7 10 75 https://digitalcollections.lakeheadu.ca/files/original/03cef75d9ec3cc907fdd12d97a288082.pdf 3915f7abb5aab6dff27864b48fd34248 PDF Text Text TECHNICAL SESSIONS SESSIONS ABSTRACTS For 15TH ANNUAL INSTITUTE ON LAKE SUPERIOR SUPERIOR GEOLOGY Sponsored by DEPARTMENT OF GEOLOGY WISCONSIN STATE UNIVERSITY, UNIVERSITY, OSHKOSH, OSHKOSH, WISCONSIN May 8—9, 8-9, 1969 Wisconsj, Geo!ogsa1 VliscOnsi:l Geo'ogjr-a ~r.'" . to '" •l ,.ard ,U Naturat Hbto B:m'c,',' ,.,N <l!ural History Sr'cy 381/Minoral M;nr Po:nt RO.d uS11 RocI Madison, Wi VII 531"05 ---------------------------------~~---- ---- �15th Annual Institute Institute on Lake Superior Superior Geology Wisconsin State University Oshkosh, Oshkosh, ¶'Jisconsin Wisconsin May 8—9, 8-9, 1969 1969 Institute Institute Board of Directors J. W. Avery (Treasurer), *J. (Treasurer), Jones F& Laughlin Laughlin Steel Steel Corp., Corp., Negaunee, Michigan Michigan *R. *R. C. C. Reed (Secretary), (Secretary), Michigan Geological Survey, Survey, Lansing. Lansing, Michigan. A. A. K. K. Sneigrove, Snelgrove, Michigan Michigan Technological Technological University, University, Roughton, Houghton, Michigan. W. J. Hinze, Hinze, Michigan State W. J. State University, University, East Lansing, Lansing, Michigan A. A. B. B. Dickas. Dickas, Wisconsin vlisconsin State University, University, Superior, Superior, Wisconsin G. G. L. L. LaBerge, LaBerge, Wisconsin State University, University, Qshkosh, Oshkosh, Wisconsin Permanerit *Permanent members. members. Local Committee Committee G. L. G. L. LaBerge (General (General Chairman) Chairman) B. B. E. E. Karges B. B. K. K. McKnight HcKnight N. W. Jones N. W. R. G. G. Hennings Hennings R. Sally LaBerge Field !,rip Trip Committee Committee L. hleis L. 'ft.]. W. Weis ..-......) C. E. E. Dutton >-Co-leaders Co-leaders C. G. L. LaBerg~ LaBergJ G. L. �'0' ~ ~ ~ ~ '06,y LM· //// //;~ .,.....,.,.,.~,..., w. ) ELMWOOD AVE. ~ .-. #. ~1 r-' jJ)'''R"§P D'0 ~~.~ (J •. t.:l~ Li w > e::t r tA•••~.8 ~_~0 - W;;'0 z~ z I B 0 t(Z9i! Lj /'>~ ~a2C:~ ~ W TECHNICAL SESSIONS ALGOMA BLVD. D 0 [1 ........ TITUTE iJ'OLOGY r-::t. 35 34 33 ~lJ' f\-2?rV ~) r:~-=-..::J ...ARK1NG ~ I F KEY TO CAMPUS CAMPUS BUILDINGS BUILDINGS KEY TO Aibee Hall I. Albee Hall BungRlow 2. Bungalow 3. Music Mu.lc Annex Annex 4. 4. Dempsey Dempsey Hail Hall 5. Guidance Psychology Center & Psychology Guidance Center Reeve Memorial Union 6. Reeve 7. Campus School 7. Swart Carepus 8. Science Center 8. Ha\sey Halsey Science 9. 9. Planeta;lu!n Plnetarlun 10. l-larrlngton Harrington Flail Hall 111. L Donner Donner 1-fall Hall 12. Pollock Poilock House 12. Hou.e 13. Radford Radiord Hall Hall 13. Hall 14. Webster Web.ter Hall 15. Taylor Taylor Hail 15. Hall 16. Breeze 16. Bree.e Hall Hall 17. C leman. Hail Hall Clemans 17. 18. Fletcher F letcher Hail Hall 18. 19. Forrest Forre.t R. R. Polk Polk Library Library 19. 20. Heating Heating Plant Plant 20. Woodland House Hou.e 21. Woodland Nel.on Hall Hall 22. NelsOn 23. Swewart 23. Swewart Flail Hall Hall 24. Evan. Hall 24. Evans 25. 25. Ciow Clow Social Soclal Science Science Centet Centet Elmwood Commons Common. 26. Etmwood 27. House Hou.e of of Education Eclucatlon 28. 28. Gruenhogen Gruenhagen Hail Hall Commons River Commons 29. River 30. 30. East Ea.t Hall Hall 31. 31. Scott ScottF-fall Hall 32. 32. Site Site of of Fine Fine Arts Art. Building Bulldlng 33. 33. Extended Extended Services Service!!. 34. Speech 34. Speech Clinic Clinic 35. Center 35. Te.tlng Testing Center 36. 36. Comrnurrlty Community House House �1. PROGRAM PRO G RAM Wednesday., Nay 7, Wednesday, May 7, 1969 1969 7:30 a.m. a.m. to 5:30 p.m. of volcanic, volcanic, Field trip to exposures of a variety of sedimentary, and and intrusive sedimentarYi intrusive rocks in in a volcanic belt belt in L. W. W. Weis, in central Wisconsin. Co-leaders: Co—leaders: L. C. C. E. E. Dutton, and and G. G. L. L. LaBerge. LaBerge. Thursday, May 8, Thursday, 8, 1969 1969 7:30 a.m. a.m. to 9:00 a.m. am. 9:00 85 a.rn. 8'45 a.m. hour, gymnasium (basement), (basement), Registration and coffee hour, Swart School. Swart Campus School. Technical Sessions, Little Theater (second (second floor), floor), Swart Swart Technical Sessions, Campus School. School. Welcome, Welcome, Roger E. E. Guiles, Guiles, President, President, Wisconsin State University, Oshkosh. Oshkosh. Session II Co-chairmen: 9:00 9: 00 9:20 9: 20 930 9:L0 9:40 10:00 10:30 10:50 11:10 11:30 Gregory Gregory Mursky Mursky and and M. N. E. E. Ostrom Rubidium-Strontium ages of Keewanawan Keewanawan intrusives Range, intrusives near near Mellen and South Range, Wisconsin S. Chaudhuri Chaudhuri,J D. Hisconsin S. D. G. G. Brookins, Brookins) and and G. G. Faure Faure from the K-Ar dating dating of of two twodyke.-.swarrns dyke-swarms from D. Lake Superior Superior D. York and H. H. C. C. Halls Halls north shore of Lake Isotopic Baraboo and Isotopic dating dating of the the Barahoo R. Waterloo Quartzites R. H. H. Dott, Dott, Jr. Jr. Geology of the Saganaga-Northern Light Light Lakes Lakes area, Minnesota-Ontario Minnesota-Ontario .... .... S. S. S. Goldich and C. G. N. N. Hanson Hanson area, Coffee break (in (in gymnasium downstairs) downstairs) and pre-Keewatin(?) pre-Keewatin(?) Precambrian granitic rocks and para-gneiss of the the Nashwauk-Buhl Nashwauk-Buhl sector, sector, para—gneiss Northern Minnesota--metamorphic or igneous complex? S. S. Viswanathan and W. W. C. C. Phinney Phinney of the the Duluth Duluth Rare Earths in rocks and minerals of E. B. B. Denechaud, Denechaud, and and L. L. A. A. Haskin Complex ... T. P. P. Pas-ter, Paster, E. Solution iron in in Solution and and deposition of iron sediments George H. H. Spencer, Spencer, Jr. Jr. Lunch Break (Student Lunch (Student Union) Union) Session II II Co-chairmen: 1:00 1:00 1:20 Wm. ~m. J. Hinze and I. I. Edgar Odom The Geology of the Sbuth South Range Range Quadrangle, Quadrangle, Douglas Douglas County, Wisconsin ..... R. County, R. W. W. Johnson and and J. J. T. T. Mengel, Mengel, Jr. Jr. to the the Relationships of regional magnetics to bedrock geology of the the South South Range Range Quadrangle, Quadrangle, Douglas Douglas County, County, '•isconsin Wisconsin ... A. B. B. Dickas, Dickas, E. E. U. H. Frodeson, Frodeson. B. A. Kososki, B. A. Kososki, and C. C. A. A. Wolosin �2, 2. Thursday, May 8,1969 8,1969 (continued) Thursday, (continued) Session II (continued) (continued) 1:40 Shallow in western Shallow seismic seismic refraction profiles in Lake Superior and their relation to Superior their relation to geologic geologic structures Rodolfo structures. Rodolfo Anzoleaga, L. C. C. Ocola and and R. R. P. P. Meyer Anzoleaga, L. 2QO 2:00 Shallow Shallow seismic seismic studies studies in western Lake Superior Richard J. J. Wold lfilold 2:20 2: 20 seismic profiling profiling in in Green Green High resolution seismic Bay Bay P. Meyer Robert P. 240 2:40 Coffee break break 3:10 studies of of Michigan Michigan Electrical anisotropy studies Precambrian rocks Donald G. G. Hill Hill 3:30 A A regional gravity survey survey of southwestern Minnesota J. Ikola Rodney J. 3:50 A reconnaissance paleomagnetic study of A the Series in in the the the South Range Lava Series Peninsula of western Upper Peninsula Michigan R. Middleton, J. Murray and and G. G. Aho Aho R. Middleton, J. 14:10 4:10 Seismic Seismic refraction studies of the the Ames Anticline, Am~s, Ames, Iowa .. L. V. Anticline, Iowa .. Wm. P. P. Staub Staub V. A. A. Sendlein and Wm. 4:30 A magneto-telluric study of the northeastern Lake Superior area Lake Hans Hans Tammemogi 5:20-6:30 Pioneer Inn Inn Cocktail Hour, Pioneer 6:30-7:30 Banquet, Pioneer Inn Inn Banquet, 7:45 Address: by Professor Paul Paul M. M. Clifford, Clifford, of of McMaster McMaster speaking on on "Structural IlStructural evolution evolution University speaking in aa Keewatin Keewatin belt and the nature of in Archaean orogenesis". . Friday, Friday, May 9, 9, 1969 1969 Session III Co-chairmen: Co—chairmen: 9O0 9:00 9:20 9: 20 A. E. A. E. Boerner and Robert C. C. Reed Geology of the the southern southern part part of of the the Bill Bonnichsen Duluth Comp1ex, Complex; Minnesota ...•............. Bill Felsic rock associations of the the Duluth Complex Donald M. M. Davidson, Davidson" Jr. Jr. Petrology of the Rearing Pond Pond Intrusion, Mellen, Wisconsin James F. Olmsted Intrusion, Mellen, James F. Coffee break break Hydrothermal alteration of a a breccia pipe George A. A. Armbrust deposit, Batchawana Bay, deposit} Bay, Ontario Ontario George The Rainy Lake "greenstone" Ojakangas "greenstone" belt belt ..•.... Richard W. W. Ojakangas Exploration of the the Round Round Lake Lake Anomaly, Anomaly, Wayne R. Sawyer County, County, Wisconsin R. Zwickey Zwickey Lunch Break (Student (Student Union) Union) (Little Theater, Theater, Swart Swart Campus Campus School) School) Business Meeting (Little . 9'40 10:00 10:30 10:50 11:10 11:30 1:00 �3. Friday, 9, 1969 1969 (continued) (continued) Friday, May 9, Session IV IV Co—chairmen: Co-chairmen: 1:30 1:50 2:10 2:30 2: 30 2:50 3:20 3: 20 3:40 3:0 L.:l0 4:10 A. Poppin Foppin and John John S. S. Owens Owens Richard A. Ma.fic Mafic dikes dikes in in the the Precambrian Precambrian rocks rocks of Gogehic Gogebic County, Michigan .... Robert G. County, G. Schmidt and and Virgil Virgil A. A. Trent Trent Geologic examination of pipeline trench through Geologic Range, Michigan Hichigan Virgil A. A. Trent the East Gogebic Range, Rejuvenated faults as a Rejuvenated Precambrian faults cause of Paleozoic structures in cause in G. B. southeastern Minnesota G. B. Morey and D. D. C. G. Rensink Rensink Statistical the Portage Lake Lake Statistical study of the Lava Series Stephen C. C. Nordeng Coffee break Organic structures from from the the Negaunee Negaunee (iron) Marquette Range, Range) (iron) Formation) Formation) Marauette Michigan thomas G. G. Wygant and Joseph J. J. Mancuso Thomas Bars and and Troughs, Troughs, Formation of Longshore Bars Lake Superior, Ontario John S. S. Mothersill Stratigraphical Stratigraphical and and sedimentological comparison of early Proterozoic rocks of S.E. S.E. Wyoming and the Great Lakes region Lakes Grant M. M. Young Saturday, May 10, 1969 1969 Saturday. 7:30 a.m. a.m. to 5:30 p.m. p.m. Field trip trip to to exposures of aa variety of Field of volcanic, volcanic, sedimentary) and intrusive rocks in a volcanic belt sedimentary) and intrusive rocks a volcanic in central Uisconsin. Co—leaders: L. Wisconsin. Co-leaders: L. W. Weis, Weis, C. G. L. L. LaBerge. LaBerge. C. E. E. Dutton, Dutton, and G. �4. L. AUTHORS AND TECHNICAL SESSION CHAIRMEN AHO G AHO, G , • ANZOLEAGA, RODOLFO ANZOLEAGA, RODOLFO University, Michigan Technological University, Houghton, Houghton, Michigan University of Wisconsin, Madison, Madison, Wiscons vJiscons in ARMBRUST GEORGE A. A. ARMBRUST, GEORGE i Iowa University, University,Cedar CedaiFAlls, F1s, Northern Iowa Iowa BOERNER~ A. A. EE. BOERNER, Anaconda-American Brass Ltd., Port Port Arthur, Ontario BONNICHSEN, BILL BONNICHSEN, BILL .........• Cornell University, Ithaca, New New York York University, Ithaca, BROOKINS, BROOKINS, D. D. GG Kansas State Kansas State University, University, Manhattan, Kansas CHAUDHURI, SAMBUNDAS CHAUDHURI, SAMBUNDAS Kansas State University, Manhattan., Manhattan~ Kansas CLIFFORD, PAUL M CLIFFORD, PAlTL M HacMaster University, Hamilton, Hamilton, Ontario MacMaster University, DAVIDSON, DONALD M., M., JR. JR. DAVIDSON, DONALD University of Minnesota—Duluth, Minnesota-Duluth, Duluth, Duluth, I"linnesota Minnesota DENECHAUD, E. E. BB. University of Wisconsin, Madison, Madison, Wisconsin DICKAS, A. A. BB DICKAS, Wisconsin State State University, University, Superior, Superior, WI s cons in vJisconsin ROBERT H., H., JR. JR. DOTT, ROBERT of Wisconsin, Wisconsin, Madison, Madison, University of Wisconsin lr.!isconsin DUTTON, CARL CARL EE. DUTTON, U.S. U.S. Geological Survey, Survey, Madison, Madison, Wisconsin FAURE, FAURE, GUNTER Ohio State University, Columbus, Columbus, Ohio Ohio FRODESON, E. E. W~7. FRODESON, Wisconsin State University, University, Superior, Superior, Wisconsin v.Jisconsin GOLDICH, S. S. S S Northern Illinois University, DeKaib, DeKalb, Illinois HALLS) H. H. CC HALLS, Toronto, Toronto, Toronto, Ontario University of Toronto, HANSON, HANSON, GILBERT NN. State University of New York, State York, Stoney Stoney Brook, New York Brook, HASKIN, LARRY A HASKIN, A University of Wisconsin, Madison, Madison, ~~7isconsin Wisconsin HILL, HILL, DONALD GG. Michigan State University, University, East East Lansing, Lansing, Michigan �5. 5• HINZE, HINZE? WILLIAM WILLIAM JJ Michigan State State University., University, East Lansing, Lansing, Michigan Michigan HOPPIM, RICHARD A HOPPIN? A Iowa, Iowa City, City, Iowa University of Iowa, IKOLA,RODNEyJ IKOLA, RODNEY J Minnesota Geological Survey, Survey? Minneapolis, Minneapolis, Minnesota JOHNSON, JOHNSON, R. R. W W State University, University, Superior, Superior, Wisconsin State Wisconsin KOSOSKI, B. KOSOSKI, B. AA ~isconsin State State University, University, Superior, Superior, Wisconsin Wiscons in Wisconsin LaBERGE, GENE L LaBERGE, L Wisconsin State University, Oshkosh, Oshkosh, Wiscons in Wisconsin MANCUSO, JOSEPH J MANCUSO, J Bowling Bowling Green State University, Bowling Green, Ohio Ohio MENGEL. JOSEPH T., MENGEL T., JR . . . . . tATisconsin Wisconsin State StateUniversity, University, Superior, Wisconsin MEYER, MEYER~ ROBERT ROBERT PP University of Wisconsin, Madison, Madison, W is cons in Wisconsin MIDDLETON, R R Michigan Technological University, University, Houghton, Houghton, Michigan MOREY, MOREY, G. G. BB Minnesota Geological Survey, Survey? Minneapolis, Minneapolis, Minnesota MOTHERSILL, MOTHERSILL, JOHN SS . . . . , ... Lakehead Arthur, Ontario Lakehead University, University, Port Arthur, MURRAY, J MURRAY, J Technological University, University, Michigan Technological Houghton, Michigan Houghton) MURSKY, GREGORY MURSKY, GREGORy of Wisconsin, Madison, Madison, University of WI scans in Wisconsin NORDENG, STEPHEN C NORDENG, C University, Michigan Technological University, Houghton, Michigan 000LA, LEONIDAS CC OCOLA, Madison, University of Wisconsin, Madison, Wisconsin ODOM, I. ODOM, I. EDGAR Northern Illinois Illinois University, University, DeKaib, DeKalb, Illinois OJAKANGAS, RICHARD RICHARD W. W University of Minnesota-Duluth, Duluth, Minnesota OLMSTED, JAMES JAMES F. F State University of New York, York, College at Plattsburg, Plattsburg, Plattsburg, New New York York �66,. OSTROM, M. OSTROM, M. EE Wisconsin Geological Geological Survey, Survey, Madison, Madison, Wisconsin Wiscons in Wisconsin OWENS, JOHN OWENS, JOHN SS....•........ The Hibbing, The Hanna Mining Co., Agents, Hibbing, Minnesota FASTER, PASTER, T. T. PP University of Wisconsin, Madison, Madison, Wisconsin PHINNEY, PHINNEY, WILLIAM CC University of Minnesota, Minneapolis, Minneapolis, Minnesota REED, REED, ROBERT ROBERT CC Michigan Geological Survey, Survey, Lansing, Lansing, Michigan RENSINK, D. RENSINK, D. G. G .... of Minnesota, Minneapolis, Minneapolis, University of Minnesota . U.S. Geological Survey, Washington, D.C. D.C. SCHMIDT, ROGERT GG. SENDLEIN, L. L. V. V. AA. SENDLEIN, . . Iowa State University, Ames, Ames, Iowa Iowa Iowa SPENCER, GEORGE H., SPENCER, H., JR. JR Duluth, Duluth, Minnesota STAUB, WILLIAM P STAUB, College of St. St. Thomas, Thomas, St. St. Paul, Paul, Minnesota TAMMEMOGI, HANS HANS Toronto, Toronto, Toronto, Ontario University of Toronto, TRENT, VIRGIL A TRENT, A U.S. Geological U.S. Geological Survey, Survey, Washington, Washington, D.C.. D.C. VISWANATHAN, SS of Minnesota, Minnesota, Minneapolis, Minneapolis, University of Minnesota WEIS, LEONARD W WEIS, W Bay, Fox Fox University of Wisconsin-Green Bay, Campus, Menasha, Menasha, Wisconsin Valley Campus, WOLD, WOLD, RICHARD JJ University of Wisconsin-Milwaukee, Wisconsin-Milwaukee, Milwaukee, Wisconsin Milwaukee, WOLOSIN, C. A A WOLOSIN, C. Wisconsin State State University, Superior, Superior, Wiscons in Wisconsin WYGANT, THOMAS WYGANT, . Bowling Green State State University, Bowling Bowling Green, Ohio Green, D YORK, D University of of Toronto, Toronto, Toronto, Toronto, Ontario Ontario YOUNG, YOUNG) GRANT NM University of Western Ontario, Ontario, London, London, Ontario ZWICKEY. ZWICKEY~ WAYNE Zinc Corp., Platteville, Platteville, New Jersey Zinc Wisconsin �7. PROFILES IN IN WESTERN WESTERN LAKE LAKE SHALLOW SEISMIC REFRACTION PROFILES TO GEOLOGIC GEOLOGIC STRUCTURES STRUCTURES SUPERIOR AND THEIR RELATION TO Rodolfo Anzoleaga, Leonidas C. C. Ocola and and Robert Robert P. P. Meyer Rodolfo Anzoleaga, Leonidas Department of Geology and and Geophysics Geophysics Geophysical Geophysical and and Polar Research Center University of Wisconsin, Madison, Madison~ Wisconsin, Wisconsin, 53706 53706 The shallow structure structure of of the The the western half of Lake Superior is is interpreted on the the basis basis of four four seismic refraction profiles interpreted on profiles along aa line line between Knife River River (Minnesota) (Minnesota) and and Otter-Cove Otter-Cove (Canada). (Canada). Five refractors are are observed. observed. The first (3.3-3.5 (3.3-3.5 km/see) km/sec) is is at a a The first depth except depth of of 0.3-0.5 0.3-0.5 km km and and aa thickness thickness of of 1.2 1.2 km km on on the the average, average except for aa 50 wide T7depression at about about 150 km east of for 50 km wide Y;depression 1i centered at Knife River. where this refractor reaches reaches aa thickness thickness of of 3.5 3.5 km. km. Knife River. (4.5-4.7 km/see) km/sec) is 1.4 km thick east of the the depression The second (4.5-4.7 and 2.5 and 2.5 km under and and west west of of it. it. This refractor pinches pinches out out at at about 30 km east of about of Knife Knife River. River. The third (5.4-5.6 (5.4-5.6 km/see) km/sec) is is about 6 km km thick thick east east and and under under the the depression wedging out towards about towards The fourth Knife River where its its thickness is is less less than than one one km. km. The Knife (6.5 km/sec) for about 120 km from from Knife Knife River River to to the the east east (6.5 km/see) is is found found for fifth (6.9 with with aa dip dip of of about aboutLt°. 4°. The fifth (6.9 km/see) km/sec) is is at at aa depth depth of of 8-10 depression. This refractor is is not not 8-10 km km under under and and east east of the depression. observed as as first arrivals on on the the profiles profiles between Knife River and observed first arrivals the depression. the The satisfies the requires the The model model which which satisfies the observed observed gravity requires 6.9 6.9 km/sec km/sec material material to to continue continue under under the the 6.5 6.5 km/sec km/sec refractor refractor towards Knife Knife River. River. The topography of the 6.9 6.9 km/sec upper interface--as interface--as required required by by the the gravity--is gravity--is probably probably related related to to the the northward continuation of the Mid-Continent Gravity High in the part of of Lake Lake Superior. Superior. westernmost part �88.. HYDROTHERMAL ALTERATION OF OF A A BRECCIA BRECCIA PIPE PIPE DEPOSIT, DEPOSIT, EATCHAWANA BAY, BATCHA~vANA BAY, ONTARIO ONTARIO George A. A. Armbrust Department of Physics and Earth Science Department Science University of Northern Iowa, Iowa, Cedar Cedar Falls, Falls, Iowa, Iowa, 50613 50613 The Tribag mine is situated approximately 45 45 miles northnorthwest of Sault Ste. northwest Ste. Marie, Ontario. Ontario. Precambrian rocks exposed in the area consist consist of: of: acid basic metavolcanics, metavolcanics) rnetasediments metasediments acid to basic and iron formations; formations; granite; granite; diabase diabase dikes dikes and and sills; sills; and a series and a of olivine basalts interlayered with conglomerate and sandstone. sandstone. The metavolcanics, metasedjmen-ts metasediments and formations represent and iron formations an accumulation of 30,000 30,000 feet feet of material was later intruded material which was by granitic batholiths. batholiths. All are faulted faulted and and intruded intruded All of these rocks are by diabase dikes and and sills. sills. Overlying this older rock complex complex is is aa thick series series of into the the Lake Lake of olivine olivine basalts basalts which were were extruded extruded into Superior basin. basin. Conglomerate and sandstone sandstone are are interlayered interlayered with with the basalts, basalts, which dip southwest the southwest at at 20 20 to to 40 40 degrees. degrees. Felsite bodies bodies intrude the volcanic and and sedimentary sedimentary layers. layers. The Tribag mine is is in in the the Breton Breton breccia, breccia, one of five five breccia the eastern eastern margin margin of of Township Township 28, 28, Range Range 13. 13. The pipe pipes near the has surface dimensions of 1,400 by 350 350 feet, feet, and the size increases has slightly with depth. depth. The sub-rounded The breccia contains contains angular to to sub-rounded fragments sodic granite, granite, basic basic volcanics, volcanics, fragments of of trondhjemite or sodic felsite, and. diabase. These are felsite) and diabase. are set set in in a. a matrix of of quartz, quartz) calcite., calcite, pyrite pyrrhotite, pyrite., pyrrho-tite,chalcopyrite, chalcopyrite, sphalerite, sphalerite, marcasite marcasite and galena. Minor amounts molybdenite, scheelite, amounts of molybdenite, scheelite, fluorite, fluorite) laumontite and also occur occur in in the the matrix. matrix. barite also j Secondary effects on the rock fragments fragments include include hematization, hematization, sericitization, kaolinitization, chioritization, chloritization, sericitization, silicification, kaoljnjtjzatjon, and minor carbonatjzatjon. carbonatization. A small amount of pyrite and and leucoxene leucoxene are associated with sericitized sericitized biotite. biotite. Hematization of the the feldspars preceded brecciation. feldspars brecciation. Quartz, Quartz, sericite, and kaolinite kaolinite mineralized areas. areas. Hydrothermal chlorite chlorite are abundant near highly mineralized bears no special special relationship to to the the mineralized mineralized areas. areas. the extrusion of basaltic magma Hydrothermal alteration and the have both been dated at near 1,050 million years years by the the K-Ar nearby have method. An amygdaloidal dike having a a similar similar mineralogic composition to the basaltic lava cuts the the breccia at the Tribag mine. This indicates a mlne. a possible genetic relation between the Middle Keweenawan extrusives and and the the Tribag Tribag copper copper deposit. deposit. The presence of abundant sericite sericite and and quartz quartz in in and and near near the the The mineralized at Tribag, Tribag along mineralized zone zone at along with with the the mineralogy mineralogy and and general general geologic setting, setting, suggests depositions depositions in a a moderate moderate to to high The large amount of open intensity environment. The open space space between between breccia fragments pressure fragments suggests suggests deposition in a a relatively relatively low pressure environment. �9. GEOLOGY OF THE SOUTHERN PART PART OF OF THE DULUTH COMPLEX, COMPLEX, MINNESOTA:! MINNESOTA' DULUTH Bill Bill Bonnjchsen Bonnichsen Sciences Department of Geological Sciences Cornell University, Ithaca, Ithaca, New New York, York, 14850 l85O Two Two groups groups of of intrusive intrusive igneous igneous rocks are abundant abundant in in the the southern part of of the the Duluth Complex. Complex. The earliest group is the The is the Anorthositic Series; it Series; it consists anorthosite consists primarily of gabbroic anorthosile and troctolitic anor-thosjte. and.t~octolitic anorthosite. In In general, general, the mafic minerals (olivine, pyroxenes7 (ollvlne, pyroxenes, oxides) oxides) in these rocks rocks are paragenetically later later than than the the plagioclase. plagioclase. The is the the Troctolitic Troctolitic The latest group is Series in which troctolite Series in which troctolite and and augite augite troctolite are the most common rock types. rock types. Plagioclase Plagioclase and generally are are contemporaneous contemporaneous and olivine divine generally in these rocks in these rocks and are paragenetically earlier earlier than than the the accompanying pyroxenes and and oxides. oxides. The Troctolitjc Troctolitic Series Series is is present along the western margin of the the southern part of the the Duluth Duluth Complex and intrudes rocks of the the Anorthosjtjc Series that Anorthositic that lie lie to the east. east. The Anorthositic Series Series is hypothesized hypothesized to to be be genetically related to is some of the Keweenawan to some flows; flows; it is is suggested that some flows represent differentiated some flows liQuids liquids that were expelled from from magma chambers chambers in in which rocks of the Anorthosj-tjc Anorthositic Series were accumulating accumUlating by by crystal crystal settling. settling. the Anorthosj-tjc Anorthositic Series After the Series had had been been emplaced, emplaced, troctolitic magma evidently intruded along a a widening fracture fracture zone zone to to form form the the Troctolitic Series between the Anorthositic Series to the east and Troctolj-tjc Series between the Anorthositic Series to the the Early and Middle Precambrian Precambrian basement basement complex complex to to the the west. west. The sulfide deposits in the the southern part the Duluth Complex The sulfide deposits in part of of the Complex that that currently are of economic interest interest for for their their Cu-Ni Cu-Ni potential potential are are believed believed to to be be syngenetic syngenetic segregations segregations within within the the lower lower part part of of the Troctoljtic the Troctolitic Series. Series. "Work done :!Work done on behalf of the Minnesota Geological Geological Survey. Survey. �10. RUBIDIUM-STRONTIUM AGES OF KEWEENAWAN INTRUSIONS NEAR MELLEN AND SOUTH SOUTH RANGE RANGE IN IN WISCONSIN WISCONSIN S. Chaudhuri Chaudhuri and and D. G. Brookins S. D. G. Department of Geology Kansas University, Manhatton, Manhatton Kansas Kansas State State University, Kansas 5665014 66504 and G. G. Faure Faure Department of Geology Ohio State University, Columbus Ohio Columbus, Ohio, Ohio,143210 43210 Rubidium—strontium Rubidium-strontium ages ages were measured on whole rocks rocks and mineral separates separates from the Mellen Granite and and the the Mellen Mellen Gabbro Gabbro in in Wisconsin. Wisconsin. A suite of porphyritic granite chosen for isotopic isotopic study of the Granite was was collected collected from from sections sections3232and and33, 33,T'45N, T45N, R3W. Mellen Granite Samples in the Samples of of the the Mellen Mellen Gabbro Gabbro were were obtained obtained from from outcrops outcrops in the In addition, a whole-rock rubidiumvicinity of Mineral Lake. of Mineral Lake. In addition, a strontium age was determined determined on on monzonite monzonite which which cuts cuts the the iKeweenawan Keweenawan basalts near South South Range Range in in Douglas Douglas County, County, Wisconsin. Wisconsin. The ages wer1calulated bybyusing werelcal~Iulated usingthe thedecay decay constant constant for for Rb87 Rb 87 = 1.39 xx 10-~ 10- y- . The calculated age of whole rocks and biotites from the The Sr87/Sr86 porphyritic granite granite is is 9140 940 + Sr 87 /Sr 86 ratio ratio of of primary primary + 12 m.y. porphyritic strontium is is found to be 0.7137 0.7137 ++ 0.0005. Samples of the Mellen Gabbro range in values of Sr87/Sr86 Sr 87 /Sr86 ratio ratio from from 0.7057 0.7057 to to 0.7161. 0.7161. The isotopic composition of samples do not the The isotopic of these these samples not agree agree with with the isochron the porphyritic granite. granite. The Mellen Gabbro isochron defined defined by the appears assuming it to to be be related to appears to to be be about about 1100 1100 m.y. m.y. old old by assuming related to the the intrusion of the the Duluth Duluth Gabbro. Gabbro. The whole-rock whole—rock rubidium-strontium isotopic The isotonic analyses analyses of the the 87 The initial Sr87/Sr86 monzonite yield an age age of of 935 935 ++ 15 15 rn.y. m.y. The-initial Sr /Sr 86 ratio is is 0.7100 ++ 0.0008. (1) the porphyritic granite west of Our data indicate that (1) Gabbro, and the cognate Mellen is much younger than the Mellen Gabbro, unlikely, (2) (2) the emplacement of relationship of these two rocks is unlikely, the the porphyritic granite granite near Mellen Nellen was was contemporaneous contemporaneous with with that that of of The data also demonstrate that the monzonite near South Range. Range. The that the the 87 /Sr 86 Sr87/Sr86 ha~e significantly significantly high high initial initial Sr granite and the monzonite have ratios, which point a rubidium-rich environment ratios, point to their origin in a indicate aa previous previous crustal crustal history history for for these these rocks. rocks. and may indicate �11. II. THE FELSIC ROCK ASSOCIATIONS OF THE DULUTH COMPLEX Donald N. Davidson; Davidson Jr. Donald M. Jr. Department of Geology Department University of Minnesota~ Minnesota Duluth, University of Duluth, Minnesota, Minnesota~ 55812 55812 supported by by the the Minnesota Minnesota Geological Geological Field research has been supported Survey in Kawishiwi Lake, Lake, Lake Lake Polly Polly and and Kelso Kelso Mountain Mountain quadrangles, quadrangles; Lake and and Cook Cook Counties; Countjes Minnesota. Lake Minnesota. This subsequent This research and subsecuent revealed the the presence of several several laboratory investigation have revealed felsic felsic rock rock types types spatially spatially associated associated with with anorthositic anorthositic and and gabbroic Complex. gabbroic rocks rocks of the Duluth Complex. Rock types types thus Rock thus far delineated are: granite) granodiorite, granite, granodiorite, grano-gabbro) dioriteC?). These rocks are are grano-gabbro7 granophyre, granophyre, and diorite(?). rocks of the the gabbro complex with at least least genetically younger than rocks two separate intrusive intrusive periods. periods. indicates Petrographic evidence indicates the dioriteC?) diorite(?) may be the be aa hybrid from intrusive intrusive hybrid rock type derived from of gabbroic gabbroic rocks. rocks. contamination of �12. RELATIONSHIPS TO THE RELATIONSHIPS OF REGIONAL MAGNETICS TO OF THE THE SOUTH SOUTH RANGE RANGE QUADRANGLE, QUADRANGLE, BEDROCK GEOLOGY OF DOUGLAS COUNTY, COUNTY, WISCONSIN A. B. B. Dickas A. and E. W. W. Frodesen~ Frodesen B. E. B. A. A. Kososkj Kososki and C. C. A. A. Wolosin (Students) (Students) Department of Geology Geology Wisconsin State University3 University, Superior, Superior, Wisconsin, 54880 54880 Bounded by latitudes latitudes 46° 46° 33' 33' to 46° 37.5' 37.5' and longitudes longitudes 910 91° to 46° 52.5' to 92°~ 92° the 52.5' to the South South Range in central central Douglas Douglas Range quadrangle lies in County) approximately five County) five miles southeast southeast of of Superior, Superior, Wisconsin. Wisconsin. During the Fall and Winter of 1968-69. one one hundred hundred and forty forty station readings employing aa Schmidt readings Schmidt type type vertical magnetometer were recorded along all primary and secondary secondary roads within the northern northern recorded thirty-six square mile sector of this t~irty-six this quadrangle. quadrangle. This spacing spacing yields ylelds a a density of four four stations stations per square square mile. mile. A A centrally located station was located base and and drift drift analysis. analysis. As the the was used for base magnetometer was initially initially zeroed zeroed at all other other at this this position, all station data, data, after proper corrections, are relative to station to the the base point. The The purpose of this study study was to determine the degree to which surface rriagnetics magnetics would wouldreveal reveal the the structure structure and and trend trend of the northern Wisconsin bedrock when buried under several several tens tens to to hundreds of feet of Pleistocene hundreds Pleistocene till. till. Outcrops common Outcrops are not at all common in this this region. As and Mengel (these (these proceedings), proceedings), As outlined by Johnson and this quadrangle is subdivided by the Douglas Douglas Fault Fault into into two two this petrologic provinces. provinces. North of the fault the Pleistocene till and Recent lake sediments sediments overlie sandstones interbedded interbedded with shale, shale, the the Recent lake latter all of Keweenawan (Cambrian?) (Cambrian?) age. The thickness of of these these clastics is estimated by the Wisconsin Geological Geological Survey Survey to to be be in in elastics excess of twenty twenty thousand thousand feet. feet. In the magnetic trend trend In this this province the is non-uniform. Regionally, is Regionally, a a northeast-southwest strike strike is is observed at a a rate of 400 400 to to 600 600 increasing in magnitude to the northwest at gammas per gammas per mile. Scattered and apparently non—related non-related magnetic noses and interrupt this this weak regional trend as and closures closures interrupt as they range in from north-south north-south to to east-west. east-west. These orientation from These anomalies, anomalies, which have a a residual magnitude of 100 to to 200 200 gammas) gammas) might be attributed in the the subclastic subclastic basement basement to mineralogic irregularities either in complex or within the the surficial surficial till. till. The latter is is the more more probable probable cause Keweenawan (Cambrian?) (Cambrian?) cause due due to to the very great thickness of the Keweenawan the basement basement complex. complex. sandstones overlying the South a strong strong and uniform South of of the the Douglas Douglas Fault is found a regional magnetic fabric fabric striking striking NN 75° 75° E. E. As many as as seven seven separate trends, trends, marked marked by related related closures, separate closures, are present forming a a "wash-board" effect. effect. Each trend averages one—half one-half mile mile in in width, width" has 800 to 1600 gammas and can can be traced has aa residual residual amplitude of 800 across across the entirety of of the the study study area. area. Station control suggests suggests these trends possess possess on their northwest these trends nor~hwest flank a a magnetic gradient �13. that is that is two to three times as found on on the the opposing opposing as steep as that found flank. flank. These are in agreement with the the known These differing differing gradients gradients are southerly dip dip of the basaltic flows flows erratically erratically exposed exposed in in the the region. region. Assuming aa 30 30 to to L0 40 degree dip flows (various (various dip within the flows sources) sources) and and magnetic magnetic trends trends averaging averaging one-half mile, mile, basaltic basaltic flows flows up to three three thousand thousand feet feet in thickness thickness associated with each trend up would be be expected. expected. In the North Shore Shore Volcanic Volcanic group, group, In stUdies studies on the J. C. C. Green (1968) (1968) lists the "common" "common" thickness thickness for for flows flows similar similar in in J. composition to the South South Range Range quadrangle quadrangle group to be ten ten to to fifty fifty feet. feet. From the view~ it it would thus thus seem logical the g~ophysical geophysical point of views the effects of multiple mUltiple rather that each magnetic trend is recording the than single layer conditions. than conditions. Considering the pe-trogrephy petrography of this Considering the quadrangle as outlined by by Johnson Johnson and Mengel (these (these proceedings), proceedings), the magne-tics are recording recording either basalt—basalt magnetics are basalt-basalt or or intrusiveintrusiveextrusive sequences, sequences. The N) RR 13 13 WW is is marked marked by a a The trend trend centered centered In in section section 15, 15, TT 47 7 N, gabbroic gabbroic outcroD) outcroD, while while that that trend trend centered centered in in section section 11, 11, TT 477 N W is In the latter 13 W is closely associated with with basaltic basaltic exposures. In the R 13 area aa magnetic is located located on the the axis axis of a a positive magnetic reversal reversal is closure, supportin b evidence for arenaceous units lying lying closure, suggesting suggesting supporting evidence for between flows flows as found found northeast along along strike strike by by Johnson Johnson and and Mengel. Mengel. It thus pattern is is related related to a a more It thus seems seems that that this this \!vJash-board uwashboardf11 pattern complex situation than a a simple layered basalt basalt sequence. sequence. hi1e While magnetic magnetic trends trends can be be traced traced throughout this this area, area~ their continuity is is interrupted. interrupted. In South Range Range In the the center of the South left-lateral off-setting off-setting is is noted. noted. This quadrangle an apparent left-lateral is remarkedly coincident with the western border of the large large trace is mass seen seen in in sections sections31, 31,3232and and3333ofof T 48 N, R 12 N. W. The gabbro mass T Ll.8 gabbro mass appears to to be true offset rather than than gabbro mass appears be associated with aa true a a cancellation of the the magnetic trends. trends. It would seem logical logical It would thus seem that this off-setting off-setting is is a a result of left—lateral left-lateral transform transform faulting. faulting. Possibly at a later date the the gahbro gabbro was was activated and conceivably partially used the fault plane plane as an avenue avenue of of intrusion. intrusion. Final this faulting--intrusion faUlting-intrusion relationship analysis of this relationship will will have to await the local local basement basement rocks. rocks. eventual age dating of the This transform fault, This fault. with a a strike of NN 30 30 to to 40° 40° N~ is is parallel parallel to known in in the the Lake Lake Superior Superior area. area. to other similar fault patterns known Each of these faults faults strike strike at at right to the the regional regional right an~les an1es to structural grain. grain. Nhile While the apparent amount of off—setting off-setting in in the South Range area measures approximately approximately one mile) is postulated mile, it is this fault this fault is is part of the very fault system very extensive extensive transform fault by Thiel Thiel (1956) (1956) and and-Coons, Woollard and and Hershey Hershey (1967). (1967). portrayed by Coons, Woollard References Coons, R L. Coons, R. L., Woollard, P .. and Hershey, Hershey, C., G., Woollard, G. C. P.. Significance Significance and and Analysis of Hid-Continent Amer. Assoc. Amer. Assoc. Pet. Pet. Geol., 51, 51, December, December, pp. pp. (1967), Structural (1967), Gravity High, High, Bull. Bull. Gravity 2381-2399. 2381-2399. �iLl.. 14. Green. J. Green, (1968); Varieties of Flows in the North Shore Volcanic J. C., C.. (1968), Group, Minnesota ~1innesota (abstract), (abstract)? Proc. Froc. Institute Institute on Lake Superior SuperlOr--Group, Geology, pp. pp. 52~S3. 52--53. Johnson R. R. W. W. and and Menge1~ Mengel, J. J. T. T.,~ (1969), Johnson, (1969), Economic Implications Implications of of the the South South Range Range Quadrangle, Quadrangle, Douglas Douglas County, Countv, the Geology of (abstract)~ Proc. Proc. Institute Institute on on Lake Lake Superior Superior Geology. Geology. Wisconsin (abstract), Thiel) Thiel, E.; E., (1956), (1956), Correlation Correlationof ofGravity GravityAnomalies Anomalieswith withthet Keweenawan Geology Geology of of Wisconsin Wisconsin and and Minnesota~ Minnesota, Bull. ul1. Geol. Keweenawan Geol. Soc. Soc. Amer., 67~ 67, p. p.TO79. Amer., 1079. �15. BARABOO AND WATERLOO WATERLOO QUARTZITES QUARTZITES ISOTOPIC DATING OF THE BARABOO Dott, Jr. R. H• B. Dott, and Geophysics Geophysics Department of Geology and University University of of Wisconsin, Wisconsin, !4adison, ~adison, Wisconsin, 53706 53706 The long has be correlative The Baraboo Quartzite Quartzite long has been assumed to be (i.e. between between about 2.5 2.5 and and with Huronian and/or Animikean rocks (i.e. 1.6 b. 1.6 b. y. y. old). old). This was based only upon This correlation, correlation, however, however, was similarities of lithology and seauence similarities sequence of quartzite, iron iron formation, formation~ beTween the the Baraboo Baraboo region and northeastern dolomite and slates between Wisconsin and and adjacent adjacent Michigan. Michigan. Isotopic Baraboo and its inferred Isotopic dating dating suggests suggests that that both both the the Baraboo and its equivalent near (25 miles miles east east of of Madison) Madison) are are equivalent near Waterloo, Waterloo, \Jisconsin Wisconin (25 younger than Animikean. Animikean. Rb8?Sr07 Rb 87 _Sr 87 dating of five five samples samples of of dark dark rhyolite that underlies rhyolite that underlies the the Baraboo Quartzite yields an isochron of l.51+ .7Rb87 1'~11~ 0.0 0.04l xx 10 10 9years years(assung (assuw~ng ~ Rb 87decay decayconstant constant of of 1.47 1.47 x 10 yr. 10 yr.and initial Sr°°/Sr Sr /Sr 7 ratio of 0.705 0.705 ++ 0.005). and an initial 0.005). AA K-Ar date date was was attempted for a K-Ar a phyllite zone zone near near the the-top of the the top of quartzite the formation, formation, but quartzite in in the the hope hope of of dating dating metamorphism of the the potassium content was too low the low to provide aa meaningful result result 6 (760 +50 x 106 yrs.). (760 ~ 50 x 10 yrs.). The younger age limit of red) red) Baraboo-type Baraboo-type quartzite seems seems to to be be provided provided near Waterloo, ~aterloo, however. however. Bass (in Bass (in Tuve, Tuve, 1959) reported a'Rb·-Sr for muscovite muscovite from from aa a Rb-Sr date date of of 1.44 1.44 b. b. y. y for that cuts cuts the the "Waterloo IlWaterloo Quartzite", Quartzite") and and Goldich, Goldich, coarse pegmatite that et ~t al ~l (1966) (1966) reported reported aa K-Ar date of of l.'41 1.41 b. b. y. y. from from muscovite muscovite in a schistose zone within that that quartzite. quartzite. It Baraboo-Waterloo type It appears appears that the Baraboo-.Waterloo type quartzites quartzites of of southern Wisconsin originally were as sands in a a subsiding subsiding mobile were deposited as belt between about about 1.4 1.4 and and 1.5 1.5 billion years ago, thus the quartzite belt quartzite probably is probably is both both post-Anirnikean post-Animikean and and post-Penokeari. post-Penokean. This This strengthens the the possibility that the the Baraboo Baraboo is is a a southern, thicker thicker equivalent equivalent of of the Sioux Quartzite, the Quartzite, which is is known known only to be from 1.2 1.2 to to 1.7 1.7 billion years old old (Goldich, (Goldich, et al, aI, 1966). 1966). Rb-Sr dating of three three samples of the Baxter Hollow~ranite (on the south side of. the samples of the Baxter Hollow Grite (on the south side of,the Baraboo Syncline) allow Syncline) a total range of 1.36 1.36 -- 1.67 b. b. y., y" so so does does a not indicate not indicate if the granite is is older older or younger than the the quartzite, quartzite. �16, 16. GEOLOGY OF LIGHT LAKES LAKES AREA AREA OF THE THE SAGANAGA-NORTHERN LIGHT MINNESOTA-ONTARIO S. Goldich S. S. Division of Geology Geology Northern Illinois University, DeKaib, DeKalb, Illinois, Illinois, 60115 60115 and C, N. G. N. Hanson Department of Earth and and Space Space Sciences Sciences State State University of New Ne~7 York York at at Stony Stony Brook, Brook, New New York, York, 11790 11790 The Early Precambrian rocks The rocks along the Minnesota-Ontario boundary are are of special special interest because they were were involved involved in two orogenies giving rise to granites of two ages. giving of two ages. The older granite, granite) defined and pre-Knife Lake, Lake, is is typified typified by the the geologically as post-Keewatin and Saganaga Granite (tonalite) which was folded Keewatin Granite (tonalite) was emplaced in folded rocks and and was was eroded rocks eroded to to supply cobbles and and boulders boulders to the the Knife Knife Lake sediments, sediments. The younger Algoman granite was defined geologically as post-Knife Lake and pre-Animikie. as pre-Animikie. Examples Range Examples are the Giants Range Granite Granite. Granite and the Snowbank Granite. The in the the Saganaga-Northern Light Lakes Lakes area The Keewatin Keewatin rocks rocks in are some intermediate intermediate to to silicic pyroclastic are basaltic basaltic volcanics volcanics with with some rocks and graywacke. rocks graywacke. The Northern Light Light Gneiss Gneiss is is aa fine-grained fine-grained leucocratic rock of of trondhjemitic trondhjemitic composition that leucocratic rock that represents represents a a in the the Keewatin Keewatin volcanic volcanic pile. pile. The NW-SE synkinematic intrusive in is well well exposed structure developed during during the the Laurentian Laurentian orogerly orogeny is By contrast the Algoman along Trafalgar Bay along Bay of Northern Northern Light Light Lake. Lake. By orogeny the folding folding of the the Knife Knife Lake Group Group orogeny which which resulted resulted in the developed NE-SW structures mapped by J. W. Gruner west west and developed structures mapped J. W. and southwest of Saganaga Saganaga Lake. Lake. The Saganaga Granite was was emplaced in the metavolcanics The Saganaga Granite the Keewatin metavolcanics and Northern Northern Light Gneiss in aa late kinematic and Light Gneiss kinematic stage of the the Laurentian orogeny. It was followed followed by by the the intrusion intrusion of of quartz quartz dioritic dioriticplutoris plutons It in the the vicinity of Icarus Icarus Lake Lake east e~st of of Northern Northern Light Light Lake, Lake. The in F. Grout, latter latter vJere were referred referred to to as as l'younger younger syenites" syenites n by by F. F. F. Grout. In In our interpretation of the the structural structural development development of of the the region, the Northern Light Gneiss and the Saganaga Saganaga Granite formed formed a region, F. R. R Harris massif that rose rose diapirically diapirically along along faults. faults. F. Harris has has recently mapped the granite-greenstone contact contact along the north shore On the of Saganaga Saganaga Lake Lake as as aa fault. fault. the west side the the displacement was was accomplished by by downfoldirig downfolding of faults. of the the Knife Knife Lake Lake beds beds and and along along faults. Thus the Laurentian massif was rising throughout the time of deposition Lake, and and the the conglomerate conglomerate which deposition of the the Knife Knife Lake, which rests rests on on the is the the basal Knife Lake Lake unit in the the Saganaga Saganaga Granite Granite and and which which is basal Knife unit in the vicinity of Cache Bay occupies a a higher position in in the Knife Lake succession as as a a whole, whole, as earlier earlier determined determined by by J. J. W. W. Gruner. Gruner. The present interpretation does not require the large large amount of F. Grout's Grouts erosion and avoids the structural structural problems problems inherent inherent in in F. F. F. earlier interpretation interpretation in in which the the Saganaga batholith batholith was was emplaced emplaced later tilted tilted to to the the west west during during the the in aa vertical position and was later Algornan orogeny. orogeny. Algoman �17. ELECTRICAL ANISOTROPY STUDIES OF MICHIGAN PRECAMBRIAN ROCKS ROCKS Donald G. G. Hill Department Department of Geology Michigan Michigan State State University, University, East East Lansing, Lansing, Michigan, Michigan, 48823 8823 Alternating Alternating current current dielectric dielectric constant constant and electrical conductivity conductivity measurements selected rock samples samples collected collected measurements were made on selected from from the the Precambrian Precambrian of Michigants Michigan's Northern Northern Peninsula. Peninsula. The The directional variation d~rectional variation (anisotropy) studie? (anisotropy) of these properties was studied with wlth variations variations in in rock fabric, fabric, lithology, lithology, and signal signal frequency, freque~cy, in In the range the range from from 20 20 to 300,000 cps. cps. Measurements were ~vere made using uSlng both to 300,000 two and and four electrode methods. two methods. Theoretical methods of interpreting geoelectrical data data generally assume that assume that earth earth materials materials do not exhibit significant tri-axial do significant tri-axiai aniso-tropy. anisotropy. The this study to date indicate indicate that that some The results results of this rocks, rocks, particularly particularly those with pronounced lineation or banding are those with lineation or banding are characterized by characterized by strongly anisotropic electrical properties. This strongly electrical properties. aniso-tropy is increasingly increasingly evident at lower anisotropy is lower frequencies, frequencies, in in the the range of those used in E. range used in E. M. M. and I. I. p. P. prospecting. prospecting. This study has confirmed the confirmed the theoretical theoretical prediction that the electrical anisotropy symmetry is symmetry is related related to to rock fabric symmetry. symmetry. Thus laboratory laboratory and/or field electrical field electrical anisotropy measurements may be be used to predict rock fabric symmetry. symmetry. �18. A A REGIONAL REGIONAL GRAVITY GRAVITY SURVEY SURVEY OF OF SOUTHWESTERN SOUTHWESTERNMINNESOTA:/ MINNSOTA' Rodney J. J. Ikola Ikola Minnesota Geological Survey Survey University of University of Minnesota, Minnesota, Minneapolis, Minneapolis, Minnesota, Minnesota, 55455 5555 Approximately 2500 2500 gravity stations stations have been established by by the the Minnesota Geological Survey Survey in in southwestern southwestern Minnesota. Minnesota. The majority of the stations stations are are located located on a a two mile grid with wider spacing control is is limited. limited. The presented as as aa where vertical control The results are presented Bouguer gravity map contoured at at 22 and and 10 10 milligals. milligals. The area underlain by the Morton Gneiss, Gneiss, which is is exposed at Morton in the the Minnesota River valley, valley, is is represented on the gravity map as as a a generally smooth smooth featureless featureless area. area. The contact between between the the gneisses represented by exposures at Morton Gneiss Gneiss and more more mafic mafic gneisses Granite Falls is is marked by by a a sharp sharp gravity gravity gradient. gradient. Within ~lithin the the area of the mafic gneisses gneisses there there are are two two positive positive gravity gravity anomalies, anomalies, one the other north of Granite Falls, Falls, which are one south of of Dawson and the thought to represent mafic intrusive intrusive rocks. rocks. Granitic intrusive bodies are Granitic lows on on the the are indicated by gravity lows A gravity low at New Ulm corresponds to to known outcrops of A granite in the the Minnesota River valley. granite valley. A much larger gravity low low extends to the the extends from from south south of of Granite Granite Falls Falls in in the the valley valley westward westward to South Dakota border. border. Outcrops Granite and the Outcrops of the the Sacred Heart Granite granite at the Larsen Larsen quarry are present within this this low. low. map. map. Areas rocks with associated sediments Areas of possible mafic mafic volcanic rocks are are delineated by the gravity gravity survey. survey. One One example is is an elongate elongate in the the extreme extreme western part of the the positive anomaly at Hendricks, in state. state. A series series of anomalies anomalies extending extending from from Lake Lake Beriton Benton southeastward A also are are thought thought to to be be caused caused by by niafic mafic volcanics and to Worthington also associated sediments. sediments. A positive gravity feature extending westward from from Hutchinson Hutchinson to A to Lake Lillian may represent the Lake the southern a sedimentary southern edge edge of a sequence lies unconformably unconformably on the sequence of of Middle Middle Precambrian Precambrian age, age, which which lies older Precambrian. Precambrian. The areal extent of the Sioux Formation is is not readily delineated by by the the gravity gravity method. method. appears to to be be little little or or In many areas there appears difference between the the Sioux Formation and the older rocks rocks no density difference on which it it was deposited. deposited. ~I ~1Work Work done done on behalf of the Minnesota Geological Geological Survey. Survey. �~--------"---------I--------r--------;------, r r-- --- ----- ~ , ~ i ~ I .. __ ... ... - .. -._-_ .. _ . .-;I I / I , "0QUARRY QUARRY I f. i.-.-. I I 1+/ I :/J?4>~ MORTON ~O ~ ....J I Ii, ! , i EN D R IC KS HENDRICKS --J .-- ..,I ' " LARSEN 10 L L., 1-' !I , HEART I' , ._.~ HUTC~INSON C f----------.------.-.---, 0 0 r----....J----.-.!:.~KE. L1L~~~i.. i DAWSON DAWSON ! )_ I o i ~ I 'L , I __ ._.-i I , \, .__L . ~./'t>­ i <[I ~~ f-, F- 0 1 ~ ~ LAKE LAKE BENTON BENTON _j 0 <l. J I I' , I I .r-.---........ I I 1 r.--------,----.-.-----l.--T------.-.j o -I ~ J: i fH- i• I :::l I ! 0 °1~ C/) (J) :.-__ . I I i I I I, ! I ,I l-·-------·t·-·---·-------·-l·-----·----I,' , I I I i I i WORTHINGTON WORTHINGTON0 O i SCALE seA LE 5 0 W miles I !, IOWA o WA TI.iP MAP -PAVI TY GRAVITY SHOWING SHOW'ING i SuV. Y SURVEY LOC.A LI TI T'wNTiONE LOCALITIES 1\IlENT!ONED IN II' ST1CT OF ABSTRACT OP' OF OF SO UT -1w STIN 1yUNNESOT.A. SOUTH"WESTERN IyINI'.7 S OT..A.. _ �20, 20. THE GEOLOGY OF THE SOUTH SOUTH RANGE RANGE QUADRANGLE, DOUGLAS COUNTY, COUNTY~ WISCONSIN WISCONSIN Rudolf W. W. Johnson (student) (student) and Joseph T. T. Nengel, Mengel, Jr. Jr. Department of Geology Wscons1 WisconsinState StateUniversity, University, Superior, 54880 Superior, Wisconsin, Wisconsin, 54880 Copper Copper shows shows are found wherever Keweenawan lavas lavas outcrop in are found Douglas County contains a substantial substantial percentage of of the the known known outcrop a majority of the Pleistocene outcrop and a subcrop of subcrop of the the lava lava sequence, sequence, all of which must must be be looked looked on on as as prospective for prosp~ctive for copper. copper. No detailed mapping of the the bed bed rock rock geology geology of this of thlS county county has has been published since the turn of the present century. century. The Wisconsin State University (Superior) (Superior) Geology The Department, in cooperation with the State Geological Survey Department, Survey has recently begun mapping along the the Douglas Douglas Copper range near the City of Superior of Superior to to provide provide basic information on on bed bed rock rock geology. geology. The purpose of this this mapping is purpose is to determine the nature and geometry of of the geometry the bedrock units the bed rock units present and to establish the the character character of of their their geophysical responses to serve serve as as a a guide guide to systematic copper prospecting in the drift-covered areas. The South Range, Range, Wisconsin Wisconsin 7-1/2 minute quadrangle is 7-1/2 is the first area to to be be mapped. mapped. the first northwestern Wjcsj. northwestern Wisconsin. The South Range quadrangle is The is located about 5 5 miles southeast southeast of Superior) of Superior) Wisconsin, Wisconsin, on flank of the Lake Superior on the the south flank basin. basin. It and It lies lies near near the the middle middle of the the Douglas Douglas Copper Range and exhibits exhibits geology representative of that of the entire entire Range. Range. The quadrangle the steeply south-dipping Douglas Douglas fault which quadrangle straddles the brings the Keweenawan lava brings lava flow sequence in contact with younger flow sequence sandstones to the the north. north. The flows are typically tholeiitic tholeiitic basalts The flows with medium grained ophitic interiors interiors and amygdoloidal margins. margins. Individual flows flows are less than 100 feet thick t~ick and dip SSE SSE are typically less at 35--40°. 3540°. A at A horizon marked by by basaltic basaltic cinders cinders and and fine-grained fine-grained quartz sandstone occurs near the the middle of the exposed sequence in in southwest corner corner of of T147N_R12W. T47N-R12W. the southwest Medium South Range percentages percentages of ilmenite is widely distributed distributed in in the the to coarse grained gabbro is quadrangle. The typical rock consists of of equal equal plagioclase and pyroxene, pyroxene) together with a a few few per cent cent of plagiociase or titanjferous titaniferous magnetite. magnetite. A gabbro gabbro body, body, centering centering in in 32-48N--12W 32-48N-12W underlies about four four A part of of the the quadrangle. quadrangle. square miles of the northeastern part body are exposed in in the NW 1/4 of Anorthositic portions of this body 32-48N-12W; 32-48N-12W; reddish portions crop crop out out along along the the Amnicon River south of Bardon State Park and finer grained portions occur within the the Park. Park. The gabbro body body is is not not noticeably noticeably layered layered in in character. character. The Douglas fault fault cuts cuts off the the gabbro to the the north in in the SE SE 1/4 of Douglas 29-48N-12W, 29-48N-12W, but but elsewhere elsewhere it it is is bounded bounded by by the the lava lava sequence. No lava-gahbro lava-gabbro contact exposures exposures are are known, known, but the suspected position is is marked by magnetic anomalies. anomalies. l/ �21. Outcrops S70W from the the main body across across the the Outcrops of gabbro gabbro extend S7OW S 1/2 1/2 of 1-7N-13W S 1-47N-13W in in aa zone zone about about 500 500 feet feet wide. wide. These outcrops lavas both both to to the the north north and and south. south. A A body of reddish are bounded by lavas granodiorite outcrops in in l5-47N-13W. 15-47N-13W. Its Its boundaries are covered, covered~ but the the high mafic mineral content of the border portions, but portions, and and the of lavas lavas immediately immediately to to the the west west suggest suggest that thatthe thecoufltiy co un ll'Y occurrence of rock is is basaltic basaltic lava. lava. A basaltic dike with excellent columnar joint development has intruded intruded the the granodiorite granodiorite body. body. Magnetic joint relations suggest that other intrusives intrusives are present present in in the the southern southern relations half of the the quadrangle, quadrangle, but a a thick cover of Quaternary sands sands and clays cover the the entire entire area. area. Minor native copper and and copper copper sulfide sulfide mineralization mineralization is is found found The best of in fractures in in amygdaloidal amygdaloidal lavas. lavas. in amygdules amygdules and along fractures the observed mineralization mineralization occurs occurs at at about about the the horizon horizon of of the th the observed fragmental materials boundary of the fragmental materials and close to the western boundary Exposures of the gabbro are too limited to principal gabbro mass. mass. Exposures the possibility possibility of of sulfide sulfide segregations segregations within permit evaluation of the it, it. sulfides into into the the lava lava sequence sequence can can be Local introduction of sulfides noted to the southeast southeast of of the the gabbro gabbro in in the the Poplar Poplar quadrangle. quadrangle. �22, 22. HIGH RESOLUTION SEISMIC PROFILING IN GREEN BAY P. Meyer Meyer Robert P. Department of Geology and Geophysics Geophysics Center Geophysical and Polar Research Center University Madison, Wisconsin, 53706 University of of Wisconsin., Wisconsin) Madison~ 53706 Several thousand thousand miles miles of high resolution--high frequency Several frequency seismic seismic reflection in Green Bay, Lake Lake Michigan) reflection profiling in Green Bay, Michigan, have have provided provided both test for for this this technique technique and and aa surprising amount aa test amount of data on the the sediments structural history history of of the the Bay. Bay. Eutrophic sediments under and structural sediments, characterized low reflectivity, sediments, characterized by by low reflectivity, have have been consistently found when predicted from from the acoustic acoustic data. data. The converse is is not not found true,1 for for sediments sediments of this this type type have have been found found where where the the true and, in this this case, case, entrapped gas gas bubbles are reflectivity is high and, thought responsible. Underlying the the eutrophic muds, muds) are seen, seen, yet unsampled, finely finely layered sediments, sediments) themselves greatly contorted contorted unsampled, dimly appears appears as as aa reflective reflective conformable conformable layer. layer. and resting on what dimly foot. Resolution kc, pulse pulse used used is is about about one one Resolution of the single cycle, 77 kc, Maximum penetration achieved was was about about 150 150 feet. feet. The method appears appears to have have great promise in in combined and detailed geological-geophysical geOlogical-geophysical studies of the immediate immediate sub-bottom including programs in eutrophication and and mineral mineral search. search. �23. A A RECONNAISSANCE PALAEOMAGNETIC STUDY STUDY OF OF THE THE SOUTH SOUTH RANGE RANGE LAVA SERIES IN THE WESTERN UPPER PENINSULA OF MICHIGAN LAVA SERIES J. Murray, G. G. Aho Aho (Graduate (Graduate Students) Students) R. R. Middleton, Middleton, J. Department of Geology and Geological Engineering Michigan Technological Technological University, University, Houghton, Houghton, Michigan, Michigan, 49931 993l Michigan A total of eleven block samples samples of of the the South South Range Range Lava Lava Series Sel'ies were collected at at Silver Silver Mountain,, Mountain, Bond in the the Bond Falls, Falls, and Wakefield in the Upper Upper Peninsula Peninsula of of Michigan. Michigan. Forty core western part of the specimens inch diameter diameter were were obtained obtained from from the the samples. samples. specimens of one inch Remanent a Permalli spinner Remanent Magnetism was was measured using a magnetometer. A-C demagnetization studies studies were were carried carried out to to test test stability. The The results of the the survey survey were were compared compared the remanence stability. with previously published published palaeomagnetic studies studies of the Lake Superior region. �2'4. 24. FAULTS AS AS AA CAUSE CAUSE REJUVENATED PRECAMBRIAN FAULTS OF PALEOZOIC STRUCTURES IN IN SOUTHEASTERN MINNESOTA C. G. B. B. Morey and D. D. G. G. Rensink Rensink Minnesota Geological Survey Survey and and and Geophysics Geophysics Department of Geology and University of of Minnesota, Minnesota, Minneapolis, Minneapolis Minnesota, Minnesota, 551455 55455 j The upper midwest is is part part of of a a tectonically stable stable province province large sedimentary basins and arches in Paleozoic characterized by large rocks. It is is known large basins and arches It known that that the the large basins and arches overlie equivalent features on the the Precambrian surface3 surface, and that a a close equivalent features correlation commonly exists between small-scale structures in commonly exists Paleozoic Paleozoic rocks rocks and and inferred older structures structures in the the basement rocks. features and The detailed relationships between basement features Paleozoic structures structures seldom have established, however, however, because Paleozoic have been been established, the basement basement is covered and and integrated data on on subsurface geology geology the is covered and and geophysics rarely rarely are are available. available. Such Such an integrated study study has been been completed completed of of aa recently recently recognized Paleozoic Paleozoic structure--called the anticline--in Dakota Dakota County, County, Minnesota. Minnesota. the Vermillion anticljne--jn The \Jermjlljon Vermillion anticline anticline is is aa northeast-trending northeast-trending structure about wide. It It is is doubly doubly plunging about six miles miles long and two miles wide. and asymmetrical asymmetrical in in cross-section; cross-section; the the northwest northwest limb dips about about and limb dips 20 feet/mile, limb dips dips about about 40 40 feet/mile. feet/mile. 20 feet/mile, whereas the southeast limb The anticline is modified by at least two northwest-trending crossfaults and and one northeast-trending fault faults fault that that parallels parallels and and is is slightly southeast of the anticlinal axis. axis. The faults faults are are interpreted interpreted as as having having steep steep dips dips and and reverse reverse movements; movements; the the apparent apparent vertical displacement displacement does does not exceed 100 feet feet on any of the faults. Concurrent Paleozoic Paleozoic deposition deposition and and vertical vertical movements movements in Concurrent in the the (1) vicinity the anticline are indicated indicated by: by: (1) displacement on on vicinity of the the cross-faults apparently apparently decreases decreases upward upward in in the the section, section) (2) (2) thinning thinning of of several several stratigraphic intervals intervals in in Cambrian Cambrian strata strata occurs over the the fold fold crest, crest, and (3) (3) an erosional unconformity separates rocks at at the the fold fold crest. crest. separates Cambrian and Ordovician rocks An analysis analysis of structural and isopach contour maps maps for various intervals within the Paleozojc section indicates that warping in intervals within the Paleozoic section indicates that warping in aa northwesterly direction took place prior to movement along the crossfaults) and and ~Jas was sufficient sufficient to to modify modify the the depositional depositional pattern pattern during during faults, late Cambrian Cambrian time. time. That movement along along the the the middle part of late northeast-trending fault fault took place during the the last phase of Cambrian deposition or before the first first phase of Ordovician deposition is is before the indicated by by the the Cambrian-Ordovician Cambrian-Ordovician unconformity, unconformity, where where approximately approximately indicated 30 feet feet of Cambrian strata 30 strata are are missing. missing. Combined drilling and geophysical geophysical data data in in this this area area indicates indicates Ve~million an-ticline anticline in that the Vermillion in part part overlies overlies an an uplifted block of Middle Keweenawan basalt called called the the Hudson-Afton Hudson-Afton horst. horst. The basalt basalt �25, 25. is is in fault fault contact with Upper Upper Keweenawan Keweenawan sedimentary sedimentary rocks rocks on on three three sides; apparent apparent vertical vertical displacement displacement on on these these faults faults is is on on the the order order sides; of 8,000 of 8,000 to 12,000 feet. feet. Two of the three Paleozoic faults faults coincide with with the the Precambrian faults, that geographically coincide faults, suggesting suggesting that they have resulted from minor isostatic they isostatic readjustments readjustments in in the the Other nearby nearby Paleozoic Paleozoic structures~ structures such basement. Other such as as the the HudsonHudsonanticline, also are geographically coincident with the Afton anticline, Hudson—Afton Hudson-Afton horst, suggesting suggesting aa similar similar origin origin for for them. them. �26. 