1127 10 13635 https://digitalcollections.lakeheadu.ca/files/original/82858b8f595b98020f0953e1a612ab90.pdf b1079fef31aa6fb4274a211f38225596 PDF Text Text �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 Eustis St., Please Publications Sales, Minnesota Minnesota Geological 1633 Eustis St. Paul, Minnesota sales tax tax where where applicable. Minnesota 55108. 55108. Price Price$5.00 $5.00 (U.S.), (U.S.), plus 496 496 sales Make Make checks payable to Minnesota Minnesota Geological Geological Survey. Survey. Printed at: Printed University of Minnesota Minnesota Minneapolis, Minnesota 55455 Minneapolis, 55455 �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 �1 tr ?fkt? \ N '\\\ III 1ri4 I —- . I - L i FL 'Lii NJI\. ------—------ .... -- :- 1111 - • 1-94 to 1m -... -~ 0 sr . F - - / IF F-r-irt r7—1 rr-i / .5 .s- IL. .. \.Jr =-T: — ... S 0 ___ :: Pa -- LJiiEijF IJ JUf r1Jc?tLTi1JA1)o 1 —.-.i[ '- ii . N CAMPUS ..- z.4 I - ,/ 4.. J _ J i V. __ I r:: .... � 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/008f2fe217dc97b3cfe51ab8334afc2d.jpg 2ea4b7fbad2ecf02dbbac8beabfaa59f 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 Cairine Budner fonds 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 Kiri Athletic Club gymnasts Subject The topic of the resource Sports Description An account of the resource Black and white photograph of Kiri athletic club men's gymnasts. Athletes are standing and kneeling on one knee posing for the photograph Date A point or period of time associated with an event in the lifecycle of the resource 1920s Contributor An entity responsible for making contributions to the resource Donor E. Takala Rights Information about rights held in and over the resource Public domain Format The file format, physical medium, or dimensions of the resource Photograph Type The nature or genre of the resource Still image Identifier An unambiguous reference to the resource within a given context PHIII-0012b (viii) scan#BUD-0033 1920s athletes gymnasts Kiri Athletic Club https://digitalcollections.lakeheadu.ca/files/original/4bb0a6fba9bbfb19e411edf5ac90c7da.jpg 4c9f76c5feea071f94ba1e12e3b21d00 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 Cairine Budner fonds 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 Jyru Athletic Club Subject The topic of the resource Sports Description An account of the resource Black and white photograph of Jyru athlete suspending a woman gymnastics with one arm Date A point or period of time associated with an event in the lifecycle of the resource 1920s Contributor An entity responsible for making contributions to the resource Donor E. Takala Rights Information about rights held in and over the resource Public domain Format The file format, physical medium, or dimensions of the resource Photograph Type The nature or genre of the resource Still image Identifier An unambiguous reference to the resource within a given context PHIII-0012b (v) scan#BUD-0032 1920's athletes gymnasts Jyru suspending https://digitalcollections.lakeheadu.ca/files/original/118f590c7256fda60e65cf070c680ac3.jpg 3b7c20810edae391420d05b01e8dc8bc 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 Cairine Budner fonds 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 Nahjus Athletic Club building gymnastic pyramid Subject The topic of the resource Sports Description An account of the resource Black and white photograph of the Nahjus athletic club men's gymnastics pyramid at the Finn Hall stage Date A point or period of time associated with an event in the lifecycle of the resource 1920s Contributor An entity responsible for making contributions to the resource Donor E. Takala Rights Information about rights held in and over the resource Public domain Format The file format, physical medium, or dimensions of the resource Photograph Type The nature or genre of the resource Still image Identifier An unambiguous reference to the resource within a given context PHIII-0012b (iv) scan#BUD-0031 1920's Finn Hall gymnastics mens' Nahjus Athletic Club pyramides https://digitalcollections.lakeheadu.ca/files/original/1fd7c945743a19048d401359e5afc5b3.jpg d6812bad613730c89410b0dd4c6037cf 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 Cairine Budner fonds 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 Mixed pyramid Jyru Athletic Club Subject The topic of the resource Sports Description An account of the resource Black and white photograph of the mixed pyramid at the Finnish Labour Temple. Athletic director Heikki Roine is at the base of the pyramid. The group is dressed in Jury uniforms for the time Rights Information about rights held in and over the resource Public domain Format The file format, physical medium, or dimensions of the resource Photograph Type The nature or genre of the resource Still image Identifier An unambiguous reference to the resource within a given context PHIII-0012b (iii) scan#BUD-0030 athletic director Finnish Labour Temple gymnasts Heikki Roine Jyru mixed pyramid https://digitalcollections.lakeheadu.ca/files/original/02ccd22010c6a26959f5b0298d72ee3e.jpg 24a3ff0b407384848e5514576f526843 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 