o
MARATHON AREA
COLDWELL COMPLEX a VICINITY
_____
______
LAKE
SUPERIOR
�-7-
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CENTER 3 -
Syenite,
quartz syenites
thewestern
westernportion
portion of
ofthe
thecomplex
complexare
arefound
founda a
InInthe
widevariety
varietyofofsyenites,
syenites,quartz
quartzsyenites
syenitesand
and granitic
granitic
wide
The
quartz
rockswhose
whosepetrology
petrologyisispoorly
poorlyknown.
known. The quartz
rocks
syenites
syeniteshave
havebeen
beenfound
foundto
to intrude
intrudeall
allearlier
earlierrocks
rocks
by
an
Theserocksare
arecharacterized
characterized by an
Center2.2. These.rOcks
ofofCenter
abundanceof
ofzircon,
zircon,paucity
paucity of
ofpyroxene, arfvedsonitic
abundance
amphiboles,
amphiboles,fluorite
fluori and quartz.
MINORINTRUSIONS
INTRUSIONS
MINOR
Theplutonic
plutonicrocks are cut by two groups of minor
The
intrusions. (a)
(a)diatremes
diatremes (b)
(b) dikes
dikes
intrusions.
DIATREMES
Threediatreifles
diatremesare
areknown
knownin
inthe
theColdwell
Coldwellregion,
region
Three
I
oneof
ofwhich
whichcuts
cutsthe
the intrusive
intrusiverocks
rocksof
of the
the
only y one
Thisdiatreme
diatremelocated
locatedon
on the
the west
west side
sideof
ofthe
t
complex. This
complex.
ColdwellPenninsula
Penninsulacontains
containshornfelsed
hornfelsedmetasediments
metasediment
Coidwell
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and
and inclusions
inclusionsof
ofCenter
Center 22rocks
rocksas
asxenoliths
xenoliths (Balint
(Balint
rocks,
such
as
Diatremesin
inthe
theArchean
Archean rocks, such.asthe
the
1977). Diatremes
1977).
be
Deadhorseand
andMcKellar
McKellarCreek
Creekdiatremes,
diatremes,may
may be
Deadhorse
Coldwell
rocks
have
contemporaneous,
yet been
been
contemporaneous,but
but no
no Coldwell rocks haveyet
amongtheir
theirxenolith
xenolithsuites.
suites.
found among
DIKE ROCKS s
I
widevariety
varietyofof dike
dike rocks
rockscut
cutthe
thecomplex
complexand
and
AA wide
of
These
dikes
In
order
surroundingcountry
countryrocks.
roc
surrounding
I
vedabundance
abundanceare:—
are:
observed
1
1
I
1) ocellular
�--S
C
2) analcite tinguaites
1
3) porphyritic (Al—Cr—cpx) lamprophyres
4)
4) glomeroporphyritic
glomeroporphyritic and
and alkali
alkali basaltic
basaltic dikes
dikes
(?
Pukasaw swarm)
( ? Pukasaw
swarm)
.
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5) porphyritic (resorbed
5)
(resorbed quartz)
quartz) lamprophyres
lamprophyres
6) nepheline
nepheline syenite
6)
syenite
7) rhyolitic
7)
rhyolitic dikes
dikes
8)
syenites with a
8
) syenites
a high organic
organic content
content
TECTONIC
TECTONIC SETTING
SETTING
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The complex
The
complex is
is aa part
part of
of the
the Keweenawan
Keweenawan igneous
igneous
activity
activity centered
centered around
around Lake
Lake Superior
Superior which
which includes
includ
the Keweenawan basalts,
basalts, the Duluth Complex
Complex and the
the
the
Logan sills.
summary of the
the regional
regional geology and
and
Logan
sills. A summary
tectonic
framework is
2. The complex
complex
tectonic framework
is given
given in
in figure
figure 2.
is located at the Thinge
'hinge point' of
of two
two belts
belts of
of
essentially tholeiitic
essentially
tholeiitic volcanics,
volcanlcs, i.e.
i.e. the
the North
North Shore—
ShoreOsler volcanics and the Mamainse-Michipicoten
Mamainse—Michipicoten volcanics
Osier
north—south
and is itself the southern most member of a north-south
trending belt of
belt of
of
trending
of alkaline
alkaline intrusions.
intrusions. A belt
alkaline intrusions,
alkaline
intrusions, some
some being
being contemporaneous
contemporaneous with
with
the Coldwell
Coidwell Complex,
Complex, is found along the "Kapuskasing
the
"Kapuskasing
High" but no
no petrological or
or tectonic
tectonic connection
connection
between these two
The tectonic
two belts
belts is
is known
known to
to exist.
exist. The
setting and type
setting
type of
of igneous
igneous activity
activity is
is similar
similar to
to that
that
found in the Kangerdlugssqaq
Kangerdlugssuaq area of East Greenland and
the Gregory-Kavirondo
Gregory—Kavirondo Rifts
the
Rifts of
of East
East Africa.
Africa. Both
Both of
of
these areas
these
areas have been considered
considered to
to be
be the
the sites
sites of
of
plume
plume generated
generated triple
triple junctions,
junctions, the
the alkaline
alkaline rocks
rocks
being associated with the failed
ed arm of the spreading
center.
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Figure
Figure 22 -- Tectonic
Tectonic setting
setting of
of the
the Coidwell
Coldwell alkaline
alkaline
from data
data given
given by
by Card
Card
complex, complied
compiled from
complex,
et
et al
a1 (1972),
(1972). Currie
Currie (1976),
(1976), Gittins
Gittins et
et a1
(1967),
(1967). Halls
Halls and
and West
West (1971).
(1971). Alkaline
Alkaline
complexes
complexes and
and carbonatites
carbonatites are
are designated
designated
** and
and their
their radiometric
radiometric ages
ages (mostly
(mostly K—Ar)
K-Ar)
are
of years.
are given
given in
in millions
mill
years.
~,
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.m
A
ARCHEAN
ARCHEAN
0
50
50
1do
00
150
ISO
00
200
KILOMETRES
200 KILOMETRES
150 MILES
Ar, A
SOUTH RANGE
TRAPS
KEWEENAWAN BASIN
STRUCTURALAXIS
AXIS OF
OF
STRUCTURAL
MAJOR KEWEENAWAN
MAmR
KEWEENAWAN INTRUSIVES
I
EARLY
EARLY
PRECAMBRiAN
PRECAMBRIAN
UNCONFORMITY
UNCONFORMITY
A
-
LOWER KEWEENAWAN
LOWER
KEWEENAWAN
UNCONFORMITY
UNCONFORMITY
MIDDLE
PRECAMBRIAN
t
MIDDLE KEWEENAWAN
LL.. CAMBRIAN
CAMBRIAN
UPPER
KEWEENAWAN
UPPER KEWEENAWAN
U.
U. KEWEENAWAN
KEWEENAWAN
SILURIAN
SILURIAN
-
U.
U. CAMBRIAN
CAMBRIAN
UNCONFORMITY
UNCONFORMITY
PRECAMBRIAN
f
LATE
PALEOZOIC
-
A
P
LEGEND
_7_
Ar
NIPIGON
NIflGON PLATE
PLATE
MICHIGAN
PUCKASAW
:/
/
I
/
j Seabrook Lake 1100
Lackner Lake 1090
SAULT STE. MARIE
Mamainse
Car gantua F.
Ar
1/
"
Nemegosenda 1010
Portage 1090
/1
'i/la
ía'
Is I0Io*I
Goldray 1695
Valentine Tp**
4Herman Lake.)
Borden *
Arg2655 *
Sextant Rapids *
Teetzel Tp. 1155
GRAVITY HIGH
KAPUSKASING
CargilI 1740*
Clay — Howel
Firesand 1048/
lola Lake 1185
1000
Coldwell 1
000
* Chipman Lake
see
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Two
EXPLOSION DIATREME - DEADHOBSE CREEK
small
explosion diatremes (Deadhorse Creek &
McKeller Creek) are located in the Arehean greenstone
belt just to the west of the Coldwell alkaline complex.
A third subcircular diatreme (The Neys Diatreme) cuts
rocks of the Coidwell complex.
Located on the west
side of the Coldwell Peninsula, this latter diatreme
has been studied by Balint (1977).
Neither diatreme
in the greenstone belt has been studied in detail.
This stop examines the small diatrerne exposed on
the Ministry of Natural Resources access road which
parallels Deadhorse Creek. Here the diatreme
cuts Archean metavolcanics and pyroclastics.
cross—
The matrix of the diatreme, when unweathered, is
dark green in colour and consists of carbonate and a
greenish amphibole.
Embedded in this are clasts of
varying size and angularity. By far the most prominent
are fragments from the greenstone belt. Of regional
geological interest are occassional clasts of
orthoquartzite.
Similar clasts, together with red—
purple shales, are found in greater abundance in the
McKeller Creek diatreme. These clasts closely resemble
rocks formed extensively in the paleohelikian Sibley
l
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Group.
Until now, the most easterly extension of this
group of rocks was thought to he some forty miles to
the west in the vicinity of Rossport.
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Fragments similar in appearance to certain felsic
Fngments
similar in appearance to certain felsic
porphyries of the Keweenawan Osier volcanic rocks are
porphyries of the Keweenawan Osler volcanic rocks are
present. This may indfcate an easterly extension of
present.
This may indicate an easterly extension of
Keweenawan volcanism, although the seeming total lack
Keweenawan volcanism, although the seeming total lack
Keweenawan basaltic rocks makes this assumption
ofof Keweenawan
basaltic rocks makes this assumption
problematical.
problematical
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-22 STOP
STOP
WESTERN MARGIN
MARGIN OF
OP THE
WESTERN
THE ALKALINE
ALKALINECOMPLEX
COMPLEX
This stop investigates
This
investigates the
the complexities
complexities of
of the
the
western
stern contact region of the Coldwell Complex as
exposed in the outcrops
outcrops and road cuts
exposed
cuts adjacent
adjacent to
to
Hwy. 17.
region, the border intrusive
Hwy.
17. In this region,
intrusive rocks
rocks
of the complex are in contact with folded Archean
of
metasediments.
metasediments.
The rocks of the intrusion exposed in this region
The
are extremely
extremely varied,
varied, ranging
ranging from
from ultramafic
ultramafic cumulates,
cumulates,
olivine gabbros
olivine
gabbros and syenodiorites
syenodiorites to
to nepheline
nepheline syenites,
syenites,
quartz
pegmatites with
with and without
without
uartz syenites and syenitic pegmatites
natrolite.
atrolite. Later diabasic and lamprophyric dykes also
cross
ross cut the
the region.
region.
The interrelationships
interrelationships between these
these various rock
rock
types
ypes is still somewhat problematical as
as is
is their
their exact
exact
relationship to the intrusive history of the complex in
general. Webelieve,
We believe, however,
however, that the geographic
general.
relationships of the major intrusive
relationships
intrusive phases of the
the contact
contact
zone are at least in
in part fault
fault controlled.
controlled.
It
convenient, for the purposes of this stop,
stop, to
It is convenient,
body of the intrusion
traverse the contact zone from the body
towards the
purposes, we
out towards
out
the contact.
contact. For descriptive purposes,
will consider
consider the
the rocks
rocks exposed
exposed in
in three
three major
major zones.
zones.
These are outlined
outlined as the accompanying sketch map
map and
These
described below:
below: described
Zone 1
The main Coldwell
Coldwell rock of this zone
The
zone is
is a banded
syenodiorite consisting
consisting of subequal amounts of oligoclase
syenodiorite
and alkali feldspars,
feldspars, the latter showing incipient
exsolution. Apatite is ubiquitous and the mafic minerals
minerals
exsolution.
consist
of ferroaugite,
ferroaugite, fayalitic olivine
olivine and exsolved'
exsolved
consist
ilmeno—magnetite. Thick ultramafic bands develop by the
ilmeno-magnetite.
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accumulation
minerals, particularly
particularly the
accumulation of the mafic minerals,
ilmeno-magnetite.
ilmeno-magnetite.
wide
Cross cutting the syenodiorite is a relatively wide
Cross
syenite, most probably
dyke or sheet of nepheline syenite,
associated with
with Center
2. Alkalic feldspar
feldspar is
is the
the preassociated
Center 2.
dominant felsic phase with nepheline occurring in the
interlath regions.
interlath
regions. Green (acmitic)
(acmitic) pyroxene
pyroxene is
is the
the major
major
mafic
phase, while opaque minerals and accessory fluorite
mafic phase,
fluorite
make up the
the remaining
remaining mineral
mineral phases.
phases.
Cutting both the syenodiorite
Cutting
syenodiorite and the nepheline
nepheline
syenite is
syenite
is a coarse—grained
coarse-grained natrolite
natrolite syenite
syenite pegmatite.
pegmatite.
In this,
this, the natrolite
In
natrolite is
is seen
seen as
as large
large reddish
reddish patches.
patches.
At least two thin lamprophyres intrude the rocks of
of
At
this zone.
zone.
this
These zone
These
zone 11 rocks
rocks have not been recognized along
along the
the
coastal section of the contact region lying
lying some
some 1
1 mile
Here gabbros
the south
south of our
to the
to
our present
present location.
location. Here
gabbros of
of
with ferroaugite
ferroaugite syenites,
syenites, as shown
zone 2 are in contact with
the geological,
map
of the
margin of themargin of the
on the
peolWica1
map
ofsouthwestern
the southwestern
complex below
below (Aubut
(Aubut 1977).
1977).
Zone 2
A zone of banded olivine gabbro intruded by syenite
natrolite—bearing syenitic
and natrolite-bearing
syenitic pegmatites.
pegmatites.
The gabbros show considerable evidence of textural
The
plagioclase
mineralogical readjustment.
and mineralogical
readjustment. Invariably the plagiocla
crystals have been granulated and recrystallized giving
crystals
olivines
rise to microscopic 'augen'—like
rise
'augenl-liketextures.
textures. The divines
by coronas of
of amphibole and
are commonly surrounded by
are
mica and in many instances
instances the original olivine
olivine is
is now
represented by somewhat rounded replacement zones of
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green-blue
green-blue amphibole
amphibole and
and pale
pale green—brown
green-brown mica.
mica. Thin
Thin
,
microscopic
microscopic shear
shear zones
zones cross
cross cut
cut the
the gabbro.
gabbro.
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Again, later
Again,
later lamprophyric
lamprophyric dykes
dykes intrude
intrude the
the main
main
Coidwell
Coldwell intrusive
intrusive rocks.
rocks.
Along the
Along
the coastal
coastal section
section lying
lying to
to the
the south,
south, this
this
combination
combination of olivine
olivine gabbro
gabbro intruded
intruded by syenitic
syenitic
pegmatites
pegmatites can
can also
also be
be identified.
identified. Here
Here the
the gabbros
gabbros
are somewhat
somewhat coarser
coarser than
than those
those seen
seen on
on the
the highway.
highway.
The
The olivines
divines in
in general are
are fresh,
fresh, although the
the plagioclase
crystals
crystals still
still show
show considerable
considerable evidence
evidence of
of readjustment.
readjustment.
On
On the
the coast,
coast, the
the gabbros
gabbros are
are in
in direct
direct intrusive
intrusive
contact
contact with Archean metasediments and often
often contain
contain
inclusions
inclusions of the
the latter.
latter. (Aubut,
(Aubut, 1977)
1977)
The
The Highway section
section however,
however, shows
shows aa third
third zone
zone of
of
rocks
rocks lying
lying between
between the
the gabbro—pegmatite
gabbro-pegmatite grouping
grouping and
and the
the
Archean
Archean country
countrv rocks.
rocks.
Zone 3
I
This
This zone
zone consists
consists of
of quartz
quartz syenite
syenite which
which is
is often
often
seen
seen intruding
intruding aa 'hybrid'
'hybrid' rock
rock of
of overall
overall syenitic
syenitic
mineralogy.
mineralogy.
I
The
The quartz
quartz syenite
syenite is
is yellowish
yellowish to
to pink
pink in
in colour
colour and
and
consists
consists predominantly
predominantly of
of perthite
perthite with
with interstitial
interstitial
quartz
quartz and
and minor proportions
proportions of
of biotite,
biotite, amphibole,
amphibole, zircon
zircon
and
and fluorite.
fluorite. As yet,
yet, we
we do
do not know
know if
if there
there is
is more
I
than
than one
one generation
generation of
of quartz
quartz syenite.
syenite. Thin
Thin veins
veins and
and
dykelets
dykelets are
are seen
seen invading
invading the
the country
country rock.
rock. These
These
syenites
3.
syenites have
have been
been ascribed
ascribed to
to Center
Center 3.
The
The colour
colour of
of the
the 'hybrid'
'hybrid' syenite
syenite of
of this
this zone
zone is
is
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generally
generally purple—brown,
purple-brown, although
although this
this varies,
varies, as
as does
does
the degree to
to which
which it
it is
is invaded
invaded by
by the
the quartz
quartz syenite.
syenite.
�— 16
.
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.
-
. .
This 'hybrid'
'hybrid' syenite
syenite
is
Us
This
..
.
is of problematic
problematic origin.
origin. Lts:..
..-$<
.
, , '
mineralogy is
is syenitic
syenitic consisting
consisting predominantly of
perthitic alkali
alkali feldspars.
feldspars. The large
large red—pink
red-pink alkali
alkali
invariably
feldspar crystals
crystals visible in hand specimens
specimens invariably
have remnant cores
have
cores of
of plagioclase.
plagioclase. The visible mafic
spots, common
spots,
common throughout
throughout the
the rock,
rock, consist
consist of
of biotite
biotite
and/or
amphibole. Texturally the
and/or amphibole.
the rock
rock is
is hornielsic.
hornfelsic.
No later dykes
dykes are
are seen
seen to
to cut
cut this
this zone.
zone.
of quartz
quartz syenitelhybrid
syenite/hybrid
We believe that this zone of
syenite is in fault contact with the
syenite
the banded gabbro—
gabbropegmatite complex
pegmatite
complex of
of zone
dbne 2.
2. We also feel that the
the
quartz
quartz syenite rocks represent a higher structural
structural
level of the intrusion
intrusion and that
that the
the hybrid syenite
syenite
represents aa block
highlymetasomatised
metasomatised country
country rock.
rock.
represents
block of
ofhighly
�I->
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Xs
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000
0000
000 Syenodiorite
iiIlllllIIIii' Nepheline Syenite
/ I -\ ,
\\'i../V
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Olivine
Gabbro ((banded)
"
J.
Olivine
*'
Gabbro
ban
'I ;
Xxxx
X X
Syenite
xx xx Quartz Syenite
¥ Â
•Â0•.••
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''Hybrid
Hybrid Syenite'
syenitel
-------- - Archean Sediments
--- Archean Sediments
Dyke(s)
D
NP
NP
Natrolife Pegmatite
Natrolite
Pegmatite (s)
sP
SP
Syenite Pegmafite
(s)
Syenite
Pegmatite ($1
w
'v\/- '\/\-
Fault
Fault
o0
400
400
800
800
2000 FEET
1200
200 1600
600 2000
FEET
M
600 METRES
600 METRES
400
200
0
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Western Central
Stop 2.
Stop
2. Western
Central Region.
Region
r %______
�--
I
unsubdivided
{b) -—--l porphyritic (Al—Cr Augite)
(c) 2--—--2 acellular
(a)
==
4
6--—-6
layering (in intrusive racks
bedding laps unknawn (inclined
breccia zone (abundant xenoliths)
sa
L o ke
Superior
2..
a
SOUTHWEST MARGIN of the COLDWELL COMPLEX
Sand and Gravel
Pyraxene Horntels (including xenaliths
Gabbra
Augite Syenite
Red Syenile Pegrnatite
calloidal residua
gabbro
Cd) 3—3 parphyritic (resarbed quartz)
4--—--4
porphyritic (feldspar) 5--—-5
lamprophyre
DYKES
—-
_____
'
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23
_
a
ac
after A. Aubut
Z.3
2(0
50
90°
1977
sa
200 METRES
.
an
;_ a us
�I
STOP
STOP
3 LITTLE
LITTLE PlC
PTC LOOKOUT
LOOKOUT
3
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Parking
Parking Lot
Lot
To
seen cliffs
cliffs of
of xenolith
xenolith free
free
To the
the southwest
southwest can
can he
be seen
I
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I
ferroaugite
ferroaugite syenite
syenite along
along the
the west
west bank
bank of
of the
the Little
Little
Plc
Pic River.
River. The
The river
river probably
probably occupies
occupies aa fault
fault zone,
zone,
the
down faulted
faulted block
block of
of Center
Center -- 22
the east
east bank
bank being
being aa down
and
and 33 rocks
rocks from
from higher
higher levels
levels of
of the
the intrusion.
intrusion. To
To
the
the south
south lies
lies the
the Coldwell
Coldwell Penninsula
Penninsula and
and Pie
Pic Island.
Island.
Densely
Densely wooded
wooded shores
shores are
are alkali
alkali gabbro
gabbro and
and nepheline
nepheline
syenite.
syenite. The
The distant
distant barren
barren shores
shores are
are syenite
syenite and
and
quartz
quartz syenites.
syenites.
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Highway
Highway Cuts
Cuts
The
The highway cuts
cuts on
on the
the north
north side
side of
of highway
highway 17
17
provide
provide excellent
excellent examples
examples of
of the
the complex
complex multiple
multiple
igneous
whiah are
aTe characteristic
characteristic of
of the
the Little
Little
igneous breccias
breccias which
Pie
Pic - Redsucker
Redsucker Cove
Cove block.
block. The
The oldest
oldest breccias
breccias are
are of
of
-
Center
rocks, alkali
alkali gabbro
gabbro and
and nepheline
nepheline syenites
syenites
Center 2 rocks,
similar
similar to
to those
those exposed
exposed on
on the
the West
West side
side of
of the
the
These breccias
Coidwell
Coldwell Penninsula.
Penninsula. These
breccia* are
are found
found as
a
large
large xenoliths
xenoliths in
in the
the later
later Center
Center 33 quartz
quartz syenite
syenite
Xenoliths
Xenoliths in
in the
the quartz
quartz syenite
syenite are
are oligoclase
oligocla
basalts
basalts showing
showing all
all stages
stages of
of assimilation
assimilation from
from
relatively
sericitized basalt
basalt to
to almost
almost
relatively unaltered
unaltered sericitized
completely
completely digested
digested xenoliths
xenoliths of
of amphibolite
amphibolite mineralogy.
mineralogy.
Development
Development of
of "clots"
r'clots''of
of biotite
biotite and
and amphibole
amphibole is
is aa
breccias.
breccias.
characteristic
characteristic metasomatic
metasomatic feature
feature of
of the
the xenoliths.
xenoliths.
The
The oligoclase
oligoclase basalts
basalts probably
probably are
are remnants
remnants of
of
Proterozoic
Proterozoic extrusives
extrusives which
which originally
originally capped
capped the
the
complex.
complex.
These outcrops
These
outcrops demonstrate
demonstrate conclusively
conclusively that
that Center
Center
3
quartz syenites
syenites are
3 quartz
are younger
younger than
than Center
Center 22 undersaturated
undersaturated
�g
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rocks.
rocks.
,
Two types
types of
of lamprophyre
l a m p r o p h y ~ ecan
can be
be found
found crosscutting
crosscutting
Two
the breccias.
the
(a) porphyritic
porphyritic lamprophyre,
lamprophyre, characterized
characterized by
by
(a)
greenish phenocrysts
phenocrysts of
of Al—Cr
Al-Cr augite,
augite, possibly
possibly
greenish
of high
high pressure
pressure origin.
origin.
of
(b) ocellular
ocellular lamprophyre,
lamprophyre, characterized
characterized by
by ocelli
ocelli
(b)
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of carbonate,
carbonate, quartz
quartz and
and fluorite.
fluorite.
of
,
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A
hi,
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p
S
p.
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Red quartz syenite with angular to rounded xenoliths
of oligoclase basalt. Xenoliths show all stages of assimilation
from sericitizecj basalt to almost completely digested ,9host
xenoliths of amphibolite. Prominent biotite — amphibole clots"
of metasomatic origin. Nepheline syenite xenoliths.
A
p.
Large xenolith of Centre 2 rocks, biotite gabbo
Large
xenolith
of Centre
2 rocks,
vetned
by nepheline
syenites,
cutbiotite
by pegmatitic
gabbro
veined
by
nepheline
syenites,
cut
by pegmatitic
notrolite syenite dikes. In thin section
biotite
natrolite
syenite
In thincorono
section
biotite
gabbro
showsdikes.
extensie
structures.
•'55
.
gabbro shows extensive corona structures.
• ••
.S
.
'
doo_/
a
Centre 2 rocks veined by
quartz syenite.
<0
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4\
'
4
Red to ye1 low quartz
Red to yellow quartz
syenite breccia,
syenite breccia.
ow
Porphyritic lamprophyre. Alurninous
-
Porphyritic
lamprophyre.
Aluminous
in a cpq
cpx phemcrysts
biotite
cpx
phenocrysts
feldspar
matrix. in a cpx — biotite —
feldspar matrix.
-
Ocellular lompophyres. Ocel li ore corbonoteOcellular
lamprophyres.
Ocelli
are carbonate—
quartz fluorite,
matrix is
amphibole,
cpx ,
quartz — fluorite, matrix is amphibole, cpx,
feldspar,
biotite.
feldspar, biotite.
-
0
50,
100
200 FEET
150
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25
50 METRES
Stop 3.3. Little
Little Plc
Pic River
River Lookout.
Lookout.
Stop
\
quartz syenites
quartz syenites
�STOP
STOP 44
-
-
BRECCIA
BRECCI DIKES
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At
At this
this locality
locality are
are found
found several
several natrolite
natrolite
syenite
These dikes
dikes are
are of
of variable
variable
syenite breccia
breccia dikes.
dikes. These
thickness,
thickness, they pinch and
and swell
swell and
and terminate
terminate in
in
thin
thin natrolite
natrolite syenite
syenite veins.
veins. Bifuroations
Bifurcations of
of the
the
dikes
dikes are
are common.
common. The
The outcrop
outcrop of the
the dikes
dikes are
are sinuous
sinuous
and give
impreesion that they may have been em—
emgive the
the impression
placed
placed in
in relatively
relatively plastic
plastic host
host rocks.
rocks. The
The thicker
thicker
portions of the
the dikes
dikes are
are crowded
crowded with dark grey
xenoliths
xenoliths set
set in
in aa fine
fine grained
grained reddish
reddish natrolite
natrolite
syenite.
syenite. As the
the dikes
dikes thin the amount of xenolith
decreases
decreases and the terminating veins are composed
composed of
xenolith
coarse grained
xenolith free coarse
grained natrolite
natrolite syenite.
syenite. The
The
xenoliths
xenoliths are
are rounded
rounded to
to very
very irregular
irregular in
in shape.
shape.
Crenulated margins
Crenulated
margins are
are typical.
typical. No angular
angular xenoliths
xenoliths
are present although the wedging action of the syenite
syenite
on
comonly
on the xenolith causing
causing further
further fragmentation
fragmentation is commonly
visible.
visible. The
The shape
shape of
~f the
the xenoliths
xenoliths is
is considered
considered to
to
be the result
result of brecciation and corrosion both in situ
situ
and
and during
during transport.
transport.
The
The xenoliths
xenoliths are
are of
of two
two types,
types, the
the most abundant
abundant
being
being a fine
fine grained dark grey rock which in thin section
section
is seen
of amphibole and mica,
mica, alkali
composedo€amphibo
alkali
seen to
to be
be composed
sericitized
feldspar
feldspar and plagioclase.
plagioclase. Rare relict sericitized
phenocrysts
The xenolith
xenolith
phenocrysts of
of plagioclase
plagioclase are
are present.
present. The
margins
margins are enriched in amphibole and mica relative
relative to
the
5 mm. in
the interior.
interior. Rounded aggregates of mica up to 5
diameter
diameter are
are common.
common. Although the
the xenoliths
xenoliths have
have been
been
bear a resemblance
extensively
extensively metasomatized they be+r
resemblance to the
the
western end
metavolcanic xenoliths
metavolcanic
xenoliths seen
seen at
at Stop
Stop 3.
3. At the western
of
of the
the outcrop
outcrop occur xenoliths which consists
consists of rounded
aggregates of greenish mica set in a matrix of pale green
aggregates
pyroxene
clinopyroxene and
clinopyroxene
and minor
minor oligoclase.
oligoclase. Rare euhedral pyroxen
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�1
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phenocrysts are
are found.
found. The
The mica
mica "rosettes"
"rosettes" are
are the
the result
result
phenocrysts
No comparable
comparable rocks
rocks
of intense
intense metasomatism
metas~matism
ofpyroxenite.
pyroxenite. No
of
of
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are known
known elsewhere
elsewherein
inthe
theintrusion.
intrusion.
are
The
The matrix
matrix of
of the
the dikes
dikes is
is aa leucocratic
leucocratic natrolite
natrolite
syenite composed
composed of
of alkali
alkali feldspar
feldspar (patch
(patch perthites)
perthites)
syenite
with
with albite
albite replacements,
replacements,natrolite,
natrolite,minor
minor green
green alkali
alkali
amphibole
amphibole and
and accesory
accesory zircon
zircon and
and fluorite.
fluorite.
The host
host rock
rock of
of the
the dikes
dikes is
is aa leucocratic
leucocratic syenite
syenite
The
composed
perthite, minor
minor amphibole
amphibole and
and accessory
accessory
composed of
of patch
patch perthite,
zircon and
and fluorite.
fluorite. Although
Although natrolite
natrolite has
has not
not yet
yet been
been
zircon
observed
observed these
these rocks
rocks bear
bear aa remarkable
remarkable mineralogical
mineralogical
These rocks
rocks have
have
similarily to
to the
the matrix
matrix of
of the
thedikes.
dikes. These
similarily
been
been intruded
intruded by
by aa very
very dark
dark quartz
quartz syenite.
syenite.
The breccia
breccia dikes
dikes are
are considered
considered to
to be
be intrusive
intrusive
The
breccias,rather
rather than
than multiple
multiple intrusions,
intrusions, connected
connected
breccias,
tabular lamprophyre
lamprophyre dike
dike can
can
activity. AA tabular
with Center
Center 22activity.
with
be
be observed
observed at
at the
the eastern
eastern end
end of
of the
the outcrop.
outcrop.
�r
STOP
STOP 55
-
--
MINK
MINK CREEK
CREEK -- REDSUCKER
REDSUCKER COVE
COVE
-- NEPHELINE
NEPHELINE SYENITES
SYENITES
-
--
r
This
This area
area is
is located
located at
at the
the eastern
eastern margin
margin of
of the
the
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faulted
faulted block
block characterized
characterized by
by extensive
extensive igneous
igneous breccia
breccia
development.
development. Here
Here the
the arcuate
arcuate structure
structure defined
defined by
by the
the
gabbros
gabbros and
and
by
Center
by Center 33
nepheline
nepheline syenites
syenites of
of Center
Center 22 is
is truncated
truncated
quartz
syenite.
quartz syenite. The
The Center
Center 22 rocks
rocks contain
contain
abundant
abundant xenoliths
xenoliths of
of earlier
earlier rocks,
rocks, whilst
whilst the
the Center
Center
33 rocks
rocks are
are relatively
relatively xenolith
xenolith free.
free.
Biotite
Biotite gahbros
gabbros are
are the
the oldest
oldest rocks
rocks at
at this
this locality
locality
and
are
found
as
greenish
massive
coarse
grained
to
and are found as greenish massive coarse grained to
pegmatitic
pegmatitic rocks
rocks which
which in
in many
many places
places are
are commonly
commonly
brecciated
brecciated and
and veined
veined by
by natrolite—nepheline
natrolite-nepheline syenites.
syenites.
The
The gabbros
gabbros are
are composed
composed of
of hortonolitic
hortonolitic olivines,
olivines,augite,
augite,
plagioclase
plagioclase (andesine—labradotite)
(andesine-labradotite) biotite
biotite and
and alkali
alkali
feldspar
feldspar which
which in
in some
some examples
examples becomes
becomes sufficiently
sufficiently
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abundant
abundant that
that the
the rocks
rocks should
should be
be termed
termedsyenodiorite,
syenodiorite.
Corona
Corona structures
structures of
of alkali
alkali amphibole
amphibole and
and biotite
biotite are
are
comnionlv
developed around
commonly developed
around olivine
olivine and
and augite.
augite.
The
The nepheline
nepheline syenites
syenites are
are leucocratic
leucocratic rocks
rocks
containing
containing patch
patch perthites,
perthites, nepheline
nepheline and/or
and/or natrolite
natrolite
together
together with
with acicular
acicular crystals
crystals of
of hastingsitic
hastingsitic
amphiboles.
Quartz
Quartz syenites
syenites in
in this
this area
area are
are reddish
reddish rocks
rocks which
which
have
have been
been extensively
extensively brecciated
brecciatedand
andsheared.
sheared.
At
At the
the localities
localities shown
shown can
can be
be found
found the
the following:—
following:A.
A.
of
of carbonate
carbonate ocelli
ocelli into
into the
the upper
upper portions
portions of
of the
the
dike,
dike, aa characteristic
characteristic feature
feature of
of many
many of
of the
the
lamprophyres
lamprophyres in
in this
thisarea.
area.
I
B.
B.
I
AA lamprophyre
lamurophyre dike
dike which
which illustrates
illustrates the
the segregation
segregation
AA lamprophyre
lampro~hyredike
dike which
which illustrates
illustratesthe
the intense
intense
metasomatism
metasomatism associated
associated with
with many
many of
of the
the Coldwell
Coldwell
minor
minor intrusions.
intrusions. The
The metasomatism
metasomatism is
is manifested
manifested
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�—25—
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C.
D.
D.
E.
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by
by aa "reddening"
"reddening" of
of the
the host
host rock
rock feldspars.
feldspars. Widths
widths &
of
of the
the metasomatic
metasomatic zones
zones are
are commonly
commonly much greater
greater
than
than the
the width
width of
of the
the dike
dike causing
causing the
the alteration.
alteration.
Igneous
Igneous breccia.
breccia. Xenoliths
Xenoliths of
of greenish
greenish biotite
biotite
gabbro
gabbro in
in natrolite—nepheline
natrolite-nepheline syenite.
syenite.
Hybrid
Hybrid grey
grey syenites.
syenites.
Coarse grained amphibole—nepheline—natrolite syenites.
�P
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U
. .. . . . .
.. . . .. .. . . .
I
1*: :.•..I QUARTZ SYENITE
NEPHELINE SYENITE
SYENITE with gabbro
gabbro and
and
NEPHELINE
metavolcanic
metavolcanic xenohths
xenoliths
j £j
--
BIOTITE GABBRO as massive rock or
in nepheline syenite
— — Lineaments
Lineaments
I
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0
-
0
1
200
I
400
I
600 METRES
Redsucker
Cove
Stop 5. Mink Creek
—
. ..... ..
. .. :
., .'
...
..
- : . .... .. .. . .....
.. . ... . :.. . . .....1 ' .
/2 MILE
1(4
Redsucker Cove.
n
'
sTS
�r
STOP 66 -STOP
-
FERROAUGITE SYENITE
SYENITE
QUARRY AND ROAD CUTS, HIGHWAY 17
FERROAUGITE
- QUARRY AND ROAD CUTS, HIGHWAY 17
--
I
I
Ferroaugite syenite was formerly quarried at Marathon
Ferroaugjte
syenite was formerly quarried at Marathon
for use
use as
as aa building
building stone
stone under
under the
the name "laurvekite", a
for
name ttlaurvekite, a
term first
first used
used by
by Kerr
Kerr (1910)
(1910) because
because of the supposed
term
of the supposed
I
similarity between
between the
the Coidwell
Coldwell complex
complex and rocks of the
similarity
and rocks of the
Oslo
igneous
province.
Unfortunately
this
term has
has permeated
permeated
Oslo igneous province. Unfortunately this term
much of
of the
the geological
geological literature
literature concerning
concerning the Coldwell
much
the Coldwell
I
complex..
complex..
j
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~3,
The only similarity in fact between the Coldwel
The only similarity in fact between the Coldwell
ferroaugite
syenites and the Oslo larvikites is the
ferroaugite syenites
and the Oslo larvikites is the
presence
of
cryptoperthitic
intergrowths which impart an
presence of cryptoperthitic intergrowths which impart an
intense schiller
schiller to
to the
thefeldspars.
feldspars. The Oslo larvikites
intense
The Oslo larvikites
are monzonitic
monzonitic rocks
rocks which
which grade
gradeinto
intonepheline
nephelineplagi—
plagi
are
foyaite (lardalite).
(lardalite). They do not show extreme iron
foyaite
They do not show extreme iron
chment nor
nor do
do they
they differentiate
differentiateto
tooversaturated
oversaturatedresidua.
enrichment
residua.
The
quarry
at
this
stop
exposes
highly
weathered
The quarry at this stop exposes highly weathered
oaugite syenite and illustrates the typical deep1
ferroaugite syenite and illustrates the typical deeply
weathered friable
friableappearance
appearance of
of ferroaugite
ferroaugite syenite
weathered
syenite
away
from
the
polished
glaciated
outcrops
on
the lake
away from the polished glaciated outcrops on the
lake
shore (Stop
(Stop8).
8).
shore
The fresh ferroaugite syenite exposed in the roa
The fresh ferroaugite syenite exposed in the road
cut
to
the east
east of
of the
the quarry
quarry is
is an example of one of
cut to the
an example of one of
I
the most highly differentiated .portionsof the ferrothe
most highly differentiated portions of the ferroaugitesyenite.
syenite. Olivines are fayalite (FaQ4Tp4F02),
augite
Olivines are fayalite (Fa94Tp4Fo2),
pyroxenes are light greenish brown ferroaueite (Di
pyroxenes
are light greenish brown ferroaugite (Di10Hd85
1oHd85
I
I
I
zoned to
to acmitic—hedenlergite
acmitic-hedenbergite(Ac50Hd50).
(Ac50Hd 50) . Amphiboles
Ac 5 ) zoned
Ac5)
Amphiboles
are
light
green
ferrorichterite
(Na2CaFe5Si8On2(OH),,)
are light green ferrorichterite (Na2CaFe5Si8o22(O}J)2)
with minor
minor mantles
mantles of
of arfvedsonite
arfvedsonite (Na3Fe5Si8O29(0H)2)
(Na3Fe,Si8022(OH)2)
with
Aenigmatite (Na2Fe5TiSi6O20) is abundant and calcite
and quartz can he found as interstitial residual phases.
I
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— 27
—
�STOP
STOP 77
-
-
GABBRO
GABBRO
p
I
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The
The arcuate
arcuate mass
mass of
of basic
basic rocks
rocks which
which define
define the
the
eastern
eastern margin
margin of
of the
the complex
complex is
is commonly
commonly referred
referred to
to
as
as the
the eastern
eastern gabbro
gabbro to
to distinguish
distinguish it
it from
from the
the
alkaline
2. This
This eastern
eastern gabbro
gabbro is
is
alkaline gabbro
gabbro of
of Center
Center 2.
considered
considered to
to belong
belong to
to Center
Center 11 activity
activity as
as it
it is
is
intruded
intruded in
in many
many places
places by
by ferroaugite
ferroaugitesyenite.
syenite. The
The
petrological
petrological relationship
relationship between
between the
the two
two magmas
magmas is
is
however
unclear.
however unclear. Ferroaugite
Ferroaugite syenite
syenite is
is unlikely
unlikely to
to be
b
aa direct
direct differentiate
differentiate of
of the
the gabbro
gabbro because
because of
of the
the
greater
greater volume
volume of
of the
the former
former and
and lack
lack of
of mineralogical
mineralogical
gradations
gradations between
between the
the two
two rock
rock types.
tyoes. The
The zone
zone of
of
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gabbro
gabbro defines
defines aa prominent
prominent magnetic
magnetic low
low on
on figure
figure lB
1B and
and
is
is considered
considered by
by Lilley
Lilley (1964)
(1964) to
to be
be due
due to
to reversed
reversed
magnetization
magnetization of
of the
the gabbros.
gabbros. The
The gabbros
gabbros are
are composed
composed
of
plagioclase (An6035)) and
) , augite,
augite, plagioclase
and
of olivine
olivine (Fo67_43),
minor
minor orthopyroxene
orthopyroxene (Efls5rc)
(En55-..c
) (Lum,
(Lum,1973).
1973). The
The ortho—
orthopyroxene
pyroxene may
may be
be aa product
product of
of assimilation
assimilation of
of Archean
Archean
metasediments,
metasediments, aa xenocryst
xenocryst derived
derived frpm
from the
the pyroxene
pyroxene
hornfels
hornfels thermal
thermal aureole
aureole or
or aa relict
relict high
high pressure
pressure
phase.
phase. The
The gabbro
gabbro has
has been
been extensively
extensively prospected
prospected with
with
regard
regard to
to its
its copper
copper potential
potential as
as accumulations
accumulations of
of
pyrrhotite
pyrrhotite and
and chalcopyrite
chalcopyrite with
with minor
minor pentlandite,
pentlandite,
cubanite,
cubanite, pyrite,
pyrite, bornite,
bornite, arsenopyrite
arsenopyrite and
and mackinawite
(vatkinson
(Watkinsonet
et al.
al. 1973,
1973, Lum,
Lum, 1973)
1973) are
are common.
common.
The
The excursion
excursion stop
stop is
is close
close to
to the
the contact
contact between
between
the
the gabbro
gabbro and
and the
the ferroaugite
ferroaugitesyenite.
syenite. Many
Many pegmatites
pecmatites
of
of ferroaugite
ferroaugitesyenite
syenitecut
cut the
the gabbro
gabbroat
at this
thislocality
locality
and
and demonstrate
demonstrate that
that the
the gabbro
gabbro is
is the
the earliest
earliest activity
activity
present
present in
in the
thecomplex.
complex. The
The gabbro
gabbro is
is widely
widely variable
variable
in
in appearance
appearance due
due to
to the
the presence
presence of
of variable
variable amounts
amounts
of
of Archean
Archean xenoliths.
xenoliths. At
At this
this location
location the
the gabbro
gabbro shows
shows
all
all transitions
transitions from
from massive
massive homogenous
homogenousgabbro
gabbroto
torocks
rocks
I
I
I
-28-
�1
I-
-3
F-Q
CD
O
P
CO
-C
CD
CD
CD
P
o
c-f
CD
0
0
H-
CO
C
p
H- Q
o
ow
ci-
CD
CD
.w wc
p
P0
<p
CO CD
H
CD
H,
o
ci-
H-
OqGq
lipli
(t
ci-
CD
—
CD
ot
(DO
-C
-C
CD
CD
0
ci-
w
CD
—
—
CD
P'
CD
o
c-I-
c-I-p
c*
0
c*
Elill
—
F"
tt
pa
____
____
____
w i t h w e l l developed igneous l a y e r i n g . The l a y e r s a r e
not t r a c a b l e o v e r l a r g e d i s t a n c e s and do not s e r v e t o
o u t l i n e t h e s t r u c t u r e o f t h e gabbro i n t r u s i o n .
�a
STOP
STOP 88 -- LAKE
LAKE SUPERIOR
SUPERIOR SHORE
SHORE LINE
LINE CENTER
CENTER 11
- PLUTONIC
PLUTONIC
-
ROCKS
ROCKS AND
AND MINOR
MINOR INTRUSIONS
INTRUSIONS
I
Proceed
Proceed fron
from the
the parking
parking lot
lot at
at the
the foot
foot of
of Howe
Howe
St.,
St., Marathon
Marathon along
along the
the trail
trail through
through the
the woods
woods to
to avoid
av
the
the boulder
boulder beach.
beach. The
The trail
trail emerges
emerges at
at location
location F,
F , from
from
that
that point
point follow
foil the coast to
to location A.
I
Location
AA
Location
~Hornfelsed
Hornfelsed Archean
Archean metasediment
metasediment cut
cut by
by analcite
I
,
I
tinguaite
tinguaite dikes.
dikes. These
These rocks
rocks were
were initially
initially described
described
by
by Coleman
Coleman (1900)
(1900) as
as heronites.
heronites. The
The tinguaites,
tinguaites, after
after
I
lamprophyres,
lamprophyres, are
are the
the second
second most
most abundant
abundant type
type of
of
minor
minor intrusion
intrusion at
at Coidwell
Coldwell and
and are
are probably
probably associated
associated
with
magmatism. Xenoliths
Xenoliths
with the
the undersaturated
undersaturated Center
Center 22 magmatism.
I
of
of coarse
coarse grained
grained nepheline
nepheline syenite
syenite can
can be
be found
foundin
in
some
some examples
examples at
at Heron
HeronBay.
Bay. The
The majority
majority of
of the
the tinguaites
tinguaites
I
I
are
are intensely
intensely hematized
hematized and
and carbonatized,
carbonatized,are
are very
very fine
fin
grained
grained and
and brick
brick red
red to
to dark
dark reddish—brown
reddish-brownin
incolor.
color.
At
At this
this locality
locality is
is found
found aa relatively
relatively fresh
fresh 3—4
3-4 ft.
ft. wide
vertical
vertical dike.
dike. Black
Black margins
margins with
with conchoidal
conchoidalfractures
fractures
may
may represent
represent an
an original
original chilled
chilled glassy
glassy margin.
margin. The
The
tinguaite
tinguaite is
is porphyritic
porphyritic with
with phenocrysts
phenocrysts of
of pale
pale green
green
I
I
ferroaugite
ferroaugite with
with titan—acmite
titan-acmite rims,
rims, brown
brown hastingsite
hastingsite and
and
anorthoclase
anorthoclase set
set in
in very
very fine
fine grained
grained groundmass
groundmassof
of
apatite,
apatite, acicular
acicular pyroxene,
pyroxene, hematized
hematized feldspar,
feldspar,fluorite
fluorite
and
and analcite.
analcite.
I
I
Location_B
Location B
-
Glomeroporphyritic
Glomeroporphyritic diabase
diabase representative
renresentativeof
of the
the
post-Coldwell
post-Coldwell alkali
alkali basaltic
basalticmagma
magma activity.
activity. The
The
glomeroporphyritic
glomeroporvhyritic feldspars
feldspars are
are labradorite
labradoriteset
set in
in aa
I
groundmass
groundmass of
of andesine
andesine and
and aluminous
aluminousaugite
augite(8%
(8%A1203).
Alp03).
Several
Several thin
thin ocellular
ocellular lamprophyre
lamprophyredikes
dikescan
canbe
be
I
I
-30-
,
�-3'-
P
observed between locations A and B.
I
I
I
Location C
Location
I
Ocelli in these
observed between locations A and B.
rocks contain quartz plus calcite orOcelli
dolomite.
in these
rocks contain quartz plus calcite or dolomite.
Extensive deposits of sand and gravel cover the
Extensive
deposits
of sand and
and the
gravel
contact between
the intrusion
Archean
covercountry
the
contact
between
the
intrusion
and
the
rocks and no outcrops are found between
locations
B
Archean
country
rocks and no outcrops are found between
and C. The area however presents excellent
exposures
locations
B
and C.
The
area
however
presents
excellent
of the lowest of the six beach terraces at exposures
Marathon.
of the lowest of the six beach terraces
at Marathon
c
Xenolith bearing gabbro considered to be equivalent
Xenolith bearinggabbro
gabbroobserved
considered
to be7.equivalent
to the hypersthene
at Stop
to the hypersthene gahbro observed at
Stop 7.
Location
-
Location
I
I
I
I
D
0
Fayalite-ferroaugite syenite with well dev
Fayalite_ferroaugite
with well
developed
igneous layering defined syenite
by the mafic
minerals.
Crossigneous layering defined by the mafic minerals.
bedding, slump structures, and diffuse turbulentCross—
layering
bedding, slump structures, and diffuse
are all well developed in this area. turbulent layering
are all well developed in this area.
The mafic minerals
ferroaugite, and
amphiboles
belonging toare
thefayalite,
ferroedenite-hastingsite
amphiboles belonging to the ferroedenite_hastingsite
series (NaCa2Fe5Si~102~OH)2-NaCa2Fe5SinA1202(OH)2).
series (NaCa2Fe5si7Alo22(OH)_NacaFesiAlo(0H))
Location E
Location E
Ferroaugite syenites representative of the more
I
I
I
I
I
I
Ferroaugite syenites representative of the
extreme
differentiates of this magma. Pyroxenes
more
are
extreme differentiates of this magma.
members of the acmite-hedenbergite series
and amphiboles
Pyroxenes
are
members of the acmite_hedenbergite
series and amphiboles
are subaluminous ferroedenite (NaCa2Fe5Si7.5Alo.
are suhaluminous ferroedenite (NaCa2Fe5si7Alo(OH))
or ferrorichterite (Na2CaFe3Si8o2 (OH)
(Na2Fe5Tisi6O)
is
)
abundant.
Aenigmatite
�— 32
—
Location FF
Location
Ferroaugite syenite cut by very coarse patch and
Ferroaugite
syenite cut by very coarse patch and
I
sheet pegmatites. The pegmatites illustrate the oversheet pegmatites.
The pegmatites illustrate the oversaturated nature of the ferroaugite syenite differentiation
saturated
nature of the ferroaugite syenite differentiation
trend, and contain ferrorichterite altering to ferrotrend, and contain ferrorichterite altering to ferro—
I
actinolite,
i
I
I
I
I
I
I
I
I
I
I
I
I
I
C
feldspars, quartz and zircon.
�I
parking lot
ii
I
I
I
I
I
I
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F
FERRQ4UGITE
SYENITE
C,
/
/
/
0
I-
0
1/2
500
4-
J
1000
Mile
1500 Metres
4RCHE4N
Stop 8. Layered
Ferroaugite__Syenites.
�.
r
~
.
REFERENCES
REFERENCES
I
I
•
•
I
I
I
I
I
I
I
I
I
Aubut,
Aubut, A.J.
A.J. (1977):
(1977): Geology
Geology of
of the
the southwestern
southwestern margin
margin
of
of the
the Coidwell
Coldwell alkaline
alkaline complex,
complex. Northwestern
Northwestern
Ontario.
Ontario. H.B.Sc.
H.B.Sc. Thesis,
Thesis, Lakehead
Lakehead Univ.,
Univ.,
Thunder
Thunder Bay,
Bay, Ontario.
Ontario.
Ayres,
Ayres, L.D.,
L.D., Lumbers,
Lumbers, S.B.,
S.B., Mime,
Milne,V.G.,
V.G.,and
andRoherson,
Roberson,
D.W.
D.W. (1970):
(1970): Ontario
Ontario Geological
Geological Map.
Map. East
East
Central
2198a.
Central Sheet,
Sheet, Ontario
Ontario Dept.
Dept. Mines
Mines Map,
Map, 2198a.
Balint,
1 dwell alkaline
Balint,F.
F. (1977):
(1977): The
The Neys
Neys diatreme,
diatreme, Co
Coldwell
alkaline
complex,
o. H.B.Sc.
complex, Northwestern
Northwestern Ontari
Ontario.
H.B.Sc. Thesis,
Thesis,
Lakehead
Univ.,
Thunder
Bay,
Ontario.
Lakehead Univ., Thunder Bay, Ontario.
Card,
Card, K.D
K.D., Church,
Church. W.R.,
W.R., Franklin,
Franklin,J.M.,
J.M., Frarey,
Frarey, M.J.,
M.J.,
Robertson,
J.S., West,
West, G.F.,
G.F., and
and Young,
Young, G.M.
G.M.
Robertson,J.S.
(1972):
hem
Province.
Variations
(1972): The
The Sout
Southern
Province. In
In : Variations
in
in Tectonic
Tectonic Style
Style in
in Canada.
Canada. Eds,,
Eds., Price,
Price,R.A.,
R.A.,
and
and Douglas,
Douglas.J.W.
J.W. Geol.
Geol. Assoc.
Assoc. Canada
Canada Spec.
Spec.
Paper
Paper 11,
11,335—380.
335-380.
:
Coleman,
Coleman, A.P.
A.P. (1900):
(1900):
ileronite
Heronite or analcite
analcite tinguaite.
tinguaite.
Ann.
Rept.
Bur.
Mines
Ontario
9,186—191.
186-191.
Ann. Rept. Bur. Mines Ontario 9,
Currie,
Currie,K.L.
K.L. (1976):
(1976): The
The alkaline
alkaline rocks
rocksof
of Canada.
Canada.Geol.
Geol.
Surv.
Surv. Canada
CanadaBull.
Bull., 239.
239.
,
Einarrson, G.W.
G.W. (1973):
(1973): Variations
Variations in
in the
the style
styleof
of
metamorphism
in
Archean
supracrustal
units
metamorphism
in
Archean
supracrustal
units
Einarrson,
of
of the
the Superior
Superior Province.
Province. H.B.Sc.
H.B.Sc.Thesis,
Thesis,
Lakehead
Univ.,
Thunder
Bay,
Lakehead Univ., Thunder Bay,Ontario.
Ontario.
Gittins,
Gittins,J.,
J., MacIntyre, R.M., and York, D. (1967): The
ages
ages of
of carbonatite
carbonatite complexes
complexes in
in eastern
eastern
Canada.
J. Earth
EarthSci.
Sci. 4,
4,651—655
651-655.
Canada. Canad.
Canad.J.
Halls,
Halls,H.C.,
H.C.,and
and West,
West.G.F.
G.F.(1971):
(1971):
AA seismic
seismic refraction
refraction
survey
survey in
in Lake
Lake Superior.
Superior. Canad.
Canad. J.
J. Earth
Earth Sd.
Sci.
8,
8,610—630.
610-630.
Kerr,
Kerr,H.L.
H.L.(1910):
(1910): Nepheline
Nepheline syenites
syenites of
of Port
Port ColdwelL
Coldwell.
Ann.
Ann. Rept.
Rept. Bur.
Bur. Mines
Mines Ontario,
Ontario,19,
19,194-232.
194-232.
I
I
I
— 33
—
�ri
Lilley,
Lilley, F.E.M.
F.E.M. (1964);
(1964):
An analysis
analysis of
of the
the magnetic
magnetic
An
features
features of
of the
the Port
Port Coidwell
Coldwell intrusive,
intrusive.
M.Sc,
M.Sc. Thesis.
Thesis. Univ.
Univ. Western
Western Ontario,
Ontario. London,
London.
I
I
Ontario.
Ontario.
Lum,
Lum, H.K.
H.K. (1973):
(1973): Petrology
Petrology of
of the
the eastern
eastern gabbro
gabbro and
and
associated
associated sulphide
sulphide mineralization
mineralization of
of the
the
Coldwell
Coldwell alkalic
alkaliccomplex.
complex. B.Sc.
B.Sc. Thesis,
Thesis,
Carleton,
Carleton, Univ.
Univ., Ottawa,
Ottawa, Ontario,
Ontario.
,
I
'
Milne,
Milne,V.G.
V.G. (1967):
(1967):
Geology
Geology of
of the
the Cirrus
Cirrus Lake—Bamoos
Lake-Bamoos
Lake
Lake area.
area. Ontario
Ontario Dept.
Dept. Mines,
Mines,Rpt.
Rpt.43.
43.
Mitchell,
and Platt,
P1att, R.G.
Mitchell,11.11.,
R.H., and
R.G. (1977):
(1977):
Mafic mineralogy
mineralogy
Mafic
of
of ferroaugite
ferroaugite syenite
syenite from
from the
the Coidwell
Coldwell alkaline
alkaline
I
I
I
I
I
I
complex!
complex. 23rd
23rd Ann.
Ann. Instit.
Instit.Lake
LakeSuperior
SuperiorGeology,
Geology,
Thunder
ThunderBay
Bay (abstract).
(abstract).
Puskas,
Puskas, P.P.
F.P. (1967):
(1967): The
The geology
geology of
of the
the Port
PortColdwell
Coldwellarea
area
Ontario
.No.
Ontario Dept.
Dept. Mines
Mines Open
Open File
FileRpt
Rpt.
No.5014,
5014,
Thunder
Thunder Bay,
Bay,Ontario.
Ontario.
Thompson,
Thompson, J.E.
J.E. (1931)
(1931)- Geology
Geology of
of the
theHeron
HeronBay
Bayarea.
area.
Ann.
Rept.
Ontario
Dept.
Mines,
40,
21—39.
Ann. Rept. Ontario Dept. Mines. 40. 21-39.
Walker,
Walker,J.W.R.
J.W.R. (1967):
(1967): Geology
Geology of
of the
theJackfish-Middleton
Jackfish-Middl
area,
area,Ontario
OntarioDept.
Dept.Mines
MinesGeol.
Geol.Rpt.
Rpt.50.
50.
Watkinson, ,D.H.,
D.H.,Mainwaring,
Mainwaring,P.R.,
P.R.,and
andLum,
Lum,H.K.
H.K.(1973):
(1973):
Petrology
Petrology and
and copper
copper mineralization
mineralizationof
ofthe
the
Coldwell
Coldwellcomplex,
complex.Ontario.
Ontario. Geol.
Geol.Soc.
Soc.Amer.
Amer.
Abs.
Abs. Ann.
Ann.Mtg.
Mtg. 5,
5,856.
856.
ACKNOWLEDGEMENTS
ACKNOWLEDGEMENTS
I
I
I
I
Research on the
thepetrogenesis
petrogenesisof
ofalkaline
alkalineintrusions
intrusions
in
in Northwestern
Northwestern Ontario
Ontariois
issupported
supportedby
by the
theNational
National
Research
ResearchCouncil
CouncilofofCanada.
Canada.
Sam
SamSpivak
Spivakis
isthanked
thankedfor
fordrafting
draftin services involved
in
in the
theproduction
productionof
ofthis
thisguide
guidebook.
book.
�a
8
(4)
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Text
Iwety Ihipti
Aonoal
Institute
Meeting
Thunder
Bay, Ontario
Superior
PROTEHOZOIC TRIP
�PROTEROZOIC ROCKS OF THE THUNDER BAY AREA
NORTHWESTERN ONTARIO
May 3—4,
11.977
FIELD EXCURSION GUIDE
PREPARED BY
C.R. Kustra, Ontario Ministry of Natural Resources
W.H. Mcllwaine, Petro-logic Limited, Thunder Bay
K.G. Fenwick, Ontario Ministry of Natural Resources
J. Scott, Ontario Ministry of Natural Resources
�1
Guide to the Proterozoic Rocks of the Thunder Bay Area,
Northwestern Ontario
INTRODUCTION:
The Proterozoic rocks of Northwestern Ontario, which form part of
the itAnimikiet and !TKeweenawantt units, represent one of the most
complete geological records of Middle and Late Precambrian sedimentation
and igneous activity in eastern North America. These rocks are virtually
unmetamorphosed and relitively undeformed.
Mineral depsits in the Proterozoic rocks include silver in
Keweenawan dikes and the Rove Formation, iron in the Gunf lint Formation,
nickel in mafic intrusive rocks, copper in various volcanic and
sedimentary strata, and lead-zinc-barite, amethyst and uranium associated
with the Sibley Group. During the last century, the famous Silver Islet
mine produced over 2.8 million ounces of silver.
REGIONAL GEOLOGY
The Proterozoic rocks lie unconformably on the peneplained Early
Early
Precambrian (Archean) surface of the Superior Structural Province.
Precambrian rocks form several northeast-trending "belts" of metamorphosed
and complexely deformed metavolcanic and metasedimentary rocks intruded
by felsic, and intermediate to ultramafic intrusive rocks.
The lithostratigraphy of the Proterozoic rocks is shown in Table 1.
API-JEBIAN
The Gunflint Formation (Fig. 2) has been studied by Goodwin (1956,
1960) and Moorhouse (1960). The petrology has been studied in detail by
Floran and Papike (1975).
Detailed descriptions of fossils from the
Gunf lint Formation are recorded by Barghoorn and Tyler (1965), Barghoorit
(1971) and Edhorn (1973). The Rove Formation has been described by
Morey (1969) and Geul (1970, 1972). Much of the descriptive detail is
taken from these authors.
Gunf lint Formation (adapted from Goodwin, 1956)
The Gunflint Formation extends continuously for 110 miles (177km)
from Gunflint Lake east to beyond Thunder Bay, from where it can be
traced intermittently to the Slate Islands, (Sage et al 1975), southeast
of Schreiber.
It averages 400 feet (122 m) in thickness (Goodwin, 1956)
Except for local faulting and brecciation caused by intrusive activity
and slumping, the Gunf lint Formation is structurally simple and uncomplicated, with an average southeast dip of 5°.
�2
TABLE 1
Proterozoic Stratigraphy of Northwestern Ontario
Neohelikian
Osler Group:
basalt, minor rhyolite and sedimentary rocks
Intrusive Rocks:
gabbro stocks
undersaturated stocks
Iayered bodies
northeast trending dykes
Logan diabase sills
Paleohelikian
Sibley Group:
Kama Hill Formation
Rossport Formation
Pass Lake Formation
Aphebian
Animikie Group:
Rove Formation:
shale, greywacke
Gunflint Formation:
iron formation (taconite) algal chert,
limestone, tuffaceous shale.
TABLE 2
Stratigraphy of the Gunf lint Formation
(modified from Goodwin, 1956)
Limestone-dolomite Member
Upper Member
Taconite-chert carbonate submember:
taconite (west) facies
chert carbonate (east)
facies
Tuffaceous shale submember
Algal chert submember
Lower Member
Taconite-chert carbonate submember:
Tuffaceous shale submember
Algal chert submember
Kakabeka Conglomerate Member
west taconite facies
chert carbonate facies
east taconite 1 acies
�Fig. I
LII
UPPER TACONITE i
—
-
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20
•
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S ••••
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F 40
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LOWER EAST TACONITE
-
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Thunder Bay
Slate River
UPPER TUFF ARGILL1TE
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Northeast
Longitudinal section of the Gunf lint formation. (after Goodwin ,1956).(Rove fm. added by author).
Stops described in field guide
BASAL CONGLOMERATE MEMBER
LOWER WEST TACONITE
—urrLn P4L%)ML .ncni-—
MEMBER ci'-
LOWER
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UPPER
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SLATE RIVER
HWY 61, SW. OF CLOUD LAKE ROAD
I
2
5
KAKABEKA FALLS (SWIM AREA)
KAKABEKA FALLS RIM (WEST SIDE)
KAKABEKA FALLS (HYDRO SPILLWAY)
6
DICKSONS QUARRY (BELROSE ROAD)
7
—S,
HILLCREST PARK (HIGH STREET)
BOULEVARD LAKE ( LYONS BRIDGE)
THUNDER BAY LOOKOUT (EXPRESSWAY)
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STOP LOCATION
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Fig 2 Geology and
Field Stop Locations
a
�5
Deposition of the Gunflint Formation was in part cyclical. A basal
conglomerate member is overlain by two members each composed of chert,
tuffaceous shale, and carbonate-taconite submembers. These members are
in turn overlain by a discontinuous limestone member, (Fig. 1 and Table 2).
Although no isotopic investigation has satisfactorily established the
time of sedimentation, various studies suggest that deposition of Animikie
sediments took place 2,000 m.y. B.P. (Floran and Papike, 1975).
Stratigraphic Descriptions
(a) Basal Kakabeka Conglomerate Member
This member ranges to five feet (1.5 m) in thickness and is composed
of polymictic conglomerLte. Clasts of Archean volcanic rocks, granite
and quartz are cemented in a matrix of chlorite and quartz. The unit is
highly irregular in thi.kness but persistent.
(b) Lower Member
The lower algal chert submember (Fig. 1) consists of reef-like
mounds of finely banded black, red, and white oolite chert. These mounds
This submember forms the
are intergrown and cemented in dolomite.
western margin of Gunflint outcrop (Fig. 1), but is continuous to just
It contains abundant microflora remains
west of Kakabeka Falls.
(Barghoorn and Tyler, 1965, Barghoorn, 1971, Edhorn, 1973).
The lower tuffaceous shale (lower tuff argillite, Fig. 1) submember
It overlies the lower algal chert subranges to 20 feet (6 m) thick.
member in the area west of Kakabeka Falls and is composed of fissile
black shale containing much volcanic ash.
The uppermost submunber of the lower member is subdivided into three
facies (Fig. 1). The lower west taconite facies, which is 150 feet (45 m)
thick, extends northeast from Gunf lint Lake to Kakabeka Falls and is
composed of wavy-banded granular chert, carbonate, and oxides. The lower
half contains disseminated greenalite granules in pale grey chert;
siderite forms local beds. The upper half contains increasing amounts of
hematite and magnetite.
This facies grades upward into jaspilitic upper
algal chert and grades laterally into the lower banded chert-carbonate
facies.
The lower banded chert-carbonate facies extends from Kakabeka Falls
to Thunder Bay city, and consists of 4 to 6 inch (10 to 15 cm) siderite
beds, with interbedded 2 to 6 inch (5 to 15 cm) grey cherty beds.
Carbonaceous material and pyrite are common in shale interbeds. This
facies grades into granular taconite towards the northeast.
The lower east granular taconite facies extends from Thunder Bay to
The basal 2 to 6 feet (60 to 180 cm) are formed of interbedded granular chert and ankerite. The upper 10 to 20 feet (3 to 6 m)
consist of interbedded red to green mottled chert and dolomitic limestone.
This facies grades upwards into the tuffaceous shale (upper tuff argillite,
Fig. 1) submember of the upper member.
Loon Lake.
�6
(c) Ujper Member
The upper algal c iert submember extends west from Nolalu to Gunf lint
Lake and consists of b sal granular chert overlain by algal chert and,
in the Mink Mountain area, amygdular basalt flows. The flows and algal
chert are overlain by granular chert and bedded jasper. Jasper beds
grade into tuffaceous shale of the overlying submember.
The upper tuffaceous shale (upper tuff argillite) is the only
continuous submember in the Gunf lint Formation and forms a key stratiIt ranges to 100 feet (30 m) thick and thins
graphic marker (Fig. 2).
laterally in either direction from Kakabeka Falls. It consists of black
tuffaceous shale and siltstone with interbedded siderite and pyrite and
The ash contains ellipsoidal, aceretionary
extensive beds of volcanic ash.
lapilli and concentric layers of small angular tuff fragments, arranged
Similar lapilli have formed due to the
about a larger central fragment.
accumulation of volcanic dust in water droplets and on water coated shards
(Moore and Peck, 1962).
The upper tuffaceous shale submember grades into the upper taconite
and chert-carbonate submember. The upper taconite facies extends from
Gunflint Lake to Thunder Ba, (Fig. 1), and is composed of wavy bands of
granular greenalite-bearing chert. The greenaTite-bearing granules are
round to oval, evenly distributed throughout a layer, and appear to have
The unit exhibits a rusty weathering, contains abundant
formed "in situ".
hematite and magnetite in granules towards the top, and grades laterally
(Fig. 1) into the upper banded chert-carbonate facies which extends from
west of Thunder Bay to Loon Lake. The latter facies consists of interbedded grey chert and brown carbonate (siderite with lesser dolomite arid
Brecciation and folding, apparently contemporaneous with
ankerite).
deposition, are common.
(d) Upper Limestone Member
The upper limestone member marks the top of the Gunflint Formation.
Minor chert beds, illite and volcanic shards are present, and tuffaceous
shale is most prevalent in the eastern area of Gunflint outcrop.
Stratigraphic Interpretation
Goodwin (1956) concluded that Gunf lint deposition occurred in a
After
shallow basin which had limited circulation with an open sea.
initial algal activity in the neritic zone, volcanic activity (tuffaceous
Silicate-bearing material
shale) was accompanied by sinking of the basin.
(taconite) was deposited in the deepest portions while in the neritic, or
intertidal zone (between Kakabeka Falls and Thunder Bay) banded chertFarther to the northeast, the lower east taconite facies
carbonate formed.
formed in agitated, oxygenated waters. As the basin filled, conditions
of algal growth returned, initiating the "Upper Gunflint" cycle.
Volcanic activity, marked by local basalt flows, terminated the upper
algal chert deposition and resulted in widespread distribution of pyroclastics of the upper tuffaceous shale. Downwarping resulted in deposition
�7
of granular iron silicate rocks in the deeper, southwest portion of the
basin, while on the shallow northeast shore, chert carbonate was
deposited.
As the basin filled, sporadic but violent volcanic activity
was accompanied by the entry of sea water, resulting in formation of the
upper limestone.
Goodwin (1956) in drawing an analogy with the Santorin volcano of
the Aegean Sea, suggests that volcanism was the chief source of iron
and silica.
Alternatively, Hough (1958) suggests deposition in a fresh
water basin, with material derived through weathering of an adjacent
landmass, and deposition controlled by limnic cycles.
Rove Formation
The Rove Formation conformably overlies the Gunflint Formation.
In the Thunder Bay and Pigeon River areas, it may attain a thickness of
at least 1,250 feet (380 m), and possibly more than 2,000 (610 m),
Geul (1970). The formation consists of three lithologic units (Geul,
1970) which are, from base upwards:
(1) black pyritic shale and argillite (base)
(2) interbedded argillite and greywacke and shale (transition
sequence of Morey, 1969)
(3) quartzitic greywacke with argillite interbeds (top)
The lower argillite is the dominantly exposed unit in Ontario and
commonly enclosed carbonate concretions of varying size and complex in
The transition sequence consists of thin-bedded greyform and texture.
wacke, consisting of grey to pink greywacke and sandstone, is the
thickest unit of the Rove Formation and is exposed mostly in northeastern Minnesota.
The metamorphic age of the Rove Formation is considered to be
1.7 billion years (Peterman, 1966).
Morey (1969) notes that the detrital matenal comprising the Rove
Formation was derived from Archean terrain to the north.
PALEOHELI KlAN
The Sibley Group
This section is adapted from Franklin et al (in press).
Introduction:
The distinctive red and white sandstone and dolomite of the Sibley
Group were first described by Logan (1863) who considered them as part
of his "Upper Copper-Rearing Series". Logan included the Gunflint and
Rove Formations, as well as the Sibley rocks, in this "series".
�8
Robert Bell (1872), in completing the first comprehensive description
of these rocks, considered them as the Upper Group of the Upper CopperBearing Series.
He compared the Sibley Group with rocks of Nova Scotia
and concluded (p. 321) that "they (Sibley rocks and the overlying
()sler volcanic sequence) may now be considered as of Permianand Triassic
age".
Logan (1872), in strongly reprimanding Bell, outlined evidence
for a pre-Silurian age. T. Sterry Hunt (1873) divided Logan's Upper
Copper-Bearing Series into Animikie (now the Gunflint and Rove Formations)
and Keweenawañ Groups, and assigned the Sibley to the latter Group.
Uilson (1910, p. 69) indicated that these rocks occupy a "trough-like
depression between two areas of Archean rocks" in the western Lake
Nipigon area, and tentatively assigned them to the Paleozoic.
The name "Sibley" was first assigned to this group by Tanton (1931).
Hs description of the "Sibley Series" of the Sibley Peninsula is
accurate, but unfortunately he did not have an opportunity to map the
more northern areas, and thus his stratigraphic analysis is of somewhat
limited value.
Although local studies of the Sibley Group rocks were undertaken
in subsequent years by Hawley (l)29) and Moorhouse (1960) the first
comprehensive mapping was completed by Coates (1972) and Mcllwaine
(l971a, 197lb)
Recent geophysical studies by duBois (1962) and Robertson (1973)
have underscored the need for a comprehensive study of the stratigraphy
and paleogeography of the unit. Red-bed sequences like the Sibley
Group are important environmental indicators and in addition this
occurrence may have tectonic implications.
Age:
The age of the Sibley Group is a key question with respect to
the position of these rocks within the framework of the Keweenawan
tectonic event, and the Helikian polar wandering curve.
A rubidiumstrontium whole rock isochron was completed in the laboratory of the
Geological Survey of Canada.
The analytical procedure is outlined
by Wanless and Loveridge (1972). The Geological Survey of Canada uses
an R87 decay constant of 1.47 x l0-1yr, as physically determined
and outlined in the aforementioned paper. The widely used 1.39 x 10-11
yr'. a 'geologically determined' decay constant results in ages
approximately 5.75% older.
The age, using the 1.47 x l0-11yr constant, is 1294 t 31 m.y.
Samples were selected from the Kama Hill and Red Rock formation; the
areas near diabase sills were avoided as their metamorphic effects are
extensive (Robertson, 1973).
The Kama Hill section is cut by multiple
thin sills; the data for one of the samples probably reflects this
metamorphism, and should be discounted.
The Sibley Group is apparently older (by at least 150 m.y.) than
the accepted age of the Keiceenawan igneous event as typified by the
�9
Duluth complex (1,115 m.y. RbSr, Faure et al 1969) and the.Keweenawan
extrusive rocks (1,142 m.y. RbSr Faure and Chaudhuri, 1967).
However well documented comparable age determinations have notbeen
published on either the Logan sills or the lower Osler group; These
latter units are magnetically reversed (duBois, 1962) and are the
oldest Keweenawan igneous rocks in this area. K-Ar dates of 1,060
m.y. on Logan sills (Franklin, 1970) probably represent a minimum
age due to possible argon leakage.
Unpublished RbSr data indicates
that the sills may be as old as 1298 ± 33 m.y.
(Robertson and Fahrig,
1971), and thus very close in age to the Sibley Group.
The Sibley Group exhibits both normal and reversed magnetic
polarity (Robertson 1973); igneous rocks of similar paleomagnetic
characteristics have a very similar age to that obtained for the
Sibley Group (Peterman et al, 1968, Murthey et al, 1968).
Thus the
determined RbSr age of the Sibley Group is probably reliable.
Stratigraphy of the Sibley Group
The Proterozoic rocks of the Southern Province of the northern
Lake Superior region have been described in a general way by Card et al
(1972).
Although the Sibley Group has not been heretofore formally
subdivided, subdivision into formations is possible. The subdivisions
are given in Table
and locations of type sections are included in
the formation descriptions.
The Pass Lake Formation
The type section for the Pass Lake Formation is exposed along the
Canadian National Railway tracks in southern McTavish Twp.
(Mcllwaine,
1974) near the north shore of Pass Lake where it is SO m thick; it
continues eastward along the tracks for about 3 kms where it is overlain
by the Red Rock Formation.
Reference sections are located under the
type section of the Red Rock Formation at Red Rock cuesta, at Mousseau
Mountain north of Nipigon and on Quarry and Channel Islands in Lake
Superior near Rossport.
The formation is composed of lensoid basal conglomerate overlain
by quartz-rich arenites.
It thins rapidly northward; scattered patches
are present along the eastern edge of the Sibley basin, but the unit is
absent along the western basin margin.
The Pass Lake Formation overlies the Rove Formation in the south
and to the north lies unconformably on Archean Rocks. The contact with
the Rove is exposed over a distance of about 20 m at Pass Lake; the
Rove has been altered for about 50 cm from the contact. This normally
black shale has been partially oxidized to a dark reddish brown.
Where
the Pass Lake Formation lies directly on the Archean there is little
or no evidence of a reaction; at the site of the old Enterprise Mine in
McTavish Township (Mcllwaine 1971b) the sandstone rests directly on
quartz monzonite with no apparent affect.
�1 U
Overlying the basal conglomerate with sharp contact is a succession
of arenites which are generally buff to pale pink with a minor number of
red interbeds. The arenites are commOnly very thickly bedded (greater
than 1 m) at the base of the sequence and range to very thinly bedded
(1-3 cm) with increasing stratigraphic height. The sharpness of bedding
boundaries also increase with stratigraphic height. They 'are commonly
fine-grained (2-3 phi) but are locally very fine-grained (3-4 phi), with
generally moderate sorting and locally poorly (especially at Pass Lake)
and moderately well sorted (e.g. Mousseau Mountain). There appears to be
no systematic variation in grain size or sorting with stratigraphic. height
Thin section examination and modal analyses indiëate the rocks range
from quartzose arenite to quartz arenite1 in composition. Detrital grains
range from angular to well rounded but are generally subrounded with
larger grains tending to be more rounded than finer grains. Quartz grains
with undulatory extinction are more abundant than quartz with straight
extinction.
Total quartz at Pass Lake appears to be lower in the upper half than
the lower half but this is mainly a function of cement content. For the
most part there is little or no cement in the lower half and induration
isapparently due to conpaction.
Feldspar is a mino:' constituent, especially at Pass Lake. There is
a suggestion of a systeiiatic decrease in feldspar with stratigraphic
height in the Rossport section.
Chert is present in all areas.
Chert content is greater in the
top half of the formation than in the bottom half at Pass Lake, other
sections exhibit no apparent variation.
Cementing material includes carbonate, mainly at Pass Lake, Red
Rock and Rossport, and silica, which is more common at Mousseau Mountain.
The matrix, generaUy fine mica and clay, forms consistently less
than 15%; this is the content generally accepted as the dividing line
between arenite and wacke.
The Rossport Formation
The type section of the Rossport Formation, is exposed on the
shore of Channel Island, near the Village of Rossport. This formation
overlies the Pass Lake Formation disconformably through much of the area,
and unconformably on Copper Island near Rossport. In the northern area it
lies nonconformably on the Archean basement. The Rossport Formation is
distinguished by its brick red color, high dolomite content, and concoidal
fracture. The formation maintains a relatively constant thickness of about
lOOm in all measured sections except on the Sibley Peninsula, where it thins
to approximately 2Om. In the southern area of the basin the formation may
be divided into three members (a) lower dolomite, (b) central chert-carb.onate
(stromatolite to the north) and (c) upper dolomite. In the northern area
these members are less clearly distinguishable due to the lack of exposure.
Much of the description is thus based on the more southerly sections.
1
.
.
.
.
.
The limits used here are based on Pettijohn's (1957) classification
but his rock names have been changed.
�11
The lower and upper members exhibit enly minor lateral facies
changes in the east and west direction, but to the north both members
become distinctly more clastic.
The central member is lithologically
distinct and forms a lateral (east/west) continuous 'marker bed traceable from Rossport to Sibley Peninsula.
The upper and lower members can be distinguished on the basis
of mineralogical composition and bedding development.
The lower
member has distinct bedding, whereas the upper is. more massive. The
lower is richer in carbonate and quartz whereas the upper member is
clearly richer in clay and feldspar.
Dolomite is the dominant carbonate mineral present.
No easy distinction between the lower and upper
members on the basis of calcite-dolomite ratio may be made, although
in general. the calcite-dolomite ratio is higher in the upper unit
than the lower.
iKama Hill Formation
The type section of the Kama Hill Formation is located along the
northern-most powerline, on the west side of Kama Hill, 17 miles
(27 km) east of Nipigon.
Reference sections are available at Albert Lake,
Stewart Lake and Channel Island.
The boundary with the underlying
Red Rock Formation is placed at the disappearance of carbonate and the
change in color. The maximum preserved thickness is 50 m.
The Kama Hill Formation is distinguished by its deep red-purple
colour, silt to clay sized particles, thin bedding, moderately well
developed fissility, its mineralogy and distinctive structures.
Due to its fine-grained nature, mineralogical analysis is possible
only by x-ray diffraction.
Two clay minerals, quartz, microline and
minor calcite and hematite constitute the mineralogy.
Colour in outcrop varies from deep red to deep purple and is duç
to hematite. The amount of hematite varies widely betweei 'beds from
less than 1% in a few course silt beds to over 90% in a fw clay rich
layers.
It normally constitutes approximately 4% of the rock.
The
coloration is quite homogeneous within individual beds. Conspicuous
"bleaching" is present only along a few bedding plane fractures and
joint planes.
Microscopic variation in coloration intensity is
related to grain size, with finer clay rich beds containing more hematite.
The lower portion of the formation has up to 10% white spherical
"reduction" spots; these are much less common in the upper portion of
the unit.
Hematite occurs as evenly disseminated very fine grained
aggregates.
In the coarse silty beds it forms a coating and is interstitial to the clasts.
Bedding is very difficult to distinguish in outcrop but is readily
apparent in thin section and cut surfaces. The three types of beds
which may be distinguished are:
�12
(a) regular finely laminated clay rich regular beds.
(b) irregular partially reworked course silty beds.
(c) stromatolitic beds.
Types (a) and (b) are intermixed but the type (a) beds appear
more dominant with stratigraphic height.
Bed types (a) and (b) are
distinguished by their lack of carbonate. Beds of type (c) are
confined to the lower part of the formation.
*
Sedimentary Structures
Mud cracks are pervasive and a characteristic featur• of the
Kama Hill Formation regardless of the bed composition (sand,
silt, or clay).
Linear and polygonal cracks occur on most bed surfaces.
Small scale erosional features are common. Disturbed bedding is locally
present.
Ripple marks are present only in the sand and silt rich beds.
These are symmetrical current ripples, with wave lengths of 1.0 to 3.5
cm and amplitudes of 0.5 to 1.5 cm, covered with fine mud; ripple
surfaces have small spindle shaped flute casts, superimposed at an
oblique angle to the ripple axis. Interference ripples are most common
in the more coarse-grained beds on Sibley Peninsula. Rain-print surfaces
occur rarely at Kama Hill. Evaporite casts (probably halite) are present,
and are particularly evident at Stewart Lake.
$
Summary of the Depositional History
The Sibley Group was depositod in a elongate, north/south basin
The
which was initially probably deepest in the south.
basin formed relatively rapidly and along its margins fans of locally
The
derived and rapidly deposited conglomerate formed.
initial period of rapid deposition gave way quickly to relatively slow
deposition of the arenites of the Pas's Lake Formation. The basin transgressed northwards towards the end of the deposition of the Pass Lake
Formation and extended far to the north (at least to southwestern Lake
Nipigon) during deposition of the lower member of the Red Rock Formation.
Moderately rapid regression marked the middle stage of Red Rock deposition,
accompanied by increased clastic deposition and stromatolite growth to
the north of Nipigon and chert precipitation to the south.
Transgression
followed as the basin extended northward at least to Armstrong.
The
basin depth was relatively constant, and it slowly filled with clay-rich
dolomites. * The transition to the Kama Hill Formation marks a change
from predominantly sub-aqueous to predominantly sub-aerial deposition.
Deposition of the Kama Hill Formation continued in an extremely consistent
very quiet mud flat environment. Primitive life flourished during
quiescent periods of deposition of the Kama i-Jill sediments.
Tectonic Implications
$
The relation of the Sibley Group in any tectonic reconstruction can
only be reviewed in the context of the entire Helikian history of eastern
�13
North America.
The dominant tectonic event in the Lake Superior
area was the development of the Keweenawan rift zone which forms an
inverted U, extending roughly from the northern area of the Michigan
basin, around Lake Superior and continuing southwest from Duluth
as the mid-continent gravity high.
Although nomajor "opening ocean"
event has been firmly documented during the Helikian, Baer (1974)
in summarizing papers present at the Grenville symposium (Ottawa,
Feb. 1974) indicates that a pre-Grenvillian orogenic event may have
initiated with a divergent phaseat 1,300 m.y. As part of this
rifting, the Keweenawan arm may have developed at this time (Burke
and Dewey, 1973).
This arm ultimately (at 1,100 m.y.) underwent
limited spreading (Burke and Dewey, 1973).
It is probable that igneous activity was initially very limited,
but rifting occurred by means of crestal rifts about which developed
"rrr" triple junctions.
These rifts meet at 120°, and are located
at major strike changes of a rift valley (Burke and Dewey, 1973).
The major flexure in the Keweenawan rift valley occurs immediately
south of Nipigon.
Should a triple junction have formed in association
with the Keweenawan rifting, the Nipigon area would be the most
probable area of development. The 'failed' arm would thus extend north
from Nipigon.
The Sibley group occupies a N-S block which is the result of a
failed arm developed about the Nipigon crestal rift.
Later reactivation of the Keweenawan rift was accompanied by intrusion of the Logan
sills into the same failed arm.
Many problems related to the time of development remain unsolved.
The Sibley Group is similar in age to the proposed age of initial
spreading of the Grenvillian orogen (Baer, 1974). However, little
evidence related to time of initial development of the other ultimately
actively spreading arms of the Keweenawan rift is available.
Minor
igneous activity has been recorded at 1400 m.y. (Books 1969). Sibley
sedimentation appears to have been controlled by a rapidly developing
fault scarp in the southern area, as indicated by a rapid increase in
coarse clastic material near the basin margin.
Limited exposure of the
Sibley Group in the northern area precludes examination of the nature
of the basin margins here.
The elongate basin shape is suggestive of
rift-valley filling, but the possibility remains that the Sibley basin
has been preserved in a failed arm, rather than the 'arm' actually
controlling sedimentation.
�14
Description of Stops and Road Log for the
Gunf lint and Rove Formations
Time and seasonal water level conditions may prevent access
to all stops indicated on Figures 1 and 2.
For alternate and addItional stops of the Gunflint and Rove
Formations, the reader is referred to Franklin and Kustira (1972).
Mileage count begins at the intersection of Highways 11-17 and
61, near the Airlane Motor Hotel, Thunder Bay. Proceed south on
Highway 61.
Figures in brackets record accumulated mileage.
MILES
KM.
00.
0.0
The prominent
Intersection Highways 17-11 and 61.
hill to the southeast is Mount McKay, the most
northerly of the "Norwesters" range of hills.
Towering over the Kaministikwa River delta, it is
1,581 feet (481 m) above sea level and 978 feet
Mount McKay is a large
(298 m) above Lake Superior.
mesa, made up of shales and greywackes of the Rove
Formation overlain by a hard, protective 200 foot
(61 m) thick capping of diabase (Pye, 1969, p. 39).
The upper half of the mesa is 3,000 feet (914 m)
long and has a maximum width of 1,100 feet (336m).
A second sill, about 15 feet (4.6 m) thick is found
in the Rove sedimentary rocks and is 474 feet (141.5 m)
It forms the base of a
below the top of the hill.
wide and prominent terrace to which the tourist may
drive his automobile for a magnificent view of the
City of Thunder Bay (Pye, 1969, p. 39).
5.9
9.5
7.1
11.4
20th Si.deroad; turn right (north).
Riverdale Road, turn left (west) and follow to end of
road.
8.5
13.7
Parking spot; follow cottage road (J.C. Kirkup);
this is private property and permission for access
to the Slate River must be obtained from the owner.
�15
BASAL CONCRETION-BEARING SHALE OF Th ROVE FOkMATION,
SLATE RIVER CANYON (FIG. 1).
STOP 1
The black, graphitic, fissile Rove shale contains
These vary
an abundance of carbonate concretions.
from
a
few
inches
(cm)
to
8
feet
(2.4 m)
in size
Although
commonly
in
the
shape
of
in diameter.
oblate spheroids, they display a complexity in shape
and texture. Some show radial septarian cracks on
their surfaces.
The concretions form bedded unitsin the canyon walls.
They are in various stages of weathering out of the
host shale, some slumping into the river bed and
many others lying in the river bed arranged in imbriShale bedding is warped around the
cate fashion.
top and bottom of the cpncretions.
Moorhouse (1963) describes these concretions in
detail.
Return to Highway 61.
0.0
(11.1)
0.0
(17.9)
Intersection of Highway 61 and 20th Sideroad.
Continue south on Highway 61. The range of hills
to the south are the Nor'westers.
5.4
(19.1)
19.4
(33.1)
STOP 2
8.7
Highway 130; continue on Highway 61.
(30.7)
31.2
(53.3)
Entrance to abandoned quarry, west side of Highway 61,
approximately 1,600 feet (410 m) beyond Cloud Bay Road.
UPPER THICK-BEDDED QUARTZITIC GREYWACKE, ROVE
FORMATION,
(FIG. 1).
Quarry operations have exposed thin to thick bedded
quartzitic greywacke interbedded with lesser amounts
Greywacke displays sole
of black fissile argillite.
markings and graded bedding.
The quarry walls are bounded by two dikes bifurcating
from a single olivine diabase dike of Geul's (1973)
Pigeon River intrusions. The west dike is approximately SO feet (15 m) wide and vertically dipping;
the narrower east dike dips steeply southeast, its
attitude well exposed at the back of the qvarry.
�16
Due to the development of a closely spaced fracture
pattern in the Rove Formation, the quarry walls and
hack may be unstable; extreme caution is advised.
Return to Highway 130.
(47.1)
0.0
(75.8)
Intersection of Highways 130 and 61.
Proceed
north on Highway 130; continue to end of road.
3.2
(50.3)
5.1
(81.0)
Paipoonge Concession 1 Road. Turn left (west).
Proceed for 1.8 miles (2.9 km) to unmarked gravel
•road; turn right (north).
Continue for 3;4 miles
(5.5 km) to steel bridge over Kaministikwa River.
Turn right and proceed over bridge on paved road
(Highway 588) for 1.2 miles (1.9 km) to Highway
Turn •left (west) and proceed for approxi11-17.
mately 3.5 miles (5.6 km) through village of
Kakabeka Falls into Kakabeka Falls Provincial Park.
Turn right at the park gatehouse, before crossing
the old bridge in the park, and follow road under
Highway 17, to its end at the swimming area.
Proceed on foot past cabins to the Kaministikwa
River shore.
0.0
STOP 3
BASAL CONGLOMERATE AND LOWER ALGAL CHERT, GUNFLINT
FORMATION, (FIG. 1).
Here, the basal conglomerate and algal chert mounds
rest directly on Archean granitic gneiss basement.
Basal conglomerate may be seen in place only at very
low water.
However, large, angular, locally derived
Note the
blocks of conglomerate are abundant.
angularity and polymictic nature of the pebbles.
All can be assigned to various Archean rocks to the
west and north.
The Ep-Archean
Note also the absence of a paleosol.
interval, here occupying 800 million years, is
represented by little or no "in-situ" weathered
basement, suggesting absence of normal weathering
conditions, or pre-Gunflint strong fluvial or
glacial transport action,
The algal mounds here are similar to those found 1.8
miles (2.9 km) west of Nolalu (Franklin and Kustra,
1972, p. 31). Return to park gate house, turn right
and cross the bridge. Proceed to parking area,
thence by foot to the rim of the falls.
�17
STOP 4
UPPER TUFFACEOUS SHALE SUBMEMBER (UPPER TUFF
ARGILLITE) AND OVERLYING UPPER CHERT CARBONATE,
GUNFLINT FORMATION, FIG. i.
Kakabeka Falls drops 128 feet (39 m) into a gorge
formed in fissile, thinly bedded upper tuffaceous
shale submember (Goodwin, 1956)
A more resistant massive two-foot bed of thinly
banded chert-carbonate caps the escarpment. Note
apparent cross lamination in the chert carbonate
and the undulating nature of the surface.
The chert carbonate capping is overlain by tuff
argillite and a second chert carbonate bed,
exposed in a parking lot on the east side of the
gorge.
A bed of lower chert carbonate occurs at
the base of the falls, (Fenwick, personal communication).
Return
to Highway 17, turn right and proceed
approximately 1/3 mile (0.5 km) Ontario Hydro
station access road imrpediately west of the
Kakabeka Falls Motel.
Turn right (south) and proceed to parking lot by
the generating station.
Access to STOP 5 is through the genenting station
to its west side.
Permission must be obtained from
The spillway serves as a
the station supervisor.
safety feature to bleed off excess water in the
event of generator failure at the power station.
Follow the river bank for approximately 600 feet
(183 mj to the"spillway" cut. Beware of Poison Ivy.
STOP 5
UPPER TUFFACEOUS SHALE SUBMEMBER (UPPER TUFF ARGILLITE)
GUNFLINT FORMATION (FIG. 1).
The best section of upper tuffaceous shale submember
is exposed at this locality. Pyrite-bearing chert,
possibly of the upper algal chert submember; occurs
It is overlain by shale
at the base of the section.
containing pyrite nodules and calcareoüs concretions,
interbedded shale and tuff and a cap of thinly bedded
upper chert-carbonate.
�_____—
18
One of the best exposures of "mud
ball
tuff" in
the shtle occurs near the bottom of the section;
the tuff is formed of closely packed accretionziry
lap ill F elongated a long the bedding.
ellipsoids contain
mdiv idual
small, angular fragments of
uniform size, grouped concentrically around a
larger shard fragment. The remainder of the
material comprising the beds consists of volcanic
fragments in a groundmass of green illite:
Higher than background radioactivity (0.004% U3O8
has been noted in the tuff argillite by Fenwick
(personal communication).
Note downwarping of beds on the west side of the
exposure and the fault filled with quartz-carbonate and anthraxolite for which Kwiatkowski (1975)
reported a 0.2% nickel content.
Return to Higiway 11-17 and proceed east.
0.0
(64.7)
0.0
(104.1)
9.8
15.8
(74.5) (119.9)
10.9
17.5
(75.6) (l2l7)
16.3
(81.0)
STOP 6
26.2
(130.4)
Junction Highway 11-17 and Oliver Road (formerly
Highway 590),.
Proceed on Oliver Road.
Thunder Bay city limit.
Good ''iew of a series of
mesa type hills, the Nor'westers, all capped by
Logan diabase.
Junction of Oliver Road with Highway 130;
continue east.
Belrose road.
Turn left, proceed 0.5 miles
(0.8 knflto quarry on west side of road,
(Dickson's Quarry).
UPPER TACQNITE SUBMEMBER, GUNFLINT FORMATION,
(FIG.
1)
In this quarry wavy-banded, red jàspilitic and
darker greena],ite-bearing taconite is capped by a
Neohelikian (Logan) diabase sill. The taconite
contains approximately 50 percent shale, interbedded with 6 to 12 inch (15 to 30 cm) irregular
taconite beds that are best exposed at the north
end
of the outcrop where quarry operations
exposed the taconite at a lower stratigraphic level.
The diabase sheet displays an irregular, undulating
�19
bottom
surface
at a slight angular discordaneL
The upper surface is polygonally jointed and contains
occasional patches of a thin veneer of argitlite.
Return to Highway 130, turn left (east), and proceed
across Highway 11-1.7 and past Lakehead University
to High Street.
19.8
31.9
(83.5) (134.4)
Intersection Highway.130 (Oliver Road) and High
Street. Turn left at the traffic lights and proceed
up High Street.
20.4
(84.1)
Entrance to Hillcrest Park.
32.8
(135.4)
STOP 7
UPPER LIMESTONE MEMBER, GUNFLINT FORMATION, (FIG. 1).
Hillcrest Park stands about 160 feet (48 m) above
the level of Lake Superior and offers a panoramic
view
the
of Thunder Bay harbour, the Seqping Giant,
WelcomeIslands, Pie Island and the Nor'westers.
Dolomitic limestone and chert layers arc exposed
at the base of the flag pole and bell.
Follow stairs to base of hill where fragmental
limestone (upper limestone member) is exposed.
The rock consists of many angular tci rounded chert
fragments in a matrix of coarsely crystalline,
iron-bearing carbonate, and thin chert interbeds.
Volcanic shards and fragments occur in the limestone (Goodwin, 1956).
Proceed north on High Street.
35.2
21.9
(85.6) (137.8)
Intersection with Balsam Street: Turn lefton
22.5
36.1
(86.2) (138.7)
Huron Street, 300feet (90 m) south of Highway
17-11.
Turn right on Huron Street, then
Balsani Street.
immediate left.
23.9
38.4
(87.6) (141.0)
Bridge over Current River, cross bridge, turn
right into Boulevard Lake Park and proceed 0.3
miles (0.5 km); park on right side of road.
Traverse begins in river bed.
�20
STOP S
UPPER CHERT CARBONATE FACT ES, GUNFL I N
FORMATION (FIG. 1)
The upper chert carbonate fades is overlain by
the Rove Formation.
An upstream traverse
encounters ferruginous carbonate, interrupted by
thin layers and lenses of granular and algal
chert, dark, fissile shale and dolomitic limestone.
At the beginning of the traverse, note the rounded
chert lenses showing concretionary structures,
attributed to action of algae.
Features to observe include stylolite surfaces
lined with anthraxolite, pyrite veinlets, imbrication of thin chert layers and the striking
weathered app3arance of the rock.
Under the bridge, a bed of gray, massive limestone,
possibly the Upper Limestone member, contains
pancake-like lenses of serpentine material, and is
interrupted by a thin band of pyritic and pyrrhotitic
Note the hununocky upper surface of the
chert.
limestone at the shale-limestone interface. The
overlying shale is probably Rove Formation,
Several hundred feet north of the bridge, at the
lookout, a diabase sheet caps the shale. Heat from
the cooling of this sheet metamorphosed the limestone,
forming serpentine and pyrrhotite.
East:of the bridge, in the picnic area, several well
developed river terraces are preserved.
From bridge, proceed east along Arundel Street.
40.7
25.3
(90.0) (144.9)
Intersection, Arundel Street and fodder Avenue.
Turn left on fodder Avenue at the fodder Avenue Hotel.
Highway 17-11: Turn right.
26.9
43.3
(91.6) (147.4)
Scenic lookout.
Park
View of Thunder Bay harbour.
car and walk 500 feet (150 m) east to roadcut on
north side of road.
�21
SioP 9
UPPER LIMESTONE MEMBER, GUNFLINT FORMATION,
OVERLAIN BY DJABASE, (PIG. 1).
Sill of
Logan diabase overlies argillite and
fragmental limestone of the upper limestone
member; The contact i gently undulating and
visible effects of contact metamorphism are little
In this section, however, a microporphyevident.
roblastic texture is developed in the argillite.
Pyrite is altered to pyrrhotite.
Note the lenticular chert patches within the
limestone, some veined with pyrrhotite, exhibiting
agate textures.
Additional
End of Animikie portion of trip.
points of interest concerning a more complete
picture of Gunf lint Formation stratigraphy are
given in Fra1lin and Kustra (1972),
�______
INSET SCALE
4
KM.
Stop Locations
Pass Lake
Railroad
tracks east of Pass Lake
No. 5 Road (Pass Lake Area)
Ouimet Canyon
Kama Fiji
Thunder Bay Amythest
SIBLEY
THUNDER
-
BAY
40 KILOMETRES
Locations.
�_____ _____
23
A
A
an
•
-
.
•. -H-—:-
+
+
+
- -:-
+
+
+
+
+
+ ARCHEAN
+
+
+
+
+
+
÷
+
÷
FT. 00-,
t
.+
+
+
+
+
+
+
+
B
÷
+
+
+
÷
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
SANDSTONE
÷
+
+
+
+
+
CONGL)MERATE
+
+
+
+
+__+
+
+
+
+
+
20 KM.
I0
0
B'
'10 MILES
•.7CSLTSTONE_1-SHALE.T
.
7
-.
.
.
.
BRECCIA . .....
RED'
QOLOSTONE
/
SANDSTONE
ONGLOMERATE
ROVE
FM,
KAMA HILL FM. ( Dots indicate increased silt-sand content
ROSSPORT
PASS
Fig.
FM.
LAKE FM.
4. Longitudinal and Cross-sections of the Sibley Group.
t
÷
25 METRES
'O
q
ROVE
FM
+
+
�24
Description of Stops and Roadlog for the
Sibley Groip
Mileage count begins at the junction of Highways 11-17 ad 61
near the Thunder Bay Airport.
Figures in brackets recprd
accumulated mileages.
MILES
KM.
0.0
0.0
Proceed north along Highway 11-17.
*
1.9
3.1
Golf Links. Road.
2.9
4.7
Oliver Road (Highway 130).
4.9
7.9
5.6
9.0
7.1
11.4
Balsam Street.
9.7
15.6
Hodder Avenue.
19.3
16.6
Scenic Lookout.
12.1
19.5
Spruce River Road (Highway 527 -
21.6
34.8
Lakeshore Drive.
31.2
50.2
Highway 587: turn right and proced southeast.
35.0
56.3
A large azea of outcrop extends along the north
side of the C.N.R. railway tracks and Highway 587
where they parallel Pass Lake,
*
John street.
Red River Rowi (Highway 102).
formerly
800).
�25
This cliff is the type section for the Pass Lake
Formation.
Exposure is almost continuous for
about 2 miles (3.2 km) along the tracks and gives
a stratigraphic thickness of 164 feet (50 metres).
STOP 1
At the western end of this outcrop, a sandstone
quarry provides an excellent exposure of Sibley
sandstone.
In the railway cut at the western edge
of the quarry, Rove shale is altered.to a reddish
colour. This alteration affected the Rove for
several fçet below its contact with the Sibley
Group.
Also present is a thin lens of basal conlomerate.
PLEASE EXERCISE EXTREME CAUTION CLIMBING ON THE
DEBRIS.
35.3
56.8
The conglomerate is better exposed behind'the
railway shed at the east end of Pass Lake.
Clasts in the basal polymictic conglomerate are
composed of 93 per cent Gunflint iron formation,
6 per cent quartz and 1 per cent granite.
Boulders are of variable size and angularity,
The contact
and are cemented in a sandy matrix.
with overlying sandstone is sharp; only a few
pebbles are found in the base of the overlying
unit.
The sandstone is moderately to poorly
indurated, thick bedded at the bottom of the
section, and composed of quartz, with minor chert
and feldspar, in a calcite matrix.
Continue along Highway 587.
35.7
57.5
Pass Lake East road:
37.6
60.5
No. 4 Road:
37.9
61.0
Y Junction - bear left.
38.6
62.1
Field on left side (west) of road:
park here and
proceed on foot across field and through bush to
CNR tracks - about 1/4 jnije (400 metres);
turn left and proceed east.
turn left and proceed north.
�26
this outcrop is red intraformational breccia
Angular fragments vary
of the Rossport Formation.
from 0.4 in. to 15.7 in. (1 cm up to about 40 cm.)
Several clastic dikes are also present.
STOP 2
Much of'
The lithology is generally a red sandy limestone.
Return. to No. 4 Road and continue north.
39.9
64.2
Gravel Pit - for turning vehicle around.
back to Pass Lake East Road.
42.3
68.1
Pass Lake East Road -
turn
Proceed
left.
***********************
0.0
0.0
Proceed along Pass Lake Eas; Road from Junction
with No. 4 Road.
0.8
(43.1)
1.3
(69.4)
Right angle bend to left.
1.5
(43.8)
2.4
(70.5)
No. S Road -
2.1
(44.4)
3.4
(71.5)
Juncticn -
4.0
(46.3)
6.4
(74.5)
Area of outcrop.
STOP 3
turn
turn
left.
left.
KAMA HILL SANDSTONE
Poorly exposed reddish-brown to reddish-purple
sandstone of theKama Hill Formation. Generally
Although
fine- to medium-grained sandstone.
not evident at this location mudcracks and ripple
marks are common in this unit. These occur along
the shore of Lake Superior to the east, (see
The main difference between
Mcllwaine, 1972).
this sandstone and sandstone of the Rossport
Formation is the lack of carbonate in the Kama
Hill Formation.
�27
Continue north along No. S Road.
15.9
9.9
(52.2)
(84.0)
10.3
(52.6)
(84.7)
16.6
Cross CNR Tracks.
Highway 11-17 - Turn right.
***********************
0.0
0.0
(84.7)
Proceed northeast along Highway 11-17.
(52.6)
2.0
(54.6)
3.2
(87.9)
Road to Enterprise Mine.
7.8
(60.4)
12.6
(97.2)
Road to Ouimet Canyon - Turn left.
8.4
(61.0)
13.5
(98.2)
Y Junction -
9.2
(61.7)
14.8
bear
left.
*
Sharp right turn.
(99.3)
9.7
15.6
(62.3) (100.3)
Sharp left turn.
10.2
16.4
(62.8) (101.1)
Junction - proceed straight.
10.7
17.2
(63.3) (101.9)
Junction - proceed straight.
12.8
20.6
(65.4) (105.3)
Junction -
13.3
21.4
(65.9) (106.1)
Turn off to Gulch Lake Picnic Grounds to Ouimet Canyon.
15.2
turn
24.5
(67.8) (109.1)
Bridge.
15.4
24.8
(68.0) (109.4)
Quimet Canyon.
right.
turn
left
�28
Ouimet Canyon, a spectacular steep-walled gorge, is
located in a thick Keweenawan (Logan) di;tbase sill.
The canyon can be traced for over two miLes (3.2 km)
and is approximately 600 feet (183 m) wide at its
It has a maximum depth. of 400 feet,
southern end.
STOP 4
(122 in).
Although diabase is the most conspicuous rock type,
a pink quartz monzonite occurs in the south central
portion of the canyon, and a calcareous red mudstone
of the Sibley Group has been noted localLy at the
base of the west wall of the canyon (here bleached
grey) and surrounding the southern portion of Gulch
Lake.
Mapping along the western rim and wall oF the
canyon indicates the presence of two major, continuous joint sets and three less-continuou.; minor
It appears that the canyon
sets (Stacey, 1976, p.3).
is a deep erosional depression, carved out of the.
diabase along two major joints by the action of
glacialice, running water and freeze-thaw action.
An interesting feature within the canyon is a
prominent diabase pinnacle, referred to as the
Indian Head, which has been isolated from the west
rim by erosion.
The canyon has been declared a Provincial, Park
under the Quetico Nature Reserves system.
Return to Highway 11-17.
Highway 11-17 -
38.2
23.8
(76.4) (123.0)
turn
left.
***********************
0.0
0.0
(76.4) (123.0)
9.0
5.6
(82.0) (132.0)
12.4
7.7
(84.1) (135.3)
Proceed northeast along Highway 11-17.
.
Bridge over Wolf River.
Road to Stewart Lake at end of Itinerary)'.
(see extra stop descriptions
�29'
20.4
32.8
(96.8) (155.8)
Highway 627 - proceed straight.
21.3
34.3
(97.7) (157.2)
Highway plaque describing Red Rock Cuesta. The
cuesta features a thick sequence of red sandy
limestone capped by a diabase sill.
22.6
(99.0)
36.4
(159.3)
Road cut here shows a diabase sill cutting Archean
rocks and Sibley Group.
25.7
41.4.
(102.1) (164.0)
Road to Mousseau Mountain - (see extra slop
descriptions at end of Itinerary).
28.3
45.5
(104.7) (168.5)
Junction of Highways 11 and 17, - Proceed straight
along Highway 17.
40.6
65.3
(117.0) (187.3)
Junction of Domtar Road - (see extra stop
descriptions at end of Itinerary).
66.5
41.4
(117.8) (189.6)
First Lookout, Kaina Hill.
STOP SA
ROSSPORT FORMATION OVERLAIN 'BY KAMA HILL FORMATION
WITH A CAPPING OF DIABASE.
A broad anticline of sandy red carbonate is
exposed in the prominent road cut to the north of
this lookout. This represents the lowest member
of the Rossport Formation.
Soft-sediment deformation may have produced this
structure. Three thin diabase sheets follow
bedding planes; the sills pinch out, and locally
Thi:
cut across bedding at a high angle
homogeneous, calcareous sandy mudstone
:orms a
distinct horizon at the base of the sand red
mudstone unit.
Follow the road (south) to the distinctive red and
white interbedded sandy mudstone.
Sand:.tone
beds (white) are lenticular in shape, anti are
interbedded with red, sandy mudstone.
�30
42.1
67.8
(118.5) (190.7)
Second Lookout, Kama Hill.
In the roadcut to the north of the second lookout,
the following features may be observed:
(1) Two thin Keweenawan diabase sills, partially
replaced by carbonate, cut across the poorly
developed bedding place at a low angle.
(2) Finely laminated chert of the chert-stromatolite unit is exposed below the lower sill.
Up to six inches (15 cm) of anthraxolite
carbonate has accumulated at the base of the
chert.
An oily smell may be detected when
this anthraxolite is freshly broken.
(3) Limey red mudstone above this unit is marked
by many cream-coloured spots, (average diameter
0.5 inch, 13 mm). Similar spots are evident
throughout this unit, and commonly have a small
amount of graphite or hydrocarbon at the centre.
In thin section, the only apparent mineralogical
change in the spots is the lack, of hematite
coating on clay and carbonate grains.
(4) Irregular, flame-shaped, bleached zones follow
structures and bedding plane cleavage in the
Leaching of hematite and
red limey mudstone.
destruction of clay mjnerals and feldspar has
occurred along the fractures.
(5) Above the road cut and overlying the talus
It is
slope, the purple mudstone crops out.
more highly fissile, and contains approximately
4 per cent hematite, which coats very fine
grained corrensite and microcline, and forms
Bleaching
blades of specularite in tiny vugs.
along fractures is common in this rock. Purple
mudstone contains abundant syneresis cracks,
and to the west, at Stewart Lake, contains thin
stromatolite beds.
119.6
192.5
Outcrop on east side of Highway.
�31
STOP SB
Red Shale of the Kama Hill Formation is exposed
here underneath a cap of diabase.
Turning Point - Proceed back towards Thunder Bay.
*
* * * * * * * * * * * * *+ * * * * * * * * *
0.0
0.0
(119.6) (192.5)
Proceed west along Highway 17.
55.2
88.8
(174.8) (281.3)
East Loon Road - turn right (north) and proceed to end of
road to Thunder Bay Amethyst Mining Company Limited.
STOP 5
THUNDER BAY AMETHYST MINING COMPANY LIMITED
The Thunder Bay Amethyst Mine is the largest
producing amethyst mine in Ontario and is open
annually to the public, from May 1st to November 1st.
The property has been in production since 1962.
The number of rockhounds and tourists visiting the
mine site has increased steadily from 900 visitors
There are
in 1967 to 24,396 visitors in 1976.
sufficient reserves to give the mine an expected
life of 65 years at current mining rates (R. Hartviksen,
Mine Manager, personal communication).
The amethyst deposit is located in an east-west fault
zone cutting an intrusive body of massi'e, mediumgrained, red to pink Archean quartz monzonite.
Spectacular breccia is noted in the floor of the quarry
and in large blocks in the display area exhibiting
fragments of unaltered quartz monzonite and highly
silicified dolomite of the Sibley Group.
Quarrying, diamond drilling and stripping has
delineated the deposit for a length of approximately
1000 feet (305 m) and for a width of over 80 feet
(24th).
Individual amethyst veins vary in width from 1/4 inch
(7.6 mm) to 4 feet (1.2 m) and include numerous
cavities lined with purple crystals. Well formed
crystals (points) line the cavities and vary in size
from 1/4 inch (7.6 mm) diameter to large crystals
measuring 9 inches (22.9 cm) from tip to root and
6 inches (15.3 cm) in diameter.
�32
Coloration of crystals and-the more massive material
is dark purple.
Variations in intensity of purple
colour occur, and locally, colourless am! smokycoloured quartz is found.
Crystals are )ccasionally
coated with a reddish brown hematite. The colour of
ametht results from substitution of small quantities
of ferric iron for silicon followed by irradation,
(Dennen and Puckett, 1972, p.448).
The deposits of the producing amethyst mLnes in
McTavi;h Township are found either in fradtures that
extend below the.Sibley-Archean unconformity or. at
the coittact of the Sibley Group with Archean granite.
END OF ITINERARY
For anyone interested in a more complete view of the Sibley Group,
the following additional areas may be visited.
From Rossport, a boat trip to Quarry Channel and Wilson Islands,
which lie one to two miles off shore, will allow the visitor
On Quarry
to see an almost complete section of Sibley rocks.
Island, Rove shale is overlain by a thick section of Pass Lake
sandstone. Here, crossbeds and ripple marks are abundant.
1.
On Channel Island, the upper part of the sandstone unit, sandy
red mudstone units are all exposed. The latter is disconformably
overlain by Osler volcanic rocks.
The type section of the Kama Hill Formation at the top of Kama
Hill.
The best access is provided by following the Domtar
Logging Road (0.8 mi., 1.3 km west of the first lookout at
The
Kama Hill) for 0.3 mi (0.5 km) to the first powerline.
section is at the top of the hill and is exposed on the powerline.
2.
3.
-
good section of Pass Lake sandstone is exposed along the road
up to Mousseau Mountain.
The top of this hill also provides one
of the best views of Lake Superior and the surrounding country.
A
MILES
KM.
0.0
0.0
Leave Highway 11-17 point).
(see Itinerary fox Junction
�33
turn
1.5
2.4
Road junction -
1.9.
3.1
Road junction - turn left.
Proceed along this
road to Mousseau Mountain (see Coates 1972).
left.
4.
A further section of Kama Hill Shale may be viewed at Stewart
Lake, salt casts may be found here.
5.
The stromatolites near Disraeli Lake may be reached by
following the Armstrong road north from Hurkett for 21.6 miles,
(34.7 kin) to the Disraeli Lake road, which connects the Armstrong
road with the Spruce River Road (Hwy. 527). Follow the Disraeli
Lake road west for 22.2 miles (35.7 km) past Shillaber and
Seagull Creeks to the Disraeli campground road. Proeed for 3/4
of a mile (1.2 km) beyond this, to the first bush ro.sd leading
north.
Follow this road for two miles (3.2 km). Blocks of
stromatolite are strewn along side the road for some distance.
Stromatolite blocks are common throughout the Disraeli area,
and may be found in outcrop and float along most of :he bush roads.
AC KNOWLEDGEMENTS
The authors wish to acknowledge the assistance of Mi. S. Spivak
who compiled and drafted the figures and Mrs. Cathy LeBnn for typing
the manuscript. The cover plate was taken by J.F. Scott.
�34
SELECTED BIBLIOGRAPHY OF ThE PROTEROZOIC ROCKS 'OF THE
THUNDER BAY AREA *
Abelson, P.H. and Hare, P.E. 1968:
Recent Amino Acids in the
Gunf lint Chert; Carnegie Inst. Washington, Yearbook 67,
pp. 208-210.
Alexandrov, Eugene A. 1955:
Contribution to Studies of Origin of
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pp. 459-468.
40Ar39Ar Studies of Precambrian
Alexander, E. Colvin, Jr. 1975:
Cherts: An unsuccessful attempt to measure the time evolution
of the atmospheric 4OAr/36Ar Ratio; Precambrian Research,
Vol. 2, pp. 329-344.
Proterozoic Flood Básalts of Eastern Lake
Annells, R.N. 1973:
Superior: The Keweenawan Vblcanic Rocks of the Mamainse Point
Area, Ontario; Geol. Surv. Canada, Paper.72-1O, Slp.
Keweenawan Volcanic Rocks of Michipicoten
Annells, R.N. 1974:
Island, Lake Superior, Ontario; An Eruptive Centre of Proterozoic
Age; Geol. Surv. Canada, Bull. 218, PUp.
Geoscience
Baer, A.J. 1974:
Grenville Geology and Plate Tectonics;
Canada, 1, pp. 54-60.
Diffusion in gatO Point Vitrophyres; Amer.
Jour. Sci., Vol. 211, pp. 74-88.
Bain, George IV. 1926:
Barghoorn, E.S. 1971:
No. 5, pp. 30-42.
The Oldest Fossils; Sci. Amer., tol. 224,
Microorganisms Three
Barghoorn, Elso S., Schopf, William, J. 1966:
Billion Years Old from the Precambrian of South Africa; Science,
Vol. 152, pp. 758-763.
*
Barghoorn, Elso
Microorganisms from
S., Tyler, Stanley, A. 1965:
the Gunflint Chert; Science, Vol. 147, No. 3658, pp. 563-577.
Barghoorn, Elso.S., Tyler, Stanley A. 1965: Mitroorganisms of Middle
Precambrian Age from the Animikie Series, Ontario, Canada;
Chap. 3, in Current aspects of exobiology, Calif. Technol., Jet
PropulsionLab., Fasadena, pp. 93-118.
'[he Animikie Sea; a talk given at Institute On
Bartley, M.W. 1958:
Lake Superior Geology, Minneapolis, Univ. Minn. Center
Continuation Study, 9p.
*
* All
*
references are on file with Regiona' Geologist, Ontario Ministry of
Natural Resources, Ontario Government Building, 435 James St. S.,
Thunder Bay, P7C 5G6.
�35
1960:
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Superior Geosyncline; U.S. Geol. Surv. Prof. Paper 400-B,
Bath,. Gordon, D.
pp: B'212-B213.
Minera1oy and S.tdimentation in the Kama Hill
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Paleomagnetism of Keweenawan Intrusive
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On the Geology and Economic Minerals on the NorthBell, R. 1870:
east Coast of Lake Superior and Adjoining Country from Pigeon
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Metamorphic Pyroxenes and Amphiboles in
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Books, Kenneth G.
1972:
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Further Paleomagnetic
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Economic Geology and Stratigraphy of the
Broderick, T.M. 1920:
Günflint Iron District, Minnesota; Econ. Geol., Vol. 15, pp. 422452.
�36
Broughton, Paul L. 1975:
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Gem, July, pp. 58-62.
Burke, K. and Dewey, J.F. 1973:
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Some Geological and Environmental Aspects
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Accompanied by Maps 2233, 2234, 2235, 2236, scale 1 inch to
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Lavas of the Keweenawan Series; Econ. Geol., Vol. 46, pp. 51-67.
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Differentiation in Lavas of the Keweenawan
Series and the Origin of the Copper Deposits of Michigan; Geol.
Soc. Amer. Bull., Vol. 62, pp. 159-202.
Cornwall, Henry R. 1951:
Differentiation in Magnias of the Keweenàwan
Series; Jour. Geol., Vol. 59, pp. 151-172.
�37
Courtis, W.M. 1887:
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shown at Duncan Mine, Lake Superior; Amer. Inst. Mi
Eng.,
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Craddock, Campbell, 1972:
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Davies, F. Bryan, and Windley, Brian, F. 1976:
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Nature, Vol. 263, pp. 383-385.
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On the Chemistry and
colour of Amethyst; Can. Mineralogist, Vol. 11, No. 2, pp. 448-456.
Dott, R.H. 1972:
A Post-Animikean - Pre-Keweenawan Transgressive
Sand Blanket over the Lake Superior Region; Geo. Soc. Amer.,
Abstracts with Programs, Vol. 4, No. 7, pp. 490-491.
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Banded Iron Formations; Geol. Soc. Amer. Bull, Vol. 85, pp. 10991106.
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District by Palaeomagnetic Methods; Geol. Asoc. Canada, Vol. 11,
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�38
Faure, Gunter; Kovaçh, Jack, 1969:
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to 1/2 mile.
*
�39
Giguere, J.F. 1975:
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pp. 407-460.
�40
Halls, H.C. 1966:
A Review of the Keweenawan Geology of the Lake
Superior Region; in The Earth beneath the continents (edited by
J.S. Steinhart and T.H. Smith), Am. Geophys. Union, Monograph 10,
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Halls, H.C. 1969:
Compressional wave velocities of Keweenawan roèk
specimens from the Lake Superior region; Can. Jour. Barth Sci.,
Vol. 6, pp. 555-568.
Halls, H.C. 1972:
Geophysical Studies in Northern Lake Superior;
Geo. Soc. Amer., Abstracts with Programs,. Vol. 4, No. 7, pp.525:
Halls, H.C. 1972:
Magnetic Studies in Northern Lake Superior; Can.
J. Earth Sci., Vol. 9, No. 11, pp. 1349-1367.
Halls, H.C. 1974:
A Paleomagnetic Reversal in the Osler Volcanic
Group, Northern Lake Superior; Can. J. Earth Sci., Vol. 11, No.
pp. 1200-1207.
9,
Halls, H.C. 1975:
Shock
induced remanent magnetization in late
Precambrian rocks from Lake Superior; Nature, Vol. 225, pp. 692-695.
Halls, H.C., and West, G.F. 1971:
A Seismic Refraction Survey in
Lake Superior; Can. J. Earth Sbi., Vol. 8, No. 6, pp. 610-630.
Hamblin, William Kenneth, 1961:
Palaeographic Evolution of the Lake
Superior Region from Late Keweenawan to Late Cambrian Time;
Bull.
Geol. Soc. Am., Vol. 72, pp. 1-18.
Hanson, Gilbert N. 1975:
4OAr/39Ar Spectrum Ages of E4ogan Intrusions,
a Lower Keweenawan Flow, and Mafic Dikes in Northeastern MinnesotaNorthwestern Ontario; Can. J. Earth Sci., Vol. 12, pp. 821-835.
Hanson, G.N., and Malhotra, R. 1971:
K-Ar Ages of Mafic Dikes and
Evidence for Low-Grade Metamorphism in Northeastern Minnesota;
Geol. Soc. Amer. Bull., Vol. 82, pp. 1107-1113.
Harris, F.R. and Kustra, C.R. 1968:
Field Excursion Guide: Gunflint
Iron Formation - Sibley Group; Ontario Dept. Mines Geol. Field
Trip, Canadian Lakehead Area, 11 p.
Hawley, J.E. 1929:
Lead and zinc Deposits, Dorion and McTavish
Townships, Thunder Bay District. Ontario Dept. Mines, Vol. 38,
pt. 6, pp. 58-85. Accompanied by Map 38f, scale 1 inch to 1 mile.
Heslop, John Boyd, 1968:
Mineralogy and Textural Relationships of the
Mount Mollie Sulphides, Pine Bay Area, Thunder Bay District;
Unpubi. B.Sc. Thesis, University of Western Ontario, London,
Ontario.
68p.
Hinze, W.J., Roy, R.F. and Davidson, D.M. 1972:
The Origin of Late
Precambrian Rifts; Geol. Soc. Amer. Abstracts with Programs,
Vol. 4, No. 7, pp.723.
�41
Hofmann, H.J. 1969:
Stromatolites from the Proterozoic Animikie
and Sibley Groups, Ontario; Geol. Surv. Canada, Paper 68-69, 77p.
Hofmann, H.J. 1969:
Attributes of Stromatolites; Geol. Surv. Canada,
Paper 69-39, 58p.
Hofmann, H.J. 1971:
Precambrian Fossils, Pseudofossils, and Problematica in Canada; Geol. Surv. Canada, Bull. 189, l46p.
Holden, Edward F. 1925:
The cause of color in smoky quartz and
amethyst; The American Mineralogist, Vol. 10, No. 9, pp. 203-252.
Hotchkiss, W.O. 1923:
Amer.,
Vol. 34,
The Lake Superior Geosyncline; Bull. Gepl. Soc.
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Fresh-water Environment of Deposition of PreHough, J.L. 1958:
cambrian Banded Iron Formations;
Jour. Sed. Pet.,V. 28, Np.
pp. 414-430.
4,
Intensity of the Geomagnetic
Hubbard, T.P. and Ade-Hall, J.M. 1972:
Field during the Extrusion of the Keweenawan Lavas; Geol. Soc.,
Amer., Abstracts with Program, Vol. 4, No. 7, pp. 546.
Keweenawan Geology of Isle Royale, Michigan;
Huber, N.King, 1972:
Geo. Soc. Amer., Abstracts with Program, Vol. 4, No. 7, p. 546.
The Portage Lake Volcanics (Middle Keweenawan)
Huber, N.K., 1973:
on Isle Royale, Michigan; Geol. Survey Prof. Paper 754-C, 32p.
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James, Harold J. 1954:
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Changes in Mineral Assemblages with
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�42
Konda, Tadashi, and Green, John C. 1974:
Clinopyroxenes from the
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and Chemistry of the Late Precambrian Osler Group, District of
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Geology of the Black Bay
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Peninsula Area, District of Thunder Bay; Ontario Div. Mines,
Accompanied by Map 2304, scale 1 inch to 1 mile.
GR 133, 54p.
�43
Mcllwaine, W.H., Wallace, Henry, Franklin, J.M. and Poulsen, K.H., 1974:
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Gunflint Range; inSims, P.K., and Morey, G.B.,eds.,
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Late Precambrian Structural Evolution of
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�44
Mudrey, M.G., Jr. and Weiblen, P.W. 1972:
Diabase Intrusions of
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Murthy, G.S., Fahrig, W.F. and Jones, D.L. 1968:
The Paleomagnetism
of the Michikamau anorthositic intrusion, Labrador;, Can. J.
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Palmer, H.C. 1970:
Paleomagnetism and Correlation Of Some Middle
Keweenawan Rocks, Lake Superior; Can. J. Earth Scia, Vol. 7,
No. 6, pp. 1410-1436.
Peterman, Zell E., 1966:
Rb-Sr Dating of Middle Precambrian
Metasedimentary Rocks of Minnesota; Geol. Soc. Amer. Bull.,
Vol. 77, pp. 1031-1044.
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Age of
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Guide for Field Trip in the Duluth Complex
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A Petrographic Study of the Textures of Basic and
Ultrabasic Igneous Rocks, unpubl. Ph.D. Thesis, University of
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A Preliminary Study of the Shapes of Plagioclase
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*
Pye, E.G. 1968:
Geology and Scenery, Rainy Lake and East to Lake
Superior; Ontario Dept. Mines, Geol. Guide Book No. 1, ll4p.
Pye, E.G., 1969:
Geology and Scenery, North Shore of Lake Superior,
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Petrology and Mineralogy of a Gabbroic
Intrusion in Pardee Township Near Port Arthur, Ontario; Unpubl.
M.Sc. Thesis, University of Wisconsin, Milwaukee, Wis., 79 p.
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Pole Positions from the Mamainse Point Lavas
and Their Bearing on a Keweenawan Pole Path and Polarity Sequence;
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Pole Position From Thermally Cleaned Sibley Group
Sediments and its Relevance to Proterozoic Magnetic Stratigraphy;
Can. J. Earth Sci., Vol. 10, No. 1, pp. 180-193.
*
Robertson, W.A. and Fahrig, W.F., 1971:
The Great Logan Paleomagnetic
Loop - The Polar Wandering Path from Canadian Shield Rocks During
the Neohelikian Era; Can. J. Earth Sci., Vol. 8, pp. 1355-1372.
�45
Sage, R.P., Treacher, K., Meloche, D., and Bathe, D., 1975:
Slate
Islands, District of Thunder Bay; Ontario Div. Mines, Prelim.
Map P.997, Geol. Ser., Scale 1 inch to 660 feet or 1:7,920.
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The Origin of the Pre-Cambrian Banded Iron
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Concretions of the Thomson Formation,
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Rock Series in
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Vol. 51, pp. 1135-1172.
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The Animikie Iron Range; Annual Report, Ontario
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Silver, Leon T., and Green, John C.
Time Constants for
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Keweenawan Igneous Activity; Geol. Soc. Amer., Abstracts with
Programs, Vol. 4, No. 7, pp. 665-666.
Phase Relations
Simmons, E.C., Lindsley, D.H. and Papike, J.J. 1974:
and Crystallization Sequence in a Contact-Metamorphosed Rock
from the Gunf lint Iron Formation, Minnesota; Jour. Petrology,
Vol. 15, pt. 3, pp. 539-565.
Sims, Paul K. 1976:
Early Precambrian Tectonic-Igneous Evolution in
the Vermillion District, Northeastern Minnesota; Geol. Soc.
Amer. Bull., Vol. 87, pp. 379-389.
Sims, P.K., 1976:
Precambrian Tectonics and Mineral Deposits, Lake
Superior Region; Econ. Geol., Vol. 71, No. 6, pp. 1092-1118.
Smith, W.N., 1905:
Loon Lake Iron-Bearing District; Annual Report,
Ontario Bur. Mines, Vol. 14, Pt. 1, pp. 254-260.
Smith, T. Jefferson, Steinhart, John S., and Aldrich. L.T. 1966:
Lake Superior Crustal Structure; Jour. Geophys. Research, Vol. 71,
No. 4, pp. 1142-1172.
Spall, Henry 1971:
Evidence
Precambrian Apparent Polar Wandering:
from North America; Earth Planet. Sci. Letters, Vol. 10, pp. 273280.
Stacey, P.E., 1976:
Report to Division of Parks, Ontario Ministry
'of Natural Resources on the Stability Aspects of the Development
of Ouimet Canyon; Golder Associates, Vancouver, B.C., 14p.
Steacy, Harold R. 1974:
Our Beautiful Little Known Gemstones; Can.
Geog. J., Vol. 89, No. '6, pp. 4-13.
�46
Stewart, John H. 1976:
Late Precambrian Evolution of North America:
Plate Tectonics Implications; Geology, Vol. 4, No. 1, pp. 11-15.
Geochronology of Stratified Rocks of the
Stockwell, C.H. 1968:
Canadian Shield; Can. J. Earth Sd., Vol. 5, pp. 693-698.
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Tectonic Evolution of Continents
in Early Proterozoic Times; Nature, Vol. 247, Feb. 13, pp. 433-435.
A Paleomagnetic Study of the Gunflint, Mesabi,
Symons, D.T.A., 1966:
and Cuyuna Iron Ranges in the Lake Superior Region; Econ. Geol.
Vol. 61, pp. 1336-1361.
Iron Formation at Gravel Lake, Thunder Bay District,
Tanton, T.L. 1923:
Ontario; Geol. Survey Suimnary Report., Pt. Cl, pp. 1-5.
*
Tanton, T.L. 1925:
Evidence of Liquid Immiscibility in a Silicate
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Stratigraphy of the Northern Subprovince of the
Tanton, T.L. 1927:
Lake Superior Region; Bull. Geol. Soc. Amer., Vol. 33, pp. 731-748.
Tanton, T.L. 1928:
pp. 66-68.
Emulsions of Silicates; Amer. Jour. Sci., Vol. 15,
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Fort William and Port Arthur and Thunder Cap Map
Areas:
Thunder Bay District, Ontario; Geol. Surv. Can., Mem. 167,
222 p.
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Copper-Nickel Mineral Occurrences in Pigeon Area,
Ontario; Canada Dept. Mines., Bur. Econ. Geol., Paper 35-1, llp.
Radioactive Nodules in Sediments of the Sibley
Tanton, T.L. 1948:
Series, Nipigon, Ontario; Trans. Roy. Soc. Canada, 3rd Series,
Vol. 42, Section 4, pp. 69-75.
The Origin of Iron Range Rocks; Trans. Roy. Soc.
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Canada, Vol. 44, Series 3, pp. 1-19.
Three Great Basins of Precambrian Banded Iron
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Formation Deposition: A Systematic Comparison; Geol. Soc. Amer.
Bull., Vol. 79, pp. 1527-1544.
Development of Lake Superior Soft Iron Ores
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from Metamorphosed Iron Formation; Bull. Geol. Soc. Amer., Vol.60,
pp. 1101-1124.
Tyler,. Stanley A. and Barghoorn, Elso 5., 1954:
Occurrence of
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Studies
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of the Lake Superior Pre-Cambrian by Accessory-Mineral Methods;
Bull. Geol. Soc. Amer., Vol. 51, pp. 1429-1538.
�4
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Differentiation Trends in Osler V'olcanics,
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A Hot Spring Analog for the Depositional
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�PROCEEDINGS
TWENTY - SECOND
SECOND ANNUAL
ANNUAL
INSTITUTE ON
INSTITUTE
ON LAKE
LAKE SUPERIOR
SUPER lOR
GEOLOGY
held at
held
RADISSON ST.
ST. PAUL
11 East Kellogg Boulevard
11
St. Paul,
Minnesota 55101
55101
Paul, Minnesota
May
May 3-7, 1976
1976
under the sponsorship
sponsorship of
Minnesota Geological Survey
Survey
IS11
l5jl University
University of Minnesota
Minnesota
1633 Eustis
Eustis Street
Street
1633
St. Paul,
Paul, Minnesota
Minnesota 55108
55108
G.B.
and R.F.
R.F. Beltrame
G.B. Morey
'\:\orey and
Be1trame
General Editors
Editors
p
�SALES
Please order from: Publications
Geological Survey,
Survey, 1633
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Please
Publications Sales, Minnesota
Minnesota Geological
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sales tax
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(U.S.), plus 496
496 sales
Make
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Printed at:
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�TABLE OF
TABLE
OF CONTENTS
CONTENTS
v
GENERAL INFORMATION
V
INSTITUTE
INSTITUTE BOARD
BOARD OF DIRECTORS
v
V
LOCAL COMMITTEE
COMMITTEE
Vi
vi
SESSIONS CHAIRMEN
SESSIONS
Vi
vi
ANNUAL BANQUET SPEAKER
ANNUAL
SPEAKER
Vii
vii
ACKNOWLEDGEM ENTS
ACKNOWLEDGEMENTS
VII
vii
CALENDAR OF EVENTS
EVENTS AND PROGRAM
PROGRAM
VIII
viii
ABSTRACTS
3
FIELD TRIPS
TRIPS
71
A. MINNESOTA
MINNESOTA RIVER
RIVER VALLEY
VALLEY FIELD CONFERENCE
CONFERENCE
73
B.
B. ENGINEERING
ENGINEERING AND
AND PLEISTOCENE
PLEISTOCENE GEOLOGY
GEOLOGY IN
IN THE
THE TWIN
TWIN CITIES
AREA
75
111
iii
�GENERAL INFORMATION
GENERAL
INFORMATION
22nd Annual
INSTITUTE ON LAKE SUPERIOR
SUPERIOR GEOLOGY
GEOLOGY
Radisson
Radisson St. Paul
Paul
St. Paul,
Paul, Minnesota
Minnesota 55101
5510 1
May 3-7, 1976
May
1976
by
Sponsored by
Minnesota Geological Survey
Survey
University of Minnesota
Minnesota
1633 Eustis
1633
St. Paul,
Paul, Minnesota
Minnesota 55108
55108
INSTITUTE
INSTITUTE BOARD OF DIRECTORS
DIRECTORS
RE. Giblin,
of Mines,
Mines, Ministry
Ministryofof Natural
Natural Resources,
Resources, Sault
Sault Ste.
Division of
P.E.
Giblin, Ontario Division
Marie, Ontario
1D. Hughes,
J.D.
Hughes, Department of
of Geography,
Geography, Earth Science and Conservation, Northern
Michigan
University,
Marquette,
Michigan
Marquette, Michigan
Michigan
M.E.
Geological and
and Natural History
Wisconsin Geological
History Survey,
Survey, Madison,
Madison, Wisconsin
Wisconsin
M.E. Ostrom, Wisconsin
*R.C. Reed (Secretary-Treasurer),
(Secretary-Treasurer), Geological
Geological Survey
Survey Division,
Division, Department of
Natural Resources,
Resources, Lansing,
Lansing, Michigan
Michigan
M.S.
Walton, Minnesota
MinnesotaGeological
GeologicalSurvey,
Survey,University
Universityof
of Minnesota,
Minnesota, St.
St. Paul,
M.S. Walton,
Minnesota
*Permanent
*Permanent Member
Member
vv
�;;
LOCAL COMMITTEE
COMMITTEE
Conference Chairman
Chairman
Matt Walton, Minnesota Geological Survey, University of
of Minnesota,
Minnesota, 1633
1633
Eustis St., St. Paul,
Paul, Minnesota
Minnesota 55108
55108
Eustis
Technical Program
G.B.
Minnesota Geological
Geological Survey,
Survey, University
University of Minnesota, 1633
G.B. Morey,
Morey, Minnesota
1633
Eustis St., St. Paul,
Paul, Minnesota
Minnesota 55108
55108
Eustis
P.W. Weiblen,
Weiblen, Department
Department of Geology
P.W.
Geology and
and Geophysics,
Geophysics, University of Minnesota,
Minnesota,
Minneapolis, Minnesota 55455
Minneapolis,
55455
Field Trips
Trips
Stanley E.
E. Chernicoff, Department
Stanley
Department of
of Geology
Geology and
and Geophysics,
Geophysics, University
of Minnesota, Minneapolis,
of
Minneapolis, Minnesota
Minnesota 55455
55455
S.S. Goldich,
Goldich, Department
Department of Geology,
S.S.
Geology, Northern Illinois
Illinois University, DeKaib,
DeKalb, illinois
Illinois
60115
G.B. Morey,
Morey, Minnesota
MinnesotaGeological
GeologicalSurvey,
Survey,University
Universityof
of Minnesota,
Minnesota, St.
St. Paul,
Paul,
G.B.
Minnesota 55108
55108
V.R. Murthy,
Murthy, Department
Department of Geology
University of Minnesota,
Y.R.
Geology and
and Geophysics,
Geophysics, University
Minneapolis, Minnesota 55455
55455
C.R. Nelson,
C.R.
Nelson, Department of
of Civil
Civil and
and Mineral
Mineral Engineering,
Engineering, University of
Minnesota,
Minneapolis,
Minnesota
55455
Minnesota, Minneapolis, Minnesota 55455
D.H. Yardley,
Yardley, Department of Civil
D.H.
Civil and Mineral
Mineral Engineering,
Engineering, University
of Minnesota, Minneapolis,
of
Minneapolis, Minnesota
Minnesota 55455
55455
Physical Arrangements
Physical
i\rrangements
Gordon J.
3. Amundson,
Arnundson,Department
Departmentofof Conferences,
Conferences, Nolte
Nolte Center for Continuing
Gordon
Continuing
Education, University of Minnesota,
Minnesota, Minneapolis,
Minneapolis, Minnesota
Minnesota 55455
55455
SESSION
SESSION CHAIRMEN
D.M. Davidson,
Davidson,Jr.,
3r., Department
Department of Geology, University of Minnesota,
D.M.
Minnesota, Duluth,
Duluth,
Duluth, Minnesota
Minnesota 55802
55802
S.S. Goldich,
Goldich, Department
Department of Geology,
Geology, University of Northern
Northern Illinois,
Illinois, DeKaib,
DeKalb,
S.S.
Illinois 60115
Department, 3M,
Clare Goldsmith, Geology
Geology Department,
3M, Bldg.
Bldg. 526-2, St. Paul,
Paul, Minnesota.
Minnesota.
Alan
M. Goodwin,
Goodwin,Department
Department of
of Geology,
Geology, University
University of
of Toronto,
Toronto, Toronto,
Alan M.
Ontario,
Ontar
io, Canada.
vi
�1C. Green,
J.C.
Green, Department
Departmentof
of Geology,
Geology, University
University of
of Minnesota,
Minnesota, Duluth,
Duluth, Duluth,
Duluth,
Minnesota 55802
55802
R.W. Marsden,
Marsden, Department
Department of Geology, University of Minnesota,
R.W.
Minnesota, Duluth,
Duluth,
Duluth, Minnesota 55802
55802
Z.E. Peterman,
Peterman, U.S.
Z.E.
U.S. Geological
Geological Survey,
Survey, Denver,
Denver, Colorado
Colorado 80225
80225
F.i Sawkins,
F.J.
Sawkins, Department
DepartmentofofGeology
Geologyand
and Geophysics,
Geophysics, University
University of
of Minnesota,
Minnesota,
Minneapolis, Minnesota 55455
55455
Weiblen, Department
Department of Geology
Geology and Geophysics,
Geophysics, University of Minnesota,
Minnesota,
P.W. Weiblen,
Minneapolis, Minnesota 55455
55455
of Civil
Civil and
and Mineral
Mineral Engineering,
Engineering, University
University
D.M. Yardley, Department of
of Minnesota, Minneapolis,
of
Minneapolis, Minnesota
Minnesota 55455
55455
BANQUET GUEST
GUEST SPEAKER
ANNUAL BANQUET
Prof. Eugene
Shoemaker, Geology
GeologyDepartment,
Department, California
California Institute of
Eugene M.
M. Shoemaker,
of
Technology,
Pasadena, California.
Technology, Pasadena,
ACKNOWLEDGEMENTS
The
organizing committee
committee of the
The organizing
the 1976
1976 Institute
Institute on
on Lake
Lake Superior
Superior Geology
Geology
gratefully acknowledge
in typing
typing the
the final manuscript
acknowledge the work
work of 3o
Jo Behm
Behm in
manuscript for
for
the Proceedings.
Proceedings. Richard
Richard Darling
Darling prepared the cover
cover illustration.
illustration.
vii
�CALENDER OF
OF EVENTS
CALENDER
EVENTS
AND
PROGRAM
MONDAY, May 5, 1976
3:30 p.m.
3:30
Pre-Institute field
Pre-Institute
field trip
tripA,
A,1976
1976Minnesota
Minnesota River
River Valley
Valley Field
Field
Trip and
and Conference
Conference departs from the Radisson
Trip
Radisson St. Paul
Paul for
for
Donovan's Motel,
Motel, Redwood
Donovan's
Redwood Falls, Minnesota.
Minnesota.
TUESDAY, May
May 6,1976
6, 1976
TUESDAY,
8:00 a.m.
8:00
Minnesota
River Valley
Field Trip
Trip departs from Redwood
Minnesota River
Valley Field
Redwood Falls
to Granite Falls
Falls and
and Montevideo.
Montevideo.
5:00 p.m.
Minnesota
River Valley
Field Trip
Trip returns
returns to Redwood
Minnesota River
Valley Field
Redwood Falls.
8:00
8:00 p.m.10:00 p.m.
10:00
Discussion
session, Minnesota
Minnesota River
River Valley
Valley Conference,
Conference, Z.E.
Discussion session,
Z.E.
Peterman, Chairman.
G.B. Morey
Morey
Introduction
L'1troduction
R.L. Bauer
Bauer
OF PRESTRUCTURAL STUDIES
STUDIES OF
CAMBRIAN ROCKS
ROCKS IN
IN THE MINNECAMBRIAN
SOTA
SOT
A RIVER VALLEY
VALLEY
C.E. Hedge
Hedge &
&
S.S. Goldich
S.S.
Rb-Sr GEOCHRONOLOGY
GEOCHRONOLOGY OF THE
THE
MONTEVIDEO GNEISS,
GNEISS, MINNESOTA
MONTEVIDEO
RIVER VALLEY
VALLEY
W. Wilson &
w.
&
GEOCHRONOLOGY AND GEOGEOCHEMISTRY OF
OF GRANULITE FACIES
CHEMISTRY
ROCKS NEAR
NEAR GRANITE
GRANITE FALLS
FALLS
IN THE MINNESOTA RIVER VALLEY
IN
VALLEY
V.R. Murthy
Murthy
B.R. Doe
B.R.
Doe &
&
M.H.
M.H. Delevaux
LEAD ISOTOPE INVESTIGATIONS
LEAD
INVESTIGATIONS
IN
THE
MINNESOTA
IN
MINNESOT A RIVER VALLEY
VALLEY
S.S. Goldich,
J.L. Wooden,
Wooden,
PRECAMBRIAN HISTORY
PRECAMBRIAN
HISTORY OF THE
THE
MORTON-NEW ULM
ULM REACH
REACH OF
MORTON-NEW
THE MINNESOTA RIVER VALLEY
VALLEY
G.A.
]r.
Ankenbauer, Jr.
G.A. Ankenbauer,
TM.
T.M. Levy
Levy &
&
R.U. Suda
Suda
P.W. Weiblen
Weiblen,,
P.W.
K.3.
K.J. Schulz
Schulz &
&
B.V.
B.
V. Nielsen
COMPOSITIONAL VARIATIONS
VARIATIONS
OF MINNESOTA
MINNESOTA RIVER
RIVER VALLEY
VALLEY
AMPHIBOLITE
S.S. Goldich
S.S.
Summary
viii
4
�F
WEDNESDAY,
May 5,1975
WEDNESDAY, May
8:00 a.m.
8:00
Minnesota
River Valley
Field Trip departs Redwood
Minnesota River
Valley Field
Redwood Falls for
for
Morton and New
New Ulm.
Ulm.
8:00 a.m.
8:00
Field Trip
on Engineering
and Pleistocene Geology
Trip B on
Engineering and
Geology in the
Twin
Cities area departs
Twin Cities
departs Radisson
Radisson St.
St. Paul.
Paul.
5:00 p.m.
5:00
Field Trip on
and Pleistocene Geology
returns to
on Engineering
Engineering and
Geology returns
to
Radisson
Radisson St. Paul.
Paul.
6:00 p.m.6:00
9:00 p.m.
9:00
Paul.
Early registration, Minnesota
Early
Minnesota East,
East, lower
lower level,
level, Radisson
Radisson St.
St.
8:00 p.m.
8:00
Conferences Smoker
Smoker (cash bar) Capitol Ballroom,
Ballroom, lower level
Radisson St. Paul.
Radisson
8:00 p.m.
8:00
Minnesota River
River Valley
Valleyfield
field trip
trip returns,
returns, Radisson
Minnesota
Radisson St. Paul.
THURSDAY,
THURSDAY, May
May 8, 1976
1976
7:30
7:30 a.m.9:30
9:30 a.m.
Registration, outside
outside Minnesota
Minnesota East, Radisson
Radisson St. Paul.
Paul.
8:00 -
General Chairman, 1976
Welcome, Matt \Valton,
Walton, General
1976 Institute on
on
Lake Superior
Super ior Geology.
8:10
8:10
SESSION I - SYMPOSIUM ON GEOLOGY AND
SESSION
AND GEOCHEMISTRY
GEOCHEMISTRY
PRECAMBRIAN ROCKS,
ROCKS, 5.5.
S.S. Go1dich
Goldich and A.M.
OF EARLIEST
EARLIEST PRECAMBRIAN
A.M.
Goodwin, Co-Chairmen.
Goodwin,
8:10
G.P. Beakhouse
Beakhouse
A REAPPRAISAL OF
OF THE
THE WESTERN
WESTERN
PORTION OF THE
THE ENGLISH
ENGLISH RIVER
RIVER
SUBPROVINCE, NORTHWESTERN
SUBPROVINCE,
ONTARIO AND SOUTHEASTERN
ONTARIO
MANITOBA
8:30
C.F. Gower
Gower
THE GEOLOGY
GNEISSIC ROCKS
THE
GEOLOGY OF GNEISSIC
IN THE
IN
THE KENORA DISTRICT, ENGLISH
ENGLISH
RIVER GNEISS
RIVER
G NEISS BELT
BEL T
8:50
A.M. Goodwin
LITHIC
ELEMENT
LITHIC AND MAJOR ELEMENT
COMPOSITION IN
IN THE
THE SUPERIOR
COMPOSITION
GEOTRA
VERSE, 0ONTARIO
G
EOTRA VERSE,
NT ARlO
9:10
C.-L. Chou,
Chou,
N.B.W.
&
N.B.W. Harris, &
ABUNDANCES
OF RARE EARTH
ABUNDANCES OF
EARTH
AND OTHER ELEMENTS.
IN ARCHEAN
ELEMENTS- IN
GRANITIC AND GNEISSIC
GRANITIC
GNEISSIC ROCKS
FROM THE
THE ENGLISH
ENGLISH RIVER
RIVER GNEISS
GNEISS
BELT, ONTARIO
A.M. Goodwin
9:30
G.N. Hanson
Hanson &
&
S.S. Goldich
5.5.
RARE EARTH
EARTH ELEMENT
ELEMENT STUDIES
STUDIES
OF THE
THE ARCHEAN
ARCHEAN GNEISSES
GNEISSES OF
THE MINNESOTA
MINNESOT A RIVER VALLEY
VALLEY
ix
�9:50
Welsh
J.L. Welsh
J.L.
PETROLOGY
PETROLOGY OF
OF THE
THE ARCHEAN
ARCHEAN
GNEISSES
GNEISSES AT
AT THE
THE NORTHWEST
CORNER
CORNER OF THE SACRED HEART
PLUTON;
PLUTON; MINNESOTA RIVER
VALLEY,
VALLEY, MINNESOTA
10:10
10:10
W.R. Van
&.
W.R.
Van Schmus &
J.L.
J.
L. Anderson
GNEISS
GNEISS AND
AND MIGMATITE
MIGMATITE OF
OF ARCHEAN
AGE
BASEMENT
AGE IN
IN THE
THE PRECAMBRIAN BASEMENT
OF CENTRAL WISCONSIN,
WISCONSIN, U.S.A.
10:30
Z.E. Peterman,
Z.E.
R.E. Zartman, &
R.E.
&.
P.K. Sims
OLD
W GNEISSES
GNEISSES
OLD PRECAMBRIAN W
IN
MICHIGAN
IN NORTHERN MICHIGAN
10:50
M.M. Kehlenbeck
M.M.
NATURE
THE QUETICO-WABIGOON
QUETICO-WABIGOON
NATURE OF THE
BOUNDARY
BOUNDARY IN
IN THE
THE de
de COURCEYSMILEY
SMILEY LAKES
LAKES AREA,
AREA, NORTHWESTERN
WESTERN ONTARIO
11:10
D. Birk
ELEMENTS IN
THE ARCHEAN
TRACE ELEMENTS
IN THE
GRANITOID
GRANITOID DIAPIRS PIERCING
WABIGOON GREENSTONE
THE WABIGOON
BELT
11:30
I.E. Smith,
T.E.
Smith,
A. Turek,
Turek, &
&.
C. Riddle
THE
THE GEOCHEMISTRY
GEOCHEMISTRY OF THE
GAMITAGAMA LAKE COMPLEX,
GAMITAGAMA
WAWA, ONTARIO
WAWA,
11:50
E.C.
E.C. Perry, 3r.
Jr.
SN. Ahmad
S.N.
Ahmad
IN METAMORPHOSED
METAMORPHOSED
CARBON IN
ISUA, WEST
WEST
SEDIMENTS FROM ISUA,
GREENLAND
THURSDAY,
THURSDAY, May
May 8, 1976
1976
8:10
8: 10 am
SESSION
SESSION IIII-- ENGINEERING
ENGINEERING AND
AND ENVIRONMENTAL
ENVIRONMENTAL GEOLOGY,
D.M.
Yardley and
and C.
C. Goldsmith,
D.M. Yardley
Goldsmith, Co-chairmen.
8:10
H.O. Pfannkuch
Pfannkuch
SYSTEMS APPROACH TO
TO ENVIRONENVIRONA SYSTEMS
MENTAL GEOLOGY
8:30
8:30
D. Pollack
Pollack &
&.
H.O. Pfannkuch
IMPLICATIONS
ENVIRONMENTAL IMPLICATIONS
GROUNDW ATER-LAKE INTEROF GROUNDWATER-LAKE
WITH LAND USE APPLICATION
ACTION WITH
8:50
8:50
W.
W. Rohrer &
&.
H.O. Pfannkuch
Pfannkuch
GROUNDW ATER SPREADING OF
GROUNDWATER
HYDROCARBON SPILLS
SPILLS WITH
WITH
HYDROCARBON
EMPHASIS ON MONITOR
MONITOR
SPECIAL EMPHASIS
SYSTEM DESIGN
DESIGN IN
DRIFT
SYSTEM
IN GLACIAL DRIFT
9:10
9: 10
D.I.
D.I. Siegel
Siegel
OF DISSOLVED
OISSOL VED SOLIDS
SOLIDS
SOURCES OF
IN GROUNDWATER
GROUNDW ATER FROM SUPERIOR
SUPERIOR
IN
AND RAINY
RAINY LOBE
LOBE TILL
TILL
AND
xx
�ji
9:30
S.!.
S.I. Jacobsen
THE TRACE ELEMENT
THE
ELEMENT GEOCHEMISTRY
GEOCHEMISTRY
OF PEAT
PEAT BOGS
BOGS OVER
OVER DIFFERENT
BEDROCK TYPES,
TYPES, SOUTHERN
BEDROCK
HOUGHTON COUNTY, MICHIGAN
MICHIGAN
Coffee
9:50
10:10
10: 10
M.G.
Mudrey, Jr.
M.G. Mudrey,
B.C.
B.C. Parker,
K.
K. Cartwright
Cartwright &
&.
L.D.
McGinnis
L. D. McGinnis
DIAMOND
DIAMOND DRILLING
DRILLING IN ENVIRONENVIRONMENTALLY SENSITIVE
SENSITIVE AREAS
- ENVIRONMENTAL IMPACT:
MONITORING
MONITORING AND
AND ASSESSMENT
ASSESSMENT
10:30
E. Booy
Booy &
&.
STRATIGRAPHIC
STRA TIGRAPHIC VARIATION
VARIATION IN
IN
MINERALOGY AND ENGINEERING
MINERALOGY
ENGINEERING
CHARACTERISTICS OF ONTONAGON
ONTONAGON
CLAY NEAR A
CLAY
A MAJOR SLOPE
SLOPE
FAILURE, ONTONAGON
ONTONAGON COUNTY,
COUNTY,
MICHIGAN
S.). Dyl,
S.J.
Dyl, II
II
10:50
A.M.
A.M. Johnson
Johnson &
&
H.O. Sorenson
Sorenson
ENGADINE DOLOSTONE OF
OF MICHIGAN'S
MICHIGAN'S
EASTERN UPPER PENINSULA:
PENINSULA:
GEOLOGY AND RESOURCE EVALUATION
GEOLOGY
EVALUATION
11:10
E. Booy
Booy &
&.
R.D. Harris
SECONDARY MINERAL GROWTH
SECONDARY
OF THE
THE WHITE
WHITE PINE SHALE
SHALE COMPARED
WITH
WITH CLASSIC "HEAVING" SHALES
SHALES
C.R. Nelson
Nelson &
&.
D.H. Yardley
D.H.
MODIFICATION OF ENGINEERING
MODIFICATION
ENGINEERING
PROPERTIES OF ST.
ST. PETER
PETER SANDSTONE
SANDSTONE
11:30
12:10
12:
10 p.m.—
p.m.1:30 p.m.
1:30
12:10
12:
10 p.m.1:30
1:30 p.m.
1:30
Lunch
Informal
meeting of
of geologists
geologists interested in
Informal meeting
in Precambrian
Precambrian of
of
Wisconsin.
Mudrey,Jr.,
Jr., convenor.
convenor. All
Wisconsin. M.G.
M.G. Mudrey,
All interested
interested geologists
geologists
bulletin board
board for
for notice of location).
are welcome.
welcome. (See
(See bulletin
locaticn).
SESSION III
III - GENERAL
GENERAL GEOLOGY,
D.L. Southwick and R.W.
SESSION
GEOLOGY, D.L.
R.W.
Marsden, Co-Chairmen
1:30
R.W.
R.W. Ojakangas
ANATOMY OF
OF A WELL-COVERED
ANATOMY
WELL-COVERED
GREENSTONE BELT, NORTHWESTERN
NORTHWESTERN
MINNESOTA
1:45
D.L. Southwick
D.L.
HIGH-GRADE
HIGH-GRADE METAMORPHISM
METAMORPHISM
ASSOCIATED
WITH
THE VERMILION
ASSOCIA TED
VERMILION
BATHOLITH, MINNESOTA-ONTARIO
BATHOLITH,
2:00
R.S. Maass
Maass &
&.
L.C. Medaris,
L.C.
Medaris, Jr.
PENOKEAN STRUCTURES AND
PENOKEAN
AND
PLUTONIC ROCKS
ROCKS IN
PLUTONIC
IN PORTAGE
AND WOOD
AND
WOOD COUNTIES, WISCONSIN
WISCONSIN
xi
�——
2:15
G.L. LaBerge
LaBerge &
&.
P.E. Myers
Myers
THE CENTRAL
CENTRAL WISCONSIN
WISCONSIN BATHOLITH
BATHOLITH
2:30
P.E. Myers
Myers
THE WAUSAU
SYENITE OF
OF CENTRAL
THE
WAUSAU SYENITE
WISCONSIN
2:45
E.J. Smith
GEOLOGY AND
AND GEOCHEMISTRY
GEOCHEMISTRY
OF THE PRECAMBRIAN
PRECAMBRIAN MARCELLON
RHYOLITE, COLUMBIA
COLUMBIA COUNTY,
WISCONSIN
Coffee
3:00
3:15
P.K. Sims
Sims
MIDDLE PRECAMBRIAN
PRECAMBRIAN AGE
AGE OF
MIDDLE
VOLCANOGENIC MASSIVE
MASSIVE SULFIDE
DEPOSITS IN
IN NORTHERN
NORTHERN WISCONSIN
WISCONSIN
3:30
W.C.
W.C. Prinz
CORRELATIVE
CORRELA
nVE IRON-FORMATIONS
IRON-FORMAnONS
AND
VOLCANIC
ROCKS OF
OF PREAND VOLCANIC ROCKS
CAMBRIAN X
X AGE,
AGE, NORTHERN
CAMBRIAN
NORTHERN
MICHIGAN
3:45
M.S. Lougheed &
&.
3.1.
J. J. Mancuso
ORIGIN OF LAMINAE
ORIGIN
LAMINAE IN
IN PRECAMBRIAN
IRON-FORMAION
4:00
T.-M. Han
GEOCHEMICAL PROCESSES FOR
GEOCHEMICAL
THE FORMATION OF MAGNETITE
MAGNETITE
IN LOW-GRADE METAMORPHIC
IN
METAMORPHIC
PRECAMBRIAN IRON-FORMATIONS
IRON-FORMATIONS
4:15
W.F.
W.F. Cannon &
&.
L.J. Drew
Drew
RESOURCES OF RECOVERABLE
RECOVERABLE
IRON ON THE
THE MARQUETTE
MARQUETTE RANGE,
RANGE,
MICHIGAN
BY A
MICHIGAN —
- ESTIMATES BY
MONTE
CARLO SIMULATION
SIMULATION
MONTE CARLO
METHOD
4:30
D.W. Snider
D.W.
A GROUND INVESTIGATION
INVESTIGATION OF
AN AEROMAGNETIC
AEROMAGNETIC ANOMALY,
ANOMALY,
DICKINSON COUNTY, MICHIGAN
MICHIGAN
DICKINSON
5:30 p.m.5:30
6:30
6:30 p.m.
SOCIAL HOUR
HOUR(cash
(cashbar)
bar)CapitAL
CapitAL Ballroom,
Ballroom, Radisson
Radisson St.
St. Paul
SOCIAL
6:30
6:30 p.m.
ANNUAL
BANQUET,Capital
Capital Ballroom,
Ballroom, Radisson
Radisson St.
St. Paul,
ANNUAL BANQUET,
Eugene
M. Shoemaker,
Shoemaker, Guest
Guest Speaker.
Eugene M.
FRIDAY,
FRIDAY, May
May 9, 1976
1976
8:00 a.m.
8:00
SESSION IV
GEOLOGY. P.W.
P.W. Weib1en
Weiblenand
and J.C.
J.C.
IV - GENERAL GEOLOGY.
Green, Co-Chairmen
8:10
8: 10
F.3.
F.J. Sawkins
Sawkins
ORE DEPOSITS
DEPOSITS IN RELATION TO
TO
HOTSPOT-GENERATED
HOTSPOT-G ENERA TED INTRACONTINENTAL RIFTING
RIFTING
xii
~
�8:30
8:30
1M. Robertson
J.M.
GEOLOGY AND MINERALOGY
GEOLOGY
MINERALOGY
OF SOME
SOME COPPER SULFIDE
SULFIDE DEPOSITS
DEPOSITS
NEAR MOUNT
BOHEMIA,
KEWEENAW
MOUNT BOHEMIA, KEWEENAW
COUNTY, MICHIGAN
MICHIGAN
8:50
W.A. Bartlett,
Bartlett,
W.A.
M.S.
Lougheed,
M.S.
U.J.Mancuso
J.
Mancuso &
&
L.3. Walters
L.J.
DISTRIBUTION
IN
DISTRIBUTION OF
OF SULFUR IN
THE
WEST KIERNAN
THE WEST
KIERNAN SILL,
SILL, IRON
COUNTY, MICHIGAN
MICHIGAN
9:10
B. Bonnichsen &
B.
&
R.I. Botto
R.I.
THE BEHAVIOR
OR PRECIOUS
BEHAVIOR OR
METALS
METALS AND
AND OTHER
OTHER TRACE
ELEMENTS DURING
ELEMENTS
DURING THE FRACTIONAL
CRYSTALLIZATION OF DULUTH
CRYSTALLIZATION
COMPLEX SULFIDES
SULFIDES
9:30
LA. Vogel,
T.A.
Vogel,
M.B. McBride &
M.B.
&
R. Ehrlich
Ehrlich
SYNGENETIC
MODEL FOR THE
THE
SYNGENETIC MODEL
ORIGIN
WHITE PINE
ORIGIN OF THE WHITE
PINE COPPER
DEPOSIT
9:50
N. Scofield
CHEMISTRY OF PRIMARY AND
CHEMISTRY
AND
SECONDARY
MINERALS OF SOME
SOME
SECONDARY MINERALS
PORTAGE LAKE
LAKE LAVAS,
LAVAS, KEWEENAW
KEWEENAW
PENINSULA:
PENINSULA: DEVELOPMENT OF
MODELS OF
MODELS
OF DIFFERENTIATION
AND LOW-RANK METAMORPHISM
METAMORPHISM
Coffee
10:10
10:30
1G. Grimes
J.G.
Grimes
APPLICATION OF A
A FLOW
FLOW DIRECTION
DIRECTION
PORTAGE
TECHNIQUE TO THE PORTAGE
VOLCANICS, MICHIGAN
MICHIGAN
LAKE VOLCANICS,
10:50
C. Brumleve
Brumleve
FRACTURE
PETROLOGY AND FRACTURE
THE KINGSTON
KINGSTON
CHARACTERISTICS OF THE
CONGLOMERATE,KEWEENAW
CONGLOMERATE,
KEWEENAW
COUNTY, MICHIGAN
MICHIGAN
11:10
B.E.
B. E. Aaquist
AN INTERPRETATION OF THE
THE
AN
KINGSTON CONGLOMERATE AS
AS
KINGSTON
IN THE
THE PORTAGE
PORTAGE
A
A RHYOLITE
RHYOLITE TUFF
lUFF IN
LAKE LAVA
LAVA SERIES,
SERIES, KEWEENAW
KEWEENAW
PENINSULA, MICHIGAN
MICHIGAN
11:30
3.M.
J.M. DeGraff
STRUCTURAL AND
AND AGE
AGE RELATIONRELATIONSHIPS AT THE LAC
LAC LA
LA BELLE
BELLE
SHIPS
ANOMALY, KEWEENAW
KEWEENAW
MAGNETIC ANOMALY,
COUNTY, MICHIGAN
MICHIGAN
11:50
L.L.
L. L. Babcock
Babcock
CONTACT RELATIONSHIPS
RELATIONSHIPS BETWEEN
BETWEEN
CONTACT
THE IACOBSVILLE
SANDSTONE
JACOBSVILLE SANDSTONE
AND THE
THE PORTAGE LAKE
LAKE LAVA
LAVA
AND
A PROGRESS
PROGRESS REPORT
GROUP: A
xiii
xiii
ji
�;;;
12:15
12:15 p.m.1:15
1: 15 p.m.
Lunch
12:15 p.m.12:15
1:15
1:
15 p.m.
Annual Business
BusinessMeeting,
Meeting,Institute
Institute Board
Board of
of Directors.
Annual
1:30 p.m.
1:30
SESSION V - GENERAL GEOLOGY,
GEOLOGY, F.J. Sawkins
Sawkins and
and D.M.
D.M.
Davidson, Jr.,
Jr., Co-Chairmen.
Davidson,
1:30
F.M. Swain,
F.M.
1. Baysinger &
J.
&
3.M.
J.M. Bratt
HYDROCARBONS OBTAINED
OBTAINED BY
BY
PYROLYSIS
PYROLYSIS OF SOME
SOME PRECAMBRIAN
PRECAMBRIAN
ROCKS OF MINNESOTA
MINNESOTA
1:50
S.W. Stuhr &
&
S.W.
E.N. Cameron
E.N.
GEOLOGY OF THE ROUND LAKE
GEOLOGY
INTRUSION, SAWYER
INTRUSION,
SAWYER COUNTY,
WISCONSIN
2:10
R.M. Tyson
Tyson &
&
B.
B. Bonnichsen
HORNFELSED BASALTS
BASALTS IN THE
THE
DULUTH COMPLEX
2:30
1R.
J.R. Burnell,
Burnell, 3r.
Jr.
THE PETROLOGY AND
AND STRUCTURAL
STRUCTURAL
RELATIONS
OF THE
THE LATER
RELATIONS OF
LATER PREPRECAMBRIAN BRULE LAKE
LAKE INTRUSIONS,
INTRUSIONS,
COOK
MINNESOTA
COOK COUNTY, MINNESOTA
2:50
D.M.
Davidson, Jr.,
D.M. Davidson,
H. Halls &
&
3.R.
J.R. Burnell, 3r.
Jr.
PALEOMAGNETISM OF
OF THE
THE LATE
PALEOMAGNETISM
PRECAMBRIAN BRULE LAKE
LAKE
INTRUSION,
INTRUSION, COOK
COOK COUNTY,
COUNTY,
MINNESOTA
Coffee.
3:10
3: 10
3:30
N.M. Pope
N.M.
PETROLOGY AND STRUCTURE
STRUCTURE
OF THE
THE LATE
LATE PRECAMBRIAN
PRECAMBRIAN
SILVER
CREEK CLIFF AND
SILVER CREEK
AND LAFAYETTE
LAFAYETTE
BLUFF MAFIC INTRUSIONS,
INTRUSIONS, LAKE
COUNTY, MINNESOTA
MINNESOTA
3:50
R.P. Meyer,
Meyer,
GEOPHYSICAL PROSPECTING
OFF THE
THE KEWEENAW
KE.WEENAW PENINSULA
3.R. Moore,
J.R.
E.L. Nebrija
Nebrija &
&
C.T.
C. T. Young
Young
4:10
H.C. Halls
Halls
THE SLATE
THE CENTRAL
THE
SLATE ISLANDS:
ISLANDS: THE
UPLIFT OF
OF A
A METEORITE
METEORITE IMPACT
IMPACT
CRATER?
xiv
�U)
—1
C)
-1
U)
w
ABSTRACTS
•
�I
AN
AN INTERPRETATION
INTERPRETATION OF
OFTHE
THEKINGSTON
KINGSTON CONGLOMERATE
CONGLOMERATEAS
ASAA
RHYOLITE
INTHE
THEPORTAGE
PORTAGELAKE
LAKELAVA
LAVASERIES,
SERIES,
RHYOLITE lUFF
TUFFIN
KEWEENAW
KEWEENAW PENINSULA, MICHIGAN
MICHIGAN
B.E.
Department of
of Geology,
Geology, University
University of
of Western
Western Ontario,
Ontario,London,
London,
B.E. Aaquist,
Aaquist, Department
Ontar io N6A
N6A 5B7
5B 7
Ontario
ABSTRACT
The
The rock
rock type included
included under
under the
the formation
formation name
nameof
ofKingston
Kingston Conglomerate
Conglomerate
within
quadrangleisis interpreted
interpreted as
as having
formed by
by the fracturing
within the Ahmeek
Ahmeek quadrangle
having formed
fracturing
and
reworkingof
of aa rhyolite
rhyolite tuff.
tuff. The
and minor
minor reworking
The average
average thickness
thickness of
of the
the formation
formation isis
10
layers, which
which commonly
commonlyare
are lenticular
lenticular in
IO meters and individual
individual layers,
in shape and
and cross
cross
bedded, range
thickness from
from 1I mm
mm to
to 65
65 cm.
cm. Fragments
Fragments consist
consist entirely of
of
bedded,
range in thickness
rhyolite
rhyolite having
having quartz and
and plagioclase
plagioclase phenocrysts
phenocrysts in a cryptocrystalline
cryptocrystalline groundgroundmass.
deep embayments
embayments characteristic
characteristic
mass. The
The phenocrysts
phenocrysts have
have vague
vague boundaries
boundaries and
and deep
parts of
of the formation
volcanic origin.
origin. Sandy
Sandy parts
formation consist
consist of angular
angular quartz
quartz and
and
of a volcanic
feldspar
feldspar crystals, feldspar
feldspar laths, fine
fine angular
angular grains
grains of cryptocrystalline
cryptocrystalline material,
and
grainsofofhematite.
hematite. Some
and rounded
rounded grains
Some of the
the poorly
poorly sorted,
sorted, coarse-grained
coarse-grained layers
layers
have a texture indicative
indicative of
of in
in situ
situ fracturing
fracturing of
of fragments
fragments with
with separation
separation the
theonly
only
Also,
sand
around
fragments
in
these
layers
appears
movement
of
the
fragments.
Also,
sand
around
fragments
in
these
appears
movement of
fragments.
to have
have formed by
by the breakdown
breakdown of
fragments.
of adjacent fragments.
The
distribution of
of the Kingston
rhyolite plus
plus similar
similar rhyolitic
rhyolitic facies
facies in
The distribution
Kingston rhyolite
in three
other interflow
interflow horizons
horizons in the overlying
overlying basaltic
basaltic sequence
sequence suggests
suggests the source
source of
of
the rhyolite
rhyolite was
was to
to the
the southeast,
southeast, and
and indeed,
indeed, rhyolite
rhyolite domes
domes outcrop
outcrop within
within the
lower
part of
from the
the area
lower part
of the
the Portage
Portage Lake
Lake Lava
Lava Series
Series from
area of
of the
theAhmeek
Ahmeek
quadrangle to
east end
end of
ofthe
theKeweenaw
KeweenawPeninsula.
Peninsula. Native copper has
has been
been
quadrangle
to the east
mined from
from the
the rhyolite
facies of
mined
rhyolite facies
of all
all four
four interflow
interflow horizons
horizons in
in the
the Ahmeek
Ahmeek
quadrangle
quadrangle map
map area.
3
�CONTACT RELATIONSHIPS
RELATIONSHIPS BETWEEN
BETWEEN THE JACOBSVILLE
JACOBSVILLE SANDSTONE
SANDSTONE
AND THE
THE PORTAGE
LAVA GROUP:
AND
PORTAGE LAKE
LAKE LAVA
A PROGRESS
PROGRESS REPORT
Larry L.
of Mineral
Mineral Research,
Research, Michigan
Michigan Technological
Technological UniverUniverLarry
L. Babcock,
Babcock, Institute of
sity, Houghton,
Houghton, Michigan
Michigan 49931
49931
ABSTRACT
Logs of
of all
theLaurium
Laurium quadrangle
quadrangle which
which collar
collar
Logs
all diamond
diamond drill
drill holes
holes in
in the
between the Scales
between
Scales Creek
Creek Flow
Flow (PSc)
(PSc) and
and the
the Jacobsville
Jacobsville Sandstone
Sandstone (JS)
(JS) - Portage
Lake
contact were
were officially
Lake Lava
Lava Group
Group (PLLG)
(PLLG) contact
officially obtained
obtained from
from Universal
Universal Oil
Oil
logs comprise
105 holes
holes and
Products. These
These logs
comprise 105
and represent
represent 25,000
25,000 m
m of
of drilling.
drilling.
Stratigraphic correlation
correlation between
Stratigraphic
between the southernmost
southernmost four
four field
field sections
sections along
along the
contact trace
contact
trace and
and adjacent
adjacent drill
drill holes
holes has
hasbeen
beencompleted.
completed. These
These sections
sections are
Gooseneck, Quincy,
Oneco (ON),
(ON), New
New
Gooseneck,
Quincy, Dover,
Dover, and
and Dover
Dover (north)
(north) Creeks
Creeks and
and the Oneco
(NB), and
A) drill
Baltic (NB),
and New
New Arcadian
Arcadian (N
(NA)
drill holes,
holes, respectively.
respectively.
The stratigraphic
stratigraphic succession
four
The
succession across
across the
the JS-PLLG
JS-PLLGcontact
contact zone
zone in
in the four
field
consists of
of the
the following
following units, from
from oldest
oldest to
to youngest:
youngest: (1)
(1) "typical"
"typical"
field sections consists
(3) "contact"
"contact" conglomerate,
conglomerate, and
and PLLG
PLLG
flat-lying JS,
JS, (2)
(2) basal
basal PLLG
PLLG melaphyre,
melaphyre, (3)
flat-lying
lavas. However,
However, an
is present
present between
between (1)
(1) and
and (2)
(2) in
in the
theQuincy
Quincy
an additional
additional unit
unit is
Creek
gravel quartzite
Creek section: 35
35 to
to 48
48 m
m of
of steeply
steeply dipping
dipping JS beach sand-beach
sand-beach gravel
conglomerate.
The
contact zone
The JS-PLLG
JS-PLLG contact
zone on
on Quincy
Quincy Creek
Creek was
was mapped
mapped in
in detail.
detail. An
asymmetrical
this
asymmetricalbuttress
buttresszone
zoneextends
extends250
250toto300
300mmacross
acrossthe
the contact
contact at
at this
south%ast
from
PLL$
lavas,
dip
ste8pen
in
location. Proceeding
Proceeding southeast
from
PLLG
lavas,
theth dip
steepen3
in three
three
successivestages
stagesfrom
from15~290+
l5-29 + NW to 22-55
successive
22-55 0++ NW to 30
30 0++ NW÷-90
NW+-90 0—50
-50 ++ SE. The
latter
in the
la tter stage
stageisisan
anantieinal
anticlinalflexure
flexureconsisting,
consisting,-in
thecrushed
crushed axial
axial portion,
portion, of
of large
large
quartzite blocks
blocks (NW
(NW limb)
limb) and
and sandstone
sandstone blocks
blocksand
andslabs
slabs(SE
(SElimb).
limb). Typical
Typical flatflatlying JS
JS is
is encountered
encountered immediately
immediately southeast of this buckle.
buckle.
Results of field and diamond
drill section correlations are
are outlined
outlined below:
below:
Results
diamond drill
(1)
Interbedding between
between the JS
JS and
and PLLG
PLLG is
is noted
noted in
in four
four of
ofsix
sixNA
NAholes
holes
Interbedding
near Gooseneck
Gooseneck Creek.
Creek.
Isopach maps
constructed on
on two
two
Isopach
maps were
were constructed
successive,
successive, essentially
essentially flat-lying undisturbed
undisturbed stratigraphic intervals
interVals in
in
these four
four holes:
holes: volcanics
volcanics (3-14
(3-14 m)
m) and
and sediments
sediments (4-18
(4-18 m)
m) which
which
these
underlie
underlie these
these volcanics.
volcanics.
Two transport
transport direction
direction solutions
solutions were
were
Two
0
computed0for
each interval:
computed for each
interval: volcanics,
volcanics, S27°E
S27 E and
and S45°E;
S450E; sediments,
sediments,
both N15
E. The
N150E.
The latter direction
direction is
is identical
identical to
to those
those measured
measured on
on
"typical" JS
JS exposed
in the bed
Creek and
and represents
represents the
bed of
of Gooseneck
Gooseneck Creek
"typical"
exposed in
"normal" JS
JS transport
transport direction
direction in the
"normaF'
the Laurium
Laurium quadrangle.
quadrangle. Sediments
Sediments
exposed
in the
the bed
bed of the
the creek
creek directly
directly overlie
overlie the
theabove
above mentioned
mentioned
exposed in
volcanic interval.
(2)
The contact conglomerate
conglomerate is
is exposed
exposed in all four
four field
field sections
sections and
and was
was
The
intersected by
by five
five adjacent
adjacent drill
drill holes.
holes. In
In three of
of these
these holes,
holes, 12
12 to
120
120 m
m of lava
lava separate
separate this
thisconglomerate
conglomerate from
from the
theunderlying
underlying Baltic
Baltic
No.
conglomerate, i.e.
i.e. the contact
4.
No.33 conglomerate,
contact conglomerate
conglomerate is
is No.
No.4.
(3)
Between
Creek section
section and
and the
the nearest
nearest dr!Hdrl holes
Between the Dover
Dover Creel<
holes(0N9),
(ON9),Nos.
Nos.
3 and
conglomerates exhibit
exhibit identical
identical dips,
dips, 6.2
6.2 NW,
NW, and
and identical
identical
and 44conglomerates
4
�stratigraphic separation
stratigraphic
separation intervals,
intervals, 120+
120+44m.
m. These
These values
values are
are constant
constant
over aa horizontal
horizontal distance
distance of 2.3 km.
over
km. (4)
(4)
The uppermost
The
uppermost JS conglomerate
conglomerate in
Section isis
in the
the Dover
Dover Creek
Creek Section
correlative with
with the
the Baltic
correlative
Baltic No.
No. 33 of
PLLG:
the
lowermost
of the PLLG:
the lowermost
conglomerate, No.
2.
conglomerate,
No.2.
(5)
(5)
A regionwide
regionwideunconformity
unconformityininthe
theJS
JSoccurs
occursatatthe
the top
top of
of the
the uppermost
A
uppermost
JS conglomerate
conglomerate on
JS
on Dover
Dover Creek
Creek (Babcock,
(Babcock, 1975).
1975). This
This unconformity
unconformity
represents aa definitive
at
represents
definitive rock-and
rock-and time-stratigraphic
time-stratigraphic break
break (timeline)
(timeline) at
the top
top of the Baltic
3 conglomerate which
is present
present in
in both
both the
the
Baltic No.
No.3
which is
JS
the
and PLLG.
and
the JS
JS exposed
exposed on
These
These correlations
correlationsrequire
requirethat
that virtually
virtually all
all of
of the
on the
Keweenaw Peninsula
Peninsulaisistime
time equivalent
equivalent to
to lowermost
lowermost portions
portions of
of the PLLG.
Keweenaw
PLLG.
REFERENCE
Babcock, L.L.,
L.L., 1975
Babcock,
1975 The
The Jacobsville
Jacobsville Sandstone:
Sandstone: Evidence
Evidence for a Lower-Middle
Lower-Middle
Keweenawan Age:
Age: Field
Field Trip
Trip 3,
3, Proc.,
Proc., 21st
Inst. on
Keweenawan
21st Ann.
Ann. Inst.
on Lake
Lake Superior
Superior Geol.,
Geol.,
pp. 87—123.
87-123.
55
�DISTRIBUTION
DISTRIBUTION OF SULFUR
SULFUR IN
IN THE
THE WEST
WEST KIERNAN
KIERNAN SILL,
SILL,
IRON
IRON COUNTY,
COUNTY, MICHIGAN
MICHIGAN
W.A.
Bartlett*, M.S.
iJ. Mancuso,
W.A. Bartlett*,
M.S. Lougheed,
Lougheed, J.J.
Mancuso, and
and L.J.
L.J. Walters,
Walters, Department
Department of
of
Geology,
Green University,
University, Bowling
Green, Ohio
Ohio 43403
43403 *Current address:
Bowling Green,
address:
Geology, Bowling
Bowling Green
Lindgren
Lindgren Exploration Co., Wayzata,
Wayzata,Mn.
Mn.55391
55391
ABSTRACT
The West
West Kiernan
Kiernan Sill, located
located in
in eastern
eastern Iron
IronCounty,
County,Michigan,
Michigan, is
is a
The
differentiated body
body of
of mafic
mafic igneous
igneous rock
rock ranging
ranging in
in composition
composition from
from peridotite
in age, and
through gabbro
gabbro to
to granophyre.
granophyre. It
It is
is Middle
Middle Precambrian
Precambrian in
and has
has been
been
through
metamorphosed to
greenschist facies. The
The sill was intruded into the
the Hemlock
Hemlock
metamorphosed
to the
the greenschist
formation, and
occupies an
an outcrop
outcrop area of
and now
now occupies
of approximately 26
26 square
square miles.
miles.
The
The sulfur
sulfur content
content of
of the
the West
West Kiernan
Kiernan Sill
Sill varies
varies with rock
rock type,
type, but
but in
in
general
averages for
for similar
similar rocks.
rocks. The
general is low
low as compared
compared to published
published averages
The peridotitic
rocks of
sill average
average 55 micromoles/gram sulfur, the gabbroic
gabbroic rocks
rocks average
average 40
40
rocks
of the sill
micromoles/gram
sulfur and
micromoles/gram sulfur
and the
the granophyric
granophyric rocks
rocks average
average 11
11 micromoles/gram
micromoles/gram
on statistical analyses
sulfur. Based
Based on
analyses and
and graphical
graphical techniques
techniques the
the distribution
distribution of
of
of sulfur.
copper and
copper
and nickel
nickel in
in the
the sill
sill isis shown
showntoto correlate
correlate with
with the distribution of
Because
copper and
and nickel
nickel ore deposits in
Because copper
in mafic
mafic igneous
igneous rocks are made
made up
up of
concentrations
of sulfide
sulfide minerals,
minerals,the
the distribution
distributionofof sulfur
sulfur can
can be
be used
concentrations of
used as
as aa
in
mafic
prospecting
tool to
to indicate the
prospecting tool
the relative
relative abundance
abundance of
of sulfide
sulfide minerals
minerals
mafic
igneous bodies.
66
�I
STRUCTURAL STUDIES
STUDIES OF PRECAMBRIAN
PRECAMBRIAN ROCKS
ROCKS
IN THE
THE MINNESOTA
MINNESOT A RIVER
RIVER VALLEY
VALLEY
Robert L.
L. Bauer,
Bauer, Department
Department of
of Geology
Geology and
and Geophysics,
Geophysics, University
University of
of Minnesota,
Minnesota,
Minneapolis, Minnesota
Minnesota 55455
55455
ABSTRACT
ABSTRACT
The
The gneisses in the
the Minnesota
Minnesota River
River Valley
Valley between
between Montevideo
Montevideo and
and Morton,
Morton,
Minnesota
have
been
folded
into
a
series
of
shallow,
eastward-plunging
Minnesota have been folded into a
of shallow, eastward-plunging antiforms
antiforms
and synforms, (F2),
(F2)' with wavelengths on
on the order of
of several kilometers
major structures
structures are
are pre-dated
(Himmelberg, 1968;
1968; Grant, 1972).
1972). These
These major
pre-dated in
in the
the
(Himmelberg,
Granite Falls
Falls area
area by,
by, rare
rare isoclinal,
isoclinal, intrafolial
intrafolia1folds,
folds, (F1),
(F 1)' which
which are
are coaxial
coaxial with,
with,
but deformed
deformed by
by the F2 structures.
structures.
A third
(F),), not
third period
period of folding,
folding, (F
notevident
evidentfrom
from aathe
themapping
mapping of
of the
themajor
major
structures,
from aa det'ailed
of the minor
structures, is
is deduced
deduced from
deiailed analysis
analysis of
minor folds
folds and
and mineral
mineral
Heart area
area this third
lineations
lineations in the
the gneisses.
gneisses. In
In the Morton-Sacred
Morton-Sacred Heart
third period
period of
of
0
folding yields minor
minor folds trending
trending about
about N53°E,
N53 0 E,plunging
plunging 200
20 (Grant,
(Grant, 1972).
1972). In the
Granite
area the orientations
Granite Falls
Falls area
orientations of the
the minor
minor folds
folds vary
vary with
with their
their location
location on
on
the Granite
). On the north
of
the
antiform
Granite Falls
Falls antiform
antiform (FJ).
north limb of
antiform the
the folds
folds have
have
an average
average orientation
orientation of
of N6°E,
N60 0 E, plunging
plunging 30°.
30 0 • The
The axial
axial planes
planes of
of these
these folds
folds
is very
very close
close to the
generally
with aa moderate
moderate to steep
generally trend NE-SW
NE-SW with
steep SE
SE dip.
dip. This
This is
the
orientation ofof the
the south
orientation
south limb
limb of
of the
the Granite
Granite Falls
Falls antiform
antiform and
and the
the foliation
foliation
near coincidence
results in aa
orientation
orientation in the
the outcrops
outcrops near
nearMontevideo.
Montevideo. This
This near
coincidence results
large variation
in the F.
to
variation in
F 3 fold
fold axis
axis orientations
orientations in
in these
these areas,
areas, ranging
ranging from
from NE
NE to
axial
plane
foliation
defined
by
flattened
quartz
lenses
is
SE
to
SW-plunging.
An
SE
SW -plunging. An 53
plane foliation defined by
quartz lenses is
locally well
well developed
developedon
onthe
the south
southlimb
limbofofthe
theGranite
GraniteFalls
Fallsantiform.
antiform. L.
locally
L 3 quartz
quartz
lineations
defined by
by the
the intersection
lineations defined
intersection of
of SS(compositional
<Compositional banding)
banding) and
ana S3
S3 are
are
common
in this
this area, and
show the
the same
same rangg
range in
in orientation
orientation as
as the F3
common in
and show
F 3 fold axes.
A
fourth generation
A fourth
generation of
of minor
minor folds,
folds, (F4)
(F4) is
is common
common only
only in
in the outcrops
outcrops near
near
Montevideo. F,
Montevideo.
F 4..axial
axialplanes
planesgenerally
generallytrend
trendNW-SE
NW -SE and
and are
are moderately
moderatelyinclined0to
inclined to
0
the northeast.
northeast. The
1 heF4
F 4fold
fold axes
axes in
in this
this area
areahave
havean
anaverage
averageorientation
orientation of
of S80
S80 E,
E,
4Q0 and generally occur as open warps of the gneissic banding with amplitudes
40° and generally occur
open warps of the gneissic banding with amplitudes
ranging from
from 20-50
20-50cm.
cm. A
folds on
onthe
the north
north limb
limb of
of the Granite
ranging
A few
few NW-trending
NW-trending folds
Granite
Falls antiform
antiform have
have orientations
orientations which
whichare
are consistent
consistent with
with that
that expected
Falls
expected of
of F4
F 4folds superimposed
superimposedon
onthis
this limb.
limb. Unlike
area, these
folds
Unlike the F4
F lJ. folds in
in the
the Montevideo
Montevideo area,
folds
folds are concentric,
concentric, parallel
parallel folds
folds with
with wavelengths
wavelengths ranging
ranging from
from 1-5
1-5 meters.
meters.
Both FF4
fold types
types occur
occur in
in granitic
granitic gneiss
suggesting aa distinct
distinct difference in the
Both
4. fold
gneiss suggesting
the
mechanical properties
properties of
of the
the gneiss
at the time of
mechan'lcal
gneiss at
of folding.
folding.
A
similar difference
properties of
of the
A similar
difference in
in mechanical
mechanical properties
the gneiss
gneiss is
is suggested
suggested by
by
the difference
the
difference in
in the
the character
characterofofnarrow
narrowNW
NW and
andNE-trending
NE-trending shear
shear zones
zones which
which
The shear
occur in both
occur
both the
the Granite
Granite Falls
Fallsand
andMontevideo
Montevideo areas.
areas. The
shear zones
zones near
near
Similarly oriented
Granite
Granite Falls
Falls are mylanitic
mylanitic and
and have
have aa cataclastic
cataclastic microfabric.
microfabric. Similarly
zones
in the
the Montevideo
area are
are generally
diktyonitic structures
structures rather than
zones in
Montevideo area
generally diktyonitic
than shear
shear
zones, commonly
commonlycontaining
containingremobilized
remobilizedgranitic
graniticmaterial
materialwithout
without aa cataclastic
zones,
microfabric.
REFERENCES
REFERENC
ES CITED
CITED
Grant, J.A.,
Grant,
J.A., 1972,
1972, Minnesota
Minnesota River
River Valley,
Valley, southwestern
southwestern Minnesota,
Minnesota, in Sims,
Sims, P.K.
P.K.
and Morey,
and
Morey, G.B.,
G.B., eds., Geology
Geology of Minnesota: A centennial volume;
volume; Minnesota
Minnesota
Geol. Survey,
Survey, p. 177-196.
Geo!.
177-196.
F-Iirnmelberg,G.R.,
G.R.,1968,
1968,Geology
GeologyofofPrecambrian
Precambrian rocks,
rocks, Granite
Granite Falls-Montevideo
Himmelberg,
Falls-Montevideo
area, southwestern
southwestern Minnesota;
Minnesota; Minnesota
Minnesota Geol.
Geo!. Survey
Survey Spec.
Spec. Pub.
Pub. Ser. 5, 33
33 p.
7
�I
A
A REAPPRAISAL
REAPPRAISAL OF
OF THE
THE WESTERN
WESTERN PORTION
PORTION OF
OF THE
THE
ENGLISH
ENGLISH RIVER SUBPROVINCE,
SUBPROVINCE, NORTHWESTERN
NORTHWESTERN ONTARIO
ONTARIO
AND SOUTHEASTERN
SOUTHEASTERN MANITOBA
MANITOBA
Department of
Beakhouse, Centre
Centre for Precambrian
Precambrian Studies,
Studies, Department
of Earth
Earth Sciences,
Sciences,
G.P. Beakhouse,
University of
of Manitoba,
Manitoba, Winnipeg,
Winnipeg, Manitoba, Canada.
ABSTRACT
ABSTRACT
The
River subprovince
has been
been considered
consideredtoto be
be a high
The English
English River
subprovince has
high grade,
grade,
Archean
metasedimentary
basin
flanked
by
typical
greenstone-granite
terranes.
Archean metasedimentary basin flanked by typical greenstone-granite
Recent investigations,
suggest that this
investigations, however,
however, suggest
this is
is an
an oversimplification
oversimplification and
and that
divisible
into
two
units;
a
northern,
the English
English River
River subprovince
subprovince is
is divisible into two units; a northern, largely
largely
sedimentary,
gneiss belt)
belt) and
sedimentary, unit
unit (Ear
(Ear Falls-Manigotagan
Falls-Manigotagan gneiss
and aa southern,
southern, mainly
mainly
plutonic unit
River batholithic
batholithic belt).
unit (Winnipeg
(Winnipeg River
The
gneiss belt
belt comprises
The Ear
Ear Falls-Manigotagan
Falls-Manigotagan gneiss
comprises aa high
high grade
grade metagraymetagrayThe
wacke-metasiltstone
sequence intruded
wacke-metasiltstone sequence
intruded by
by subordinate
subordinate felsic plutons.
distribution
primary sedimentary
sedimentary structures imply
distribution of lithologies and
and recognizable
recognizable primary
imply a
major
sedimentary basin
basin with
with sediment
sediment deposited
below wave
wave base
base from
major sedimentary
deposited below
from turbidity
turbidity
sedimentationis,
is, at
at least
least in part,
flows. This
This sedimentation
part, aa distal
distal facies
facies of
of volcanism
volcanism in
in the
the
Red
subprovince to
to the north.
Red Lake
Lake subprovince
In contrast, the
River batholithic
batholithic belt
belt is
In
the Winnipeg
Winnipeg River
is largely
largely aa felsic
felsic plutonic
plutonic
terrane comprising
two major
major suites;
suites; an
an earlier, massive
comprising two
massive to weakly
weakly gneissic,
gneissic, prepreand syn-tectonic trondhjemite-granodiorite-quartz diorite suite and a later,
massive,
post-tectonic granodiorite-quartz
A complex
massive, post-tectonic
granodiorite-quartz monzonite-granite
monzonite-granite suite. A
complex
assemblage
of well
assemblage of
well layered,
layered, felsic
felsic orthogneisses
orthogneisses with
with subordinate
subordinate interlayered
interlayered
remnants
of recognizable
metavolcanic and
and metasedimentary
metasedimentary rocks
remnants of
recognizable metavolcanic
rocks occurs
occurs on the
the
The
southern
southern flank
flank of
of this plutonic
plutonic terrane.
terrane.
The origin
origin of
of the
theWinnipeg
Winnipeg River
River
are currently
batholithic belt
belt is problematic,
problematic, and
and several
several possibilities are
currently being
being
batholithic
evaluated,
includingthe
the possibility
possibilitythat
thatthe
the belt
belt could
evaluated, including
could represent
represent aa reactivated
reactivated
ancient crustal remnant.
Regional
geophysicalanomalies
anomaliessupport
support the
the two-fold
of the
Regional geophysical
two-fold subdivision
subdivision of
the
gneissbelt
belthas
has aa thicker
English
subprovince. The
The Ear Falls—Manigotagan
Falls-Manigotagan gneiss
thicker
English River
River subprovince.
granitic crust,
than the
granitic
crust, thinner
thinner total curst,
curst, and
and higher
higher Bouguer
Bouguer gravity
gravity values
values than
Aerornagnetic
patterns also
also are
Winnipeg
River batholitic
Winnipeg River
batholitic belt.
Aeromagnetic patterns
are disintincly
disintincly
different in
In the two belts.
8
I
�I
TRACE
AEAN GRANITOID
TRACE ELEMENTS
ELEMENTS IN
IN THE
THE ARCH
ARCHAEAN
GRANITOID DIAPIRS
DIAPIRS
PIERCING
PIERCING THE
THE WABIGOON
WABIGOON GREENSTONE BELT
BELT
Dieter
Dieter Birk,
Birk, Department
DepartmentofofGeology,
Geology,McMaster
McMaster University,
University, Hamilton,
Hamilton, Ontario
OntarioL8S
L8S
4Ml
4M1
ABSTRACT
ABSTRACT
Major
and trace element
element analyses
analyses are
are reported
reported for
for twelve
twelve synkinematic
synkinematic to
to
Major and
late-kinematic granitoid
granitoid diapirs
diapirs intruding
intruding Keewatin
Keewatin greenstones
greenstones of
of the
theWabigoon
Wabigoon
are included
Greenstone Belt
Belt of
of northwestern
northwestern Ontario.
Ontario. Analyses
Analyses are
included of
of associated
associated
Greenstone
enclaves and aplitic
dikes
to
evaluate
the
role
of
endomorphism
and
late
diking.
aplltic dikes to evaluate the role of endomorphism and late diking.
Despite
Despite a common
common tectonic setting,
setting, these
thesediapirs
diapirsrange
rangefrom
fromhomogeneous
homogeneous
granodiorites
to concentrically zoned
granodiorites to
zoned plutons
plutons or
or complexes
complexes of
of granite-monzodiogranite-monzodiorite. The
Therange
rangeofofelement
elementconcentraitons
concentraitons(4.3>Na/K>O.9)
(4.3>Na/K>O.9) is not compatible with a
"late K
K granite"
granite" classification
classification as required
required by
by current Archaean
Archaean models
models of secular
secular
of trace
granitoid chemistry.
chemistry. Each
Each pluton
pluton carries
carries a distinctive
distinctive "fingerprint"
"fingerprint" of
trace
granitoid
element abundances,
but as a group
abundances, but
group these granitoids
granitoids carry
carry high
high Sr
Sr and
and Ba,
Ba, and
and low
low
Th, and
and U.
U.
Rb/Sr, Th,
The
The lensoid
lensoid mafic
mafic enclaves,
enclaves, ubiquitous
ubiquitous in these
these plutons,
plutons, have
have undergone
undergone
basification
and/or alkali
alkali rnetasomatism,
resulting in
in trace element
basification and/or
metasomatism, resulting
element abundances
abundances
markedly different
different from
from either their
markedly
their granitoid
granitoid hosts
hosts or
orsuggested
suggested metavolcanic
metavolcanic
sources. Strong
Strong enrichment
enrichment in
in Rb,
Rb, Ce and
and Th
Th can be
be demonstrated,
demonstrated, whereas
whereas Sr
Sr and
and
Although aa reciprocal
reciprocal reaction process
Ba values
more erratic. Although
process is
is envisioned
envisioned
Ba
values are
are more
between enclave
enclaveand
andhost,
host,there
there isis little
little evidence
of large scale
between
evidence of
scale contamination
contamination of
Homogeneousgranodiorite
granodioriteplutons
plutons(such
(suchasas the
the Burditt
the
host plutons.
plutons. Homogeneous
Burditt Lake
Lake
the host
Stock,
Scattergood Stock)
show heterogeneous
heterogeneous enclave
enclave distribution
distribution without
without noticeStock, Scattergood
Stock) show
able
modal
mineral
or
chemical
effect.
able modal mineral or chemical effect.
Aplitic
patches and
and dikes
show trace
trace element
of late
Aplltic patches
dikes show
element contents
contents typical
typical of
late
core-to-rim zoning.
differentiates complicated
complicated by
by strong
strong core-to-rim
zoning. Aplite
Aplite apophyses
apophyses cutting
metavolcanic rocks
rocks differ
differ little
little from
metavolcanic
from the intraplutonic aplites.
99
�THE BEHAVIOR
BEHAVIOROF
OF PRECIOUS
PRECIOUS METALS
METALS AND
AND OTHER
OTHER TRACE
TRACE ELEMENTS
THE
ELEMENTS
DURING THE
THE FRACTIONAL
FRACTIONAL CRYSTALLIZATION
CRYSTALLIZATION OF
OF DULUTH COMPLEX SULFIDES
DURING
Bill Bonnichsen,
Bonnichsen,Department
Department of
of Geol.
Bill
Geo!. Sciences,
Sciences, Cornell
Cornell Univ.,
Univ., Ithaca, N.Y.
N.Y. 14853
14853
and Robert I.
and
1. Botto,
Botto, Exxon
Exxon Corp.,
Corp., Box
Box 4255, Baytown, Texas 77520
77520
ABSTRACT
In the Duluth
the sulfide
can be
be described
Duluth Complex,
Complex, the
sulfide mineral assemblages
assemblages can
described in
In
terms of the
terms
the high
high temperature
temperature phases
phases that
that crystallized
crystallized from
from sulfide
sulfide melts.
melts. The
(1)(1)MSS
three principal
principal phases
phases that
thatformed
formedfrom
fromsuch
suchmelts
meltsare
are
MSS(monosulfide
(monosulfide solid
solid
solution) which
which cooled
cooled to
to pyrrhotite
solution)
pyrrhotite with
with exsolved
exsolved chalcopyrite-cubanite
chalcopyrite-cubanite and
and
pentlandite,
(2) ISS
ISS (intermediate
solid solution)
solution) which
pentlandite, (2)
(intermediate solid
which cooled
cooled to
to chalcopyrite
chalcopyrite and
cubanite (commonly
in exsolution
cubanite
(commonly in
exsolution intergrowths),
intergrowths), and
and (3)
(3) BSS
BSS (bornite-chalcocite
(bornite-chalcocite
solid solution),
solution), which
whichcooled
cooledtotobornite-chalcopyrite
bornite-chalcopyrite intergrowths.
solid
For normal
For
normal Fe-rich sulfide melts,
melts, the
the early
early crystallization
crystallizationofofMSS
MSS leads to Cu
Cu
field
enrichment in the
the liquid.
liquid. On
Onthe
theCu-Fe-S
Cu-Fe-Ssystem
systemliquidus
liquidus surface
surfacethe
theMSS-ISS
MSS-ISS field
boundary
not aa cotectic, but
boundary isis not
but isis aareaction
reactionboundary,
boundary, with
with the
the ISS
ISS field on
on the low
temperature
side.
temperature side. Thus,
continued crystallization
crystallization of MSS
MSS will
will enrich
enrich the
the
Thus, the
the continued
residual melt
melt in Cu
residual
Cu until
until its
its composition
composition migrates
migrates into
into the
the ISS
ISS field,
field, causing
causing the
cessation of MSS
andstart
start of
of ISS
crystallization. The
has aa lower
lower CufFe
Cu/Fe ratio
ratio
cessation
MSS and
ISS crystallization.
The ISS
ISS has
than the melt
melt so
so that
thatits
itsremoval
removalwill
willcause
causefurther
furtherCu
Cuenrichment,
enrichment,which
which can
can lead
lead
to liquid compositions
compositions reaching
reaching the
theISS-BSS
ISS-BSS field boundary.
boundary.
In
In the
the Duluth
Duluth Complex,
Complex, the
thesulfide—rich
sulfide-rich basal segregations
segregations crystallized
crystallized as
MSS, whereas
MSS-ISS mixtures.
MSS,
whereas the
the disseminated
disseminated sulfides
suifides crystallized
crystallized as MSS-ISS
mixtures. The Curich epigenetic sulfides which
which percolated
percolated into the footwall
footwall and
and inclusions,
crystallized mainly
and BSS.
BSS. Fractional crystallization of
mainly as ISS
ISS and
of sulfide
sulfide liquids,
liquids, as
outlined
above, is
is one
that may
outlined above,
one of several mechanisms
mechanisms that
may account for the
the wide
wide range
range
that characterize
of compositions
compositions that
characterize the
theDuluth
Duluth Complex
Complex sulfides.
sulfides. Such
Such a process
process
seems particularly applicable
seems
applicable to the Cu-enriched
Cu-enriched epigenetic occurrences.
Six
samples, chosen
chosen to
to encompass
the observed
Six Duluth
Duluth Complex
Complex samples,
encompass the
observed range
range of
Cu/Fe
CufFe ratios, were
were analyzed
analyzed by
by neutron
neutron activation,
activation, spark-source
spark-source mass
mass spectrospectrometry,
to further
metry, and
and atomic
atomic absorption
absorption to
further examine
examine the
the fractional
fractional crystallization
crystallization
process. The
for fractional
The results
resultsare
areininvery
verygood
good agreement
agreement with
with our predictions for
crystallization
During
crystalliza
tion trends.
During sulfide
sulfide crystallization,
crystallization, Ni,
Ni, Co,
Co, and
and Mo
Mo were
were
incorporated into MSS
MSS along
whereas Ag,
Ag, Au,
Rh, Ir,
Ir,
selectively incorporated
along with
with Fe,
Fe, whereas
Au, Pd,
Pd, Pt, Rh,
Zn,
Zn, Cd, Pb, TI, Se, Te,
Te, Sb,
Sb, Bi,
Bi, W,
W, and Sn were enriched
enriched in
in the
theliquid
liquid along
along with
with Cu,
CU,
to eventually
in the
eventually become
become incorporated
incorporated in
the Cu
Cu minerals.
minerals.
Our investigation
investigation of
of
Our
element
indicates preferences
preferences for
for octahedral lattice
element behavior
behavior indicates
lattice sites
sitesininMSS,
MSS, verses
tetrahedral
tetrahedral sites
sitesininISS,
ISS, which
which largely
largely governs
governs element
elementdistributions
distributionsduring
during sulfide
sulfide
liquid crystallization.
crystallization.
10
10
�STRATIGRAPHIC VARIATION
IN MINERALOGY
MINERALOGY AND
AND ENGINEERING
ENGINEERING CHARACTERISTICS
CHARACTERISTICS
STRATIGRAPHIC
VARIATION IN
CLAY NEAR
OF ONTONAGON
ONTONAGON CLAY
NEAR A MAJOR SLOPE FAILURE,
FAILURE, ONTONAGON
ONTONAGON COUNTY,
COUNTY, MICHIGAN
MICHIGAN
Emmy Booy
Booy and
and Stanley
Stanley J. Dyl, II, Department
Geology and
and Geological
Geological
Emmy
Department of Geology
Engineering, Michigan
Engineering,
Michigan Technological University, Houghton,
Houghton, Michigan
Michigan 49931
49931
ABSTRACT
45 for
for approximately
one mile
mile north
north and
and south
south of
of the East
U.S. 45
approximately one
East Branch
Branch of the
OntonagonRiver
River on
on the Keweenaw
Keweenaw Peninsula
Peninsula of Michigan
Michigan is
is plagued
plagued by
by slope
slope
Ontonagon
failures of
of varying
types and
and sizes
sizes along
the road
road cuts.
cuts. The
particular
failures
varying types
along the
The area
area of particular
interest for this
the largest
largest slide
whichlies
lies to
to the
the north
interest
this discussion
discussion isis the
slide which
north of the East
East
Branchalmost
almostatat the
the crest
crest of the
Branch
the hill.
hill. The
is one
one in
in which
which the river
river has
has
The area
area is
incised a valley about
200 feet
feet deep
deep into
into aaflat
flatglacio-lacustrine
glacio-lacustrinedeposit
depositofofthinly—
thinlyincised
about 200
layered red clays and silts.
The particular
is approximately
The
particUlar slide
slide under
under discussion
discussion is
approximately 700
700 feet long
long and
and 400
400
feet high.
high. ItItisisimmediately
immediatelyadjacent
adjacenttotoHighway
Highway 45
45 and
and causes
causes annual
annual disruption
disruption of
the drainage
the
drainage on
on the west
west side
side of
of the
theroadway.
roadway. Both
Bothmud
mudflows
flows and
and block
block gliding
gliding
contribute at various
and in
in different
different areas to the slope
various times and
slope recession.
recession.
contribute
Material of
of the
the slope
was studied
studiedatat 11 meter
meter vertical intervals
in the
the as-yet
intervals in
Material
slope was
unfailed zones
zones north
north and
and south
south of
of the
the failed
failed area
area in
in order
order to
to ascertain variability of
unfailed
the clay-silts
of the clay—size
fraction, Atterberg
Atterberg Limits,
the
clay-silts in situ.
situ. Mineralogy
Mineralogy of
clay-size fraction,
Limits,
shear strengths were determined.
particle-size distribution, and vane
vane shear
The material,
previously studied
regional scale,
scale, ranges
ranges
The
material, like that previously
studied on
on a regional
throughout the clay
throughout
clay and
and clay-silt
clay-siltregions
regionsof
ofthe
theCorps
CorpsofofEngineers
Engineersand
andU.S.
U.S. Bureau
Bureau
of Soils
Soils classifications. In
In general, sand content isis less
less than
than5%
5%although
although in
in some
some
layers this is not true.
The
the layers,
layers, in
of the
The mineralogy
mineralogy ofof the
in agreement
agreement with
with the
the variability
variability of
the
particle sizes,
layer to layer.
particle
sizes, varies
varies from
from layer
layer. However,
However, itit may
may be
be accurate
accurate to
to state
that the
rock
flour
includes
quartz and
the rock flour includes considerable
considerable quartz
and feldspar
feldspar in
in the
the clay-size
clay-size
fractions as
as well
fractions
well as the
the clay
clay minerals
minerals kaolinite,
kaolinite, iiite,
illite, and
and mixed-layer
mixed-layer material
material
which appears
appears to
to be
be dominantly
dominantly smectite.
smectite.
which
Plastic limits
limits vary
vary in
in the
the general
general range
range of
of24-30
24-30 and
and liquid
liquid limits
limits vary
vary from
from
35
to 70
in particle size and
clay mineral
mineral content.
content. The
35 to
70 reflecting variation
variation in
and clay
The natural
moisture content
content of the
moisture
the material
material generally
generally approach
approach the
the plastic
plastic limits
limitsalthough
although in
in
certain cases it is
is higher
higher than the plastic
plastic limit.
limit. This
This moisture
moisture content
content increases
increases in
general
the base
general towards
towards the
base of the
the hill,
hill, but
but not
not atataauniform
uniform rate.
rate.Anomalously
Anomalouslyhigh
high
values occur
occur part way up
higher clay content.
values
up the hill in zones of higher
Shear strengths
strengths are
are extremely
extremely variable,
variable, generally
generally in
in the
the4—25
4-25 tons/sq.
tons/sq. ft.
Shear
region.
This variability occurs
occurs not
only on
up the
the slope,
slope, but
region. This
not only
on aa scale
scale of
of tens
tens of feet up
within
hole at vertical
distances of
of inches.
inches. The
vertical and
and horizontal
horizontal distances
The variation
variation
within aa single
single hole
within
hole may
may be
be as
as much
much as
as 10
10 tons/sq.
tons/sq. ft.
ft.
within a hole
11
11
U
�SECONDARY MINERAL
GROWTH OF
OF THE WHITE
SECONDARY
MINERAL GROWTH
WHITE PINE SHALE
COMPARED
COMP
ARED WITH
WITH CLASSIC "HEAVING"
"HEAVING" SHALES
SHALES
Emmy Booy,
Booy, Department
Geology and
Emmy
Department of
of Geology
and Geological
Geological Engineering, Michigan
Technological
Co.,
Technological University,
University, Houghton,
Houghton, MI,
MI, 49931
49931and
andRobert
Robert D.
D. Harris,
Harris, Gillette Co.,
South Boston, MA.
MA.
ABSTRACT
Workersinin the
the eastern United
Workers
United States
States and
and Canada
Canada have
have observed
observed secondary
secondary
mineral
growth, particularly
particularly gypsum
gypsumand
andaa variety
variety of iron
mineral growth,
iron sulfates
sulfates which
which have
have
caused "heaving"
of shales
caused
"heaving" of
shales under
under buildings.
buildings. Because
Because of
of conditions
conditions
of similarities of
(i.e.
high oxygen
(i.e. high
oxygen contents
contents and
and presence
presence of
of moisture)
moisture) between
betweenshales
shalesat
at the
the surface
of the
of
the earth
earth and
and along
along the
the surfaces
surfacesofofmine
mineopenings,
openings, the
the possibility
possibility that similar
similar
phenomena might
might be
the White
phenomena
be taking place in the
White Pine
Pine Mine,
Mine, Michigan
Michigan was
was
investigated.
shales near
In occurrences in shales
near Ottawa,
Ottawa, Ontario, Cleveland, Ohio, and
Pittsburgh,
substantial (up
Pittsburgh, Pennsylvania,
Pennsylvania, substantial
(up to several
several inches)
inches) vertical
verticalexpansion
expansion has
has
taken place
taken
place in shales
shales which
which contain
contain some
some pyrite
pyrite and
and calcite.
calcite. It
has been
been
It has
hypothesizedthat
that the
the reactions
take place
place in
in the
the shales
hypothesized
reactions which
which take
shales are catalyzed
catalyzed by
by
oxidizing
bacteria.
oxidizing
These
would include
include Thiobacillus
Thiobacillus ferroxidans
ferroxidans and
and
These bacteria would
Ferrobacillus
ferrooxidans. Repeated
Repeated efforts to
to grow
grow such
such bacteria in
in cultures
cultures of
of
Ferrobacillus ferrooxidans.
proven unsuccessful.
unsuccessful. Therefore,
Therefore, a bacterial
the White
White Pine
Pine Shale
Shale have
have proven
bacterial mechanism
mechanism
growth on
on White
White Pine
Pine shales
shales has
has been ruled out.
for gypsum
gypsum growth
Samples
ranging in
in time of exposure
exposure to the
the mine
mine atmosphere
atmosphere from
from 11 day
day to
to 10
10
Samples ranging
years were
years
were collected
collected from
from the
the mine
mine roof
roof —
- most samples
were from the
the Brown
Brown
samples were
Massive
but several
several were
Massive but
were from
from the
the Dark
DarkGray
GrayMassive.
Massive. These
contain
These strata contain
scattered nodules
source for
for Ca
Ca in
in the expected
nodules of calcite
calcite which
which provide
provide a logical
logical source
reactions. Microscopic
0.2 and
and 0.4
0.4
Microscopicexamination
examinationsuggests
suggeststhe
the presence
presence of
of between 0.2
percent pyrite
coincideswith
withdata
data for
for sulfur
of the material.
percent
pyrite which
which coincides
sulfur analyses
analyses of
material.
Therefore, the basic
for the generation of gypsum
are present.
Therefore,
basic chemicals needed
needed for
gypsum are
Soluble
sulfates in
in the samples
Soluble sulfates
samples were
were on the order
order of
of magnitude
magnitude of
of 10
10 ppm
ppm or
less. However,
careful examination
examination of
of samples
samples exposed
exposed to
to the mine
However, careful
mine atmosphere
atmosphere
showed some
gypsum on
surfaces of the
the samples.
samples. However,
showed
some growth
growth of
of gypsum
on the
the surfaces
distribution
throughoutthe
the samples
samplesstudied.
studied. The
The absence
absence of
of aa linear
distribution was
was random
random throughout
relationship between
between time
time of
of exposure
to the
relationship
exposure to
the mine
mine atmosphere
atmosphere and
and quantity
quantity of
of
gypsum
present isis attributed
attributed to the
gypsum present
the anisotropic
anisotropic distribution
distribution of parent materials
materials in
in
the mine.
mine. Subsequently,
Subsequently, similar
similar gypsum
gypsumgrowth
growth was
was observed
observedon
on the
the surfaces of
polished
thin sections
sections made
made of
of the
the interior of the rock.
polished thin
rock.
It has
of the strata
has been
been concluded
concluded that
that possible
possible weakening
weakening of
strataby
byprogressive
progressive
growth
does not
not present
present aa major
growth of secondary
secondary gypsum
gypsum does
major hazard at
at the
theWhite
White Pine
Pine
Mine. However,
some such
such growth
growthisis possible
possibleand
andisis concentrated
concentrated at
at the
However, some
the rock
rock
surfaces. Further, halite
halite may
may also
also be
be growing
growing on
on the
the surfaces
surfaces of
of the
theWhite
White Pine
Pine
Shale.
Shale. The
The relatively
relatively low
low rate
rateof
ofgypsum
gypsum growth
growth in this
this atmosphere
atmosphere may
may be due
due to
relatively high
high pH
pH (about
(about 8)
mine which
which inhibits
the relatively
8) in
in the mine
inhibits growth
growth of
of the
the bacteria
which
elsewhere are
are reported
which elsewhere
reported to catalyze
catalyze the
thechemical
chemical reactions
reactionsresponsible
responsible for
for
shale deterioration.
12
12
�PETROLOGY AND
AND FRACTURE
FRACTURE CHARACTERISTICS
OF THE
PETROLOGY
CHARACTERISTICS OF
KINGSTON CONGLOMERATE,
CONGLOMERATE, KEWEENAW
KINGSTON
KEWEENAW COUNTY, MICHIGAN
MICHIGAN
Charles Brumleve,
of Geology
Geology and
and Geological
Geological Engineering,
Engineering, Michigan
Michigan
Charles
Brumleve, Department of
Technological University, Houghton,
Technological
Houghton, Michigan
Michigan 49931
49931
ABSTRACT
The Kingston
Kingston conglomerate
conglomerate is
is composed
of subangular
subangular to
to subrounded
subrounded clasts
clasts of
The
composed of
quartzy feldspar porphry.
60
quartzy
porphry. These
rhyolite gravels
gravels make
make up
up approximately
approximately 60
These red rhyolite
percent of
of the
percent
the total
total rock.
rock. The
matrix is predominantly
predominantly sand
the same
same
The matrix
sand of
of the
compositionasas the
the clasts,
of copper,
composition
clasts, with
with secondary
secondary mineralization
mineralization of
copper, hematite,
hematite,
calcite, and
calcite,
and chlorite,
chlorite, in
in order
order of
ofincreasing
increasing abundance.
abundance. The
whole is
is
The unit
unit as aa whole
unsorted but is made up
of bands
bands or
or lenses
lenses of
of poor
poor to
to well
well sorted
sorted clasts.
up of
unsorted
The intensity
intensity of
of mineralization
mineralization isis related
related to the amount
The
amount of matrix
matrix present
present and
and
is an indication
indication of the original
original permeability
permeability of the
the rock.
rock. The
Thehanging
hanging wall
wall zone
zone has
has
is
the most
the
most matrix
matrix and
and received
received the
themost
mostsecondary
secondary mineralization
mineralization whereas
whereas the
the
has the
the least matrix
intermediate zone
zone has
matrix and the least mineralization.
mineralization.
Permeability tests
tests using
air demonstrated
demonstrated the
the tight cementation
Permeability
using compressed
compressed air
cementation
of the rock.
Conductivitytests
tests were
were used
usedtoto determine
determinethe
the nature
nature of
of the
the native
of
rock. Conductivity
copper framework
framework in elongate lenses parallel to
copper
to bedding.
bedding.
The
The fracture characteristics
characteristics of
of the
theconglomerate
conglomerate are
are controlled
controlled by
by the
the degree
degree
of cementation
cementation and
and type
type of
of matrix
matrix mineralization.
mineralization. Silica
cement produces
produces a
of
Silica cement
competent, nonfriable
rock which
tends to fracture
competent,
nonfriable rock
which tends
fracture transgranularly
transgranularly across
across clasts.
clasts.
Chlorite and
in the matrix
Chlorite
and copper
copper mineralization
mineralization in
matrix produces
produces weak
weak clast bonds.
bonds. This
This
results
results in failure
failure by
by intergranular
intergranular fracturing
fracturing of
of matrix,
matrix, clasts
clasts and
and native
native copper
copper
masses.
13
13
�THE PETROLOGY AND STRUCTURAL RELATIONS
RELATIONS OF THE LATER
LATER PRECAMBRIAN
PRECAMBRIAN
BRULE LAKE INTRUSIONS, COOK
COOK COUNTY,
COUNTY, MINNESOTA
MINNESOTA
James R.
R. Burnell,
Burnell, Jr.,
Jr.,Department
DepartmentofofGeology,
Geology, University
University of
ofMinnesota,
Minnesota, Duluth,
Duluth,
Duluth, Minnesota
55801
Minnesota 55801
ABSTRACT
The
splits into two
tonguesatat its
its eastern
east-trending tongues
eastern
The Duluth
Duluth Complex
Complex splits
two east—trending
extent
extent to
to form
form aanorthern
northern and
and a asouthern
southernprong,
prong, exposing
exposing a strip
strip of
of older
older
Brule
Keweenawan
volcanic rocks
rocks between
between them.
them.
Brule Lake
Lake is
is located at the
Keweenawan volcanic
westernmost
extent of
of the strip
westernmost extent
strip of
of volcanic
volcanic rocks
rocks just east
east of
of the
the point
point where
where the
the
gabbro
prongscoalesce.
coalesce. The
rocks are
are intruded
by aa series of large sillgabbro prongs
The volcanic
volcanic rocks
intruded by
like
terminate against
like bodies
bodies which
which terminate
against rocks
rocks of the
the nearby
nearby Duluth
Duluth Complex.
Complex. Thus,
Thus,
these intrusions, known
informally as
as the Brule
Lake sills,
sills, were
were formed
formed between the
Brule Lake
known informally
time of
of the
theeruption
eruptionofofthe
thelocal
localKeweenawan
Keweenawanvolcanic
volcanic rocks
rocks and
and the
thesubsequent
subsequent
gabbroic intrusions.
The
the Brule
Brule Lake
Lake area,
area, which
which occur
occur as
as both
both dikes
dikes and
and
The intrusive
intrusive rocks
rocks of the
non-porphyritic intrusions.
intrusions. The
sills, consist of porphyritic intrusions and subsidiary
sUbsidiary non-porphyritic
The
porphyritic
intrusionsform
form the
the most
features at Brule
most striking
striking geologic
geologic features
Brule Lake.
Lake.
porphyritic intrusions
These diabase
porphyries are
are approximately
approximately 80
80 to
to 300
300 meters
meters thick and
and extend for 22
diabase porphyries
kilometers along
along strike.
strike. Most
Most contain
contain 50-60%
50-60% plagioclase
plagioclase phenocrysts.
phenocrysts.
to 88 kilometers
Mineralogy
simple, consisting
consisting of
of plagioclase,
plagioclase, augite, opaque
opaque oxides
oxides (magnetite
Mineralogy isis simple,
A typical mode
and
and ilmenite)
ilmenite) with
with minor
minor quartz and
and potash
potash feldspar.
feldspar. A
mode includes
includes
plagioclase
plagioclase 68%,
68%, augite
augite (—uralite)
(-uralite) 17%,
17%, opaque oxides
oxides 9%,
9%, quartz
quartz2%,
2%,K—feldspar
K-feldspar
chlorite-groundmass-epidote
3%.
1 %, chlorite-ground
1%,
mass-epidote 3%.
The
units are
are tabular
tabular in
in form
The porphyry
porphyry units
form and
and are tilted
tilted totoform
formsteep
steepnorth-northfacing
and more
gradual south
south slopes.
slopes. Several sills are concordant
facing slopes
slopes and
more gradual
concordant with
with the
the
trnd
trendofofthe
theintruded
intrudedflows
flows whereas
whereas others
others transect
transect this
this trend
trend at
at angles
angles of
of up
up to
to
0
30 •
is dominated
The texture
texture of
of the
theporphyry
porphyry units
uni ts is
dominated by
by abundant
abundant plagioclase
plagioclase
The
Fine—grained groundmass
groundmass
phenocrysts
textures poorly
poorly developed.
developed. Fine-grained
phenocrysts with
with subophitic
subophitic textures
occurs
in the interstices of
of the
the plagioclase
plagioclase laths, commonly
commonly including
including vermicular
occurs in
intergrowths of quarzt-plagioclase or quartz-potash feldspar.
Small bodies
bodies of
of non-porphyritic
diabase intrude
intrude both
both the volcanic
Small
non-porphyritic diabase
volcanic rocks and
the diabase
intruded into
into one
diabase porphyries.
porphyries. When
When intruded
one of the porphyritic
porphyritic bodies,
bodies, they are
typically irregular in form
thetrends
trends of
of the
the larger
larger intrusions.
typically
form and
and cross—cut
cross-cut the
intrusions. When
When
intruded into
into volcanic
volcanic units,
units, they
they form
form small
small tabular
tabular sills,
sills, several
several meters
meters in
intruded
The mineralogy
mineralogyofof these
these smaller
smaller intrusions
intrusionsisis identical
identical to
to that
that of the
the
thickness. The
porphyries although,
although, modally,
modally, the
the proportions
porphyries
proportions of plagioclase
plagioclase are
are less
less (45-52%)
(45-52%) and
and
of augite, more
more (19-25%).
(19-25%).
Chemically the
the Brule
intrusions represent
represent aa tholeiitic magma
Chemically
Brule Lake
Lake intrusions
magma saturated
MgO is
They are
are characterized by
with
to silica.
silica. They
by values
values of Si02
Si0 == 50%. MgO
with respect
respect to
the2 non-porphyritic
low, ranging
ranging from
from 2-3%
2-3% in
in the
low,
the porphyry
porphyry units,
units, 5-6%
5-6% in
in the
non-porphyritic
intrusions. Na20
NaZO isis particularly
particularlyhigh
high (>4%
(> 4%in
inthe
theporphyries)
porphyries) as
as isis Ti02
TiO Z(2.25%).
(2.25%).
intrusions.
Consideringthe
the abundance
abundance of
of plagioclase
phenocrysts inin the Brule
Considering
plagioclase phenocrysts
Brule Lake
Lake
intrusions
the bulk
chemistry of
of the intrusive
intrusive melt
melt closely
closely approximates
approximates the
intrusions the
bulk chemistry
chemistry of several
several Keweenawan
Keweenawan basalts of
of the
the North
NorthShore
Shore Volcanic
Volcanic Group.
Group.
14
l~
�RESOURCES OF
OF RECOVERABLE
IRON ON THE MARQUETTE
RESOURCES
RECOVERABLE IRON
MARQUETTE RANGE, MICHIGAN—
MICHIGANESTIMATES BY
BY A
A MONTE
MONTE CARLO SIMULATION MODEL
ESTIMATES
W.F. Cannon
Cannonand
andL.J.
LJ. Drew, U.S.
Geological Survey,
Survey, National
National Center, 12201
W.F.
U.S. Geological
12201 Sunrise
Sunrise
Valley Drive,
Drive, Reston, Virginia
Valley
Virginia 22092
22092
ABSTRACT
The
Negaunee Iron-formation,
MarThe Negaunee
Iron-formation,the
the principal
principal iron-bearing
iron-bearingunit
unitinin the
the Marlong tons
tons of material averaging
quette Iron Range, contains about 205
205 billion
billion long
averaging about
about
32 percent iron.
About 49
49 billion
billion tons
tons are
are within
within 1,000
1,000 feet
feet of the surface,
32
iron. About
surface, which
which
we consider
consider aa reasonable
reasonable average depth for
some present
present
we
for open-pit
open-pit mining,
mining, although
although some
mines will
probably be
be deeper.
mines
will probably
Three classes
Three
classes of iron-formation
iron-formation are now
now being
being beneficiated
beneficiated on
on the
the range.
range.
These are:
These
coarse-grained hematitic
hematitic and
1)
coarse-grained
and magnetic
magnetic iron-formation
iron-formation beneficiated by
by
froth flotation,
2)
magnetic iron-formation
iron-formation beneficiated magnetically, and
magnetic
3)
fine-grained (less
(less than
than 0.05
0.05 mm)
mm) nonmagnetic
nonmagnetic iron-formation beneficifine-grained
ated by selective flocculation and
and flotation.
We have
have divided
dividedthe
the range
range into
into 1/4 square-mile
We
square-mile areas and
and computed
computed the
the tonnage
tonnage
and characterized
in each
characterized the iron-formation
iron-formation in
each according
according to its
suitability for
for
and
its suitability
beneficiation
by one
one of these
beneficiation by
these processes,
processes, using
using a detailed
detailed computerized
computerized data bank
bank
developed
by the
the senior
senior author.
author. By
By using
using available
available metallurgical data
data and
and by
by means
means
developed by
of
by the
the junior
junior author,
author, we
we have
have
of aa Monte
Monte Carlo
Carlo simulation
simulation model
model designed
designed by
estimated the
the total
total amount
amount of
of metallic
metallic iron
iron recoverable
recoverable from
from the
the Marquette
Marquette range
range
by
surface mining
miningtoto 1,000
1,000feet.
feet. The
by each process,
process, assuming
assuming surface
The model
model considers
considers the
quality
of concentrate,
quality standards
standards of
of Fe
Fe >60 percent
quality of
concentrate, using
using quality
percent and
and Si09
SiO <10
< 10
percent; itit estimates
estimatesthe
theamount
amountof
ofiron-formation
iron-formation that
thatwill
willmake
makeconcentra4tes
concentrates of
this quality.
empirical distribution
distribution of
of recoverable
recoverable iron
iron derived
derived from
from
quality. From
From the empirical
many
metallurgical tests,
tests, the
the total recoverable
recoverable iron
iron is
is then
then estimated.
estimated. Figure 11
many metallurgical
indicates that
that ifif recoverable
recoverable grades
grades of
of about
about 20
20 percent
percent Fe
Fe are
areeconomically
economically
indicates
feasible,
short tons
11 billion
billion short
tons of metallic
metallic iron
iron can
can be
be recovered
recovered from
from
feasible, then
then about
about 11
iron-formation
iron-formation that responds
responds satisfactorily to
to beneficiation
beneficiation by
by an
an existing
existing process.
process.
Most
7.2 billion
billion tons-is
tons—isininfine-grained
fine-grained nonmagnetic
nonmagnetic iron-formation.
iron-formation.
-about 7.2
Most of this
this —about
About
tons is
is in magnetic
in
About 3 billion
billion tons
magnetic iron-formation,
iron-formation, and about 0.7
0.7 billion
billion tons is in
coarse-grained
hematiticiron—formation.
iron-formation.
coarse-grained hematitic
These
These figures
figures indicate
indicate the
the geologic
geologic availability
availability of
of iron
ironand
andplace
placemaximum
maximum
limits on
on iron
iron reserves
reserves on
on the
the range
range in
in terms
terms of
ofcurrent
currentmining
mining and
and beneficiating
beneficiating
technology.
percentage of
of this
this iron
iron that
thatisisnow,
now,or
orever
everwill
willbe,
be,economically
economically
technology. The
The percentage
available cannot
cannot be estimated
estimated without
without much
much more
more detailed study.
study.
15
15
�a
"c0
30
...
~0
7
S
<II
6
C
C
......~
5
a
3
::: 4
~
a
"a
".~S
~
0
o
2
1
flocacion
"0
<lJ
'"
20
20
25
25
30
35
35
40
45
45
50
50
Recoverable
(%)
Recoverable Fe
e (Z)
Figure 1. —
between estimated
estimated tonnage
- Relationship between
tonnage of recoverable
recoverable iron
iron and
and
percentage of recoverable iron for three
three beneficiating
beneficiating processes.
processes.
16
16
�ABUNDANCES
OF RARE EARTH AND
ABUNDANCES OF
AND OTHER ELEMENTS
ELEMENTS IN
IN ARCHEAN GRANITIC
AND
AND GNEISSIC
GNEISSIC ROCKS FROM
FROM THE
THE ENGLISH
ENGLISH RIVER
RIVER GNEISS
GNEISS BELT,
BELT, ONTARIO
ONTARIO
C.-L. Chou,
Goodwin, Department
Department of
Chou, N.B.W.
N.B.W. Harris, arid
and A.M.
A.M. Goodwin,
of Geology
Geology and
and Erindale
Erindale
College, University of Toronto,
Toronto, Canada
Canada M5S
M5S IAI.
1Al.
ABSTRACT
ABSTRACT
The
rocks in
in the eastern
The early
early Precambrian
Precambrian rocks
eastern Lac
Lac Seul
Seul region
region of
of the
the English
English
River
River gneiss
gneiss belt consist mainly
mainly of tonalitic and
and trondhjemitic
trondhjemitic gneisses
gneisses overlain
overlain by
by
tonalitic migmatized
migmatized metasedimentary rocks.
rocks. Both
Both are
are intruded
intruded by
by granitic
granitic plutons
plutons
and
sills and
and pegmatite
pegmatite veins.
veins. Smaller
and sills
Smaller bodies
bodies of amphibolitic
amphibolitic gneiss
gneiss also are
are found.
found.
Using
neutron activation
activation techniques
techniques we have analyzed
analyzed an amphibolitic
amphibolitic gneiss,
gneiss, two
Using neutron
tonalitic gneisses,
gneisses, two granites, and
and two pegmatites for
for 24
24 elements
elements (Na,
(Na, K,
K, Sc,
Sc, Cr,
Cr,
Mn,
Mn, Fe, Co, Ni,
Ni, Zn,
Zn, Rb,
Rb, Zr,
Zr, Sb,
Sb, Ba,
Ba, La,
La, Ce,
Ce,Nd,
Nd, Sm,
Sm, Eu,
Eu, Tb,
Tb, Yb,
Vb, Lu,
Lu, Hf,
Hf, Ta
Ta and
and Th).
Th).
Scandium,
Mn,and
andCo
Coare
are positively
positivelycorrelated
correlatedwith
with Fe,
Fe, as
as they
they generally
generally are
are
Scandium, Mn,
concentrated
in
mafic
minerals.
The
K/Rb
ratios
of
three
granitic
rocks
concentrated
minerals. The K/Rb ratios of three granitic rocksare
are290-.
290Slight variation
Zr/Hf ratios
ratios in
in granitic
granitic and
and tonalitic
tonalitic rocks
rocks(32-28)
(32-28)
variation of
of Zr/Hf
440. Slight
contrasts
contrasts with large variation
variation of Hf
Hi by
by a factor of
of 3.
3. AAfine-grained
fine-grained amphibolitic
amphibolitic
gneiss
has aa flat REE
gneiss has
REE pattern and
and a total
total REE
REE content
content of
of 12X
12X chondritic
chondritic abundance.
abundance.
It resembles
basalts, suggesitng
suggesitngthat
that its
its parent
resembles Archean
Archean basalts,
parent is
is basaltic,
basaltic, formed
formed by
by
partial melting
old gray
gray tonalitic gneiss
melting of upper
upper mantle
mantle material.
material.AA3.04—Gyr
3.04-Gyr old
gneiss (74(74115)
has aa smooth
smooth and
and steep-sloped
steep-sloped REE
REE pattern with
with remarkable
remarkable enrichment
enrichment of
of
115) has
light REE
REE and
and depletion
depletion of
of heavy
heavy REE
REE (LaN
(LaN == 71, and YbN
Yb == 6.4). It has
has a total
total
N
REE
and aa CeN/YbN
REE content of about 2X
2X and
CeN/Yb ratio
ratio of
of 0.5X
0.5X those
those of
of Saganaga
Saganaga tonalites
analyzed
by Arth
Arth and
and Hanson
Hanson(1975)'.
(1975) ItIt i~isNlikely
likely that
that this tonalite
analyzed by
tonalite may
may have
have formed
formed
from
from a granitic
granitic melt
melt which
which has
has been
been significantly
significantly contaminated by
by mafic material.
material.
A
secondtonalitic
tonalitic gneiss
gneiss (74-222B)
(74-222B)has
hasa atotal
total REE
REEcontent
content 2X
2Xhigher
higherthan
than that
that of
A second
74-115 and
and aa significant
suggesting that
that a plagioclase-rich
74-115
significant negative
negative Eu
Eu anomaly,
anomaly, suggesting
plagioclase-rich
component
was removed
removedfrom
fromthe
themagna.
magna. The
REE patterns
patterns of two
component was
The REE
two granites
granites have
have
very steep
ratios are 160
steep slopes,
slopes, their
theirCeN/Yb..,J
CeN/Yb N ratios
160 and
and 85,
85, respectively, significantly
higher
than that of
higher than
of granitic
granitic roèks
roCks from
from the
the Vermilion
Vermilion distirct.
distirct. These
These granites
might have
formed by
by crustal
crustal anatexis of
might
have formed
of earlier
earlier Archean
Archean metasedimentary
metasedimentary rocks.
rocks.
Two
pegmatites
show
a
strong
positive
Eu
anomaly,
but
differ
in
total
REE
Two pegmatites show a strong positive Eu anomaly, but differ in
REE and
and
other trace element
contents
reflecting
that
they
are
derived
from
different
source
element
that they are derived from
source
materials.
17
�PALEOMAGNETISM
PALEOMAGNETISM OF THE LATE
LATE PRECAMBRIAN
PRECAMBRIAN
BRULE
BRULE LAKE
LAKE INTRUSIONS,
INTRUSIONS, COOK
COOK COUNTY
COUNTY MINNESOTA
MINNESOTA
Donald
M. Davidson,
Davidson,Jr.,
Jr., Henry
Henry Halls*,
Halls*, and
and James
James R.
R. Burnell,
Jr., Department
Donald M.
Burnell, Jr.,
Department of
of
Geology,
Geology, University
University of Minnesota,
Minnesota, Duluth,
Duluth, *Department
*Department of
of Geophysics,
Geophysics, University
University
of Toronto
Toronto
of
ABSTRACT
ABSTRACT
Paleomagnetic
involving ac
ac demagnetization
demagnetization up
up to
to 40
Paleomagnetic analysis,
analysis, involving
40 oe, has
has been
been
carried
carried out
out on
onone
onerhyolite
rhyoliteflow
flow(Keweenawan)
(Keweenawan) and
and two
two porphyritic
porphyritic intrusions
intrusions which
which
flows in
in the
the Brule
Brule Lake
Lake area.
area. These
These flows
flows and
and intrusions
intrusions are truncated
truncated by
by
cut flows
the Duluth
Duluth Complex.
Complex.
of the
various units of
The
The Brule
Brule Lake
Lake intrusive units
units give indications of
of primary reverse magnetizamagnetization which
which has
has been
been altered by
by normal
normal intrusive
intrusive activity,
activity, probably
probably associated
associated with
emplacement of
of the
theDuluth
DuluthComplex.
Complex. The
Thenorthern
northernintrusion
intrusion(Fishbox
(FishboxIsland)
Island) shows
shows
a hard
is closer
closer to a reversed
primary component
component which
which is
reversed than
than normal
normal direction. The
The
hard primary
southern
intrusion (Jock
(Jock Mock
Mock Point)
Point) exhibits
exhibitsstable
stable end
end points
points but
but with
with aa two
southern intrusion
two
component
responsewhich
whichininatatleast
least one
one sample
sampleindicates
indicatesaa soft,
soft, reversed
reversed state.
state.
component response
The rhyolite
The
rhyolite flow
flow exhibits
exhibits aa mixed
mixed magnetic
magnetic response
response with
with aa harder
harder normal
normal
reversed components.
components.
and soft reversed
Mean
site determinations
and paleo
paleo pole
pole positions
positionsfor
for these
these sites
sites are given
Mean site
determinations and
given
below:
Paleo Pole
Position
Mean
Mean Site
0
Intrusive- u
No.
No. Intrusive-u
Intrusive-c
No.
No. Intrusive-c
139°
139
0
120
120°
So. Intrusive-u
Intrusive-c
So. Intrusive-c
So.
316
0
317
317°
Rhyoli
te Flow-u
Rhyolite
Rhyoli
te Flow-c
Rhyolite
N
N
K
<95
0<95
12
0
22°
22
3
3
3
35
35
35
4800
3
3
31
31
II
D
D
00
0
307.5
307.5°c
0
299
Lat.
Long.
21
31
34.04N
145.41E
23
23
45.70N
173.35E
173.35E
_66
-66°0
_75
-75°0
0
48
55
uu - uncorrected
cc - corrected structurally
Thus itit appears
appears that
that the southern
Thus
southern most
most intrusion
intrusion and adjacent flow
flow unit more
more
Although the
the
clearly show
show the
the effects of
clearly
of remagnetization
remagnetization than
than the
the northern
northern sill.
sill. Although
results are consistent
results
consistent with
with available
available data
data on
on both
both normal
normal and
and reversely
reversely magnetized
magnetized
rocks of
age, positive
positive correlation between
rocks
of Keweenawan
Keweenawan age,
between the
the Brule
Brule Lake
Lake intrusions
intrusions
and
Logan sills
and the
the Logan
sills does
does not
not appear
appear feasible.
feasible.
18
18
�STRUCTURAL AND
AGE RELATIONSHIPS
AT THE
THE LAC
LAC LA BELLE
STRUCTURAL
AND AGE
RELATIONSHIPS AT
MAGNETIC ANOMALY,
COUNTY, MICHIGAN
KEWEENAW COUNTY,
MICHIGAN
MAGNETIC
ANOMALY, KEWEENAW
James M.
M. DeGraff, Department
DepartmentofofGeology
Geologyand
andGeophysics,
Geophysics, Michigan
Michigan Technological
Technological
University, Houghton,
Houghton, Michigan
Michigan 49931
49931
ABSTRACT
Along the Keweenaw
Peninsulaof
of Michigan
Michiganthe
thecontact
contact between
between the
the Portage
Keweenaw Peninsula
Lake
Lake Lava
Lava Series and the Jacobsville
Jacobsville Sandstone
Sandstone has generally been considered
considered to be
thrust fault.
fault.This
ThisKeweenaw
KeweenawFault
Faultdescribes
describesaasite
sitealong
alongwhich
which the
theMiddle
Middle
a great thrust
KeweenawanPLLS
PLLSononthe
the north
north has
has been
been thrust
thrust southward
southward over
over the
the Lower
Lower
Keweenawan
Cambrian(?)
Jacobsville Sandstone,
Sandstone,with
withaa possible
possible vertical
vertical throw
throw of 10,000
10,000 feet
feet
Cambrian(?) Jacobsville
(Bacon, 1966).
1966). Aeromagnetic maps
(Bacon,
maps for this
this region
region compiled
compiled by
by Baisley
Balsley et
et al
al in
in 1963
1963
delineate this regional
well. However,
However, an
an earlier
earlier map
map comiTed
compiled from
from
delineate
regional contact quite well.
the same data by
shows that
that a prominent magnetic anomaly exists along
by L.O.
L.O. Bacon
Bacon shows
this contact
This anomaly
anomalytakes
takes the
the form
form of
of a
contact near
near the site
site of
of Lac
Lac La
La Belle.
Belle. This
this
magnetic
"high" which
which projects
projects southward
southwardfrom
from the
the nearly
nearly east-west magnetic
magnetic
magnetic "high"
lineations of
of the PLLS
by
lineations
PLLS into
into aa region
region of
oflow
lowmagnetic
magnetic gradients
gradients underlain
underlain by
Jacobsville Sandstone.
Sandstone. Diamond
has shown
shown that
that this Lac
Jacobsville
Diamond drilling and
and field mapping
mapping has
Lac
associated with
with aa lobe
La
lava flows
flows
La Belle
Belle magnetic
magnetic anomaly
anomaly is
is associated
lobe of
of basaltic
basaltic lava
southward from
from the PLLS
into the Jacobsville Sandstone.
PLLS into
extending southward
this project
The purpose
project was
was to
to investigate
investigate the
the structural
structural and
and age
age
The
purpose of
of this
relationships of
of the
the PLLS,
Jacobsville Sandstone
Sandstoneand
andbasalts
basaltswithin
withinthe
thearea
area of
of the
relationships
PLLS, Jacobsville
In order
Lac
Lac La
La Belle
Belle magnetic
magnetic anomaly.
anomaly. In
order to accomplish
accomplish this, the
the following
following four
four
field methods
methods were
were used:
used:
(1)
ground magnetic
magnetic work
over the Lac La Belle magnetic anomaly,
ground
work over
anomaly,
(2)
palaeomagnetic
palaeomagnetic studies of basalts
basalts in
in the
theanomalous
anomalous zone
zone in
incomparison
comparison
with basalts of the PLLS
immediately to
to the north,
PLLS immediately
(3)
geologic mapping
mapping and
and diamond
diamonddrill
drill hole
hole correlations,
correlations, and
geologic
(4)
two regional
PLLS—Jacobsville
regional gravity
gravity traverses
traversesacross
acrossthethe
PLLS-Jacobsville Sandstone
Sandstone
contact, one
contact,
one on
on either
either side
side of
of the
the Lac
Lac La
La Belle
Belle magnetic
magnetic anomaly.
anomaly.
Some conclusions
conclusionswhich
whichcan
canbebedrawn
drawnatatthe
thepresent
present time
time are that:
Some
that:
1)
1)
the flows
rotated up
up to
to 45
flows within
within the
the anomalous
anomalous zone
zone have
have b0een
been
rotated
45 degrees
0
counter-clockwise with
with respect
respect to
to the N.70
N.70 E.
E. strike of
of the
the PLLS
PLLS to the
counter-clockwise
north,
(2)
faulting
on both
east and
and west
west sides
sides of
of the
theanomaly
anomaly has
has been
been very
very
faulting on
both the east
important in controlling the emplacement and rotation of
of the
the anomalous
anomalous
lavas,
(3)
the
basalts associated
associated with
with the
the anomaly
are the
the eastern
eastern
the exposed
exposed basalts
anomaly are
extension of a larger
larger block
block of
oflavas
lavaswhich
whichhas
hasbeen
beendowndropped
downdropped on
on the
the
west and
and covered by Jacobsville Sandstone,
(4)
lavas in the
lavas
the lower
lower section
section of
of the
thePLLS
PLLS and
and within
within the
the anomalous
anomalous zone
zone
19
I
�are not
not reversely
reversely magnetized,
magnetized, and
and therefore correlate
correlate with
with the
theMiddle
Middle
Keweenawan
rocks of
of the Lake
Keweenawan rocks
Lake Superior
Superior basin,
basin, and
and
(5)
in
in this
this area
area the
theevidence
evidencepoints
points totothe
theJacobsville
JacobsvilleSandstone
Sandstone being
being
younger than the PLLS.
PLLS.
younger
REFERENCES CITED
CITED
Bacon,
L.O., 1966,
1966, Geologic
Geologicstructure
structure east and
Bacon, L.O.,
and south of the
the Keweenaw
Keweenaw fault on
on the
basis of geophysical
basis
geophysical evidence, in The
The Earth Beneath the Continents-A
Continents-A Volume
Volume
of Geophysical
Studies in
in Honor
A. Tuve:
Tuve: Am.
Am. Geophys.
Geophys. Union
of
Geophysical Studies
Honor of Merle
Merle A.
Geophys. Mono.
10, p. 42-55.
Geophys.
Mono. 10,
20
�LEAD ISOTOPE
ISOTOPE INVESTIGATIONS
INVESTIGATIONS IN
IN THE
MINNESOTA
MINNESOT A RIVER
RIVER VALLEY
VALLEY
B.R.
and M.H.
Delevaux, U.S.
Geological Survey,
Survey, Denver, Colorado 80225
B.R. Doe,
Doe, and
M.H. Delevaux,
U.S. Geological
ABSTRACT
The
isotopic systems
systems have
have been
been investigated
investigated for
for whole-rock
whole-rock and
and
The U-Th-Pb
U- Th-Pb isotopic
feldspar
of the foliated
feldspar samples
samples of
foliated and
and also
also more
more massive
massive phases
phases of
of the
theMontevideo
Montevideo
Gneiss
of Lund
(1956),the
the Sacred
Sacred Heart
Heart Granite,
Granite, and
Gneiss of
Lund (1956),
and the adamellite
adamellite of
of Section
Section 28
28
near
near Granite
Granite Falls.
Falls. We
We have
have not been
been able
able to
to resolve
resolve events
events which
which affected
affected the
the
that time
Montevideo
Gneissprior
prior to
to 3.0
Montevideo Gneiss
3.0 b.y. ago.
ago. At approximately
approximately that
time a thermal
thermal
event
event reset
reset the
the U-Th-Pb
U-Th-Pb system
system in the
the older,
older, dark-colored
dark-colored foliated
foliated phase.
phase. This
event may
by or
or resulted
resulted from
from the introduciton of granitic
may have been
been accompanied
accompanied by
magma which
formed the massive phase of
of the gneiss.
which formed
gneiss.
The
age of
Scared Heart Granite
Granite has
has aamicrolirie-whole-rock
microline-whole-rock isochron
isochron age
of 2590
2590
The Scared
m.y. The
age is
is in
The feldspar
feldspar isochron
isochron model-lead
model-lead age
in excellent agreement at
at 2560
2560 m.y.,
m.y.,
whereas the Pb-208/Pb204
age is
is somewhat
m.y. The
Pb-208/Pb204 model
model age
somewhat younger
younger at 2300
2300 m.y.
The cause
cause
for this variation is not
not understood
understood at present.
The
adamellite of Section
The epizonal
epizonal adamellite
Section 28
28 has
has aa feldspar-whole-rock
feldspar-whole-rock isochron
isochron of
of
approximately
1850m.y.,
m.y.,determined
determined by
byan
anacid-leach
acid-leach method.
method. The
approximately 1850
The modellead
modellead age
is 2200
age is
2200 m.y.,
m.y., but the
the Pb-208/Pb-204
Pb-208/Pb-204 model
model age
is in excellent agreement with
with the
the
acid-leach,
isochronatat 1850
1850m.y.
m.y. The
acid-leach, feldspar-whole-rock
feldspar-whole-rock isochron
The anomaly
anomaly of about
about 350
350
m.y.
m.y. in the
the model
model ages
ages isis similar
similar to
tothat
thatfound
foundininrejuvenated
rejuvenatedcratons
cratonswhere
where
Mesozoic and
and Cenozoic
Cenozoicigneous
igneousrocks
rockshave
havepenetrated
penetrated an 1800
Mesozoic
1800 m.y.-old basement.
The
m.y.-old adamellite
adamellite of
of Section
Section 28
has penetrated
penetrated an Archean
The 1850
1850 m.y.-old
28 has
Archean basement of
3800 m.y.
m.y. in
rocks ranging
from 2600
rocks
ranging from
2600 to 3800
in age. It is one
one of the
the few
few Precambrian
Precambrian
examples
displayingderivation
derivationofof lead
lead from
from aa cratonzied
examples displaying
cratonzied continent and the
the only
only
example as old
old as
as 1850
1850 m.y.
'V
All
rocks appear to have
have lost about
about half
half of
of their
their uranium
uranium fairly recently,
recently,
All the rocks
but thorium
thorium has
hasbeen
beenaffected
affectedtoto aa lesser
lesser degree.
degree. These
appear to be
but
These relationships
relationships appear
common
in near-surface
near-surface crystalline rocks
and may
may reflect
reflect dilatancy.
common in
rocks and
dilatancy.
21
�PRECAMBRIAN
PRECAMBRIAN HISTORY
HISTORY OF THE MORTON-NEW
MORTON-NEW ULM
ULM REACH
OF THE
MINNESOTA
RIVER
VALLEY
THE MINNESOTA RIVER VALLEY
S.S. Goldich,
S.S.
Goldich, 3.L.
J.L. Wooden,
Wooden, G.A.
G.A. Arikenbauer,
Ankenbauer, 3r.,
Jr., T.M.
T.M. Levy,
Levy, and
and R.U.
R.U. Suda,
Suda,
Northern Illinois
illinois University,
University, DeKaib,
DeKalb, Illinois
Illinois 60115
60115
ABSTRACT
On
the basis
On the
basis of current
current research
research on
on the
thePrecambrian
Precambrian rocks
rocks in
inthe
theMinnesota
Minnesota
River
of events
area is
River Valley
Valley aa tentative chronology
chronology of
events in the
the Morton-New
Morton-New Ulm
Ulm area
proposed.
Time
- M.Y.
Time-M.Y.
Event
(?)
Folding
1800 - 1200 (?)
of the Sioux
Deposition of
Deposition
Sioux Formation.
Uplift and
and erosion.
1900 - 1800
Emplacement of
of diabasic
diabasic dikes
dikes and
and small
small granitic
granitic plutons.
Emplacement
Thermal
strong enough
enough to
to reset mineral
Thermal metamorphism
metamorphism strong
mineral ages.
ages.
rv2600
rv
2600
Late tectonic emplacement
emplacement of
of aplitic
aplitic and
and pegmatitic
pegmatitic dikes.
dikes.
Late tectonic or
Late
or syntectonic
syntectonic emplacement
emplacement of Sacred
Sacred Heart
and related adamellites.
and
(?) 2700 - 2550
2800
3000 ++ 150
3050
Deformation and
and low-grade
low-grade metamorphism.
Deformation
Emplacement of
of granodiorite
granodiorite and
and adamellite.
adamellite.
Emplacement
Deformation and
and metamorphism
metamorphism of
of high-potash
high-potashgranite,
granite, basaltic
basaltic
Deformation
rocks, and
and gray
gray tonalitic gneiss.
rocks,
gneiss. Possible
Possible formation of
of speckled
speckled
gneiss in shear zones.
gneiss
Emplacement of
of high-potash
high-potash granite
granite and
and pegmatite.
Emplacement
high- and
and low-alumina
low-alumina basaltic dikes
Emplacement (?)
(?) of highor sills.
Deformation and metamorphism.
3550+ 125
-
Extrusion and
and intrusion
intrusion of
of trondhjemitic,
trondhjemitic, tonalitic, and
Extrusion
and granodioritic
Possiblybasaltic
basaltic magma
magmaalso
alsoatat this
this time.
time.
magma. Possibly
22
�LITHIC
LITHIC AND MAJOR ELEMENT
ELEMENT COMPOSITION
COMPOSITION IN THE
THE
SUPERIOR GEOTRA
VERSE, ONTARIO
GEOTRAVERSE,
A.M. Goodwin,
Goodwin,Department
Department of
of Geology,
Geology, University
University of
of Toronto,
Toronto, Toronto,
Toronto, Canada.
Canada.
A.M.
ABSTRACT
2
The
Geotraverse
constitutes0 a a recta~ular
rectanular area
The Superior
Superior Geotraverse
constitutes
area of
of 24,610
24,610 mi2
mi
0
0
bounded
by 90
90° and
and 92°W
longitudeand
and 49
49° and
and 52
52 N
N latitude
92 W longitude
latitude in
in the
the western
western
bounded by
Superior Province
Provinceofofthe
the Canadian
CanadianShield.
Shield. The
The area
area crosses
crosses or
or includes
Superior
includes parts of six
six
major east-trending
or belts
belts which
major
east-trending subprovinces
subprovinces or
which in alternating
alternating succession
succession from
from
south to north
south
north are:
are: Wawa
WawaVolcanic,
Volcanic, Quetico
QueticoGneiss,
Gneiss,Wabigoon
Wabigoon Volcanic,
Volcanic, English
River Gneiss, Uchi
and Berens
Berens Plutonic Belt.
River
Uchi Volcanic,
Volcanic, and
Lithic proportions
proportions (percent) in the Geotraverse
Geotraverse are
are as
asfollows:
follows: Granitic
Granitic rocks
rocks
Metasedimentary rocks
rocks - 5.3; Volcanic
- 69.2; Migmatite - 10.5; Metasedimentary
Volcanic rocks - 14.0; Mafic
to ultramafic
ultramafic intrusions
intrusions - 0.5; and Syenite - 0.4. Granitic rocks
rocks are
are equally
equally divided
divided
rocks comprise
comprise mafic
between gneissic (34.8)
(34.8) and
massive (34.6)
(34.6) phases. Volcanic
Volcanic rocks
mafic
and massive
(12.8)
and
felsic
(1.2)
phases.
The
ratio
of
mafic
to
felsic
volcanic
rocks
is
91.5
(12.8) and felsic (1.2) phases. The
to felsic volcanic rocks is 91.5 to
to
8.5.
Lithic proportions
in the
the two gneiss
Lithic
proportions in
gneiss belts differ significantly
significantly with
with the
the English
English
River
equally high
high proportions
proportions of
of migmatite
River Belt
Belt containing
containing equally
migmatite (49.7)
(49.7) and
and granitic
granitic
gneiss (46.1)
and negligible
metasedimentary material,
material, whereas
gneiss
(46.1) and
negligible metasedimentary
whereas the Quetico
Quetico Belt
Belt
has
has predominant
predominant migmatite
migmatite (64.8)
(64.8) and
and metasedimentary
metasedimentary material
material (29.0).
(29.0). This
contrast reflects
reflects aa higher
higher degree
degree of
of metamorphism
metamorphism together
together with
with greater
greater exposure
exposure
of older
basement gneiss
gneissdated
datedto
to be
be at least
of
older basement
least 3040
3040 m.y.
m.y. old
old in
in the
the English
English River
River
Belt to
to the north.
Belt
The three
The
three volcanic
volcanic belts
belts are
are essentially
essentially similar
similar in
in lithic
lithiccompositon.
compositon. A
A
salient feature
feature is the
of granitic
in the two
salient
the high
high proportions
proportions of
granitic rocks
rocks especially
especially in
two
northern
Wabigoon - 77.1) equally
northern belts
belts (Uchi
(Uchi - 65.0; Wabigoon
equally divided
divided between
between numerous
numerous
latter appears
massive plutons
plutons and
massive
and adjoining
adjoining gneissic
gneissic rocks.
rocks. The
The latter
appears to
to represent
represent
foliated plutonic
foliated
plutonic rocks
rocks intrusive
intrusive into
into nearby
nearby volcanic
volcanic rocks
rocks which
which would
would imply
imply aa
post-volcanic age dated at
2750-2850
m.y.
at 2750-2350
The weighted
mean major
major element
element composition
of the
the Geotraverse
is as
The
weighted mean
composition of
Geotraverse is
as
follows in
in weight
weight percent:
percent: Si0
SiO,2 _-- 65.64, AL,O
FeO (total)
follows
A1 2 0 3 -- 15.96, FeO
(total) - 4.98, MgO
MgO 2.32, CaO - 4.20, Na2O
CO2
H20 - .88, CO
Na 20 - 3.85,1C,O
3.85'£<.2° - 2.32, TiY2
Ti0 2 - .45, MnO
MnO - .09, H....O
2 This
compares
c'losely
with
that
of
the
Red
compares
closely
with
that
Red Lake-Lansdown
Lake-L~nsdownregion
regIOn
.09, P,O5
P 20 - .07. This
5
of northwestern
Ontario (Shaw,
(Shaw,et.
et. a1.)
a!.) as
as well
well as
as both
of
northwestern Ontario
both of
of the
theCanadian
Canadian Shield
Shield
(Fahrig
and Eade)
and the
the Ukrainian
shield (Ronov,
(Ronov,et.
et. al.),
(Fahrig and
Eade) and
Ukrainian shield
al.), the
the only
only significant
significant
K20
and higher
higher CaO
CaO contents
contents in
in the Geotraverse.
difference being
being low
low K
Geotraverse.
0 and
2
tectonic development
Although
Although the
the tectonic
development of the Geotraverse
Geotraverse crust remains
uncertain, available
available data
data indicate
of (1)
uncertain,
indicate some
some blend
blend of
(1) spreading
spreading of older
older gneissic
gneissic
crust (older
(older than
than 3.0
3.0 b.y.)
b.y.) with
with (2)
(2) accretionary
accretionary growth
growth of
of ensimatic
ensimatic volcanic
volcanic belts
belts
(2750
-2900m.y.)
m.y.)ininresulting
resultingtroughs
troughsand
andbasins
basinsrelative
relativetotoaa metastable
metastable craton to
(2750 -2900
to
the north.
north.
23
�I
THE GEOLOGY
GEOLOGY OF GNEISSIC
GNEISSIC ROCKS IN
IN THE KENORA DISTRICT,
DISTRICT,
ENGLISH RIVER
GNEISS
RIVER GNEISS BELT.
BELT.
C.F. Gower,
Gower, Department
Department of
of Geology,
Geology, McMaster
McMaster University, Hamilton,
Hamilton, Ontario
Ontario
ABSTRACT
ABSTRACT
After
After an
an initial
initial reconnaissance
reconnaissance geological
geological investigation
investigation of
of 2400
2400 sq.
sq. km. in the
southwest part
part of
of the
the English
English River
River Gneiss
Gneiss Belt, an area of
of 100
100 sq. km. near
near Kenora
Kenora
detailed study.
study.
was selected for detailed
Most
of the area
range from
from granitic
granitic to
Most of
area is
is underlain
underlain by
by gneissic
gneissic rocks
rocks which
which range
are best
withthe
the aid
aid of
of aa trianguiar
untramaiic composition.
composition. They
They are
best described
described with
"triangular
untramafic
diagram
diagram" having
having granitic
granitic pegmatoid
pegmatoid gneiss,
gneiss, biotite
biotite tonalite
tonalite gneiss,
gneiss, and
and amphibolite
amphibolite
end members.
members.
as end
BIOTITE
BIOTITE
TONALITE
TONALITE GNEISS
GNEISS
1
Mixed biotite tonalite —granitic
pe~matoid gneiss,
gneiss,
granitic pegmatoid
minor
amphibolite
minor arnphibolite
.
..
.
Tonalite/leucotonalite gneiss,
gneiss, minor
minor
amphiholite
amphibolite and granitic gneiss
Hornblende—biotite
Hornblende-biotite tonalite
tonalite gneiss,
gneiss,
common amphibolite enclaves
enclaves
.
Amphibolite—leucotonalite gneissic
Amphibolite-leucotonalite
association, minor hornblende—
association,
hornblendebiotite tonalite gneiss
Amphibolite, medium
Amphibolite,
medium grained,
grained,
network leucotonalite
leucotonalite veins
veins
Granitic
pep,matoid
Granitic pegratoid
gneiss
Amphibolite, fine grained,
Amphibolite,
concordant leucotonalite,
leucotonalite,
uartz—epidote pods
quartz-epidote
pods
GRANITIC
PEGHATOID GNEISS
GRANITIC PEGMATOID
AMPHIBOLITE
AHPHIBCLITE
(1) much
muchofof the
the granitic
Field
studies suggest
suggest that, (i)
granitic material
material represents
represents
Field studies
pegmatite, (ii),
represents both
both mafic
intensely
Oi), the amphibolite
amphibolite represents
intensely deformed
deformed intrusive pegmatite,
(iii) do
do not
not assist
assist in
in determining
protolith for
for the
the
lavas
and mafic
mafic dikes,
dikes, but
but (iii)
determining aa protolith
lavas and
biotite
gneiss.
biotite tonalite gneiss.
isodilnal folds
folds have
have been
The tectonic
tectonic history
The
history is
is complex.
complex. FF isoclinal
been refolded by
by
been
used
to
define
major
F2
folds.
iLve
tight to open
F2
folds.
The
minor
F,
folds
open
folds. The minor F?_ folds ~ave been used to
F2
These major
major structures have
have been
been re'folded
rerolded by
by an
an F3
F fold which
which appears to be a rim
rim
These
3
synformassociated
associatedwith
withthe
the margin
marginofofaalarge
largetonalIte/granodiorite
tonalite/granodiorite
batholith. Two
synform
batholith.
Two
later
(F4,
also are
are recognized.
recognized. Mafic
ter periods
periods of
of open
open folding
folding (F
4' FF5)
5) also
Mafic dikes
dikes which
which have
la
with
of the area which,
been
intruded throughout
together with
throughout the history of
been intruded
superimposed fold
fold relationships
superimposed
relationships assist in
in distinguishing
distinguishing individual
individual deforrnational
deformational
phases.
24
24
�APPLICATION OF A FLOW
APPLICATION
FLOW DIRECTION TECHNIQUE
TO THE PORTAGE LAKE
TO
LAKE VOLCANICS,
VOLCANICS, MICHIGAN
MICHIGAN
James G.
James
G. Grimes,
Grimes, Department
Department ofofGeology
Geologyand
andGeological
GeologicalEngineering,
Engineering, Michigan
Michigan
Technological University, Houghton,
Houghton, Michigan
Michigan 49931
49931
ABSTRACT
A study
study was
was made
made to
to test ifif the
theflow
flow direction
directiontechnique
techniquedeveloped
developed by
by Elston
Elston
A
and Smith
Smith (1970)
(1970)could
couldbe
be applied
appliedto
to the
the Portage Lake
in Michigan.
Lake Volcanics
Volcanics in
Michigan. The
The
and
technique, as
as modified
for basalts,
basalts, presumes
presumes that
technique,
modified by
by Smith
Smith and
and Rhodes
Rhodes (1972)
(1972) for
elongated
will statistically
align themself
elongated fragments
fragments (i.e.
(i.e. crystals)
crystals) will
statistically align
themseif in
in the direction
of flow.
Samples were
were collected
collected from
from various
various locations
locations within
within the
the series.
series. The
Samples
majority of
of samples
were collected
collected within
majority
samples were
within the City
City of
of Houghton
Houghton and
and represent a
rough
stratigraphic section
section through
The remaining
through the series.
series. The
remaining samples
samples were
were
rough stratigraphic
collected between
South
Range
and
Keweenaw
Point.
between South Range and Keweenaw
The orientation
orientation of
of plagioclase
crystals having
havingaa length/breath
length/breath ratio
ratio greater
plagioclase crystals
The
than three was
in oriented
oriented thin
thin sections.
sections. The
than
was measured
measured in
The results
results were
were then
then submitted
submitted
for statistical
statistical analysis.
to a computer program
program for
analysis.
Lineation values
values all
all had aa chi—square
valueabove
abovethe
the90
90percentile
percentile for
for two
two
Lineation
chi-square value
degrees of
of freedom.
effect
degrees
freedom. Aximuth
Aximuth was
was determined
determined by
by imbrication
imbrication and blocking
blocking effect
criteria.
Two samples
samples were
were collected
collected within
withinfour
four feet
feet of each other
Two
other within
within the
the same
same
flow to
to check
the repeatability of the
flow
check the
the method.
method. In
In addition
addition to these
these two
two samples,
samples,
another thin section
The difference
another
section was
was measured
measured twice.
twice. The
difference between
between the two
two flow
flow
directions were
were 10.3
and 11.2
11.2 in
in each
each case,
case, respectively.
respectively. This
This difference could
could be
directions
10.3 and
mostly
accountedfor
for by
bythe
the ten
ten degree
degree intervals
intervals that
that the data
data is
is divided
divided into for
for
mostly accounted
analyses.
The
of the Scales
Scales Creek
Creek Flow
Flow also
also was
was
The upper,
upper, middle,
middle, and
and lower
lower portions
portions of
sampled
to
test
the
application
of
the
method
to
some
of
the
thicker
flows
in
the application of the method to some of the thicker flows in the
the
sampled to
sequence. Flow
S35.OE,and
andSO.6E
S0.6Erespectively.
respectively. The upper
Flowaximuths
aximuthswere
wereS16.GW,
S16.6W, S35.0E,
and lower
lower samples
generally conform
conform to
to the aximuth
aximuth directions
directions of
of samples
samples above
above
and
samples generally
(S2.8W)and
and below
below (S9.DE)
(S9.OE)the
theScales
Scales Creek
Creek Flow.
(S2.8W)
Taken
together, the results
Taken together,
results indicate
indicate aa general
general flow
flow direction
direction from
from the
the north.
north.
Within
City of
of Houghotn,
Houghotn, the
theflow
flowazimuth
azimuthwas
wasS9.OE
S9.0E for
for the
thelower
lowerpart,
part,S2.OW
S2.0W
Within the City
for the
for the
the upper
upper part
part of the series.
the middle
middle part,
part, and
and S28.OW
S28.0W for
series. Individual
Individual sample
sample
directions
for the
directions are
areS17.OE
S17.0E and
and SLOE
SLOE for the
the lower
lower part,
part,S7.2W,
S7.2W,S4.OE,
S4.0E, and S4.5W
S4.5W for
middle
and S33.7W
S33.7Wfor
forthe
the upper
upper part.
part.
middle part, and
and S23.4W
S23.4W and
Further application
application of the
the technique
technique could
could demonstrate
demonstrate regional
regional patterns for
for
directions of
of lava
lava flow
flow movements,
movements, and
and multiple
multiple sampling
sampling of long
long strike lengths of
of
certain
certain flows
flows might
might allow
allow triangulation
triangUlation of the source
source area.
area.
25
25
�REFERENCES
REFERENCES
Elston, W.E.,
flow direction of rhyolitic
rhyolitic
Elston,
W.E., and Smith,
1970, Determination
Smith, E.1.,
E.I., 1970,
Determination of
of flow
ash-flow tuffs
tuffs from
ash-flow
from fluidal
fluidal textures:
textures: Geol.
Geol. Soc.
Soc. America
America Bull.,
Bull., v.
v. 81,
81, pp.
pp.
3393—3406.
3393-3406.
Smith, E.1.,
E.I., and
and Rhodes,
R.C., 1972,
Flow direction
direction determination
determination of lava
Smith,
Rhodes, R.C.,
1972, Flow
lava flows:
flows:
Geol. Soc.
Soc. America Bull., v. 83,
Geol.
83, pp. 1869-1874.
1869-1874.
26
26
�I
I
THE
THE SLATE
SLATE ISLANDS:
ISLANDS: THE CENTRAL UPLIFT
UPLIFT
OF
OF A
A METEORITE
METEORITE IMPACT
IMPACT CRATER?
Department of
of Geology,
Halls, Department
Geology, Erindale
Erindale College,
College, University
University of
of Toronto,
Toronto,
H.C. I-Jails,
Mississauga, Ontario
L5L 1C6
IC6 and
Grieve, Earth
Earth Physics
Physics Branch,
Branch, DepartDepartMississauga,
Ontario L5L
and R.A.F.
R.A.F. Grieve,
of Energy
Energy Mines
'Mines and
Ontario
ment of
and Resources,
Resources, Ottawa, Ontario
ABSTRACT
ABSTRACT
Shock
metamorphic effects in
in samples
samples from
from the
the Slate
SlateIslands,
Islands,Lake
Lake Superior
Superior
Shock metamorphic
0
(48°40'N,
87°OOW)
suggest
thatthetheislands
islandsare
arepart
part of
of aa meteorite
(48 0 40'N, 87
00'W) suggest
that
meteorite impact
impact
structure. The
The islands
islands form
form the
the central
central uplift
upliftof
ofaacomplex
complex crater
craterand
andare
areringed
ringed
by aa submerged
trough and
and annular
annular ridge
ridge with a dimater
dimater of
of 30
30 km.
km. Precambrian
Precambrian
submerged trough
bedrock
units are
are locally
breccia dikes.
bedrock units
locally brecciated and
and cut by
by aliochthonous
allochthonous breccia
dikes. These
These
clasts of identifiable country
country rock
rock and
and also
also fragments
fragments of
of a
dikes contain clasts
sedimentary unit,
in age,
age, which
is no
longer present in
unit, possibly
possibly Upper
Upper Keweenawan
Keweenawan in
which is
no longer
in
of shatter
The orientations
orientations of
shatter cones
cones present
present in
in the
the breccia
breccia host
host rocks
rocks
outcrop. The
indicate
indicate the interior
interior of
of the
the islands
islands as
as the
the approximate
approximate shock
shock centre. Microscopic
Microscopic
planar
features, equivalent
planar features,
equivalent to those
those described
described from
from other
other impact
impact sites, occur
occur in
in
quartz and
and piagiociase
plagioclase and
and the level
level of
of shock
shock deformation
deformation increases
increases towards
towards the
the
interior of
of the
the islands.
islands. The
The shock
shock event postdates
postdates Keweenawan
Keweenawan igneous
igneous activity
interior
(about 1.1. b.y. old)
old) and
on the basis
basis of
of the
the erosion
erosion level,
level, may
may be
be early
early Paleozoic
Paleozoic in
in
(about
and on
age.
27
27
�GEOCHEMICAL PROCESSES
PROCESSES FOR THE
GEOCHEMICAL
THE FORMATION
FORMATION OF
OF MAGNETITE
MAGNETITE IN
IN LOW-GRADE
LOW-GRADE
METAMORPHIC PRECAMBRIAN IRON FORMATIONS
METAMORPHIC
FORMATIONS
Tsu-Ming Han,
Han, The
The Cleveland-Cliffs
Cleveland-Cliffs Iron
Iron Company,
Company, Ishpeming,
Ishpeming, Michigan
Michigan 49849
49849
Tsu-Ming
ABSTRACT
A substantial
substantial number
number of
of magnetite ores, magnetite-containing
magnetite-containing specimens
specimens and
A
collected from
their oxidized equivalents collected
from the low-grade
low-grade metamorphic
metamorphic iron
iron
formations
in
the
Mesabi,
Gogebic,
and
Marquette
districts
of
the
Lake
Superior
formations in
Mesabi, Gogebic, and Marquette districts
the Lake Superior
region, and
and the Lake
region,
Lake Albanel
Albanel District of
of the
the Quebec
Quebec Province,
Province, Canada
Canada have
have been
been
study reveals
reveals that the
microscopically investigated. The
microscopically
The study
the magnetite
magnetite in
in these
these iron
iron
crystallinity, external
formations not
only varies
formations
not only
varies in
in grain
grain size,
size, crystallinity,
external morphology,
morphology,
inclusion composition,
composition,distribution,
distribution,and
and genetic
genetic relationships
inclusion
relationships to its coexisting
minerals
but also
also significantly
significantlydiffers
differsinininternal
internalmicrostructures.
microstructures. The
minerals but
The last variable
was
found to
to be
was found
be the
the most
most useful
useful key
key to
to the
theinterpretation
interpretation of
of the
thegeochemical
geochemical
processes of
of the
the magnetite formation.
processes
formation. These
These internal
internal microstructures
microstructures are
are normally
normally
not microscopically
visible unless
unless aa laboratory-induced
oxidtion
precedure
not
microscopically visible
laboratory-induced oxidation
precedure is
employed. The
sections were
were heated
heated at
at about
about 300
3000 C for three to
employed.