26 FORMATION OF LONGSHORE-BARS AND TROUGHS, TROUGHS, LAKE SUPERIOR, ONTARIO ONTARIO S. Mothersill John S. Department of Geology Lakehead Lakehead University, University, Port Port Arthur, Arthur, Ontario Grain size analyses of of 186 186 samples samples from from the the axes axes of of longshuic-longshul'Cbars and troughs troughs along the lake shelf shelf at Batchawana Batchawana Bay Bay and and Pancake Pancake bars Bay, Lake Lake Superior, Superior, Ontario, Ontario, show the the longshore-bar sands Bay~ sands to to be be and finer finer grained than the adjacent shoreward shoreward longshoielongshol'ebetter sorted and trough sands. sands. In addition the the longshore-bar sands are unimodal and tend to to be be positively positively "skewed" whereas the tend "skewed" whereas the longshore-trough sands sands iTIay either unjinodal unimodal or may be either or biwodal bimodal and and show show aa tendency towards negative skewness. skewness. This This would would suggest suggest that that the the longshore-troughs longshore_rOUghS were formed by the were formed the action of breaking waves that preferentially set the finer grained particles into into motion. motion. These finer grained the finer particles were were then then moved moved lakeward lakeward by the undertow to form the the particles by the to form longshore-bar areas. areas. �27. STATISTICAL STUDY OF THE PORTAGE PORTAGE LAKE LAKE LAVA LAVA SERIES Stephen C. C. Nordeng Nordeng . - Department of Geology Geology and and Geological Geological Engineering Department of Engineering Michigan Technological University, University) Houghton, Houghton, Michigan, Michigan) 49931 993l The frequency frequency of occurrence of conglomerates in the Portage Lake Lava Series fits fits aa Poisson distribution, distribution, implying that such events intervals. events occur at random intervals. The frequency distribution for for thickness thickness of of the the different types types of lava flows flows and for the conglomerates fall impossible fall in the impossible region for the Pearson Pearson Type Type Curves. Curves. The single exception exception was was ophitic ophitic (coarse-grained) (coarse-grained) flows flows with a a cellular amygdaloidal top top which have aa Type Type II (Beta (Beta "J" IlJ" shaped) shaped) distribution. distribution. This type of distribution can result from aa random variable operating over an an upper and and lower lower limits, limits. The failure of other interval with definite upper The failure types, the overall thickness distribution, distribution, to to fall in in aa types, including the class is is reflected in their standard deviations being similar class commonly equal to to the the mean. mean. This This shows an overabundance of thin flows degree of of fluidity fluidity for for the the lavas. lavas. flows suggesting a high degree transitions as as aa Narkov Harkov process process gives gives Treating the flow type transitions an expected sequence sequence of of textural textural and and flow flow top top combinations combinations as as follows: follows: 1) cellular top; top; 2) 2) melaphyre melaphyre with with fragmental fragmental tops; tops; 1) me1aphyre melaphyre with cellular 3) ophites ophites with with fragmental fragmental tops; tops; 3) ophites with with cellular cellular top; top; 1+) ) ophites glomerophorphyri-tes with cellular tops; 5) glomerophorphyrites tops; 6) 6) glomerophorphyrites glornerophorphyrites This is with fragmental tops; tops; and and 7) 7) conglomerate. conglomerate. This is accompanied by aa tendency toward greater flow flow thickness. thickness. Plotting the the flow flow types types as Plotting as a a time time series and smoothing shows shows four incomplete cycles of this four this type type in in the the Portage Portage Lake Lake Lava Lava Series, Series. �28. l ; THE RAINY LAKE BELT::/ LAKE "GREENSTONE "GREENSTONE" BELT' Richard W. W. Ojakangas Ojakangas Department of Geology University of Minnesota, Minnesota, Duluth, Duluth Minnesota, Minnesota, 55812 55812 j The 'iKeewatin Greenstone Greenstone Belt" Belt" of of A. A. C. C. Lawson Lawson (1887, (1887, The Rainy Lake 'Keewatin 1913) has been restudied in 1913) in detail detail on the United States States side side of of the the International Boundary. Boundary. The wide in in this this area, area, The belt, belt, 22 to 33 miles wide trends is bounded sides by Lawson's Lawson's "pre-Keewatin trends ENE ENE and and is bounded on both sides ll Series of biotite schists. schists. The dominant rocks within Coutchiching Series" the belt are schists, massive "tuffaceous" the are chlorj-tjc chloritic schists, "tuffaceous" greens-tones, greenstones, minor rock rock types types include include pillowed pillowed greenstones, greenstones, and meta-arkoses; minor conglomerates, and conglomerates, and "felsic Hfelsic tuffs". tuffs". These rocks rocks are generally interbedded and gradational. gradational. Most of the metasedimentary rocks rocks in the area are vertical or lineations generally plunge to the ENE at angles nearly vertical and lineations of of 3Q0 30° to to 500. 50°. Lawson interpreted the structure here as a a Lawson interpreted the regional regional structure here as synCline composed of Coutchiching biotite biotite schists schists on on the the outside, outside, syncline composed greenschists and Keewatin greenschis-ts and greenstones greens-tonesnearer nearerthe thecenter) center and Huronian (Seine) the center. center. of In light of (Seine) meta-arkoses meta-arkoses and and conglomerates at the this study, study, a a different structural structural interpretation interpretation seems seems more more probable. probable. in the the bioti-te biotite schists the meta-arkoses Graded beds in schists and and cross-beds cross-beds in in the stratigraphic tops. tops. provide information on stratigraphic Tops in the meta-arkoses towards -the the south} are consistently towards south, rUling ruling out out any any syncline within the unit. unit. The belt appears to be in fault fault contact with the biotite schists to to the the North North and and South: South: shear shear is is evident evident and and the the structure structure schists directions within'the Ilgreenstone belt" and the adjacent based on top top directions within the "greenstone bioti-te schists schists is is difficult difficult to to resolve resolve without without the the presence of these biotite these faults. biotitic and and chloritic chioritic A unit composed of of intimately intimately interbedded. interbedded biotitic schists to form aa gradational unit i!greenstone schists appears appears to unit between the "greenstone belt" and the biotite belt" biotite schists. schists. Apparently the assemblage of the "greenstone is gradational with and and overlain overlain by by the the biotite biotite "greenstone belt" belt" is The entire entire sequence of the the region thus represents a schists. The sequence of thus represents a thick accumulation which resulted from from relatively relatively continuous continuous deposition; deposition; volcaniclastic volcaniclastic sediment, sediment, clastic clastic sediment, sediment, and and minor volcanics grade upward into dominantly clastic (terrigenous?) upward (terrigenous?) sediment. sediment. Sulfides Sulfides are are quite quite commonly commonly disseminated in these these rocks rocks and small gossans several localities. localities. from the the small gossans were noted at several Rocks from Little some gold the Little America America Mine Mine which which produced produced some gold in the the 1890's 1890's from the the south south edge edge of of the the "greens-tone "greenstone belt" shear zone at the belt" contain gold and contain anomolous and silver, silver, and and rocks rocks from from aa few few other other localities localities contain anomolous values of gold, values gold, silver, silver, and and copper. copper. 'Work done :/Work done on behalf of the the Minnesota Minnesota Geological Geological Survey. Survey. �29. PETROLOGY OF THE REARING POND INTRUSION, INTRUSION, MELLEN9 WISCONSIN MELLEN, J. F. J. F. Olmsted Department of Physics Physics and and Earth Earth Sciences Sciences State Science State University College of Arts and Science Plattsburgh, Plattsburgh, New York, 12901 Intrusion is is part of the Keweenawan igneous The Rearing Pond Intrusion complex limb of the Lake Lake Superior syncline syncline complex which which lies lies along along the the south limb of the in Wisconsin. The intrusion is is roughly elliptical in plan and displays graded banding which dips toward the center from all displays directions, suggesting suggesting that that it it has has aa funnel-like funnel-like shape. shape. The directions, intrusion in contact the Mineral intrusion lies lies directly directly north north of, of, and and in contact with~ with9 the Mineral Lake anorthositic unit unit of of the the complex. complex. These two units are mineralogically and texturally in strong contrast with one another and the field field as as well as under the and are are readily recognizable recognizable in the microscope. The Intrusion is is emplaced emplaced into into what what appears appears The Rearing Pond Intrusion to to be be South Range Range type Middle Keweenawan volcanics, volcanics, but probably Lake Intrusion. Intrusion. earlier than the Mineral Lake The Rearing Pond Intrusion contains three major rock units that The The three types are best are in the the field. field. are readily distinguishable in described by listing the the cumulus cumulus minerals minerals in in order order of of abundance, abundance, according to the practice of of L. L. R. R. Wager Wager and and co-workers. co-workers. The earliest unit unit is earliest is an olivine cumulate (peridotite) (peridotite) which forms forms an outer shell, shell, followed followed by aa plagioclase-olivine cumulate (picritic (picritic gabbro), the latest part of the intrusion gives way to a a gabbro), which in the plagioclase-pyroxene-olivine cumulate cumulate (gabbro). (gabbro). The latter two two units The second combined form the core core or or inner inner zone zone of of the the intrusion. intrusion. The gabbro) also also contains contains fairly fairly large large amounts amounts of what unit (picri-tic (picritic gabbro) appears to be intercumulus appears to be intercumulus pyroxene which actually may also be cumulus. This thesis is is developed on the the basis of the fact fact that the This thesis banding noted above is banding noted above is largely due to the the variation of the content The fact of these poikilitic pyroxene pyroxene crystals. crystals. The fact that these crystals a pile of plagioclase and olivine could not have have developed in a crystals lying on the the bottom of the magma chamber can be reasonably crystals well shown shown on on textural textural grounds. grounds. Mineral compositions compositions in each of the Mineral the three units units show small changes but fractionation is changes is not not strong. strong. Plagioclase varies from from about An. An . ..80 80 (cores) the picritic gabbro gabbro to to about about An. An . ..60 60 (cores) (cores) (cores) in in the in the the latest gabbro. in gabbro. Normal zoning is is very common common and and in in any any crystal crystal the the change from core to rim is from 10 to 15 percent, percent, in either rock -type. type. Olivine and orthopyroxene both both have have compositions compositions either rock in the the range range of 80 percent Mg end-member in the peridotites to about 80 Mg the about LIttle difference is 65 in the the gabbros. gabbros. Little is seen seen 65 percent Mg end-member in in. the mineral mineral compositions compositions between between the the peridotite and in. the and the the picritic Intercumulus gabbro. Intercumulus myrmekite is is common common in in the the latest latest gabbros gabbros indicating fractionation has has proceeded. proceeded. indicating the the extent to which fractionation picritic �30. 30. RARE EARTHS IN IN ROCKS AND MINERALS MINERALS OF OF THE THE DULUTH COMPLEX T. T. P. P. Faster, Paster~ E. E. B. B. Denechaud, Denechaud, and L. L. A. A. Haskin Department Department of Chemistry University of Wisconsin, Madison, Madison, Wisconsin, Wisconsin, 53706 53706 Rock Rock samples samples of of all all principal principal types types from from the the Duluth Duluth Gabbro Gabbro complex in in Gabbro Gabbro Lake Lake quadrangle, quadrangle, Lake Lake County~ County, Minnesota, Minnesota, have have been complex analyzed for for rare rare earths. earths. As a first first approximation, the the relative relative As a abundances of the the whole rocks appear to reflect only the rare-earth abundances whole rocks Separated minerals from mineralogical compositions compositions of of the the rocks. rocks. from aa troctolite, a gabbro, and and aa pegmatite pegmatite are are now now being being analyzed. analyzed. troctolite, �31. MAFIC DIKES IN THE PRECAMBRIAN,ROCKS PRECAMBRIAN ROCKS OF OF GOGEBIC GOGEBIC COUNTY, COUNTY, MICHIGAN~/ MICHIGAN' Robert G. G. Schmidt and Virgil Virgil A. A. Trent Trent Robert U. U. S. S. Geological Geological Survey, Survey, 11ashington, Washington, 0. D. C., C., 20242 20242 Dark, sulfide-bearing, maf ic dikes dikes of of two two ages ages are are common common in Dark, mafic the of the the Gogebic Gogebic area. area. Although there is is the older Precambrian rocks of a a considerable range range in in the the dimensions, dimensions, composition, composition, age, age, texture, texture, and metamorphism, the most abundant dikes are hornblendeand degree degree of metamorphism, rich.:, containdisseminated disseminatedpyrite~ pyrite, and and are are moderately moderately metamorphosed. rich, contain The The youngest youngest dikes dikes are are mostly unmetamorphosed and at least some are younger than the oldest "South "South Range Range Traps". Traps". Detailed study study of the the dikes provides provides information useful in solving the geology of the dikes information useful the geology the enclosing rocks. rocks. The same general field field relations have been found found in in the Marenisco area and and in in the the area area south south of of Ironwood and Ramsay, Ramsay, 10 10 to to 20 miles to to area Ironwood and 20 miles the west. west. Most older dikes trend trend northeast, northeast, but but some some trend trend eastward; eastward~ younger dikes dikes trend trend northeast and and northwest; northwest; and both types appear to be joint well—defined younger dikes were found joint controlled. controlled. Many well-defined found within the the older dikes dikes in both areas, areas, and in exposures near McDonald Lake young young dikes dikes seem seem more more abundant abundant in in the the old old dikes dikes than than in the Lake in the adjacent granitic rocks. rocYs. Old dikes dikes are are particularly abundant Old abundant and thicker in a a northeast3-mile-wide belt Ironwood and and Ramsay. Ramsay. trending 3—mile--wide belt 22 miles miles south of Ironwood Some Some are are at at least least 600 600 feet feet wide, wide, and and others others can can be be traced traced several miles; drift on the south intermittently for for several miles; thick glacial drift us from from determining determining the the full full width width of of this this dike dike swarm. swarm. prevents us Furthermore, no hornblendic hornblendjc dikes dikes were were identified in the Furthermore, no the IronwoodIronwoodRamsay area age, and these older dikes dikes are Ramsay area within within rocks rocks of Animikie Animikie age, and these rare or perhaps perhaps absent absent in in the the northernmost northernmost 2-mile--wide 2-mile-wide band of prepreAnimikie granitic granitic rocks. rocks. dikes cropping out in the the central part of the Marenisco Most dikes quadrangle which intrude intrude metasedimentary rocks and derived gneiss quadrangle and schist are young, Both older and young, diabasic types. types. Both and younger dikes are common in the Presque Isle Granite to the south. are in Presque Isle Granite to the south. Although the old dikes near Ironwood old dikes Ironwood and Ramsay are undeformed, many are essentially undeformed, the Marenisco area are strongly strongly sheared. sheared. in the All dike contacts contacts we we have have seen are chilled. chilled. Even though a a particular contact is not exposed, we interpret partiCUlar interpret the abrupt diminution of grain size size to to represent represent aa chilled margin. margin. Most dikes have relatively uniform uniform compositions compositions and several large large and grain sizes, but sever.l ones are notably on~s.are notably inhomogeneous. inhomogeneous. Rhythmic color banding of of unknown unknown origin and local local segregations segregations of of llgabbroic gabbroic pegmatite" o~lgln.and pegmatite" were found. found. Diabasie textures Dlabasl: textures predominate predominate but but eQuigranular equigranular gabbroic textures are ar2 common in ln the coarse—grained coarse-grained bodies. bodies. */ done in cooperation with the , -"Work - W?rk.done the Geological Geological Survey Division of the of tne Michigan Mlchlgan Department Department of Conservation, Conservation. - �32, 32. The older The older dikes dikes owe owe their present mineralogical assemblage to metamorphism under conditions of the greenschist facies (Turner the upper greenschis-t facies (Turner and Verhoogen, and Verhoogen, 1960), 1960)j followed a very unevenly unevenly distributed distributed followed by a retrograde metamorphism. retrograde metamorphism. The fresher rocks contain mainly hornblende and plagioclase, plagioclase, but and but chlorite, epidote, clinozoisite, clinozoisite, and calcite chlorite, epidote, are also present in most places, places, depending upon the extent extent of of metamorphic effects. effects. retrograde metamorphic The younger dikes The dikes are are augitic, augitic, with strongly zoned plagioclase laths; locally these dikes are considerably altered, laths;.locally altered, perhaps perhaps deuterically. deuterlcally. The possibility that a a late late period of metamorphism has affected has affected some area must must still still be be some of of the the young young dikes dikes in this area tested. tested. In both the retrograde or deuteric In both types types of of dikes dikes either the effects, effects, or both, both, principally principally affected the the mafic mineral, mineral, but locally the plagioclase is is preferentially preferentially altered. Our work to date does not not permit to say anything regarding direction of metamorphic permit us us to gradients. The old hornblendjc hornblendic intrusives intrusives may be be contemporaneous contemporaneous with sills that that cut cut the the Ironwood Ironwood Iron-Formation east of sills of Wakefield. Wakefield and are truncated by lower Keweena.wan Keweenewan strata as truncated W. C. C. Prinz Prinz (1967). (1967). as mapped by W. The younger augitic dikes intrude lower Keweeriawan Keweenawan quartzite and quartzite and some of the the ttSouth "South Range to Range Traps" Traps?? both both at at Bessemer Bessemer and, and, according to C. E. E. Fritts Fritts (written (written communication, communication, 1966), just just west of of the the Cisco Cisco C. Branch of the Ontonogon River. River. Appreciable magnetic variations are are rarely found associated with the old old mafic mafic rocks rocks observed, observed, but a the a very notable exception exception is is the the magnetite-rich sill magneti-te-rich rock rock in in the the northern northern part part of of the the metamorphosed sill described by W. W. C. C. Prjnz Prinz (1967). (1967). The The augitic augitic dikes dikes contain enough magnetite to magnetite to be detected with aa small small hand hand magnet magnet and generally have strong with them. them. Near Ironwood and strong magnetic magnetic anomalies anomalies associated with Ramsay the anomalies anomalies are sign, in contrast are probably probably all all of of positive positive sign, to to the the consistently negative negative anomalies anomalies associated with dikes of Keweenawan by Keweenawan age age farther farther east east in northern Michigan as described by J. R. Balsley, H. L. James, and K. L. Wier, (1949). Near Marenisco J. R. Baisley, H. L. James, and K. L. Wier, (1949). diabase dike dike anomaly was determined to be be of negative negative sign. sign. one diabase A special interest in the dikes developed when it it was noted noted that that many of the the large large mafic mafic masses masses contain contain sulfides. sulfides. The largest are at at least 600 600 feet wide and and perhaps perhaps 3000 3000 feet feet long. long. Disseminated sulfide least generally ranges 0.20.l4 0.2-0.4 per per cent. cent. Semi-quantitative Semi-quantitative spectrographic analyses analyses and atomic absorption spectrometry determinations determinations indicate indicate low low copper, copper nickel, spectrometry nickel, cobalt, cobalt, and and silver contents in in all all these these rocks. rocks. An attempt was made made to to relate relate age and and minor element composition of the mafic rocks, rocks, but no age differences were noted although there is is a suggestion suggestion significant differences of somewhat amounts of titanium, of somewhat higher amounts titanium, beryllium, beryllium, copper, copper, and augitic dikes. dikes. we strontium in the younger, augitic For the present we conclude that that although although sulfide—bearing, conclude sulfide-bearing, neither type type of dike is is of economic interest for its its metal content. content. �33, 33. References Baisley, J. J. R.; R., James; James H. Balsley, H. L., L., and and Wier, Wier, K. L., L., 1949, Aeromagnetic 199, Aeromagnetic survey of of parts parts of Baraga, survey Baraga, Iron, Iron, and and Houghton Houghton Counties, Counties, Michigan, with preliminary S. Geol. Geo1 preliminary geologic geologic interpretation: interpretation: U. U. S. Survey) Geophys., Prelim. Rept. Rept. Survey., Geophys., Inv. mv. Prelim. Prinz, w. W. C., C., 1967, 1967, Pre-Quater'nary Pre-Quaternary geologic geologic and and magnetic magnetic map map and and Prinz, sections of of part of the eastern Gogebic sections Gogebic iron iron range, range, Michigan: Michigan: U. U. S. S. Geol. Geol. Survey Survey Misc. Misc. Geol. Geol. mv. Inv. Map MapI_1497, 1-497. Turner, F. J., and and Verhoogen, Turner, F. J., Verhoogen~ John, John, 1960, 1960, Igneous Igneous and and metamorphic petrology: 2nd ed., N. Y., Y., McGraw—Hill McGraw-Hill Book Book Company, Company, 2nd ed., New York, York, N. 69L p. 694 p. �3L4 34. SEISMIC REFRACTION REFRACTION SURVEY OF THE AMES ANTICLINE, AMES, AMES, TOt'A IOWA L. V. A. Sendlein L. V. A. Sendlein Department of Earth Science Science University, Ames, Iowa State University, Ames, Iowa, Iowa, 50010 50010 and W. W. P. P. Staub Staub Department of Geology College of of St. St. Thomas, Thomas, St. St. Paul, Paul, Minnesota, Minnesota, 55101 College 55101 If Ames, Ames, Iowa Iowa lies lies astride astride the the mid-continent mid-continent gravity gravity high. high. this geologic this important important anomaly anomaly is is to to be be properly properly understood, understood, geologic information is is essential. essential. The method was was The seismic refraction method selected selected to to investigate investigate the the geology geology of of the the drift drift covered Ames Ames region because of its its economy economy and and reliability. reliability. There There is is a a remarkable remarkable correlation between seismic selsmlC and gravity data from the the Ames Ames region. region. This suggests that the This correlation suggests field is is influenced by the thickness of residual gravitational field glacial structure. Seismic data were used used glacial drift drift as as well as geologic structure. produce a a structure contour map of a a high speed Mississippian to produce marker horizon. horizon. The map illustrates an arched horst (Kinderhook) marker is consistent with the the residual residual gravity gravity map. map. Evidently the that is horst is associated with the the mid-continent mid-continent gravity gravity high. high. �35. SOLUTION AND DEPOSITION OF IRON IRON IN IN SEDIMENTS SEDIMENTS G. H. G. H. Spencer, Spencer, Jr. Jr. 619 619 First American Bank Building Building Duluth, Minnesota, 55802 55802 iron minerals minerals are are found found in in many many geologic geologic Sedimentary layers of iron areas associated associated with with volcanic volcanic materials materials sandstone, areas sandstone, clays, clays, limestones and even even coal coal beds. beds. The theories of of origin of of these these iron bearing conflicting because an inability inability to iron bearing beds beds are are often often conflicting because of an to discover the the chemical chemical and and sedimentary processes processes involved in the discover the different environments. j Dissolution of of iron acid waters waters may may be be due Dissolution iron in ln acid due to to either dissolved volcanic gases or to organic acids produced by by bacterial In acid acid volcanic waters, action on plant material. In waters 5 northern lakes, lakes, and possibly in Pre-Cambrian seas iron has and seas , iron has been leached from from bottom sediments either as chlorides or sulfates or as organic complexes. Organic complexes or chelates chelates of of iron iron are are soluble soluble to to several thousand parts per million and and are are as as effective effective solvents solvents several for for iron as volcanic waters. waters. , as aa carbonate, Deposition of iron as carbonate, silicate, silicate, sulfide sulfide or even as an an oxide oxide is due to to aa gradual or sudden relative relative increase as is due increase of This may may be be due due to to loss of gases gases from from alkalies in in solution. solution. This loss of solution by a a pressure or temperature temperature change change or or to to actual actual increase increase of alkalies ions ions in in solution. solution. A few examples of the the various various types types are discussed. �36. A MAGNETO-TELLURIC STUDY STUDY OF OF THE THE NORTHEASTERN LAKE LAKE SUPERIOR AREA Hans Tammemogi Hans Department of Physics University of of Toronto, Toronto, Toronto~ Toronto, Ontario University from stations stations at at Port Port Arthur, Arthur,1'iarathon, r1arathon, Chapleau Results from Chapleau and Michipicoten Island Island will be be presented. presented. These include include polarization polarization and anisotropy studies, as as well as geomagnetic depth sounding and and anisotropy studies, well as magneto-telluric resistivity profiles. Preliminary results indicate indicate magneto--telluric resistivity Drofiles. anisotropy and and unusually unusually high high apparent apparent resi.stivities. resistivities. �37. GEOLOGIC EXAMINATION OF PIPELINE TRENCH EAST GOGEBIC GOGEBIC RANGE, RANGE, NICHIGAN!/ MICHIGAN:'!/ THROUGH THE EAST Virgil Trent U. S. Geological Survey, U. S. Geological Survey, Washington, Washington, D. D. C., C., 20242 20242 surficial deposits deposits exposed exposed along along 16 16 miles miles of of a. a Bedrock and surficial natural gas pipeline trench through the Wakefield-Marenisco area natural area prior to to backfilling. backfilling. Thirty-five samples samples were were collected collected were mapped prior for hand hand specimen and laboratory The location of the pipeline for laboratory study. study. The on standard topographic base maps was was facilitated on standard topographic base maps facilitated by pipeline survey maps supplied through the courtesy of Williams Bros. Bros. Co. Co. of Tulsa, Okla. Geologic data obtained from the trench across the southern southern half of the Marenisco 7-1/2 minute quadrangle were compared with data from previous geologic mapping. mapping. The 88- to to 10-foot--deep IO-foot-deep trench trench exposed shallow shallow ledges ledges in many places, places, and and numerous cuts were were made made exposed in many numerous cuts into bedrock. Near the center of the Wakefield NE quadrangle in in the SW SW 1/4 of sec. 28, W.,1 1toto2 2feet feetof of white white Quartzite quartzite was sec. 28, T. T. 47 44 W., 347 N., N., R. 3434 exposed for for 20 20 feet feet along the the trench and numerous scattered scattered boulders of thinly laminated siliceous dolomite were found 200 200 feet to the east. Sunday Quartzite and/or Bad Bad These rocks probably represent Sunday This trench trench exposure River Dolomite. Dolomite. This exposure extends extends the the known area underlain by these these units southward one mile from exposures mapped by W. C. Prinz (U.S.G.S.). (U.S.G.S.). It is the of these these W. C. It is the southernmost occurrence of middle Precambrian Precambrian rocks. rocks. W., the the South T. 47 47 N., N., R. R. 3434 44 W., South of of Wolf Wolf Mountain Mountain in in sec. sec. 35, 35 T. trench exposed a a wide belt of gneissic rock striking northeast appears to which appears to be quite similar to rocks rocks which crop out near the Recent center of the Marenisco quadrangle. quadrangle. Recent mapping in in sections sections 28, 28, 21, and and 22, 22, T. T. 47 47 N., N., R. R. 43 43 W., W., support support the the thesis thesis of of R. R. C. C. Allen Allen 21, and L. and L. P. P. Barrett Barrett that that these rocks rocks were derived from metasedimentarv metasedimen-tarv rock of their Palms Formation. Formation. Paragneiss and paraschist which crops out in the crops the center of sec. sec. 28, 28, T. T. 47 47 N., N., R. R. 43 43 W., W., can be traced outcrops to the where, over a traced in aa series series of outcrops the northeast, northeast, where, a distance of of 1/2 1/2 mile, mile, their transition distance ~ransition to metasedimentary rock of the the Palms Formation Formation is is evident. evident. Numerous blasted exposures of the Presque Presque Isle Isle Granite along along the that many of the the the trench trench in the the Marenisco Marenisco quadrangle quadrangle suggest that transitional lithologic changes in in this unit are a result of stress mineral formation formation and and mineral mineral alteration. alteration. Rather Rather abrupt transitions from granite granite porphyry, porphyry, pegmatitic pegmatitic granite, granite, or equigranular granite granite from ll a mottled, Tl con taminated-appearing to a mottled, "contaminated—appearing" rock containing wisps or lameliae micaceous minerals minerals and which grade from incipient lamellae of dark micaceous Work ~/Workdone doneinincooperation cooperation with with the the Geological Geological Survey Division the Michigan Department of of the of Conservation. Conservation. �38. to good foliation foliation are are common. common. No evidence was found along the trench for granite of more age, and geologic field field mapping to date for more than one age, indicates indicates this this granite granite intrudes intrudes the the Animikie Animikie strata strata with with considerabl.e considerable previously reported reported by by R. R. C. C. Allen Allen and and L. L. P. P. contact effects as previously Barrett. Barrett. Two wide wide fracture were exposed in cuts in granite along Two fracture zones zones were the trench east of the Marenisco mine the mine road. road. Previous mapping gave gave Fault traces are little extent of of fracturing. fracturing. are little indication of the extent zones from 66 to 24 24 inches inches wide within marked by mylonitized shear zones the shattered rock. the rock. The radioactivity was continuously monitored along the the pipeline model T-l T-l scintillator. scintillator. Higher than ordinary trench using a McPhar model readings readings were noted in sections of sheared granite, granite, and mass effect effect was along the the bottom bottom of of the the trench. trench. Thin sections of was quite apparent along pegmatitic granite contain sphene, sphene, zircon, zircon, allanite, allanite, and probable monazite as as common common accessory accessory minerals; biotite biotite enclosing enclosing many many of of shows radiation halos. halos. A chemical analysis of these minerals shows megascopic sphene sphene crystals from from pegmatitic pegmatitic granite granite in in the the Presque Presque Isle Granite gives gives 1500 1500 parts parts per million (ppm) (ppm) yttrium, yttrium, 1000 ppm Isle lanthanum, niobium, suggesting that the Presque Isle lanthanum, and and 300 300 ppm niobium, pegmatitic pegmatitic granite granite has has aa higher background radioactivity than other intrusive intrusive rocks in in the the area. area. Radioactive thorium oxide is commonly associated with the rare earth earth elements elements and and sphene. sphene. Glacial deposits deposits were were very well exposed along the 16 miles of Glacial pipeline trench. trench. Boulder till till made made up up the the bulk of of the material material but swamp accumulations and and stratified sand and gravel deposits swamp or bog accumulations were exposed exposed locally. locally. Clearly, profile section section such such as as Clearly, an extended profile that a that provided provided by aa pipeline pipeline trench would be be of great value in a study of the surficial surficial deposits. deposits. Because pipeline excavations are are temporary temporary and and progressive, progressive, Because geologists concerned with areas through which they pass pass should should be be forewarned construction. The forewarned about the planned construction. The State Geological Surveys are are probably probably in the best best position to to provide provide this Surveys in the this important information to interested interested workers. workers. �39. PRECAMBRIAN PRECAMBRIAN GRANITIC GRANITIC ROCKS ROCKS AND AND PRE.-KEEWATIN PRE-KEEWATIN (7) (?) PARA-GNEISSES OF THE NASHWAUK-BUHL SECTOR, SECTOR, NORTHERN MINNESOTA _METAMORPHIC OR IGNEOUS COMPLEX? COMPLEX? S. Viswanathan Viswanathan and and William C. S. C. Phinney Minnesota Geological Survey Survey Department of Geology and Geophysics Geophysics University of Minnesota, Minnesota, Minneapolis, Minneapolis, Minnesota, Minnesota, 55455 55455 Previous and petrology petrology of of the the granitic granitic Previous knowledge of the geology and complex north of the Nashwauk-Buhl sector of the Mesabi iron range, in limited to to the the work work of of I. I. S. S. Allison in Northern Northern Minnesota, Minnesota, has been limited (1925). Allison regarded this area as being part of an elongate (1925). Giants Giants Range Range batholith (Algoman) (Algoman) extending for for some some 100 miles from the vicinity of Grand Grand Rapids Rapids to a point 15 15 miles and the to a miles east of Ely and having an average width of of 88 miles. miles. He believed that that the the batholith batholith attained its maximum width, a north-south attained its width, about about 18 18 miles, miles, in a direction in the area of our our present present study. study. Detailed some 500 500 square square Detailed reconnaissance reconnaissance geological geological mapping mapping of of some miles north of the Nashwauk-Buhl sector of the range during the summer of 1968 has shown shown that the the width width of of the the batholith batholith in in this this is substantially SUbstantially less than previously believed, believed, and that it area is seldom exceeds 88 to to 10 10 miles. miles. Further, our work has revealed that that Further, the the granitic granitic rocks rocks exposed exposed in in this this area area are are mappable mappable as as four four major major zones; from south to north northeast-southwest trending conformable zones; these are: are: Zone (1) (1) a a medium-grained, massive biotite biotite granite granite (8 (8 Zone miles long and 44 miles wide), (2) a coarse-grained, coarse-grained, foliated, foliated, wide), Zone (2) granite (12 (12 miles miles long long and and 55 miles miles wide), wide), Zone Zone (3) (3) porphyritic biotite granite a medium-grained, a medium—grained, muscovite- and biotite-bearing gneissic granite which is is garnetiferous garnetiferous in places (15 (15 miles long and 4 miles wide) and and miles wide) is associated with several types of of inclusions inclusions of of Knife Knife Lake Lake is (Timjskamjarj) affinities, affinities, and and Zone Zone ('4) fine-grained, compactly compactly (Timiskamian) (4) a a fine-grained, foliated (15 miles miles long long and and 44 miles miles wide). wide), foliated biotite-muscovite granite (15 (4) and (3) (3) could be ascribed to processes of The evolution of zones (4) partial melting and replacement of pre-existing sedimentary country (Knife Lake Group) Group) during during metamorphism. metamorphism. rocks (Knife '4 the area is is characterized by thick sequences The western half of the (Ely) pillowed pillowed basalts basalts (massive (massive as as well well as as of presumed Keewatin (Ely) schistose)) ortho-amphibolites, striped schistose), striped (para) (para) epidote-amphibolites, epidote-amphibolites, minor intercalated meta—sediments, meta-sediments, gabbro dikes dikes and a a suite of granitic rocks rocks altogether altogether different different from from those those in the eastern eastern half half granitic in the of the area in that they contain hornblende and are granodioritic in composition. Within this complex) complex) it it is is possible possible to to map map aa meta— metasedimentary--migmatitic rock rock unit, unit, measuring measuring at least sedimentary--migmatitic least 10 10 square square miles, miles, is petrographically petrographically diverse. diverse. The unit is is composed composed of of quartzquartzthat is plagioclase-biotite--epidote-gneisses, plagioclase-biotite-epidote-gneisses,quartz-plagioclase--b±otite--quartz-plagioclase-biotitemuscovite-gneisses, quartz—plagioclase--hornblende-biotite-epidotequartz-plagioclase-hornblende-biotite-epidotegneisses, gneisses, quartz-plagioclase-biotite-staurolite (7) (?) rock, rock, quartzplagioclasebiotite-epidote--sillimanite (?) •-gneisses, plagioclasebiotite-epidote-sillimanite (?) -gneisses, layered hornblende—quartz-plagioclase hornblende-quarTz-plagioclase rocks, rocks, hornblendites, hornblendites, and granitic This unit unit is be of of pre-Keewatin is tentatively considered to to be mylonites. This (1) it is is stratigraphically stratigrahica1iy below age following reasons: reasons: (1) it below age for the following �40. the presumed Keewatjn volcanic and meta—volcanic sequence, Keewatin (Ely) (Ely) volcanic and meta-volcanic sequence, and (2) it it is is wholly wholly unlike unlike any any known component of the Knife (2) Knife Lake Lake Group. Group. The implications implications of this find could could provide a fresh fresh impetus to the the this find provide a Coutchiching controversy. controversy. In addition addition to to conventional conventional petrographic petrographic work, work, the the techniques techniques of of In oxygen isotope isotope geochemistry and and trace element analysis and major and trace element analysis by x-ray fluorescence and electron microprobe microprobe methods methods are fluorescence and are being used in the study of the rocks discussed herein. the herein. �410 SHALLOW SEISMIC STUDIES IN IN WESTERN LAKE LAKE SUPERIOR SUPERIOR Richard J. J. Wold v.70ld Department of of Geology Geology University of Wisconsin-Milwaukee, Wisconsin—Milwaukee, Milwaukee, Milwaukee, Wisconsin Wisconsin9 53201 University of 53201 A continuous seismic seismic reflection profiling profiling program program was was begun begun in in A Lake Superior in in 1965 1965 with with an an EG&G EGG Boomer, Lake Superior Boomer 9 continued continued in in 1966 with an an EGG Sparker. The regional regional study ended in 1967 with a EG&G Sparker. The a Bolt air—gun air-gun used as as the seismic energy used energy source. source. Altogether some 6000 6000 miles of profiles were obtained in in Lake Lake Superior. Superior. This paper will report report on on the of the the tip tip of of the the Keweenaw Keweenaw Peninsula. Peninsula. the profiles obtained west of Sufficient detail detail was was obtained in most areas Sufficient areas to correlate from one one profile profile to to the the next next so so that that an isochron map was was constructed of -the material above above "bedrock". the material "bedrock!!. The isochron map shows shows lines lines of of equal equal difference; large numbers indicate indicate thick accumulations reflection time difference; above ?bedrock? Iibedrock" and thin accumulations are indicated indicated by small isochron isochron numbers. Several buried valleys are outlined on Several on the the isochron isochron map. map. Two impressive valleys valleys parallel parallel the the north-shore north—shore from to Isle impressive from Duluth to Isle It is is quite quite likely likely that that the the valley valley closest closest to to shore shore is is due due Royale. It to differential erosion between between volcanics volcanics and and sediments. sediments. Other to valleys are observed near the center of the Lake Superior Syncline valleys to outline outline it. it. The data also indicate indicate the the apparent apparent and seem to the underlying underlying bedrock bedrock in in many many areas. areas. direction of dip of the �42. p42. ORGANIC STRUCTURES (IRON) FORMATION, FORMATION, STRUCTURES FROM THE NEGAUNEE (IRON) MARQUETTE RANGE, RANGE, MICHIGAN G. Wygant and Joseph J. J. Mancuso Thomas C. Department of Geology Bowling Green State State University, University, Bowling Bowling Green, Green, Ohio, Ohio, '43'O2 43402 In the the course of aa continuing In the mineralogy and continuing study of the stratigraphy of the the Negaunee (Iron) (Iron) Formation, Formation, curious curious structures structures were found which in in form form and and occurrence appear to be organic in origin. origin. These structures are present in in specimens specimens taken taken from from the the magnetite-chert-silicate unit of the Negaunee Formation Formation which which is is exposed in the Empire Pit, exposed Pit) Palmer, Palmer, Michigan. Michigan. The iron formation formation at at this this locality has has suffered suffered the the least least amount amount of metamorphism, structural is known in the the Marquette structural deformation, deformation, and and oxidation that that is Iron Range. Range. the structures are If the In origin, origin, it would add are indeed organlc organic in credibility to to the theories which postulate postulate an organic or biochemical biochemical control on on the control the deposition of iron iron formation. formation. �""': :,";{/ '':'-',,--:',' . -' "',~' ': ... " , ' . . " ç .3 1 ' . ' I .:! ii- ":' - I i. : " ...., 2mm 2 mm , — 2 •r ::: .:. :.. ' \ '& L 2 mm - ....... '. ~ it '" 2 - - - — I .1 , ,,' .. . ,', . ... ... I I ;'" '-' .. ~,,:,,: .":~: " ' ' �L4.LL 44. K-Ar K-Ar DATING DATING OF TWO DYKE-SWARMS FROM THE NORTH SHORE OF LAKE SUPERIOR D. H. C. C. Halls Halls D. York and H. Physics Geophysics Division3 Division) Department of Physics Toronto, Toronto, Toronto, Ontario Ontario University of Toronto, geographic'.ly . .Whole been carried carried out out on on two two geographi0~J Jy Whole rock K-Ar dating has been Four Superior. dlst1nct sets sets of of dyke.s dykes from distinct from the the north north shore shore of Lake Superior. Four MjChiP±C0t1 dykes from north of of MichipicoteJl dykes from aa swarm swarm in in the the Pukaskwa Pukaskwa region) region north The among Island, 1020 and and 1070 1070 m.y. m.y. The scattel' scatter among Island, give K-Ar ages between 1020 and it seems the results results lies lies within the range of experimental experimental error error anJ it seems the 1050 JT1.V. ago. that all the the dykes dykes in this this group were emplaced emplaced about about 1050 m.~'· ago. each gwarrn were Two dykes dykes from the Sibley Peninsula-Grande Portage Portage swarm were each and analysed in duplicate and give mean ages of approximately approximately. 1150 lISa and analysed of dvkes m.y. It therefore) that that this this set set of dvkes Is 1S It appears, appears, therefore, 1210 m.y. Whether more region. measurably measurably older older than those from the Pukaskwa region. Whether more Sibley_Grande than than one one age age of emplacement is represented in the Sibley-Grande general The results Portage dykes remains to to be be determined. determined. The results in in general Portage dykes their radiogenic radi0g'-° argon indicate that that the the diabase diabase dykes dykes have have retained retained their argon indicate material for K-Ar extremely extremely well well and and are are evidently evidently satisfactory material for K-Ar dating in this age range. dating range. �L5 450 STRATICRAPHICAL, AND SEDIMENTOLOGICAL STRATIGRAPHICAL SEDIMENTOLOGICAL COMPARISON OF EARLY PROTEROZOIC ROCKS ROCKS OF S.E. S.E. WYOMING AND THE GREAT LAKES LAKES REGION Grant N. t1. Young Department of Geology University of Western Ontario, Ontario, London, London~ Ontario The The Huronian Huronjan rocks rooks of the the north shore of Lake Huron were 2.5 and and 2.1 2.1 b.y. b.y. ago ago (van (van Schmus, Schmus, deposited between approximately 2.5 1965) and and were were folded 1965) folded in an orogeny (Penokean?) (Penokean?) which was was initiated more than 2.1 2.1 b.y. b.y. ago ago (Church, (Church, 1966). 1966). The Animikie "Series" "Series!! of of the the Lake laid down between 2.0 2.0 and 2.5 2.5 b.y. b.y. ago Lake Superior region was was laid (Aldrich et et al. al.) 1965). A recently suggested stratigraphic correlation of the Huronian succession with the of the the upper part part of the lower part part of of the the Animikie Animikie (Young, lower (Young~ 1966) 1966) results results in a a combined sequence of of sedimentary formations which closely resembles resembles that sequence sedimentary formations that of Early Proterozoic rocks of the the Medicine Medicine Bow Bow Mountains Mountains of of S.E. S.E. Wyoming. Wyoming. Early Proterozoje The Wyoming rocks were deposited between 1.65 and 2'41 2.41 b.y. b.y. ago (Allan Hills et al., The stratigraphic succession (Allan al., 1967). 1967). The succession in in the the Medicine (1926) and Medicine Eow Bow ~10untains Mountains area area was was described described by Blackwelder (1926) been divided divided into into two two parts parts by by Houston Houston (1967). (1967). The has recently been lower is aa highly varied succession lower part, part, the the Deep Deep Lake Lake Formation) Formation, is highly varied chloritic schists, schists, metaconglomerates, metaconglomerates, quartzite and siliceous of chioritic marble. Quartz in the the basal basal part part of of the the Quartz pebble pebble conglomerates in succession are are strongly reminiscent of of the the basal basal uraniferous uraniferous conglomerates Formation is is conglomerates of the Ontario Huronian. The The Deep Lake Formation succeeded succeeded by by the the more more extensive extensive Libby Libby Group Group which which oversteps oversteps the the commonly lies lies directly directly on on basement basement rocks. rocks. older units and commonly The oldest unit of the Libby Group contains polymictic interpreted by by Blackwelder Blackwelder as as tillites. tillites. conglomerates which were interpreted Associated finely finely laminated argillites contain scattered scattered (ice (ice rafted?) rafted?) clasts. The overlying Heart Formation is a a highly varied succession succession The mudstones and and sandstones sandstones with with ball and pillow of meta—siltstones., meta-siltstones) mudstones pillOW structures, cross beds. beds. These two formations formations structures, ripple marks and cross Formation of Ontario (a (a correspond very closely with the Gowganda Formation twofold division of the the Gowganda Gowganda is is possible possible in in many many areas). areas). Above the Heart Formation of of Wyoming Wyoming occurs occurs the the Medicine Medicine Peak Peak Quartzite, Quartzite. This unit This unit closely resembles resembles the Lorrain Formation of Ontario in that upwards, both contain jasper jasper both become progressively mature upwards, pebbles, kyanite (probably a metamorphic derivative from kaolin) pebbles, (probably a kaolin) and the chrome mica fuchsite. the fuchsite. The overlying overlying Lookout Lookout Schist Schist and. and Sugarloaf Quartzite of the the Wyoming area show show close similarity similarity to the Gordon Lake respectively of of Ontario. Ontario. Thicknesses Lake and and Bar River Formations respectively of the corresponding units units are are closely closely comparable comparable in in the the two two areas. areas. The regions occur in similar The Early Proterozoic rocks of both regions tectonic settings settings (southern edge of of the the Superior craton) craton) and and display display tectonic (southern edge remarkably similar similar sedimentary sedimentary structures structures in in corresponding corresponding formations. formations. The in such such widely separated areas The presence presence of of tillites tillites in widely separated areas as as Wyoming Wyoming and (Chibougamau) indicates indicates an and N. N. Quebec Quebec (Chibougamau) an extensive extensive North North American American glaciation in in Early Early Proterozoic Proterozoic times times and and lends lends support to the the idea idea glaciation support to that contemporaneous. that these deposits are approximately contemporaneous. �46. References Aldrich., L.L. T. T., Davis, Davjs G. Aldrich) G. L. and H. L., L., 1965. 1965. Ages of minerals and James, James, H. from igneous rocks near Iron Mountain, Michigan. Michigan. from metamorphic and igneous J. J. Petrol.5 Petrol., V. v. 6, p. 445. p. j I... 5. Hills)F., F. Gast, Gast)P.P.W., W.,Houston, Houston R. R.S.S.and and Swainbank J J.J. G.., G., Allan Hi11s Swainbank., 9 1968. 1968. Precambrian Precambrian geochronology geochronology of of the the Medicine Medicine Bow Bow Mountains, Mountains Bull. Bull. Geol. Geo1. Soc. Soc. Amer., Amer., v. p. 1757. 1757. V. 79, p. j Blackwelder, E., Blackwelder, E. 1926. 1926. Precambrian Precambrian geology of the the Medicine Medicine Bow Mountains. Bull. Geol. Geol. Soc. Soc. Amer., v. v. 37, 37, p. p. 615. 615. Bull. j Church W. Church, W. R. R.~ 1966. The Penokean orogeny orogeny in in Ontario. Ontario. The status of the Penokean Prog. Ninth Conf. Conf. on Great Great Lakes Lakes Research, Research, Chicago, Chicago p. p. 25. 25. Prog. j Houston, R. R. S., S., 1967. 1967. Geologic map of the the Medicine Bow Bow Mountains, Mountains~ Albany and and Carbon Carbon countjes counties,Jyorning. Wyoming. Plate 1, 1, Mem. Mem. 1 1 (in (in press), Geo1. Surv., Surv., Wyoming. Wyominp. press), Geol. van Schmus, Schmus, R., R., 1965. 1965. The geochronology of the the Blind Blind River-Bruce River-Bruce Mines area., Ontario, Canada. area, Ontario, Canada. Jour. Ge01., v. v. 73, 73 p. p. 755. 755. Jour. Geol. j Young) G. Young, G. M., M., 1966. 1966. Huronian stratigraphy of of the the McGregor McGregor Bay Bay area, area) Ontario; the Lake Lake Superior Ontario; relevance relevance to to the the paleogeography of the region. Can. p. 203. 203. Can. J. J. Earth Earth Sci., Sd., v. v. 3, 3 p. �L7 47, EXPLORATION OF THE ROUND LAKE LAKE ANOMALY, ANOMALY, COUNTY, WISCONSIN SAWYER COUNTY, Wayne R. R. Zwickey The The New Jersey Zinc Company Plattevj11e Wisconsin, Platteville~ Wisconsin~ 53818 53818 The Round Lake magnetic anomaly, located located on on the the east east side side of The Round Round Lake Lake in in T41N) T'JN R7W, Round R7W, Sawyer Sawyer County, County, Wisconsin, Wisconsin, was was discovered by In 1960 a Wisconsin Geological Geological Survey Survey dip dip needle needle survey survey in in 1914. 1914. In a and The New New Jersey Jersey Zinc Zinc Company Company investigated investigated this this intense intense and 1961; l961 The magnetic anomaly anomaly by by detailed detailed magnetic magnetic and and gravity gravity methods, methods, negative magnetic as well well as diamond drilling. as drilling. The this investigation investigation will will The results of this be discussed. -= � https://digitalcollections.lakeheadu.ca/files/original/614a122132f4385220a1c4d955129e39.pdf 06be3b139084257ee0756ebd1180b55a PDF Text Text �U h I CENTRAL WISCONSIN VOLCANIC BELT Leonard W. Weis University of Wisconsin-Green Bay Fox Valley Campus By: Gene L. LaBerge Wisconsin State University-Oshkosh With The Collaboration Of: Carl E. Dutton U. S. Geological Survey Madison, Wisconsin Guidebook for Fifteenth Annual Institute on Lake Superior Geology, May, 1969 �U I TO: Dr. Carl E. Dutton, who pointed out the significant exposures from his first hand knowledge of the area. He gave freely of his time and knowledge--both of particular areas and from his 40 years experience in the Precambrian of the Laira Superior region. His generous help, encourage- ment, and thought-provoking approach made preparation of this Guidebook a stimulating learning experience. L.W,W. G.L.L. �I ACKNOWLEDGMENTS The success of any field trip depends in large part upon the cooperation and We wish to express our thanks to all assistance of many individuals and organizations. those who have played a part in this trip. Mr. George Hanson, Director of the Wisconsin Geological and Natural History Survey furnished the Geologic Map of Wisconsin. Financial support for publishing the guidebook was furnished by the Geology Departments of WSU-Oshkosh, UW-Center System, and UW-Green Bay. given both in drafting and handling of the trip. drafting maps are due Man Student help has been generously Special thanks for her work in Poythress, of WSU-Oshkosh. The manuscript was typed by Mrs. Pamela Spaulding. In addition, we wish to thank the following property owners for permission to visit their properties or use their facilities: Employers Insurance of Wausau Mr. & Mrs. Robert Zielsdorf, Wausau Mr. Ray Slocum, Wausau Mr. Alfred Reimes, Town of Easton Mr. Herman Marquardt, Town of Easton �I U GEOLOGIC MAP OF WISCONSIN I AFTER BEAN, 1949 I SCALE OF MILES Milwaukee Formation (cbofly doiomt,c shIe( Niagara Formation (dolomde) Maquoketa Formation (dokomti shale) Platteville-Galena Group (doiomite odh some f,mestoee) St. Peter Formation (soodst000) Prairie du Chien Group ;LI (dniomte) Upper Cambrian Group (chefiy sandstones) Lake Superior Group (sandst0005) Quartzite, Slate and Iron Formation Gabbro and Basalt Granite and Undifferentiated Igneous and Metamorphic Rocks Border of Wisconsin (Cary) Drift Border of Older Drift Umv*ity of Wisconsin Wisconsin Geological and Natural History Survey George F. Hanson, Director and State Geologist ELEVATION ABOVE SEA LEVEL IN FEET 0 10 20 30 40 HORIZONTAL SCALE IN MILES �U SHORT GEOLOGIC HISTORY OF WISCONSIN ii The bedrock of Wisconsin is separated into two major divisions: (1) older, predominantly crystalline rocks of the Precambrian Era, which were extensively deformed after their deposition by movements of the Earth's crust; and (2) younger flat-lying sedimentary rocks of the Paleozoic. The Precambrian Era lasted from the time the earth cooled, over 4,000 million years ago, until the Paleozoic Era which began about 500 million years ago. During this vast period of 3,500 million years sediments, some of which were rich in iron and which now form our iron ores, were deposited in ancient oceans, volcanoes spewed forth ash and lava, mountains were built and destroyed, and the rocks of the upper crust were invaded by molten rocks of deep-seated origin. Only a fragmentary record of these events remains but, as tree stumps attest the former presence of forests, the rocky roots tell the geologist of the former presence of mountains. At the close of the Precambrian Era most of Wisconsin had been eroded to a rather flat plain upon which stood hills of more resistant rocks as those now exposed in the Bamboo bluffs. There were still outpourings of basaltic lava in the north and a trough formed in the vicinity of Lake Superior in which great thicknesses of sandstone were deposited. The Paleozoic Era began with the Cambrian Period, the rocks of which indicate that Wisconsin was twice submerged beneath the sea. Rivers draining the land carried sediments which were deposited in the sea to form sandstones and shales. Animals and plants living in the sea deposited calcium carbonate and built reefs to form rocks which are now dolomite—a magnesiumrich limestone. These same processes continued into the Ordovician Period during which, as indicated by the rocks, Wisconsin was submerged three more times. Deposits built up in the sea when the land was submerged were partially or completely eroded at times when they were subsequently elevated above sea level. During the close of the Ordoician Period, and in the succeeding Silurian and Devonian periods, Wisconsin is believed to have remained submerged. There are no rocks outcropping in Wisconsin that are younger than Devonian. Absence of this part of the rock record makes interpretation of post-Devonian geologic history in Wisconsin a matter of conjecture. Available evidence from neighboring areas, where younger rocks are present, indicates that towards the close of the Paleozoic Era, perhaps some 250 million years ago, a period of gentle uplift began which has continued to the present. During this time the land surface was carved by rain, wind and running water. The final scene took place during the last million years when glaciers invaded Wisconsin from the north and sculptured the land surface. They smoothed the hill tops, filled the valleys and left a deposit of glacial debris over all except the southwest quarter of the State where we may now still see the land as it might have looked a million years ago. Prepared by U. of W. Geological and Natural History Survey, 1963. ..-.1 �2. CENTRAL WISCONSIN VOLCANIC BELT I This field trip represents a progress report in the early stages of the investigation of the Precambrian geology in central Wisconsin. Although we cannot provide many of the answers, we have identified a number of problems in the area. Some of these problems are presented in the following Guidebook with the hope that at least a few answers will be forthcoming. Introduction Precambrian volcanic and sedimentary rocks cut by intrusions of a wider range in composition and separated by broad expanses of gneisses and granites were mapped at the beginning of this century in central Wisconsin. Recent inves- tigation suggests that these volcanic and sedimentary rocks are similar in type, arrangement and separation to the greenstone belts which make up a substantial part of the Early Precambrian portions of the Precambrian Shield in many continents. They are lithologically similar, and may be roughly comparable to the Uobile Beltstt of most post-Precambrian geosynclines. Both appear to have formed in areas of prolonged tectonic activity. The rocks which will be visited are presumably considerably younger than the greenstone belts of Canada, yet their similarity to these belts cause us to believe that central Wisconsin may be part of a heretofore unrecognized greenstone belt. �3. Lithology Within a greenstone belt, the volcanic rocks range in composition from basalt to rhyolite, and typically form sequences with pillowed basalts at the bottom and grade uqward through andesites to rhyolites at the top. This general sequence may be incomplete, repeated, or reversed in a particular area. Some greenstone belts are composed predominantly of mafic volcanics; some have greater amounts of felsic rocks. The central Wisconsin area appears to have a greater than normal anount of rhyolitic volcanics, but their relationship to the basalts is not clear. The sediments of a greenstone belt consist largely of graywacke and slates with lesser amounts of chemical sediments (mainly cherty iron—formations). These sedimentary sequences may overlie, underlie, be sandwiched between the volcanic sequences, and some sediments (particularly iron—formations) occur within the volcanic sequences. Intrusions into the volcanic—sedimentary rocks range in composition from peridotite to granite, and in some areas (as at Wausau) alkaline complexes, including nepheline syenites, are present. Intrusive igneous activity appears to have occurred over a very long period; some intrusions may represent the "feederstt and dikes associated with the volcanism which characterizes the belts. Later batholithic intrusions of more granitic rocks seem to bring the tectonic cycle to a close. Relative Determining the relative age of rocks within a greenstone belt requires unravelling the complex structure so characteristic of these regions. Because there are no fossils available to determine the relative age, it is necessary to resort to various "sequential" features (such as pillow structures and graded bedding) and structural techniques to determine stratigraphic tops (since many beds dip nearly �4. vertically, the, erosion surface is essentially a cross section), The relationship of structure (tectonic activity) and igneous and metamorphic activity which have affected certain parts of the sequence may be interpreted differently by different workers due to shortage 3f outcrops at critical locations. of stratigraphic sequence often cannot be found. Thus, a unique solution to the problem As new evidence is found and as new concepts and tools are available, the relative age of certain units may be changed—— hopefully toward a more accurate sequence. On a broader scale, the relative age of one greenstone belt as compared to others in a given area is even more difficult to ascertain because the belts are almost invariably separated from one another by batholithic expanses of gneisses and granitic rocks, Individual bodies of granite are not of sufficiently large size to show age relationships between adjacent belts. Furthermore, radiometric age dating on the granites yields the date of intrusion (or later metamorphism) and gives only a minimum age for the intruded rocks, As a result, the ages of greenstone belts in a particular shield area can be established in only a very general way. Absolute Absolute (radiometric) age determinations show that almost all the recognized greenstone belts in the Canadian Shield are more than about 2,500 million years old. In fact, they are generally referred to as Archeangreenstcne belts because of their age. The absolute age determinations available for a few rhyolite and granite localities in Marathon County indicate that rocks were formed about 1,500 million years ago. Therefore, this greenstone belt may be nearly 1,000 million years vounaer than most other greenstone belts, If this proves to be true, then an understanding of the rocks in central Wisconsin would contribute significantly to our knowledge of middle �I 5, and late Precambrian history of the Canadian Shield, Although we do not yet have anything like a clear—cut picture of the geological history of the central Wisconsin area, we are proposing the "greenstone belt" concept as a working hypothesis for your evaluation. Thus, central Wisconsin may be an important area which will add to the overall story of the development of the North American continent, particularly during middle Precambriir tine. Economic Significance 'n the past five to ten years, there has been developing an increasing awareness of the imprtance of greenstone belts as targets for prospecting activities. outgrowth of 'the tormulation of a new concept of ore genesis. This i an The concept of strata— bccnd sulfide and volcanic exhalative deposits has given great impetus to prospecting in volcanic—sdiiientary sequences which are represented by greenstone belts. In sirplest terms, this concept relates the formation of many disseminated and massive sulfide ores to ocanic activity rather than to later hydrothermal activity. Many of the large suIfide deposits (both massive and disseminated) in the Canadian Shield (for exmp1e, Manito.wadge, Timmins, Noranda, Mattagami, Timagami, and others) as well as many pos -Precambrian sulfide deposits have recently been interpreted as volcanic exhaative in 'rigin. In fact, there are relatively few greenstone belts in the Canadian Shield that do not contain important sulfide ore deposits. Therefore, the importance of recogaizlt.g central Wisconsin as possibly a greenstone belt seems self evident, Rot general features and economic importanc' of greenstone belts, the intere;ted rder is referred to: "Symposium on Strata—bound Sulfides and their Formative Enironment", Canadian Mining and Metallurgical Bulletin, Sept., 1965, and otl;er articles listed in the references. �6. Previous Work A comprehensive account of the regional geology in the area, "Geology of North Central Wisconsin", by Samuel Weidman was published in 1907 as Bulletin XVI of the Wisconsin Geological and Natural History Survey. Considering that the field work was done about the turn of the century, it is remarkably thorough in its areal coverage. The publication is very good insofar as outcrop location and description is concerned, but Weidman does not attempt to interpret the geologic setting for the area as a whole. While certain revisions may be possible in the map and stratigraphic sequence presented by Weidman, the chances would presumably be relatively minor and involve both additional data and use of geologic concepts not developed at the time the Bulletin was published. The geology of the Wisconsin Rapids—Wausau area was examined in 1917 to 1921 as part of a land classification survey by the Wisconsin Geological Survey. Township maps showing location and classification of outcrops and a series of related geologic reports are in files in Madison. Selected aspects of the geology in the central Wisconsin area were discussed by Emmons (l953b), who was leader of the 17th Annual Tn—State Geological Field Conference in 1953. However, the theme for his work is very different from ours, and we will not be stopping at any of the exposures visited on the 1953 trip. Particular aspects of the geology in the Wausau area have also been covered in a number of theses prepared at the University of Wisconsin. Recent work by the U. S. Geological Survey and the Wisconsin Geological Survey has resulted in a series of four open file sheets on the Precambrian geology of northern Wisconsin compiled by Carl E. Dutton and Reta E. Bradley. The interesting variety of formations seen during field checking have led to the present field trip. The purposes of this field trip are to examine the different rock types in the area and attempt to determine how well they fit a concept which may tie together �7. all of the rocks into a logical relationship. So far as we know, this is the first attempt to interpret the tectonic setting for the central Wisconsin area. Keep in mind, 1 I however, that this is a progress report in the early stages of an investigation, and the greenstone belt concept should be considered as a working hypothesis. Therefore, we will examine some of the rock types in an attempt to determine the tectonic setting of the area. Because we are trying to show features which suggest that central Wisconsin is part (or all) of a greenstone belt, a brief statement pointing out the relevance of each stop will be given. Stop 1 illustrates features of felsic intrusions into greenstone belts. Both syenite and granite are intrusive into the greenstane; however, we do not know the relative age of these intrusions to one another �STOP 1. Assembly Point at Employers Insurance. This exposure Is fairly represertative of the syenite in :he Wausau area. Most of the syenite at this stop is acLually a quartz syenite A few miles northwest are exposures of nepheline syenite and çuarries in gray and in red syenite. Mineralogically, the syenite contains potassium feldspar, plagioclase, sodic hornblende, biotite, sodic pyroxene, minor apatIte, zircon, magnetite, carbonate, with or without quartz. In some samples, the feldspar is highly perthitic, consisting of almost any mixture of sodic plagioclase and potassium feldspar. boundaries between feldspars are common in some samples. appreciable percentage of samples from certain localities. Highly sutured Quartz makes up an The mafic minerals, especially the hornblende, are typically very poikilitic (i.e., include numerous other minerals——especially apatite). Some of the hornblende has been altered to fine—grained biotite, magnetite, and carbonate At a number of places immediately west of Wausau, the syenite contains masses of quartzite. In most cases, there appears to have been a reaction between the syenite and quartzite to produce a halo of magnetite—bearing "granite" around the inclusions or pendants of quartzite. The typical syenite Is weakly to non—magnetic, and is composed mainly of highly perthitic alkali feldspar and probably sodic hornblende. or may not be present. Quartz may As one approaches a quartzite body within the syenite, the quartz content increases; the hornblende is replaced by biotite, accompanied by a notable increase in the magnetite content. A small scale example (not containing all the features described above) may be seen in the roadcut on U.S. 51 about 500'(?) east of the parking lot behind Employers Insurance. �9. Crochiere farm, Sec. 29 T 29N R 6 E Artus Creek Greenstone. (Pillow Lavas) (1968 Tn—State Stop 3..) One of the most abundant rocks in many greenstone belts is pillowed basaltic and andesitic lavas. In fact, as it is used in the Lake Superior region, the term denotes a somewhat metamorphosed intermediate to basic volcanic rock. The greenstone color derives from the abundance of chlorite, epidote, and actinolite in most examples. greenish You will notice on the colored geologic map that the major area of mafic in this region lies west of Wausau. Although there are exposures of volcanics basic volcanics east of the Wisconsin River (northeast of Wausau), they are preI sumably of more limited extent. At this stop, there are numerous exposures of pillowed greenstone with pillows U exposed in the outcrops farther south from the road. better of the pillows at this stop. Figure 2 shows an example Due to the irregular fracture pattern on the surface of the outcrops, the pillows are best seen on the southwest-facing ledges formed by joint surfaces. The pillows range in size from less than one foot to at least three diameter. feet in Pillow shape indicates top to the southeast, and in some places, it appears that the dip may also be to the southeast. not pillowed. Note that all exposures (all flows?) are Pillowed greenstones are typically interlayered with non-pillowed greenstone, and at least some of the non-pillowed material is a basaltic tuff as illustrated at the next stop (Figure 3). The rock consists of sodic plagioclase, amphibole (actinolite?), chlorite, and minor quartz; a typical greenstone mineralogy. epidote, Epidote and amphibole are the major minerals in some samples, and carbonate is common in some. At the time of formation, the selvages around the pillows were probably a hydrous basaltic glass (palagonite); however, the selvages are now dominantly quartz and epidote. The rock probably owes its present mineralogy to the metamorphism it has undergone. Greenstone belts are commonly intruded and separated by granitic rocks. greenstone is intruded by granite at Hwy. 29 and Co. Rd. 0. This �10. Figure 2. Pillow structures in greenstone at Artus Creek. Top of flow is toward the upper right hand side of the photo. Figure 3. Tuffaceous phase of Artus Creek greenstone. is approximately lOOx. Magnification �ii STOP . Artus Creek Greenstone. (Massive Phase) THIS IS AN EXTREMELY DANGEROUS PLACE BECAUSE OF POOR FOOTING KEEP OFF THE OTJTCROP! AND IS HAZARDOUS FOR THE PEOPLE BELOW YOU. A relatively new roadcut has exposed massive greenstone in which it is nearly impossible to determine the attitude. Several parallel slabby zones on the north side of the road strike N6O°E and dip 3O°SE and may represent original layering of the unit. Inasmuch as definite shear zones are present, the slabby zones may also be formed by shearing. Poorly formed, and poorly preserved, pillow structures may be seen at several places on the exposure. Some flows——or parts of flows——do not develop pillow structures; they simply crystallize as massive greenstone. cut on the north side of the road are the "best pillows. At the western end of the Other pillows elongated N6O°E can be seen on the top of the eastern end of the cut on the north side of the road, but they are not well enough preserved to determine stratigraphic tops. In the central, massive, part of the exposure is a tuffaceous phase of the greenstone. A number of thin sections of this material reveal relatively well preserved shard structures (Figure i). To see the shards, break the rock to get a fresh surface, wet the surface, and examine it with your hand lens (your TONGUE is an indispensable geologic field tool). Massive greenstone may also be flow material which does not contain shards. Petrographically, the rock consists of chlorite, carbonate, relict plagioclase laths (near albite in composition), amphibole (actinolite?) and extremely fine grained Some sections show extensively epidote and zoisite. Quartz is not especially uncommon. uralitized pyroxene. (Pyroxene altered to fine grained amphiboles.) More or less circular patches of chlorite or carbonate may represent vesicle filling. Some fractures are filled almost entirely with epidote—zoisite. In most slides, the intergranular texture is well preserved, even though the mineralogy has been. �12. modified considerably. In general, this seems to have been a rather coarse grained basalt alternating with tuUaceous material. The occurrence of fragmental material interbedded with pillowed greenstone is not uncommon, but it poses problems as to the environment of eruption and deposition. Some of the fragmental layers have a texture similar to graywacke and a composition nearly the same as the pillowed layers; other layers contain sharply angular fragments which may represent basaltic tuff. Eecause pillow lavas are generally taken to indicate subaqueous eruptions, or at least flQwing of lava into a body of water, the following questions may now be raised: 1) Do the fragmental layers represent material from subaerial eruptions ("lava fountains") which was carried by wind and/or water to the site of deposition? 