Cairine Budner fonds 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 Kiri Athletic Club Subject The topic of the resource Sports Description An account of the resource Black and white photograph of gymnasts performing a balance routine on stage floor. Men are dressed in the Kiri uniforms for the time Date A point or period of time associated with an event in the lifecycle of the resource c1911 Contributor An entity responsible for making contributions to the resource Donor E. Takala Rights Information about rights held in and over the resource Public domain Format The file format, physical medium, or dimensions of the resource Photograph Type The nature or genre of the resource Still image Identifier An unambiguous reference to the resource within a given context PHIII-0012b (ii) scan#BUD-0029 1911 balance routine E. Takala gymnastics Kiri Athletic Club https://digitalcollections.lakeheadu.ca/files/original/48efc2050905b1fc3c6480b1dfa4bc66.jpg 0ca88ea4910c618a43ea31a815f87e5f 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 Cairine Budner fonds 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 Boy's gymnastic pyramides, Karhu Club Subject The topic of the resource Sports Description An account of the resource Black and white photograph of Karhu Club boy's gymnastic pyramides in front of Fort William Finn Hall on Robertson Street. Boys are dressed in uniforms for the time Date A point or period of time associated with an event in the lifecycle of the resource c1910 Rights Information about rights held in and over the resource Public domain Format The file format, physical medium, or dimensions of the resource Photograph Type The nature or genre of the resource Still image Identifier An unambiguous reference to the resource within a given context PHIII-0012a scan#BUD-0028 1910 Fort William Finn Hall gymnastics Karhu Club pyramides Robertson Street https://digitalcollections.lakeheadu.ca/files/original/a43721083bd00ae42788730f5cc8a7fd.jpg f57cbfcc528baeae6472713a03662438 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 Cairine Budner fonds 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 Henry Akervall with javelin Subject The topic of the resource Sports Description An account of the resource Black and white photograph of Henry Akervall, a member of the Michigan College of Mining & Technology track & field team, Houghton, Michigan. Henry is posing with the javelin in throwing position Date A point or period of time associated with an event in the lifecycle of the resource 1959 Contributor An entity responsible for making contributions to the resource Donor Henry Akervall Rights Information about rights held in and over the resource Public domain Format The file format, physical medium, or dimensions of the resource Photograph Type The nature or genre of the resource Still image Identifier An unambiguous reference to the resource within a given context PHIII-0011d (i) scan#BUD-0027 1959 athlete Henry Akervall Houghton javelin Michigan Michigan College of Mining & Technology team track & field https://digitalcollections.lakeheadu.ca/files/original/0daeff655abbb5ae9b6606fcbc8710ab.jpg 710933734bf56e519e5dec0f9b662626 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 Cairine Budner fonds 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 Pentti Hirvonen with sports trophies & awards Subject The topic of the resource Sports Description An account of the resource Black and white photograph of Pentti Hirvonen showing his trophies and awards won in competitive cross country running and track & field meets Contributor An entity responsible for making contributions to the resource Donor P. Hirvonen Rights Information about rights held in and over the resource Public domain Format The file format, physical medium, or dimensions of the resource Photograph Type The nature or genre of the resource Still image Identifier An unambiguous reference to the resource within a given context PHIII-0011d (iv) scan#BUD-0026 athlete medals Pentti Hirvonen runner track & field trophies https://digitalcollections.lakeheadu.ca/files/original/7af91dac2e421d2f8e34425df713d618.jpg 34df76497e4f566b167a1019b1c14641 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 Cairine Budner fonds 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 Ray Kotanen of Nahjus Athletic Club winning a race Subject The topic of the resource Sports Description An account of the resource Black and white photograph of Ray Kotanen member of the Nahjus Athletic Club crossing the finish line at a track & field meet Date A point or period of time associated with an event in the lifecycle of the resource 1960s Contributor An entity responsible for making contributions to the resource Donor Anttila Rights Information about rights held in and over the resource Public domain Format The file format, physical medium, or dimensions of the resource Photograph Type The nature or genre of the resource Still image Identifier An unambiguous reference to the resource within a given context PHIII-0011c (xxxvi) scan#BUD-0025 1960s athlete meet Nahjus Athletic Club race Ray Kotanen runner track & field