The well-polished
well-polished sections
to four
four
days
and then
then cooled
days under
under weakly
weakly to moderately
moderately oxidizing
oxidizing conditions
conditions and
cooled to room
room
temperature for
for reexamination.
reexamination. The
The most
most important
important internal microstructures
microstructures in
in
by the
the artificially produced
this study, as outlined by
produced hematite are
are listed
listedas
asfollows:
follows:
1. Lath-like,
Lath-like, bladed,
bladed, wedge-shaped,
wedge-shaped, rhombhedral,
rhombhedral, and
and hexagonal
hexagonal crystals
crystals
arranged
or subparallel,
arranged randomly,
randomly, or
subparallel, or in
in such
such forms
forms resembling
resembling druses
druses and
and inner
inner
linings
of geodes
crystals, clusters,
geodes within
within individual
individual crystals,
clusters, granules,
granules, and
and laminae
laminae of
of
linings of
magnetite.
Irregular bodies
Irregular
bodies resembling
resembling spheroids
spheroids uniformly
uniformly scattered throughout
throughout
granules,
of magnetite.
granules, clusters, and laminae
laminae of
2.
3. Botryoidal
Botryoidal structures
structures in
in clusters,
clusters, laminae,
laminae, and
and granules
granules of magnetite.
magnetite.
Zonal and
and core-and-shell
concentric structures
structures in
4. Zonal
core-and-shell concentric
in individual
individual magnetite
crystals with
of the
the preexisting
preexisting lath-like crystals.
with or
or without
without inclusions
inclusions of
All of
of the
ore mentioned
All
the af
afore
mentioned internal microstructures
microstructures have
have been
been found
found in the
the
magnetite
(b) hematite
hematite and
and chert,
chert, (c)
(c) carbonates
carbonates and
and
magnetite coexisting
coexisting with:
with: (a)
(a) chert,
chert, (b)
chert,
chert, (d)
(d) silicates and chert, and
and (e) carbonates, silicates, and
and chert.
chert.
The outlines of crystals, irregular bodies, and botryoidal masses
masses are
are
apparently of
of restored
apparently
restored preexisting
preexisting hematite
hematite which
which was
was probably
probably deposited
deposited as
Fe(OH)3
gel. The
Fe(OH)3 gel.
The later
later magnetite
magnetitewas
wasdeveloped
developedby:
by:(a)
(a) nucleation
nucleation followed
followed by
by one
or several stages
replacement of
of hematite
or
stages of
of enlargement,
enlargement, and
and (b)
(b) pseudomorphic
pseudomorphic replacement
supplemented by
by extensive overgrowth.
overgrowth.
Based
onthe
the ratio
ratio of:
of: (a)
(a)the
the size
sizeofofthe
the existing
existingmagnetite
magnetite crystals
crystals to
to that of
Based on
their initial
nuclei, and
and (b)
(b) the
the amount
amountofof magnetite
magnetitetoto that
that of
of the
their
initial magnetite
magnetite nuclei,
restored preexisting
preexisting hematite,
hematite, the
thefollowing
following conclusion
conclusion is
is drawn:
drawn: The
The migration
migration of
of
in conjunction
with the
the redepositoin
of iron
iron as
conjunction with
redepositoin of
as magnetite
magnetite on
on nuclei
nuclei of
of
iron in
magnetite or
or preexisting
magnetite
preexisting hematite is
is aa much
much more
more important
important magnetite
magnetite forming
forming
process
than the simple
process than
simple reduction
reduction of
of hematite or
or the
the metamorphic
metamorphic oxidation
oxidation of the
primary ferrous
ferrous minerals
like siderite and
minerals like
and greenalite.
The
The presence
presence of
of preexisting
preexisting hematite
hematite in
in the
the magnetite
magnetite laminae,
laminae, clusters, and
and
28
�granules
of the silicate
granules of
silicate and
and carbonate
carbonate iron
iron formations
formations indicates
indicates that
that some
some iron
iron
formations
normallyreferred
referred to
to as "silicate",
fades
formations normally
"silicate", "carbonate",
"carbonate", and
and "mixed"
"mixed" facies
might
fades prior
might have
have been
been oxide
oxide facies
prior to
topost-depositional
post-depositional alterations
alterations - silication,
matter isis believed
magnetitization,
magnetitization, carbonatization,
carbonatization, etc. Carbonaceous
Carbonaceous matter
believed to be
be
responsible
for the facies change.
responsible for
change.
On
On the basis
basis of the
the results
results of
of these
theseiron
ironformation
formationstudies,
studies,one
onecould
could conclude
conclude
that the
the magnetite
magnetiteininthe
thelow-grade
low-grademetamorphic
metamorphic Precambrian
Precambrian iron
iron formations
formations of
of
the Lake
elsewhere may
may well
well have
have the
the same
same ancestry.
Lake Superior
Superior type found
found elsewhere
29
�RARE
RARE EARTH
EARTHELEMENT
ELEMENT STUDIES
STUDIES OF
OF THE
THE ARCHEAN
ARCHEANGNEISSES
GNEISSES
OF
OFTHE
THEMINNESOTA
MINNESOTARIVER
RIVERVALLEY
VALLEY
G.N.
G.N. Hanson,
Hanson, Department
Department of
of Earth
Earth and
and Space
Space Sciences,
Sciences, State
State University
University of
ofNew
New
York,
York and
and 5.5.
S.S. Goldich,
Goldich, Department
Department of Geology,
Geology, Northern
Northern
York, Stoney
Stoney Brook,
Brook, New
New York
Illinois University,
University, DeKaib,
DeKalb, Illinois.
Illinois.
illinois
ABSTRACT
ABSTRACT
Rare earth
earth elements
elements (REE)
(REE) have
have been
been analyzed
analyzed on
on tonalitic
tonalitic to
to granodioritic
granodioritic
units
units of
of the
the up
up toto3800
3800m.y.
m.y.old
oldMorton
Mortonand
andMontevideo
Montevideo gneisses,
gneisses, mafic
mafic and
and
ultramafic units
units within
within the
the gneisses,
gneisses, and
and later
later granitic
granitic intrusions.
intrusions. The
Thesubparallel
subparallel
REE
patterns along
with similarities
similarities inin other
other geochemical
geochemicaldata
data suggest
suggest that
that the
REE patterns
along with
upper
upper amphibolite
amphibolite to granulite
granulite grade
grade gneisses
gneisses and
and later granitic
granitic intrusions
intrusions have
have aa
similar
origin resulting
resulting from
from partial
partial melting
of maf
Ic quartz
quartz diorite
similar origin
melting of
mafic
diorite or diorite
diorite
crust.
sources, perhaps in the crust.
Significantly
Significantly different REE
REE patterns for
for K-rich
K-rich pegmatoidal
pegmatoidal veins
veins and
and zones
zones
containing
hornblende within
within the nebulitic
containing porphyroblastic
porphyroblastic hornblende
nebulitic Morton
Morton Gneiss
Gneiss suggest
suggest
that
tha t under
under conditions
conditions of recrystallization
recrystallization and
and major
major element
element mobilization,
mobilization, the
the REE
REE
mobilized on
may have been mobilized
on dimensions
dimensions of
of many
many centimeters.
centimeters.
A
relatively flat REE
A relatively
REE pattern for
for aa tholeiitic
tholeiiticamphibolite
amphibolite is
is similar,
similar, although
although
slightly more
more enriched
enriched in
in REE,
REE, to
to the 2700
m.y. old
old Archean
Archean basalts
basalts in
in aa greenstone
slightly
2700 m.y.
Hornblende
belt in northeastern
northeastern Minnesota
Minnesota (Arth
(Arth and
and Hanson,
Hanson, 1975).
1975).
Hornblende rich,
rich,
komatiitic
amphibolites have
havepatterns
patterns with
with about
about 30
30 times
times chondrites
komatiitic amphibolites
chondrites for
for Ce
Ce and
and
about 8 times chondrites
for
Yb.
This
would
suggest
that
if
the
REE
have
not
been
chondrites for Yb. This would suggest that if the REE have not been
affected by
the source
(the mantle?)
for this
this rock
affected
by recrystallization,
recrystallization, the
source (the
mantle?) for
rock type
type also
also is
is
REE enriched.
light REE
30
30
I
�w
Rb-Sr GEOCHRONOLOGY OF
OF THE
THEMONTEVIDEO
MONTEVIDEO GNEISS,
GNEISS,
MINNESOTA
MINNESOTA RIVER
RIVER VALLEY
VALLEY
C.E.
Denver, Colorado
Colorado 80225
80225 and
and S.S.
5.5. Goldich,
Goldich,
C.E. Hedge,
Hedge, U.S.
U.S. Geological
Geological Survey,
Survey, Denver,
Northern illinois
Illinois University,
University, DeKaIb,
DeKalb, illinois
Illinois 60115
60 115
ABSTRACT
Gneiss of
of Lund
Lund (1956)
(1956)isis aa hybrid
hybrid rock
rock consisting
consisting of biotitebiotiteMontevideo Gneiss
The Montevideo
quartz-feldspar gneissic,
and granitic
granitic phases
phases of
of different ages.
gneissic, amphibolitic,
amphibolitic, and
ages. The
biotite gneiss,
gneiss, the
the oldest
oldest major
majorphase,
phase,was
wasprobably
probably derived
derived from
from volcanic
volcanic material
material
of andesitic
andesitic to
to rhyodacitic
rhyodacitic compositon
compositon and
and is
is 3700
3700 ++ 100
100 m.y.
m.y. old.
old. Amphibolite
Amphibolite
clasts in
represent basaltic
basaltic lavas
lavas or
or dikes
diks that
in the gneiss
gneiss may
may represent
thatwere
were broken
broken up.
up.
At approximately
3000 m.y.
m.y. ago,
ago, granitic
granitic magma
was intruded
intruded in
in the form of
approximately 3000
magma was
small
irregular masses,
masses, sheets,
sheets, and
and lit-par-lit
lit-par-lit injections.
small irregular
injections. The
The Rb-Sr
Rb-Sr systematics
systematics in
in
the
at this
the older
older gneiss
gneiss were
were disturbed
disturbed at
this time.
time. Failure
Failure to recognized
recognized the age
age
difference
between
the
older
foliated
gneiss
and
the
younger
more
massive
difference between the older foliated gneiss and the younger more massive
leucogranitic
of the
leucogranitic phase
phase invalidates
invalidates the earlier
earlier geochronologic
geochronologic investigations
investigations of
the
Montevideo Gneiss.
to lower
metamorphism (upper
(upper amphibolite
amphibolite to
lower granulite
granulite facies)
facies)
High-grade metamorphism
High-grade
affected
phase as
as well
well as
as the
the older
but we
we are
are not certain
affected the massive
massive phase
older gneiss,
gneiss, but
certain
whether
this occurred
occurred shortly
shortlyafter
after emplacement
emplacementofofthe
theleucogranite
leucogranite(N( 3000 m.y.
whether this
ago)
or during
the interval from
ago) or
during the
from 3000
3000 to 2600
2600 m.y. ago.
A 2600-m.y.
2600-m.y. event
event isis represented
represented in
in the
the emplacement of large granitic masses
masses
exposed inin the
the Minnesota
Minnesota River
River Valley
Valleysoutheast
southeast and
and northwest
northwest of
of the Montevideoexposed
Montevideointensive cataclasis
cataclasis affected the
Granite Falls
Granite
Falls area. Locally
Locally intensive
therocks
rocks approximately
approximately
These events
events also
also affected
affected the
the Rb-Sr
in the older
2400 m.y.
ago. These
Rb-Sr systematics
systematics in
older
2400
m.y. ago.
rocks.
Small
masses of
of adamellite
adamellite and numerous
diabasic dikes
dikes were
were intruded
intruded in
in the
Small masses
numerous diabasic
Montevideo
Gneiss1850
1850m.y.
m.y.ago,
ago,and
andlocally
locallythese
these intrusions
intrusions affected
affected the
Montevideo Gneiss
the Rb-Sr
Rb-Sr
system in the older
older rocks.
rocks.
31
31
I
�I
THE TRACE
TRACE ELEMENT
ELEMENT GEOCHEMISTRY
GEOCHEMISTRY OF PEAT
PEAT BOGS
BOGS OVER
OVER
DIFFERENT BEDROCK
BEDROCK TYPES,
TYPES, SOUTHERN
SOUTHERN HOUGHTON
HOUGHTON COUNTY,
COUNTY, MICHIGAN
MICHIGAN
Department of
Jacobsen, Department
of Geology
Geology and
and Geological
Geological Engineering,
Engineering, Michigan
Michigan
Sue I.I. :Jacobsen,
Sue
Technological University,
University, Houghton,
Houghton, Michigan
Michigan 49931
49931
ABSTRACT
A
investigation of
of the feasibility
preliminary investigation
feasibility of
of using
using peat
peat iningeochemical
geochemical
A preliminary
prospecting
was carried
carried out using
prospecting in
in the Upper
Upper Peninsula
Peninsula of Michigan
Michigan was
using twelve peat
peat
to determine
bogs
bogs in
in southern
southern Houghton
Houghton County.
County. The
The bogs
bogs were
were sampled
sampled to
determine if
if
difference
type isis reflected in
difference in
in bedrock
bedrock type
in the
the trace
trace element
element geochemistry
geochemistry of the
the
peat layers
layers above
above them.
them. The
The bogs
bogs were
were selected
selected to
to provide
provide as
asmany
many bedrock
bedrock
varieties
varieties as
as possible:
possible: Portage
Portage Lake
Lake Lava
Lava Series,
Series, Copper
Copper Harbor
Harbor Conglomerate,
Conglomerate,
Nonesuch
Shale, Freda Sandstone, and
Nonesuch Shale,
and 3acobsville
Jacobsville Sandstone.
Sandstone.
Samples were
weretaken
taken at
at sites 100
Samples
100 ft. apart along
along at least
least one
one line
line run
run through
through
both the Davis
each bog.
bog. As
As both
Davis and
and the Hiller
Hiller peat
peat samplers
samplers proved
proved inadequate,
inadequate, a
simple
sampler was
simple aluminum
aluminum piston—type
piston-type sampler
was used.
used. Peat samples
samples 15
15 inches
inches long
long at
depth
intervals of
depth intervals
of 3
3 feet
feet were
were taken,
taken,asaswell
wellasassamples
samplesofofthe
theliving
livingSphagnum
Sphagnum
moss
mat and
mineral material
material where
where possible.
possible. Peat
and the underlying
underlying mineral
Peat was
was identified
identified
moss mat
in the field
field as
as to
to type
type and
and degree
degree of
of humification.
humification. Maximum
Maximum peat
peat depth
depth differed
differed
from
to bog
bog and
and ranged
rangedfrom
from33feet
feet to
to 30
from bog
bog to
30 feet.
The
pH was
was0determined
thelaboratory
laboratoryand
andranged
ranged
om 3.1
3.1toto 6.0.
6.0. After
The pH
determined ininthe
from
oven
dryingatat 85
850 CC for
ashedat
at 500
5000 C
oven drying
for 24
24 hours,
hours, the peat was
was ashed
C for
for 22 hours.
hours. Trace
Trace
the Atomic
element concentrations are being
being determined
determined using
using the
Atomic Absorption
Absorption
Spectrometer.
As
peat profiles
profiles are
are not
As element
element distributions
distributions inin peat
not uniform,
uniform, a study
study of the
the
vertical distribution
of trace elements
vertical
distribution of
elements is
is being
being made.
made. Spatial
Spatial distributions
distributions of
of
elemental concentrations
concentrations and
and pH
pH are also
also being
being investigated.
investigated.
32
I
�ENGADINE
ENGADINE DOLOSTONE OF MICHIGAN'S
MICHIGAN'S EASTERN UPPER
UPPER PENINSULA:
PENINSULA:
GEOLOGY
GEOLOGY AND
AND RESOURCE
RESOURCEEVALUATION
EVALUATION
Allan M.
M. 3ohnson,Institute
Johnson,Institute of
of Mineral
MineralResearch,
Research, Michigan
Michigan Technological
Technological University,
University,
Allan
Houghton,
and Harry
Houghton, Michigan
Michigan 49931
49931 and
Harry 0.O.Sorenson,
Sorenson,Michigan
Michigan Geological
Geological Survey
Survey
Division,
Division, Department of
of Natural
NaturalResources,
Resources,Stevens
StevensT.T.Mason
MasonBuilding,
Building,Lansing,
Lansing,
Michigan 48926
48926
Michigan
ABSTRACT
ABSTRACT
Results
Results of
of geologic
geologic mapping
mapping and
and core-drilling
core-drilling of
of the
theMiddle
MiddleSilurian
SilurianEngadine
Engadine
The
work
is
part
of
a
continuing
cooperative
project
dolostone
are
reported.
The
work
is
part
of
a
continuing
cooperative
project
dolostone
reported.
between
Geological Survey
Surveyand
andthe
the Institute
Institute of Mineral
between the
the Michigan
Michigan Geological
Mineral Research
Research to
evaluate
limestone resources
resourcesofof the
the State.
evalua te high-purity
high-purity limestone
State. Preliminary
Preliminary results
results of
of
similar
work
on
the
Fiborn
limestone
were
reported
last
year
at
this
similar work on the Fiborn limestone were reported last year
this Institute
Institute
(Johnson and
and Sorensen,
Sorensen, 1975).
1975).
(Johnson
The
Engadinedolostone
dolostoneisisexposed
exposedasasaa resistant
resistant cuesta for
massive Engadine
for more
more
The massive
100 miles along
along the northern
northern margin
margin of
of the
theMichigan
Michigan Basin
Basin from Manistique
Manistique to
to
than 100
Drummond
Island. Despite
Drummond Island.
Despite a thickness of only 200
200 feet the
the shallow
shallow regional
regional dip
dip of
of
50
50 feet/mile south
south allows
allows the unit
unit to
to form
form aa belt
beltfrom
from 55to
to10
10 miles
miles wide
wide along
along the
the
northern shores
shores of
of Lakes
Lakes Michigan
Michigan and
and Huron.
Huron.
northern
Three
Three steel
steel companies
companies quarry
quarry
grade stone
stone from
from the
the Engadine.
Engadine.
metallurgical grade
Previously unpublished
field work by
by G.M.
G.M. Ehlers, University of Michigan,
Michigan, and
and
unpublished field
establishe the following
for the
H.O. Sorenson,
Sorenson, M.G.S.,
M.G.S., establishe
following stratigraphic subdivisions
subdivisions for
H.O.
Engadine dolostone:
Engadine
Name
Descriotion
Description
.
Thickness
Bush
Bush Bay
Bay dolostone
-massive, It. gray with cream
-massive,
mottling, med.
med. to coarsely
mottling,
crystalline, porous
porous
50'
Swede
Swede Road
Road dolostone
-massive (weathers
(weathers thin), buff-massive
brown,
brown, finedly
finedly crystalline
crystalline
33'
Prentiss
Prentiss Creek dolostone
-thinly bedded,
bedded, gray to brown,
brown,
chert layers, med. crystalline
chert
26'
26'
Rapson
Rapson Creek
Creek dolostone
dolostone
-massive, It.
It. gray-buff
gray-buff with
with
-massive,
lighter mottling, med-coarsely
lighter
crystalline, porous
crystalline,
porous
60'
60'
Rockview
Rockview dolostone
dolostone
-massive, gray,
gray, med-coarsely
med-coarsely
-massive,
crystalline, stromatolitic
stromatolitic
crystalline,
at
at base
base
TOTAL
TOTAL
44'
44'
2flT
2TY
33
33
-
---~-------------------
�These
were established
established from
from field
field mapping
in the eastern
These divisions
divisions were
mapping in
eastern portion
portion of
of
the
Engadine.
Examination
of
16
cores
drilled
during
1975
spanning
100
miles
of
the
the Engadine. Examination of 16 cores drilled during 1975 spanning
Engadine,
support these
these stratigraphic subdivisions
in the eastern
Engadine, support
subdivisions in
eastern portion.
portion. Cores
Cores
However,
if
the
the western
westernportion
portionshow
show some
some inconsistencies.
inconsistencies. However,
the Engadine
Engadine is
is
from the
interpreted
interpreted to
to have
have formed
formed as
as aareef
reefororcarbonate
carbonatebank
bankalong
alongaashelf
shelfmargin
marginwhere
where
minor
minor onlap-offlap
onlap-offlap fluctuations
fluctuations occurred,
occurred, these
these inconsistencies
inconsistencies can
can be
be resolved.
resolved.
Features
Features of
of the
the Engadine
Engadine dolostone
dolostone supporting
supporting this
this origin
origin include
include its
its massive,
massive,
porous
porous structure, complete
complete dolomitization,
dolomitization, fossil
fossil assemblage,
assemblage, and
and its position
position in
in
relation to
to other
other shelf
shelf formations
formations and
and to
tothe
theMichigan
Michigan Basin.
Basin.
Core logs
be employed
employed to
to evaluate
evaluate the potential
logs and
and chemical analyses will
will be
potential of
of
Engadine as aa high
high purity
purity dolostone.
dolostone. Results
Results are
are scheduled
scheduled for
for publication
publication by
by
the Engadine
the Michigan
Survey inin 1977.
Michigan Geological
Geological Survey
1977. This
This year
year similar
similar work
work will
will begin
begin on
on
Traverse group
in the
the northern part of
group limestones
limestones (Devonian)
(Devonian) in
of the
theLower
LowerPeninsula
Peninsula
Michigan.
of Michigan.
REFERENCES
Ehlers,
and Kesling,
R.V.
Silurian rocks
rocks of
of the
the Northern
Kesling, R.
V. 1957,
1957, Silurian
Northern Peninsula
Peninsula of
Ehlers, G.M.,
G.M., and
Michigan,
Mich. Basin
Basin Geol.
Geol. Soc., 63 p.
Michigan, Guidebook
Guidebook Mich.
Ehiers,
G.M., 1973,
1973, Stratigraphy
Stratigraphy of
of the
the Niagaran
Niagaran Series
Series of the
the Northern
Northern Peninsula
Peninsula
Ehlers, G.M.,
of Michigan,
Univ.
of
Mich.
Papers
on
Paleontology,
no.
3,
200
Michigan, Univ. of Mich. Papers on
200 p.
3ohnson,
A.M., and
and Sorensen,
Sorensen, H.O.,
H.O., 1975,
1975, Michigan
Michigan Upper Peninsula
Peninsula Middle
Middle Silurian
Johnson, A.M.,
Limestones: Geology
Geologyand
and Resource
Resource Potential,
Potential, (abs.),
Limestones:
(abs.), 21st
21st Annual
Annual Inst.
Lake
Superior Geology,
16-17.
Lake Superior
Geology, p. 16-17.
34
34
on
I
�•
NATURE
NATURE OF
OF THE
THEQUETICO-WABIGOON
QUETICO-W ABIGOON BOUNDARY
BOUNDARY IN
IN THE
THE
dE
dE COURCEY-SMILEY
COURCEY-SMILEY LAKES
LAKES AREA,
AREA, NORTHWESTERN
NORTHWESTERN ONTARIO
ONTARIO
M. Kehienbeck,
Kehlenbeck, Department
Department of
of Geology,
Geology, Lakehead
Lakehead University,
University, Thunder
Thunder
Manfred
Manf
red M.
Ontario
Bay, Ontario
Bay,
ABSTRACT
ABSTRACT
In
area, the boundary
In the de
de Courcy-Smiley
Courcy-Smiley Lakes
Lakes area,
boundary between
between the Quetico
Quetico and
and
\Vabigoon
Beltsisisexpressed
expressedbybya asequence
sequenceofof pelitic
pelitic to semi-pelitic
Wabigoon Belts
semi-pelitic schists
schists and
and
gneisses. At
At the
the present
present level
level of
oferosion,
erosion, these
these metasedimentary
metasedimentary rocks
rocks are
are in
in
gneisses.
contact
contact with
with granodioritic
granodioriticgneisses,
gneisses, granites,
granites,and
and pegmatites,
pegmatites,which
which are
areexposed
exposed to
to
the south.
south.
the
To
To the north of
of this
this area,
area,regional
regional metamorphism
metamorphism of
of volcanic
volcanic and
and sedimentary
sedimentary
rocks
rocks has
has resulted
resulted in
in greenschist
greenschist facies
facies assemblages
assemblages which
which characterized
characterized the
Wabigoon Belt
In the boundary
boundary zone the metamorphic
metamorphic grade
grade increases
increases
Wabigoon
Belt in
in general. In
de Courcey
Courcey and
and Smiley
Smiley Lakes.
Lakes.
southward toward de
Formation of
of three distinct
Formation
distinct foliation
foliation surfaces
surfaces was
was accompanied
accompanied by
by synsyntectonic
as well
well asaspost-tectonic
post-tectonicrecrystallization
recrystallizationproducing
producingpolymetamorphic
polymetamorphic
tectonic as
schists.
In the boundary
In
boundary zone,
zone, mineral assemblages comprising
comprising andalusite, sillimanite,
cordierite,
garnet, biotite,
biotite, and
form aa facies
fades series
cordierite, garnet,
and muscovite
muscovite form
series of
of the
theAbukumaAbukumatype.
The boundary
between Quetico
Quetico and
and Wabigoon
WabigoonBelts
Beltsinin this
this area
area is a complex
The
boundary between
complex
zone
belts have
have been
been reconstituted
reconstituted by
bymultiple-phase
multiple-phase
zone in
in which
which rocks
rocks of
of both
both belts
metamorphism and
melting.
metamorphism
and partial melting.
35
35
�J
THE
THE CENTRAL
CENTRALWISCONSIN
WISCONSIN BATHOLITH
BATHOLITH
Gene L.
L. LaBerge,
LaBerge, Geology
Geology Department,
Department,University
UniversityofofWisconsin-Oshkosh,
Wisconsin-Oshkosh, Oshkosh,
Oshkosh,
Wisconsin 54901
54901 and
and Paul
Paul E.
E. Myers,
Myers, Geology
Geology Department,Washington
Department,Washington State
State
Wisconsin
University, Pullman,
Pullman,Washington
Washington
University,
ABSTRACT
ABSTRACT
1500 square miles
miles in
in Marathon
Marathon County,
County,Wisconsin,
Wisconsin,
Geological mapping of over 1500
Geological
has
has revealed
revealed an
an extensive
extensive complex
complex of
of volcanic
volcanic and
and possible
possible co-genetic
co-genetic intrusive
intrusive
The volcanic
volcanic rocks, as
as pendants
pendants and
and xenoliths,
xenoliths, are
aresurrounded
surrounded by
by granitic
granitic
rocks. The
intrusions showing
an inward
inwarddecrease
decrease inin the
the volume
volume of
of contaminant
contaminant material.
material. The
showing an
The
volcanic
"pendants" generally
generally decrease
decrease in
in size and
volcanic "pendants"
and relative
relativeabundance
abundance westward
westward
across
County, thus
thus suggesting
suggestingexposure
exposureofofthe
the eastern
eastern portion
portion of
of a
across Marathon
Marathon County,
convex
batholith
roof
with
its
apex
extending
approximately
along
the
west
edge
convex
roof with its apex extending approximately along the west edge of
of
county. The
The batholith
batholith comprises
comprises at least
least twenty
twenty separate
separatestock-like
stock-likeplutons,
plutons,
the county.
which has
has its own
own contaminated
contaminated margin.
Mafic quartz diorites and
and quartz
each of which
margin. Mafic
monzonites
grade inward
inward to
to a more
monzonites grade
more granitic core.
core. The
The younger
younger plutons
plutons are more
more
felsic.
Gravity and
Gravity
and aeromagnetic
aeromagnetic maps
maps and
and geological
geological reconnaissance
reconnaissance suggests
suggests that
Marathon
County and
and most
most of
of central
are underlain
Marathon County
central Wisconsin
Wisconsin are
underlain by
by granitic
granitic rocks
rocks
containing
scattered volcanic
containing scattered
volcanic roof
roof pendants. We
We suggest that
that this
this plutonic
plutonic complex
complex
the "Central
"Central Wisconsin
Wisconsin batholith."
be called the
Aeromagnetic
and geologic
geologic mapping
mappingshow
showthat
thatseveral
several major
majorstructural
structural trends
Aeromagnetic and
intersect within
within Marathon
Marathon County.
County. These
These structural
structural trends
trends coincide
coincide with
with zones
zones of
intense cataclasis which
intense
which occurred before,
before, during
during and
and after batholith
batholith emplacement.
emplacement.
Most of
of the six
to date terminate
Most
six northeast-trending
northeast-trending cataclastic
cataclastic zones
zones mapped
mapped to
terminate
against or merge
merge with
with aa major
major northwest-trending
northwest-trending zone
zone which
which crosses
crosses the
the
the cataclastic
cataclastic zones
locally acted
acted as
southwestern
county. Although
Although the
zones locally
as
southwestern part
part of
of the county.
conduits for
for magmas,
conduits
magmas, most
most of the
the plutons
plutons show
show features
features of
of pervasive
pervasive shearing,
shearing,
suggesting
Available isotopic
suggesting aa long
long period
period of
of intrusion
intrusionalternating
alternating with
withcataclasis.
cataclasis. Available
ages
indicate the
the batholith
batholith was
was formed
formed during
duringMiddle
Middle Precambrian (Penokean?)
(Penokean?)
ages indicate
time.
36
U
�ORIGIN
ORIGIN OF
OF LAMINAE
LAMINAE IN
IN PRECAMBRIAN
PRECAMBRIAN IRON-FORMATION
IRON-FORMATION
M.S. Lougheed
Lougheed and
and 3.1
J.J. Mancuso,
Mancuso, Department
Department of
of Geology,
Geology, Bowling
Bowling Green
Green
M.S.
University,
Green, Ohio
Ohio 43403
43403
University, Bowling
Bowling Green,
ABSTRACT
ABSTRACT
The original
original particulate
particulate constituents
constituents of
of Precambrian
Precambrian iron-formation
iron-formation are
are
The
biogenic-carbonate
minerals, opaline
opalinesilica
silica tests
tests and
biogenic-carbonate minerals,
and organic
organic material.
material. These
These
constituents control
control Eh
Eh and
and pH
pH of
of contiguous
contiguous water
water which
which is
is replenished
replenished from an
an
open
open sea source.
source. Important
Importantsecondary
secondaryminerals,
minerals, which
which include
include ferroan
ferroan carbonates,
carbonates,
iron oxides,
oxides, iron silicates, chalcedony-quartz,
chalcedony-quartz, and
and pyrite,
pyrite, are
are produced
produced in
in response
response
to environmental
environmental factors
factors affecting
affectingthe
theoriginal
originalconstituents,
constituents,and
andwe
wehave
havediscussed
discussed
genesis over
over the past
past several
several years
years at
at these
these meetings.
meetings. Typically, in
in banded
banded
their genesis
iron-formation,
the thickness
and lateral
lateral extent of
iron-formation, the
thickness and
of the
the bands
bands or
or laminations
laminations are
are
determined
by the
the presence
determined by
presence of
of opaline
opaline slurry
slurry or gel.
gel. An
An exception occurs
occurs when
when
grains
of secondary
carbonate constitute the bedload
grains of
secondary carbonate
bedload during
during current transport and
and
then deposited
deposited as
as thin
thin laminae
laminae of
of nearly
nearly pure
pure carbonate,
carbonate, (ex.
(ex.Empire
Empire mine,
mine,
are then
however, laminae
laminae are deposited
Negaunee-siderite facies.). Most
Most commonly,
commonly, however,
deposited from
from
Negaunee-siderite
a bedload
composed
primarily
of
biogenic
opaline
gel
or
slurry
which
functions
bedload composed primarily of biogenic opaline gel
which functions as a
medium
iron-formation.
medium of
of support
support for
for any
any combination
combination of
of the
the other
other constituents of iron-formation.
Siliceous
laminae, which
whichmay
maybe
be more
more than
than one
Siliceous laminae,
one centimeter thick,
thick, often
often contain
contain
components such
components
such as flakes
flakes and
and shreds
shreds of
of algal
algalhash,
hash,which
which commonly
commonly show
show evidence
of having
by laminar
of
having been
been transported
transported by
laminar or
or turbulent
turbulent current
current flow.
flow. Commonly
undulating
bedded algal
algal mats
mats are inundated
undulating bedded
inundated by
by an opaline
opaline slurry mix
mix to produce
produce an
an
anoxic
conducive to
to the
anoxic environment
environment conducive
the production
production of
of pre-greenalite
pre-greenalite(greenaloid)
(greenaloid)
which
the precursor
precursor of
of greenalite.
greenalite. Beds
Beds of
of this
this nature,
nature, as
as well
well as
as beds
beds principally
principally
which isis the
composed
of greenalite granules,
composed of
granules, upon
upon dewatering
dewatering and
and concomitant
concomitant compression,
compression,
produce
thin undulating
laminae, notably
notably in
in "slaty"
"slaty" facies, but
produce thin
undulating laminae,
but when
when oxidized
oxidized they
commonlyoccurs
occurs in
in chert
produce iron-oxide
iron-oxide chert laminae.
laminae. Graded
Graded bedding
bedding commonly
produce
laminae
containing particulate
particulate material such
laminae containing
such as
as granules.
granules. The
Thesuspended
suspended load
load was
was
apparently
coming to
to rest,
rest,
apparently transported in aa tenuous
tenuous silica slurry
slurry or gel,
gel, which
which upon
upon coming
is at
at least
allowed
the load
load to
to gravitationally
allowed the
gravitationally settle into aa graded
graded profile.
profile. There
There is
least
one case in
one
in which
which chalcedonic
chalcedonic laminae
laminae were formed
formed by
by gravity
gravity accumulation
accumulation of
siliceous tests
tests of planktonic
planktonic organisms.
organisms. Normally
Normally the tests
tests would
would be
be comminuted
comminuted
siliceous
to a slurry during
bedloadtransport
transport by
bywater
water currents.
currents. These
during bedload
These few
few genetic
genetic examples
examples
of
laminae
in
iron-formation,
emphasize
the
complexities
involved
when
we
use the
of
iron-formation, emphasize the complexities involved when
"banded iron-formation."
term "banded
37
37
�•
PENOKEAN
PENOKEAN STRUCTURES AND
AND PLUTONIC
PLUTONIC ROCKS
ROCKS IN
IN PORTAGE
PORT AGE
AND
AND WOOD
WOOD COUNTIES,
COUNTIES,WISCONSIN
WISCONSIN
Jr., Department
R.S. Maass
Maass and
and L.G.
L.G. Medaris,
Medaris, Jr.,
Department of
of Geology
Geology and
and Geophysics,
Geophysics,
R.S.
University
University of
of Wisconsin,
Wisconsin, Madison,
Madison, 53706
53706 and W.R.
W.R. Van
Van Schmus,
Schmus, Department
Department of
of
Geology, University of Kansas,
Kansas, Lawrence,
Lawrence, 66044
66044
Geology,
ABSTRACT
ABSTRACT
Three
Three exposures
exposures of Precambrian
Precambrian rocks
rocks along
along the
theWisconsin
Wisconsin River
River (Stevens
(Stevens
Point,
Point, Conants
Conants Rapids,
Rapids, and
and Biron
Biron Dam)
Dam) have been investigated in
in order
order to
to establish
establish
the relative
units and
and to
to characterize the
relative and
and absolute
absolute ages
ages of lithologic
lithologic units
the geometry
geometry
and
age
of
folding.
and age of folding.
Relative
Rela tive ages
ages of
of the
the lithologic
lithologic units
units from
from oldest
oldest totoyoungest
youngest are:
are:banded
banded
quartzo-feldspathic
quartzo-feldspathic gneiss
gneiss and
and amphibolite
amphibolite (the
(the Basal
Basal Group
Group of
ofWeidman,
Weidman, 1907);
1907);
medium-grained
tonalite; aa series
series of fine-grained
medium-grained tonalite;
fine-grained tonalite dikes,
dikes, less mafic
mafic with
with
decreasing age of
of intrusion;
intrusion; maIic
mafic dikes;
dikes; and
and diabase.
diabase. All
All these rock
rock types
types except
except
diabase have
have been
been recrystallized
recrystallized under
under middle
middle grades
grades of
ofmetamorphism.
metamorphism.
for diabase
Quartzo-feldspathic
gneiss and
and tonalites
Quartzo-feldspathic gneiss
tonalites contain
contain quartz,
quartz, microcline,
microcline, plagioclase
plagioclase
(oligoclase to andesine), biotite, hornblende, epidote, sphene,
sphene, and
and opaques;
opaques;
amphibolite
amphibolite and mafic
mafic dikes
dikes contain
contain hornblende,
hornblende, plagioclase
plagioclase (andesirie
(andesine to labradolabradoite and
rite), and
and sphene
sphene +=blot
biotite
and epidote.
rite),
An early
An
early deformation
deformation produced
produced isoclinal
isoclinal folds,
folds, F1
F 1 ,' and a
a penetrative
penetrative
foliation, SS,l' inin the
is parallel
to to
compositoinal
foliation,
thebanded
banded gneiss.
gneiss. S S1
is parallel
compositoinalbanding,
banding, S0,
SO'
except in fold
fold hinges,
where So
S0isistransected
transected by
by St'
S1. A later deformation
except
hinges, where
deformation produced
producea
broad
open folds,
folds, F2'
F2, in the
at aa high
broad open
the gneiss,
gneiss, with
with axial
axial surTaces
surfaces at
high angle
angle to
to Sl' The
gneiss
contains
a
pronounced
mineral
lineation,
L1,
parallel
to
F1
and
F2
fold
F1
foW axes.
gneiss contains pronounced mineral lineation, L l'
The
Ic dikes,
dikes, although
although intrusive
intrusive mto
into the gneiss
The tonalites and
and maf
mafic
gneiss and
and discordant, at
at
least in
least
in part,
part, to
tostructures
structuresininthe
thegneiss,
gneiss,contain
containmineral
mineral lineations
lineations which
which are
parallel
steeply to the
parallel to the
the linear
linear elements
elements in
in the
thegneiss,
gneiss, plunging
plunging steeply
the southeast.
southeast. In
addition, S1 is
medium-grained tonalite.
is present in the medium-grained
A
A U-Pb
U-Pb age of
of 1900
1900 m.y.
m.y. from
from zircons
zircons in
in the
themedium-grained
medium-grained torialite
tonalite (Van
(Van
Schmus, et
et al,
al, 1975)
indicates that intrusion
1975) indicates
intrusion and
and deformation
deformation occurred during
during the
Schmus,
Penokean Orogeny.
Orogeny. Although
the banded
gneiss may
may be
be Archean
Archean inin age,
age, itit was
Penokean
Although the
banded gneiss
was reworked during
duringthe
the Penokean
PenokeanOrogeny,
Orogeny,and
andthe
the predominant
predominantstructures
structures inin itit were
worked
produced
produced during
duringthat
that event.
REFERENCES
REFERENCES
Weidman, S.,
S., 1907,
1907, The
The geology
geologyofofnorth
north central
central Wisconsin,
Bull. No.
No. 16,
16, Wis.
Wis. Geol.
Geol.
Weidman,
Wisconsin, Bull.
Na
tural History Survey.
Survey.
Natural
1975, Geology
Geology and
and Rb-Sr
Van
Schmus, W.R.,
W.R., et
Rb-Sr chronology
chronology of Middle
et al.,
aL., 1975,
Van Schmus,
Precambrian rocks
Precambrian
rocks in eastern
eastern and
and central
centralWisconsin:
Wisconsin: Geol.
Geol. Soc.
Soc. Am.
Am. Bull.
Bull. 86,
86,
1255-1265.
1255- 1265.
38
38
�GEOPHYSICAL PROSPECTING
PROSPECTING OFF
OFFKEWEENAW
KEWEENAW PENINSULA
PENINSULA
Robert
Robert P.
P. Meyer,
Meyer, 3.
J. Robert
Robert Moore,
Moore, Edgardo
Edgardo L.
L. Nebrija
Nebrija and
and Charles
Charles T.
T.Young,
Young,
Department
and Polar
Department of
of Geology
Geology &
&. Geophysics,
Geophysics, Geophysical
Geophysical and
Polar Research
Research Center,
Center,
University of
of Wisconsin,
Wisconsin, Madison
Madison 53706
53706
University
ABSTRACT
With
SeaGrant
Grant sponsorship,
sponsorship, we
we have
With NOAA-Wisconsin
NOAA-Wisconsin Sea
have been
been conducting
conducting
experiments using
using towed resistivity
resistivity and
andactive-source
active-sourceaudiomagnetotelluric
audiomagnetotelluric(AMT)
(AMT)
measurements
measurements and
and magnetic
magnetic and
and high-resolution
high-resolution seismic
seismic profiling
profiling to explore
explore for
for
copper
copper deposits
deposits offshore
offshore of Keweenaw
Keweenaw Peninsula.
Peninsula. Among
Among the areas
areas studied
studied were
were
Copper
Copper Harbor
Harbor and
and Silver
Silver Island
Island where
where there
there are
areknown
known underwater
underwater copper
copper veins,
veins,
Great Sand
Sand Bay
Bay where
where offshore
offshore extensions
extensions of
of onshore
onshore copper-bearing
copper-bearing fissures
fissures may
may
exist, Five-Mile
Points where
where we
we searched
searched for
for a chalcocite deposit
Five-Mile and
and Seven-Mile
Seven-Mile Points
deposit
within
and Bete
Bete Grise
where aa potential placer
Nonesuch Shale,
Shale, and
Grise Bay
Bay where
placer deposit
deposit
within the Nonesuch
may exist.
may
Surface- and bottom-towed
bottom-towed arrays
arrays were
were both
both used
used in
in resistivity
resistivityprofiling.
profiling. In
In
1975, AM
AMT
tests were
were started
started using
1975,
T tests
using a 150
150 m diameter circular
circular loop
loop of
of wire
wire laid
laid on
on
the lake
lake bottom
bottom and
and excited
excited by
by aa 400
400 Hz
Hz AC
AC generator
generator as source.
source. With
With the
the ship's
ship's
position
regulated by
by electronic
electronic navigation,
concentric arcs
arcs were traversed about
position regulated
navigation, concentric
about
the loop
the
loop to
to measure
measure the
the vertical
vertical magnetic
magnetic field,
field, radial
radial magnetic
magnetic field,
field, and
and
Both
methods
yielded
distinct
and
reproducible
anomalies
field. Both methods yielded
and reproducible anomalies
tangential electric field.
in apparent
apparent resistivity
resistivity and
and E/H
E/H ratios
ratiosover
overknown
known copper
copper veins
veins at
at Copper
Copper Harbor
Harbor
A
zone
and
anomalies over
over expected
expected lithologic
lithologic contacts.
zone of heavyheavyand correlatable anomalies
mineral concentrations inside
with towed
towed resistivity
mineral
inside Great
Great Sand
Sand Bay
Bay was
was discovered
discovered with
The apparent
and verified
verified with
with AMT.
AMT. The
apparent resistivity
resistivity correlates inversely
inversely with
with the
the
and
A
heavy-mineral
of the sands.
sands.
A probably
probably underwater
underwater vein
vein was
was also
also
heavy-mineral content
content of
At
discovered in
in this area.
At Five-Mile
Five-Mile and
and Seven-Mile
Seven-Mile Points,
Points, the
the offshore
offshore
discovered
extensions of
of the Nonesuch
Shale were
were mapped
mapped and
and structures
structures favorable
favorable to copper
extensions
Nonesuch Shale
copper
Both methods
methods are
are strongly
delineated. Both
strongly affected
affected by
by topography.
topography.
deposition
deposition were
were delineated.
For
For resistivity profiling,
profiling, aa first-order
first-order correction
correctionfor
fortopography
topography has
has been
been developed
developed
and applied.
High-resolution seismic
seismic and
and magnetic
magnetic profiling
profiling at
at Bete Grise Bay
Bay delineated a
High-resolution
basin off
the Montreal
Montreal River
River characterized
characterized from
from grab
grabsamples
samples by
byanomalous
anomalous
basin
off the
concentrations of
of trace
trace metals that decrease
concentrations
decrease outward
outward from
from the center of
of the filled
filled
Within this
this area
area we
also delineated
offshore manifestation
manifestation of
of the
basin. Within
we also
delineated aa logical
logical offshore
Keweenaw Fault.
Fault. Whether
Keweenaw
Whether the anomalies
anomalies represent the lake
lake bottom
bottom expression
expression of a
deeper hydrothermal deposit, a placer
deeper
placer deposit
deposit formed
formed during
during lower lake levels from
results from
materials delivered by
the Montreal
Montreal River, or results
from more
more current
current
by the
enrichment of
of surficial sediments
enrichment
sediments is
is not
not presently
presently known,
known, and
and this
this question
question awaits
awaits
the opportunity
for physical
sampling at
at depth.
depth.
the
opportunity for
physical sampling
39
39
�DIAMOND DRILLING IN ENVIRONMENTALLY
DIAMOND
ENVIRONMENTALLY SENSITIVE
SENSITIVE AREAS
AREAS —
ENVIRONMENTAL IMPACT: MONITORING
MONITORING AND
AND ASSESSMENT
ASSESSMENT
M.G. Mudrey, Jr., Wisconsin Geological
and Natural
Geological and
Natural History Survey, 1815
University Avenue,
Avenue, Madison,
Madison, Wisconsin
Wisconsin53706,
53706,Bruce
BruceC.C. Parker,
Parker, Department of
University
of
Biology, Virginia
Virginia Polytechnic
Polytechnic Institute
Institute and State
Biology,
State University,
University, Blacksburg,
Blacksburg, Virginia
Virginia
24601, Keros
State Geological
Cartwright, Illinois
Illinois State
Geological Survey,
Survey, Natural
Natural Resources
Resources
24601,
Keros Cartwright,
Building, Urbana,
Urbana, Illinois
Illinois 61801,
61801, and
and Lyle
Lyle D.
Building,
D. McGinnis,
McGinnis, Department of
of Geology,
Geology,
Northern illinois
Illinois University, DeKaib,
DeKalb, illinois
Illinois 60115
60115
ABSTRACT
A
drilling program
program can
can be
sophisticated exploratory
exploratory diamond
diamond drilling
be mounted
mounted to
to
A sophisticated
moderate
modera
te depths,
depths, and
and environmental
environmental disturbance
disturbance minimized
minimized in aa conscientious
conscientious
program
involving impact
impact assessment,
assessment, training,
training, and
and real-time feedback
program involving
feedback among
among all
parties. Although
not normally
Although not
normally the case
case with
with exploratory
exploratory drilling,
drilling, environmental
environmental
disturbance can occur
occur in
in sensitive
sensitive areas
areassuch
suchas
aswilderness
wilderness areas,
areas,public
public park
park lands,
lands,
and delicate,
delicate, unique
regions,such
suchasasthe
the polar
polar regions.
regions. One
One factor,
factor, of course,
and
unique regions,
course, is
the public
public fear
fear that
thatthe
theproposed
proposedexploratory
exploratorydrilling
drilling program
program might
might irreversibly
irreversibly
disturb
environmental
conditions
in
areas
noted
for
their
recreational
and
disturb environmental conditions in areas noted for their recreational and scientific
value. AA secondary
value.
secondary fear
fear isis that
thatexploitable
exploitable natural
natural resources
resources will
will be
be found,
found, and
and
that
that they
they will
will be
be developed
developed causing major
major impact to the
the local
local environment.
environment.
It is
is important
important to
to recognize
recognize that
that the
theconcept
concept of
of no
no impact
impact is
is an
an unrealizeable
unrealizeable
The objective
objective of
of all
human goal. The
human
all impact
impact statements
statements is
is to
to minimize
minimize or
or reduce
reduce
potential adverse
adverse impacts
impacts to
to the
theenvironment,
environment, whenever
whenever and
and as
as far
far as
aspossible
possible and
and
practical.
We
propose to
to address
address only
only the
the design
design and
and implementation
implementation of
of an
an environmentWe propose
ally
exploratory drilling
drilling program
programinin aa sensitive
sensitive area,
area, the
ally responsible
responsible exploratory
the dry
dry valley
valley
From lanuary
region of
of Antarctica.
region
Antarctica. From
January 1973
1973 until
until December
December 1975,
1975, aa comprehensive
comprehensive
diamond drilling
drilling program
program inin antarctic
antarctic permafrost
diamond
permafrost and
and under
under severe
severe environmental
environmental
Dry Valley Drilling Project
restraints —
restraints
- the Dry
Project—
- was carred on.
on. A
A total
total of
of 13
13 months
months
of
resulted inin the
the recovery
of over
meters of
of core
of drilling
drilling resulted
recovery of
over 2100
2100 meters
core at 15
15 sites.
sites.
Although scientific
scientific in
in objectives, the
Although
the international,
international, multidisciplinary
multidisciplinary program,
program, and
and
analysis are
are applicable
applicable to resource-oriented drilling
its techniques
techniques of
of environmental
environmental analysis
drilling
programs
in other
other areas
programs in
areas of
of environmental
environmental and
and public
public concern,
concern, such
such as
as the
the scenic
scenic
vistas of the Lake
Lake Superior
Superior region.
The
evaluation, after
after identification of
of the target
of environmental
environmental evaluation,
target
The first stage of
sites, was
was the
the preparation
preparation of
of an
anenvironmental
environmental assessment,
assessment, in
in which
which the
theproposed
proposed
engineering
operations plans,
environmental impacts
impacts were
engineering operations
plans, and
and possible
possible environmental
were identified.
These were
were addressed
addressed by
by an
an impact
impact matrix which
These
which identified
identified all projected
projected actions
extent, and
Probability, areal extent,
environment.
and
and all characteristics of the environment.
significance were
were assessed
assessed atat this
significance
this time
time by
by an
an impact
impact committee
committee consisting
consisting of
of
environmentalists, project engineers,
environmentalists,
engineers, and
and other
other knowlegeable
knowlegeable scientists. Potential
environmental impacts
impacts were
were identified,
identified, and
environmental
and revision
revision of proposed
proposed operations
operations were
made without
without undue
hardshiptoto the
the environment
environment or
or to
to the
the drilling
drilling contractor,
contractor, in as
made
undue hardship
much
as no
no operations
operations had
had yet
yet started.
started.
much as
Subsequently,appropriate
appropriate documents
documentswere
weresubmitted
submittedfor
for review
review to
to governSubsequently,
governQuestions raised
raised were
were addressed
mental bodies.
bodies. Questions
addressed by
by the environmental
environmental committee.
Pertinent documents
Pertinent
documents directly
directly addressed
addressed the proposed
proposed program,
program, and
and the
the language
language
Technical details
details were
were appended.
appended. An
was directed
directed to the
the general
general public.
public. Technical
An effort
was
was
made to
to make
make the
the main
was made
main text of
of the
the document
document readable
readable and
and concise.
40
�I
In
In the case
case of
of DVDP,
DVDP, the antarctic
antarctic soil
soil and
and lake
lake ecosystems
ecosystems are
are particularly
particularly
delicate, and
and consequently
consequently vulnerable
vulnerable to any
any human
human activity.
activity. An
An environmental
environmental
of each
scientist
scientist on
on the
the drill site, and
and prior
prior environmental
environmental discussion
discussion of
each site by
by
scientists
scientists and
and drill
drill team
teampersonnel
personnel comprised
comprised the
thebasis
basis for
forthe
theDVDP
DVDP environmental
environmental
An
protection program.
program.
An operations
operations procedure
procedure and
and monitoring
monitoring scheme
scheme was
was
implemented
to detect
implemented to
detect and
and control
control environmental
environmental impact.
impact. Monitoring
Monitoring before,
before,
during,
during, and after
after the
thedrilling
drillingoperations
operationsidentified
identifiedenvironmental
environmentalchanges
changescaused
causedby
by
the activities at all
all sites,
sites, and
and those
those results
results were
were reported
reported to
to enhance
enhance the accuracy
accuracy
of the
the predictive
predictive model,
model, the Environmental
Environmental Impact
Impact Appraisal.
Appraisal. One
One objective was
was to
to
prevent
prevent or reduce
reduce impacts
impacts by
by DVDP,
DVDP, and
and thus
thus assist
assist planning
planning for any
any future
future
projects
in Antarctica.
projects in
Antarctica.
For DVDP,
critical environmental
DVDP, critical
environmental limitations included
included no
no surface transport,
transport,
minimal
crew size,
size, few
few drilling
options with
with respect to
minimal crew
drilling options
to equipment
equipment and
and circulating
circulating
fluids,
fluids, an absolute
absolute requirement
requirement that
that all
all waste
waste and
and equipment
equipment be
be removed
removed from
from the
be in
site areas,
areas, and
and that
that an
aninteractive
interactiveenvironmental
environmental monitoring
monitoring program
program be
in
operation.
constant operation.
41
�SYENITE OF CENTRAL
THE WAUSAU
WAUSAU SYENITE
CENTRAL WISCONSIN
WISCONSIN
Myers, Paul
Department of
ofGeology,
Geology, Washington
Washington State
State University,
University, Pullman,
Pullman,
Myers,
Paul E.,
E., Department
Washington 99163
99163
ABSTRACT
The Wausau
syenite-quartzsyenite
syenite pluton
pluton inin two
two segments
and the more
The
Wausau syenite-quartz
segments and
more
alkalic Stettin
Stettin syenite
syenite pluton
pluton are
areexposed
exposed west
westof
ofthe
theWisconsin
Wisconsin River
River near
near Wausau
Wausau
in central
These Middle
plutons are
in
central Wisconsin.
Wisconsin. These
Middle Precambrian
Precambrian (1650
(1650 ÷
+ 50
50 m.y.) plutons
concentrically zoned
zoned and
and show
concentrically
show a distinct
distinct north-northeasterly
north-northeasterly elongation.
elongation. Each
pluton has
has a contact
pluton
contact metamorphic
metamorphic zone
zone of
of fenitized
fenitized wall
wall rocks,
rocks, an
an alkalic,
alkalic,
laminated, xenolith-rich
laminated,
xenolith-rich wall
wall zone,
zone, an
an intermediate
intermediate zone,
zone, and
and a core.
core. Silica
content increases
increases inward
inward in each pluton.
pluton.
The southern
southern segment
segment of
of the Wausau
pluton isis circular
circular in plan with a diameter
Wausau pluton
diameter
The
of eight miles.
half of
of this
this caldera-like
caldera-like structure were
of
miles. Although
Although the core
core and
and south half
were
intruded
the Ninemile
preserved as
as a
intruded by
by granite
granite of the
Ninemile pluton,
pluton, its structure is preserved
discontinuousring
ringofoflarge
largexenoliths
xenolithsfive
fivemiles
milesinindiameter.
diameter. The
discontinuous
The largest of
of these
these
over two miles
in the
xenoliths
xenoliths -- the Rib Mountain
Mountain quartzite
quartzite —
- is over
miles long.
long. Bedding
Bedding in
The top
top of
xenolith
dips very
very steeply
toward the
the granite
xenolith dips
steeply southward
southward toward
granite core.
core. The
of the
the
xenolith has
has been eroded
xenolith
eroded leaving
leaving aa keel-shaped
keel-shaped mass,
mass, slightly
slightly convex
convex northward,
northward,
and surrounded
at depth
depth by
by quartz
quartz syenite
and
surrounded at
syenite of the
the crescentic
crescentic intermediate
intermediate zone.
zone.
Quartzite xenoliths
xenoliths near
near intrusive
intrusive contacts
contacts are
aretypically
typicallyveined
veinedand
and impregnated
impregnated by
by
Pyroxene
and
amphibole
syenite
commonly
containing
volcanic
K-feldspar.
Pyroxene and amphibole syenite commonly containing volcanic
xenoliths, form
form a discontinuous
outer rim
rim (wall
zone) of
of the southern segment.
discontinuous outer
(wall zone)
xenoliths,
The northern
northern segment
segment of
of the Wausau
is semicircular
The
Wausau pluton
pluton is
semicircular in
in plan
plan with
with its
truncated southern
southern edge
edge along
along the Rib
Rib River.
River. The
TheStettin
Stettinpluton
plutonisiscontiguous
contiguous with
with
it on
internal structure are similar
on the northwest.
northwest. Although
Although its size and
and internal
similar to that
that of
of
the southern
southern segment,
segment, its intermediate
intermediate zone
zone consists
consists of coarse
coarse gray
gray syenite,
syenite, and
and
volcanic xenoliths
xenoliths predominate.
predominate. The
probably represents
represents aa
The older
older northern segment
segment probably
volcanic
caldera
caldera structure,
structure, which
which was
was partially
partially destroyed
destroyed by
by intrusion
intrusion of
of the
the southern
southern
segment.
The Stettin pluton
The
pluton is
is oval
oval in
in plan
plan with
with dimensions
dimensions of
of 5.0
5.0 x 3.5 miles. Three
major
in mapping
were: (1)
major zones
zones distinguished
distinguished in
mapping were:
(1) a wall
wall zone
zone comprising
comprising aplitic
aplitic
biotite syenite,
an intermediate
syenite, nepheline
nepheline syenite
syenite gneiss,
gneiss, and "tabular syenite", (2)
(2) an
zone,
zone, aplitic
aplitic to
to pegmatitic
pegmatitic amphibole
amphibole and
and pyroxene
pyroxene syenite
syenite with
with swirled
swirled flow
flow
lineation, and
and (3)
(3) a circular
circular core zone
zone one
one mile
mile in
in diameter
diameter comprising
comprising aa rim
rim of
of
magnetite-rich nepheline-hedenbergite-fayalite
nepheline-hedenbergite-fayaiite
syenite,andandananinner
inner core
core of
magnetite-rich
syenite,
pyroxene syenite.
Both
Both the Wausau
Wausau and
and Stettin
Stettin plutons
plutons possess
possess strongly
strongly metasomatized,
metasomatized, but
but
Concentric cataclastic
unassimilated xenolith-rich
xenolith-rich wall
unassimilated
wall zones.
zones. Concentric
catac1astic lamination
lamination was
was
developed by
displacements accompanying
accompanying the
the forceful emplacement of
developed
by high-angle
high-angle displacements
of
these plutons.
plutons. Subsequently,
Subsequently, more
more passive
passive intrusion
intrusion of
of the
the Ninemile
Ninemile granite
granite caused
caused
a partial
partial foundering
foundering of the
the southern
southern part
part of
of the
theWausau
Wausau pluton.
pluton.
42
�MODIFICATION
MODIFICATION OF ENGINEERING
ENGINEERING PROPERTIES
OF ST.
ST. PETER
PETER SANDSTONE
SANDSTONE
C.R.
C.R. Nelson
Nelson and
and D.H.
D.H. Yardley,
Yardley, Department
Department of
of Civil
Civil and
andMineral
MineralEngineering,
Engineering,
University
University of
of Minnesota,
Minnesota,Minneapolis,
Minneapolis, Minnesota
Minnesota55455
55455
ABSTRACT
ABSTRACT
The
Peter sandstone
sandstone is
is aa formation
formation of
of major
major geotechnical
geotechnical importance
importance in
in
The St. Peter
the Twin
Twin City Metropolitan
Metropolitan area
area as
as well
well as
as elsewhere
elsewherein
inMinnesota
Minnesota and
and some
some nearby
nearby
states. Nearly
Nearly 200
200 miles
miles of
of tunnels
tunnels and
and other
other openings
openings have
have already
already been
been
constructed in it in
in the
the Metro
Metro area.
The
The St. Peter
Peter is
is aa rather
rathermassive,
massive,weakly
weakly cemented,
cemented, very
very pure
pure sandstone
sandstone of
of
98.5%
98.5% - 99%
99% SiO2.
Si0 2 • The
compressive strength
strength varies
varies between
between 670
670 and
and 2800
2800 psi
psi in
in
The compressive
harder zones,
zones, but
but in
In softer
softer zones
zones ititcommonly
commonly varies
varies from
from less
less than
than100
100to
to300
300psi,
psi,
hence
some openings
openings inin itit will
hence while
while some
will support
support themselves
themselves most
most need
need some
some type of
of
support. Because
Because most
most of
of its strength
strength is
is aa result
result of
of compaction
compaction and
and grain
grain
is water-sensitive
to the
the degree
that if water
interlocking,
interlocking, it is
water-sensitive to
degree that
water agitates
agitates the
the grains
grains
St. Peter has
much
of the sandstone
will deteriorate
deteriorate r':!Jidly.
raidly. The
much of
sandstone will
The St.
has aa porosity
porosity of
of
per second.
about 28%
28% and
and a permeability
permeability of 3.5
3.5 xx 10
10 cm
cm per
second. The
The grains
grains are quite
quite
about
rounded,
have aa frosted
frosted surface and
rounded, have
and a diameter
diameter of
of 0.1
0.1 mm
mm to
to 0.5
0.5 mm.
mm.
A spray-grouting
technique has
has been
been developed
by the senior author,
spray-grouting technique
developed by
author, using
using a
silicate-based liquid
liquid that
that can permeate
for a few
silicate-based
permeate into
into exposed
exposed sandstone
sandstone for
few inches.
inches.
This
forms aa hardened
of sandstone
with aa compressive
strength on
on the order
This forms
hardened shell
shell of
sandstone with
compressive strength
of 1500
psi in
in the
the soft zones. Test
of
1500 psi
Test patches
patchesin
inplace
placefor
for 33years
yearsshow
show no
no evidence
evidence of
deterioration.
This
system of artificially
for rehabilitaThis system
artificially stengthening
stengthening sandstone
sandstone is being used
used for
It
is
also
being
used
as
the
main
excavation
support
tion
tunnels.
is also being used
the main excavation support on
on aa 10
10
tion of utility tunnels.
foot tunnel
where itit has
the use
at a
foot
tunnel where
has replaced
replaced the
use of
of steel
steel rings
rings and
and oak
oak lagging
lagging at
substantial cost reduction.
substantial
reduction. Elimination
Eliminationof
ofsteel
steeland
andwood
wood support
support makes
makes itit possible
possible
to pour
so that when
to
pour aa final
final concrete
concrete lining
lining directly
directly against
against the sandstone
sandstone so
when the
tunnel is
is pressurized
the resistance
tunnel
pressurized the
resistance of
of the
the coupled
coupled sandstone
sandstone wall
wall will
will so
so greatly
decrease lining
lining deformation
deformation that
that steel reinforcing
decrease
reinforcing is
is not
not required.
required. Spray-hardening
Spray-hardening
also makes
makesitit possible
possiblefor
forthe
the first
first time
to the
also
time to apply
apply shotcrete
shotcrete to
the St.
St. Peter
Peter
sandstone in
in this
this area.
sandstone
It has
has been estimated that
that the
thecost
costsavings
savings on
on one
one large
large tunnel,
tunnel, and
and for
for one
one
utility
utility tunnel
tunnel repair project,
project, both
both in
in progress,
progress, will
will be
be about
about 1.3
1.3 million
million dollars.
dollars.
Support funds
funds of
of less than
from the NSF,
program have
have led
led to the
Support
than $100,000
$100,000 from
NSF, RANN
RANN program
the
development.
43
�ANATOMY
ANATOMY OF A WELL-COVERED
WELL-COVERED GREENSTONE BELT,
BELT,
NORTHWESTERN MINNESOTA
MINNESOTA
Richard W.
W. Ojakangas, University of Minnesota,
Minnesota, Duluth,
Duluth, Duluth,
Duluth, Minnesota
Minnesota55812
55812
ABSTRACT
The
rocks of
of the Birchdale-Indus
Birchdale-Indus area are part
part of
of aapoorly-exposed
poorly-exposed volcanicvolcanicThe rocks
sedimentary sequence
sedimentary
sequence within
within the
the Wabigoon
Wabigoon Volcanic
Volcanic Belt.
Belt. The
bedrock is Early
Early
The bedrock
Precambrian in
in age,
age, and
includes mafic
mafic to intermediate
Precambrian
and includes
intermediate flows
flows and
and intrusives; felsic
dikes,
dikes, agglomerates,
agglomerates, tuffs and
and volcaniclastic
volcaniclastic rocks;
rocks; iron-formation
iron-formation and
and associated
associated
metasediments;
and granitic
granitic rocks
of Algoman
age. All
of these lithologies
are cut
metasediments; and
rocks of
Algoman age.
All of
lithologies are
by
by northwest-trending Middle
Middle Precambrian mafic
mafic dikes.
dikes. The
The area is
is well-covered
well-covered
by
by Pleistocene deposits.
deposits.
The volcanic-sedimentary
sequence has
has been
been isoclinally
folded; northeastThe
volcanic-sedimentary sequence
isoclinally folded;
trending
beddingand
and foliations
foliations are
are generally
generally steep
steep to
to vertical.
trending bedding
vertical. One
One doublydoubly-
plunging
anticline and
and one
one syncline
syncline have
have been
been mapped
mappedwithin
withinthe
thearea.
area. AA second
plunging anticline
second
folding with
with more
folding
more northerly-trending
northerly-trending fold
fold axes is
is indicated
indicated by
by some
some general
general and
and
detailed relationships.
sets of faults
relationships. Three
Three sets
faults and
and fractrures
fractrures are
aredocumented;
documented; the
the
first set
set trends
trends east-west,
east-west, the
the second
second northwest,
northwest, and
and the third
third northeast.
northeast. All of
the Lower
Lower Precambrian rocks
rocks have
have been
been metamorphosed
metamorphosed to amphibolite
amphibolite grade.
grade.
Synthesis ofof the
the geology
of the Birchdale-Indus
area with
with that
that of the
Synthesis
geology of
Birchdale-Indus area
the Emo
Emo
area in
allows an
an interpretation of
in adjacent
adjacent Ontario
Ontario (Fletcher
(Fletcher arid
and Irvine,
Irvine, 1954)
1954) allows
of the
the
Mafic and
and intermediate volcanic
development
of the volcanic
development of
volcanic accumulation.
accumulation. Mafic
volcanic and
and
intrusive
rocks apparently
apparently constitute
constitute the lowest
intrusive rocks
lowest stratigraphic
stratigraphic unit.
unit. An
An explosive
felsic volcanic
volcanic center,
center, marked
marked by
by abundant
abundant agglomerates, developed
developed upon
upon the mafic
platform
and Emo.
Emo. Felsic tuffs, volcaniclastics,
platform in the
the vicinity
vicinity of
of Birchdale,
Birchdale, Indus
Indus and
volcaniclastics,
and iron-formation
iron-formation were
were deposited
deposited outward
outward from
from this
this center.
center.
and
The Birchdale-Indus
Birchdale-Indusarea,
area, and
and areas
areas to
to the west and
The
and south, have been actively
explored for
for base
base metal
for the past
explored
metal sulfide
sulfide deposits
deposits for
past decade.
decade. Thick
Thick zones
zones of
of
massive, sub-massive,
sub-massive, and
and dissemianted
dissemianted pyrite and/or pyrrhotite have
have been
been
penetrated at
at several
several localities,
localities,but
butcopper
copperand
andzinc
zincminerals
minerals have
have not
not been
been found
found
Several
of
the
drilled
iron-sulfide
bodies
are
associated
in economic
economic quantities.
quantities. Several of
drilled iron-sulfide bodies
associated
in
with oxide iron-formation.
REFERENCES CITED
CITED
Fletcher,
Fletcher, G.L.,
G.L., and
and Irvine,
Irvine, T.N.,
T.N., 1954,
1954, Geology
Geology of the Emo
Emo area:
area: Ontario
OntarioDivision
Division of
of
Mines
63rd annual
annual report,
report, V.
V. LXIII,
LXIII, part
part5,5,3636p.p.plus
plusmap
mapNo.
No.1954—2,
1954-2, scale
scale 11
Mines 63rd
inch to 11 mile.
inch
44
�CARBON IN METAMORPHOSED SEDIMENTS
CARBON
SEDIMENTS
FROM ISUA,
ISUA, WEST
GREENLAND
WEST GREENLAND
FROM
Eugene C.
C. Perry,
Perry, 3r.
Jr. and
and Syed
Syed Neaz
Neaz Ahmad,
Ahmad, Department
Department of
of Geology,
Geology, Northern
Northern
Eugene
illinois University, DeKaib,
Illinois
DeKalb, illinois
Illinois 60115
60115
ABSTRACT
ABSTRACT
0/00 ~.
aphitic carbon
carbon (S13
(6'3C
vs. PDB)
About 2.5% §aphitic
C == -16.1 0100
PDB)occurs
occurs in
in aa specimen
from the
the 3.7
10 year
year old
at Isua,
Greenland. The
from
3.7 x 10
old supracrustal
supracrustal sequence
sequence at
Isua, West
West Greenland.
The
specimen, which
whichcontains
containsquartz,
quartz,amphibole,
amphibole,and
andminor
minormagnetite
magnetiteand
and pyrite,
pyrite, is
specimen,
is
associated with
with a thick
associated
thick succession
succession of
of metamorphosed
metamorphosed chert and
and magnetite-bearing
magnetite-bearing
iron-formationand
andwithin
within2.4
2.4km
kmacross
acrossstrike
strikeofof aa thick
thick quartz-magnetite
iron-formation
quartz-magnetite unit
unit
containing sufficient
sufficient iron
iron to
to be
commercial significance.
significance. Rocks
in the
the
containing
be of possible
possible commercial
Rocks in
area have been metamorphosed
to amphibolite
facies and
area
metamorphosed to
amphibolite facies
and are sufficiently
sufficiently sheared
sheared
so that
that primary
textures are
are obliterated.
so
primary textures
Carbonaceous organic
organic matter
matter is a common
Carbonaceous
common constituent of
of iron-formation,
iron-formation, and
and
it has
has been
suggested
that
the
iron
oxide
of
iron-formation
been suggested that the iron oxide of iron-formation is aa biogeneic
biogeneic
facies ironprecipitate. Thus,
Thus, the
theassociation
association of
of carbonaceous
carbonaceous material
material with
with oxide
oxide facies
for mationatat Isua
Isua isis consistent
with an gganic
formation
consistent with
larganicorigin
origin for1
for; this ancient
ancient carbon.
carbon.
However, the
the Isua
Isua carbon
carbon is
However,
is enriched
enriched in
in jc
about 15
15 0/00
0 00 compared
compared to
C by about
to later
Precambrain material
material of
of known
knownbiogneic
biogneicorigin.
origin. Since
Since metamo~phism
metamophism accompanied
Precambrain
accompanied
/oo carbon
reactions could
by isotope-fractionating reactions
could produce
carbon isotope
isotope
produce a 15 0/00
fractionation, the stratigraphic
fractionation,
stratigraphic association
association of
of this
this carbon
carbon with
with iron-formation
iron-formation may
may
to its origin than is its present
be a more reliable guide
guide to
present isotopic
isotopic composition.
composition.
45
45
I
t
�OLD PRECAMBRIAN W GNEISSES
GNEISSES IN
IN NORTHERN MICHIGAN
OLD
Zell E.
ZeU
E. Peterman,
Peterman, Robert
Robert E.
E. Zartman,
Zartman, and
andP.K.
P.K.Sims,
Sims,U.S.
U.S.Geolgoical
Geolgoical Survey,
Survey,
Denver, Colorado
Colorado 80225
80225
ABSTRACT
dating of
of gneisses
in the western
Radiometric dating
gneisses in
western part
part of
of northern
northern Michigan
Michigan has
confirmedthe
the presence
presenceofof an
an ancient
ancient sialic
sialic terrane
terrane that formed
confirmed
formed more
more than
than 3400
3400
m.y. ago.
An antiformal
antiformal structure
structure in
in the
the Watersmeet
area contains
contains aa core
core of
m.y.
ago. An
Watersmeet area
of
tonalitic to
to granitic
surrounded by
by folded
tonalitic
granitic gneiss
gneiss that
that is surrounded
folded and
and metamorphsed
metamorphsed
Precambrian
X graywackes.
graywackes. The
is cataclasitcal!y
cataclasitcally deformed
and recrystalPrecambrian X
The gneiss
gneiss is
deformed and
lized, and
and geochronologic
geochronologicdata
datareflect
reflectthe
the effects
effects of
of severe tectonic and
lized,
and thermal
thermal
events. Whole-rock
Whole-rock Rb-Sr
Rb-Sr systems
systems are
are highly
highly disturbed,
disturbed, but
but data
datafor
forsamples
samplesfrom
from
two localities
localitiesdefine
definesecondary
secondary
isochrons
of aut 00 m.y.
two
isochrons
of 19ut
m.y. AAsubstantially
substantially older
older
age of the
Sr/ Sr
age
the gneiss
gneiss is
is indicated
indicated by
by high
high initial Sri
0.773 to 0.717
0.717 for
Sr ratios of 0.773
These high
high i~7ial
int7ial ratios
ratios resulted
resulted from
from local
the two
two isochrons.
isochrons. These
local redistribution
redistribution of
previously generated radiogenic
Sr during
the major
previously
radiogenic
Sr
during the
major period
period of
of cataclasis
cataclasis and
and
Metamorphismofof adjacent
adjacent Precambrian
X rocks
recrystallization.
Metamorphism
Precambrian X
rocks occurred
occurred
synchronouslywith
withthe
the reactivation and mobilization
of the gneiss
synchronously
mobilization of
gneiss as suggested
suggested by
1810 m.y.
m.y. isochron
obtained on
on four
an 1810
isochron obtained
four whole-rock
whole-rock samples
samples of
graywacke
of graywacke
immediately adjacent
adjacent to
to the gneiss
along the
the northern
northern contact.
contact.
immediately
gneiss along
U-Pb
data obtained
on zircon
from the gneisses
also reflect
reflect the
U-Pb data
obtained on
zircon separated
separated from
gneisses also
complexgeology
geologyhistory
historybut
butclearly
clearlyplace
placethe
the time
time of
of primary
crystallization at
complex
primary crystallization
90 rn~~b
agoago
or more.
Three
size
fractions
ofofzircon
~890
or more.
Three
size
fractions
zirconfrom
froma atonalititc
tonalititcgneiss
gneiss have
have
Pb ages
ages ranging
ranging from
from 3310
to 3370
m.y. and
Pb/
Pb
3310 to
3370 m.y.
and a primary
primary age
age of
of about
about 3500
3500
m.y. is
is suggested.
suggested. Zircon
Zircon from
from aa compositionally
compositionally similar ~~t mU<i~&;10r20tj;or~ly
m.y.
defogpd
aj
recrystallized
phase
Pb!
Pb!
U,
U,
def02~d ~ recrystallized phaseofofthe
thegneiss
gneissyields
yields
Ph/
Pb/
Pb
ages that are
Pb/
Pb ages
are concordant
concordant at
at 1760
1760 m.y. This
This lower
lower age
age agrees
agrees with
with
and
Pb!
Rb-Srages
ages and
andapparently
apparently indicates
indicates total
total resetting or
the whole-rock
whole-rock Rb-Sr
or perhaps
perhaps even
even
crystallization
of
the
zircon
during
this
metamorphic
episode.
Data
for
two
zircon
crystallization of
zircon during this metamorphic episode. Data
two
fractions
from aa leucocratic
phase of
of the
the gneiss
gneiss plot
plot on
on aa chord
fractions from
leucocratic phase
chord that intersects
intersects
concordia at about
data may
indicate the
the presence
concordia
about 2600
2600 m.y.
m.y. These
These data
may indicate
presence of granitic
granitic
intrusions
that were
intrusions that
were emplaced
emplaced in
in the
the older
oldergneisses
gneisses during
during the
theAlgoman
Algoman orogeny.
orogeny.
About
2710
m.y.—old
About 20
20 km
km northwest
northwest of
of the
thegneiss
gneissatatWatersmeet,
Watersmeet,thethe
2710
m.y.-old Puritan
Puritan
Quartz Monzonite
and Precambrian
Quartz
Monzonite and
Precambrian W
W metavolcanic
metavolcanic and
and metasedimentary
metasedimentary rocks
rocks
form aa greenstone-granite
form
greenstone-granite terrane that
that evolved
evolved in an ensimatic
ensimatic environment.
environment. The
The
presence
of Algoman
granitic rocks
rocksininthe
the older
older gneiss
gneiss terrane
terrane may
presence of
Algoman granitic
may indicate
indicate that
that
both blocks
blocks were in juxtaposition
juxtaposition at
at 2600
2600 to
to 2700
2700 m.y.
m.y. ago
ago and
and subsequently formed
a continuous
continuous and
and coherent
coherent sialic
sialic basement
basement to the
the Precambrian
Precambrian XX sedimentary
sedimentary
basins.
tgOO
46
U
�APPROACH TO
A SYSTEMS
SYSTEMS APPROACH
TO ENVIRONMENTAL
ENVIRONMENTAL GEOLOGY
H.O.
of Geology
Geology and
and Geophysics,
Geophysics, University
University of
of Minnesota,
Minnesota,
H.O. Pfannkuch,
Pfannkuch, Department of
Minneapolis, Minnesota 55455
55455
ABSTRACT
term "environmental
geology" has
has been
been loosely
loosely applied
applied to
to situations
The term
"environmental geology"
situations
ranging
from pure
problems to
to those
ranging from
pure engineering
engineering problems
those of
of traditional
traditional general
general geology.
geology.
The concept
concept needs
needs clarification
clarification and
and definition
in order
order to
to provide
the reference
The
definition in
provide the
reference
space in
in which
solutionsfor
for the
the most
most pressing
pressing problems
problemscan
canbebeattempted.
attempted. This
space
which solutions
This is
attempted
attempted by
by aa systems
systems approach
approach where
where the
the three
three interacting
interactingprincipal
principalcomponents
components
are human
on aa global
human ecology,
ecology, geology
geology on
global scale, and
and clutural
clutural anthroplogy
anthroplogy from
from aa
socio-economic point of view.
socio-economic
The
based on
approach is based
on an
an
The approach
analogy argument,
argument, that is that human
analogy
human
ecosystems
behave inin a similar
ecosystems behave
similar way
way as
as other
otherecosystems.
ecosystems. This
This means
means that
ecosystem concepts
concepts such
ecosystem
such as structure,
structure, process
process dynamics
dynamics and
and evolutionary
evolutionary trends
trends
from
to mature,
from young
young and
and unstable
unstable but highly
highly productive
productive to
mature, complex
complex and
and stable
stable
systems can
can be used
systems
used as parallels. The
Theinterface
interfacewith
withgeology
geologyisisprovided
provided by
by global
global
material cycles and energy
flow processes.
processes. The
impact of
material
energy flow
The impact
of interaction is
is measured
measured
in a first order
simple mass
mass change
changeto
to total
total mass,
in
order approximation
approximation by
by simple
mass, and
and rate change
change
It has
to geologic
geologic rate relationships.
relationships. It
has to be refined to include
include effects of
of additivity
additivity
and accumulation,
and those
those of
of stability
and
accumulation, and
stability of
of feedback
feedback relations.
relations. In
In the
the latter
latter
category fall the
the triggering
triggering effects
effectsofofpossibly
possiblysmall
small temperature
temperaturechanges
changeson
on world
world
Limitations of geological nature can be
climatic changes.
be expressed
expressed by
consumption or
or use
use rates, such as in resources where rate of
consumption
of formation
formation is
is compared
compared
to rate
to
rate of
of consumption
consumption or
or with
with the
the carrying
carrying capacity
capacity of
of the
the earth
earthwhere
where loading
loading
or regeneration rates.
rates are
are compared
compared to dissipation
dissipation or
In
In the socio-economic
socio-economic context, environmental
environmental geology
geology has two
two contributions
contributions
to make.
help
make
environmentally
to
make. On
On a short
short term
term basis
basis itithas
hasto to
help
make
environmentallysound
sound
compromisesthat
that can
can be
be achieved
achieved within
within the
the present
present structure of time
time and
and space
space
compromises
references in
in the
the decision
decision making
making process.
process. This,
This, however,
however, is only
only a temporary
temporary and
and
transitional solution,
solution, in
in the end
will have
have to
to provide
transitional
end environmental
environmental geology
geology will
provide the
the
basis on
on which
new and
and consistent
consistent time
time and
basis
which new
and space scales will
will have to be
be developed
developed
for environmentally
environmentally acceptable
acceptable decision
decision making
making processes.
processes.
47
I
�ENVIRONMENTAL IMPLICATIONS
IMPLICATIONS OF
OF GROUNDW
GROUNDWATER-LAKE
ENVIRONMENTAL
ATER-LAKE
LAND USE
USE APPLICATION
INTERACTION WITH
WITH LAND
Dave Pollack
Dave
Pollack and
and H.O.
H.O. Pfannkuch,
Pfannkuch, Department
Department of
ofGeology
Geology and
andGeophysics,
Geophysics,
University of Minnesota,
Minnesota, Minneapolis,
Minneapolis, Minnesota
Minnesota 55455
55455
ABSTRACT
Many lakes, if not
Many
the majority,
majority, have
have to
be viewed
viewed as
of and
and an
an
not the
to be
as part
part of
expression of
of local
local and
and regional
groundwater flow
flow systems.
systems. Lake
expression
regional groundwater
Lake level
level variations
variations
are therefore
are
therefore strongly
strongly related
related to
to watertable
watertable fluctuations,
fluctuations, especially
especially in
in lakes
lakes
Current methods
without surface water inlets or outlets.
Current
methods of
of establishing
general lake
lake water
groundwater contribution to the general
water balance
balance only
only give
give net
net
contributions which
whichare
are insufficient
insufficient to
to calculate
contributions
calculate residence
residence times of
of chemical
chemical or
or
biological inputs. An
An areal
areal flow
biological
flow net
net method
method is
is discussed
discussed to
to calculate
calculate absolute
absolute
amounts of
of groundwater
inflow and
and outflow
outflow and
and its
its spatial
amounts
groundwater inflow
spatial relationships
relationships with the
the
lake.
Analysis
of aa cross
cross section
section through
through aa lake
lake and
and its
its aquifer shows
Analysis of
shows that even with
a fully
lake bed
of streamlines
streamlines near
fully permeable
permeable and
and uniform
uniform lake
bed there will
will be crowding
crowding of
the shore,
the
shore, which
which means
means relatively
relatively higher
higher flow
flow velocities
velocities of
of groundwater
groundwater and
and
enhanced transport
transport activity in
enhanced
in this
this region.
region. Analog
Analogand
and dimensional
dimensional analysis
analysis of some
some
very simple
simple cases
cases are carried
very
carried out
out to
to demonstrate
demonstrate the
thedependence
dependence on
on lake-aquifer
lake-aquifer
geometry and
and toto define
define the
the critical
critical parameters.
geometry
parameters. These
These are
are thickness
thickness of
of the
the lakelakeaquifer,
degree
of
depth
penetration
of
the
lake,
and
ratio
of
the
aquifer
flow
aquifer, degree of depth penetration of the lake, and ratio of the aquifer flow
section
is given
given by
bythe
the lake
lake diameter.
diameter. Further
section to the
the lake-aquifer
lake-aquifer interface which
which is
Further
increase of
of flux
large portions
of the lake
increase
flux near
near shore
shore occurs
occurs when
when large
portions of
lake bottom
bottom are
are
sealed by
by impermeable sediments.
sediments.
The
The direct environmental
environmental implications
implications are two
two fold:
fold: First
First it is
is necessary
necessary to
have a clear picture
outflow ininorder
ordertoto relate
relate it to
picture of
of true
true groundwater
groundwater inflow
inflow and
and outflow
the
into the
the total
total lake
lake budget,
budget, this
this provides
provides insight
insight into
the relative
relative importance
importance of
of
groundwater
groundwater carried pollution.
pollution. Localization
Localization and
with high
high
and identification
identification of areas with
groundwater
flow activity in
groundwater flow
in the
thenear-shore
near-shoreregion
regionhave
haveobvious
obvious application
application to
to land
land
use planning
and regulation
regulation such
such as
as the
the implacement of domestic sewage disposal
planning and
disposal or
treatment facilities.
The severity
treatment
facilities. The
severity of impact
impact depends
depends on
on length
length of
of flowpaths,
flowpaths,
residence time
time of
of pollutants,
or regeneration
capacity of
of the
residence
pollutants, and
and adsorption
adsorption or
regeneration capacity
hydrogeologic
Guidelines are
are given
given to
to classify
hydrogeologic unit.
unit. Guidelines
classify lakes
lakes on
on a semi-quantitative
semi-quantitative
basis
to the expected
basis according
according to
expected volume
volume contribution of the
the active
activeflow
flow region
region near
near
shore.
48
�PETROLOGY AND
AND STRUCTURE
STRUCTURE OF THE LATE
PETROLOGY
LATE PRECAMBRIAN
PRECAMBRIAN
SILVER CREEK
CREEK CLIFF AND LAFAYETTE BLUFF
BLUFF MAFIC
MAFIC
SILVER
INTRUSIONS, LAKE
LAKE COUNTY, MINNESOTA
INTRUSIONS,
MINNESOTA
Neil M.
M. Pope,
Pope, Department
Department of
of Geology,
Geology, University
University of
of Minnesota,
Minnesota, Duluth,
Duluth, Duluth,
Duluth,
Neil
Minnesota, 55801
55801
ABSTRACT
Approximately4-1/2
4-1/2 Miles
Miles northeast
northeast of Two
Approximately
Two Harbors,
Harbors, Minnesota,
Minnesota, the North
North
Shore Volcanic
VolcanicGroup
Groupisisintruded
intrudedby
bythe
the Silver
Silver Creek
Creek Cliff
Cliff sill
sill which
which trends
trends northnorthShore
northeast from
Cliff for
for 66 miles.
northeast
from Silver
Silver Cliff
miles. The
The Lafayette
Lafayette Bluff
Bluff sill,
sill, approximately
approximately 61/2 miles northeast of
1/2
of Two
Two Harbors,
Harbors, intrudes
intrudes the
theNorth
NorthShore
ShoreVolcanic
VolcanicGroup
Group and
and
trends north toward the Silver
Silver Creek Cliff sill.
sill.
The Silver
Silver Creek
Creek Cliff sill
The
sill is
is dominantly
dominantly olivine
olivine diabase
diabase with thin layers
layers and
and
lenses of
of olivine-free diabase.
lenses
diabase. Commonly
Commonly aa plagioclase
plagioclase - augite pegmatitic
pegmatitic facies
borders
the lenses
lenses or
or an
an entire
entire lens
be pegmatitic.
pegmatitic. The
borders the
lens may
may be
The Silver
Silver Creek
Creek Cliff
Cliff sill
sill
is
is approximately
approximately 200
200 feet thick
thick and
and is
is conformable
conformable with
with the
the lava
lava flows
flows throughout
throughout
most of
of its
its extent. In
In the Encampment
Riverarea
area the
the contact
contact of
of the sill is steep
most
Encampment River
and
crosscuts
the
flows.
This
area
may
represent
the
feeder
zone
and crosscuts the flows. This
zone for the
the sill.
sill.
The
The Lafayette Bluff
Bluff sill
sill isis an
anamygdaloidal
amygdaloidal porphyritic
porphyritic olivine
olivine diabase
diabase with
with
plagioclase
phenocrysts which
which average
average 22 cm
plagioclase phenocrysts
cm in
in length.
length. The
The sill is
is approximately
approximately
600
600 feet thick
thick and
and isisdeformed
deformedinto
intoa south-plunging
a south-plunging syncline
syncline and
and anticline.
anticline.
Subsidence
of the
the underlying
flows into
into the magma
Subsidence of
underlying flows
magma chamber
chamber is
is proposed
proposed for the
the
origin of
of this deformation.
The mineral
mineral compositions
compositionsof
of the
the sills
sills are similar. The
The
The olivine
olivine diabase
diabase of each
sill
sill normally
normally consists
consists of an
an average
average of
of66%
66% plagioclase,
plagioclase, 12%
12% olivine,
olivine, 16%
16% augite,
2%
Ca-poor pyroxenes,
pyroxenes, 2%
2% altered
altered interstitial
interstitial material,
2% Ca-poor
material,2%
2%opaques
opaques (ilmenite
(ilmenite and
and
magnetite),
magnetite), and
and trace amounts
amounts of apatite and
and aa interstitial
interstitialgranophyric
granophyric intergrowth
of quartz and alkali feldspar.
Field
evidence does
does not
not support
support any
any definite
definite structural relation
Field evidence
relation between
between the
the
sills. The
The Lafayette
LafayetteBluff
Bluff sill
sill isis poorly
poorly exposed
exposed where it appraches
appraches the
the Silver
Silver Creek
Creek
Cliff
contact between
them. AA
Cliff sill, and
and there
there are
are no
no outcrops
outcrops which
which show
show any
any contact
between them.
whole
rock analysis
analysis (by
(by 5.5.
S.S. Goldich,
Goldich, 1939)
1939)ofofthe
the diabase
diabase from
from the
the Lafayette
Lafayette Bluff
Bluff
whole rock
4.7% MgO.
MgO. An
An average of
of
sill shows
46.9%Si0
SiO2,
21.0%A1Al2O,
8.8%total
total Fe, and 4.7%
sill
shows 46.9%
, 21.0%
0 , 8.8%
2
2 3
three new
new whole
whole rock
rock analyses
analyses of'
of the
the Silver
Silver Creek
CreekCliff
Cliffolivine
olivinediabase
diabase shows
shows
47.8%
Si02,
AL,03,
11.2%
total
Fe,
and
6.5%
MgO.
The
Fe/Mg
is
1.73
for
0
,
11.2%
total
Fe,
and
6.5%
MgO.
The
FelMg
1.73
47.8% Si0
, 17.5%
17.5% A1
2 3
2
the Silver
Silver Creek
Creek Clift
Clift sill
SIll olivine
olivine diabase
diabase and
and 1.86
1.86 for
for the
the Lafayette
Lafayette Bluff
Bluit sill
sill
olivine
diabase. Both
Both sills
sills contain
contain normative
normative hypersthene.
hypersthene. The
The olivine diabase
diabase
olivine diabase.
from the Silver
indicating the diabase is
Silver Creek
Creek Cliff
Cliff sill
sill has
has 7.1%
7.1 % normative
normative olivine indicating
an olivine
of the Lafayette
olivine tholeiite.
tholeiite. The
The diabase
diabase of
Lafayette Bluff
Bluff sill
sill has
has 0.2%
0.2% normative
normative
quartz
the diabase
diabase isis on
on the border
or of
quartz suggesting
suggesting the
border of
of oversaturation
oversaturation or
of being
being a
quartz tholeitte,
tholeitte, despite
despite the
themodal
modal olivine.
olivine.
49
�CORRELATIVE IRON-FORMATIONS
IRON-FORMATIONS AND
AND VOLCANIC
VOLCANIC ROCKS
ROCKS
CORRELATIVE
OF PRECAMBRIAN
X AGE,
AGE, NORTHERN
NORTHERN MICHIGAN
MICHIGANj J
OF
PRECAMBRIAN X
C. Prinz,
William C.
Prinz, U.S.
U.S. Geological
Geological Survey,
Survey, National
National Center
Center -— Stop
Stop 954, Reston,
Virginia 22092
ABSTRACT
The Ironwood,
Ironwood, Vulcan,
Vulcan,and
and Neguanee
NeguaneeIron-formations
Iron-formations have
have long
long been
been accepted
accepted
The
as correlative.
They, along
slate and
as
correlative. They,
along with
with immediately
immediately underlying
underlying slate
and quartzite
quartzite
(Palms, Felch,
Feich, Siamo,
and Ajibik),
are sandwiched
sandwiched between
between shallow-water
shallow-water quartzite
quartzite
(Palms,
Siamo, and
Ajibik), are
and dolomite
and
dolomite below,
below, except where
where locally
locally absent
absent because
because of
of erosion
erosionor
ornondeposinondeposition, and
tion,
and eugeosynclinal
eugeosynclinal graywacke
graywacke and
and slate
slate above
above (Michigamme,
(Michigamme, Copps,
Copps, and
and
Volcanicrocks
rocksofof the
the Hemlock
Formation in
in Iron
Tyler). Volcanic
Hemlock Formation
Iron County,
County, the Emperor
Emperor
Volcanic Complex
Complexofofthe
the eastern
eastern Gogebic
Gogebic range,
range, and
and possibly
possibly the
the volcanic
volcanic rocks
rocks at
Volcanic
Blair
Lake
near
Watersmeet
also
occupy
this
stratigraphic
interval.
Except
for the
the
Blair Lake near Watersmeet also occupy this stratigraphic interval. Except for
eastern end
eastern
end of the
the Gogebic
Gogebic range, the distribution
distribution of the
the iron-formations
iron-formations and
and the
the
volcanic units
units is mutually
volcanic
mutually exclusive.
exclusive. Volcanic
Iron
Volcanicunits
unitsare
are centrally
centrally situated
situated in Iron
and eastern
eastern Gogebic
Gogebic Counties,
Counties,whereas
whereasthe
theiron-formations
iron-formationsare
aretoto the
the east
east in the
the
and
Marquette and
and Menominee
Menomineedistricts
districts and
andtoto the
the northwest
northwest in
in the
the Gogebic
Gogebic range.
range. The
Marquette
The
ironformationsare
are relativley
relativley thin compared
ironformations
compared with
with the
the highly
highly variable
variable and
and locally
locally
great thicknesses of the volcanic
volcanic units.
Volcanic
rocks of
of the
Volcanic rocks
the Emperor
Emperor Volcanic
Volcanic Complex
Complex are interbedded
interbedded with
with and
and
overlie the upper
in the
the eastern Gogebic
upper part
part of
of the
theIronwood
Ironwood Iron-formation
Iron-formation in
Gogebic range,
and tuff
tuff beds
and
beds are present in
in the
the lower
lower part
part of
of the
theIronwood
Ironwood in the main
main part of
of the
the
and the Ironwood
range. Thus,
Thus, the Emperor
Emperor Volcanic
Volcanic Complex
Complex and
Ironwood Iron-formation are,
are,
at least
at
least in
in part,
part,equivalent
equivalent in
in time.
time.Hemlock
Hemlockvolcanics,
volcanics, on
on the
the other
other hand,
hand, have
have
been
been thought
thought to be
be younger
younger than
than the
the iron-formations.
iron-formations. This
This isis based
based on
on correlation
correlation
of
ferruginous conglomerate
conglomerate beneath
Hemlock with
Goodrich Quartzite,
Quartzite,
of ferruginous
beneath the
the Hemlock
with the Goodrich
which
suggest here
here that
that this conglomerate
which overlies the Negaunee
Negaunee Iron-formation.
Iron-formation. I suggest
conglomerate
is not Goodrich,
and that Hemlock
rocks correlate
correlate with the Emperor,
is
Goodrich, and
Hemlock volcanic
volcanic rocks
Emperor, and
and
thus, at
at least
leastininpart,
part,with
withthe
theIronwood,
Ironwood,Vulcan,
Vulcan, and
and Nagaunee
Nagaunee Iron-formations.
Iron-formations.
I postulate
postulate that the
the iron-formations
iron-formations were
were deposited
deposited in relatively
relatively stable and
and
slowly
subsiding areas
areas bordering
bordering aa tectonically unstable
slowly subsiding
unstable and
and rapidly
rapidly subsiding
subsiding basin
basin
series of
troughs in
in which
or series
of basins
basins or
or troughs
which large
large volumes
volumes of volcanic
volcanic material
material
accumulated.
near the eastern
accumula ted. The
The northwestern
northwestern margin
margin of the volcanic
volcanic basin
basin was
was near
end of the
the Gogebic
Gogebic range,
range, probably
probably striking
striking west-southwest
west-southwestinto
intoWisconsin
Wisconsin south
south of
of
the main
main iron
iron range.
range. The
Theeastern
easternmargin
margin of
of the
thebasin
basin lay
lay approximately
approximately along
along the
boundary
between Dickinson
and Iron
IronCounties.
Counties. The
may have
have extended
extended south
boundary between
Dickinson and
The basin
basin may
and
to include
and the
and southwest
southwest to
include the
the volcanic
volcanic units
units in
in north-central
north-central Wisconsin
Wisconsin and
volcanogenic base-metal
The extension
extension of
of the
the basin
basin to
to
volcanogenic
base-metal deposits
depositsthat
that they
they contain.
contain. The
the north
north is
is uncertain.
/Work
the Geological
/Work done
done in cooperation witfE
with the
Geological Survey
Survey Division,
Division, Michigan
Michigan
Department of
of Natural
Natural Resources.
Resources.
50
50
�GEOLOGY AND MINERALOGY
GEOLOGY
MINERALOGY OF SOME
SOME COPPER
SULFIDE DEPOSITS NEAR
NEAR MOUNT
MOUNT BOHEMIA,
BOHEMIA,
KEWEENAW
KEWEENAW COUNTY, MICHIGAN
MICHIGAN
James M.
M. Robertson,
Robertson, New
New Mexico
Mexico Bureau
Bureau of
of Mines
Mines &
& Mineral
Mineral Resources,
Resources, Socorro,
Socorro,
New Mexico 87801.
87801.
ABSTRACT
Copper
sulfides, in
in interesting amounts, have been recently discovered
Copper sulfides,
discovered in
in the
the
Keweenaw Peninsula
Peninsula of
of northern
northern Michigan,
Michigan,aa district
district long
long famous
famous for
for its deposits
Keweenaw
deposits of
of
The sulfides
occur extensively
native copper.
copper. The
sulfides occur
extensively in the
the vicinity
vicinity of
ofMount
Mount Bohemia,
Bohemia,
chiefly
flow tops,
chiefly as open-space
open-space fillings
fillings and
and replacements
replacements in
in amygdaloidal
amygdaloidal flow
tops, aa
of occurrence of native copper
in the
the region.
traditional mode
mode of
copper in
region. An
An andesite dike
dike (or
(or
dikes), almost
almost invariably
associated with
with the mineralized
invariably associated
mineralized flow
flow tops,
tops, typically
typically
dikes),
carries at least trace
traceamounts
amounts of
of sulfides.
sulfides.
The
The present
present study
study indicates
indicates that
that both
both copper
copper and
and sulfur
sulfur have
have been
been added
added to
to
dikes and
flow tops in the
dikes
and flow
the Mount
Mount Bohemia
Bohemia area,
area, probably
probably by
by hydrothermal
hydrothermal solutions
solutions
moving
upward along
along zones
zones of
of structural
structural weakness,
moving upward
weakness, and
and outward
outward along
along relatively
permeable flow
flow tops
tops and
and broken
broken dike
dike margins.
margins. The
permeable
The sulfur
sulfur and
and most
most of the
the copper
copper
are most
most likely
likely of
of direct
direct magmatic
magmatic origin,
origin, although
although some
some copper
copper may
may have
have been
been
derived
der
ived at depth from pre-existing
pre-existing flows.
flows.
Microscopic studies,
studies, supplemented
supplemented by
by X-ray
Microscopic
X-ray fluorescence
fluorescence analyses,
analyses, have
have
defined aa zonal
defined
zonal pattern
pattern of
of total
totalcopper,
copper,sulfur,
sulfur,and
andsulfide
sulfideminerals
mineralsdeveloped
developed
about the Bohemia
Fault, a northwest-trending
break on
on the
the northeast
about
Bohemia Fault,
northwest-trending break
northeast flank
flank of
of
Mount
Chalcocite predominates
predominatesnearest
nearest the
the fault,
with bornite,
Mount Bohemia.
Bohemia.
Chalcocite
fault, with
bornite,
chalcopyrite, and
chalcopyrite,
and finally
finally pyrite
pyrite becoming
becoming increasingly
increasingly abundant
abundant with
with increasing
increasing
distance from
from the break.
break.
The
sequence developed
developedinin the
the Mount
area is:
The chronologic
chronologie sequence
Mount Bohemia
Bohemia area
is: dike
dike
emplacement and
and alteration, faulting and fissuring,
and sulfide
sulfide mineralization.
mineralization. At
emplacement
fissuring, and
At
least some
least
some of the
the faulting
faulting isis related
relatedtotoregional
regionaldeformation
deformation thought
thought to
to have
have
occurred in
in later Upper
time. Regionally,
is
occurred
Upper Keweertawan
Keweenawan time.
Regionally, native
native copper
copper deposition
deposition is
also
believed
to
have
followed
this
period
of
deformation
and
preceded
copper
have followed this period of deformation and preceded copper
also believed
sulfide mineralization.
sulfide
Mineralization in
in the Mount
several chemical trends
Mineralization
Mount Bohemia
Bohemia area followed
followed several
trends
during the
the period
with each
each point
point in
in a mineralized
during
period of
of sulfide
sulfide deposition,
deposition, with
mineralized dike
dike or
flow top
top undergoing
at least part
flow
undergoing at
part of
ofa ageneralized
generalizedsequence
sequencewhich
whichincluded:
included: (1)
(1)
solutions whose
whose initial
initial Cu/S
Cu/S ratios
introduction of solutions
ratios were
were relatively
relatively low;
low; (2)
progressiveincrease
increaseinin the
the Cu/S
progressive
Cu/S ratios
ratios of
of the
theore-forming
ore-forming solutions;
solutions; and
and (3)
(3)
022 of the
progressive increase in the ff0
the solutions.
solutions.
51
�GROUNDWATER
SPREADING OF HYDROCARBON
GROUNDW
ATER SPREADING
HYDROCARBON SPILLS
SPILLS WITH
WITH
SYSTEM DESIGN
DESIGN IN
IN GLACIAL
GLACIAL DRIFT
SPECIAL EMPHASIS
EMPHASIS ON MONITOR
MONITOR SYSTEM
W. Rohrer
Rohrer and
and H.O.
H.O. Pfannkuch,
Pfannkuch, Department of
W.
of Geology
Geology and
and Geophysics,
Geophysics, University
of Minnesota, Minneapolis,
Minneapolis, Minneosta
Minneosta 55455
55455
ABSTRACT
The introduction
introduction of immiscible
immiscible hydrocarbons
hydrocarbons into the
the hydrogeologic
hydrogeologic environThe
ment by accidental spills
ment
spills or
or subsurface
subsurface pipeline
pipeline breaks
breaks presents aa class
class of
of problems
problems
that is
is different
different from
from miscible
miscible leachate
leachateor
or soluble
soluble contamination
contamination propagation.
propagation.
The mechanisms
of subsurface
spreading comprise
comprise three
three distinct
The
mechanisms of
subsurface spreading
distinct stages;
stages;
downwardmovement
movementofof the
the free hydrocarbon
downward
hydrocarbon phase
phase through
through the unsaturated
unsaturated zone,
zone,
spreading on
on the
the groundwater
table and
spreading
groundwater table
and through
through the capillary
capillary fringe,
fringe, and
and finally
finally
transport of
transport
of the
the dissolved
dissolved hydrocarbon
hydrocarbon phase
phase vertically with infiltrating recharge
recharge
water
and
horizontally
in
the
groundwater
flow
field.
Each
one
of
these
processes
water and horizontally in the groundwater flow field. Each one of
processes
is characterized by
is
by different material
material constants.
constants. For
Forthe
thedownward
downward movement
movement it
it is
is
the retention capacity
capacity of
of the
the unsaturated
unsaturated zone
zone that determines
determines the total amount
amount of
hydrocarbonphase
phase reaching
reachinggroundwater,
groundwater,the
the capillary
capillary characteristics
characteristics of
of the
hydrocarbon
capillary fringe
fringe system
system defines
defines the
the extent
capillary
extent of
of spreading
spreading on
on the watertable,
watertable, and
and
hydrodynamic dispersion
the dissolved
dissolved
hydrodynamic
dispersioncoefficients
coefficients delimit
delimit the
the shape
shape and
and extent
extent of the
phase spreading.
about these
these material
phase
spreading. Very
Very little is
is known
known about
material constants
constants in
in drift
drift
material, since
material,
since most
most reported research
research has
has dealt with
with alluvial
alluvial deposits.
deposits. This
This work
work
presents
results for
for retention capacity
presents experimental
experimental results
capacity of
of glacial
glacial drift
drift and
and hydrocarhydrocarbon depth
depth in
in the capillary
bon
capillary zone
zone of
of spreading.
spreading. The
The retention capacity
capacity depends
depends on
on
grain size
size distribution,
distribution,initial
initialwater
watersaturation,
saturation,and
andsurface
surfacecharacteristiss
characteristis of the
grain
the
liquids invol~ed.
invol'ed. The
liquids
The values
values for
for outwash
outwash sands
sands are on
on the
the order
order of
of 20
20 1/rn
11m and for
tills 80
80 1/rn
11m.. Furthermore some
some preliminary
preliminary values
values of hydrocarbon
hydrocarbon thickness in
in
is given
givenfor
for the
the same
same material.
the capillary fringe of equilibrium
equilibrium is
The design
design of
of aa monitoring
system deals
deals with
with the
the recognition
of the
the spatial
The
monitoring system
recognition of
distribution of
of the free
phase ininthe
the subsurface
subsurfaceafter
after the
distribution
free and
and dissolved
dissolved hydrocarbon
hydrocarbon phase
spill,
spill, the reconstruction
reconstruction of inflitration
inflitration site
site and
and infiltration
infiltration mechanism
mechanism (intergranOntergranular or
or preferred path), the determination
determination of
of general
general flow pattern and
and emplacement
emplacement
of interceptor
wells,
and
the
establishment
of
background
noise,
well
interceptor wells, and the establishment of background noise, well sampling
sampling
and analytical methods.
techniques and
methods.
52
�ORE DEPOSITS
DEPOSITS IN
IN RELATION
RELATION TO
TO HOTSPOT-GENERATED
ORE
INTRACONTINENTAL RIFTING
INTRACONTINENTAL
3. Sawkins,
Sawkins, Department
Department of
of Geology
Frederick J.
Geology and
and Geophysics,
Geophysics, University
University of
Minnesota, Minneapolis,
Minnesota,
Minneapolis, Minnesota 55455
ABSTRACT
ABSTRACT
It can be demonstrated
It
demonstrated that the
the tectonic,
tectonic,igneous,
igneous, and
and sedimentary
sedimentary processes
processes
associated with
associated
with subcontinental
subcontinental hotspot
hotspot activity
activity provide
provide favorable
favorable environments
environments
within which
whichore-generating
ore-generating systems
systems can
can operate.
operate.
within
In particular
particular certain
certain tin deposits
In
deposits are associated
associated with the products
products of crustal
melting during
during the
the early
early stages
stages of hotspot
melting
hotspot activity. Copper
Copper mineralization
mineralization is
is in
some cases
cases closely
some
closely associated with
with hotspot
hotspot controlled
controlled geologic
geologic regimes,
regimes, and
and both
both
hydrothermal and
and stratiform
stratiform copper
hydrothermal
copper deposits
deposits can results.
results. Copper-nickel
Copper-nickel mineralization in some
rocks isis also
to be
be aa product
zation
some layered
layered mafic igneous
igneous rocks
also considered
considered to
product of
hotspot-associated basaltic
basaltic magmatism.
magmatism. Other
Other metal
metal deposit
deposit types
types that,
that, at least in
hotspot-associated
some instances,
instances, appear
appear to
to bear
bear a relationship
to hotspot
stratiform
some
relationship to
hotspot activity include
include stratiform
in shales
shales and
and lead-zinc
lead-zinc replacement
replacement deposits
deposits in
in carbonate
carbonate rocks.
rocks.
lead-zinc deposits
deposits in
Two major
continental fragmentation
Two
major continental
fragmentation events
events related to subcontinental
subcontinental
hotspot activity,
activity, have
in the geologic
hotspot
have occurred
occurred in
geologic past and
and aa number
number of
of important
important
metal deposits
deposits can
can be
be correlated with
metal
with each.
each. This
age
This approach,
approach,that
that relates
relates the age
and
geologic
environment
of
intracontinental
ore
deposition
to
hotspot
activity,
and geologic environment of intracontinental ore deposition to hotspot
holds
holds significant promise for exploration geologists.
geologists.
53
53
�KOMATIITES AND
AND THEIR CHEMICAL
KOMATIITES
CHEMICAL VARIATIONS
VARIATIONS
K.3.
K.J. Schulz, University of
of Minnesota,
Minnesota, Minneapolis,
Minneapolis, Minnesota
Minnesota 55455
55455
ABSTRACT
komatiites from
from South
South Africa, Canada, Australia and
Examination of komatlites
Minnesota
(Vermiliondistrict)
district)shows
showsthat
that distinct
distinct chemcial
Minnesota (Vermilion
chemcial suites can
can be
be defined
defined
which,
while showing
showingaageneral
generalsimilarity
similarity also
also have
have notable
notable differences
differences (Fig.
which, while
(Fig. 1).
1). A
A
striking difference
difference isis the
the CaO/Al203
ratio
of
the
striking
CaO/ Al 0 ratio
the South
South African
African ( :>
1,
Fig.
1a)
>
1,
Fig.
la)
2 3
versus the
the Australian
Australian and
and Canadian
Canadian
(generalIy1,
(generally
$1, Fig.
Fig. ib,
1b, c)
c) komatiites.
komatlites. Vermilion
Vermilion
versus
samples
are relatively
high Fe,
Fe, Ti
(Thisisis also
also true
true of
of the
samples are
relatively high
Tl and
and PP (Fig.
(Fig. 1d).
the
id). (This
Minnesota
River Valley
low Al
Al2O.
amphibolites,
see
Weiblen
and
others,
this
Minnesota River
Valley low
amphibolites,
see
Weiblen
and
others,
this
0
2
meeting). Work
Workinin progress
progresssuggesis
suggest'sthat
thatononaa global
globalscale
scaleat
at least
least two
two distinct
distinct
Archean
komatiite suites may
Archean komatlite
may exist,
exist, distinguished
distinguished not
not only
only by
by CaO/A1203
CaO/ Al 0 ratio but
2 3
In
Minnesota,
appears
that the
also by
FeO/MgO
and
AL,03/TiO.,.
also
by A1203
Al 0 vs
vs
FeO/MgO
and
Al 03/TiO. In
Minnesota,
itit appears
that
2 3
unique occurrence
occurrenceofof komattites
komattites witi
witi norrnar
tholeiites isis repeated
repeated in
unique
normJ tholeiites
in time in
in the
the
Lower
and Upper
Upper Archean
Archean and
and the Keweenawan.
Lower and
Keweenawan •
.;:1°
10 .1\
.4+ ~
.J t
.3 t
'.
• ,-,'
i
? TI
._
.2+
1
• L
:
.6
.5
SOUTH ~F~ICRN
qFHICRN KOMATIITES
SOUTH
KOMRTIITES
.2
·1
I
T
t
.0
.1
•1
.2
.3
•
.33T~
.5
.5
•.1<1
.5
.6
l
T
I
1
.6++
.6
.55 1 C
.; t . ~~
,,' t ~\\
.6-
ORNROIRN
ITES
CRNRDIRN KOMRTI
KOMRTIITE5
.:J
A
.1
I
.0
.11
t!
d
•
t
+ /
+ /
.1 +
.2 +
.2
.3!
.3 1
+
t
.1
I
L
.00
+
l
j
VErMILION
VERMiLIC~ KOMRTIITES
<OMRTIITES
i
.2 t
.1 .;.i.
.2 i
'3
+
'"
T
• .J r
.t
.2
PUSTRRLIRN
I TES
RUSTRRLIRN OMRTI
KOMRTIITES
.3
\
.0
.1j_
.1 T
.21
.2 ~
4.
b
.<1
'.
.._,.
/
//
\\
'I
I
"
X
t
.1
.J +
.5
.6
.5
.0 .;.
MS
RL SI
MG FE
FE MN
MN OR
CR AL
51 TI
iI
P NR
NR
' cCi
"
T
t
MGFE
FEMN
MN~RCRRLL St
MG
Sf II
TI
K
K
.11
40
+ 23
P NR
NR
F
38
27
~
1. Log
Fig. 1.
Log plots
plots of komatilte
komatilte compositional
compositional normalized
normalized to Hawaiian
Hawaiian tholeiite (as
(as
oxides,
right to left:
left: 8.1,
8.1, 10.04,
10.04, .17,
.17, 10.9,
10.9, 13.4,
13.4, 50.4,
50.4, 2.7,
2.7, .28,
.28, 2.3,
2.3, .53).
.53). Numbers
oxides, right
below
0 have
have negative
negative values.
values. Data
Data from
from various
various sources.
sources.
below a
54
�CHEMISTRY OF
OF PRIMARY
PRIMARY AND
AND SECONDARY
SECONDARY MINERALS
OF SOME
CHEMISTRY
MINERALS OF
SOME
PORTAGE LAKE
LAKE LAVAS,
KEWEENAWPENINSULA:
PENINSULA: DEVELOPMENT OF
PORTAGE
LAVAS, KEWEENAW
MODELS OF
OF DIFFERENTIATION AND
MODELS
AND LOW-RANK
LOW-RANK METAMORPHISM
METAMORPHISM
Nancy Scofield,
Scofield, Department
Department of
of Geology
Geology and
and Geological
Geological Engineering,
Engineering, Michigan
Michigan
Nancy
Technological University, Houghton,
Technological
Houghton, Michigan
Michigan 49931
49931
ABSTRACT
Minerals from
from the
the Scales
Scales Creek
Creek flow
flow (SCF)
(SCF) and
and two thinner
thinner (40',
(40', 55')
55') basalt
Minerals
flows above
above SCF
SCFwere
were analyzed
analyzedby
byelectron
electron microprobe.
microprobe. The
interior of
flows
The interior
of the
the SCF
SCF
shows some
some igneous
igneous differentiation
differentiation as
shows
as evidenced
evidenced by
by increases
increasesofofFe/Fe-s.Mg
Fe/Fe+Mg (9%)
and Fe/Fe+Ca
Fe/Fe+Ca (14%)
an increase of
and
(14%) in augite and
and an
of Na/Na+Ca
Na/Na+Ca (6%)
(6%) in
in plagioclase.
plagioclase.
plag (ZAn)
(%An)
(40—702modal)
aodal)
(40-70%
Drill—hole
Drill-hole
depth
depth
cpx (20—402
da1)
cpx
(20-40: modal)
Wo En
Pa
\00
la
Fsl0*
Fe203*
MgO
HgO
CaO
<:40
Na20
K20
Je20
10.3
10.5
11.1
11.1
2.06
7.83
18.8
18.8
6.9
6.9
0.07
0.07
4.30
0.02
0.02
0.07
0.07
85
85
180
180
(3)
(3)
12.0
12.0
(J)
(3)
11.7
11.1
(2)
(2)
(2)
(2)
12.2
12.2
12.3
12.3
12.3
5,b4
5.04
7.75
7.75
7.43
7.45
7.80
3.90
5.90
8.2
8.2
9.9
9.7
9.1
10.4
10.4
8.4
3.90
3.90
2.26
2.26
2.15
2.15
2.32
2.90
0.30
0.27
0.30
0.31
2.10
2.10
455
455
130
130
110
110
150
130
420
420
puap 081-1832
081—1832
pWllp
ab
081—1839
081-1839
055—1185
055-1185
5C
1233
SCF
1233
1285
1285
200'
1320
1370
1310
2—3
2-3
(6)
(6)
42—
4239
39
42
38
62— 1616—
4239 22
38 20
44
44 18
34
44 22
14
44 16
40 44
42— 43—
15—
4243- 1538 39 23
2—3
(5)
(5)
2-3
48—80(11)
(U)
48-80
50—82 (8)
(8)
50-82
65—80 (5)
65-80
(5)
43—30
(3)
43-30 (5)
CII
(p"lII)
Cu (pptu)
(5)
(5)
(8)
(8)
a.
Mumthr
analyses in
in parenthessu.
"uaber ofotanalyae.
parentheae••
Pump
pupsL1yits•••tadolll&1n
astadosaln
Pump —• p~.llyit
*Total iron
*Total
iron am 1e203,
1e203'
albitized ba.aalt
ab
basalt
ab —• albit1zed
C4EMICAL TRENOS IN SC..LES CREEK FLOW
0.4
0.5
Fe/Mg
F'/M9
0.&
*—
.mi.$ry
• -llulIl .....' "
OJ
0.4
0.5
0.6
BOTiOY
0—.9ts; peq .dçsa
I
2
3
..
NoICo
FuCo
D—cflnft.
Q-c/lIOIit.; pIaqcoss
plaqc:or..
A—oiyi
0.05
Q.l 0.15 0..$
Ci
X/Ne
K/Nn
C'!·;:J-4lt......
The basalts
basalts are
are altered by
by low-rank
low-rank metamorphism
metamorphism of the prehnite-.
prehnitepumpeilyite
of secondary
pumpellyite facies.
facies. The
The proportion
proportion of
secondary minerals,
minerals, as alteration
alteration products
products
and in
and
in veins
veins and
and amygdules,
amygdules, increases
increases toward
toward flow
flow tops. Augite
Augite is replaced
replaced by
by
chlorite
chlorite and
and plagiodase
plagiodase is
is albitized. The
Ca thus
thus released
released is
is available
available for
for
The Ca
pumpellyitization
pumpellyitization of plagioclase,
plagioclase, which
which occurs
occurs concurrently
concurrently and
and subsequently
subsequently to
to
a.Ibitization,
releasing
albitization, releasing Na.
Na.
However, aa closed-sytem
closed-sytem model
model demands
demands overall
overall
However,
participation
of the
participation of
the relatively
relatively unaltered
unaltered flow
flow interiors
interiors by
by a depletion
depletion of
of aa few
few
percent of the
the Na
Na present,
present, but
but this
this isis not
notobservable
observable petrographically.
petrographically. Pyroxene in
in
pumpellyite
metadomains isis altered
altered to pumpellyite
pumpellyite metadomains
pumpellyite and/or
and/or epidote.
epidote. The Mg
Mg thus
thus
mobilized
augments the
the Mg
content of chlorite
mobilized augments
Mg content
chlorite and
and results
results in
in higher Mg
Mg values in
in
chlorite
chlorite than
than in
in augite
augite from
from which
which chlorite
chlorite isis derived.
derived. Both
Both pumpellyitized
pumpellyitized and
and
albitized
are depleted
in K
K relative
relative to less
albitized zones
zones are
depleted in
less altered
altered parts of
of flows,
flows, and
and K
K is
is
concentrated
concentrated in
in the
the base
base of
of the SCF,
SCF, where
where sericitization
sericitization of
of plagioclase
plagioclase isis
extensive.
extensive.
.
55
55
�SOURCES OF DISSOLVED
GROUNDWATER
DISSOL VED SOLIDS
SOLIDS IN
IN GROUNDW
ATER
FROM SUPERIOR AND RAINY
FROM
RAINY LOBE TILL
Siegel, Department of
Donald I. Siegel,
of Geology
Geology and
and Geophysics,
Geophysics, University of Minnesota,
Minnesota,
Minneapolis, Minnesota 55455
ABSTRACT
Preliminary study
study of
of recent analyses
Preliminary
analyses of water
water quality
quality shows
shows that groundwater
groundwater
within
surficial aquifers
aquifers related
related to Superior
within surficial
Superior and
and Rainy
Rainy lobe
lobe deposits
deposits contains
contains
significantly less
less sodium
than is found
significantly
sodium than
found in bedrock
bedrock aquifers
aquifers within
within igneous
igneous rocks
rocks of
central and northeastern Minnesota.
Minnesota. Inasmuch
Inasmuch as
as Superior
Superior and Rainy
Rainy lobe
lobe deposits
consist mainly
of materials
consist
mainly of
materials derived
derived from
from these
these and
and similar
similar igneous
igneous rocks,
rocks, the
the
observeddifference
difference in
in sodium
sodium content
content between
between groundwaters
groundwaters within
within the
the surficial
observed
surficial
and bedrock
and
bedrock aquifers
aquifers may
may be
be considered
considered anomalous
anomalous assuming
assuming that
that groundwater
groundwater
most influenced
Possible mechanisms
chemistry is most
influenced by
by aquifer mineralogy.
explaining the
the differing sodium
values and
and gross
gross water
water chemistry
chemistry are suggested,
explaining
sodium values
suggested, in
particular, by
theoretical reconstructions
of surficial
particular,
by using
using theoretical
reconstructions of
surficial and
and bedrock
bedrock waters.
waters.
Initial results
results highlight
Initial
highlight the importance
importance of
of compositional
compositional differences within aquifers
in local
local and
and small,
small, intermediate
intermediate flow
flow systems
systems as
as the
the dominant
in
dominant control of both
both gross
gross
groundwater chemistry
chemistryand
and ultimately
ultimately the
the gradual
gradual evolution
evolutionofof water
water types
groundwater
types as
as
deduced by
by Chebotarev and
deduced
and others.
56
56
�MIDDLE
MIDDLE PRECAMBRIAN AGE OF VOLCANOGENIC
VOLCANOGENIC MASSIVE
MASSIVE SULFIDE
DEPOSITS IN NORTHERN
NORTHERN WISCONSIN
WISCONSIN
P.K. Sims, U.S.
Denver, Colorado
Colorado 80225
80225
U.S. Geological Survey, Denver,
ABSTRACT
The copper-zinc
at the
copper-zinc massive
massive sulfide
sulfide deposits at
the Flambeau
Flambeau mine,
mine, near
near
The
Ladysmith
and
at
Pelican
River,
east
of
Rhinelander,
Wisconsin,
have
model
lead
Ladysmith and
Pelican River, east of Rhinelander, Wisconsin, have model
ages of 1,830+150
m.y. (J.S.
(iS. Stacey,
ages
1,830+150 m.y.
Stacey, B.R.
B.R. Doe,
Doe, and
and L.T.
L. T. Silver,
Silver, written
written commun.,
commun.,
Inasmuchas
as the
the deposits
1976). Inasmuch
deposits are considered
considered as
as being
being of
of submarine
submarine volcanic
volcanic
exhalative
also are interpreted
exhala
tive origin,
or igin, the associated volcanic rocks
rocks also
interpreted as
as being
being middle
middle
Precambrian (Precambrian X)
X) in age.
The analytical
analytical data on
The
on the leads
leads from
from the
the two
two ores,
ores, provided
provided by
by Stacey,
Stacey, Doe,
Doe,
and Silver,
Silver, are tabulated
tabulated below.
below.
206 Pb
204 Pb
207Pb
204 Pb
204
208Pb
204 Pb
Model
Model age
in m.y.
Flambeau
15.323
15.167
35.016
1,820
Pelican River
15.688
15.359
35.202
1,835
Deposit
The
isotopic composition
compositionofof the
the leads
leads is
is similar to the
the least
least radiogenic
radiogenic leads
leads from
from
The isotopic
The model
model lead
lead ages
the massive
massive sulfide
sulfide deposits
deposits at Flin
Flin Flon,
Flon, Manitoba.
Manitoba. The
ages are
and granitic
grartitic rocks
rocks
consistent with
with zircon
zircon U-Pb
U-Pb ages
ages of
of 1,800-1,900
1,800-1,900 m.y. on volcanic
volcanic and
in
and adjacent Michigan,
in northeastern
northeastern Wisconsin
Wisconsin and
Michigan, determined
determined by
byW.R.
W.R. Van
Van Schmus
Schmus
and his
and
his associates in
in 1975.
1975.
The volcanic
volcanic rocks
rocks in
in the
the Ladysmith-Rhinelander
Ladysmith-Rhinelanderbelt
belt are
are interpreted
interpreted as
The
as being
being
approximately correlative
correlative with
with the
the dominantly
submarine volcanic
volcanic rocks
rocks that
that are
approximately
dominantly submarine
are
interbedded with
with turbidite-like
the upper
of the
interbedded
turbidite-like sedimentary
sedimentary rocks
rocks in the
upper part of
the
Marquette
northern Michigan.
Apparently these
these rocks
Marquette Range
Range Supergroup
Supergroup in
in northern
Michigan.
Apparently
rocks
accumulated in
in a eugeosynclinal
environmentininthe
the southern
southern part
part of the
accumulated
eugeosynclinal environment
the middle
middle
Precambrian basin
basin in the
the Lake
Lake Superior
Superior region.
region.
57
�GEOLOGY AND GEOCHEMISTRY
GEOCHEMISTRY
OF THE
THE PRECAMBRIAN
PRECAMBRIAN MARCELLON
MARCELLON RHYOLITE,
RHYOLITE,
COLUMBIA COUNTY, WISCONSIN
COLUMBIA
WISCONSIN
Smith, Divsion
Divsion of Science,
Science, University
University of
ofWisconsin-Parkside,
Wisconsin-Parkside, Kenosha,
Kenosha,
Eugene I. Smith,
Wisconsin 53140
531ltO
ABSTRACT
The
inlier isis formed
formed by
by four
four mineralogically
mineralogically and
and chemically
chemically distinct
distinct
The Marcellon
Marcellon inlier
rhyolite
tuffs which
rhyolite flows
flows and
and ash-flow
ash-flow tuffs
which are folded
folded into
into aa northeast-striking,
northeast-striking,
asymmetric
arjifom.
Rhyolite
asymmetric antiform.
Rhyoliteononthe
thewestern
westernlimb
limbofofthe
theantiform
antiformstrikes
strikesN.N..50
50
0
0
E. and
E.
and dips
dips 50
50 -85
_85 to the
the northwest.
northwest. The
The units
units on
on the
the eastern
eastern limb
limb also
also strike
strike N.
N.
0
50
50 E.,
E., but dip
dip steeply (80°
(80 to vertical)
vertical) to
to the
the southeast.
southeast.Two
Twochemically
chemicallydissimilar
dissimilar
greenstone dikes
intrude
the
rhyolite
flows.
dikes
rhyolite flows.
The
The core of the
the antiform
antiform isisformed
formedby
bya aquartz
quartz(2%),
(2%),plagioclase
plagioclase(15%),
05%), and
and
alkali
(2%)rhyolite
rhyolite with
with well
well preserved
preserved shard
shard outlines
outlines in
in the matrix
alkali feldspar
feldspar (2%)
matrix (unit
(unit
unit probably
is an
Structurally above
It).
This unit
probably is
an ash-flow
ash-flow tuff. Structurally
above unit 4It is:
is: (a)
(a) well
well
4). This
banded,
plagioclase-bearing Olt-18%)
(14-18%)rhyolite
rhyolite with
with local
local spherulitic
spherulitic lenses (unit
banded, plagioclase-bearing
(unit 3);
3);
(6%), alkali feldspar
feldspar (4%),
(It%), plagioclase (1%)
0 %) rhyolite (unit 2);
(b) flow
(b)
flow banded,
banded, quartz (6%),
and (c)
(c) quartz
quartz (296),
(296),alkali
alkalifeldspar
feldspar (2%),
(2%),plagioclase
plagioclase0(1%)
rhyolitecharacterized
characterized by
%) rhyolite
and
spherulites up
up to 15
15 cm in diameter
diameter (unit
(unit 1).
1).
The
rhyoliteisis one
one of
of ten major
The Marcellon
Marcellon rhyolite
major rhyolite
rhyolite and
and granite
granite inliers
inliers in
in
south-central Wisconsin.
Chemicallymost
mostofof the
the rocks
form the inliers
Wisconsin. Chemically
rocks which
which form
inliers can
can
be divided
divided into
into three
threegroups:
groups:(1)
0)high
high CaO
CaO(1.48-1.68%),
(1.48-1.68%), high
high TiO,
Ti0 2(0.30-0.42%),
(0.30-0.42%), and
and
low
rhyolitesand
andgranites
granites(Observatory
(ObservatoryHill
HillRhyolite
hyolite dikes
dikes and
and
low Rb/Sr
Rb/Sr (0.37-0.79)
(0.37-0.79) rhyolites
the Baxter
Baxter Hollow
Hollow Granite);
Granite); (2)
(2) intermediate
intermediateCaO
CaO(1.28#O.32%)
(1.28+0.32%) and
and Rb/Sr
Rb/Sr (1.09+
0.09+
0.29) rhyolite
rhyolite (unit
(unit 33 at Marcellon
0.29)
Marcellon and
and the
the Marquette
Marquette Rhyolite);
Rhyolite); and
and (3)
(3) low
low CaO
Cad
Rb/Sr (159)
(0.37+0.14%),
(0.37 +0.14%), high Rb/Sr
05~) rhyolites
rhyolites and
and granites
granites (Observatory
(Observatory Hill,
Hill, Berlin,
Berlin,
Utley, and
rhyolites, and
and granophyric
granophyricgranites
granites at
at Moritello
Utley,
and Endeavor
Endeavor rhyolites,
Montello and
and Red
Red
Althoughunit
unit 33 at Marcellon
falls into chemical
2, the other
Granite). Although
Marcellon falls
chemical group
group 2,
other
Marcellonunits,
units,along
alongwith
with rhyolites
rhyolitesinin the
the Baraboo
area, are transitional
Marcellon
Baraboo area,
transitional in
chemistry
chemistry between
between groups
groups 2 and
and 3.
3. For
For example,
example, units
units 1 and 22 are
are more
more closely
closely
related to
to group
group 33 in
in terms
termsof
oflow
lowCaO
CaO(0.29-0.36%),
(0.29-0.3696), but
but differ
differ by
by having
having lower
lower
Rb/Sr (2.27+0.57).
Unit 44 isis similar
similar to group 2 because of intermediate
Rb/Sr
(2.27+0.57). Unit
intermediateCaO
CaO(0.94%)
(0.9lt96)
and
but it isis higher
and Rb/Sr (1.32),
0.32), but
higher in
in K2O/Na20
K 0/Na 0 and
and lower
lower in
in Ba
Ba than
than typical
typical group
group 22
2
2
rocks.
Rocks
of the three
with the
the transitional
Rocks of
three chemical
chemical groups,
groups, along
along with
transitional types,
types, fall
along aa trend
along
trend typical
typical of
of aarock
rockseries
seriesshowing
showing strong
strong caic-alkaline
calc-alkaline affinities.
affinities.
Rhyolites are
are cornagmatic,
and the granophyric
Rhyolites
comagmatic, and
granophyric granites
granites are apparently
apparently the
the
subvolcanicequivalents.
equivalents. These
chemical data along
subvolcanic
These chemical
along with
with available
available U/Pb dates (1.8
(1.8
b.y.)
confirm that
that these rhyolites
the last stages of
rhyolites and
and granites formed
formed during
during the
of the
the
b.y.) confirm
Penokean Orogeny.
58
�THE GEOCHEMISTRY
GEOCHEMISTRY OF THE
THE GAMITAGAMA
GAMITAGAMA LAKE COMPLEX,
COMPLEX,
WAWA,
WAWA, NORTHERN ONTARIO
I.E. Smith,
T.E.
Smith, A.
A. Turek,
Turek, and
and C.
C.Riddle,
Riddle, Department
Department of
ofGeology,
Geology, University
University of
of
Windsor, Windsor,
Windsor, Ontario, Canada
Canada
ABSTRACT
The
The Gamitagama
Gamitagama Lake
Lake Complex
Complex is
is aa calc-alkaline
calc-alkaline stock
stock (Ayres,
(Ayres, 1969),
exposedwithin
within the
the Abitibi volcano-plutonic
exposed
volcano-plutonic belt in
in the
the Superior
Superior Province
Province of
of
Canada, south
Canada,
south of
of Wawa
Wawa in
in Ontario.
It penetrates
penetrates a
a series
series of regionally
metamorphosed
felsic and
and mafic
mafic volcanic
volcanic rocks
metamorphosed felsic
rocks interbedded
interbedded with metasedimentary
metasedimentary
rocks
with aa variety
variety of
of other plutons.
rocks and
and iron-formation,
iron-formation, and
and is associated
associated with
plutons. The
The
metamorphic
gradevaries
variesfrom
from greenschist
greenschisttoto amphibolite
amphibolite facies
facies within
within the
metamorphic grade
the area
area
and
is overprinted
by contact metamorphic
aureoles adjacent
adjacentto
to the
the plutons.
plutons. The
and is
overprinted by
metamorphic aureoles
The
plutonic rocks
plutonic
rocks include
include cataclastic
cataclastic and
and gneissose
gneissose trondjhemites,
trondjhemites, gabbros,
gabbros, norites,
diorites,
dior ites, syenites,
syenites, and
and granites.
Major
Major and
and trace elemental
elemental contents
contents of the
the volcanic
volcanic and
and plutonic
plutonic rocks
rocks are
are
usedtoto identify
identify the
igneousrock
rocksuites
suitesofofthe
the area,
area, to
to follow
used
the various
various igneous
follow their
their
evolution and
Comparisonswith
with recent
evolution
and to determine
determine which
which are
are co-magmatic.
co-magmatic. Comparisons
recent
igneousrock
rock suites
suitesare
areused
usedtotoreconstruct
reconstructthe
the development
developmentof
of the
the Archean
Archean crust
crust in
in
igneous
this
this area
area and
and to
to identify
identifythe
thetectonic
tectonicenvironments
environments ininwhich
whichthe
themagmas
magmas were
were
generated.
59
�A
A GROUND
GROUND INVESTIGATION
INVESTIGATION OF AN
AN AEROMAGNETIC
AEROMAGNETIC
ANOMALY,
ANOMALY, DICKINSON
DICKINSON COUNTY,
COUNTY, MICHIGAN
MICHIGAN
David
Snider, Geology
and Minerals
David W.
W. Snider,
Geology and
Minerals Research Unit,
Unit, Geological
Geological Survey
Survey Division,
Division,
Michigan
Department of Natural
Natural Resources,
Resources,Lansing,
Lansing, Michigan
Michigan 48926
48926
Michigan Department
ABSTRACT
ABSTRACT
During the
the latter
latter part of
of September,
September, 1975,
1975, the
the Geology
Geology and
and Minerals
Minerals
During
Research
Research Unit
Unit of the
the Michigan
Michigan Geological
Geological Survey
Survey conducted
conducted a ground
ground reconnaisreconnais-
sance
of aa small,
sance investigation
investigation of
small, closed
closed aeromagnetic
aeromagnetic anomaly
anomaly in
in north-central
north-central
Dickinson
County. The
The purposes
purposes of
of the
the study
were two-fold: (a)
Dickinson County.
study were
(a) to determine
determine what
what
geologic
feature caused
geologic feature
caused the
the aeromagnetic
aeromagnetic anomaly
anomaly and,
and, (b)
(b) to
to investigate
investigate any
any
mineral
resource
potential
associated
with
the
area
in
and
around
the
anomaly.
mineral resource potential associated with the area in and around the anomaly.
Nearly
Nearly all of
of the
the closed
closed anomaly
anomaly lies
lies within
within an
an east-west
east-west trending
trendingswamp
swamp covering
covering
an area of
of nearly
nearly three
three square
square miles.
miles.
The
of investigation consisted of sampling
The methods
methods of
sampling outcrops for petrographic
and chemical
chemical analyses,
analyses, ground
ground magnetic
magnetic surveys,
surveys, and
andaaVLF-EM
VLF-EM survey.
The
results of
of the
the study indicate that
The combined
combined results
that the
theclosed,
closed, airborne
airborne anomaly
anomaly
peridotite that
was caused
caused by
by the
the near-surface
near-surface occurrence
occurrence of
of serpentinized
serpentinized peridotite
that
was
contains appreciable
of magnetite. This
appreciable amounts
amounts of
This ultrarnafic
ultramaficbody
body underlies
underlies most
most of
of
the northern
northern portion
portion of
of the
the swamp
swamp area,
area, strikes
strikesN75°-80°W
N750 -800 W and
and dips
dips to the
the south.
south.
The
relative position
positionofof the
the body
body with
with respect
respect to
to metasedimentary
rocks to
to the
The relative
metasedimentary rocks
south and
and southwest
southwest suggest
suggest that
that this
this ultramafic unit
south
unit was
was emplaced as a sill.
The results of the
The
the chemical
chemical analyses
analyses show
show no
no anomalous
anomalous Ni-Cu-Co values.
surveyshow
showthe
the presence
presence of
of two
The
results of the
the VLF-EM
VLF-EM survey
two separate
separate
The results
first is
anamalous
zones within
withinthe
the project
project aera. The
anamalous zones
The first
is caused
caused by
by the
the relatively
relatively
magnetic,
serpentinized peridotite
peridotite that crops
magnetic, serpentinized
crops out within
within the
the swamp.
swamp. This
This area
produced aa high
high ground
ground magnetic
magnetic response
response as
as well
well as
as aa VLF-EM
response. However,
produced
VLF-EM response.
However,
the
combined
geophysical,
geological,
and
chemical
evidence
indicate
that the
the combined geophysical, geological, and chemical evidence indicate that
the
surface exposures
of the
the magnetic,
surface
exposures of
magnetic, serpentinized
serpentinized peridotite has
has limited
limited ecomonic
ecomonic
potential.
The feature responsible
The
responsible for
for the
thesecond
secondVLF-EM
VLF-EM anomalous
anomalous zone
zone does
does not
not
express itself
itself at
at the
express
the surface,
surface, nor
nor does
does ititcorrespoind
correspoind with
with any
any ground
ground magnetic
magnetic
anomalies.
All of
of the
anomaliesgenerated
generatedinin the
the project
All
the major
major VLF-EM
VLF-EM anomalies
project area were
were
correlated with
with the
the serpentinized
correlated
serpentinized peridotite
peridotite and
and showed
showed aa reverse
reverse cross-over
cross-over
to
anomaly
was determined
determined that
that the
theVLF-EM
VLF-EM instrument
instrument was
was responding
responding to
anomaly form. It was
It was
the magnetic
permeabilityofof the
the rock
the
magnetic permeability
rock rather
rather than
than its
itsconductivity.
conductivity.
It
was
survey yielded
yielded no
no reliable
therefore concluded
concluded that the
the VLF-EM
VLF-EM survey
reliable data concerning
concerning
the
the conductivity
conductivity of
of the
the serpentinized
serpentinized ultramafic.
ultramafic.
The VLF-EM
VLF-EMinstrument
instrumentused
usedininthis
thisstudy
studyisisa arather
rather restrictive,
restrictive, reconnaisThe
reconnaissance tool,
tool, and
and as
as such
be used
sance
such cannot
cannot be
used for
for detailed
detailed interpretation
interpretation of
of buried
buried
conductive bodies,
bodies, especially
especially when
when those
those bodies
bodies possess
possess high
high magnetic
magnetic permeabilpermeabilconductive
this occurrence
of ultramafic
therefore suggested
ity.
suggested that this
occurrence of
ultramafic rock
rock be
be
ity. ItIt is therefore
investigated in
in more
investigated
more detail by
by those
those using
using a more
more discriminating
discriminating EM
EM method
method which
which
wouldbetter
better determine
determine its economic
economic potential.
would
60
60
�HIGH-GRADE
HIGH-GRADE METAMORPHISM
METAMORPHISM ASSOCIATED
ASSOCIATED WITH
WITH THE
THE
VERMILION
VERMILION BATHOLITH, MINNESOTA-ONTARIO
MINNESOTA-ONTARIO
David L.
L. Southwick,
Southwick, Department
Department of
of Geology,
Geology, Macalaster
Macalaster College,
College, St. Paul,
David
Minnesota.
ABSTRACT
Aluminous,
magnesianschists
schistsalong
alongthe
the north
north contact
Aluminous, magnesian
contact of
of the
theVermilion
Vermilion
batholith contain
various combinations
combinationsofofsillimanite,
sillimanite,cordierite,
cordierite, staurolite,
staurolite, garnet,
contain various
is rarely
and
and sapphirine
sapphirine along
along with
with biotite,
biotite, oligoclase,
oligoclase, and
and quartz.
quartz. Muscovite
Muscovite is
rarely
So
far
as
present;
tourmaline
is
a
common
and
sometimes
abundant
accessory.
present; tourmaline is a common and sometimes abundant accessory. So
as
known,
this
is
the
first
reported
occurrence
of
sapphirine
in
Minnesota
or
western
known, this is the
reported occurrence of sapphir ine in Minnesota or western
Ontario.
Ontario.
Staurolite-bearing
assemblagesappear
appeartoto represent
represent the
the highest
Staurolite-bearing assemblages
highest metamorphic
metamorphic
grade.
grade. There
There is
is excellent
excellent textural
textural evidence
evidence that the
the reaction
reaction garnet
garnet ++ staurolite +
taken place. Experimental
quartz-cordiertie has
has taken
Experimental work
work indicates that this
this reaction
reaction
quartz—cordiertie
is
with lower
lower pressure
pressure favoring
favoringthe
the formation
formation of
of cordierite.
is pressure-controlled,
pressure-controlled, with
cordierite.
Sapphirine
occurs together
together with
with staurolite
staurolite in some
Sapphirine occurs
some rocks,
rocks, indicating
indicating formation
formation at
the highest
metamorphicgrade.
grade. There
is no
no clear-cut evidence
as to the reactions
highest metamorphic
There is
evidence as
reactions
governing
sapphirine formation.
governing sapphirine
Field
relations indicate that the
Field relations
the high-grade
high-grade schists are the
the product
product of
of thermal
thermal
assemblages inin the
the schists
metamorphism by
adjacent batholith.
batholith. Observed
Observed assemblages
schists
metamorphism
bythe
the adjacent
0
suggest maximum
suggest
maximum temperature and
and pressure
pressure in
in the
theneighborhood
neighborhood of
of 600-700°C
600-700 C and
and
This environment
environmentisiscompatable
compatablewith
withthe
the inferred
inferred temperature
temperature and pressure
3-5 kb. This
at crystallization
crystallization of
of the
the major
major part
partof
ofthe
theVermilion
Vermilion batholith.
batholith.
Detailed investigations
investigations of
of the phase chemistry currently are
are underway.
underway.
61
�GEOLOGY OF THE ROUND
GEOLOGY
ROUND LAKE
LAKE INTRUSION,
INTRUSION,
SAWYER COUNTY, WISCONSIN
SAWYER
WISCONSIN
S.W.
Stuhr and
and E.N.
S.W. Stuhr
E.N. Cameron, Department
Department of
of Geology
Geology and
and Geophysics,
Geophysics, University
University
of Wisconsin,
Wisconsin, Madison,
Madison, Wisconsin
Wisconsin 53706
53706
ABSTRACT
enclosed in
in Archean
rocks aa short
The Round
Round Lake
Lake intrusion
intrusion is enclosed
Archean rocks
short distance
distance
southeast of the edge
southeast
edge of
of the
theLake
LakeSuperior
SuperiorSyncline
SynclineininSawyer
SawyerCounty,
County,Wisconsin.
Wisconsin.
Geophysicaldata
dataindicates
indicatesthat
that the
the intrusion
intrusion isis at
at least five
Geophysical
five miles
miles long
long but
but less
less
The intrusion
intrusion may
maybe
be aa derivative
than
than one
one mile
mile wide.
wide. The
derivative of aa gabbroic
gabbroic magma.
magma.
Diabasic gabbro
gabbro occurs
occurs as
as inclusions
inclusions inin the
the outer
outer portions
Diabasic
portions of
of the oxide-rich
oxide-rich core.
core.
Magnetite-troctolite,
and mafic pegmatite
Magnetite-troctolite, magnetite, anorthositic
anorthositic olivine
olivine gabbro
gabbro and
form the troughshaped
form
troughshaped core of the intrusion.
intrusion.
The dominant
dominant minerals
minerals are olivine,
and titanomagnetite
titanomagnetite in
The
olivine, plagioclase and
in various
various
In
the
core
of
the
intrusion,
olivine
and
plagioclase
crystallized
early
proportions. In the
intrusion, olivine and plagioclase
and
the iron-titanium
oxides crystallized
crystallizedlate.
late. At
and the
iron-titanium oxides
At the
the base
base of
of the
thenarrow
narrowintrusion
intrusion
of magnetite
magnetite troctolite was
aa thick zone
zone of
was formed.
formed. The
The iron-titanium
iron-titanium oxides
oxides became
became
enriched
in the
the residual
liquid and
andaalarge
largezone
zoneofofmagnetitite
magnetitite formed
formed in
in the
the central
central
enriched in
residual liquid
part of the intrusion.
intrusion. As
As differentiation
differentiation proceeded,
proceeded, additional
additional magnetite-troctolite
magnetite-troctolite
clusters accumulated
formed
toward the
the top
formed toward
top of
of the
the intrusion.
intrusion. Plagioclase
Plagioclase clusters
accumulated into
lenses
of anorthositic
olivine gabbro
gabbro inin the
the lower
of the
lenses of
anorthositic olivine
lower and
and middle
middle portions
portions of
the
intrusion. Finally,
Finally, mafic
mafic pegmatites,
pegmatites, consisting
consisting of
of plagioclase,
plagioclase, perthite, augite,
augite,
iron-titanium oxides
and apatite
apatite as major
oxides and
major minerals,
minerals, developed
developed in the upper
upper portions
portions
of the intrusion.
intrusion.
Chemical variation
variation of
of specific
Chemical
specific minerals
minerals is
is a function
function of both
both the
the oxide/silioxide/silicate ratio
cate
ratio and
and cryptic
cryptic changes
changes related
related to
to position
position in the
the intrusion.
intrusion. Olivine,
plagioclase
plagioclase and
and iron-titanium oxides
oxides show
show slight but consistant
consistant chemical
chemical changes.
changes.
Cryptic variations
variationsare
are most
most pronounced
pronouncedininthe
the portion
portionofof the
the intrusion
Cryptic
intrusion that
crystallized last.
The
oxides were
were concentrated
concentrated in
in the
The iron-titanium
iron-titanium oxides
the residual
residual liquid
liquid under
under
the intrusion
the product
conditions
of low
conditions of
low oxygen
oxygen fugacity.
fugacity.
If the
intrusion is the
product of
of iron
enrichment of basaltic magma, it must have migrated
migrated from
from the site of
differentiation. After
After the
the iron-rich
iron-rich magma
magma was
was intruded,
intruded, itit followed
followed aa "normal"
"normal"
path of differentiation in
in place.
place.
62
U
�HYDROCARBONS
HYDROCARBONS OBTAINED
OBTAINED BY
BY PYROLYSIS
PYROLYSIS OF
OF SOME
SOME
PRECAMBRIAN
ROCKS
OF
MINNESOTA*
PRECAMBRIAN ROCKS OF MINNESOTA*
F.M.
:i. Baysinger,
and 1M.
F.M. Swain,
Swain, J.
Baysinger, and
J.M. Bratt,
Bratt,Department
DepartmentofofGeology
Geologyand
andGeophysics,
Geophysics,
of Minnesota,
Minnesota, Minneapolis,
Minneapolis, Minnesota
Minnesota 55455
55455
University of
ABSTRACT
ABSTRACT
Drill
Drill core samples
samples of
of 42
42 Precambrian
Precambrian sedimentary,
sedimentary, igneous,
igneous, and
and metamorphic
metamorphic
rocks
partial vacuum
rocks were
were analyzed
analyzed by
by heating
heating under
under partial
vacuum at 100°C
1000C and
and at 400°C
400 0 C to
to
release hydrocarbons
and other volatile products.
hydrocarbons and
products.
The
yielded methane
methane inin amounts
amounts ranging
rangingfrom
from traces
traces to
to 33
The core
core samples
samples yielded
way of comparison,
but averaged
averaged much
much less.
less. By
By way
comparison, samples of
microliters per gram, but
Middle
Marcellusblack
black shale,
shale, from
Middle Devonian
Devonian Marcellus
from Pennsylvania,
Pennsylvania, yielded
yielded methane
methane in
in
am ounts up to 77 ul/g.
ul/g.
amounts
Other
up to
to C11
were
Other straight
straight chain
chain hydrocarbons
hydrocarbons up
C
were found
found in the
the volatile
volatile
ll
o
products, especiall'
especiallj: those
those obtained
obtained atat400°C;
400 C;benzene
benzenealso
also was
was aacommon
common product,
product,
mainly
in the
the 400
mainly in
400 C
C experiments.
experiments. Carbon
Carbon dioxide
dioxide and
and nitrogen
nitrogen appear
appear to form
form aa
large part of
of the
the non-hydrocarbon
non-hydrocarbon volatiles in at least
least some
some of
of the
the samples.
samples.
Spectral data
data indicate
of the
Spectral
indicate that the
the straight
straight chain
chain pyrolysis
pyrolysis products
products of
Precambrian
rocks
are
mainly
alkenes,
whereas
those
of
the
Devonian
rocks,
Precambr ian rocks are mainly alkenes, whereas those of the Devonian rocks,
to above,
above, are
are aamixture
mixture of
ofalkanes
alkanes and
and alkenes.
alkenes. Alkanes
Alkanes were however,
however,
referred to
Available
obtained from
from several
several algae-bearing
algae-bearing Middle
Middle Precambrian
Precambrian argillites.
argillites.
obtained
evidence indicates,
indicates, although
not conclusively,
conclusively, that
that the alkenes
evidence
although not
alkenes were
were contained
contained in
the rock
rock rather
ratherthan
thanbeing
beingproduced
produced from
from alkanes
alkanesduring
during pyrolysis.
pyrolysis.
The
writers believe
believe that surface contamination
The writers
contamination in most
most of the drill
drill cores
cores was
was
minimal
owingtotothe
the low
lowpermeability
permeabilityofofthe
the rocks
rocks studied,
studied, and
and that
that contamination
minimal owing
by drilling was also minimal.
by
not formed
that the
There
is aa reasonable
reasonable possibility
possibility that
the volatiles,
volatiles, if not
formed from
from
There is
kerogeri residues
residues by
bythe
the pyrolysis
pyrolysisexperiments,
experiments, are
are in
in part juvenile
kerogen
juvenile igneous
igneous gases
gases or
or
are substances
substances that
that were
were distilled
distilled out
out of
of the
thedeeper-lying
deeper-lying rocks
rocks during
during intervals
intervals of
of
folding and
and metamorphism,
metamorphism, and
and subsequently
subsequently accumulated
accumulated at
at higher
higher levels.
folding
*The paper
paper isis scheduled
scheduled for
for publication
publication in
in July 1976
"Origins of
of Life."
Life."
*The
1976 "Origins
63
63
�—-
HORNFELSED BASALTS
BASALTS IN THE
THE DULUTH
DULUTH COMPLEX
COMPLEX
Department of
of Geological
R.M.
B. Bonnichsen,
Bonnichsen, Department
Geological Sciences,
Sciences, Cornell
Cornell
R.M. Tyson
Tyson and
and B.
Ithaca,New
NewYork
York14853
14853
University, Ithaca,
ABSTRACT
ABSTRACT
Two
typesofof hornfelsed
basalt (see
(see figure)
figure) occur
occur in
compositional types
hornfelsed basalt
in the
the
Two compositional
Babbitt-Hoyt
of the Duluth
Babbitt-Hoyt Lakes
Lakes region
region of
Duluth Complex.
Complex. The
The Erie
Erie Hornfels
Hornfels (Sec.
(Sec. 18,
18,
T.59N.,
Dunka Railroad
Railroad Hornfels
T.59N., R.13W.),
R.13W.), Dunka
Hornfels (Sec. 33,
33, T.60N.,
T.60N., R.
R. 12W.)
12W.) and
and Reserve
Reserve
Hornfels
(Sec. 32,
(Type1)I) are
are olivine
Hornfels (Sec.
32, T.60N.,
T.60N., R.12W.),
R.12W.), (Type
olivine tholeiites
tholeiites consisting
consisting of
of
plagioclase
augite (16-45%),
olivine (0-2196),
(0-21%),and
and inverted
inverted pigeonite
plagioclase (40-62%),
(40-6296), augite
06-45%), olivine
pigeonite (018%).
1896).- The
The Reserve
Reserve body
body has less than
than 1%
1% opaque
opaque oxides and more than
than 10%
10% olivine,
whereas
whereas the others
others have
have 1-3%
1-396 opaque
opaque oxides
oxides and
and generally
generally less
less than
than 10%
10% olivine.
olivine.
The
range from
from granoblastic
granoblastic in
in the
theDunka
Dunka Railroad
Railroad and
and Reserve
Reserve bodies,
bodies,
The textures range
which
are surrounded
surroundedby
byintrusive
intrusiverocks,
rocks,totoaabetter-preserved
better-preserved basaltic fabric in
which are
in the
This
type
contains
plagioclase-two
Erie
Hornfels
at
the
base
of
the
complex.
Erie Hornfels at
base of the complex. This
contains plagioclase-two
pyroxene
and plagioclase
pyroxene metamorphosed
metamorphosed amygdules
amygdules and
plagioclase phenocrysts.
phenocrysts. The
The Colvin
Colvin
Creek Hornfels
and T.59N.
T.59N. R.13W.)
R.13W.)isisan
an example
example of
of Type
Hornfels (T.58N.
(T.58N. and
Type H,
II, and contains
contains
(28-34%),
equant plagioclase (52-56%), irregular to locally poikilitic augite (28-3496),
hypersthene
mantling augite, and
hypersthene (1-6%)
0-6%) mantling
and magnetite
magnetite(10-20%).
(10-2096). It represents
represents an
an
type has
oxidized
basalt which
which has
has been
been metamorphosed.
metamorphosed. This
This type
has aa granoblastic
granoblastic
oxidized basalt
texture
texture and
and contains
contains zoned
zoned plagioclase
plagioclase phenocrysts
phenocrysts and
and metamorphosed
metamorphosed amygdules
amygdules
. composed
composed of
of augite enclosing plagioclase.
\Ve believe
believe these
these hornfels
hornfels bodies
bodies were
were originally
originallyflows
flowsthat
that were
were part of the
We
the
Their
metamorphism
to
the
pyroxene
North
Shore Volcanic
Volcanic Group.
Group. Their metamorphism to the pyroxene hornfels
hornfels or
North Shore
sanidinite
facies was
thermal in
sanidinite facies
was predominantly
predominantly thermal
in nature. Devolatilization
Devolatilization was one
one
major
major effect as
as shown
shown by
by the
the anhydrous
anhydrous minerals
minerals now
now constituting the
the amygdules
amygdules
and the
the scarcity
scarcityofofhydrous
hydrousminerals
mineralscommon
common in
inunmetamorphosed
unmetamorphosed North
North Shore
Shore
and
Volcanicrocks.
rocks. Partial
Partial melting
locally occurred
occurred with
with the
the formation
melting locally
formation of syenite and
Volcanic
Such dikes,
dikes, composed
composedofof Na-plagioclase,
Na-plagioclase,quartz,
quartz, chlorite
chlorite and local
dikes. Such
granite dikes.
biotite and
occur in
in the Dunka
and tremolite,
tremolite, conspicuously
conspicuously occur
Dunka Railroad
Railroad- Horniels
Hornfels and
and have
have
been observed
many other
been
observed at
at many
other localities.
The volcanic
volcanic horfelses
horfelsesatat the
the base
base of
of the
lie above
only aa few
The
the complex
complex lie
above only
few
hundred
feet of
of Virginia
VirginiaFormation.
Formation.This
Thisisismuch
muchthinner
thinnerthan
thanfarther
farther to
to the
the west.
hundred feet
suggests the
the Virginia
was eroded
eroded prior
prior to extrusion
Virginia was
extrusion of
of the
the volcanic
volcanic rocks.
rocks.
It suggests
Perhaps this
this accompanied
preceeding the Keweenawan
Perhaps
accompanied regional
regional doming
doming preceeding
Keweenawan episode
episode of
continental
continental rifting
rifting.•
....
L
01
+
.
/I
pi
px
40
so
64
64
60
70
�I
SYNGENETIC
SYNGENETIC MODEL
MODEL FOR THE
THE ORIGIN OF
OF THE
THE
WHITE
WHITE PINE COPPER
COPPER DEPOSIT
DEPOSIT
Thomas
Geology Department,
Department, Michigan
Thomas A.
A. Vogel,
Vogel, Geology
Michigan State University,
University, East
East Lansing,
Lansing,
Michigan
48824; M.B.
M.B. McBride,
McBride, Department
Department of Agronomy,
Michigan 48824;
Agronomy, Cornell
Cornell University,
University,
Ithaca, New
New York
York 14853;
14853; and Robert
Robert Ehrlich,
Ehrlich, Geology
Geology Department,
Department, University
University of
of
South Carolina,
Carolina, Columbia,
Columbia, South
South Carolina
Carolina29208.
29208.
South
ABSTRACT
ABSTRACT
The
syngenetic model
model for the
the mineralization
mineralization of
of the
thelower
lowerNonesuch
Nonesuch Shale
Shale at
at
The syngenetic
White
Pine,
Michigan
depends
upon
copper
entering
the
basin
complexed
White
Michigan depends upon copper entering the basin complexed to clay
clay
In order
order for this
this model
model to
to be
be viable
viable for
for the
the White
White Pine
Pine deposit,
deposit, it
it isis
minerals. In
necessary
to demonstrate
necessary to
demonstrate that significant
significant copper
copper can
can be
be complexed
complexed to clay
clay
minerals
and that
that these
in the source
minerals and
these minerals
minerals can be
be produced
produced in
source terrane for
for the
the
lower
Shale. Furthermore, if copper
lower Nonesuch
Nonesuch Shale.
copper entered
entered the
the basin
basin complexed
complexed to clay
minerals, the clay
clay mineral
mineral fraction
fraction present
presentininthe
thelower
lowerNonesuch
Nonesuch Shale
Shale may
may record
occurrence.
its occurrence.
Basalts
and andesites
are extensively
exposed inin the
the rocks
Basalts and
andesites are
extensively exposed
rocks of
of the
theMiddle
Middle
Keweenawan
and all
all workers
workers agree
agree that
that the sediments
Keweenawan and
sediments of
of the
the Nonesuch
Nonesuch Shale
Shale are
derived
from weathering of these rocks.
derived predominantly
predominantly from
rocks. In
In most environments, the
first clay
clay mineral
mineral to
to form
form from
from weathering
weathering of
of basalt
basalt isismontmorillonite.
montmorillonite. The
dominant
clay mineral
mineral assemblages
assemblagesthat
that exist
exist in
Shale are
are aa
dominant clay
in the
the lower
lower Nonesuch
Nonesuch Shale
complex
intergrowth of
of chlorite
chlorite and
and illite.
illite. AA probable
for these intergrowths
complex intergrowth
probable origin for
dlagenetic alteration of
of montmorillonite.
montmorillonite. Many
Many workers
workers have
is due to a diagenetic
have traced the
change from
from montmorillonite
montmorillonite to chiorite-illite
chlorite-illite intergrowths
intergrowths in
in the
thegeologic
geologiccolumn
column
and
the alteration
to chlorite-illite
and experimentally,
experimentally, the
alteration of
of montmorillonite
montmorillonite to
chlorite-illite is
is well
well
known. It
It is
is reasonable
reasonable that
that the
thechlorite-illite
chlorite-illiteintergrowths
intergrowthsininthe
thelower
lowerNonesuch
Nonesuch
known.
Shale
been diagenetically
Shale represents
represents montmorillonite
montmorillonite that
that has been
diagenetically altered.
their ability
One of
of the
One
the characteristic
characteristic features
features ofofmontmorillonite
montmorillonite is
is their
ability to
to
adsorb
cations, and
and considerable
considerableresearch
researchhas
hasbeen
been devoted
devotedtoto the
the study
adsorb cations,
study of the
the
adsorption
and exchange
exchange properties
properties of
of copper
adsorption and
copper and
and clays.
clays. Heydemann
Heydemann (1959)
(1959) 1959,
1959,
was
the first
firstworkers
workers totoshow
showexperimentally
experimentally that
that copper
copper could
could be
be
was one
one of
of the
In addition,
selectively adsorbed
from copper
selectively
adsorbed on
on montmorillonite
montmorillonite from
copper ions
ions in
in solution.
solution. In
well-knownthat
that organic-clay
organic-clay complexes
complexeswill
will adsorb
adsorb copper
copper from
from dilute
it is well-known
dilute
Steger has suggested
aqueous solutions
solutions (Kaufherr,
(Kaufherr, et.
et. al., 1971;
aqueous
1971; Steger, 1973).
1973). Steger
suggested that
organic-clay complexes
complexes could
could be
be used
used to
to remove
remove trace amounts
organic-clay
amounts of
of copper,
copper, zinc
zinc and
and
Many workers
workershave
have shown
shownthat
that copper
copper is
is bound
lead from
from water.
water. Many
bound preferentially
lead
over
on organic-clay complexes.
over other divalent cations on
A study
study of
of the clay
A
clay fraction
fraction of
of samples
samples from
from aa copper-rich,
copper-rich, black
black shale
shale was
was
undertaken
determine if some
some of the
the copper
copper was
was structurally
structurally bonded
bonded in
undertaken in
in order
order to determine
the clay
lattice and
state of the
the
clay mineral
mineral lattice
and also
also to determine
determine the oxidation
oxidation state
the iron
iron in
in
order to
to better
of formation
of these
these minerals.
minerals. The
order
better understand
understand the
the environment
environment of
formation of
The
original samples
samplescontained
contained4.75%
4.75%copper
copperand
andthethe <<22 micron
micron (clay)
(clay) fraction
fraction
original
micron
fraction
After leaching
leachingthe
the << 2 micron fraction with
contained
0.96% copper.
copper. After
with sodium
sodium
contained 0.96%
no Cu
Cu II
was removed,
chloride (NaTPB
NaC1), no
tetraphenyl
boron - sodium
(NaTPB - NaCl),
II was
removed, thus
tetraphenyl boron
sodium chloride
A
indicating that
that the copper
indicating
copper is
is not
not present
present as
as interlayer
interlayer Cu
Cu IIII or
or soluble
soluble Cu
Cu II.
II. A
detailed electron
microscopeand
and microprobe
microprobestudy
studyofofthe
the <<22 micron
detailed
electron scanning
scanning microscope
micron
fraction failed
failed to show
the presence
presence of
of any
any free
free native
native copper
copper or
or chalcocite grains.
fraction
show the
grains.
Electron Spin
Resonance studies
studies of
of these samples
Electron
Spin Resonance
samples show
show Fe
Fe III
III (G
(G about 4.0)
4.0) in
octahedral sites
sites in
in the
the clay
of Fe III
is
octahedral
clay minerals.
minerals. Abundance
Abundance of
III in
in the clay
day minerals
minerals is
65
65
�probably
about 2-3%
probably about
2-3% (determined
(determined by
by comparing
comparing the spectrum
spectrum with
with known
known clays).
clays).
The
presence of
of Fe
Fe III
HIininthe
the octahedral
octahedral sites
sites must result
The presence
result from
from the
themontmorillonite
montmorillonite
having formed in an
an oxidizing
oxidizing environment.
environment.
These
These data are
are consistent
consistent with
withaamodel
modelininwhich
which montmorillonite
montmorillonite formed
formed in
in
the weathering
and copper
probably as
as a copperweathering environment
environment and
copper was
was complexed,
complexed, probably
coppercopperinin the
the <<22 micron
organic complex.
complex. The
The insoluble
insoluble copper
micron fraction
fraction indicates
indicates that
that
when
broke down,
some of
of the copper
when the copper-organic-montmorillonite complex
complex broke
down, some
copper
was
was forced
forced into
into the octahedral
octahedral sites
sites of
of the
theresulting
resulting chiorite-illite
chlorite-illite intergrowth.
intergrowth.
However,
most of
of the
the copper
copper was
was released
released and
and provided
provided the
the source
source of
of copper
However, most
copper for
for
the mineralized
mineralized zone.
zone.
REFERENCES CITED
CITED
Heydemann,
A., 1959,
Heydemann, A.,
1959, Adsorption
Adsorption ans sehr
sehr verdUnnten
verdUnnten Kupferlösungen
Kupferlosungen an reinen
reinen
Tonmineralen; Geochim.
Geochim. Cosmochim.
Cosmochim. Acta. v. 15,
15, p.
p. 305-329.
305-329.
Kaufherr, N.,
N., Yariv,
Yariv, S.,
S., and
and Heller,
Heller, L.,
L., 1971,
1971, The
The effect
effectof
ofexchangeable
exchangeable cations
cationson
on
the sorption
by montmorillonite;
montmorillonite; Clays
Clays and
and clay
clay minerals, v.
sorption of chiorophyllin
chlorophyllin by
19, p. 193-200.
193-200.
Steger, H.F.,
the mechanism
of adsorption
adsorption of
of trace copper
Steger,
H.F., 1973,
1973, On
On the
mechanism of
copper by bentonite;
Clays and clay minerals,
minerals, v.
v. 21,
21, p.
p. 429-436.
429-436.
66
�GNEISS AND
AND MIGMATITE
MIGMATITEOF
OF ARCHEAN
ARCHEAN AGE
AGE IN
IN THE
THE PRECAMBRIAN
GNEISS
BASEMENTOF
OF CENTRAL
CENTRAL WISCONSIN,
BASEMENT
WISCONSIN, U.S.A.
W.R. Van
Van Schmus,
Schmus, Department of
Geology, University
University of
of Kansas,
Kansas, Lawrence,
Lawrence,
W.R.
of Geology,
Kansas, 66045,
66045,and
and J.L.
1L. Anderson,
Department of
of Geological
Kansas,
Anderson, Department
Geological Sciences,
Sciences, University
University
of Southern
Angeles, California
California 90007
of
Southern California, Los
Los Angeles,
90007
ABSTRACT
Many of
of the
the southernmost
of the
the Precambrian
in central
southernmost exposures
exposures of
Precambrian shield
shield in
central
Many
Wisconsinconsist
consistofofgneiss,
gneiss,migmatite,
migmatite, and/or amphibolite with associated younger
Wisconsin
younger
intrusive rocks
rocks ranging
ranging in
in compositon
compositonfrom
from tonalite
tonalite to granite. Rb-Sr
intrusive
Rb-Sr whole-rock
whole-rock
analyses
and
U-Pb
zircon
analyses
show
that
analyses and U-Pb zircon analyses show that the migmatitemigmatite- and
and gneiss-forming
gneiss-forming
events occurred
events
occurred about
about 2.8 b.y.
b.y. ago.
ago. Ages
Ageson
onminerals
minerals and
and younger
younger plutonic
plutonic rocks
rocks
indicate that older
indicate
older gneiss
gneiss and
and migmatite
migmatite were
were intruded
intruded and
and locally
locally metamorphosed
metamorphosed
during major
major events
events 1.5
during
1.5 to 1.9 b.y. ago.
Rb-Sr
isochrons for
for the
the migmatite have
Rb-Sr isochrons
have elevated initial
initial Sr87/Sr86
Sr 87 /Sr 86 ratios (ca.
0.710), suggesting
suggestingthat
that the
the migmatites
migmatites formed
formed from
from crustal rocks
0.710),
rocks of intermediate
intermediate
to granitic
were themselves
themselves formed
formed more
more than
than 3.0
b.y. ago.
granitic composition
composition arid
and which
which were
3.0 b.y.
ago.
If this
If
this is true,
true, then
then the
thegneissic
gneissic and
and migmatitic
migmatitic rocks
rocks inincentral
centralWisconsin
Wisconsin may
may
represent an
an eastward
extension of
of the
the ancient
represent
eastward extension
ancient ( >> 3.3
3.3 b.y.
b.y. old)
old) Minneosta
Minneosta River
River
Valley
Valley Terrane.
67
�COMPOSITIONAL VARIATIONS
VARIAnONS OF MINNESOTA RIVER VALLEY
VALLEY AMPHIBOLITES
AMPHIBOLITES
P.W.
K.3. Schulz,
Schulz, and
and B.V.
B. V. Nielsen,
Nielsen, Minnesota
Minnesota Geological
Geological Survey,
Survey, St.
P.W. Weiblen,
Weiblen, K.J.
Paul, Minnesota
Minnesota 55108
55108
ABSTRACT
Studies
of Archean
at Morton,
reveal that hornStudies of
Archean amphibolites
amphibolites at
Morton, Minnesota
Minnesota reveal
horn-
blende-plagioclase
enclaves(two
(twometers
meters inin size)
size) contain
contain only
blende-plagioclase enclaves
only rare
rare clinopyroxene,
clinopyroxene,
whereas
larger enclaves
Both types
types are
whereas larger
enclaves (20
(20 meters long)
long) contain
contain up
up to
to 30%.
30%. Both
rimmed
by biotite.
biotite. Except
rimmed by
Except for
for K,
K,compositional
compositional variations
variations within
within and between
between the
two types
types reflect
reflectigneous
igneous processes
processes and
and resemble
resemble northern
northern Minnesota
Minnesota greenstones
greenstones
(Figs. la &
& b). Some
Some amphibolites
amphibolites from
from near
near Delhi
Delhi and
and Montevideo
Montevideo contain
contain -<< 10
10
wt, % Al2O..
wt.
Al 20 j • Their
Their compositions
compositions mimic
mimic komatilte-like
komatlite-like greenstones
greenstones (Figs.
(Figs. Ic
lc &
& d).
d).
The data
that magmas
data 'uggest
suggest that
magmas of
of igneous
igneous precursors
precursors of
of certain southwest
southwest
The
Minnesota
amphibolites and
and northern
northern Minnesota
greenstones were
were generated
generated from
Minnesota amphibolites
Minnesota greenstones
similar source rocks in comparable tectonic regimes.
regimes.
.6
.5 to
ta
1•
.4
.4
.33
MINN
l'lINN
' .6
.EttI
.5 + b
T\iC;::l
RVEP
VRLlEY TH
TH MPHI60LITES
• '. L. \ RLLEY
RMPHI80LITES
;
i
! .4
! .3
t
r
.1 T
1.2
.2
.1
.2
.2
.1
:L
t
t
.0 +
.1
•
i
.0
EN—S
9N-S
SN—7
5N-7
...
.4
.il
c.
.5
(!)
CD
.:J
t
;9
m 19
17
•
:
T
'!'
CD
<:>
c.
!
.b
.~
i
I
.5Ir
iCJ
.6+ d
, .6
.5 Td
.6'-
PVE9 \IPLLEY
MI~·j~. Fl:VER
W,U_EY HEL
HBlPMPHISOL1TES
RMPHI80LITES
.34- cC MINr\
.4
.3
.3
17
15
IS
1d
13
12
x 12
÷3
+ 32
:~.4 ~
8N-3
3N-2
EN—i
8N-I
36
'A 32
20
y 20
t
1.3
.6
1
VERMILION KOMRTIITES
VERMiLION
KOMRTI ITES
I
I
.~ T
.2
:~ ~
.11-
i .0
.0+
.
~
.2
.2
<:>
CD
.3
.3
+
. 1 TiI
EN—S
'" 8N-6
SN-S
3N-5
8N-4
xx SN—4
I
.2 +
t
O-F,EENSTONE
VERMILION GREENSTONE
__
'"
t
.1
•.2
2 ~I'
.3
~b-I~1 j
.; K56-75 '
x 56-756
i- 56-754
to 56-665 .• J T
(!)
56-66:J i .5
cD
1-
.3 +
. -1-
T
.5.
.o-
~
I'
-i.
W
MO
FE .I1N
MN CR
OP Rl
PL SI
MS FE
SirIII
PNR
P NR
T
(!)
CD
39
35
38
37
I
.,.
i
K
K
j
40
6.
t
1
<:>
xX
CD
MG FE MN
OP RL
TI
MG
MN CR
Rl SI
5 I TI
PNP
P NR
K
i<
Log plots
plots of
of compositions
compositions normalized
normalized to Hawaiian
tholeilte (as
Fig. 1.
1. Log
Hawaiian tholeiite
(as oxides,
oxides, right
right
to left: 8.1,
8.1, 10.04,
10.04-, .17, 10.9,
10.9, 13.4,
13.4-, 50.4,
50.4-, 2.7,
2.7, .28,
.28, 2.3,
2.3, .53).
.53). Numbers
Numbers below
below 00 have
negative values.
negative
values. (Data
(Data from Nielsen,
Nielsen, in
in prep.,
prep., Sims,
Sims, P.K.,
P.K., 1972,
1972, and
and Green
Green and
and
Schulz, in prep).
REFERENC
ES
REFERENCES
Sims, P.K.,
1972, Metavolcanic
and associated
Metavolcanic and
associated synvolcanic
synvolcanic rocks
rocks in
in Vermilion
Vermilion
Sims,
P.K., 1972,
district, in
district,
in Sims,
Sims, P.K.
P.K. and
and Morey,
Morey, G.B.,
G.B., eds.,
eds., Geology
Geology of
of Minnesota:
Minnesota: A
A
Centennial Volume,
Volume, Minnesota Geological Survey, p. 632.
68
�Rb-Sr GEOCHRONOLOGY AND TRACE ELEMENT
ELEMENT GEOCHEMISTRY
GEOCHEMISTRY OF GRANULITE
FACIES ROCKS NEAR
FACIES
NEAR GRANITE
GRANITE FALLS,
FALLS, IN
IN THE
THEMINNESOTA
MINNESOTA RIVER
RIVER VALLEY
VALLEY
Wendell E.
E. Wilson
Wilson and
and V.
V. Rama
Rama Murthy,
Murthy, Department of
of Geology
Geology and
andGeophysics,
Geophysics,
Wendell
University of Minnesota,
Minnesota, Minneapolis,
Minneapolis, Minnesota
Minnesota 55455
55455
ABSTRACT
Sr- isotopic
isotopic composition
compositionand
and the
the trace-element
trace-element abundances
abundances of K, Rb,
Rb, Sr,
Sr,
The Srand Ba
Ba have
have been
been determined
determined in
in several
several whole
and mineral
and
whole rocks
rocks and
mineral separates from
from
four lithologic
four
lithologic units
units in the
the Minnesota
Minnesota River
River Valley,
Valley, near Granite
Granite Falls,
Falls, Minnesota.
Minnesota.
The
sampled units
units are
are the inner
The sampled
inner and
and outer units
units of
of hornblende-pyroxene
hornblende-pyroxene gneiss,
gneiss, the
biotite-garnet gneiss,
gneiss, and
and the
the metagabbro
metagabbro originally
originally included
included in
in the
the"hornblende"hornblendepyroxene gneiss" of Himmelberg
Himmelberg (1968).
(1968).
Rb-Sr data
give
The
The whole
whole rock
rock isochron
isochronages
ages (T)
(T) obtained
obtainedfrom
from the
the Rb-Sr
data are give
below; ages
ages obtained
obtainedfor
for metamorphic
metamorphic events,
events, as
as determi~ed
determiied by
below;
by mineral
mineral isochrons
isochrons
are given
giveni21;ra8~ets.
ibraets. All All
ages
areare
in inunits
yrs); all
all errors
errorsare
are 20-.
2-.
are
ages
unitsofofaeons
aeons (10
(10 yrs);
The initial Sr/
Sr ratios
ratios (I)
refer to the
Sri Sr
(I) refer
the whole
whole rock
rock isochrons.
isochrons.
The
Garnet-.Biotite gneiss
Garnet-Biotite
0.14 (1.81);
(1.81); I == 0.7008 +÷0.0009.
0.0009.
T == 3.54 ~÷0.14
I-Iornblende-Pyroxene Gneiss
Gneiss (outer
(outer unit)
Hornblende-Pyroxene
T == 3.31 ~÷0.26
0.26 (1.78);
(1.78); I == 0.7011 :-÷0.0012.
0.0012.
Gneiss (inner Unit)
Unit)
Hornblende-Pyroxene Gneiss
Data
Data scatter precludes
precludes attempts at dating.
dating.
Meta-gabbro of
of Himmelberg
Himmelberg (1968)
(1968)
T ==2.68 :+ 0.20 (l.80);
(1.80); I == 0.7037 :-÷ 0.0001.
Interpretations
of the
the above
Interpretations of
above data
data are
are subject
subject to
to the
theusual
usualambiguities
ambiguities in
in
discussions
ofgeochronological
geochronologicalproblems
problemsofofearly
earlyArchean
Archeanterranes.
terranes. The
discussions of
The simplest
simplest
explanation
seems
to
be
that
the
combined
section
of
hornblende-garnet-pyroxene
explanation seems
be that the combined section of hornblende-garnet-pyroxene
granuLitefacies
faciesrocks
rocksatat Granite
age of
granulite
Granite Falls
Falls has
has aa minurnum
minumum age
of 3.55
3.55 AE
AE with
with a
pronounced metamorphism at
at 1.8
1.8 AE.
AE.
The
element patterns
patternsofofthe
thehornblende-pyroxene
hornblende-pyroxene gneisses
gneisses and
and garnetgarnetThe trace element
biotite gneisses
graywackesofof island-are-alkali
island-arc-alkalibasalt
basalt affinities
affinities and
gneisses resemble
resemble graywackes
and the
metagabbros
resembles aa low-K
metagabbros resembles
low-K tholeiite.
tholeiite. The
rocks at Granite
Granite Falls
Falls
The granitic rocks
therefore
represents aa very
very old
old layered
sequence of
of basaltic
therefore probably
probably represents
layered sequence
basaltic rocks
rocks and
and
graywackes intruded by
by the
the Montevideo
Montevideo Gneiss.
Gneiss.
69
69
t
�I
PETROLOGY
OF THE NORTHWEST
CORNER OF
PETROLOGY OF THE ARCHAEAN
ARCHAEAN GNEISSES
GNEISSES OF
NORTHWEST CORNER
THE SACRED HEART
THE
HEART PLUTON;
PLUTON; MINNESOTA
MINNESOTA RIVER
RIVER VALLEY,
VALLEY, MINNEOSTA
MINNEOSTA
lames L. Welsh,
James
Welsh, Department of
of Geology
Geology and
and Geophysics,
Geophysics, University
Universityof
ofWisconsinWisconsinMadison, Wisconsin
ABSTRACT
Approximately 66 miles
miles south
south of
of Sacred
Sacred Heart, Minnesota,
Approximately
Minnesota, along
along the Minnesota
Minnesota
River Valley,
the Sacred
Sacred Heart
Heart quartz monzonite
River
Valley, the
monzonite is intrusive
intrusive into
into an
an older
older gneissic
gneissic
complex. Detailed
in the
the gneisses
along the
the northwestern
Detailed mapping
mapping in
gneisses along
northwestern portion
portion of the
the
outcrop
outcrop belt reveals
reveals four
four structurally
structurally concordant
concordant lithologies,
lithologies, which
which are
are described
described
below from
from south
south to
to north.
below
The
southern part
part of
of the
the area consists
of the Sacred
The southern
consists of
Sacred Heart
Heart pluton.
pluton. To
To the
the
north, the pluton
is in
in gradational,
gradational, but
but apparently
apparently intrusive
intrusive contact
contact with a salmonnorth,
pluton is
salmonpink clinopyroxene
clinopyroxene syenite,
syenite, which
which contains
contains abundant,
nebulitic, mafic
pink
abundant, commonly
commonly nebulitic,
Manyofof the
the larger inclusions
inclusions. Many
inclusions are zoned,
zoned, consisting
consisting of
of pyroxene-rich
pyroxene-rich
rinds and
rinds
and hornblende-rich
hornblende-rich cores. Separated
Separated from
from the syenite
syenite by
by aa sill-like
sill-like body
body of
of
quartz monzonite
is aa sequence
of interlayered tonalitic
monzonite is
sequence of
tonalitic gneisses
gneisses and
and amphibolites,
amphibolites,
which are
are in
in turn
which
turn separated
separated by
by another
another sill
sill of quartz
quartz monzonite,
monzonite, from
from a layered
layered
gneiss consisting
consisting of
of alternating
alternating pink
leucogranitic gneiss
pink microcline-rich
microcline-rich bands
bands and
and yellow
yellow
plagioclase-rich bands.
bands. Numerous
inclusionsofof tonalitic
tonalitic gneiss
gneiss are
are contained
contained in
in the
the
plagioclase-rich
Numerous inclusions
quartz monzonite
quartz monzonite
monzonitelies
lies toto the
the north,
monzonite sills.
sills. More
More quartz
north, with
with tonalitic
tonalitic
gneisses again
again cropping
cropping out
out across
across the
the river.
gneisses
The
represent the oldest
The interlayered
interlayered tonalitic
tonalitic gneisses
gneisses and
and amphibolites
amphibolites represent
oldest
Isoclinal folding
foldingand
andshearing
shearingwithin
withinthe
the unit
unit indicate
rocks exposed
exposed in
in the
the area. Isoclinal
rocks
deformation
and probable
probable metamorphism
metamorphismprior
priortoto the
the intrusion
intrusion of
of the quartz
deformation and
quartz
monzonite. Field
monzonite.
Field relations
relations and
and modal
modal data suggest
suggest that
that the
theplagioclase-rich
plagioclase-rich bands
bands
of
are part
of the
the layered
layered leucogranitic
leucogranitic gneiss
gneiss are
part of
of the
thetonalitic
tonaliticgneiss
gneisscomplex.
complex.
Mineral
textures and
Mineral textures
and modal
modal data also
also suggest
suggest aa possible
possible relationship
relationship between
between the
microdine-rich
microcline-rich bands
bands of
of the
the layered
layered leucogranitic
leucogranitic gneiss
gneiss and
and the
thepyroxene
pyroxene syenite.
syenite.
Although the
the microcline-rich
microcline-rich bands
bands of
of the layered leucocratic
Although
leucocratic gneiss
gneiss are
are somewhat
somewhat
the syenite
more
more quartz-rich
quartz-rich it is thought
thought that desilication
desilication of
of the
syenite occurred
occurred by
by
conversion of
of aa former
former amphibolite
conversion
amphibolite to aa pyroxene-rich
pyroxene-rich rock,
rock, during
during the intrusion
intrusion of
a potassium-rich
potassium-rich magma. This
This reaction
reactionisisevidenced
evidenced by
by the
the zoning
zoning of
of the
the inclusions
inclusions
within the
the syenite.
within
The
following sequence
sequence of
of events
events is
is thought to have
The following
have occurred: (1)
(1) deformation
and metamorphism
and
metamorphism of a volcanic pile forming
forming the
the tonalititc gneisses and
amphibolites;
(2) dilatation
dilatation of
of the gneiss
followed by
by infiltration
infiltration of
of a
amphibolites; (2)
gneiss sequence
sequence followed
potassium-rich magma
magma into
into the
the rupture zones, forming
potassium-rich
forming the pyroxene
pyroxene syenite and the
layered leucogranitic gneiss;
intrusion of
of the
the quartz monzonite.
gneiss; (3)
(3) intrusion
70
�FIELD
TRIPS
�I
FIELD TRIP A
FIELD
MINNESOTA RIVER VALLEY
MINNE50TA
VALLEY
FIELD TRIP AND
FIELD
AND CONFERENCE
No formal
formal guidebook
for the
the Minnesota
No
guidebook for
Minnesota River
River Valley
Valley Field
Field Trip
Trip has
has
been prepared
prepared at the
been
the specific
specific request
request of
ofS.S.
5.5. Goldich,
Goldich, convenor.
convenor.
Abstracts of talks
talks given
given at
at the
theTuesday
Tuesday evening
evening discussion
discussion at
RedwoodFalls
Fallsare
areincluded
includedasasa apart
partofof these
these Proceedings.
Proceedings. A
Redwood
A collection
collection of
of
reprints pertaining
reprints
pertaining to the
the geology
geology of
of the
theMinnesota
Minnesota River
River Valley
Valley and
and an
an
informal set
set of stop
informal
stop descriptions
descriptions will
will be
be provided
provided to the
the participants.
participants.
However,inasmuch
inasmuchasasthe
thelatter
latter are not
However,
not quotable
quotable for
for publication
publication they are
not included
included here.
73
73
I
�•
FIELD TRIP BB
ENGINEERING
GEOLOGY, PLEISTOCENE GEOLOGY AND
ENGINEERING GEOLOGY,
GEOMORPHOLOGY IN THE
THE TWIN
TWIN CITIES AREA
AREA
INTRODUCTION
INTRODUCTION
8:00
May 5th
5th St. Paul
8:00 a.m. Wednesday,
Wednesday, May
Paul Radisson
Radisson Hotel,
Hotel, St.
St.
Paul.
cost parking
parkingisis available
available just
just across
across the
the river
river from
Paul. Low
Low cost
from the
the hotel,
hotel,
immediately
west of the
immediately west
the first
firstexit
exitfrom
fromthe
theWabasha
WabashaAvenue
Avenue bridge.
bridge. Field
Field
clothes are recommended
for underground
construction inspection.
inspection. Bring
recommended for
underground construction
Bring aa
hard
by bus
bus to
to the
hard hat if
if you
you have
have one.
one. Transportation
Transportation by
the University
University of
of
Assemble:
Assemble:
Minnesota
pus.
Minnesota cam
campus.
a.m.,back of Pillsbury
Optional
Optional Assembly
Assembly Point:
Point: 8:30
8:30 a.m.,back
Pillsbury Hall,
Hall, University
University of
of
Minneosta
campus. Near-by
opportunities are
are limited. Those who
Minneosta campus.
Near-by parking
parking opportunities
who
find it convenient
may join
join the
the field
field trip
trip at this point rather than
find
convenient to do
do so
so may
than
going
Paul.
going to
to St. Paul.
MORNING ITINERARY
MORNING
The
will divide
divide into
into two
two equal
at the
The excursion
excursion will
equal groups
groups at
the University
University of
of
Minnesota
campus. One
One group
groupwill
willbebetransported
transportedtoto site
site A
A by
by bus
bus for
for the
Minnesota campus.
on foot
foot to site B.
first half
half of
of the
the morning.
morning. The
The second
second group
group will
will proceed
proceed on
B.
In mid-morning
mid-morningthe
the two
two groups
groups will
willexchange
exchangesites
sites via
via bus
bustransportation.
transportation.
In
Site A;
Site
A; Como
Como Avenue
Avenue Storm
Storm Sewer
Sewer Tunnel.
Tunnel r City
City of
ofMinneapolis:
Minneapolis: Ralph
Rabus
and Ray
Ray Sterling;
Sterling; guides)
guides) The
The portal
portal of
of the
the tunnel
tunnel isis located
located at the
Rabus and
the
foot of the
River on
on the
the northeast bank
foot
the bluffs
bluffs along
along the
the Mississippi
Mississippi River
bank about
The site
site affords
view of
of the
half a mile
half
mile below
below St.
St. Anthony
Anthony Falls. The
affords aa good
good view
incised gorge
gorge of
of the Mississippi,
carved since
since the
the end
incised
Mississippi, carved
end of
of the
the Pleistocene
Pleistocene
glaciationasas St.
St. Anthony
AnthonyFalls
Fallsretreated
retreatedfrom
fromits
its original
originalsite
site at
at the
glaciation
confluence of
of the Minnesota
and Mississippi
Riverstotoits
its present
present site,
confluence
Minnesota and
Mississippi Rivers
about 88 miles
miles upstream.
upstream. The
about
The falls
falls is
is now
now stabilized
stabilized by a lock
lock and
and dam
dam as
facilities for
control and
well as water control
and diversion facilities
for the experimental
experimental
operations of
of the St.
operations
St. Anthony
Anthony Falls
Falls Hydraulic
Hydraulic Laboratory of the University
University
of Minnesota.
Abovethe
the falls
falls the
the river
river flows
flows on
on aa pavement
pavement of
of hard,
hard, slabby
slabby
Above
Platteville Limestone.
Limestone.
The Platteville
Platteville Limestone
is underlain
by two
two to
The
Limestone is
underlain by
75
�three feet
feetofofsoft
softshale,
shale,known
knownasasthe
theGlenwood
Glenwood Formation,
Formation, beneath
beneathwhich
which
is the St.
St. Peter
PeterSandstone,
Sandstone, aa light
light yellow
yellow to
to almost
almost white,
white, medium-grained
medium-grained
to fine-grained,
fine-grained, friable
friable sandstone
sandstone composed
composed almost entirely
entirely of
of well
well rounded
rounded
but
of quartz sand
or two
but frosted grains
grains of
sand with
with one
one or
two percent of
of clay
clay binder.
binder.
The
is very
The sandstone
sandstone is
very massive,
massive, and
and in
in many
many exposures
exposures appears
appears to
to have
have
almost no
no bedding.
bedding. It is
is about
about 150
150 feet thick
thick in
in the
theTwin
Twin Cities
Cities basin.
basin.
These
formations are
are well
exposed inin the
the river
These formations
well exposed
river bluffs
bluffs visible
visible from
from the
the
portal site.
A
storm sewer
A storm
sewer tunnel,
tunnel, 10
10 feet in
in diameter,
diameter, is
is being
being excavated
excavated in
in the
St. Peter Sandstone
by hydraulic
hydraulicmining
miningmethods.
methods. AA jet
jet of
of water directed
Sandstone by
directed
at the
the St.
St.Peter
PeterSandstone
Sandstoneloosens
loosensthe
theclay
claybinder
binderand
andthe
therock
rockdecomposes
decomposes
into a slurry
into
slurry of
of incoherent
incoherent sand.
sand. The
The properties
properties of the
the sandstone
sandstone which
which
allow
it to
allow it
to be
be mined
mined by
by this
this method
method also
also allow
allow the
the rock
rock to
to ravel
ravel upon
upon
exposure, especially
especially where
where skin
skin stresses
exposure,
stresses are
are developed
developed ininunderground
underground
at the
The Department
Department of
of Civil
Civil and
and Mineral
Mineral Engineering
Engineering at
the
openings. The
University
of Minnesota
has developed
University of
Minnesota has
developed aa sodium
sodium silicate based
based chemical
chemical
grout which
grout
which penetrates porous
porous rocks
rocks and
and hardens
hardens to consolidate
consolidate the rock
rock
into aa strong,
strong, durable
durable material.
material. The
is sprayed
sprayed on
on the
the surface
surface of
of the
into
The liquid
liquid is
tunnel to form
tunnel
form aa strong
strong skin,
skin, which
which supplies
supplies all of the
the support
support needed
needed where
where
has not
not been
the St. Peter
Peter Sandstone
Sandstone has
been adversely
adversely affected by
by fracturing and
and
In weaker
weaker zones
decomposition. In
zones shotcrete and
and epoxy-cemented
epoxy-cemented rock
rock bolts
bolts
are used
used for additional support.
Research
Research by
by Walter
Walter Parham
Parham of
of the
theMinnesota
Minnesota Geological
Geological Survey
Survey has
has
shownthat
that the
the primary
primary clay
clay minerals
minerals inin the
the St.
St. Peter Sandstone
are illite
shown
Sandstone are
and montmorillite,
montmorillite, which
which form
form an
an effective
effective binder,
and
binder, even where present in
in
where these clays
very
small quantities. In
very small
In zones
zones where
clays have
have been
been converted
converted by
by
diagenesis toto kaolinite,
kaolinite, the
the kaolinite
diagenesis
kaolinite tends
tends to occupy
occupy interstices between
between
sand grains,
grains, rather
rather than
than coating
sand
coating the grains,
grains, and
and much
much of the intergrariular
intergranular
slight change
cohesion
This slight
change in
in mineralogy
mineralogy greatly weakens
weakens the St.
cohesion isis lost. This
Peter Sandstone
and has
has strongly
strongly affected underground
Sandstone and
underground construction locally
locally
This phenomenon
phenomenondoes
doesnot
not appear
appear to
to have
in the Twin
in
Twin Cities
Cities area. This
have been
been
encountered
encountered in
in the
the present tunnel.
Experimental Tunnel
Tunnel and
and Test
Site B;
Test Chamber:
Chamber: (Donald
(Donald Yardley
Yardley and
and
13; Experimental
Charles Nelson,
guides). The
Charles
Nelson, guides).
The Department
Department of
of Civil
Civil and
and Mineral
Mineral Engineering
Engineering
at the
at
the University
University of
of Minneosta,
Minneosta, aided
aided by
by aa grant
grantfrom
from NSF-Rann,
NSF-Rann, is
is
construting an
an experimental
experimental tunnel
tunnel and
and large underground
chamber beneath
construting
underground chamber
76
�I
the University
University of Minnesota
Minnesota campus
campus to develop
develop construction
construction methods
methods and
and
structural parameters
spaces. One
parameters for the
the design
design of
of large
large underground
underground spaces.
One of
of
the primary
is to take advantage
primary purposes
purposes is
advantage of
of the
the very
very large
largeenergy
energy savings
savings
that may
may be
be achieved
achieved through
through the
the better
better use
useofofunderground
underground space.
space.
Underground space also
also provides
provides opportunities
opportunities for
for relieving
relieving urban
urban congesconges-
tion
tion and
and mitigating
mitigating the
the environmental
environmental impacts
impacts of many
many transportation,
transportation,
industrial and
and utility facilities.
The
will be
The experimental
experimental excavation
excavation will
be entered
entered through
through an
an existing
existing
steam tunnel
tunnel of the
the University
University heating
heating system
system (The
(The temperature
temperature is
is high.
high.
steam
Be
to shed
prepared to
shed your
your jacket).
jacket). At
At one
one point
point in
in the
the passage
passage through
through the
Be prepared
concrete-lined steam tunnel there is
is an
an intersection
intersection with
with an
an unlined
unlined tunnel.
tunnel.
This
tunnel, excavated
excavated in
in the
the St.
This tunnel,
St. Peter
Peter Sandstone,
Sandstone, exhibits
exhibits a persistent,
persistent,
vertical crack or fissure in its crown
which makes
makesitit appear
appear that
that the
crown which
the tunnel
tunnel
follows aa vertical joint
joint zone.
zone. In
In fact, the
the fissure
fissure has
has developed
developed as
as the
the
follows
result of the tensional
characteristically develops
tensional stress which
which characteristically
develops in
in the crown
crown
of a circular
circular arch
archininan
anunderground
underground structure
structure when
when the
the overlying
overlying load
load is
is
of
shifted
from the
the rock
that was
to the
the rock
on either
either side
side of
of the
shifted from
rock that
was removed
removed to
rock on
tunnel in
arch.
tunnel
in the
the abutments to the arch.
The stratigraphic
stratigraphic succession
successionatat the
the site consists
The
consists of: Glacial
Glacial drift, 45
45
St. Peter
Platteville limestone,
30 ft.;
ft.; Glenwood
shale, 44 ft.
ft. to 55 ft.;
ft.; Platteville
limestone, 30
Glenwood shale,
ft.; St.
Peter
sandstone, penetrated
penetrated 99 ft.
ft. to 10
ft. at
sandstone,
10 ft.
at invert
invert elevations.
elevations.
The experimental
tunnel and
and chamber
chamber isis partly
partly excavated
The
experimental tunnel
excavated in weak
weak
shale
of the Glenwood
Formationand
andpartly
partly in
in St.
St. Peter
shale of
Glenwood Formation
Peter Sandstone.
Sandstone. The
roof
the chamber
chamber is
is formed
formed by
by hard,
hard, slabby
slabby limestone
roof of the
limestone of
of the Platteville
100feet
feet of
of unlined
access tunnel
tunnel isis traversed
Formation. About
About 100
unlined access
traversed in the
the
GlenwoodFormation,
Formation,a ashale
shaleunit,
unit,two
twototo three
three feet thick,
Glenwood
thick, characterized
characterized
by aa persistent
by
persistent soft mud
mud seam
seam about
about one
one inch
inch thick
thick containing
containing pyrite
pyrite
The shale
severe deterioration
and air
crystals. The
shale shows
shows severe
deterioration and
air slaking
slaking due
due to
to
exposure.
About 70
70 feet
feet of
excavated in
in St.
St. Peter
About
of the access
access tunnel
tunnel have
have been
been excavated
Sandstonewhich
whichhas
hasbeen
been grouted
grouted by
by spraying
spraying with
with the
the sodium
Sandstone
sodium silicate
compound
A.
compounddescribed
described under
under Site
Site A.
Another 70
70feet
feet of
of the
the tunnel
Another
tunnel in
in St.
Peter Sandstone
Sandstone has
has been
beenleft
left untreated as a control.
The test
test chamber
is in
of excavation.
excavation. A
The
chamber is
in the process
process of
A drift
drift has
has been
been
driven the
the full
full length
lengthofof 100
100feet,
feet, and
and aa cross
cross drift has been
driven
been driven
driven the full
width of
of 50
50 feet.
feet. The
in one
one section
section to
to 20
20 feet.
feet.
width
The long
long drift
drift has
has been
been widened
widened in
Thecompleted
completedchamber
chamberwill
willbebe100
100byby5050feet,
feet,8 8feet
feethigh.
high. The
The Platteville
Platteville
The
77
77
I
�Limestone
will form
form the
the roof
roof of
of the
the chamber.
Limestone will
chamber. The
The invert
invert will
will be
be in
in the
the St.
St.
Peter Sandstone.
from the
the roof
will cut
cut about
Sandstone. The
The walls
walls from
roof down
down will
about 4 feet of
of
Glenwood
shale and
andabout
about 44feet
feet of
of St. Peter
Glenwood shale
Peter Sandstone.
Sandstone.
Excavation
of the
the access tunnels
Excavation of
tunnels and
and chamber
chamber has
has been
been entirely
entirely by
by
hand
using pneumatic
pneumatic drills
drills and
and spades
hand operations,
operations, using
spades and
and hydraulic
hydraulic rock
rock
splitters. This
This has
has been
been necessitated
necessitated by
by the small
small size of the access
access tunnels
both the
the St. Peter
(4
(4 feet wide
wide by
by 6.5 feet
feet high).
high). However
However both
Peter Sandstone
Sandstone and
and
the Glenwood
shale are
are readily
readily excavated
excavated in
in this
Glenwood shale
this way.
way. The
The hydraulic
hydraulic rock
rock
splitters have
very useful
useful in
in spalling
spallingoff
off the
the shale
splitters
have proved
proved very
shale to the
the bedding
bedding
surface in the
surface
the overlying
overlying Platteville
Platteville Limestone
Limestone which
which has
has been
been chosen
chosen to
to
form
form the roof. As
As construction
construction proceeds,
proceeds, the
the underground
underground chamber is being
being
thoroughly
instrumentedtoto determine
determine rock
rock deflections,
deflections, stresses,
stresses, and
thoroughly instrumented
and the
influence
of an
an overlying
overlying perched
perched water
water table on
structure.
influence of
on the underground
underground structure.
Instrumentation includes six-point extensometers,
extenso meters, two-point extensometers, and
the roof
meters,
and inverted
inverted piezometers
piezometers installed
installed from
from below
below through
through the
roof
into the perched
into
perched water
water table
table above
above the
the Platteville
PlattevilleLimestone.
Limestone. A boresupport for
for the roof
scope is being
used to
to examine drill
being used
dr ill holes. Principal
Pr incipal support
roof is
is
provided
by epoxy-grouted
rock bolts
provided by
epoxy-grouted rock
bolts which
which consolidate
consolidate the
the overlying
overlying
Platteville Limestone
Limestone into a rigid
rigid plate.
Noon:
Box lunch picnic.
Noon: Box
AFTERNOON ITINERARY
ITINERARY
Stanley Chernicoff, Field Leader
Stanley
Leader
the Twin
The
surficial geology
geology of
of the
Twin Cities
Cities Metropolitan
Metropolitan Area
Area is
is
The surficial
dominatedby
bythe
the effects
effects of
of the late
dominated
late Pleistocene
Pleistocene glaciation
glaciation of
of Minnesota.
Minnesota.
The glacial
glacial events
events that modified
are reconstructed
The
modified the regional
regional landscape
landscape are
by interpreting
the deposits
of glacial
by
interpreting the
deposits of
glacial materials
materials and
and their
their associated
associated
landforms.
landf or ms.
In the Metro
In
Metro area,
area, glacial
glacial deposits
deposits from
from two
two points
points of
of origin
origm have
have
been identified.
identified. Approximately
years ago,
ago, an
an ice lobe accumulating
been
Approximately 20,000
20,000 years
basin advanced
in the Lake Superior basin
advanced along
along aa bedrock
bedrock conduit
conduit (the
MinneapolisLowland)
Lowland)totoaa terminal
Minneapolis
terminal position
position topographically
topographically expressed
expressed
locally as
as the St. Croix
locally
Croix moraine.
moraine. This
This land
land form, characterized by
by hills
hills and
and
is composed
of poorly
depressions
ice-block lakes,
lakes, is
composed of
poorly sorted
sorted
depressions dotted
dotted with
with ice-block
traversed eastern
mineral constituents
constituents entrained
entrained by
by the
the glacier
mineral
glacier as
as it traversed
eastern
78
�Minnesota. The
quantities of red
The bedrock
bedrock supplied
supplied quantities
red sandstone,
sandstone, basalt,
basalt, and
and
red
that impart
impart the
the characteristic
red granophyre
granophyre that
characteristic red
red hue
hue to
to Superior
Superior lobe
lobe
drift.
drift.
Approximately
16,000 years
years ago,
Approximately 16,000
ago, ice
ice originating
originating in
in southeastern
southeastern
Manitoba
and northwestern
northwestern Minnesota
Minnesota advanced
advanced along
along the
the Red River
Manitoba and
River valley
valley
toward a terminal
terminal position
position near
near Des
Des Moines,
Moines, Iowa.
Iowa. A
A short-lived
short-lived extension
extension
of the
the Des
Des Moines
Moines lobe
lobe (the
(the Grantsburg
Grantsburg sublobe)
sublobe) entered
entered the
the Minnesota
Minnesota
lowland
from the
the southwest
across the northwest
lowland from
southwest and
and proceeded
proceeded across
northwest corner of
the metropolitan
the recently
metropolitan area overriding
overriding the
recently deposited
deposited red
red glacial
glacial drift.
The
of the Grantsburg
are markedly
different from
The deposits
deposits of
Grantsburg sublobe
sublobe are
markedly different
from the
Superiorlobe
lobematerials.
materials. A
long its
its route
route of
of advance,
advance, the
the ice
ice traversed
Superior
A long
traversed a
sedimentary
sedimentary terrane
terrane incorporating
incorporating fragments
fragments of
of Paleozoic
Paleozoic limestone,
limestone,
The
and the
dolomite,
dolomite, and
and siliceous
siliceous shale.
The carbonate
carbonate composition
composition and
the
diagnostic grey
grey color
color (yellow
(yellow or tan
tan in
in oxidized
oxidized exposures)
exposures) easily
easily distinguish
distinguish
sublobe drift from
Grantsburg sublobe
from the
thereddish—colored
reddish-colored Superior lobe sediments.
A field review
review of the
the geology
geology of
of an
an urban
urban center
centershould
should describe
describe the
the
geologic character
character of
of the area and,
geologic
and, wherever
wherever possible,
possible, relate the
the observed
observed
physical conditions
conditionstoto their
their land-use
land-use potential.
potential. The
The object
object of
of this part of
physical
of
the excursion
to introduce
the salient features
excursion isis to
introduce the
features of
of the
thelocal
localgeology
geology and
and
promote discussion
regarding responsible
responsible urban
urban development
development within
within the
promote
discussion regarding
geologic framework.
ace:
Stop
Grey Till
Till - Red Till
Till Interf
Interface:
Stop C;
C; Grey
New
New Brighton
Brighton Quadrangle
Quadrangle - N.
The stratigraphic relationship
and Matterhorn
Matterhorn Drive.
Drive.
Danube Road
Road and
Danube
till and
between the
the red
between
red Superior
Superior lobe
lobe till
and the
theoverlying
overlying grey
grey Grantsburg
Grantsburg
of red
red till have
sublobetill
till isis demonstrated
demonstrated at
at this
sublobe
this locality. Masses
Masses of
have been
been
incorportated into
into the
the grey
till creating the thin
incorportated
grey till
thin interlaminations.
interlaminations.
Stop
D; Anoka
Anoka Sandplain:
Sandplain:
Stop ID;
New Brighton
Quadrangle-County Road
Road I and
New
Brighton Quadrangle-County
and
Lexington Ave.
Ave. Sand-charged
Sand-chargedmeltwaters
meltwatersassociated
associated with
with the
the wastage
Lexington
wastage of
of
the Grantsburg
sublobe constructed
constructed this
this extensive
extensive sandplain.
sandplain. The
the
Grantsburg sublobe
The plain is
characterized by
characterized
by ice-block
ice-block depressions
depressions and sand
sand dunes.
dunes.
The high
The
high water
of the relatively
table is a consequence
consequence of
relatively low
low transmissivity
transmissivity of
of the
the underlying
underlying
glacial till.
glacial
River;
Abandoned Valley
Valley of the Mississippi
Stop Ej
Mississippi Riverj
E; Abandoned
Quadrangle—WheelockParkway
Parkwayand
and Nebraska
Nebraska Ave.
Quadrangle-Wheelock
Ave.
79
Paul East
St. Paul
East
Alongthe
the route
Along
route of
of
�travel
travel from
from the
theAnoka
Anoka Sandplain
Sandplain to this locality, the
the alignment
alignment of
of ice-block
ice-block
lohanna, Josephine,
Josephine, McCarron)
McCarron) represents
represents a
lakes (Round,
(Round, Valentine, Johanna,
lakes
former course
course of
of the
theMississippi
Mississippi River.
River. The
The bedrock
bedrock valley
valley is buried
buried by
by
deep deposits of glacial drift.
drift.
Stop
Park: St. Paul
Stop F;
Fi Indian
Indian Mounds
Mounds Park:
Paul East
East Quadrangle
Quadrangle -- Warner Road. This
This
site affords
affords aa view
view of
of the
theMississippi
Mississippi River
River floodplain.
floodplain. The
The geological and
and
environmental
elements of
environmental elements
of the floodplain
floodplain management
management issue
issue (ie. the
construction
of dikes
dikes at
at the Holman
construction of
Holman Field
Field airport
airport and
and the Pig's
Pig's Eye
Eye coal
coal
terminal) are visible.
visible.
Stop
Stop G;
G; Perched Lake
Lake Plains
Plains within
within the
the St.
St.Croix
CroixMoraine:White
Moraine:White Bear
Bear Lake
Lake
This
This level
level plain
plain
represents
reversalofofaa glaciated
glaciatedterrain.
terrain. At
represents aa characteristic topographic
topographic reversal
At
one
byice
ice that
that fed
one time,
time, the plain
plain was
was surrounded
surrounded by
fed meitwater
meltwater into
into an
an
East Quadrangle
East
Quadrangle - County Highway
Highway 99 and
and 115
115 St.
St.
The subsequent
subsequent wastage
wastage of
of the surrounding
enclosed basin.
basin. The
surrounding ice resulted in
in
the perching
perching of basin
basin sediments
sediments above
above the surface
surface previously
previously covered
covered by
by
ice.
Stop Hi
H; Land-Use
Land-Use Planning
PlanningininaaGlaciated
Glaciated Terrain:
Terrain: Marine
Stop
Marine on
on the St. Croix
This
This site was
was one of
of
several proposed
County Sanitary
Sanitary Landfill.
Landfill. The
proposed for the
the Washington
Washington County
The glacial
glacial
drift of the
drift
the locality
locality includes
includes a mantle
mantle of
of bess
loess(windblown
(windblown silt) and
and dense
dense
red till. The
red
The suitability
suitability of
of this
this site
sitefor
foraalandfill
landfillwill
will be
be discussed.
discussed.
81 (May
Ave.) and
and 155
Quadrangle - County Road 81
Quadrangle
(May Ave.)
155 St.
80
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Dublin Core
The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/.
Title
A name given to the resource
Institute on Lake Superior Geology
Dublin Core
The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/.
Title
A name given to the resource
Institute on Lake Superior Geology: Proceedings, 1976
Description
An account of the resource
Institute on Lake Superior Geology. St. Paul, Minnesota. May 3-7, 1976.
Creator
An entity primarily responsible for making the resource
Institute on Lake Superior Geology
Date
A point or period of time associated with an event in the lifecycle of the resource
1976
Contributor
An entity responsible for making contributions to the resource
B.E. Aaquist
J.L. Anderson
G.A. Ankenbauer
Larry L. Babcock
W.A. Bartlett
Robert L. Bauer
J. Baysinger
G.P. Beakhouse
Dieter Birk
Bill Bonnichsen
Emmy Booy
J.M. Bratt
Charles Brumleve
James R. Burnell, Jr.
Keros Cartwright
E.N. Cameron
W.F. Cannon
C.L. Chou
Donald M. Davidson, Jr.
James M. DeGraff
B.R. Doe
M.H. Delevaux
L.J. Drew
Stanley J. Dyl
Robert Ehrlich
S.S. Goldich
A.M. Goodwin
C.F. Gower
James G. Grimes
N.B.W. Harris
Henry Halls
Tsu-Ming Han
G.N. Hanson
C.E. Hedge
Sue I. Jacobsen
Allan M. Johnson
Manfred M. Kehlenbeck
Gene L. LaBerge
T.M. Levy
M.S. Lougheed
R.S. Maass
J.J. Mancuso
M.B. McBride
Lyle D. McGinnis
L.G. Medaris, Jr.
Robert P. Meyer, Jr.
Robert Moore
M.G. Mudrey, Jr.
Paul E. Myers
Syed Neaz Ahmad
Edward L. Nebrija
C.R. Nelson
B.V. Nielsen
Richard W. Ojakangas
Bruce C. Parker
Eugene C. Perry, Jr.
Zell E. Peterman
H.O. Pfannkuch
Dave Pollack
Neil M. Pope
William C. Prinz
V. Rama Murthy
C. Riddle
James M. Robertson
W. Rohrer
Frederick J. Sawkins
K.J. Schulz
Nancy Scofield
Donald I Siegel
P.K. Sims
Eugene I. Smith
T.E. Smith
Harry O. Sorenson
David W. Snider
David L. Southwick
S.W. Stuhr
F.M. Swain
R.U. Suda
R.M. Tyson
A. Turek
W.R. Van Schmus
Thomas A. Vogel
L.J. Walters
P.W. Weiblen
James L. Welsh
Wendell E. Wilson
J.L. Wooden
D.H. Yardley
Charles T. Young
Robert E. Zartman
Format
The file format, physical medium, or dimensions of the resource
PDF
Language
A language of the resource
English
-
https://digitalcollections.lakeheadu.ca/files/original/e35ceec1dbed2f5f4680805765eddaaa.pdf
dd07255052a20bd1b07f793d1b8cec30
PDF Text
Text
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Dublin Core
The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/.
Title
A name given to the resource
Institute on Lake Superior Geology
Dublin Core
The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/.
Title
A name given to the resource
Institute on Lake Superior Geology: Proceedings, 1975
Description
An account of the resource
Institute on Lake Superior Geology. Northern Michigan University, Marquette, Michigan. April 30-May 4, 1975.
Creator
An entity primarily responsible for making the resource
Institute on Lake Superior Geology
Date
A point or period of time associated with an event in the lifecycle of the resource
1975
Contributor
An entity responsible for making contributions to the resource
D. Jay Johnson
J.R. Mangham
M.L. Cummings
J. Wood
Norris W. Jones
Eugene I. Smith
P.K. Sims
Zell E. Peterman
Frank W. Holcomb
S.C. Nordeng
B.M. Hamil
A.M. Johnson
Milton A. Gere Jr
E. Wm. Heinrich
David G. Meineke
K.B. Rundman
J.J. Mancuso
M.S. Lougheed
R. Seavoy
R. Shaw
Erich Dimroth
Ronald F. Bacon
G.E. Frantti
Lloyal O. Bacon
John H. Karl
S. Chaudhuri
D.T.A Symons
L.J. Pesonen
C. Patrick Ervin
M.G. Mudrey Jr
Format
The file format, physical medium, or dimensions of the resource
PDF
Language
A language of the resource
English
-
https://digitalcollections.lakeheadu.ca/files/original/eddbd61b970180849763678b02b3769c.pdf
1ac2e8ab662d00b13fc5c7262915a1e8
PDF Text
Text
������������������������������������������������������������������������������������������������������������������������������������������������������������������������
Dublin Core
The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/.
Title
A name given to the resource
Institute on Lake Superior Geology
Dublin Core
The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/.
Title
A name given to the resource
Institute on Lake Superior Geology: Proceedings, 1974
Description
An account of the resource
Institute on Lake Superior Geology. Sault College of Applied Arts and Technology, Sault Ste. Marie, Ontario. May 1-5, 1974.
Creator
An entity primarily responsible for making the resource
Institute on Lake Superior Geology
Date
A point or period of time associated with an event in the lifecycle of the resource
1974
Contributor
An entity responsible for making contributions to the resource
L.L. Babcock
Ronald F. Bacon
R.L. Bauer
Emmy Booy
Theodore J. Bornhorst
W.F. Cannon
B.A. Carlson
W.J. Hinze
Jeffery L. Clarke
A.R. Coyner
K.J. Freeman
T.A. Vogel
Gene L. LaBerge
John C. Green
H.C. Halls
J.B. Heslop
W.M. Tupper
D.G. Innes
J. Kalliokoski
William H. Listerud
M.S. Lougheed
J.J. Mancuso
P.R. Mainwaring
A.J. Naldrett
S.C. Nordeng
David I. Norman
R.V. Oja
Richard W. Ojakangas
James M. Robertson
A.P. Ruotsala
C.A. Salotti
D. Weirauch
R.W. Sersor
P.C. Thurston
N.F. Trowell
M.A. Vos
P.I. Wallace
J.W. Cosgrove
P.M. Clifford
David H. Watkinson
Format
The file format, physical medium, or dimensions of the resource
PDF
Language
A language of the resource
English
-
https://digitalcollections.lakeheadu.ca/files/original/11c9d1d86b50e5a7348f083a877476c3.pdf
671b46482ec80859cddc170b04d8d1d3
PDF Text
Text
C O O P E R A T I V E EXTENSION
E X T E N S I O N PROGRAMS
PROGRAMS
COOPERATIVE
I University
U n i v e r s i t yofo fWisconsin—Madison
Wisconsin-Madison
U n i v e r s i t y of
o fWisconsin—Extension
Wisconsin-Extension
University
Nineteenth Annual
Annual
Nineteenth
Lake Superior
Superior Geology
Geology
Institute on Lake
May 3-6,1973
3-6,1973
Madison,
Madison, Wisconsin
Wisconsin
I
P1
ERTS-1 satellite Photo
Far infrared band
photographed on August 12, 1972
Sponsored
Sponsored by the
the
Geological and
and Natural
Natural History
History Survey
Survey
Wisconsin Geological
Extension
Wisconsin - Extension
University of Wisconsin
and the
Departments
of the
theUniversity
University of
of Wisconsin
WisconsinSystem
System
Departments of
of Geology of
-
�Technical Program
Program
and
Abstracts
ffor
or
tthe
h e 19th Annual
GEOLOGY
INSTITUTE ON LAKE SUPERIOR GEOLOGY
held
held at
at
Sheraton Inn
Inn
Madison, Wisconsin
May
May 3—6,
3-6, 1973
1973
�MADISON
PRAIRIE
Central
South
South --Central
MADISON,
MADISON, WISCONSIN
WISCONSIN
OREGON
OREGON
4
0
SHERATON
SHERATON INN
INN
1
1
MADISON
MADISON INN
INN
22
MAYFLOWER
MAYFLOWER MOTEL
MOTEL
33
44
NATIONAL
NATIONAL MOTOR
MOTOR INN
INN
55
QUALITY
QUALITY INN
INN
66
Short
Short Course
Course Dorms:
Dorms:
77
MURPHY'S
MURPHY'S
88
99
POOLE'S
POOLES
PARK
PARK MOTOR
MOTOR INN
INN
HUMPHRY
HUMPHRY HALL
HALL
JORNS
JORNS HALL
HALL
RESTAURANT
RESTAURANT
CUBA
CUBA CLUB
CLUB
ROHOE'S
ROHDES STEAK
STEAK HOUSE
HOUSE
10
107777SIRLOIN
SIRLOIN
STRIP
STRIP
11 DEPARTMENT
DEPARTMENT of
of GEOLOGY
GEOLOGY
11
and
and GEOPHYSICS,
GEOPHYSICS, SCIENCE
SCIENCE HALL
HALL
12
GEOLOGICAL
12WISCONSIN
WISCONSIN
GEOLOGICAL
and
and NATURAL
NATURAL HISTORY
HISTORYSURVEY
SURVEY
�19th
1 9 t h Annual
Annual
Institute
I n s t i t u t e of Lake Superior
S u p e r i o r Geology
Geology
Sheraton
Sheraton Inn,
Inn, Madison,
Madison, Wis.
Wis.
May
May 3—6,
3-6, 1973
1973
Sponsored
Sponsored by
by the
t h e Wisconsin Geological & Natural History Survey
Survey and
and
Departments of
of Geology,
Geology, the
t h e University
U n i v e r s i t y of
of Wisconsin
Wisconsin System.
System. Individuals
Individuals
from
from the
t h e U.S.
U.S. Geological Survey,
Survey, Department of Geology
Geology of
of the
t h e University
University
of
of Kansas,
Kansas, and
and the
t h e Inland
Inland Steel
S t e e l Corporation
Corporation also
a l s o contributed
c o n t r i b u t e d greatly
g r e a t l y to
to
arranging
arranging the
t h e program
program and
and field
f i e l d trips.
trips.
INSTITUTE
BOAFZI OF
OF DIRECTORS
DIWCTORS
INSTITUTE BOARD
* J.W.
J.W.
*
*
*
Avery
Avery (Treasurer),
( T r e a s u r e r ) , Jones
Jones && Laughlin
Laughlin Steel
S t e e l Corp.,
Corp.,
Negaunee,
Negaunee, Michigan.
Michigan.
R.D.
R.D. Reed
Reed (Secretary),
( S e c r e t a r y ) , Michigan
Michigan Geological
Geological Survey,
Survey,
Lansing
Lansing Michigan.
Michigan.
M.E.
M.E. Ostrom,
Ostrom, Wisconsin
Wisconsin Geological
Geological && Natural
Natural History
H i s t o r y Survey,
Survey,
Madison,
Madison, Wisconsin.
Wisconsin.
J.
J. Kalliokoski,
K a l l i o k o s k i , Michigan
Michigan Technological
Technological University,
University,
Roughton,
Houghton, Michigan.
Michigan.
D.M.
D.M. Davidson,
Davidson, Jr.,
Jr., Dept.
Dept. of
of Geology,
Geology, University
U n i v e r s i t y of
of
Minnesota
Minnesota at
a t Duluth,
Duluth, Duluth,
Duluth, Minnesota.
Minnesota.
M.W.
M.W. Bartley,
B a r t l e y , Thunder
Thunder Bay,
Bay, Ontario,
Ontario, CANADA
CANADA
* Permanent
Permanent members
members
*
LOCAL
LCZALCOMMITTEE
CWITTEE
M.E.
M.E. Ostrom,
Ostrom, Conference
Conference Chairman
Chairman
Technical
Technical Program
Program
C.
C. Craddock,
Craddock, Chairman
Chairman
B.
E. Cameron
Cameron
C.
C. Dutton
Dutton
G.
G. Medaris
Medaris
G.
G. Mursky
Mursky
Field
F i e l d Trips
Trips
M.
M. Roshardt,
Roshardt, Coordinator
Coordinator
W.
W . Broughton
Broughton
C.
Dutton
C. Dutton
A.
A. Heyl
Hey1
H.
H. Klemic
Klemic
G.
G. LaBerge
LaBerge
G.
G. Medaris
Medaris
P.
P. Myers
Myers
G.
G. Mursky
Mursky
J.
J. Ohlson
Ohlson
L.
L. Weis
Weis
W.
W. West
West
ft.
Van Schmus
R. Van
Schmus
11].
iii
Physical
P h y s i c a lArrangements
Arrangements
P.
P. Olcott,
O l c o t t Chairman
, Chairman
Short
Short Course
Course Office
Office
College
College of
of Agricultural
Agricultural
and
and Life
L i f e Sciences
Sciences
U n i v e r s i t y of
of Wisconsin—
WisconsinUniversity
Extension
Extension
�CARL
APPRECIATION
CARL E.
E. DUTTON
DIJTTON -- AN APPFZCIATION
Carl
Dutton's career
half
C
a r l Dutton's
c a r e e r in
i n geology extends through nnearly
early h
alf a
century,
and
most
of
this
time
his
headquarters
have
been
in
Science
century,
of t h i s
h i s headquarters
in
Hall
H
a l l on the
t h e Madison campus
campus of
of the
t h e University
U n i v e r s i t y of
of Wisconsin.
Wisconsin. H
has
Ree has
worked extensively
Michigan, Wisconsin,
Wisconsin, and Minnesota,
Minnesota, and he is
e x t e n s i v e l y in
i n Michigan,
is
well
Precambrian geologists
Superior
w
e l l known to
t o Precambrian
g e o l o g i s t s throughout
throughout the
t h e Lake S
uperior
meeting, h
his
t h e occasion of
of this
t h i s meeting,
i s ccolleagues
o l l e a g u e s and friends
f r i e n d s in
in
area. On the
Madison extend this
t h i s appreciation
a p p r e c i a t i o n for
f o r his
h i s many
many contributions.
contributions.
iv
�Carl
C a r l was
was born
born in
i n Dunkirk,
Dunkirk, Ohio,
Ohio, on
on January
January 24,
24, 1904.
1904. H
Hee was educated
DePauw University
University (LA.,
aatt DePauw
(B.A., 1926),
1926), the
t h e University
U n i v e r s i t y of
of Illinois
I l l i n o i s (M.A.,
(M.A., 1928),
1928),
and tthe
University
and
he U
n i v e r s i t y of
of Minnesota (Ph.D.,
(Ph.D., 1931).
1931). Carl
C a r l and
and Val
Val Dutton
Dutton have
have
two sons
professor
sons — John, a meteorology p
r o f e s s o r at
a t Pennsylvania
Pennsylvania State
S t a t e University,
University,
and Robert,
Robert, aa physician in
i n San
San Francisco
Francisco — and ffive
i v e grandsons. They have
have
H i l l s , just
j u s t west
w e s t of
of the
t h e Madison
Madison campus,
campus, since
s i n c e 1946.
1946.
llived
i v e d in
i n Shorewood
Shorewocd Hills,
Carl
C a r l has divided his
h i s life
l i f e between various
v a r i o u s academic positions
p o s i t i o n s and the
the
U.S. Geological
Geological Survey,
Survey, and
and he
he iis
widely respected
respected aas
s widely
s a tteacher
e a c h e r and a ffield
ield
U.S.
geologist.
Assistant
g e o l o g i s t . He was aa Teaching A
s s i s t a n t at
a t Illinois,
I l l i n o i s , an
an Instructor
I n s t r u c t o r at
at
Minnesota,
Assistant
Minnesota, and
and an
an A
s s i s t a n t Professor
P r o f e s s o r at
a t Wayne State
S t a t e University
U n i v e r s i t y and
and at
a t the
the
University
Hee joined
U
n i v e r s i t y of
of Michigan.
Michigan. H
joined the
t h e U.S.
U.S. Geological
Geological Survey
Survey in
i n 1943,
1943,
becoming Regional Geologist in
i n 1946
1946 and
and Research
Research Geologist
Geologist in
i n 1962.
1962. Since
has p
participated
Mineral Resources
Resources ccooperative
coming to
t o Madison he has
a r t i c i p a t e d in
i n tthe
h e Mineral
ooperative
program of
History
i s t o r y Survey and the
the
of the
t h e Wisconsin Geological & Natural H
U.S. Geological Survey,
Survey, he has taught
some cclasses
e c t u r e d in
i n tthe
he
U.S.
taught sane
l a s s e s & llectured
Department of Geology and
and Geophysics,
Geophysics, and
and he has been a valued counselor
and friend
f r i e n d to
t o many professors
p r o f e s s o r s and
and students.
students.
During his
Carl
h i s stay
s t a y at
a t the
t h e University
U n i v e r s i t y of
of Minnesota C
a r l was introduced
intrcduced
geological
problems of
of tthe
Canadian S
Shield
Professors
tto
o tthe
he g
e o l o g i c a l problems
h e southern Canadian
h i e l d by P
rofessors
Grout, John Gruner,
His
doctoral
dissertation
Frank Grout,
Gruner, and
and George
George Schwartz.
Schwartz. H
is d
octoral d
issertation
on the
t h e conglomerates and
and structure
s t r u c t u r e of
of the
t h e Ensign
Ensign Lake
Lake area,
a r e a , Cook
Cook County,
County,
Minnesota,
Minnesota, under Professor
P r o f e s s o r Gruner was the
t h e beginning of
of his
h i s life—long
life-long
Hee also
ffascination
a s c i n a t i o n with
with the
t h e Precambrian.
Precambrian. H
a l s o became interested
i n t e r e s t e d in
i n iron
iron
formations and llater
Michigan, eeventually
formations
a t e r began a rresearch
e s e a r c h program in
i n Michigan,
ventually
achieving
achieving international
i n t e r n a t i o n a l rrecognition
e c o g n i t i o n as
a s an authority
a u t h o r i t y on
on iron
i r o n ores.
o r e s . He
He
paper on U.S.
U.S. iiron
ore
deposits
att tthe
Geological
gave a paper
ron o
re d
eposits a
h e International
I n t e r n a t i o n a l Geological
Algiers
U.N. Committee on Iron Ore
Congress in
in A
l g i e r s in
i n 1952,
1952, served on tthe
h e U.N.
Resources in
1953-54, and spent
spent ssix
weeks sstudying
deposits
Resources
i n Geneva in
i n 1953-54,
i x weeks
t u d y i n g iron
iron d
eposits
AID
I D program in
i n Yugoslavia
Yugoslavia in
i n 1961.
1961. Carl
C a r l is
i s aa Fellow
Fellow of
of the
the
with the
the A
Society
of America
America and
and sserves
Membership S
Secretary
Geological S
o c i e t y of
e r v e s as
a s tthe
h e Membership
e c r e t a r y ffor
or
tthe
h e Society
S o c i e t y of
of Economic
Economic Geologists.
Geologists.
Through the
papers and
t h e years
y e a r s Carl
C a r l has
has produced
prcduced many
many papers
and geologic
geologic maps,
maps,
has worked
worked ffor
many y
years
and only aa few
few can
can be
be mentioned
mentioned here,
here. lie
H e has
o r many
e a r s in
in
the
district
of Michigan
Michigan and Wisconsin,
Wisconsin, and is
co—author
t h e Menominee iron
iron d
i s t r i c t of
i s GO-author
of USGS P.P.
i s also
a l s o co—author
co-author of
of USGS Maps MF—99
MF-99
of
P.P. 513
513 and
and Map
Map 1—466.
1-466.
He is
MF-l81 on the
He
and MF-181
t h e bedrock geology
geology of
of the
t h e Cuyuna
Cuyuna district,
d i s t r i c t , Minnesota.
Minnesota. He
iis
s widely known for
f o r aa series
s e r i e s of
of papers on
on iron
i r o n ore
o r e resources
r e s o u r c e s of
of the
t h e U.S.,
U.S.,
some foreign
f o r e i g n countries.
c o u n t r i e s . He is
i s co—author
co-author of
of USGS
USGS P.P.
P.P.
North America, and
and some
MF—225 on the
ore
deposits
of tthe
River—
570 and Map MF-225
t h e geology and o
re d
e p o s i t s of
h e Iron
I r o n RiverCrystal
C r y s t a l Falls
F a l l s district,
d i s t r i c t , Michigan.
Michigan. A very important contribution
c o n t r i b u t i o n is
i s aa series
series
of llithologic,
geophysical, and mineral
mineral commodity
commodity maps of
of Precambrian rocks
of
i t h o l o g i c , geophysical,
Wisconsin, published as
These maps are
iin
n Wisconsin,
a s USGS
USGS Map
Map 1—631.
1-631.
a r e aa complete
of a
available
Wisconsin Precambrian,
Precambrian, including
compilation of
v a i l a b l e information on tthe
h e Wisconsin
including
previously
unpublished d
data
numerous field
many p
r e v i o u s l y unpublished
a t a ccarefully
a r e f u l l y eextracted
x t r a c t e d from numerous
field
Carl
notebooks on hand in
i n the
t h e files
f i l e s of
of the
t h e State
S t a t e Survey.
Survey. IIn
n aaddition,
ddition, C
a r l has
has
written
has served as
w
r i t t e n papers ffor
o r several
s e v e r a l guidebooks and has
a s a leader
l e a d e r on many
ffield
i e l d trips,
t r i p s , both formal
formal and
and informal.
informal.
Carl
i s indeed
indeed a gentlemen and aa scholar
s c h o l a r in
i n the
t h e highest
highest
C a r l Dutton is
and aa wonderful
wonderful man
man tto
have aas
ttradition,
r a d i t i o n , and
o have
s aa cco1league
o l l e a g u e We
W e thank
thank him
him for
for
his
h
i s long service
s e r v i c e and
and numerous contributions
c o n t r i b u t i o n s to
t o our
our profession,
p r o f e s s i o n , our
our state,
state,
and our u
university;
his
n i v e r s i t y ; for
for h
i s enduring interest
i n t e r e s t and ccareful
a r e f u l work in
i n the
the
Precambrian; for
his
patient
his
Precambrian;
for h
i s generous and p
a t i e n t assistance
a s s i s t a n c e to
to h
i s ffellow
ellow
geologists
g
e o l o g i s t s in
i n the
t h e classroom,
classroom, the
t h e office,
o f f i c e , the
t h e laboratory,
l a b o r a t o r y , and
and the
t h e field;
field;
and for
his
We
for h
i s cheerful
c h e e r f u l optimism,
optimism, quiet
q u i e t modesty,
modesty, and
and gently
g e n t l y dignity.
d i g n i t y . We
having C
Carl
us
campus, and w
wee hope
enjoy and appreciate
a p p r e c i a t e having
a r l among u
s on tthis
h i s campus,
he remains with
with us
u s for
f o r many
many years.
years.
-
-
v
�TABLE
TABLE OF
OF EVENTS
EVEWTS
Wednesday, May
2, 1973
May 2,
1973
7:00—9:00
7:OO-9:OO p.m.
p.m.
Registration
R
egistration
Conference Smoker (Cash
Conference
(Cash Bar)
Bar)
Mezzanine
Mezzanine
Ballroom North
Registration
Registration
Technical Session
S e s s i o n 11
Luncheon
Technical Session
S e s s i o n 22
Happy Hour (Cash
Happy
(Cash Bar)
Bar)
Banquet
Mezzanine
Ballroom North
Ballroom South
South
Ballroom North
Ballroom South
South
Ballroom South
South
Technical Session
S e s s i o n 33
Luncheon
Technical Session
S e s s i o n 44
Business Meeting
Buses for
f o r Field
F i e l d Trips
T r i p s 22 && 33
leave
Sheraton
Inn
leave
Inn Parking
Parking Lot
Lot
Ballroom
Ballroom
Ballroom
Ballroom
Thursday, May
Thursday,
May 3,
3, 1973
1973
8:00—10:00
8:OO-1O:OO a.m.
a.m.
8:30—12:00 noon
8:30-12:OO
12:00—1:00 p.m.
12:OO-1:OO
p.m.
1:30—5:10
1 ~ 3 0 - 5 : l Op.m.
p.m.
6:00—7:00
6:OO-7:OO p.m.
p.m.
7:00—8:30 p.m.
7:OO-8:30
p.m.
Friday,
F
r i d a y , May 4,
4, 1973
1973
8:30—12:00 noon
8:30-12:OO
12:00—1:00
12:OO-1:OO p.m.
p.m.
1:30—4:45
1:30-4:45 p.m.
p.m.
4:45—5:00
4~45-5:00 p.m.
p.m.
7:00 p.m.
7:OO
p.m.
Saturday,
Saturday, May 5,
5 , 1973
1973
7:30 a.m.
a.m.
6:00 p.m.
10:00 p.m.
Bus for
leaves
f o r Field
F i e l d Trip
T r i p 11 leaves
Sheraton Inn Parking Lot
Bus ffor
Field
or F
i e l d Trip
Trip 1
1 returns
returns
Sheraton Inn Parking Lot
Field
Trip
Bus ffor
or F
ield T
r i p 2 returns
returns
Sheraton Inn
Inn Parking
Parking Lot
Lot
Sunday, May 6,
6 , 1973
1973
7:00
7:OO p.m.
p.m.
Bus for
f o r Field
F i e l d Trip
T r i p 33 returns
returns
Sheraton Inn
Inn Parking Lot
vi
North
South
South
North
North
�TECHNICAL
TECHNICALPROGRAM
PROGRAM
-
SESSION
SESSION 11 — Morning,
Morning, Thursday,
Thursday, May
May 3,
3, 1973
1973
Co—chairmen:
Co-chairmen:
Alan
Alan T.
T. Broderick
Broderick and
and L.
L. Gordon
Gordon Medaris,
Medaris, Jr.
Jr.
8:30
M.E.
M.E. Ostrom
Ostrom
Welcoming
Welcoming Remarks
Remarks
8:40
P.K.
P.K. Sims
Sims
Tectonic
Tectonic history
h i s t o r y of
of Early
E a r l y Precambrian
Precambrian
rocks
in
the
Vermilion
district,
rocks i n t h e
d i s t r i c t , northnortheastern
e a s t e r n Minnesota.
Minnesota.
p. 34—35
34-35
p.
9:05
Edward
Edward M.
M. Ripley
Ripley &
& '
Donald
Donald M.
M. Davidson,
Davidson, Jr.
Jr.
Structural
Structural
ultramafic
ultramafic
9:25
M.S.
M.S. Lougheed
Lougheed &&
J.J.
J. J. Mancuso
Mancuso
9:50
Discussion
Discussion of
of papers
papers
evolution
e v o l u t i o n of
of the
t h e Deer
Deer
complex,
Minnesota.
complex, Minnesota.
p.
p.
Lake
Lake
29
29
The
The biogenic
biogenic origin
o r i g i n of
of primary
primary minerals
minerals
in
i n Lake Superior
Superior Precambrian
Precambrian ironironformation.
formation.
p. 21—22
21-22
p.
10:00
Coffee
Coffee break
break
10:30
Klaus
J. Schultz
S c h u l t z &&
Klaus J.
Edward
Edward M.
M. Ripley
Ripley
Petrology
Petrology of
of some
some Early
E a r l y Precambrian
Precambrian
differentiated
d i f f e r e n t i a t e d ultramafic
u l t r a m a f i c bodies
bodies in
in
northeastern
n o r t h e a s t e r n Minnesota.
Minnesota.
p. 32—33
32-33
p.
10:50
M.G.
M.G. Mudrey,
Mudrey, Jr.
Jr. &&
A.L.
A.L. Geldon
Geldon
AA Lower
Lower Precambrian
Precambrian lamprophyre
lamprophyre pluton
pluton
near
n e a r Ely,
Ely, Minnesota.
Minnesota.
p. 25
25
p.
11:10
John
John S.
S. Klasner
Klasner &&
Thomas
Thomas R.
R. Turner
Turner
Precambrian
Precambrian north—south
north-south oriented
o r i e n t e d faults
faults
in
the
western
Marquette
i n t h e western Marquette district,
district,
northern
n o r t h e r n Michigan.
Michigan.
p. 17—18
17-18
p.
11:30
Jens
F. Touborg
Touborg
Jens F.
11:50
11:50
Discussion
Discussion of
of papers
papers
12:00
12:OO
Adjourn
Adjourn
12:00
12:OO
Luncheon
Luncheon
Structural
S t r u c t u r a l and
and stratigraphical
s t r a t i g r a p h i c a l analysis
analysis
of
of the
t h e Geco
Geco sulphide
s u l p h i d e deposit
d e p o s i t in
in
Manitouwadge,
Manitouwadge, northwestern
northwestern Ontario.
Ontario.
p. 38-39
38-39
p.
Ballroom
Ballroom South
South
vii
vii
�-
SESSIII
SESSION 22 — Afternoon, Thursday, May
May 3,
3, 1973
1973
Co—chairmen:
Co-chairmen:
Paul G.
G. Schmidt
Schmidt and
and Greg
Greg Mursky
Mursky
Paul
1:30
M.D. Lewan
M.D.
Lewan
Geochemistry
Geochemistry of the
the calcium-carbon
calcium—carbon
dioxide metasomatism
dioxide
metasomatism at
a t Presque
Presque
Marquette, Michigan.
p. 19—20
19-20
IIsle,
s l e , Marquette,
Michigan.
p.
1:50
D.M. Mickelson
D.M.
Summary
l a c i a l geology of
of
Summary of g
glacial
north—central Wisconsin.
p. 24
24
north-central
p.
2:15
E. Wm.
Wm. Heinrich
E.
A
n unusual manganese
manganese deposit in
in
An
Keweenawan lava,
lava, Copper
Copper Harbor,
Michigan.
p.
12
p. 12
2:35
Thomas A.
A. Vogel &
&
Nancy Alyanak
"Framboidal"
"~ramboidal" chalcocite from White
Pine, Michigan.
Pine,
p. 42
42
p.
2:55
Discussion of papers
3:05
Coffee break
3:35
Roger W.
W. Cooper
Cooper
The Keweenawan volcanics north of
of
Gogebic range
range in
i n Wisconsin.
Wisconsin.
the Gogebic
p.
P. 99
3:55
John C.
C. Green
Progress report
Progress
report of
of the
t h e Coimuittee
Committee
on Keweenawan
Keweenawan Stratigraphy.
Stratigraphy.
p. 11
11
p.
4:15
R.J.
R. J. Stevenson
Stevenson
A Keweenawan
Keweenawan layered
layered mafic intrusion
intrusion
Finland, Lake
near Finland,
Lake County,
County, Minnesota.
Minnesota.
p. 36
36
p.
4:35
W.F.
W.F. Cannon
Cannon
High
grade magnetite
magnetite deposits
deposits at
High grade
at
Republic, Michigan:
Their bearing
Republic,
Michigan: Their
on the genesis
genesisof
ofMarquette
MarquetteRange
Range
hard ore.
6-8
hard
ore.
p. 6—8
5:00
Discussion of papers
5:10
Adjourn
6:00
Happy
Ballroom South
South (cash
(cash bar)
Happy hour Ballroom
7:00
Banquet
Ballroom South Address by
Dr.
Cameron
Dr. Eugene Cameron
ANIM&L, VEGETABLE,
VEGETABLE, OR
OR M
MINERAL?
ANIMAL,
INERAL ?
viii
v
iii
�-
Friday, May 4,
SESSION
SESSION 33 — Morning, Friday,
4, 1973
1973
Co-chairmen:
Co—chairmen:
Ralph W.
Carl
E. Dutton
Ralph
W. Marsden
Marsden and
and C
a r l E.
8:30
Richard Berger
Richard
and oothers
and
thers
Environmental
Environmental geology
geology and
and land
land use
planning, Chassel
planning,
Chassel quadrangle,
quadrangle,Houghton
Houghton
p. 3—4
County, Michigan.
p.
3-4
8:50
Ennny
Booy &
E
mmy B00y
Ruth J.
J. Sobanski
Sobanski
Engineering geology of
of the
t h e Military
Military
Hill
H i l l landslides,
l a n d s l i d e s , Ontonagon
Ontonagon County,
County,
Michigan.
P.
5
p. 5
9:10
C.R. Bentley
C.R.
Magnetotelluric evidence for
f o r lateral
lateral
variations
v
a r i a t i o n s of
of ccrustal
r u s t a l structure
s t r u c t u r e in
in
northern
n
o r t h e r n Wisconsin.
P. 2
2
p.
9:30
F. Touborg
Jens F.
The Atikokan Iron
I r o n Range
Range and
and its
its
iron-copper m
mineralization.
iron-copper
ineralization.
p.
p. 40
9:50
Discussion of
Discussion
of papers
10:00
Coffee break
10:30
G.
G. Mursky
Mursky
and others
others
Mineralogical and
and chemical studies
studies
of greenstones in
26-27
of
i n Wisconsin.
Wisconsin. p.
p. 26—27
10:50
W.R. Van
W.R.
Van Schmus
Schmus
Geochronology of
of Precambrian Rocks
iin
n eeastern
a s t e r n Wisconsin.
p. 41
41
p.
11:10
L.G. Medaris, Jr.
L.G.
Jr.
and others
others
late
b a t h o l i t h — a late
The Wolf River batholith
massif in
Precambrian rapakivi
r a p a k i v i massif
in
northeastern
n o r t h e a s t e r n Wisconsin.
Wisconsin.
p. 23
23
p.
11:30
J.L.
J.L. Anderson
Graphical analysis
a n a l y s i s of
of portions
p o r t i o n s of
of
the
granite
the g
r a n i t e system with application
application
biotite—bearing
tto
o b
i o t i t e - b e a r i n g granitic
g r a n i t i c melts
melts
and
gneisses.
and g
neisses.
P.
p. 11
11:50
Discussion of
of papers
12:00
Adjourn
12:00
Luncheon
-
Ballroom South
South
ix
�-
SESSION
SESSION 44 — Afternoon, Friday,
Friday, May 4,
4, 1973
1973
Co—chairmen:
Co-chairmen:
Paul C.
Paul
C. Tychsen
Tychsen and
and Perry
P e r r y Olcott
Olcott
The ppetrology
e t r o l o g y and geochemistry of
Round Lake
Lake iintrusion,
n t r u s i o n , northwestern
Wisconsin.
p. 30
30
p.
1:30
D.L.
D.L.
E.N.
E.N.
Roder &
Cameron
Cameron
1:50
J.E. Thresher
J.E.
The formation of
of the
t h e Pittsville
Pittsville
(Wisconsin) migmatite.
37
(Wisconsin)
p. 37
p.
2:10
Robert A.
A. Jenkins
Jenkins
The geology of
of Pembine and
and Beecher
townships, Marinette
townships,
M a r i n e t t e County,
County,
Wisconsin.
p. 15—16
15-16
p.
2:30
John M.
M. Ohlson
Ohison
The iron
i r o n ore
o r e deposits
d e p o s i t s at
a t Black
River Falls,
F a l l s , Wisconsin,
Wisconsin, geology
operations.
p.
28
and o
perations.
p. 28
2:50
Discussion of
of papers
papers
3:00
Coffee break
3:30
0.H. Dury
G.H.
Southwest Wisconsin as
a s aa duricrusted
duricrusted
pediplain.
p
ediplain.
p. 10
10
p.
3:50
A.V.
A.V. Ileyl
Hey1
Mississippi
Upper M
i s s i s s i p p i valley
v a l l e y lead—zinc
lead-zinc
district.
d
istrict.
p. 13—14
13-14
p.
4:10
S.B. Romberger
S.B.
Upper Mississippi
M i s s i s s i p p i valley
v a l l e y base
base metal
metal
deposits:
d e p o s i t s : experimental solutions
s o l u t i o n s to
to
p.
31
problems
of
ore
genesis.
p. 31
problems of o r e g e n e s i s .
4:30
Discussion of
of papers
4:45
Business Meeting
Business
5:00
Adjourn
7:00
from parking
parking lot.
Buses for
f o r field
f i e l d trips
t r i p s 22 and
and 3
3 leave
l e a v e from
lot.
x
�GRAPHICAL
ANALYSIS OF
OF PORTIONS
GRAPHICAL ANALYSIS
PORTIONS OF
OF THE
THEGRANITE
GRANITESYSTEM
SYSTEMWITH
WITH
APPLICATION
TO
BIOflTE—BEARING
GRANITIC
MELTS
AND
GNEISSES
APPLICATION TO BIOTITE-BEARING GRANITIC MELTS AND GNEISSES
Department of
Geology and
Anderson, Department
of Geology
J. LL.. Anderson,
Wisconsin,
Madison,
Wisconsin
Wisconsin. Madison, Wisconsin 53706
53706
Geophysics. University
University of
Geophysics,
of
ABSTRACT
ABSTRACT
- phase relations in biotite—bearing
modelto
to describe
describe phase
granitic melts
ite-bearing granitic
melts
model
analysis
SiOy - KA1Si3O8
analysis of
ofthe
thesystem
system SiC2
KAlSi30g NaA1Si1OS —
FeO
Fe2O3
provides a tentative
Hz0
- K2MgSiAL20
1120 provides
KgMgfiSifiAlzOzo
Graphical
Graphical
CaAl2Si2O8
CaAl SigOg
—
—
—
gneisses. Defining
and gneisses.
Defining 'FeO'
'FeO' as
as an
an arbitrary
arbitrary combination
combination of
of FeO
FeO
and
Moreover,it
it has
specifies the
and Fe20
theoxygen
oxygen fugacity. Moreover,
has been
been
and
Fe20 specifies
split the system
system into three four comoonent
comoonent subsystems
necessax
necessary to split
to
of the
the components
components 110, KMgSi6fl2G20,
to evaluate
evaluate separately
separately the effect of
and
Quartz, alkali feldspar,
and CaAl2Si2Op
on the
the rest
rest of
of the
the system.
system. Quartz,
CaAl Si 0 on
plagioclase,
iotite, magnetite,
plagioclgse: !?iotite,
magnetite,granitic
granitic melt,
melt, and
and vapor
vapor are
are the
the
considered phases.
considered
phases. Application
Apolication of
of Schreinemakers'
Schreinemakers' rules
rules combined
combined
biotite — magnetite
magnetite
with
with experimental
experimental data
data on
on alkali
alkali feldspar
feldspar — biotite
and
of topologies.
topologies. The
The
and crystal—melt
crystal-melt equilibria
equilibria generates
generatesan.
an array of
system
system is
is characterized
characterized by
by degenerate
degenerate equilibria,
equilibria.
-
-
In
In application,
application, several
several conclusions
conclusions can
can be
be made
made which
which are
are as
as
1)
degrees of
1
) Dependent
Dependent on
on the
the number
number of
of degrees
of freedom,
freedom, the
the KK/Na
/N~
Fe/Mg
ratios
in
biotite can
and ~
e/~
ratios
g
in biotite
can be
be aa function
function of
of temperature,
temperature,total
total
pressure,
potential of water,
water, oxygen
fugacity, and the
pressure, chemical
chemical potential
oxygen fugacity,
the bulk
fugacity is buffered and fluid
fluid
If oxygen
oxygen fugacity
composition
composition of
of the
the rock.
rock. If
pressure equals
equa total
totalpressure,
pressure,divariant
divariant assemblages
assemblages (with
(with respect
respect to
to
F) have
T and
and P)
have fixed
fixed biotite
biotite compositions.
compositions. Such
Such assemblages
assemblages become
become
T
trivariant
H20 is not in
in excess such as in %O
H2O - undersaturated
trivariant if
if HgO
undersaturated
additional degree of freedom allows only one of
of the two
melts,
melts. One additional
ratios
will vary with
ratios (i.e.,
(i.e., Fe/Mg
~e/Mgor
or K/Na)
K/N~)to
to be
be fixed.
fixed. The other
other will
the bulk composition
the
composition of
of the
the rock,
rock. As to which of
of the
the two
two ratios
ratios
will
Another degree
degree of
of freedom
freedom will
this is
is depends
depends on
on the
the assemblage,
assemblage. Another
Biotite
allow
ratiosto
tovary
varywith
withthe
thebulk
bulkcomposition,
composition. 2)
2) Biotite
allow both ratios
follows:
follows:
-
stability can
of partial
stability
canstrongly
stronglyinfluence
influencethe
thecomposition
composition of
partialmelts
melts
derived
assemblage
quartz—plagioclase—biotite—
quartz-plagioclase-biotitederived from
from gneisses
gneissesofofthe
the
assemblage
of partial
partial
Ifthe
thebiotite
biotiteremains
remainsstable
stablebeyond
beyond conditions
conditions of
magnetite.
magnetite. If
melting
onlytonalitic
tonalitic melts
can result.
result. 3)
melting only
melts can
Alternatively, this
this
3) Alternatively,
coexist in
assemblage
assemblage cannot
cannot coexist
in equilibrium
equilibrium with introduced granitic
granitic
south of Stevens
melt. A possible example is an injection gneiss south
Point,
Wisconsin, where the
Point, Wisconsin,
the alkali
alkali feldspar
feldspar in
in the granitic
granitic veins
veins
isolated from
to
is isolated
from the
the host
host rock
rock by
by plagioclase.
plagioclase. LiV)
4) Application
Application to
ranakivi
massifs, such
batholith of
ranakivi granite
granite massifs,
such as
as the Wolf River
River batholith
of
Topological changes
Wisconsin,
Wisconsin, is
is possible,
possible. Topological
changes suggesting
suggesting feldspar
feldspar
mantling and
replacementofofalkali
alkalifeldsoar
feldsparby
bybiotite
biotite exist.
exist.
mantlinc
and the
the replacement
The
feasibility of
is being
The feasibility
ofsuch
such explanations
explanations is
being studied,
studied.
1
�MAGNETOTELLURIC
EVIDENCE FOR
FOR LATERAL
LATERAL VARIATIONS OF
MAGNETOTELLURIC EVIDENCE
OF
CRUSTAL STRUCTURE
CRUSTAL
STRUCTURE IN NORTHERN
NORTHERN WISCONSIN
WISCONSIN
C. R.
R. Bentley,
Bentley, Department
Department of
Geology and
of Geology
and Geophysics,
Geophysics,University
University of
of
C.
Wisconsin—Madison,Madison,
Madison, Wisconsin,
Wisconsin, 53706.
Wisconsin-Madison,
53706.
ABSTRACT
ABSTRACT
IIff two-dimensional
two-dimensional inhomogeneity
inhomogeneity iis
s the reason
reason ffor
o r apparent
apparent anisotropy
anisotropy
studies, then
of the
the pair of
iinn magnetotelluric
magnetotelluric studies,
then one
one of
of curves
curves at
a t each
each site
site
should be
close to
t o that
t h a twhich
whichwould
would be
be observed
observed over
over aa one-dimensional
one-dimensional earth.
should
be close
Ontthis
On
h i s basis, sites
s i t e sini nWisconsin
Wisconsin can
can be
be divided
divided into
i n t o three
three geographically
geographically
The systematic
systematic
distinct
w i t h decidedly
decidedly different
d i f f e r e naverage
t average curves.
curves. The
d i s t i n c tgroups
groups with
grouping
implies tthat
grouping ofof ssites
i t e s implies
h a t the
the differences
differences rreflect
e f l e c t real
real differences
differences
justvariations
variationsin in
local
near-surface conditions.
conditions.
the crust,
crust, not
notjust
within the
thethe
local
near—surface
That implication
boundary
That
implication isi sstrengthened
strengthenedby
bythe
thefact
f a cthat
t t h one
a t one
boundarybetween
between
groups
correspondstto
groups corresponds
o an
an abrupt change
change iinn structure
structurededuced
deduced completely
completely
independently from
from seismic
seismic and
andgravity
gravity data
in
independently
data alone
alone (Ocola
(Ocola and
and Meyer,
Meyer, in
The two-dimensional
two—dimensionalassumption
assumption
alsoimplies
implies tthat
press, J.G.R.).
press,
J.G.R.).
The
also
h a t the
the
c o r r e c t " curve
curve of
of each
each pair corresponds
corresponds t otocurrent
t o the
the
"correct'
currentflow
flow parallel
parallel to
current direction
directioncorresponding
corresponding to
t o the
the
two-dimensional boundary.
two-dimensional
boundary. Plotting current
acceptedcurve
curveaat
eachs site
accepted
t each
i t e reveals
reveals a
a parallelism
parallelism with
withcontours
contours ofofBouguer
Bouguer
gravity anomalies,
controlling
gravity
anomalies, suggesting
suggesting tthat
h a t the
the two—dimensionality
two-dimensional i t y control
1ing the
the
tensor orientation isi snot
notnear—surface
near-surface aatt all,
a l l ,asashas
haspreviously
previouslybeen
been
tensor
assumed,
associatedinstead
insteadwith
withgross
grosscrustal
crystal structure.
t i sis associated
assumed, b ubut
2
�ENVIRONMENTAL GEOLOGY
GEOLOGYAND
ANDLAND
LAND U
USE
ENVIRONMENTAL
SE PLANNING,
CHASSELL QUADRANGLE,
COUNTY, MICHIGAN
QUADRANGLE, HOUGHTON
HOUGHTON COUNTY,
CHASSELL
Richard
M. Hamil,
Hamil, Department
Department of
of Geology
Geology
Richard Berger,
Berger, Eniny
Emy Booy,
Booy, and
and Brenton
Brenton M.
and
Geol
ogi
cal
Engineeri
ng,
Michigan
Technol
ogi
cal
University,
and Geological Engineering , Mi chi gan Techno1ogi cal University,
Houghton,
Mi chi gan 49931.
Houghton , Michigan
ABST
RACT
ABSTRACT
The Chassell
ChassellQuadrangle
Quadrangle
locatedinin the
the southeastern
southeasternquarter
quarter of
of the
The
i s islocated
It
formerly uutilized
I t includes
includes land
land which
which was
was formerly
t i l i z e d for
f o rcopper
copper
area iiss sparsely
o r agriculture. The
The area
sparselypopulated
populatedand
andmay
may
mining as
aswell
well as
as ffor
mining
evaluation of geological
be
developmenti ninthe
the future.
future. An
An evaluation
geological
be expected
expected tto
o undergo
undergo development
factors affecting
such
development
factors
affecting
such
developmenthas
hasbeen
beenmade.
made.
Keweenaw
Peninsula.
Keweenaw Peninsula.
About 85
85 percent
percentof
of the
the land has
About
has a
a slope less
less than
than 15
15 percent,
percent, with
withmore
more
About one
one quarter
quarter
than
than half of
of that
t h a thaving
having aaslope
slope less
less than
than 55percent.
percent. About
of the
the land
land ininthe
thequadrangle
quadranglehas
has more
more than
than 50
50 feet
f e e t of
ofoverburden,
overburden, another
another
quarter (mostly
(mostly overlying
overlying the
the Jacobsville
Jacobsville sandstone
sandstone in the
the eastern
eastern area)
area)
30 tto
30
o 50
50 ffeet,
e e t , and
and the
the rest
r e s t (mostly
(mostly in
in the
thewesterly
westerly areas
areas overlying
overlying the
the
Portage Lake
Lake Lava
Lava flows)
flows) between
and 30
30 ffeet
Portage
between 00 and
e e t of
of overburden.
overburden.
Most of
of these
Most
these
soils
loam
s o i l s are
are classified
c l a s s i f i e dasassilty
s i l tto
y sandy
t o sandy
loam(USDA
(USDA cclassification)
l a s s i f i c a t i o n )oro rSM
SM or
or
SC
(Unified Soil
Soil Classification)
SC (Unified
Classification)having
havinga alow
lowshrink—swell
shrink-swell potential
potential and
and
There iiss aa prevalent
prevalent hardpan
hardpan layer
good permeability
permeability (about
(about 2.2
2.2 inches/hour).
inches/hour). There
good
pHofof the
the soils
s o i l s isi ssomesomeThe pH
at
a t variable
variabledepth
depth which
which isi sa asandy
sandyloam
loam or
o rSC.
SC. The
The corrosion
corrosion hazard
hazardf for
metal and
andconcrete
toncrete iiss low.
- 55 ttoo 6.6. The
o r metal
low.
what acid —
what
10 percent
percentofof the
the land
There
generally aa thin
thin topsoil. About
There iis
s generally
About 10
land area
area is
is
Theseare
aremostly
mostly on
on the
the floodplains
underlain
organic ssoils.
underlain by
by alluvium and
and organic
o i l s . These
of
wouldseverely
severely
thepotential
potentialf ofor
of rivers
rivers which
which would
r e restrict
s t r i c t the
r uutilization.
tilization.
areas
are generally classified
areas are
c l a s s i f i e dasasmarshland.
marshland.
These
Underground
water
supply
providedbybythe
theglacial
glacial ddrift
Underground water
supply
i sisprovided
r i f tand
andbedrock.
bedrock.
Wherethe
theglacial
glacial ddrift
Portage
Where
r i f tisi sdeep
deepand
and ini nparts
partsofofthe
the
PortageLake
LakeLava
Lava series
series
Jacobsville
The Jacobsvi
l l esandstone
sandstone
there
there is
i s sufficient
s u f f i c i e n water
t waterfor
f o domestic
r domestic supplies.
supplies. The
There are some
problemswith
with Fe
has
some problems
Fe content
has ssufficient
u f f i c i e n twater
water for
f o rdomestic
domestic use.
use. There
in water
water from
from the
the glacial
glacialand
andJacobsville
Jacobsvillesources;
sources;septic
s e p t itanks
c tanksmay
maycontaminate
contaminate
some
the shallow
shallow aquifers.
some ofof the
About 80
80 percent
percent of
of the land
theChassell
ChassellQuadrangle
Quadrangleisi swell—drained.
well-drained.
About
land ini nthe
There
The
Pilgrim, Pike,
The Pilgrim,
Pike, and
and Sturgeon
Sturgeon Rivers
Rivers drain
drain the
thearea
area tot oPortage
PortageLake.
Lake. There
and during
during spring
spring thaw
flooding
permanent marshland
marsh1 and and
thaw temporary
temporary flooding
iiss substantial
substanti a1permanent
occurs iinn many
uplandareas
areasdue
duet otothe
theimpermeability
impermeability of
of the
the underlying
many upland
underlying bedbedoccurs
areasdirections
directions of
of surface
drainage ddiffer
rock. In some
some areas
surface drainage
i f f e r from
from the
the drainage
drainage
patterns at
bythe
the glacial
glacial
patterns
a t depth
depth due
due to
t o the
thepresence
presence of
of bedrock
bedrock ridges
ridges masked
masked by
ddrift.
rift.
Old
mine openings
openingsdodonot
notappear
appeart otobe
beaamajor
majorhazard
hazardinin future planning,
Old mine
planning,
bbut
u t shaft locations
locations will
willhave
have to
t obe
be taken
taken into
intoaccount.
account.
3
�About
20percent
percentofof the
the land
land iiss currently
About 20
currentlyowned
owned by
by large private
private organorganExceptffor
holdings, most
of the land
izations. Except
o r small
small state
s t a t e and
and municipal
municipal holdings,
most of
land
of the
the quadrangle
quadrangle iis
s held
held by
by small
small individual
individual landholders.
landholders.
Current
forestryand
andfarming
fanningwith
w i t hpotatoes,
potatoes,
Current uutilization
t i l i z a t i o n isi smostly
mostlyini nforestry
There iiss less
less
strawberries, and
and dairy
dairy products
products being
being the
thedominant
dominant crops.
crops. There
commercial and
g h t industrial
industrial purposes.
purposes.
than
used ffor
o r connnercial
than 10
10 percent
percent of
of the
the land used
andl ilight
Recreational
useofof the
the land,
land, e.g.
e.g. hunting
snowmobilingi sisf afairly
hunting and
and snowmobiling
irly
Recreational use
usewill
will probably
widespread. Future
Future use
probably include
include mining
mining and
and recreation as
as well
well
as agriculture. Development
Development
industry
willbebep partially
as
of of
industry
will
a r t i a l l y controlled by
by
access
water which
which iiss abundant
along the
the shores
of Portage
u t less
less
access tto
o water
abundant along
shores of
Portage Lake
Lake bbut
accessible
in major
majorquantities
quantities further inland.
accessible in
inland.
4
�ENGINEERINGGEOLOGY
GEOLOGY
THEMILITARY
MILITARYHILL
HILL LANDSLIDES,
ENGINEERING
OFOFTHE
LANDSLIDES,
ONTONAGONCOUNTY,
COUNTY, MICHIGAN
MICHIGAN
ONTONAGON
EmmyBooy
Booyand
andRuth
RuthJ.3.Sobanski,
Sobanski, Department
Department ooff Geology
Geology and
and Geological
Geological
Emmy
Engineering,
Technological University,
U n i v e r s i t y , Houghton,
Houghton, Michigan
Michigan 49931.
Engineering, Michigan
Michigan Technological
ABSTRACT
The vvalley
The
a l l e y of
o fthe
t h eEast
EastBranch
Branchofo the
f t hOntonagon
e OntonagonRiver,
River,Ontonagon
Ontonagon County,
County,
Michigan i is
throughaat hthick
Michigan
s downcut
downcut through
i c k sseries
e r i e s of
o f glacial
g l a c i a lake—deposited
l lake-deposited clays,
clays,
Thesecclays
have proven
provenaa hazard
hazardt to
tthe
h e Ontonagon
Ontonagon clays. These
l a y s have
o construction
c o n s t r u c t i o n and
and
maintenanceoof
45because
becauseo foft hthe
numerous
slopef afailures
maintenance
f tthe
h e U.S.
U.S. Highway
Highway 45
e numerous
slope
i l u r e s ooff
various sizes
are rrepetitive
These f afailures
i l u r e s are
e p e t i t i v e in
in
various
s i z e s abutting
a b u t t i n g on
on the
t h ehighway.
highway. These
nature, rreflecting
nature,
e f l e c t i n g variation
v a r i a t i o n ini nmoisture
moisture content
content with
w i t h precipitation
p r e c i p i t a t i o nand
and
snowmelt.
snowmel
t.
The
nature ooff the
clayscauses
causes
The llayered
a y e r e d nature
t h e Ontonagon
Ontonagon clays
s usubstantial
b s t a n t i a l v avariability
riability
in
i n the
t h e physical
p h y s i c a l properties
p r o p e r t i e s of
o f the
t h e mass
mass bboth
o t h l alaterally
t e r a l l y and
and vvertically.
e r t i c a l l y . IInn
general tthe
material
be cclassified
general
he m
a t e r i a l can
can be
l a s s i f i e d as
as clays
c l a y s and
and clay—silts
c l a y - s i l t s with
w i t h fine
f i n esand
sand
percent to
contents ranging
contents
ranging from
from less
l e s s than
than 11 percent
t o 14
14 percent.
percent.
Atterberg
those ffor
A
t t e r b e r g LLimits
i m i t s of
o f these
these materials
m a t e r i a l s range
range from
from those
o r inorganic
i n o r g a n i c clays
clays
P l a s t i c limits
l i m i t srange
range from
from
of
o f low
low pplasticity
l a s t i c i t y to
t o those
those of
o f high
high pplasticity.
l a s t i c i t y . Plastic
24
50,.liquid limits
l i m i t sfrom
from 27
27 to
t o 100,
100, and
and pplasticity
l a s t i c i t yindices
i n d i c e s from
from 12
12 to
t o 58.
58.
24 tto
o 5O,Jiquid
There
appearst otobebenonoc oconsistent
of physical
There appears
n s i s t e n t p apattern
t t e r n o of
f vvariation
a r i a t i o n of
p h y s i c a l properties
properties
of
(e.g. at
o f the
t h e material
m a t e r i a l wwith
i t h llocation
o c a t i o n wwithin
i t h i n iindividual
n d i v i d u a l sslides
l i d e s (e.g.
a t toes
toes of
o f slides
slides
or
o r on
on the
t h e failure
f a i l u r eplace
placeata the
t t h escarp)
scarp)nor
n owith
r w i t helevation
e l e v a t i o above
n abovea adatum
datum nor
nor
along
along the
t h e general
general north—south
north-south ttrend
r e n d of
o f the
t h ehighway.
highway.
The nnatural
moisture content
content ooff these
The
a t u r a l moisture
these failure-prone
f a i l u r e - p r o n e materials
m a t e r i a l s ranges
ranges from
from
18 tto
percent iin
takeni nint hthe
18
o 41
41 percent
n samples
samples taken
e l late
a t e Fall
F a l l of
o f1972.
1972. This
T h i s approaches
approaches
water has
observed aatt various times
the
Free water
has been
been observed
times
t h e pplastic
l a s t i c llimits
i m i t s of
o f the
t h e soils.
s o i l s . Free
of
water ttable
o f year
y e a r on
on these
these slides
s l i d e s and
and the
t h e ground
ground water
a b l e is
i s frequently
f r e q u e n t l yextremely
extremely close
close
to
Averagep rprecipitation
e c i p i t a t i o n i in
n tthis
h i s area
area is
i s 34
34 inches,
inches, much
much oof
f iitt
t o the
t h e surface.
surface. Average
meltwater
iinn the
t h e form
form of
o f snowfall
s n o w f a l l whose
whose meltwater
i s isa as isignificant
g n i f i c a n t ffactor
a c t o r in
i n the
the
frequent
frequent occurrence
occurrence ooff Spring
Spring sslides.
lides.
IIttisi sextremely
extremely uunlikely
n l i k e l y tthat
h a t chemical
chemical o or
r e electrical
l e c t r i c a l sstabilization
t a b i l i z a t i o n ooff
these
slopes wwill
Surface drainage
drainage appears
i l l prove
prove useful.
u s e f u l . Surface
appears tto
o be
be the
t h e most
most
these slopes
economic
formo fofslope
slopec ocontrol
economic form
n t r o l i in
n tthis
h i s instance.
instance.
5
�HIGH-GRADE MAGNETITE
HIGH-GRADE
MAGNETITE DEPOSITS
DEPOSITS AT
AT REPUBLIC,
REPUBLIC, MICHIGAN:
MICHIGAN:
THEIR BEARING ON THE GENESIS O
F MARQUETTE RANGE HARD ORE*
ORE*
OF
U.S. Geological Survey,
Survey, Washington, D.C.
D.C. 20244
20244
W.F. Cannon, U.S.
W.F.
ABSTRACT
ABSTRACT
Hard ore (60—65
(60-65 percent Fe) in
i n the Marquette Iron Range consists
c o n s i s t s of
I
t characteristicalcharacteristicalconcentrations of specularite,
s p e c u l a r i t e , magnetite, and
and martite.
martite.
It
thethe
Negaunee
lly
y occurs at
a t the
thetop
topofof
NeqauneeIron—formation
Iron-formation and
and over
over a few feet
feet
grades
grades llaterally
a t e r a l l y and downward into
i n t o jaspilite
j a s p i l i t e (30-35
(30-35 percent
percent Fe).
Fe). Van Hise
Hise
classic
and Leith (1911)
(1911) developed the now c
l a s s i c concept tthat
h a t tthe
h e ore was formed
by surface weathering and leaching of silica
s i l i c a from
from the iron-formation
iron-formation prior
prior
to
deposition
of
the
unconformably
overlying
Goodrich
Quartzite,
and
the
t o deposition of the unconformably overlying Goodrich Quartzite, and the
ore
produce tthe
o
r e was
was later
l a t e rdeformed
deformed and
and metamorphosed
metamorphosed t to
o produce
h e present
present specularite—
speculariterich
"This hypothesis
hypothesis has
has withstood
withstood critical
c r i t i c aexamination
l examinationby
bymany
many
r i c h rock.
rock. This
geologists;
evidence
in
its
support
is
especially
compelling
in
the
eastern
geologists; evidence i n i t s support i s especially compelling i n the eastern
part
p
a r t of the
t h e Marquette
Marquette Range.
Range. Boyum (1964)
(1964) and Anderson (1968)
(1968) have suggested
suggested
that
concept, although
although probably
probably valid,
v a l i d , is
i snot
not adequate
adequate tto
o explain
explain aall
ll
t h a t this concept,
ffeatures
e a t u r e s of
of the
the ore
ore bodies.
bodies. M
y own
leadsme
me
My
ownreexamination
reexaminationofofthese
these deposits
deposits leads
to support
conclusions. II believe
to
supportBoyum's
Boyum's and
and Anderson's conclusions.
believe that
t h a tmuch
much of
of the
the
ore,
o r e , especially
e s p e c i a l l y specularite—rich
s p e c u l a r i t e - r i c h ore,
ore, has formed as suggested
suggested by Van
Van Hise
and Leith,
magnetite-rich ore (commonly
Leith, but that
t h a t magnetite-rich
(commonly greater
g r e a t e r than
than 90
90 percent
magnetite) has
has aa different
magnetite)
d i f f e r e n t origin.
origin.
-
At the Republic open pit, the jaspilite unit at the top of the Negaunee
A t the Republic open p i t , the j a s p i l i t e u n i t a t t h e t o p of the Negaunee
Iron-formation
Iron-formation iiss presently
presentlybeing
beingmined.
mined. The
The jjaspilite
a s p i l i t e is
i s the
the host
h o s t rock
rock
The
ffor
o r magnetite-rich
magnetite-rich hard
hardore,
o r e which
, whichwas
waspreviously
previouslymined
minedunderground.
underground. The
piti t provides
p
provides exceptional
exceptionalexposures
exposures of
ofthe
t h ehigh—grade
high-grade magnetite
magnetite ore
ore bodies
bodies
and
and ttheir
h e i r contacts
contacts with
with the
the surrounding
surrounding j jaspilite.
aspilite.