2) To what extent are the fragmental layers derived from the erosion of adjacent volcanic islands? 3) May the fragmental material (and the pillow lavas) be formed during subaqueous eruptions? �l3 STOP 3. Marshall Hill Conglomerate. This exposure is an example of what seems to be the youngest Precambrian rock in the Wausau area, and although it illustrates no principle of greenstone belts, it is important in interpreting the geologic history of the area. At different places where it crops out, the formation is variously a conglomerate and/or a "quartzite". The conglomerate at this locality contains pebbles and boulders up to eight inches in diameter of rhyolite, greenstone (basalt), trachyte, chert (or jasper), and quartite. It is of interest that granite pebbles are conspicuously absent, even though there are abundant glacial boulders less than half a mile to the north, and outcrops of granite within a mile. Until recently, the only readily accessible exposures of Marshall Hill conglomerate occurred two miles east northeast of here. The roadcuts here expose a much fresher part of the Marshall Hill conglomerate. In thin sections, the rock shows abundant sericite, both within the pebbles and in the matrix. Fine hematite is abundant and disseminated. In the samples examined, most of the fragments are rounded and range in size up to about one-half an inch in diameter. Angular to rounded quartz grains occur in the matrix, and occasional pebbles of "dirty quartzite" were found. Both texture and composition suggest that a vast majority of the fragments are altered volcanics (probably rhyolite) . material are decidedly subordinate. Fragments of definitely non-volcanic The abundance of sericite in the matrix suggests that it too may be derived from volcanic material. A large volcanic component in the conglomerate is not surprising considering the close spatial relationship of the conglomerate to rhyolite. Because the contacts are not exposed, the relationship of the conglomerate to the underlying rocks is uncertain at this stop. However, on the west side of the Wisconsin River at the Brokaw Dam (Figure 4), a similar conglomerate and "quartzite" �Partly Looking Figure 4. G.L.L. the west Sketch of the on Rhyolife side of the relationship ONSIN Banded covered Partly non-banded west I River rhyolite Wisconsin between RI S. II at and Brokaw. conglomerate 'I Approximately 50' Scale I — N. — r —I I— �— 1 S. — Figure 5. G.L.L. 2 l'Approximately Scale • 2 I mile 2 —I Lookrng west — 2 Stop8 U — typse en the east side of the I Stop 7 I River. relationships of Wisconsin DiagrammatiC sketch showing the structurol rhyolite Mainly tuffaceous and conglomeratic Stop 9 I the rock Silt stone Tuffaceous N. — —.—.— ..I — I I — �16. unconformably banding. overlie fresh, unmetamorphosed, rhyolite with The elastic rocks are vei- 1 flow(?) therefore, younger than the rhyolite at that locality. On the east side of the Wiscoasin River (Figure. 5), the 'tructtral relationships indicate that the conglomerate Is not only youT7,er than the rholite, but a siltstone—tuff sequence (Stop .) ocur between them. This sequence is further confirmed by exposures alcrg the railroad track between Wausau and Brokaw (on the west side of the hill at Stop this trip. ; however, time wiLi, not permit visit'ng these exposures on Thus, the conglomerate may be the youngest Precambiari rok in this area. �I STOP 4, Tuffite. Tnis exposure Lilustrates ore cf the features assoc4ated with acid volcanisi; tIat is, the Irixing of vo1canc and fine dental me-.terial in water laid d€posits. The rock is primarily a tuffite (tuffaceous s.ltstone) or a bedded tuff. We will see at least one lapilli tuff layer as we proce-d down che hill. Along the railroad track at the west side of the hill are ood expures of tuff and agglomerate stratigraphically underlying, and trachyte and conglonerate ovenlyirp the tuffite. Lapilli tuff layers are interbedded with the fine grained material, much of which is also tuffaceous. In thin section, these rocks consist of virious size fragments of quartz and feldspar (plagioclase is the dominant recognizable variety) in a f1n. grained matrix of quartz, altered feldspar(?), sericite, chlorite, and carbonate. Many fragments consist of a fine mosaic of minerals which are virtudily indistinguishable from the matrix material. Most or all of the fragments are ery angular and at least some are almost certainly of volcanic origin. The rock, therefore, is herein classified as a tuffite. Others may classify it as a volcanic—rich graywacke, or argillite, or a bedded tuff with appreciable detrital material. The beds generally strke nearly N—S and dip from 30—40°W, although t'iere are local variations in the attitud,. Therefore, the roadcut is almost parallel to the strike so that we are seeing a rather restricted stratigraphic suence. Slump structures (folds) ranging in sie from a fraction of at, incFi t' nearly a foot high are at several horizons (Figure 6. t least one of the massive unts appears to be a slumped bed, with randomly oriei ed blocKs within a massive layer. It is possible that these slump structures were caused by earthquakes accompanying e volcanic activity during the deposition of the layers. �I 18. I I Figure 6. structures in the tuffite at Stop . relatively straight and evenly bedded; Slump are Most layers however, slumped layers are not uncommon. Figure T. "Conglomeratic rhyolite" representative of much of the rhyolite at Highland Grove (Stop 8) and in the Wausau area in general. �I I 19 Near the north end of the exposure (at ti top of the hill) is a quartz feldspar porphyry dike with an exposure width of about 40 feet. not well exposed, so we do not know the true width of the dike. 1h ontacts are �I I PRELIMINARY GEOLOGIC MAP OF THE AREA EAST OF WAUSAU, WISCONSiN Adapted from Thomas I I I2 I HYBRID I GRANITE A. Henricksen & Robert METAGABBRO I4I METADIABASE [51 GREENSTONE 161 FELSIC METAVOLCANICLASTIC 1969 Stevenson GRANITE 131 L.W.W. U. 0 I I I Miles 2 —I 1 �I Dells of the Eau Claire River. Stop 5, At the Dells of the Eau Claire River we have our felsic volcaniclastic rocks. trs ex:ensL:e exposure of The abundant vertical and horizontal surfaces show the principal joint systems, which are approximately normal to each other. joints is generally parallel to the banding. of N35-40E, One set of The banding is vertical with a strike A few mafic bands are present. Several textures are seen in the volcaniclastic rocks. Some bands are Others have granulare with grains mostly in the coarse silt to very fine sand range. large grains set in a fine grained groundmass and, according to Weidman, are all por— phyries. In some bands schistosity occurs with the long dimensions of the micas and amphiboles aligned. Minor con- The abundant minerals are quartz, feldspar, mica and amphibole. stituents include carbonates and opaque minerals. covite. Biotite is more abundant than mus- On stained slabs potassium feldspar is far more abundant than plagioclase. From preliminary study, we think it possible that the banding is parallel to original layering and that some of these layers are sedimentary in origin. gestive for a sedimentary origin is the granular texture of some bands. amphiboles are aligned only in some of the bands. Most sug- The micas and Volcanic origin for many bands, especially those in which the large grains are clearly phenocrysts, is recognized. However, comparison of the texture of granular bands here with some bands at other locations, particularly Stop 6, cause us to continue the search for conclusive evidence of sedimentary origin. Orientations at Stops 5, 6 and 7 show a slight curving for this volcaniclastic belt, with the trend more northerly to the east. The possibility that Stops 5 and 6 are at similar stratigraphic positions can be seen on Figure 8, p. 23. �U 21. STOP 6 Felsic volcaniclastic rocks and greenstones along the Eau Claire River in section 27, T 29 N, R 9 E The rocks e. include both felsic volcaniclastic rocks and greenstones. In the vicinity of the bridge the rocks exposed along the banks are generally volcaniclastic; a quarter of 1 mile to the southwest the rocks exposed along the river are greenstones, with a I patches of felsic volcaniclastic rocks occurring beside greenstones and on the side from away in I the river. On the west of the river felsic volcaniclastic rocks occur a belt roughly a half mile wide. The relationship to the granitic rocks to the northwest is described following the description of this stop. The felsic volcaniclastic rocks vary in banding from very thin bands about ½ mm, thick to bands about 2 cm. thick, Th greenstones They are usually very fine to fine grained. do not show clear banding or layering. The strike of the volcanic- -i,tic units varies from N35E to N5OE, while dip is vertical to very steep towards iie west. 1 I bu South of the stop a few partial pillows were seen in the greenstones, they are not well enough developed for determining orientation. Shearing with an orientation parallel to the layering of the volcaniclastic units occurs many places. It shows best where there are micaceous minerals. The felsic volcaniclastic rocks consist primarily of fine silt size grains of feldspar, quartz, biotite, hornblende, carbonates and opaques. feldspar and plagioclase occur. Both potassium They are usually clear and frequently untwinned, re- quiring staining to tell them apart and from quartz. the samples and do not have relative percentages yet. We have just started staining In the sheared bands biotite and hornblende are more common than in the unsheared ones, The greenstones have a varied mineralogy. Preliminary study shows that amphibole and plagioclase are the most abundant minerals, with grain sizes up to I I I .3mm., although usually not over 1 mm. as do epidote and chlorite. Opaque minerals, including pyrite, occur, �22. To the west and north of Stop 6, along Pleasant View Road, felsic volcaniclastic rocks and granitic rocks occur, with the latter north of the former. volcaniclastic rocks are similar to those of Stop 6. rocks and the volcaniclastics is buried. The The contact between the granitic The granitic rocks are exposed in a ditch- crop at the junction with East Tower Road, and here they look like "granite". On the crest of the hill the material was exposed by the telephone company when it buried its cables. The samples were collected this April. The granitic rock shows great variability in hand specimen, particularly in color, but prior experience in the area shows that a noticeable color variation may be independent of similarity of major mineralogic content. Although age relation of the units is unknown, yet we suggest the following possibilities as the most likely. The variability of the "granite" (i.e., rocks) and its close relation to the volcaniclastics, which contain significant amounts of potassium feldspar, give the following possibilities: the volcaniclastics and "granite" are related in origin, or the granite is younger than the volcaniclastics and we see a border phase which is variable because of the incorporation of older volcaniclastics. The absence of recognizable granitic pebbles in the volcanic- lastics suggests that the granite was not exposed at the time of formation of the volcaniclastics, although we recognize the possibility that pebble-bearing volcaniclastics can occur in the five hundred feet between the northernmost exposure of the felsic volcaniclastics and the southernmost exposure of the "granite." �24. STOP 7. Big Sandy County Park The felsic volcaniclastic sequence here is steeply tilted with an orientaMafic units up to a foot thick occur at various intervals tion of roughly N65E65NW. and have the same orientation as the felsic bands. parallel to the banding. Some units seem to be sheared Feldspar grains are visible in many bands. The groundmass of the felsic volcaniclastic rocks is composed of grains in the very fine silt range while the large grains are in the coarse silt to very fine sand range. In some sections the large grains are phenocryStS, while in some they may be sedimentary particles. The groundmass is composed principally of biotite, feldspar and quartz, with opaque minerals up to 57 (estimate) in some bands. The large grains are predominantly plagioclase. From stained slabs we found that plagioclase is far more abundant than potassium feldspar. The mafic units have a similar mineralogy, with biotite far more abundant and quartz much less abundant. The grain size is more uniformly silt size. Included in the opaque minerals is pyrite, which is easily seen in the hand specimen. Comparison of the felsic volcaniclastic rocks in the belt visited at Stops 5, 6 and 7 shows potassium feldspar more abundant to the southeast and clase more abundant to the northwest, plagio- Despite this mineralogic difference, the grain size and band thickness is generally the same, Some mafic units within the felsic volcaniclastic bands presumably owe their greenish black color to the abundance of biotite plus, perhaps, very fine opaque minerals. As mapping has proceeded, we have enlarged the area of felsic volcaniclastic rocks at the expense of the greenstones shown on Weidmants map. localities we have mapped. However, in his text he describes many of the �j Corrections to Figure 5. The Stop numbers on Figure 5 are for th 32nd Annual Tn-State Geological Confcrence, 1968. The table shows the corresponding stop numbers for this field conference. I. L, S. C. Tn-State Stop 3 Stop 7 Stop 4 Stop 8 Stop 8 Stop 9 The Institute is visiting the Marshall Hill conglomerate on the west side of the Wisconsin River because the exposures are fresher and larger than those on the east side. �I 26. STOP 8. Highland Grove "Conglomeratic Rhyolite" WE WOULD BE SORRY TO LOSE YOU IN THE WOODS!!! PLEASE FOLLOW INSTRUCTIONS CAREFULLY. This exposure illustrates a variety of rocks present in the "rhyolite" area as mapped by Weidman and may be typical of the features associated with rhyolitic volcanic activity in general. They include: massive fine—grained rhyolite, some of which may be flow banded; porphyritic rhyolite, with a variable amount of quartz and feldspar phenocrysts; and conglomeratic rhyolite. At least three types of rhyolite, with the relationships shown in the accompanying sketch (Figure 9 ), are present in exposures in the woods south of the school. A massive, fine grained, generally non—porphyritic rhyolite forms the small cliff and the break in slope of the hill. South of this massive unit are porphyritic rhyolite and "conglomeratic" rhyolite in that order. To the north is In the conglomeratic phases, both more porphyritic and "conglomeratic" rhyolite. pebbles and matrix are rhyolitic, and both angular and rounded fragments occur. The contact between the massive (non—porphyritic) unit and the porphyritic unit is a vertical cliff suggesting that the sequence may be standing nearly vertically. N Scale Po r ph yr it i C I": Approximately 50' and "Conglomera tic Porphyrific R hyo life Rhyolife J I"Conglome rat ic" GLL Rhyolite Figure 9. �I 27. In the farmyard east of the woods, the "conglomcratic' rhyolite contains a Note block of flow(?) banded material about 5' long in a coarsely fragmental matrix. that many fragments have good flow banding, although definite flow banding has not been seen in outcrop. Note that the conglomeratic units so well developed in the woods are not exposed along the road. Fragmental texture is present in nearly all material from this locality. Approximately 757 of the exposure is conglomeratic. The finer grained material is Some samples of porphyritic rhyolite contain deformed shards largely tuffaceous. and other features suggestive of welded tuffs, and non-porphyritic rhyolite contains probable shard structures. Glacial boulders with good flow-banding may be found in the woods and farmyard, but as stated above, we have not observed definitely flow-banded rhyolite in outcrop. Thin sections of the rhyolite reveal a fine quartz-feldspar matrix, more or less sericitized. some samples. Patches of carbonate and quartz veins are relatively common in Although the gragmental nature is evident in most hand specimens, the similarity in composition between fragments and matrix make thin section determination of grain boundaries difficult. generally show shard structures Thin sections of the fine grained rhyolite Similar rhyolite from the outcrop at Ninth St. and Winton Ave in Wausau contain unusually well preserved shard structures (shown in Figures 10 and 11). Spherulitic and axiolitic structures are present in some slides. Asquith (1964) reported shard structures in rhyolite from the Brokaw Quarry on the west side of the Wisconsin River north of Wausau in the NW-l/4 Sec. 11, T.29N, R.7E. (Minnesota Mining & Manufacturing operates the quarry to obtain roofing granules) and in a number of Precambrian rhyolites farther consin. He interprets them as welded tuffs. south in Wis- The shard-bearing phases of the rhyolite in the Wausau area may also be, at least in part, welded tuffs. �28 Figure 10. Shard structures in rhyolite from Ninth Street and Winton Avenue, Wausau. Magnification approximately 140x. Figure 11. Shard structures with phenocrysts in rhyolite from Ninth Street and Winton Avenue. Magnification approximately 140x. �29. Therefore, the rhyolites in the Wausau area seem to have formed in more than one way--some may have been flows, some presumably are welded tuffs (ignimbrites). some may have formed from "mud flows", and some may be intrusions. Bedded (water laid) material such as that at Stop 4 may represent eroded volcanic material or may have resulted from direct volcanic (tuff) contribution to the sedimentary basin If this is a subaerial deposit, how is it related to the bedded tuffs we saw at Stop 4? Both east and west of the Wausau area are large exposures of metamorphosed, sheared rhyolite. Due to the almost complete lack of shearing and metamorphism of the rhyolites in the immediate Wausau area, we feel that these rocks are younger than the altered rhyolites and may represent a renewal of acid volcanism within the greenstone belt �:30. REFERENCES Asquith, G. B., 1964, "Origin of the Precambrian Wisconsin Rhyolites", Journal of Geology, Vol. 72, pp. 835-847. Dutton, C. E. and Bradley, R. E., 1968, "The Precambrian Geology of Northern Wisconsin", U. S. Geol. Survey, open file report, four maps. Emmons, R. C., l953a, Guidebook for 17th Annual Tn-State Geological Field Conference, 11 p. Emmons, R. C., l953b, "The Argument", in Geol. Soc. Amer., Memoir 52, pp. 111-117. Goodwin, A. M. (editor), Precambrian Symposium: The Relationship of Mineralization to Precambrian Stratigraphy in Certain Mining Areas of Ontario and Quebec, The Geol. Assoc. of Canada, Special Paper No. 3, 144 p. Goodwin, A. M. and Gross, W. H. (co-chairmen), 1965, "Symposium on Stratabound Met. Bull., Vol. 68, Sulfides and Their Formative Environment", Can. Mi pp. 253-300. Goodwin, A. M. and Schklanka, R., 1967, Archean Volcano--Tectonic Basins: Pattern, Can. Jour. Earth Sci., Vol. 4, pp. 777-795. Form and LaBerge, G. L., and Weis, L. W., 1968, A Greenstone Belt in Central Wisconsin? Guidebook for 32nd Annual Tn-State Geological Field Conference, 42 p. Weidman, Samuel, 1907, The Geology of North Central Wisconsin, Bull. XVI, Wisconsin Geological and Natural History Survey, 697 p. �ITINERARY FOR 15th ANNUAL INSTITUTE ON LAKE SUPERIOR GEOLOGY FIELD TRIP Section 1. Go north on Westwood Dr., turn 1 and Assembly Point are at Employers Insurance. right on Bridge St., cross over U.S. 51, turn north onto U.S. 51. Turn west on Co. A, Stop go 5 miles to Stop 2. Stop 2, go east on Co. A to U.S. 51, turn south to Co. WW, turn east. From to Stop 3 on west side of Wisconsin River. Go 1½ miles From Stop 3 continue east on Co. WW to Co. W., turn south, go 1 mile to Stqp 4. Stop 4 continue south on Co. W to Wis. 52 (Wausau Ave.), turn east. At Co. Y turn south, go 2 miles to Marathon County Park at the Dells of the Eau Claire, Stop 5. From Lunch will be served after visiting the outcrop. From Stop 5, continue south on Co. Y to Co. Z, turn west for 1½ miles to Eau Claire Rd., turn south 1½ miles to Forestville Rd., turn east, cross bridge to Stop 6. NO SMOKING AT STOP 6, From Stop 6, return to Eau Claire Rd., turn south 1/8 mile to Pleasant View Rd., turn west. Notice ditch crops. Turn west on Co. Z, turn south on Co. J and park in Mara7. thon County Park on the Big Sandy, From Stop 7, go north on Co. J, go west on Co. Z. Continue west on Hamilton Rd. mile. Turn north on 25th St., go 3/4 mile to Stop 8. about From Stop 8 continue north to Wis 52, turn west. Turn south at 6th St. (Co. W), west on Bridge St., cross Wisconsin River, U.S. 51, and return to Assembly Point. Section 2. Point are at Employers Insurance. Go north on Westwood Dr., 1 and Turn north, turn east on Bridge St., cross U.S. 51, Wisconsin River, to Wis. 52. Stop then east and northeast on Wis. 52 to 25th St., turn south to St 8. Continue east on Co. From Stop 8, go south on 25th St., turn east on Hamilton Rd. Z, turn south on Co. J and park in Marathon County Park on the Big Sandy, Stop 7. From Stop 7, go north on Co. J, turn east on Co. Z to Pleasant View Rd., turn south. Notice ditch crops. Turn north at Eau Claire Rd., go 1/8 mile, turn east on Forestville Rd., cross bridge to Stop 6. NO SMOKING AT STOP 6. From Stop 6, return to Eau Claire Rd., turn north to Co. Z, turn east to Co. Y, Lunch turn north to Marathon County Park at the Dells of the Eau Claire, Sto2 5. will be served after visiting the outcrop. From Stop 5 go north on Co. Y to Wis. 52, go west. (Sixth St.) and go about 2½ miles to Stop 4. In Wausau turn north on Co. W From Stop 4, go north on Co. W to Co. WW, turn west, cross Wisconsin R. to Stop 3. From Stop 3, go west to U.S. 51, go north to Co. A go west 5 miles to From Stop 2, go east on Co. A to U.S. 51, south on Belt Line, exit to Assembly Point. �t— !i-- - i1,tes — ———— Annual 1. L.S.G. ROUTE MAP 15th ——.——— � 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, 1969 Description An account of the resource Institute on Lake Superior Geology. Wisconsin State University, Oshkosh, Wisconsin. May 8-9, 1969. 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 1969 Contributor An entity responsible for making contributions to the resource Rodolfo Anzoleaga Leonidas C. Ocola Robert P. Meyer George A. Armbrust Bill Bonnichsen S. Chaudhuri D.G. Brookins G. Faure Donald M. Davidson Jr A.B. Dickas E.W. Frodesen B.A. Kososki C.A. Wolosin R.H. Dott Jr S.S. Goldich G.N. Hanson Donald G. Hill Rodney J. Ikola Rudolf W. Johnson Joseph T. Mengel Jr R. Middleton J. Murray G. Aho G.B. Morey D.G. Rensink John S. Mothersill Stephen C. Nordeng Richard W. Ojakangas J.F. Olmsted T.P. Paster E.B. Denechaud L.A. Haskin Robert G. Schmidt Virgil A. Trent L.V.A Sendlein W.P. Staub G.H. Spencer Jr Hans Tammemogi S. Viswanathan William C. Phinney Richard J. Wold Thomas G. Wygant Joseph J. Mancuso D. York H.C. Halls Grant M. Young Wayne R. Zwickey 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/294356dd6f6accae5a2df2b677204335.pdf e09761aa4bca8a891f0732d5bf36e316 PDF Text Text SPONSORED BY DEPARTMENT OF GEOLOGY, WISCONSIN STATE UNIVERSITY, SUPERIOR AND MINNESOTA GEOLOGICAL SURVEY MAY 5.6.7, 968 0 R �VCHNICAL SFSSIONS 43STRACPS For 14TH ANNUAL INSTITUTE ON IAK]F SUPERIOR GDDLOGY Held On Campus Of UISCOUSIN &TATE UNIVERSITY, SiJp4COi, VJLiCONSIN HcCASKILL HALL May 6—7, 1968 PECRNIC;'.L S3SION CHAIRMAN A. B. DICKAS �14th ANNUAL INSTITUTE ON LAKE SUPERIOR GEOLOGY McCASKILL HALL WISCONSIN STATE UNIVERSITY SUPERIOR, WISCONSIN May 6-7, 1968 BOARD OF DIRECTORS - INSTITUTE ON LAKE SUPERIOR GEOLOGY P. K. Sims, Minnesota Geological Survey, Minneapolis, Minnesota A. K. Sneigrove, Michigan Technological University, Houghton, Michigan VI. J. Hinze, Michigan State University, East Lansing, Michigan D. H. Hase, University of Iowa, Iowa City, Iowa A. B. Dickas, Wisconsin State University, Superior, Wisconsin SECRARY-TREASURER1 INSTITUTE ON LAKE SUPERIOR GEOLOGY D. H. Hase, Department of Geology The University of Iowa, Iowa City, 52240 LOCAL CO4ITTJii1 TECHNICAL SESSIONS CO)41T1'EE A. B. Dickas (Chairman) P. C. Tychsen J. P. Mengel VI. LUnking R. Johnson FIELD TRIP COMMITTEE B. Bonnicheen and W. C. Phinney (Co—Leaders) The field trip conducted in connection with the Institute was held in the Duluth Complex area of Ely, Minnesota on Sunday, May 5th, 1968. This Minnesota Geological. Survey, trip was hosted by the P. K. Sims, Director. Extra field trip guides are available. 2 �fr—' PROGRAM Ito 14th Annual 2!I11SUPERIOR GEOLOGY :: c.c.i: ait:. E?iIIc; •ç•j ON k.KE INSTITUTE MoCaskill . C EIJI0IJ .;L Auditorium •%c3j.rct IJ State 2L*5( CToi. 2JH6 Wisconsin University Superior, Wisconsin HC:t* May 5, 1968 Sunday1 :yç p.m. 8:00 — 10:30 = &1L2 .I1i'Y.:U1 2oCco Smoker 2JJ0 and Advanced Registration b6._1k0L1&rJ. E00. ILTY). Union Hiawatha Room, Student Monday, May 6, 1968 (t) cL: 7:45 a.m. rcCLI ]t)T21 = :2t-kt19 Hall Registration — Lobby, ?McCaskill 8:30 a.m. EL1I?JPJ.: SESSION I TECHNICAL C:AwC, 1. 1., / -t1/ 0i4iT11 Auditorium 3, 2::R. . 1:0L4*1):;mM C. Iverson and L. Bleifuss Co—chairmen: .1elcome McCaskill1. • . . r: t&I70 Meyer, President c&t00t0 coo- o1:: c't.1cVlisconsin State University, Superior Karl tJ. I'::i :2a :t: oo&:ofc*Iron hCv Formations .1L50Minnesota rI Trace Elements in Henry Lepp 1 t)- t'-:.: t\,1 " 2A --th Eemnts in the Duluth Gabbro \7 1/ :—' '(—' Larry A. Haskin and Barton Denechaud Geophysical Study of ):iS-Vi Lake 3j::r:2L.C3: Superior 7:&i4:32I CJH 3. I 00: :4 Richard J. VJold ->3CC 2 L-L. [c* Mo V. .o Keweenawan 3fl&k:3t :t The Paleomagnetism of Middle 4. . 5, 2 iç3J.yiA Units Volcanic H. C. Palmer ¼-e ;>fr;ec51 Rb—Sr Ages of Intrusions Along the c230fQ(cJ) .0o& I 00:1 Keweenawan Fault in Northern Michigan Sambhudas Chaudhuri, •I•.. G. Faure and Douglas G. Brookins ?I An Investigation -.0:0 Velocity, 0: '1 of — the Vertical 3 -2 Density and Porosity Distribution in the I&0:1120ThJ>l. Sandstone, I :.62{3C?),Houghton I Thoil County, 1110:11:9 Jacobsville Michigan Lloyal 11: 0. Bacon, R. W. Ingalls 010> 0:Q :3 >9-2:3 0310 and J. F. Stafford .3: A — Gravity . -1ILI1i &3g>:o: Survey0:2. of a cIIHoo:o Portion of the 701010t03I If-I 0 1c.Greenstone .c ;o8\o--co3Belt 9J. inC Northeastern FUn flon 10000: Saskatchewan YC0c!0:Sfli ( 0LI Cc)Th;20 6. 7. .-, LfzccTo:1 1Gendwi11 Donald 8. ¶29 — 12:30 C- C,X> p.m. L—-: .. IL 211 The Penokean the -90> and 0: Hudsonian Orogeriies in if 3: .o>f the flco t:r:) Io.oo241 Great Lakes Region, 1001I))102and coolthe 02 Age of ')'0-sSi>s.:0:t: Front .6:3993 Grenville 9. Church c1 William R. 1- Luncheon jOn Hiawatha >j,6'- 32 Room, Student Union 1 2 1 I 3 �1:30 :'. : T•p.m. McCaskill TECHNICAL SESSION II - t,1A1gi Co—chairmen: ILO 1. A 2. LfrII1t23!2A1iiA21f Auditorium R. W. 014 Marsden 4AA_21and OAA$G. <C L. LaBerge I1 $t fAiA0C 51A 1L3hr UAOKYAI Framework Stratigraphic and Structural of the L Vermilion District and Adjacent Areas, NorthtLl_ 41L !l4113flA eastern Minnesota Ufll lk1 Paul K. Sims, G. B. Morey, A P. W, Ojakangas and W. L. Griffin of Volcanism, Sedimentation, and Stratigraphy S< I j41 the Western Vermilion District, Northeastern Minnesota 1 Richard W. Ojakangas and G. B, Morey Geology of the Duluth( Complex in the Perent Lake and Kawishiwi Lake Quadrangles, Lake and Cook County, Minnesota .CIV2Th Jr. rk:.1C Donald iI M. Davidson, ofr Rocks of ) Possible Coutchiching ILC An Investigation C Age, Walberg Creek Area, St. Louis County, Minnesota ] A, I S. Viswanathan and Paul K. Sims h 11 1 > Iron i < of the Biwabik A Formation, Metamorphism Dunka River Area, Minnesota t LL< Bill Bonnichsen Differentiation Sequence of the Great Lakes Ijlj < I' Nickel Intrusion C'; t3-<-,-AIT '.,Ai<<CX- -and '7 Reeve N. D ( MacRae I 5, - J. j< 1 Lakes Nickel b?rL_' Assemblages of the Great Sulfide Intrusion R Mainwaring Paul B, A LL1 1 of a Selected A At Lake Superior: Area of Study Progress Report 1) P. C. Brown, oseph W. Horton, C I Davidson, A. B. Dickas, D. W. 4Lt'70 Afl4and dt1< W, Lunking P. ¶4 K. JAfl21)eiJ Roubal C ci -H :1At -ts {AL1J IjI 2 '< 1-. 3. 2 I — 1 k. 5. 6. l C c I <l-t 11 I 11 JL< r - . 5c 2 1_ 7. 14 8. ¼ — 111 r< L ANNUAL BANQUET 6:30 p.m. 13ij'7< 771 II C427Ic Sky Lounge, Student Center Address: S1CS44CLU1 1<17. t(ACA32iA.t LjJ;2 F0JLA2tiA/C2"Recent Lunar Exploration Results" McCauley Dr. John F. USGS Branch of Astrogeology J 2< C54'71171 4 , Itrizona �Tuesday, Nay 7, 1968 — I 8:+O (jI3I a.m. 73 7 TECHNICAL 117ELJ7: SESSION III — 37CC The Federal—Provincial -1i7*Z :7fl 41 i7 7I3 Committee on Huronian Stratigraphy LbL1 —— Progress Report James A. Robertson, K. D. Card and M. J. Frarey 1, 71: 1 — 2. j ik; Stratigraphic Relationships of Some Keweenawan 3 43 111itC Wisconsin and Rocks of Michigan L3L LI — — A. Hubbard Distribution Patterns of 3" Harold 7 3. +. Auditorium I3kii4t115i371 J. W. 1&! and P.c E. Giblin C[ Trow Co-chairmen: 1. McCaskill LtJ C- EI Post-glacial Sediments in Lake Superior William R. Farrarid Bottom Palynological Study :0CiLL: of Post—glacial :.cT.7i3jj La35J Sediments from Deep-Water Localities viT 43:(y;,!i73 ;tc13;CC2> in tx: Lake Superior William S. Benninghoff and Ij' L(I Judith M. Franklin I 1i" _ Through New Light on ci ThC Animikie Algal LC4L Structures C; t Darkfield Illumination W. W. Moorhouse Origin for Three Precambrian Possible Glacial r 4icr o3 (Huronian) Conglomerates, North 1h Shore of Lake Huron 'X J y;c . k 5. I cr flL- 3I R jlfl\ I CC 6. L 1) G. Features of the Bloomer Moraine, Ice—stagnation 3 8. Northwest 13; Wisconsin Robert F. cLt€3HCCJC C! Black Y(T!; The (i Seaman Method of Mineral Identification as Used at i; Lake ?P7 Superior State College 1 - C C. 12:20 p.m. 0 C M. Young and F. W. Chandler 7. Ernest 34xa Kemp T:?:ciiç Luncheon Hiawatha Room, Student Union b 1-' �1:15 p.m. Business Meeting — McCaekill Chairman: Paul K. Sims 1:30 p.m. T:cHtiTc.L SESSION IV — McCaskifl Auditorium Co-chairmen: 1. 2. Auditorium 0. Durfee and H. H. Vloodard Current Investigations of Meteorite Impact Structures in the Canadian Shield Michael IL Deuce and Nicholas N. Short Petrographic Evidence for a Meteorite Impact Origin of the Sudbury Structure, Ontario 3. Bevan 74. French Progress of Geologic Investigation of the }4ellen Granite, Ashland County, Ylisconsin Michael 4. 5. M. Katzman Varieties of flows tu the North Shore Volcanic Gr'oup, Minnesota John C. Green Structure and Significance of Intrusive Sandstone I)fles of the Siamo Slate of the Marquette trough, Upper Peninsula, Michigan 6. 7. 8. C. McA. Powell the Sedimentology of the Middle Precambrian Thomson Formation 0. B. t4orey and P.W. Ojakangaa The Sequence of Geological Events in the Marquette Iron Range During the Penokean Orogenic/Metamorphic Cycle Larry L. Babcock Cbert Bed Characteristics in the Lake Superior It-on Formations Joseph T. Mengel 6 �r AUTHORS BLACK, R. :a F. Technological University CC2C3lJWv Michigan Technological University LT&FH1 TT<TflfC 1*LTSTTlTT University of Michigan University 7-7fflT-rJcj LY12;Y-; ofL)Wisconsin, Madison BONNICHSEN, B. Minnesota BROOKINS, C:"•[ G. 3VTifl,L D. Vc Kansas Michigan BABCOCK, L. L. CCCI BACON, L. OI' 0. C: BENNINGHOFF, L:;$TlIJ:,:S-&T W. C S. C BROWN, (: kl Geological Survey State IT University LU:I.k:LCCl1ç Wisconsin State C'ILT R. C. 3 jTrTr:T University, T1LII t.CC CL4 Superior K. CARD, CI: D. :II-rtCCC> Ontario Department of Mines 1C © CHANDLER, F. Cj W. C, University of Western Ontario CHAUDHUPI, S. Kansas State ::T University L3ITTT CHURCH, W. R. University of TI Western Ontario (IT.ITir- dcCJ DAVIDSON, D. M. 1JT'I CC(Cj[ JR. C 1 DAVIDSON, D. W. DENCE, Cc;J,:.zIc[ N. CIC,[ R. C DENECHAUD, B. C rt1:tiç University of Minnesota, Duluth q(rcp' lIT: Tt Wisconsin State University, ick&inTLiJt Superior 15!j[tflrf Ijt7 s: : Dominion -II(:II 1V1% Observatory 1tUJcLici (Ontario) University of Wisconsin, Madison C DICKAS, A. B. FARPAND, C R. II1C :,:mCrCcI W. Wisconsin T1LR5OCC State University, Superior University of Michigan i :IT FAURE, G. Ohio State .JL—I University JL FRANKLIN, J. N. Oakland (Michigan) Community College C - N. C J. Geological Survey of Canada FRENCH, B. N. C Goddard riçIirsC:C-i Space Flight Center GENDZWILL, D. Saskatchewan Research Council YtVJ FRAPEY, C cInt :rtc43c iIIi tE©) GREEN,II J. C. University of Minnesota, Duluth X?H [;!•• GRIFFIN, W. L. Minnesota Geological Survey HASKIN, L. il.:l'TI, CU7 A. University of C!E Wisconsin, Madison HORTON, J. V W. Wisconsin State 4i4j University, Superior HUBBARD, ,TVaVfV H. 'V Cpr A. U. cc S. Geological Survey INGALLS, r I:TA[ liT R. W. Michiganir Technological University }C4L2J; KATZMAN, N. CIJt M. Michigan State University KEMP, C. B. Lake LEPP, H. CI Macalester College C±T1rJiCd LUNKING, W. Wisconsin State University, Superior — I: I C MACRAE, 'C fl72 14t1 J:iJ1t©J 9LZ *ii Superior 4fl% 2•CL CY9 N. D. C' NAINWARING, P. R. --[in State College 4i:T-.rt. University of Western Ontario -rCn:; L2tI :rc University of ';c Western Ontario C: (continued on next page) 5C r'CJCCj 7 �:ircftC c1fi AUTHORS (continued) MENGEL, J. T. Ii"3 Wisconsin State University, Superior cccrciik cck:tc? MCORHOTJSE, 'J (H •Vi. University of Toronto MOREY, G. B. Minnesota V!. OJAKANGAS, R • vi,. H. C. PALMER, PO!ELL, C. McA. REEVE, E. J. i. 4-r cf i-c Geological Survey Minnesota, cc ccUcDuluth i:inic Lyrniz; ctofMJ University 19'yI Ontario ç Western University of fckh1icctc University •ccc Northwestern University of Wisconsin, Wkecc•ccccfcc? Milwaukee I7cc'&Lt7f c•L •cicyic. iccp cct, ci ROBERTSON, J. A. Ontario Departlilent of Mines ROUBAL, jc.) R. Wisconsin State University, Superior SHORT, N. M. Goddard Space Flight Center 3IL, p, Pr Minnesota !c. cc-ca Geological iccc ct ci•. Survey SIMS, ::. H.. STAFFORD, J. F. icc: 1icc'c L : !fci: •ccit3 cic-.ai University Michigan flkc. Technological VISVJANATHAN, S. 2_ccccpc &c 7cL:;Nf of •- Minnesota, University .L Minneapolis ILi IiR. J. hOLD, University rci&c of ct Wisconsin, i cc.cLc: Milwaukee Uc. YOUNG, G. M, ci c:&-:cT! University of Western•:.ci.ccc.c Ontario ci . 8 I �4UJ :'''rC-mr FORMATIONS TRACE 0*01hiflI1 ELEMENTS 4710137100 IN rIl MINNESOTA IRON :0171 1' 0011 1.0011 Chairman Henry Lepp, 7jj rjc:c .14Lr: Department of Geology J.E-1437 'oc4;r': 12 Macalester College 0101 St. Paul, rJ-. Minn. C p -;, investigation of minor This is a progress report on a continuing 101171 oo0110o0.crO10o -cccooo. 00c4t1IK7ii-JiLr' oI.OLo'o1J•O=rOoii01 PA' 30 The elements cobalt, nickel, elements in Minnesota 011Cr Ci iron 1oca formations. r:4r'-I:?CIcCJLl)1i 047 00'AcCii'O'SIY. •-l03ci rOOT GSC_r171i71i1c in composite samples of the C and gallium were determined CC ci A1 7iwabik iron 00 11C jl 3_ 01 3 7c-r material from the formation, the Tromxnald formation, and of oxidized A COOL K00110V Ic 1rl01Ci©7 APT 01I001 :r01J magnetite, iron Biwabik formation. LCJ.!,. flIC-0' 'CS! Samples 1vi.:CH'C of CE© <701 silicate (grunerite), ICI5fOACAO formation also were chert, and dolomite separated from the Biwabik Cc 11:1=101 71O0r ICc ::.iOJCflO rC4J 000101101001017 011IC- 414 14 çCiC% analyzed. of the Cobalt and gallium 0110000 0111140 were determined at IC- the 010 fl'fl laboratories 0j00-J:c1;0A'r21I'o, t0 A composite analysis. II General Atomic Corporation by neutron activation IC 010 01 C- 11 ; cobalt and i6 sample of the — CI Biwabik iron formation showed7 9.51 p.p.m. 101 Composites of Oxidized Biwabik formation gave gallium. p.p.m. I3 L thesimilar 0 0 )r North A composite sample of the Trommald formation from results. IfIAo1 The cobalt and 27 p.p.m. gallium. Cuyuna district C_ showed 36 p.p.m. CV S p.p.m. South Cuyuna district 5_L composite showed 25 p.p.m. cobalt and 01P 57 1L00 the Biwabik Analyses of minerals separated from specimens of gallium. 00 P[} TP344. AvIlTPc; 04 c'p''o'fc1Iy CCJ.ICi240.j014' formation show cobalt to range from 1.7 p.p.m. in chert to 10.1 p.p.fli. 00 'c_I oIl cL17'C7 000 :H'vLso 14 zo1 and for Gallium values for chert are 1.8 p.p.m. in iron silicates. ii010 A&oic00C 7'[i7-7 GOCV 01A 4771 c,-C7'ir iron silicate, 1C51Ji 3: 18 OP p.p.m. CV)L3[ Icr time of Nickel is colorimatrically at the 010 being ciCV IthJ determined 00P101 000. ciCLo7. OLA OIXPA01017C7 070101 A ;01A010074 7C1 and Preliminary results this writing replicate analyses are being run. :1001 •ycA. pcr.o acoI 40010 oi, ;P19 0000010 op 5coTt XCC PcICP;c highest indicate that A "C1correlate :2,:r cobalt. The CVCJJ. VIp. nickel :1çJ:.s to eO7 ci&r2 with j1i( .$'c0.2 000.0, seems nickel values were found in samples of the Trommald formation. 11 Very little is available in the published literature on trace -c CCI Moreover, as pointed out elements Cr iron 501 in '(07 formations r.•cCVY5: COA 70:CV<7:A LTL:A c0-2\tc?uyA0/ or 200 ironstones. viewed with caution bi by James (1966) the available analyses must be 5 L4 II 0 7 samples by because OA00Vt0 marked differences have been reported • for JdJ the 3j1 samepublished CcT7 Oi .:1'AJ 10,J001 11AOTJ; :1CV_ comparison with the few different hYCA9SJ laboratories. The k0 even O1LC 'JOCV t00AA A.yi; :c001 the realiza— values that are available, therefore, must be viewed t7C.Th 1) 'CA7i2.! CAACC7 L0 r%i;Ts with and the - analytical tion çF' that '7'3 the variation in values due to the analyst variation. p? method may be as great greater thanthat between sample &C& or 9J00 .1OJ 7Y13J2. 7WA i±Ii1 corroborate the The results of this investigation to date seem to JO Ic; 1J 0. AcOJ0 AY0IA OJC ¶3 rocks in that A work of Landergren (1948) on trace elements s5_A1r in iron richformations are the abundances in these AZii trace :AA element €'yyl7f:"4..V5E14/L: C.i77ij 0j", iron V:t,:710. Precambrian There low eJ'77 .0i[ when compared 1fi;3CVC tot similar CCCAAi values in younger A1yAC. ironstones. 7acciC0A0.0Af in the Cuyuna appears toA; be a general increase in trace elements CVAV 1 5:AAiC c4yt. basin. district which AJt represents the deeper A*WA part ofA the depositions.]L 11.4 001=1 c c:4oo :0,31 0 01' ]t : - S L — . 01.'I't4 L — L — L J4 11 e17' C4J C I 17 C VOOR CO ic _v 01 7.01 'I r0: r :;ri r r7 1 I l L C 1 — — iiiN jCj Ak 7ij C 1 0J2,0 cffiCI c'j-acc iJiAA i.3c ri:i0Ct; 0 I c . — [Ii 3 0 1, 01 I :T C3 'L23A ti : jc.ijYjo e3:J 5CJ sedimentary rocks: James, H. 1966, Chemistry of 73: the iron—rich f:CT :k•2A IEi L., CVI: 7iiq 1 U. S. Geol. Surv., Prof. paper 440..-w, 60 mi p. Swedish iron ores Landergren, Sture, 'Pc:1. 1948, On the geochemistry of and associated C.)tL4fli17 rocks: Sueriges A&IA&J)Lt Geol. u][3f Under., Arsbok 42, No. 5, Ser. C, JN. 496, 3TL p. 9lT 182 ocic- 9 �II JICC1 f1iil./j GABBRO :!TJ;1 THE DULUTH RARE-EARTH ElEMENTS IN Wis., Madison jpCZP:tIiO of •i:1 CCIlI5Pk !5!i of :sssL:s1cS Chemistry, University Larry Haskin, Department Ci' CU j_ University of us., Madison CI ±L' Department of Chemistry, jBarton Denechaud, -I_ ç — I, I 1 Rock samples been analyzed for (C U __ from the Duluth complex have S 'UI 1t the gabbros Like most of — [1 I rare earths by a neutron activation method. —S and diabases investigated from other locations, the DuluthI gabbros C' p I and lower ratios IC_CC rIE haveS significantly lower total rare—earth contents CI _51C Variations in rare— 5_C C of light heavy rare earths than basalts. C SiC_I to C for Duluth samples CC I _ I s will earth abundances with rock typeC and location 'C Thsi be discussed. C — C U — ij 1 — I C : I C CE — C I L E 1 — C — — — I ' 1 1 I 10 to C U —— J �01 COP}tk8 J. STUDY S' 'ilfl Of GEOPUYSICL Richard J. SP •3tP12r:F L:Jc SUPL'11110P Jld, .ssistant Professor ;.nran! ??75s30r v;c cZS-iof r.Geology 'fl?t' Derartr.ient tept of'4'l Jisconsin c:.:ir4n ttnnz'&Lty of University Milwaukee II 'sa,kee 1964 tic theDtn'.truitj University isconsin has been;omLL:.xqc conducting tf of bIroawi.z !uu bee-i Since U54 32t".Upof yr Lake Iak Superior and has occupied an underwater gravity survey SC '*wista'tW' gçVjt1;j7 The 'uL,otity majority La3:o and bays. test, lake ntztz.o'u sfl over 1600 gravity in the ga'c.t 'w stations nn .iâCiO grid with closer ??:'•; a1Zc of tiu' the vtcttcc€ stations an are located .cc.ccd on w a.a five mile çnA of & FH The survey with L & tiXVit7was as conducted &Wu.ota vatS spacing V. in t.Di) some T*8V. areas. 'The £S.CJS provided by pXCV.dt1 underwater ra%isatecE gravimeters saO and the positioning was L0PC Service Corporation. Sct.s:'iot *r' a; octr;ie't .crt tVSd te :.ôtt' fO'G 3: .i is tc . rat 9et tiL sPJ! ?' aeromagnetic vaflcy 4ata ;h aazamag!t;aX The gravity dataart1rttssn analyzed .n in c's¼rbSutt conjunctionii with Tba. western .z. the kb cce.;e'iI part data f%Q13G5 suggest two major5tXCCflt?'Ui structural features t3 flOS' 3.ar'a:*J in ru..Grc t north—south One of taati.zee;is1.ca aridge rI 1 running of the lake. Cnr tV the features :ie .4C'..s. The second major feature is a ridge xajvz' Xsahzn in the i2ta vicinity of 91 0O'. extending southwestward from Isle iloyale. r;ut! f 33 j)'LI. 2ne ni.c•. exii"c sstv'ec:i*'itü "r C.e Roa&.e. s a rt:g* tt 9ot n' 4:y north 1'st rcct.S Both gravity and magnetics indicate a ffalor major?&V...t fault just 1v4 aM n&gieti (!.'%tC: Superior Shoal. sat c? of Isle :r,'... Hoyalee trending to Ta'i the area of tkvsriot en'tw.erd ¾o trst5'ns eastward 3 PrefltIjtc from frcb Isle St. ..nother fault noted a' in rhe the r*urntscss magnetics trending ;...t .otec There Th.ozt gravity. Ignace tc. to Isle Royale :.e is .J.sc also confirmed by the eonfi wod b:' tt.. Rr.c.c..e fault extending is no ot4r.c*evidence in the gravity for the postulated Pc_tze'da from Superior Shoal to the Keweenaw Peninsula. t:oa r! Itile ,.isctne tt v. tbe rs, ;it ftc the poatu is ,ttpnthr ihos.t 4.t tn hti'j-..4 ,h. nk'rtt ibl.l: C at *cute p'.tl.L$t.A o'kthe ths basis btiai of an Most of postulatedb7 by EiVLs Hinze on MN.L ci the Itte faults supported by the 'e Ztut:tEC by tas aeromagnetic survey in Lake Superior are Li'.eastern crtcnt tat 3vp:w.t..r the The two rae strongest positive anomalies in gravity Et2Vi-5 'ttc CI5C4t7 survey. Ft.&y wLt.''.magnetic €L?4 r. highs. They eastern..&t part the Lake correspond with Ot9ttfl: GZofV4,c ap-uoa\ tc&cid Michipicoten Island. fltk ss occur around Stitc&Ar" Standard Rock and tpo;thq:tt northwest of 141 *30W orovr auce ctrr',sb ;n&ti'r Cnrd!$t fl ttt j,.i1e anaec' .jM'n r nØ Een rafl flr tn lot r.4taiLe. cc4 Ic eet. 1vs Bt:p.x!.oi ecnt s'igpcrt tie 4.;t'iLTh 2 th3t t! itLc £VL,'Ct ty!fleflne cs.; *rctt:t tAa E'.nrst. ecLty field ix. etstn ta The gravity field in eastern Lake Superior does not show the :he strong anomalies seen in western Lake Superior except for the low i seems 9:.a'â to support the suggestion 'tG field $ttht,, The north Superior Shoal. ett :.t CofS%thcfltZ r.rts.Cs that the Lake Superior syncline curves around the Keweenaw Peninsula to the southeast. te tt U 11 �?±7LPALEOMAGNETISM Li±7JjII±i4±7I1±7±7V 4:jCj± KELENAWAN VOLCANIC UNITS OF V MIDDLE THE H. C. Palmer, Assistant Professor F4±7±7±7c 1±7±7hI&Ji of Geophysics 7±7±t±71777±7 Department .i22)±7c :LJj9±7:r:! I51111 'L Jty)I ±71 London, of Western Ontario, Ontario 7) The University J/ T1 i:\- l !C.± Middle Paleomagnetic results1±7ri from over 300 samples of ±7 7L1.±7 - ± Keweenawan volcanics and sills from the Lake Superior region ±7 ±7±7 ±71 The logan sills, the sections of volcanics —1 have been obtained. 9IW!±7J ±7x-J 4±71L!7! polarity. :1CJTC±±79±7C±7 L have reversed ';I.±7 volcanics at Alona Bay and -±7itt the Osler all positive CI Island 1I1J'7is1: of ± ±7i±t ![1±7 of 7!JIvolcanics t! The 1)±77 section on i.±7±7;. ±- Michipicoten I The North of Minnesota, the lavas at ;,( ±7Shore C _i±±_ volcanics polarity. :'— I±7T!C. both ±7.i±ic±7:L±7jL±7&rPoint 1776±7±7 have ±7±71±7 ±7 ±7±7 at Mamianse JJ±.±7(31 Gargantua Point and the section ;J.,±7±71 o reversed All ±711 sections ±7±7±7±7±71?:. p76L±±±±7.itp sequences. normal and reversed •C±Ve±e±7 polarity ±77. 77Vi, 500 N) 77±7±71±7±7±7 (mean 148 ±7: polarity ±1±7±71±7grouped J±77CC2 ±7:1±7 pole positions III C 77 yield±7 closely •7?±7JCI±7±7I7;±7C 77±7 .Lti !717±7 which are different from the pole positions calculated from sections of positive- ppolarity which are also closely grouped about a mean 340 The assymetry of normal and reversed r N N. position of 1770 VJ, ThI 1 but small 5_ directions of magnetization may be attributed to a very hard I t±7177 to all secondary component 77 ±7-7L ±7of magnetization which has been added 7V±71 I76pI ±77:597C.±!it :±7R±7.t eruption. these 7±7I7.LKe±7 Keweenawan rocks subsequent to 7± their 777:775±7 r' 1 ±!.\_ i: .77! — — ±7 L iC)±/! ±7±77 ±7±7 ±7±7±7±7 1 ±7 1 ±7 ±7 — 1 r ±7 — I I I I 12 I —II I ±7 — �4:1zINTRUSIONS .fJ2T1LLN4, JaL1V1 AGES ij4215 OF RB-SR 1115j0; THE 1UEENAVJAN . L. t4: NORTHERN t292fo1 MICHIGAN ALONG FAULT IN 'j :: S. 1; StCl115Univ., o'sLs. Manhattan Chaudhuri, Department Geology, Kansas State '>sjssLoosoiS of st Cso iL2gy ±E5S5c1T 4Jo2QcL tt5]f51551e 15']! o;'. 1150; r1 15J sssj; 1j15y55, IL' Geology, Ohio State University, Columbus G. Faure, :0;5istIS0;22t Department of L3!Jstl 0; I,50L577ci of Geology, Ott15r'S'EL D. G. :ESDOLI,o)bm Brookins, Department Kansas State Univ., Manhattan . n15'' .,i'i'I5 552151 50; 555Cr 4 In northern Michigan several bodies occur at' 1515 different 0515012: intrusive '124 21111572 the T0]5115 ?socL-:s &50;0;51 0.0ce.4'*2] 1152015 2 :1r:'ts15551 near y55 the Keweenawan locations fault. These bodies occur near 14 ioi;:15 11r2c51 Series', 5115,05.1 but their base &772''t!421 of the0;t25&12 Middle 1stoo;s..oss Keweenawan .15.011.51%. Portage Lake :155 Lava 1411:22(15 572'. not ls,7 clear. exact geologic age 575: and T05. mode of origin are ,-:-15107t, 51515 I 4555755 from 1515] tk.'s ¶515 felsite '5(1.' sS7&s 515, & 5-4 samples Rb—Sr •1•11)flI1 whole rock study of four the IS-tos' Bare £ initial I 0 Hills yields a least—sciuares isochron age of 934 ÷ 6 m.y. with 415 14 Sr (87/86) = 0.7166 + 0.0003. A similar study of the syenodiorite 5T 44:15 "1l.'Y'T41' 11455 Bohemiaarea 4. 25 4.5? m.y. with initial 6711. c15of :0 1130 JLi-.7' + of Shs' st' the Mount .41124714. yields age 6L5 an 5,7/42.1. •f1'j; Sr (87/86) Cst,;. 0.7045 ÷0; 0.001. — 11 2 415 4 705(4:3,470;' SICk?. of 7516 These 777517 suggest 444], .SCIat1/OSIs least 5547 two"i51ciLL17'7 distinct 7;14.j periods igneous 717047 data 55 53 4J 44.late J5 Precambrian I activity in Michigan during Sc time, an early syenodioritic 1 u.'h "S— S -0 5j and later felsitic These two intrusions also intrusion intrusion. c — 4 47. 1 PP 4 <Ott 51734121025 12(1< large 25 -•74) difference 551564.2515 641567]544.'0;:45 ]15tt:15.± 15 resulted from different 152-6<1145:41 magma sources as .indicated by the /3; 14 Sr (87/86) ratio. .J,1.117 :2, 151 in AS initial 1515is 15xss rs:',st soS •527,l:,-651250;LS SC 15 SC of 77<74 lsSICTS 71550;571454 Since both2osso.J1.oss: contemporaneity and consanguinity the Mount Bohemia 1' are 5511 the Middle Keweenawan syenodiorite and Portage Lake Lave Series 6 IF '1' /111462S7;< -' 7I-7fi7515172712 possible 5154'CL and J2.k71I117'S-1-09 plausible, the period of intrusion of'2 tOss the syenodiorite 7.14544. 71,71.54 57146 Bare cOllist '07 Later 45471447515 emplacement of the 5-'7475771570'7-jIj.' L57754 71155 4]s0;s the 27 1511705156754, 70 may date culuminatjon of1 extrusion. 7515 775115:7 '?-1T15(55.170 SIs 15 Hills felsite may have occurred at when the Keweenawan 272277' 7575< tss -550;:s'50;51] cl a10 time sedimentation was already o.lrs:e.J.;' s.in '57 progress. •C.152-Sis,< (F 13 — �'s7!•&:r ::r THE ¶11tT VERTICAL fIi AN INVESTIGATION OF fTI VELOCITY, DENSITY AND Tt ;_r rii ., Cr POROSITY DISTRIBUTION IN THE JACOBSVILLE SANDSTONE, HOUGHTON COUNTY, MICHIGAN Ifr4J)t! EI;j ti jkcIt JtII S iit 1ItlAtI University iL:c Professor Geophysics, Michigan Technological ©C of Y jI Michigan Tech. University u Applied Geophysics, P. W. Ingalls, Senior in WTILIttIt71 J. F. Stafford, Senior in Applied Geophysics, Michigan Tech. University &TIIt. L. 0. Bacon, :T t It ..jLI)IL c:cIn:aa M L)I:Ci t]'0 dttt laboratory ILCC1;It? study was made of the pulse velocity, density - and porosity on core samples taken at ten foot intervals from a 3628 foot -L diamond drillii hole in the Jacobaville sandstone near Rice Lake, Houghton I4izLCTh •LYFiLLY kt.i±tr County, Michigan. A A 9 1 — - jI"1 Calculations based on the data provides a vertical velocity func3 Z of 1200 feet and a velocity tion, V = 10,200 - 2.1+2 z to a depth, z, III z. The large velocity gradifunction to 3600 feet of V = 8100 + 1.90 IL these functions were extrapolated I_3 ent might cause considerable error if Cm to depths below 1200 feet and 3600 feet respectively; therefore use of r disconCl _( ç11 to the )_L-L first major velocity a constant velocity of 9000 ft/sec LIt I3jL3k.33c1 3bCLL3t I'Ck tI is recommended Ii 313 discontinuity C1:; bL! that b-C Cft/sec beyond tinuity of It:L 13000 C:: and CL iIt,7LCtL&ILCi l'Itt±ILHL -StibiL. It 3I/ULCftJ:ItL for IL)t useti LUL on all reflection seismic calculations. L ft 'I f- 'L i1 Ij U I iC L0 19 U j 3Ittt 5 area—2 -b3 reBacon's Li-b Application of the constant value functions to C of Rice Lake C C_ miles I flection data (1964) from a location 10 southwest CY feetCaand the C gives a thickness of formation of 10,000 3_the I Jacobsville IL discontinuity of approximately 2000 — major velocity depth first it to the U .3141 Cr3 feetCIt:IPiz.i in that area. & tt-ttIfl ItLIC CCII LCILCL L 11) CI1 Itl CbL;lLL[. .ciC;-' II.tolItthe uLcC CIt-A 111t1i-L H3 L3LP The average value of zi porosity 1200 foot depth is 14.2 per—_ 1200 feet the porosity Below -_ cent with aCItJT range of 10C to 17 percent. _C decreases to 3.5 percent at 3600 feet. The density of the Jacobsville L-II - cubic centimeter to the 1200 had an average L_ value of 2.25 grams per t A b C;C.lItC LLAt IC-411 bi-Ui- PIt foot depth and .i-3b/hC33313CLi a constant 2.55 grams per ftLL.C cubic centimeter below 1800 ' I3 fta ir.lli &jIts C: U It t- It feet. 11+ I It �;Hc(LJH: I5T GRESTONE A GRAVITY OF SASU'SCS PORTION5OF THY THE'1iJit FLIN FLON Z5J7HY :f £. 5: Lg:cSrS SURVEY ST. L IN *TLSLT BELT •HJNORTHEASTERN SASKATCHEWAN tT'iiLJ5i '.r•(i! r' iI D. Gendzwill, Assistant Research Officer t' , C-S Saskatchewan Research )C Council 2(c:1;Rm:. Saskatchewan Saskatoon, F itSc'.FC2. I iFiCX, A C'C5JLc) .Cf;.t' C1CC5t7 :LCj 5SPrecambrian C'ftS CC Amisk An 5HS interpretation of thetC2tCH B.ouguer gravity in the Lake—FUn Flon Area of northern Saskatchewan shows that the outcropping Sk Group of basic to acidic volcanics and clastic — Amiak sediments is limited with more or CC rocks (C in depth to a maximum of about 55 kilometers. Lighter !tL4ThJ(] JTCCC1TCflt less uniform CJi CC-CUCit5 density underlie (nCi.C:; tthe C ::tH Amisk 1 CCC.C Group. Granite and granodiorite r but are also Most - limited '5 E_,L 9_ic sequence rocks intrude the in depth. C volcanic TCC,Jr C)i1 t'C of density variations not5CTbCT persist to depths of more than 3 to 5 5 :ii S do 1ciCJ 5 the t• 5C t5 CtccL kilometers. h:cnw CCL .'t.S •.H_ Sj: 5ç j? — L 1 jiS 1Tht 5.&&tçCo J(flz:Fa çS C:C Densities;5C of 1585 rocki?.&1Ci samples were determined in thet5laboratory. -E ci-*CL-C 1TCCH1 Irii shows Analysis of the 4V1 ddensities ittS;'Yc that some basic volcanic rock units :i75Li(have 57 mean densities . C1LCi itC-;as. 2.66, IC have mean densities as low other C5H51C units as C F volcanic rocks due to variationsI high as 3.03. Gradations in density of 1.)( anomalies. u::CCc5. 111Cc (:sI. gravity H. metamorphic in JJH'LT grade or composition cause broad y ç 5 1C11C*- 11y1H•1C i:J1 the C:54 area iC Ct11CC1C S-Mt S Crustal seismic work in shows that P wave velocities of H Sj). .5 Ctct?;C, ç', with J152Hi exist to Sc depths 55c11( cS JC515SC? 6.0 to 6.15 km/sec ofJQ 10SJkmSt to km... Material t.:vzcF<such &C11SCrflt±mt5this:SC5?Sy i,55 velocity 11CC at -T1CtJL such depth C11Cc can tCcL€!LT/ only be 5si low density rock as grano— supports 11 diorite. This conclusion 2; i the gravity interpretation since St SC This low density both methods 5 indicate lighter material at depth. tTC@Amisk Sw&S tfr-t*hC rock might)e2;cc111ccL represent. older 1rocks on tC.:ctS which the Group 111111 was deposited 5 s'ScSSC CCfS.t5tmaterial 1LC ?iL& 1155 emplaced cc€C CCtMCLLICCtC5 or it could indicate an t.L,tLLI/ increased quantity of granitic 55 5t 1C1C ]ISLbf HiLl 5iv( at St depth. in the ccci. SC rocks 5511 Amisk 1 5 i'1 :c I 1 ' . -If; 15 -- L �I 'p 1lL THE PENOKEAN [JTV AND HUDSONIAN OROGENIES IN THE GREAT LAKES REX3ION, .jV1L HFLIL.1,_cFI._JI -:y' :THE GRENVILLE FRONT AND THE AGE OF 51 a 1- 1 i — - i Williai:i R. Church 11] Assistant£_Professor II. L Department of Geology-jUniversity of 1estern Ontario, I.1F?y/London -' i —-r----. ]k -— SI I p 1 1-. L I the Penokean orogeny define an [ --.--.;---- .-. during Huronian rocks deformed 1I —--..--- —--•-.---L--approximately east-west trending fold belt modified in the form ofI a fS 17 II as far large Z—shaped orocline, which extends from Minnesota to. Ontario _c nJ1 eastZ as the Grenville Front. The long held view that the folds in the Huronian of Ontario are coeval with r— those of the Penokean fold belt of — Lake Superior region is supported the by the correlation made by Young r the "Ani— (1966) of the Cobalt Group of Ontario with the — lower part of :L -T'4 This correlation is based on mikie Series" of Michigan. II ItTH iD the occurrence 2F1thI _ tillite, aluminosilicate— including exotic rock types of in both units H J1IIJ LI —Fl _-I 1 -H. bearing orthoquartzite, and banded ferruginous quartzite. _c- . i_1 — — I — I — — I L I S 1 1 1 I I I — — — 11 I I, F I F I I m I -if' , Nipissing diabase of- Ontario, which has a Rb—Sr age ofI -' isochron IE4-_ 2100 m.y. (Van Scbmus, 1965), was intruded after initiation __I — l(I - of Penokean the latter deformation (Church, 1965), andL it is therefore certain, if 4 1— of the Huronian and the major age is valid, that both the deposition Fj H - H L 7 - The Huronphase of£ Penokean deformation are older than Ca. 2100 m.y. I1 1I=, of the order of ian of Ontario is everywhere metamorphosed, and ages 2000 m.y. cited by Fairbairn, Pinson, andr Hurley (1966), and also I flLF and volcanics, Knight (1966), to represent the age of Huronian sediments ¶ I metamorphism. more probably minimum ages of the Penokean are — ? LIr I 1 ) — 11) F t; ji II F I — — F 1 a — L — a — -, — F a III rII- 1 — — I I I F F r I — I c:i:L of the Huronian of Ontario :c:. is irregularly developed Metamorphism Hg;. :%!L•f!(•1!2 sequence. both geographically and with reference to the Penokean fold I,margin of the southern H is most strongly It along the northern I z cLi developed c:t_ r1 LIt: from lower greenschist _ - _ -Th_ belt of folded Huronian, where it varies in grade _I L (Card, ) (chlorite) to lower almandine—amphibolite (staurolite) facies 1 ½k rLr J strongly Secondary diabase deformation is also 196Lf). :1!!\Z1: post—Nipissing 7Xr (: . r t:lnTTc ©cA-•? pre—dating the developed in this region, andV early Penokean structures 1 '_l : deformation. diabase are usually completely transposed by the later ii ;ft V-i -, weakly developed Towards the south the secondary deformation is more 7L — 1_'i, With respect to the second 'and large -, scale primary folds are prominent. L' -L pre—kineniatiC, phase of deformation, metamorphism in the north —1 was syn—kinematic whereas to metamorphism was both pre- or : the south the Y!L ]k::I! •I? :Ip.1cnL:i*xMT The relationship of the earlier metamorphism, and post—kinematic. 5_ 1_1(9 _ to the secondary during kyanite <-' j '17 which I \_,J was ,—- formed in orthoquartzites, I 1) 4_ Andalusite in quartzites, deformation is C not at present entirely L I clear. I_ the post-1dne— —— and biotite and garnet in pelites, were produced during r eT In Michigan, granites and associated pegmatic phase of metamorphism. iv be post—deformation and post—metamatites considered by James I T- R (1955) -:7 rr.: to and James, 1965). morphic have ages of ca. m.y. (Aldrich, Davis, r 1900 r the isotopic data of These ages being minimum ages they corroborate n r r - - I[ I1- & =I ' : I I I T i I j I I: a ) i cr -: I I J r i - I ii1J[ . — i EF L I ;' 11 — ia II I I I a LL/ I N j; r — 1 ::ii1( L j I I 1 I LLI I a 1 1 I a Il[. I ' TL' t E I a a &i- (continued on next page) ' I -r ] rS-13 — �I l that Fairbairn, ?L ThI Pinson andI Hurley (1966) and Knight (1966) in suggesting 1__ I the regional metamorphism of the is' related to fl Huronian 1C - the Penokean I1Th_[I) given an orogeny, rather than to the Hudsonian orogeny which is commonly -C T1 intrusive into age of Ca. 1750 m.y. _— However, granitee and the penatites the Huronian have both Rb-Sr T— of Ca. -j- ages 1D of Ontario j1 I '1—1 isochron I lj and Rb-Sr 1E 1967), 1750 m.y. (Wetherill, Davis and Tilton, 1960; Davis and others C — ICTI _9C The granites '—I described as Hudsonian. and- may therefore correctly be —L—I -C' post—date t1/fT; the jIiji second I7IF*c31 phase I3IjIj metaCIIIIV' of Penokean deformation and regional L Brooks morphism, but pre—date a late phase of brittle deformation. -j j IL Jk 1'—TJ[ p (1967), considers the pre—granite deformation and regional metamorphism I—IIT1,1 Iof the Huronian in the vicinity of the Front to coincide with — ILLI — -.1 Grenville the formation of the Front, from which it therefore follows that the I Grenville Front mustI be a Penokean feature. It is not jconceivable that it was also feature at the time of Huronian sedimentaL1 L 1 C_L a 1 significant 7 __ -positive T tion, the area east of the Front possibly being a region of Ifl 1 FDC—__ttThe late relief during early Huronian time T1_ (Young, 1968). I phase of post-granite brittle deformation, which is quite strongly developed I 1L) 1 along the northern margin of the southern belt of Huronian, may be L1J 9E' related to the post—granite cataclastic deformation commonly observed The cataclastic deformation, according to Brooks along the Front. T 7 \FI : (1967) deforms Keweenawan olivine—diabase dykes, and is therefore 2c&JIL7 probably Grenville in age. — — — 1 I 1 1 ( _- — 1 — — I — 1 L — 1111 1 1 1 _ I [ — I 1 — It I I I 1II(2'' — 1L 1j -S-I, r- 1 'rm I' I — I L _ L — I L — tt — r — T1 i L i 3 — — 1 I !MY — I i: i — 1 The length of time during which Phanerozoic orogenic eventsc takes i I C less. place is in general of the order of tens of millions of years or r -Gc -' 7 The age of the t)flI difference in OH[ CC7. éfL Penokean and ç.':r Hudsonian ;!7J. orogenies is of j:( the . L=' In terms of Phanerozoic geology therefore, the Peno— L— m.y. order of 350 L 1 during kean orogeny represents no more than a relatively minor episode f 3 2400 n.y. to 1700 m.y. a period of' crustal from 1T-' stability r extending L 7 I of Alternatively, the Penokean orogeny may represent the initial phase CF 2 — -r LTh Th Hudsonian the break down in crustal stability leading ILJ C 1,__t i—i— to the extensive _ of sediments in the _j cycle of &maatic activity. The general L -' _1% e I- absence age range 2100 would tend to Lb. support the latter possibility. .t. to c: 1700 m.y. ±: — L F i — ) I I —\ '' ç — Y — — 1 I : I ——- I ( — 4 (— i j r t1t; kY (continued on next page) 17 :":Pi! 1 r �REFERENCES i-r ct r -1i: 0 Ages of minerals Aldrich, L. T., Davis, G. L. and Jaries, H. L. 1965. from metamorphic and igneous rocks near Iron Mountain, Michigan. - oUr Jour. Petr. 6, 41+5_LF72. 7.0 7A. - c) _c) c . - % U L2b 1.ti:tL ç.-3-: L.tt oo]3o J-o; 3Ptthe 3c)p: 1--IJ3 J]01tIL.;. metamorphism along Grenville Front, Brooks, E. R. 1967. Multiple America., Bull. 78, =3== North of Georgian Bay, Ontario. Geol. Soc. LtP33PI, 1267—1280. L I : 3€ tioiffDistrict, gn:.-3.-t area, Sudbury -tJo- OA-.-t-.)t, Card, K. D. 196k. Metamorphism in the Agnew Lake 3;pj;, ?U,LrU1AUYUc)o 1011—1030. tUo-,2JL ?'PJ Geol. Soc. -'oUL. Am., Bull. 75, OU7J-TJO..T Ontario, 3iYtUtt.c)c) Canada. 23-3--t- -•4.tn UUc . 3ti0 Penokean .iorogeny in I)y:,j:Lp I0of the Ontario --4-Ninth 3t* c)iAiiiF, 3k,.R.3.°E1. status ç.)0 Church, W. 1966. The cç YU0td1?JUS 7i737Lakes $J 1P: --.itrpU Chicago, :.-34\,; p. 25. Conference onJO) Great Research 71cc z.o. -0 -.0---0-...'- S. P., rI31c-.7,,, Geochronology %ct.J_71)7L0Lc)' of 03001 Aldrich, .'._ 1967. .o—t.-v.0-.-, and L. T. Davis, G. L., Hart, 0 H. Abeli50*,0 I in P. the Grenvjlle .-. 379—386 d Province in Ontario, Canada., 71. .c) = .7. ). —.5 c. ,1._u. 10. .7!03r .:70J27. son, Ann. .oo-.cU. Pept. of the Geophysical Lab., Carnegie Inst 00 Y' of S0401t30'L4010' OTto Director 00 ..--çP ]1.o0O. Year Book 65, 'OO)-. 10. . - , - H. H., and Hurley, ::Uto,, 1U P.Y& M. 1966. Preliminary ?1 W., Pinson, W. L U° I M.I.T.—1381-lk. 3 whole—rock age of Huronian sediments, Ontario. V 0 :c7-U: 3.o, g--po-om,Ui.- Ann. Aiit0 Prog. Fourteenth Rept., =c00:.1sAU.S. U.c3-. Atom. Energ. Comm., 127-128. .o--Tt.0 Fairbairn, 3. U- c A I ' I 1= oc7 ?U.c'oUUookt 37; 1955. Upi the a7oUol '7 cc.. L. James, H. 31/5 ,_,i:03. Zones of regional metamorphism in Precambrian cU U of Northern Michigan. Geol. 3 L Soc. — America, Bull. 66, lk55—l'+88. -.- 7c S i0 oppc:,aA,tstudy '50'; of Knight, C. J. U 1966. n-;-: whole cUdo Tt-ccoU. Rb—Sr rock L30-A ages of "'.Cf0.'o-r. volcanics -iTton tY3 33 ,k..c1 M,I.T.-1381—11+. 137o-tk-, cPo-co the North Shore of ot' Lake .:3o £tpc';r Huron, Ontario, Canada. 30U32025 ir.022 IToP, 129—139. Fourteenth Ann. Prog, Lc)7-D' Atom. Tt.0.i'. Comm.,, o-ocA- Energ. dg71 Rept., U.S. Mines t[t3 'h2-Tt *20 70t0c0 Van Schmus, P. 1965. The geochronology of the Blind River --, Bruce 03:2 3:"o2Ttt' -d5H-oU'tt0t. .7• 00t:—:Lo.. Canada. area, Ontario, LLACO Geol. 73, 755—780. ..ou:t Jour. '100 &oio 030032=uct,OV.-c)measurements 3t .1. Wetherill, G. :U5AAJTtTt.cG. = L., .-., and Tilton, G. R. 3'3/1, 1960. Age 0; ii., Davis, i::=--5 Jour. I3& Ontario. Pc)C-.tioTLo,,7 dtTt 0233I2, 7.ooso on minerals from the Batholith, Ut.s Cutler -0'/ 5B20.:c3.,t t3571 Cutler, - Geoph. Pea. 6, 2k6l—2+66. )? ''10) Young, the McGregor Bay area, cOt0cc.*37'004.41-7of t 5c±cTt 0._c cG.37M. 1966. 'A2:.c Huronian stratigraphy Ontario:c:. relevance It c7-,0,,_. to -o4!the tr: LakeOTtTttAc..d0t the paleogeography Superior to 'o.L.o UooTh'.o:ococ7tOTU4O4t/ of region. I.TtJc: Canadian Jour. 203—210. Uor0 JTtjt,3' Earth Sci. 3, 0;A0Tt 3 J0C--0L0tc of ,oO Ontario. structures700c in Huronian 3d02-Tttttoioi rocks 0337220 Uo,r- oOoo'.-ottocAo —.- 1968. 3-:3e3 Sedimentary 0r.,';3&73c)7-)2)7) 10. Palaeogeog. PalaeocLjm, Palaeoec. k, 103 0- 125—153. tc=C-. 0t7)c 18 �5727,']P '.7 t.77S ATD 31111z1571 <2317. F'531-SiJllS[ 31i31 : STRUCTURAL 921 VEIILION '52525j7 5:; STRATIGRAPHIC FPANE!OPK :'71ja' CF THE !-,[7155721-<<'s A31[152.. 111 [±12112 :<15l7 It 3121 DISTRICT MD ADJACT ARFS, NORTHEASTEPJ MINNESOTA <1i['72I"3131s1,i21 3131701. Director, SJL,'31 c31-c-c P. K. Sims, 77 15217317:;1€, S'255'7:i52 55&51 Survey, Minnesota Geological Minneapolis, 31555"31 27- 1*ht 3131:317175531, Minn. 55<75<, 0,013 Minnesota 55n"Hçr - Survey -B. Morey, Geologist, Geological 552,''555j33131,, Department 72 21o5514515255551' of :31Geology, 431,o:525o University R. W. 575-&3152. Ojakangas,513.313553155555"; Assistant Professor, i]IiH"31:'<5<1t;' fJ ''- arid Minnesota of Minnesota, Duluth, Geological Survey J G. 7 5- W. 5. <Sc-? :1152, 1}s31<J5.5.31r<.'ss.. L. Griffin, Geologist, Minnesota 112311553152Geological 312'5'111721S1, Survey 1 ,31 311 1' 7< 1 551 ,< S,c.0'571?15517,. 11152 31 :5531-5-':, district, 155555131.5117 in '111' northern J'C3[31 311531:t7 The Vermilion St. Louis County, lies ,<.01055 between <311171313131 1155 7255*j 3155.315 H tgo. 731 Vermilion batholith the 315711 the ':721' 55553<21 on the north and Giants Range521215211 batholith 7:2-'. 'S4sr 52 5135255 21 on (1 /c I_ rocks "Ha It contains the dominantly l31[ mafic0 volcanic that '131k comprise 3<,, '7u55 Ely 1 - 571g'-Th55 I 3131;L55 rocks the Greenstone and- younger clastic have- been called the <11 that 5 <1 550 i31Ic - Lake 1< Knife Group. — I 255 <<a'.' Iron—formations of Keewatin0 'type, which include the 3113131 at 5251 several @31 )44f.1[ 7231c-t1 I3,.c.5557.55;!.:. positions Soudan, occur stratigraphic i'57131.'1F,15ç1331 5±131 Greenstone Ely in the ".1555 2135511 311H.:i,-sL\1 157 171r3 and in the overlying volcani—clastjc .5' '311"1L72155572 13.5531313<;. • 3131'ci 31 rocks. 31311s31 A "1031105555 variety 1555' of 5<71 porphyries 3*331111121 101 the I <- bedded rocks and "1 intruded in part 3131o are contemporaneous with them. 2 <55 1 <571 13 07LI1'017 131 .II55 All the bedded rocks are_57151 older than the intrusive rocks of the 7Vermilion jr_3'f.,.lo, Giants 311' -i4<< and Range batholiths, which have been dated as Algoman <.55550 (2,+OO— 1 1,55011' 31155,,311 2,750 rn.y.) in age 0by S. S. Goldich I __ I< and others. The Algoman intrusive 5. 55-1 2 31 r-refl<'--r" with 557<1 rocks in 255553117 2< the area aI'31syntectonic are to the±152metamorphism H'1' respect '3 5555315551. <113131 311 55717311331531.73131 and deformation of '.31 the ±3113 older 'oL',';' rocks. 1.5513.52 '<15131 10 the south, 31355 5231 'a — 5 < I-; 5 1 ' J '' 31 ' ) 55 31. 55 — I < <1531 The 5152 ;'i.: 31:.'s355'55''55'bt.7,5271 1115231. described 51133 district sequence of bedded 73155±152 rocks in 1:., the 55312111-5,55'.35531153173555 resembles ¶31'3111315535?31 that <55greenstone •" i 2 belts 1 from the 3131' of Canada by A. M. Goodwin _ < <31 and others. In gene7,1t3131'52[, volcanic 51572, initial ral, "11.L72c713131 flows, 5555'11'<1s I' [1131529 dominantly 1131125' basaltic composition, "131"a in 55115331,4551.7J5-'511< pass 13335 1<1'<' upward into volcaniclastic rocks of intermediate and, locally, felsic com55 5512 ,, 517,31155 3.3151< 4,57.31 these position, and 313315555- in 3157 turn 7'55,5a'n. upward '5<37<555557';, into 3,351531 clastic 7'41311.333'317i5551557 rocks, .3'I.15'017113L33 sedimentary pass 211555'.,, o 1r31 L55 mainly originally 2'l graywacke g' 03 composition. 1.- 311473< '7 mudstones <'531 311<1 and 5_513157 of similar Depo3, sition of iron—rich sediments <2 ?.mt=:1152 311-31553, ;7<5131 735255' 7<4315<17 numerous ,'< 3101]yi<< times, particularly was 15513 repeated 1"H t-52'3t 7L<710 51 5t.314'31'55.7235 parts 52< in 231 the lower 3155355, and intermediate 722121 of 3131the 5is 31:7.331552155. 171315113155-52 •n7:t'ai-5'555, sequence. volcanic 3155:511 and clastic 2< Jt21 152553131155,.' 31313131were 555f, extruded Pillowed basaltic flows 7'35':j'1j55355.311' 13131311-,-during 5i::55'52 y3 155131152.I57 31(1, of locally the deposition 'o5531 '313<3.33 :31755,71317:' and 31,531573170' rocks. the volcaniclastic 3135555. clastic 10<523,, '3131: '5ss'1" 31I 3< <1313±1377 511;'3131' from To judge .7: :52: their distribution 3157 H-c- 31 and thickness, the flows and associated 3152 1 volcaniclastic rocks accumulated 5371 ss'3 '.'s,'52 ±52 Ct'23151, in local 5<553<314,3155,15 '52'3131" to great thicknesses fl3<', volcanic 7231,<:5 :51,512155'L discontinuous centers<1s21c and formed .11111571131 C55 '3155' 72" 1' contrast, 531 :35 '305755) the deposits. In 1531. 5311331105553.75 31'3157'P 5531313131? 1152. 315111s, 55'31.75 younger rocks probably were deposited 7 '313112:1 clastic .3<1<31.1' 14.i1,.n'31315:. over .31 a 31155331 much wider area. <1 57 11 a ,., _ 1_41' C - a 11H _ 55 55 35 il- 1 55< 31'S 2".31 rocks .:15<5.,- of 1<.31',31( The the 72331' Vermilion 5'22553±755L5531< district ?±-<721::' .55! are 151[3c'31'2<31 9553 Vermilion 5'<;.cJO 357 separated from the 3155 high-angle fault, 52 571 3131 batholith by a major t-55_,i1øl,_ 5 Ho Vermilion fault, 3152 the and lesser —57 31155555,-15731375 ,'33553,531, 3331's 53131331 faults. 315355". sub—parallel and branching 315375555573-31 1731'-,,.abrupt 3"51a5531'.:transition 311552.55<1 SIts from The 121131' granite "HIlL and4,3313117<31<3.4,1 associated high—grade 3171313-731<535531 metamorphic 31.2'11&sT:531 1<5555 ,"C-'c13155 335552 rocks on .31 *'ta31i:55'tt the north 155711131± side of the 0 5- 5, 0 55'31 fault 5 5755 1 to greenachist—facies rocks in the r 55° 311<31 that district proper suggests ]031 <.31 Vermilion the 131531 -' 5131_ _.t fault 553 had a dominantly '31 0 II' ci The 11153< vertical component of movement. 55 Jt':31131531•:'s. '5"< v:52i '55133112331 Precambrian I1135<,55'3155'3571. displacement of steeply—dipping 131<37531 3555,35:31 a 55 rocks along metamorphic L.'57<311'1123555531:'t;'1:31'f branching fault 511,3 is 5251<1 left lateral—-a 5531,555545-31 horizontal .5235552 s'331'-<7,'31:.-'7553L '?'3:;'31ss. C'7< one distance of mile——sug317531' 111153159155511.315131 31552there 555'-n' 131313 gesting that also "311 was a 131<53<:n315.3131"i7.4, substantial horizontal 155'."31I"5311'H<3. .331111331<.5557513'3155"H"5'-' component of move3557-1531. 55531-00-11'! initially prior 55131 ment. --'' formed ±i15saLl,3 1155 s"31';53<7to '1 have 7,5515739 The fault is thought 172 [5113111 "•<l Lsss. to or 3155' during 071<131', 51<12553<73131<0, Sul 5155. 57;31'< 35512-.5 4,55-31 3113<117553155311.1555 13n, '5 igneous intrusion but to have moved also subsequent to emplacement. 311152L..-2c't'513115531 II 55 1 1 I — <55 — '1 5 31 5555 31: 7171 3115512 135? the :131- district, 55.1ss'52, 355< the On '51.7the south side of '35: the ":531 granitic 31'5-51.31 ['3531 rocks 5031:5731 of "331 ±ai;.. 1_ 1J5231 ,57'Giants Range batholith have intrusive relations to the17 older 5—" volcanic — S , — — '- - l< 31<311, on (continued 5531 next <12.553 page) 571031<3, is 19 �t d&i-r iL: 2i.iicr rocks. Adjacent to the batholith, the older and sedimentary bedded rocks are regionally metamorphosed to the aiuiphibolite 2' t-cLlocally 1cLJ jt 2TC--E facies 12 both along and across strike. Staurolite and almandine are i2&J developed in pelitic rocks having appropriate composition, the mafic rocks are rnetariiorphosed to amphibolites. h (81LL c±itiz :1tJ% La:TAg i•cj:rii -çy,2;Iv)t$;: --- h-Th -t-5 YL •L t-,&: 1•- -•: are Internally, the rocks comprising the Vermilion district i±c::L locally, Tt:s12L;;the 1t strata deformed by both folding and faulting. xcept 5:ax- .i It dip steeply and generally plunge steeply, thus, the present earths ft2the t2- 7:-r2v: 2T.L24 to surface is essentially a section perpendicular plunge. 1E4J Faults of variable trend cut the rock sequence and break it into 2 t is -H &l Correlation from block to block a number of separate blocks. LJI 22c,difficult, and complicated distinguishing 1-e by the difficulty of 1Lt TTh2o minor and intermediate-scale folds from lithologic lenses. -ii&z- -!2& I S :.H1t; i•i 2't:i-.'2J2 2 i;iY2 o2c t J --L 1 I 2 l 1i 11 I :1t--c .itI22t. xi l- sulfides, c•2f-ç-22 2tt:!Y 1JC72 2'-.2J The and copper :_-i_-r widespread showings of disseminated iron 43221 the 7-223'ç and 2:2-243and uri quartz along fault zones, the occurrence of iron sulfides 22L3#1-23 -243r22 t2 resemblance 22 of the rock to t243,-2 that --In in areas known 22 to contain 43 sequence :I2-2c3M2.-2'2 43 4343 a 23172443137 34321©% 2f 143 r J1232. as 4L2II3232 2fl13iY warrant investigation of the region base metal sulfide deposits Formerly the district potential source of base metal sulfide ores. more 42S323L yielded j 212143i 2433223Rki&74312 hematite, Ji332C. 17ç having 17i 22 2-f was a significant of R'2 high—grade 21 17L13 -743222 source 77317fj17-27 cf :Lt23., than t?123: 2. $100 million worth of iron ores. .'i& tt1t22C 2 -- 2 hi:22t2-. 12 '' C l,I 2 , :i f2:. ç I 20 �I L.'_ i-LH VOLCANISM, SEDIMENTATION, OF THE i'i 1716-i _ICC /AND STRTIGPAPHY i•iINNESOTA. 21.UICcCc.12U.i..1 WESTERN VEPiJILION DISTRICT, NC'RTHEASTi Ci'LCL-13-: j1Q5162r}C; CI.,-,:CC1 .iIf,5ir. I -. R. J. Ojakangas, 521 11616225 Professor 5242tIjl;C2 Assistant of Geology Department 1-54of ili.nnesdta, Univcroity £2.2SU2C2fl -2 iU,F71,711i.L16fr Duluth. and -.717_C Minneso.ta Geological Survey I,1c..CiC 1.7:;r.IiCiC 7-#.,4..CICIC -1 and G. B. iIoi'cy, Geologist Lc.xC- ic-1L_;.-.9r..C.\ Minnesota Survey, Minneapolis .ic1LC1 LI flc{.14 Geological y :i- - ) - - c' a . a wide 1- in .L Louis 3U-.i1j[ 2.22 ic;. The Vermilion district County 1.:L. k2L 116 northern U'C162141C16 St. C42E2C2 --7 -------C.-C--—--------... 17- contains either one of two of 1) assigned to 'C rocks that in the past have been domigroups are the Ely Greenstone, composed 161 —1L —)2 (1) —c C large groups. These sediments, T nantly of pillowed mafic flows with minor diabase, tuffaceous 'CT .Jt Lake C Group, 1—_ T and lenses ofT iron—formation, and (2) the overlying Knife I composed of a heterogeneous mixture of clastic volcaniclastic sediU r 1C[I —— and the Saganaga Granite intrudes the Ely at the 'T Greenstone JI;_L ments. Because 2 '-— eastI end of the district, arid because the r Knife Lake Group contains peb-i these two groups bles derived from the granite, it has been assumed - that U:i were formed in separate Ltti22L1i ZL and j;2; distinct -22Li$2 geologic environments 2L2;iC;LLtL:22 separated '22Li:6iL22i2 in Li2LUfThisC- stratigraphic time by a- period of igneous intrusion and 2 L" erosion. ii2 concept led most early workers — to assign almost all occurrences of pu— lowed mafic flows to the Ely Greenstone without regard to their detailed L.2 — The areal distribution of these rocks was stratigraphic relationships. 1LrUpTr©,; then iC;i\C explained qby structural P ;rL1tL:2C isoclinal folding. 22;&C t%iiTh complexities L?222I2tLr1c2LL such as tight - -variety I 2 l :c— I LC — C I C L I — e C C 1 -li 1 71 11 i1 I h — r — j 1 6 I U C F -1 — I — I 1 1 .i Detailed end of in the '1L western CF1i LT 21; Ct7f12i field studies ;27ti2ii at the ;2 the district, vicinity of Tower .311 arid Soudan, indicates that IIno major unconformity exists 11 between the rocks previously assigned to and the Knife ; Ely Greenstone 1LL 2 the Rather, the lithologic associations and tectonic history in Lake Group. , _ _ i r rc this part of the Vermilion district appears to "volcanic : to- be analogous 1_ pile accumulations1t in Archean basins Goodwin '— I' cr of Canada as described by Ld (1967), in which thick sequences of mafic flows grade through increasing _1c (; T ) proportions of volcanic fragmental rocks to thick piles of felsic pyro— Jc) —cT r clastics intercalated with and overlain by clastic ::,i ir::c:!:c sediments. I L a i £ L Li — I L[ i; ;;: t: 1 1 I L i1 a )I JL ;r' ' "* ' J ' -:tc f j — — c- — I — tJ' Three principle r(•:1 t:IE:.L. lithologic ::2 assemblages are Tt: tentatively recognized in the Tower—Soudan area, but their age relationships to one- another are 'obscured by stratigraphic complexities, faulting and folding. ' — L FrT b_I i ; t:IIL ' \::' 1b I , 31r fLT :c The oldest rocks, composed primarily of pillowed mafic flows with 1: minor amounts of intrusive diabases and' diorite, tuffaceous sediments, D1 III _ L —1 ' of iron-formation that extend _tr ,* and lenses from Tower eastward through 3 TVflL1 •4J-J The second assemblage t $ Ely, are still assigned to the Ely Greenstone. t1/, —-"-nc ic consists jpredominantly ofi "typical" gray to black graywacke andL inter— The remaining 1 bedded slate with rare tuffaceous beds and mafic- flows. 2 -/ It is composed of t 2 assemblage is.. characterized by its- heterogeneity. L CJ',t ' r' i ' L _' _ I (5 I I - J I I 21 a (continued on t;(';Lc:: :o next page) 21 '\;r I �II .1 I I' several lensoid and gradational rock units including iCc C I lLl tuffaceous= (greenish gray) graywacke and greenish-gray interbedded slate, feldapathic quart= -C-I - lmIW IC zites, conglomerates, quartz-rich tuffs, quartz porphyries, pillowed LIL Hfl1 'C1111 H1 sericite schists, volcanic agglomerates flows, minor ilL Jr mafic to intermediate CCL75 2 black slates, and iron-formations and breccias, _ greenstones, 6iS diabasic -: — (including the Soudan Iron Formation which has traditionally been UL =\ -4H CTI3i c3 assigned LI Thus it contains rock to the Greenstone). U11 ?l upper part of the L IC U C3 Ely jr51 = - Y types that are both typical of and intermediate between the other two assem1Ll 1L711 %ç L1a23 1L H1= =1 Pjllowed mafic flows are not necessarily indicative of the early blages. 5flTh(! ¶LfL cH stages of this volcanic accumulation and, therefore, cannot be assigned jç: z;ci'. ¶©± 1' 74©! HCliTL> IIICTI rfl[ ILH! apriori to the Greenstone.! This stratigraphic i)L Ely 3 succession presents J!333L in establishing many as yet unresolved problems, especially iLl _ stratigraphic CI 1L_ formal stratigraphic names for rocks in the two younger lithologic h assemblages, and in redefining between the Ely L TC\II a regionally 1pAIr useful —C 1fl contact J Greenstone and the Knife Lake Group. C 5J CC I I C-j _c -l r1 J L S t"L'j L clcFlH — L tLHtL a I a S c 1c,' 3? _ L I ?' Ij I rr, ]St L 3)-Hii, ¶ I J I C 3i43 Ht 1Th C- S — ; 1 Lll:llTI j 3 CC!L5? y I1 'k- in lL II this area of low— Original sedimentary features are abundant LF rocks have all grade metamorphism. The sedimentary 'V1i the- essential characteristics of true volcaniclastic sediments in that =— L3 Lr?1 L the clastic constituents have their counterparts in associated volcanic rocks and LI r tYHt Lt5 1JQ appear to gray-= have- been derived from them iT cz by rapid, contemporaneous erosion. The wacke beds of the intermediate and upper litholo.c assemblages C' H c—Tht commonly display excellent graded bedding, some- have loadedt soles, and some show -c c,Ic,C D7C33 porphyry scour features. The conglomerates, generally composed of quartz LH clasts minor iron—formation clasts, commonly have "disrupted framei ç—& and L C :3_!TJ r?:j1 They are works" with the pebbles not being in contact with each other. 2T3!!, t 7;r[.••;4 k t-x interbedded )' I1__ with and commonly grade into gritty and sandy quartz-rich Th__ t tuffs which are difficult to distinguish from quartz that ,,4J porphyries ' [ ki were çL q The gradpenecontemporaneously extruded or emplaced at shallow depths. j rkJ?k E ing and the gradients JLt fl r' "disrupted frameworks" indicate that basin 'ic— were sufThe ficient for turbidity currents and submarine slumping to be active. L' _( .c1 _1' I:,Th IJrc2 --ç '' lack of large—scale cross-bedding and features, and C related 1cr- the preservadeep tion of fine laminations suggests deposition in at least moderately ff I - rc' c/!: :k )) 1% D' ji C ! — C I I H C / — C C s 5 U 0 3CI) ) - iJt I S L ' SI 3çfl L c 1 ' "çi1 ' J- i cTi1 -Tj -: ! Ei: ; rL 1 —rS (_I I r i The thickness of the pile is difficult of complex !!" Ti4c2;c!!:!;i to estimate because rji!c3L•tS! tt!134I, +0,OOO feet structure, but probably totals somewhere between 10,000 y' Tcc1c and -q:-ff and hence is probably of geosyncinal !!c!•Tdimensions. tiTt Pt:e 5! S S a S 'S I '!1 ' water. a : 1t i — j ii C 22 ?:, !C �(2Ifl2t ,7J.J44::4-2.Jri2Ics-. L/tKE r)%.I$i LAKE QUADRANGLES, KAWISHIWI AND tIflIct J7 4171 1-747411-11 tk5II /L 11F COMPLEX IN THE PERET LAKE GEOLOGY OF THE IL1C DULUTH J17.21 747iitE274J:A 127; COOK 5-'211%COUNTY, C4 1174', MINNESOTA AND 217 1:442-1.2.1 74 2.12ac/.2..::rH Davidson, Jr. Donald M. Li74'cwai Assistant Professor Department -?42.2t9.R41of IL Geology Univ3r3ity .11of'1L:nrJedY[ Iiaesot - Duluth, iinnnesota "da quadrangles c1t'dltS 1712 : ;$a4L•P.are 1/2 - minute "474 Perent JY2- 4412 Lake 4274 and144c:h441 Kawishiwi ±12120 Lake ? 7 7174 The '7412 4J"" 2. - 17' thirty miles north "'1112 located in Lake and Cook about 4 1 .a counties, Minnesota, r 2. a a i74t..7171 Field mapping and research was done during 1966 and -. ,. 441 of Little Marais. IC2.. i:a4aaa:- 1-2 Geological 74±: -41720412 41"a? 1967 and was "2.1 by the Minnesota Survey. 2-2- supported a'.': 74 — I 1 —, — 71,12271/'Complex '.41.2.1-2.4 1241 c,l the '17c± Duluth The .4111041 area isliIcc'-1222.4. situated 2/1 in the part of and 174- upper '<aT.i;"' 74/2.1 4I4fc.714 12cti .41441;4V74 mainly The bedrock 1122.1- 1 consists -2211102. of gabbroic and associated granophyre. 1122-7471411211 74"12;.:171i2— 2 and 4 troctolitic anorthosite, although troctolite, gabbro, anorthosite I 1I4-od/a-112-t4; 11±1412: Leucocratic rocks, in -7474-74 1/41174types 47/9-41have 172-0 also 74i:j '1:1-121 intermediate rock been noted. I,2':71c11742'i is ¶41 Also of -74 interest d2.2L12—the 1711.complex. L74J.d11 17412/ 41.41ca741127:2 addition to the granophyre, intrude .c 1774 c4I.4/1.i1.-/,'l medium—grained 74 IM I1I JI I the presence of a weakly mineralized (Cu—Ni), fine— to a 74± the r-f'olo'-o41274 11122.-I gabbroic anorthosite, 112a.-1711±±-' similar 1±a, to a , part of the mineralized rock in 274 41171:2 a,1.1.2.-U1Ii,71±±1212dc Gabbro- Lake quadrangle, South Kawishiwi River area. Structural analysis 1 a "Jil i'7441112—2-22'-C:t 171.741217740177. 2'2j4i'4hIis t 741:c 4414-2.1112 1-i74 with ''S'- recent and interpretation being coordinated geophysical investi14.11-9.1:2-0 ,4)1 I a a" Preliminary71—'L analysis of the fracture pattern 17'lPPlIal 2-a gations, as yet unfinished. suggests distinct trends, 11114112 which 0±171. may 412-4 have 727442-1241.212implications 42. on the tectonics 2.1 /-74'J'2-1 two 4 -7441471-4741 0:12-11-27 al '::7.-.i of the 74174 Lake .l4v-12:l Superior /2' Basin. If — i" "a 1 1 I a_ j 714 7 '''' — 2" 23 I — I �I OF ROCKS 1jICiiC:!rJCOTJTCHICHING A1 :777777 OF POSSIBLE 777:7 77-7 INVESTIGATION 77777777777(7707: AGE, AREA, ST. LOUIS COUNTY, iiINNESOTA CREEK WAIBERG IL{t7L5 7Ij S. Vi ino.than, )Cufl,t622t1 T:cIijn u7iJ:771CO ssocite arid Research ct212J i7or'2[ Assistant ICflIL'LtV Dopart.ert i9 of L) Goloy Minnesota, Minneapolis University of I I 2T — C — —% and Sims, Director ii -Li Is I; 2t7y Minnesota Geological Survey, Minneapolis 77 UI!I :1-1271; Paul K. 7; —. r (Ely) pillowed The discovery of a cataclastic gneiss -1-:L;2i 1yl1fK. below Keewatin metasedimenta during reconbasalts, amphibolites, and minor intercalated r [7 — -; -2 of 1967 led to L 1naissance mapping in the Walberg Creek area in the summer The area a detailed field investigation r followed by laboratory studies. 1along its conis on the northern fringe of the "1 Giants Range batholith, LIIL east of Idington. tact with the Ely—Knife Lake sequence of rocks, just 1 I —2 complex anti— The cataclastic gneiss occurs on the northwest limb t -I of a dine, three miles Th '- wide, that Lr trends east_northeasterly and plunging The core of the foldr is occupied by a foliated horn—= steeply eastward. ç 1 blende granodiorite of Algoman age, cut by an apliticC- leucogranodiorite. Inclusions of Both of these intrusive rocks are mylonitized at places. —) of the fold. amphibolite occur rarely in the granodiorite Ui ,l within the _r core 27:7i7T1 I I U CL — 1 — C II I I ' — j - LI 1 L rU1Cr j ¶51 fl C I: — 2 i7s1 I ]F 1 C- — I ft U I\iJr -y I — 3 I [ I HI Three possible explanations gneiss L I _UI were con— 1ii for the cataclastic sidered during the mapping: — f U S It1 22t12L21t represents 1J21, part of a succession that is older than the green— 2 stone, and thus is equivalent to the Coutchiching of A.C. Lawson. r5° It represents a sheared facies of the foliated I 1 I'JL hornblende grano— diorite that characterizes the core of the anticline, and modified in represents a segment of the Keewatin 1L volcanics, texture and composition by shearing with synchronous introduction of granitic ]1_'material. 1. 2. t — It — 3. Th r 1 L determination Results of © petrographic studies, modal D:T L1V.7:1. analyses, ' and _ — - E•. critical )_ of the jcompositions of plaoclases and;' hornblendes from the : 1 1 below. lithologic units, using the electron ••cL1}*; microprobe,: are summarized tL1. ' k a ri Lri' The cataclastic gneiss is !IP 'L i"I; composed of 52cT percent hornblende, LUi',. -? 12—26 calcic oligoclase, 3—12 percent K—feldspar, 1—5 percent percent 67—73 L z and - r a ) a' c& apatite, pyrite quartz, of epidote, .; . _ and &—-- total •' 1-5 percent k± -.1Ot-•Y.i sphene, .:; : ,.--;-;..J7 -'c-:? The The plagioclase ranges rJin composition from i8 — 27d opaques. L-1 hornblende contains 11.6—12.9 percent MgO, l5.i-—l7.1+ Spercent Fe-oxides, 1flrIF phenocrysts L The gneiss contains plagioclase and 11.7—12.2 CaO. - percent L ) r J L Most of the plagioclases are 'interpreted as a relict volcanic texture. t R 1 ' h n 5L and saussuritized; microscopic evidence indicates that the K—feldspars -— . J ---. '' I ' - - rj• — ' j' -- ' — 1[ L — - y — n ;; 3 - -c ' ) : S ' — quartz were •>JP introduced into 51!.?; the rock. :;Tr/, .; L I r( 4 t!LICi J L L :1 L hornblend-e, 53 percent andesine, 1—2 The '.7 amphibolite has S%1 39 tc percent ' percent sphene, percent K—feldspar, 1 percent quartz, and a tot1 of 6 r! :. 3JL- p - •: (continued on next page) 24 :'a �The plagioclaSe is unzoned and has a chlorite, apatite, and opaques. NJ (;FLiui 4'3F1F-F45IF i-&?:& 17.1f The hornblende contains 11 percent MgO, composition of An_Ank. hI The presence of euhedral zoned percent CaO. percent iiFe-oxides'and t2.1 — ¶&5— —— indicative of a volcanic parentage. relict plagioclase phenocrysts is & tVI < tI -- N---Li -FLi — i — — I — I c-_ F discontinuous layers geneThe jnterlayered ::F;I4 metased3inents 4z4N2iI i. ±LiLiC occur as FIYIiLiLi; by biotiteand are represented -rally three inches to one foot thick, — schist with minor amounts of horn— -F plagioclase (An2)_quartz—microclifle ILL — s—7 0b1ende_plagioClase.4fliCrOc11fle_qu'tz schist with subordinate itHi i*2I --'-.--- - ( - I —— — -<: I blende, — i2_ — 1 (An31)_epidotemicroClifl biotite, and striped hornblende_plagiOClase I— quartz rock. ::;.:cFy F L F - — percent Li The foliated hornblende granodiorite is composed of 15—18 F1 lr __— calcic albite, 8-12 perquartz, itii6 percent K-feldspar, 5k-59 percent sphene cent hornblende, and a total of about 1 percent biotite, chlorite, --1 has sodic oligoclase and apatite. The plagioclase is distinctly zoned, percent cores, and ranges from An to An1 • The hornblende contains io.8 I_i CaO. The rock is MgO, 17.9 percent Fe-odds, and +1.3 percent _iF L lE L allotrioand hornblendes with has myrmekitic intergrowths morphic-granular, and -1 Ni poikilitic quartz. 4[F-%i/N — L — F I — I L L — — I — — — II F — — I — — L — Ir l__ F — __C— L _4 — 1tt7t1i2 L Graphical analyses of these data lead to the following conclusions: LL I the amphibolite in closely resembles The cataclastic gneiss Ci) 2 _iI_and hence are textures Both rocks have composit.ofl. )!_ relict .4JL HAflf volcanic represent the Coutchiching therefore, does not meta—igneous. The gneiss, —t formation. of A.C. Lawson, which is a metasedimentary 7 foliated hornbleflde granodiorite The cataclastic gneiss and the(2) — -1 gneiss The plagioclase in the are two distinctly different rock types. ' C, I granodiorite, shearing of the -— by Qi1 (÷ L -iJ An2,,) is too calcic to be produced the composition An10; shearing of has plagioclase granodiorite for tile 1 _' :— zç D 'i:i c';F4- rr f) - I I N ç1:w L i — F — F ) Ii I lL)I ) ' t plagioclase. a more calcic L _ r- I I ' L i [ this rock would produce (JL L a more sodic and ' — not W amphibolite which has: a (3) On the other hand, shearingI of- the produce the more sodic plagio— calcic plagioclase (+ An1,6) could indeed : -'--lic < I-%_c clase observed T, in the cataclastic gneiss. O;ç7c.i4f: we conclude that From and laboratory evidence, *!<:. the tc• available field ] ?--._c >•rT !?• modified the Keewatin volcanics, -#- is the cataclastic gneiss of Lk' -- c_ C]•!! •:- ay segment Ir cy7kTC synchronous introduction _ bc 'in texture- andr composition shearing with ni ri Algoman pluton. This conclusion of granitic material by the invading 1R1 IL[ that the L U 1967) is tonsistent with observations elsewhere (Griffin, L1 jJ -modified various country rocks by metasoniatiC of 11 -r rL i1YC cr Giants Range ' I r - — 1 Uj — — — ( 1 r :i _I -<•:-!-• ",-., -c-: I ç ¼ I & (_ i-I IThi I4! rf batholith has c arnphibolite. processes, including the development of granodiorite from 25 �•44• 1-'i/A :E[/L:LY. :L7i 1CC .L*C/jt7Ri iCLACc!ALLr.3. THE BIWABIK IRON FORMATION, META}4OPPHISM OF AREA, MINNESOTA 71LES7 PJL4, DTThKA RIVER - .k1C1.; )LYC&1:L AAiiBill Bonriichen. iI-3Cf7 Cj1tC/ASurvey AC ;C.Zt14/ACCA Geological Geologist, CYC:CCL- -v. Minnesota , YCi: Mesabi /AA1JCLrange CZ'CA .t I&5l eastern 14/AC.ii\/ end of ;7 the RiverFCCS area is Altat the LtC Dunka iCAIC L'A2 The /A7 J..\44s-C /A-AAC:i. CC. -AC/ACICAC :C: :LC A71 where the Biwabik Iron Formation lies unconformably on older granitic CCItL: flC-C-A = The iron rocks and is IL-C overlain conformably by the Virginia Formation. tL.CC7AL 5cC,C?:C?.:/A facies formation was intruded and metamorphosed to the pyroxene hornfels CCILC C*/ACThtlcfl CLC1 &.C;CLCL rCtCC: C/A CC—C CC/A CC. The iron formation is tC C'C/AC-. C:--CCtiC by mafic rocks i1.C-CLCC of the overlying Duluth Complex. L7 /AAJ•f — 350 CirAC. --C—-CJ/A/AcCC il; beneath the Duluth C-i/AC Complex. •tk:ti SE., iCC-c/-ICC ai CCCI1JC and CC/AC dips 15 IC C/AC- thick 175—300 feet Ill —, members are JLV/-/( mined for ICtheir The Upper Cherty and portions of adjacent CrLrSCCCC :C3/Afl&?. Company. :C L/-.1ft1&1 tICC L-:7 =t1ti miles along C7:C CCCC/A,*-C± for content strike by Erie Mining /ACIti ftC three magnetite C.. j= &?T cC rJ ,b/A tt'iY — Sc /A11 C -CCL.CCCA- IC, '' CC,A4LtiA, C Ccomposed -1,/Ci -tC/ACC:i6.CffJLi7 C.,quartz, 7CC-C magnetite, dominantly of .;.iCIC&.fliACC is Ci cC-:C-C formation The iron :1.C:/-- ,C /A:- CC :ftLC ;7Le2 •tiCi-41 i- Ly local CC 1C/A-J by pyroxenes, fayalite, and amphiboles; these are accompanied = r II4l i quantities - ii: pyrrhotite, apatite, /A of garnets, plagioclase, biotite, = 4I1i'/A CCft: ic. :i.CCc C-&Ff; C.A • wollastonite, talc, ite, calcite, serpentine and1JCCW/ other minerals. ttCi I[ graph- L C LCCL CjC!:Cl ,- -LIft. L.A/A CCftACC and IC54 'C/CC during CLL: PC/A IC/AIC content C/A/A I did not The the Cmetamorphism J:-t change L.Vl magnetite where C much original grain size, especially CC c of - the magnetite retains its ta/Aeft C-liti most Quartz CC the C/C,C2;/A is 1C I-1CL4ti. by CCI'ferrohypersthene. Z/AC1CThKtiPCCCLC J/A,/ CC IjL I 17.LC enclosed it is poikilitically /A1/ACCC 82jC/A7 CCIACCS IF-i 5CC -c..ci.C size is -e,CC AlCC'IC abundant L.CCLC mineral and was /-t'-.cCI. entirely CCC'CC:J recrystallized; its grain ALftflC./A/AC. -c/Ati/A .CCc. log (average amer) = A (perCiLft u-Ct/AC-/A4: 7i.?by: 'C related to C:CCtACti'd ta abundance approximately C -' ratios of 1(11 /0 The LC 0 C IC - A and B are constants. cent quartz) + B, where ' C/A 11j1 111 /A1r =,C coeisting quartz and niagnetite from the iron formationL imply that 700 -= /A 1/A/A/A C - SL the C. Cwas the maximum metamorphic temperature Aattained beneath — 750 = C= iIrj1 Complex. C—4'iC Duluth =r-,-=4--. llL = st n ti=ft r - - 1 1 4- crL'/A I I — — A :7 — CI I CC-C'. ''I ft/PCCc4/A rr j1 r _ _=&-r -fta- CC1ft Orthopyroxene most abundant ferromagnesian silicate; ISmost H. the tftj/A,:.:c7 Ci i/ASCii. s is AC I —= Fe/(Mg + Fe) ratio of greater than t==cCr CL with an atomic 1/A ferrohypersthene is II 1+ Fe) ratio of orthopyroxene, occurring LI The maximum Fe/(Mg 50 percent. /percent. == r = ft 76.7 7 in rocks ¶1 that contain quartz- and fayalite, is approximately I/A/ftC-Cl, iLincftrocks CACSC, A j/ALd portion the CC-tiC ferrohypersthene, occurring that tiCijCCCS-C,A'. contain suffiCC:of C C-/A :14Cc-Cl cC - CCCC L/C/ACCCCCCCC) LC.CL/A-CC/C CC/A. cient C//ACt. iron, crystallized as pi pigeonite and inverted to ortho— CC/A.CCSLI? Alt-/A CCItt-CA/i initially C-CCt1/Aic-iCcg .C[rc., pyroxene cooling. IC/AC/cl/A during - 1 — C 4 ti I I -.- I I & .-;C .1-I-C :ç/A('.c cCCI':'t/L.Al.::.. geneIt--& iron A/A/C/c formation, Calcium pyroxene is abundant in parts /11k-A of the -1/At-C1•?Li :C'-t;-:/A ICC CAiC/AT.jA4CI1C ICI Fe/(Mg + c/A C ti-Ct., is hedenbergite Most with a rally where quartz predominates. CIA/AC C/dC/ALL//A :-/Ait/ACr'/AC: /AbtLCs/AICl/A 7/Ac/tAil//AC/AI-i/C/ALL] 'i abundant, isCt locally CC/a/A/CC50 7C and 70 C --: CCC Fayalite ratio between percent. IA.) CC/tIc/A Fe) c,'11ct-/A'///C. //A- CIL/!/-c,C It occurs with quartz f/A commonly Cp3sparse. C/CACti: generally where CC Ca pyroxene :Cft c/iCC/ill/C is fl ÷ Fe) ratio be-; /A or and has an average Fe/(Mg ofCftCrlC/'/A approximately 90.7 percent; ratio. /11/cU-C /Ac .:.k-C/A :, :ftcjjjTh/A CCC. locally, where quartz 1/cC is absent, fayalite has Al a Alt/C/A lowerJC/A"'71/AFe/(Mg + Fe) -t. /A5CCCt/ 1Ci-ca&Li-.; - CII .t 7Cft /A C — •/Ci'I/t -C/Al li/c/Act C/AC/AC formation; Cummingtonite is common throughout most %i1/ has Ca C/I//c iron CtCcC the C/CC 1.-CC) i-/A. CCC oCca !/cti/Al/Ai.iCt I/i C texturally is C/AL j:7 C to 80 - percent. Most cummingtonite 1 Fe) ratio of 50 Fe/(Mg + 14 /P fayalite. The Fe/(Mg + Fe) & late; it replaces ferrohpersthene mainly, t and cccti./— rind less. S- percent li-cl/A:- c/Cc//CC/A/c ratio of the /2/C tAlc/Ac/C minor /-CC/ACCCC; amount C-A' of -C/AC/I/AC early cummingtorite is ftGO Cc-/LA/CC t &/- ft CA — 1 tiCL'ti /Lc -C A/A/C/C page) (continued 41L/AitcjCcCA1-iI on -C-S iaext 26 4 srI. Ittic �3fl-:l .rtiH Small amounts :[1I tt p-t,t ttyt- 1-Ttttt.formation; fcii-ILLct' of hornblende are present throughout the iron cThtIL Lt 7t 7Ct £ILiv1 HIL ?IL tI-L.JJI2L metamorphism but most replaces hedenbergite. ILt-d .y- rt' H.1;-IL.'• some formed LhIL during prograde I 25 to 75 L + 7Fe) ratios The Fe/(Mg encountered in hornblende range from ILLL ti. A1203 c11l1 weight Jli}'± percent t '33t- of -Yll Mg. ç.. The Fe generally 1 -.:p1IL predominates kits III IL over c percent; 71 Cfl11. in hornblende ranges from 2.+ to 10.2 percent. H.j '-- — :• - ILILILI (ILi.abundant ILtUILttt iron carbonates tIL-Fr contained The It-IL iron formation cILt-ILIt originally ILYf Htlii and 1itL°H, to pyroxenes '1J 1;11 Jt,11ñ2 these lVtIIH IQ11H and hydrous iron phyllosilicates; were converted IL metamorphism was isochemifayalite during prograde metamorphism. The r _1_Cl Locally, fayalite t cal, except for loss of the original H20 and CO2. 1 IL and pyroxenes- constitute quartz—free layers; these imply that the origi_ '1 to = CI =çl_t directly nal siderite-rich and ankerite—rich layers were converted ]1 IL1 Thu I fayalite rather than progressing through an intermediate IL and pyroxenes amphibole step. H 1 r l1tt_flIL r Lt I1 IL —1IL: I — H. LtLIL[ I R -- — — 1\ — 1 — -tt ILt-tIL .rt c-.t-•tILzILlif tt. ta ;fLt.:i t1LLtLt t.ILcT Prior to metamorphism the iron formation contained several percent Most of this was expelled during of 1120 and C02, with CO2 predominating. l.tILthbyIL1120) 7iV-1'LLIL :IILChS metamorphism; however, (probably dominated IL-Vt IL. a small proportion 1ll IL 1 IL HO combined ThIL residual lILiftlIL L-.C PILLItIL remained along grain boundaries and fractures. This IL tYILt \LJtIL mineL11 other ta6? Ihyrous ILIL, with :the pyroxenes and fayalite to form amphiboles and ti-l1L, iTS filled ILH. ILLIL Numerous JIL1ILLIL hairline fractures, with tILL— CUlT'— Th•StH tL&IL Jp:-trttt rals as the rocks cooled. gj 14 mingtonite and oriented perpendicular to the layering, are the probable t'ltTfltiL%71.it&IL Similar :tt cummingtonite— escape route for a portion of the volatiles. ILtnt dH.J54tI in the overlying Virginia Formafilled veins are conspicuously developed lZ,l©lt iq-i1 -ILyi1 .-tLLIL 1;1TS1 -c thin veins, along with JIIIILL±1 locally abundant ILtIl. biotite-t 1.1. in TLIL the LI tt These tion. ILL-.ttt. It7H:I-VtCtIHx portion 1)7tILt that Itlttc ata substantial basal part of the m-:ILIL Duluth Complex, .c-sm r H- suggest r escaped from the iron formation sz1ot wiTS ILt Virginia of the volatiles which and the PIta overlying Duluth Cominto the LILT-IL TL(111n Formation during metamorphism migrated y fr IL ±.:HlL X 1 l-=l •t- .4 L ifILIL.rttt- :ti T-tc LcDIL faHi 5i L tf tL-JL- iy L IL Jtii I1IL — st IL c .r-ct 7tIçIL* t::')' lt: Ij4?L P14 Hnt IL . .-:1r:IL -H-L i4 L1 I plex. 27 — tVIL*ILd ILuL �IFI, I(3 THE JJ1.1I-71 NICKEL 1i1JIrLT1IIF111IF1PI73.NSE 8822u12C.i2 GREAT LAKES CF:F12 DI'ERENTIJkTION UEIICE OF INT2USION :7712 1iF77227731, IJIFiL F University of Jestern Ontario 1Ft1121'I IL FF7 119112 2117 N.I D. MacRae, Department of Geology, 'y7..5rLT 1 1111 I Geology, University of 'us., 1IL of E. J. Reeve, Department I I MilwaukeeI 212 cross—cutting 7177.7771772:7 77iIjriL jL 17-7171F#Th7177 body of Great LF1JF#F Lakes Nickel intrusion is. a 771 The ¶±2};' 1712*Ft Thi1 ILH-- Ft. 7 1•. William area, gabbro in the Keweeriawan Rove shale of the u) Ontario. The intrusion is at least 1 1/2 miles in length, 1500 177 east. 721 20 degrees toward the 71fl 221 plunges 71(77 feet in width and approximately 7:f72477171ri II direct evidence )7777' F 71 In north—south section it is funnel—shaped, but no fF12-IF j1g 7177rI mainly 911I Rock types consist of olivine LF F been found. of a feeder has 1112 il gabbro, troctolite and anorthositic gabbro. Within the lower olivine [3 has become 711 I —enrichment _I71I which gabbro is a broad horizon of Ni-Cu sulfide 177_ companies 77F1J with property in 21_77 711 the772 focus of attention for several mining -' % 7377- horizon sulfide I Chromian spinel is scattered throughout the 71 the U area. _'L_ F— 71 1U7 extensive and conformand particularly concentrated in a remarkably 1-112iC:I7fl 177 3©7ç71, (:y[71 .211777121[fI(12 .21177 7777 sulfide horizon. .77771 7127L77 177 layer of chromitite above the able thin II7 77. —2 41 I ) \7 . rF L J — 'i _77 1 'l, L-I RI £( I 1 77 I I — — C — - )ILI ,JI( _ 1 77 i:.c..::. traced 72714777121 by .7121 7771147177±2 means 2HL1 217117777771 Compositions major 111221717771-1 mineral 7177171177471 phases were 7777: the 7FF©7$77 27712777121 of 171 T localities, 77 _3 from various but I 71 of the electron microprobe for samples An average 77I77 1171 _71ts— intersection. 3c1; particularly core 2-c from one complete drill —t 1; distance upward I 211 toward less mafic composition L11 with increasing trend 77177 _(I 177 short section the _ from the base 77 I_f 71 is apparent, but within any one 777111 1717711111:731 mixed. 7171171172777711 is pattern 7775 considerably III 77 Cl 71 1 1 1 I 77 FF 1 f 1 I 12.713i717131411177.±L:.IfS textural 1. 77Ft7177FFl. relationships 1771177725,#71©717711 117171713172177 variations, 171±77L71 of 177371 basis .7772 chemical On the _ 1_.1I lLIj of 1 that at the time I 1 and mineral associations- it is concluded :c7'171111.c:1177: crystalline component. .77111511777,.±.l71,1L171 711.1, 71777777515 371, SIIFIIII-2151117L7. 711,177: injection magma 771177-71 had an unusually large 717171,7777 the 7777711 IL 71 28 �SULFIDE ASSEMBLAGES I.4LLHJ1ito S3±2MJXtS± OF t)FTHE '±±. GREAT J ±C11 LAKES NICKEL 110.111 JitP IL i u10; INTRUSION :1 SI'Ifl pri'I :±'Itpto1 Student, 'IJa1ibiJ'I'I±, H. Department of Geology, University ILt Mainwaring, ±±Zirtto'I Senior LHC311toLi. 1 Ontario pCi3estern t Ctoto• .•t.."P.1Ci1=1 of Ontario,3 London, P. '° PP II ppi.i intrusion it , The Great Lakes Nickel is located in the south— {P01 of district, Ontario. itP" toito7 CI,P ]iJflVC,1I IFQi' Lp0110t1CLto1, Thunder central part Pardee township, Bay ,V$ — 1 I HP ...oa I I 1.LI'I and toI'±1 I'IiI±toQIto of mafic sills The tot one 'I'I'IP of a great number iT±.ttoto,lc:ttotto is ±ILto intrusion '1 a Hto to This particular intrusion is interesting dikes in the area. iIL21ato horizon because of its differentiated nature and the sulfide III it. 11Pl:tito:IIpi,. iCflh-.Jfij located within 11 °i4 I C I Cto13I'I1P to ±ct 31T,1p'IC. ®Iti=3 T,i1P1HlL,3 oit in order Sulfidet4H.H,HiIQ'IIH1p1.3HH11 assemblages wereIPIP® examined optically iP. sulfides and r 'I CIil [I determine the nature and mutual relations of the H1'I then U.'I•to1studied ttii±&p7 with .:i.P3):.J3HPC were Certain of .toP these assemblages silicates. I:H'I,±t iTIppt±'I i)L the electron microprobe. the CC'IP. aid of IH ±1P i j -- 7i totoitttoI primary tipd and H1.01. found 'Ip ILt to ±FP: 'I)ttoPji. to ttto be St of The sulfides were two kinds: p of high The primary magmatic assemblage consists secondary. _1 system. — 1- ± a temperature sulfide phases belonging to the Cu—Ni—Fe—S I C ili a C 111 chalcopyrite, These include two toll-° phases of pyrrhotite, pentlandite, 11P IN lIla a11 assemblage consists of rnackinawite, toi and'IL cubanite. The secondary °flLJto marcasite, and nickeloan toIL torto'I±I.,toA5 pyrite. p 11P[,. ,1 — 1i1t ' 1' I — It I ±I. H r — C, 3[ _ appears to Mackinawite have exsolved from chalcopyrite and I r1'I AtT and Delabio, pentlandite at a- very low temperature (Chamberlain 1I Clark, !l ± 'I'I P9P'Ito.t 1965; .., ( P i 1 1966). Gt'IpI(PtolI'It1, it Itt .lI.a'Hp:io.Ci iiy$S:;1C of On ib1ti Ct the basis textural and mineralogical evidence, immiscible j1t ata appears the sulfides crystallized from an 'Ii çJc that rims are L Sulfide droplets surrounded by oxide sulfide liquid. HP I in miniature common. These may represent closed sulfide systems (Chamberlain, 1966). r1 I'IIlI-' toL' °'°' Cam to I al ± l C and PigLAi tPLL,HI I101ttt, to ± origin to,'I,tit to to explain Several ideas attempting tttoP3r±LiIto the tot lItopilot oooHt.fr, H:iiHIaH,. Hi JIIC.l.a Pr ment of sulfide Coa minerals area considered. a_ 1s the HI IC 29 develop- �LAI INTERDISCIPLINARYC±1tJC STUDYCl OFJ\A SECTED AREA OF 1.2--; PROGRESS REPORT SUPERIOR: f ]i4±flii10t of 4;1:Chemistry i11:04 J. W., Associate Professor, Department Brown, P. C., Professor, Department of Geography I D. W,, Associate Davidson, Professor, Department of Biology V , P. Associate I Dickas, A. B., Professor, Department of Geology C Lunking, W., Faculty Assistant, Department of Geology 1.) K., Associate Professor, Department of Chemistry Roubal, 5.21. 2. Horton, r - U — I -. 11 I .: 21 s-. she University, :5; :1 authors i::121 above 172; are )-: 2.on00-2 ±2 .1-17 All the the fs;'o faculty of Wisconsin State fso11i;:; -1515j 5. Superior, Wisconsin. : J1I 'N __ State University, An interdisciplinary group Superior, 5 from Wisconsin - ± 2 comprised of members from the departments of biology, chemistry, geo—s graphy and geology have completed a pilot baseline study of a selected C fe" f5. sooth --y. -2 Cl a-area of study is hhl±4% 7 03 hI IlL --oo1 The area the south shore of Lake Superior. 2:401 2along •rm two—mile stretchb of 16shoreline from the base of Wisconsin Point to a 1 Sections 35 andI 36 of — _i of '1 point east of the mouth Morrison Creek, in 0 (;: — L iJi L 1 - 1 — I , 1 9N and P13W, Ca — i 5I1 ILls — -; ±272022±2201 o- tur14 sediment sieving analysis, 405-4:, 1 -0 ;-H for study were: .or 'Looi;C: ±2 11': j:.o-l Parameters selected 6;_, I 1_ — II bidity, ;— pH, electrical conductivity, dissolved oxygen, total dissolved .7' -L46 -'-4;33 .10-22 cioe dis'-'-;*N''I' ets±2oC solids as well .44, as qualitative analyses for certain selected ions S *4 were obtained along a set of five solved in the lake water, Data traverses spaced one—half mile apart along and at right angles to the I_ were taken 2L 4 -.at water depth inil L shoreline. Samples along these traverses :.opIoi. ±2 15' 10±lr.5 tervals of ten (10) feet, from surface to bottom, to '2 a 222112222 maximum depth of .I5 21:322±24.01.i 41112 2 thirty (30) feet, resulting in .# a 22±2 set of ten samples of of water and four YLC-ooC:LL ijLo& per traverse. O'Lt'142' sediment samples : 1 11 ,-l 1 ., — o5s±,1osoto;:Leo;sC±L:.±5dfto.oc sJo-. 'H- 52 ;-;.1:4,55 1! *se±2 - 1±3 ..;t 1 r 1 1 1. '.-41'CL. '5i .5 ±15 .4 traverse At each station, lake bottom samples with a- Peterson 5-1211: 111711.. -f were caught 57'f (-:41-.,,,' ± ,..1-OOcl dredge. 4 One hundred (lao) grains were oven-dried and size :1 '2 of each II sample , .6 '. or _o 15 employing I 3:21 I I sorted aa 10—unit sieve nest.fl rI 1 The 1 median size ranged from a .16 Il -, , 4 r negative 2.70 0 (small pebbles) to a positive 3.05 0 (very fine sand) -;H I.:rJ15:4 1241 ; 213513 :2s.-NL:L,'o value. j22111C1 high Along L027,the f35typical 'Cf±1 traverse, medium 1-1-1.2. sand 0541 was found on the beach and in the littoral zone. Fine ,s52. II—' sand was recorded at the ten (10) #14 r;::-1J'7. foot and the twenty (20) fr-I. foot depths and very 'ine sand was dredged at :L21 ±2': 11 2 '' depth. r _, the2quarthe thirty I (30) foot Using Trask (1932 . ±2 deviation (coefficient of L4'I tile sorting) varied from 1.51 to 0.69 --.I'-' -C ' -I — I These results indicate well sorted clastics, he skewness (symmetry) I 2I 41a negative 2.21 to a positive I urtosis ranged from 1.09 while the fTYi2ItA 2101135.1 ranged from a negative (peakedness) O.+2 to ria negative 0.21 '±2-'' 0:51 CO •.. II' II1 1< . [ -. .. — r-:s: — :5',I4, 1 1 ) 1 I - - — Ic .•.f-','1'41I; I U — -. — I L, 'r22'vtf statistics, 1 1lj4 — [ ._ 41 .,, — - - - - , — -- " 6'" '- ..41.4 4t00Cld3.tIfH,,C .0:N.1±a standard ,.±r.:L.202 distribution 11 These statistics indicate of the Lake Superior 26'01i.kS',r0[C' 14 the I:141,. considering I: '3 clastics within the area studied, This ía not unusual 4 I lI lake within the The few S high energy conditions ofi the six-fathom mark. 007211 1,112 zones or:2-or -±2:1-LU a-:--: floor 235-IC' to anomolous which are recorded -.5-341.1113 1541 are attributed 1L4i1S lake 2-11 :' ±2 small s--:;.1s1-:: 0;__' 312:2111141pockets TL2'52 11 of clay 02222 which :70-02410 into surface are slowly being 404110'' -lb. transported f7ri 9.1 Sjf;: slumping ;I from 1-214 ±2Irao I; 2Jo[-41 deeper water. 423211-3'. ±2±-s 2±2032f: These clays, C1Y1122 derived gravity along the -. - . — LU 2 2, 41 13 f, &7I21 — — . - 13 . l 1 16 1.1:. :--±2241502; in ±2:-1,3'a •; P. D., Origin and Environment I of Sediments Petroleum, s-h LL7-:'--sjcoo of Source pp. 71-72, Gulf Publishing Company, 1932, o.:r±2o: (-log2) 1511 on All calculations 1223 phi a-fl aL1L2 22241 based ±211 scale Trask, 0041222 l - 2 (continued '16.on 5 next page) -L 30 �Cl 'ice as the region elecethe in t. the ?..It.were iec Ce.iilSor11 south shoreI.line, initially deposited iirctN thece Lake the in s:b.ejc ck the:ing the WleecThSo c eroeprih lacustrine sediments during the Wisconsin Superior. Lake of al bigr. etee :t:t et lake ICe 'i%I the ancestral glacial high water ma:k Duluth, .e , e' e±Tha :ethclece. Secchi 0Ap 4C Ilie a?tee? &e cet;eeee.n,ed ,ee of turbidity water was determined byCt; means )jrC0l eofI the The 'c a depth of 55 6 (1.67 Sightings on the disk cC ranged from Ii.;,., average eecen? cNrc valueeeoc was 1h&, ec;?QL'c,O okir1 of el NI cx? a depth meters) to 12 (3.66 meters). The intensity iT;rect• 2.95 meters. Sunlight was approximately of the same 2,95 ?Cth Lyre depths I. U'& the OJIICAICdata thJC?indicate U ri0!). ULAthat T,le I at liA?Ci1L all CJL ?Nt,tI?OL re CloltIi, These during determinations. e)c I:.IcCJC eyr,).i?C±'LCl action and shoreline L;;.:.c.?eco;x1. Creth wave where water transparency wasCete; determined, Ur '?yrfieC the suspension to increase d,° yyr ,tinrey eyre; cit tO; . C sediment currents an amount eeer•e: of ceei eee held xiyr : ;ymid-lake. eI& t;J :eeIe ci cc1 in turbidity ill above ;Iy; I otC as determined U'/C. that disk. t.t1lCithl ee e.thcd.:?cl:?L thIth &Cioi li oCIf ct Beckman IC? means cc ei,C of a tcurtce by tI eN rite water 4.ç, ycotnc; Thee pH of the samples ee. was obtained .CtOithl ?j .t.frryyr ;ftyrp cc Oft. S R-' Sargent Noc No pH meter with f'e Ox) 0 Model No. S—30072-15 combination electrode. The average 8.02. pH ranged from a low value of 7.84 to a high of ecril those thee taken rest as lie compared ectIftt with highr values, Lie e.optie" CT?.LL'e $?'t7.90. cNU. The value was C1h1 Cf of I increased leaching LcttoiOiC0io,' ?IctO at n:,JUoSilver Lte.. Bay, Minnesota,may be the due IC tocctCLtyTr•. et; shore of Lake e11te alkaline certhe earthsIcece from INc the eel redthee clays alongIce the south thkiteti,e ejettoc t CLatC Superior. ro: 0: it left approximately CL!i efrJc ,1. ctiir:thee. Freas type cells withcccell constantsccofct?eceLt0oi T;Ntie conductivity IceriC r OxCO r Model RC cont 0.3 reciprocal ohm were used in conjunction with a 17: ft operating at .cxi.'C. 1. cL-it'. LC,L JLc1ttrcmcettc jç -. lee. ductivity bridge from Industrial InstrumentsJIInc. Ic I: eft 'cc LI Specific conductivity". C17 s 1000 Hz, to determine the electrical 1711717 104.5, thIN with a oiL C of of :°:N'H5 OIl250 2± 15 i eoct:cftyrc conductance C) had an average value :e,ecct 1e:: (k ftc x10l0 at Homogeneity was within C" reasonable limits, S c,; CC + 1.2. standard deviation 17 thirty samples down to Cr2r1712.'CL-l? eeoC tiNiest ft that thel cc17ei cc dtcrn according to conductivity and indicated 01 oIL-LIft IC lecte-Lo': iS (30) feet depths were still within the active mixing zone. ccL A e: 1 — C C _ 1r C ;f.ftth IctI Ne aste stIll it Ce 'I xr Ieee cee an ee,rcyt from tee W;Ltthcct *.e. t. ranged cc cmeasured Dissolved oxygen, as teeth by the Jinkler method, Cc 171,''17T surface ft 'he Hoerlayer titci to 10.5 parts avarage of 10.8 JJILL'lC-e parts per fi'C million i eecc. at theceec [I 17 per million at the ten (10) and twenty (20) foot levels, and to io.6 .17115Cc 0117 CeLl Thus there was no J.ecel. Ieee level. tIe'.1 (30) the thirty .211 foot 17-million tilLilee at ft lee parts JtectHc per .eelLetNe,e. :17tiIL7 et ceeLu trotfrom tIc-ceo i' Cdepth to significant iniCe theticparts per million one tee variation eftel 1t0. from the mixing zone. 3ftir'1t'LJ-t the tIe tte:eee 17 octoHi another, 211 and apparently sampleseec-s were all taken triLl ç jt ec°c el :sl ç - xrC i •' 11te 100°C, e';tetoel cthfjer ceeCecioeec,o, 'Hot s..rzeectt17C. Nftt . averaged Total solids, determined by evaporation atcc parts per million. :2110cc0 71.5 71 .5 eN or a yrce1c-tCthe I.e use of fx'ec-o. involved Qualitative dissolved rN dticccJ.e ft ions -r oue,rtrer of cc determination Reading YeVreeland Iloretter.. Icc-se'S Fisher C1.; Duo—Spectranal Model 80 DirectS.ceeLeYf:tHixn.caJc NcC.eL ct and cc-2 a e17:17e jIlt so 17 ions 171 1 I 17 C I a detailed analysis was not performed, Spectroscope. While and iron. •treeNee e.eleoere'0 far 1cc-ct found etc are cc; sodium, calcium, 17$7:e000-a magnesium Sc-I tic: .Lcc potassium, 3. 5: Upper Part II Crcc-ec:irtI:JofcC iJrcecJtt'. 11. ci N., M., tel andftftcccncl Prokopovich, Stratigrajthy Cede. Swain, IF. h,COSt? :',' Soc. 0217 Bull. Geol. i1J17,.. Superior, eoJott SXttCc-: erce;'cceo cc' cicose Coo .rct'ce CI. Sediments of Silver Bay Area, Lake of 527 ('Tori/Co Amer., 68, (1957). 502 52.7 1. 4. :t Let; the the .5cereNe*i tc1 Hoicleed Public rOStLeCI Health Association, Standard:/uctl,eC's Methods for 'IyoI,;:l?trs c-rH..re American 1td' 4, American 1 Examination of Water and iaste Water, twelfth- edition, I: 1J! New 17cYork, N.Y. 10089, ft , i e Public Health Assoc., Inc., 1790 Broadway, F (1965) A (continued teece eN on cx; next reef page) 31 1 �is• samples showed only small L.' variations '? the water The quality of' sampled, it is from site to site, and thus, within the CSL area •i'Dr1 and 1ong—she cn.rrerts have produced concluded that wave action a fairly homogeneous region vithin the study area. I&LJ 's{, v; iA J:':ui L::LiL qp- These data, assumed to be normal considering the near pristine condition of the lake, could be employed on a quantitative evaluation of possible future pollution of western Lake Superior. ;- %:t 32 �J rrJY rrL iJ:cJ.n: J rJ-IIR; •J Jt4Jli-J HiJEONIAN STRATIGRAPHY -:.t --. THE FEDERAL - PROVINCIAL COMMITTEE ON ?R-CL'TJ,Y PIPJPCIL PRCGRSS ROIT crli-3rteXIU Mic hines, 2ccLccttl; -Ontario -r A. t. Robertson, Geologist, of cf Jc.t ncDeparb:;cat J. Toronto, Ontario prrtcict of limes, Jr-Jt-i Department Geologist, Ontario J-. Card, -J- JliCiEc-l-; K. D. -, Sudbury, Ontario (cL •Jtt. Jcc:;Lci Geological Survey of Canada, Ottawa, N. J. Jrc:c-e4 Frry, Geologist, Ontario S -- I-o1js icti --s ----o--'--=/d L ) This paper (a) reviews the history of geological work in the Ji ttLi. i(b) summarizes the A Lake — Sudbury area, c0 Marie — SaultCSte. cliJcl Huronian --ce c,t i:ic3J P-Jc;rtH —Pi--itctJ Jo terms of reference of iJ the Federal-Provincial Committee on -c.: ccJtt-trcc .di4$lirLJi?tcJLliJiliEi ci cJ• Stratigraphy, (c) summarizes the recommendations of the committee, lid coIjrr the anticipated I further work of the committee "_I to date, and (d) outlines ----O !:ooccH:ccc r-tLt1cT.cJ-o-c.±li°r :•;L specific problems requiring and further research. S. Elliot J — r -c — C - S.CL - Joo 1. IIiCI :iI:-2ttC The Huronian te : a cfl be J t.orclili.as: rcrt 'U-Es defined to 1I cli ji cT'tJLc.; nc-LcccliiC? i-t occurring Jcl.tcrJ.t "The assemblage of sedimentary and volcanic rocks in the vicinity of the North Shore of Lake Huron, Cobalt, Ittlilictoli on the 2cl*J-unconformity Ifli tcctlicli and cliii lying with li-ili1li marked cci clt.li-ct areas and ccl adjacent Llic CIfltli °r• lit*li diabase A-i tlrA-I by U f d1J li-ciA Archean and intruded the Nipissing ". — I - L T - 2. -. ccciolio-t c-liciclc Recommended ct Huronian IAIIclIliLli[tt Stratigraphic Nomenclature: Jic-cli-'rc: Nipissing i*tcicclic Diabase S5 - Intrusive Contact_ -- EILL15JItcLSuper ccttiir Ck:ctc Huronian Group :cc c/°li (Top not seen) 's-ç1- J1N-cl Cobalt Group tc U:River ocr :dli-Atcn Bar Formation -fl:c-t -ci seen) ccU' (Top not Ii; a5oi:i c c:Acc5 GordonI4AliIli Lake Formation tliCili.ctcilit tti>icL°! Formation Lorrain (Local Members) Gowganda Formation cccocc (Local Members) Unconformable to disconformable contact Jc'ccç-;tic o!CiJtli Quirke Lake Group lr-t-çcct&c-it Serpent Formation fi Ct 1OCiI Espanola Formation :g)Ili5. UrtLc$ Bruce Formation Local tiscontormable Contact cr- next t-eiA-page) tccc. (continued on 33 t)9-of -Jcc:oA (Local Members) �Rough Lake Group Miesissagi Formation Pecors Formation Ranisay Lake Formation Local Disconformable Contact Elliot Lake Group HcKiin Formation (Local. volcanic assemblages Matinenda Formation (Uranium deposits lie at base of Hatinenda to be individually named) Formation) Unconformity — Archean The Principal Reference S Groups and Formations listed I Reference Sections for the to define the Ruronjan in each (a) The "Original Huronian" (b) The Blind River - Elliot (c) The "Southern Huronian' e Mines area. 3. Of three areas: urn Mining area. anola — Sudbury belt. A composite section in the Elliot Lake area will contain reference sections for the individual foxeations and principle reference sections for the groups. It is recommended that this composite section becomes the principal reference section for the Ruronian Supergroup. These principal, reference sections and reference sections to be measured, described1 and marked daring the next two years. 4. 3k �S?tSICiE?4NiWAN flBskWdi ROCKS STRATIGRAPHIC R2LATIONS3HIPS OF SOK3 S'1tLTW2A2fl EXtOtBiPE OW MIcHIGAN AN]) !ISCQNSIN tOF !CttCGPN MW 7TSCONSZN Geologist Harold A. Hubbard., Gn.ufle* ttSsgtTs,D.t C. W U. S. Geological Survey, 7ashington, tLte34 A. t!t&fl. t 81 Gc1E14aL 5wva n- ?:ct'.jc 1ac v.can5t Zvnettat •nnren re-4fl1tatt*b. ,t Ls strtttgttp2 ant. ntw:trfl j.g pt's1c ovr ywkere bawi ssaijç'td .j. ; t.'b Ceeet*zt b't ittrti ': tatter sf Identification of an extensive pre—Portage Lake volcanic formaat extersivo eS tion requires re—evaluation of the stratigraphy and structure of larger area. ext tttA LKvça 3t3&3 northern Michigan 4I% and 7isconsin, and perhaps over an even acn'ezt M.oKi.tct Neweenawan volcanic rocks to C :-.C.3 Ca voi.s,asi.1 Previous workers have assigned all of the 1.ffsrSouth Range differ the traps trq€ a2 the lava sequence, of the the 8cttb foz.cc atwe a9v& tsepanc e but the the same distribution ôiisttibtttifl2 from the Portage lithologically, magnetically, and in areal aM Sn s.-cal 1Ltho1og±caty tr4pe of the tbzt traps separate the Lake Lava Series. TJnconformities appear to Eepcat4 Laze ryiatSne0 South Range South RaLt from fto& overlying ovei'.yin formations. wotvrM and pinches out east r Ser± ;ban' westward Thee Portage Lce Lava Series thins itt P rts.e. ias9 higher flows .'J.ozt Magnetic anomalies suggest that the bigtsr tTi nusfl1 Mellen, Yisconsin. of Hells: c1i; t,ha Jest of the pinchout, on the Wert t the W .cht't.. LjuyIthe ttwlower icw,rflows. tin;. extend Xc4he? fartherWesst west than tX'âfl6 undisturbed conglomeratic Lsturbc coitgto"in'atiO Bad River, steeply eeplT dipping but otherwise sandstone ¾LeCopper 0c5pr Harbor Conglomerate is disconforiable on partly of the e1DtD1t of eroded felsite of ths the tre traps of the orc-c.g ie1t.:' z,f -, oX ns* South 3;ntIt Range. RA.t. The Portage Lake Lava eM Black and Series thins by wcrs more than thsr. a third between the mouths of the B2s"k vaic by and the Bad River thrust Montreal Rivers, a distance of about 15 miles, is not now needed to explain the absence of the Portage Lake Lave Series :r tha! -ht mguer.nLir Lase& 1cs Ju;oc±biai spear t a4 sir.ab.et' tnt nt 4t.tflc ar.on...ise wgg; }eat te t.d SJrsr ;jt Lt&i ct rtarei o 'u Ssrbov ur4etr&Lt' ts dSatoThfl'bt :' 9n P*ratt )4iks a;t thtr tctie.' Urn snCw of *" ?srte 'tsI te 'at tbciist $,ttrat Mvcrs; t óJ.&nn : 't r gt! to ZL t.S tr4ed ,5att tht abcsi:e nf the Pc?tcLgt take ia'e Sefls on ': the Bad1t-fs? River. r. B.i o r Co., wJsconls)4 Misconsin), bae'- EX Ctc4Bayfield Sjsti t" SoiVs traps of the South Viest Watztof? Mellen, flellcnbnear 'at Davis Hill (T44fl, :ap Z •'t Bufl 'tintj iz;. .. sn ±e Xatftea. Y'nw a5Tisa ? ki)G the eesra toseparate ;c;r*L tie appears to f an angular unconformity 563) of uncertain Range and the Northern Flow Series of Aldrich (1923, p. 563) JWac Davis Hill with the thea,e.c%txar;a conglomerate at ILÜrteAcorrelated c o.zesi the at relative age. &ge.. Aldrich correlation c4d this thU casrci&i .n as Ccntome?ete tas*axaw Pstand itt ht "Great "of"ciKeweenaw Point he used "Groat Conglomerate The conglomerate Tr..t :wsfløu4r&t.O faulting. tza to thrust proof of ?e;etC-ttcc) repetition ofcfstrata etntt due ptooi Risga(Aldrich, tAl4xia. of IrA the E,cttb South Range ?apt' of at Davis Hill Iis conformable with ';1r5 the traps Lsttr tLt2 k3 the traps of the ¼be irsp cf the s'ibe ss31'e.t:atti3 of 1929, 125—126), resembles rsststaiee some conglomerates of 929 p. :fl...t2bt fragmental andesites, and fl,mSGt&. atthsts*, South.t Range, similar interbedded ft Bt,z 3az4c,contains c, )cba..n. szt)r tt,erbecds:e Aldrich ".10: (1923) (1523 Zc'ttFesrFlow TttsSeries Satt3soff La The Southern contains bST.SX' similar felsite. •wxLat.a :o1g.,n0 "The 334t4*t bate Davis Hill together have ray,.a B Lii and the conformable t,teCyt1t overlying conglomerate at ant tk et,iz*zsYji.* Range in Tn3(* IS of the traps :repa aX of Lba the South 5,ttth a magnetic :3tt'fl pattern similar tc to Uax that c the ztht:aar The conglomerate has little matrix material Z%SicMretb at et Davis Hill trsi Michigan. ma fragments .tn in the Copper tc f?v.t7cv.ve atai whereas pebbles are set in a matrix of smaller tO Hill appears Lww.?ate *v £zwta }ifl aAC6 to Thus, the conglomerate at Davis co t2a.ltt vS C'azig atre.e Harbor Conglomerate. Lake be part of the traps of the South Range. Poace3 The existence of the ah'a correlation, should be considered Owens fault, requiredt4' byA24rf Aldrich's Ovona fisu.i nvixed as not yet demonstrated. of cn the lower member of is untu 0rbe tfc. on The Jacobsville Sandstone is unconformable and at Sturgeon Falls, ogsbic c2 Lake Gogebic the South Range traps east of This unconformity has been used by by ae.r1 nearly' all writers to ssnxitcviLty 'ut5 tna tssct Thi Michigan. Nfu)iiz.c'Ze Portage Pctsg* the Isc'abe 4 cJ.cSandstone Zcsdor.neis %cyounger ycrnga'than can the demonstrate that the Jacobsville Lake tst'tc Lava Series. eriesD Mke ter.a WI: pitt the r"tsatin xhCfltafls pjt .: tryst t4Iir4.. t:ingn&tfltt at tea ntt.ec re set tt a ic'tt'iz pert ,f te r4 at ke 'a h is J:otc LLe Serdav3e !C2 li tci" tt* cer:&t the rTtde fltc r.'Set'fltt f t)t Lnte ..;)7:Lfltt'ti, swtS itt th se: :iabt' aia at Etrgrm fl.Us f.J ttit31' k' tS 3ot t Bangs raj,e aet tt39tflgtt tfliLt (continued on next page) if, *Jork done .Zr' the Geological Cc'1'gaa1 S'.zx ;ey' D.' tieitr4 in cooperation Survey Division cur*per's cieg with the PubUcation mthorized by by Coantios. ?ubtioati,n authartred of;k.: the!iJo}ssgaL Michigan Dtpt,. Dept. off Conservation. at the Director, U.'I. S.LGeological SurceyJZrccto:.. Ceo1ors Survey. ;ti 35 �_______ t b r't [I ':* 'c ): tti iJ .t .1j-:.1t rnJt: 1'2 5fl'c The unconformity at the top of the traps of the South Range •c-:i.Pc: On the northern Minnesota shore, may be regional in extent. tTc same ¶•iL? paleorna;netic pa..CL2.fle:7. y field1 direction South Range type rocks have the r L.. L rocks as the traps of the South Range, whereas the higher volcanic An unpaJ differ in lithology and paleoniagnetic field direction. C,:.:L River '7.sy near Pine City, conformity can (-j) be inferred along the St. Croix 1ct 4i:e - (1967), and Minnesota from the aeromagnetic maps of Si:ns and Ziietz some of the volcanic rocks at nearby Taylors Falls appear to be •:Ythe b- South Range (Hall, 1901). similar to the Ha traps of -ruc iti4 c: tC2 c f&d 3.]it; )-1± C-t L ¶-1: F'z1•TJ •gyt D ;k; 72-er;. ;-r s:-' C References: r -k VAiC:[ Aldrich, H.R., 1923, Magnetic Surveying on the Copper Bearing Rocks of 'wisconsin, Econ. Geol., v. 18, p. 562—574. CC.-LCtC &e -c .L?2( Iron Range of lisconsin, 1929,j The Geology of the Gogebic ç;? Yc 1isc. t-2Ji7 History Surv., Bull. 71. —c--Geol. 51C and Natural U*y $r-) 1f Butler, The CrV:: Copper Deposits Th:;: ? BS., Burbank, V.1.3., and others, 1929, JIL . 37-*7 i:-A of Michigan, U. Lr S. Geol. Survey Prof. Paper 144. :?J ic-. -a-ccfi; of Y Keweenawan &-!r;L DuBois, P.M., 1962, Paleomagnetism and Correlation 1L iocks, Geol. Survey of Canada, Bull. 71. L -rj s:i . j tc-' i dci5'z:L Soc. Hall, C. W., 1901, Keweenawan area of eastern Minnesota, Geol. ---I --.. ., Bull., v. 12, p. 313-342. Am., )._.,, - JLr.:---21 pre-Cainbrian .r9G Aeromagnetic and Inferred Sims, P. K. and Zietz, --,- xI., 1967, Paleogeologic Map of East Central Minnesota and part of IJisconsin, 4--. UcCI Y .is-ti ., e 13 JS. Geol. Survey, a GP—563. U. 53. (continued on next page) 36 :zt- �______ ___________ TABLE OJ' NOLNCLATU1 I oisr Nonsuch and younger formations C7t - CtCCConglomerate IC,4iji-C (including Great Copper Harbor Ei C Cong].oerate as used by Butler and Burbank) Sediments include abundant pebbles of C of the iC-J CL:flTCC volcanic rocks derived from traps South Range I vL(ttM ! $itk Portage Lake Lava Series CLicC 2LCC!Ccinclude ijL!CZ abundant Interbedcled h! II.sediments II pebbles 4II-= of C volcanic rocks derived from traps of the South Range z unconformity — ___ -- ——- fljiy kiiCt Y&L! Traps of the South flange It.&;tJ1iC -cis1 2 flows, basaltic andesite 1rC fragmental rock; felsites conglomerate 1Etat Davis including the conglomerate Hill Andesitic basalt flows :cwcY liember: !W?1I1, LCJtCC Lower &r- ICC Upper lIember: 1 1 1Zi I -C Quartz sandstone NOTE: Sc • Ct :CI çi C:c c7f Cc CLt*li\ Aldrichs Southern Flow Series is equivalent h 32 kL& ;FLn (1923) CaC CC in Michigan. to part of the traps of the South Range I equivalent to C the His Northern Flow Series may be I Portage Lake Lava Series. — 37 �Lfl Ct1CC16II l7Li[JPCC1CYI PLI-631I*J-C CFPOSTGLACIAL 1 CL &LLLCHE:iSEDIMENTS DISTRIBUTION PATTERNS OF IN 11P1C.L Li1t6jiLiHIL LAKE SUPERIOR C, tH:cicCiL i;LLC -, jcLLi:1rl)1; Frd, Assoc.iat, Professor William R. IC ;rc 1 I\ri R Department of D Geology and Mineralogy —F I1 University of Michigan Ann Arbor,-i Michigan — — C! C on some 100 cores LCEl L for study, a distinct Based now available I (c rL of the lake tC— deeper —C?- parts ltIi F1CJ pattern of sediment distribution in the from U I?. - no cores in shallow water, that is, have is C emerging. We )16 16 which to about 800 feet brown mud, O to 400—foot depths. From 400 C iLIiIHLdi W2 This brown 1eILl dIll -:± i;ilC4!ifrtLlLiIItittiJ 11.1. i-L& 1 is is gritty the uppermost sediment. g1HLi hy in some places, l,iL CC1 cent smaller CL than 1 mud averages 82 c-Cs cm. H in thickness and 44 per stratified and J not C weakly III it appears to be massive or micron; ClltlILi1Hj2Q JLlt 11cLCV 11ileILCI11I JgI11tI of hydrotroilite. contains moderate amounts C — 6 1L I& r' I I-— I ! C I CJC I ? clay tu a1lLJCI I:ICIL,Y 1L7H, brown 11•tL ILL.ltltIIIac 11H1 Underlying the mud is a very fine-grained gray -:Cy 1 r4l brown mud which, in water depths greater than 800 feet where the — __This gray clay is r-1-massive FC tC the topmost &CC!C4I C1413 sediment. is lacking, LC11 I(i becomes LLlJC4LL4 i-tLL13IHHFH thickness H 1HILI i/ CCF. CL; it LFi?.LiYLLICI1 averages 98 cm. in thickness and IiI!IHiLLI attainsI 11CCLFHJL a maximum known 111 C and 85 per cent of this clay is finer than 1 micron. cm; of 445 C 1 1 JI C11_ gray The the massive clay is marked by the abrupt C — lower — contact of 1 The varved clay appears to be -C1 laminations. iL_IYl I —1L 4nC of varve appearance I C 1C gray clay except for the presence of the identical to the overlying L.LLOCL L*HC-iuiaFL©1140 distinct laminations. I 4 jr 1 lI_LILL fl R I6 IT — [ C CL III L — stratigraphy C. CC-I CLHbLCY of Pollen and geochemical studies,I as well as theCCLtCI I4 I is —I no sedimentation CIt_! these sediments, suggest that very little or LII — nL uI the central 01)6 occurring at present in parts of Lake Superior deeper 1C 0 The massive gray clay is apparently a late—glacial LC L1 800 feet. than ;14lt6the CC OTI1O© deposit which lake bottom. OTt exposed •H0I;C01C on ;C;Co;:0iiiLlli 'WLiILCik is Co still I cL! 4 6 4 1 3ff 1 �icfftToMSEDIMENTS I ILIMSUcCIcFROM ItIS-& PALYNOLCGICALSIllS' STUDY kim OF 7;:S.lI*STLlAciTcAl,-1 POSTGLACIAL BOTTCII .ll.lI:ir,LdiIfj.l ?cIti Iln1ncimiLOCALITIES 'f-5jfTCYif Iji-li IcC IJfThRI&f: DEEP-WATER IN LAKE SuPERIOR 1:51 W. L"?' University Botany, The u-1H:cact ifof:3Ci71d1c Jri-Ilc-cc?I.. Department lcmc;cctjngrcc:c, Professor, S. c Benninghoff, Michigan, if !ScL-Cccda.c of .Acur Arbor Ar:::c-Ann and c-giuIttrt I:cc.ic.ca.c.Judith N. Franklin, Sa.c1:ciru Assistant Professor 5'ac'di: .i-L 17i Orchard Ridge Campus of Oakland Community College i'ji Farmington, -nfl .1, --- Michigan ' I'd\ LI_F --k---- I 1 Ucicca:-f cfl1deep—water flIt- V-iTh-i•i Ia-cf ..:cca Ii taken Palynological investigations cores from fuy11:a:±naLc:I Itacicu ScLcc;tcrc-r.L:c of ?J long Farrand revealed IS' CJc::flfi ict1c I;lIlI3cilmbt :CriIcifIl5 ca-cl 1962 aIl1:- by Zumberge and areas 1961 and cip ailci in Jr .f51:1: ar:-icc-ofiS Lake Lift: Superior 5ilI1ILLIct ca1:Jilt;_:iL cicc,au.f.cacavc, ii&1i iLl youngest sediment ac'ca-S 1::-' of microfossils, even in the a itiilYiLiIL'i surprising paucity n_ -C 1* rca -I '[ layers, and steep gradients in distributional anomalies (Benninghoff, for further c]7tillr inquiry Icati-ic ccii was ccvi suggested calif by: i;cftid/1 Need c'd IclI Taylor, and ficIll'd till ticDole, St 1968). Ic, the III fcct;fli;t a. —fica (b) (a) -c--ca the cc.is:nscjccj general itm'caca'-cccc absence idof — plankton general ttctiti.7scarcity Lutciricic remains, ci-Churin n Ucci aid pollen and spores, (c) the variation but local abundance of fossil ar-i ha uaccrS.ac:c-i i- cIl,u in Cc cores atciliL I ci non-arboreal arboreal to equivalent levels c?lc--ciim-cr: ccci pollen pcc.fltc ratios i-utaru Itatcircd.ca-rtc: ItcLIt= Itt widecccat Cd) the UncUt,different ;i,.ffSc:cau, c-ca, tn-S different .cS1Ia-.cct nUn fLcscmi.-icifrom locations water depths, and Scccc-ccc and ctcc-ag:cfHcof cc?degraded d'c'ccccIt—c1d:iccc1c_i 5cIlLnllli spread occurrence and fcc-:.u,S. local scarcity fossil bi-saccate r-r--ch ct-c crtrcarcu .1-ic;: :.i;;c.it. rather i-utica cic-c'tfimr fhcc-imJurllll ct ,c'- JISa:-?resemble rccct-rctu :;ca—Jclr dccc; that .:itc ctlii conifer jc-c1: pollen grains certain early Tertiary forms -: Itt-; rccuiiihiclL1 II means Opportunity -1:: explore problems by UTI;: iictUc cirtic forms. f.:cactu cac;iaccc. these cJep;::c*i; cUll to than Quaternary Y Umct imTh of greater sampling flexibility came in 1967 when the University of Michigan Glacial Geology and Polar Research Laboratory was given 92 _It nc —- 3 to 5 meters long, flbJt1i? I ru by the geothermal bottom sedimentr cores, each imi Terrestrial urn t &' the Carnegie — ci Washington research team of Institution of I_ chic MagnetismI Laboratory. The photographed, and logged r cores were split, Xi Cores were then c1t selected according toI their location, stratigraphically. C_ Utt-t ftc-it their cii analyzed c:ici:cati. for u-crII'civc to tic be water-depth, bottom physiographic vctcr-li-ic fLc or icc:57- Cci cac :;c'ca'- setting ac-c-LcirThe study was ca supported Ilklarge ItiiJi Ia.I part Sic' by .dacL.rca National Science microfossils. Uchi uSic-:' ucci c. r-tctdin c-iccNSF Sc-CSummer Ida in 51:c.unccr-d-j Shithtmcl-5-fl Foundation -c-icc Grant I-nIt Itt-Jill GA-l122 c-crc7 and aided by an Research Participact-c bitt 'cc tion Ucliuc Grant. ISc--crf;c- i1 1LcaII Il _li_ fcci.-.fl hI i1fluiq •I-:c'.i if 1T Cci rtimlLt ¶ — 1 n? Ii :' I'-I-ic 5 t6ii — — 1 — k-J=fl.kLI cc,ti I [ - Lt-' 5iXparti11;: tic-i waters Itidi itiC Microscopic —c-jc'tci planktonic and airborne -D cic-IttUict -rorganisms crcauccra. in the cles cat such as pollen and spores falling onto the lake surface would be c-fCc-ct cc-c2-t'Sc icacacciccit: c-tic bottom flhtfici-tI€I ca :iftnrt expected icc to ;ccIcctciccai contribute 1.niicP more or less ct-ca.itc-c evenly to accumulating sedii-ed ic-ic- I. spores tail hat and urrcc-tIc:f ic-f -i Near 54 -ca It-cacacci absence of and scarcity of pollen ments. cf-uplankton urIc lcc- forms fcc-cc:tt uctcc: Sr ICc aIim cci lc'5's alci Ic-icc-a ca-icc--ccSti at uc: in theue:u-me±asediments frIrIcluf implied redistribution before deposition on -1:5-n the bottom. L'c ccitt-cc ctc-itTh:tcct'cctccI To test 'Sc Cut fIrthe i.ed'ct.titt assumption C 11 of LIt-cc-cc'S lateral transport and gcc greater sedimentation cccc-arfccrcc ct-iI —-along JCf2 lines norrEIc nearer the shore, analyses cores lI 1 -- were made of selected J1ii-fltYnitic-c-r cca—the concentration graccfr:cJ:ca, cores 15cc cccl. to U: adjacent shores. mal For in tifr a cmctuc-nctcl series of c-it 8 cia--ui 1:ptSccJt-iw ac-cc dients and tac-tittill spores c's at 0.05 core depth show an Lcnct*iicfft( increase from cUcitci of It pollen 'cc-I 'Lii cab 5- IcESma i-c--ti-i nearshore areas (1,000 to 3,000 m from shore) to offshore (25,000 m) T5_I — — cincac-clhtciis hi cc-it c-IIcutc-.c5:fl 4' ffg 5 this -I'cLci relation locations. There are indications, however, -- '-i- that not Even where pollen cc-tI and cc-pcnnued spores c-cc-crc were J-:c.'d-relacccl cn:t©cS 'dc-c oriented the same areas. inc-ic in Fin Cuz-s cc--clJ..c-rcc tic;all cii cc-tScc, clcc:i,ca -hlcnh'a; ci.-ci-cim;ch "ccSic-tic-' •c:accscc1c. tively abundant, t1:cc the only plankton microfossils cl;nc: -itt 57? found were diatom fruscrckI-ccc -bc-c-Il-- I: cu-I cicic-f-- and c-?:fccccll:cI€lt5 iLl-it' '-ttaiict sponges, tules cccii CL-crc-c and simple rsictc1t iccludnlcr spicules (megascieres) ofcfresh—water cc--u'-Lc-cu lILt icc-bc-tact •YcICit StiLt Cc-c-c-cc ic ilIc-cdeur these Sicicuc: in concentrations twoi-ac:, to three orders c-c'it of magnitude less iSacc than tc;k1 the Itcuccuct thin pollen 'jc:crrc-cc those for 'c-cl ian. c-rccf and spores, -cjlIlk-Lt? 1_u-rm - -c — It_ caid— 1 I — - -?'Pt7L mc?, next 'c--im'd (continued page) — ..on - 3k'5 - -" - ,cim— -—- 39 — �jc 553 C? -3 !rfl(fll1 ! •3 3•d, 5 CL:L.0Iand 335), l1oç14:int;, given .55333.stratigraphic 3 577. tI; C;]bA The j1Th52 relative abundance of pollen spores ;114e taken within 3 C c j groups tIld be correlated levels could even within of cores ac 'c not 1a) could the abundance be correlated with a 13 3 a few miles of each other, nor C Some promise is indicated 4c -CC'— small d1dI)3 135 given matrix lithology or size grade. S C1d for correlation of pollen and spore abundance with bottom topography, i'_J C j 3 for CIv 4h needed adequate however, but considerably more sampling will be 3n_ a _ (I CtC l3 —13 1 — I II IN - o l1Ia3 jl 5)1JJ. t --3c1 % I l II L c — lCI V — I 1 L testing. ACC333l7 groups 5113 of 5I 3C3iC.;ii. •; •)j343IL to SC 3e5;c;crsL5 Shift in3 the non-arboreal arboreal m;f)!i pollen within ;L;• ratio 115) .: CLL:I5 —c11 i_L between nearby d l33 a1 — ]L of cores may have significance for differentiating çT 5 35 present) and distant sources (only long3 INs sources of pollen (more NAP 3 a a and oak), although differential 31 LCJsc a0 range AP present, such as pine, spruce, a 5ttoç3; cci;t:C3i311 placering 35 ofFC3I1L33C pollen and 3CL spores tby bottom currents remains a possible 131I i3 L li iI d13 cause. I III 33 conifer ) 33i1451SCfossil 5c3C:c bi-saccate All the flSL 'Js cores examined have degraded Il - been exhumed These must have -a pollen resembling early : Tertiary forms. Li 0 There are 3 —C 3 from geologically older deposits and then re-deposited. conifer pollen small variations in the absolute densities of the ancient Ca ancient conifer 3 populations, but much greater variation in the ratio of c _I referable to Quaternary age. SIt is possipollen to pollen definitely — N ;3 - of transport and sedimentation —3 3 ble are indications S C that these variations ii —topographic depressions. 11 C along 53 depositional in certain bottom 3a#L3 51 gradients L ancient grains But the greatest Jmystery is the source or sources of the 1361glacial LtI4 3333 311133-IC 33113175613111 by 43 Ctt:1 613 3753 reworked that were evidently action. C3N:' (3 l 1 13I 3 I Ll — l J I I I I ç1I 31_C1 Ic I I1 1 33 -t cr773-Is to contributed little 75s .73133313 133333-3 sediments 3 Microfossil has 333373173361 of bottom 3c*CL61cCa IL analysis Superior and Ca CN. its biotic 1301 LL in Lake 35 organisms the3 post-glacial history of C 513 Suspended the lake. 113 i5 province, but more to knowledge of sedimentation in 131 3 75 ]j1 levels4 of the water 3533 in offshore areas 5are evidently particles in dli the upper 3— 33135 flh;,a.c:n 53353.3:31 Pollen and ,53355-35c3 1337533 dIv)3S1i.7) 3-n inshore areas 3111±51 transported laterally with shallow water. CRC552Ct33 133 133537)37 to 1333±437 flocculant £IL:s,3353:33tJ. material 17 :I3335n.3JL 13o3t byINbottom .13 1133 spores are probably moved also in bottom I3&1333 ClOt 3;137-1333 153 33Cc(I4C1 LII_C The wide variation from place 11 currents and gravity flows of sediments. 131 in proportions 375 1I2LI13C3to place in pollen and spore accumulation densities and 33uL)so1cd3s)I.tctEv 345543330) particulates indicates 3t35c17 5e37 355353753; tIN;t .31L3333) of -51.751-3533377 different categories within that class of 73333111 3 of the nature of j75ti strongly process for particles 1 that the- sedimentation E_t descent to the bottom. 