Three ccritical
r i t i c a l features
features
Three
common
hard—oredeposits
deposits iinn the
common t otoaall
l l magnetite—rich
magnetite-rich hard-ore
t h e Marquette
Marquette Range
Range and
and
difficult
d
i f f i c u l ttot oexplain
explainby
bythe
theweathering
weathering hypothesis
hypothesis are
a r e shown
shown tthere
h e r e bbetter
e t t e r than
than
at
other
a t any
any o
t h e r locality.
locality.
1) Although
Althoughsspecularite
alll lhard—ore
bodies, magnetite
1)
p e c u l a r i t e is
i scommon
common tto
o a
hard-ore bodies,
magnetite
i s the
thepredominant
predominant mineral
n many,
a r t i c u l a r l y in
i n higher
higher grade
grade
is
mineral iin
many,pparticularly
metamorphic rocks toward
toward the
the west
west end
end of
of the
the Marquette
Marquette Range.
Range.
The magnetite-rich
magnetite-rich ore
ore contains
contains ttextural
The
e x t u r a l evidence
evidence iindicating
n d i c a t i n g tthat
hat
formedaafter
it has formed
f t e r regional
regional deformation.
deformation.
it
a)
a)
The
ore iiss massive,
textures are
massive, deformational
deformational textures
a r e absent,
absent, and
and
"The ore
magnetite
grains aare
magnetite grains
r e largely
l a r g e l y euhedral
euhedral and
and undistorted.
undistorted.
b)
b)
Bodies
of massive
massiveore
ore sharply
sharply truncate
truncate schistose
Bodies of
s c h i s t o s e and
and
crenulated specularite—rich
crenulated
specularite-rich jjaaspilite.
spilite.
c
c))
The magnetite-rich
oreis icommonly
s commonlysomewhat
somewhat vuggy
vuggy and porous,
porous,
The
magnetite-rich ore
containing sspecularite,
containing
p e c u l a r i t e , dolomite,
dolomite, and
and quartz crystals
c r y s t a l s in
i n vugs.
vugs.
6
�2)
2)
Magnetite—rich
Magnetite-rich ore
ore is
i s characteristically
c h a r a c t e r i s t i c a l l y associated
associated with
w i t h quartz
quartz
veins.
(+
dolomite,
s
u
l
f
i
d
e
)
veins.
dolomite,
sulfide)
±.
±
3)
3)
Although
~ l t h o u g hthe
the magnetite—rich
magnetite-rich ore
ore invariably
invariably occurs
occurs in
i n hematitic
hematitic
iron—formation
iron-formation (jaspilite),
( j a s p i l i t e ) , the
the ore
o r e bodies are
a r e surrounded
surrounded by
by
narrow
narrow haloes
haloes in
i n which
which jasper
jasper was
was converted
converted to
t o gray
gray chert
c h e r t or
or
milky
milky quartz
quartz and
and some
some specularite
s p e c u l a r i t e was
was reduced
reduced to
t o magnetite,
magnetite,
i s associated
associated
i n d i c a t i n g that
t h a t the
the formation
formation of
of magnetite-rich
magnetite-rich ore
ore is
indicating
with
w i t h aa reducing
reducing process
process rather
r a t h e r than
than an
anoxidizing
oxidizingprocess
process such
such
as
as weathering.
weathering.
+
The
magnetite—richore
oreiis
s probably
probably of
of hydrothermal
hydrothermal origin
o r i g i nand
andbecause
because
The magnetite-rich
s the only
only recognized
recognizedpost
postiron—formation
iron-formation
Penokean regional
metamorphism iis
Penokean
regional metamorphism
the fluids
f l u i d swere
wereprobably
probably derived
derivedby
by dehydration
dehydration and
and dedethermal event,
event, the
thermal
carbonatization
carbonatization of
ofthe
theiron—formation
iron-formation and
and underlying
underlying rocks
rocks during
during progressive
progressive
regional metamorphism
metamorphism which
which reached
reached sillimanite
s i l l i m a n i t e grade
grade at
a t Republic.
Republic.
regional
topt oof
thethe
Negaunee
l o c a l i z a t i o n of
of the
t h eore
o r eatathe
t the
p of
NegauneeIron-formation
Iron-formation
The localization
The
might
be explained
explained through
throughthe
the buffering
buffering aaction
might be
c t i o n of
of the
theiron-formation
iron-formation on
on
A s fluids
f l u i d s(considered
(consideredhere
hereasa sF120
H20 for
for
the oxygen
oxygen fugacity
h e fluids.
f l u i d s . As
the
fugacity of
of tthe
CO2 rrich)
i c h ) are
a r e expelled
expelled during
during metamorphism
metamorphism
s i m p l i c i t y but
but probably
probably also
a l s o CO2
simplicity
w i l l contact
contact first
f i r s t the
the
and pass
pass upward
upward through
through the
t h e rock
rock section,
s e c t i o n , they
they will
and
magnetite-silicate and
r e l a t i v e l y reduced
reduced magnetite-silicate
andmagnetite—carbonate
magnetite-carbonate uunits
n i t s iin
n the
the
relatively
lower
lower part
p a r t of
ofthe
theNegaunee
Negaunee and
and will
w i l ltend
tendtoward
towardan
anequilibrium
equilibriumoxygen
oxygen
fugacity
determined
on figure
f i g u r e1,1,
determined by
by aa buffer
b u f f e r curve
curve
fugacity (f02),
( f o 2 ) ,such
such as
a s point
p o i n t 11on
such as curve
curve A,
A, and
and will
w i l l contain
contain concentrations of ferrous
ferrous and
and ferric
f e r r i c iron
iron
such
A s fluids
f l u i d spass
passupward
upward and
and
species appropriate
appropriate for
f o r that
t h a tf02
f o 2and
andtemperature.
temperature. As
species
contact
the jaspilite,
whichthe
thej jaspilite
contact the
j a s p i l i t e , a aredox
redoxreaction
reaction must
must occur
occur iin
n which
a s p i l i t e is
is
partly
of sspecularite
p a r t l y reduced
reduced by
by the
the conversion
conversion of
p e c u l a r i t e to
t o magnetite
magnetite and
and the
the fluids
fluids
are
bybythethe
hematite—
a r e oxidized
oxidized to
toachieve
achievean
anf07,
f o such
suchasa point
s p o i n2,
t 2determined
, determined
hematiteThe increased
increased f02
f
of
of the
t h e fluids
f l u i d sand
andconsequent
consequent
B). Tfie
magnetite buffer
magnetite
buffer fcurve
urve B).
02
lower
species
lower ssolitility
o l u b i l i t yofofferrous
ferrousiron
iron
speciesand
andthe
theoxidation
oxidationofofsome
some ferrous
ferrous
iron
i r o n to
t o less
l e s s soluble
soluble ferric
f e r r i c species
species results
r e s u l t s in
i n the
the precipitation
p r e c i p i t a t i o n of
of
Textures clearly
clearly
magnetite. Textures
magnetite.
indicate
i n d i c a t e that
t h a t silica
s i l i c a was removed
removed during
during the
the
wasp precipitated
its
hydrothermal activity
a c t i v i t yand
and the
themagnetite
magnetite presumably
presumably was
r e c i p i t a t e d iin
n its
hydrothermal
Because t the
h e equilibrium
equilibriumff02
of
the
buffered
assentlages
is
of
the
buffered
assemblages
i s very
very
place. Because
small
atmffor
the02
probable
small
small (10-40
(10-40 to
t o10—20
10-20 atm
o r the
probable conditions
conditionsof
ofmetamorphism),
metamorphism), small
volumes of
l a r g e volumes
volumes of
l u i d , and
and the
t h e system
system can
can
volumes
of rock
rock can
can buffer
buffer very
very large
of ffluid,
buffered until
u n t i l all
a l l hematite
hematite in
i n the
the jaspilite
j a s p i l i t e is
i s converted
converted to
t o magnetite.
magnetite.
remain buffered
I propose that
t h a t the
the magnetite—rich
magnetite-rich ore
ore has
has formed
formed by:
by: 1)
1) the reduction
reduction
of hematite to
t o magnetite
magnetite during
duringa ahematite—magnetite
hematite-magnetite b
u f f e r reaction;
reaction; 2)
2)
buffer
of
the precipitation
p r e c i p i t a t i o nofofmagnetite
magnetitefrom
fromhydrothermal
hydrothermal (metamorphic)
(metamorphic) ffluids
l u i d s as
a s the
the
the
fluids
oxidized during
duringt that
reaction and
and tthe
f l u i d s were
were oxidized
h a t bbuffer
u f f e r reaction
h e ssolubility
o l u b i l i t y of
of
i r o nwas
was decreased.
decreased.
ferrous iron
7
�2
t
HEM.
1
Fe—SILICATE
T
Figure
Figure 1.-—
I.-- T—f0
T-f
diagram showing
e l a t i v e positions
p o s i t i o n sofof
hematite-magnetite
diagram
showingrrelative
hematite—magnetite
02
buffer
buffer curvi
curveand
and aabuffer
buffercurve
curvedetermined
determined by
by the
the equilibruim:
equilibruim:
quartz
magnetite == Fe—silicate.
F e - s i l i c a t e . Points
Points 1
1 and
and 22 iillustrated
l l u s t r a t e d difdifquartz ++ magnetite
ference
ference in
i n f02
f o2 controlled
controlledby
by the
thebuffered
bufferedassemblages
assemblages at
a t constant
constantT.
T.
The formation
ore
t oto
require
e s t r i c t e d set
set
The
formationofof magnetite-rich
magnetite—rich
oreappears
appears
requirea ar restricted
of
of conditions:
conditions :
1)
must
reach
1)Metamorphism
Metamorphism must
reach
a t at
l eleast
a s t bbiotite
i o t i t e grade,
grade, although
although most
most
l l large
l a r g e ones
ones are
a r e in
i n garnet
garnet or
o rhigher
higher grade.
grade.
ore bodies
bodies and
and aall
ore
2)
2 ) Iron-formation
Iron-formation with mostly ferric
f e r r i c iron,
i r o n , such as
a s jaspilite,
j a s p i l i t e , must
be physically
physically above
above iron-formation
iron-formation with
w i t h abundant
abundant ferrous
ferrous iron.
iron.
3)
3) A stratigraphic
s t r a t i g r a p h i c or
o r structural
s t r u c t u r a l trap
t r a p capable of concentrating
concentrating the
the
flow
flow of
of fluids
f l u i d s must
must be
be present.
present. The
The Goodrich
Goodrich Quartzite
Quartzite and
and
metadiabase
metadiabase sills
s i l l s and
and dikes
dikes were
were apparently
apparently relatively
r e l a t i v e l y impermeable,
impermeable,
and
the Negaunee—Goodrich
Negaunee-Goodrich contact
contact near
near anticlinal
a n t i c l i n a l crests
c r e s t s and
and dikedikeand the
quartzite
q u a r t z i t e intersections
i n t e r s e c t i o n s were
were favorable
favorable loci
l o c i for
f o rore
o r eformation.
formation.
The
absenceofofany
anyofof these
these tthree
The absence
h r e e conditions
conditions iinhibits
n h i b i t s the
t h eformation
formation of
of
magnetite-rich
magnetite-rich ore.
ore.
References
References
Paderson,
G . J . , 1968,
1968, The
The Marquette
Marquette district,
d i s t r i c t , Michigan,
Michigan, in
i n Ridge,
Ridge, J.D.,
J.D.,
Anderson, G.J.,
(ed.),
(Graton-Sales
(ed. ) , Ore deposits of the
t h e United
United States,
S t a t e s , 1933—1967
1933-1967T~raton-Sales
Volume),
V. 1:
1:New
New York,
York, Pat.
Am. Inst.
I n s t . Mining, Metall.,
Metall., and
and Petroleum
Petroleum
Volume), V.
Engineers,
Engineers, p.
p. 505—517.
505-517.
Boyum,
B.H., 1964,
1964, The
The Marquette
Marquette mineral
mineral district,
d i s t r i c t , Michigan:
Michigan: Inst.
I n s t . on
on
Boyum, B.H.,
Lake
Lake Superior
Superior Geology,
Geology, 10th,
l o t h , Ishpeming,
Ishpeming, Mich.,
Mich., May
May 1964,
1964, Guidebook,
Guidebook, 13
13 p.
p
Van
C.R., and
and Leith,
Leith, C.K.,
C.K., 1911,
1911, The
The geology
geology of
of the
the Lake
Lake Superior
Superior
Van Hise,
Hise, C.R.,
region:
region: U.S.
U.S. Geol.
Geol. Survey
Survey Mon.
Mon. 52,
52, 641
641 p.
p.
* Work
Work done
doneinicooperation
n cooperation
with Geological
Survey
Division,
with Geological
Survey Division,
Michigan
Dept.
*
of
of Natural
Natural Resources
Resources
8
Michigan Dept.
�THE
VOLCANICS NORTH
THE KEWEENAWAN
KEWEENAWAN VOLCANICS
NORTH OF
OF THE
THE GOGEBIC
GOGEBICRANGE
RANGE
IN
I NWISCONSIN
WISCONSIN
Roger W.
W. Cooper,
Cooper, Department
Department of
o fGeology
Geologyand
andGeophysics,
Geophysics,
Roger
U n i v e r s i t yofoWisconsin—Madison,
f Wisconsin-Madison, Madison,
Madison, Wisconsin
Wisconsin 53706
53706
University
ABSTRACT
ABSTRACT
The
sequencennorth
The Keweenawan
Keweenawan v ovolcanic
l c a n i c sequence
o r t h of
o f the
t h eGogebic
GogebicRange
Range has
has aa
total
t o t a lthickness
thicknessofo more
f more than
than 35,000
35,000 feet
f e e t and
and an
an attitude
a t t i t u d e ofo fabout
about
This
sequence
of
volcanic
flows
was
investigated
NW.
T
h
i
s
sequence
o
f
v
o
l
c
a
n
i
c
f
l
o
w
s
was
i
n
v
e
stigated
N65-75
E,
70-80
N65—75
70—80 NW.
to
t o determine
determine iiff aa stratigraphic
s t r a t i g r a p h i c division
d i v i s i o nofothe
f t h eflows
f l o w sinto
i n tmappable
o mappable units
units
Four
units
have
been
defined
on
the
basis
of
texture,
Four
u
n
i
t
s
have
been
d
e
f
i
n
e
d
on
t
h
e
basis
o
f
t
e
x
t
ure,
c o u l d be
be achieved.
achieved.
could
petrographic characteristics,
c h a r a c t e r i s t i c s ,and
andchemical
chemi c a l analyses.
analyses.
petrographic
Unit
U n i t 1,
1, which
which is
i s the
t h e basal
basal unit,
u n i t , consists
c o n s i s t s of
o fabout
about 5000
5000 ffeet
e e t of
of
p i l l o w basalts
b a s a l t sand
and subalkaline
subal k a l i n e basalts.
basalts. The
The basalts
b a s a l t sare
aremedium—
medium- to
to
pillow
The ttextures
e x t u r e s most
most common
common i nint hthis
i s unit
unit
f i n e - g r a i n e d and
and grayish—green.
grayish-green. The
fine—grained
are
are intergranular
i n t e r g r a n u l a r and
and subophitic,
s u b o p h i t i c , with
w i t hophitic
o p h i t itexture
c t e x t u rless
e l e scommon.
s common.
Unit
U n i t 22 is
i sabout
about 20,000
20,000 ffeet
e e t thick
t h i c k and
and consists
c o n s i s t s of
o f flows
flows more
more alkaline
alkaline
are aaphanitic
The fflows
l o w s are
p h a n i t i c tto
o fine-grained,
fine-grained,
than those
those found
U n i t 1.
1. The
than
found iinn Unit
most common
common
The most
t e xtextures
t u r e s a are
r e i nintergranular
tergranular
b l u i s h - g r a y to
t oreddish-brown.
reddish-brown. The
bluish-gray
Flows ooff rather
r a t h e r basic
basic
and iintersertal
n t e r s e r t a l with
w i t hmicrophenocrysts
microphenocrysts of
o f plagioclase.
plagioclase. Flows
and
composition
neart hthe
bottomo of
and f felsic
composition near
e bottom
f t hthe
e uunit
n i t give
g i v e way
way tto
o intermediate
i n t e r m e d i a t e and
elsic
flows upward.
upward.
flows
Unit
p o o r l yexposed
exposed but
b u t estimated
estimated to
t o be
be 2000
2000 tto
o 4000
4000 ffeet
e e t thick.
thick.
U n i t 33 isi spoorly
ItI tisi scomposed
composed o of
f pporphyritic
o r p h y r i t i c f felsic
e l s i c flows
flows that
t h a t have
have aa ppink
i n k t to
o sslightly
lightly
purple
abundantphenocrysts
phenocrystsoof
p u r p l e groundmass
groundmass wwith
i t h abundant
f ffeldspar
e l d s p a r and
and quartz.
Unit
by gglacial
U n i t 44 is
i swidely
w i d e l y covered
covered by
l a c i a l drift
d r i f but
t b uestimated
t estimatedtot obe
beabout
about
The
flows
appear
to
be
mainly
mafic,
gray,
and
usually
The
flows
appear
t
o
be
m
a
i
n
l
y
m
a
f
i
c
,
gray,
and
u
sually
10,000 ffeet
e e t thick.
thick.
10,000
The
flows
are
highly
vesicular;
pipe
The
flows
are
h
i
g
h
l
y
v
e
s
i
c
u
l
a
r
;
p
i
p
e
n o t more
more than
than 20—25
20-25 f efeet
e t tthick.
hick.
not
amygdules and
e s i c u l a rtops
topsare
are
common. Interbedded
Interbedded wwith
i t h these
these flows
f l o w s are
are
amygdules
and vvesicular
common.
The pebbles
pebbles found
found
sedimentary
rocks ranging from
sedimentary rocks
from conglomerate
conglomerate ttoo shale.
shale. The
interbedded flows and
These interbedded
and
i n these
these beds
beds are
are predominantly
predominantly f felsites.
e l s i t e s . These
in
sedimentary beds
beds pass
pass upward
upward into
i n t othe
t h eCopper
CopperHarbor
HarborConglomerate.
Conglomerate.
sedimentary
The
sequenced idisplays
general compositional
The Keweenawan
Keweenawan v ovolcanic
l c a n i c sequence
s p l a y s aa general
compositional
trend
upward
t r e n d from
from subalkaline
s u b a l k a l i n e ttholeiitic
h o l e i i t i basalts
c b a s a l tat
s athe
t t hbase
e base
upwardthrough
through
After
the
extrusion
o f these
these
the
t h e porphyritic
p o r p h y r i t i c felsic
f e l s i c flows
flows of
o f Unit
U n i t 3.
3. A f t e r t h e e x t r u s i o n of
f e l s i cflows
flowsthere
t h e r eappears
appears to
t ohave
have been
been iintermittent
n t e r m i t t e n t volcanism
volcanism of
o f aa
felsic
more
alongwwith
more mmafic
a f i c nnature
a t u r e along
i t h eerosion
r o s i o n o of
f t the
h e ffelsic
e l s i c flows.
flows.
9
�SOUTHWEST WISCONSIN
PEDIPLAIN
SOUTHWEST
WISCONSINAS
ASA ADIJRICRIJSTED
DURICRUSTED PEDIPLAIN
Dury, Departments of
GG.
. HH.
. Dury,
o f Geography and
and Geology,
Geology, The
The
University
U n i v e r s i t y of
o f Wisconsin-Madison,
Wisconsin-Madison, Science
S c i e n c e Hall,
H a l l , Madison,
Madison,
Wisconsin
Wisconsin 53706.
53706.
ABSTRACT
ABSTRACT
The Driftless
D r i f t l e s s Area of
of Southwest Wisconsin and
and adjacent
adjacent
parts
p
a r t s of
of Minnesota, Iowa,
Iowa, and
and Illinois
I l l i n o i s consists
c o n s i s t s of
o f dissectdissected
e d plateau
p l a t e a u country
c o u n t r y traversed
t r a v e r s e d by
by the
t h e Wisconsin
Wisconsin and
and MississMississhas
iippi
p p i Rivers.
R i v e r s . IIn
n tthe
h e ppast,
a s t , the
t h e area
area h
a s been described
d e s c r i b e d in
in
terms o
of
orr more
more ppeneplains,
terms o
of
terms
f one o
e n e p l a i n s , aand/or
n d / o r iin
n terms
f a
sseries
e r i e s of
o f cuestas.
cuestas.
IIn
n aactuality,
c t u a l i t y , it
i t is
i s recognizable
r e c o g n i z a b l e as
a s aa dissected
d i s s e c t e d pedipedithe
few
residuals
that
have
escaped
plain:
p
lain: the
residuals t h a t
e s c a p e d planation
p l a n a t i o n rise
rise
ssharply
h a r p l y from the
t h e summit surface
s u r f a c e and
and exhibit
e x h i b i t typical
t y p i c a l pedipedii s widespread,
widespread,
ment profiles.
p r o f i l e s . Evidence of
o f deep
deep weathering
w e a t h e r i n g is
On
carbonates,
the
rregardless
e g a r d l e s s of
o f lithology.
l i t h o l o g y . On c a r b o n a t e s , t h e deep
deep weatherweathering
i n g pprofiles
r o f i l e s consist
c o n s i s t of
o f rotted
r o t t e d rock
r o c k and
and red
r e d residuum;
residuum; but
but
part
p
a r t of
o f the
t h e latter
l a t t e r may have been introduced
i n t r o d u c e d subsequently
subsequently
weathering.
tto
o deep w
e a t h e r i n g . On
On arenites,
a r e n i t e s , the
t h e profiles
p r o f i l e s are
a r e varyingly
varyingly
horizonated
h o r i z o n a t e d into
i n t o pallid,
p a l l i d , mottled,
m o t t l e d , and
and duricrusted
d u r i c r u s t e d zones,
zones,
tthe
h e ppallid
a l l i d zones
zones frequently
f r e q u e n t l y showing tthe
h e rresults
e s u l t s of
o f attack
attack
on q
quartz
grains,
and
the
crusts
ranging
from
highly
uartz grains,
the c r u s t s ranging
highly
fferruginous
e r r u g i n o u s to
t o highly
h i g h l y siliceous.
s i l i c e o u s . Crust
C r u s t texture
t e x t u r e can
can be
be
Ferruginous
nodules
rreplicated
e p l i c a t e d in
i n Australian
A u s t r a l i a n samples.
s a m p l e s . F e r r u g i n o u s n o d u l e s in
in
Wisconsin pprofiles
widely
have developed
tthe
h e Wisconsin
r o f i l e s aappear
ppear w
i d e l y tto
o have
within
w i t h i n bedrock.
bedrock.
On
O
n eeither
i t h e r side
s i d e of
of the
t h e lower
lower Wisconsin river,
r i v e r , the
the
deeply-weathered
d
e e p l y - w e a t h e r e d and
and d.uricrusted
d u r i c r u s t e d ssurface
u r f a c e defines
d e f i n e s aa wide
wide
of
which tthe
glacial
sshallow
h a l l o w vvalley,
a l l e y , iinto
n t o tthe
h e ffloor
loor o
f which
he g
lacial
ssluiceway
l u i c e w a y is
i s incised.
i n c i s e d . IInvestigation
n v e s t i g a t i o n of
o f ppossible
o s s i b l e comparcompari s in
i n proproaable
b l e rrelationships
e l a t i o n s h i p s for
f o r the
t h e Mississippi
M i s s i s s i p p i trench
t r e n c h is
Ass could
c o u l d bbe
e expected,
e x p e c t e d , there
t h e r e is
i s evidence
e v i d e n c e that
t h a t the
the
ggress.
ress. A
weathering
was, to
deep w
e a t h e r i n g was,
t o some extent
e x t e n t at
a t least,
l e a s t , aa groundgroundwater
and some
some thin
t h i n crusts
c r u s t s appear
a p p e a r to
t o have
have been
been
w a t e r phenomenon; and
ddeposited
e p o s i t e d under carbonates
c a r b o n a t e s in
i n the
t h e subsurface.
subsurface.
Outstanding
problems include
O
u t s t a n d i n g problems
i n c l u d e the
t h e distribution
d i s t r i b u t i o n of
o f the
the
deeply-weathered
d
e e p l y - w e a t h e r e d surface
s u r f a c e in
i n glaciated,
g l a c i a t e d , in
i n addition
a d d i t i o n to
t o ununglaciated,
g
l a c i a t e d , areas;
a r e a s ; the
t h e relationship
r e l a t i o n s h i p of
o f some
some ferruginous
ferruginous
ccrusts
r u s t s tto
o ssuiphide
u l p h i d e deposition
d e p o s i t i o n or
o r translocation;
t r a n s l o c a t i o n ; and the
the
off the
ttime-stratigraphic
i m e - s t r a t i g r a p h i c pposition
osition o
t h e latest
l a t e s t local
l o c a l episode
episode
off deep weathering.
o
weathering.
10
�PROGRESS REPORT
PROGRESS
REPORT OF
OFTHE
THECOMMITTEE
COMMITTEEON
ONKEWEENAWAN
KEWEENAWAN STRATIGRAPHY
STRATIGRAPHY
C. Green,
Green, Geology Department,
Department, University of
of Minnesota,
Minnesota, Duluth,
John C.
Duluth, Duluth,
Duluth,
Minnesota 55812 and Minnesota Geological Survey
ABSTRACT
A
BSTRACT
An
A
n informal Committee on Keweenawan Stratigraphy was formed in
in
February 1973
of p
participants
1973 in
i n response to
t o tthe
h e wishes of
a r t i c i p a n t s at
a t the Symposium
Symposium
on Late Precambrian Geology of
of the
t h e Lake Superior Area at
a t the Annual Meeting
members are
a r e George V.
V. Cohee,
Cohee, Campbell
Campbell
t h e G.S.A.
G.S.A. in
i n Minneapolis.
Minneapolis. Its members
of the
Craddock,
H. Dott,
A. Hubbard,
Hubbard,
Craddock, Robert H.
Dott, John C.
C. Green (chairman),
(chairman), Harold A.
Wm. H.
Vs.
H. Mcllwaine,
McIlwaine, Glenn
Glenn B.
B. Morey,
Morey, and
and Walter
Walter S.
S. White.
White. Some
Some rather
r a t h e r wide
differences of
of opinion and usage aare
by tthe
differences
r e represented by
h e members and because
of
s i n c e its
i t s organization,
organization, few
few areas
a r e a s of complete
of the short
s h o r t time elapsed since
consensus have developed by the
t h e mid—March
mid-March abstract
a b s t r a c t deadline.
deadline.
name "Keweenawan"
The name
"Keweenawan" appears
appears to
t o be
be widely
widely considered
considered as
a s applying to,
to,
not formally defined as,
as, aa p
provincial
supergroup, a
ass
iif
f not
r o v i n c i a l llithostratigraphic
i t h o s t r a t i g r a p h i c supergroup,
part
well as
a s to
t o that
that p
a r t of
of geologic time
t i m e when the Keweenawan Supergroup was
being formed.
formed. It would then be composed
composed of
of various groups and formations,
formations,
but many of these stratigraphic
s t r a t i g r a p h i c units
u n i t s have yet
y e t to
t o be formally
formally defined.
defined. An
An
attempt will
w i l l be
be made
made to
t o clarify
c l a r i f y their
t h e i r stratigraphic
s t r a t i g r a p h i c relationships.
relationships.
wrestling with
with tthe
of tthe
most appropriate
The Committee is aalso
l s o wrestling
h e problem of
h e most
which tto
of the
sstratigraphic
t r a t i g r a p h i c llevels
e v e l s aatt which
o define the base and tthe
h e top of
Keweenawan,
the assumption that
t h a t there
there should be some
some unifying geotectonic
geotectonic
Keweenawan, on the
many respects
respects tthe
Disturbance"
coherence implied
implied by
by the
t h e name.
name. IIn
n many
h e "Keweenawan Disturbance"
could be compared with
with tthe
of Late T
Triassic
h e Palisades Disturbance of
r i a s s i c time,
time, and
8,
"Keweenawan"
rocks could be defined a
as
of tthis
Keweenawan" rocks
s those formed aass a result
r e s u l t of
his
event
ofevents
eventsiin
the area
Mid—Continent Gravity High
event or
o r complex
complex of
n the
a r e a of
of tthe
h e Mid-Continent
High
or
o r aatt least
l e a s t the
the Lake Superior
Superior District.
District.
11
�AN
AN UNUSUAL
UNUSUAL MANGANESE
MANGANESE DEPOSIT IN
I NKEWEENAWAN
KEWEENAWAN LAVA
LAVA
COPPER
HARBOR, MICHIGAN
COPPER HARBOR,
MICHIGAN
E.
Heinrich, Department
E. Wm.
Wm. Heinrich,
Department of
o f Geology
Geology and
and Mineralogy,
Mineralogy,
U n i v e r s i t y of
o fMichigan,
Michigan, Ann
Ann Arbor,
Arbor, Michigan.
Michigan.
University
ABSTRACT
ABSTRACT
One ooff the
t h e rare
r a r enon—cupriferous
non-cupriferous mineral
mineraldeposits
depositsin iKeweenawan
n Keweenawan lava
lava
One
i s the
t h emanganese
manganese occurrence
occurrence just
j u s teast
e a sof
t oManganese
f ManganeseLake
Lake and
and about
about one
one
is
m i l e south
south of
o fCopper
Copper Harbor
Harbor in
i n sec.
58N,R.R.26W.
26W. Butler
sec. 4,4, T.T.58N,
mile
B u t l e rand
andBurbank
Burbank
(1929, p.
p. 59)
59) rrefer
e f e r to
t o that
t h a t deposit
d e p o s i t as
t h e Manganese
Manganese mine"
tate
as "... the
mine" and
and sstate
that
t h a t "... some
some ore was
was shipped
t h e mine."
mine. "
shipped from
from the
"...
"...
The ddeposit
e p o s i t is
i s aacalcite—rich
c a l c i t e - r i c hreplacement
replacement lens
lensini nananamygdaloid
amygdaloid
The
t h a t is
i sstratigraphically
s t r a t i g r a p h i c a l lay short
a s h odistance
r t d i s t a n cbelow
e belowthe
t h ebase
baseofo fthe
t h eCopper
Copper
that
Harbor
Harbor ("Great")
("Great") Conglomerate.
Conglomerate. Old
workingsi nindicate
Old workings
d i c a t e tthat
h a t the
t h e mineralimineral iz a t i o n extends
extends east-west
along
t h ethe
s t strike
r i k e oof
f tthe
h e amygdaloid
amygdaloid f ofor
r aatt least
least
zation
east—west
along
a few
few hundred
hundred ffeet.
e e t . The
The replacement
o n s i s t s ooff material
m a t e r i a l grading
grading
replacementrock
rockcconsists
from nearly
n e a r l y pure
pure coarse—grained
coarse-grained wwhite
h i t e ccalcite
a l c i t etot ohigh—grade
high-grade black
black
from
manganese
oxide ore. The
manganese oxide
The manganese
manganese minerals
c l u d e hypogene
hypogene brauni
te,
mineralsi ninclude
braunite,
o r i e n t i t eand
andmanganite
manganiteand
andsome
some supergene
supergene ppyrolusite.
yrolusite. A
orientite
A trace
t r a c e of
o f chalcochalcocite
c i t eand
and very
very minor
minor goethite
g o e t h i t eare
arethe
t h eonly
o n l other
y o t h ehypogene
r hypogene species,
species, and
and
l i m o n i t e , chalcedony
chalcedony and
and opal
opal ini nsmall
smallamounts
m o u n t sare
aresupergene.
supergene. The
The
limonite,
manganese minerals
i n and
ace t hthe
e ccalcite.
alcite.
manganese
mineralsv evein
andrep1
replace
T h i s occurrence
occurrence of
o f orientite,
o r i e n t i t ea, hydrous
a hydrous
calcium-manganese s silicate,
ilicate,
This
calcium—manganese
i s believed
b e l i e v e d to
t obe
beonly
o n l ythe
t h esecond
second recorded
recorded ffor
o r the
t h e world.
world. (The
is
(The type
type
locality
l o c a l i t yisi in
s i Oriente
n O r i e n t Province,
e Province,Cuba.)
Cuba.) The
mineral appears
as gglistening
The mineral
appears as
listening
copper-red
needles
forming minute
minute rradial
exceedingly
copper-red need1
es forming
a d i a l aggregates
aggregates and
and exceeding1
y ffineine-
grained matted
matted lenses.
lenses.
The
amygdaloid,oother
than being
beingeextensively
replaced by
by ccalcite,
The hhost
o s t amygdaloid,
t h e r than
x t e n s i v e l y replaced
alcite,
which
which aalso
l s o f fills
i l l s the
t h e vesicles
v e s i c l e s eentirely
n t i r e l y alone,
alone, iis
s relatively
r e l a t i v e l y fresh.
f r e s h . Neither
Neither
native
n a t i v e copper
copper nor
n o r the
t h e characteristic
c h a r a c t e r i s t i suite
c s u i of
t e accompanying
o f accompanyingsecondary
secondary
s i l i c a t e sisi present,
s present,although
althoughnative
n a t i v ecopper
coppermineralization
m i n e r a l i z a t i o nofothe
f t hcross—
e crosssilicates
f i s s u r e type
type occurs
occurs at
a t the
t h e Clark
Clark mine
mine a short
s h o r t distance
d i s t a n c e to
t o the
t h e south.
south.
fissure
The ddeposit
e p o s i t is
i s believed
b e l i e v e d to
t obe
bepenesyngenetic
penesyngenetic and
rigin.
The
and volcanogenic
volcanogenici nin oorigin.
12
�UPPERMISSISSIPPI
MISSISSIPPI VALLEY
UPPER
VALLEY LEAD—ZINC
LEAD-ZINC DISTRICT
DISTRICT
A. V.
V. Heyl,
A.
Heyl, U.S.
U.S. Geological
Geological Survey,
Survey, Denver,
Denver, Colorado
Colorado
80225.
ABSTRACT
ABSTRACT
The
UpperMississippi
MississippiValley
Valley ddistrict
The Upper
i s t r i c thas
hasbeen
been the
the source
source of
of about
about aa
billion
bi
1 liondollars
do1 l a r (present—day
s (present-day prices) worth
worth of
of zinc
zincand
and lead,
lead, and
and minor
minor
amountsofof copper
copper and
and barite.
barite. Ore
amounts
Ore deposits
deposits are
are chiefly
chiefly ininlimestone
limestone and
and
dolomite of
of the Galena,
Decorah,and
andP lPlatteville
dolomite
Galena, Decorah,
a t t e v i l l e Formations,
Formations, aall
l l of
of Middle
Middle
Locally, small
of lead,
Ordovician age.
age. Locally,
small deposits
deposits of
lead, zinc,
zinc, and
and iron
iron sulfide
s u l f i d ehave
have
been mined
mined from
from underlying
underlying Lower
been
Lower Ordovician
Ordovi cian dolomite
do1 omi t eand
andUpper
Upper Cambrian
Cambrian
sandstoneand
andover1
overlying
UpperOrdovician
Ordovicianshale
shale and
andSiSilurian
sandstone
yi ng Upper
1uri an dolomite.
do1 omi t e . No
No
post—Precambrian
igneous
rocks
known
theregion,
region, and
andggranitic
post-Precambrian
igneous
rocks
areareknown
in in
the
r a n i t i c and
and
metasedimentaryPrecambrian
Precambrian
basement
rocks
unconformably
underlie
metasedimentary
basement
rocks
unconformably
underlie
thethed idistrict
strict
at
algal reefs
a t depths
depths of 1,500
1,500 to
t o 2,000
2,000 feet.
f e e t . No
No algal
reefs are
are known
known in the
the Middle
Middle
Ordovician rocks,
rocks, and
b u t not
not an
an unconformity,
unconformi t y , separates
separates these
these
Ordovician
and a diastem,
di astern, but
rocks
rocks from
from Upper
Upper Ordovician
Ordovician shale. The
The sstrata
t r a t a are
are gently
gently flexed and
and faulted,
probably largely
largely the
probably
the result
r e s u l tofofgentle
gentlecompressive
compressive and
and rotational
rotational adjustments
adjustments
in the
along
the underlying
underlying crystalline
c r y s t a l l i nbasement,
e basement,especially
especially
alonglineaments
lineamentsbetween
between
basement blocks.
blocks. Folds
basement
Folds of three
three orders
orders ofofmagnitude
magnitude are
are recognized,
recognized, and
and
many
relatedjoints
joints and
reverse, sstrike—slip,
normalf faults
of small
many related
and reverse,
t r i k e - s l i p , and
and normal
a u l t s of
small to
to
moderate displacements
displacements are
are present.
moderate
The
zinc—leaddeposits
depositsrange
rangei ninplan
plan from
fromllinear
The zinc-lead
i n e a r through
through arcuate
arcuate to
to
Theyare
areepigenetic
epigeneticand
andp opostlithification
Most ore
eelliptical.
l l i p t i c a l . They
s t l i t h i f i c a t i o n deposits.
deposits. Most
and
vugs,
i n fractures,
fractures,breccias,
brecci as,
and
vugsbut
, b usome
t someimpregnated
impregnated
openspaces
spaces in
ffilled
i 11edopen
and replaced
replaced wall
wallrock.
openspace
spacei is
along
shears, small reverse
and
rock. The
The open
s a1
ong shears,
reverse and
and
bedding—plane
joints re1
related
bedding-pl
ane f a ufaults,
l t s , joints
ated tto
o intermediate
intermediate tto
o small
small folds,
folds, and
and
within
structures. Sphalerite and
galena are
are the
the principal
within solution—slump
solution-slump structures.
and galena
ore minerals, and
ore
and the
the general
general sequence
sequence of deposition
depositionofofmain
mainore
oreand
andgangue
gangue
minerals was:
quartz, iillite,
was: quartz,
l l i t e dolomite,
, dolomite, pyrite,
pyrite,marcasite,
marcasite, cobaltite(?),
cobal t i t e ( ? ) ,
sphalerite, galena,
chalcopyrite,mmillerite,
sphalerite,
galena, chalcopyrite,
i l l e r i t e , barite,
b a r i t e , and
and calcite.
c a l c i t e . Wallrock
Wall rock
rocks,ssilicification,
aalterations
l t e r a t i o n s include
include solution of the
the carbonate
carbonate rocks,
i l i c i f i c a t i o n dolomiti—
, dolomititype of
of clay,
zation, changes
changes i in
n type
clay, addition
additionofoftrace
traceelements,
elements, and
and sanding
sanding of
dolomite. Country
rock between
orebodies
bodiesiis
Country rock
between ore
s unaltered.
Oxygen-isotope,
carbon-isotope, lead-isotope,
Oxygen-isotope, carbon-isotope,
lead-isotope, sulfur—isotope,
sulfur-isotope, and
and
Bubbles in
sphalerite—stratigraphy studies
studies are
or in progress.
sphalerite-stratigraphy
are completed
completed or
progress. Bubbles
sulfide and
mineralsare
are ffilled
sulfide
and gangue
gangue minerals
i l l e dwith
withconcentrated
concentratednear—neutral
near-neutral chloride
brines that
lead iinn the
brines
t h a t have
have filling
f i l l i n temperatures
g temperaturesofof1200
120' tot o40°C.
40°C The
The lead
the
galena iiss notably
galena
notably radiogenic.
radiogenic.
Themetals
metals and
andsulfur
sulfur are postulated
The
postulated to
t o be
be derived
derived from
fromheated
heated basin
basin
brines
that
were
later
diluted
by
meteoric
waters.
magmaticf lfluid
brines t h a t were l a t e r diluted by meteoric waters. A
A magmatic
u i d contribution
possible, but
b u t iti tisi snot
notsupported
supported by
by present
present ffluid
l u i d inclusion
inclusion data.
data.
bution is possible,
magmatichearth
hearthinin the
the basin
basin areas
AA magmatic
areas ttoo the
the south
south and
and southwest
southwest is
i s the
themost
most
possible heat
possible
heat source.
source. AA large lateral
l a t e r a component
l component of
of flow
flowthrough
throughpermeable
permeable
Cambriansandstone
sandstone
updip
from
basinsi sisprobable,
probable, bbut
u t available
available evidence
evidence
Cambrian
updip
from
thethebasins
13
�the ddistrict
Within the
istrict
suggests
flow through
fracture zones.
suggests some
some flow
through basement
basement fracture
zones. Within
the ore
from tthe
aquifers through
ore solutions
solutions flowed
flowed upward
upward from
h e aquifers
through available
fracture
fracturesystems
systems into
i n t oMiddle
MiddleOrdovician
Ordovician strata
s t r a t awhere
wherethey
theyleached
leachedcarbonate
carbonate
physicalrrestraints
properties of
of the
rocks.
rocks. Changes
Changes i ninphysical
e s t r a i n t s and
and chemical
chemical properties
the ore
ore
solutions
n andnear
nearopen
openspaces
spaces
solutions allowed
allowed ore
ore minerals
minerals tot obebedeposited
depositedini and
derived from
from leaching.
leaching.
derived
14
�THE
THE GEOLOGY
GEOLOGY OF
OF BEECHER
BEECHER AND
AND PEMBINE
PEMBINE TOWNSHIPS
TOWNSHIPS
MARINETTE
MARINETTE COUNTY,
COUNTY, WISCONSIN
WISCONSIN
Robert
A. Jenkins
Jenkins
Robert A.
Department of
of Geology
Geology and
and Geophysics
Geophysics
Department
University of
of Wisconsin—Madison,
Wisconsin-Madison, Madison,
Madison, Wisconsin
Wisconsin
University
Four
Four metavolcanic
metavolcanic formations,
formations, separated
separated by
by major
major faults,
faults,
occur
occur in
in Beecher
Beecher and
and Pembine
Pembine townships
townships in
in northeastern
northeastern
Marinette County,
County, Wisconsin.
Wisconsin. The formations
formations are
are the
the Quinnesec
Quinnesec
Marinette
Formation, the
the Mc Allister
Allister Formation,
Formation, the
the Beecher
Beecher Formation,
Formation,
Formation,
the Pemene
Pemene Formation.
Formation. The relative
relative ages
ages are
are uncertain
uncertain
and the
but
but the
the order
order of
of naming
naming is
is suggested
suggested as
as the
the order
order of
of decreasing
decreasing
age. All
All the
the formations
formations have been
been folded
folded and
and regionally
regionally metametaage.
morphosed
morphosed to
to greenschist
greenschist facies.
facies. In
In general
general the
the rocks
rocks have
have
not
not been
been strongly
strongly sheared
sheared or
or altered,
altered, and
and primary structures
structures
volcanics have been
been intruded
intruded by
by
are well
well preserved.
preserved. The
The volcanios
are
granite,
granodiorites,quartz
quartzdiorites,
diorites,and
andultrainafics.
ultramafics.
granite, granodiorites,
The
The Quinnesec
Quinnesec Formation,
Formation, over
over 10,000
10,000 ft. thick,
thick, consists
consists
predominantly
predominantly of
of tholeiitic
tholeiitio metabasalts
metabasalts and
and cala-alkaline
cala-alkaline metametaandesites. The formation
formation is
is isoclinally
isoclinally folded;
folded; axial
axial planes
planes
andesites.
of the
the folds
folds are
are vertical
vertical and
and strike
strike east.
east. The
The andesites
andesites are
are
of
of
of two
two types,
types, one
one nonporphyritic
nonporphyritic and
and pillowed,
pillowed, having
having its
its
source to the west and the other,
other, porphyritic
porphyritic and mainly
agglomeratic,
100 to
to 1,000
1,000
agglomeratic, having
having its
its source
source to
to the
the east.
east. AA 100
ft. thick
is interlayered
interlayered with
with the
the
thick porphyritic
porphyritic rhyolite
rhyolite flow
flow is
andesites.
andesites.
The Mc Allister Formation,
Formation, 1,000
1,000 to
to nossibly
~ossibly10,000
10,000 ft
ft
The
thick, consists
consists of
of metamorphosed
metamorphosed tholeiitic
tholeiitio basalt
basalt agglomeragglomerthick,
ate.
alps vertically,
vertically, and
and faces
faces
ate. The
The formation
formation strikes
strikes east,
east, aips
south. Fragment
Fragment size in
in the formation
formation increases
increases from
from west
west to
to
south.
east, suggesting
suggesting aa vent
vent to
to the
the east.
east.
east,
The Beecher
Beecher Formation,
Formation, at
at least
least 10,000
10,000 ft. thick,
thick, strikes
strikes
N50°W,
N~O'W, dips
dips vertically,
vertically, and
and faces
faces north.
north. The
The lower
lower 9,000
9,000ft.
ft.
consists mainly
mainly of
of rhyolite
rhyolite and
and rhyodacite
rhyodacite flows.
flows. The
The upper
upper
consists
1,000 ft. of the formation
rhyformation is
is an
an alternation
alternation of
of bedded
bedded rhy—
olitic
olitic tuffs
tuffs and
and acidic
acidic fragmentals.
fragmentals. The lower
lower part
part of
of the
the
formation
formation is
is more highly sheared
sheared and
and altered than
than other
other formformations
ations in
in the
the area.
area. This
This may be
be due
due to
to intrusion
intrusion of
of the
the
Amberg
Amberg granite
granite into
into the
the lower
lower part
part of
of the
the formation.
formation.
Formation consists
consists of 7,000 ft. of
microspher—
The Pemene Formation
of microspherulitic
ulitic soda
soda rich
rich rhyolite
rhyolite and
and rhyodacite
rhyodacite flows.
flows. The
The flows
flows
are interlayered
units and
interlayered with a few
few thin
thin sedimentary
sedimentary units
and were
Individual flows
apparently
apparently extruded
extruded subaqueously.
subaqueously. Individual
flows are
are 500
500
to 1,200
1,200 ft. thick and traceable
traceable laterally
laterally for
for over
over four
four miles.
miles.
the
The formation
formation is
is folded
folded into
into an
an east
east trending
trending asemmetric
asemmetric
on the north limb
limb dip
dobly
doublyplunging
plunging syncline.
syncline. The units on
55 SS and
and those
those on
on the
the south
south limb
limb are
are vertical.
vertical.
55
Thin
various rock
rock types
Thin sections
sections of the various
types have been
been examined
examined
15
�ffor
o r primary structures
s t r u c t u r e s and to
t o determine
determine metamorphic
metamorphic grade.
grade.
Whole rock major element analyses
a n a l y s e s have
have been
been run
r u n using
u s i n g the
the
eelectron
l e c t r o n microprobe.
microprobe. These analyses
a n a l y s e s have been used to
to
iidentify
d e n t i f y rock types
o determine
h e petrochemical
types and
and tto
determine tthe
petrochemical
c
h a r a c t e r i s t i c s of the
t h e voloanios.
volcanics.
characteristics
t r e n d s indicate
I n d i c a t e that
t h a t the
t h e rocks
r o c k s of
of the
the
The petrochemical trends
aarea
r e a may be the
t h e products of several
s e v e r a l cycles
c y c l e s of
of volcanism.
volcanism.
Each formation is
i s chemically
chemically distinctive.
d i s t i n c t i v e . The Qtxinnesec
Quinnesec
the n
north
Formation grades from
f r o m tholelitic
t h o l e l i t i c bbasalts
a s a l t s Iin
n the
o r t h to
to
ccab-alkaline
a l c - a l k a l i n e andesites
a n d e s l t e s in
i n tne
tne south,
south, suggesting
suggesting that
t n a t it
It
may have formed at
a t the
t h e edge
edge of
of an
an island
i s l a n d arch
a r c h enviornment.
enviornment.
Mc
Ablister
Preliminary analyses
a n a l y s e s indicate
i n d i c a t e that
t h a t the
the M
c A
l l l s t e r Formation
basaLts. It may therefore
t h e r e f o r e correlate
correlate
cconsists
o n s i s t s of ttholeittic
h o l e l l t i c basalts.
Formation oor
may rrepresent
with part
p a r t of
of the
t h e Quinriesec
Quinnesec Formation
r Iit
t may
epresent a
sseparate
e p a r a t e volcanic
v o l c a n i c cycle.
c y c l e . The Beecher Formation
Formation rhyolites
rhyolltes
and rrhyodacites
are
typical
cab—alkaline
h y o d a c i t e s a r e t y p i c a l c a l c - a l k a l i n e acidic
a c i d i c vobcanics.
volcanlcs.
They may tie
be the
of the
t h e aacidic
c i d i c end product of
t h e Quinnesec
The pemene
Pemene Formation rrhyolites
volcanism.
h y o l i t e s aare
r e characterized
characterized
These
These
by higher
h i g h e r Na20
Na20 and lower
lower K20
K20 than
t h a n normal
normal rhyolites.
rhyolites.
volcanios
are
distinctly
different
from
the
rocks
of
the
volcanics are d i s t i n c t l y d i f f e r e n t
the rocks
the
Beecher Formation and therefore
t h e r e f o r e probably rrepresent
e p r e s e n t a separate
separate
period of volcanism.
volcanism.
The age of
of the
not
t h e volcanism in
i n the
t h e area
a r e a is
is n
o t positively
positively
known b
but
Rebelbo (1969)
U-Pb d
date
z i r c o n U-Pb
ate
(1969) rreport
e p o r t a zircon
u t Banks and Rebello
for
a
rhyolite
just
to
the
west
of
the
area
of
1905
(+30
for
r h y o l i t e just t o the
of
a r e a of 1905 (+30 to
to
-10) m.y.
This rrhyolite
-10)
m.y.
h y o l i t e probably correlates
c o r r e l a t e s with the
the Beecher
If
this
correlation
is
correct
then
the
acidic
Formation.
cidic
Formation.
I f t h i s c o r r e l a t i o n i s correct then the a
possibly
volcanism and p
o s s i b l y tthe
h e mafic volcanism in
In the
t h e area
a r e a is
is
upper Middle
Precambrian
in
age.
Middle Precanbrian i n age.
16
�PRECAMBRIAN
PRECAMBRIAN NORTH-SOUTH
NORTH-SOUTH ORIENTED
ORIENTED FAULTS
FAULTS IN
IN THE
THE
WESTERN
WESTERN MARQUETTE
MARQUETTE DISTRICT,
DISTRICT,NORTHERN
NORTHERNMICHIGAN
MICHIGAN
John S.
S. Klasner
Klasner
John
Western
Illinois
W e s t e r n Illinois University
University
Macomb,
Macomb. Illinois
Illinois
Thomas
Thomas R.
R. Turner
Turner
Michigan
Michigan Technological
Technological University
University
Houghton,
Michigan
Houghton, Michigan
ABSTRACT
ABSTRACT
Recent
has
R e c e n t mapping
mapping in
in northern
n o r t h e r n Michigan
Michigan h
a s indicated
indicated the
the presence
p r e s e n c e of
of
prominent
100W
W to
t oNN 200
20' E
E faults,
faults, many
many of
of which
which offset
offset east-west
east-west
prominentNN100
T h e s e faults
faults are
a r e expressed
e x p r e s s e d as
a s shear
shear
trending Keweenawandiabase
Keweenawan diabase dikes.
dikes. These
trending
zones
zones in
in lower
lower Precambrian
P r e c a m b r i a n granites,
g r a n i t e s ,offsets
offsetsininthe
thecontact
contactbetween
between middle
middle
and
anddiscontinuities
discontinuities
and lower
lower Precambrian
P r e c a m b r i a n rocks,
r o c k s , topographic
topographic lineaments,
l i n e a m e n t s ,and
in aeromagnetic
a e r o m a g n e t i c trends.
trends.
in
Regionally
Regionally tthese
h e s e faults
f a u l t s are
a r e on
on trend
t r e n d with
with major
m a j o r lineaments
l i n e a m e n t s observed
observed
ontthe
Hinze and
and others
o t h e r s (1966)
(1966) on
h e bbasis
a s i s of
of aaeroeroby
by other workers
w o r k e r s in
in the
the area.
a r e a . Hinze
magnetic
studies
in
eastern
Lake
Superior
show
a
major
north-northeast
a
m
a
j
o
r
n
o
r
t
h
n
o
r
t
h
e
a
st
magnetic studies i n e a s t e r n Lake S u p e r i o r show
trending
trending fault
fault extending
extending nnorth
o r t h aacross
c r o s s the
the lake
l a k e just
just east
e a s tof
of the
the tip
t i pof
of the
the
in nnorth
Keweenaw Peninsula.
Peninsula. La
L a Berge
B e r g e (1972)
(1972) in
o r t h central
c e n t r a l Wisconsin
Wisconsin has
has
Keweenaw
mapped
These
mapped major
m a j o r northeast
n o r t h e a s t trending
trending shear
s h e a rzones
zonesup
u pto
t oone
onemile
m i l eininwidth.
width. These
features
f e a t u r e s coupled
coupled with
with major
m a j o r lineations
lineations on
on psuedo
psuedo radar
r a d a rphotographs
photographs suggest
suggest
that
t h a t aa major
m a j o r fault
fault zone
zone bisects
b i s e c t s the
the arcuate
a r c u a t eshaped
shapedarea
a r e aoutlined
outlinedby
by the
the midmidcontinent
continent gravity
gravity high
high and
and proposed
proposedKeweenawan
Keweenawan rift.
rift.
With
movement, studies
With rregard
e g a r d to
to the
the timing
timing of
of movement,
studies in
in the
the western
w e s t e r n part
part
of
near
of the
the northern
n o r t h e r n complex
complex n
e a r Herman,
Herman, Michigan
Michigan suggest
s u g g e s t that
that at
a t least
l e a s t some
some
of the faults may
m a y have
have been
r i o r tto
o Penokean
e t a m o r p h i s m . For
For
of
been active
active pprior
Penokeanmmetamorphism.
example,
north-south fault
example, aa body
body of
of gabbro
gabbro occupies
occupies aa north-south
fault tthat
h a t cuts
cuts granite
granite
gneiss,
g n e i s s , and
and the
the gabbro
gabbro is
i sinterpreted
i n t e r p r e t e dtot ohave
havebeen
beenmetamorphosed
m e t a m o r p h o s e d by
by
Penokean oorr some
s o m e earlier
e a r l i e r thermal
t h e r m a levent.
event.
Penokean
In
places
dikes aare
In many
many p
l a c e s east-west
e a s t - w e s t Keweenawan
Keweenawan dikes
r e offset
offset at
a t the
the northnorthhas
found ffor
the dikes
No evidence
evidence h
a s been
been found
o r sshearing
h e a r i n g of
of the
d i k e s at
a t these
these
south faults. No
faults
faults and
and in
in some
s o m e instances
i n s t a n c e sthe
theKeweenawan
Keweenawan dikes
dikes have
have been
been found
found to
t o intrude
intrude
N e v e r t h e l e s s , the
the conclusion
conclusion seems
s e e m s inescapable
inescapable that
that
along the fault
f a u l tzone.
zone. Nevertheless,
along
the
numerous
occurrence
of
offset
dikes
at
the
north-south
faults
must
denote
the n u m e r o u s o c c u r r e n c e of offset dikes a t the north-south faults m u s t denote
post-Keweenawan
post-Keweenawan fault
fault movement.
movement.
17
�References
Hinze, Wrn.
O'Hara, N.
W., Trow,
Wm. J., O'Hara,
N. W.,
Trow, 3.
J. W.
W. and
and Secor, G.
G. B., 1966,
1966,
Aeromagnetic Studies
Studies ofofEEastern
Lake Superior,
Superior, in the
the EEarth
Aeromagnetic
a s t e r n Lake
arth
Beneath
the Continents,
G. U.
U. Geo& Smith, ed.
ed. ,, A. G.
Beneath the
Continents, Steinhart
Steinhart &
physical
physical Monograph
Monograph 10,
10, pp.
pp. 95-110.
95-110.
La
Zones in
in the
the PPreL a Berge, G.
G. L.,
L . , 1972,
1972, Lineaments
Lineaments and
and Mydonite
Mydonite Zones
re1: 18th
18th Ann.
Ann. Inst.
Inst. on
on Lake
Lake
ccambrian
a m b r i a n of
of northern
n o r t h e r nWisconsin
Wisconsin [abs.
[abs,}:
Superior Geology,
Michigan, ppaper
27.
Superior
Geology, Houghton,
Houghton, Michigan,
a p e r 27.
18
�-
GEOCHEMISTRYOF
OF THE
THE CALCIUM
GEOCHEMISTRY
CALCIUM - CARBON
CARBON DIOXIDE
DIOXIDEMETASOMATISM
METASOMATISM
AT PRESQUE
MICHIGAN
PKESQUE ISLE,
ISLE, MARQUETTE, MICHIGAN
M. D. Lewan,
Lewan, Department
Department of
of Geology
Geology and
and Geological
Geological Engineering,
Engineering,
M.
Michigan
Michigan Technological
Technological University
Presently
With Shell
Presently With
Shell Oil
Oil Company,
Company, New
New Orleans,
Orleans, Louisiana
Louisiana 70160
70160
ABSTRACT
ABSTRACT
A highly veined rock
rock composed of
of dolomite
dolomite and quartz
quartz with
with
peridotite at
minor hematite,
hematite, overlies
overlies the
the Presque
Presque Isle
Isle serpentinized
serpentinized peridotite
Marquette, Michigan.
Marquette,
Michigan. Petrographic
Petrographic and field observations
observations clearly
clearly
indicate
indicate that
that this
this rock
rock was
was originally
originally highly
highly serpentinized
serpentinized peridotite
peridotite
which
has since
since been
been subjected
subjected to
to metasomatic
metasomatic solutions.
solutions.
which has
The
The author
author (Lewan,
(Lewan, 1972) has interpreted
interpreted this
this dolomite-quartz
dolomite-quartz
rock as originally being a peripherial shear zone which
which developed during
the tectonic
tectonic intrusion
intrusion of
of the
the peridotite.
peridotite. Either during
during or
or after
after its
its
emplacement water
water from the surrounding country rocks circulated through
emplacement
this highly fractured
fractured peripherial
peripherial zone
zone causing
causing extensive
extensive serpentinizaserpentinization
tion to the
the still
still warm
warm but
but cooling
cooling peridotite.
peridotite. Following
Following the
the period of
of
serpentinization a potash rich granite was
was emplaced and
and was
was apparently
serpentinization
illitized by late
late stage
stage magmatic
along its
its outer
outer boundary
boundary where
where
illitized
magmatic water
water along
it
contact with
with the
comes in contact
it comes
the peridotite.
peridotite. Both the
the highly
highly serpentinized
serpentinized
peridotite and illitized
metasomatic soluperidotite
illitized granite were susceptable
susceptable to metasomatic
soluwhich resulted in the formation of the now
now existing
existing dolomite-quartz
tions which
rock.
objective of this
was to investigate
rock.
The objective
this study was
investigate the chemical
conditions which may
may have induced this period
parameters and prevailing conditions
of
metasomatism.
of metasomatism.
Comparative analysis of the chemical
chemical composition
composition of the
Comparative
the
dolomite-quartz rock
dolomite-quartz
rock with the serpentinized peridotite and illitized
granite indicates
were introduced into
granite
indicates that calcium and carbon dioxide were
system with
with partial removal
the system
removal of
of silica
silica and
and magnesium. Experimental
Experimental
work by Gordon
with free
work
Gordon and
and Greenwood
Greenwood (1970)
(1970) and Ellis (1959),
(1959), along
along with
free
metasomatism probably never
energy calculations
calculations suggest
suggest that
that the metasomatism
exceeded 300°C.
Luce (1972) has
has shown
shown that
that serpentine
serpentine is
is most
most soluble
soluble
300°C Luce
exceeded
waters which
which gradually become
become more
more basic
basic as
as the serpentine
in acidic waters
dissolution continues.
dissolution
continues. This increase in
in pH probably also accompanied
metasomatic solutions
serpenthe metasomatic
solutions during
during the
the dissolution
dissolution of
of the
the highly
highly serpenperipherial zones which
which eventually
eventually resulted
resulted in
tinized and illitized peripherial
mobilization of silica
the mobilization
silica released
released from
from the
the serpentine
serpentine lattice
lattice and
and the
the
precipitation of
precipitation
of dolomite.
dolomite.
pre-Jacobsville
This period of metasomatism has been dated as pre-Jacobsville
peridotite
sandstone and post-granite
sandstone
post-granite illitization.
illitization. The occurrence of the peridotite
greenstone terrain offers
offers an-attractive
anattractive hypothesis
in greenstone
hypothesis that
that this
this metasomatism may
may have been a result
somatism
result of
of the
the expulsion
expulsion of
of fluids
fluids from
from neighneighboring rocks
rocks during
during the
the regional
regional metamorphism
metamorphism of
of the
the area.
area.
19
�REFERENCES
REFERENCES CITED
CITED
Ellis,
Carbon Dioxide
(1959), The
The Solubility
Solubility of
of Calcite
Calcite in
in Carbon
Dioxide
Ellis, A. J. (1959),
Solutions,
Am.
3.
Sci.,
257,
pp
354-365.
Solutions, Am. J.
257, pp 354-365.
Cordon,
M., and
and Greenwood,
Greenwood, H.
H. 3.
J. (1970),
(1970), The
The Reaction:
Reaction: Dolomite
Dolomite
Gordon, T.
T. M.,
+
Quartz +
Water == Talc
+Quartz
+Water
Talc + Calcite
Calcite + Carbon
Carbon Dioxide,
Dioxide, Am.
Am. 3.
J. Sc!.,
Sci., 268,
268,
pp 225—242.
225-242.
pp
+
+
Lewan,
and Weathering
Weathering of the
Lewan, M. XL
D. (1972),
(1972), Metasornatism
Metasomatism and
the Presque
Presque Isle
Isle
Serpentinized
Serpentinized Peridotite,
Peridotite, Marquette,
Marquette, Michigan,
Michigan, Michigan
Michigan Technological
Technological
University,
University, unpublished
unpublished M.S.
M.S. Thesis,
Thesis, 55
55 pp.
pp.
Luce,
Luce, R.
R.
Kinetics
Kinetics
W., Bartlett,
W., and Parks,
Parks, G.
0. A
A.
Dissolution
W.,
Bartlett, R.
R. W.,
. (1972),
(1972), Dissolution
of
Magnesium
Silicates,
Geochim.
Cosmochim.
Acta,
of Magnesium Silicates, Geochim. Cosmochim. Acta, 36,
36,pp
pp 35-50.
35-50.
20
�THE BIOGENIC ORIGIN
THE
ORIGIN OF
OFPRIMARY
PRIMARY MINERALS
MINERALS IN
IN
LAKE
LAKE SUPERIOR
SUPERIORPRECAMBRIAN
PRECAMBRIAN IRON-FORMATION
IRON-FORMATION
M.
Lougheed and
7. J.
Mancuso, Department
M. S.
S. Lougheed
and J.
J. Mancuso,
Geology,
Department of
of Geology,
Bowling
Bowling Green University,
University, Bowling
Bowling Green,
Green, Ohio
Ohio 43403
43403
ABSTRACT
ABSTRACT
Primary
Primary minerals
minerals in
in the
the Lake
Lake Superior
Superior Precambrian
Precambrian ironironformations
formations are
are the
the direct
direct products
products of
of the
the life
life processes
processes of
of
a melange of filamentous
filamentous and
and unicellular
unicellular organisms
organisms together
together
with
minerals so
with associated
associated bacteria.
bacteria. Primary
Primary minerals
so formed
formed are
are
aragonite
Pyrite is
aragonite and/or calcite,
calcite, magnetite,
magnetite, and
and opal.
opal. Pyrite
is
formed
formed during decay
decay of
of organic
organic material
material with
with attendant
attendant sulfate
sulfate
reducing bacteria and is therefore later in origin than
reducing
than the
the
above
above three
three minerals although
although it
it too
too is
is of
of biogenic
biogenic origin
origin
and may be
Hematite occurs
be considered
considered primary.
primary. Hematite
occurs as
as an
an alteraalteration product of earlier
earlier formed minerals and is not considered
a
primary mineral.
a primary
mineral.
bacteria and is therefore later in
Aragonite
Aragonite or
or calcite
calcite crystals
crystals are
are biogenically deposited
deposited
structural
structural elements
elements occurring
occurring as
as submicron
submicron width
width prisms
prisms
oriented normal to an algal mat,
mat, and producing in turn a
carbonate mat.
carbonate
mat. A succession
succession of
of algal
algal and carbonate
carbonate mats
(laminae) occurs
occurs in horizontally
horizontally banded
banded iron-formation;
iron-formation; in
in
domical or columnar
domical
columnar stromatolites;
stromatolites; as
as coatings
coatings on
on granules
granules
(pellets); or forming
forming micro—oncoliths.
micro-oncoliths. Micro-oncoliths
Micro-oncoliths are
are
typically
0—50 microns
microns in
Calcium carbonate
typically 220-50
in diameter.
diameter. Calcium
carbonate can
can
be dolomitized,
dolomitized, sideratized,
sideratized, or
or silicified.
silicified.
Magnetite initially occurs
subMagnetite
occurs as
as a
a diffuse
diffuse cloud
cloud of
of subwithin the
micron sized
sized crystals
crystals within
the protoplasm of unicellular
unicellular
Too
plants.
plants.
Too high aa concentration
concentration of
of oxygen
oxygen produced
produced by
by
photosynthesis in
photosynthesis
in these
these unicellular
unicellular plants can
can be lethal
lethal to
them; they therefore
therefore oxidize
oxidize iron
iron that
that is
is dissolved
dissolved in
in the
the
water to
to produce magnetite, thereby attenuating
attenuating a
a lethal
lethal
buildup
of oxygen.
oxygen. During
During deposition
deposition and
and early
early diagenesis
diagenesis
buildup of
magnetite may
may be
be recrystallized to
the submicron crystals of magnetite
form
Diagenesis may subseform coarser
coarser octahedra
octahedra of
of magnetite.
magnetite. Diagenesis
subsequently produce
quently
produce megascopic
megascopic subhedral
subhedral masses
masses of
of magnetite.
magnetite.
Some magnetite is produced by oxidation of siderite during
the depositional
depositional stage,
stage, which
which subsequently
subsequently may
may be
be recrystalrecrystallized during diagenesis
diagenesis in
in aa similar
similar manner
manner to
to that
that of
of primary
primary
biogenic magnetite.
biogenic
magnetite.
Siliceous
Siliceous tests
tests of
of microorganisms
microorganisms yield
yield the
the hydrous
hydrous
silica, which during deposition is almost invariably comminuted
to an
an opaline
opaline slurry.
slurry. This slurry
slurry readily
readily dehydrates
dehydrates during
during
diagenesis to
diagenesis
to chalcedony
chalcedony or
or more
more often
often to
to chert.
chert. From
From five
five
to seven
seven types
types of siliceous
siliceous tests
tests of
of unicellular
unicellular organisms
organisms
21
�occur.
occur.
Usually
Usually the
t h e cavities
c a v i t i e s are
a r e filled
f i l l e d with
w i t h organically
organically
stained
s t a i n e d chalcedony,
chalcedony, and
and often
o f t e n submicron
submicron sized
s i z e d anhedra
anhedra of
of
carbonate
c a r b o n a t e are
a r e present.
p r e s e n t . The
The test
t e s t walls
w a l l s are
a r e not
n o t organically
organically
stained;
clear. Occasionally
O c c a s i o n a l l y the
t h e core
c o r e and
and
s t a i n e d ; they
t h e y are
a r e water
w a t e r clear.
test
t e s t are
a r e recrystallized
r e c r y s t a l l i z e d to
t o an
an optically
o p t i c a l l y oriented
o r i e n t e d sphere
s p h e r e or
or
ellipsoid
e l l i p s o i d of
o f quartz.
q u a r t z . The
The tests
t e s t s range
range in
i n width
w i d t h from
from 55 to
to
25 microns although
a l t h o u g h aa few
few may
may exceed
exceed 50
5 0 microns.
microns. PreservaPreservation
t i o n of
o f siliceous
s i l i c e o u s tests
tests occurs
o c c u r s only
o n l y when
when they
t h e y were
were deposited
deposited
in
n e v e r when
when water
w a t e r current
c u r r e n t activity
a c t i v i t y prevailed.
prevailed.
i n quiet
q u i e t water,
w a t e r , never
They therefore
t h e r e f o r e are
a r e not
n o t found
found in
i n association
a s s o c i a t i o n with
w i t h granules
granules
or
o r stromatoljtes.
stromatolites.
P y r i t e may be thought
t h o u g h t of
o f as
a s primary in
i n the
t h e sense
s e n s e that
that
Pyrite
it results
r e s u l t s from
from iron
i r o n in
i n the
t h e water
w a t e r reacting
r e a c t i n g with
w i t h sulphur
sulphur
produced
produced by sulfate
s u l f a t e reducing
r e d u c i n g bacteria
b a c t e r i a during
d u r i n g decay
decay of
of
organic
o r g a n i c debris.
d e b r i s . Pyrite
P y r i t e occurs
o c c u r s as
a s discrete
d i s c r e t e octahedrons
o c t a h e d r o n s or
or
octahedrons
o c t a h e d r o n s modified
m o d i f i e d by aa cube,
cube, as
a s framboidal
f r a m b o i d a l octahedra,
o c t a h e d r a , or
or
as
a s framboidal
f r a m b o i d a l mats
mats or
o r spheres.
s p h e r e s . Secondary
Secondary replacement
replacement pyrite
pyrite
formed during
d u r i n g diagenesis
d i a g e n e s i s is
i s ubiquitous.
ubiquitous.
22
�--
THE WOLF
RIVER BATHOLITH
BATHOLITH -- A L
LATE
THE
WOLF RIVER
ATE PRECANBRIA1
PRECAMBRIAN RAPAKIVI
MPAKIVI
MASSIF
I NNORTHEASTERN
NORTBBASTERN WISCONSIN
WISCONSIN
MASSIF IN
L. G.
G. Medaris,
. Nyles,
Medaris, Jr.,
Jr., J. L.
L. Anderson,
Anderson, and J.
J. R
B.
Myles, Department of
Geology
Wisconsin, Madison 53706
Geology and Geophysics,
Geophysics, University of
of Wisconsin,
53706
ABSTRACT
AESTRACT
Anorogenic, epizonal
batholith,
epizonal ggranitic
r a n i t i c rocks
rocks of
of the
t h eWolf
Wolf River
River b
atholith,
covering an aarea
of approximately 3600 square miles,
miles, represent a major
covering
r e a of
element of the
t h e Precambrian
Precambrian terrain
t e r r a i n in
i n northeastern
northeastern Wisconsin.
Wisconsin. This
batholith,
1500 m.
m. y.
y. iin
age, has llithologic,
n age,
i t h o l o g i c , mineralogic,
mineralogic,
b a t h o l i t h , 11150
1450 tto
o 1500
chemical, and structural
respect to
that are
a r e similar
similar in
i n every
every respect
to
chemical,
s t r u c t u r a l ffeatures
e a t u r e s that
those
those of
of the
t h e classic
c l a s s i c rapakivi
rapakivi massifs
massifs in
i nFinland.
Finland.
A vvariety
been distinguished,
distinguished, including
including ggranite,
A
a r i e t y of
of rock
rock types
types have
have been
ranite,
quartz
monzonite,r rhyolite,
trachyandesite, but
quartz monzonite,
monzonite, ssyenite,
y e n i t e , monzonite,
h y o l i t e , and
and trachyandesite,
but
quartz monzonite
of tthe
monzonite iiss predominant,
predominant, accounting
accounting for
f o r 87%
87% of
h e exposed
exposed area.
A porphyritic
porphyriticttexture
of aalkali
A
e x t u r e iis
s characteristic,
c h a r a c t e r i s t i c , ini nwhich
which phenocrysts
phenocrysts of
lkali
feldspar
f e l d s p a r and,
and, to
t o a lesser
l e s s e r extent,
e x t e n t , plagioclase and quartz
quartz are
a r e set
s e t in
i n aa
medium— tto
mediumo fine—grained
fine-grained matrix of quartz,
quartz, two feldspars,
f e l d s p a r s , and mafic
minerals. Rapakivi texture
t e x t u r e is
i s extensively developed in
i n the
t h e Waupaca
Waupaca
quartz monzonite and
and occurs
occurs in
i n minor
minor amounts
amounts throughout
throughout the
t h e batholith.
batholith.
Quartz iis
many llithologic
units;
s euhedral iin
n many
ithologic u
n i t s ; bbiotite
i o t i t e and hornblende are
Quartz
generally anhedral and interstitial
i n t e r s t i t i a l to
t o feldspars
f e l d s p a r s and quartz.
quartz.
The
The granitic
g r a n i t i c rocks
rocks of
of the
t h e batholith
b a t h o l i t h tend
tend to
t o be
be rich
r i c hini nSiO
SiO and
alkalies,
, CaO, and
and MgO.
TLg batho—
andpoor
poor in
i nAl20
A120 ,
MgO. ~
bathoe
a l k a l i e s , particularly
p a r t i c u l a r l yKK0,0,and
11th
l i t h has
has alkaline
a l k a l i n e affiniies,
a f f i n i z i e s , although only
only eraluminous
Jeraluminous and metaluminous
metalminous
types
have been recognized
recognized so
so far.
f a r , Values of
of normative Q—Ab—Or
Q-Ab-Or for
for
representative
r e p r e s e n t a t i v e specimens
specimens plot
p l o t close
c l o s e to
t o a low
low pressure thermal trough and
and
minimum
minimum for
f o r the
t h e experimental
experimental "granite"
"granite" system,
system, with
with aa slight
s l i g h tdisplacement
displacement
towards normative Or.
Or.
towards
Perthitic
P
e r t h i t i c alkali
a l k a l ifeldspar
feldsparisi the
s t hpredominant
e predominant mineral
mineral in
i n the
t h e bathoJ.ith,
batholith,
accompanied
quartzand
andplagioclase,
plagioclase, ranging
accompanied bybyquartz
ranging in
i ncomposition
composition from
from An
An 3 to
to
)tO,
An
Iron—richbbiotite
40, with most values falling
f a l l i n g between A
n 10
1 0 tto
o 25.
25. Iron-rich
i o t i t e and
hornblende are
minerals, although olivine,
a r e the
t h e predominant mafic minerals,
o l i v i n e , clino—
clinopyroxene, and
pyroxene,
and orthopyroxene
orthopyroxene occur
occur in
i n monzonite
monzonite and
and trachyandesite.
trachyandesite. Fluorite
Fluorite
is
batholith,
i s tthe
h e most widespread accessory mineral in
i n tthe
he b
a t h o l i t h , and a halogen—
halogenrich
biotite
i s reflected
r e f l e c t e d in
i n high Cl
C l and F
F contents of
of b
i o t i t e and
r i c h environment is
hornblende.
Wolf River b
batholith
The Wolf
a t h o l i t h may have crystallized
c r y s t a l l i z e d from
from relatively
r e l a t i v e l y dry
dry
granitic
partial
off pre-existing
pre—existing
g r a n i t i c magmas tthat
h a t were derived by p
a r t i a l melting o
crustal
materials,
basaltic
volcanics, v
volcaniclastic
crustal m
a t e r i a l s , consisting
c o n s i s t i n g of
of b
a s a l t i c volcanics
olcaniclastic
sediments, and quartz dioritic
sediments,
d i o r i t i c to
t o granodioritic
g r a n o d i o r i t i c plutonic
plutonic rocks.
rocks.
,
23
�SUMMARY
WISCONSIN
SUhMkRY OOF
F GLACIAL GEOLOGY
GEOLOGY OF
OFNORTH—CENTRAL
NORTH-CENTRAL WISCONSIN
D. M.
Department
of
M. Mickelson,
Mickelson,
Department
of Geology
Geology and
and Geophysics,
Geophysics, University
University of
Wisconsin, Madison, Wisconsin
Wisconsin 53706
53706
ABSTRACT
ABSTRACT
The
The Pleistocene glacial
g l a c i a lchronology
chronology of
of central
c e n t r a land
andnorthern
northernWisconWisconnot
not well
well established.
established. Early
Early workers
workers (Owen,
(Owen, l8t7;
1847; Chamberlain,
Chamberlain,
1907) outlined
o u t l i n e d the
t h e distribution
d i s t r i b u t i o n of
of glacial
g l a c i a l deposits
deposits and
and
1882, Weidman, 1907)
recognized aa presumed older
o l d e r drift
d r i f t outside the
t h e terminal moraines of
of WisWisconsin
consin age.
age. Hole
Hole (1943)
(1943) and
and Thwaites (l913)
(1943) concluded that
t h a t the
t h e older
older
d r i f t (Border
order Drift)
rift) was of
of one
one age
age and
and was deposited
deposited in
i n the
t h e pre—Cary
pre-Cary
drift
(pre—late
( p r e - l a t e Woodfordian)
woodfordian) time.
time. Radiocarbon
Radiocarbon dates
d a t e s (Black
(Black and
and Rubin,
Rubin,
1968) beneath
beneath the
t h e Border
Border Drift
D r i f t in
i n Wood
Wood County
County are
a r e >>i5,O00
45,000 years
years B.P.
B.P.
1968)
In
I n southern
southern and
and western Wisconsin wood
wood from
from an
an old
o l d till
till possible
possible
B. P.
P.
c o r r e l a t i v e with
with the
t h e Border
Border Drift
D r i f t is
i s dated
dated at
a t about
about 30,000
30,000 years B.
correlative
and
and is
i s considered
considered Rockian
Rockian (late
( l a t e Altonian)
Altonian) age.
age. The
The Border
b r d e r Drift
D r i f t may
may
actually
a c t u a l l y consist
c o n s i s t of
of 22 tills
t i l l s of
of differing
d i f f e r i n g age.
age. The
till was
was
The lower
lower till
deposited by
by ice
i c e moving
moving from
from the
t h e west in
i n Marathon County
County (LaBerge,
(~a~erge,
deposited
1972)
1972) and
and the
t h e upper
upper till
till by
by ice
i c e moving
moving from
from the
t h e northwest
northwest in
i n southern
southern
Lincoln
Lincoln and
and Langlade
Langlade Counties.
Counties.
sin
s i n is
is
Three
Three ice
i c e lobes
lobes built
b u i l t terminal
terminal moraines
moraines in
i n Lincoln
Lincoln and
and Langlade
Langlade
Counties
Counties during
during late—Woodfordian
late-Woodfordian time.
time. The
The Wisconsin
Wisconsin Valley
Valley Lobe
Lobe
advanced
advanced from
from the
t h e northwest
northwest depositing
depositing aa reddish—brown,
reddish-brown, sandy
sandy basal
basal
till.
To the
t h e east,
e a s t , the
t h e Langlade
Langlade Lobe
Lobe deposited
deposited aa dark
dark reddish—brown
reddish-brown
till. To
basal
b a s a l till
till as
a s ice
i c e flowed
flowed from
from the
t h e northeast.
northeast. Further
Further east,
e a s t , the
t h e Green
Green
Bay
Bay Lobe,
Lobe, advancing
advancing from
from the
t h e east
e a s t and
and southeast,
southeast, deposited
deposited aa brown,
brom,
sandy,
sandy, dolomitic
dolomitic till.
till.
No
No absolute
absolute dates
dates are
a r e available,
a v a i l a b l e , but
but stratigraphic
s t r a t i g r a p h i c and
and geomorphic
geomorphic
evidence
evidence suggests
suggests that
t h a t the
t h e advance
advance of
of these
t h e s e lobes
lobes to
t o their
t h e i r terminal
terminal
moraines
moraines was
was not
not contemporaneous
contemporaneous as
a s reported
reported by
by Thwaites
Thwaites (1943).
(1943). At
At
the
t h e junction
junction of
of the
t h e Wisconsin
Wisconsin Valley
Valley Lobe
Lobe and
and Langlade
Langlade Lobe
Lobe no
no strati—
stratigraphic
till
graphic sections
s e c t i o n s showing
showing 22 tills
t i l l s are
a r e available.
a v a i l a b l e . Relationships
Relationships of
of till
fabric
f a b r i c azimuths,
azimuths, moraine
moraine alignments
alignments and
and drainage
drainage features
f e a t u r e s indicate
i n d i c a t e an
an
early
e a r l y advance
advance of
of the
t h e Langlade
Langlade Lobe
Lobe and
and the
t h e formation
formation of
of the
t h e Parrish
Parrish
Moraine.
This was
was followed
followed by
by an
an advance
advance of
of the
t h e Wisconsin
Wisconsin Valley
Valley Lobe
Lobe
Moraine. This
and
was followed
followed shortly
shortly
and the
t h e formation
formation of
of the
t h e Harrison
Harrison Moraine
Moraine which
which was
thereafter
t h e r e a f t e r by
by aa readvance
readvance of
of the
t h e Langlade
Langlade Lobe
Lobe to
t o aa position
p o s i t i o n 66 miles
miles
short
and tthe
short of
of its
i t maximum
s maximum advance
advance and
h e formation
formation of
ofthe
t h eSummit
SummitLake
Lake
Moraine.
Moraine.
Stagnant
Stagnant ice
i c eofofthe
t h Wisconsin
e WisconsinValley
ValleyLobe
Lobemay
may have
have been
been
present
present during
during this
t h i sreadvance.
readvance.
To
To the
t h e east,
e a s t , the
t h e Green
Green Bay
Bay Lobe
Lobe advanced
advanced to
t o its
i t s maximum
maximum position
position
and
and retreated
r e t r e a t e d at
a t least
l e a s t 20
20 miles
miles before
beforethe
t hmaximum
e maximum advance
advance of
of the
the
Langlade
Bay
Lobe
till
is
stratigraphically
beneath
Langlade Lobe.
Lobe. Green
that
Green Bay Lobe till i s s t r a t i g r a p h i c a l l y beneath that
of
of the
t h eLanglade
Langlade Lobe
Lobe aat
t lleast
miles in
i~from
from the
t h e margin
margin of the
the
e a s t 55 miles
Langlade
Outwash streams
h e Langlade
Langlade Lobe
Lobe iice
c e cut
c u toutwash
outwash
streams from
from tthe
Langlade Lobe.
Lobe. Outwash
and
thet hGreen
Bay
and till
tillofof
e Green
BayLobe.
Lobe.
24
�A
PLUTONNEAR
NEARELY,
ELY, MINNESOTA
A LOWER
LOWER PRECAMBRIAN
PRECAMBRIAN LAMPROPHYRE
LAMPROPHYRE PLUTON
MINNESOTA
M. G.
M.
Mudrey, ~
r .and
and
'
A.
L. Geldon,
Geldon, University
U n i v e r s i t yofoMinnesota
f Minnesotaand
andMinnesota
Minnesota
G. Mudrey,
Jr.1
A. L.
Geological Survey.
Survey.
ABSTRACT
ABSTRACT
Oneoof
bodies ooff lamprophyre
One
f tthe
h e bbetter
e t t e r exposed
exposed bodies
lamprophyre wwithin
i t h i n tthe
h e Early
E a r l y PrePrecambrian
Vermilionddistrict
cambrian Vermilion
i s t r i c t of
o fMinnesota
Minnesota is
i s located
l o c a t e d88km
km northwest
northwest ooff Ely,
Ely,
on tthe
on
h e north
n o r t h side
s i d e of
o fBurntside
Burntside Lake.
Lake. The
The ccrudely
r u d e l y e elliptical
l l i p t i c a l pluton,
p l u t o n , about
about
by0.5
0.5 km,
km,i is
Lower
Precambrian
1 km
km by
s situated
s i t u a t e d in
i nthe
t h ecore
coreofo a
f afold
f o loutlined
d o u t l i n eby
d by
Lower
Precambrian
migmatizedb ibiotite
amphibolite;
howevert hthe
migmatized
o t i t e sschist
c h i s t and
and amphibol
i t e ; however
e p lpluton
uton i sisvvitually
itual l y
1
unmetamorphosed
unmetamorphosed andand
i s is
d i sdiscordant
c o r d a n t t otot hthe
e sstructure.
tructure.
The
has aa narrow,
narrow, discontinuous
discontinuousborder
borderzone
zoneo fofuuralitized
The ppluton
l u t o n has
ralitized
phlogopite-bearing
These two
two
phlogopite-bearing pyroxenite
p y r o x e n i t e and
and an
an inner
i n n e r zone
zone of
o flamprophyre.
lamprophyre. These
rock types
based
relations,
petrography,
f i efield
1 d re1
a t i o n s ,petrography,
rock
types are
a r e considered
considered comagmatic
comagmati c based
on on
Both the
t h e pyroxenite
p y r o x e n i t e and
and the
t h elamprophyre
lamprophyre are
are cut
c u tbybynumerous,
numerous,
and
and chemistry. Both
thin
adamell i t i composition,
c composition,which
whichcontain
c o n t a i nxenocrysts
xenocrysts
t h i n dikes
dikes of
o fmonzonitic
monzoni t i c to
t oadamellitic
of
mafic
minerals tthat
o f the
t h e same
same m
a f i c minerals
h a t occur
occur in
i nthe
t h epyroxenite
p y r o x e n i t eand
andlarnprophyre.
lamprophyre. The
The
dikes
representa al alate
dikes are
a r e probably
probably comagmatic,
comagmatic, b ubut
t c ocould
u l d represent
t e ppink
i n k lleucocratic
eucocratic
phaseoof
adjacent VVermilion
phase
f tthe
h e adjacent
e n n i l i o n ggranite.
ranite.
The lamprophyre
lamprophyrei is
Approximately213
2/3 ooff the
The
s a melanocratic porphyry.
porphyry. Approximately
the
exposed
lamprophyrei sisaa bbiotite—bearing
hornblendes spessartite;
exposed lamprophyre
i o t i t e - b e a r i n g hornblende
p e s s a r t i t e ; the
t h e remainremainThe sspessartite
byuuralitized
ing
113 is
i s augite
a u g i t e inokersantite.
i n o k e r s a n t i t e . The
p e s s a r t i t e iiss dominated
dominated by
ralitized
i n g 1/3
with
subordinatec hchloritized
ddiopsidic
i o p s i d i c aaugite
ugite w
i t h subordinate
l o r i t i z e d bbiotite,
i o t i t e , sericitized
s e r i c i t i z e dandesine,
andesine,
andi interstitial
and
n t e r s t i t i a lpotassium
potassium feldspar;
feldspar; the
t h e relatively
re1 a t i v e l yunaltered
u n a l t e r e d inokersantite
inokersantite
is
by ddiopsidic
i s dominated
dominated by
i o p s i d i c augite
a u g i t e and
and biotite
b i o t i t ewith
w i t hsubordinate
subordinateandesine
andesineand
and
interstitial
crude subhorizontal
subhorizontal llayering
i n t e r s t i t i apotassium
l potassium feldspar.
feldspar. A
A crude
a y e r i n g within
w i t h i n both
both
types ooff lamprophyre
byananupward
upward
increase
types
lamprophyre i is
s marked
marked by
increase
i ning rgrain
a i n ssize
i z e oof
f the
the
groundmassand
and
decrease
phenocrysts; an
groundmass
decrease
i n in
s i size
z e o of
f tthe
h e phenocrysts;
an increase in
i n amount
amount of
of
potassiumf efeldspar
potassium
l d s p a r aatt the
t h e expense
expense ooff total
t o t a l ferromagnesian
ferromagnesian minerals;
minerals; and
and
aa change
change iinn the
t h e compositions
compositionsofo the
f t hferromagnesian
e ferromagnesianminerals——mainly
minerals--mainly an
an
increase
increase in
i n the
t h e iron/magnesium
iron/magnesium rratios.
atios.
Calculated compositions
Calculated
compositions for
f o r the
t h erocks
rocksbased
basedon
onmodal
modal data
data and
and microprobe
microprobe
analyses
analyses oof
f cconstituent
o n s t i t u e n t phases
phases i nindicate
d i c a t e tthat
h a t this
t h i s pluton
p l u t o nmay
may be
be related
r e l a t e d to
to
an alkali
an an
uncommon
b a s a lparent,
t parent,
uncommon petrochemical
petrochemical type
type ini nLower
LowerPrecambrian
Precambrian
a1 k a l ibasalt
an
terranes.
terranes.
The
wasemplaced
emplaced
cooled rrapidly.
The ppluton
l u t o n was
i nina as esemicrystalline
m i c r y s t a l l i n e sstate
t a t e and
and cooled
apidly.
byeearly
IInitially
n i t i a l l yhigher
h i g h e roxygen
oxygen ffugacity,
u g a c i t y , as
as indicated
i n d i c a t e d by
a r l y ccrystallization
r y s t a l l i z a t i o n of
of
magnetite
andapparently
apparently
magnetite and
h i ghigh
h f e ferric/ferrous
r r i c / f e r r o u s rratios
a t i o s in
i n biotite,
b i o t i t e decreased
, decreased
Disequilibrium
i s e q u i l i b r i u m ttextures
e x t u r e s iindicate
n d i c a t e that
that
somewhat
somewhat d uduring
r i n g c rcrystallization.
ystallization. D
crystallization
c r y s t a l l i z a t i o nbegan
beganata depth
t depthand
andconcluded
concluded at
a t shallower,
shallower, synvolcanic
synvolcanic depths.
depths.
1Nowa tatDry
DryVValley
INOW
a l l e y DDrilling
r i l l i n g Project,
P r o j e c t ,Department
Department of
o f Geology,
Geology, Northern
Northern
Illinois
University,
DeKaib,
Illinois
60115.
I l l i n o i s U n i v e r s i t y , DeKalb, I l l i n o i s
25
�Mineralogical
Mineralogical and
and Chemical
Chemical Studies
Studies
of Greenstones in
i n Wisconsin
by
G.
G. Mursky, G.
G. Schriver
S c h r i v e r and
and A.
A. R.
R . Venditti
Venditti
Department of
o f Geological
Geological Sciences
Sciences
University
U n i v e r s i t y of
of Wisconsin—Milwaukee
Wisconsin-Milwaukee
Milwaukee,
Milwaukee, Wisconsin
ABSTRACT
Central,
C e n t r a l , northern
n o r t h e r n and
and northeastern
n o r t h e a s t e r n parts
p a r t s of
o f Wisconsin
contain
volcanic—sedimentary
c o n t a i n numerous belts
b e l t s of
of Precambrian volcanic-sedimentary
sequences
sequences which
which are
a r e commonly
commonly referred
r e f e r r e d to
t o as
a s greenstones.
qreenstones. The
The
units
u n i t s appear
appear to
t o be chiefly
c h i e f l y of
of middle Precambrian age
aye and
and they
they
have been
been included
included by Stockwell
Stockwell (1970)
(1970) in
i n the
t h e Southern
Southern Province
Province
have
B e l t which forms
forms the
t h e southern
s o u t h e r n extension
e x t e n s i o n of
of the
the
o r Penokean
Penokean Fold
Fold Belt
or
2.5
2.5 to
t o 2.7
2.7 b.y.
b.y. old
o l d Superior
Superior Structural
S t r u c t u r a l Province
Province of
of the
the
Canadian
Canadian Shield.
S h i e l d . The
The volcanic
v o l c a n i c rocks in
i n Wisconsin have chemical
chemical
c h a r a c t e r i s t i c s similar
s i m i l a r to
t o Archean volcanic
v o l c a n i c assemblages
a s s e h l a q e s of
of the
the
characteristics
S u p e r i o r Province
Province and
and these
t h e s e similarities
s i m i l a r i t i e s are
a r e reflected
r e f l e c t e d by the
the
Superior
following
following trends:
trends:
(1)
The alkali—lime
a l k a l i - l i m e index,
index, as
a s proposed
proposed by
by Peacock
Peacock (1931),
(19311,
The
f o r Wisconsin's
v o l c a n i c rocks has a range from 59 to
to
for
Wisconsin's volcanic
64 and
and thus
t h u s parallels,
p a r a l l e l s , very
v e r y closely,
c l o s e l y , the
t h e alkali—lime
alkali-lime
index of volcanic
v o l c a n i c rocks
rocks from
from the
t h e Superior
Superior Province
Province
index
which show
show aa range
ranqe from
from 56
56 to
t o 64
6 4 (Wilson
(Wilson and
and others,
others,
which
1965).
1965).
(2)
volcanic
Volcanic rocks
rocks from
from Wisconsin
Wisconsin are
a r e potassium—poor
potassium-poor and
and
compare to
t o Goodwin's (1968)
(1968) trend
t r e n d of
of potassium-poor
potassium-poor
compare
volcanic
v o l c a n i c rocks
rocks in
i n the
t h e Superior
Superior Province.
Province.
(3)
The
The Niggli
N i g y l i silica
s i l i c a and
and total
t o t a l alkali
a l k a l i values
v a l u e s for
f o r volvolcanic
c a n i c rocks
rocks from
from Wisconsin, when plotted
p l o t t e d in
i n relation
relation
to
t o Wilson's
Wilson's (1965)
(1965) standard
s t a n d a r d curve
curve drawn
drawn for
f o r oceanic
oceanic
alkaline
and
orogenic
calc-alkaline
suites,
plot
alkaline
c a l c - a l k a l i n e s u i t e s , p l o t on
on
t h e orogenic
o r o q e n i c calc—alkaline
c a l c - a l k a l i n e side
s i d e of
of the
t h e standard
s t a n d a r d curve
curve
the
nearly
same region
r e g i o n as
a s the
t h e plots
p l o t s for
f o r the
t h e volvoln e a r l y in
i n the
t h e same
canic
c a n i c suites
s u i t e s from
from the
t h e Superior
S u p e r i o r Province.
Province.
The greenstones
ureenstones have
have been
been metamorphosed
metamomhosed to
t o greenschist
areenschist
facies
~ k o n n a i s s a & z eand
and
f a c i e s or
o r -lower
l o w e r amphibolite
amphibolite facies.
f a c i e s . Reconnaissance
detailed
s u l p h i d e mineralization
mineralization
d e t a i l e d work
work has
has not
n o t revealed
revealed any
any sulphide
except
e x c e p t for
f o r some
some disseminated
disseminated pyrite.
pyrite.
26
�References
References
Goodwin,
Goodwin, A.
A. M.,
M., 1968,
1968, Evolution
Evolution of
of the
t h e Canadian
Canadian Shield:
Shield:
Geol.
Assoc.
Can.
Proc.,
v.
19,
P.
-01. Assoc. Can. Proc., v . 1 9 , p. 1—14.
1-14.
Peacock,
Peacock, M.
M. A.,
A., 1931,
1931, Classification
C l a s s i f i c a t i o n of
of Igneous
Igneous Rocks:
Rocks:
Geology,
V.
39,
p.
54—67.
Geology, v. 39, p. 54-67.
Jour.
Jour.
Stockwell,
Stockwell, C.
C. H.,
H., 1970,
1970, Geology
Geoloqy of
o f the
t h e Canadian
Canadian Shield
Shield
(Introduction),
Chapter
IV
in
Geology
(Introduction),
I V i n Geology and
and Economic
Economic
Minerals
Minerals of
of Canada,
Canada, 5th
5 t h Ed.,
Ed., Department
Department of
of Energy,
Energy,
Mines,
and
Resources,
Ottawa,
Canada,
p.
Mines, and Resources, Ottawa, Canada, p. 44—54.
44-54.
Wilson,
H. D.
D . B.,
B., Andrews,
Andrews, Peter;
P e t e r ; Moxham,
Moxham, R.
R. L.,
L . , and
and Ramlal,
Rarnlal,
Wilson, H.
K.,
1965,
Archean
Volcanism
in
the
Canadian
Shield:
K., 1965, Archean Volcanism i n t h e Canadian S h i e l d :
Can.
Can. Jour.
J o u r . Earth
Earth Sci.,
S c i . , v.
v. 2,
2 , no.
no. 3,
3, p.
p. 161-175.
161-175.
27
�TEE IRON
OREDEPOSITS
DESITS AT
TIE
IMN ORE
ATBlACK
BUCKRIVER
WJER
FALlS, WISCONSIN,
FALLS,
WISCONSIN,GEOlOGY
GEOLOGYAND
ANDOPERA.TIONS
OPEFATIONS
John
M.
Ohison, Inland
John M
. Ohlson,
Inland Steel
S t e eCompany,
l Compsw, Ishpeniing,
Ishpeming, Michigan
Michigan
h498h9
W9
ATBAC'P
Thepresence
presenceofofiron
iron bearing
bearing rocks
rocks iin
the Black
River Falls
Falls area
The
n the
Black Mver
Attempts ttoo
known since
since 1839.
1839. Attempts
of west-central
nest-centralWisconsin
Wisconsinhas
hasbeen
beenknown
wereunsuccessful.
unsuccessful.
u t i l i z ethis
t h i sresource
resourcebefore
beforethe
theturn
turnofofthe
the
centumwere
utilize
century
1nlandts facility,
f a c i l i t y ,which
whichopened
opened iin
n 1969,
1.969, u
t i u z e s standard
standard grinding
grinding
Inland's
utilizes
and
nagnetic separation
and mgnetic
s e p m t i o n techniques.
techniques.
The
rocks of
of the
the area are
The rocks
are aa sequence
sequence of
of steeply
steeply dipping
dipping highly
highly
metaaorphased
sedimentsincluding
includingaa thin-banded
thin-banded mgnetite-quartz
nagnetite-quartz
metamorphased sedkmnts
iron fornation.
iron
formtion. The
The ssediments
e d h e n t s l lie
i e on a granite
granitegneiss
gneissbasement
basement
and
intmded by
by both
both acid
acidand
and basic
bssicdikes
dikes.• The
and are intruded
%e eentire
n t i r ePrecambian
Ft-ecambian
sequenceiis
sequence
s overlain
w e r l a i n by
by flat
flatlying
lyingC*mbrian
Cambrian sandstones.
sandstones. Water
Water iiss
obtained
wells iinn aa concealed
disobtained from
from wells
concealed Pleistocene
Pleistocene valley
valley which
which was
n s discovered by
by geo@ysical
geoaysical methods.
covered
methods.
Plant water
water circulates
circulates in
Plant
i naaclosed
closedsystem.
system. Experimental
Experimental ttree
r e e and
and
grass
Wisconsin
gmss planting
planting with
with the
t h ehelp
helpofofthe
the
WisconsinDepartment
Ceprixent of Natural
Natural
Resources,
the University of
ExtensionService,
Service, and
and the
the SSoil
Resources, the
of Wisconsin
Wisconsin Extension
oil
conservation Service
Servicewwas
started on
on the
the waste
waste ddisposal
Conservation
as started
i s p s a l ppiles
i l e s within
within
a year
and aa half
half of
of plant
plant startup. %e
a
year and
The plant
plant and
and waste
waste disposal
disposal areas
were designed
designed from
from the
the outset
environmentaleffect.
effect.
were
outset to
t ohave
havea aminimum
minimum environmental
28
�STRUCTURAL
EVOLUTION O
OF
STRUCTUm EVOLUTION
F TEE
THE
DEER
DEER LAKE
LAKEULTRAMAFIC
ULTRAMAFIC COMPLEX,
COMPLEX, MINNESOTA
MINNESOTA
M. Ripley
Ripley and Donald N.
M. Davidson,
Davidson, Jr.,
J r . , Geology Department,
Department,
Edward M.
Edward
University of Minnesota,
Minnesota, Duluth,
Duluth, Duluth,
Duluth, Minnesota
Minnesota 55812.
55812.
ABSTRACT
ABSTRACT
Lake Ultramafic
Ultramafic Complex
Complexisislocated
located 6.5
6.5 kilometers
The Deer
Deer Lake
kilometers southsouthThe
The magnetic
magnetic anomaly
anomaly associated
a s s o c i a t e d with
with this
this
Effie,
E f f i e , Minnesota.
Minnesota. The
east
e a s t of
of
Archean Complex
Complex is
is 13
13 kilometers long
long and
and 33 kilometers wide
wide and
and
trends S.
45W.from the
of Deer Lake to
just n
northeast
o r t h e a s t of the
the
S. 45W.from
t h e south tip
t i p of
t o just
town of
of Big
Big Fork.
Fork,
The stratigraphic
within
s t r a t i g r a p h i c succession w
i t h i n this
t h i s Complex
Complex consists
c o n s i s t s of two
stratiform
s t r a t i f o r m differentiated
d i f f e r e n t i a t e d gabbroic sills, one nonstratiform gabbroic
s t r a t i f o r m sills
sills
s i l l and
and two
two locally
l o c a l l y discordant
discordantultrainafic
u l t r a m a f i c lenses.
lenses. The stratiform
sill
(700-1,100 m.
m. thick)
t h i c k ) are
a r e composed
composed of:
of: basal
b a s a l peridotite
p e r i d o t i t e (160—330
(160-330 m.),
m.),
(700—1,100
orthopyroxene
m.), gabbro 450—650
m.)
450-650 m.)
orthopyroxene clinopyroxenite (less
( l e s s than 160
160 m.)
plus
medium— to
p l u s or
o r minus mediumt o fine—grained
fine-grained differentiated
d i f f e r e n t i a t e d felsic
f e l s i c cap
cap rock.
rock.
Zones of plumose texture
all
t e x t u r e have been observed
o b s e ~ e dalong contacts
contacts between all
zones are
a r e interpreted
i n t e r p r e t e d as
a s spinifex—like
s p i n i f e x - l i k e chill
c h i l l contacts
contacts
mafic
mafic units.
units. These zones
r a t h e r than sequential
s e q u e n t i a l contact
contact metamorphic
metamorphic effects.
effects.
rather
,
Deformation of the
t h e Complex
Complex commenced
commenced with a period of
of folding
f o l d i n g which
The
axial
The
a
x i a l plane
plane
produced two
anticlines
with
an
intervening
syncline.
two a n t i c l i n e s with an i n t e ~ e n i n gsyncline.
trends of
of these upright,
nonpiunging, isoclinal
N. 45 E.
E. with
upright, nonplunging,
i s o c l i n a l folds
f o l d s is N.
Folding
a
a wavelength of
of 1200
1200 meters
meters and
and an
an amplitude
amplitude of
of 400
400 meters.
meters. Folding
was produced in
response
to
the
emplacement
of
the
Zeisser's
Island
i n response t o t h e
the Zeisser's Island
Pluton located
located just
j u s t southeast
southeast of the
t h e central
c e n t r a l portion
p o r t i o n of the
t h e Complex.
Complex.
Local bending
of
the
Complex
to
an
east—west
trend
around
bending of t h e Complex t o an east-west t r e n d around the
t h e north
north
end of the
t h e Pluton also
a l s o occurred
occurred at
a t this
t h i s time.
time. Conjugate
Conjugate shear
shear fractures
fractures
trending N.
N. 20 W.
W. and N.
N. 80 W.
W. developed in
i n response to
t o the
t h e same NW—SE
NW-SE
stress
s t r e s s system
system which
which produced
produced folding.
folding.
The
The second
second stage
s t a g e of deformation
deformation resulted
r e s u l t e d from
from extensional
extensional release
release
The
with
The ffaults
a u l t s trend
trend
with the
t h e development
development of
of normal
normal faults
f a u l t s and
and joints.
joints.
W. and have minimum
minimum dip
dip separations
separations on
on the
t h e order
o r d e r of
of 400
400 meters.
meters.
N. 45 W.
Faulting produced 800
Longi800 meter—wide
meter-wide graben
graben and
and horst
h o r s t structures.
s t r u c t u r e s . Longitudinal
W.)
(N. 45 W.
) release
r e l e a s e joints
j o i n t s are
a r e believed
t u d i n a l (N.
(N. 45 E.)
E.) and traverse
t r a v e r s e (N.
to
t o have developed under the
t h e same stress
s t r e s s orientation
o r i e n t a t i o n as
a s the
t h e normal faults.
faults.
Strike
N. 45 E.
E. trend
t r e n d characterizes
c h a r a c t e r i z e s the
t h e final
final
S t r i k e slip
s l i p faulting
f a u l t i n g along a N.
U g h t - l a t e r a l strike
s t r i k e separation
s e p a r a t i o n displacement offset
offset
s t a g e of
of deformation.
deformation. Right—lateral
stage
Renewed movement along this
t h i s fault
f a u l t preprenormal faults
f a u l t s about
about 300
300 meters.
meters. Renewed
sumably produced an additional
a d d i t i o n a l 100
100 meters strike
s t r i k e separation displacement
displacement
Precambrian diabase
diabase dikes.
dikes.
of middle Precambrian
29
�THE
CHEMISTRY OF THE
THE PETROLOGY
ETROLOGY AN])
AND CHEMISTRY
THE ROUND
ROUND [AKE
L A E INTRUSION,
INTRUSION,
NORTHWESTERN
NORTIMESTERN WISCONSIN
WISCONSIN
D. L. Roder
Cameron
Roder and E. N. Cameron
Department of
Department
of Geology
Geology and Geophysics
Geophysics
University
University of
of Wisconsin,
Wisconsin, Madison,
Madison, Wisconsin
Wisconsin
53706
53706
ABSTRACT
The
The Round
Round Lake
Lake intrusion
intrusion is
is aa northeast-trending
northeast-trending Precambrian
Precambrian
mafic
layered intrusion
by subsurface
subsurfacedrilling
drilling of
mafic layered
intrusion found
found by
of an
an area
area ten
ten
miles east
miles
east of Hayward,
Hayward, Wisconsin.
Wisconsin. The
The body may
may be as
as much
much as
as eight
eight
miles long
long and
two miles
magnetitemiles
and two
miles wide.
wide. Portions
Portions drilled
drilled consist
consist of
of magnetitetroctolite
troctolite with
with anorthositic
anorthositic gabbro
gabbro layers
layers that
that range
range from
from threethreefourths
fourths inch
inch to
to more
more than
than eighty
eighty feet
feet in
in thickness.
thickness. Diabase
Diabase interintersected
sected by the
the drill
drill holes
holes appears
appears to
to form
form later
later intrusions.
intrusions.
Mineral
Mineral assemblages
assemblages in
in the
the magnetite-troctolite
magnetite-troctolite and
and anorthositicanorthositicgabbro
gabbro are
are the
the same,
same, the
the two
two rock
rock types
types differing
differing only
only in
in mineral
mineral
proportions.
ilmenite, and
and
proportions. Plagioclase,
Plagioclase, olivine,
olivine, titanomagnetite,
titanomagnetite, ilmenite,
apatite
apatite are
are cumulus
cumulus minerals.
minerals. Clinopyroxene,
Clinopyroxene, biotite,
biotite, and
and plagioclase
plagioclase
are
minerals. The
are intercumu.lus
intercumulus minerals.
The magnetite-.troctolite
magnetite-troctolite averages
28
averages 28
volume
volume per
per cent
cent plagioclase,
plagioclase, 36
iron36 per
per cent
cent olivine,
olivine, 33
33 per
per cent
cent irontitanium oxides,
oxides, 33 per
per cent
cent augite
augite and
and biotite,
biotite, and
and aa trace
trace of
of
titanium
anorthositic gabbroaverages
averages 66
66per
per cent
cent plagioclase,
plagioclase,
apatite. The anorthositicgabbro
22
22 per
per cent
cent olivine,
olivine, 88 per
per cent
cent iron-titanium
iron-titaniumoxides,
oxides, '-t
4 per
percent
cent augite,
augite,
and
and less
less than
than one-half
one-half per
per cent
cent apatite.
apatite.
Titanomagnetite in
in these
these rocks
rocks is
is an
an irregular
irregular microintergrowth
microintergrowth
Titanomagnetite
of
ulv%pinel.
of magnetite
magnetite and
and ulv1spinel.
Ilmenite
Ilmenite occurs
occurs as primary granular
granular
aggregates,
(111) lamellae
lamellae in
in titanomagnetite,
titanomagnetite, and
and as
as granular
granular
aggregates, as
as (111)
aggregates
aggregates around
around titanomagnetite
titanomagnetite grains.
grains. Hercynite
Hercynite is
is found
found as
as tiny
tiny
"dots"
"dots" in
in titanomagnetite.
titanomagnetite. Magnetite appears
appears to
to have
have settled
settled as
as
euhedral
euhedral crystals.
crystals. Anhedral
Anhedral aggregates
aggregates are
are thought
thought to
to be
be due
due to
to
enlargement or partial recrystallization
recrystallization of touching crystals after
settling.
settling.
Only
Only small-scale
small-scale cryptic
cryptic layering
layering is
is displayed
displayed by
by the
the intrusion.
intrusion.
Plagioclase ranges
ranges from
from An51
AnS1 to
to Anits,
An~r,, but
chemical
Plagioclase
but no consistent
consistent chemical
trend
trend is
is evident.
evident. In
X-3, anorthositic•gabbro
In core
core from
from drill
drill hole X-3,
anorthositic gabbro and
and
magnetite-troctolite are interlayered; olivine
magnetite-troctolite
olivine in
in anorthositic-gabbro
anorthositicgabbro
ranges from
from P053
FoS3 to
to Fo56,
FoS6, whereas
whereas olivine
olivine in
in magnetite-troctolite
magnetite-troctohte
ranges
ranges from Fo5,
Fo57 to
to Fo
Fo2.
2 . In
In core
core from
from drill
drill hole
hole X-2,
X-2, anorthositie
anorthositic
gabbro
developed. In
gabbro layers
layers are
are poorly
poor y developed.
In this
this core,
core, olivine
olivine ranges
ranges from
from
Fo57
of Ca4$lg3,Fel8.
CaqMg37Fe18.
FoS7 to
to Fog1.
FoS1. Augite
Augite has
has an
an average
average composition of
Microprobe analysis
analysis of
of titanomagnetite
titanomagnetite gives
gives the
the following
followmg range
range of
of
Microprobe
composition:
composition: total
total iron
iron as
as FeO
FeO 65
65 to
to 7'-!74 weight
20 to
to
weightper
percent,
cent, Ti02
Ti02 20
21l
per cent,
cent, MgO
MgO 0.5
0.5 to
to 3.8
3.8 per
per cent,
cent,A1203
A12O3 2.3
2.3 to
to 3.9
3.9 per
per cent,
cent, V203
V03
24 per
1.0 to
to ]J3
L.3 per
per cent,
cent, and
and Cr203
Cr203 0.1
0.1 to
to 1.2
1.2 per
per cent.
cent. Primary
Primary ilmenate
ilmen~te
has an
an average
average composition
composition of
of Ilmg8Hem2
Ihg8Hem2 and
and contains
contains up
up to
to S5 weight
weight
has
per
per cent
cent MgO.
MgO.
!?
Information
Information at
at hand indicates
indicates the
the presence of
of sizeable
sizeable concentraconcentrations
tions of
of iron-titanium
iron-titanium oxides,
oxides, but
but further
further exploration
exploration will
will be
be necessary
necessary
to determine
determine their
their form,
form, extent,
extent, and
and relations
relations to
to the
the Round
Round Lake
Lake
to
intrusion
intrusion as
as aa whole.
whole.
30
�UPPER
MISSISSIPPI VALLEY
EXPERIMENTAL
UPPEX MISSISSIPPI
VALLEYBASE
BASEMETAL
MET& DEPOSITS:
DEF'OSITS: FXPERIMEIiTAL
SOLUTIONS
TO
PROBLEMS
OF ORE
ORE GENESIS
GENESIS
SOLUTIONS TO mOBLEMS OF'
B. Romberger,
Romberger, Department of
of Geology and Geophysics,
Geophysics, University of
S. B.
Wisconsin, Madison,
Madison, wisconsin
Wisconsin 53706
Wisconsin,
53706
ABSTRACT
A
BSTRACT
Chemical models for
of base metals
f o r tthe
h e ttransport
r a n s p o r t and deposition of
in
Mississippi
Valley
Type
Deposits
are
studied
experimentally
using
i n Mississippi Valley Type Deposits a r e
using
object is
i s tto
o supply evidence tto
o
a mineral synthesis
synthesis approach.
approach. The obJect
support tthe
hypothesis tthat
have been
been deposited
deposited from metalmetal—
support
h e hypothesis
h a t tthese
h e s e oores
r e s have
containing, sulfur—deficient,
chloride—rich solutions
containing,
s u l f u r - d e f i c i e n t , chloride-rich
s o l u t i o n s entering a
sulfur—containing reducing environment. Copper, iron,
sulfur-containing
i r o n , lead,
l e a d , and
and zinc
zinc
were synthesized together
together iin
molal sodium chloride
chloride ssolutions
olutions
ssulfides
u l f i d e s were
n 3 molal
between 200
20' and
and 200°C
200° under the
t h e vapor
vapor pressure
pressure of
of water.
water. Copper, iron,
iron,
lead,
barium, and calcium were introduced a
ass solid
l e a d , zinc,
zinc, barium,
s o l i d carbonates or
or
The amount
amountofof ssulfur
soluble chlorides
soluble
chlorides along
along with
with elemental
elemental ssulfur.
u l f u r . The
ulfur
The
of tthat
added
a l l metal.
metal. The
added was iin
n excess
excess of
h a t necessary
necessary tto
o rreact
e a c t with
with all
products depended
dependedonont hthe
of tthe
products
e sstarting
t a r t i n g composition
composition of
h e experiments,
experiments, but
pyrite,
galena, digenite,
barite,
were generally covellite,
covellite, p
y r i t e , sphalerite,
s p h a l e r i t e , galena,
digenite, b
arite,
Morphology of
of some
some of tthe
he
anhydrite,
anhydrite, and
and aa second
second generation
generation calcite.
c a l c i t e , Morphology
composite m
metallic
e t a l l i c sulfide
s u l f i d e grains
g r a i n s suggest
suggest initial
i n i t i a l rreaction
e a c t i o n occurred
above the
indicated by
by
t h e melting temperature
temperature of
of sulfur.
s u l f u r . Nonequilibrium iiss indicated
with
of unreacted
unreactedssulfur
tthe
h e presence
presence of
u l f u r iin
n tthe
h e cores
cores of
of grains
g r a i n s together with
metal concentrations
concentrations in
i n the
t h e co—existing
co-existing solutions.
solutions. No
No metal
high metal
carbonates remained in
i n the
t h e run products.
products.
The sulfides
s u l f i d e s showed a regular zonation in
in
rrelation
e l a t i o n to
t o the
t h e un—
unzoningiin
terms of
reacted ssulfur
u l f w and
and ccalcite.
a l c i t e . Summarizing
S m a r i z i n g t hthe
e zoning
n terms
of
paragenesis,
c o v e l l i t e is
i s early,
e a r l y , followed
followed by
by galena
galena and
and sphalerite.
sphalerite.
paragenesis, covellite
Pyrite
F y r i t e forms before galena and s p h a l e r i t e but i t s r e l a t i o n s h i p t o
s unclear. Barite
B a r i t e and anhydrite form independently of
of the
the
ccovellite
o v e l l i t e iis
ssulfide
u l f i d e zoning,
zoning, however the
t h e second
second generation c a l c i t e i s t h e l a s t phase
galena and sphalerite but its relationship to
generation calcite is the last phase
whichappear
appeart otocause
causep precipitation,
ttoo form.
form. The
The ffactors
a c t o r s which
r e c i p i t a t i o n , iin
n order
order of
of
activity,
sulfur a
c t i v i t y , increasing
increasing pH
pH of
of solution,
solution,
importance, are:
a r e : increasing sulfur
and decreasing temperature.
temperature.
To aid
a i d in
i n determining tthe
h e chemical conditions underwhich sulfide
sulfide
precipitation
p r e c i p i t a t i o n took place,
p l a c e , tthe
h e aqueous solutions
s o l u t i o n s were analyzed for
f o r copper,
zinc, llead,
barium, and
concentration of
of the
t h e metals
metals
zinc,
e a d , iron,
i r o n , barium,
and calcium.
calcium. The concentration
with decreasing temperature
temperature and increasing time;
time;
and barium decreased with
that
t h a t of calcium either
e i t h e r increased or
o r decreased, depending on the
t h e starting
starting
variation
i s a ttypical
ypical v
a r i a t i o n of the
t h e molar ratio
ratio
conditions. The following is
Cu:Fe:Pb:Zn iin
of l1.0:1.0:1.0:1.0:
.O:l.O:l.O:l.O:
aatt
Cu:Fe:F'b:Zn
n solution
s o l u t i o n aafter
f t e r aa starting
s t a r t i n g rratio
a t i o of
200°C, 1.0:0.114:1140:360;
120°C, ~1.0:1.0:830:2280;
20O0c,
~ . 0 : 0 . ~ & : ~ 4 0 : 3 6a0at
t ; 12O0C,
. 0 : ~ . 0 : 8 3 0 : 2 2 8 0 and
;and at
a t 25°C,
25OC,
1.0:0.15:3.3:150. The copper concentration ttypically
y p i c a l l y dropped from
from a few
few
1.0:0.15:3.3:150.
200°C, to
l000ppm
t o less
less
100Oppm in
i n the
t h e starting
s t a r t i n g solution
s o l u t i o n to
t o less
l e s s than
than 55 ppm aatt 20o0C,
v a r i a t i o n s are
a r e consistent with the
t h e paragenesis
than
than 11 ppm
ppm at
a t 25°C.
2F°C These variations
not established
observed in
observed
i n the
t h e minerals. Because equilibrium was not
e s t a b l i s h e d tthe
he
major significance
s i g n i f i c a n c e of
of these
t h e s e data is
i s to
t o demonstrate relative
r e l a t i v e tendencies
ffor
o r metal sulfides
s u l f i d e s to
t o precipitate
p r e c i p i t a t e under
under the
t h e conditions
conditions of
of the
t h e experiment.
experiment.
31
�PETROLOGY
OF
PETROLOGY O
F SOME
SOME EA1LY
EARLY PRECAMBRIM
PRECAMBRIAN
DIFFERENTIATEDULTRAMAFIC
LlLTRAMAFIC BODIES
BODIES
DIFFERENTIATED
IN
I NNORTHEASTERN
NORTHEASTERN MINNESOTA
MINNESOTA
Klaus
J. Schulz
Schulz and
and Edward
Edward M.H.Ripley,
of Minnesota,
Minnesota, Duluth,
Duluth,
Klaus 3.
Ripley, University of
Duluth, Minnesota
Minnesota 55812.
55812.
ABSTRACT
Mapping iin
n the
t h e Newton
Newton Lake
Ely, Minnesota
Minnesota and
and
Mapping
LakeFormation
Formationnorth
north of
of Ely,
the
t h e Deer Lake
Lake Area
n northern
I t a s c aCounty,
County, Minnesota
Minnesota has
l o c a t e d aa
Area iin
northern Itasca
has located
number
number of
of mafic—ultramafic
mafic-ultramafic bodies of
of Early
Early Precambrian age, many
many of
which
which are
a r e differentiated.
differentiated.
Detailed mapping
mapping of
of these
t h e s e bodies
bodies has
has shown
shown
Detailed
that
t h a t they
they are
a r e conformable
conformable to
t o the
t h e surrounding
surrounding country
country rocks,
rocks, indicating
indicating
they are either sills or flows.
that
t h a t they a r e e i t h e r sills o r flows. Country
Country rocks
both areas
a r e a s conconrocks iinn both
sist of
of medasedimentary
medasedimentary and
r g e l y pillowed metavolcanic
metavolcanic rocks.
rocks. No
andl alargely
No
sist
evidence
evidence for
f o r contact
contact metamorphism
metamorphism has been
been observed
observed between
between the
t h e bodies
bodies
and
the
country
rocks.
and t h e country rocks.
The bodies
o 1,000
e e t in
i n thickness
thickness and
and have
have
The
bodies range
range from
from400
400t to
1,000ffeet
lateral
miles. The
l a t e r a lextents
e x t e n t sfrom
from aa mile
mile to
t o several
s e v e r a l miles.
The rocks
t h eDeer
Deer
rocks of the
Lake
Areahave
havebeen
beenf afaulted
andt itightly
while those north of
Lake Area
u l t e d and
g h t l y folded
folded while
of Ely
Ely
are
a r e faulted
f a u l t e dand
and only
only broadly
broadly folded.
folded. Serpentinization
S e r p e n t i n i z a t i o n and
t h e r aalterlterand oother
isextensive
extensiveini nalla lthe
l t hbodies
e bodies
with
metamorphism generally
generally of the
the
a t i o n is
ation
with
metamorphism
green—schist
green-schist facies.
facies.
I n both areas,
areas, bodies composed
composed solely
s o l e l y of
of gabbro
gabbro or
o r peridotite
p e r i d o t i t e exist,
exist,
In
however
however most
most appear
appear to
t o be
be differentiated.
d i f f e r e n t i a t e d . The
The typical
t y p i c a l sequence
sequence in
i n the
the
is peridotite,
p e r i d o t i t e , pyroxenite,
pyroxenite,
d i f f e r e n t i a t e d ones,
ones, from
from bottom
bottom to
t o top,
top, is
differentiated
porphyritic
p o r p h y r i t i c gabbro,
gabbro, gabbro.
gabbro. The
The peridotite
p e r i d o t i t e is
i s composed
composed of
of rounded
rounded to
to
euhedral
euhedral olivine
o l i v i n e and
and rare
r a r e chromite
chromite surrounded
surrounded by
o i k i l i t i cpyroxene
pyroxene
by ppoikilitic
and
and amphibole.
amphibole. At
A t least
l e a s t some
some of
of the
t h e peridotites
p e r i d o t i t e s contain
contain both
both ortho—
orthopyroxene
h e r z o l i t e . The
The
pyroxene and
and clinopyroxene
clinopyroxene and
a s s i f i e d as
andwould
wouldbebec lclassified
as IIherzolite.
pyroxenite
contains
sub—
pyroxenite is
is in
i nsharp
sharpcontact
contactwith
withthe
t h eperidotite
p e r i d o t i tand
e and
contains
subhedral
h e d r a l diopsidic
d i o p s i d i c augite
a u g i t eand
and in
i nsome
some cases
cases also
a l s o contains
contains bronzite.
bronzite.
With
Plagioclase,
Plagioclase, in
i nvarying
varyingamounts,
amounts, forms
forms the
t h e intercumulate
i n t e r c u m d a t e phase.
phase. With
increasing
increasing plagioclase
p l a g i o c l a s e content
content the
t h e pyroxenite
pyroxenite grades
grades into
i n t o porphyritic
porphyritic
gabbro composed
composed ofofaaugite,
u g i t e , plagioclase
p l a g i o c l a s eand
andpyroxene
pyroxene phenocrysts,
phenocrysts,which
which
gabbro
are
gabbro contains
contains pplagioclase,
a r e now
now completely
completely aaltered.
l t e r e d . The
The gabbro
l a g i o c l a s e , augite,
augite,
t e r s t i t a l quartz
quartz and
and
and secondary
secondary aactinolite
c t i n o l i t e with
with varying
varying amounts
and
amountsofofi ninterstital
micrographic
micrographic intergrowths.
intergrowths. Cumulate
Cumulate t textures
e x t u r e s in
i n the
t h eperidotite,
p e r i d o t i t epyrox—
, pyroxandporphyritic
p o r p h y r i t i cgabbro
gabbro along
along with
with minor
minor layering
layering and
and size
s i z e grading
grading
e n i t e , and
enite,
i n d i c a t e that
t h a t selective
s e l e c t i v e crystallization
c r y s t a l l i z a t i o nand
and gravity
g r a v i t y settling
s e t t l i n gofofphases
phases
indicate
were the
the main
main mechanisms
mechanisms ofofddifferentiation.
i f f e r e n t i a t i o n . Many
Many of
t h e bodies
bodies examinexaminwere
of the
ed
ed were
were also
a l s o found
found to
t ohave
have complex
complex chilled
c h i l l e dmargins.
margins.
A
of sulfide
A ddetailed
e t a i l e d study
study of
s u l f i d e mineralization
m i n e r a l i z a t i o n in
i n the
t h e bodies
bodies of
of the
the
Deer
Areashows
showst hthat
copper, and
and iron
i r o n sulfides
s u l f i d e s are
a r e conconDeer Lake
Lake Area
a t nnickel,
i c k e l , copper,
The
centrated
centrated in
i n the
t h e chilled
c h i l l e d margins,
margins, making
making up
up 22 to
t o 3%
3%of
of the
t h e rock.
rock. The
32
�basic
b a s i c sulfides
s u l f i d e s appear to
t o have formed
formed from
from an immiscible
Immiscible sulfide—
sulfideof intrusion,
oxide lliquid,
i q u i d , which aatt the
t h e time of
i n t r u s i o n , coexisted with the
the
of ssulfide
also
silicate
s i l i c a t e magma. A general llayering
a y e r i n g of
u l f i d e phases was a
l s o found
to
t o exist
e x i s t through
through the
t h e bodies
bodies with
with nickel
n i c k e l sulf
s u l f iides
d e s concentrated
concentrated in
i n the
the
peridotite,
pyroxenite and p
porphritic
p
e r i d o t i t e , copper sulfides
s u l f i d e s in
i n the pyroxenite
o r p h r i t i c gabbro
gabbro
u l f i d e s appear to
t o have
and iron
i r o n ssulfides
u l f i d e s in
i n the
t h e upper gabbros.
gabbros. These ssulfides
magma, p
precipitating
i l i c a t e magma,
r e c i p i t a t i n g aass late
l a t e phases
been in
i n solution
s o l u t i o n in
i n the ssilicate
with the
t h e intercumulus
intercumulus minerals.
chemical
analyses of
of samples
from tthe
bodies north
north of
Chemical analyses
samples from
h e bodies
of Ely
Ely show
show a
a
bodies appear
appear to
The bodies
t o be
be
general
withddifferentiation.
general iron
i r o n enrichment
enrichment with
i f f e r e n t i a t i o n . The
ttholeiitic
h o l e i i t i c in
i nnature
n a t u r e and
and very ssimilar
i m i l a r to
t o differentiated
d i f f e r e n t i a t e d ultramafic
ultramafic
bodies
age in
i n Canada,
Canada, Africa,
Africa, and
and Australia.
Australia.
bodies of Early Precambrian age
33
�TECTONIC HISTORY
HISTORY OF
OFEARLY
EARLY PRECAMBRIAN
PRECAMBRIAN ROCKS
THE
TECTONIC
ROCKS IN
IN THE
VERMILION DISTRICT,
DISTRICT, NORTHEASTERN
NORTHEASTERN MINNESOTA
VERMILION
MINNESOTA
P.
P. K.
K. Sims,
Sims, Minnesota
Minnesota Geological
Geological Survey,
Survey, St.
St. Paul,
Paul,Minnesota
Minnesota55108
55108
ABSTRACT
ABSTRACT
The
Vermilion district, ini nnortheastern
The Vermilion
northeasternMinnesota,
Minnesota, contains
contains aa sequence
sequence of
of complexly
complexly
bordered on
on the
the north
north by
by the
the
intertonguing volcanic
volcanic and
and volcaniclastic
volcaniclasticrocks
rocksthat
thatisi sbordered
intertonguing
Vermilion granite—migmatite
granite-migmatite massif
massif and
Vermilion
andon
on the
the south
southby
by the
the Giants
Giants Range
Rangebatholith.
batholith.
The supracrustal rocks
adjacent to
rocks dominantly
dominantlyhave
havegreenschist—facies
greenschist-facies assemblages;
assemblages; adjacent
to
the intrusive
they
have
amphibolite—facies
intrusive granitic
graniticrocks
rocks(Ca.
(ca. 2700
2700m.y.
m.y. old)
old)
they
hove
amphibolite-focies
assemblages.
assemblages.
The
supracrustal rocks
rockstrend
trendgenerally
generally eastward,
eastward, are
are steeply
steeply inclined, and
The supracrustal
andhave
have
and faulted. Two
Twogenerations
generationsofoffolds
foldshave
havebeen
beendistinguished
distinguished
been complexly folded and
in
part of
of the
i n the
the western
western port
the district. The older generation is
i s represented
represented by
to
by tight
tight to
that trend
trend northwestward
northwestward and
axialsurfaces
surfaces
close folds that
and have
have planar,
planar, steeply
steeply inclined
inclined axial
and
axes. The
and gently—plunging
gently-plunging axes.
Theyounger
younger generation
generationfolds
foldsare
aresuperposed
superposed on
on the
the older
older
folds
of the district.
folds in
i n the
the extreme
extreme western
western part of
district. These
These folds
trend eastward
eastwardand
and
folds trend
axialsurfaces
surfacesand
andsteep
steep plunges;
plunges; they
they are
are accompanied
accompanied by
by ao
have planar upright
upright axial
have
pervasive steep
steep cleavage
cleavage and
and associated
associated lineations
lineationsthat
thatobscure
obscuremost
moststructures
structures
pervasive
related
relatedto
tothe
theolder
olderdeformation.
deformation. Judged
Judgedfrom
fromthe
thedivergent
divergenttrends
trendsofofstructures
structuresand
and
generally steep
steep plunges
the rocks
rocks in
i n the
the eastern
eastern part of the
the district
district
the generally
plungesof
of lineations,
lineations, the
also
also were
were folded
folded during
during two
two or
or more
more periods
periods of deformation.
deformation.
Three steep fault
fault systems,
systems, each
each of
of which
whichhas
hasassociated
associatedmylonite,
mylonite,post—date
post-date the
the
Three
folding.
folding. The
The oldest (2)
(?) faults
faults have
haveaa dominant
dominant vertical
verticalcomponent
componentof
ofmovement.
movement.
The
The major
major fault
faultini nthis
thissystem
systemoccurs
occursat
atthe
theapproximate
approximateboundary
boundarybetween
betweenthe
thelow—
lowgrade supracrustal
supracrustal rocks and the Vermilion
Vermiliongranite—migmatite
granite-migmatite massif;
massif; another fault
fault
grade
separates
separates the eastern part of the
the Giants
GiantsRange
Range batholith
batholithand
andassociated
associatedamphibolite—
omphibolitefacies
facies rocks
rocks from
from the
the supracrustal
supracrustal rocks.
rocks. These
These faults
probably
have
vertical
movements
faults probably have vertical movements
of 3,000
3,000 to
to5,000
5,000 feet,
feet,and
andappear
appeartotohave
havedeveloped
developedlargely
largelyini nresponse
response to
to isostatic
isostatic
of
adjustments
between crustal
crustal blocks
blocks having
having different
different rock
adjustments between
rock densities.
densities.
The
younger (?)
represented mainly
mainly by straight, steep,
(?) system
system iiss represented
steep, north—northnorth-northThe next younger
east trending
trending faults that cut
cut both
both the
the granitic
graniticrocks
rocksand
and the
the volcanic
volcanicrocks
rocksand
and have
have
east
left—lateral
miles. These
These faults
locallyare
areabundant
abundant
left-lateral displacements
displacementsof
ofas
asmuch
much as
as 44 miles.
faults locally
and
and closely
closelyspaced.
spaced. Some
Someofofthem
themappear
appeartotodisplace
displacesupracrustal
supracrustalrocks
rocksmore
more than
than
the
the intrusive
intrusiverocks,
rocks,suggesting
suggestingthat
thatthey
theypre—date
pre-dote emplacement
emplacementof
ofatatleast
leastsome
some
of
of the
the granitic
granitic rocks.
rocks.
The
youngestfaults
faultsare
aretranscurrent
transcurrentfaults
faultshaving
havinghorizontal
horizontalright
right lateral displaceThe youngest
ments.
this
system
this
systemisi sata least
t least250
250miles
mileslong
longand
andtransects
transectsseveral
several
ments. The
Themajor
majorfault
faultini n
greenstone—granite
greenstone-granite complexes.
complexes. In
I n northwestern
northwestern Minnesota
Minnesota iti tappears
appears to
to have
have disdisplaced distinctive
distinctivegravity
gravityanomalies
anomalies aa distance
distance of about
about 35 miles;
miles; in
i n the
the Vermilion
Vermilion
placed
district,where
whereit iconsists
t consistsofofseveral
severalstrands,
strands, iti thas
hasdisplaced
displacedthe
the upper
upper part
part of
of the
the
district,
volcanicpile
p i l ea adistance
distanceofofabout
about1212miles,
miles,distorting
distorting
i t from
a thick
almond-shaped
volcanic
it from
a thick
almond—shaped
lens
lens to
toaatenuous
tenuouseast—trending
east-trending mass.
mass.
Metamorphism, folding, and
andemplacement
emplacement of the
the granitic
graniticrocks
rockswere
werebroadly
broadly
Metamorphism,
34
�synchronous, and
andoccurred
occurredduring
during the
the Algoman
Algomanorogeny.
orogeny. The
synchronous,
The foldng
foldingofofthe
thesupra—
supraresulting from
from the
the relative
relative upwelling
crustal rocks is attributed to
to compression
compression resulting
upwelling
convergence of
of the
the flanking batholiths,
experiand convergence
batholiths, aamechanism
mechanism demonstrated
demonstrated experimentally by Romberg
(1967). The
Vermilion massif
andat
at least
least aa part
part of
of the Giants
Ramberg (1967).
The Vermilion
massif and
Giants
Range
batholith continued
continued to rise because
becauseofof their
their buoyancy
buoyancy after
after crystallization
crystalUzation
Range batholith
of the
the granitic rocks.
rocks. The
Thetranscurrent
transcurrent faulting
faultingtook
took place
placeduring
during aa fate
latestage
stage of
of
the orogeny,
orogeny, after
after the
the crust
crust had
had attained
attained sufficient
sufficient strength
strength to
to transmit
transmit regional
regional
related to the fracturing can
compressive
compressive stresses.
stresses. Cataclasis
Cataclasis related
can account
account for the
the
disparity between
andmineral
mineral ages
agesi n
in the
the Giants Range
batholith
between whole—rock
whole-rock and
Range batholith
(Prince and Hansen,
Hansen, 1972).
1972).
35
�LAYEREDWMAPIC
INTRUSION
A KEWBENAWAN
KEWEENAWAN LAYEmD
I C INTRUSION
NEAR
NZAR FINLAND,
FINLAND,LAKE
LAKECOUNTY,
COUNTY,MINNESOTA
XIRXTSOTA
R.J.
R.J.
Stevenson, Department
Department of Geologys
Geology, University of
Stevensons
Minnesota-Duluth, Duluth,
Ninnesota-Duluth,
DuLuth,Minnesota
Kinnesota55812
55812
ABSTRACT
ABSTRACT
and one
The
NNE
The Sonju
Sonju Lake
h k e Intrusion,
Intrusion, four
four and
one half
halfmiles
milesNN3
Finland,
has an
Finland, Minnesota,
Minneeota, has
an exposed
exposed area
area of
of one
one and
and one
one
intrusion isissurrounded
miles •
The intrusion
half
two and
and one
one half
half miles.
The
surrounded
half by two
granite ,of the
granophyric granite,of
on
three sides
on three
sidesby
by diabase
diabase and
and granophyric
the
side is
Beaver
Beaver Bay
Bay Complex,
Complex, and
and the
the western
western side
isobscured
obscured by
by
lamination, cryptic
cryptic layering,
glacial. drift. It
Itshows
shows igneous
igneous lamination,
layering,
and
layering, and
and rhythmic
rhythmic layering,
and has
has a
a stratigraphic
stratigraphic thickness
thickness of
of
dip of
approximately
3500feet
feet based
basedon
onthe
the strike
strike and
approximately 3500
and dip
of the
the
rock units
units comprising
the intrusion
intrusion
igneous
igneous lamination.
lamination. The
The rock
comprising the
picrite;
are, from
the base
to the
are,
from the
base to
the top
top respectively:
respectively: basal
basal picrite;
troctolite; a gabbro;
an
a
gabbro; an
an apatite-rich ferrogabbro; an
a troctolite;
olivine-hedenbergite
quartz-bearing diorite;
diorite; a hedenbergite
hedenbergite
olivine-hedenbergite quarts-bearing
The ferrogabbro
granodiorite;
granodiorite; and
and a
a hedenbergite
hedenbergite adamellite.
adamellite. The
ferrogabbro
contains
43.50$ SiC2.
Si02.
contains 19.26%
19.26s FeC
FeO and
and 43.50%
of
of
glacial drift.
The
The compositions
compositions of the
the major
major minerals
minerals vary
vary with
with strati—
etratigraphic height;
height; they have been studied by electron
electron microprobe
plagioclase varies
varies from
An33 in
and optical
optical methods.
methods. The plagioclase
from An
in the
the
and
The
piorite to
to An
An ininthe
thehedenbergite
hedenbergite adamellite.
adame~lite?~
The
basal picrite
basal picrite to
in
to Fo12
3'0
in the
the
divine
?07 in
in the basal
olivine varies
varies from
froml#o
12
uppermost
uppermost apatite—rich
apatite-rich7$errogabbro.
The cumulus
cumulus clinopyroxene
d~nopyroxene
hrrogabbro. The
ranges
ranges from
from Ca
Ca Mg
Ng 6Fe
Fe 1 in the lowest gabbro to Ca 0Mg
Mg Fe
Pe
injrmjiatg5ana
The int?%ne%!atJ5and
ferrogabbro.
in
the uppermoM
upperno@ jatite-rich
&ti&rich
ferrogabb~o. The
in the
felsic rocks
rocks have hedenbergites
hedenbergites clustered
felsic
clustered around
around Ca49Mg03Pe43.
Ca49Mg03Fe48*
lamination, cryptic layering,
The
The igneous
igneous lamination,
layering, and
and rhythmic
rhythmic
P
extreme
iron—enrichment
layering
the
and the extreme iron-enrichment
3'
layering and
establish this
this intrusion
trend all establish
intrusion as
as a
a
differentiated, tholeiitic intrusion of the
differentiateds
Skaergaard type.
type.
Skaergaard
trend all
tholeiitic intrusion of the
A
36
N
�THE
THE PITTSVILLE
PITTSVILLE (WISCONSIN)
THE FORMATION
FORMATION OOF
F THE
(WISCONSIN) MIGMATITE
MIGMATITE
J. E.
Thresher, Department
Department ooff Geography
Geography and
niversity o
E. Thresher,
andGeology,
Geology,UUniversity
off
Wisconsin—Extension,
W
i scons i n-Extens ion, Madison,
Madison, Wisconsin
Wisconsin 53706.
ABSTRACT
The
Pittsvi
The P
i t t s v ilie
l l emigmatite
m i g m a t i t ewas
was formed
formed during
d u r i n g the
thePrecambrian
PrecambrTan by
by the
the
iintrusion
n t r u s i o n of
o faahydrous
hydrous granitic
g r a n i t i cmagma
magma into
i n t o aa series
s e r i e s ofo fdiabases
diabases and
and
Duet to
the hydrous
hydrousnnature
spatially extensive
extensive
b a s a l t s . Due
o the
a t u r e o of
f t the
h e ggranite,
r a n i t e , spacially
basalts.
transport
of
magma
into
the
country
rock
took
place
which
hasbeen
been
t r a n s p o r t o f magma i n t o the c o u n t r y rock took p l a c e whichhas
recordedbybyppoikiloblasts
off quartz
potash ffeldspar
e l d s p a r wwithin
i t h i n the
t h e older
older
recorded
oikiloblasts o
q u a r t z and
and potash
rocks, and
and the
the presence
presenceo of
the ggranite.
rocks,
f ooriginal
r i g i n a l hydrous
hydrous mminerals
i n e r a l s wwithin
i t h i n the
ranite.
The
observedl ilithologic
The observed
t h o l o g i c layering
l a y e r i n g ini nthe
t h emigmatite
migmatitehas
has formed
formed axial
axial
planar
p l a n a r to
to a
a series
s e r i e s of
o f subisoclinal
s u b i s o c l i n a lnorthwest
northwest plunging
p l u n g i n g folds.
f o l d s . Contemporaneous( (or
so) w
with
was
raneous
o r nnearly
e a r l y so)
i t h this
t h i sfolding
folding
wasthe
t h edevelopment
development of
of
almandine-amphibolitef afades
minerals wwithin
almandine-amphibolite
c i e s minerals
i t h i n the
t h e migmatite.
migmatite. Later
Later
more
openeast-west
east—west
were i imprinted
on tthis
more open
t r etrending
n d i n g s usubhorizontal
b h o r i z o n t a l f ofolds
l d s were
m p r i n t e d on
his
ffabric,
a b r i c , and
and this
t h i swas
was followed
f o l l o w e dby
bya agreenschist
g r e e n s c h i s tfacies
f a c i e smetamorphic
metamorphic event,
event,
apparently
a p p a r e n t l y uunrelated
n r e l a t e d tto
o tthe
h e folding.
folding.
Two
episodes
wererecorded
recorded
therocks,
rocks,the
thef first
irst
Two episodes
o fofj ojointing
i n t i n g were
w i within
t h i n the
of
o f which
which effected
e f f e c t e d only
o n l ythose
thoseofo fPrecambrian
Precambrian age.
age. The
The llater
a t e r episode
episode also
also
sandstonesand
andi sisthus
thus aatt least
ffractured
r a c t u r e d the
the overlying
o v e r l y i n gupper
upperCambrian
Cambrian sandstones
least
thesej ojoints
lower Paleozoic
Paleozoic in
lower
i n age.
age. Many
Many o fofthese
i n t s aare
r e f filled
i l l e d with
w i t h quartz,
quartz,
granite
and/or cchlorite.
hlorite.
g r a n i t e and/or
The
rnigmatiteswere
werel alater
byaaggranitic
The migmatites
t e r i nintruded
t r u d e d by
r a n i t i c pluton
p l u t o n which
which is
is
considered
be rrelated
considered tto
o be
e l a t e d to
t o the
the greenschist
g r e e n s c h i s t facies
f a c i e smet
met and
and possibly
possibly
Several
youngerggranitic
Several younger
r a n i t i c and
and bbasaltic
a s a l t i c dikes
dikes
tthe
h e ffilling
i l l i n g of
o f the
t h e joints.
joints.
crosscut
the ccrystalline
c r o s s c u t the
r y s t a l 1 i n e rocks
rocks locally.
locally.
The eentire
The
n t i r e sequence
sequence is
i s unconformably
unconformably overlain
o v e r l a i nby
byupper
upperCambrian
Cambrian
sandstones
andconglomerates
conglomerates
which
sandstones and
which
a r are
e e sespecially
p e c i a l l y pprevalent
r e v a l e n t in
i n the
the
southern
the PPittsville
area.
southern ppart
a r t oof
f the
i t t s v i Il earea.
37
�STRUCTURALAND
ANDSTRATIGRAPHICAL
STRATIGRAPHICALANALYSIS
ANALYSIS OF
STRUCTURAL
OF THE GECO
GECO SULPHIDE DEPOSIT
DEPOSIT
IN
I N MANITOUWADGE,
MANITOUWADGE, NORTHWESTERN
NORTHWESTERN ONTARIO
ONTARIO
Jens
Geology, U
University
Jens F.
F. Touborg,
Touborg, Department
Department oof
f Geology,
n i v e r s i t y of
o fOttawa
Ottawa and
and
Departmentoof
Geology,UUniversity
Department
f Geology,
n i v e r s i t y of
o f Toronto,
Toronto, Ontario,
Ontario,Canada.
Canada.
ABSTRACT
ABSTRACT
In
area hhigh
rocksc oconsisting
I n the
t h eManitouwadge
Manitouwadge area
i g h grade
grade metamorphosed
metamorphosed rocks
n s i s t i n g ooff
metavolcanic—and
metasedimentary
downfoldedi in
metavolcanic-and metasedimentary
s e rseries
i e s l i lie
e downfolded
n a northeast
northeast
plunging ssyncline,
plunging
y n c l i n e , the
t h e core
core of
o f which
which is
i soccupied
occupied by
by aa granodiorite
g r a n o d i o r i t ebody.
body.
Regionalssuiphide
occurs wwithin
Regional
u l p h i d e mmineralization
i n e r a l i z a t i o n ooff stratabound
stratabound nnature
a t u r e occurs
i t h i n aa
quartz-muscovite schist
quartz-muscovite
s c h i s t horizon
h o r i z o nalong
alongthe
t h econtact
c o n t a coft metasedimentary—and
o f metasedimentary-and
ooverlying
v e r l y i n g metavolcanic
metavolcanic sseries
e r i e s iinn the
t h e upper
upper part
p a r t of
o fthe
t h esequence.
sequence.
The
GecoCopper-Zinc-Silver
Copper-Zinc-Silvers usulphide
beingl located
The Geco
l p h i d e ddeposit
e p o s i t being
o c a t e d wwithin
i t h i n aa
synclinal
s y n c l i n a l dragfold
d r a g f o l d on
on the
t h e northeast
n o r t h e a s t limb
l i m b ooff the
t h e syncline
s y n c l i n e consists
c o n s i s t s of
o f aa
ttabular
a b u l a r body
body of
o f massive
massive sulphides
sulphides enveloped
enveloped by
by a
a haloe
haloe of
o f disseminated
disseminated
pyrite—pyrrhotite—chalcopyrite
mineralization.
p y r ite-pyrrhoti te-chalcopyri t e m
i n e r a l i z a t i o n . A discontinous
d i s c o n t i nous zone
zone ooff
disseminated chalcopyri
chalcopyrite—pyrrhotite—sphalerite—gahnite
disseminated
te-pyrrhotite-sphalerite-gahni t e mmineralization
ineralization
The
occurs
along tthe
occurs along
h e north
n o r t h contact
c o n t a c t of
o fthe
t h equartz—muscovite
quartz-muscovite sschist
c h i s t horizon.
horizon. The
south ccontact
mineralization
south
o n t a c t ooff this
t h i s contains
contains disseminated
disseminated ssphalerite
phalerite m
i n e r a l i z a t i o n in
i n aa
discontinous
by magneti
magnetite-chert
discontinous zone
zone ffollowed
o l l owed by
t e - c h e r t iiron
r o n formation.
f o r i n a t i on.
The
massives suiphide
bodywhich
whichs tstrikes
east-west and
andddips
The massive
u l p h i d e body
r i k e s east-west
i p s ssteeply
t e e p l y to
to
the
elongatedlenses
lensesbecoming
becoming successsuccesst h e north
n o r t hisi scomposed
composed of
o f aastring
s t r i n of
g o5—6
f 5-6elongated
plungeo of
thesepparallels
iively
v e l y smaller
s m a l l e r towards
towards the
t h e east.
east. The
The plunge
f these
a r a l l e l s tthe
h e aaxis
x i s of
of
the
t h e dragfold.
dragfold. IIn
n detail
d e t a i l the
t h emassive
massive sulphide
s u l p h i d e body
body cconsists
o n s i s t s oof
f 33 pprincipal
rincipal
rock types:
coarseggrained
rock
types: 1)
1) compact
compact ore: coarse
r a i n e d p pyrite
y r i t e rrich
i c h sphalerite
s p h a l e r i t e ore.
ore.
coarsegrained
grainedppyrrhotite-chalcopyrite-sphalerite-pyriteayered ore: coarse
yrrhotite-chal copyrite-sphaleri te-pyri te22)) 1layered
Mg
schistose ore:
3 ) schistose
ore: ffine
i n e grained
g r a i n e dkneaded
kneaded ('durchbewegte")
("durchbewegte")
Mg ssilicate
i 1i c a t e rich
r i c h ore.
ore. 3)
ore
These33 types
types ddefine
o r e of
o f similar
s i m i l a rcomposition
composition to
t o the
t h e layered
l a y e r e d type.
type. These
e f i n e aa
mineralogical-textural-compositional
zoningppattern
the
m
i n e r a l o g i c a l - t e x t u r a l - c o m p o s i t i o n a l zoning
a t t e r n wwithin
i t h i n tthe
h e lenses;
lenses ; the
compacttype
typei siscconfined
andt hthickest
compact
o n f i n e d t otot hthe
e ccentral
e n t r a l and
i c k e s t ppart
a r t of
o f the
t h e lenses,
lenses, the
the
layered
l a y e r e d ore
o r e is
i s arranged
arranged along
along the
t h e north
n o r t h contact
c o n t a c tand
and increases
increases in
i namount
amount with
with
decreasingwwidth
decreasing
i d t h ooff the
t h e lens;
lens; the
t h eschistose
s c h i s t o s eore
oredominates
dominates in
i nthe
t h epinch—out
pinch-out
areas. W
Within
i t h i n the
t h e compact
compact oore
r e sphalerite
s p h a l e r i t e rich
r i c hzones
zonesare
aredeveloped
developed towards
towards
the
t h e south
south contact.
contact.
Textures iindicate
Textures
n d i c a t e aa metamorphic
metamorphic r erecrystallization
c r y s t a l l i z a t i o n of
o fsulphides
sulphides and
and
Annealingf fabrics
Annealing
a b r i c s exist
e x i s t ini nmonomineralic
monomineralic aggregates;
aggregates; ppyrite
yrite
porphyroblasts reveal
reveal aacomposite
composite aggregate
aggregate structure
s t r u c t u r eand
andare
a r ecomposed
composed of
of
2
2 varieties
v a r i e t i e s of
o f pyrite;
p y r i t e ; microfold
m i c r o f o l dstructures
s t r u c t u r e s are
are characteristic
c h a r a c t e r i s t i c of
o f the
t h e layeredlayeredand sschistose
massivetypes
types as
aswwell
and
c h i s t o s e massive
e l l as
as the
t h e disseminated
disseminated types.
types.
silicates.
silicates.
3 sets
s e t s of
o fsynkinematic
synkinematic dyke
dyke intrusions
i n t r u s i o n semplaced
emplaced as
as
Dyke chronology:
chronology: 3
Dyke
q u a r t z ddiorites,
i o r i tes, 2)
2 ) amphibolites
amphi b o l i t e s and,
and, 3)
3) granodiorite
g r a n o d i o r i t e and
and
ffollows,
o l l o w s , 1)
1 ) quartz
granite
showdiscordant
discordantr erelationships
g r a n i t e pegmatites
pegmatites show
l a t i o n s h i p s tto
o the
t h e layered
l a y e r e d rocks
rocks
None ooff these dyke
dyke generageneraiincluding
n c l u d i n g all
a l lthe
t h edisseminated
disseminatedmineralized
m i n e r a l i z e dzones.
zones. None
Dykes ooff
ttions
i o n s transect
t r a n s e c tthe
t h massive
e massiveore—quartz—muscovite
ore-quartz-muscovite sschist
c h i s t contact. Dykes
38
�1) and
and 2)
2 ) generations
generations occur
occur as
as highly
highly folded
foldedboudinaged
boudinaged fragments
fragments wwithin
i t h i n the
the
Significant
metamorphic
reaction
zones
are present
present
massive
sulphide ore types.
massive sulphide
types. Significant metamorphic reaction zones are
in-and
as follows:
follows: niagnetite-sulphide
in-and around
around the fragments
fragments and
and appear
appear as
magnetite-sulphide
impregnated
zones
thes isilicate
rock and
andsphalerite
sphalerite rich rims
impregnated zones
in inthe
l i c a t e rock
rims up
up to
t o 5"
5"
rims, Zinc
Within the
the sulphide
sulphide rims,
Zinc rich
around the
the boudinaged
boudinaged fragments.
fragments. Within
wide around
sphalerite
nearthe
thessilicate
sphalerite zones
zones are
are concentrated
concentrated near
i l i c a t e contact,
contact, Iron
Ironrich
richsphal—
sphale r i t ezones
zones away
away from
his.
erite
from tthis.
In conclusion
as as
a metamorphosed
conclusion the
thesulphide
sulphidemineralization
mineralizationis regarded
i s regarded
a metamorphosed
lithological zoning
in in
thethe
boudin—shaped
The lithological
zoning
boudin-shaped
bedded
sulphide deposit.
bedded sulphide
deposit. The
massive sulphide
massive
sulphideore
orerepresents
representsaaprimary
primarystratigraphical
stratigraphical configuration,
Stratigraphical tops
tops have
have not
not
although
although accentuated
accentuated during the
the deformation.
deformation. Stratigraphical
thedistribution
distribution of
However the
of
been
determined in
been determined
in the
theManitouwadge
Manitouwadge area.
area. However
relatively
r e l a t i v e l ycopper
copper rich zones
zones tto
o the
the north, zinc
zinc rich
richzones
zones to
t o the
the south
south
followed by
by magnetite-chert
magnetite-chert iron
iron formation
formationdefines
definesa abroad
broadpattern
patterncomparable
comparable
I tisi sproposed
proposed
to
othersynvolcanic
synvolcanicsulphide
sulphidedeposits.
deposits. It
t o the
the vertical
verticalzoning
zoningini nother
that
syncline represents
represents the
the refolded limbs
t h a t the
theManitouwadge
Manitouwadge syncline
limbs of
ofan
anoverturned
overturned
nappe
structure with
w i t hananeast—west
east-west axis.
axis.
nappe structure
39
�THE ATIKOKAN
THE
ATIKOKAN IRON
IRON RANGE
RANGE AND
AND ITS
ITSIRON—COPPER
IRON-COPPER MINERALIZATION
MINERALIZATION
dens. F.
F. Touborg,
Touborg, Suite
S u i t e1006,
1006, 77
77Howard
Howard St.,
St., Toronto
TorontoM4X
M4X IJD,
lJD, Ontario
O n t a r i oCanada.
Canada.
Jens.
ABSTRACT
The Atikokan
Atikokan IIron
The
r o n Range
Range iin
n northwestern
northwestern Ontario
O n t a r i o contains
containswidespread
widespread
magnetite—basemetal
suiphide
whichi sissspatially
magneti
te-basemetal sulphide
m i mineralization
n e r a l i z a t i o n which
p a t i a l l y associated
associated
with
w i t h lensoid
l e n s o i dbodies
bodies ofo ultrabasic—basic
f u l t r a b a s i c - b a s i cigneous
igneousrocks
rockscomposed
composed ooff pyroxenites,
gabbros,
amphibolites and
and pperidotites.
gabbros, amphibolites
eridotites.
The lenses,
lenses, having
The
having a strong
s t r o n g geophysical
geophysical response,
response, are
are concordantly
concordantly
enclosed
enclosed iinn metavolcanic
metavolcanic rocks
rocks of
o f basaltic—andesitic
b a s a l t i c - a n d e s i t i c composition
composition and
and
16 mmile
zoneo of
strikes
ddefine
e f i n e aa 16
i l e llong
o n g zone
f sstratigraphical
t r a t i g r a p h i c a l continuity.
c o n t i n u i t y . IItt strikes
uniformly
andddips
The zone
zonel lies
i e s aa few
few
u n i f o r m l y eastnortheast
eastnortheast and
i p s ssteeply
t e e p l y tto
o the
t h e north.
n o r t h , The
hundredso of
whichi in
hundreds
f f feet
e e t nnorth
o r t h ooff the
t h e Quetico
Q u e t i c o Shear
Shear S&tructure,
t r u c t u r e , which
n tthis
h i s area
area
separates Archean
Archeanmetavolcanic
metavolcanicsseries
e r i e s to
t o the
t h enorth
n o r t hfrom
fromSeine
Seinemetasedimentary
metasedimentary
separates
The impact
impact ooff metamorphism
area iiss low.
metamorphism i nint hthe
e area
low.
sseries
e r i e s to
t o the
t h e south.
south. The
Concentrations
occuri in
Concentrations ooff Iron—Copper
Iron-Copper m imineralization
n e r a l i z a t i o n occur
n ttabular
a b u l a r deposits
deposits
up
Examples are: The
The Atikokan Mines-,
Mines-,
up ttoo 3000
3000 feet
f e e t long
l o n gand
and50-250
50-250 wide.
wide. Examples
SapaweLake-,
Lake—,Archibald-,
Archibald—,Pattison-Roberts
Pattison—Roberts and
and Mark
Mark prospects.
Sapawe
rospects. IIn
n detail
detail
the
disseminated
t h e mineralization
m i n e r a l i z a t i o n consists
c o n s i s t sofo lenses
f lensesdominated
dominated by
by 1)
17 massive—or
massive-or disseminated
magnetite
minor sulphide
sulphide vveinlets
massive—or disseminated
disseminated
magnetite wwith
i t h minor
e i n l e t s and
and 2)
2) massive-or
ppyrrhotite,
y r r h o t i t e , lesser
l e s s e amounts
r amounts of
o f pyrite—chalcopyrite
p y r i te-chal c o p y r i t e (.3-.6%
(. 3-. 6%Copper)
Copper) and
and trace
trace
mineralized
amountsoof
Nickel—Cobaltbearing
bearing sulphides.
sulphides. The
amounts
f Nickel-Cobalt
The m
i n e r a l i z e d lenses
lenses are
are
characterized
by aa banded
bandeds tstructure
concordanti nintercalations
c h a r a c t e r i z e d by
r u c t u r e wwith
i t h concordant
t e r c a l a t i o n s ooff the
the
zonest the
mineralization
ultrabasic—basic
host rock.
u l t r a b a s i c - b a s i c host
rock. Within
W i t h i n pinch—out
pinch-out zones
he m
i n e r a l i z a t i o n and
and
interbandedwwith
tthe
h e host
h o s t rocks
rocks become
become hheavily
e a v i l y interbanded
i t h tthe
h e surrounding
surrounding volcanic
volcanic
rocks. Geometrically
Geometrically the
t h e ruagnetite-and
magneti te-and ssulphide
u l p h i d e lenses
lenses are arranged
arranged in
in
en—echelon
sometimesw with
aa complex
complex en-echelon
s t rstructure,
u c t u r e , sometimes
i t h t hthe
e ssulphide
u l p h i d e rich
r i c hzones
zones
confined
c o n f i n e d tto
o tthe
h e ffootwall
o o t w a l l side;
side; this
t h i sfeature
f e a t u r emay
may be
be a
a possible
possible iindicator
ndicator
ooff stratigraphical
s t r a t i g r a p h i c a l tops.
tops. Preliminary
P r e l i m i n a r y microscopic
microscopic work
work reveal
reveal the
t h epresence
presence
of primary
of
primary magmatic
magmatic ttextures
e x t u r e s in
i n both
both the
t h eoxide-and
oxide-and sulphide
s u l p h i d ephases.
phases.
Origin
Available
t h e mineralization
mineralization
O r i g i n of
o f mineralization:
mineralization: A
v a i l a b l e data
data suggest
suggest 1)
1 ) the
forms an
an i Integrating
forms
n t e g r a t i n g part
p a r t of
o f the
t h eultrabasic—basic
u l t r a b a s i c - b a s i c host
h o s t rocks.
rocks. 22)) there
t h e r e is
is
no
evidencet to
no evidence
o iindicate
ndicate a
a possible
p o s s i b l e relationship
r e l a t i o n s h i p to
t othe
t h ebedded
bedded iron
i r o n formations
formations
Wall rock
rock
contained within
w i t h i nthe
t h eSteep
SteepRock—and
Rock-and Caland
Caland deposits nearby.
nearby. 3) Wall
alteration
a l t e r a t i o n isi slacking
l a c k i n gapart
a p a r from
t fromminor
minorquartz-carbonate
quartz-carbonate vveining
e i n i n g ooff the
t h e host
host
There i is
4) There
s no
no ddirect
i r e c t relation
r e l a t i o nbetween
between the
t h e mineralized
m i n e r a l i z e d uultrabasicltrabasicrock. 4)
synvolcanic i intrusive!
A synvolcanic
ntrusive/
bbasic
a s i c series
s e r i e s and
and the
t h e Quetico
Q u e t i c o shear
shear sstructure.
tructure. A
extrusive
e x t r u s i v e origin
o r i g i n isi sproposed
proposed for
f o rthe
t h estratabound
stratabound ultrabasic-basic
u l t r a b a s i c - b a s i c series
s e r i e s and
and
iits
t s associated
associated mineralization.
mineralization.
40
�GEOCHRONOLOGY
PRECM4BRIANROCKS
ROCKSIN
IN EASTERN WISCONSIN
GEOCHRONOIAGY OFOFPRECAMBRIAN
WISCONSIN
W.
Schxnus,Department
DepartmentofofGeology,
Geology,University
University of
. Van
Van Schmus,
of
W. RR.
lawrence, Kansas,
66044
Kansas, Lawrence,
Kansas,66024k
Kansas,
geochronological studies
studies by the author, in
Recent geochronological
in
Recent
conjunction with other published and unpublished data, now
conjunction
permit the
the delineation
delineation of
of major
major chronologic
chronologic units
units for
for
Precambrian rocks
Precambrian
rocks in
in eastern
eastern Wisconsin.
Wisconsin.
The
The oldest
oldest rocks
rocks in
in the
the eastern
eastern part
part of
of the
the state
state
are the metavolcanics, gneisses,
gneisses, and intrusive rocks
rocks in
northeastern corner,
the northeastern
corner, including
including the
the Quinnesec
Quinnesec Fm.,
Fm.,
Dunbar Gneiss,
Dunbar
Gneiss, Hoskin
Hoskin take
Lake Granite,
Granite, Newingham
Newingham Granodiorite,
Granodiorite,
and AtheLstane
Athe-"Sane Quar'z
QuaiJ%Monzonite.
Monzonite. These
These rocks
rocks are
are about
about
1900 m
m.y.
whole-rock data and
1850
1850 to 1900
.y. old based on Rb-Sr whole-rock
published U-Pb
U-Pb zircon
zircon data.
data.
Apparently the bulk of
of the
the state
state is
is made
made up
up of
of metametavolcanics and
volcanics
and granitic
granitic rocks
rocks that
that yield
yield ages
ages of
of 1650
1650 to
to
rocks in
Waushara
1700
1700 m.y.
m.y. The
The author
author has
has analysed
analysed such
such rocks
in Waushara
Co. (granites)
(granites) and
and to
to the
the south
south (rhyolites),
(rhyolites), and
and other
other
workers
workers have
have reported
reported similar
similar ages
ages from
from near
near Monico,
Monico, Wausau,
Wausau,
and Baraboo.
Baraboo.
Intrusive into the 1650—1700
m.y.
1650-1700 m
.y. old complex
complex is
is aa
Intrusive
large
large plutonic
plutonic assemblage
assemblage that
that is
isabout
about12450
1450 to
to 1500
1500 m.y.
m.y.
old and is
is now
now referred
referred to
to as
as the
the Wolf
Wolf River
River Batholith.
Batholith. It
It
includes a wide variety of
includes
of rocks
rocks from
from Mountain,
Mountain, to
to Wausau,
Wausau,
Point, to Waupaca and apparently is
to Steven's
Steven's Point,
is the last
major
major plutonic
plutonic or
or metamorphic event
event in
in the
the state,
state, except
except
for
for the
the Keweenawan
Keweenawan rocks
rocks in
in the
the far
far northwest.
northwest.
absolutely dated are
Not yet absolutely
are gneissic
gneissic and
and related
related
rocks in
Published
rocks
in the
the Steven's
Steven's Point-Wisconsin
Point-Wisconsin Rapids
Rapids area.
area. Published
mineral ages
from these rocks
rocks suggest
suggest they may be related
mineral
ages from
to
Resolution
to the
the northeastern
northeastern Wisconsin
Wisconsin complex,
complex, or
or older.
older. Resolution
of this problem, plus extending
extending our
our knowledge
knowledge westward
westward and
and
northwestward, is currently
currently in
northwestward,is
in progress.
progress.
41
�"FRMIBOIDAL"
WHITEPINE,
PINE, MICHIGM
"ERAMBOIDAL" CHAJJCOCITE
CHALCOCITE FROM
FROM WHITE
MICHIGAN
Thomas A.
A. Vogel and
and Nancy
Nancy Alyanak,
Alyanak, Geology
Geology Oepartment,
Department,
Michigan
48823
Michigan State
S t a t e University,
University,East
EastLansing,
Lansing,Michigan
Michigan48823
ABSTRACT
ABSTRACT
Chalcocite
with nnuclei
Chalcocite with
u c l e i occurs
occurs throughout
throughout the
t h e mineralized
mineralized zone
zone aatt
White
White Pine,
Pine, Michigan.
Michigan.
They
They are
a r e more
more abundant
abundant in
i n the
t h e well—laminated,
well-laminated,
black,
black, fine—grained
fine-grained lithologies
l i t h o l o g i e s than
than in
i n the
t h e massive
massive lithologies.
l i t h o l o g i e s . In
In
polished section
nuclei
s e c t i o n these n
u c l e i are
a r e either
e i t h e r circular,
c i r c u l a r , ellipsoidal
e l l i p s o i d a l or
o r con—
cont o the
t h e shape
shape of
of the
t h e grain,
g r a i n , with
with aa median
median circular
c i r c u l a r diameter
diameter of
of four
four
fform
on to
microns
microns and
and aa median
median ellipsoidal
e l l i p s o i d a l long
long axis
a x i s of
of eight
e i g h t microns.
microns. Microcrysts
Microcrysts
at
a t least
l e a s t as
as small
small as
as 0.2
0.2 microns
microns are
a r e found
found in
i n each
each nucleus.
nucleus. The
The nuclei
nuclei
are
pyrite
a r e similar
s i m i l a r to
t o the
t h e framboidal texture
t e x t u r e commonly observed in
in p
y r i t e assoassociated
c i a t e d with
with sediments.
sediments. The
The chalcocite
chalcocite nuclei
n u c l e i can
can only
only be
be observed
observed after
after
the
t h e polished section
s e c t i o n has been etched and stained
s t a i n e d with a weak hydrochloric
acid
acid and
and potassium ferrocyanide solution——a
s o l u t i o n ~ astain
s t a i n very sensitive
s e n s i t i v e to
t o low
concentrations
concentrations of
of iron.
iron.
e l e c t r o n microscope shows that
The scanning electron
t h a t the microcrysts within
c i r c u l a r or
o r ellipsoidal
e l l i p s o i d a l nucleus are
a r e densely packed,
a well-defined
well—defined circular
packed, with a
few scattered
s c a t t e r e d microcrysts in
i n the
t h e surrounding
surrounding grain.
grain. However, the
t h e micro—
microfew
crysts
c r y s t s are
a r e less
l e s s densely
densely packed
packed where
where the
t h e nucleus
nucleus occupies
occupies the
the entire
e n t i r e grain.
grain
All
A l l gradations between
between dispersed
dispersed and
and densely
densely packed
packed microcrysts
a r e found.
found.
microcrysts are
Preliminary microprobe
d i c a t e s t hthat
a t the
u c l e i aare
r e higher
iron,
Preliminary
microprobedata
datai nindicates
the nnuclei
higher iinn iron,
potassium
and carbon
carbon than
than the
the surrounding
potassium and
surrounding grain.
grain.
Two
Two origins
o r i g i n s are
a r e possible
possible for
f o r the
t h e framboidal
framboidal chalcocite:
chalcocite: 1.)
1.) replacement of
2 . ) formation of primary framboidal
framboidal chalco—
chalcoof framboidal
framboidal pyrite
p y r i t e and 2.)
cite.
c i t e . We
We are
a r e currently
c u r r e n t l y evaluating
evaluating these
these alternative
a l t e r n a t i v e genetic models and
and
their
t h e i r implications.
implications.
42
�WISCONSIN OF LANDFORMS
Na
.., ii:
Or-
tLJ ni
story
irvey
FII
rrF
F
F.
Su
Unoron
I
rd
Geolo irsi
Hanson. Dirnotor and Stoto Genlngiot
L'Fur
UNIVERSITY ESTENSION, UNIVERSITY OF WISCONSIN
1971
30
Ti
__
0
UCALE OF VILEU
EU
�A
A'
lie Cassai
Racine
boo
too
002
455
StiLES
IS SCALE
iuniuue
Fat it]
A S imL
HOtFrtFTs
-
id
200
SL
Or)
_c
10
-
0
-
203
400
25
boo
500
Jr
loon,
In Leoal
cool Sea
boo
Peat Fr
F
'a Fr sri
"r ron
taboo
and Adaoe
toFu Eieoatian
GriP Gla(n
D!der at
trio (OrryF
(Otto) dssnsnsin
V2snirainn ci
oi Hordes
-.
DriP
r
data) (sisarne
Seeks
Mntantrri and tgnenes
Boors 0rorphie
imenLated ii and Graean
UndiffererrlLFud
h
r -tamest
iF Marc and Ugeenas
irks
toeke
.1 is
miii ndiI
UrFjfersrtiarnd
and Granite
[E
a
-
-
BasalE and Gabbrn
'c
P r
Oornraii000
'chin For tree and Ps'
0mm Graaneitc
senptnmerale)
'rotc ncr-rninuodir
wirb (sandstones
I-crrn',c"s tlnwennerrrn
Formutioos
Upper
a-rd
-
corns with (sandstones
nrA. aed
shale)
a-ri 5dolomite
dotoir snore
_55 °oncrr Oncbrinr'
air Cumb i_poor
Formations
Jeo
(dolomin)
iso "mine
dr
Pr
Ar,a? Chine
Group
Crrhs
none and
shale (snrho,crs
doreen in
usutnF rrsrcrr
torrreratr-(
ruEd
rFFr Parer
Fm)
'0nr StS (mainly 'usr,
Group Aneell
Oscs'l
F,rtr
r--ssils some
rune )dclsrnitcoirh
shale)
oh5 sF and
ccc lanresroon
with (dolomite
Group Sponipea
dtu,
'F
dolomrtn) srd
arrd (ehuls
irrein
Oct. Forrtiati
°rrnurrorr
iolrntn Mc,,
S'iapaiokr--lu
hdcLoortn;
(oolomitu(
sir Is, Si
Formations lurian
Furoariors
II
1—
a
a
skis'
shale)
dod
O'i (doloroipsin rho
Forrrratronn Dovoniuo
S
LEGEND
-
-1-
I
Co
L
SilLhd
GO
SCALE
30
1971
1)JF[°lVflLjyj1
WISCONSIN Fj•
OF UNIVERSITY
)s:H
EXTENSION. UNIVERSITY
an
Geologist State and Director
h( F. George
1rr::ni Hanson.
'r
:r-:.n.
Forli' History
'ir Geological
Survey
Natural
s:•-•j and
!YF:
F
WISCONSIN
iF'fl In::)
MAP GEOLuGIC
fl-il' )l
S
,.'f:s
d
�SHORT GEOLOGIC
GEOLOGIC HISTORY
HISTORY OF
OFWISCONSIN
WISCONSIN
The bedrock
separatedinto
intotwo
twomajor
majordivisions:
divisions:(1)
(1) older,
older, predominantly
predominantly crystalline
crystalline rocks
rocks of
of the
bedrock of Wisconsin
Wisconsin isisseparated
Precambrian
Precambrian Era; and
and (2)
( 2 )younger
youngerrelatively
relativelyflat-lying
flat-lyingsedimentary
sedimentaryrocks
rocksof
of the
thePaleozoic
Paleozoic Era.
Era.
The Precambrian
Precambrian Era
Era lasted
lasted from
from the
the time
time the
theearth
earthcooled,
cooled,over
over4,000
4,000 million
million years
years ago,
ago, until
until the
thePaleozoic
Paleozoic Era
Era
which began
began about 600 million
years ago.
ago. During
During this vast period
which
million years
period of
of 3,400
3,400 million
million years
yearssediments,
sediments, some
some of
of which
which
were rich
rich in iron
iron and
and which
which now
now form
formiron
ironores,
ores,were
weredeposited
depositedinin ancient
ancient oceans;
oceans; volcanoes
volcanoes spewed
spewed forth
forth ash and
and
lava; mountains
were built
built and
and destroyed,
destroyed,and
and the
the rocks
rocks of
of the upper crust
mountains were
crust were
were intruded
intruded by
by molten
molten rocks
rocks of
of deepdeepseated origin. Only a fragmentary
fragmentary record
record of
of these
these events
events remains
remains but,
but, as
as tree
treestumps
stumpsattest
attesttotothe
thepresence
presenceofofformer
former
forests,
forests, the rocky
rocky roots
roots tell
tell the
thegeologist
geologist of
of the
thepresence
presenceofofformer
formermountains.
mountains.Nowhere
Nowhere does
does any trace
trace of
of the
the original
original
crust remain,
remain, and
and the
theoldest
oldest rocks
rocks yet
yet found
found in
inthe
thestate
stateare
areabout
about2,000
2,000million
millionyears
yearsold.
old.With
Withthe
theexception
exception of
ofthe
the
Upper Keweenawan
formationsthat
that outcrop
outcrop in
in the northwest,
northwest, all of
of these
these rocks
rocks have
havebeen
beenextensively
extensively deformed,
deformed,
Keweenawan formations
and in
altered that their
in many
many areas
areas they
they are
are so
so highly
highly altered
their original
original nature and
and origin
origin are
are extremely
extremely difficult
difficult to interinterpret.
I n the
the north-central
north-central part
partof
of the
thestate
statesurface
surfaceoutcrops
outcrops are
areso
sosparse,
sparse, due
due to
to aa cover
cover of
of glacial
glacial deposits,
deposits, that
In
that details
of the bedrock
bedrock are
are obscured.
obscured. In
In such
such areas
areasthe
theonly
onlyclues
clues to
t othe
theunderlying
underlyingrocks
rocksare
areobtained
obtainedindirectly
indirectlyby
bysuch
suchgeogeophysical
methods as
as airborne
physical methods
airborne magnetics.
magnetics. IIn
n the
the past
past much
muchhigh-grade
high-grade iron
iron ore
ore was
was produced
produced from the Precambrian
Precambrian
rocks of
of northern
northern Wisconsin,
Wisconsin,and
andmuch
muchlow-grade
low-gradeore
ore("taconite")
("taconite") awaits development.
work indidevelopment. Recent
Recent geologic
geologic work
cates that
that the
the area
areahas
hasa ahigh
highpotential
potentialfor
forfinding
findingores
oresofofother
othermetals
metalssuch
suchasascopper.
copper.
At the
the close
close of
of the
the Precambrian
Precambrian Era
Eramost
mostofofWisconsin
Wisconsinhad
hadbeen
been eroded
eroded to
to aa rather
ratherflat
flatplain
plainupon
uponwhich
which stood
stood
hills of more resistant rocks as those now exposed
in
the
Baraboo
bluffs.
There
were
still
outpourings
of
basaltic
exposed in
still
basaltic lava
lava
in the
the north
north and
and aatrough
troughformed
formed in
inthe
thevicinity
vicinity of
ofLake
LakeSuperior
Superiorininwhich
whichgreat
greatthicknesses
thicknesses of
of sandstone
sandstone were
were
deposited.
deposited.
The Paleozoic
Era began
began with
with the
the Cambrian
Cambrian Period,
Period, the rocks
Paleozoic Era
rocks of which
which indicate
indicate that
that Wisconsin
Wisconsin was
was twice
twice subsubmerged
beneath
the
sea.
Rivers
draining
the
land
carried
sediments
which
were
deposited
in
the
sea
to
form
merged
the sea. Rivers draining the land carried sediments which were deposited in the sea to formsandsandstone
and plants
plants living
in the sea
stone and shale.
shale. Animals
Animals and
living in
sea deposited
deposited calcium
calcium carbonate
carbonate and built
built reefs
reefs to
toform
formrocks
rocks
which are
magnesium-rich
continued into the
dolomit-a
magnesium-rich limestone.
limestone. These same
same processes
processes continued
the Ordovician
Ordovician Period
Period
are now
now dolomite—a
during which,
was submerged
submergedthree
three more
more times.
times. Deposits
Depositsbuilt
built up
up in
in the sea
which, as indicated
indicated by the
the rocks,
rocks, Wisconsin
Wisconsin was
sea
when
when the land
land was
was submerged
submerged were partially or
or completely
completely eroded
eroded at
at times
times when
when they
theywere
weresubsequently
subsequently elevated
elevated
above
sea level.
level. During
During the
the close
close ofof the
the Ordovician
Ordovician Period,
Period, and
and in the
above sea
the succeeding
succeeding Silurian
Silurian and
and Devonian
Devonian Periods,
Periods,
Wisconsin
is believed
Wisconsin is
believed to have remained
remained submerged.
submerged.
The youngest
youngest rocks
rocks outcropping in
in Wisconsin
Wisconsin are of
of Devonian
Devonian age
age and
and are
areabout
about350
350million
million years
years old.
old. Absence
Absence of
The
of
If the
thedinosaurs
dinosaurs
younger rocks makes
makes interpretations
interpretations of post-Devonian
post-Devonian history in Wisconsin
Wisconsin aa matter of
of conjecture.
conjecture. If
younger
roamed Wisconsin,
as well
well they
they might
might have some 200 million
million years
years ago, no trace
Wisconsin, as
trace of
of their
theirpresence
presenceremains.
remains.AvailAvailevidence from
from neighboring
neighboring areas,
areas, where
whereyounger
youngerrocks
rocksare
arepresent,
present,indicates
indicatesthat
thattowards
towardsthe
theclose
closeof
of the
the PaleoPaleoable evidence
some 250 million
present. DurDurzoic Era, perhaps some
million years
years ago,
ago, aa period
period of
of gentle uplift began which
which has continued to the present.
ing
ing this
this time
time the
the land
land surface
surface was
was carved
carved by rain, wind
wind and
and running
running water.
water.
The final
final scene
scene took
took place
place during
million years
when glaciers
glaciers invaded
invaded Wisconsin
Wisconsin from
north and
and
The
during the last million
years when
from the north
sculptured
thevalleys
valleysand
andleft
leftaadeposit
depositof
ofdebris
debris over
over all
all exexsculptured the
the land
land surface.
surface.They
Theysmoothed
smoothed the
thehill
hilltops,
tops,filled
filledthe
cept the southwest
southwest quarter of
of the
theState
Statewhere
wherewe
wemay
maynow
nowstill
stillsee
seethe
theland
landasasititmight
mighthave
havelooked
lookedaamillion
millionyears
years
ago.
ago.
�fI;Director
si;p 5Hanson,j
J•!U]%9#IC
State and
Geologist
:'
Survey,, History Natural
!4[c
au
'FiJOG->
d 'ge
!tñJiS%
Geological .!IHCOIISIfl
i]1.y of University
Wisconsin
)I.Ii1
PtisIt uqen
ds n 'H
irf 'tjsoap0
pitted
SLft LJSDaiflfl
unpitted
ne 1t)15.tJ
Morn ptrnOJ9
4
or,es
.YY;_JOW p'q
L
r
,•
tR: OF
dç SCALE
MILES
40
p
-.
iHFI.Jj after
1956 Tliwaites,
q
Hi
1
'i• _r' n
1]
DEPOSITS GLACIAL
WISCONSIN
F
L
�I
SHORT
S
HORT HISTORY OF
OF THE ICE AGE IN
I N WISCONSIN
WISCONSIN
U
1,000,000 years ago
The Pleistocene Epoch or
o r "Ice
"Ice Age"
Age" began about 1,000,000
ago which,
which,
in
f o u r separate
separate
s h o r t time
time ago.
ago. There were four
i n terms of
of geologic
geologic time,
time, i s a very short
g l a c i a l advances
advances iin
n tthe
h e Pleistocene
Pleistocene each
each followed
followed by
by an
an inter—glacial
i n t e r - g l a c i a l period
period
glacial
is
whent the
The ffourth
o u r t h gglacial
l a c i a l stage
s t a g e is
i scalled
c a l l e dthe
t h Wisconsin
e Wisconsin Stage
Stage
when
h e iice
c e receded.
receded. The
because
wasi nint hthis
that
it was
first studied
detail.
because itit was
i s SState
tate th
a t it
was first
s t u d i e d iin
n d
etail.
The gglaciers
snow
The
l a c i e r s were
were formed
formed by
by the
t h e continuous
continuous accumulation
accumulation of
of snow.
snow. The snow
i n t o ice
i c e which reached a maximum
maximum thickness of
of almost
almost two
two miles.
miles. The
The
turned into
sheet spread
spread over
over Canada and ppart
of it
it flowed
flowed iin
general southerly
southerly
iice
c e sheet
a r t of
n aa general
direction
d
i r e c t i o n toward Wisconsin and neighboring states.
states.
f r o n t of the
t h e advancing
advancing iice
c e sheet
sheet had
had many
many tongues or
o r "lobes"
"lobes" whose
whose
The front
direction
wereccontrolled
by tthe
of tthe
d
i r e c t i o n and
and rate
r a t eofofmovement
movement were
o n t r o l l e d by
h e topography
topography of
h e land
land
surface over
by tthe
surface
over which
which they
they flowed
flowed and by
h e rrates
a t e s of
of ice
i c e accumulation in
i n the
the
different
d
i f f e r e n t areas from which they were fed.
fed.
sheet transported
transported aa great
rockddebris
"drift".
The ice
i c e sheet
g r e a t amount
amount ofofrock
e b r i s ccalled
a l l e d "drift".
was
was
"Drumlins"
p
i l e d up
up aatt the
t h e margins
margins of
of the
t h e ice
i c elobes
lobestot oform
form"end
"end moraines".
moraines".
piled
are
of ddrift
byt the
a r e elongated
elongated mounds
mounds of
r i f t which
which were
were molded
molded by
h e iice
c e passing
passing over
over them
them
and
hencei nindicate
and hence
d i c a t e tthe
h e ddirection
i r e c t i o n of
of ice
i c e movement.
Some
"ground
Some ofoft this
h i s was
was deposited
deposited under
under the
t h e ice
i c etot form
o form
"groundmoraine"
moraine"and
andsome
some
pattern
of end moraines,
moraines, iin
red, shows tthe
was occupied
occupied
The p
a t t e r n of
n red,
h e pposition
o s i t i o n tthat
h a t was
advanced down
down the
t h e basin
basin of
of Lake
Lake Michigan,
Michigan,
by four
f o u r major ice
i c e lobes.
lobes. One lobe advanced
Green Bay,
Bay, aa third
another
another down
down Green
t h i r ddown
down Lake
Lake Superior and over the
t h e northern peninsula
The
Michigan and yet a fourth
of Michigan
fourth entered
entered the
the state
s t a t e from
from the
t h e northwest
northwest corner.
corner. The
of
"Kettle Moraine"
well-known "Kettle
Moraine" was
was formed
formed between
between the
t h eLake
LakeMichigan
Michigan and
andGreen
Green Bay
Bay
well—known
lobes. As
A s tthe
h e ice
i c e melted
melted the
t h e drift
d r i f was
t wasreworked
reworked by
by the
t h e running
running water.
water. Large
amountsofof sand
sand and
andgravel
gravel were
weredeposited
deposited tto
"outwashplains";
plains"; ppits
amounts
o form
form "outwash
i t s were
were
formed iin
whereburied
buriedblocks
blocks of
of ice
of these are
formed
n tthe
h e outwash
outwash where
i c e melted
melted and
and many
many of
are
now
now occupied
occupied by
by lakes.
lakes.
The action
profoundly modified tthe
landscape, smoothing o
off
a c t i o n of
of tthe
h e ice
i c e profoundly
h e landscape,
f f tthe
he
places ititchanged
changed
I n some
some places
of hills
ccrests
r e s t s of
h i l l s and ffilling
i l l i n g the
t h e valleys
v a l l e y s with
with ddrift.
r i f t . In
the
of tthe
Wisconsin
t h e course of rivers
r i v e r s forcing them to
t o cut new channels such aass tthat
h a t of
h e Wisconsin
River at
a t tthe
h e Dells;
Dells; elsewhere it
it dammed
dammed the
t h e valleys
v a l l e y s to
t o create
c r e a t e lakes
lakes such
such as
a s those
those
of tthe
of
h e Madison
Madison area.
area.
During rrecent
e c e n t years there
t h e r e have been intensive
i n t e n s i v e studies
s t u d i e s made
made of
of the
t h e polar
polar
caps, and methods have been developed for
iice
c e caps,
f o r dating glacial
g l a c i a l events
events from
from the
the
of tthe
wood, bones,
bones, eetc.
which aare
found iin
many of
of
rradioactivity
a d i o a c t i v i t y of
h e carbon iin
n wood,
t c . which
r e found
n many
of these
these sstudies
previously accepted
e s u l t s of
t u d i e s aare
r e causing many previously
tthe
h e deposits.
deposits. The rresults
concepts to
t o be changed
changed or
o r challenged.
challenged.
We
thought tthat
were rrather
extensive gglacial
W
e once thought
h a t tthere
h e r e were
a t h e r extensive
l a c i a l ddeposits
e p o s i t s oolder
lder
than Wisconsin age
age in
i n the
t h e State,
S t a t e , but
but age
age determinations
determinations do
do not
not support
support this.
this,
It was aalso
thought that
It
l s o thought
t h a t the
t h e ice
i c e left
l e f t Wisconsin some
some 20,000
20,000 years
years ago
ago but
but aa
Countywas
wasburied
buriedunder
under an
an advancing
advancing iice
fforest
o r e s t aatt Two Creeks in
i n Manitowoc
Manitowoc County
ce
i s accumulating
accumulating to
t o indicate
i n d i c a t e that
t h a t ice
ice
11,000 years ago.
tongue
tongue only 11,000
ago. Evidence is
may have occupied the
Area" of
of tthe
southwestern p
part
of
t h e so—called
so-called "Driftless
" D r i f t l e s s Area"
h e southwestern
a r t of
the
t h e State
S t a t e which hitherto
h i t h e r t o has
has been
been held
held to
t o be
be unglaciated.
unglaciated.
Most sscientists
believe
Most
c i e n t i s t s now b
e l i e v e that
t h a t the
t h e cause of the
t h e Pleistocene "Ice
"IceAge"
Age"
was
duet to
was due
o vvariations
a r i a t i o n s in
i n the
t h e solar
s o l a renergy
energyreaching
reaching the
t h eearth,
e a r t h ,but
buthow
howthese
thesemay
may
We
haveoccurred
occurredisissstill
have
t i l l aa matter
matter of
of conjecture.
conjecture. W
e a are
r e sstill
t i l l in
i nthe
t h eIce
I c eAge
Age and
and
it
anybody's guess whether future
millenia
it is anybody's
future m
i l l e n i a will
w i l l see
s e e the
t h e melting
melting of
of
cities,
or
the
regrowth
coastal
caps and the
slow
drowning
of
our
t h e slow
our c o a s t a l c i t i e s , o r t h e regrowth and
and
oftthe
more tthe
more
h e inexorable
inexorable advance
advance of
h e gglaciers.
laciers.
the
t h e ice
ice
once
once
Prepared
by tthe
Natural History
HistorySurvey,
Survey, August
August
Prepared by
h e University
University of
ofWisconsin
Wisconsin Geological
Geological £& Natural
19641
1964'
�WiSCONSIN OF unIVERSITY
A
A
U
II Al IA
OAR
._<__,1<.,
Spruce White Fir, Balsam
FOREST BOREAL
Cedar Tamarack, Spruce, Black
SWAMPS CONIFER
——
•—fl.l- Maple,
<r—
Birch Yellow
Hemlock,
N
FOREST MESIC NORTHERN
i:_
t' .',
F —.
Pine Red Pine, White
FOREST PINE
Grasses Prairie pine, Jock
BARRENS PINE
—
r
4/
'C<L<.. Joint, Blue Sedges,
Cordgrass
MEADOWS SEDGE
L___J
•
r—
<Willows,
Ash Maple,
Soft
-
HARDWOOD LOWLAND
Elm
- -c
- Stigar
Basswood, Maple,
FOREST MESIC SOUTHERN
Oaks Red ond Block White,
FOREST OAK SOUTHERN
1
LI±J
7
t
Bluestem Oak, White Oak, Bur
I
SAVANNA OAK
-,
-1";,;]
Composites
Bluestem,
-<
PRAIRIE
a
LEGEND
6
I
r
a
/
a
S
C
C
a
L
Miles at Scale
80
40
0
1965 Wisconsin of University
Director
L
L:s4
Hanson, G.E.
Survey History Natural and Geological Wisconsin
1I\L
H
j ccc
WISCONSIN OF VEGETATION
EARLY
-.
I
f
pi
�INTERPRETATION OF
OFTHE
THEVEGETATION
VEGETATIONOF
OFWISCONSIN
WISCONSIN
about the
the middle
middle of
of the
the llast
This map
map iiss based on the original
original land
land survey
survey conducted
conducted about
a s t cencenSurveyorswere
wererequired
requiredtotoplace
placeaa stake
stake eachhalfmile,
tury. Surveyors
eachhalfmile, identified
identified by
by notation
notation of
of nearby
nearby
trees, and
and to
to note
note briefly
briefly the
the general
general plant
plant cover
cover of
of each
each quarter
quarter section. These records
records have
have
been used to
been
to reconstruct
reconstruct the
the presettlement
presettlement distribution
distribution patterns
patterns of
ofplant
plantcommunities
communities shown
shown on
on
the map.
map.
The plant communities
recognized,however,
however,are
arebased
basedon
on systematic
systematic studies
studies of presentThe
communities recognized,
presentday vegetation.
vegetation. The
day
The results
results of
of these
these studies
studiesare
aresummarized
summarized in a recent
recent book
book (J. T. Curtis,
Curtis, The
The
Vegetation
of
Wisconsin,
University
of
Wisconsin
Press,
1959)
in
which
each
community,
with
Vegetation of Wisconsin, University of Wisconsin Press, 1959) in which each community,
its history,
history, location,
location, and
and relationship
relationship to
toother
othercommunities
communities and tothe
tothe environment,
environment, iiss considered
considered
Since
some
of
the
factors
determining
vegetation
vary
gradually,
the vegetation
vegetation itself
itself
in
detail.
in
Since some of the factors determining vegetation vary gradually, the
varies gradually
and
boundaries
on
the
map
are
somewhat
arbitrary.
gradually and boundaries on the map are somewhat arbitrary.
The vegetation
vegetation of
of the
the state
floristic provinces
The
s t a t e is
is divided
divided into
into northern
northern and southern
southern floristic
provinces by
by aa
line that runsinans-curve
runs in an S-curvenorthwest
northwestfrom
fromMilwaukee
MilwaukeetotoHudson.
Hudson.North
Northofofthis
this line
line the vegetation
vegetation
Southwest of
of the
the line,
abroadleaf forest containing
containing conifers—pines,
conifers-pines, hemlock,
is abroadleaf
hemlock, spruces,
spruces, and fir. Southwest
conifers are
are much
much lless
andare
are replaced
replacedby
byforests
forests with
with several
several species
species of
conifers
e s s important
important and
of oaks, and
by the
the prairies—areas
dominatedby
bygrasses
grasses and
and tall herbs.
by
prairies-areas dominated
herbs.
Fire has
has been
been important
important in
in determining
determining almost all of
of the
the plant
plant communities
communities and
and their
their lolothe coming
of white
white man,
man, the
the prairies (1)
(1) and
and the
the open
open woodlands
woodlands burned
burned almost
almost
cation. Before
Before the
coming of
every year.
year. Thus
every
Thus most
most of
of the
the southern
southern part
part of
of the
the state
s t a t ewas
was covered
covered with
with prairie
prairie or
or oak
oak savanna
savanna
(2), an orchard-like
withaa few
few large
large bur
bur or
or white
white oaks
oaks growing
in fields
fields of
(2).
orchard-like community
community with
growing in
of grass.
grass.
Only in
in the
the more
more protected
protectedplaces
places did
did forests
forests survive.
(3) but
but many
many were
were
Only
survive. Some
Some of
of these
these were
were oak
oak(3)
sugar
elm forests (4).
sugar maple-basswood-slippery
maple-basswood-slippery elm
(4). The
The lowlands
lowlands were
were occupied
occupied by
by river
river bottom
bottom
Withsettlement,
settlement, the
the fires
fires were
(51, and
and sedge
sedgemeadow
meadow (6).
( 6 ) . With
were stopped, and the oak
oak savannas
savannas
forest (5),
of the prairies
grew up
dense white
white oak-black
oak-black oak
oak forests
forests found
found today.
today. Most
Most of
prairies have
have been
been
grew
up to
to the dense
cultivated, andat
and a tpresent,
present,with
withthe
theoak
oaksavannas,
savannas,are
areamong
amongthe
therarest
rarestofofour
ourplant
plantcommuaities.
communities.
In
part of
of the
the state, aa combination
In the northern
northern part
combination of fire and
and poor
poor soil resulted
resulted in
in the
the develdevelopment
of
pine
barrens
(7)
on
the
sandy
soils,
and
pine
forests
(8)
on
somewhat
better
soils. In
(8) on somewhat better soils.
opment of pine barrens (7) on the sandy soils, and pine
the
the absence
absence of
of fire,
fire, the
the white
white pine
pine forests
forestsgradually
gradually changed
changed to
to the
thenorthern
northern equivalent
equivalent of
of the
the
sugar
forests, aa community
sugar maple-basswood
maple-basswood forests,
community containing sugar
sugar maple,
maple, yellow
yellow birch
birch and
and hemlock,
hemlock,
with beech
beech added
added in
in the
the eastern
eastern counties
counties (9).
(9). Also
Also present
present in
in the
the north
north were
were large
large tracts
tracts of
of lowlowwith
land, with
with tamarack
tamarack and
andblack
black spruce
spruce bogs
bogs in
in the
the wetter
wetter areas,
areas, and white cedar swamps
land,
swamps in drier,
but still
still very
very moist
moist habitats
habitats (10).
(10). In
In the extreme
extreme north
north are local
local occurrences
occurrences of
of the
thenorthern
northern
but
conifer
by fir and spruce.
conifer forest
forest (11)
(11) dominated
dominated by
A comparison
comparisonofof this
this map
map with
with maps
maps ofof climate,
climate, soil, and
A
and glacial
glacial deposits
deposits shows
shows many
many
The
correspondences, indicating
relationships between
correspondences,
indicating many
many relationships
between vegetation
vegetation and the
the environment.
environment. The
original vegetation
vegetation was
was thus
by the
the distribution
of both
original
thus determined
determined by
distribution of
both climatic
climatic and
and soil
soil factors,
factors,
modified
modified by fire.
fire.
0.
G. Cottam,
Cottam, 0.
0. L.
L. Loucks
Loucks
Department of Botany
Department
The University of
of Wisconsin
Wisconsin
�
https://digitalcollections.lakeheadu.ca/files/original/ac9dd9c98d82d2009fc6fa2432059ff8.pdf
cc4f1f23c1fae5b8a1976c91c2b31a0d
PDF Text
Text
University of Wisconsin—Extension
GEOLOGICAL AND NATURAL HISTORY SURVEY
Meredith E. Ostroin, State GeoIogSt and Director
GUIDEBOOK TO THE
PRECAMBRIAN GEOLOGY OF
NORTHEASTERN AND NORTHCENTRAL WISCONSIN
18th Ausnuul
Institute on Luke Superior Geology
Madison, Wisconsin, 1973
�UNIVERSITY
UNIVERSITY OF
OF WISCONSIN-EXTENSION
WISCONSIN-EXTENSION
GEOLOGICAL AND
AND NATURAL
GEOLOGICAL
NATURAL HISTORY SURVEY
SURVEY
E. Ostrom,
Ostrom, State
State Geologist
Geologist && Director
Director
Meredith E.
GUIDEBOOK TO
TO THE PRECAMBRIAN
PRECAMBRIAN GEOLOGY
OF NORTHEASTERN
NORTHEASTERN AND
AND NORTHCENTRAL WISCONSIN
with Special Papers on
Chronology of Precambrian
Precambrian Rocks
Rocks in
in Wisconsin
Wisconsin
W.R. Van
Van Schinus
Schmus
The Wolf River Batholith——a
Batholith--a Late
Late Precambrian
Precambrian Rapakivi
Rapakivi
Massif in
in Northeastern Wisconsin
Wisconsin
L.G.
L.G. Medaris,
Medaris, Jr.,
Jr., J.L.
J.L. Anderson,
Anderson, and
and J.R.
J.R. Myles
Myles
Precambrian Geology of Marathon County
G.L. LaBerge
LaBerge and
and P.E.
PE. Myers
G.L.
Field Trip Committee
Committee
C.E.
C.E. Dutton,
Dutton, U.W.
U.W. Geological Survey
Survey
G.L. LaBerge,
LaBerge, UW—Oshkosh;
mV-Osh~osh; Wis.
Wis. Geol.
Geol. && Nat.
Nat. Hist.
Hist. Sur.
Sur.
L.G.
L.G. Medaris,
Medaris, Jr.,
Jr., UW—Madison
UW-Madison
G.
G. Mursky,
Mursky, UW-Milwaukee
P.E.
P.E. Myers,
Myers, UW-Eau
mV-Eau Claire;
Claire; Wis.
Wis. Geol.
Geol. && Nat.
Nat. Hist.
Hist. Sur.
Sur.
W.R. Van Schmus,
W.R.
Schmus, University
University of Kansas
L.W.
L.W. Weis,
Weis, UW Center System-Fox Valley
Valley
printed in
in limited
limited quantities
quantities for
for the
the 19th
19th
This guidebook was printed
Annual Institute
Institute on
on Lake
Lake Superior
Superior Geology.
Geology.
Madison, Wisconsin
Madison,
1973
Available from
from the
the Wisconsin
Wisconsin Geological
Geological and
and Natural
Natural History
History Survey,
Survey,
Wisconsin—Extension, 1815 University
University of Wisconsin-Extension,
University Avenue, Madison,
Madison,
Wisconsin
Wisconsin 53706.
53706. Price: $5.00.
�DEDICAT
I
DEDICATION
This guidebook is
is dedicated to
to Carl E.
E. Dutton
Dutton in
in appreciation
appreciation for
for
his continual encouragement and
and advice
advice to
to us
us all
all and
and in
in recognition
recognition of
of
toward an
an understanding of the
the Wisconsin Precambrian.
his contributions toward
I
�INTRODUCTION
I NTRODUCT ION
With the exception of early bulletins of
of the
the Wisconsin
Wisconsin Geological
Geological
and Natural
Natural History Survey produced between about
about 1900
1900 and
and 1930
1930 little
little
had been published on the Precambrian geology of
of Wisconsin
Wisconsin until
until the
the
appearance
appearance in
in 1970 of
of "Lithologic,
"Lithologic, Geophysical,
Geophysical, and Mineral Commodity
Maps of
of Precambrian Rocks
Rocks in
in Wisconsin" by
by Carl
Carl E.
E. Dutton
Dutton and
and Reta
Reta E.
E.
Bradley, which was the product of aa cooperative effort of
Bradley,
of the
the State
State
Survey and
and the
the U.S.
U.S. Geological
Geological Survey.
Survey. That publication is
is aa compicompilation which drew together in
in concise form at
at aa scale
scale of
of 1:500,000
1:500,000 all
all
that was generally known about Precambrian geology of
of Wisconsin
Wisconsin and,
and,
thus,
thus, served to focus
focus attention on the
the mineral potential of
of Wisconsints
Wisconsin's
Precambrian rocks and
and to indicate the inadequacy
inadequacy of
of available
available geological
geological
and
information. As aa direct consequence of the
the publication
publication
and geophysical Information.
company exploration activity increased
increased markedly and
and the
the interest
interest of
of
university and
and survey
survey geologists
geologists was
was revived.
revived.
As aa part
part of
of this
this revival
revival the
the Wisconsin
Wisconsin Geological
Geological && Natural
Natural History
History
Survey has initiated a program to survey and
and map the
the Precambrian geology
geology
of the state in cooperation with geologists on the
the faculty
faculty of
of the
the UniverUniversity of Wisconsin System
System at
at its
its various
various campuses.
campuses. At the
the present time
time
L. LaBerge (UW—Oshkosh),
Professors Gene L.
(UW-Oshkosh), Paul Myers (UW—Eau
(UW-Eau Claire),
Claire), and
and
Joe Mengel
(UW-Superior) are supported by the Survey on aa part—time
part-time
Mengel (UW—Superior)
basis during summer months to map Precambrian geology in
in Wisconsin.
Wisconsin.
Other university geologists contributing to the program have obtained
support from
from various grant programs including the University—Industry
University-Industry
Program, the Wisconsin Alumni Research Foundation and
Research Program,
and from
Industry.
industry.
The Survey will soon
soon publish aa bouguer
bouguer anomaly
anomaly gravity
gravity map
map of
of the
the
state prepared by Professors C.
C. Patrick Ervin (formerly
state
(formerly UW—Madison,
UW-Madison, now
Northern Illinois
(UW—Madison) at
at a scale
Illinois University)
University) and
and Sigmund
Sigmund Hanuner
Hammer (UW-Madison)
of 1:500,000,
1:500,000, utilizing over
of
over 16,000
16,000 stations.
stations. In
In addition,
addition, the Survey
has begun aa program under the
the leadership
leadership of
of Prof.
Prof. John
John Karl (Department
(Department
of Physics,
Physics, UW—Oshkosh)
UW-Oshkosh) to
to produce an
an aeromagnetic
aeromagnetic map of
of the
the northern
northern
two—thirds of the
the state at
north—south flight
two-thirds
at a
a north-south
flight line spacing of one—half
one-half
mile. This study was initiated
initiated by aa grant from
from the
the Upper Great Lakes
Lakes
Regional
Regional Commission and has been strongly supported by aa substantial
substantial
grant from NL Industries
Industries and
and by aerial
aerial photograph prints
prints provided
provided by
by INCO.
INCa.
This field
field guide and accompanying
accompanying maps,
maps, printed for the
the 19th
19th Annual
Institute on
on Lake
Lake Superior
Superior Geology,
Geology, will
will be included in what
what is
Institute
is hoped
be aa complete series
series of
of Precambrian
Precambrian field
field guides
guides and
and
will eventually be
maps
for Wisconsin
Wiscsin atata ascale
maps for
scaleofof1:250,000,
1:250,000, published
published as
as Geological
Geological and
and
Natural History
History Survey
Survey Information
Information Circulars.
Circulars. When used in
in combination
with the
the bouguer gravity anomaly
anomaly map and
and the
the aeromagnetic
aeromagnetic map
map they
they will
will
provide aa basis for identification
identification of
of areas
areas of
of above
above average
average mineral
mineral popotential in
Wisconsin which can then be made the subject for detailed
tential
in Wisconsin
study.
M.E. Ostroin
Ostrom
& Director
State Geologist &
�SPECIAL PAPERS
Chronology of Pncainbrimn Rocks
by
W.R.
Van Schaus
Wolf River Satboiith——a Lst• Precabrian
Rspakivi Kant! La Wcrtheasten Wisconsin
The
by
b.C. Medaris, Jr., J.L. Anderson, and J.R, kyle.
Ptecnibrtan
Geology of
Marathon County
by
G.L. Laflerge and P.E. Myers
�Superior
Lake
Superior
u
o
N
....o
--'
""
Q
Waupaca
River Falls
Map
Symbol
Age
Im.y.)
Chronologic
Unit
PALEOZOIC
Keweenawan
COVER
1115
.:20
Wolf River Batholith
gr
•
•rhy• •
1500
.:50
rhy
•
>1500
Quartzite
<1675
1675
.: 50
Central Wisconsin
Complex
o
~
~
> 1500
TIgerton Anorthosite
<
NE Wisconsin Complex
??
o
1875
.:50
Metavolcanics and
metasedi ments
1900
.: 50
Archean Complex
>2500
Age uncertain or unknown
I.
Figure 1.
Madison
Miles
0
0
Kilometers
Milwaukee
40
50
• = Primary
age determinations
Primary age
WRVS
2/73
Generalized geochronologic
geochronologic map
mapofatPrecambrian
Precambrianrocks
rocksin
in Wisconsin
Wisconsin and
Michigan.
Generalized
and Upper
Upper Michigan.
I
�11
Chronology of Precambrian Rocks
Rocks in
in Wisconsin
by
W.R. Van Schmus*
W.R.
Geochronologic data for Precambrian rocks
rocks in
in Wisconsin have
have existed
existed
for
for more than aa decade,
decade, but until recently the
the data were limited
limited to
to
analyses of
of separate
separate minerals
minerals and
distributed, so that
analyses
and were widely distributed,
that exact
interpretation of primary formational ages
ages and
and delineation of
of chronologic
chronologie
provinces was not possible.
possible. These early data were summarized
summarized by
by Dutton
Dutton
and
(1970) and will not be
be reviewed
reviewed in
in detail
detail here.
here.
and Bradley
Bradley (1970)
In
terms of
of obtaining primary ages
In terms
ages of Precambrian rocks,
rocks, as opposed
to metamorphic ages,
ages, the geochronologic methods most likely
likely to
to yield
yield
reliable results are the Rb-Sr whole-rock isochron
isochron method and
and U-Pb
U-Pb
analyses on cogenetic suites
suites of
of zircons.
zircons. Application of these
these procedures
procedures
to Precambrian rocks
rocks in Wisconsin has recently been done by P.O.
p.O. Banks
(Banks
(Banks and
and Cain,
Cain, 1969;
1969; Banks and
and Rebello,
Rebello, 1969;
1969; and
and unpublished
unpublished data),
data),
by Z.E.
Z.E. Peterman (unpublished
(unpublished data),
data), Dott
Dott and
and Daiziel
Dalziel (1972),
(1972), and
and by
by
the author
Schmus, 1972,
the
author (Van Schmus,
1972, 1973;
1973; Thurman and
and Van Schmus,
Schmus, 1973;
1973; and
and
unpublished data).
data). A
A summarization
summarization of
of these
these data
data is
is presented
presented in
in Table
Table 1.
1.
unpublished
Based on the
the available
available geologic
geologic and
and geochronologic
geochronologic data,
data, aa genergeneralized chronologie
alized
chronologic map
map has
has been prepared for Precambrian rocks of
Wisconsin and
and Upper
Upper Michigan
Michigan (Figure
(Figure 1).
1). A
the various
various
A few comments on the
chronologic
brief discussion
discussion of
of their
their significance
significance is:
is
chronologie units
units and
and a
a brief
presented below,
below, but space does not jermit
permit detailed
detailed description
description or
or disdiscussion.
The "Pb
The "Precambrian X",
etc. terminology
terminology used below
below refers
refers to
to the
the
Xt, etc.
current U.S.
U.S. Geological Survey subdivisions of
of Precambrian time:
time:
Precambrian Z,
Z, base
base of
of Cambrian
Cambrian to
to 800
800 m.y.
m.y. ago;
ago; Precambrian
Precambrian Y,
Y, 800
800 to
to
1600 m.y.
m.y. ago;
X, 1600 to
ago; Precambrian X,
to 2500
2500 m.y.
m.y. ago;
ago; and
and Precambrian
Precambrian W,
W,
oldçr than
old~r
than 2500
2500 m.y.
m.y.
Archean Complex (Precambrian
(Precambrian W)
The oldest rocks
rocks in
in the
the area
area are
are exposed
exposed in
in the
the northern
northern part.
part. In
In
Upper Michigan these have been shown to be 2.5 to
to 2.7
2.7 b.y.
b.y. old or
or older
older
(Aldrich,
1965; Woolsey,
Woolsey, 1971;
1971; Banks
Banks and
and Van
Van Schmus,
Schmus, 1971,
1971,
(Aldrich, and
and others,
others, 1965;
1972),
1972), but no dates have been reported
reported as
as yet
yet from
from presumed
presumed Archean
Archean rocks
rocks
in northwestern Wisconsin.
in
These latter units unconformably underlie
the metasediments
metasediments and
the
and metavolcanics of the Gogebic Range (Aldrich,
(Aldrich, 1929)
1929)
and there seems little doubt that
and
that they
they are
are in
in fact
fact Archean.
Archean. However,
the southward extent of these
these rocks is
is not well known,
known, as
as outcrops
outcrops are
are
widely scattered throughout the
the area
area and
and lithologic
lithologic correlation
correlation of
of PrePrecambrian crystalline rocks
rocks is
is risky
risky at
at best.
best.
** Department of
University of
of Kansas.
Kansas.
of Geology,
Geology, University
�2
T&bl.1.
1.
'fable
Sury
of Primary
Gscohronologio
S~
of PJ-1aaI7
GeoohronologioData
Datafor
torPreoeabrisn
PNoaabrianRocks
Boob in
inWisconsin.
Vlnouin.
Northea.tern Wisconsin
Visoonsin COmplezl
Compl.xz
1. Northeastern
P. (rhyoiit.)
Quinnl.. o VIa. (rhyolite)
Quinnissc
1906 ~ 25
1805
25 11.7.
..y.
Ho skinLake
Iske granite
granite
Hoskin
1880
15
(z)
(Z) Banks
Banks and Cain, 1969.
1969.
Dunbar
.iss
Dunbar gneiss
1880 2~ 15
1880
15
(Z)
Bank8 and Cain, 1969.
1&69.
(z) Banks
1860~ 21~l
1880
(2) Banks
and Cain,
Cain, 1969.
(Z)
BanD and
1969.
1930 2 o
(Z)
Aldrioh and
and others, 1965.
1965.
(z) Aldrich
1810 : 50
(R) Van Sebmus, Unpub.°
N.vinghamgranodiorite
granodiorit.
Newingham
"*mb.rg pink
"Jllberg
p1nk graniti'
granit'"
(Ath.lstan. quartz
(Athel8tane
quartsmonzonit.)
IIOMOnitlO)
}3
ainstte quartz
JIuoinett.
quartz diorits
diorite
Atbelatane quartz
quarts monsoniti
lIOn&onit.
Athelotano
Hoskin Lake
lake granite
Hoskin
granite
}
Overall oo.slt.
oompo.it..estimate:
Ove1"&ll
.t1lrate I
:t
(Z) Banks
and RebellO,
Rbello, 1909.
(z)
Bank8 and
1969.
1875
50
1875 ±~ 50
VisooMlnComplex:
COmpleZI
Central Wisconsin
2. Central
Baraboo rWolite
Baraboo
rI'o1ite
1840
lMO :2 40 m.y.
a.,y.
(R) Dott and DaIziel,
Dalziel, 1972.
1972.
So, Wisconsin
rbyolit.s
So.
Wisoonsln rbJo1ites
1665
4D
1666 :2 40
(a)
(R)
Wausau-Mbnioo
voloanios
Wausan—bnioe volcanic.
1640
4D
1840 2~ 40
(R)
Petel'llllUl,Unpub.°
Unpub.*
(a) P.t.rman,
Co. granites
granites
Waushapa Co.
Waushera
~ 70
70
1846
1646 ±
andVan
VanSohlllU.,
Sobmus,19'7a.*
1975.
'l'hurman and
(R) Thurman
Vausau
area
Waumau
areagranites
granite.
1600
:t 85
85
1600 ±
CR)
(R)
Jackson
JacksonCo.
Co.granit.s
granite.
1690
CR)
Overall composite
OOIlPOsite estimate:
e8t1Jla'te I
3.
llna.*
Thurman
and Van
Van SobIua,
Sobaus, 1975
.''
'!'hU!'lllUl and
P.t.rman,
Petel'lllU'1,Unpub.*
Unpub.*
and P-'-run,
P.teruan, 1972.
1972.
(a) nKismia
..io and
1675 ±
16715
: 50
Volt
Wolf River
River Batholiths
Batholith:
Wolf
Volt River-Bad
River-a.d River
quartz
quartz monsonites
IIODSOnit.s
1450 :± 30
50 lI.y.
a.y.
1450
(R) Van Sobmus, Unpub.
Belongia
Belongia gNnite
granite
1~
1500 :t2 20
(Z) Banks,
Banks, Unpzb.'
Unpub.**
(z)
1480 2
(a)
Onpub.**
CR)Van
VanSohlllU.,
Sciu5, Unpub.'
Wolf
River batholith
Wolt River
batholithoombinad
oombined
Wolf River
River quartz
Volt
quarts monzonits
lIOn&onite
a.d River
quazo1;s monzonits
lIOn&onite
Red
River quartz
Hager complex
oomplez
B.longla
Belongia granite
viborgit. granite
Vaupaca wiborgite
granite
Waupeoa
Big Palls
Big
Yells med-gr.
m.d-gr. granite
Stevens
gNnite
Stevens Point
Point grq
gray granite
Wausau
oomplez
Wausaueyenite
syenit. complex
St.tin iyenit.
complex
St.tin
~nite
oollPlez
Hogvty
Hogarty hornblende
hornblende granite
granite
Overall
Overall oolllpOsit.
compositee8tiDate
.stimatsI
1500 ± 50
(Z)
denote. zircon
Zircon U-Pb
U-Pb oonoordia
age; (R)
(R) denotes
denote. tho1e-rock
whole-rcok
(z) denotes
oonsordiaintercept
intsrc.pt age;
Rb-Sr
Rb-Sr isochron
isoobron a.gs.
~.
in preparation.
Sohmus, ThtmDan,
Thurman, and
and Peterman,
** Van Sohmus,
'etel'lDan, 1n
preparation.
and Banks,
*" Van Sohmu.,
**
Medari., and
1laDU, in
in preparation.
preparatlon.
ScLnu5, Madaris,
�3
No Archean rocks
rocks are
are conclusively present
present in
in northeastern
northeastern Wisconsin.
Wisconsin.
Although the
the Quinnesec metavolcanics
metavolcanics have
have often
often been
been referred
referred to
to as
as pospossibly being Archean,
Archean, it
it now seems
seems probable
probable that
that they
they are
are much
much younger,
younger,
as
mentioned below.
below. The lack
lack of
of Archean rocks
rocks in
in this
this area
area is
is
as will
will be mentioned
major geologic
geologic problem,
problem, for
for they are exposed just to
aa major
to the
the north in
in
Michigan (James,
(James, and
and others,
others, 1961).
1961). Recent maps of
of the
the area
area (Dutton,
(Dutton,
1971, Dutton and
and Bradley,
Bradley, 1970) show
show the
the presence
presence of
of aa major
major east—west
east-west
1971,
trending
Formation
trending fault
fault system
system separating strongly deformed Quinnesec Formation
rocks on the south from much less
less deformed Badwater Greenstone
Greenstone on
on the
the
rocks
north; and this fault system may therefore
north;
therefore coincide
coincide with
with or
or be
be part
part of
of
an
an old
old major tectonic boundary.
remaining problems
problems are
are to
to determine
determine how
how far
far
Some of the other major remaining
south Archean
Archean rocks
rocks can be
be recognized,
recognized, to determine their
south
their ages,
ages, and
and to
to
determine the
the nature of their
their disappearance (burial,
(burial, faulting,
faulting, orogenic
orogenic
destruction, etc.).
d~~truction,
etc.).
"Animikie" Metasediments
and Metavolcanics (Precambrian
(Precambrian X)
Metagediments and
These rocks represent the
the major units of
of sedimentary
sedimentary and
and volcanic
volcanic
origin in the northern part of
of the
the area
area and
and include
include the
the economically
economically
vital sedimentary
sedimentary iron
iron formations.
formations.
Geochronologic data (Aldrich,
(Aldrich, and
and
others,
others, 1965;
1965; Banks and
and Van Schmus,
Schmus, 1971,
1971, 1972)
1972) indicate
indicate that
that these
these rocks
rocks
in the
the Iron
Iron Mountain
Mountain area
area are
are about
about 1900
1900 m.y.
m.y. old.
old. Banks and
and Rebello
(1969) obtained
a 1900 million year age
age for zircons from a
a Quinnesec
(1969)
obtained a
Formation rhyolite in
Wisconsin, and
in Wisconsin,
and the
the author
author regards
regards these
these rocks
rocks as
as
approximately, if
if not
not exactly,
exactly, equivalent
equivalent to the units
approximately,
units in Michigan (for
(for
example, the
example,
the Badwater
Badwater Greenstone).
Greenstone). No direct data exist
exist for
for similar
similar rocks
rocks
from the northwestern part of the
the state,
state, namely the
the Gogebic Range,
Range, but
but
with the lack of any evidence to
to the
the contrary,
contrary, the
the commonly
commonly used
used correcorrelation with rocks
rocks to
to the
the east
east is
is accepted
accepted here.
here. Clearly,
Clearly, however,
however, direct
direct
analytical
is required.
required.
analytical confirmation is
As with the
the Archean rocks,
rocks, the
the maximum
maximum southern
southern extent
extent of
of these
these
rocks is
is unknown.
unknown.
Northeastern Wisconsin Complex (Precambrian
(Precambrian X)
are exposed several gneissic
gneissic
In the northeastern corner of the state are
and
plutonic units
units which are
and plutonic
are younger than the
the Quinnesec Formation,
Formation, and
and
in
in places intrude it
it (Cain,
(Cain, 1964).
1964). U—Pb
U-Pb ages on zircons
zircons and
and Rb-Sr wholerock isochrons (Table
(Table 1)
1) show
show that
that these
these rocks
rocks are
are about
about 1875
1875 m.y.
m.y. old.
old.
They can be traced
traced southward
southward for
for more than
than 50
50 Km.
Km. south
south of
of the
the MichiganMichiganWisconain border,
Wisconsin
border, but their
their maximum southern
southern limit
limit is
is not
not known.
known. Although
these rocks
rocks are
important in
Wisconsin, only small plutons
these
are important
in northeastern Wisconsin,
of this age exist in
in Michigan (Peavy
(Peavy Complex and
and scattered
scattered dikes
dikes and
and
area; Aldrich,
and others,
others, 1965;
1965; Banks
Banks and
and
pegmatites in the Felch Trough area;
Aldrich, and
Again, it
Van Schmus,
Schmus, 1971,
1971, 1972).
1972). Again,
it appears
appears that
that the
the E—W
E-W fault
fault system
system
be part
part of
of aa major
major boundary.
boundary.
may be
The westward extent of these
these 1875 m.y.
m.y. old rocks
rocks is
is also
also not
not known,
known,
but it
it is
is quite possible
possible that
that many
many of
of the
the rocks
rocks in
in the
the northern
northern part
part of
of
the state (north
the
(north and
and west
westof
of Rhinelander)
Rhinelander)are
are similar
similar in
in age.
These and
and
the older
older rocks
rocks are truncated on the south by the
the
the volcanic—plutonic
volcanic-plutonic rocks
rocks
of the
Central Wisconsin
Wisconsin Complex,
but
exact
the Central
Complex,
butthethe
exactnature
natureofofthe
the transition
transition
is also unknown (intrusive,
is
(intrusive, fault,
fault, suture
suture zone?).
zone?).
�4
4
Central Wisconsin Complex (Precambrian
(Precambrian Y)
Rocks which yield Rb—Sr
Rb-Sr whole—rock
whole-rock ages
ages of
of 1650
1650 to
to 1700
1700 m.y.
m.y. appear
appear
to make up the
the bulk of the
the Precambrian basement
basement of
of Wisconsin, extending
extending
from Rhinelander in
in the
the north to
to at
at least
least as
as far
far south
south as
as Baraboo
Baraboo and
and for
for
at least
least 150 Km.
Km. in
at
in an
an east—west
east-west direction
direction (Figure
(Figure 1).
1). These rocks
rocks are
are
mainly volcanic,
volcanic, volcaniclastic,
volcaniclastic, and
and associated
associated granitic
granitic intrusives;
intrusives; the
the
exposures of these rocks in the
the Wausau area
area are
are described in
in aa later
later section
section
of this guidebook.
guidebook. Other areas
areas of these
these rocks
rocks are
are the
the Monico area,
area, the
the
granites
granites of Waushara County and
and the rhyolites to
to the
the south,
south, the
the rhyolites
rhyolites
underlying the quartzite at Baraboo,
Baraboo, and
and some of
of the
the rocks
rocks in
in the
the Black
Black
River Falls area
area (Table
(Table 1).
1). Although several types
types of
of rock
rock are
are represented,
represented,
outcrop control
control is
outcrop
is presently insufficient for purposes of
of major correcorrelations. The full
full extent of
of these
these rocks
rocks is
is unknown,
unknown, particularly
particularly to
to the
the
south and
west, and represents a major problem in
south
and west,
in Midcontinent Precambrian geology.
The geochronologic control on
on this
this complex
complex to
to date
date is
is only
only by
by Rb—Sr
Rb-Sr
whole-rock isochrons,
isochrons, and
and it
it is
is possible that
that the
the 1675
1675 m.y.
m.y. age
age given
given
here is a time of widespread alteration
alteration of
of slightly
slightly older
older rocks.
rocks.
U-Pb
U—Pb
zircon
ages will
for many of these units in the
the near future
future
zircon ages
will be
be measured
measured for
in order
order to
to get
get a
in
a better handle on the true age of these rocks and
and to
to
look for any resolvable age
age differences within the
the complex.
complex.
Quartzites (Precambrian
(Precambrian Y)
Y)
Dott and Dalziel (1972)
(1972) have recently
recently extensively
extensively summarized
summarized the
the
Precambrian quartzites in
in Wisconsin.
Wisconsin. The age of the quartzites is
is
bounded by
by the
the underlying
underlying 1675
1675 m.y.
m.y. old
old rhyelite
rhy~lite at
at Baraboo
Baraboo and
and 1450
1450
to 1500 m.y.
m.y. old intrusive rocks at
at Waterloo (pegmatite)
(pegmatite) and
and at
at Wausau
Wausau
(syenite intruding Rib Mountain Quartzite).
(syenite
Quartzite).
(Precambrian Y)
Y)
Wolf River Batholith (Precambrian
The youngest
youngest plutonic
plutonic event
event in
in the
the state
state was
was the
the formation
formation of
of aa large
large
It
complex referred to in this guidebook as
as the
the Wolf River batholith.
batholith.
includes
includes a
a large variety of felsic intrusive
intrusive rocks
rocks which occur
occur from
from
Mountain to
to Wausau to
to Stevens
Stevens Point
Point to
to Waupaca
Waupaca and
and are
are all
all about
about 1500
1500
m.y. old
old (Table
(Table 1;
1; Figure 1).
1). This complex is
is described in
in detail in
in
m.y.
later sections of this guidebook and
later
and will not be elaborated on
on here.
here.
Published mineral
mineral ages
ages from
from several
several localities
localities (Bass,
(Bass, 1959)
1959) indicate
that
this event
event was
was the last major thermal event in
that this
in Wisconsin except
except
for the Keweenawan activity
for
activity to
to the
the north.
north.
This complex is
is relatively
relatively well
well defined
defined as
as to
to its
its areal
areal extent,
extent, and
and
it
on all
all sides
sides by
by older
older units.
units. However,
However, the
the exact
exaot shape
shape
it is
is surrounded on
still needs to
to be better defined,
defined, and
and more
more U—Pb
U-Pb ages
ages on
on zircons
zircons will
will
have to
to be determined on
on individual
individual units
units to
to fully
fully tie
tie down
down their
their absolute
absolute
age(s).
age ( s).
�5
Keweenawan Rocks
Rocks (Precambrian
(Precambrian Y)
y)
Keweenawan volcanics,
volcanics, sediments,
sediments, and
and intrusive
intrusive rocks
rocks occur
occur in
in
the
but will
will not
not be discussed here.
the northern part
part of
of the
the area,
area, but
here. The age
age
of 1115
1115 m.y.
m.y. for
of
for these rocks (Figure
(Figure 1)
1) is
is primarily based on
on the
the
U-Pb
(1963, 1972).
1972). Chaudhuri (1972)
(1972)
U—Pb zircon data of Silver and Green (1963,
and
Chaudhuri and Faure (1967,
and Chaudhuri
(1967, 1968)
1968) have also
also reported
reported Rb—Sr
Rb-Sr ages
ages on
on
similar rocks in
Michigan.
in Michigan.
Miscellaneous
The major rocks
rocks included
included in
in this
this category
category are
are the
the granites,
granites,
gneisses,
schists,
and
migmatites
in
central
Wisconsin,
gneisses, schists,
Wisconsin, extending
extending
westward from
Waupaca
to
Stevens
Point—Wisconsin
from Waupaca to Stevens Point-Wisconsin Rapids,
Rapids, and
and west.
west.
These rocks have apparently
apparently been
been intruded
intruded by
by the
the 1675
1675 m.y.
m.y. old
old
complex, and Bass
Bass (1959)
complex,
(1959) has obtained some mineral ages
ages as
as old
old as
as
Thus, it would appear
1900 m.y.
these rocks.
rocks. Thus,
appear that
that these
these rocks
rocks
m.y. from these
exact
are
are at
at least 1900 m.y.
m.y. old
old and
and may
may even
even be
be Archean.
Archean. Clearly,
Clearly, exact
determination of
of the
the primary ages
ages of
of these
these rocks
rocks is
is important
important since
since
it will
will help
help define
define the minimum southern limit of sialic rocks
it
rocks
younger than 1900 m.y.
m.y. in
in North
North America.
America.
Regional Significance
Significance
Several major discrete igneous,
Several
igneous, metamorphic or sedimentary periods
or events can now be recognized in
in Wisconsin and
and Upper
Upper Michigan.
Michigan. The
2500 m.y.
m.y. and
older rocks
rocks represent the southern edge of the
2500
and older
the Superior
m.y. old rocks
Province of
of the
the Canadian
Canadian Shield.
Shield. The 1850 to 1900 m.y.
represent aa major
major period
period of
of sedimentation,
represent
sedimentation, volcanism,
volcanism, and
and orogeny and
and
is considered
considered by
by the
represent the so—called
is
the author to represent
so-called "Penokean
Orogeny" in the area
Orogeny"
area (Van
(Van Schmus,
Schmus, 1972).
1972). The 1650 to
to 1700
1700 m.y.
m.y.
old rocks can be correlated roughly with rocks
rocks of
of similar
similar age
age in
in the
the
Rockies and the Southwest,
Rockies
Southwest, although
although exact correlations will need
need to
to
await further data.
In
case, it
await
data.
In any
any case,
it appears
appears that rocks with ages
ages of
1650 to 1750 m.y.
m.y. comprise a
a major structural
structural belt from
from Arizona
Arizona to
to
Wisconsin.
The 1500 m.y.
m.y. old complex correlates well in
in age,
age, litholithologic character,
to 1500 m.y.
m.y. old
old
logic
character, and tectonic setting with 1450 to
plutons throughout the Southwest and
plutons
and volcanic and
and plutonic
plutonic rocks
rocks in
in
Missouri. These rocks probably are
are part of another
another structural
structural province
province
of and
south of
and partially overlapping the 1650 to
to 1750 m.y.
m.y. old
old rocks
rocks
(Bickford and Van Schmus,
Schmus, 1973).
1973).
In summary,
summary, it
it now
now appears
appears that
that the
the various
various chronologic
chronologic units
units
In
recognized in Wisconsin can be related to other rocks throughout
recognized
throughout
North America,
America, and
and these
these correlations may ultimately
ultimately provide
provide the
the
framework upon
upon which we
we can determine the detailed evolution of the
framework
the
continent during
during Precambrian
Precambrian times.
times.
�6
Acknowledgements
This work has
has been largely supported by National Science
Science Foundation
Foundation
The author gratefully acknowledges the
Grants GP—1362
GP-1362 and
and GA—15951.
GA-15951.
The
cooperation of all
all his
his colleagues who are
are mapping and
and carrying
carrying out
out petro—
petrologic
studies in the area and
logic studies
and whose work provides the
the base
base necessary
necessary for
for
sample collection and
and data
data interpretation.
interpretation.
I
�7
References
Aldrich,
Aldrich, H.R.,
H.R., 1929,
1929, Geology
Geology of
of the
the Gogebic
Gogebic iron
iron range
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Aldrich,
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L.T., Davis,
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Ages of
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minerals
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Banks, P.O.,
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Cain, J.A.,
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p.
907—910.
v. 80, p. 907-910.
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and Van
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Chronology of
of Precambrian
Precambrian
rocks
of Iron and
and Dickinson
Dickinson Counties,
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(abs.):
17th
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9-10.
Banks, P.O.,
Banks,
P.O., and
and Van Schmus,
Schmus, W.R.,
W.R., 1972,
1972, Chronology of
of Precambrian
Precambrian
rocks of
of Iron and
rocks
and Dickinson
Dickinson Counties,
Counties, Michigan.
Michigan. Part II
II (abs.):
(abs.):
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Inst. on Lake Superior Geology,
Geology, Houghton,
Houghton, Mich.,
Mich., May.
May.
Bass, M.N.,
M.N., 1959,
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1959, Mineral age
age measurements—Wisconsin:
measurements-Wisconsin:
Inst. of
of Washington Year Book
Inst.
Book 58,
5~, p.
p. 246—247.
246-247.
Carnegie
Bickford, M.E.,
M.E., and
Bickford,
and Van Schmus,
Schmus, W.R.,
W.R., 1973,
1973, Possible Middle and
and
Late Precambrian igneous arcs
arcs in
in the
the Mid—continent
Mid-continent region
region of
of
North America
America (abs.):
(abs.): Program,
Program, North-Central
North-Central GSA
GSA Meeting,
Meeting,
Columbia, Mo.,
Columbia,
Mo., April.
Cain,
Cain, J.A.,
J.A., 1964,
1964, Precambrian
Precambrian geology
geology of
of the
the Pembine
Pembine area,
area,
northeastern Wisconsin:
Acad. Sd.
northeastern
Wisconsin: Mich.
Mich. Acad.
Sci. Arts,
Arts, and
and Letters,
Letters,
Papers, v.
Papers,
v. 49,
49, p.
p. 81—103.
81-103.
Chaudhuri,
Chaudhuri, S.,
S., 1972,
1972, Radiometric
Radiometric ages
ages of
of Keweenawan
Keweenawan intrusions
intrusions
and extrusions in
in Michigan
Michigan and
and adjacent
adjacent areas
areas (abs.):
(abs.): Geol.
Soc. Amer.
Amer. Abstracts with Programs,
Soc.
Programs, v.
v. 4,
4, p.
p. 470.
470.
Chaudhuri, S.,
Chaudhuri,
S., and
and Faure,
Faure, G.,
G., 1967,
1967, Geochronology
Geochronology of
of the
the
Keweenawan rocks,
rocks, White Pine,
Pine, Michigan:
Michigan: Econ. Geology,
Geology,
62, p.
v. 62,
p. 1011—1033.
1011-1033.
Chaudhuri, S.,
Chaudhuri,
S., and
and Faure,
Faure, G.,
G., 1968,
1968, Rubidium—strontium
Rubidium-strontium age
age of
of
the
Mt. Bohemia intrusion,
the Mt.
intrusion, Michigan:
Michigan:
Jour.
v. 76,
76,
Jour. Geology,
Geology, v.
p.
p. 488—490.
488-490.
Dott, R.H.,
Dott,
R.H., Jr.,
Jr., and
and Dalziel,
Dalziel, I.W.D.,
I.W.D., 1972,
1972, Age and
and correlation
correlation
of the
the Precambrian
Precambrian Baraboo
Baraboo Quartzite
Quartzite of
of Wisconsin:
Wisconsin:
Jour.
Geology, v.
Geology,
v. 80,
80, p.
p. 552—568.
552-568.
�8
Dutton, C.E.,
C.E., 1971,
1971, Geology
Geology of
of the
the Florence
Florence area,
area, Wisconsin
Wisconsin and
and
Dutton,
Michigan:
U.S.
U.S. Geol.
Geol. Survey
Survey Prof.
Prof. Paper
Paper 633,
633, 54
54 p.
p.
Dutton,
Bradley, R.E.,
Dutton, C.E.,
C.E., and Bradley,
R.E., 1970,
1970, Lithologic,
Lithologic, geophysical,
geophysical, and
and
mineral commodity maps of
of Precambrian
Precambrian rocks
rocks in
in Wisconsin:
Wisconsin: U.S.
Geol. Survey Map set
Geol.
set 1—631,
1-631, with
with accompanying
accompanying pamphlet
pamphlet (15
(15 p.).
p.).
James, H.L.,
C.L., and
and Pettijohn,
Pettijohn, F.J.,
James,
H.L., Clark, L.D.,
L.D., Lanley,
Lamey, C.L.,
F.J., 1961,
1961,
U.S. Geol.
Geology of
of central
central Dickinson
Dickinson County,
County, Michigan:
Michigan:
U.S.
Survey Prof.
Prof. Paper
Paper 310,
310, 176
176 p.
p.
Kiemic, H.,
H., and
Klemic,
and Peterman,
Peterman, Z.E.,
Z.E., 1972,
1972, in
in Geological Survey
Survey Research
Research
1972.
Chapter A:
U.S. Geol.
Geol. Survey Prof. Paper
1972.
Chapter
A:
U.S.
Paper 800—A,
800-A, p.
p. 3.
3.
Silver, L.T.,
L.T., and
Silver,
and Green,
Green, J.C.,
J.C., 1963,
1963, Zircon
Zircon ages
ages for
for middle Keweenawan
Keweenawan
rocks of the
Am. Geophys.
Geophys. Union
the Lake
Lake Superior
Superior region
region (abs.):
(abs.): Am.
Union Trans.,
Trans.,
v.
v. 44,
44, p.
p. 107.
107.
Silver, L.T.,
L.T., and Green,
Green, J.C.,
Silver,
J.C., 1972,
1972, Time constants for
for Keweenawan
igneous activity
activity (abs.):
(abs.): Geol.
Geol. Soc. Amer. Abstracts
Abstracts with
with Programs,
Programs,
v. 4,
v.
4, p.
p. 665.
665.
Thurman, E.M.,
Thurman,
E.M., and
and Van Schmus,
Schmus, W.R.,
W.R., 1973,
1973, Rb-Sr
Rb-Sr age
age of
of Precambrian
Precambrian
volcanic and
and plutonic inliers
inliers in
in southeastern
southeastern Wisconsin
Wisconsin (abs.):
(abs.):
Program,
Program, North—Central
North-Central GSA Meeting,
Meeting, Columbia,
Columbia, Mo.,
Mo., April.
Van Schmus,
Schmus, W.R.,
W.R., 1972,
1972, Geochronology of
of Precambrian
Precambrian rocks
rocks in
in the
the
Penokean Fold Belt subprovince
subprovince of
of the
the Canadian
~anadian Shield
Shield (abs.):
(abs.):
Program,
Program, 18th Ann.
Ann. Inst.
1nst. on
on Lake
Lake Superior
Superior Geology,
Geology, Houghton,
Houghton,
Mich., May.
May.
Van Schmus,
W.R., 1973,
Schmus, W.R.,
1973, Chronology of
of Precambrian
Precambrian igneous
igneous and
and metamorphic
metamorphic
in eastern Wisconsin and
and Upper
Upper Michigan (abs.):
(abs.): Program,
events in
1973 Ann.
Ann. Meeting Amer.
Amer. Geophys.
Geophys. Union,
Washington, D.C.,
April.
1973
Union, Washington,
D.C., April.
Woolsey,
Woolsey, L.L.,
L.L., 1971,
1971, A
A Rb—Sr
Rb-Sr geochronologic
geochronologic study
study of
of the
the Republic
Republic
metamorphic node,
node, Republic,
Republic, Michigan:
Michigan: Unpub.
Unpub. M.S.
M.S. Thesis, Univ.
Univ.
of Kansas,
Kansas, Lawrence.
Lawrence.
�9
t33:ir
JTh
f4 i:tc 2LTY
y
2j; 2GIC1
1f1:i--=
ii-i
4jLj
yEa
WOLF RIVER BATHOLITH--A LATE PRECMvIBRIAN RAPAKIVI MASSIF IN
NORTHEASTERN WISCONS IN
-.
\2
TIlE
by
--:, a::
2L
J.L. Anderson*,
Jr.*,
2'
rf-
Medaris,
L.G.
Myles**
and J.R.
C- iEE.CJL.JZINTRODUCTION
LL--
aLa-aU
.-:
co
tf
•-
1L!•
Classic rapakivi texture, in which grains of ovoidal alkali feldspar are mantled by plagioclase, has been described from several
localities of Precambrian granite in northeastern Wisconsin (Gates,
1953; Elders, 1968), but until the present time, the regional distribution and petrologic significance of these rocks have not been
Our investigation, in conjunction with chronologic
fully appreciated.
studies by W.R. Van Schmus (this guidebook), has established that an
extensive rapakivi massif, the Wolf River batholith, underlies an area
of at least 3600 square miles and represents a major feature of the
This anorogenic,
Precambrian terrain in northeastern Wisconsin (Fig. 1).
epizonal batholith, 1450 to 1500 million years in age, consists predominantly of reddish, hypersolvus quartz monzonite and granite.
In
addition to the widespread occurrence of rapakivi texture, the Wolf
River batholith has textural, mineralogical, chemical, and structural
features that are similar in every respect to those of the classic
rapakivi massifs in Finland.
L
t •-i&;t
Li'
k:y.a
4121
2
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2UU
r, :ytLr,
:
C:KCLiliCT.CCCiI
i-Li'CfCt.CC. i-;
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t!LtcL
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ca
aqiy-:
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iiE '5iTh-yrC
aU
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LiiTT eJ'
:caCyL& a1€TTICi'-2
y'iñk;I L1ra. lyai;Lt. 2ii,<: 'LirJL Ct C;iag:f,
:':C'iTCtC LtC.. ::,J'.tCi'irt:C2.CCIIi, EyLa? 'i:r.
flI
•'CY-fl:C, 1\
t!f2T7 2T'jir
:;MiC:i.
C2C ta- I CCC ix
rc'L;-c 2€ 1O29Lfl
bxü
iTnat
'Li]. ntUi
C—tt2
nct-
I
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-
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CLE
-u.
-.
.
-
UU- -z-i
j•aditiCtL-• t€ CICCitC
CtCiitti:LCC!
LCI k.CiLC
ITCaC
tfi- lit
1
fr
L5LitiCC.iL.,
'iir:ic:a.
:11Z"'2t11";f
TC
;.;CT
:
::rol,: :iZi1
.;yji
g:aiUL'ii
i:,J
ii4cJsiucLi
45{j
?:U-UUL. cJ
T7,r,::At :.a'::i:d •U
t::
C
•:
t]TLC'2
:
T-Lj
.-Ci
irCaLi?
:,y.,
----2
ICoILt'i
C€C
tttat
1'---, --,
C'axiLal. aa.
-
L.,'
LITHLOGY
rtCr
±..1i.:1L'::::s€
ih-
-—
-
-
't]'.
CCC'
General Characteristics
liLVtJC
1ACC
Cxii
•iiy
'k:.C'
ECliTcJ. lCJhra;
ny;]i
Lta'y,Li
7ç1;'T'
;-CCLi
A variety of rock types have been recognized in the Wolf River
batholith, including granite, quartz monzonite, monzonite, trachyandesite, syenite, and rhyolite.
Quartz monzonite and granite are by
far the most abundant rock types in the batholith, adcounting for 94%
The predominance of alkali
of the exposed area (Table 1, Fig. 1).
feldspar over plagioclase in the batholith is illustrated by a plot
(Fig. 2) of modal quartz, alkali feldspar, and plagioclase for representative specimens, obtained by point counts of both thin sections
and stained polished surfaces of hand specimens.
2
1li-li
ii-c t-a niii1 iL
U a:c--.xli
Li
€lufrCI CE
ix
-uCla
titi
)Ei
1.. r
LaU-uUSL
lila
t:IC.Jliuii
U
pta
U.
€L-€L
'yiyfl
-.
cr..
cE 2B12
1s,i'fT
I
tCli,
-
C-CT
xAs?IT'r2'
'Liii
i1.ii
iLiT-ii
'
-
]
a1kaL- tzau€E
Lii-
',j-c 'It,-:
ar
tL.2iCiiCT ruT-fT
x
lixvxuia,
'JL'i.- :uc'J-€l
:1-
iL:s uf
lifC-iULihtiii..
')2vt.1€Th
p..
I
1R
La TLi1--R,g-IC-9€ tu..-C C.çi-Cr
xr).dt •-a :tp€E t
P
b.u-t:x
Li'U LExy Cli
',yc.t'h •.:i -u-TxxuT'tx.
CCCL.
i'--n.ix
1
ILJC
Cxli
:xfJ.Jt
'-zr:'.LiCibla-ii
c-C
3€
-CT.C.
itiyii:C
iLiH
'r'
auuTi-iCL ccxL
L€Tituic
Rapakivi texture is one of the most characteristic features of
being most extensively developed in the
Waupaca quartz monzonite, but occurring in minor amount in all of the
other granite and quartz monzonite units.
Equally characteristic is
the development of porphyritic texture in all lithologic units of the
batholith.
Typically, phenocrysts1 of alkali feldspar, and to a lesser
LLi&:•iuiLci
7
JULia.U. Lii" x--.,cy.i-Cl,li-: lyxaiTta
ir-vrut .'UCa U: C2itT'-xfJT4T tI-LIt
et311C Li-U 11CC- 'C b-a iit rCttlii,i
J.CLfl.fTl
rxcii,.E
CIxe
xrit.ciE .1LC?LiiC I
I
J'IZIl
=itlL'L-
-L
.
t:;rtaaa' p-CTiU.j:it:lC
iLL
.xj.:,f
nuuiiaaCC'---ixx---
-.---.j-
:€-l'1TF
itl
-c
-i,
-
h-iiuci-xca.2.t-
,,.I,Cxeyftxi :t-r
CE
CCJ-f
ui''1r 4p.iiii
.iHc-
:ii-.7tnt_-i irE
lkui
1
-i-U;
-CILL
xxix- Def
of Geology & Geophysics, University of Wisconsin—Madison
of Geological Sciences, Univ. of California—Santa Barbara
A non—genetic descriptive term, such as megacryst, might be more
appropriate to describe the large alkali feldspar grains, but since
phenocryst is still the term accepted by Finnish geologists, this
convention will be followed here.
-filL'.
WLiifT 'c-a .e:''Lt
:CT.
'Ii -_'
Li
1
C---
aL.'
-c-Sf
-C
it I-
U-fl"
fx-x.tC-x, ,LL:xi'a;y
C.€-LilgiCtl.
CL-Cf
,j
7:
Li..
u'xlx
..,
taL:-Cxx€
trti.,
IJ'.raul. •:$p2Y
vniiui
xixi
i.-.LL
2:Li.'litf
lIC'iLC'i'C
CE--x
C '-,e-Li
--C
-a--€ fit
lrxiac. Lc--ii-II E1 Ix:
'IcC ttxx Ut-Il
.CC-€1Lib-iU
If
aiaza'n
trLC-T,:J.Cs1.
-'' cliaUca
**
1
Department
Department
.
:11
:CL
**
I
*
It_i
the Wolf River batholith,
�P.-
89
-
0
- ':*--
-
LjLi -
/F:
LIMITED EXPOSURE
us
/
- —0
/
LIMITED
EXPOSURE
EXPLA NATION
IsLofls5 granite
Belongia
i
LtC1Ctj% 5
Wolf River granite and
sd C11oT
quartz monzonite
0*
Red
porphyritic
r5CiRiser
ru-p0-i:: quartz monzonite
it;C-
Waupaca
J!&Ci wiborgite
r7 CEJiUt
Stevens Poist grey
granite
I
Hay Creek C!Cifr-C:cI1CC9.
quartz monzoriite,
T
rIi
::rIi F
Hsç!s! rfr:c1Cis
Hager
rhyolite
Hager
feldspar
-]-sQsC
-ici5ir porphyry
bxsspi'y
k{wsr Ci$Clci
Hager
syenite
Peshtigo 1q:-liL
nlonzonite
CiC
and -:sch-'is5Ci
trachyandesite
i-:i!(I :i-CIIC
High
Falls51CiCittCi
granite
1 H THE WOLF RIVER
?rk•,:BATHOLITH
-4—IH1iI1H
GEOLOGIC MAP OF
Anorthosite
:-iIC, rii5PscN],
i4C tLG
BY
G. MEDARIS. JR J L ANDERSON,
01]
[j
y-y__
':UJs AP-II
Mi_t
WA VANVi
SCHMUS.
AND J,jI:.
A. MYLES
10
6
10
Ci
20
22
30
2t MILES
Precambrian rocks older than 1450
—- Contact,
dashed
where
C'6C365.
16232
46 approsimaie
— Fault
Mylonite
1500 M Y
�4214
11
Table
1
Proportions of lithologic units in the Wolf River batholith
areas only) and key to symbols used in Figures 1—7.
I7717'!110
11,1rcp:4rl 21.21:.
20's. 2 :7172 07203111120i
'7:'i -fl
:10012. 202171:11 22;
Areal extent, %
.47!',47t1
:212-21:7
o
Belongia
•
Belongia granite, coarse—grained
£
Wolf River granite
fine-grained
7122 71!-.1'7-'-12-!-"4.;
granite,
2 7
'' 1-210,27 2120-2120
'7:2.7020 21-27207 '171 ";fl
C''
and quartz monzonite
51.0
2t"'3i.101 -::'a'fl'3
21
72721172102-021,1024:
(14.-
Red River porphyritic quartz monzonite
20.6
Waupaca quartz monzonite (wiborgite)
10.5
721:
24 (77,1.71' 07-212110 21017;
•
Hager rhyolite
3.6
57
Hager feldspar porphyry
0.2
- 3-CT':
27212 11204:0177 ,!C14J
221:-i
-
-
Hager syenite
1.9
Hay Creek quartz monzonite
0.1
'6-
21:72021'.';317. C1.-.4? 4:i$-10. •2
•
•
0
'17
";-fl:7-73:..-3
141
0114 4212'.
Unit
y- :r
74,7o
;lj
'4' -
Symbol
(exposed
Peshtigo trachyandesite
2'0c20T'710'2'?
0 4
32424:!370
-'4-,
Peshtigo monzonite
J
-2041002112110 •U-31,1W7,
Not Shown
Stevens Point grey granite
5.0
Not Shown
High Falls granite
4.0
7212 ,'
21
.102121
4: 0140)1
707102-2;-
'24i l-
24
;411'TP
21.27.121
extent plagioclase and quartz, are present in a medium— to fine—grained
granitic matrix, consisting of quartz, microcline, plagioclase, and
mafic minerals.
In all cases, matrix plagioclase is more sodic than
plagioclase phenocrysts.
Quartz is interstitial to feldspars in some
units, but in others, particularly
in granite and some varieties of
quartz monzonite, quartz displays a distinctive idiomorphic habit and
apparently was one of the earliest phases to crystallize.
'71100
2
—
7;;
I
:12:; 272-721 21-724.: 117 3-10 71721.211171 115:21123-; '2021212' TT FL
p0'; 102121,1-77:21077 A-trocoao-fw 4,,•;I_1rT; - :c;:-1-:-20.1i;'o--
212)03 1)1
1'-.r.'327:;720-07
723-0421122
421
'21if;t2152 07712!!
21JL2---L22L SI
;cnr-o$ -n
.LjJ720;0 0 ,10207077> s—p ','7c7-Jt- •-0 ,L2 Z:'20J'
7!::214r44:1014 A;10:A-•: 171 10-
2121:22;
277371 274710'7721l 2-4
1112
02 21-42022
72111210('7.A:!
7:107.417
7
24Ti,;
-'-,m-.
-
',:''''
.',-
—
.-.•
7
Iron—rich biotite and amphibole are the most common mafic minerals
in the batholith, although orthopyroxene, clinopyroxefle, and olivine
Biotite and
occur in some of the darker rocks, such as monzonite.
to
subhedral
and
occur
in areas interamphibole are anhedral
typically
Such
an
occurrence
stitial to feldspar and quartz.
suggests that
in
the
biotite and amphibole appeared relatively late
crystallization
sequence of the granitic rocks.
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Descriptions of the Lithologic Units
IT
Twelve lithologic units have been distinguished in the Wolf River
batholith, and the following descriptions are intended to summarize
only the most salient features of each unit. Actually, some lithologic
units are quite heterogeneous with respect to variations in texture
and grain size, and the brief descriptions given here are not intended
to encompass every conceivable variant that might exist within each
of the twelve units.
21321:7
41-221
1t:2a'y-:p.a21;i 202321,2121212;
2I'' 2(12:-I pL1-Lt
$4 )C'1
%21';#210'
22-f
• -.'-
04:
--.;
ç0ccJ2;E--
i4J2
IlL
211
--
14:2 C-
-21-rn4:-ap. 7t.'7TL5 421221
21.-I!
4-
LIII
21-21,'.
-21'tL
221 2 21 flEC 1ç42r11-2
CC
-:72)121!. 01CC.L -Ca210 214 1,141
T4 flt21 7212111 2111
flafl ifl;'. ai2a'-21 2•L21
I 114212-2
21.21;t21tCC12fl 17-114-;
.72-Li
�12
Quartz
Fl
2E
/
50
50
2,•
I!-
/•
A
-----
10
;CttT
___
—
-—
T
feldspar
eOD[J
10
Plagioclase
Figure 2.
2
Wolf
Modal analyses of lithologic types from the
&q;4
TP°N Xyen?
:;bTLflhi. sñ2(
CJ
rig
River batholith.
u':t7cCC44q
2°-f
i22
(Sbo1s listed in Table 1)
-T
E
bCCjUAA$
;j'it:.fl1. .
This coarse—grained quartz
Waupaca quartz monzonite (wiborgite).
21
CCfl resembles
z2=:.;:'n
rapakivi
texture
and closely
monzonite has abundantly developed
I-)ç.
Approximately 70 to 80% of the:tCe;1
pink
the classic wiborgite in
:T Finland.
pL(Civtv.I
5U2 ;L: 4i,
21i
5.0
cm
in
length)
are
mantled
with
ovoidal
grains (1.5 to
]:i%-r:A;) alkali feldspar
.tthCVTC& LCçP-J2
common.
1 to 6 mm thick, and multiple layers are
a layer of
4C plagioclase
LCfl
(rjtC,
:2
The
thicker
a
plagioclase
mantle•Ci is, the smaller and more rounded is the
)LJ
texture is characteristic,
alkali feldspar
the
[
2T- Ci in
Cfl core. A porphyritic
.s#_1_plagioclase,
and idiomorphic quartz
with the
mantled feldspars,
Cfl large
[
<•:.LdTs
microcline, plagioclase, quartz,
set in a medium—grained matrix
::±:t:1 of
;o; 1U Ibiotite, and amphibole.
:i
C
LE
4
LLifl
i'an2
:i
;r
p
cr
]tYL
:
(k;
fIYIii ar
5i:;
IL:
ro-t
r.
'v: iij;•t
: .D':t
Wolf
granite and quartz
monzonite. The Wolf River granite and
'! River
::.Y12;.
quartz monzonite in being coarse—
quartz monzonite resembles the
Dt Waupaca
<crIL: ovoidal alkali feldspars (1 to
grained
and prophyritic with prominent
c
:2
texture is much less abundant,
3 cm in length),
except that rapakivi
L
f
';i
;r1TI
the alkali feldspar ovoids.
plagioclase rims occurring on
only 3 to 10% of
2:
r:•
2L1J
r;zcq
-
;dtr
:c1
I
r;icP
:i
rr
i;fl
�.11
-:1
1.
1J
a
1:.4Ti1 and
groundmass. fine—grained
in Yi4':7CC.
phenocrysts olivine
feldspar
—
li
iii
L1
..
a is trachyandesite
4
40% with monzonite,
the of
equivalent
porphyritic
::tIiI?t interstitial of traces and opaques, biotite, amphibole,
The
quartz.
-'E•I:LYL!rC and
tL1' r;:T•+:1i:
clinopyroxene, orthopyroxene, olivine,
amounts TP'::.'1' in
subequal
feldspar
:):j.'jL;::o.c I slightly
vp-: L and (IrU
alkali and plagioclase 4;yic1
containing
porphyritic,
mm) (3
?;TTiio •."° t1.1fl*.1i.] relative
11
medium-grained isT monzonIte 1J[
The
minerals.
Ic
maf
of
abundance
yii Zi11t1..
and quartz, of paucity color,
to grey dark
brown
their by guished
4:. are rocks These trachyandesite. and 1°
distinmonzonite Peshtigo
I
—
T
I
1
L
11R1.:i4i.Z
flt.1l
.
:
Tin.1ar7i1 T.i..T°tfl ..lt:1:t.i i:i.1
c11t 12.1r
JT1
41 /-.
core.
the
in
that
iJ
i111:r1z) :1I9944L.trw
r
°T
with continuity
optical
in
is
rim
granophyric
the
in
feldspar
alkali
°7Th
II
cores
occur
The feldspar. alkali of
euhedral
around
quartz
and spar
1j
J_L
°
L,C1
.4 texture, granophyric
presence
feld- alkaliE. of
intergrowths which in
of
Ii 1'Lf'L CII grains
LC 41 °
1r
the is granite
this of feature 1.4L14..'
characteristic
A
matrix.
the
in
7'ji
7't occurs
':71 r'r' n°U aInriI IC '7CILC
.present.
IC17rCI IC?
ECIçLIIr jr'i as
.j
of IC
clusters
mineral
only
the
is
and
mafic
Biotite
iICCI2I:LCI:t421cIcJrI:.7CI
is texture rapakivi of amount minor a and boundaries,
resorbed show
U
°0iFk-U
r
.3
—
commonly
phenocrysts
quartz The
in cm) 24
matrix.
mm)
(1 fine—grained a
çL;r0 It: ; In £11 •,•0nLI7I :tM50C: IC
CI°4
to (0.5 feldspar alkali ovoidal and
rum) 5 to (3 quartz idiomorphic of
:riLIJ is
I.I "nhLn1t
.11iC
I-i: ii:;
:CIrTrmfl of up made
phenocrysts
granite Inr0r':.P.=t1:I
20%) to
(15tI7.
fine—grained The
C
'
I
.,1 1 1 irflll'l
oi.f
rOr'?).
T7(,j
'oLi'
11
I't1 .:?i
I
47 :° rI'4 &.
t
'
1
7
Tt.tl c 4i1
CrIC IlITTI
C:
1CIC
are texture granophyric
present.
and '.:
rapakivi of amounts Small
—
14
IC'
21
a
are
in
set
to
quartz
and
feldspar
mm). (2 matrix medium—grained
45%)
(35
sr c7IC0'CCc7II'.Ii? ICIlilfi. 21 1r0::vr.Cc7 oL1.:.rrJl a CI',ig'ICCI °LIL.
alkali of
phenocrysts
which
in
texture
porphyritic
acquires
unit
zI1:1
IC',:, rT"7T
some
as biotite
I
this however, localities,
mafic
sole
the
mineral.
Jt
' I
,:CI
I.
41.'1; U.CIC.t
4
quartz,
and feldspar
and
plagioclase
of
amounts
small
with
idiomorphic
C'AcLI
floiIir'1i of
[CII U subhedral
.:cCc1In mm),
:'IC mainly consisting
to (3 even—grained
alkali
5lIlT,
I
yi
I
I
l::t rt7r
4.rCt4C4 1W '-
U,:'
ir
:.J].:
7'' itiriCi
CIiICt
,T7ii7t pink,
i-c'rTCI7.IilThe
ilc
:::U°t'CVCCJLl:
5r477 €7
predominantlyT1Ct
and massive,
isal7CTrrrTC'I
granite coarse-grained
?LIni. 0iC:iSJInr€2CY1?
07T:Irn [,.IInIC7LCi €ICC'ICLt'Iz'la
variety
equigranular grained
variety.
porphyritic
fine-grained
and
lIt ICBelongia
JICl"7'oofIn types
ffCiiL €74
coarse— a
exist: granite
Two granite. Belongia
liT tI I
lIC 7111 CI'liltCJ[°'Ia
114C
rock. the to
fabric
planar
imparting
':r'Ti4 [--1iJ !71:njTIrfr'5 C'
,17 l4:2'i Xiiii.I)41 .
are
aligned,
commonly
phenocrysts
feldspar
The
slabs.
stained
in
0'
,i*r_
:
417 to up
n' rC.ç.',
1il1I.inCCl
on
4 IlL,' the of 15%
apparent are phenocrysts
feldspar
alkali
mantles
U
Yr' not
4C171 €4
plagioclase discontinuous thin, although conspicuous,
is texture
' ICCCt: ILU mineral,
01
4. IC ''
CIT II
71141 il'27L l7CI5I
111111711 although
CI
CII T?1
some at
Rapakivi
localities.
present
is amphibole
mafic sole the as biotite usually and predominant, is plagioclase
40
L1!
C'
_T "—r'l
CI
"11
which of feldspars,
two
quartz,
anhedral
to
idiomorphic
of
matrix
iL'Ino'1iC 1 1i C. m91Tcir:
.L,IUTW.C101.
2 with
mm) 2 to '14
(1 medium-grained a of consisting 80% remaining the
7jTi:
'sTh'cC ri
€17
11'
I0 InTL
cm
14''1
rock, the of 20% about constitute size)
in
2.0
to
phenocrysts
(0.5
o.loo1oooocrr: feldspar
K%cc no
L'T1CIT74404J[
ZC2t!7t alkali
t411 Typically,
IC:l subhedral
phenocrysts.
feldspar alkali
t.Cl1j[CtCii i::,ti Ti .1771 :fl 711104:j::C'Ti'.T° 717 phenocrysts
rather angular,
and
to
in
ovoidal, ICCITI'l
than ,nT.'zo!Uj
matrix
proportion
.'01..t CCI
riI00 quartz
.r,I,; Wolf and
.0C'CIl; River
UTL4.CI 411:711
1€174
111 contains
nyCv"
'1 LI Waupaca
fewer
unit
this
monzonites,
'T:i;°7rLo€ quartz porphyritic River Red
LC,LiiLLCI1 In
the to comparison
ThJ
monzonite.
0 llTr 'I • 10
Fn',
CT7C
CT.
L
I
p'4 4ltt4'L
1 '€': ;4.:Tlt
CC
IttTIC' l.
4
.1
I::-,:.Cc::
2 nt t'1:. In lT'r
i41
r'o
.,
.
.iiTit
C:
7:711 predominant
4:11-ri 71717 CI: I 1144
11 C€1CC4 granite
II 417.714
type. rock
the becomes
0C1CrI.4. 'C01:nx 1c714 IC '1777141.
it,
1 t'€
rr" 1411
as appearsI quartz
and grains,
idioblastic
iron,
in
richer
becomes
r:ç'T -- TLC .121:?
:,rc2€I.rnCI 1141.
In
7111171
4:717111
it; .7:, :U amphibole
C'1,:°°
141,':
-. ;c:T14 :amount,
biotite
inIcdecrease
and
plagioclase
northeast,
the to
Yto171I ?.;LI: monzonite,
ICC..n:CUJ€Cr: quartz
'7,711:2: is
ff':0y$-r7114 71111
711111742
granite Belongia
the with Xl'TiiiICI
contact *11
the towards but
0;:
:..Th:nr..LIiIIU:
2r'i'''n plagioclase,
iln41C.nIT
4111.the
I,14 of
CI .i'0U
unit River Wolf
bulk The amphibole.
and LI
biotite,
.71t.LCC:L;I
IC'Ct,
:mi,'C:2t °tn:
l,7f.:cl:'4LrICC: interstitial
'ircTCI71IC.':I:c:I.40CIiT
microcline, quartz,4lIC]71'4rli1
anhedral to subhedral
of
matrix
grained
:1 feldspar
.1
€JIC7fr'[l and
'To,., Alkali
Jr
II'C set1111':
1'.ilrCsC 14 plagioclase
CI1 a
'IL
I
1L11
are phenocrysts
mediumin
0
--':
1
r'
CCCI
13
�14
:-:cirL:r&10154122:?1'1
222111Lc'-l'ZIIOSLI idiomorphic
0C:.*-2, I'll conspicuous
The Illoco:Hager rhyolite
t'-L'a-L--rlL:Lt-r contains
'L1''1L,-h2, 131-to
Hager rhyolite.
1110L112112112'
51220130772101.
IlSoc ;oc.:lI-.ILO-co,
:1121(1 less
quartz
phenocrysts
mm) and
prominent feldspar
phenocrysts
-50to
to 44 co]
:'0311.01 1F'.,Lo
:--' 0110 (3
7-tn-:.]rcrcc:
:1* quartz,
701911011. feldspar,
11121.0.221.221
f1 11101
ll--15L1.-O-0 matrix
(4 to
mm) 170
in a '1111-f
very ULIOIIfine—grained
(0.1
mm) of
--14
to-i5 too)
'01: -:11-too
The
pheno—
01111,11.511713.
ortcc 11-0 8/00211.
con:21
7-: -- and
and fL'
clusters
of li-tc-:.
biotite,
to ac I]
lesser
extent, amphibole.
;ooo o:f
120
"1122€: '4201911.
:r7ycLito, commonly
:2211201-00 0 3322111
crysts, constituting
30
CUL 0'
of±2222
the rhyolite,
show resorption
37 to 45%
1. :10112.lt,101
t-:-'i4I,-?11t1 of
-cd
02101011102 evidence
:.o2:22.(112t.80101, without
: tO is
The 1-105221::
rhyolite
cool] homogeneous,
111 massive
.1--'-12,11011 and
5-:att
11-:;:;
features.
:1001: is
tS-co:'otto
to lot;
IrSc-oO:': brecciation
or573112-12'
pyroclastic
01- thought
be intrusive,
ir.ot thus
0,122 -It'f.to- and
911180 010 01'
:11:1,10 activity,
-1'31.1,2iD112S'1-22,
rather
1-ftc-ac-c- extrusive.
1201,52112 than
111112211
0711fine—
fi'-o '
:1-12.101' 100 03.0.822431
121.1 the
"Cr0701111 somewhat
In :ccy;f
hand op8o?4-1112.
specimen the Hager-- rhyolite
resembles
In
2212 ort
c]h-oHager
,1]:cc rhyolite
oIlo'o' 0 to has
Sac ac much
grained
Itoh the
:'-c±- that
to-Il cicpzl-ogranite,
: ---.01 ic, except
:21
cOol-Il Belongia
,7119 pink,
110221111.,
71I-IOF. .C'at.012:'
001be
028
101.12k-I,
4-11-411 to
finer grained
pii.
:ish—grey,
rather than
10-: tends
40'2ILILL1O-1. groundmass
3C-912.In.r111123,'211 and
jlb:i:-o-':'
o
5.'-I,.1-9
ci,rtc:::
on a fresh surface.
or-
2222220
(11Y1011'l:lIc,
f.'-O-.'t I'712'51 is
al somewhat
The
'1:10/ ' feldspar
Oolon IC' porphyry
'3702 Hager
j;111'5.:
5ti1-7-t1ifl50
Hager feldspar
porphyry.
22 o..'(' 00,
I
is
':3111
12210
10511-5021
-p-202t74-'
:-o
similar
to
the
rhyolite,
differing
in
that
the
feldspar
porphyry
t4.tf.:-oI22c€9*
:"ft-,-OJIL.:--:,
12:12001110 0-c- 'Lbo
feldspar
407
.01,5
t.1'12t110'C221-'-c1111112 001-C,
>71'- n:-o
o1J11lt;.tlld1 more abu:Ldant
darker
grey00in
color and
-woC contains
and conspicuous
01cc-Icr .t2211
0011:22.-to LIc
:-oc- ol Or
is
the0cr13'
only oo,i-c
mafic:01
mineral
in
714-1:;: 1
0035' 0?1:1.'
phenocrysts
to1730000
quartz.- Biotite
p54:
-01:5122 iL-: compared
71.42-1.0porphyry.
:oo.c2 705
the feldspar
11*1:1.1
Scm' SOtO and
r11122011.o&, .522'07', foliate,
The
isOL'-217grey to
12-0 reddish—grey,
111401010 Sw
117.1"dtlt-O
131. syenite
Hager syenite.
1971214.011feldspar
7-01
C
o: 11:'
fCctSl
:0
11
Lo:lm-f
porphyritic,
with
aligned
phenocrysts
(25%)
of
anhedral
alkali
>a2L
I
:00011
pL>cocm
c-51.to
C2-1"%
:td7-15h5--,'v:o1t -In-I tI:
SOo000:
feldspars,
biotite,
oil
Solic:
rco.'c,
Jr;11-015:;.
-,:.
5'.l.oo=-If.'coi.clrCand 1:25cm-cr
minor plagioclase
1111 a fine—grained matrix of
t1b077.L11t 0011 in
01101
C-?
Granophyric
iL103Di'9*7'0t't'011 of
'7c1,c-cochdc: . intergrowths
wo-r:-:cc- rJ:
81,3121:
c,:.L amounts
amphibole,
small
of1111811011quartz.
c131:11
702 1.1: and
alkali
feldspar
0-3102
01010
±122
12-0111102
a.'1Y22:-38IC to some
qua.tz
and alkali
1142110,1.110 occur adjacent
01111:0.'- 1 feldspar
5'-,t::r:-.4l01-.
77-s'1307'C"o:
22,
phenocrysts.
¶ 11 massive
icr-nA
:1011111.IL'-iir and
This
quartz
monzonite is
5.100 1112,122
Id lltItC1.7'coStLO
,-1071.1-;:0i -1
Hay 17ClLc
Creek
quartz monzonite.
]1I1,'L
.111111:123,8101':
0
(1
cm)
in
a
7)2:3:52210
'
0111
14
5112
-0051212'
11017.:C-.'D 437
..'fl'11L40
porphyritic,
pink
alkali feldspar'phenocryStS
-1-oOp°-y'2' '21I, containing
70-0121±.--:',
'oS -.lcp.c' cc, biotite,
7711112:' 12, two
too feldspars,
:-00clcJo'.rtl.t
11'-fl,l
medium—grained
matrix
mm) of
anhedral quartz,
:12.11101.12121*.
-950-4] 401,
801011 (2
1-5111lIlkt
amphibole,
01022 sphene.
'l'c-,Lct , and
-
2110
1.011-LI unit
*1.14- in
71,101.00-37 this
have not
yet studied
-not 5114
'>O '.5001-:c..:' ,572 We
granite.
-to
5082'
:,oL,OILIL1V"
actually
a
grey
31.1:1 -x;t.o-'inorth
ocr-IS Ifof
,7002201:.1:o1:,o0 50One
Stevens Point
is
::-01:711d collected
71.c sample
detail.
tloc-c.Oi.,
11-c.] -21 op to-'
alkali feldspar
22 Ltao'n: 17%
122c1h111t122L2-aa
porphyritic
quartz
10%
subhedral ,1,iL:s1:1
'-cttrt about
12210:211(1 022 with
0±11 -110':
12 monzonite
o:_r1
iI
allotriomorphic
'IL
0
1100101 in a fine—grained
pJenocrysts
(0.5 to 1 cm in length)
I
:750
tOot-Otto
,
This
and
biotite.
711! ,:c:-±oU 1.11-1.,, 0111L7
'3:011:: c-oitsc:, plagioclase,
.-.:-i1 quartz,
granular 1111.1&1lCit1c
matrix of
'-ttc-0o. microcline,
41'20C.'91.5F'
'I,0.72 '41-123
finer
grained varieties
:1::f5o-o.cc'',0-.11cI
1.12 some
11.0111,of
of the
rocktois
lithologically
2-111.111,11,1 to
rook,
11'1411c.1C-J.4
cc 113' similar
.'-Io-'111c1:1.t3
flo-7,"lil-T-:OlCci quartz
0,8111 River
1111.02712' porphyritic
110S12'L-S monzonite.
of the
-1-221 Red
0"
'1'.oIt:-1h:11-'a-:
5':81911100
Stevens Point
grey
21
',i
21
ca"c.
-151-1.- hetero1151125 granite
High
0:1-cool t.: is
rather
1-c a
:'s;- 5i
oil: Falls
.:&-c: t-:, The
High 42-S'LS,:
Falls granite.
5(122:
.lJ0;:1.1..771.1222I12':cLllt-I0
oo'-i22 1911, '12013,-I,1-l allotriomorphic
geneous
mainly ofdt medium—grained
OCI'SI 01LT9* 11.01:174
011111 unit,
12227 -1 consisting
octorw': oIl-Ill
Shear
zones 011are extensively
51.12.0 2103.01
9*-L-02011*o.1
wt1oor.. of
:7.'911'1712
granular granite
and
quartz(19-3>1101.0-0,
monzonite.
11711
other
units
11 the
oLir1 11111 -il:':211t
10305-1111 absent
developed
It'll? 0021,2107:01
outcrops, a1- feature
from 12-1510 22222:1.1,0 of
18: '211.1' -1: in some
-lb
rcr'0"
:7110024±22:
Eau '-IILOOIci
Claire River mylonite
:0 '11c-'o,..'.7f
1712,11:
:'r50 11:11 of
-11.':L'klt the
Wolf River
exception
the 11:::,
catrl-:clLlLibI, with
1i',tmr batholith
'i&3,:77oo1,
It
is ::,.1.o1c150V
uncertain
1;,
.0 11?
this
guidebook).
1770-1'.
.015
122/11121.1117zone
(LaBerge,
field
trip
locality
8,
:1'
-015
1210: (1 a17c1-cbS-..