30313333 533 71313one CCCof IN 35375L27 3-333130175 3..C6113- 33 7333 these5 13) microfossils is not simple vertical R — 1 J 11 I — — — I 1 T . ic c flt 3- sC I-1_ - • 3-d-_c Il .73137 +0• Ca_ I33 ç5c v — �Th - NEW LIGHT ON THROUGH :':: ANfl'IIKIE AI.WL TyLr-STRUCTURES rCtC;'?j1¼ LS5rI[iCjt. DAR1'IELD ILLUN INATION W, 1 , S9!t5 W. Moorhouse, Professor Department CC 7Cfl; of Geology University of Toronto Ontario, rSC111C Canada 1 1 ¼ci:n Algal filaments and rnYt;; 1'71z other 'j5E5 Animikie :..7rsc structures are preserved in some cherts as lines of inclusions of minerals such as hematite, of organic U\1 ! r Such inclusions may be quite unimpressive matter II 5 ra-1 r- in ordi— ;L, _— or of fluids. 5 3 JL character, and nary illumination, and yet acquire a three-dimensional _11, <rv — '[i irt; darkfield illumination. greater continuity, in -even an appearance of ¼ 'HL :'-c Grain boundaries and which ¼ n" cracks, C ?LL(i in darkfield may simulate filaments, reveal their true nature in phase-contrast, available with the same gr1 equipment as ¼ darkfield. l &- ' L ¼JCu ' -cr , 4 LL -C,', — ryr '¼ — - It is possible i) that 55[1 replacement :ryyrci©y: (diagenetic) cherts can be distinguished from cherts deposited in cavities by the character of their — 'r darkfield nor phase contrast appears to be of much inclusions. Neither yr,1 value in interpreting microetructures in carbonate or silicate rocks, 1 because the strong contrasts in index of refraction emphasize the exist¼ ing grain boundaries and texture, at the subtle —, expense of the more F traces of organic remains. _ç mr U ir ) — LfJJ j �73 POSSIBLE GL'LCIAL 277133731 .3'Ji< ?7:3 ORIGIN ±727. FOR ThREE PRECrJ1BRLN L. •: ' -Ill: OF NORTH ..I4.J_ SHORE I ,i i_1)t3T L J<.. 313 CONGI (HtJRONIAN) <rrp-<7<<clr <f. m)77:iP.c — .wIf LUcE M .rt:n.anaip- Ct?L P Assistant The G. N. 37 Western <fl Young, <cai<*& Professor, )t2Qr:3(1-13 IT? University :i31237$3 of 13113.31:73 Ontario, P.l1C<<). T311311< r113 if'c Departhent of 317 Geology, London, Ontario The F. !, 13 Chandler, 11133. It Graduate :1:1 _Cfi Student, )5C)3$Thi1Ir 3t3 University 3t[ f]i33f :-;' of ) II Western <3J32I3) Ontario, C75I7f73 ' Lc<r Department of 31 Geology, 31 )n1V .11731:, London, Ontario f Cli For origin has 3TT7Z more 2:-ty3 than 1 3<3): been suggested 31qjC. fifty years 3131321 a glacial 1C333C 71 Recent work for the Gowganda Formation of Ontario. 77) III confirmed <333w <3L' has 3<v<'H 1431i )1313<313f31: <P7 the of early workers. The Gowganda Formation includes a wide r-=_ 3<3 opinion -_ ,. p I variety of rock types including polymictic paraconglomerates, ortho— 11 conglomerates, sandstones, siltstones and massive and laminated C-1,, The laninated argillites commonly contain large dropped argillites. 1L of about thickness Gowganda Formation clasts. The f3Yt;r3 143pL3t has a3232 a '3 maximum .rs3 12333 :r7©i. i1/333[' ;4t?3H1% 3,000 ft. (in the southern part of the outcrop belt) and the present C areal extent is of the order of 8,000 square miles, 731 31.7t3t J4<3 <3t ;173fl1)3 32. P,l f ry3 I 1P — ' r - 7 CL , -J -. fl : - C - L Regional paleocurrent (Lindsey, 'C <Ju <P!L)Pu}Q 1967, Young, PJ(Tf IfILI investigations Rfr3. •rc3f: -cTI3LP 1968) indicate Formation was N fri TC 3 that P14i the Gowganda f__I -cI_p derived from a northerly of 30 new chemical analyses of argillites and matrix source. Results 1? materials 3711 from Inc-1LT the Gowganda conglomerates <i13: 1331C7 indicate 1313 :3a3 differences 3&c3I.cIP3-qc 3ct3T3ic3 chemical hf-jJ between the western parts of the Gowganda outcrop cr;-t eastern and Li: Jfr 31ta C-i13.II3. c: i33-Jjf> belt. These differences are consistent with differences in the hinterland çt I33 32L33 ;clct as )-P-:r33)TT37V P7 :Y 'ct C-Pj[)--f<fE C of indicated P3 similar P. i2'k373t3 by YI3T ;3J3<t studies. C31';f131< Glacial 13L3f3 deposits ucPr. aa3-;ct age <h; paleocurrent p: described by Pettijohn (1943) were and Puffett (1967) from areas in r 3 —CT Michigan, 1 - r-' C'3i3 :;,&c i -- ii .)1•- c — — Polymictic conglomerates also occur lower <Ir) çt E).L333f331t1 •31s33_ in '<1< the 3) Huronian 313 succession ThtI'31-s T.C_.: The most extensive of of Z?: Ontario. tçP333; )fCCa.1*.!H .c'i&f<4.c of these form1 part 32. )I3 :- the Bruce ptp.I3 and The conglomerates of the BruceP and Vfhiskey Formations (Roscoe, 1957). 1 33< Whiskey Formations contain successively larger amounts of sand—sizep3 material. The Bruce conglomerate has a present minimum extent of about 1,700 sq. miles and F3 a maximum thickness of the order of 600 ft. The Whiskey area of the 1,000 a.331 conglomerate a ;:.<c ic: .33:2 of t: 1IIcPT3fP is known .3ftlIrY to cover an 3 6tc order 133) sq. miles and has a maximum ICtt tIT thickness Ct-3ttT3.CT?Tt. of :1 about 600 ) c — < I, : '$ 2 H J I iç3r 3if i:Thft ft. Although many geologists the of glacial ;;cCi:3P5 mentioned ct'I9'.? ii<. possibility .t,.l . these L — origin for conglomerates they were formerly: interpreted as mudflows 1L lpC — Dropped clasts have been found in bedded related to tectonic uplift. • 3 6;.? If; <2??'' t13, 7j;3 tIl. j)<!:rf(<:iC sediments above both conglomerates. Together with this new evidence the following support :cr <i')iIS<: points 4©?3a a glacial origin for these conglomerates: j'I ttX ' ?- — ;3a :1 rr':it 1' II 1. The widespread occurrence nature X32t'13 and homogeneous PC' %33:)t33 of the conglomerates. -'c33)L31t© 2. C?. The polymictic nature of the conglomerates, <13! çCfp:P.. I with (*s'P,7;C?i3 many plutonic rock fragments. 3. 7314 (t: ç Ii Chemical immaturity of the conglomerate matrix materials. (continued on 0c next page) )*i?:. �S r4ttencse f isig,ifloit The &:alCi' 'ib.absence of zt evidence of significant topographic relief tectonicsuM activity V t4jor5fl9 n.kcf øt' or teft.or,.Q in the source area. J?i 4. Lt the sot'.c orq , The ?vuii conglomerates ia.c vary S. in tbt:nvsee thickness from Cbz c,cg)oaomttcse place to place, but •j4.*tQ i) ')j4Cd. bt there is au gradual thickening from source. td3ktsirg LWaway i?,Tá) DDIL?Stc 5. ...., opt:no ' ti.. Urn oacjt4tec t pK.i*r stcAtttaL orierba' 6. Kcçtr4,c Elongate & megaclasts of all three conglomerates exhibit a r.ti%.rai regional preferred azimuthal orienta- tion. I st z ttttos wcter Most of ttth the etw,asei associatedsedtaeat. sediments*&n wereae,oafts3 deposited i4cut 7. in shallow water. tJst 'c Glacial interpretation *5' of these conglomerates Thc.itl icflrpcta±iw. tcwltYa..3pisLainit.keeping ?cseptizwith dtk .ee!?tt *ib5titvtiC investigations, wattt,.3rs. both recent paleomagnetic Animikie Lake ;S ?1is bc. ciin 4,.the he 2h?gi7 iktsoff the Superior region ou c@(Symons, Thspecis 1966)a1and GowgandaYoncuton Formation or of Ontario u.ire .tç'&i '.viinlisttheecwe$ie Sto:t £97j (Symons, 1967) wEt which indicate ba€: high iatat,.ito latitudes tinthese these !'9stC13 regions 1J in Early c' a.r4Lttc Proterozoic fltS?CViO times, t4s.'i References: tn.rçrt t s Presssbsz La 'iL 11. Lindsey, D.A., Za5.flCaP7 DA', ., 1966. Sediment transport in a Precambrian ice age: i96G Seni#tt .. 154, t4i24. The Huroniari Gowganda Fcthati*c0 Formation. £QiSZY3Cc titi Science, v. p. 1442—3. LSL. p. 2. 2. Pettijohn, I'ou, F.J., Petttü.-, çsi* .., Puffett, 3, Patfl' 3. ., Gout- " Iç In.tct"rt em tty s/ta; {g earari tsst !cSnr nirt, ?azvt14 At.si Xr.tt W.P., 1967. .z.9& Structure and stratigraphy,s including Precambrian tillite in eastern Dead River Basin, i'Iarquette County, Mt'cUsan Michigan '4.$.ct..' (abst.) 13th Annual Inst. on Lake Superior C:n.t;9 It!at i4apaior Geology, p. 33. tsoit pa % 4. , 1943. Basal HuronianC*bgJ.?7tflt+U conglomerates 3! of %crn'nzte, Menominee £)vrzDt?t 190.. Ec4 and districts, CC! Calumet QtAt&t1t JStfl.OlflqMichigan. Kttjpzt1. J. Geol. v. 51, p. 387. 3fl., Roscoe, itcw** BY...? S.M., 15'.T. 1957. Geology uranium deposits,QCQu.c Quirke i,tk.t Lake w = acal©y ziand ..2-3.nLs topAcLt';,. , Elliot rss0 Paper 56-7. Tiflvt !.stku 6.. Lake, Blind River, 3s..wi.o.. Ontario. Geol. Ce*i- Surv. Can. With i2v&Symons, D.T.A., 1966. A paleomagnetic study z' onth5 theGtLfU.rtc5 Gunflint, 5. ;tuinijrnatA'i flidr 5. Spas 196C0 A i@bj1and satCuyuna tiir iron ranges Mesabi, S.,certur region. etns*i in .:t the :us Lake t'&s Superior flc.11. Econ. ttbta Geol. v. t,ra 61, p.a 1336—1361. j6 t, nt c.., a of . 1967. Paleomagnetism rocks nokL near t"tv Yn 'cY oc1a3t '5 of Precambrian Ontario. Can. Journ, Xenkt n&.—n69. Earth Sciences, v. 4, SS.DOb3 'Va ., p. 1161-1169. 6. tt. Symons, D.T.A., E;.ttua9 Di'. 7. Young, ioz, 3CM.,. G.M., L$S 1968. Btditer:r-r Sedimentary ct structures in Huronian of it, En: r&.ea rocks : :sts *1 r'.';t Ontario. Palaeogeography, Palaeoecology, Cai 7siaeat;ç ttp? Y: Palaeoclimatology, Pc:i aec iinflJny, 2h'ir. 3t Cobalt, Ctt*ltç .'. 4, J., v. a tr p. ],2:3 125—153. �'ft itti jftifp/'f .f'/tIL NORTHWEST Lcit. if i-f/P• CL//I FEATURES 12-f 1f-1f.f' Tfi'fiLf'ii WISCONSIN* tic-fitti OF THE BLOOMER MORAINE ICE—STAGNATION - IIo.::-i2'f..Li: Robert F. J.it-Y'$icCEi.Black, :it1a-k.., Professor ft-c-cct.C,Ic-cciof ii Geology Department University of Wisconsin Madison, Wis. -Yc1cccccc t-/c; S I _II i/Vt /i2,c ic--c -/ of ./-///V? part J-C/t The outer -li/c/-CC/IC Lobe c/I' Late—Woodfordian (Cary) -i-i the i-f/I Chippewa ---' / of IIIL characteristic a striking and age stagnated in situ, leaving behind a i_ s—a a'-' c- ice—stagnation c H glacial or dead—ice features assemblage of forms. The -If/I -I-i buried The /.//ii '-ci, ice c-/cc-li/il-a It//tic. of melting i/i/c- of partly are the t..Ii1 result Icc-i- blocks. C/.ICL:/,1 out lilt northeast l_./-'c-l/" is characterized Iric.Jl-tfc/-Cc 1/ of Bloomer J/Ici-Ia/' ic/tI-fl-i lakes moraine ic/i /. kettle 'IJcIJC'c.iC/I' c-cnc-'ci by b-I: small I(commonly ccltcc2C-l/iHIt.r4 iiL..IlessJI'//i-c-/ than 1/4 mile C.across, although a f/Ia few Thixc-Jr larger /'tiC ones are i'c'/C 5LtIL/I121/. 21 i--J1 j< ¶/I I - -ici i '/' cc- -t:c i-it-hf. i-f"i-' kettles, present),i- of kettle swamps, of /iic-ii of ci intervening 'Ic- :;I-rc,cc- and c/I dry /Vic CT till and -irregular 21,1 c CC1 small knobs of red, sandy, stony C' 'I kame deposits. 21 dark / i--ScIlarge mounds c-Il p j /ci-C ii jc-=c —iiS grew \i-cNumerous genetically-related, Ti-,, during deglaciation c f/I I Csurface These mounds / c-ti debris plunged through as water and the& ice. & I— Lrii.cfc i/ic-i -C/IL Cr C El/it include l//.'I/cL.cCIL conical /lcC-\-Iiic/i'. moulin )cc:ici--c kames, straight sinuous eskers and icticI/Icilicicrevasse iiruuit-c'li.'/ to cci I &ri' large C sizes, and like deposits from fills of different "butte ' — 1_K— i//c feet f-ic/-i 2/cc to ;c'fst-iI;r -iiL-c-L lakes.. 12//a Generally, cc-c-Hi 20 'It- 60 formerly f/cice—walled relief if is only Licicc-i-c-fJi-ti ii-'C'iI C/i-— C a_ in the knob Cc and c-in swale topography, but some of the kanes and ice— /i&/_ C 1//cI I -u/I Iclargest mounds Cc are one walled lake deposits exceed 200 feet. The c-1-a —_ _ mileLi in diameter. Several &-I/V( P ¶3/' are aligned ic--i- c- northeasterly and northwesterly, ic-cc movement. /ciç'-///I//c/V c-%lLI.c--:-c-r1t 3/C.-i/'-/ACi/i-Cc-/i to ti/i-' former Ic-i-C/iCc' ice parallel and perpendicular /1/c the c-c c - — c c /' ic , 1. — & -i 1 V y/ L U t- — 1_i- c 1 — 'i-:: present fc-t-C/9/c'I geometry cc--tIii'-D-; of i -I/C-/Icc-. -./tlake ll/tlti/I/)/IL/i/ cci-L -// c-i--C-ill-/ic The -ii c/ti the ice—walled deposits and exposures -. i-a -r c-1L show them to have been the material large openings with ponded r tic-h /_ water iCti '/i/l/ .Ccc/clIiIc, /2 f-iccDebris was supplied c-tic/ic-"I-IiCtitcil/C f-chic/ic much of the time the deposits were being licci i//c' laid /V/c,i. down. it-/Ifli Ci_'I/c.,Il C -, at various places around the periphery of the openings, building 1,C i/-C '— C deltas and slump a/i1 '. ._Lj_ ridges. Much ofic/I-' the material is bedded; most is /t-ti.l: ,a_-rCciL_c/I1_ i,Y/cIl-r///f./'/I'/l -C-ft//ic--' '-Vi-] .iC/3cIcfc.'LI/1c.t't-cc --/;LcI/fI-/cii t/c/cCiiI/ poorly—sorted, fine—grained clastics unsuited for f/IC construction aggrej i0& -icC ¶//—1 i-c-ic-i-c gates. Locally, poorly—sorted, clastics are inter— Y2=c i-/I coarse—textured c- i-- / 11c- sediment. Small stratified with till and other —cl/i C/cu' kettles dot the tops 'c-.i-cC—ct--i-/I-/a c/I/Ill C ti/IcC ic-i/cci:/c-ccaIi of c-c-i-.some -cJ'1 of the Lii /Lt/IC large ice—walled lake deposits, and I/CciIi-C large lii'kettle lakes adjoin them. cat /icViews from the top of mounds are excellent. - several C r'-L)c-I/ c/i/te i/I- /2-i/11- C/cl" Some k//iC are I/-i. now in Chippewa Park, the 1Ccci--it best 4/Ic) are outside it. C-- but ic/it.- i/ti-c, fill.c-IC. County :/i///tfll' it/Ic c/l I —c/ c-c- should i-i A larger area the better -aic be set c- aside to preserve some of ic/I-l/cI-C/-i-1,l//cc-cc5/'-i-c//i-c IC,.cCL now [c/CCprotected. yL/-/}t'c-/c///I. representative features not ci of , 'c-i- I ¶3 1 cc—, - ici — j 3 ri ' & 'ii- 1 ' ccl ti — C/I c-ri/c C J /'c-Ci. it-i- lit--il ic-- the r-iI.t'cc;tC- by *Field '1CC-C work leading 11/c. 'tcI'c-ciabstract this C//CC//C: c-Ic-i was supported National IicditI/t to .f-iccic-f/cPark :Y.rck Service. 4k �tw oi nv rjr:ptkLZQ is ts, THE SEAMAN METHOD OF iINERAL IDENTIFICATION AS USED AT LAKE STATE COLLEGE tME SUPERIOR Si"fl2 AZ 4.(STh>. C. Ernest Kemp WnssL Yei' of c:aszt.sc tt v:wnt e! Chairman, Department i: st . Geology and Geography .'xf 04cawt$7 Lake Superior State College Sault Ste. Mat.e Marie,Ucbi1rar Michigan £a;..t )*ao rct) t ffihipst t# srfrtta::cu lAit t!cr, tc4't 7'r *ws' f;ttj 7o.' 1s sp;caSt tc m."zncc'p a, n&cctrtztin r..tsr' ati*it t.t 1.s tsst tL., LtcS4flrzLCi .:t1'ai IJye':.: t'7..aeau.ut At Michigan Technological University unique method of mineral identification has been taught for over forty years. useful '&c a This tCJLZO., method, the method, many a1"c:.ttszn advantages as a ti'!C:'. "%tMMt S.'Ac has !'3y Z& Seaman ii.to i iteci :tt Oat&*'h approach to macroscopic, nondestructive mineral identification, and besides be,nç ca useful tool for teaching the fundamentals of,Y. a;sd t•caL3ee being 3Ctb At Lake Superior State College, .'t tc. Ft4%SttCC an appreciation for, mineralogy. SC: r.iA4 has 3A b.ar'r.. kth,iedbut tccwith eitt' MTU, the theez.r sameate method been adopted Sa branch of ts'U .?c primary ptia-n' is based on cleavage as the e1;.?a1: P5 modifications. The system 3g property. Because cleavage is directly related to crystal btC&.re1 structure rdr_tI and has not been intensively studied, it is believed 'I.lSD-r this method can be developed further ttC, and should be more widely t?Lc t•; th.t bow gc3 LtLCc &q The paper will attempt to show how the method has been .ttsu'3çb adopted. tAt. ps.-t' and how it could be improved. tL:r; !tC4 &.i.d ban LY weaknesses applied, its advantages and its fk.'5tst'j;V tfl'gt gilbez%.. to y 3atsc: itt cs!.V flntisn u.iiiCfl It f.ft f :fl5 .j1tS2ICiV#i' stiLtt1'• .tt f! rviW aji4 si'! a3r si' ttd ,fl:cr.2r,s aLtEl? 1+5 �flACT STRUCTURES 7:'C74I3J 54 545454554 7 541154HJ'54IN 13 THE CURRENT IN-esIcLsP,515543 INVESTIGATIONS 54OFIi'MEORITE CANADIAN 1541 SHIELD 554L3C&tL1 Ont. '14,54":tLt9(5 (5bs,;y55,ci1'1:, •'(5SX5 54445., L(5Ltssc, Research (5fy .4555 ?:t54t4CS(5C1 R. Dence, Scientist, Dominion Observatory, Ottawa, 71, Md. . 54 (5:i'-t 411(541,5 c;:'54,,:: 1.5(5. Space Flight Center, Greenbelt, 4(5(54:44,54 j(5c#55 NASA, Goddard Nicholas C's 547 1(5,5: H. Short, Michael 1 (54455-4(5.7 11 large ancient 6I' (5555L yiIlll meteorite (5':H545 54(5. 5(5(5 of '(5 possible Scientific (5:54 4471771 14; investigations I) I' 1 7 (4 in 1950 with the study of the craters in the Canadian Shield began 5lss41;s'8:Icw of .54 the V. B. Meen and SIts the discovery 5, 4:553Y, '1C1'sCrater 5kI 51 Pleistocene New Quebec by'V Ps54(5.54SMS' 55444 of c (5s By 1955 a systematic search (51S' in 1951. Ordovician Brent Crater (5:55-5554 Several '454'IL(5 44754(5 5445443 underway. craters was :i'j7,'(45(5 (55(5(54(47(5 q541 (5452(5. for aerial m3.C44,5444's35 photographs 54(5 and maps other 55574(54, 15(5 '54157(5 of which 5(55(5 C:.1*54Yi. have been studied, .554154557' :)744454'SJ' t,ts"541.si' 'Hc"J dozen circular structures ''?- approximately 's.5,t';s '.7154":W 5.;7:2fl4-21i'(5'n.:e .1:.(55( of meteorite impact. (541515 kr;.I-i', 'Es show (57 are 16 known to positive evidence 2k 4 4 I S . 54(55575,' C's' based on tk,t' the541541545515 analysis 's'? of topography C47;'5d54 (5541 s-s' 1s'st;sC Early 11 investigations were ''II41's and .5514(5 lunar ,?t?I:444741W. "(4;,"; Barringer crater, Arizona 5454ti" ' 5454;t:Lrsts41 4444t15; 54,,(5L11(5hi'iii5I data taking 5551 44(5,k$5(5 and surface structural and seismic methods (55'. (555(5 (55(51 .54441111.::'.,. '4754411551'(5 154(5 The use of ItS gravity, magnetic (55(5454 55 craters as :5(5 models. -(5(4W J111 and at depth was begun at Brent in 1953, 155 Ci' I to (5 probe promising structures These crater. 5 11 drillingY'(5 at the same 1 5 was followed in 1955 by diamond 4' (5 55' in use, so that geophysical data are available methods have '(55 continued (5455 11(5 24 5(5 (5"1J*(5 sites for ¶5:55' (544:51, carried (5547515-4 out at seven -(545. been 15:1- .s'74: has (51(41 drilling for 17554(5 most (5(55:7754(5(5 craters and :5(55 (5545,. of rock core. 54':1k'(5 feet f.ss'. (5(57(55, of 7ts:: IJCI holes and '.s(411(5 over 35,000 1(5 (541(5'. S.(5sI-S't(5 two a total CII thirty I 44 75 I ' 4 (5'1 C (5 ç C' L s 44- ."i' IS'S cIC'L1'1 core and of drill 5577 mineralogic 's54s5C'54-1V- study 1(47 Detailed petrographic and (515 5515(5 57,i,155.5(5I concentrated on .1.' At first .54sslt efforts ,;154r54 were 111s'?. 11i'11 71(5 surface 4437155.1441 samples began in 1961. (535::54's(5 41,4-4,') high pressure (517 c';44;'2" 141ryr'19.lc(5.,:"54;4.: 44)4 fragments 4444(5 and (54154 the shockproduced, ;: for (5':'5:SyC"55 i41'44j's"7yTh' .54': a(54455Jc' search meteorite 1st 4 1' (5 stishovite, as recorded atr Barringer (5 polymorphs of quartz, coesite and 7' to 55 (5 C44 1_Q WI elusive, largely due This(5 search continues but has proved 47 Crater. 5L.)T51-5 54sss'54&, recrystallization 1,5 in these old, deeply C,41,E5i"silt7';11 and 551L(5'55415'5't'51the i54tasl54 alteration '54's abundant 5155' C other 5l4 criteria of shock Thus attention has turned to 4 eroded craters. 44 744 1554'75 5(5554444.7: meteorite craters, (5(5554.5 underI1'&L'55 ;3'c"(y ':isC(5osC7'44(515 metamorphism known from meteorites, recent (5575541(57775 i'(4 1(5544:1 "I 54 These include H4 1'1 experiments. ground nuclear and laboratory shock 51, [S's tests planar (57 and other mafic(51447444445415, minerals, of 's1 5' (5(51*71 %1S7J-© : 44 *51'I ',547"41;f)MSIQLS- 4(5 the development of ,.k5'17i(4754 kinking SIlL in :5:yt' mica 317 :47 (54'f:5 (5(5151 feldspars5' orientations and 'ii'sL,'41.:71545 441: 5i''lQH1 in quartz .t.5ji'44t(5.1 .7(5' s,s i'5'; '54.7-1*ctc'1e features with distinctive crystal '7'k5 '(5:5'1'41i 'Ic t154 in the (5544554;S'H',tji"CAphases, 545'S:' particularly .1154 (thetomorphic) JS1417'54(5 i"t 'ss*s5,I547i7 flIt: of and peculiar isotropic 544444;,,y', at the i6 (47,54744(51 4(51.are 55: found 44741 54 12 Well—preserved 215 :49y51754'.(57[S54 examples 1fl;"sC111(5'(471 framework silicates. .-,.,j,,,,.55,,,,k' I(5 C I 14 i) 15 I C (5 1 1 I :5i554'(55455 Canadian '54-44514'.y5,(5 craters. (5555, (55554T7, ;'.,:"1,I1",fl,7'55 particular (.11'74.:45454L(5L attention has been :'5't's5412544' craters i'1: Canadian In the analysis of 754 1.154.74(554 541 701,554(5 scsSlSIS(5:'ji.1s514"(5 41'41,15, arid grades of shock metamorphism 1(4,i(5L54.5.542 54"'71sL54h':154 given relationships between It's 44441(5 c the 1-1551 to "44(5457(55(57 54(5 diameter) Vl;(5 .4 ¶7jIH1s'Brent 7i''": (3.7 :- km The extensively drilled ,151J5 1 541".; .s7i(55c5, (54(55y(5k' crater structure. 1-15151(5(5 747.747(55' craters '7') "(5 of simple 5'(54:;55'!75' (5' .4 74.47515(5(5757(5:4. 545 craters and 54 West 174;1'"4 Hawk 441(5744(54' Lake (2.7' km) are representative 557 rocks 'i'i'55 72.5(5(5 s* :4,4 altered fragments of glass and 54! 15s'57s1; 44145454 511154(5 (5",i5144i5't'5t. with a lens of breccia containing .5-17 741; ft,ï-i' 1*5. underlain by fractured auto'j',,7s255.s44(-;. 554'1'47-(4 :':.5444ssss54CS55l: 771", (5744 at various grades (555,574(5 of (55 shock metamorphism, (57 (5s:3744,kSS&:71 454 7,5( .s't's*stLarger craters, w'nken downwards. 5(54(54147 i'544 74c;,11(55','3l chitonous 75'447,41'(55, rocks, in L's which '4i'i'5 shock zones ",:4',4;L'(5:5(Ht "C / and [ 55 S2 441J such as at IClearwater Lake (14 and 32 km), at La Malbaie (35 km) 55(554.544 whichh55,s shock zoning similar uslcsssl (55151777 5,s'stss-s77,t'tc Manicouagan (60 km), have central' s5455 peaks 7,in 554*, ,sss,. 121 13144'441 I 5i' — 4115555 :t.' 1' :'.'7 next (continued page) ,,';5.5i'57 on J �T eigJ trji The central :.L* developed. to that in the autochthone at Brent is region is surrounded by an annulus of breccia, and 1LCC1: massive, probably -cidLd. 1'y have a peripheral depression ft½T 1-1? shock melted igneous rocks. They Lc>:tt, hasaC>7 been produced at1 1iki crater form instead of an elevated rim. This C the Suffield Research Station, Alberta in alluvial TE materials by a 11LL1LGlat ;c surface explosion of 500 tons of çj TNT, and has been recognized L1 suggest a mechanical many cryptoexplosion structures. These studies rather than volcanic origin for central peaks in Lunar craters. :it-f wk :a:LC jUj,- tLct•i-i! :;.*ç rtL21;) ;ct \C?. Lf7 icW2 •?0 �O-ibb A 1'iTORITTIYPACT II IPACT OiIGIN :n0.-(1D07:71jlbCd ft 2:ToI P MtthiaC?flF PETROGAPHIC VIDNC tay t.cr:m2-r! sTh2C1'.RE, d±!:&r::c; OF THLL SUDEIJRY STAUCTUR, ONTARIO -tw and coc: c-ca!: .bcorcL cc and M Planetology Eranch, National Aeronautics :nc:: 1hao:cto] tat d-aco1aFrench, Bevan ?-an-a: M. tpc:-a Flight CLLgI.:Center, :atec: Administration, Goddard Space 20:01- Idnal :1:2::! O-c:. tUdicoc Space '2-cot land Greenbelt, :sc-!L-cIc Maryland - cpe:b-::: :ib::t&.L to byanr:oicaty o: rock :c-b: specimens subjected to hypervelocity Recently, studies of Pc:cnlf. ctl?ct:a: nate-oral:? impacts and by by meteorite ty c-at:n coal expinancua '5R1£c:Hrb shock elosions ant lb-3a waves generated by artificial sO: araL o4o:J ccI cab.: which U oh and mineralogical criteria a:: abo.basd s-as: have some petrecaan-bn: petrographic nor bcot: established 1965; i0l-5O of such processes (El Goresy, of ouch p-coos:: ta jH. c-lyon: -U or-b talc::: appear to Ia be cocoqon unique indicators These effects, which appear a, 1967b). 1-: I 1' Chao, 1967a, Short, 1966; --c-.t-c-:tao. normal geological c-rg.-coa-. deformat-cat ttncs pntr--ic ch.stnct1y different by nos:.:. CaO0.rJatlb ::tc::oacr: from those produced by such as cc ytocoLt: ocof 0.5 fc—psaa C tcaaal.I a-riof ci fthigh—pressure polymorphs (1) nIt:: .: tion, include: ) formation ra:c:J on decomposition reactions 011 :d bc-an!-si 22cc fual i,cirsics.1 coesite and stishovite', (2-) (2) unusual fusion and s_a developwidespread indicating temperatures Cl in excess of 1500 C; (3) 2 L in a asets of pplanar lamellae a a 0 quartz; (4) multiple ment of cleavage in (notably octO - -OOOland lOl3, I p V quartz, oriented pallel1 toc specific planes, features in associated ma:::cras -Ui together a: with 2: faa-Ac development p-act:: of of analogous a:-C.cigcc: planar tcl -tb disordering of single crystals of quartz and Ilaccanoug b :1 oslo oryo.C: of cactrica intense 5cp:09 (5) feldspar; I 5) inc-rose original g-incb lbphases ybas-awhich whachpreserve 2rc:-rra feldspar, ott-an often pa-odocc:cng producing glasslike folanyar-. cccl structures. oct-at-br-as. qgrain asia boundaries h-anal:.:::: and coca some e-,lo-.: lal. explained :oata:± -H: I aacc—t:nc:ts :o.-:.:o-t Dietz (1964) argued that meteorite impact corigin L:lSHt (195-4) Sudhury basin, the #1 with H e° associated of structural peculiarities ± the I South 2-c-c-b Range 2.:. tgoo:oL and the cbs 21:: cJt cc.::.carcrc chiefly the overturning ta;-h.:.tc of .5! rnetasediments ala-: on the the a-: U an Dietz yiewed :2 ecc: the Nickel La- JJtecawidespread of 2:d.hanySudbury bc:::4: breccia. w*f.aap:cac—.ddevelopment fe l.c:'-cc-n:of the Sulbob Sudhury IncUs basin as 4: he a1e!Th0a0rct_f andand :.ac1J cc.-?: in Irruptive an as derived internally emplaced Formation the overlying Onaping F:::a.t1on c- 0: .0an!. Oca-cp1iag lIe to±t 22cc.; ohs le. cccl: :1: '. He an "extrusive a 000U-i± vs lopolith a: _of 0 represented a "chill- zone of ash—flow tuffs, in which evidence0 0 view was tie: This c'tew 1mpact—produced shock metamorphism might be found. dnha t:acb--p: c-th:-:o-i nho-:ft rca iaiccrthoE.cac:; ba development ''Ian 1 supported by OX andI discovery of the widespread b-, his prediction an :.: wan basin, and it was coca the hofanal cc c-?oa-: ac--b: :.rCcOi of cones in older rocks around the Sudbury hasI. 5:2:10cc- -coos:: cc-: shatter basement rocks in the I;-XoobIdesirable deal:-cbl: i-n '-i Ican-can cii thought to c-anal:.:: examine inclusions of older cX:o:J-I? 5—u-nbc' i:-:: Onaping Formation. 2: a-tie thick, is the The approximately :2-u-! 4000 feet dr.:;o.ngFormation, ?ctanttc:- alnran.rnOtb Us: --:hfosc LII Onaping U occupies the center of the ct-c :— na of the lowest member of !hitewater series which (micropegmatite) :1-a cocoa: '--fl--i-n: basin. :-:n-liee the upper The Tb: 2:formation :-ajccb on overlies lato Sudbury of —a -——a' from it by a— alp unitI of Sudbury Nickel1 Irruptive, and is separated at the ln KU quartzite and 2: and "quartzite .:unoc: a-fof of tengs largeHIcob-: blocks -:2 ofç4oani-o: 2: breccia' composed the r:-ecUou: v4c.rhe:-s hoot aocSoaoaf r:nto.z-:cb Previous workers have considered tOO interstitial melt ±ntereth tb: a-a] -c material. extrusive fragmental ab-onifli f0:.gcL?.T:OU corn: ioc:ecl sea-ic-s U Onaping formation be oa complicated series of caciattc:i to in ha lae--1n -Ia: relation oc to the ga:: cot ocI at-a volcanic arocks and its ,r-ac-: exact an: origin and c-alan.tur cola can 171flows, c-an, hut —-cc:lrsn:a o-i-pt-i-c: have ha-a not no: been Leer:definitely ueVisoia- established. oUch Nickel Irruptive NIcciasi. Jcso- Pil 1tI rC5 A:: — : Is e:d aciahobte 0 5t :L 1:: : - c--.gio. o1 -Lo :r:.t.4: felt that f rnd. il — J 1 I c1-r basso:':: oca5 in t cc.:i l_ H - - ( t) a--na: the -cbs U-na-' c-n- formation: foot ac:t:-n: (1) pre:'-:accU- :.:c-c-p-nail It has been previously accepted that Onaping material; (2) also aevitro. -I devitrified numerous glassy -canfragments fc-ay:a:ta of o-,,-u.nana-,:c contains :.p to 2: Lana. of tens of .-arck:aoc - rocks cc--abe up contains numerous :colu:i inclusions various "basement" o-:r-tb an: ;cccacc-:e c-n: e-°ofo-020c-oC ha-ge size, from ba-:1 large el gradation Ic in ±::fc:an: fragment lb add olco : agaei-fatcc': exhibits 5-1 an (3) :1: size; feet in contact : (4) --i: abase c-sactoto fine La: OS cabal- :0at tic:the opp1an c:cc:o-oot blocks a: at the material upper respect to the coning it: i-cob t;;:-:: ':h c-as-sot U concentricc: zoning in rock types with tao: aac-taos-it exhibits correlated with 2oire&:,J-a: formations U- definitely ctetinl-aTy -:: :aniarad wiLl': -c-&c-in: be 51 cannot 5-nato roars-i a (5) basin margin sOnyts arc a single apparently deposited as clot-na--I-el (6) H?was we onne:cecU -? outside Sudbury basin;; :1 ccci a: do the :2: Sultn:oca- U an: saa :2 g°: catecLol: :2' also - 1ççi co-:±inua-t cc (continued on nc-at nextco-og: page) a 8 �*fl 0 'Ct' unit during czrp Su aa brief period of time. Preliminary petrographic investigations (French, 1967a, 'za tT0 '91.9E1of 'ycis'S,c;nS &JD?TCV2'L4tf4M33 f.13) inclusions l967b) provide evidence that quartzofeidspathic a IC 3tr9t?J ot4ap&pojonaaD Fcrinatiori bow microscopic textures basement rocks in the Onaping 4UiW, su; zr' ACTa generated bys.3r3zG$ L&SZVUV4 Sc-cCmo meteorite typical of rocks subjected to sh'c: jresruu'es yncqi ,vu.jlZ!93.A! ZJ0Vtt tO by artificial explosiond. paanimS Ci) planar These include: impact or t'. ee;q .pntOWc $4 -cJ'r.QOibcd ,.wtstJ lOi3 features in quartz, concentrated at or near the OOOl and I" %% 4tJOUIW* '1t50U t213 planar features (2) intense deformation and development of planes; s-nc1tn tw'r.'wvJa. :aIav ;o .1xL4s\ç tvsgc1 in 'oa;fl2'Cfl associated feldspar; (3) unusual deformatioflal flow textures 'Cc ':') These "melting" by shock. that may 'S be the result¶ of JD selectiveint..smaller C.. /q fragments that constitute features are also observed ci' *flV rarely ..-sx 1tQ13 4'C" 4;tflqcvu the matrix of the inclusions. ats zç4ws 'aLo'y;('vn Subsequent studies of additional inclusions have allowed the jo tt3tat.a7i pflsflV uaibacu-j tentative recognition of five types or grades of deformation which ', -o ;': n::L' e.peS 40 "i' pccoa Q$J The petrographic original shock intensities. may reflect increasing .I0O3 \L affic 99fl%P.t'! compared with material from textures observed pa.tawç can taa be tn qualitatively padw 7n* Kessel, Germany, and the Brent ieteor Arizona, the Pies J101')11 Crater, r..fl 4: 'n"i%t3 'flO'2hiatV between the groups are gradational and Crater, Ontario. Boundaries ce;:Wc!ttT ueu4eq 6Ji%4' adtoa thina.re section. The observed in a single several ' grades "may be eq - development Ca 190t4': Lw atiX":s (i) of multiple are characterized by: different 'grades d IUD1ttP $.aetb'Wfltttt and feldspar; f s.POtJSt (2) preferential sets of planar features in quartz 'qvaj 'in, €ztur6 sçaw2' of feldspar; 7W5MAfl (3) strong deformation destruction and recrystallization p.1w 7")r"J$'*P !.rwwpy.; recrystallization of associated quartz; of feldspar and complete ;c p*te"i&QVC t:fPrRtit .iiCw.zfl €'te-'¼s 1flrLC4..! eutectic . melting in strongly deformed development of local e;e.G$&O1. (4) LGFSP :n&d:' incipient melting of2r,ç"in to an the whole £tA.ene inclusionfl'&ZOtfl (5) inclusions ;c tfl VN £:I wfl 6•Jqs Sit' showing incipient flow texture; aggregate of heterogeneous glasses at; IcTaccs of :otnflow d eua' .o.iz3oa;o; '-n3development structure, with sw2saIfrP and strong complete fusion (6) ,;:;V'at* ra mineral t'- fragments 'tc-rLr-an; wai&?3c into rock and admixtures of o'..'27 s:.a14Xj4.P' zO shocked and unshocked Q7fttIPUtL 1cG.tL pU! 'V fllS•f the molten material. etwwele the Reent collateral evidence for meteorite impact, predicted by •qt itt-kin taze;rrCC .03 pe:"-% f.q (1) the recognition'-sovdw of high_temperature impact theory, includes: flfl peJer inclusion, and (2) the discovery cc4t20DL eJtfl.PSIa-CR;4 fusion (melting of sphene) in one t,V3 (planar features in quartz) in %tSIb.T45 criteria of shock wç 4i3 weakly_developed eatkcva; wy and related pa3; 2qarL nnnrt'L) Levack breccia inclusions and walirock in the footwall c• tr ',qc. tiVSiQ3 vo}9cttCts breccias along the North Range of the Sudbury basin. tn. q'42 'riatc Suora ds¾21I £znurE lihese observations establish a strong similarity between Sudbury iSP'iw C'46b!QdQC St.C qwrqnue V gQfls iceegm;eq Lr4ptl3 which a meteorite impact origin is either and other structures for Fe .70j s Bfr for the ptJwc ITV7JO Acceptance of an impact origin indicated. proven strongly UG'$- or Jt aC'M 4C te Lit) a03 fl's petrographic it! L 'pG3%c4pt4 imply: ;axdaq tii2 (1) that shock_induced Gudbury structure would pttcn also periods in excess inc ono..,flZ ;ecr_—?to04 years; Lcrqçtq of 1.5 billion featuresz can I 1s33 ser. be preserved for ..%$ spc,.ed 7 at 950CL3 :o t may c' :rq C flVha udhury, constitute (2) that shatteranea' cones, which ie uomrnon OTW T V eç'. air4r4o ig3qO t(c;OY DU'fa.L lcnfl-'svtt otooritc impacts £ccr definite criterion for meteorite impact', and (3) that Z0,, atracn.In (C large voluniesir,,vdir of processes involving may produce CA T1#tW ;': SCfl*fl or£ trigger igneous Gw9Qt-' 1.ZC Cfl itoSUS magma and economic ore o•wuu; a.t deposits. iew3v,. tscdsj impact origin helps to explain the The theory of' mofoorite It)the Sudbiiry tinetore eq c; of the Onaping jcç'& r-1Ipo thetitt nature and peculiaritleS of ;e aç ttcv.xç. s prs 70NickelBuithfla There is, however, no unit analogous to the Formation. ca flWZP structures, ')$4! atJOTj - Sfrtc) 3flC,$ '1fl impact and the impact of the larger known Irruptive ! qv any A'W JO artlittle to1Z*3\L-j tvJitrç cJTS%T'I the long—standing problempte of the theory can contribute o; S)0etT$ LIV'- 0(4TatfltU G4 710t0.ArS and its associated ore Jo deposits. origin and emplacement of this body ,n,grz—9c%Jt :a43 'psut!co 4u3A0W1dW9 ;c woj; £pac ?''1 ?t?6: t Ltflfl:.7 accc 'c n:o- fl;osttv pr'r;lUV i14t atnatCa ctcU'P1 fl fl N a ti n- 'rtT '-oaP ., e'et flC ',nt.LG 4 t St crec c v" e; ) an t'4 'itj n. pa pr' -;tCtt(V%t1Aa tXD!'.'I t' o ;: zat ' tartn gp:flq n n ) fl j •A' t0 'fl cflJ 2'tr4 ;: s.;—cijn'. ' TBt0t1t w-' 9t.t'-s0 t\r art sac3 :q roc:,'t' ( nc cn LSv eq flfl,, t42O v - jifl?c fl nmt aai ent..:e aa!rrr.S i41U2t, wt a o;udtad j-.t&r t-r-q'r;t, o;.wo;n ai '- tD'fl 2W:'Ott (It at;tOfln *nLfl Lxia fl P :ec.o6P9rqs 4 n. Q'Jlfl) sts s- 'ntqattr o qvc j2t (continued on next page) pnnnt'rcg s; :°w -e2,c' u çs'ntosB Lf 9 r..y fl'4 Cfl'j v:,.s ;; : ea8 ' '&i;a.t , 4 ;---';t' 3&'fl lwiOtflfl . a tOO ncnft M 2ir! -,.,a' esv &-zadtt'.;' ;nLtw,. vntqnj its t) fl f tn .v. �.i.r the :i hit-tel Nickel orreOt on.] unlikely 1-h. that lot hi :100? it seems ott: ofcFknow1ede, At present state Air the ::roseat c:C rico si So: cod Ste of the iupact vthich formed the holop oh be the direct re.3ult top Si c oo.r the tIre d iroco roorho could Irruptive hart c::r:or:i sod ot :ratl no.] tool li could have exercised structural control OCJLJ arorrci impact an boo but otr-:-h. such to nar.ln basin, 7-70 view 0± of the hi SO iteW iotion. his road-1 In inricrtion... processes tialready in directing igneous ?roo! 0 p:::000000 - -: It 1:r-rT 000 ILdicr.ro structure hie hi; iii rroo:y ol .tr0 importance or meteorite tory of the Sudbury l- iror I So imuact i:pcc S inSrthe ro-roroanie of flcx hi]-.e thocofec pc:oo:d co atootro: lit too does not contradict any of the theories nroposed to account for the acts 7tL icotret et trot:: riot ant on.: aOco-7-er tflio Resolution of the terrestrial and extraterrestrial Pr cc_or tote. of or ic-ti .i--nopti i-i Nickel Irruptive. 7 .r L. components Sudbury 0history will depend on future detailed studies zOThI. .t ofI o._ of the hi:- structure hir;otoroof ofcts theti-ott basin cod and tiethe -it-tractor character no.1 andschotihiase subsurface orhizr: extent of of the Nickel Irruptive itself. 1. ' -_ of hit hi*z-r I:olriiro itor References Pc for lb.] oo5oc:.rChao, Impact metamorphisr, in P.H. Abelson, oiL edo, 1015r:ir !oot00000.or1:ilnn.H,.iO Chao E.C.T. Y.OJh (l967a)•, hou Researches in Rercr,inciic.o 4oGeochemistry, flonclicc.o.r:o v0 2, New York, John Jiley and Sons, 6:0.0 pp. 204—233. 2 ' [tr cihi r Chao, E.C.T. (l967b), Shock effects of certain rock—formingy, minerals, Science, 156, 192—202. - Dietz, R.S. .OCSh (1964), Sudhury structure as an astrobleme, J. Geol., toot 72, 412—434, srO- PT :965 tattoo icr-ac S aid ito iS.Scoc Sr El and its-sootY si5nificance in impact ILr±to P0 Goresy, A. (1965), Baddeleyite 456 glasses, 2. J. 2:o:ro-e, Geophys. too.-. 2es., 52. 70, 5455 3453_3456 0io -i:ctcrl rr bitt r c-bcircHo'no structure, Ontario: boo-rio B.M. P1t; ii(1967a), 967-o Sudhury French, evidence for an 1094—1098. i:;:Oh.:i!:t: .!24CO fl origin(LIt by meteorite impact, ci !rT!i T7r' or some petrographic .— Science, 156, -2 Stit .:rc:.cp±o &]t my no: oicrro btteol: French, B.N. (1967b), structure, Ontario: Some petrographic h.fO ;r2 Sudhury evidence for aan origin by L meteorite impact, NASA Document 56 p. x—64l—67—67, 56 0! -r- tr-r5rc 0 0Oi Ij 0hroa: Short, N.N. (1966), Shock pressures in geology, J! Geol. hih- Education, 14, 149—166. a a 50 �ill 11±1±7 71-N 111 1±I71-.-172 ±7(2±7211 MIIT11Fit PROGRESS OF GEOLOGIC INVESTIGATION OFThE THE HILET 611sLI(:LTci GRANITE, - :ISOOi... -11. UT11CcLiIN ASHL.ND ±51± COUNTY, XatlsIc Michael M-, ii. Iatunan Graduate Student State 5:2±6.11 2122.2.1: Michigan II2 t2252i. 2—S 22 University, East Lansing -; 11 121 1-c 1 tllcl; City ±-±11 215 Ii of The72=11 Mellen Granite is 2-1212-4. ±1.212 west and north the 412 located 1 granite body, 1Lj County, _ The main II Mellen, Ashland _-i. of Jisconsin. 1-, in the southern half i 5-4 12 encompassing some 13 square miles, lies W. 2221t-4L1I17I N, )k11c.115t2:3IL211-L1L12.H2k.plll VJ 1;. P 3 N, and the northern portion of T 44 of 124-.± T 45 P 3 — L I — IL I I1 14j4.; c;141F' unconformably 1L::-c-1--;x.sL:-7 2overlay (2±-±.:. and .21. basalts Keweenawan gabbros Middle .CiI '1 .1 the Animikian Tyler = formation 54 and are unconforrnably overlain by -755554 .11; 15-27; 15.2 t6..4nr The granite is intrusive sIc :-511t1; 15-22,fl Oronto the Upper I1-k122 Kevreenawan :122; Group. L1I421 It SIlL 2-Ic Mj.:U-1175T4sis55.Is;c24 gabbros and basalts into the Middle Keweenawan and1511-21.1522 intrudes --and Li— 4 22 abuts against the Animikian P Tyler formation; the granite is older 2411 42ç4±5 12: 2151717I1212-2S.. Controls 21121 for emplacement appear to be 517221Oronto 5$C21.t. U5..2.1217-.= than 214-21 the Group. -1-15L12-sL1; ft=.15: :55sjT2 slip 55 the 5215area. 22555 sIft. northwest ic:4114f451-1 trending .22.2±12 in l::s-zc±.-L-7, strike the 111512 'cross faults' v 1 ii] I 4iI2 — — — — I I iLiI 21 al-n s-::11 :4: 1.21117-.2.4L15. -P.rcc 1151I4112c15:1I2.IlSIT The :2IJ:SI Mellen S Granite is composed of -three mineralogically4-517 and :22l±212142.57..s;122Y.—.1, 5i--ir1522 5-512I17; distinctive texturally phases; (1) a 2121-52-2 coarse t121222-.grained porphyritic LI. a (rl,-25.s 15 —:±i.r--12, 1.2 27411 fl.t221 t,11225 granite, 7kSl3Li'15-4-, equigranular to porphyritic (2) medium grained, quartz 115 557115524In monzonite, and (3) a2 725.9 ©rpt.y-;..s: to 5--1..;;2-NJ porphyritic fine to medium grained, 4-Q 1212±2521 tcis:---t-li-J5granodiorite. 1IJ5.1514 The fL.4H72 monzonite 4.,; SIS-SItI: 15/I P114 quartz and granodiorite equigranula± -5=5- -1-25k/I 12-1/IS- -4277's '1214 body, I[7;2-J2;t7 of the 1511±111-7 -- boundary phases, which 7'24-2: 1-./I-J7 occur only 45, at the are It-n southern -.;r;c-; 1- and 5-15:-4 the 54 ns:nstc transitional. The 5544-555 contact between quartz monzonite ,-I-55-;- SLL 5—s±. porphyritic) 5-55/I55 granite, on hand, --1-5-714 varies considerably; in 2172the 1±2other -2 712 222 -23SI 42.15 22-455-452 pISnct 222. c-2:j -2places this 222'2,211t contact is sharp /Istswith no apparent gradation, while It contact I 42 JJ elsewhere the The coarse grained porphyritic 5 is transitional. aSS 11 granite 74 is the predominant phase. -=4 - = The intrusive apparently occupies xti.2::'TI..751215. rocks. 5'-1S-12 12 a sill-like position generally concordant 2±-5.=111±-2 52c1.t2 1-c 211112-2±154: 2222-212-111:2:; to -1124 surrounding 1-72 the -17 I) - —2-21 1 21 I 11 4!J L t't 17 — -5c. surrounding 55-:5I-21212-SSL/ It-I;--15.-:Stll is -11Lr 1172112111524 Is :; the The granite not 2± an2211112-2-51.5*7 immediate differentiate of ±12 2:521 2212-2--;. but -±s± 21.4 2± 125it may -55: have gabbros L71ft5 developed -1 of -4255-74:by ±77anatexsis -54-154221or 24 granitization 1554s'.2 LJ71LI2 = 1272 from :1:2-211 a 4 deep— Animikian sediments, with 5 subsequent !±:2.-:r 551272 :4:15 --Ls11L I:n-Lt(;:±-:-:. mobilization, 1';I.2It22I1I22 . or 121 seated parent magma. 51 h -— �a rYrLC NORTH SHORE VARIETIES OF sLThtti;CC IN THE ssi FLOWS JSSS 5f5:(J3Lt VOLCANIC GROUP, MINNESOTA John C. Green Associate Professor University of i1innesota Duluth IC; Survey iinnesota Geological and ;-c 51sttrc -r rn7c47 ,571L4 474-:fl7 CflirL - a to North Shore Volcanic Group o Keweenawan U,•.t14t,' age, once trconsidered sstt, of •54 'beThe exclusively basalt and rhyolite, ['Y Ci has been found during 1'-ici7. the C:IC course 4tV47 of lakeshore, wide sampling, and miles recent detailed mapping of 58 r'4 TC1-j 'L51 - Vi'L7 — 41-[i1L1 4SJik at a i V it7f 1- 7LdV -'7çi 7 — •L9 of tholeiite. - t ti t Ti 2i — a fl9-I5' 5rI4LLt of 5 Ct chemical analysis of 22 specimens, to include representatives of a nearly LE1C 1-1 complete series ranging from both olivine tholeiite and alkali-olivine 5f•.5 Ci[Ic[ 4ttt:517 1rcA52 4477Th basalt through trachybasalt and mafic quartz JC: :44 CCLs7s latite or I7 dellenite to fel— -IL So far the alkali basalts are not known to be widesic quartz latite. '-1-s rI51-— information, spread, preliminary 1c 51-ct but the other compositionalI types, 1 _1- from stratigraphic and geographic appear to be well intermixed throughout the 1The only clear exception is that at least the extent of the sequence. 71-f'11n entirely uppermost 1500 feet that are exposed in Minnesota are composed Ct 4 4 C I a C ;r 1L7: An cJ outline of the characteristics of c the different compositional classes of flows is given in the accompanying C5VL 2tr PTicU table. flt7Lkt}, i&1TL ?S ii57 C:ñI!f ;Jn:: rvc's Older 7cir5 terminology in this district can be roughly equated compo:f71-' sitionally as follows: "ophites" are tholeiites; "melaphyres" are -— "porphyrites" siliceous tholelites, andesitic to 77L .LO!JL7 basalts FIL7H! 72f trachybasalts quartz—latites; and both C are trachybasalts, alkali—basalts, and mafic jCi "rhyolites" are quartz latites. and 57T r77 J5c5 L 1- , -h' fl1_ •7s5-r L 51- (continued on rn ncxt page) a' 52 �'f Quartz latite 7271+ T . oa1L;!i7 3.5-5.5 'Ut' LJ:cQ Ij19 .*:t tp?:2?c, up to 1000 100-600 viscous ;:iL))' fl1ZTf€ kf:crTt highly vesicular, breccia 1'4 ttt lflçI cl/l2;:::yo platy, subhorizontal columns in thick flows stretched, irregular, round pyroclastic evidence rare; top zones poorly ex- i7c Ti t'fi"f'fi - :" .flifft2i4 &:itFqI: VC)L Zfl C' itFrj ;o 'fUtiIIt2 :crC.x7 flif-Thflt4' t?fff,I.t[ =:2r& ( . III ( Cth f'Jf: ff ,rC.L I I iz?C.Yii I Tii?7if4t'f:ie-J4 — L'I.f- It'7 — ,,m _ L_____i_±1%l .i_ —— 62-65 Mafic quartz latite 51—56 2.5-5 Trachybasalt 1—2 viscous mostly porphyritic (plagioclase, quartz, rarer orthoclase, augite); flow— banding common — — I — I a iii if-" :.nr,riii <.. ,v t:J!I' I "LF1 I fTfl'iiflj F'i, ,_ _1IC I: ;v5TrT 1 Yc)L :2 :. :1 HS EflS:.-C F,. :'CiVft: := I Generalized Characteristics of Lavas of the North Shore Volcanic Group Tholeiite '+6-51 <1 porphyritic (plagioclase, augite, rare olivine, K—feldspar) up to 200 highly vesicular, some breccia sub-horizontal, platy round or stretched top zones poorly exposed posed. i TABLE 1. Alkali basalt '+7 1—2.5 up to 250 20-100 2Lji: C2 columns ::ktY l'e.: IV:td T- one 1 1 aphanitic clase, augite) K—feldspar; (1 to rather viscous I I I :':i,.jri &t I ic.'klTfl I 1l o/:.L C sheeted top zones; big columns in medium thick flows round or irregular stretched at base and top quartz, agate common in amyg— dules; 1 Sj02 wt.% K2Owt.% Textures porphyritic (plaglo— some Interstitial generally porphyritic only chilled margins are porphyri— (plagioclase) tic (plag.) Ophitic interstitial K— feldspar fine banding in some Plag. —augite micrographic intergrowths in mediumgrained thick flows 15—100 very fluid Thickness Range, feet common more viscous than tholeiites ropy or smooth 100 Relative viscosity roughly corrugated 10-50 Structures flow tops I I trtkUl 4 ;,- least well known stretched scoriaceous rubble lower massive part small jointing vesicles Other olivine common; mostly crystallized after flow; Calcic zeolites common miles thick flow traceable over 5 �STRUCTURE AND 2c:13Im CkPP :CJJV( INTRUSIVE SIGNIFICANCE OF m SANDSTONE DYKES IN THE 1(Z .Ci [-rXL _l OF THE MARQUETTE TROUGH, SIAMO SLATE CUPPER PENINSULA, MICHIGAN LtCfLLOL 11. trc:tkI Research Fellow C. McA. '•iCf-Cf; Postdoctoral J3'[1Cf13 C.7i Powell, NASA T3313CfSJCf 31 Tt7Cf©iX? c. 1 Department of Cf Geology Northwestern I I University Evanston, Illinois nicTm a a J meters long Sandstone dykes up to than 3C 15 cms CmLCN 3IrLC wide C5(1Cr and :iCce more 3cJLC:Q; IICfLIC three CrThM[L 33I33i7, X13L cleavage in transect the bedding, and are essentially parallel toI the ml Cf These clastic dykes are the CfJI com;çy Siamo CfrE=r Slate 3ThCf[I of 5• the Marquette ©:4' Cf 3IijO7I tCCf( . trough. :2CfC:9Negauriee, and are composed of mon in the zeolite—facies slates east of CfCi CIb to 6O% fine— to very fine—grained sandstones commonly containing up EfC1 L 1(3 Detailed study of large thin-sections (up to 7 dolomitic I1_ Cf carbonate. ribbons lie along the x 16 cms) has Cf I shown that pelitic L3J I 1f cleavage inI both i the 1iC slates and the interbedded psammites. Individual cleavage ribbons y band which are refracted in the psammite can be traced from one pelitic L1 —, IP: 3 Microstructures through a psammitic layer into- the next pelitic 3 C: T band. indicate that in the disrupted sandy laminations within the slate 3 iC— r the IJ and were dykes were formed penecontemporaneously with the cleavage, :Cfl emplaced by forceful C1flCJ,© intrusion upwards. Both the cleavage and the dykes of the Siamo Slate during L may have been produced by tectonic dewatering L b_C either late diagenesis of very low-grade metamorphism. tw 3•'•! L iL a r3': irytI 1' f ' - jil t V1 I 32e1 r ti 51C JCCrb. L _ ttr i3: — C 5k I !I' �,j' ' j. 41 MIDDLE 771 j PRICA1iBRIAN '7 r 57>rri THE SEDIMENTOLOGY OF THE sC7ZV174M THOI'ISON FOR1vLTION* > G. B.c Morey, Geologist 1k >7-5 $ 5t IS'I5.CS Minnesota Geological survey, Minneapolis and 51Is'rf 71717775.1 Professor R. W. Ojakangas, Assistant 7775tçç77f>'7 77 L5!>L) lL-'c"ss'-'[ 'I \I> Department of Geology University of 77'>7i'71('7>'3'7 Minnesota, Duluth L 7r$ ! •t: :: 7 5.7 of Canton, gs I and The i77'U77SU5.5.'7.77777. Thomson Formation 77ii is LI'7777777(7'77 exposed T7'I7 in 77755 parts Pine, >C77-ms• i>L -5. counties 5.-i of 77' Louis 5. (7 Ii >7 southern St. northeastern Minnesota. The formation -'C 5'>L5 77 1— 5" 9 1, TLI was folded and metamorphosed during the Penokean orogeny (1,700 million 7 -ygI 7'> >'LT,A1 textures >_r' 77jI structures years old), but primary sedimentary and are well 555, 777 the 'L tc an 5575 excellent 5117s1k7'r&1(ltik, area r57i77ts to i5sL_I15i775555' !it';L7 making it preserved in Cloquet-Cariton area, 7TI15.111C7 study sedimentologic features. I77.s5i5r';CiL5ciF>tJijtiiIi5i 777797i. S I ir-' I 5r' 7'j 'SL1 stratigraphy ii7Iiç7 structure 7L7c'7L7Lc15.7'i7 of 777 the Thomson '217777n7i Formation in the The £'I777'c77w77i77 and k I ir7 5' area 17 '7r has >[LJ' Cloquet-Cariton been described by L. A. Mattson (1958). 'L 77 , i> approximately 7' I 7>_I '7 5'5''1C 77 >i'77 Mattson estimated that 3,000 feet of the formation is s77 exposed along a north—south section, three miles long, that is composed 711111 rl-1 77 &7 with many minor folds "5' — on of three major synclines and two anticlines — 'I folds are open and symmetrical, strike 15 5V nearly east— their limbs. Most j 7'77I I -° iJ'7 '7 i I 2 5'L I west. ):ss7r I, I C. i; r47 5 7I777 77 is 771 characterized in this area PT K' slate, 5Tçj The7 formation 7®ic by intercalated IL two t? siltstone, and graywacke. Detailed Fg analyses of 5. ThIL sections, measured I77 —in thickness at the type 1I IP1 Canton aggregating 565 feet locality near 1 -1 about [ -I 7 indicate that graywacke comprises 34 per cent, siltstone 34—42 IL' per cent, and slate 23—31 per cent of the formation. Although¶ individual iinter— r. graywacke or siltstone beds (defined as the 7interval between slate F) be more than 10 feet Th2 beds) may thick, most are thin. Seventy—two per cent of the graywacke beds and 83 per cent of the siltstone beds are less thaxi l5! 80 per cent of J — less one foot thick and more Ithan the slate interbeds are . I j ii' pronounced '" than half a foot thick. Because — such c of features as Ci) 2 jV individual beds, :(2) lateral continuity of sharp bottom contacts and - '-' c' gradational ? —' r 7—tc tops, (3) r-1,4'-well—defined internal structures common to other e Ii 4 frç turbidite—d.eposited sequences, and (4) sedimentary features that exhibit 7r J r consistent directional properties, the graywacke and siltstone beds are \j r@ by CL L interpreted as individual sedimentation units, apparently deposited ()? - A_CT -.---e waning sediment laden turbidity currents. I Irs a I 1 C5" 57>55.515 east or west, and h7j plunge >s>t777t77l0°—20 a 'O I j iT t _I — i L 5 e 2 a l11 L: çir II 1L\t1 5' gIL L [')t ir I i ( 1 ,r ;e; ); L - 1 ç; I r I_ _ - —, _'_-, L r1agc 2 L"; 7t: L A detailed analysis T!) of crossbedding and of slump structures ILl cT?, indicate that much of the sedimentary material was deposited by currents ? OO4 t1 presence of strucflowing southward down a regional slope. However, the zeYR p'c groove casts, which trend tures cf&.flfl tentatively interpreted E}5;44Q1 as flute and ) Lt to :; y:Ci- some currents probably flowed. east—west, implies that perperidicm1r .:3a 1 - flILtTT rc 1 . J4 *\iork done Yj( on z?ct. behalf of •rT. the Minnesota Geological Survey. cr ( 2t next page) (continued on . 55 I -: �paleoslope. fIS LISV'l±d the of ISV' dip of the inferred IPV'II-'.©5S f-SI direction SIPIl Cl LC $I.L'l,71LLV LIlt I comIV—the graywackes are I SLIVII:reveal I-It IV that f-Il tIllL'cCV TIC X—ray and thin section studies ICC SITILtL. tCIIcl 2-28 percent feldspar, 1-10 percent rock -SI VIl CCl SIS.I5VVN OL1Cquartz, ciLIlSI II L,_55 posed of 1-f35 percent consisting It'VS: etSI it. Lmaterial 11115 C'ICLILTII ;i1LIofII quartz, 5 LT'LCZ muscofragments, S.9.-"Sf l9—8 percent matrix Mineralogically, the V V vite, and calcite. & I chlorite, and 1—17 percent graywackes. 1,!:LL I-I' the :ICLlVL.LPLCl E:7:Cl SI of siltstones ILCLI are fine—grained equivalents LI C C1 ' jIL,'L 1-1111 similar rocks :11 Cl tIu:tL.I&'T ILl other 'L: correlation LII *t,CIt5CILSLL SlITI:nIFl with The of the Thomson Formation :LlLi :r:.xSIlg L: IC CC since Irving first suggested Ttlr cC tIVt 7V.p. dS'CC•,IS-ft CIt region in TISI the Lake has been debated 1C7IlSIck Superior '1 T:57I.CCCtS. tTIcl11SlCL physical isolation Ij1t,l, C MJSs IV ILl a MiddlekZ'LLC,t<T'If.IXL Precambrian age in 1883, but the formationts r c The marked similarity of the mine— has left all correlation in doubt. I'lLtIlIlLI-l IS VT 'FILl-Il Thomson Formation with those 'Cl VT TI-Y ralogic and Itdc sedimentologic aspects of the TI-S OfLC V11 !tL&LLsIIILCSI-I .CIt.ILL'i L3 151 implies that both -. I. 1IlS1 Cl tLVTS;LlinFCl fltLIf LI :SIlIItP, CCL CLII' observed the Viiddle Precambrian Rove Cl'':LLIl Formation 1111 i:_.,:C. CXLS SLLCIcI4 I-LLI"l and were deposited IILVV terrain formations were 'IV? derived a IiI'iu.LCl similar source :VI:Lt I. 'lLI from V IV:, SC LV C-CL' processes. by similar I T - 'F , I :- 56 �Pt:? 9J3 •.::;AJi I:! t:RiLtC :::i;i. EVENTS IN THE TiLE SEQUENCE OF MARQUETTE I::;r IRON RANGE THE GEOLCGICAL ; •:;fl 1j!L!c THE PENOKEAN OPCGENIC,4ET[MORPHIC CYCLE DURING P :54 h!L? Cl tit? ::i :IJL Research ( ;:I.'CJ19 J:; &;Ct*L Engineer, ;i"L. Babcock, Research Institute ofPT:LI Mineral :L:. \t,t;çy,i: . . Michigan Technological University, Houghton, Michigan i2C i 1\.:L.1:±. r1Qb.11L. Larry Li f : rISL 1Ct I 4L Four Penokean (post-Animikian, pre-Keweenawan) deformational phases j field stuare discernable on the basis of photo—lineament and regLonal _c4 ]?[4 (_ I The—chronological sequence of deformational events, respective dies. 1V) _ M J major compressional axis intensity of each .J.t trend,, and C apparent regional .H.LH54 1.511 syl phase are listed below: 1 4 j jjtd L ' L-5 L I I t' -; -1 ' I S (N82—8+°W) — Moderate to strong £ 4 - . . . . D2 : (NL3_k5°E) - Very weak D3 iii - WeakC (N6-8°E) Dk (N12—l4°W) .:1. .5. ...5: Very strong - Sr rotation I S _t 900 counterclockwise This sequence indicates that an approximate I C - to late Penokean of the major compressional- stress occurred )L from early 15 555. 45.55SY. by James. 1..4:.I..:.s t(S IL!<y. has been described time. Post_Dk regional thermal metamorphism i Sf :'L45 t.:,.fl!: 5555::ô,S,5j515 :415 granites, r5511 45'..' 45 and migmatites 5ST Pre-Animikian 4541j:C,Z..5.r banded granitic gneiss, L.a porphyritic granite "core" in the complex south of the Marquette r 'I_4 Included within the core region are roof pendants, migma— synclinorium. Porphyritic 41 assimilated 5? L5L/ L5 sediments. 5 tite belts, and partially Animikian 1 granite is synkinematic with D • Intense D2 folding of the Republic 14 rj had negliwhich Trough appears to have been a focalized basement event, .ç r I — The Republic Trough acted tee— 7L effect on adjacent structures. gible 4-4 :s45.Js 5S:511.I:i, complex during later deformational tonically as a portion of the southern JL I5 - 1 flank !s't- — 1 — £ 1 — — 1 phases. 1; ©44i1rTh14, Events .kJ4 which occurred between and 1i• Dk include district— :;cs51411c7, phases D2 5II. wide mafic dike intrusion, minor D folding end stress—releasing fracturing, and increased regional uplift. 14. rj L1 15 5t — J çl1I — 4 — I -- ç and WNW, NNW and and EW and NS :5,i:J NNE -14. 55 141ç ENE, Conjugate sets which sIi•i.cr trend Ste_C of re-— during the early C were developed —s-ti Pre-Cambrian and acted as sites çs[L -' foci of nine- regional J H newed fracturing until late Keweenawan time. The 4 _— a line which 4 and 4j N60_7Lf°W, define lineament fans, trending N16—30°E 4 rdimensional axes of the southern complex congruent to the present major Us. _s axes trend N82—8k°W and sugand porphyritic granite core. These three ,-ssr ::4s-sss.gest 4 a zone of major regional 5:Li4 uplift. k 1- — 1 Ii - I £ - £ - s— — — — 1 — ii — s--sa4 s :ss.t 4 e_. (continued on next page) 57; l is _r- �may The fliL1Tfl Animikian sediments present in the Marquette ?i synclinoriufli 7.i!:..U7U17': 31L 3i;I% c€31k:,J 3Uan 1:3[U4Jiti,t,73 1U: elongated basin on te ci be of ancient have been in an : fllfluC;1 tL3&[ 33t.Lc CT 3 deposited aTt and southern complexes. wrench—fault system which di1aced the northo:n 1mr1tPm.1 ,3j..t71PI ticmt. ,U:PtiPU basin and present major axis of The postulated wrench_fau1t/StllCtUral 7 — N32—8k°W. the Marquette synclinorium trend 4 U1U3571Th l7fl Pfl -flc— — 1:1 fl flic 3;1 east—west folding of the Marquette Province was subjected to a of The southernI portion Ui!'U.cUU*7kC3 CJflUIUL1U flt: 3: ff•: the Superior Induring late Penokean time. major north—south compressional stress J1t1331 cflTcr7P 23Ti II' synclinorium is attributaUP tense 1 ] — I ——- U I — ble to oth increased uplift in the southern complex and major northsouth compression. 'c 2 PJJ immediately adjacent to the The JJ[t2HJ7 PTtV L33 cP11 portion of the northern complex 3 P'3. T;yxc 3)737.© block during the Penokean oroMarquette synclinorium acted as a stable —[ genic cycle. :3fl333 3Tcti fl metamorphism, dynamic arid Prior to late Penokean 37 z:::32Jc7 regional thermal U!pF-.•. m7rLc=rfl 7p ipIXi Superposiiofl insignificant. dynamo—thermal effects were relatively LJ deformational phases is manifested by N52 W fault L5 of the major -: D1 and 7L fold structures, and NLF5_i+8°W macrolineaments. zones, northwest-plunging 11rj Portions of the biotite, garnet, and staurolite isograds shown by James are congruent to northwest trending macrolinearnents. r 3 — P — Pc 2' — — U rI I U Reference — r Precambrian James, H.o L., cr 1955, Zones of Regional Metamorphism in the 66, 1, pp. 1455—1488. pt. of Northern Michigan, Bull. 'mr1G. S. A., v. 3 — 58 ii �ETI'Ufl'KE IRON ]j'OPMATIONS Li\.KL SUPERIOR :..:cK IUKIIUSIN IlKTHE TI lAKE SKUEUIUR CTERISTICS •UZ.t KilT :KEr:i CHERT BE]) CHA Ke7aJt4.,; P;cc.re; Joseph T. Mengci., ProfessOr KoaooKco:it Department of ofG.2IOK ceoiey Wisconsin State University Superior iTLUoUL ITo Six thousand bed thickness measurements establish the KE r throughout the Lake similarity of the non-granular cherts -f metamorphic rank or Ob_ t the age, Superior region regardless of about associatedU iron mineralogy. The typical chert bed is lo rco tUtU in 00 common with ooooUL Bed thicknesses to are log lLt -.©K normal, bl•t 1 cm. ©Oi thick. those of younger detrital sediments. -I lUlL ot& — or I — ftOft o IfI) 'c)fI structures composed of II c0 composite Thicker chert beds are ft0ILl0L0c bedding; f,:wt SOO tT0itf 00©0O lToiiog oscillaSome lenses exhibit cross tTUL0rO fCy0.0: smaller lenses. tion ripple marks are present locally. No lense or bed coalesces lLf0[tIiOc li01, with V7 vertically adjacent layers. I 0'Ji — L j ;j-L tU0 the too TIM ofl0M%ft$f ?0-ic 0 s00LLU:Lt0H..; ©TIP for The evidence argues against a secondary origin I0 beds comparability to detrital typical OL chert bed and indicates 0©L0;OL IL f Enigmatic amoeboid ç> found in and adjacent 0! to lio the fr.:n iron formation. Icoot oftAotheoomo same origin. layers suggest that is 0! to otooM. IS!. not all chert 0! Ic 1 ]!; TI! 59 �ANNUAL MEETINGS of liC;.±.S.t11/JtF INSTITUTE ON LAKE 51JD} SUPERIOR GEOLCOY Sponsor Number Year First yITc,L)A Minnesota Minneapolis, t.J4c St5.Pr1 Michigan Houghton, University of Minnesota Second 1955 1cI9 1956 Third 1957 East 1tL..•. Michigan ccx Lansing, Michigan State University Fourth 1958 Duluth, Minnesota University of Minnesota )J iSt Duluth Fifth 1959 r..1;i3teL Minneapolis, Minnesota rftr<:I:;: University of .:: Minnesota £LL Sixth 1960 cct:Lcc Madison, Wisconsin 35cc Geology i'ct2 tLrI Department, University of Wisconsin and Wisconsin Se:c cty;tc Geological LI J.j,Lit .. History and Natural Survey Seventh 1961 5 I'J• Arthur, 5tL Port Ontario Canadian Institute of $lL1j)II 2'; Mining and Metallurgy, i,Iv: Lakehead Branch, and 1 Ontario of Y.i iCI1 Department Mines Eighth 1962 Houghton, Michigan .-,I:C'X. tIc:cI Michigan College of 5 Mining and Technology rI Place (L: Michigan College of Mining and Technology .;i2'ItL1t j[ Y2t &I/Icti. ti14 LI CILL* tc . &5 Ninth 191S: 1963 IK,1cLh.. Duluth, Minnesota University of Minnesota Duluth Tenth 1964 ItI Ishpeming, tc1SL Michigan Mining Companies: Inland Steel, Cleveland-Cliffs Iron, S.ticItR Jones and Laughlin, North Range itt4* Li 111cc ctcct Eleventh 1965 tcE %t1L Minnesota c,Lccct4 St. St. Paul, Tie1fth 1966 Sault Ste. Marie, Michigan ThirteenthI 1967 East Lansing, . Michigan Fourteenth 1968 Superior, Wisconsin rt Etc.. 'tctc !.tcc.ght) ltc ,IIt. L. Minnesota Geological cQH' University of Survey c'Lccclr and ;.1 Minnesota II'• Michigan Y1 cc5Stcc Technological University r rj Z-I University Michigan State C-.J EIL;- LL .tLI,2j Geological and Michigan Survey I 2fl.JJL 4I. Department of Geology trcc tLUL L35 L-., University ISic' c-4c I Wisconsin State t (o11'ril. ctc SSaa:i3oFa and Minneo1 I,'cLo.iL Survey 60 �9 R{[gratitude 1 -J:dny+2is! given to A special note o± 1? Kruk Dr. Arthur F. ©± Art Chairman of the Department of Wisconsin State University, Superior iTh f L or (?&57 design consideration cover 61 � https://digitalcollections.lakeheadu.ca/files/original/d83788cb2209624be318b39a90663b46.pdf 52c7589a0f2307bb12f416c07519b817 PDF Text Text Guide 1o, Field Trip 'n Th'" Dllluth Complex near Ely, Minne.ota In.titute Oil Lake Sllperior Geology May 5 and 8, /968 by Wm. C. Phinney Univer.ity of Minne"ota �I ELY ~\. •• . ' ....••• ...' ,<F • EXPLANATION Granitic rocks ? Gran.tic int, usian 01 Arrow lake Bald Eaqle Intrusion (gabbro troctolite) a DULUTH COMPLEX IN ~ ~ A"ow Lake IntruSion (OOObro 8 troctolite) LAKE COUNTY Ko_ishi"", Intrusion (troctolite) ..... .... [;'··1 ~ • o Stops 5 ~OMILES �field Trlp in Dll1tlth co-plu f.ut of Ely, HUlll..ot. In.rittlt. On Lcke Stlperior Glolol1 Hay S .nd 8, 1968 IntrodtltUon On th.. ,ccOIIPIIllYinl up th.n .ra aisht .top••bOWEl. How....r. lt 1. unl1kaly th.t .11 .top' w111 b. vilit.d .nd they w111 not D.ca••arily b. viait..d in the n.... ri~.l ord.r liven. a.c.uee of the larl' numb.r of r.gl.tr.nta for the li.ld trlp (ov.r 200) it iI nec••••ry tblt ••verll group. "i.it tb. outcrop•• i-u1t.naouely .nd ••cb Iroup will b••tlrting .t diff.r.nt outcropl. Hop.fully ••ch group will ~ka I .ini.~ of .ix atop" Gen.tll GeolOlic R.1atlona Gener.l ..ppiDI of the Seology in north,.at.rn Hinn••ota ov.r the p•• t fev ye.r. has .bOWEl th. Ilbbroic. ~luth coapl•• to b••••rlas o( lnortho.ltic, tro~tolitic, granodiorlti~••nd Iranltic intrual"... Th.a. intruai"... outcrop in an .rcuat. p.tt'rn .xt.nding .bout ISO ml1•• north....tw.rd (roil Duluth tow. rd. tb.. IUIrth.uurn tip of l'UnJluot.. Old.r granit•• , .ehi.t., gr••n.too.....nd .lat•• occur .long the bl.al ~ontact on th.. northweat; Ind n.t. ~~.nlw.n flowa for- th.. upp.r cont.et to the .outh- Rldio""'tric dlting of lircon. froll rhyolitic flove .nd sranitic fraction. of the munic.tion) ~luth ~OIIpl.x indi~lt. (5ilv'r .nd Gr.en, 1963 Ind p.r'onll COlI- thlt the lntru-iv•• end th.. flov. ar••Iaenti.lly eontamporan.ou. to within experill8ntal error. at 1120 + IS million y..ara. Stop. 1. 2. 3, and 4 ara loeltaG in the Gabbro Lak. 15 IliDtlte quadranll. for which a d.teilad leologi~ ..p i. aVliI.ble through the Hinn.lot. �Sto~ GoIo1ollical Sur"e,. 15 II1tlu~ ,- 5, 6, 7 aIl4 8 .... locate<! ill the FoUIt Co:nter quadratl.Ie vlulttl aOIM p .... Uodul")' . .ppiog h •• bea.. tlcc.olDplhh.d but no ._ologic ..p 18 availabla. A ubulation of _-re fo'r the ... ariollll lIDitil of thl! Cabbro LalLa Quad- About 400 thiR •• ctlOfla han huon atud1ed and CQuota raDsl.. 18 incl...aed. of lSOO or _de. paiatll in .ach chi" ."cHoq b. . . the lllDdaJ. .. cs.-c... h. ~t a.- ...d u .. bui_ for of the 'l'oeIL ....ltl1 thera 18 ...1Ib.tantial ".dactoa of the IIOde about an .... '1'• • • but ill S....r.l ••ch type can be di.tllll~.h.d fro. another 00 textural differallc••• The old.at btruah. . . .d " I t ."t.... 1'" unit of tlla Duluth cO"'l'bx in tha two 'luAdranal•• t& ••bbroie anorthoaita (80 to 901 p1as1oel...). . . .n A _ppable lillie of anorthodt1c: .&bbro (70 co 80:: plagioc1&..) Dccun 18 tha ~w>ro J...oJl.- quadt-ale AI' .. "Ilit "!thin the gabbroi" &l\orthodte. In d l of th... pla.locl... -ric:h uDiu the only cu",uhte-type ll1",ral ia plaslocLa.. of about An 6S -.1....:ala ara int.ntitial. to An 7S co-poiition. Tha re..iodar of tha Tha abundanca ...01 ta.["ra1 rahtiOns of the .ario... iDtanUUal ion_S.....ian phaau of tan ..y be ....01 aa • buia for diatinsuiahing .maller Croaa-cuttinS ~nita within tha gabbrolc anorthoatce. at~t"ral r.1.tio... baa.d on detai1&d obearvationa of a..l1er unita within the gabbrolc anorthoait. aod planar plagioclaa. orientation ln a..ll .reaa, indi.,.te that the gabbroic anortho.lte conatata of a number of lntrusloD8. Intr...iYa into the gabbroic anorthoaita ara at leut threa _jar troetol1tie to sabbroic iotrueiol\8 and othar .....l1er intnMiYea. Gabbro £,d" intr~alva 10 the q...,jrallg1&'. fr08 S..ld E..gla Lake to tha .outh ia • lI&jor which 1& diff.rantiat"d fro", • troctolit" II&rgin to • g.bbro eore. Layering and plauar phaiocla•• ori.ot.tion indieate thi. intrusion to be �til m'" ~n~~o O~ ~oa op .uw•• ol '11.1 o~qCflI .(n.nlll ....q 1111 11 lOV qf!nOqlTI eu02 TI~Td.(l ~IIU 'T .~;oq llqlo 0' l'l'" "'11.1 UAD~ ".ydooo~ 'uO~T '~lddo~ T''PTV pn "'11 lO 'lnOl~o~l UftO~q lATqllA~ 'Ilnrno 'ql ]0 ,,~vIl~n~~o TI~IUr- ~JmOVO~' ~lqlO 11. lATq'lIdll a'll JO l.uqlno. 1I0TerInaT ~I'U ln~:IO '~nyn' '~aAfB AlJ • T'TTI~d '002 P'2lPTXO '~'J~n"41 P..... ~.lP ''1. 01 .vo .{Tao 'ql lnq 01 p.~panq yl"q 111.1 01 ~o ·v•••ol aOT'''~dx. lael m~l l~lllJ<Y.) 111.1 jO ~n~~o I al 111.1 'T •• ~va~~n~~o "'ql lO '11.1 ~lld ~1.alT ATq'n~ 'l~'lVO~'ql '~IAT1 TI,I'I. "11 1~1l1lO~ JO ..I.T"". . . . .noplA 'l~allJ"~~O T'~"'llol 1J1ll0"0~1 'I~aq P"'In~'TP ~ ~n~~o "Ill 110 UADq. lOU Il. l"q I~" Ol'l.q.~ I~ Ul "lPOO ••• ~1'~' IVTAV.dmO~~1 loa TTlA pv. d.. o'TI II'l[TP Ilnol~~l 100T'''11a, q~' ITlv.~p.nb pn ~eyT~' TllIAIS 'oolln~lllT 011.1... 10 ll~ lIO~j 'l~1d aJ Alq"""ld 'llJwoq PIOlill ll"n JO 'PI~OJ ~lOlq'l.I' P"P"I'I.-Tl"A Iq] 'J uOJ~lvl 'lql 10 UlIl.. 01'1'" 11Ilpuno.un. "'11 JO uonll""l'" 'p"uJI~'-l,ulJ V 1.....11.(11 IOJddJP Aldill' .111. 'T'Il 0' PUg Olqqll JO ITlvup1nb ~'lUe:> 11l~Od "lUllT ''I. 01 ln~~o I ~llddl ~Oj UDT'"~lUl ~1'oToll"d ""VIol: ·••o~~. ~or.... '111 "l 'O'TV - ( - .al'~" pul 'P'qllTdmO~~1 P"Tll'l"ll a..q ·r.lnOl~O~l I JO 'ln~~o Ulq10 1"'1. 'TIIl JO •• ~. I'll 1noql"01q1 "TP 9 lftoq. 'TIll JD llid lOr. . I'll ·.yIUf~pI"b I~" o~q~ ~"1l111 'lUol",y~ul Iq " . . 'VOl~lV' • IllTA UO''''llO' IllT0110n llTl .(tyl~"l~n~lS 11'lU"i! "'11.1 JO amos "]J,oql~oal 1<[1 II~JqA UOl'~lol ~or.. Pll~ al 'l'l"'Ol I'll a, 1'" Mqou,., Illl0'lllOU, ~n-lJ'IlP _qlnol l~.d qHA "HVlll lOATI"ll"l 'r.l11TPVJ IlJh... 'IUOll~od T'~lV'~ 1". ]011 IAIII vOllnnvJ 'Jql JO IIJpn]. l~ld "'''IIl\T~vT Il(l ]0 'l,,]:;m~ll 11fll-u,nq ·] ••• ~~oo 1111 01 .1'Pu.ddl 'l nATI l"ltlll_" lllll JO 1'" ·VOll1•• I'O~~ 0l pldlll'_IUD~ �• • 4 • til' allClrthoaitlf;: rock. but rather iD the troctoUte in<;ludi". the dike-like .Ppl"o.ll of troctolite ....cloned ••r11Ir. Th. troctolite 11> the vlciPity of thl .dUd.. u..... Uy cOlltalu -.ny uu:.lu.lllllni 10"'" of which .ppear to b' fin, Itliud t.bbro. otheu are boratet. which fo~tloD, ~,. ha¥e b.... part of th_ Vlrlln1& fD~tlon and Itl11 othera Ite labbroic lDOtthoalt... or lroo Vithin th_ .lbbr01e .n<l troctollt1c r~k. th_ av1Ud.. occur with vlriO\>8 cOllbiDIUona of ty,'. ,ud .1~. of liliclte m1~r.l.. tn ea.a cal•• the hOlt il vary pl.,loci... rich and ill other. quite olh'1rle rich. lD._ c.... the hoer 11 .... ry cOltae-lrained and 1n other_ quit. f101-lrI1,,14. howevlr, chi .ulfl~••pp•• r end aUrlnl 1-r.1.... til n••rly all c••••• to fill thl ioelrarlc•• b'~'D th, p11.10c1,•• �• • i~ •••• 1~ •• •• •i •• • ••0 •i• I •~ •• • • •• i • ••" •i • • •= • ... • -• -" -• -• • - • - • ... • • • • • • . ... • • -• ,.• .,'" • • • • • • -• -•• • -• -- -• • -, •- I- -- • • .' - -• • "' • - - " -- - - " - -• •• ..,.• Q, i. •• • •,~ • • •• •• Ii•• •• •• •• •• •-' • ~. • w w •• • • •• •w •• w • •• •• ~• •• •• • •i• i • w • • w w ••• ••• •• !• ••J i ~ • • •• •l •• ~ ••• •~ ;~ • • •• ~ • •• •• •• •• I ~ • • I • ••• w • •• •w •w w • •• • •• •• • w •• • ! • • w • ~ • •• w •w •• ! • ~ •• • • • •w • •• w •w • " • " • w • •• •w • •• ! w •• •g ••• •• •w • w w • • • • •• • "• •w •w • w w • ••w • •• •• Z • •" "• • •• •w• • • ! • • w •• " •w I • " " w • • ••w • • • • • • w • •• " •w• " •w •• • • " " ADorthc.ittt Gabbro ( "') • •• ~ I Jl'orlUc ADorthc.lte (37) I• • •• Cabbroic Anorth...lu (l76) '1- -• • ~ ....1 Contact loo.... of c.bbrolt ADorth...lta (11) ADorth...lu Troctolite (l~ lIorito! South • • of c..bbrolc Coatact •• -• '1- F , (6) ~~t.hlvl lroc:toUte f •• AUlic. • eU) ~ 50\1tb l.h'1ab1vi PolUUt!t Troctolite (27) •• I1ar.ln of hld Eall. Illcr...1.... (12) c.ntul Zone of Bald !alh Intrua:i<>n (7) '1 ,r Q \)iu of So ..th ll:..,hbbrl 1D t 'CO.a1on (68) ADorthoal~ 10 South ':_hhtvl 10c.....100. (6) ••• l• • •w• • �Individull1 Stopa Stop 11 thh gOlla. Stop 12 ae"oll&bly fneh ,urfac.. of • ..lUcIa C&ll bl! found 111 thl. teat pit from whlch urea took. b..lk u..pl... Agaio • ".-ril!ty of taxt...,.,a and IIlnara1.a c.n b. ael!n. Stop '3 Stop h Stop '5 Stop 16 '1 Stop '8 Stop nea-r b 1I>t-r... 1o" .how. 1I:I,;:1...io ~ of So..th l:_hhiV1 t-r~tolite a"d a vad..ty of t ••t"N•• Cootact batva..o gabb-roic .oo-rthosit.. &lid dike-llke app.ndag.. of troctolite. aalld10g .nd 10clu.iOO8 ~y ba .....n in the troctolit.. which i. lacad with pag~titic 'lei..... Th.. cORpleX ....tur. of the COlltact .lao ... y ba .aao. Gravity influenca4 tha 8.ttling of oliviAI! to produca gr.datiooal byuing. Thta outcrop in tha II1ddh. of the troctoUn ba.1I:I .how&" aeVlil-r.l l:udJ cycl_ of sudation.-l J'-yl:u. o-r th-r"" typ,,* of ,abbroic .no-rtho.ire occu-r h .. r... 111 f:act, .n inclusion nf one typ" io anoth"r .ay ba s....o. Simil.r o..tcrop. form a monotono... p.tt.. rn of g.bb-roit ano-rtho.ite over tens of squa-r.. IIlile. io thi••1'.... 1'\00 Th.. fine_g-r.ined ~-r,io of thi. intrusioo .how. aff..ct. of ••aimilatioo of tha ...-rroundiog g.bbroic &Oo-rrho.ire. w"ll banded zona of thi. intz... ion indicat... the comple. lI.r..rs of th. iotru.ioo and '''I,a.ra the dynamica lnvol~d. The gr.oitic e.. tern ...