7t-I1'1:,11L11-'
It' whether
of the
1,12.1
batholith
022000121
I'Ll]: or
lIlt" 114r I.½0:C
'1-;: truly
n"mCft ilL granite
01 II;111l'1.' is
whether the 4111911'?
High Falls
part 122
:.137L&1t1b,1€02011;1
to ItoIn
the
1.> '1"°111i12:.
3ii:1"11'32212.2L111-4 terrain.
0' 480- surrounding
71.0 older,
it
represent
:5' the
1211:11 of
11 might
mtgkb 0017
.c10IL::, part
-:
>s tac-]]'
assigned
to
the
bath—
it.
SOS
tOlctO:
1
021-10
3:30
oso
L,oliac
to
absence
of
isotopic
dates
it
has
tentatively
been
ooto-ptc
1,0120110
21201-so cooS
tçlOIolti
-.150
ol'
and
is
spatially
.10:1
1:c-cr:,'-lllm'
01-8
cool-cIlo':
,1T:8.'11L'.tO
olith
because
it
intrudes
the
Macaslin
quartzite
dli;:1,I'5bl 0-1-30:1012
-'tC-OLCIO. Ito.
-oob :101410 monzonite.
and Peshtigo
::l -19-12 .1, . -110.:
11c5 Ct29ttl: granite,
i'oç'to..*tl- , Belongia
7;: the
1(14 —cr1 : rhyolite,
related
-o Hager
c-tm .al,e-21 to
'1
21111
�/t
c-'5c-,, at.1; c-y cc;c
cc'C:Ic'C'cc6 cCEcIICECcZ /Ld:,LLL
-cc:.
:c;:ccicc cc ,.C1 ::cc-:cc---5-
To illustrate the chemical compositions of the granitic rocks,
mesonorms have been calculated after the method suggested by Parslow
(1969) (Fig. 4).
Such a calculation takes into account the amount
of potassium incorporated in biotite, thereby reducing the amount of
normative Or and presumably providing a more realistic comparison
of normative Q-Ab-Or with experimental data in the "granite" system.
SJc-ccCc..,.C: ccL?c:.,lcccp
cc,c.
ic.
c :c-iaccc :1;-: 2cc,:-,cccj 22-c--cU'. /p:p cc: ptc;ccc-T:cccr c::ccccct.c-i cc
-''
P :1 cc-C-S
-I ci 1•:as I
:;:cvccc- 'cy 1c2JIC:cC,'5 cci;: cccfl c-cc::'
ILL.Ii;,6;5 Ct fClC:-cC:;f.c.Lc :;c-:cc: cc-i. ,;IC:'1'. 31.;-ccc ccCci C'PL
rv,cc.,mc I:; 1CTC6ttc-:e 'CC!. —25:cc:cll
c,;
'c2cp.;
..:I3_':L:CC:ci.
'ZLj
cc
'—
I
cccc,irc,Li cp'.:cc;cc: L.ttXI6
c-'2J cc' ccc-: :ca'TLt:ccaci;
riS4 c; "iccic ! Icc. cc: I!TCiL p,cITC. cc-.;. CttEC PLC:,' Cp; ;C:LC:C: (IN
CSLC:LCC:5 l'Lc1, cclcc
c['ci
A Peacock plot of analyzed specimens (Fig. 3) illustrates the
alkalic or aikali—calcic nature of the Wolf River batholith.
Despite
the alkalic affinities of the batholith, all of the lithologic units
so far recognized are peraluminous or metaluminous.
However, syenite
and associated nepheline syenite in the Wausau area yield isotopic
ages of 1450—1500 m.y. (Van Schmus, LaBerge, and Myers, this guidebook)
and may represent the peralkaline complement to the peraluminous
granitic rocks of the Wolf River batholith proper.
PILc.cccc
cc
cc:'
cc-c
'cYs,ccc-rm
:':f'c;1C:;';c-C'c-LcccC: c;
C.:LI
ccc'
C C:/L,IIL1'L:ciiP'JL
ci ;'--;, ;'.::
'fltcc
CC:C:
C:CtcL .Jccc-'C:6L
.C-1;
iC:177ci1:
c:L:JC: clC:;1l..iC::.Ic I 'C:CJ cc:; "IL 6F1'i:C:ciYTl ccc ;c CC.IL'i
C:ii,c-,L c',;:CCL.c.=.T'\a,[T PC:
Cc-c
Lc'ff'Ct5 I'5.c.15 5Cc S':.L
°Zji TCC:LC:UtC:915' iC2-CISL" .1c. "ccc :1:'c:ccc1J
PLC: cWUCJVL"1: 51
:1:5,
a/c-c' ic.
Bulk chemical analyses of specimens from the eastern part of the
batholith, including Wolf River quartz monzonite, Belongia granite,
Peshtigo monzonite, and Hager rhyolite, feldspar porphyry, and syenite
have been obtained by electron probe analysis of fused rock samples,
following the method described by Gulson and Lovering (1968).
From
the analyses listed in Table 3, it is evident that these rocks are
relatively rich in Si02 and alkalies, particularly K20, and poor in
A12O3, CaO, and MgO, features shared by the Finnish rapakivi granites
(Sahama, 1945).
ccc'.CCP leST
.Y'CC'i"CI' cci
"5
I-i
'ctc-c,
2C:J'. c-C:
:
'CC:CPTIcC T
(
C.
—
I
L
cccc'c.'.c C H'
C:'c-Cc-
'C:'.';
'"1'EIP6/
'ci cli;';
'c--Cc
sic-
LT
-I
LI c.'-c-Ii:-', cc;
IL
-.1
'
cc :ccc
c.c.cc.:ccpr cc-C c-CRc-c- (c c-ac-.ac-c;cc. pc'pc'c. 2L S
r,,c,.Cc-1' ccc5ct'S' :C: çc6"csc-'c 'ccci: c'c'
' ;cI PC ;!.cLT'Ccrc
cctccci:' ;cn 'c-cc"; tTc: c--c 5;; 5,5 Thp 'lrI.Tc-c
ti i-;":.CC: ccicl.'Lc .'C:
cc
'C7"Z'
'Ci-c1'fl p-C:,
C:'cTC.i LC.'CC.ilT :6;Ipr'::z'c-;
C'IC:PC:']C' Ic c3?SCIC7CCS
Ec'PCC:IC.1L
:'ctc- :
'cc-;
cc 4.rCI 'ccc ic-Cc
:
'.5':
c-cc;.i:c
si:cc
ROCK CHEMISTRY
From published descriptions of rock types in the Finnish rapakivi
massifs (Vorma, 1971) and from examination of rapakivi specimens in
the petrology collection at the University of Wisconsin, it is apparent
that each of the lithologic units in the Wolf River batholith corresponds to one of the distinctive rock types recognized in the Finnish
occurrences. A correlation of rock types from the two regions, based
on textural, mineralogical, and chemical characteristics, is given
in Table 2.
The only dubious correlation is that of the Hager rhyolite and
feldspar porphyry with granite porphyry and quartz porphyry dike rocks.
Texturally, the correlation seems to be valid, and perhaps the only
difference is a higher level of emplacement for the Hager rhyolite and
feldspar porphyry compared to the rapakivi dike rocks described by
Vorma.
p'6,:',::: p 'ip ciTc:
cc-
'2,TC:c-'2c- .,''ccj ',';
cci. cccccPC
cc
"155 "S i.
cc';
:,'Irc.cc':'c'.i:c'
1."cr:
-
C: H; ;,L',,L,'.cm 'IC Cc- ,'
C:C:U'C'STC
CL2tit S
ic c-c. C P':.:
CC:c-?
(-7
I
I
cc- PC cc-cc "ccc:'ClCl-ccctc c-Er
c':
cc " A,c:T-cP,c': cc cc p PTLC:c-Cc:C:cc'c.c"- 't
cc- s. :c'i-icC:'c- ccc': pip;'
C:T'1cc,-:
cc-c cc .,,: :1Cl;C:2cc7- p,'c,;'"c-,l' '2 -c' 'C"l."
;c-r' c-c
L'icC 6):PC57
'-;'::':c'c',, 'I'P
rIct'L,.6L i'' L"c- C:'pr—c-ici; Lit.
'aciccC:",ccc;c-;XL1 I'C'
icc-i
I1c..J'15 :'1Cc-C i'L ,,,''.:'c'Tc-cr.,,:te '1
c',.
c-.:ctc,ci
cc,
',Th
-c-c-
'LC,-cTCPP'C:LL'
P1 ]'ci',1C I/c cci
L.,:m:cp.p'
L..(CiPC.: cij; PC c" cc
:'c.:;L; cc-cc
c':c-cIcP'C '
WE c-Cc-C ci
,?,Lc;/
pc L::6;:c6 cc, ccI-cc-
C: P':tJ'ic-'i icc-lIT,' '.,5 'CIT,
'c
cc
:cc
,,r6Cc ccc-:
lcC:c';: :rc-y -'l:: c-Si. cc; ciT ccc,
: 'cc-, 1,6:1:! ,;1:CCc
..
cc'c'c ic-'J
L'JC:c:,:cl:
Sc-c-cia ic"cc: c c-Cc' ::_SIP :LlcC:1C:c 1cc'p.r c-i' P 'ccc
'..
.,c- rpcp7;:i,;i:r'p':L5c. I :7PIH HH'.i
sic's; ccc-.. cci fc;:mlcic-c-c:c- ;c,ii":7:ccx: c
LITHOLOGIC CORRELATION OF THE WOLF RIVER BATHOLITH
AND FINNISH RAPAKIVI MASSIFS
LcI'Si2C:J111L
1::C:::ici
Pc-c' :cac''1 pccc.:c-'.Ic-cc :tc;G1E:.ir 5,'c-'p' c'S
a Cicc cc C:-i':"lC:c.C.PL :P'i"c-UC:r CfCui 'ic-C:4
Anorthosite.
Anorthosite, containing plagioclase of about An 50
composition, occurs within the batholith, where it is intruded by
granite (Fig. 1 and Weis, field trip locality 7, this guidebook).
Interestingly, anorthosite of similar nature is associated with
Finnish rapakivi, where it is also intruded by granite. A genetic
relation between anorthosite and rapakivi has been suggested by
Kranck (1968), among others, but some Finnish geologists believe
that the spatial association is simply fortuitous and that there is
no direct genetic connection (Savolahti, 1956).
c:';":
CC c-cc-pp
6:flC:C:'C':cIlC'C:
c-i'll.
cc-'PCic c-c-
,_F.cL
1'C:. i;-cc-:ci'
P
cc-';ccAPc ccc ,
ia,C
PC'cUC"l c-CC:' CT,,
c—-c——
"
ctwc-
C:T'Ic-PH
A?
:ci, .ccc.:cccc ucic-ciCC; nctp'-ccP
I'c-
J
C
"
6',c
'icmL,L..-,,'_Lc_',
''.2'-. 1—c—_c,
- Si ClC .1CC:;' 'p
c: :cc-c,'CL"P'
4-"':"'c--''4
,•,—.
C-'1'.1
ccccc'
.-—
'cc-it-C.'
c-nc
(..'la
SCCC'ST,JC.i
Ic-SIC
::.cCc;c..6I ,;12T75:1',r
5:. PJ' Lc-cc'c-/
C 'p, C:.Tc-,,cC:i'iIk. 'f;CC'i'ic''' c-c
?'-'I'CLC:;''i cc-p
•"
ii's
4.
Lj',
C:
"1
. cic-'c- '
L
6/'—
in
15
�16
Table 2
tC.i!
Correlation
units in the Wolf
River
with onrc:
those
2ar-o:- batholith rrntr
O:r'-cLrct Ui -ifof1. lithologic
t.n01['J-f .' nyt+
in the
i5rr9t Wiborg rapakivi massif in Finland.
Et
n1ri :irn
Er
at1i :''!tAL.
Wolf River batholith
'.ai
Wiborg rapakivi massif
cr;a•r:te
Peshtigo
27&II'C' monzonite
Tirilite
1Ckt2C3flI :8
Waupaca quartz monzonite
'i
Wiborgite
-t
Wolfr River
izt1'C granite
;c&-t.. and quartz monzonite
Pyterlite
L1i 1/rL
ri:
Red
quartz monzonite
r\ct! River porphyritic
Porphyritic granite
::
t-•i rrttt
L•L.Z'c9 -pL1T_:;r'
Belongia
crsgL granite, coarse—grained
lilt Even—grained
granite
3Jis 7 *1Ci: biotite
Belongia
aririCt granite, fine—grained
Porphyry aplite
rg aIL1c
rrqy1 ( iCrp
Dike
granite
porphyry
rr:c2asaa
a
.e- rocks;
and quartz porphyry
grL';Q
ja( r.rirr'
Hager rhyolite and
arci feldspar
Z&T.t' porphyry
ac
Na
1:
Na20 + K20
-p
Ilt
2.-
I
lU
52
56
-
CaO
-—
58
6o
2
76
Sc
,
wt. % Si02
Fl.gur
igure 3.
3'
ncco1ith
River atholith
cloif 1ri'nz
torn Ure
forhpec:iraens
specimenc from
the Wolf
grapb ftc
Peaconk
Peacock graph
�1
17
Table
3
Bulk Chemical Analyses
66.14
0.68
1.13
13.112
51.8
1.145
r
71.14
7,
o.6i
:i
0.28
iy:'-
nC'":
'"3:
0.20
'F'"'
".cr's
-A-;
0.39
69.6
%9i
'r6.2
714.5
7
6
5
9L2.
Tb2
14
5:
69.6
Si02
3
:5';
2
1
3:-c
12.1)4
1'9°J
99° IJI
-r' -Sc
1)4.33
s:.
i6.6
14.18
2.53
3_I
2.29
3.72
11.29
6.31
io.8
MnO
o.o6
0.03
1—"
0.02
0.02
3
0.02
;i1F.;.
0.03
::.-:,
0.12
MgO
0.33
0.13
c_'I'-3
0.08
:5ri3
0.18
51°11
0.37
7".:;'
0.90
1.36
CaO
1.69
0.58
0.58
L
1.111
F[
2.39
24.07'
Na20
L
1.38
3.83
3.13
3.22
11.142
CI
3.3)4
3.611
11.119
1(20
5.83
5.85
5.56
6.02
'"fl-'j
.,
6.28
..-.;3
5.111
T':°
.-..i
24.35
100.21
99.09
100.03
100.31
100.9)4
100.5)4
101.0)4
1-
F'
c-A
:4.
I
—-
ii
Cc
c.w
3%
Wolf River ciuartz monzonite
2
?
Belongia granite, coarse, average of four analyses
3
Belongia granite, fine, average of five analyses
14
1T
Hager rhyolite
5
Hager feldspar porphyry, average of three analyses
,T'31.33II33. •c;11;'rx
6
Hager syenite, average of three analyses
7
Peshtigo monzonite
(c°
ci:
1
11
--
Fe as Fe203
',o.
:7
F""
Total
IF
—
*
I
Total
CIT
1)4.3
31
"ii
A"
Fe203*
11.80
ti:
111.3
991
A1203
3333) .D:3,T?
9-3 73,1: :13
J:33:3 ':.3'i.73
7,33.:F3'3J,?3 tFnL;cToca
1:7 ?32c-' :cc;,cT,
CiX313 co7'Fc:i:
?17700:19
5'3ç1':f33ci
OX1i9t j3
:9co±935301.
•33Y.3 r3v'i,:iO;
Jo
LI-
3F
.9
�18
Q
i
o--:JorL8!a fC&OAt
Belongia
granite
-5
tatr hcres granite
Wolf River granite
and
quartz c-rr7onlt-e
monzonite
and 4uartz
A
feldspar
ris cii he • feldspar
Hager
ffac;-er rhyolite,
raritcporphyry,
n-or piriTy. and syenite
/
--
ii- L-—
-
L2
Or
Figure 4.
.
ilivar
compositions of
Pull
of specimens
spec incas from
from the
ih-c Wolf
boll River
Bulk c-orapos;tLcns
hr.
bat-holith in
p. Ab,
lb. and Or.
batholith
in t-crzss
terms of
of mesooornotI-Vi
mesonormative Q,
8ourxdarycurve
c-ursafor
for P11
P1
BounOary
=
bars shown
-shon: for
for
1030 hu
1000
2
comnant son.
comparison.
batals fist-cd
(Symbols
listedIn
inTable
Table 11)
-
I
�;
TCC -'.-"Yt(
7-it F
k-CELl -'C
to up
determined.
been have
1.5% -Ci
-'-'-I Cl
(CCCI 11.12 7 CC
CLCtLCLILI7'fliC( of
,,LIC;
'7C'.If a is
7LCiLI'ICC-C- high
ITT- (CT.' VCL.C:'L,.T'CkI
and
to up
contents -IC, -Cl)
1.8%
of
far,
So
halogens.
content
ILCI',LCC, River
C-Il. L'21fl'C7
CL characteristic
;TCLiI, the
"I 7-s77[ of
C 'C-CCI.C;-I
11 C!.IITL'.t .7L1112 III '- CI A
'-(1
1'-CC.i Wolf
batholith
from biotite
feature
11
-
granite. Belongia
YC:.7C7.i7.lL'L t(C' .T 5
IT c"CCC-Ci-'-'C YI'LIC"C 1147
IC-' .2C.1LCC-),,'C
SIC, - 71121 2(9-112(12Fe+++
4
-.1!
coarse—grained
the
of
biotite
in
Al
octahedral
for
substituting
5'
LkIC'Ct.CI1l of
may granite
'C to
-LII due
iDI1Li,1)';-;'LCL.
7.7 '74t
C-Cl) be
-CI'4, 7-1(220
11757
CI- 7L2100;.CICY.X1Li1LI711.IL
amount larger a
of
varieties two
the from
LLL7-.L7.CT'C (CC 2,'C€'2.ii'I1OI- LLI,(ILlCi7IL.CT1Li 71; C-C,C'-I'CC',.,, 4. CC'
11511C-cC"P-&,
'C3C.Tfl,-.CI Belongia
biotite
of
content
aluminum
in
difference
The
granite.
:(.7,, 7,'C2;'7i2ucL11-C-LI? C-CC- T515
C
'1 octahedral
CLIC.CCT& IC-C
CCIII
9-7.r.CCTL'C
21'L,-'0--C
fine-grained
the
from
compared
when
biotite
with
Al,
C'7,IIC 'CC7TCC1C-i "II5CC5CLIL'-CC
C?-CCLICCIC I '21201111
C2.(1i1'4 CL? but
'lLCI'.Ci?I[2-?
5.121
particularly
aluminum,
amounts
small
relatively
of
contains
' 7711L'i. LL.TCLCL '-"I' ('7
1:20 71
5,L7:.u.t I(C 2CC-c O' "CL 7'1C-0C 'C.' CC.CCcIzi.. -'CL
mineral
mafic
sole
the
is
which
in
granite,
Belongia
biotite
grained
,p.7f
-coarse—
1111-112111?
1l)C-'C.LC
('11 '1-" '1','C'5.CCCCC
- LII CCII. ' River
hI'7 216 P
'CCC
'CC
the
by
is
rule
to
exception
I
TI
provided
this
An
granite.
Ii '0. the
'1(177.
7721.'CC Hager
.I-.5.7I'(' the
TIC-47
C)JL7ICL.CC IC"?,
LI-CCItT:' C
CCI? rhyolite,
quartz
Wolf
and
monzonite,
porphyritic River
CC"IC(I
7217':CICCCCCC.'5r7
LIt'IC
7?- -CC' 1.i:I1Ci'2-CJCLCCCLI7,:ICILC7I
some
as
CLI'
Red the of
members
granite,
Belongia
fine—grained
the
such
C'C5'C-711'C7. 74 211T-1,1.LILI'C.CL- 2177117CC
LYfiC
'LI
?1i.I-77'C'C'l'
'((PCI!
lithologies k-Camphibole—free
in
occurring
biotite
aluminous
most
the
.-i4.'7 'C'L7'YC River
'C-C,(CC-.,!
I 7(7 12
.1
-CC, followed
(It CLCCCCJ
C.L5I,c.C-T':t:L is
117,74?
('71 by
batholith,
Wolf
the from
biotite
pattern 22Tt7
This
CIII
CI
'-21,1? a
t'-. 5(C
CC'? c:L' 75. "...L'LI.
7'fC"--'- as
-W't-C(C
1(1-717
'C'CCIEC
C-C.yC.-C21'i,
well.
amphibole
containing
rock
from
biotite
than
aluminous
CCCIII
CI
more
a
as 2"CC
occurs
1127
97
iCi-"kCs
177
CCC'. CC
1'?'-'?
;C(
'"1(121.1
C-711'ICUIL
-C'
LI-CC
be
to
tends
it
rock,
in
mineral
L'-""CI-'mafic
sole
the
C-IC?-.(1947),
-2.77, 45971.C,CC-k.i
7,Cl7CI37l-iC-'CCL previously
.IL2'CC.-C'C"J As
211
biotite where
Nockolds C'S,
by recognized
L
7Cr pis
'C'I11:LkiC,C7 per C11-CCCIC LI 2,,,
CI C'CC;SL!CCLI1
CLLI'CI
'CCC' formula
CI?'.
C-Y"'
to
unit.
atoms
0.5
than
less
amounting
low,
'7mT
''.LLcI'©YIICC(
,i1PCC- 7L7'lç..ICCIC-ZCC ,12ITLILZ
C'
LI' -CTI'7?7 in
:(CCIC7,CCLTCVC
'11-7
01Cr
Ci Al
biotite
octahedral
monzonite,
quartz
porphyritic
River
Red
and
1-1. ('1111.7? Belongia
"41'CTCTLIC(l C171t
CL't 3.2
'CI' C'
12192 9CS-CCICC- the
"-kkC.C-'CILL
.1"CII With
'114;
.2 - C
tI 1 with
granite
the IL?
of exception
atoms. Al 3.5
to
1TI-IL'Ci1LI2-t-1Lk2 C-c'9i1C
-1.1211117. CLC7CIC
cl- fine—grained
CSLCIC-TC,, 2CCC'L'II.C-Lbiotite
contain 1721717-'.
which 7.'
of pecimens
most granite,
Belongia
ranges oxygens,
0,IC.LC117 I'IC,C7
2232' 721111
CLI. 2.35
2172117-CC 11
7 -CL to
7.uCL'CI units
1all
'V .1-4,1
1,7 '7 about
the 7except
from CC'211C2'LCL
for 3.10
C
an 11
CIII- ;'H-172121 ul
uCIlLfiCC,LC The
7-C basis
LCICI'C'Cl anhydrous
Itl?"CI.- 'LI:.CI4'k
'CCj'
on7-1217
"CCLI
I?.. of
22
calculated
atoms, Al
of
number
-.
(CCI
(:,7,IC 71-11211
'C'ICC'7
River. ;i,9.?
the 41
portion 97--.
granitic
and '2.1.2011,,'!
granite, '12'?'CL"C7
Belongia
Wolf 'CCI.
of Cl
CILI,177213'.LC'
L-1'7C
-.2:117-I
,(1C1 219-C! consistently
67 -nICIT -CCCLII being
CCII-177 than
U&LI7C'rLIi
'Cl-CC
rhyolite, Hager
the (17-51
greater
for -:i
90 about
-7127-f':: silica—rich
'7.20 C.II'CiC'Y'
CCLI.
?'7175L_12-217777most
1CC-ILthe
(1.7 1i,
I'I'4:Y'(1 L4CC-4
'ILITt.'t :1,1 are
rocks,
in highest
ratios
Fe—Mg expected,
CuI-wC39I(C,'r 11Cit..C,.CC!i'TC7'CI° IL, values
10'.."
01-25221,
..;i'CC(C
2CI,,,)"21.,L,
';"I'II(c( As
to 70.1 from
ranging
be might
98.6.
lOOxFe/Fe+Mg of 3iLI"li'"CI with
""'.CT.-LC'CLp.Ci'7.
011.772217 1 The
'TL'I'.u,, in
71121'
.77 biotite
'517 siderophyllite
--'37(11017 tIC -C"7, 1'',I-C,JC'iLL':C and
'217
C1 i'
eastonite,
iron—rich, is
5.7 Fig.
C'.CLIT,..10T1LL-'5L
011.731 have
C CLfl'LI-iC,-"T-CC'C of
1-1151111
9i-!'f( analyses
73- terms
LII ,C'I-"l phlogopite,
'ICC TILCIIIC (Il)'-[ end—member
'CC plotted
H -2(1,771 been
in
annite,
..L(', elements
L1 C'4L
I'7IC:"T'C'7.I eleven
122111
'97'
C1'21C4'
I.C means
7"ILC1'UP by
'CC-' 12277?
J1f_.LE1T
'k'3,1J.
analyzed
the and
probe,
electron
the of
for
01(117-CC
CC -22I'I'c''CC'-?C,2',
1i-.C(1''ILCCL'CCCCC'pC 47
'i'-IC(4
, CCCI!
Biotite
Biotite.
been have
specimens representative
from CCII'C'C-.7,
-
2
11
C.u'CCL!LC.,:p, CC:Ck19C.C-I-3 the
accessory
minerals.
1!1LC'. :111 and
011772'(C"Y-' 121421177 and
777' widespread
1-CC'
C7-1.'I5'-k.:-1 —' most
74??' 'CCC.
LIt 'CL
pyroxene.
7(7,
.LCCI'.i,i
Fluorite
of characteristic
the is
7771)207 iron—rich
''Ilk and
'i..71170u7
1IY''7-C,
(CC'!.-'' C'C.C CC.C..fl.,2u74'.Li(I
112.77 biotite
olivine locally,
and
amphibole,
plagioclase,
(120.1(1CC-CC- smaller
.L:-:L-7 :s -:sl
fl'"7'-',Q'
77- 42t -11-1.2171-1-C.;:
C:'.'L7 73sodic
of amounts
with
quartz,
and feldspar alkali perthitic
up made
are batholith
'CI 1771 (1507
C'" 1'171'T-2111k7-1'2 7r-,
717- 7721.,I1"-L,River
C&,"71 .Wolf
11-I' (IT'
of predominantly
the ,of
Rocks
,
7.
(9C t
MINERALOGY
CCLI.
219:9771 47,7.
'C17.l C' 1120
-- -1'.7--I (Luth,
to respect
withj7ILII7JCI21C-:
saturated
1969).
(12113-1120" could
-_.Cc72LEC1
magma aP in -'c;11-I'C'['CC , CIa-7CC C'C..,IC 4LCI-'I72'-i
conceivably
under— 'CCC7LC"ci
equilibria
crystal—melt
reflect C1"'.7C,
-'ic LCL1TIC
7'ICC-CLCnLL'
[ -71C77 a
'1 41C5'C
LCt'7''L-- 'Cs-I- rapakivi
7121>7211.15' IffCt7lLICCCl
(('4121 '1;,
displacement
Such
granites.
Finnish the
by 721.771711
shared -7feature
,-:
13122120 L',,'C,1-"'-C1C'C
71.112
a1 12177.21,21
corner, Or
2194. 11,21217711:
-: still
917 from
TI .5-C are
the
toward LL'1I20.'-LL'1CCL
minimum C7''I:'I.C;-C
granite the
displaced
(1Y-c' C/-C
-7-TI
1 .2,'C Hager
IC 7i'Ii,C.'LlC.cLI the
Ci313':'c-CC'21-'of
7C calculation
'('977114(7(1!,')
310117"'.-! Belongia
mesonorms,
rhyolite
and granite
1,5-C
"[(7 CC.
4C':'CIC'(L'LLIO.LLithe
1177. in
0115-77'
(''2777: despite
C' C feature
7 712110515 'II of
C 1174 is
112117-) i3'C IC
CCI
amount
that,
by Or
normative
reduction
.C'.77 toward
177191117
\''7'7)
IC-It)-?,, 1721CC'
'C1CC' Ab—Or
II
along extend
'C7'Iti the
significant A
join.
trough thermal
the "7)5771
79((15C;the
I'll near
'017.:-?..: granitic
u'C.C,,'11-7LI,
-317-k-IC- 711.-'-'
'17';. '7-I7- 7.1
and minimum (Cc
granite
plot rocks
the(1-77
for Mesonorms
1121
-
,
19
�Al
20
atoms
1002
1OUx
3
90
80
•4
Hager
Hay Creek
Peshtigo
10
100
90
•
A
•
AAI
•A
As
A
80
o
A
A
Belongia
S1
A
A
Wolf River
10
U
K2Fe5A1Si5Al3020(0H)
K2Fe6Si6A12020(0H)
V
80
vvV
V
Waupac a
Red River
60
40
23
20
gA
•OH
K2Mg5A1Si53020(0H)
(.M-SA1 1:(DH).4
KMg6Si6A10000(0EI)
Figure 5.
FiRure
a
of
Cumpos'Y cf
Comuosition
hatholith.
tTL frcn
from
biotite
cL:River
Fir
the Wolf
ir LL7L
(Symbols listed in
Table 1)
�21
fr
i-i-U li-U)- fli- 15Ui-1 tci ThTZti'-i-iitUp Ut
; Ti-I
[-i-U)-'P
Si-U
-Ui- _..t Ui-ill U4 .U'LJitLU
the
Biotite from the Wolf River batholith is similar to that
Finnish rapakivi granite in displaying high Fe—Mg ratios, relatively
low Al contents, especially octahedral Al, and enrichment in halogens
(Simonen and Vorma, 1969).
i-C Li-
i-lU
f7' U)lIUi-Ui5Ufl LU U r;
•Q:U)i-,i-J 5
r-:
-•l
i-li-C Ti- U iLiSU)cU3-SlL-U)
Lii-U)
i--i-2
I?*81
c)iir.a
U5U)UUl)'i-U LI k-i-- I
i-IHLUTtC U
i-i-J-U2
)fl
TtitU)i U
U
U)flj'.L U)I2. Lii- itLUI: t-p
ioi-i- ri-i- UI -U-li-f UU)UUU U -i-I
4fl2 Li-a..,
Ui-U U -i-T-U U 4€LU2:UU U2t1iUU)L 'i-U Ut
i-i-i- 2rim '--rU 1
LU'ti-UL ,-LLJ i-C- S
A ubiquitous textural feature exhibited by the Wolf River rocks
of biotite and alkali feldspar wherever
phases
are
in
contact.
Configuration of the contact suggests
these two
at
the
expense
of alkali feldspar, perhaps rethat biotite has grown
of
intensive
variables
during or after crystallization,
flecting a change
in
equilibria
among
alkali feldspar, biotite,
with a resultant change
and magnetite, as studied experimentally by Wones and Eugster (1965)
and Rutherford (1969).
fl 'flU
li-I) 5i".'i-
UUU
.xU:UQ :i-j.
i-U)21it\J[3L
•
L---.1ff5
an intimate intergrowth
UU[l-i-2
is
i-•
I
-;
4liUi-U
1U)iI t.1Ul
:U):
U)li-i_ Cri-IlLi[ i-riI iii- :yi- SUU( i- i-i- LUlL. i-i- -TTLi-1 1Y ir&-; 1-i-)
U)Uc i-UUU:flU)U2
i-U LI:
1 U'i-i-ti i-i-i-CLkçU):U)J Ui-U)fl[U iur -U ;-tp-; ;1i.U lit I
_U))L2 i-i li-U E
-CTU cC-fl flfl- i-U- atcLU.I.t- 14 U)ifl'i- UTU:U€ ''L
11
1
-
U)li- ii: p-i-t i-i-i-i- i-.7$v- :c p
Amphibole.
Electron probe determinations were made for ten
elements in amphibole from eleven specimens. According to the classification proposed by Leake (1968), most of the amphibole Is a hasting—
sitic hornblende, with values of Ca+Na+K ranging from 2.54 to 2.71,
Si from 6.33 to 6.50, and lOOxFe/Fe+Mg+Mn from 77.3 to 93.4, calculated
on an anhydrous basis of 23 oxygens.
In a few samples Si values around
6.6 were obtained, indicating ferroedenitic hornblende, according to
Leake's classification.
Like biotite, amphibole contains appreciable
amounts of halogens.
—r;a L.i-U)L
iiC4Ui-i-
-
Ui-.
iI[U.i-
•_'
U)
LCi-U1I
:—, rt;: Ifl:-I-:r42
i-U)
.S. ii.:
•1 U
a:r
U I.
1.
U)
U)12Ur
•qr[U.Ui): i—U Li-
U
rii- zY2 - T:L4c acITr y
- -U)-1
- -U)Uç ç--
i-LU)
lifihili-.
:JtU) Si-
li-Ui
U)U)ui.U)i,U
'U
IEi.[U:L: cUll—Ut t'
.CflU)1r )CI;
Ui-1.:.fU
fl
UITltl
CLJçJ
U)
iiU -IUYUU ri.
TU);UUL
U)'UiLU)LU-
UUrU)
1jiy2t-4- Lii- i-JU) fl-l:v
:i- i-•5'j1- Ui-
LU
atL1i-:
:2.U)ILL
LtYL u1it-*
U)c:cUiLUU)JU) U4UkOL1
T LcL i3t
nr;
For comparative purposes the analyses have been plotted in terms
of atomic Ca, Fe, and Mg (Fig. 6).
Amphibole from the more silica—rich
rocks tend to have higher Fe—Mg ratios than that from syenite and mon—
zonite.
Coexisting amphibole and biotite have similar Fe—Mg ratios,
but generally the Fe—Mg ratio in amphibole is slightly higher than
that in biotite.
:1.: 11
L :_rU
-UU)rL
I
tiIj
\_41
—
T1-
•L;:.
2UCLL1Lt
LyU
[U(
L
SL EE
U)) i-iIi--:
C.U:;Uç.
ULU)
r;
U)
1JQZtU
r
21
1tyu2T':u
1i iv-
2
)
12
çtt:. Ii(:.3U)
UT.LUL
I [U)UU)IU
—e
r-.r
-
cn
Ca 20 Fe 80 Mg 0
Ca
[U-ti
0
U
Composition
of amphibole from the Wolf River
ct;:-
(Symbols listed in Table 1)
LU J
-[& L {Ct
t
LY';
k LUT1
u:
batholith.
3Tft1: a: PUETt
U
6.
Ca 20 Fe 50 Mg 30
c
I
Figure
uc
Ca 50 Fe 50 Mg
flhc
�22
41-3'5'
The (13]
hastingsitic hornblende in
Wolf River batholith is closely
'57 the
501, ;-,-.
05(17'] i
5751'.
similar in chemical
composition
to
ferrohastingsite
i'7135145: 7(17:5175 1(3
41.315155555:35. from
55/57 Finnish
'4530-5353/ rapakivi
'ç',7./512t*z
described
:.o'/ Vorma
UVL(1."', and
51,551 (1969).
415375513i1 by Simonen
301137
17
'i
Olivine,
Anhydrous mafic
minerals.
1114 '(4-414213
4144 (317(3 clinopyroxene,
[0 57(I5'5513.'OU/L I orthopyroxene,
7"/3"55:../'13 /i5775;
amphibole,
and
biotite
occur
in
the
Peshtigo
10415117513
sos 7 '5411' (151354- '13(7 .511(1, :4135(07 monzonite
4'55 trachyandesite,
57,03 (I': and
3/15113/3
and
where
generally surrounded
pyroxene
amphibole,
.3775504 olivine
':7753 51/I is
04', 5(15% .5'
.13/
-'13557/415,0 by
3041375 or
35111
(1't5( hiIS
21:
Electron
probe
analyses
have
only
been
completed
pyroxene, by
amphibole.
0
ci:5/43(l'(; : 75/453-[5' 345-51.
3173
13221/ 53:2.3 441310 13553 (15(0' 13'(1.53
Fa
for olivine
one specimen,
yielding
an
iron—rich
composition
5413
L( from
115(11 01/101,
5
T31—5(1'
5 of
,,5(
L'•lk'L21•
1321:ss
However,
it
is
evident
from
optical
properties
that
olivine
92.2
toi1, 92.8.
'V
'27' -7.
7.30751
(17 4(s-t
'IrlO,37 4101'S/D
130410 57
iron—rich
from
and
pyroxenes as
well,
will prove
to be
3:/3( 'sojs-ss.17:
•/k•[ other
354:.': specimens,
sssur..
57trs
#n
5:3
3
(1170,
'241.
545(5(1.14
when analyzed
114(1' by
'5717051 probe.
5
:32 electron
4'7'',"
''/51,
s
C
17(3
'1
'2
3
C
Similar
olivine from green and gray varieties of Finnish
55157:414, iron—rich
5C4(11--'13t1[l53k :(11[/ 35 (15[ 5041's 1551312155 4(2.4151(1: 41 353544
rapakivi
have
Simonen
513
-(1553 been
1/5(41 described
S1531E (1961).
414155555' by
1 416'
:3.4
s
The Wolf
by
Alkali feldspar.
441 4 River
55541. batholith
('55557 is characterized
"413 1.5J:5 çsrxs13
41
1::T-1;:4;
perthitic
hypersolvus
S and
[:5113 quartz
55 which pink,
5ft/1(A554 granite
(:1113
54541 monzonite,
(I5,ic3/13.s in
21c:2 3/515
of perthitic
alkali feldspar
predominant
mineral. A variety
41
5L-/k 35 is
47 the
s-s
:/:4513cc5C513r-1'. js:its13ci
.2- LI #;T13L'
patch
as
textures are
including
sss exhibited,
2147TI41 vein, and
41 tssis:21 perthites,
415 film,
qLCS2 433541 i?t1
In
general,
alkali
feldspar
in
granite
well
7113(1 as
41 combinations
31535 51:13 55i 5/I of
13 these.
55557
1755
:/)
contains
larger
amounts
of
extensively
313125 5'11133
a331431 L4/I(V
5'. perthite and
413 more
i:/133
'3515 fl5.(1çi5 developed
5:4.: 553I grid
r.'t:.21
twinning
does alkali feldspar
monzonite.
15134141 5(541135/4
35 quartz
13t41' in
/i71i21T/5I than
/415.13(14 311r:riy'(AL
-5
513-
'
',s5.
-
-
'13
21
i-tI— L
from
only
To date,
feldspar
''1-l21 alkali
41
'L5 /113 has
13131 been
54135 examined
41 detail
414335
13,
ttXS/
135531(5 in
Hager
feldspar
four units,
including
Belongia granite, Hager rhyolite,
—
141
"
'F
study of
porphyry, and
River granite
:. 45 Wolf
V s:s X-ray
"2112141/
11r/'
s-41s.41 and quartz
1v-: 141:15 s•
sJszC2 monzonite.
and
Stewart
nine specimens, utilizing
the method described
by Wright
J
—1
(IL _5
4
1155. 53
feldspar
(1968), reveals
that
the
host
portion
of
peithitic
alkali
41(1
41- 21 C5oiLL
53 Th7 st;-(:yssC 51415 312fl 5' in
314
these
13241 units
53P1 consists
51551335 of
27 maximum
i55(7'15( microcline
AYA11321 5c with
4>:• compositions ofr Or 99
22
to
that yielded values of Or 95 and
(1 100,
... except for
(13/ two
5:/k specimens
443 97.
7
(155(215 71!3 t35735 s21 13' T35V3..•;
s'
—
13
i5/
1
'1
t
11
I
tt5tft5
21
. 2©
samples and
Perthitic
3•-. 54.55 alkali:- feldspar
12 -S1i; was hand picked
L,. 5(3 four
5Tht%t TiAS
Tu5
sA:cTs from
for K, Na,
analyzed by means of
atomic
absorption
spectrophotometer
: "55
;5
The
and Ca.
-m bulk compositions of
s perthite obtained
lfl this fashion are
-pITASISS in
Or
83,
77,
76,
and
72
(Fig.
7).
3Vi
0/
54 :t32'}3
444J
?.:1;4
sits
.
f4; tt5554
ir
.
Orthoclase,
and
feldspar
with intermediate
/55k Y
(:tV alkali
212,713
2T5
A7(5751L2. microcline,
rapakivi (Vorma,
structural states have
been described
from Finnish
0'
21
3.1C355/
i12121:'.:: VJUSC::..;
from
the Wolf River
1971), but
has not
Vt
1
557 yet
ILAA4 1$
15
i55J orthoclase
55 been
V353(A identified
However, alkali feldspar from
batholith.
&_,. only the more silica—rich
1[T
JV•%
°5JL5
lithologic
units has been
date,
and orthoclase,
:35 2154.
jtes•. examined
.rr((!;:p to
(1:1.
ic
çi5 if present,
would probably
::2 occur in
C7 units
55 the
51; Waupaca quartz monzonite
SCCCL such as
21
(wiborgite) and
Peshtigo
monzonite
(tirilite).
(V
c1n/k1fl:ri
t11
Li
3i.A3
L
21.
s
/lIAA'(
5T.ZLk
Plagioclase in
Plagioclase.
57 the
•54 batholith
1 is relatively sodic,
,5
.y.T:5-%
i:s7fl:21
ranging
in
composition
from
sodic
andesine
to
£. albite (Table 4),
4.5 r:iç
Li as
215
Within each
determined by universal stage measurements.
L lithologic
Iw1
i1
composition
on
the order of
unit
T
4•'r::; is a3 variation
tWt.:-J/kc, in plagioclase
;irv' there
L2uiytL
and
phenocrysts
are
consistently
more
calcic
anorthite,
5 to 15 mol %
2
COAC
cicvJr.
Act21
Slight
normal
zoning
of
phenocrysts
than
1/k associated matrix grains.
:.2Tzoning has2'Ttcti7
only
occurs in allr units, but
rL4 oscillatory
21t :L
o[1t been observed in
the Red River porphyritic quartz monzonite.
;:V"CW1
—
I
fl
ncrla
t
ci
qiz'i
I
L
L
Cz
lA:
irç
�'
ti
iTii11Zi.L7ci zoned
iiii ;;:c)jirc1i4
Li
-LnLzr4 '[:J4ciiLLN
cores.
roundedzUriU
enclosing
overgrowths
subhedral o-c
to euhedral of
1c1;rtJ
11 'I'7
consisting
malacon the is Zircon
1940),
others,
and
(Tyler,
variety
iiff. cJ.1Ir-çci7iJ2.
'
Yi'TTTLiC also
I,ccI3 is
ix mineral,
accessory
granites.
rapakivi Finnish the in common
btWci
'V :VtFTi. J&cj
L©Lithe
c€ij in
Ti tions
ubiquitous most the Lqc
Fluorite,
batholith.
River Wolf
cr,'-j are
I
TV'' ILt apatite, rutile,
iT
combinavarious
in
present
sphene
and
allanite,
i:iiTitT?
magnetite, zircon,'t Fluorite,
minerals. Accessory
ILL I'
I
I
-
iriti1-:T TitIt •TV.
- cIs'.iii 3n'ri
•
ilmenite,
• ijh
.crc:ii ij'f
-
•
-
•
i'
iY'TiC4ii, rapakivi
LT 21ii 7..L.
texture.
of development
i:-- LCDi iic L
L'i
Li may plagioclase
flCtt1('7
the in role a •:iic
play
by
feldspar
alkali
replacement
of
ti mantles of growth
IL" IT pin
1ti1Cli1 c2
TSU.L
yi'2 related genetically
are
ii
that and
and perthite
[i -c&L:ii2-uc ic;Tj. 'i2 rLcI':PL 1
'ir.:Iic:2 that suggests observation
patch of formation
This
plagioclase.
•1Ti with continuous
rjii
i
niair:i: tiCi r'1ii2c
mantle the to similar compositionally
and
optically
it •2i'q!cLTL
7 •nplagioclase situation this In feldspar.
is
perthite 1'i1I,l1i
parch the in
i'1iiJC •"TitTJLi
P 'L1TDDL
alkali mantled of core the within occurs
commonly
perthitebT'LIL',i
Patch
•
Ti•c'i ic'iitIii
i-i? £L. 4L i-i'
"'-
---
ct--irp.
I
:C' iiii i:pci ciit tI'I
Lint L'f:CT that
Lt—ic
specimen.
1.7:
115d1I2iIi
in fr-iiL2LL'-I
phenocrysts iTiz;i'TL:c
plagioclase the of part sodic most the to
corresponds
9-iii77 specimen
J-'iHT77,tt
.97'i'27 any
L:' in
YM7-composition
iPtitiTci' 79a has TiTit7';iri7ii
that
plagioclase mantle
individual
'I17?
tT2TT c-cLLT1Ci t2ciiTL i: 17(7 979
ii fliclIiI but
Furthermore,
quartz
Waupaca
in
23
An
about
(wiborgite). monzonite
t2777 in
ri 7XL17Xf7I
-PCi 7'a has
.T 9 An
TIL( plagioclase
ri Ci' Li' Li
granite, Belongia the
about ofii 1iC7tJ.t7
composition
p174.9 exaniple,
'i Lc17?kFor unit. that
yn-. ; '1i
ULi 7-1bulk
:T1 the
7C1LJC.
mantle
of i-:pt
chemistry
reflects clase
IL:lJ: " ";(? lithologic
c;S14c:7 ''7'1799c117
'i2 a Within
l7t' IL IcLY'9LL477C the
'i
given
plagio—
mantle of9 composition
unit 9'i:L'L79''7iT
217
1717'Y
it2iT:.
/7 ETi13
774
TCi
'
Table
in
listed
(Symbols
y-j(;9L 1);c ?1i1 i'
p17Li1'
C" granite
porphyry.
feldspar
Hager
and
i17Ot7
WC79
4C)Composition
UiTiIi'LiL4C'9
the
from nPcDtej
feldspar of
BelongiaiL',
14
—
Or
-'
•
'c
•
•
•:
-
Figure
1.
'
•
Ab
23
�24
Table
plagioclase
from the
Composition
Coepoiition otofpi.agiocJ
aee .Cooii
the
1$
Wolf River
Rrvoo batholith
•
-.
iThcC ielc:oi.r P°l°WW
i
.-—-•
=
=_
-
-
-
j
E.oiIetdt9
3e-J.oo1oI1&.
- =--•=-r••••=
—
—
T:T'.l
=
.LdOt}cJ
P•:loer
ra,mto 1uoI1.
çrot?1 IrDroo.,Io
=
-
jFzt_ttJfl 1j Ij
=
=
I
L
0
10
30
20
)ThL
rnol %
•R•:riT. i±oro
?orpIh..vrLh14
Or:tIThflTO
40
Anorthite
or larto graln
tetrtt gfl1O
Phenocrysts
-oiemoero1:e or large grains
Matrix grains
4
�:33114
.191'
1.
113113
:1,1c:,tL.:1111 111 131114 773.1-31 31 2.21437, 33J, 'in
1171' 1313;.:
13..$1133.9: cI7111.4, '1471 :141147.313351 155 u7--T17 71
311- 131 c31311414;lc 053.1721173:33'.- -17- 147112.3:14 1111111 14.137- :1133371317-7-353,3
2.
A foliated, gradational zone about six inches thick occurs between
the Hager rhyolite and feldspar porphyry.
The feldspar porphyry
is believed to represent a border phase of the rhyolite.
3.
Dikes of Red River porphyritic quartz monzonite intrude the Wolf
River quartz monzinite at several localities along the Wolf River.
4.
The contact between the Wolf River quartz monzonite and Belongia
granite is inferred to be gradational, because of the change in
lithologic and mineralogic character displayed by the Wolf River
quartz monzonite in proximity to the Belongia granite, as summarized previously.
:0:3f3
32373 7 4113:
tT21
2141.1211111
'11 1T1113-;'l: 31,li%1'JC5
13314
ff:
7-111
14331
1114'.
:.,
11
2313111
2:ThtrvlIl21l;
111
1
14117-
2111 07 111413-21141113 13
12211-171i1
3111L%;.21141
17','1131113 721
1111137-117227.
3.311112113
121
11::7c3311::6:ar
T21-1313
313.1 0111L'0'2 14l,11131113
11
7-121
Ilt.131 l 41 ,L
I:
121.31
:1t7
14:1'
'131151: 4'15l9 11-31 14 ::14'.13721.: 1314 in
3;. 7-2212-1733 13,cll':i111 .-cin7- 72133111; :1911113313 1:11-7-3111 1117-
-Lin- 71 7-' 1T. 31(4
3117
5.3113-1433)
132-143,1131
311-11L'71
111?
2'l
'11 17-215313; T143T1:
12111111:1,124
'1: 7-14.
27-'
:1:.%331323 cIt
3147-115 1414-l31lj 31 7121114141321 CC
1114
-lt*3(313;147 114:;:;t11. I,11& 247 c-23'7-L .317-371 23-4
1313 :312351 71.11 114.11143715 çç7-1 1:131733: 133 24
11-131:1:17-
Peshtigo monzonite and trachyandesite have been intruded by dikes
of Belongia granite at High Falls reservoir on the Peshtigo River
and on the Oconto River near Mountain.
cr;: 17 213:. 17137-
-c112.711"1:lI
311;
1-::1:1113:14
:1:17-:
Internal contacts of the batholith. Contacts between different
lithologic units within the batholith have been found so far in only
a few places, with the following relations:
514
1211 3-13371
511 22.21 31 '3111-114:;
113113
4112:-)
'111111T747-'1117
.C:i'1V731141
3114,
1-33-13.2131157-211
211133.71131
ii'
,l
31
1
71:4
14:3:7-11:
3)11311
14Ll21:21:
11
7
-1:1451:3 p111c314Ii
!114
'7-33l4C-247--
.tl2A1%_1l:1111434,331:r:.
The second feature of importance is found at the northeastern
end of the batholith, where the Belongia granite, Hager rhyolite,
Hager feldspar porphyry, and Peshtigo monzonite are arranged in an
arcuate pattern, perhaps reflecting their emplacement in a ring
complex.
Such an interpretation is supported by the distinctly por—
phyritic textures and high—level characteristics of the lithologic
units involved.
In addition, metasedimentary rocks that occur in the
postulated ring complex dip steeply and have strikes that are concordant to the arcuate arrangement of the enclosing igneous rocks. (Ring
structures occurring in rocks of similar age occur in the Wausau area,
N
LaBerge and-Myers, this guidebook.)
-
_
1
3311 5 133 2111c 21.7-. 11 1-c.31C0
p213
1147311.3111
1111.
113157-' s. inii 21 7:33
111411.
1141111
2*:2i7-.11r1437
3;3133311.1'311'3
'131111211
141,1233 :
31-7 117;:tl%-:33 43173
:21
2.
33143:'
33114111214-1'
25137.133' 2331
'Cl,clL1:
y11c1T1.#c51rb-:1
721-
43-'11'': :7-: 'r :11:1211:
.;-2111'13133:1331a1 112-:
11-33112i
1414 3;
11
1:.t1;14%112'J
111:31521
1(7-,.73,1117 C1413%
77-
''11:1113,3131n
1121 73 :11: 33:; L3 ..1'33'&43 7- 6314331' 7-913 21331341311,. 91432142
0-7110 .13:-i31
11:c:7115141131
J1414-7-33 112 1731;
'
3111111117-.: '11 'cii 41'1u1421'cIci1s '
13,3373.213 1111:321:14
4
S'1:1:31: 7-311 1111-c',3$:13
41'l : r1r1n713:cj2.21z1131o
7'f"'l31r: 13; 7141311 3 73,212113
:3:-' -311111
17124:1114
l 1414113112;
127 1r::11)31,2, .3131') :
13
31; 7321114 173214
411333 114733,1314 1'.71-
17
13C.:'1-11
34
221111.11;
3737-1117213
214
2-1314
41731:12
141 1314.427-
1131131537 7133!.'131
2113111)511
14441111131414 :7-11:1:; 3123',
.111723113 433'1J1!L33: 111
31,7 ,C17111'3.
'77-4-141 ,141.31413',
121 321'1'137- 54111117111 ':3117-rI-Ic' 11417
137-3111111 1131:'113;1114
1214
7-3133141113317 1:1s:'t 113211 1': 1 14172 .71:13117 7-1151
. '313j% a.T13121' 1'373 212 14111311111 P*1 '$131111414
tIlt II, in 1131,k'117t I
1u211317-133'7-,L3 31"7 4;,311.ff.1'3;L :47- 7; 1131 _12412111 14-14L311 -371i3121 37
:-'lljl 41i3 331347 4131175'7"l37 4." 1111I1,.1 132113 '11413233231 322 33,13 11.11"
Although structural studies of the batholith are still in progress,
In
two major features are readily apparent from the map (Fig. 1).
the south—central portion of the batholith, the distribution of the
Waupaca, Red River, and Wolf River quartz monzonites defines a major
ENE trend that was previously recognized on a more local scale by
Borst (1958).
The contact between gneiss and Waupaca quartz monzonite
probably represents the southern margin of the batholith.
1
.144:15111-53111.
1,c3::. ::( ::'
sIll
-12 _'&11
14
3-31
14117
14
2311
c—,
,&31
'17
r
113147-
'1
1 " '113
1
'77 i11'5L147.
1121lC7-.'1,11-'331"t' 3313,'
lf%-:rl,©1r,
;
,' 7-24221-2 .51411
3;':'
Many of the granitic rocks in the batholith are
Structure.
massive, but within some units, in dikes, and near contacts, feldspar
phcnocrysts may have a planar or linear orientation, presumably due
Shearing is confined to well defined zones along
to magmatic flow.
Some of this
the eastern and western borders of the batholith.
emplacement
of
shearing may be related to
the batholith, but some may
be later than, and unrelated to, emplacement of the batholith (LaBerge,
field trip locality 8, this guidebook).
11t13217-1374137 14;1
312-23:135333
'31,17-3r;37; '437
111'7,
'F;.,;,
314:213313
321:
t'%'7-711117- "11
5151113
.14213
1331
73121713
31111-7
'c'- :113tT,)
—$
LH11.34
3312
13312 37147314113 15:31
5:721-41411137
13
111
:12375
742
14
-32:
.
31143
'.1311111": 11
31:111131*31111 07
5114.11113.lI113111414J21
33111
31r12115
:14:;; 7114
3111343
1.11.1 117,1
.1
r33.1.1t...23 31:;
2.112%:.
133'
12Cr,:
53' 31213,.: 32311
111
141:3191111I:111 11111111 44 11117-1137114
21'
11)51711
7-7137131:11111. 111.323-1 ''i'11 113,:53.3111:'.. 3313
-33-14;:
174311114'
111113 14 7,141:c7, 711'433311 '3'
.7.
:1:131116
L111'T131411-31 '?l51i'11l1114'3.in1 c.:1c1:,
14113111,231:
3113113
- 11317-17-1
.3:1: '1:1
31141s317'll 7
'1541113
14411
111
STRUCTURE AND CONTACT RELATIONS OF THE BATI-{OLITH
711,71
17,
:7-171.1 1113
31747-11111737- ,1741 '077 3J1 l31tTl'7- III1I 111
37:
25
cia
�26
ocarI o 070t2 of Lt bab- J! tio m::rL1.i,et: pt of
In the northeastern part of
External contacts of the batholith.
::.c Lcowl a
the Belongia
coo ac:0 a±cr•t
several
well
exposed
contacts
where tioa
:ttJ
0 .00
afoot a are
the
there
0 t batholith
tLtkLc.
U1t- tLOtOO.OtX0000
metasedimen—OO0 09L2 2'; and
0 LU0Z ptoP
7200 intrude metavolcanic
granite and
porphyry
coo Hager feldspar
to
2
1o!flal;1;
act
ri):-'
sharp
and
discordant,
and
In all cases the contacts are
tary rocks.
000t'0'0000
present
in
the
intrusive
rocks.
ot oc3anCc1o
chilled oar0ta
margins are
commonly 7t000ff't
cotlttO
: 0.11 oa iJ :
fl :ia fotrof ca rco
010.0
00. the
assemblages,
much of
&c
0
L'0rl0
WOO,
basis0±
oftEa000Ot
textures
and mineral
'o1.00o
ocoka
cat ha
intrusion
of
the
granitic
rocks
can
be
CO
tjo
ft
rW
'rI
'o
tooof bya
contact
metamorphism induced
o-c,tatt totorcoçO
:'f
too
iftiacotacy
However,
the
discovery
of
012:01
footca
-.
facies.
fob
:01-i hornblende
WC coolo ltoot',i:
assigned
hornfelS
to' the
f000ti to
;a.bcLOt00
201
1.0=2010001
cto
-oct
o
assemblage,
quartz_biOtite_mUsC0vitePota5
.bbo co01t1
the lcTos;'WOtlf
apparently stable
tOo
0001
;:ota2Jat410'L;;,0 rock
pelitic
a; specimen
01 aco'onof
of ;a
L 0200 metasedimentary
feldspar_afldalUsite,
in a
folIo-pat
•cLJ oootC La
0010 01W-.
have
been
the
pyroxene
hornfels
facies
may
of
flo
ooo.u;002sO
010it:0'
.co-.oo
O07
suggestsfathat
conditions
0.77010
foot .o.o'01It
f.o:a of
roT
at
07007
r:.;r
Ic
tO-a
•ocoi'Occ
0
in
the
contact
Scapolite
to
,:cf: :; 01 is relatively abundant
f cro]'L.
attained
01. locally.
7114
i-ccbatholith.
Ltfocf ttI;
2W the
0:; I.:oo'000,1%010102W:;at:tr-0 of
metamorphic
rocks,21012W
attesting
the halogen—rich nature
t tCC00,
a-ac to
0.0010:
On the
fiLo
Co
1
2
CONCLUS IONS
of
cotta cot
0 oafaIltat000
been fo
to point
out1;the
existence of
toot oat
till paper
The7';.i
purpose of this
has Loot
7t
ct
00201t0
tic
and
to
describe
its
Woo:
'0.0
zn:1
northeastern
:02LI10Lmassif
701 :.:Lincart
OFt4 01W- WisconSin
,
a
major rapakivi
c ;aojo-r
2W
Ot 001711
o01o-7rI o in
It
seems appropriate,
101
characteristics.
crcrcI.o?tZ
;-ofmineralOgic
iLt 000ta.0200
petrologic and
ffn
batho—
hypothesis
for
the
origin
of
this
100
fLo
001
Carl
of
r2.cifaC-0'±
i-- offer
-141401NJ 01'
conclusion,
to
o±'tr- aa working
:1cn.cl aol
ct: frfuture
2Woo studies.
c';tai i to,
direction
of
too-loot
tO
0712W
too
tOo
lith
and
to
outline
the
blob Ci I
must talCi
take
7 r7' t-atLo'I
I ;t coot
of 0017
the Wolf
batholith
of
'oi.I River
too- scheme
14-iY01W;
Oc 0origin
cot:
Any
forIcrthe
features:
11170
'cc LC11/
into
accounttOo
the toOl
following
!.
1)
1)
2)
bulk c.:
of
'L 7-Abc
constitute
the
01,1 granite
f 010Ci1 0010
05t::
1 ocota 11'
1200-00 ,0 and
hypersolvUS
monzonite
oct quartz
the batholith,
in0027102W
nature,
7. c!'ZCP-IL ot
10 epizonal
the
batholith is
io :oo,1vobtti;
a'•ooa tOO
batholith
the
tOo ta:Tho)
' oft plot
itt-ct near
;!!rto. of
oti the
granitiC
members
otOfl7t
a,:ft
A
the
compositions of
00000
displaced
01 normative
. 4:Q—Ab--Or,
=001o1- but
tot toO
are
Ic, terms
too: a of
granite
minimum in
t-a;ott•o o!oLo!L!lilr
.0,0020 7-c
toward
Or,
:0111 0 t'ob-t7fli
feldspar by
cI' alkali
andratreplacement
to 002202 of
fcc::- to is
-cct0'-011.
25- 012
c;,00c of.
there
extensive
mantling
'P.',
oligoclase,
aflbote
to
-clILIfot
000.
composition from albite to
It ooocol01050I0
plagioclase 017,01200
ranging in
respect
02W010t oa_with
:2 -7; talc o:t to
to
be interstitial
:ik.ill020 00010)100hydrous
tend to co
001010012 mafic
177,t-tc minerals
IL!
quartz and
feldspar, and
on fo1tIo0Y
007012003
of Ltz:0
biotite
;' I cthe
expense
O1717'AP growth
noCiCi -A
.11 at
Oil act.a:0101
apparent late-stage
there
Ut:---: is
to rn-i
of alkali
OOILO17LIO feldspar.
oil.
'
3)
4)
-fl
,fl
5)
P
6)
t'rocoriginated from
laothcJ,Of:2 may
coo hoc:
Wolf?:t
River
havecooL1oL0-lC1
or '7c'o
cOt batholith
±00
oogo.ot that
tcti'f the
We suggest
H20,
initially undersaturated with
:n çMtc ct0.0 0-C parent
jJOi'tct magma,
01101 monzonitiC
a
0 pquartz
taboO 0
crustal material.
.1700,12170
700=-0 i.atcaig 0117-octalpartial
melting
of00pre_existiflg
-70l derived
:'AOSd 00
.21t
that was
by J0L'."I1OLJ.
batholith
precludes
I
(87Sr/86Sr)0 in
the
01
1002
An average
of 0.705 for
0100 value
Cii origin
00 000
1
0
i20tat.i
1410 with an
crust
but
is
compatible
lOt
:lcI1tlt
5 01, from
focat older
r hO 70
lOiittl,C 0'
derivation
granitiC
ott:
50.071012
:':-OcOJOi
volcanic
and plutonic
* atatmood°
basic 0701
and intermediate
lifor: .Ci,O.t!:
(10 0001-0
)77 older
from an
terrain of
01001
--i't
For
example,
partial
Nil'
eo0J-c.
±:folotllIfl.
northeastern
Wisconsin.
110010.
00aa in
It ;1.Ot000000717'O
material,
as09that
:oat01.
01 such
1090071
101140 (mean
020-0 granite
or :7'10!L0t)
Hoskin Lake
2,tLhc,000170Lc
co,ast-zmonzonite
0110 -01 10 01
melting
of Athelstane
quartz
trIo IJI
cci.
LII). years
141110
,, million
rIit
a
c:oA
10,
(87Sr/SGSr)0,
0.7021)
after
a
period
of
350
, ,01"
0
Rb/Sr, 2.5;
55,
ftC.
ratio of
'OtCf.r 001701
of 0.714.
strontium
01!.initial
tot I 01 0,0-otti
.710 isotope
:11 07 an
would
produce aa :7112
rock with
nIl 7 pt-cl'017'
oh-ct
oortaltt an abunMo northeastern
'ocotfcae$°'
Wisconsin!, contains
c'ao-::aiia in
'to: terrain
However, the
toto older
fb-o'o-000T1,
chemically
equivalent
oI-::amtsooi
:01701
17th.
intermediate
volcanic
rocks
and
dance of
-c-I basic
La boo tocO.0'lr0k'5.CL000 0100- tcfit
material
would
01015
tx'IlCta
00-0
'i'col
.1 be
of :2W,'o
Rb/Sr for
b-c this crustal
0101values
01200 os:
plutonic
rocks,
01010 00 and
o'tcro
f
and Ot!0OI0
others, 1970).
01171
ETC.Oc
01C'I I Hart,
and
1967;
c.'.'21020:
00.11 others,
ACt-0 17fl0fl
'jless
:C
than
tOol 2.5t (Peterman,
OIL: 77
much
irtta2.Hy oa1t1J.'i toat
I'll
3
,i
I
I
-
1702,
�27
i
the mean value of Rb/Sr were 0.6 or less in such crustal material,
partial fusion after a period of 350 million years would yield a rock
with an initial strontium isotope ratio like that in the Wolf River
j
.4c.
icc
I[
L1
ctr
ccl
I
L-tn ic
IL
cc1
I
N
L.
I
cc'
Ii
Il')
ci
I
1111
1
1y
''
cccc
flycSc
r
cccc
1
I
batholith.
c" Lh1
If
nYc
cc.
Future investigation of the Wolf River batholith will include:
'LCcIP.2Fc
c1cS1cc
ccc
O©_LJ1L=iccc cic7IccnLIr
-r9
F) Wc1. ccZcc4cc
additional mineralogical studies that should enable us to
evaluate intensive parameters, such as T, Total' H20
O2
TNcEcicccTcpcc
lI
--
1j
In
cc1
F,
and
tc.n-iccFcIcL-cc
and
detailed chemical studies of major, minor, and trace element
contents in the batholith that should provide constraints on
the mode of origin of this rapakivi massif.
;cci;c;iT1zi yi iic
-c
*cLcr cccL-- ccjl cYtc icicc
cci
cIcccc1
ccc
i:q,:
cc 4iJfliL
1ELI
c'7qI'
cP4©IF:
cj
j:-crc2
Lc1cLc
2)
Lptccc
1)
�28
REFERENCES
of Big
Falls,
':-pc:c9.c. cC
W7 Ccl
2424.1958,
12 The Granites
Borst, R.I.,
!lm/.c,,2 9.7 4Wisconsin,
•lcLc Madison.
Univ.
Wisconsin:
12,2. Thesis,
M.S.
:)
24. Wisconsin:
21cm granites of
from the
:2 c14c4w' -cm-22
".2. ir242c2
Elders,
\V.A.,
1968,
Mantled feldapars
24 .c
11 cmLc::::
2-i 37—49.
2c2- V.- 76, p.
Jour. Geol.,
-.
,1'.c-citccPtIL'$ of
:4 perthite, p. 55—70 in
c-:L. :24cc.) 7: significance
12.4. 1953, Petrogenic
2iCi] R.M.,
Gates,
cl plagioclase:
c.cm42'cHcrelationships
re ccm2L. cc-; of
2c1.cc:i[ ppetrogenic
.241-; Selected
:r-nLcmcm (ed.)
R.C. Emmons
20...
?9'2l 52.
dC
:ciirr0 Mem.
Geol. Soc.
Ccc Amer.
-
"•
dL'AElectron
.c,2:t.c',
2;; -cd: ij,ctc-:
using the
,E-cm-L analysis
J.F.,
iccmcmr.1..cS
Qi21968,
.24. Rock
Gulson, B.L. and Lovering,
LJ
2)i27
C2 cm
p. 119—122.
Geochim. et
Cosmochim. Acta, v. 32,
>22121:2:"
Probe:
2.
a
volcanic rocks:
ccm2cmcmcmcULcrC.'c2Cc:2r
'cct an modern
.24'::;4 1970,
cl:2- 2:Ancient
cm-C. others,
Hart, S.R.,
52 and
Lett., v. 10, p. 17—28.
Earti. Plan. Sc
trace element model:
.:..:j2I:Lt(1y4.'24 .c.:flcwi.!cJ-r
>2.7cJ..;1.-
c lower
I
ccc' -2:24 :ccIcm-d
AnorthositeS and
magmas from the
;'-5. rapakivi,
:124. H'C5
Kranck, E.H.,
1968, k:'uct2'c72'.9d
Rcc..'.:dc:.
:244.7
Origin of anorthosite and
7cccmcccc (ed.)
'7244 Isachsen
crust, p. 93—98 :1:':
inY.W.
18.
C':--C
i24c
-l12c
Univ.
State
New
York,
Mem.
11:
cm
.fl.,i;; cC :ncy.r:ccd.t:
cc:2cc
related rocks:
and subcalciieroUS
ccm:cm 224,
.i'cm;:). calciferoUS
cc
of analyzed
cm
dcit2I'i cC
Leake, B.E.,,lc:2?.
1968, A2. catalog
c22;'d, Paper 98.
Geol.
Soc.
Amer.,
Spec.
Ccci,
C..c..'t'r-.
amphiboles...
tR:i
-
2.
iidc.'\i
=
Si02 to
NaAlSi3O8 — Si02 and KA1S13O8 —.24224
..
'it> systems
Luth,
-c,. 1*22).
1969, The
..LniC, W.C.,
cc
betweenc H2O content,
p1-120, and Tota1
'
9
t1' the relationship
20 kb
and
267—A, p. 325—341.
12227
,24';
Amer.
Jour.
Sci.,
v.
in granitic magmas:
''
L
).21-''
.'
[
-
.-,i-cc'c:cCLcomposition
ccm,-:c,24tic'c and
ccC
>c2cccz chemical
relation
241'cL•c:-. between
2-cm
Nockolds, S.R., 1947, The
Amer.
Jour.
igneous
rocks:
!:-244r221
cuiT:1
cI
r4dL2lLkiLC2'c
:: the biotite micas of
'12922 in
paragefleSiS
c--'. 242,c.,
2422, p. 401—420.
-. 245,
Sci., v.
224
;u24c,
24':-24,1y
Mineral. 12
Mag.,
cc :2.t7'
'cmiTanalyses:
mJ.24cm
ccc.crcm'1' c; of granitic rock
'2:224 Mesonorms
Parsiow,
';y>2-di"- G.R., 1969,
2. 22).
37, p.
262—269.
c24-2424
v.
.
].'C'
>2:19 eugeosynclinal
Li some
5::>'>I: -: ratios in
...]:2447', 87Sr/86Sr
.2,'2i'9 1967,
2
Peterman,
and
others,
24±; )i9iy' Z.E.,
22::'::magma
24cc
dc)".
cd
bearing
on
the
origin
of granitic
tac
ic
Ccc'.:
424
cr24.> and
iriS their
sedimentary
92CiJ'P3i].2.24 rocks
.
:
4.21
2;
2,
p.
433—439.
2-cm24
Lett.,
V.
'4o
ccc' 2-Plan.
24:, Sc
24
rcmicc iCc belts:
':cmtc - Earth
in
24. orogenic
.,
lIlt.". .
iron biotite —
,cccmcmc2cmc'7,J1>
determination of'>d2
c;2)
Rutherford, M.S.,
1969, An experimental
2
L,
10,
1:,,.:,.
p. 381—408.
cccmcmcm.449
Jour.
Petrology,
V.
equilibria:
-jC-241feldspar
icm±:1;,c'''rhi:lcJ;"'
alkali
t'r,::24'124
4* 'cr22
its -9L'U'I'.7-1- rapakivi
the chemistry
of the
east Fennoscafldian
Cc ±2cc
d%2:c!:C'7 24
?:"'d On
Sahama, T.G., 1945,
2424
136,
p.
15—67.
J1'.2,.'L22d. v.
c;c":i Finlande,
24472, comm.
ccrcm geol.
>;
ciC24c: Bull.
graniteS
'ill,,
..
Savolahti,
Icr
ci.'::'':l, A.,
Finlande,
,
211'.,L ccl:.
2cm Finland:
AhvenistO
massif
Cc: 24
:c'dtcrd ;ccc
24.' in
1214 The
1956,
114, p. 1—96.
v.
c 174,
from rapakiVi
:2cc I'cmc:224;'
:7:
CL
Simonen, A., 1961, Olivine
2-I
SN.
.26. p. 371—376.
v. 196,
2424
Bull.
:.c"ir, geol.
FcC , comm.
'
FcrCHcC22
2411. •c2c,'
-. Finlande,
Bull.
comm. ccc"
geol.
I
�29
I
'J >? c
and Vorma, A., 1969, Amphibole and biotite from rapakivi:
Bull. comm. geol. Finlande, v. 238, p. 1—28.
cL
lEE
Simorten, A.,
cL
-
c
C,.71)ClfrTVEE5r
07
11)
1 ¶-c,c5 cwLc3 rTr.
1971, Alkali feldspars of the Wiborg rapakivi massif in
southeastern Finland: Bull. comm. geol. Finlande, v. 246,
LC::1).çY.I2.,
LlCC
I)2t:) cdwf:L
!J5LLLC7
caE:
I
II
1—72.
1flL
'1):
l_I ©ICLL
p.
cC7I7CCEEE L.tC[tcd5IC
Vorma, A.,
Wones, D.R., and Eugster, H.P., 1965, Stability of biotite:
Amer. Mineral., v. 50,
experiment, theory, and application:
1228—1272.
p.
I 7)EEI
diTcl.AlJ1l
CilCt51)cL
CLIEC d•dSl1)LCdi
C
CcC
1i 1Ih'
I &tEEEi;IEEIk'EL
I
L?1)
C?
7
3T57d cdi
Wright, T.L.,, and Stewart, D.B., 1968, X—ray and optical study of
alkali feldspar: Amer. Mineral., v. 53, p. 38—87.
51) LJiCcst rtld:;ditl
713:
lJIlTl-l
C
77&;J=d
c,C,
Cc-r.1:
.1
. c1
C .cc
c•
L7CllC;C.1)liJ :cT
df 13f0
�This page intentionally left blank
�51'4.i?'71 11113132.33 >'1"" >, LI?
3fl 331 24.141111 •1'1c
University of WiSCOflsln—Oshkosh
University of Wisconsin—Eu Claire
1,,'
'•,•i2.:327'7 324.3
of Geology,
of Geology,
4121733123 377.12113131 /:.
13>33-
'1
131
111)51 .17%:T :3:::
Department
Department
'3'
23
11411201111:
*
23411321113 0311 3313111413
**
Some of these problems are included as stops on this field trip.
Tentative interpretations of the geology of some of these areas are
presented below. However, we emphasize that the interpretations are
based almost entirely on field relations, with little petrographic work,
and almost no chemical or isotopic studies.
Therefore, the interpretations presented here may be subject to change as additional field
and laboratory studies are completed.
12143 3.'-
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In 1969 the W.G.N.H.S. initiated a program of regional mapping of
Approxithe Precambrian in Marathon County at a scale of 1:24,000.
mately twelve
minute quadrangles (about half of Marathon County)
have been mapped to date.
Progress reports and data maps of this work
have been placed on open file by the Survey (LaBerge 1969, 1971,
This field work has provided much new
LaBerge and Myers 1972, 1973).
data and has identified a number of problems in the area.
>3>31323
1)723, 2)23)2.. 1:0 115153 1131371
'(13212273 33273312,1251 310
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1131
1211)7
The only comprehensive account of the regional geology of north
central Wisconsin, including Marathon County was published by Weidman
He recognized many of the major aspects of the geology, although
(1907).
his work was mainly reconnaissance in nature.
The geology of the
Wausau—Wisconsin Rapids area was examined in 1917 to 1921 as part of a
land classification survey of the Wisconsin Geological and Natural
History Survey (W.G.N.H.S.). These data are on file in Madison. An
unpublished W.G.N.H.S. report by Enunons and Snyder (1944), and geo—
physical studies by Vickers (1956), Allingham and Bates (1961) and
Henderson, Tyson, and Page (1963) cover parts of Marathon County.
Selected aspects of the geology in cntral Wisconsin were presented
as the topics for field trips by Emmons (1953), LaBerge and Weis (1968)
Theses prepared at the 13W—Madison and
and Weis and LaBerge (1969).
at 13W—Milwaukee have also dealt with certain aspects of the geology.
Recent cooperative work by the U.S.G.S. and the W.G.N.H.S. to compile
the geological and geophysical data on the Precambrian of Wisconsin
was published by Dutton and Bradley (1970), and Dutton (1971) showed
some volcanic—sedimentary belts and sulfide occurrences in Wisconsin.
1', :133211211132
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The Wisconsin River Valley in central Wisconsin constitutes the
southernmost extent of the continuously exposed Canadian Shield.
Available radiometric ages indicate that these rocks are mainly of
late Middle Precambrian age (Dutton and Bradley, 1970, and Van Schmus,
this guidebook), yet the character of these rocks, their relationship
to one another and to Precambrian rocks of other parts of the Lake
Superior region has been largely unknown.
'1J',,'1)7"1:3710:
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311,3
INTRODUCT I ON
513121331.111
Ill'
Gene LaBerge* and Paul E. Myers**
[7.123
7,324.211311723 751'5
11711'
by
341321"
PRECAMBRIAN GEOLOGY OF MARATHON COUNTY
131131'.41, M7113.;31i11'.13..'131,1
711
31
�32
General Geology
.ici:'
dfl!, River
ifl Wolf
'fl'Y granite
Q the
ci;ii 'Cciatflt
TLcci
The Wausau region in
Marathon
County west of
ciici1
Thi. ci.cc3. and
c1 Tbv
flcifltThS11%t .;:d kci4 pfl;fl:twccrc
batholith is characterized
by a.t. northeast—trending
patchwork cci
of folded
hn :•a been
flEfla intruded
cci:
cicii which have
flE
tc. felsic volcanic
block
rocks
tid (?) maficci. to
bjiflcflci faulted
Ji
ci tI cifltLfl •.c.fl.Ec events.
aj:i1 deformational
)fii3citfl and
:cces]IflTh plutonic
and
:ccJ1 mylonitized during succeeding
1
iciZflL
ci
tJh
ciciri
(1)
gabbro—
-jC.,::Ycici
generalized
sequence:
:i:flLfl.:
The
plutonic
rocks
were
intruded
in
the
Tkci p
'o.ci1:
Li
cy:
i
t.?'•
.iwtc
tti•ci
i
(3)
quartz
monzonite,
flul.LCr
.2
anorthosite(?),
(2) diorite—quartz diorite,
fl
3fl
cirtflcj7cilci dia—
L- Eci
fiLciL by
The granite isv cut
ENE—trending
cci and (5) granite.
(4) syenites,
1flflk.3tci
CtTL.JH,fl
grcinit3
3S
ttit;
filotci
Some
granitic
intrusions,
such
as
the
Granite
Heights
granite,
cic.LIvfl rsTh1
ccie
base cijfl.flF
dikes.
tflL3Lt:
OLJLO
fci'
as
indicated
JL.t•C3JH•l
by
the
fact
that
it
has
.J
flfltflflflti
;icttIci b'S
evidently predate
this1flJ,:flfl-•
sequence,
t, i'h rcitz
,T-.clcirci.ci:-- plutons werefl
t5.s younger
:_ cicicicici
been
in
zones along which
some of the
flflOi. mylonitized
rfllLlbi.b
.fl-fl1 y'cii- the
tcici Granite
flOO for
O2flb'
0
cicir1i
:'u
-.
Peterman
(1970)
established
a
1600
m.y.
age
)Ci iflfrrijfl!
Pcit•JLLr ficib
intruded.
Ibiccis
TEtiui1'?
91L)3flJf
rcitrci
Thus,
these
ages
",cci'
i
Heights granite, and 1450
m.y. for the Wausau pluton.
Ccci
mci
ci
f0nt
ton:
ci!
Some
of
the
plutonic
units
are
citLotorat
0rt
,
!1acJ
ciiat
sm
are consistent with the field relations.
51'q'ci
::ii:
ouiiut'
cici.:
contaminated
and
fil
C'1.L'
i-iltcicij
cci
cocii-uicibci
intru.ve breccias; their contacts tend to be highly
ocicot—
cifluflt well—
0Th:,alflccontacts,
fiCaicitci, abundant,
a
Strongly discordant
cc zcfl:t
li-yl:
are cic:cic::L::
commonly mylonitized.
!i&tfluit..citciflfl
d1ci
fl'
cOcci21
,
ta,
t
1
ciJL
metamorphic
aibi- flflici of middle to high grade
SflXkCI absence
oriented
:cEfl ru 1:Jti, and
iflThtci' xenoliths,
ciplcccii- cucit.
icH crlitcc
epizonal emplacement.
cit 1Cm suggests
ci ':ci:
cu rafted xenoliths
wallrocks
except as
lower
nrccicicixcc:
ci
LJc e
in
a
broad
mylonite
NE and ENE—trending shear zones appear to converge
!c.flOcii'
L'C
a!
margin
to t1'c
cci::r.:M
ci of the Hogarty hornblende
oacacJ i-iL to
c:,.i1 parallel
zone rc'ar
near and
the cciatr:
western
1i.c.' bci2::JJoib)
granite (Wolf River
batholith).
:
±C
1
'c.
a- ciii -ra1-
gr:tttc
it:
ti:
!trily C
rJC '
1, flL3.
ccc
I
7u1]
tnni-c'- Rocks
L.ciC0
Volcanic
i-i-X'1 i'by shear
LvCL0.masses,
cifliF3 generally separated
boiccici2ci rccH4lfl
cic cci as large
Volcanic
rocks occur
03JLi
i-ira
taaflTciLci
ic
air
iitLl '1 Ti ci. and
'ci
accici are basaltic to rhyolitic
The
rocks
Ii-'fl volcanic
'
cicici.or fihicirci,
20rci3 and/or
zones
plutons.
nub.
ra1c7-iciciLiC.
and fragmental
ircici- include
crc. Ii-ir',pillowed,
r:t Iciccic,,massive,
ccci
TLs
The rabta
mafic'7Cc:
volcanics
trachytic.
'ccc. less
1 i-nc.
ci' Oi-ILCiLi are
'ticifldii-,. 3fr, volcanics
The intermediate
ctv.cc cci. iThi-i
i-ccitt
acicicic
1 i-Oct sediments.
unitscat
and
associated
cc
,uI
ci'.
Ui-i-i-, the "basaltic" varieties.
rncty rEutflflTa1t
chloritic
and cucac
more commonly
fragmental than
fl1
ii'CLbiat
ti-cc Lob
tuffOs,
s, welded
cclcioci'.tcifl include
:CcLcsC 0 volcanics
;"i-riC cti- 0, felsic
The predominantly
,,j, pyroclastic,
cici'.J'Ll.fl
•iThacc
Ttr:
nit
bbas
Eastt of the
lJcc':.fl-'
tuffs,
laharscci,23.cfl'Oitu'fl
and associated volcaniclastic sediments.
irtilu, 'k,-:rc
3' seg00:
ci'fluicilfl
the volcanic
i-b. cio
-atciw ti- contact)
in-c western.c batholith
'rC,u nrciu: the
Rb."c'ci (nearer
Wisconsin
- £ciOci'uci 1fi1. River
'r''cflci,fl
ciuci-il
cdaiciii-cLbycolithologic
Li'bt',j ci
trends and
i-fl '1evidenced
chicir,t i-c'
ci
i-na.. .ti-2 have
ments
0
ai-i northeasterly
strike as
:cMa:cc
''4i
Land Ci1,.itOciiacci
Classification
Maps).
Ii. b.- tacit
c baciu'FlCtp
WL.L1:uC
cci on
magnetic "lines"
township
maps (W.G.N.H.S.
1
-? icni:J-i-bc.-:'Ly.
No
7i-• 000n'.River
northwesterly. 1-4:
b1ticO" trend
cci'fl'ocJ is more
tort: their
tI—i- Wisconsin
West of the
i—cd,
bcthe
'to volcanics
cC L:i1, Tci'c
nabbeen
iranrecognized.
;ncntacd,
stratigraphic 1Cm
base to
has yet
1
ci'
—
-
.1'
circcitici' a.
:1
''" i'
"'
'1
'lJrcrS' i-H
ofcc1oan:o
volcanic rocks
'Ca-ti-r :0the
cnscit'tcc:u
Hi cict
It
notycit
yettcz:'cic
known whether
various "blocks"
at is
a'
aoccci-n.ir.
once—continuous
sequence
(a
volcanic—
:Lci,cccic'
cnan.=c0'fl
cci-'c.
rf
are
segments of a
ic'.adt
at
i-t
represent
different
1u000fl.iJciTit&i-Y
'Jr
iTciJ
to
sedimentary
"greenstone"
belt)
or
whether
they
incicluci': occc.md1c'a'ci
ni Ccc
at work
-T,ccic-ttccc"i,5.; c, from
ci-'i-ci-'
The answer
may3-H
not',te
be forthcoming
field
i--i-C 0 ci'. "Ce
i-fl tt't.ciLc episodes.
volcanic
;J'cn'a;rtfi
dismembered
CLaim.alone.
licor.'c:
it:, Rocks
Plutonic
cit plutonic
c.
(Stop
8) 'P11:
The largest mass
of
•tt-Lcip fl,•'
:Hjifluflfl "ti-'
flood Li-iCc Cflrcc1.;;ci1
Hogarty
Hornblende
Granite:
i'nCi
anCrLitt
ciacoorcic
acinulaL
granite"
to
which
underlies
eastern
itiaçc:
s
rccjci'ritiLe:rCc
tb.: "Hogarty hornblende
rocks cciatn;sci
mapped isc the
'-cob..':
'r
t.o
rnir
Tigerton
u-c•.u
ciciZat
lucc'ni-mOi-This
pluton
probably
extends
eastward
to
the
'21:., a pLat -ci'
rCca:.or
Marathon Cci;:oty
County.
'fltci 'ti-i-cc.
to 'Ii'2H.nlcap9
lihologically
coLic ccitc.a''
indistinguishable
Cc.: act,
'i-r'ci- County,
Anorthosite
mass in Shawano
is
cc:a'r ibrc -H
:c&at.
quartz
monzonite
(Medaris,
M
uJ.[b.'mr
oiccrba
cicrcicin.L:1-r
ci ci Wolf River
ott the
i-i'm ractc.' part
oar-b of
from
the coarser
2 '-cii ticiac:'oj
Itti-ccdla.
locally
intrudes
volcanic
cub
:11001
L:y
flTJcLi-0CL14i-?
Ortu ci guidebook), and
b..' .["fi,, this
Anderson, and
i-tb Myles,
,.ci Ti-ac
:c tati-.
0': cc-l at
It is nj,ri-u
myionitized
along
the lc.ni-'
Little
Eau
.mnaafrcErTh
o.ircifit
In western
rocks
&Uoucg its
margin.
cci. along
21L011'c?
b.bva:
Claire River.
icc tn
.
r'
ft
cai
�icc'!, ci.jcc'cc
I',
' [1Li'i
"ccc. rc' c LLTh ci'
ci,
'i,ccci:.ic.ccC ,iT:'
Diorite, quartz diorite, and quartz monzonite intricately intrude volcanic rocks in the region northwest of Marathon City.
Alignment of metavolcanic xenoliths is northeasterly.
'-cccl
,
ccc
i", ic':' .'4.tccc.'. ccc: cISr,Sii cL,"1"c i,,.,
L[ccl'cLit 4LL :tLiCR: zcic',i
cci'
Tccii'ciccccic.;"cci ccc'.iici's'iic
5c1c tic. t,cc
c'iccc'cclc
Lc L.ir:ccn,cc:,.ci
'rrcicca'.i cc.'c',icc.cc,rcc,.c'cccc.c:ciL'{cc ti5 i;'i2ii
c cc''.'c.cicc':ccc iccic,crclcC c2c'ci cA'c'ccccc c''[ccctui s-tic' t!C4 ccco.cc'ccci
'c1'Ei
Mafic Intrusive Masses:
Several small mafic bodies separated by
granitic rocks occur southeast and south of Wausau.
The largest mass
is a gabbro body which interrupts the Eau Claire River mylonite zone
near Callon.
Smaller blocks of quartz diorite, gabbro, hornblendite,
altered pyroxenite, and anorthosite enclosed mainly in leucogranite
extend southwest from the Callon gabbro.
Inclusions of pyroxenite and
layered gabbro occur in diorite—quartz diorite southwest of Mosinee.
It is possible that these mafic rocks are uprafted fragments of an
older, subjacent, differentiated gabbro—anorthosite pluton.
(Stop 11).
',LL!L
cciii.
cii
'c'. itc"i't cii
ti,'lci'.cic'i :cc 54.c.ci'c:;c ,','T,c",yccc c,.scica
'cci5cciJ,,'cc. c cc':.
c"s.q,'tccciC
TO' c5'ifci. "Si,,
ii". Tic: L'T
'ci:i'
ccci ;C,Tccc:cc'
ccc"
cc'iccscTCtc7c.t UI_
'
'2Tc c.ciI:. [itci'
.I'c'":c'.'A'S
c
.L'c'ccc,ct1t
icc:'
'i''i.T_l'ictft ,dc,i'c,C .ji 'c.4't't'C
it'.
*"; c,:,s'c'.'c V:it's..t"
'!n.:',ccct
cii'St"ccc
cctc'c-ccc
iiccc?,_cci: ccccczcct cç..Zt r,crn.cIL"< LII
c'.tt,Tc.ci :'i',SL
,c,c:c'c '4 ccc
cc.tcc.c
cc'.
'''ccc' s'' scIc. tic::": 'cii.c'2
,,.c!LI c4.ccC..cci "ccci
"L'uii.'2.S. ic ;'- ccc'
c,:5ttc 'ccii'c'i c,T;'rcc— ,,;',cRci
i—4cic2cc 'tii'IctL li"l'.'ci
[2
'ci'i'',ct
Itcccc'briI'[C;ctc'ci
.'.,c'Cl'LL
ccc
ii:'IIL
L',,Ii',I''ccL,:'','5
Although elongated northeasterly these two alkalic plutons
interrupt several major shear zones, and appear to have been "punched
up" through rocks having a pronounced northeast structural grain.
They are probably the roots of volcanoes, and their concentric
structure must be due in part to caldera collapse.
'yccick"sic''c cc'c .c'c
cccrL':,c:
c'icI.cccicic..cc.cc.c
ciii:':
':c;ci;ccc'.cIci,
,:.
'cc'rc.ccccc.:e'cc
',.ccTh
.,c'_
cI.cc"cc
ci'ccici-i ic'T'
ic"cc'Lc'It'
,cirtcci'c,'icci S.t :c1'Jj(.
'C
iifi'Jci tjiic.cc.[
r;',ci" :cicccL cci, i'cccidct ccct' [ccclii's .c',,cc:i?ci .1cc,!,,,,
csiiyccy't ctc'I'ccH5t tic ;tccrcc ccc'.sci.'.'.c'cc oc'ci':cO.ci'Lc 1,1cic.i. ''5
'c'c'ccjcc'r'c
,.'cccc: c,.,'::
The nearly contiguous, smaller (5 x
mile) Stettin pluton
(Stop 10) to the northwest is more alkalic and has more pronounced
concentric structure.
A border zone comprises gneissic nepheline
syenite.
A more massive intermediate zone of
syenite and tabular
The
coarse amphibole—bearing syenite has swirled flow structures.
core margin (1 mile diameter) of nepheline syenite is donut—shaped,
rich in magnetite, and encloses a core of massive, gray pyroxene—
amphibole syenite.
.""[.cc''c [2 l]'tci"i.'CciciSL' c'
Cccii
c"citccl[c"-cctc:tii ci:
ciit
ccc''c.'cc',Ci
:c
,s"is cc'::
'c,:
::,ccc.c:c :)i,
i-cc'st"icc.::.3
ii 'jc
•cicrcLL;.,'lcc
'ccci
ccl
:Pc',ic.'ccccij'c.. 'ii' cc
'cicfct'ccc
cc;cCcc
c5r',"c]i
c'Hc cit'c'.cLl2 C'hciui.:fl.tc'cci'Tctc.,cc:-tcJcc
lc:i['.c':
'cc'; ';,'1:"C'5
c..-,c"cicc .,t'-' 1:4]. SiIL.
cicr'c.'t'ccc"ccuc,
'c
cc
=c"cccc'z'
ccc ''c,c' tc[tc:'i"c
C'
3
c''c4ci'c'.r ccc"' ccc
cicc:'cc:cc'::ci
;'
ci'
c'
"'cs'IRcc.ic,ci:'Li ,t'c.c4,.;L'2.cc"r
;ccIc2ci'c'c.ts
ccicc,.cc'c:
1c'ci1
ii Jc t' L:,ccc,t
:]L:II:L
C
''
ci; 'cc'::
icc's
cii ii'. c
' ct.Ii'.c't'i [2
The larger (17 x 8 mile)
Alkalic Plutons; Wausau, Stettin:
(Stop
is
elliptical
in
plan and comprises: (1) a
Wausau pluton
9)
hornblende-biOtite
granite
(Ninemile granite),
core of younger
intermediate
zone
of
quartz
syenite containing
(2) a semicircular
large lensoidal quartzite and schist xenoliths, and (3) a crescentic
The southwest
north rim of xenolith—rich pyroxene—amphibole—syenite.
rim of the pluton is breached by the Ninemile granite which "spills
out" to form a nearly circular mass to the southwest.
Abundant
xenoliths are found in the granite where the "xenolith circle" should
Although the Ninemile granite intrudes the syenite, the contact
close.
In general, where the syenite intrudes
between the two is gradational.
it
is
alkalic,
and where it intrudes more
mafic volcanic rocks
it
siliceous volcanics and sediments
is granitic.
cs.:
i.c .'-ccc.cs
cc..cccc
cc':
"',. c..cciicc.'H1
.cs.çLcl.,.'lIc.'l
iCC,
cc..
cii"il:i:.
ci'
'c':'c'cc.c
'it,JtLT
ccci'.
cclj'"cic"Icsc
',' '.'
C'5
'ccc's:,
ccii cccii
'2"
ccitT '[2.
cc,
1'.'ci'C
Pc
ciSc"
ci2icc;cc"cci':
cc.
cic'(VLcicCE.T
ic]".'Tlt:'.it' c'Pc'.c'cc ccc.': L""i,c"tc
[2.":
',c[2
ic.2jcc"ic'
'vcic:c'c.c-Lstci"
'ci
':cilI:L!:"c ciC,ci.tr ttcc'tLc";c:
'.'c',i'i:: cci
;.ict, cc4c
t':riC;;:
tc',cci. :.;':t,,O ciSc', ut '":cc[2,
[2 ciccs:i cccc'I.":c'cc'ccci ,c!,L'cii'c
cc
. .cuiiccc'c,$
cc
.
ccs.1.ç'cc cciii:
ccco
ci
ALt'
Ccci
rI"cp'cc1.c'!c.'c.'i[ 'c[ccccic'
""1"'"' f
-"S 'ciC,cic,','ccc: ci
,Ic ccu1cc "cc' cc.: ci,.,t'S
ccr.;c', 14 .c:cc c.'flc iic';c,L'ici C iI[2Lt"V"c- .c"Itccc'tI Ci-''i[ iici..'l,c'c c-icc ci ccc.
7"c;'cCIci";..l'.Tt
ccic'.cc5':
'ccici[ 'r'c,'cccc,cica:'cc'
''ccC',c'icic':.'Cci cc.' ccc; :91 cr'rc'cccc Ii
ti,
'ii
'ccIccccccc.tJxc.c
ii
iccc':c'ci'c
ccC'ii.:JY ocr 2.lfc
Ac
c',c,"cct ccci ccc
'cic',''ric]:
Several other felsic plutons have been
Other Felsic Plutons:
They include the Kalinke quartz
intruded into the volcanic complex.
monzonite, the Granite Heights granite, which intrude volcanics north
A granite
and east of Wausau, and are cut by several shear zones.
aplite intrusion of, as yet, undetermined size extends southwest from
Marathon City.
A leucocratic granite, which interrupts the Eau Claire
mylonite
zone
and cuts gneissosity in the Hogarty hornblende
River
occurs
south
of Callon.
granite,
.Te,Tccci.i ccv.
S :.LiT'[2cic'c'.c
c',,iic
cc 'c
0' 'c"'
.1cc"cir-'ccccc',
,ccc.c
.'Ii;cc;;':cc
:'cccc'.ccc.ccrc1c,c
ccc'cccc's
'cc'
I,cc.,iccii c,ccc:ciic'ciJic
,"c-ci;
cc,c'.cc,
':c'c'c'Ccc.,ic;'c
ccii .'
4"c-n-
rIicicici'Cc':c
1c2 ii4c ccccc
'c'; ''ci'c'.'ciT'c'L:] p;rccc cc. ci ccc.ccc cit 'ccc
'cc"cLt'cc'L c,t',,'.Jliccc.7S:l cA,t,.,c
'cc'
ci:'c'c.[cc
it'Lci cc",,cc;c:tcc'cici'
cc's'cc-c
c"ciicc,.,c:c' .ci[
ccccLcc,cc
ccccics;cc:'c
"cc"
'.
cicc'c'nc cc,"c:'"ci;
a",
'cccc'cl
"i
ccci
cLccii
[ccc
ccc:ccci,'cci':
r"hii,C',
,:
l'cc'ccic'ci
ccc cc'cf'c'tic
Ccci
'ccc'cccci
;c1i.c21'cct
c.rrc'ccc''cc,c'cPci)'c cL'ci"'c,,c"C" LIt
cc; 'mc,' c' ccc'ic
cc:.cciccctc'L
.':ccC",',c'C, cc]c1s,c,c
cc',
A' J,'I[ Ci's::
c'c:'r[.cc
cic'cc'sccccc
33
�34
Structural
i-->>'*i
sn.i
-
Geology
:575y5515c1'j, >>LCIC,naa.
fcs.rsra a'.
C i,1955'slfi-35-7
ti-::>> dominant
Shear
are the
feature
in Marathon
County.
daawdr'ar" structural
'sa' as ar-a
Isls
sa::- zones
rocks, including
'nani:55 5535-Cit
The major zones
wide variety
of
sheared-s-sac>
-> s.csan'r aa :1
si-i-is-s comprise
lads
si-:-ssc
:aaa->>,a,s- these
Nature
displacement
i-nt dCa;
:>a.aaisaa'Ss across
1:55s3'axa of
'n-'5 can' -i-si-i.
n-sal mylonites.
gneisses, schists,
s-s'SiaXa- and
i-i-laX atlh'sa:
5-aC51-ai-i Marathon
Several
zones
extend completely
Lssi-si1-u"i-c-CCC
C-Cad-a-CS. - across
s-s-tiG->>--,-sasiCi shear
-5
C-fti--Xzones
is, :551kin'ThT's,
unknown.
—'cs'ss.d-sal: zone
liLa. laS'S
most555a557511-51a'
conspicuous shear
5:55-C-Is' CiCts,>55a'
:JC-1n1i-151*Lu:d
County and an
distancea555735ad-.
beyond. The
a:-. unknown
which
>55
155 .171:
':5:
Ca'
'Jh.nis-an
CLn>sr
sari-a'
mapped
thus
far
is
the
N30°S
Eau
Claire
River
zone
(Stop
8)
S
LIsa
daC
5:
51n>5
-5-"
a,t.-c3-3
marginasof
ad the
tdu
-:'- 'Sd the
-"a>>-as-- i-tugS
ad-n, western
is 555155
i-jars'. with,
parallels,
places is
coincident
tin plsc->>-a
,a-i-si in
355>>- and
inns,>>
Other
C-'.
h_Cr shear
>neR : zones
l>>55jfRiver
5551-tnPluton).
lIla 59.;
Hogarty
hornblende
'Ksgarty dais:?-:
n-Crs'agranite
;raa 55, (Wolf
in Marathon
-.---ar5 Ca:
55a-tdss west
n-.:i-a-sc-",-- farther
;15i ta'nnd
a::, present
approximately
trend are
-s this
aasnTCn:aci-a i-al.:' parallel
pa's-a. -a-I to
r55
sc-as:
aS
La-s
ad
an the
lisa
of
rock
affected
to
It
vCL-::i-:r
:;';a,nS
County,
but
none
appears
to
be
equal
in
volume
llla.sai-1:a, 5-sn: awn- n-nsa's-as-- to 5:
t.
Sn-annasS-a
,>>-a-arn,s
Thus,
intensity
of
>>a'>>siT">>'
shearing
seems
to
diminish
C-C
a5TLL,a
'
55'
'l'i'
Cs
ic-nC-,
Cl sic--n: River
d.s-ar- zone.
Eau Claire
55na:l.
lbs 5:Cc '
'-s front.
i:lC-s batholitic
westward
away from
tic--sri- the
::'aarrarC :;a.ay
:-
-
1
I
-
1.
and across
n-i-Cc-SC
las 5±1:35
Lithology
rocks Ii:
in s55'nr
shear nsasea,
zones, —a55C''j.
which i-i-n-s
varies
along s-nC
iIlssa51Lss557 of
ad :sa.:'C':
texture
of
the
original
Cast-inn
cl
tn-s
an--i-CL-ass
515:
-'3>5S,c
5.'>ra
ristrike,
is-srss"
probably
controlled
-aiaJiy carat
-:'-c-TLsic.s- by mineralogy and
C
ts-d li-a, is
partial
pressure
of
H2O
as::
sar-ial
saass
-s
ad
51Ctsr>>si-:'s:'ftassc
rock, intensity
ci> shearing,
sdass--lsnS:, temperature and
tntasa-S 55s' of
a-s-sd,
5555
Mafic
rocks
are
5f-i-n
?-ssILa
iSCCC_C
the
rock.
:'a-i-i-I:n>
c-as-sshiars-ns;
C
lsCc'i->-iad
during
shearing,
ar.d post—shearing history of
.dsrS's'g a'baa::::>> and
155:
->>'i'-sa
Granitic
015.555>>'
convertedCs
toI sad-CL
banded as
amphibolites
oranchioritic
phyllonites.
cssvsx'::-d
SitS n-as: I"Cnalislc'r:tis -51111
From
and CL
mylonites.
icnj',n-a,, Th5'35
gsan.aaan-> ;;-lha.JLcsain-aa
as' a-is-a'
rocks are
converted to
augen gneisses,
phyllonites, and
-ar's CsrrC-rt-n-'3
:>:-slica'
I
nan--5:r115'sn5553'
characterized
by
interlensing
a':,saa
arssi
an
-u-i-rnstarts-ed
:;
'n-anti--sn-i, shear zones are
map scale
to >ck'in:
thin section,
si-aL-c Cc
ti-ni-cjill an-s-s-a'>
slip
as planes.
-
c-s'-- example,
5ui5'siQsS shear
alIas-a zones.
a':sas> For
IFS-Si-n intruded
Several small plutons
i155>>t'uiiS have
nn-ni-'-C>>i
C;'.,
In-'
Claire
River
zone
i53':r'i- near
Callon.
5'
-s-S. CCI s-iar
i--a' Eau
gabbo
and leucogranite
5c'51a"->>J-,d
5.51,,5557'alffltainterrupt
275.35 ''CL the
sn-33C
sass
as--cl
trend
also
occur
northeast
and
i_Can
a-; srann - -',n-sahythe
515; same
55CC - Ta'S
Shear
aaitln approximately
s->-v n-n- with
151-a'
as zones
a-r'as'9 ha
The'-.iraza-la
Granitefls.t:.ls
Heights
Ida
1,5- granite
s>> 'an-cadtS:'.-i"-- pluton.
-Isl.s-u-o-:->::ac-s Stettin
southwest
-alar- discordant
-CL the
a,-y',
-i-la--n-cc of
ass-c
ca-->
sheaied
and
therefore
tibaaT--n-SCaare
proascii-h
CC_CC-C: 5 i-;have
n-2t lan-a',::
and
Kalinke
quartz monzonite
been ulc-,an,'i--sI
s-nd dali
>sr,'C -55555_Ca
::r—a- lI-sasis.tC-', >a
:ra-pre—shearing).
5-n-i-5'5JC5-5CL'
bably
(or
cs.l:'1- pre—kinematic
ion's:' repeatedly
have been
'_C 57 isas-aC
'n-5-n--as19-3lf 15
i-a tin-ass-C
SOs- County
aaa'Cs in
Most of
the Precambrian rocks
Marathon
31' '5a-s
Miss-isoji-;;,cali!'sc'ss:
55-.-?
The
differing
-n-s-all.>>>
:is:.iI-san.5 compositions.
-s-S widely
t—;s'rs"n-ar
sheared and
magmas of
is:5'ar-'s'd -s>.l by
an- l intruded
a'Ca'ss'nnti
;53LsC:--?tCl'X->
aca'i-2 of
75 3135I
the intrusions.
'as some
-51- san:: for
nibs—i
as-s -5>1-s-i- channeiways
::,-.--i-Css,siCIn provided
shear
au-Si-Si-I evidently
alCoa>>: zones
-ad
of
the
an"':.
many
as:
asi
small
51,
5
plutons
5-n t;as--a::'d
and
:5.>>
s-1Ci-5C55I.S'i?'753'>>-'>>'
cn-'355t:'C'
The
relationship
of
shearing
to
intrusion
sad
all'
sn--o5isa
s-ui-i(Hogarty
hornblende
granite)
Sd
-cICL5s
55
1:5'
.i":ttarIs
'asn-t,t)
5,-s-ad-sI
3tti-'-n-s
si--I'd
the
emplacement
of
a-I
the
Wolf
River
batholith
i-he
si-C 51115'? n--n-s'iPrecambrian
geology
ICC-a
a,iss1a-:si at
a>n-all JTof
5" Marathon
C
am—is
s'f Ida
-aa,>:'C
;n-rciCl>s-n-C
remains
one of
the
major
problems in
the
resun&a.a cat:
--
>55._CC u5i,
County.
i—:-SidLs:; -:
Major
55aJa' Problems
s-ca
In-ma's- sCant anai-s
Some
the i-an
morea important
ones are
anI 51—c
Sara's of
'—s-":aaa>
ad- can- remain.
Many major
si-CL a-a problems
-rcsn-n--s-Ci-r':..
discussion
and
sn-sal research.
5
.bsanasa:C-ta:
ratIaa':L'Lasas
Class
:>,:>,
sr's.
-'>i5ai
iS'-s'
listed
below
in
the
hope
that
they
may
stimulate
i-it ba-S balsa- S's
Li
Cataclasis:
-i'- Lan-IS:
Shear Zones — Cr:
-
-
-
1.
5,
and mapped?
'l'ci,
-an-lan
sacS's
sariSclassified
-staaaiiiIas- ars:
How ass
areaa-aa-c71
cataclastic
rocks
best
2.
5,
1155-1-35"
CC dated?
Can
mylonites be
dais: vsssLc:cflin&n-s
3.
determined?
.>>I5lII aaes:a,s:: c-:ot
n-rrrr: 3-55
si--saC- 51
How
i-sad amount
of displacement
55155 and
-3T5- type
ia-" are
13
44.
Class'?
How?
-,
i-i- -isas-bs:nsa'fl
p-': tcdcs':st'ia:dp:- between
csdlsnc'n-s
What, if
any, are
and
space relationships
avisthe
j'e time
it: nsa.
Wl'at,
atsiasas;
a-n?
,'i-s5:'i9a,aBt'5
shearing
magmatic intrusion?
cbacvrlsa; and
�s? ane err t
older subjacent of samples ted upraf they Are variation?
fC =— xenoliths
Cji, 1t2At4v and orientation
(:ICC ofjC Significance
lithologic
iCZ [
r:• ft$CCEY:1 <%-Y9
C
Subvolcanic?
—
syenite
(e.g.
7i;T !ttZ
i)r,; When
' ?Ji-•i ci?1j
lILCrCYqISC
Ccnj
intruded?
syenites
the were f.CtCR
how and
volcanics
Brokaw)? near
C CC
5.
C
4.
trachyte
7
I
i—C
It—
and plutons between
Relations
comagmatic? are plutons Which
iCCCCIV
emplacement? of mechanisms
and Depth
3.
2.
C
1.
i:t:C7
Geology: Plutonic
35
I
�1!
36
atrSW
Bates, •fl0
R.G., fl'.
1961,
geophysical data
and
Allingham,
J.W.
Xfl '3Ut
- "Use
34) of *t.tss%•;o.
t'Zflfl
';'r geology
i4tç to
4•1
interpret
in
Precambrian
rocks
of
central
Wisconsin":
!fliS'V1'13 £.Ptrctl bV
$%Y
wea 1>
U.S.G.S. Prof. Paper
rn-cs — D—296.
zt •IrJ.
.(%',.; 424—D, p.
°' D—292
SELECTED REFERENCES
5tF:SS.a'ffi
't1.
j
,
L,
'
%.'f
Dutton, G.E., 1971, "Volcanic—sedimentary
belts and
sulfide —rae
occur87Ps fl1'r7rC2L
StCt C4fl(U
U.S.G.S.
Prof.
Paper
750—B,
p.
B96—Bl00.
rences in
Wisconsin":
r, r.oswç,s, tr :
;c.a.y rcb.a '—,;çj
OtZ
tn.
•
'°q.'
•.
t"i
';a'tIrtnrxrc;s
Dutton, C.E.,. and '..'73SZ
Bradley, R.E., 1970,
geophysical, and
>.E
'char "Lithologic, DLC'4Ln32
mineral
commodity
maps
of
the
Precambrian
of
Wisconsin":
U.S.G.S.
1c
w:42L Arxa•nu ..f,q'g ;ta
Misc.
Geol. mv. Map
•4gfl -15ee
•"flf 1—631,
:%.I4... 6C sheets.
-:rj
;r
ru :'wt:.jtn(,
pUtfla
V
$ ()
r.qe;.p at;
Emmons, R.C.,
Annual
Tn—State3 Geological
O'eQ 1953, Guidebook for 17th
v, :ia(
.t$q,
flD4tC
Field sv,.'-.xarr
Conference, 11
yr p..
,t0Ij
rt4'7ii.'9 !rag
r'
Emmons,
and
F.G.,
fl•j Snyder,
c'& 1944,
y€L "A
'Ii, Structural Study of the
cç
Cztc.,&a R.C.,
xq,:iz
ta•a
Unpublished
rept.
in
the
files
of
the
Wisconsin
Wausau Area":
i1SW%
WV
;qa
4
aj;
t,Wt47tttft
;'etBr.tV14 ';de..
Geol.
'TU. Survey,
'it&flS 16 p.
C
'ba(
a:;:
t
•,'( 'CT, "g'g
t:\ttsc. tj) .j
•.
:,
':
i
t:b
Henderson, J.R., Tyson, N.S., and
map
P%7I Page,
'at
'o.Qwj J.R., 1963, "Aeromagnetic
rr.,:i4'rney
U.S.G.S.
Geophys.
mv.
Map
GP—40l.
of the
Wis.":
jo
:qt Wausau
:'sa.rajç, area,
SM
49'
'SS't
'ts1
,.
:sfljr "It v'
ar
LaBerge, G.L.. 1969,
report on
P.tnnrEsJ. .acSe.t
uz' the geology
".ZiGT "Preliminary
a5 ma of the
northern part of the
en Wausau East quadrangle,
.nacsfl
:tth 'c,2as. Wisconsin
Wis. Geol. Nat. Hist. Survey,
Open
File
Rept.,
13 p.,
'2s.C?3
"C map.
iee
;*
rnas ;ntj
i:'t. t.jff f'L
•'vc'-
LaBerge,
on mapping of i1
Precambrian geology
:.qh? 1971,
s25v.; Report
s.r'sg co
SZ'LWS$
'GW4e.q G.L.,
'ca1t "Progress
Wis.
Geol.
Nat.
in t7flcW
Marathon County, Wisconsin":
ELf
a-a • Survey,
:::Tt•sIflr3J4
'tu,c list.
Open fli.J
File Rept., 27
!Z p., maps.
'4rc3
'?3
C.1
'Ai. L0
'.r.
'craet't, vx nrnc4w
r taCaaST&
tfli:
UC'4Ojq n;i 4flc;
'1.2?
'flL
5
LaBerge, G,L.,
sv 1972, "Lineainents and Mylonite Zones in the Precambrian
of
Wisconsin"
(Abstract):t North Central Section Meeting,
T2
G.S.A.,
DeKaib,
*e.q.n.z) '•ezoa Ill.
U::z*r1
't' •t .trj
ts 't.St3 ''O
LaBerge, G.L.,
"1971 %eclSord
Progress t•.dej
Report on
.:,. Mapping
t1.3E TL€T,;
4"u'f and Myers, P.E., 1972,
Wis.
Geol.
Nat.
Hist.
of
Precambrian
Geology
of
Marathon
County:
1;b C4taPN.Ls: J.$2t->' &.O %'.at1 fl '&.1C1s5
Survey, Open
File
Rept.,
28
p.,
illus.,
maps.
&j
nd'ag
bw4, c.çg
'd 4-aç
"!na
:.
1Ltui VII
.vc flo rt
LaBerge, G.L.,
P.E., 1973,
"Precambrian Geology of tr)4flflfr(
Marathon
nrn..*twse.
1an and Myers, Lard
sue. Wis.
Geol.
Nat.
Hist.
Survey,
County; 1972 Progress
Report":
Sp.4 1.C-)
20.aC
4Z'a.t1
Open fl%C
File Rept. (in
C;) progress).
'cs.azs.c5
)T
"djj
'fly
W
flr:
;r•i fl.1a3
?rr,
LaBerge,
Ci Central
..:.t; and Weis,
k"! 1968, "A• Greenstone
fltLrj%S'LVaTh Belt in
'I3J4(i. G.L.,
'.t!Cr4 L.W.,
Guidebook
for
32nd
Annual
Tn—State
Field
Wisconsin?":
Yt33—(aZ1
,.4t1.i.CCfliVTk )OtOflt3 aC$ t.LV,
Conference,
42
p.
.3
4DrdXtat)
c'rq
'
''re: 'c;si
Vickers,
ra part of
UJSttCs R.C., 1956, "Airborne
.a'q.r:y,, ':t and
pfl ground
1WdCUCte.F' of
;n4>s1 reconnaissance
U.S.G.S.
the syenite
0cm
rie.I Wausau,
;utsI'r.JCT c c°u 'p Bull.
nit.ts s.a complex near
rgnip. Wisconsin":
1042—B, d
p. 32—33.
xwgna
'tn'ab1
a
Weidman,
bTId... geology
'Z4ni Central
u4TLBt Wisconsin":
çu:w.CCCTa.
Cktz'ia of North
t•::....;#'.•-q S., 1907,
'.a.cr "The
Geol. Nat. Hist.
697
p.
•t$
•V1J! Survey
r..t..s Bull.
•IrR 0 16,
09
;I
.
'TZ
'*1t 'h°1
Wis.
'3;j.4
"Central Wisconsin Volcanic
Weis, L.W., and
Z.1Ct LaBerge,
.n)'ja;s G.L., 1969,
'44%tJ_ zu:awc,, 4.3VCr.s'
Guidebook
for
15th
Annual
Superior
Belt":
I.?:.2t.p;a3
:'a.it.t Institute
rj-4n(fl w on Lake
dOfl
Geology,
Oshkosh,
Wisconsin,
30
p.
VØ
(.j
tSo ".atcers
;•1t
-—
.n;
ft 'u;snt:
ae
a...
..
a
..j4uQ
�This page does not
have a number
1
1:500,000 scale,
Wisconsin, northcentral and northeastern in terrain
Precambrian the of map geologic and itinerary trip Field
2
1:250,000 scale,
Wisconsin, Sheet, Mountain Iron the of map geologic Preliminary
3
1:250,000 scale,
Wisconsin, Sheet, Bay Green the of map geologic Preliminary
Plate
Plate
Plate
pocket In
LaBerge G.L.
leucogranite and Masses Gabbroic
Locality: Additional
Myers P.E
breccla intrusive diorite quartz Sheared 11: LocalIty
Myers PE.
zone pluton—wall syenite Stettin 10: Locality
PE
Myers
Institute Technical syenlte-.Old quartz Wausau
volcanics
mafic
9
Locality
LaBerge G.L.
Rivr Wolf between Contact 8B:
Park County Dells Claire Eau 8A: Locality
and batholith
LW
Weis
anorthosite Tigerton The
Scftnus
Va.n
Schmus Van
W•R• and Anderson, J.L. Jr., Medaris,
R
Schmus Van
7:
6:
monzonite quartz porphyritic River Red The
and Jr., Medaris,
LG
Locality
LG.
5:
W and Anderson, JL. Jr., Medaris, L.G
monzonlte quartz River Wolf The
WR
Locality
Locality
MM
Lahr,
area Mountain the
3
Anderson JL. and Mylés, JR. Jr., Medaris, L•G
trachyandesite Peshtigo and granite Belongia
4:
of geology and porphyry feldspar and rhyolite Hager The
Locality
Locality
JL
and Myles, JR.
Anderson
Lahr, M.M Schmus, Van W.R. Jr.,, Medaris, L•G•
monzonite
quartz gray Amberg and monzonite quartz pink Athelatane
2:
Locality
G
Hall G.I and Mursky
Wisconsin northeastern in volcanics Quinessec
1:
Locality
Wisconsin Northcentral and Northeastern
of
Geology Precambrian the to Guide Field
�37
L CI'C,':'i
7TCHJ
Field Trip Locality
1
TITLE:
Quinessec Volcanic.J in Northea;t rn Wisconsin
(l'I-7J!,I C C3'CSI CC-XCk? 7
St .7;:; 'T'y
CICCC,IYC.,C,:4
LOCATI(
MC.:
T.37N., RJOE., Marinette County
IJ,
"
"na
sec.
1,
LI7tC 7',;aa.;:7t7r;
Centr,
AUTHORS:
t,c;:'?L± .CCi. 7':,';ai,r,
i"C[ 'a
fI:r.17; ,;:a,1 ,'r• C"Ca. ''Ii; I,7C,C"7M: L,uZ77
Gregory Mursky, Department of Geological Sciences, UW—Milwaukee
George I. Hall, Hudson Bay Mining & Smelting Ltd., Calgary
'7CC,
I ;:a CC KtI•
":H':aaf"7 1yT7',
DATE:
February
1,
1973
't 2C7'C'i1S
SUMMARY OF FEATURL$:
part
oi Marintte County in northeastern Wisconsin
Northeastern
is underlain by Quinessec volcanics which consist of pillowed and
•;:;: :;r,:CZJC '7., '77CC "CThCC
"TC'taCQ C'C7
Cc
"IC,:': :7';:
CC 'CJ . ,C13C
S$LCNCI,
aT'tC [ YI' iC1P'4"t 1CC 'C7CL
i'" •,7C [':'C '!tC '1 t 'Y'CJ' )':ICIL3E1 aC"<tIitC'T,C,C'
rLiC'Ci7C
I1C'CQ1C,4
S.'.ICCC'
C4 vi"CC",LC1CC1a a .
fragmental basalt, massiv basalts, amygdaloidal basalts, myrmekitic
basalts and a very small percentage of tuffs and rhyolites (Fig. 1).
The volcanics display shearing as a dominant structural feature with
two distinct trends at N60°E and S6O°E and signs of regional metamorphism
which varies from quartz—albite—epidote—chlorite subfacies, away from
the granitic intrusions to quartz—albite—epidote—almandine subfacies
near the Hoskin Lake granite (Hall, 1971).
C' r
1Ia
'.';:aa. •a/;!.:zc•Z.
wa474t1ir2-.
I'C.':z1I,:,
7C
CI
C':
[::;:"L'1 C,7;,;,LC
.,
;3,'IC'T'zJi.
CICLC
VT7CTCLC
'a : :;;:;:
'a
C'C1
'E1?C:,,Cd Titt7 'CC''
il;:
1ia
'C
CCt's''a:
J7117
7 C';:
C" L1•
cs• '1' C'C1C tCi CcC'7XtY ;:''aI
;:,C:,;:. c_.;:01©.'11 ;,1:a::C ''' ':' a. •aicaa ttp17
'CCC17::. '.C'Ck",a,I] CLt
I'i7-ç m',7 'C=; lP'
'flC1ICC "ai 7T4COLL
'-'T'1 C12
jrcr';
The Quinessec volcanics have chemical characteristics comparable
t:7Y'J1
ICCICfC :3CLC4C a:'7'q 'C
7u7CCvI-'. y{I• CY',TY' tI;, •'•'• C
JU
.CCL
v'ç
'flit;
CCC. :?
Ct7 CC a a Y' f:a'j,,Cu;:;:CtI C4 7C7t'T'17
IaaR12T71
C'5.
C'
.
CT'7I
to the Archean volcanic assemblages from the Superior Province o the
Precambrian Shield in Manitoba, Ontario, and Quebec, and thus show the
WCZJ '- 'St L
silica:
alkali values from Quinessec volcanics, when
plotted in refernce
oceanic alkaline and orogenic calc—
alkaline curve of Wilson (1965), plot in the same orogenic
calc—al :aline wield as suites from the Superior Province (Fig. 2).
iwa;:
o
—pa
';:'y'a
'17a7
'n ©;::
I
:
CLL± •;:rL •.':q
°9.jj7 C'CIiC_C"z.ç[ •:s-C'CCL' CT1C cY'1; i'.'C•4-'1.C
cCC:iicti'
,;:,Cat ''JC7 JC iC''LC ""CiCVI,''y C'Cj,
JC
j :i
t;1r7.C'Ja
The c tion equivalent percnt of An—Ab—Or for Quinessec volcanics is quite similar to Goodwin's (1968) Archean assemblages
from th Superior Province (Fig. 3).
t/I'i,L7LCC 'Ci
;:tir:;r:'a IJiI;77ji
C
c:e Y"1 JC I
II,7":i
CY'R1;
?i'C;fl
:,Li
a;:
,c-:7t'r
a
CCjj
(2)
t'C
Nili
ii "c.'qa CTçi ;;t
(1)
4't
following similarities:
:
A plot o.. oxide ratios relative to stratigraphic thickness (Fig. 4)
does not show any pronounced chemical trends although there appear to
be three separate zone within the pillowed and fragmental basalts.
c: Ca:ttc1:; :T7hCTYI,flL ::4
L: :CCC; apCC:C
:::,1aCa ac.r.i.
:: aiqC 7CL7 '..
L•;'..Lta, ;- .,'.CC
3C'''i' •C.:C:. :,Th:,c.'.:ia, a'p.aac. 'nz .'i'c•,.:; pc:',:C.::;:'.,ri ira tu'çc .-;r
''i
C'
�ii
38
-Ii
8800
7'07
-
--.,
--
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1
177
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-
' 'Nk.
i-'7-%_
-
a
VI
7-N.
I
LEGEND
1-
Precambrian
mt
rusive
—'
L
rocks
70,
-
-
'7-.-'o
21
7-—
1i
.1Fraqmenta1
7-4
I
'I volcanics
1Arnygdaloidal
/LjJ basalt
ara:J 6-I!77If
721/'CJIN
I
0
7,-;.J-1
p
o— '' "N I
Myekitic
C
•
-
H —-
I
a
-''S-—
-
- •..
'1d
basalt
-L
*
-
-
- Chr-'Nt 1-731---c'
rk.,0i'Nu:.,elco
Acidic
volcanics
7-
0
7. 7
LCCAON
MAP
CE
o_jbasalt
U)
.
(1
r1
-
-
0
-o
Luny
>,
-
i/f,-,ç
Wi
•-ns',--
—
12
-'
--
Mo r,,.?te
-* ----
k,om.er
-
-
�'r\ LI
I.
3',j
'C[' ''Th'
C.C' Hall,
1971)
3'
(After
7—U- Canadian
3
'1
the of
Province
Superior the in
Shield.
13'22IOft J37;1-C-l,-"
assemhlaes7 volcanic
Archean 3'23'2L;c.
three ;.122;,
for trend
'uT1-2/3'33'T-C
curve ri:Cj3'crr
Dashed
Wisconsin.
(1968) Goodwin's is 333'1'.3'
3':.,-'''7 acidic
County, Marinette NE in rocks volcanic
-= '— 2:1523 Cation
:.3'7.-( in
23' .2:1
13'-3'--23'[2percent
11,12.322 equivalent
Ic
3' basic
and
ith—An-Or
C
,
I
22;
/\
\
\
'
I:
3.
Figure
\
0
3
/C
II
Number Sample ,z
C
An
/-,1'V"Ci
T., G.
'3'3'1;121i
:1:3''121
caic—alkalifle
rocks.
p33'.A1
'ri13:_: (Mter
Hall,
::
1971)
rocks3' alkaline oceanic separating
orogenic from _l
3'
with made is
curve standard (1965) Wilson's
County, Marinette NF
c
WiscOnSin.
—
r' '1
I
cI'
I_
:
C--—
comparison
1721/
:!C
"
C—
-''
aniilyzed
and
basic
)'C
acidic
ci
volcanic
rocks
in
3'/ ofci Plot
3'003,
I3'.3' ':• I13'Gr;2. Niqqli
:17 :511123:'
values silica-alkali
of
-
-
-
-
,
—
—C
VLj
c
400
500
12'
2. 5172.3'
Figure
CO
4gI
Sit
300
00
200
7
l0
I
7/
4
/
/ /7
/
/
// /
20
12
>
0
/
12
CALCALKALNE
,"
OROGENIC
12
7-V
39
0:
-
30OCEANIC
ALKALINE
40-
�40
40
V
Si/I.E
N,crn.H
.: i
54-
.
Cl
—
/
-.
25
0.23.
50
.5,
—
75
H\
'N'1;\l
.7'
01
-
I
-.
—
N,1
- ------!
1/
:
0.3
,0',,
C
.04 A'
10.
/
..'
H
— -1
xA
—
C
.4.
/1/ /,/
A ,.'
.Jo1
-
-
/A
H
/
//
r
Ceo 0332
L.tSiUI
I
.
20
(I; t P.
nu5' i I
it
.-
t
II
-—
-1
7.
fly
04-."
7
--- /
00 —-
0
I
'4-
I
c
'4-
0
::
((S
3
C.
:;
5-—.,.
I.
•1
-o
1A
C
- ' I-..
C
0
//
•1
0
-c
/7
/7
'I
10-
7
7
—.. —
1
a.'-C'-.
-'
'. "
•
.'0.'
I:
--
5
--
.7'
T
1
/
JL.'
0
H
--
-
,±J1
Bottom
Bc
-1-L_
Ir
tr'Sit'
dItIIn
5.
5,
.:''H''sv,-,I,''12 ('IL.'
—
-
l(C7
Figure 4.
' 0)01
/I'fl(
t'kr'
-
—- -.
Tt1 0.5
0.3
V
sc.
Bottom
'3's
A55 (ion
l..I ",
I
-t FeC)
)
J
'3
A
1515504:
Plot of chemical
5555c/:t c- with stratigraphic
d0457nS,2.C .sjI. variation
4 04552044335533555504/04
04"r:5e33335 in
Ni Marinette
:;1;t-5-.t Cocsit.y..
thickness
7555 hasalts
NIE
County,
bsc/c.5T.tS ins.c
'55
shows:
Wisconsin.
,55..'(-5,33j/5r5
5550 JL07
zhz': 001
Generalized qeoloqv
r->.
Si 550455355.555
sc1s' scs's
d5Ct??04*5
3
qrain size
-4555.5.04
75.5,55; increase;
grain
size
decLse;
-.-- hcsc4
(i55 7 i r (EnrpBc'cT
L.':3 basalts;
isis Bc 55' Ct /4
shearing;
porphyritic
(.4
2"?'10455.a"''(S 55: basalts;
CtjiL55557L
045575.A 55555 q
fragmental
modal
StC'. iLL auartz.
55-75,
'JcS"I'
(AfterssBcI,
Hall, '.'s.
G. I.,
Bc, 1971)
.5
c.
"
Wi,
I,
,_,-_.,
5_
A'.'
Si
�41
DESCRIPTION:
U
l/ce
n:cYk
t,jc
14i.V
a'oci' ri'
'u :a:aL
:xn
vi 'UU
Massive basalts crop out to the north of myrmekitic
(1) Massive basalts:
basalt and comprise one unit within which there are three quartz—rich
zones containing up to 10 percent of quartz grains measuring 0.15 mm in
Massive basalts contain varying proportions of albite, epidote,
diameter.
Most of these minerals
clinopyroxene, chlorite, actinolite and leucoxene.
average 0.2 mm in size.
Clinopyroxene is commonly altered to actinolite
and plagioclase to epidote.
Pyrite constitutes up to 1 percent of the
rock but may occur in greater quantities in the quartz—basalt zones.
:1L
c
:
tecc1 tsa
I
I cLa: cc Ui
tr ci
c21i
Ct
F3eELcL1
S.
-
Xccii p I 'U
cc.
rJ
c
cccc/.
a1:
cctt'cUL
UJ"c/RLtc
cU eca Pitci
tititre
L±i-UILI. 'U
a
i
Mctcc
c'tkcc.tQ
L& :crc k
nc
-
c.
:rr
a-cc-i
e•:c:'c cay
cc.YCLC:ic ftS 134L1
irL 'U
aft
aagc
.fctc0 cc cr .ccJLaSe
i caL act
iic.: c-c
cUr r--eUicd cii 2eachae
g
cc
-
chsaccic sL'trect ii: cU-fl.. ratrcc tibia calLer icaci lice cc
fl
iL
fS;.-iIi-Lf.IL-- 5rtt
ataice c cc
Ltii
a cc U 'Ucr I rca -cc
cc lUC cciiai a cc -L c'c:•H
ate Ifcar UI U Ucac'U cc a a ';Lcc-c ccii
at.
- calU iniic-U; a'cc.ab
cc;: ticac cc aa.lian
cii a -racial
Ha
t
UcccU
ccc
ti
T1LL
JUic
-.leTh
tS±L ace
C/c. CccThL'
:-
cmi- icc ccc
a-ta
-
cc-rat
a
t'U
1tJR
-ar:
t'a.
1Li
ccc
as::.:
;c'Ua
ic:
ii
i;ufl9L
cc :c:a
cc-
cit
cL:-r
1:
-
-cc ccc
cccc p1 cc-I- crit.trL cccci--:
ccc- c' a iii:;' i-c
U
Urit ii:, hit-cc Ui
'U ccl
cc-i
:cycLnta_
iliac-. LL ci
(2) Pillowed and fragmental basalt:
Rocks to the north of massive
basalts are fragmental and pillowed with well developed shearing and
flow structures.
The fragments are mostly angular, at times elongated,
The pillows, where present, are
and measure up to 5 inches in length.
deformed.
These rocks are made up of plagioclase phenocrysts and a
groundmass consisting of epidote, actinolite, some chlorite and dm0pyroxene and occasional grains of quartz.
,-
ccii :;1ccctth i-cc-cpa-c
H
rath
-ira
pUL:c-i1 aiU ci ecai'vccc ccc
ar-ella
(Y:i/Lc'IL_ 'IL ccalc.c ccciii ic-eU ccci i-rca i:
ci cci 'U ccl -ci CC.' La.. SLLC !CtiC atiLcag --crc
a cci ytmic-cacctr ccc ;PL-rgtcU -f
cc Lie c cciL -cciiti
:ci:ci hiU
ccc
L
UIL
1ccckSct.
t'ca-a
tTI
11
LltJc
-a
iia'hccc
iitt& I C
--j.c-ac dcci :i.ILc
'Up-aL ILLC7 Ce 'U IL tm3i TLC
(cjCC.?:ILtS
-
r:-i
-
cccl
a1
2/c Ui iT
iciacla ti-al arc etacitcaca kcic'cL
La
-cica
lea icaraIra
criiaJ.
Tic
(3) Amygdaloidal basalts:
These rocks in hand specimen are uniformly
fine grained, massive, gray in color, and contain up to 20 percent of
disseminated dark green chlorite grains which measure up to
mm in
size.
In thin sections the chlorite grains form amygdules which are
Plagioclase in the form of
surrounded by a fine mosaic of quartz.
laths averaging 1—2 mm in length forms about 30 percent of the rock.
The groundmass is composed of a fine mass of chlorite and epidote.
cc
Ii.
cc
ccc
ccc
ccc-
icc
icc
••-
aac
-
'c
-ii-
cc-.
aca)r.ci/L'c
aca7
yr
LC-H-H c-c-ct
teucia
elite
culcrt-cc
cha
acce cci cc Ian
uccancre
greca
-U ilaccc the hr.:
-ccc taLc-Ui cc Iii-
claciccicita-
:L.r.caJ'U'U ctcbc-clai
i
1
1ccttc-
nnr:ccc icuc
a cacic -rtcc a CI :-ecci can
a-
a
I
Ic
ccU
aJjuJ:jIcc
u-Y
1
-
cia -ci eccacat era cicica it-c n,air,ec-LaI.. yrea:Urc nrccniti-ci-i
cci
La ac-a
ca:cLcca-lla
ecnii
'Li';
inacicica]
'U :cuut.cuThflil'l ycceacca
n-cc
'U ccc arc-scec.a
::acc-L.i.-z cci c-ac- aUcta1
iat'U j:Iapa-.:cIea-e cc.tc1 ci: -ccci ace c-c-ai-acl --aria tiatacig a .lcrr.nti
ear
ccc "C•Cti'U a:
ci
i-cf cc-ecU a:
'I-c.
Ua-i
iac
ccc rn'-: car
-:r'ar a
ccci c•ihc
rljtflfl'Ulitcarccc cc
J lr
-ii
(4) Myrmekitic basalts:
To the north of amygdaloidal basalts the
volcanics become slightly coarser grained and do not show the abundant
chlorite amygdules.
Under the microscope the rocks are composed of
myrmekitic intergrowths of plagioclase and quartz, plagioclase laths,
quartz, chlorite, epidote, and actinolite.
Clinopyroxene may be
present occasionally and some carbonate minerals are to be found as
interstitial groundmass material.
The southern contact of the
myrmekitic basalts with the amygdaloidal basalts is gradational.
c
t cc ccc 'rica
ct:ia
'C
c1/.'tj
c)'J1CU tU SU 'U
tLcr:O
Massive basalts contain isolated patches of welded ash flow tuffs
and rhyolites which indicate acidic variety of volcanism in this region.
The
The thickness of tuffs and rhyolites is estimated at 400 feet.
tend
clastic
with
rounded
quartz
tuffaceous rocks
to show
appearance
grains up to
inch in diameter and cherty fragments up to 1 inch in
size embedded in fine grained chloritic matrix with distinct shards
which have devitrified to quartz and feldspar.
The rhyolites are dark
gray to black and very fine grained and contain quartz, orthoclase,
cherty material and plagioclase.
icc
-a
J
ala c-cia
1
arcifc;r.
bIl
-b-c
:r
11cr
cc
a -ccccL.r-ci
ccc
ic-acita
lU
i
aia;yca,1c:a2.-c!L
Air ccciii.
tcc
TcaU ccc ccci::
cii;
�42
42
SELECTED BIBLIOGRAPHY
8'Liv:.t
Goodwin, A.M.,
A0M., 1968,
J!S% Evolution
'o1t'.ionof*2the
•b Canadian
.AU1 W4Shield:
Oucihilti.
7
19, P.
Canada Proc., v.
Cer.&Ss
.L;
. 1—14.
T"r.;
Ct.C.
Geol. Assoc.
t9fl.
G.I.,
A Study
of the
'r.z?Precambrian
fl3x,brtt1 Greenstones in Northeastern
6xsy a2
0,1,
a 1971, J.
Unpublished£.t?
M.S. Thesis,
tr:i.r,
'fl:t,g.Jv, Univ.
Marinette County, Wisconsin:
V:.nctctt; I':'jjj.b*
flrcgotce
Wisconsin—Milwaukee,
¶Mt' watuxMt,
Wise.,
'n4, ac.
80 p.
kaecariu-kUvriks. Milwaukee,
Hall,
'*3.3,
l:.tt
MacDonald,
Gtsj of Hawaiian
rbra'.w T•cvn;
Lavas:
tact Origin
Cct.a.ceit:.cct and
Jor.z'.Id G.A.,
2.JL. 1968, Composition
II.
In
ic
C1A..
Studies in
R.R., Hay, R.L.,
Anderson, C.A.,
Li L., and
im3 PZ'13't1D,
.ntR; E.3..,
13 Volcanology, Coats,
Geol.
Amer.
Memoir 116,
..1. p.
!Lrtc.t'
ed.:
p. 477—522.
41''.-.t.
C...
. Soc. Ln
td..,.
5c.
A ?i3 tflTlti
Wilson,
H.D.B., and
Archean Volcanism in the Canadian
s'td others,
3*h1b. 1965, £racar.
4ssct, '1fl,fl.,
TIC?,3,
& p. 161—175.
Can..c."r
Jour. Earth
ttr1tt Science,
¼c1tfl?G, v.
7- 2, no.
Shield: (!a
isiC
',
�'111101-32072quarries.
rinP0Ni'L-lI:
are monzonite
11:0,' (CLI 11110
0 - n:ioAmberg
,12375' of o'coon
.049 0-23
areasS.1--401001-,C
exposed:420
quartz
extensive east,
the
70.
1 7'LTU -4- About
17>77:010dates.
_.t (1- isotopic
07 40701' by' indicated
LJ'>--'7 70-4 UZ'LOLIO
2370: these
-040;.1of. age
to mile
types rock
107
OLE,1101L7 I 101009 grey
4,04 i[0--0 901: 2oii::.o>oo,o:'- ,0Ci
1o .17 2,177011027175
22
relative
the
confirming
thus
monzonite,
quartz
Amberg
of dikes
217 intruded
po°i:coi:ii 0>
"i÷11:,CL2i.E0TiJ C"C703177
07110. At
to
by
is monzonite
quartz 1'1tJLI
pink 1tTht.7'100'[:7
Athelstane .02110017:.
locality this
-o%io in
't'I m.y.
age.
ill CLY
2o':o-p ':,[1723100LL
1670 to 0070:1
1640 being
possibly
ICY
04 01,1.11711711, 0:01,0-1 .$1t,:$1
younger
grey 10.01117 1t10 Jon 'to0 23o' '0 .0':.is
quartz
monzonite
Amberg
the
that
suggest
data
isotopic
'7700 .r7010E0 .21 10170. 2 m.y.
770' with
141-704.171
1110 0,
o;17 the
)SCm:
023C and
Preliminary
Cain
Banks by given 2. ->24fl
18604-C
of age
(1969).
70: 171>41101
I Co7j,i407'01- (111110'
9:.
17'7
232
0
agreement
1
9IL2
good
in
monzonite,
quartz
pink
Athelstane
the
for
C
2017101>2"
obtained
sJtI}fr (Rb-Sr,
'UJCY'l[LO'ILOlL '1--Il-,:
7001-'> has
- " '707
-1210 An
m.y.
3011 isochron)
CI'
0.17 age
70-0,
>.
been
rock whole
50 ± 1810
"[2 of
-
'1
-
'
op
grey tro7artL
monzonite. quartz :,co2
Amberg the
((10077017 be
L14401-r2Zt1i!quartz
Y.O&ol5 ¶'7"J
J.04236y '7070'
grey31the
.iool0o?'
'1. and
(7-71- monzonite
92(
variety,
pink71170
the called
Athelstane
oN 0" 20'. 701-LI
971.
0.0144
-oo''rNj2
c-c
L1277017'J'L177
1-4
ICLO';71'1
2>[
CoO
0211.
propose
we
variety
pink
the
that
two
the
lithologies,
of
distribution
[013 1 (Plates
79 -°Oi'0170[j
0-0107010345.1
9'; 0"
0t'7'([71]'1area
geographic the of
Because '2).
'17 and
Atheistane -7
the
in
in :-',-ntI being
4"-0, variety
,Costot:, pink
'.distribution,
11 141171.' 101711 501>O
'0 has
t!C72J'1112-I
4111 U 9'.
231 of 11101
abundant ,7'.:ctc
particularly
wide a
the
411 J'1 1042'
I 04, and
1173 plutons,
"OIJ
O'ji'14,;
02,-2,O'n300
-'>4702711:1
7.110.
17°
0.1
-230.01:
2
270
that
distinct
four
in
occurring
Amberg,
of
vicinity
the
in
4LITOTJ'011,10"-ilCo
c'9 110 the
oioo01mm grey
0o:o 05o11104:NL
99 040
%"4(",,'IIIL(U
10,>
predominant €0is variety
that
established
has
mapping L7[0"4,;1
Field
7
were I(grey?) 0'.
1-14 ,n'c'L711012 2-0074LL'y
11047.2)
417(1
-distinguished.
c'71II1I":0071194[: .0o-1
granodiorite
Amberg S703L117110
separate atO 1770
and (pink)
ite
10
granuI,,11.o 4L1
map a
'm:'fl'170:1,c4
.jo,74 which
0017 granite
23 170,% 27:3
t04' 711017I
1023 2Amberg
on IJ.'00,
presented and
pink >0
of sample
Amberg
't'rp
0427±701:
011:0,
4,0 103
2347--i';o (U—Pb,
a ,00::
m.y.
an pc'ooccoo
:237:1:: Cain
for zircon)
15 ± CCCI
1860 of age
reported (1969)
4173 Banks
.f0704" Beckman
tLJ01"JG'?1110.01 ;7102,.$([4'141.1.''4114j,itN
.lOfOO(1
"200112779
((140
,211 recognized
were subsequently
and
(1964).
and '1400
Cain by
i.17'33by
'- .21."OJ.2
,:OILO.1t
710':.
opo0 and (1963),
so:
'(Efn.C. .24227
grey '7-vo:7.1-707- Cain
name the
granite2oop1:
varieties
and pink
Amberg
13,0 $:c04w-'0'7290'. originally
0d200in
70 1727fl..j
LI'I'J17'>[-°'
13777> area
rocks Granitic
given:5 were
Athelstane—Amberg1 the
'
L41
DESCRIPTION:
'$'L41.E-'-i-'2-2ltt 0.071372
quartz771.701
pink
monzonite.
170131.1' 14
17704>023
40.7 0170.4.
Atheistane
into intrusive
C:
'7307414
41 11040,701.1 quartz
are
0.'.II7 1%' grey
-J1,0070'0'1'1' of
970.' monzonite
Amberg
Dikes
217>274-, '0
23 >7,47077(27,0
FEATURES:
OF
SUMMARY
1'00
1973
4,4:41
24 1972
700>07070 to
March,
'>C001111'25
Summer,
DATE:
04 707
'1LIIO..:I5''o0 J.L.
011,207(2117,1Santa
'0,1144
11(10:11270(1 -1771 Anderson,
UW—Madison
and Barbara;
'"12077Cotter
722,73 0,70'j
''4>01
,174'12°0Jy Corp.,
Lahr, M.M.
111>1"
California- of 'opcq
Univ. "o"7707;
Myles, J.R.
Colorado;
0.7 Medaris,
4"1VtC1(. 74 Van
€L7.O
0007123 7-2
':l7C'94[17'o4i o.fl Jr.,
- 41-123471
-"oLIlO
L.G.
'417 :1> UW—Madison;
Kansas;
of Univ.
Schmus,
W.R.
0
'
-
AUTHORS:
.,
1230
'720
sec. SW,
72 '7019,1171, R.20E., T.35N.,
''741
C'T
10,
County Marinette
C
*lUi:
NW-&,
LOCATION:
°-: nol 01070
11111000
I 1.1110.,:Coo3ik.4 17-CO
012101-c quartz
9' :7041171: quartz
2310 2 >-fofl
grey Amberg
pink
Athelstane
monzonite
and OIL
monzonite
TITLE:
17
2
i7'7"J7-[14137'7 Trip
171 Field
Locality
43
so
�44
to cra'n-g: tnc8,
The Atheistane
•' ?ti.rtar.squartz
qta rmonzonite
mennritehasana amedium—
.tdtt- to coarse—grained,
allotriomorphic granular
contains tnC1
both biotite
hornblende,
grnttiisc texture,
cazte, aotlafla
blit.t: n:and
!ctDbJSilfl4,
and laSt
has a
a distir4ctivs
distinctiveappearanze
appearancedts
due
the;?4aGtLcS
presence of pink perthitic
toto
VSe
tH
from five
specimens
tve pasine
.i
microcline and white plagioclase
:L%4iC41dZiP(An
fLu23—28).
2ti- 2E. Biotite ttog
yielded
values
of
lOOxFe/Fe+Mg
from
71
to
78,
but
two
other
samples
gave
free
'1
tc
10:.
but
ti.,
gavu
y.eideC
'mpiUte aisSrhastingsitic
iaorsgatzt'hornblende
hrLh 'nieorr magnesian
values of
85 said
and 91.
of 3?
SI. Amphibole
"aluts
Foliation
is
common
in
this
as are
'atit. as
an
hastingsitic hornblende. .yaattcr So acts's 4, tbta unit,
recrystallization
textures,
such
as
aggregates
of
quartz
grains
aoryista.IUnt lea tn'.'a.'t, eush as s.srnstt'v e. 'vact endnmwith
'nts
Saussuritizationof
of;1.gtoe1.wsc
plagioclase is is
widespread,
''S'ep,d and
a..J
mosaic outlines.
wunic
c.t :.taa a*ssaLtrezcc
epidote is usually
bpdct9
43'S Jy associated with biotite and hornblende.
tat
flontc*rrp.nc
n4.trocive •n 'stit.
-/aluc. o 1cCflefZkt
ot $.ct tbi
sai;In
hntsti: iorcts&e.
ii
aErcJx!? ittib bloti.u rx1 'bunfl.su's.
The
greyntet'
quartz
monzonite
has a medium—
kcdL'r'totc'fine—grained,
fuav.znaad,
?ns Amberg
3btng rns
nnvzcut.e
PSLS
Although
hornblende
few
J) tto4L bovir
twtdt occurs
catynj in
ft c.a ...fl
hypidiomorphic
hypi5 cnrfl to granular
:'saaigir texture.
tO
Values of
sinisrsl. Vctun
samples, L1o;ite
biotite is
the most
a4teant waCts
mafic mineral.
'c. by
'ayfar
tn t)as
sol abundant
martin.
tn
lOOxFe/Fe+Mg of 67
69 have
been
obtained
C?and
rn E3
Jte.ve
t#sn
ctcwkfor
i'vrbiotite
?Co:ictfrom
trri two
i3 the
ji, ..tflstit
;uac
vcctv'.ib",
toLiecSn
Atheistane
quartz
monzonite,
foliationsad
and
specimens. As
saetnon.
4.c: in
recrystallization
textures
common in the
Amberg. Plagioclase
tat nbov,.
P\'aioo3 we
ita.tt ! tmcn@'. tezttns
b.ry,are
CC!14vfl
n' IJ, slip
nd
(An fl
22—39)
is sxartrc
extensively
saussuritized, bsat.tt
biotite is
Li partially
altered
39) iu
y gna:c:ttzcci,
to
chlorite,
and
epidote
plagioclase and
with
is, iS
0p2.*t*
14iis1 present
t'bSift.t in
:r p134.CtSta*
satassociated
6rcctttsti R±1.
tO CLLtZi
biotite.
blDt ito -
I
�,V
45
REFERENCES
CJ[.idul!
.CC r! y:'
Banks, P.O., and Cain, J.A., 1969, Zircon ages of Precambrian granitic
Jour. Geol., v. 77, p. 208—220.
rocks, northeastern Wisconsin:
T-'C ça&;
-
a
a
3ZaC
iRi1&t VVvrVy-::
:•L1.fC
citA:C
-: .J:
-
7—14.
J.A., and Beckman, W.A., 1964, Preliminary report on the
Precambrian geology of the Athelstane area, northeastern
Ohio Jour. Sci., v. 64, p. 57—60.
Wisconsin:
c:V. wViyr2;i:J t3-.r) aw
V
a
L7V-7VVC
p.
#cl;lJ'C,
r
p.ct
3cn1V:.Cavr
1
or :.fc.TraC3Cr7
CICC
C..
VVCC
Cain,
C C-
1963, Some problems of the Precambrian geology of
a review:
Ohio Jour. Sd., v. 63,
northeastern Wisconsin:
Cain, J.A.,
a
�This page intentionally left blank
�I
47
Field Trip Locality
:771177
3
7
4Ci . 7217.
.
TITLE:
.1:177,7.1
Belongia granite and Peshtigo trachyandesite
: [7777717777177 77 774777'
77
1
777]7 '- 's771:p 774
1"
LOCATION:
T.32N., R.18E., Marinette County, west end of
'.713?
77i:L'3.1": 77' 5r.: ,fl]7:
1,
.777777,
sec.
77"
NW,
.774
High Falls Dam
17,7]
:1
t
1777
AUTHORS:
Medaris, Jr., UW—Madison; J.R. Myles, Univ. of California—
Santa Barbara; and J.L. Anderson, UW—Madison
77177771 °1f
7,7 .1"":77',.7]
11771"[7t7,!
L.G.
"7'77.I7i7.7]]
1'
7
5777777t3
DATE:
1971 and 1972
Summers,
SUMMARY OF FEATURES:
fl.:""
Peshtigo trachyandesite has been intruded by Belongia granite.
A syenitic border phase of the Belongia occurs at contacts between
granite and trachyandesite and as veinlets in the trachyandesite.
.77'773 1777,7
.4,7
1"177177711.11
:
'7711
77.
074(7!!I'777'7777L
:7711
_•.••.1"7'[71.i77i7:7P77
2rc "l' 13:77
777
IL )7S,77:11. .72
77:77
.1777:11777.771
''1"" 1 2777' 77
777777137717721377
7:77
'1771,
.11'37i777
DESCRIPTION:
Belongia granite and Peshtigo trachyandesite are in contact at
but we were initially puzzled by the rather ambiguous
However, after examination of thin sections,
relations displayed here.
chemical analysis of rock and mineral specimens, and discovery of
more explicit Belongia—PeshtigO outcrops near Mountain, we believe
that the Belongia granite has intruded the Peshtigo trachyandesite and
that the syenitic rocks occurring here are a border phase of the Belongia.
I
1'!
'771.74
7771715'r.:]1i711
-'7
''1"'
.7
.1::.:.
7:7
1"
L:771477727117
:714
777:
.7
1:7117]. 77'I )hif'
%7'.:''7r
1:) 72277
--"i"-j-L77.77
fl
71
717717717777:
17r1':ln ..7277i777...171,'7717.cL7:7'C€
.1:177.7
7)1
.7777777
57,777:7 '7'":'7c 7.777 1'
3.277]. 41 7'r.7]
71.7717
,
77
7777
577's
7772'71117771:1C1 7772 :7;7.
this locality,
4"" tO.€
:r71"j0 7777."
13771
771"
7Y77 17'1]Z1.i7 7771
7717':
7
In thin section the Belongia granite is typical in appearance,
consisting of euhedral to subhedral phenocrysts of alkali feldspar
and quartz in a fine-grained matrix of biotite, quartz, and feldspar.
Granophyric texture, a characteristic feature of the fine—grained
Belongia granite, is present at the margins of alkali feldspar pheno—
crysts.
In contrast, the Peshtigo trachyandesite clearly shows
evidence of recrystallization. Relict feldspar phenocrysts are set in
a fine—grained granoblastic matrix, and the phenocrysts are surrounded
by a well—defined rim that is intergrown with minerals of the matrix.
In addition, anhedral poikiloblastic hornblende and biotite are
scattered throughout the matrix.
Thus, thin section study suggests
that the Peshtigo has been recrystallized, presumably due to intrusion
by the Belongia.
Th7.T177':
1171:17.
"775fl[ 7717
77
71773177112
7777:1777 L77 :fl
777".5.7 7["'777
.1]];
"
)74fl14177
"i::7flfl 72.7.177 77
7
7771[:7
7
"L"'
7:7717
.77177'777j' 77777 13 21 27712772
7:.] 71" "
773.i77771771: :7L 71777.7777* L :777. 71.7:1fl7>
.
[77
:7
.777 1.7777
7:
1]:
L,7]17711111717;
7
11277777 1
W.%' 77:'7.1 1]7:'77
7:2 71752 .17 •'1 771: J3.:'777 771". 777
1-:j7..;71.)7
]77.t. c..11-:1tse.J
Cc::"777]i T.7771":1 :7 ::71,
.7"7L)777TI"".177#' 47 77111 :7,Ltl
'77 1)7771277
17
2
:7777
5)771
•70777a'!l 777
77.7:
7.
7271]
7!1$ILTZJT'73
.771
7]12777]LItflLl7. 777
L"p: 7j7 77127.21477
c'77 711'1
771r!717"1:771.I.
"1,7
57177C71321.'717T.77T7]77]1.:17:7777t 7771
777777 177,772' 2
7777
7157: 1:.7
177":
77.]
77,)*"
-ij
777]
71
71717247
,:7117'71$.C7]1 7717
751 1T\77.1.777
:7c.477t?
13
.717
]717
7i:17"77'.121*" 7.17777.771
:]771]7ifliJ7,77, '• I LI 1177)77771 7.127 F*"V 247711€ 1.!
777
1<"L 777
7,1'
LI
£2
�48
If sooolttc
con'ca'o
to Do
Lweaothe
th: tctcocgla
The occurrence
syeniteatat
contacts
between
Belongia ot'oi.
and
5l,o(1''3'i1Ct of
33,0
1130
?'aootlg'c.
o:gc,rthat
tool the
Ito
Peshtigo
and as
Peshtigo,
suggest
:'sii,I 543 :ijcutting
','to'nc the
at- veinlets
PSOJt
ig'IcLc"
31 soil ai coct'iaco;
t%o Fir
'Loll :a Chemical
syenite
phase cS
of the
Belongia.
analyses-'o,,,:-cio'a":'o±o
demonstrate
'a border
to,'1oo ;l,ooo
to' a
371 33 Ic is
t'Ic,t of
i,'30j nie4!,r::e between
teI-'co-a' that
,:3 granite
tYct I to La
that
composition ofI syenite
is intermediate
to'a ocopcoTttitoia
tin—
'1 the
laic na!c'ci: , 3
Lilt Tot
I -oo 0 of
E' biotite
t1"aI amphibole
I:' 433,'a' and
and trachyandesite
analyses
-L a tO 1), but
ai'aca'noD'aioitirJ
1,9 (Table
to-,':- mafic
t',3333c 3:01375330
(Table
reveal
that To
Fe—Mg
St :aL:Lco
ratios
acoare
'Li (1.':(1,ir
higher for
minerals from
coal 'toao
1,3 jilT:- 2)
iD 101
cAlthough
i,'Oli oc'aOI::'a1013o
I .;
granite and
syenite
for those from
trachyandesite.
300 tiJti"
.3 to than
Inca :Fctr'.ooov't
010'tlL71liOtaiOili
o'aY3been
toot due
coo ppartly
cool4 to contamination
development
ofaDo
thest-coin
syenite
could have
cçco'at 33
:c' COOLO.
40::3 in the
it':
'000lL-:icof
granite
by
in':'
reaction
i"ac",3or
'ttL
with
i33--oij5i,'o'ac't1:atotrachyandesite,
perhaps
reflected
00 47-0233 :'
oco
(1969)
have
occi
'['.4':
'-orb.
a
'ta'o;tatvc
:3"a:c(J,o
1:
Ti02
content
of
the
syenite
(Table
1),
Luth
and
Tuttle
TaL 3Iii"L/i'ji_
:looo,
in
a
granite
DLI
'a
7
cici'S
flO:
shown
experimentally
that
a
syenitic
border
phase
may
form
3,1:3233 3:0303 tool: 333t4- tl"at a rot' tiC bcc'do:'t
margin
of
'1,
t'ova,
'lino
cov'c,'a1iotto
5'ai'içO,
04
113(133
taicc,:'o
:3
m:at,a33al,
due to
'.0 vapor transport of material between the crystallized
'cot'
olcJLly
a:-'
-,
to.
still
partially
molten.
3
1-111
33:3.
'30
Theinterior
attot' ci.' portion,
an intrusive
body and the
otto- oat:": 1:33:
.,
113Th
: fl331
53123'i'34 other
o':'oi"c, Belongia
iIOiL'Cv' 'a
1 coal 1,':i:t where
:441301 localities
Syenite
hasU'o'co
been observed
'ja'aor'co:I at
3-' several
St-a'otts tao
03713231(1
to-i
0?
'Di':,t3o
alliLlOl'
4001111
40'
1PC'(1'0'flL
'to,
granite40has
intruded either Peshtigo monzonite or Waupee volcanics.
030'L3'
30: 'Il,tflhiilo',I
Doctirltig'; lco'30
monDi,: _.a Peshtigo
on.:4L4' intrusive
oa o'ic'CLT?t into
For example,
a clearly
1T33J'cI1.2 'a granite
03:7(1(10 to is
JILt:'
co:'o'pl c'. Belongia
t:'at-ooc:t
33310,
tiT
3
037'L':to'
''at
((1311
0307' 1:130:175
- (at the boundary between sees.
zonite
Mountain
133. a
a arailroad
aOL -i,-.ti cut near
'':'tc'c.t'o in
o"o.II:',,. over
-ova::
-33-toogranite
7aznt to grades
::co)a:::
:113,T.31N.,
3 2a - R.l6E.,
toar'lc County),
14
and 23,
5, 1411, -' Oconto
where
44 an'S
"
14
sharp
that
lb-ta
:':."icoo
several inches
into aa ot-a':.ita
syenite zone
11 inches thick that has a
"-'23,0' 18
L,n too :co,,c
orCosi.
contact against
monzonite.
00(1,3107
0-33--o- Peshtigo
Foahtig'o acoacasi,'ne
.
-
-
-
:1
os:: 32'
23 7110 Jtra--O
IT,
Electron
probe analyses
of331
Belongia
granite,
-o'ot'o-ta 37:130and
Poolct:t
1(1:03
•o:ctoco-to
Belongia
border phase,
and Peshtigo trachyandesite
117230
Do: cog La 3-o'--do"
Table
1'fc:lo 1.
:
-
1
31133
Si02
Ti02
1144
153'
Al203
76.8
2
65.2
3
.68.3
4
57.8
0.21
0.70
0.64
'3-14
1.45
11.62
13311
15.31
141,43
14.28
16.60
Fe203*
3.20
:- .
6.67
4.48
10.80
MnO
0.03
0.02
0.05
0.12
MgO
C, 13
0.10
0.57
0.63
1.36
CaO
0.75
1.52
1.74
4.07
Na20
3.16
3.66
11,13
3.76
41,434.49
K20
TO
5.15
6.69
5.73
4.35
101.02
130, 4
100.40
99.61
101.04
331,331
Total
*
1
1
2
:j
3
Iii l-i'
as Fe203
Total FtFe151
Total
Belongia
TM' 2C
7-si cng1s granite,
g"iaou' <.0',
tb
TM 2B
,': ar in
iic Po,3c''
<ki<:.Y-i,?3-.,.,0a113
Syenitic veinlet
Peshtigo
trachyandesite, 'TI
44-',ji,-'
'at LcOAi±,.Yc,'0
localities
Ji'0335 at
In-oi"co: border
o':'tii,-' phase
Average
two coca:yooo..
analyses, Belongia
'3 433
7.7 '23135 of
iLt'i - 33 and
331-3 M2
near
cr4 69
'1va:c. 507'L, 171.2G
:0: Mountain,
-S
4
33-4
Po:t'cSoci
Peshtigo traco'H'ctd-oo''
trachyandesite,
to, PP3
�r ;ratictf. rnn.tt:
513—548.
115, 144S.
Mem. Amer.
513-tk4 p.p 113,
magmas:
ra4xnc granite and
cqut
Soc. Geol.
'wti granite with
-v..tl' equilibrium
in phase
't
p)tas vapor hydrous Thc
The 1969, o.',,
0.F., Tuttle, sa
and W.C.,
Luth,
'c4., u.ctb,
b.1.
'rico:
hynct
Lr br
RENCE FE RE
Tfl
PP1 ittu.
trachyandesite,
Peshtigo
hyeztlc tr Psuitico
2B
ai
e •nvhth:
frar
from Amphibole
iii
33
from toltts
Biotite
i?n
44
TM nttD)et,
veinlet, syenitic
nctatti o's
from1 Amphibole
te.ptf'ace
trachyandesite,
Peshtigo
psgi;
t.1'v&&Sp' 'r
ytr2.sj,
PP1
13.07
3$'
8.81
33.18
32.07
32.eV
28.91
0.95
t\t
LT4
0.74
..Jt
1.06
3.85.r
——
.
9.76
:..
10.00
.0
——
l.fl
1.75
1.76
•,fl
1.33
1.45
98.18
98.51
94.5
80.8
95.1
•—-.
- z ''.3
Mg + Fe
Fe x 100
t caE
Total
a; Fe
LeO as
FeO
•
1.59
8.37
t
•
22
2B TM
CL veinlet, syenitic
M\I&).tfrkl from
trON Biotite
g:aat,
granite,
85.2
93-4
96.4
0.92
3.72
3.tt
2.81
2.3'
1.92
40.97
41.40
96.22
93.54
43.4
95.72
9.12
.aC
CaO
MgO
0.74
—-
MnO
34.96
541S6
34.4
34.98
'*
Total
Na20
-—
——
1.02
ipr
ItS
3.23
K20
8.59
8.61
——
——
t
——
——
14.26
13.22
2
3
1•,•
5
1
Belongia
Biotite
lainsgLt from
fr3u' igtite
2C TM
2
ts.'
'5.i
34.07
34
34.17
.fl.fl
37.81
4
5
FeO*
A1203
Ti02
TiG
Si02
FtC2
.1
1
Peshtigo svt
granite, Belongia
Bc1cv.hs
trachyandesite kcsht.7.
tp.cl';'w&lsssatu
and tw.e,
phase, border
:cndc: Belongia
$,1tvtga gns:.ts..
amphibole and btuu.tr,
Electron ¾,
2. Table
Yc,tle
'ca
from açb±ao.s
biotite of
a! PaL:flS
analyses ;tct*
probe :O4v,n
49
�This page intentionally left blank
�ICnI
CCiT
4.
201CC C of
rocks. older
CI:o--otcCoo::
CC. contact
CC diorite quartz Hines the of Emplacement
T CCC 505 and
metamorphism
5.
p1Cc gneiss, Macauley
quartzite. and
I51!C
q11CC. Waupee
50CC coo and
CI:;:cLt-o of
i 'n5-5 CjC
C-C clasts contains
metasediments,
metavolcanics
which
conglomerate, Baldwin the of deposition subsequent and Erosion
Ill
I
1
::LncF -C
v.
s> iir.y
contemporaneous).
IC5Ci 2:CIT
been
have may
1.
-;:Yr;o
os:TzCCpL
C5=-C4
5505
rocks.
sedimentary
quartz—feldspar
"Cp;C1Ci:tCnCoiC:. pooo CC53I5.0CCC !4TN pzoo
agglomerates
and
volcaniclastic,
and
3P5:17
"0C0CJbCfi0C
I?C'IP"Ss the
t? 1531
001;. of
Deposition
formation, Waupee
2.
rCLiCTCCCIFICrC CCCIILYIC
1:*.CCJI-:;J:L1.
metamorphism.
contact
attendant
with
TC7CC5 CC0CC
quartz to 5CJr2;0C2C2(C
gneiss ;;CLCtCVC
Macauley t5]5
the of Emplacement
monzonite)
(granodiorite 55050:
3.
CC.OUI101111C55.C
cCCCCJ Ccn
ECO
metamorphism
andpC1
Deformation
(Events
3 CCC
and
IF
2
T
CI?C-lC;1CUC
•Pco "OCCOCCOSS tuffaceous,
and
calcareous,
s-si: , o::coopJ..
o500CCC
flows
volcanicC —
of consisting
i:
CCC;:
CCss5 CIIICn-5-I 1o
youngest: to oldest from
events,
following
the
including
"00CC 5105
CQ:CC5 515.
05 [CCC C C
area,
03. preserved
CC SCC0s Pis
s'; history
CC T :oo 0C3[inCCcC.
Mountain
the in
Precambrian complex
A
AREA MOUNTAIN THE OF GEOLOGY
DESCRIPTION:
5Th CC
C
yocovos:siffare
0CCarea
5525 Mountain
5055 •5fljp 55
theC10
of history
geologic
presented.
j%05
" iTs
I?
p5±5:05-C: C 5CC
are
001.
0iIL
map iIT:iiT55
outlineIbCC
sketch A
this
at
illustrated
the C
ofr:rT1[1s,t
and iCtC
locality.
T20,.tC.ssclfeldspar
.5005 ç;- Hager and rhyolite,
C5'5C.C..:C 5503 Baldwin
1: l:10flp
--F po Hager
iCStsy:3 conglomerate,
Th;
porphyry
115100551
c
CCC0?2Ci CC
0111 the
soI1C.1CC.54:L
;cs member
upper
:51 Waupee
Cs:. between
formation,
the of
Relations
5-: C
.JX5. :1 Th
FEATURES:
OF SUMMARY
0±1:31
C3 C53,
"CCSummers,
515 0151
1972 and
1971
DATE:
Kansas; of Univ.
ChlC"
I"C"1 Lahr,
"1.soo; Cotter
C CT and
M.M.
Colorado -Corp.,
''I iS0CICi5iC1I._L33L
":— Medaris,
1To_ -"_y; L.G.
Schmus, Van W.R. UW—Madison;
Jr.,
AUTHORS:
.05:550 R.l6E., T.31N.,
505 Oconto
P110:3
County
1,-
"51511
sec.
OilS
SE,
NE-,
LOCATION:
5525 15Mountain
area
C51CCC1
5I5 rooTs and
5i-i'5j: The
55 of geology
:'o:c: P5511550:3
CS and ".
1:50.10. Hager
rhyolite
the
porphyry 3"Ci1±5:5
feldspar
TITLE:
;-iIs
55±:13[
4
Locality
•P-sp
Trip P1
Field
51
�52
".
6.
H7495707)f,aJ:Ci .7,5',
o'ios.t batholith
OItco.asIs"Th (1450—1500
cf"1sc
of
the4aosf
Wolf River
m.y.),
including
H, .5nc1s0J,
7.57l5y7$),L5,
1's-Is'S
Igo ,)ç71(33t
Ott Hager
51'051'," syenite,
Oju'tlfS. feldspar
the Peshtigo
monzonite,
and
:t'IJ .137 '.7" porphyry,
9,00
)159551:17ç0755:7,351 of
xa0 Ool
0777.0 granite,
son's tO with
rhyolite,
Belongia
'2, and
75. lOs contact
1c)ltol, S metamorphism
.1:)' older
..dcicr
,&557'J.Kt9'77:,51'5
Emplacement
11
:
rocks.
r"77''3'1 1' and
11153. steeply
2713 Waupee
0'1157'55',t.'sOi dips
The
'l1710'cs formation
'.111 strikes
N55E.
M15)507•O' about
'55ss011't
Ot.o':,
7-oH sot
Relict
llTGaO cross-stratification
-3)77)3'- 555333711 '1' 370- :1'
3111W
'1.7 cccfs.Loss.g
¶959 155a55'3 that
graded
bedding and
consistently
indicate
'I,7ll'075'1,0'I'L'
17'a'lst tops
llTs
0:
of1150053:9
beds are to
to tilt
the.5-cotio;
north; there
1't$9. is no
evidence
repetition
"16 01531.
)1a955' for
''01 '25197:5
Hc:is of
of. beds
3159 '90101199
15. 0571115 the
within
Waupee formation.
C'r'flt CI'S,
5
15
/Ot. 51531191 has
11751 Waupee
l'a'ITJSOOI formation
,sLo-a9 units
ooc'ossI,s.tLrs'.
The
fIlLS. been
i35,t")5757'5
divided
offosSinto
fo'•:a three
(Fig. 1):
1)5
1195107 ot.55:1i3. of
SI'S' metavolcanic
a basal
member consisting
17I1''ois aIl91a1:f'9$
£9.;-5.."OsLC-2.111.5: and
llat'95. volcaniclastic
10 0jIt,L3'jLI4111-'1O meta—
1s-tS5-'
0 and
sedimentary 1701
rocks,
.s.
.i:r: .L 515517
.9075 '91317 :o'o 1115719
1:71)517'
2'3t1J510'LsttiO'7
3,'
a :nmiddle
metasedimentary
member,
IsIS. an
Ii's upper
505,105 577, the
1•''hP'S'a9omo 97i5'31-,9'.1.
995'"a,Y'T member. Within
7155711]
tuffaceous
metasedimeutary
0)19 'bas,sT.
basal member,
.111-:'5JLY-157
basalt
7r)t),51.f"7'1i75777,7
7:7357, but
71j'95j577l977.90al5 type
is tHe
the predominant
of volcanic rock,
andesite39 and
so
553,'5.7171,55,9,
95,7 rhyolite
7'575:.7J 17553
LL77of
3-"'11M
53'H.
occur toward the
IsIt top
the unit.
'0091a5)5L.
ll,rt5719 505
Chemical analyses
of 18 specimens
fo:..caa,r1c
7'''-L1' belong
)1 calc—alkaline
'S's a
'IL's.volcanic
'loScolt: rocks
demonstrate that
:la57', the
5505)7259, to
:::li053&1OI,5L.i1S sequence
61'.7617101100
)1.Ja-5
7"t9.?aO 'lOs
7,15:7 setting
7
15571,5 '1717 (Lahr,
'7755
and 55557:J
could
have
originated
in an
Ifs island
si 1010 arc
0511:57:7 - 1972).
15
.,
flC."')071,079
in
formation
have not
been
'50aup:c' .ls:-as
1395 11513'I
'.1 the
'LOso Waupee
IICIiU.tO 75377' evaluated
091.955077: 73
L 55S
.e.1700 of
completely
yet
because
0.1 complexities
'3 lo.ç'I357._ '0.5555 introduced
5517 1710'7953050 by
over11' 9523.'
lapping ro),.esn0:s'caJI',:ot.'oaotlll
metamorphic events. 02551
Most ,ss.jsocoLccoI
specimens cOOT)
display
2157710 :)0'9t7'107
9' assemblages
119515 :.os05bs.s5-os.., but
characteristic
of amphibolite
775555a'l 1a1'OT
:3 facies
'9) 57's metamorphism,
ffl'.,'I:,'esso
5253 505 s :05
S:,'I garnet,
99251r17:IL, idocrase,
951-7','s occur
5j05'51,']0i05 :7'): of
.a5.,7.2:0i1rs)Ls7o origin
07 contact
1:50795'
.15371757 in
scapolite, and
917551 andalusite
1c5715515535 metamorphic
151. rocks
11052.957rhyolite
05120112:07
a-'.1'.'.':112 ' S LOs, .11,93,1
51'-55 1591.Ca1s7'lOsSI Hager
i05"15'7i 719 and
of15i.lr-a7-si:5:''so.as
appropriate composition
near the
Belongia
11 granite
'2
91507
191519315's porphyry.
poJ1o1'-a-r7.
and feldspar
54.5tss,j/:1''701H1s
Metamorphic assemblages
sC71i07.,L1,a-535I'
-
I
.Yo' 0505137'rIrtf
FIELD TRIP
LOCALITY
Oi'
'12 57t11&5.' W are
9552 tuffaceous
In
the woods
south ofofCounty
:17025 outcrops
'3'S '15' '5152 of
oco51 S'a.a53'j,
Ccor Highway
Jo. 255-1
3'S:.
the upper
:sLseWaupee
'Ozcspeo formation.
I scoaost)'oRl ,
Cot
On
.sp,o"— member
co-s 5500of
c2 the
:),',5
r,"i1a'J5711
a
7H50'1a9
15i517'N3,.,9
rr
351L75o1Tll
015
232
the
north
side
95)
of
the
highway
",
are
outcrops
of
Baldwin
conglomerate.
155'
571111
'5550
1,i,a 1
:1195'i.99 t'LaI of
isiS Hager
7:55:95 consists
7150151105:112
00,'I1t1:. in
.,5sli05751'
10959, prominent
The highest, most
outcrop
area
1I.osOOr feldspar
071 this
51513.51517':53'9
porphyry, and
between
porphyry
s7157 Baldwin
iOssl7,'sr
305. '9 S l91:1tt
fa57']feldspar
2T1515 10071950.)
fl:. and
-170-a an
501 intrusive contact
l'07a55211
,.$j)07JL base
7J115
5 '),995':'
Ca.JI1L/ii0'7
On
conglomerate
is 9-97,1,35,7
exposed along
of the
'571.9 outcrop.
f37,5 the
7,75'55 5' IsO
a95to'10 the
1.150 southern
3a-1,-,j,,'7,
:55
7'7';:177:711'5'.7551
S
a,'505a5751117
97
55515s5.t
3117.11
1':571,Wf90
15157,955
north side
istot)'
'5577,1 of the
171 prominent outcrop a gradational contact between Hager
513:571555775115 is exposed.
512,25,'s'4'955,
rhyolite
feldspar porphyry
Cf 'Ccilooosao'
"Jr fl I SLISO and
55)
1sot1.rl.aio'rocks
"3/3171]inr,
metasedimentary
.579
55'-
:
REFERENCE
77:111715.153'? of a greenstone
a:o Oconto
7:173,j1595'S.'1 a
lbol.. in
Lahr, M.M.,
belt
i0'1k, Precambrian
.51]39s95.5'5 95, geology
.1,19.: 1972,
'.i1,57'.715'çj'iT
eoa;c-- ''3L7;5J115O.
93'0)'i95!'s'11,17',: of
County,
Wisconsin and
isiS the
117,15 Waupee
volcanics:
on'I geochemistry
-50155117;
')'b"cO' Univ.
i'a'yl
797j'sis,,
505555
M.S. Thesis,
Wisconsin,
'55'H.s')'1n7 LI, Madison.
'a
I
�P4/
//
-.
.
'
1?
/
P.
/
Jp \j
r4 (
"/ /7/
\4
.
A
/i '-I (
-
ILI
1
i-i;-'
7
ILk
.1'<•
-
'4/
)
LL
L.G.MedarJr&MJviLahr
Baldwin conglomerate
bc
Macauley gneiss
WI
wm
wu
mgn
Hines quartz diorite
hqd
JUM
['?IL¼
4 LI
bg
Peshtigo morizonite
pm 1
metasedimentary rocks
metavolcanic and
metasedimentary rocks
::;.
tuffaceous metasedimentary rocks
Waupee formation
'
fl4LA!1..
../ 4..I/;1'.
i
:-.-'I
bg
Hager feldspar porphyry
Hager syenite
hs
hfp
/)7I:4.75
Ii5r!
L_
'/.fl/II/1,lp J4I.,
T"L4//J A/. H
a..'
7
1//—/-.
://j//
Mountain
Hager rhyolite
hr
4/'.'' J11 [7 tiar'I•t I
[7 d
I4/iiA]
/1//
1/4
—117
hr
Belongia granite
bg
EXPLANATION
±iL
j
*¼-;
C,T R /
7
\/
7:;
/1/4/
I
mile
iL ¼ijI(4//
ri
4/
17/
If•;
Tij
1
A
S
J.
I//v
hs
I'..
j((
/
-.
/
L A" j
,;
;.f/.:/,H LdhiJI.%
'I 1kv\/ D.cH (T.
¼'
GEOLOGIC MAP OF THE
MOUNTAIN AREA
1•
j
I
i
�This page intentionally left blank
�55
Field Trip Locality
5
[17
TITLE:
The Wolf River quartz monzonite
t1ILL_JJT C:tCHH[1 I_• L
LOCATION:
Menominee County,
on the
11°
IL
—
-t
IT
VT
—
Z,?
—
H:.
_—
SE*,
L
sec. 22, T.28N., R.15E.,
of
the Wolf River
west bank
NEQ,
V
IZ"'I]°(
AUTHORS:
L.G. Medaris, Jr., UW-Madison; W.R. Van Schmus, Univ. of Kansas;
J.L. Anderson, mv—Madison; and J.R. Myles, Univ. of California-
•1Ii
C!
H
HHF4 <Jj
'C
°
HL1
I
°
c-HTrI
-
—
I
I
—
Santa Barbara
l1J&flL H >(j(! j
DATE:
and 1972
1971
1LIIC [L
4IT°'I HHTI
Summers,
FHHU1H
SUMMARY OF FEATURES:
1;2
(FFjj!i'
Exposure of typical Wolf River quartz monzonite.
rT4I ;i
HLT
DESCRIPTION:
VJHCcYi
The Wolf River quartz monzonite is the most extensive lithologic
unit in the Wolf River batholith, accounting for 51% of the exposed
area (see Fig. 1, page 10, this guidebook).
:cc çT
:I
I
TI
.T1FIHTJH
H
i
:•
L
—
The quartz monzinite consists of large, pink, ovoidal alkali
feldspar grains (1 to 3 cm) with a medium—grained interstitial matrix
of quartz, two feldspars, biotite, and hornblende.
The quartz mon—
zonite is massive to slightly foliated and is cut by aplite dikes,
some of which contain scattered, subhedral alkali feldspar phenocrysts.
'yHT-H[iE
i1 H=1I3 C)CCI
JTflT1 ''HH TcH
Z:tC cq
4T'L©H t=
2Hi)II
He;C5 c(qI
HHItJ:HI .CCI
HIP
'IHI L.V :H
!F
L
H4
I
C
L
;4Q
p'
tJ
L
—
II
F'
:H
-(
At several localities along the Wolf River the quartz monzonite
has been intruded by dikes that resemble the Red River porphyritic
quartz monzonite. Two such occurrences are well exposed at Beartrap
Falls on the West Branch of the Wolf River (sec. 4, T.28N., R.l5E.)
arid at Ducknest Falls on the Wolf River (sec. 27, T.30N., R.l5E.).
F
1PE I
(C
°
(
°]i
1 IF
Cc 4j1
—
t7• :.:Z '1J
:__L: 1
I
Tj
)14V
C CvI&L
i:;:
1
IH
T1?
�This page intentionally left blank
�57
l.it:c
Field Trip Locality
T:
TITLE:
6
The Red River porphyritic quartz monzonite
LV' VeEV' n!I41.V'iSLVt
eL'ç
LOCATION:
:;l :.*T1Ti
°fl
R.14E., Shawano County,
T.27N.,
2,
V
sec.
on the Red River
)çy) LV' 3IV'C Lyi;
SE-,
aL •IpLVI:.
SW-,
37
AUTHORS:
UW—Madison; W.R. Van Schmus,
Univ.
rV)Vi IV'
L.G. Medaris, Jr.,
and J.L. Anderson,
of Kansas;
13W—Madison
3:
3
-3rL-t
uTmfl )JV
DATES:
Summer, 1972
LLZ1
SUMMARY OF FEATURES:
V'J
Exposure of typical Red River porphyritic quartz monzonite
IL c:V'VLVV'I
ty r)1[ V'L TT.
fl.d:c r
DESCRIPTION:
IV'
The Red River porphyritic quartz monzonite constitutes 20.6% of
the exposed area of the Wolf River bgtholith and is located in an
ENE-trending belt between the Wolf River quartz monzonite and the
Waupaca quartz monzonite (see Fig. 1, page 10, this guidebook).
')t
ç
•iV'
i
ThLV' t)L7-
V':tJ
V11:rL LVV'
1V'V tT LV'4'Fli
i ir
—
-
Fl
I1
—ft
VD& :: j VS Cif1V2
'LIL7
4•II.E
'11
1> tcCL7
At this locality the quartz monzonite consists of 10 to 20%
subhedral alkali feldspar phenocrysts (0.5 to 2.0 cm in length) in
a medium-grained matrix (1 to 2 mm) of idiomorphic to subhedral
quartz, two feldspars, and biotite.
The quartz monzonite displays a
prominent foliation due to alignment of feldspar phenocrysts.
çJ t.
;"zV':i' 2QVSLLtIL tLY-
zci rzc1;
LV')
° C)51
I
i
i
—n
nj:tccri cj
'
LI I
$3 'I
TTi3i. LTfl- LJ
H7Q7f 1'4.T 7Lta1V'fiIflC
LC TL6I;=LY
c
11
I
€4
i)v&:
�This page intentionally left blank
�Dissertation.
i iv
.pcc...Lc
I cli7Vl LiC/, 447, 4I -
1965, The Origin of the Tigerton Anorthosite.
IITIL
W.,
Cl-1c41J,
L.
C-.Il-:
unpubi. Ph.D
U.
ci
ycv
Weis,
Wis.,
fill-a,.- (IL.fl
Reference
-ccr-aiI avccc-vcc E
NY.
y'cc
1s14.;
The most common twin is the Aibite twin.
Pericline and Carlsbad
twins are common, the latter has reentrant angles.
External optical
scatter occurs.
Grain size reflects cataciastic deformation, with some
outcrops, e.g. SW-, Sec.11, T27N, R11E, appearing almost layered.
-
--21
a-
1,1:1cc1 ILsCflacc
C-nt-C-I c Ct d-yC- 411'tL)CC-Ll IltILl I Ill-till :?fii.a-fl ILl cca(a II4Cfi\C
vral3cc c mc,ff'lvaw.;. cc-vt tc-;fl,; cat- rcrt-ntc'c c-cc- crr.a-:
ma- t'r d-a 'cacc:ca1
-
-
1fl'- l-714kC)ll 111
-q. [I
'C
-
1t11-:cO1'ILLclnCI :ccw
cn4
ccc a, La-trcitczcc JlaC(.)© 1-ILl
The composition of the plagioclase by outcrops has a median value
of An53, with only one outcrop having an average over An56 (An60).
The
larger common inclusions in the plagiociase are hematite, hornblende,
biotite, ilmenite and magnetite.
Very fine rods of these plus rutile
also occur commonly in the 010 plane.
C
-1:15
;fi--
11117 CCflV
II
c-4;4c-a]aiI fill 9hiT
..
-----Cr r'CCccc-accrC I41( 1,ji .11-I-1141".LT flC.'-iiftL)tCCll.iCCrIlr
1.-I
Ti Ic'.: fl1-cr ar-;a 511:5-Il pa 71 ccv caaltC- cat
iall: tilcIlla SILL
l4t1c cccync
city CLLLCa-l .- I aCvcc'-.'L-rcr-- a-y1 a-ILL
-
-
72-rn C--m:ig
c- Lid pita-
fill-cl cia: 111:,ILlfl t 14
a-fl TIc c-c 4p1fi.1471: 4 Tdll
The Tigerton anorthosite outcrops always include granitic material.
The anorthosite exposures generally are small with the largest continuous
The contact with the Wolf
masses exposed only about 35 meters long.
River batholith is sharp, both megascopically and microscopically.
C-
l.-L1IL
C
4llIIlLlli s-1
Cr1: 1ILfitilT1
4-c-
-fit-IL? .111 pat.-: mc
--fl icy c--cc -r-;nt 7ia-a-- ccc Sr Lccr;-:c-5- CCr.L!-C,IC.S, I4cc)I1IJtLcI
LCt -? ll1-rcill cLttcc ducc-ca:-c cc macc-Cr ,Lt c- -I-Li- cU
I cct—aa;caac
1111 'i'jj
.clcCnrczv
4(
ififi 'wIIc
C_i.4jL
:c'ca [IICLS
The Tigerton anorthosite may cover 125 sq. ml. in western Shawano
Most exposures are anorthosite, hornblende anorthosite, biotite
anorthosite, or gabbroic anorthosite; a few are anorthositic gabbro.
The plagioclase ranges from An32 to An64, with most of it An4 to An56.
Grain size of the plagioclase is riab1e; 5 cm. grains are common and
There is local foliation.
grains up to 20 cm. occur in porphyritic parts.
Biotite is second.
Hornblende is the most conspicuous mafic mineral.
At some localities pyroxene occurs as cores within hornblende, occaIlmenite/magnetite are common, with ilmenite
sionally it is discreet.
Locally, as in the SW-, NE-, Sec. 33,
far more abundant than magnetite.
T.28N RilE, these affect the compass.
-
1'C--Pfi-dP
'lftT
-cCL
C
0147
C
'-
cc-a-c1::' c:n-::--c4crn 1r1k1 a1.c71rcL-c
CflC:rT fit
c-fl ?cuvfi 1tcc flalcILa -mir cc -s- CL3r1:c-; ca-c-i 71
I .rrjrcLflcC, 1 fl1
imLad
I.- 71
--••c•'.1,T-fi ;ICL
:1111-ca-
II
.11
40 lIla
47
v-IL-v1- I;LIc
711LC:L.
It
l-
'ta- - fl
Tha-LLa-..Lr.plc :2
-: IL11 v; 1OCT11
iv
'my H ;1:;l1caifl: cc-co'rcicaa'Crl
a.CflILc-1 cc Cfl
l.t
iltrI.II. IL? 1-IL -ca-; 1i-filc.1iCi ct-cl pcc---J- C'IfiL di -cPU Cm II- iIL-0I- ILL/v a-;
l'1fi-c-LJlJtC..,-lc- It -ILlIC
d-ll-t.'
11:
C., I
CCCII
Ii
CJyII13 tt:tdt.IL-'c9 ca--n vcc:
-Il 210
c-ala-crap
wcc-.
alIt
.1
: ma-arc :ra-171IL-.:l?
--cc
7.
c-t7
v5rycrcrcc
-c-laIr 1:1:
lift
—flIc fl -I-fl
7a-
F
I?P 1a--A5.IIL am cap-ct s.
3111ilyfitLcilfl SI-Il iccr:ILC Or?
Ca-a-la- I71ui cmiv
Cq
ILI-i'.-p
Co.
acILCLICL4
DE SCR I PT ION:
'-c-c cLLcaI-zccrcrcc r-;r-c-c3y, - p
:l.l?lIlfll- Lt--[
a-c
Contact relationship of the Tigerton anorthosite.
-
?S'7cfl,,:cc £4
SUMMARY OF FEATURES:
-,,-
1,
7.S4aJJOIS
Summers,
1962,
1963,
1972.
DATES:
::cy-=crv-aw-14- ::.r,,-1l-
.
dd?IC/
-c
a
W.
;a--Il1.
L.
UW Center System—Fox Valley
Weis,
AUTHOR:
pcc-c
a::.:ip-[ cva-vc.xct1ta5 7'IlL.I-J
1C
Art 50i1,
SW--, sec. 23, T.27N., R.l2E., Shawano Co., Middle
Branch Embarrass River & Co. Road J.
CrC
-cT
m4fl Cr1a'
Cram m.-ra-1rv
iafi
4c
NW, SW,
LOCATION:
0711104 211?' iti J(?lirtj,
a-kr.
The Tigerton Anorthosite
TITLE:
Lcc-mca- -rfl;a- p407,1
Field Trip Locality
7
59
1
�This page intentionally left blank
�61.
61
;'
r:iLca
ctr:L,o
'1
Field Trip Locality 8A
TITLE:
Ec1. :9.e
1
au b
Eau Claire Dells County Park
LOCATION:
CR
sec.
T.29N.,
7,
R.1OE., Marathon County
c
SW-,
AUTHOR:
LFLtirg;
UW-Oshkosh
]1
Gene L. LaBerge,
DATE:
i61TL
iTa\
31.1b721
Summers 1970, 1971, 1972
k
''..J1i1S
J.5l AH1A: A
SUMMARY OF FEATURES:
i2]7s;
bt
izA1I
ti2
D:1L :Laite
Ia
•iL9.:g;,
Eau Claire Dells is on the western margin of the Wolf River
batholith, consisting of a large expanse of relatively homogeneous
"granite".
This is in marked contrast to the volcanic rocks with a
myriad of small plutons and large scale shearing which characterizes
the geology of Marathon County mapped by LaBerge and Myers.
ti;i
2'
Ai
Ian©b
Ja
ct
eTk
aag
1xaa a; g$gj
;a-& iLt:.ny riA
by
i2t
:-J tztiL L(C)
:tLCJ
.CCRH
;cauaacti.c th;. I bt]huA
ijc1i
ThISCZ
ra'
IaL'Ltari±n
C,oaarA
•f gaagy
a.:atEcat
a3tcrc tXT CBC
a arIact
A major shear zone which strike approximately N30°E occurs at
or near the western edge of the Wolf River batholith (informally called
This shear zone is
the Hogarty hornblende granite by LaBerge, 1971).
particularly well exposed at Eau Claire Dells, where it is more than
However, the zone has
a mile wide and consists mainly of mylonite.
been mapped for about 30 miles along strike, and reconnaissance to
the southwest indicates that it probably continues for at least another
A number of other shear zones parallel to this trend have
10 miles.
The magnitude and
been recognized farther west in Marathon County.
number of these shear zones thus constitute a major aspect of the
Precambrian geology of central Wisconsin.
Cl
AIaL9©11
V
.t 72i
icr:
race
Ltaa :cccta
it b
isad ArAc:
c'c.
c:'.rc;r
CL
raiUj
La
icl.IrcI•de
LjC
I
Ac blacaIb-ci Ia; -cc-el; arAbic: I ciA re:ecIgi7i.: beea
icrccc Are-i .-; cc! 1ircbac *.
Ire.- at IA
air.
LId cIt asp-c-cl c-rIce
a
:c11
C
I-rrAL.i-cc
1Iae
at
cc;iele
I
-
11
cr
jCHCcTiHcUJ7
Eta ci; S.t$yO€;Sdl
wthta- yc tcrabI3Tc2e c.cCcty tIAa
:
Able
lad
9
]a:JLCcga
Ia
ccntc
1JL -c
;cA
.
LTz
I Ia7
il;
—r
bare
Tb
CR
ciA
acre
Lcccc
c
ride-Al tbviic Re-s
aç•9 ccii
elI tic ceec
1
cc!
JPU.c:aci-lLeIaa
-cieiLcyy
cC;
DESCRIPTION:
maccc-rely
•rGii ttccccidy iii; IlIad
cartacci, dcc ci:;; Li
;icii
'rr-4 Al
irL
Ac
?LaIcI
At Eau Claire Dells county park the exposed rocks are moderately
to well banded.
The banding dips vertically and strikes approximately
N30°E.
At the Dells proper (just downstream from the highway bridge)
the rocks are relatively fine grained, felsic, and homogeneous, and
CL-fluid
—U
c1.LCRc
ip Idri iCc
1
cc
A
It
d
cc
bT1
f-c
,CRiLHC
Icac
D
y-ç
-j
Cj91[
—
AIcr; be c-:acum i:Incd
ccrccc Ac
;clc-;w]c
LCRLL.
l
1
Irpli A
caR
1-I___
cccl; Ac
do not display conspicuous banding. However, further downstream (near
the foot bridge) the rocks are more mafic and are more banded.
Upstream
from the highway bridge the rock is well banded with alternating mafic
and felsic lenses and well developed quartz lenses (boudinage structures)
evident near the dam.
Small garnets are abundant in several zones
immediately below the dam on the north side of the river.
East of the
swimming and picnic area are outcrops of banded amphibolite. Thus,
cicpriic 1R-cCCIVelrhtdLii
U
cci
i
lb
izerc;i-cl elcuic bccrAiw4igc
'ii
L
11411
c
Ic clIcL
eCu;
4
I
LLi
tK2
:iJi'Gii'CClCR
:i jiij lrcc-c-c-: i51C_it
re
tic 4
44i Lw
ci
cc—'
C
I
rcuurc; la-c'c-:--iiia!,,
c
ICc_
1
cc
airi
Ii 4uiliLc2,H
-
-r
—
I
1
—
IcceciLl
IcLL
_c
U-1i
'ci
11
TiItdV
1'
i1
l111l
eccA
L
I
Ll1'
-_-'
it
II
�62
EXPLANATION
FOR MAPS OF EAU CLAIRE DELLS AREA, MARATHON CO.
II
Scale 1:24,000
—
L
cd
Cary drift; terminal moraine.
m
2
Mylonite- and related cataclastic rocks.
kqm
Kalinke quartz monzonite.
'1±
LI'J
hhg
[ dJ
mvJ
k',j?'J,j,'2, granite.
JJt,.:L' hornblende
Hogarty
Diabasic
intrusions.
1.25 '''1
1'
:":1., '±:2 and
Maf Ic volcanics (locally metagabbro
amphibolite).
Outcrops, or outcrop areas
Geological
0i'jc2';
contacts
Rockpiles
'
Quarries
I
�—
2J
N6
I.
—
—
1
F
r
i
¶1
_________
I
/--"
,
U
-
-
5-'
-
,_"
-
:-
LU
-
/
4'
——
———
——
I
-'
,k7e
4':—...
F
'
I'
I
US
5'
U,:
U
—F'
'
-:;
—'
-
II
-U
-
1
:
I,
-
It/I
//
-s
--
-
-
4
-
t114q
-':4
':1],
Il
•
44--
IC
t—-_
I:
-
4si
-
•1
•
/
I
z
2\J -
C'
-I
-
-
-
�64
J1
Figure 1.
j-• l3
and lens-structures in Eau Claire Delic
Ba ding
LÀ
•
-
upstream fjAL.
±'om the
t1t Licge
brdg on CTH—Y Light gray iense%
al
Larker gray banded materifl
1± i
rt
prcb1
v boudin.
quartz,
i babl
areqatz
:;mjH
Park
•fic rich.
::
Ltthth mafth
is rrelatively
structures
a-
aoth
the
banding and the lens
t
P
fJ-
tearing.
thrmed as a result of sh
thg
hct
are believ 1 to ihave
L
D
Figure 2. Ba1d.
CnJin!.g mc' ltns structures in fe]sic mylonite
±L_tJ.
just downstrE?arr from dir bridge on CTH-Y. Where the rock
is
i
more homogt
--meous, the
I
L.
banding
and lens structures are
less obvious, hut they are still a common featureS
ktl
-
-
I
-
�Lcturestru flow
groundrass.
ndirr
-
f
surrou the
tH of
and feldspars the of most fof shape lens the
:- the grained
Not matrix.
Felc 4. Figure
fine a in "eyes" flJrkspar
L
.1
-
ce
p fracturec the that Y1
sir'± irrdu
ua
rt'1air
pc
overall
or
Cl
De S L'ie
from 'tevct' au&rtz formed
lens-shaped taller
grain, z
River
LC2
ç
the
f
nt.
JJTh t7±.
Eau
'e
lens
.
-
-
30
X31
X
fragments.
also note and
i.
zone. shear
Figure
-
-
Jhe
iote
Nc
u
3.
65
�66
tti the
n-Itt
IT:
'IL'aaicittlct' on
the
composition
range from
cc,'lr,'S 4ILy of
nIL' the
cir'n mylonitic
L ciaci i'arocks
:'4m- :"a4ILa
ttam "basaltic"
east
nan C
4" the
LitmCenter
'L'a'vI:';'Dells
tam Inarea
tans taIL
Itt ti"basaltic"
mta,t a a
to
"granitic"
in
and'ILant
back to
'ct 'gamin
,,
- j ci,r::;:m
ttS':L2
Compositional
acmIncn i'll'
'nau4nci ' I'
downstream
alongrhthis
cross—section
of tin
the
ci,caama"
shear zone.
ILcirn,a:
tt"na'n: attiama
LaS tat a'of I-isa
4' a.;
'r;:r,lmn.
Inca? are
variations
inca. common
both
andacitacts
across
talUs
thea strike
the shear
cltit:i:iCLL 1,t
tact,": anal
". maalong
,
'r,' appearance
alt: character
'tint aa,ncnic'
'tr:ar"aan-m'.c':a'a and
with the
LIt':: result
variation in
I' the
:a'Tata' 1 of
zone
nIL aa -'a:'ttti.'nLr'
zcanni,LL
cof the
1:'am zone.
Variations
aa'ci,aaadepending
ILanami - na 'W4t'?
upon cU
whether
Ct,Rt> t hydrous
act-n :Yr C,
7am
a an lcra also
tItan' arise
a ant' ,
eat' anhydrous
;acrla',L,:c:,m minerals
Lan'aILt during
i'iaairL4:
',
t,,p'aJ,,, (feldspars)
yam tna'tra'ti formed
minerals (micas, etc.) or
cn:i',r,'tatILai'a:i,tac1
'tamIli an,tIL'an,
recrystallization.
alt.
taIL 5t
5çc laSt along
it, and
aititaL::the
tic:
Most
of the
Dells
elsewhere
act Eau
tat CIClaire
:- a' Cal
cl,:, Itbanding
itt; c-IL?
ac'aaIta tIg at
acatactal and
'actc
atic'a,it,S' of
aiRvariously
-'nainacs" ILflattened
Eau Claire
River
actually
Fain,
:lcIrt F.
''a' zone
?a';ta;tlIa?
,s consists
IL: length
IT ttgn
aILS ni'::range
cnsct in
ft nit, material
elongated
::tt,:t of
na .-hrla which
caL mafic
tInt" canand
IL' felsic
at
at;:rzm'a:d lenses
Snnclr.
Figures
ansi 22
Fi':na'te 1IL and
mci a
':-rtc:',c:Th'aof
cL aim
from more
than
a fraction
an inch.
f;ncc
accca
tacta amile
Lit' to
Microscopically
cataclastic
mnymlJiaja lenses.
lcanams
ott the
ant smaller
illustrate some
'l'l';raenco; - aaiLLI' oanaTLca,atI,n
a: of
Thus,
"tb-as: maIL4 4are
art tcnaa'-features,
such
inifS
Figures
4:t'i'5t 31 and
common.
at SU:as
asillustrated
i,, tt.ttitdI La
IL
anti a cia
?'ni;Tc:5[ tectonically.
,,:,itt :tr}n,:c tt,i 1
i, a have
'tarn formed
'a'n Ut!
t-a'agt to
the
rocks in this zone
believed
,,cy'c are
'itt rc,nlUaL::ltmt'
a-n
9::crnags:
Shearing ttai7
may ;'acmctt:t
produce the
banding (as
well as
ar, cataclasis)
ta:cacilaaai R't'ji
from an
tI't 4anILiLf
aa 'antI
a:c'ac zone
stint ap;;:ci,aILan
a: crosses
'actitac aa shear
initially L,'n',o'gaa':a't''as
homogeneous rock,
maIL' when
approaches or
t,it:,mLam,,l.::
"cot-, and
raIL,
a cattaIL
4at,c'nc:'i
'$.":nai '5 'n "L:tl,t:j:aaia,,
Inca at's
Lam
contact
between:tacontrasting
lithologiesLas
thetam
banding
may
be r:na'i'nna
pronounced.
-Its
ILLs rocks
r';tim ILn'tk'c'n'n*'c
This
situation is
ta 14::, II represented
ac.,cr-'caicadT by
4; the
between the
ti-n evidently
'"a
"a latter
!a'nls " ittaiat;':Ta
tim-n
hut tin'''
road
bridge
damLa;
upstream.
anaL the
titan 'IL:
''caaa and
-
I
-
�67
Field Trip Locality 8B
:811 1IC'I"7j 1)1011. )ITS1I
TITLE:
Contact between Wolf River batholith and mafic volcanics
!Y1II
CtI 111 it IFi11i,1I
CIlUlCIf
1C'070U
'C
11111
OCII-0L.fCtCTI k1ao':
II
LOCATION:
I
P1) IL -'r
T.29N., R.1OE., Marathon County
18,
sec.
oqLCC1I:Ip Ct0-flUC$UII't
I
ej C;-. 5j3
I
I
N,
N4, NE,
AUTHOR:
Gene L. LaBerge, UW-Oshkosh
DATE:
Summers 1971, 1972
s
OF FEATURES:
SUIVUVIARY
The locality is typical of the contact between the Wolf River
batholith (Hogarty hornblende granite) and mafic volcanics. Near
the granitic rocks the greenstone has been converted to an amphi—
bolite and, as at this locality, when shearing occurs the amphibolite
may be well banded.
Although lack of outcrops prevents determining
the width of the contact metamorphic effects with certainty, it is
recognizable in the field in a zone 'about one half mile wide.
J.LU'0.i
—
CU-CI
=-p•P;::
—I _ :
-
8flU
RC{i 1111 : ItO
—'
,
r,_ .
t"— T
L-CI41 OCIl
1-
I
1
St
CICIL
' 4 jV •lfl
:8
1
zIr;I1C'jr,J:CCplTII 1U111LIT18t- ICC -:
11C
U' E C P:ICi,CIU'C 'I.lU' 8C'U-iIiCU
p3 U
L
'—'-
CII ,-CCCOfl 0€-
CU'
j
:11
I1tI;_.CI TIll ILIfUtCI -CIp (1 71:1:111 Ci
€17412
:-: TiI.11I
L
IC tq
CCII-C
I
--c iwIr 1r.;iPT-173*V
1I) L1
Although the contact between the "granite" and greenstcne is
poorly exposed, it was mapped on the basis of lithology of rockpiles.
Rockpiles along what is believed to be the contact consist of a
mixture of amphibolite (meta—greenstone), granite (commonly pegmatitic),
vein quartz and in places metagabbro.
Small dikes and veins of granite
vein
the
amphibolite
blocks were observed at a
and
quartz cutting
east
of
the
"contact zone" consisted
number of places.
Rockpiles
granitic
rocks,
whereas west of the
almost entirely of porphyritic
"contact zone" the rockpiles and small float in fields consisted almost
This change in rock
entirely of slabby amphibolite and greenstone.
40
type was generally restricted to a
acre (-- mile) width or less, and
at least locally the change in lithology takes place on opposite sides
of a creek bed.
Thus even without outcrops one can locate bedrock contacts quite closely in many (but not all) areas on the basis of the
lithology of rockpiles and/or float. Trenches dug for burying telephone
cables were especially useful in providing information on underlying
bedrock.
,I7'C7
CIIIZ
CIT
- I j -
-
TUU'"U'
s-
U':Ux,7UJ
r' -
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U
11
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8)U't
r& '1118. OCL.
-y
- I'
-
U
EU1I-i UICICIU
1
tJL"I:I?cA
1
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—
1t tL 8 t
I
7cU1:.:j: U-J1ETh:::U±DIT1t
I
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CI
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I
$Illt.
—T :1i c
li
;Lcn Cc::t
811711
Vfi :155I8
T &[
-Cit
;xirU
tJ.E7 UI
-f
'YI)i
c3;ILz
1ifLt;
-.
5t
I
r•:r
i3
-
1tL
¼'LrL1CtJJI
,CU'
'
8IU7
I- 93T;dItcC--
I .CyC.! rF71I2!t2
—
C'
¶1-I
C
i'31:c7U:15i;U214-IIi Ui Y:oU:CUvU
L
-
L-C
;CIiLi4 1fr:c
118
8I1Ut
t:1:I
t5';icIv:i-:I
:I7rrI 11 6Ut
r-
C
::: t:LX ct: rzt L;::
it if I
Tr;Lez: i1ir:i:i89 :-:
r
a:rq z
�68
'<if•'i
FOR MAPS
c)
EXPLANATION
?.c0
:L,:J 'q AREA, fJA'SJEu1
ILP<J<2.L DELLS
OF EAU CLAIRE
MARATHON CO.
<2<J
,i-•;<2 LIi
Scale 1:24,000
5:.<
<21?L7h SL moraine.
Cary drift; terminal
cd
1
m
<2T<2
Mylonite and related cataclastic rocks.
'UT<2
kqm
Kalinke quartz monzonite.
hhg
Hogarty
hornblende granite.
:i:Y•y i'l'c,v±c..
dj
JD* L.1L"1<2:
my
.:&J=.l1
and
• L i.<2.'L;<
Mafic:i't2z1;
volcanics
(locally metagabbro
amphibolite).
1
L
Diabasic
H
intrusions.
<j:c1HH ''<2<2
<22' outcrop
Outcrops, or
areas
,-'..-
<2
Geological
':•1 c"
2'
XL<2<22contacts
Rockpiles
'
Quarries
I
�1'
R.IOE.
I
-
-
I0
M
/
hhg
-
my
k
,
19
..
V
-
I
•1
-
,
I
—
d
/
—
-
—
—
C.
/
I
/
1.
d
-
/ /
'•-•--
r
•,' ,'
my
hhg
/
/
29
I
/
m
I-
/1
C.
—
:
/
I.
hg h
i•
I.
,Tr
r
It.
1
/
,
'I
I
I.
I
'I ,
i,i
,
,
I
.1.
•
/
I,.
Ir
/
A
m
/
/
m,
—
—I
m
'.4
/
/
A
/
A
A'
A
0
/
A
my,
.-—
- C-
//
.1••'
my
/
/
,mv
/
/
1L)
m
m
/
4-
A
l,
(iI
--
'p
—
/
C
/
/
qm
/
A
'A
,
-
——
/
,/
I
I
rtitt•
.tii—z.
C
I
PV
-4
K
Th
4
/
f
I
,1
'I
K
——
/'
/
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• .—
C.
C
.•
'K
:
III
I
/
•_—\
Q
tr
Cc
4
C
I
i.)C
•--:-.
,;;
N.
R.9E.
-J
i1es
F'
/
/
C.
•,
—
C
--
C,
N
- -T-J
.--
Cj
CtJ
I.
cd
¼
It
••
K
S
-.—-
'-.4
JJ
1'
"'C
•\C
/ a::H
,$/
-
A
,
/
N.
/
kqm
/
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1
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-
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"C
�70
DESCRIPTION:
5cL iLSS'
au f!/
@5the
Sbc contact
.lLc.rttc- @rs
cc ccl
are coarse
Outcrops of "granite" within 100 feet of
St.:
:1.
cc
cc-lcc712
ctc:c
"granite"
for
several
miles
to
the
east.
Sc
N•ciT-S of the
cc.c
grained
tcU ccitt
and typical
4111
ir
icc to "granite" throughout much
Indeed the rock is strikingly similar
T'ti
fltLtt
lt.TSiT-tc
c::Jcc
and
Menominee
counties
to
the
east.
1ftIllJ
.ctt.
lIt cc. - valley in Shawano
ck.c 55.? River
of the
Wolf
@5
of :
-.
l
-
'
ii
L-
'
lcici
-I con@t:,i is
itiL1l1SC'f', but
? IN cit tcc'
The contact
hasc,:ct
notb3i,fl
beenLCICI@
found inci outcrop,
I'!lcift
cc,'i-c/ itself
c:.c?r
ccl
itc:LI191
Y
Along
this
valley
one
can
-.j:citcac swamp.
c'ccif.t•r under
•rcrciLiLl; or
Sift. a
ri. valley
veniently in
:;c&ct
icc,ccc:
::;cinc'sIlc
-'c-IfS
granite with abundant mafic inclusions.
.iIij:Cc1.lc 11@cY¾
find
blocks @5
of the tcccciiccit1
:L—i-: numerous
Vi:LIV narrow
liTil
rsrc'cc zone
evidently frccr
form a very
5c"-•ct@, cy1.i±-itijJ
5 :.:- Ctc-,, however,
'ctiii ¶-5,cJ1 blocks,
• -c5.
The inclusion—rich
-'ciii
Ic-cd
S
t-c
rcnSc@
tI,cc
tcic'
@'Iit. 'I and the granitic rocks on
55cr west
cc the
between
Sc
'.-iittr.ithe
55 amphibolitic
' iic.Ttiti IS : rocks on
-
.-
r1,•c *311
5
the
east.
:'c'c-ticmapped
ccpcJ1 all
r15
rocks
'?-cc'iplutonic
cIt5cc.
:ct± the
'5t ct•cs
t if also
: C$flLT'J
This
stop is
typical&cin that
itt7
-,-,c5.cr.r:i'-i',r oiLcttcc-'
Sr.,c
:-45.:- the
intrude
older volcanic
sequence.
I
121-il is the
;L
itT' iccgeneral
dLfl''da area
Ic this
cccI dccl ci:
cit. '.c,ia in
5 important
,i9cTcft1 and
An interesting
problem
Sc-•:jt
•c@;3 uc&jnrci: of
:5 cS@
the Il-SLI
Wolf River
:1*
[i; the
cSc@z
SI'.a shearing
relationship
to
emplacement
cr5 c± crlI.. of the
5?LciccLJ,c-cr1
cccc
crc
cii:'
cc 'clcflcc:IS of here one can demonc:? localities
ccc': S
5cc
At a number
of
southwest
;tt,
5wi5kircJt'S?'
batholith.
cd'rclu21ti-I
55cdiL5lI
hcti
rdrcT'lT'-ji hornblende granite) has
:.'i'r-.r- batholith
Sn:ccS ± :1: (Hogarty
-cc:t ttct
55cca' River
strate
that
theWcI
Wolf
clLc::
Sc
nc-c:
1cim:crgneiss,
-:'.Ccc - mylonite and
granite,
i.ct.-i5cc gcrcc5.
51, augen
;-L.cccC ar1. gneissic
-Ic produce
been c,;i-ccic'cC!
sheared to
'c-cic.
c@iL-cill. will
:-: if -R This Iproblem
123511cataclastic
c-cd---?,ocd:,r-j.c
i:cScon
cc a¾ rather
1 -aIccI large scale.
other
rocks
c.cclclcifL
and512cc-nINatural
1:--the
t@ Wisconsin
:crcrcc GeologicalticS
-ccc tc.c by
ea mapping
--:--c- as
be @zclitrcl@
examined further
Lnt
pr.'c
ccci:-:,
The
presence
tibitI
cd
southwest
along
zone.
LL:-LtLS-± this
dc-ic
101
-cc
History
Survey continues to the
c: c.'rcc' c.-.'c-tb7
1515' crocks
r dcc may
ct c 15115
of the
batholithiC
icc S'rcrii.:
c±L:c.cof
major s;cc-,.cT'rL.t
shear zone along
the
front @5?
@2 a
¾ cii
c-tc-cticd
c-c
Cit-I batho—
the
c-cc
emplacement
5la3ftLlt-tL-t
of
the
ccJ
ncc.2
cc
ccinftncirc,gT'T'I
indicate
that cISc',
the shearing is related to
ccilT'
crits cc-icr,
cf-ic-cf which
i-SlitS
Lt1TT,CnCI@ along
1,-.,r,U1L L.J
±'l-ck- as
iii a buttress
behaved
,l' 5-ltIitlfltL
51
lith,
or
perhaps itc&t
that 'Tcd
the batholith
Ni:- t@•1¾L.SL.
the
shearing occurred.
-
1
-".
�71
Field Trip Locality
i±CC
9
J,
iji
TITLE:
L-'UI
Wausau quartz syenite — Old Technical Institute
c-
'U-2:'CTioC.:'ojt.
:iTcC0C,c',1Lc-itCIt' :i-r
-'=r
LOCATION:
Marathon County
T.29N., R.7E.,
'U'U-
'U
35,
'U
sec.
!:fl_'
NE*,
'U
AUTHOR:
UW—Eau Claire
0—C1T:2:
Ltc-Uc-
:
Paul E. Myers,
"I'U,:OOUiYO
'U
DATE:
2:-fl
February,
1973
.TTt7tJEt€.C
SUMMARY OF FEATURES:
c;crIIU 7n'q(U!
An early, medium—grained pyroxene—amphibole quartz syenite containing NW-oriented quartzite, schist, and volcanic xenoliths is cut
by coarser-grained, flow-lineated quartz syenite of similar composition
(Figure 1).
Average xenolith orientation here is structurally continuous with the concentric lamination of the Wausau syenite pluton
whose granite core is in Ninemile Swamp 5 miles southwest of here.
"Rootless", lenticular pegmatite with walls of coarse K—feldspar and
cores of quartz were probably differentiated from the nearly crystallized
syenite at places of greatest quartzite assimilation.
Thin screens
of biotite schist and quartzite were raf ted up(?) and brecciated in
the viscous syenite magma (Figure 2).
—"CCC IlçU4'UU.c-I CCCC1C
TC05TCthC.=c-QCCCCfC CC'C'çCC2:-=TO'C'0Ci
Tj ijC
C
i'C,C
T
flTh
TOC2: CC t
ri ' r ;
tiiI ki
3'4 CCC CC CiCi:2t" tk'
i J(il
=ur
0
TiQi :4Io2:T i::'TCC
LL
'Ito
r:;mitt.
i'Itt1ci
,i,'l; &\trli
UC,0CCii 2:1L7 WT(1'
CC
-
CX4TX'v22'0'L
,2:
000 ii:•::c-rc
104.T1!iX
U'
Lc
—
fl'IL''tT00ii c:iz,o.Lni0t o:2 2:0
CT:7
r,4,,)itiic-l
t
''•rC',C 7CC
C''Ct Ut
c-
I
I
4
i20U,k Ci
O,c-c-i[
YT'0tiit±
F.T.04
'Ti
C
tian
DESCRIPTION:
4iTP TI' fi ' 1T'1r
cf iLi 4"1[I
According to Weidman (1907, p. 203—208) the "Wausau-type" quartz
syenite is composed of alkali feldspars (orthoclase, microcline, albite,
and microperthite), barkevikite, hedenbergite, fayalite, biotite, and
quartz. Accessories include fluorite, apatite, magnetite, zircon, and
allanite(?).
L'.tlc-.[
'--r
T
ti
Ir
]0Iic--0act
::ti2L 0 S'
c-i
viJI3p;4:
0
r
I
iT - <)
1JT
:
tcCL :1 -
I
i(iflT0t1flT
;Y:B 4i;$
Structures and cross—cutting relations of the syenite phases
exposed here typify those seen throughout the crescentic northern
rim of the Wausau syenite pluton.
They are listed and described
below in order of decreasing age.
[)1L4
0c-Ti. ..1-c- 00 ?f0T.an:1-
c-c-OfI.
0.:ThflI!Jc-;t&:4=
uii-ic--•o
ThJDL
ji4c
:4: :j. r2Ii7. o-rot
(LLtt -iT-i
OLIL
fC•
c-i
i0C TJ.1
i1i
�72
-:
II
.4
I-
—
1
5-
4
5
I
—
-5-
—
—
,_zl.,
-A"
A
L,:;-'
--r •
1
j
V
' -A
I
*I•-••_
•
-
-
'-21
-
—
'
-
I
At
—
'
-
4-
---S
-•
-
-
C—
-
•'-"
'1—
4A
--
_••__IA
-
•
-"
-
—
_•',
1'
-1'
—
-
-
-
_•1,
I
-'
--
--
-
,
/
••
-
-
5-
: -'
'
-'
':
-II,
--
-
I
-
••
—-
,'4' ':4
-
-
':
''4/'
-
'.-:
'
1,
-
5-:'
I-I-
-
--5-_k
-,
15s'I -A
•,,
s,'I
'hi
.
45-', , ,
—
A
A
—
I
'•,5A-42-'_
-
/
—
-,
-- '
—
-''2-
•
-
I'
1
•
'/4
2-
-—
-
_;A
--
-
-_
-
-h
//5_
-
-
A
•
•
5-5-
A
-
'—S
5-
-
-
'
—
-
l.'\',', 41'
•
I
5-
,,
'-'5- 5,5 •
-
-
L
-
-•
'5. •
.
I"1
-lw',' 4'',5-:5-5'
—
'
-
çt5
5-ç
I
-
I,
•
-
I
.
•
-
4-
-
'4
-
•
--
'-,-T:_ •
-l
-
-
::4'
:
-
—
I
—
'•
7
5-
I
-
,::-'- • II5I
5-
•
ft
J,_
-•
••
I
—
-•
I
- 1"
-
-:
,-•
-
'
-•,•,'
••-
,.
'
-
I:
•
k
,.
I
T
I'
--.
-
H-
-5-
A_I' '.1
I,,2121'IA_
A
'-
:2_' '
•
9'
A
I
5
''-'''-"
C-
-
•
1
A
-A5-5-'
--'-
P
'I
2-
I
55-
-
-----—I
A
-
•21:--- ---2s.
.1
'
-
•,
'_&••*,
-
fl5-:4s":
seams
5-2-slt4.,::LElj:l,L:5-.2-2-1I
with swirled lineation and thin
Amphibolite (a) xenolith
•:lc:.JA,._i'1421L1b1,A,42Figure 1
Lenticular veins with
-
;- A.534'P2-'5Thf"ftL-1'2-
1
1''
'11
of syenite is
'El cut by coarse pyroxene syenite (psy).
c:'1,-.1tatQ
; ,,—
t1LZ4-1L'-1L1_'i
EHsIJA mutually crossq-:2-r- (q) show
walls of K—feldspar-: (Kf) and cores of quartz
2(ICI_
Joint
f'!VLt'rhI:2-Ifl',s1
intervening offset
a small fault.
111 W
_'-2-_ along
cutting
relations
an1Th,C2-'VL1'2*1'th'1
15-21?
'-'15- with
24
115-Al I'
-1,11 amphibole.
1_s.
A"'
i'i- 5-s'
coatings
are
of coarse, sodic
Ah-
'f2-- 5' 4Ui
-
I
151,5-
•,
-
1.
1.
21---1H41:;2 syenite.
They
in2-12-il i-La
xenoliths in
2-21 the
:c: X'lh,!IA1'L".2i5
The oldest
15.5- cAt :'::5cIftt,:
rocks :1:4::':
here are
'.'2
ILC21
*1 2-4,IC I
meta—
-:-c1,t1t-21151 amphibolitiC
1-2-21.112 4121 -: -lr,-J, schistose,
clude
recrystallized,
212FA!41214442
:121.1.4 thoroughly
L*2-1AV'
±2,15*12-S tuff(?).
unaltered
felsic
5-1-2-211:5'-.L,fll22-2t45-2l
4*1*1
volcanics(?),
quartzite,
'I222-2-5-A/flH'
and
virtually
2CsJ.A!1_i:,2-LI4)IC-I parallel to
xenoliths tend
2-14: to
- be
.r2I1-•1*1ltl
-T5-±
aer,:: 5.2-2-2 of
Note that long dimensions
it1'2 ::i4 disparity,
despite
lithologic
211-152-45441
21%
tIal15471.4%:,
lamination
and/or
foliation
and
that,
*1124121
i-Cl
:*14:.6j4)Ic,1I-:
-s
1:4211%'
:5"a.L "grain" to
distinct
structural
a
ã.2-tlLCC
,—:ar
i:
-Lka±r
c:52-tkP:
1117:5:2their mutual alignment imparts a
21.?
:::s21.21j2,
considerable
2-21 of
tCi- be
factor believed
14211-2112- to
fa:'.tc:2,
tlLc
1:2- — a
the21'rJCL*1%21
enclosinghIyE21LI
syenite
*1l1it21L5
4' this
11545-LI pluton.
rnechanisma
55-2--2122- 1:2154 :15 for
'5,2-,1a-iI-211412t
42-151221
45I:215--ICç
I
significance
in working out emplacement
2-I
2-'
l--
14
5-4
rai ,
2-'-
22.
ilyllIl-ib I
4.1? .-: 2-: syenite
flow—laminated
-1-2-C :; 21.-I quartz
- -E'It1i5.5424' lensoidal
41:csm15rair.L?2- - '152-121
An early, fine—grained,
.-IrC
phase.
—. chilled
-.m15!lal 2155-2242-.
may represent
Ta-'--Y,C
45-Al/-C_I a
I
-
�'3I,3L'1$ 'UI'?
377$i'35(7'3'7573
Segmented metadiabase(?) screen in flow—banded, quartz syenite.
117'
4- L4"712337—11A7-"[
36
-
'y77'.e33-:
''
357-:cI'316P'75-17
r7nam,, rr-,---', -'
—
-
—
—
2
Of,4f
•
7":
Figure
7/
-
—
"4-
8
N
-
,84
8.
N
•
A
A-
—
A-I
—
1
t
'
I
'4-4
-
-
8
j
'4--
4-"4-54
—
a_A-'
24-
--
:4
8 : -I,;
:44
'448-
A-
—4
-
4-4
-4
x
2
-.
eA—
'I
:4
'
A
A
41
—
2
-
'4
A- A
—
—
A
—
,
1
- Ar
-
—
31
A
--
A-
-
4-'
71
H
:
-
'"'8'.I7'LJC, 33,%1. 'L31[t :7823_H'TA':A531.:Y-c':y.'':-:',':PTS-
-=A-A-A--"
Coarse,
sodic amphibole crystallized along joint surfaces.
'7/'31!, 7'7':
7'31:':L:18(:73
''
5.
2323331':?
3.
4-5-
Coarse—grained, flow—lineated pyroxene—amphibole quartz syenite
cuts the fine—grained phase with sharp discordance.
This unit
contains irregular, lensoidal and tabular inclusions of amphi—
bolite, schist, and quartzite most of which show little assimilation. Although most of these inclusions show northwesterly
elongation, the enclosing quartz syenite displays highly discordant flow—lineation with swirls and eddies suggesting
considerable turbulence and viscosity in the quartz syenite
magma. After gaining access to the xenolith along its banding
or schistosity, the magma pulled loose segments from its
surface.
With increasing magma/xenolith ratio the xenoliths
became plastic and were strongly deformed in the flowing magma.
Quartzite xenoliths appear to have been more readily plastiA screen of
cized presumably because of lower melting point.
schistose metadiabase(?) crosses the south end of the outcrop.
Its thin western end shows plastic deformation and "pull—outs",
whereas its more brittle eastern end is segmented into many
angular fragments (Figure 2).
'74
Late—stage, lenticular granite pegmatite veins with quartz
cores probably represent residual liquid segregations along
incipient contraction fractures in the already crystallized
syenite.
They appear to be "rootless" and of local derivation
perhaps from zones of abnormally high quartzite assimilation.
—
—
77t11'3
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�74
a ih*
the syttitea
syenites eM
and
It is
'.s suggested that many of the structures in
itt
San1v.
Sntfr
L,.&zbr3cn
.Liin1'
indicate
forceful,
subvolcanic
stS3L*a
•(
t?
ii
Ytuasu.
quartz syenites of the Wausau pluton
4trIN,tULa1
aftt."'tlS
.!
Careful
structural
analysis
may
'22e-ILL
o
trz
w5.uclrJs
avafltt
V3$tVjection of dry, viscous syenite magma.
of
magma
flow
and
xenolith
mixin
rithi:.
1i
themchanism5
;wasntnt
in time
time s'ts'WRl
reveal the
twc instance,
traLtrce, nC
?t&t' t fn.çcmwrcs
fnt 1.a
Do the xenoliths, for
represent
fragments from
the magma.
thvtM'vJ
g
:salttr&
eM
ta;;;.
aatl
J
aflr
during
caldera
collapse
and
later
invaded
fault breccia formed initially
a:rLt -asvnn?
by ticw,fllflA
upwelling syenite
magmas?
t,q
cvg..;tz;'rl :tat nr 2! the 3tflfl4rfl
the marjn D the ntc] t;o.
f wit brte3. i £:sst
atE anz f;nv efl r: ,t; tt':tg *itt'D
2rrY
tJJ!
RE FERENCE
a*rth
of north
iTLoraw,
g..tcsL,
w,The
fl' nalts:
Weidman, Sanluel,
1907,
geology cS
'Faaa3L3Lr:
central Wisconsin:
£'C.
Bulletin
c7taat and
ax! Natural
Fsti..nl' History
£4tctcfl Survey,
!wtey1 BCLsttft XVI.
Geological
tV::cscs.':D
Wisconsin
I
�uiclrYrkJ,,
south. the to
tc FuNiclgJNtcuru
volcanics
1
ru
t j Ncontiguous from derivation suggest iN
mafic
syenite
nepheline
the in
auruiuui
ui
lenses and
INuruNuisur;
bands
ft'NYI7 tAtut1]
Mafic vr'I;rur,
pluton. the of
ciLL ucuuru)7113U1cuucuruizt
emplacement urvt
duringi-il itization
itttRrNutiNiN
mylon— by segmented and lenticulated locally were crystals feldspar
-5
'
2.
ICL'I
C
contorted: strongly is syenite
nepheline
the
in
banding
positional
54)
ui,:iUuiLuii))YN) and clinochlore(?)
iC lirY'lui JUNNNNN1L 1117 cancrinite,
c-r-irNrr::Nrr
tJtcu7cuuiu-I'Nb5'u
Comallanite(?).
thorogummite,
uruyIu.
(red)
(N
WL
N
apatite,
r' here), cu5
fluorite,
abundant (unusually
I_ Yui_t zircon
include
Accessories
Jj
(lepidomelane).
1—
mica brown, and (arfvedsonite)
amphibole
sodic ±± sodalite
at::riuiuia nepheline,
uiNil rc:rjoNtir1
vNINiii composed
aegirine,
Ltak:r±LNuj1il1r-i microperthite,
anorthoclase, of mainly
&NCYçJ.YiP1Nr1 is
:t4a nepheline
o'7N:di7-Nug
here syenite
k-iNN
7i2iiil Dvrrriel the
N17N 235—264)
T'7'7N) p. (1907, Weidman
'7aaz1
'7 to According
I
4
't[ 5Ni ±' c'
UYTY
I
I
t,fl
.i -
L
,_
1
NI
U
[
'- _i2
t:
l'7I
:r
NY
location. this at
N tI
across east—northeasterly strikes
property mine
N:1a
zircon
tN17
abandoned
the
syenite
N$IriN77N trtLN,JT:
tabular and syenite
N'7GiJZr nepheline
brirrNarr contact
r1ccN1tazu The
!Tjr,_
LiliN ttrryrl banded
J1iFilri.
b between
7UN
It:'ly
DESCRIPTION:
i:r,
rI5Ier7
:
(Nt$Z; ivN1:1i2lI
NJJNN,
near zone wall the
:crrr
ibe 1J.
ILJ stop
in is
t.zNyr
This
pluton. the
INI
of edge
south the
1
pyroxene
s
Ii
(psy). syenite
anorthoclase—rich
of core a and 235—245) p.
tite—rich
1907, (Weidman, syenite nepheline—hedenbergite—fayalite 1L
magne1 Nil, -:r:
caa 1:: in
of rim a comprising diameter
7:i, atIl2
mile a zone core circular a (3)
'
> pyroxene and amphibole
vu
t
and lineation, flow swirled
with
syenite
—RH
—
I'
an (2) (lsy), syenite
LjCL'
pegmatitic to aplitic of zone intermediate
aplitic lensoidal,
La
and (tsy) syenite tabular (nsy), syenite nepheline
banded comprising zone wall a (1)
mapping: field in distinguished
were zones
yr
major
Three
zoned.
concentrically
a2d
and
northeasterly,
1L!• is
J!
elongate
]1LL)t. in
oval
pluton
'JLi.7c syenite
;7v(J!c1f Stettin
S.tit7tz, The
JL2tcL
L:a1,
1) (Figure plan,
1,TJ
1
r
lIV
1rl_
i :iaKair
Ii c
at
1
I
i7
L
'
1b
JL
—
7_I'
N17i=/Jcrv
FEATURES: OF SUTvIMARY
February,
1973
DATE:
\ib,Lf1 UW—Eau Myers, E. Paul
Claire
AUTHOR:
t>/
County Marathon
XCaJtJrYs
R.6E., T.29N., 22, sec.
SE--,
corner, NW
C.T.H.
'7
& Rd. Stettin7
0:
LOCATION:
zone
'wall
tr'ita, tt!t;
Stettin
It•
— pluton
:L':N
syenite
TITLE:
j-1!IJ Trip
-H 1:
I' Locality
10
jc7,r'7
Field
75
�Figure
FF'/ .7/
I
76
'4-'
4-""
-
,: /7
"
SYv
4--"
my
"4-
.7/'
4-——.
'F'-
tsy
1
F•"
F
/
7r
/
-
/
1,7-Ft
-'7
4/
7.7.-
'>' '',7
C4---
7-
-".-
-'
1
1
--i-i-"
4-
/
/
,
'1/
'
44-
1_F
'/
7-",
-:
1/4-
1,,
'4-
4---'
i,
,
-
,
''
4-4
2
''j''i
,-'_f
/
-
-.
-
/_
F'-.
F
'
F/$&f,
.,.
4-''"
-
4-'
F"
/./
'
F-
-F
'FFF4-
'4 /
'-"F
4-7
4-'
,_e/4'
/7/ '4
4/
--
4-4-
-4-'
/
4/
'F'
-
.4/
4./'
j
'
\ /L
4-'
4--
F,4/4-f
-"'"-
—
4-'--F4--V4--F-
->ç4-74-
-
-- - -.
—9
4/
"-'
/4-
1
''fl-
.- -I
1.1
7'
'-4- - y':-
.—--",-,--.4-
- 4- '
4-—"
-
F'
F,
"7'
'27"-
-
-
-
-S_,4__-,,_.,
'4-'F'7'4-I
7-
'-74-'
.#
4-1
7'
4-
/4-
1/4' ,t,,,,
4.
'"-F
-4-
cii - -
-
'1
—-F 4-4-,4/
-,
my
—
'-"iFt7-,- /4-1
IF-_>,,
74-
5TTTIN
L'-17'TT"7''
7-7
4-
/
C
4->
4-
77/7/
-
.4-4
'"l
c
'.4-'..->-
,•_,,,..
-
1
' "'-,.
F
.'F'47
.1
r•f$F
-
1-'
-' ,".77'i
.;
'-4-'/',.'/I
-
Ii
'
4-V
--
—/4-
1
fv
,.' 4,,.
I
-'
IL
/
/ts
/
-—
/
I
C
F
4-
——-—4-
:
1
4
•
-
,
:.
/
/
4,
/
71
-
-
F
I
7/v
7'
I
/
._
4-F7.
I:
4'
/'
'
,
I
-
1,
>4-
F.4
/
'C ,,,
-
''v-1"'" /.- / F,-..: I
'
F
I
ilL ri
N
/
t
Ii
STETTIN
H
LIT I
PWTON
4-'-
"
1
I
-
4/'
F
.
1"
OF THE
4-
/
-
,,,,,
F
c7-
my
F
H
4-/F
4-p).'
MAP
'.!
•
,,
—
'F
/7
"•'-"•
"S
-
/fr/LE
- - '44/
,,0
F
I.-
4-
4-'
',,
,,/
by
PE.Myers
'1 ,_
Geology
F'—.
'4/174/4 p:'!,1,1
111:1 IF/-F)
Nil '. Survey
Wisconsin Geol.
& Nat. Hist.
4-i
I
I
I
I
4-
973
>Hi-.ft1 Li,yI4711C
EX7>PLAN
ATION
Qal
; LL'II
r
Lii
tsy
1f L/4-V!U-•)
A]]uvum
::
(U
C
L
I)
i-fl
Qgt
n sy
TM]
p
UNCONFORM
TY
C
gr
•
F
•I
Syenitized vo]canics
:'."ti,itispyroxene syenite
- —7
rsyap
ic/Fr /74/ .j,4,
5- 5/fl
Lensoida]
syenite
V
Granite
Amphibole syenite
Svenite
5'2i'- 4-/i ap]ite
t-> -
-
3/4/i/i
Nepheline syenite
7sy
-
:4--n'
Tabular syenite
r
mvb
--'--F-,--.
,,F_1 is -' -½ '-,'
, vo]canics
Brecciated
mafic
4-, F4-F.,
fv
Felsic vo]canics'I
mv
I
Mafic
F,,•
•
-
•
volcanics
a
�77
2
.
L....
Figure 2B
Figure 2A
Porphyroblastic(?) tabular syenite with mafic lenses
(Fig. 2A) in a matrix of alkali feldspar and interstitial sodic pyroxene and amphibole. With increase
in mafic content, the tabular syenite becomes poikil—
itic (Fig. 2B)
H..
-.-' ;4=
'H
:•..
IJ_,
='H
H'
'H'
'H
'H
H'. H•'--
-'H
H—•-=-''
==;
'H
-;-=.
H:
Ci
. _;'H
'H
'H
'H E
'H
H.-
ii
'H
"H
— 'H
'H
'H-
'l
'H
'H
'H
Li:
'H-:
Figure 3 —— Tabuar syenite with abundant mafic
lenses. Note para
alignment of feldspars in
maf Ic lenses and serrated margins. (3/14 x)
L
(A
1/
H--
'H
'H
H)
-
.;-..'
I
'H
'H
'H
'H
21
'H
Ci;
amphi bole.
'Hr.
'H
1.4
'H
'H
'H
-'H
C')
'H
'H
I,L
14
H-.
H.
'H
Figure
——
Detail of mafic tabular syenite from
NE Sec. 22, T.29N.,R 6 E, Porphyroblasts(?) of
microperthite (white) Black crystals are sodic
�78
ii
cr
Zircons
''C
CL'ICCCC and
I'C% some
IRiCS thorogummite
(C'C,C L3ltrIC II, may
C collected
'CtCC :13(113 from
hit: be
hiitCC. pegmatitic
tC).ClCIZliL'C
phases of
the
nepheline
syenite
along
the
pit
wall
and
west of the
•C' C.. Ict-I
:CC.C:LC
Ctfli just
iCac'
(LII
C.CC
Please
mill
headframe,
where
a
jig
table
was
set
up
to
separate
zircons.
YC(". 7ZIL.ICC,.I:j
iiC'i-iizz e
iiCCCIj,C
iCr C-C'; it CLSAC 'ikit Cc ci r:3Ii'CC'3 'g3C(3
stay
out
of
the
building
as
it
is
very
dilapitated.
CCC
CC.
.L?.dlt:.. Lila (CC '3:3
].:CIC C.:: ,L3 aq: liiTC':I.1
s:
s
':
1
;3
The tabular syenite
itniCt a: at
i.E this location (Weidman,
ILIC p. 255—264)
auCrLL: 1907,
is pale
orange
with
long,
slender
porphyroblasts
(?)
of
zi1tCi C$cCtL: (Lilt r14 .Y&Ci'HLiC HEICYLICC(C5 ii4 C.-" HI gray micro—
Smaller
perthite and
2A).
Ct mafic
r.itti ii lenses
C:31C5: (Figure
:1iiCLhii1 felcspar
t,:,( aadii:' laths
'C'ykLC are
a,ra
CLCLCiT:,I
The
feldspar
crystals
show
considerable
size
variation
pinkish.
Th
ii,'i- SCCC 2t1 Cm: 1a3
CcaitlI'cCtCC
CC in
'Lr this
All
are
in
planar
array
so
that
the
rock
is
banded
but
not
Why? i1Vi.,i Cit CII, ,J5Ii71C •CiXC,CL 3:3 ThIEC.. II1[1 CacC
rock.
.Ctt•Ci
LI'
2t31iC
Some
of
the
microperthite
porphyroblasts(?)
conspicuously lineated.
°?CCLCdCYI
(CIII'', 5C' CCIC.L (TiTiiCCi.CflCC:,l 14 iCCLLtLiCiCtC, (L1HE-i
contain
zoned mafic
have
rims. Concordant
(C
:3 licCi inclusions
ICC. C tt[' CCC ' and
tiuC'ii. some
ICC
C4LTCCII mafic
CCC
mafic lenses (altered mafic volcanic xenoliths)
ciCaTiicc 131:1 are
,za composed
;c sodic
atçiCa
çC'CCtCE-C't: of
amphibole, brown
mica, and
and
contain
perthite
porphyro—
i,Lt
CILC't hit
(-tiC green pyroxene
Pfl
'CCC
IlL
CTC::iC..
ci-)XCL.C1
C
blasts(?) of
to
CC similar
1LPI C'' size,
L 'lE-C shape,
CC and
3IC orientation
CLC'IC
Ci those
iiCC.i4 in
u:.1 the
C1CC. enclosing
2ciiCtp:::C
suggesting
pink syenite — aii feature strongly
t33CCCrL HE5r origin of
;C the
Cfl7
iS
r;2CCLC Ct metasomatic
Tabular
syenite
l-mile
east
of
here
consists
dominantly
microperthite.
C
HIJ
ii
JargC.
CiCC!CC
&ii:a2c
At another
of crJCi'1
poikilitic
and
Pt33 , pyroxene
4.j
c-:l sodic
;YI'C amphibole
C.nj::
ti,cLnrs çoaj - (Figure
'C'tc; €1 2B).
riCiJ
d
location 0.8
north—northwest
contains
C)L.LCC
a°c mile
i-IP CCC
::CCCCCLC of here
C-C.L the
LCH tabular
FCCYF-C syenite
C.c rCC_:
Some
C
much more
'HEflCi
C,ii( abundant: maf Ic lenses (Figure
ELLcL 3).
3CCC boulders at
CC this
Cli. ii same
location irT
are composed entirely
this
mafic rock
(Figure
-i Cc 4).
•2LCiC
C
$CCi- taL1
CCC
iCLCtCC of
''
-
C,.
L
a' ,
e-ic 1f:"14C
CC
!c'-t
iatty
C
rii
Itt
L
j-Iir3C3ij ii
rica
'CCtiC
C
C
cfa
It CC
is suggested
shearing
C3.,th5eiFL that
CViC
iiUIS mylonitization
J[C:C i. TC3tLZ accompanied
-.rTli3..C333
CCL and
Fragments
forceful
injection of
pluton.
TaTZi.tiJ subvolcanic
aCCflC .:CaC
;.- the
j.L Stettin
XstsJ,-, syenite
c:tuiitE-E iC
of ?3if;
mafic volcanic
loose
C,t7TL rocks
33CC broken
rct.2C
SiiCCtI from
)EC2![ the
€CC walls were
EJ3- rafted up
ZiL along
£(art
These
fragments
locally
acted
as
them in the
magma.
3C viscous
C37C 'it syenite
cii1t,j
c4!Taa;
c.rCaLii cia-iit
nuclei
L-4 crystallization
SL1 ICc of
1:3 the
C./1C syenite,
itLCC to
CC. have
IIL2iICutt for
C&itii r-. although thqy appear
Considerable
metasomatic
alteration
been resistant
to
assimilation.
LJC%QJ
T
CL
znC
ufl54
C
fl1C
of the early wall zone complex
Cti at
ni emplacement
Lii followed
1i...:.Ir7 its
ri original
J.: çrc;:;: as
evidenced by the coarse, euhedral microperthite
porphyroblasts(?).
')Cfld: 1'.th: ::1c€
Textures in poikilitic
phases
of
the
tabular
syenite suggest nearly
Cç7$ TC.L
izCc CC.LI7 ;tc.J
simultaneous
crystallization
of
feldspars
and
CC2iS'LLiC 52EZC ..Ei
C5TTT C Y(fl mafic minerals,
:ir- although
T1
the amphibole is 2L:ruDi.
younger than
the
pyroxene.
xyj.
7
iC
F24.
•CC
!'-
t
:•:j
ittn;9Ji a
>Ij
:
j
1?
I.
:c
Your ideas are solicited! These
CLJL tentative
SricFGC conclusions
[CLCC
?7 are
CC presented
to
stimulate
discussion
and
debate.
C. CcCt TX
RE FE HENCE S
L'
X'S
ST
Emmons, R.C.,
V Wausau
':1: and Snyder, F.C., 1944, A structural study of the
Wisconsin
Geological
&
Natural
History
Survey,
unpub.
report.
area:
iC
icc;1rL
rj$)CrCr
igxt'Q .C1t J.
EZ
dci
:qtu
Geisse, Elaine, 1951,
The petrography
L
AF!T of the syenites, nepheline
C1 sye—
M.A.
Thesis,
nites
and
related
rocks
west
of
Wausau,
Wisconsin:
'T
t&r:u piTc; iiE7CSJ L4CC;L CC•k ICt i'&.'P
Smith
4LL( College.
:JC;.
rr ;.
C'
i
Turner, D.S., 1948,
minerals
tt- Heavy accessory
t'T radioactive
CQC3
511CifL and
LE1PCTP13T studies of
Ph.D.
Dissertation, Univ.
the igneous
Croi rocks in the Wausau area:
of
IC Wisconsin.
t':i*
''J1
u
Weidman,
Samuel, 1907, The
of North Central Wisconsin:
JIL geology
tC1
1.ZC
Geological and Natural
aj, jttJi1I History
j(..
EStJjI1 Survey Bulletin XVI.
TLkityD
.•&![•
Wisconsin
i ii- 2tcr;iz
�l
fl
-.344 4747)
,4i217L
247-417.' low
2112 Ii
'444 bridge
-"=" 77
water.
at
only
of times
C1
. west the from
it
117,
210 location this
1
the
of end
reached
be may
Note: gabbro.
t1:21I17r214i.21212 :1421,17:171 ;141:7,T[4?1! 'I11'11117147 1242
4171:
171113'111I12121171L11$11
the of
consolidation
complete
before
stratification
of
disturbances
17
" 1717 the
11 inI layers
I
t121 clase
r212LI in
represent probably 2) Figure
detail (see
gabbro
ij4
114''
211 1
'44
I
Di
plagio- ¶
strong
I
21
in
crenulations
discordance.
with
gabbro
"Stair—step"
$42134
2
7 1 —The
c211JL
IL
the in banding the into cuts diorite quartz
NE. strike
planes
311212
3717174214 -14'2'117.
1-211) axes
'21: 41274 quartz
211211? fold
- 1'-1-7'44
2444444
7112)1' The
are
axial
their and
vertical, nearly
diorite.
1r_
4411714
14T77442.
2
271
11?,.i 3
was
xene
'247
the
in
incorporated
then
and
open—folded
xenolith
gabbro
21214417 a in
pyro— large
221274121141 At
111-1
:1: 211.prLln
banding compositional
I,: 3':' tl-L#. '47
1) 2-411311412:
(Figure #1, Location
1
I
I
L14
i
1
I
'Ii1
I
I
4
-
1
I
101
—
1
1-1
37.4?.'
r'
magma.
47
24414114412
quartz
diorite
14242
—1Pj vertical
AL
1414
'1
the in 4447'
xenoliths
of transport
considerable suggests This
east.
1447'(1711111
71:1:15 -441241114.7172 212I['71I14
1 4441144 411 74412
171112217 12,
-- 1111444.it[2.
2412117
northat
least
at
:7
miles
2
least
and
here
from
southwest
miles
4
extends
4711112237 '11
4711171. 2711-1114
hIlt 17111:1121:
11741'5%'
121:42121714
447.1212,14
1t2444'±
371.
probably which
body,
diorite
quartz
the
around
place
in
found
is
them
of
J4i44274337 4444:14..
:,L7iIt1LIrw:p
7i47'3- I
none 174217 2: -.14-Tc11:l5.14 as
2141
.2412 '311 .4423115 and
are
121-12±1
121442.
17242
yet
xenoliths,
here
found
types
rock
dominant
the
quartz
3-1
774T_42
17
schist, chlorite—epidote metapyroxenite, banding,
showing
depositional(?)
7112 in- 22
some gabbro, PyroxeneC $122
- 421 2 outcrops
here. of
east mile
exposed
2126
are 141211440
:1141'047ItI11'444
'147424-2.2.
114441117411
21111i117
2242271721-41117
117114'
1
i-'211''2'which
rocks,
volcanic
and
diorite
quartz
hornblende
taminated
$1224471211014 2371437.
14'14.:71j1
con- 11212212224
11241211422I10 excellent
between1713144211124
contact 412112122'22
sheared 1477747
the near
is outcrop
This
'ccl5Il
11
111L12i2H[— rir1
'It?""
17
j''
[47117
[1717 7J.r1411A72127J[1'
DESCRIPTION:
5
.17411:41714414 of
.1r 2lt[11:4.147-71t:17712
stress. shearing
conditions '[1714,7
different
7444±11 1l$44771i12177114
:1.1110:c41:7-1
rare 12a
1410-f.111i-liltl.±1
[1212..'.171.
i-;17[2'24121t_d!C
4424
1l-7s'['L['.[i[714
compare
under types rock
specific
of
behavior
to
opportunity
a
1 142/'7[3' branching,
1i17 zone, shear ENE.-trending
:1
'
T''H ii
affording thus
along
mylonitized
1.17-44 .[4773fl%1_
'4751741114471
:11t1 'ii:424n
'42.4122112 771121:
3724
was quartz
37 747242-2 pyroxenite, gabbro, banded
and schist
xenoliths
angular
of
514,-,fl4-:44:14
221 7i=121 21114111424421344
127.174421114 quartz
:3117142:i,47:71 44514'$1-41417'
'14237,4
abundant,
containing diorite
hornblende
Flow—lineated
'i,1
'
TA
A
1
2717±U.L 14172 OF SUMMARY
174151444474417174
FEATURES:
;i7417i
'1%:-nj--t;tFebruary,
1717-1717
1973
DATE:
4111.115
-47422s171s:ir
Myers,
E. Paul
211113151
Claire 1)[274'-'[4417
UW—Eau
AUTHOR:
R.7E.
:47.4411)7
771,4
'4:444
'07sec.
T.27N.,
29,
SE--,
[1
4:110
u&14111'31
®211'$172 at
Mosinee:
River 7412411'1"-111171)
Wisconsin
LOCATION:
7442.1(111124147
[31,fl57'711' Sheared
51t,111'112 quartz
2114127 intrusive
425-. '1.214:144.111171
breccia
diorite
74 22 41
TITLE:
5i1J[. Field
37M7
Locality Trip
11
79
�1
-- LOcat°'
�/
,
/
Ill ,
diorite. quartz
'
/
/
/
1
\
"
'
/
in
/
/
''
1
i,
/
/
I
I'
/
_
I
I
'-
/
i
/
/
'
NI
/
/
,
I
/
I
v
/
/
f
\
/
/1
/
'S
/
-
/
I
—
/
3
"
/
1"
/
/
Figure
/\
I'
/
—
I
t
/__.:
—
—
/
/
•-
:- /
'I t/
/\
/
(Detail.) crenulated locally Banding
quartz in gabbro pyroxene Folded —
—
it':
U•
/
—
r
/
/
/,
1
/
'
/
diorite.
Figure
2
•
U_U
:,
•.
U:
4
S
/
S
—
t
I
'
---
- —=-- ir—
/
1;
I
/
,
,
/
\
maic
:/ /
T—
i
'•I
44
I
U
- 44
54'
US
—
'5
'\
4,
',,.'lI
5,
.5
'S.
I
••
/
o
I
/
—
-
I
A
Epidote—chiorite
/'L_____________—J
/5incs
'
—
—
__
U
-:,-eQ
/
//
xenolith schist
I
'/
I
'
-—-=-- -:
—
'
•/,i
'A
-A
A
I,
'
5-.-44(5-.;
I
5
)
•
•-•:•
U,
U
-.c,-'4 :h-.?-H','
I
I
" UI
s1I
/
U,,
•
•'
U,
5/
A
'U
•.
•
—4
A
U
ç
Ii
I.!
I
•, —,.,
..A
.
H '.:
SI
U:
c.,,.4'
rI
H
'-S
•
-
4,,
U
-.
•<,
.tA/",,'
44-
'4,2171,
'4•1A
-1
U-
1
U
U
-
U
•;•_•i
:1
54
5-
—U'
54'
--U
AT
45
.5-A
•'"•''
•
'I
.
5,
U,'4
4
1*
'.:-
H
H ..
-.
A
-
•
,U
S
-I
A
U
••
•
•
2
•-
—I
/
5,
/
'1
V
44.
*
544'—
/
US.
•
1':
/
—I
12''
5,
—
I
-1-
5,.,..
4',
.±...
/
-'
U
—
•'
I
I
—
AlE_
TA/1 LE
L
81
�82
7
H
:;'
L
i'ittntditw Pitcc'cisa
brecciatsi'tct
withq!ciartc:;
quartz
3tctctht intrusive
Figure 4 —— Sheared
alL ILLquartz
wnaztc
cars 'c-at I with
tic-. contact
lenses (cross—ruled)
(crcna= ratia:2 I along
aJLc'ic: the
Criasas
tc'wcJt 2 "Pt a,
tHr!c:;te acm
ccc ±;tti-,cggabbroic
gt5. 'ci' it xenoliths.
diorite
containing
ac±lPa,t
criica—ra-a i.ir:li;.$ schist
xenolith cc'
of rtial
chiorite—epidote
LttItLt4@W
#2(Figure
'FCUris 1)
L: a dttLL'tmt-itt\
AtIt Location
#2,
vxlittct,:; are
i:c: truncated
rUt
I rt,acattt4 tc;
pl.a.cnttzt which
is segmented
;.C.(+t cciii by
shear planes
by the
:r.tntrJLttttgi; a2iria'r
ii;:; interlensing
Ia!
awl
ath.t'ari.nrlP (and
It
clear tinalP
that shearing
,;,It therefore
tt.ttriiftrtt claw':;
5-t. is
UlLitic'r 3).
2)
±t!±Ks:ritii (Figure
quartz
3;anr-ta- diorite
tr,rst episodes
.tmt±cn&taIt
2caw two
th'crcncri - Thus,
wcvl Lttintrusion.
çrttittttittctquartz
qiticir diorite
metamorphism?) preceded
3a2r'nrcrp1i2aaU)
ccc the
tle snibiat
cawtsainp
crn..cc:;cw.
development of
schist
contemporaneous
S i t '25Iw'!LC;!ISL,i:;t:;
ni:;:svalidated,
rat I C atarI, Was
Its.iddtcLt3 are
cii shearing
of
r,n
iLl the
cit ii in
The
a absence
-"°- cc of syenite xenoliths
riP the gabbro?
Ciii
with folding
of
nii: two
'Wti 'Its
'c"t" units
:Tw'Ltiiti'tage
aa of the
ticS PwUsy
quartz diorite
only cncdcc.,:;.scti
indicationsciF
of relative
its the
Lc'rJcc-c3 is
qinartc
satin:;
it:;
ctiatiStt
seen
in
contact.
nit
twit
snLca'nncLcs
n'
yt
'Pccan
been
since they have not yet
n
arc
£
it'itsltw Lrwcni,i.a
tact itria;t
:;
the intrusive
breccia has
been rcaran'titlP
converted
:.gccra 1)
i 21w
Lcccttcnr #3,
#3, (i
Figure
ci Location
At
itt:;
'w
c
_ig
tnt
by shearing to a lensoial gneiss showing differential lenticulation
1.
xenoliths
with
resultant
length/width
ratios
largely
litha
with
racai't-aicnt
m:LIq'cIh!cticta
ccaicicsc
acacacit
cclP
cci cai.crvcc,ca'cjw'
and
segmentation of
lr.awtcta, Several
tt1tt crc-alLintermediate
:1wcr,a.c:;
St ' texture.
ccc ir ic c!iofrcenctL
ittI tflt.tLttdd.i
Ll" and
xenolith
mineralogy
a function
Lilt
a
mLacc;ati,©h,
Cit
ctsac"acd
at
erc1H'Incs!.
car:;
stages cf
of tracali
xenolith
Ut attenuation can be observed at this location. There
stct-;ac
Liatcancri. intrusive
thtcctiaiLvc:3aLlitcLa!Kti between
as
is
throughout titia
thisragiani
regiona ac'urizci'tc
curious association
It tJcct!CJlfTtitt?Jt'
gmindtt
4.
miia
See
Figure
4.
aTc.Lat..i'
l,tLic
I
-nUt
tcstititi'ci' (rich
(a-Icc in
Ic ac-cal
contacts
xenoliths) and shear zones.
ij'itwt 1c l'
itit.
bci4
mma;:'a.racl gabbro
naL±tzc body
ani-iccitic a ni'-fcjitcttat'it
CUrl the
subjacent layered
cp:ca'ctz diorite
.2±ctr:'te intrude
lists quartz
Did
r'
L:;1
4
j
!LIt,i
is
this
body
related
Li.
If
so,
Ce H
ii
cvii,,
and raft the
xenoliths
up to this level?
atj,crtttosttc'
:;li-'st:;.-srtcicc
± the
to
Tigerton anorthosite?
F
F
-
�83
Additional Locality
iC L ttctYT'L'T'iiu'21
119-C
TITLE:
Gabbroic masses and leucogranite
iiL.ILIttU
.11'L7?11'T:'C
'- IITTI
LOCATION:
sec. 31, T.28N., R.9E., Marathon County.
Low
and
CTH
J
southeast
of
Callon.
outcrops
float along
TLLYL.
'c:.cctL11LLCtcE'.'TI 'ZPL,IL ,:
it
W-, W-,
'-ccc 1,
L
'.iLYii Cf'' C H-TC 1:-c mc 'i'i•• cTc: c'i',w
AUTHOR:
::
UW—Oshkosh
LaBerge,
L.
$
DATE:
Summers 1970,
cr
Gene
1972
SUMMARY OF FEATURES:
T:T
These exposures will not be visited on this trip but constitute
an interesting part of the overall geology along the trend of the
Eau Claire River shear zone.
.3Ct:j9y
I'
CC T-:-'IL'H Ct ;c i'9-c
LLi-.',?C1Ct2
In -Tc:-- :ttL22 "c:Ln;c
1111
iLçu,.qcT:.j-
;!:L
-
1-i
'3'u- IL 'iY
T-:11C,:
fl
The Eau Claire River mylonite zone is interrupted in the vicinity
of Callon by a gabbroic mass, at lest some of which appears metamorphosed (mg). Although the gabbro mass lies athwart the shear zone,
it is substantially unsheared, and it contains inclusions of banded
Thus
amphibolite (sheared meta—greenstone?) and other sheared rocks.
this mass seems to be younger than the major shearing in this area.
Tc1
"11;Cti
.111117111
..L';Lm;
3CrL. :c'ti'111'tt
1-UEC CUEIa
11c.li.E
ccci;
,
11.i:tlc
-cc TLTC1TL,TJ1LL3
3r'
1Ic'cc
C-9T
:±-cT, -r.
-ccyç ii uLLcc: tt:LcuJ.I,L
p-nL:
Lr,L.c, t-Ec-:c:E
U11t'
11
!TE'.c'
u-.E
:'•I', Ct
" :;:T) '1H•
T:ICI TTTIY5L I
-L1 iT1'9c: ' IL:&ct_c:'J 61
611cc-cc .-Ur:uT
TT1i t.t11'-.LLi.&7LLf .t'c:Ic:C EL:. ic. ,,.t- .,-rIc:tt
cc tiL •'C'C CCt:4t''iYE .';,7)uC:q.:cI11CCX :-- LL! :—c ": cut': 1132. -nq u97'
'1'
I
Southwest of the Callon area are numerous blocks of mafic rock
The
surrounded and intimately intruded by leucocratic granite (lg).
maf Ic rocks have a range in composition, including hornblendite, gabbro,
cliorite, quartz diorite; the leucogranite contains much pegmatite and
graphic granite. A small altered pyroxenite (now talc-serpentine—
actinolite, etc.) (ts) which outcrops near the N* corner, sec. 10,
T.27N., R.8E. and a number of probably indigenous blocks of anorthosite
near the SE corner sec. 8, T.27N., R.8E. may also be related to the
gabbroic masses. And inclusions of pyroxenite and what appears to be
layered gabbro are present in the dioritic rock in the Wisconsin
River Valley at Mosinee (NW, SE-, sec. 29, T.27N., R.7E.).
If all
these rocks are related, it would indicate the presence of a well—
differentiated mafic intrusion which was subsequently segmented and
intruded by granitic rocks, mainly the leucogranite. An additional
piece of this maf Ic jigsaw puzzle may be the large roadcut of grano—
phyre just north of the intersection of U.S. 51 and WIs. 153 at
Mosinee (near the center of SW*, sec. 28, T.27N., R.7E.).
:19111
iiLi2I 'L :1:,'1'C '1'' L
.''•'" flL E-
,',,bCT ,-T;
'CT T1CL. L;;ci:'.c.l1. fiI:L,i,L>n
c;c c<1 )c9i:"Lm
-
cu
-Ic:
T9,IiLLT'
.Lr
t-L:Tii9 .JL2 C:,sL1cT
:Izm i-TcUETE'.n
',.c.,m:uc
.':,'€iLi'LLC:,iILI
;—cc:cct- :c; -;n
Eu' ttt .n-c ;CLCIityQ
T.:c::
. L9L"?LL' cTc.;cuc:. E: c-,.9c.J pc)Cc'
L(T'CLL L.t' EL
L'-L'.\''Li
1cLLt
cci. CL pcnLc :.'1 .,nL icn C:T.
i-;
jCC.Li
C
:-Y7--L
C,:Ls
TUE C.'L
2tEL
iTT
JI i'4 -c:::Etrt,
:Yi
'c-nc-cc :c-;cZ
- ;i;-ci 2[P Cj- :tcI.
CLt
:1(J TT :Cr
ju ct.' cT c<-. 'C:Iitc tTyTht.
'LLY ;TrULLt.tTLCL cu- Ti titl1-T.
-1t• :
)i
LT
tIt9tCiL- rIcv-:J
ii
1
ccc:- u-nc
71,. tl'mL
':
E.tCtT'V'tEL?[LtCLcCCtLr Tm
f'
iLH 'I
.TT
•
uin ccLclJIYT
-1I)auI
uu
pcLcuLtC...
L
.L9tO
kz-
I
L2,itL c4LL. Li9
?LV
; ct:cc .QYj:T tLCL. L [ccacr i99-
Cc
LLL
H:,'41:y,,
r
•9u
c; Ii
:t
�84
,y
EiE
EXPLANATION
JLk*17
i.711 AREA MAP
FOR
ict1l CALLON
gal
Quaternary alluvium
ss
Lower
iLc;: PaleozoiC sandstone
ig
LeucocratiC granite
mg
117 gabbroMetagabbro and related(?)
±7j1t• 7:Hr:
diorite
rocks
ts
Talc-Serpefltiflite
m
1tL.(I :1h:iH
Mylonite and:1related
sheared rocks
g
Small granitiC bodies
hhg
:fl[:i.X.1
granite
HogartyF, hornblende
qd
Quartz diorite -
fv
Felsic volcanics and associated volcano-genic sediments
my
Mafic volcanicS and associated volcano•?I& sediments
jd:J-iir±b?
genic
1
•
granodiorite
tH
masses
7:.-r 'fli1
ii9:
j:jTi
Geologic contact
Shear zone
�'f"%.
31
Th!
qal
P
-
-
T.28N.
F
IS
ft
2'-
1
-,
I
I
-.
-"ml
I
-
if!
ft
P
((ft
"2
2
'
/
I
121
/
-P
qI
qal
mg
-
Jl
/7
-
:7i[
—
2
I
2
—
-
2
I
2
-
"2
3
i1!
-'.
7
Ig
/
qal( —
I. itilIt
-ft
-
12
-
t
-
'— (
/1
1._I
2
—
2
'1
'1k
—
-L
/
—-.
"2
—.
-P
K-
C
J
I
---I
—
.
J
I
£
-(
ig
—
L A -__..__m_
I
/
1
-
I
c-s
--
—
-
I
7
-
—
-
I?
-
2
-L'1"
ç
'I
1$,
-
Miles
—
.
Ig
C
2
ft
/
/
/
1.
hhg
1
/
I
7..
.1
I
"--
LI
—
11/71
SS
(2(
-'-
:
_.—-c'
PU2TILI"
d 1')
qal
-'/H
1/2TPJ
--
---
T.28N.
-
IC
mg
hhg
2
-
--;:.
_'
Jv
ICI
I). --='---71'---'---"=',
-._i_--'
-1
.1
qd / '(
_4-P.1tL;._t
1
-'1-71
- —--
i7't
L
,/'
rng
——
ILi:'&
'1.41
;Yi-..'-' a4:-
2-P
ft
,/, m
7
h- .
,1-1
_D-P
'A'
¶2H
..-
"
'
]
-
•'•
1
12
C
k—I
i'L
.)hh94
-?
(),-'
,/
'(2 p--'/'
I-P
- —1 ±A,;i _.71-S.LJ
Ig
731
/5Ii"2
l9 :-————
——
'
—
-1
lID
m'
,1
'/211
1'
P2
.1
/
hhg
'(U
l\ I[o
/
I
— —__=—tC41E
——
AT
Ig
1/fl
-J
'U.'1
.
Ig
\
'9
J mg
/1'
7o7'17'
mg\ .'
.—'----''--
'1.:
1
[
mg J
2
ft
:11.11
qal
—
m
r.
—
mg
2
4icti)Ec.
'-.4,
,t;t+_.I_I.+4.+4*
-
—
/ '3
I
-. —
11
7 A 11• 1/'
ní2 ...7(2 ?
my
' / /?/
____ ___ ____
____
___
____
_______
_____
E. R.
C_i1Iory_\
-
-—
'
-'
mg,
.k%.:.L—II
',
'11
\
1-
-
Sç. -
26 25
2
-
L
cI9-L\
.1_i
-
-'
qc
nI
\Ig)
'1'tJx(/
- Alt2
/
-
H
—
ii ,
--
4"—1
jH
qal
,7')
-
—
ft1
ft' 1-; "
33—-'
H.
-
"21---''
/
15
—jI
jr
ft/I •.pft;q77
t1/1
-:' '
ft
V
- — -'
— i-P'—i
ii
,
I
1.
(1
28??,/
-.
21
—--- -
— —ç-—--.-
T4
\m4
'-
-
-
/
A
IL I'I,L
I
. _,Ig /
1_—-
—
/
11
TT
—
Ig
I
(x)
29
J-.------
... —
I"
'r
- , J uit—
,LJL.
/fi L'
_1-
'
fv
——
L'
17
Li
T
I
—
"
c/iT1V/
L
•
al
1 'N
tL__—,Ia 1
/
r
-
-
____
________
�'c:c;y&at the
-t'ii- cLL-cin. ac-c-u-scccs
ccm-rcc-tc
'Ii tk
F
Field
Ld ccc]
relations
a-c',ILc• suggest
following
sequenceccof
events in
the
cc-: Hogarty
-)d the
ccc; a,;:•r1 of
cc ;t-c
.cc.
1)
clb-c'ic'' on
iY emplacement
area shown
theacccy;-iccc:5CLcr
accompanying map:
cc-cc.
)iLr-cc
31
T3'ccJ-m.y.
,c-c;into the mafic volcanic
hornblende
granite l5OO
ago
vcJtcaccLc sequence;
cccc-ca;cccii
:C'JrJLILF uii3.@:;i9jd,.i
-s:
ltc-a- mylonite
a-tc]cc vi: zone
scc-:c
'L:c
3L:irZ
2) c;Fc•ca::L
shearing 33
to t;cctcu.cFcproduce the Eau Claire
River
(the
shearing
LlFricict,acrcc:c:-i.
ilL
iL::F
ficil:-::
rcJ
ct-cd
c
d'-dcif't3'
may
be
at
least
in
part
related
to
the
emplacement
of
the
Hogarty
3ist-L-ldd.'
L
c-c:• cci
,:c-cii;.5 t:.cct5 of
:tc '.-i ' ,c Lac4
-c
hi--c gabbroic
hornblende
3) intrusion
(and differentiation?)
the
c-iccclls granite);
ccc'ca-c'ci-:
d-c.r:,cb
is:iLc?
'CI'')
3
iccis;s:
;"rv-:Isc:--3
ci'
Fr3ii-5ThI3F5
:1,
ct
-u:cc
mass; 4) intrustion of the leucogranite with segmentation of the
&'St
sr- a_ri
:5,,, subsequent to emplacement
I) has
L
-icc place
Minor shearing
taken
gabbroic
,,3
mass.
ti-s
ac
:gxzt.t.c
ic—c the
tici youngest
Thus
seems -Ic
to be
"hac the leucogranite -cccc
-- cr-c cyvtcvic,ii of
c
the leucogranite.
3;
iF tC'33
igneous rockmapped
Yc2c-iic.F-t. in
this FFTiL
area.
• iii Li?
ijcc c
"3
'-
I
P
'
P
:
DESCRIPTION:
Iiic,u-3
c-ct maf
.c ,scStrvtc-3 and
Low
-cr' outcrops
cc:,'ir-'rp aid
and3iLFFs-t
float of
Ci leucogranite
ic -'cc--S
rocks c-c-icc
occur Icrfor
:ti,.iIic
-;.c.;c
;'-J,;rc the
ciclll
tIc-: fields and woods along
approximately a
mile along
c :1. in the
c 1iL-cac-csCTH
t3 J and
xc:-c-:ic of
JEt IdE5.
ftJ_iLaii'cttc- zones
Alternating
-:31
maf
c ciIc rocks
-EL, T.28N.,
-:7. tic-iLL
-;j:3zc; edge of
sicsec.
iiiis 31,
western
R.9E.
iii the
tci.
Leucogranite is
cr'.ccB&ciialong
cio•ccthe
lix ccroad.
-cidi- iL-xsr5u;-i-c-'tx-c present
and leucogranite are
W1
:33ofit granite
predominant rock type
2:3cvc:c1c-it-3-'t
cic ii-',,'-i:
in the cccc,
area, cad
and veins and dikes
'-Zi s'cc
cutting the mafic rocks were
seencc
atcccra1
several;Ic-ccaplaces. Lack of outcrops
tIc
tI--c---:
:1FLi3
:tar— cc
F idF- and
precludes
shape
of the
mafic
zLstc-cr :3 sii the size
'3lC
;Iii4, accurately
2c c—ic:-'. IF-Li.- determining
I -is leucogranite.
ciLa;-.
32 I3j-J.I)SU by the
No clear
c-c5c-c-ccc:'t
a] seem to be surrounded
masses, but
Il-ct all
tccscia.
15 ]clFcit
Is ic-c--c
-t.;;--'.-s-i
iii.-:
cc cc-Itt33 the
occurrences of
maf Ic
rocks
cutting
granite
were ccc-c
seen.
cd the
c-tt
-
;'i
-
,Lcca il u': :/ci
scr'c'
c-lIt: the
icc-c
Ii ccccQL—ICat
t-'c EL with
-F--cc,:,:AIL.L- have
ii :rcr-g-c
The ccxc
mafic
rocks evidently
range in
composition,
1ccicc a
'-cc
:cccccic
5-r
;5r33r Biotite
differences reflected
Fr in the ferromagnesian minerals
present.
FtDcdWiLt, and
lbLcci—lIcLtcbdIs is
'3- abundant,
cct -3i--Fr--!
Is 7--t,-clt:1?ar-t
predominant in
ccc:c samples,
others hornblende
3-cii iF5. in
ii some
iccctc iiiscc-icc5
commonly present
Iiinc-Iothers
Lac-ci :--t
r--c'cvsca
accl
icc:-cfl-c-c-c1c
both
pyroxene
and
hornblende c-cc'uic
occur. Quartz
-"tc:Li.L,,'tCI
it-c cccxc:
cccLUt;usEL
c'c;cc. variation
Lit-c
The c:-:5ctcccc
extent to
which cc;
the
compositional
'tctctcc:.,c itt-icc--c
It;
In the
phases.
'ic-b-S blotitic
fxc_'ic
S.F
11cc to
1-c- partial
it-aft cclc original
-r-i1.c:ill cCtccFc
t-i:-- ej
in vii:
the cc,
maflc
rocks reflects
compositions
orIs-;
is due
F,-s ax-sic
cc-i: known.
No it2cc'c;c-ac±ic
petrographic work
$itlc Fcc
has yet
c:ca-v. tV
"digestion" by the
Ilta ic;cxf'..-s
granite is
it not
L77"'2cJ1c
Cii -.
c-cplagioclase
rc;t :';,t cc: cccccsb
I dcxc are
arc Lcc'
been done
on these
so
compositions
largely
unknown.
c2i,i,cc rocks,
c--cctcc
'FLisi 'ccc
I
-
i_3 3
����
https://digitalcollections.lakeheadu.ca/files/original/e490e5cc4d21cd046bce02006cfdf9de.pdf
dce4b4bbbee755b78cfd691154fc6c7f
PDF Text
Text
University of Wizcensir,—Extsnsien
GEOLOGICAL AND NATURAL HISTORY SURVEY
Meredith E.Ostrom, State Geologist and Director
GUIDEBOOK TO THE GEOLOGY AND MINERAL DEPOSITS
OF THE CENTRAL PART OF JACKSON COUNTY
AND PART OF CLARK COUNTY, WISCONSIN
Prepared in cooperation with the U.S. Geological Survey
and the Inland Steet Company
tor the
19th Annual Institute on Lake Supetior G.otogy
Madison, WisconsIn, 1973
�UNIVERSITY OF WISCONSIN-EXTENSIa1
GEOLOGICAL Afl NATURAL HISTORY SUit flY
Meredith E. Ostrcn, State Geologist & Director
GUIDEBOOK TO THE (ZOLOGY AND MINERAL DEPOSITS
OF TH CENTRAL PART OF JACKSON COUNTY AND
PART OF CURE COUNTY, WISCC*ISIN
by
Harry Alemic, U.S. Geological Survey, Washington, D.C. 20244
John
M. Ohisan, Chief Geologist, Inland Steel Co., Ishpeming, Michigan
This guidebook was printed in limited quantities for the 19th
Annual Institute on Lake Superior Geology.
Madison, Wisconsin
Publication authorized by the Director, U.S. Geological Survey.
Available from the Wisconsin Geological and Natural History Surveys
University of Wisconsin—Extension, 1815 University Avenue, Madison,
Wisconsin 53706. price $1.50.
�GUIDEBOOK
THE
GUIDEBOOK TO
TO THE
AND MINERAL
MINERALDEPOSITS
DEPOSITS OF
PART OF
GEOLOGY AND
OF THE
THE CENTRAL PART
OF
JACKSON COUNTY
COUNTYAND
ANDPART
PARTOF
OF CLARK
CLARKCOUNTY,
COUNTY,WISCONS
WISCONSINJJ
JACKSON
INlI
by
Harry
and John
Harry Klemioa"
Klemi~/ and
John M.
M. Oh1son/
Ohlso~
IINTRODUCT
NTRODUCT ION
This field
field trip is designed to provide an introduction to the
general
central part of
of Jackson
general geology and the economic geology of the central
It includes
includes aa visit
visit to the Jackson
County and part of Clark County. It
magnetic taconite
mine and
County Iron Company's modern magnetic
taconite mine
and agglomeration
plant, examination of
plant,
of outcropping Precambrian features,
features, Upper
Upper Cambrian
strata,
strata, and various local
local physiographic
physiographic features.
features.
will include
Stops 1 through 9 (Figure
1), if
if
The trip will
include visits
visits to Stops
(Figure 1),
time permits. Additional places of interest
interest are
are shown as
as localities
10 through 27 on the
the maps and
and are
are described
described briefly
briefly in
in the
the text.
text.
general geology of
of the
northern part
part of
of this
this area and
of the
The general
the northern
and of
the
the north has been
been described
described by
by Wiedman
Wiedman (1907).
(1907).
adjoining area to the
Ostrom, Davis,
Davis, and
and Cline
Cline (1970)
have made
made excellent
excellent
Ostrom (1966)
(1966) and
and Ostrom,
(1970) have
descriptions
and correlations
descriptions and
correlations of
of the
the Upper
Upper Cambrian
Cambrian strata that
that cover
cover
much of west—central
west-central Wisconsin and
and extend into
into Jackson
Jackson and
and Clark
(1961) discussed the clastic sedimentation
Counties. Potter and Pryor (1961)
of the
the Paleozoic rocks of this general area
of
area and
and noted
noted the
the presence
presence of
of
phosphatic material in
in the
the Cambrian
Cambrian rocks.
rocks.
The modern mining and
and beneficiation facilities
the Jackson
facilities of
of the
County Iron
Iron Company have
have been
been described
described by
by Skillings
Skillings (1970).
(1970). An occurrence of wavellite in Jackson County was described
rence
described by
by Klemic
Klemic and
and Mrose
Mrose
(1972). The senior author is indebted to the Jackson County Iron
Company for information
information concerning
concerning the
the iron
iron deposits.
deposits. The cooperation
and access
access to their
their property
of many others in providing information and
is gratefully acknowledged.
is
acknowledged. Much unpublished information
information concerning
the local
local geology was
was also
also obtained from the
the Wisconsin Geological
Geological and
and
Natural History
History Survey.
Survey.
Most of Jackson
Jackson County and
and parts of Clark County are in the "drift—
"driftless area',
but thin
thin gravel
gravel deposits
deposits interpreted
interpreted to
to be
be glacial
glacial drift
drift
less
area", but
or outwash from glacial
glacial deposits are present in many places east of the
Black River.
River.
11
Publication
Publication authorized
authorized by
by the
the Director,
Director, U.S.
U.S. Geological
Geological Survey.
Survey.
~/ U.S.
U.S. Geological Survey,
Survey, Washington,
Washington, D.C.
D.C. 20244.
1/ Chief Geologist, Inland
Inland Steel
Steel Co.,
Co., Ishpeming,
Ishpeming, Michigan.
Michigan.
�2
9O0Os
I1r d
N
(P
I
r
2
it
S ho rtv ill e
/J1c(T
_ 141
rrc 1
\
atfi
1 6-
eth7
2Q__.
KSON
/
I c'°cT'r1 if
0
-18
41oj
'lL
1
23
IT
Figure 1.
1.
Figure
S4
I
I887
7
IJI (77)
N
Ti
I
i
-o
\
milee _44°15t=4
Field trip etops
end other localities of geologic interest
stops and
in Jackson
Jackson and
end Clark
C1rk Counties,
in
Counties, Wisconsin,.
Wisconsin .. Base by U.S.
Claire, 1964.
196)i.
Eau
Geological
Survey, 1:250,000,
Claire,
l:2S0,000,
Geological Survey,
�r
r
3
Exposures of Precambrian rocks in Jackson County and in the
southern part
part of
of Clark
Clark County
County are
are largely
largely limited
limited to
to the
the valley
valley of
of the
the
southern
Black River and
and its
its tributaries.
tributaries. A
A few
few mounds of Precambrian iron—
ironformation and
and associated
associated schists
schists and
and some
some quartzite
quartzite knobs
knobs occur
occur as
as
windows in the Upper Cambrian sedimentary strata which form the
the bedrock
over most of
of the
the area.
area.
The exposed Precambrian rocks
rocks consists
consists mainly
mainly of
of paragneisses,
paragneisses,
schists,
schists, phyllites,
phyllites, quartzites, and,
and, locally,
locally, iron—formation.
iron-formation. Granite
and associated rhyolite and
and aplitic
aplitic dikes,
dikes, and
and gabbroic,
gabbroic, dioritic,
dioritic, and
and
doleritic dikes are
are exposed in
in many places.
places.
gneisses are
are mostly
mostly of
of granitic
granitic to
to granodioritic
granodioritic composition,
composition,
The gneisses
and volcanic
volcanic rocks.
rocks. Thin chloritic
and are metamorphosed sedimentary and
layers of greenstone in
in the
the gneisses
gneisses may
may be
be sills
sills or
or volcanic
volcanic rocks.
rocks.
The foliation of the gneisses generally dips steeply and in some places
In most
most places the
the gneisses are highly contorted migmatites. In
the
the
weathered zone
zone at
at the
the top
top of
of the
the Precambrian
Precambrian rocks
rocks is
is relatively
relatively shallow,
shallow,
and
or no
no saprolitic
saprolitic zone
zone at
at the
the top
top
and it appears that there was little or
of the
the Precambrian
Precambrian at
at the
the time
time of
of deposition
deposition of
of the
the basal
basal Upper
Upper Cambrian
Cambrian
of
sediments.
age, totaling more
Sandstone strata of Late Cambrian age,
more than
than 400 fe~t
feet
in thickness
thickness in
in places
places in
in Jackson
Jackson and
and Clark
Clark Counties,
Counties, rest
rest unconformably
unconformably
in
on the Precambrian
Precambrian rocks.
rocks. In most of the area
area east of
of the
the Black
Black River,
River,
however,
however, the
the sandstone cover
cover is
is less
less than
than 200
200 feet
feet thick.
thick. In
In ascending
order, the
formations include
include the
Mount Simon and
and Eau
Eau Claire
Claire
order,
the Cambrian formations
the Mount
Sandstones and
and the Wonewoc and
and Lone
Lone Rock
Rock Formations
Formations of
of Ostrom
Ostrom (1966).
(1966).
units are
are described
described in
in Figure
Figure 2.
2.
These units
The Cambrian formations
formations dip
dip very
very gently
gently (less
(less than
than 10)
1°) southwest.
southwest.
or minor
minor features
features related
related to
to the
the sedimentary processes involved
Except ffor
involved
gradual transgression and
in gradual
and regression
regression of
of seas
seas in
in aa marine—shelf
marine-shelf
sediment zone,
zone, these formations are
are conformable
conformable with
with each
each other.
other. Most
of the rocks
cemented, very porous
porous
rocks are quartz arenites
arenites which are weakly cemented,
and permeable,
permeable, and which have been intensively
and
intensively leached.
leached. Loose sand
accumulated by the disintegration of the
accumulated
the sandstone
sandstone mantles
mantles large
large areas
areas
and conceals
conceals formational
formational contacts in
and
in most places.
Deposits of river gravel derived largely from glacial deposits
of the
few tens
of feet
feet thick
thick on some
some terraces
terraces along
along
north of
the area are
are a
a few
tens of
the Black
Black River.
River.
STOPS OF GEOLOGIC INTEREST
STOPS
STOP 1:
STOP
1: Upper part of Mount Simon Sandstone.
Sandstone.
Location:
quadrangle. West side of U.S.
Black River Falls quadrangle.
U.S. Rte.
Rte. 12
about 500 feet north of Interstate
about
Interstate Rte.
Rte. 94
94 (Figure
(Figure 3).
3).
The roadcut exposes flat—lying,
medium—bedded, cross—
flat-lying, thick—
thick- to medium-bedded,
crosslaminated, poorly
poorly cemented,
cemented, pale-gray
pale—gray to
to buff,
buff, mediummedium- to
to fine-grained
fine—graiñed
laminated,
quartz sandstone with a few thin,
white, clayey partings
partings and
thin, white,
and minor
�4
Upper Cambrian
Cambrian formations
Lone Rock
Rock Formation
1966). Sandstone
Sandstone
Formation (Ostrom,
(Ostrom, 1966).
buff to
to greenish-grey;
greenish-gray; sandstone,
sandstone,
and shale,
shale, huff
and
thinto
medium-bedded,
thinly
crossbedded,
thin- to medium-bedded, thinly crossbedded,
some
layers ripple
ripple marked,
medium- to
to finesome layers
marked, mediumgrained, glauconitic end
grained,
and micaceous,
micaceous, fossiliferous;
shale,
buff
to
gray,
mostly
in
very
to gray, mostly in very thin
thin
erous; shale,
exposed in borrow
borrow pits on
on
layers. Unit is
is well
well esoosed
ridgetops
FEET
FEET
~·~·;.:i:;;:{f~~t~:~~.ji~:~·i·;·::::
200 ·,;':":::::;"'W.,,\(.l!II.!t~·.?\;.::>
·..·.·...::"i' .. ~·zone .:.,::.."......
Wonewoc Formation (Ostrom, 1966).
Wonewoc
1966). Sandstone,
white, pale-yellow to light-yellowish-brown,
white,
light-yellowish-brown,
thick- to
thicktomedium-bedded,
medium-bedded,crossbedded,
crossbedded, some
some
thin layers
layers and
and shalay
shaley partings.
partings.
PredomiPredomiranges from coarse
nantly medium grained,
grained, but
but ranges
grained
silty; weakly
weakly cemented
cemented escept
except for
grained to silty;
thin
zonesthat
thatare
arecemented
cemented by
by brown
brown
thin irregular
irregularzones
Unit forms
forms bluffs
iron osides.
oxides. Unit
Eau
Eau Claire
Claire Sandstone.
Sandstone. Sandstone and
and shale;
shale;
sandstone, pale-yellow-brown
pale-yellow-brown to
to buff, mediumsandstone,
to thin-bedded, croasbedded, medium- to very
~wtjA2)i~~lJ/jJ~I\1~:lil;~~~~{~::~~:~~!~~~~~~~~i~:J,~;~~~~
fine grained, some thin coquinoid layers of
·:,::•.···..,;·;,;,··:·..... :·c>::"... :.:·
small brachiopods, weakly cemented, friable,
except for thin irregular
megular zones
zones that are
are locally
escept
cemented by iron osides; shale, light-greenish-
~~ltl'~ §ig~i~·Y:5.:;~~~:r:i:~l~.:.;:
gray to buff, generally in thin partings, but
locally more than 1 foot thick.
Unit generally
poorly esposed
o
C • • • • ••• ..
'~
"
Mount Simon
Simon Sandstone.
Sandstone. Sandstone and shale;
shale;
sandstone, pale-yellow-brown
pale-yellow-brown to
to white.
white, thickthicksandstone,
to thin-bedded,
thin-bedded, crossbedded,
crossbedded, mainly
mainly mediummediumgrained, but ranging from
grained,
from pebble
pebble conglomerate
conglomerate
in
basal layer
layer to
to very
very fine
fine grained
grained and
and
in thin basal
silty, weakly
weakly cemented,
cemented, friable;
friable; shale,
shale, lightlightgray,
greenish-gray, locally
locally red,
red, mostly
mostly
gray, buff, greenish-gray,
foot
thin partings,
partings, but
but locally
locally more
more than
than 11foot
in thin
bluffs along
along streams.
streams. Unthick. Unit forms bluffs
conformity at
base
at base
-:!.f":: ;'-':~/~"~~~\to
',' ,'.
',',:: \ ;
I_'~
,-, " <
", -I: ~ A •
;, _', \,' ~ ~,
.,
" ,', ,,-;. ~,- ~"...
, -, - < '" < v
Precambrian metamorphic and igneous
igneous rocks
Figure 2.—Generalized
stratigraphic section
aection of Paleozoic
2.-Generalized stratigraphic
Paleozoic aedisnentary
sedimentary
rocks near
near Black
Black River
River Falls,
Falls, Jackson
Jackson County,
CoWlty, Wia.,
Wis., showing
showing the
approximate position
position of
of the
the wavellite
wavellite occurrence.
occurrence.
Data from Klemic
DRtA
1972.
Kiemic end
and Mroa8,
l4roee, 1972.
�5
Figure 3.
Blsck
Rivsr Fall. area:
Stop.
1, 2,
4,
6, and
localities
11, and 25. Base by U.S. Geological Survey, Black River
Falls nuadrangle, 1968, 1:62,500.
10,
�6
partings stained by iron oxide. The Cross—beds dip southeast. No
fossils noted here. this outcrop is typical of exposures of the upper
part of the Mount Simon Sandstone west of the river. These beds are
about 100
the Black
to 120 feet above the base of the formation as exposed near
River to the northeast and to the south. The lower part of
the formation in most areas has thicker bedding and
in average grain size.
is
slightly coarser
The forested mound 3. mile to the east is Tilden Mound or section u
Mound.
It is a motadnock of Precaubflan iron-formation, schist, and
phyllite. The relief on the Precambrian surface between the top of the
mound sad the surface of the Precambrian rocks on the west side of Black
River is 170 feet in a horizontal distance of about 400 feet.
Unfoliated Precambrian granite crops out in the river valley locally
between Tilden Mound and Interstate Rte. 94.
Castle Mound, $ miles to the
south—southeast is
Upper Cambrian
sandstone.
STOP 2t Precambrian monadnock of iron—formation.
Location: Black River Pails quadrangle in the NE
sec. 12,
T. 21 N., R. 4 W. near the junction of Levis Creek Road and West Bottom
Road (Figure 3).
Precambrian iron-formation flanked and partially capped by remnants
of the Upper Cambrian Mount Simon Sandstone extends 50 feet above the
surrotmding plain that is underlain by the Mount Simon Sandstone. The
surf icial part of the iron—formation contains both itagnetite and martite.
The strong magnetic anomaly associated with the mound of iron—formation
extends both northwest and southeast of the mound.
The extent to which
the magnetic anomaly at the crest of the mound has been altered by
lightning strikes is an interesting question.
STOP 3:
Jackson County Iron Company magnetic taconite mine and
agglomeration plant.
Location: Hatfield SW 71—minute quadrangle, SE fr, sec. 15, P. 21 74.,
R. 3 W. (Figure 4).
The open pit mine is at the site of iron Mound, a nonadnock of
Precambrian iron—formation that fornierty extended about 150 feet above
the surrounding plain. Eron Mound was flanked and partly capped by the
Mount Simon Sandstone. The uppermost part of the mound was approtiraately at the altitude at which the Lau Claire Sandstone (which overlies
the Mount Simon Sandstone) formerly occurred.
Iron—formation here dips about iV SW and is in an interval as much
as 350 feet thick. This thickness may represent an isoclinally folded
unit or it may be a faulted segment of a thick formation. It extends to
below 650 feet above sea level. Quartz—chlorite schists border the iron—
formation. Magnetite is the predominant iron-rich mineral, but some
thin layers contain abundant specular hematite.
The iron—formation has
Mat Sc dikes, granitic
been metamorphosed to garnet—actinolite grade.
or aplitic dikes, and quartz veins cut the iron—formation.
A zone of
tRic schist parallela the layering of the iron—formation near the center
of the pit.
�7
'-I
I'
S
�S
The ore
averages 20 to 23 percent in recoverable iron. About 3
of
crude ore are required to produce 1 ton of pellets containing
63.5 percent iron and 1 percent silica. The nagnetite and gangue minerals
are so finely interlocked that in order to obtain suitable iron ore
concentrates, a final grind is made to a size at which 93.5 percent of
the ore will pass through a 325—mesh screen. The Tnagnetite t€ separated
from the gangue minerals by magnetic separators.
Twenty pounds of hen—
tonite clay is added per ton of concentrate in a mixer. The nixture is
fed to a balling mill in which the powdered concentrates are converted
to pellets, about 85 percent of which are 3/8 to 5/8 inch in diameter,
The pellets are dried and preheated and then are heated to 2500 degrees F.
In this process, the nagnetite is converted to hematite, and the finished
pellets become hardened enough to withstand a compression of 800 lbs.
tons
Pellet shipments in 1972 were 887,000 long tons. More details
concerning the iron deposit and the mining, beneficiaticrn, and pelletizing
of the ores, tailings disposal, water supply, and environmental factors
will be discussed at stop 3.
ST4W 4:
Eau Claire Sandstone and Wonawoc Formation of Ostron (1966).
Black River Falls quadrangle, SW fr, sec. 24, T. 21 N.,
Location:
R. 4W. Esst end of Castle Mound, 500 feet west of U.S. Rte. 12 on
Castle Mound Road (Figure 3).
Castle Mound is an elongate ridge capped by the lower part of
The upper part of the Mount
Siron Sandstone forms the basal part of the ridge from about 880 to
Wonewoc Formation of Late Cambrian age.
995 feet above sea level, and, except at the eastern end of the ridge,
it is largely concealed by talus and soil derived from the overlying
rocks.
The Eau Claire Sandstone, which includes fossiliferous tedium—
to fine—grained sgndstone, forms the strata at altitudes of 995 to
1025 feet above sea level. The fossils in the Ea Cl.tre Sandstone are
snail white phosphatic brachiopod shells composed of fluorapatite.
These distinctive white shells are chars.cteflstic of the Lao Claire
Sandstone In the area west of the Black River. East of the river the
formation has been intensively leached, and although the fossiliferous
zones are present, the fossil shell remnants are generally stained by
iron oxides. Commonly the shells have been coaipletely removed and are
represented by empty molds in the sandstone. A noticeable anount Of
glauconite is generally present in the formation. Close exaninstion Of
specimens of the coquina of phosphatic brachiopod shells reveals that
quartz grains in contact with the shell mates-ia]. have been partially
dissolved, leaving flat surfaces that conform to the adjoining smooth
shell surfaces. Empty molds of fossils also show this modification of
the innermost layer of quartz grains. Remnants of the Esu Claire Sandstone capping low hills in the area to the ecist are generally stained
and cemented by brown iron oxide and weather out as small platy fragments
that contrast with the pale—colored and weakly cemented and nonfossilt—
lerous rock of the underlying Mount Simon Sandstone. The Mount Simon sad
the Wonewoc, however, also contain iron oxide—cenented layers, but these
are
generally inedium—grained s andstane s.
�9
STOP 5:
STOP
5: Lone Rock Formation of
of Ostrom
Ostrom (1966).
(1966).
1
Black
River
Falls
quadrangle, NW
NW 4'
, sec. 10,
10, T.
Location:
River Falls quadrangle,
T. 21
21 N.,
N.,
Borrow
pit
on
south
side
of
Pine
Creek Road
Road near
R.
W. (Figure
(Figure 5).
5).
pit
of
R. 5 W.
crest of
of hill.
hill.
The Lone
Lone Rock Formation of
of Late
Late Cambrian age
extends from
from near
near the
The
age extends
the
1120 foot
foot contour to
to the
the crest
crest of
of the
the hill.
hill. The formation
formation consists
consists
mainly of light brownish—gray,
brownish-gray, medium—
medium- to
to thin—bedded,
thin-bedded, medium fine—
fine- to
fine—grained cross—laminated
fine-grained
cross-laminated sandstone
sandstone and
and thin
thin layers
layers of
of shale.
shale. The
sandstone is argillaceous and
and glauconitic.
glauconitic. Some beds are
are abundantly
abundantly
fossiliferous, and
trails, ripple
ripple marks,
marks, and
and mud
mud cracks
cracks are
are well
well
fossiliferous,
and worm trails,
in thin
thin sandstone
sandstone layers.
layers. The rock exposed here
here is
is typical
typical
preserved in
of
the rock in the
of the
the Lone
Lone Rock
Rock Formation at
at other "shale
"shale pits"
pits" near
near the
the
crests of ridges in both the
the Black
Black River
River Falls
Falls and
and adjoining
adjoining quadrangles.
quadrangles.
The environment of deposition of the Lone Rock Formation was similar
It was
was one in which shallow seas
to that of the
the Eau
Eau Claire
Claire Sandstone.
Sandstone. It
seas
transgressed over
over lagoonal
lagoonal areas
areas and
and in
in which
which marine
marine life
life flourished
flourished in
in
transgressed
Local concentrations of brachiopod
the littoral and
the
and neritic
neritic zones.
zones. Local
shells in coquinalike layers resulted from
from the
the winnowing
winnowing of
of sediments
sediments
containing abundant
abundant shells
shells and
and shell
shell fragments.
fragments.
chitinous
The rocks have been extensively leached of calcareous and
and chitinous
material, leaving fossil molds. Phosphatic brachiopod shells,
material,
shells, however,
however,
have been more
more resistant
leaching, as
white
resistant to leaching,
as indicated by the
the remaining white
brachiopod shells.
shells.
The sandstone and
and shale of the
the Lone Rock Formation are extensively
used for
for surfacing dirt
dirt roads
and for
for fill
fill at
bridges and
and culverts
culverts in
used
roads and
at bridges
Jackson County because
they are
to erosion
because they
are more
more cohesive
cohesive and
and resistant
resistant to
the readily
than is
is most
most of
of the
readily available
available rock
rock of
of the
the underlying
underlying Cambrian
Cambrian
sandstones in
in this
this general
general area.
area. Soil developed on
on the
the Lone
Lone Rock
Rock ForFormation is rich in potash because of the presence of glauconite and clay
and is
and
is rich in phosphorus from marine organisms.
organisms. In
In comparison,
comparison, poor
soils occur
occur on the
the Wonewoc
Wonewoc and
and the
the Mount
Mount Simon,
Simon, which
which consist
consist largely
largely
soils
of quartz
quartz sand.
sand.
STOP 6:
STOP
6: Wonewoc Formation
Formation of
of °strom
Ostrom (1966).
(1966).
Location: Black River
River Falls
Falls quadrangle,
quadrangle, SE
SE
sec. 31,
T. 22
22 N.,
N.,
31, T.
W. (Figure
R. 5 W.
(Figure 3).
3). On south side of Wisconsin Rte.
Rte. 27,
27, at
at roadside
roadside
rest area and dirt road leading
leading up
up hill
hill to
to shale
shale pit.
pit.
t,
The Wonewoc Formation is well
well exposed in large roadcuts on the
Rte. 27 and
south side of Rte.
and on the
the north side
side of
of Interstate
Interstate Rte.
Rte. 94.
94. More
than 100
100 feet
feet of
of beds
beds of
of the
the Wonewoc
Wonewoc Formation
Formation are
are visible
visible in
in the
the face
face
than
of the
the large
large roadcut
roadcut to
to the
the north.
north. The top
top of the
the formation
formation is near
altitude
altitude 1210
1210 feet
feet and
and is
is approximately
approximately at
at the
the top
top of
of the
the exposed
exposed rock
rock
formation is
is below road
face. The base of the formation
road level
level and
and is
is probably
near altitude 1040,
1040, at
at the
the base
base of
of the
the steep
steep slope
slope of
of the
the ridge.
ridge.
�1.0
Figure .
Creek Rod ere!* Stop . Base by U.S. Geological Survey,
Black River Falls cuadrangle, 1968, 1:62,500.
Pine
�11
white, pale yellow to
The sandstone of the Wonewoc Formation is white,
to thick
thick bedded,
bedded, cross-laminated,
cross—laminated, and
and predominantly
predominantly
light
light brown,
brown, medium to
coarse— to very fine—grained
medium grained,
grained, but includes coarsefine-grained sand and
and minor
amounts of
of clay.
clay. Some thin zones are
are cemented
cemented by
by brown
brown iron
iron oxides.
oxides.
A large
large chamiel
channel in
in the
the sandstone
sandstone is
is exposed in
in the
the lower part of the
the
A
The rock here
here is
of that
Wonewoc Formation
The
is typical
typical of
that in the
the Wonewoc
roadcut.
In some
some places,
places, iron—oxide
throughout this general
general area.
area.
In
iron-oxide cement is
is more
fossils were
were found
found at
outcrop, but
but in some
some places
places
abundant. No fossils
at this
this outcrop,
vertical tubular markings may represent
represent burrows
burrows made
made by
by marine
marine creatures.
creatures.
At Wildcat
quadrangle, and
quadrangle,
and
and cemented
cemented by
by
and
has been called
has
Humbird, in
in the
the southern part of Fairchild
Mound east of Humbird,
at
several other localities,
localities, variegated
variegated sandstone
sandstone colored
colored
at several
iron oxide
oxide is
is very
very distinctive
distinctive in
in appearance
appearance and
and locally
locally
iron
"Zebra rock"
rock" because
because of
of the
the pattern
pattern of
of its
its markings.
markings.
Although the
the Wonewoc Formation forms bluffs and
and cliffs,
cliffs, the rock
is
is generally only weakly cemented, and
and bedrock
bedrock on
on the
the lower
lower slopes
slopes of
of
ridges
hills underlain
underlain by
by this
formation is
is commonly
commonly concealed
concealed by
by
ridges and
and hills
this formation
loose sand and
and rubble from
flom overlying
overlying beds.
beds.
STOP 7:
7: Eau Claire Sandstone
Sandstone and
and Wonewoc
Wonewoc Formation
Formation of
of Ostrom
Ostrom (1966).
(1966).
STOP
35,
T.
Black
River
Falls
quadrangle,
SW
-,
sec.
Falls quadrangle, SW~,
35, T. 23
23 N.,
N.,
Location:
R. 55 W. (Figure
(Figure 6).
6). At Silver Mound and in the field
field on the southwest
R.
of Silver Mound.
of
Fossiliferous and glauconitic sandstone beds of the Eau
stone
stone are
are well
well exposed
exposed in
in aa small
small excavation
excavation on
on aa prominence
prominence
field
Mound, and loose fossiliferous
fossiliferous Eau
field southwest of
of Silver Mound,
stone occurs
occurs at
at an
an altitude
altitude of
of 1025
1025 feet
feet on
on the
the south
south tip
tip of
of
stone
near the
the highway.
highway.
Claire
in
in the
the
Claire
Silver
Silver
SandSandMound
Mound
Silver Mound is
is an
an important
important archeological
archeological locality.
locality. The mound is
is
capped by the
the Wonewoc
Wonewoc Formation.
Formation. The lower
lower part
part of
of the
the formation
formation is
is
largely concealed.
concealed. The uppermost 100 feet or so of beds,
beds, however,
however, is
thoroughly cemented by silica,
silica, and
and the
the rock
rock is
is aa brittle
brittle quartzite.
quartzite.
This rock was
was extensively
extensively used
used by
by prehistoric
prehistoric Indians
for the
manufacThis
Indians for
the manufacture of tools
tools and
and weapons.
weapons. Artifacts are numerous in the fields
fields surrounding the
part of
of Silver Mound,
Mound, and
artifacts and
and whitish
whitish
rounding
the southern part
and artifacts
flakes of quartzite from this
flakes
this locality
locality are
are widespread
widespread in
in Jackson
Jackson County.
County.
Similar quartzite occurs in lesser amounts
miles
amounts on a ridge several miles
northwest of
of Silver
Silver Mound.
Mound. The source of the
the silica that
that cemented the
sandstone
sandstone and
and the
the conditions
conditions under
under which
which it
it was
was deposited
deposited in
in the
the formation
formation
of the quartzite in this
this almost isolated occurrence require
require an explanation.
Upper Cambrian strata of this
There is no lack of silica in the
the Upper
this
general
but most
most of
of it
form of
of quartz
quartz
general area,
area, but
it is
is in the
the relatively inert
inert form
sand.
Therefore,
Therefore, some
some local chemical environment that
that differed from the
the
general conditions must have made silica
general
silica available
available in
in solution.
solution. Perhaps
the chemical
the
the
chemical environment
environment of
of the
the fossiliferous
fossiliferous beds,
beds, particularly of
of the
coquina layers,
layers, may have been the
the source
source of
of the
the silica.
silica. As previously
described, the
the quartz sand grains in contact with the phosphatic brachiopod
described,
shells have
have been
been partially
partially dissolved
dissolved into
into hemispherical
hemispherical forms
forms having
having their
their
shells
�·OO$'G9:!
'996! 'a!~ue~penu
r'uadrangle, s!!ed
Falls
1:62,OO. 1968,
l:iw~:20!OalJ
U.S.
fleological ·S"n
Aq
by aseg
Base "L
7. dOlS
Stop
~ooH
Rock ~oe!g
Black
'AaAInS
Survey,
:a~.Ia
pree: punai'{
Silver
Mound .leAHS
"9
Figure
6. e.:nj,:.!I
(';1
12
�13
flat
against the
the shell
shell surfaces.
surfaces. The chemical environment
environment that
that
flat surfaces against
produced this
result in the
Eau Claire
Claire and
the Lone
Lone Rock,
Rock, both
both of
of which
which
produced
this result
the Eau
and the
are
are fossiliferous and
and contain phosphatic
phosphatic brachiopods,
brachiopods, would
would have
have made
made
available large quantities of
of silica
silica in
in solution.
solution. Such silica—bearing
silica-bearing
waters percolating from the fossiliferous
fossiliferous Lone Rock Formation may have
the silica
silica cement
cement in
in the
the Wonewoc
Wonewoc Formation
Formation at
at Silver
Silver Mound.
Mound.
deposited the
Small zones of silicified sandstone a few inches thick,
thick, in the Mount
Simon Sandstone near its contact with the Eau Claire Sandstone have been
noted in
in several
several places
places in
in Jackson
Jackson County.
County.
STOP 8:
8:
STOP
Exposure showing complexities
complexities of
of Precambrian
Precambrian rocks.
rocks. This stop
also provides an opportunity to
also
to examine
examine some
some economic
economic uses
uses of
of local
local
geologic features
problems and
possibilities arising
features and some of
of the problems
and possibilities
from the pressures of demands
demands for
for their
their use.
use.
Hatfield 7-i-—minute
quadrangle, SE -,
Location: Hatfield
7!-minute quadrangle,
~, sec. 3,
3, T.
T. 22
22 N.,
N.,
R.
W. At Black River,
River, north of County Rte.
Rte. K
K and
and south
south of dam at
at
R. 33 W.
Lake Arbutus (Figure
(Figure 7).
7).
Because of
of load
load limitations
limitations at
at the
the bridge
bridge over
over the
the canal
canal at
at Hatfield,
Hatfield,
it will be necessary to
to walk about
about 11 mile
mile to
to the
the large
large exposure
exposure of
of PrePrecambrian metamorphic
immediately below the
at the
metamorphic rocks
rocks immediately
the unconformity at
the
the Upper
Upper Cambrian
Cambrian sandstone.
sandstone.
base of the
Lake Arbutus is an
an artificial
artificial lake impounded behind a dam built
bedrock in
in the
the valley
valley of
of the
the Black
Black River.
River. Water level
upon Precambrian bedrock
in the
the dam
dam is
is maintained
maintained at
at or
or near
near the
the level
level of
of the
the unconformity
unconformity at
at
the top of the
the
the Precambrian. A
A canal
canal aa little
little more than
than 22! miles long
long
has been cut in the Upper Cambrian sandstone to carry water to the penpen—
stocks of aa small
small electrical
electrical power
power plant.
plant. The hydraulic
hydraulic head at the
power plant is
is nearly 100
100 feet.
feet. This power plant is
is an
an important
important local
local
nonpolluting source
source of electric energy.
energy.
Lake
Lake Arbutus
Arbutus has
has a
a surface area of
of slightly more
more than two square
miles and
and is
is aa popular recreation center,
center, having two
two county parks and
and aa
State campsite on
its
shores.
on its shores. Hatfield,
Hatfield, aa small resort community on
the
the west
west side
side of
of the
the lake,
lake, is
is in an
an area in
in which
which only
only about
about 10
10 to
to 30
30
feet of
of beds
beds of
of Upper
Upper Cambrian
Cambrian Mount
Mount Simon
Simon Sandstone
Sandstone overlies
overlies the
the metametafeet
morphic and
and igneous
igneous Precambrian
Precambrian basement
basement rocks.
rocks. The community obtains
obtains
its water supply largely from wells in
its
in the
the sandstone.
sandstone. A
A few wells
extend into
into the
the Precambrian
Precambrian basement
basement rocks.
rocks.
disposed into the surficial
mantle of
Sewage from the
the community is
is disposed
surficial mantle
of
sand and in the
the upper layers
layers of
of the
the sandstone
sandstone strata.
strata. Thus the
the possipossibility exists for pollution of
of the
the water
water supply.
supply. Should the local
local
substantially, both the
the amount
amount of waste redemand for water increase substantially,
quiring disposal and
and the
the possibility
possibility of
of pollution
pollution of
of the
the local
localgrc*ind
ground
waters would
would also
also increase.
increase. Alternative sources
sources of
of water
water and
and improved
improved
facilities
eventually be
be needed.
needed.
facilities for sewage disposal will eventually
-
�14
'U
.
JAO CO
21
T. 22 N.
25'
C"
C"
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;
19
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897
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200000
FEET
HIGH BANK
1jii
889112$
i7,ei Pits
16
440
Locality 25 -
22'30"
900 45'
Pigure
Figure
mile
7.
680
1810000
FEET I
c.1ty 17
°
4.2 MI. To WIS. 54
'23J
42' 30"
localities 17,
17, 24,
24, and
and 25.
2.
Stop 8 and
and localities
Hatfe].d quadrangle, 1970,
Base from U.S. Geological Survey, Hatfield
1970,
].: 214,000.
1:24,000.
Lake
Arbutu8 area:
area:
Lake Arbutue
�15
1
The contact between the Mount Simon Sandstone and the underlying
west end of the bridge where
Precambrian rocks
rocks is at road level
level at the west
mile southwest
County Rte.
southwest of
of the
the dam
dam at
at
Rte. K
K crosses the Black River
Lake Arbutus. A
A thick
thick bed of
of coarse—grained
coarse-grained cross—laminated
cross-laminated sandstone
sandstone
is
is exposed
exposed on
on the
the west
west side
side of
of the
the road,
road, and
and Precambrian
Precambrian granitic
granitic gneiss
gneiss
the east side
side of
of the
the road.
road. The channel of the
the Black River
crops out on the
has been cut about
about 50
50 feet
feet into
into the
the Precambrian
Precambrian rocks
rocks at
at the
the bridge.
bridge.
t
-'
Rte. K,
K, then go northeast
northeast on Clay School
School
Proceed east on County Rte.
Road about 0.2 mile to
to aa dirt
dirt lane
lane on
on the
the west
west side
side of
of the
the road.
road. Follow
woods and
dirt lane to clearing in woods
and turn north on path leading down into
valley. Proceed northeast
northeast toward
toward the
the foot
foot of
of the
the dam.
dam.
the river valley.
This large
large exposure of bedrock shows
shows some
some of the
the complexity of the
the
basement rocks.
rocks. Granitic and
and chloritic
chloritic gneisses,
gneisses, schists,
schists,
Precambrian basement
A large
and greenstones trend
trend northwest and
and dip
dip steeply
steeply northeast.
northeast. A
northeast—trending metagabbro dike
dike at
east end
end of
of the
the dam cuts
cuts the
the
northeast-trending
at the
the east
gneisses. Another large dike on the west side of the east channel of
the river is more dioritic in
in composition.
composition. The intervening granite
the
gneisses and
chloritic sills
sills are
are contorted
contorted in
in sinuous
sinuous forms
forms on
on which
which
gneisses
and chloritic
there is
is well-developed
well—developed quartz
quartz rodding
rodding or
or slickensides
slickensides that
that dip
dip to
to the
the
there
A
feet southwest of the dam a prominent siliceous
east.
A few hundred feet
metarhyolite(?) and the adjoining gneiss are cut by a contorted
mass of metarhyolite(?)
dipping
mafic dike or
or sill.
sill. An east—trending
east-trending swarm of narrow steeply dipping'
unfoliated siliceous
siliceous and
and chloritic
chloritic dikes
dikes cut
cut all
all the
the other
other rock
rock types.
types.
Minor quartz—filled
quartz-filled fractures
fractures cut the younger dikes and the other rock
units.
At one place on the west side of the river a quartz vein is
more than three
three feet
feet thick.
thick. Minor amounts
amounts of
of pyrite
pyrite are
are evident in
in the
the
rocks,
and
fine—grained
pyrite
is
abundant
in
the
youngest
dike.
rocks, and fine-grained pyrite is abundant in the youngest dike.
STOP 9:
STOP
9: Wavellite occurrence
occurrence in
in the
the Eau
Eau Claire
Claire Sandstone.
Sandstone.
quadrangle,
SW
Location: Black River Falls
Falls quadrangle, SW -, sec. 23,
23, T.
T. 22
22 N.,
N.,
R.
(Figure 8),
8), roadcut
roadcut on
on East
East Snow
Snow Creek
Creek Road.
Road.
R. 4 W.
W. (Figure
t,
Wavellite (Al3(P04)2(OH)35H20)
(A13(P04)2(OH)3'5H20) occurs
occurs as
as thin
thin botryoidal
botryoidal crusts,
erusts,
small
masses, and
cement in the
the sandstone
sandstone at
outcrop
small spherical
spherical masses,
and as
as cement
at this
this outcrop
and at several other places where
where this
this stratigraphic
stratigraphic unit
unit is
is exposed
exposed
in this general
general area.
area. The source of the phosphorus is believed to have
been phosphatic
phosphatic fossil
fossil material
material such
such as
the phosphatic
phosphatic brachiopod
brachiopod shells
shells
as the
in the Eau Claire Sandstone.
Sandstone.
The Wonewoc Formation which crops out on the west side of the road
is
weakly
cemented,
is
cemented, very porous and
and permeable
permeable sandstone.
sandstone. It
It is
is coarser
in
grain
size
than
the
underlying
rock
in grain
rock and
and is
is thoroughly
thoroughly leached.
leached. The
Wonewoc-Eau Claire contact zone
zone is
is favorable
favorable for the
the development of aa
Wonewoc—Eau
perched water table in places
is abundant
abundant in
in the
the
places where
where shale or clay is
Claire.
Eau Claire.
in many places in Wisconsin where the Eau
Wavellite probably occurs in
Claire Sandstone is
is present and where conditions for movement of ground
water were comparable
comparable to
to those
those in
in this
this area.
area. In
addition, similar conIn addition,
ditions for occurrences of wavellite in association with the Lone Rock
Formation may exist. Wavellite,
however, may
may be
be readily
readily overlooked,
overlooked,
Wavellite, however,
particularly
icial stains of
particularly in
in cases
cases where
where it
it contains
contains surf
surficial
of iron
iron oxides.
oxides.
�16
-I
ZLji
*_—:•1:
-
°•
-.-i----
19•
25
F
IF
LocalY
24
Locality 23.
I 23N
Ei
928
1
'
cc;
25
O1I
96
III\
EVERG EEN
:T
-3
'p23
\
,**
-
o
T.22N
—
M
48
13 889
f
OF
-
POWERHO
LOcZty
16 17
GreI
I
21
Fj \1],'?'Locality
iave1
15
.x-=
Figure 8.
8.
localities 12,
Merrillan ares:
area: Stop
Stop 99 and localities
12, 15,
1', 19,
19,
20,
20, 21,
21, 22,
22, and
and 27.
27. Base
Base by
by U.S.
U.S. Geological
Survey,
Geological
Black
cuadrangle, 1968,
1968, 1:62,500.
l:62,O0.
Black River Falls
Falls quadrangle,
�17
ADDITIONAL LOCALITIES OF GEOLOGIC INTEREST
INTEREST
of Precambrian
Precambrian rocks.
rocks.
Exposures of
Falls 15-minute
15—minute quadrangle,
quadrangle, SE
SE ~,
, sec. 15,
Locality
10: Black River Falls
Locality 10:
T. 21
21 N.,
N., R.
R. 44 W.
W. (Figure
(Figure 3).
3). North of U.S.
U.S. Rte.
Rte. 12 at Black River
T.
Falls. Accessible from
from east
east end
end of
of bridge
bridge crossing
crossing Black
Black River.
River.
Unfoliated jointed granite
granite at
at the
Falls below the
the dam
dam appears
appears
Unfoliated
the Falls
fresh, but much of the
fresh,
the hornblende is
is altered
altered to
to chlorite.
chlorite. Similar
granite cuts
cuts iron-formation
iron—formation and
rocks adjoining
adjoining the
the iron-formation
iron—formation in
granite
and rocks
Z.E. Peterman
Peterman of
of the
the U.S.
U.S. Geological
Geological Survey
Survey has
has deterdeterthe subsurface. Z.E.
mined that
that the
the rubidium—strontium
rubidium-strontium ratios in these granites indicate an
age of
years (U.S.
(U.S. Geol.
Geol. Survey,
Survey, 1972).
1972).
age
of about 1,690 million years
Locality 11:
11: Black River Falls
Falls 15—minute
15-minute quadrangle,
quadrangle, NE
NE -,
~, sec. 22,
the valley of Black River at
T. 21
21 N.,
N., R.
R. 44 W.
W. (Figure
(Figure 3).
3). In the
at the
the base
base
T.
On south side of river.
of
river.
of bluff of Mount Simon Sandstone. On
Granitic gneiss and gray chloritic gneiss are cut by dolerite
In
In contrast to the deep channel cut
cut by
by the
the Black
Black River
River in
in the
the
Precambrian rocks
Arbutus, the-channel
rocks below the dam at Lake Arbutus,
the· channel here
here is
only about
only
about 10 feet
feet down into
into the
the Precambrian
Precambrian rocks.
rocks. The outcrops here
may be concealed if
if water
water level
level is
is high.
high.
dikes.
15—minute quadrangle,
quadrangle, NE
NE ~,
, sec. 30,
Locality
12: Black River Falls
Falls 15-minute
Locality 12:
T.
N., R.
R. 33 W.
W. (Figure
(Figure 8).
8). West side
side of Black River near junction
junction
T. 22 N.,
Creek and
and river.
river. Readily accessible by road
road to
to canoe
canoe landing.
landing.
of Hall's Creek
bluffs leads
leads to exposures
exposures of
of phyllite
phyllite and
gneiss
Path to south along bluffs
and gneiss
beneath unconformity at
at base
base of
of Mount
Mount Simon
Simon Sandstone.
Sandstone.
Weathered schist and
and phyllite at
at the
the base of cliffs of Mount Simon
Sandstone are
are exposed
a short
exposed a
short distance
distance upstream from
from the
the mouth of
of Hall's
Hall's
Creek;
Creek; chloritic
chloritic mafic
mafic intrusive
intrusive rocks
rocks also
also occur
occur in
in the
the creek
creek valley.
valley.
t,
Locality
Falls 15-minute
15—minute quadrangle,
quadrangle, SE
SE , sec. 17,
Locality 13:
13: Black River Falls
T.
W. (Figure
(Figure 8).
8). West side
side of
of Black River
River about
about 0.4
0.4 mile
T. 22
22 N.,
N., R.
R. 33 W.
quarry near
near river.
river.
southwest of power plant.
plant. Abandoned quarry
Strikingly contorted dark gray and
and white hornblende gneiss of
and a fine—grained
fine-grained intrusive rock
granitic to granodioritic composition and
of gabbroic composition are
present
are exposed in the
the quarry face
face and
and are
are present
in loose blocks.
blocks. The composition of
of feldspar
feldspar augen
augen in the
the gneiss
gneiss has
has
not been determined.
Locality
-, sec. 25,
25, T.
Locality 14:
14: Hatfield 15—minute
15-minute quadrangle,
quadrangle, NW
NW~,
T. 23
23 N.,
N.,
R.
R. 33 W.
W. (Figure
(Figure 9).
9). West side
side of
of Black
Black River
River near
near French
French Island.
Island.
Pink granite typical of that in several
several localities along
along the Black
River north of
of Lake
Lake Arbutus is
is well
well exposed
exposed along
along the
the river.
river. The basal
beds of the
the Mount Simon
Simon Sandstone
Sandstone crop
crop out
out on
on the
the west
west side
side of
of the
the road.
road.
Similar granite crops
crops out
out at the abutment of the abandoned bridge
on the east side of
of the Black River 0.2 mile
mile south of Wisconsin Rte.
Rte. 95
95
in
the
NW
,
in the NW~, sec. 19,
19, T.
T. 23
23 N.,
N., R.
R. 22 W.
W.
�18
15
17
Levis Mound
I
Sch
. ·r
l
own Hall
~
2~
,, .
·.,
.~
I
"Locality
.. 14
~.:~:;.'
"-29
\
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/
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34
I(
(,
If
/I
If
figure
Figure 9.
'-<
.. -<
L
I
II••
v·
t.ke Arbutus
Arbutu area:
L.ke
(
.l'Gravel Pit
-
(
I
Localittea 14
and 15.
1. Base
Locelities
14 and
Baseby
by U.S.
U.S. Geological
Geo1op,ica1
Survey, Hatfield
Hatfield planimetric
l98, l:1L8,000.
Survey,
planimetric map,
map, 1958,
1:48,000.
�19
Locality
Locality 15:
15: Hatfield 15—minute
15-minute quadrangle,
quadrangle,
R.
2
W.
(Figure
9).
North
side of
of East Fork
R.
W. (Figure 9).
east of
of the
the bridge.
bridge.
t,
NW
4, T.
T. 22
NW -, sec. 4,
22 N.,
N.,
of Black River
River 250
feet
of
250 feet
Large outcrop of
of granitic
granitic and
and migmatitic
migmatitic gneiss
gneiss cut
cut by
by maf
mafic
and
ic and
aplitic dikes. During periods of normal or low water level this outcrop is
is well exposed.
exposed. Quartz rodding or slickensides on minor folds
folds
in the
the gneiss
gneiss is
in
is similar to that in the
the outcrop near
near the
the dam
dam at
at Lake
Lake
(Stop 8),
8), but
but the
the rodding
rodding here
here plunges
plunges east
east at
at aa low
low angle.
angle.
Arbutus (Stop
of the
mafic and
aplitic dikes
dikes at
at this
this locality
locality have
have
The relative
relative ages
ages of
the mafic
and aplitic
not been determined. Pink granite and
and small aplitic dikes crop out at
several
several other places along
along the
the East Fork
Fork of
of the
the Black
Black River.
River.
t,
20, T.
T. 23
Locality 16:
16: Hatfield 15—minute
15-minute quadrangle,
quadrangle, SW
SW -, sec. 20,
23 N.,
N.,
R. 1 W. (Figure
(Figure 10).
10). Brushy Ridge Road.
Road.
R.
Quartzite,
a small
Quartzite, probably of Precambrian age,
age, is exposed in
ina
small
roadcut
tributary of
of Rock
Rock Creek.
Creek. Quartzite
roadcut on the south side of aa tributary
zones in
in the
the Mount
Mount Simon
Simon Sandstone
Sandstone occur
occur in
in aa small
small knob
knob on
on the
north
zones
the north
side of the east-trending
east—trending road 0.8 mile north
side
north of
of this
this roadcut.
roadcut.
t,
Hatfield 15-minute
15—minute quadrangle,
quadrangle, NE
NE , sec. 22,
Locality
Locality 17:
17: Hatfield
22, T.
T. 22
22 N.,
N.,
R.
R. 3 W.
W. (Figure
(Figure 7).
7). Morrison Creek at
at County Rte.
Rte. K.
K.
Granite gneiss cut by mafic dikes is
is exposed beneath the
the bridge
during periods of
of low
low or
or normal
normal water
water level.
level. Bluffs of
of the
the basal
basal beds
beds
of the Mount Simon Sandstone and
metamorphic
and outcrops
outcrops of
of the
the Precambrian metamorphic
rocks and mafic
maf Ic and
and granitic
granitic intrusive
intrusive rocks
rocks are
are exposed
exposed along Morrison
rocks
Creek to the
the east of
of this
this locality.
locality.
15—minute quadrangle,
quadrangle, NW
NW t,
, sec. 9,
9, T.
T. 21
Locality
18: Hatfield 15-minute
21 N.,
N.,
Locality 18:
R.
W. (Figure
(Figure 11).
11). On north side of Battle Point Road.
Road.
R. 2 W.
Precambrian quartzite is
is exposed
exposed in
in aa small
small quarry.
quarry. The quartzite
is
is brecciated and recemented by
by silica.
silica. Basal sandstone of the Mount
fragments of
of the
the quartzite
quartzite at
the unconformity
unconformity
includes fragments
at the
Simon Sandstone includes
between the Precambrian and
and the
the Cambrian
Cambrian rocks.
rocks.
Exposures of
of Cambrian
Cambrian rocks.
rocks.
t,
Locality
Black River
-h-, sec. 19,
Locality 19:
19: Black
River Falls
Falls 15—minute
15-minutequadrangle,
quadrangle,SE SE
19,
T.
T. 22
22 N.,
N., R.
R. 33 W.
W. (Figure
(Figure 8).
8). At bridge on
on County Rte.
Rte. E
E crossing
crossing
Hall's Creek.
Creek.
Basal beds of Mount Simon Sandstone
Sandstone are
are exposed
exposed near
near stream
stream level.
level.
bedded, cross-laminated,
cross—laminated, medium to very coarse
coarse
The sandstone is
is thick bedded,
grained, and has
at the
the base
the
grained,
has a thin pebbly layer at
base in places
places along the
creek.
�20
NEILLSVILLE 1S.4 MI.
MI. TO WIS. 91S
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. "I / _.
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@.
.
73 ...........
R1W rf'o
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1 660000 FEET
6
5
0.
BM
1005
ShortviIle
9
'v"
16
13
1--....·.
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24
9
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Figure 10.
10.
Figure
}
-:-
.. ,,'-
mile
---..
by U.S.
3bortville
Shortville area:
area: Locality
Locality 16.
16. Base by
U.S.
plazimetric map,
Geologieal
map,
Survey, Hatfield
Hatfield planimetrie
Geological Survey,
1958,
1:48,000.
l98, l:1.i8,000.
�21
, F'1inmak r
',Flowage 36
,.r:..-;-"
~~\~:.:.
,
,-- /
J
f!t>:3,)
.......\
\1
L
I:
Ii
II
II
ft
II
II
II
II
1/
II
..
~
~~~~~:.:_;~
f~~( "'
)'
vp
,
"
/1
(~~/
/
,,
>dk'2 .
--' /.-9~.
/;
/'
r,
/I.
::~
l \'./ /
- - :;',
,
~ ....
..... _ _
:',
/"
...
~ ';'
1\,
\\~
1
~~~
{3
. t \{} ....... ,
,\\.'-..,'~'.~,\
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{
\\.
I.' {~ ~- ....."'\.,-:-. "-
{\.
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.......
t.
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Figure 11.
11.
•
Town Line Flovege
area: Locality
F1owge area:
18. Base by U.S. Geological
Locality 18.
1958,l:Ii8,000.
1:48,000.
Survey, Hatfield
Hatfield planimetric
planimetric map,
map, 19S8,
�22
Locality 20:
?, sec. 26,
Locality
20: Black River Falls
Falls 15—minute
l5-minute quadrangle,
quadrangle, NW
NW~,
26,
T.
T. 23
23 N.,
N., R.
R. 44 W.
W. (Figure
(Figure 8).
8). At park on west side of U.S.
U.S. Rte.
Rte. 12 at
at
south edge of Merrillan.
Thick-bedded sandstone of the Mount Simon Sandstone is well
well exposed
at
on Hall's
Hall's Creek
Creek where
where there is aa scenic
at the darn
dam on
scenic waterfall.
waterfall.
Locality 21:
Locality
21: Black River Falls 15—minute
15-minute quadrangle,
quadrangle, sec.
sec. 30,
30, T.
T. 23
23 N.,
N.,
R.
R. 3 W.
W. (Figure
(Figure 8).
8). At Bruce Mound, in
in Clark
Clark County.
County.
Prominent cliffs of the Wonewoc
Wonewoc Formation are
are strikingly exposed
exposed
along the southwestern side
side of
of the
the mound.
mound. The Lone Rock
Rock Formation
Formation caps
caps
the mound at
at the
the lookout
lookout tower.
tower. The Eau Claire and
and Mount Simon Sandstones
stones are largely concealed on the
the lower
lower slopes
slopes of
of the
the mound
mound but
but are
are
partly exposed
exposed near
near the
the ski
ski resort
resort facilities
facilities on
on the
the east
east side
side of
of the
the
mound.
Locality
River Falls
Locality 22:
22: Black .River
Falls 15—minute
15-minute quadrangle,
quadrangle, sec.
sec. 22,
22, T.
T. 22
22 N.,
N.,
R.
R. 4 W.
W. (Figure
(Figure 8).
8). Along road following the top of ridge leading from
West Snow Creek Road
Road toward
toward radio
radio tower.
tower.
Shale pits in Lone Rock Formation have
have excellent exposures
exposures of
of the
the
fossiliferous glauconite sandstone
sandstone and
and shaly
shaly strata.
strata.
Locality 23:
15—minute quadrangle,
quadrangle, NW~,
NW , sec. 29,
Locality
23: Black River Falls
Falls 15-minute
29,
T.
N., R.
R. 44 W.
W. (Figure
(Figure 3).
3). Roadcut on east side of Moss Hill
Hill Road.
Road.
T. 21 N.,
Exposures of upper part of Mount Simon Sandstone are
are capped at
at an
an
altitude of 940 feet by the
the Eau
Eau Claire
Claire Sandstone
Sandstone which
which has
has thin
thin layers
layers
of
brachiopod shells.
shells. A
of coquina consisting of white brachiopod
A similar occurrence
is
miles to the west.
is at an altitufe
altitufe of
of 940
940 feet
feet along
along Wold
Wold Road
Road l-- miles
Note the concentration of brachiopod shells along some of the cross
It
laminae.
14, T.
T. 22
Locality
Hatfield 15-minute
15—minute quadrangle,
quadrangle, SW~,
SW , sec. 14,
Locality 24:
24: Hatfield
22 N.,
N.,
On northwest
northwest side
side of
of Mollies
Mollies Creek,
Creek, at
at sharp
sharp bend
bend
R.
R. 33 W.
W. (Figure
(Figure 7).
7). On
about
about 1000 feet
feet northeast
northeast of
of junction of
of Mollies
Mollies Creek
Creek and
and Morrison
Morrison
Creek.
Thin basal beds of the Mount Simon Sandstone have a thin basal
basal
layer of
acts.
The underlying Preof quartz
quartz pebbles
pebbles that
that resemble
resembleventif
ventifacts.
cambrian gneiss and schist is
is deeply weathered to greenish—gray
greenish-gray clay
at the
the unconformity
unconformity between
between the
the Precambrian
Precambrian rocks
rocks and
and the
the Cambrian
Cambrian
at
sandstone.
Locality
Locality
22, T.
T. 22 N.,
Hatfield 15-minute
15—minute quadrangle,
quadrangle, NE
NE ~,
, sec. 22,
Hatfield
N.,
On
south
bank
of
Morrison
Creek
about
1600
feet
R.
(Figure 7).
7).
of
feet
R. 3 W.
W. (Figure
mouth of
of Hay
Hay Creek.
Creek.
southwest of mouth
25:
25:
the Mount Simon Sandstone is
is cemented
Basal quartz conglomerate of the
by pyrite in small
about 6 inches
inches thick a few feet
small lenticular zones
zones about
feet
above normal water
water level.
level. The streambank is
is slightly overhanging in
in
places,
places, and
and careful search may be required to
to find the
the pyritic conglomerate.
conglomerate.
1
�23
Locality
15—minute quadrangle,
quadrangle, NE
NE ~,
, sec. 33,
Locality 26:
26: Hatfield
Hatfield 15-minute
33, T.
T. 22
22 N.,
N.,
R. 1 W.
(Figure 12).
12). Saddle Mound,
Mound, north
north of
of Wisconsin
Wisconsin Rte.
Rte. 54.
54.
R.
W. (Figure
The crest of the mound at
at the lookout tower is capped by about
60 feet
feet of the Lone Rock Formation. Glauconitic sandstone
60
sandstone is
is well
well
exposed in a small
small abandoned quarry near the foot
foot of the tower,
tower, and
Ostrom's
Ostrom's (1966)
(1966) Birkmose
Birkmose Member
Member of
of the
the Lone
Lone Rock
Rock Formation
Formation is
is exposed
exposed
near the
the guard rail
rail several
several hundred
hundred feet
feet east
east of
of the
the tower.
tower.
steep southern slopes
slopes
The Wonewoc Formation is well
well exposed on the steep
the mound.
mound. Minor amounts of weathered fossiliferous
fossiliferous sandstone,
sandstone,
of the
probably of the Eau Claire Sandstone,
Sandstone, can be found
found on the
the spur on the
northwestern side
side of the
the mound near
near an
an altitude
altitude of
of 1100
1100 to
to 1130
1130 feet.
feet.
Most of
of the
the Eau Claire Sandstone,
Sandstone, however,
however, is
is concealed by debris from
the overlying formations,
formations, and
of the
loose fossiliferous
fossiliferous rock on
and some
some of
the loose
the lower slopes is
is talus
talus from
from the
the Lone
Lone Rock
Rock Formation.
Formation.
Holocene river
river gravels.
gravels.
Locality 27:
Falls 15-minute
15—minute quadrangle,
quadrangle, SE
SE ~,
, sec. 20,
Locality
27: Black River Falls
T.
T. 22
22 N.,
N., R.
R. 33 W. (Figure
(Figure 8).
8). Gravel pit on
on west
west side
side of
of Black
Black River.
River.
gravel deposits
deposits at
this locality are
are on aa wide
wide terrace
terrace
Sand and
and gravel
at this
about 20 feet
feet above
above river
river level
level and
and cover an area of
of more
more than
than one
one square
square
about
mile.
The gravels include aa wide variety of siliceous igneous and
rock types
types and
and minor
minor amounts
amounts of
of sedimentary
sedimentary rock.
rock. Most of
metamorphic rock
the gravel
gravel is
is outwash from
from glacial
glacial deposits
deposits that
that are
are abundant
abundant to
to the
the
the
north.
gravel deposits occur on the west side of the Black
Similar gravel
River in Clark County north of Wisconsin Rte.
Rte. 95,
95, and in Jackson County
as indicated on
on both sides of the river south of Black River Falls,
Falls, as
the
of these
these areas.
areas.
the topographic maps of
During construction of
these deposits
of Interstate Rte.
Rte. 94,
94, these
deposits were
were
important sources of sand and gravel,
important
gravel, and
and they
they currently
currently supply
supply local
local
needs.
�r
24
~(~4
Figure 12.
.\
Saddle Mound: Locality 26. Base by U.S. Geological
Survey, Hatfield SE quadrangle, 1970, 1:62,500.
I
�25
25
REFERENCES
Klemic, Harry,
Harry, and Mrose,
Mrose, M.E.,
M.E., 1972,
1972, Geologic relations and X-ray
X—ray
Klemic,
crystallography of
of wavellite
wavellite from
from Jackson
Jackson County,
County, Wisconsin,
Wisconsin,
U.S. Geol.
Geol. Survey
and
implications: U.S.
Survey Prof.
Prof.
and their geologic implications:
Paper 800—C,
BOO-C, p.
p. C53—C62.
C53-C62.
Ostrom,
M.E., 1966,
Ostrom, M.E.,
1966, Cambrian stratigraphy
stratigraphy in
in western
western Wisconsin:
Wisconsin:
Wisconsin
Wisconsin Geol.
Geol. and
and Nat.
Nat. History
History Survey
Survey Inf.
Inf. Circ.
Circ. 7,
7, 79
79 p.
p.
Ostrom, M.E.,
M.E., Davis,
Davis, R.A.,
R.A., Jr.,
Jr., and
Cline, L.M.,
L.M., 1970,
1970, Field
Field trip
trip
Ostrom,
and Cline,
guidebook for Cambrian-Ordovician
Cambrian—Ordovician geology
geology of
of western
western Wisconsin:
Wisconsin:
Wisconsin Geol.
Geol. and
and Nat.
Nat. History
History Survey
Survey Inf.
Inf. Circ.
Circ. 11,
11, 131
131 p.
p.
Potter, P.E.,
P.E., and
Pryor, W.A.,
W.A., 1961,
1961, Dispersal
Dispersal centers
centers of
of Paleozoic
Paleozoic
Potter,
and Pryor,
and
and later clastics of the
the Upper
Upper Mississippi
Mississippi Valley
Valley and
and adjacent
adjacent
areas:
Geol.
Geol. Soc.
Soc. America
America Bull.,
Bull., v.
v. 72,
72, no.
no. 8,
B, p.
p. 1195—1250.
1195-1250.
Skillings,
DN., Jr.,
Skillings, D.N.,
Jr., 1970,
1970, Jackson
Jackson County
County Iron
Iron Co.:
Co.:
Mining Rev.,
Rev., v.
v. 59,
59, no.
no. 24,
24, p.
p. 1,
1, 10—14.
10-14.
Skillings
U.S.
U.S. Geological Survey, 1972,
1972, Iron—formation
Iron-formation in
in Jackson
Jackson County,
County,
Geol. Survey Prof.
Wisconsin: U.S.
U.S. Geol.
Prof. Paper
Paper 800—A,
BOO-A, p.
p. A3.
A3.
Weidman,
Samuel, 1907,
1907, The
The geology
geology of
of north
north central
central Wisconsin:
Wisconsin:
Weidman, Samuel,
Wisconsin Geol.
Geol. and
and Nat.
Nat. History
History Survey
Survey Bull.
Bull. 16,
16, Sci.
Sci. ser.
ser. 4,
4,
697 p.
p.
697
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Institute on Lake Superior Geology
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Institute on Lake Superior Geology: Proceedings, 1973
Description
An account of the resource
Institute on Lake Superior Geology. University of Wisconsin, Madison, Wisconsin. May 3-6, 1973.
Creator
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Institute on Lake Superior Geology
Date
A point or period of time associated with an event in the lifecycle of the resource
1973
Contributor
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J.L. Anderson
C.R. Bentley
Richard Berger
Emmy Booy
Brenton M. Hamil
Ruth J. Sobanski
W.F. Cannon
Roger W. Cooper
G.H. Dury
John. C. Green
E. Wm. Heinrich
A.V. Heyl
Robert A. Jenkins
John S. Klasner
Thomas R. Turner
M.D. Lewan
M.S. Lougheed
J.J. Mancuso
L.G. Megaris Jr
J.L. Anderson
J.R. Myles
D.M. Mickelson
M.G. Mudrey Jr
A.L. Geldon
G. Mursky
G. Schriver
A.R. Venditti
John M. Ohlson
Edward M. Ripley
Donald M. Davidson
D.L. Roder
E.N. Cameron
S.B. Romberger
Klaus J. Schulz
Edward M. Ripley
P.K. Sims
R.J. Stevenson
J.E. Thresher
Jens F. Touborg
Thomas A. Vogel
Nancy Alyanak
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PDF
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English
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https://digitalcollections.lakeheadu.ca/files/original/3ecd85424de1d35eb6f0359af1235823.pdf
916dcba45175acb8a04524d427dc4144
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Text
�18th ANNUAL INSTITUTE ON LAKE SUPERIOR GEOLOGY
MAY 3-6, 1972
MICHIGAN TECHNOLOGICAL UNIVERSITY
HOUGHTON, MICHIGAN
PART I.
TECHNICAL SESSIONS
AGENDA
and
ABSTRACTS
Edited by W. I. Rose, Jr.
�AGENDA
Tuesday May 2, 1972
8:00 a.m.
Field Trip A leaves Michigan Tech Memorial Union
Wednesday May 3, 1972
6:00 p.m.
7:0010:00 p.m.
Field Trip A arrives back in Houghton.
Institute Registration, St. Albert the Great
Student Parish, MTU Campus
Thursday May 4, 1972
7:3010:00 a.m.
8:00-
Registration, Fisher Hall Foyer
12:00 noon
General Session I, 135 Fisher Hall
1:305:00 p.m.
General Session II, 135 Fisher Hall
7:00 p.m.
Banquet and Address, Onigaming Supper Club
Friday May 5, 1972
8:0011:00 a.m.
1:30—
Penokean Session I, 135 Fisher Hall
4:45 p.m.
Penokean Session II,
5:30 p.m.
Departure of
General Session III, 135 Fisher Hall.
Field Trips B and C. from MTU Memorial Union.
Saturday May 6, 1972
8:00 p.m.
Departure of Field Trip D from MTU Memorial Union
6:00 p.m.
Field Trips B, C. and D. arrive back in Houghton.
�7
8-12
Paper No.
GENERAL SESSION
MAY 4, 1972
TECHNICAL SESSIONS
I.
Time
8:15 a.m.
34
8:0.0 a.m.
8:35a.m.
10:40 a.m.
10:20 a.m.
10:00 a.m.
18
10
8
15
9:00 a.m.
11:00 a.m.
17
6
11:20 a.m.
11:40 a.m.
Co-chairmen:
Ehrlich
0.
Lewan
M.
G. Mudrey
W. Weiblen
J. C. Green
K. G. Books
P.
M.
T. A. Vogel
R.
Author(s)
Robert C. Reed and Donald M. Davidson, Jr.
135 Fisher Hall (Building #15, See Map)
AM
Title
Introductory remarks, Announcements
Based on Lithologic Variation
Deposition Model for the Lower Nonsuch Shale
Weathering and Metasomatism of the Presque Isle
Serpentinized Peridotite, Marquette County, Michigan
Break for coffee
Petrologic and Structural Aspects of the Gabbro
Sill on Pigeon Point, Minnesota
Keweenawati Lavasin Minnesota
Peleomagnetic Evidence for the Extent of Lower
Dimroth
W. O'Hara
J. Hinze
Oray
A. Robertson
J. A. Kilburg
E.
N.
W.
E.
W.
Upper Precambrian Ely's Peak Basalts
Petrology, Structure and Correlation of the
Magnetic Reversals and Polar Shifts as Markers
in a Proterozoic Time Scale
The Eastern Terminus of the Lake Superior Syncline
The Labrador Trough — not a Precambrian
Plate Boundary
�II.
GENERAL SESSION
1:30 p.m.
13
4
E.
Brown
Author(s)
Randall J. Weege and Gerald Anderson
Title
B.
Lou gheed
Co-chairmen:
Iron Segregation in Precambrian Iron Formations:
Effects on Sedimentary Compositions
S.
Geologic compilation and Nonferrous Metals
Potential , Precambrian Section, Upper Michigan
M.
w.
w.
J. LeAnderson
M. Lahr
A. Bodwell
J. J. Mancuso
The Newly Compiled Geological Map of the
Precambrian of Upper Michigan
P.
W. Ojakangas
Waupee Volcanics
R. Smith
H. McNutt
Kal 1 iokoski
A. Bodwell
The Geology of the Garlic River Greenstone Belt
R.
D.
R.
P. M. Clifford
Cuddy'
P. M. Clifford
G.
Nature
Effect of a Rigid° Ultrebasic Sill on Deformation
R.
Archean Salic Volcanic Rocks at Kakagi
Lake, NW Ontario - Their Physical and Chemical
J.
Lower Precambrian Metavolcanic-Metasedimentary
Sequence, Rainy River, Northernmost Minnesota
J. L. Berkley
Precambrian Geology of a Greenstone Belt in Oconto
County, Wisconsin, and Chemistry of the
The Geology of the Deer Lake Gabbro-Peridotite
Complex, Itasca County, Minnesota
Formations
Morphology of Magnetite in Precambrian Iron
M.
1:30- 5PM
Paper No.
1:50 p.m.
2
Time
2:10 p.m.
9
12
2:30 p.m.
3:10 p.m.
16
11
3:30 p.m.
2
2:50 p.m.
3:50 p.m.
19
5
4:10 p.m.
4:30 p.m.
In Adjacent Rocks, Kakagi Lake, NW Ontario
�III.
IV.
BANQUET
9:55 •a.m.
27
23
J. Naldrett, University of Toronto
7:00 p.m.
May 4, 1972
Relation of Penokean Polyphase Deformation to
Regional Metamorphism In the Western Marquette
Range, Northern Michigan
The Penokean Orogeny
Title
W.
J.
S.
A. Trent
F. Cannon
S.
S. Goldich
Author(s)
Co-chairmen Carl E. Dutton and Stephen C. Nordeng
Penokean Tectonics in Northern Michigan
V.
G.
G.
W.
B. Morey
L. LaBerge
R. Van Schmms
Kiasner
Three-phase Deformation Associated with the Penokean
Orogeny, East Gogebic Range, Michigan
0. Banks
Coffee and Discussion
Precambrian Rocks in Minnesota
Stratigraphic and Tectonic Framework of Middle
Lineaments and Mylonite Zones in the Precambrian
of Northern Wisconsin
Dickinson Counties, Michigan, Part II
Chronology of Precambrian Rocks of Iron and
Short Break (10-15 minutes)
P1.
8-11 A.M.
Archean Ultramafic Lavas and Their Associated Nickel Suiphide Deposits"
A.
Onigaming Supper Club (U.S. 41 South, Houghton)
ADDRESS
MAY 5, 1972
PENOKEAN SESSION .1
Paper No.
25
Time
8:00 a.m.
24
26
8:50 a.m.
20
8:30 a.m.
9:20 a.m.
10:15 a.m.
28
9:40 a.m.
10:35 a.m.
11:00 a.m.
�V.
____
PENOKEAN SESSION 2 and GENERAL SESSION 3
1:30-5:00 p.m.
Author(s)
J. W. Avery and Robert Seasor
Title
Geochronology of Precambrian Rocks in the
Penokean Fold Belt Subprovince of the Canadian
Shield
Regional Relationships in the Penokean Province
Stratigraphy and Sedimentation of the Espanola
Formations an Early Aphebian (Middle Precambrian)
Carbonate Unit.
Granitic Plutonic Rocks of the Southern Province
of the Canadian Shield
J. T. Mengel
M.
E.
W.
H.
G.
Haddadin.
Booy
R. Van Schmus
B. Stonehouse
M. Young
J. A. Robertson
S. Goldich
J. S. Stuckless
Structured Clay Products Industry, Keweenaw
Peninsula, Michigan
J. Warren
S.
lvii nnesota-Wi sconsi n
E.
G. Winter
Glacial On ft on the Mesabi Iron Range, Minnesota,
Its Characteristics, Origin and Hydrologic
Bedrock Morphology in the Vicinity of Portage
Subsurface Geology of the Duluth Superior Area,
Potential Sources of Raw Materials for the
Lake, Keweenaw Peninsula, Michgan
1.
Minnesota
Ages of Some Precambrian Rocks in East Central
Co-chairmen:
31
Paper No.
1:30 p.m.
29
Time
1:50 p.m.
33
30
2:10 p.m.
2:30 p.m.
32
3
2:50 p.m.
3:20 p.m.
21
14
4:00 p.m.
22
3:40 p.m.
4:20 p.m.
Signi ficance.
p
�Paper
THE GEOLOGY OF THE
DEER LAKE GABBRO—PERIDOTITE COMPLEX
ITASCA COUNTY, MINNESOTA
John L, Berkley
University
of Missouri, Columbia
ABSTRACT
The Deer Lake Gabbro—Peridotite Complex is located in northern
Itasca County, Minnesota, three miles southwest of Big Deer Lake.
It is intruded into a terrane composed of quartzofeldspathic,
tuffaceous metasedimentary rocks and pillowed metabasalts of
Lower Precambrian age (Sims, et. al., 1971). In recent years
the area has been investigated by several mining companies as
a possible source of exploitable nickel deposits.
Detailed mapping has revealed that the complex is composed of
five, separate, sheet—like, basaltic intrusions, averaging
approximately 700 feet in thickness, each, Magma was supplied
to the area in chronologically, widely dispersed episodes, allowing time for earlier intrusions to differentiate and lithify
before the emplacement of a later sheet above those already
present. Observed contacts between any two sills are character—
Ized by chilled dolerite against a thin zone of amphibolite,
The chilled do].erite is thought to represent the parent magma,
while the amphibolite is probably a result of contact metamorphism by the magma, For any given sill within the complex,
a sharp contact separates the chilled dolerite from the layered
sequence above which consists of, from stratigraphic bottom to
top, an augite—hornblende peridotite, diopsidic or augitic
pyroxenite, and gabbros of varying compositions. This layered
series of rocks is a result of selective crystallization and
gravity settling of phases, Typical cumulate—intercumulate
textural relations as described by Jackson (1961) from the
Stllwater Complex of Montana may be seen in rocks from the
peridotite up to and including certain lower gabbro units. Small
scale layering structures may occassionally be observed in pyr—
oxeniteg and lower gabbros. Figure one shows the ideal sequence
of rock types for any particular intrusion within the complex and
gives the expected cumulate and intercuinulate phases for each
unit,
The peridotite is composed of rounded to elongate olivines
surrounded poikalitically by augite, hornblende, or both, Evidence of reaction rims may be seen surrounding some olivine
crystals. The peridotite grades sharply into a pyroxenit.,
usually composed predominately of subhedral to euhedral diopside
1
�Paper
enclosed by plagioclase, diopsidic overgrowth, or oikocrysta
originally of pyroxene composition but now completely altered.
With increasing cumulate plagioclase content, the pyroxenite
grades gradually into an augite gabbro. Upper units may exhibit
a significant quartz content and micrographic intergrowth. Micro—
pegatite veins cut many gabbro exposures and pegmatitic material
has been observed in certain pyroxenite units as well.
Post—intrusive folding in the area has deformed the formerly
horizontal sills into a sequence of tightly folded anticlinee
and sync].ines with axial traces trending N4OE.
The complex
plunges to the southwest at an undetermined magnitude.
Exposure
of the intrusive units is now restricted to a narrow band
six miles long and a maximum of about one and one half miles
wide.
Metamorphic grade does not surpass lower amphibolite
or hornblende hornfels facies in the rocks of the complex with
most assemblages, including those of the adjacent country
rocks, falling into the greenschist fades,
REFERENCES CITED
Jackson, Everett D.,, 1961, Primary textures and mineral
associations in the ultramafic zone of the Stiliwater
Complex Montana, U. S. G, S. Prof. Paper 358, 106 pp.
Sims, P. K., Morey, G. B., Ojakangas, R. W., and Viswanathan, S.,
1971, Geologic Map of Minnesota, Hibbing Sheet: Mimi. Geol,
Survey.
1
�FIGURE I.
-— —
ZONE
CONTACT
.
ZONE
ULTRAMAFC
ZONE
GABBRO
ZONES
—
SINGLE
NONE
I4ORNBLENDE
AUOITE/
PLAGIOCLASE
AUGITE
OLIVINE-
PYROXENE
OIKOCRYSTS
DIOPSIDE
QUARTZ
PYROXENE
OIKOCRYSTS
PLAGIOCLASE
PY ROXENE
AUGITE
QUARTZ
PHASES
CUMULATE
PLAGIOCLASE
N ONE
N ONE
PHASES
CUMULATE INTER
—
INTRUSIVE SHEET. DEER LAKE
AMPHIBOLTE
DOLERITE
PERIDOTITE
PYR OX ENI T E
GABBRO
CUMULATE
LOWER
GABBRO
AUGITE
GABBRO
AUG ITE
BEARING
MEMBERS
QUARTZ
IDEAL STRATIGRAPHIC COLUMN FOR A
COMPLEX, MINNESOTA.
ETAMORPHICFAdES
CONTACT
FACIES
BORDER
SERIES
LAYERED
GENETIC
FACIES
�Paper 2
GEOLOGIC COMPILATION
AND
NONFERROUS METALS POTENTIAL
PRECAMBRIAN SECTION, NORTHERN MICHIGAN
W.
A. Bodwell
Michigan Technological University
ABSTRACT
The geology and nonferrous metal occurences of the PreCambrian section, Northern Michigan, have been compiled
at the scale of 1:250,000. The map incorporates considerable new data which has become available since the previous regional map of 1936.
Review of the regional geology and mineral associations
indicates several geologic environments or conditions
considered to have potential for mineral deposition.
1) The effective coverage of past exploration drilling in the Michigan copper district was assessed. From
this data, it appears that as much as 80 - 85% of presumed favorable ground is yet to be penetrated by drilling according to criteria developed herein:
a) The strata-controlled ore deposit sought
has a minimum strike length of 2000 feet.
b) Maps showing drill holes were reviewed and
all strike segments with 2000 feet or more between drill
holes were outlined. These areas were measured by planimeter and compared to total area of the favorable strata.
c) All strike segments of greater length constitute untested ground.
2) A series of small felsic porphyry intrusives
occurring near the base of Portage Lake lava series appear
to have potential for copper sulfide deposits based on
analogous features with mineralized felsic porphyry bodies
on north limb of the Lake Superior syncline in Ontario.
3) A greenstone belt northwest of Marquette, Michigan
exhibits certain characteristics of mineralized greenstone
belts of the Canadian shield. The presence of numerous
base metal occurrences and one small gold deposit suggest
that significant base metal or precious metal depsoits may
yet be found.
�Paper 3
POTENTIAL SOURCES OF RAW MATERIALS
FOR THE STRUCTURAL CLAY PRODUCTS INDUSTRY
KEWEENAW PENINSULA, MICHIGAN
EMMY BOOY AND MUSA S. HADDADIN
Michigan Technological University
ABSTRACT
The Keweenaw Peninsula of Michigan was explored for potential
sites for the establishment of a structural clay products plant.
The most favorable location for the establishment of such an
industry was in Ontonagon County, in the southwestern portion
of the Peninsula.
The sedimentary cover overlying the Precambrian to possibly
Cambrian bedrock varies rapidly both laterally and vertically
because of the conditions of deposition during the Pleistocene.
In general, the average particle size decreases from North to
South. Otherwise, no consistent variations were observed.
Most sediments having suitable properties for raw materials
for the structural clay products industry have been mapped as
glacial lake sediments.
An attempt was made to identify distinctive flora which might
provide a mapable criterion for distinguishing between sediments
for structural clay products manufacturing and those
unsuitable. Although there is variation in floral assemblage
with topography (e. g. well vs. poorly-drained areas) there was
no distinguishable variation with sediment size.
suitable
Requirements for suitable materials for structural clay products
include good workability, low drying and firing shrinkage, good
dry and fired strengths, and good fired color. Most of the
samples studied met all criteria for most structural clay products.
The mineralogy of the samples did not vary appreciably in
major constituents throughout the area sampled. Illite, expandable vermiculite, and chlorite were the dominant clay minerals.
Quartz and feldspar were ubiquitous, while minor kaolinite,
calcite, and dolomite were present in many samples.
Certain fundamental soil mechanics tests were run on the
materials in conjunction with the ceramiô tests performed.
In general, the samples tested were relatively stable clays
to silty clay soils.
�Paper 3
In the area studied the most desirable location from the view-
points of volume of material available and ease of transportation
to markets would be in the area around Ontonagon. Most of the
samples studied from this area would be useful for all types of
structural clay products.
�Paper 4
IRON SEGREGATION IN PRECAMBRIAN IRON FORMATIONS:
EFFECTS ON SEDIMENTARY COMPOSITIONS
BRUCE E. BROWN
Department of Geological Sciences
Milwaukee, Wisconsin
ABSTRACT
According to Ronov's (1964) estimates, cherty iron
formations of the pre-Cambrian type were present in the
amount of 15% of the total sedimentary rock volume
during the time period around 2 b.y. ago. The segrega-
tion of iron to this degree would seem to require significant shifts in the iron contents of other types of
sediments, particularly shales. A sample mass balance
calculation after the manner of Garrels and Mackenzie
(1971, p. 242) illustrates this. Using a present day
"average igneous rock" (Brotzen, 1966) as a source for
limestone, sandstone, and shale, and considering just
the total iron percent we have, after Garrels and
Mackenzie (1971, p. 242):
Average igneous rock
Fe oxides in gms/kg
62
limestone
shale
sandstone
62
4
if one considers a situation where 15% by weight of the
sediments are of iron formations containing 30% iron
oxides, we must subtract 45 grams of iron oxide to supply
this source, leaving only 17% to go into shales and
sandstones.
The assumption is made that iron normally going into
shales (such as might happen during the weathering of a
basalt today) has been diverted into iron formations.
If this assumption is valid, shales formed during times
when iron formations were a significant portion of the
sedimentary column, should contain less iron than might
otherwise be expected considering possible igneous
sources. Since iron is the heaviest common element
this might have implication regarding the composition,
density and isostatic relationships ofrocks such as
granitic gneiss formed by metamorphism of shale.
�Paper 5
EFFECT OF A "RIGID" ULTRABASIC SILL ON DEFORMATION
IN ADJACENT ROCKS, KAKAGI LAKE, NW. ONTARIO
by R. G. Cuddy, P. M. Clifford
Department of Geology, McMaster University, Hamilton, Ontario
ABSTRACT
The greenstones of Kakagi Lake consist of about 7500 metres
of basic to acid volcanic rock, and some associated sedimentary
rocks. Embedded within this assemblage are "sills" of ultrabasic
material
Study of the western portion of the Kakagi Lake area shows
that the ultrabasic sills have a fold form of class 1-B or 1-C
(cv. Ramsay; 1967 pp. 365 ff.), as revealed by thickness, measurement and isogon plots. Petrographic study of one sill (Ridler,
1966) suggests that very little strain has occurred within the
sill.
The rocks in contact with the sills are with very few exceptions,
acid pyroclastic volcanics. They lack significant primary layering
and, mechanically, form thick, rather homogeneous units. Cleavage
density rises, as does consistency of orientation of cleavage,
in the vicinity, and along axial surface continuationsof tight
folds in the sills. Conversely, open folds in the sills are
adjacent to areas of low cleavage density and locally variable
cleavage orientation. In addition, fragments in the pyroclastic
rocks, though flattened to lie roughly parallel to cleavage, are
poorly oriented within the cleavage, a situation which suggests
rather low strains within the cleavage plane compared to the high
strains across it, or alternatively, a fluctuation of pyroclast
long axes over 1800 in the pre-strain state. Fold axes, few in
number, are everywhere of moderate to steep plunges.
These features are the product of an early phase of deformation. Subsequent deformation has produced kink folds and en
echelon quartz-filled gash arrays. These suggest local orientations
of principal axes of stress or strain, apparently not of regional
value.
It is not clear from our data, or any other data available
whether the granites surrounding these rocks are fully responsible
for the deformation, or have merely modified a prior fold array
whose axial surfaces were aligned east-west. What is clear is the
marked effect of the sills with their low ductility compared to
the pyroclastic rocks in which they occur.
Ramsay, J.
G.
(1967) Folding and Fracturing of Rocks.
Ridler, R.
H.
(1966) M.Sc. thesis (unpublished) Univ. of Toronto.
�Paper 6
THE LABRADOR TROUGH - NOT A PRECAMBRIAN
PLATE BOUNDARY
Erich Dimroth,
Service d'Exploration gologizue,
Mjnistre des Richessea naturelles, Qubec
ABSTRACT
The boundaries between the Precambrian age provinces
are the natural location where to look for Precambrian
plate boundaries. This is specifically so for the .junction between the Superior and Churchill Provices, which
are separated by the Circum-Ungava geosyncline.
Deep erosion has removed the whole of the original
geosynclinal filling in the sector between Labrador
trough and Cape Smith belt, and the relations between
the geosynclinal filling and its basement can be studied.
Other segments of the Labrador trough are deeply enough
eroded to infer the presence of a basement.
At the level of the basement (that is between the
Labrador trough and the Cape Smith belt) the contact
between the Superior of Churchill Provinces appears to
be gradational. The Archean gneisses are continuous
to Ungava bay, but they give Hudsonian K-Ar ages east
of line indicated in Wanless (1969). The Archean gneisses east of the age front appear to have suffered
Hudsonian deformation, as indicated by the folded outline
of the contact between the basement and the Lower Proterozoic sequence. Beau et al. (1963) noted that the
Hudsonian biotite isograd intersects the basement-cover
contact, and retrograde metamorphism has been noted in a
few basement outcrops visited. It appears therefore
that a Hudsonian tectonic, metamorphic and age (K-Ar)
front, intersects a uniformly Archean terrain between
the Cape Smith belt and the Labrador trough.
The northernmost Labrador-trough and the easternmost Cape Smith belt are synclinoria plunging south-southeast and west-northwest. The Lower Proterozoic sequence
of both belts, which includes very voluminous oceanic
tholeiites rests on the basement gneiss with an absolutely sharp contact (Hardy, 1969; Schimann, 1972).
�Paper 6
-2-
In the centre of the Labrador trough a very thick
sequence of oceanic tholeiite rests on continental red
beds and on shallow water sediments (for example
sandstone with coarse current cross-bedding, stromatolitic dolomite). Units of stromatoljtjc dolomite, of
oolitic iron formation and similar shallow-water deposits is continuously exposed across the whole trough,
and, in its east, mantles domes of basement gneiss.
There is not a trace of a sheeted gabbro complex,
and in fact the source of the basalts is still enigmatic.
Only very few and generally thin gabbroic dykes intersect the sedimentary sequence and are the only possible
conduits known at present.
In the extreme east of the Labrador trough a metamorphosed meta-pelitic sequence, comprising interbeds
of orthoquartzite, dolomitic sandstone (now diopsidequartzite), para-aniphibolite, is exposed. Arkoses,
arkosic conglomerates, are present here and there and
perhaps indicate the presence of occasionally emergent source areas east of the trough. According to
Wanless (1970) granitoid gneisses east of the trough
give at one locality a K-Ar age of 2160 m.y., that is
somewhat older than the Rb-Sr age of the Labrador
trough rocks (Fryer, 1971). This seems to confirm
the basement nature of at least some granitoid gneisses east of the trough.
There appears little doubt that the Labrador
trough formed by differential subsidence and that it
is not related to a continental margin existing at
Lower Proterozoic time.
REFER EN C ES
Beall, G. H., Hurley, P.M., Fairbairn, H.W., and
Pinson, W.H., Jr. (1963), Comparison of K-Ar and
Rb-Sr dating in New Quebec and Labrador. Am. J.
Sci., V. 261, p. 511-560.
Fryer, B. J. (1971), Rb-Gr whole rock ages of Proterozoic Strata bordering the eastern part of the Superior Porvince, Canada. Geol. Soc. Amer., Abs with
programs, 3, p. 574-575.
�Paper 6
-3-
Hardy, R.1(1969), Gologic de la re9ion du lac des
Chefs, These de maitrise, non publiee; Ecol
Polytechnique.
Travaux sur le
Department of Natural Resources,
Quebec, Report S-126AF, p. 7-10.
Schimann, K. (1972), Wakeham Bay In:
terrain 1971.
Wanless, R. K. (1969), Isotopic age map of Canada.
Geol. Surv. Canada, Map No. 1259A.
Published with the permission of the Minister of Natural
Resources, Quebec.
�Paper 7
I
DEPOSITIONAL MODEL FOR THE LOWER NONESUCH
SHALE BASED ON LITHOLOGIC VARIATION
Robert Ehrlich and Thomas A. Vogel
Geology Department
Michigan State University
48823
East Lansing, Michigan
ABSTRACT
The White Pine copper deposit is one of the classic strata—bound
Not only is the mineralization restricted to a small lower
portion of the Nonesuch Shale but the vertical succession of lithologies
within the mineralized section is remarkably similar in all parts of
This striking similarity in vertical succession has in the
the mine.
past been used as a basis for assuming wide scale lateral continuity
of subunits within the Lower Nonesuch Shale. This in turn led to models
of deposition, diagenesis, and ore emplacement in which the layercake
The
aspect of the lower Nonesuch stratigraphy played a key role.
purpose of this report is to integrate the observed lithologic variation
into an overall depositional model for the Lower Nonesuch Shale.
deposits.
The lower fifty feet of the Nonesuch is composed of numerous
textural modes such as graded, well—laminated, crudely laminated,
fragmental, blebby, massive, etc. Various combinations of these textural
elements can be found in varying proportions in each of the formal
stratigraphic units and each of these (Domino, Brown Massive, etc.)
have extensive lateral continuity whereas the individual textural elements
included within each unit are not persistent. These lateral changes
arise in three principal ways: (1) abrupt changes apparently resulting
gradual and
(2)
from slumping and sliding of plastic sediments, and
continuous changes in lithology within a major stratigraphic unit such
as massive units becoming crudely laminated and then graded. Similar
lateral variations can be seen with major elements within one formal
stratigraphic unit varying laterally into a lithology which is a characteristic of an adjacent stratigraphic unit above or below.
Most of the textural elements can be seen in varying proportions in
the massive units. When observed in detail, it can be seen that there is
a non—random juxtaposition of the elements; that is, certain elements
tend to be adjacent to certain others. Figure 1 shows the most probable
�Paper 7
PAGE
2
associations between textural elements. Elements adjacent in the
diagram tend to be intimately associated with each other on a hand
sample scale. Elements far apart on the diagram are rarely seen
juxtaposed.
Figure 1
Mutual Occurrence of Textural Elements in Massive Units
Textural elements relatively closer on diagram occur
together more often.
,Massive ————
Crudely Laminated ———— Graded ———— Laminated
Fragmental'
"Blebby ———— Crudely Laminated
In these massive units the textural elements on the left side
diagram (e.g., fragmental, massive, blebby) are more abundant than
on the right. Because each of these elements, except those on the
extremes, is associated with two others, these inter—relationships
the basis for the pattern of vertical and lateral variation within
massive units.
of the
those
are
the
A characteristic vertical succession is from bottom to top; massive,
crudely—laminated, fragmental, scoured surface, massive, blebby, crudely—
laminated, graded, well—laminated. A section such as this is composed of
two depositional units, each beginning with a massive textural variety
Within each
and terminated by a fragmental or laminated variety.
depositional unit there are no sharp boundaries as one proceeds from one
textural element to another, indicating that the sequence of textural
elements arose from a single genetic event.
The textural varieties and lateral and vertical relations observed
are consistent with a depositional model involving progressive infilling
of a depositional basin with coarse, denser materials being deposited
over materials of low specific gravity that are mechanically weak. The
pattern seen here can be understood if the effects of lateral migration
and loci of sedimentation are considered as well as general infilling in
the basinward direction.
In general terms, the dynamic model consists of coarse—grained
material deposited on muds, triggering its accompanying flow components.
In the Nonesuch two modes of deposition and transport were involved in
most slumps.
The uppermost, least consolidated materia],, generally
(1)
hematite—rich, moved rapidly, partially as suspended material, partially
as bonafide turbidity flow, and fanned out into a roughly lobate deposit.
�Paper 7
PAGE 3
(2)
The slightly more consolidated material underlying this zone, in
a more reduced condition, either flowed plastically, more slowly, down
the depositional slope with relatively little rotation or, if it was
reasonably coherent, behaved as a rotational slump with a well—developed
concave upward slip surface.
Sediment that has moved further downslope is more laminar and less
rotational in nature. This, coupled with longer time involved in transport, allows the previously homogenized sediment to differentiate itself
with respect to grain size. The sequence, updip to downdip, is thickest,
but of least lateral extent at the updip end, and thinnest (perhaps only
one graded bed thick) but most laterally extensive at its downdip
extremity where it fans out in an unrestricted fashion.
This process model can explain the three dimensional pattern of
rock variation and provides an important framework for a discussion of
the origin of the other geochemical and petrological variations in the
Lower Nonesuch Shale.
�Paper 8
PALEOMAGNETIC EVIDENCE FOR THE EXTENT OF LOWER
KEWEENAWAN LAVAS IN MINNESOTA
by
John C. Green
Geology Department
University of Minnesota, Duluth
and
Minnesota Geological Survey
Kenneth G. Books
U. S. Geological Survey
Silver Spring, Maryland
ABSTRACT
Most of the North Shore Volcanic Group of Gehman (1958), from central
Duluth northeastward to the diabase complex at Hovland (Fig. 1), is now known
to be middle Keweenawan on the basis of its normal magnetic polarity (Books,
1968; Palmer, 1970; new data). Beneath (north of) the Hovland diabase and
the southern prong of the Duluth Gabbro Complex in Cook County is a series of
lavas, approximately 8,000—10,000 feet thick (the Hoviand and Grand Portage
lavas of Green 1971) that were extruded during an earlier period of reversed
polarity, and are therefore lower Keweenawan. These two units can be traced
for at least 25 and probably 50 miles westward, where they are intruded by
the Duluth Gabbro Complex.
The Hovland lavas include many porphyritic basalts
with platy plagioclase phenocrysts.
These two lava units thus correlate with
the lithically similar reversed "Traps of the South Range" in the Ironwood
area, Michigan—Wisconsin, (Books, 1968) and with the Osler Series of Ontario
(Palmer, 1970).
The Grand Portage lavas are cut by a dike swarm of basalt
and porphyritic basalt that also show reversed polarity and may have been
feeders for the porphyritic Hovland lavas.
The Grand Portage lavas rest disconformably on the Puckwunge Formation
of Schwartz, 1942, an orthoquartzite that overlies the middle Precambrian
Rove Slate. Although the samples showed only weak magnetization, new
determinations give an unequivocal reversed polarity for the Puckwunge, and
support its correlation with the lithically similar Sibley Series sandstones
of the Thunder Bay district, Ontario. At the southwest end of the basin also,
the Duluth Gabbro Complex intruded between lavas of normal and reversed
polarity, i.e. between middle and lower Keweenawan volcanic rocks.
New
determinations show that most or all of the basalts at Ely's Peak (the wedge
of lavas that underlie the Duluth Gabbro Complex west of Duluth) have reversed
polarity, and thus correlate with the flows at Ironwood and Grand Portage.
The basal pyroxene—porphyritic lavas in this unit bear a very close resemblance
to the basal lavas on Lucille and Magnet Islands east of Grand Portage, further
supporting this correlation; such lavas are not known from anywhere else in
the North Shore Volcanic Group.
Samples from the conformably underlying "Nopeining sandstone" and from
the lowest flow at the "Grandview Golf Course" locality show weak magnetization and considerable scatter, but normal polarity. What is believed to be
the same flow (certainly part of the same unique pyroxene—basalt flow group)
3/4 mile to the south shows reversed polarity. Although these normally polarized
samples were taken at least 500 to 800 feet (structural distance) from the base
of the Duluth Gabbro Complex and are not visibly recrystallized, even in thin
section, it appears likely that the basalt's polarity has been inverted to
�Paper 8
normal during contact metamorphism by the Duluth Gabbro Complex.
No conclusions can yet be made regarding the original polarity of the sandstone;
it may have been normal, thus correlating with the Bessemer Quartzite of
Seaman, 1944, beneath the lowest Keweenawart flows at Ironwood, or it may
also have been changed from an original reversed state, thus correlating
with the Puckwunge and Sibley. Further investigations will be carried
out.
References
Books, K. G., 1968, Magnetization of the lowermost Keweenawan lava flows
in the Lake Superior area: U. S. Geol. Survey Prof. Paper 600—D,
p. D248—D254.
Gehman, H. M.,, Jr., 1958, The petrology of the Beaver Bay Complex
[Minn.J [abs.], in Institute on Lake Superior Geology, Apr. 21—22,
1958: Minneapolis, Univ. Minn. Center Continuation Study [19581, p. 1.
Green, J. C., 1971, Stratigraphy of the North Shore Volcanic Group northeast
of Silver Bay, Minn. [Summary]: Inst. on Lake Superior Geology, May 5—8,
1971: Duluth, Univ. of Minn., Duluth, 1971, p. 20—22.
Palmer, H. C., 1970, Paleomagnetism and correlation of some middle Keweenawan
rocks, Lake Superior: Can. Jour. Earth Sd., v. 7, No. 6, p. 1410—1436.
Schwartz, G. M., 1942, Correlation and imetamorphism of the Thomson Formation,
Minnesota: Geol. Soc. America Bull., v. 53, no. 7, p. 1001—1020.
Seaman, W. A., 1944, Summary of the geology of the Marquette iron range [Mich.]:
Michigan Geol. Survey Prog. Rept. 10, p. 11—17.
�a
II
ntrusjve rocks
a
L owes
af
Keene.wen teuas
tt44t Kewn.n u&s
ktween&u,an
Kilo", ee's
S
)s
_______
�Paper 9
THE NEWLY COMPILED GEOLOGICAL MAP OF THE PRECAMBRIAN
OF THE UPPER PENINSULA OF MICHIGAN
J. Kalliokoski and W. Bodwell
Department of Geology and Geological Engineering
Michigan Technological University
Houghton, Michigan
With the retirement of the older staff, the Department of Geology and Geological
Engineering found itself in a position of requiring a mechanism whereby it could
refamiliarize itself with the Precambrian geology of the Upper Peninsula, in
order to identify good field-thesis problems and to become knowledgeable about
the mineral potential of the region. The most direct approach seemed to be in
compiling all geological data on the most suitable scale.
With the help of the Institute of Mineral Research (M. T. U.) and the full cooperation of the Michigan Geological Survey, the U. S. Geological Survey, various
mining companies, and land owners, this task has now been completed. The
resulting map, "Precambrian Geology of the Upper Peninsula" (M. T. U. Press,
Geological Series, Map 2, 1972) is on a scale of 1:250, 000. A second map
"Geology of the Marquette-L'Anse Region, Michigan", (M. T. U. Press,
Geological Series, Map 1, 1972) shows the available outcrop data for the
"Northern Complex" on a scale of 1:62, 500. Both maps, uncolored, show the
location of known base metal and precious metal showings.
The 1:250, 000 map (released April, 1972) is priced at $3. 00 and the 1:62, 500
map (released in late August, 1972) is $5. 00, both including postage, prepaid.
They are available from the Department of Geology and Geological Engineering,
Michigan Technological University, 49931.
Although the maps are complete in themselves, they represent part of the
documentation for an M. S. thesis by W. Bodwell, entitled "Geologic
Compilation and Non-ferrous Potential, Precambrian Section, Northern
Michigan". Copies of the thesis may be obtained from the Department for
the cost of reproduction.
�Paper 10
PETROLOGY, STRUCTURE, AND CORRELATION OF THE
UPPER PRECAMBRIAN ELY'S PEAK BASALTS
JAMES A. KILBURG
University
of Minnesota, Duluth
ABS TRACT
The Upper Precambrian Ely's Peak basalts crop out in a north—south
trending, wedge shaped belt in the area around Nopeming, southwest of
Duluth, Minnesota.
These Lower Keweenawan flows overlie the basal Upper
Precambrian quartzite in the southwestern portion of the Lake Superior
basin.
There are about 18 individual flows totaling some 1,200 feet of
thickness, the thickest flow being 125 feet thick while the thinnest is
less than 10 feet thick. Many of the flows show lateral continuity, for
example, one flow is traceable for about three miles along strike.
Petrographically, there are three main types of flows.
Five of the
first six that form the basal portion are dark gray, porphyritic basalts.
Of these, four contain euhedral, zoned, single and glomerophorphyritic
augite phenocrysts up to 5 mm in diameter. Some ilmenite phenocrysts and
some olivine pseudomorphs are also present. The groundmass contains altered plagioclase, magnetite, augite, actinolite, chlorite, and sphene.
The sixth flow up from the base is a dark gray, porphyritic basalt with
single and glomeroporphyritic plagioclase phenocrysts up to 7 mm in diameter; there are also occasional augite phenocrysts.
The groundmass
contains altered plagioclase, augite, actinolite, ilmenite, sphene, epi—
dote and chlorite. The third type of flow is a dark gray, commonly ophitic,
altered basalt.
It consists of plagioclase, occasional olivine pseudo—
morphs, actinolite after augite, augite, ilmenite, magnetite, epidote,
sphene, and chlorite.
Structures within the flowsinclude ropy surfaces, vesicular and
amygdaloidal tops, straight and bent pipe vesicles, straight cylinder
vesicles, columnar joints, and pillows in the basal flow.
Several northeast trending basalt dikes cut the flows and have been deeply eroded
leaving pronounced lineaments.
The whole sequence has undergone regional hydrothermal metamorphism
to the high zeolite—low greenschist fades. Minerals present which demonstrate this are actinolite, chlorite, and epidote.
The only zeolite
present is wairakite which has been discovered probably for the first
time in the Lake Superior region.
It is the highest temperature zeolite.
Intrusion of the Duluth Complex is thought to be responsible for elevating the geothermal gradient and thus, permitting the formation of
wairakite. The gabbro intrusion also contact metamorphosed the lavas
to a medium grained pyroxene hornfels for a distance of up to one—fifth
of a mile from the contact.
�Paper 10
Pressures of metamorphism are thought to have been around 2,000
bars, although a range of pressures between 1,500—2,500 bars seems
feasible.
This pressure was produced by the weight of up to 30,000
feet of overlying Upper Precambrian lavas and Duluth Complex which
underlie the North Shore of Lake Superior; however, as little as about
16,000 feet of overburden could have produced the minimum pressures of
about 1,500 bars needed for metamorphism.
Based on their distinctive petrology and reversed magnetic polarity
(Green and Books, 1972), the Ely's Peak basalts appear to correlate with
the basal flows at Grand Portage, Minnesota. This implies that the time
of deposition at these localities was approximately the same, and the
source area from which these lavas were derived was probably the same.
�Paper 11
PRECAMBRIAN GEOLOGY OF A GREENSTONE BELT IN OCONTO COUNTY,
WISCONSIN, AND CHEMISTRY OF THE WAUPEE VOLCANICS.
Melvin M. Lahr
University of Wisconsin, Madison, Wisconsin
ABSTRACT
Detailed mapping has been carried out in the northern
half of the Mountain Quadrangle in order to establish the
geologic history and evolution of a Precambrian greenstone
belt and to determine the nature of volcanism. The sequence
of Precambrian events was the following (oldest to youngest):
1. Deposition of the Waupee formation, including flows,
agglomerates, tuffs, volcaniclastic sediments, and
sandstones.
2.
Emplacement of the Macauley intrusive (granodiorite
to quartz monzonite).
3.
4.
5.
Deformation and regional metamorphism.
Deposition of the Baldwin conglomerate.
Intrusion of the Hager granite and contact metemorphism of the older rocks.
The Waupee formation trends approximately N450E and has
a steep dip. Relic graded bedding and cross-stratification
indicate that tops of beds are to the northwest. Three
lithologic units have been distinguished in the Waupee formation: a basal member consisting of massive flows, volcaniclastic sediments, and minor agglomerates; a middle sandstone member with a subordinate amount of massive flows; an
upper thin-bedded tuff member. Pyrrhotite mineralization is
concentrated along the boundary between the basal and middle
members of the formation.
Sedimentary features and volcanic textures have been
preserved in the Waupee formation, but recrystallization
under conditions of the amphibolite facies has produced the
following mineral assemblages:
basic volcanic flows: plagioclase-hornblende-clinopyroxene.
p1 agi ocl ase-hornbl ende-cummi ngtoni te.
quartz-biotite-hornblende-plagioclase+
sedimentary rocks:
epidote.
quartz -microcline-biotite-mu scovite+
p1 agiocl ase.
Contact metamorphism due to intrusion of the Hager granite has been superimposed on the regional metamorphic
assemblages, resulting in the appearance of garnet, vesuvianite,
scapolite, clinopyroxene, hornblende, and plagioclase in the
metavolcanic rocks. In the aluminous metasedimentary rocks the
assemblage quartz-plagioclase-alkali feldspar-muscovitebiotite-andalusite+ sillimanite has developed.
�Paper 11
Eighteen samples of massive volcanic flows from the
Waupee formation were fused and analyzed for nine elements
(Si, Al, Ti, Fe, Mn, Mg, Ca, Na, K) by means of an electron microprobe. The majority of samples are basalts
(Sio2, 46 to 51%) containing 15 to 20% A1203 and 2.0 to
5.8% Na20 + K20; a few samples are andesiEic, containing
up to 6T% Si02.
If the chemical compositions of the massive flow
rocks have not been modified during regional metamorphism,
then the Waupee volcanics can be classified as high-alumina
and alkalic basalts. As yet, no tholeiitic basalts have
been recognized in this area.
The chemistry of the metavolcanic rocks and the nature
of associated metasedimentary rocks suggest that the
Waupee formation originated in an island ac environment.
�Page 12
THE GEOLOGY
OF THE GARLIC RIVER GREENSTONE BELT
P.
James LeAnderson
Queen's University, Kingston, Ontario
ABSTRACT
The Garlic River Greenstone Belt is the Archaen greenstone belt
northwest of Marquette, Michigan.
It consists of a series of basalt flows,
tuffs, greywackes, arkoses and iron formations formerly referred to as the
"greenstone" or as Mona Schist. The belt is twenty miles wide along the
southern boundary, at the contact with the Marquette Synclinorium, and
extends ten miles to the north (See Fig. 1).
Discernable tectonic history indicates gentle folding of the flows
and sediments, followed by intrusion of quartz monzonite pegmatites, large
diabase dikes and finally granodiorite pegmatites.. The flows and sediments
were metamorphosed to chlorite schists and amphibolites.
The chlorite and
chloritic amphibole schists may represent greywackes and/or reworked or
waterlain tuffs. The amphibolites are thin bedded or massive; some of the
latter have pillows or relict plagioclase laths, indicating a volcanic origin.
Felsic volcanics are uncommon, but form a zone of sheared rhyolitic
at the east end of the Dead River Basin. Small extrusive bodies of
porphyritic dacite are found throughout the chlorite and amphibole schists.
tuffs (?)
The Arkoses (Gar) occur commonly as thin units in the chlorite and
amphibole schists, but are the dominant rock type in two areas near the
northwestern boundary of the belt.
Iron formation (IF) consists of thin discontinuous lenses of
Neither carbonate nor sulfide facies iron formation
ntagnetite in arkoses.
were found.
Two synclines have been mapped trending northwest—southeast and
plunging southeast, one in the northwest corner of the belt and the other
some six miles to the south in the central part. Additional detailed
mapping may reveal other folds.
Two large downfaulted basins with lower (Ar) and middle and upper
(Amu) Animikie Sediments, partially covered with thick deposits of Pleistocene
sand, truncate the northern and western boundaries of the belt.
A third smaller
basin occupies the center of the belt.
In the northern part of the area two ages of felsic intrusives can
be distinguished, but this distinction cannot be made southeast of the Dead
River Basin. The younger intrusives are predominantly quartz monzonites, and
are cut by the second set of intrusives which are weakly metamorphosed, non—
porphyritic granodioritea. The felsic intrusives in the southern part are
porphyritic granodiorite pegmatites.
Diabase dikes consisting of unoxiented subhedral hornblende and
plagioclase crystals trend east—west across the regional foliation but are
not folded. They appear to belong to one set, intermediate in age between
the quartz monzonite and the granodiorite.
�2
Paper 12
TFie uniformity of mineral composition of the greenstones and the
ubiquitous and commonly complete alteration to chlorite and sericite, makes
However, the trend, from
determination of the metamorphic grade difficult.
predominantly pale green amphiboles to dark blue—green amphiboles, from the
center to the margins of the belt, indicates that the metamorphic grade
increases in the same direction from the greenschist to the amphibolite facies.
Although stratigraphic and time relationships in the belt are unknown
the following generalizations can be made, 1) the sediments, tuffs and lavas
were deposited in shallow water, possibly subaerially, as indicated by the
pillow lavas and oxide facies iron formations, 2) the series of thick and
extensive metabasalts, tuffs, greywackes and rhyolites south of the Dead
River Basin indicate continuous and voluminous outpourings of lava and
pyroclastics, and 3) the thin discontinuous layers of basalt, greywackes,
tuffs, dacites, arkoses and iron formations to the north, suggest local
eruptions of short duration with frequent erosional breaks.
After folding of the greenstones, magma intruded and assimilated
the lower units, leading in turn to first stages of development of the
The magma spread further into the greenstone and
lit—par—lit gneisses (Gu),
formed pegmatite dikes and sills in the nose of the northwestern syncline.
This was followed by the intrusion of a series of diabase dikes; at this time
the metamorphic grade reached it's peak.
The area was then covered by Animikie sediments which were folded
by the Penokean Event, when the structural basins were formed. The intrusion
of Keweenawan dikes, followed by deposition of the Jacobaville sandstone in
late Precambrian or early Cambrian times, closed the geological record, with
the exception of that attributed to the Pleistocene glaciation.
�GENERALIZED
GEOLOGIC MAP
OF
THE
GARLIC
RIVER
GREENSTONE
BELT AND
of Michigan.
PCg
Lower Precambrian Garlic
River Greenstone Belt
Oneiss
Complex
Pgn, Lower Precambrian
where approximately located
where approximately
northern peninsula
Dotted
Shoet dashed
located
complex in the
Location map of the Lower Precambrian
Garlic River Greenslone Belt and the
Gneisx
Geologic contacts
Faults
VICINITY*
�Paper 12
COLUMN'
GEOLOGIC
GENERALIZED
C
.00
a
NE
Sandstone
Jacobsviile
2
a--I
unconformity
Dikes
Diabase
Keweenowan
Middle
and
tAmu)
Upper
0
Lower
and
N
(A)
Animikie
(Aim)
Middle
2
Reony
Lower
0
Creek (Ar)
Formation
—
Serpentinized
Peridotites
2
2
Granodiorites
Intrusive contact
Metadiabase Dikes
Intrusive contact
Quartz Monzonites
Intrusive contact
Gu
Gar
— IF
Z
Garlic
River
3
Greenstones
Gri
GIpa
GI
Gm
(G)
U
Gneiss
and
Intrusive
Complex
(Gn)
�Paper 12
Based in part on maps by Case, J.E. and Gair, J..
(i5), Gair,
J.E. and Thayden, R.E. (1968), Puffett,
w.P. (1969) and LeAnderson, P.J. (1969).
1Units with symbols are included on the map with
Units without symbols
descriptions in the text.
are not included on the map due to the scale
involved.
2The age is uncertain.
They may be post—Anamikie
and pre—Keweenewan.
3The stratigraphic succession of the units of the
Garlic River Greenstone is indeterminate.
BI BLIOG.APHY
Case, J.1. and Gair, J.E., 1965, "Aeromagnetic Map of
parts of Marquette, Dickenson, Baraga, Alger, and
Schoolcraft Counties, Michigan, and its Geo1o'ic
Interpretationt', U.S. Geological Survey Geophysical
mv. Map GP—467
Gair, J.E. and Thayden, R.E., 1968, "Geology of the
Marquette and Sands Quadrangles, Marquette County,
Michian", U.S. Geological Survey Professional
Paper397
LeAnderson, P.J., 1969, "The Pre—Animikie Greenstone
Complex of a small area in Narquete County, "ichignn",
Unpub]Jsed Msc. Thesis, Michian State University
Puffett, W.P., 1969, "The Reany Creek Formation,
Marquette County, Michigan", U.S. Geologicl Survey
Bull. 1274—F
�Paper 13
MORPHOLOGY OF MAGNETITE
IN PRECAMBRIAN IRON FORMATIONS
M. S. LOUGHEED and J. 1. MANCTJSO
Bowling Green University, Bowling Green, Ohio
ABSTRACT
The morphology of magnetite in all metamorphic fades
of unoxidized Precambrian iron formations in the
Lake Superior region is remarkably similar. Particularly noticeable are discrete symmetrical or distorted
octahedral crystals of magnetite disseminated within
individual lamina of chert. Several other features
are noteworthy:
1) the crystal diameters range from
sub—micron to over fifty microns; 2) the concentration
of crystals in a particular lamina can range from a
fraction of a percent to aggregates constituting the
entire lamina; 3) the invariant associate of magnetite
is chert; 4) the variant associates are iron carbonate
and/or iron silicate minerals; 5) the minor but not
uncommon associates are minute hematite crystals as
disseminated spherical clusters, and pyrite as fram—
boids, octahedra, and crystal aggregates generally
within laminations of digital stromatolites or in
laminations of mat algae.
The morphology of magnetite, its variation in grain
size, and its relationship to chert (quartz) siderite,
iron silicate minerals, pyrite and/or hematite indicate
that it is primary and that no chemical interreactions
took place during diagenesis or metamorphism even to
extremely high grades.
�Paper 14
SUBSURFACE GEOLOGY OF THE DULUTH-SUPERIOR AREA,
MINNESOTA-WISCONSIN
J. T. MENGEL, JR.
University of Wisconsin, Superior
ABSTRACT
Study of about 300 borehole records for the Wisconsin Geological Survey
indicates that the Quaternary succession in the western end of the
Superior lowland consists of glacial, lake, and river deposits which
record stages in the development of Lake Superior which are not presently
evident in the high-level shore deposits around the rim of the basin to
the west or in deeper water lake deposits to the east. Preliminary
interpretation of the sequence suggests two times of deep water red clay
accumulation separated by a low water stage during which sands and gravels
were laid down across an unconformity. A prominent boulder bed overlies
the youngest red clay deposit, suggesting a late pulse of ice development
during about Nippissing time.
The Duluth Complex forms the north wall of the lowland in the Twin Ports
area and is found in borings along St. Louis and Superior Bays, where wells
encounter the same lithologies known from surface exposures. Fluvial red
clastics - mainly quartzose sandstones with limited amounts of conglomerate
and shale - of the Bayfield group are unconformable on the Complex and
subcrop beneath most of the plain. Throughout the subcrop the Bayfield
Group is identified as a "sandstone" or "brownstone" and an aquifer.
Similar red clastics underlie most of the western end of the Superior Basin
and are the principal source from which the Ouaternary sediments were
derived. Along the base of the South Range the red clastics are cut off
by the Douglas Fault which brings the Keweenawan basalt sequence of the St.
Croix Horst upward and northward over the sandstones. Basalts crop out
locally along the crest of the South Range and subcrop beneath the
Quaternary succession southward to the Lake Duluth beaches (elevation
about 1070) and beyond.
The most notable feature about the configuration of the erosion surface on
which the Quaternary succession lies is the buried western extension of the
major depression along the northerly shore of Lake Superior (cf. Farrand,
1969).
Twenty-five to 50 feet of local relief is present on the bedrock
One local high forms a prominent outcrop along the
bay front at the foot of 27th Avenue West in Duluth and a belt of subsurface
surface everywhere.
bedrock highs are known in the northern half of 48N-13W, extending westward
into the center of 48N-14W in Wisconsin.
�Paper 14
2
A maximum thickness of about 600 feet of sediments are present along the
axis of the north shore depression between Fond du Lac and Superior Bay
and 100 to 300 feet are present under the plain as far south as the crest
of the South Range. Less than a hundred feet of glacial drift overlain by
clays and/or sands is present along the crest of the South Range.
Glacial drift everywhere overlies the bedrock of the plain. Typically
about 25 feet is present except toward the bottom of the north shore
depression, where as much as 200 feet is known. The drift ranges from a
silty or sandy clay to an argillaceous sand and generally contains gravel
and erratic boulders. Clean sand/gravel lenses are presently locally
most commonly at or near the base of the drift, and are an important
source of ground water when encountered.
Lake deposited stiff red clay overlies the drift and is more or less
gradational with it. Along the northerly side of the St. Louis River in
West Duluth, and beneath the plain to the south of Superior almost the
entire Ouaternary succession is medium to stiff red brown clay containing
scattered ice rafted pebbles and cobbles. Silty, sandy/gravelly layers,
some of which contain small amounts of water are encountered in the clays,
most comonly at depths of about 20 to 50 feet below the general level of
the plain. At higher elevations i.e., about 900-1000 feet the clays are
gradational with sandy materials representing shore reworking of the
underlying drift and materials introduced by small tributary streams.
Locally the sandy materials extend to lower elevations-lying on top of the
clay sequence.
Along the St. Louis River the clays are largely replaced in the stratigraphic
succession by brown, poorly permeable dense argillaceous silty to sandy
deposits which become coarser and cleaner and may contain gravels toward the
top of the sequence. These deposits, which reach a maximum thickness of
about 200 feet lie on a stiff red clay unit, which in turn rests on glacial
drift deposited in the north shore depression. Deep engineering bore
control is not adequate to define lateral relationships with the middle part
of the clay sequence. It presently appears that there is little or no
interbedding of sand and clay either in West Duluth or in Superior, suggesting
the possibility of introduction of the sandy materials by ice or in part by
turbidity flow or river deposition along the general trend of the north shore
depression.
The coarseness of the upper part of the sandy sequence, its considerable
degrees of sorting, and prominent cross bedding indicate the existence of
high energy conditions at the Lakehead prior to deposition of the 15 to 50
foot thick red clay which overlies the sandy unit, forming the surface of the
Superior plain. The uppermost clay layer lies on an undulating surface
having up to a few tens of feet of relief. Contours on the base of the clay
define the north shore depression and indicate slopes toward the depression
and toward Lake Superior. The clay dips beneath present water level in
Howards Bay and is known beneath the younger sands and gravels of Connors
Point and the outer end of Rice's Point.
Both of these points are built along
�Paper 14
3
the erosional zero edge of the clay as it subcrops under St. Louis Bay,
suggesting that this fact may have influenced their construction. The
same red clay subcrops beneath the outer end of Minnesota Point and
under Wisconsin Point. This uppermost clay rests on a thin sandy or
gravelly unit which overlies the main clay sequence in West Duluth and
Morgan Park and conditions are similar in Superior. Prominent develop-
ment of clays to elevations of about 700 feet on the Duluth hillside
may indicate flooding of the plain to this level during development of
the clay layer.
A later very low water stage, perhaps Ferrand's (1969) Houghton Stage,
allowed deep incision of drainage along the north shore depression,
exposing the sandy sequence and initiating the present drainage system.
A general rise in lake level toward a maximum of about 610 feet during the
Nippissing Stage caused the deeper parts of the drainage to become aggraded
with sandy materials and subjected the upper red clays to strong wave
attack. The rise of the uppermost clay away from the north shore depression
made it particularly subject to wave erosion, causing steep bluffs from the
central part of the Superior Bay waterfront eastward to the present shore
line of the lake. A prominent clay platform was developed offshore from
the bluffs. This platform is the floor on which Minnesota and Wisconsin
Point are built. It is presently blanketed by twenty to at least 70 feet
of clean fine to coarse sand containing small amounts of gravel. A greater
thickness of such sandy deposits may lie below present control depth under
the central part of Rice's Point and the northerly third of Minnesota Point.
A great number of large crystalline rock boulders occur at or near the base
of these young sandy deposits under Superior Bay.
Maximum boulder size
recorded so far is 5 x 6 x 7 feet for one recovered during construction of
the Cloquet water line. Large boulders are known throughout the length of
the Superior Front Channel and the open lake shore to the southeast,
their number, size and wide distribution, together with the existence of
a higher lake level more or less following their deposition may suggest
a late pulse of ice development. An alternative view is that they are
developed by exposure of the top of the sandy unit beneath the upper red
clay. This unit is known to contain boulders locally, as in the vicinity
of the local bedrock high at the foot of 27th Avenue West in Duluth.
However, the fact that boulders lying on a few feet of sand overlie the
top of the young red clay under Connors Point suggest that ice transport
may be involved. It is quite possible that some of the sand present on
south shore beaches comes from exposure of the underlying sands. Much of
the modern south shore sand is derived from reworking of the underlying
till which is exposed along several drainages as the bedrock surface rises
to the east of the Twin Ports.
A period of declining lake levels during
which water levels dropped from about 610 to perhaps 590 feet, witnessed
the sequential development of the lake-head barriers of Grassy Point,
Rice's—Connors Points, and Minnesota-Wisconsin Points (cf. Loy, 1963).
All are built primarily from materials derived by the erosion of the
sandy sequence of the north shore depression by the St. Louis River and by
lake activity during the high waters of the Nippissing stage.
The eventual
decline in water level during the subsequent Algoma stage was low enough
�Paper 14
4
to permit development of spruce woods rooted in the sands of what is now
Allouez Bay.
Later flooding, which is apparently continuing at present (cf. Moore,
1948), has led to development of organic-rich mucks, locally capped by
peats as the main sediments above the most recent harbor sands. The
upper parts of the organic deposits often contain sawdust, wood fragments
and horse manure, a legacy of late 19th century activities in the harbor.
Slag, wood derivatives, etc. of more recent origin are also present.
Dredging for harbor development and slip construction have largely altered
the natural stratigraphic sequence of the young sands and organic materials
but the natural bottom contours, sediment types, and shore features can
still be studied on the excellent 1861 chart directed by Captain G. C.
Meade for the Army Corps of Engineers.
REFERENCES
Farrand, W. R., 1969, The Quaternary history of Lake Superior:
Proc. 12th Ann. Conf. Great Lakes Res., International Assoc.
Great Lakes Res., p. 181-197.
Loy, W. G., 1963, The evolution of bay-head bars in western Lake
Superior: Pub. No. 10, Great Lakes Res. Dir., Univ. Michigan,
Ann Arbor.
Moore, Sherman, 1948, Crustal movements in the Great Lakes area:
Bull. Geol. Soc. Amer., 59, pp. 697-710.
�Paper 15
PETROLOGIC AND STRUCTURAL ASPECTS OF THE GABBRO SILL ON
PIGEON POINT, MINNESOTA
M. G. Mudrey, Jr. and P. W. Weiblen
Minnesota Geological Survey
and University of Minnesota, Minneapolis
Detailed mapping on Pigeon Point, Cook county, Minnesota,
discloses petrologic and structural complexities heretofore
not reported.
The sill on Pigeon Point ranges in composition
from a tholeiltic olivine gabbro to ilmenite gabbro, to quartz
gabbro, and to potassium feldspar-bearing gabbro. The red
granitoid rock above the sill is intrusive in the upper parts
of the gabbro, but the origin of these red rocks by differentiation of the gabbro or fusion of the Rove sedimentary rocks
is not clear.
Analyses of coexisting phases in the gabbrô indicate iron—
enrichment during the differentiation history of the sill.
Analysis of phases also sets limits on petrogenetic relations
to the Logan Intrusive Rocks, and to the Pigeon River Intru—
sions of Geul.
The Pigeon River Intrusions appear to have a
simple direct relation; however the Logan Intrusive Rocks of
Geul cannot be directly related by simple fractional crystallization to the sill on Pigeon Point.
Since emplacement and cooling of the sill, faulting and
fracturing on northwest and east-west trends has occurred.
The northwest faulting is marked by barite—calcite veins, and
the east—west direction by late olivine diabase dikes.
�Paper 16
Lower Precambrian metavolcanic—metasedimentary
seguence, Rainy River, northernmost Minnesota
Richard W. Ojakangas
University of Minnesota, Duluth
ABSTRACT
A thick metavolcanic—metasedimentary sequence is exposed in northernmost Minnesota, south of the Rainy River and about midway between
International Falls and Baudette.
The previously undescribed volcanic
rocks range In composition from basalt to rhyodacite.
Intermediate—felsic
tuffs and agglomerates and dacitic flows and hypabyssal intrusions apparently are the dominant rock types.
These rocks are intermittently exposed along the edges of two younger
200—400 ft wide diorite—gabbro dikes that trend nearly perpendicular to the
northeasternly regional strike of the steeply dipping country rocks.
Stratigraphic top determinations are limited to a few pillowed metabasalts.
However, the scanty data indicate that the sequence may be as much as 25,000
feet thick.
Massive suif ides are present in prospect pits and in drill holes in
the western part of the area.
References:
Fletcher, G. L., and Irvin, T. N., 1955, Geology of the Emo Area: 63rd
Annual Report, Ontario Department of Mines, part 5, 36 p.
Ontario Department of Nines, 1967, Kenora—Fort Frances Sheet, Geological
Compilation Series, Map 2115.
�Paper 17
THE EASTERN TERMINUS OF
THE LAKE SUPERIOR SYNCLINE
ERDOGAN ORAY
W. S. HINZE
N. W. O'HARA
Michigan
Purdue University
West Lafayette, Indiana
Naval Weapons Center
China Lake, California
State Univ.
East Lansing, Michigan
ABSTRACT
A regional gravity Investigation of the eastern portion of the
Northern Peninsula of Michigan was conducted and combined with previously
observed gravity stations in the Southern Peninsula of.Michigan, Beaver
Island, northern Lake Huron, northern Lake Michigan and the Sault
Ste. Marie area of Canada to investigate the eastern terminus of the
Lake
Superior syncline.
The Bouguer gravity anomaly map of the eastern portion of the Northern
Peninsula shows three major positive gravity anomalies.
One of these
anomalies trends southeast from Grand Island in Lake Superior and can
traced orthwestby magnetics to the Middle Keweenawan volcanics of
This anomaly represents the margin of the
western limb of the Lake Superior syncline. Another positive anomaly
trends south from Whitefish Point on the south shore of Lake Superior
be
the Keweenaw Peninsula.
and is interpreted as a horst of basalts which can be traced magnetically
to
the Middle Keweenawan volcanics outcropping on Mamainse Point, Ontario.
The eastern limb of the syncline near the eastern edge of the Northern
Peninsula is also defined by a positive gravity anomaly. These three
positive gravity anomalies which are associated with positive magnetic
anomalies merge in the vicinity of Beaver Island in Lake Michigan and
mark the termination of the Lake Superior syncline. South of Beaver
Island, the Keweenawan basalts continue in a south—trending narrow belt
and are expressed by the "Mid—Michigan gravity high".
The Bouguer anomaly
map indicates two local gravity minimums
in the Whitefish Bay area on
the south shore of Lake Superior. These are interpreted to result from
a thick accumulation of Upper Keweenawan clastic sediments.
The results of two dimensional model studies suggest that the Lake
Superior syncline in the eastern portion of the Northern Peninsula
consists of up to 12,000 feet of basaltic flows overlain by Upper
Keweenawan clastic rocks. Two geological models can be fitted to the
observed anomalies of the northern tip of the Southern Peninsula of
Michigan. The basalts either extend throughout the northern tip of the
Southern Peninsula where they are highly faulted into a series of horsts
and grabens or they are confined to the Grand Traverse Bay area in
which case pre—Keweenawan extrusives and intrusives make up the basement
of the northern tip of the Southern Peninsula.
�Paper 18
MAGNETIC REVERSALS AND POLAR SHIFTS AS MARKERS
IN A PROTEROZOIC TIME SCALE
W.
A. ROBERTSON
Geomagnetic Laboratory
Earth Physics Branch
Department of Energy, Mines and Resources
Ottawa, Canada
A B STRACT
The construction of a useful Precambrian time-scale
Fossils are scarce. Sedimentary basins are widely separated, and deposition
rates may have been different from today. Small errors
in radiogenic age determinations represent many millions
of years. Geologists should consider the help that is
presents great difficulties.
becoming available from paleomagnetic sources when
attempting to divide Precambrian time into useful time
units.
Difficulties using paleomagnetic methods of dating
so far back in time are no greater than those of other
methods, and have one unique advantage. The pattern of
reversals of the earth's magnetic field is world-wide;
it is not diachronous, and any identifiable marker horizon occurs at the same point in time wherever it is
found. This is not true of polar-wandering curves, however,
which apply only to their own continent.
The figure shows a hypothetical reversal pattern
for the earth's magnetic field, with time as abacissa.
Above and below it are hypothetical movement rates, on
the same time scale, of two continents, EG and AS.
It is hypothetical for the Proterozoic due to lack
of data, but is based on patterns emerging from Phanerozoic time. M intervals are ones of mixed polarity, whereas
N and R. are of wholly normal and reversed polarity
respectively. Reversal nodes marked X, between wholly
normal and wholly reversed polarity intervals provide
unambiguous, universal marker horizons. G nodes, where
one double polarity inversion took place, give good
marker horizons but may be hard to find in rock sequences.
The F nodes also yield marker horizons, but may be harder
to identify precisely.
�Paper 18
-2—
At the first and third polarity node the continents
are shown as accelerating sympathetically at the time of
change of reversal frequency. Further back in time they
are shown as independent of each other, and more indern.dent of the polarity rhythm. Whether there are links between motions at the earth's surface and reactions at the
core-mantle boundary is still an unsolved problem. In
any case, the location of a pole position on the polar
wandering curve of the same continent will be a measure of
its age. The accuracy will be highest for rocks formed
at times of rapid polar movement: conversely if a conti-
nent is static relative to the pole for a long interval
pole positions will not differentiate ages of rocks formed
in that interval
Working out the polarity scheme for a Precambrian
period is a very big task. Unconformities will leave
gaps that have to be filled in from elsewhere. Nevertheless a pattern is : beginning to emerge in the Hadrynian
and Helikian (880-1640 m. Y.) of the Canadian Shield, although large gaps remain to be filled. An older normal
interval ( 1400 m.y.) appears to be followed by a mixed
interval. Then a second normal interval is succeeded by
a reversed interval about 1100 m.y. ago (a potential X
node). A possibly longer normal interval then appears
to be followed by one of mixed polarity.
It is still too early to use paleomagnetic nodes
as boundaries to help form a Proterozoic time-scale,
but new polar wandering and reversal pattern data are
accumulating fast, and we would be wise to consider the
possibility of using them to help to split the Precambrian into time strati graphic units of wide application.
�Ic'
1¼.
rr,
WORLD -WIDE
POLARITY
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4
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—4
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fl
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z
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�Paper 18
'vv'ORLJ) —WIDE
C.Di
/tr
POLAR IT
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�Paper 18
-2SELECTED REFERENCES
Cox, Allan, 1968, Lengths of geomagnetic polarity intervals. J. Geoph. Res. V. 73, p. 3247-60
Cox, A., Doell, R. R., and Dairymple, G. B. 1964,
Reversals of the earth's magnetic field, science,
V.
144, p. 1537-43.
Gough, 0. I., Ondyke, N.D., and McElhinny, M. W., 1964,
The significance of paleomagnetic results from
Africa. J. Geoph. Res.
V.
69, p. 2509-2519.
Heirtzler, J. R., Dickson, G. 0., Herron, E.M., Pitman
III, W. C., and Le Pichon, X., 1968, Marine
magnetic anomalies, geomagnetic field reversals,
and motions of the ocean floor and continents,
J. Geoph. Res. V. 73, p. 2119-36.
Irving, E., and Robertson, W. A., 1969, Test for polar
wandering and some possible implications.
Res. V.
74, p. 1026-36
J. Geoph.
McElhinny, M. W., 1971, Geomagnetic reversals during
the Phanerozoic. Science, V. 172, p. 157-9.
Minkovitch, D., Opdyke, N.D., Heezen, B. C., and Foster,
J. H., 1966, Paleomagnetic stratigraphy, rates of
deposition and tephrachronology in North Pacific
deep-sea sediments. Earth and plan. Sci. 1st.
V. 1, p. 476-92.
Robertson, W. A., and Fahrig, W. F. 1971, The Green
Logan Paleomagnetic Loop -- the polar wandering
path from Canadian Shield rocks during the Neohelikian
Era. Can. J. Earth Sci. V. 8, p. 1355-72.
Vine, F. J.., 1968, Magnetic anomalies associated with
Mid-Ocean Ridges. The History of the Earth's
Crust. Ed. R. A. Phinney, p. 73-89.
�Paper 19
ARCHAEAN SALIC VOLCANIC ROCKS AT KAKAGI LAKE, NW
ONTARIO - THEIR PHYSICAL AND CHEMICAL NATURE
by D.R. Smithl R. H. McNutt P. M. Clifford?
ABSTRACT
At Kakagi Lake, and Archaean (older than ca. 2500 my)
supracrustal assemblage has, for its upper portion, salic
volcanic rocks, approximately two thousand metres thick.
These rocks are somewhat unusual , being almost devoid of
outcrop-scale layering in rhyodacitic and andesitic
scoriaceous breccias and having limited or crude layering
in crystal tuffs. Within the fragmental rocks, there is
only poor sorting of size fractions. Moreover, in any
given outcrop, the accessory fragments which make up the
bulk of the framework are monolithologic.
Analysis of variation of maximum fragment size, and
framework - matrix ratios reveal a "cryptic° macroscopic
layering, not visible in individual outcrops. In addition,
there are two, possibly three, areas having both large
values of maximum fragment size, and a high framework matrix ratio. These areas are interpreted as projections
of emission centres into the present day outcrop plane.
Chemical analyses of 23 pairs of fragments and adjacent matrix show that, in general, the fragments are
the richer in Si02 and perhaps Na20, with matrix the
richer in total Fe and MgO. Discriminant function analysis of our data, using the four oxides mentioned, properly
identifies fragments from the matrix in 80% of the samples.
These pyroclastic rocks have rather strong caic-alkaline
affinities, and tend to be normal or low in K)O. Normatively, matrix is: 33% basaltic, 48% andesiti, 19%
dacitic; fragments are: 29% basaltic,29% andesitic,
42% dacitic. These chemical differences are echoed in
thin sections. Fragments commonly have polycrystalline
quartz aggregates and felspar phenocryst in a felsic background: matrix is markedly chloritic. Alteration is
ubiquitous.
There are no discernible chemical trends along "strike
or upwards through the volcanic pile. This reinforces
the evidence from physical properties-considerable thickness,
lack of layering, poor sorting, monolithologic fragment
1. Texaco, Calgary, Alberta.
2.
Department of Geology, McMaster University, Hamilton,
Ontario.
�Paper 19
—2-
character locally - which indicate a pyroclastic flow origin
for these rocks. Presence of a fabric possibly pseudomorphic
after shard structure is further support for this interpretation.
�Paper 20
Three-phase
deformation associated with the Penokean
orogeny,
east Gogebic Range, Michigan-'
by Virgil A. Trent
U.S. Geological Survey,
Washington, D.C.
Abstract
Three phases of deformation in the east Gogebic area resulted
in tight folding of Precambrian X (Marquette Range Supergroup) strata
followed by folding and block tilting of the Precambrian Y (lower
Keweenawan) and Precambrian X (Animikie)
phase of orogeny.
sections during the last
The deformationa]. periods are marked by coeval
volcanism and by three angular unconforniities. Although the deformations may be widely spaced in time, lithology and structural morphologlj
suggest that they are separate phases of a single orogenic episode.
Near the east end of the Gogebic Range, Precambrian X (Marquette
Range Supergroup) strata lie between tilted metamorphosed Precambrian Z
volcanic rocks
(lower Keweenawan) to the north and strongly meta-
morphosed Precambrian W or X gneiss complex, Algoman Granite of
Lawson (l9lL), and
volcanic
rocks (Keewatin) to the south.
Three
defoniiational phases can be identified in Precambrian X rocks of the
eastern Gogebic Range:
-'Work done in cooperation with the Geological Survey Division of
the Michigan Department of Natural Resources.
1
�Paper 20
i) The earliest was folding of the
Sunday Lake Quartzite,
Bad River Dolomite, Palms Formation, and Ironwood Iron-
Formation.
Mafic
lava
flows intercalated with the Ironwood
Iron-Formation indicate that extrusive volcanic activity
preceded folding. The large Wolf Mountain anticline began to
form,
followed by
erosion and
Copps Group of Allen and
unconformable
Barrett
(191S) and
deposition of the
the
Tyler
Formation.
2)
The strongest deformational phase, the Penokean orogeny, as
defined by Goldich and others (1961, p. 120-122, i6-i6o),
took place at the end of Precambrian X ("Animikie")
The
this
time.
Wolf Mountain anticline was more tightly folded during
event.
Mafic sills, also intercalated with the Ironwood
Iron-Formation were intruded syntectonicafly.
The northernmost thick sill truncated by the pre-Keweenawan unconformity
(Prinz, 1967), appears to be genetically related to flow
breccia cropping out along its eastern margin.
Erosion of
these volcanic rocks, parts of the Tyler and Copps, and
older
rocks preceded the unconformable deposition of the oldest
Keweenawan strata.
3)
Post-lower
Keweenawan deformation, upon which Blackwelder
638) based his original definition of the Penokean
orogeny, warped and
the whole Precambrian succession
(191)4, p.
tilted
except for the Jacobsville Sandstone.
folding
seems to mimic major
Penokean
The last phase of
trends of the preceding
folding, especially in the area close to Lake Gogebici.
Torsional
basement movements related to block tilting
probably contributed to the assymetry of the Wolf Mountain
anticljrie.
2
�Paper 20
A large
Wolf
Mountain
in the area.
flat-lying niass of
(T. 147
N.,
R.
1414
eflipsoidal
basalt north of
w.) may be the youngest volcanic rock
It lies athwart the Precambrian X (.Animikie) structural
trend and has not been blocktilted.
The youngest major fracture in
the area passes nearby, and to the southwest the fracture is filled
by a thick mafic dike which I interpret to be the feeder.
Two miles
to the northeast, this fracture truncates the lower Keweenawan ridge.
This field evidence suggests that these ellipsoidal lavas were
extruded in post-early Keweenawari time and were perhaps associated
with the terminal phase of folding.
3
�Paper 20
References cited
Allen, R.C., and Barrett, L.P., l9l, A revision of the sequence
and structure of the pre-Keweenawan formations of the eastern
iron range of
Gogebic
(Geol.
Michigan: Michigan Geol. Survey Pub. 18
Ser. l), p. 33-61; in part, Jour. Geology, v. 23, p.
689—703.
Blackwelder,
geologic
Eliot, l91L, A summary of
the orogenic epochs in the
history of North America: Jour. Geology v. 22, no. 7,
p. 633-65)4.
Goldich, Samuel S., Nier,
John H., and
Krueger,
Alfred 0., Baadsgaard, Halfdan,
Harold W.,
Hoffman,
1961, The Precambrian
geology
and geochronology of Minnesota: Minnesota Geol. Survey Bull. 141,
193
p.
Lawson, A.C., 191)4, A standard scale for the pre-Cambrian rocks of
North America: Internat. Geol. Cong., 12th, Canada, 1913,
Comptes rendus, p. 31i.9-370.
Prinz,
W.C., 1967, Pre-Quaternary geologic and magnetic map and sectioriLs
of part of the eastern Gogebic iron range, Michigan: U.S.
Geol. Survey Misc.
Geol.
mv. Map 1-1497.
14
�Paper 21
BEDROCK
MORPHOLOGY IN THE VICINITY OF
PORTAGE LAKE, KEAW PINSULA, MICHIGAN
E. J. WARREN
Department
of Geology and Geological Engineering
Michigan Technological University
ABSTRACT
Portage Lake stretches across the Keweenaw Peninsula of
Michigan between Keweenaw Bay and Lake Superior. This
circumstance was put to good use by the Indians and later
by French voyaguers and Jesuits who used the long sinuous
lake as a shortcut in their travels along the south shore
of Lake Superior. Modern shipping uses the same shortcut,
now known as the Keweenaw Waterway.
Portage Lake has a maximum depth of about 50 feet located
On the other hand, Torch
in the main body of the lake.
Lake, which is connected to Portage Lake by Torch Bay and
a dredged ship channel, was once 170 feet deep before it
was partially filled by mill tailings from various copper
recovery operations.
Several geologists have speculated about the origin of
these unusual lakes (Martin, 1911; Scott, 1921; Hughes,
1963).
However, they were handicapped by their lack of
knowledge of the bedrock morphology around and under the
lakes.
The bedrock morphology was determined from water well and
diamond drill logs and by geophysical methods.
Seismic
refraction profiles were run on land and on the mill tailings in Torch Lake. On the lakes, sparker and air-gun
surveys were performed. Unfortunately the sparker survey
lacked penetration and the air-gun profiles were rendered
nearly useless by excessive reverberation. Gravity profiles
were then run over Portage Lake, on ice, in an attempt to
extrapolate the land based information.
Interpretation of
the gravity surveys, now being performed, is hampered by
the large regional gravity gradient due to the Keweenaw
fault (Bacon, 1966).
Preliminary results indicate that both Portage and Torch
Lakes lie in a complicated network of buried bedrock valleys.
A water well next to the narrow northwest arm of Portage
Lake reaches a depth about 380 feet below lake level and
a diamond drill hole east of Hancock Michigan reaches
bedrock about 280 feet below lake level. Of course, there
is no assurance that either of those wells have reached the
deepest part of the bedrock valley.
�Paper 21
Torch Lake lies in a bedrock valley with a floor 250 feet
This valley underlies the pre-.
below present lake level.
sent Traprock River valley to the north and continues south
of Torch Lake into Portage Lake under Torch Bay. The bedrock valley under Torch Lake is also connected to Portage
Lake by a bedrock valley 200 feet below lake level which
parallels the Keweenaw fault and passes under the town of
Dollar :ay.
bedrock valley about 150 feet below lake level extends
from the southeast part of the main body of Portage Lake
out through Portage Fh-itry, curving to the east of the
present channel.
The deepest bedrock valley, however, extends south of the
main body of Portage Lake under the present Sturgeon River
valley where a depth L50 feet below present Lake Superior
level was found.
The southern extension of this deep
It is interesting
valley still remains to be explored.
that this valley has bedrock depths on the same order as
the depth of Keweenaw Bay. A bedrock valley 200 feet below
lake level branches off the west side of the Sturgeon valley and passes under Otter Lake.
It is probable that these buried bedrock valleys were
originally a product of stream erosion.
It is possible
that some glacial overdeepening has taken place also, but
this cannot be detexmiined until all the data is compiled
and a contour map of bedrock elevations is completed. At
any rate, it is apparent that the base level for stream
erosion was once considerably lower than the present Lake
Superior level. This discovery may have some bearing on
the controversy about whether Lake Superior is mainly a
result of subaerial erosion, of glacial scour, or of some
combination of the two.
References
Bacon, L. 0., 1966, Geologic Structure East and South of
the Keweenaw Fault on the Basis of Geophysical
Evidence: The Earth Beneath the Continents, A.G.U.
Mon. 10, pt2—55.
Hughes, J. D., 1963, Physiography of a Six Quadrangle Area
In the Keweenaw Peninsula North of Portage Lake:
Unpublished Ph.D. Dissertation, Northwestern Univ.,
Evanston, Ill., 228 pp.
Martin, L., 1911, Physical Geography of the Lake Superior
Region: Chapt. IV in U.S.G.S. Mon. LII, The Geology
of the Lake Superior Region, p85-l17.
Scott, I. D., 1921, Inland Lakes of Miohigan: Mich. Geol.
and Biol. Survey, Lansing, Mich., 383 pp.
�,,
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LAKE SUPERIOR
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�Paper 22
GLACIAL DRIFT ON THE MESABI IRON RANGE, MINNESOTA
ITS CHARACTERISTICS, ORIGIN, AND HYDROLOGIC SIGNIFICANCE'!
THOMAS G. WINTER
U.
S.
Geological Survey
ABSTRACT
Glacial deposits in the Mesabi Iron Range area consist
ments. The basal till occurs in only a small number of mines,
but they are scattered across the entire Iron Range. The
is dark gray to dark greenish gray and brownish gray,
sandy, silty, and is calcardous. The middle till unit, a
of three major till units and associated glaciofluvial sedi-
till
bouldery till, is the thickest and most widespread of the
three tills. It is grey, yellow, red, orange or brown,
sandy, silty, contains abundant cobbles and boulders, and
is non-calcareous. The till was depsoited by the Rainy
lobe, which has a minimum age of 14,000 to 16,000 years
before present. The surficial till was deposited contemporaneously by two minor sublobes of the same ice lobe
about 12,000 years ago. The brown silty till occurs in the
western and north-central part of the area. It is light
to medium brown, sandy, silty, and calcareous. Red clayey
till
the south-central part of the area is red to
reddish brown, clayey, silty, and calcareous.
Stratified fluvial sediments occur within the glacial
drift at many places in the Mesabi Iron Range area. These
sediments, which are important aquifers, occur extensively
between the three main till units. The thickest and most
extensive aquifer consists of glaciofluvial sediments that
lie between the surficial till and the bouldery till. The
thickness of the glaciofluvial sediments is greater than
50 feet in much of the area, and the transmissivity is
greater than 100,000 gallons per day per foot at a number
of localities. Glaciofluvial sediments underlying the
bouldery till occur largely in the western half of the
area. These sediments are generally less than 50 feet
thick and their transmissivity is generally less than
50,000 gallons per day per foot. Surficial glaciofluvial
sediments are a source of ground water for high yield wells
only in the eastern part of the area in the general
vicinity of the Biwabik bedrock valley. Thickness of these
sediments is greater than 100 feet in some places, but
their transmissivity is generally less than 50,000 gallons
per day per foot.
�Paper 22
-2-
The glacial drift aquifers can yield as much as 40
mgd (million gallons per day). Assuming that the ratio
of area underlain by aquifer to total area is constant
for the study area (about 20 percent where mapped in
detail), it is concluded that as much as 80 million
gallons per day could be developed from glacial drift
aquifers without causing excessive water declines and
depleting streamfiow.
Publication authorized by the Director, U.S. Geological
Survey
�Paper 23
CHRONOLOGY OF PRECAMBRIAN ROCKS OF
IRON AND DICKINSON COUNTIES, MICHIGAN
PART
II
P. 0. Banks
Department of GeologyCase Western Reserve University, Cleveland, Ohio 44106
and
W. R. Van Schmus
Department of Geology
University of Kansas, Lawrence, Kansas 66044
Ertensive K-Ar, Rb-Sr, and U-Pb data available for the Precambrian
rocks of Iron and Dickinson Counties, Michigan, permit considerable
clarification of the chronologic development of this area.
The following ares are considered well established (rounded to nearest 25 m.y.):
Peavy complex 1900 m.y., Hemlock volcanics 1950 m.y., and Porphyritic
Red Granite 2100 m.y.
A U—Pb concordia intercept ago of 2575 ni.y.
for the Norway Lake gneiss is considered minimal for this unit because
of probable multiple secondary events. The pre—Animikie post—Dickinson
Granite Bluffs gneiss gives an apnarent Rb—Sr whole rock age of Ca.
2700 m.y. whereas its apparent zircon U—Pb concordia intercept age is
ca, 2100 m.y.
This anomaly can be explained either by urusual migration
of radiogenic Sr or by multi-stage Pb loss. Additional mineral analyses
are in progress to resolve the issue.
Our previous conclusion (Banks
and Van Schmus, ILSG 1971) remains unchanged that the Animikie Series
of James et al. is bracketed between 1900 and 2100 m.y. and therefore
is not correlatable with the original Huronian of Ontario.
Resolving
the ae of the Granite Bluffs gneiss will determine whether the Dickinson Group Is or is not a candidate for correlation with the original
Huronian.
Additirnal data of interest include a Pb/Pb age of 2900 m.y. for
detrital zircon from the East Branch arkose, and a suggestion from
K—Ar h.ornblende and U-Pb apatite and sphene data that the last major
metamorphism in the area occurred 1500—1600 m.y. ago.
�Paper 24
PENOKEAN TECTONICS IN NORTifERN MICHIGAN
by W. F. CANNON
U. S. Geological Survey
Washington,
2O242
D.C.
ABS TRA CT
The major Penokean deformation in northern Michigan
occurred between 1.9 and 2.0 b.y. ago. Lower and. middle Precambrian
rocks were deformed independently of, and mostly before, regional
metamorphism; the deformation took place at low temperatures. The
subsequent metamorphism was a low-pressure type in which andalusite
was stable over a wide temperature range.
The maximum confining
pressure is set by the aluminosilicate triple point at about
5 kilobars (about 13 miles burial depth), but the true pressure
may have been much less.
Structural interpretations must be consonant with mechanisnis
of rock deformation possible at low temperatures and low to
moderate confining pressures. Lower Precambrian granitic rocks
form the basement for the Marquette Range Supergroup in much of
northern Michigan.
granitic
Experimental rock deformation indicates that
rocks have very high strength and very low ductility
under probable conditions of Penokean deformation, and kinematic
interpretations of Penokean deformation must consider the probability of a strong nond.uctile basement; interpretations requiring
a weak ductile basement are difficult to reconcile with the
probable physical environment of deformation.
The first-order regional structures in northern Michigan are
uplifts of lower Precambrian rocks with middle Precambrian rocks
of the Marquette Range Supergroup in intervening synclinorial
basins. A wide divergence of trends for these structures suggests
vertical tectonism rather than regional horizontal compression.
The lower Precambrian cores of many uplifts are cut by diabase
dikes.
These dikes are older than the Penokean orogeny, and
many are probably associated with mafic intrusive and extrusive
rocks in the middle Precambrian section, yet these dikes were
not externally deformed during Penokean folding; they remain
planar and. largely massive. These relationships substantiate
inferences from experimental rock deformation of a strong nonductile basement and strongly suggest that the lower Precambrian
rocks remained rigid and were not penetratively deformed d.uring
Penokean deformation. The uplifts are interpreted, as fault-
bounded blocks of lower Precambrian rocks which were uplifted
V
The Gogebic Range is excluded from this discussion
because of cnp1ications introduced by younger deformation.
�Paper 24
along steep faults, many of which are steep reverse faults.
The
blocks may have moved either as single units or, more likely,
with internal adjustments occurring along relatively narrow shear
zones and parallel to dike margins. During this phase of deformation, middle Precambrian rocks were passively draped over the
fault
blocks, forming
the presently preserved synclinal structures
which occupy the relatively dow'nfaulted segments of the basament.
Second-order and, smaller folds in middle Precambrian rocks
indicate that these rocks have undergone substantial horizontal
shortening, whereas the underlying lower Precambrian rocks have
not.
Furthermore, the trends of second-order and smaller folds are
mostly in west and west-northwest directions and are much more
uniform than trends of first-order structures (block uplifts).
In
some areas, second-order folds cross the trends of first-order
structures at high angles. Many of these smaller folds seam to
have formed independently of first-order structures, and their
genetry requires a thin-skinned compressive deformation which has
affected.
only the middle Precambrian rocks and not the lower
Precambrian basament. Many of these folds may be due to gravity
sliding or spreading which, because of relatively uniform fold
trends, appears to have occurred in response to a region-wide gradient.
This phase of deformation must have occurred before block
faulting produced sithstantial structural relief on the contact of
lower and middle Precambrian rocks.
The suggested sequence of events is:
1) Regional gravity sliding which produced folds in middle
Precambrian rocks with west and west-northwest trends but did not
deform the lower Precambrian basament rocks. This event was
probably associated with early uplift of the depositional basin.
2) Uplift of fault-bounded basament blocks with widely divergent
trends, accompanied by passive draping of middle Precambrian rocks
and earlier gravity folds into basins or tight synclines between the
uplifts. A second set of folds formed in middle Precambrian rocks in
areas marginal to the uplifts.
�Paper 25
THE PENOKEAN OROGEM
S. S. Goldich
Northern Illinois University
DeKalb, Illinois 60115
ABSTRACT
The Penokean orogeny (Blackwe1der, 1914) was redefined by Goldich arid others
(1961) as Middle to Late Precambrian event that involved the Anuinikie Group of
Minnesota and Ontario and similar rocks that were formerly assigned to the
Huronian in Wisconsin and Michigan. Time limits from 1600 to 1800 ni.y. were
set for the orogeny; however, Peterman (1966) showed that the metasedimentary
rocks of the Cuyiina district were folded 1850 n.y. ago. New data for the
Thomson Formation of east-central Minnesota give a minimum age of the folding
and metamorphism of 1900 n.y. ago (Stuckless and Goldich, 1972). Thus, the
Penokean orogeny is a Middle Precambrian event, using 1800 m.y. as the time
boi.]ndary between the Middle and Late Precambrian (Goldich, 1968).
Limiting ages have been placed on the type Huronian rocks by dating of
the Nipissing Diabase in the Blind River—Bruce Mine area (Van Schmus, 1965)
and of the Nipissing Diabase and Gowganda Formation at Gowganda (Fairbairn and
others, 1969). The type Huronian rocks are at least as old as 2280 n.y. (Gow—
ganda Formation)
and were folded at least 2160 m.y. ago (Nipissing Diabase).
Fryer (l97l has reported ages of 1800, 1870, and 1790 m.y. for volcanic
and metasedimentary rocks from the Belcher Fold Belt, the Labrador Trough, and
the Mistassini Lake area. Rb—Sr ages, however, must be used with caution.
They do not necessarily date the time of deposition or of a specific metamorphic
event.
In Minnesota, for example, isochron ages on Aniniikian rocks range from
1900 to 1660 n.y., but all were probably deposited at essentially the same time.
Considerable radiometric dating of Middle Precambrian rocks is now in
progress. Until the new data from a number of laboratories are published and
can be assessed, it is premature to correlate the rocks of widely separated
areas of North America.
References
For references prior to 1969 see Goldich (1968).
Fairbairn, H. W., P. M. Hurley, K. D. Card, and C. J. Knight (1969) Correlation
of radionietric ages of Nipissing Diabase and Huronian metasedinients with
Proterzoic orogenic events in Ontario: Canadian Jour. Earth Sci., v. 6,
p. 489—497.
Fryer, B. J. (1971) Rb—Sr whole—rock ages of Proterozoic strata bordering the
eastern part of the Superior Province, Canada (abs.):
Geol. Soc. America
Abstracts with Program, v. 3, p. 574—575.
Goldich,
S. S. (1968) Geochronology in the Lake Superior region:
Jour. Earth Sci., v. 5, p. 715—724.
Canadian
Stuckless, J. S. and S. S. Goldich (1972) Ages of some Precambrian rocks in
east-central Minnesota: 18th Annual Institute on Lake Superior Geology,
Houghton, Michigan.
�Paper 26
RELATION OF PENOKEAN POLYPI-IASE DEFORMATION
TO REGIONAL METAMORPHISM IN TI-fE
WESTERN MARQUETTE RANGE, NORTHERN MICHIGAN
John S. Kiasner
Michigan Technological University
Houghton, Michigan
ABSTRACT
Recent work at Lake Michigamme at the western end of the
Marquette Trough suggests that some metamorphic minerals began
to form during the early stages of Penokean deformation contrary
to previous studies (Powell 1970) that suggest that regional
metamorphism almost completely postdates deformation. The new
studies indicate that metamorphism peaked late in the deforrna.tional sequence as shown on figure 1.
F
F1
F2
F
Deformational events
Andalusite
Garnet
S t.au ro lit e
Actinolite
Grunerite
Biotite
Sericite
Thermal metamorphism
ically shown
Chlorite
Fabric elements
Time
Figure 1, Kinematic relationship of metamorphism to
deforrnationQ
The deformational sequence, characterized by four phases,
started with regional soft sediment deformation (F
that produced a penetrative N 75° W trending foliation, th8 early stages
of which can be identified as slaty cleavage (S ). Selective
migration of silica (Williams 1972) during continued deformation
(F1) along the early formed slaty cleavage enhanced this cleavage
an formed the numerous quartz veins.
The F -F1 deformational
couplet produced the regional S foliation. °
)
�Paper 26
Crenulation folding (F2) of S1 foliation resulted in the
formation of S2 fracture cleavage and formation of lineations
(L2) due to the intersection of S1 and S2. The L2 lineations
are flat lying because the strike of S2 and S1 are nearly parallel.
Kink—banding (S) that affects S0, Si, 2 and L2
characterizes the last eformationai event in the area.
Regional thermal metamorphism accompanied the sequence of
deformation.
The growth of pre-F1 andalusite porphyroblasts
(figure 1) indicates that metamorphism started early in the
deforinational sequence.
It probably peaked between F2 and
deformation as indicated by the growth of post-, pre-F2
staurolite porphyroblasts and post-F2 brown biotite and grunerite. Abundant retrograde metamorphism is shown by andalusite
and staurolite porphyroblasts that have been replaced by sericite, and by garnet porphyroblasts that have been replaced by
chlorite.
References
James, H. L., 1955, Zones of Regional Metamorphism in the Precambrian of Northern iviichigan, Bull. Geol. Soc. Am., v. 66,
p.
1Li55_1483.
Powell, C. McA., 1970, Relict Diagenetic Textures and Structures
in Regional lVletarnorphic Rocks, Northern Michigan, North-
western University Report 20, N.A.S.A. Geol. Test Site
No. 126, 35 p.
Williams, P. F., 1972, Development of Metamorphic Layering and
Cleavage in Low Grade Metamorphic Rocks at Bermagui,
Australia, Am. Jr. Sci., v. 272, p. 1—7.
�Paper 27
LINEAMENTS AND MYLONITE ZONES IN THE
PRECAMBRIAN OF NORTHERN WISCONSIN
Gene L. LaBerge
Wisconsin Geological and Natural History Survey
and University of Wisconsin-Oshkosh
ABSTRACT
Recent geological mapping in Marathon County by the
Wisconsin Geological and Natural History Survey has shown
that a number of major zones of shearing cross central
Wisconsin. At least 3 directions of major shearing have
been recognized: N300_350E, N60°E, and N800E. The
N300_350E trend is best developed in the area mapped, but
reconnaissance indicates that other directions are impor-
tant in other parts of the county.
The major shear zones are represented by zones of
mylonite and variously sheared rocks up to a mile wide.
Because a number of different rock types, ranging in
composition from granite to greenstone, have been granulated, mixed, and recrystallized to varying degrees to
form the mylonite, the zones are lithologically variable
both along and across the strike. However, they are
structurally rather uniform, displaying a lensoidal
structure on all scales from map scale to thin section.
Indeed they seem to be composed of a myriad of overlapping lenses which show different degrees of flattening.
Excellent examples of the progressive shearing of a
granitic rock to produce a mylonite were observed along
several of the shear zones.
The best example of a mylonite zone mapped is that
along the Eau Claire River in northeastern Marathon
County. It has been mapped for a distance of approximately
20 miles, and almost certainly continues an additional
15 miles across the county. Furthermore, it is on a
topographic lineament which can be traced across Wisconsin for at least 120 miles. At least 4 other major
N300_35oE shear zones cross Marathon County, and some of
these also occur on topographic lineaments 100 miles or
more long. Numerous stream valleys and other topographic
lineaments in northern Wisconsin are oriented approximately
N30°E, and these may also represent shear zones. Significantly, the N600E and N80°E directions of shearing are
also common trends of topographic lineaments.
�Page 27
-2-
The origin of these major shear zones is not yet
certain; however, the lithologic associations in the area
mapped coupled with the major shearing suggest that northern
Wisconsin
be part of a Precambrian subduction zone.
Whatever the explanation of the shear zone, it is evident
that they represent a major feature in the Precambrian of
the Lake Superior region which has not previously been
recognized.
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LINEAMENTS AND'S POSSIBLE SHEAR ZONES IN MARATHON COUNTY
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�Page 27
00
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LIMIT OF OLDER DRIFT
—......—LIMIT OF YOUNGER
DRIFT
S10.
LINEAMENTS AND POSSIBLE ShEAR ZONES IN NORTHERN WISCONSIN
�Paper 28
STRATI GRAPHIC AND TECTONIC FRAMEWORK OF MIDDLE
PRECAMBRIAN ROCKS IN MINNESOTA
G. B. MOREY
Minnesota Geological Survey
St. Paul, Minnesota
ABSTRACT
Sedimentary strata of Middle Precambrian age in Minnesota predominantly consist of
argillite and graywacke with lesser amounts of iron—formation, quartzite, quartzose siltstone,
limestone, and dolomite. These strata unconformably overlie folded metasedimentary and
igneous rocks approximately 2,700 m.y. old; locally they also appear to unconformably
overlie diabasic gabbro or diorite dikes that may be approximately 2,000 m.y. old
(Hanson and Malhotra, 1971).
Except for an older unnamed dolomite unit in east—central Minnesota, all the sedimentary
rocks are assigned to the Animikie Group, a wedge-shaped body that thickens from less than
100 feet in the northern part of the State to at least 15,000 feet in areas 100 miles to the
south. The Animikie Group comprises a single depositional event that began with well—
sorted clastic detritus characteristic of a stable shelf —— Kakabeka, Pokegama, and Mahnomen
Formations ——, passed through a phase of iron—formation deposition —— Gunflint, Biwabik, and
Trommald Formations ——, and ended with deposition of fine sand and mud characteristic of a
"deep" basin with poor circulation —— Rove, Virginia, Rabbit Lake, and Thomson Formations.
Locally, the "deeper" water clastic rocks contain intercalated lava flows, thin to thick beds
of pyroclastic material, and layers of carbonate— to sulfide—facies iron—formation.
During or subsequent to the time of deposition, the sedimentary rocks in east—central
Minnesota were folded —— perhaps more than once —— into numerous large antic lines and syndines that have many second-order folds on their limbs. The major folds are asymmetric,
with steeply—dipping to locally overturned north limbs and more gently—dipping south limbs.
Fold axes trend within 300 of east, and plunge from horizontal to 300 east. In addition, a
part of the Thomson Formation was regionally metamorphosed to at least the lower range
(staurolite and garnet) of metamorphic grade in the amphibolite facies; however, definable
metamorphic isograds are not everywhere parallel to recognizable structural trends, suggesting
that deformation and metamorphism were independent variables in the orogenic scheme for
this region. The time of folding is unknown, but the metamorphism on the Cuyuna range has
been dated at 1,850 m.y. ago (Peterman, 1966). The Animikie strata in northern Minnesota
also were deformed about northeast-trending axes, although the degree of deformation and
the metamorphic grade is less pronounced. In addition, these rocks appear to have been
subsequently folded about north-northwest—trending axes. Available isotopic data cluster
around an age of 1,650 m.y. and these data may reflect a period of mild deformation and
metamorphism at that time.
A variety of igneous rocks also were intruded into the sedimentary pile in east—central
Minnesota. Several discrete events can be recognized, which together with the deformation
and metamorphism comprise the Penokean Orogeny. These include (Woyski, 1949; Goldich
and others, 1961): (1) pre—tectonic emplacement of small mafic intrusions; (2) syntectonic
emplacement (1.78 — 1.63 b.y.) of intermediate—size intrusions of tonalitic to granodioritic
composition -- the quartz monzonites at Warman, Isle, and Pierz, the tonalites near Hillman
and Freedhem, and the gray granodorite at St. Cloud; and (3) late-tectonic to post—tectonic
emplacement (1.73
1 .68 b.y.) of Woyski's "Stearns Magma Series" consisting of the
augite—hornblende (red) granite at St. Cloud, the porphyritic quartz monzonte at Rockville, and other similar intermediate to silicic rocks. Lastly,rocks of the Stearns Magma
Series are cut by basalt dikes which may have been emplaced during a single period, at
least 1,570 m.y. ago (Hanson, 1968).
—
�Paper 29
GRANITIC PLUTONIC ROCKS OF THE SOUTHERN PROVINCE OF THE
CANADIAN SHIELD
James A. Robertson
Division of Mines, Ontario Ministry of Natural Resources, Toronto
*paper presented by permission of the Director, Geological Branch.
AB STRACI
In Ontario granitic rocks associated with the eastern
portion of the Penokean fold belt comprise: (1) Archean basement;
(2) early post-Huronian intrusives (= Penokean of Church, 1968),
and (3) late post-Huronian intrusive ( Hudsonian of Church).
Other authors eg. Stockwell (1964) have used Hudsonian and
Penokean interchangeably and have not named the earlier orogenic
event.
The individual granitic bodies are named on Figure 1.
Algoman = Archean (Robertson, 1960) granitic rocks may be
divided into massive quartz monzonite and gneissic to migmatitic
Bodies of quartz monzonite were formed during the
terranes.
Early workers placed these
Kenoran orogeny circa 2,500 MY.
Overprinting
bodies with the "young" post-Huronian granites.
of age dates becomes pronounced as the Penokean fold belt is
approached (Van Schmus, 1965).
1)
The Creighton and Murray Granites (Card, 1968; Ginn, 1958)
They were intruded prior
lie south of the Sudbury Irruptive.
to the irruptive and local anomalous cutting relationships
The
reflect remobilisation of the granite (Hawley, 1962).
granites pre-date the regional metamorphism and deformation.
Gibbins et al (1971) have obtained 2,200 MY, which suggests
that they are earlier than the Nipissing Diabase (2,155 MY
Whether they are synchronous with the
Van Schmus, 1965).
earlier post-Huronian orogenic cycle or with early Huronian
volcanism remains an open question (Card et al, 1972).
2)
�—2—
Paper29
3)
The Cutler Batholith (Robertson, 1969; 1970a; Cannon, 1970)
lies some eighty miles west of Sudbury and intrudes folded and
metamorphosed Huronian sediments and Nipissing Diabase and is
itself foliated.
Age-dates (Wetherill et al, 1960; Van Schmus,
1965) indicate a minimum age of 1,750 MY with some thermal
resetting at 1,350 MY.
The Cutler granite is clearly
synchronous with the Hudsonian orogeny.
The granite is
intrusive but may have been derived from Huronian rocks at depth
and metasomatism may have been an important factor (Cannon, 1970).
The Croker Island Complex (Card, 1965; Robertson, 1970)
lies some twelve miles southeast of Cutler and comprises a
circular complex of comagmatic mafic to granitic rocks
accompanied by a marked magnetic anomaly.
The complex postdates regional metamorphism and folding.
Age-dates (Van Schmus,
1965) and paleomagnetism studies (Palmer, 1969) indicate 1,445
MY.
The complex is clearly late Hudsonian.
Similar magnetic
anomalies under Manitoulin Island were drilled by Union Carbide.
Core of granitic rock resembling that at Killarney was obtained
and submitted to Van Schmus for dating.
4)
Grenville Front Granites (Card et al, 1971;
Frarey and
Cannon, 1969; Hnderson, 1967; Quirke and Collins, 1930) are
intrusive bodies in the Southern Province adjacent to the
Grenville Front.
To the northwest these bodies are intrusive
but to the southeast they become strongly mylonitised passing
into the deeper crustal granite-gneiss complex of the Grenville
Province.
The mylonite zone marks the Grenville Front.
5)
5a*) The Killarney batholith featured in the classical work of
Quirke and Collins (1930) with a minimum age of 1,585 MY
comprises porphyritic quartz monzonite.
5b*)
The Lake Panache and Eden Lake Intrusives, (Card et al, 1971)
range in composition from gabbro-granite with a minimum age of
1,430 M.Y. from mica.
5c*)
The Chief Lake Batholith comprises quartz diorite to
quartzonzonite marking the northeast continuation of the
Killarney granite.
Near Coniston, Phemister (in Grant et al,
1962) interpreted the rock as feldspathised sediment. Krogh (1971)
indicates an initial age of 1,730 MY with some granites at
1,590 MY - 1,460 MY reflecting early movement on the Grenville
Front.
*Individual bodies not shown on Figure 1.
�Paper 29
—
—
Conclusion
The granitic rocks of the Ontario Sector at the Southern
Province may be classified with respect to petrography,
mineralogy, chemistry, isotopic composition and they can be
fitted into the historical and structural scheme established
by regional mapping (Robertson et al, 1969; Card et al, 1972).
However, much detailed work on individual bodies remains to be
done.
References
CannQn, W.F. (1970)
Plutonic Evolution of the Cutler Area, Ontario;
G.S.A., Vol. 81, p. 81-94.
Card, K.D. (1965)
The Croker Island Complex;
No. 14.
Bull.
Ont. Dept. Mines, Geol. Circ.
Card, K.D. (1968)
Geology of Denison-Waters Area, District of Sudbury, Ont.
Dept. Mines G.R. 60.
Card, K.D., Palonen, P.R., and Siemiatkowska, K.M. (1971)
Geology of the Louise-Eden Area, District of Sudbury;
Ont. Dept. Mines and Northern Affairs, Open File Report
5065.
Card, K.D. et al (1972)
The Southern Province in Canada in Structural Styles in
Canada, in press. Geol. Assoc. Can., Contribution to 24th
mt. Cong. Montreal 1972.
Church, W.R. (1968)
The Penokean and Hudsonian orogenies in the Great Lakes
region and the age of the Grenville Front, 14th Annual
Ints. on Lake Superior Geology, p. 16-18.
�Paper 29
—4—
Frarey,
M.J., and Cannon, R.T. (1969)
Notes to accompany a map of the Geology of the Proterozoic
Rocks of Lake Panache.
Collins Inlet Map Areas, Ontario.
Geol. Surv. Can. Paper 68-63
Gibbons, W.A., McNutt, R.H., and Adams, C.J.D. (1971)
Rb-Sr Isotopic Studies of the Murray Granite, Geol. Assoc.
Can. Abstracts, Sudbury 1971, p. 27-28.
Ginn, RM. (1958)
A Study of the Granitic Rocks in the Sudbury Area.
Unpublished M0Sc. Thesis, Queen's University.
Ginn, R.M. (1961)
Geology of Porter Township, Ont. Dept. Mines, Geol. Rept0
No 5.
Grant, J.A., Pearson, W.J., Phemister, T.C., and Thomson, J.E. (1962)
Geology of Broder, Dill, Neelon and Dryden Townships
District of Sudbury, Ont. Dept. Mines GR 9.
Hawley, J.E. (1962)
The Sudbury Ores:
Their Mineralogy and Origin, Can. Mm.
Vol. 7, part 1, 1962.
Henderson, J.R. (1967)
Structural and petrologic relations across the Grenville
Province-Southern Province boundary, Sudbury, District of
Ontario.
Ph.D. Thesis, McMaster University, Ontario.
Krogh, T.E. (1971)
Isotopic ages along the Grenville Front in Ontario.
Assoc. Can. abstracts Sudbury 1971.
Geol.
Palmer, H.C. (1969)
The Paleomagnetism of the Croker Island Complex, Ontario,
Canada;
Can. Jour. Earth Sci., Vol. 6, p. 213-218.
Quirke, T.T., and Collins, W.H. (1930)
The Disappearance of the Huronian;
Geol. Surv. Can. Mem.
160.
Robertson, J.A. (1960)
The General Geology of Part of the Blind River Area;
Thesis, Queen's University, Kingston.
Robertson, J.A. (1969)
Geology of the Cutler Map-Area;
File Rept. 5026.
Robertson, J.A. (l970a)
Geology of the Spragge Area;
M.Sc.
Ont. Dept. Mines, Open
Ont. Dept. Mines, Geol. Rept. 76.
�—5-
Paper 29
Robertson, J.A. (1970)
Geology of the Massey Area, Districts of Algoma and
Sudbury; Ont. Dept. Mines Open File Rept. 5043.
Robertson, J.A., Card, K.D., and Frarey, M.J. (1969)
The Federal-Provincial Committee on Huronian Stratigraphy
Progress Report; Ont. Dept. Mines, M.P. 31, 26p.
Van Schmus, R. (1965)
The Geochronology of the Blind River-Bruce Mines Area,
Ontario Canada; Jour. Geol., Vol. 73, p. 755-780.
Wetherill, G.W., Davis, G.L., and Tilton, G.R. (1960)
Age Measurements on Minerals from the Cutler Batholith,
Cutler, Ontario; Jour. Geophys. Research, Vol. 65,
p. 2461-2466.
Structure, metamorphism and Post-Huronian granitic
intrusions of the eastern Southern Province.
Fig. 1.
�Paper 30
REGIONAL RELATIONSHIPS IN THE PENOKEAN PROVINCE
H.
B. STONEHOUSE
Michigan State University
ABSTRACT
Investigations over the last few years in that area
of the Southern Province of the North American Shield known
as the Penokean Fold-Belt Subprovince, allow some of the
following conclusions to be made:1.
2.
Similar sequences of sediments deposited over a period
of about 600 my (roughly 2.2 by to 1.6 by ago) are of
predominently shallow water origin.
Local tectonic activity occurred during deposition of
these sediments.
3.
Intrusive igneous activity during this period resulted
in basic dikes and/or sills; acid intrsives are minor.
4.
The regional E-W folding increases in intensity to the
5.
Older geological events tend to occur in the eastern
part of the region and younger ones in the west.
6.
Regional tectonism was most intense at some time before
south.
the end of the period.
Events which took place within this region during this
time period are pit into the context of cause-effect relationships and a regional-time pattern; a better geological
understanding results.
The evidence strongly suggests that the area be re-
designated as "The Penokean Province" and that the term
"Penokean Orogeny" be replaced by "Penokean Tectonic Sequence".
�Paper 31
AGES OF SONE PRECAi4BRIAN ROCKS IN EAST-CENTRAL NINNESOTA
J. S. Stuckless
Department
Northern
and
S. S. Goldich
of Geology
Illinois University
Illinois 60115
DeKaib,
ABSTRACT
The McGrath Gneiss, formerly assigned to the Penokean orogeny, l6Oo-lOO m.y.
ago, was actually emplaced in a Lower Precambrian terrane during the Algoman
orogeny, approximately 2700 m.y. ago. Locally the gneiss is intensively
sheared. This phase of the deformation is related to epeirogeny that followed
the regional metamorphism of the Middle Precambrian formations.
Rb—Sr isochron studies of igneous rocks that were emplaced following
folding and regional metamorphism place a minimum age of 1900 m.y. on the Mid-
This age is somewhat older than the 1850
m.y. age obtained by Z. E. 'Peterman for the metasedimentary rocks of the Cuyina
district and is considerably older than the previous K-Ar and Rb-Sr mica age
determinations.
The McGrath Gneiss appears to be extensive in east-central Minnesota; hence,
it is likely that the Middle Precambrian rocks of Minnesota were all- deposited
on an erosion surface developed on an Archean continental crust rather than on
oceanic crust.
dle Precambrian Thomson Formation.
�Paper 32
GEOCHRONOLOGY OF PRECAMBRIAN ROCKS IN THE PENOKEAN
FOLD BELT SUBPROVINCE OF THE CANADIAN SHIELD
W.
R.
Van Schmus
Department of Geology
University of Kansas
Lawrence, Kansas
66044
ABSTRACT
The Penokean Fold Belt subprovince is that part of the
Southern Province consisting of the folded and metamorphosed
Middle Precambrian rocks which occur in an E-W trending belt
running south of Lake Superior and north of Lake Huron.
Included within this belt are strata of the Huronian, Marquette
Range, and Animikie supergroups and associated economic deposits.
For many years these rocks have been considered possible corre-
latives, and the folding, metamorphism, and intrusive activity
have been referred to as the Penokean Orogeny.
Recent and current field and laboratory studies now show that
the orogenic history of this region can not be represented by a
single major orogenic episode. Instead, this portion of the
North American continental plate was affected by a succession of
events over the interval 2.7 to 1.1 b.y. ago.
The oldest Proterozoic rocks are apparently those in
Ontario, north of Lake Huron. In this area Huronian strata
overlie a 2.7 b.y. old basement and are intruded by the 2.16
b.y. old Nipissing Diabase. To the west, in Upper Michigan, the
Proterozoic sedimentary and volcanic rocks, the Marquette Range
supergroup, are apparently younger, being between 1.90 and 2.05
b.y. old, and thus not correlative with true Huronian rocks.
Farther west, in Minnesota, the Animikie rocks may be partly
correlative with and partly younger than those in Michigan and
Wisconsin.
There have been multiple periods of intrusive, metamorphic,
and tectonic activity. The oldest Proterozoic deformation
apparently occurred about 2.15 b.y. ago in Ontario, affecting
the Nipissing Diabase and Huronian rocks. A major episode of
igneous, metamorphic, and tectonic activity occurred about 1.9
+ 0.1 b.y. ago, affecting most, if not all, of the E-W trending
belt from Minnesota to Ontario.
This event would appear to be the
one most representative of a uPenokean Orogeny.'
Subsequent to the main orogenic activity several intrusive and!
or metamorphic episodes have occurred, about 1.65, 1.5, and 1.3
b.y. ago. Several of these younger events may be correlated with
the Middle Precambrian history of Wisconsin and the rest of the
Midcontinent. Finally, much of the area was affected by Keweenawan
igneous activity and associated metamorphism 0.9 to 1.2 b.y. ago.
�Paper 32
-2-
On the basis of present geologic and geochronologic data,
it appears reasonable to interpret the Penokean Fold Belt as an
orogenic belt developed along the southern edge of the
Superior craton about 1.9 billion years ago. The exact nature
of this structural belt and its possible relation to arc-trench
sequences of present models of plate tectonics must await further
work.
�Paper 32
SELECTED BIBLIOGRAPHY
Aldrich, L. 1., Davis, G. L., and James, H. L., 1965, Ages of
Minerals from metamorphic and igneous rocks near Iron
Mountain, Michigan: Jour. Petrology, v. 6., p. 447-.472.
Banks, P. 0., and Cain, J. A., 1969, Zircon ages of Precambrian
granitic rocks, northeastern Wisconsin:
77, 208-220.
Jour. Geology,
R. , 1971, Chronology of Precambrian rocks of Iron and Dickinson Counties, Michigan
(Abs.). 17th Annual Institute on Lake Superior Geology,
Duluth, Minn., May.
Banks, P. 0. and Van Schmus, W.
Bass, M. N., 1959, Mineral age measurements --Wisconsin:
Inst. of Washington Year Book, 58, 246-247.
Carnegie
Dickinson, W. R., 1971, Plate tectonic models of geosynclines:
Earth Plan. Sci. Letters, 10, 1965-174.
Dott, R. H., Jr., 1969, Isotopic dating of the Baraboo and Waterloo
quartzites. 15th Institute of Lake Superior Geology,
Oshkosh, Wisc., p.15.
Dutton, C. E. , and Bradley, R. E. , 1970, Lithologic, geophysical,
and mineral commodity maps of Precambrian rocks in Wisconsin.
U. S. Geol. Surv. Map set 1-631, with accompanying pamphlet
(15 pp.).
Fairbairn, H. W., Hurley, P. M., and Pinson, W. H., 1960, Mineral
and rock ages at Sudbury-Bling River, Ontario: Geol. Assoc.
Canada Proc., 12, 41-66.
Fairbairn, H. W., Hurley, P. M., Card, K. D., and Knight, C. J.,
1969, Correlation of radiometic ages of Nipissing diabase
and Huronian metasediments with Proterozoic orogenic events
in Ontario. Can. J. Earth Sci., 6, pp. 489-497.
Faure, G., and Kovach, J., 1969, The age of the Gunflint Iron
Formation of the Animikie Series in Ontario, Canada. Geol.
Soc. America Bull., 80, 1725-1736.
Goldich, S. S., Nier, A. D., Baadsgaard, H., Hoffman, J. H., and
Krueger, H. W. , 1961
nology of Minnesota:
Krogh
T.
E. ,
,
The Precambrian geology and geochro-
Minnesota Geol. Survey Bull. 41.
and Davis, G. L. , 1971, the Grenville Front inter-
preted as an ancient plate boundary:
Washington Year Book, 70,. 239-240.
Carnegie Inst. of
Peterman, Z. E., 1966, Rb-Sr dating of middle Precambrian metasedi-
nientary rocks of Minnesota.
1031-1044.
Geol. Soc. America Bull., 77,
Van Schmus, R., 1965, The geochronology of the Blind River-Bruce
Mines area, Ontario, Canada: J. Geol., 73, 755-780.
Woolsey, L. L., 1971, A Rb-Sr geochronologic study of the Repi.iblic
metamorphic node, Republic, Michgn. Unpub. M. S. Thesis,
Univ. of Kansas, Lawrence.
�Paper 33
STRATIGRAPHY AND SEDIMENTATION OF THE ESPANOIA FORMATION,
AN EARLY APHEBIAN (MIDDLE PRECAMBRIAN)
CARBONATE UNIT
GRANT M. YOUNG
Department of Geology
University
of Western Ontario
London, Ontario
ABSTRACr
The Espanola Formation is unique among Huronian formations in its
high carbonate content. It forms part of the Quirke Lake Group, lying
between the Bruce Formation (beneath) and the stratigraphically higher
Serpent Formation. The Bruce Formation is mainly unstratified sandy
polymictic paraconglomerate (tillite) whereas the Serpent Formation
consists mainly of cross bedded felspathic quartzites.
In the Quirke
Lake area the Espanola Formation is divisible into three units, here
called, in ascending order, limestone member, siltstone member and
dolostone member. Some fifty miles to the southeast these three members
can still be recognised but the central, dominantly terrigenous clastic
unit, is much thicker.
In the southern area there is also an additional
thick upper member which displays fining upwards cycles (from conglomerate
to mudstone) similar to those attributed to fluvial deposition.
In the Quirke Lake area the Espanola Formation contains both intraformational and intrusive breccias. The intrusive breccias are later
than some faulting and transect clastic dykes. They are considered to
be downward intrusions caused by release of high pore pressure in watersaturated sediments along fissures in the already lithified Espanola
Formation. The triggering mechanism for the breccias may have been earth
tremors associated with early (pre-Gowganda) earth movements for the
breccias appear to be spatially related to areas where there is evidence
of disconformable/unconformable relations between the Gowganda Formation
and older Huronian rocks.
Cross bedding studies, mainly from the highest member of the Espanola
Formation in the southern part of the Huronian outcrop belt, reveal a
bimodal pattern with dominant modes in the south-west quadrant and towards
the E.S.E.
Microprobe analyses of the carbonates of the dolostone member showed
that the rusty-weathering dolostones are composed of ferruginous dolomite.
The Espanola Formation is interpreted as a post-glacial transgressiveregressive cycle (Fig. 1). The limestone and dolostone members are thought
to be shallow water deporits while the siltstone member represents a deeper
water facies (involving some turbidite transportation). The sandstone
member of the southern region is thought to have been laid down from
meandering streams which initiated sedimentation of the thick prograding
fluvial sequence of the Serpent Formation.
�0
.,-4
C.
S
S
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'.4
00
00
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0
FIG. 1,
F-
LU 0.0
,-l
us
C
w
C. .0
'0
NW
I
I
(turbidite facies)
SERPENT FORMATION
SPACE - TINE RElATIONSHIPS DURING SEDIMENTATION OF THE ESPMTOLA FORMATION
TRANSPORT DIRECTION
DOMINANT SEDIMENT
UPLIFT AND EROSION
REGION OF CONTEMPORANEOW
UPLIFT
—
ESPANCLA
Southern limit of
SUBS! DEN CE
REGION
ZONE OF TECTONIC
Northern Limit of
preserved Huronian
ZONE OF TECTONIC
TECTONIC HINGE
ORMATION
SE
III
•
�Paper 34
WEATHERING AND METASOMATISM OF THE PRESQUE ISLE SERPENTNIZED
PERIDOTITE, MARQUETTE COUNTY, MICHIGAN
M. D, LEWAN
Michigan Technological University
ABSTRACT
Presque Isle Park, Marquette, Michigan is underlain by a mass
of peridotite, probably cut by Archean granite and definitely cut
by a diabase dike of probable Keweenawan age. The three rock
types grade upward into a complex altered zone that has variable
thickness and mineralogy, depending upon the rock type it occurs
on. This zone is comprised of a lower zone of dolomite-silica.
and an upper zone rich in silica, which in turn is unconformably
overlain by Jacobsville Sandstone.
Data from major element analysis of 42 rocks, qualitative mineralogy determinations by X-ray diffraction, and field observations
indicate that the peridotite has undergone three periods of alteration; 1 )early s erpentinization, 2)carbon dioxide meta somatism
after emplacement, and 3)weathering after the area was exposed
to surface conditions. The granite has also undurgone the same
sequence of alteration with the exception that the first period of
alteration was illitization. On geological and geochemical grounds
the serpentinization and illitization processes could not have been
contemporaneous.
The forming of the silica rich weathered zone, which is best developed over the granite, is the result of weak acidic meteoric
waters dissolving dolomite out of the dolomite-silica zone. Chemical and mineralogical profiles show that the removal of dolomite
results in the upward concentration of residual minerals such
as quartz, rutile, hematite, chlorite, and illite. The weathered zone
was searched for nickel concentrations such as garnierite, but
none were found.
Field evidence indicates that the weathering and metasomatic
alteration post-dates the intrusion of the probable Keweenawan
dike and pre-dates the deposition of the Jacobsville Sandstone.
Jacobsvifle Sandstone
p
Basal Conglomerate 8
Silica-Rich weathered zone
c
°
-—
Dolomite-Silica zone
,
Diagramatical sketch(not to scale) showing the relationship
between
the rock units on Presque Isle..
�
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,CY C
�FIELD GUIDE TO THE GEOLOGY
GEOLOGY OF
OF THE
THE
KEWEENAW PENINSULA,
PENINSULA, MICHIGAN
BY
J. Bornhorst
Theodore J.
William I.
I. Rose,
Rose, Jr.
Jr
William
James B.
B. Paces
Department of
of Geology and Geological Engineering
Michigan Technological University
University
Houghton,
Houghton, Michigan 49931
FOR SALE
SALE AT:
AT:
E. R.
R. Lauren Bookstore,
Bookstore, Memorial Union
E.
Michigan Technological University
Houghton, Michigan 49931
Houghton,
Prepared as
field trip
trip guide
guide for
for the
the 29th Annual
Institute
as aa field
Annual Institute
on Lake Superior Geology held
held at
at Michigan
Michigan Technological
Technolo~ical
University on May 11—14,
11-14, 1983.
1983.
FIRST EDITION
May, 1983
May,
COVER PHOTO: Miners
Miners at
at the
the
Mine(?) circa
circa 1910.
1910.
Baltic Mine(?)
Michigan Technological University Archives and Copper
Country Historical Collections.
Collections.
�PREFACE
—
It
is presumptuous
presumptuous for
for us
us to
put together
is based
based mainly
mainly on
on the
the work
work
It is
to put
together aa book which is
of others. We have done so because hundreds of people come to
of
to the Keweenaw each
year to
to look
look at
at geological
geological features
features and
and many
many of
of them
them ask
ask us
us for
for advice.
advice. So we've
tried to
tried
to communicate with people
people who
who are
are doing
doing serious
serious geological
geological field
field trips.
trips.
This is
is a first
first draft of an evolving document,
document, which we expect to
to continually rerePlease help
help us
us make
make it
better by
by suggesting changes,
changes, finding
finding mistakes
mistakes and
and
Please
it better
vise.
telling us what we've
we've left
left out.
out.
Starting with Douglass
Douglass Houghton almost
almost 150 years
years ago,
ago, dozens
dozens of
of geologists
geologists have
have
contributed aa mountain of
of geological
on the
the Keweenaw
Keweenaw which
which makes
makes it
it
contributed
geological information
information on
aa real challenge to
to compile this
this book.
book. The greatest
greatest contribution by far
far has come
come
from
from Walter
Walter S.
S. White,
White, who
who devoted
devoted much of
of his
his professional
professional career
career to
to Keweenawan
Keweenawan
whose impact
geology and whose
impact can
can be traced
traced to
to virtually
virtually every
every page
page of
of this
this book.
book.
of his
his
We hope that
that we have faithfully
faithfully transmitted his
his ideas with a
a fraction
fraction of
enthusiasm.
ingenuity and enthusiasm.
Houghton
Houghton
30 March 1983
i1
�TABLE OF CONTENTS
Page
i
PREFACE
iii
HOW TO USE THIS GUIDE
GUIDE
iv
LIST OF
OF STOPS
STOPS
vlii
viii
LIST OF MAPS
ix
LIST OF FIGURES
xi
LIST OF
OF TABLES
TABLES
INTRODUCTORY NOTES ON THE GEOLOGY
OF THE KEWEENAW PENINSULA
11
17
17
ROAD LOG AND STOP DESCRIPTION
INDEX TO GEOLOGY ON NAPS
MAPS IN
IN THE FIELD
FIELD GUIDE
GUIDE
111
111
112
112
REFERENCES
11i
i
�HOW TO USE THIS GUIDE
To make all the
the stops
stops listed
listed in
in this
this guide
guide would
would take
take three
three days.
days. If
If you wish
to
to emphasize certain types
types of
of stops,
stops, we
we recommend
recommend the
the following
following subsets:
subsets:
Suggested Stops
Stops
Sediments
Sediments
Volcanic Rocks
Mineral Deposits
Broad Coverage
5,
6, 8,
8, 9,.
16, 17,
17, 19,
19, 20,
20, 24
24
10, 13,
13, 16,
5, 6,
9, 10,
1,
15, 16,
16, 17,
17, 18,
18, 21
21
1, 3,
3, 11,
11, 12,
12, 13,
13, 14,
14, 15,
2,3,4,7,11,13,17,22,23
2,
3, 4, 7, 11, 13, 17, 22, 23
3,
6, 10,
10, 11,
11, 13,
13, 16,
16, 18,
18, 19,
19, 20,
20, 24
24
3, 6,
Be imaginative and make up
up your own
own subset
subset of
of stops.
stops.
stops are
are on
on or
or near
near private
private land.
land. Please respect private property.
property. The preMany stops
Sent
problems
of
access
are
minimal,
but
obviously
we
could
ruin
we don't
don't
sent problems of access are minimal, but obviously we could ruin things
things if
if we
use low profile outdoor principles.
principles. AA few
few stops
stops are
are located
located ot
on old mine dumps.
dumps.
These can be hazardous,
hazardous, especially
especially where
where bad
bad ground
ground occurs.
occurs. Use common sense.
sense.
-
have north
north to
to the
the top
top and
and are
are 1:24,000
1:24,000(4(4cmcmtoto1 Ikin).
km).
All maps have
road log route on the
the maps,
maps, while
while stars
stars mark
mark the
the stops.
stops.
follow the
the
Dots follow
Mineral collectors have long
long flocked
flocked to
to the
the Keweenaw to
to collect its
its unusual minerals.
minerals.
One of the best
in the world
located at
this
best mineral museums in
world is located
at the starting point
point of
of this
field trip.
trip. The Seaman Mineralogical Museum,
Museum, open from 9:00—4:30
9:00-4:30 weekdays,
weekdays, is
is housed
housed
in the
the EERC
EERC Building,
Building, Fifth Floor,
in
Floor, on
on the
the Michigan
Michigan Tech
Tech Campus.
Campus. The mineralogical
over the
the Keweenaw and is
collection includes
includes samples
samples from
from all over
is aa must for
for all
all rockhounds.
rockhounds.
111
iii
�STOPS
LIST OF STOPS
The following
used to
to help
help you
you design
design your
your own
own field
field trip
trip
following list of stops can be used
to
to see the geology of the
the Keweenaw Peninsula.
Peninsula. The location
location of
of stops
stops are
are shown
shown
in Figure la.
la. The appropriate maps for
for each stop and trip
trip route are located
in Figure
Figure lb.
lb.
—
—
STOP
MAP)
(APPROPRIATE MAP)
STOP DESCRIPTION
STOP
11
(1)
(1)
Ophitic Scales Creek basalt flow and Keweenaw
view, 7th
7th St.,
St., Houghton.
Houghton.
Waterway view,
2
2
(1)
(1)
Secondary minerals in
in amygdaloid
amygdaloid at
at dump
dump of
of
Isle Royale Mine, Dodgeville.
Dodgeville.
'-" 3
(2)
(2)
Section through a lava
lava flow
flow at
at South
South Range
Range quarry.
quarry.
....---4
(2)
(2)
Secondary minerals in
in amygdaloid
amygdaloid at
at dump
dump of
of
Baltic Mine.
Mine.
5
5
(3)
Glacial deposits on M—26
M-26 south
south of
of Houghton.
Houghton.
6
6
(4)
(4)
Overlook of Keweenaw Waterway,
Waterway, Houghton and the
Range towns;
towns; Quincy
Quincy Hill,
Hill, Hancock.
Hancock.
7
7
(4 )
(4)
Secondary minerals of amygdaloid at
at dump
dump of
of
Quincy
Quincy Mine.
Mine.
8
(6)
(6)
Flat—lying
Flat-lying Jacobsville
Jacobsville Sandstone
Sandstone along
along M—26,
M-26,
near Dollar
Dollar Bay.
Bay.
9
9
(7)
(7)
Hungarian Falls,
Falls, near
near Hubbell.
Hubbell.
Keweenaw Fault at Hungarian
10
10
(8)
(8)
Keweenaw Fault at
at Natural Wall
Wall Ravine,
Ravine, near
near Laurium.
Laurium.
11
(9)
(9)
Secondary minerals in amygdaloid at
at dump
dump of
of
Wolverine
Wolverine Mine.
Mine.
12
(9)
(9)
Ophitic Scales Creek basalt flow,
flow, at Scales Creek
near Copper City.
City.
—- 13
...../13
(9)
(9)
Lava flows
flows of Portage Lake Volcanics and mineralized conglomerate with an excellent
ized
excellent view
view of
of the
the
central part of
of the
the Keweenaw
Keweenaw Peninsula,
Peninsula, Bumble—
Bumbletown Hill.
14
(12)
(12)
Ophitic Greenstone flow and vein mineralogy at
dump of Phoenix Mine.
15
15
(12)
(12)
part of
of the
Portage Lake
Lake
Section through
through the
the upper part
the Portage
Volcanics along
along Eagle
Eagle River.
River.
16
(12)
Contact between Portage Lake Volcanics
Volcanics and Copper
Contact
Harbor Conglomerate
Conglomerate at
at Eagle
Eagle River
River Falls.
Falls.
~.
t/
iv
�STOPS (Cont'd.)
(Contld.)
LIST OF STOPS
STOP DESCRIPTION
STOP
(APPROPRIATE MAP)
17
17
(13)
through the
the upper
upper part
part of
of the
the Portage
Portage
Section through
Lake Volcanics along Owl
Owl Creek
Creek and
and amygdaloid!
amygdaloid/
vein mineralogy at dump
dump of
of Copper
Copper Falls
Falls Mine.
Mine.
v"J.8
"18
(16)
(16)
Lava flows of the
the Lake Shore
Shore Traps
Traps at
at Esrey
Esrey Park.
Park.
V19
\/19
(17)
Overlook of Lake Superior
Superior and
and the
the eastern
eastern end
end of
of
the Keweenaw
Keweenaw Peninsula and outcrops of Copper
the
Harbor Conglomerate at
at Brockway Mountain.
Mountain.
flO
(17)
(17)
Copper Harbor Conglomerate
Conglomerate at
at Dan's
Dan's Point.
Point.
21
(20)
(20)
Diorite and granophyre stock
stock at
at Mt.
Mt. Bohemia.
Bohemia.
22
(21)
Secondary mineralogy of
of veins and
and conglomerate
conglomerate
at Delaware
Delaware Mine'.
Mine~ The Delaware Mine is
is open to
to
tourists for
for aa fee.
fee.
23
(28)
Amygdaloid mineralogy of
of dumps
dumps at
at Osceola
Osceola Mine.
Mine.
24
(30)
at Hancock
Hancock campground
campground quarry.
quarry.
Nonesuch Shale at
v
�I
(
I
.
···i·9*··..······..·····;:;:
;
~
"'-~'L"'"alre Bailey
.
Eagle
. . . f~~;I~.·.:::::::···:< . . . ""C~~r~·I
La e
M.,!dO'~
C
............
Delawar~.~.,2
..'····· ....·····
Copper
Harbor
20
\ 0 "
fifo"
5 IJ
Eagle H ...r-nnr
:._. _
- .~
.-:--~"::::~tS
~-~.
Lak
e Fanny Hooe
Schlstter('..,
•....1
(?
········\···'>... 21
=
LakeV
~
Manitou Island
Island
........ Phoenix
.-:,.,
<f.2
.~.'
i-~
Lake
.../
"to
A:::;!l\(~~:,..•
o
Kearsargei..,.J 1
..i
'···12
-<
~.
McLain State Park
McLain
Park
.rC"aiun;-~t·'·
.f
.-.,1.0...
~~
~~
~\
o~
C,
Laurium
23*/
. Lake Linden
.....
....
Scale
Scale
1
0o
M
I
1
1
2
3
4 miles
4miles
~
Freda
Atlantic
South
~
~ly
~
'"
Painlsdale
Pa in ed a le
12
Stopnumber
number
•2 Stop
Figure
Figure 1A:
1A: Route
Route and
and stop
stop map
map
�SU
~~
\\ \
17
o
o~
13~
~
23
o
12
'I-~
... '"
_0_"
27
./'
<~
t-<t-<.
-.)~
~
~
\
o
~
c.,
8
SCALE
in
in miles
01234
,....
ji"Wiij
o
1
2
.....,
3
p>
4
Dil2
Map number
12
,.*"
I'l
+
~
"
Figure 1B:
18:
*'2
number
Stop number
Index of
of 1:24,000
Index
1:24,000 scale
scale maps
maps
�LIST OF
OF NAPS
MAPS
Page
MAP
MAP
1
18
MAP
MAP
2
22
MAP
MAP
33
26
MAP
MAP
44
31
MAP
MAP
5
35
MAP
MAP
6
39
MP
MAP
77
42
MAP
MAP
88
46
MAP
MAP
9
49
MAP
10
MAP1O
60
MAP
MAP 11
63
MAP 12
MAP
64
MAP13
MAP 13
71
MAP 14
MAP
74
MAP15
MAP 15
76
MAP 16
MAP
77
MAP17
17
MAP
79
MAP 18
MAP
82
MAP
MAP 19
86
MAP2O
t-1AP 20
87
MAP
MAP 21
88
MAP 22
MAP
91
MAP
MAP
23
95
24
MAP24
MAP
96
MAP25
MAP 25
98
MAP26
MAP 26
99
NAP
MAP 27
100
MAP
MAP 28
104
MAP
MAP 29
106
MAP
MAP 30
109
viii
viii
�LIST OF FIGURES
Page
vi
Vi
Figure
1:
1:
Index map
map of
of route,
Index
route, stops and 1:24,000 scale
scale maps.
maps.
Figure
2:
2:
Location of the
the Mid—Continent
Mid-Continent Rift
Rift System.
System.
2
2
Figure
3:
3:
Simplified geologic map,
map, cross—section,
cross-section, and
and strati—
stratigraphic column,
column, western
western Lake
Lake Superior
Superior region.
region.
3
3
Generalized geologic
geologic map of
of the
the western
western Upper
Upper
Peninsula and stratigraphic
stratigraphic section
section of
of the
the Portage
Portage
Lake Volcanics.
4
4
Columnar stratigraphic Section
section of
of rocks
rocks northwest
northwest of
of
the Keweenaw Fault in the Calumet—Ahmeek
the
Calumet-Ahmeek area.
area.
66
rocks
Location of silicic to
to intermediate intrusive rocks
the Portage Lake Volcanics.
in the
Volcanics.
8
8
Figure
Figure
Figure
Figure
4:
4:
5:
5:
6:
6:
7:
7:
Schematic diagram showing interrelationships between
northwest of
of the
major stratigraphic units
units northwest
the Keweenaw
Fault in the
the Keweenaw Peninsula.
10
Geologic and structure
structure maps of
of the
the Keweenaw
Keweenaw native
native
copper district.
district.
13
and paragenesis of
of secondary
minerals
Distribution and
secondary minerals
in
Volcanics.
in the
the Portage Lake Volcanics.
14
14
Elemental mobility in
in an
an idealized
idealized lava
lava flow
flow and
and
diagrammatic
diagra~matic regional model for
for metamorphism
metamorphism of
of
the Portage Lake Volcanics.
the
16
16
Figure 11:
11:
Geologic cross—section
cross-section for
for Map
Map 1.
1.
20
Figure 12:
12:
Geologic profile of South
Sou~h Range quarry.
quarry.
21
21
Figure 13:
13:
Speculative ice—marginal
ice-marginal positions
positions during
during the
the Wis—
Wisconsin ice retreat.
retreat.
27
Figure 14:
14:
End moraine of the
End
the Keweenaw Bay Lobe glacier.
glacier.
27
Figure
Figure 15:
15:
Enlarged view of ice—marginal
ice-marginal positions.
28
Figure
Figure 16:
16:
High level drainage
drainage through
through the
the Portage
Portage Gap.
Gap.
29
29
Figure
Figure 17:
17:
View from
from Portage overlook
overlook facing
facing south.
south.
32
32
Figure
Figure 18:
18:
Structures of the
the Quincy Mine location.
location.
36
Figure 19:
19:
Geologic cross section
section for
for Maps
Maps 4,
4, 5 and 30.
30.
37
37
Figure
Figure
8:
8:
9:
9:
Figure 10:
10:
ix
�Page
Figure 20:
20:
Relationships of
of Jacobsville Sandstone.
Sandstone.
40
21:
Figure 21:
Geologic sketch map of
of Hungarian Falls
Falls area.
area.
44
Figure 22:
22:
Wall Ravine.
Ravine.
Geologic sketch map of
of Natural Wall
47
Figure 23:
23:
Geologic
Geologic map
map and
cross section,
Wolverine Mine and
and
section, Wolverine
arid cross
vicinity.
51
Figure 24:
24:
Thickness of
of the
the Kearsarge
Kearsarge flow.
flow.
52
Figure 25:
25:
Paragenesis of secondary minerals in
in the Kearsarge
amygdaloid.
52
Cross section
section of
of Kearsarge
Kearsarge amygdaloid
amygdaloid showing
showing the
Cross
the
banding of
of mineral assemblages.
assemblages.
54
Distribution of quartz,
quartz, microcline and high grade
ore in
in the
the Kearsarge
Kearsarge amygdaloid.
amygdaloid.
native copper ore
55
Figure
Figure 28:
28:
Outcrop map of
of the
the Allouez—Bumbletown
Allouez-Bumbletown Hill
Hill area.
area.
57
Figure 29:
29:
Map and section of the Greenstone flow between
Seneca and the
the Cliff
Cliff Mine.
Mine.
61
Figure 30;
Figure
3O
Map and section
section of
of the
the Greenstone
Greenstone flow
flow near
near Phoenix.
Phoenix.
66
66
Figure
Figure 31:
31:
Stratigraphy of the Portage Lake Volcanics
Volcanics above
above the
the
Greenstone flow.
flow.
Greenstone
68
68
Plot of K20 and P205 content of 106 individual
individual Portage
Lake Volcanic flows
flows in
in stratigraphic
stratigraphic order.
order.
69
69
Schematic cartoon
cartoonofdepositional
Schematic
of depositional environment
environment of
of the
the
Copper Harbor Conglomerate.
Conglomerate.
83
83
Measured section of Copper Harbor Conglomerate at Dan's
Dants
cartoon of
of the
the depositional
depositional environment.
environment.
Point and cartoon
84
84
Geologic map showing andesitic dikes near Mount Bohemia
and occurrence
occurrence and
and paragenesis
paragenesis of
of secondary
secondary and
and opaque
opaque
and
in the
the dikes.
dikes.
minerals in
90
90
map and development of
Sketch map
of the
the Keweenaw
Keweenaw Fault
Fault in
in
of Deer
Deer Lake.
Lake.
vicinity of
93
93
Figure 26:
26:
Figure 27:
27:
Figure
Figure 32:
32:
Figure
Figure 33:
33:
Figure 34:
34:
Figure 35:
35:
Figure
Figure 36:
36:
Figure 37:
37:
Figure 38:
38:
Schematic illustration
of the
the funnelling
effect on
on
Schematic
illustration of
funnelling effect
fluids, Kingston
Kingston conglomerate.
conglomerate.
mineralizing fluids,
102
102
Results of gravity
gravity measurements across the Bear Lake
on Map
Map 29.
29.
traverse plotted on
108
108
x
�LIST OF TABLES
Page
Table 1:
1:
Secondary minerals found
found within
within the
the Portage
Portage
Lake Volcanics.
Volcanics.
11
Table 2:
2:
Major—element
Major-element composition
composition of
of the
the Kearsarge
Kearsarge flow.
flow.
51
Table
Table 3:
3:
Volume percent amygdule minerals from mapped
assemblages shown in
in Figure 26.
26.
54
Average major—element
major-element composition of the
the Scales
Creek
Creek flow.
flow.
57
57
Table 4:
4:
Table
xi
�INTRODUCTORY NOTES ON THE GEOLOGY OF
THE KEWEENAW PENINSULA
PENINSULA
General Background
The Mid-Continent
Mid—Continent Rift
Kansas to
Lake Superior
Superior
Rift System extends northeasterly from Kansas
to Lake
It was
was formed
and then southeasterly through
and
through lower
lower Michigan
Michigan (Fig.
(Fig. 2).
2). It
formed about 1.1
1.1
to
1.2 b.y.
b.y. ago
ago (Keweenawan
age) by
by extensional
extensional thinning
of the
the rigid
rigid Precambrian
Precambrian
to 1.2
(Keweenawan age)
thinning of
Superior crustal block (Kiasner
(Klasner and
and others,
others, 1982).
1982). Present day crustal thickness
thickness
the Lake Superior region,
region, however,
however, is
is between
between 40
40 and
and 50
50 Km,
Km, which
which is
is thicker
thicker
in the
than
than adjacent areas
areas (Halls,
(Halls, 1982).
1982).
-—
Peninsula is
is located
located on
on the
the margin
margin of
of the
the Lake
Lake Superior
Superior Basin,
Basin,
The present Keweenaw Peninsula
one of
of the
one
the basins within the
the Mid—Continent
Mid-Continent Rift
Rift System
System (Fig.
(Fig. 3).
3). The volcanic and
sedimentary rocks
rocks on the northwest side
side of
of the
the Keweenaw
Keweenaw Peninsula
Peninsula generally
generally dip
dip
toward Lake Superior and include the Portage Lake Volcanics,
moderately toward
Volcanics, Copper
Copper
Conglomerate, Nonesuch Shale
Shale and
and the
the Freda
Freda Sandstone.
Sandstone. The Jacobsville Sand—
SandHarbor Conglomerate,
stone
stone occupies the southeast side
side of
of much of
of the
the Keweenaw
Keweenaw Peninsula
Peninsula and
and is
is in
in
fault
along the
the Keweenaw
Keweenaw Fault.
Fault. The Jacobs—
Jacobsfault contact
contact with the Portage Lake Volcanics along
ville Sandstone is
however, it
it
is probably slightly younger than the
the Freda Sandstone,
Sandstone, however,
is
still most
most likely upper Keweenawan in
is still
in age
age (Kalliokoski,
(Kalliokoski, 1982).
1982).
At some time after the deposition of basin filling
filling sediments,
sediments, the Lake Superior
region was
was subjected to compression roughly
region
roughly normal
normal to
to the
the basin
basin axis.
axis. These
stresses
in the
the Keweenaw
Keweenaw and
and Isle
Isle Royale
Royale Faults,
Faults, both
both high
high angle reverse
reverse
stresses re~ulted
reulted in
faults
faults near
near the margins of the
the Lake Superior
Superior Basin
Basin (Fig.
(Fig. 3).
3). This faulting steepened
the dips
the Peninsula
Peninsula and
and on
on Isle
Isle Royale.
Royale. Definite age
the
dips of
of strata exposed on both the
relationships between
between reverse
reverse faulting
faulting and
and deposition
deposition of
of the
the Jacobsville
Jacobsville Sandstone
Sandstone
relationships
are unclear:
unclear: faulting
syn- or wholly post—depositional.
post-depositional.
faulting may
may be partially syn—
The Lake Superior Syncline was affected
affected by aa regional
regional burial metamorphic and/or
hydrothermal event.
event. Remobilization of many elements,
elements, particularly within the
the Portage
Lake Volcanics,
Volcanics, caused
lava flow
caused strong alteration of
of lava
flow tops
tops and
and interbedded
interbedded concon—
glomeratic units.
units. Native copper deposits of the
the Keweenaw Peninsula are believed to
to
formed wholly or in
in part
the deposition of
of the
the Freda SandSandhave formed
part after
after the
of much or all of
stone (White,
(White, 1968).
1968).
Paleozoic geologic
geologic processes
processes were
were largely
largely atectonic.
atectonic. Sediments associated with the
the
Michigan basin probably once covered the
the Keweenaw Peninsula,
Peninsula, as evidenced by the
the
isolated
limestone at
at Limestone
Limestone Mountain
Mountain and
and Sherman
Sherman Hill,
Hill,
isolated occurrence of
of Ordovician limestone
about 20 miles south
about
south of Houghton. The present day landscape of the
the Keweenaw Peninsula
is strongly
strongly influenced by Pleistocene glaciation.
is
glaciation.
Stratigraphy
The bedrock geology of the
the Keweenaw Peninsula consists of five major stratigraphic
units. Portage Lake Volcanics,
Volcanics, Copper Harbor Conglomerate,
Conglomerate, Nonesuch Shale,
Shale, Freda
Sandstone and Jacobsville Sandstone
Sandstone (Figs.
(Figs. 33 and
and 4).
4). The accumulated maximum
thickness of
of these
these units
units is
is over
over14,000
14,000in.
m. The bedrock in the Keweenaw Peninsula
is unconformably capped by a variety of
is
of glacial
glacial deposits.
deposits.
�2
2
A.
o0
-=
KM
t000
1000
KM
ORIENTATIONS
ORIENTATIONS OF SEGMENTS
SEGMENTS OF
THE MIDCONTINENT RIFT
RIFT
B.
---1\
l.
I
"----...
N670,E
N67 E
"~
f,
,
1.
----,j--,
,
~
0
N38 E(
i---~~
;:'-3~'E
\
,
1
j
2: Location of the
the Mid—Continent
Mid-Continent Rift
Rift System.
System. A.
Major Proterozoic
A.
Figure 2:
rifts of
of North
North America
America (from
(from Burke,
Burke, 1980).
1980). B.
B. Orientation of
and Paleozoic rifts
individual
the Mid—Continent
Mid-Continent Rift
Rift System
System (from
(from Kiasner
Klasner and
and others,
others,
individual segments of the
1982).
�r-
lie
i
~
"
II
iA*'
I
0
-
Nipigon
Sand,,,,",,.
o
JACOBSVILLE-BAYFIELD
UP
UPTO
TO5000'+
500O
I
f Cambrian &nd
_
latesa: Kewc:etUlwu
49.
'9"
ONTARIO
'\
Coppc:r Harbor Conalomcf1ue
-/'-'-,
'\;Z~'-S~10' /",-,
-
""~O'~';ES
o
Kewecnaw&.l'l voleank: s.cquence,
including Portage Lake Voleanic;s
,- __
~
FREDA SANDSTONE
SANDSTONE
UP TO
UP
70 12,000'+
2000+
-1030
Ma (m,n.)
IO30Mo(n,n.)
0::
W
0..
0..
0
MINNESOTA
=:l
.,.
aa..
:3
:::>
47.
0
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REGION—distribution of
of selected
selected rock units.
SUPERIOR REGION-distribution
units,
o0
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zz
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COPPER HARBOR
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PORTAGE LAKE
PORTAGE
VOLCANICS
9000'
9000 -15,000'.
-(5,000.
::J
I
(include unnamed
ufl0med
(Include
formation in west
UP)
formation
west U.P.)
VW
·YW
ThUNDER BAY
THUNDER
REGION
REGK>N
KEWEENAW
1Sl..£ ROYALE
[,lK£
SUPt.RIOR
S£
ct jjjp
LU
W
1
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o
co
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VERTICAL SCALE
VERTICAL
EXAGGERATED
EXAGGERATED
SOUTH RANGE
RANGE
SOUTH
VOLCANICS
(North Shore
~
Volcanics)
Volconics)
G]J
t'ostvolcanic
rrvludrg
Poslvolcamc sodimenbo
sc:dimenUry rocks.
rocks. including
the Copper
Copper Harbor
Harbor Conglom.::rale
Conglomerate
the
tntrrbnddnd volcanic
sedimentary ro<:h.
rnck,.
InltrbeJded
VOIcMic and
and seJimcntary
nolading the
the Portage
Portage Lake
Lake VolcanICS
'olratncs
Including
Prevolcanic
Pynvolcanic rocks
rock,
a:
indrcale relative
relative directions
directions
Arrows indicate
of movement along faults
BESSEMER &
BESSEMER
B BARRON
BARRON
QUARTZ lIES
QUARTZITES
LU
w
~
LAKE
LAKE SUPERIOR
SUPERIOR BASIN—cross
BASIN--cross section.
MIDDLE
-
I
BASEMENT
PRECAMBRIAN ,v•°°: I
Figure 3:
3: Simplified geologic map,
map, cross—section,
cross-section, and
and stratigraphic
stratigraphic column
column of
of upper
upper
Precambrian rocks
in
the
western
Lake
Superior
region
(map
and
cross—section
from
rocks in
Lake Superior region (map and cross-section from
Huber,
column from
from Daniels,
Daniels, 1982).
1982).
Huber, 1975; stratigraphic column
w
�4
NE
SW
NATIVE COPPER
< aw
2
0
2
•°
.
.4
EEl
>
wo
0a—a-
.4
F
MINES
—
2000 —,
oo —1
1000
2000
3000 —
4000
5000
€000
—
Location at onion within
atratigraphic anc lion
Aanraalmnln upFnn limIt at apiaatn & aaa'tn
Approalmate
Figure
lawn, lion It at
A. Generalized geologic map of upper Precambrian rocks of western Upper
4:
B. GeneralPeninsula, Michigan. Hatched area is represented in cross—section in B.
ized stratigraphic section of the Portage Lake Volcanics from Victoria to Copper Harbor (modified from Stoiber and Davidson, 1959). The major marker horizons and mines
are shown. The dashed and dotted lines represent the approximate stratigraphic limits
of secondary epidote and quartz and prehnite respectively.
�Portage Lake Volcanics
The Portage Lake Volcanics is a succession of more than 200 individual basaltic
lava flows with a total thickness of 2500 m to 5200 m (Butler and Burbank, 1929;
Huber, 1973; White, 1968) (Fig. 4).
White (1960) recognized these volcanics as
a thick pile of subaerial tholeiitic flood basalts.
They are the product of rift
zone magmatism and are comparable to the rift zones of East Africa and Iceland
(Basaltic Volcanism Study Project, 1981; Chase and Gilmer, 1973; Green, 1977 and
1982; White 1960 and 1972).
Volcanism was apparently controlled mainly by eruptions from fissures located under Lake Superior.
The Portage Lake Volcanics are
others,
1982).
about 1,100 m.y. old (Van Schmus and
Most of the lava flows are difficult to follow laterally with confidence.
The
Scales Creek, Kearsarge and Greenstone flows are the best documented laterally
continuous flows.
The Greenstone flow can be correlated to Isle Royale (Huber,
1975; Longo, 1982).
There are thin conglomerate and sandstone beds throughout
the section and these are excellent marker horizons (Fig. 4).
The sediment inter—
beds in all but the uppermost part of the Portage Lake Volcanics have been given
names and are shown on the maps included in this field guide (Fig. 5).
The inter—
bedded sediments make up approximately 3 to 8% of the formation (White, l971a). The
conglomerates of the Calumet area the host rocks for large native copper deposits.
The lithology of the conglomerates is dominated by clasts of rhyolitic volcanic
rocks (Merk and Jirsa, 1982).
The frequency of interbedded sediments increases in
Eventually volcanism waned and sediment deposition
the upper part of the formation.
became dominant, the overlying Copper Harbor Conglomerate.
The dominant composition of the lava flows of the Portage Lake Volcanics is tholeiitic
basalt.
Dikes of mafic and intermediate composition cut the volcanic pile but are as
unconmion.
a whole
Silicjc. volcanic and subvolcanic rocks comprise less than 1% by
volume of the exposed Portage Lake Volcanics (Bornhorst, 1975; Grimes, 1977; Robertson, 1974; Robertson and others, 1979).
They tend to be in the lower part of the
stratigraphic section in the Keweenaw Peninsula (Fig. 6).
The composition of volcanic rocks of the Portage Lake Volcanics was affected by both
Primary magmatic differentiation has long been
igneous and metamorphic processes.
recognized both within and between tholejitic flows (Broderick, 1935; Broderick and
For example, the Greenstone flow, the thickest
Hohl, 1935; Cornwall, l95la and b).
individual flow in the formation (Figs. 4 and 5), is chemically stratified due to
Copper may have conceninternal differentiation (Cornwall, l951b; Longo, 1983).
differentiation
trated in the pegmatitic
and more importantly in the flow tops.
Work by Scofield (1976) demonstrated that copper can also be concentrated in the
Rose and Grimes
base of individual flows by gravitational setting of magnetite.
(1979) showed the existence of three magmatic cycles within the Portage Lake Vol—
canics which initiate with basalts that have high incompatible element abundances.
The degassing of volatiles during and after eruption in an oxidizing subaerial
environment was also important in that it allowed degassing of SO2 (Cornwall, 1951c).
This created a sulfur deficient environment which favored the later deposition of
native copper. A third pre—metamorphic process was deuteric or diagenic alteration
of olivine and glass to hydrous minerals, the most important of which is chlorite.
Ljvnat and others (1976) used '3D and '3180 to show that the basalts have undergone
extensive isotopic exchange with low—temperature meteoric waters prior to metamorphism/hydrothermal mineralization. After emplacement the volcanic pile was subjected to extensive low—temperature, low—pressure hydrothermal/metamorphic alteraThe Portage Lake Volcanics on the Keweenaw Peninsula are in fact a classic
tion.
�6
Feet
FR EDA SANDSTONE
ci
,.,', Lava unit
0
AND
fn
..
COPPER HARBOR
0
NONESUCH SHALE
CONGLOMERATE
0
06
0.-A
0
00
0
12,000
c
a
15,000
=-
- Lava unit
c
000
o
—
QO
4
00
0
0
0
0-0
•0
0
o00
000
00
0
•2.0
.
00
.
0
0
0
11,000
c
14,000
1.
.:
PORTAGE LAKE
LAVA SERIES
Lava unit
ci
:0
10000
c
13,000
.
Figure
Columnar stratigraphic section of rocks northwest of the Keweenaw
5:
Fault in the Calumet—Ahmeek area (from White and others, 1953). The labels
for units within the Portage Lake Volcanics are consistent with those used on
the maps in the field guide.
�C
phc
paf
T
Hancock conglomerate
(No. 17)
Ashbed flow
pp
9000
—
-—
Pewabic West conglomerate
(No. 16)
pk
Kearsarge flow
pv
Wolverine sandstone
(No, 9)
4000-
poc
Old Colony sandstone
(unnumbered)
3000pg
Greenstone flow
pa
Allouez conglomerate
(No. 15)
4
orta
-
Lak
'r,Icanics
ph
Houghton conglomerate
(No. 14)
7000
pi
Scales Creek flow
psc
2000 -
Iroquois flow
——
=
pc
-
conglomerate
TI
(No. 13)
1000P0
pkc
flow
Kingston conglomerate
(No. 12)
Pcc
Copper City flow
PS
5000
St. Louis conglomerate
(No.6)
Figure
5
continued.
�8
STUDY AREA
Lake Superior
COPPER HARBOR
INDEX MAP OF NORTHERN
MICHIGAN
EAGLE RIVER
Fish Cove
I..: LacLo_
atiot Lake
Cambrian
Jacobsvil le Sandstone
Upper Keweenawan
Precambrian
loge - .-.•.
.
.
10 Miles
Figure 6:
Portage Lake Lava Series
Intrusive or extrusive body
Bedrock geology of the Keweenaw Peninsula showing the location of silicic to intermediate volcanic and subvolcanic rocks (from
Robertson, 1975).
�9
locality of abundant and widespread low temperature alteration minerals (Table 1).
Penetrative deformation did not accompany the metamorphic episode and primary
textures are preserved even in the most intensely recrystallized areas.
Copper Harbor Conglomerate
The Copper Harbor Conglomerate conformably overlies and locally interfingers with
the Portage Lake Volcanics (Fig. 3).
It varies in thickness from about 100 m to
1800 m.
The Copper Harbor Conglomerate is a red—brown basinward—thickening wedge
of volcanogenic clastic sediments.
These clastic sediments fine distally and up—
section.
Sandstones are lithic graywackes and conglomeratesare composed of volcanic
clasts with a ratio of mafic to intermediate + silicic composition of about 2:1
(Daniels, 1982).
Daniels (1982) has interpreted the Copper Harbor Conglomerate as
Mafic to intermediate lava flows are
a prograding alluvial fan complex (Fig. 7).
interbedded in the exposed Copper Harbor Conglomerate
(Fig. 5).
These lava flows
are termed the Lake Shore Traps and occur predominantly within the middle section
of the formation.
Nonesuch Shale
—
The Nonesuch Shale is a succession of gray—black siltstone, shale and sandstone
which overlies and interfingers with the Copper Harbor Conglomerate (Fig. 3).
The
Nonesuch has a thickness of between 40 m and 215 m.
The Nonesuch was deposited in
a reducing, rift—flanking lacustrine environment initiated through disruption of
drainages (Fig. 7) (Daniels, 1982). This differs from the over and underlying
redbeds that formed in an oxidizing environment.
Freda Sandstone
The Freda Sandstone is a cyclic succession of red—brown, ferruginous, sandstone
The Freda
and mudstone overlying and gradational with the Nonesuch Shale (Fig. 3).
It is dominantly fluvial in origin with
has a maximum thickness of over 3700 m.
The top of this
greater compositional maturity than the Copper Harbor Conglomerate.
formation is not exposed.
Jacobsville Sandstone
The Jacobsville Sandstone is a red to bleached white succession of coarse—to—fine—
grained feldspathic and quartzose sandstone with varying amounts of siltstone, shale
and conglomerate which rests in fault contact with the Portage Lake Volcanics in the
Keweenaw Peninsula.
Elsewhere it can be found overlying Middle Precambrian basement.
Jacobsville is probably slightly younger than Freda Sandstone. Jacobsville has a
Sandstones are fluvial in origin whereas conmaximum thickness of over 3,000 m.
glomerates are believed to be alluvial fan deposits (Kalliokoski, 1982).
Structure
Structure of the Keweenaw Peninsula is dominated by the Keweenaw Fault (Fig. 4),
a high angle reverse fault where older Portage Lake Volcanics are thrust to the
Both units are affected by this major
northeast over younger Jacobsville Sandstone.
the normally flat—lying Jacobsville Sandstone is often strongly
tectonic feature:
deformed by drag folding near the fault contact and the Portage Lake Lavas are often
highly fractured.
The Keweenaw Fault cuts off the base of the Portage Lake Volcanic
Series along its entire strike length so that the total stratigraphic thickness
�__
10
NONESUCH SHALE DEPOSITION
POSSIBLE "LAVA-DAMMED LAKE" MODEL FOR
SANDSTONE
FREDA
STREAM
BRAIDED
FLUVIAL
BASIN
MA
IN
BASIN
CENTRAL
FLUVIO-DELTAIC
0
00
0
O
-
LUVIQ°Th
0
o
00
0
o°
x0
x
0
0
0
0
PORTAGELAKExVOLCxANICSxxX
x
O
0
0
x
x
_—
o0xxXxx
XXX
0
CONGLOMERATE
0 o_—T
0
ALLUVIAL°PLAIN
OCOPPER HARBOR
0
0
x
00
x
-
x
-
x
:
x
x
tINTERFLOW
0
0
SEDIMENTS
X
-------- ±±±
RELATIVE
PAL ED F LO W
DIRECTIONS
Figure
7:
Schematic diagram showing the interrelationships between major
stratigraphic
units found northwest of the Keweenaw Fault in the Keweenaw
Peninsula (from Daniels, 1982).
x
�:ii
Table 1:
Secondary minerals found within the Portage Lake Volcanics, Keweenaw
Peninsula, Michigan (from Butler and Burbank, 1929; Stoiber and Davidson, 1959;
Jolly and Smith, 1972).
Widespread Minerals
Locally Important
Minerals
Rare Minerals
Laumontite
Analcime
Apophyllite
Prehnite
Sericite
Atacamite
Pumpellyite
Orthoclase /Nicrocline
Bowlingite
Quartz
Chalcedony
Brucite
Epidote
Thompsonite
Chlorastrolite
Albite
Natrolite
Chrysocolla
Chlorite
Chabazite
Cuprite
Hematite
Native Silver
Faujasite
Sphene
Sulfides
Fluorite
Calcite
Arsenides
Powellite
Native Copper
Datolite
Serpentine
Heulandite
Stilbite
Ankerite
Tenorite
Sulfates
Tourmaline
Clay Minerals
Whitneyite
Wairakiite
�12
The regional tectonic
as well as the total displacement along the fault is unknown.
context of the compressional stresses which caused development of major reverse
faults is unknown at the present time, although it is probably unrelated to processes which formed the Mid—Continent rift.
—
The Keweenaw strata dip moderately northwesterly toward the centr of the Lake
This
Superior Basin and their dip angles increase toward the base of the section.
is in part due to modification attributed to the Keweenaw Fault, but White (1960)
has demonstrated syn—depositional downwarpage of the basin. Thus, lava flows and
sediments formed wedge—shaped beds thickening basinward such that a relatively
constant horizontal datum level was maintained throughout the life of the basin.
Smaller scale, post—depositional folds are also present as broad synclines and
anticlines (wavelengths from 5 to 10 miles) (Fig. 8). The regional context of
these folds is not clearly understood, however, they appear to predate major reverse
Late high angle faulting occurred throughout the area and produced several
faulting.
major offsets of the Keweenaw Fault. This type of fracturing and faulting is partiSignificularly abundant in the upper portion of the section northeast of Mohawk.
cant deposits of massive native copper later filled many of these cross—cutting
channelways (summarized from White, 1968).
Mineralization and Alteration
The Keweenaw Peninsula is the location of a dormant billion—dollar copper mining
district. From 1845 to 1968 the mines of the Keweenaw native copper district produced about 11 billion lbs. of refined copper (Weege and Pollack, 1971). The major
ore producing horizons are geographically restricted to a 45Km long belt within the
Portage Lake Volcanics in the Keweenaw Peninsula (Fig. 8a). There is a close relation—
ship in both time and space between native copper mineralization and alteration in the
Native copper, the principal ore mineral in the
Portage Lake Volcanics (Fig. 9).
Keweenaw Peninsula, occurs in amygdaloidal and brecciated flow tops, interflow conglomerate units, and fracture systems (Butler and Burbank, 1929; White, 1968 and
197la).
The predominant native copper deposits are lenticular blanket—like ore bodies that are
found along certain stratigraphic horizons such as the tops of lava flows and conWeege and Pollack (1971) estimated that 58.5 percent of the district
glomerate beds.
copper production came from flow top ore bodies and 39.5 percent came from conglom—
erate ore bodies. The remaining 2 percent of copper production was from fissure (or
vein) ore bodies.
There are three main varieties of lava flow top recognized in the Keweenaw native
1) fragmental or flow top breccia; 2) nonfragmental! cellular
copper district:
or vesicular basalt; 3) "scoriaceous" or flow top breccia with a sandy or silty
White (1968) estimated that 21 percent of the lava flow tops in the Portage
matrix.
Lake Volcanics are brecciated (fragmental). These flow tops consist of a rubble of
The interstices between fragments and the vesicles are
vesicular and massive lava.
commonly filled with secondary minerals. Most of the major flow top (amygdaloid)
copper ore bodies are of the fragmental type. White (1968) has estimated that uppermost 5 to 20 percent of most individual lava flows is vesicular and contains between
5 and 50 percent vesicles which are commonly filled with secondary minerals. The
abundance of amygdules decreases downward and the middle and lower parts of flows
The tops of these flows are locally termed cellular
are amygdule—free massive basalt.
Cellular
amygdaloid may have traces of native copper but
and often have smooth tops.
�1968). White, (from district copper native Keweenaw
B.
the of Folds
amygdaloids. in quartz of limit northwest approximate the
is line dotted The
amygdaloid. (ashbed) Atlantic 7) and amygdaloid; Royale
Isle 6) amygdaloid; Osceola 5) amygdaloid; Pewabic 4) amygdaloid; Baltic 3)
amygdaloid; Kearsarge 2) conglomerate; Hecla and Calumet 1)
production: of
order in number, bold the by identified are deposits Major 1968). White,
(from district copper native Keweenaw the of map Geologic
A.
8: Figure
3 •l
�14
Eagle Harbor
Section
• o,f4
FEET
Top of Portage
Lake Lava Seriea
I
Hancock Congl.
2000
I-Il
I
Greenstone Flow
Allouez Congl. —
Houghton Congi.
Calumet & Hacla Congl.
0
I
-
I
-
2000
King8ton Congl.
PUMPELLY lIE
ZONE
Kearaarge Amyg, 4000
Scale8 Creek Amyg.
8000
Upper Limit of
Zone at Dehydration
Gratlot Flow
Bohemia Congl.
8000
10,000
Keweenaw Fault
-
I
EPIDOTE
ZONE
12,000
Micwcline —
Chlorite
——
—
Epidote — — — —
Pumpellyite — — —
Prehnite
— — —
Copper — — — —
Datolite — — — —
Silver — — — —
Ankente — —
Quartz — — —
—
—
-
Sericite — — — —
Colcte —
—
Arsenides —
Sulfides —
.-_
—
— —
— —
Albite — — .._
Aduloria — —
—
—
Saponite — —
—
Laumontite —
—
Analcime — —
Sulfates(barite,anhydrrte, gypsum)
Figure 9: A.
Distribution of secondary minerals in the Eagle Harbor section
of the Portage Lake Volcanics (compiled from Butler and Burbank, 1929; Jolly,
1974; Jolly and Smith, 1972; Stoiber and Davidson, 1959; White, 1968).
Location of section is between Copper Falls and Delaware Mines shown in Figure 4.
B.
Paragenesis of secondary minerals in the flow tops and veins (from White,
1968).
Solid black symbols are the more abundant minerals.
Secondary minerals
shown here are nonmagmatic and not of supergene origin.
�15
—
A few smooth topped flows show a tendency
no ore deposits are only of this type.
forming what are locally
for the amygduies to be laterally interconnected in bands,
important host rock for ore
termed "coalescing cellular amygdaloid". This is an
"ScoriaceouS" amygdaloid is used locally for flow top breccia
at the Quincy Mine.
filled with sandy or silty
in which interstices between vesicular fragments are
mineralized example of
The Ashbed amygdaloid is the onl-y significantly
detritus.
this type.
—
native copper deposits,
Conglomerates interbedded with lava flows are host for major
of copper distrifundamental
control
The
particularly in the vicinity of Calumet.
Permeability
is decreased by
conglomerate.
bution is the permeability of the host
greatly
on sedimen—
Localization
of
ore
depends
abundant fine detrital material.
which
might
bedrock
topography
tological and environmental factors, such as the
conglomthickness
of
influence location of a stream channel resulting in differing
erate.
—
right
deposits are tabular and commonly crosscut the bedding at nearly
Large masses of native copper weighing many tons were first
angles to strike.
the
fissure
deposits. These deposits are economically much less
discovered in
types.
important than the other
Fissure
Copper sulfides are a minor constituent of the system, and are found as small veins
cutting the flow top native copper deposits, joint—coatings in the conglomerate
units, and in association with Mt. Bohemia intrusive (Butler and Burbank, 1929;
Copper sulfidesandarsenides are paragenetically
Broderick, 1931; Robertson, 1975).
Significant copper sulfides with minor
late in flow tops and conglomerates (Fig. 9b).
native copper also occur at the base of the stratigraphically higher Nonesuch Shale
and top of the Copper Harbor Conglomerate (Brown, 1971) at White Pine, approximately
70 Km southwest of most of the discovered mineralization in the Keweenaw Peninsula.
The solutions that formed the White Pine deposit may have been related to those which
formed the deposits in the Keweenaw Peninsula (Ensign and others, 1968).
Vesicular and fragmented flow tops of the Portage Lake Volcanics were prevasively
altered by hydrothermal fluids, producing low temperature metamorphic mineral associations occurring as amygduie and vein fillings as well as whole rock replacements
in the most permeable hOrizons.
The systematic metamorphic zoning varies vertically
within the volcanic pile and is equivalent to zeolite, prehnite—pumpellyite facies
(Jolly and Smith, 1972; Stoiber and Davidson, 1959), and possibly lower greenschist
facies (Fig. 9a). The copper deposits lie stratigraphically within the pumpellyite
The copper, in the deposits, may have been leached from dehydrated lava flows
zone.
(epidote zone) in the deep parts of the pile and migrated up dip and precipitated
in the zone of hydration where conditions were sufficiently reducing (Jolly, 1974;
Scofield, 1976; White, 1968).
These workers and Cornwall and Rose (1957) suggest
that most of the copper was probably initially tied up in Fe—Ti oxides and their
oxidation released the copper.
The oxidation reactions of magnetite to hematite
and pumpellyite to epidote may occur along with native copper deposition (Jolly,
1974).
The intensity and degree of alteration varies as a function of position within individual flows, position in the volcanic pile, and proximity to cross—cutting fractures
(Jolly and Smith, 1972).
Local controls, such as pre—alteration composition, appear
to govern the assemblages of final alteration products and their major—element compositions.
Figure 10 shows a summary of known elemental mobilities and a schematic
picture of alteration conditions.
�PERMEABILITY
LITHOLOGY
DIA GNOSTIC
MINERALOGY
Added to
flow top
Redistributed
within flow
Hgh
''''''
e'°r :
FLOW
TOP
-
FLOW
INTERIOR
Low
,
None
—r---- Pumpellyite
Epidote
Metadomain
-
Ca Al
f
..
Albitized
Basalt
Albite
Chlorite
Unmetamorphosed
Basalt
Ca—Plagiociase
16
ELEMENT MOBILITY
from
Outside flow
-
114
Na
Clinopyrosepe
Olivme
Si
-
-
1
H2
Lost from
flow top
Remained
Immobile
— K, Fe, Ti, Mg, Zn
Cu —w-
Cu(s)
HO—*-HO
2
(p)
2
Ni
Ce)
Elements Remained
Immobile
I.
DEPTH
4.
TEMPERATURE
I
Basal chill zone
ii Least—altered flow interior
lIE
Amygdular flow top
Arrows denote tluid movement
Figure 10: A. Possible elemental mobility pattern in an idealized lava flow
in the pumpellyite and epidote zones within the Portage Lake Volcanics (based
on chemical data of Jolly and Smith, 1972; Jolly, 1974; Scofield, 1976; Stoiber
According to Jolly (1974) Cu and H20 were derived from
and Davidson, 1959).
the epidote (dehydration) zone and deposited in the pumpellyite (hydration) zone.
Diagrammatic regional model for the Portage Lake Volcanics showing local
B.
thermal/chemical gradients superpositioned on the regional geothermal gradient
and showing the movement of fluids along flow tops and bottoms and through frac—
tures (modified from Jolly and Smith, 1972; Scofield, 1976).
�17
ROAD LOG AND STOP DESCRIPTION
Mileage
MAP 1
0.0
Assemble at the Memorial Union on
University.
Begin the field trip
the northeast side of the Union.
on a kame terrace to the south of
the campus of Michigan Technological
from the circular drive lqcated on
The Michigan Tech campus is located
the Portage Lake.
0.1
Right turn.
0.2
Immediately after there is a right turn on to Townsend Drive.
Left turn.
The Quincy Mine can be seen on the ridge on the skyline.
0.55
Left turn on Agate Street, where we go up the steep hill on the south
side of the Portage.
We are climbing off of the kame terrace.
0.8
Right turn on Seventh Street.
1.0
STOP 1.
Scales Creek flow on Seventh Street, City of Houghton.
This stop is marked by a prominent ridge of ophitic basalt, which is an
outcrop of the Scales Creek flow, one of the great Keweenawan flows, which
can be traced continuously for a strike length of more than 160 Km along
the Peninsula.
It is about 70 m thick, with an amygdaloidal top which is
typically not resistent and a prominent, ridge—forming, ophitic core. The
ridge at this site can be followed down hill all the way to Shelden Avenue,
where it is covered by glacial deposits.
It can be traced across the
valley, where it passes through the Ripley School, a prominent brick building across the Keweenaw Waterway.
This bearing, about N3OE, is the regional strike of the Portage Lake Volcanics which dip about 500 to the NW.
Another clue to the attitude of the rocks is given by the Quincy #2 shaft
house on the horizon which heads up an inclined shaft down dip along the
amygdaloidal ore bodies of lava flows just over 2000 m higher in the
Portage Lake section. Throughout the Portage Lake section between Baltic
and Mohawk, most amygdaloidal and conglomerate zones show well developed
zeolite and prehnite—pumpellyite facies metamorphism and native Cu mineralization.
At this site the amygdaloids just below the Scales Creek flow
are strongly mineralized.
One mine, the Sheldon Columbian, operated just
a few hundred m to the east in the early 1900's.
This same horizon is
exploited by a series of shafts called Isle Royale Mines, for several km
to the SW.
Stop 2 is at one of these mine dumps.
The most obvious geomorphological feature here is the Keweenaw Waterway,
The waterwhose origin was thoroughly investigated by Warren (1981).
way formed in a fault zone like many which crosscut the Portage Lake
stratigraphy. A bedrock valley, more than 200 m deep formed along the
fault as a result of stream superposition through a cover of flat—lying
This valley, like others on the Keweenaw, was deepened and
sediments.
widened by glacial erosion, in a fashion similar to the finger lake
The complex glacial deposits, consisting of
region of New York State.
moraines, terraces, varved clays and gravels were the result of the
pattern of ice retreat from the region, which had profound and complex
effects on the drainage patterns.
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1.1
Left turn on Portage Street.
1.25
Grand Portage Mine dump on left.
1.45
At this spot the Scales Creek ridge is
Near the Houghton water tower.
slope
exposed higher on the south
of the Keweenaw Waterway.
There are
many bald knobs with more or less east—west trending deep glacial
grooves on them.
To the east of the prominent ridge, there are many mine
oprIings from the series of Isle Royale shafts.
The Adams Township takes
its water supply from these Isle Royale mines which are now filled with
water, and this is the source of water for Hancock and several other towns.
1.55
Cross Sharon Avenue and continue on Portage Street east of the City of
Houghton fire station.
2.15
Right turn immediately followed by a left turn so we are now on Bridge Street
heading south.
3.0
Entering Dodgeville. On the right hand side of the road is one of the prominent Isle Royale mine dumps.
3.2
Center of Dodgeville.
If you turn on the road to the right through the
Trailer Park, there is access to the Isle Royale mine dumps from Shaft
No. 4 and 5.
The Isle Royale Mine is described at Stop 2, continue ahead.
3.6
Junction to the Green Acres Road and make
3.7
STOP
2.
Isle Royale Shaft No.
6
a
right turn.
mine dump on the Green Acres Road.
The Isle Royale mine worked the top of the Isle Royale flow.
Production
from the Isle Royale amygdaloid began in 1855, the mine closed in 1948.
A total of about 350 million lbs. of refined copper was removed from this
mine (Weege and Pollack, 1971).
The Arcadian Mine (see Map 4) may also
work the Isle Royale amygdaloid.
The Isle Royale flow varies in thickness but is about 70 to 150 ft. thick
and lies just below the Scales Creek flow discussed in Stop 1.
It dips about
50 to 60° to the northwest (Fig. 11).
A gentle fold accounts for the curvature
of the flow (see Map 1), Isle Royale syncline.
The flow from the top down
is characterized by fragmental zone, banded amygdaloid, foot inclusion zone,
The fragmental zone consists of irregular fragments
and massive main trap.
of amygdaloid and fine—grained basalt ranging from small grains to tabular
The vesicles and spaces between the
blocks several feet in long direction.
secondary
minerals.
The banded amygdaloid is an
fragments are filled with
considerable
area.
Amygdules
are commonly abundant
unbroken rock body over
zone
a
banded
appearance.
Below the fragat certain horizons giving this
amygdaloid
is
the
foot
inclusion
zone
which is indemental zone or banded
foot
inclusion
The
finite patches or inclusions of amygdaloid basalt.
devoid
of
amygdules
(summarized
zones grades into massive basalt practically
from Butler and Burbank, 1929).
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11:
Cross section A—A' on Map 1 (from White, 1956).
Labels are as follows for the
Pewabic West conglomerate (pp), Creenstone
Portage Lake Volcanic Series (P) and its subunits:
flow (pg), Allouez conglomerate (pa), Calumet and Mecla conglomerate (pc), Kingston conglomerate (pkc), National sandstone (pn), Kearsarge flow (pk), Wolverine sandstone (pw), Scales
Creek flow (psc), Bohemia conglomerate (pb), St. Louis conglomerate (ps), Baltic conglomerate
(pbc), and Unnamed conglomerate (pu).
Figure
P
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A'
�21
Butler and Burbank (1929) recognized two distinct periods of alteration.
The earliest alteration was oxidation which caused the development of
This oxidation could essenhematite, which produced reddened basalt.
alteration
shortly
after eruption.
tially represent deuteric
The second
after
the
period of alteration was probably
flows had been tilted.
This
period was complex and resulted in deposition of native copper.
This
stage :L divisible into three substages:
1) An early stage of deposition
of epidote, pumpellyite quartz, calcite, most of the native copper and
minor prehnite, alkali feldspar, and laumontite; 2) an intermediate
stage characterized by the development of sericite with quartz, calcite,
anhydrite, gypsum and minor barite; 3) a final stage of copper sulfides
and arsenical copper accompanied by calcite, sericite, quartz, chlorite,
and specular hematite occurring in numerous veinlets.
Stoiber (unpubthe
following
estimate
of
the
lished data) made
percentage of alteration
the
Isle Royale Mine:
quartz, 26—
minerals on dumps from four shafts of
59; calcite, 5—39; prehnite, 6—32; pumpellyite, 1—17; epidote, 1—10;
sericite, 0—12; chlorite, 0—3; K—feldspar, 0—trace.
This dump and the
ones near Dodgeville are freshly reworked and good specimens of native
copper and alteration minerals can be found.
3.9
Junction M—26 at the Copper Country Mall and you are going to make
a
left turn.
MAP
2
5.6
Entering Atlantic Mine.
6.9
Right turn at the sign that says South Range Village Limit and drive about
150 yards into the road and walk to the right through a notch up the hill
another 60 meters to Stop 3, the South Range Quarry.
NW
SE
Felsite
bed
9
IEE
Fragmental
amygdaloid
i
Non-fragmental
amygdaloid
190 FEET
F(a)
Masve basaft
PegmatEte layer (a)
and zone of thin
Figure 12: Geologic profile of the South Range quarry along the northeast wall (from Cornwall, 1951; White, l97lb).
Location of the quarry
is shown in Map 2, Sec. 17, T54N, R34W.
�22
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STOP 3.
South Range Quarry.
South Range quarry provides an excellent cross sectional view of a massive
to amygdaloid lava flow (Fig. 12) of the Portage Lake Volcanic Series. The
base of the section is a conglomerate bed, about 4 m thick; it is exposed
This is overlain by an 18 m thick fine—
on the main path to the quarry.
grained basalt flow, followed by a 42 m thick ophitic basalt flow and
finally the lower 17 m of another ophitic basalt flow.
The conglomerate is well indurated and consists mostly of pebbles and
cobbles of rhyolite with subordinate clasts of basaltic lava set in a
sandy matrix of similar composition. The clasts are subangular to sub—
The overall character is similar to the Copper Harbor Conglomrounded.
This conglomerate is
erate which will be seen later in the field trip.
one of a number of sedimentary beds which are interbedded with the Portage
This particular bed is correlatable with the National
Lake lava flows.
Sandstone, a marker bed in the Nass—Rockland area.
The basalt flow that occupies most the quarry face has features which
The
characterize the thicker flows of the Portage Lake Volcanics.
lower half of the flow is massive basalt, overlain by a zone with progressively smaller pegmatitic layers, topped with cellular amygdaloidal
basalt, and at the top a discontinuous layer of flow top breccia (called
fragmental amygdaloid). A typical pegmatitic layer, consists of 4 cm to
1.3 m core of green amygdaloidal lava surrounded by a 4—9 cm border zone
at the top and bottom. The border zone is composed of a medium to coarse
grained aggregate of albite/oligoclase, augite, ilmenite, and magnetite.
Pegmatitic layers toward the top of the zone are more amygdaloid. Quartz,
prehnite, and a green or red cherty substance occurs in flattened vesicles
The pegmatitic layers are products of cooling
at the top of the layer.
and differentiation as it cooled (description of pegmatitic layers from
Cornwall, 1951). Amygdules and interfragmental spaces are filled with
Locally the basalt is
quartz and prehnite containing traces of copper.
intensely epidotized or prehnitized.
Outside of the Quarry and to the north are a series of glacially grooved
outcrops in which the exposures of the pegmatitic zones are spectacular.
Take a right turn on M—26, going into the town of
7.9
Return from Stop 3.
South Range.
8.4
At stop sign in South Range, take a left turn.
8.6
Right turn at the church and immediately foiJowed by a left turn as the
whole road jogs to the left.
8.7
Entering the town of Baltic.
8.8
Right turn.
9.2
The main road turns to the left, we go to the right on a small paved road
driving past a concrete building towards some very large mine dumps.
�24
9.4
STOP 4.
Baltic Shaft No.
3 Mine Dump.
The Baltic, Champion, and Trimountain mines worked the Baltic amygdaloid.
Total proThe Baltic Mine opened about 1898, the others opened in 1902.
duction from the Baltic amygdaloid was about 1.85 billion lbs. of refined
copper which was the third largest producer in the Keweenaw native copper
district (Weege and Pollack, 1971). The amygdaloid was developed for
about 7 Km along strike and to the 38th level in the Baltic Mine.
The Baltic flow is an ophite that varies considerably in thickness but
The Baltic amygdaloid in many places is 17 m
is around 50—70 m thick.
or more in thickness and is composed of fragmental amygdaloid, the average
stoping width is about 5—8 m. However, like all fragmental amygdaloids
of the district, there are significant variations, e.g. the lode can
thin to only a few feet thick composed of trappy or cellular amygdaloid.
The lode dips at about 70°NW (summarized from Butler and Burbank, 1929).
The abundant minerals associated with copper in the Baltic amygdaloid are
Copper sulfides are unusually
quartz, pumpellyite, epidote and carbonate.
The
sulfides
characteristically
occur
in fissures that dip 75
abundant.
Most of the copper sulto 900 and strike nearly parallel with the lode.
fide in the lode is chalcocite associated with iron—bearing carbonate,
there is some bornite and rare chalcopyrite. Native copper is irregularly
distributed through the amygdaloid ranging from minute specks to masses
weighing several tons. Native copper occurs at the margins of sulfide
veins and it may occur with quartz in the center of veins. Sulfides are
in general paragenetically late (Fig.9h Introduction) (summarized from
Butler and Burbank, 1929).
The majority of the dump at this stop is amygdaloid basalt. R. E. Stoiber
(unpublished) made the following estimate of the percentages of the seconcalcite, 91; quartz, 5; epidote, 3;
dary minerals in the dump as a whole:
Paragenetically epidote and chlorite were early minerals;
chlorite, 1.
calcite, quartz and native copper were intermediate; and copper sulfides
Excellent specimens of chalcocite
and iron—bearing carbonate were later.
can be found on this dump as well as native copper.
9.4
Retrace route in Baltic.
9.9
Stop sign in Baltic, make a left turn to go back in the direction of
South Range.
10.1
Right turn, immediately followed at the church by a left turn.
10.3
In the center of South Range, right hand turn off M—26.
10.8
Passing the South Range Quarry, Stop 3.
12.5
M—26 jogs to the right at the center of Atlantic Mine
�25
MAP
3
14.7
STOP 5.
Glacial Deposit Near Pamida
The Keweenaw Peninsula has probably been modified by all of the major
glacial episodes of the Pleistocene. During maximum glaciation the
entire Keweenaw Peninsula is believed to have been overridden by around
3000 m of ice. The present form of Portage and Torch Lakes is related
to the final retreat of the Laurentide ice sheet in the Lake Superior
The final glacial advance and stillbasin (shown in Figs. 13 and 15).
stand over the Keweenaw Peninsula was made by the Keweenaw Bay Lobe,
marked by an end moraine of Wisconsin stage (Fig. 14) (summarized from
Warren, 198]).
The earliest recognized channel cut by drainage through the Portage Gap
area is the Huron Creek channel (Nap 3). The channel is waterworn bedSince there is no delta at the southern end
rock due to southward flow.
of this channel perhaps the source of water was a large lake where glacial
The drainage
sediments had time to settle before the water was removed.
in
Fig.
16
(summarized
from
pattern through the Portage Gap is shown
Warren, 1981).
A delta kame is just west of the Huron Creek channel and is the location
The sediments, in this dissected knob, show strong
of Stop 5 (Map 3).
evidence of being deposited by a braided stream closely associated with
Extreme variations in grain size and sorting occur within a
a glacier.
This suggests differing flow regimes during
distance of a few meters.
Poorly to well—worked unconsolidated sands predominate but
deposition.
Numerous cut—and
poorly sorted pebble conglomerates are also present.
Large
striated
boulders
of basalt within
fill structures are present.
from
a
nearby
glacier. This
the gravel and sand must have originated
large exposure is capped by a thin (less than one meter) poorly sorted
clay till which thickens rapidly to the south; it is about 7 meters thick
The later unit may be a flow till(?)
at the top of the nearby hill.
which slumped off the nearby glacier (description by S. Beske—Diehi and
S. Nordeng, Dept. of Geol. & Geol. Engrg., MTU).
15.75
Between Junction of M—26 and US—4l, so turn right on US—4l past the Mobil
and Erickson gas stations.
16.2
Excellent outcrop of basalt with exposed amygdaloid on both sides of the
road.
16.35
Make a left U—turn back onto US—4l going one way back through the City of
1—loughton.
16.45
Amygdaloidal basalt with pegmatitic zones at Burger King Restaurant,
Shelden Avenue, Houghton.
This stop is an alternate to the South Range Quarry Stop. Excellent exposures of the cellular amygdaloid and pegmatitic interior of a thin Portage
Lake lava flow are found to the west of the restaurant and along Montezuma
The flow top is strongly metamorAvenue, just a few steps to the north.
phosed with a variety of amygdule minerals of the prehnite—pumpellyite
The green color of the basalt is due to the abundance of epidote.
facies.
Below the amygdaloid the basalt is virtually unmetamorphosed except where
thin pegmatite zones cross it.
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(from glacier Lobe Bay Keweenaw the of moraine End
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Prest, 1975; Huber, (from America North central from retreat ice
Wisconsin the during positions ice—marginal Speculative 13: Figure
1969).
46) (Fig.
1257A). Map Canada of Survey Geological 1969, Prest, K. V. (from basin Superior Lake the
readvance, or surge, ice major Note Amenca. North central from RETREAT ICE WISCONSIN
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15:
(from Prest 1969) . Note the major ice readvance in the Lake Superior Basin and
withdrawal pattern over the Keweenaw Peninsula.
S.
�29
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Figure 16:
High level drainage through the Portage
Gap during the Washburn Stage (from Warren, 1981).
�30
16.9
Right turn on US—41/M—26 and crossing the Portage Lake Lift Bridge into
Hancock.
The bridge was built in 1957, and is designed to accommodate Great Lakes
ore boats, who prefer the Keweenaw Waterway route to rounding Keweenaw
The present bridge abuts the Hancock side of
point in stormy weather.
the canal at approximately the site of the old Quincy Mill where the
tramway descended Quincy Hill from the mines.
MAP
4
17.15
Left turn on TJS—41 into Hancock.
17.35
Right turn and immediately followed by US—41 going to the left
but we go straight at 17.4.
17.5
Bear to the left on White Street.
18.0
Junction between White Street and Lincoln Drive which is US—41,
we take a right turn.
The fenced ground near this locality surrounds an area of recently
caved ground, which is thought to be related to shallow stopes of
the Hancock Mine. The detection and distribution of such openings
is a problem of considerable concern to local authorities, since many
mines had shallow workings, since towns grew up adjacent to mines and
since maps of the underground workings are incomplete and/or inaccurate.
18.3
Turn off US—41 to the right to the overlook of the Keweenaw Waterway or
Portage Lake which is Stop 6.
STOP 6.
Keweenaw overlook near Quincy Mine.
This overlook, near the crest of Quincy Hill, allows a broad overview
of all the previous stops and also the best general view of the Keweenaw
The features which can be seen are, from east to west (left
Waterway (Fig. 17).
to right):
1) On the skyline, the knobby terrane of the Huron Mountains,
which lie across Keweenaw Bay. The mountains are underlain by the Archean
gneisses and granites of the Northern Complex, and are the main source
2) In the forearea for the extensive deposits of Jacobsville Sandstone.
ground, underlying the flat topography of Jacobsville Sandstone is clearly
The Jacobsville extends from the Keweenaw fault, which crosses
visible.
the Waterway just east of the Michigan Tech campus, across the Keweenaw
The formation is genBay and under the Huron Peninsula (Pointe Abbaye).
erally flat—lying, while all of the other rocks of the Peninsula dip north3) Within the town of Houghton several
westward toward Lake Superior.
ridges of basalt can be traced downhill, the most prominent being the
The attitude of the
Scales Creek flow horizon, where Stop 1 was made.
Portage Lake flows and the alternation of resistent flow interiors and
interflow conglomerates with less resistent flow tops makes site investigation work critical for construction projects, to accurately determine
For example,
depths to bedrock and to make hydrologic interpretations.
site investigations of the extensive area south of the main campus,
where the Michigan Tech Student Development Complex (visible from the
overlook) is now located, provided the focus of several Masterts theses
for students in Geological Engineering (Stevens, 1971; Hase, 1973). A
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�View from Portage overlook facing south. Notable features include:
17:
1) Huron Mountains,
2) Flat—lying Jacobsville terrain, 3A) Scales Creek flow ridge, 3B) Student Development Complex,
4A) Houghton water tower at Isle Royale Shaft #1, 4B) Isle Royale dump 114, 4C) Isle Royale dump 115,
4D) Wheelkate Bluff (Trimountain, 5) Highway M—26, 6) Contact between the Portage Lake Volcanics
and the Copper Harbor Conglomerate, 7) Houghton County Courthouse, 8) Quincy Smelter, 9) Michigan
Technological University Main Campus. Previous stops are located with stars and stop numbers are
prefixed with an S.
Figure
w
�33
general map, showing the detailed bedrock geology of the City of
Houghton (Holcomb, 1975) is used routinely by developers in the area.
4) On the skyline on the opposite side of the Waterway, beginning at
the Houghton water tower a series of mine dumps representing the Isle
This marks the
Royale lodes can be seen extending into the distance.
approximate route of the road between Stops 1 and 2, and shows the
The knob on the skyline is Wheel—
strike of the Portage Lake Lavas.
kate Bluff near South Range which is one of several residual bedrock
5) The divided M—26 highhighs and is located just south of Stop 3.
way is visible, traversing the glacial deposits described at Stop 5.
6) To the right, the Waterway traverses the upper contact of the Portage
Lake Volcanics and the Copper Harbor conglomerate, Nonesuch Shale and
Freda Sandstone.
The Stop is the best single locality to observe the Keweenaw Waterway.
The Waterway and the peninsula are named for an Indian word for Portage
route, but to make the Waterway accessible to Lake Superior shipping,
This
canal work was necessary at both the northern and southern shores.
The geological history of the Waterway was investwas completed in 1873.
igated in detail by Warren (1981). This and other major bedrock valleys
were formed by stream superposition as ancient rivers eroded through flat—
But the valleys
lying Paleozoic rocks into the tilted Keweenaw strata.
Then
the
Pleistocene.
were greatly deepened by glacial erosion during
as the Keweenaw Bay sub—lobe retreated at the end of the Wisconsin glaciation, the Waterway allowed eastward drainage across the Peninsula to lower
First, drainage occurred in the Portage Gap
lake levels to the east.
(between Houghton and Hancock) while a tongue of ice remained in what is
As the ice retreated further, the valley now
nowwestern Portage Lake.
occupied by Portage Lake was formed by eastward drainage of successively
Torch Lake was formed
lower proglacial lakes in western Lake Superior.
by a trapped block of ice which later melted in place to form the lake
Warren's study includes a complete bedrock topographic map of
basin.
the Keweenaw and a series of maps showing the pattern of ice retreat,
based on the distribution of glacial deposits.
Houghton was named for Douglass Houghton, the geologist who sparked the
Michigan copper mining boom by publishing his Michigan State Geologist
Houghton was settled in 1852 and is the site of several
Report in 1841.
historic buildings, the most important of which is the Houghton County
Courthouse (1887), a prominent yellow brick building with Jacobsville
Sandstone facing and copper roof and a flag pole, on the hill above the
main part of town. Hancock was settled in 1859. Across the road and
just slightly up hill is Quincy Hill House (1871), the mine manager's
house for the Quincy Mine. The Quincy No. 6 mine shaft house dominates
the skyline behind the viewpoint. A map of the Quincy operations in
its heyday are given in Figure 18. The inclined No. 2 shaft descends
at about a 45° angle more than 3 Km (1.7 Km below the surface) making
this one of North America'a deepest mines. The surface projection of
the area mined is shaded on Map 4.
18.35
Right turn back on US—4l going up the hill.
18.75
Prominent outcrop of basalt with glacial grooves.
�34
18.85
Right hand turn would lead to the Quincy Steam Hoist, we're in the center
The Quincy Steam Hoist can be
now of the Quincy Mine area (Fig. 18).
visited during the summer months for a small admission charge.
Inside
is the largest steam mine hoist in the world.
This great machine,
invented by Bruno Nordberg and installed in 1920, could lift a 10 ton
ore load at a rate of more than 1000 m per minute.
The hoist is still
in pristine condition and a full museum of the Quincy Mine is maintained
inside as well.
MAP 4 or 5
On the left hand side, immediately after
19.3
Turn right on Arcadian Road.
the turn are some of the Quincy mine dumps, nearest Shaft No. 1.
This
will be Stop 7.
Please respect private property signs and stay within
the public right—of—way.
STOP
7.
Quincy Mine Dumps.
The Quincy Mine worked the Pewabic amygdaloid.
Production from the Quincy
Mine began in 1856 and ended in 1967.
Total production from the Pewabic
amygdaloid was about 1 billion lbs. of refined copper, ranking fourth in
the district (Weege and Pollack, 1971). Lankton and Hyde (1982) give an
outstanding illustrated historical account of the history of the Quincy
Mining Company which earned the name "Old Reliable" because it paid dividends so regularly.
The Pewabic amygdalLoid deposit consists of a group of relatively thin flows.
These basaltic flows are
A geologic cross section is shown in Figure 19.
Some
texturally distinctly porphyritic with large feldspar phenocrysts.
of the thicker flows have an ophitic texture.
The tops of flows in some
places are cellular whereas thick flows may be either cellular or fragmental.
The amygdaloids of Pewabic flows are characteristically of a type
Flows of this type typically have smooth
termed ].ocally as coalescing.
tops in which individual vesicles are larger than average, reaching an inch
or more in diameter.
VesiciLes in the same layer may coalesce to form a
A series
thin, jagged gash with a lateral extent of up to 12 feet or more.
of such openings provided an almost continuous path for the flow of mineralizing hydrothermal solutions.
Several such layers may occur in the same
flow top.
Where coalescing is well developed in the Pewabic amygdaloid
there may be 2 to 10 layers from 3 to 5 feet thick.
There is every gradation from coalesced layers of vesicles to those that show only a moderate
tendency to collect in layers (summarized from Butler and Burbank, 1929).
quartz is the most abundant secondary mineral assoCalcite is also abundant.
ciated with native copper.
Pumpellyite, epidote
Laumon—
and chlorite are common but not abundant and prehnite is present.
tite and datolite are common in upper levels but not lower levels (summarized from Butler and Burbank, 1929).
In the Pewabic lode,
The majority of the dump at this stop is amygdaloidal to massive basalt.
Secondary minerals in this dump are mostly quartz and calcite with lesser
amounts of pumpellyite followed by epidote.
Paragenetically epidote and
pumpellyite seem to be early whereas quartz, calcite and native copper
formed later.
�__
35
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1982).
location (crom
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Figure 19:
19: Geological cross
cross sectionfromB
section from Bto
to B'
B' on
on Map
Map 30,
30, B'
B' to
to B"
B" on
on Map
Map 4,
4, B"
B" to
to B"'
B'" on
on Map
Map 5.
5.
This
This cross section
section illustrates
illustrates the
the general
general geologic
geologic relationships
relationships of
of the
the Keweenaw
Keweenaw Peninsula.
Peninsula. The
successively by the
the Copper Harbor Conglomerate,
Conglomerate, the
the Nonesuch
Portage Lake Volcanics are overlain successively
Shale and the
the Freda
Freda Sandstone.
Sandstone. The Portage
Portage Lake
Lake Volcanics
Volcanics are
are in
in fault
fault (reverse)
(reverse) contact
contact with
with the
the
Introduction). Labels for
Jacobsville Sandstone
Sandstone (see
(see Fig.
Fig.
for the
the Portage
Portage Lake
Lake Volcanics
Volcanics (P)
(P)
younger Jacobsville
are
follows: Hancock conglomerate (phc),
(phc) , Pewabic
Pewabic West
West conglomerate
conglomerate (pp),
(pp), Greenstone
Greenstone flow
flow (pg),
(pg),
are as follows:
Allouez conglomerate
Kear—
canglomerate (pa),
(pa), Calumet and
and Hecla
Hecla conglomerate
conglomerate (pc),
(pc), Kingston conglomerate
conglomerate (pkc),
(pkc), Kearsarge flow
flow (pk),
sarge
(pk), Scales Creek flow (psc),
(psc), Bohemia
Bohemia conglomerate
conglomerate (pb),
(pb), St.
St. Louis
Louis conglomerate
conglomerate (ps).
(ps).
W
--.J
�38
38
MAP 55
19.5
Entering Coburntown.
Coburntown. This is
is another one of the
the communities that
that sprung
up around the
the Quincy operations,
operations, most of the
the houses built and owned by
by
up
Several ethnically distinct neighborhoods existed
the company. Several
existed "on
"on the
the
hill" in
in the
the early
early 1900's.
1900's. In
lived on
on the
the
In all
all more than 6,000 people lived
hill in
in 1905.
1905.
20.45
Y in
There is a Y
in the road,
road, we take the right hand branch which is essentially aa straight
tially
straight road with a sign
sign saying
saying Arcadian
Arcadian Scenic
Scenic View.
View.
20.7
Passing a radio
radio tower
tower on
on the
the right.
right. We are now crossing the
the Scales Creek
flow
the top
top of the small
small ridge
ridge (see
(see Map
Map 5).
5). The Arcadian Mine worked
flow at
at the
an amygdaloid just
just below
below the
the Scales
Scales Creek
Creek flow.
flow. The amygdaloid may corcoran
relate with the
the Isle
Isle Royale
Royale amygdaloid discussed
discussed at
at Stop
Stop 2.
2. North of the
the
road is
is Shaft
Shaft No.
No. 11 of
Mine. Stoiber (unpublished
(unpublished date)
date)
of the Arcadian Mine.
estimated the percentages of
of non—metallic
non-metallic secondary minerals in
in the dump
calcite,
from Shaft No.
No.11 as:
calcite, 43;
43; prehnite,
prehnite, 25;
25; quartz,
quartz, 16;
16; K—feldspar,
K-feldspar,
8;
8; epidote,
epidote, 6;
6; pumpellyite,
pumpellyite, 1;
1; chlorite
chlorite 1;
1; and
and laumontite,
laumontite, trace.
trace.
21.4
see the
the largest
largest part
part of
of Portage
Portage Lake,
Lake,
Down to
to the
the right of
of the
the road
road you
you can
can see
of view is
the field
field of
is basically
Keweenaw Bay and the
the Huron
Huron Mountains.
Mountains. Much of the
flat—lying
flat-lying Jacobsville terrane.
terrane.
21.6
Road turns
turns to
to the
the right
right and
and changes
changes to
to gravel.
gravel.
21.8
descending off
off the
the Portage Lake Volcanic
Volcanic Series
Series across
across the
the Keweenaw
We're descending
Fault onto Jacobsville Sandstone.
Sandstone.
23.0
have aa view of
of the
the Isle
Isle Royale sands
sands
We are descending the
the hill and
and we have
across Portage Lake in
in Houghton.
Houghton. These are tailings from the Isle Royale
out and
and into
into Portage
Portage Lake.
Lake.
dumps (Stop
(Stop 2)
2) which were brought
brought out
23.15
Junction with M—26
M-26 and
and take
take aa left
left turn
turn at
at the
the Portage
Pottage Lake
Lake Coal
Coal Dock.
Dock.
23.6
Entering Dollar Bay
Bay on
on M—26.
M-26.
MAP 66
25.2
of flat—lying
Exposure of
flat-lying cross—bedded
cross-bedded redbeds of the Jacobsville Sandstone
on the left hand side
side of
of the
the road
road (northwest
(northwest side).
side).
STOP 8.
8.
Jacobsville Sandstone.
Sandstone.
The Jacobsville Sandstone is a
a fluvial
fluvial succession of feldspathic
feldspathic and
quartzose
quartzose sandstones,
sandstones, conglomerates,
conglomerates, siltstones,
siltstones, and shales
shales up to 1,000 m
m
thick (Fig.
(Fig. 20a).
20a). There are no interbedded lava flows
flows or cross—cutting
cross-cutting
dikes.
The Jacobsville Sandstone is separated from the Portage Lake Valcanics
Volcanics
by the Keweenaw Fault,
Fault, aa reverse
reverse fault.
fault. The Jacobsville Sandstone is
is probably
upper
upper Keweenawan in
in age and
and may
may be slightly younger than the
the, Freda Sandstone.
Sandstone.
Current
the Keweenaw Peninsula are to the northeast and east
east
Current directions
directions in the
suggests transport
transport to
to deeper parts
parts of aa basin located
located northeast of
of
which suggests
Keweenaw
Keweenaw Bay
Bay (Fig.
(Fig. 20b).
20b). West of Lake Gogebic thickness
thickness and
and current direc—
directions
tions suggest another deep
deep part
part to
to the
the basin.
basin. East of Calumet,
Calumet, near the
the
Keweenaw Fault (Stop
(Stop 10)
10) the
the Jacobsville Sandstone contains boulders of
basalt which suggests a topographic
topographic high in the
the Portage Lake Volcanics north
north
of the
the fault
fault during
during this
this period
period of
of Jacobsville
Jacobsville sedimentation.
sedimentation. Metamorphosed
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40
Sandstone Thickness
Current Directions
9400 Geophys. est. (ft.)
597
Weillft.l
o
50
I
j
Km.
B.
A.
I
rocks
Iron ranges
0
-
0
km
mi
30
I
50
so
N
--...... ,.
\
c.
C.
Figure 20:
20: Relationships of Jacobsville Sandstone
Sandstone (from
(from Kalliokoski,
Kalliokoski, 1982).
1982).
of Jacobsville
Jacobsville Sandstone with minimum thickness denoted
Thickness of
denoted by
+'.
'+'. B. Current
in the
the Jacobsville
Jacobsville Sandstone.
Sandstone. C.
Location of
of
Current directions in
C.
possible
source areas
iron formation
staurolitic metasedimentary
possible source
areas of
of iron
formation and
and of
of staurolitic
metasedimentary
rocks.
A.
A.
�41
iron-formation
quartz-staurolite pebbles
pebbles suggest
suggest aa source
source from
from the
the
iron—formation and quartz—staurolite
jacobsville
Jacob
sville sedimentation
sedimentation was
was preceded
preceded by
by aa long
period of cratonic stability
stability with
with little
little or
or no
no volcanic
volcanic activity.
activity.
Erosion was
was apparently initiated by late Keweenawan warping along the
the
mid—continent
mid-continent rift
rift system.
system. The major movements on
on reverse
reverse faults
faults were
were
after
deposition (summarized
(summarized from
from Kalliokoski,
Kalliokoski, 1982).
1982).
after Jacobsville deposition
southeast
southeast (Fig.
(Fig. 20c).
20~.
sandstones varies from
from subarkose
subarkose to
to quartz
quartz sublithic
sublithic
Lithology of sandstones
arenite. There are some
some beds of
of arkose
arkose and
and quartz
quartz arenite.
arenite. Grain size
size
varies from
from fine
fine to
to coarse.
coarse. Quartz grains show
show evidence
evidence of
of volcanic
volcanic and
and
metamorphic origin.
origin. Microcline is relatively
relatively unaltered
unaltered and
and plagioclase
is
is unaltered to
to highly altered.
altered. Other clasts
clasts include:
include: volcanic rocks,
rocks,
schist,
the minerals epidote,
epidote, biotite,
biotite, muscovite
muscovite and
and chlorite.
chlorite.
schist, shale and the
Sandstone varies in
in color
color from
from red
red to
to aa cream—white
cream-white or
or purplish—red
purplish-red color.
color.
The color depends on
on the
the alteration of
of ferromagnesian
ferromagnesian minerals
minerals and
and the
the
amount
of iron oxide deposited
deposited as
as rims
rims on
on feldspar
feldspar grains.
grains. Ripple marked
amount of
bedding surfaces
surfaces and
and cross—bedding
cross-bedding are
are common
common in
in some
some localities.
iocalities. Sandstones are fluvial
stones
fluvial and conglomerates probably represent
represent alluvial fan
fan
deposits (summarized
(summarized from
from Kalliokoski,
Kalliokoski, 1982).
1982).
At this
this stop
stop the
the character
character of
of the
the Jacobsville
Jacobsville Sandstone
Sandstone can
can be
be seen
seen in
in
The
exposures
here
can
be
the exposures on the
left
side
of
the
road.
the left side of the road.
exposures here can be
compared and contrasted to
to Jacobsville that
that will be seen at Stop 99 and
Stop 10.
10.
25.9
the small
small town
town of
of Mason.
Mason. Mason was the
the site
site of company housing
Entering the
for
for the Quincy mill operations
operations from
from 1890.
1890.
26.5
On the
the right
right hand
hand side
side of
of the
the road
road is
is an
an old
old dredge
dredge which is
is stuck
stuck in
in
in Torch
Torch Lake.