-r'io of thi. intrusion haa some incl~ions at the .o..th and of the o..tcrop. The granite exteod. nearly 8 Ddla to the north but eod. abo..t One to two huod-red yards "outh of the ro.d. � 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, 1968 Description An account of the resource Institute on Lake Superior Geology. Wisconsin State University, Superior, Wisonsin. May 6-7, 1968. Date A point or period of time associated with an event in the lifecycle of the resource 1968 Contributor An entity responsible for making contributions to the resource Henry Lepp Larry Haskin Barton Denechaud Richard J. Wold H.C. Palmer S. Chaudhuri G. Faure D.G. Brookins L.O. Bacon R.W. Ingalls J.F. Stafford D. Gendzwill William R. Church Paul K. Sims G.B. Morey R.W. Ojakangas W.L. Griffin Donald M. Davidson Jr. S. Viswanathan Bill Bonnichsen N.D. MacRae E.J. Reeve P.R. Mainwaring J.W. Horton R.C. Brown D.W. Davidson A.B. Dickas W. Lunking R.K. Roubal J.A. Robertson K.D. Card M.J. Frarey Harold A. Hubbard William R. Farrand W.S. Benninghoff Judith M. Franklin W.W. Moorhouse G.M. Young F.W. Chandler Robert F. Black C. Ernest Kemp Michael R. Dence Nicholas M. Short Bevan M. French Michael M. Katzman John C. Green C. McA. Powell Larry L. Babcock Joseph T. Mengel Format The file format, physical medium, or dimensions of the resource PDF Language A language of the resource English Creator An entity primarily responsible for making the resource Institute on Lake Superior Geology https://digitalcollections.lakeheadu.ca/files/original/914bfd47574dffafd8ce8132d6703a58.pdf 20e580fa2bfddbbe3ce84367c828bbc5 PDF Text Text 7i -(2 S -1ETh* 'TH 13 ANNUAL INSTITUTE ON LAKE SUPERIOR GEOLOGY Department of Geology Michigan State University and Geological Survey Division Michigan Department of Conservation East Lansing, May Michigan 1-2, 1967 �13th ANNUAL INSTITUTE ON LAKE SUPERIOR GEOLOGY Kellogg Center Michigan State University East Lansing, Michigan May 1—2, 1967 BOARD OF DIRECTORS - INSTITUTE ON LAKE SUPERIOR GEOLOGY A. T. Broderick, Inland Steel Company, Ishpeming, Michigan D. H. Hase, University of Iowa, Iowa City, Iowa W. J. Hinze, Michigan State University, East Lansing, Michigan P. K. Sims, Minnesota Geological Survey, Minneapolis, Minnesota A. K. Sneigrove, Michigan Technological University, Houghton, Michigan SECRETARY-TREASURER - INSTITUTE ON LAKE SUPERIOR GEOLOGY D. H. Hase, Department of Geology The State University of Iowa, Iowa City, Iowa 52240 LOCAL COMMITTEE W. J. Hinze H. B. Stonehouse (Technical Session Chairman) H. F. Bennett J. A. CoIwell G. E. Eddy (Field Trip Chairman) H. J. Hardenberg C. E. Prouty R. C. Reed S. B. Romberger R. Ehrlich J. H. Fisher B. T. Sandefur J. W. Trow The Field Trip conducted in connection with the Institute was held in the Grenville Province of Southeastern Ontario, in the BancroftMadoc Area, on April 29-30. It was led by Dr. H. B. Stonehouse, Department of Geology, Michigan State University. A Field Trip Guide is available. �PROGRAM 13th Annual INSTITUTE ON LAKE SUPERIOR GEOLOGY Kellogg Center Michigan State University East Lansing, Michigan Sunday, April 30, 1967 8:00 10:30 p.m. Smoker - Centennial Room, Kellogg Center Monday, May 1, 1967 7:45 a.m. Registration - Lobby, Kellogg Center 8:40 TECHNICAL SESSION I - AUDITORIUM Co-chairmen: J. W. Avery and C. E. Dutton Welcome C. E. Prouty The Structural History of the 'Archean" Rocks of UpperMichigan W. E. C. Taylor Geology of Part of the East Gogebic Range, Michigan William C. Prinz Stratiçjraphy, Structure and Metamorphism of Upper Animikie Rocks in the Marenisco-Watersmeet Area Crawford E. Fritts Keweenawan Volcanic Rocks Near Ironwood, Michigan Harold A. Hubbard Mineralogy and Petrology of the Mineral Lake Intrusion, Northwestern Wisconsin James F. Olmsted Structure and Stratigraphy Including Precambrian Tillite in Eastern Dead River Basin, Marquette County, Michigan . .Willard P. Puffett A Study of Clastics in the Negaunee Iron Formation of Michigan Robert W. Henny Influence of Faulting on Deposition of Clastic Interbeds in Negaunee Iron Formation Near Palmer, Michigan. . .Jacob E. Gair �3 Monday, May 1, (continued) 12:30 p.m. Luncheon 1:30 TECHNICAL SESSION II - AUDITORIUM .Big Ten Room Co-Chairmen: R. K. Hogberg and H. B. Stonehouse Geochronology in the Lake Superior Region K-Ar Hornblende Ages for Granites and Gneisses and K-Ar Ages for Dikes in Minnesota The Geochronology of the Keweenawan Rocks at White Pine, Michigan S. S. Goldich Gilbert N. Hanson Sambhudas Chaudhuri and Gunter Faure John A. Colwell Geochemistry of the Nipissing Diabase. Oxygen Isotopic Evidence of Metamorphism in the Biwabik Iron Formation, E. C. Perry, Jr. and Minnesota J. W. Morse A Spectrochemical Method for Differentiating Between Carbonate and Silicate Fades An Aeromagnetic Survey of Lake Huron A Regional Geophysical Study of the Por.t Coldwe.U Complex, Ontario Thomas Waggoner G. B. Secor, W. J. Hinze, N. W. O'Hara, and J. W. Trow J. D. W. J. Characteristics of Magnetic Data over Major Subdivisions of the Precambrian Shield ANNUAL BANQUET 6:30 p.m. Big Ten Room, Kellogg Center Address: Search for Precambrian Life" Professor Elsa S. Barghoorn Harvard University G. Corbett, Hinze, and B. Secor A. S. MacLaren and B. Charbonneau �4 Tuesday, May 2, 1967 8:40 a.m. TECHNICAL SESSION III - AUDITORIUM Co-Chairmen: L. 0. Bacon and A. S. MacLaren Gravity Anomalies Over Lake Superior and Surrounding Area and Their Structural M. J. S. Innes and A. K. Goodacre Implications J. S. Steinhart, S.R. Heat Flow in Lake Superior Hart, and T. J. Smith Progress of Geophysical Studies in Richard J. Wold Lake Superior Relationship Between Seismic and R. P. Meyer and Aeromagnetic Surveys in Eastern L. Ocola Lake Superior Identification of Seismic Refractors in Henry Halls and the Lake Superior Syncline G. F. West Refraction Seismic Surveys on the MidContinent Gravity Anaomaly in Minnesota and Wisconsin Preliminary Magnetotelluric Resistivity Results Across the Wisconsin Arch. 12:10 p.m. Luncheon 1:20 Business Meeting - Auditorium 1:30 TECHNICAL SESSION IV - AUDITORIUM S. H. Tohnson and P.R. Farnham . Forrest L. Dowling Centennial Room Co-Chairmen: R. A. Hoppin and W. T. Swenson Hydrocarbon Compounds in Igneous Rocks. E. Win. Heinrich Copper Mineralization in Animikie Sedi— ments of the Eastern Marquette Range, Robert C. Reed Michigan Textures and Compositions of Silicate and Sulfide Ore Minerals from Mineralized P. W. Weiblen enry Hall Zone, Duluth Gabbro Complex Subdivisions of the Negaunee Iron ForJoseph J Mancuso and mation, Sections 7, 8, T 47 N, Jack W. Avery R 26 W, Michigan Evidence on the Physical Environment of Gene L. LaBerge Iron Formation Deposition Paleobiology of a Precambrian Shale. . . Elso S. Barghoorn Some Properties of Michigan Cherts. . . Allan M. Johnson and Albert P. Ruotsala . �PALEOBIOLOGY OF A PRECAMBRIAN SHALE Elso S. BarghoornW The existence of both coal and petroleum in shale sequences of Precambrian age in the Lake Superior region has been demonstrated in recent years. Although these 'fossil fuels" occur in miniscule amounts in terms of post-Precambrian sediments, they are of great theoretical interest in problems of the antiquity of Precambrian life and the organic geochemical indicators of biological processes in ancient terrestrial environments. Attention is centered here o the paleobiological aspects of the Nonesuch Shale of Northern Michigan, but reference is made also to the much older "Michigamme" coal and associated shale. Concerning the latter, chemical analyses, X-ray diffraction studies, petrographic examination and paleontological study indicates that the coal is a true coal, partially metamorphosed and of biological origin, probably derived from blue—green algae. The Nonesuch Shale, a 1000 million year old economically important cupriferous sedimentary ore shows remnants of organic preservation interpreted as algal residues and quite remarkably, the presence of small amounts of a syngenetic paraffiriic crude oil. Analysis of the oil reveals the presence of a wide range of aliphatic and aromatic hydrocarbons. Gas liquid chromatographic analysis of organic extractives of the shale reveal the presence of the isoprenoid hydrocarbons phytane and pristane, presumably derivatives of chlorophyll breakdown. Another presumed chlorophyll derivative a vanadyl porphyrian complex has been identified. A general discussion is presented concerning the presumed paleoenvironment of the Nonesuch Shale deposition. (1) Department of Biology, Harvard University; Cambridge, Massachusetts. �THE GEOCHRONQLOGy OF THE KEWEENAWAN ROCKS AT WHITE PINE, MICHIGAN Sambhudas Chaudhuri(1) and Gunter Faure(2) Age determinations by the total-rock Rb-Sr method of several suites of felsite from the White Pine area of Michigan indicate dates ranging from 978+40 m.y. to 1100+25 m.y. A specimen of felsite from Government Peak of the Porcupine Mountains was dated at 1042+6 m.y. Assuming that the Porcupine Mountains are an anticline, this date sets an upper limit to the time of deposition of the overlying Nonesuch Shale. Another upper limit is provided by dates of 1107 m.y. and 1180 m.y. for two pebbles from the lower sandstone unit in the White Pine Mine. Nine samples of mineralized and unmineralized rock from the basal section of the Nonesuch Shale exposed in the mine workings of the White Pine Mine were analyzed. These samples form a good co-linear array in coordinates of Rb87 / Sr86 and Sr87 / Sr86. The apparent age, calculated from the slope of the isochron, is 1075± 50 m.y. The initial Sr87 / Srd6 ratio is 0.7080+0.001. The apparent age for the Nonesuch Shale is interpreted to be slightly greater than the time of deposition because of the probable incorporation of inherited radiogenic Sr8' into the sediment at the time of deposition. The isotope composition of strontium of a thin bed of limestone in the basal portion of the Nonesuch Shale was measured. The Sr07 / Sr86 ratio was found to be 0.7058. Using the data of Hurley, Fairbairn and Pinson on the isotope composition of carbonate rocks, a time of deposition of about 1000 m.y. is indicated for this limestone. This appears to be the first age determination of a carbonate rock by the isotope composition of its strontium. The isotope composition of lead extracted from chalcocite in the ore at the White Pine Mine was found to be anomalous. This suggests that the lead in the ore was mixed with radiogenic lead and favors an epigenetic rather than a syngenetic origin for the copper sulfide in the basal portion of the Nonesuch Shale. (1) (2) Department of Geology, Kansas State University; Manhattan, Kansas. Department of Geology, The Ohio State University; Columbus, Ohio. 6 �7 GEOCHEMISTRY OF THE NIPISSING DIABASE John A. Coiweii(l) The Nipissing quartz diabase intrusives occur as sheets and dykes intruding the Huronian rocks in the area between the eastern end of Lake Superior and Lake Temiskaming. An acceptable age for the Nipissing is about 2.1 billion years * , and is significant in placing a lower limit on the age of the Huronian in Ontario. Pe trographic, chemical, and spectrographic studies indicate that the various phases of the diabase, which range from olivine norites to granophyres and aplites can be explained as due to gravitational differentiation of the diabase magma. Lateral as well as vertical differentiation has occurred in the sheet intrusions due to their undulating character. * References: Lowdon, J. A., et al. 1963. Age determinations and geologic studies. Geological Survey of Canada Paper 62-17, p. 92. Van5chumus, R. 1965. The geochronology of the Blind River-Bruce Mines Area, Ontario, Canada. Jour. Geol., v. 73, p. 755—780. Department East of Natural Science, Michigan State University; Lansing, Michigan. �8 A REGIONAL GEOPHYSICAL STUDY OF THE PORT COLDWELL COMPLEX, ONTARIO John D. Corbett(1), William 5. Hinze(2), and George B. ecor(2) Regional geophysical studies were conducted on the north shore of Lake Superior in the vicinity of Marathon, Ontario, to study the structure of the Port Coidwell Complex, a sub-circular intrusive approximately 16 miles in diameter. Surface geological mapping indicates that the complex is composed predominately of syenitic rocks with a discontinuous peripheral band of gabbro. A positive magnetic anomaly is associated with the intrusive, but strong negative anomalies correlate with the gabbro on the east and northeast margins. Analysis of a suite of oriented samples shows that the gabbroic rocks have a strong, variable remanent magnetic polarization. The results of two and three dimensional magnetic model analysis, using both induced and remanent magnetic polarizations, proved to be only partially successful in matching the observed anomaly. A highway gravity profile from White River to Schreiber, Ontario, a distance of 110 miles, shows a positive 65 milligal gravity anomaly over the Port Coidwell Complex. Comparison of this anomaly with the theoretical gravity effect of two and three dimensional models based upon available geological information indicates that the Complex consists primarily of gabbroic rocks extending to a depth of 8 miles. The intrusive is an asymmetric truncated funnel structure having a near vertical contact on the east and an approximate 450 contact on the west. Combined gravity and magnetic analysis utilizing Poisson's relation was employed as an alternate method of investigating the physical properties of the intrusive. The results of this study verify the presence of a strong remanent magnetic polarization associated with the gabbro along the eastern margin and also indicate a strong, positive remanent magnetic field over the central portion of the complex. This evidence suggests an explanation for the difficulty in matching the observed magnetic anomaly with the magnetic model study. (1) Geophysical Division, The Anaconda Company; (2) Department of Geology, Michigan State University; East Lansing, Michigan. . , Utah. �PRELIMINARY MAC NETOTELLURIC RESISTIVITY RESULTS ACROSS THE WISCONSIN ARCH Forrest L. Dowling(l) Magnetotelluric resistivity measurements have been made at five of a projected fourteen sites across the Wisconsin Arch. Surface electric impedances are being computed from the measurements to yield apparent resistivity and phase information as a function of frequency. Resistivity models of the crust and upper mantle are fitted to the measured curves. Tentative results are to be presented. w Geophysical and Polar Research Center, University of Wisconsin; Madison, Wisconsin. �10 STRATIGRAPHY, STRUCTURE, AND METAMORPHISM OF ROCKS IN THE UPPER PART OF THE ANIMIKIE SERIES IN THE MARENISCO-WATERSMEET AREA, MICHIGAN * Crawford E. Fritts (I) Recently completed mapping has shown that a monoclinal sequence including the Copps Formation of Allen and Barrett (1915) and four con- formably overlying stratigraphic units is at least 40,000 feet thick. This sequence is placed above the Menominee Group within the Animikie Series of James (1958) and is interpreted as one of the least deformed parts of what Allen and Barrett (1915, p. 131) referred to as the "Michigamme slate series' of late Huronian age. A thin conglomeratic quartzite at the base of their Copps Formation is correlated with Goodrich Quartzite of the Marquette district. At least 10,000 feet of graywacke—slate of the Copps Formation and many thousands of feet of east-trending, graywacke-slate in the upper part of the monocline near Paulding are lithologically similar to rocks in the Marquette and Iron River -Crystal Falls districts mapped as Michigamme Slate, which previously was thought to be about 5, 000 feet thick. It would appear that east—trending rocks formerly interpreted as isoclinally folded Michigamme Slate in a broad region east of the map area may actually be part of the monoclinal sequence. An east-trending fault accounts for a 5-mile apparent right lateral offset of Ariimikie rocks near Barb Lake and for the abrupt termination of iron—formation at the Banner exploration. The fault also forms the north boundary of a dome-like stock of the Wolf Lake Granite of Allen and Barrett (1915). Emplacement of this granite, metamorphism of the Animikie Series, and displacement along the fault most likely occurred during the Penokean orogeny in post-Animikie, pre-Keweenawan time. References: Allen, R. C., and Barrett, L. P., 1915, Contributions to the pre-Cambrian geology of northern Michigan and Wisconsin: Michigan Geol. and Biol. Survey, Pub. 18, geol. ser. 15, p. 13—164. Hamblin, W. K., 1958, The Cambrian sandstones of northern Michigan: Michigan Geol. Survey Pub. 51, 146 p. James, H. L., 1958, Stratigraphy of pre-Keweenawan rocks in parts of northern Michigan: U.S. Geol. Survey Prof. Paper 314-C, p. 27—44. * Work done in cooperation with the Geological Survey Division of the Michigan Department of Conservation U. S. Geological Survey; Denver, Colorado. (1) �rr mafic lava flows Keweenawan Series UNCONFORMITY Graywacke—slute near Paulding of Allen and Barrett 11915) Wolf Lake Granite wg UNCONFORMITY ks, quartzific sandstone k, Cj Jacobsville Sandstone of Hamblin 1958) L) Hcc -.iz 2 e bu EXPLANATION 4 B 0 MILES 1 Cup Lake z Figure I--Generalized geologic nap of the Morenisco—Watersmeet area, Metatut f and tuffaceus metagraywacke; mb'rar quartzite, conglomerate, and magnetic iran-formation i/n lower part, includes possible pillow /ava(y) east of Cup Lake Rocks near ci Graywacke near Banner Lake Upper part includes magnetic iron-formation, especially south of Barb Lake fault bt, metatuff and magnetic iron -formation bf, p//low lava and fragmental va/conic racks Rocks near Blair Lake bu, mefavo/canic and mefasedimentary racks undivided 0 Mich. Gneiss gn near Mount Kimberly r Grnnite near Nelson Creek UNCONFORM/TYf?) part of Ankn/kie Series, possibly older than granite near Ne/son Creek Magnetic sfrata of Marenisco Range Strotigraphib position uncerfai/n possibly ml UNCONFORMITY Copps Formation of Allen and Barrett/IBIS) Groywacke-slafe overlying thin basal conglomerate �INFLUENCE OF FAULTING ON DEPOSITION OF CLASTIC INTERBEDS IN NEGAUNEE IRON-FORMATION NEAR PALMER, MICHIGAN * Jacob E. GairW Interbeds and lenses of ciastic sedimentary rocks-—graywacke and impure quartzile—•-rre conspicuous in the chemically deposited hematitic, meg netitic, and sideritic Neaunee Iron-Formation near Palmer, Michigan (S. A. Tyler and V;. H. Twenhofel, 1952; J. T. Mengel, 1956; J. F. Davis, 1965.) The ciastic interbeds range in thickness from about 1/30 inch to S9 feet, Detrital quartz occurs not only in discrete layers hut also a- scattered grains in many ferruginous leminee of iron-formation. Clastic sediment in the south—central part of the Palmer hasin makes up 3 to 9 percent of the Negaunee: 3 to 6 psrcent measured in discrete layers and an estimated 2 to 3 percent as scoterec1 querta jreins. In any one drilled section, there are h'mdred3 of rather evenly spaced clastic lenses less than 1/2 inch thick and relatively fcw irregularly spaced layers more than 1. foot thick. In several drill cores of 300 to 700 feet of iron-formation, oniy a few intervals of more than 10 feet do not contain some clostic sedimentary beds. In contrast to the iron-'fcnnatioj-A near Palmer, the Negaunee of neighboring areas end :recamb:ian iron-fcrmation generally are virtually devoid of clastio debris. The depositional environment near Palmer during Negaunee tiate, therefore, must have differed in some respect from that of ncighrorin areas and from that of most other Precambrian iron•iormstions. South of the areas c.i ciasti—bearing iron-formation——along the south ec'ge of Lhe Palmer basin and to tIi west far about 2 miles al.ong the flank of the lvIarquctto rynclincrilmm-—cra;:itjc gneiss older than the Negaunee has beer. piLfted to die south along conspicuous zones of shearino and fauting. dthouqh ost of d e movement in the fault zones occurred ter c.epcsition of the Negaunee Iron—Formation, it is inferred from the oresanci e cl' obe:::jyn iron—formation adjacent to the faults that diploceme befl, 'a at 1mst as early as Negaunee time, and that the c1atic mF riel c !nsn-formatjon was eroded : (Continued next page) * Publication wthorized h the Director, U. S. Geological Survey. Work done in cooperation with the Geological Survey Division of the Michigan Department of Conservation. U. S. Geological Surrey; 1i �12 from the up-faulted areas of gneiss. The numerous small lenses of clastic sediment isolated in the iron-formation suggest that unconsolidated detritus collecting at the edge of upfaulted areas was repeatedly dislodged in small portions by minor crustal movement in the fault zones and dumped into iron-silica muds accumulating to the north. References: Davis, J. F., 1965a (1) A petrologic examination of iron-formation associated graywackes and pyroclastic breccias within the Negaunee formation of the Palmer area, Marquette district, Michigan: Unpub. Ph.D. thesis, University of Wisconsin, 179 p. (2) Petrology of Precambrian iron-formation and associated rocks, Palmer area, Marquette district, Michigan: Geol. Soc. Am., Program, 1965 Annual Meeting, p. 42. Mengel, J. T. , Jr., 1965, The relationship of clastic sediments to iron-formation in the vicinity of Palmer, Michigan: Unpub. M. S. thesis, University of Wisconsin. Tyler, S. A. and Twenhofel, W. H., 1952, Sedimentation and stratigraphy of the Huronian of upper Michigan: Am. Jour. Sd., V. 250, p. 1—27; 118—151. �GEOCHRONOLOGY IN THE LAKE SUPERIOR REGION S. S. Goldich1 During the past 10 years advances in the analytical techniques and a growing appreciation of the geologic factors have broadened the scope and usefulness of radiometric dating. Specific advances include improvement in the lead-alpha method, application of K-Ar to amphiboles, developm ent of Rb-Sr through the whole-rock and mineral-component technique, and the wider application of U, Th-Pb isotopic analyses. Early lead—alpha age determinations on Lake Superior rocks are not reliable. The large number of K—Ar and Rb-Sr determinations made in a number of laboratories, largely on micas, are analytically reliable within the limits of error assigned. The micas, however, are highly susceptible to metamorphism, and mica ages, as a result, cannot be assumed to give the time of initial crystallization or formation. In some cases K-Ar ages on hornblende have given some assistance, but the greatest progress in penetrating the metamorphic barriers has come through the use of Rb—Sr and U-Pb analytical procedures. K-Ar and Rb-Sr age determinations on micas from the Morton Gneiss of southwestern Minnesota, for example, indicate an age of 2.5-2.6 b.y. The improved lead-alpha method, however, gave an age of 3.0 b.y. for zircon, and isotopic U-Pb determinations on zircon from the Morton Gneiss gave Pb207/Pb206 ages of 3.2 b.y. and a conchordia age of 3.5 b.y. Isotopic U-Pb age determinations on zircon concentrates and Rb-Sr data for whole-rock and mineral component samples from the Lake Superior region show some of the geologic complexities that are now becoming apparent. One of the geologic factors that complicates the interpretation of radiometric ages is the effect of weathering on the K-Ar, Rb-Sr, and U-Pb decay systems. Department of Earth and Space Sciences, State University of New York; Stony Brook, New York. �IDENTIFICATION OF SEISMIC REFRACTORS IN THE LAKE SUPERIOR SYNCLINE H. C. Halls(1) and G. F. west(l) P-wave velocities at hydrostatic pressures of up to 2 kilobars have been measured in Keweenawan volcanic and sandstone cores collected from numerous localities around Lake Superior. Seismic refraction surveys seem to indicate as many as four refractors within the upper 15 Km. of the crust beneath the lake. An attempt here is made to identify the refractors in terms of Keweenawan geology by comparing the velocities obtained in the laboratory and the field. Some implications of these results on the regional structural picture will be presented. Geophysics Laboratory, Department of Physics; University of Toronto; Toronto, Ontario. �K-Ar HORNBLENDE AGES FOR GRANITES AND GNEISSES AND K-Ar AGES FOR DIKES IN MINNESOTA Gilbert N. HanSon(l) A number of investigators have shown that hornblerides retain radiogenic argon during metamorphism to a greater extent than do the micas. As a comparison with K-Ar and Rb-Sr ages for biotite and other ages, such as zircon U-Pb, K-Ar ages have been determined on hornblende concentrates from six igneous and metamorphic rocks in Minnesota. Hornblende from the Giants Range Granite near Ely gives an average K-Ar age of 2.6 by, from the Saganaga Granite an average age of 2.65 by, from the Knife Lake schist near Birch Lake an age of 2.65 by, from the Rockville Porphyritic Granite at Rockville an age of 1.80 by, from the Morton Quartz Monzonite Gneiss at Morton an average age of 2.6 by, and from the hornblende-pyroxene gneiss at Granite Falls an age of 2. 75 by. In each case the hornblende age is essentially the same or older than the biotite ages and essentially the same or younger than the zircon U-Pb ages. Mineral and whole-rock K-Ar ages indicate that besides the late Keweenawan mafic intrusions at about 1.1 by there are two more periods of mafic intrusion in Minnesota at 1.6-1.8 by and at about 2.1 by. (1) Department of Earth and Space Sciences, State University of New York; Stony Brook, New York. 15 �HYDROCARBON COMPOUNDS IN IGNEOUS ROCKS E. Wm. Heinrich(1) Solid uraniferous hydrocarbon compounds in igneous and hydrothermal rocks have long been known (1868) from Swedish (granite—gneiss, iron-ore skarns, pegmatites, veins), Canadian (pegmatites), and Australian occurrences (Cu lodes). In 1928 Ellsworth applied 'thucholite' (Th, U, C, H, 0-lite) to radioactive hydrocarbon in pegmatites in Ontario and Quebec. Since then other occurrences of thucholite have been noted in veins and lodes, including Boliden, Sweden; Goldfields, Saskatchewan; Port Arthur and Blind River, Ontario; Laxey, Isle of Man; Witwatersrand, South Africa; and Front Range, Colorado. Non-radioactive hydrocarbons in such deposits, being less conspicuous, have not been recorded as frequently. Among these are solid bitumen and methane in the Keweenawan Cubearing basalts of northern Michigan. Until recently all such material was reported only from calc-alkalic igneous rocks (granite to basalt) and their derivative dikes, veins and lodes. In the late 1950's organic compounds (solid and gaseous) were discovered in alkalic rocks of the Kola Peninsula, U.S.S.R. In the Khibina and Lovozero massifs large quantities of hydrocarbon gases occur in intergranuler pores, microfractures and vacuoles in minerals. They are composed of 70-90% hydrocarbons and 3-10% hydrogen with some CO2 and CO. Among the hydrocarbons methane predominates; also present are ethane, propane, commonly isobutane, rarely pentane. Volumes up to 243 cm3/kg have been obtained. In Colorado carbonatites and related thorium veins in the Wet Mountain district (Fremont and Custer Counties) and in the Iron Hill district (Gunnison County) have long been known to emit fetid gas when broken. Our studies on the Goldie carbonatite show this gas is a mixture of C5 and C6 hydrocarbons along with F2, HF and F20. The fluorine has been derived from the radioactive structural degradation of fluorite, and the noisome odor comes from the fluorinated hydrocarbons. Several genetic theories have been applied to the origin of thucholites: 1) radioactive polymerization of natural gas or petroleum; 2) interaction of uraninite and aqueous solutions containing organic materials (oil—water emulsion); 3) derivation from humic coal constituents. Whatever the process, there is evidence that this carbon at one time was biogenic-sedimentary. For gaseous (Continued next page) (l) Department of Geology and Mineralogy, The University of Michigan; Ann Arbor, Michigan. �and solid hydrocarbons of alkalic rocks and carbonatites the evidence is strong that these compounds are primary and rnagmatlc or hydrothermal and that the carbon is juvenile: 1. They occur in primary vacuoles formed and filled at the time of crystallization of such host rock-forming species as nepheline. 2. The ratios of individual hydrocarbon compounds are specific for a particular mineral. 3. Wall rocks of the complexes contain anomalously high amounts of methane for about 100 meters from the contact. 4. No geologically realistic models can be constructed that show that sedimentary natural gas or petroleum could have reached the alkalic rocks. 5. The 12C /13C ratio of gases and bitumens from alkalic rocks differs markedly from those of sedimentary gases and petroleum. �A STUDY OF CLASTICS IN THE NEGATJNEE IRON FORMATION OF MICHIGAN RobertW. Henny(l) An investigation was conducted on the relationships between a number of clastic lens-shaped bodies and a portion of the Negaunee Iron Formation. The principal study area was located at the abandoned Moore Mine in the Cascade Range, a downfaulted block on the southern flank of the Marquette Synclinorium, approximately 12 miles south of Negaunee, Michigan. Here the iron formation is continuously exposed in cross—sectional profile along its strike for a distance of 0.3 mile (360 feet wide.) More than forty clastic lenses ranging from a foot to over a hundred feet in length and up to fifty feet in width were mapped in detail. The depositional relationships between the lenses and the iron formation are varied; the majority of lenses are essentially conformable with the iron formation. Some of the conformable lenses are gradational at their lateral boundaries, some exhibit miniaturized on-lap off-lap features, while others have merely warped the underlying layers of iron formation. The unconformable lenses are of two types, channel fills and isolated blocks. The iron formation contains a two percent background of rounded sand grains which are equally dispersed among the chert and hematite layers. This percentage of sand grains is observed to increase noticeably when a clastic lens is approached from beneath. The clastics consist of metamorphized mixtures of rounded and angular fragments of chert, hematite, quartz, quartzite and granite, together with varying quantities of sand all in a matrix consisting of varying proportions of , chert and hematite. Petrographic and binocular analyses were used to divide the clastics into five lithological groups and a number of sub-groups on the basis of their mineralogical and textural characteristics. It is deemed significant that only one lithology is found in a given lens and that a particular lithology always maintains the same depositional relationship with the iron formation. A method for chemically disaggregating some of the clastics was developed enabling roundness, sphericity, and size distribution analyses to be made. Results showed the sand grains to be similar to those found in typical beach washed sands. Using the above relationships, mechanisms of deposition are postulated for each lens type. The analysis is then extended to several other clastic zones in the immediate vicinity with areal correlations made. (Continued next page) Department of Geology, Michigan State University; East Lansing, Michigan. �9 Conclusions would support a shallow water environment of deposition where chert and hematite were deposited in alternating layers under proper environmental conditions. The major source of clastics was derived from a low lying land mass to the south. Except for one occurrence all the clastics observed appeared to have been well worked sediments prior to their transportation into the basin. Re-worked beach sands were regularly supplied to the basin while occasionally off—shore currents created lenses and beds of sands out into the basin. The dispersion of these sands appears to have been a normal condition in the area since they are observed throughout the area. During intervals when portions of the basin were above wave base or even above water level, clastics were introduced to the basin by stream transport. Finally at a few localized areas large masses of clastics were rapidly deposited via slides and/or turbidity currents. �20 KEWEENAWAN VOLCANIC ROCKS NEAR IRONWOOD, MICHIGAN * harold A. HubbardW Two sequences of Keweenawan volcanic rocks are present in the Ironwood area, Michigan, west of the 90th meridian. A younger sequence, about 15,000 feet thick, is equivalent to the Portage Lake Lava Series of Keweenaw Point. An older sequence of traps of the South Range, about 8,000 feet thick, is separated stratigraphically from the younger rocks by more than 7,000 feet of sedimentary rocks. These volcanic rocks have previously been described as one continuous sequence. The equivalents of the Portage Lake may be traced to outcrops of the Portage Lake Lava Series on Keweenaw Point by a continuous broad band of large linear magnetic anomalies. Their lithologic continuity is also confirmed by the presence of many ophitic basalts and volcanic conglomerates in both areas. The upper flows of the South Range contain groundmass feldspars that are uniformly more sodic, and generally finer grained, than the Portage Lake flows. A few of the upper South Range flows are porphyritic, having feldspar phenocrysts as much as 1-1/2 inches across. The lowermost South Range flows are interbedded with a few well-sorted lower Keweenawan-type sandstones. West of Bessemer, the lowest flow is a 'pillow" lava whose emplacement locally contorted the upper few inches of the underlying even-bedded sandstone layer. These features indicate that the lower Keweenawan sandstones in the South Range traps probably are an uninterrupted sequence. Re-examination of regional relationships may show that the oldest volcanic rocks in some localities should be assigned to the lower Keweenawan or that the middle Keweenawan should be sub-divided. Although no consolidated rocks are exposed in the 2-mile-wide belt between the uppermost South Range extrusive rock and the lowermost Portage Lake flow, the belt is characterized by uniformly small magnetic anomalies that differ in character from those of the South Range and Portage Lake volcanic sequences. These unexposed units (Continued next page) * Publication authorized by the Director, U. S. Geological Survey. Work done in cooperation with the Geological Survey Division of the Michigan Department of Conservation. 1 U. S. Geological Survey; Washington, D. C. �21 are probably sedimentary rocks or acid volcanic rocks. East of the Ironwood area, the band of linear magnetic anomalies associated with the South Range traps diverges from that of the Portage Lake. Kenneth Books of the U. S. Geological Survey has found that the paleomagnetic field directions of the Portage Lake Lava Series near Ironwood are similar to those of the lavas of Keweenaw Point, and that the paleomagnetic field directions of the South Range traps are distinctly different. The paleomagnetic properties of the rocks within each sequence are internally consistent. For these reasons a significant age difference between the sequences Is indicated. �22 GRAVITY ANOMALIES OVER LAKE SUPERIOR AND SURROUNDING AREA AND THEIR STRUCTURAL IMPLICATIONS M. j. s. inries(1) and A. K. Goodacre(l) During 1963 and 1964 the Dominion Observatory carried out reconnaissance underwater gravity measurements in Lake Superior, and regional gravity surveys over the adjacent Canadian Shield in Ontario. These surveys outlined large areas of relatively positive Bouguer anomalies in Lake Superior and in a zone extending 600 km north from Chapleau through Kapuskasing to Moosonee on James Bay. The anomalous areas reflect large quantities of basic material that have been emplaced high within the crustal column, perhaps through process of crustal rifting. Geological and geophysical mapping by provincial and federal government departments has defined a north to north-east. trending zone of shearing and faulting with associated linear magnetic anomalies. This fault zone, and the gravity and magnetic anomaly belts cut directly across regional trends of early Precambrian rocks. Uplifted blocks of high-grade metamorphic rocks, minor basic and ultrabasic intrusions, and the presence of alkaline intrusive complexes together with the disappearance of the Archaean volcanic-sedimentary rocks along the axis of the gravity high suggest that the Kapuskasing fault zone may be a deeplyeroded counterpart of an East African rift valley. Gravity and magnetic anomaly patterns over the Michigan Basin suggest a possible extension of this structure to the south. Dominion Observatory, Department of Energy, Mines, and Resources; Ottawa, Ontario. �23 SOME PROPERTIES OF MICHIGAN CHERTS Allan M. Johnson(l) and Albert P. Ruotsala(1) Michigan Pleistocene gravel deposits contain some aggregate types that fail under freeze-thaw and other severe conditions. Cherts, of the variety associated with carbonate rocks, comprise a large percentage of the non—durable aggregate. The major minerals comprising cherts, in highly variable proportions, are quartz, calcite, and dolomite. X-ray diffraction patterns exhibited peaks attributable to clay minerals and possibly some unstable hydrated calcium silicates. Textures of the minerals comprising cherts also vary considerably. Petrographic studies of quartz showed that sizes varied from coarse sand to cryptocrystalline varieties. An X-ray line broadening technique indicated an average grain size of 700 angstroms for cryptocrystalline quartz. Water vapor adsorption values were variable and apparently reflected the available surface area. Cation-exchange capacities of Michigan cherts were found to be low and on the order of those exhibited by kaolinite (3 to 15 meq/100 gm). Evidently these two phenomena are related. Dissolution rates of calcium and magnesium from cherts were also variable and may be useful in predicting the durability of chert under freeze-thaw conditions. Department of Geology and Geological Engineering, Michigan Technological University; Houghton, Michigan. �24 REFRACTION SEISIvIIC SURVEYS ON ThE MID-CONTINENT GRAVITY ANOMALY IN MINNESOTA AND WISCONSIN S. h. JohnsonO) and P. R. Farnham0Steep gravity and magnetic gradients over the prominent Midcontinent gravity anomaly suggest major fauling of Middle Keweenawan basic igneous rocks which are thought to underlie Upper Keweenawan red clastics into southeastern Minnesota. Seventy short (4-8 miles) refraction profiles were taken at regular intervals perpendicular to the anomaly trend. Results indicate a vertical displacement of at least 7000 feet along the southward projection of the Douglas fault into eastern Minnesota and a similar vertical displacement along the projection of the Lake Owen fault in western Wisconsin. The resulting horst structure is bounded on both sides by thick wedges of presumably Upper Keweeriawan red clastics. No clastics appear to overlie the horst except in possible graben structures within the western part of the horst itself. The presence of thick wedges of sedimentary material on both sides of the horst as suggested by gravity data is confirmed. Underlying the red clastics in the flanking sedimentary troughs appear to be Keweenawan basic extrusive igneous rocks close to the fault and older Precambrian crystalline basement at a greater distance from it. In southeastern Minnesota, the basement is overlairi by up to 4000 feet or more of Keweenawan red clastic sandstones and Paleozoic sediments. Department of Geology and Geophysics, University of Minnesota; Minneapolis, Minnesota. �EVIDENCi ON THE PHYSICAL ENVIRONMENT OF IRON-FORMATION DEPOSITION Gene L. LaBerge(1) Physical features, such as size, shape, and character of the grains, bedding characteristics, and sedimentary textures and structures indicate that iron-formations may have behaved essentially as particulate sediments at the time of deposition. Granule—bearing iron—formations have a grain size and a variety of sedimentary features remarkably similar to those of sandstones. Non-granular (even-bedded or "banded") iron-formations have a grain size and bedding characteristics similar in many respects to siltstones or argillites. There are, in fact, a number of important similarities between iron-formations and clastic limestones which will be pointed out. Microscopic features in granule bearing iron-formations suggest that many granules have been formed by reworking of earlier formed silt size particles--perhaps from a non-granualr iron deposit. In other words, it appears that most iron-formations, particularly the chert in them, may have been initially deposited as silt size particles. The factors controlling the size of these "original(?)" silt size particles is problematical; however, it is possible that their size may have been organically controlled. Physical conditions, such as depth of water, current action, and wave action would have been paramount in determining whether the resulting deposit was thinly laminated silt size particles or more massively bedded and of sand size grains. If this hypothesis is correct, the nature of observable physical features should provide impoartant clues regarding the depositional environment--both physical and chemical--in which iron-formations formed. Department of Geology, Wisconsin State University; Oshkosh, Wisconsin. �26 CHARACTERISTICS OF MAGNETIC DATA OVER MAJOR SUBDIVISIONS OF THE PRECAMBRIAN SHIELD A. S. MacLaren(l) and Brian CharbonneauU) Airborne magnetic data when correlated with regional geology indicate major dislocations at contacts of subdivisions of the Canadian Precambrian Shield. These are described between the Superior and Churchill provinces in Manitoba, between the Grenyule and Superior provinces south of Sudbury and east of Chibougamau in Quebec. An internal disruption of the crust in the Superior province is described and contrasted with the 'fronts between the Churchill and Superior provinces and between the Grenville and Superior provinces. It is concluded that airborne magnetic data is useful in the delineation of major rift zones and sub-provinces in Precambrian Shield areas. Geological Survey of Canada; Ottawa, Ontario. �SUBDIVISIONS OF THE NEGAUNEE IRON FORMATION SECTIONS 7, 8, T47N, R26W, 1v1ICHIGAN Joseph j. wiancusoU) and Jack W. Avery(2) Accurate stratigraphic correlations within the Negaunee Iron Formation have been difficult previously because of the apparent mineralogical and textural uniformity present coupled with the lack of persistant marker horizons. However, recent work on the unoxidized and related oxidized iron formation of sections 7 & 8 T47N, R26W has made it possible to subdivide the Negaunee Iron Formation into 8 members based on mineralogy, texture, and metallurgical analyses. The subdivisions, which vary in thickness from less than 50' to over 300', were originally distinguished for economic reasons, but have been clarified, refined and extended to include several marker horizons which can be traced laterally for more than a mile. Members were picked to include layers which could be recognized and traced through the unoxidized iron formation and its oxidized equivalents. (All of the hematite and goothite that has been noted is secondary after magnetite, siderite, or iron silicate.) Because of stratigraphic work the structure of the northeastern portion of the Marquette Range has been greatly clarified. The extreme apparent thickening of the iron formation and the apparent complex system of diabase sills can be successfully explained by repetition due to a series of east-west and north-west trending fault systems. The correlations can be traced very generally south through the Bellevue and Empire sections of Cleveland Cliffs but more detailed work must be done in order to delineate fades changes and thickness changes in the individual members. (1) Department of Geology, Bowling Green University; Bowling Green, Ohio. Jones & Laughlin Steel Corporation; Negaunee, Michigan. �RELATIONShIP BETWEEN SEISMIC AND AEROMAG NETIC SURVEYS, EASTERN LAKE SUPERIOR R. p• ivleyerW and L. Ocoia(1) In the course of seismic work along the 1963 east-west Main Line a fault has been found in about the position predicted from Seismic evidence rests princiaeromagnetic data (Hinze, et al) pally on the redundancy of data provided by three remote-controlled tape recording buoys moored northeast of Keweenaw Point combined with data taken by the University of Toronto at Otter Cove, Ontario, . in 1963 (Steinhart) References: Hinze, W. J., N. W. O'l-Iara, J. W. Trow, and G. B. Secor, "Aeromagnetic Studies of Eastern Lake Superior," Geophysical Monograph No. 10, 1966. Steinhart, John S., "Lake Superior Seismic Experiment: Shots and Travel Times, J. Geophys. Res., Vol 69, No. 24, 1964. (I) Department of Geology and Geophysics, The University of Wisconsin; Madison, Wisconsin. 2B �MINERALOGY AND PETROLOGY OF THE MINERAL LAKE INTRUSION, NORTHWESTERN WISCONSIN James F. Olmsted(l) The Mineral Lake Intrusion is a 4500 meter thick tabular body which has been emplaced near the base of the Middle Keweenawan volcanic series of northwestern Wisconsin. It is a moderately well differentiated strataform intrusive consisting of: ultrabasics 1%, anorthosltic olivine gabbro 11%, cjabbroic anorthosite and anorthosite 73%, ferrodiorite 8% and granitic rocks 7%. A basal chill zone has been located and its iron rich composition indicates that it is not representative of the whole intrusive but is the product of the differentiation. A pronounced primary laminar arrangement of piagioclase laths is developed parallel to the base of the intrusion, suggesting the direction of flow during emplacement, but with rare exception, compositional layering is absent. Cryptic zoning of the mineral constituants has been determined with compositions varying from the base upward as follows: Clinopyroxene (Wo39, En42, Fs19) to (Wa36, En28, Fs36), Orthopyroxene (En70, Fs30) ton42, Fs58), Olivine (Fo65, Fa35) to (Fo22, Fa78) and Plagioclase (An60) to (An20). Plagioclase composition is constant from just above the basal chill zone nearly to the base of the ferrodiorite, suggesting the plagioclase was in contact with a large volume of liquid. Olivine is confined to the lower anorthositic olivine gabbro and the ferrodiorite. that during crystallization The trend of fractionation toward enrichment in iron and decrease in silica is similar to that of most large basic intrusions in which crystallization took place under low P0 conditions. This is confirmed by the strongly reduced state o2f iron throughout much of the intrusion. The highly anorthositic composition is explained by early crystallization of large amounts of mafic minerals which tended to settle in the magma body during its upward transport, while the lower density, more tabular plagioclase crystals were carried upward and concentrated at higher levels. The iron rich chill zone further indicates that considerable amounts of magnesian mafic minerals were removed from the magma before it reached the present level of exposure. (Continued next page) (1) College of Arts and Sciences, State University of New York; Plattsburgh, New York. �30 The strong orientation of the plagioclase laths and lack of compositional banding supports the view that any movement of the magma was in one direction (parallel to the base and upward along its tilted surface) rather than in the form of convection currents. This hypothesis is further supported by the presence of small volumes of ultrabasic rocks near the base and gradual upward decrease in mafic content until the anorthositic composition is obtained. �31 OXYGEN ISOTOPIC EVIDENCE OF METAMORPHISM IN TEE BIWABIC IRON-FORMATION, MINNESOTA E. C. Perry, Jr.0) and J. W. Morse(1) Oxygen isotope fractionation between coexisting quartz and magnetite (expressed as 1000 1nM) has been measured in samples collected along the easternmost 60 miles of the Biwabic Iron-formation outcrop belt. Fractionation varies from about 7 .5 (corresponding to about 7000 C) at the Duluth Gabbro Complex contact to a maximum value of 24. 3 (which probably corresponds to a temperature of (ioo° C). The metamorphic aureole produced by the Duluth Gabbro Complex is narrow and isotope fractionation measured between Auroa and Keewatin is constant within 1.5 units. Minnesota Geological Survey, The University of Minnesota; Minneapolis, Minnesota. �3 GEOLOGY OF PART OF ThE EAST GOGEBIC IRON RANGE, MICHIGAN * William C. prinz(1) Recent work in and near T. 47 N., R 44W. in the East Gogebic iron range essentially substantiates the mapping reported by R. C. Allen and L. P. Barrett in 1915, with a few noteworthy exceptions. Apparent thickening of the Ironwood Iron—Formation is now attributed to repetition of beds by strike faults; and the so-called "great graywacke-slate member" of the Ironwood is probably the Palms Quartzite brought up along these faults. Mafic volcanic breccia or agglomerate, tuff, and greenstone in the eastern part of the township are interbedded with rocks equivalent to either the upper part of the Ironwood IronFormation or the Tyler Slate. These strata are overlain unconformably by the Copps Formation of Allen and Barrett (1915). Large sills of mafic igneous rock that cut the Ironwood Iron-Formation have been metamorphosed, and one of them is truncated by Keweenawan basalt flows; they are therefore older than the Keweenawan. The unconformity at the base of the Copps still is recognized as one of great magnitude, but no evidence has been found to indicate that granite was emplaced during the post—Ironwood, pre-Copps interval. In this area, t.h Pr.que Isle Granite is a mixture of granite gneiss, and schist of early rather than middle Precambrian age. Rocks formerly described as "metamorphic phases" of the Palms Quartzite adjacent to the granite are mainly lower Precambrian gneiss. The close proximity of iron-formation and gneiss in the southeastern part of the township and the local absence of the Palms Quartzite are explained by faulting. The geologic structure of the Animikie Series is complex in the eastern part of T. 47 N., R. 44W. and the western part of T. 47 N., R. 43 W. To the west the period of major deformation of these rocks postdated the Keweenawan basalt flows, whereas to the east it was pre-Keweenawan. * Work done in cooperation with the Geological Survey Division, Michigan Department of Conservation. (1) U. S. Geological Survey; Beltsville, Maryland. �33 STRUCTURE AND STRATIGRAPhY, INCLUDING PRECAMBRIAN TILLITE, IN EASTERN DEAD RIVER BASIN, MARQUETTE COUNTY, MICHIGAN * Willard P. PuffettW The Dead River Basin in Marquette County, Michigan is a northwest-trending lowland floored by metasedimentary rocks of middle Precambrian age. Lower Precambrian rocks bound this basin in the Negaunee 7 1/2' quadrangle; they include layered amphibolite and massive greenstone of the Mona Schist on the north border and granodiorite and syenite on the east and south. Sheared metavolcanic rocks, mainly rhyolitic tuff, extend into the central part of the basin from the east, separating rnetasedimentary rocks on the south from those on the north. The metasedimentary rocks in the southern part of the basin include thin ferruginous graywacke, a thin iron-formation, and a thick sequence of slate, in part pyritic and carbonaceous. These strata are correlated with the Michigamme Slate. , The metasedimentary rocks underlying the north flank of the basin are markedly different from those on the south, and include coarse conglomerate as much as several hundred feet thick, conglomeratic graywacke, and chioritic graywacke and slate. A few contorted thin beds of pinkish-gray arkose are interbedded in the slates. These north-flanking rocks are probably in the basal part of the Arilmikie Series and are much older than the metasedimentary rocks underlying the southern part of the basin, which have been downfaulted for hundreds to thousands of feet along a zone of shearing now occupied by the metavolcanic rocks. Of particular interest in the northern group of strata are widely scattered rounded to subangular boulders of granitic rocks in the slates and graywackes. These boulders range in size from a few inches to nearly two feet in diameter. In some areas only one or two boulders are present in exposures of several hundred square feet of slates and graywackes; in other areas the boulders form lenses or beds that can be traced for several tens of feet. The anomalous occurrence of the very coarse material in the slates and graywackes is a significant and identifying feature of rocks that are considered tiflites in other Precambrian terranes, and a glacial origin is suggested for the metasedimentary rocks north of Dead River in the Negaunee 7 1/2' quadrangle. * Publication authorized by the Director, U. S. Geological Survey. Work done in cooperation with the Geological Survey Division of the Michigan Conservation Department. (1) U. S. Geological Survey; Marquette, Michigan. �34 COPPER MINERALIZATION IN ANIMIKIE SEDIMENTS OF THE EASTERN MARQUETTE RANGE, MICHIGAN R. C. Reed Early exploration in Kona dolomite of Middle Precambrian age copper mineralization at three locations in the eastern Marquette iron range. Veins of copper minerals were also encountered in iron formation in a mine at Ishpeming, Michigan. This is one of two areas of significant copper in Animikie sediments known to the writer. exposed The eastern-most mineralization is located in the NE 1/4 NW 1/4 section 1, T. 47 N., R. 25W. Chalcocite occurs in a tan, highlysheared siliceous slate, in veins and irregular masses, occasionally replacing pyrite. It is closely associated with quartz, chlorite, sericite and minor dolomite. At depth, some native copper is also found in red quartzite, occupying fractures and interstitially replacing quartz boundaries. Chalcopyrite replaced by ixior bornite is found approximately 4500 feet to the west in the NW 1/4 SE 1/4 section 2 of the same township. It occurs in veins, pods and coarse clastic bands in gray and tan slate. This mineralization, also, is associated with quartz, dolomite, chlorite and sericite. On the north limb of the syncline, near Enchantment Lake, copper was exposed by a test pit in the SW 1/4 NE 1/4 section 32, T. 48 N., R 25 W. Chalcopyrite, bornite, chalcocite are present in siliceous dolomite and vein quartz. Specular hematite and pyrite also occur. Veins of copper mineralization were exposed by development in the Cliffs Shaft iron mine in section 13, T. 47 N. , R 27 W. The veins cut the upper part of the Negaunee iron formation approximately 725 feet below the surface. The dominant mineral is bornite followed by chalcopyrite, pyrite and hematite. Bornite replaces chalcopyrite and is in turn penetrated by specular hematite. Most of the pyrite occurs as somewhat spherical masses of crystals enclosed in quartz. Spectographic analysis of ore samples from the Kona formation show the mineralized rock to be practically devoid of trace elements. Some titanium and manganese exist and barium and strontium were found in the eastern-most mineralized area. (Continued next page) (1) Geological Survey Division, Michigan Department of Conservation; Lansing, Michigan. �35 It is concluded that this mineralization most nearly approximates copper sulphides with some native metal found within and surrounding intrusives in the Keweenawan of Michigan. Similar mineralization has been reported within and adjacent to Keweenawan diabase intruding Animikie sediments in Minnesota. �3: AN AEROMAGNETIC SURVEY OF LAKE HURON G. B. ecor(1), w. j. HinzeW, N. W. OIHaraU) arid J. W. TrowW A regional aeromagnetic survey was conducted to determine the basement geology and tectonics of Lake Huron. During this survey approximately 6100 miles of flight lines spaced at six mile intervals were recorded with a digital recording proton precession magnetometer. The analysis of the aeromagnetic data combined with known geology suggests the following interpretation. The gneiss-amphibolite assemblage of Grenville age found in the northwestern portion of the Parry Sound District extends under Georgian Bay to the eastern shore of the Bruce Peninsula. A granite gneiss province underlies the Bruce Peninsula and continues southward toward Lake St. Clair. A discontinuous belt of positive magnetic anomalies extends from the Thumb of Michigan northeasterly to Killarney, Ontario. These anomalies originate from basic rocks, perhaps amphibolite such as are encountered elsewhere in the Grenville Province. The western portion of Lake Huron is divided into four major magnetic provinces with approximately east-west boundaries. The northern province coincides with the Penokean Fold Belt. The province immediately to the south in the vicinity of the North Channel is predominately granitic. This province lies adjacent to a basic igneous complex which extends south to Rogers City, Michigan. The province south of Rogers City and north of Alpena, Michigan has tentatively been correlated with an extension of the Animikie lithologies from the Northern Peninsula of Michigan. The Grenville Front trends southwesterly from the vicinity of Killarney, Ontario, through the eastern end of Manitoulin Island and continues southward to the northern tip of the Thumb of Michigan. (U Department of Geology, Michigan State University; East Lansing, Michigan. �37 HEAT FLOW IN LAKE SUPERIOR JohnS. SteinhartW, s. R. Hart(l), and T. J. Smith(1) The Lake Superior region is of particular interest to heat flow studies because of its location on-trend with the mid-continent gravity high and its situation on a crust which reaches anomalous thickness (>55 km). During summer 1966, 92 heat flow stations were occupied from the U. S. Coast Guard cutter Woodrush, concentrated chiefly in the central and western areas of the lake. Using oceanic sediment probe techniques, 75 of these stations achieved sediment penetrations (5-7 meters) such that corrections for the annual temperature cycle of the bottom water are rather small (0%). Uncorrectec heat flow values for these stations range from 0.43 — l.24J cal/cm —sec, and delineate two distinct regions: a belt along the western shore characterized by low values (0 . 4 0 and a central region of higher but very uniform values (1 .0 - 1. 2). The twenty measurements in this central region, covering an area of 5000 km2, show a mean deviation of less than 5%, and the average value for the region agrees within 10% with adjacent land borehole measurements reported by Roy and Birch. Values in the eastern lake are too scattered to establish a pattern but suggest at least a small region of lower values (0.7 — 0.8), with variations of up to 0.4 occurring in lateral distances of 15 km. A general correlation seems to exist between crustal structure and heat flow in the Lake Superior region. — The new data on the mean annual bottom water temperature of Lake Superior, considered with the data already in hand, supports the hypothesis that mean annual bottom temperature of temperate lakes is independent of climatic differences. This means that the heat flow measured in such lakes is not affected by small long term temperature fluctuations, provided the lake stays in the temperate class. U) Department of Terrestrial Magnetism, Carnegie Institution of Washington; Washington, D. C. . 9) �39 A SPECTROCHEMICAL METHOD FOR DIFFERENTIATING BETWEEN CARBONATE AND SILICATE FACIES Thomas waggoner(1) A spectrochemical method of differentiating a predominantly magnetite-chert-carbonate fades from a magnetite-chert-silicate facies has been developed and successfully applied to the primary magnetite—chert deposits of the Negaunee Iron Formation. Interpretation of the spectrochemical data depends on the distribution of the elements: magnesium, manganese, aluminum and iron. Manganese ions substitute readily for cations in the iron carbonates and only to a very minor extent in the iron silicates; the amount of manganese present can be used to approximate the quantity of carbonate present. A plot of manganese values versus magnesium values shows a trend of both elements which indicate higher concentrations of carbonate and possibly silicate. The Mn substitution is controlled by ion availability. To evaluate the amount of silicate present when both Mg and Mn values are high, a plot of magnesium values versus aluminum is considered. Aluminum occurs exclusively in the iron silicates which are products of a similar chemical environment to those of carbonates and magnetite. The comparative analysis becomes vague when detrital feldspar contributes to the aluminum values. High iron values in conjunction with low Mn and Mg values may show the presence of iron oxides, but caution must be exercised in accepting the apparent analysis due to the variable iron substitution of both the carbonate and silicates. Similarly, low Mg and Mn values with lower Fe show a predominence of chert. Indications are that the actual silica and phosphorous values do not help evaluate the fades types. Silica cannot be used to correlate facies types due to its erratic occurrence which is governed by stability fields not sufficiently clear at the time of the present study. Phosphorous has little value in making an accurate correlation due to its dependence on a pH condition and not on the other elements or their stability fields. (Continued next page) The Cleveland-Cliffs Iron Company; Ishpeming, Michigan. �:3 A practical use for determining a carbonate facies from a silicate facies is in ore separation and blending. Silicate ore is twice as hard as carbonate ore so that metallurgical difficulties are apparent. To predetermine the type fades, the spectrochemical method could be utilized, when standardized, for given types of carbonate—silicate ore. �41 TEXTURES AND COMPOSITIONS OF SILICATE AND SULFIDE ORE MINERALS FROM MINERALIZED ZONE, DULUTH GABBRO COMPLEX P. W. Weiblen(1) and Henry HaIIU) Mineralized gabbro samples from International Nickel Company's test pit on Spruce Road, near the South Kawishiwi River, Lake County, Minnesota, have been studied by microscopic and electron microprobe methods, as a first step in an investigation of the textures and compoitions of the mineralized rocks of the Duluth Gabbro Complex. The predominant rock type is a troctolite containing 10-20 percent olivine (Fa50), 50—70 percent plagioclase (zoned An50_65), 15—30 percent pyroxene (En35Fs20Wo45 and En61Fs36Wo3), 5—10 percent sulfide, 5-10 percent iron oxides, and minor biotite. Plagioclase and olivine occur as cumulate minerals; other phases are interstitial. Grab samples range in modal composition from anorthosite to troctolite having as much as 50 percent olivine. Silicate grains range in size from a few millimeters to several centimeters. The sulfide minerals have three textural modes of occurrence: 1) Interstitial, associated with or enclosed in interstitial pyroxene. Myrmekitic intergrowth with late stage interstitial pyroxene and plagioclase. 3) Fine—grained inclusions in silicates. The textures suggest that the sulfide minerals formed from an immiscible sulfide melt in a silicate melt in which gravity settling was the dominant rock-forming process. 2) Chalcopyrite, cubanite, pentlandite, hexaçonal and monoclinic pyrrhotite, and sparse sphalerite are the sulfide phases. Chalcopyrite and cubanite are intergrown; pentiandite forms separate grains, commonly euhedral, fractured, and enclosed in chalcopyrite or pyrrhotite. Sphalerite occurs as inclusions. Compositions of chalcopyrite, cubanite, pentlandite, and pyrrhotite are approximately stoichiometric within the error of electron microprobe analyses (1-5 percent). Department of Geology and Geophysics, University of Minnesota; Minneapolis, Minnesota �12 PROGRESS OF GEOPHYSICAL STUDIES IN LAKE SUPERIOR Richard J. Vold(1) Since 1964 the University of Wisconsin has been conducting an underwater gravity survey of Lake Superior and has occupied a total of 759 gravity stations. Since 1965 it has also been conducting a sub—bottom profiling survey, obtaining over 2300 miles of profiles. The results of the studies through 1965 were reported at the 1966 meeting of the Institute on Lake Superior Geology. Last seasons gravity efforts were concentrated east of 860 / longitude and west of 88° W longitude. The Isle Royale fault can be traced eastward to at least 88° W longitude. Between Isle Royale and the Keweenaw Peninsula a gravity low seems to reflect the synclinal structure. East of 86° V'J longitude a rel.ative gravity high indicates that the Keweenawan basic volcanics pass eastward through Michipicoten Island and turns south off Cape Gargantua. The gravity high continues its trend south just touching Mamainse Pt. where the gravity expression of the volcanic s disappears. The sub-bottom profiling appears to have penetrated to bedrock (upper Keweenawan or Lower Cambrian sandstone) in most areas. A few sub-bottom valleys were found, notably the deep trough just south of Beaver Bay, Minnesota which contains over 1000 feet of sediments. In the area between Isle Royale and the north shore up to 750 feet of sedimenLs were penetrated. Most of the deep north-south topographic features in eastern Lake Superior are filled with about 400 feet of sediments. A north-south profile in the center of a valley at 85°l6'VV longitude showed several deep gouges or eastwest sub—bottom valleys, with the largest being over 10 miles wide with over 600 feet of sediments. Department of Geology and Geophysics, University of Vvisconsin; Madison, Wisconsin. � 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, 1967 Description An account of the resource Institute on Lake Superior Geology. Michigan State University, East Lansing, Michigan. May 1-2, 1967. 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 1967 Contributor An entity responsible for making contributions to the resource Elso S. Barghoorn Sambhudas Chaudhury Gunter Faure John A. Colwell John D. Corbett William J. Hinze George B. Secor Forrest L. Dowling Crawford E. Fritts Jacob E. Gair S.S. Goldich H.C. Halls G.F. West Gilbert N. Hanson E. Wm. Heinrich Robert W. Henny Harold A. Hubbard M.J.S. Innes A.K. Goodacre Allan M. Johnson Albert P. Ruotsala S.H. Johnson P.R. Farnham Gene L. LaBerge A.S. MacLaren Brian Charbonneau Joseph J. Mancuso Jack W. Avery R.P. Meyer L. Ocola James F. Olmsted E.C. Perry Jr. J.W. Morse William C. Prinz Willard P. Puffett R.C. Reed N.W. O'Hara J.W. Trow John S. Steinhart S.R. Hart T.J. Smith Thomas Waggoner P.W. Weiblen Henry Hall Richard J. Wold 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/a15a5e130c20b64c45aa696010cca14f.pdf b21924937cbd5a866330efbd12a51453 PDF Text Text /SrT, %_ —W•#' .1W Twelfth Annual Institute on Lake Superior Geology May 6-7,1966 In Conjunction with the Mineralogical Society of America and the Society of Economic Geologists Host: Michigan Technological University Sault Ste. Marie, Michigan �U INSTITUTE BOARD OF DIRECTORS M0 A. D. H. A. W. Bartley, M. W. Bartley & Associates, Port Arthur, Ontario T. Broderick, Inland Steel Company, Ishpeming, Michigan H. Hase, State University of Iowa, Iowa City, Iowa Lepp, Macalester College, St. Paul, Minnesota K. Sneigrove, Michigan Technological University, Houghton, Mich, INSTITUTE SECRETARY- TREASURER D. H. Hase, Dept. of Geology, The State University of Iowa, Iowa City, Iowa 52240 LOCAL COMMITTEE General Co—chairmen: A. K. Snelgrove and C. E. Kemp Social Hour Arrangements R, D, Burns K. D. Card P. E, Giblin Mrs. Jean R. Moran R. R, Ranson J. D. T. V. C. R. A. Robertson E. Smith J. Smith Venn Walker W. White (Chairman) R. R. Ranson D. E. Smith V. Venn Ladies Mrs. D. Howe, Mrs. C. E. Kemp, Mrs. R. R, Ranson, and Mrs. A. K. Sneigrove MINERALOGICAL SOCIETY OF AMERICA C 0mm it tee L, G, Berry Queen's University Kingston, Ontario J, A. Mandarino Royal Ontario Museum Toronto, Ontario G. R. Switzer U.S. National Museum Washington, D.C. SOCIETY OF ECONOMIC GEOLOGISTS Committee E. N. Cameron University of Wisconsin Madison, Wisconsin J. S. Stevenson McGill University Montreal, Quebec R. J. Weege Calumet & Hecla, Inc. Calumet, Mich. —1— �I FIELD TRIP LEADERS Institute on Lake Superior Geology - M. P. 5, J. J. E. M, A. Elliot Lake: Frarey, Geological Survey of Canada Giblin, Ontario Department of Mines Roscoe, Geological Survey of Canada Robertson, Ontario Department of Mines (Leader) Mineralogical I Society of America — Manitouwadge: J. A, Mandarino, Royal Ontario Museum E, G, Pye, Ontario Department of Mines (Leader) Society of Economic Geologists K. D,. Card Ontario Department of Mines D, Rousell Laurentian Univ. I Sudbury: J, M. Holloway International Nickel Co. of Canada, Ltd. P. Potapoff Falconbridge Nickel Mines, Ltd. B. E. Souch International Nickel Co. of Canada, Ltd. G. Thrall International Nickel Co. of Canada, Ltd. J, S. Stevenson McGill University (Leader) I 1 I I I I I I I —ii— I �PROGRAM 12th Annual INSTITUTE ON LAKE SUPERIOR GEOLOGY in conjunction with MINERALOGICAL SOCIETY OF AMERICA and SOCIETY OF ECONOMIC GEOLOGISTS Michigan Technological University Sault Ste. Marie Branch Sault Ste. Marie, Michigan Wednesday. May 4, 1966 Eastern Daylight Saving Time* :OO a.m. Pre—session Field Trip, Mineralogical Society of America. Meet at Manitouwadge Hotel, Manitouwadge, Ontario, for tour of zinccopper mines. (See Guidebook) Thursday, May 5 :OO a.m. Pre—session Field Trip, Mineralogical Society of America (continued). Assemble at Marathon, Ontario, and examine road cuts en route to Sault Ste. Marie, arriving early evening. Thursday, May 5 Eastern Standard Time 7:00 p.m.—9:OO p.m. Registration, Science Building, Michigan Tech. University, Sault Ste. Marie Campus. Friday. May 6 :Oo * — 9:00 a.m. Ontario Registration (continued). is on Eastern Daylight Saving Time. �1 —2— Friday, May 6 (continued) PLENARY SESSION I Science Building Co—chairman: E,3.T. 9:00 I A0 K. Sneigrove and C. Ernest Kemp I Vice President Kenneth J. Shouldice, Director of Sault Ste. Marie Branch, Michigan Technological University Regional Geology of the Sault Ste. Marie Area.....,...C. Ernest Kemp Metallogenic Study, Lake Superior— ChibougamauRegion.......,............S.M. Roscoe Recent Investigations of Raised Shorelines, East Shore of Lake Superior and the Sault Ste. Marie Area. . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. Tovell, C. F. M. Lewis, and R. E. Deane Aeromagnetic Studies of Eastern Lake Superior.William and James W. Trow J. Hinze, Norbert W. OTHara, for Relaxation Aeromagnetic, Gravity, and Sub-Bottom Profiling Studies inWestern Lake Superior.........0......... .................Richard J. Wold and Ned A. Ostenso New Bathymetric Map of Lake Superior and Some Geological Implications............... .......W. R. Farrand, J. H. Zumberge, and J. Parker Copper Deposits of the Batchawana Area, p.m. Ontario. . . . • . . . . . . . . . . . . . . . . . . . . . . . . . .P. E. Giblin Interval a0m. 9:05 9:25 9:50 Welcome: .....W 10:15 Pause 11:15 11:40 12:05 Lunch SESSION IIA INSTITUTE ON LAKE SUPERIOR GEOLOGY Science Building Co—chairmen: F. S. Turneaure (University of Michigan) and P. E. Giblin (Ontario Department of Mines) I I I E.S.TO 2:00 2:30 3:00 Some Aspects of Huronian Paleogeography and Sedimentation in the Canadian Shield.Grant M. Young The Geology and Geophysics of the Moose River Belt, Northern Ontario.........A. S. MacLaren New Field Studies of the Keweenawan I LavasofMinnesota.........,..........JohnC. Green Pause for Relaxation I I �—3— Fridays May 6 (Continued) 4:00 p.m. 4:25 4:45 Precambrian Stratigraphy and Structure of the Tower, Minnesota Quadranglee...Richard W. Ojakangas Cutting Oriented Samples,......,....John Q. St. Clair Sugar Loaf Conglomerate, Marquette County, Michigan. Spiroff .... , ,......