Lake. This is the
the C&H dredge #1,
#1, built in
in 1913,
1913, bought
tailings in
by Quincy in
by
in 1955
1955 and
and used
used until
until 1967.
1967.
26.7
Now we pass
pass the
the remains
remains of
of the
the main
main buildings
buildings of
of the
the Quincy
Quincy Mill,
Mill, built
built
in 1890
1890 to
to accommodate
accommodate steam stamps,
required when
when the
Quincy operation
operation
in
stamps, required
the Quincy
expanded to
to the
the Pewabic
Pewabic Lode.
Lode.
27.0
Along the road on the
the left there
there are more outcrops of flat—lying
flat-lying Jacobsville
Sandstone.
27.3
On the right,
right, Torch
Torch Lake.
Lake.
27.7
On the right hand side of the
the road
road are tailings
tailings which have been revegetated.
revegetated.
These tailings
tailings now as we are entering Tamarack City are part of the
the mill
operation of the
the Calumet && Hecla company mines and the
the Calumet region
region which
have major mills located
located at
at Tamarack
Tamarack and
and Hubbell.
Hubbell.
28.15
On the left hand side of the
the road
road are the
the footings
footings from
from one of the
the Tamarack
Mills.
MAP 7
28.6
On the right
right hand side of the
the road
road are the
the remains
remains of a steam
steam stamp
stamp mill.
mill.
28.7
Left turn,
turn, going
going up
up the
the hill
hill toward
toward Stop
Stop 9.
9. Follow the paved road
road which
jogs a little
little to
to the
the left
left and
and goes
goes up
up the
the hill.
hill.
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�43
28.85
Cross the
the old Copper Range
Range railroad
railroad grade.
grade.
29.0
Sign indicating
indicating Hungarian
Hungarian Falls.
Falls. This is
is the
the lower
lower part
part of
of the
the falls.
falls.
Continue going up the
the hill,
hill, straight
straight ahead.
ahead.
29.25
Junction of a
a four—wheel
four-wheel drive
drive road
road to
to the
the left.
left.
Stop
and walk
Stop here
here and
towards
towards Tamarack reservoir/Hungarian
reservoir/Hungarian Falls
Falls upper
upper part
part where
where excellent
excellent
exposures of
of Jacobsville
Jacobsville Sandstone
Sandstone are
are found
found near
near the
the Keweeriaw
Keweenaw Fault.
Fault.
STOP 9.
9.
Hungarian Falls.
Falls.
The Keweenaw
Hungarian Falls is
is located
located near
near the
the Keweenaw
Keweenaw Fault
Fault (Fig.
(Fig. 21).
21). The
Fault is
reverse fault
Volcanics and
and
Fault
is aa reverse
fault that
that juxtaposes older
older Portage Lake Volcanics
the
In this
the younger Jacobsville
Jacobsville Sandstone.
Sandstone.
In
this locality,
locality, the
the Keweenaw Fault
presumably dips
dips at
at a
west similar to
presumably
a high angle to
to the west
to that
that illustrated
illustrated
in Figure 19,
in
19, Stop
Stop 7.
7. The
The Keweenaw Fault
Fault at
at the surface
surface varies
varies from
from aa
single fault
single
fault plane to
to aa more complex
complex fault
fault zone,
zone, such
such as
as described
described hear
near
Structural relationship
Lac La Belle.
relationship of
of beds
beds near
near the
the fault
fault
also varies
varies from steepened
also
steepened dips
dips to
to folds.
folds.
In general the
the dip of the
the
In
Portage Lake Volcanics and Jacobsville Sandstone
Sandstone steepen
steepen appropriately
appropriately
as one approaches the
the fault.
fault.
as
At Hungarian
Hungarian Falls the
At
the fault
fault contact causes very little
little deformation of
the Jacobsville Sandstone,
the
Sandstone, which
which is
is only
only tilted
tilted slightly.
slightly. To
To the west
of
of the fault
fault at this
this site
site the
the Portage Lake Volcanics are unusually shallow
shallow
If not
not viewed in the
If
the context of
of many
many other
other localities,
localities, the
the fault
fault
dipping.
might not
might
not be recognized as such
such a
a profound feature,
feature, and could appear as a
a
conformable contact.
contact. The
the fault
fault exposure
The contrast
contrast between
between the
exposure here
here and
and
that at
at the
the next
next stop
stop (Stop
10) at
at Hungarian
Hungarian Falls
Falls is
and illusthat
(Stop 10)
is striking
striking and
illustrates
of rocks
rocks along
along this
this major
major feature.
feature.
trates the
the structural variability of
The Portage
Portage Lake Volcanics near the
The
the Keweenaw Fault at Hungarian Falls conInterbedded
sists of
of basaltic lava flows
sists
flows with interbedded
interbedded conglomerate.
conglomerate.
sediments make
make up
up aa small
small part
part of
of the
of the
Portage
sediments
the stratigraphic
stratigraphic section
section of
the Portage
Lake Volcanics
Volcanics and
and are found
found as relatively thin
thin widely separated
separated beds.
beds.
However,
in the
the Keweenaw Peninsula conHowever, here and at some other localities in
glomerates
glomerates within the Portage Lake Volcanics are either near or at the
the
fault contact.
fault
Walking downstream
downstream along
along the
the stream
stream to
to the
the upper
upper and
and lower
lower falls
falls allows
allows
examination of
good
exposures
of
Jacobsville
Sandstone
with
cross bedding,
of
Sandstone
bedding,
interbedded shaly
shaly and
and conglomeritic
conglomeritic horizons
horizons and
and many
many typical
arkosic redred—
interbedded
typical arkosic
bed sedimentary features.
features.
29.25
Turn around and
and go
go back
back down
down the
the hill
hill to
to Tamarack
Tamarack City.
City.
29.8
Stop sign.
sign.
29.9
Entering Hubbell
30.5
On the right are Calumet &
& Hecla mill buildings which have recently
recently been
taken over
over by
by Michigan
Michigan Tech
Tech Ventures
Ventures as
as aa pilot
pilot plant
plant location
taken
location for
for small
small
industries. Torch Lake is
is still on the
the right with many of the
the tailings
tailings
out in
in the
the lake.
lake.
Stamp mill
mill remains are straight
Stamp
straight ahead.
ahead.
Turn left
left on
on M—26.
M-26.
�Ta arack
reservoir
metal gra
Jacobs yule
sands tone
100
feet
-.- z —
fIIs
D
fault
basalt
c Ong!omer
Figure 21:
Geologic sketch map of the Hungarian Falls area
(by J.M. Robertson, 1973).
Basalt and conglomerate are part
of the Portage Lake Volcanics.
Note that north is toward
the left margin of the page.
�45
31.4
Entering the town of Lake Linden.
The Houghton County Historical Museum
is on the right hand side of the road.
The building (1917) was donated
by the C&H Company to the Houghton County Historical Society in 1963.
Among the best displays are scale models of underground mines and a rich
photographic record of the boom copper days.
32.2
Right turn on Ninth Street (the so—called Bootjack Road) in Lake Linden.
32.35
Follow the signs to the Lakes
Left hand turn at two blocks after 32.2.
This is Gregory Street.
Drive—In Theatre.
MAP 8
33.3
On the left hand side of the road is the Lake Linden cemetery.
The road
heads north along the Trap Rock River Valley. On the left hand side of
the road at the top of the steep slope is the Keweenaw Fault.
On the
right hand side of the road is a flat—lying Jacobsville terrane.
The
Trap Rock River follows another of the glacially eroded, deep bedrock
valleys described by Warren (1981).
34.5
Pavement ends.
34.6
The gravel road bears to the right.
34.9
Cross a bridge over the Trap Rock River.
35.0
Left turn at the Trap Rock Schoolhouse.
35.0
Cross the Trap Rock River again.
35.7
Left turn on to another dirt road that begins to go up hill.
36.1
Access to the
Cross the railroad grade of the Copper Range railway.
Natural Wall ravine for mapping purposes can be gained by walking a
couple hundred yards to the left along this railroad grade and then walking along the stream valley up toward the fault line.
36.2
Poor exposures of flat—lying conglomerate beds within the Jacobsville Sandstone on the left hand side of the road.
36.4
Stop by an old wooden sign on the left hand side of the road.
200 meters to the left (south) to the Natural Wall ravine.
STOP 10.
Walk about
Keweenaw Fault at Natural Wall Ravine.
The Natural Wall is a bed of sandstone within the Jacobsville which has
a near vertical attitude and because it is more resistant, it forms a
On the sides of
wall which extends outward from the walls of the ravine.
the ravine the lithology of the Jacobsville here includes conglomeritic
The attitudes of beds in the creek
beds, sandstones and shaly horizons.
flat—lying
to
the
bottom change from
east, to vertical and even locally
overturned as the fault is approached. An anticline in the Jacobsville
trends parallel to and 300 m east of the fault.
West of the fault the
Portage Lake Volcanics dip to the WNW at 35—40° (Fig. 22).
�__
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Figure
22:
Geologic sketch map of the Natural Wall Ravine.
Note that north is toward the right margin of the page.
2
�48
37.95
The beginning of pavement, we are entering the town of Laurium.
38.7
Left turn which is followed immediately by a right hand turn at the next
stop sign on School Street.
38.8
Turn right.
Junction of School Street and Calumet Avenue, which is US—41.
This is Calumet, Michigan, the center of the Michigan Copper District,
and a site of the Calumet & Hecla headquarters. Here Edwin Huribut
discovered the Calumet conglomerate load in the early 1860's and this
Greater
became the most important ore body in the whole district.
Calumet (including Red Jacket, Blue Jacket, Yellow Jacket, Laurium and
Among many historic
Rambaultown) had a population of 33,000 in 1910.
buildings here are the Calumet Theatre (1900) and the C&H Community
Library Building (1898).
MAP 9
40.0
Entering Centennial
40.3
On the left hand side of the road you can see the Centennial Mine
After closing in 1968, this mine was dewatered in the
Shaft No. 6.
This operation has since been abandoned.
mid—l970's by Homestake.
The Centennial Mine Shaft Nos. 3 and 6 worked the Calumet and Hecla
The ore body lies up dip and northeast from the main ore
conglomerate.
body in the C&H conglomerate mined by the Calumet and Hecla Mine in the
The C&H conglomerate yielded about 4.2 billion lbs. of
Calumet area.
refined copper, the largest lode in th district and is over one—third
of the total production from the Keweenaw native copper district (total
district production of about 11 billion lbs.). The C&H lode had the
highest average grade in the district of 57 lbs. of Cu per ton of rock
treated (Weege and Pollack, 1971).
The Calumet and Recla conglomerate can be followed along strike for more
Along most of this length it is less than about 1 m thick.
than 65 Km.
In the Calumet area it averages over 3 m thick and tends to thicken with
The bed consists of north trending thicker and thinner zones
depth.
representing channels. At the Centennial Mine Shaft Nos. 3 and 6 thickness is often less than 3 m and the C&H conglomerate was deposited in
The pebbles in conglomerate at Centennial
a tributary stream channel.
The pebbles in
are almost all quartz—feldspar phenocrystic rhyolite.
the main channel conglomerate are a quite varied suite of rhyolite and
Main and
granophyre with some quartz—feldspar phenocrystic rhyolite.
tributary channel conglomerates tend to be coarser and contain less fine
Outside of the 5—foot thickness contours the
material where thicker.
bed is usually shaly or sandy. At Centennial, copper mineralization
tends to occur in bands with the bed and the intensity is related to the
type and amount of interstitial material and location of pinch—outs or
Higher grade areas are related to conglomerate with coarse
barriers.
sand or small pebbles as interstitial material, especially when pebbles
Evidence
and sand grains are quartz—feldspar phenocrystic rhyolite.
also strongly suggests that the mineralized areas follow the axis of
stream channels and grade is highest adjacent to the 5—foot thickness
contour where the conglomerate bed increases greatly n thickness down
These pinch—outs localized ore deposition from mineralizing soludip.
Sedimentological relationships are
tions that were migrating up—dip.
�S.
Q.
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�50
important in exploring the conglomerate ore bodies (summarized from
Wee and Pollack, 1971).
40.6
Entering Kearsarge, Michigan.
41.1
Stone boat on the
41.3
Right turn onto Water St1 .t just before the Wolverine Market.
straight ahead on the main paved road.
41.5
STOP 11 is the Wolverine Mine dumps. There are dumps both on the right
and left hand side of the road. The oner on the righL hand side of the
road (south), just on the other side of some old buildings, ar somewhat
dangerous because of bad ground. Mining in this are.a waS Very shallow
(Shaft No. 3).
The dumps on the left hand side of the road appear to be
(Shaft ice. 2).
much safcr
Park along the road and walk about 100 in to
right
hand side of the road.
Continue
the north.
The Wolverine Mine is one of seven different mines that worked the Kear—
Centennial, South Kearsarge, &orth Kearsa rge, Ahneek.
sarge amygdaloid:
Allouez, Mohawk, and Seneca. Production of copper from the Kearsarge
amygdaloid began in 1887 and stopped in 1967. About 2.3 billion lbs. of
ref -i:ied copper Were produced frccn the Kearsarge amygdaloid making it the
second largest producer of the Keweenaw native copper district (Weege and
Underground workings are continuous far more than 12 Km
Pollack, 1971).
and extend down dip as much as 2500 m. The Kearsarge amygdaloid is one
of the best documented ore bodies in the district.
The Kearsarge flow has been recognized for a distance of around 55 Kit along
strike,
it lies directly above the Wolverine sandstone. The flow dips
between 35 and 40 degt-ees to the northwest (Fig. 23). The interior of the
Jt
flow is a well developed ophite with a compositi:irI shown in Table 2.
has an amygdaloid top that ranges from near zero up to 10 in in thickness.
Just below the amygdaloid there is a zone in which the glow is distinctly
Abundance and size ol
porphyritic with tabular plagioclase phenocrysts.
the plagioclase phenocrysts in this zone is variable but they can make up
a large percentage of the rock and can be up to 2.5 cm in length. This
zone. is probably the result of plagioclise floating during in situ
crystallization of the flow. The stratigraphic and textural relRtionships
makes this flow wore easiiv recognized than most. The near—surface
thickness of the Kearsarge flow clearly shows that the most productive area
is where it is thickest (Fig. 24). The flow top in the productive ares is
Individual fragments
mostly a fragmental amygdaloid (flow top breccia).
are generally less than 15 cm in greatest dimension and contain nwnerous
small amygdules. The fragmental amygdaloid makes up the uppermost part
of the flow grading downward into banded cellular atnygdaloid with arnygdules
This grades downward into a zone with fewer
abundant at certain horizons.
and large amygdules with less tendency to be found in bands and stilt further
The amygdaloid top of the Kearsarg flow in
downward into massive basalt.
the mined area has an average thichness of around 2 rn (summarized from
Butler and B'jrbsnk,
1929).
�51
I
A'
A
C
ln,IIe
4000t1
Figure 23: Geologic map and cross section showing
Mine and vicinity (modified from White and others,
me Mine Shaft No. 2 dump (see Map 9). Labels are
(pi); Calumet and Hecla conglomerate (pc); Osceola
merate (pkc); Wolverine sandstone (pw); Old Colony
conglomerate (ps).
Table 2: Major—element composition of the
Kearsarge flow (from Stoiber and Davidson,
This is a weighted average exclu1959).
sive of the top 12 feet and thus represents a close approximation to the
original composition of the flow.
the Kearsarge flow, Wolverine
1953).
Stop 11 is the Wolver—
Iroquois flow,
as follows:
flow (po); Kingston conglo—
sandstone (poc); St. Louis
Weight Percent
Si02
A1203
Fe203*
MgO
CaO
Na20
1(20
Ti02
MnO
H20+
H20—
CO2
Total
ppm Cu
48.55
16.51
11.54
6.68
9.44
2.82
0.58
1.49
0.18
0.16
2.06
0.63
0.15
100.79
90
�52
300
Thickness 200
feet
100
Top of Wolverine
sandstone
C)
CD
0
CD
0
a
CD
CD
Butler and Burbank, 1929).
Figure 24: Thickness of the Kearsarge flow (modified from
from
This is the near surface thickness along a strike distance of around 35 miles
directly
to Mandan (Map 20). The thickness is relative to the
Isle Royale (Map
)
underlying Wolverine Sandstone which is arbitrarily shown as horizontal.
Th
Chlorite
Epidote
Microcilne
Hematite
Prehnite
Pumpellyite
Quartz
Sericite
Native Copper
Calcite
early
—
TIME
late
Figure 25: Paragenesis of secondary minerals in the Kearsarge amygdaloid at the
Wolverine Mine Shaft No. 2 (Paces and Bornhorst, unpublished data). The relationships are based on a limited megascopic and thin section study of samples from the
Shaft No. 2 dump and may be modified slightly as research proceeds. The exact
timing of the later minerals are difficult to determine because they do not occur
together.
�interior. flow Kearsarge the of outcrops find can
one
dumps
3
and
2
Nos.
trace. quartz, and 1;
Shaft
the
of
vicinity
the
In
prehnite, 10; epidote, 38; microcline, 51; calcite,
minerals: of percentage
following the estimated data) (unpublished Stoiber whole, a as dumps 2 and
Nos. Shaft the For
found. be can copper native with specimens Excellent
1
relationships. paragenetic their and assemblages mineral of variety a see to
opportunity the have will you dump 2 No. Shaft Mine Wolverine the At
trict.
dis- copper native Keweenaw the in bodies ore amygdaloid of complexity the
of illustration excellent an is amygdaloid Kearsarge the of area ductive
pro- the within minerals amygdule of variation spatial and temporal The
Bornhorst). and Paces of data unpublished of addition with 1959
Davidson, and Stoiber from summarized (mostly zones regional the within
islands free prehnite and quartz are there that suggests data detailed
zones. prehnite and quartz the within lies amygdaloid Kearsarge the
Thus,
scale regional a On
mineralization. copper significant of limit the mark
also may microcline of limit The
boundary. zone quartz the straddle to
appears ore copper richest The
zones. mineral the than irregular more much
is present copper native of amount The
absent. is it until depth with
irregularly decreases microcline of amount The
depth. increasing with
zone quartz the within content quartz in increase irregular an is There
zone. quartz the within percent 15 about averages whole a as and depths
shallower at percent 10 than less considerably is Quartz 27). (Fig. depth
with vary mineralization copper native of grade and minerals amygdule the
However,
mineralization. copper native of grade the and banding between
correlation strict no is There 25). (Fig. samples individual in seen
relationships paragenetic the with consistent is This openings. remaining
the in calcite of deposition finally and channel the of center the in
epidote and quartz by followed channel solution the of parts outer the
along first deposited been have would microcline and Chlorite channel.
permeable a along moving solution hydrothermal a from minerals secondary
of deposition by explained be may banding The
26). Fig. in corner wall
hanging (north flow overlying the of base the in found is assemblage last
The microcline. ± chlorite—calcite and epidote; ± calcite—microline
calcite—epidote; quartz—epidote; microcline; ± calcite ± chlorite layer:
amygdular the of top to bottom the
mineral major five are
from
assemblages
There
bedding. to parallel roughly are
bands
The
Table
and 26 (Fig.
3).
amygdaloid Kearsarge of bottom to top
from
minerals
amygdule
of arrangement
banded a is there 3 No. Shaft Mine Ahmeek the In
25). (Fig. chlorite and
calcite, copper, native quartz, are minerals formed latest the and minerals
formed early are prehnite and microcline epidote, chlorite, Paragenetically
spatially. and temporarily both vary assemblages mineral secondary The
1959). Davidson, and Stoiber
from (summarized minerals amygdule secondary the with associated occurs
copper Native sericite. and laumontite,
pumpellyite, prehnite, chlorite,
K—feldspar, epidote, calcite, abundant):
of amounts lesser and quartz
least to (most are whole, a as amygdaloid Kearsarge the in minerals
filling space interfragmental and amygdule The plagioclase. replacing
pseudomorphically pumpellyite fine—grained of consists basalt lyitized
Pumpel—
groundmass. cryptocrystalline to fine—grained a in set laths
albite euhedral percent 60 about is basalt Albitized pumpellyitization.
and albitization
alteration: of types two by affected been has basalt
top flow The
oxidized. well is amygdaloid Kearsarge the in basalt The
53
�54
NORTH
SOUTH
Ii
chlorite-mlcrocline-calcite
SCALE
Eli:;
10
0
3Oleet
20
copper
,, Contact between Kearsarge amygdaloid
and overlying flow bottom
Figure
26:
Cross section of the Kearsarge amygdaloid showing the banding of
amygdule mineral assemblages, Ahmeek Mine, 35th level, 399 to 500 feet south
of Shaft No. 3 (from Stoiber and Davidson, 1959). The footwall is the bottom
of the Kearsarge flow. Data from the back and walls are projected to a horizontal plane.
In one mapped locality Stoiber and Davidson (1959) found a
laumontite—quartz—calcite zone.
Amygdule mineralogy of the various zones
are given in Table 3 below.
Table 3: Volume percent of amygdule minerals from mapped assemblages shown
in Figure 26 (from Stoiber and Davidson, 1959).
Mineral Assemblage
Band
Chlorite
Chlorite—
Microcline—
Calcite
Microcline—
Calcite
Quartz—
Epidote
Calcite—
Epidote
0—3
45—82
0—47
5—10
0—trace
0—8
0
0
Volume Percent
Amydule Filling
Chlorite
Microcline
Calcite
Epidote
Pumpellyite
Quartz
100
0
trace
0
69—74
15—25
0—5
0—1
0
0—6
0—5
1
2
0
2
0
0—1
90—96
0
87
12
0
trace
4—9
1
2
1
�copper
SCALE
2
27:
4
SENECA
N
K
(thousands of feet)
W
Distribution of quartz, microcline and high grade native
Microcline present on hachured side of line only
-" Lower limit of microcline
l?igure
A
Over 10% quartz on hachured side of line
Upper limit of quartz
Very high grade copper ore
NORTH
KEARSARGE
AHMEEK
MO H
ore in the Kearsarge amygdaloid (modified from Stoiber and
Davidson, 1959).
The
Calcite and epidote are present in all zones.
Kearsarge amygdaloid dips about 35 to 40 degrees to the northwest.
Data from the incline are projected to a horizontal plane.
CENTENNIAL
WOLVERINE
SOUTH
KEARSARGE
�56
41.5
Continue on the same road and in the same direction as before (.isr),
away from Kearsarge.
42.1
There is a dirt road junction to the right, stop here. We are now in the
vicinity of Scales Creek, which is the type section of the Scales Creek
flow.
This Is the sane flow seen at Stop 1, about 14 miles to the south,
in Houghton.
STOP 12.
Scales Creek.
This stop gives one an opportunity to look at the Scales Creek flow, a
regionally extensive basaltic flow.
This is the same unit observed at
Stop 1, and it has been traced for more than 150 Km along the Keweenaw.
There are outcrops of the Scales Cteek flow on both sides of the main
road and along Scales Creek, just to the north and paralleling the road.
The Scales Creek flow Is characteristically ophitle.
This flow was studied,
from drill core northeast of here, by Scofield (1976).
The Scales Creek
The massive
flow has an amygdaloidal top and base and a massive interior.
interior of this flow is believed to be for the most part geochemicallv
unaltered (Table 4). Mineralogically primary and secondary minerals are
present. Modes estimated for the massive interior are plagioclase, 40 percent; pyroxene, 48 percent; olivine, 10 percent; and opaque oxides, 2 percent.
Primary plagioclase, pyroxene, and opaque oxides can be found but
olivine is pseudomorphically replaced by talc, serpentine, and/or chlorite.
In the amygdaloidal flow top no primary minerals are present but all have
P]agioclase is
been replaced by a suite of secondary alteration products.
now albite with some replacement by sericite, chlorite, and puinpellyite;
clinopyroxene is replaced by chlorite; olivi.ne is replaced by chlorite,
epidote and pumpellyite, and opaque oxides are altered to hematite and
sphene.
Scofield (1976) has studied these changes in some detail.
42.1
Turn around and retrace route back to US—4l.
42.7
Passing the Wolverine mine dumps, Stop 11.
42.9
Right turn on 115—41 at Wolverine Market.
44.2
Entering the Village of Allouez. We have an excellent view of the southeast side of a prominent ridge. This ridge is held up by the Greenstone
flow which is the thickest and volumetrically Largest single flow within
the Portage Lake Voicanics.
It wili be seen at Stop 14.
44.4
Left turn on a paved road called Bumbletownkoad, just before a Standard
gas station.
44.6
Stay on the paved road, bearing right.
44.75
STOP 13.
Allouez Conglomerate and flumbletown Hill (Fig. 28).
The description of this stop is modified onj.y slightly from White
(1971b).
The stop begins with a survey of the dumps of the Allouez conglomerate
mine (1869—1392, 1300T Cu).
�Table 4: Average composition of three samples
from the massive part of the Scales Creek flow
(from Scofield, 1976).
Weight Percent
5i02
47.57
A1203
16.10
Fe203*
12.54
MgO
7.67
CaO
10.00
Na20
2.24
K20
0.29
Ti02
1.43
97.84
Total
0
1000
L
Figure
28:
Outcrop map of the Allouez—Bumbletown
Hill area (White, 197lb).
2000 FEET
�58
The lithology of the conglomerate is best studied in the dumps. The
largest boulders in this conglomerate are about 2 feet in diameter,
and the median size is about 3 inches. A pebble count of boulders
mafic rock,
more than 8 inches across gave the following results:
mostly amygdaloidal, 16 percent; quartz porphyry, 36 percent; feldspar
porphyry, 11 percent; granophyre, 37 percent. The greater heterogeneity
of this assortment suggests a less restricted source terrane than the one
that supplied the Kingston and Houghton Conglomerates in this area; the
Kingston, in particular, is made up almost entirely of fragments of
quartz porphyry.
These dumps are well known to rockhounds as a chryso—
colla locality. Thin black veinlets cutting the conglomerate are calcite
full of chalcocite dust.
From the dump, it is a short walk to the top of the hill, which is an
area of exceptionally good exposure and provides an opportunity to see
several key units of the Portage Lake Lava Series. One has a unique
view of both an area of intensive mining activity and of the general
physiography of the Copper Range. From here, on a very clear day, one
can see Isle Royale to the northwest. The Huron Mountains lie beyond
Keweenaw Bay to the southeast.
Bumbletown Hill is on the southwest side of Allouez Gap, a saddle crossing
the Copper Range, similar to, but much less prounounced than, the valley
at Houghton—Hancock. At this gap, the strike of the lava flows swings,
going northeast from about N35°E to N50°E. Fractures and minor faults
associated with this bend are probably the reason for the gap.
To the northwest, the land slopes off very gradually toward Lake Superior,
The southeast
as it does through most of the length of the Copper Range.
flank of the Copper Range has a steeper slope at the skyline, more or less
along the line of the Keweenaw Fault. The low—lying plain between the
fault and Keweenaw Bay to the southeast is underlain by flat—lying Jacobs—
ville Sandstone.
Looking northeast along the strike of the Copper Range, one can see the
At Bumbletown
cuesta form of the ridge upheld by the Greenstone Flow.
Hill, this flow is only 85 m thick; it thickens abruptly to more than
300 m at the near end of the cuesta ridge. To the right of the Greenstone
ridge, the more distant hills are upheld by lavas much lower in the section;
dips of bedding are steep, and cuesta forms are less pronounced.
The amygdaloidal top of the Kearsarge Flow has been the principal producer
in this area. The line of shafts along its outcrop is a little more than
a mile southeast of Bumbletown Hill, and the bottom levels are almost
vertically below the surface trace of the Houghton Conglomerate (see outThis immediate area is unique in that five different and widely
crop map).
separated layers have been at least modest producers, suggesting a common
Stratigraphically highest is the Allouez Conglomerate;
plumbing system.
dumps of the old Allouez mine (1869—1892, l3,000T copper) lie along the
A small headframel200m N65°E of the
foot of the hill, 300 m southeast.
hilltop is the Allouez No. 3 Shaft, which produced (1944—1964) about
l7,000T of copper from the Houghton Conglomerate (No. 14) and 2000T
copper from the Iroquois Amygdaloid, 170 m stratigraphically beneath;
The large headframe 6200 feet due
both were found by diamond drilling.
�59
east of the hilltop serves the shaft of the Kingstone Mine; this deposit,
discovered in 1962 also by diamond drilling, is in the Kingston Conglomerate
(No. 12), 300 m stratigraphically above the Kearsarge Flow.
The outcrops on the top and upper slopes of Bumbletown Hill represent a
series of andesite flows, some slightly porphyritic.
The flows range
Unlike the basaltic flows found below the
up to 20 m in thickness.
Houghton Conglomerate, these flows are not individually very extensive;
the map shows two flows pinching out within this small area.
As a group,
the
hilltop
are
stratigraphically
equivalent
the flows in the vicinity of
whose
and lithologically similar to those
tops were mined at the Quincy
Mine, just north of Hancock.
The Greenstone Flow is exposed in a series of outcrops 160—300 m southIts thick amygdaloidal top is exposed at the end
east of the hilltop.
of a private roadway 200 m south—southeast of the hilltop.
Columnar
fine—grained basalt and ophitic basalt can be seen in exposures farther
down the slope.
45.05
Take a left turn on US—4l and cross into
Retrace route back to US—4l.
Keweenaw County from Houghton County.
45.9
Entering Ahmeek.
46.25
Junction to Cliff Drive.
MAP 10
47.65
49.5
Turn left on Cliff Drive.
Passing Seneca Lake on the right hand side of the road. We are driving
Along the road are
along strike, near the base of the Greenstone flow.
several small basalt outcrops mostly on the left side of the road,
At this point the Greenstone Flow abruptly thickens to nearly 400 m.
It
dips northward at about 25° toward the Lake Superior Syncline.
This lava
flow can be traced along much of the Keweenaw and has been stratigraphically
and geochemically correlated with a similar unit on Isle Royale, 90 Km away
on the other side of the syncline (see Fig.
Thus the areal extent
3a).
of this great flow exceeds 5000
and its volume is of the order of 800—
1500 Km3 according to White (1960) and Longo (1983).
It rivals the composite Roza flow (Columbia R.) as the largest known lava flow on earth,
The Greenstone typically shows spectacularly developed pegmatites, ophitic
horizons and columnar jointed areas. A cross section of the Greenstone
Flow at this locality and a map of the zone where the flow thickens rapidly
The pegmatoid zone is unusually thick in the northern
are in Figure 29.
part of this map.
The ophitic zones of the flow are relatively unaltered
portions and Longo (1983) has shown that the composition of these zones
are remarkably constant and demonstrated the great chemical similarity
of the composition of the Isle Royale and Keweenaw ophitic exposures of
The rapid thickening of the Greenstone here was sugthe Greenstone Flow.
gested by White (pers. comm., 1982) to be caused by the separation of the
upper part of the flow into multiple flow units, which appear to be separate
flows.
To the north the flow may be a continuous, single flow unit, while
to the south it may have been made up of many flow units.
�—_
. ,.//
!
•
•
,•//Moh
/7
0
)
/
(
-
/
•1'
2
Io
/
)
)
�10
I
EM
0
7
SCALE
1 mile
Figure 29: Map and cross section showing vertical
zones within the Greenstone flow between Seneca and
the Cliff Mine (from Longo, 1983).
I
92
1
2
20
15
225
285
680
(feet)
Thickness
Vertical Scale: 1"=200'
Sub-ophite
Pg: 2nd Pegmatoid Zone
-Sub-ophite
Pg: 1st Pegmatoid Zone
LOp: Lower Ophite
Pg: 3rd Pegmatoid Zone
UOp: Upper Ophite
Mel anophyre
EM: Columnar Jointed
Top of Flow
Vesiculated Flow Top
�62
MAP 10 and 11
50.0
Crossing the Cratiot River
MAP 11
50.6
52.5
We are now driving on the southeast side of a prominent ridge which is
held up by the Greenstone Plow.
We are at the site of the Cliff Mine which was the first mine in the
district. The dumps ind old footings for the mine building are mainly
on the 1.eft hand side of the road and the townsite, of which little remains, is on the right hand side of the road.
optional stop where one can look at the Greenstone Flow and
the Cliff Mine dumps.
In this region the Creenatone Flow is mainly
ophitic basalt and sometimes shows quite well dev.loped coarse columnar
jointing.
The Cliff Mine worked the Cliff fissure. The mine operated
discontinuously from 1845 to 1887.
It produced a tote] of abcwt 38 million
The productive portion of the fissure lies under
lbs. of refined copper.
the Creenstone Flow.
The Cliff fissure is nearly at right angles to the
attitude of bedding and dips steeply to the east. Most of the mineralization was confined to the fissure although SOL1C amygdaloids were mineralized
(Cliff Mine suinmarizedtromsutler and Burbank, 1929). Many large masses of
native copper were mined from the Cliff Mine and larger masses weighed up to
100 tons. The large 100 ton mass had to be cut, by hand, into smaller pieces,
it could not be blasted (Clarke, 1976). Among the fissures rhr Cliff was the
In addition to native copper and silver the followmost productive of silver.
caling minerals are found at the Cliff Mine (not in order of abundance):
cite, epidote, chlorite, laumontite, prehnite. datolite, thomsonite, chlora—
strolite, apophyllite, adularia, gypsum, sphalerite, galena, pyrite and
surface oxidation minerals.
This is zir
53.1
Tunction of U5—41/M—26.
Turn left (north).
MAP 12
53.4
Entering Phoenix
54.5
Turn left on a dirt road just before (0.1 mile) the junction between US—41
It is about 100 meters from the paved road to the base of the
and M—26.
Phoenix Nine dump which is Stop 14.
STOP 14.
Phoenix Mine and Greenstone Plow.
At this stop one can look at the Phoenix Mine dump and the lower ophite of
The Phoenix Mine worked numerous veins below the
the Creenstone Flow.
Greenstone Flow. Like the Cliff Mine discussed at mileage 52.5, the Phoenix
t'Iine was one of the. eatltet mines in tze d.Lstrict and opexattd off and cc'.
from 1849 to 1917. It produced a total of about 17 million lbs. of refined
The Phoenix Mine also worked the Ashbed
copper (Butier and Burbank, 1929).
ainygdaloid where it is mineralized in the vicinity of vein copper occurrences.
The Phoenix Mine dump is notable for halfbreedS (native copper plus native
silver) and for spectacular secondary analcite. Other minerals reported in
the Phoenix Mine ares (Clarke, 1974a) include: pumpellyite, chlorite,
natrolite, chlorastrolite, and apophyllire.
�It I
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Phoenix Ashbed1..
-
Workings !
LI9
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A9i-PhoenIx Mine
-
K
Stop
11'
MAP 12
--
�54.6
Flow. Greenstonie the cross and strike to perpendicular drive
River. Eagle towards M—26 on left Turn
55.0
flow. the in middle cooling slower the represent which exposures, these on
found be can cm 5 to up pyroxenes individual with texture, ophitic coarse
Exceptionally
road. the of left the to Flow Greenstone the of Outcrops
55.4
River.
Eagle
along traverse a begin also can one road,
the up just 15, Stop At
spring. the of periods water high the in done
be can't This contacts. flow many at looking River Eagle to way the all
here from downstream river the follow can You pools. deep many are there
locality this in and road the of site the from m 25 about is River Eagle
River. Eagle along seen be can Flow Greenstone the above flows the where stop
optional an is This
road. the of side hand right the on pull—out a is There
55.7
downstream. or upstream either River Eagle along traverse a begin to
possible is it stop this At
flow. Ashbed the of north River Eagle in bend
sharp very a is There flow. Ashbed the crosses River Eagle locality
this In
right. the on pull—out road dirt maintained poorly a is There
to begin and River Eagle Cross
l951b). (l951a, Cornwall by papers in described
was Flow Greenstone the of differentiation of petrology and chemistry The
Sn
Sc
28
Zr
Zn
Y
V
Sr
195
259
92
84
14
wt.%
ppm
0.14
1.2
0.4
2.1
9.9
7.8
12.8
15.1
46.7
214
104
6
8
186
1680
11
66
Rb
Ni
Mn
La
Cu
Cr
Ba
Ti02
K20
Na20
CaO
MgO
FeO*
A1203
Si02
is: (1983) Longo of study
from determined Flow, Greenstone unaltered the of composition average The
1877—1887. from 1,000 of population a had which
Phoenix, of townsite the of and flow great the of strike the of view
a is there Ridge Greenstone the of top the From
observed. be all can
zones ophitic and subophitic pegmatoid, the cliff the along exposures the
following By
30. Figure in shown ophitic lower the is zone ophitic The
Flow. Greenstone the of portion ophitic
the of exposure spectacular a is there where hill the of top the to climb
and ahead Proceed
shaft. the above just zones fissure the of one pass
then and dump the over up climb must you Flow Greenstone the at look To
65
�1
mIle
PHOENIX
(Longo, 1983).
Figure 30:
Section and map of the zonation of
the Greenstone flow near Phoenix, Michigan
SCALE
I
78
540
5
62
8
170
35
25
250
(feet)
Thickness
I
____.
______
Lower Ophite
Vertical Scale: 1"200'
Bottom of Flow
LOp:
Sub-ophite
Pg: Pegmatoid Zone
_—Pg: Pegmatoid Zone
Sub-ophite
C'
a.'
Pegmatoid Lenses
with intercalated lenses
of ophites and sub—ophites
Sub-ophite
Pg: Pegmatoid Zone
Pg
UOp: Upper Ophite
Ml: Melanophyric Zone
Top of Flow
�67
STOP 15.
Eagle River
Eagle River, Jacobs Creek and Owl Creek each make excellent stream traverses which are regularly mapped as an introductory exercise in the
Michigan Tech field camp. At this point, approximately at the Ashbed
amygdaloid, a traverse along the stream north to Eagle River allows
excellent observations of the upper stratigraphy of the Portage Lake
Volcanics.
The Ashbed is a very distinctive fragmental amygdaloid traced over a distance of almost 100 Km in outcrop and drill holes.
It is the second flow
top below the Hancock Conglomerate (Fig. 31 and Map 12).
The amygdaloid
is a jumble of amygdaloid fragments and interstitial brown, fine—grained
detrital material.
The secondary minerals filling the amygdaloid are
calcite quartz, chlorite and minor epidote.
Some vesicles contain minute
Exposures of the Ashbed are found both in
flecks of Cu (White, 197lb).
Small mines were found along this horiroadcut and within the streambed.
zon in many places, from Atlantic Mine (near Stop 3) to Copper Falls
(Stop 17)
The stream traverse to Eagle River traverses the section shown in Figure 31.
Among the features seen in the traverse are:
1) excellent sections through
individual lava flows showing amygdaloidal tops, and massive melaphyric,
2) Interbedding of sediments
glomeroporphyritic or ophitic lower portions.
with the lava flows, which becomes more prevalent up section.
3) The
occurrences of several dikes which cut the section at low angles. These
dikes make up a very small portion of the volume of the section and may
be analogous to the dikes described in the Tertiary lavas of eastern Iceland by Walker (1975).
If you decide to take this traverse, it's best to
to
wet
feet and the traverse is not advisable in the
just resign yourself
water.
spring because of high
The flows just above the Greenstone Flow are compositionally different from
Although they are tholeiitic basalt like
most of the Portage Lake Lavas.
nearly all the PLy, these rocks are distinctly higher in K20 and other inLower in the stratigraphy below the Gratiot
compatible elements (Fig. 32).
flow another zone of K—enriched basalts occur.
This caused Rose and Crimes
(1979) to divide the PLV into three cycles of basaltic lavas each of which
The cycles may reflect different
begins with relatively K—enriched basalts.
It is interesting to note that
degrees of partial melting or fractionation.
one of these cycles begins after emplacement of the Greenstone Flow.
55.9
There is an outcrop of amygdaloidal basalt on the left side of the road.
Further off of the road is a rock dump from the Phoenix Ashbed workings
(1855—1862, 1913—1917, 400T Cu).
56.6
Entering Eagle River. On the left is the road to Five Mile Point. The
stone monument is a memorial to Douglass Houghton who was the first State
He did pioneering geologic studies in the Keweenaw
Geologist of Michigan.
He drowned off Eagle River in 1845.
Peninsula.
56.8
Cross Eagle River on the Eagle River Bridge.
Park NE of the bridge.
�COPPER HARBOR
CONGLOMERATE
68
14000
Stratigraphy of
Figure 31:
the Portage Lake Volcanics
above the Greenstone flow in
the vicinity of Eagle River and
Phoenix, Michigan (from Cornwall and Wright, 1954).
Melaphyre
Tongue of Copper Harbor conglomerate
MelophyreS
13000—
Ophihc flows; thickest flow pegmatific
Melaphyres
flows; thickest flow pegmatitic
Melaphyres; thicker flows slightly
glorneroporphyritic and ophitic
12000—
—Hancock conglomerate (No. 17)
gygaloid}t egrained rnelaphyreo,
Ashbed
porphyritic
Melaphyres; thicker flows glomeroporphyritic
and pegmatitic
melaphyres, porphyritic
lomeroporphyritiC flows
Upper chill zone
Greenstone flow
PORTAGE LAKE
LAVA SERIES
�•
.S
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S
.••
S
•
•
•
S.
S
•
S
S
I
•
S
S
S. ••
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S
S
S.
S
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S
S.
S.
••S.
S
•
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• •S
•
S
•
•
2
S
S
S
•
1(20
3
'
S
M-O
5wt%
75
50
-
25—
No.
S ••
•
S
S
:.
S
S
S
S
S
.
S
•
S
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S
S.
•
.2
S
S
S
S
•
S
.3
P205
I
.4
.5
GS
wt%
top) sampled
Figure 32: Plot of K20 and P205 content of 106 individual PLV flows in stratigraphic order (1
in drill holes across the section in the vicinity of Delaware by W. S. White (pers. comm., 1976) and reported
GS represents the Greenstone flow horizon, M—0 represents the melaphyre—ophite line,
by Rose and Grimes, 1979.
a texturally traceable line in the PLV below the Gratiot flow in this area. The stratigraphic position is
plotted by flow no. and is not to scale.
75.
50
25
No.
S
S
1
I
�70
STOP 16.
Eagle River Falls.
The falls occur at the contact between the top of the Portage Lake Volcanics
and the base of the Copper Harbor Conglomerate. There are some spectacular
If the water is low, like it is
potholes that have developed on this face.
sometimes in the summer, you can see ropy surfaces on flows at the top of
The contact dips about 30° NNW. The contact
the Portage Lake Volcanics.
relationships suggest very little erosion between the flow and deposition
Under the bridge one
of the basalt beds of the Copper Harbor Conglomerate.
can get a good view of the lithology of the lower part of the Copper Harbor
It consists of mostly rhyolite pebble conglomerates but inConglomerate.
cludes many sandstone and even some shaley beds.
There is an optional route to Eagle Harbor via Sand Dunes Drive
given after the Garden City road log.
NOTE:
Eagle River to Eagle Harbor via Garden City Road
MAP 12
56.85
Go straight after crossing the bridge. M—26 goes to the left which is
the optional route. Passing in front of the Keweenaw County Courthouse
and offices.
57.1
Gitche Gumee Bible Camp, continue on paved road.
57.2
Pavement ends.
MAP 13
60.2
This is the Garden City Road.
Junction with paved road.
Turn left towards Eagle Harbor.
60.3
Cross Jacobs Creek.
60.5
Junction of a dirt road on the left.
Continue ahead on paved road.
From this road, a short distance to the west, there is access into Jacobs
Creek, at the site of the Arnold Mine, along the Ashbed amygdaloid. This
is the end of a traverse one can make across the upper part of the Portage
It is recommended to begin the traverse at the lower end
Lake Volcanics.
of Jacobs Creek where it crosses M—26 (Sand Dunes Drive optional route to
This is a very tough traverse with many steep and dangerous
Eagle Harbor).
There are excellent exposures of many individual lava
points within it.
At the Arnold Mine, one of the nearly conformable
flows along Jacobs Creek.
Geologic traverses made along
massive dikes is exposed in the streambed.
ahead),
and Jacobs Creek allow
Eagle River (Stop 16), Owl Creek (Stop 17
lateral
variations
in
the
upper part of the Portage
one to look in detail at
Lake Volcanics.
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71
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MAP 13
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�72
61.2
On the left is a roadside park with a tower.
From the top of this tower
there is an excellent view of Isle Royale on a clear day.
You can also
see some of the ridge—valley topography due to the dipping lava flows
and conglomerates in this part of the section.
61.9
Dirt road that slants to the right goes to the old townsite of Copper
Falls.
Copper Fails was settled in about 1846 and had a population
of 500 in 1877.
Today there are a handful of residents.
62.2
Cross Owl Creek.
62.3
Road to the right goes upstream to the dumps of the Copper Falls Mine
which is part of Stop 17 described below.
62.4
If you follow this road several hundred
Road to the left goes downhill.
meters, you will reach the 30—mile stampsands which are the tailings dump
from the Copper Falls mining operation.
From this stampsand you can gain
access to the bottom of Owl Creek and can begin a one—hour traverse upIf you continue upstream beyond
stream to the bridge along this road.
the bridge, you will reach poor rock dumped along Owl Creek from the
Copper Falls mining operation. By climbing out of the creek bed, to the
east, one can reach a dirt road which will come out on the main road at
62.3
STOP 17.
Owl Creek — Copper Falls Mine.
Owl Creek is another one of the streams that cut across the upper part of
The traverse begins downstream where the base
the Portage Lake Volcanics.
of the Copper Harbor Conglomerate and top of the Portage Lake VoiLcanics
interfinger.
There are excellent exposures of interbedded conglomerate!
There are
sandstone and lava flows along the bed and sides of Owl Creek.
several well exposed amygdaloidal flows.
The Copper Falls Mining Company worked several fissures and the Ashbed
The mine operated from 1847 to 1893.
It produced about 18
amygdaloid.
million lbs. of refined copper from the Ashbed amygdaloid and about 9
Copper Falls
million lbs. from fissures, mostly the Owl Creek fissure
was the only mine in the north end of the district above the Greenstorie
flow that paid dividends but was not a profitable venture (summarized
from Butler and Burbank, 1929).
The Owl Creek vein starts near the base of the Copper Harbor Conglomerate
and extends through the Portage Lake Volcanic Series, probably into the
Greenstone flow. The vein was productive only in the vicinity of the Ash—
bed amygdaloid.
The Ashbed flows are distinctly porphyritic.
The amygda—
bid is scoriaceous with a notable clastic component. In some localities
The mineralpebbles and boulders of amygdaboid are set in a sandy matrix.
ization of the Ashbed amydgdaloid is similar to that found in other amygda—
bids in the Keweenaw Peninsula. At the Copper Falls Mine the more abundant
minerals are:
calcite, quartz, epidote, and pumpellyite.
Datolite is
abundant in the Ashbed near fissures. Datolite is abundant in fissures
Native copper was more abundant toward the top part of
such as Owl Creek.
the deposit.
Other minerals reported in the Copper Falls area include:
�73
laumonitite, prehnite, native silver, adularia, analcite, apophylite,
faugasite, natrolite, stilbite (summarized from Butler and Burbank,
The Copper Falls Mine is stratigraphically one
1929; Clarke, l974b).
highest in the Keweenaw native copper district and is near the top of
the pumpellyite zone (see Figs. 4b and 9a in the Introduction).
MAP 14
63.75
63.85
Crossing Eliza Creek
There is a dirt road that goes off to the right. From this dirt road
just a few hundred meters up hill you can begin a traverse upstream
on Eliza Creek to get the exposures of the Portage Lake Lava flows of
this region.
64.9
We are at Eagle Harbor where we join back up with M—26.
Turn right on M—26.
Eagle River to Eagle Harbor via Sand Dunes Drive (M—26).
MAP 12
o
At Eagle River Bridge make a sharp left turn, follow M—26.
0.1
Sharp right turn.
MAP 13
3.05
Jacobs Creek Falls. From this point one can begin a traverse up Jacobs
Creek that ends near the Arnold Mine on the Garden City Road (mileage
There are excellent exposures of the upper part of the Portage
60.5).
For those who are hardy, the stream
Lake Vol.canics along Jacobs Creek.
offers virtually continuous exposures through thin pahoehoe flows,
especially in the first several hundred meters. This is a steep and rough
traverse, and should not be attempted in high water periods.
4.9
Great Sand Bay.
5.9
The Lake Shore Traps form the offshore ridge. The Lake Shore
Cat Harbor.
Traps are mafic lava flows interbedded with the Copper Harbor Conglomerate.
MAP 14
7.8
Right hand turn by the Eagle Harbor Store.
8.0
We are at the Junction of M—26 and Garden City Road Route.
Return to Main Road Log Mileage.
Stay on M—26.
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65.0
65.75
MAP 15
66.9
67.5
67.65
The harbor at Eagle Harbor is controlled by the occurrence of units which
These are basalt flows which are inter—
are called the Lake Shore Traps.
bedded with conglomerates of the Copper Harbor Conglomerate and form typiThere are excellent exposures of the Lake Shore
cally resistant ridges.
Traps that occur at the Eagle Harbor Marina and continuing along the shore
through Grand Marais Harbor and into Agate Harbor and eastward through
small boat from the
Copper Harbor. These are accessible by canoe or
winds
are
on—shore.
Marina, but don't try it if the
Junction to the left to the Eagle Harbor Marina.
Continue ahead on M—26.
On the right hand side you can see the offA view of Grand Marais Harbor.
shore islands and ridges which are controlled by the occurrence of the
Lake Shore Traps. We are driving along a conglomerate ridge.
this
Road passes along the shores of Lake Bailey on the right hand side of
Harbor Conglomerate
conglomerate ridge. The ridges throughout the Copper
the
valleys
are
underlain by the
tend to be held up by the conglomerates,
On
conglomerate.
and
shaley
members
within
the
more easily eroded sandy
The
(on
the
right)
is
Mount
Lookout.
the opposite side of Lake Bailey
Vol—
contact between the Copper Harbor Conglomerate and the Portage Lake
canics runs through the back side of Mt. Lookout.
sandstone
On the left hand side of the road there are exposures of the
members of the Copper Harbor Conglomerate.
NAP 16
69.1
69.2
69.7
70.0
Crossing the Silver River there are excellent exposures of the Copper
Brock—
Harbor at this locality and along the left hand side of the road up
look
at
the
Copper
Harbor
way Mountain. This is an optional stop to
At Eagle River Falls (Stop 16) one had the opportunity to
Conglomerate.
At this locality
look at the basal beds of the Copper Harbor Conglomerate.
of
the
formation,
just bewe are stratigraphically in the more central part
(20)
one
low abundant interbeds of Lake Shore Traps. At an upcoming stop
The
formation.
will get the opportunity to look at the upper part of the
of
other
stops.
lithology of the sediments here can be compared to those
the summit
On the south side of the road at this stop a 3 Km trail leads to
in
the
of Mt. Lookout (Map 15), one of the most spectacular viewpoints
contact
The summit is located on conglomerate, but very near the
Keweenaw.
with the Portage Lake Volcanics. Allow at least 1½ hours.
this
Junction to Brockway Mountai1 Drive. We are going to come back to
Go
to
Park.
point but we are going to first take a side trip to Esrey
the left on M—26.
shallow dipping
We are now at the shore of Lake Superior where there are
approxilava flows of the Lake Shore Traps. The road follows the shore
mately parallel to the strike of the lava flows.
STOP
18.
Esrey Park.
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�78
The rocks cropping Out at Esrey Park are lava flows of the Lake Shore Traps.
The Lake Shore Traps consist of a number of lava flows interstratified
within the Copper Harbor Conglomerate. The Lake Shore Traps extend from
the tip of the Keweenaw Peninsula west and south to just north of Hancock.
They lie stratigraphically near the middle of the Copper Harbor Conglomerate.
They consist dominantly of mafic flows similar to those of the
Some intermediate compositions have also been
Portage Lake Volcanics.
reported.
The Lake Shore Traps represent the waning stages of Keweenawan
volcanism in the Keweenaw Peninsula.
Several of these flows have been
traced offshore by prominent magnetic anomalies.
The large outcrop between the parking lot and the lakeshore is the massive
interior of a fine grained basaltic flow which strikes approximately parallel
to the shore.
The flow's amygdaloidal top can be observed along the lakeThe metamorphic grade of these rocks is substantially
shore to the east.
lower than that of the Portage Lake Volcanic Series, i.e. within the zeolite
zone.
Note the "fresh" appearance of massive interior basalt (with olivine
phenocrysts) and the low temperature amygdaloidal minerals (in order of
calcite, chlorite, laumontite quartz, adularia
decreasing abundance):
and analcite.
70.1
Turn around and head back towards the junction of Brockway Mountain Drive.
70.9
Sharp left turn onto the Brockway Mountain Drive followed by some more
exposures of the sandy conglomerate zones within the Copper Harbor Conglomerate.
We will drive for several kilometers along a conglomerate ridge
with many conglomerate exposures.
MAP 17
75.9
At the summit of Brockway Mountain we take a right turn a short distance
to the observation site.
STOP 19.
Brockway Mountain Viewpoint.
This high conglomerate ridge reaches an elevation of over 1300 feet and
is one of the best known tourist stops in the whole Keweenaw.
Excellent
views of the ridge and valley topography of the northern shore of the
Keweenaw can be had here, because the scrub vegetation allows a 360°
panorama.
The conglomerate here dips at about 20° to the north.
To the
west the Lake Shore Traps form prominent drowned ridges in the vicinity
of Esrey Park.
Lake Bailey (with the small island) and Lake Upsom occupy
a topographically low valley of finer grained clastic sediments within
the Copper Harbor Conglomerate.
Just to the south of Lake Bailey the
conglomerate ridge of Mt. Lookout can be seen, marking the contact between
The inland
the Copper Harbor Conglomerate and the Portage Lake Volcanics.
lake almost directly south is Lake Medora, and just beyond the lake is a
prominent ridge which marks the stratigraphic position of the Greenstone
flow.
In the distance, farther to the south across Lake Medora, Mount
To the southBohemia (Stop 21) with a fire tower on top can be seen.
west a distant ridge with white Air Force tracking buildings on it, marks
Gratiot Mountain, which is underlain by andesitic dikes and small rhyolite
bodies.
To the east, Copper Harbor is visible and Lake Fanny Hooe (see
Map 18) which occupies the same stratigraphic horizon as Lake Bailey.
Beyond Copper Harbor to the east, East Ridge, a conglomerate ridge, is
To the north, on the skyline 65 Km
the prominent hill on the skyline.
away is Isle Royale, easily visible on a clear day.
The skyline of Isle
�8-
Map 16
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Lake Shore Tr,ps
26
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�80
Royale is the Greenstone Ridge, underlain by the Greenstone flow, which
is apparently a continuous unit all the way from one side of the syncline
to the other.
It may be the largest single lava flow on earth, with a
volume of more than 1500 Km3 (Longo, 1983).
75.9
MAP 18
79.45
80.5
MAP 17
81.7
83.35
We turn to the right and follow the road straight ahead toward Copper
Harbor now going downhill and continuing along the ridge with excellent
views all the way down.
There is a pull—out on the right hand side of the road to give an excellent
Copper Harbor is controlled by
view of Copper Harbor and Lake Fanny Hooe.
The islands offhsore including
the occurrence of the Lake Shore Traps.
Porters Island are underlain by lava flows. From the Copper Harbor Marina,
with a small boat you can have access to excellent exposures of the Lake
Shore Traps along the edges of Copper Harbor. There are exposures of the
Copper Harbor Conglomerate along the road descending into Copper Harbor.
Junction at M—26, turn left.
We come to the shore of the lake again at a place called the Devil's Washtub.
If you stop here by the right hand side of the road and take a short walk
along the conglomerate along the shore, you come to wave washed exposures
of the conglomerate at the Devil's Washtub.
STOP 20.
Dan's Point.
There is a small gift shop observation tower on the right hand side of the
road.
Walk just a few yards down to the shore of Lake Superior to look at
the lithology of the Copper Harbor Conglomerate and the occurrence of
stromatolite in well exposed and wave washed exposures.
Dan's Point consists of a lakeshore outcrop of Copper Harbor Conglomerate
that is characteristic of the upper two—thirds of the formation (sometimes
called the Outer Conglomerate).
As a whole, the Copper Harbor Conglomerate
is a red—brown, basin—ward thickening wedge of volcanogenic clastics which
attains a maximum thickness of 1830 m (Daniels, 1982).
A coarse conglomerate facies consisting of well—rounded, poorly sorted clasts of mafic to
silicic volcanic rock fragments directly overlies and locally interfingers
with the lavas of the Portage Lake Volcanics (Elmore, 1981).
The
conglomerate facies is generally clast—supported and contains a ratio of
mafic to silicic intermediate clasts of about 2:1.
The Copper Harbor Conglomerate fines both distally and upsection so that sandstone interbeds
become more frequent in the upper two—thirds of the formation.
Sandstones
are predominantly subangular to angular lithic graywackes which exhibit
current—ripples, festoon trough—cross beds, parting lineations and dessica—
tion features.
Laminated crystalgal carbonate horizons are interbedded
within the conglomeratic and sandstone facies in the upper two—thirds of
the formation.
Stromatolites occur as laterally—linked drapes over cobbles,
as laterally—linked contorted beds in mudstone—siltstone lenses and as
poorly developed mats in coarse sandstone (Elmore, 1981).
�81
The depositional environment of the Copper Harbor Conglomerate has been
interpreted as a prograding alluvial fan complex (Fig. 33) with proximal—
to—distal braided stream and sheet flood facies on coalesced alluvial fans
and sand flats (Elmore, 1981; Daniels, 1982).
Isolated cryptoalgal carbonate and ooid lenses formed in shallow, medial fan lakes receiving very
low rates of sediment influx (temporarily abandoned stream channels)
(Elmore, 1981).
Paleocurrent indicators suggest sediment transport was
from the southeast to northwest indicating that a basin was located toward
the center of the rift zone (Daniels, 1982).
The stratigraphic section of the "Outer Conglomerate" (that part of the
Copper Harbor Conglomerate above the Lake Shore Traps) exposed at Dan's
Point consists of about 80—90 ft. of interbedded conglomerates and sandPredominantly clast—supported conglomerate beds consist
stones (Fig. 34).
of rounded, cobble—to—small boulder—sized clasts with a matrix of coarse
sand—sized sub—angular grains cemented with iron oxides.
Conglomerate
clasts are predominantly felsic volcanics (approx. 70%) with sub—ordinate
basalt, pyroclastic, plutonic and metamorphic lithic fragments.
Several
silty—sandstone interbeds higher in the exposed section exhibit cross—
bedding, current lineations, ripple marks, parting lineation and (reduction spots along bedding.
In particular one should note the white stromato—
lite (genus Colleria) horizon draping cobbles about one—third of the way up
the exposed section. Algal growth occurred during a period of depositional
quiescence and was halted by an influx of silty material followed by renewed conglomerate deposition.
Please do not remove stromatolite from the
outcrop.
Good specimens can be found in the pebble beach.
83.35
MAP 18
86.65
87.1
Turn around and go back toward Copper Harbor on M—26.
To the left is the junction
Junction, again, to the Brockway Mountain road.
to the Copper Harbor Marina.
Continue straight ahead on M—26 to Copper Harbor.
Junction between M—26 and US—4l in Copper Harbor.
out of Copper Harbor.
Turn right on US—41,
south
Copper Harbor was suddenly a boom town in 1843, following the discovery of
Porter's Island was the site of the first governcopper in the vicinity.
ment land office and in 1844 Fort Wilkins was built on the shores of Lake
Fanny Hooe, to protect the miners from potentially hostile Indians. The
lighthouse was built in 18o6. Fort Wilkins is now a state park with campMuch exploration activity took place in the
ing facilities and a museum.
fort
and there are shafts and exploration pits
immediate vicinity of the
all along the land between Lake Fanny Hooe and the Harbor, mostly from
In 1853 and for several decades thereexploration in the 1843—46 period.
after mining activity took place south of the fort in a series of workings
called the Clark Mine. The mineralization is of the fissure and amygdaloid
type and consists of prehnite, epidote, analcite, quartz, laumontite,
adularia, microcline, chlorite, datolite, calcite and several copper minerals
including chalcocite, cuprite and tenorite as well as native copper. Agates
are conspicuous in the amygdaloids here, and the area is well known for
datolite collecting. One occurrence of manganese minerals in a fissure
The manganese minerals found
accounts for the name of Manganese Lake.
brannite
and
manganite,
orientite.
The Estivant
here were pyrolusite,
of
the
Clark
Mine
lands
which
were deeded to
Pine tract represents a part
are
now
a
nature
preserve,
containing
some of
the C&H Company in 1942 and
Upper
Peninsula.
the last virgin pine tracts in the
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EXPLORATION
Copper
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�1982). Daniels, from (modified
deposits stromatolitic containing lakes ephemeral shallow and deposits
plain flood and stream braided fans, alluvial coalescing showing Conglomerate
Harbor Copper the of environment depositional of cartoon Schematic
33. Figure
—
BAStNwARD
83
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�85
Keweenaw Point, Horseshoe Harbor, East Bluff and other
points of interest
can be reached by taking an unmarked dirt road which
goes eastward from
the end of US—41.
This road is rough and poorly maintained and may be
followed around to Mandan. Horseshoe Harbor has excellent
exposures of
the Copper Harbor Conglomerate (Fig. 34).
88.2
MAP 19
91.45
MAP 20
94.3
94.55
MAP 21
97.3
MAP 20
101.4
101.6
Nice exposures of the Copper Harbor Conglomerate to the left of
the road
as we are going up the hill.
Lake Medora on the right hand side of the road,
Junction to the left to Mandan.
Mandan now is only a few houses, it had
300 residents in 1910.
Continue ahead on IJS—41.
Road to the left. This is the entrance to the outer portion of the
Keweenaw Peninsula, all on poorly maintained dirt roads. To visit Mount
Houghton and Keweenaw point, you may exit here.
Junction of the road to Lac La Belle,
Turn left and continue to Stop 21
at Mt. Bohemia.
If you wish to skip this stop, you may jump ahead to
mileage 105.45.
On the left hand side of the road is a large outcrop of amygdaloidal basalt
of the Portage Lake Volcanics.
These exposures are flows in the lower part
of the formation below the Scales Creek flow (see Fig. 4 and
in the
Introduction).
Dirt road turning off the main road to the left.
This is STOP 21 at Mt.
Bohemia,
It is about one half mile walk up this road to. the summit of Mt.
Bohemia; this is a four—wheel drive vehicle road.
STOP 21.
Mt.
Bohemia.
An intrusive body of diorite and granophyre crops out on the south slope
of Mt. Bohemia.
The majority of the intrusive body is a massive, medium—
grained, miarolitic diorite. The major constituents of the diorite, are
oligoclase and hornblende with lesser amounts of orthoclase, magnetite,
uralitized augite, apatite, sphene, quartz, sericite, epidote, chlorite,
and calcite.
The later are alteration products or are introduced secondary
minerals. The central core is a fine— to coarse—grained, miarolitic
granophyre.
The major constituents of the granophyre are albite, quartz
and granophyric intergrowths of quartz and feldspar with lesser amounts of
orthoclase, sericite, hornblende, apatite, sphene, magnetite and chlorite.
Miarolitic cavities are lined with quartz, albite, calcite, chalcopyrite,
and chalcocite (summarized from Cornwall, 1954).
The Mt. Bohemia intrusive
body yielded a Rb—Sr age of 1,130 ± 35 m.y. (Chauduri and Faure, 1968).
The diorite and granophyre at Mt. Bohemia intrude basaltic lava flows of
The basalts are slightly
the lower part of the Portage Lake Volcanics.
metamorphosed at the contact. The intrusive body is cut by the Lac La Belle
This fissure is mineralized with
fissure which trends north—northwest.
copper sulfides, mostly chalcopyrite and bornite and in gangue of calcite,
chlorite, and quartz (summarized from Juilland, 1965).
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Andesitic dikes are found in the vicini.ty of Mt. Bohemia (Fig. 35a). They
average about 5 m in thickness.
The dikes intrude flows of the Portage
Lake Volcanics, two flow tops are shown in Figure 35a as alpha and beta.
The dikes and amygdaloidal flow tops carry copper sulfides.
Copper sul—
fides in other parts of the district are found typically as fracture fillings.
Native copper is typical of amygdaloids. A variety of secondary
The
and opaque minerals are found in the dikes and flow tops (Fig. 35).
paragenetic sequence is consistent with that for the other deposits in the
district (compare Fig. 35c and Fig. 9b in the Introduction). Copper sul—
The copper and sulfur in this occurrence
fides are paragenetically late.
is believed to be of direct magmatic origin related to the magma source
that produced the andesite dikes and Mt. Bohemia intrusive body. The
emplacement of flows, subconcordant faulting and
chronologic sequence is:
fracturing, dike emplacement, renewed movement along subconcordant breaks,
regional low—grade metamorphic/hydrothermal alteration, minor folding and
faulting, and sulfide mineralization (summarized from Robertson, 1975)
The road Up to the summit of Mt. Bohemia crosses flows of the Portage Lake
Volcanics.
The diorite and granophyre intrusive complex crops out to the
southeast of the summit.
Intrusive stocks are not common in the Keweenaw
Peninsula,
Most of these occur in the lower part of the Portage Lake Vol—
canics and are rhyolitic in composition. Mt. Bohemia is the only occurrence
of a diorite stock in the Keweenaw Peninsula.
OPTIONAL SIDE TRIP TO Lac La Belle
Discussion of complex relationships along the Keweenaw Fault and the Keweenawan
rhyolite bodies,
Go straight ahead (south) towards Lac La
O
At turnoff to Mt. Bohemia.
Belle down hill.
O4
Junction of roads to left and right at Lac La Belle.
MAP 21
To Bete Grise turn left.
(See Map 22)
Bete Gi se is located on the shore of Keweenaw Bay on the Keweenaw Fault.
Along the shoreline east of the point where the road reaches the shore
are several exposures of the Keweenaw Fault which crosses on and off
These may be visited in canoe or small boat. Also
shore several times.
to the east are several of the rhyolite bodies which are chiefly found in
the lower part of the Portage Lake Volcanics. Three tenths of a mile north
of Bete Grise, four—wheel drive road continues east of the paved road to
Smith's Fisheries. The road intersects the Bare Hill Rhyolite body, a shallow
Beyond the end of the road at Smith's Fisheries a trail continues
intrusive.
eastward along the shore to the mouth of the Montreal River. From here one
may traverse up river to several falls over fine outcrops of basaltic flows
or continue along the shore to the Fish Cove Rhyolite, a compositionally
zoned shallow intrusive (Bornhorst, 1975). Inland and not far from Bete
Grise is the Mt. Houghton Rhyolite. This is an extrusive rhyolite dome
�14
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FIRE TOWER
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Amyqdoloids and dike projected to 1300 elevation
-
)iogy and drQ hole locations in the Mount Bohemia area (modi
-
from a preliminary Calumet
and ilecla Mining Company map).
Secondary minerals
MINERAL
Chlorite
Vesicle-
Frocture-
fillings
fillings
in dike matrix
0
Epio'ote
Quartz
0
0
0
0
ca/cite
5cr/cite
Pumpe//y/te
Microc/ine
o
0
-
o
Hem
Pyri
1,
Cc,
su/fides
Noth
Copper
-
Common
o
G Minor
Nonpyrogenic
0 Rare
0
—Absent
Minerals in the DPis
MINERAL
Pyrogenic I Deuteric
Hydrothermal
Supergene
Magnet/fe
Chlorite
Pumpe//ylte
3cr/cite
.-
'ucrt
Microc/ine
Su/idj
Cha/capyr,te
Ga/eva
5p/,o/er,fe
———
Epidote
Colch
Hei I,
Hematite Z
Pyrite
——
——
—
——
ti
——-——
———
——
P2
ietic sequence of secondary minra1s
in the dikes.
Pink born,te
Purple born/fe
Diqenife
Ojucleite
Cha/coc/te
Hematite I.E
Cove/life
—-—
Paragenesis of opaque minerals in dikes and flow
tops at Mount Bohemia.
Figure 35: Geologic map showing andesitic dikes near Mount Bohemia and
occurrence and paragenesis of secondary and opaque minerals in the dikes
(from Robertson, 1975).
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Houghton
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�92
with prominent flow banding and block and ash flow deposits on its
flanks.
Mt. Houghton is best approached from the Mandan Road (Map 19).
Rhyolites make up less than 1% of the mass of the Portage Lake Volcanics
Considerable textural variety of
as seen in outcrop on the Keweenaw.
rhyolites are found including intrusive and extrusive rhyolite and even
But the abundance and variety of rhyolitic boulders
small ignimbrites.
and cobbles within the interflow conglomerates demands that a large
number of rhyolitic source areas must underly the Jacobsville south and
east of the Keweenaw Fault.
To Gratiot River.
Turn right and proceed ahead 1.2 miles on paved road.
At the west end of Lac La Belle, in the vicinity of Deer Lake, the rocks
south of the Keweenaw Fault are Portage Lake basalts (Fig. 36). These
rocks may represent the lowest stratigraphic horizons exposed in the
The area has been studied by geological and
Portage Lake Volcanics.
geophysical methods by DeGraff (1976) and his model for the development
It is still
of this unusual feature is shown graphically in Figure 36.
another example of confusing deformation which is typical of this great
A traverse down the Little Gratiot River from the Lac La Belle—
thrust.
Gay Road crosses many outcrops of the basalts. The fault—bounded, tilted
body of Portage Lake Volcanics was defined by dense array of magnetic and
gravity profiles and a few key drillholes, The attitude of the beds was
altered by the faulting, but the rocks, like the rest of the Portage Lake
Volcanics, have normal magnetic polarity.
AFTER OPTIONAL SIDE TRIP to Lac La Belle return to main road log.
MAP 21
101.6
At Mt. Bohemia turnoff.
105.45
Back at the junction of US—4l,
106.5
Dirt road to the right goes to Stop 22 at the Delaware Mine.
on the dirt road and follow the signs to the Delaware Mine.
106.2
STOP 22.
Turn around and retrace route back to US—41.
Make a left turn towards Mohawk.
Turn right
Delaware Mine.
The Delaware Mine, first known as the Northwest Mine, has had a long and
It was operated by various companies from about
unprofitable history.
The
mi:ie
mostly worked veins for mass copper. Three shafts
1847 to 1887.
were opened in 1881 to mine copper from the Allouez Conglomerate (#1, #2,
The Allouez Conglomerate was seen at Stop 13. Total production from
#3).
the Delaware Mine was about 7.5 million lbs. of refined copper. As with
other vein deposits in the Keweenaw, the Delaware Mine is a notable locality
for datolite. Other minerals reported from the Delaware Mine poor rock
piles include (not in order of abundance): chlorastrolite, prehnite,
calcite, laumontite, analcite, chlorite, epidote, native copper and native
silver (summarized from Clarke, 1975; Zelenka, 1978).
�±
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Portage Lake VolcaflaS
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Lee LaBeIle
To sete Bo8e
N
N
S
S
S
llasalts and sandstones in a
block south of the fault are exposed and overturned.
l3asalts and sandstones in a
block south of the fault are exposed and dip to the south.
Classical fault contact between
basalt and sandstone.
Sandstone still exposed north
of the IKeveenaw Fault.
Sketch map of part of the Keweenaw Fault in the vicinity of Deer Lake, where the
Figure 36:
Portage Lake Volcanics are found south of the Keweenaw Fault. At right successive cross sections
show stages in the development of the Keweenaw Fault at Deer Lake as envisioned by DeGraff (1976),
P = PLy, J = Jacobsville.
11
\
Portage Lake VolcanicS
1'
Mt Bohenja
N
Prior to faulting.
�94
The Delaware Mine is open to tours for tourists during the summer months.
It is owned and operated by Jack and Tom Poynter. At this stop one has
the opportunity to look at the dumps from the Delaware Mine and to visit
(for a fee) the underground workings.
106.35
MAP 23
109.0
Junction of Delaware Mine and US—4l.
ahead towards Phoenix.
Left
turn on TJS—4l and continue
Ahead we can see cliffs of the Greenstone flow.
contact of the flow.
Road nears the basal
110.3
Exposure of one of the flows beneath the Greenstone flow.
111.1
In the
To the right one can see the Greenstone ridge in the background.
foreground is the ghost town of Central and its associated dump piles.
111.45
Junction of paved roads to the right and left. Continue ahead on US—4l.
The road to the left goes to Gratiot Lake and an Air Force Base; road
to the right goes toward the ghost town of Central and the Central dump
piles.
The Central Mine worked a fissure vein striking nearly at right angles to
bedding and dipping steeply to the east. The mine operated from 1854 to
1898 and produced about 52 million lbs. of copper. The fissure extends
from just below the Greenstone flow to the Kearsarge Conglomerate. A
strike fault at the Kearsarge Conglomerate offsets the vein to the west
and below this it is not mineralized.
The town of Central, settled in 1854, was settled mainly by Cornish immi—
Although the area was mostly abandoned after the mine closed,
grants.
the descendants of these immigrants now living all across the country,
hold a yearly reunion in July at the townsite. Later immigrant groups
to the copper mining towns included: Italian, German, Croatian and
Finnish people.
MAP 24
112.8
Continue ahead on US—41. The road to the
Junction of road to the right.
right connects with an earlier part of this field trip at Jacobs Creek
(mileage 60.3).
113.9
Another view of the ENE striking Greenstone flow holding up the prominent
ridge.
114.6
Again another excellent view of the Greenstone flow ridge.
MAP 12
115.4
Junction of M—26 and US—4l at Phoenix.
There is an optional route from Phoenix to Ahmeek via US—41/M—26 given after the
Five Mile Point road log.
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�97
Phoenix to Ahmeek via Five Mile Point (a scenic route along the
Lake Superior shore).
MAP 12
115.4
Right turn toward Eagle River.
117.4
Left turn on to the road to Five Mile Point.
MAPS 25 and 26
On the right hand side of the road is a turn—off to the Five Mile Point
112.2
In the front
You must get permission to enter this area.
lighthouse.
yard of the lighthouse, there is a thin lava flow of the Lake Shore
Traps with the Copper Harbor Conglomerate bed above and below it
121.5
MAP 27
126.9
Five Mile Point beach turn—off at the right hand side of the road. Along
this beach there are many exposures of the Copper Harbor Conglomerate.
Cross the Gratiot River.
128.45
A thin basalt flow, from a position just above the Greenstone flow, forms
an outcrop here which displays a well—developed columnar jointing. The
Greenstone flow itself shows spectacular columnar jointing in some areas,
most notably along the Palisades shown on Isle Royale where columns 2 m
In a few areas the colonade/entablature
or more in diameter are found.
jointing pattern described in Columbia River flood basalts is well—
developed in the Greenstone. On the Keweenaw columnar jointed exposures
in thin flow sequences are rare, probably because the underlying horizons
were not water—saturated when covered by the next lava flow.
128.7
Stop sign.
128.8
Another stop sign.
130.0
Right turn which is immediately followed by a stop sign in front of a
Join US—4l with a right turn. Directly ahead at about 11:00
church.
This is a shallow mine that worked the Kingston
is the Kingston Mine.
Total proConglomerate. The Kingston ore body was discovered in 1962.
duction was about 20 million lbs. of copper until mining stopped in 1968
The mine was left open as a research operation
(Weege and Pollack, 1971).
in the late 1970's.
Go straight ahead.
Turn left followed in block by a right turn.
The Kingston Conglomerate is stratigraphically about midway between the
It is overlàirt by a
Calumet Conglomerate and the Kearsarge amygdaloid.
A
bedding
plane
fault
separates the over60 m thick ophitic basalt flow.
The
conglomerate
rests on a
lying basalt from the Kingston Conglomerate.
The
Kingston
Conglomerate
can
be
traced
along
scoriasceous amygdaloid.
strike for over 100 Km and ranges in thickness from 0.3 to 30 m. In
vicinity of the ore body it averages about 13 m. Where the bed is thick
it consists of a lower layer of shale and siltstone, 10—15 cm thick and
an upper congloineratic layer (summarized from Weege and Pollack, 1971).
�MAP 25
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Fivemile Poini
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MAP 26
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Lake Shon
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MAP 27
Ma,
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�The Kingston Conglomerate is typical of rhyolite pebble conglomerates.
Pebbles are largely subangular to subrounded quartz—feldspar porphyry.
Quartz—free porphyritic and nonporphyritic rhyolite pebbles, common in
Interstitial sand
other conglomerates, are not present in the Kingston.
Sandstone composition is similar to the peb—
and sand lenses are common.
The intensity of mineralization is related to the amount of matrix
bles.
present which is an indication of the original permeability. The main
alteration minerals are kaolinite and chlorite. Introduced calcite and
copper are found as fillings in healed fractures, interstitially filling
A few individual pebbles are replaced
voids and replacing the matrix.
Economically important copper is found as rims around clasts
by copper.
Matrix filling takes place along
and as matrix replacement or filling.
texture bands parallel to bedding. Epidote and quartz are also found as
introduced minerals. Bleached rock is commonly associated with mineralization in the Keweenaw native copper district but is not present in the
Kingston ore body. The abrupt thinning of the conglomerate bed localized
the ore body with high grade ore nearest the pinch—out (Fig. 37) (summarized
from Weege and Pollack, 197; Brumleve, 1976).
PHOENIX TO AHMEEK VIA US—4l/M—26.
MAP 12
O
Continue straight ahead on US—4l/M—26.
0.5
Bear left on US—41/M—26.
Junction of US—41 and Cliff Drive.
excellent view of the Greenstone flow ridge.
Another
MAP 10
5.2
Lumber mill on the left side of the road.
6.0
Entering Mohawk.
6.1
On the left hand side of the road are mine dumps from the Mohawk Mine.
The Mohawk Mine worked the Kearsarge amygdaloid which is described at
Stop 11.
7.0
MAP 9
The hill on the skyline with the four towers on it is Bumbletowfl Hill,
the location of Stop 13.
7.9
Junction of US—41/M—26 and Cliff Drive in Ahmeek.
8.0
Junction of US—4l/M—26 and the road from Five Mile Point.
RETURN TO MAIN ROAD LOG MILEAGE.
130.0
Junction of US—41/M—26 and the road from Five Mile Point.
134.1
Junction of US—41/M—26 and M—2O3.
�--
-
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contact
- .'
ore body
footwall
-..'
N
N
N
N
N
N
N
N
N
N
N
N
-
N
'
contact
ha ngwall
•'
N
N
Schematic illustration of the funnelling effect on mineralizing
37:
fluids causing localization of ore deposition (modified from Butler and
Burbank, 1929 by Brumleve, 1976).
Figure
basalt
ridge
-—
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�103
There is an optional route from Calumet to Hancock via M—203/Mctain State Park
given after the TJS—41/M—26 road log.
Calumet to Hancock via US—4l/M—26.
134.1
Continue straight ahead on US—41/M—26.
MAP 28
134.8
Flashing light
135.7
Continue straight ahead.
center of Calumet.
A right turn leads to the
The Osceola Mine Shaft No. 13 can be seen on
Southern edge of Calumet.
Follow
the right hand side of the road behind the Holiday gas station.
Mileage
is
not
logged
the roads on Map 28 if you wish to go to Stop 23.
to this stop.
STOP 23.
Osceola Mine Shaft No. 6.
ProThe Osceola Mine worked the Osceola amygdaloid in the Calumet area.
duction from the Osceola amygdaloid began in 1879 and continued until 1920
when mining activity stopped. The mine reopened between 1925 to 193L
A total of
The mine reopened in 1925 and production continued until 1968.
about 600 million lbs. of refined copper was removed from this mine which
The amygdaloid was
ranks fifth in the Keweenaw native copper district.
developed for about four miles along strike and to a depth of 4,500 ft.
along incline (2,700 ft. vertically) (summarized from Weege and Pollack,
1971).
The Osceola flow is an ophitic basalt and varies in thickness from 35 to
The thickest part of the flow, near Calumet, has been the most
210 feet.
The Osceola flow has been traced from the Cliff Mine to the
productive.
In the Calumet area the flow strikes N35°E and dips around
Arcadian.
The top of the flow is a well developed fragmental amygdaloid
37°NW.
consisting of well oxidized, reddish, angular fragments of vesicular lava
which typically range in size from a few inches up to a foot in diameter.
The lode ranged in thickness from 1 ft. up to and sometimes greater than
Amygdules and the voids in the brecciated flow top are filled
60 ft.
mostly with calcite, epidote, K—feldspar, chlorite, and native copper.
Quartz is present in certain areas and there is also minor amounts of
The fragmental amygda—
prehnite, pumpellylte, laumontite, and analcite.
bid is frequently interrupted by sill—like layers of dense basalt which
may have been emplaced by injection of lava from the interior of the flow
into the solidified, brecciated crust. These dense basalt layers proNative copper
vided barriers to the movement of mineralizing solutions.
in the Osceola ranges from disseminated to small masses up to an inch
in diameter to large masses weighing hundreds of lbs. (summarized from
Weege and Pollack, 1971; Butler and Burbank,
1929).
The Osceola Shaft No. 6 is at the southwest end of the ore body and was
A barrier zone is believed to have
the richest part of the deposit.
funnelled mineralizing solutions moving up dip resulting in the high
Textures and colors characteristic of fragmental
copper contents.
Stoiber (unpublished data) made
amygdaloid can be seen in this dump.
secondary
minerals in the dump as a
an estimate of the percentages of
�Map.
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104
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�105
whole: calcite, 59; microcline, 29; prehnite, 4; epidote, 1; quartz, 1;
These and pumpellyite, laumontite and native copper can be
chlorite, 5.
found on this dump. Bleaching of the basalt in vicinity of native copper
can be seen in individual specimens.
135.7
Continue ahead on US—4l/M—26 towards Hancock.
No Maps Until Hancock
Turn left on White Street.
145.45
Junction of White Street on the left.
145.9
Right turn on Tezcuco
146.0
Stop sign at Quincy Street.
Go straight ahead through this stop sign
one more block to Hancock Street where you make a left hand turn.
146.55
Middle of the Portage Lake Lift Bridge.
146.8
Junction of US—4l/M—26.
Stay left on US—4l to the left past the Mobil
and Erickson gas stations.
148.1
Left hand turn off Townsend Drive back into the Michigan Tech Campus.
Street in Hancock.
CALUMET TO HANCOCK VIA M—203/McLain State Park.
O
Junction US—41/M—26 and M—203 on the edge of Calumet.
turn on M—203.
Make a right hand
No Maps Until Near McLain State Park.
0.5
Village Limit of Calumet.
2.5
Junction of road to Calumet Township Waterworks Park.
4.2
Bear right on Y
4.6
Nice view of Lake Superior.
MAP 29
6.7
with
Continue straight ahead.
another paved road.
Continue on M—203. Road to the right is Lakeshore Drive which goes to
Calumet Township Waterworks Park; road to the left is Salo Road to the
Bear Lake Rhyolite. The Bear Lake Rhyolite cuts the Freda Sandstone
bedrock.
It is the youngest known igneous activity in the Keweenaw
Peninsula.
The Bear Lake Rhyolite is a minimum of 1054 ± 34 m.y. years
old based on a K/Ar age date (White, 1968).
7.0
Exposures of sand dunes on the right.
7.5
Bear Lake on the left hand side of the road.
glacial Bear Lake Channel.
Cross on top of the filled
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Pond
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MAP 29
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26
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�107
The Bear Lake Channel (Map 29) represents a deep bedrock valley, the
Although the Waterway was dredged
extension of the Keweenaw Waterway.
to the west of McLain Park, because the distance was less, the Bear
Lake Channel is a much more profound feature, with more than 600 feet
The definition of this and other similar bedrock valleys
to bedrock.
is shown by gravity data. One such traverse, plotted on the map, is
See also the discussion of the origin of the
displayed as Figure 38.
Keweenaw Waterway under Stops 1, 5 and 6.
8.4
Entrance to McLain State Park and the other edge of the Bear Lake Channel.
Camping facilities are located here.
9.2
Continue on M—203. Road to the right is to the Coast Guard Station;
road to the left is the Bear Lake Road, location of gravity traverse.
10.6
Access road to Lily Pond.
At this point the End Moraine of the Keweenaw Lobe, a great mass of glacial
ice which was stabilized here during the Wisconsin glaciation, is crossed.
The
The regional distribution of this moraine is plotted in Figure 14.
positions of lobes as they retreated at the end of the Wisconsin period are
shown in Figure 15.
13.5
High Point Road, continue ahead on M—203.
NAP 30
16.1
Cross Swedetown Creek. To the northeast along Swedetown Creek there are
If one is interested in looking in more
expcsures of Freda Sandstone.
detail at the Freda Sandstone, excellent exposures can be found elsewhere.
In the local area excellent exposures of Freda Sandstone are present along
Redridge/Freda can
the shore of Lake Superior between Redridge and Freda.
be reached by following the Houghton Canal Road which begins on the west
side of Houghton (see Fig. 17).
16.55
Access to Hancock Campground. The Nonesuch Shale is exposed in an abanThis is Stop 24 and
doned quarry located just NE of the boat launch.
mileage is not logged from the main road to the quarry.
STOP 24.
Hancock Campground.
As a whole, the Nonesuch Shale consists primarily of siltstone with subordinate amounts of shale and sandstone. It can be distinguished from the
formations above and below by its generally grayish color. Most Nonesuch
Lithologically
is a rippled, laminated siltstone with reddish—gray partings.
siltstones and sandstones of the Nonesuch are composed of around 30 to 40
The rock fragpercent rock fragments and 60 to 70 percent mineral grains.
ments are mostly volcanic with a 2:1 ratio of mafic to silicic + intermediate
The Nonesuch is stratigraphically between the
composition (Daniels, 1982).
Copper Harbor Conglomerate and Freda Sandstone (Fig. 5).
It is
The Nonesuch crops out around the margin of the quarry at this stop.
a fine— to medium—grained, gray to reddish brown sandstone with subordinate
interbedded, reddish—brown laminated siltstone and shale (Cornwall and
The attitude of bedding here is about N30°E, 25°W.
Wright, 1956).
�108
BEAR LAKE
9
8
7
6
5
4(
I
2
I
I
4
6
8
0
12
14
x
0
2
-3
Q)
S
a)
Li
Results of gravity measurements across the Bear Lake
Figure 38:
traverse plotted in Map 29. At top is Bouguer anomaly with regional
In the middle the regional trend is subtracted to get the
trend.
solid line which is compared with the modelled topography (X's).
Below is the model of the valley and the density difference of the
bedrock (Freda Sandstone) and the valley fill (Warren, 1981).
�109
n
'I
-
•
McI31fl State Park
/
I
V
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t
,
.,,
-I
-
.4
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--
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;
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/
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-
�110
16.7
Hancock Beach.
16.85
Sharp left hand turn on M—203.
17.9
Turn right on the one—way road.
Junction M—203 and US—41.
US—4l back to the Michigan Tech Campus
Edge of Hancock.
Follow south
�111
INDEX TO GEOLOGY ON MAPS IN THE FIELD GUIDE
Map No.
—
—
—
Quadrangle
Reference
1
Chassell
White, 1956
2
South Range, Chassell
White & Wright, 1956; White, 1956
3
Chasseli
Warren, 1981
4
Chassell, Hancock
White, 1956; Cornwall & Wright, 1956a
5
Chasseil, Hancock
White, 1956; Cornwall & Wright, 1956a
6
Laurium
Cornwall & Wright, l956b
7
Laur ium
Cornwall & Wright, l956b
8
Laur ium
Cornwall & Wright, 1956b
9
Ahmeek
White & Others, 1953
10
Mohawk
Davidson & Others, 1955
11
Mohawk
Davidson & Others, 1955
12
Phoenix
Cornwall, 1954a
13
Eagle Harbor
Cornwall & Wright, 1954
14
Eagle Harbor
Cornwall & Wright,
15
Delaware
Cornwall, l954b
16
Delaware
Cornwall, l954b
17
Lake Medora
Cornwall, l954c
18
Lake Medora, Fort Wilkins
Cornwall, l954c; Cornwall, 1955
19
Lake Medora
Cornwall, l954c
20
Delaware
Cornwall, 1954b
21
Delaware
Cornwall, l954b
22
Lake Medora
Cornwall, l954c
23
Eagle Harbor
Cornwall & Wright, 1954
24
Eagle Harbor
Cornwall & Wright, 1954; Cornwall, l954a
25
Phoenix
Cornwall, l954a
26
Phoenix, Mohawk, Ahmeek
Cornwall, l954a; Davidson & Others, 1955;
White & Others, 1953
27
Ahmeek
White & Others, 1953
28
Laurium
Cornwall & Wright, 1956b
29
Hancock
Cornwall & Wright, 1956a; Warren, 1981
Hancock
Cornwall & Wright, 1956a
MTU Campus Map (Cover Page)
White, 1956; Hase, 1973
1954
�____________
_____________
112
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�______________
______________
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U.S.
Geological Survey Geologic Quadrangle Maps of the United States Map GQ 34.
1954c, Bedrock geology of the Lake Medora Quadrangle, Michigan:
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Cornwall, H.R. and Wright, J.C., 1954, Bedrock geology of the Eagle Harbor quadrangle,
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Map GQ 36.
1956a, Geologic map of the Hancock quadrangle, Michigan:
U.S. Geolo—
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Oronto Group, MichiDaniels- P.A., Jr., 1982, Upper Precambrian sedimentary rocks:
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Davidson, E.S., Espenshade, G.H., White, W.S. and Wright, J.C., 1955, Bedrock geology
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DeGraff, J.M., 1976, Structural and age relationships of rocks associated with the
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Elmore, R.D., 1981, The Copper Harbor Conglomerate and Nonesuch Shale: Sedimentation
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Elmore, R.D. and Van der Voo, R., 1982, Origin of hematite and its associated rema—
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Ensign, C.O., Jr. White, W.S., Wright, J.C., Patrick, J.L., Leone, R.J., Hathway,
D.J., Trammell, J.W., Fritts, J.J. and Wright, T.J,, 1968, Copper deposits in the
Nonesuch Shale, White Pine, Michigan:
in Ridge, J.D., ed., Ore Deposits of the
United States, 1933—1967:
American Institute of Mining, Metallurgy and Petroleum
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Fritts, C.E., 1952, A petrologic study of the Mount Houghton felsite, Keweenaw
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Michigan Technological University, Houghton, 42 p.
Green, J.C., 1977, Keweenawan plateau volcanism in the Lake Superior region:
Geological Association of Canada Special Paper No. 16, p. 407—422.
�_____________
____________
Green, J.C., 1982, Geology of Keweenawan extrusive rocks;
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Geological Society
114
Grimes, J.G., 1977, Geochemistry and petrology of Keweenaw rhyolites and associated
rocks, Portage Lake Volcanics, Michigan (M.S. thesis): Michigan Technological
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Halls, H.C., 1982, Crustal thickness in the Lake Superior region:
of American Memoir 156, p. 239—243.
Geological Society
Hase, H.W., Jr., 1973, Geological—geophysical site investigation of a portion of the
Student Development Complex, Michigan Technological University, Houghton County,
Michigan (M.S. thesis): Michigan Technological University, Houghton, 35 p.
Holcomb, F.W., 1975, Urban Geological Map of the Eastern Half of the City of Houghton,
Michigan (M.S. thesis): Michigan Technological University, Houghton, 87 p.
Huber, N.K., 1975, The geologic story of Isle Royale National Park:
Survey Bulletin 1309, 66 p.
U.S. Geological
Jolly, W.T., 1974, Behavior of Cu, Zn, and Ni during prehnite—pumpellyite rank metamorphism of the Keweenawan basalts, Northern Michigan:
Economic Geology, v. 69,
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Jolly, W.T. and Smith, R.E., 1972, Degradation and metamorphic differentiation of
the Keweenaw tholeiitic lavas of northern Michigan, U.S.A.: Journal of Petrology,
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Juilland, J.D., 1965, Mineralization of the Mount Bohemia intrusive, Keweenaw County,
Michigan (M.S. thesis):
Michigan Technological University, Houghton, 78 p.
Kalliokoski, J., 1976, End moraine map of northern Michigan—Wisconsin:
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156, p. 147—155.
Michigan
Geological Society of America Memoir
Klasner, J.S., Cannon, W.F. and Van Schmus, W.R., 1982, The pre—Keweenawan tectonic
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continent rift: Geological Society of America Memoir 156, p. 27—46.
Lankton, L.D. and Hyde, C.K., 1982, Old Reliable — an illustrated history of the
Quincy Mining Company: The Quincy Mine Hoist Association, Inc., Hancock,
Michigan, 159 p.
Livnat, A., Rye, R.O. and Kelly, W.C., 1976, Stable—isotope and fluid inclusion
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Society of America Abstracts with Programs, v. 8, p. 980—981.
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�_______________
115
Merk, G.P. and Jirsa, M.A., 1982, Provenance and tectonic significance of the
Keweenawan interflow sedimentary rocks: Geological Society of America
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Prest, V.K., 1969, Retreat of Wisconsin and recent ice in North America:
Survey of Canada Map 1257A.
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�__________
___________
____________
_____________
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Local Publication, 20 p.
�i:
r
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V
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25
1.
4
14
Figure 1B:
15
r
1.
2
in mites
SCALE
0
17
I
r
i
3
4
k12
18
12
i
Stop n!Jmher
Map number
Index of 1:24,OOC caIe 'naps
0
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I
2
29
r
1
�'Freda
McLain State Park
Atlantic
South
Painesdale
p4
Chassell
Eagle
rm
4
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0
1
4
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2
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3
+
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Copper
Harbor
12
Manitou Island
Stop number
Figure 1A: Route and stop map
Michigan Technological University is an equal opportunity educational institution/equal opportunity employer.
�
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Title
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Institute on Lake Superior Geology
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Title
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Institute on Lake Superior Geology: Proceedings, 1972
Description
An account of the resource
Institute on Lake Superior Geology. Michigan Technological University, Houghton, Michigan. May 3-6, 1972.
Creator
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Institute on Lake Superior Geology
Date
A point or period of time associated with an event in the lifecycle of the resource
1972
Contributor
An entity responsible for making contributions to the resource
John L. Berkley
W.A. Bodwell
Emmy Booy
Musa S. Haddadin
Bruce E. Brown
R.G. Cuddy
P.M. Clifford
Erich Dimroth
Robert Ehrlich
Thomas A. Vogel
John C. Green
Kenneth G. Books
J. Kalliokoski
James A. Kilburg
Melvin M. Lahr
P. James LeAnderson
M.S. Lougheed
J.J. Mancuso
J.T. Mengel Jr
M.G. Mudrey Jr
P.W. Weiblen
Richard W. Ojakangas
Erdogan Oray
W.J. Hinze
N.W. O'Hara
W.A. Robertson
D.R. Smith
R.H. McNutt
Virgil A. Trent
E.J. Warren
Thomas G. Winter
P.O. Banks
W.R. Van Schmus
W.F. Cannon
S.S. Goldich
John S. Klasner
Gene L. LaBerge
G.B. Morey
James A. Robertson
H.B. Stonehouse
J.S. Stuckless
Grant M. Young
M.D. Lewan
Format
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PDF
Language
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English
-
https://digitalcollections.lakeheadu.ca/files/original/d56384bb82b7055c0dd8947ef3feb5c3.pdf
6eac8e3073122c599c349c7c53f10d11
PDF Text
Text
17TH ANNUAL
17TH
A UA
INSTITUTE
ON
LAKE SUPERIOR
UPERIOR GEOLOGY
MINNESOTA
DULUTH, MINNESOTA
MAY
5-8,1971
MAY 5-8,1971
1
-4',
�TEOINICAL
ThGL?J
CAL SESSIONS
ABSTPACFS
ABSTRACfS
and
FIELD GUIDES
GUIDES
for the
the
17th
17th A\'NU.t\L
ANNUAl..
INSTITUTE ON
ON L!\.KJ::
LKE SUPERIOR
INSTITUTE
SUPERIOR GEOLOGY
GEOLOGY
Sponsored by
Sponsored
UNIVEPSI1Y
; IIr-,rNESOTA,DULUTI
DULUTHI
UNIVEPSIfl OF
OF IINNESOTA,
held at
held
DULU'fl!, ?IINNESOTA
DULUTIl,
i'UNNESOTA
..lay
1971
Jay 55 -- 8, 1971
Edited
D.ll. Davidson
Edited by
by D.
D.G. Dafoy
Darby
D.G.
J.e. Green
J.C.
Green
J.A. Grant
Grant
�TABLE OF
TABLE
OF COYI'EN]7S
CONTENTS
Page No.
Prtge
~~o.
INSTITIJTE
A!\JDLOCAL
IDCAL CCLt1IflEE
CCl:IMITTEE
INSTI'IlJTE DIRECTORS
DIRECRS AND
PIJGRAt4 (TflLE of ctpirgwrS
pt*R 4S1RfrtCrS)
ABSFRACI'S OF
OF TECIWICAL
TECINICAL SESSIONS
ABSTRACTS
SESSIONS
11
2
2
77
FIELD
FIELD TRIPS
Shore Volcanic Group
A - North Shore
Group
(Keweenawan)
73
B - Cross-Section, Precambrian Rocks,
Rocks,
Minnesota
I'brtheastern
Northeastern ~tinnesota
97
C - ~Iesabi
Mesabi Range
Range - Biwabik Taconite
US
128
D - Vermilion District
141
�-1-1-
17th
17th Annual
INSTITIITE
ON LAKE
LAKE SUPERIOR
SUPERIORGEOLOGY
GEOLOGY
INSTITUTE ON
Sponsored by
University of
of Minnesota,
Minnesota, [*iluth
Duluth
at
Duluth,
Duluth, Minnesota
May S5 -- 8, 1971
May
INSTITUTE BOARD
BOARD OF
OF DIRECTORS
DIRECTORS
INSTITUTE
Laughlin Steel
Steel Corp.,
* J. IV.
W. Avery
Avery (Treasurer),
(Treasurer), Jones
Jones &Laughlin
Corp.,
Negaunee,
Negaunee, Michigan.
ilichigan.
C.
C. Reed
Reed (Secretary),
(Secretary), Michigan
J'Hchigan Geological
Geological Survey,
Survey,
;"Iichigan.
Lansing, Michigan.
D. M.
M. Davidson,
Davidson, University
University of
D.
of Minnesota,
Minnesota, [Ailuth
IW.uth
Duluth, Minnesota
Minnesota
W.
J. Hinze,
State University, East
W. J.
Hinze, Michgian
Michgian State
East Lansing,
Lansing,
Michigan.
A. B. Dickas,
Dickas,
Wisconsin
State Superior,
University, Superior,
Wisconsin
State University,
Wisconsin.
Wisconsin.
G.
LaI3erge, Wisconsin
Wisconsin State
State University,
University, Oshkosh,
Oshkosh,
G. L.
U LaBerge,
Wisconsin.
Wisconsin.
U. W.
[;1.
],V. Bartley,
Bartley, Thunder
Thunder Bay,
Bay, Ontario
Ontario
** R.
* Permanent
*
members
menvers
LOCAL C(J.·tUTTEE
LOCAL
CCt1ITrEE
Chairman:
Coordinating Oiainiian:
D.
D. M.
M. Davison
Davison
Arrangements Connittee:
Committee:
R. W.
R.
W. Marsden
C. L.L. Matsch
lttsth
C.
Program
Program Comnittee:
Coninittee:
D. C.
D.
G. Darby
Darby
3.
J. C. Green
Green
Field Trip Committee:
Conrrni ttee:
J.
J.
A. Grant
Grant
A.
R.
R. 14.
W. Ojakangas
Ojakangas
�-2-2-
PROGRAM
~~y 4, 1971
1971
Tuesday, May
5:00 p.m.
p.m.
Field
(North Shore
Shore Volcanics)
leaves
Field Trip
Trip A (North
Volcanics) leaves
Hotel liadisson
Hadisson Duluth.
Hotel
Duluth.
Wednesday, May
~,~y 5, 1971
1971
6:00 p.m.
p.m.
to
7:00 p.m.
p.m.
7:00 p.m.
7:00
p.m.
to
9:30 p.m.
Field Trip A
A returns to
to Duluth
Duluth
Institute Registration
Registration - Poolside, Hotel
Radisson Duluth
Radisson
Duluth
Tnursday,
~hy 6, 1971
1971
Thursday_, May
7:30
a.m.
to
12:00 a.m.
a.m.
Registration, Superior
Superior Street
StreetFoyer,
Foyer,Hotel
IbtelDuluth
Duluth
�-3-
SESSION
S E S S ION
11
i,lorning
;lorning
Thursday,
l11Ursday, i.fay
1971
'ay 6,6, 1971
Symposium on Keweenawan
Keweenawan Geology
Geology—- Lake Superior Region
Region
Symposium
Co-chairmen:
Co-chainnen:
Jack
and Walter
Jack Phillips and
1/alter White
Page No.
No.
8:
45
8:45
J. C.
C. Green
Green
IntroductoryRemarks
Remarks
Introductory
9:00
IV. White
Iv.
&
Keweenawan
lVesterrunost
KeweenawanStratigraphy
Stratigraphy ofofTYesternimost
Michigan
Hichigan
71
9:20
N. K.
N.
K. Ih.xber
Huber
The Keweenawan
KeweenawanGeology
Geology
Isle Royale,
The
ofofIsle
;.1ichigan
Michigan
31
9:40
II. A.
A. Hubbard
Hubbard
H.
Keweenawan Geology
Geology of the
the Porcupine
Porcupine
Keweenawan
;"buntains,
tuntains, Western Upper Peninsula
30
20
Others
~·,tichigan
Uchigan
10:00
J. C.
C. Green
Green
of the
theNorth
North Shore
Shore Voltanic
Vo1tanic
Stratigraphy of
Group Northeast
Bay, 1innesota
;··linnesota
Group
Northeastof
of Silver Bay,
10:20
R.
R. N.
N. Annells
Armells
Middle
~·liddle
Keweenawan
VolcanismofofEastern
Eastern Lake
Keweenawan Volcanism
Lake
Superior
7
7
10:40
A.
P. Jtotsala
A. P.
Ruotsala
Characteristicsof
ofSome
Some Alteration
Alteration Minerals
~tinerals
Characteristics
Lake Lava
Lava Series,
Michigan
Portage Lake
Series, Michigan
59
11
:00
11:00
IV. T.
T. Jolly
W.
Fades
Puinpellyite Facies
Zeolite
and Prehnite
Prehnite -- Pumpellyite
Zeolite and
theKeweenawan
Keweenawan Basalts
Northern
in the
Basalts of
of Northern
:.tichigan
The Role
Roleof
of Volatiles
Volatiles
Michigan II:
II: The
34
11:
20
11:20
T. A.
T.
A. Vogel
Vogel &
R.J.
R.J.
Chemically Zoned
Native Copper
Chemically
Zoned Native
Copper and
and
from White
IVhite Pine
Pine Michigan
Michigan
Rohrbacher Chalcocite from
11
:40
11:40
1!. C.
C. halls
H.
Halls
G.
G. F.
F. West
\\Test
12:00
12:
00
DON
NOON
The Isle Royale
Royale Fault
Fault
& The
Mjourn for
Adjourn
for Lunch
Lunch
There 'vi1l
be a lunch
lunch meeting
meeting of
Board of
the
There
will be
of the
the Board
of Directors
Directors in the
Hotel Radisson
Radisson ililuth
fuluth—.
- location to be
be announced.
announced.
hotel
70
25
�-4-
SESSION
S E S S ION
22
Afternoon
Thursday,
Thursday,
May 6,
~my
6, 1971
Symposium on
on Keweenawan
Keweenawan Geology
Geology -- Lake Superior
Superior Region
Region
Co-Chairmen:
Co-01ainnen:
1:40
1:40
2:00
2:00
2:20
2:20
J. Leone
K. Siiis
Raymond J.
Leone and
and Paul K.
Sims
J. T.
T. Mengel,
Mengel, Jr.&
Jr. Exploration
J.
Exploration Geology
Geology of
of Douglas
Douglas County,
County,
R.
R. A.
A. Hendrickson
Hendrickson Wisconsin
Wisconsin
D.
Davidson ,Jr.
D. vI.
M. Davidson,Jr.
Ne,.. View
View of
of the
the Duluth
Duluth Complex,
Complex,
A New
A
Minnesota
B. Bonnichsen
B.
Bonnichsen
in the
the Southern
Southern Part
Part of
of the
the
Hornfelses in
Hornfelses
Page
Page No.
No.
47
13
13
11
Duluth Complex,
Il1luth
Complex,?•linnesota
Minnesota
2:40
2:40
M.
M. G.
G. i4idrey
M.ldrey
&
P. W.
W. Weiblen
P.
Reinvestigation of
of "Red
"Red Rocks"
Rocks" in
Reinvestigation
in the
the
Pigeon
Pigeon Point
Point Area, Minnesota
Minnesota
53
53
The
Great Logan
Logan Paleomagnetic
Paleomagnetic Loop
Loop
The Great
58
58
3:00
3:00
to Coffee Break
to
3:20
3:20
3:20
3:20
W.
A. Robertson
Ibertson
W. A.
W. F.
F. Fahrig
Fahrig
W.
&
3:40
3:40
A. Me.ttis
A.
1'-attis
Lower
Lower Keweenawan
Keweenawan Sediments
Sediments of
of the
the Lake
Lake
Superior
Superior Region
Region
45
4:00
4:00
D.
Myers
D. ;"fyers
The
and Tectonic
Tectonic Significance
Significance
The Sedimentology
Sedimentology and
of
the Bayfield
of the
Bayfield Group,
Group, Wisconsin
Wisconsin
54
4:20
4:20
C.
Merey
G. B.
B. ~brey
Revised Keweenawan
I{evised
Keweenawan Subsurface
Subsurface Stratigraphy,
Stratigraphy,
Southeastern Minnesota
50
50
4:40
H.
C. Halls
H. C.
C. F.
F. West
West
C.
and Stratigraphy of the
the
Shallow
Shallow Structure
Structure and
Lake
from Seisnic
Seismic Refraction
Refraction
Lake Superior
Superior Basin
Basin from
Measurements
Measurements
23
&
********
* * * * * * **** ****
**
Evening
7:30 p.m.
p.m.
Banquet -- Great Hall
Banquet
Hall - Hotel Radisson
Radisson Duluth
Duluth
-
ADDRESS
ADDRESS --
Dr. Carl
Carl R.
R. i\nnhausser
Arrmlausser
Economic
Economic Geology
Geology Research
Research Unit
Unit
University
University of
of Witwatersrand
Witwatersrand
Johanneshurg, South
South Africa
Africa
Johannesburg,
�-5-5—
S
E S S ION 33
SESSION
!trning
~'brning
Friday, May 7,
Friday,
7, 1971
1971
General
General Session
Session
Co-Chaitnen:
Co-Chairmen:
Cedric.
Cedric. L.
L. Iverson
Iverson and
and J.
J. Ka11iokoski
Kalliokoski
Page It.
No.
Page
8:40
8:40
F. C.
F.
C. Tan
Tan 4&
E. C. Perry,
Perry,Jr. Jr.
Implications of Carbon
Carbon Isotope
Isotope Ratio
Ratio
Variations in
in Carbonates
Carbonates from
from the
the Biwabik
Biwabik
Variations
Iron
Iron Formation,
Formation, Minnesota
Minnesota
64
9:00
9:00
S.
Viswanathan,
S. Viswanathan,
Ii. C.
C. Perry,
E.
Perry, Jr.
J r.
&
P.
Sims
4
OxygenIsotopic
Isotopic Studies
Studies of
Oxygen
of Early
EarlyPrecambrian
Precambrian
Granitic and
and Metamorphic Rocks
Rocks from
from the
the
Western
Giants Range
Range Batholith,
WesternPart
Part of
of the Giants
Northeastern
Minnesota
Northeastern Minnesota
66
9:20
G.
1. LaBerge
LaBerge
G. L.
Some Geology of
Harathon County
County Volcanic
of the ?larathon
Some
39
Belt
P.
O. Banks
Banks 4~
P. 0.
W.
Van Sc!llTlUS
W. R.
R. Van
Schmus
Rocksof
of Iron
Chronology of Precambrian
Precambrian Rocks
chronology
L.
L. A.
A. Prince
Prince 4&
Geochronology of the
the Giants
GiantsRange
P~ge Granite
Granite
Geochrono]ngy
57
10:20
G. Klein
G.
Precambrian Clastic
Paleotidal Sedimentation
Sedimentation
Precambrian
Clastic Paleotidal
36
10:40
Pt. ii!inze,
Continental
Continental Rifts
W.
Jinze,
H. iiavidson,Jr.
D.
Daviclson,Jr.
I). Iv!,
&
4 R. Roy
11:00
1\la1an &
It C.
R.
C. Malan
1]. A.
A. Sterling
D.
9:40
9:40
10:00
G.
C.
N.
. I·ranson
Hanson
Fj
and Dickinson
Dickinson
and
99
Counties, Michigan
Michigan
Thoriumin
in PreDistribution of Uranium
Uranium and
and Thorium
cambrian
Rocks of
of the Western
cambrian Rocks
Western Great
Great Lakes
Lakes
29
42
42
Region
11:20
20
11:
N. 11[.
N.
Pt.
O'Hara 4&
w. J. I:inze
Hinze
Lake nichigan
Michigan Aerornagnetic
Aeromagnetic Survey
Survey
56
56
/u
An Aeromagnetic Survey
Survey of
Southern
of the Southern
ofMichigan
~lichigan
Peninsula of
35
iv.
11:40
11
:40
.
R. 1.
L. Kellogg
Kellogg 4l]"
Pt. J.
W.
J. I-Jinze
Hinze
12:00 NWN
12:00
NOON —
- Lunch
�-6-6-
SESSION
S
E S S ION 44
Afternoon
Afternoon
1971
Friday,
Friday, I,1ay
lay 7, 1971
General Session
Co-Chairmen:
Co-Chainnen:
C. Tychsen
1'chsen
Meredith F.
E. Ostrom and
and Paul C.
Page No.
Page
No.
1:20
1:20
Business
of the
the Institute
Institute
&zsiness Meeting
Meeting of
1:40
1:40
M. S.
S.
M.
2:00
2:00
J. Mancuso
t,.1.ancuso
J. J.
J.
F. Dimroth &
E
E.
J. Chauvel
.J.
2:20
2:20
W. ]Aihling
W.
fuhling
Precambrian Iron Formation
Precambrian
Formation at
at Copper
Copper
~·ibuntain,
FremontCounty
CountyWyoming
1Vyoming
Nbuntain, Fremont
18
2:40
E.
Frodeston
F. Frodeston
Some Sedimentary
in the
the Lower
Lower
Sonic
Sedimentary Structures in
Cherty nember
Fonnation:
Memberofofthe
the Bhvabik
Biwabik Iron Formation:
Cherty
The Virginia
Virginia Horn
The
Horn Area
Area
32
32
3:00
G. Spencer
Spencer
G.
Chert
in Sediments
Sediments
Chert in
62
3:20
J. Mathersill
~bthersill
Limnogeological
ofThunder
Thunder Bay,
Bay,
Limnogeological Studies of
Lake Superior,
Superior, Ontario
Lake
Ontario
51
3:40
R.
Shegelski
R. Shegeiski
TI1e
ofThunder
Thunder Bay,
Bay,
The General
General Stratigraphy
Stratigraphy of
Lake
Lake Superior
61
4:00
4:
00
End
of Technical
End of
TecJmical Sessions
Sessions
Lougheed &
Hematite Pseudomorphic After
After Biogenic
Biogenic
Pyrite
in the
the Negaunee
Negaunee Iron
Iron Formation
Fonnation
Pyrite in
Textural Facies
Facies Analysis of Precambrian
Textural
Precambrian
Cherty Ironstones
Ironstones
***
* * * **** **** **** **
**
5:00
5:
00
(Dinner and
lodging are included
and lodging
included in the field
field trip
trip fee.)
fee.)
Departure for
for Field
Field Trips:
Trips:
Field
Field
Field
Field
Field
Trip A Trip
Trip BB -Trip CC -Trip UD --
North Shore Volcanic
Group
Volcanic Group
Cross-section, Precambrian
Rocks
Precambrian Rocks
Mesabi
j\!esabi Range
Taconite
Range -- Biwabik
Biwahik Taconite
Vermilion District
District
Vemiilion
Buses will
will depart
Buses
depart from
from Hotel
Hotel Radisson
Radisson Duluth.
Duluth.
***********
Saturday, nay
May 8th, 1971
Saturday,
6:00
to
to
7:00
(approx
.)
(approx.)
REThRNOF
OFALL
ML FIELD
RETIJRN
FIELD TRIP
TRIP BUSES.
BUSES.
41
41
15
15
�-7-
-7--
KEWEENAWAN VOLCANISM
VOLCANISM OF
OF EASTERN
EASTERN LAKE
LAKE SUPERIOR.
SUPERIOR.
MIDDLE KEWEENAWAN
R. N.
N. ANNELLS
R.
Geological Survey
Survey of
of Canada,
Canada, Ottawa.
Ottawa.
ABSTRACT
Following the study of the Michipicoten Island
Island Keweenawan flows
flows reported
reported
elsewhere (Annells,
(Annells, 1970),
srone type
type of detailed stratigraphic/petrographic
1970), the same
has been carried out on the Keweenawan volcanic rocks
study has
rocks of the
the Mamainse
Point,
the east shore
shore of Lake
Lake Superior.
Superior.
Point, Alona Bay and Cape Gargantua sections on the
three east
east shore
shore sections
sections are
are mostly
mostly made
made up
up of
of inafic
mafic olivine—tholefite
olivine-tholeiite
These three
types of
texture, accompanied by
by aa smaller
smaller number
number
types
of medium-coarse
medium—coarse ophitic or diabasic texture,
of fine—grained
fine-grained olivine—poor
olivine-poor tholeiite
tholeiite flows.
flows. Flows of intermediate composition
composition
found in these
these sections
sections and
and the
the flows
flows show
show little
little variation
variation in
in mineralogy.
mineralogy.
were not found
Small
rocks occur
occur interbedded
interbedded with
with the
the
Small volumes
volumes of both basic and acid pyroclastic rocks
flows
flo\vs in the
the lower part of the 14,300 foot
foot Mamainse Point section,
section, and
and conglomerconglomerates
partings showing good cross—bedding
cross-bedding outcrop in
in the
the upper
upper half
half
ates with
with sandstone partings
of this
this section and in that
that at
at Cape
Cape Gargantua.
Gargantua.
Evidence of
the simultaneous availability of basaltic and
and rhyolitic
rhyolitic material
material
of the
is
is seen in the Mamainse
Matnainse Point
Point section;
section; plugs,
plugs, dykes
dykes and
and sheets
sheets of
of fine-grained,
fine—grained,
often flow—laminated
flow-laminated and
and autobrecciated leucorhyolite
leucorhyolite occur
occur at
at all
all levels
levels of
of this
this
one such intrusive sheet was found to
section and one
to he
be composite,
composite, having
having aa 2—foot
2-foot
basal selvage of fine—grained
fine-grained basalt and
and aa 50—foot
50-foot acid
acid upper
upper part.
part.
Fetrographic
Petrographic similarities found
found in
in flows
flows of
of the
the Mamainse
Mamainse Point
Point and
and Cape
Cape
good basis
basis for
for lateral
lateral correlation
correlation of
of these
these two
two
Gargantua sequences provide aa good
sequences. Near the basal unconformity of theMamainse
therlamainse section
section there
there occurs
occurs aa highhighly
olivine-tholeiite flow
flow crowded
crowded with large
large plagioclase
plagioclase
ly distinctive glomerophyric olivine—tholeiite
laths concentrated
concentrated in spherulitic clusters up
laths
up to
to two
two inches
inches in
in diameter
diameter (Ciblin,
(Giblin,
1969); aa flow
flow of
of exactly similar type
1969);
type outcrops 40
40 miles NNW
NNW along
along strike
strike near
near the
the
base of the
the Cape Gargantua section
section (Ayres,
(Ayres, 1969).
1969). Both
these occurrences are assoBoth these
ciated with
with aa group
group of olivine-tholeiite
olivine—tholeiite flows
ciated
flows rich
rich in
in large
large pseudomorphs
pseudomorphs after
after
\vhich may make up
up to
to 35
35 per
per cent
cent by
by volume
volume of
of the
the rock
rock in
in parts
parts
olivine phenocrysts which
of such flows
This striking similarity of the
flows at
at Mamainse
Mamainse Point.
Point. This
the flows
flows in
in the
the
levels of the
lower levels
the Mamainse Point and Cape Gargantua piles
piles suggests
suggests simultaneous
simultaneous
effusion of the
the same
S~le mafic magma supply
supply over
over aa wide
wide area
area to
to preduce
pr~duce lava
lava flows
flows of
of
sii,!lar
extent to
to that
that of
of the
the Greenstone
Greenstone Flow
Flow of
of the
the Michigan
Michigan Keweenawan.
siIIl~Lar extent
Point, Alona
Alana Bay
Bay and
and Cape
Cape Gargantua
Gargantua flo9s
f1o'to.{s are
are also
also petrographical—
petrographicalThe Mamainse
Hamainse Point,
ly similar to
olivine—tholeiite flows
ly
to the
the olivine-tholeiite
flows forming the
the basal part
part of
of the
the Michipicoten
Michipicoten
Island section and it is possible that
that these
these latter
latter flows,
flows, also
also cut
cut by
by acid
acid intruintrusions,
sions, may represent the
the upper part of
of an
an extensive
extensive and
and largely
largely uniform
uniform flood
flood babasalt pile whose earliest members rest
rest directly
directly on
on the
the Archaean
Archaean on
on the
the east
east shore
shore of
of
Lake Superior.
Superior. The more highly differentiated
differentiated andesite
andesite and
and rhyolite
rhyolite flows
flows of
of
Hichipicoten
Island are
thus interpreted
Michipicoten Island
are thus
interpreted as
as being
being of
of much
much later
later extrusion
extrusion than
than the
the
A general increase in the deMamainse Point,
Point, Alona
Alana Bay
Bay and
and Cape
Cape Gargantua
Gargantua flows.
flows. A
flows is
gree of alteration
alteration of
of lava
lava flows
is apparent
apparent as
as the
the Keweenawan
Keweenawan lava
lava pile
pile is
is followed
followed
downwards
of the
the Michipicoten
Michipicoten Island
Island section
section to
to the
the base
base of
of the
the
downwards from
from the
the top
top of
Mamainse Point
Point section.
section.
Mamainse
�-8—8—
Some differences
differences in general chemistry exist between flows
Some
flows newly
newly analysed
analysed from
from
Island and
and Maniainse
Mamainse Point
the Island
Island flows
flows
the Michipicoten Island
Point sections;
sections; 36
36 analyses of the
tholeiitic trend
trend of moderate iron—enrichment
iron-enrichment on
on an
an Nfl
MFA plot;
plot; aa similar
similar plot
plot
follow a tholeiltic
of 46 analyses of Mamainse Point flows
flows gives
gives aa tholefitic
tholeiitic trend
trend of
of high
high iron—enrichiron-enrichment.
References;
References:
Annells,
R. N.,
N.,
Annells, It.
1970,
geology of
of Michipicoten
Michipicoten Island,
Island,
1970, Keweenawan volcanic geology
Lake Superior
Lake Superior; Program,
Program, 16th
16th Ann.
Ann. Inst.
Inst. on.
on. Lake
Geol., Thunder Bay,
Bay, Ont., May
May 1970,
1970, 7.
7.
Ceol.,
Ayres, L.
L. D.,
D.,
1969,
31 and 30,
30, Ranges 20
20 and
and 19;
19;
1969, Geology of Townships 31
Ontario Dept.
Dept. Mines Ceol.
Geol. Rept.
Rept. 69,38.
69,38.
Giblin,
P. E.,
E.,
Giblin, P.
1969,
Prelim. Geol.
Geol. Naps
Maps 553
553 and
and 555.
555.
1969, Ontario Dept.
Dept. Mines,
Mines, Prelim.
�-9—9—
CHRONOLOGY OF PRECAMBRIAN ROCKS
ROCKS OF
OF
IRON
IRON AND
AND DICKINSON COUNTIES, MICHIGAN
P.O.
P.O. Banks
Department of Geology
Geology
Case Western Reserve University,
University, Cleveland, Ohio, 44lO6
44106
and
W.R. Van Schmus
W.R.
Department of Geology
Geology
University of Kansas,
Kansas, Lawrence,
Lawrence, Kansas,
Kansas, 6604k
66044
U—Pb analyses of cogenetic zircon suites and Rb-Sr whole rock analyses
U-Pb
from
from selected Precambrian
Frecambrian units
units in Iron and Dickinson Counties, Michigan,
suffice to
for this classic
suffice
to establish an internally consistent chronology for
area. Stratigraphic nomenclature used herein is adopted from
from James et
et al.
al.
(1961).
(1961).
Zircons from
the Norway Lake Gneiss, which underlies the Dickinson
Zircons
from the
Group,
2375 m.y., but
Group, yield aa concordia intercept age of approximately 2375
Rb-Sr
from the Norway Lake Gneiss do not define
define an
an
Rb-Sr whole
whole rock
rock analyses
analyses from
isochron, and the isotopic
isotopic composition
composition of
of Pb
Pb from
from separated
separated feJ.dspars
feldspars is
isochron,
is
abnormal. Thus,
from the
Thus, we
we conclude that
that the 2375 m.y.
m.y. "age" obtained from
zircons
zircons is
is probably the
the result
result of complex metamorphism and deformation of
the Norway Lake Gneiss and does not indicate
indicate its
its true
true absolute
absolute age.
age. The
2375 m.y.
m.y. event
event that
that affected the
the Norway Lake Gneiss may be pre—Dickinson,
pre-Dickinson,
2375
thus establishing a possible older limit for
for the
the age
age of
of the
the Dickinson
Dickinson Group.
Group.
Earlier published zircon analyses suggesting
suggesting aa much greater
greater antiquity
antiquity for
for
the Dickinson Group
etal.,
Group (2700
(2700 m.y. or more: Aldrich
Aldrich et
al., 1965)
1965) are
are interpreted
interpreted
to reflect detrital
detrital zircon
zircon components
components in
in the
thernetasedimentary
metasedimentary gneisses.
gneisses.
The pre—Animikie
pre-Animikie Porphyritic Red Granite,
Granite, whose
whose field
field relation
relation to
to the
the
Dickinson Group is
is uncertain, gives aa zircon
zircon conoordia
concordia intercept
intercept age
age of
of
approximately
rock Rb—Sr
approximately 2100
2100 m.y.
m.y., and whole rock
Rb-Sr analyses are also consistent
consistent
with this
We interpret
interpret this
this age
age to be post-Dickinson, thus bracketing
this age.
age. We
the age of the Dickinson Group between 2100
2100 m.y. and,
and, perhaps,
perhaps, 2400
2400 m.y.
m.y.
,
A single zircon analysis from
from the Hemlock Volcanios
Volcanics of
of the
the Animikie
Animikie
A
but the
the zircon
zircon is
is somewhat
somewhat discordant,
discordant,
Series yields a Pb-Pb age of 1985 m.y., but
so that
that the concordia intercept
intercept age is
is expected
expected to
to be
be slightly
sligh~ly older
older at
at
approximately 2000
2000 m.y.
m.y.
Rb-Sr whole rock analyses on the
the post-Animikie
post-Animikie Feavy
Peavy Complex
Complex yield
yield
Rb—Sr
an age of approximately
1700
m.y.
approximately 1700 m.y. However,
However, previously published mineral
age
age determinations
determinations on other post—Animikie
post-Animikie units
units indicate
indicate that
that the
the Animikie
Animikie
Series is
is definitely
al., 1965).
1965). Thus,
Series
definitely older
older than
than 1900
1900 m.y.
m.y. (Aldrich
(Aldrich et
etal.,
deposition of the Animikie Series appears to
to be
be bracketed
bracketed in
in the
the interval
interval
between 2100
2100 m.y.
m.y. and
and 1900
1900 m.y.
m.y.
A
A maximum age of 2100 m.y.
m.y. for the Animikie
Animikie Series,
Series, in
in conjunction
conjunction with
with
published Rb-Sr data on
on the
the post—Huronian
post-Huronian Nipissing
Nipissing Diabase
Diabase (2160
(2160 rn.y.)
m.y.) and
on Huronian
1-luroniansediments
sedimentsthemselves
themselves(2285
(2285m.y.)
m.y.) (Van
(Van Schmus,
Schmus, 1965;
1965; Fairbairn
Fairbairn
et
al., 1969),
1969), severely
severely restricts
restricts possible
possible correlations
correlations between the Animikie
etal.,
Animikie
Series
and
the
Huronian
formations
of
the
North
Shore
of
Lake
Huron.
Series
Shore of Lake Huron.
�—10—
-10-
References
Aldrich, L.T., Davis,
Davis, C.L.,
G.L., and
and James,
James, FI.L.,
H.L., 1965,
1965, Ages
Ages of
of minerals
minerals from
from
metamorphic and
and igneous
igneous rocks
rocks near
near Iron
Iron Mountain,
Mountain, Michigan:
Michigan: Jour.
Petrology, v.
~
v. 6,
6, pp.
pp. +47-472.
447-472.
Fairbairn, H.W.,
H.W., Hurley,
Hurley, P.M.,
P.M., Card,
Card, K.D.,
K.D., and Knight,
Knight, C.J., 1969,
Fairbairn,
Correlation
of radiometric
radiometric ages
ages of
ofNipissing
Nipissingdiabase
diabaseand
and1-luronian
Huronian
CorrelaL on of
metasedimen-ts with
with Proterozoic
Proterozoic orogenic
orogenic events in Ontario: Can.
metasediments
Jour.
Earth Sci.,
Sd., i.
Jour. Earth
v. 6, pp. Lt89_497.
489-497.
James, ILL.,
H.L., Clark,
Clark, L.D.,
Lamey, C.L.,
C.L., and Pettijohn, F.J.,
F.J., 1961, Geology
Geology
James,
L.D., Lamey,
U.S. Ceol.
of central Dickinson County,
County, Michigan:
Michigan: U.S.
Geol. Surv.
Surv. Prof.
Prof.
310, 176
176 p.
p.
Paper 310,
Van Schmus,
Schmus, R.,
R., 1965, The geochronology of the Blind River—Bruce
River-Bruce Nines
Mines area,
area,
Ontario, Canada:
Canada: Jour.
Jour. Ceol.,
Geol., v.
v. 73,
73, pp.
pp. 755-780.
755-780.
�—11--11-
HORELSES IN THE
DULUTHCOMPLEX,
COMPLEX,MINNESOTA
MIIESOTA
HORNFELSES
THE SOUTHERN
SOUTHERN PART
PART OF
OF THE DULUTH
Bormichsen
Bill Bonnichsen
Cornell University
Hornfels
of feet
feet in
in
Hornfels bodies ranging from less than an inch to thousands of
dimensions
are abundant in the southern part of the Duluth Complex. They
dimensions are
were derived from
from a wide
wide variety of initial rock types,
types, many of which occur
in the complex footwall.
footwall. The
The most
most abundant
abundant types
types were derived from argillaceous
ceous sediments of the Virginia Formation,
Formation, mafic to intermediate volcanic
rocks of Keweenawan age and various intrusive rocks indigenous to the complex.
rocks
complex.
Others include iron
iron formation,
formation, quartzite
quartzite and
and d.ioritic
dioritic rocks
rocks from
from the
the prepreKeweenawan basement
basement and.
and clastic
Keweenawan age.
age.
elastic sediments
sediments of probable Keweenawan
Virginia inclusions are
are very
very similar
similar to
to metamorphosed
metamorphosed footwall
footwall Virginia;
Virginia;
however,
the relative
relative mineral
mineral proportions are
hovrever, the
the grain
grain size
size is
is larger
larger arid
and the
are
slightly different. The silicate mineralogy of argillaceous inclusions
inclusions inincludes coexisting cordierite,
orthopyroxene, biotite,
cludes
cordierite, orthopyroxene,
biotite, plagioclase and
and potassium
potassium
feldspar. Minor amounts
amounts of
of pyrrhotite,
pyrrhotite, graphite,
ilmenite and
and traces of chalchalgraphite, ilmenite
copyrite and pentlandite are common, but
olivine and
and Ca pyroxene
invariably
but olivine
pyroxene are invariably
absent. Various types
types of
of relict
relict se.imentary
sedimentary structures
structures are distinguishable
distinguishable in
all but the smallest
smallest of
of hornfelsed
hornfelsed Virginia
Virginia inclusions.
inclusions.
all
inclusions are
are characterized
characterized by
by their
lack of
of relict
Volcanic hornfels inclusions
their lack
sedimentary structures,
local round
round to
ellipticalplagioclase
plagioclase and
and Ca pyroxene
structures, local
to elliptical
segregations that probably were
segregations
were amygdules
amygdules and their mineralogy. They consist
largely of
niagneof plagioclase
plagioclase and
and Ca pyroxene,
and normally contain abundant magnepyroxene, and
tite and
tite
and orthopyroxene (commonly
(commonly inverted
invertedpigeonite).
pigeonite). Olivine, brown
brown hornblende, apatite,
ilmenite, and
and traces
traces of biotite
biotiteoccur
occurininsome
some bodies
bodies but
but none
none
apatite, ilmenite,
graphite, or
or more
more than
than traces
traces of
of potassium
potassium
are known
knovm to contain cordierite,
cordierite, graphite,
feldspar.
FeO+MgO of various
The proportions of
of weight
weight percent
percent 3102,
Si0 , Al20~ and.
and FeO+MgO
2
types of hornfelses
hornfelses and equivalent
equivalent rocks
rocks are
are plotted
ploted in
in figure
figure 11 (Bonnichsen,
(Bonnichsen,
in prep.).
A, B
prep. ). The A,
B and CC groups are materials from
from the
the Virginia
Virginia Formation,
Formation,
vlhereas the
the D, EE and
and FF groups
groups are
are volcanic
volcanic hornfelses
homfelses and.
and their equivalents.
whereas
Note
Note that,
that, although
although both
both groups
groups show
show considerable
considerable range
range in their proportion
A12O3.
of Si0
the
Virginia
materials
have
higher
proportion
of Al
0 .
,
SiOa,
the
Virginia
have
a
higher
proportion
2
2 3
The group A
unmetamorphosed Virginia and
and equivalent hornhomA samples are unmetamorphosed
felses from the
felses
the footwall
footwall of
of the
the complex.
complex. The group BB samples are
are from
from incluinclusions vlithin
within the complex.
sions
complex. Note their depletion in 8i0
relative
to
the
A
5102
the
A
2
group.
This
This suggests
suggests that Si02
8i02 was lost from
from the inclusions;
inclusions; this
this loss
loss is
is
accompanied by a similar depletion of K20
~O in several
several samples
samples and
and suggests
suggests loss
loss
of aa grantic
grantic partial
partial melt
melt during
during the
the hornfelsip.g
hornfelsipg process.
process. The group CC samples
samples
are
are from the margins
margins of hornfels bodies and
and thus
thus were in
in direct
direct contact with
with
initial
the
the intrusive
intrusive rocks.
rocks. Their
Their compositions
compositions deviate
further from
from the initial
deviate farther
values than do those of group B;
B; they are considered to be refractory resiresiduals which
which had
had become
become nearly
nearly equilibrated
equilibrated with
vlith the
the adjoining
adjoiningmagnias.
magmas. Part
group BBrocks
feldspars and
and cordierite
of the
the group
rockscontain
containtexturally
texturallyinterstitial
interstitial feldspars
which are interpreted
interpreted as
as recrystallized
recrystallized partial
partial melts.
melts. During the hornfelsing
process aa melt
melt with
,nth the
the composition
composition ofofcordierite
cordieritearid,
and alkali
alkali feldspar evidently developed after a granitic fraction had
had been
been lost.
lost. Hornfelses with the
group C
where this
this later type
type of melt
melt
C compositon are considered to have formed
formed where
had been lost. The formation of granitic dikes
dikes and
and the
the production
production of
of abundant
abundant
C pyroxene are the
biotite and orthopyroxene
orthopyroxene at
at the expense of olivine arid
and Ca
principal effects on the enclosing intrusive
intrusive rocks
assimilation
rocks \vrought
wrought by the
the assimilation
of such partial melts.
�—12—
-12-
Si02
:7
Figure
I.
'F
A1203
FeO*
A
00
E
F.
c@
50
to 41203
AI203
V
v
vV
v
V
vV
to
to FeOtMgO
FeO+ MgO
V
v
Group E consists of hornfelsed.
basalts; they
they have
have bulk
bulk compositions
compositions that
that
hornfelsed basalts;
show little deviation from
from the
the compositions
compositions of
of ordinary
ordinary basalts.
basalts. Group
Group FFrocks,
rocks,
however, have
and Si02
Si02 and
and higher
higher Ti0
Tb22 and
and FeO
have lower
lower K20 and
FeO contents
contents than
than ordinary
hornfelses may have been inbasalts and
and have high
high Fe/Mg
Fe/Mg ratios.
ratios. Two of these hornfelses
trusive residual
residual liquids
liquids which
which separated
separated from
from trocto].ite
troctolite but
but the
the other
other one
one evidently
is aa hornfe].sed
hornfelsed volcanic
rock that
that contains
contains probable
probable relict
relictaxnygdules.
amygdules.
dently is
volcanic rock
Sample D
D is
is an
magnetite-richbasaltic
basaltic rock from
an unmetamorphosed
unmetamorphosed magnetite-rich
from along
along the
the
eastern margin
of the complex;
its Fe/Mg
ratio is
is like that of group F. The
margin of
complex; its
Fe/lf~ ratio
volcanic rock in group F may initially have had a composition
composition similar to that
that
of sample D.
D. If so
, it
material during
during
so,
it lost
lost aa substantial amount
amount of granitic
granitic material
hornfelsing process.
the hornfelsing
process.
in the
The abundance and distribution of hornfelsed volcanic rocks in
system of
southern part of the complex supports the concept that an extensive system
Keweenawan flows
was present throughout the region and had been laid down
Kew"eenawan
flOivS was
dOim on
an erosion
erosion surface
surface cut
cut in
in the
the Middle
Middle Precambrian
Precambrian rocks.
rocks. The
the
Theintrusion
intrusion of the
an
Troctolitic Series
Series and accompanying crustal extension evidently broke up the
volcanic
volcanic rocks.
rocks. As
distributed throughout
As a result
result the
the hornfelses
hornfelses are
are widely
ddely distributed
the southern half of
of the
the complex.
complex. Many
l~ of
of the
the large
large bodies occur
occur as
as septum
septum
betvreen
adjacent intrusive
intrusive bodies.
bodies. The great number of inclusions of various
between adjacent
types along the
the footwall
types
footwall of the complex indicated that the intruding troctoconsiderable mechanical
mechanical strength.
strength. Evidently,
litic magmas had considerable
Evidently, these
thesemagmas
magmas
were
mushes
were in the
the form
form crystal-rich
crystal-rich
mushesduring
duringemplacement.
emplacement.
Ref:
Bonnichsen,
the Duluth
Duluth Complex,
Complex, St.
st.
Bonnichsen, B.
B. (in prep.);
prep.); The southern part of the
Louis and Lake
of Minnesota,
Minnesota,
Lake Counties,
Counties, Minnesota;
Minnesota; to
to be
be publ.
publ. in
in Geology
Geolor of
Schwartz commemorative
volume;P.K.
P.K. Sims,
Sims, ed.
G.M. Schw"artz
connnemorative volume;
�-13—13—
A NEW VIEW OF THE DULUTH
DULUTH CO~PLEX,
COMPLEX, MINNESOTA
A
by
Donald H.
M. Davidson,
Davidson, Jr.
Jr.
University of Minnesota, Duluth
Duluth
and
Minnesota Geological Survey
Hinnesota
ABSTRACT
A B S T R ACT
The late Precambrian (Keweenawan)
(Keweenawan) Duluth Complex is
is a sequence
generally discordant intrusive rocks
of generally
rocks extending
extending northeastward
northeastward from
from
Duluth to
to 1-loyland,
Hovland, Minnesota
Minnesotain
in a a roughly
roughly crescentic
crescentic configuration.
The
the Complex
Complex is
is bifurcated
bifurcated on
on the
the east
east and
and south
south
The outcrop
outcrop pattern of the
by rocks
rocks of the
the North Shore
Shore Volcanic
Volcanic Group.
Group.
in Table 1,
1, three
three rock
rock series
series (anorthosite,
(anorthosite,
As may be noted in
troctolite—olivine gabbro
gabbro and
and felsic)
troctolite-olivine
felsic) constitute the
the major petrologic
petrologic
units
of
the
Complex.
units
the Complex. Anorthosite series rocks were apparently emplaced
as large, crystal-liquid
as
crystal—liquid masses
massesinin ~.,hich
whichcumulus
cumulusplagioclase
plagioclaseisis the
the prepredominant mineral.
mineral. The anorthositic rocks,
which form the central portion
dominant
rocks, t.,hich
of the
of
the Complex,
Complex, have been subsequently intruded
intruded by
by the
the troctolite
troctolite series
series
along the northern and western footwall
footwall and
and by
by the
the olivine
olivine gabbro
gabbro series
series
to
troctolites and
to the southeast. The
The troctolites
and gabbros
gabbros are
are aa sequence
sequence of
of genergenerally
containing cumulus plagioclase and
and olivine
olivine and
and poik—
poikally layered
layered rocks
rocks containing
ilitic pyroxenes. The
The basal
basal troctolite series dips
gently
(15°)
towards
dips gently (15°) towards
Lake Superior,
Superior, whereas
whereas the
Lake
the attitudes of the
the upper
upper olivine
olivine gabbro
gabbro series
series
vary
(e.g. Sawbill
vary from northward dips
dips of
of 40°
40° (e.g.
Sawbill Lake
Lake area)
area) to
to southward
southward
at low Q5°)
cLS°) angles
angles (e.g.
(e.g. along
along the
the Brule
Brule River Prong). Felsic series
at
rocks are
are predominantly granophyric granite which occur
rocks
occur as
as subhorizontal
subhorizontal
sheet—like masses
sheet-like
masses above
aboveboth
bothmargins
marginsofofthe
theolivine
olivine gabbro
gabbro series.
series. Separate minor
arate
minor intrusives
as the Endion Sill,
Sill, the
the Beaver
Beaver Bay
Bay Complex
Complex
intrusives such as
and
to be younger than
than the
the Duluth
Duluth Complex,
Complex,
and the
the Hovland Complex appear to
whereas only Lie
the Gunflint
Gunflint Prong
Prong Layered
Layered Complex
Complex appears
appears older.
older. Petrologic
relationships
sources derived
derived from
from the
the mantle,
mantle, to
to
relationships suggest
suggest multiple magma sources
account for
account
for the
the petrogenetic sequence of the
the Duluth
Duluth Complex.
Complex.
The Duluth Complex
Complex is
is coincident
coincident with
with the
the axis
axis of
of the
the Mid—Continent
Mid-Continent
Gravity High.
High. Footwall shearing and the
the asymmetric
asymmetric position
position of
of the
the
Complex
Complex with
with respect
respect to
to the
the Lake
Lake Superior
Superior Syncline
Syncline suggest
suggest Complex
Complex
emplacenent consanguinous
emplacencnt
consanguinous with
with rifting.
riftine. Gravity studies to
to date
date suggest
suggest
the Complex thins
thins or is absent beneath Lake
Lake Superior.
Superior. Dominant Complex
Complex
the
N.20E.—N.SOE.) are common
fracture trends
trends (N.-.
(N.-~.90E.
or W.
W.,, ~.20E.-~.80E.)
common throughout
throughout
90E. or
the Lake
regional post—intrusive
post-intrusive extension.
extension.
the
Lake Superior area suggesting regional
Significant base-metal
base—metal mineralization
mineralization occurs
occurs within
within selected
Significant
troctolite
controls afforded
afforded by
by host
host
troctolite series
series horizons
horizons with local ore controls
rock lithology and structural settling
settling shelves.
shelves. Should the proposed
funnel
the central complex
complex be verified, subsurface
subsurface
funnel configuration
configuration of the
exploration of the
the Southern Complex
Complex appears
appears warranted.
~varranted.
�Table
1.
Table 1.
Summary of Principal Petrologic Series and Units,
Units, Duluth Complex,
Complex, Minnesota
Late Minor
Hinor
Intrusive
Complexes
Felsic
Troctolite—
TroctoliteDuluth
"
G hb
Duluth Complex
CompleX01i
Gahbro
Ol l.Vl.ne
,cambrian
a ro
cambrian (l.ltO.2b.y.)
(l.10.2b.y.)
Endion Sill
Sill
Er.nst~ W.
W. C.,
G., 1960,
1960, Jour.
Jour.
Ernst,
Beaver Bay
Complex
Gehman, H.
H. M.,
M., Jr.,
Jr., 1957,
1957~ Unpub.
Unpub. Ph.D.
Ph.D. Thesis,
Thesis, Univ.
Univ. of
of Minn.
Minn.
Konda,
T., 1970,
1970, Contr.
Contr. Min.
Mm. Pet.,
Konda, T.,
Pet., Vol
Vol 29,
29, p.
p. 338—344
338-344
Hovland
Complex
Hoviand Complex
Jones, N.,
N., 1963 Unpub.
Unpub. M.S.
M.S. Thesis, Univ.
Univ. of Minnesota
Granophyric
Granite and
and
Minor Felsic
Hinor
Intrusives
Davidson, D.
D. M., Jr.,
Jr., 1969,
1969, Minn.
~linn. Geol.
Geol. Surv.
Surv. Misc.
Misc.
Map Ser.,
Ser.~ M—7,
M-7, M—8
M-8
Grout,
F. F.,
F., and
and others,
others~ 1959,
1959, Minn.
Minn. Geol.
Geol. Surv.
Surv. Bull.
Bull. 39.
39.
Grout, F.
Grout,
F. F.,
F., and
and others,
others, 1959,
1959, Minn.
Minn. Geol.
Geol. Surv.
Surv. Bull.
Bull. 39.
39.
Grout, F.
Basal
Troctolite
Troctolite
,1969, Minn.
Minn. Geol.
Geol. Surv.
Surv. Rept.
Rept. Inv.
mv. 99
Phinney,
W. C.
C.,1969~
Phinney, W.
44
Bull.
R. B.,
B., 1964,
1964~ Minn.
Minn. Geol.
Geol. Surv.
Surv. Bull. 44
Taylor, R.
Central Anorthosite
Early Minor
Ninor
Intrusive
Complexes
North
~orth
and
Anorthosite
Inclusions
Bonnichsen, Bill,
Bill, 1969,30th
1969,30th Annual
Annual Min.Sympos.,Univ.Minn.pp.8993
~lin.Sympos. ,Univ.Minn.pp.89-93
Bonnichsen,
,Univ.Mlnn.pp.89—93
Bonnichsen,
Bill~1969~30th
AnnualI'lin.Sympos.
Hin.Sympos.,Univ.Minn.pp.B9-93
Bonnichsen, Bill,1969,3Oth
Annual
Misc. Map
Davidson, D.
D. }[.,
Jr.~ 1969, Minn.
Minn. Geol.
Geol. Survey
Survey Misc.
Hap
M., Jr.,
Ser. 1—7,
Ser.
H-7~M—8
M-B
Sd. Mem.
Phinney, W.,
W., 1966,
N.Y. State,
State~ Mus.
Mus. Sci.
Hem. Vol.18,
Vol.18, p.135—147
p.135-l47
1966, N.Y.
Phinney,
44
Taylor~ R.
R. B.,
B., 1964,
1964, Minn.
Minn. Geol.
Geol. Survey
Survey Bull.
Bull. 44
Taylor,
Gunflint Prong
Prong Sill
Sill
Babcock~ R.C.,
R.C., 1959,
1959, Unpub.
Unpub. M.S.
M.S. Thesis,
Thesis, Univ.
Univ. Wisc.
Wise.
Babcock,
Brule Lake Sills
Bull. 39.
Grout and
and others, 1959,
1959 ~ Minn.
Hinn. Geol.Survey
GeoI. Survey Bull.
39.
Granoels
Granofels
Shore
Pet.,
Pet.~ Vol.
Vol. 1,
1, p.
p. 286—303
286-303
Upper Olivine
Gabbro
,e
Anorthosite
Anorthosite
Principal References
Principal
Unit
Series
Map Ser.
Ser. M—7,
D.H., Jr.,
Jr., 1969,
1969~ Ninn.
lorinn. Geol.
Geol. Survey
Survey Map
M-7, N—8
H-B
Davidson, D.M.,
Volcanic
Volcanic Group
Group
Volcanics—
VolcanicsUndifferentiated
;-1iddle
'Ii ddle
Lower
Duluth Complex
Early Hinor
Minor
Early
Intrusive
Intrusive
Complexes
Gunflint
Gunf lint Prong
Layered Complex
Complex
Nathan~
H., 1969,
1969,
Nathan, H.,
I
I
Unpub.
Ph.D. Thesis, Univ.
Unpub. Ph.D.
Univ. Minn.
Minn.
I
HI
~I
�-15-15—
TEXTURAL FACIES
IRONSTONES*
FACIES ANALYSIS
ANALYSIS OF
OF PRECAMBRIAN
PRECAJfBRIAN CHEItTY
CHERTY IRONSTONES*
by
by
Erich Dimroth,
Dimroth, Service de Pl'Exploration
Erich
Exploration geologique
des Richesses
Richesses Naturelles,
Naturelles, Quebec,
Quebec, P.Q.
P.Q.
Ministere des
and
Jean-Jacques
Jean—Jacques Chauvel,
Chauvel, Departement de Geologie,
Rennes, France
France
Universite Rennes, Rennes,
ABSTRACT
A B S T R ACT
cherty ironstones
ironstones are
are very
very similar
similar to
to those
those
Textures of Precambrian cherty
of limestones
limestones (Dimroth
(Dimroth 1958).
1958). Accordingly the
the methods of limestone
limestone petrology
petrology
can be applied in the
the study
study of
of ironstones.
ironstones.
Ironstones can be
be conceived to
Ironstones
to be composed of textural
textural elements.
elements.
Textural ironstone types are defined by the
the kind
kind and
and proportion
proportion of
of textural
textural
elements present.
present. Textural facies
facies types
types compose
compose thin
thin (3
(3 feet—lOO
feet-lOO feet)
feet)
units; they
they are either texturally
texturally homogeneous,
homogeneous, or
or are
are comcomstratigraphic units;
textural rock
rock types
types that
that form
form beds
beds alternating
alternating in
in aa
posed of several textural
characteristic sequence.
sequence. It
It is
to determine
determine the
the paleo—
paleois generally possible to
environment
envi~onment in which the
the various textural
textural facies
facies types
types formed,
formed, and
and by
by
sections, to gain a view of
of the
the paleogeography
paleogeography
correlation of
of stratigraphic sections,
of the depositional basin.
of
the following
following textural
textural elements
elements in
in the
the ironstones:
ironstones:
We distinguish the
I
I
Orthochems
—
1.
Femicrite: A
A past of fine—grained
fine-grained iron
iron silicate
silicate (minnesotaite,
(minnesotaite,
Femicrite:
1.
sti1pnome1ane)
from iron
iron silicate
silicate and
and iron
iron carbonate
carbonate
stilpnomelane) or of siderite derived from
muds.
2.
2.
~~trix chert;
chert:
Matrix
3.
Cement
chert:
Cement chert:
3.
deposition.
Chert deposited as
as aa silicagel
silicagel matrix.
matrix.
after
Chert that
that formed between allochem
allochem grains
grains after
chert and
and cement
cement chert
chert can
can be
be distinguished
distinguished only
only in
in some
some
Matrix chert
hematite
tones.
hematite irons
ironstones.
II
IL
—
Allochems
1.
Pellets:
particles 0.2
0.2twa.
mm. across unsharply
unsharply bounded,
bounded,
Ellipsoidal particles
Pellets: Ellipsoidal
1.
Pellets
are
interpreted
as
aggregated
always
embedded
in
matrix
chert.
Pellets
are
interpreted
as
aggregated
always embedded in matrix chert.
particles.
with the premission of the
*Published with
the Deputy Minister, Department
Department
of Natural REsources,
REsources, Quebec.
Quebec.
�-16—16—
Entraclasts: Fragments of the unconsolidated sediment that
2. Intraclasts:
that
have been
been redeposited.
redeposited. Previously (James,
(James, 1954)
1954) described from
from intra—
intra(large intraclasts)
intraclasts) and
and as
as "granules"
"granules" (=
(= sandformational conglomerates (large
sand—
size intraclasts).
3.
3.
Oolites and
and Pisolites.
Pisolites.
4.
4. Shards: Shards
textures. Two sub—types
sub-types predominate
Shards are complex textures.
(a)
(accommodation
(a) welded
welded and
and extremely
extremely deformed
deformed oolites
oolites and
and intraclasts
intraclasts (accommodation
shards).
(b) shards
fragments of oolites and
and
(b)
shards composed mainly
mainly of peeled off fragments
shards).
intraclasts (exfoliation
(exfoliation shards).
shards).
types are
are defined
defined by the
the combination
combination of
of textural
textural elements
elements
Textural rock types
present.
Main types
types are:
are:
I.
I.
Femicrites:
II.
II. Matrix
Matrix chert:
chert:
Laminated or ribboned silicate—carbonate
silicate-carbonate ironstones.
ironstones.
Lamina~ed
Laminated
or ribboned cherts,
cherts, generally
generally with pellets.
pellets.
III.
intraclastic or
or oolitic
oolitic ironstones.
ironstones.
III. Cemented intraclastjc
IV. Intraclastic or oolitic rocks with chert
chert matrix.
matrix.
IV.
V.
Intrafemicrjtes:
Intrafemicrites:
Intraclasts embedded
embedded in
in aa femicrite
femicrite matrix.
matrix.
types, particularly containing
containing shard
shard textures,
textures, are
are quantitatively
quantitatively
Some other types,
less important.
important.
The paleogeographic application of the
the method will be
be demonstrated
demonstrated at
at
the
the example of the lower jaspilite member of the
the Sokoman
Sokoman Ironstone
Ironstone in
in the
the
western half of the
the Labrador trough
trough between
between latitudes
latitudes 54°45'N
54°45'N and
and 55°15'N.
55°l5'N.
Close to
Close
to the
the western margin of the trough
trough this
this stratigraphic
stratigraphic unit
unit is
is
thickly bedded
bedded finely
finely intraclastic
intraclastic
locally represented by a massive or thickly
and oolitic
(facies type
type 1).
1). Toward
o.olitic chert
chert cemented
cemented hematite
hematite ironstone (facies
this type grades into
into interbedded
interbedded oolitic—intraclastic
oolitic-intraclastic hematite
hematite
the east this
ironstone with chert
alternating with
with laminated matrix
chert cement
cement or
or matrix,
matrix, alternating
chert containing
type 2).
2). This type
type is
is thin
thin to
to medium
medium
chert
containing hematite
hematite (facies
(fades type
bedded (2—30
(2-30 cm.)
em.) andcharacteristically
andcharacteristically shows
shows lenticular
lenticular bedding.
bedding. It
It grades
into aa type
type that
that contains
contains intercalated
intercalated beds,
beds, 2—100
2-100 cm.
ern. thick,
thick,
basinwards into
east the oolitic intra—
femicrite (facies
(facies type
type 3).
3). Farther east
intraof laminated femicrite
beds are lacking in type
clastic beds
type 4 and finally
finally type
type 55 is
is composed
composed only
only of
of
laminated femicrite
femicrite with interbeds of
of laminated
laminated femicrite
femicrite bearing
bearing matrix
matrix
chert. Facies
types 33 and 4 are characterized
characterized by
by siump
slump structures
structures and
and
Pacies types
structures indicating strong synsedimentary deformation.
structures
deformation. Toward the
the centre
centre
of
the
trough
types
4
and
3
reappear,
and
grade
into
a
facies
containing
of the
types
3 reappear, and grade into a facies containing
interbeds
(2 cm.)
em.) intraclasts
intraclasts and
and pisolites
pisolites embedded
embedded in
in
interbeds with very coarse (2
matrix chert
chert (facies
(facies type
type 6);
6); the intraclasts and pisolites were very
soft at time of deposition.
soft
deposition. Facies
is tentatively interpreted
interpreted as
as
Facies type 1 is
a sand bar facies that
that separates
separates aa lagoonal
lagoonal environment
environment (not
(not discussed
discussed
here) farther west from
from the
the open
open basin.
basin. Facies
Facies type
type 22 has
has been
been deposited
deposited
here)
in
the intratidal.
intratidal and
in the
and shallow
shallow sub-tidal
sub—tidal zone
zone in
in the
the foreshore
foreshore of the sand
bars.
facies and
and
bars. Types
Types 33 and 4 represent
represent a relatively
relatively deep
deep subtidal
subtidal facies
�-17—17—
facies zone
zone 55 was
was deposited
deposited in
in aa relatively
relatively deep
deep basinal
basinal environment
environment
fades
(maybe
50-100
m.
water
depth).
Facies
type
6
was
likely
deposited on
Fades
type
6
was
likely
deposited
(maybe 50—100 m.
depth).
shallow sub-tidal
the centre
centre of the
the Labrador
Labrador
sub—tidal shoals that extended in the
trough.
The coarse intraclastic and pisolitic beds may represent
represent
storm layers.
layers.
References:
James, II.
James,
H. L., 1954: Sedimentary
of iron
iron formation.
formation.
Sedimentary facies
fades of
v. 49,
49, p.
p. 235—293.
235-293.
v.
Econ.
Geol.,
Econ. Ceol.,
Dirmroth, 13.,
1968:
Dimroth,
E., 1968:
Sedimentary textures,
textures, diagenesis and sedimentary
Ironstones. N.
N. Jb. Geol.
Geol.
environment of certain Precambrian Eronstones.
Palaeont., Abh. v. 130,
130, p.
p. 247—274.
247-274.
�—18—
-18-
IRON FORMATION
At COPPER
FORMATION AT
COPPER
PRECAMBRIAN IRON
MOUNTAIN,
FREMONT COUNTY,
COUNTY, WYOMING
MOUNTA
IN, PREMONT
H. Duhling, Jr.
Jr.
William H.
Natural Resources Research Institute
Institute
University of Wyoming,
Wyoming, Laramie
ABSTRACT
A B S T R ACT
iron formation
formation is
is exposed
exposed along
along the
the south-facing
south-facing
Precambrian banded iron
flanks
Shoshoni, in
in
flanks of
of Copper
Copper Mountain,
Mountain, approximately 15 miles north of Shoshoni,
northeastern Frenont
Fremont County,
County, Wyoming.
Wyoming. The Precambrian metamorphic comcomconsists of interlayered
interlayered quartzofeldspathic
quartzofeldspathic gneisses,
gneisses, amphibolites,
amphibolites,
plex consists
amphibole schists,
schists, peliric
pelitic rocks,
rocks, and iron
iron formation
formation into
into which
which granite,
granite,
complex
pegmatite,
and
mafic
dikes
and
sills
have
been
intruded.
The
pegmatite,
sills
been intruded.
has been metamorphosed to
has
to the
the kyanite-muscovite
kyanite-muscovite subfacies
subfacies of
of the
the almanalmandine-amphibolite facies.
facies. Sedimentary rocks
rocks of Paleozoic or Cenozoic
dine-amphibolite
the Precambrian
Precambrian complex
complex on
on all
all sides.
sides.
age abut the
The mineralogical composition of
of the
the iron
iron formation
formation is
is very
very simple,
simple,
quartz, and
and any
any combination
combination of
of blue-green
blue-green hornhornconsisting of magnetite,
magnetite, quartz,
blend,
Magnetite, in
blend, grunerite, and
and cummingtonite.
curnrningtonite. Magnetite,
in all degrees of alteration to hematite,
hematite, occurs in
in thin
thin laminae
laminae and
and fine
fine clusters
clusters with
with angular,
angular,
sharply embayed boundaries and as very fine
fine inclusions
inclusions in
in quartz
quartz and
and
amphibole grains.
grains. Banding is
is developed by apparent increase
increase in
in grain
the expense
expense of
of quartz
quartz and
and amphibole
amphibole grains.
grains.
size of the magnetite at the
The iron formation,
formation, interlayered
interlayered with amphibolite
amphibolite and
and quartz-mica
quartz-mica
schist, is
is exposed for
for a distance of
of about
about 66 miles
miles over
over an
an approximate
approximate
schist,
width of
of 1000
1000 feet.
feet. The strike of
of the
the formation
formation is
is NN 80°E
80 0 E and
and the
the dip
dip
is
to the
the south.
south.
is 70°
700 to
Liberation and concentration tests
tests indicate
indicate the
the presence
presence of
of roughly
roughly
million
iron and 22%
22% silica.
silica. The
The
million tons
tons of concentrates
concentrates containing 56% iron
fine magnetite in
in quartz
quartz and
and amphibole
amphibole grains
grains and
and the
the
amount of very fine
amount
interstitial quartz
quartz in
in the
the magnetite-rich
magnetite-rich bands
bands account
account for
for
amount of interstitial
the high
high silica content of the
the
the concentrates.
concentrates.
l3~
13¾
Rail
comes within ten
ten miles of
of the
the outcrop
outcrop area,
area, but
but
Rail transportation comes
the nearest markets
for a blast furnace
furnace feed
feed are
are over
over 240
240 miles
miles away.
away.
the
markets for
to market,
market, high silica
silica content,
content, low
low tonnage,
tonnage, and
and steep
steep
The distance to
to indicate
indicate that
that this
this iron
iron formation
formation has
has aa questionable
questionable
dip combine to
economic potential.
potential.
�-19—19—
Selected References
References
1.
1.
Duh1ing, William
William H.,
H., Jr, 1970,
1970, Oxide
Oxide facies
facies iron
iron formation
formation in
in the
the
Duhling,
Owl Creek Mountains,
Mountains, northeastern Fremont
Fremont County,
County, Wyoming: unpublished MS thesis,
thesis, University
University of
of Wyoming,
Wyoming, 92
92 p.
p.
2.
2.
G1iozzi,
James L.,
L., 1967,
1967, Petrology and
and structure
structure of
of the
the Precambrian
Precambrian
Gliozzi, James
rocks
the Copper Mountain district,
district, unpublished
unpublished PhD
PhD dissertation,
dissertation,
rocks of the
University of Wyoming, 141
141 p.
p.
3.
3.
Kopp,
S., 1964,
1964, Reconnaissance geology
geology of
of metamorphic
metamorphic strucstrucKopp, Richard S.,
tures
district, Fremont County,
County, Wyoming:
tures of
of the
the Copper
Copper Mountain Mining district,
Compass,
v. 43, p.
p. 6-20.
6~20.
Compass, v.
4.
4.
Millgate,
Mi11gate, M.
M. L.,
L., Gliozzi,
G1iozzi, James
James L.,
L., 1966,
1966, Reconnaissance
Reconnaissance of
of iron
iron forforin the
the Copper
Copper Mountain
Mountain area,
area, Fremont
Fremont County,
County, Wyoming:
Wyoming: unpubmation in
lished
Survey of
of Wyoming
Wyoming files.
files.
lished report Geological Survey
�-20-
Stratigraphy of the North Shore Volcanic Group
Northeast of Silver Bay, Minn.
by
John C. Green
University of Minnesota, Duluth
Minnesota Geological Survey
A B S T RAe T
A sequence of flows and flow vPups, totalling about 21,500 feet,
makes up the northeast limb of the North Shore Volcanic Group of
Keweenawan (late Precambrian) age between Tofte and Grand Portage.
Exposures are generally good to excellent along the Lake Superior
shore or abandoned wave-cut cliffs, and although cut by several
large intrusive bodies and obscured by glacial cover over wide areas,
many of these lithostratigraphic units can be traced inland from
Lake Superior for many miles. Table 1 shows the informal volcanic
units at the northeast limb (top of section at Tofte,base at Grand
Portage); Table 2 gives the sequence (less well established because
of faulting and intrusion) of the upper part of the southwest limb
from Tofte as far as Palisade Head near Silver Bay. The Schroeder
basalts at the top of the southwest limb are at least in part
equivalent to the Lutsen basalts of the northeast limb.
The basal 5,000 feet, near Grand Portage, Minn., have reversed
magnetic polarity (Lower Keweenawan) whereas all the rest have normal
polarity (Middle Keweenawan). The lowermost 250 feet of lavas on
Lucille Island, directly overlying the basal Upper Precambrian
Puckwunge Sandstone, are porphyritic melabasalts with abundant
olivine and augite phenocrysts, identical to those in the same
stratigraphic position at Nopeming, west of Duluth.
�—2]—
-2J-
Table 11
Stratigraphy of
(Tofte to Grand Portage) of
of
of Northeast
Northeast Limb
Linb (Tofte
North Shore Volcanic Group
Group (Exclusive
(Exclusive of
of Interf
Interflow
low Sediments)
Sediments)
Approx.
Approx.
- Thickness()
Thickness.J ft.)
Lithostratigraphic unit
unit
Lithic eharacter
Character
Lithic
Top
(near Tofte —- Lu
Lutsen)
Top (near
t sen)
1020
--
Lutsen basalts
olivine tholeittes
tholeiites
olivine basalts, olivine
160
160
Terrace Point basalt flow
Thomsonite—bearing ophitic
Thomsonite-bearing
ophitic basalt
basalt
310
310
Good Harbor
Harbor Bay
Bay andesites
andesites
brown, porphyritic andesite,
brown,
andesite,
trachyandesite
360
flow
Breakwater trachybasalt flow
brown, columnar, granular
trachybasalt
500
Grand I1arais
Marais rhyolite flow
pink,
pink, red,
red, gray porphyritic
porphyritic rhyolite
rhyolite
600
Croftville basalts
various fine—grained
fine-grained basalts
basalts
felsites
Devil Track felsites
aphyric
flows
aphyric and
and porphyritic rhyolite flows
Red Cliff basalts
amygdaloidal,
amygdaloidal, ophitic olivine basalts
1300
Creek felsite
felsite
Kimball Creek
pink to
to tan,
tan, porphyritic felsite
1800
Marr Island lavas
lavas
mixed tholeiitic
basalt,intermediate,
intermediate)
tholeiltic basalt,
felsic lavas
felsic
lavas
1000
Brule River basalts
granular—diabasic
granular-diabasic amygdaloidal
amygdaloidal basalts
basalts
3500
3500
Brule River rhyolite flow
pink
pink to gray porphyritic rhyolite
Hoviand
Hovland lavas
lavas
mixed porphyritic basalt,
basalt, trachybasalt,
trachybasalt,
rhyolite
200
Red Rock rhyolite flow
red, porphyritic rhyolite
red,
260
Deronda Bay andesite flow
flow
gray-brown,
gray—brown, aphyric andesite
4500
Grand Portage basalts
basalts
nixed tholeiitic
mixed
tholeiitic to
to diabasic
diabasic basalts
basalts
Base
(at Grand Portage)
(at
1020
— 400-900
400—900
4000
21,430
2l~430
(est. )
(est.)
�-22—22—
Table 22
Stratigraphy of Upper
Upper Part of Southwest Limb (Tofte
(Tofte
to Palisade
Palisade Head)
Head) of North Shore Volcanic Group
to
Approx.
Thickness
Thickness (ft.)
(ft.)
Lithostratigraphic unit
Lithic character
character
4000
Schroeder basalts
ophitic olivine
olivine
amygdaloidal, ophitic
tholeiites
>300
>300
trachybasalt flow
flow
Manitou trachybasalt
red-brown,
red—brown, granular trachybasalt
to basalt
(at Tofte)
Tofte)
Top (at
(more
(more of the Schroeder basalts)
basalts)
>280
>280
Bell Harbor lavas
lavas
tholeiites, aphyric
aphyric
quartz tholeiites,
trachybasalts
>300
Palisade rhyolite
rhyolite flow
flow
gray
to pink,
pink, porphyritic rhyolite
gray to
lavas
Baptism River lavas
mixed lavas, mostly basalts
basalts
Few 100's
�~23-2
3—
SHALLOW
THE LAXE
LAKE SUPERIOR
SHALLOWSTRUCTURE
STRUCTUREAND
ANDSTRATIGRAPHY
STRATIGRAPHYOF
OF THE
FROM SEISMIC
SEISMICREFRACTION
REFRACTIONMEASUREMENTS
MEASUREMENTS
BASIN FROM
F1.C. Halls
Halls and C.?.
H.C.
G.F. West
Geophysics Laboratory, Dept.
Dept. of Physics, University of
of Toronto.
ABSTRACT
Between 1966 and 1969 thirty—three
thirty-three seismic
seismic refraction
refraction profiles
profiles were
obtained in Lake Superior using aa single ship sonobuoy
sonobuoy technique
technique (Halls
(Halls and
and
West, 1971).
1971). The seismic data have led
led to
to aa number of
of conclusions
conclusions concerning
concerning
the shallow
shallow structure
structure and
and stratigraphy of the late Precambrian Keweenawn basin
the
that underlies the
the lake:
lake:
that
Faults with their
bound the
(1)
their north
north side
side downthrown
downthrown at
at least
least 1—2
1-2 1cm
krn bound
the north
(1)
Isle Royale
Royale and
and Michipicoten
Michipicoten Island.
Island.
shores of Isle
(2)
the Keweenawan basin just
just southeast
southeast of
of Isle
Isle Royale
Royale
The northern limb of the
(2)
appears
appears to
to have undergone a deformation that
that is
is perhaps
perhaps related
related to
to movement
movement
along the
the Isle
Isle Royale
Royale fault.
fault.
(3)
In
to the
the main basin between Isle Royale and the
the Keweenaw Peninsula,
In addition
addition to
(3)
there
the Slate Islands
Islands in
in the
the
there is
is aa suggestion of
of a smaller one southwest of the
part of
of the
the lake.
lake.
northern part
(4)
(4)
Cambrian Bayfield—Jacobsville
Bayfield-Jacobsville sandstones
sandstones appear
appear
Late Keweenawan or early Cambrian
to underlie most of Lake Superior.
Superior. Although the
the site of the
the lake
lake is
is governed
governed
to
by the
the position of the
the underlying basin, the
the principal
principal factors
factors determining
determining the
the
size and shape of the
the lake depression
depression are
are the
the distribution
distribution of
of the
the Bayfield—
BayfieldJacobsville sandstones and their
their susceptibility
susceptibility to
to erosion
erosion compared
compared with
with older
older
rocks.
rocks.
(5)
For
those seismic profiles
that have a certain degree of geological
geological
For those
profiles that
(5)
control, such
such as
as those between Isle Royale and the
control,
the Keweenaw Peninsula, refraction
refraction
agree well with those
those estimated
estimated (Halls,
(Halls, 1969)
1969) from
from sasple
sample
velocities generally agree
in the
the laboratory.
laboratory. One notable exception occurs in
in those
those profiles
profiles
measurements in
that
that lie just off the
the Minnesota
Minnesota shore.
shore. Here velocities of
of 55 km/s
km/s are
are recorded.
recorded.
These values are typical
typical of
of Freda—Copper
Freda-Copper Harbor
Harbor sandstones,
sandstones, but
but the
the presence
presence
these rocks
rocks adjacent to
to the
the Minnesota coast
coast is
is discounted
discounted on
on magnetic
magnetic
of these
evidence. Instead the velocities of S5 km/s are assigned
assigned to
to the
the North
North Shore
Shore
volcanics that
that crop
crop out
out along
along the
the mainland.
mainland. The apparently low velocities of
these
these rocks
rocks compared
compared to
to those
those for
for volcanics
volcanics between Isle
Isle Royale and the
the Keweenaw
kmfs) can be explained if
Peninsula (5.7—6.2
(5.7-6.2 km/s)
if the
the North Shore
Shore sequence
sequence contains
contains
a greater proportion of interflow
interflow sediment
sediment and/or
and/or amygdaloidal
amygda10idal flow
flow top
top material.
material.
The seismic penetration of the
(6)
the refraction
refraction profiles
profiles was
was generally
generally insufficient
insufficient
(6)
to
to record the
the Upper Refractor (Berry
(Berry and West, 1966)
1966) with velocity 6.7±
6.7± km/s.
km/s.
However, one profile
profile northeast of
of Isle
Isle Royale
Royale recorded
recorded aa velocity
velocity of
of 6.5
6.5 km/s
km/s
at a depth of
of about
about 66 km.
km. This observation demonstrates the
the existence
existence of
of Upper
Upper
Refractor—type
Refractor-type velocities in the
the marginal parts
parts of the
the Keweenawan basin.
basin.
�-24—24—
References
and G.F.
G.F. West.
West. 1966.
1966. An interpretation of the first
first arrival data
Berry, M.J. and
of the
the Lake Superior experiment
experiment by
by the
the time—term
time-term method,
method, Bull.
Bull. Seismol.
Seismol.
Soc. Amer., 56,
Soc.
56, 141—171.
141-171.
Halls, H.C.
H.C. 1969.
1969. Compressional wave velocities of
of Keweenawan rock
rock specimens
specimens
from
the Lake
region, Can.
Can. Jour.
Jour. Earth
Earth Sci.,
Sci., 6,
~, 555—568.
555-568.
from the
Lake Superior region,
Halls,
H.C. and
and G.E.
G.F. West.
West. 1971.
1971. AA seismic refraction
refraction survey in
in Lake
Lake Superior,
Superior,
Halls, H.C.
Can. Jour.
Jour. Earth
Earth Sci.(In
Sci. (In press).
press).
Can.
�—25—
-25-
THE
THE ISLE ROYALE FAULT
FAULT
B.C.
H.C. Halls and
and G.F.
G.F. West
West
Geophysics Laboratory, Dept.
Dept. of Physics, University
University of
of Toronto.
Toronto.
ABSTRACT
A
fault bounding the northwest shore of Isle Royale was originally postupostuA fault
lated by
by Irving
Irving and
and Chamberlin (1885)
lated
grounds. However, with
(1885) on physiographic grounds.
the exception
exception of
of recent
recent aeromagnetic
aeromagnetic studies
studies (Wold and
Ostenso, 1966; Hinze et
the
and Ostenso,
al.,
1966) very little extra evidence has been produced as
as to
to whether the
the faiTt
faurt
al., 1966)
really exists. The aeromagnetic data show a linear
linear anomaly that
that follows
follows the
the
northwest shore of Isle Royale and extends eastward to
to Superior
Superior Shoal.
Shoal. Although
the
sediments, it
the anomaly
anomaly indicates
indicates aa contact
contact between
between Keweenawan volcanics and sediments,
does
or faulted
faulted one
one (Halls,
(Halls,
does not
not reveal whether the contact is a stratigraphic or
Evidence to
1970).
to date for the so—called
so-called Isle
Isle Royale fault
fault has therefore
therefore been
been
1970).
rather inconclusive. This
lines of evidence that
that support
support
This paper discusses some lines
the existence
existence of the
the fault,
fault, in the
the light of new magnetic and
and seismic
seismic data:
data:
the
(1)
(1)
Seismic data (Halls
(Halls and West,
West, 1971)
1971) show that
that the
the uppermost layer that
that
underlies
the channel north of Isle Royale and also the
the region
region further
further northeast
northeast
underlies the
the Slate Islands
Islands has
has aa velocity
velocity of
of about
about 3.7
3.7 kin/s
km/s and
toward the
and aa thickness of
about 1—2
This seismic layer is all but continuous
1-2 km.
km. This
continuous with
witih a similar
similar one
one in
in
eastern Lake
Lake Superior
can be firmly
firmly identified
identified as
as Eayfield—.Jacobsville
Bayfield-Jacobsville
Superior that can
sandstones. These
thought to
the Isle
IsleRoyale
Royale channel
channel
These rocks
rocksare
are thus
thus thought
to underlie the
and if so,
so, their
their existence
existence necessitates
necessitates the
the inclusion
inclusion of
of the
the Isle
IsleRoyale
Royale fault
fault
with
its downthrown
downthrown side
with its
side to
to the
the north.
1970) show a remarkably
(2) Paleomagnetic
Books, 1968;
1968; Palmer,
Palmer, 1970)
Paleomagneticdata
data (e.g. Books,
consistent pattern
pattern for
for Keweenawan extrusive
extrusive rocks.
rocks. Whereas the
the lower parts of
the
the volcanic sequence (such
(such as
as the Osler and South Range
Range lavas)
lavas) tend
tend to
to be
be
reversely magnetised,
the upper parts such as the
the Isle
Isle Royale
Royale and
and Portage
Portage Lake
Lake
reversely
magnetised, the
lavas are
are normal.
normal. In the
the Isle Royale channel
channel a linear
linear magnetic anomaly
anomaly (C
(C in
in
Fig.l),
Fig.l), which
which is
is attributed to
to Keweenawan volcanics, is
is strongly
strongly positive
positive with
with
an
attendant minimum to
to the
the north,
north, signifying that
that the
the volcanics are
are normally
normally
an attendant
magnetised. Anomaly CC continues
continues beyond
beyond the
the channel
channel to
to both
both the
the east
east and
and west
west
where it broadens considerably
considerably to
to form
form anomalies
anomalies AA and
and DD (Fig.l).
(Fig.l). The sharpness
and DD together
together with the
the seismic
seismic data
that the
thevolcanics
volcanics
of anomalies A,C and
data indicate that
are
overlain
Thus
north
of
the
postulated
Isle
by Keweenawan
are
Keweenawan sedimentary
sedimentary rocks.
rocks. Thus
the
Isle
If
Royale fault
buried, normally magnetised, Keweenawan volcanics.
Royale
fault there
there are
are buried,
volcanics.
the
Isle Royale 'fault'
'fault' anomaly were due
due to
to aa stratigraphic
stratigraphic contact
contact
the magnetic Isle
between volcanics and
and sediments
sediments it
it would imply
imply that
that the
the sedimentary
sedimentary unit
unit was
was
sandwiched between two
two thick
thick sequences
sequences of
of normally
normally magnet3sed
magne~ised volcanics
volcanics (i.e.
(i.e.
the Isle
Isle Royale
Royale lavas
the
lavas and those causing anomalies A,C
A,C and
and D).
D). Such a sequence
is of
course possible but it is not a known feature
feature of
of Keweenawan
Keweenawan stratigraphy.
stratigraphy.
is
of course
The only thick
thick sedimentary unit
unit that
that occurs
occurs in
in the
the Keweenawan
Keweenawan volcanic
volcanic sequence
sequence
is that
is
that in Michigan and Wisconsin but it lies
lies between the
the normal
normal and
and the
the
reversely magnetised
sequence (e.g.
(e.g. Meshref and
and Hinze,
Hinze,
magnetised parts of the volcanic sequence
1970).
Thus in
1970).
in northern
northern Lake
Lake Superior
Superior aa duplication
duplication of
of the
the normally
normally magnetised
magnetised
volcanics through
movement along
along the
Isle Royale
Royale fault
fault is
is favoured
favoured over
over aa
through movement
the Isle
stratigraphic sequence of a sedimentary unit between
between two
two normal
normal volcanic
volcanic ones.
ones.
(3)
of Fig.l
Fig.l shows
shows that
that the
the Isle
Isle Royale
Royale 'fault'
'fault' anonaly(E)
anomaly (E)
The magnetic map of
(3)
A weakening of the
gradually
assumes a more southerly trend
trend toward
toward the
the west. A
the
gradually assumes
anomaly in this
anomaly
this direction is more compatible
compatible with the
the presence
presence of
of aa fault
fault rather
rather
than aa stratigraphic volcanic-sediment
volcanic—sediment contact
than
contact (Balls,
(Halls, 1970).
1970).
�—26—
-26-
(4)
Anomaly.C in Fig.l is essentially continuous
continuous with aa belt of
of prominent
prominent
the Minnesota shore before
before turning
turning
positive anomalies that extends along much of the
south and
the Bayfield-Peninsula
and terminating
terminating in
in aa hook-shaped
hook—shaped anomaly over the
Eayfield—Peninsula
(Wold and
and Ostenso, 1966). White (1966)
(1966) concludes
concludes that
that this
this anomaly is
is due
due to
to
volcanics in the upper .part
sequence. The volcanics
volcanics
part of the Keweenawan extrusive sequence.
Isle
causing
causing anomaly
anomaly C
C should
should thus
thus be
be equivalent,
equivalent, at least in part,
part, to the Isle
Royale lavas.
lavas. Again, aa fault
fault would be
be necessary
necessary to
to explain
explain the
the apparent
apparent
of the
the sequence.
sequence.
duplication of
The foregoing
foregoing observations therefore
therefore all tend to
to suggest
suggest that
that the
the Isle
Isle
Royale fault
fault does
does exist.
exist. A
A two—dimensional
two-dimensional magnetic model interpretation of
the Isle
Isle Royale
Royale fault
fault anomaly
anomaly at
at its
its eastern end (Balls,
1970) suggests that the
the
(Halls, 1970)
fault dips to the
fault
the south.
south. The fault
fault is
is thus
thus of reversad
reversed type
type as
as its
its downthrown
do'~thrown
side is
is to
to the
the north.
north. The displacement along
along the
the fault
fault is
is at
at least
least 1—2
1-2 km.
km. The
reversed nature
the fault
fault and
and its
itsincreasing
increasingsoutherly
southerlytrend
trendtoward
toward the
the west
west
nature of
of the
that
support the
the idea
idea initially
initially
raised
Irving
Chamberlin (1885)
(1885) that
(Fig.l) support
raised
byby
Irving
andandChamberlin
it
it
is
of the
the Douglas
Douglas fault
fault in
in Wisconsin.
Wisconsin.
is an easterly continuation of
References
Books, K.G.
K.G. 1968.
1968. Magnetisation of the lowermost Keweenawan lava
lava flows
flows in
in the
the
area, USGS Prof.
Prof. Paper
Paper 600—0,
600-D, 248—254.
248-254.
Lake Superior area,
Halls, H.C.
B.C. 1970.
Halls,
1970. Geological interpretation of geophysical data
data from
from the
the Lake
Lake
Superior region,
region, Ph.D.
Ph.D. Thesis, University
University of
of Toronto,
Toronto, 203
203 pp.
pp.
Halls, H.C.
B.C. and G.E.
West. 1971.
Halls,
G.F. West.
1971. A
A seismic refraction survey in
in Lake Superior,
Superior,
Can.
Sci. (In
(In press).
press).
Can. Jour.
Jour. Earth Sci.
O'Hara, N.W.,
N.W., Trow,
Trow, J.W.
J.W. and
and Secor
Secor G.B.
G.B. 1966.
1966.
Hinze, W.J., O'Hara,
of eastern Lake Superior,
Superior, AGU
AGU Mono.,
Mono., 10,
la, 95—110.
95-110.
Aeromagnetic studies
studies
Observations on the junction between
Irving,
T.C. 1885.
1885. Observations
Irving, R.D.
R.D. and Chamberlin, T.C.
the eastern
eastern sandstone
sandstone and
and the
the Keweenaw Series
Series on Keweenaw Point,
Point, Lake
the
Superior, Bull.US.
Bull.US. Geol.
Geol. Surv.,
Surv., 23,
~, 385—498.
385-498.
Meshref, W.M.
W.J. 1970.
Meshref,
W.M. and Hinze, W.J.
1970. Geologic interpretation
interpretation of
of aeromagnetic
aeromagnetic data
data
in
in western
western Upper
Upper Peninsula of Michigan,
Michigan, Mich.
Mich. Geol.
Geol. Surv.,
Sun., Kept.
Rept. of
of lxiv.,
Inv.,
12, 25
25 pp.
pp.
Palmer, B.C.
and correlation
correlation of
of some
some Middle
Middle Keweenawan
H.C. 1970.
1970. Paleomagnetisni
Paleomagnetism and
rocks, Lake
Lake Superior,
Superior, Can.
Can. Jour.
Jour. Earth
Earth Sci.,
Sd., 7, 1410—1436.
rocks,
1410-1436.
l?
White, W.S.
W.S. 1966.
1966. Tectonics of the
the Keweenawan basin, western Lake
Lake Superior
Superior region,
region,
White,
USGS Prof.
Prof. Paper
Paper 525—E,
525-E, 23
23 pp.
pp.
Aeromagnetic, gravity and sub—bottom
Wold, R.J.
R.J. and
and Ostenso,
Ostenso, N.A.
N.A. 1966.
1966. Aeromagnetic,
sub-bottom
studies in western Lake Superior,
AGU Mono.,
Mono., 10,
profiling studies
Superior, AGU
10, 66—94.
66-94.
�FIGURE
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88°00'
BAY
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NORTH SHORE VOLCANICS
47° 50'
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TI, 1V/
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COPPERHARBOR
HARBOR CLASTICS
CLASTICS
COPPER
89c2O•
$9000'
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X-·-··Y-
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MILES
CONTOURS
(X tOO)
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CONTOURSIN
IN GAMMAS
GAMMAS 1*
88 0 20'
20'
88°
88 0 00'
NORTHERLY
LIMIT OF
OFKEWEENAWAN
KEWEENAWAN VOLCANICS
VOLCANICS
NORTHERLY LIMIT
Total
intensity magnetic
magnetic map
map of
o tnt
Total intensjty
the Isle
Isle Royale
Royale channel.
channel. Survey
H. C.
C. ILdIs
Halls
Survey by
by N.
F. West
West in
in 1966,
1966, using
using aa shipborne proton precession spacing:
and C.
G. F.
spacing: About
About 33 miles.
miles.
N 300
c1:csjt in extreme
Profile orientation: N
30 0 W.,
W.,except
extreme northeast where it
it is
is more
more northerly
northerly
87°40'
I
�-28-
RELIABILITY OF U-PB AGES OF SPHENE IN NORTHEASTERN MINNESOTA
AND NORTHWESTE~~ ONTARIO
G. N. Hanson
Department of Earth and Space Sciences
State University of New York
Stony Brook, New York
and
E. J. Catanzaro
Department of Geology
Southampton College
Southampton, New York
A B S T R ACT
U-Pb ages have been determined on sphenes from early Precambrian granitic rocks in relatively undisturbed areas and in
a thermal aureole. The granitic bodies investigated are the
Icarus pluton and the Saganaga tonalite in Ontario and the Linden
Syenite and Giants Range Granite in Minnesota. A total of six
sphene concentrates were analyzed. One sphene from the Linden
Syenite had an unfavorable U/Pb ratio and no age could be calculated. Three sphenes from the Saganaga tonalite, the Icarus pluton,
and the Giants Range Granite gave internally concordant U-Pb ages
of 2710 ± 30 m.y. 'T'ivo sphenes from the Giants Range Granite and
the Linden Syenite were internally discordant, but gave Pb207/Pb206
ages of 2730 and 2740 m.y., respectively. It is suggested that the
discordance may be related to a relatively high uranium content in
one sphene and to shearing of the host rock in the other. Sphene
from near the contact of the Giants Range Granite with the 1100 m.y.
Duluth complex gives internally concordant 2700 m.y. ages at 7.4
kilometers from the contact. As the contact is approached the sphene
ages become internally discordant suggesting lead loss at 1100 m.y.
At about one-half kilometer from the contact, where biotite and
hornblende have lost essentially all of their radiogenic argon,
sphene still retains about 60% of its radiogenic lead.
�-29-
CONTINENTAL RIFTS
William J. Hinze
Dept. of Geology
Michigan State Univ.
Donald M. Davidson
Dept. of Geology
Univ. of Minnesota,
Duluth
Robert F. Roy
Dept. of Geology
and Geophysics
Univ. of Minnesota
A B S T R ACT
Comparison of late Precambrian, linear, tectonic features
transecting the Mid-Continent region of the United States (e.g., the
Mid-Continent and Mid-Michigan Anomalies) with relatively recent
continental rift zones, such as the East African Rift System, indicates
many similarities suggesting a common mode of origin. Hence, a
mechanism is proposed for the development of linear Precambrian rifts
and subsequent overlying sedimentary basins based upon observed geological
and geophysical characteristics of modern rifts. Dissimilarities in
stage of development, depth of erosion and geological age are parameters
which limit the extent of comparison.
Rift formation is initiated by plate splitting and subsequent
upwelling of low velocity layer material into the upper mantle along
the base of the crust. Although inherently denser than adj acent mantle
rocks, the low velocity layer material becomes lighter and therefore
rises upon partial melting and fractionation. Uplift of the earth's
surface and igneous activity along pre-existing zones of weakness is
associated with the vertical rise of this material, while lateral movement results in thinning and rupture of the crust producing extensional
rift grabens. Subsequent magmatic activity in the rift zones results
in local structural downwarping.
Upon cooling, the low velocity layer residuml becomes dense
and ultimately sinks into the mantle causing the uplifted rift zone to
deflate. The convergent movement of adjacent mantle material into
the void produced by the sinking residuum places the crust under compression, thus accounting for not only compressional features associated
with rift systems, but the subsequent development of sedimentary basins
over rift zones.
�—30—
-30-
Keweenawan Geology of
of the
the Porcupine
Porcupine Mountains,
Mountains,
upper Peninsula,
Peninsula, Michigan
Michigan
Western Upper
Harold A.
Hubbard
A. Hubbard
u.
Geological Survey
Survey
U. S.
S. Geological
Washington, 0.
C. 20242
D. C.
20242
Washington,
ABSTRACT
The Porcupine Mountains,
Mountains, Michigan, are
are underlain by
by tue
the upper
upper
northwarLl-dipping
limb of
of an
an overturned
overturned asymmetric
asymmetric anticline,
antiline, not
northward-dipping limb
not aa
dome with quaquaversal
~ua~uaversal dios
dips as
as usually
usually shown.
shown. The anticline is
is faulted
near its
its axis1
axis, and at the southern margin
the mountains
mountains middle
middle
margin of
o the
diDpi1i to overturned
Keweenawan volcanic rocks are thrust over
over steeply
steeply dipping
Keweenawansedimentary
sedimentaryrocks.
rocks. The
rocks, which
upper Keweenawan
The middle
middle Keweenawan
Keweenawan rocks,
which
are
younger than
Lava Series, can
can be
be divided
divided into
intotwo
two
are younger
than the
the Portage
Porta3e Lake
lake lava
sequences. The
Theolder
older se~uence,
sequence,which
whichincludes
inducesmost
nostof
of the
he volcanic
se~uences.
volcanic
of fine-grained
fine-grained northward-dipping
rocks
the mountains,
mountains, co:isists
consists of
rocks in the
mafic to
to intermediate
intermediate lava
lava flows
flows and
and two
two interbedded
interbedded felsic
felsic lava
lava flows.
flows.
southern felsic flow
flow is
is nonporphyr
nonporphyritic
The southern
itic and
and constitutes about half
the outcrrp
outcrop area.
area. The younger
younger sequence,
se~uence, which
which is
is present
present only
only in
in the
the
easternmost part
part of
of the
the mountains,
mountains, consists
consists of
of gently
gentlyeastward
eastwardand.
and
easternmost
northeastward-dipping fine-grained and aphanitic flows
flows overlain by
volcanic conElonerate
conglomerate and sandstone. The younger sequence
se~uence is either
either
in fault contact or unconformable on
on the
the older.
older. Both
Both sequences
se~uences are
are
repeao1L
in part in
fault slices
repeated in
in imbricate
imbricate fault
slices in
inthe
the southeasteru
southeastern part of
of
the mountains.
mountains. A
A tear fault separates
separates these rocks from the
the upper Keweenawan rocks to
to the
the east.
east.
In the
the Copper Harbor Conglomerate
Con81omerate consists
consists of
of saidstone
sandstone
the north,
north, the
interbedded
lavas.
It
appears
to
be
conformable
on
middle
containing
interbedded
lavas.
It
appears
to
be
conformable
on
middle
containing
Keweenawan
lavas
in
the
lake
of
the
Clouds
valley.
To
the
south
tle
Keweenawan lavas in the Lake of the Clouds valley. To the south ofo the
mountains, the
theupper
upperKeweenawan
Keweenawan rocks are folded in
in an asymmetrical
as~nmetrical
syncline with
with aa steep
steep north limb.
structural relIef
syncline
limb. The
The structural
reliefbets-een
between the
the
size of
and the synciline
syncline is
is more
more than
than 8000
8000 feet.
feet. The size
of the
the PorcuPorcumountains iid
sug3ests that the Keweenawan rocks of
pine Mountain
of western
Mountain structure suggests
icichiganwere
were strongly
st;unly folded in
Michigan
in post-Freda time,
time, and not just
just broadly
warped.
�—31--31-
ThE KEWEENAWAN
THE
OFOFISLE
ROYALE, MICHIGAN
MICHIGfu~
KEWEENAWNGEOLOGY
GEOLOGY
ISLE ROYALE,
N. King Huber
U.S.
U.S. Geological
GeologicalSurvey
Sury
Menlo Park, California
California 94025
94025
ABSTRACT
A B S T R ACT
Isle Royale
lies on the north limb
limb of the Lake Superior syncline,
syncline,
Royale lies
and the
the stratigraphic section exposed on the island is correlative
correlative with
the
the much-studied
much—studied middle
middle Keweenawan
Keweenawan Portage
Portage Lake
Lake Lava
Lava Series
Series and upper
}ZeHr.awan Copper Harbor Conglomerate
Cunglomerate on the Keweenaw Peninsula, on
Keweenawan
on the
the
south limb of
of the
the syncline.
syncline. Dips of
of the
the strata
strata range
range from
from less
less than
than
5Q0;
100 to over 50°;
10°
side of
of the
the
they are generally steeper on the north side
the south and
and average less
than 20°.
20°.
island than on the
less than
Exposures on Isle Royale indicate a minimum thickness
thickness of
of 10,000
10,000
feet for
for the
the Portage Lake Lava Series at
The base
feet
at this
this locality.
locality. The
baseofoftiiei
the
series is not exposed.
exposed. As on
on the
the peninsula, the
the series
series consists
consists largely
largely
of basaltic and andesitic lava flows,
flows, with lesser amounts of
of interfiow
interflow
sadiotaoy and tuffaceous rooks.
sedimentary
rocks. No felsie
felsic flows
flows are known from
outcrops, although one has
about
outcrops,
has been reported from diamond drilling, about
6,200 feet below the
the top
top of
of the
the lava
lava series.
series. The interflow clastic
clastic rocks
rocks
do not
not crop
generally do
crop out,
out, and mast
most of the individual units are
are known only
only
from diamond drilling.
drilling. Within the
the lava
lava series,
series, which probably
probably contains
contains
over a hundred flows
flows in the
the exposed section,
section, certain stratigraphic units
units
representing
flows or groups of flows
flows can
can be identified
identified
representing individual lava flows
and traced on the basis
and
and
basis of characteristic textures or structures, and
relative stratigraphic
stratigraphic position.
position. Twelve such units have been distinguished
distinguished
within the
the sequence and
and provide stratigraphic
stratigraphic and
and structural
structural control
control for
for
geologic mapping.
On both the Keweenaw Peninsula and Isle RoyaTh,
Royale, the
the Copper
Copper Harbor
Conglomerate is
is largely derived from lowermost Keweenawan volcanic source
source
terranes,
shed debris
debris into the subsiding Lake Superior basin from
from
terra
as, which shed
opposite sides;
sides; for
for Isle Royale,
this would be from
from the
the North Shore
Royale, this
Volcanic
Group of
of Gehman
Gehman (1958)
(1958) in
in Minnesota.
Minnesota. The depositional en'i:onment
environment
Volcano Group
is
is interpreted as
as being one of a combination of fluvial
fluvial and
and lacustrine
lacustrine
conditions resulting in piedmont fanglomerates
fanglomerates and
and playa lake
lake or
or flood
flood
conditions
plain deposits.
deposits,
Royale, various
various sedimentary features
On Isle
Isle Royale,
features indicate that
that the
the
general direction of sediment transport was easterly,
easterly, with aa range
range from
from
northeast to
to southeast. In thio
this same direction the
the Copper Harbor
increases in
Conglomerate Jr.i-eases
in thickness
thickness and
and in
in textural
textural and
and compositional
maturity--namely
conglomerate, through
through aa mixture of
of cobble
cobble
maturity——namely from a boulder conglomerate,
and pebble conglomerates
conglomerates and
and sandstone,
sandstone, to
to sandstone
sandstoneand
andinudstone.
mudstone. In a
miles this
distance of 20 miles
this clastic wedge thickens
thickens from
from aa minimum
minimum of
of
1,500 feet
feet to over 6,000 feet
feet between stratigraphic marker horizons; the
the
top of
of the
the formation
formation is
is nowhere
nowhere exposed and
and the total thickness must be
top
appreciably greater.
greater.
�-3232—
SOME PRIMA.RY
PRIMARY SEDIMENTARY
SEDIMENTARY STRUCTURES
STRUCTURES IN
IN THE
SOME
THE LOWER
LOWER CHERTY
CHERTY MEMBER
tJfMBER OF
OF THE
THE
BIWABIK IRON FORMATION
BI~/ABIK
FORMA.TION : VIRGINIA HORN
HORN AREA
ERIC FRODESEN
Department of Geology and Geophysics
Geophysics
University
Wisconsin, Madison,
University of \.Jisconsin,
Madison, Wisconsin 53706
53706
BSTRACT
A B S T R ACT
A
The writer
wri ter discovered
di scoverecl and collected
collected some
some unusual
unusua I sedimentary
sedimentary
oF the
the Biwabik
structures in the
theLower
Lower Cherty
Cherty Member
t-lember of
Biwabik Iron
Iron Formation
Formation
addition of
at aa locality
localitynea;r
near the
theMidway
Midway addition
of Virginia,
Virginia,Minnesota.
Minnesota. Polished
Polished
and x—radiographs
overturned and
and disturbed
disturbed bedding
bedding reresections and
x-radiographs reveal
reveal overturned
sembling convolute—type
convolute-type bedding,
bedding, load
load casts
casts with
with flame
flame structures,
structures, and
and
other structures
structures characteristic
characteristic of
of soft
soft sediment
sediment deformation.
deformation. SmallSmall—
other
scale cross-bedding
cross—bedding and small
small local
local thrust
thrust faults
faults also
also are
are present.
present.
Recent experiments
experi ments on
on the
the Formation
formati on of
of contorted
contorted structures(McKee
s truc tures (Mcl<ee and
and
Goldberg,
show that
that convolute—type
convolute-type bedding
bedding and
and small—scale
sm~ll-scale thrust
thrust
Goldberg, 1969)
1969) show
faults, simi
lar to
to those
those found
in the Biwabik,
Biwabik, can be
be formed
formed by
by loading
loading
similar
found in
mud which was
was deposited
deposited on an existing
existing slope
slope of
of 15—20
a semi—cohesive
semi-cohesive mud
15-20
degrees.
The
The preservation of the
the fine
fine alternating
alternatin~ dark
dark and
and light
light laminae,
laminae,
small—scale
small-scale cross—bedding,
cross-bedding, and possible
possible graded
graded bedding,
bedding, suggest
suggest that
that
these
wave base with only periodic
these rocks
rocks were deposited below wave
periodic current
activity.
The alternation of the
The
the laminae
laminae is
is generally attributed to
to seaseasonal changes{Hough,
changes(Hough, 1958),
or periodic
periodic influxes
of iron—rich
and ironiron—
sonal
1950), or
influxes of
iron-rich and
impoverished
impoverished layers
layers due to
to tectonic
tectonic activity
activity coupled
coupled with
with isostatic
isostatic
semi—rigid crust,
crust, or
or aa cornbina,tion
combination oF
adjustment of
of a.
a semi-rigid
of the
the two
two procecess
procecess
(Cullen, 1963).
1963). Cullen's
Cullen's idea
idea that
(Cullen,
that banded iron
iron formations
formations can
can he
be rerell
garded as
as corresponding
corresponding to aa syn-orogenic
syn—orogenic "flysch
"f1ysch'
type
of deposition
deposition
type of
applications in explaining
explaining some
some of the
structures found
may have applications
the structures
found in
in the
the
Lower Cherty Member.
Similar sedimentary
sedimentary structures
structures are
are found
found in
in the
the
Lower
Member. Similar
laminites of
of documented flysch facies.
The presence
presence of
ofallochthonous
The
allochthonous black chert
chert pebbles
pebbles within
within the
the beds
beds
poses
poses aa problem as to
to mode of
of emplacement. Turbidity
Turbidity currents,
currents, subaqueous
subaqueous
sliding or
or gliding
gliding down
down aa slope,
slope, or
or ice
mechanisms have
have to
be ininsliding
ice rafting
rafting mechanisms
to be
voked
explain their
their presence
presenceg
voked to
to exrlain
If
represent the
the products
proc'ucts of
of chemical
chp.mical weathering
If iron
iron formations
formations represent
under warm humid conditions in
in semi—restricted
semi-restricted basins,
basins, then
then ice
ice rafting
rafting
under
is not
not aa very
very likely
is
likely possibility. If,
If, however,
however, the
the iron
iron formations
formations were
were
�-33—33—
deposited
rlepositerl in aa cool
cool polar
pot~rclimate
climateasassuggested
suggestedby
bypaleonagnetic
paleomagnetic data
data
(Symons,
1966),then
thenthese
thesepebbles
pebblesmay
may
productofofice
ice transport.
(Symons, 1966),
behe
thetheproduct
structures are
are characteristic
characteristic of
Iff thesc
these sedimentary
sedimentary structures
of the
the entire
entirefor—
formation,
and iron
iron Formations
general, then
detailed regional
mation, and
formations inin ~eneral,
then aa detailed
regional study
study
could produce
someenlightening
enlighteningresults.
results.
could
pro~uce SOMe
refer~nces:
1'efercnces:
Cul Ten,D•.
U.J.,
1963, Tectonic
Tectonic implications
implications of
Cullen,
J., 1963,
of banded
banded iron formations:
formations:
Jour.
p.327—392.
Jour. Sed.
Sed. ret.,
Pet.,v.33,
v.33,
p.387-392.
Gruner,
J.'.,
Mineralogy
andandgeology
thethe
Mesabi
Gruner, J.l
!.,l96,
1946,
i~ineralogy
geologyofof
MesabiRange:
Range:
Office of
Iron
Range
ofthe
theComisioner
Commisionerofof
Iron
RangeResources
Resources and
and
t
Rehabilitation,
rehabilitation, St. Paul,
Paul, tlinn.
f1inn& 127
ppe
127 Pp.
Gundersen,
J.N., end
Schwartz, 196Z,
The geology
geologyof
of the metaGundersen, J.N.,
and G.M.
G.M. Schwartz,
1962, The
metamorphosedRi\-.abik
SiwabikIron
IronFormation,
Formation,Eastern
Eastern~lesabi
Mesabidistrict,
district,
morphosed
Minnesota:Minn.
Minn.Geol.
Geol.Sur.
Stir. Bull.
Bull. 43,
Minnesota:
43, 137pp.
l37pp.
resh_waterenvironment
environmentofofdeposition
deposition of
of PreHough,J.L.,
J.L., 1958,
Yough,
1958, Fresh-water
Precambrian
iron formations:
p. 41t+_1130.
cambrian iron
formations: Jour.
Jour.Sed.
Sed. Pet.,
Pet.,v.28,
v.l8,
p. 414-430.
James,
H.L., 1966,
Chemistry of
of the
J~mes, H.L.,
1966, Chemistry
the iron—rich
iron-rich sedimentary
sedimentary rocks:
rocks:
'J.S).S.
Prof.
Paper
(-4O41,
6lpp.
IJ.S.G.S. Prof. Paper 440-Iy" 61pp.
Mcee,
~1c:\ee,
E.fl.,
on formation
formation of
of conE.0., and
and M.
M. Goldberg,
Goldberg, 1969,
1969, Experiments
Experiments on
torted
Bull., v.80,
torterl structures
structures ininmud:
mud: G.S.A.
G.S.A. Bull.,
v.BO,p.23l—24-+.
p.23l-244.
Symons,
P.T.A., 1966,
A peleomagnetic
paleomagneticstudy
study on
on the
the Gunflint,
Gunflint, Mesabi,
Symons, ~.T.A.,
1966, A
Mesabi,
and Cuyuna
the Lake
Lake Superior
Superior Region;
Region:
and
Cuyunairon
iron ranges
ranges in
in the
Econ.
Econ. Geol.,
Geol., v.G1,
v.61,p.p.1336—1361.
1336-1361.
hite,
\.'hi te, [l.A.,
[l.A.,
1954,
Thestratigraphy
stratigraphy and
195 1f, The
and structure of
ofthe
theMesabi
~1esabi
Minnesota:
]{angc,
ta: Minn.
Hinn. Geol.
Ceoi. Sur.
Sur. Bull.
Bull. 38,
38, 92pp.
92pp.
Range, fHnneso
�-34—34—
ZEOLITE AND
AND PREHNITE—PUELL?ITE
PREHNITE-PUMPELLYITE FAdES
FACIES IN
INTHE
THE KEWF.ENAWAN
KEHEENAHAN BASALTS
OF
NORTHERN HICH:LGAN
ROLE OF
OF VOLATILES
VOLATILES
OF NORTHERN
MICHIGANII:
II: THE
THE ROLE
Wayne
WayneT.T. Jolly
Jolly
ofSaskatchewan
Saskatchewan
University of
Saskatoon,
Canada
Saskatoon. Canada
ABSTRACT
A B S T RAe T
Keweenawpeninsula,
peninsula, ~lichigan,
:Iichigan.
The
lava flows
flows of
of the
the Ke\\'eena,\v
Thetholeiitic
tholeiitic lava
have undergone
underone metamorphism
of the
the zeolite
ite
have
metamorphism of
zeoliteand
andprehnite—punpelly
prehnite-pumpellyite
facies.
the latter,
fractures and upper flow
flO\\1 contacts
contacts
latter, rocks
rocks along
along fractures
facies. In
In the
been transformed
have been
transformed to
to monomineralic
monomineralic rocks
rocks (metadomains)
(metadomains) corposed
composed
of either pumpellyite
pumpellyite or
or epidote,
epidote, depending
depending on
on stratigranhic
stratiranhic position
of
position
metadomains are
are enriched
enriched in
in CaO
CaO and
and /\1')03
A1,O retitive
in the pile. These metadomains
relative
to their
their unaltered
unaltered basalts
basalts through
of pre-existlnG
pre—exiting plagio—
to
through albiti.zation
albitization of
plagioclase. Bulk compositions of the
the altered
altered parts
parts of
of the
the flows,
flows, deduced
deduced
re
through ,veighted
weighted averages
averages of
of the
through
the rock compositions,
compositions, are sinilar
similar to
to ti1e
parental basaits.
parental
basalts. Thus,
Thus, little or no material was
was added
added from
from extraneous
extraneous
sources. This metamorphic differentiation occurred
occurred as
as aa result
result of
of
migration of
of both
both volatile
volatile and
non-volatile
components
over
short
and non—volatile components over
Calcium
distances through aa fluid
fluid pressure
pressure gradient
zradient with
\vi thr'f<
r f<P total
t
l' Calciumalinninum silicates
silicates were
were formed
formed preferentially
preferentially near rupture
alwninum
rup~S~e zones,
zones,
at its
its lowest
lowest levels.
levels. Theoretical considerations suggest
where PP was at
differentiation ofofessentially
homogeneous
that mdamorphic
metamorphic differentiation
essentially
homogeneous bodies
bodie~ of
of
rock
thim P
l' During the
theKeweenawan
Ke\\1eenaHan
rock may
mayoccur
occuronly
onlywhen
whenPf Pfisisless
less tian
metamorphic event,
dehydration. As
As aa
metamorphic
event,the
the rocks
rocks underwent
underwentext~g~rve
etensve dehydration.
depth from
result,
secondary phases
phases decreases
decreases with
uith depth
result, water content
content of
of secondary
from
water—rich
or more)
more) to
water—acor epidote
water-rich chlorites
chlorites and
and zeolites
zeolites (1120=12%
(H 0=12% or
to '\-later-poor
2
(H
about 2%).
2%). At lowest exposed levels
levels P02
P0 may have
have reached
reached levels
levels
(HO0 about
2
2
sutficient
sufficient to
to subdue formation of pumpellyite in
in favor
favor of
of pistacitic
pistacitic
epidote.
PCOZ was very low
10\\1 during
during the
the peak
peak of
of the
the metamorphic
metamorphic event.
event,
Co2
�—35—
-35AN
AN AEROMAGNETIC
AEROMAGNETIC SURVEY
SURVEY C1"
GF THE
THE SOUTHKciilJ
PENINSULA
OF MIOsiIGAN
MI~dIGAN
PENINSULA OF
SOUTHE
Richard L.
J. Hinze
L. Kellogg and William 3.
Geology
Department of Geology
Michigan State University
Lansing, Michigan
Hichigan
East Lansing,
ABSTRACT
A B S T R ACT
Only fragmentary direct information is
is available on
on the
the basement
basement
complex underlying the Phanerozoic sediments of
of the
the Michigan
Michigan Basin
Basin
because of the
the limi;ed
limited and poorly distributed basement
basement drill
drill tests.
tests. To
supplement this limited
limited information
information a
a regional
regional aeromagnetic
survey
has has
aeromagnetic
survey
been
of of
thethe
Southern
Peninsula.
Approximately 17,000
17,000 miles of
beenconducted
conducted
Southern
Peninsula.
Approximately
total magnetic intensity
total
intensity data
data were
were recorded
recorded along
along north—south
north-south flight
flight
lines spaced at
lines
at three
three mile intervals.
intervals.
A hasement
A
basement configuration map prepared
prepared from
from magnetic
magnetic depth
depth estimates
estimates
and basement
basement drill
drill tests
and
tests confirms that the basement surface
surface under
under the
the
Southern Peninsula of Ni
Michigan
has the
the form
form of
of an
an oval
oval depression
depression reachreachiar has
ing aa maximum
maximum depth
depth of
of approximately 15,000 feet
ing
feet below sea
sea level
level on
on the
the
western shore
shore of
of Saginaw
Saginaw Bay.
Bay. A
A basement high underlies the
the Howell
Howell
.Anticilne and
Anticline
roughly north-south
and aa roughly
north—southstriking
strikingregional
regional basement
basementtrough
trLg
plunges into
into the
boundarypoint
poin of
of Indiana, Ohio,
plunges
the basin
basinfrom
from the
thecommon
common boundary
Ohio,
and iIichigan
Ilichigan to
to the
the vicinlty
vicinity of 42°30'N. The map
map shows a broad basement
north\-lest in
in the
the extreme
extreme southwest
southwest corner
corner of
of the
the
platform striking northwest
peninsula.
Interpretation of the :esidual
=~sidual aeromagnetic
aeromagnetic map
map in
in conjunction
conjunction with
with
geologic and
other regional geophysical data
seologic
and other
data from
from the
the Southern
Southern PeiLtsula
Peninsula
and
indicates that
that the
the basement
basement of
of the
the :1ichigan
Hichigan Basin has
and adjacent areas indicates
geologic history.
history. Several
Several basement
provinces are
are defined
had a
a complex
complex geologic
basement provinces
defined
on the basis of
magnetic and
and isotope
isotope
of magnetic
and gravity
gravity anomalies,
anomalies, lithologies
lithologies and
ages of
samples
obtained
from
basement
drill
holes,
and
extrapolation
of samples obtained from basement drill holes, and extrapolation
of
of known Precambrian geology from the
the margin of
of the
the basin.
basin. The Penokean
province can
be traced from
into the
can be
from northern
northern Nichiga
Michigan and
and Wisconsin
Wisconsin into
the
area the
northern
the Southern
Southern Peninsula.
Peninsula. In this area
the province
province
northern portion
portion of the
is characterized
is
characterized by east—southeast
east-southeast striking
striking anomalies.
anomalies. Central and
southwestern Michigan
Michigan isis underlain
rocks correlating
correlating
underlain primarily
primarily by
by felsic
felsic rocks
with the
the Central Province.
Basement
rocks in
Basement rocks
in southeastern
southeastern ~lichigan,
Michigan, which
which strike
strike generally
generally
north—northeast are
interpreted as
as mafic
mafic and
and felsic
felsic gneisses and
north-northeast
are interpreted
amphibolites.
amphiboli
tes. They are correlated
correlated with the
the Grenville
Grenville province
province which
\vhich
is bounded on
the west
is
on the
west by
by aa line
line extending
extending south-southwest
south—southwest from
from Saginaw
Bay to
south to
Michigan—
to west
\vest of the
the HowellAnticline
HowellAt,ticline and
and then
then du.e
du.e south
to the MichiganOhio boundary. A
A Keweenawan rift
rift zone
zone characterized
characterized by
by mafic
mafic intrusives,
intrusives~
extrusives and uplifted
uplifted gneisses
gneisses transects
irom the
the
extrusives
transects the
the Peninsula from
ic.neousactivity
activity
area to southeastern
Traverse Bay
Bay area
southeasternMichigai
Nichigan. Keweenaean
Ke\veenmVan igneous
mayalso
also be
be reflected
reflected ininthe
may
thenumerous
numerous local
local magnetic
magnetic anomalies
anomalies in -•
southwest
whichoccur
occuralong
alongnorthvest
norLn'eststriking
strikingtrE!lllds
treds whith
soutlHvest Mi-htgan
Nichigan which
\vhich
the regional
pattern.
parallel the
regional gravity
gravity anomaly
anomaly pattern.
�-36—36—
PRECAMBRIAN CLASTIC
CLASTIC PALEarIDAL
SEDTI1ENTATION
PRECAMBRIAN
aarna SEDENTATION
GEORGE
deVRLES KLEIN
GEORGE deVRIES
Dept.
of Geology,
Univ.ofofIllinois,
Illinois, Urbana,
Dept. of
Geology, Univ.
Urbana, Illinois,
Illinois,61801
61801
ABSTRACT
ABSTRACT
The
Lm;er Fine-grained
of Scotland
Scotland and
and
The Precanbrian
Precrbriari Lower
Fine-grained Quartzite
Quartzite of
both
both the Precaubrian
Precanbrian Sterling
Sterling Quartzite and
and Precanbrian
Preccmbrian part
part of the
the
Wood
Canyon
Formation
easternCalifornia
California and
are
Wood Canyon
Formation
of of
eastern
and Nevada
Nevada are
characterized
by primary
primary sedimentazy
sedimentary features
which are
characterized by
features which
are indicC'ltive
indicative
of sediment
transport and
and deposition
deposition by
bytidal
tidal currents.
sediment transport
currents. Sedimentary structures
structureswhich
which occur
occur in these
these formations
fonnations are
are grouped
grouped into
sty
seven
which are
produced by
seven associ~tions
associations which
am produced
by seven
sevenphases
phasesofof tidal
tidal
sediment
sediment transport:
transport:
ASSOCIATION 1:
1: Cross-stratification
sets,
Cross-stratificationorganized
organized into
into herringbone
herringbone sets,
with bipolar-bimodal
bipolar—bimodal
orientation;parallel
parallellaminae;
laninae; these
these features
with
orientation;
features
indicate
indicate tidal
tidal current
current bedload
bedload transport
transport with
with bipolar
bipolar reversals
reversals of
of
flow directions
directions (Reirieck,
flow
(Reineck, 1963).
1963).
ASSOCIATION
2: Reactivation
surfaces:Multimodal
Multimodalfrequency
frequencydistribdistribASSOCIATION 2: Reactivation
surfaces:
utions of cross-strata
utions
cross-strataset
setthickness
thicknessand
andofofdip
dipangles;
angles;unirnodal
unimodal
orientation
of directional
directional current
orientation of
current structures
structures parallel
parallel to
to basin
basin
topographic strike;
producedbybytime—velocity
t:ime-veloci ty assymetry
assymetry of
of
topographic
strike; allallproduced
tidal
tidal current
current flow
flow (Klein,
(Klein, l970a3.
1970a).
ASS<X;IATION
3: Interference
ripples;
superposition
ASSOCIATION
3: Interference
ripples;
superpositionofofcurrent
current ripples
ripples
at 900
crests and
at
90 0 and
and 1800
180 0 on
on crests
and slip
slipfaces
facesofofdunes,
dunes,sand
sandwaves
waves and
and
internal cross-strata;
cross-strata;"B-C"
"B-C" sequences
sequences ClIf
of cross-strata
cross-strata overlain
overlain by
by
micro-cross-laninae; highly-variant
highly-var! antorientation
orientation of
of current
current ripples;
micro-cross-lcminae;
all
late-stage emergence
runoff prior
prior to
all produced
produced by
by late-stage
emergence runoff
to anergence
emergence of
of
an
intertidal
flat
(Klein,1963,1970a,l970b).
an intertidal flat ~Klein,1963,1970a,1970b).
ASSOCIATION It:
4: Cross-stratification
with flasers
fla.sers and
and clay
clay drapes;
drapes;
Cross—stratification with
flaser bedding;
flaser
bedding; lenticular
lenticular bedding;
bedding; "tidal
"tidalbedding';
bedding"; convolute
convolute
bedding; all
all produced
alternation
bedding;
produced by
by al
terna.tion of
ofbedload
bedloadand
and suspension
suspension
sed:imentation associated
alternating bedload
bedload and
and slack-water
slack-water
sedimentation
associated with
with alternating
tidal current
tidal
currentflow
flow(Reineck
(Reineckand
andWunderlich,l968a,1965b;
Wunderlich,1968a,1968b; Wunderlich,
Wunderlich,
1970).•
197Q)
ASSOCIATION 5.
\lJashout structures,
structures,sane
sanefilled
filled
with
mUd-chip
with
mud—chip
ASSOCIATION
5. Washout
conglanerates; rill
casts; all
allproduced
produced by
by tidal
tidal scour
scour
conglctnerates;
rill marks;
marks;flute
flute casts;
(Van Straaten,1954;
Straaten,l951j; Reineck,
(Van
Reineck, 1967; Klein,1970a).
�—37—
-37-
ASSOCIATION 6:
6: MUdcracks;
Mudc racks; mt
intraformational
conglanerates;
rafo tin ational congicrie
rates; birdseye
structure;
allproduced
producedby
byexposure
exposure and
and evaporation (Shinn,1968).
stricture; all,
Tracks and
and trails;
trails; burrowing
burrowing structures,
"escape"
ASSOCIATION 7: Tracks
structures,"escape
burrows; all
all produced
burrowingorganisns
orgaxüausadapted
adaptedtotoaa tidal
tidal
burrows;
produced by
by burrowing
regime (Rhoads,1967;
(Rhoads,l967; Remneck
1968).
Reineck and others,
others,
approximatedin
in these
Precanbrian paleotidal
paleotidal ranges
can be
be approximated
ranges can
similar to
rock units
units finn
rock
from analysis of fining-upward sequences similar
date, Late
those occurring in
in prograding
prograding tidal copstlines.
COAstlines. To date,
Precambrian paleotidal
ranges from
from 0.3
paleotidal ranges
0.3 to
to 13.0 meters
meters have been
measured.
This Late
measuitd. This
Late Precanbrian
Precaubrianpaleotidal
paleotidal range
rangevariation
variation is
tidal
less than
thRn the
theknown
known variation
variation measured
measured along
along Holocene
Holocene tidal
ranges fran
fran 00 to
to 17.5
17.5 meters).
meters). Perhaps
coasts (variation of tidal ranges
Precambri~n
range variation is
not greatly
greatly difforent
different
is not
Precanbripn paleotidal range
fran present-day
present-day variation. If further work substantiates such
Precambrian, it
a
a limited paleotidal
paleotidal range
range variation
variationfruit
fram the Precambrian,
poses critical
critical problems
poses
problems for various
various geophysical
geophysical pxtblms
problens that
that have
have
been
and age
earth-moon systan.
systen.
beenproposed
proposedfor
forthe
the origin
origin and
age of
of the earth-noon
REBERENCES
REFERENCES CITED
intertidal zone sediments: Jour.
Klein, C.deV,1963,
G.deV,1963, Bay
Bay of
of Plindy
Fundy intertidal
Jour.
Sedimentary
Sedimenta~ Petrology,
Petrology, v.
v. 33,
33, p. 844-854
8tb—85t
-——,l97Oa,
dynanics of intertidal sand
---,1970a, Depositional and dispersal dYnanics
sand
bars:
Jour. Sdimentary
S~dimentar,yPetrology,
Petrology, v.v.140,
40, p.
p. 1095-1127.
--—,1970b, Tidal
Quartzite -- The Lower
---,1970b,
Tidal origin of
of aaPrecambrian
Precambrian Quartzite
Pinc—grairdQuartzite
Quartzite (Dalradian)
(Dairadian)ofof Isl~;
Islay. Scotland:
Fine-grained
Scotland: Jour.
Jour.
Sedimentary
Sedimentary Petrology,
Petrology, v.v.140,
40, p.p.973—985.
973-985.
Reineck, H.E.,
H.E., 1963,
un Bereic;h
der sudliche Nordsee:
Reineck,
1963, Sedimentgefuge
Sedimentgefuge im
Bereich der
Nordsee:
Abh. ~enckenbergischen
SenckenbergischenNaturfor.
Naturfor.Gesells.
Gesells. No.
5O5, p.
p. 1-138.
Abh.
No. 505,
1-138.
--—,1967,Layered
Layeredsediments
sediments
tidal flats,
flats, beaches
---,1967,
ofoftidal
beaches and
and shelf bottoms,
p. 191-206:
in Lauff,
p.
191-206: in
Lauff, (hR.,
G.H., Editor,
Editor,1967,
1967,Estuaries:
Estuaries:Am.
Am. Assoc.
Assoc.
Adv. Sci.
Sci. Pub.
Pub. No.
No. 83.
83.
Reineck, H.E.,
and WUnderlich,
H.E., and
Wunderlich,F,F,1968a,
1968a,Classification
Classification and
and origin
origin of
flaser
99-1014.
fiaserand
and lenticular
lenticularbedding:
bedding:Sedimentology,
Sedimentology, v.
v. U,
ll,p.p.
99-104.
---, &,
---,
&, ---,
---,1968b,
1968b, Zeitmessugnen
Natur und
und
ZeitanessugnenananGezeitenschichten:
Gezeitenschichten: Natur
Musetun, v.
Museum,
v. 97,
97, p.
p. 193—197
193-197
Reineck, H.E.,
H.E., Dorjes,
Dorjes, J,
J, Gadow,
Garlow, 5,
S, and
and Hertwick, 0,1968,
S3dimentologie,
Reineck,
0,1968, Sadiznentologie,
Faunenzoniening and
Faunenzonierung
und Faziesabfolge vor
vor der
der Ostkuste
Ostkuste der
der inneren
inneren
Jeutschen
Deutschen Bucht:
Bucht: Senck.
Senck. Lethaea,
Lethaea, v.v.149,
49, p. 261-309
261-309
�-':;8—L8—
Rhoads, D.C.,1967,
and subtida
subtidal
D.C.,1967, Biogenic
Biogenic reworking
reworkingofofintertidal
intertidal, and
sediments in
in Bamstable
sediments
BarnstableHarbor
Harborand
and Buzzards
Buzzards Bay,
Bay, Massachusetts:
Massachusetts:
Jour.
Jour. Geo1or,
Geology, 'r.
v. 75, p.
461-476.
t. b61—L76.
E.A.,],968,Practical
Practicalsignificance
significance of
of birdseye
birdseye structure
structure in
in
Shinn, E.A.,1968,
carbonate rocks:
rocks: Jour. Sedimentary
Petrology, v.
v. 38,
carbonate
Sedimentar,y Petrology,
38, p.
p. 215—223.
215-223.
Van Straaten,
Van
Straaten, L.M.J.U.,
L.N.J.tJ., 1954,
195h, Sedimentology
Sedimento1o'ofof Recent
Recenttidal
tidal fla.t
flat
and the
thePsamnites
Psanmitesdu
duC0ndroz
Condroz (Devonian):
(Devonian): Cleol.
Geol. en
en
deposits and
Mijnb.,
v. i6,
Mijnb., v.
16,
25-47.
p. 25-217.
Wunderlich, F,1970,
envirornent ofofthe
T1NellenkopfschenWunderlich,
F,1970, Genesis and
and environment
the
"Nellenkopfschenschichten
Il(Lower sian,
EInsian,Rheinian
RheinianDevonian)
Devonian) at
at locus
locus typicus
typicus in
in
schichten"(Lower
canparison
ecinparisonwith
withmodern
modem coastal environments
enviroanents of the Cern
GeImclTI
n Bay:
Bay:
Sedimentary Petrology,
Petrology, v. 240,
Jour. Sedimentar,y
40, p. 102-130.
102-130.
�-39—39—
GEOLOGYOF
OF THE
SOME GEOLOGY
THE 'ARATHON
MARATHON COUNTY
COUNTY VOLCANIC
VOLCANIC BELT
BELT
by
Gene L.
L. LaBerge
Wisconsin Geological Survey and
and
Department of Geology
Geology
Wisconsin State University
Oshkosh, Wisconsin
Oshkosh,
ABSTRACT
ABSTRACT
The area east
The
east of Wausau in Marathon County consists
consists largely
largely of
of
rocks which range
range in
in composition
composition from
from basaltic
basaltic to
to rhyolitic.
rhyolitic.
volcanic rocks
The
rocks are mainly to the southeast and
and the
the rhyolitic
rhyolitic rocks
rocks
The basaltic rocks
to
top of
the sequence is northwest:
northwest;
to the
the northwest,
northwest, suggesting
suggesting that
that the
the top
of the
however,
however, no
no definite
definite evidence
evidence of
of stratigraphic
stratigraphic top
top \vas
was found.
fond.
Trachytes
are a1..
so present
edge of
of the
the napped
mapped area.
area. Sedimentary
are
also
pr?sent at
at the
the northwestern
northwestrn edge
rocks
rocks are virtually
virtually absent.
absent.
The volcanic rocks
The
rocks have been intruded by v;rious
various sized masses of
of
gabbro,
and syenite.
syenite. There appears
appears to
to have been
been
gabbro, diorite, granite, and
several ages of granitic intrusion.
intrusion. Available radiometric ages
ages indicate
indicate
are late
late Middle
Niddle Precambrian.
Precambrian.
that the rocks arc
Structurally, the
the area is
is characterized by at least
least two
two directions
directions
Structurally,
of large
large scale faulting
faulting with
with niajor
major fault
faultzones
zonestrending
trendingapproximately
approximately
N8O°E to
to N60°E.
1180°£
~~60°E.
The
\vhich also shows
shows up
on the aeronagnetic
aeromagnetic
The faulting,
faulting, which
up well
well on
map
many of
mapcovering
coveringthe
the area
area mainly
mainly west
west of
of Wausau,
Wausau,has
hasresulted
resalted in many
of the
lithologli units
units being in
Perhaps the
lithologic
in fault
fault contact.
contact. Perhaps
the most significant
fault
zone is
is the
the N300E
N3OF trend
fault zone
trend whiàh
which has
has produced
produced aa zone
zone nearly
nearly aa mile
mile
in the
the Eau
Eau Claire
Claire River
River valley in
in which mylonite
mylonite is
is aa major
major rock
rock
wide in
This zone truncates
type. This
truncates the N8O°E—N60°E
N800E-N600E trend
trend more prevalent
prevalent to
to the
the
,,,,est.
west.
The current
napping project,
The
current mappins
project, funded
funded by the
the Wisconsin Geological
Geological
S"rvey, has
Survey,
revealed significantly
significantlymore
morevolcanic
volcanicrocks
rocksthan
than
shownOLI
on
has revealed
areare
shown
Weidinan's
1907 map.
\veidman's 1907
map. This
This has
has important
importantimplications
implicationsfor
formineral
min al exploration
A previously unreported gold prospect, on
tion programs. A
on which mining
attempted about 1920,
1920, is
is probably
probably the
the most
most interesting
interesting locality
locality from
from
was attempted
an economic point
point of
of view.
view.
References
Dutton,
E. (1970)
Dutton, C.
C. B.
E. and
and Bradley,
Bradley, R.
R. E.
(1970) "Lithologic,
and
"Lithologic, Geophysical, and
;·lineral
:•lineralCommodity
CommodityHaps
MapsofofPrecambrian
Precambrian Rocks
Rocks in
in Wisconsin";
Wisconsin"; U.S.G.S.
Miscellaneous Geologic
InvestigationsMao
Map 1-631.
Geologic Investigations
1—631.
Henderson, J.
J. IL,
Henderson,
R., Tyson,
Tyson, ;i).
R. (1963)
"Aeromagnetic
N. S.,
S., and Page,
Page, J.
3. R.
(1963) "Aeromagnetic
Map
of the Wausau Area, Wisconsin";
Map of
Wisconsin"; U.
U. S. G.
G. S. Geophysical
Investigations Map
Map CP—40l.
GP-40l.
Laberge, G.
U. and l,Jeis,
LaBerge,
G. 1.
L. W.
Iv. (1968)
Central
Weis, L.
(1968) "A
'A Greenstone
Greenstone Belt
Belt if
in Central
Wisconsin?", Guidebook
Guidebook for
for 32nd
32nd Annual
Annual Tn—State
Tri-State Geological
Geological Field
Field
Wisconsin?,
Conference.
�—40—
-40-
Weidman, S.
S. (1907)
(1907) The
The Geology
Geology of
of North
North Central Wisconsin;
Wisconsin; Wisconsin
Geological and Natural History
History Survey
Survey Bulletin
Bulletin 16.
16.
Weis,
L. W.
W. and
and LaBerge,
LaBerge, C.
G. L.
1. (1969)
(1969) "Central Wisconsin Volcanic
Volcanic Belt,"
Belt,"
Weis, L.
Guidebook for 15th Annual Institute
Institute on
on Lake
Lake Superior
Superior Geology.
Geology.
�—41—
-41-
HEMATITE PSEUDOMORPI-1IC
AFTER BIOGENIC
BIOCENIC
HE~1ATITE
PSEUDOMORPHIC AFTER
PYRITE IN
INTHE
THENEGAUNEE
NEGAUNEE IRON
IRONFORMATION
FORMATION
N.
M. S.
S. Lougheed
and J.
J. 3.
J. Nancuso
Mancuso
Bowling Green State University,
Green, Ohio 43403
43403
University, Bowling Green,
ABSTRACT
A B S T R ACT
Spherules
(limonite), ranging in diameter from
from
Spherules of
of hematite (limonite),
5 microns
microns to
to 20
20 microns
microns but generally of similar size in each
each
as disseminated
disseminated octahedral
octahedral crystals
crystals
particular population, as well as
of pseudomorphic hematite occur in
in many laminations
laminations of
of the
the Negaunee
Negaunee
iron formation.
formation. Mineral associations
associations include
include chert,
chert, magnetite,
magnetite, iron
iron
carbonate,
silicates. A
A common associate is
is fossil
fossil fila—
filacarbonate, and iron silicates.
A tentative conclusion based on two
mat algae.
algae. A
two microprobe
mentous mat
Thermal experiments
carbon in
the filaments.
filaments. Thermal
analyses indicates
indicates carbon
in the
result
considerableremoval
removal of the filamentous material suggesting
suggesting
result ininconsiderable
the presence
presence of both
both amorphous
amorphous carbon
carbon and
and graphite.
graphite.
Framboidal pyrite with diameters ranging from 55 microns to
to 20
20
microns
sedi—
nlicrons and
and pyrite octahedra,
octahedra, occurring in two
two unconsolidated sediinents
with contrasting
contrasting environments,
environments, one
one aa Pleistocene fresh
ments with
fresh water
water
lake deposit,
deposit, the
lake
the other a Recent marine tidal
tidal lagoon, unequivocally
unequivocally
demonstrate their
their biogenic
biogenic origin.
origin.
Paleozoicanalogs
analogsofofsomewhat
somewhatsimilar
similar lithology
lithology to
to iron
iron formation
formation
P-Jzoic
the
following associations:
carbonate, biogenic
biogenic euhedral
euhedral
the following
associations: chert, carbonate,
pyrite, biogenic framboidal
pyrite,
framboidal pyrite
pyrite 55 microns
microns to
20 microns
microns in diameter,
diameter,
to 20
sparce euhedral magnetite
microflora.
magnetite and
and fossil
fossil microfcunz:
microfauna and/or microflora.
the biogenic
biogenic origin
origin of
of pyrite.
pyrite.
They further demonstrate the
have
A
finely laminated
A finely
laminated chert
chertcarbonate
carbonatespecimen
specimen from
from the
thePennsylvanian
Pennsylvanian
formation, Texas,
Texas, clearly shows the
Dimple formation,
the transition
transition of
of biogenic
biogenic
pyrite to pseudomorphic hematite
hematite (limonite)
(limonite) by
by oxidation.
oxidation.
features are
These various
various features
are illustrated by photomicrographs
phbtomicrographs to
to
that the
support the
the hypothesis
hypothesis that
the spherules
spherules of
of hematite (limonite)
(limonite)
possibly other
other hematite
hematite in
in the
theNegaunee
Negaunee iron formation
formation are
pseudomorphic
after biogenic
biogenic pyrite,
pyrite, and together
pseudomorphic after
together with the
the presence
presence
of
the bio~enic
bio3enic (in
part) genesis
of probable
probable algal
algal mat
mat strongly
strongly support the
(in part)
of the Negaunee
Negaunee iron
formation.
of
iron formation.
and
and
�—42—
-42-
DISTRIBUTION OF URANIUM
URANIUM AND
AND THORIUM
THOP.IUM IN PRECAMBRIAN
PRECAMBRIAN
ROCKS
RE GION
ROCKS OF
OF THE
THE WESTERN
WESTERN GREAT
GREAT LAKE:
LAKE: RE3ION
by
Roger
C.
Roger C.
N~alan and
and David
Sterling
Malan
David1_A Sterling
ommission, Grand
Thiorado
U.S.
Atomic Energy
Energy :::ommission,
Grand Junction,
Junction,:::olorado
U.S. Atomic
AE<:::;TRACT
AECTRACT
1
Prospecting during
during the
the 1950
1950's
resulted in
Prospecting
s resulted
in the
the discovery
discovery of
of several
several
uranium
and
thorium
prospects
in
Precambrian
rocks
in
the
westuranium and thorium prospects in Precambrian rocks in the westeconomic deposits
ern
Great Lakes
Lakes region
region of
of the
the United
United States.
States. No
No economic
deposits
ern Great
were delHeated
the few
few small
small exploration
efforts that
were
delineated by
by the
exploration efforts
that were
were underunderSince then
exploration for
for radioradiotaken. Since
then there
there has
has been
been very
very little
little exploration
active minerals
minerals in
active
in that
that region.
region.
In Wisconsin
Wisconsin and
and inin upper
upper Michigan,
Michigan, Lower,
Lower, Middle,
PreIn
Middle, and
and Upper
Upper Precambrian silicic
cambrian
silicic and
and hyperalkalic
hyperalkalic plutonic
plutonic rocks
rocks contain
contain anomalous
anomalous
In upper
amounts of
upper Michigan,
Michigan,
amounts
of disseminated
disseminated radioactive
radioactive minerals.
minerals. In
the Middle
Middle Precambrian
Animikie Series
contains uranium
uranium veins
veins in
in
the
Precambrian Animikie
Series contains
slate,
monazite placers
placers in
in conglomerate,
conglomerate, and
and irregular
concentraslate, monazite
irregular concentrations
utanium
in iron
iron formation
adjacent to
to slate.
tions of
of Ul
anium in
formation adjacent
slate. These
These prosprospects do
do not
of uranium
uranium or
or thorium
thorium that
that
pects
not contain
contain important
important reserves
reserves of
are
at present
are economically
economically mineable
mineable at
present but
but some
some may
may contain
contain large
large
long-range, low
low-grade
resources.
long-range,
- grade re
sources. For
Forexample,
example, limited
limited sampling
sampling
indicates that
that masses
masses of
indicates
of silicic
silicic igneous
igneous rocks
rocks in
in northeastern
northeastern WisWiscousin
may contain
contain 50
50 to
to lOO
100parts
parts per
per million
consin may
million uranium.
uranium. This
This is
is
greater than
than the
the uranium
uraniumcontent
content in
inany
any of
of about
about 250
250 bulk samples
greater
of
igneous rocks
rocks that
analyzed in
in aa recent
of igneous
that have
have been
been analyzed
recent study
study of
of the
the
distribution
of uranium
rocks in
in the
the
distribution of
uranium and
and thorium
thorium in
in Precambrian
Precambrian rocks
western United
United States.
potentially great
great low-grade
low-grade resource
resource of
of
western
States. AA potentially
thorium may
thorium
may exist
exist in
in the
the monazite
monazite placers
placers in
inAnimikie
Animikie conglomconglomerates in
erates
in the
the Marquette
Marquette Range,
Range, upper
upper Michigan.
Michigan.
In other
other areas
areas of
of the
the world,
world, stratiform
stratiformuranium
uraniumdeposits
depositsin
inMiddle
Middle
In
Precambrian
Precambrian coarse
coarse clastic
clastic sediments
sediments are
are of
of major
major importance.
importance.
The world's
world's greatest
resource of
uranium is
is in
The
greatest known
known resource
of uranium
in basal
'::asal conconglomerates
of the Middle
Middle Precambrian
Huronian Series
glomerates of
Precambrian Huronian
Series in the
Elliot Lake
Blind River
Elliot
Lake -- Blind
River district
district in
in southern
southern Ontario.
Ontario. Important
stratiform
uranium deposits
deposits have
have not
not been
been discovered
discovered in
in the
the
stratiform uranium
Animikie
Series which
is in
Animikie Series
which is
in part
part correlative
correlativewith
withthe
theHuronian;
Huronian;
�________
-4343—
however,
however, limited
limited sampling
sampling ia
L.1. the
the iviarquette
Ivlarquette Range,
Range, upper
upper Michigan,
Michigan,
indicates
that anomalous
anomalous amounts
indicates that
amountsofofuranium
uraniumare
are present
present in
in coarse
coarse
clastic facies. Also
in the
the Animikie
Animikie in the
Also uranium/thorium
uranium/thorium ratios in
elastic
Blind River
Marquette
Range
and
in
the
Huronian
in
the
Elliot
Lake
River
Marquette Range and in the Huronian in the Elliot Lake -- Blind
More study
area increase
increase in
in descending
descending stratigraphic
stratigraphic positions.
positions. More
study of
of
area
the distribution
of uranium
the
distribution of
uranium and
and thorium
thorium in
in the
the Animikie
Animikieisis warranted.
warnnted.
CELECTED REFERENCES
:ELECTED
REFERENCES
T.llsley,
':llsley, C.
C.T.,
T., Bills,
Bills, C.
C. W.
W.,
Some geoand Pollock,
Pollock, J.W.
J. W.,, 1958, Some
chemical
methods of uranium exploration,
exploration, in
inSurvey
Survey of
of Raw
Raw
chemical methods
Materials Resources:
Materials
Resources: United
United Nations,
Nations, New
New York,
York, Proc.
Proc. Second
Second
lnternat. Conf.
Energy, 1958,
v. 2,
Internat.
Con£. Peaceful
Peaceful Uses
Uses Atomic
Atomic Energy,
1958, v.
2, p.
p.
126-130.
,
James, H.
James,
H. L.,
L.,1958,
1958,Stratigraphy
Stratigraphyofofpre-Keweenawan
pre-Keweenawan rocks
rocks in
in parts
parts
of
Northern Michigan:
Michigan: U.
U. E
E Geol.
Geol. Survey
Survey Pro£.
Paper314-C,
314-C,42
42 p.
p.
of Northern
Prof. Paper
King, J. W.,
W.,1960,
1960,Report
Reportofofexamination,
examination,Little
Little
WolfMining
Mining&& MinMinKing,
Wolf
erals, Inc.,
erals,
Inc.,Anklam
AnklamProperty
PropertyBig
BigFalls,
Falls,Waupaca
WaupacaCounty,
County, WisconWisconsin:
file rept.
sin: U.S.
U. S. Atomic
Atomic Energy
Energy Comm.
Comm. open
open file
rept.
Malan,
C., and
and Sterling,
Sterling, D.
Do A.,
A.,1969,
1969,An
Anintroduction
introduction to
to the
the disdisMalan, R.
R. C.,
tribution
thorium in
in Precambrian
Precambrian rocks
tribution of
of uranium
uranium and
and thorium
rocks including
including
the
the results
results of
of preliminary
preliminary studies
studiesin
inthe
thesouthwestern
southwesternUnited
United
States:
States: U.S.
U.S. Atomic
Atomic Energy
Energy Comm.
Comm. AEC-RD.-9,
AEC-RD-9, 54
54 p.,
p., open
open file.
file.
Roscoe,
Roscoe, S.
S. M.
M., 1969, 1-luronian
Huronian rocks
conglomerates
rocks and
anduraniferous
uraniferous conglomerates
Canadian shield;
shield: Geol.
Geol. Survey
Survey Canada Paper 68-40.
68-40.
in the Canadian
,
Stead, F.
F. W.,
F. J.,
Stead,
W., Davis,
Davis, F.
J., Nelson,
Nelson, R.
R. A.,
A., and
and Reinhardt,
Reinhardt, P.
P. W.,
W.,
1950, Airborne
Airborne radioactivity
radioactivity survey
survey of
of parts
parts of
1950,
of Marquette,
Marquette, DickDickinson, and
open—
inson,
and Baraga
Baraga Counties,
Counties, Michigan:
Michigan:U.S.
U. S.Geol.
Geol.Curvey
:urvey
openfile map.
file
map.
Vickers, R.
of t>-e
te Goodrich
Vickers,
R. C.,
C.,1956a,
1956a,Geology
Geology and
and monazite
monazite content
content of
Goodrich
Quartzite,
Quartzite, Palmer
Palmer area
areaMarquette
Marquette County,
County, Michigan:
Michigan: U.S.
U. S. Geol.
Geo!.
Survey Bull.
Bull. 1030-F.
Survey
1030-F.
1956b, Ai
Airborne
rborne and
and ground
groundreconnaissance
reconnaissanceofofpart
partof
of the
the
----syenite
complex near
near Wausau,
Wausau, Wisconsin: U.S.
syenite complex
U. S. Geol.
Geol. Survey
Survey
Bull. 1042-B.
�Is..
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�-45—45—
LOWER KEWEENAWAN
KEWEENAWAN
SEDIMENTS
THELAKE
LAKE SUPERIOk
SUPERIOR REGION
LOWER
SEDHlENTS
OFOFTHE
REGION
Allen
F. Mattis
Mattis
Allen F.
Department
Department of Geology
Geology
of Minnesota,
Hinnesota, Duluth
Duluth
University of
A
B S T RAe T
ABSTRACT
Lower Keweenawan sediments directly
directly underlie
underlie the
the Keweenawan
Keweenawan
Studies
of the quartz—
volcanic series in the
the Lake Superior
Superior region.
region.
quartzvoi:anic
rich Puckwunge Formation (Minnesota)
rich
(Minnesota) and the Bessemer Formation
Formation (Michigan
(Michigan
and Wisconsin),
Wisconsin), which include thin section petrography, heavy mineral
and
mineral
analysis,
and measurement of paleocurrent indicators,
indicators, provide
provide new
new data
data
analysis, and
Keweenawan events.
events.
on Lower Keweenawan
The Puckwunge Formation of Cook
Cook County,
County, northeastern
northeastern Minnesota,
Minnesota,
from
is
exposed along
along aa 25
25 mile
mile belt
belt extending
extending westward
westward from
is LT.termittently
intermittently exposed
Pigeon Point on Lake
Lake Superior.
Superior. Although the lower contact
contact of this
this
formation is
is not exposed,
exposed, outcrops of
of the
the formation
formation thicken
thicken from
from 30
formation
feet on Grand Portage Island to
to over 100
100 feet
feet in
in the
the westernmost
\vesternmost
feet
of basal conglomerate
exposures. Fifteen feet
feet-of
conglomerate exposed
exposed on
on Grand
Grand Portage
Portage
exposures.
Island contains flat
flat chips
chips and pebbles of
of argillite
argillite and
and slate,
slate, probably
probably
Island
derived from the underlying Rove
Rove Formation,
Formation, and
and rounded
rounded pebbles
pebbles of
of
feldspar content
quartzite. Thin section examinutioi
examination indicates
indicates total
total feldspar
content
quartzite.
ranges from 20 percent
percent in the eastern exposures to only a trace in the
western outcrops. Unit
Unit quartz is the dominant quartz uype,
type, with up
up to
to
Zircon, apatite,and
apatite, and
20 percent polycrystalline
polycrystalline quartz
quartz being
beingpreseriI.
present. Zircon,
with tourmatourma—
epidote are the
the common
common nonopaque
nonopaque accessory
accessory heavy
heavy ininerais,
minerals, with
line also
the outcrop belt.
also present in the central portion of the
to only a trace in the
Nopeming, just
just west of
of Duluth,
Duluth, 25
25 feet
feet of
of quartzite
quartzite and
and quartzquartz-At Nopeming,
conglomerate are
•:->.oosed
}T the basal (?)
quartzite-pebble
are
exposed bere&:
beneath
quatnJte—pebble conglomerate
(?)
Keweenawn
Keweenawan flow over a distance
distance of
of half
half aa mile.
mile. In the
the sand—sized
sand-sized
fractions,
unit quartz
quartz is
is the
LUe dominant
dominant quartz
quartz type,
tye, with polycrystalline
fractions, unit
polycrystalline
also preseit.
present. Zircon is
the principal nonopaque accessory heavy
quartz also
is the
amounts of
of a;atite
apatite and
and tourmaline
tourmaline present.
present. Gravity
mineral, with minor amounts
and magnetic
suggest the
the presence
presence of
of aa tabular,
tabular,
and
magnetic profiles
profiles across
across the
the area
na suggest
dike—like
dike-like mafic body beneath the
the Puckwunge exposures
exposures at
at Nopeming;
Nopeming; aa
greater degree of recrystallization in
in the
the lowermos:
lowermost sediments
sediments may
may be
be
related to
related
to this
this probable intrusive.
intrusive.
and
and
The Bessemer
:-:ohigai-r
BessemerFormation
Formationof of
Hichigan and Wisconsin
lHsconsin is intermittently
intermittently
exposed
:nile belt
belt extending
extending eastward
exposed along
along aa 40 mile
eastward from
from >leflen,
~le~len, Wisconsin.
formation is
is over 150
The fonnation
150 feet thick
thickwhere
where both
both the
the upper
upper i-td
and lower
lower
contacts are
are visible.
visible. A
contacts
A basal
conglomerate contains
rounded pebbles
pebbles of
basal conglomerate
contains rounded
quartz, qu;E2ite,
quartzite, flint,
flint, and
and jasper
jasper in
in aa qnartzite
rruartzite matrix.
matrix. In the
the
sand—si-:d
qunrtz is
sand-sized fractions,
fractions, unit
unit quartz
is the dominant
dominant quartz type,
type, with
polycrystalline quartz
quartz also
also present.
present. The average total feidsrar
feldspar content
content
is less than
than 10
10 percent.
percent. Zircon is
is the
tlte dominant nonopaque nccesscry
accessory
h!avy
withapatite,
apatite, rutile.
rutile, and
heavy hliner&I,
ltlineral, \vith
and tourmaline
tourmaline also
also present.
presenL
�—46—
-46-
sediments along both limbs
the lower
lower IKeweenawan
Keweenawan sediments
Exposures of the
the Lake
SuperiorSync:ine
Synclinesuggest
suggestthe
thedeposition
depositionofof aa thin
thin sheet
of the
Lake Superior
sheet
of
sediment throughout
throughout the
region. The
cross-bedded, rippie—mariced,
ripple-marked,
of sediment
the region.
The cross—bedded,
of Hell
well rounded
well sorted
sorted quartz—rich
quartz-rich sediment
sediment composed
composed of
rounded grains
suggests aa shallow
shallow water
waterenvironment.
environment. Cross-bedding,
mark,
Cross—bedding,ripple
ripple mark,
in these
these sedimentary
sedimentary rocks
rocks indicate
indicate
and parting lineation measurements in
sediment transport,
transport, with the
the sediments
sediments
a general southerly direction of sediment
being derived from the
the Pre—Keweenawan
Pre-Keweenawan rocks
rocks to
to the
the north.
north. Thus,
Thus, these
these
Lower Keweenawan sediments were probably deposited
deposited during
during the
the northward
transgression of
of aa sea into
into the
transgression
the region,
region, and were apparently the
the final
final
region prior to
to formation
formation of
of
sediment deposited in the Lake Superior region
the Lake Superior Syncline.
Syncline.
�—47—
-47-
EXPLORATION GEOLOGY
GEOLOGY OF
OF DOUGLAS
DOUGLAS COUNTY,
COUNTY, w::scoNSIN
WISCONSIN
by
Joseph T.
T. Mengel,
Mcnge1, Jr.,
Jr., Professor and Ronald A.
A. Hendrickson
Department of Geology
Geology
Wisconsin State University,
University, Superior, Wisconsin 54880
54880
and
and
and Natural
Natural History
History Survey,
Survey, Madison
Madison 53706
53706
Wisconsin Geological and
ABSTRACT
A B S T R ACT
The oldest bed rock units in Douglas County are
are the
the Keweenawan
Keweenawan
basaltic fissure flows
flows of the St.
St. Croix horst south
south of the line
lin~
Brule,
raple, Wentworth,
Wentworth, South Range,
Brule, Maple,
Range, Pattison State Park,
Park, Patzau.
Patzau.
These flows
flows have a N6OE3SS
N60E35S attitude along tha
the north margin
margin of
of the
the
horst and N5OE15S
N50E15S along
along the
the south.
south. They are intruded by "red
"red rock"
.95 b.y.
b.y. and
and by aa gabbro
gabbro mass
mass in
in 32—48N—
32-48Nin 15-47N-13W,K/Ar
l5—47N-13W,K/Ar dated at .95
12W.
l2W.
flows occur again south of the line Totagatic River—
Basaltic flows
RiverOunce Creek where the attitude is N4SE3ON
N45E30N and
and there
there are
are extensive
extensive
conglomerate
lavas.
conglomerate and sandstone interbeds with the lavas.
Native copper
ides are
copper and
and copper
copper suif
sulfides
are found
found in
in ainygdaloidal
amygdaloidal
horizons and along fractures wherever the
the Keweenawan
Keweenawan lavas
lavas outcrop.
outcrop.
Almost all lava outcrop is within the
the following
following limits:
limits:
(1)
A
a,uth of
of the
the line Brule—Patzau
A 22 mile wide
wide band
band south
Brule-Patzau
(2)
(2)
A
nile wide band north of
A 22 mile
of the
the line
line Winnebaujou—St.
Winnebaujou-St.
Croix River in 43N-14w
44N-13W
43N—14W and 44N—13W
(3)
(3)
43N-15W
The NW half of 43N—1SW
(4)
(4)
The south half of 44N-15W
44N—l5W and SW quarter 44N-14W
44N—14W
(5)
(5)
The NE quarter of 45N—l2W
45N-12W
(6)
The SE haf
half of
of 43N—1OW,
43N-lOW. especially
especially along
along the
the valley
valley of
of
Dingle Creek in sections 12 and 13 where an
an extensive
extensive
section is exposed
the last
last century and a half
the properties
During the
half the
properties listed below
have all
all been the
have
the locus of shafts and/or test
test pits and
and drilling
drilling for
for
copper in
in the
the lavas.
lavas.
�—48—
-48-
Location
Property
Nature
NE 12—43N—1OW
l2-43N-lOW
Weyerhauser
Amygdaloid
Ainygdaloid and
and in
assoc. sediments
SW 28—43N—1OW
28-43N-lOW
Williams
Ashbed amygdaloid
NW 6—43N—13W
6-43N-l3W
Superior Copper Mines
C.F.
C.F. Irving Mon 5,
5,
pI.
25
p1. 25
8—43N—13W
SW 8-43N-l3W
Copper Mine Dam
(? )
Ainygdaloid
Amygdaloid (?)
SE
34—44N—J.4W
SE 34-44N-l4W
Nowell (Crotty
Brook Arnold)
ArnoL)
Nowell
(Crotty Brook
(? )
Anygdaioici
Amygdaloid (?)
SE
14—44N—13W
SE l4-44N-l3W
Aac
ía
Arnold
Amygdaloid
Amygdaloi<l
7N—liJ
NE 31-4
3l-47N-l4W
Culligan
Amygdaloid
SE 28—47N—14W
28-47N-l4W
Bardon
Amygdaloid
Amygdaloid('l)
()
SW l4-47N-l4W
1447N—14W
SW
Copper Creek
Creek
Cc1:ier
Amygdaloid
NE 8—47N—13W
8-47N-l3W
Fond
Fond du Lac
Lac
Amygdaloid
SE 2—47N—l3W
2-47N-l3W
Starkweather
Wisconsin
Edwards
Zdwards
NWdip
dip
75 NW
NE strike 75
Centerll—47N—13W
ll-47N-l3W Amnicon
Center
Fissure vein
vein4—6'
4-6' wide
wide
Narrow steeply
dipping
Narrow
steeply dipping
vein
Houghton
Amygdalcid
Amygdaloid
NE 8—47N—12W
8-47N-l2W
Badger
Amygdaloid
Nnygdaloid (?)
NW
NW 1O—47N—12W
lO-47N-l2W
Chippewa
Fractured
Fractured Amygdaloids
Amygdaloids
St 1O—47N—12W
SW
lO-47N-l2W
Copper King
King
Amygdaloid (?)
(?)
Amygdaloid
23--48N--lOW
NE 23-48N-lOW
Cascade
Amygdaloid (?)
(?)
Miygdaloid
NE
NE
Percival, Jr.
Jr.
Percival,
Amygdaloid
NE
NE 27-48N-lOW
27—48N—1OW
Percival
Veinlets ininamygdaloid
amygdaloid
NW
NW 28—48N—1OW
28-48N-lOW
Astor
Amygdaloid
SE 29—48N—12W
29-48N-l2W
Mrnicon
Amnicon
Amygdaloid (?)
Mtygdaloid
SE
SE 34-48N-l3W
34—48N—13W
Catlin
Amygdaloid
4—47N-12W
4-47N-l2\.J
24-48N-lO\.J
24-48N—lOW
�—49—
-49-
The
the
The U.
U. S.
S. Bureau of Mines
Mines reported on extensive tests of the
Property in 1947 and the
the Chippewa
Chippewa Property
Property in
in 1955.
1955.
Weyerhauser Property
The Keweenawan Oronto Group occupies the
the Lake Superior
Superior syneline
syncline
of the
Croix River. Resouth of
the line
lineWinneboujou,
Hinneboujou, Solon
SolonSprings
Springs—- St. Croix
Shale, and
portedly the
the Copper
Copper Harbor
Harbor Conglomerate,
Conglomerate, the Nonesuch
Nonesuch Shale,
and the
the
Prospecting
in
Freda
Sandstone
units
are
all
present
in
this
area.
Prospecting
Freda Sandstone units are all present in this area.
the
the syncline
syncline has
has centered
centered on
on attempts
attempts to
tolocate
locatea acopper—bearing
copper-bearing facies
facies
of the
the Nonesuch
Nonesuch Shale, but
but has
hasbeen
beenhampered
hampered by
by complete
complete absence
absence of
outcrop except
the St.
St. Croix River Valley.
Valley.
except along the lower portion of the
Conglomerates
in: NWNW
NWNW 10—
10Conglomerates have
have been reported from exploration tests in:
half lO—45N—1OW,
44N-llW, SW corner 3l—44N—1OW,
3l-44N-lOW, WW half
10-45N-lOW, SWSW
SWSW l6—45N—llW,
l6-45N-llW,
NE
27—45N-lOW,
NENE
34—45N—llW,
10—46N—llW,
NESE
25—46N—11W;
NE corner
corner
27-45N-lOW,
NENE
34-45N-llW,SESE
10-46N-llW,
NESE
25-46N-llW;
Shale rrom
from.near
center
of 34-47N-llW;
Sandstone
NE 3-45Nnear thethe
center
of 34—47N—llw;
andand
Sandstone
fromfrom
NE 3—45N—
NWSWll-46N-lOW,
ll—46N—lOW, W
Whalf
half 15—47N—1OW,
lOW, SW
SW 8—46N—lOW,
8-46N-lOW, NWSW
l5-47N-lOW, SE
SE19—47N—1OW.
19-47N-lOW.
Waterwells do
estimated 200
200 foot
foot depth
depth of
of sandy
sandy
Waterwells
donot
not penetrate
penetrate the estimated
overburden
in
this
area.
overburden in this
References
Grant,
Grant, U.
U. S.,
S., 1901,
1901, Preliminary
Preliminary
Douglas County, Wisconsin:
Douglas
6,
55 p.
p.
6, 55
report on the
the copper—bearing
copper-bearing rocks of
report
Wisc.
Wise. Geol. and
and Nat.
Nat. Hist.
Hist. Surv.
Surv. Bull.
Bull.
Holliday,
it.
W.,
Holliday, R.
W., 1955, Investigation
Investigation of
of Chippewa
Chippewa copper—nickel
copper-nickel prospect
prospect
near Rockmont,
Rockmont, Douglas County,
County, Wisconsin:
Wisconsin: U.S.
Bur. Mines Rept.
Rept.
U.S. Bur.
mv. 5114,
Inv.
5114, 11
11 p.
p.
Irving, R.
R. Do,
D., 1883,
1883, Copper-bearing
Copper—bearIng rocks
Irving,
rocks of Lake Superior:
Superior:
Mon. 5,
5, 464
464 p.
p.
Geo1. Survey Mon.
Ceol.
U. S.
S.
U.
,p
Smith, N.
H. C., 1947,
1947, Copper deposits of Douglas County,
County, Wisconsin:
U.S. Bur.
4088, 7
7 p.
p.
Bur. Mines
MinesRept.
Rept. Inv.
mv. 4088,
Sweet, F.
E. T.,
1880, Geology
Geology of
in
T., 1880,
of the
the western
western Lake
LakeSuperior
Superiordistrict
district in
Geology of Wisconsin 1873—1879:
1873-1879: Wisconsin
Wisconsin Geol.
Geol. Survey,
Survey, v.
v. 4,
4,
p. 305-362.
305—362.
�-50—50-REVISED KEWEENAWAN
KEWEENAWAN SUBSURFACE
SUBSURFACE STRATIGRAPHY
STRATIGRAPHY
SOUTHEASTERN MINNESOTA
SOUTHEASTERN
B.
Morey
B. Morey
Minnesota
Geological Survey
Minnesota Geological
Survey
Minneapolis~ Minnesota
Minnesota
Minneapolis,
G.
G.
ABSTRACT
TheMid-continent
Mid—continent
Gravity
High
themajor
majortectonic
tectonicfeature
feature of
of the
The
Gravity
High
is isthe
the
Detailed geophysical
northern mid-continent
mid-continent region.
region. Detailed
geophysical surveys
surveys over
over the
the 600
600
northern
mile-long
consists mainly
mainly of
ofa asequence
sequence of babamile—longbelt
belt show
showthat
that the
the structure consists
saltic lava
blocks that are
saltic
lavaflows
flowswhich
whichform
formsteep—sided
steep-sided blocks
are an
an average
average of about
about
40
miles wide
wide and
and several
several miles
miles thick. Clastic rocks
40 miles
rocks occur
occur in flanking
flanking babaBecause much
much of
of
sins
and in grabens
grabens and
the blocks.
blocks. Because
sins and
andaxial
axial basins
basins on
on top
top of
of the
the structure isis covered
rocks, little
little is is
known
the
covered by
by Paleozoic
Paleozoic rocks,
knownabout
about the
the rocks
rocks
However, the
the Paleozoic
away
outcrop area
area around
around Lake
Lake Superior.
Superior. However,
awayfrom
from their
their outcrop
cover is
is relatively
southeastern
severaldrill
drill holes
cover
relativelythin
thinin in
southeasternMinnesota,
Minnesota, and
and several
holes
Of particular
particular
have
penetrated considerable thicknesses
strata. Of
have penetrated
thicknesses ofofIceweenawan
Keweenawan strata.
rocks which
whichflank
flank and
andoverlie
overlie the
interest here
here are
are the
the sedimentary
sedimentary rocks
the St. Croix
Croix
an uplifted
upliftedbasalt
basaltblock
blockin in
southeasternMinnesota.
Minnesota.
horst, an
southeastern
Keweenawan
sandstone
shalehave
havebeen
beenknown
known
fromthe
thesubsurface
subsurfacefor
for aa
Keweenawan
sandstone
andand
shale
from
Because ofoftheir
red color,
color,they
theyhave
havebeen
been grouped
grouped together
together ununhundred years. Because
hundred
their red
der
the Red
Red Clastic Series,
Series, aa"temporary"
IItemporaryllname
name proposed
proposed by
der the
byHall
Hall and
and others
others in
1912. Mooney
Mooney and
Geophys. Res.,
Res., v.
v. 75,
75,p.p.
5056-5086) have
have
1912.
andothers
others (1970,
(1970, J.
J. Geophys.
5056—5086)
subdivided
number of
and concluded
concluded that sevsevsubdivided these
these rocks
rocks into aa number
of seismic
seismic units, and
eral of
already
named
of their
theirsubdivisions
subdivisionscould
couldbebecorrelated
correlatedwith
with
already
named formations.
formations.
A detailed
detailed petrographic
petrographic study
study of Ii,000
4,000 feet
feet ofofdiamond
diamond drill
drillcore
corefrom
froma number
a number
thepresence
presence
leastthree
threelithologically
lithologically
of localities
localitieshas
hasdemonstrated
demonstrated the
of of
atatleast
distinctintervals
intervals
whichmore—or-less
more-or~less correspond
correspond to
seismic units. Therefore,
distinct
which
to seismic
it will
be be
recommended
in prep.)
it
will
recommended (Morey,
(Morey, in
prep.) that
thatthe
theterm
termRed
Red Clastic
Clastic Series
Series be
be
abandoned
andreplaced
replacedby
by aa more
moresuitable
suitable nomenclature.
nomenclature. Accordingly,
Accordingly, three
three
abandoned and
formations
be recognized:
recognized: (1)
Hinckley Sandstone,
Sandstone, a abuff
tan rock
rock conconformations will
will be
(1) Hinckley
buff to
to tan
taining 95
(2) Fond
du Lac
Lac Formation,
Formation, consisting
consisting of
95 percent
percent or
or more
more quartz.
quartz. (2)
Fond du
intercalated
intercalated moderate
moderate red
red shale
shale and
and sandstone
sandstone containing
containing 6o
60 percent
percent quartz, 30
30
percent orthoclase,
orthoclase, microcline
microcline and
and sodic
sodic plagioclase,
plagioclase, and
10 percent
percent"granitic"
"granitic"
percent
and 10
rock fragments.
fragments. (3)
(3) An
An as
as yet
yet unnamed
unnamed formation,
consisting ofofdark
darkreddish—
reddishformation, consisting
brown mudstone
containing
plagioclase
brown
mudstoneand
andsandstone
sandstone
containingvariable
variable amounts
amountsofofquartz,
quartz, plagioclase
of intermediate
intermediate composition,
composition, and
and aphanitic
aphanitic igneous
igneous rock
rock fragments.
fragments. The
The first
first
two formations
are known
known from
two
formations are
fromsurface
surface exposures,
exposures,however
howeverthethethird
third formation
formation is
confined
sub—surface.
confined entirely
entirelytotothe
the
sub-surface.
A stratigraphic
stratigraphic analysis
A
analysis indicates
indicates that
that in
in the
the flanking
flanking basins,
basins, the
the ununnamedformation
formationisisoverlain
overlain by
by the
du Lac
LacFormation,
Formation,which
whichininturn
turn is gradanamed
the Fond
Fond du
gradationally
tionallyoverlain
overlainbybythe
theHinckley
HinckleySandstone.
Sandstone. On
the horst,
horst,the
theunnamed
unnamed
On top
top of
of the
formation
overlies
formation overl
ies basaltic
basalticrocks
rocksand
and is
locallyoverlain
overlainbybyHinckley
HinckleySandstone;
Sandstone;
is locally
at places,
places, aa regolith
regolithasasmuch
much as
as 100
100 feet thick
thickseparates
separates the
the two
two formations.
formations.
Either the
the Fond
Fond du
du Lac
Lac Formation
Formation was
was
wasnever
neverdeposited
depositedonontop
topofof the
the horst, ororwas
removed
prior to
to Hinckley
removed prior
Hinckley deposition.
Any
attempttoto explain
explain the
the geologic
geologic evolution
evolution of
of this structure
Any attempt
structuremust
must take
take
thesestratigraphic
stratigraphic relationships.
into account
account these
relationships.
�-51—51—
LIMNOGEOLOGICAL STUDIES
OF THUNDER
THUNDER BAY,
BAY,
STUDIES OF
LAKE
LAKE SUPERIOR, ONTARIO
ONTARIO
J.
S. Mothersil1
Mothersill
S.
LAKEHEAD UNIVERSITY
LAICEHEAD
ABSTRACT
A B S T R ACT
studies were carried
carried out
out in
in Thunder
Thunder Bay,
Bay,
Limnogeological studies
Lake Superior during the
the 1970
1970 field
field season.
season. Ponar grab samples
and Ph1eger
taken at one hundred and forty—seven
forty-seven
and
Phleger cores were taken
stations
stations on a 1.5 mile grid for geochemical and mineralogical
In addition three
echo sounding traverses
analyses. In
three echo
traverses were
carried out using an
an MS
MS 26F
26F metric
metric echo
echo sounder.
sounder.
Thunder Bay which is partly silled to
to the
the south
south by an
an
east—northeast trending horst from Victoria Island
east-northeast
Island to
to Spar
Spar
Island
basins. Recent sediments
sediments which
Island contains
contains three separate basins.
bay—floor grade from a thin
cover the bay-floor
thin veneer of
of sand,
sand, less
less than
than
centimeters thick,
thick, to
clay—silts, up to 14
33 centimeters
to aa sequence of clay-silts,
meters thick,
thick, in
in the
the central
central parts
parts of
of the
the basins.
basins. Tight foldfoldclay-silts in
in the
the deepest
deepest part
part of
of the
the central
central
ing of the Recent clay—silts
basin is probably caused
caused by
by gravity
gravity slumping.
slumping. Geochemical
investigations
the bottom-sediments
investigations of
of the
bottom—sediments show that there appears
to
towards negative Eh and low pH values in the
the
to be
be aa tendency
tendency towards
deep—water areas.
deep-water
areas. In the
the vicinity of the Kaministikwia Delta
anomalous Eh and pH measurements were recorded
recorded which were
were
anomolous
probably caused by industrial pollutants entering
entering the
the bay
bay from
from
the
the Kaministikwia River.
River.
overlie Pleistocene
Pleistocene
The Recent sediments unconformably overlie
varved sediments of undetermined thickness.
The
Recent clay—
thickness.
claythe Pleistocene varved sect±on
sectton each
each form
form aa
silt section and the
typical
thin upper
typical syndiagenetic sequence with a relatively thin
oxidized zone (initial
(initial stage)
stage) and
and aa lower
lower reduced
reduced zone
zone (early
(early
burial stage).
stage). The oxidized zone
zone is
is caused
caused by
by the
the dissolved
dissolved
oxygen in the
the trapped
trapped waters of
of the
the upper
upper layers
layers of
of sediment
sediment
and the
the action of
of aerobic
aerobic bacteria.
bacteria. The depletion of oxygen
results
results in the
the underlying reducing
reducing zone
zone with anaerobic
anaerobic
and aa sharp
sharp increase
increase in
in pH.
pH.
conditions and
�—52—
-52-
REFERENCES
Bissell, H.
H. J., 1959,
1959, Silica in sediments of
of the
the Upper
Upper
Paleozoic of the
the Cordilleran
Cordilleran area.
area. Spec.
Publ.
Spec. Pubi.
of Soc.
Soc. Econ.
Econ. Paleontologists and
of
and Nineralogists,
Mineralogists,
7, pp 150—185.
7,
150-185.
Dapples, E.
E. C., 1962,
1962, Stage of diagenesis in
in the
the developdevelopment of sandstones.
sandstones. Bull,
Bull, Ceol.
Soc.
Geol. Soc. Am.,
Am., 73,
73,
pp 913—934.
913-934.
pp
Emery,
Emery, K.
K. 0.
O. and
and Rittenberg
Rittenberg S.
S. C.,
C., 1952,
1952, Early diagenesis
of California Basin sediments in
in relation to
to origin
of oil.
Bull. Am.
Am. Assoc.
Assoc. Petrol.
oil. Bull.
Petrol. Geologists,
Geologists, 36,
36,
pp
735-806.
pp 735—806.
Larsen, C.
Larsen,
G. and
and Chilingar
Chilingar C.
G. V.,
V., 1967,
1967, Introduction.
Introduction. In
In
Diagenesis in
in sediments.
sediments. Univ.
Univ. of
of Southern
Southern
California, Los Angeles,
Angeles, pp
pp 1—17.
1-17.
W. H.,
H., 1942,
1942, The rate of deposition of
of sediments:
sediments:
Twenhofel, W.
a major factor connected with aiteration
alteration of
Jour. Sedimentary
sediments after deposition.
deposition. Jour.
12, pp
pp 99—110.
99-110.
Petrology, 12,
Changes produced by microC. E.,
E., 1942,
1942, Changes
ZoBell, C.
organisms in
in sediments
sediments after
after deposition.
deposition.
Sedimentary Petrology, 12,
12, pp
pp 127—136.
127-136.
Jour.
�—53—
-53-
REINVESTIGATIONOF
OF "RED
"RED ROCKS"
REINVESTIGATION
ROCKS" IN THE
THE
PIGIY)N POINT AREA,
PIGEON
AREA, MINNESOTA
MINNESOTA
C. M::drey,
Jr., and
and P.
P. W.
W. Weiblen
Weiblen
M. G.
Mudrey, Jr.,
Minnesota Geological Survey
Survey
and
University of Minnesota, Minneapolis
ABSTRACT
ABSTRACT
Keweenawan granitic rocks
rocks of reddish
reddish color
color as
as exemplified
exemplified
by the "red rocks"
rocks" of the
the Pigeon Point, Cook
Cook County,
County, area
area are
are
divisible into red quartzites,
quartzites, porphyritic red
red rocks
rocks and
and granular
granular
with this
this division
division reduces the problem
red rocks.
rocks. Retnapping
Remapping with
problem of
of
excess granophyre abundance associated with the
the Pigeon
Pigeon Point
Point sill.
sill.
Reddish quartzites
quartzites contain abundant recrystallized quartz
Reddish
quartz
iicrstitial sericite—biotite
feldspar—
with minor
minor interstitial
sericite-biotite and granophyric feldsparquartz intergrowths.
A
faint foliation
A faint
foliationdefined
defined by
by biotite
biotitelinea—
lineation and
tion
quartzite inclusions
inclusions
and relict
relict bedding
bedding can be discerned in quartzite
found in intermediate rock
rock of dioritic
dioritic composition.
composition.
Porphyritic red rock displays euhedral feldspar
feldspar phenocrysts
in a granophyric quartz—feldspar
quartz-feldspar groundmass.
groundmass. This rock type cuts
Miaro—
the Pigeon Point gabbro. Miarothe Rove formation and
and intrudes the
litic cavities
are
found
filled
with
calcite
and
zeolite
minerals.
cavities
zeolite
Granular
and feldspar
feldspar
Granular red rock contains granoblastic quartz and
tic groundmass
groundinassof
of quartz
quartz and
and feldspar
feldspar with
with minor
set in a granophy
granophyric
minor
sericite-biotite
and epidote.
epidote.
sericite—biotite and
and rounded grains or sphene and
Phase relations
relations and overgrowths on quartz suggest
suggest that
that aa
sedimentary parentage is
is possible,
possible, however intrusive
intrusive relations
relations on
on
Pigeon Point require that the granular red rocks
rocks must
must have
have been
been a
crystal mush.
Point area
area in
in excess
excess
The abundance of red rock in the Pigeon Point
of
that
to
be
expected
by
differentiation
has
been
noted
since
of that
since
1893,
the eastern
eastern exposures
exposures of
of
1893, and is
is part of a reinvestigation of the
Keweenawan rocks
rocks in
in Minnesota.
�—54—
-54-
THE SEDIMENTOLOGY AND TECTONIC SIGNIFICANCE
THE
SIGNIFICANCE OF
OF THE
THE
BAYFIELD GROUP,
GROUP ~ WISCONSIN
HISCONSIN AND MINNESOTA
MINNESOTA
Wallace Darwin
Darwin Myers,
Myers~ II
II
University of Wisccnsin
Wisconsin
ABSTRACT
ABSTRACT
A study of the mineralogical and
A
and physical
physical characteristics
characteristics of
of the
the
Bayfield Group was made to determine 1)
1) depositional
depositional environment,
environment,
paleogeography, and source terrane
paleogeography,
terrane during
during Bayfield
Bayfield time,
time, 2)
2) the
the
of the
nature of
the contact
contact of
ofthe
theBayfield
BayfieldGroup
Group with
with the
the older
olderOronto
Oronto
Group,
Group, and
and 3)
3) the early
of the
the Douglas
Douglas fault.
early history of
fault.
study included
included detailed
detailedmapping
mapping of
of Bayfield
Bayfieldand
andOronto
Oronto
Field study
Group rocks
outcrops, the lithology
lithology
Group
rockstotoestablish
establishthe
thelocation
locationofof all
all outcrops,
and
stratigraphy of
of all
stratigraphic
and stratigraphy
all formations,
formations, the
the geographic
geographic and
and stratigraphic
distribution
distribution of
of sedimentary structures and the
the structural relationships
relationships
between rock
rock bodies.
bodies. Analyses of rock
rock specimens
specimens in
in the
the laboratory
laboratory
included 1)
1) petrographic study of the
the bulk
bulk mineralogy
mineralogy and
and textural
textural
characteristics of sandstone specimens, 2)
2) x—ray
x-ray diffraction
diffraction study
study of
of the
the
clay mineralogy of shale beds and
and chemical
chemical analyses
analyses of
of the
the boron
boron conconcentration of the clay mineral illite, 3)
3) x—radiography
x-radiography study
study of
of the
the
sedimentary structures,
structures~ and
and 4)
4)
internal stratification of selected sedimentary
statistical study of directional sedimentary structures.
structures.
Petrographic studies of Bayfield
Bayfield Group
Group sandstones
sandstones indicate
indicate that
that
constitutes approximately
approximately 80
80 percent
percent of
of framework
framework grains,
grains, that
that
quartz constitutes
the
feldspar population is dominated
dominated by microcline,
microcline, and
and that
that Bayfield
Bayfield
the feldspar
Group sandstones
sand·stones are
are better
better sorted
sorted and
and exhibit
exhibit aa higher
higher degree
degree of
of
rounding than
than the
the Freda
Freda Sandstone of the
the Oronto
Oronto Group.
Group.
The
high compositional
compositional and
and textural
textural maturity
The high
maturity of
ofthe
theBayfield
BayfieldGroup
Group
suggests that
that the
suggests
the source
source area
area for
forthese
thesesediments
sediments was
was not
not aa simple
simple
volcanic terrane. Petrographic
Petrographic data
that the
the Bayfield
Bayfield and
and
volcanic
data indicate
indicate that
Freda
possibly recycling of
of the
the Freda
Freda
Freda sandstones
sandstoneshad
hada asimilar
similar source;
source; possibly
Sandstone was an
an important
important source
source of
of sediments
sediments during
during Bayfield
Bayfield time.
time.
The
Tl~ sedimentary structures of the
the Bayfield Group are those which
are typically developed in fluvial
are
fluvial environments,
environments~ including
including trough
trough cross—
crossbedding, current ripple marks,
sandstones, mudcracks,
bedding,
marks, channel sandstones,
mudcracks, and
associated structures.
structures. The stratification and bed forms
forms of the
the Bayfield
Group are
Group
are characteristic of those
those formed
formed in
in the
the upper
upper part
part of
of the
the lower—
lowerwith modern alluvial
(Harms and
and Fahnestock,
Fahnestock, 1965).
1965). By analogy ,.,ith
alluvial
flow regime (Harms
channels
channels the
the general geologic setting of
of the
the Bayfield
Bayfield Group
Group can
can be
be
inferred to
to have been an alluvial plain
plain characterized
characterized by
by loz—gradient,
100.,-gradient,
perennial streams.
streams. The strong N40°E
N400E trend
trend of
of trough
trough cross—
crossmeandering, perennial
bedding indicates
was from the
indicates the
the direction of sedimentary transport
transport was
the
southwest to the
the northeast. This inference is
is supported
supported by the
the orientation
tion of parting lineation and
and current
current ripple
ripple marks.
marks.
�—55—
-55-
the Bayfield and
and Oronto
Oronto Groups
Groups is
is not
not exposed;
exposed;
The contact of the
petrographic data provide~he
provide the clearest evidence of the
petrographic
the nature of
of this
this
boundary. On the
the basis of the
the high compositional
compositional and
and textural
textural maturity
maturity
boundary.
Group sandstones,
exhibited by Bayfield Group
sandstones, it
it is
is suggested
suggested that
that these
these
elastics represent
represent a new cycle of sedimentation in
clastics
in the
the synclinal
synclinal Lake
Lake
This
interpretation
is
supported
by
the
contrasting
Superior basin.
basin. This
supported
the contrasting
clay mineralogy
mineralogy of the two sequences (illite—
clay
(illite- and
and chlorite—rich
chlorite-rich Oronto
Oronto
rocks, but kaolin—rich
rocks,
kaolin-rich Bayfield
Bayfield rocks).
rocks).
compelling evidence
evidence that:the
that: the Douglas
Douglas fault
fault was
was active
active
There is no compelling
during Bayfield time.
time. Conglomerates are
are known
known at
at only
nittytwo
two exposures
exposures of
the Douglas
Douglas fault,
the
fault, and in each case their
their distribution
distribution is
is restricted
restricted to
to
the zone immediately adjacent
the
adjacent to
to the
the fault.
fault. Furthermore,
Furthermore, the conglomconglomerates do
do not
not resemble true tectonic conglomerates either
erates
either texturally
texturally or
or
compositionally. Additional evidence is provided by the
the orientation
orientation
of directional sedimentary structures
structures at
at the
the Douglas
Douglas fault
fault localities.
localities.
These structures
which include
include parting
parting lineation and
and cross-bedding,
cross—bedding, show
show
structures which
no apparent relation to
the
Douglas
fault.
to the
fault. Thus,
Thus, there is no geologic
evidence of major faulting
faulting during
during Bayfield,
Bayfield, or
or at
at least
least Orienta,
Orienta, time.
time.
�—f
LAKE
LAKE MICHIGAN
MICHIGAN AEROMAGNETIC
AEROMAGNETIC SURVEY
SURVEY
by
W. O'Hara
Norbert W.
Great Lakes Research Division
University of Michigan
Arbor, Mi
Michigan
Ann Arbor,
chigan
William J.
J. Hinze
Hinze
Department of Geology
Michigan State University
East Lansing,
Lansing, Michigan
Michigan
E;t
ABSTRACT
A B S T R ACT
The Precambrian
Precambrian basement
basement complex
complex beneath
beneath Lake
Lake Michigan,
Michigan, which
which lies
lies
on the western
western and
and northern
northern flank
flankofofthe
thePaleozoic
PaleozoicMichig.E.n
Michigan Basin,
Basin, is
is
only known from a few widely scattered
basement
drill
holes
around
the
scattered
drill holes around the
perimeter of
of the Lake and
and aa single
single drill
drill hole
hole -ithin
within the Lake
Lake on
on 3eaver
Beaver
Nevertheless, the basement
geologyof
of Lake
LakeMichigan
MichiganisissignifisignifiIsland. Nevertheless,
basement geology
cant
frameworkofofthe
theMidcontinent
Midcontinentandand
critical to
cant to the
the Precambrian
Precambrian framework
is iscritical
to
the extrapolation
extrapolation of
ofbasement
basement structural
structural trends
trendsfrom
from Lake
Lake Superior,
Superior, orth—
Northinto the
fill this
ern Michigan,
and Wisconsin into
theMichigan
Michigan Basin.
Basin. To
To fill
thisgap
gap an
an
em
Michigan, and
aeromagneticsurvey
surveyconsisting
consistingof
of 7,000
7,000 miles
miles of
of total
aeromagnetic
total magnetic
magnetic intensity
were collected along flight traverses separated
data were
separated by
by six
six mile
mile intervals.
intervals.
traverses were
were flown
flown over
over northern
northern Lake
Lake Michigan in aa general northFlight traverses
east direction and over southern Lake
Lake Michigan in
in aa northwest
northwest direction.
direction.
The residual total magnetic intensity map
map prepared from
from the
the collected
To general the magnetic
data exhibits three regional
regional magnetic
magnetic positives.
positives. In
anomalies are related in
in aa direct
direct manner
manner to
to gravity
gravity anomalies
anomalies on
on the
the periperimeter of the Lake.
Lake. The
strikes northwest
northwest from
from the
the
The southernmost
southernmost positive
postive :rikes
Michigan shore from
from +2°
42 0 to 13°
43 0 30'N.
30'N. This anomaly is associated with aa
positive and
and local
local magnetic
magnetic positives
positives extend—
extendsoutheast striking gravity positive
icLg
across southwestern
southwestern Michigan
Michigan and northeastern
ing across
northeastern Indiana
Indiana into
into Ohio.
Ohio. It
It
is
gravity and
and magnetic
magnetic anomaly
anomaly in
in northeastern
northeastern
is on strike with the positive gravity
Indiana which has been found
found by basement
basement drilling
drilling to
to be
be underlain
underlain by
by basalts
basalts
similar to Keweenawan flows
flows of
of the Lake
Lake Superior
Superior region.
region. The central
central regional
positive, which is made up of several individual anomalies,
roughly easteast—
anomalies, strikes
strikes roughly
450
0
0
t140
The
northern
components
west across ·the
Lake
between
44
and
45
15'N.
The
northern
components
of
the
l5'N.
this anomaly can be traced into
into Wisconsin and
and across
across the southern
southern Peninsula
Peninsula
this
of Lchigan
except
where
they
are
transected
by
the
Mid—Michigan
rift
Michigan except where they are transected by the Mid-Michigan rift zone.
zone.
trends are believed to be assrciated
with the
the Penokean basement
basement provprovThese trends
associated with
ince. A
A marked regional magnetic anomaly minimum striking east-west
east—west occurs
occurs
to the north of the regional
regional positive.
positive. The anomaly is on
on strike
strike with the
the
felsic
felsic rocks of the Mountain—Amberg
Mountain-Amberg area
area of
of Wisconsin
Wisconsin which
which is
is also
also charcharacterized by magnetic
magnetic minimums.
minimums. The minimum reappears
reappears east
east of
of the
the Mid—Michi—
Mid-Michigan rift
rift zone anomaly and
and strikes
strikes east—southeast
east-southeast across
across to
to Lake
Lake Huron.
Huron. The
The
northern regional positive magnetic anomaly
anomaly strikes
strikes north—south
north-south from
from Traverse
Traverse
where it
it bifurcates
bifurcates with
with one
one limb
limb extending
extending
Bay to north of Beaver Island where
north—northwest through Lake
north-northwest
Lake Superior
Superiortotothethe
Keweenawanbaa
basalts
Keweenaw
Keweenawan
alts ononKeweenaw
Point. The other limb
the eastern
eastern portion of
of the
the Northern
Northern
Point.
limb continues
continues into the
Peninsula of Michigan and another
another segment
segment of
of this
this branch
branch connects
connects to
to the
the
Keweenawan flows
on
Mamainse
Point.
flows on Mamainse Point. In the
the Traverse Bay area the regional
connects to the
positive becomes
becomes strongly negative and connects
the south with the
the midmid—
Michigan gravity and
and magnetic
magnetic anomaly.
anomaly.
�-57—57—
GEOCHRONOLOGY
OF THE GIANTS RANGE GRANITE
L.
A. PRINCE
FRECE AND
L. A.
AND G.
G. N.
N. HANSON
HANSON
State University of New York
Stony Brook, N.
N. Y.
Y. 11790
ABSTRACT
A B S T R ACT
Seven whole rock samples of two—mica,
two-mica, foliated
foliated quartz
~uartz
monzonites
monzonites from the central part of the Giants Range Granite,
Granite,
north of Hibbing,
Hibbing, Minnesota, give aa Rb—Sr
Rb-Sr isochron
isochron age
age of
of 2670
2670
1) and a 3r87/Sr86
± 65 m.y. (Rb
(Rb 87
x 10yr _1)
Sr 87 /Sr 86 initial
initial
87 AS
A == 1.39 x
i0'11 yr
ratio
ratio of 0.7002 ± 0.0019
0.0019 at
at the 95% confidence level.
level. Epidote,
plagioclase, potassium feldspar,
biotite—chiorite, apatite
plagioclase,
feldspar, biotite-chlorite,
apatite and
and
muscovite
separates
from
one
of
these
whole
rock
samples
give
muscovite separates
samples give mineral
—whole
rock
ages
ranging
from
2350
m.y.
for
epidote
-whole
ages ranging from 2350 m.y. for epidotetoto26140
2640 m.y.
m.y.
for muscovite.
mineral—whole rock ages
muscovite. The lowered mineral-whole
ages suggest
suggest that
at least
least one event
event occurred after intrusion of the granite,
at
granite, but that
that
the individual mineral phases
the
phases were not completely homogenized
homogenized with
Sr 87 /Sr 86 ratios.
ratios. The 2350 m.y.
epidote-rock
respect to their 5r87/5r86
m.y. epidote—rock
age
age probably is
is a maximum for the time of the last
last event.
event. The
mineral data provide no conclusive evidence for
for the sequence
se~uence of
of
events after intrus
on, but are not inconsistent
events
intrusion,
inconsistent with aa regional
regional
low-grade
low—grade metamorphism at around 1600 m.y.
This
is in agreement with U—Pb
U-Pb data
data on
on sphene
sphene
This whole rock age is
Giants Range Granite which suggest
suggest an
an age
age of
of
and zircon from the Giants
2700
for hornblende from
from the
the Giants
Giants
2100 m.y.
n.y. and also with K-Ar
K—Ar ages for
Range Granite which generally
generally are
are 2600—2100
2600-2700 m.y.
m.y. These ages
ages
however
are older than most of the Rb—Sr
Rb-Sr and
and K—Ar
K-Ar ages
ages for
for biotite
biotite
however are
which range from 2260—2630
2280-2630 m.y.
m.y. The age of the post-kinematic
post—kinematic
Linden
Linden Syenite
Syenite just
just to
to the
the north
north also
also limits
limits the
the age
ae of the syn—
syn?b207_Pb2u6 data on sphene
to late—kinematic
late-kinematic Giants
Giants Range
Range Granite.
Granite. Pb207_Pb206
sphene
and aa Rb-Sr
b—Sr mineral—whole
mineral-whole rock
rock isochron
isochron with
with an
an initial
initial ratio
ratio of
0.7009£-0.0004 suggest an age for the Linden Syenite
Syenite of
of about
about
0.1009±O.000b
2700
m.y.
2100 m.y.
87 /Sr 86 initial
The low Sr
initial ratios from
from both the
the Linden
Linden Syenite
Syenite
Sr87/5r86
and the
the Giants
Giants Range Granite suggest
suggest aa source
source with aa low
low Rb/Sr
Rb/Sr
and
ratio, perhaps
mantle, and
and it is
is unlikely that appreciable
appreciable
ratio,
perhaps the mantle,
mixing with preexisting continental crust
crust took place.
place.
�—58—
-58-
THE GREAT
GREAT LOGAN PALEOHAGNETIC
PALEOMAGNETIC LOOP —- THE POLAR
THE
WANDERING PATH FROM
FRaN CANADIAN SHIELD ROCKS
ROCKS DURING
DURING THE
THE HELIKIAN
HELIKIAN ERA
ERA
by
W. A.
W.
A. Robertson
}{obertson
Geomagnetic Laboratory
Energy,Mines
Energy,I'Iines &
& Resources
Resources
Ottawa,
Ottawa, Ontario
w. F. Fahrig
H.
Geological Survey of Canada
Ottawa, Ontario
Ottavla,
ABSTRACT
ABSTRACT
Normally magnetized dykes
dykes and reversely
reversely magnetized sills
sills of
of
Neohelikian age
age near the
the north west
take Superior
Superior form
form
west shore of Lake
two distinct
distinct paleomagnetic groups
groups with mean pole positions of
two
179W, 35N,
179\\1,
35N, and 140W, 47N
47i'J respectively.
respectively. Thermal and
and alternating
alternating
field
field paleomagnetic studies
studies and
and the study of magnetic properties
and opaque
opaque minerals
minerals indicate that
and
that directions
directions of magnetization of
of
these
rocks were acquired at
at the
the time
time of
of their
their intrusion.
intrusion. Field
these rocks
evidence indicates
indicates that
evidence
that the
the reversely magnetized sills are older
than the
normally magnetized
magnetized dykes
than
the normally
dykes and radiogenic age determinations
indicate intrusion between 1000
1000 and
and 1100
1100 m.y.
m.y. ago.
ago.
These pole
pole positions,
positions, together with those for the
These
the Franklin
Franklin
intrusions pole
pole at
at l67E-08N,
167E—08N, assigned age 675
m.y., the
intrusions
675 m.y.,
the Abitibi
dykes,
the NacKenzie
MacKenzie
dykes, at
at 134W.
134W, 27N,
27N, assigned aged 1150 m.y.
m.y. and the
Igneous events, at
Igneous
at 171W,
l71W, 4N,
4N, assigned
assigned age
age 1200
1200 iu.y.
m.y. are
are used
used to
to
define Logan's Loop,
the pole
pole took
took in
in Neohelikian
Neohelikian
define
Loop, the
the path
path that.
that the
time
to the Canadian Shield.
Shield. Other poles well defined
defined
time relative to
magnetically, but less well dated,
magnetically,
dated, from
from rocks
rocks of
of this
this era
era fit
fit
the curve quite well.
the
of available
that the
available data
data supports
supports the
the hypothesis
hypothesis that
the
Analysis of
relative
polarmovement
movement that
gave rise
Logan's Loop
Loop was
was prerelative polar
that gave
rise totoLogan's
preceded
and followed
follmved by
vis a vis
ceded and
by polar stability vis
vis North America,
quite rapid
rapid during
during the
the forforwhereas polar movement may have been quite
The depositional environment of Neohelikian
the loop.
loop. The
Neohelikian
mation of the
rocks of
the Canadian Shield should be tested
tested against
against their
their
rocks
of the
probable paleolatitude as
probable
as indicated by the
the 5 key points on Logan's
Logan's
Loop.
�—59—
-59-
CHARACTERISTICS
CHARACTERISTICS OF SOME
SOME ALTERATION MINERALS,
MINERALS,
PORTAGE
FJRTAGE LAKE
LAKE LAVA
LAVA SERIES,
SERIES, MICHIGAN
MICHIGAN
A.
A. P.
p.RUOTSALA
RUOTSALA
Michigan
Technological University
Michigan Technological
ABSTRACT
Many
silicate, carbonate,
Many silicate,
carbonate, and
and oxide
oxide minerals
minerals are
are associated
associatedwith
with
copper mineralization
mineralization in
the Portage
Series and
copper
in the
Portage Lake
Lake Lava
Lava Series
and associated
associated
conglomerates.
complete listing
listing was
was published
published by Butler and
and Burbank'.
Burbank l •
conglomerates. AA complete
Amygdule
studied by
Amygdulezoning
zoningpatterns
patterns associated
associated with
with mineralization
mineralization were studied
2
Stoiber and
and x-ray
x-ray diffraction
Stoiber
and Davidson
Davidson .. Chemical and
diffraction studies
studies are
are being
being
carried out
out at
atMichigan
Michigan Technological
Technological University on
on a continuing
continuing basis.
carried
basis.
In the
the past
-'n,
In
past some
some of
of these
these studies
studies were
weresupported
supportedby
bythe
theCalurnet
Calumet Divisi
Divisi:::n,
Universal
Universal Oil
Oil Products
Products Company.
Company.
Epidote isis characterized
characterized by
Epidote
by wide
wide ranges
ranges in
in unit
unit cell
cell dimensions.
dimensions. In
general,
general, epidotes
epidotes from
from amygdaloids
amygdaloids have
have larger
larger unit
unit cell
cellvolumes
volumes than
than those
those
from conglomerates.
congloITlerates.
Calcites
wide ranges
ranges inin trace
trace element
composition, especially
especiaiy
Calcites show
show wide
eleITlent cOlnposition,
in
Mg, and
and Mn.
Mn. There
is a
a positive
positive correlation
correlation bebeThere is
in concentration3
concentratiois of Fe,
Fe, Mg,
tween
Mncontent
contentand
andcopper
copperITlineralization
mineralizationininthe
theKearsarge
Kearsargeamygdaloid,
amygaloid, and
tween Mn
and
therefore
is potentially
potentially useful
useful as
as an
an exploration
exploration tool
therefore is
tool in
in the
the district.
district. 3
in many
ITlany forms
and at virtually every
every stage
sh.ge of
of the
the
Chlorite occurs in
forms and
sequence in
alteration sequence
in the
the district.
district. An
An interesting
interesting occurrence
occurrence is
is as an
essentially pure
essentially
pure clay
clay mineral
ITlineral in
inthe
the fault
faultgouge
gouge in
in the
the Allouez
Allouez Gap
Gap Fault
Fault
This is
and
of the
the Kingston
Kingston Mine4.
Mine~. This
is one
one of
of the
the few,
few, if
if not
not
and hanging
hanging wall
wall slip of
the
the only
only occurrence
occurrence of
of pure
pure clay
clay chlorite
chloriteknown,
known. It
essentially of
of
It consists
consists essentially
In ITluch
much of
ofthe
thehanging
hangingwall
wallslip,
slip, chlorite
chlorite is
is intimately
the type Ub
lIb polytype5.
polytype 5 . In
intiITlately
absorption properties
(plastic and
and liquid
liquid
mixed with hematite. The
The water
water absorption
properties (plastic
liITlits)
greaterfor
for chlorite-hematite
chlorite-heITlatite mixtures
mixtures than
than for
for pure
pure chlorites,
chlorites,
limits) are;
are greater
suggesting the
the pas
possibility
of SOITle
some ITlixed
mixed layering
layering of
of chlorite
chlorite and
suggesting
sibility of
and hematite.
heITlatite.
References Cited
Cited
1.
Butler,
Butler, B.
B. S.,
S.,and
andW.
W.S.S.Burbank
Burbank(1929)
(1929) The
The copper
copper deposits
deposits of
of
U. S. Geol.
Geol. Surve.,
Surve., Prof.
Prof. Paper
Paper144,
144, 238
238 pp.
pp.
Michigan. U.S.
2.
Stoiber,
R. E.
E.and
andE.E.S.S.Davidson
Davidson(1959)
(1959)Amygdule
AITlygdule mineral
mineral zoning
zoning in
Stoiber, R.
the Portage
the
Port age Lake
Lake Lava
Lava Series,
Series, Michigan.
Michigan. Econ.
Econ. Geo!.
v. 54,
Geo. v.
1444-1460,
p.
1250-1277 and p. 1444-1460.
p. 1250-1277
�-60—60—
3.
Ruotsala,
P., S.
S.C.
C.Nordeng,
Nordeng,and
andR.
R. 3.J.Weege
Weege(1968)
(1968) Trace
Ruotsala, A.
A. P.,
Trace
elements
the
elements in
in accessory
accessory calcite -- aa potential exploration tool in the
Michigan
Copper District.
District. Cob.
of Mines
MinesQuart.,
Quart., Jour.,
Jour.,
Michigan Copper
Colo. School
School of
(International Geochemical Exploration
v. 64,
64, p.
p. 451-455.
451-455. (International
v.
Symposium)
4.
Ruotsala,
Ruotsala, A.
A. P.
P. (1968)
(1968) Clay
Clay alteration
alteration associated
associated with
with mineralization
mineralization
Clays and
and Clay
ClayMin.,
Mm., v.
in
Michigan Copper
v. 16,
16,
in the Michigan
Copper District.
District. Clays
p.
400-402.
p. 400-402.
5.
Brown, B.
Brown,
B. E.,,
E., and
and S.
S. W.
W. Bailey
Bailey(1962)
(1962) Chlorite
Chlorite polytypism.
polytypism.
Am.
,v. 47,
Am. Mineral.
Mineral.,v.
47, p.
p. 819-850.
819-850.
�—61—
-61-
THE
THE GENERAL
GENERAL STRATIGRAPHY
STRATIGRAPHY OF
OF THUNDER
THUNDER BAY,
BAY,
LAKE
LAKE SUPERIOR
SUPERIOR
R. J.
J. Shegelski
LAKE-lEAD UNIVERSITY
LAKEHEAD
ABSTRACT
A B S T R ACT
Petrographic studies of the sediments taken from
from Thunder Bay
Bay
combined with x-ray diffractometer analysis have indicated
indicated distinct
lithologic types
in the
the bottom sediments
sediments of
of Thunder
Thunder Bay.
Bay. Stratitypes in
graphic correlation
correlation of
of thc
the bottom
bottom sediments
sediments from
from Thunder
Thunder Bay
Bay has
has
the aid
aid of
of echo
echo sounding
sounding traces.
traces. These traces
been developed with the
boundaries, nature and thickness
indicate the boundaries,
thickness of the various litholithofacies.
facies.
The sediments in
in Thunder
Thunder Bay
Bay can
can be
be divided
divided into
into five
five categories;
categories;
(1)
(2) Weathered
Weathered Varved Clay,
(1) Varved Clay,
Clay, (2)
Clay, (3)
(3) Intermediate
Intermediate Clay,
Clay,
(4) Upper
Upper Deltaic Sediment,
Sediment, (5)
Sediment. The Varved
(4)
(5) Upper
Upper Trough Sediment.
Clay is
overlain
is of Post
Post Valders
Valders glacial
glacial origin
origin and
and is
is disconformably
discoi:fom*Lj overlain
by the Weathered and Intermediate
Intermediate Clays.
Clays. The latter are
are products
products
of weathering of
of the
the older
older Varved
Varved Clay.
Clay. The Intermediate Clay is
conformably overlain
overlain by
by Upper
Upper Deltaic
Deltaic and
and Upper
Upper Trough
Trough Sediment.
Sediment •
conformably
The
.T
he latter units are sediments
sediments derived
derived dominantly
dominantly from
from the
the Kaministikwia
Kaministikwia
River.
River. Thin
Thin iron
iron and
and manganese
manganese beds
beds are
are formed
formed through
through diagenetic
diagenetic
solution, upward migration,
migration, and precipitation at
solution,
at a chemical
chemical interface
interface
in the Upper Sediments.
Sediments.
�—62—
-62-
CHERT
IN SEDIMENTS
SEDIMENTS
by
G.
G. Spencer
Spencer
Duluth, Minnesota
A B S T R ACT
ABSTRACT
silica solution
solution becomes
becomes supersuperAmorphous silica is produced when aa silica
some silicates
silicates are
are dissolved
dissolved
saturated and a precipitate forms or when some
in acids.
In
the silica is
is in a colloidal form and remains
remains
In either case
case the
so for long periods of
of time.
time. Eventually crystallization begins,
begins, and
heating the substance can speed up the
the process to
to aa great
great extent.
extent. In
In
natural conditions
conditions opal
opal is
is the
the first
first step
step followed
followed by
by chalcedony
chalcedony and
and
finally cristobalite. All of these
finally
these forms
forms of silica
silica have
have been
been termed
termed
chert.
Chert has·long
has long been regarded as a chemical precipitate.
Chert
precipitate. This
is sufficient to
to explain
explain hot
hot spring
spring deposits
deposits and
and hydrothermally
hydrothermally
view is
deposited chert or opal
opal near
near the
the surface.
surface. Cooling volcanic waters
become supersaturated with silica
silica in
in solution
solution and
and amorphous
amorphous is
is deposited
deposited
as
as a sinter or in
in thin
thin layers.
layers.
There are,
are, however, many other
other environments
environments in
in which
which chert
chert is
is found
found
such as:
as:
a)
a)
b)
c)
c)
d)
d)
e)
e)
f)
f)
g)
black slate with chert lenses or beds
limestones
limestones with chert nodules or joint
joint fillings
fillings
bedded cherts
containing
sponge
spicules
cherts
spicules or Radiolaria
Radiolaria
chert stringers
in oxidized sulphides
sulphides
chert
stringers and crusts in
fillings of vesicles in
in lava
lava flows
flows
agate fillings
oxide granules
chert
chert as
as a
a matrix for iron oxide
opal or chert
chert replacing organic matter
The author
author ascribes chert to
to the
the decomposition
decomposition of
of clays,
clays, detrital
detrital
In acid environsilicates,
ash or sand grains in
in carbonates.
carbonates. In
silicates, volcanic ash
ments alumina
alumina and
and alkalies
alkalies are
are removed
removed and
and aa silica
silica gel
gel is
is left.
left. In
alkaline waters
waters silica is dissolved and
and is deposited
deposited in
in aa more
more neutral
neutral
zone or will replace a dissolving particle such
such as
as organic
organic matter.
matter. The
relative solubility
solubility of
of alumina and
alkalies compared to
relative
and alkalies
to silica is
is the
the
determining factor.
factor.
iturata
(1946) investigated
investigated many
many silicates
silicates ,vhich
which produced gels when
i'lurata (1946)
\<Then
treated
with acid. He
alumina ratio
ratio of 1:1 or
or
treated with
Hefound
foundthat
that aa silica
silica totoalumina
2:3 was
Other silicates
silicates prpduced
was conmion
common toto gel
forming silicates. Other
produced silica
gel forming
particles larger than
than colloidal size or were not
not affected
affected by
by acids.
acids. Any
particles
silicate structure from
from which alumina has
has been
been removed
removed is
is halfway
halfway along
along
to
chert.
to becoming chert.
In
and silicate iron formations
formations mixed with
,.,rith quartz,
quartz, minerals
In carbonate
carbonate and
become unstable when
when the
the temperature
temperature is
is raised
raised and
is removed from
from the
the
and CO,
CO. is
point
sediment. The ionization
ionization of
at whicli
,..d lich Doint
of \vater
water increases
increases up
up to
to 230°
23°CC at
silica both in
in quartz and silicates becomes
hecomes increasingly
incren3in~ly soluble.
soluble. Sand
grains
such as
as
grains in oolites
oolites might
might dissolve and secondary silicates such
�-63—63—
minnesotaite and
and stilpnonielone
stilpnomelone would appear.
appear. Chert in this
this case
case is
is
minnesotaite
clearly
clastics
clearly diagenetic
diagenetic and
and came
came from
from aa breakdown of original elastics
even if the
the original texture
texture remained
remained the
the same.
same.
formations would appear to
to be
be examples
examples of
of late
late
Precambrian iron formations
they would also contain
contain early
early diagenetic
diagenetic silica
silica
diagenetic chert although they
as well.
as
Silica
content is
these rocks because
Silica and
and iron
iron oxide content
is higher in these
of the
the loss
loss of carbon dioxide,
dioxide, water,
water, and small
small amounts
amounts of
of alkalies
alkalies in
in
solution.
�—64—
-64-
IMPLICATIONS OF CARBON ISOTOPE RATIO VARIATIONS IN
IN CARBONATES
CARBONATES
FROM THE BIWABIK
BIWABIK IRON FORMATION,
FORMATION, MINNESOTA
F. C.
C. Tan and E.
F.
E. C.
C. Perry, Jr.
Jr.
Minnesota Geological Survey
Survey
University of Minnesota
Minneapolis, Minnesota 55455
Minneapolis,
55455
ABSTRACT
A B S T R ACT
Carbon isotope ratios from carbonates of
of the
the Biwabik
Biwabik Iron—formation
Iron-formation
obtained from core samples of Mesabi Deep Drilling
Drilling Project
Project (Pfleider
(Pfleider and
and
others, 1968)
1968) show the following significant features.
others,
features.
13
(1) SC
SC13 values
values of
of carbonates
carbonates associated
associated with
with magnetite
magnetite from holes
holes
(1)
5 and 7 show a range of from —7
-7 to
to —19
-19 per nil
mil (relative
(relative to
to aa Cretaceous
Cretaceous
belemnite standard
standard calcite
calcite PDB)
PDB) in
in comparison
comparison with
with1he
he carbonates
carbonates from
from
is strongly correlated
the magnetite-free
(0 to
SC 13 is
the
magnetite—free horizons
horizons (0
to -7
—7 per
per mil).
mu).
with magnetite
magnetite content
content in
in hole
hole 7.
7.
13
(2)
The Gc
SC13 values
values of
of carbonates
carbonates from magnetite and non—magnetite
(2) The
non-magnetite
horizons
of
hole
2
with
one
exception,
do
not
show1ignificant
horizons of hole 2 with one exception, do not show1~ignificant difference
difference
range of from
in contrast with holes
holes 55 and
and 7.
7. They exhibit a SC
from —7
-7 to
to
—19 per
-19
per mU..
mil.
13
(3)
values do
do not
not show
show any
any significant
significant stratigraphic
stratigraphic
(3) The
The bC
C13 values
correlation
correlation with
with tlia
the percent iron.
iron.
(4)
between
(4) There
There appears
appears to
to be
be a correlation between
individual members of
of the
the Biwabik
Biwabik Iron—formation.
Iron-formation.
13
C1-3 values and the
~C
the
13 In explaining the observed correlation between magnetite and
and the
the
13
values based on our
SC
our preliminary
preliminary results,
results, we
we proposed
proposed (Perry
(Perry and
Tan, 1970) that
that aa diagenetic
diagenetic oxidation—reduction
oxidation-reduction reaction
reaction producing
producing
permitted exchange
exchange between
between organic
organic carbon
carbon and
and
magnetite from hematite permitted
carbonate carbon reservoirs:
reservoirs:
r 44FeO
bFeO
+CO
6 Fe 22033 +C
+ C(organic)~f----~~Fe 33044 +
CO 22
(organic)
(1)
(1)
12
13
C1202
Fec 0
C
0 + FeC3O3
2
3
(2)
(2)
<
12
13
cC1-3O
0 +
+ FeC2O3
Fec 0
2
3
recent detailed
detailed studies
studies have
have strengthenI~
strengthen our
Our recent
our previous
previous observaobservavalues (—18
tion on hole 7 but have found anomalously low SC
(-18 per
per nil)
mil)
tion
from
from the
the non-magnetite
non—magnetite horizons of hole 22 (Lower
(Lower Slaty
Slaty Unit).
Unit). These
anomalous values may be related
related to
to metamorphic
metamorphic reactions
reactions accompanying
accompanying
the intrusion of the
the
the Duluth Complex because hole 22 is
is located
located near
near
metamorphic zone
zone (1)
(1) of French
French (1968).
(1968).
C13 values
Our observation that
that there is a correlation between ~el3
and the
and
the individual members of the Biwabik Iron—formation
Iron-formation would suggest
suggest
l3 variations
that
SC1-3
variations are
are depositional
depositional or
or early
early diagenetic
diagenetic features
features
that the
the ee
and bear no relationship
relationship :o
~o the
the genesis
genesis of
of niagnetite
magnetite (model
(model above).
above). The
�-65—65—
l3
values may be explained by the
differences in IC13
bC
the variable
variable contributions
contributions
of organic carbon and oceanic bicarbonate to
of
to the
the depositional
depositional or
or
diagenetic environments.
environments.
13
SC13 values of
We are currently investigating the
theoC
of co—existing
co-existing
graphite-tarbonate
pairs
and
oxygen
isotope
fractionation
graphite-carbonate
fractionation between
between cocoquartz—magnetfte at various stratigraphic
existing quartz-magnetite
stratigraphic levels
levels of
of holes
holes 22
and 7 to
to see if they have different diagenetic
diagenetic or metamorphic
metamorphic histories.
histories.
Co—existing
quartz—carbonate oxygen isotope
Co-existing quartz-carbonate
isotope fractionation
fractionation In
in samples
samples
from hole 2 compared to that
that in
in holes 55 and
and 77 suggests
suggests that
that the
the post—
postdepositional history of these
these two
two areas
areas is
is indeed
indeed different.
different.
References
rrench, B.
B.
French,
M. , (1968) Progressive contact metamorphism of the
M.,
the Biwabik
Biwabik
Iron—formation, Mesabi
Mesabi Range,
Ninnesc:a, Minn.
Minn. Geol.
Iron-formation,
Range, Minnesota,
Geol. Surv.
Surv. Bull.
Bull. 45,
45,
Univ.
Univ. of Minn., Minneapolis.
Ninneapolis.
Tan, F.
Perry, E.
E. C.C.,
Jr., and Tan,
F. C.,
C., Significance of carbon
carbon isotope
isotope
Perry,
, Jr.,
variations in carbonates from
from the
the Biwabik
Biwabik Iron—formation,
Iron-formation, Minnesota.
Minnesota.
symposiumononthe
thegeology
geology and
and genesis
genesis of
International symposium
of Precambrian
Precambrian
iron/manganeseformation
formationand
andore
oredeposits,
deposits, Kiev,
Kiev, 1970
1970 (In
(In Press).
iron/manganese
Pfleider, E.
E. P.,
P.,Morey,
Morey, C.
G. B.,
B., and
and Bleifuss,
Bleifuss, F.
R. L.
L.
(1968) Mesabi deep
deep
drilling project,
project, progress report
repo~t no.
no. 1,
1, Minnesota
Ninnesota section,
section,AIME
AIME forty—
fortymeeting, Dniv.
Univ. of Ninn.,
Minn., Minneapolis.
Minneapolis.
first
first annual meeting,
�—66—
-66-
Oxygen isotopic studies of Early
Early Precambrian
Precambrian granitic
granitic and
and
metamorphic rocks from
from the
the western
western part
part of
of the
the
Giants Range batholith, Northeastern
Northeastern Minnesota
Minnesota
S. Viswanathan,
Viswanathan, E.C.
s.
E.C. Perry, Jr.,
Jr., and
and P.K.
P.K. Sims,
Sims,
Minnesota Geological
Survey,
University
of
Minnesota,
Geological Survey, University of Minnesota,
Minneapolis, Minnesota 55455
55455
ABSTRACT
A B S T R ACT
objectives: (1)
demonstrate that
that oxygen
oxygen
The paper has two main objectives:
(1) to
to demonstrate
isotope geochemistry is a valuable tool
tool in
in elucidating
elucidating granite
granite petrogenesis,
petrogenesis,
provided it is
is integrated
integrated with
with detailed
detailed field
field and
and laboratory
laboratory studies,
studies, and
and
(2) to
to give
give values
values for~(018/016)guartz
for f(O18/016)qrtz in
(2)
in the
the Early
Early Precambrian
Precambrian granitic
granitic
and metamorphic
metamorphic rocks,
which are rather scarce
and
rocks, data for wnich
scarce in
in the
the literature.
literature.
Geologic mapping of
of aa 500—square
500-square mile
mile area
area in
in the
the western
western part
part of
of the
the
2.1 b.y.
b.y. old Early Precambrian Giants Range batholith of
2.7
of northeastern
northeastern
Minnesota has revealed eleven
eleven distinct
distinct granitic
granitic phases
phases (Sims
(Sims and
and others,
others, 1970).
1970).
Field observations, petrography, petrochemistry,
petrochemistry, and
and trace
trace element
element
geochemistry suggest that
that five
five of
of the
the phases
phases are
are magmatic,
magmatic, four
four are
are metasomatic,
metasomatic,_
and two are anatectic.
anatectic.
r 18 16
The
~O
10 ratios of quartz separated from
from 28
28 rocks, relative
relative to
to
meIo'8/o'6
Standard Mean Ocean
are presented
presented in
in the
the accompanying table.
Ocean Water
Water (SNOW),
(SMOW)Jare
table.
The values are consistent with the
the postulated
postulated genetic
genetic grouping
grouping for
for the
the
Early Precambrian granitic succession.
succession. The following
following conclusions
conclusions can
can be
be
drawn from the
the data:
data:
(1)
Values of
of 9 to
to 10 permil are characteristic of relatively
(1) Values
relatively
uncontaminated, probable mantle—derived
uncontaminated,
mantle-derived granites
granites and
and granodiorites.
granodic~ites.
These
tharhave been reported for
are consistent with the
the S(O18/ol6quartz
~(018/016)quartz values
values that-have
granites, granodiorites,
granodiorites, and
and tonalites,
tonalites, which
which range
range from
from about
about
plutonic granites,
9 to
to about 11 permil (Taylor,
(Taylor, 1968,
1968, p.34).
p.34).
(2)
several special
special
(2) Values
Values greater
greater than 10 permil require one of several
explanations, such
such as:
as:
18
(a) syntexis of large amounts
amounts of
of 0018—rich
-rich country rocks
rocks
(a)
into a primitive or first—cycle
first-cycle granitic
granitic magma
magma
18
18
(b) co-mingling
co—mingling of an 0 -enriched
—enriched magma and a primitive
(b)
or first
first cycle granitic magma
18
(c)
of 0018_
sediments
(c) anatexis of
—rich
rich sediments
�—67—
-67-
18
(d)
potash metasomatisin
metasomatism of
of aO'8—rich
-rich sediments
sediments
(d) potash
(e)
recrystallization (treptomorphisin)
(treptomorphism) of
of
(e) simple recrystallization
relatively 018_
018—rich
clastic sediments such
such as
r ich elastic
arkoses and graywackes, which thereby
thereby assume
assume aa
granitic fabric and composition
(f) recrystallization
recrystallization of
of granites
granites under
under shearing and
(f)
aplogranites, accompanied by
crushing to produce aplogranites,
late—tectonic metasomatism in mobile zones
late-tectonic
(g) post-consolidation
post—consolidation eataclasis,
cataclasis, and
and other
other
(g)
episodes which
which facilitate
facilitate exchange
exchange
metamorphic episodes
origin and
granitic rocks
rocks of
of magmatic
magmatic origin
and
between granitic
between
through a pore—fluid
pore-fluid medium
medium
018_
O'8—rich
r ich country rocks through
(h) post-consolidation
(h)
post—consolidation endoblastesis/autometamorphism
endoblastesis/autometatOrphism
involving 018018—enriched
enr iched fluids
(i) processes such as
imbibition
(i)
as petroblastesis and imbibition
in which the
the participants are
are O'8—rich
018_r ich sediments
sediments
and 018-enriched
fluids
018—enriched fluids
(j) selective
(j)
selective exchange between granitic intrusions and
018_
host rocks
rocks
O'8—rich
r ich host
(k) tectonic
tectonic styles
styles of
of emplacement,
emplacement, whether
whether synkineinatic,
synkinematic,
(k)
post-kinematic or late—kinematic,
late-kinematic, and
and
post—kinematic
18
(1) early segregation of aO'8—depleted
-depleted minerals which
(1)
in O'8—enrichment
018- enr ichment in
in late
late granitic
granitic differentiates.
differentiates.
results in
(3)
in granitic rocks of anatectic origin
origin are nearly
nearly
(3) The
The values
values observed in
identical to
to those
those of
of their
their source
source rocks.
rocks. They are either low or high
such granitic
granitic rocks
rocks were
were formed
formed from
from O'8—poor
018_poor or
or
depending on whether such
OIS_rich
018_r ich sources, respectively.
respectively. The values will be grossly
grossly different
different only
only if:
if:
(i) the
the anatectic
anatectic melt
melt undergoes
undergoes subsequent differentiation,
differentiation, and (ii)
(i)
(ii) the
the
consolidated anatectic melt is subjected to
to later
later metasomatism
metasomatism (see
(see data
data
under "C"
"e" and "0
(2)", of
of table).
table).
"D (2)",
(4)
The main
main intrusive phases of
(4) The
of granites
granites and
and granodiorites
granodiorites of
of maginatic
magmatic
origin have values nearly identical
to
those
of
their
satellitic
phases
identical to those of their satellitic phases
(sve
(sve data under "A"
"A" of
of table).
table). Interestingly,
Interestingly, a value of 9.2
9.2 permil
permil was
obtained for
for a leucogranite (satellitic
(satellitic late—magmatic
late-magmatic differentiate)
differentiate) that
that
transgresses an 018—rich
Ol8_r ich metasedimentary host
host rock
rock having
having aa value
value of
of 12.4
12.4
transgresses
perinil.
permi!.
This result indicates
that there
indicates that
there was
was hardly
hardly any
any oxygen
oxygen communication
differentiate and
and its
its alB-rich
o8—rich
late-magmatic differentiate
between the satellitic late—maginatic
metasedimentary
metasedimentary host
host rock.
rock. This is
is in
in sharp
sharp contrast
contrast to
to the
the conclusion
conclusion of
of
Shieh and Taylor (1969,
(1969, p.353)
p.353) who report
report that:
that: "Samples
"Samples from
from tiny
tiny intrusive
intrusive
bodies and dikes and from the marginal portions
portions of
of most
most of
of the larger plutons
18 /0 16 ratios
igneous rocks
have unusually high 0
018/016
ratios relative to "normal"
"normal" igneous
rocks from
from
�—68—
-68-
the central portions of plutons. This is interpreted
interpreted to
to be the
the result
result
of large-scale
large—scale oxygen isotopic
essentially molten
of
isotopic exchange
exchange between
between essentially
molten igneous
igneous
rock and metasedimentary country
country rock,
rock, either
either through
through aa medium
medium of
of aqueous
aqueous
1I
fluids or
or by
by contamination
contamination with
with xenolithic
xenolithic blocks
blocks of
of country
country rock.
rock."
fluids
(5) The
The sequence: sedimentary
(5)
sedimentary parent
parent ——)'
-~ partially
partially granitized
sediment --~granitic
—>-granitic rock
progressive
sediment
rock of
of metasomatic
metasomatic origin
origin reflects a progressive
decrease in the 018/016
0 18 /0 16 ratio, and
and encompasses
encompasses only
only aa narrow
narrow range
range of
of
11 to 2 permil, and
(6) Global comparisons of oxygen isotopic
isotopic ratios
ratios from
from granitized
granitized
18 /0 16 ratios of the
sequences should not
not be attempted,
attempted, unless:
unless: Ci)
sequences
(i) the 0018/016
parent rocks of two widely separated
separated granitized
granitized sequences
sequences are
are comparable,
comparable,
and (ii)
their
geological
settings
are
nearly
identical.
(ii)
are nearly identical.
18 16
Problems involving a possible time—dependence
time-dependence of
of the
the 018/0
0 /0 16 ratios in
in
minerals from
from specific
specific rock—series,
rock-series, representing
representing the
the entire
entire geological
geological column,
column,
are under study by one
one of
of us
us (Per;y).
(PerJY).
Ref
e—ences cited
References
Shieh, Y.N.
Y.N. and H.P. Taylor,
Shieh,
Taylor, Jr.
Jr. (1969): Oxygen and hydrogen isotope
isotope studies
studies
in the
the Santa
Santa Rosa
Rosa Range,
Range, Nevada
Nevada and
and other
other areas:
areas:
of contact metamorphism
metamorphism in
Contr.
Mineral. and Petrol., v.20, p.306—356.
Contr. Mineral.
p.306-356.
Sims, P.R.
P.K. and
and others
others (1970):
(1970): Geologic
Geologic map
map of Minnesota, Ribbing
Hibbing Sheet
Sheet
Sims,
(scale 1:250,000):
1:250,000): Minn.
Minn. Geol.
Geol. Survey, University of
of Minnesota, Minneapolis.
Minneapolis.
Taylor,
H.P. Jr.
Taylor, H.P.
Jr. (1968):
(1968): The oxygen
oxygen isotope
isotope geochemistry
geochemistry of
of igneous
igneous rocks:
rocks:
Contr. Mineral.
p.1-71.
Contr.
Mineral. and Petrol., v.19, p.'—71.
Other useful References
Allison, 1.5.
I.S. (1925):
(1925): The
The Giants
Giants Range
Range batholith
batholith of
of Minnesota:
Minnesota: Jour.
Jour. Geology,
Geology,
v.33, p.488—508.
p.488-508.
v.33,
Goldich, S.S.
S.S. and others (1961):
(1961): The Precambrian
Precambrian geology
geology and
and geochronology
geochronology
of Minnesota; Minn.Geol.
Minn.Geol. Survey Bull.41, University
University of
of Minnesota,
Minnesota,
Minneapolis, p.62—65.
p.62-65.
�-69—69—
Table
.{'*
b(O
18
/0
16
ratios of
of quartz in Early Precambrian granitic
)SMOW
ratios
SNOW
and metamorphic
metamorphic rocks from the western part of the
and
the
Giants Range batholith
batholith of Northeastern Minnesota
Range
(perlil)
(perilil)
Average
(permil)
A. Rocks of magmatic origin:
origin:
(1) Granodiorites
Granodiorites (main
(1)
(main intrusive
intrusive
phase,
phase t two
two samples)
samples)
9.4 —- 9.9
(2) Leucogranodiorite
Leucogranodiorite (satellitic
(2)
(satellitic
phase of
of (1),
(1). one
one sample)
sample)
9.7
9.7
9.8
9.8
(3) Granites
Granites (main
(main intrusive phase,
phase t
(3)
two
two samples)
9.5
9.5 —-
9.6
9.6
(satellitic phase
phase
(4) Leucogranites (satellitic
of (3),
(3)t two
two samples)
samples)
9.2 —- 9.6
9.4
10.7 -— 11.4
10.9
10.9
B. Rocks
~~.Rocks
of metasomatic origin:
origin:
(1)
(five samples)
samples)
(1) Granites (five
10.2
(2) Aplogranite (one
(2)
(one sample)
sample)
(3) Partially granitized
(3)
volcanogenic metasediments
(three
samples)
(three samples)
10.4 —
10.4
- 12.5
11.1
11.1
9.2
9.2 —- 10.1
10.1
9.6
9.6
c.
C. Rocks of anatectic
anatectic origin:
origin:
(derivatives of relatively
relatively
alB_poor
source rocks)
rocks)
0'8—poor source
(1) Quartz tonalites (four
(four samples)
samples)
(1)
(2) K-feldspathized
K—f eldspathized tonalite
tonalite
(2)
(one sample)
12.1
12.1
D.
D. Parent volcanogenic metasediments
metasediments of:
of:
(1)
B (four
(four samples)
samples)
(1) Group
Group B
11.1 —
1l.1
- 12.9
12.2
�—70--70-
ZONED NATIVE
NATIVE COPPER
CrIEHICALLY
COPPER AND
A<\lD CHALCOCITE
CHALCOCITE FROM
FRaN
CHEMICALLY ZONED
WHITE PINE,
NICIIIGAN
WHITE
PINE, MIChIGAN
T. A.
A. Vogel
Geology Department
Michigan
~ichigan State
State University
University
East
East Lansing,
Lansing, Michigan
and
T.
T. J.
J. Rohrbacher
Staff Geologist
Staff
\'~ite
White Pine Copper Company
Pine, Michigan
\.Jhite
White Pine,
tHchigan
ABSTRACT
A B S T R ACT
A
the copper ore
are minerals at
at White
~.Jhite Pine,
A microprobe study of the
Hichigan,
has shown that
that zoned copper—mineral
copper-mineral grains occur in
in the
the
Michigan, has
This zoning is
ore-bearing
of the
the Nonesuch
Nonesuch Shale.
Shale. This
is developed
develofled
ore—bearing horizons of
in
the most
type of
in both
both chalcocite
chalcocite and
and native
native copper,
copper, and
and the
most prominent type
zoning is
zoning
is iron enrichment towards
to\vards the
the edge
edge of
of the
the grain.
grain. Some
chalcocite grains
grains are
are highly
highly zoned,
chalcocite
zoned, containing about
about four
four times
times as
as
as in
much iron
(at least
the edge of
of the
the grain
grain as
in the
the core.
core.
least 10%)
10%) on the
iron (at
Aluminum,
magnesium
siliconshaH
showthe
thesame
sametype
typeofof zoninf,
zoning, hut
Aluminum, magnesium
andand
silicon
hut
are
to a lesser extent.
are developed to
extent.
copper
grains are
also zoned
respect
to iron,
Many native
native
copper
grains
arewith
also
zoned
with respect to iron,
with
the edge
of the
iron
wi
th the
edge of
the grain
grain containing
containing about
about twice
t\<7ice as
as much
much iron
(about
1%)asas the
the core.
an enrichenrich(about 1%)
core. All zoned
zoned copper
copper minerals show
show an
ment
of iron
iron towards
of the
ment of
towards the
the edge
edge of
the grain;
grain;however,
ho\·7ever, both
both within
,·7ithin and
and
between
between samples,
samples, the
the amount
amountofofzonin~
zoningand
andthe
therelative
relative proportion
proportion
This variation
zoned to
unzoned grains
highly variable.
varia1)le. This
variation does
c:oes
of zoned
to unzoned
grainsisis highly
not appear
to be
be controlled
controlled by
by the
the major
majorlitholof,ic
lithologic variAtions
variations in
not
appear to
in
the ore
ore zone,
zone, but
but may be controlled
controlled by
uy subtle differences in lithology
or by
environmentrttat the
the time
variations in
by variations
chemical environment
time of
of
in the local chemical
deposition.
Any
Any j:lotlel
modelofof'1re
're Genesis
genesis must
must take
take into account
account the
the occurrence,
occurrence,
minerals.
distribution and
and type
distribution
type of
of zoning in
in these
these copper
copper minerals.
�—71—
-71-
STRATICRAPHY OF
KEWEENAWAN
KEI.vEENAWAN STRATIGRAPHY
OF WESTERNMOST
i-JESTERN}[OST MICHIGAN
HICHIGAN
W.
S. Wtite
W. S.
i-n1i te
U. S. Geological
u.
Survey
Agriculture Research Center
Center
Beltsville,
Naryland
Beltsville, Maryland
E. R.
R. Brooks
E.
Department of Earth and Physical Science
Science
California State
State College
College
Hayward, California
Hayward,
H.
3. A.
A. Hubbard
U. S.
S. Geological Survey
Survey
U.
Washington, D.C.
D.C.
Robert F.
Robert
F. Johnson
449 Boynton Avenue
Berkeley,
Berkeley, California
J. T.
J.
T. Wilband
iVilband
University of Toledo
Toledo
Uepartment
Department of Geology
Geology
Toledo, Ohio
ABSTRACT
A B S T R ACT
surveysprovide
provideaa skeletal
skeletal
Recent geologic
geologic and
and aeromagnetic
aeromagnetic surveys
fracieworkfor
forthroughgoing
throi:ghgoing
stratigraphiccorrelations
correlations of
framework
stratigraphic
of the
the
Keweenawan rocks
rocks of westernmost
westernmost Michigan.
Michigan. The stratigraphy of the
the
middle and upper Kel.".eenawan
Fceweenawan
rocksofof the
the Keweenaw
Peninsula has
rocks
Keweenaw Peninsula
long been known in
in great
great detail,
detail,thanks
thanks to
tothe
thelarge
largeamount
amount of
of
drill—hole and
drill-hole
and surface geologic information.
information. The recent
recent work perpermits
certainty,
mits certain
certain key
key horizons
horizons to
to be
be traced,
traced, with
with moderate
moderate certainty,
westward into Wisconsin.
Wisconsin.
Stratigrapitic relationships
relationships for
for the
the middle
middle and
and upper
upper Keweenawan
Keweenawan
Stratigraphic
rocks
best shown
rocks are best
shown in a longitudinal stratigraphic section
section drawn
drawn
rocks and having
along
strike of
of the
the middle
middle Keweenawac
Keweenawan rocks
along the general strike
most striking
striking
base
the Nonesuch
Nonesuch Shale
rlA.tum plane. The
The most
base of the
Shale as
as aa datum
(1)
The
predominantly
features
of such
such aa diagram
diagram are the
the following:
following:
(1) TIle predominantly
features of
basaltic
Portage Lake
Lake Lava
Lava Series
Series maintains
maintains aathickness
thicknessofof10,000—
10,000basaltic Portage
12,000
from 1-loughton
Houghton to tothe
near
12,000 feet
feet from
theJHack
BlackRiver
Riverand
andisis thinnest
thinnest near
the Ontonagon
Ontonagon River. IItt is
isabout
about 8000
8000 feet thick
thick atatthe
theMontreal
Montreal
River. (2)
(2) An
An unnamed
lenticular
unnamed
lenticularunit,
unit,10,000
10,000feet
feetthick
thick at
at the
Liver on
Presque
Presque Isle River
River and
and pinching
pinchinp, out
out near
near the
the Ontonagon River
on the
the
and the
the Montreal
Montreal River
River on
on the
the west,
west, lies
liesabove
above the
thePortage
PortageLake
Lake
east and
Lava Series
Series and
and below
below the
the predominantly sediientary
sedimentaty Copper
Copper Harbor
Harbor
Conglomerate.
to fine—
Conglomerate. The
The unit
is mainly
mainly composed
composed of
fineunit is
of thin
thin aphanitic to
grained andesitic
andesitic flows
flm,s and
and contains
contains minor rhyolite
rhyolite and
and intermediate
intermediate
rocks,
the top.
top. It
to represent
represent accumulation
rocks, particularly near the
It seems
seems to
\Vithin
fe\.". miles of aa volcanic center
south of
of the
the Porcupino
Porcupine
within a few
center south
Mountains. (3)
HarborConglomerate
Conglomerate
less than
than 500
500 feet
feet
f·jountains.
(3) The
The Copper
Copper Harbor
is isless
thick over
over the
thick
tile thick part of the
theunnamed
unnamed unit,
unit,and
and4000—5000
4000-5000 feet
thick
near the
tIle pinchouts
pinchouts of
of tile
theunnamed
unnamed unit.
combined thickthickthick near
unit. (4) The combined
ness of
of tue
tlle three
three units
units suggests
sugr,ests aa strongly
strongly asynnetric
asymmetric basin,
basin,
deepening
from aa minimum
minimum near
more than 25,000
25,000
deepening from
nearthe
the Ontonagon
OntonagonRiver
River to
to more
feet
between the
the next
next
feet between
the Black
Blackand
andPresque
PresqueIsle
IsleRivers,
Rivers, and
and then,
then, in
in the
15
than 10,000
10,000 feet
the
15 miles
miles toto the
the \Vest,
west, thinning
thinning rapidly
rapidly toto less
less than
feet at
at the
Montreal
These findinf's
findings reinforce
reinforce the
hontreal River. These
the concept
concept that
that the
themiddle
middle
rather than
Keweenawan
Ke\VeenaVlan lavas
lavas accumulated in separate tectonic
tectonic basins
basins rather
in aa single
single large
large one.
one.
the
�-72—72—
The
Ke,,,eenawan lavas,
so-called South
South Trap
Trap
The lower
lower Keweenawan
lavas, !'"hich
which form
form the
the sc—called
Range, lie
beneath the
the Portage
Portage Lake
Lake Lava Series,
Series, from
from
lie unconfonnably
unconforably beneath
&hich they
differ in
in lithology,
lithology, metamorphic grade,
("hich
they differ
grade, and magnetic
properties. The
feet consists
consists predominantly of very
properties.
The lowennost
lowermost 5000 feet
thin basalt
the next
4000 feet
feet mainly
to
thin
basalt flows,
flows, and
and the
next 4000
mainly of aphanitic to
The uppermost
fine-grained flows
flows of intermediate
intermediate composition.
composition. The
uppermost part
fine—grained
of this
sequence is
iseverywhere
everywhere concealed
concealed by
by the
the Jacobsville
JacobsvilleSandstone
Sandstone
this sequence
or deep
deep overburden,
overburden, but
inferred from
from gravity
gravity and
and magnetic
magnetic data
data
or
but is
is inferred
This lower
is lC,000
to
to consist
consist largely
largely of
of felsic
felsic flows.
flows. This
lower sequence
sequence is
10,000
and
uncertainty
and perhaps
perhaps20,000
20,000feet
feetthick,
thick, the
the difference
difference reflecting
reflecting uncertainty
about
the location
location of
about the
of the
the top.
top.
The
rocksare
are more
metamornhosedthan
than the middle
The lower
lm"er Keweenawan
Keweenm"an rocks
more metamorphosed
middle
Their metamorphic
grade appears
metamorphic grade
appears to
to increase
increasewestward
westl,vard—
Keweenmvan.
Keweenawan.
actinolite is
actinolite
found in Hisconsin
but is
is rare
rare near
near Ironwood.
Ironwood.
is found
Wisconsin but
Kenneth Books
Hooks has found that
that the
the lower and middle Keweenaw€n
Keweenawan
rocks also
also differ
differ from
rocks
from one another in
in magnetic
magnetic direction.
direction.
In contrast
contrast with
with the
the belts
belts of
of middle
middle and
and upper
upper Ke,,,eenal,van
Keweenawan rocks,
roes,
In
dips of
of bedding
bedding generally
generally decrease
decrease !"'ith
with stratirraphic
dips
stratigraphic depth in
in the
lower Keweenawan
Ke\veenawan belt.
belt. If
If this
this represents
represents soutlnvard
southward thickening
thickening
rather
rather than
Lian folding,
folding, it
it suggests
suggests that
that the
the axis
axis of
of the
the lower Keweenal,van
Keweenawan
basin lay
lay to
to the
the south.
south.
�-73—73—
THE NORTH SHORE
SHORE VOLCANIC GROUP
GROUP
May 5 and
8, 1971
by
Prepared by
C. Green
John C.
University of Minnesota,
Minnesota, Duluth
Minnesota Geological Survey
�—74--74-
Croup
The North Shore Volcanic Group
John C.
C. Green
Introduction
Previous Work
Hork and
and Acknowledgments.
Acknowledgments. Detailed mapping of the Minnesota
A. S.
E. Sandberg's
Sandberg's study
study (1938)
(1938) of
of the
the
shore of Lake Superior began with A.
Grout and Schwartz (1939)
section between Duluth
Duluth and
and Two
Two Harbors.
Harbors. Grout
(1939) and
and
(1957) studied the
the intrusions
intrusions and
and flows
flows in
in eastern
eastern Lake
Lake County;
County;
Gehman (1957)
the lakeshore
Two Harbors
Harbors and
and Split
Split Rock
Rock
Grogan (1940)
(1940) mapped the
lakeshore between Two
River; Schwartz (1949)
River;
(1949) studied the Duluth
Duluth area;
area; and
and Grout
Grout and
and others
others
(1959)
(1959) mapped most of
of Cook
Cook County.
County. Most of
of the
the data
data reported
reported in
in this
this
account derive from studies by the
account
the writer who, starting
starting in
in 1965,
1965, has
has
mapped the shoreline between Silver Bay and Grand
Grand Portage,
Portage, with conconsiderable reconnaissance inland (Green,
(Green, 1966;
1966; 1968a;
1968a; 1968b;
1968b; 1970).
1970).
The report
does, however,
however, also
also lean
lean considerably
considerably on
on Grout
Grout ~
etal.
report does,
al. (1959)
(1959)
and, for
for the Duluth-Two
Duluth—Two Harbors area, on
and,
on Sandberg
Sandberg (1938).
(1938). The field
field
studies have
have been supported by the
studies
the Minnesota Geological
Geological Survey,
Survey, and
and
most of the laboratory studies
have
been
supported
by
the
National
studies
the
Science Foundation.
Sincere gratitude for
for this
this support is
is extended
extended to
to
both agencies.
agencies. The writer's ideas
ideas have benefitted
benefitted from
from discussions
discussions
with many
other geologists
rocks, esoecia11y
esnecially
many other
geologists concerned
concerned with
with Keweenawan
Keweenffivan rocks,
including Bill
Jr., H.H.Hubbard,
including
BillBonnichsen,
Bonnichsen, D.
D. M.
M. Davidson,
Davidson, Jr.,
Hubbard, C.
G. B.
B. Morey,
Horey,
W.
W. C.
C. Phinney,
Phinney, ·P.
W. Weiblen, and
and W.
W. S.
White.
P. W.
S. White.
Regional Setting.
"North Shore
has been
~egional
Setting. The name "North
Shore Volcanic
Volcanic Group"
Group" has
been used
used
et al.
al. (1961)
(1961) for
by Goldich et
for the
the lavas
lavas and
and interbedded sediments of
Late Precambrian.
rocks, as well
Precambrian age in northeastern Minnesota. These rocks,
as
and sedimentary
sedimentary rocks
rocks in
in the
the
as all
all other Late Precambrian volcanic and
district, have traditionally been called"Keweenawad'by
called "Ke~veenffiolan" by
Lake Superior district,
rocks exposed on the
general lithic and structural correlation with rocks
and paleomagnetic
Keweenaw Peninsula of Michigan,
Michigan, but recent radiometric and
investigations
as \-lell
indicate that
that aa more
more precise
precise
investigations as
well as geologic mapping indicate
stratigraphic
stratigraphic framework
framework is
is needed
needed to
to adequately
adequately describe
describe the
the complex
complex
events and
and deposits
deposits in
in this
this area.
area.
series of Late Precambrian events
In
(Grand Portage
In the
the northeast
northeast corner
corner of
of }linnesota
Minnesota (Grand
Portage area)
area) the
the lowest
lowest
Upper Precambrian flows
which in
flows overlie a thin quartzite (Puckwunge)
(Puckwunge) \.;rhich
1.n
turn
turn overlies,
overlies, apparently disconfornably,
disconformably, the
the shales
shales and
and graywackes
graywackes Of
6f
the Middle Precambrian Rove
Formation;here
hereboth
both sequences
sequencesstrike
strike nearly
the
Rove Formation;
nearly
east—west and dip at approximately 10°
east-west
100 to
to the
the south.
south. At the
the southwest
southwest
end of the basin immediately west
west of
miles away),
of Duluth (155
(155 miles
away), the lowest
lowest
Upper Precambrian flows
flows also conformably
conformably overlie
thinquartzite
quartzite
(Puckoverlie aa thin
(Puck—
wunge?) which there
there overlies the
the vertically folded slates and metagray—
metagraywackes of the
the Middle
}tiddle Precambrian Thomson Formation,
Formation, which is
is correlated
with the
the Rove.
Rove. Here the flows
flmols strike north and dip
dip at
at about
about 25°
25 0 to the
unconformity here
here reflects
and subsesubseeast. The angular
angular unconformity
reflects the
the diastrophism and
quent
the Penokean
Penokean orogeny,
orogeny, which
which evidently
evidently did
did
quent erosion associated with the
the northeastern
northeastern corner
corner of
of the
the state.
state. Across the
the axis of the
the
not affect the
flows
Lake Superior Syncline in northern Wisconsin and Michigan the lowest flows
�MINNESOTA
\-n
I
ONTARIO
J)
I
I
\
'—-7
-
rHCVL AND
EARLY
PRECAMBRIAN
GRAND M AR A IS
LEGEND
LUTSEN
JOFTE
uACONITh
INTRUSION S
i., '\~r KEWEENAWAN INTRUSIONS
Wf0J
KEWEENAWAN LAVAS
"'to
FIELD TRIP STOP
I
-....J
U'
\Jl
I
ITLC MARAIS
MARAIS
ER BAY
JBEAVER BAY
BAY
LAKE SUPERIOR
SCALE
°
!
•O HARBORS
WISCONSIN
MINN.
10
20
Miles
MICHIGAN
30
40
�—76—
-76-
conformably overlie aa similar
similar quartzite
(Uessemer) that in
in turn overlies
overlies
quartzite (Bessemer)
Middle Precambrian shale and
and graywacke with only
only minor discordance.
discordance. These
quartzites have always been referred to as
as Lower
Lower Keweenawan,
Keweenawan, but
but no
no
radiometric age determinations are
are available
available and
and they
they may
may be
be much
much older
older
than the volcanic
volcanic rocks
rocks of
of the
the iCeweenaw
Keweenaw Peninsula.
The North Shore Volcanic Group is cut
The
cut by aa. great
great variety
variety of
of intrusive
intrusive
rocks
rocks that are
are also
also of
of Late
Late Precambrian
Prec&~brian age.
age. These range
range from
from the
the great
great
Duluth Complex,
Complex, dominated by anorthositic and
and troctolitic
troctolitic rocks,
rocks, to
to
smaller sills,
sills, stocks,
stocks, dLkes,
dikes, and irregular plutons of
of diabase,
diabase, 'crro—
ferroabbro,
trachybasalt, granocdorite,
an
gabbro, troctolite,
troctolite,syenogabbro,
syenogabbro, trachybasalt,
granodiorite, and.
Someofofthese
thesebodies
bodiesalso
also cut
cut the
the older
graoQphyric, adamellite. Some
older rocks
rocks
grarophyricadanellite.
to the
to
the north,
north,northwest
northwestand
andwest
west of
ofthe
themain
mainLate
LatePrecambrian
Precambrian outcrop
outcrop
area
of Cook
Countyand
andthe
the Thunder
BayDistrict
District
area (e.g.
(~.g. the
the Logan intrusives
intrusives of
Cook County
Thunder Bay
of Ontario).
of
Ontario).
Paleonagnetism and Age. Recent
paleomagnetic studies
studies (Dubois,
Paleomagnetism
Recent paleomagnetic
(Dubois, 1962;
1962; Beck
Deck
that two
and Lindsley,
Lindsley, 1969;
1969; Books,
Books, 1968;
1968; Palmer, 1970)
1970) have
have shown
shmm that
two
reversals of magnetic polarity occur within
reversals
'loTi thin the Late
Late Precambrian
Precambrian volcanic
volcanic
rocks of the Lake Superior
The 1m-rest
lowest strata
stnta show
'nor'ial"
rocks
Superior district.
district. The
shoYr "normal"
(north—seeking) polarity
polarity similar to
to orientations
orientations in the underlying
(north-seeking)
underlyinp; Middle
Precambrian rocks,
rocks, but
but this
this group
group of
of rocks
rocks has
has not
not been
been recognized
reconized in
Precambrian
Minnesota.
Keweenawan
Books (1y68)
(l9~8) has
ha.s proposed that the Lover
Lower —- Middle ~eweenawan
Books
boundary be redefined
the second
reversal where
redefined at
at the
second macnetic
magnetic reversal
where rocks
rocks of
normal polarity. The North
reversed polarity
aresucceeded
succeeded by
by rocks of'
of normal
North
po]arity are
Volcanic Group
Groupcontains
containsatatthe
the ba.se
base of
of the
Shore Volcanic
t~e section
section atatGrand
Grand Portage
Portage
about 5000 feet
feet of lavas
lavas tnat
that show reversed polarity, and
and are
are thus
thus Lower
Lower
Keweenawan
magnetically defined.
defined. The
thick wedge
of flows
Keweenawan asasmagnetically
The thick
wedge of
flows west
west of
Duluth
that underlie
ut overlie the Puckwunge
Duluth that
underlie the
theDuluth
Duluth Complex
Complex but
Pucki-runge (?)
(?)
quartzite have
quartzite
but on
on
have not
not been
beenadequately
adequatelytested
testedinin the
the laboratory,
laboratory. hut
regional magnetic
magnetic maps
maps give aa negative
negativemagnetic
map;neticanomaly
anonaly which
which implies
implies
regional
reversed
polarization. Furthermore
reversed polarization.
very similar to
Furthermorethey
theyare
arelithically
lithically very
reversed-polarity lavas of
of Grand
Grand Portage.
Portage. The
the reversed—polarity
The remainder
remainder of
of the
::orth
North Shore Volcanic
Volcanic Group
polarity,
Grouphas
hasnormal
normalmagnetic
magnetic
polarity,similar
similar to
to the
bulk
bulk of
of the
the associated
associated intrusive
intrusive rocks
rocks and
and to
to the
the rocks
rocks of the Keweenaw
Peninsula.
Only
available on
on rocks
rocks
Onlylimited
limited radiometric
radiometric age
age determinations
determinations are
are yet
yet available
of
al. (1961)
of the
the North
North Shore
Shore Volcanic
Volcanic Group. Goldich
Goldich ~~
(1961) found aa
!! ~~.
1.1 ±± 0.1 b.y.
1.1
intrusive rocks
rocks of
of the
the Duluth
Duluth Complex
Complex
b.y. age for associated intrusive
and K/Ar
K/Ar methods, and
and Silver
Silver and
and Green
Green (1963)
(1963) found
found an
an isotopic
isotopic
by Rb/Sr and
age
age of 1.125 by U/Pb isotopes in
in zircons
zircons of
of both
both lavas
lavas and
and intrusive
intrusive rocks
rocks
and Mellen,
Mellen, Wisconsin
Wisconsin areas.
areas. Paure
Faure et al.
al. (1969)
(1969) determined
determined
from the Duluth and
the
age of the Endion sill,
sill, which cuts
cuts the flows
flows at
at Duluth,
Duluth, as
as 1.092
1.092 b.y.,
b.y.,
the age
and that
that of
of the
the Duluth
Duluth Complex
Complex .at
at Duluth
Duluth as
as 1.115
1,115 b.y.
b.y. by
by the
theRb/Srmethod.
Rb/Srmethod.
However, all of these sampled rocks
rocks are in areas of normal magnetic
However,
rr..agnetic polarity
polarity,
to the
the age
so no data are available
available as
as to
a~e of the Lower Keweenawan lavas
lavas of,
of, for
for
Grand Portage
Portage area.
area. Hanson and Malhotry (1970)
(1970) have recently
instance, the Grand
a 1.380 b.y.
(K/Ar) of aa "Logan
"Logan Intrusive'
Intrusive" in
in southern
southern Ontario,
Ontario,
found a
b.y. age (K/Ar)
indicate the
the possible
possible age
age span
span of
of the
the Lower
Lower Keweenawan.
Ke'lveena"ran. Isotopic
which may indicate
studies over
over the
the range
range of
of Upper
Upper Precambrian
Precambrian rocks
rocks iii
in the district
district are
are
U/Pb studies
currently in
in progress.
progress.
�—77—
-77-
Structure
Structure
The
Group is
is that
that of
of aa
The general structure of the North Shore Volcanic Group
great nest of
dishes tilted
tilted gently
gently to
to the
the southeast into
ofmshes
into Lake
Lake Superior.
Superior.
endthe
thestrata
strata at
at the
strike slightly
At the
the northeast
northeast end
the base
base strike
slightly north
north of
of
west and dip about
about 10—12°
10-12° south,
south,whereas
whereasatat the
the southwest
southwest end,
end, 155
155 miles
miles
away, they strike north and
and dip about 25° east.
east. In between the strikes
strikes
c-raually converge
convergealong
alongthe
theshore
shoreof
of Lake
LakeSuperior
Superiorasashigher
higher stratigraphic
stratigraphic
gradually
levels
are reached,
reached, until
flows strike
to the
the shore
shore in
in the
the
levels are
until the
the flows
strike parallel
parallel to
vicinity
southwestern
vicini
ty of
ofSchroeder,
Schroeder, Torte,
Tofte,and
andi,utsen
Lutseninin
southvresternCook
Cook County.
County.
Herethe
the highest
highest stratigraphic
stratigraphic units are
the dip
Here
are exposed,
exposed, and
and the
dip is approxiapproximately 12° to the southeast.
southeast.
The lavas
lavas are
The
are intruded by a great variety and bulk of intrusive
intrusive rocks,
rocks,
including
several large
large diabasic
diabasic sills
sills at
at Duluth,
Duluth, the
the Beaver
Beaver Bay
Bay Complex,
Complex,
includim several
the 1-iovland
andReservation
ReservationRiver
River diabase
diabase complexes
complexes and
and the
the Logan intrusions.
the
Hovland and
intrusions.
Where
Hhere these intrusions are
are discordsnt
discordant and
and abundant
abundant they
they have
have deformed
deformed the
the
lavas considerably,
lavas
considerably, with local strongly divergent strikes and
and steep
steep to
to
overturned dius.
dips. Along with the thick glacial cover inland,
inland, they
they have
have
also made
made difficult
difficult to
to impossible
impossible the
the long-distance
long-distance tracing
tracing of
of stratigraphic
major
flows or
or groups
roups of
in the
the lava
lava series.
series. Several
Several maj
or flows
of similar
similar flows,
flovrs,
units in
however, can
be traced inland from the lakeshore for
however,
can be
for at
at least
least 15
15 to
to 25
25 miles.
miles.
Faulting is
COffi.J;lon in the flows
flows near the areas of abundant intrusions
intrusions (such
(such
is common
as from Silver
~jilver Bay
Day to
to Little
Little:iarais).
:'1arais). These faults appear to
to be
be of
of minor
as
displacement and are
are :r.lostly
mostly transverse and steeply dipping with no
displacement
no strongly
strongly
preferred strike or displacennnt,
displacemnnt, but aa few
few longer
lon~er strike—faults
strike-faults have
have been
been
found, one
one of which probably extends for
found,
for at least five
five miles.
thickness of the
has been measured and
and estimated
estimated by
by
The thickness of the lava succession has
feet between
and Split
Split
~)andberi!,
and Gror-an
Grof.\an (l90)
(19)j·0) as
as 23,148
behreen Duluth
Duluth and
Sandberg (19::38)
(1938) and
23,lB feet
Rock
complex) by adding
Pock River (the
(the beginning
beginning of
of the
the Beaver nay
Bay intrusive complex)
Whether
the
lakeshore. ~TIether
the individual
individual flow thicknesses
thicknesses intersected along the lakeshore.
j.ile at
at Split
Split Rock
Rock River
Biver is
this
conforms to the
is not
not
this conforms
the true
true thickness of the pile
Northeast of the Beaver Bay Complex about 5000
lmovn.
Hortheast
5000 feet
feet of
of lavas
lavas are
are
known.
estimated
recent mapping to form the lakeshore section
section between
between 'ilver
Silver
estimatcd from recent
Rortheast
of
and
Lutsen,
where
Bay
and
the
uppennost
flows
at
'T'ofte.
IJortheast
Tofte
uppermost
flows
at
°ofte.
Bay
the
flows are
are parallel to the shore, lavas totalling about
about 16,500
16,500 feet
feet
the flows
have
River diabase
diabase near
near }iovland.
Hovland. Below
been measured
measureddovn
downtotothe
the Reservation
Reservation River
have been
(northeast
of)
this
is
an
older
section
of
about
5,000
feet
of
(northeast of) this is an older section of about 5,000 feet of lavas,
lavas, for
for
total on
on this
thislimb
limb of
ofabout
about 21,500
21,500 feet.
a total
Estimate50f volcanic
volcanic thicknesses
thicknesses by
by constructing
constructing cross—section
cross-section profiles
Estimateof
profiles
give between
between 11,000
Tofte, above
above the
the Duluth
Duluth Complex,
give
11,000and
and18,000
18,000feet
feet at
at Tofte,
depending
20°. Although
Although the
the average
average
on ass~~ed
assumed dips
dips between 12° and 20°.
deDendng on
is
very
little
control
on
dips
near
dip
at
Tofte
is
about
12°,
there
is
very
little
control
on
dips
near the
the
at
Tofte
is
about
12°,
dip
flow contacts.
contacts.
base
section as
as the
thefew
fe,., inland
inland outcrops
outcrops rarely
rarelyexpose
expose flow
base of
of the section
northeast at
at the
theCascade
Cascade River,
River, about
about 15,000
15,000 feet
feet of
of lavas
lavas above
above
Farther northeast
of
12°;
another
the Duluth
Duluth Complex
Complex are
calculated
with
an
average
dip
of
12°;
another
are calculated with an average dip
lies beneath
thick section,
section , possibly
possibly
as much
much as
thick, here
here lies
beneath
thick
as
as 5,000
5,000 feet
feet thick,
'.
the Complex.
Complex.
~
�—78--78-
GenerallDesptiq
Description,
The North Shore Volcanic Group bears many resemblances, both physically
physically
and chemically, to plateau lava sequences of various geologic
geolo~ic ages.
ages.
Similarities to
the Tertiary
Tertiary plateau
plateau lavas
lavas of
of eastern
eastern Iceland
Iceland are
are
to the
particularly
particularly striking.
striking. The lavas
lavas are almost entirely subaerial,
subaerial, showing
showing
highly vesicular (now
(nmr amygdaloidal)
amygdaloidal) upper portions and
and massive interiors,
interiors,
and.various
various types
types of
of jointing,
jointing, surface
surface features,
features, and
and textures
textures depending
depending
and
on their specific composition.
composition. Evidence of submarine extrusion
extrusion is
is almost
almost
Portage and
entirely limited to the
at Grand Portage
and at
the base of the section both at
Nopeming, west
west of Duluth, the lowest flow
Duluth; at
at Nopeming,
flow is
is piflowed
pillowed and
and on
on
Portage Island the lowest flow shows
shmrs spheroidal
spheroidal forms that could
could
Grand Portage
possibly be pillows, but excellent,
excellent, thick—rinded,
thick-rinded, vesicular
vesicular pillows
pillows
constitute
the lakeward side of the island aa few
constitute aa flow
flow on the
few flows
flmrs above
above
of the
the section.
section. Unequivocal hut
but less well—formed
well-formed pillows and
and
the base of
pillow-breccia have been seen
seen only
only rarely
rarely higher
higher in
in the
the section.
section. These
pillow—breccia
could
or stream
stream beds
beds on
on the
the lava
lava surface.
surface. The
could have
have formed in local lakes or
flows
tabular, and since some individual flows
flows are
are in general tabular,
flows or
or flow
flow
groups
groups can
can be traced along strike for at least 20 miles, the general
general
impression is
is that
that of
of aa broad,
terrain. In contrast
contrast
broad, rather flat volcanic terrain.
to
clear
to the
the situation
situation in
in eastern
eastern Iceland,
Iceland, however
however (Walker,
(Walker, 1964),
l96), no
no clear
evidence of volcanic centers, representing shield or composite
evidence
composite volcanoes
White
contemporaneous with the plateau volcanism, has yet been found.
found. \'mite
contemporaneous
(1960)
on to
some Keweenm-ran
(1960) has
has drm-rn
drawn attenti
attention
to the
the remarkable
remarkable extent
extent of some
Keweenawan
flows (especially in Michigan)
Michigan) and with ample justification
flows
justification calls
calls them
flood basalts.
basalts.
Interflow sediments
of the
the section.
section. They
Interfiow
sediments make
make up
up aa minor
minor part
(l—3) of
-part (1-3%)
are principally red,
cross—bedded sandstones, that occur sporadically
are
red,cross-beddedsandstones,
sporadically as
as
beds aa few
few inches
inches thick
thick between flows,
flows, but
but aa few
fe"T local
local accumulations
accumulations of
of
over 100 feet
feet are
are found.
found. Conglomerate is
is rare.
rare. Some
Some sand has
has filtered
down into
down
into cavities
cavities in the upper
unper parts of flows,
f10vs, and
and also
also forms
forms aa matrix
for
flow—top breccia
for flow-top
breccia in
in others.
others. These sediments appear
a.ppear to have been
deposited by occasional temporary streams winding across the volcanic
surface. There is
is little evidence
evidence of
of erosion.
erosion. Pyroclastic deposits
deposits are
are
but welded tuff and mixed sand and
extremely scarce,
scarce, but
and shards
shards have been
the Cascade IIiver
River in Cook County (Johnson
reported from the
(,Tohnson and
and Foster, 1965)
1965)
and basaltic to
to andesitic
flow top breccia, is
is present
present
andesitic breccia,
breccia, other than flow
in a few localities.
,
exception of
of aa high
high potassium
potassium content
content in
in some
some oaf
mafic
With the exception
ic and intermediate
abundance of
of rhyolite,
rhyolite, the
the compositions
compositions of
of the
the lavas
lavas
members and the relative abundance
are also
also very
very similar to those
those of plateau lava series in Iceland and
are
and elsewhere.
vhere.
characteristics and
and abundance
abundance of
of the
the
Table 1 shows the general characteristics
major types.
types.
The most abundant general type is
is olivine
olivine basalt
'basalt of
of several
several varieties;
varieties;
important, and distinctive variety is
is mottled
mottled (ophitic),
(ophitic),
one widespresd,
widespread, important,
and is
is similar
similar to
to what
what has
has been called olivine tholeiites in other areas.
and
areas.
Rough
columnar
These typically have ropy surfaces and
and were very fluid.
fluid.
col~~nar
joints are
Other olivine
olivine basalts
basalts are
with diabasic
are common.
common. Other
are coarser,
coarser, some i-rith
and some ,.ith
with other
other characteristic
characteristic textures.
textures. In the Tofte—Lutsen
Tofte-Lutsen area,
area,
high in
the
section,
is
a
group
in
of olivine base.1ts
th abundant,
abundant, small
basalts "ri
with
(1-3
phenocrysts or
or crystal
crystal clots.
clots. At
section
(1—3 nun)
mm) bytownite'
bytownit&phenocrysts
At the base of the section
both t
at Duluth
Duluth and
and on
on Lucille
Lucille Island
Island east
east of
of Grand
Grand Portage
Portage are
are distinctive
distinctive
basalts
basa.lts that contain abundant phenocrysts, 2—3
2-3 mm across,
across, of
of augite
augite and
and
�_____
______
TABLE 1
Generalized Characti±ritics
Characteristics of
of Major
Major Lava
Lava Types
Types of
of North
North Shore
Shore Volcanic
Volcanic Group
Group
___
~
I
Wt %
% Si02
Si0
2
-_ -_.
'
--~
,.
--...--..........
I
2
·~"-··""'''''''·~''-'''''''''''-''''-'''~~··i''''~·
Wt %% MgO
-..---~.--'.<.~."'-"'.'
.. _ ..•,,_'__
"~_ _~
46-49
1
0.1-0.5
I
~
~--~·_""""~:~'.....,-'T-'·_.-.~
~
·
I{
Andesite— t"P.
Intermediate
Andesit~:i
Intermediate
Trachyandesite
Quartz
Tr~rtz Latite
L~~
Quartz
Quartz
Tholelite
I
~- " - - - - " , .. , . • .~-w••• _ -" ~".~~~ ••• ~.-+,~.
Wt %%1(20
K 0
-,
Tholei te
I
Olivine
:ic
1 Olivine
Characteristic
Tholeilte
Characteri~~~i~te
4,,52-57
52-57
50—51
50-51
!
0.6-0.9
~'~l.·.~ ~ol.AA' .!::..~< 1-,,••
1,--.' •• _.,,-,
1
."~.- ~"'-" ·~·~,.._'S...·_"'
5.9:6.8
5.
9-6 . 8
1
I
I __
"',..
,""~
••• .,J • • • •
~
~
I
•
,
1 Very
fine—
finet Very fine—
finegrainS, inter—
l grained,
inter~ grained,
granular. Some
pot—
{ granular.
commonly porphyritic (plag.,
~ flow structure,
~ phyritic
,
..1 augite) (plag.,
fine oxidationoxidation—
i, fine
banding
Ophitic
Occasionally
Occasionally
porphyritie
porphyritic
(plagioclase)
--------.--.--------!..-----~---~-~t~:~~~~-.-~--+----~
72—75
72-75
2.8—5.0
2.8-5.0
3.9—6.2
3,.9-6.2
r
'_<'~~',
0.9- 1 • 9
,.,--,~
<J ..
_ _ ;·
·",·
P _ > ' _ • - . _• •-
~ ~
, " ' _ ••.•• -:...
.
<
-
I aphanitic~
.
aphanitic,
mostly pot—
porphyritic (plag.,
(plag.,.
augite, 01.)
augite,
oh)
.
.
_
_~--~
.-
0.0—0.4
0.0-0.4
,,,n"~"·.·~,.,-.•~,,·,,,. ,'-~.~ ..,< , .• ~"'_'_,
.I
•... ,
< •• ,, ..•, .•--.- .. --.
aphanitic
aphanitic to
to
felsitic;aphyric
felsitic;
aphyric
or porphyritic
(plag., orthoclase,
(plag.,
)
quartz, mag., pyrox.)
pyrox.
occas. spherulitic
~.--_ _,--.;,::::~:lt::l~~~.~ . . -
—
J
62—65
62-65
._-
!
:
Thickness,
Thickness, feet
feet
Range
'-
--.--.,,' j'" -"
I
'
l \
Textures
t ': -
1.9—2.7
1.9-2.7
.•Y.
_ _ w .• .•
~yolite
ithyolite
..~~~'-~·~~,.. ..,..-".-·.-'''' --..~•...".-.-...."....-.~...,.--~ -"'. ~~-~"~---'-'-'-~---~ _.V·_·__
1
I 4. 3-5. 9
1. 9-4 . 5
11:9—4.5
~ ~;~'-<'~~""_ '"-->-"'"'-'~/"""~-"';""'~1--~-'>""'.w.".>--."'-•.,./A~_~C'~~'_"h,,·_, t-'_.,··",._·.·r;.,,·~ . ,..'.,. ".~.,
!I'
__ .
Quartz
Quartz Latite
Latite
I'
.
50-1300
50—1300
perhaps 3500
3500
1
2 0 ' " · ·_..5
. 0=500 ..··
50—500
120
—
···------struc~~:-t:=-:-:py--i~c==~=tc=:=::--i·:::=:- -====:-c'oIiIIDo~
.'.. --
]-
-~
>100
<1 to >100
~." ·I6~46
10—40
·"'
'
30—150
30-150
~
-,·--···l
'so
80
-
1
50—240
50-240
~
i
1".
. var:Gibier'
varIable
80—200
80-200
-
Structures
smooth, ropy
flow tops
oi;ti';;-
jointing
j
vesicular
wrinkled
scoriaceous rubble scoriaceous,
rubbly
vesicular, rolled,
flow—banded
platy, sub—horizontal
big columns in thick
irejilai tâ ,'~~~~~:~:h~:i~~~~~l
··t-~~~:i~:}~::T.::-t~~~ii,irreg;;i;r-ts~if;~~~;~g;;iarh~~~~;!!~:~~l
-
sheeted tops["
small, irregular
small, 1rregiIar
subhorizontal,
flows
platy
..
round
stretched 'o"r"
or ···... i . stretched, round
vesic1es
round or 1rregu1ar stretched ...._,··_- . stretched or
round
round
~
~--_ ·-··-~·i
~
~ -14
,-- ,-- - - ~ . _·--_····_..·.
~."i'----. __ -- -.~~- - - ~~"Q
~ .,~_.-..
'".~-~--'very_fluid
Other
! very
fluid
1 more
viscous
~ brown—weathering
brown-weathering I few flow
: pink,
pink, red,
red, or
more_viscous
contacts exposedt
exposed light
Characteristics
;omewhat variable
variable contacts
Characteristics
J,
pipe amygdules
some contain
tomewhat
light gray
gray
at
at base
~
~ more
more 1(20,
K20,
!
segregation veins,
l segregation
veins, i Kspar;
~
vesicle cylinders
quartz, agate
agate
vesicle
cylinders ~: quartz,
I
common
in
cavities
l
common in cavi ties'
columnar centers
ve·si-~i;;~·_ -·--l--·;(;~d·-~-;· 'i;~~g~i~·~+·;t~et"~h'ed
--- ~-. -"'-'--- -----..-
1
I
i
~
~~
---.. -.-.-.. -..
-"..
!
-
i
l··.-,-.----- .- . -.- ---,..
l
Ksr
I
Ij
--+;tretch~d· O~.. t"';~~:iche~f
I
I
I
I
f.
~~~:~·ched·:
- " " - . _.. •
-,-
-
�—80—
-80-
(serpentinized) olivine:
olivine: these
these are
are particularly unusual
unusual in
(serpentinized)
in having
ferromagnesian instead of
of plagioclase
plagioclase phenocrysts.
phenocrysts. Another moderately
abundant and distinctive
distinctive rock
rock ty-pe
type is
tholeiite" which is
is
is the
the "quartz tholeiite
fine grained
grained and
and slightly
slightly more
more siliceous
siliceous and
and viscous
viscous
aphanitic or very fine
The quartz—tholeiites
than the olivine
olivine basalts.
basalts. The
quartz-tholeiites characteristically
characteristically have
a rubbly or brecciated top with the highly vesicular
vesicular fragments
fra~ments set
set in
in aa
matrix of washed-in
washed—in red sand
sand or
or occasionally
occasionally calcite
calcite and
and zeolites.
zeolites. They
also
~ thick, along subhorizontal
subhorizontal
also commonly
commonly show narrow oxidation bands,
bands, 1-3 mm
flowage planes.
planes. This quartz—tholeiite
quartz-tholeiite grades
grades into
into more
more potassium—rich
potassium-rich
varieties (trachybasalt,
(trachybasalt, trachyandesite) that
that can
can be
be distinguished
distin~uished only
only
by chemical analysis and
and microscopic study;
study; patches of
of interstitial
interstitial KK
feldspar are
are present
present in these
these rocks
feldspar
rocks but are invisible in
in hand specimen.
speci~en.
Intermediate varieties are
are nearly all
all porphyritic with plagioclase,
plagioclase, augite,
ausite,
magnetite, and in some
magnetite,
SOTIe specimens iron—rich
iron-rich olivine
olivine phenocrysts;
phenocrysts; they
they have
have
the compositions of andesites, trachyandesites, and
the
and intermediate
intermediate quartz
quartz
Most are aphanitic, but one
latites.
Most
one unusual flow,
flow, here
here called
called the
the Manitou
Manitou
trac~ybasalt,
is exceptionally thick (at
(at least
least 300
300 feet)
feet) and
and granular,
granular,
traciybasalt, is
for 55 miles although it
it originally continued
continued for an
an
and can be traced for
These flows
in both
both directions.
directions. 'I'hese
flows are commonly
cOTlJ1!1only brown or
unknown distance in
red and irregularly jointed
jointed or with platy,subhorizontal joints.
joints.
The felsic
The
felsic lavas
lavas are anomalously abundant
abundant for
for aa simple
simple differentiation
differentiation
series from aa basaltic
basaltic parent
parent magma.
mae;m.a. They are red, pink, or
or light
li~ht gray.
gray,
These flows
composition of
of quartz
quartz latites.
lati tes. 'l'hese
flows tend to be much
and have the composition
thicker than the other
other types:
types: the thickest is
is 1300 feet,
feet, aa few
few miles
~iles east
east
of Grand Marais;
Marais; the 3500'
3500' Brule Flyer
River rhyolite
rhyolite west of
of Hovland
Hovland may
may be aa
lava dome.
dome. Their top surfaces are mostly strongly
strongly flow—banded,
flow-banded, vesicular,
vesicular,
and.
contorted, b~t
but not
not brecciated,
brecciated, and
and their
their bases
bases are
are cornmonly
commonly flow-banded
flow—banded
and contorted,
brecciated. Spherulites are
are occasionally
occasionally present.
present. Jointing
Jointin~
and locally brecciated.
ranges
across in the thickest flows
flows to sub—
subranges from large columns 44 feet across
horizontal platy joints;
joints; small tectonically—produced
tectonically-produced parallel fracture
fracture
sets a
a few mID
ccooling joint
joint fragments
fra~ments into
into
sets
mm apart commonly break up the ccooling
felsites are
are porphyritic, with
,-rith quartz
quartz and
and
small pieces. Most of the felsites
feldspar
feldspar phenocrysts (oliogclase—andesine
(oliogclase-andesine and/or orthoclase)
orthoclase) but
but some
some
are only weakly porphyritic
porphyritic or
or arhyric.
aphyric. Poikilitic quartz surrounding
are
stout
stout alkali—feldspar
alkali-feldspar laths ("snowflnke
("snowfla1:e texture:)
texture';) is
is aa common
common microscope
texture in the thicker
thicker flows.
flows. Even these siliceous
siliceous lavas
lavas have
have evidently
evidently
flowed
great distance;
distance; one
one lava
lava or
or ffow
flowed aa great
..J..mr group
group can
can be
be traced
traced for
for at
B.t
least 23 miles
miles \-lest
west from the Devil Track Fiver,
least
River, Grand
Grand Marais (see
(see man,
Man,
fig.
1).
fig. 1).
Alteration
The lavas
lavas have been strongly
stronlJ,ly but irregularly
irrerularl;v affected
affected by
b;f secondary
secondary
solutions that have deposited
denosi ted low—temmerature
lml-temner?ture minerals in
in vesicles,
vesicles>
solutions
fractures, and other
some of the minerals of
fractures,
other cavities,
cavities, and
and -altered
altered sot'!.e
of the
the
no fresh
fresh olivine
divine has
lavas themselves. For instance,
instance, no
has been
been detected
detected in
in
any of
of the
the lavas,
lavas, although
although it
it is
is common
the intrusive diabases.
any
co~mon in the
diabases. A
zonation of
of this alteration
alteration is
is anparent;
anparent; at
at Duluth
Duluth and
and at
R.t Grand
Granel
broad zonation
of the
the ~round~ass
groundmass
Portage (in
(in the lower
lower parts
parts of
of the
the lava
lava section)
section) r'uch
~uch of
has been
been converted
convertedtoto actinolite
actinolite (although
many larger
pyroxene has
(althoup::h nan'.'
laT£ser aurites
aur.j te:=>
are unaffected)
unaffected) and
has been
been saussuritized.
saussuritized. [ere
Iere also
andsome
SOIne plagioclase
plar:ioclase has
also
the
minerals
characteristicallyquartz,
quartz, prehnite,
prehnite, calcite,
calcite,
the arnygdule
amygdule p.dnerals
areare
characteristically
�-81—81—
epidote, and chlorite,
epidote,
chlorite, the
the same basic assemblage as
as is
is found
found in
in the
the
Porta~e
Lav~ Series
Keweenaw Peninsula (Stoiber
(Stoiber and
and Davidson,
Davidson,
Portage Lake
Lake hava
Series on the Keveenaw
1959).
In and northeast of Duluth K—feldspar
K-feldspar is
is also
also occasionally
occasionally found,
found,
In
arid
laumontite becomes
becomes abundant.
and laumontite
in the section
section variouS
various zeolites,
zeolites,
Higher in
along with
vith calcite,
caThite, are
are dominant
dosnant except
along
except In
in the
the quartz
quartz tholeiites
tholeiites and
similar
agate, crystalline quartz and
and chlorite
chlorite are
are common.
common.
similar lavas
levas where aaate,
The most
most abundant
abundant zeolites
The
zeolites are
are laumontite, stilbite, heulandite,
thorrsonite
and scolecite
scolecite but
but analcite,
analcite, natrolite,
natrolite, mesolite,
mesolite, mordenite,
thomsonite and
apotbvllite have also
and apophyllite
~lso been found.
Saponite is
is common in olivine
basalts.
Andradite carnets
garnets have been discovered in
in several
several localities
localities
amydules and
andveins
veinsfrom
froma awide
widerange
range
lavatypes
tres (basalts
in ~!'lY8dules
of of
lava
(basalts to
rhyclites) and
and levels
levels in
rhyolites)
in the
the sequence,
sequence, and
and traces
traces of
ofnative
nativecopper
copper have
have
been found
foundininseveral
severallocalities.
localities. Thus
the secondary
zonation in
in the
been
Thus the
secondary zonation
:rorth Shore
Grout spans
spans both
both the deeper—level,
iTorth
Shore 1oThanic
Volcanic Group
deeper-level, higher—temperatre
higher-temperature
tyte
of
the
Keweenaw
Peninsula
and
the
higher—level,
cooler
tyte charactertype of the lCe,.,eenaw Peninsula and the higher-level, cooler type
characteristic of
istic
of the
the icuer
Imler parts
partsof
ofthe
theTertiary
Tertiaryplateau
plateau lavas
lavas of
of eastern
eastern Iceland
Iceland
as described
upper, zeolite—free
is
as
described by
by Walker
'ilalker (1960).
(1960). Walker's
Halker' s uDper,
zeolite-free zone
zone is
apparently
not represented
representedinin Hinnesota.
innesota. According
Accordingtotohis
his estinates,
estirsates, the
apparently not
the
presently exposed
top of the
exposed top
the section
sectionon
onthe
theLake
Lake Sunerior
Superior shore
shore could
could have
have
been
anrrcxirratel'r 5,000
5,000 feet
feet below
the surface
surface during
been approximately
belm., the
during mineralization.
Althoughdetailed
(tetal led1-Tork
workhas
hasnot
notyet
yet been
been done,
done, no
JUthou~h
no clear
clear cross—cutting
cross-cutting
relations of'
to stratigraph
the
relations
of zeolite
zeolite zones
zones to
stratirr,raphywithin
witp_~~
thelavas
lavashave
havebeen
been
recocnized. hut
reco~nized,
but the
theevident
evidentUpper
Upper Precambrian,
Precambrian, nostvolcanic
postvolcanicunconformity
unconformity
;·rhi-chch;;robe.bly
Shore must
mineralization,
wit'
probablyfollm.,s
followsthe
the~Torth
lorth Shore
must have
havepostdated
postdated the
the mineralization,
since it
it does
since
does crosscut the zeolite
ZGolite zones.
zones.
It should be
be stressed,
It
stressed, however,
however, that none of the flows
flows has
has been
been entirely
entirely
in fact,
converted to
to secondary
secondary minerals. In
fact, the
the plaioclase
plagioclaseand
and augite
augite are
are
tynic8,11yunaltered
unalteredororonly
onlylocally
locallyaltered
altered
mostmafic
maficand
andintermediate
intermediate
tvicall'r
in in
most
has typically
typically
rocks.
althour:h no
no fresh olivine
olivine has
has been
been discovered,
discovered. There
There h~s
rocks, although
been
sore oxidation
oxidation of
of the
the opsnue
minerals, especially
especially of
of nagnetite,
been sor.e
opaque minerals,
magnetite, and
and
interrsediate and
ni~eonite is
iscoirnonly
com~only oxidized
borders. In many
nany intermediate
and
pi'eonite
oxidizedatat its
its borders.
felsic
lavas, plarioclase
pladoclasephenocrysts
phenocrysts have
have been
been albitized
and/or zeolitized:
zeolitized;
felsic lavas.
albitized and/or
Fresh, undevitrified volcanic
some
could be
be deuteric.
deuteric. Fresh,
volcanic
someofofthis
this alteration
alteration could
glass
present
in in
occasional
samples,
r,lass is
is still
still
present
occasional
samples,notably
notably inina abasalt
basaltfrom
fromabout
about
t"m r'liles
r10uth of
Brule River.
River.
two
miles ,{est
west of
of the mouth
of the
the Prule
Etnra•iv
The
Thias of
of the ;orth
The lavas
!.JorthShore
;3horeVolcanic
VolcanicGroup
Group can
can be
be conveniently
conveniently
divided
lithostratipTanhic units
unitsof
ofcoherent
coherent petrographic
petrographic
divided into
into several
several lithostratir'ranhic
character
the basis of
character nrimarily
nrimarily on
on the
of exposures
exposures at or
or near
nearthe
theLake
L~ke Superior
Superior
shore. Hany of these
shore.
these units can
ca,n he
be traced
traced for
for aDoconsiderable
considerable distance
distance
inland,
but interruntions
and structural
structural corwlicatipns
complicatiens by
by intrusive
intrusive bodies
bodies
inland, buU
nterruntions and
as well
lacial denosits
as
\·rell -as
as ;o;lacial
denosi tsprevent
prevent the
thereconstruction
reconstructionof'
of aacomplete,
complete, conconp •
tinuous
sequence.
ofJoclear
tinuous sequenc
cleartrend
trendofofconnositional
compositionalchange
chanF':e is
isevident
evidentfrom
from
base
to top;
at the
base to
top; in
in fact,
fact,although
althou~hthe
themost
r'lost ferrora-'nesian
ferro~arrnesinn lavas
lavas occur
occur at
the
base,
flows, in
in the Tofte—Lutsen
area,are
areentirely
entirely olivine
olivine
~ase, the
the unnermost
u:!Jnermost flmrs,
Tofte-Lutsen area,
oasalts. It
basa,lts.
It should
3hould be
be kept
kent in
in rind
r;ind also
also that
that aamajor
ma,jor stratigraphic
stratigraphic break
break.
mayoccur
occurbeheween
the Grand
GrandPortap-e
Portagelava
lavasection
section (sho'ing
f:lay
t"teen the
(shO\.,ing reversed
reversed magnetic
magnetic
polo.ri ty) and
and the
llig-her strnta.
polarity)
the lhgher
strata.
qir
Table
lists the
To.ble 22 lists
the informal
informal stratigraphic
strntif.rcmhic units
unitsnroposed
proposed for
for the
the
northeast limb
liMb (Torte
(Tofte to
toGrand
Gr8.nd Portage)
Porta,g;e) forth
~JorthShore
;3horeVolcanic
Volcanic Group,
Group, with
"lith
estimated thicknesses
thicknesses and
and ~eneral
characters,and
and Table
Table 33
their estimated
general lithic
lithic characters,
Ltivessimilar
sinlar data
p:ives
data for
forthe
thesouthwest
southwest limb.
limb. 'I'his
tabledepends
depends largely
largely
This latter
latter table
on
the work
(1038) and
and Grogan
Grogan(1940),
(iqito), penclin.Q;
pending restudy.
restudy.
on the
"lork of
of Sandberrr
Sandberr:: (1°38)
�—82—
-82-
Table 22
Stratigraphy of
of Northeast Limb (Tofte-Grand
(Tofte-Grand Portage)
Portage)
North Shore Volcanic Group
(Exclusive
of interflow sediments)
(Exclusive of
sediments)
Approx.
Approx •
..IhiCkness(ft.
ThigkneaL&Q)
Lithostratigraphic
Lithostratigraphic unit
unit
Lithic character
character
Lutsen basalts
divine basalts,
olivine
basalts. olivine
olivine tholeiites
tholeiites
160
Terrace Point basalt flow
flow
thomsonite—bearing ophitic
ophitic basalt
thomsonite-bearing
310
Good Harbor Bay andesites
brown, porphyritic
porphyritic andesite,
brown.
trachyandesite
360
Breakwater trachybasalt flow
flow
brown,
brown, columnar,
columnar,granular
granular trachybasalt
500
Narais rhyolite
Grand Marais
rhyolite flow
flow
pink, red, gray
pink,
gray porphyritic
porphyritic rhyolite
600
Croftville basalts
various fine-grained
fine—grained basalts
Devil Track felsites
aphyric and porphyritic rholite
rholite fJows
flows
Red cliff basalts
basalts
amygdaloidal,
amygdaloidal, ophitic olivine basalts
1300
Kimball Creek felsite
pink to
to tan,
tan, porphyritic
porphyritic felsite
felsite
1800
Marr Island
Island lavas
tholeiitic basalt,
basalt, intermediate,
intermediate,
mixed tholeiitlc
felsic
felsic lavas
1000
Brule River basalts
granular-diabasic
granular—diabasic basalts
3500
Brule River fhyolite
fhyolite flow
pink to
to gray porphyritic
porphyritic rhyolite
rhyolite
(est.)
4000 (est.)
Havland lavas
Hovland
lavas
mixed porphyritic
porphyritic basalt,
basalt, trachybasalt,
trachybasalt,
rhyolite
200
Red
Red Rock rhyolite flow
flow
red.
red, porphyritic
porphyritic rhyolite
260
Deronda Bay andesite
andesite flow
flow
gray-brown, aphyric
aphyric andesite
andesite
gray—brown,
Grand Portage basalts
basalts
mixed tholeiltic
tholeiitic to
to diabasic
diabasic basalts
basalts
Top
'fop
1020
1020
1020
400—900
400-900
4500
Base
�—83—
-83-
Table 33
Generalized Stratigraphy of Southwest Limb (Tofte—Nopeming)
(Tofte-Nopeming)
North Shore Volcanic Group
Group
(exclusive
(exclusive of interflow sediments)
Approx.
TbLekness_'ft)
Thickness
(it)
Lithostratigraphic
Unit
Lithic character
Tp
4000
Schroeder basalts
ainygdaloidal ophitic
ophitic olivine
olivine tholeiltes
amygdaloidal
tholeiites
>300
>
300
Manitou trachybasalt flow
flow
red—brown granular trachybasalt to
red-brown
to
basalt
(more of
of the
the Schroeder basalts)
(more
>
280
> 280
> 3CC'
>
3CO
few 100's
few
—
—
mostly quartz tholeiites, other
other
basalts
Palisade rhyolite
rhyolite flow
flow
gray
to pink,
gray to
pink, porphyritic rhyolite
Baptism River lavas
mixed lavas, mostly basalts
basalts
— Beaver
Beaver Bay intrusive complex
—
basalts, one felsite
mixed basalts,
felsite
River basalts
basalts
Gooseberry River
3200
—
Bell Harbor lavas
lavas
--
—.
LaFayette Bluff,
Bluff, Silver
Silver Creek
Creek Cliff
Cliff intrusions
intrusions —
—
—
1025
fine—grained basalts
Two
Two Harbors fine-grained
"melaphyres",
"melaphyres", some quartz tholeiites
1615
Larsmont ophitic
ophitic basalts
basalts
amygdaloidal ophitic
basalts.
amygdaloidal
ophitic olivine
divine basalts.
—
—
Knife River
River diabase intrusion
— Knife
—
—
—
—
—
4930
Sucker River basalts
mixed basalts,
basalts, mostly ophitic
4400
Lakewood basalts
mixed basalts, mostly non—ophitic
non-ophitic
—
3600
3600
—
mixed basalts,
basalts, andesites,
andesites, felsites
felsites
Lakeside lavas
lavas
—
diabase sill
sill —
Endion diabase
— Endion
—
Leif Erickson Park lavas
lavas
2560
—
Lester River diabase
diabase sill
sill
— Lester
—
Duluth Complex
— Duluth
—
2300
Nope'iuingbasalts
basalts
Nopeming
Base
Puckwunge Sandstone
Sandstone
Puckwunge
—
—
mixed basalts,
basalts, andesites
andesites
—
porphyri tic meLbasalts,
melc.basal ts, diabasic
diabasic
porphyritic
basalts
basalts
�_____
—84--84-
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M. E.,
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�—85—
-85-
page 22
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Amygdule mineral
mineral zoning in the
Stoiber,
R. E.,
E.• and
and Davidson,
Davidson, E.
E. S.,
Portage Lake lava series,
series, Michigan copper district:
district: Econ.
Econ. Geol.
Geol. v.
v. 54,
54,
p.
1250-1277.
p. 1250—1277.
Walker, G.
G. P.
P. L., 1960,
1960, Zeolite zones and dike distribution in relation to the
structure
basalts of eastern Iceland:
structure of the basalts
Iceland: Jour.
Jour. Geology, v. 68,
68, p.
p. 515—528
515-528
1964, Geological investigations in eastern Iceland:
Iceland: Bull.
Bull. Voic.,
Vole., v. 27,
27,
— - - , 1964,
p.
351-363.
p. 351—363.
�—86—
-86-
Field Trip
Trip A
A
Field
The North
North Shore
Shore Volcanic
Volcanic Group
Group
Leader:
Leader:
John C.
C. Green
Green
University of Minnesota,
~finnesota, Duluth
are intended
intended to
give aa broad
broad picture
picture of
of
The stops
stops described below are
to give
the
the chemical,
chemical, petrographic, and
and structural varieties
varieties of
of lavas
lavas of
of the
the Group,
Group,
some representative exposures of
of the
the minor
minor intrusions
intrusions that
that cut
cut the
the flows,
flows~
and the general structural characteristics
characteristics of
of these
these Upper
Upper Precambrian
Precambrian racks.
rocks.
The area northeast of
of Silver
Silver Bay,
Bay~ where
where Green
Green has
has done
done most
most of
of his
his work,
work, is
is
stressed. The trip excludes the
the Duluth Complex,
Complex, aspects
aspects of
of which
which have
have been
been
or are covered elsewhere (GSA
Guidebook, ILSG 1968 Guidebook,
Guidebook, and Field
Field
(GSA 1956 Guidebook,
Trip BB of
this
program).
of this program). Many more stops are listed below than will be
possible to examinein
but they
included for
examine in a one—day
one-day trip,
trip, but
they are included
for the benefit
of those
those who can
can visit or
or revisit
revisit the
the area
area at
at aa later
later time.
time. The U.S.G.S
U.S.'G.S
7
1/2 minute
quadrangle name
nameisis given
given for
for each
The stops
stops which
7 1/2
minute quadrangle
each stop. The
which are
planned as
as a minimal
frameworkfor
forField
Field Trip
Trip A
are designated
planned
minimal framework
A are
designated with
with an
an
asterisk after
are listed
listed for
asterisk
afterthe
thenumber.
number. Mileages
Mileages are
fordistances
distancesbetween
between
easily identifiable
along
USUSHighway
for
easily
identifiablepoints
points
along
Highway 61
61 (not
(not cumulative
cumulative mileage
mileage for
wholetrip)~
trip), for
thethe
U.S.A.fCanada
whole
for travel
traveleither
eithersouthwest
southwest (starting
(startingatat
u.S.A./Canada
or northeast
Midway
border—- Pigeon River: left—hand
left-hand column)
column) or
northeast atatthe
the
~fidwayRoad,
Road,
border
(St. Louis
Louis Co.
Co. 13),
13),Nopeming,
Nopeming,WESt
west of
of Duluth:
Duluth:right—hand
right-hand column).
column). Mileages
are in
for
side trips
tripsoff
offHwy
Hwy 61
in parentheses
parentheses or
or not
not given.
given. All
All stops
stops are
are
for side
61 are
shown on
1. Descriptions between stops
stops are
are written
written for
for southwestward
southwestward
shown
on Fig.
Fig. 1.
The total
total distance
travel.
The
distancecovered
covered isisapproximately
approximately160
160 miles
mileseach
eachway.
way.
travel.
stops volcanic
volcanic structures
are well
well preserved.
preserved. Visitors
Visitors are
are
At
At several
several stops
structures are
destroying
them,
urged to refrain
refrainfrom
from loosening,
loosening~removing
removing or otherwise
otherwise
them~
urged
since they
they constitute
irreplaceable evidence for
for flow
flow direction,
direction, etc.,
etc.,
constitute irreplaceable
since
and
valuable teaching
students and
teachingfeatures
featuresfor
for local
local students
and future
future visitors.
visitors.
and are
are valuable
GoingGoing
SW
SW
NE
7.4
-0:0
7.4
0.0
3.7
3.7
3.7
Minnesota—Ontario (Pigeon
Start of Trip
River, Minnesota-Ontario
(Pigeon Point,
Point,
Trip A
A -— Pigeon River,
Travel
SW
along
flat
post—glacial
lake
bed,
Minn.
quad.).
SW
along
flat
post-glacial
bed,
—
Mich.
quad.).
Minn.
then rise
rise along
along shoulder
shoulder of
ofa alarge
large
NE-trending dike
then
NE—trending
dike of
of the
Several road
Keweenawan
road cuts
cuts ininMiddle
MiddlePrecambrian
Precambrian
IceweenawanLogan
LoganIntrusions.
Intrusions. Several
Excellent
views
Rove
Formation
shales
small
branch
dikes.
Excellent
views
cut
by
small
branch
dikes.
Rove Formation shales
Pigeon
from
parking rest
rest areas
areastotothethe
Wauswaugoning Bay,
Bay, Pigeon
easteast
overover
Wauswaugoning
from parking
(Rove Fm.
Point (thick
(thickcomplex
complex Keweenawan
Keweenawan sill)~
Susy Islands (Rove
Fm. and
and
sill), Susy
flo's),
Hat
Lower
Royale(Keweenawan
(Keweenawan flows), Hat Point
Point
Lower Keweenawan
Keweenawanflows),
flows), Isle
Isle Royale
with Mount
Mount Josephine
(Logan dike).
Josephine (Logan
At
Stop
1. Logan
Formation (Grand
(Grand Portage
Portage quad.)
quad.) At
Logandik~
dike and
and Rove
Roc Faauction
Stop 1.
the
top of the
the rise
riseisisa adeep
deepcut
cuttrirough
through the
the thick
thickKeweenawan
Keweenawan
the top
Farther
oint.
diabase
dike
that
forms
Mt.
Josephine
and
Hat
Point.
Farther
forms
Mt.
Josephine
and
flat
diabase dike that
the
are
good
cuts
in
the
Rove
down
the
highway
the
southwest
are
good
cuts
in
the
Rove
highway
to
down the
Formation
which
is
here
dominated
by
graywacke.
which
is
here
dominr4lc-J
by
graywacke.
Formation
�—87—
-87-
Going
SW
Going
NE
(At the
the base
base of
of the
the slope
slope an
an interesting
interesting detour
detour can
can be
be
(At
to Grand
Grand Portage Chippewa village and bay and
made to
to the
the SE
to
SE
Grand Portage National
National Monument.
Monument. The base of the Upper
Precambrian sequence forms
forms Grand Portage Island.
Island. Continue
out the west end of the
the village to
to Highway
Highway 61).
61).
7.4
7.4
0.0
0.0
14.8
basalts, Grand Portage (Grand
Stop 2.* Basal Lower Keweenawan basalts,
(Grand
At
the
top
of
the
next
rise
(at
the
Junction
Portage
quad.).
the
top
the
rise
(at
the
Junction
Portage quad.).
of Cook Co.
Co. 17)
17) are
are low cuts exposing basalts near or at
of
at the
the
These
basalts
base of the Keweenawan reversed
reversed polarity
polarity sequence.
sequence.
have aa somewhat
somewhat diabasic texture and have been strongly though
have
though not
not
completely retrograded to prehnite—pumpellyite
prehnite-pumpe11yite facies
facies minerals.
Amygdules contain weathered agate,
Amygdu1es
agate, prehnite, and
and epidote.
epidote.
The basal Upper
Uppe~ Precambrian sandstone
sandstone (Puckwunge)
(Puckwunge) underlies
underlies
the
the gentle slope to the
the north but is
is not exposed
exposed at
at the
the highway.
highway.
It
It can be seen by bushwhacking about
about 1/4
1/4 mile to
to the
the NNW.
NNW. It is
is
aa clean-looking,
somewhat feldspathic
feldspathic quartz sandstone,
sandstone, in
in marked
marked conconclean—looking,somewhat
trast to
low sandstones
to the
the red,
red, immature,
immature, volcanic
volcanic interf
interf10w
sandstones above.
above. The
anC all the
is underlain
lowland beyond
beyond is
underlainby
bythe
theRove
RoveFm.
Pm.,, and
the ridges
ridges are
are
held up
held
up by
by large
large Logan
Logan dikes.
3.0
11.9
Stop
Stop 3.
3. Tholeiitic basalt and
and porphyry
porphyry dike
dike (Grand
(Grand Portage
Portage quad.).
quad.).
unmaintained little
Walk or drive off
off Highway
Highway 61
61 on
on an
an inconspicuous,
inconspicuous,unrnaintained
branch on the lake side to
to an
an old cabin
cabin site
site at
at aa small
small cove
cove (1/8
(1/8
mile). On RR (SW)
(SW) is the
the basal, massive portion
portion of
of aa fine—grained
fine-grained
the Lower Keweenawan Grand
Grand Portage
Portage lavas.
lavas. On
tholeiitic basalt of the
the
the L is a thick,
thick, compound dike
dike of
of porphyritic
porphyritic trachybasalt
trachybasalt that
that
trends E
A large swarm of similar dikes is
E into
into lake.
lake. A
is present
present in
in
this
studied. They are
are unusually
unusually rich
rich ji
in Fe and K.
K.
this area and is being studied.
3.7
3.7
11.1
Stop 4.
4.
Stop
Red Rock rhyolite
rhyolite (Mineral Center
Center quad.).
quad.). At Deronda
to the
the SE
SE to
to the
the breccia—rubble
breccia-rubble base
base of
of
Bay the beach leads out to
feet) porphyritic
porphyritic rhyolite
rhyolite flow
flow which
which is
is the
the
aa thick (over
(over 600 feet)
uppermost flow found to
to show
show magnetic reversal
reversal by
by Books
Books (1968).
(196 8 ).
More scenic exposure can
can be seen
seen by climbing
climbing up
up the
the ridge
ridge and
and
walking out to
to the
the point
point on
on the
the open
open lake.
lake. Less scenic but more
accessible exposure is in
in a road
road cut
cut 1/2
1/2 mile
mile beyond.
beyond.
4.6
10.2
Stop 5.
5. Reservation River Diabase and
and abandoned
abandoned beach
beach ridges.
ridges.
(Mineral Center quad.)
quad.) At the
the top
top of the
the next rise
rise is the
the eastern
edge of the extensive Reservation River
River diabase
diabase complex:
complex: one
characteristic phase
phase is
is exposed
exposed here
here that
that shows
shows faint
faint banding
banding on
on
sonic
surfaces.
Lcrge
some
Large gravel
the lowland
lowland to
to.the
northeast,
gravel pits
pits in
n the
the northeast,
mined out for the
the new highway,
highway, were large abandoned beaches of
late postglacial Lake
Lake Superior.
Superior. Excellent
Excellent smaller,
smaller, later ridges
can still
still be
be seen
seen on
on aa little
little track that
that goes
goes to
to the
the lake
lake shore
shore
can
the base
base of
of the
from the
the slope.
slope.
�—88—
-88-
Going
Going
Going Going
SW
NE
SW
9.0
9.0
5.8
10.0
il.8
14.8
--00
0.0
4.0
----".
0.0
4.8
0r
0.0
0.0
10.6
10.6
Cross Reservation River and out of Grand Portage Indian
Indian
Slope is
is at
at contact
contact of
of Reservation River diabase
Reservation. Slope
complex and lavas (a
(a rhyolite
rhyolite here).
here).
6.* Hovland porphyry
Stop 6.*
porphyry lavas.
lavas. (Hoviand
(Hovland quad.) Opposite aa
on
the
lake
side
are exposures of a remarkable
house
the
remarkable porphyritic
trachyandesite lava flow with platy plagioclase phenocrysts up
to 10 cm
em across.
across. By following
following the
the low scarp to
to the
the NE behind aa
house (private
(private property) two
two flows
flows can
can be
be ueen,
~een, the
the top
top of
of the
the
one being vesicular and showing a slightly uneven crust.
lower one
crust.
These are near the
the base of
of the
the Middle Keweenawan
Keweenawan (normal
(normal polarity)
polarity)
lava sequence,
sequence, and
and are
are assigned
assigned to
to the
the Hovland
Hovland lavas.
lavas. They are
are
here cut by a large
large dike,
dike, at
at least 22 miles long,
long, of brown
elinopyroxenephenocrysts,
phenocrysts, that
that also
trachyandesite with
with small.
small.elinopyroxene
crops out across
across the
the road.
road.
Highway descends to
to old
old lake—bed
lake-bed flat;
flat; then,
then, past
past Big
Big Bay,
Bay,
rises onto higher
higher ground
ground of
of Hovland
Hovland Diabase
Diabase complex.
complex. Cross Flute
Reed River,
River, pass
pass through village of Hovland at Chicago Bay,
Bay, and
and up
onto aa large
large sill—like
sill-like body
body of
of syenogabbro.
syenogabbro. Many road
road cuts;
cuts; some
some
show good foliation of
of plagioclases,
plagioclases, dipping
dipping gently
gently S.
S.
Syenogabbro, basalt pillow-breccia,
pillow—breccia, and rhyolite at Brule
Stop 7.
7. Syenogabbro,
Brule
River (Marr
River
(Marr Island quad.). Opposite Naniboujou Lodge,
Lodge, park in
in lot
of Judge Hagney
tmgney State
State Park.
Park. Walk up trail,
trail, cross rivet
river on footbridge,
footbridge,
Take care
and
follow fisherman's
W bank.
bank. Take
care -—
and follow
fisherman's trail and bushwhack up W
steep and unstable slope in
in places.
places. At footbridge
footbridge is
is medium—grained,
medium-grained,
foliated syenogabbro of
of "Hovland
"Hovland diabase
diabase complex."
complex." This is cut by
basalt dike,
dike, then gives way to a rather coarse—grained
coarse-grained basalt
aa later basalt
lava with chlorite
chloritescraps
scrapsand
andamygdules.
mnygdules. Soon
overlain by
by
Soonthis
this is
is overlain
basaltic—scoriaceous tuff—breccia.
basaltic-scoriaceous
tuff-breccia. After a short
short gap
gap in
in exposure,
exposure,
steep bank resumes
resumes which is made of basalt pillow—breccia,
steep
pillow-breccia, with
altered volcaniclastic matrix. This is
is one of the
the few
few places
places where
evidence for
evidence
for underwater extrusion can
can be seen
seen in
in the
the North Shore
Shore
Volcanic Group (others
(others are
are on
on Grand
Grand Portage
Portage Island
Island and
and WWof
of Duluth
Duluth
in the Lower
Lmyer Keweenawan).
Keweenawan). Farther upstream this
this can
can be
be seen
seen to
to overlie
the altered,
altered,flow—banded
flow-banded and
rled top
top of aa very
very large porphyricic
porphyritic
and styi
swirled
rhyolite
the Bride
Brule has
has cut
cut aa deep
deep gorge
gorge above.
above.
rhyolite flow through which the
Return by fisherman's trail
tr~il at
at top
top of
of bank.
bank.
After crossing
After
crossing the
the Brule (Arrowhead)
(Arrowhead) River,
River, the
the highway rises
rises
over and cuts
cuts through
through three
three hasalts
basalts of
of the
the Brule
Brule River
River group,
group, then
then
crosses a porphyritic trachyandesite
trachyandesite or
or intermediate
intermediate quartz
quartz latite
latite
the }larr
Island lavas
lavas at
at Paradise
Paradise Beach.
Beach. AA few
few more low
low cuts
cuts of
of
of the
Marr Island
this mixed group are
this
are passed
passed in
in next
next 33 miles.
miles.
3.8
3.8
5.8
Stop 3•x
Stop
8.~
Porphyritic
~arr Island
Islan~
Porphyritic intermediate
intermediate quartz
cuartz latite
latite of
p Marr
lavas one
one mile
mile past
past Cook Co.
lavas
Co. 14 (Kadunce
(Kadunce Creek quad.)
quad.) Two large
road cuts
cuts on N.
thick, intermediate
intermediate quartz latite
latite
road
N. side of a thick,
K 0)
plagioclase,
ferroaugite,
and rare
lava (62%
(62% SiO
Si0 , 4.1% K
0)with
with
plagioclase,
ferroaugite,
and rare
2
2
ex-olivine
ana magnetie
magnetitephenocrysts.
phenocrysts. Contacts not exposed.
exposed.
ex—olivine an
,
�-89—89-Going
SW
Going
NE
1 1/2 miles
to the
the west at Kadunce Creek (Kodonce
(Kodonce River)
River)
miles to
State Park a thick porphyritic felsite is exposed, especially
especial~y
in
in a deep
dl~ep and narrow canyon that begins about 1/8 mile upstream
upstream
from highway
highway -— this
this is part of the
from
the Kimball
Kimball Creek
Creek felsite
felsite group,
group,
also exposed in Kimball and Cliff creeks farther
also
farther west.
west. Excellent
wave—cut cliffs
abandoned wave-cut
cliffs of
of Nipissing
Nipissing stage.
stage.
7.3
3.2
3.2
Stop 9.
9. Olivine basalts of
of Red
Red Cliff
Cliff series
series (Kadunce
(Kadunce Creek
Creek quad.).
quad.).
Just past large gravel pit and
and creek
creek gully,
gully, highway
highway rises
rises onto
onto aa
series
flows totalling
totalling between
between
series of
of 5 or 6 ophitic olivine basalt flows
400 and 900 feet
feet in thickness.
thickness. Amygdules contain
contain saponite,laumontite,
saponite,laumontite,
calcite, quartz,
calcite,
quartz, and
and agate.
agate. Plagioclase phenocrysts have floated
floated to
to
top
0.5% K20.
K 0.
top in some,
some, sunk to
to bottom
bottom in
in others.
others. 47% Si02
Si0 , 0.5%
2
2
Past Durfee Creek (near
(near top of Red Cliff basalts) highway (and
(and
cliff) pass onto Devil
Devil Track
Track felsite
felsite group,
group, here
here composed
composed
Nipissing cliff)
of two thick flows.
of
flows.
9.6
1.0
Stop 10.* Felsite of Devil Track sEries,
series, at promontory of
of abandoned
abandoned
Nipissing wave—cut
wave-cut cliff.
cliff. N
N side of highway, 0.85
0.85 miles west of
of
Pink, nonnon— or weakly porphyritic
Durfee Creek (Kadunce
(Kadunce Creek
Creek quad.).
quad.). Pink,
rhyolite
K20)
slabby
jointing
rhyolite or quartz latite (72%
(72% SiO
Si0 2 , 5.5% K
0) with
with
slabby
jointing
2
Bushwhack?ng along old cliff to E
and faint flow—banding.
flow-banding. Bushwhacking
E for 1/4
1/4
mile one eventually passes down
down into
into vesicular,
vesicular, locally
locally spherulitic
spherulitic
and
flow banded top
top of a porphyritic flow
flow of
of similar
similar composition.
composition.
and flow
These two
two flows
flows total
total about
about 1020
1020 feet
feet in
in thickness.
thickness.
Five Mile
(Guano) Rock,
Rock, aa mile
mile out
out in
in Lake
Lake Superior,
Superior, is
~uano)
is made of diabase.
,
10.6
0.0
0.0
3.7
Track~.
upstream
Cross Devil Track
River. This cuts a deep gorge just upstream
felsite flow.
flow. Continue on Hwy 61 into Grand Marais, or
or
in the upper felsite
alternatively turn
turn off just before rise on small side road
alternatively
road (Cook
(Cook Co.
Co.
87)
Stop 11.
11.
87) toward
toward lake
lake to
to Croftville settlement and optional Stop
(off Hwy 61)
61)
(off
(1.3)
_~~
(0.0)
(0.0)
(0.45)
Stop
11. Spherulitic hasal phase,
phase, Grand Marais rhyolite, Croftville
Croftville
Stop 11.
(Grand
quad.) Drive about 1.1 mile along Nipissing terrace
terrace
(Grand Marais
Marais quad.)
over
(about 0.45 mi.
from WWend
this road).
road).
over Croftville
Croftville basalts
basalts (about
mi. from
end of this
Private Property.
?roperty. Ask permission at
at the
the house
hous~ in
in birches
birches on
on lake
lake
side,
beach-back. Slabby,
Slabby, spherulitic
spherulitic
side, exwline
examine outcrops
outcrops at
at modern
modem beach—back.
red rhyolite
rhyolite is
is exposed here (73.4%
(73.4% SiO
SiO , 4.65% K20)
K20) that
that contains
contains
red
hedenbergie,
ex—fayalite
and
magnetite
andesine-oligoclase
and
rare
hedenbergite,
ex-fayalite
and
magnetite
andesine—oligoclase and rare
Nearby
is
cross—bedded,
calcite—cemented
interflow
sand.
phenocrysts.
cross-bedded,
calcite-cemented
interflow
sand.
phenocrysts.
Strata have been steeply tilted
tilted by diabase
diabase intrusions.
intrusions. Continue on
on
road until
until it
it re—joins
re-joins Hwy
Hwy 61.
61.
Croftville road
,
(0.45)
(0.0)
(0.0)
(2.1)
(2.1)
Continue SW
SW to
to Grand
Grand Marais.
Marais.
(off Hwy
H'YY 61)
61)
Stop 12.
12. Breakwater trachybasalt (Good
(Good Harbor Bay
Bay quad.).
quad.). Drive
to
E end of Grand Marais harbor.
harbor. Tombolo
to Coast
Coast Guard
Guard Station at E
here is
is made by gravel bar connecting mainland to
to resistant
resistant island
and
and ledges
ledges of
of aa massive,
massive, locally
locally columnar-jointed,
columnar—jointed, porphyritic
porphyritic
trachybasalt or basalt with small phenocrysts of
of plagioclase,
plagioclase, augite,
augite,
trachybasalt
and rare olivine.
olivine. It
360 feet
feet thick.
thick. It
It is not known
It is
is about 360
this is
is a big flow
certain whether this
flow or sill; to
to the
the west is
is has
has
for certain
aa sharp,
sharp, chilled basal contact
contact against
against felsite
felsite but
but its
its top
top
is covered.
covered. It
It becomes amydgaloidal and zeolitized
zeolitized near
near
contact is
�Going
SW
Going
—90—
-90-
NE
its
to be
be aa flow.
flow. As can be seen
seen from
from
its top and is assumed to
point, it
it forms
forms one of the
the major
major strike—ridges
strike-ridges of
of
vantage point,
"Sawtooth Range"
Range" to
to the
the west (as
(as does the
the big "thomsonite
"thomsonite
sta~ting
Good Harbor
Harbor Bay).
Bay). The harbor at Grand Marais
Harais
starting at Good
probably eroded from
from rhyolite.
rhyolite.
3.7
0.0
0.0
9.2
this
this
the
the
flm.,"
flow"
is
is
lint Trail
Trail
Highway 61 passes corner
corner of
of harbor,
harbor, near
near start
start of
of Gunf
Gunflint
(Cook Co.
Co. 12).
(Cook
Then highway rises
rises to W
W past a good norphyritic
porphyritic rhyolite
rhyolite cut
cut
(Breakwater trachybasa1t
trachybasalt cuesta
cuesta ahead),
ahead), then
then
onto higher level (Breakwater
down across the
the Breakwater
Breakwater trachybasalt
trachybasa1t and
and across
across Fall
Fall River
River
back down
(Rosebush Creek). About 1 mile past this
this creek, low
low road
road cuts
cuts start
start
in two
two thick porphyritic trachyandesite
trachyandesite to
to andesite
andesite flows
flows (55%
(55% Si02,
5i0 ,
2
phenocrysts and
and
2.7% K
K 0)
0) with small plagioclase and clinopyroxene phenocrysts
2
ahead is
vesicular-rubble
is held up by Terrace Point
vesicuar—rubble tops. Big cuesta ahead
Continue across
thomsonite-bearing basalt
basalt flow.
flow. Continue
across Cut
Cut face (Good
(Good
thomsonite—bearing
Harbor) Creek.
Creek.
5.2
3.9
Stop 13.* Thomsonite—bearing
low sediments (Good
Stop
Thomsonite-bearing basalt,
basalt, interf
interflow
(Good
Bay quad.).
quad.). In this
this large road cut one of the major cliff
Harbor Bay
formers
(130') section of
formers of
of the
the "Sawtooth
"Sawtooth Range"
Range" overlies a thick (130')
interf
low
sediments.
The
Terrace
Point
basalt
is
dominantly a
interflow sediments. The
Point
massive,
massive, fine—grained,
fine-grained, ophitic basalt that
that characteristically
characteristically contains
contains
thomsonite
its lengthy exposure (including
(including in
thomsonite in amygdu1es,
amygdules, but
hut in its
this cut)
cut) several
several flow units
units of
of varying character show complex
this
relations with the major, massive
relations
massive part
part of
of the
the flow.
flow.
The interfiow
interflow sediment Is
is here mainly thin—bedded
thin-bedded siltstone
siltstone
shale, but by walking up
up the
the bed of
of Cutface
Cut face Creek
Creek at
at
and silty shale,
the bottom
bottom of
of this
hill one passes
the
this hill
passes outcrops of the
the basal contact
contact
the amygdaloidal—scoriaceous
amygdaloidal-scoriaceous top
top of
of
of the sediments resting on the
an
flow and
wellan andesite
andesite flow
and eventually reaches large banks cut into well—
bedded sandstone showing abundant ripple
ripple marks.
marks.
9.2 —
0.0
0.0
16.9
0.5
0 5
16.4
16 4
cuts of the
the complex
complex upper
upper parts
parts of
of the
the
Highway 61 passes low cuts
Terrace Point flow complex,
complex, with big cuesta
cuesta on this
this flow
flow visible
visible
ahead,
ahead, then
then at
at jct.
jct. of
of Cook
Cook Co.
Co. 7 passes
into coarse—grained
coarse-grained olivine
olivine
passes into
basalt of the
the Lutsen
Lutsen basalt
basalt series.
series. Cross
Cross Cascade River in State
Park.
Park. Trail up W
W side provides access to
to good
good river
river outcrops
outcrops of
of
Terrace Point thomsonite
thomsonite basalt,
basalt, the
the underlying
underlying sandstones,
sandstones, and
and
several andesite flows
flows of
of the
the Good
Good Harbor
Harbor Bay
Bay series.
series. Drive past
Cascade Lodge.
Lodge.
Stop 14* Cascade
(Deer
Cascade olivine
olivine basalt
basalt of
of Lutsen basalt
basalt series (Deer
Yard Lake quad.). 0.5 miles W.
W. of
of Cascade
Cascade River.
River. Shore outcrops
of aa thick (100
more), relatively
of
(100 feet
feet or more),
relatively coarse—grained
coarse-grained olivine
basalt
this Cascade—Lutsen
Cascade-Lutsen area.
area.
basalt of a distinctive group in this
Segregation cylinders
cylinders up
up to
to 6"
6" or so
so in
Segregation
in diameter and segregation
lenses
lenses or sills can
can be
be seen
seen within
within this
this flow.
flow.
Highway continues
continues on
on long
long straight
straight stretch roughly parallel
parallel
to strike of Lutsen basalts,
topmost series of the
the North
North Shore
Shore
to
basalts, topmost
Volcanic Group.
Group. Pass
Pass through Lutsen village (big
(big ridges
rid?,es to
to
W held up
W
up by Leveaux trachybasalt
trachybasa1t sill),
sill), to
to Poplar River.
Rive~,
�—91—
-91-
Going
SN
SW
9.3
Going
NE
---7.1
Stop 15.
15. Poflyritic
Porphyritic olivine basalts of Lutsen series
series (Lutsen
(Lutsen
Poplar River.
River. Watch
Hatch your step
step -- dangerous. Private land.
land.
quad.), Poplar
Several flows
flows of a distinctive ophitic olivine basalt characterized
characterized
by abundant small
small(1—3
(1-3nun)
mm) blocky bytownite phenocrysts are
are exposed
exposed
by
the Poplar
from
Poplar River
River at
at Lutsen
Lutsen Resort,
Resort, up
up through
through an
an
frcrnthe
the mouth
mouth of the
canyon to
to the
the highway bridge
bridge and upstream to left bend
impassable canyon
(1/10
highway). Take fisherman's
fisherman's trail
trail on
on WWside.
side. This
(1/10 mile
nile from highway).
flow
Ilprimitive" composition
composition (lowest
(lowest K,
K, highest
highest Mg)
Mg)
?low type
type has
has the
the most
most "primitive'
Si02,
0.l2I K20).
L bend in river
,
0.12%
K20).
At
of the North Shore lavas (1+7%
(47% Si0
2
it overlies breccia-rubble
breccia—rubble top of aa basaltic andesite
andesite flow;
flow; red
red sand
sand
has
been
washed
into
all
the
interstices
between
the
lava
blocks,
has
lava
a typical situation.
situation.
12.3
4.6
Leveaux —- Onion HtIl=Stop 16. Leveaux_
porphyry !411.
Eill (Tofte
Mtn. trachybasalt
trachlbasalt porphyry
SWof
of Poplar
Poplar R..
at slight L
quad. ) . 2.5 mi.
R•..at
L bend cross
cross Rollins
Rollins
quad.).
ml. SH
Creek and irnediately
immediately turn up U.
U. S.
S. Forest Service gravel road
road
(No.
336). Continue on it
it as
as it contours back to SW, then
then cuts
cuts up
up
(No. 336).
OnionRiver
Mvergap
gapininbig
big ridge
ridge held
held up
up by
by aa big
big trachybasalt
into Onion
into
porphyry sill.
sill. This sill forms
forms Leveaux Mtn., the high ridge
ridge with
a
fire tower
a fire
tower on
on it
ittotothe
theSW,
SW, and
and comes
comes out to the lake
lake shore
shore to
to
form the islands at
Taccnite
Harbor
SN
of
Tofte.
Its
contacts
at Taconite Harbor SH .of Tofte.
contacts are
are
not exposed but it
it crosscuts
crosscuts the
the lavas.
lavas. Park as near as
as possible
possible
to the S
S corner
corner of
of the hill
hill on
on the
the NE
NE side
side of
of the
the gap,
gap, and
and bushwKack
bush~ack
a short distance N
n to
to· the
the steeper,
steeper, rocky
rocky rise.
rise. Here the lower
lower part
exposed
fine—grained, pigeonite-augite
pigeonite—augite trachytrachy—
of the sill
sillis is
exposed—- a fine-grained,
to trachyandesite.
trachyandesite. Farther up
up the Glope
slope aa bit
bit abundant
abundant large
large
basalt to
(1
blockylabradorite
labradorite phenocrysts
phenocrystsappearroruptly;
appeartruptly; they appear to
(1 cm)
cm) blocky
to
floated. This porphyritic phase forms
have floated.
forms the upper part of
of the
the
throughoutits
its extent.
extent.
sill throughout
16.9
2....
0.0
0.0
---12.1
Continue SW
svr past
Tofte.
pastSawbill
SawbillTrail
Trail (Cook
(CookCo.
Co.2)2)atat village
village of Tofte.
Town
Town park
park on
on lake
lake shore 0.3
0.3mi.
mi.SW
SW of
ofEdgewater
Edgewater Motel
Motel has
has good
good
exposures of
of thin-bedded
thin—beddedophitic
ophiticolivine
olivine basalts.
basalts. DO
DO NOT
exposures
NOT DESTROY
DESTROY
FEATURES.
These
the top
top of the section
section of the orth
NorthShore
Shore
FEATI.ffiES.
Theselie
lie at
at the
Volcanic Group.
10.1+
10.4
anorthosite in diabase (Tofte
Stop 17.
17. Carlton Peak ?lloythosite
(Tofte quad.) 1.7
1.7 mi.
mi.
jet., opposite
opposite large
large Superior
Superior National
National Forest
Forest
SW of Sawbill Trail jct.,
Sign,
Sign, turn up road of Erie Mining Co.
Co. to large quarry in
in side
side of
of
Carlton Peak,
anorthosite xenoliths
xenoliths in
in
Peak, which is held up by massive anorthosite
intrusion. Private Property.
Property. The
The complex
complex rela.tions
relations
a gabbroic intrusion.
between the
the anorthosite
anorthosite and
and various
various phases
phases of
of olivine
olivine gabbro
gabbro are
are well
well
1.7
exposed.
2.5
9.6
Stop 18.
Thin—bedded ophitic olivine tholeiites of
Thin-bedded
of Schroeder
Schroeder
18.
basalts, Temperance
Temperance River
River (Tofte
(Tofte quad.).
quad.). Park at State Park lots,
lots,
walk down
down trail to bridge near
near river
river mouth.
mouth. Note excellent erosional
Several thin flows
flows or flow units, with ropy
ropy surfaces,
surfaces, pipe
pipe
potholes.
anygdules
amygdules and lensing
lensing shape
shape are
are well
well exposed
exposed here.
here. If more time is
is
available, walk up NE side of river above
available,
above highway to
to the
the main
main gorge
gorge
where the river
river has
has cut
cut aa very
very deep
deep and
and narrow
narrow slot
slot with
with larger
larger
into thicker olivine
olivine basalts.
basalts. Warning:
people have
have been
been
potholes into
Warning people
killed trying
trying to
to jump
jump across.
across. Large joint
joint columns
colUmns visible
visible on
on trail
trail
killed
cylinders are
are present in
in thicker
thicker flows.
flows.
and overlooks,
overlooks, and vesicle cylinders
�—92—
-92-
Going
SW
SH
Going
3.8
3.8
NE
8.3
8.3
9.14
2.7
Drive SW
SI'! through Schroeder and
and Taconite
Taconite Harbor
Harbor (power
(power
pellet shipping
facility of
plant and taconite pellet
shipping facility
of Erie
Erie fining
Mining Co.)
Co.)
with occasional
occasional low
low cuts
cuts of
of ariygdaloidal
amygdaloidal or ophitic olivine
olivine tholeiite.
tholeiite.
Stop 19*.
19*. Thin—bedded
Thin-bedded ophitic
ophitic olivine
olivine tholeiite
tholeiite of
of Schroeder
Schroeder basalts
basalts
at Sugar Loaf Point (Little
at
(Little Marais
Marais quad.).
quad.). Private property.
property. Drive
down side road (just
(just opposite gravel
gravel road
road from
from uphill)
uphill) at
at Consolidated
Consolidated
Paper Co.
storage and
and handling
handling facility.
facility. Drive down to cove,
cove,
Co. pulpwood
pupwood storage
end ask
ask permission
permission to
towalk
walk onpoint
opoint at
and
at office.
office. Notice great old
Walk around
pine boom—logs
to raft
raft pulpwood
pulpwood across
cross lake.
boom-logs used to
lake. Halk
Excellent exarrioles
Sugarloaf Point clockwise
clockwise from
from end
end of
of beach. Excellent
examples
up) and thicker flows
flmv units
units (6"
(6" and up)
flo1>ls of ophitic "olivThe
" olivine
of thin flow
tholeiites ,It with ropy
ropy surfaces,
surfaces, bent
bent pipe
pipe amyvdules,
amye:dules, and
and clastic
clastic
tholeiites,"
dikes
dikes where sand was washed into
into open
open ;oints
joints in
in the
the tops
tops or
of flows.
flows.
not remove or destroy
structures! On
On the
the sides
sides of
Please do not
destroy these
thes~_Et~.~ures!
the high
high knob at the end can
the
can be seen
seen vertical
vertical tube—like
tube-like concentrations
concentrations
arnydules ("vesicle
of amygdules
("vesicle cylinders")
cylinders") in
in the massive
Massive Imler
lower nart
tart of the
topmost flow.
flo",.
11.77
11.
0.14
0.4
12.1
0.0
0.0
11.0
Cross Cook/Lake
Cook/Lake County
County line.
line.
Ophitic
olivine!-holeii:~s,
tholeiites,
Ma! !-S.?-chY.Easalt.,
tracybasalt, and
Qphiti c_ olivine
~If~it0l.!
strike—fault,
Caribou River
River (Little
(Little ~larais
arais quad.)
strike-fault, Caribou
quad.) Park
Caribou
Park at Caribou
Falls State Park 1°t
side of the
the hip-;h,.,ray
highway and "Talk
walk ut
Falls
lot on the HH side
up the
(Between the
the highway
highway and Lake
Lake is
is private property including
trail. (Between
typical ophitic
falls over typical
ophitic olivine
olivine basalts).
basalts). In
In the river
riverand
and aiocg
alonr;
the trail are a few outcrops
the
outcrops of the red
red volcanic
volcanic breccia
breccia and
and basalt
basalt
that underly the "Manitou
"lvlanitou trachybasalt," then
then at
at aa LL bend
bend is
is the
the NE—
NEmost outcrop of
most
of the
the trachybasalt.
trachybasalt. lis
ap]Jroaches the falls
falls
As the trail anproaches
the river has
the
has cut through aa thick section
section of
of volcanic
volcanic breccia,
breccia, nut
but
aa large
strike-fault intervenes between this and
and the
the typical
typical ophitic
ophitic
large strike—fault
olivine
thoeiites (flio2=5-.7%,
oli
vine tholeiites
(Si02==45-47%, K
the cli f f
Torn tt:e
:20=o.3_o.5z)
20"'0. 3-0.5%) that form
over which the
the river
river fells.
fa.lls. Several
flovs,
10-30'
each,
Several flows, 10—30' each, are visible
in the
the cliff each with a massive lower part and
in
and an
an amygdaloidal
amygdaloidal and
and
slabbv-jointed
top.
slabby-jointed
These
nearly all
allthe
thelavas
lavasbetween
between
Theseare
are typical
tynical of nearly
1:ittle arais
Little
Maraisand
andLutsen,
Lutsen, the
uppermost sequence
sequence of
of tbe
the North
North Chore
Shore
the uppermost
Volcanic Group.
Group.
Stop
Stop 20.
20.
cli'
2.2
8.8
8.8
Dri ve SW,
8\1, cross
cross anitou
~ftanitouRiver,
River,'.rhich
lIhi ch has
Drive
has cut
cut aa deep
deep f!;orge
aorge throup;h
throu'h
drift and olivine basalts (trail
in State
State Land
Land accessible
accessible
drift
(trail up
up streaxn
stream. in
on SW
S1:T side via
via gravel
gravel pit
pit road),
road). Commercialized
has
Cornniercializedgonre
gorge dmmstrear'l
downstrean has
falls, sea arches.
falls,
Continue LW
bend at
at Little
Little I·,farais
Marais R.
.
SH almost to
to I?
H bend
14.5
4.5
6.5
6.5
Stop 21.
21.
Manitou trachsasait
(Little
Stop
!5~j.~.sm
!-!_a~J1_x.:!?~a1.!-.
(Littlei'larais
Marais quad.).
quad.). Turn
'I'urndo'.in
down
road at Ben Fenstad's
Fenstad's Resort,
Resort. Private
ask permission
Private nrqperty;
property; ask
for entry at
for
at office.
office. Continue down to lakeshore, bearing
bearinp. left
left to
to
end of driveway
dri vevay loop at
at fishhouse.
fishhouse. here
here at
B.t the
the end
end of
of the
the slit
slin is
is
exposed the base of an 1arre
larp,e flow
flow of
of granular
granular trachvbasalt,
trachybasalt, at
at least
least
300'
rLles lonp"
long, that forns
ofth~SDreledges
t1roreledges Croa
300' thick and 55 miles
forms !'uch
much of
fro~
breakwater on,
HE of M8ni
this breaki-mter
on, both SW
G\l and
and tIE
tou FLyer.
Pi vel". It contains
contains
Menitou
Si022 and 2.3%
about 52%
52;~ Si0
K2 (), and
and has
has labradorite.
labradorite, augite,
aup.;i te, and
and
2.3 K20,
and abundant
ahundant KK feldspar
feldspar and
and
altered rare olivine phenocrysts and
pigeonite
piGeoni
te in
in the
the groundviass.
groundmass. higher
hip:,her in
in the flow
fIm, it
it is
is coarser—
coarser-
�—93—
-93-
Going
SW
Going
SE
HE
grained, less
less potassic and
Its top is
grained,
and less
less porphyritic.
porph~ritic.
Its
is not
exoosed.
It overlies
overlies aa sequence of interLedded
eXDosed.
It
interbedded basalts and red
red
volcanic
volcanic breccia
breccia or
or conglorierate.
conglomerate.
high ridge inland is held up by
Continue
Li ttle 'arais.
~1arais.
High
Continue S\J
SW past Little
a
thick
intrusive
diabase
sill
containing
a thick intrusive diabase
containin~ some anorthosite blocks.
blocks.
8.0
8.0
9.1
9.1
2.6
Stop 22.*
.iartz tholeii
tholejite—trachybasalt,
Kennedy Landing
22. * QJ.artz
te-trachybasalt, Kennedy
(Finland quad.)
quad.) Good cuts for
for about
about 1/3 mile through
throu~h several
several
typical auartz
quartz tholeiites
tholeiites to
to trachybasalts.
trachybasalts. They show the
the charcharacteristic fine-grained,
fine—grained, aphyric
anhyric texture,
texture, oxidation lamellae, and
acteristic
and
scoria-rubble
feldspar
scoria—rubble tops. They contain interstitial alkali feldspar
and about
about 51-53%
5l—53 5102
and
Si02 and
and up
up to
to 2%
2% K20.
K20. Red sand,
sand, locally cross—
crossbedded,
fills the interstices between fragments.
fragments. Large knob
knob
bedded, fills
is made of the thickest of
of these flows.
flows.
overlooking the bay is
7.8
7.8
Stop 23.
in ~y~nogllR..br~;
syenoabbro; overturned
Anorthosite in
23. ** An_,?rth,?sitE:.
ove!:turned lavas
l~vas
(Illgen City quad.).
quad.). After crossing
crossing Kennedy Creek
Creek come
come to
to deep
deep
vertical cut
cut in an irregular discordant intrusion
intrusion (part
(part of
of Beaver
Beaver
Bay complex)
Day
complex) of altered syenogabbro that contains
contains aa great,
great, massive
massive
of rather
After examining
this, walk
block of
rather pure
pure anorthosite.
anorthosite.
After
examining this,
walk or
drive SW
drive
SW downhill
cut that
sequence of
of
downhill to
to lower cut
that is
is composed of a sequence
several basaltic
basaltic lavas
lavas with an interflow sediment bed —
several
- all
all of which
which
have been overturned,
overturned, probably as
as aa result
result of
of forceful
forceful intrusion
intrusion
of nearby diabases. These basalts show
show aa variety
variety of
of structures,
structures,
including
at the NE end
end some
some
including some
some lobes
lobes that
that look like pillows and at
red scoria,-rubble
scoria—rubble that
that is
is characteristic of the top part of the
red
fine—grained tholeiites,
tholeiites, basaltic andesites,
fine-~rained
andesites, and trachybasalts.
trachybasalts.
11.0
42
0.0
0.0
0.0
It.9
~
Continue
to Ulgen
lilgen City,
City, ~
Lc•• •with
Rte.ito
Continue SW to
Tith Minc.
Minn. Rte.
-.l to Ely.
Ely.
Just
.Just to NE are cuts
cuts in
in quartz tholeiite flows,
flows, to
to SW
SW cuts
cuts in
in
altered rhvolite.
rhyolite.
0.45
0.45
4.5
24.*
Stop 21~.
Palisade .!1~_a~
Head P.s>E1?-~)'Ti
pohyritic
Stop
* ~~~isad~,
tic:: rhyolite,
rhyolite" Shovel
Shovel Point
Point
(Illgen
(Ingert City quad.3.
quad.). 0.45
0.b5 mile SW
SW of
of Illgen
Illgen City
City jct.,
jet., or
or 0.145
0.45 mile
NE of Baptism River,
River, search for
NE
for unmafled
unmarked trail leading
leading to
to shore
shore
Here is
at Shovel Point in
at
in Baptism
Baptism 9.
R. State
State Park.
Park. Here
is well exposed
the upper-middle
upper—middle part of
porphyritic rhyolite
rhyolite
the
of the
the thick
thick (>300'?
(>30d: porphyritic
(quartz
(quartz latite)
latite) that
that also
also forms
forms Palisade
Palisade Head to
to the
the SW and the
road cuts at
at Tllgen
III~en City.
City. Take care on
on clifftop.
clifftop. View to SW
over underlying lavas ("Baptism
( "Baptism basalts")
basalts ") and
and some
some mafic
mafic intrusive
intrusive
bodies,
bodies, to Palisade
Palisade Head.
Head. Follow trail down dipslope to end
end and
and
corner: view TIE
toward overlying
overlying quartz
quartz tholeiite flows.
NE corner:
NE toward
flows. Return
on sa1Ie
same trail
trail
_._----~
Drive
Head (big
(big hill
hill with
with
Drive 811
SW across
across Baptism !liver
River to Palisade head
radio beacon).
2.1
2.7
(Iliren
joint
(Tity quad.).
quad.),
Stop 25.
25. Palisade
Drive up
up
Palisade Head
Head rhvolite
r1yaUiq. (Illgen City
narrow, winding road--C,ju;t'"
road (just past--Palisade
past Palisade Creek)
Creek) to
to top
top of
of cliff
cliff
next to raOio
careful —
columns are
radio beacon.
beacon. ,9areful
- joint colwnns
are se-narating
separating
Excellent views
from rest of
of hill.
hill. ~xcellent
views to
to .N,
~, NE, SE,
SE, SW.
SW. Ridges to
�—94—
-94-
Goin,:?;
GoinI
SW
Going
NE
"[IT, NE aie
B,Te held up by intrusions
intrusions of
of Beaver
Beaver Bay
Bay complex.
complex. Up
Up
N.
lakeshore to NE is columnar—jointed
columnar-jointed Shovel Point,
Point, made
made of
of same
same
rhyolite flow,
is smoke from Taconite Harbor
flow, and far
far beyond is
plant and
and Carlton
Canton Peak
power plant
Peak anorthosite
anorthosite knob
knob at
at Tofte.
Tofte. To S
across lake
lake are
are Apostle
Apostle Islands
Islands and Bayfield Peninsula, Wisc.
across
Wise.
To SW is Reserve Mining Co.
Co. taconite plant at
at Silver
Silver Bay
Bay and
and humpy
humpy
Palisades
made
of
thick,
por—
topography of Beaver
Beaver Bay
Bay complex.
complex. Palisades
porrhyolite with quartz
quartz and
and feldspar
feldspar phenocrysts,
phenocrysts, flow—
flowphyritic rhyolite
banded at the base. Return to
to highway.
highway.
1.9
4.9
0.0
0.0
0.0
0.0
i1.8
14.8
0.4
l.3
14.3
0.14
at Silver Bay,
2.15 ml.
mi. to traffic light
light at
Bay, site of
Drive 2.75
Co. 's taconite plant where
where about
about 100,000
100,000 tons of '
Reserve Mining Co.'s
rock from the eastern
eastern Mesabi
Mesabi Range
Range are
are processed per day.
day.
Stop 26.
26. Anorthosite in
in diabase
diabase of
of Beaver
Beaver Bay
Bay complex,
complex, Silver
Silver
(Silver Bay
Bay 15'
15' quad.).
quad.). Stop at road cut
cut directly
directly opposite
opposite
Bay (Silver
the main building
taconite plant (after
building of
of the
the Reserve
Reserve Mining
Mining Co.
Co. 's
's taconite
(after
Here
several
large
blocks
of
anorthosite
the' 2nd
lights).
anorthosite
the
traffic
lights).
2nd
are
in the Beaver
Beaver Bay
Bay
are included in diabase, a typical assemblage in
complex. Large patches of
of interstitital,
interstitital, poikilitic
poikilitic olivine
olivine occur
occur
in
anorthosite. No definite source
source for
for the
the
in some parts of the anorthosite.
Small red
red veins
veins and
and dikelets
dikeletsofof"granoph~y'.(e"
"granophe"
anorthosite is
is known. Small
cut the diabase and
and anorthosite.
anorthosite.
across Beaver
Beaver River
River to
to Beaver
Beaver Bay.
Bay.
Continue SW 2.8 miles across
3.2
3.2
11.6
Stop 27.
St,up
27. Beaver
Beaver Bay
ferrogabbro and
and Black
Black_ Bay_ gabbro (names
(names after
y ferrogabbro
Gebman)
Gehman) of Beaver Bay
Bay complex
complex (Silver
(Silver Bay
Bay 15'
15' quad.).
quad.), Drive or
down to shore
shore on
on gravel
gravel road
road opposite
opposite the
the main
main restaurant
restaurant In
tn
walk down
Beaver
Beaver Bay.
Bay. Walk E
E through woods across little
little point
point to
to shore
shore
ledges. These are well-foliated
ferrogabbro of
of the
the Beaver
Beaver Bay
Bay
well—foliated ferrogabbro
Ferrogabbro, one
one of
of two similar
similar plugs
plugs in
in this
this area.
area. On walking NE along
the shore, the contact
contact with an
an enclosing
enclosing ring—dike
ring-dike of
of Black
Black Bay
Bay Gabhro
Gabbro
is reached;
reached; such rings
rings surround both ferrogabbro
is
ferrogabbro plugs.
plugs. It
is
rather
It is
inhomogeneous and locally contains very abundant apatite.
inhomogeneous
apatite. The
The ophitic
ophitic
Beaver River Gabbro can
can be seen farther
shore below some
some
farther along the
the shore
cabins. Return to
to highway.
highway.
-
Continue SW through Beaver Bay complex;
complex; most outcrop
outcrop is
of
is of
coarsely mottled,
mottled, ophitic olivine gabbro ("Beaver
("Beaver River
River Gabbrot'
Gabbro"
of
of Gehman),
Gehman), well
well seen
seen opposite
opposite Kings's
Kings's Landing
3 miles
miles from
from
Landing Marina
Marina 3
Beaver
Beaver Bay.
Bay. After 2.2 more miles road
road branches to
to Split
Split Rock
Rock
Lighthous,buil on
Lighthouse,built
on anorthosite
anorthosite in
in diabase.
diabase. At
Day Hill
Hill (parking
(parking
At Day
and
1.0 mile beyond, is
and trail),
trail), 1.0
is last exposure of Beaver Bay
Bay
complex.
Re—enter volcanics,
continue 5.14
5.4 miles to
to Gooseberry
Gooseberry
complex. Re-enter
volcanics, continue
Falls State Park.
Park.
114.8
14.8
0.0
0.0
0.0
13.1
l3.i
Stop 28.
Stop
28. Smooth—surfaced
Smooth-surfaced olivine
olivine basalt,
Gooseberry Falls
Falls State
basalt, Gooseberry
State Park
Park
(Split Rock
Point quad.).
~Split
Rock P6int
quad.). Below highway
bridge
are
good
exposures,
highway bridge are good exposures,
in. and between falls, of Columnar—Jointed olivine
ln, and between falls, of columnar-jointed olivine basalt
basalt lavas
lavas with
with
ainygdalojdal tops,
tops, and
amygdaloidal
and smooth, gently
gently billowing
billowing surfaces.
surfaces.
Continue SW through Castle Danger (2.L
Continue
(2.4 mi.),
across Crow
Crow Creek
Creek
ml.), across
(a diabasic
diabasic intrusion
intrusion here
(a
returns soon
soon to
to SW
SWat
here returns
at deeply
deeply weathered
weathered
Lafayette
Lafayette Bluff),
Bluff), through
through Encampment
Encampment Porest
owned old—
oldForest(privately
(privately owned
growth
forest
with
growth forest with summer
to to
Silver
tni~~
summerhomes)
homes)
SilverCliff
Cliff(anothp~
(anoth' +1I41-
�Going
NE
Going
SW
SW
—95—
-95-
intrusion) to outskirts of Two Harbors.
gabbroic intrusion)
12.7
0.5
Stop 29.
29. Quartz tholeiite basalt, Two Harbors city park (Two
(Two
Stop
Just before entering town,
Harbors
town, turn
turn toward
toward lake
lake at
at
I:arbors quad.).
quad.).
Drive past Burlington
Wa—Ke—Ya Motel.
road to
to city
city camp
camp ground and
and Wa-Ke-Ya
Burlington
road
Bay,
and up
up aa hill.
hill. Park at hilltop picnic area, walk
walk EE to
to shore,
shore,
Bay, and
then S.
S. Well exposed contact between amygdaloidal,
amygdaloida1, weathered
weathered
then
(ex—laumontite)
top of
of one basalt and massive basal part of an
(ex-laumontite) top
analyzed fine—grained,
fine-grained, aphyric quartz tholeiite
tholeiite (50%
(50% 5102,
Si02, 0.6%
K20). Local thin sand lenses near and
and at
at contact;
contact; traces
traces of
of
Cu have been
been found.
found. The tholeiite shows
shows occasional small
small quartz—
quartzagate and chlorite amygdules
amygdu1es and
and typical
typical incipient
incipient sheeting—
sheetingfractures with thin
.of this
this thick
thick
thin bands
bands of
of oxidation.
oxidation. Upper
Upper zonezone' ,of
tholeiite can be examined to
to S.
S. toward
toward power
power plant;
plant; it
it becomes
becomes
rubbly,
vesicular, brecciated, with abundant
rubb1y, vesicular,
abundant laumontite.
laumontite. Return
to Hwy 61.
13.1
0.0
0.0
20.6
20.6
20.6
0.0
0.0
0.0
5.9
(3.0)
(3.0)
(3.0)
Continue SW to traffic light in
in Two Harbors.
Harbors. At west end of town
town
take express highway
highway to
to Duluth.
Duluth. Many cuts
cuts of basalts and minor
diabase intrusions. At-about
At- about 17.7
11.7 miles Moose
Moose Mtn. is
is seen
seen inland,
inland,
held up by Lester River diabase sill.
sill. At 20
20 miles jct.
jet. with old
old
St. Louis
Louis Co.
Co. 61),
61), and
and at
at 20.6
20.6 miles
miles Lester
Lester River
River
Hwy 61 (now
(now St.
either continue
continue straight on Hwy
bridge. Just beyond,
beyond,either
Hwy 61
61 (London
(London Rd.)
Rd.)
direct to downtown 6 miles ahead,
ahead 9 or
or turn
turn uphill
uphill on
on Minn.
Minn. 23
23
(60th Ave.
Ave. E)
E) across ItR
tracks to
to Superior
Superior St;
St; go left.
(60th
RR tracks
left.
Stop
Stop 30.
30. Tischer Creek felsite
felsite and
and Endion
Endion sill,
sill, Congdon
Congdon Park
Park
(Duluth quad.). Examine outcrops beneath bridge; then
then walk
walk up
up
on WWside
side of
of creek.
creek. There are some
some impassable
impassable
trail that starts on
places where you must climb
climb up
up to
to aa bank—top
bank-top trail
trail on
on WWside.
side.
part of
of section cuts
cuts through
orange, foliated
foliated felsite
felsite with
with
Lower part
through orange,
flow
inclusions, Clut
by two
two
flow structure,
structure, quartz veinlets, occasional inclusions,
out by
or three basaltic
basaltic dikes.
dikes. Upstream at top of
of steeper
steeper part
part of
of gorge
gorge
the stream cuts down into red granophyre top
top of
of Endion
Endion sill.
sill. Upcuts gradually
gradually down
down into
into intermediate,
intermediate, then
then gabbroic
gabbroic
stream the creek cuts
rocks
of
main
part
of
Endion
sill.
rocks of
Endion sill. At Vermilion Road bridge (second
(second
bridge above Superior St.)
St.) still
still in
in lower—middle
lower-middle part
part of
of sill;
sill;
return via trail
trail or Congdon
Congdon Parkway
Parkway on
on W.
W. side.
side. See Ernst,
Ernst, 1960.
1960.
Continue SW on Superior St.
St. over rise
rise held
held up
up by
by Endion
Endion Sill.
Sill.
5.0
5.0
0.9
0.9
5.9
5.9
0.0
0.0
0.0
0.0
11.2
11.2
Stop 31.
31. Basaltic-andesitic
interflow sandstone,
sandstone, Leif
Leif
Basaltic—andesitic lavas, interflow
Erickson Park, Duluth
Duluth (Duluth
(Duluth quad.).
quad.). At lath
10th Avenue E.
E. turn
turn off
off
Superior St.
Road at
at Leif
Leif Erickson
Erickson Park.
Park.
St. toward lake to London Road
I
Walk over footbbridge
footbbridge near
near "viking
"viking ship"
ship' to
t shore.
shore. Weakly por—
porphyritic basalt or basaltic
basaltic andesite
andesite ledges
ledges behind
behind stage.
stage. Rubbly
Rubbly
(weathered?)
(weathered?) top
top to
to NE
NE is
is directly overlain by a thick
thick cross—bedded
cross-bedded
sandstone,
that is
is cut
cut by
by aa small
small dike
dike at
at NE
NE
sandstone, strongly epidotized, that
more flows
end of beach. Several more
flows exposed along shore
shore to
to SW.
SW.
anc Superior
Superior Street,
Street, downtown
downtown Duluth.
Duluth.
Lake Avenue and
(approx.)
~approx.)
1L
11-22
approx.))
:approx.
o. a
0.0
Drive SW on Hwy 61 past Point of Rocks
Rocks through Duluth Complex
Thomson Hill
Hill to
to Nopeming.
Nopeming. Turn R
R at
(St. Douis
13),
up Thomson
at Midway
Midway Road
Road (St.
Louis ~o.
o. 13),
drive uphill about 0.9 mi.
mi. almost
almost to
to top
top of
of rise.
rise.
�—96—
-96-
Stop 32.
32. Basal (Puckwunge?)
(Puckwunge?) sandstone, basal basalts of
of Lower
Lower
Keweenawan
Ke\veena\van ('Grandview
("Grandview Golf Course" locality,
locality, Esko
Esko quad.).
quad.).
Drive or walk E
E on road toward
toward Cloquet
Cloquet city
city water supply
supply tank
tank on
on
hill.
Pass low outcrops of vertical Thomson slate
slate and
and graywacke
graywacke
(Middle Precambrian: more are exposed
(Middle
exposed on
on rise
rise and
and roadcuts
roadcuts to
to
N.). At
slope, go either RR or LL along
along base of
of slope
slope to
to outcrops
outcrops
N.).
At slope,
of basal Upper Precambrian quartzite and
and conformably
conformably overlying
mafic, porphyritic basalt with small augite
mafic,
augite and
and altered
altered olivine
olivine
to rocks
rocks on Lucille Island
Island at
at Grand
Grand Portage.
Portage.
phenocrysts identical to
Note pillows subtly outlined by small vesicles and
and color
color zones.
zones.
�—97-.
-97-
TO THE
GUIDE TO
THE PRECAMBRIAN
PRECAMBRIAN ROCKS
ROCKS
OF NORTHWESTERN COOK COUNTY
COUNTY
AS
EXPOSED ALONG
ALONGTHE
THE GUNFLINT
GUNFLINT TRAIL
AS EXPOSED
Prepared by
by
Paul
Paul W.
\~. Weiblen
Department of Geology and
and Geophysics
Geophysics
University of Minnesota
Hinnesota
Minneapolis, Minnesota
Minneapolis~
G.
B. Horey
G. B.
Morey
Minnesota Geological Survey
Survey
University of Minnesota
Minnesota
St. Paul, Minnesota
'1.
G. Mudrey
H.
G.
Minnesota Geological Survey
Survey
University of
of Minnesota
Minnesota
St. Paul,
Paul, Minnesota
�—98—
-98-
Geology of Northwestern Cook County,
County, Minnesota
INTRODUCTION
An exceptionally complete
complete Precambrian section is exposed in
the vicinity of the
the Cunf
Gunflint
County.
lint Trail
Trail in
in northwestern
northwestern Cook County.
Rocks
Precambrian age,
age ,
represented by a volcanic
Rocks of Early Precambrian
succession and the
the Saganaga Granite, are
are unconformably
unconformably
overlain by
by the
the Middle
Middle Precambrian
Precambrian Animikie
Animikie Group,coiLsisting
Group, cOllsisting of
of
A low anglular unconformity
the
Rove Fotmations.
Fo~ations.
A
the Gunflint and Rove
separates
strata from
from the
the nverlying
f1verlying Puckwunge
Puckwunge
separates the t-1iddle
Middle Precambrian strata
Rocks
Formation of Late Precambrian
Precambrian age.
age. The Logan Intrusive
Intrusive Rocks and
the Duluth
Duluth Complex,
Complex, which
which intrude
intrude and
and truncate
truncate the
the Middle
Middle Precambrian
Precambrian
the
strata,
strata, comprise
comprise the
the major
major part
part of
of the
the Upper
Upper Precambrian
Precambrian section.
section.
However,
However, possible remnants
remnants of the North Shore Volcanic Group occur
at the top of Duluth Complex
at
Complex rocks.
rocks.
The geology of the area was summarized in 1959 by Grout and
Because geologic mapping
mapping since
since 1962 has
has considerably
considerably reBecause
revised the
the geologic history of the
the area,
area, and because much of
of this
this
work is
is as yet unpublished,
unpublished, aa comprehensive
comprehensive summary
summary is
is presented
here. This discussion is meant to
to provide a framework for the
the
specific aspects of the
the geology
geology which
which the
the chosen
chosen stops
stops illustrate.
illustrate.
others.
Lower Precambrian
Introduction
The Lower Precambrian rocks
rocks in Cook County are the eastern
extension of the Vermilion greenstone
greenstone belt
belt (Sims
(Sims and
and others,
others, 1971,
1971,
has shown that the district contains many
in press). Gruner (1941)
(1941) has
major longitudinal
longitudinal faults
faults that
that divide
divide it
it into
into long
long segments
segments or
or belts,
belts,
each with distinct
distinct characteristics.
characteristics. They cannot be connected
stratigraphically with each other in
in any
any simple
simple way.
way. One segment
segment
extends from
from Gabimichigami Lake
Lake across
across the
the Gunflint
Gunflint Trail
Trail (Fig.
(Fig. 1).
1).
It
It includes aa metavolcanic assemblage consisting
consisting of
of metabasalt,
metabasalt,
metaandesite,
tuff, hornblende andesite porphyry,
porphyry,
metaandesite, agglomerate and tuff,
metagraywacke and
and slate.
the Saganaga
Saganaga
and intercalated metagraywacke
To the north,
north, the
slate. To
Granite has
has intruded and
and metamorphosed
metamorphosed the
thevolcanic
volcanicsuccession;
succession; it
it
is
overlaintotothe
thesouth
south
youngerrocks
rocksofofMiddle
Hiddleand
andLate
LatePrecambrian
Precambrian
is overlain
bybyyounger
age.
�-99—99—
The metavolcanic assemblage constitutes
constitutes aa homoclinal
homoclinal sequence
sequence
towardwhat
whatGruner
Grtinerinferred
inferredtoto be
be the
the axis
\"hich dips
dips southward
southward toward
which
Pillow—topdirections
directions
of aa southeastward—plunging
of
southeastward-plunging synclinorium. Pillow-top
indicate that
thatthe
thesequence
sequence alsO
also becomes
becomes stratigraphically
stratigraphically younger
younger
the south. However,
However, some pillows
pillm"s top
top to
to the
the north
north indicating
indicating
to the
folding, but
but poor exposure
exposure precludes
precludes detailed evaluation of the
folding,
structure.
wasthought
thoughttoto separate
separate the
Previously, an
an unconformity
unconformity was
the
mafic and
rocks; thus
thus the
thesuccession
successionwas
was subdivided
subdivided
mafic
and more
morefelsic
felsic rocks;
metabasaltswere
werereferred
referredtoto as
as part
part of
into two
two formations.
formations. The
The metabasalts
of
the Ely
whereasthe
themore
morefelsic
felsicvolcanic
volcanic and
andclastic
clastic
the
Ely Greenstone
Greenstone whereas
rocks
\Vere placed
placed within
within the
theKnife
KnifeLake
LakeGroup.
Group. Recent mapping
mapping
rocks were
(Fiorey
andothers,
others, 19(9)
1969) has
has sho\Vn
shownthese
theset\VO
twolithologies
lithologies to
(i-iorey and
to be
be
other parts
parts of
district
gradational, and
gradational,
an(~ nappin
mapping in other
of the
the Vernilion
Vermilion district
(lorey
1968; 1971,
(~Iorey and
and others,
others,1970;
1970;Green,
Green, 1970;
107(); Sims
Sims and
and others,
others, 1968;
1971,
in press) has shown
shm.;n that
that specific
specific rock
rock types
types are
are not
not diagnostic
diagnostic
particular strati~raphic
stratigraphichorizon
horizon—i.e.,
any particular
- i.e., lithologic
lithologic units
units
therefore no formal
are
formal stratigraphic
stratigraphic
are not
not time-stratigraphic
time—stratigraphic units
units -— therefore
used for
for these
nomenclature is
is now
no\V used
these rocks.
rocks.
of
Descriptive Stratigraphy
Descriptive
Stratigraphy
Volcanogenic Rocks
Volcano;;enic
Detailed mapping
in the
Long Island
Lake quadrangle,
Detailed
mappinR in
the Lonfl
Island Lake
quadrangle, reconnaissance
reconnaissance
as
far west
\"est as Va>'
Fay Lake
Lake in the
the Cillis
GillisLake
Lake quadrangle,
quadrangle, and
and
as far
Gruner's
area have
have indicated
that the
thevolcanigenic
volcani8enicsequence
sequence
Grunerts Hark
work in
in the area
indicated that
of approximately 60 percent inetabasalt
metabasalt and
fragconsists of
and associated frag—
mental
rocks,
30
percent
netnandesitic
agglomerate,
conglomerate,
tuff,
mental rocks, 30 percent metaandesitic agglomerate, conglomerate, tuff,
and
flows, and
and slate.
slate.
and flows,
and 10
10 percent intercalated
intercalatednetagraywacice
metagraywacke and
mappin
rr.appin,~
IjuLLaaLs.st±1psis!;
percent ofofthe
:i.eta_~~i1.sa-h.~~_?.~(LQ.~sg
..0at~_~.t ro_c±,-s_: Over 95
95 percent
themeta—
metabasalt is
basalt
is extrusive;
extrusive; there
thereare
areseveral
severaltabular
tabularbodies
bodiesofofmetadiabase,
metadiabase,
rLall to
too small
at aa scale of
to show
shmv at
of 1:24,000.
1:24,000. Nany
Manyofof the
the metabasalts
exhibit pillow
exhibit
pillm-J structure. The pillows
pillo\Vs are
are as
as much as
as three
three feet
feet in
in
diameter, but many
diameter,
manyhave
havebeen
beendeformed
deformedsosothat
that they
they are
are now
no\V two
two or
three
three times
times as
as long
lonf, as
as they
they are
are wide.
\"ide. Chilled rinds
rindsare
arewell—developed
1vell-developed
and
as much
much I1Sasone-half
inch
thick:
in
and are
are as
one—half
inch
thick:typically
typicallythey
theyare
are lighter
lighter in
color than
interiors. Inter-pillm"
color
than the
the dark
dar:( green
green or
ordark
darkgreenish—gray
fJreenish-Rray interiors.
Inter—pillow
material locally
material
locally is
iswell
welldeveloped
developed and
and co!nists
con~ists of
of tuffaceous
tuffaceous material
material
cEtert,
chert, or
or pillow—rind
pillm,,-rind fragments.
fragments.
Themetabnsalts
metaasalts shot:
intense retrograde
retrograde alteration;
alteration; many
The
shoH intense
many thin
thin
sections
sections are
nre nearly
nearlyopaque.
opaque. Recognizable
Recognizable minerals
include
minerals includerelict
relict
augite
augite and
anu calcic
cnlcic plagioclaso,
plagioclase, and
and secondary
secondary sodic
sodic plagioclase,
plagioclase,
actinolice, chlorite,
actinolite,
chlorite, epu'ote,
epidote, calcite,
calcite,quartz,
quartz,leucoxene,
leucoxene, and
opaques.
Property of
oj
C.
C. Patrick Ervin
Ervi n
�—100—
-100-
The tabular bodies of metadiabase have
have aa relict
relict poikilitic
poikilitic
texture
texture -— actinolite pseudomorphs after augite -— and a mineralogy
much like that
that of
of the
the metabasalts.
Thin beds
and mineralogically immature
immature meta—
metabeds of texturally and
clastic rocks are locally intercalated
intercalated with the
the metabasalt.
metabasalt. Several
beds are crudely graded and have a texture suggestive of a
pyroclastic
a pyroclastic
Most layers,
layers, however,
however, appear to
be epiclastic with
with pebblepebble—
Most
to be
origin.
to silt-size
silt—size clasts of locally derived
to
derived metadiabase
metadiabase in
in aa finer—grained
finer-grained
matrix of chert,
chert, plagioclase,
plagioclase, hornblende,
hornblende, chlorite,
chlorite, and
and sericite.
sericite.
Hornblende andesite prophyry and
and related
related rocks:
rocks: There are two
two
types of hornblende-biotite
hornblende—biotlte phenocryst bearing
types
bearing rocks.
rocks. Both are light
light
greenish—gray
greenish-gray in
in color.
color. One type
type lacks
lacks internal
internal structure.
structure. The ground
plagioclase, lesser
biotite, opaques
opaques and
and
mass consists of plagioclase,
lesser amounts
amounts of biotite,
rare
secondary calcite.
calcite. The other type
type has
similar
rare quartz and secondary
phenocryst and groundmass mineralogy
mineralogy but
but is
is composed
composed of
of angular
angular to
to
rounded, cobble—s,'ze
clasts and
and is
is inferred
inferred to
to be
be aa volcanic
volcanic breccia
rounded,
cobble-s~ze clasts
or agglomerate.
Metagraywacke and
and slate:
slate: In the vicinity of Fay
Fay Lake in
in the
the
Gillis Lake quadrangle,
quadrangle, the
volcanic rocks
inter—
Gillis
the felsic
felsic volcanic
rocks apparently interfinger,
meta—
finger, or are infolded with agglomerate
agglomerate or conglomerate,
conglomerate, metagraywacke, and
and slate.
slate.
Amphibolites:
The metamorphic effects of
of the
the Saganaga
Saganaga Granite
Granite
metabasalts becomes
becomes apparent
apparent only
only within
within several
several hundred
hundred feet
feet
on the
the metabasalts
of the contact.
contact. Away from
from the
the contact,
contact, the
the metabasalt contains
incipient hornblende;
hornblende; nearer the
becomes granular
granular
incipient
the contact,
contact, the
the rock
rock becomes
and consists of hornblende and
and
and calcic
calcic plagioclase;
plagioclase; at
at the
the contact,
contact,
the rock is strongly
strongly schistose.
schistose. The
the
The schistosity parallels the
granite contact,
contact, as does
does a well—developed
well-developed foliation
foliation within
within the
the granite.
granite.
Saganaga Granite
General
General Statement:
Statement: The Saganaga
Saeanaga Granite
Granite (A.
(A. Winchell,
Hinchell, 1888)
1888)
(Fig. 1)
1) is
is aa late-kinematic
late—kinematic composite intrusion emplaced
(Fig.
arouno
emplaced around
2,700 m.y.
m.y. ago in older volcanic rocks
rocks and
and the
the Northern
Northern Light
Light Gneiss.
Gneiss.
Inch—
Inch- to foot—sized
foot-sized inclusions
inclusions of
of both
both rock
rock types
found in
in the
the
types are
are found
granite.
granite. The main phase,
phase, which comprises
comprises 85
85 percent
of the
the outcrop
outcrop
percent of
area,
"quartz—eye hornblende—bjotjte
area, is
is aa medium—graineci
medium-grained "quartz-eye"
hornblende-biotite tonalite.
tonalite.
Other
Other phases
phases include:
include: 1)
border phase,
phase, found
found along
aloTIC' the
the southern
southern
1) a border
margin
of the
the batholith
margin of
batholith and
and along
along the
the base
base of
of a roof
roof"pendant
of
pendant of
the
the Northern
Northern Light
Light Gneiss;
Gneiss; 2)
2) aa younger
younger fine—grained
fine-grained tonali
te which
,vhich
tonalite
lacks conspicuous
lacks
conspicuous tquartz_eyes?T;
"quartz-eyes"; 3)
3) aa coarse—grained
coarse-grained biotite—fluorite—
biotite-fluoritebearing
bearing granodiorite;
granodiorite; and
and 4)
4) aa quartz—feldspar
quartz-feldspar pegnatite
pegmatite which
which occurs
occurs
as veinlets
as three
three feet
as
veinlets as
as much
much as
feet wide
wide in
in the
main
phase.
the main phase.
�—101--101-
Hain Phase: This
"quartz eye"-bearing
:iain
This phase
phaseisis aa "quartz
eye"bearing tonalite
containing 20
20 percent
1-6 percent
percent
percent quartz,
quartz, 60 percent oligoclase, 1—6
microcline,
up
to
8
percent
biotite,
6
percent
hornblende,
and
microcline,
to 8
6 percent hornblende, and
1-4
epidote. Other minerals include clino—pyroxene,
clino-pyroxene,
1—4 percent epidote.
muscovite, chlorite,
muscovite,
chlorite, sphene,
sphene, apatite,
apatite, zircon,
zircon, calcite
calcite and
and opaque
opaque
oxides. Cataclastic deformation of the
the tonalite
tonalite· is
is indicated
indicated by
by
strong undulose extinction and granulation of
strong
of the
the quartz
quartz and
and abunabundant mortar and mylonite
mylonite zones.
zones.
dant
Phase:
The border phase is
is aa quartz
quartz bearing,
bearing, hornblende
hornblende
Border Phase:
diorite that
that is gradational with the
the "quartz—eye"
"quartz-eye" tonalite.
tonalite. This
diorite
is well developed along the
phase is
the southern
southern edge
edge of
of the
the batholith
batholith in
in
feet wide,
the
is as much as
as 1000 feet
the Long
Long Island
Island Lake
Lake quadrangle
quadrangle where it is
and
Moose Bay area in Ontario where
and in the Noose
,,,here it
it is
is found
found along
along the
the
roof pendant of the
the Northern
Northern Light
Light Gneiss.
Gneiss. Foliations
Foliations
underside of a roof
rock are everywhere
similar,
in
and in
in the
the country rock
everYWhere similar,
in the
the border phase and
and it is inferred that
that the
the border phase
phase was
was produced
produced by
by partial
partial
assimilation
country rocks of mafic composition
composition (Halford,
(Halford, 1969).
1969).
assimilation of
of country
Younger Tonalite:
Tonalite: A
A tonalite characterized
characterized by
by aa lack
lack of
of
"quartz—eyes," aa fine—grained
"quartz-eyes,"
fine-grained equigranular texture,
texture, and
and abundant
abundant
hornblende and biotite
biotite crops
out in the
the Horseshoe
Horseshoe Island
Island area
area of
of
hornblende
crops out
Saganaga Lake.
Lake. This tonalite
tonalite is
is not
not sheared
sheared which
,,,nich indicates
indicates that
that
it
the main phase.
phase.
it was
was emplaced after deformation of the
Internal Structure:
Structure: Linear structural elements marked by an
an
alignment
"quartz eyes" and/or elongate hornblende grains
grains are
are
alignment of 'quartz
in the
the border
border phase.
phase. Lineations in
in the
the border
border
well developed only in
phase plunge gently southeastward.
southeastward. In contrast,
contrast, lineations in
in the
the
main phase are
are random.
random.
Structure
All the
minor structural elements
elements in
in the
pre—Saganaga rocks
rocks in
in
All
the minor
the pre-Saganaga
the
plunging
the Long
Long Island
Island Lake
Lake quadrangle reflect a southeasterly plunging
synclinorium.
synclinorium. In
northwesterly-trending fault
fault
in addition,
addition, a major,
major, northwesterly—trending
(Lookout
Fault, Sims
Sims and others,
(Lookout Fault,
others, 1969)
1969) separates rocks
rocks showing
showing no
no
metamorphic
effect of
of the
the Saganaga
SaganagaGranite
Granitefrorn.those
from;those that
that do.
do. The
metamorphic effect
fault is
is marked
marked by
by aa topographic low
fault
1m" developed in
in aa breccia
breccia zone
zone
as much as 50 feet
as
feet wide.
wide. The breccia consists
consists of highly sheared
metabasalt in aa matrix of massive quartz
quartz and
and calcite.
calcite. Fracture
cleavage is
is present
present throughout the
cleavage
the area and
and commonly
commonly parallels
parallels the
the
Fault. Southeastward
Lookout Fault.
formed by
by bedding/
bedding/
Southeastward plunging
plunging lineations
lineations formed
cleavage intersections
developed. These lineations
intersections are locally well developed.
are consistent
are
consistent in orientation with mineral lineations
lineations developed
developed in
in
the amphibolites
itself; obviously
obviously all
all of
of these
these
the
amphibolites and in the granite itself;
structures
tectonic event.
event.
structures are related to the same tectonic
�—102—
-102-
related to
to the
the final
final
The Lookout Fault also apparently was related
the Saganaga
Saganaga Granite.
Granite. Previously it was assumed
emplacement of the
(Grout,
(Grout, 1936)
1936) that
that the
the granite
granite was
was emplaced
emplaced into
into its
its present
present
position via a west\vard
westward rotation
rotation of about
about 700
70° about
about aa north—south
north-south
that the
the eastern part
part of
of the
the granite
granite and
and the
the
axis.
This implies that
represent roots
roots of the
Light Gneiss
Gneiss represent
the batliolith
batholith that
thatwere
wereonce
once
Northern Light
However,Goldich
Goldichand
andothers
others (1968)
as
much as
25 miles
deep. However,
(1968) have
have
as much
as 25
miles deep.
that
the
granite
was
originally
intruded
at
a
shallow
depth—
suggested that the granite was
at a
depthan observation more consistent
consistent with
with the
the regional
regional Abukurna
Abukuma greenschist
facies
(Mudrey, 1969)
to its present
present
facies metamorphism
metamorphism (Mudrey,
1969) -— and brought to
relative position
position by
by dominantly vertical movements along several
relative
several
westerly-trending
border faults.
faults. The granite—greenstone
granite-greenstone contact
contact
westerly—trending border
mapped by Harris (1968)
(1968) on the
the north shore
shore of
of Saganaga
Saganaga Lake
Lake was
was
interpreted to
be the
interpreted
to be
the northern border fault,
fault, and it is here inferred
inferred
that the
that
the Lookout Fault is
is its
its southern
southern analog.
analog.
The block
block was
was emplaced
emplaced during
during E8~ly
E:ly Precambrian
The
Precambrian time,
time, in
in as
as
much as
as detritus now found
found in the
the Knife
Knife Lake
Lake Group
Group of
of Gruner
Gruner (1941)
(19/+1)
was derived
there has
derived from
Granite. Although
from the Saganaga
Saganaga Granite.
Although there
has been
been later
t.,as
movement on the
the Lookout Fault,
Fault, it
it is
is dominantly
dominantly aa Lower
Lower Precambrian
Precambrian
structure.
MIDDLE
~UDDLE PRECAMBRIAN
PRECANBRI!u~
Introduction
Gunflint and
and '\ove
Rove Formations
The Animikie Groun
Group consisting of the
the Gunflint
comprises
These rocks
the entire
this area.
comprises the
entire Middle
:oliddle Precanibrian
Precambrian inin this
area. These
rocks
unconformably overlie Lower
Lm.,er Precambrian rocks
rocks and
and in
in turn
turn are
are intruded
intruded
and truncated
truncated by gabbroic rocks
rocks of Niddle
i'·liddle Keweenawan
KeweenaT,oJan age.
age.
The time
time of Animilcie
!mimikie deposition
deposition has
has not
not been completely
completely documented.
documented.
Hurley and
iron—
that deposition of the
and others
(1962) have
have suggested
suggested that
the ironothers (1962)
6
io6
Although
this
years.
formation
around 1,900
1,900 ±± 200 xx 10
this K—A
K-A
formation occurred
occurred around
age includes
age
includes an
an arbitrary and perhaps unnecessary
unnecessary correction
correction of
of 20
20
percent assumed
assumed argon
argon loss,
loss, it
it nevertheless
nevertheless has
has been
been widely
widely quoted
quoted
In contrast,
contrast, Faure
Faure and
and Kovacg
Kovac (1969)
in the literature. In
(1969) obtained
obtained aa
Rb-Sr
age of 1,685 ±± 24 x 10 years
years from
from the
the
Rb—Sr tvhole-rock
whole—rock isochron age
Gunflint Iron—formation.
Iron-formation. They interpret
interpret this
this age
age to
to be
be the
the time
time of
diagenesis, however,
similartotoother
otherages
agesobtained
obtainedfrom
from rocks
rocks
however,itit is similar
Misra and Faure
metamorphosed during the
the Penokean orogeny.
orogeny. Later Nisra
Faure
(1970)
Iron-formation
(1970) showed
showed that
that argillite
argillite from
from thr2e
three Gunflint
Gunflint Iron—formation
. .1.7
localities
Rb-Sr ages
ages that
that decrease from
from "'....
1.7 b.y. at the eastern
localities have
have Rb—Sr
end to
to 1.2 b.y.
b.y. near...
near ... the
the western..
\vestern ...
variation of
of
. this systematic variation
apparent
ages
may
be
related
to
metamorphic
effects
caused
by
Keweenawan
apparent ages may
related to
effects caused by Keweenawan
. . ".'. Thus there
diabase sills.
sills ••••
there is
uriequivical depositional age for
for
is no
no unequivical
these rocks.
b.y. at the eastern
.
�-103—10 3—
Descriptive Stratigraphy
Gunflint Iron—formation
Iron-formation
The Gunflint Iron—fori:iation
crops out
out in
in aa northeasterly—
Iron-formation crops
northeasterlytrending belt
Superior to
trending
belt that
thatextends
extendsfrom
fromThunder
Thunder Bay
Bay on
on Lake
Lake Superior
a point
it is
point in
inMinnesota
Minnesota 12
12 miles
miles west
west of Gunflint
Gunflint Lake
Lake where
where it
is
truncated by the
truncated
the Duluth
Duluth Complex.
Complex.
In Canada
Canada the
iron—formation is
In
the iron-formation
is only slightly,
slightly, if at
at aF.,
al:_,
metamorphosed and consists of silica, much of
of which
\"hich is
is chalcedonic,
chalcedonic,
Consequently, Goodwin
iron oxides,
oxides, iron carbonates,
iron
carbonates, and
and greenalite.
greena1ite. Consequently,
(1956)
recognized six
six sedimentary
sedimentary facies
facies which
which serve
serve to
(1956) recognized
to subdivide
In Minnesota
theoriginal
oriina1
the iron-formation
fourmembers.
members. In
Hinnesota the
iron—formation into
into four
nature of
metamorphism by the
nature
of the
iron-formation is
is -obscured
obscured by
TIetamorphism
the
the iron—formation
Duluth Complex.
The
carbonates
and
greenalite
are
replaced
by
Complex.
carbonates and greenalite are replaced by amphibole,
amphibole,
pyroxene, fayalite,
and locally by garnet and
pyroxene,
fayalite, and
and other silicates. In
In
addition,
addition, many of the
the small—scale
small-scale sedimentary
sedimentary textures
textures have
have been
been
almost completely
completely destroyed;
destroyed; however larger
larger structures,
structures, and especially
complex bedding
bedding relationships
relationships are
are still
still preserved.
preserved. Therefore the
the
four—fold nomenclatural
nomenclatural scheme -— originally
four-fold
in the
the Biwabik
Biwabik
originally outlined in
Iron-formation (Wolff,
(Holff, 1917)
1917) and
and later
later extended
extended to
to the
the Gunflint
Gunflint Iron—
IronIron—formation
retained by Morey
and others
formation (l3roderick,
(Broderick, 1920)
by 1'1orey
and (1969)
others (1969)
1920) -— ,vas
was retained
Accordingly, four
because it
it emphasizes various bedding aspects.
aspects. Accordingly,
members are recognized;
members
recognized; Lower Cherty,
Cherty, Lower
Lower Slaty,
Slaty, Upper
Upper Cherty,
Cherty,
Slaty. Although the
do not
and Upper
Upper Slaty.
the boundaries of
of these
these members
members do
coincide
coincide witll
those recognized
recognized by
by Goodwin
Goodwin (1956),
(1956) , the
with those
the two
two schemes
schemes can
be equated
equated \vith
withonly
onlyslight
slight difficulty.
difficulty.
Lo\ver ChertLMemhe.r:
Cherty Hember:
Lower
The Lo,ver
is isthin,
The
Lower Cherty
ChtertyNember
Member
thin, ranging
in thickness
Feldspathic quartzite
quartzite that
thickness from
from 15
15 to
to 45
45 feet.
that contains
contains
feet. Feldspathic
granite
cobblesisis present
present locally
locally at
at Lie
granite and
and greenstone
greenstone cobbles
the base
base of
of the
the
formation; these beds
beds are
are equivalent
equivalenttotoGoodwin's
CoodHin' s basal
basalconglomerate
conglomerate
formation;
member. AA persistent
persistent magnetite-rich,
magnetite—rich,silicate-bearing
silicate—bearingunit
unit five
five to
Feet thick occurs
15 feet
occurs within
IVithin this
thismember
member and
an excellent
and serves
serves as
as an
marker—horizon.
marl(er-horizon. :Iost
commonly it
liesdirectly
directly
uponbasement
basement rocks,
rocks,
:c'st commonly
it lies
upon
but loc<llly
locaii.v it
it overlies
overlies either
eitherthe
thefeldspathic
feldspathicqtiartzite
quartziteorora chert—
a chertcemented
fragr.ents of
cemented conglomerate
conglomerate containing
contctininr, frctgments
algal structllres;
in
of algal
structures; itit in
is overlain
overlainbyhya massive,
a massive,chert—rich,
chert-rich,magnetite—poor
magnetite,-poor unit about
about
turn is
15 feet
thick.
15
feet thick.
'
\
Lower-,:,?-latY---l~~emher:
Slaty Member: This
This member
memberisis8080toto 95
95 feet
feet thick. The
Lower
lOHennost,
magnetite-free 10
is a ablack,
black,thin—bedded
thin-bedded
lowermost, nearly
nearly magnetite—freo
10feet
feet is
argillitecomposed
conlposcd dominantly
dominantly of
derived material.
It
argillite
of volcanically
volcanically derived
It
is equivalent
equivalent to
to the
the intermediate
InterPlcdi"tc slate
slate on
on the
the 'esahi
;lesabi range
range and
and to
to
is
the lower
the
lOh·er tuffaccous
tuffaceous shale
shale f,icies
fD-cLcs ininCanada.
l,<ln"da. The beds
beds immediately
aove
the Intermediate
.:1iJove tile
IntenneJiate slate
massive and clierty
cherty and
and resemble
resemble
slate are massive
the upper
upor aert
the
part of
of the
the lower
LOIver Cherty
;'[e1l1her. This unit passes
passes abruptly
ahruptly
Chcrty :-;ember.
ipuird
into cherty
uith spilrse
sparse inagnetite
interuTl\!;]rd into
cherty si.licate-hci1rini;
beds ':lith
magnetite inters iJ.icate— carjn beds
calated
calateJ with
\vi til aa few
fe\\' thinly—laminated
tilinly-la:ninated silicate—rich
silicate-rich beds.
heels. The
The remaining
50 feet is
is ai1 thiin—bndciel
laminatedrock
rockcontaining
containingvarious
varioussilicates
silicates
thin-beJded totolill\linated
and
percent magnetite.
and Cro
from 20
2C to 35
35 percent
map;netite. AA few
fe'" cherty-silicate
cherty—silicate beds,
definitely
amount are
elefillitely subordinate
subordinate in
in illllount
this interval.
interval.
are intercalated
intercalated in
in this
�—104—
-104-
Upper Cherty
Cherty Member:
Member: There is
is a complete
complete gradation
gradation between
between
The
Upper
Cherty
the Lower Slaty and
and Upper
Upper Cherty
Cherty Members.
Members.
Cherty Member,
Member,
the
The lower
as
defined, is approximately 50
50 feet thick.
thick. The
10loJer
as presently defined,
cherty layers
part
to lenticular
lenticular cherty
layers
part consists of irregularly bedded to
intercalated with thinly—laminated
thinly-laminated silicate—rich
silicate-rich layers
layers that
that increase
increase
in abundance
abundance upward.
upward. Thin irregular layers of magnetite are
are common
common
in
in the cherty beds near the
the bottom of
of the
the member,
member, but
but become
become less
less
abundant upward.
upward. The top
top of the
the member—equivalent
member-equivalent to
to Goodwin's
Goodwin's
abundant
upper algal chert facies—is
facies-is characterized
characterized by
by several granular
granular
chert
conglomerate fragments,
fragments,
chert beds
beds containing algal structures, conglomerate
and abundant magnetite.
Upper
Member: The Upper Slaty
Slaty Member is
is approximately
approximately
Upper Slaty
S1ay Member:
Thick lenticular chert
chert beds
beds with disseminated
disseminated
few tens
tens of
of feet,
feet, but
magnetite characterize
characterize the
the lower
lower few
but most
most of
of the
the
member consists
consists of a thin—bedded
thin-bedded to
to laminated
laminated quartz—silicate
quartz-silicate rock
rock
thinly laminated
layersofofgraphitir::
graphiticargillite,
argillite,
interbedded with
with thinly
laminated layers
and
pure chert.
chert. The
and one
onetoto two
twoinch
inchthick
thick beds
bedsofof relatively
relatively pure
upper 10 feet
feet is nearly magnetite free
free and
and consists
consists of
of limestone
limestone
and chert interbedded
interbedded with
with argillite.
argillite.
150 feet thick.
thick.
150
Rove Formation
Rove Formation gradationally overlies
The Rove
overlies the
the Cunflint
Gunflint Iron—
Ironformation and is intruded by Logan Intrusive
formation
Intrusive Rocks
Rocks and
and truncated
truncated
detailed description of
Duluth Complex.
Complex. A
A detailed
of the
the formation
formation
by the Duluth
is presented
is
presentedby
byMorey
Morey (1969).
(1969). In
In the
the Long
Long Island
Island Lake,
Lake, Gunflint
Gunflint
Lake,
and Hungary
Hungary Jack
formation
Lake, Southlake, and
Jack Lake
Lake quadrangles,
quadrangles, the formation
is
characterized by
by intercalated
black to
to grayish
grayish black,
black, locally
locally
is characterized
intercalated black
carbonaceous
argillaceoussiltstone
siltstone
and
fine-grained
carbonaceousargillite,
argillite, argillaceous
and
fine—grained
gray\oJacke. In
the silt
silt
sandstone
beds
becomecoarse—
coarsegraywacke.
In general the
andand
sandstone
beds
become
formation. In
grained, thicker,
thicker, and
and more
more abundant
abundant upward in the formation.
tn
are several
addition,
there are
several lenses
lenses and
and irregular
irregular bodies
bodies of
of limelimeaddition, there
dolomite, and chert and a number of
of calcite—dolomite
calcite-dolomite con—
constone, dolomite,
cretions of
of various shapes and sizes, similar
cretions
similar to
to those
those described
described
in the
the formation by
by Tanton (1931)
(1931) and
and Moarhouse
Moorhouse (1963)
(1963) scattered
scattered
near the
the base
base of the
the formation.
formation.
Horey
deep
Morey(1969)
(1969)has
hassuggested
suggestedthat
thatdeposition
depositionstarted
started in aa deep
basin in
inwhich
which fine—grained
fine-grained sediment
sediment accumulated
accumulated under
under reducing
reducing
conditions. The
The siltstone
siltstone and
conditions.
andsandstone
sandstonebeds
beds contain
containmany
many primary
primary
sedimentary
structures indicative
indicative of
of turbidite
sedimentary structures
turbidite deposition.
deposition. There
is
of this
this type
is also
also evidence
evidence of
of an
an increase
increase infrequency
infrequency of
type of
of deposition
upward in
in the
the section.
section. The
graY\oJackes contain abundant
abundant framework
framework
The graywackes
grains
grains of
of quartz,
quartz, feldspar
feldspar and
and Igranitici
"granitic"rock
rockfragments
fragments indicative
indicative
of a granitic source
area.
source area. Sedimentary structures including cross—
crossbedding and various kinds of
of sole
sole marks
marks indicate
indicate that
that sediment
sediment
transport dominantly
dominantly was
\oJas from
from north
north to
to south.
south. These observations
observations
and the
gray\oJacke mineralogy
the
the graywacke
mineralogyled
led Horey
Morey(1969)
(1969)toto conclude
concludethat
that the
source
terrane now
exposednorth
north of
of the
source area
area was
was the
the Lower
Lower Precambrian
Precambrian terrane
now exposed
the
outcrdp area of
outcrop
of the
theRove
Rove Formation.
Formation.
�—105—
-105-
Structure
The Animikie
SE
Animikie strata
strata form
form aa homocline
homocline that
that dips
dips 10°-15°
1O—l5° SE
except where intrusive bodies and
and secondary
secondary structures
structures have
have disdisFor example,
example, complex folding
torted
the beds. For
torted or disturbed the
commonly
zones adjacent to
to many of
of the
the Logan
Logan
commonly occurs
occurs in narrow zones
Intrusive
is most likely related
related to
to the
the forceful
forceful ememIntrusive Rocks
Rocks and
and is
the sills into
into restricted
restricted space.
space. There is aa fairly
fairly
placement of the
regular
as much as 600
60° near the
the Duluth
Duluth Complex.
Complex.
regular increase
increase in dip
dip to as
is most likely
likely pre—Duluth
pre-Duluth Complex
Complex in
in age.
age.
However, this structure is
However,
in the
the Animikie
Animikie strata
strata inakestecognition
makestEcognition of
Lack of marker beds in
faults
northwesterly- and
and northerly—
northerlyfaults difficult;
difficult; however,
however, a number of northwesterly—
trending
faults have been mapped.
mapped.
trending faults
faults have displacements
displacements of
of less
less than
than 50
50 feet;
feet; however,
however,
Most faults
the Lookout
Lookout fault
has aa displacement
displacement in the
the iron—formation
iron-formation of
fault has
of at
at
least
least 200
200 feet.
feet. All
All faults
faults so
sofar
farrecognized
recognizeddisplace
displaceLogan
Logan
Intrusive rocks,
Intrusive
Complex; thus
thus
rocks, but
but none extend into the Duluth Complex;
movement apparently
apparently occurred in Middle
Middle Keweenawan
Keweenawan time
time prior
prior to
to
movement
of the
the Duluth
Duluth Complex.
Complex. The fault
fault pattern is similar
emplacement of
to
1960; Goodwin,
Goodwin, 1960)
1960) near ,.,hat
what can
to that
that in Canada (Moorhouse,
(Moorhouse, 1960;
be inferred
inferred to
to be the
the northern
the Lake
northern hinge
hinge of
of the
Lake Superior syncline.
syncline.
TIlis
structure
must
have
formed
at
least
in
prior
to
emplacement
part
prior
to
emp1acenen.t
This
must
at least in
of the Duluth
Duluth Complex.
Complex.
Hovement
during Keweenawan
Keweenawan time
time duplicates
duplicates
Movement on the Lookout fault during
iron—formationwest
westofofthe
theGunflint
Gunflint Trail,
Trail, and
the iron-formation
and aanortherly—
northerlytrending
segment of
fault separates
separatesthe
the
iron-formation into two
two
trending segment
of the
the fault
iron—Formation
structurally distinct terranes.
structurally
terranes. East of the Gunflint Trail,
Trail, the
the
rocks dip
dip gently southward;
southward; accordingly the outcrop area
Animikie rocks
of
relatively wide
most of
of the apparent
of the
the iron—formation
iron-formation isis relatively
wide and
and most
apparent
irregularities
mappattern
patternresult
result
fromthe
the
super-position
irregularities ininthethemap
from
super—position
of aa rugged
rugged topography on gently—dipping
gently-dipping strata.
strata. The south side
side
of
fault is
is upthrown,
upthrown, and
and the
the Anirnikie
Animikie strata on this
of the
the Lookout fault
side
outcrop belt.
belt.
side dip
dip steeply and thus form a narrow outcrop
A
also can
can be
be recognized.
recognized. Just
A number of smaller structures also
east of
Gunflint Trail
Trail the
the iron—formation
iron-formation and
of the Gunflint
andthe
thesills
sills are
folded into
anticline with
with a
a steeply
steeply
into a southeasterly plunging anticline
dipping north limb
limb and a gently dipping
dipping south
south limb.
limb. This structure
post-Logan in age has an anticlinal axis which
which is obviously post—Logan
into the
the trace
trace of
of the
the Lookout
Lookout Fault.
Fault.
projects into
Metamorphism
i'letamorphism
In the
the Animikie
Animikie rocks
no textural or
or atineralogic
mineralogic
In
rocksthere
there is
is no
evidence for aapervassive
metamorphism
evidence
pervassiveregional
regional
metamorphism beyond
beyond minor
minor
of the
the clay—size
clay-size detritral
frac'don. The
The obvious
recrystallization of
detritral. fraction.
the Animikie
strata are
are associated
in the
Animikie strata
associated with
with the
the
metamorphic effects in
emplacement of the Duluth Complex and Logan Intrusive Rocks of Middle
Ke,,,eenawan
Keweenawan age.
�—106—
-106-
The contact
contact aureole
aureole of
of the
the Duluth Complex has
has not been studied
in detail in
in the
the Gunflint
Gunflint Trail
Trail Area.
Area. Preliminary work in
in the
the
Gunflint Iron—formation
shows
there
are
a
number
of
metamorphic
Iron-formation
there are a
of
facies similar to those
those described from
from the
the Biwabik
Bh\Tabik Iron—formation
Iron-formation
facies
by French (1968)
(1968) and
and Bonnichsen
Bonnichsen (1969).
(1969). Unmetamorphosed iron—
ironformation like that described by Goodwin
Good\vin (1956)
(1956) is
is found
found in
in Minnesota
Hinnesota
lint and North Lakes.
only in
in aa small
small area
area between
between Gunf
Gunflint
Lakes. There the
the
iron-formation consists of chert,
chert, iron
iron carbonates,
carbonates, greenalite,
greenalite, abundant
abundant
iron—formation
amounts of finely disseminated hematite, and
and traces
traces of
of magnetite.
amounts
However,
lint Lake,
Lake, the
the iron-formation
iron—formation has
has been
been metamorphosed
metamorphosed
However, west of
of Gunf
Gunflint
and three
three metamorphic zones
zones have been distinguished
distinguished by
hy changes
changes in
in
mineralogy along tI
tie strike of the
the formation
formation toward
tm'Jard the
the Duluth
Duluth Complex.
Complex.
Zone 1,
1, or slightly metamorphosed iron—formation,
iron-formation, occurs
occurs in
in the
the
area immediately west of
Gunflint
Lake.
It
consists
of
quartz,
iron
of Gunflint Lake. It consists
quartz, iron
carbonates, greenalite, minnesotaite, and
carbonates,
and stilpnomelane.
stilpnomelane. FinelyFinely—
divided hematite
hematite occurs
occurs in the
divided
the east
east end of the zone,
ZOne, hut
but disappears
mid—way in
mid-way
in it.
it. Disseminated
Disseminated and
and interlocking grains of magnetite are
are
abundant, especially as
abundant,
as rims
rims around
around granules.
granules. This part of
of the
the iron—
i ronformation
is much like
like that
that described
described by
by French
French (1968)
(1968) in
in 'unmetaniorphosed
"unmetamorphosed"
formation is
Biwabik Iron—formation.
Iron-formation.
Zone 2,
moderately metamorphosed iron—formation,
Zone
2, or moderately
iron-formation, is
is about
about 1.2 miles
wide and extends to
to within
\vithin 0.3
0.3 miles
miles of
of the
the Duluth
Duluth Complex.
Complex. GruneriteGrunerite—
cummingtonite, hornblende and actinolite,
cummingtonite,
actinolite, as well as
as quartz and magnetite
map,netite
As in
characterize this
this zone.
zone. As
in zone
zone 1,
1, much of the
the magnetite is
is between
hetHeen
0.002 and
in diameter;
and 0.02
0.02 mm in
diameter; a
a size—range
size-range similar to
to that
that observed in
various other
other Lake
Lake Superior
Superioriron—formations.
iron-formations. S:'1all-scale
pre-metAmorphic
Small—scale pre—metamorphic
sedimentary
structures such
such as
as granules
granules and
andoolites
oolites are
sedimentary structures
are partly
partly destroyed,
destroyed,
but
primarystructures
structuresand
andbeddinr,
bedding
featuresarearelittle
little
but larger—scale
larger-scale primary
features
affected.
Zone 3, or
orhighly
highlymetamorpl-iosed
metan,orphosed iron-formation,
iron—formation,occurs
occurs adjacent
to the
and is
is characterized
the Duluth
Duluth Complex
Complex and
characterizedby
bya awholly
",hollymetamorphic
metamorphic
fabric. The
The rock
composed chiefly
quartz, magnetite,
magnetite,iron—rich
iron-rich
fabric.
rock is
is composed
chiefly of quartz,
euliedraloror suhl1edral
subliedral grains
pyroxenes, and
Very commonly,
commonly, eultedral
(.~rains
pyroxenes,
and fayalite.
fayalite. Very
of
are poikilitically
poikilitically enclosed
'Tithin large
large silicate
silicate grains;
of magnetite
magnetite are
Ptlclose.d \orithin
(~rains;
they
are of
of essentially
they are
essentially the
the same
Si1Iile size
size as in
inthe
thelower
lOHer grade
grade rocks.
rocks.
However
a significantpart
partofoftile
themagnetite
ragnetite is
is extensively
Hmvever a significant
extensively recrystallized,
recrystallized,
.-:IS
and
grains as
as aa millimeter
and grains
as much
much <18
millimeter in
in diameter
diiwleter are
arc concentrated
concentrated along
along
Actinolite
bedding planes.
planes. Actinoli
bedding
te isiscommon
cor:lJl1on in magnetite—rich
rnagm~ti te-rich layers,
layers, and
and
both prograde
and
retrograde
cummingtonite
:Ls±un(lantly
oresent.
In
pro~rade and retro0rrtde cummin;>:tonitc is -:hundnntly nresent.
In
general this
this zone
zone is
is very
very similar
similar to
tothat
thCltdescribed
de~;cribedinin
thetheJ)unka
Dunka!~oiver
Piver
area
on the
the I'lesabi
:olesabi range
ranre by
by Bonnichsen
nonnicbsen (1)69).
(l,)6~l).
area on
contactt aureole o0 fthe
l\Tork on
on the contnc
theDuluth
lluluthComplex
Complex in
Preliminary work
RoveFormation
Formationindicates
indicates aa complex
mixtureofof rock
rock tyPes
Rove
complex mixture
tyoes suggesting
sUfgcstinR
partial melting,
and textural
textural variations
variations due
to original
original
partial
meltint, and
and mineral
mineral and
due to
Tue met"mop)!losed
metamorphosedrocKs
rocks :HC
are
netainorphilari. The
inhornogenities
and degree
degree of
of liletamorr1dsr,l.
inhoinogenities and
commonly layered
Individual layers
layers
commonly
layeredane!
andhave
haveil agranohlastic
granoblastic texture.
texture. Individual
contain; 1)
hiotite and
contain;
1) cordierite
corcJieriteand
and Iyperstliene
hynersthene with
'\Tith minor
loinor biotite
and ilmenire,
ilmenite,
hiotite, and
plagioclase, hiotite,
and ilmanite,
ilmenite, J)
aur-ite,
hypcrsthene, plagioclase,
3) augite,
2) hypersthene,
plagioclase ±± minor olivine,
ilmentte, or 1+)
4) hvperstliene,
plagioclase
olivine, biotite,
biotite, and
"at! ilmeni.t0.,
hypersthe.ne,
contact
plagioclase, K—feldspar,
andbiotite.
hiotite. Calcareous
K-feldsrar, and
Calcareous beds
GeJs near
ncar the contact
have aa skarn—minera.logy
consisting
wollastonite,diopsi<le,
diopside, tremolite,
tremolite,
have
skarn-mineralogy consisting
of of
lvollastonitc,
fromtile
the contflct
contact - and
piece to
and
p:arn0.t. Away
AI<7ay frol'l
nnd from
fron plnee
to eLace
Dlace
and 8rossularite
grossularite garnet.
the
the
�—10 7—
-107-
distance varies
varies from
several tens to several hundreds of feet
this
from several
feet —
this distance
or may
most peletic rocks are
are rich
rich in
in biotite, and
and cordierite
cordierite may
mayor
may
not be present.
present.
The Logan Intrusive
Intrusive Rocks
Rocks also
also have
have metamorphosed
metamorphosed the
the Gunf
Gunflint
lint
and
Fonnations. The width of the metamorphic aureoles are related
related
and Rove Formations.
to sill
sill thicknesses and range from less than
to
than one foot
foot to
to more than
than 30
30
Gunflint Iron—formation
feet. In
In the
the Gunflint
Iron-formation it is difficult
difficult to
to recognize
recognize
unique metamorphic assemblages
mineral
assemblages adjacent
adjacent to
to sills.
sills. In zone 2,
2, mineral
assemblages characteristic of zone 3 occurs in
assemblages
in aureoles around
around the
the sills.
sills.
Similarly In
in zone
zone 1, ininnesotaite,
minnesotaite, which
which is
is characteristic
characteristic of
of zone 2
to the
the sills.
sills.
metamorphism is found next to
In
the Rove Formation
Fonnation thick
thick sills have assemblages
assemblages that
that can
can be
be
In the
assigned to
to the
the pyroxene—hornfels
pyroxene-hornfels facies
facies whereas
whereas thinner
thinner sills
sills have
have
assemblages characterisitc of the
assemblages
the hornblende—hornfels
hornblende-hornfels facies.
facies. Locally
1969) and chloritoid (Grant,
andalusite (Morey,
(Horey, 1969)
(Grant, 1971)
1971) have
have been
been identified
identified
in certain beds.
beds.
UPPER PRECAMBRIAN
Introduction
In northeastern Minnesota two
In
two units are
are recognized
recognized in
in the
the Upper
Upper
Precambrian:
the Lower
Lower Keweenawan represented by the Puckwunge
the
Formation and
and the
Formation
the Middle Keweenawan which consists
consists of
of the
the Logan
Logan Intrusive
Intrusive
Rocks, the
the North Shore Volcanic Group (Green,
Rocks,
(Green, this
this volume), and
and the
the
Duluth Complex.
Complex.
Puckwunge Formation
Fonnation
The Puckwunge Formation consists
consists of conglomerate
conglomerate and
and sandstone
sandstone
which unconformably
North
unconfonnably overlie the Rove Formation
Fonnation and underlie the
the North
Shore Volcanic Group. The type locality was described by N.
N. N.
H. Winchell
Winchell
(1897) on
Sec. 25,
25, T.
T. 64 N.,
N., R.
R. 33 B.
E. where about
about 18
18
(1897)
on the
the Stump
Stump River in Sec.
feet of section is
feet
is exposed.
exposed. Exposures
Exposures of
of similar
similarlithology
lithologyare
arefuund
in
frnind in
the Grand Portage area (Grout
(Grout and
and others, 1959).
1959).
the
If these
these isolated exposures are equivalent to
to the
the Sibley
Sibley Series
Series
If
in Canada (Tanton,
in
(Tanton, 1931)
1931) they represent
represent aa period
of sedimentation
sedimentation around
around
period of
1376 *± 36 m.y.
m.y. ago (Franklin
Kustra, 1970)
1970) followed
by possible
possible
1376
(Franklin and Kustra,
followed by
uplift and erosion prior to
to the
the onset
onset of
of volcanic
volcanic activity
activity in
in Middle
Middle
Keweenawan time.
time.
Intrusive Rocks
Rocks
Logan Intrusive
The
sills was
was applied
applied to
intrusive
The name
name Logan
Logan sills
to tabular,
tabular, diabase intrusive
rocks
in
the
Rove
Formation
rocks in the Rove Formation(Lawson,.
(Lm"rson, 1893,
1893, p.
48). Similar
intrusive
p. 48).
Similar intrusive
in Animikie
formations are
Animikie and
and Lower
Lm.,rer Keweenawan
Keweenawan formations
are currently
referred
to
as
Logan
referred to as Logan Intrusive Rocks.
Rocks. As
As now
now defined,
defined, they
they include
include
sills and
dikes of
sills
and dikes
of diabasic
diabasicgahhro
gabbrowhich
which range
range in
in measured
measured age
age from
from
rocks
rocks
1300 n.y.
~300
m.y. (hanson
(Hanson and
and [alhotra,
Ha1hotra, 1971)
1971) to
to 963
963 m.y.
m.y. (Franklin,
(Franklin, cited
cited
Ln Hanless
Wanless and
In
and others,
others, 1970,
1970, p.
57).
Thus
the
Logan
Intrusive Rocks,
Rocks,
57).
Thus
the
Logan
Intrusive
p.
�—108—
-108-
North Shore
Shore Volcanic Group
Group may
may
units of the Duluth Complex,
Complex, and the
the North
have overlapping time—stratigraphic
time-stratigraphic relationships.
relationships.
rocks
In
County the
the predominant exposed volume
volume of
of the
the Logan
Logan rocks
In Cook County
from
the
sill-like, and
and the
the present sawtooth
smvtooth topography
topography results
results from the
is sill—like,
The
the inclined
inclined sills
sills and
and Rove
Rove Formation.
Formation. The
differential erosion of the
feet
sills
and
sills range
range in
in thickness
thickness from
from aa fe\v
few feet
feet to
to over
over aa thousand
thousand feet and
thick sills
for several
several miles.
miles. In
In three
three
sills can be mapped along strike for
dimensions
dimensions they
they form
form aa boXtVork
boxwork pattern,
pattern, their
their emplacement
emplacement having
having been
been
~ntro11ed
fault plane connections
connections between
nntrolled by bedding,
bedding, joint and possibly fault
sills
sills but
but in
in the
the Grand
Grand Portage
Portage in
in northeastern
northeastern Cook
Cook County
County area
area there
there
and extent
are
extent to
to the
the
are major
major northwest-trending
northwest—trending dikes
dikes comparable
comparable in
in size
size and
sills
(Grout and Schwartz,
Schwartz, 1933, P.
p. 36—59).
36-59).
sills (Grout
Early detailed studies
the Logan Intrusive
studies of
of the
the petrogenesis
petrogenesis of the
Rocks were primarily restricted to
to the
the sill
sill on
on Pigeon
Pigeon Point
Point (Bayley,
(Bayley,
Reinvestigation of
1893;
Daly, 1917;
1917; Grout
Grout and
and Schwartz,
Sch\vartz, 1933).
1933). Reinvestigation
of these
these
1893; Daly,
rocks
currently in
in progress
follmving generalized descripdescriprocks is
is currently
progress and the
the following
textures, and
is based
the unpublished work of
tion of
of textures,
and mineralogy
mineralogy is
based OIl
on the
of
J. A.
A. Grant,
Grant, E.
E. Mathez,
Mathez, G.
G. B.
B. Morey, N.
N. Mudrey and
and P.
P. Weiblen.
Weiblen •
J.
margins, fine—
.Texture:
T exture: Rock types
types include aphyric chilled margins,
fine- to
medium-grained
diabase
with
ophitic
clinopyroxene
enclosing
plagioclase,
medium—grained diabase
clinopyroxene enclosing plagioclase,
porphyritic diabase with plagioclase
plagioclase phenocrysts,
phenocrysts, plagioclase
plagioclase cumulates,
cumulates,
margins form sharp contacts
and granophyre. Chilled margins
contacts with
with country
country rocks.
rocks.
Clino—
from fine
fine to
to medium
medium toward
toward the
the center
center of
of sills.
sills. ClinoDiabase grades from
remains ophitic even though the
the grain size changes
changes and enclosed
pyroxene remains
plagioclase crystals rarely
rarely exceed
exceed 55 mm
rom in
in length.
length. Plagioclase phenocrysts
as 10
10 cms
ems long
long in
in thick
thick sills.
sills. Diabasic
crysts however
however are as much as
rocks
with plagioclase
plagioclase phenocrysts
phenocrysts grade
grade into
into accumulations
of essentially
rocks with
accumulations of
Such accumulations are found
coarse-grained
plagioclase. Such
found in
in the
the upper
upper
coarse—grained plagioclase.
to the
the
parts of some large sills and their origin has been attributed to
floating of
of plagioclase (Grout
floating
(Grout and
and Schwartz,
Schwartz, 1933,
1933, p.
p. 50).
50).
M1neraly: Minor olivine is found
Mineralogy:
found in the
the lower part of
of some
Plagioclase
as small grains
grains enclosed in
Plagioclase both
both as
as phenocrysts
phenocrysts and as
pyroxene is generally highly
highly seriticized.
seriticized. Clinopyroxene is
is altered
altered to
to
amphibole within single oikocrysts.
oikocrysts. The
The remnant
remnant pyroxene varies
varies in
composition from pigeonite through augite and has a mottled birefringence
which resembles
resembles that
that of
of the
the complex
complex lunar
lunar pyroxenes.
pyroxenes. Ilmenite
lirnenite and
and minor
minor
magnetite appear at distinct horizons in
in some
some sills.
sills. The
is
The ilmenite is
commonly skeletal.
skeletal. Minor interstitial
interstitial quartz
quartz is
is characteristic
characteristic of
of
much of
of the
the diabase.
diabase. Biotite is
is ubiquitous
ubiquitous in the diahase
diabase and texturally
appears to
appears
to be of both igneous and
and metamorphic
metamorphic origin.
origin. Granophyric
intergrowths
the diabase \vhere
intergrowths are
are common
common in
in the
the upper
upper part
part of
of the
where they
impart
a pink mottling which can
can be
be recognized
recognized In
in hand
hand specimen.
specimen. Separate
impart a
Separate
o~currences of granophyre in mappable units are rare,
rare, except for
for the
the
occurrences
Pigeon Point sill (Mudrey
P~geon
(Hudrey and
and Weiblen,
Weib1en, 1971).
1971).
sills.
sills.
�-109—10
9—
Structure: In
Structure:
the Duluth Complex truncates the
the various
various
In plan view the
along strike
strike at
at aa low
low angle
angle (Fig.
(Fig. 3).
3). Where exposed, the
the
Logan sills along
base of the Duluth Complex dips
gently southward,
southward, whereas
whereas both
both the
dips gently
country rocks
rocks may
may dip
dip as
as much
much as
as 60°
60° to the south.
south.
Logan sills and country
Drilling in
in the
the vicinity
vicinity of
of the
the contact
contact indicates
indicates that
that the
the base
base of
of the
the
Drilling
Complex steepens to as much as 60° and levels
levels off
off to
to about
about 30°
30° 11 km.
km.
This structural
structural configuration
configuration is
i
down-dip
(Johnson, 1970,
1970, p.
p. 82).
82). This
down—dip (Johnson,
zuch like that
Mancuso and Dolence (1970)
the East
much
that described by Hancuso
(1970) in the
?Iesabi
district. They suggested that
Mesabi district.
that the
the emplacement
emplacement of the Duluth
that area was in part controlled
controlled by
by aa pre—Complex
pre-Complex structure.
structure.
Complex in that
:1inor hydrothermal
hydrothermal mineralization
mineralization is
is found
found within
within
>inera1ization:
Mineralization: Hinor
the Logan Intrusive Rocks. The mineralization is probably similar
similar to
to
the
the
important occurrences
occurrences
the Thunder
Thunder Bay
Bay silver
silver deposits,
deposits, but nO
no commercially important
Island where
where aa shaft
shaft was
was sunk
have been found
found in
in Minnesota.
Minnesota. On Susie Island
along
a
fracture
zone
filled
with
calcite-barite
and
lesser
amounts
along a fracture zone filled with calcite—barite and lesser amounts of
of
quartz, bornite,
bornite, chalcocite,
chalcocite, chalcopyrite,
chalcopyrite, pyrite,
pyrite, covellite
covellite and
and
quartz,
malacite,
malacite, ore was recovered which
which contained 6.22 percent copper and
At Loon
trace
trace amounts of silver
silver (Grout
(Grout and
1933, p.
p. 64).
64). At
and Schwartz,
Schwartz, 1933,
Lake, R.
S. Blankenburg
Blankenburg has
has investigated
investigated aa prospect
prospect in
in aa quartz-calcite
quartz—calcite
Lake,
vein that
that contains arsenopyrite with minor cobalt
cobalt (Johnson,
(Johnson, 1968).
1968).
Duluth Complex
consists of
a variety
The Duluth Complex consists
of a
variety of
of anorthositic,
anorthositic, troctolitic,
troctolitic,
granodioritic, and
and granophyric
granophyric rocks
rocks which
which crop
out in
in an
an arcuate
arcuate belt
belt
granodioritic,
crop out
A
brief
review
from
the Gunflint Trail (Fig.
(Fig. 1).
1). A
review of
of
from Duluth
Duluth to
to east
east of
of the
the early literature
literature and
and recent work up to
to 1969
1969 is
is given
given by
by Phinney
Phinney
the
of subsequent
subsequent mapping and study of
of the northeastern
(1969). The results
results of
limb of the
the Complex
Complex are
are presented by
by Nathan
Nathan (1969),
(1969), Morey
Horey and
and others
(1969),
Johnson Q970),
and Davidson
Davidson (1970).
(1970).
(1969), Johnson
a970), and
Nathan (1969)
mapped aa layered series of sheet—like
(1969) mapped
sheet-like intrusions
intrusions across
across
the Gunflint,
and Hungry
Hungry Jack Lake quadrangles (Fig.
(Fig. 2).
2). To
the
Gunflint, South Lake and
the west,
west, in
in the
the
the Long Island quadrangle, Nathan's
Nathan's layered
layered series
series is
is
truncated
the Tuscarora Intrusion and
and other
other associated
associated rocks.
rocks.
truncated by
by the
Nathan
Layered Series of Nathan
The layered
layered series
series extends
extends from
from the
the east
east edge
edge of
of the
the Hungry
Hungry Jack
The
Jack
Lake quadrangle across
across the South Lake quadrangle and into
into the Gunflint
\vhere it
it is
is truncated
truncated by
by the
the Tuscarora
Tuscarora Intrusion.
Intrusion. This
Lake quadrangle where
truncation is
is marked by an irregular northwest trending
trending scarp
scarp (Fig.
(Fig. 3).
3).
truncation
For the
most part,
part, the
the series
series consists
consists of
of aa sequence
sequence of
of conformable
conformable
For
the most
The sheets thicken
sheets
15-25° to
to the
the south.
south. The
sheets having
having a regional dip of 15—25°
to
west and
and are
are locally
locally interrrupted
interrrupted by
by minor
minor crosscutting stockstock—
to the
the west
and dike—like
dike-like bodies.
bodies. On the
the east side of the Hungry Jack Lake
Lake
quadrangle aa nortlnvest
northwest trending
trending fault
fault offsets
offsets the
the series
series with
with an
an unknown
unknown
quadrangle
amount of
amount
of displacement,
displacement, but
but as
as much
much as
as 140
140 feet
feet of
of vertical
vertical displacement
displacement
northeast side
side is
is inferred
of the
the northeast
inferred (Fig.
(Fig. 3).
3).
�-110—110—
The series consists
consists of
of troctolitic,
troctolitic, gabbroic,
gabbroic, and
and associated
associated
felsic rocks.
rocks. Several of the major units represent
represent uniqud
unique occuroccurrences in the
the Duluth Complex of oxide—rich
rences
oxide-rich gabbros
gabbros and
and two—pyroxene
two-pyroxene
gabbros. For the most part, fine—grained
fine-grained rocks
rocks are
are not
not chilled
chilled
margins but occur principally as
or inclusions
inclusions
as separate intrusions
intrusions or
of mappable size.
size. Planar orientation of
of minerals is
is common,
cornman,
indicating flow
flow or
or crystal
crystal setting.
setting. Differentiation resulting
resulting from
from
these processes can be demonstrated within some
some units,
units, however
however the
the
layered series does not form
form aa regular
regular stratigraphic
stratigraphic sequence.
sequence.
Intrusive relationships for
27
different
units
were
established
for 27 different units
established
using cross-cutting
cross—cutting structures,
structs, fine—grained
using
fine-grainedmargins,
margins, inclusions
inclusions
and thermal effects,
effects, the latter being principally aa development
development
of dark clouded plagioclase near intrusive
intrusive contacts,
contacts, Nathan (1969,
(1969,
p.
99). On the basis of field
field relationships,
relationships, mineralogy, and
and composicomposip. 99).
tion,
tion, Nathan concluded the 27
27 units could
could be
be combined
combined into
into eight
eight
cogenetic
cogenetic groups.
groups.
Detailed rock descriptions and interpretations
interpretations are
are given
given by
by
Nathan (1969,
(1969, p.
p. 38—185)
38-185) and are
are summarized
summarized here
here using
using his
his nomennomenclature. The descriptive rock
rock names have
have several
several textural
textural prefixes
prefixes
clature.
that
that characterize the primary mineral assemblages.
assemblages. AA size
size classclassification for these rocks,
rocks, based on
on visually—estimated
visually-estimated mean
mean grain
grain
diameters, is:
diameters,
is: >10 mm,
mm, very coarse—grained;
coarse-grained; 4—10
4-10 mm,
rnrn, coarse—grained;
coarse-grained;
1—4 mm,
mm, medium-grained;
medium—grained; 1/2—1
1-4
1/2-1 mm, fine—grained;
fine-grained; <1/2
<1/2 mm,
mm, very
very fine—
fineA
'granular'
grained.
fabrics are
are recognized.
recognized. A "granular" rock has
Four basic fabrics
grained.
If elongate
elongate grains
grains are present and
only equidimensional
equidimensiona1 minerals.
minerals. If
are randomly oriented, the
the rock is
is "decussate,"
"decussate," if
if the
the grains
grains define
define
aligned, the
a plane,
plane, the rock
rock is "foliated,"
"foliated," and
and if
if the
the grains
grains are
are aligned,
the
rock
l'lineated. II All rocks
rocks are named by the
the characterizing
characterizing
rock is
is "lineated."
primary mineral assemblage,
assemblage, in
in order
order of
of increasing
increasing abundance;
abundance; the
the
primary mineral assemblage
assemblage refers
refers to
to early
early crystallizing
crystallizing phases
phases in
in
Modes are indicated by sub—
contrast to
to late
late interstitial
interstitial phases.
phases. Modes
subIf
scripts.
If a significant part of the
the primary assemblage
assemblage was
was
scripts.
transported in the magma the rock
rock is
is referred
referred to
to as
as an
an allocrystallate,
allocrystallate,
aa cumulate
cumulate being
a special
special case
case in
in which gravity
gravity settling
settling has
has occurred.
occurred.
being a
Rocks formed
formed by crystallization in
in place
place are
are called
called autocrystallates.
autocrystallates.
Rocks
Thus a
Subscripts are used to
to indicate modal composition.
composition. Thus
a descriptive
descriptive
Subscripts
fine—
rock name
name for
for aa troctolite
troctolite formed
formed by
by gravity
gravity settling
settling could
could he
he aa fineinter—
grained foliated olivine20—plagioclase70
cumulate
with
minor
01ivinezo-plagioclase70 cumulate \-lith minor interstitital augite5and
augitesand oxides5.
oxides S •
Group 11
da
The oldest unit (da)
(da) in
in the
the layered
layered series
series now
now appears
appears
in the upper part of the
the section
section as
as dilated
dilated septa
septa as
as
It is
is 8a fine-grained
fine—grained foliated
much as
as 200
200 feet
feet thick.
thick. It
much
cumulate with
with minor
minor pigeonite9
—plagioclase63 cumulate
01ivine~s-plagioclase63
pigeonite 9
olivine
which are
and
aug1te
are also
also cumulus
cumulus in
in the
the middle
middle of
of
and aug?e
the unit.
unit. ~his
unit grades
grades into
into aa 1,000 foot—thick
foot-thick
his unit
the
sheet of
foliated augite15—pigeonite26
augiteIS-pigeonite26of medium-grained,
medium—grained, foliated
A very fine—grained
piagioclase cumulate (dh).
(dh). A
fine-grained
plagioclase59curnulate
S9
ollvine1
—augite27—plagioclase61
rock
olivine o-augite27-plagioclaseGl rock (dc)
(de) occurs
occurs as
as
sizes
near
the
base of
masses o9
~f various shapes and Slzes
of
masses
the layered
layered series.
series. Nathan speculated that
that it might
the
represent aa chilled margin of the
represent
the Group 1 intrusive
intrusive
rocks.
-
db
db
dc
de
�-111—111—
Groip22
Group
dg
the major
part of
of the
group comprises
comprises the
major oxide—rich
oxide-rich part
the
This group
The main unit
layered series.
unit (dg)
(dg) is a
a coarse—grained
coarse-grained
series.
—augite —olivine
foliated ilmenite—titanomagnetite
foliated
ilmenite-titanOmagnetitell-augitel~-olivineI4
plagioclase
cumulate. Within tff~s unit
unit fe efollowing
followrng
plagioclase
S66crystallization appears: (1)
(1) ilmeniteilmenite—
sequence of
of5crystallization
olivine-plagioclase;
(Z) ilmenite—titanomagnetite—olivine—
ilmenite-titanomagnetite-olivineolivine—plagioclase; (2)
augite—plagioclase; and finally
augite-plagioclase;
finally (3)
(3) apatite—pigeonite—
apatite-pigeonitetitanomagnetite-ilmenite-olivine-augite-plagioclase.
titanoinagnetite—ilmenite—olivine—augite—plagioclase.
dd
de
Very fine—grained
fine-grained foliated
foliatedolIvine—oxide—augite—plagioclase
olivine-oxide-augite-plagioclase
Very
plagioclase
(dd) and
(dd)
and fine—grained
fine-grained granulo—decussate
granulo-decussate augite
augite—
- plagioclase
(de) rocks
occur in
in unit
(de)
rocks occur
unit dg
dg as
as inclusions
inclusionsasasmuch
much as
as 400
400
A number of mappable units are
across. A
are gradational
gradational
feet across.
with
(1) at
at the
the base
base of
of the
the complex,
(1)
complex, a fine—
fine- to coarse—
coarsegrained decussate
decussate augite—olivine—plagioclase
augite-olivine-plagioclase autocrystallate
autocrystallate
(df) grades into rocks
rocks having a texture
texture and
and mineralogy similar
(df)
to that
unit dg,and may
may be the
to
that in unit
the base of the
the cumulates
cumulates of
of
Unit df
unit dg.
dg. Unit
df shows sulfide mineralization
mineralization similar
similar to
to
unit ttf
ttf of
of the
the Tuscarora
Tuscarora Intrusion
Intrusion (Johnson,
(Johnson, 1970,
1970, p.
p. 68).
68).
unit dg:
dg:
unit
df
df
di
dj
dj
dk
Groyp3
dm
din
(2)
A fine-grained,
fine—grained, olivinezo-plagioclase66-olivine20
olivine2Q—p1agioclase6—o1ivine90
(Z) A
cumulate
with minor
miner augite5-oxide4-pigeon~te4-apatiEel
augite —oxide4—pigeonie —apatite1
cumulate with
within unit
* fine—grained,
as aa thin
thin sheet
sheet ,vitfiin
unit dg.
dg. (3)
(3) A
fine-graine4,
occurs as
autocrystallatee
decussate, oxide2
—augite28—plagioclase
decussate,
oxideZ3-augite2S-plagioclase45
autocrystallat
5
containing minor livine2
olivine and
and apatite2
apatite tntrudes
intrudes unit dg and
and
Z
z
is
(4) Unit
Unit dg
is presumed to
to be aa late
late differentiate
differentiate (di).
(di). (4)
grades upward into 100—200
grades
100-ZOO foot—thick
foot-thick discontinuous
discontinuous sheets
sheets
of
coarse—grained,
foliated
pigeonite4—titanomagnetite4—
of coarse-grained, foliated pigeonite -titanomagnetite 4
4
augite6—plagioclase83
cumulatescontaining
minor potass~um
potassium
augite -p1a gioclase
cumulates containing minor
S3
6
feldspar2
fine—grained granular
feldspar and
and quartz1
quartz (dj).
(dj).
A fine-grained
granular
2
l
plagioclase, quartz, orthoclase
orthoclase rock
rock (dk)
(dk) occurs
occurs as
as dikes
dikes
cutting
rocks.
cutting other Group 22 rocks.
Unit din,
the upper
upper part
part of the
dm, the
the layered
layered se•:ies,
se~ies, is a
2,000 foot—thick
2,000
foot-thick sheet of coarse—grained
coarse-grained decussate
decussate
pigeonite11—augite24--plagioclase59
pigeonite13-augite24-~lagi~clase59autocrystallates
and cumu1aes
cumulates containing
conta~n~ng minor
nanor oxides2,
oX~desZ' quartz2
quartz
2
and potassium
potassium feldspar1.
feldspar . This
unit is thought
thought to
to
This unit
l
have been emplaced along
along foliation planes
planes and thus
thus to
have dilated
dilated the
the earlier
earlier units.
units. Variations in
in grain
grain
size and
and modal mineralogy suggest
suggest th.t
that this
this unit
unit may
be a multiple intrusion.
intrusion. A
A related
related intrusion
intrusion may be
be
dl
c..ll
dn
do
do
geonite unit dl, aa inedluin—grained
medium-grained decussate
decussate pi
pigeonite17—
17
augite20—plagioclase50 rock containing
augite20-plagioclase60
containing minor oxide,
oxide,
quartz,
which occurs
occurs as
quartz, and
and potassium feldspar,
feldspar, ''''hich
as a
small stock
about 1—1/2
1-1/2 miles
stock about
milesacross
acrossininthe
the central
central
part of the Hungry Jack quadrangle.
quadrangle. Another related
related
intrusive
granular oxide19—
oxide intrusive unit
unit is
is aa fine-grained
fine—grainS granular
19
plagioclase41—augite4
rock (dxi)
which occurs
occurs as aa
plagio~lase4l-a~gite40 rocl~
(dn) 1vhich
sheet 6
sheet
6 feet thick
tlack anI
and 4 mlles
the northern
miles long in the
the
part of
Souti
of the South Lake quadrangle.
quadranp;le. Felsic dikes which
intrure
were given
given aa separate
separate designation
intrude unit
unitdcL
dm \vere
designation (do)
(do)
and may represent a
a late—stage
late-stage differentiate of
of unit
unit dj
dj
or partially fused
fused country
country rock
rock (Nathan,
(Nathan, p.
p. 115).
115).
�-112—112—
Group 44
dp
dq
Group 55
dr
ds
Group 66
dt
du
dw
The next intrusive unit
unit (dp)
(dp) occurs
occurs as
as aa concordant
concordant
as 1,200 feet
feet thick
thick between
bet'}7een units
units dg
dg and
and
sheet as much as
It is
is aa fine—grained
db. It
fine-grained foliated augite32—plagioclase58
augite32-plagioclaseS8
andtrace
trace amounts
cumulate with olivine3—hypersthene.7
olivine -hypersthene"? and
amounts of
oxides. Plagioclase
augite occur
in aa granular
oxides.
Plagioclase and
~nd augite
occur in
granular
fabric, hyperstheneas
as as
pheno—
hypersthene as oikocrysts,
oikocrysts,and
andolivine
olivine
phenocrysts.
of late-stage
late—stageinterstitial
interstitial material
crysts. The absence
absence of
material
suggests the
suggests
the unit
unit formed by flow
flow or
or crystal
crystal settling
settling
with exchange
exchange between
between the
the magma
magma and
andthe
the inner cumulus
cumulus
melt. Near
melt.
Near the
the top
top of
of unit
unitdp,
dp,a 100—foot—thick
a 100-foot-thick sheet
of medium—grained
foliated olivine17—plagioclase83
of
medium-grained foliated
olivine17-plagioclase83
cumulate
gradational with
with unit dp.
dp.
cumulate(dq)
(dq)isis gradational
In the southwestern
lint Lake
southwestern part
part of
of the
the Gunf
Gunflint
Lake quadrang!le
quadrangiLe
pyroxene-plagioclase and
and
aa heterogeneous assortment of pyroxene—plagioclase
olivine-plagioclase
olivine—plagioclase rocks
rocks possibly
possibly related
related to
to unit
unit tta
tta
of
the Tuscarora Intrusion truncate
truncate the
the layered
layered series.
series.
of the
A typical example is a medium—grained
A
medium-grained decussate
decussate tironals5—
tironals S
ollvine5—augite
5—plagioclase75
autocrystallate
(dr).
olivines-augitelS-plagioclase75 autocrystallate (dr).
Near the
the base
base of
o the layered series a medium-grained
Near
medium—grained
foliated augite1
—plagioclase77 rock
foliated
augite17-plagioclase77
rock with minor
minor oxide3—
oxide 3
pigeonite
and olivine
oivine (ds)
pigeonite? and
(ds) is
is intruded
intruded as
as aa sheet
sheet
300 feet
feet chick
hick between
300
between units
units df
df and
and dg.
dg. Unit ds
ds is
is
highly altered with montmorillonite
montmorillonite after
after plagioclase,
plagioclase,
and
and
amphibole
amphibole and chlorite after
after pyroxene.
pyroxene. Locally
chalcopyrite and
and bornite occur within interstitial,
chalcopyrite
interstitial,
altered pyroxene.
pyroxene.
A number of oxide—rich
A
oxide-rich stock—
stock- and
and dike—like
dike-like bodies
bodies
3/4 miles
miles across
the Complex
Complex
across occur near the base of the
in the South Lake
Lake quadrangle.
quadrangle. Nathan recognized
recognized four
four
varieties:
varieties: (1)
olivine (1) medium-grained
medium—grained granular olivine16—
oxide73 rocks
oxide
amount of
of plagioclase
plagioclasel6 and
and
73 rocks with a minor amount
augite
(dt).
augite (dt). The ilmenite andtitanomagnetite
anddtanomagnetite occur
occur
as
the latter generally has
has exsolved
exsolved
as primary
primary phases;
phases; the
coarse ilmenite lamellae with intra—titanomagnetite
coarse
intra-titanomagnetite
granules which have in
in turn
turn exsolved
exsolved to
to a
a fine
fine reticulate
reticulate
intergrowth of magnetite
magnetite and
and hercynite.(')On
hercynite.C)On Little
Iron
Little Iron
Lake in the South Lake quadrangle
quadrangle aa medium-grained
mediunv-grained
granular
plagioclase 1—oxide24—olivine
gra~ular,plagioclase
1-oxide -olivine
(du) rock
rock
(du)
24
49
having
minor hypersttene
hyperstLne and
hav1ng m1nor
1/2 mile
mile
and augite
augite forms
fogs aa 1/2
long composite sheet
long
sheet within unit
dt.G)A coarse--grained
coarse-grained
unit dt.(3)A
granular
plagioclase8—oxide23_pjgeonjt2,
granular plagioclase
-oxide -pigeonite -augite
—augite
'·
i nor8 olivine
I' ,23
44
rock
rock containing
minor
m
0 1Vlne occurs as
as 24small
con t a1n1ng
inalldisdi
cordant
cordant masses in the
the South
South Lake
Lake quadrangle.
quadrangle.
UI)
(4) Two
Two
occurrences of a coarse—grained
occurrences
coarse-grained decussate
decussate oxide
oxide —_
augite31_p1agioc
't
l
' 1ase
10mapped
a~g1,e3l-~
ag10c
autocrystallate (dw)
(dw) were
wer0mapped
S5 autocrystallate
within
wlth1n unit
unlt dg.
dg. This unit exhibits an
amphibole
an amphibole
alteration
alteration similar
similar to
to that
that in
in unit
unit ds,
ds but
but is
is conconsidered
sidered to
to be
be part
part of
of group
5
rocks
b;cause
of its
its
group 5 rocks because of
large oxide content.
content.
�-113—113—
Groupj
dx
dy
dy
dz
Group 88
daa
dmaa
Several fine—grained
Several
fine-grained decussate rocks occur as
as
discontinuous thin sheets
discontinuous
sheets along the base of the
the comcomand dikes
dikes higher
higher in
in the
the
plex and as small stocks and
section.
represent either
either fused
fused fractions
fractions
section. They may represent
country rock
rock or contaminated
contaminated melts, but
but all
all are
are
of country
They consist
to be intrusive. They
consist of:
of: (1)
(1) fine—
finethought to
grained
-augite 2-plagioclase66
grained decussate
decussate oxide
oxide7—augite2plagioclase66
7
olivine -quarrz and
and potassium1
potassluffi 1
rock having minor olivine2—quartz2
2
(2) fine-g~ained
fine—grained decussate
decussate oxide
oxideçfeldspar (dx);
(dx); (2)
—augite31—plagioclase55
autocrystallate
hypersthene
-augite
-plagioclase
autocrystal1ate
hypersthone
SS
(dy); and
and (?Y
(~t fine—grained
fine-g1~inedaugite3—oxide9
augite -oxide g decussate
3
quartz10—orthoclase15—hornblende29—plagioclase34
rock
quartzlO-orthoclaselS-hornblende29-p1agioclase34 rock
(dz)..
(dz)
The youngest intrusive unit within the layered series
1—1/2 miles
dikes and
and stocks
stocks as
as much
much as
as 1-1/2
occurs as dikes
across
the Hungary Jack Lake quadrangle. This unit,
unit,
across in the
inedium-grained granular
granular quartzls-alkali
quartz18—alkali feldspar
feldspar77
aa medium-grained
oxide2 (daa),
rock ,vitl,
(daa) , truncates
truncates
rock
with minor augite and oxide
2
1
unit din.
unit
dm. Across an
an interval
at the
the
inerval over a mile wide at
there is
is aa prog,ressive
progressive increase in
end of
of unit
unit din,
dm, there
in
east end
the amount
amount of
of late stage interstitial material that
the
that has
has
a composition similar to
to unit
unit daa.
daa. This unit
unit (dmaa)
(dmaa)
might be aa late
late stage
stage differentiate
differentiate ofofdin.
dm. Nathan found
however that
hm-lever
that unit
unit dx
dx has
has been
been intruded
intruded and
and altered
altered by
by daa.
daa.
n
Therefore,
unit daa
Therefore, it
itisispresumed
presumed that
thatdin
dm was
\Vas cold
cold when
,vhen unit
daa
was intruded and that
that the
the gradational zone
zone represents
represents
melt from daa
daa that
that was introduced
introduced into
into unit
unit dm.
dm.
Intrusion and
and Associated
Associated Rocks
Rocks
Tuscarora Intrusion
In the
Long Island quadrangle (Fig.
the Long
(Fig. 2)
2) a
a sequence of rock types
common to
to other
appear in
in the
other parts
partsofofthe
theDuluth
DuluthComplex
Complex appear
the following
following
succession away
succession
away from
the base: (1)
(1) aa fine-grained
augite
from the
fine—grained poikilitic augite
gabbro (tp),
(tp), (2)
(2) aa fine-grained
(hornfels) (th),
(th),
fine—grained granoblastic gabbro (hornfels)
(3)
(ttf-ttm), (4)
(4) interlayered
interlayered
(3) aa finefine— to
to medium-grained
medium—grained troctolite (ttf—ttm),
troctolite and
troctolite
and poikilitic gabhro
gabbro (tta),
(tta), (5)
(S) anorthositic
anorthositic gabbro
gabbro (ag),
(ag),
(6) ferrograndiorite
ferrograndiorite (tg),
(6)
(tg), (7)
(gr), and (7)
(7) metamorphosed
(7) granophyre
granophyre (gr),
flows (:mv).
(kmv). Although the
the outcrop pattern suggests aa simple differentiated
differentiated
layered sequence,
the stratigraphic position of
units tp,
tp, ag,
tg and gr
layered
sequence, the
of units
ag, tg
have not been unequivocally established.
established. Hm.;rever,
ttm, and
and
However, units ttf, ttn,
are clearly
clearly parts
a separate troctolite intrusion that
that truncates
tta are
parts of
of a
part
layered series
series (Fig.
(Fig. 3).
3).
part of
of Nathan's layered
ynits
ttm,tL,ad
ttf, and
tta:
The
unit of the Tuscarora Intrusion
The main unit
Units
tta:
is aa niedium—grained
medium-grained troctolite
(ttm, Fig.
is
troctolite (ttrn,
Fig. 2),
2), consisting
consisting of
of 6S-70
65—70
percent
and 10-lS
10—15 percent cumulus
percent cumulus plagioclase (An
(An 56
S-60)' and
cumulus
divine
amouns 09
ol~vine (Fo0).
(F~50). Relative amoun~s
of poikilitic augite and iron—titanium
iron-titanium
oxides
oXldes varies
varles locally.
locally. Orthopyroxene mantles olivine and
and occurs
occurs in
in
simplectic
plagioclase. Biotite
biotite is associated with
sitaplectic intersrowth
intergrowth with plagioclase.
tile
oxides. Planar orientation of
of plagioclase and modal—
modalthe iron-titanium
iron—titanium oxides.
layering are
are locally
locally well—developed
well-developed and
and mutually concordant.
concordant.
mineral layering
poikilitic
�-114-114—
The troctolite grades into
The
into an
an upper
upper unit
unit which
which consists
consists of
of
interlayered poikilitic augite gabbro and
and troctolite
(Fig. 3).
3).
troctolite (Fig.
The poikilitic augite
augite consists
consists of
of about
about 70
70 percent
percent plagioclase
plagioclase
15—20 percent augite,
(An SO - 60 )' 15-20
augite, 5—10
5-10 percentilmenite
percent ilmenite and
and is
is
medium—
med1um- to coarse—grained
coarse-grained with
withwell
well developed
developedaugite
augite orthocrysts
orthocrysts
as much
as 1—1/2"
across. The
as
much as
1-1/2 across.
The troctolite
\vithin the
the layered
layered
troctolite within
interval
interval is similar to
to that
that in
in unit
unit ttm.
ttm. Contacts
Contacts between
between layers
layers
are generally
generally sharp
sharp and
and in
in general
gener& conformable
are
conformable with
with layering
layering in
in
the
the troctolite.
troctolite. Interlayering
of several
several inches
inches
Interlayering occurs on a scale of
to
to several feet,
feet, and is undulatory with wave lengths
lengths of
of ten
to twenty
twenty
ten to
feet
feet and amplitudes of two
two to
to three
three feet,
but the
the gross
gross structure
structure
feet, but
is nearly flat—lying.
is
flat-lying.
11
A belt of fine—grained
Unit ttp;
ttp: A
fine-grained rocks
rocks occur
occur beneath
beneath unit
unit
ttf.
It
ttf.
It consists
consists of fine—
fine- to medium—grained
medium-grained augite
augite troctolite
troctolite
with
60—70percent
percentcumulus
cumulusplagioclase
plagioclase (An50),
with 60-70
(An ), 5-10
cumulus
5—10 percent cumulus
50
olivine
percentpoikilitic
poikilitic augite,
.5—10
~livin~ (Fo35),
(F~35)' 15—20
~5-20 perce~t
augite,
5-10 percent
.
iron—titanium oxides,
minor orthopyroxene-plagioclase
orthopyroxene—plagioclase simplect1te.
simplecite.
1ron-t1tan1um
oX1des, and mlnor
As yet the upper contact
As
contact of tins
this unit
unit has
has not
not been
been observed
observed and
and it
it
is not clear from outcrop data
is
data if
if it
it is
is aa separate
separate intrusion
intrusion or the
the
basal unit of the
the overlying
overlying rocks.
rocks. Johnson (1970,
(1970, p.
p. 76)
76) concluded
concluded
from
from drill
drill core data that
that it is
is aa separate
separate intrusion.
intrusion.
Unit th:
th: Several areas of fine—grained,
fine-grained, granoblastic
granoblastic gabbro
gabbro
consisting of 50 to 60 percent short tabular
tabular plagioclase,
plagioclase, 30
30 to
to
40 percent rounded
rounded augite,
augite, minor
minor subhedral
subhedral iron—titanium
iron-titanium oxides,
oxides,
olivine, and
and blades of biotite are
olivine,
are exposed
exposed on
on topographic
topographic highs.
highs.
These rocks
however
rocks may be a remnant
remnant capping over the
the troctolite;
troctolite; hOlvever
there
is no noticeable chilling of
of the
the troctolite
troctolite next
next to
to the
the
there is
hornfels and they
they more likely
likely represent
represent large
large inclusions.
inclusions.
Unit ap;
ag: A
break in
in plagioclase
plagioclase content
content separates
separates
A distinct
distinct break
units tta
tta and
and ag.
ago Unit ag
ag —
- an anorthositic
gabbro—
- contains 75
units
anorthositic gabbro
75 to
contrast
to
the
85
(in
to
the 50
50 to
to 70
70 percent
percent
S5percent
percentplagioclase
plagioclaseAnAn5560
(
55 60
Plagioclase is
phase, and
and interinterof
is the
the only
only cumulus
cumulus phase,
of unit
unit tta).
tta). Plagioclase
stitialminerals,
minerals,occurring
occurring in
invarious
various proportions
proportions are
are augite,
augite,
stitial
olivine,
and iron
texture. Orthopyroxene
olivine, and
iron oxides
oxidesinin aa poikilitic
poikilitic texture.
occurs in
in siciplectic
occurs
sil:lplec tic intergrowth
intergrm-Jth with
W'i th late—stage
late-stage plagioclase.
associatedwith
\'liththe
theiron—titanium
iron-titanium oxides.
oxides. Planar
Biotite isisassociated
orientation of
orientation
of plagioclase
plagioclase is
is developed
developed locally.
locally. At
At the
the top
top of
of
unit
ag, quartz
quartz and
and potassium
potassium feldspar
unit ag,
feldsparoccur
occurinterstitially.
interstitially.
Tue
flat—lyingoutcrop
outcroppattern
patternofof the
the ferrogranodiorite
ferrogranodiorite (tg)
The flat-lying
(tg)
and granophyre
concordant with
\vithin the
the
and
granophyre(gr)
(gr) isis concordant
with the
the structure
structure within
troctolite (ttm)
troctolite
(ttm) and
and the
the anorthositic
anorthositicgalibro
gabbro could
could be
be just
just another
another
part
of
the
layered
intrusion.
IImvever
some
field
evidence
contrapart of the layered intrusion. however some field evidence contradicts
this interpretation.
interpretation. llornfels
Hornfels inclusions
inclusions and
and sulfide
sulfide mineralmineraldicts this
ization are
are found
found in
at several
several localities
localitiesalong
along the
the contact
contact
ization
in unit
unit tta
tta at
with unit ag.
ago Thus
the troctolite may be intrusive
into the
the
Thus the
intrusive into
anorthositicgabbro
gabbro as
asininthe
the
GabbroLake
Lake quadrangle
quadrangle (Green
(Green and
and
anorthositic
Gabbro
Phinney (1969)
(1969)has
hasextended
extendedthe
theolder
older anorthositic
anorthositic
others, 1966).
1966). Phinney
gabbro from
from the
Gabbro Lake quadrangle eastward
the Gabbro
eastward and
and this
this extension
extension
projects toward
toward unit
unit ag.
ago Thus
TIluS unit ag
ag may be aa thin
thin wedge
wedge of
of an
an
In this
anorthositic gabbro.
gabbro. In
this case, units
units
areally extensive older anorthositic
fg
to the
the troctolite
troctoliteand
and intruded
intruded
fg and
and gr
gr could
could be either related to
the ancirthositic
gabbro or
or aa differentiated
differentiated part
into the
anorthositic gabbro
part of
of the
the
anorthositic gabbro.
gabbro.
anorthositic
�-115—115—
Unit
f: This unit is restricted
Unit fg:
restricted to
to aa topographically
topographically high
high
area in the southwest
corner of the
the Long
Long Island
Island Lake
Lake quadrangle
quadrangle
southwest corner
(Fig. 3).
3). It
medium-grained ferrogranodiorite
which contains
(Fig.
It isisa amedium—grained
ferrogranodiorite which
50
to
60
percent
cumulus
plagioclase,
10
to
15
percent
amphibole,
50 to 60 percent cumulus plagioclase, 10 to 15 percent amphibole,
minor clinopyroxene,
amounts of
potassium
minor
clinopyroxene, and
and varying
varying amounts
of quartz,
quartz, potassium
anorthositic
feldspar, and magnetite. Contacts with the underlying anorthositic
gabbro and overlying granophyre are
are gradational
gradational over
over tens
tens of
of feet.
feet.
The former
former could
replacement by
by intrusive
intrusiveferrograno—
ferrogranocould represent replacement
diorite or
or differentiation
differentiation within
within the
the anorthositic
anorthositic gabbro.
gabbro. Further
diorite
study is
needed to
the stratigraphic
stratigraphic relationships.
relationships.
is needed
to clarify
clarify the
i the
Unit
Unit gr:
The
ferrogranodiorite grades
grades into
into and
is cut
The ferrogranodiorite
and is
cut by
by
It consists
It
consists of
of quartz,
quartz,
The texture
texture ranges
plagioclase, potassium
plagioclase,
potassium feldspar and
and magnetite.
magnetite. The
ranges
from
from granophyric
granophyrictoto granitoid.
granitoid.
fine- to medium—grained
medium-grained granophyre.
fine—
granophyre.
Unit kmv:
kmv: The
The granophyre
granophyre intrudes
intrudesblack
black
fine-grainedmeta—
metafine—grained
volcanic
rocks whch
whch are
remnants of
ofMiddle
Middle
volcanic rocks
are interpreted
interpreted totobeberemnants
groundmassisishighly
highlyaltered.
altered. Acicular
Keweenawan
The groundmass
Keweenawan flows.
flows. The
blades of ilmenite
and plagioclase
plagioclase phenocrysts
blades
ilmeniteare
arecommon
common and
phenocrysts are
are
clouded similar
intruded rocks
rocks in
layered series.
clouded
similar to
to intruded
it'. the
the layered
series.
the
the
Mineralization: Two
Two types
types of mineralization are found in
Duluth Complex
1m., grade
gradecopper—nickel
copper-nickel
Duluth
Complexininthis
this area:
area: (1)
(1) low
concentrations
are associated
associated with
with the
the basal
basal rocks
concentrations are
rocks of
of the
the
Tuscarora Intrusion and
Tuscarora
the layered series
series intrusions
intrusions
and several of the
(Johnson, 1970),
(2)
Ilmenite— and
and titanomagnetite-rich
titanomagnetite—rich rocks
(Johnson,
(2) Ilmeniterocks
occr
occur in
in several
several units
units of
of Nathan's
Nathan's layered
layered series.
series.
With
\-lith regard
regard to
to the
the mineralization, the
the unpublished
unpublished Ph.D.
Ph.D.
thesis
(1970) warrants
warrants special
special mention.
mention. The thesis
thesis
thesis of
of Johnson (1970)
summarizes the
the results
results of
summarizes
of an
an exploration program conducted by
the Cleveland—cliffs
the
Cleveland-Cliffs Iron
IronCompany
Company and
and the Amerada-Hess
Amerada—Hess Corporation
Company from
from 1966
1966 to
to 1969.
1969. This
program
ass~ssed
This
assessed the economic
potential
of
the
base
of
the
Duluth
potential of the base of the Duluth Complex in
in aa 38
38 km corridor
along the Gunflint Trail adjacent
adjacent to
to the
the Boundary
Boundary Waters
Waters Canoe
Canoe
Area.
Area.
The drilling program (10
(10 holes)
holes) provides
provides an unique opportunity
opportunity
to
to assess
assess the
the effects
effects of
of drilling
drillingononthe
thearea
area
comparison with
with other
other
inin
comparison
activities
activities such
such as
as logging
logging and
and recreation.
recreation. More
importantly the
the rereMore importantly
lease
lease of
of geophysical,
geophysical, drill
drill core,
core, and assay data,
data, along
along with Johnson's
Johnson's
study represents
represents a
study
a major contribution by
by aa mining company
company to
to the
the
concern for
for the
the environment of the
the area.
area. The
The correlation
correlation of
of geogeophysical and
physical
and drill
drill core
core data,
data, discussed
below, makes
makes possible
possible aa
discussed below,
more accurate
accurate evaluation
more
evaluation of
of mineral
mineral resources
adjacent areas
areas
resources in
in adjacent
and
in other
and in
other areas
areas of
of similar
similargeology
geology using
using less
less expensive
expensive and
and
disruptive
disruptive preliminary
preliminary investigations.
investigations.
Coç—Nicke1_Iinera1izatjon:
~0J?E.£!:.-Nickel
~'lineralization:
Discontinuous
gossan
Discontinuous areas
areas of gossan
and
visible sulfide
and visible
sulfide mineralization
min~r-;li~-ation ,.,ithin
have been
been mapped
mapped
within unit ttf
ttf have
across the
across
the Long
Long Island
Island quadrangle.
quadrangle. Similar
Similar isolated
isolatedexposures
exposures have
have
been
found in
in unit
tta atat the
been.found
unit tta
thecontact
contact with
with anorthositic
anorthositic gabbro.
gabbro. The
The
sulfide
assemblage, consisting
sulflde assemblage,
consisting of
pyrrhotite and
and minor
minor
of chalcopyrite
cI:alcopyrjte,pyrrhoi,
pentlandjte occurs
occursinterstitially
interstitially to plagioclase
pentlandite
plagiocla~e and
and olivine. Because
Because
of the
size of
of the
of
the smaller
smaller grain
grain size
the troctolite
troctolite a
a distinct
distinct interstitial
interstitial
texture,
texture, like
like that
thatfound
found in
the sulfide
sulfide mineralization
mineralization in
in the
Kawishiwi
in the
the iCawishiwi
area
in
the
Gabbro
area in tQe Gabbro Lake
Lake quadrangle,
quadrangle, is
not apparent
apparent ininhand
handspecimen.
specimen.
is not
�-116—116—
Drilling across
across the
the quadrangle
quadrangle (Johnson,
1969) has
has indicated
indicated aa
Drilling
(Johnson, 1969)
tabular,
tabular, possibly continuous volume of
of low
low grade
grade ore
ore (0.3%
(0.3% combined
combined
copper-nickel) about 50 feet thick
thick in
in the
the unit
unit ttf.
ttf. A
A thinner
thinner 10—20
10-20
copper—nickel)
foot-thick
zone, 50—100
50-100 feet
feet above
above the
the lower
lower mineralized
mineralized zone,
zone, has
has
foot—thick zone,
aa higher combined copper—nickel
copper-nickel content
content that
that approaches
approaches one
one percent
percent
84). The mineralization can be correlated3with
correlated with a
(Johnson, p. 84).
the order of 700 x 10 3 ohmcentimeters
detectable resistivity anomaly on the
in the troctolite (ttf,
(ttf, ttm).
ttm).
Mineralization: The primary titanium
titan1um oxide
oxide phases
phases
Titanium Mineralization:
) and titanomagnetite
are i].menite
ilmenite solid
0 -MgTi0
solid solution
solution (Fe
(Fe20
—MgTiO -FeTi0
—FeTiO3)
3
3
2 3
(Fe304—Fe
(Fe 0 -Fe 2TiO
Ti0 4).
). Subsolidus exsoLtion
exsolution as
fiasresulted
resulted in
in the
the complex
complex
3 4
intergrosAhs âescribed
intergrowEhs
described above. Johnson (1970,
(1970, p.
p. 87)
87) estimates
estimates
that
that Ti
Ti recovered
recovered from
from ilmenite
ilmenite in
In unit
unit ttf
ttf in
in the
the Tuscarora Intrusion
Intrusion
could add $1.50 per ton to
to sulfide ore
ore from
from this
this unit.
unit.
The largest titanium concentrations
at Little
Little Iron
Iron Lake
Lake in
in the
the Gunflint
Gunflint Lake
Lake
at
exposures in the
the South
South Lake
Lake quadrangle.
quadrangle.
do not exceed
occurrences at the surface do
however are in units dt and du
quadrangle
quadrangle and
and other
other isolated
isolated
Unfortunately, most of these
Unfortunately,
these
about 35 feet
feet in maximum
about
dimension.
A large low—grade
A
low-grade titanium
titanium resource also is contained within
unit dg (Fig.
unit
(Fig. 3).
3). Oxide—rich
Oxide-rich layers as much as
as 5 feet
feet thick are
common,
common, although individual layers seem
seem too
too thin
thin and
and discontinuous
discontinuous
to be mined separately. Unit dg should he
to
be considered
considered in its
its entirety
for commercial evaluation with the
the potential of
of developing a very
large tonnage
tonnage of
of low—grade
low-grade ore.
ore. The unit is very heterogeneous and
and
exposures are scarce and
discontinuous, so only widespread
field exposures
and discontinuous,
systematic drilling will reveal
reveal which
which parts
parts have
have the
the greatest
greatest promise.
promise.
�_____
_____,
-117—117—
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2.
Grout,
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Minnesota
Grout, F.
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�_____
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_____, 1970, Economic geology of aa portion
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�-119—119—
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,
1897, Some·
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_____ , 1897,
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41-51.
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Wolff,
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�-120—120—
FIELD
FIELD TRIP
TRIP GUIDE
GUIDE TO
TO THE
THE PRECAMBRIAN
PRECAMBRIAN ROCKS,
ROCKS, ~UL'
i'u.._
•• _ .. _
COOK COUNTY ALONG THE GUNFLINT TRAIL
Stop 1
End of Trail Campground -- Main Phase of Saganaga Granite
the Saganaga Granite
Granite at
at this
this stop
stop is
is aa
The main phase of the
medium—grained
medium-grained hornblende—"quartz—eyet'
hornblende-"quartz-eye" tonalite
tonalite having quartz2o—
quartZ20plagioclase (An27)60_lO—hornblende6—microljne3_5
(An27)60-70-hornblende6-microline3_S and
and accessory
accessory
biotite, chlorite,
chlorite, epidote,
epidote, sphene,
sphene, apatite,
apatite, allanite
allanite
muscovite, biotite,
and magnetite.
magnetite. The apparent lineation of
of the
the "quartz—eyes"
"quartz-eyes" is
is
25_300 ENE.
25-30°
ENE. This structure is
is parodied in
in the
the hornblende—biotite
hornblende-biotite
inclusions.
inch-sized inclusions
related to
to
These inch--sized
inclusions are
are probably related
the
the south
south of
of Seagull
Seagull Lake.