•a.....,. . .Kiril Annual Banquet Windsor Hotel, Sault Ste. Marie, Ontario Eastern Daylight Saving Time 6:45 p.m. 7:30 Social Hour Dinner Address: "Modern Trends in Precambrian Exploration" Dre Duncan R. Derry SESSION IIB INSTITUTE ON LAKE SUPERIOR GEOLOGY Brady Hall Co—chairmen: D. H. Hase (State University of Iowa) and J. S. Stevenson (McGill University) E.S.T. Michigan's Building Stone Resources..Joseph P. Dobell Occurrence of Base Metals South of Dead River, Negaunee Quadrangle, Marquette County, Michigan,...,,,00.0.....,.......Wil1ard P. Puffett Geologic Structure East and South of the 3:00 Keweenaw Fault Based on Geophysical Evidence. . • • • .. .,. . , . . . •. . ._.. .L. 0. Bacon Pause for Relaxation A Structural Analysis of the Michigamme 4:00 Slates,..,..,.....,W. 0. Mackasey and A. M. Johnson Zoning of the White Pine Copper Deposit, 4:25 Ontonagon County, Michigan, . a a a .e a a .e. a. . a o.. . a. ...,,.,.,..,Alexander C. Brown and John W. Trammell 2:00 2:30 . Annual Banquet Windsor Hotel, Sault Ste. Marie, Ontario �1 -4Friday, May 6 (Continued) Eastern Daylight Saving Time 6:45 7:30 p.m. Social Hour Dinner Address: "Modern Trends in Precambrian Exploration" Dr. Duncan R. Derry I Saturday, May 7, 1966 I SESSION lilA INSTITUTE ON LAKE SUPERIOR GEOLOGY and SOCIETY OF ECONOMIC GEOLOGISTS Science Building Co—chairmen: I I E. N. Cameron (University of Wisconsin) and R. J. Weege (Calumet and Hecla, Inc.) I E.S.T. New Zealand Ilmenite Sands................M. E, Volin Irish Strata—bound Base Metal Deposits............... K. Sneigrove • • • • • • • •.• • • . . • . • . .A. Notes on Lake Superior Type Iron Ores at 9:45 Barsua, Orissa, India..................G. G. Suffel The "Rock Cut", Lower St. Marys River, 10:05 ,Harold J. Lawson Michigan..,......, ee Engineering Geology on New Second Lock, St. 10:25 Marys Falls Canal....,..,...,.....Terrence J. Smith Pause for Relaxation The Probability of a Single Station Being a 11:10 Representative Sample in a Magnetic Survey..L. 0. Bacon, W. A. Longacre, and A. Stevens Results of Detailed Geochemical Prospecting in 11:30 the West—Central Part of the Negaunee Quadrangle, Michigan... ........ . .Kenneth Segerstrom 9:00 9:25 I . ....... ,.. .. PLENARY SESSION II Science Building 12 noon 1:30 INSTITUTE ON LAKE SUPERIOR GEOLOGY: Business Meeting. Briefing on Field Trips. Post—session Field Trips start. Institute: Algoma Steel Plant Elliot Lake, Ontario, Uranium.(See Guide- Society book) * of Economic Geologists: Nickel—copper.(See Guidebook); Sudbury, Ontario, I �—5— Saturday. May 7,(continued) SESSION IIIB MINERALOGICAL SOCIETY OF AMERICA Brady Hall Co—chairmen: L. G. Berry (Queen's University) and J. A. Mandarino (Royal Ontario Museum) ESOT 9:00 p.m. 9:25 Michipicoten Scheelite Deposit near Michipicoten Harbour, Ontario...... .......... , . .. .. . . .Louis Moyd A Barite-Quartz Phase in the Firesand River Carbonatite, Wawa, Ontario......... ... .. . . . ...,,.....,.e.,.E. Wm. Heinrich and Richard W. Vian Clay Minerals in Glacial Deposits, Houghton, 9:4.5 ...... Baraga, and Ontonagon Counties, .....A. P. Ruotsala, G. J. Koons, and S. C. Nordeng The Mn—Bearing Minerals of Champion Mine, 10:05 Champion, Michigan.................Larry L. Babcock Unique Intergrowth of Calcite and Pyrite............. 10:25 • . . . • • • . . • . . . • . . • . . • • . . . . . . • . • . • • . • . .Paul W. Zimmer Pause for Relaxation Short—Range Chamical Variations in a Managanoan 11:10 Axinite from the Mesabi Range, Minnesota........... ....................................Bevan M. French Textural Relations of Hematite and Magnetite 11:30 in Some Precambrian Metamorphosed Oxide Iron Formations......... . • • • ........ . . . .Tsu—Ming Han PLENARY SESSION II Science Bui1ding 12 noon 1:30 INSTITUTE ON LAKE SUPERIOR GEOLOGY: Business Meeting. Briefing on Field Trips. Post—session Field Trips start. Institute: Algoma Steel Plant Elliot Lake, Ontario, Uranium. (See Guidebook) Society of Economic Geologists: Sudbury, Ontario, Nickel—copper. (See Guidebook) �1 THE MANGANESE-BEARING MINERALS OF CHAMPION MINE, CHAMPION, MICHIGAN Larry L. Babcock Michigan Technological University Hought on Champion Mine is a tthard iron ore producer on the southern limb of the Marquette synclinorium, The mine vicinity underwent staurolite-grade regional metamorphism during the post—Animikie, pre-Keweenawan interval. Manganese-bearing quartz shear veins, generally conformable with the schistosity of the host Negaunee iron formation, are found at depths greater than 2,000 feet below the No. 7 shaft collar. These veins cut non—schistose host rock containing major percentages of spessartine and spessartine—andradite, with the former garnet zoned on the latter. Associated minerals include tabular hematite, magnetite, anhydrite, talc, manganese carbonates, diopside, actinolite, and manganoan cummingtonite — Tourmaline, molybdenite, pyrite, and chlorite are associated with some manganese carbonates. Randomly oriented actinolite, hematite, and talc folia, and other criteria indicate that the manganese minerals are late—stage metamorphic. The presence of zoned garnets suggests that the processes of contact metasomatism acted to remobilize primary manganese in an iron—rich environment. Spessartine—andradite (spandite) has been reported from the contact metasomatic manganese ores of India, i.e., "kodurites". tirodite. Other manganese minerals under study include jacobsite, rhodonite, rhodochrosite, manganosiderite, manganankerite, kutnahorite, and several associated unknowns. Jacobsite, MnFe2O4, has 'previously been unreported from the Western hemisphere. Champion represents the first known occurrence of an amphibolitegrade manganese—bearing iron formation in the Western hemisphere, with mineralogical similarities to deposits in Norway, Some of the above minerals have been Sweden, India, and Japan. reported from Franklin, New Jersey. �I GEOLOGICAL STRUCTURE EAST AND SOUTH OF THE KEWEENAW FAULT BASED ON GEOPHYSICAL EVIDENCE L. 0. Bacon Michigan Technological University Houghton Gravity and magnetic data indicate that a Middle Range of basalt lavas lies beneath the Jacobsville sandstone and that this is the north limb of a shallow syncline, plunging to the west at a low angle. The South Range of basalt lava is the southern limb of this syncline. The north side of the Middle Range lavas is interpreted as a fault contact downthrown to the north. Within the graben structure between the Keweenaw fault and the Middle Range fault there appears to be a third fault. These faults appear to be cut by three to four cross faults to account for local anomalies. Maximum thick- ness of the Jacobsville sandstone is of the order of 10,000 feet. �3 THE PROBABILITY OF A SINGLE STATION BEING A REPRESENTATIVE SAMPLE IN A MAGNETIC SURVEY L. 0. Bacon, W. A. Longacre, and A. Stevens Michigan Technological University Hought on In a magnetic survey one presumes that each station reading is a representative sample of the magnetic field of the immediate area. A study of this assumption in a glaciated region indicates that, for the areas studied, variations in magnetic field around the point are randomly distributed and that the probability of a value deviating from the mean of the field in the area is essentially that to be expected from a single valued field where variations follow the Gaussian error curve. Magnitude of the anomalies varies as a function of the type of overburden, underlying rock type, and thickness of cover over the magnetic source. �4 ZONING OF THE WHITE PINE COPPER DEPOSIT, ONTONAGON CO., MICHIGAN Alexander C, Brown University of Michigan Ann Arbor John W. Trammell Copper Range Company — As described by White (l96O) the top of the cupriferous zone at the White Pine copper deposit is characterized by an abrupt Present studies indicate that 'this zonation of Cu—Fe sulfides. narrow fringe occurs at only one position in any vertical section and forms a blanket—like surface between the cupriferous zone and Although ore horizons at the overlying barren pyritic shales, White Pine show strict stratigraphic control, the sulfide fringe, marking the uppermost limit of chalcocite mineralization, occurs at various stratigraphic levels near and above the ore horizons0 In general this surface cross—cuts bedding at gentle angles, but locally it appears to be more irregular. Disseminated chalcocite, native copper, and native silver are the dominant ore minerals of the cupriferous zone; pyrite and minor amounts of chalcopyrite occur in the shales above. The transition between these zones (normally measured in inches) consists of digenite, bornite, and. chalcopyrite in ascending order. Textures indicate replacement of iron—rich sulfides by copper-rich minerals. Abnormal concentrations of disseminated Cd, Zn, and Pb sulfides occurs immediately above the curiferous zone and in the marker bed; they have not been observed within the cupriferous zone proper. ?t3tripey*t It is suggested that the Cu—Fe transition represents the farthest advance of a copper "front't, behind which syngenetic or diagenetic pyrite was replaced by chalcocite and native copper. Silver in the Nonesuch was probably associated with the copper front0 Cd, Zn, and Pb were swept ahead of the front and formed anomalous concentrations immediately above the cupriferous zone. Sulfur may have been partially removed from the present cupriferous zone during copper mineralization. I I I * White, W0 S., "The White Pine Copper Deposit:" Econ0 Geol, V0 55, pp. 402—414 1 �U 5 MICHIGAN'S BUILDING STONE RESOURCES Joseph P. Dobell Michigan Technological University H ought on An investigation of the building stone resources of the State of Michigan was undertaken in the summer of 1965. Emphasis was on undeveloped materials in the Upper Peninsula of Michigan but a number of areas in the southern part of the state were also studied. Geologic investigation consisted of selecting and visiting the potential building stone deposits, determining the geology of the local site, sampling the deposits, and evaluating factors such as proximity of the material to transportation facilities, location of the potential quarry, and possible water and overburden problems. In the course of the field work the most common building stone collected was of the type used as decorative aggregate surfacing for pre—cast concrete slabs. Colorful and durable materials of this category were obtained from thirty-four localities in the Precambrian terrain of Michigan's Upper Sandstone, limestone and dolomite suitable for Peninsula. dimension stone were obtained from fourteen different sites. Eight localities yielded decorative stone which could be cut Terrazzo stone into polished slabs up to four feet square. could be quarried from seven locations and five rock types are suitable for use in the lapidary arts. The mineralogy of all specimens was determined by microscopic study of thin-sections. Standard chemical analyses were provided by the Institute of Mineral Research at Michigan Tech. The same agency also has conducted abrasion, hardness, absorption, specific gravity, compressive strength, modulus of rupture,and freeze—thaw tests on all specimens. Funds for this investigation of the building stone resources of Michigan were provided by the Michigan Department of Economic Expansion. The project was proposed and administered by the Institute of Mineral Research at Michigan Technological University. �ij 6 NEW BAThIMETRIC MAP OF LAKE SUPERIOR AND SOME GEOLOGICAL IMPLICATIONS * J. H.Zumberge Grand Valley State College V. R. Farrand University of Michigan J. Parker White Pine, Michigan Parker has compiled a new bathymetric map with a 100-foot contour interval for the eastern half of Lake Superior on the basis, of recent U.S. Lake Survey souddings. This map has"been completed, in connection with the University of Miàhigan Lake Project, by the addition of the best depth data The strong 'valleyavailable for the western half of the basin. and-ridge topography of the eastern part of the basin contrasts Superior strongly with the rest of the lake where broad, emooth—floored basins are the. characteristic form. However, Sbbottom depth recorder (Sparker) surveys show that bedrock valleys similar in size to those of the eastern basin exist also in the west, where they have been áompletely filled with glacial and postglacial sedimints so that they no longer find expressIon in the topography of the lake bottom. In one of these buried valleys near the Minnegota coast late Pleistocene sediments are more than 700 feet thick. In the eastern.: basin, on the other hand, Pleistocene sediments form, in general, only a thin veneer over a rugged bedrock topography which resembles that of. the Finger Lakes area of New fork. * See map, back cover �7 SHORT-RANGE CHEMICAL VARIATIONS IN A MANGANOAN AXINITE FROM THE MESABI RANGE, MINNESOTA Bevan M. French Laboratory for Theoretical Studies National Aeronautics and Space Administration Goddard Space Flight Center Greenbelt, Maryland A new occurrence of the calcium borosilicate axinite has been identified in a pegmatitic vein cutting metamorphosed Biwabik iron formation on the eastern Mesabi ange, Minnesota. The mineral occurs as yellow—brown, poorly—crystalline patches associated with Two different large crystals of quartz and potassium feldspar. size fractions of the crushed axinite, separated by identical heavy—liquid and magnetic methods, give different chemical — 100 + 150 mesh) gives: SiO2 41,66, compositions. Fraction 1 18.00, Fe2O3 0.10, FeO 3,27, MnO 11.66, A1203 Ti02 0.01, B2O 5.96, +1100) 1.26, Na20 _llOo) O.01j, H20 MgO 0.25, CaO 18.00, H20 mesh) gives, by contrast: + 200 0.15, K20 0.02. Fraction 3 ( — 150 Similar significant A1203 14.23, Fe203 1.95, FeO 5.25, MnO 10.60. differences exist in unit—cell parameters of the two fractions obtained by computer treatment of X—ray powder diffraction data. An unexpected discrepancy in the calculated unit—cell contents of the Fraction+ can be removed by substituting about 25 percent and aluminum, although the existence of both Mn Mn as Mn ) with Refractive same silicate has yet to be demonstrated. Mn+3 in the indices of the two fractions appear identical within the 1.678, = 1.678, determinative uncertainty (+0.003): = 1.692 (Fraction 1). ( ( ( Petrographic and electron microprobe studies suggest that the more iron—rich axinite (Fraction 3) has originated by fracture— controlled alteration of the original axinite during a period of more ''*idespread secondary alteration indicated by (1) idespread sericitization of feldspar, and (2) almost complete chioritization of garnet. Relative higher Po2 values during this latter stage are indicated by the increased Fe+3/Fe2 in Fraction 3 and are consistent with the suggested partial conversion of Mn'2 to �COPPER DEPOSITS OF THE BATCHAWANA AREA, ONTARIO P. E, Giblin Resident Geologist Ontario Department of Mines Sault Ste0 Marie Recent exploration in the Batchawana area, Ontario, located 40 miles north of Sault Ste. Marie, has led to new and significant discoveries of copper; underground development at one property; and production of copper from another. Copper deposits are of three types: Fissurefilling calcite—quartz veins, carrying 1. chalcocite, bornite, chalcopyrite, and native copper. Breccia pipe depo sits, in which the mineralization 2. consists of chalcopyrite, pyrite, molybdenite, galena, and sphalerite. Disseminated chalcopyrite, pyrite, and molybdenite in 3, altered quartzfeldspar porphyry, possibly representing a porphyry copper type of deposit. Deposits of the first Breccia pipe deposits are suggests mineralization is the third type may also be type occur in Keweenawan strata, found in Archean rocks: K— dating The deposit of Keweenawan in age. of Keweenawan age. Copper deposits of the area are probably associated with magmatic activity of middle to late Keweenawan time, which in the eastern Lake Superior region appears to have been restricted to the immediate vicinity of the present lake basin. It is suggested that the Archean terrain near the east shore of Lake Superior might warrant prospecting for breccia pipe and disseminated deposits of copper and molybdenum. I I I I I I �.9. NEW FIELD STVDIE3 OF ThE KEWEENAWAN LAVAS OF MINNESOTA John C. Green University of Minnesota Duluth, and Minnesota Geological Survey Field work was begun in the suier of 1965. on the Keweenawan lavas and related intrusive rocks of northeastern Minnesota, with •the support of the National Science Foundation and the Minnesota Geological Survey. Detailed mapping along the shore of Lake Superior in Lake and Cook counties has been concentrated on a restudy of the stratigraphic sequence, estimates of thickness, and direction of flow of the lavas. Measurements of 118 ropy structures at the tops of flows and of 38 bent pipe amygdules at the bases of flows show no clear preferred erientation and thus no uniform direction of flow or of regional slope in the area studied. Petrographic and preliminary x-ray studies show that lavas of intermediate composition are more abundant than heretofore recognized. An extensive area of flows, of both felsic and mafic composition, has been found well within the area previously mapped as Duluth Gabbro Complex northeast of Isabella. Minor intrusions, possibly oonnected with the Duluth Gabbro Complex at depth, show compositions that range continuously from troctolite, much .of which is banded, to highly leucocratic granophyric granite. All intrusive phases contain xenoliths of anorthosite. �I 10 TEXTURAL RELATIONS OF HEMATITE AND MAGNETITE IN SOME PRECAMBRIAN METAMORPHOSED OXIDE IRON—FORMATIONS TsuMing Han Cleveland—Cliffs Iron Co0, Ishpeming, Mich. Hematite—magnetite is a common ore mineral assemblage in the Precambrian oxide ironformations. The textural relationship of the two minerals changes with the grade of metamorphism. in the low-grade metamorphosed iron formations (ore minerals co—existing with fine—grained dusty quartz and/or sheet iron silicates), one may find hematite with magnetite rims; hematite crystal outlines reappearing in partially oxidized magnetite; magnetite veinlets in fine—grained hematite; fractures in hematite bands cross—cut by magnetite; and magnetite crystals embedded in jaspilites. These textural relations suggest that magnetite is stable whereas hematite tends to be reduced to magnetite during the metamorphism. In iron formations of medium—grade metamorphism (ore minerals co-existing with medium-grained fairly clean quartz and/or double— chain iron silicates), specularite embedded in fine—grained magnetite; specularite containing magnetite remnants; magnetite cross—cut by specularite; and specularite bands with relicts of magnetite clusters are commonly observeth Such features suggest that during the metamorphism speculariteia stable phase whereas magnetite tends to be oxidized to specularite. Hematite and magnetite in iron formations of high—metamorphic order are more or less simultaneously developed, and commonly associated with coarse—grained clear quartz and/or double— and single—chain iron—rich silicates However, the cross—cutting of specularite by magnetite in some ores may suggest the earlier development of specularite0 In conclusion, reduction and oxidation do occur in iron formations during metamorphism although in general ore mineral assemblages are governed by those of the ppe-metamorphic Such processes are believed to be repponsible for the sediments0 development, at least in part, of the magnetite—bearing jaspilite, oölitic magnetite and specu1aritemagnetite ore types. The degree of such types of metamorphism tends to improve the concentrating characteristics of ores and has a direct effect on the process chosen for iron ore beneficiation. I I �11 A BARITE—QUARTZ PHASE IN THE FIRESAND RIVER CARBONATITE, WAWA, ONTARIO E. Wm. Heinrich and Richard W. Vian The University of Michigan Ann Arbor The Firesand River alkalic complex, 4.5 miles east of Wawa, Ontario, is unusual in that it consists predominantly of carbonatite with a highly subordfriate outer ring of rnafic to ultramafic alkalic silicate rock. The carbonatite core is composite, with an inner core of rauhaugite encircled by sovite The ferruginous rauhaugite body, which and silicate sóvite. appears to be pipe—like and vertical (in contrast to the sovite ring, which represents the accretion of a series of inward— dipping cone—sheet slices), is itself a composite of several texturally and mineralogically distinctive rocks. Among these are 1) a porphyritic phase in which calcite phenocrysts are set in a finer-grained matrix of iron—bearing carbonate; and 2) a This rock contains barite barite—quartz-carbonate rock. euhedra, quartz grain fragments deeply corroded by carbonate, and euhedral smoky quartz crystals, some as long as three inches. Most of the quartz grains appear to have been metamorphosed, showing undulatory extinction, mosaic structure, and a strong parallel alignment of "bubble train" inclusions. Against the carbonate they are locally armored by "reaction rims" of very fine-grained ferruginous feldspar. It is concluded that this unusual rock was formed by the carbonatization of a quartzite cut by small quartz veins into which were introduced (in order): 1) barite, 2) alkali feldspar, and 3) carbonate. �U 12 AEROMAGNETIC STUDIES OF EASTERN LAKE SUPERIOR William J. Hinze, Norbert W. O'Hara and James W. Trow Michigan State University East Lansing A regional aeromagnetic survey was conducted to determine the relatively unknown basement geology and tectonics of eastern Lake Superior and the eastern half of the Northern Peninsula of Michigan. During this survey approximately 6,500 miles of flight lines spaced at six—mile intervals were recorded with a digital recording proton precession magnetometer system. The results of the survey generally supported the geological interpretation that the Lake Superior structural basin consists of thick basic volcanies overlain by clastic sediments. This basin extends southward into the Northern Peninsula of Michigan with the basic volcanics of the Keweenaw Peninsula curving southward through Stannard Rock and Grand Island. The Isle Royale fault parallels the general curvature of the Keweenaw Peninsula to the vicinity of Superior Shoal where it là terminated by a cross fault striking from Ashburton Bay to the Keweenaw Peninsula, A fault on the north side of Michipicoten Island continues to the southeast toward Gargantua Point and northward, paralleling the shoreline at a distance of 10 to 15 miles. Midway between Michipicoten Island and Pie Bay, this fault turns northwest and continues south of the Slate Islands to the volcanics outcropping on the islands of Nipigon Bay. South of Michipicoten Island the basic volcanics have been uplifted by an east—west striking fault which may be a continuation or a branch of the Keweenaw fault. On the east side of the basin, south of these basic volcanics, the volcanics appear to be discontinuous with major volcanic rock areas extending southwest from Mamainse Point and the eastern margin of the Northern Peninsula of Michigan. I I I I I �13 THE "ROCK CUT", LOWER ST. MARYS RIVER, MICHIGAN Harold J. Lawson Project Engineer U. S. Army Corps of Engineers Sault Ste. Marie, Michigan The "Rock Cut" is a channel nearly two miles long and 300 feet wide cut through Trenton limestone that was initially excavated in 1904. It is between Neebish Island in the St. Marys River and the mainland of the Eastern Upper Peninsula. Completion of the project permitted large navigation ships to take a more direct route downbound to Detour Passage at the northern tip of Lake Huron. The work consisted of constructing cofferdams upstream and downstream of the cut, 9,000 feet apart; dewatering the area; channeling and line drilling the ledge rock on the east and west channel limits; blasting and removing the rock to adjacent disposal areas; constructing an ashlar masonry guide wall at the channel limits on the ledge rock; flooding the area; and removing the cofferdams within the channel. blasting was done without blasting mats. The blasts were all monitored with a seismograph to maintain an Energy Ratio of 1.0 or less and to prevent excessive concussion. The largest blast was l,00 lbs. of 60% hi—velocity gelatin. Usually the The blasts were less than half this amount. The work started in late summer 1960 and was completed in January, 1961. �1 14 A STRUCTIJ RAL ANALYSIS OF THE MICHIGAIvllE SLATES W, 0. Mackasey and A, M. Johnson Michigan Technological University Hought on The Animikie Michigamme slates of Michigan's Upper Peninsula represent a thick monotonous assemblage of fine—grained elastic rocks which apparently lack marker horizons suitable for interpretation by conventional field methods, For this reason, a statistical structural analysis utilizing small—scale features should be considered. A preliminary investigation during the fall of 1965 was started in the Covington area to test the applicability of this Outcrops along a ten—mile stretch of highways M-2 and method. U.S. 141 north of the BaragaIron County line were examined. Features measured within the slates included bedding, rock cleavage, axes of minor folds, and lineations produced by inter section of bedding and cleavage, etc. These data were plotted by means of an equal-area stereonet. periods of deformation have been recognized and some information on the style of folding has been obtained. Two Such studies may provide useful clues in determining the complex history of deformation of the Anirnikie rocks of the Upper Peninsula. Further work, on a continuing basis, is planned. I U I I I I I �15 THE GEOLOGY AND GEOPHYSICS OF THE MOOSE RIVER BELT, NORTHERN ONTARIO A. S. MacLaren Geological Survey of Canada Since 1959 the Geological Survey of Canada and the Ontario Department of Mines have cooperated in systematic aeromagnetic surveys of the Precambrian Shield of Northern Ontario. In 1965 a major anomalous magnetic zone named the Moose River magnetic belt was recognized in these surveys. This feature extends for a distance of 160 miles south of James Bay and transects the Superior Province trends at a large angle. It coincides with granulites, gabbro, and basic dykes and is cut by a major fault along which ultramafics occur0 Detailed gravity and magnetic work indicate that the granulite and gabbro occurring explained magnetic belt can be by local magnetic and gravity measurements over surface material. major in this This magnetic belt lies on the east flank of a gravity feature, the Kapuskasing gravity anomaly. �16 1 MICHIPICOTEN SCHEELITE DEPOSIT NEAR MICHIPICOTEN HARBOUR, ONTARIO I Louis Moyd Curator of Minerals National Museum of Canada A scheelite deposit on the shore of Lake Superior about 12 miles west of Michipicoten Harbour was explored. The host rock is a nearly vertical northwest—trending septum of biotite and hornblende schist about 200 feet thick enclosed in a large body of granodiorite. Scheelite is irregularly distributed through quartz pods which form vein—like elongate swarms along the central portion of the tabular mass of schist, The mineralized zone can be seen under the lake and has been traced inland for about a mile. The quartz pods are lenticular and vary greatly In size. Each swarm consists of pods, side by side or en echelon in both horizontal and vertical aspects, with long axes paralleling the foliation of the enclosing schist, Individual swarms may reach 30 feet in width, but are irregular and patchy, with some portions along the strike of the zone nearly free of the pods. Individual pods are separated by septa of contorted schist from a fraction to several inches in width, Locally, adjoining portions of two or more pods have coalesced, with the intervening schist completely replaced or now represented only by strings and patches of coarsly crystallized mica and feldspar. The scheelite is in the form of cream to buff anhedral grains and clusters from i/ inch to about 12 inches in diameter, Most of the scheelite occurs near the margins of the pod, or if well within them, along the zones of coarsely crystallized mica and feldspar which represent earlier schist septa. I I I �17 PRECAMBRIAN STRATIGRAPHY AND STRUCTURE OF THE TOWER, MINNESOTA QUADRANGLE. Richard V. Ojakangas University of Minnesota Duluth The Tower 74 minute quadrangle is a strategically located area in the older Precambrian rocks of northeastern Minnesota. Rocks representing the Ely Greenstone, the Soudan Iron Formation, the Knife Lake Groups, and the Algoman granitic complex are present. Mon of the area is underlain by Knife Lake rocks, but a large nose of Ely Greenstone is present in the eastern portion of the area, entering from the adjacent Soudan quadrangle. The minor lower portion of• the Knife Lake unit is comprised of conglomerates, impure quartzites, and tuffaceous rocks. These an overlain by a great thickness of alternating graywackes and •slates' (formerly mudstones). Most of the rocks have been only slightly metamorphosed, but metamorphic grade increases to the south. Pillows in the Ely Greenstone and graded graywacke beds in the Knife Lake permit top, determinations and structural interpretations. A series of tight, generally eastward—plunging folds cross the quadrangle. Overturned greenstones and graywackeslate beds are conaon. Aerial photo analysis revealed abundant lineaments in the area, generally trending about N. 35 E; one can be traced into a fault with about 1,000 feet of horizontal displacement. this area under auspices of the Minnesota Geological Survey. Major objectives are the solution of the regional structure (several workers are involved) and the sedimentary history of the Knife Lake rocks. Work is continuing in �l OCCURRENCES OF BASE METALS SOUTH OF DEAD RIVER, NEGAUNEE QUADRANGLE, MARQUETTE COUNTY, MICHIGAN* Willard P. Puffett U. S. Geological Survey Marquette, Michigan In the south half of the Negaunee quadrangle, Marquette County, Michigan, rocks of early Precambrian age are bounded on the northwest and on the south by metasedimentary rocks of the Animikie Series of middle Precambrian age. The lower Precambrian rocks include massive and layered greenstones of the Mona Schist, pyroclastic rocks of the Kitchi Schist, and a syenite—diorite—granodiorite pluton that intrudes the Mona The metasedimentary rocks to the northwest, in the Schist. Dead River Basin, rest on an erosional surface cut on the pluton. The metasedirnentary rocks in the southern part of the area are on the north limb of the Marquette syncline and are separated from the lower Precambrian rocks by a profound unconformity. Small and widely separated deposits of base—metal sulfides have been found in the lower Precambrian rocks, The most common type is chalcopyrite with sparse pyrite in steeply—dipping These veins have been found in both quartz-carbonate veins. massive greenstone and coarsely crystalline granodiorite. They range in thickness from a few inches to more than 5 feet, and some can be traced along strike for several hundred feet. The sulfides make up only a small part of the veins and commonly are most concentrated near the footwall. Assays of selected specimens of vein material indicate that gold and silver are not present in measurable quantities. Small amounts of chalcopyrite and copper carbonates occur in a shear zone in greenstone that has been carbonatized and Tests for heavy metals in this shear zone indicate sericitized. a rather broad mineralized area in which both copper and zinc occur in anomalous amounts. No zinc minerals have been identified. In one locality, galena has been found with chalcopyrite in a quartz vein in granodiorite near its contact with greenstone. Elsewhere chalcopyrite has been found in joints in the granodiorite; no other vein material is exposed. Some of the veins occur in topographic lineaments that are conspicuous on aerial photographs. Areas containing sulfide—bearing veins also coincide with magnetic lows shown on aeromagnetic maps of the region. Commonly the aeromagnetic lows occur above diabasic intrusions, suggesting a possible genetic relationship between the sulfide-bearing veins and diabase * Publication authorized by the Director, U. S. Geological Survey. Work done in cooperation with the Geological Survey Division of the Michigan Department of Conservation0 �19 METALLOGENIC STUDY, LAKE SUPERIOR-CHIBOUGAMAU REGION* S. M. Roscoe Geological Survey of Canada Mineral deposits in the region are assOciated with rocks are te'ctonic activities of five different ages: Early Archaean (—3.1 to 2.7 x109 yrs.) iron formations, Zn and Cu — bearing iron suiphide deposits, Ni, Cr, asbestos, Cu—Ni, Cu, and Au deposits in volcanic, sedimentary, and associated ultrabasic, basi; and acidic intrusive rocks. Late Archaean (—2.7 to 2,4 x 109 yrs.) Mo, Li, and Be in Kenoran pegmatites; minor Pb—Zn veins; Au and Cu—Mo deposits associated with late Archaean alkalic volcanic and intrusive rocks; remobilized early Archaean deposits. Early Aphebian (—2.4 to 2,0 x i09 yrs.) conglomeratic U-Th deposits in Huronian rocks; veins containing native silver, Cu, Pb—Zn, Au, or U associated with Nipissing diabase and correlative intrusives0 Late Aphebian (—2,0 to 1.6 x l0 yrs.) iron formations in Animikean strata; Zn—Pb—Cu — bearing pyritic deposits in White— water strata in the Sudbury basin; Ni—Cu deposits associated with the Sudbury irruptive0 Neoheikian (—1.3 to 0.9 x 109 yrs.) native copper and other Cu deposits in Keweenawan strata; Ag deposits associated with basic intrusives; Pb—Zn and pitchblende veins; disseminated Cu deposits in breccia and in acidic intrusives; Nb and Cu deposits in alkalic syenite complexes. Analyses of minor element contents of suiphide minerals and lead isotope analyses aid in classification of deposits and interpretation of their histories with respect to associated rocks dated by K—Ar and Rb—Sr methods. Many deposits contain radiogenic lead presumably generated during inter—orogenic It is not clear in every case whether this was added periods0 at the time of formation or at a time of metamorphism of the deposit. * See map, inside back cover �20 CLAY MINERALS IN GLACIAL DEPOSITS, HOUGHTON, BARAGA, AND ONTONOGAN COUNTIES, MICHIGAN A. P. Ruotsala, G. J. Koons, and S. C. Nordeng Michigan Technological University Hought on The clay—sized fractions from surficial glacial tills, outwash, and lacustrine deposits from 13 Baraga, Houghton, and Ontonogan County localities have been examined by x—ray diffraction. Results show that the clay fraction of most recent deposits consist of lute (clay—mica) and chlorite approximately in equal amounts. Clay fractions from older glacial deposits contain substantial amounts of expandable mixed—layer clay minerals in addition to illite—chiorite. Basal reflections of expandable clays typically consist of single broad 12.6 peaks or double 11.2 - 12.6 peaks which expand to 17 upon treatment with ethylene glycol. The difference in clay mineralogy with depth may represent a weathering sequence in the local area and suggests the possibility of. correlation of glacial deposits on the basis of clay mineralogy. �21 ORIENflD CHANNEL SAMPLES John Q. St. Clair Mining Geologist, Duluth, Minnesota Chqnnel samples of rock outcrops may be easily taken and oriented in the field by using a specially—equipped, lightweight Romelite gasoline motor unit operating two parallel, diamonds impregnated sawing blades spaced about one inch apart on the high—speed drive spindle. The same unit may be used to trim the specimens to• required dimensions, a convenient size being 1" by 1" in cross— section and 6" in length. Water collant may be supplied by a standard portable pressure tank. Orientation of the channel samples is accomplished by using a simple goniometer device in conjunction with an ordinary Brunton compass. �______ 22 RESULTS OF DETAILED GEOCHEMICAL PROSPECTING IN THE WEST—CENTRAL PART OF THE NEGAUNEE QUADRANGLE, MICHIGAN* Kenneth Segerstrom U. S Geological Survey Denver, Colorado Surficial materials in Marquette County were sampled and analyzed for lead, copper, and zinc during 1963-64 (Segerstrom, 1965).** Five areas where anomalously high concentrations of base metals were found in the soil were sampled in greater The 1965 localities and their microtopographic detail in 1965. 200 feet. Where setting were mapped at a scale of 1 inch anomalies were especially high, small portions of the larger mapped area were resampled and remapped at 1 inch = 50 feet. Four of the five major areas are in T. 49 N., R. 27 W., as sec. 36, and vicinity sec. 35, N follows: NE I sec0 30, NW sec. 7, of corner secs. , 9, 16, 17. The fifth area is in W sec0 12, T. 49 N., R. 2 W. T. 49 N., R. 27 W., and adjacent NE Analytical results from the entire 1963—65 mapping program indicate that anomalous concentrations of lead, copper, and zinc in soils of the region are in large part post—glacial and reflect a local source. Results from the 1965 work have made it possible to delineate within each of the five areas relatively small targets for further exploration. Their geologic setting indicates that most of the targets in the first, fourth, and fifth areas may reflect sulfide mineralization along crosscutting (north— striking) faults or shears, The mineralization indicated by targets in the second and third areas appears to be largely related to bedding-plane (east—striking) shears. I I I •1 * Work done in cooperation with the Geological Survey Division of the Michigan Department of Conservation. ** Segerstrom, Kenneth, 1965, "Preliminary Results of Geochemical Prospecting North of the Marquette Iron Range, Michigan (abs.): in 11th Ann. Inst. on Lake Superior Geology, St. Paul, Minn., p. 30. I �23 ENGINEERING GEOLOGY ON NEW SECOND LOCK, ST. MARYS FALLS CANAL SAULT STE. MARIE, MICHIGAN Terrence J. Smith U. S, Army Corps of Engineers Sault Ste, Marie, Michigan As part of navigation improvement between Lake Huron and Lake Superior, the U. S. Army Corps of Engineers is replacing an obsolete lock with a new lock 1,200 feet long, 110 feet wide and 32 feet deep, Construction is on Cambrian sandstone and shaly sandstone which dips three degrees west. The sandstone is massive, and hard The shaly sandstone to very hard, with soft shaly seams. is hard with soft seams, slakes readily, and deforms and rebounds when unloaded. Good-quality rock was required for maximum stability. Consequently, more than 7,000 linear feet of 6—inch diameter core were drilled and examined. Construction requirements are unique because the lock is in a trench excavated O feet below river level on an island of Adjacent structures rock separated from land by adjacent locks. and rock are protected against blast damage by pre—splitting or close—line drilling and broaching, and blasts are monitored with a seismograph. Dangerous hydrostatic forces are controlled during construction with cofferdams and by dewatering adjacent locks. A foundation grout curtain, drain and weep holes, and lateral drains in the lock floor, metal waterstops between lock wall monoliths, and a strutted lock floor will protect the structure against hydrostatic forces after construction Approximately 950,000 cubic yards of rock, old lock masonry and overburden,will be removed, and 350,000 cubic yards of concrete will be placed during excavation and construction, The lock will be completed in August 1967 at a cost of O million. �24 IRISH STRATA-BOUND BASE METAL DEPOSITS A, K. Sneigrove Michigan Technological University Hought on In the Central Plain of Eire two important stratiform zinc— lead deposits, Nenagh and Tynagh, are about to come into production. A disseminated zinc—lead deposit, Riofinex, and a disseminated copper deposit, Gortdrum, are being explored. These deposits occur in Lower Carboniferous limostones, some as massive suiphides, other as disseminations; some conformable with limestone bedding, others evidently remobilized andforming replacements and veinlets. Association with or near Waulsortian The Reef Limestone muds is common but not necessarily genetic. paleophysiography is fairly well established, and provides a broad guide in ore search. Tuffs may indicate volcanic exhalative contribution of metals, including relatively high silver values, thus differentiating these deposits from the Mississippi Valley type. The deposits occur near normally faulted inliers, and Armorican (late Carboniferous) movements may account for their diplogenetic character as well preservation of gossans. Mantle fissures have been invoked as regional controls of mineralization. Geochemical dispersion as determined at Tynagh was predomin— ately mechanical and syngenetic with till. Cu, Zn, Pb, and Hg dispersion trains are detectable in stream sediments and are related to soil/till anomalies rather than bedrock source in Peat is a largely undetermined areas of glacial overburden. factor as a metal collector. Conditions favorable for the occurrence of strata—bound Isotope and other geochemical deposits appear to be widespread. studies are needed for a better understanding of genesis and improved exploration techniques in this renascent mineral industry. I I I I �25 SUGAR LOAF CONGLCNERA'?E, MARQUETTE COUNTY1 MICHIGAN Kiril Spiroff Michigan Technological University Houghton A few miles to the north of. Sugar Loaf. Peak on the shores of Lake Superior is a conglomeratic outcrop which is of particular interest. It is located in Section 20, T. 49 N., R. 25 1., being.6 miles north of Marquette, Michigan. The boulders making up the conglomerate are up to a foot• diameter and are of weathered granite and red shaly sandstone. They overlie a gray granite and grade into a red, horizontal bedded sandstone believed to be of Cambrian age. This outcrop, having shaly sandstone boulders along with in granite boulders, corroborates the belief as expressed in an article1'by the writer that the Cambrian. sandstone is substantially a product of an older sandstone, probably Sibley. 1. Spiroff, Kiril, 1952 "Sandstones near L'Anse, Michigan". Rocks cM Minerals, 1.1. 27, No. 3-4, p. 149. �26 NOTES ON LAKE SUPERIOR TYPE IRON ORES AT BARSUA, ORISSA, INDIA G0 G. Suffel University of Western Ontario London, Ontario, Canada The Barsua mine, 250 miles 1961 to supply the new Rourkela Reserves were 117 million tons, than half sinter ore. Expected west of Calcutta, was opened in steel plant, 42 miles north. between 5.2 and 64.5% iron, more output was 3.0 million tons yearly. Barsua is on the Precambrian Bonai iron range, which extends f or 75 miles as a ridge of peaks and saddles from 2,600 to 3,000 feet in elevation, with ore confined to the top. Relief is 1,300 feet. Dips are steep and structures are complex. "Banded hematite—quartzite" about 900 feet thick, is part of the Iron—ore Series, largely shale with local limestone, unconformable on Archaean—type metamorphic rocks. The Series was folded, and intruded by the Singhbhum granite about 203 m.y. ago. Six varieties of hematite ore are found. Massive hard cap— ore comprises only 3.7%. Most production comes from porous laminated ore, over 59% iron, comprising about 49% of reserves. Unfortunately at least 34% of total reserves is "Blue Dust", nearly 60% iron but difficult to handle and requiring sintering. Complex structures seen in the pit have three causes: original soft—rock deformation, seen locally in hematite—jasper; tectonism; slumping due to leaching and oxidation. Similarities to ores and iron formations of the Animikie are numerous and counterparts of almost all types can be found in Michigan or Minnesota. According to recent work, even the age of the sediments is comparable. In contrast, geothite, magnetite, The ores specularite, and iron silicates seem virtually absent. fade out downward, usually at less than 200 feet. Laterite caps the ferruginous shales and there are over 4 million tons of lateritic ore, $ I I I I �27 RECENT INVESTIGATION OF RAISED SHORELINES, EAST SHORE OF LAKE SUPERIOR AND THE SAULT STE. MARIE AREA Walter M. Tovell Curator of Geology Royal Ontario Museum Toronto C. F. M. Lewis Geological Survey of Canada R, E. Deane* The eastern shoreline of Lake Superior and the Sault Ste. Marie area have yielded some good evidence for the former levels of Lake Superior. The investigations of Stanley (1932) and Farrand (1960) have been added to by surveys of raised or perched beaches at Montreal River Harbour, Batchawana and Sault Ste. Marie. These studies strongly suggest that water planes were present up to nearly the 1,100 ft. contour both in the Batchawana Bay area and at Sault Ste. Marie. These data suggest that Lake Algonquin penetrated into the Superior Basin, All profiles presented have been surveyed by transit. The report is the preliminary stage of a general program for a more precise correlation of water planes between the Sault Ste. Marie area and the Southern part of Georgian Bay, by the Royal Ontario Museum, and a general investigation of the history of the Lake Huron Basin by the Geological Survey of Canada. * Deceased. �1 28 NEW ZEALAND IIIVIENITh SANDS M. E. Volin* Director, Institute of Mineral Research Michigan Technological University Houghton Ilmenite and lesser amounts of zircon, rnagnetite, rutile, monazite, and gold occur in beach sands distributed along the .1 West Coast of the South Island for a distance of over 200 miles. Extensive accumulations form raised beaches, associated dunes, and filled lagoons around the outlets of the larger rivers. Detritus deposited off—shore was sorted and transported along the coasts by northward—trending littoral currents, and resorted by wave and eventually wind action. The sands have a uniform grain—size distribution with the various mineral reporting into size classes according to their hydraulic equivalences. Ubiquitous quartz is accompanied by heavy silicates, mica, and The ilmenite is found in discontinuous lenses in some spinels. the beaches and in lesser amounts distributed throughout the dunes. Clean ilmenite grains from the active beaches have nearly a stoichiometric ratio of iron to titanium, but microscopic study shows minor rutile intergrowths occurring along the basal planes, minor hematite composites containing ilmenite ex—solution bodies, and clouds of silicate inclusions less than 10 microns in size. Leucoxenization is not notable; apparently the New Zealand climate has not been favorable for this process0 A consolidated "iron pan", conforming with the ground surface, a feature of the old beaches, and the sands in both the old beaches and dunes are coated with yellow iron oxide and contain concretions up to several inches in diameter. These features, along with the presence of heavy silicates, complicate mineral separations by conventional methods, and the fine inclusions in the ilmenite are a problem in maldng a commercial product. is I I I I * Fulbright-Hayes New Zealand0 Grantee (1965), University of Otago, Dunedin, �29 AEROMAGNETIC, GRAVITY, AND SUB—BOTTOM PROFILING STUDIES IN WESTERN LAKE SUPERIOR Richard J. Wold and Ned A. Ostenso Department of Geology, The University of Wisconsin Madison, Wisconsin The structure of western Lake Superior is studied by magnetic, gravity, and sub—bottom profiling surveys. About 7,500 miles of north—south aeromagnetic tracks were flown, 275 bottom gravity stations occupied, and 900 miles of sub—bottom profiles obtained. The magnetic and gravity surveys support the structural interpretation of White (1966)* for the far western part of the area and indicate a medial ridge, extending southwestward from the western end of Isle Royale that, divides the area east of the Bayfield Peninsula into north and south basins or synclines. The north syncline is cut by a fault that extends westward from Isle Royale, runs north of Isle Royale, and continues eastward to the edge of the survey area. Another fault extends from Isle St. Ignace to the eastern end of Isle Royale and may continue southwestward along the medial ridge. The sub—bottom reflection profiles show many interesting details, such as sediment—filled troughs and old stream channels. The penetration of the reflected wave was 0,25 sec., distinct horizons deeper than 0.1 sec. being commonly observed. * White, W. S., "The Tectonics of the Keweenaw Basin, Western Lake Surv Prof. aDer 524 E 23p. 1966. Superior Region:" U..e �U p .30 SCRE ASPECTS OF HURONIAN PALEOGEOGRAPHY AND SEDIMENTATION IN THE CANADIAN SHIELD Grant Pt. Young University of Western Ontario London, Ontario) Canada A sequence of formations almost identical to those of the of Manitoulin Island in Lake Huron. The pr.-Oowganda Proterozoic rocks of the north shore of Lake Huron appear to be a unique occurrence in Canada. In the north shore region the unconformity beneath the Oowganda Formation is local and an unbroken succession of Proterozoic rocks occurs at McGregor Bay. However, rocks thought to be correlatives of the Gowganda Formation and younger Aphebian sedimentary rocks are widespread throughout the Churchill Province and may be recognized in parts of the Superior and Slave original" Huronian occurs in the McGregor Bay area, north—east Provinces, so that 2. the unconformity beneath the Oowganda Formation i. of regional significance. • I I In the McGregor Bay area the Gowganda Formation conformably succession by the Lorrain Formation, a banded "cherty" quartzite, overlies the Serpent Formation and is followed in upward - I a white vitreous quartzite, and ferruginous slates, siltstone* and quartzite. The iron—bearing beds are thought to be approximate equivalents of the Animikie iron formations of Port Arthur and the south shore of Lake Superior. The oldest Proterozoic rocks of Michigan and adjoining areas are thought to be correlatives of the Cobalt Group of Ontario. The absence of the older Huronian rocks in the north-central United States may be attributed to the presence of a positive area there in pre— Cobalt times. Paleocurrent analysis and dimensional fabric analysis indicate an essentially southerly direction of transport of the Hurorian sediments of the McGregor Bay area. Abundant sedimentary structures indicate that all the Huronian sediments of the McGregor shallow—water conditions. A comparison of the Lower Proterozoic sediments of Canada with - Bay area were deposited in those of south-west Greenland, Scandinavia, India, and Australia suggests the existence of frigid conditions over a large part of the earth's surface at that time. I .1 I �31 UNIQUE INTERGR(MTH OF CALCITE AND PYRITE Paul W. Zimmer The Hanna Mining Company Iron River, Michigan A rather unique intergrowth of calcite and pyrite is here described. These crystals were found in the (Iroveland Iron Mine of the Ranna Mining Company near Iron Mountain, Michigan. The pyrite and calcite show evidence of simultaneous crystallization. The pyrite grew on the vertical symmetry planes of the calcite with the triad symmetry axis of the pyrite parallel to the triad inversion axis of the calcite. This intergrowth gives the geometric symmetry of the Ditrigonal hemimorphic class to the combination. It is felt that because the intergrowth does not satisfy the symmetry of the calcite in its entirety, the pyrite was the "seed' crystal to the intergrowth. The interspacings of the planes in the calcite in the direct ion of the triad axis is very close to the spacings of the planes in the pyrite in the direct ion of the tritd axis and it is felt that this similarity in spacings was the controlling factor to this unique intergrowth. More work is needed in the field of crystallogeny. Evidence of partial parallel orientation of crystals may be characteristic of simultaneous crystallization that can be used in the interpretation of age relations in mineral deposition. ��REGIONAL GEOLOGY OF THE SAULT STE. MARIE AREA C. Ernest Kemp Michigan Technological University Sault Ste. Marie, Michigan p INTRODUCTION The contact between the Precambrian Canadian Shield and the main body of Paleozoic rocks to the south is nowhere more obvious than in the Sault Ste. Marie 'area. Here a marked unconformity is reflected in changes in the vegetation and topography. The• that the visitor going from one area to the next is immediately aware of the 'marked difference between the two regions. result is This paper will be confined to the areas near or adjacent the twin cities of Sault Ste. Marie in Michigan and Ontario, although better known areas of geological interest can be found beyond the limits of this discussion, at Blind River to the east and Wawa to the north. For the student of' geology the area is rich in diversity of lithology, structures, topography, and mineralogy. Being' close to Lakes 'Superior and Huron, and to the St. Mary's 'River, it is an area of considerable natural beauty which has become a popular tourist center for visitors from both Canada and the United States. to Although regional geological studies of this region have been made since early in the nineteenth century, only a few have dealt specifically with areas involved in this paper, and some of these are noted in the references.*' Since the discovery of uranium at Theano Point, copper in commercial quantities near Mamainse, Ontatio,, and dolomite in Chippewa and Mackinac Co!lntiós in Michigan, more detailed work has been carried on. However, there • are many interesting,' unsolved geological problems throughout the district, to of the fact that there is still a consider- say nothing able potential for the discovery of new, economically valuable, deposits. Sault Ste. Marie, Ontario and Sault Ste. Marie, Michigan are situated north and south, respectively, of the rapids in the St. Marys River. These rapids are fifteen miles downriver from the outlet of Whitefish Bay, Lake Superior, and forty-seven miles upriver from Lake Huron. The general direction of the river is slightly north of east from Whitefish Bay to St. Mary's Rapids. At the rapids which are also the location of the famous locks and over the head of which passes the International Bridge lintcing * Numbers refer to references listed at the end of this paper. �U p 2 t the two cities the river drops about twenty feet southward and }lows into Lake Huron at Detour. and then turns Climate and Ventation The area immediately surrounding the two Saults has a typical northern continental climate modified by the proximity of Lake Superior. The latter his in the path of the prevailing windp, and most of the major air masses in migrating eastward have to pass over the lake before reaching the Saults. It is fl interesting to note that this area lies only a relatively short distance south of a tongue of sub—ArctThc climate which encompasses the southern tip of James Bay. The severity of the winters increases rapidly landward from the shores of the lake, part ice ularly in the Ontario section of the area. Total precipitation approaches 30 inches annually, and average mean temperatures range from 64.6°F in July to l5.S°F in January.l7 Inland from the lake it is not uncommon to find temperatures of ..400F, and unofficial records are far below that. A noticeable difference in vegetation separates the areas underlain by Precambrian rock from those underlain by Paleozoic, even though a veneer ef Pleistocene deposits partially covers them all. Originally there was probably a greater similarity of vegetation between the two areas, but cultivation and more intensive logging of the flat lands characteristic of the Paleozoic areas have radically changed the flora. The vegetation on the Precambrian areas consists mostly of maple, birch, and aspen, and extensive areas of coniferous growth. Such farm land as exists is generally confined te small glacial drift—filled valleys between rocky hills with little soil cover. The Paleozoic areas, on the other hand, comprise broad areas of farm 'forested areas of hardwood, including beech, and extensive sand plains and swamps on which conifers dominate. Dense dedar growth characterizes the southern Paleozoic area. land, part of the 1 paper deals with five distinguishable subsections of the geology of the Sault Ste. Marie area and its environs, viz. This Granite Complex 2. Metamorphic Complex 1. 3• 4. 5. 1 Keweenawan Paleozoics Glaciation g I 1 L. �3 Granite Comlex From Sault Ste. Marie, Ontario northward to the Montreal River and westward to Lake Superior lies an area which, with . the exception of the Keweeawan, to Le describeQ later consists almost entirely of granite and granite gneiEs.°,l2 fn this area there are a few extensions of the metasediments and meta- volcanics to be found farther east, but anyone travelling through this country is bound to be impressed by the overwhelming amount of granite and granite—like rocks. The granites are mostly pink and quite uniform in the southern end of the area. Both gray and reddish varieties, sometimes porphyritic and often with pegmatitic phases, occur in the northern end. Granodiorite monsonite, and related phanerites are also present in smaller amounts. The gneisses are well banded and are very likely metasediments; they contain large masses ef amphibolite and biotite schists, which may be xenoliths of partially granitized basic volcanics or intrusives. The granites are mapped as Algoman but more intensive study of the batholiths is likely to Show several different ages of granite activity. Some younger granitesl° have been recognized but a complete description of the age relationships is beyond the scope of this paper. The entire granite area is cut by basic dikes)4 The dikes are often sheared to some degree and have been altered to chloritic and serititic equivalents. Some fresh diabase dikes are obviously of i younger age, and ire presuMed to bs Keweeawan. Characteristically the granite areas are rugged, with relief as much as 800 feet.. The drainage is youthful with several lakes and many swift-running streams. The soil is generally thin except in the valleys, End in many places thegranites form rugged rock bluffs. Where the basic dikes cut the granite masses, differential erosion of the dikes has resulted in deep chasms, the most obvious erample of which is at the mouth of the Montreal River. Here the walls of the ccnyon are practically the contact surfaces of the dike which is now visible only during stages of low water. The area here called the Granite Complex has not produced any commercially valuable deposits, although some near misses have occurred and there Is a possibility that a copper porphyry type of deposit will be developed near the edge of the Keweenawan.' The original discovery of uranium in 194.8 by Robert Campbell, which set off one of the greatest staking rushes in hi4pry, occurred in the northern end of this area at Theano Point.'4 Here mineral- ization is found along the contacts of one Of the dikes cutting a pegmatitic phase of the granite. Pitchblende and related minerals are sufficiently concentrated in hydrothermal veins to have warranted some serious development lork. Several other similar occurrences of pitchblende were found, the most noteworthy of which was in a similar geological environment north of the Montreal River on the property which has become the Ranwick mine. Here specimens �4 of massive pitchblende are found along with some selenides such as clausthalite, PbSe, and a mineral close to Klockmannite, CuSe. Native selenium has also been reported. Although an adit was driven into the potential ore zone, bulk sampling yielded results The mine has since too low to continue further development. become a tourist attraction and the property continues to yield excellent samples of pitchblende for the mineral collector. Several pits and adits scattered throughout the area are testimony to earlier hopes of developing some of the mineralized veins which contain chalcopyrite, galena, and spalerite, but none of them has proved of sufficient size or grade to be minable. Metamorphic Complex Extending eastward from the Granite Complex to the area north of and including Bruce Mines, the geology is radically The dominant rock types of this extensive area are different. metasediments and metavolcanics with some large basic igneous intrusire, This area includes part of the type section of the Huronian.' This area is dominated by prominent hills of quartzite, metaconglomerate, and diabase. The topography in many parts is In some of the valleys quite rough, with relief about 600 feet. between the ridges north of the town of Bruce Mines enough glacial debris has accumulated to provide soil for farming, and although the flat areas are not very extensive, they seem to be relatively fertile. The area also contains many lakes; drainage is in the youthful stage. The general strike is northwesterly, and in the abundant outcrops north of Bruce Mines the ridges and valleys tend to The Murray fault has been traced follow the regional strike. through the middle of the area and strikes northwesterly as well,' Secondary faults probably associated with the Murray fault system occur throughout the area. With the Murray fault almost along its axis, the main structure is a syncline, boldly outlined by resistant quartzite ridges. To the south a paralleling anticline can be traced, with the south limb exposed along Highway 17 near Desbarats where some conspicuous ripple marks are preserved in the quartzites outcropping in road cuts along the highway. (See Elliot Lake guidebook in this program.) Most of the rocks in this area are considered Lower and Middle Huronian, though some of the greenstones, which have been called the "Basement Series", are possibly Archean.2,1° The age relationship of the diabasos and metadiabases is not completely clear; some of them have been considered Keweenawan, and others probably much older. The Huronian rocks are mostly quartzites, metaconglomerates, and metagraywacke. Minor outcrops of Lower Huronian limestone occur; and some slates and a metamorphosed chert—like siltstone are associated with the more prominent One formation in particular deserves special mention quartzites. I I �U r 5 that is the very colorful Lorraizie metaconglomerate which contains jasper and white quartz pebbles in a white matrix and and forms a conspicuous horizon. Economically the area has yielded a few minable deposits most noteworthy being the copper deposits of Bruce Mines. Here, veins ef quartz, siderite, ankerite and chalcopyrite cut the diabase and were rich enough to sustain an intermittent operation in the past with a total production of between 300,000 and 400,000 tons of ore since discovery in 1646. many similar occurrences of chalcopyrite are known throughout the area. Galena and sphalerite in veins cutting metamorphic rocks completely surrounded by granite yielded a small production at Jardun Mines north of Garden River. Other lead-zinc occurrences are also known. Iron formation inter— bedded with metavolcanics or quartzite, magnetite concentrations as magnatic segregations in some of the larger basic igneous the masses, and some vein deposits of specularite in the quartzites have led to prospecting for iron. The last type yielded a small tonnage of high grade ore from the old Stobie mine near Gordon Lake. No. substantial quantities of iron ore are known. Gold has been mined from quartz veins near Ophir, north of Bruce Mines, but results were disappointing. The diabase has been quarried for road ballast and a rather extensive processing plant was erected eastof the Bruce Mines and operated for a few years during World War I. More recently the quartzite of the Bellevue ridge has been quarried for use by the Algoma Steel Company in Sault Ste. Marie, Ontario. Altheugh results of mining attempts have been generally disappointing there is still reason to believe that, with modern techniques, deposits of economic value may yet be found. Prom Harmony Bay north of Sault Ste. Marie, Ontario, and extending north to Mica Bay, the granites and metavolcanics are overlain by basic lavas and clastic sediments of Keweenawan age.1 As these rocks are similar in all respects to the Keweenawan of Michigan it is reasonable to assume that they represent an extension of the lavas found in Upper Michigan and Michipicoten Island. In this area rocks of Keweeawan age are never more than five miles from the shore. They lie comformably on the erosion surface of the older granites or on the Mamainse diakast, an older and more altered basic rock mass, mapped by Moore' asà:single lithologic unit but actually containing a variety of metavolcanics. The exact correlation ef the Mamainse diabase is not clear and in places it is difficult in the field to distinguish between this rock and the overlying Keweewanan. The topography of the area underlain by Keweenawan rocks is generally less rugged than the adjacent granite areas, but the total relief is about as great • The area is one .of ridges formed by the upturned edges of the flows and the conglomerates, so that the ridges trend in the same direction as the strike of the beds. t �________ 6 Along the shore of Lake Superior these ridges form long peninsulas The extending into the lake or islands paralleling the shore. topographic similarity between this shoreline and that of the northeastern part of the Keweenaw Peninsula of Michigan is striking. Cutting the Keweenawan are intrusives of felsite and felsite porphyry, which, curiously enough, appear to be more metamorphosed than the enclosing basic lavas, Thse acidic rocks constitute a very minor part of the Keweenawan,1 The rocks of the area mapped as Keweenan are amygdaloidal basalts and basalt porphyries and in the thicker flows the rocks grade into dolerites and gabbro. These flow units are interbedded The dip of the entire with conglomerates and sandstones. Keweenawan is generally westward toward the Lake Superior basin and dips average around 300. All of the formations have been affected by faulting but no large—scale displacement has been The general direction of the faulting is either parallel noted. to the strike and dipping normal to the beds, or at right angles to these and dipping vertically, Mineralization along the fault I I zones, some of which are brecciated, i inthé'foi ofcopper minerals, including minor amounts of native copper. This led to an early interest in the area in hopes of finding dépôits similar to those mined in Michigan. Recent interest in the area has resulted in the development of one producing mine and two promising prospects. The mineralization appears to be of three different types as described by Giblin.3 These are fissure—filled vein deposits, breccia pipe deposits, and disseminated deposits in what appears to be a copper porphyry type of occurrence. The latter two contain molybdenum as well as copper and occur outside the Keweenawan area but all seem to be associated with a post—lava flow period of mineralization, and therefore may be late Keweenawan in age. Some of the felsites have been explored for hydro-thermal clay deposits. Paleozoics South and west of St. Mary's River lies the area described as Paleozoic. Actually areas of Paleozoic rocks can be found in the previously described subdivisions, but these are minor and in themselves would not contribute much to the geological history This area represents the northern rim of the of the region. Michigan Basin, and therefore includes the oldest of the Paleozoic sediments found in the State.1 The rocks are quite unaltered and nowhere is there any evidence of igneous activity; therefore this subdivision provides a completely different topography as well as lithology from the Dips are very gentle, mostly to the south preceding subdivisions. and occasionally flat. Some local northerly dips are encountered. I I I I �7 The lowest formation in the series is a sandstone which has been correlated with a massive sandStone farther we4 and is considered therefore to be Middle or Lower Cambrian,' although ne direct evidence of this can be found in this area. This sandstone, known as Jacobsville crops out in numerous places and is especially well defined in die area of the locks. A well drilled to a depth of 1,500 feet south of Sault Ste. Marie, Michigan, failed to penetrate the bottom of this formation, but three miles north of the St. Mary's River along Highway 17, conglomerates in the Root River appears to be the basal conglomer- ate of the series. If this is the Jacobsfllle, and the origin of the latter is as postulated by Hamblin,4 it really as part of the Michigan Basin. Overlying Munising formation which can be seen outcropping along the shores of Whitefish Bay and in the Tahquamenon Falls. This latter sandstone is agreed to be the oldest formation of the Basin and is Upper Cambrian in age. does not fit this sandstene is the It is quite different in character from the red Jacobsvillo, being more thoroughly sorted, in some places a very pure quartz sand, and more uniform in thickness. It represents the farthest known advance of the Late Cambrian seas. Some gray sandstone and Shales found along the shores of Lake Superior near Mica Bay and Alona Bay are very likely of this age. Above the Cambrian, the Ordovician is represented by shales and limestones which crop out only sparingly. On St. Joseph's Island the limestone is highly fossiliferous, and crops out only a short distance from the Precambrian basement. The islands from St. Joseph south to the north tip of Druimnond in Lake Huron and west to the mainland contain many areas of Ordovician outcrops and in the Neebish cut there are excellent exposures.7 The material thro*n Onto 'the .:bank5 during the excavation yields good Ordovician samples. The most prominent of the Paleozoic formations are those of Silurian age. They crop out along an east-west, north—facing cuesta and all along the shores of Lake Huron at the south end of this area. These rocks are chiefly dolomite and the cuesta is an extension of the Niagara cuesta of New York and Ontario. In many places the dolomite is elposed or covered by only a very thin overburden. Where Lake Huron and the former glacial Lake Nipissing6 have eroded the dolomites, cliffs and other shore line features . have been developed. The Devoniant is present in only very minor amounts, outcropping near St. Ignace, particularly along the shores of Lakes Huron and Michigan, and in the c'its along the approaches to the Mackinac Lridgôa, The Devonian..eflthe Upper Peninsula consists of the Mackinac Breccia, a formation well described by Landes Ehlers, the and Stanley.t Several prominent sea stacks, now stranded retreat of the Lake since the Nipissing stage of the glacial development of the Great Lakes, occur along the shore in and near St. Ignace. Economically the Paleozoic has yielded metallurgical—grade �a dolomite as well as dolomite for construction purpose.5 Two prominent quarries are operating today, one at Cedarville and the other on Drummond Island. Sandstone of Cambrian age has been used for building stone, but none is quarried today. Pure quartz sandstone of Upper Cambrian age crops out along the shore of Whitefish Bay, particularly at Naomikong Point. Here the sandstone is almost of glass—sand quality without any b'eneficiation, but development of the deposit is interdicted by the Federal Forest Service, as the area is one being developed for tourists and the two operations are not considered compatible. Several attempts to find oil in the Paleozoics have failed. No systematic geopiysical work for the purpose of locating possible petroleum—bearing structures appears to have been done. Some bituminous shales and shaly limestone have been encountered, and reports of oil in some of the wells dug in the district have led to sporadic interest..ia As this area represents the margin of the Michigan Basin, and as the sediments are known to become thicker toward the center of the Basin, the possibility of oil and gas traps along pinch—outs or shoe—string deposits cannot be ruled out, although evidence is very meagre. Glaciat ion The entire area has been deeply affected by the Pleistocene glaciation, and all of it was covered during the Mankatoan substage of the Wisconsin.13 The evidences of recent glaciation are everywhere present, and it is not improper, in studying an area such as this, to discard the term flRecenttt and to include present time in the Pleistocene. During the time of maximum glaciation all of the area being discussed was under the áe, and not even nunataks could have occurred. All of the features which the glaciers left were formed at the bottom of the tremendous ice sheets, or represent features developed during the last stages of the retreat of the ice. In the resistant rocks of the Precambrian are found large These glacial valleys, reminiscent of mountain glaciation. valleys have a modified U-shaped cross section, and are therefore bounded on both sides by steep rocky walls and have a characterThese valleys appear to radiate away from istically flat floor. the highland areas, and were thereftre possibly carved out by tongues of ice descending from the ice caps which probably dominated the highlands during the last stages of the glaciation, while the main mass of the ice retreated to the north. This accounts for the east—west direction of the valley of the Goulais, That and the north-south direction of the valley of the Root. these valleys should also tend to follow zones of rock weakness, such as shear zones, columnar jointed dikes, and similar linear features is self—evident. Glacial grooving and striations are pronounced throughout the outcrop area, and are particualrly noticeable in the quartzites I �9 of the Precambrian and some of the dolomite ridges of the Paleozoic. Glacial polish occurs on some of the exposed quartzites and, due to only minor weathering, some exfoliation can been seen. In places where the Precambrian rocks crop out through the glacial drift, typical roches moutonnees are common. Whereas the area underlain by the Precambrian is characterized by the erosional features of glaciation, the area underlain by the Paleozoics contains mostly constructional features.