Lake.
the greenstones to the
The bay leading north to Saganaga Lake was
The
Has considered
considered by
by
Grout (1936)
(1936) to
to be aa shatter
shatter zone.
zone. It
It is here interpreted as
as a
fault
in
the
granite.
fault
the granite. At this stop, aa minor secondary
secondary east—
eastnortheast
and epidote
epidote
northeast trending foliation is marked by shears and
veinlets, and
and may be related
related to
to faulting.
faulting.
veinlets,
Stop 22
Gunf lint Trail
Trail near
near the
the Campground —- Lamprophyre dike in Saganaga
Gunflint
Granite
larnprophyre dike at this stop is
is 50
SO feet
feet wide,
tv-ide, and
and can
can be
be
The lamprophyre
traced to
to the north shore of Saganaga Lake where it
it is
is found
found to
to cut
cut
the northern boundary fault
fault (Harris,
(Harris, 1968, p.
p. 21).
21). This observation
the
sets aa 10lv-er
lower age
sets
age limit for faulting and uplift
uplift to
to the
the west
Hest for
for the
the
Goldich
and
others
(1961,
p.
52)
date
the
biotite
Saganaga Granite.
Granite.
(1961, p. S2) date the biotite
(KA—70B)fromasmall
(KA-70B)from a small island
island to
to the
the north
north at
at 1.75
1. 7S h.y.
b.y.
Sundeen (1936)
(1936) reviewed
reviewed the
the petrography
petrography of
of the
the larnprophyre
lamprophyre
dikes
the Saganaga Lake
are.a and found biotite,
biotite, hornblende,
dikes in the
Lake area
and
the mafic phenocrysts in a groundmass of
of either
either
and pyroxene
pyroxene as
as the
plagioclase or
This dike
dike contains
contains plagioclasesoplagioc1ase5—
plagioclase
or "orthoclase.
"orthoclase"11 This
pyroxenel5_20—pyroxenei5_20—biotite513
pyroxenelS-20-pyroxeneI5_20-biotiteS_IO and
and hornblende5.
hornblendes. Accessory
Accessory
minerals include
minerals
include quartz,
quartz, apatite,
apatite, magnetite, chlorite,
chlorite, carbonate,
carbonate,
sphene, pyrite,
pyrite, zircon,
sphene,
zircon, serpentine,
serpentine, talc
talc and perovskite.
perovskite.
Stop 3a
Stop
Saganaga
Saganaga Granite
Granite -— Border Phase
The strongly foliated
foliated hornblende diorite
diorite exposed
exposed at
at this
this stop
stop
is typical
typical of
the border phase of the
the Saganaga Granite.
Granite. The foliation
is
of the
is defined
defined by
by aa layering characterized by various proportions
is
proportions of
of dark
dark
and
light minerals;
it is
is nearly vertical and strikes N70°W.
N70oW. Elongate
and light
minerals; it
the foliation
foliation plane
plane define
define an
an elongate
elongate
hornblende needles within the
ilneation
lineation that
that plunges gently
gently to
to the
the east.
east.
A
A transition from the border to the
the main phase involving
involving an
an
'quartz—eye' structure
structure
increase in quartz - with
tv-ith the
the development
development of
of "quartz-eye"
-— and aa decrease in hornblende can be seen in
in a number of
of outcrops
outcrops
lint Trail
Trail to
to the
on either side of
of the
the Gunf
Gunflint
the north of
of this
this stop.
stoP.
�—121—
-121-
Stop 3b
3b
Ietabasalt and associated rocks
Netabasalt
rocks
vicinity of
of this
this stop,
stop, vaguely pillowed meta—
metaIn the general vicinity
basalt
thin-bedded to
to laminated pyroclastic
pyroclastic material
material typical
typical
basalt and thin—bedded
of the
the mafic
the volcanic succession
succession are
are exposed.
exposed. Layering
of
nafic part of the
is
is nearly vertical and strikes in
in aa northwesterly
northwesterly direction.
direction. Fracture
Fracture
cleavage
direction
cleavage also
also is
is near
near vertical and strikes in a northeasterly direction
parallel to
to the
the trace of the
the Lookout
Lookout fault.
fault.
The mafic
cut by
byconformable
conformable layers
layers of
offine—grained
fine-grained
mafic rocks
rocks are cut
graphic
feldspar granite. Locally
graphic feldspar
a
thin
layer
of
iron-formation
Locally a thin layer of iron—formation
overlies the older
composed
and chert
chertunconformably
unconformably overlies
composedofof magnetite
magnetite and
rocks.
Iron-rich
the lower
lower part
the Cunflint
Gunflint
Iron—richstrata
stratatypical
typical of
of the
part of the
Iron—formationare
are exposed
exposedon
on the
the steep north—facing
Iron-formation
north-facing slope immediately
immediately
to the
to
the south
south of
of these
theseexposures.
exposures.
Stopj4
Stop
lint Iron-formation
Iron—formation
Rock Trail
Trail—- metamorphosed Gunf
Gunflint
Along Magnetic Rock
Along
of Zone 22
Thin-bedded,
Thin—bedded, fine—grained,
fine-grained, chert—axnphibole—inagnetitebearing
chert-amphibole-magnetite-bearing
strata assigned to
to the upper part of
of the
the Lower
Lower Slaty
Slaty member
member are
are
exposed along Magnetic Rock
Rock Trail
Trail at
at this
this locality.
locality. These exposures
are
the transition between moderately and
and strongly
strongly metamorphosed
metamorphosed
are near the
iron-formation;
small, poorly developed
developed pyroxene
pyroxene porphyroblasts
porphyroblasts
iron—formation; small,
can be
be seen,pecially
seen,especiallyinin
moremassive
massive beds
beds at the
the top of
of the
the
thethemore
member.
Along
to the
thesouth,
south,the
theiron—formation
iron-formation is
Alongthe
thepower
powerline
linetrail
trail to
locally
with beds
at 15°.
locally deformed
deformed with
beds dipping
dipping northward
northward at
15°.
Approximately7575feet
feetfarther
farther to
Approximately
to the
thesouth
southa anorthwesterly—
northwesterlytrending, medium-grained
medium—grained diabase
diabase sill
sill cuts
cuts slaty
slaty iron—formatin.
iron-formatin.
Approximately
200 feet
the slaty
to
Approximately 200
feet to
to the
the south
south the
slaty beds
beds again dip
dip to
the south
south and
coarse-grained, magnetite-rich
the
and are
are interlayered
interlayered with
with coarse—grained,
magnetite—rich
cherty beds.
beds. On the same knob,
knob, algal chert—bearing
chert-bearing beds characteristic
of the Upper Cherty Member also
of
also are
are exposed.
exposed.
Stop 55
Along the Kekabeic
Kekabeic Trail
Trail—- Metamorphosed Gunflint Iron—formation
Iron-formation at
at
Zone 3.
The Kekabeic
oror
less
base of
of the
the Gunflint
Gunflint
The
KekabeicTrail
Trailmore
more
lessparallels
parallels the
the base
Iron—formationand
andthe
thenorth-facing
north—facing
slopeimmediately
immediately
southofofthe
thetrail
trail
Iron-fornlation
slope
south
The iron—formation
contains exposures
exposures of
ofthe
theLower
Lower Slaty
SlatyMember.
Hember. The
iron-formation everyhas been extensively metamorphosed and now consists
where in this
this area has
of various
quartz—cummingtonite—grunerite—fayalite—
various assemblages
assemblagesofof
quartz-cun~ingtonite-grunerite-fayalite
magnetite and
magnetite
andquartz—cummingtonite—grunerite—pyroxene—magnetite.
quartz-cummingtonite-grunerite-pyroxene-magnetite.
�-122—122-are in
Test
along the
the Trail.
Trail. IIost
Host are
iI:. the
the lowe.:
10HE;::
Test pits can be seen along
magnetite-rich
the Lower
Lower Cherty
Cherty Member.
Member. Various sulfides,
sulfides,
magnetite—rich part of the
especially pyrrhotite,
the magneti:e.
magnetL:e.
pyrrhotite, also are associated with the
Stop 66
rail cut -— Basal Contact of the
dIe Duluth
Along the Paulson Mine
Mine railcut
Complex.
Complex
The Paulson Mine railcut
railcut exposes
exposes the
the base
base of
of the
the Duluth
Duluth Complex
Complex
from the
from
the Kekabeic Trail to
to the Tuscarora Lodge
Lodge road,
road, aa distance
distance of
of
about 1—1/4
1-1/4 miles. Contacts between
bet\veen beds of
of the
the Upper
Upper Cherty
Cherty Memhe:
Hembe:.:
of the Gui-if
Gunflint
Iron-formation
lint
Iron—formationand
andfine-grained
fine—grained poikilitic
poikilitic augite
augite
troctolite,
troctolite, unit
unit tp
tp of the Duluth Complex, are
are exposed
exposed at
at the
the west
west
end of the
the railcut.
railcut. Also at the
the west end
end truncation
truncation of
of aa thin
thin sill
sill
of the Logan Intrusive
Intrusive Rocks
Rocks can
can he
be seen.
seen. About half—way
half-l'1ay along
along the
the
railcut,
railcut, argillite and graywacke of the
the Rove
Rove Formation
Formation are
are in
in contact
contact
The contact aureole here is
,-lith the
the base
base of
of the
the Duluth
Duluth Complex.
Complex. The
is
with
narrow with no visible recrystallization
recrystallization of
of Rove
Rove Formation
Formation rocks
rocks
except within a few
few feet
feet of
of unit
unit tp.
tp. This is inferred to
to be aa
100—1,000
feet.
reflection of the
the thickness
thickness of unit
unit tp
tp
100-1,000 feet. The dip
lint and
and Rove
Rove Formation
Formation varies
varies from
from 15-60°
15—60° to
to the
the south
of the Gunf
Gunflint
along this part of
of the
the contact.
contact.
Stop 7a
7a
Scenic overlook
overlook on
on the
the Gunf
Gunflint
lint Trail above
above Gunf
Gunflint
lint Lake -— Copper—
Coppernickel mineralization at
at the
the base
base of
of the
the Tuscarora
Tuscarora Intrusion
Intrusion
The base of unit
unit ttf of the
the Tuscarora Intrusion
Intrusion is
is exposed
exposed on
on
the northeast side
lint Trail
Trail at the
side of
of the
the Gunf
Gunflint
the overlook. The fine—
fineto mediuin—grairied
troctoliteshows
shows no
no regular
regular increase
increase in grain
medium-grained troctolite
grain size
size
away
away from a contact with unit tp
tp and
and the
the upper
upper part
part of
of aa Logan
Logan sill.
sill.
Visible chalcopyrite,
chalcopyrite, pyrrhotite,
pyrrhotite, pentlandite occur
occur interstitial
interstitial
and olivine
olivine in
in the
the troctolite.
troctolite. This is a typical
typical
to plagioclase and
of the
example of
the copper—nickel
copper-nickel mineralization of
of unit
unit ttf,
ttf, which
which was
was
found by
by Cleveland-Cliffs
Cleveland—Cliffs Iron Company (in
found
(in five
five holes
holes along
along the
the base
base
of the
Complex) to
of
the Complex)
to occur constantly in aa 150 feet
feet thick
thick interval
interval near
near
the base of unit
unit ttf.
ttf. The combined nickel—copper
nickel-copper content
content is
is about
about
the
0.3 percent in this
this interval.
interval. A
A slightly richer
richer zone
zone 10
10 to
to 20
20 feet
feet
thick was
was intercepted about
about 50—150
50-150 feet above the
the lower
lower zone.
zone.
Stop7b
Stop
7b
2000
feet northeast
Rocks and
2000 feet
northeast of
of Stop 7a -— Logan Intrusive Rocks
the
the Rove Formation
Thin bedded argillite is
is exposed
exposed on
on the
the north
north face
face of
of aa ridge
ridge
capped by diabase.
diabase. The argillite is recrystallized
recrystallized to
to aa biotite—
biotitean interval
interval of
of aa few
few inches
inches at
at the
the contact.
contact.
bearing hornfels over an
is typical
typical of fine—
fine- to
to medium—grained
medium-grained diabase
diabase in
in thin
thin
The diabase is
sills
the lower
lower parts
parts of
of thick
thick sills.
sills.
sills and in the
�—123—
-123-
Stop 88
Northwest arm of Poplar
Lake on the
the Gunflint Trail
At
this stop
stop typical exposures and
and intrusive
intrusive relationships
relationships of
of
At this
four of Nathads
Nathans units
units will be
be examined.
examined. On the
the north
north side
side of
of the
the
unit
unit df,
df, a fine—grained
fine-grained decussate augite—olivine—plagioclase
augite-olivine-plagioclase rock
rock
the Tuscarora Intrusion intrudes
(troctolite) similar to unit ttf
ttf of the
intrudes
(troctolite)
unit dc, aa very
veryfine—grained
fine-grained granular
granularolivine—augite—plagioclase
olivine-augite-plagioclase
rock
whichmay
mayrepresent
representa achilled
chilled margin
marginofof the
the oldest
rock (gabbro)
(gabbro) which
unit of
About 50 feet
(da). About
feet north of the
the Trail
Trail
of the layered series (da).
at the
east end of the
northwest arm of Popular Lake,
at
the east
the north~vest
Lake, a small
small mass
of unit dt,
dt, aa medium—grained
medium-grained granular
granular olivine
olivine oxide
oxide rock,
rock, occurs
occurs
within unit
unit dc.
dc. A
A small isolated exposure of
of unit
unit ds
ds with
with uncertain
uncertain
contact
contact relationships occurs
occurs between units dc
dc and
and df
df about
about 500
500 feet
feet
Lake and
and 400
400 feet
feet north
north of
of the
the Gunflint
Gunflint Trail.
Trail.
northwest of Popular Lake
South of
of the
the Gunflint
Gunflint Trail there are exposures of
of the
the large
large oxide—
oxiderich sheet
sheet unit dg
(coarse—grained,
foliated
oxide,
augite,
olivine,
dg (coarse-grained, foliated oxide, augite,
plagioclase rock).
plagioclase
Stop 9
Sto2j
Gunflint Trail
Trailsouth
southofofBear
BearClub
ClubLake
Lake—
- Late granitic
granitic rocks
rocks
Cunflint
of the
theDuluth
DuluthComplex
Complex
Unit daa,
daa, a medium-grained
quartz-feldspar rock,
rock, is
is
medium—grained granular quartz—feldspar
as aa dike
on the
the north
north side
side of
exposed as
dike in
in unit
unit dm
dm on
of the
the Gunflint
Gunflint Trail.
Trail.
The
mainmass
massofofdaa
daaoccurs
occurssouth
southofofthe
th Trail
1—1/2
The main
Trailasasa astock
stock
1-1/2 miles
miles
across. Unit dm,
across.
dm, aa cumulate
cumulate sheet
sheet ofofpigeonite—augite—plagioclase
pigeonite-augite-plagioclase
rockhas
hasvisible
visibleinterstitial
interstitial quartz
rock
quartz and
and alkali
alkali feldspar
feldspar in
in an
an
This interinteraureole
much as
wide around
daa. This
aureole as much
as 11 mile
mile wide
aroundthe
the stock
stock of daa.
stitial material is interpreted as
as replacement associated with the
intrusion of unit daa.
daa.
stitial
�This page intentionally left blank
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P LANATION
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[+++
+ +++J
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xx )( xx xx
Duluth
Duluth Compte.
Complell
. O~
so'
+)"
~~{
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Bo.y
~V
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INDEX
MAP
Figure 1
L
0
o
1
I
10
1O
20
!
I
C A
A L E
if
s
S e
3Orniles
30
miles
I
~{
4?
C
2
N
V'1
Mci ic intrusive
nt, usive rocks
Mafic
rocks
ci
rIrirt Shore
of North
Shore
I
,
1/7"-:
N I // I
?
Ettrus,ve
Extrusive rocks
rocks rongrnq
ranging
in
from olilJine
diem.
in Composition
composition from
bosolr
totile and
basalt to quartz
Quartz lotite
local
rhyolite
tocot rt.yolite
[02
4cg lite and
Argillite
cnd Groywocke
Groywacke
in Cook
Rove Fm.
includes Rove
Fm. in
Cook County
County
C
~
to ond
and Vrginio
Virginiaand
andI horneon
Thomson Fm.
Fms.
St. Louis
Louis County
..
in
in St.
County
VO
S/
I
/-'
I
Lrl
~
ron —Fottitoijon
Iron
- Formation
ncluces Gunflint
C u,f tilt in Cook
includes
Cook County
and B'wo
bitt in
in St.
cnd
Biwabik
Louis County
County
SI. Louis
o
l'iitiu
Undiv dod
ided
>lap
showing the geologic
1ap of
of northeastern
northeastern Hinnesota
Minnesota showing
settinE of Cook County
setting
County and
and the
the location
location of
of Figure
Figure 2.
2.
C
c:
,,=!
n
.0
E
"'C"
4?
.t'"
a-
�I
~)
SAGANAGA
ISAGANAGA
GRANITE
4800730
—H—
CANADA
~ +
0
CMATION AN
ROVE
FORMATION
ANO
INTRUSIVE ROCKS
LOGAN
INTRUSIVE
ROCKS
df
L
ds
—
I
i-a
I-'
Gunflint
dq
tta
I
dp
db
dm
-~
ag
~f9+
DULUTH
WLUTH COMPLEX
LAYERED
SERIESOF
OF NATHAN
NATH\
LAYERED SERIES
dm + da
DIAGRAM
BLOCK
0
dgL---------
DULUTH COMPLEX
TUSCARORA INTRuSION
'~f\
N
0'
Trail
BLOCK
A
DIAGRAM
DIAGRAM
+
B
•
dm + do
Quadrangles
Studied
Field trip
hip stop
Field
stop
seA L E
Contact
o
Fault
3
2
4
=
t>
~
~
5 mi.
.~'*'tl)
~~
",0",
"
"
~<b
s-v
G.:J
BWCA boundary
boundary
BWC.A
~
.'"
V
~'(§q,
c§'t:: ;§
%o3T•3O'
Figure 22
Figure
I
I
Generalized geologic map
map of part of
of northwestern
northwestern Cook
Cook County.
County. The
The Gunflit-it
Gunflint
Iron-formation is
is stippled.
stippled. Only the
the major units
units of
of the
the Layered
Layered Series
Series of
of
Iron—formation
in the
the Duluth
Duluth Complex
Complex are
are shown.
shown. The area designated
designated df
df also
also includes
includes
Nathan in
dc,de,dk,ds,du,dy,dx, and dz; similarly ds
dc,de,dk,ds,du,dy,dx,
ds includes
includes dc,de,dg,dk,dt,du,dv,dw;
dc,de,dg,dk,dt,du,dv,dw;
dg includes dc,dd,dh,di,du,dv,dt,
dc,dd,dh,di,du,dv,dt, and dz;
dz; dp
dp includes dg,dj,and
dg,dj,and dq;
dq; db
db includes
includes
(Nathan, 1969).
da,dd,
da,dd, and dm;
dm; and
and dm
dm includes
includes da,dd,de,dn,do,
da,6j,de,dn,do, and dx.
dx. (Nathan,
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
-,'"
'"
"-~~
","''I
0/'
�SAGAN.GA &EANtTS\
MET
*VOLC ANICS
LGI.JNFLINT lION FM.
M El A V Ot C A N I C S
FL
I N1,\
.106 A N
.IOVE ff N.
M.
dy
I
t-'
tv
---J
I
in
a
\ \ 'I.-~-"'-----
\\ \
\\
\
,
Ii iJlm,l
0
o
md
9r \
------- -,
.)l
Figure 33
'I
,fg
' , II
\ ~
lmile
I
dm
—1900
-1900
/
og
1900
C190°
1100
1700
1700
db
1500
I Soc
1500
A
B
300FEET
FEET
1300
~1
FfET
L_L-----------.... 1 300
300 EE1
diagrams showing
showing the
the irif
inferred
Block diagrams
erred geologic
geologic relationrelationships of
of rock units in the
ships
the Long Island Lake and Gunflint
Gunflint
Lake quadrangles
quadrangles (location
Lake
(location of diagrams shown in Figure 2).
2).
f
�-128—12
8—
Mesabi Range Magnetite
Hesabi
Nagnetite Taconite
8, 1971
1971
May 8,
by
by
R.
R. W.
W. Narsden
Harsden
Minnesota, Duluth
University of Hinnesota,
Duluth, Ninnesota
Hinnesota
�—129—
-129-
MESABI RANGE
RANGEFIELD
FIELD TRIP
MESABI
INTRODUCTION
at the
Mineinin Virginia,
Virginia,
The
MesabiRange
Rangefield
fieldtrip
trip starts at
The Mesabi
the Auburn
Auburn Mine
Minnesota
andproceeds
proceedsto
to the Erie
Minnesota and
Erie Mine
Mine near
near Aurora,
Aurora, the
theReserve
ReserveMine
Mine
at
Babbitt and
and ends
ends at
at the
the Dunka
Dunka Pit
theeast
eastend
endofof
MesabiRange
Range
at Babbitt
Pit atat the
thethe
Mesabi
near Birch
trip isisdesigned
show
near
Birch Lake.
Lake. The
The trip
designedtoto
showthe
themetamorphic
metamorphic changes
changes
the Biwabik iron
iron formation
formation caused
caused by
by the
the intrusion
intrusion of
of the
the Duluth
Duluth
in the
Complex. The trip plan is shown on the index
index map.
The Mesabi
esabi Range
The
Range trip
trip is
is made
made possible
possible by
by the
the cooperation
cooperation of
of the
the
Minnesota Ore Operations, United
United States
States Steel
Steel Corporation,
Corporation, the
the Erie
Erie
other inforMining Company and
Reserve Mining Company. Maps and
and the Reserve
and other
Leaders
for
each part of
furnished by the
the mining
mining companies.
companies. Leaders
mation were furnished
the trip are
are shown in the trip
trip log.
log.
Stop 1.
1.
Stop
AUBURN MINE
Leader:
Wayne L.
L. Plummer
The accompanying
map, section
section and description
description of the
The
accompanying map,
stratigraphic sequence gives the geologic
geologic setting
setting of
of the
the
Auburn
Auburn Mine.
Mine. The unit numbers shown
shown on
on the
the stratigraphic
stratigraphic
sequence
sequence are
are painted on
on the
the rock
rock to
to aid recognition
recognition of the
the
horizons. The upper part of the Pokegama quartzite and the
Cherty, Lower
Lower Slaty and 145
3*5 feet
feet of the
the Upper
Upper Cherty
Cherty
Lower Cherty,
members of the Biwabik formation
members
formation are
are exposed.
exposed. Oxidized
and partly
partly leached Biwabik formation is exposed on
on the
the west
west
pit wall
wall and the Upper Slaty member and leached Virginia
pit
formations are
exposed in
north
are exposed
in the
the slump
slumpstructure
structure at
at the north
end
end of
of the
the pit.
pit.
�44
E
S
C'
RESERVE
<4
CQ(\
-1
0÷
I
I-.
f-'
w
o0
#9
I
1-
Os
,Figure
.Figure 11
INDEX MAP
INDEX
MAP
OF THE
OF
THE
MESABI DISTRICT
DISTRICT,, MINNESOTA
MESABI
I
I
�---ex---•
I
f-'
GRANITE
Figure 22
Figure
MESABI RANGE
RANGE
IRON FORMATIONS
IRON
( BLACK
BLACK AREAS
AREAS ARE
ARE DIRECT—SHIPPING
DIRECT-SHIPPING ORE
ORE BODIES
BODIES))
U)
W
I-s
f-'
I
�-132—132—
AUBURN MINE
MINE
AUBURN
The
is isone
the
The Auburn
AuburnMine
Nine
oneofofa agroup
groupofofopen
openpits
pits located
located near the
city
of
Virginia,
Minnesota.
It
city of Virginia, Minnesota. It was
was originally
developed as
asan
anunderground
underground
originally developed
mine
by the
during the
and promine by
the Minnesota
Minnesota Iron
IronCompany
Company durin?,
theperiod
periodfrom
from1894—1902
1894-1902 and
duced 2,143,000
2,143,000tons
tons of
of ore prior
1902
duced
prior totoclosing
closingin in
1902when
whenownership
ownership passed
passed
to the Oliver
Iron Mining
Nining Company,
Steel 'Cor'CorOliver Iron
Company,a asubsidiary
subsidiaryofof United
United States
States Steel
poration. Reopened as an
poration.
an open
by Oliver in
in 1951,
1951, the mine produced an
openpit
pit by
11,219,000 tons
tons of
of ore
ore by
by the
the end
end of
of 1969
1969 when
whenthe
themine
minehecirne
became
additional 11,219,000
inactive because the remaining ore is
is under
under the
the approach
approach traccs
tracks totothe
theViridrtia
Virr,inia
rescreening plant
plant located
located just
just west
west of
of the
the nine.
mine. Most of the
the
crushing and rescreening
open pit ore was loaded
loaded by
by electric
electric shovels
shovels into
into side
side dump
dump cars
cars and
and hauled
hauled to
to
the
plant by electric locomotives, but in
the plant
in the
the last
last few
few years,
years, ore
ore from
from the
the
lower benches
benches was
was loaded
loaded into
into trucks,
trucks, hauled
hauled to
to aa stockpile
stockpile beside
beside the
the track
track
lower
in the
the upper part of the
in
the pit and reloaded into
into railroad
railroad cars.
cars. The Auburn
Auburn
Nine and other former Oliver Iron }Iining
Mining Company mines
mines on the
Mesabi Ran?,e
Rance are
are
the Mesabi
Mine
now operated by U. S.
S. Steel
Steel Corporation,
Corporation, Minnesota
Minnesota Ore
Ore Operations.
Operations.
The rocks
rocks exposed in the
the mine starting
startin~ at
at the
the bottom
bottom are
arc the
the
the lower
lower three
three members
members of
of the
the Biwabik
Biwabik iron
iron formation:
formation:
Pokegama Quartzite and the
Lower Cherty,
Cherty, Lower Slaty
Slaty and
and part
part of
of the
the Upper
Upper Cherty.
Cherty. These dip
dip from
from
degrees to
to 20
20 degrees
degrees to
to the
the northwest
northwest as
as the
the formation
formatcy lies
north
5 degrees
lies on
on the
the north
side of the gently southwestward plunging Eveleth anticline and the center
center
fold known as the
fold
the Virginia
Virginia Horn.
Horn.
formed in the Biwabik formation
formation by removal
The Auburn ore body was formed
leaving less
less
of silica from iron bearing rock by leaching ground waters,
waters, leaving
soluble iron
iron Oxides.
oxides. The
The ore
body follows
formation for
ore body
follows drnvn
downthe
thedip
dipof
of the
the formation
for
fissure scarcely 50
about
3000 feet.
as a aSlr::.
small fissure
50 feet
feet
about 3000
feet.
Beginning as
at the
the southwestern
southwestern part
part of
of the
the mine, the
the ore
ore body gradually
gradually widens
wide at
toward the
the northwest into a larger
larger trough
trough with
with aa maximum
maximum width
width of
of about
about
toward
500 feet.
feet. In the
the vertical walled fissure
fissure at
at the
the southwestern
southwestern end
end of
of the
the mine,
mine,
the ore
the
ore extends
extends from
from slightly
slightly above
above the
the Quartzite
Ouartzite (here
(here reduced
reduced to
to aawhite
wite
sand)
feet of
the Lower
sand) through
through 115
115 feet
of the
Lower Cherty
Cherty member,
memher, whereas
whereas near
near the
the west
west end
end
of the
mine, the
ore extends
extends to
depth of
of about
about 260
260 feet
feet from
from the
the surface
surface
of
the mine,
the ore
to aa depth
Duetoto the
the leaching
to
contact.
Due
leaching of
to the
the Lower
Lower Cherty-Lower Slaty contact.
silica, ore zones
zones are commonly slumped into structures
resembling synclinal
structures resembling
folds.
folds. Where slumping occurs adjacent to
to taconite
taconite walls,
walls, sltnp
slump faults
faults may
ii
silica,
occur.
Glacial deposits
deposits consisting of reddish—gray—brown
reddish-fray-brown till containing
containinff
numerous boulders
boulders of
of granite
granite and
and greenstone
greenstone covered
covered the
the entire
entire area
area to
numerous
to aa
depth of 10 to
to 35
35 feet.
feet.
years
An earth slide in the northwestern bank of the mine several years
was stabilized
stabilized with
with aa rock fill
which now covers
covers much
much of
of previously
ago was
fill which
previously
exposed
exposcd formation
formation in
in this
this area.
area.
�-133—13
3—
I
I
I
I
I
I
I
I
ROUCHLEAU
MINE
VIRGIJ1IIA
I
--l--
I ------
I
I
I
I
-j-----t----
!
i
I
I
I
"
\/Jf'~O~
~Oo
@
V
CRUSHER
SCREENING
-L __ PLANT
---
\
\
RIqQ:
\
.::>((
\
\
\---_--I
\
Figure 33
Figure
~
II1-
GEOLOGIC MAP
AND VICINITY
VTCINITY
GEOLOGTC
MAPOF
OF AUBURN
AUBURNMJr~E
M:rE AND
�-134-134—
Table 11
Table
STRATIGRAPRIC SEQUENCE
G'mATIGRAPHIC
SEQUENCE IN THE
THEBIWABflC
BIWABIK ThON
IRONFORMATION
FORMATION
AUBURN
ICIE
AUBURN KmE
Thickness
'l'h1ckness
in feet1
in
teet l
UPPER CHERTY MEMBER
16.22 Jaspery,
algal chert (G
16.
Jaspery, conglorieratic
conglomeratic and
and algal
submember I)
(a and S
$ submember
x)
15.
14.
14.
13.
13.
12.
10 (eat.)
(est.)
Covered
Covered interval
interval
10 (est.)
(eat.)
Nodular hematitic chert
chert. beds interbedded
interbedded with
with laminated
hematite-eilicate-magnetite beds
hematite-silicate-magnetite
48
48 +1'
+f
Laminatedhematite-uilicate-magnetite
heniatite-ailicate-magnetite beds with subordinate
Laminated
jaspery chert beds
Jaspery
beds and
and lenses
31
Jaspery, conglcaneratic
chert beds
with subJaspery,
conglomeratic chert
beds interbedded
interbedded with
ordinate laminated
laminated heinatite-ailicate-magnetite
hematite-silicate-magnetite beds
beds
28
liberty taconite
taconite with
magnetite
Cherty
with thin
thinirregular
irregular
magnetitebeds,
beds,mqgfl*
magneanddisseminated
disseminated
'retite
tite mottles
mottles and
mBgnetite
16_ _--=~
....,;;1;;,;;6
143
LUiQER $LATY MEMBER3
11.
U.
10.
silicate magnetite
Laminated silicate
magnetite taconite
taconite with
withsubordinate
subordinate
silicate chert
chert lenses
lenses
silicate
Laminated non-magnetic
silicate
taconite,
part.
Laminated
non-magnetic
silicate
taconite,fissile
fissile in
in part.
6'
of fissile
fissile"intermediate
"intermediate slate"
slate" at
atbottom
bottan (a
(G and S
6' of
submember Q)
6ubmember
Q)
101
.....37
3;.;7_--=~
138
ER
LC1WER
CHERTY MEMBER
LO
CHERTY
Cherty
with irregular
irregularrnngnetite
magnetite beds. Upper
Upper 10'
liberty taconite
taconite with
has
silicate rich
has dark-colored
dark-colored silicate
richbeds
beds instead
instead of
ofmagnetite
magnetite
beds,
ng base of lower
indefinite
beds, mak4
making
lower slaty
slatysomewhat
somewhat indefinite
37
37
8.
Mottled
with chert "pebbles" and
and
Mottled silicate-magnetite
silicate-magnetite chert with
abundant coarse
coarse granules.
abundant
U
11
7.
7.
Cherty taconite with
with thick
thick (i"±)
(1 t)magnetite
magnetite beds
beds and
and mottles
mottles
liberty
84
9.
9.
6.
1f
Mottled cherty
very irregular
irregularmagnetite
magnetite
Mottled
cherty taconite
taconite with
with thin,
thin, very
beds.
14
5."
Thick jaspery chert beds
beds interbedded
interbedded with
with varying
varying proporproporThick
5.
tions of
of thin,
thin,regular
regularlaminated
lBDlinatedinngnetite-hematite-.
magnetite-hemat1te-s1l1cateilicate-
carbonate
carbonate beds
beds.•
66
�-135—135—
Thlckneoo
Thickne
on
l
feet1
in feet
(ConYd)
Ldwer
Cherty Member
Member (Cont'd)
Lover Cherty
Fflyft,
'rhi
c k henicstitic
hem~~ti tic
chert beJa
beis with
witb subordinate
sulJordinate laminated
laminated
zonos.
Seineclastic
elastic sand
sand grains
grains near
zones. Some
near bottcn.
bottan. Much
carbonate.
8a
Jaspery,
ehert with subordinate
Jaspery, conc'lomeratic
conglomeratic and algal chert
subordinate
laminated zones.
lnminnted
zonea. Sand graino
graino common.
common.
4:4
2.
z.
l'lassivechlorit1c
chioritic (or
(or hematitic)
hematitic) sandstone
sandstone
l-lilsslve
8
8
1.
1.
Jaspery,
Juapcry, conglomeratic and algal
algal
4..
3.
chert
4
4:
236
Total thickness exposed
Total,
5I7
Base not exposed
Base
exposed
P0iGAl4A QUARTZ ITE
** **
* **
*
*
*
**
1.
1.
Units 15 and
onbank
bankbetween
betweentruck
truckroed
road,and
andrailroad
railroad near entrance
Units
and 16 measured
measured on
entrance
to pit.
pit. Units
measured on
on SW
bank, at
at BE end
end,ofof pit.
pit. Remainder measured.
to
Units 11 - 5 measured
S\rl bank,
measured
above
railroad.
above railroad.
2.
Unit
correspondtoto numbers
numberspainted
paintedon
onthe
the walls
walls of the
Unit nwubers
numbers correspond
theAtthun
Auburn Mine
Mine and
and
are not Intended
intended to be a new stratigraphic
stratigraphic system.
system.
3.
3.
exists
The lower
lower slaty-upper
slaty-upper cherty
cherty contact
contact is
1s not
not well—marked,
well-marked and
and disagreement
disagreement exists
to its
its position.
position.
as to
**
**
**
**
**
*
*
orebody
bodyisis of
of the fissure or
The Auburn
Auburn ore
or trough
trough type
type and
and its
and
its location and
0 W,
400
W, nearly
nearly
appear to
be controlled
controlled by
set striking
strikingabout
aboutNN 40
orientation appear
to be
by aa fracture set
at right
At the SE
of the
the mine
at
right angles
angles to
to the
the strike
strikeofofthe
theiron
ironformation.
formation. At
SE end.
end. of
mine the
trough is only
from the
the quartzite
quartzite through
trough
only 50'
50' wide
wide and
and the
theore
oreextended
extended upward
upward from
through about
about
U5' ofofthe
At the
the northwest
end the
the trough
trough 1s
is 500
115'
theLower
LowerCherty
Chertymember.
member. At
northwest end
500 feet
feet wide
wide
and
and ore
ore occurs
occurs for about
about 260
Z60 feet
feetfrcmt
fran the
the Lover
Lower Slaty-Lcwer
Slaty-Lower Cherty
Chertycontact
contact to
to the
Exceflent examples
examplesofofore
oreslump
slumpstructures
structurescan
canbebeseen
seenin
in the
the ends
of the
outcrop. Excellent
eDds ot
pit,
pit, especially
especiallyatatthe
thenorthwest
northwestend..
end.
�-136—
-136-
Mine
sLown
ERIE MINE
MINE —- The stops in
inthe
theErie
Erie
Mineare
are
shownon
onthe
theaccompanying
accompanying
map. The Erie geologists designate units in
in the
the Biwabik
Biwabik formation
formation
as follows:
A—F
A-F
G-O
G—O
P—Q
P-Q
R—W
R-W
Leader:
Stop 2.
2.
Upper
Upper
Lower
Lower
Slaty member —
- .av. 110'
110'
av.
Cherty member - avo 185'
185'
Slaty member —
- av.
avo 105'
Cherty member —
- av.
avo 125'
Forrest W.
W. Boyce
Bovee
Erie —- Pit 1 West
This stop
the upper part
part of the
the Lower
Lower Cherty member
This
stop is
is in the
(units are
are designated TT and
and SS layers
layers by
by Erie).
Erie). The Biwabik
(units
formation is
is composed
composed of
of tine
fine Stilpnomelane,
Stilpnomelane, I!innesotaite,
Minnesotaite, magnetite
and cherty quartz
and
contains
bands,
mottles
quartz and contains bands, mottles and
and blotches
blotches of'
of pink
to yellow carbonate.
carbonate.
Stop 3.
3.
Erie Pit 2 West
This stop
stop is
is in
in middle to
to upper
upper part
part of
of the
the Upper
Upper Cherty
Cherty
with the
the
member and the lower part of the Upper Slaty member (F)
(F) with
in this
this pit
pit are
algal layer (I)
(I) well exposed.
exposed. (Units
(Units in
are designated
(Upper Slaty), G,
G, H,
H, I,
I, JJ and
and KK by
by Erie).
Erie). A
A diabase sill about
about
F, (Upper
feet in thickness occurs near the bottom of
33 feet
of the
the exposed
exposed iron
iron
formation in the KK layer.
layer. Some green
green mottles
mottles of
of cuminingtonite
cummingtonite
occur in the I
J layer
layer and
and carbonate
carbonate mottles
mottles in
in the
the KK layer.
layer.
Stop
Stop 4.
.
Erie Pit
Pit 33
This stop is in
in the western part
part of
of Pit
Pit 33 in T, S.
S. and BR
of the
the Lower
Lower Cherty
Cherty member.
member. The
layers in the middle part of
rock is a cherty, silicate
silicate taconite
taconite with
with layers
layers of
of cummingtonite.
cummingtonite.
Stop
5.
Stop 5.
Erie Pit
Pit 33
This stop
stop is
is in the
the eastern part of pit 33 in the T, CS and R
F
in about
about the
the same
same stratigraphic
stratigraphic
layers of the Lower Cherty member in
zone as
as stop
stop 4.
4. Much of the chert in the Biwabik formation
formation has
has
gone to form
form actinolite
actinolite and
and cumniingtonite.
cummingtonite. The rock is termed
taconite. Locally pyrrhotite occurs
occurs in
in the
the
a magnetite-silicate
magnetite—sflicate taconite.
iron formation.
formation.
�ERIE
MINING COMPANY
COMPANY
ERIE MINING
Of
MAP OF
E-1835.2
E—
1835 • 2
PLANT 8
MINE AREAS
AREAS
& MINE
LEGEND
o
CRUSHER
CDCOAR
COARSE
CRUSHER
®FINE
FINE CRUSHER
CRUSHER
®
@ CONCENTRATOR
CONCENTRATOR
®
.j)PELLET
@
PELLET PLANT
®
®
® LOADING
LOADING POCIET
POCKET
®STOCKPILE
STOCKPILE
®
CD GENERAL SHOPS
SHOPS
.1;
ADI.IINISTRATION
AOMINISTRATION BUILDING
S
I
I-'
La)
LV
.......
I
AREA I
S
Figure 44
Figure
Plan of
of Erie
Pit
Plan
Erie Pit
—
�—138—
-133-
RESERVE MINING COMPANY
COMPANY
Minil1g Company
Company mine
mine is
is situated
situated in
in aa zone
zone with
~vith aa
The Reserve Miniqg
considera~le
considerable range in mineralogy and texture
texture shown
shown by
by the
the Biwabik
Biwabik
formation.
formation.
The
The Reserve
Reserve geologists
geologists designate
designate units
units of
of the
the Biwabik
Biwabik
formation as follows:
follows:
A—G
A-G
11—0
H-O
P—Q
P-Q
R-V
H—V
Stop
Stop
6.
Upper
Upper
Lower
Lower
100130 av.—120
Slaty member
member -— 100'-130'
av.-120
Cherty
120—160' av.—140
Chertymember
member—- 120-160'
av.-140
Slaty member —- 75—120'
75-120' av.'90
av.-90
Cherty member —
- 30'-50'
av.-30
30'—50' av.—30
Reserve Mine
Mine (Peter Mitchell
HitcheEMine)
Hine)
Leader: James
James i1.
W. Emanuelson
Emanuelson
This sstop
is in
This
top is
in the
the western
~ves tern part
part of
of the
the mine,
mine, northwest of
of
Crusher No.
No.22 in the
the middle
middle part
partofofthe
theUpper
UpperCherty
Chertymember
member in
in the
J, KK and
rock is
silicate taconite with
J,
and L
L zones.
zones. The
The rock
is aamagnetite
magnetite—- silicate
abundant cuznnhingtonite.
cummingtonite.
Stop
Stop 7.
7.
Reserve Mine
Mine
This stop is in same general stratigranhic
stratigraphic zone
zone as
as stop
stop 6.
6. with
Hith
The rock
rock is
layers from
from FF to 00 exposed.
exposed. The
is aamagnetite—quartz—silicate
magnetite-quartz-silicate
taconite with
and garnet.
garnet. There
taconite
with hedenbergite,
hedenbergite, ferro—hypersthene,
ferro-hypersthene, and
There are
local
local areas
areas of
of pegmatite.
pegmatite.
Stop 8.
8.
Dunka Pit
The Dunka
Erie ['lining
Mining Company
Company isissituated
Dunkapit
pit of
of the Erie
situated near
near the
eastern end
of the
Rangewhere
wherethe
the Bhvabik
Biwabik formation
formation is
eastern
end of
the Hesabi
Nesabi Range
by the
theDuluth
DuluthComplex.
Complex. This
Hill show
show the upper
upper
This stop will,
intruded by
part of the
part
Upper Cherty
the Upper
Upper Slaty
Slaty
the Upper
Cherty member,
member,the
thelower
lowerpart
part of
of the
member,and
and gabbro
gabbro of
of the
member,
the Duluth
DuluthComplex.
Complex.
The
is composed
composed of
magnetite, hedenbergite,
hedenbergite,
The taconite
taconite is
of quartz,
quartz, magnetite,
fayalite with
with andradite
andradite garnet
garnet and
and locally
locallysome
some hessingerite
hessingerite
fayalite
The
contains suiphides,
sulphides, chalcopyrite
chalcopyrite and
and
Thegabbro
gabbroininthis
this area contains
pyrrhotite with
pyrrhotite
with pentlandite.
pentlandite.
The iron
iron formation
formation and
andgabbro
gabbrowill
willbe
be observed
observedinin the
the pit
pit and
The
and
in
north of
of the
the pit.
pit.
in outcrops
outcrops north
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�—141—
-141-
of the
Metavolcanic—
Geology of
the Vermilion MetavolcanicMetasedimentary Belt,
Belt, Northeastern Minnesota
May 8, 1971
Prepared by
R.
R. \v.
U. Ojakangas,
Ojakangas, University
University of
of Ninnesota,
iinnesota, Duluth,
Duluth, and
and
Ninnesota Geological Survey
P.
P.
K. Sims,
Sims, Minnesota Geological Survey,
K.
Survey, Minneapolis,
Minneapolis,
Minnesota
C.
G.
B. Norey,
Morey, Hinnesota
Minnesota Geological Survey
B.
Survey
Minneapolis,
Minneapolis, Minnesota
J.
J.
C.
C. Green,
Green, University
University of
of Minnesota,
Minnesota, Duluth,
Duluth, and
Minnesota Geological Survey
�—14
2—
-142-
Guide to
Metavolcanicto the
the Geology of
of the Vermilion Metavolcanic—
Belt; Northeastern Minnesota
Metasedimentary Belt;
INTRODUCTION
The
The Vermilion district is
is a
a belt of metavolcanic-metasedimentary
metavolcanic—metasedimentary
rocks
rocks more than 100
100 miles long
long and
and as
as much
much as
as 20
20 miles
miles wide.
wide. It is
is
bordered on
on the
the north
north and
and south
south by
by younger
younger granitic
granitic batholiths
batholiths (Fig.
(Fig. 1)
1)
of Algoman
Algoman (Kenoran)
(Kenoran) age.
age. The region is typical of Lower Precambrian
(>2,500
greenstone—metasediment--granite complexes
complexes of
of the
the Superior
(>2,500 m.y.) greenstone-metasediment-granite
province.
metavolcanic—metasedimentary sequence constitutes a complex
The metavolcanic-metasedimentary
volcanic pile,
pile, characterized
characterized by interfingering of lithologies and local
local
volcanism. Most of the
the metasediinents
metasediments are composed of
of
repetitions of volcanism.
volcanic detritus,
detritus, and probably include volcaniclastic and
and epiclastic
rocks.
Numerous
Numerous coeval and younger igneous rocks
rocks occur locally within
the sequence.
sequence.
The stratified sequence was metamorphosed and
and deformed
deformed before
before and
and
during emplacement of the bordering granitic rocks
rocks of the
the Giants Range
and the
the Vermilion
Vermilion batholith.
batholith. Pervasive greensehist
greenschist facies
facies
batholith and
assemblages were developed except adjacent to the
the intrusive bodies where
metamorphism
attained aniphibolite
amphibolite grade. Deformation consisted
consisted of
of two
two
metamorphism attained
major foldings
foldings and
and of
of later
later faulting
faulting on
on aa major
major scale.
scale.
STRATIGRAPHY
ST
RATIGRAPHY
The metavolcanic and metasedimentary rocks
rocks are
are assigned
assigned to
to five
five
The oldest
oldest formation,
(Morey and
and others,
others, 1970).
1970). The
formation, the
the Ely
formations (Morey
is overlain
Greenstone
overlain
Creenstone -— composed mainly of mafic
mafic metavolcanic
metavolcanic rocks
rocks -— is
stratigraphically in the west by the Lake Vermilion Formation and
locally,
locally, the Soudan Iron—formation,
Iron-formation, and in the central part by the
the
Knife Lake Group (Figs.
(Figs. 22 && 3).
3). Both the Lake Vermilion Formation and
the
Knife Lake Group
Group are composed mainly of intermediate—felsic
the Knife
intermediate-felsic pyro—
pyroand volcanogenic
volcanogenic sandstones.
sandstones. The Newton Lake Formation,
Formation,
clastic deposits and
a younger mafic to
to intermediate-felsic
unit, overlies the
a
intermediate—felsic metavolcanic unit,
Knife
Knife Lake
Lake Group
Group in the
the central part
part of
of the district and interfingers with
it to the east (Fig.
it
(Fig. 3).
3). A
A generalized and idealized pre—deformational
pre-deformational
stratigraphic sequence
the western part
part of the district is shown in
sequence for
for the
figure 4.
4.
Ely Greenstone
Greenstone
Ely Greenstone,
Greenstone, as
as redefined
redefined (?Iorey
(Horey and others, 1970),
1970), is
is an
The Ely
an
elongate body of dominantly mafic metavolcanic rocks,
rocks, on the
the average
2—4
2-4 miles
miles wide,
wide, that
that extends from the vicinity of Tower eastward to
to
distance of
of about
about 40
40 miles
miles (Figs.
(Figs. 22 && 3).
3). Pillowed or
or
Moose Lake, aa distance
lavas and metadiabase dominate
dominate the
the formation.
formation.
massive metabasaltic lavas
pyroclastic
Pillowed lavas of andesitic comnosition,
composition, interinediate—felsic
intermediate-felsic pyroclastic
�-143—14 3—
ic—intermediate epiclastic
epiclastic deposits,
deposits, chert
chert and banded
deposits, maf
mafic-intermediate
iron-formation,
tuff (?)
(?) comprise
comprise the
the
iron—formation, and siliceous carbonaceous tuff
remainder.
Andesite and
and dacite
dacite porphyry
porphyry are
are conmion
common hypabyssal
hypabyssal
intrusive rocks.
rocks. The green color of most of
of the
the rocks
rocks is
is due
due to
to
abundant secondary chlorite and green amphibole.
abundant
amphibole.
at about
The ruaxinul
maximum exposed
estimated at
about
exposedthickness
thicknessofofthe
the Ely
Ely is
is estimated
feet; the
are consistently
to the
15,000 feet;
the tops
tops of
of separate
separate flows
flows are
consistently to
the north,
north,
as
indicated by
by pillows.
pillows.
as indicated
Soudan Iron—formation
Iron-formation
The
The Soudan Iron—formation,
Iron-formation, the
the thickest
thickest and
and most
most continuous
continuous banded
iron-formation
iron—formation in
in the
the sequence,
sequence, extends
extends from
from Tower
Tower and
and Soudan
Soudan eastward
eastward
for a
a distance of about 16 miles (Fig.
(Fig. 2).
2).
for
In
In the
the Tower-Soudan
Tower—Soudan area
area it
it is
is ov~rlain
overlain directly
directly by
by intermediate—
intermediatefelsic volcaniclastic rocks of the
felsic
the Lake
Lake Vermilion
Vermilion Formation,
Formation, whereas
whereas east
east
(Fig. 2)
2) it
it is
is overlain directly by at least 7,000
7,000 feet
feet
of Armstrong Lake (Fig.
of
metavolcanicrocks
rocks with
with lenses
of mafic—interinediate
mafic-intermediate metavolcanic
lenses ofofbanded
bandediron—
ironThus, the
formation, which are
are assigned
assigned to
to the
the Ely
Ely Greenstone.
Greenstone. Thus,
the Soudan,
Soudan,
which represents a time—stratigraphic
time-stratigraphic unit,
unit, is
is a useful indicator of the
the
essential contemporaneity
contemporaneity of
of intermediate-felsic
intermediate—felsic volcanism in
the west
west
essential
in the
(Lake Vermilion
Vermilion Formation)
Formation) and
and mafic
mafic volcanism in the east (Ely
(Lake
(Ely Greenstone).
The Soudan Iron—formation,
as redefined
1910),
The
Iron-formation, as
redefined (Morey
(Morey and others,
others, 1970),
consists
of several
several types
of ferruginous
ferruginous cherts
cherts that
consists of
types of
that are interbedded
meta—
with fine—grained
fine-grained carbonaceous
carbonaceous and
and sericitic
sericitic tuffs
tuffs (?)
(7) and local metabasalt; all are
are intruded
intruded by
by metadiabase
metadiabase and
and dacitic
dacitic porphyries.
porphyries. The
thickness
thickness of
of the
the formation
formation has
has not
not been
been determined
determined accurately
accurately because
because
probably is
of complex folding,
folding, but probably
is less than 1,000 feet.
feet. It
It should be
noted that the
in the Ely
the iron—formation
iron-formation in
Ely trough
trough (Reid,
(Reid, 1956),
1956), which
which has
has
yielded
hematite iron
iron ore,
ore, probably
yielded large quantities
quantitiesofofhigh—grade
high-grade hematite
probably is
is
not equivalent
equivalent to
to the Soudan Iron—formation.
Iron-formation.
The high—grade
high-grade hematite
ores that
that were
the Soudan Iron—formation
Iron-formation at
at Soudan (Klinger,
(Klinger,
ores
were mined in the
1956) and
and in
in the
the banded
banded iron-formation
iron—formation at
at Ely
Ely (Machamer,
1968) are
are
1956)
(Machamer, 1968)
considered to
to have been formed
formed by
by hydrothermal
hydrothermal processes
processes (Gruner,
(Gruner, 1926).
1926).
FO~lation
Lake Vermilion Formation
In
the extreme
the district
~Fig. 2),
2), the Lake
In the
extreme ~~estern
western part
part of
of the
district (Fig.
Vermilion Formation
Formation overlies
theEly
ElyGreenstone
Greenstone or
orthe
theSoudan
Soudan
overlies either
either the
Iron—formation. Until recently these strata were assigned to the
Iron-formation.
the
Knife Lake
Lake Group.
Group. They were reassigned (Morey
(Morey and others, 1970) to
to
the Lake Vermilion Formation because they
the
they are not demonstrably concontinuous
the Knife
tinuous with
with strata
strata exposed
exposed in
in the
the type
type area of
of the
Knife Lake,
Lake, in the
eastern part
part of
of the
the district.
district.
formation which has
has been
The Lake Vermilion is aa heterogeneous formation
divided (Morey
(Morey and
and others,
others, 1970)
into four
fourinformal
informal
members —
- a fe1dspathic
1910) into
members
feldspathic
quartzite member,
member,
member, a metagraywacke-slate
metagraywacke—slate member,
member, a volcaniclastic member,
and a mixed metagra~vacke-felsic
metagraywacke—felsic conglomerate
conglomerate member.
member.
�—144—
-144-
The feldspathic quartzite member,
member, composed dominantly of
-ts
volcanogenic minerals and
and rock
rock fragments
fragments of
of dacitic
dacitic composition,
composition, is
in
at the
the fold
fold nose
nose southwest
southwest of
of Tower
Tower
in contact
contact with
with the
the Ely
Ely Greenstone
Grenstone at
(Fig. 2),
than the
the metagraywacke-slate
as indicated
indicated
(Fig.
2), and
and is
is older than
metagraywacke—slate member, as
by graded
graded beds.
beds. The metagraywacke-slate
metagraywacke—slate member,
member, which Is
is areally
area11y the
most extensive member,
overlies the
the Ely Greenstone locally,
locally, as
as
member, directly overlies
the south
south limb
limb of
of the
the fold
fold at
at Tower,
Tower, but
but for
for the
the most
most 'part
,part Is
is in
in contact
contact
on the
with the
the older quartzite. The graywacke
graywack~generally
generally are well bedded and
commonly are
are graded;
graded; like
like the
the feldspathic
feldspathic quartzite,
quartzite, they
they consist
consist mainly
mainly
commonly
of volcanogenic
volcanogenic debris.
debris. A
A chioritic
chloritic facies
occurs on
on the
the shores
shores of
of the
the
fades occurs
eastern part
part of
of Lake
Lake Vermilion,
Vermilion, but
but aa biotitic
biotitic facies,
fades, containing
containing scattered
scattered
amphibole,
amphibole, is
is dominant
dominant elsewhere.
elsewhere. The member contains several interbedded
lenses of metabasalt that
that are
are sufficiently
sufficiently large
large to
to be
be shown
sho\vu on
on figure
figure 2.
2.
The volcaniclastic member is
is of interest because it was interp:eted
inter~~eted
previously to
1903) related to
to be mainly aa conglomerate (Clements,
(Clements, 1903)
to the
the
Laurentian orogeny.
Instead, it
it is
orogeny. Instead,
is dominantly tuff
tuff and
and agglomerate
agglomerate of
of
dacitic composition, with lesser
lesser dacitic
dacitic lavas,
lavas, banded
banded iron—formations,
iron-formations s
and euxenic black
black slates.
slates. Locally,
Locally, dacite porphyry intrudes the
the various
rock types.
The agglomerates,
agglomerates, which
which are
are interbedded
with tuffs,
types. The
interbedded with
tuffs, consist
consist
cobbles and
boulders in a
of sub—rounded
sub-rounded felsite
felsite to
to felsite
felsite porphyry cobbles
and boulders
txotic rock fragments,
fine-grained matrix of similar
similar composition.
composition. Exotic
fragments, mainly
fine—grained
iron-formation and greenstone, constitute
constitute only
only one
one or
or two
two percent of the
the
iron—formation
rock.
metagraywacke—felsic conglomerate member,
member, which occupies
The mixed metagraywacke-felsic
occupies
an
of about
about 30
square miles
miles on the
south limb
of the
of
an area of
30 square
the south
limb of
the fold
fold south of
Tower, interfingers
with and
and is
is stratigraphically
stratigraphically overlain
overláin by the
meta—
Tower,
interfingers with
the metaIt consists
consists of
of a
graywacke-slate member
member (Fig.
(Fig. 2).
2). It
a maximum of about
graywacke—slate
10,000 feet
feet of
to mafic
rocks, felsite
felsite flows,
flows, several
several
of felsic
felsic to
mafic volcaniclastic
volcaniclästic rocks,
types
and metagraywacke
metagraywacke (Griffin,
(Griffin, 1969;
1969;
types of
of cong1.omerates
conglomerates and agglomerates, and
Griffin and Morey, 1969).
1969).
The thickness
thickness of the
the Lake
its constituent
constituent
Lake Vermilion Formation and its
members is poorly known because of complex
complex folding and faulting
faulting and
and
rather poor exposures.
exposures. In the
the Tower quadrangle,
quadrangle, the quartzite member
is estimated to
to be
the volcaniclastic member
is
be 1,500-2
1,500—2,000
feet thick and the
t OOO feet
metagraywacke—slate
to be a maximum of about
about 4,000—5,000
4,000-5,000 feet
feet thick.
thick. The metagraywacke-slate
to
is at
at least
least 3,000
3,000 feet
feet thick
thick and
and is
is probably
probably much
much thicker.
thicker.
member is
Knife Lake Group
Rocks of the Knife
Knife Lake Group directly overlie the Ely Greenstone
Rocks
from the vicinity of Ely,
Ely, where the
the Knife
Knife Lake
Lake terminates
terminates against
against aa fault,
fault,
from
The Knife
Group, as
eastward to
to Moose
Moose Lake
Lake (Fig.
(Fig. 3).
3). The
Knife Lake Group,
as redefined
eastward
(Morey
consists dominantly of graywacke,
gra~vacke, slate,
slate, and
and
(Morey and
and others,
others, 1970),
1970), consists
lava
phyllite but includes
includes substantial amounts
amounts of pyroclastic rocks,
rocks, lava
flows, and
and conglomerates.
conglomerates. Gruner (1941,
(1941, p.
p. 1624) estimated that
that the
the
flows,
15,000
the eastern end of the district
district is about 15,000 feet
feet
Knife Lake near the
thick, but
this figure may be conservative.
conservative.
thick,
but this
�—145—
-145-
Newton Lake Formation
The Newton Lake
Lake Formation
Formation was
was mapped
mapped earlier
earlier (Clements,
(Clements, 1903)
1903)
as Ely
Greenstone, but has been renamed (Morey
as
Ely Greenstone,
(Morey and
and others,
others, 1970;
1970; Green,
Green,
l970)because it is stratigraphically younger
1970)because
younger than
than the
the Knife
Knife Lake
Lake Group
Group
(Fig.
the north
north by
by the
the Vermilion
(Fig. 3).
3). The formation
formation is
is truncated
truncated on the
fault and
and along
along strike to
fault
to the
the northeast by granitic rocks
rocks of
of the
the
Vermilion batholjth.
batholith. At its
its western extremity,
extremitYt near
near :olf
Wolf Lake,
Lake, the
the
is truncated
truncated by
by aa fault
fault (Fig.
(Fig. 2).
2).
formation is
The western
western part
part of
of the
Lake formation
formation is
is composed principrinciThe
the Newton Lake
pally of
of mafic
mafic volcanics
volcanics and
and the
the eastern
eastern part
part of
of intermediate-felsic
intermediate—felsic
pally
members,t which interfinger in
volcanic members
in the
the vicinity
vicinity of
of Newton
Newton Lake.
Lake.
volcanic member
member consists
consists dominantly
dominantly of
of metabasalt
metabasalt and
and metameta—
The mafic volcanic
andesite
and fine—to—coarse—grained
fine-to-coarse-grained
andesite lavas
lavas,t some
some of
of which are pillowed, and
metadiabase and tuff
tuff or tuff—breccia.
tuff-breccia. Several small bodies of serpen—
serpentinized peridotite are
are associated spatially with the
tinized
the metabasalt
metabasalt and
and
metadiabase. Small
Small lenses
lenses of
of siliceous
siliceous marble
marble and
and banded
banded iron-formation
iron—formation
in the
the formation.
formation. The felsic member, east
east of
of Newton
Newton Lake,
Lake t
occur locally in
is composed
composed of
of felsic—intermediate
is
felsic-intermediate volcanics, dominantly
dominantly tuff—breccia
tuff-breccia
deposits and
and lesser
lesser flows.
flows. At places, metabasalt is
is interbedded
interbedded with
the
dominantly
felsic
volcanics.
the
Intrusive Rocks
Five
activity are
are recognized
recognized in
in the
the
Five distinct
distinct episodes of intrusive activity
region. In
In order
age, from
from oldest to
to youngest,
youngest, these
these are
are
order of
of inferred age,
(1) synvolcanic
have aa
(1)
synvolcanic bodies,
bodies, including
including hypabyssal porphyries, which have
metadiabase and
and metagabbro,
metagabbro, and serpentinized
wide range of composition,
composition, metadiabase
serpentinized
peridotite
(2) lamprophyres and related
related hornblende—bearing
hornblende-bearing rocks,
rocks, (3)
(3)
peridotite,t (2)
plutonic
plutonic rocks
rocks of
of the
the Giants
Giants Range
Range and
and Vermilion
Vermilion batholiths,
batholiths, which
which are
are
syntectonic,
(4) altered diorite—gabbro
diorite-gabbro which forms
forms large
large dikes
dikes that
that are
are
syntectonic, (4)
post-tectonic,
(5) basalt,
basalt, which forms
forms small,
small, discontinuous,
discontinuous, scattered
scattered
post—tectonic, and (5)
dikes. In
the Saganaga Granite of Winchell (1888)
(1888) at
at the
the eastern
eastern
In addition,
addition, the
end of the district (Fig.
end
(Fig. 1)
in age
age to
to the
the
1) is
is approximately equivalent in
rocks of the
rocks
the two
two batholiths
batholiths and
and intrudes
intrudes the
the older
older rnetavolcanics
metavolcanics (Grout,
(Grout,
1929;
and Goldich,
Goldich, 1970).
1970).
1929; Hanson and
The
rocks of
The plutonic
plutonic rocks
of the
the Vermilion
Vermilion and
and Giants
Giants Range
Range batholiths
batholiths proprofoundly affected the
the volcanic—sedimentary
volcanic-sedimentary sequence.
sequence. Granitic rocks
rocks of
of the
the
foundly
on the
the south,
south, irregularly
irregularly intrude
intrude the
the
composite Giants Range batholith, on
sequence or are in fault contact
contact with it,
it, and
and have
have cut
cut out
out an
an unknown
unknown amount
amount
of section at
Where the granite is
at the
the base
base of
of the
the Ely
Ely Greenstone.
Greenstone. ~~ere
is not in
in
fault
with the
the lower-grade
lower—grade volcanic-sedimentary
volcanic—sedimentary rocks,
rocks, it
it has
has normal
normal
fault contact
contact with
to the
the older
older strata,
strata, with
with the
the development
development of
of
intrusive relationships to
amphibolite-facies
to the
the contact.
contact. The Vermilion
amphibolite—facies assemblages adjacent to
batholith, on
on the
the north side
the district,
transects the
the upper
side of
of the
district, transects
upper stratistrati—
graphic part of the
the supracrustal sequence.
sequence. This leucocratic biotite
biotite granite
granite
includes wide
wide zones
of abundant inclusions of biotite schist
includes
zones of
schist and
and amphibolite
amphibolite
STRUCTURE
The metavolcanic
metavolcanic and
rocks dominantly constitute a
and metasedimentary rocks
homoclinal, northward—younging
homoclinal,
northward-younging sequence
sequence in
in the
the central
central part
part of
of the
the district,
district,
�-146—146-whereas they are
faulted in
in the
the western
western and
and
are both complexly folded
folded and
and faulted
eastern parts.
parts. Deformation was not pervasive,
pervasive, and
and primary
primary structures
structures
Graded bedding and other primary features
remain in most of
of the
the rocks.
rocks. Graded
features
remain in the
the graywacke—slate
gray\vacke-slate successions, and
and pillow
pillow structu:es
structu::es and
and
variolites are remarkably
well
preserved
in
the
mafic
metavolcanic
remarkably
preserved in the mafic metavolcanic rocks.
rocks.
At places, however,
hmvever, a penetrative
penetrative deformation,
deformation, mainly
mainly shearing,
shearing, has
has
obliterated the
the bedding.
bedding.
the western part of the area the
the rocks
rocks are
are complexly
complexly folded
folded as
as
In the
aa result
two distinct episodes of deformation.
deformation. The younger folds
folds and
and
result of
of two
aa pervasive accompanying cleavage largely
largely obscure
obscure the
the older
older folds,
folds, alalthough
though the
the older folds
folds were important in
in determining
determining the
the distribution
distribution
of the rocks.
rocks. Detailed studies in
in the
the Tower quadrangle
quadrangle and
and adjacent
adjacent areas
areas
(Hooper
and Ojakangas,
Ojakangas, 1971)
1971) indicate that
(Hooper and
that the metasedimentary strata,
strata,
and to
to aa lesser degree the metavolcanic rocks,
rocks, first
first were
,,,ere folded
folded on
on west'iVestThese
(F1)
folds
were
tight
to
isoclinal,
had
northwest-trending axes.
axes.
(fo ) folds tvere tight to isoclinal, had
northwest—trending
l
steep axial
axial planes,
planes, and probably had gentle or
steep
or moderate
moderate plunges.
plunges. Major
~lajor
fold axes,
axes, as
as determined by consistently facing
fold
facing or
or opposing
opposing tops
tops of
of beds,
beds,
were spaced from
from 700
700 to
to 1,500
1,500 feet
feet apart.
apart. The younger (F2)
(F ) folds,
folds, which
2
most of
comprise most
of the mappable ones,
ones, are
are strongly
strongly asymmetric
asymmetrlc and
and have
have
In most
most of
of the area the (F2)
steep axial planes that
that trend
trend eastward.
eastvlard. In
(F ) folds
folds
2
are dominantly Z—folds,
are
Z-folds, and the
the northwest—trending
northwest-trending limbs
limbs are
are two
two or
or more
more
times longer than the southwest—trending
southwest-trending limbs;
limbs; plunges
plunges are
are generally
generally
times
of aa pervasive,
pervasive, mild,
mild, axial
axial plane
plane cleavage
cleavage with
with
steep. The intersection
intersection of
In biotitebiotite— and higher—grade
to F2
fo fold
fold axes.
axes. In
higher-grade rocks,
rocks,
bedding is parallel to
2
to the
the cleavage—bedding
cleavage-bedding intersection.
intersection.
new minerals
minerals are aligned parallel to
In
joints,
In the
the Tower
Tower area,
area, several
several nearly
nearly vertical
vertical structures
structures -— faults,
faults, joints,
and
third deformation
deformation displace
displace the
the cleavage
cleavage of
of the
the F2
F
and kink bands of a third
2
deformation.
High—angle faults
High-angle
faults of two
two trends,
trends, longitudinal
longitudinal and
and transverse,
transverse, break
break
the
metavolcanic—metasedimentary sequence
the metavolcanic-metasedimentary
sequence into
into aa number
number of
of blocks
blocks or
or
segments and separate it in part from
from the
the marginal batholithic
batholithic rocks.
rocks.
segments
The Vermilion fault
fault (Sims
(Sims and
and others, 1968),
1968), aa longitudinal
longitudinal fault
fault with
with
an inferred length of 300
300 miles (Sims,
(Sims, 1970)
1970) generally
generally separates
separates the
the
Vermilion batholith and associated amphibolite facies
facies schists
schists from
from lower—
lm"ergrade rocks of
of the
the district.
district. The
directioncl the
the horizontal
horizontal
The amount and directionof
component of
of movement
component
movement is not known,
known, but
but possibly
possibly is
is several
several miles.
miles. The
vertical displacement
is
inferred
to
be
on
the
order
of
a
mile,
bring
displacement is inferred to
on the order of a mile, to
to bring
higher-temperature-facies
higher—temperature--facies rocks
rocks on
on the
the north
north against
against lower-temperaturelower—temperature—
facies
facies rocks
rocks in
in the
the district.
district. Other longitudinal faults,
faults, some
some of which
,,,hi-ch
appear to
to be
be strands
strands from
from the
the Vermilion fault,
fault, slice the
the northern part
part
of the district into
of
into separate
separate segments.
segments. The transverse
transverse faults
faults trend
trend
northeastward or north—northeastward
north-northeastward and have
have dominantly
dominantly left
left lateral
lateral
displacements; the principal faults
displacements;
faults of this
this Set
set have
have measureable
measureable
displacements
3-4 miles (Griffin
(Griffin and
and Morey,
~1orey, 1969).
19(9).
displacements of
of about 3—4
The
The major faults
faults of the area are expressed
expressed commonly
commonly as
as narrow,
narrow,
Where exposed,
linear topographic depressions.
depressions. I,'here
exposed, they are
are seen
seen to
to
of wide zones of crushed
crushed and
and altered
altered rock
rock or
or of
of intensely
intensely
consist either of
silicified and altered
altered rocks.
rocks.
�-147—14 7—
Selected References
Clements,
J. ri.,
U., 1903,
C1e~ents, J.
1903, The Vermilion iron—bearing
iron-bearing district
district of
of Minnesota:
Minnesota:
U. S.
U.
S. Geol.
Geol. Survey
Survey Mon.
Hon. 45,
45, 463
463 p.
p.
Coldich, S.
S. S.,
S., Nier,
Nier, A.
A. 0.,
0., Baadsgaard,
Baadsgaard, Ha1fden,
Halfden, Hoffman,
Hoffman, J.
J. H.,
H., and
and
Goldich,
Krue;er,
H.
U.
The
P:ecambrian
geology
and
geochronology
Krueger, H. IV., 1961, The P::ecambrian
and geochronology of
of
ilinnesota:
dinnesota: [inn.
Hinn. Geol.
Geol. Survey
Survey Bull.
Bull. 41,
41, 193
193 p.
p.
,
Green,
C., 1970,
1970, Lower Precambrian rocks
rocks of
of the
the Cabbro
Gabbro Lake
Lake quadquadGreen, J.
J. C.,
rangle,
rang1e, northeastern
northeastern Minnesota:
}1innesota: :--1inn.
Geol. Survey,
Survey, Spec.
Spec. Pub.
Pub.
Minn. Geol.
ser.,
ser., SP—10,
SP-10, 96
96 p.
p.
Griffin,
L., 1969, Embarrass quadrangle,
quadrangle, St.
St. Louis
Louis County,
County, Minnesota:
Minnesota:
Griffin, ,~.
U. L.,
Minn. Ceol.
~Hnn.
Geol. Su—vey
Su-vey Misc.
Misc. Map
Hap Sec.,
Ser., MaD
Map M—6.
1'1-6.
Griffin,
Griffin, U.
IV. L.,
L., and
and ?torey,
!'forey, G.
C. B.,
8., 1969,
1969, The
The geology
geology of
of the Isaac Lake
Minn. Geol. Survey,
quadrangle,
quadrangle, St.
St. Louis County,
County, Minnesota: Hinn.
Survey,
Special Pub.
SP-8, 57
57 p.
p.
Pub. Ser., SP—B,
Grout, F.
Grout,
F. F.,
F., 1929, The Saganaga
Saganaga granite
granite of
of Minnesota—Ontario:
Minnesota-Ontario: Jour.
Jour.
Geology,
Geology, v.
v. 37,
37, p.
p. 562—591.
562-591.
Gruner, .3.
Gruner,
J. W.,
The Soudan Formation and a new suggestion as to
to the
the
U., 1926, The
Econ.
Geol.,
v.
21,
p.
629—644.
oriign of the
the Vermilion iron
iron ores:
ores: Econ.
21, p. 629-644.
Cruner, .3.
Gruner,
J. W.,
W., 1941,
1941, Structural geolony
geology of
of the Knife Lake area of northeastern Minnesota:
Geol. Soc.
Hinnesota: Geol.
Soc. America Bull.,
Bull., v. 52,
52, p.
p. 1577—1642.
1577-1642.'
Hanson, G.
G. N.
N. and
and Go1dich,
Goldich, S.
Hanson,
S. S.,
S., 1970, Early
Early Precambrian
Precambrian geology
geology of
of
the
Saganaga-Northern Light
Inst.
the Saganaga—r4orthern
Light Lakes
Lakes area,
area, Minnesota-Ontario:
Minnesota—Ontario: Inst.
Sup. Geology,
Geology, Proc. 16th
16th Ann.
Ann. Mtg.,
Mtg., Thunder
Thunder Bay,
Bay, Ontario,
Ontario,
Lake Sup.
p.
18.
p. 18.
Hanson, C.
R., 1971,
1971, K-Ar
K—Ar ages
ages of
of mafic
mafic dikes and
Hanson,
G. N.
N. and
and >Lalhocra,
Nalhotra, R.,
evidence
for low—grade
lOVT-grade regional metamorphism
metamoJ.Tphism in
in northeastern
northeastern
evidence for
:linriesota:
Hinnesota:
Geoi. Soc.
Soc. America Bull.
Bull. (in
(in press,
press, March
March issue).
issue).
Ceol.
Hooper,
Vermilion
[looper,Peter
Peter and
and Ojakangas,
Ojakangas, R.
R. W.,
U., Multiple
Multinle deformation
deformation in the Vermilion
district, Minnesota:
district,
Hinnesota: Can.
Can. Jour.
Jour. Earth
Earth Sci.
Sd. (in
(in press,
press, April
April issue).
issue).
Klinger,
Klinger, F.
F. L.,
L., 1956,
1956, Geology
Geology of
of the
the Soudan
Soudan mine
mine and
and vicinity;
vicinity; Guide
Guide book
book
Series,
Series, Precambrian ef
of northeastern Minnesota: Geol.
Geol. Soc.
Soc. America,
America,
Ninneapolis,
Heeting, p.
p. 120—134.
120-134.
Minneapolis, Minnesota Meeting,
iachmner, J.
F.
Machamer,
J. F.,
1968, Geology
the iron are
the
Geology and
and origin of
of the
ore deposits
deposits of
of the
mine, Vermilion district, Minnesota:
Zenith mine,
Ninnesota: Minn.
Minn. Geol.
Geol. Survey
Survey Spec.
Spec.
Pub., SP—2,
Pub.,
SP-2, 56
56 p.
p.
,
Ojakangas,
Ojakangas, 11.
R. U.,
W., Sims,
Sims, P.
& Hooper,
P. K.,
K., &
Hooper, Peter,
Peter, 1971,
1971, Geology of the
Tower
Tm.,rer Quadrangle:
Quadrangle:
!'linn.
Geol. Survey
Survey (In
(In preparation).
preparation).
Minn. Geol.
Reid, 1.
I. L.,
L., 19
1956,
l:Zeid,
S6, Ceolo1y
Geo1of-y of the
the Ely
Ely Trough:
Trough: Guidebook Series,
Series, Precambrian
of northeastern Minnesota: Geol.
of
Soc. America, Minneapolis
Hinneapolis meeting,
meeting,
Geol. Soc.
i,.
135—148.
TJ.
135-148.
�—14
8—
-148-
Sims, P.
1970, Geologic
Geologic map
map of Minnesota:
P. IC.,
K., 1970,
Minn. Geol. Survey
Survey
Misc. Map Set.,
Misc.
Ser., Map M—l4.
M-l4.
Sims,
Morey, C.
Sims, P.
P. K.,
K., Morey,
G. B.,
B., Ojakangas, R.
R. W.,
W., and
and Griffin,
Griffin, N.
W. L.,
L., 1968,
1968,
Preliminary geologic map of
of the
the Vermilion
Vermilion district
district and
and adjacent
adjacent areas,
areas,
northern Minnesota: Minn. Geol.
Geo1. Survey
Survey Misc.
Misc. Map
Map Ser.,
Ser., Map
Map M—5.
M-5.
Sims,
Morey, G.
Sims, P.
P. K.,
K., Morey,
G. B.,
B., Ojakangas, R.
R. N.,
W., and
and Viswanathan,
Viswanathan, S.,
S., 1971,
1971,
(in press),
press), Geologic Map of Minnesota, Hibbing
(in
Hibbing Sheet:
Sheet: Minn. Geol.
Geol.
Survey.
Survey.
Winchell, H.
H. V.,
V., 1888,
1888, Report
Report of
of observations
observations made
made during
during the
the summer
summer
Winchell,
Minn. Geol.
(northern Minnesota);
Minnesota): Minn.
Geol. Survey
Survey Ann.
Ann. Rept.
Rept. v.
v. 16,
16,
of 1887 (northern
p.
p. 395—478,
395-478, map.
map.
�F L A NJ ATION
EXPLANATION
cc
o
C,
~
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~ E
D
°
:::)
0C
l::~~:1
3: {
cC,
0
V
~
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ill
U
"-'
ill
3:
Duluth
Duluth
0:::'"
~f
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I
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a.
CO
o
~
~
-0
E
-o-'='
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Virg1nia
Vrqinio
<..?
"'~'l
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and
Formations
Rove
ill
I
f-'
C
«
Bv,::uk and
Biwabik
and
Gunflint
Gunflinl
fornialions
Iron —
- formations
~
C
co
o
~+++++J
Gions
Giants
r:''",; ;->~,
'I ']
"::~;::::'7·{~::/,---
Range
Range Granile
Granite
Vermilion
GronLte
Granile
, /
t,/~'-J
=
co
o
—
-'='
E
Saganaqa
Sagona
go
o
S
u
~
Granite
Q...
Q;
3:
o
---.J
~Sif
epiclastic, volconiclastic
undivided epiclastic,
volcaniclastic
sedlmenlary rocks,
extrusive mafic
sedimentary
rocks, extrusive
rocks, and
and lhe
te
igneous rocks,
Soudan Iron
Iron -—formation
tormotion (sit),
(sit)
mainly greensch;st
focies
greenschist facies
o0................
jO
'0
IIoowiiIl
20
I
SCALE
5
CAL E
30
Miles
3OMiies
J5
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o
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1:
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&
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I
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92°00'
92°45'
90°45' -«)
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""
Area.
of
<:r
p1a.te
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+
+
+
+
+
+
+
+
+
+
+
+
+
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+
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+
+
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+
+
+
+
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+
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Figure 1.
1.
Figure
92°00'00"
to
quadrangles
stud ied
Generalized
the Vermilion
(Morey &
1970)
Generalized geologic map
map of
of the
Vermilion district,
district, Minnesota
Minnesota (Morey
& (thers,
cthers, 1970)
i
I
I
I
i
I
I
i
I
I
I
�C
PL
LA
AN
NA
ATTI10
N
E )C
XP
ON
foijli
North of
at Vernii/ioii
Vermilioll foull
I'.....
... '1
Range Granite
Range
Grande
G,onis
Glonts
Ver ni lion Gronile
Bionic
Biollle
Schisi
5chiSl
Newton Lake
Lake Farmolion
Formal ion
Newton
undivided
undivIded
Vif.::::
.
~v.gs.
vii
Amphibolile
Amphibolite
—7-———-—vmv
vmv
vgv
YQ
vq
c
LLake
oice
.2
.D
E
3
~
Q..
5
.':'.':'."
:"> .
Verm,tion
Vermilion
Knit
Knife Lake
Lake
vVm
vvm
Group
(undivided)
For
molio n
Formation
vgs, meiagroywocke
metagraywacke member
member
quorrziie
vg.
quartzite member
member
v q,
vgv,
mi xed metogroywacke
metagraywacke - felsic
felsic
vg v, mired
I
I-'
conglomerate member
conglomerate
member
vvtn,
vaiconicMsic member
member
vvm, volcaniclastic
bonded iron -- formation
vif > banded
vlf
cmv. dominantly
dominantly melobasoli
metabasalt and
and
vmv,
metod i a baaso
S8
meladiab
V1
I-'
I
- format On
Soudan Iron
Iron -formation
Soudon
dominantly
domlnontly jaspiiite
jospilite, jasper,
and cherl
chert
osper and
-- cit
Ely Greenstone
Greenstone
e9,
domlnontly menobosoltic
metabasaltic
eg, dominantly
p i ilowed flows
and metaandesitic
meiaandesitic pillowed
and
'nlern,ediate composition
and Intermediate
composi lIon
pyrociostic
pyroc
lost\c depOsits
deposits
elf, banded
bonded Iron
Iron -formation
- formation
9it,
Corroci,
dotled where
wiere inferred
nte- 'Cd
Contact, dotted
Vault
Faull,• oared
dotted where
where
o
'"'
22
inferred
4
5S
6
8
CAL E
CAL
E
loMites
�-g
92'30'
92°3
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9j '45'
92'00'
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(j)
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a
Z
zZ
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(II
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(j)
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· ·. . . . . .. . .. . . . . . . . . . .
·
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Figure 2.
2.
I
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..
.
. . .. . ... .. . . .. ..
..
.
...............................................................
.
92*30
92'30'
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..
91045
of the
the western
western part
part of
Geology of
of Vermilion
Vermilion district,
district, Minnesota
Ninnesota (Norey
(Norey &&others,
others, 1970).
1970).
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Figure 3.
3.
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G
eology of the
the central
Geology
central part
part of
of the
th e Vermilion
district , Minnesota
M'l.nnesota (Morey
Vermilion district,
(Morey &
& others,
others , 1970).
1970).
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-155-
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Fe1dspathic quartzite
quartzite
Feldspathic
agglomerate
Dacite agglomerate
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Graywacke-slate
Graywacke—slate
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Dacite tuff
Daci te porphyry
Dacite
Iron—formation
Iron-formation
Basalt—andesite
Basalt-andesite
GENERALIZED AND IDEALIZED
IDEALIZED PRE—DEFORMATIONAL
PRE-DEFOID1ATIONAL VOLCANIC
VOLCANIC PILE,
PILE~
WESTERN VERHILION
VERMILION DISTRICT
of
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Figure 4.
4.
(Not
(Not to
to scale.
\.
3
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,-
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0
0
"
Numbers indicate approximate stratigraphic
stratigraphic positions
positions
Numbers
field
trip stops.)
stops.)
field trip
2
"
�—156—
-156-
VERMILIONDISTRICT
DISTRICT FIELD
FIELD TRIP
VERMILION
INTRODUCTION
This field
field trip
trip is
is designed to be a one—day
one-day trip,
trip, starting
starting near
near Ely
Ely
Representative
outcrops
of
most
and ending aa few
miles
west
of
Tower.
few miles west of Tower.
of the
the major rock
rock types
types in
in the
the Vermilion
Vermilion district
district are
are included.
included. Most
stops are in
in the
the Lake Vermilion Formation,
Formation, the
the Ely
Ely Greenstone,
Greenstone, and
and the
the
Soudan Iron—formation.
Iron-formation. None are in the
the Knife Lake
Lake Group because
because good
good
exposures are not easily accessible;
accessible; however,
however, the
the Knife
Knife Lake
Lake rocks
rocks are
are
to those
those in
in the
the Lake Vermilion Formation.
Forma.tion.
similar to
Stop 1
Any
several roadcuts
Any of several
roadcuts 2—10
2-10 miles South of Ely
Ely on Hwy.
Hwy. 1.
1.
Giants Range bathalith
batholith
Most abundant facies in
in this
this area
area ('Farm
C'Farm Lake Fades'
Facies" of
of Green,
Green, 1970)
1970) is
is
medium—grained,
medium-grained, porphyritic
porphyritic hornblende—biotite
hornblende-biotite quartz—poor
quartz-pooradainellite
adamellite with
K-spar phenocrysts.
phenocrysts. Hornblende and K—spar
K-spar are
are commonly
con~only aligned
aligned in
in flow
flow
pink K—spar
structure. Monzonitic, granodioritic,
granodioritic, and
and dioritic
dioritic phases
phases also
also occur;
occur; all
all
have been cut by shear
shear zones
zones locally.
locally.
Stop 22
South of Ely on Hwy 1. Outcrops
under powerline
pmverline on EE side of Hwy 1,
l, 1.4
1. 4
Outcrops under
mi.
mi. S of junction
junction with Hwy
Hwy 169.
Ely Greens
Greenstone
tone
of a
within the
Dacitic to
to andesitic,
andesitic, pillowed lavas characteristic
characteristic of
a zone
zone within
the
Ely
trendsE—W
E-W south
shapes show
show tops face
face
Greenstone that
that trends
south of
of Ely. Pillow shapes
Ely Greenstone
are cut
These volcanics
volcanics are
north, as
as in
in most
most of
of the
the formation.
formation. These
cut by aplitic
north,
dikes
to the
the Giants
Giants Range
Range batholith;
the hidden
hidden contact
in
related to
batholith; the
contact lies
lies in
dikes related
the
the slope
slope to
to the
the southwest,
southwest, and
and granite
granite outcrop
outcrop can
can be
be seen
seen near
near the
the base
base
of the slope.
slope.
of Ely.
14.
at curve about 0.25
Stop 3 Roadcuts
Roadcuts on
on Hwy
Hwy 169, at
0.25 ml.
mi. W.
of
Ely.
StoRj
Ely
Ely Greenstone
of the
Creenstone
Pillmved metabasalt that
that is
is typical
typical of
of the
the màflc
mafic lavas
lavas of
the Ely
Ely Greenstone
Pillowed
The
pillow
structures
is exposed
in road
road cut
cut on
on north
north side
of highway.
higlmay. The pillow structures have
have
side of
is
exposed in
somewhat drawn
smoothly
tops, nearly flat
flat bases, and
and are
are somewhat
drawn out
out in
in
smoothly rounded tops,
of an
vertical
an inch
inch thick.
thick. The
The
Thechilled
chilled rinds
rinds are
are aa fraction of
vertical dimension. The
and
SE and face
U., dip
pillmv structures strike
strikeapproximately
approximately N.20°
N. 20° Eo,
dip 800
80° SE.,
face
pillow
,
southeastward.
southeastward.
The long
subparallel to
to the
the
The
long dimension
dimensionofofthe
the pillows
pillows is
is subparailel
in~ersection
cleavageand
andbedding
beddingand
andplunge-s
plunges steeply
steeply northeastward.
northeastward.
intersection ofofcleavage
�—15
7—
-157-
The exposures are on the
the northwest limb
limb of
of aa tight
tight syncline,
syncline, the
the axis
axis
The
Ely
trough
contains
an
through the
the Ely
Ely trough.
trough.
trough contains an
of which passes through
iron—formation that
was largely altered to hematite, and which was
iron-formation
that was
was aa
substantial source of
of direct—shipping
substantial
direct-shipping hematite ore.
ore.
On the
the south side of highway, fine—to—medium—grained
fine-to-medium-grained metadlabase
metadiabase is
is
exposed in road cut and on
on hill to
to south.
south. The metadiabase intrudes and
and
crosscuts the
the pillowed metabasalt. AA contact can
can be seen
seen in
in the
the southern
southern part
part
of the
tile crest
crest of
of the
the hill.
hill.
4. About 2.5 mi.
\oJ of Stop 33 on Hwy
Hwy 169, turn
turn NN (right)
(right) on
on road
road to
to Burntside
Burntside
Stop 4.
ml. W
Lodge (Co.
88).
Continue
on
road
past
bridge
over
Burntside
River
(Co. 88).
Burntside River and
and
About 1.4 miles past Van Vac
road (on
(on left).
left). About
past junction with Van Vac road
Stop in about 0.2 miles
road,
(on curve)
curve) on
on private
private road.
road. Stop
road, turn left (on
north on private road,
road, at
at curve
curve to
to right.
right.
Newton Lake Formation
Formation
Serpentinized metaperidotite
metaperidotite and
and associated
associated gabbroic
gabbroic rocks
rocks are
are exposed
exposed
Serpentinized
from base of hill northward to
from
to crest.
crest.
It is about 150
Serpentinized peridotite is
is exposed at base of hill. It
150
feet thick,
is nearly black,
black, and contains some
feet
thick, is
some poikilitic
poikilitic augite.
augite.
Iniinediately
northofofserpentinized
serpentinizedperiodite
periodite and
and apparently
apparently gradational
gradational
Immediately
north
into it
it is
is aa coarse-grained
coarse—grained hypersthene (?)
into
(?) gabbro, which grades in turn
into a gabbro (higher
The gabbro appears to
into
(higher on
on hill).
hill). The
to have some
some crude
crude
compositional layering and is in part diabasic.
diabasic. On crest of hill,
hill, part
of the
the gabbro (or
(or diorite)
diorite) contains
contains coarse,
coarse, radiating
radiating pyroxene
pyroxene crystals,
crystals,
as much as an
as
an inch
inch long.
long. There is some interstitital quartz and feldspar
granophyric material in this
this phase of the
the rock.
rock. Pyrite is widely scattered through the
the gabbroic
gabbroic rocks.
rocks.
ultramafic-mafic body at
this stop
is near the
the southwestern end of an
The ultramafic—mafic
at this
stop is
intrusive sheet that
that is about 3.5
3.5 miles long
long and
and 1,000
1,000 feet
feet or
or more
more thick,
thick,
and which underlies little
little Long
Long Lake.
Lake. The sheet appears
appears to be a differbody, from peridotite at
entiated body,
at the
the base
base to
to gabbro
gabbro at
at the
the top.
top. North
of the
eastern end
end of
of Little
Little Long
Long Lake,
Lake, aa small
small body
body of
of serpentinized
serpentinized
of
the eastern
peridotite,
peridotite, within
within metadiabase,
metadiabase, is
is exposed
exposed in
in aa roadcut
roadcut along
along the
the Echo
Echo
Trail.
The top
top of the body is truncated
truncated by
by the
the Vermilion
Vermilion fault.
fault.
Stop 55
Roadcut about
Roadcut
about 13.0
13.0 miles
miles W
W of
of Ely
Ely and
and about
about 2.5
2.5 mi.
ml. W
W of
of Eagle's
Eagle's Nest
Nest
Lake road (Co.
(Co. 408)
408) on
on Hwy
H\vy 169.
169. Other outcrops of
of similar
similar rocks
rocks are
are also
also
present along the
the highway.
highway.
Soudan Iron—formation
Iron-formation and cross—cutting
cross-cutting dacite.
dacite.
Roadcut
Roadcut in Soudan Iron—formation.
Iron-formation.
A quartz—feldspar
quartz-feldspar (dacite)
(dacite)
A
porphyry dike and Ely Creenstone
Greenstone are exposed
exposed at
at east
east edge
edge of
of outcrop.
outcrop.
The
iron-formation is
The iron—formation
is composed
composed of
of interlayered
interlayered red
red and
and white
white chert
chert and
and
opaque iron
iron oxide
that plunge
oxide layers;
layers; it
it is
is deformed into
into drag
drag folds
folds that
plunge
0
500_600
50
-60 0 N.E. Beyond a covered interval
interval of
of 0.1
0.1 miles
miles to
to the
the east,
east,the
the
�-158iron-formation
thin to thick,
thick, black,
black, red and
and white chert
chert
iron—formation consists
consists of
of thin
beds interlayered with black
black argillaceous
argillaceous beds
beds that
that contain
contain abundant
abundant
veins,
veins, stringers, and
and beds
beds of
of euhedral
euhedral pyrite.
pyrite. The beds trend
trend about
about
N.85° and W.
N.85°
W. and dip
dip 80°N.
80 o N.
This
is representative of the
This dacite
the felsic
felsic volcanic
volcanic rocks
rocks
which apparently provided the
the detritus
detritus for
for most
most of
of the
the sedimentary
sedimentary
and tuffaceous
tuffaceous rocks
rocks of the
the district.
district.
Stop 66
Outcrop just W
W of Stuntz Bay road
road at
at crest
crest of
of Soudan
Soudan Hill,
Hill, at
at the
the N,
N. edge
edge
Soudan, 1,000 ft
ft E.
E. of Soudan
Soudan mine.
mine. Conserve this
this outcrop.
outcrop.
of village of Soudan,
Soudan Iron—formation
Iron-formation
This is
much—visited classic
This
is a much-visited
classic exposure
exposure of
of folded
folded Soudan
Soudan Iron—formation
Iron-formation
comprised of alternating beds of hematite and
and jasper.
jasper. The nearby Soudan
mine was opened
opened in
in 1884,
1884, and
and operated
operated continuously
continuously until
until 1962.
1962, when
when it
it was
was
deeded to
to the
the state
state by
by U.
U. S.
S. Steel for
for the development of
of Tower—Soudan
Tower-Soudan State
State
It was
was the
the first
first iron ore mine in Minnesota; 15.5 million tons
Park. It
tons of
of
high grade
grade ore
ore (63—66%
(63-66% Fe)
Fe) were
were shipped.
shipped.
Most of the small folds
Host
folds are the
the result
result of
of the
the second
second deformation
deformation in
in
the
area, and these (F2)
the area,
(F ) folds
folds plunge to
to the
the east
east at
at steep
steep angles.
angles. However,
2
evidence of an earlier set of folds is
is provided
provided by
by structures
structures such
such as
as
these in the
the sketches below.
below.
F1 fold axis
Fl
/"
F2
F fold axis
axis
2
F
F INTERFERENCE
INTERFERENCE PATTERNS
PATTERNS
F1 AND
AND F2
l
2
Approximate
F1
F FOLD MODIFIED BY
BY F2
F
1
DEFORMATION
2
N
N
1
H
One Foot
Foot
Approximate Scale
Scale
�-159—159—
Stqpl
Several outcrops
outcrops on peninsula in Lake Vermilion, east of
Several
of McKinley
Bay, I
Bay,
E and W
W of development
development road.
road.
Lake Vermilion Formation,
Lake
Formation, Volcaniclastic Member
White
Hhite dacitic tuff,
tuff, white dacitic
dacitic agglomerate,
agglomerate, black
black carbon—
carboniferous
(?) slate
graywacke, all
all of
of the
the volcani—
volcaniiferous (?)
slate and minor chloritic graywacke,
clastic member,
are interbedded
interbedded in
in this
this area.
area. The westernmost exposures
member, are
of the
the Soudan Iron—formation
Iron-formation also occur here.
here. Good exposures of the
the
agglomerate
are
best
reached
by
boat;
therefore,
agglomerate
boat; therefore, we shall
shall only
only see
see some
some
large glacial
glacial erratics of this rock
rock type
type which are
are virtually
virtually in
in place.
place.
The dacitic tuff
tuff is
is very
very difficult
difficult (arid
(and commonly
commonly impossible)
impossible) to
distinguish from
from dacite
dacite flows.
flows. Study of thin sections is
is usually
necessary to
to resolve
resolve the
the question.
question. It
comfort to know that
It is
is some
some thmfort
(1903) and numerous other workers had
had similar
similar difficulties.
difficulties.
Clements (1903)
three main components
components —- dacitic
The tuff is composed of three
dacitic volcanic rock
fragments,
and volcanic
volcanic quartz.
quartz. Recrystallization
Recrystallization causes
causes
fragments, plagioclase, and
the volcanic
volcanic rock fragments
the
fragments to appear as a fine—grained
fine-grained quartz—
quartzplagioclase
plagioclase matrix.
matrix.
stop
Stop 88
Large
mi. WW of
of Tower
Tower on
on Hwy
Hwy 169,
169.
roadcuts 0.3 mi.
Lake Vermilion Fornation,
Formation, Felds
feldspathic
athic Quartzite
Quartzite Member
Member
This
is a
a limonite—stained
limonite-stained exposure of the
the conglomeratic
conglomeratic facies
facies
This is
of the
the feldspathic
feldspathic quartzite
quartzite member.
member. Bedding and clasts
clasts are
are best
observed on the
the glaciated surface at
at the
the western end
end of
of the
the south
south
roadcut.
Pyrite and pyrrhotite are
are the
the major
major sulfides
sulfides present,
present, and
and
to have replaced
replaced slaty
slaty fragments
fragments .in
,in the
the conglomerate.
conglomerate. Most
appear to
clasts
clasts are volcanic rocks,
rocks, probably mostly dacitic.
dacitic. The matrix is
is
the strong
Stop 10.
10. Note the
similar to the feldspathic quartzite of Stop
development
development of F2 lineation which
~vhich plunges easterly
easterly at
at about
about 600.
60°.
~t.-<?.p_J_
5t229
Small outcrop SS of thvy
Hwy 169,
169, in and across ditch,
ditch, 1.1 mi. WW of
of Tower.
Tower.
(optional)
Lake Vermilion
Vermilion Formation,
Lake
formation, FeljIiicQuartzite
feldspathic ~uartziteMember
Member
feldspathic quartzite
Lapilli
(?) in the basal part of
of the
the feldspathic
Lapilli tuff
tuff (?)
This
is
the
This is the only exposure of this
this rock
rock type
type in
in the
the immediate
immediate
it appears
appears to
area; it
to be transitional in
in texture
texture between
between the
the dacitic
dacitic
tuffs and dacitic agglomerates.
tuffs
ap,glomerates.
newiber.
melilber.
�-160-
Note:
Stop 10
South of the highway in the woods on West Two Rivers is tte folded
western end of the Ely Greenstone. The fold nose points W but the
fold plunges E at about 55°. This is an antiformal mass cored by
older, mafic volcanics whose fold axis plunges toward the older rocks
the wrong way. Some small folds at Stop 11 exhibit the same structure.
Roadcuts N & S of Hwy 169, 1.85 mi W of Tower.
Lake Vermilion Formation, Feldspathic Quartzite Member
Feldspathic quartzite is an unfortunate choice of field terms,
as the rock is largely composed of plagioclase and volcanic rock
fragments with only minor large quartz grains (see below). Faint
bedding and lamination are visible on some parts of the outcrop, and
a sericitic phyllite band occurs on the north cut. At the east end of
the south cut, felsic volcanic fragments up to an inch in diameter are
visible. The 20 ft.-thick dike of diabasic gabbro at the tvest end
of the outcrop is the youngest rock in the area. It has a minimum
K-Ar age of 1570 m.y., and similar dikes a few miles away have ages
of 1520 and 1685 m.y. (Hanson & Malhotra, 1971). The dike exhibi~s
excellent chilled contacts and some inclusions of the quartzite.
The feldspathic quartzites contain 20-30% plagioclase; 15-30%
felsic volcanic rock fragments; 30% fine recrystallized quartz and
plagioclase which probably represents, in large part, recrystallized
volcanic rich fragments, plagioclase and quartz; 5-10% micaceous matrix;
and 5-10% quartz, including some quartz which is definitely of volcanic
origin.
�—161—
-161-
-.l1.Long
Long roadcut
roadcut SSof
of Hwy
H\vy 169,
169, 2.5
Z. 5rid.
mi. WW of Tm.]er.
Conserve these
these folds.
folds.
Tower. Conserve
Stp_11
_~t...2.E
..
jjrwacke—Slate
Vermilion_Formation
Lake Vermilion
Formation, Metagraywacke-Slate Member
(The composition
Strongly
and slate.
slate.
(The
Strongly folded biotitic metagraywacke and
this rock is
is described at
at Stop
Stop 12,
lZ, where
the rocks
of this
where the
rocks are
are evenly
evenly bedded
folding results from two
and relatively undeformed.) The
The complex folding
two deformations, as
described in
in the
the text
text accompanying
accompanying this
this
tions,
as sketched below and as described
Some geologists have speculated that
field trip
trip log.
log. Some
that the
the folding
folding is
is soft
soft
sediment deformation,
deformation, rather than
than tectonic.
tectonic. However, these
these stnictures
structures
are
are unique
unique in
in the
the area,
area, this
this exposure
exposure is
is located
located near
near aa major
major anticlinal
anticlinal
axis,
well—preserved sedimentary structures
axis, and well-preserved
structures nearby
nearby are
are not
not chaotic.
chaotic.
the excellent
excellent grading.
grading.
Note the
Approximate
N
i
One Foot
F1
F fold
fold axis
l
Approximate
Scale
·····e
5Q0
50°
axial plunge
OVERTURNEJ)
F2 FOLD
FOLD
OV
ERTU R.:\IED F2
F1 FOLD
F2 CLEAVAGE
FOLD ANT)
A..~D FZ
P2 cleavage
fold axis
1
/
-7
F
F
FOLD
1ODIFIED BY
fOLD MODIFIED
HY FF
Z
2
1
DkFORMATION.
DEFORMATION.
F2 Cleavage
FZ
~
o•
F
2
cleavage
--"EYE STRUCTURE"
t1EYE
STRUCTURE" DUE
DUE TO
TO EROSION
EROSION
OF
FOLDS WHICH
OF FFI FOLDS
I-.THICH WERE
I-.TERE DEFOR1€1)
DEFORMED
BY
FOLDS.
BY FF FOLDS.
Z
�-162—162—
'I
•.
-.
C
Stop 12;Lposure
ExposureNJNWof
of bridge
bridge across
across Pike
Pike
169.
.r:S'Y
(Junction of
of Co.
Co. 77
Hwy
169.
(Junction
77
and
...
this outcrop.
Please conserve
conserve this
River
on Co.
Co. 77,
77, 0.55
0.55 mi
mi NN of
of
River an
Hwy
169
is
2.4
miles
W
of
Tower).
Hwy 169 is 2.4 miles W of Tower).
.;:
Lake
Lake Vermilion Formation,
Formation, Metagraywacke—s]ate
Metagraywacke-Slate Member
Member
This
This is
is an
an exposure
exposure of
of biotitjc
biotitic metagraywacke
metagraywacke and
and slate,
slate having
having
excellent
grading.
excellent grading. Two-thirds
the 200
200 graywacke beds
beds on
Two—thirds of the
on ~his
this
exposure are
are graded and nine percent of the
exposure
the 100
beds are
are
100 siltstone
siltstone beds
graded.
Beds here
here are
are thin,
graded. Beds
thin, but graywacke beds
beds are
are as
as much
much as
as 12
12 feet
feet
thick.
North—trending kink
North-trending
kink bands
bands were formed
formed by
by the
the latest
latest (F
(F )) deformation.
Small
Small scale
scale faults
faults are
are common. A
NNE-trending
fault
with
1000 feet
feet
A NNE—trending fault with aiout
aout 1000
of
of left—lateral
left-lateral displacement
displacement forms
the S side
forms the
side of the river channel at
this locality,
locality, and extends for
this
for several
several miles
miles to
to the
the north
north and
and south.
south.
The biotitic
biotitic graywackes
graywackes contain
contain 10-20%
l0—20 plagioclase;
The
plagioclase; 15-25%
15—25% felsic
felsic
volcanic rock
fragments;
30—50%
fine
recrystallized
rock fragments; 30-50% fine recrystaliized quartz and
and plagio—
plagioclase
which probably represents,
clase which
represents, in large
large part,
part, recrystallized volcanic
volcanic
rock
fragments,
plagioclase,
and
rock fragments,
and quartz;
quartz; 2-5%
2—5% quartz,
quartz, and
and 10-15%
lO—15
biotitic matrix.
matrix.
Stop 13 Exposures
N of Hwy 169 on Co.
Co. 77,
77, at Gruben's Resort
Resort on
Exposures about 10 mi N
(Optional)
(Optional) Arrowhead Point.
Point. Best exposures are
are just
just EE of
of wooden
wooden bridge
bridge to
to Isle
Isle
of Pines.
Pines.
Lake Vermilion
Vermilion Formation,
Formation, Hetagr~acke-Slate
Metagrywacke—Slate Member
Lake
i'lember
Exposures
Exposures of chloritic graywackes
of this
locality, pillowed greenstones
of
this locality,
slate. This
is near the axis
This locality is
is
an
ENE—trending
(F2)
is an ENE-trending (F 2) anticline,
anticline, the
the
the
west
although
the
beds
at the fold
the west
the beds at
fold
and slates. Both east and west
are
are interbedded
interbedded with the
the graywacke—
graywackethe Arrowhead Point
Point fold.
fold. This
of the
axis
axis of
of which
,,,hich plunges
plunges steeply
steeply to
to
nose are
younger
to
the
are younger to the east.
east.
The
40-50% plagioclase (albite—oligoclase),
(albite-oligoclase),
The chloritic gra~vackes
graywackes contain 40—50%
20—25% felsic
volcanic rock fragments,
20-25%
felsic volcanic
fragments, 10—20%
10-20% chioritic
chloritic matrix,
matrix, 2—6X
2-6% quartz,
quartz,
some of
of which
which is
some
is definitely of volcanic origin.
origin.
Roadcuts bet\veen
between lanes of Hwy 169 on "Confusion
Stop 14 Roadcuts
"Confusion Hill"
Hill" (the
(the Continental
Continental
(Optional) Divide)
N of Virginia and about 23
23 miles WW of
of Tower.
Tower.
(Optional)
Divide) about
about 3 mi N
Giants
Giants Range Granite
the
south edge of the
This
the complexity
complexity of
of the
the south
This exposure illustrates the
Giants Range
A gray
gneiss contaLning
containinh ailiphiholite
amphibolite
gray granite
granite gneiss
Rangebatholith.
batholith. A
inclusions
cut by
by diorite,
diorite,and
andminor
minor pink
pink granites
granites cut
cut the
theabove
above rocks.
rocks.
inclusions is
is cut
At
top of
of the
the exposure
exposure between
het\\'een the
tHO lanes of
of the
thehichway
higlmay are
At the
the top
the ttro
remnants of
mafic
remnants
of LOvIer
LowerPrecanlHian
Precanl,rianthinly
thinly bedded
bedded sediments
sediments (tuffaceous?),
(tuffaceous?), mafic
lapilli tuffs
(?y, and massive
massive amphibolites.
lapilli
tuffs (fl,
��
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Title
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Institute on Lake Superior Geology
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Title
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Institute on Lake Superior Geology: Proceedings, 1971
Description
An account of the resource
Institute on Lake Superior Geology. University of Minnesota, Duluth, Minnesota. May 5-8, 1971.
Creator
An entity primarily responsible for making the resource
Institute on Lake Superior Geology
Date
A point or period of time associated with an event in the lifecycle of the resource
1971
Contributor
An entity responsible for making contributions to the resource
R.N. Annells
P.O. Banks
W.R. Van Schmus
Bill Bonnichsen
Donald M. Davidson Jr
Erich Dimroth
Jean-Jacques Chauvel
William H. Duhling Jr
J.C. Green
H.C. Halls
G.F. West
R. Roy
Harold A. Hubbard
H. King Huber
Eric Frodesen
Wayne T. Jolly
Richard L. Kellogg
William J. Hinze
George deVries Klein
Gene L. LaBerge
M.S. Lougheed
J.J. Mancuso
Roger C. Malan
David A. Sterling
Allen F. Mattis
Joseph T. Mengel Jr
Ronald A. Hendrickson
G.B. Morey
J.S. Mothersill
M.G. Mudrey
P.W. Weiblan
Wallace Darwin Myers
Norbert W. O'Hara
L.A. Prince
G.N. Hanson
W.A. Robertson
W.F. Fahrig
A.P. Ruotsala
R.J. Shegelski
G. Spencer
F.C. Tan
E.C. Perry Jr
P.K. Sims
S. Viswanathan
T.A. Vogel
T.J. Rohrbacher
W.S. White
Robert F. Johnson
E.R Brooks
J.T. Wilband
Format
The file format, physical medium, or dimensions of the resource
PDF
Language
A language of the resource
English
-
https://digitalcollections.lakeheadu.ca/files/original/bd5c5a0c6722f2c323493f2323ab4367.pdf
af6474daa8932e237f88edd277e33cc0
PDF Text
Text
-ç
—
—
I:
.t.
F
Geology Superior Lake
On
nstitute I
S
a
>f•
i\tA
I
v
r
�TECHNICAL SESSIONS
ABSTRACTS
and
FIELD GUIDES
16th ANNUAL
INSTITUTE ON LAKE SUPERIOR GEOLOGV
heLd cit
LAKEHEAD UNI VERSITV
Thanaeir. Bay, Ont
May 6 - 9, 1910
Edited
by
JL. Talbot
J.M. Franklin
C. Kuatra
�TABLE OF CONTENTS
INSTITUTE DIRECTORS AND LOCAL COMMITTEE
1.
PROGRAM
2.
ABSTRACTS OF TECHNICAL SESSIONS
7.
FIELD TRIPS
A- Proterozoic formations in the
Thunder Bay Area.
49.
8- Sturgeon River Metavolcanic Metasedimentary Formations in
the Beardznore-Geraldton area.
69.
C- The Port Coldwell alkalic complex
8S.
�—1—
16-tk AnvwsZ
INSTITUTE ON LAKE SUPERIOR GEOLOGy
Lake head UrL.Lvex4Lty
Thandv. Bay, OntaLo
May 7-8, 1970
INSTITUTE BOARD OF DIRECTORS
* 3.
*
R.
A.
N.
A.
G.
M.
W. Avery (Treasurer),
Jones F, Laughlin Steel Corp.,
Negaunee, Michigan.
C. Reed (Secretary), Michigan Geological Survey,
Lansing, Michigan.
K. Snelgrove, Michigan Techological University,
Houghton, Michigan.
J. Hinze, Michigan State University, East Lansing,
Michigan.
B. Dickas, Wisconsin State University, Superior,
Wisconsin.
L. LaBerge, Wisconsin State University, Oshkosh,
Wisconsin.
W. Bartley, Thunder Bay, Ontario.
* Permanent members.
LOCAL COMMITTEE
Chairmen:
M. N. Bartley
E. Mercy
Progrcxnne Committee:
GeneraF Members:
3. Talbot
F. Harris
A. Boerner
3. Mothersill
V. B. Cook
A. Temple
FIELD TRIP COMMITTEE
C. Kustra
3. Franklin
H. Loubat
E. Brinley
�-2-
"P R 0 G R A M"
Tate day, Ma9 5th, 1970
6.00 p.m.
Field Trip '8' (Ceraldton-Beardjnor) leaves the
Prince Arthur Hotel, Thunder Bay, Ontario.
Wed4e2day,
7.00
p.m.
Field Trip
May 6th, 1970
'B' returns to Prince Arthur Hotel
7.00 p.m.
to
Institute Registration —
Prince
Arthur Hotel
10.00 p.m.
7.00 p.m.
American Institute of Professional Geologists,
Dinner3 Prince Arthur Hotel
Thwt4ç4y, M04 7th, 197Q
7.30 a.m.
to
9.00 a.m.
Registration, Main Cafeteria, LAKEHEAD UNIVERSITY
�-.3-
$ E S
SI
°.JL
Thwchday, May 7th, 1970
Page
8.15
R. Oja
Keweenanwan Copper Deposits in the
Archean of Northwes tern Ontario
31
8.30
D. C. Mulder
Ore Controls and Open Pit Geological
Procedures in Steep Rock Iron Mines
30
Limi ted
9.00
W. •F. Read
Is the Limestone Mountain Structure
an Astrobleme?
36
9.20
S. Viswanathan
A classification of granitic rocks
with reference to Giants Range
Batholith, Northern Minnesota
40
9.35
G. N. Hanson
R. Malhotra
K-Ar Ages of Mafic Dikes in Northeastern Minnesota
19
9.50
C. W. Keighi.n
Age and Petrology of the Fort
Ridgely Granite, Southwestern
Minnesota
26
10.10
W. Bonnichsen
The southern part of the Duluth Complex 10
and associated Keweenawan rocks,
Minnesota
10.40
J. D Mancuso
Structure of the Duluth Gabbro Complex 27
in the Babbitt area, Minnesota
J. D. Dolence
11.10
J. C. Green
Ultrainafic bodies in the Vermilion
District near Ely, Minnesota
11.40
J. M. Berkson
C. S. Clay
Side-Scan Sonar Survey of the Lake
Superior floor near Freda, Michigan
12.00 NOON
-
LUNCH
-
Student Cafeteria
17
9
No.
�-4-
SESSTOM
2
jNo.
'AjteA.vzoovz'
1.00
Business
1.30
M. Y.
Meeting
Deformation of the Seine conglomerate
I-lsu
in
2.00
11. M. Mooney
et al
Refraction Seismic Investigations of
Northern Midcontinent Gravity High
2.30
IL N. Annells
Keweenawan Volcanic Geology of
Michipicoten Island, Lake Superior
3.00
3. Wood
Evidence for a Tropical Climate and
Oxygenic Atmosphere in Upper Huronian
Rocks of the Rawhide Lake - Flack
Lake area, Ontario.
3.30
G. M. Young
Widespread occurrence of
Minerals
4.00
C. Powell
20
the Rainy River area, Ontario.
P. M. Clifford
28
7
45
A luminous
in Aphebian Quartzites
Structurat
and+rnetwnorphic history
35
of the Marquette Sync linoriurn
4.30
W. Jenks
Root severance and tectonic transport
of orebodies in Metavolcanic Host
Rocks
25
'EvekvLvlg'
6.00
p.m.
CoaktaLto
7.75 p.m. Baitque.t
-
CAFETERiA
-
RESZVENCE Vlt'1ING ROOM
AVVRESS:
speaking
-
Lakahac4 WvLv&ui.ig
Lcththead
th'tkvexaUg
J. C.
Rudolph, of
GENERAL EXPLORATION CO. OF CANADA LTD.
on 'A philosophy of exploration'.
�-5.-
FtLday,
MayUh, 1970
SYMPOSIUM ON GREENSTONE BELTS
LB.
Wilson- General Chairman
'Mokn,üig'
9.00
U. B. Wilson
Introduction
9.15
L. D. Ayres
Synthesis of early Precambrian
Stratigraphy north of Lake
Superiqr
9,45
Z. Peterinan
Early Precambrian Geology of the
Rainy Lake District
34
S. Goldich
10.15
P. Clifford
Mt. St. Joseph
14
10.45
W. C. Brisbin
The structure of the Northern Lake of
the Woods Greens tone Belt, a Deformational Mosaic
12
11.15
R. H. RidIer
Archaean Volcanic Stratigraphy of the
Kirkland-Larder Lakes area of Northeastern Ontario.
37
11.45
DISCUSSION
12 NOON
LUNCH
-
Student Cafeteria
An Archaean Volcano
S
�-6F'viday, May Slit,
1970
Page No.
1.30
G. N. Hanson
S. Goldich
Early Precambrian Geology of the
Saganaga-Northern Light Lakes
area,
Minnesota-
18
Ontario.
A Model for Tectonic Variation of
'Granitic Terrain' in Southeastern
Manitoba
16
Geology of a Greenstone Belt in
Minnesota: Rainy Lake to Lake of
the Woods
32
D. H. Watkinson
Geology of the Alkalic rock - Carbonatite
complex at Prairie Lake, Ontario.
44
3.30
P. NI. Clifford
Behaviour of an Archaean Granite
Diapir
13
4.00
R. W. Hutchinson
Mineral Potential in Greenstone
Belts of Northwestern Ontario
22
4.30
H. B. Wilson
CONCLUDING REMARKS
4.45
End
4.45
DINNER
(Field Trip participants are advised to have
dinner before leaving Thunder Bay)
6.00
Departure for Field Trip "8".
2.00
1. F. Ermanovics
2.30
R.
3.00
IV. Ojakangas
Teahnicc2 Sws.Lon4
Field Trip "C".
Field Trip "V".
(Geraldton-Beardinore)
(Port Coldwell)
(Atikokan)
Buses will depart from the University but
will call at Hotels as necessary.
*
* * * * * * * * * * *
Sa-ttvtday, May 9th, 1970
8.00
a.m.
Departure for Field Trip "Y'.
(Gunf lint-Sibley)
Buses will depart from the Prince Arthur Hotel
7.30 p.m. (approx.)
RETURN OF ALL FIELD TRIP BUSES.
�-7-
KEWEENAWAN VOLCANIC GEOLOGY OF MICIIIPICOTEN ISLAND,
LAKE SUPERIOR
it.
N. ANNELLS
Postdoctorate
Geological
Survey of
Fellow
Canada, Ottawa
ABSTRACT
Recent re—mapping and petrographic examination by the author
of the Keweenawan lava flows building Michipicoten Island shows that
they form a highly differentiated 11,500—foot sequence of types ranging
from coarse ophitic olivine—bearing basalts through olivine—free basalts
and andesitic types to glassy porphyritic andesites and rhyolites.
Some
volcaniclastic horizons are intercalated in this south—dipping lava
series and a few intercalations of conglomerate and sandstone outcrop at
the west end of the island.
The different- lava types are well intermixed and there is no
obvious vertical gradation or cyclic distribution of lava types in the
Michipicoten island succession.
The lavas tend to occur in grouj,s of
petrographically similar flows which can be traced as distinct strati—
graphic units; an andesite group near the top of the succession can be
followed across the entire island, a distance of 16 miles along strike.
Near the median part of the succession the lavas show some lateral variation which
may be the result of simultaneous extrusion of different
flow types at the same general level from different vents.
An agglomerate bearing large angular and rounded blocks of
island lava types outcrops on the northwest shore of the island, and
indicates proximity to an eruptive vent.
The lower half of the exposed
lava sequence is intruded at numerous different horizons by sheet—like
or lentJ.cular bodies of pink acid quartz porphyry crowded with large
phenocrysts of feldspar and quartz. These bodies are sometimes discordant
the lava flows and field evidence suggests that they are intrusions
Basic intrusions are extremely rare on Michipicoten Island, only about
six very thin basic inclined sheets being found on the entire shoreline.
to
The varied basalt—andesite—rhycalite sequence and associated
volcaniclastic rocks of Michipicoten Island are believed to have been
erupted from a central volcano fed by a high level magma source. The
presence of large volumes of acid material in the island sequence is a
phenomenon' very similar to that seen in the Icelandic central volcanoes,
which consist of highly diffentiated lavafvolcaniclastic edifices inter—
finggred with widespread flood basalts and often intruded by acid material.
�-8-
SYNTHESIS OF EARLY PRECAMBRIAN STRATIGRAPHY
NORTH OF LAKE SUPERIOR
LORNE D. AYRES
Ontario
Department of Mines
Toronto
A section from Lake Superior Park to Geraldton, Ontario crosses three
major, east-trending, Early Precambrian, lithologic and structural elements
of the Superior Province of the Canadian Shield.
From south to north these
are the northern part of the Abitibi island arc, the Quetico sedimentary
basin, and the southern part of the Keewatin island arc.
Both the Abitibi and Keewatin arcs are formed from coalescing, subaqueous,
basaltic shield volcanoes capped by subaerial to subaqueous, felsic to
intermediate pyroclastic cones. Volcaniclastic greywacke sequences derived
from felsic volcanism accumulated in intervolcano basins and partly overlap
the felsic pyroclastic deposits. Small trondhjemite cratons within the
island arcs were a local sOurce of sedimentary detritus. Although the
island arcs have easterly trends, individual basins and volcanoes have
diverse trends.
Along the north edge of the Abitibi arc from Schreiber to Wawa, three
isolated sedimentary formations were deposited in intervolcano basins, but
they are all tongues of an extremely thick greywacke and siltstone formation
deposited in the Quetico basin north of the arc. The formations become
progressively younger from west to east.
The sedimentary rocks of the Quetico basin, which are equivalent to the
Couchiching Formation of western Ontario, overlie and intertongue with. the
volcanic formations of the Abitibi arc and the source area was probably within
the arc.
Along the north edge of the basin, however, the sedimentary rocks
underlie and intertongue with the volcanic formations of the Keewatin arc.!
In this area, Keewatin volcanism is thus younger than Abitibi volcanism.
�-9-
SIDE-SCAN SONAR SURVEY OF THE
LAKE SUPERIOR FLOOR NEAR FREDA, MICRIGAN
J.
N. BERKSON & C. S. CLAY
University of Wisconsin
Geophysical and Polar Research Center
ABS TRACT
Approximately 300 miles of side-scan sonar profiles were made
in Lake Superior near Freda, Michigan. The instrument scans to
the side approximately 1/4 mile and gives the location of features
on the lake floor which scatter sound. The shape of the scattering features can often be correlated with geological features.
The ship's tracks were close enough together so that nearly continuous sonar coverage was obtained.
Underwater photographs and
divers were used to identify some of the scattering features.
Three distinct bottom types were observed in the survey area:
rocky, sandy, and bedrock. The bedrock appears to correlate
with the Freda sandstone, which outcrops on the land. This study
was supported in part by The National Center for Atmospheric Research
and The Office of Naval Research.
�-10THE SOUTHERN PART OF THE DULUTH COMPLEX AND
ASSOCIATED KEWEENAWAN ROCKS, MINNESOTA
BILL BONNICHSEN
Cornell University,
Ithaca, N.Y. 14850
A B ST EtA CT
The southern part of the Duluth Complex was reported to consist mainly of troctolitic rocks and older anorthositic rocks at the
15th Annual Institute on Lake Superior Geology and elsewhere (Bonni—
chsen, 1969). Geologic mapping in several 7½—minute quadrangles in
the Babbitt—Hoyt Lakes area (Bonnichsen, 1970) shows that troctolitic
rocks lie north and west of the principal occurrences of anorthositic
rocks, thus forming the footwall side of the complex in the same manner
as at Duluth (Taylor, 1964).
Between Duluth and the Babbitt—Hoyt Lakes
area, troctolitic rocks predominate across the width of the complex;
exposures of anorthositic rocks are restricted to isolated occurrences
and inclusions within the troctolitic rocks, rather than large areas
with contiguous outcrops.
In 1969, the writer suggested that troctolitic magmas had
intruded along a contemporaneously widening fracture zone between the
previously—formed anorthositic rocks to the east and the Early and
Middle Precambrian basement to the west. Field work during the summer
of 1969 and examination of drill core in recent months tends to substantiate this view. Recently obtained knowledge on the variety and
diversity of rock types within the southernpart of the complex indicates the development of the troctolitic rocks was a complex event
involving multiple injections of magma, the incorporation of a great
amount of previously—formed Keweenawan igneous rocks as inclusions and
the development of relatively small quantities of Fe— and Ti—rich magma,
some of which was ultramafic, from nagmas which initially were troc—
tolitic.
Much of the 1969 field season was devoted to looking for
and examining outcrops along, and east of, the eastern or hanging
wall margin of the complex. This margin, for the first 30 miles north
of Duluth, is mainly a contact between troctolitic and locally anor—
thositic rocks to the west and gabbroic and dioritic intrusives to
the east.
Exposures of mafic volcanics are uncommon east of the
southern part of the complex, except within one or two miles of Lake
Superior.
�In the Mt. Weber—Greenwood Lake area, about 40 miles N.N.E.
of Duluth, a number of granophyre exposures occur but the area underlain by granophyre is much less than shown on the 1932 Minnesota state
geologic map. Gabbros, ferrogabbros, and magnetite troctolites are
exposed north of the granophyre area; these rocks are responsible for
the intense magnetic anomalies in that area. Exposures of rhyolite,
other felsites and magnetic basalts occur south of the granophyre area.
In the central part of this volcanic area is a one—fourth mile long
outcrop area of strongly—laminated, locally cross—beddé4,::weakly meta—
morçhosed, feldspathic rock that is interpreted to be equivalent to
the Virginip Formation; this occurrence is about 25 miles east of the
footwall of the complex where other Virginia Formation is exposed.
Bodies of hornfels are common throughout the southern part
of the complex; many of these, especially in the Babbitt—Hoyt Lakes
area,
are inclusions of the Virginia Formation which forms the foot—
wall of the complex in that area.
The majority of hornfels bodies
in the southern part of the complex, however, are considered to be
metamorphosed basalt, probably of Keweenawan age. This type of horn—
fels occurs throughout the complex, including along the western marIt is suggested that along parts of the western margin of the
gin.
complex between Duluth and Hoyt Lakes, the footwall consists of vol—
canics which overlie the Virginia Formation and the equivalent Thompson
Slate, much like the situation af Duluth.
A feature of interest in the southern part of the complex
are a number of bodies of titaniferous peridotite and similar ultra—
These dike— or sill—like bodies are known from drilling
inafic rocks.
These rocks are
to locally have thicknesses of hundreds of feet.
characterized by lithologic heterogeneity, medium to coarse grain
sizes, local rhythmic layering and abundant titanaugite, olivine, and
ilmenite; locally, magnetite, graphite, plagioclase, and pyrrhotite
are abundant. These rocks may have crystallized from liquids approximating their present composition because they are the latest intru-
sive rocks known inthat area and because fine—grained dikes with
identical mineralogical compositions cut adjacent rock bodies in the
vicinity of the large peridotite bodies.
Re ferenc es:
Bonnichsen, Bill, 1969, Geology of the southern part of the Duluth Complex, Minnesota; Proc. of 30th Annual Mining Symposium, Univ.
of Minn.; p. 89—93.
Bonnichsen, Bill, 1970, Geologic maps of the Duluth Complex in the
i3abhitt—Hoyt Lakes area, Minnesota; geologic maps and accompanying explanation for the Allen, Babbitt, Babbitt NE, Babbitt
SE and Babbitt SW 7½—minute quadrangles, 1/24,000; on open
file with the Minnesota Geological Survey, University of Minn.,
Minneapolis, Minn.
Taylor, R. B., 1964, Geology of the Duluth Gabbro Complex near Duluth,
Minnesota; Minn. Geol. Survey Bull. 44, 63 p.
�-12THE STRUCTURE OF THE NORTHERN LAKE OF THE WOODS GREENSTONE BELT,
A DEFORNATIONAL W)SAIC.
W.
C. BRISBIN
University of Manitoba
ABSTRACT
The structure of the northern portion of the Lake of the Woods
greenstone belt may be described as a complex mosaic, consisting of
the effects of several deformation events, each of which has been
developed spatially to differing degrees.
Individual domains, within
the mosaic, may show strain effects of one, or more, of three widespread
and dominant tectonic events, the chronology and tectonic styles of
which are remarkably persistent.
The earliest deformational period is manifest by folds in layering
which are seldom unaffected by later events. Where structural overprinting is poorly developed the evidence suggests that these folds
were developed by a flexural mechanism, under conditions of low mean
ductility, where layer contacts were active. These folds are interpreted
as having developed post lithification and prior to any major metamorphic
event.
Large areas of the greenstone belt show evidence of a second
deformational event which has led to the development of a penetrative
and tectonically active foliation. Differential movements, either
leading to, or on, the foliation have resulted in passive folds which,
in many areas, have been superimposed on earlier sets. Evidence on,
all scales, from deformed clasts to deformed early plutons, indicates
that strain during this event was accomplished by a combination of
simple shear and differential pure shear.
The directions of extensive
strain and simple shear movements during this event had strong vertical
components; the strain effects of this event are linked to the reorganization of upper crustal masses which accompanied the emplacement
of the numerous granitic diapirs which have intruded the greenstone.
The third period of deformation is portrayed best in many of the
The earlier
areas where the second period penetrative foliation occurs.
foliation served as an active surface for the development of flexural
folds on all scales; from microscopic crenulations, to mesoscopic kink
bands, to major folds with structural relief of several thousand feet.
Movement directions during this event were variable within, and between,
suggesting a wide variety of late stress conditions both
temporally and spatially.
domains,
�-13-
BEHAVIOUR OF AN ARCHAEAN GRANITE DIAFIR
PAUL M. LIFF0RD
Department of Geology
McMaster University
A B S T R A C t
Much evidence now is available linking part, possibly all,
of the deform.ation in Archaean greenstone belts with the emplacement of
diapiric granites.
This is now well documented for the Keewatin—type
belts of the Canadian Shield, and their analogues in Southern Africa,
Western Australia and elsewhere. These granites are large ovoid, lobate
masses in plareview, commonly heterogeneous internally.
Between clusters
of such granites lie linear and stellate arrays of volcanic—sedimentary
rocks — greenstones. set in a granite seas
+
The Bainaji Granite about 300 kins. N.N.E. of Thunder Bay is one
such granite mass.
It and the Carling Granite lie N.W. and N.E. respectively of the Lake St. Joseph volcanic—sedimentary basin. Pillows
in the lavas within 500 metres of the Baxnaji Granite margin have suffered
considerable flattening in a plareparallel to the margin. The amount
of flattening increases towards the granite, reaching values of about
80%, with an average of 60% in this distance.
In the same zone, "granitic"
dykes which emanate from the granite into the lavas are buckled.
The
axial surfaces of the buckles are statistically parallel to the granite
margin. The shortening implied by the dykes is 40% or less.
Both these
flattening features suggest that emplacement of the granite led to
effective compression of the lower levels of the supracrustal pile on
axes everywhere normal to the granite margin, and that there was probably
stretching on subvertical axes in order to accommodate the distortion.
The discrepancy between compressions in pillows and dykes suggests that
the dykes were intruded some time after compression commenced.
At certain localities right at the granite margin, tlchocolate•
tablet" boundinage occurs in already flattened lavas. This implies late
extenson in all directions within the plane parallel to the granite
margin. This in turn implies an axially symmetric stress field, whose
unique symmetry axis lay normal to the granite margin. The best explanation for this late stage extensional strain is that the granite was
then being inflated by the introduction pf low—viscosity granitic material
(? magma).
�-14-
MT. ST. JOSEPH - AN ARC}IAEAN VOLCANO
PAUL M. CLIFFORD
Department of Geology
McMaster University
ABSTRACT
An Archaean composite strata—volcano is preserved about 300
kms. N.N.E. of Thunder Bay. Despite severe deformation and modest
metaorphism, a fairly clear picture af the histary of this volcano,
Mt. St. Joseph, can be gained.
The lower portion of the valcana pile is now some 2700 metres
thick, but allowance for tectonic flattening raises this to 3700 metres
at least, and the true thickness was probably much more, if large xeno—
liths within flanking granites can be assigned to this sequence. This
effusive sequence, dominantly mafic, consists af unstructured flaws
intercalated with piflowed lavas, autobreccias and pillow breccias.
About two—thirds up the sequence, there is an erosional unconformity
developed on a diarite intrusive into the lavas. A conglomerate lies
on the unconformity, and this is succeeded by the upper levels of the
effusive sequence.
Abave the effusive sequence lie about 3250 metres of volcanic
fragmental rocks af mainly silicic composition — the çplosive seqnce.
The lower units af the sequence consist of large accidental blocks in a
finer grained matrix. The higher units are generally finer—grained.
The effusive racks are commonly vesiculated. The degree ot
vesiculation in pillows generally increases with height in the pile.
This implies progressive shallowing af the water into which the lavas
were emitted. The upward decrease. in size of adcidental fragments in
the explosive sequence suggests an increase in the intensity of explosive force as the volcano matured.
Chemically, lavas range from 45% to 75% 5i02. The change from
effusive to explasive activity occurred at abaut 58% 5i02. The estimated
explosive index af the volcano is less than ten. The silicic materials
now preserved form a relatively minor portion of the total volume of
volcanic rocks.
In an Osborne—type plot, the lavas 'evolve' on a line
intermediate between the lines for Skaergaard and the Cascades.
The volcanic history, taken in conjunction with the tectonic
development of the area, implies very restricted areas of deposition,
�—Is—
capable of accepting considerable thicknesses of volcanic rock and
derived sediments. This, in turn, implies considerable crustal mobility at the time. Note that no deformed belts occur without a volcanic
pile. The local mobility and the vulcanicity are inextricably linked
for this area, as they seem to be for analgous areas elsewhere.
�-16-
A MODEL FOR TECTONIC VARIATION OF 'GRM4ITIC TERRAIN'
IN SOUTHEASTERN MANITOBA
I. F. ERMANOVICS
Geological Survey of Canada, Ottawa
A B ST RA CT
The Precambrian rocks of the Superior (Structural) Province
of southeastern Manitoba, between latitudes 51 and 54 degrees fall into
three groups:
metavolcanic—sedimentary rocks (domain I); an adjacent,
hybrid mobile zone (domain II) and a siliceous (sialic) nucleus (domain III).
Domain III, situated between 510 15' and
30' N, comprises
augen-gneiss and weakly layered to stratiform layered gnefss (SO per cent
of the domain) whose compositions range from quartz monzonite to gran—
odiorite; mafic hornblende gneiss and amphibolite are abdundant locally.
Siliceous mafic—noor quartz monzonite to granodiorite intrude these
gneisses and the magnetite content of the massive rocks is correlatable
to regional magnetic 'highs'. Metavolcanic—sedimentary rocks (3 per cent
of domain III) and mafic granodioritic gneiss occupy relict keels of
folds; 'down—plunge' views of such structures show that these remnants
are underlain by siliceous gneiss and massive rocks peculiar to rocks
of domain III.
Rocks of domain II, flanking belts of uietavolcanic—sedimentary
rocks, consist of high—grade aluminoüs and inafic gneiss intruded by
diapiric mafic granodiorite to quartz gabbro; large bodies of quartz
monzonite are absent from this domain. The coarse—grained igneous rocks
may be the intrusive equivalents (cogenetic magtnas) of the lavas of
domain I and both domains constitute the total volcanic—sedimentary
tectogene.
A seismic !break!, located along the lithologic boundary between
domains II and III, indicates displacement of the Conrad discontinuity
downward beneath domains I and II with respect to domain III. Thus if
the seismic break is a fault (albeit annealed by later intrusions) and
if the volcanic—sedimentary tectogene is underlain by rocks of domain III,
then the sialic nucleus (domain iii) is exposed by virtue of erosion.
It is concluded that the volcanic—sedimentary rocks were
deposited upon a sialic (relatively siliceous) basement which is now
represented by !granitic gneiss'.
�-17-
ULTRA}IAFIC BODIES IN THE VERMILION DISTRICT
NEAR ELY, MINNESOTA
JOHN C. GREEN
University
of Mitinesota, Duluth
ABSTRACT
A few dozen pods of harzburgitic peridotite have been intruded into the greenstones of the belt immediately north of Ely (Nevton
Lake Formation).
They range up to two miles in length by up to 1,000
feet in width. They have undergone varying degrees of serpentinization,
evidently after emplacement; tectonic fractures uniformly crosscut
magmatic minerals and textures (olivine and poilcilitic pyroxene) and
predate serpentinization. They carry negligible Ni, Cu, Au,, and Pt —
group values and about 5,000 ppm Cr. No significant amounts of asbestos have been seen.
Art area in the Ely Greenstone east of a1l Lake contains
unserpentinized ultramafic rocks, transitional to gabbros, that are
characterized by hornblende and biotite instead of olivine.
�-18-
EARLY PRECAMBRIAN GEOLOGY OF THE SAGkNAGA-NO1HEBN
LIGHT LAKES AREA, MINNESOTA-ONTARIO
G. N. HANSON
State University of New York at Stony Brook
Stony Brook, N. Y.
11790
5. 5. GOLDICH
Northern Illinois University
DeKalb, Illinois
60115
ABSTRACT
The principal Early Precambrian rock units in the Saganaga—Northern
Light Lakes area of Ontario and Minnesota, from oldest to youngest, include
the Keewatin volcanic and related rocks, the Northern Light Gneiss, the
Saganaga Tonalite, formerly called the Saganaga Granite, and the Knife
Lake Group. These units were intruded by numerous small plutons and dikes.
The Northern Light Gneiss, the Saganaga Tonalite, and syenodioritic
to granodioritic phases of a small pluton at Icarus Lake, from oldest
to youngest on the basis of field relationships, have been dated by the
Rb-Sr, whole-rock technique. The isochron ages range from 2700 to
2750 m.y. and are indistinguishable but suggest that
these rocks formed
within a time span o' less than 100 m.y. and probably less than 50 m.y.
all
Modal and chemical analyses show that the greater part of the Northern
Light Gneiss is trondhjemitic. in composition. As suggested originally by
Frank Grout the gneiss nay have resulted from the lit—par—lit injection
of the Keewatin greenstones during a period of folding. The gneiss,
however, may have been formed by folding and metamorphism of a Keewatin
volcanic pile composed of basaltic, trondhjeniitic, and rhyolitic volcanic
rocks, and possibly some sediments.
The Saganaga Tonalite is a late or postkinematic intrusion emplaced
in the greenstones and the Northern Light Gneiss, and inclusions of both
rock types are found in the tonalite.
The Icarus Lake pluton intrudes
both the Northern Light Gneiss and the Saganaga Tonalite.
It wnsists of
an older western phase of syenodiorite and a younger eastern phase of
granodiorite. Both rocks are alkalic, containing aegerine-augite and
hastingsite.
Rb—Sr and K-Ar mineral ages from the principal rock units range from
2500 to 2700 n.y. and are difficult to interpret. In part these ages
may be related to faulting and alteration. Movements on the major fault
zones ceased before the deposition of the Anini.ikie sediments. Metamorphism
is low-grade, greenschist facies of the Abukuma type.
�-19-
K—AR AGES OF btkFIC DIKES IN NORTHEASTERN MINNESOTA
C. N. HANSON and R. MALMOTRA
Department of Earth and Space Sciences
State University of New York
Stony Brook, New York
ABSTRACT
Sixteen mafic dikes in the Vermilion District, Minnesota and in the Saganaga—Northern Light Lakes area, Minnesota—Ontario
botder, give K—Ar whole—rock and mineral ages of 2600 m.y.., 19002000 m.y., 1500—1600 m.y., 1400 n.y., and 100—1100 n.y. One sample
of a Logan Sill near Suomi, Ontario gives a whole—rock K—Ar age of
.1380 m.y.
The dikes range in composition from hornblende andesite
with modal quartz and microcline to tholeiitic basalt. There does not
appear to be a clear—cut difference in composition as a function of
age nor. a difference in strike. Most dikes have a north—northwest
strike in the Vermilion district and a northerly strike in the Saganaga—
Nor them Light Lakes area.
Dikes with ages greater tjtan 1500 m.y. have a characteristic
alteration, possibly due to burial metamorphism, as shown by highly
sericitized plagioclase and the development of actinolite, chlorite,
The younger dikes do not show
epidote, sphene, prehnite, and calcite.
this same style of alteration nor are they as highly altered. The
dikes which give 1500—1600 m.y. whole rock K—Ar ages are extensively
altered, and these ages may indicate the time of recrystallization
rather than the time of intrusion.
�-20DEFORMATION OF THE SEINE CONGLOMERATE
IN THE RAINY RIVER AREA, ONTARIO
MAO-YANG HSU and PAUL M. CLIFFORD
Department
of Geology
McMaster University
ABSTRACT
The Seine conglomerate exposed betweexi t&ine Centre and Flanders,
>
Ontario, is of Archaean age (
2500 m.yj. The conglomerate has been
subjected to low—grade regional metamorphism, so that pebbles now lie
in a fine—grained foliated matrix of mica schist. The foliation is
intensely developed over the whole area studied, but mineral lineation
is indifferently developed.
Pebbles vary in lithology, shape, size and orientation. Most
are good approximations to oblate triaxial ellipsoids, with the XY
planes parallel to foliations and the )( axis commonly subparallel to
mineral lineation or to intersections of bedding with foliation.
Elongations of pebbles on a major fold hinge are parallel to the fold axis.
We think that buckling preceded passive slip or flow.
Principal planes of finite strain cannot be identified with
any confidence in the field. A new method has been developed which
allows the calculation of finite strain ellipsoids from average axial
ratios uieasured in any two rectiplanar surfaces in an outcrop oriented
at a fairly large angle one to another.
Plots based on these calculations for thirty—four stations show that the average pebble shape is an
oblate triaxial ellipsoid, with axial ratios which vary independently
of location when followed parallel to the foliation trace. Pebbles of
different tithology occurring on fold limbs lie along the same defor—
macion path.
This means that original pebble orientations were about
the same for all lithologies studied, and that ductilities varied from
lithology to lithology.
Pebbles of the same lithology lying on the
same shortening curve, imply that pebbles of roughly identical shape
had different original orientations. Mildly deformed granite pebbles
seem not to have suffered rotational strain.
A few examples of ripple marks and cross—bedding in metarenites
intercalated with the conglomerate imply that the palaeo transport
direction was generally towards the present day south. A plot of volcanic
pebble orientations against axial ratios of individual pebbles, measured
�-21-.
in the foliation plane (parallel or sub—parallel to bedding) has a
skewed unirnodal distribution. A comparable plot for planes normal to
foliation has a symmetrical unimodal distribution. These imply that
the original volcanic pebbles were deposited with their original iCY
planes parallel or sub—parallel to the bedding plane with their longest
axes generally easterly.
�-22-
MINERAL POTENTIAL IN CREENSTONE BELTS
OF NORTHWESTERN ONTARIO
R. W
HUTCHINSON
University of Western Ontario
ABSTRACT
The distribution of producing metal mines has, until recently,
suggested that the Archaean greenstone belts of northwestern Ontario
were favourable only for gold deposits and iron formations, in con—
trast to similar belts of northeastern Ontario — northwestern Quebec
that are obviously favourable f or base metal suiphides as well as gold
and iron formations. The metal distribution is no longer so distinctive.
Important base metal deposits were discovered at Manitouwadge
in 1953 and recently near Uchi and Sturgeon Lakes in northwestern Ontario.
Important iron production has commenced from Algoman—type iron
formations in eastern Ontario.
Detailed geologic work in the northwestern Ontario greenstone
belts shows extensive development of rhythmically—banded, shelf—fades
"Coutchiching—type" rocks, of immature, first—cycle "Tiiniskarning—type"
rocks and of thick, well differentiated "Keewatin—type" volcanic sequences1 All these have lithologic counterparts in the Abitibi region,
where the latter are long—recognized hosts for base—metal sulphides,
and where the stratigraphic succession of the three "types" appears
similar.
Age dating methods fail to reveal any significant age
differences between these rocks in northwestern Ontario and their
counterparts in eastern Ontario—Quebec. All these features suggest
that the greenstone belts of northwestern Ontario are similar in
origin and age to those farther southeast, and therefore that all have
more—or—less equivalent mineral potential for base metal sulphide, iron
formation, and gold deposits.
These three types of deposit appear
metallogenically characteristic of Archaean sequences. They may be
lithofacies—related equivalents of one another; the base metal sul—
phides forming under reducing conditions near exhalative centres, the
iron formations forming under oxidizing conditions remote from the
centres, and the gold of similar exhalative derivation but perhaps
initially "fixed" in other sedimentary lithofacies such as pyritic
or carbonate iron formations, or montmorillonitic, volcanic—derived
Timiskaming sediments.
Locally, as at Manitouwadge, the northwesterly greenstone
belts have been more highly metamorphosed than those of Ontario—Quebec,
�-23-
and this complicates exploration for base metal deposits. It Vs
essential to recognize markedly metamorphosed exhalative centres.
These centres, originally defined by accumulations of felsic flows,
pyroclastics and cherts may be represented by quartz—sericite schists
or gneisses, quartzites, quartzitic "conglomerates" or "breccias".
Their bulk composition is important, for it survives metamorphisw,
but primary textures may be much altered or obliterated. Minor—
element geochemical studies of oxide, sulphide and carbonate—facies
iron formations may be useful in guiding exploration from remote
lateral lithofacies toward exhalatLve centres.
�-25-ROOT SEVERANCE AND TECTONIC TRANSPORT OF OREBODIES
IN METAVOLCANIC HOST ROCKS
WILLIAM F. JENKS
University
of Cincinnati
ABSTRACT
Association of lenticular, concordant, semi—concordant, and
cross—cutting massive sulfide bodies with mafic and felsic volcanic
sequences is well known. Some are clearly of submarine exhalative
or replacement origin. Others may well be related to subaerial
volcanism, but near sea level in a zone of negative crustal movement, since preservation of near surface phenomena in a eugeosynclinal
environment requires relatively rapid covering and burial. Meta—
volcanic sequences originating in active and subsiding tectonic belts
have been subjected to all postvolcanic events affecting the
enclosing metasedimentary rocks; they may have undergone deformation
by overthrust faulting, nappe folding, and refolding. Separation
of the volcanic pile (and associated ores) from its roots during
such deformation would be expected.
These structures, in meta—
volcanic terranes, can go unrecognized because of originally complex
volcanic—stratigraphic relations, transposition by sliding, md
deep folding and metamorphism.
Tectonic severance appears to be the reason for the absence of
obvious plutonic source rocks in many metavolcanic sequences and
their ores.
Separation of ores from roots may be more than 50 1cm
if we take Alpine deformation as a model.
Certain types of
volcanic masses such as rhyolite domes would yield to tectonic
transport in a manner controlled by local contrasts in ductility,
shape, and size., The deformational style is quite unlike that
produced in regularly layered rocks. Orebodies, with their normal
envelopes of hydrothermal alteration, may 'be transported in an
environment especially susceptible to structural irregularity
because they are in ductile shells adjacent to irregular volcanic
masses. Resultant structural details would be expected to be
still more complicated by selective flowage of some sulfide minerals
and by migration in response to new chemical gradients.
�-26-
AGE AND PETILOGY OF THE FDffl' RIDGELY GRANITE, SOUTHWESTERN MINNESOTA
C. W. KEIGHIN
Northern Illinois University, DeKalb, Illinois
ABSTRACT
A number of small outcrops of granite were mapped by .Lund in 1949
in the Minnesota River Valley west and southwest of Fort Ridgely.
Lund
(1956) described the Fort Ridgely Granite as a pinkish—gray porphyritic
granite with aligned phenocrysts, some of which are two inches or more in
length. Lund suggested that the granite may represent a less contaminated
and more massive phase of the Morton Gneiss.
Preliminary whole-rock Rb-Sr data give an isochron age of 2650 m.y.
If this value is accepted, the Fort Ridgely granite is similar in age to
granite in the valley south of Sacred Heart and is much younger than the
Morton Gneiss, 3300—3550 m.y., as reported by Goldich in 1968.
Two rock types are present in outcrops of the Fort Ridgely Granite.
A dark—gray rock containing plagioclase, quartz, K—feldspar, hornblende,
and biotite appears to be older than a leucocratic phase composed of
K-feldspar, quartz, plagioclase, and minor biotite.
Textural features
suggest granulation and recrystallization with the development of intricately sutured contacts between quartz and feldspar. It appears possible
that the Fort Ridgely Granite may be an older rock that was metamorphosed
2650 m.y. ago. Additional isotopic analyses, field, and laboratory
studies are being made to eliminate one of the two alternatives.
�-27-
STRUCTURE OF ThE DULUTH GABBRO COMPLEX
IN ThE BABBIfl AREA, MINI'IESOTA
J.
D. Mancuso and J. D. Dolence
Humble Oil & Refining Company
ABSTRACT
The Babbitt area is located about 60 miles north of the City of
Duluth juSt northeast of where the trend of the trace of the lower
contact of the Duluth gabbro complex changes from north to northeast.
The complex in this area intrudes Archean greenstone, AlgOman granite,
and Animikie iron formation and slate-argillite. The basal contact of
the complex is irregular; the dip ranges from almost vertical to flat,
but generally dips to the southeast. Major influences on the structure
of the contact are i) stratiraphic: the gabbro selectively rode on
top of the iron formation, 2) pre-gabbro folding: an anticline is
reflected at the base of the complex, and 3) faulting: both pre and
post-gabbro faulting affect the floor of the complex. Various geologic
features at and beneath the complex are indicated by aeromanetics and
The termination of the iron formation beneath the complex is
gravity.
suggested by an inflection in the aeromagnetic data, arid a probable
contact between greenstone. and granite is indicated by gravity.
We suggest that the complex was intruded as irregular sheets
It cut weaker units such as the
and caine up from the southeast.
Virginia slate, utilized the Virginia slate--Biwabik iron formation
contact, a pre-existing zone of weakness, as a platform to ride upon,
and stoped, plucked, and assimilated pre-gabbro rock on its way up.
The bottQm of the intrusion probably did not influence the structure
of the older rocks, but instead its structure was influenced by preexisting conditions.
�-28REFRACTION SEISMIC INVESTIGATIONS OF THE
NORTHERN MIDCONTINENT GRAVITY HIGH
HAROLD M. MOONEY, CAMPBELL CRADDOCKt, PAUL R. FARNHAM2,
STEPHEN H. JOHNSON3, AND GARY VOLZ4
Department of Geology and Geophysics
University of Minnesota
Minneapolis, Minnesota
A B S T R A C T
Eighty—seven seismic refraction profiles have been obtained
to define the geologic structure in the upper crust associated with
the Midcontinent Gravity High in Minnesota and Wisconsin.
The seismic
measurements were taken across a fixed spread of seven geophones from
distances up to 13 km. A structural section was prepared for each profile by interpretation of the travel—time graph, and the individual
sections were compiled into regional cross sections.
Measured seismic velocities in bedrock fall in the 2.5 —
Observed velocities can be assigned to seven
groups corresponding to Paleozoic, upper, middle, and lower Upper Kewee—
nawan strata, Middle Keweenawaivolcanics, pre—Keweenawan felsic intru—
sives, and pre-Keweenawan mafic intrusives. These groups display good
continuity through the area and allow tentative correlation of rock
bodies between geologic provinces.
7.1 km./sec. range.
The St. Croix Horst and its flanking basins underlie the
Midcontinent Gravity High and its parallel gravity lows north of Minn-
Minimum throw along the western and eastern boundary fault
zones reaches about 3.0 and 2.0 km. Sedimentary rocks in the Eastern
eapolis.
Basin
reach a thickness of at least 2.6 km. A complex horst—like structure also underlies the Midcontinent Gravity High in southern Minnesota;
an uplifted basaltic bady is bordered by sedimentary basins about 3.0 km.
thick.
Middle Keweenawan basalts are nresent lncilly in the Eastern
and Western Basins underlying the Upper Keweenawan strata.
Rocks
probably equivalent to the Oronto Group are rare in the Western Basin,
conmion in small basins on the St. Croix Horst, and abundant in the
Eastern Basin. Rocks probably enulvalnt to the Bavfield Group are
extensive in the Western and Eastern Basins, but they have not been
found on the St. Croix Horst. The Bayfield Group seems to be several
km. thick across Douglas County north of the Douglas Fault, and it
does not appear to increase in thickness under the Bayfield Peninsula.
�-29-
1.
Department of Geology and G°oohystcs, University of Wisconsin,
Madiqon Wisconsin, 53706.
2.
Department of Geology, College of St. Thomas, St. Paul, Minnesota.
3.
Department of Oceanography, Oregon State University, Corvallis,
Oregon, 97331.
4.
Chevron Oil Comnany. Houston. Texas. 77027.
�-30ORE CONTROLS AND OPEN PIT GEOLOGICAL PROCEDURES
AT STEEP ROCK IRON MINES LIMITED
DAVID C. MULDER
Steep
Rock Iron Mines Limited,
Atikokan, Ontario
ABSTRACT
The ore controls of the Middle Arm orebodies of the Steep
Rock Iron Range have been well established as the result of an almost
continuous programme of mapping, sampling, and development drilling
from 1945 to the present time, during which period Steep Rock Iron
Mines Limited has shipped a total of thirty—five million tons of ore.
The remarkably uniform stratigraphic sequence of the Steep—
rock Group, which lies within a sedimentary—volcanic sequence of
Archean age, has proven to be the most useful ore control, particularly
with regard to projections on the smaller scale. A major fault system
strikes from 020 to 065 with steep dips mainly to the east; a minor
fault system strikes a fairly consistent 115 with steep dips to the
Both fault systems are of post—orezone age with the
north and south.
majority of the vertical and horizontal offsets ranging from 15 feet to
Cross—cutting and conformable altered basic dykes of post—
60 feet.
orezone age often occupy planes of weakness, such as faults and strati—
graphic contacts, and are erratically distributed causing considerable
dilution of high grade ore to crude ore in the mining process. Sill—
fication of the Goethite Member is quite erratic on the larger scale,
and
produces a type of crude ore which is difficult to beneficiate.
planning,
The above ore controls play a very important role in pit
Due to the complexity of
both on the short and long term.
the total geological picture, it is continually necessary to gather
new data and reinterpret previous vertical projections. A major underground development drilling programme, which commenced in 1967 and is
presently nearing completion, is establishing the position of the
major geological contacts at the proposed ultimate pit elevation for
pit planning purposes. Highly successful new techniques in drilling
and identifying rubbly goethitic formations were developed during the
early stages of this progranune. The drilling results provide an
invaluable control when projecting the geology on the vertical plane
below the present pit bottom.
Experience has provided invaluable
guidelines in the form of approximate limits of projection with relation
Besides estimating reserves over the
to allowable limits of error.
long term, the Geology Department plays a vital role in controlling the
recovery of ore during the daily mining operations.
�-31-.
KEWEENANWAN COPPER DEPOSITS IN TIlE ARCHEAN OF
NORTHWESTERN ONTARIO
by R. OJA
Thunder Bay, Ontario
AB ST RA CT
A number of copper showings related to breccia zones in highly
metamorphosed sedimentary rocks and in granitic gneisses have been
discovered north of Lake Superior but south of the volcanic—sedimentary
Leitth—Geraldton—Little Long Lac gold belt in Northwestern Ontario.
Geological mapping and diamond drilling has been carried out at some
of the more promising prospects. The mineralization, which occurs in
breccia zones up to 150 feet wide, consists primarily of pyrite and
chalcopyrite with small quantities of bornite. The breccia zones are
seen to accompany both large and small fault zones. The largest fault
zones are thought to cut both the late Keweenawan—Logan diabase sill
as well as the Keweenawan sedimentary and volcanic formations of the
Sibley and Osler series.
�-32OF A GREENSTONE BELT IN MINNESOTA:
RAINY LAKE TO LAKE OF T}E WOODS
GEOLOGY
Richard W. Ojakangas
University
of Minnesota, Duluth
and
Minnesota' Geological Survey
ABSTRACT
A poorly exposed greenstone belt located between Rainy Lake and
Lake of the Woods is currently being explored actively by drilling.
Outcrops are, in general, found only within fifteen miles of the
Rainy River; the clays of Glacial Lake Agassiz cover the rest of the
area.
A generalized geologic map has been drawn on the bases of the
limited .,outcrops, aeromagnetic maps, asd a gravity map furnished by
IL Ikola. The structural trends and lithologic assemblages are similar to those in adjacent Canada (Fletcher and Irvine, 1955; Ontario
Department of Mines Map 2115, 1967). Pillowed greenstones, felsic to
intermediate metavolcarjics, metatuffs, and metasediments are the main
rocks of the belt.
Most bedding and foliation trends northeastward and dips steeply,
and apparently reflects the limbs of major folds. Lineations in the
metavolcanics, metatuffs, and metasediments generally plunge steeply
to the southwest or northeast. Lineations in gneisses and granites
have variable orientations.
Outcrops exist on three zones of pillowed greenstone.
One zone
south of Bircbdale is apparently four miles wide and appears to lie
within a northeast—trending syncline. Another zone just east of
Clementson is less than a mile wide and appears to be on the southeastern flank of another northeast—trending syncline. The third zone
trends east—west in the vicinitg of Indus and Manitou.
Several small and large granitic plutons are present in the belt;
all except a big body on Lake of the Woods contain abundant K-feldspar.
The metamorphic grade of the metatuffs and metasediments is generally
high; biotite and blue—green amphibole are common whereas chlorite is
relatively scarce.
Biotite—quartz—plagioclase schists, hornblende—
quartz—plagioclase schists, and biotite-.hornblende—quartz—plagioclase
schists are common. Hornblende—quartz—plagioclase gneisses are prevalent in the western and southern parts of the area near the larger
plutons.
�—33-
The youngest rocks in the area are northwesterly trending dioritic
dikes up to hoc
wide. Some are intermittently exposed over a total
distance of 65 miles in Minnesota and Ontario. These contain plagio—
clase, bornblende, quartz, and opaques.
ft.
Minor gossans were observed in the field.
Cores from holes drilled
in the belt on state—owned land contain pyrite, pyrrhotite and minor
chalcopyrite. These minerals are disseminated in the metavolcanics,
inetatuffs and metasediments, and are massive in thin zones of black
shale.
Iron formation is associated with metasediments in the southeastern
part of the area.
References:
Fletcher,
63rd
0
L., & Irvin, T. N., 1955, Geology of the Emo Area:
Annual Report, Ontario Department of Mines, Part 5, 36
p.
Ontario Department of Mines, 1967', Kenora—Fort Frances Sheet, Geologicaj
Compilation Series, Map 2115.
�-34EAIUJY
PRECAMBRIAN GS)LOGY OF THE RAINY LAKE DISTRICT
Z.
E. PFTTEBIIAN
U. S. Geological, Survey, Denver, Colorado
80225
S. S. GOLDICH
Northern Illinois University, DeKalb, Illinois
60115
ABSTRACT
Geologic relations of major rock units in the Rainy Lake region
have been,.variously interpreted since the classic studies of A. C. Lawson
around the turn of the century. Although radiometric dating has not
resolved the controversy over the relative ages of the Keewatin and
Coutchiching Series, many ages determined by different methods have
provided some insight into the complex history of this region.
Results
of total rock Rb—Sr dating of major units in the area are summarized
below:
Unit
Isochron4ge (ni.y'.
I
Initial
Sr87/Sr86
Algoman Granites:
Small stocks, Rainy Lake
2540 ± 90
0.7015 ± 0.0009
Vermilion Granite
2680 ± 95
0.7005 ± 0.0012
Keewatin Series
2595 ± 45
0.7005 ± 0.0009
Coutchiching Series
2625 ± 85
0.7011 ± 0.0023
Uncertainty represents the 95% confidence level
Isochron ages for the Coutchiching and Keewatin Series probably
register a metamorphic event since zircons from both units as well as from
the Laurentian Granite gives ages of about 2750 m.y. as reported by S. H. Hart
and G. L. Davis in 1969.
The age of 2680 m.y. may represent the time of
emplacement of the Vermilion Granite. Mineral ages of small stocks of
Algoman Granite show discordances between biotite and muscovite.
Three
muscovites average 2650 m.y. whereas biotite ages are as low as 2150 xn.y.
Loss of radiogenic strontium preferentially from the biotites may have
lowered the total rack isochron. Older ages for the muscovites may approach
the true time of emplacement for these granites.
�-35STRUCTURAL AN!) METAMORPHIC HISTORY
OF ThE MARQUETTE SYNCLINORIUM
DR.
C. McA. POWELL
University of Cincinnati
ABSTRACT
The Menominee Group of the early Proterozoic Marquette Synclinorium
is composed of three formattons:
the Ajibik Quartzite grades conformably
upwards into the Siamo Slate which by stratigraphic transition and inter—
digitation passes into the overlying Negaunee Iron Formation.
Structural
analysis of the Siamo Slate reveals two periods of deformation.
The
first deformation,
was the more intense, and produced the main east—
west folds, and was accompanied by development of a quasi—vertical slaty
cleavage.
Tabular sandstone dykes and thin pelitic foliae intruded
parallel to the cleavage during deformation indicate that the cleavage
formed when the sediments were only partially lithified.
Fb deformation
continued after cleavage formation, and rotation of the more competent
psainmitic beds accompanied by plastic deformation in the interbedded
pelitic layers produced refraction of cleavage.
Little or no heat
accompanied the F1deformation.
Subsequent to Fb the Marquette Synclinorium was affected by thermal
metamorphism of regional extent.
Isograds centered on a sillimanite—
grade node near Republic cut obliquely across the Ft structures. Relict
diagenetic textures and structures including overgrowths on rounded
quartz grains are preserved in all metamorphic facies as high as the
staurolite facies near the western end of the Marquette Synclinorium.
In
the lower metamorphic grades, the banding produced by intrusive
pelitic cleavage foliae
is accentuated owing to reconstitution of the
intrafolial phyllosilicates and migration of silica into the interfolial
At higher grades crystallization of more randomly oriented
lenses.
phyllosilicates has reduced the microscopic banding, and many of the
large, overgrown, detrital quartz grains have polygonized into smaller
equidimensional grains. The regional metamorphism involved thermal
recrystallization only, and did not produce preferred dimensional
orientation of quartz.
A weak deformation, I after the climax of the thermal metamorphism
produced a steeply plunging, crenulation lineation, La, and a few open
angular folds. Pennine chlorite was developed later in many of the
rocks
during widespread retrogressive metamorphism.
�-36IS THE LIMESTONE MOUNTAIN STRUCTURE AN ASTROBLEME?
W. F. READ
Lawrence University
ABSTRACT
Limestone
Michigan.
Mountain is located about 10 miles WNW of Baraga,
The term "Limestone Mountain structure" is here used to
include, not just the "mountain" itself, but flso Sherman Hill, another
Ordovician
disturbed
outlier about 2 miles to the northeast,:.artd.an:jarea of
Jacobsville sandstone a mile and
Hill.
a half south of Sherman
Exposures are limited due to abundance of glacial drift. If the
structure has a center, i€s location is not revealed by known
exoosures,
Ellis Roberts (1940) and Thwaites (1943) attributed the deformation
here to a major fault striking NE,
Bucner put Limestone Mountain on
the TectonicMap of the United Stites (l9e4) a&.a possible 'cryptovolcanic
structure!.
If
the structure is considered as an astrobleme, then the Ordovician
outliers presumably belong to an encircling graben or downwarp.
Limestone Mountain is, in general, a syncline, but with much cross—
faulting and other complexities, In Sherman Hill, the limestone
(actually dolomite), though perhaps slightly synclinal, is nearly flatlying.
Joints are so numerous in both places as to give the rock a
"shattered" appearance.
Thin
The disturbed Jacobsville exhibits both folding and faulting.
sections show grains of quartz and feldspar with microstructures similar to
those found in quartz and feldspar from generally accepted astroblemes.
However it cannot be said with certainty that the Jacobsville here has
been Ishocked. No shatter cones or breccia dikes have yet been found.
Available gravity and magnetic readings suggest structural complexity
in
the area but do not particularly favor either the astrobleme or the
NE—trending..fault hypothesis,
�-37.ARCHAEAN VOLCANIC STRATIGRAPHY OF THE KIRKLAND-LARDER LAKES
AREA OF NORTHEASTERN ONTARIO
R. H. RIDLER
University of Western Ontario
ABSTRACT
The Archaean volcano—sedimentary complex of the Kirkland—
Larder Lakes area has served as a tectonic—stratigraphic model in
the Superior Province for over thirty years. Traditionally, an older,
predominantly volcanic sequence, the Keewatin, is separated by a pronounced angular unconformity equivalent to the Laurentian orogenic
epoch from a younger predominantly sedimentary sequence, the Timislcaniing.
The Timiskaming complex also includes a suite of hyperalkaline igneous
rocks unique in the Superior Province (Cooke and Moorhouse, 1969;
Roscoe, 1965). The accessibility, mineral wealth and geological complexity have encouraged so much geological study that the area ranks as
one of the best mapped in the Superior Province (Thomson, 1948).
Recent volcano—stratigraphic studies (Ridler, 1969 — 1970),
suggest a revision of the classical stratigraphy into a succession
of three maf Ic to salic volcanic cycles (Fig. 1).
The Tirniskaming
volcanic complex (Fig. 1) represents the salicvolcanic culmination of
the second cycle. Thus, the Tirniskaniing complex is not only preceded
but also followed by volcanics traditionally classified as "Keewatin".
Further, a major volcanic centre co—axial with the Lebel Syenite is
recognized and correlated closely with the salic phase of the second
cycle.
Typical Archaean volcano—genic ,sediments associated with this
centre include several fades of exhalative iron formation.
The volcanic rocks within a few miles of Kirkland Lake tend
to be anomalously alkaline and sub-siliceous compared to Archaean calc—
alkaline suites. Older, sub—alkalic tholeiites, andesites and dacites
are succeeded gradually by under-saturated hyper-alkaline volcanics.
Thus the uniquely alkaline volcanics of Timiskan:ing complex are preceded and presaged by a trend to potash enrichment. This overall
increase in potash with time makes relative potash content a useful
local index for correlation.
In place of the traditional concept of a pre—Timiskamir.g
orogeny followed by peneplanation, the author suggests a history of
polyphase deformation consistent with the concept of a continuously
evolving volcanic mobile belt. "Granjti" cobbles in Timiskazuing conglomerates record erosion of pre—Timiskaming hypabyssal plutons (Hewitt,
1963), during an early, geographically restricted, non-orogenic period
of deformatlou. At least two periods of ductile deformation within
the mobile belt followed Timiskaming sedimentation.
�-38REFERENCES:
Cooke, D. L., and Moorhouse, W. W., 1969, Timiskanting Volcanism in the
Kirkland Lake Area, Ontario, C&ntada: Can. J. Earth Science,
v. 6, no. 1, pp. 117—132.
hewitt, I). F., 1963, The flmiskaming Series of the Kirkland Lake Area:
Canadian Mineralogist, v. 7, pt. 3, pp. 497—522.
Ridler, R. II., 1969, The Relationship of Mineralization to Volcanic
Stratigraphy in the Kirkland Lake Area, Northeastern Ontario,
Canada; Unpublished Ph.D. Thesis, U. of Wisconsin, Madison,
p. 141.
Ridler, R. II., 1970, Relationship of Mineralization to Volcanic Stra—
tigraphy in the Kirkland—Larder Lakes Area, Ontario: Proc.
Geol. Assoc. Can. v. 21, pp. (not known at this time).
Roscoe, S. M., 1965, Geochemical and Isotopic Studies, Noranda and
Matagaini Areas; Symposium on Strata—Bound Sulphides, Bull.
Can. Inst. Mitt. Met. v. 58, no. 641, pp. 965—911.
Thomson, J. E., 1948, Geology of Teck Township and Kenogami Lake Area:
Ont. Dept. of Mines, Ann. Rept., v. 57, pt. 5, pp. 1—53.
LiST OF iLLUSTRATIONS:
Fig.
1 —
idealized Stratigraphic Synthesis of the Kirkland Lake Area
with folding removed.
�BASALTS
DACITE TUFF
MAFIC LAVA COMPOSITIONS
2
I
.4
TO RHYODACITE
TRACHYT E
LAVAS
TUFFS
ROUND
5,000'
TUFFS
LAKE BATHOLITH
THOLEIITE
1,000'—
PACAUD
MINOR BASANITE
PILLOW LAVAS
THOLEIITIC PILLOW
6,900'— 28,000'
BASALTS
CATHARINE (BOSTON)
MINOR
TUFFS & BRECCIAS
ANDESITE
0' — 23,000'
SKEAD (McELROY) PYPOCLASTICSIf
ALL
BASALTS
0"— 34,000
MCVITTIE
TRACHYTE, SYENITE
CONGLOMERATE, GREYWACKE
I000— II. 000'
TIMISICAMING
MINOR
I PILLOW LAVAS I
O'—SOOO'
THOLEIITIC ANDESITES
HIGHWAY II
oa
COMPLEX
TUFFS
-2--a
IRON
FORMATION
GREYWACIC E
7
C
C-)
IRON F0RMA1ON .,,,—
SUL PHIDE
(Co)
—
eoUSoOM"".%,,
—
SILL
C
LOCALLY\
______"" C,.,
SHEARED CONTACT
( 40)
DIFFERENTIATED
-J
a
EsITE01hhhhhhih1IIiIIIIIIIIIIIIIIII'0:
•'.'9.y':t :1:;::oo
Fe _,,OXIOE
7
AREA WITH FOLDING REMOVED
KIRKLAND LAKE
_____
OF THE
__________
IDEALIZED STRATIGRAPHIC SYNTHESIS
______
—
ARCHEAN
LOWER
'ST CYCLE
ARCHE AN
MIODLE
2ND CYCLE
RCHEAN
UPPER
3RD CYCLE
—
NJ
(S
A
x2o
R.H. RIDLER,; Figure
I
(5
--
----'
th
-O
—I
C)
rn
(-3
r
r
r
C)
—I
—I
Ca)
r
—I
Ca,
r
0-O
0
z
0
-q
1>±
'1 fl
�-4O-
A
ULASSiIUAflCbi 0 GRAiCLI'IU aQUKS iJITh Rthu Pu
GIANTS RAP.G JIATHOLITFI, N.iRThiRi L'LIJ'1'A5UTA
S.
i'iinnsota Goniogical thrvey, University : rliniiu rmth
24inneapolis, Minnesota 55455
A B S T it A U P
Figure 1 shows a clnsification or granitic and relate6 roc
Vavo'ired by many field geologists. The inadequacy of this scherac
and some of its flaws became apparent while investigating granitic
rocks from the western part of the Giants -Range tatholith (Algn:nj
in Northern iinnesota. For example, rocks which plotted in Uc
acianollitc: field were found to lack the characteristics of ar
udarncllite: their plagioclases+ were aibite rathor than olioclae,
and their muscovite conthnt was as high as 10 percent iiistrd of
Lei.nj insignificant. A revised classification proposed in this
paper, :il'own in Figaro 2, differs substantiaaly iron the other erie,
zln(i. mainly as follows:
(1) The edamelllte field is compressed, and the upper limit
of its quartz content fixed at 30 percent as against 50 percent.
chane is made lecause adamellites that plot below the 10
quartz level (Group 1 adamollites) arid those that plot
above the 30 percent quartz level (Group 2 a1ameilites) show the
This
percent
followinj
important petrographic differences:
1 adamel.lites
but rniy be present in amounts as hih as
(a) muscovite is rare in Group
10 percent in Group 2 adamellites,
(b)
plagioclase in Group 1
gonorally
ãdaraellites
is more caicic than that in
Group 2 adameilites, aid
(c)
non—opaque dalcic trace minerals (sphene,
enidote,
apatite) in Group 1 adat;iellites
total more than 1 percent, whereas Group 2
generally have a substantially
lo'er content of those trace minerals.
adarnellitos
(2) The granite Itoh is extended not only laterally to incJ1xie
the Group 2 ádarnellites, tat also vertically upto the 61) ercent
quartz level.
�—41-
(3) The upper liimit of 30 percent quartz fixed for the adFwellite
field is extended towards the Flagioclase-Quartz jnin and the Alkali
feldspar—unrtz join; thereby, the granodiorite, tonalito and l'ranite
fields of the classification shown in Figure 1 have teen sub—divided
into the granodiorite (c30 percent quartz)—quartz granodiorite S>'30
percent quartz), tonalite (<30 percent quartz)—quartz tonalitc (>30
percent quartz) and the syehogranite c30 percent. quartz)—.rarito
(>30 percent quartz) fields.
Although one cannot assert that feldenar types rt:vc'nl the tectn:ic
,;rouping of c'r&tites, a correlatioji betweezi
In
the Yeldspar tyne as well as colour,
One could thus have niodified root
the
the noenc1ature of granites, therefore, it
ainrals.
two scouts to oxist.
is desiratl to izLlicvte
text,'ire, alteration, a;.d Qccassory
ncuavz
like
calcic oligoclasegranit&', "microcline—albite—granite",
"nicroclinc—
"orthocla;..e—
ic olloc1ase—gran ite", etc. In general terms, these
three inodif led root names are correlatable with synkineinatic, late—
kineina tic, and pos t-.kiueina tic grani tes, respectively.
ml crocline—calc
An application of the revised classification combined wit!' 'idd
osorvations has enabled no to recognize twelve distinctiv major rock.
units in the western part ot' the Giants Rane batholith where only t.wo
principal units were distinguished previously.
adjacent areas of the lake Superior region, and elsewhere, needs to Le
Its applicability to
tested.
�-42Figure 1
U1ir;siVication of granitic and relatwi rock;
favotred by ninny flr!1c1 geoio:ists; it is Lased
on the modes of quartz, K—Yeldspar and plagic—
c1are rocalcuin ted to 100 percent.
Quartz
50
50
Granite
iorite
Adainelli te
10
ite
I
$srcniod ion te
-feldspar
33
67
90
rlairc
�-43-
Fjgire 2
The revised classification; it is based on the
modes of alkali feldspar, plagioclase and quartz
recalculated to 100 percent.
Quartz
90
90
Quartz
60
Granite
30
30
Syeriograni te
Adarne lute
Granodiorite
10
In
/sY
10
'eld;par
includes
dhite — An0..5)
35
65
P1
(An(
�—44—
GEOLOGY OF TEE ALKALIC ROCK — CARBONATITE
COMPLEX AT PRAIRIE LAKE, ONTARIO
DAVID H. WATKINSON
Department of Geology
University of Toronto
ABSTRACT
The Prairie Lake complex of ijolitic rocks and carbonatite (age:
1112 million years) is intrusive into granitic gneisses 25 miles
northwest of Marathon, Ontario. The complex has positive relief, is
somewhat circular in plan, and is composed of concentric arrangements
—
of carbonatites and rocks of the pyroxenite — melteigite —
urtite series. The latter series has two culminations: nepheline—
rich rocks characterized by melanite, wollastonite and alkali feldspar
with interstitial calcite and nepheline —feldspar intergrowths; and
Pyroxenitic
pyroxene—rich rocks characterized by magnetite and biotite.
The
rocks are often separated from carbonatite by micaceous zones.
carbonatites are strongly banded with near—vertical dips; banding is
Most
a consequence of biotite and olivine + magnetite concentrations.
carbonatites are calcite—rich, but some are dolomitic and breccias
Pyrochlore is
with groundmass dolomite intrude the calcitic rocks.
common in the carbonatites and in calcite—rich interstices and lenses
in pyroxenites. In some zones pyrochlore contains as much as 30 weight
Z U3O. Some fenitized country—rock occurs at the contact with
The complex is interpreted to have formed by intrusions
carbonatite.
of magmas generated by strong differentiation of a carbonated, neph—
elinitic parent.
ijolite
�—45—
EVIDENCE FOR A TROPICAL CLIMATE AND OXYGENIC ATMOSPHERE
IN UPPER HURONIAN ROCKS OF THE RAWHIDE LAKE - FLACK LAKE
AREA, ONTARIO
JOHN WOOD
Department
of Geology
University of Western Ontario
ABSTRACT
The upper Huronian of the Rawhide Lake-Flack Lake Area Ontario is
comprised of four formations - the Gowganda, Lorrain, Cordon Lake and
Bar River, in ascending stratigraphic order.
The Gowganda Formation consists of orthoconglomerates (with clasts
up to 2 metres in diarqeter), paraconglomerates, graded greywackes, finely
banded siltstones, finely banded arkoses (with dropped stones), and massive
arko ses.
The Lorrain Formation can be divided into three parts. Rocks in the
lower part, although variable in grain size and colour, are all arkosic.
Feldspar (both sodic and potassic) is fresh near the base, but towards
the top becomes progressively more weathered until only pseudomorphs are
visible.
Diaspore, kaolinite,and pyrophyllite are present at the top of
the lower unit and at the base of the middle unit. Concentrations of
heavy minerals including hematite and U/Th minerals are associated with
these aluminous minerals.
The middle Lorrain is a sequence of interbedded
kaoliniti quartzites and quartz jasper pebble conglomerates, while the
upper Lorrain is essentially an orthoquartzite sequence. Feldspar is not
present in the middle or upper parts of the Lorrain Formation.
In contrast rocks of the Gordon Lake Formation are quite feldspathic
and much finer grained. Van-coloured quartzo-feldspathic siltstones
and shales with intraformational breccias are the dominant rock types.
Chert is present near the bottom and top of the formation while gypsum
and anhydrite are concentrated in the lower parts. Authigenic hematite
and hematite ooliths occur in the middle and upper parts of the formation.
Ripple marks and shrinkage cracks are present throughout.
The Bar River Formation consists essentially of cross-bedded orthoquartzites (often cemented by hematite), with some interbedded siltstones.
The ltter who contain shrinkage cracks are ripple marked, and include
many small scale sedimentary intrusions.
Most geologists who have studied sediments of the Cowganda Formation
have concludea that these rocks were deposited during a frigid climatic
regime. Accepting their conclusions and using feldspars as indicators
of climatic conditions, there would appear to have been a rapid aninelioration
of climate while sediments of the lower Lorrain Formationwere being
deposited. Diaspore and kaolinite are considered to be the products of
'in situ' feldspar alteration under tropical climatic conditions.
The
presence of kaolinite and pyrophyllite in drill-core samples from -3,500
feet rule out a late surface weathering origin for these minerals.
This
change from frigid to tropical conditions is represented in a stratigraphic
thickness of 160 metres.
These tropical conditions persisted while sediments
�—46—
of the middle and upper Lorrain Fottuation were being laid down.
The clatic hematite beds in the Lorrain Formation, the hematite
ooliths in the Gordon Lake Formation and the hematite cement in the Bar
River orthoquartaites, together with the presence of suiphates in the
Gordon Lakc Formation, are indicative of an oxidising atmosphere in upper
Ruronian times.
This conclusion is important in relation to uranium
exploration.
The chert, aniaydrite, gypsum, and hematite as well as demonstrating
conditions of chemical sedimentation provide nvre evidence for proposed
correlations of upper Ruronian rocks with those of the Animikie Series
Marquette Range Supergroup of Michigan. Postulation of a tropical climatic
regime during deposition of part of the upper Huronian sequence removes
one of the previous barriers to this correlation, for previously only
frigid climatic regimes have been documented in the Ruronian, while the
ferruginous sediments of Michigan were considered to have been deposited
pnder tropical or sub-tropical conditions (James et al.).
REFERENCES
Frarey, M. J. 1966. Discussion:
Huronian stratigraphy of the McGregor
Bay area, Ontario: Relevance to the paleogeography of the Lake Superior
region, by Grant N. Young. Can. J. Earth Sci. 3, 997.
James, H. L., Clark, L. D., Lamey, C. A, and Pttijohn, F. J. 1961. Geology
of central Dickinson County,+Michigan, U.Sk Geol. Surv. profess. Papers,
310;
�—47--
WIDESPREAD OCCURRENCE OF ALUMINOUS MINERALS IN APH.EBIAN QUA.RTZITES
GRANT M. YOUNG
of Geology
University of Western Ontario
Department
ABSIRACT
After the conclusion of the world-wide Kenoran thermo-tectonic events
(Ca. 2.5 b.y. ago) there was development of the first extensively preserved
stable shelf assemblages of the geological record. Rocks of this type
were first studied in Canada in the region north of Lake Huron by Murray.
(1849) and Logan and Sterry Hunt (1855).
The Huronian succession includes
several polyrnictic conglomerates which have been interpreted as glacial
deposits.
The youngest of these conglomerates (Gowganda Formation) is thick
and extensive and has recently been considered correlative with other
early Proterozoic (Aphebian) tillites in a large area extending from S.E.
Wyoming to the Keewatin District of the N.W.T. (Young, in press).
The upper stratitified unit of the Gowganda Formation is overlain by
a thick (5-6,000 ft.) quartzite formation (Lorrain) that is also very
extensive. Many different subdivisions of this unit have been proposed,
but on a regional scale, a threefold subdivision seems most reasonable.
The lowest subdivision is a varicoloured (red, white and green) succession
of felspathic grits and sandstones. This is followed by a unit charac—
tensed by the presence of quartz and jasper pebble conglomerates and the
uppermost unit is an extremely pure orthoquartzite.
In many areas the
middle unit and the lower.part of the upper unit contain aluminous minerals
such as kaolinite, diaspore, pyrophyllite, kyanite and andalusite (Church,
1967; Chandler et al., 1969). These minerals are thought to represent
an in situ weathering (bauxitization) process which occurred shortly
after deposition and gave rise to kaolinite which wa.s later changed by
further diagenesis and metamorphism to the other minerals listed above.
The reasons for invoking this mode of origin rather than origin by deposition of "primary" kaolinite at the time of sedimentation or by late
post depositional weathering are as follows: -
1.
Fresh felspars are abundant in other Huronian outcrops.
2.
The kaolinite commonly occurs as "clots" of the same order of
size as the associated quartz grains, suggesting that each clot
represents an altered felspar grain.
3.
It is difficult to envisage the conditions under which fine
Jcaolinitic crystals could be sedimented together with coarse
quartz grains (see Ojakangas, 1965, for discussion of the same
problem in Jatulian quartzites of Finland).
4.
In some sections metamorphic minerals may be seen developing
from kaolinite.
�—48—
Aluminous minerals similar to those of the Lorrain Formation occpr
in quartzites in the lower part of the Animikie "Series" = Marquette
Range Supergroup (Church and Young, in press) of the south shore of Lake
Superior (Keyes Lake quartzite, Sturgeon quartzite, Ajibik quartzite and
Breakwater quartzite). Kaolinite is also present in the Baraboo and
Barron quartzites of Wisconsin and pyrophyllite and diaspore were reported
from the Sioux quartzite of Minnesota and South Dakota (Berg, 1931).
Kyanite is present in the Medicine Peak Quartzite of S.E. Wyoming, the
Petaca Schist of New Mexico and kaolinite, andalusite and diaspore have
been found in the Hurwitz C quartzites of the Keewatin District of N.W.T.
Bimodal size distribution in many of these quartzites may indicate that
much of the clastic material was wind transported prior to sedimentation
in an aqueous medium (Folk, 1968).
Similar aluminous quartzites of similar age from other continents
include those of Finland (Jatulian quartzites), Brazil (Jacobina Series),
India (Iron Ore Series) and South Africa (Witwatersrand System). Some
of these extremely widespread quartzites may be deposits formed as a
result of post-glacial transgression.
If the formation of kaolinite in
the quartzites took place under climatic conditions similar to those unde,r
which present day bauxites and laterites are formed, there must have been
a significant amelioration of climate following deposition of the Cowganda
Formation and its possible correlatives.
REF ERENCES
Berg, B. L. 1937. An occurrence of diaspore in quartzite.
.v. 22, pp. 997—999.
Amer. Mineralogists
Church, W. R. 1967. The occurrence of kyanite, andalusite and kaolinite
in Lower Proterozoic (Ruronian) rocks of Odtario (abst.) Tech. Prog.
Geol. Assoc. Can. Meet. Kingston, Ontario, pp. 14-15.
ft. and Young, C. M. (in press). Discussion of the Progress
report of the Federal-Provincial Committee on Huronian stratigraphy.
Church, W.
Can. J. Earth Sc. v. 7.
Folk,
Bimodal süpermature sandstones: product of the desert
R. L. 1968.
flc,or. XXIII International Geological Congress Section 8; Genesis
and Classification of Sedimentary Rocks.
pp. 9-32.
Logan, W. B. and Sterry Hunt,
H.
T. 1855.
Esquisse geologique du Canada.
Bossange et fils, Paris. 100 pp.
Murray,
Alexander. 1849. On the north coast of Lake Huron.
Canada, Rept. Prog. pp. 93-124.
Geol. Surv.
Ojakangas, R. W. 1965. Petrography arid sedimentation of the Precambrian
Jatulian quartzitesof Finland. Bull. Comm. Geol. Finlande. No. 214,
74
pp.
Young, G. M. (in press). An extensive Early Proterozoie glaciation in
North America? Palaeogeog. Palaeoclimat. Palaeoecol.
�—49—
PROTEROZOIC ROCKS IN THE THUNDER BAY AREA
May 9, 1970
Prepared
by.
J. M. Franklin, Lakehead University, Thunder Bay
CR. Kustra, Ontario Department of Mines, Thunder Bay
�— 50A—
lOji
1 (a):
Microfossils in Gunflint chert from shore of Lake Superior
near Schreiber, Ontario; spheroids are Huroniospora, filaments
are Gunflintia.
1 (b):
Side view of a weathered block of Sibley stromatolites; note
polygonal columns of Conopiyton.
Plate 1.
�—51—
Guide to the Proterozoic Rocks of the Northwestern
Lake Superior Area, Ontario
INTRODUCTtON:
The Froterozoic rocks of Northwestern Ontario, which form part
of the "Animikie" and Keweenawan unit; represent one of the most
complete geological records of middle and late Proterozoic sedimentation and igneous activity in eastern North America.
These rocks
are virtually uninetamorphosed and only slightly deformed.
Mineral deposits in these Proterozoic rocks include silver in
Keweenawan dykes and the Rove Formation, iron in the Gunf lint Formation, nickel in mafic intrusive rocks, copper in various volcanic
and sedimentary strata, and lead-zinc-barite associated with the
Sibley Group.
During the last century, the famous Silver Islet mine
Currently, a minor
produced over three million dollars in silver.
amount of silver is recovered from the Creswel mine near Stanley
(Fig. 1).
GENERAL GEOLOGY
The Proterozoic rocks lie unconforinably on the peneplained
Archean surface. Archean meta volcanic and meta sedimentary rocks
form a "belt" extending from west of Shebandowan to Thunder Bay city.
Another similar belt crops out in the Schreiber—Big Duck Lake area
To the north, the Geraldton-Beardmore belt may be
(Pye, 1964).
traced westward by aeromagnetic interpretation under Lake Nipigon,
and may possibly join with the Lac Des Mille Lacs—Atikokan belts.
The remainder of Archean outcrop is composed of intrusive and metamorphic granitic rocks, and small ultrainafic bodies.
The Proterozoic rocks are subdivided as shown
-
Proterozoic
in
Table 1.
TABLE 1 —
Stratigraphy of Northwestern Ontario
Neohelikian
basalt, minor rhyolite and sedimentary rocks
Osler Group:
gabbro plugs
Intrusive rocks:
undersaturated plugs
layered bodies
northeast trending dykes
Logan diabase sills
Paleohelikian
red beds, stromatolite zone
Sibley Group:
Apheb ian
Animikie Group
Rove Formation:
shale
iron formation
Gunf lint FormatioB:
�—52—
APHEB IAN
The Gunflint Formation (Figs. 1*, 3, 4, 5) has been studied
in
detail by Goodwin (1956) and Moorhouse (1960), the Rove Formation
by Morey (1967).
Much of the descriptive detail is taken from these
authors.
Gunf lint Formation (adapted from Goodwin, 1956)
Deposition of the Gunflint Formation was in part cyclical. A
basal conglomerate member is overlain by two members each composed
of chert, tuffaceous shale, and carbonate—taconite submembers. These
members are in turn overlain by a discontinuous limestone member,
(Fig. 2 and Table 2). The Gunf lint Formation was deposited 1635±24
million years ago (Faure and ICovach, 1969).
-TABLE 2Stratigraphy of the Gunf lint Formation
(modified from Goodwin 1956)
Limestone—dolomite member
Upper Member
Taconite—chert carbonate submember; taconite (west) fades
chert carbonate (east) facies
Tuffaceous shale submember
Algal chert submember
Lower Member
Taconite—chert carbonate submember;
west taconite facies
chert carbonate facies
east taconite facies
Tuffaceous shale submember
Algal chert submember
ICakabeka conglomerate member
(a)
Basal ICakabeka Conglomerate Member
This member ranges to five feet in thickness and is composed of
polymictic conglomerate. Clasts of Archean volcanic rocks and granite
are cemented in a matrix of chlorite and quartz. The unit is discontinuous but persistent.
(b)
Lower Member
The lower algal chert submember (Fig. 2) consists of reef—like
mounds of finely banded black, red, and white oolite chert. These
mounds are intergrown or cemented in dolomite. This submember forms
the western margin of Gunf lint outcrop (Fig. 1), but is continuous
only to the west of ICakabeka Falls.
It contains abundant microflora
remains (Baarghorn and Tyler, 1965) (Plate la).
The lower tuffaceous shale submember ranges to 20 feet thick
and overlies the lower algal chert in the area west of ICakabeka Falls
is composed of fissile black shale containing much volcanic ash.
*
see back cover
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The uppermost submember of the lower member is subdivided into
three facies (Fig. 2). The lower west taconite fades, which is
150 feet thick, extends northeastward from Gunf lint Lake to Kakabeka
Falls, is composed of wavy—banded granular chert, carbonate, and
The lower half contains disseminated greenalite granules
oxides.
in pale grey chert; siderite forms local beds. The upper half
contains increasing amounts of hematite and magnetite. This fades
grades upward into jaspilitic upper algal chert and grades laterally
into the lower banded chert—carbonate facies.
The lower banded chert—carbonate facies extends from Kakabeka
Falls to Thunder Bay city, and consists of 4 to 6 inch siderite beds,
with interbedded 2 to 6 inch grey cherty beds. Carbonaceous material
and pyrite are common in shale interbeds. This facies grades into
granular taconite towards the northeast.
The lower east granular taconite fades extends from Thunder
Bay city to Loon Lake. The basal 2 to 6 feet are formed of inter—
The upper 10 to 20 feet consist
bedded granular chert and ankerite.
of interbedded red to green mottled chert and dolomitic limestone.
This facies grades upward into the tuffaceous shale submember of the
upper member.
(c)
Upper Member
The upper algal chert submember extends west from Nolalu to Gunf lint Lake and consists of basal granular chert overlain by algal
chert and, in the Mink Mountain area, amygdular basalt flows. The
flow and algal chert are overlain in turn by granular chert and bedJasper beds grade into tuffaceous shale of the overlying
ded jasper.
submember.
The tipper tuffaceous shale is the only continuous submember in
the Gunf lint Formation and forms a key stratigraphic marker (Figs.
It ranges to 100 feet thick and thins laterally in either
3, 4).
direction from Kakabeka Falls. It consists of black tuffaceous shale
and siltstone with interbedded siderite and pyrite and extensive beds
The ash contains ellipsoidal structures which
of volcanic ash.
resemble mudballs and are composed of concentric layers of small
angular tuff fragments, arranged about a larger central fragment.
The upper tuffaceous shale submember grades into the upper tac—
The upper taconite facies
onite and banded chert—carbonate submember.
extends from Gunf lint Lake to the City of Thunder Bay (Fig. 2), and
is composed of wavy bands of granular greenalite—bearing chert. The
greenalite—bearing granules are round to oval, evenly distributed
throughout a layer, and appear to have formed "in situ". The unit
exibits a rusty weathering, contains abundant hematite and magnetite
in granules towards the top, and grades laterally (Fig. 2) into the
upper banded chert—carbonate facies which extends from west of Thunder
Bay city to Loon Lake. The latter facies consists of interbedded
The carbonate consists of siderite
grey chart and brown carbonate.
Brecciation and folding, apparently
with lesser dolomite and ankerite.
contemporaneous with deposition, are common.
�—54—
(d)
Upper Limestone Member
The upper limestone member marks the top of the Gunf lint Formation.
Minor chert beds, illite and volcanic shards are present, and tuffaceous
shale is most prevalent in the eastern area of Gunf lint outcrop.
Stratigraphic Interpretation
Goodwin (1956) concluded that Gunf lint deposition occurred in a
shallow basin which had limited circulation with an open sea. After
initial algal activity in the neritic zone, volcanic activity (tuff—
argillite) was accompanied by sinking of the basin. Silicate—bearing
material (taconite) was deposited in the deepest portions while in
the neritic, or intertidal zone (between Kakabeka Falls and Thunder
Bay city) banded chert—carbonate formed. Further to the northeast,
the lower east taconite facies formed in agitated, oxygenated, waters.
As the basin filled, conditions of algal growth returned, initiating
the "Upper Gunf lint?' cycle.
Volcanic activity, marked by local basalt flows and crustal unrest,
terminated the upper algal chert deposition and resulted in widespread
distribution of pyroclastics of the upper tuffaceous shale. Downwarp—
ing resulted in.deposition of granular iron silicate rocks in the
deeper, southwest portion of the basin, while on the shallow northeast shore, chert carbonate was deposited. As the basin filled, sporadic but violent volcanic activity was accompanied by entry of
sea water, resulting in formation of the upper limestone member.
Basinal sinking set the stage for deposition of the Rove shale.
Goodwin (1956), in drawing an analogy with the Santorin volcano
of the Aegean Sea, suggests that volcanism was the chief source of
iron and silica. Alternatively, Rough (1958) suggests deposition in
a fresh water basin, with material derived through weathering of
adjacent landmass, and deposition controlled by limnie cycles. Clearly, re—evaluation of both ideas is necessary in light of recent data
on both Santorin (Butozova, 1966) and bottom sedimentation studies
in Lake Superior, (Nothersill, 1969).
Rove Formation
The Rove Formation conformably overlies the Gunf lint Formation
and consists of up to 3200 feet of argillite and sandstone (Morey,
1967). Morey subdivides the Rove into three lithologic units, which
are, in ascending order:
(1) lower argillite,
(2) transition
sequence, and (3) thin—bedded greywacke.
The Lower argillite is
the dominantly exposed unit in Ontario and consists of grey to black
highly fissile, thin-bedded, pyritic shale, with minor limestone and
san4stone beds. Calcite and dolomite concretions are common near
the base of this unit.
The transition sequence consists of interbedded argillite and
The topmost thin—bedded greywacke, consisting of grey to
pink greywacke and sandstone, is the thickest unit of the Rove, and
is exposed predominantly in northern Minnesota.
sandstone.
�—55—
Morey notes that sediment transport was from the north and that
material was derived from Archean granite, gneiss and greenstone.
PALEOHELIKIAN
Siby Group
he Sibley Group is a red bed sequence, deposited 1298±33 million
years ago (Rb—Sr whole rock isochron, Franklin, 1970) extending from
the Sibley Peninsula north to Armstrong, Ontario, and east to Rossport.
The seven units which compose the Sibley Group are
(a)
basal conglomerate
(b)
sandstone
(c)
sandy red muds tone
(d)
(e)
chert—stromatolite
limey red mudstone
purple mudstone
limestone
(f)
(g)
Polymictic basal conglomerate lentils are most common on the
Locally derived Gunf lint taconite
western margin of Sibley outcrop.
boulders are found where the Sibley overlies the Gunf lint, but gran—
itic boulders prevail where the Sibley overlies Archean rock. Lentils
range to 15 feet in thickness, and occur in pre—Sibley valleys.
Cream, green, and pink sandstone forms the lowest semicontinuous
unit of the Sibley Group, and attains a thickness in the basin margins
of over 200 feet. Beds are poorly graded; ripple marks and cross
beds are present throughout, but are common only in the eastern margin
of sedimentation near Rossport.
Beds are composed of 50 to 70 per
cent quartz, up to 8 per cent chert, 5 per cent feldspar, and 5 per
cent mica, cemented with calcite and minor barite. Syneresis cracks
are common near Edward Island. At the top of the unit, interbedded
sandstone and mudstone mark the beginning of the sandy red mudstone
unit.
The sandy red mudstone unit is composed of less than 50 per cent
quartz and feldspar clasts, in a red hematite—carbonate—clay—feldspar
Bedding is
matrix, and ranges to 300 feet thick near Rossport.
moderately well developed. Brecciation and soft—sediment folding
are common in this unit; chaotic conglomerate lentils are exposed in
the western margin of outcrop near Dorion.
In the area south and east of Nipigon, the sandy red mudstone
is separated from the limey red mudstone by a thin, but laterally
continuous, chert unit.
To the north and west of Nipigon a stro—
matolite unit may occupy the same position. The stromatolites exposed
1
using l.47x10U yr. Rb87 decay constant; using l.39x1011 yr.
constant, age is 1376±33 m.y. The latter may be compared with the
date of Faure and Kovach (1969).
�a
—56—
at Disraeli Lake and near Stewart Lake belong to the group Conophyton
(Hoffman, 1969), formed of vuggy columnar "cone in cone" structures
The chert facies ranges to 10 feet in thickness at Ross—
(Plate lb).
port, and is composed of finely laminated grey to black chert and
brown dolomite. Anthraxolite, accumulations are common along the base
of this unit.
The overlying limey red mudstone contains less than 20 per cent
coarse microcline with less than 2 per cent hematite. The clay
expands itt ethylene glycol, and is a mixed layer chlorite—montmor—
illonite, similar to corrensite (Peterson, 1961). The feldspar is
very fine—grained (less than 10 p diameter) and is probably authigenic.
The overlying purple mudstone unit is finely laminated,
moderately but irregularly fissile, and is composed of approximately
40 per cent each of corrensite and microcline, with less than 4 per
cent hematite, less than 15 per cent quartz, and minor calcite. Less
than 10 per cent coarse clastic material is present in most of this
unit.
The uppermost limestone unit is grey to buff, poorly bedded,
and crops out only north and west of Nipigon.
The Sibley Group is distributed over both the edge of an older
mobile belt (the Penokean orogenic deformation of Aphebian rocks)
and the stable Archean craton. Deposition occurred in a basin restricted on the south and west by uplifted Aphebian rocks. A shallow,
periodically dry, basin transgressed northward over the craton.
Material was derived from both the Aphebian highlands and adjacent
Archean granitic rocks in a semi—arid, warm environment, (Franklin,
1970).
NEOHELIKIAN
Osler Grçp
Volcanic and sedimentary rocks of the Osler Group disconformably
overlie the Sibley Group and are exposed on an arcuate belt of islands
parallel to the shore of Lake Superior, and on Black Bay Peninsula
(Ont. Dept. Mines Map 2137). The lavas are similar to those of the
Portage Lake Lava Supergroup (DuBois, 1962) and are composed of thin,
laterally extensive sheets of vesicular, tholeiitic flood basalt with
minor interf low greywacke beds, & rhyolite (quartz porphyry) bodies.
Intrusive Rocks
The four types of intrusive rocks present in this area are as
follows:
Logan sills: laterally extensive thin diabase sheets,
(a)
cutting Archean, Aphebian, and Paleohelikian rocks
northeast—trending gabbro dykes, parallel to the
(b)
shore of Lake Superior, extending from Pigeon Point to Edward Island
�—57—
layered mafic bodies, as at Great Lakes Nickel Company
(c)
property in Pardee Township
dykes and associated stocks cutting all Helikian and
(d)
Aphebian rocks.
The Coldwell syenite complex near Marathon is an undersaturated
laccolith, similar in age to the other Helikian intrusive rocks
(Pairbairn et al, 1959).
STRUCTURE
Structural deformation is limited to block faulting and regional
tilting, imposed during and after Keweenawan intrusive and volcanic
Two parallel major fracture or fault zones bound the block
periods.
of Aphebian and Paleohelikian rocks exposed in the northwestern Lake
The most northerly of these is a steeply dipping
Superior region.
fracture zone, five miles in width extending from west of Whitefish
Lake to east of Pass Lake. Dragfolding of sediments along faults
suggests slight uplift of the southern side. The northern boundary
is marked by a fracture zone which is occupied by the northeast—
trending dyke set. The block between these faults has been slightly
tilted, resulting .in a 3 to 5 degree dip of the sediments to the southeast.
ACKNOWLEDGEMENT
The authors wish to acknowledge the assistance of S. Spivak, who
compiled and drafted the figures.
S ELECT ED
REFERENCES
Baarghorn, D.S. &
Tyler, S.A., 1965;
Micro—organisms from the Gunf lint chert:
Science, v. 147, p.563—577.
Butuzova, G.Y., 1966;
Iron ore sediments of the fumarole field
of Santorin volcano, their composition
and origin:
(Zhelezorudngye osadki
fumarol 'ngo polya vulkana Santorin,
ikh sostav i genezis): Doklady Akad.
Nauk., S.S.SR., v.168, no.6, p.1400—1402.
DuBois, P.M., 1962
Paleomagnetism and correlation of
Keweenawan rocks:
Geol. Survey, Canada,
Bull. 71.
Fairbairn, B,W.,
Bullwinkel, 113.,
Pinson, W.B., &
Burley, P.M., 1959;
Age -investigation of syenites from
Coldwell, Ontario: Proc. Geol. Assoc.
Can., v.11, i'l4ll44.
�—58—
SELECTED REFERENCES
Faure, G. & Kovach
J., 1969;
The age of the Gunf lint Iron Formation
of the Animikie Series in Ontario,
Canada. Ohio State University Laboratory
for Isotope Geology and Geochemistry
Contribution no. 8.
Franklin, J. M., 1970;
Metallogeny of the Proterozoic rocks of
Thunder Bay District, Ontario, Ph.D.,
thesis, Unpublished., University of
Western Ontario, London, Ontario.
Goodwin, A.M., 1956;
Facies relations in the Gunf lint Iron
Formation:
Econ. Geol., v.51, no.6,
p. 505—595
Roffmaii, H.J.., 1969;
Stromatolites from the Proterozoic
Animikie, and Sibley Groups, Ontario:
Geol. Survey, Canada, paper 68—69,
Rough, J.L., 1958;
Fresh—water environment of deposition
of Precambrian banded iron formations:
Jour. Seth Pet., v.28, no. 4, p.414—430.
Moorehouse, W. W., 1960; Gunf lint Iron Range in the vicinity of
Port Arthur: Ont. Dept. Mines, v.LXIX,
pt.7, p.1—leO.
Morey, G.B., 1967;
Stratigraphy and sedimentology of the
Middle Precambrian Rove formation in
Jour. Sed. Pet.,
northeastern Minnesota.
v.37, p.llS9—ll62.
Mothersill, J. 5., 1969; A grain size analysis of longshore—
bars and troughs, Lake Superior, Ont.,
Jour. Sed. Pet., v.39 no.4, p.l3l7—l324.
Peterson, N.M.A., 1961;
Expandable chloritic clay minerals from
upper Mississippian carbonate rocks of
the Cumberland plateau, in Tenn.: Am.
Mineralogist, v.46, p.1745—1764.
Pye, E. G., 1964;
Mineral deposits of the Big Duck Lake
area;
Ont. Dept. Mines, Geol. Rept.
no. 27.
�—59—
DESCRIPTION OF STOPS
Mileage count begins west of Nolalu, a small community on Highway 590, approximately 35 miles southwest of Lakehead University,
and may be reached via Highways 17—11, 588 and 590.
Mileage
0.0
STOP 1
The exposure is located in the
1.8 miles west of Nolalu.
bed of the Whitefish River, on the north side, approximately
OO feet downstream from the bridge.
LOWER GUNFLINT MEMBER, LOWER ALGAL CHERT UBMEMBER OVERLYING
BASAL CONGLOMERATE AND ARCHEAN ASEMENT (FIG. 2)
Lower algal chert in the shape of concretionary, cthuli—
flower—like growths, forms an irregular, hummocky surface.
It is underlain by a thin veneer of basal (Kakabeka) conglom—
erate, resting unconformably upon metamorphosed, little
weathered Archean granodiorite.
The chert forms thiqly banded, white, red and black algal
structures resembling piles of inverted thimbles; red, white
and brown chert—hetnatite oolitic granules are dispersed within
Fossil microflora occur in the darker, almost
the structures.
black, variety of chert.
Note several exposures of -algal chert mounds in the area
between the road and the river bank.
1.9
Co—op store, NolaLu.
2.4
Junction, Highways 588 and 590.
17.9
Turn north on Highway 590.
Junction, Highways 590 and 17—11. Outcrop is the road cut
300 feet north of junction, west side of Highway 17—11.
STOP .2a BASAL KAKABEKA CONGLOMERATE, LOWER ALGAL CHERT SUBMEMBER
(FIG. 2).
Basal conglomerate, grading-upward into reddish, lower
algaL chert and granular chert, consists of pebbles of white
quartz, chert and jasper set in a matrix of sandy quartz
grains and minor carbonate (calcite). Near the north end oif
the outcrop, the Gunf lint Formation is in fault contact with
Archean granitic gneiss.
�-bU-
STOP 2b Road cut, west side of Highway 590, 250 feet south of junction
and 500 feet south of stop 2a.
UPPER CHERT-CARBONATE EAGlES (FIG. 2).
Orange—brown weathered, banded chert—carbonate is inter—
bedded with tuffaceous shale.
18.3
STOP .3
Entrance to kakabeka Falls Park.
Proceed over old bridge to
parking lot by Greenmantle restaurant, thence by foot to
falls rim.
UPPER TIJFFAGEOUS SHALE SUBHEMER (FIG. 2)
Kakabeka Falls drop 128 feet intp a gorge formed in
fissile, thinly bedded upper tuffaceous shale subinember
(Goodwin, 1956).
A more resistant, massive two—foot bed of thinly banded
chevt—carbonate caps the escarpment.
18.7
Access road to Ontario Hydro station. Turn right just before
Proceed to the parking lot by the
the Kakabeka Falls motel.
station, thence by foot to the west side of the plant, via a
cat—walk over the penstock pipes. Follow the riverbank for
approximately 600 feet to the spiliway cut. Beware of poison
ivy.
Be advised that permission to trespass the Hydro property
must be obtained from the plant supervisor. The spiliway
serves as a safety valve to bleed-off excess water in the
event of generator failure at the power station.
STOP 4
UPPER TUFFACEOUS SHALE SUBMENBER (FIG. 2)
The best section of upper tuffaceous shale submember is
exposed at this locality.
Pyrite—bearing chert of the upper
algal chert submember occurs at the base of the section; it
is overlain by shale containing pyrite nodules and calcareous
concretions, interbedded shale and tuff and a tap of thinly
bedded upper chert—carbonate.
One of the best exposures of "mud ball tuff" in the shale
occurs near the bottom ofthe section; the tuff is formed of
closely packed ellipsoidal structures, elongated along the
Individual ellipsoids contain small, angular fragbedding.
ments of uniform size, grouped concentrically around a larger
The remainder of the materihl comprising the
shard fragment:.
beds consists of fragments of lava in a groundmass of a green,
clay material.
(Goodwin, 1956)
�—6 P-
Note downwarping of beds on the west side of the exposure
and the fault filled with quartz—carbonate and anthraxolite.
Return to Highway 17—11 and proceed east.
19.2
Junction Highways 17-11 and 590 north.
Proceed on Highway
590 north.
29.0
Thunder Bay city limit,
the Nor'westers,
30.1
Junction, Highways 590 and 130.
37.0
Lakehead University.
38.0
Intersection, High St.
Good view of the mesa topography of
Highway 590 ends.
and Oliver Road (Highway 130)
Turn left at the traffic lights and proceed up High
Street.
38.6
STOP 5
Entrance to Hillcrest Park.
UPPER LIMESTONE MEMBER (FIG. 2)
Hillcrest Park. The park stands about 160 feet above
the level of Lake Superior and offers a panoramic view of
Thunder Bay harbour, the Sleeping Giant, the Welcome Islands,
Pie Island and the Nor'westers.
Dolomitic limestone and chert layers are exposed at the
base of the flag pole and bell.
Follow stairs to base of hill where the fragmental limestone of Goodwints upper limestone member is exposed. The
rock consists of many angular to rounded chert fragments in
a matrix of coarsely crystalline, iron—bearing carbonate,
and thin chert Interbeds. Traces of volcanic shards and frag—
ments occur in the limestone (Goodwin, 1956).
Proceed north on High Street.
40.1
Intersection with Balsam St.
40.7
Huron St., 300 feet south of Highway 17—11.
Huron St., then immediate left.
Turn left on Balsam Street.
Turn right on
�—62—
42.1
Bridge over Current River, cross bridge, turn right into
Boulevard Lake Park and proceed 0.3 miles; park on right
side of road. Traverse begins on creek bed.
STOP 6
LOWER CäERT-CAR.BONATE FACIES (FIG. 2)
The lower chert-carbonate facies is overlain by the upper
tuffaceous shale subñiember. An upstream traverse encounters
ferrugineous carbonate, interrupted by thin layers and lenses
of granular and algal chert, and dark, fissile shale. At
the beginning of the traverse, note the rounded chert lenses
showing concretionary structures, attributed to action of
Please refrain from sampling some of the better prealgae.
served structures.
Features to observe include stylolite surfaces lined
with anthraxolite, pyrite veinlets, imbrication of thin chert
layers and the striking, weathered appearance of the rock.
Under the bridge, a bed of gray, massive limestone,
enclosing pancake—like lenses of serpentine material, and
interrupted by a thin band of pyrite—bearing chert, is over—
lain by upper tuffaceous shale. Note the humrnocky upper surface of the limestone at the shale-limestone interface.
Several hundred feet north of the bridge, at the lookout,
East of the bridge, in the
a diabase sheet caps the shale.
picnic area, several well developed river terraces are preserved.
Prom bridge, proceed east along Arundel Street.
Turn left on Hodder
43.1
Intersection, Arundel St. and Hodder Ave.
Ave. at Hodder Avenue Hotel.
44.1
Highway 17—11,
44.7
Park car and
Scenic lookout. View of Thunder Bay harbour.
walk 500 feet east to roadcut, on north side of road. Exercise
extreme caution.
STOP 7
Turn right.
UPPER LiMESTONE MEMBER OVEELAIN BY DIABASE
Sill of Logan diabase overlies argillite and fragmental
The contact is gently
limestone of the upper limestone member.
undulating and visible effects of contact metamorphism are
In thin section, however, a microporphyroblastic
little evident.
texture is developed in the argillite. Pyrite is altered to
pyrrhotite.
�—63—
Note the lenticular chert patches within the limestone,
some veined with pyrrhotite, exhibiting agate textures.
Turn right.
46.1
highway BOO.
47.5
highway 17-11 (Nipigon highway).
66.1
Blende Creek. The outcrop is situated 200 feet northwest
of the highway and is accessible by a dirt road +located approximately 0.7 miles southwest of the intersection of Highway
17—11 with Highway 587.
STOP S
Turn left.
UPPER CHERT-CARBONATE FACIES (FIG. 2)
Regularly bedded upper chert-carbonate is interbedded
with thin, fissile tuffaceous shale and underlain by cross—
bedded to massive greywacke.
The severe drag folding of the chert-carbonate beds on
the northwest side of the outcrop is a manifestation of a
regional fault system
Note that chert layers are brecciated and cemented +by
A vertical fracture at the east end of the outcarbonate.
crop is filled with fragments of chert carbonate cemented
by calcite.
66.8
highway 587.
68.8
First roadcut beyond West Loon road, on northwest side of
highway.
STOP 9
EAST TACONITE FACIES, LOWER MEMBER (FIG. 2)
The exposure shows wavy-banded, hematitic greenalite
taconite, locally folded and brecciated. A thin band of
algal structures at the top of the section is correlated
with the upper algal chert fades southwest of Thunder Bay.
0.0
Intersection of highways 17—11 and 587.
on
2.3
Proceed southeast
highway 587.
Quarry on west side of highway 587.
and walk back.
Park on top of hill
�STOP 10
ROVE FORMATION
Rove shale is black, carbonaceous, and forms part of
the lower argillite unit (Morey, 1967); it contains several
large, irregular "mushroom" shaped concretions.
The concre—
tions are composed of calcite with pyrite—marcasite bands and
anthraxolite, and appear to have formed diagenetically.
Remnant shale bedding planes are evident in some concretions.
Shale beds are warped around the top and bottom of some
concretions.
Concretions are found throughout the lower
argillite, and more commonly, have a distinct ablate spheroid
shape.
Proceed southeast on Highway 587.
4.1
A large area of outcrop extends along the north side of the
C.N.R. railway tracks and Highway 587 where they parallel
Pass Lake.
STOP lla SIBLEY GROUP -
+ROVE
FORMATION
At the western end of this outcrop, a sandstone quarry
provides an excellent exposure of Sibley sandstone. In the
railway cut at the western edge of the quarry, Rove shale
is altered to a reddish colour.
This alteration affected
the Rove for several feet below its contact with the Sibley
Group.
Basal conglomerate is absent at this point but is
exposed to the east behind the small railroad house along
the siding opposite the Pass Lake station.
Clasts in the basal po1ymictic conglomerate are composed
of 93 per cent Gun! lint iron formation, 6 per cent quartz
and 1 per cent granite.
Boulders are of variable size and
angularity, and are cemented in a sandy matrix. The contact
with overlying sandstone is sharp; only a few pebbles are
found in the base of the overlying unit. The sandstone is
moderately to poorly indurated, thick bedded at the bottom
of the section, and composed of quartz, with minor chert and
feldspar, in a calcite matrix.
STOP llb
At the west end of Pass Lake, a quarry, which may be
reached by a short road leading from Highway 587 just east
of the entrance to Sibley Provincial Park, has an excellent
exposure of the contact between Rove shale and Sibley sandstone.
The contact is occupied by a thin porphyritic dia—
base sheet.
Sandstone beds have a few poorly developed
cross laminations and ripple marks.
Very little basal
conglomerate is present in this outcrop.
Return to Highway 587 and follow it
11—17.
back
to Highwar
�—65—
0.0
From the intersection of Highways 587 and 11—17, proceed
east toward Dorion and Nipigon.
3.3
East Loon Road
5.2
Outcrop on southeast of road.
STOP 12
SIBLEY GROUP, BRECCIATED RED MUDSTONE
This outcrop of highly brecciated conglomeratic
red mudstone probably forms either the lower part of the
limey red mudstone or upper part of the sandy red mudstone.
Balls of red mudstone and fragments of angular chart, sandstone and mudstone are cemented iii red mudstone of similar
composition, suggesting an intraclastic conglomerate. Possibly
periodic, rapid flooding off adjacent Archean highlands caused
chaotic re—distribution of partially consolidated muds. S.ich
conglomerates are common along the western margin of, Sibley
outcrop and are generally lenticular in shape. On the eastern
margin of Sibley outcrop brecciation is less chaotic.
Continue east on Highway 17—11.
14.3
Note outcrops of brecciated red mudstone.
38.4
Historical marker, west side of Highway 17—li ilear Beaver
Valley tent and trailer park.
STOP l3a RED ROCK CUESTA
This
cUesta.
stop provides a panoramic view of the Red Rock
Diabase forms a cap on the "red rock" of Sibley mud--
stone. The colour is due to less than 2 per cent hematite
which coats clay, feldspar and carbonate grains.
Progeed to the next major road—cut.
38.6
Road—cut.
STOP 13b DLABASE SILL CUTTING ARCHEAN ROCKS AND SIBLEY GROUP
At the north end of the road—cut, a diabase dyke leaves
Archean rocks, cuts across the Sibley section and becomes a
On the top of the road—cut a small selvage of
Logan sill.
Sibley mudstone may be seen. The chilled margin at the base
of this sill in the road cut gave a K—Ar age of 1000±140
million years (Franklin, 1970). Fractures in this sill are
�—66—
filled with pectolite and calcite. An almost complete Sibley
section is evident along this hill. Above the limey red
mudstone, a white weathering unit which forms a steep cliff
beneath the diabase,is composed of purple mudstone overlain
by limestone Unfortunately, access to these units is
difficult,
Proceed east along Highway 11—17 to the town of Nipigon.
431
STOP 14
Nipigon lookout and historical marker.
CUESTAS
This lookout provides a panoramic view of the Nipigon—
Red Rock area. Diabase capped cuestas form high flat topped
hills in the, area.
Islands in the distance are composed of
Osler basalt.
0.0
From lookout, continue east on Highway 17—11 to the 17—
11 intersection; continue on Highway 17.
69
Small outcrops of interbedded white sandstone and red sandy
mudstone are exposed in road cuts near Fire Hill.
14.0
A thick sheet of columnar—jointed diebase caps the Sibley
Group at Kama Bay.
14.5
First lookout, Kama Hill.
STOP 15
SANDY RED MUDSTONE, SIBLEY GROUP
A broad anticline of sandy red mudstone is exposed in
the prominant road cut to the north of this lookout. Sof t—
sediment deformation probably produced this structure. Three
thin diabase sheets follow bedding planes; the sills pinch
out, and locally cut across bedding at a high angle.
Proceed southeast along the highway towards the second
lookout.
Kama Hill may be cut by a northeast—trending fault
system. Movement has resulted in uplifting of the west side.
Thus the sandy red mudstone north of the first lookout,
although low in the stratigraphic section, is slightly higher
in elevation than those beds described in the next stop.
This fault cuts the hill between the "anticline" and the
first lookout.
15.3
Second (southern) lookout.
�—67—
STOP 16
In the roadcut to the north of the second lookout, the following features may be observed:
(1)
Two thin Keweenawan diabase sills, partially replaced by
carbonate, cut across the poorly developed bedding plane at
a low angle.
Finely lamiqated chert of the chert—stromatolite unit
(2)
cuts out below the lower sill. Up to six Inches of anthraxolitic
carbonate has accumulated at the base of the chert. An oily
smell may be detected when this anthraxolite is freshly broken!
Limey red mudstoneabove this unit is marked by many
(3)
cream—coloured spots, (average diameter ½ inch)! Similar
spots are evident throughout this unit, and commonly have a
siiall amount of graphite or hydrocarbon at the center.
In
thiii seçtion, the only apparent.mineralogical change in the
spots is the lack of hematite coa4ing on clay and carbonate
grains.
(4)
Irregular, flame—shaped, bleached zones follow fractures
and bedding plane cleavage in the red lintey mudstone. Leaching
of hematite, and destruction of clay minerals and feldspar
has occurred along the fractures!
Above the road cut and overlying talus slope, the purple
(5)
mudstone crops out.
It is more highly fissile,a4 cokltains
approximately 4 per cent hematite, which coats.vexy fine
.grained corrensite and microcline, and forms blades of spec—
ularite in tiny vugs. Bleaching along fractures is common in
this rock!
End of Trip
For anyone interested in a more complete view of the Sibley Group,
two additional areas should be visited.
(1)
From Rossport, a boat trip to Quarry Channel and Wilson
Islands, which lie one to two miles off shore, will allow the visitor
to see an almost complete section of Sibley rocks! Op Quarry Island,
Rove shale is overlain by a thick section of Sibley sandstone. Here,
crossbeds and ripple marks are abundant.
On Channel Island, the upper part of the sandston unit, sandy
The latter is disconformably over—
red muçistone units are all exposed.
lain by Osler volcanic rocks.
The stromatolites near Disraeli Lake may be reachdd by follow(2)
ing the Armstrong road noflhfrow Hurkett for 21.6 m.iles, to the Disraeli
Lake road, which connects the Armstrong road with the Spruce River road
�—68—
800). Follow the Disraeli Lake road west for 222 miles past
Proceed
Shillabeer and Seagull creeks to the Disraeli campground road.
for 3 of a mile beyond this, to the first bu8h road leading •north.
Blocks of stroniatolite are strewn
Follow this road for two miles.
Stromatolite blocks are common
along side the road for some distance.
throughout the Disraeli area, and may be found in outcrop and float
along most of the bush roads.
(Hwy.
�—69—
ThE BEARDMORE-GERALDTON BELT
May 6 and 9, 1970
Prepared by
W. 0. Mackasey, Ontario Department of Nines, Toronto
Published by permission of the Chief Geologist,
Ontario Department of Mines
�—71—
Guide to Sturgeon River Metavolcanic—Metasedirnentary
Formations in the Beardmore—Geraldton area
INTRODUCTION
This field trip is a one—day excursion to illustrate •the
stratigraphy and structure of an Early Precambrian metavolcanic—
metasedimentary sequence in the Beardmore—Geraldton area (Fig. 1),
120 miles northeast of Thunder Bay.
Late Precambrian sedimentary
rocks and diabase sheets will also be examined. The area is part
of an east—trending metavolcanic—metasedimentary belt that is at
least 60 miles long and is bounded by younger granitic batholiths
except on the west where it is covered by Lake Nipigon and by
Late Precambrian diabase sheets.
The Mineral potential of the region has been studied since
the turn of the century; the first memoir of the Geological Surveyof Canada described the geology and mineral deposits of the
t1Nipigon Basin" (Wilson, 1910). iron was the magnet which attracted
most of the early prospectors, but the discovery of gold in 1925
near the present town of Eeardmore established the area as a major
gold camp. Many gold mines were in operation in the late 1930's,
but several of the smaller ones closed down with the entry of the
United States into the Second World War. Major producers were the
Leitch, Little Long Lac, Hard Rock Consolidated Mosher and MacLeod—
Cockshut Mines. Macleod—Mosher Cold Mines Limited is the only mine
Interest in iron, pyrite ,and base
still operating in the area.
metal sulphide deposits is continuing.
The' pulp and paper industry has played a m4jor role in the
economy ot the area in recent years, while tourism and commercial
fishing are also important industries.
Many of the Stops for the field trip were suggested by Dr.
Discussions with Dr. L. D Ayres, and his review of
E. G. Pye.
Mr. S. Spivak, Lakehead
the paper, are greatly appreciated
University, drafted the figures.
GENERAL GEQLUGY
Regional Setting
The metavolcanic—metasedimentary sequence is part of the Early
Precambrian Superior Province of the Canadian Shield and occurs
along the boundary between two major east—trending, lithologic and
structural units of the Superior Province. These are the northern
Keewatin belt composed piedominantly of metavolcanic and granitic
rocks (Goodwin, 1966)and ametsedimentary—granitic complex, termed
�—72—
the Quetico belt by Stockwell (1964). The relationship between
these two belts has been considered in recent papers by Goodwin
(1968), Kalliokoski (1968) and Ayres (1969, 1970). Goodwin and
Kalliokoski postulate that the Keewatin belt is older than the
Quetico belt while Ayres suggested that Quetico rocks are over—
lain by those of the Keewatin belt.
Early Precambrian Metavolcanic and Metasedimentar"T Rocks
1.
Lithologies:
A — Metasediments
Metasedimentary rocks form two distinct lithologic groups:
a thick sequence of relatively uniform greywacke, siltstone, and
argillite that is predominantly within the Quetico belt; and a
thinner sequence more variable and coarser—grained of conglomerate,
greywacke, argillite and iron formation that isinterlayered with
metavolcanic formations of the Keewatin belt. The finer—grained
metasediments within the Quetico belt and the southern part of the
Keewatin belt have been tentatively correlated with the Couchiching
formation by many authors (liorwood and Pye, 1955;
Macdonald, 1942;
Pye, 1952).
The coarser grained metasediments within the Keewatin
belt form part of the Windigokan series of Tanton (1921).
B —
Metavolcanics
The metavolcanic rocks in the southern part of the area are
predominantly maf Ic to intermediate, massive, pillowed and amygdaloidal
flows.
In the northwestern part of the belt, however, intermediate to
felsic volcanic breccias and flows are abundant.
2.
Stratigraphic Relationships:
Reconstruction of the stratigraphy is difficult because of
paucity of good exposure along contacts, deformation by folding and
faulting, and interfingering of the various units.
In the southern part of the area the finer—grained relatively
un:iform metasediments (Couchiching) are overlain in most cases by
the coarser—grained lithologically heterogeneous
m?tasediments (Windigokan). Both of these units thin northward
and interfinger the metavolcanic sequence.
The finer—grained metasedimentary unit contains a thin but
laterally extensive mafic metavolcanic unit that defines the boundary between the Quetico and Keewatin belts. Metasediments above
and below this metavolcanic unit are lithologically similar (Peach,
1951;
Mackasey, 1970).
Metasedimepts above the metavolcanic unit
are part of PyeTs (1952) group B defined in the eastern part of the
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ABITIBI BELT —ø.j-
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LEGEND
FINE
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AND
METAGREY WACKE
FELSIC
METAVOLCANICS
MAFIC
METAVOLCANICS
METASILT STONE
AND
METACONGLOMERATE
FIELD TRW STOP
APPROXIMATE
Figure 2.
SCALE
IN
MILES
After AYRES
I
1969
biagrammatic cross-section showing relationship between
Abitibi, Quetico, and Keewatin belts. Section through
Abitibi belt approximately corresponds to JackfishMiddleton area (Walker, 1967); section through
Keewatin belt approximately corresponds to Little Long
Lac area (Pye, 1952).
�—73—
belt.
Near Geraldton the finer—grained metasediments (Pye's group B)
are disconformably overlain by conglomerate (Pye, 1952)\which is
the lowermost unit of the upper metasedimentary sequenc (Windigokan
or group A).
The same general lithological changes havd been observed in the Beardmore area (Mackasey, 1969) but disconformble relationships have not been recognized.
A mafic to intermediate volcanic unit overlies the upper (Wind—
igokan) metagediments in the Beardrnore area.
•3,.
Origin
The metasediments in the Beardmore—Geraldton belt thin and
become coarser grained to the north.
The metavolcanic rocks on the
oiher hand, are thickest in the northern part of the belt and thin
southward (Bruce, 1937; Macdonald 1942, 1943).
Ayres (L969) suggested that the metavolcanic rocks of the Beard—
more—Geraldton area were part of an east—trending metavolcanic arc
that is now represented by the Keewatin belt. This arc developed
in an older sedimentary basin within which metasediments of the
Quetico belt were deposited Volcanism commenced with subaqueous
extrusion of mafic to intermediate flows that built up submarine
shield volcanoes. The flows interfinger southward with the metasediments of the basin.
Later felsic pyroclastic volcanism built
subaqueous to subaerial cones on top of the older mafic shield volcanoes, The change in sedimentation from relatively uniform fine—
grained sand and silt to more heterogeneous, coarser grained gravel,
sand, and silt corresponds to the initiation of major felsic
volcanism and the emergence of the volcanoes above sea level. (Ayres,
1969)
The coarser—grained metasediments of the upper metasedimentary
formations contain abundant clasts of felsic to intermediate volcanic
rocks.
Figure 2 is a diagrammatic cross—section (after Ayres, 1969),
showing the interfingerlng relationships existing between rqcks of
the Keewatin and Quetico belts.
Igneous Activity and Regional Metamorphism
The metavolcanic—metasedimentary sequence has been intrudad
by large felsic batholiths ranging in composition from granitic
gneiss to quartz diorite. These batholiths form the north and
south boundaries of the Beardmore—Geraldton belt.
Relatively
small lenticular bodies of mafic intrusives occur in the central
part of the belt.
�—74—
Most of the metavolcanic—metasedimentary sequence has been
metamorphosed to greenschist facies but metamorphic grade increases
southward within the Quetico belt (Macdonald, 1942; Peach, 1951).
Structure
The early Precambrian metavolcanic—metasedimentary sequence
has been isoclinally folded along east—trending axes. Detailed
work by Elorwood and Pye (1955) and Pye (1952), based on surface
and subsurface mapping and geophysical data, outlined the style
bf folding in the Geraldton area.
Several prominent east—trending faults have been recognized.
The Paint Lake fault is a major structural discontinuity in the
Beardmore area and marks a change in both lithology and structural
style.
South of the fault, interbedded metasediments and mafic
metavolcanic flows are folded along east—trending axes, but to
the north, intermediate to felsic pyroclastic rocks predominate
and fold axes trend north and northwest.
Late Precambrian Rocks
Relatively flat—lying sedimentary and volcanic rocks uncon—
formably overlie Early Precambrian rocks in many places along the
north shore of Lake Superior. Rare exposures of conglomerate,
sandstone, shale, and dolomite of the Sibley Group are present in
the western part of the Beardmore—Geraldton area near Lake Nipigon.
Keweenawan diabase forms north—trending dikes throughout the
Beardmore—Geraldton area and flat—lying sheets near Lake Nipigon.
A diabase sheet, 400 to 650 feet thick forms a cuesta just east of
Beardmore. The sheet dips gently westward and at the Leitch Gold
Mine, four miles west of Beardmore is 1871 feet below surface
(Benedict and Titcomb, 1948; Ferguson, 1967).
Porphyritic diabase
dikes, locally known as "Greenspar porphyry" are thought to be
older than the sheets and equigranular dikes.
Late faulting has disrupted the Keweenawan diabase sheets and
dikes and probably represents reactivation of older faults.
Pleistocene
Thick deposits of sand and gravel are present throughout the
belt and in some areas outcrop is scarce. Spillway channels, and
deltaic sand and valley train deposits have been outlined by Zoltai
(1965).
Wave—cut terraces and sand dunes are found near Lake
Nipigon.
ECONOMIC GEOLOGX
Concentrations of gold, silver, iron, copper, nickel, molybdenum,
�—75—
pyrite, zinc, lead, tungsten, sand and gravel are present within
the Beardmore—Geraldton belt.
Gold and Silver
The Northern Empire Nine (near Beardmore), which began operation in March 1934, was the first producer in the region. By
1940, 11 mines were in operation.
Today, however, MacLeod—Mosher
Mines Limited, near Geraldton, is the sole producer.
The gold deposits, which contain minor silver, were classified
by Horwood (1948) into four types:
1.
Simple fractures filled by
quartz veins, 2.
Shear or breccia zones containLng both quartz
and sulphides, 3. Fracture zones containing quartz stringers,
and 4.
Fracture zones containing massive pyrite.
Most of the gold deposits occur in metasediments of the upper
(group A or Windigokan) formation but gold mineralization is also
found in the lower metasedimencary formation, in metavolcanic rocks,
in early felsic and mafic intrusive rocks, and along the contacts
between different lithologic units,
Iron.
Iron deposits in the belt are interbedded with clastic meta—
sedimentary rocks and are composed of interlayered hematite and/
or magnetite with greywacke and argillite and, in places, jasper,
chart and iron silicates.
Sulphides
Chalcopyrite, pyrite, sphalerite, pyrrhotite, and galena
occur in fracture—filling quartz veins and in shear zones. Many
of the known occurrences are in the metavolcanic rocks north of
the Paint Lake Fault. Nolybdenite occurs near the west end of
the belt in quartz veins and is also disseminated with chalcopyrité
in altered quartz diorite Copper and nickel sulphides are associated wicha gabbroic intrusion in Elmhirst Township.
A brecciated pyritic iron formation at least 2½ miles long
within metavolcanic rocks in Summers Township has been explored
for its sulphur contentS
Other Commodities
Ninor scheelite was recovered from the gold ores of tUe tittle
Long Lac Nine during the Second World War (Pye, 1952).
Sand and gravel deposits have been used in highway and railroad construction.
�—76—
SELECTED REFERENCES
Anonymous,
1965;
Ayres, L. D. 1969;
Longlac, Ontario; Ontario Department Mines,
Geol. Survey. Canada. Aeromagnetic series,
Map 7102 G.
Early Precambrian stratigraphy of part of
Lake Superior Provincial Park, Ontario,
Canada, and its implications for the origin
of the Superior Province; Unpublished Ph.D.
thesis, Princeton University, 399 pages.
Synthesis of Early Precambrian stratigraphy
north of Lake Superior (abstract); see
this volume.
Benedict, P. C. &
Titcombe, J. A. 1948;
Bruce, E. L., 1935;
1937;
The Northern Empire Mine; in Structural
Geology of Canadian Ore Deposits; C.I.M.M.,
p. 389—399.
Little Long Lac gold area; Ontario Depart—j
1935, 6Op.
ment Nines, v.44, pt.3,
The eastern part of the Sturgeon River area;
Ontario Department Mines, v.45, pt.2, 1936,
p.l—59.
Carlisle, D., 1963;
Pillow breccias and their aquagene tuffs,
Quadra Island, British Columbia; Jour.
Geol., v.71, p.48—71.
Ferguson, S. A., 1967;
Leitch Gold Nines Limited,. surface plan of
eastern part of property, parts of Eva and
Summers Townships, District of Thunder Bay;
Ontario Department Mines, Geol. Map P.484.
Goodwin, A. N., 1966;
Archaean protocontinental growth and mineralization; Can. Mm. Jour., v.87, No. 5,
p • 57—60.
1968;
Henderson, J.F., 1953;
Henderson, J.F., &
Brown, I.D., 1966;
Evolution of the Canadian Shield; Proc.
Geol. Assoc. Canada, v.19, p.1—14.
On the formation of pillow lavas and breccias;
Trans. Roy. Soc. Canada, v.47, ser. III,
Sec. 4, p.23—32.
Geology and structure of the Yellowknife
greenstone belt, District of Mackenzie;
Geol. Surv. Canada, Bull. 141, 87 p.
�—77-.
Horwood, H, C., 1948;
General structural relationships of ore
deposits in the Little Long Lac—Sturgeon
River area; in Structural Geology of
Canadian Ore Deposits; C.IM.M.
Horwood, H. C., &
Pye, E. C., 1955;
Geology of Ashmore Township; Ontario
Department Mines, Vol. 60, Pt. 5, 1951,
lOSp.
Kalliokoski, J., 1968;
Structural features and some metallogenic
patterns in the southern part of the
Superior Province,
Canada;
Can. Jour.
Earth Sd., v.5, p.ll99—l208.
Laird, H. C., 1937;-
The western part of the Sturgeon River area;
Ontario Department Mines, v.45, pt. 2,
1936, p.60—117.
Langford, C..
B., 1929;
Macdonald, R. D., 1942;
Geology at the Beardmore—Nezak Gold area;
Ontario Department Mines, Vol. 37, pt.4,
1928, p.83—108.
Geology of the Kenogamisis River area;
Ontario Department Mines, v.49, pt.7, 1940,
p. 12—28.
1943;
Geology of the Hutchison Lake area; Ontario
Department Mines, v. 50, Pt. 3, 1941, 2lp.
Mackasey, W. 0., 1968—
Preliminary Maps of District of Thunder Bay
Ontario Department Mines
Dorothea Tp.
P479
196S
Sandra Tp.
P480
1968
Irwin Tp.
P481
1968
Walters Tp.
1969
E539
Leduc Tp.
P540
1969
Eva Tp.
(in press)
Summers Tp.
(in press)
1970;
Peach, P. A., 1951;
PrelimInary report on the'geology of the
Blaclcwater—Beardmore area;
Ontario Department Mines, Prel. Rept. 1951—7, 6p.
Petti}ohn, F. J., 1943; Archean sedimentation; Geol. Soc. America
Bull., v.54, p.925—972.
Pye, E G., 1952;
Geology of Errington Township, Little Long
Lac area;
Ontario Department Mines, v.60,
pt. 6, 1951, l4Op.
Pye, E.
Tashota--Geraldton sheet;
Mines, Map 21102.
C..
1952, &
Harris, F. R., Fenwick
-K. C., & Baillie, J.,
1966;
Ontario Department
�—78—
Stockwell, C. II., 1964; Fourth report on structural provinces,
orogenies, and time—classification of
rocks of the Canadian Precambrian Shield,
in Age determinations and geological studies,
pt. II, geological studies; Geol. Surv.
Canada, Pap. 64—17 (pt.II), p.1—21.
Tanton, T. L., 1921;
Explored routes in a belt traversed by the
Canadian National Railway between Long Lac
and Nipigon; Cecil. Survey, Canada, Sum.,
Rept., 1917, pt. E. p.1—6.
Tyson, A. E., 1945;
Report on gold belts in the Little Longlac—
Sturgeon River District; Can. Mining Jour.,
Vol. 66, no.12, p.839—850.
Walker, J.W.R., 1967;
Geology of the Jackfish—Middleton area;
Ontario Department Mines, Geol. Rept. 50,
41 p.
Wilson, A. C. W., 1910; Geology of the Nipigon Basin;
Can., Memoir 1.
Zoltai, S.C., 1965;
Ceol. Survey
Surficial Geology, Thunder Bay District;
Ontario Department Lands and Forests,
Map 5 265.
�—79—
FIELD TRIP
The
starting
belt can
exposure
field trip has been designed as a one—day excursion
from Geraldton, where some of the oldest rocks of the
be viewed, and finishing south of Beardmore at an
of the younger, Sibley Group rocks.,
A cross—section of the belt, made by traversing north on
secondary Highway 801 in Walters Township (near Jellicoe), has
been chosen to show the variety of metasedimentary and meta—
volcanic rocks types. Although some of the exposures along the
highway are relatively small, larger outcrops occur along strike
and, in &ome cases, can be reached by means of trails and/or boat
The tour continues west to Beardinore, the Leitch Gold Mine
area, and Lake Nipigon to examine Keweenawan diabase exposures,
folded iron—rich metasediments, and vplcanic structures
Emphasis has been placed on the viewing of megascopic features
and field relationships.
ROUTE
The Road Log has been set—up to enable use by others at a
later date.
I
The
Location of all Stops are shown on map in Figure 1.
relative position of some Stops has also been located on the
cross—section in Figure 2.
Time limitations may not allow viewing ofall Stops listed.
Some stops are intended for viewing frrom the bus only.
Conservation of Outcrop
Several groups will be making this tour in conjunction with
the 1970 Lake Superior Institute, and possibly on an individual
basis at a later date. Care should be taken to preserve the more
delicate features when collecting specimens, making hardness tests,
etc.
�—80—
DESCRIPTION OF STOPS
ae
0.0
Leave junction of Highways 11 and 584 (south of Geraldton).
Head west on Highway 11 (Trans Canada Route).
2.5
Turn right and leav.e Ejighway 11.
0.0
Head northeast on gravel road.
0.6
South side of road under power line.
STOP 1
This outcrop consists of fine grained clastic sediments
with interbedded conglomerate and iron formation.
Porphyry similar to that associated with the nearby gold
deposits can be found on the north side of the exposure.
Drag folds and crenulations reflect the regional, structure.
Note stretched pebbles, gentle plunges of crenulations,
and quartz veining.
Backtrack to Highway 11.
0.0
Junction to Highway 11 and gravel road.
Highway 11.
4.0
South side of Highway 11 about 400 feet west of Magnet
Walk south on old bush road for about 400 feet
then turn west (right) aht old headframe timbers and
continue for approximately 300 feet to outcrop area.
Head west on
Creek.
S
27.1
This marks the location of the disconformity separating
group A and group B sediments as outlined by Pye (1952).
The thin bedded, fine grained clastics of group B
(lithologically similai to the Quetico metasediments) are
overlain by Timiskaming—type conglomerate. See Pye (1952, P17)
for photograph of lichen—free outcrop.
General store at Jellicoe (Rock and mineral dealer)
30.8
North side of Highway 11 near bush road.
STOP 3
33.0
Road cut of Timiskaming—type greywacke succession sediments
with well developed graded bedding. These sediments form
part of the "Windigokan series" as mapped by Tanton in 1917.
Junction of Highways 11 and 801,
�—81—
G.0
Head north on Highway 801 (gravel).
1.2
Road cut at crest of ridge.
STOP 4
This stop illustrates the thin bedded aspect of the fine—
Bedding is
grained "black slate" sediments in the area.
more easily recognized on the weathered surface along the
top of the road •cut.
1.4
Outcrops on the north side of the road, approximately 800
feet northwest, display well bedded argillite, siltstone
and greywacke with thin iron—rich layers. The magnetic
expression of this horizon can be traced for several miles
west along strike, (see O.DM.—G.S.C. Map 7102G, 1965).
2.4
North end of road cut on east side of Highway 801.
STOP 5
2.8
Fine grained green lavawith jasper amygdules. Breccia
fragments are visible on weathered surface of outcrop.
On Highway 801, north and south of the gate to Pasha Lake
Lodge.
STOP 6
These relatively small exposures serve to illustrate facies
changes in the sedimentary rocks.
The southern exposure (broken outcrop) displays the
blocky, massive nature of the sandstones in the area.
The northern exposure is typical "Windigokan" conglomerate.
klthough jasper pebbles are readily apparent in the
conglomerate, pebble counts indicate that jasper is only
a minor constituent.
These two rock units can be traced for several miles
along strike.
4.3
STOP 7
The road cut at top of ridge.
Massive mafic lava typical of the area. Note epidotic
alteration and minor copper mineralization.
The disrupted banded and massive cherty horizons present
in this outcrop area can be found at several locations along
stike, and are thought to be the result of fumerolic activity.
5.6
West end of Paint Lake.
�—82—
STOP 8
6.2
STOP 9
This lineament can be traced for
(Paint Lake Fault).
several miles along strike and is considered a major
Pebbles and boulders in the sedimentary
fault zone,
rocks on the south side of the fault have undergone
marked plastic deformation.
Road cut at "5" turn on east side of Highway 801.
Stops 9 and 10 serve to illustrate the fragmental character of the voloanic rocks north of the Paint Lake Fault.
The weathered surface at the south end of the road
cut reveals the agglomeratic nature of these volcanic
rocks.
The irregular and feathery edges of some fragments
suggest that the pyroclastic material was in a plastic
condition when deposited,
Note:
outcrop.
69
STOP 10
Please do not damage the south part of the
Outcrop on the east side of Highway 801.
Volcanic breccia containing Ttcigar_shaped?t tapered frag—
merits up to six inches long.
This marks the last stop of the cross—section on
Highway 801. Now backtrack to Higway 11.
0.0
Junction of Highways 11 and .801.
Head west on Highway 11.
12.0
STOP 11
14.7
Highway 11 passes through a wind
gap in a north trending cuesta.
The cuesta is formed
by a west dipping diabase sheet which intrudes the
Archean rocks.
Junction of Highways 11 and 580.
0.0
Turn right and coptinue on Highway 580.
west to Lake Nipigon).
4.4
Turn right at intersection and head northwest along gravel
road entering Leitch Mine area.
4.5
Outcrop ridge approximately 200 feet south of gravel road,
Scattered outcrops to north of road.
(This road heads
�—83--
STOP 12
This stop illustrates tight drag folding in a unit composed
of interbedded fine grained clastic sediments, jasper, and
hematite—rnagnetite layers.
Note If collecting specimens, please do not mar the
the crenulated section of the southern exposure.
Most of the "mineral showings" near the mine have ben
covered with waste rock from underground workings.
Keep away from fenced off areas.
Continue west on
(Highway can be reached by following service
Highway 580.
road, or by backtracking).
6.4
Lake Nipigon (Poplar Lodge) and end of Highway 580
0.0
Head north (right turn) along gravel road. Peninsula near
large red—stained cottage.
(Note: road conditions may
require leaving vehicle up to 1000 feet south of here).
STOP 13
ExcelJent exposures of pillow lava, anygdaloidal lava an4
volcanic breccia can be found along the shore in this
vicinity, and on the nearby islands.
Pillow breccia may be observed along the waterline
of the northern tip of the peninsula. Here well packed
pillow lava grades into breccia containing isolatedpillows.
This occurrence is similar to pillow breccia described
by Henderson (1953), Henderson and Brown (1966) and
Carlisle (1963)
Now return to Highway 11
0.0
Junction of Highways 11 and 580.
11 (cross Blackwater River).
0.8
Turn east (left) off. Highway 11 and follow gravel road
(Empire Mine Road). Cross railway track and continue
Head south on Highway
east.
ii
STOP 14
Power line. Examine exposures along power line clearing
for approximately 1200 feet south of road.
Footpath
crosses some of the best exposures.
This Stop illustrates age relationships between two of
the Proterozoic diabase intrusives, as well as their
lithological differences.
�-84—
Outcrops near the road are of a wide, north striking,
porphyritic diabase dike that closely resembles Matachewan
diabase.
The altered green feldspar phenocrysts in the
dike have given rise to the local term "Greenspar porphyry".
Faulted offsets of what is believed to be the same dike,
can be followed for more than ten miles to the north.
A contact between porphyritic diabase and younger
massive diabase is exposed on the first main ridge south
The younger diabase is believed to be a
of the road.
part of the same diabase sheet seefl at STOP 11.
Inclusions of foliated mafic lava and rounded to
angular fragments of granitic material and quartz can be
observed further south along the footpath.
Return to Highway 11 and enter Beardmore.
0.0
Leave Beardmore and head south on Highway 11.
count begin at railway crossing.
8.6
Road cut on east side of Highway 11.
STOP 15
Mileage
This stop demonstrates the unconformable relationship
existing between the Proterozoic strata of the region and
the underlying Archean rocks.
Pink sandstone of the Sibley Group rests with angular
unconformity on an eroded Quetico metasediment surface.
Fragments of the underlying rock can be found suspended in
what is a possible paleosol or limestone layer along the
unconformity.
the pink colour of the sandstone is caused by the
presence of approximately 0J% hematite.
(3. M. Franklin,
personal communication).
�—85—
THE PORT COLOWELL ALKALI COMPLEX
May 9, 1970
Prepared by
F. PUSKAS*
*present
address:
The International Nickel Company of Canada Ltd.,
Copper Cliff, Ontario.
�—87—
Guide to the Port Coldwell alkalic complex
INTRODUCTION:
The Port Coldwell Alkali Massif (Fig. 1) is located within
an Archean volcanic—sedimentary belt extending along the North
shore of Lake Superior near Marathon. Previous work on the
complex consists of reconnaissence work by Kerr (1910), detailed
mapping by Tuominen in 1958—1959 (O.D.M. Prelim. Map P 114) and
by Puskas in 1960 (O.D.M. Prelim. Map P 114, revised). The
the
western contact of the complex wag mapped by Walker (1956);
easter-n contact by Thomson (1931) and Milne (1964).
The present study was largely carried out by the writer
and associates while employed by the Ontario Department of Mines.
The author wishes to express his thanks to Professor Henri Loubat
of Lakehead University and Clarence Kustra, Ontario Department
of Mines, Resident Geologist, for their constant interest and
co—operationh
S. Spivak drafted the diagrams.
FIELD AND GENETIC RELATIONSHIPS
The Port Coldwell Alkali Massif (Fig. 1) lies within the
eugeosynclinal portion of an Archean volcanosedimentary belt,
approximately 18 miles wide and extending westward from White
Lake, along the north shore of Lake Superior.
The volcanosediments have been tightly folded in a N 70°E
less important, more northerly trending, structures
direction;
may be attributed to cross—folding.
The Archean rocks have been successively intruded by sill—
like bodies of basic and ultrabasic composition, granitoids,
dikes of diabasic composition, and lastly by the Port Coldwell
Alkali Massif.
The Alkali Massif is a lopolith (Puskas, 1964; Corbett,
circular in plan and approximately 580 sq. kilometers in
The Massif is considered to typify the so—called (Benson)
Laccomorphic class of emplacements.
1968)
area.
The rocks of the massif can be divided into two groups
However,
called here the Main Group and the Secondary Group.
in common with many intrusions of this type the long crystal—
lisation history has resulted in numerous complex and sometimes
confusing cross cutting relationships.
The Main Group is composed of gabbros, the oldest and
more-peripherally located rock—type Map unit 2), and laurvikites
Both the gabbros and laurvikites can exhibit
(Map unit 3).
rhythmic layering which dips inward at moderate angles. The
�—88—
laurvikites highest in the group are commonly porphyritic.
Several zones are recognized within the main group.
Upper
Lower
Inner
Inner
Outer
Zone
Zone
Border Zone 'B'
Border Zone 'A'
Border Zone
massive
layered
layered
massive
chilled
laurvikite
laurvikite
gabbro
gabbro
gabbro
The Secondary Group is composed of an older, saturated series
which includes syenodiorites (Map Unit 4) and nordmarkites (Map
Unit 5) and a younger, undersaturated, series with several varieties
of feldspathoidal syeniie (Map Unit 6). Generally, within this group,
rocks comprising the saturated series are peripheral to the felds—
pathoidal syenites.
Except for the feldspathoidal syenites, which are layered at
some localities, the rocks Of the Secondary Group are massive and
apparently structureless.
The Secondary Group is characteristically associated with
xenolithic bodies. Although widespread, these bodies are thought
to belong to one large unit, the so—called Coubran Lake meta—
volcanic cap. Common variants, generally gradational one to the
other, include aphanitic amygdular and diabasic volcanics.
The
'cap' rocks and the rocks of the Secondary Group are preferentially concentrated in that portion of the massif which is west
of Wolf Camp Lake. (ref to Stop 3, Fig 4).
It is noted that the 'cap' appears to be 'free—floating'
in the north and 'attached' in the southern part1
These and other relationships suggest a near—roof
situation of the present level of exposure.
The Port Coldwell magma, which apparently contained solid
plagioclase fledspar, was emplaced (1) from a probable source
located to the SSW, (2) by a process of doming, stoping,
and
forceful injection, and (3) at P—T conditions sufficient to gener
ate a thermal aureole within the pyroxene—hornfels facies.
The rocks of the aureole show rheomorphic veining, and ana—
texites which commonly exhibit flow layering or schlieren trending
parallel to the immediate gabbro contact. Areas of more intense
migma development were probably controlled by the distribution
pattern of favourable.lithologies as modified by folding, faulting
and emplacement characteristics of the massif. The coincidence
of numerous geological contacts with lineaments is compatable with
a magma cooling history involving doming and fissuring, with
probable block subsidence, and the 'near—roof' level of Massif
exposure.
�AGE RELATIONSHIPS
The volcanosedimentary assemblage was intruded by various
bodies which are as follows (oldest first): — sill—like bodies
of basics and ultrabasics, granitoids, dikes of diabase, and the
Port Coldwell Alkali Massif.
The diabase dikes are typical of those reported throughout
the Superior Province and which have been dated at approximately
1700 m.y.
The author originally thought the Port Coidwell Alkali Massif
to have been intruded in the northwest by a younger granitoid, the
so—called Little Pic River batholith (Puskas, 1964). But the
observed field relations are better explained by assuming the
formation of a palingenetic magma from an overlying granite.
Minerals front the massif give ages of 1065 m.y. (K—Ar, Rb—Sr
ages on biotites from nepheline syenites from Stop 5) and 1225 m.y.
(Rb—Sr age on perthite from the laurvikite)(Fairbairn et al, 1959).
In view of the widespread contamination of the magma further work
is necessary. However, the massif is similar in age to the widespread Keweenawan intrusives of the Superior Basin (1000± myra)
and may be from the same parental magma.
ECONOMIC GEOLOGY
The Port Coldwell Alkali Massif has been prospected for iron,
base metals, radioactive minerals, nepheline, perthitic feldspar,
and building stone.
To date there has been no ore production.
Iron
The exposed gahbros along the periphery have been investigated
for iron and base metals.
The iron occurs as ilmenomagmetite—enriched layers or bodies,
one inch to 70 feet wide, predominantly conformable to the layering
of the adjacent gabbros.
The high titanium content, 5 to 8 percent,
and sub—marginal tonnages make the deposits uneconomic at this time.
Base Metals
Base metal investigations by various companies, including
Moneta Porcupine; Lakehead,: Denison Mines, Keevil, Anaconda, and
Conwest Exploration, have concentrated on the coarser grained,
massive, gabbros (Inner Border zone 'A').
Stone
Small scale quarrying of both 'red' and 'black', i.e. thirk
varieties of laurvikite was begun in 1927 and continued into the
l930's on a property located approximately 2 3/4 miles north of
�—90--
Marathon and transected by the C.P.R.
Although these syenites, particularly the 'dark' varieties,
are similar to the famous laurvikites from Norway, no markets
could be secured and maintained.
Nçpheline
Denison Mines Limited in 1960 attempted to determine the
nepheline potential of the feldspathoidal syenites from two areas
However,.
located south of Highway 17 and west of Red Sucker Cove.
nepheline separation proved hard to achieve, and iron content of
the concentrate was too high, so the project was abandoned.
SELECTED REFERENCES
The following is a selected list of references pertaining to
the geological features discussed in this report:
Adams, F. P., 1900;
On the Probable Occurrence of a Large Area
of Nepheline-Bearing Rocks on the Northeast Coast of Lake Superior, Journal of
Geology, Vol. VIII, pp 322—325.
Coletnan A. P., 1898;
Port Coldwell Region, Ann. Rep. Bur. of
Mines, Ont., pp 146—149.
Coleman A. P., 1899;
Dykè Rocks near Heron Bay, Ann. Rep. Bur.
of Mines, Ont., pp 172—174.
Coleman A. P., 1899;
A new Analcite Rock from Lake Superior,
Journal of Geology, Vol. VII, pp 431—436.
Coleman A. 7., 1900;
Heronite or Analcite Tinguaite, Ann. Rep.
Bur. of Mines, Ont., pp 186—191.
Coleman A. P., 1902;
Syenites near Port Coldwell, Ann. Rep. Bur.
of Mines, Ont., pp 208—213.
Collins & Camsell, 1913; The Nepheline and Alkali Syenites of the
Port Coldwell Area, Transcontinental
Excursion Cl, Toronto to Victoria and
return via Canadian Pacific and Canadian
Northern Railways, Guide Book No. 8, Part 1,
pp 16—24.
Corbett,
J., 1968;
Farrand, W. R.-,
1960;
Paper presented to I.L.S. meeting at East
Lansing.
Former Shorelines in Western and Northern
Lake Superior Basin, Unpublished Ph.D.,
dissertation, Dept. of Geology, University
of Michigan, Ann Arbor.
+
�.• ____________________
.
— .._...........LLIr,a
—91—
Fairbairn, H.
1959;
et al,
Rough, J 1.,,
Kerr, H. L.,
Age investigations of syenites from Port
Coldwell, Ontario,
Geol. Assoc. Canada,
Proc. Vol. 11, pp 141—144.
1958;
1910;
Geology of the Great Lakes, University of
Illinois Press, Urbana, Illinois, Chapter II.
Nepheline Syenites of Port Coldwell, Ann
Rep. But. of Mines, Ont.,
pp 194—232, with
map.
Logan, Sir Win. E., 1847 Report of Ptogress, G. . C.
Logan, Sir. Wm. E. 1863 Geology of Canada,
pp 29—30.
pp 80—81, 480, 647.
Mime, V. G., 1967;
Geology of Cirrus Lake—Bamoos Lake area;
Ontario Department of Mines, Report 43.
Puskas, F. P., 1964;
Geology of the Port Coldwell Area, Open
File, O.D.M. T.B.
Thomson, Jas. E., 1931; Geology of the Heron Bay Area, O.D.M.,
Vol. XL, pt 2.
Thomson, Jas. E., 1934; Unpublished Ph.D. dissertation, Department
of Geology, Wisconsin University, Madison,
Wise.
Walker, T. L., &
Parsons A. L., 1927;
lJniversity of Toronto Studies, Geol. Ser.
No. 24, pp 28—32.
Walker, 3. W. R., 1956; Geology of the Jackfish—Middleton Area,
District of Thunder Bay, Ont. O.D.M. Geol.
Cir. No. 4.
�-92—
DESCRIPTION OF STOPS
The town of Marathon is at one of the few naturally protected
harbours along this part of the North shore of Lake Superior.
An extensive sand and gravel deposit underlies the townsite
and extends eastward to Heron Bay and northward approximately 2½
miles. To the north these sand and gravel deposits are seen to
overlay
broad terrace of varved clays which trends parallel to
the present course of the Big Pie River for more than 50 miles
+
(Farrand, 1960).
There are at least six beach terraces at Marathon (Thomson,
Puskas, 1964). The highest beach is 710 feet above Mean
Sea Level or 108 feet above the present surface of Lake Superior
(Hough, 1958). The vertical interval between these beach terraces
is 5 to 45 feet. Walker (1956) states that the vertical interval
between terraces occurring 20 or more miles to the west is 5 to
10 feet.
These differences may indicate a relative increase in
the rate of post glacial isostatic adjustment to the east in dir—
ection of the Marathon area.
1934;
qae
0.0
Intersection of Highway 17 and turn off to Marathon.
Continue south east on Highway 17.
2.4
Eastern contact of Massif with country rock.
STOP 1
(Fig. 1 & 2) is a 2 mile traverse across the eastern part
of the massif beginning at the contact of gabbro and
anatexite. (Fig. 2)
Because of the close proximity of, the country rocks
to a considerable portion of the traversed gabbros, the
gabbros are highly charged with xenoliths, variably assimilated, and variably hybridized.
STOP1A EASTERN CONTACT OF MASSIF (Fig. 2).
The local contact zone between gabbro, occurring as
a topographic 'high', and anatex±tes shows the following
features;
(1)
in plan, the contact appears flexured
or arcuate.
(2)
dip relations of contact indicate 'on—
lap' by anatexite.
�—
-I-
+
I
— 'fr—s .L
0
E-E EL
rr-— n:
------2 MILES
a
LAKE
Port Coldwell Igneous Complex
SUPER/OR
Bay
OLDWELL
Pen/nsa/c
Figure 1.
-I;--—-- —,
+c
-4-\- -n—-
r_ -:?—_-= r.r..cjr..
c—_ z-_—= =—_:-=
--—-
+
—4-f1_nnn r+
4--- ;
2i.:
ISLAND
---
p/c
-4.-
-I-
-Lti+t
1-4- +
GROUP
SECONDARY
PlC
I
GRANITE
ROCKS
SYENITES
SYENODIORITE
NEPHELINE
PRE—COLOWELL COMPLEX
LITTLE
1:
I'
N)
(0
�—92 8 —
APPROXIMATE
Pig. Z
Contacts between dountry rock',
gabbros and laurvikites.
LiMIT OF PYROXENE —HORNFELS
ISOGRAD
�—93—
(3) 'flow—layering' exhi)bited by anatexite
are parallel to the contact and contact
irregularities.
C) presence of areas of breccia development.
These field relations, schematically illustrated in
Fig. 3, can best be explained by assuming the peripheral
development of migma ,in the country rocks surrounding
the cupola of gabbro.
Breccia development appears to be, in part, the
product of an irregular cooling history involving magma
pulsatidn followed by fissuring and intrusion of more—
peripheral areas.
Note the abundant xenoliths in the gabbro (apparently
reflecting the 'high' level of cupola exposure);
the
rheomorphic dikes of granophyre with tourmaline±prehnite
in the anatexites;
and dikes of laurvikite in the gabbros.
The laurvikite dikes commonly show;
(1)
angular inclusions of gabbro,
obviously locally derived;
(2)
contact relations indicative of
emplacement during periods of
extension;
(3)
composite appearance.
Thin âections of the anatexites show porphyroblasts of
•(in decreasing order of relative abundance);
clinopyroxene,
IC—spar, quartz, orthopyroxene (Fs 25—35), biotite, oxides,
and sulfides. l4ineralogically the anatexites lie within
the orthopyroxene clinopyroxene — plagioclase triangular
field of an ACF plot for the pyroxene—honfels fades.
Physical and/or optical alignment of some of the minerals
especially plagioclase (An20 to An40), is not uncommon.
The gabbros vary from fine to coarse grained but all
varieties are essentially anhydrous two pyroxene gabbros
with or without phenocrysts of plagioclase of (An65_70).
The medium to coarse gabbros of 'Inner Border Zone A' show.
anomalous amounts of quartz and K—spar, probably due to
assimilation.
Thin sections of the syenite dikes, generally composite,
show perthites (generally extensively exsolved, patch
perthite) with varying proportions of aegirine—augite,
riebeckite, calcite, zircon, fluorite, quartz, and oxide
(ilmenite ± magnetite). These dikes are considered to be
apophyses from the main body of laurvikite.
OO
Turn round and proceed north towards Marathon.
�—94—
STOP lB
XENOLITH-HYBRIDIZED GABBRO—BANDED GABBRO (Fig. 2)
A large, relatively inhomogeneous, xenolith of
anatexite appears to be engulfed within massive, inclusionbearing, hybridized gabbro.
Massive gabbro is overlain by gabbro with discontinuous and/or disturbed layering, and moderately well developed foliation of plagioclase. These gabbros are essentially
two pyroxene, olivine poor, bictite—oxide (magnetite present
up to 15 percent) rich, rocks.
STO? 1C
GABBROS - LAURVIKITES (Fig. 2)
Continuation of traverse northward, along Highway 17,
across layered gabbros, with zones of anatexite and intrudand layered laurvikites.
ed by dikes of laurvikite;
The gabbros show;
(1)
rhythmic (and cryptic) layering;
(2)
foliated and possibly lineated
fabric as exhibited by plagioclase
and clinopyroxene;
(3)
zones of reaction inclusions;
(4)
several ring (?) dikes, with
associated apophyses, of láurvikite.
Greater volume of dikes is indicative of the nearness
of contact with overlying laurvikites. Dike emplacement
occurred during periods of gabbro extension.
The gabbros contain pagioclase, clinopyroxene, olivine
(up to Fa75±5) with minor, but significant amounts of
ilmenomagnetite, biotite, sodic amphibole, apatite, idding—
site, sulf ides, and antigorite.
The contact between overlying, layered laurvikites
and layered gabbros appears conformable and gradadional
over a short distance.
The laurvikites show;
(1) zones of abundant xenoliths;
(2) colour variation from dark green to
red corresponding to a transition,
apparently gradational and cyclic,
from a more melanocratic, anhydrous
mineralogy, further characterized by
the presence of hematite perthite;
-
-a
�IN
I
/
LI THOLOG Y
POSTULATED
WITH
RELATIONS
ROCKS.
CUPOLA DEVELOPMENT.
Contact relations shown at Stop la
/
/
COMPOSITION
TOURMgLINE + PREHNITE.
GRANOPHYRIC
Fig. 3
(2)
GABBROIC
CHARACTERIZED 0Y
PARALLEL CONTACT
ARE COMMON.
ANATEXITES ARE
FLOW LINES, SCHLIEREN, WHICH
WITH GABBRO — DRAG FOLDS
le
'BLEACHED APPEARANCE.
(3 PRESENCE OF INCLUSIONS OF LOCAL LITHOLOGIES
AND RESTITE.
(1 PRESENCE OF RHEOMORPHIC VEINS AND DIKES
Iii
AUREOLE ROCKS
OF
ON -LAP CONTACT
COUNTRY
NOTE PRESENCE
IN
SULPHIDE
TYPICAL
OF 'BOULDERY'
GOSSAN ZONE
BEARING
Dr
GABBRO,
XENOLITHS
OF
GABBRO
TRACE OF
CUPOLA
PORTION
(2)
1N
GRAINED,
OF
OF
COMPOSITE
Stop la
---1
LAURVIKITE.
PERIPHERY
DIKES
OF
COARSER —
INCLUSIONS
PHASES.
IN
HISTORY.
AN
OF CRYSTAL —
REFLECTING
PRESENCE OF NUMEROUS
COUNTRY ROCK.
PRESENCE OF NUMEROUS
OF
HYBRIDIZED
PRESENCE
BY
DEGREE
SULPHIDES
COOLING
APPARENTLY
VARIATION
CHARACTERIZED
IRREGULAR
LINITY
GABBRO
(I) MARKED
�Fig. 4
Contact relations between xenolith and massif
a
w
(p
I
�—95—
(3)
feldspars variably foliated;
(4)
mafic schlieren, the attitude ot which
is conformable with the attitude of
layering;
(5)
2.4
0.0
gradation into more pegmatitic or
porphyritic varieties.
The laurvikites are primarily composed of perthitic
feldspar, with variable amounts of aegirine—augite, olivine
(up to Fa100), barkevikitic amphibole, biotite, iddingsite,
quartz, zircon, fluorite and calcite. Variations in
mineral compositions, and in the thermal histories of
alkali feldspars may be cyclic.
Marathon turn—off.
Continue west on+Highway 17.
2.3
STOP 2
DARK GREEN LAIJRVIKITE - LAURVIKITE PEGMATITE (Fig.
1)
These rocks aresimilar to the laurvikites from
The perthites from the pegmatites are extensively
exsolved, patch perthites, which are more sodic (Or27)
than the less exsolved, braided perthites (Or62) from
the less—pegmatitic, laurvikitic host.
Oslo.
4.7
STOP 3
CONTACT BETWEEN LAURVIKITE AND BASIC METAVOLCANIC
XENOLITH.
(Fig. 1 & 4).
This section of the highway reveals a broad exposure
of the contact phase of syenite which can be seen to grade
into more normal laurvikite.
The basic metavolcanic is basaltic in composition
and comprises a portion of the so—called Coubran Lake
metavolcanic cap.
Although more commonly amygdular in
appearance, fine grained to aphanitic phases are distributed in such a manner as to suggest the contacts are
flat lying.
The contact between the overlying basaltic cap and
the medium to coarse—grained, red coloured, hornblende—
rich syenite is generally sharp and fragmented. The
syenite, which is a hydrated equivalent of the laurvikite,
contains abundant mafic clots, stringers, wisps and
veinlets from 2 to 6 inches in size.
These 'enclaves',
which are amphibolite or syenodioritic in composition,
tend to be aligned parallel to the contact.
fL.5
STOP 4
TRA}ISITIONAL PHASE OF LAURVIKITE (Fig. 1).
To the south similar rocks reportedly (Tuominen)
�—96—
exhibit both gradational and sharp contact relations
to an overlying "syenodiorite" phase of netavolcanic
cap rock. Because of the gradational relations the
syenites
were included with the syenodiorites on the
revised map.
Thin sections show phenocrysts of alkali feldspar
(unexsolved) in a fine—grained groundmass of alkali
feldspar (highly exsolved) ophitically enclosed by
barkevikite.
Relict clinopyroxene (variety augite —
sodic augite) has been observed. Hematite staining
of feldspars is generally extensive.
This mineral assemblage is not much different from
the 'darker' varieties of porphyritic laurvikite and
likewise this rock type appears to represent a 'high'
level variety.
8.6
STOP 5
NEPHELINE SYENITE (Pig. 1, 5 & 6).
This outcrop (Fig. 5) is typical of nepheline
syenites where in contact with 'diabasic' lava. The
gross zonation within the feldspathoidal body is
generally parallel to the contact with the 'diabase'.
The diabase is variably nephelinized.
One can conclude that,
(1)
there were at least two periods of
dilation and emplacement (Fig. 61);
(2)
emplacement of feldspathoidal magma
was controlled by jointing within the
'diabase' (see Figs. 6a, 6b, 6c);
(3)
emplacements along the more vertical
joints preceded those along flats
lying joints (Fig. 6c);
(4)
where present,
the later feldspathoidal intrusions show
nepheline pseudomorphed by the zeolite
natrolite (with associated thomsonite)
which is orange in colour.
16.8
STOP 6
LAURVIKITE (Fig.
1)
'Red' contact variety of laurvikite highly charged with
inclusions of nearby 'diabase'.
18.4
STOP 7
PEGMATITE (Fig.
I & 7).
Traverse along a composite, nepheline (zeolitized)
pegmatite emplaced into gabbros (Fig. 7).
�—97—
.
;' TRAIL TO
GORDIE
a
LAKE
0
a
S
a
\
Fig. 6c
Fig. 6b
.-T-_
IS
—
a
a
0
C
0
-
:
'
:
•
0
o
-:
.
0
0
0
0
a
0
a
o
C,
0
ZEOLI TIZE D FELDSPATHOIDAL
INCLUDE
C
0
LEGEND
SYEN1TE
S
0
0
FEMAGS.
BIOTITE + BARKEVIKITE
AVENITE
WITH
0
8IOTITE + BARKEVIKITE
C
TUN NEL
BARKEVIKITE — NEPHELINE
LII
VARIABLY
NEPHELINIZED
8
SYENITE
DIABASIC
SUCKER
LAVA (Pp
a
0
COVE
NONOMARKITE
NUMEROUS INCLUSIONS
LINE AIdE NTS
OF
OIABASIC"
1/4
LAVA U)
I/B
0
SCALE
Fig. 5
Nepheline syenite —
"Diabase"
contacts.
/4 MiLE
Stop 5
�LOOKING
NORTH
LOOKING
NORTH
—
DYKE
z—...—
FGCN
D
LAVA ifl
BIOTITE + flRKEVIKITE
"DIABASIC
SYENITE WITA
VARIABLY NEPHELINIZED
NEPHE LINE
25° NE
15° DIP 50° NE
40° DIP
Stop 5
F€LDSPATHOIDAL SYENITE, FEMAGS, INCLUDE
BIOTITE + BARKEVIKITE
L
ZEOLITIZED
S
Details of nepheline syenite veins. (See Fig. S
for location).
STRIKE NW 50° DIP 55° NE
Rig. 6
OF COMPOSItrE
�Pig. 7
West contact of
CROSS
OF
DYICE
SECTION
Stop 7
�-100-
ACKNOWLEVGMENIS
Front Cover Photo,
Sibley Park, near Thunder Bay, Ontario.
Courtesy of Ontario Departn?ent of Travel & Publicity
Geological Maps.
All maps used in the field guides were modified from.
Ontario Department of Mines maps.
Maps covering the Field Trips are:Atikokan - Lakehead
Nipigon
-
Tashota
-
Schreiber
Geraldton
Port Coldwell
0DM
Map 2065
0DM
Map 2137
0DM
Map 2102
0DM
Ptelim Map 114
Mr. Sam Spivak drafted all of the diagrams except those on
pages 41 & 42. Many of these diagrams were compiled by Mr.
Spivak from several sources, and many of the originals were
rough field sketches. His patience and resourcefulness is
duly acknowledged by the editors.
The Committee would also like to acknowledge the secretarial
services of Mrs. Jean Helliwell, for so ably organizing us in
assembling the manuscript and pushing us towards the deadlines.
�ro
-
0
0
SCALE
BAY
THUNDER
2 MILES
ISLANDS
c5, WELCOME
Am LANE MOTOR HOTEL
®
SUPER/Of?
LAKE
UPTOWN MOTOR HOTEL
HOLIDAY INN INTERNATIONAL
ROYAL EDWARD HOTEL
SLEEPING GIANT MOTOR MOTEL
NOR-SHOR MOTOR HOTEL
SHOREL INE MOTOR HOTEL
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PRINCE AR THUR HOTEL
�
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Title
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Institute on Lake Superior Geology
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Institute on Lake Superior Geology: Proceedings, 1970
Description
An account of the resource
Institute on Lake Superior Geology. Lakehead University, Thunder Bay, Ontario. May 6-9, 1970.
Creator
An entity primarily responsible for making the resource
Institute on Lake Superior Geology
Date
A point or period of time associated with an event in the lifecycle of the resource
1970
Contributor
An entity responsible for making contributions to the resource
R.N. Annells
Lorne D. Ayres
J.M. Berkson
C.S. Clay
Bill Bonnichsen
W.C. Brisbin
Paul M. Clifford
I.F. Ermanovics
John C. Green
G.N. Hanson
S.S. Goldich
R. Malhotra
Mao-Yang Hsu
R.W. Hutchinson
William F. Jenks
C.W. Keighin
J.D. Mancuso
J.D. Dolence
Harold M. Mooney
Campbell Craddock
Paul R. Farnham
Stephen H. Johnson
Gary Volz
David C. Mulder
R. Oja
Richard W. Ojakangas
Z.E. Peterman
C. McA. Powell
W.F. Read
R.H. Ridler
S. Viswanathan
David H. Watkinson
John Wood
Grant M. Young
Format
The file format, physical medium, or dimensions of the resource
PDF
Language
A language of the resource
English