* Here the topography is dominated by the flat plains which formed the floor of former glacial lakes.9 These plains are formed by varved clays and sand, and their featureless surface is broken only by some deeply eroded river valleys, morainal ridges and hills, the prominent dolomite cuesta previously mentioned, and a second, less prominent Cambrian cuesta, over which the Tahquamenon River flows to form the Tahquamenon Falls. Outwash plains, some with prominent gravel areas, occur south of the edge of the Precambrian, and are common in other parts of the area. Post—glacial uplift of the entire eastern end of Lake Superior accounts for many of the topographic features in the area.** Raised beaches are common in the area north of Sault Ste. Marie, To the south, and are responsible for some thick gravel deposits. the drowned lower reaches of the rivers0flowing into Lake Superior, such as the Waiska and the Tahquamenon,' are evidence of gradual tilting of the Lake basin. Economically, the glaciation of the area has resulted in valuable deposits of gravel, many of which have been used for road building and concrete aggregate. The varved clays have provided reasonably fertile farm land, and the sands are being used as fill. The glacial gravels are alo a source of excellent ground water, much of which is artesian. j. abstract in this program. * See, however, Farrand ** See Tovell et al. abstract. Ref erences 1. Cohee, George V. (1945) Stratigy of Lower Ordovician and Cambrian Rocks in the Michigan Basin. U.S. Geol. Surv. Oil and Gas Investigations, Prel. Chrtg. 2. Canada Collins, W. H. (1925) North Shore of Lake Huron. Geological Survey, Memoir 143, No. 124, Geological Series. Written at Methodist Hospital, Rochester, Minnesota. �______________ 1 10 3. Giblin, 4, Hamblin, William K. (1958) The CambraSandstones of Northern Michigan, Michigan Geological Survey, Pub, 51. 5. Hogberg, Carl G. (1960) Some Aspects of the Limestone Industry P. E. (1966) Recent Exploration and Mining Developments Paper presented at Convention in the Batchawana Area. Ont. of Prospectors and Developers Association, March, 1966. (see also abstract in the present program). in Michigan. Paper presented atA,LM,E, Meeting, Houghton. 6. Hough, Jack L. (1958) Geology of the Great Lakes. of Illinois Press. University I 7. Kowaiski, John Jt1 (1961) Silurian Lithology and Correlations. I 8. Unpublished. G.M., Landes, K. K.,Ehlers, G. M.,Stanley/(1943) Geology of the Mackinac Straits Region. Michigan Geological Survey, Publication 44, Geological Series 37. 9. Leverett, Michigan State University. I Frank (1929) Moraines and Shorelines of the Lake Superior Region. U.S. Geol. Surv. Prof. Paper 154—A. 10. McConnell, R. G. (1927) Sault Ste0 Marie Area, District of Algoma, Ontario Dept. of Mines, 35th Annual Rpt., Vol. 35, 1953, pp. 1—52. I PartI, 11. Moore, E. 5, (1926) Mississagi Reserve and Goulais River Iron Ranges. District of Algoma. Ontario Dept. of Mines, Vol. 34, Part 4, 1925, pp. 1—33. 12. (1927) Batchawana Area. District of Algoma. 1 Ontario Dept. of Mines, 35th Annual apt. Vol. 35, Part II, 1926, pp. 53—85. 13. Moore, IL C, (1958) Introduction to Historical Geology, 2nd Ed. McGraw—Hill Book Co. I 14. Nuffield, E, W. (1956) Geology of the Montreal River Area, Ont. Dept. of Mines, 64th Annual apt. Vol. 64, Part 3, 1955. 15. Ontario Dept. of Mines, Ontario Minerals in Your World, 1 1965 Review. 16. Thomson, Jas. E. (1954) Geology of the Mamainse Point Copper Ont. Dept. of Mines, 62nd Ann. Rpt., Vol. 62, Part 4, Area, 1953. 17. U.S. Weather Bureau, Sault Ste. Marie, Mich. 1 Personal communi- cation. 18. Van Lier, K. E. and Deutsch, Morris (1958) Reconnaissance of the Ground—Water Resources of Chippewa County. Michigan, Michigan Geological Survey, Progress Report No. 17. 1 I �Figure I. Geology of the SouR Ste. Marie Area �GEOLOGY AND MINERAL DEPOSITS OF THE MANITOUWADGE LAKE AREA* by E. G. Pye Resident Geologist Ontario Department of Mines Port Arthur, Ontario Introduction In 1931, the Manitouwadge Lake area was surveyed for the Ontario Department of Mines by Dr. J. E. Thomson, now Chief Geologist; and on his geological map, published in 1932, he noted an occurrence of gossan and sulphIde mineralization at the site of the now famous Geco mine]-, But despite this it was only many years later that any interest was paid to the discovery. This may be owing to the commonly held opinion that "greenstone" belts of small area do not lead themselves to the occurrence of large mineral deposits — the favourable prospecting area at Manitouwadge Lake is only about 35 miles square. It may also be because of the many prospectors highly metamorphosed condition of the rocks consider that schists and gneisses are unfavourable to ore depoIn any event, the area was avoided until as late as 194.7, sition. when the suiphide deposit at Manitouwadge Lake was first staked. But even at that time, it was difficult to arouse interest in the discovery; and after two years, the prospector, Moses Fisher, was compelled to let his claims lapse because of failure to attract a mining company to undertake development. In 1953, two prospectors, Roy Barker and William Dawidowich of Geraldton, Ontario, decided to visit the area. Upon relocating the ulphide deposit, with which they were much impressed, they decided to stake. The sulphide deposit was examined by W. S. Hargraft, consulting mining engineer, and upon his recommendation, the property was quickly taken up by General Engineering Company, Limited; Consolidated Howey Gold Mines, Limited; and H. W. Knight and associates on a partnership basis, Diamond drilling in August and September indicated the possibility of a copper—zinc— silver ore body0 Geco Mines, Limited, was incorporated in October, and it was not long before the results of further drilling * Published by permission of the Provincial Geologist, Ontario Department of Mines0 Reprinted from the Second Institute on A. K. Lake Superior Geology, "Geological Explorationtt. Sneigrove ed,9 Michigan Tech Press, 1957. Subsequent developments will be discussed at the mine by the author. 1. Thomson9 Jas, E,, "Geology of the Heron Bay — White Lake Area," Ont, Dept. Mines, Vol. XLI9 Pt0 6, pp. 34—47 (with map No. 4i), 1932. �___ I N 2 a deposit of such importance that the biggest staking rush in the history of Ontario, and one of the biggest in the history of Canada, was precipitated. indicated Location of Area Means of Access I. Manitouwadge Lake area forms a small but very important part of the Heron Bay - White , 1 The Lake region along the north shore of Lake Superior. As shown in Fig. lt it lies about midway between two transcontinental railways, the Canadian National Railways line on the north and the Canadian Pacific line on the south; it is 170 miles east—northeast of the Canadian Lakehead, and 200 miles northeast of Houghton, Michigan. The area i. accessible by an Ontario Department of Mines access road connecting Manitouwadge Lake with the Trans-Canadahighway along the north shore of Lake Superior; by a spur railway line built, south from Hillsport by the Canadian National 'Railways; and by a second railway line,, built north from Hemlo by the Canadian !acific Railway. General Geolozv. All the'consolidated rocks exposed in the Manitouwadge Lake area' are of Precambrian age. They have been divided into three main groups: (1) A system of closely folded and intensely. metamorphosed, volcanics. and sediments, which, together with horizons of amphibole — biotite gneiss and banded iron formation, are believed to be of Early Archaean age; (2)' An assemblage of igneous rocks, of post—Early Archaean and possibly of Algoman age; and (3) .Diabase dikes, which have been correlated tentatively with basic intrusives of teweenawan.age exposed' around Lake Nipigon and along the 'northwest shore of Lake Superior. . I ''.1i V c c : A prominent series' made up largely of horn— blende sc st is exposed south and west of .Wowun Lake. It forms *' See instead map on inside back cover for location. . I i 1 �3 a well—defined belt, width, which extends Lake, and up to and possibly, exceeding two miles in from this locality southwest to Manitouwadge thence westward across the southwest corner of the map area. Two varieties of hornblende schist are present. One shows little evidence of banding; the other is characteristically finely laminated and resembles a thin bedded sediment in structure. Excillent exposures of the non—laminated hornblende schist are found in the west part of the belt. In places where shearing has not been too intense, vestiges of original pillow structures can bstseen. The pillows are somewhat irregular in shape and do not permit satisfactory top determinations. But their presence is significant, for they indicate that the hornb].ende schist is of volcanic origin. In consideration of the mineralogical composition — the typical shhist consists of about 50 percent hornblende with lesser amounts of andeline and a little quarts, sphene, and magnetite — it is probable that the rock is the metamorphosed equivalent of original basic lava. Thin horizons of laminated hornblende schist separate the lava flows. They are particularly well—developed in the vicflifl The rock itself is similar mineralogically to the variety Just described except that, at the expense of plagioclase, quarts is an essential rather than an accessory constituent. A further and more striking difference, of course, is the thfcn bedded structure — black layers of material rich in hornblende alternate with grey layers rich in plagioclase and quarts. These layers range from a small fraction of an inch to several inches in thickness. The laminated hornblende schist is found in places to contain lenticular fraptents of greenstone, from less than an inch to six inches and up to about three inches in thickness. The two characteristics — stratification and fragmental structure — indicate that the original rock was a of Manitouwadge and Rose lakes. tuffaceous sediment deposited subaqueously during the period of volcanism. e : As the north margin of the volcanic series s approac , we —developed horizons of sedimentary gneisseseare found to alternate with bands of hornblende schist. These increase in both number and thickness to the north so that, within a short distance,the series gives way to one in which the principal ferrcmagnesian mineral is biotite. Four principal varieties of sedimentary gneisses have been recognised. They are biotite gmeiss, quartz—oligoelase4iotite gneiss, quartzite, and quarts—microcline gneiss. In view of the evidence presented by petrologists to the effect that clay minerals combine to form chlorite and sericite, and that theie in turn combine to form biotite during metamorphism', it is thought that the biotite gneiss, the quarts— 2. Barker Alfred, "Metamorphism, A Study of the Transformations of Rock Masses," Methuen & Co., Ltd., London, 11, 45—61, 1950. �I p 4 oligoclase—biotite gneiss, the quartzite, and the quartz—micro— dine gneiss are the altered equivalents of shale, argillaceous sandstone, quartz sandstone, and arkose, respectively. Amphibole—Biotite Gneiss: In many places throughout the series the sedimentary gneisses are found to be interrupted by lenticular masses of amphibole—biotite gneiss of dark colour, This coarse to very coarse granularity; and striking appearance. rock is made up largely of anthophyllite, hornblende, and biotite, with small amounts of quartz, oligoclase, and magnetite. Red garnets are also commonly present0 They occur as large porphyro— blasts, ranging from about one—half inch to two inches or more in diameter, and in places make up 25 percent of the rock mass. The amphibole-biotite gneiss is frequently found to grade, by disappearance of amphibole and, when present, also of garnet, Because of this it is considered to into typical biotite gneiss. may represent the highly metamorphosed be sedimentary origin — equivalent of a calcareous, chloritic grit or basic tuffaceous sediment that was developed at the same time as the enclosing It is included with the sedimentary gneiss on the generalrocks. ized geological map. it Iron Formation: Commonly intimately associated with the amphilbole—biotite gneiss is a peculiar banded rock. This banded rock consists of layers of coarse-grained quartz, from a fraction of an inch to a foot or more in thickness, alternating with equally thin or thinner layers of one or more of amphibole schist, garnetiferous amphibole—biotite schist, and a very coarse amphibolite, In the field it has been variously termed quartz— chlorite rock, quartz—amphibole rock, quartz-amphibole-pyroxene rock, and iron formation. Since the rock is distinctly banded, since the schist or amphibolite layers contain disseminated crystals and thin seams of fine granular magnetite, since individual horizons can be traced by dip needle and magnetometer, and since these horizons are very persistent and follow the folded pattern of the sedimentary gneisses, it is thought that "iron formation" is the most appropriate term. I Post-Early Archaean (Algoman?) I Basic Metaintrusives: Small lenticular bodies of metagabbro are found in a number of places within or close to the belt of volcanic rocks These bodies have intrusive relations with the Early Archaean formations, but are themselves cut by granite and pegmatite0 For the most part they consist of a medium— to coarse— grained rock made up of about equal amounts of dark-green horn— I I �5 blende and plagioclase, with small amounts of biotite, quartz, and magnetite. outcrop. This rock is generally quite massive in the Granitic Rocks: The most abundant igneous rock found in the Manitouwadge Lake area is biotite granite gneiss. Together with massive granite, migmatite, and pegmatite, it occurs in three (1) the extreme southeast corner of the principal localities: area; (2) the extreme northwest corner; and (3) the whole of the The granitic rocks to the northwest and south— northeast quarter. ea8t are believed to represent a single large mass, in which .the Ear1yrchaean rocks form a deeply infolded inclusion; those in the northeast quarter of the area are believed to represent a satellite of the main mass, which has been localized along the major synclinal axis (see Structural Geology). Associated with the granite gneiss, migmatite, and the rnedium—grained, massive, intrusive biotite granite, and cutting the Early-Archaean formations, are dikes and sills of pegmatite It occurs as: and aplite0 The pegmatite is of three ages. (1) dikes which cut metagabbro inclusions in, and which are themselves truncated by, the massive biotite granite; (2) irregular bodies which grade into, and hence represent a phase of, the massive biotite granite; and (3) dikes, which cut the massive biotite granite. Some of the pegmatites are preore in age, and onthe properties of Geco Mines, Limited, and Willroy Mines, Limited, they were instrumental in the local— ization of the ore deposits Algonkian The diabase forms The youngest rock exposed is diabase, a number of narrow, but fairly persistent north—south dikes, some of which are localized along transverse faults (see Fig, 2). In that these dikes cut sharply across all the other consolidated rocks, including the various granitic rocks, it is thought that they are of Algonkain or Late Precambrian age. It is possible that they could be correlated with similar rocks of Keweenawan age, that crop out to the west of the area in the vicinity of Lake Nipigon. �6 Structural Geology Folding: The rock type described as iron formation is the only one that occurs in sufficiently distinct and peràistent horizons to be useful in outlining the structural geology. Examination of the generalized geological map of the area shows that, in the vicinity of Wowun Lake on the east, the iron formation and the gneisses strike southwest and dip vertically to steeply north. Proceeding westward to Fox Creek and the Geco mine, however, the formations assume an east-west strike; and still farther west, midway between Fox and Nama Creeks, they strike northwest and dip 50°N. Finally, at the west side of the map area, the formations assume first a northerly strike and then double back on themselves to strike northeast again. They delineate a large trough or synclinal fold, which dip measurements indicate to be asymmetrical and overturned to the north. Other dip measurements, at the nose of the fold, indicate a plunge to the northeast of from 15 to 25 degrees. In the eastern part of the area, lineation and drag folds indicate a steeper plunge of about 40 degrees. 1 Faulting: After the major folding, the Manitouwadge Lake area suffered a series of disturbances that resulted in the development of a large number of faults. These faults are of (1) Longitudinal or strike faults, which more or three types: less parallel the formations along the south limb of the syncline; (2) transverse faults, which strike in a general north-south direction; and (3) diagonal faults, which strike northwest, obliquely to the other faults. All are represented in the field by deep linear depressions in the topography. An example of a major strike fault is the Agam Lake fault, which strikes due west, from north of Manitouwadge to almost the west boundary of the map area, just north of and roughly parallel to the belt of volcanic rocks. This fault is pre—ore in age, and is represented by a wide zone of graphitic schist, in places mineralized with pyrite and pyrrhotite. The magnitude and direction of movement along this break have not been determined. However, the fault appears to truncate a number of pre-ore, right—hand transverse faults, and at the same time, appears to be terminated by the north—south, post—ore, left—hand Fox Creek fault, I At least three periods of movement are thus indicated. A possible fourth period of disturbance may be responsible for the fault that extends diagonally across the area from northwest to southeast0 In regard to this fault, the offsets shown by the In the northwest section of the rock formations are of interest. area, the formations dip rather flatly to the southeast. Here the displacement was lefthand, or east side to the north. In the I I �7 southeast section of the area, the formations dip about 650 to the Here the displacement was right—hand, or east side to northwest. the south, To the east of the Geco mine, the formations dip Here the formations have been traced across the fault vertically. Such anomalous to Wowun Lake without any apparent offset. conditions can be explained satisfactorily by assuming that the displacement along the fault was mainly vertical, and that the South of Mose Lake, relative movement was up on the west side. a diabase dike was localized along this diagonal fault. But the diabase has been brecciated, Further, north of the Geco mine, the fault cuts and offsets two diabase dikes. In view of these facts and the simple vertical displacement indicated, it is thought that the two or more movements represented occurred in Lake Precambrian time. Mineral Deposits All the important mineral deposits discovered to date are Their locations are shown in Fig. 2:. suiphide replacement bodies. They strike and dip parallel to the formations that contain them, and have been found in or closely associated with either iron formation or a variety of sedimentary rocks. A determination of the lead isotope ratios of a sample of galena, from one of the occurrences, by mass spectrometer is reported by J. T. Wilson of the University of Toronto to indicate an age of 2,60O 120 million years.3 According to Wilson, the indicated age is close to that of leads found in the Golden Manitou and Barvue deposits in Quebec and the gold ores of Timmins in Ontario0 The lead from Manitouwadge Lake, and those from the other deposits, are all much older than the Sudbury nickel-copper ores, which are believed to have been formed in Late Precambrian time. In view of this, it is reasonable to assume that the ore minerals were deposited during the period of granitic intrusion, and that they are of Late Archaean or Algoman age0 Sulphide replacement deposits Deposits in Iron Formation: in iron formation have been found on the properties of Lun—Echo Gold Mines, Limited about the nose of the Manitouwadge syncline, and Wiliroy Mines, Limited, on the south limb of the syncline. As mentioned previously, the iron formation is a banded rock, in which layers of quartz alternate with layers of amphibole schist, garnetiferous amphibole schist, or coarsegrained amphibolite. In 3 Wilson * J0 T0, personal correspondence. Two miles northwest of Nama Creek, �A the replacement deposits found in this rock, the metallic sulphides heal fractures in the quartz and occur aseeither masses or disseminated crystals and grains replacing the minerals of the schist or amphibolite layers. Where massive replacement has occurred, the deposit is a strikingly banded one, in which layers of sulphides alternate with layers of mineralized quartz. On the other hand, where disseminated replacement has occurred, the sulphides appear to be localized along planes of foliation, which they accentuate. The principal sulphide present is pyrrhotite. It is invariably accompanied by considerable pyrite, subordinate amounts of sphalerite and chalcopyrite, and in some case also by I galena. The replacement deposits in iron formation may thus contain values in copper, lead, and zinc. Silver is also Some of the usually. present, and adds to the over—all value. deposits tend to be lenticular and of small extent. On the ban—Echo property, for example,. three of them have been thoroughly tested by diamon4 drilling. In each, commercial grade material, across widths up to and exceeding 25 feet, was indicated. But none of the deposits was found to have a length greater than 500 feet, and each of the three was found to decrease in width and grade two deposits, with depth. In contrast to the Lun—Echo occurrences sufficiently rich located on the Willroy property, appear to be These are-known as the No. 2 and No. 3 ore and large to make ore. shaft zones. At the present time (19561 a vertical 4—compartment is being sunk as a prelude to their underground development. QecgpOr Body . south and 1800 here extends easteast of the Willroy No. 1 zone, and from the Wiliroy for a horizontal length of 2,650 feet • Like I 1 The Geco ore body is exposed about 600 feet feet ward No. 1 zene, it lies within the horizon of highly sericitized quartz—feldspar—biotite gneiss, which is bordered on the north by garnetiferous amphibole—biotite gneiss and biotite granite, and on the south by quartzite. It is a lode fissure rather than in Pig. 3, a simple disseminated replacement deposit. As shownthe West, can be divided conveniently into three sections: it Central, and East. The West section of the ere body lies west of Pox Creek. It has a length of 1,200 feet at the surface, ranges up to 220 feet in thickness, and rakes to the east at about 40 degrees. is in every respect similar te the Willroy No. 1 zone, In part and consists ef highly sericitized gneiss mineralized with it metallic suiphides, chiefly pyrite and chalcopyrite, and cut by occasional quartz stringers. But here the sulphides replace the I I �9 host rock outward from a narrow, tabular core of massive ore made up of pyrite and sphalerite, with considerable pyrrhotite but relatively small amounts of chalcopyrite This core occurs near the south wall of the ore body, within a few feet of the sericitized gneiss—quartzite contact0 It decreases in width and tends to pinch out both to the west and with depth. To the east, the West section is cut off sharply by the Fox Creek fault, so that 're east of the creek, the extension of the ore body lies approximately 250 feet to the north. This extension, or Central section, extends eastward from the fault for a distance of 50 feet, to a point where it is truncated sharply by a zone of north—south diabase dikes, Near the surface th idd.le section has an average width of 5 feet. Like the West section, it consists of a core of massive suiphides, chiefly pyrite and sphalerite. This is enclosed by an envelope of iron, copper, and subordinate zinc sulphides disseminated throughout sericitized gneiss, But here the core is much wider than in the West section, and the envelope of disseminated material is narrower and, in places, below ore standards0 Near the surface, the ore of the Central section is thus rich in zinc but poor in copper0 With depth the core of the ore body decreases in width and tends to tongue out, whereas the bordering disseminated ore increases in width and grade. The net result of this is a gradual transition from a high—grade zinc and low-grade copper ore near the surface, to a high-grade copper and low-grade zinc ore at This deep ore, rich in copper but containing low values depth0 in zinc, is identical in character to that found in the West section of the ore body, and there is little doubt that it represents the eastward extension of the West section down the general rake of the ore body. As mentioned above, the Middle section of the ore body is truncated by a zone of north—south diabase dikes, The East section of the ore body lies east of these dikes and extends for a horizontal length of about 600 feet near the surface, It is identical to the central section in character, except for three features: Cl) both the core of massive sulphides and the envelope of disseminated ore are narrower and tongue out eastward; (2) the core of massive suiphides attains its maximum thickness of about 50 feet at a depth below the surface of 700 feet, and pinches out upwards; and (3) at the east margin of the zone of diabase dikes, the core is represented by massive pyrrhotite and pyrite, and phalerite does not become an important constituent until a depth of about 500 feet is reached, The East section, at or close to the present erosion surface, thus represents the upper limit of the east—raking ore body0 The Geco ore body has been tested by diamond drilling to a To this depth, the three sections vertical depth of 1,300 feet0 are estimated to contain 15,227,251 tons of ore having an average �10 grade of 1.76 percent copper, 3.4 percent zinc, and 1.77 ounces of silver per ton,6 Mineralization I and Paragenesis I The principal ore minerals in all the known deposits are Galena is often also present, and chalcopyrite and sphalerite. is particularly prominent in the Wiliroy No. 2 ore zone, but nowhere does it occur in sufficient quantity to be of economic importance, Silver is present in every deposit. It has not been recognized as such, Assaying of samples from the Geco ore body indicates that high values in copper are usually accompanied by high values in silver, and the thought has been expressed than the silver is present in solid solution in the chalcopyrite.1 A qualitative spectrographic analysis of chalcopyrite from the Geco ore body indicated the presence of tin, which may also prove to be of economic importance.° Associated with ore minerals in all the deposits are Small amounts quartz, in small veinlets, pyrite, and pyrrhotite. The paragenesis, as of cubanite and mgrcasite have been found. given by Langford for the Geco occurrence, is as follows: (1) (2) (3) (4) (5) (6) formation of pyrite; fracturing and introduction of quartz; formation of pyrrhotite; formation of chalcopyrite, overlapped in part and followed by; formation of sphalerite; and formation of galena. The presence of exsolution textures of sphalerite in chalco pyrite and of chalcopyrite in sphalerite indicates that the Geco ore minerals were formed at high temperatures, and that the deposit, according to Lindgren's1° classification, is of 6. 7. The Northern Miner, April 5, 1965, p. 41. Langford, F. F0, "Geology of the Geco Mine in the Manitouwadge Area, District of Thunder Bay,tt: Unpubl. M.A. thesis, Queen's University, Kingston, Ontario, 1955. , Oo 9, Cit0 Qp, 10. Lindgren, W0, "Mineral Deposits," McGrawHill Book Co., Inc., New York, 1933 I �11 hypother1 type.]-]- This conclusion follows from the work of Buerger,-'- who points out that chalcopyrite unmixes from sphalerite at temperatures of 350 to 400°C, and from the work of Edwards,13 who states that sphalerite unmixes from chalco— pyrite at temperatures of 500 to 600 C. Structural Controls of Ore Deposition One of the most interesting aspects of geological survey work is speculation as to the reasons why ore deposits are where they are after the ore deposits have been discovered and partly Such speculation, in the hope that it may prove developed0 useful to further exploration, will constitute the balance of The structural controls of ore deposition in the this paper. Manitouwadge Lake area may be considered under two headings: Major controls, and minor controls. Major Controls The major controls over the deposition of the ores were the folded structures and certain pre—ore faults. Folded Structures: In regard to the folded structures, dip determinations, and measurements of lineation made apparent by the parallel alignment of elongate biotite flakes and prismatic crystals of amphibole, indicate a regional plunge of the This plunge ranges from l5_250 in formations to the northeast. the west section of the area to about 400 in the east section. Of interest is the fact that the rake of all the known ore bodies or mineralized zones, and in the case of the Geco ore body, also of the zonal arrangement of suiphides, is in the same direction and at the same angle as the plunge of the formations. Pre—Ore Faults: One of the most interesting features of the area is the localization of the Geco and Willroy No. 1 ore bodies along a very persistent horizon of sericitized quartz— feldspar—biotite gneiss. At the Geco mine, this horizon is cut by north—south dikes of pegmatite, which are terminated abruptly 11. Langford, F. F., op cit. l2 Buerger, M. W., "IJnmixing of Chalcopyrite from Sphalerite," Am,jrra1., Vol. 25, pp. 534—53, 1934. 13. Edwards, A. B., "Textures of the Ore Minerals," Aust. Inst0 of Mm. and Met., Melbourne, Austra1ia 1947. �12 by the massive suiphide core of the ore body and do not appear in This indicates expected positions on the other side of the core. that the massive suiphides were localized in a fault zone, and that this zone served as a channelway, along which the hydrothermal solutions, that effected the sericitization of the gneiss and the deposition of the ore minerals, actually migrated. At first consideration, it would appear that this fault zone, which is post—pegmatite in age, was developed after the formation of the major syncline, But the horizon of sericitized gneiss has been traced continuously across the area for a distance of 4 miles, throughout this length it is everywhere conformable to the folded unaltered sediments enclosing it. Because of this, and because the alteration indicates the presence of a continuous channeiway during the epoch of mineralization, it i concluded that the sericitized gneiss represents a bedding fault that was deformed with the other rock formations during the regional folding. The other ore bodies or mineralized zones in the area do not occur along persistent horizons of altered rock. Nevertheless, it is thought that they also may have been localized along folded bedding faults — faults that were of limited lateral extent and and were formed as parallel structures merely subsidiary to the In this regard, it "break" represented by the sericitized gneiss. is to be noted that mineralized zones containing pyrite and pyrrhotite have been found in numerous localities throughout the area, but that it is only close to the horizon of sericitized gneiss that such zones contain any significant amounts of copper, zinc, or silver0 Minor Controls The minor features which are known to have exerted some influence in the localization of the ore bodies are: (1) intrusive—sediments contacts; (2) local curves or bends in the formations; and (3) the presence of flat—lying bodies of granite pegmatite. I 1 Intrusive—Sediments Contacts: Examination of Fig. 3 shows that the Geco ore body lies within sericitized gneiss, which is bordered to the north by biotite granite and by garnetiferous amphibole—biotite gneiss. Where the sericitized gneiss is bordered by the granite, the best widths and values in copper have been found, On the other hand, where it is bordered by the garnetiferous amphibole-biotite gneiss, both to the west and to the east, the widths and metallic content decrease, and even It would thus appear that the sericitic alteration becomes weak. the contact, between the granite and the sericitized gneiss, localized the structural adjustments that provided the open spaces necessary for the migration of the ore—forming fluids and the deposition of the metallic suiphides. I �13 A second examp1e illustrating the effect of intrusive— sediments contacts on the localization of ore, is found in the Wiliroy No, 3 zone. Here the mineralization lies in a band of This iron formation, and the suiphide iron formation. mineralization within it, have been traced for 2,300 feet. But the zone only attains ore grade where, over a length of 1,200 feet, the iron formation is bordered along its footwall side by a narrow, sill like body of pegmatite. Local Curves or Bends in the Formations: A second minor but nevertheless important control over the localization of the ore bodies was the presence of local curves or bends in the formations. As shown in Fig, 3, the formations in the vicinity of the Geco ore body strike roughly east—west for a considerable distance, and dip vertically to steeply south. Near the west boundary of the area represented however, the horizon of sericitized gneiss assumes a The ore body strike of N. 550 W. and a dip of 65° to 750 N.E. occurs where the sericitized gneiss strikes east—west and has a vertical or near—vertical dip. Similar conditions are found on the Wiliroy property. Here there are three ore bodies, all of which trend roughly east—west, and all of which terminate westward at points where their respective host rocks curve sharply to assume northwest strikes and flatter dips0 The reason for the localization of the four ore bodies, along the east—west portions of their favourable host rocks, close to points of deflection in attitude, is found at the Geco mine. It was mentioned previously that the massive sulphide core of the ore body is localized along a fault zone which truncates bodies In the sericitized gneiss adjacent to the massive of pegmatite. suiphides numerous drag folds have been mapped. These drag folds are of two types: one type is "Z" — shaped in plan and is compatible with the major Manitouwadge syncline; the other type is "5" — shaped in plan and hence is a "reverse" structure incompatible with the major field. Such "reverse" drag folds have been found only in the horizon of sericitized gneiss, and it is logical to assume that they are expressions of the movement which culminated in the post—pegmatite faulting. They plunge at about 40° E., and indicate that the block of ground north of the fault moved down and to the west. A relative displacement of this type would result in the development of favourable open spaces along Thus, as pointed the steep—dipping portions of the fault zone. out by Newhouse,4 if one portion of a fracture surface dips steeply, and the other portion has a lower angle of dip, and if the hanging wall moves relatively down, the hanging wall will ride on the flat—dipping portion as a supporting surface, This will separate the hanging wall from a footwall along the steeply— dipping portion of the fracture surface to form an opening. 14. Newhouse, W. H., "Structural Feature Associated with Ore Deposits," in Ore Deposits as Related to Structural Features, Princeton University Princeton, N. J0, p. 17, 1942. �14 Presence of Flat-LviAr: Bodies of Peatite: The third minor contrel ever the localization of the ore bodies in the area was the presence of small, flat—lying bodies of pegmatite extending acress horizons of' favourable host-rocks. At the Geco mine the north—south pegmatites that. are truncated by the massive suiphide core dip at flat angles, in places eastward, in other places westward. These pegmatites are typically massive, pink, unaltered varieties. But, within a foot or two of their contacts, they are somewhat sericitized, and display fractures healed by metallic sulphides. According to Walter Claz'ks, chief geologist at Geco Mine, Limited, the disseminated ore in the sericit'ized gneiss toads to improve in' grade as the contacts of these flat—lying. bodies are approached. Similar re—ore pegwatites cut across the ore zone at the Willroy No.: 1 ore bedy. As each of the two pegiqatites are approached from below, an increase in the width and/or grade of the ore body ±1 apparent. Because, of this it is thought that the flat—lying pegmatites served as relatively impermeable barriers, which inhibited the migration' of the oreforming fluids and thus effected sulphide deposition in the seri— citized gneiss at or close to their contacts. Conclusions S . fl — ''I Exploration and developient work at the various properties permits tentative' acceptance of certain valuable conclusions about the mineralization in the area. These facts are as follows: "(1) The mineral deposits are of Archaean age and may' be realted genetically to the granitic rocks. All the knot' mineral deposits ,are replacement deposits, '(2) either disseminated or lode fissure in character, and occur in either iron formation or sedimentary gneiss. '(3) ,The mineral deposits were formed at high temperatures, and may be considered as representative of Lindgren' s hypothermal class. (4) 'The' deposits are controlled in their attitudes by the major folded structures, and rake flatly eastward paraflel to lineations. I ' lie within a preore folded fault zone that is' represented in the field by a persistent horizon of sericitized quartz—oligoClase—biotite gneies, or they lie within small, parallel structures 'close to the horizon of sericitized gneiss. '(5) They (6) All 'the important ore bodies are found where the formations' strike roughly east—west, and adjacent to the east of places 'where those formations curveS sharply to assume a northwest strike and relatively flat dips to the north. (7) Two ore bedies, the Geco and the Willroy No. 3, ,are localized along the contacts between granite or pegmatite and their respectitefavourable host rocks. (6) tn'two cases, at the Geco mine and in the Willroy No. 1 ore body, flat bodies of pegitatite served as relatively impermeable barriers, which inhibited the migration of the ore—forming fluids ?1 �U 15 effected a;eulphide deposition in the host rock at or close to note that in several loóalities and to their contacts. It is of interest in the area, the horizon of sericitized gneiss has. boen found to disappear beneath outcrops of• flat-lying pegmatiteso Such occur at west end of the Gecô ore body, in the extreme north— wist corner of the Willroy property, and again between the llama Creek and kin—Echo properties. In each of these places favourable ore structures may exist. But it seems unlikely that sulphide bodies can be located beneath the peuatites by geophysical methods. Rather, it is concluded that successful exploration will necessitate detailed geological mapping, to determine the approximate location and trend of the sericitized gneiss beneath the pegaatites, followed by expensive diamond drilling. �Fig. 2. Generalized geological map of the Manitouwadge Lake area. Fig. 3. Surface plan showing generalized geology in the vicinity of the Geco ore body (modified after company plans). �16 TOUR LOG* MANITOUWADGE TO SAULT STE. MARIE The rocks of the region are all Precambrian, ranging in age from Keewatin to Keweenawan. Mileage 0.0 35. Manitouwadge. Route 614. 5 Hemlo. 37.1 STOP 1 Junction Trans-Canada Highway 17, turn east. Rock cut bnN side of road in a gray quartz monzonite gneiss aundant undigested amphibolitic inclusions. Strong jointing. Glacial grooves and polish. with The dominant rock type at this stop has the composition of a quartz monzonite. Quartz, orthoclase and microcline, sodic andesine, hornblende and biotite are the major minerals. The plagioclase occurs as prophyroblasts with crenulated margins. Orthoclase is found as anhedral grains often intergrown with microcline, Quartz forms in elongated pods or is interstitial and intergrown with feldspars. Myrmekitie intergrowths are common along plagioclase boundaries. Accessory minerals are large euhedral and anhedral grains of dark brown sphene, apatite, zircon and magnetite. Alteration products are pennine, epidote, and sericite. The dark inclusions in the quartz monzonite are distinctly schistose in thin-section. Dark minerals are hornblende and chloritized biotite. A mosaic of sericitized, untwinned sodic andesine forms the groundmass of the subalighned mafics. Rounded grains of quartz are evenly distributed throughout the section. Unaltered poikilitic microcline porphyroblasts are quite common. Epidote, allanite, sphene, apatite, and magnetite are the minor constituents. 67. 7 105. 7 White River. Canadian Pacific Railways divisional point. Scattered outcrops of metasedimentary rocks enroute. Good exposures of massive quartz diorite in contact with Granite pegmatite and diabase dikes. The route now crosses several infolded belts of Keewatin and Temiskaming metasedimentary and metavolcanic rocks. STOP 2 iic schist and gneiss. *From "Geology of the Lake Superior Region", National Science Foundation, Fourth Summer Conference for Geology Teachers, Michigan Technological University, June, James M. Neilson, Conference Director; Joseph P. Dobell, Associate Director (who is also responsible for petrographic descriptions). Reproduced by 1965. permis sion, �17 Mileage — 2, cont'd, Meta-rhyolite. In a thin section of the distinctly schistose tmetarhyoliteTM the major minerals, in order of abundance, are quartz, orthoclase, muscovite, biotite, and epidote. Orthoclase occurs as scattered large subhedral crystals and in intergranular positions throughout the rock, It also occurs with quartz in the pink lenses so prominent in hand specimens. The single thin section examined provided no convincing evidence that the rock is a metavolcanic. STOP 118,3 Rock cuts in phyllitic sericite schist south of Catfish Lake. 119. 3 STOP 3 123. 5 Magpie River, incised in glacial sandplain. 124. 5 Wawa intersection. Continue on 128. 0 Road intersection. Road to right leads ot Michipicoten Harbour; continue on Highway 17, to left... 128, 8 Michipicoten River. 140. 3 Old Woman River and Lake Superior to the west. 146, 7 Rock cut at Red Rocks Lake. 157. 5 STOP 4 Outcrops of amphibolite, biotite-chiorite schist, pillow lavas (?) etc. Outcrops of Dore Conglomerate and lineated rhyolite breccia. Dore Conglomerate. The matrix of the Dore conglomerate in this area is a quartz mica schist, Biotite is more abundant than muscovite. Numerous oligoclase crystals look like original clastic fragments. An altered pebble of granite is elongated parallel to the schistosity and sheathed with biotite. Feldspars in the pebble have been fractured and are separated by fine grained feldspar or bands of quartz. Highway 17. A thin section of the amphibolite prominent at this stop was examined. About 65% of the rock consists of pale green hornblende, 25% is andesine and 5 to 7% is biotite. Minor constituents are quartz, pyrrhotite, pyrite, spheno, hematite and chlorite. The chlorite is restricted to fracture zones. 166 2 Coidwater River, 1703 Sand River. 177. 3 STOP 5 Agawa Bay scenic lookout. A series of large rock cuts with posures will be seen for the next seven miles. Quartz monzonite and other rock types. I �18 Mileage this stop a distinctly sheeted white rock of quartz monzonitic composition predominates, A point-count modal analysis indicates that microcline comprises 35% of the rock, oligoclase 34%, quartz 29% At and micas less than 1%. The texture is granular and senate, Rounded grains of quartz occur as inclusions in turbid oligoclse and a second of quartz partially replaces the oligoclase. Biotite, now much altered to chlorite, was probably contemporaneous with the oligoclase. The clear rims of al.bite which occur on most of the oligoclase grains appears to be earlier than the second generation of quartz. Microcline and muscovite, in this order, are the last minerals to form. A few grains of garnet, partially altered to chlorite, and zircon are present. generation Gradational with the quartz monzoite is a coarser grained light pink granite phase. In this rock quartz and microcline are the major minerals. Oligoclase grains have been partially altered to sericite and frequently have clear albite are present. rims, Chloritized biotite and a few flakes of muscovite A third rock type noted at this stop occurs as inclusions of tightly folded micaschist. The chevron folding is marked in hand specimen by thin quartz bands and in thin section by biotite which forms good polygonal arcs. About 20% of the rock is biotite, 45% quartz and 30% orthoclase, Zircon, magnetite and apatite are minor accessories. 178, 2 Agawa River, 180.4 Agawa Bay campground in Lake Superior Provinical Park. 189. 1 Ranwick Uranium tctouristtt mine. 190. 7 Note stratification in glacial gravels on left, 191.7 STOP 6 Montreal River. Gorge was created by erosion of columnar3itflDasalt dikes intruding granite gneiss. This very fine-grained rock shows no alteration except the chlorite on slickensided joint surfaces. Fresh laths of labradorite surround rounded Magnetite and grains of augite and pigeonite in a typical diabasic fabric. apatite 193. 9 are the minor accessories. Elevated Glacial Lake Algonquin cobblestone beach about 200 present lake levels, Granite gneiss exposed in cut. 198.4 Alona Bay Lookout. 203. 4 Extensive road cuts in Archean rocks. 207, 4 feet above Contact of Keweenawan gZloidal basalts and granite boulder conglomerate. The flows and STOP 7 Mamainse Bay on Lake Superior. beds parallel the shore and dip to the west under Lake Superior. �19 Mileage Amygdaloidal basalt, Laths of partially albitized calcic plagioclase indicate an original diabasic texture. Pyroxenes have altered to chlorite and 'limonitet1, Magnetite is abundant. Two types of amygdules are present. In one type the wall of the cavity is lined with a thin band of carbonate which is followed by wider bands of a chlorite and a center filling of carbonate. In the second type there may be several concentric bands of carbonate separated by chlorite or by chalcedony zones and the center filling is chalcedony. In hand specimen, the is 214. 4 chalcedony is a pinkish white color and calcite pink to light red to faintly greenish in color. Keweenawan basaltic flows are much in this evidence along the highway in area. 226,3 Batchawana River. 232, 3 STOP 8 iss Chippewa River. Xenolithic inclusion of diabase in granitic at falls. 1 The gneiss is the major rock type at this stop. Dark bands in Gneiss. this rock consist dominantly of actinolite, chlorite, epidote and albite to- gether with small amounts of quartz, carbonate, sphene and apatite. Light colored bands are quartz and orthoclase together with small amounts of oligoclase. The feldspars are turbid with alteration products. Acicular clusters of actinolite and rounded grains of epidote and sphene are present and some chlorite was noted. The opaque minerals are limonite-stained pyrite and magnetite. 242, 5 Batchawana Bay. 254, 9 Goulais River. 262, 0 STOP 9 Rock cut, Rough road for 5 miles. I Rock cut, Altered diabase dike cutting granitic gneiss; note in contact zones. Lamprophyre near south contact, this dike the diabasic texture is fairly well preserved. The pyroxene (augite) is altered to amphibole along the margins of crystals and the plagioclase (An65) is partially or completely altered to an aggregate of sericite, epidote group minerals, and carbonate. Minor constituents are In magnetite, biotite, chlorite and sphene. 272.4 Sault Ste0 Marie, Ontario P1 �U THE RELATIONSHIP OF MINERALIZATION TO THE PRECAJIBRIAN STRATIGRAPHT, BLIND RIVER AREA, ONTARIO* • • * James A. Robert son Geologist Ontario Department of Mines Toronto, Ontario paper preSented at the 17th Annual Meeting of the Geological Association of Canada, Toronto, May 29, 1965, and reproduced by permission of the Director of the Geological Branch, Ontario Dept. of Mines, for a Field Trip t! Elliot Lake, May 7—8, 1966, sponsored by Institute on Lake Superior Geology. £ �U 2 TABLE OF CONTENTS Page Abstract . . . a . • Introduction * . • . Acknowledgments . . . . General Geology . . . . Economic Geology . . . Conclusion . . a . . Selected Bibliography a Description of Stops . 2 3 • . . • . a . . a . . . • a 9 a . 10 3 . . 4 12 SKETCH MAPS AND FIGURES Figures 1. 2. 3. 4a 5. 6. Location of Blind River area. Blind River area, general geology. Table of Formations Lateral variation in Bruce Group. Uranium deposits in Quirke syncline. Distribution of copper deposits relative to Nipissing diabase. I ABSTRACT This paper is a result of a continuing investigation, begun in 1953, by government geologists and mining companies. The Archean rocks are Keewatin greenstones intruded by Algoman granites for which the geological age has been determined as about 2,500 million years. These granitic rocks consist of gneissic granodiorites and massive, slightly radioactive quartz The Archean complex was eroded to a peneplain with monzonite. valleys in the less resistant rock types. The Lower Huronian consists of the Lower Mississagi Formation, the Middle Mississagi Formation, the Upper Mississagi Formation, the Bruce Conglomerate, the Espanola Formation, and the Serpent Formation. These formations contain a great variety of sedimentary rocks such as conglomerate, argillite, siltstone, greywacke, limestone, and Thickness and facies changes indicate a northwesterly quartzite. source, northerly overlap, and deposition in shallow water controlled by basement topography. The Lower Huronian formations unconformably overlie the Archean rocks and in turn are Unconformably overlain by the Middle Huronian formations. The Middle Huronian rocks consist of the Gowganda and Lorrain formations of conglomerate, greywacke, quartzite, and arkose. There are three phases of post—Huronian igneous activity: (1) dikes and sills of Nipissing diabaso; (2) the Cutler granite; and (3) dikes of olivine diabase. I I I I I I I �3 Age dating methods give the age of the Nipissing diabase as million years, and the granite at Cutler as 1,750 million A few dikes of Keweenawan olivine years (Penokean orogeny). diabase are tentatively dated at 1,100 million years. 2,130 Copper mineralization is associated with the Nipissing diabase. Uranium ores in quartz—pebble conglomerates, near the base of the Lower Mississagi Formation, are generally considered Uranium to be placer deposits modified by later events production from the Blind River mining camp to the end of 1962 was valued at 944,373,25O. This was derived from 44,937,7l tons of ore grading approximately 0.1 percent U308. INTRODUCTION This paper is a discussion of the Precambrian rocks and Lake area of Ontario mineralization in the Blind River — (Fig. 1).* Blind River is located on the north shore of Lake The town Huron half way between Sudbury and Sault Ste. Marie. of Elliot Lake (Fig. 2) lies 20 miles northeast of Blind River. The area is served by the Canadian Pacific railway, the ThansCanada highway and by other roads. Elliot Early geological mapping was carried out by Logan. and Murray following the discovery of cper at Bruce Mines in i46 (Logan Later mapping was carried out by W. H. Collins 163, Chap. 4). in 1915 (Collins 1925). In 1953 uranium was discovered in the district which subsequently became Canada's chief source of uranium. Since 1953 extensive geological worL has been carried out by the Ontario Department of Mines, the Geological Survey of The Canada, mining companies, and interested individuals. Ontario Department of Mines has been responsible for regional mapping; this was carried out by E. M. Abraham in 1953—1956 (Abraham 1953, 1957) and has been continued by the writer since J. P. McDowell (1957, 1963) 1957 (Robertson, J. A. 1960 et investigated the sedimentary features of the host rocks of the uranium mineralization. ACKNOWLEDGMENTS The co—operation and interest of members of the Ontario Department of Mines, the Geological Survey of Canada, of many employees of mining companies, and of students and professors in both Canadian and American Universities, is gratefully The writer is indebted to R. Balgalvis of the acknowledged. Ontario Department of Mines for preparation of the figures. * See instead map on inside back cover for location. �4 GENERAL GEOLOGY The bedrock of the area falls into three broad units the (l the These are: distribution of which is shown on Fig. 2. Archean basement consisting of Algoman granite and Keewatin—type greenstone; (2) the Huronian edimentary rocks made up of the Bruce Group and the Cobalt Group and (3) the Post—Huronian intrusive rocks comprising the Nipissing diabase, the Cutler granite, and olivine diabase believed to be Keweenawan in age (only the Cutler granite is shown in Fig. 2), The structure is also illustrated on Fig. 2. In the north is the Quirke syncline and in the south the Chiblow anticline, the south limb of which is repeated by a major east—striking the Murray Fault. The fold axes strike slightly north fault of west and plunge gently west giving the sedimentary units a Bedding—plane slips, thrust faults, reverse—S shaped outcrop. and near—vertical faults which strike either northwest or parallel to the axial planes of the folds are common, The fault pattern, jointing, dragfolds, and other structural features suggest a north—south compression formed the folds, Figure 3 is a Table of Formations giving more detail than it is possible to show on Fig, 2. It has been Department policy to retain Collins' nomenclature making modifications only where S, M, Roscoe (1957) and P. J, Pienaar (1963) of the necessary. Geological Survey of' Canada have introduced a nomenclature using The differences are in names rather than in ideas, local names, The Keewatin-type rocks underlie the eastern portion of the Quirke syncline and are exposed to the southeast of the syncline, The rock—types found include massive and pillow lavas, pyroclastic rocks, and sedimentary rocks including lean iron formation. Strike is northwest and dips generally steep northeast. Metamorphism is of chlorite facies rising to amphibolite in hybrid zones close to contacts with the Algoman granite. Granitic rocks of Algoman age (2,500 million years; Fairbairn, Lowdon, Van Schmus et al 1963) from approximately half the area These granitic rocks may be divided into two shown on Fig. 2, (1) medium— to coarse—grained, gneissic to massive broad groups: granodiorite, generally grey to pink in colour with abundant inclusions derived from the Keewatin and 2) massive red quartz monzonite generally without inclusions and slightly radioactive. A body of the second typo is found in the Quirke Lake area. I The Huronian sedimentary rocks lie unconformably on the Algoman-Keewatin complex. A topographic low was developed over the greens4one belt, with local ridges controlled by the harder members (Fig0 5). Remnants of pre—Huronian soils are preserved particularly over the granitic rocks, The present chemical constitution of these soils suggests that they were formed under reducing conditions0 I I �5 The Lower Mississagi Formation contains the known uranium deposits and has ben studied in dótail. The general sequence consists of greenish rkose with or without uraniferous quartz-' pebble conglomerate bands and beds followed by grey quartzite, followed near Elliot Lake by argillite and impure quart zite. Cross—bedding and pebble orientation studies by McDowell (1957, 3. 1963) and Pienaar (1963) indicate the currents flowed from the northwest but were markedly. influenced by basement topography. Ore—conglomerates occur largely it valleys in the basement óurface (Fig. 5). Thickness of the Lower Mississagi Formation increases from 0 at the north shore of Quirke Lake through 600 feet near Elliot Lake to more than 1,000 feet south of the Murray Fault. As northward overlap is pronounced (Fit. 4) ore—beds at'n Pronto, Nordic, and Quirke are progressively younger. The Middle Mississagi ormation normally consists of a basal polymictic conglomerate followed by argillite. The conglomerate was used aS a marker horizon during exploration drilling. The upper part of the argillite sequence is characterized by ripple marks. The argillite thickens from less that 100 feet at the north shore of Quirke Lake to over. 750 feet near Elliot Lake (Fig 4).. Near the crest of the Chiblow anticline the conglomerate is about 5 feet thick and the argillite only 40 feet but on the south limb of the Chiblow anticline, both north and soith of the Murray Fault, the Middle Mississagi is represented by 000 feet of This indicates deeper water to the south quartzite and ef the area mapped, siltstone. The Upper Mississagi Formation Consists of greinish arkose on the north limb of the Qüirke syncline but elsewhere of well— Thickness ranges from 600 feet at Quirke bedded grey Lake to 1 500 feet near Elliot Lake and to a maximum of 2,700 quartzite. feet on tAe south limb of the Chiblow anticline, repeated south of the Murray Fault at Blind River. Current direction is from the northwest but the influence of basement topography is much diminishe4. Facies and thickening relationships again indicate deeper water to the south and southeast. The Upper Mississagi Formation is followed disconforinably by the Bruce Conglomerate — which consists of boulders of white granite and greenstone in a partially sorted1 slightly pyritic, siliceous greywacke matrix. The conglomerate can be traced There are marked local variathroughout than 200 feet tions in thickness but the unit thick. the entire district • isgenerallyless . three units, all of are mappable within the Elliot Lake district; a lower unit, The Espanola Formation consists pf which characterized by limestone — the Brñce Limestone; a middle unit, characterized by mudstone and greywacke — the Espanola Greywacke; and an upper ónit having a mirked development of ferruginous dolomite — the Espanola Limestone. Throughout much of the area mapped the Cobalt Grouperests unconformably on the Bruce Limestone. �1 6 The Bruce Limestone consists of thinly interbedded cream— coloured limestone and siltstone. Differential weathering and drag—folding give the rock a spectacular appearance. Where the unit is complete, the thickness is generally 100 feet. The Espanola Greywacke and Espanola Limestone members can be only distinguished by the brown—weathering dolomite bands. Both members are characterized by iñtraformational breccias, siltstone and conglomerate dikes, mud cracks, and ripple marks. These indicate shallow water deposition and tectonic disturbance. Occasional quartzite beds show crossbedding from the northwest and become more common to the northwest. Where complete the thickness of the Espanola Greywacke is 300—400 feet and that of the Espanola Limestone 150 feet. The Espanola Formation is overlain by the Serpent Formation — a white feldspathic quartzite only exposed in the northern and eastern sections of the Quirke syncline. The maximum known thickCrossbedding, and ness of the 3erpent Formation is 1,100 feet. lithology and thickness changes in individual members again show derivation from the northwest. Ripple marks and mud cracks indicate shallow water conditions. The lateral variation in thickness of the formations of the Bruce Group is illustrated in Fig. 4. The Bruce Group is followed unconformably by the Cobalt Lake area consists of Group which in the Blind River the Gowganda Formation and the Lorrain Formation. Within the map—area the Gowganda Formation rests on all formations between the Upper Mississagi and the Serpent Formation. Locally the contact can be seen truncating the bedding of the underlying formation and consolidated fragments of the underlying rocks are found in the lowermost beds of the Gowganda Formation. Elliot The Gowganda Formation is a heterogeneous assemblage of conglomerate, greywacke, quartzite, and aril1ite. These rock types are found throughout the sequence though the lower part is characterized by boulder conglomerate and the upper by quartzite and argillite. Within the area mapped the Gowganda Formation is about 2,000 feet thick. Dense The origin of the Gowganda Formation is in doubt. boulder conglomerates, quartzites, and argillites are definitely water laid; varved conglomerates and greywackes probably formed under conditions characterized by alternate freezing and thawing although some authorities would ascribe these rocks to turbidity currents; and sparse boulder conglomerates with disrupted grey— wacke matrix may be either tillites or mudf low deposits. Locally in the Quirke syncline the Gowganda Formation is overlain by a few hundred feet of well—stratified, crossbedded, arkosic quartzite tentatively correlated with the basal Lorrain0 The wellknown white quartzite with jasper conglomerate has not been found in the area. I �7 Following Huronian times the region. was subjected to tectonic The folding and faulting (briefly s"arised earlier) and the intrusion of the Nipissing diabase took place. The Nipissing diabase 'is divided into two phases: the earlier comprises large stress. irregular sifl-like gabipro bodies and the' later numerous vertilal dikes striking either northwest 'or west • The gabbroic 'bodies, the distribution of which shows marked structural control (Fig. 6), are differentiated frem gabbre to diorite. and, in some, cases, to granophyre. The copper deposits of the district are relAted spatially and genetically to these gabbroic bodies. Alteration (albitization, chioritization, and Carbonatization) associated with either dikes Or sills is.on a small scale but has locafly effected the uranium deposits. 'According to Tan ,Schmus (lan 1963) the gabroic bodies have a probable age of Schmus fl 2,170± 200 million years,' 'and a minimum age of 1,950 million years. . -. ' . . The only granite. of probably post-Huronian age is the Cutler Batholith to the south of Spragge. Age determinations, obtained by Fairbairn (1960) Wetherill (1960), and the Geological Survey of Canada (Lowdon 1461 fl flq.) whilst obscure in interpretation, range between 1,750 and 1,3W million' years and determinations on metamorphic mica in adjacent rocks give 1,400.million years. Sedimentary rocks of probable Ruronian age on 'the islands south of the Cutler batholith shoi an increase in metamorphism towards the Cutler bathelith. Staurolite schists and meta— quartzite are found between the batholith and the Murray Fault and as inclusions in 'the batholith. These rocks, long thought to be Archean in. age1 may be the metamorphosed' equivalent of the southern' facies of the Middle Missiesagi Formation and therefore of Huronian' age. Volcanic rocks at Spragge may. be the equivalent, of Hurronian volcanic' rocks described by .Frarey '(1961, 1962) at Thessalon. However, .,no valcanic .rocks have, been identified in the undoubted Huronian rockS of the Blind. River area 'as found north of the Murray Fault. The relationships of, the Cutler batholith will be further studied in the 'coming' field season. ..A few olivine diabase dikes Strike northwest throughout the district. Tan Schmus (personal communication) has recently established an age of. 1,190± 50 million years for olivine diabase which cuts the Cutler granite. Similar olivine diabase dikes are found throughout the 'north' shore tof Lake Huron and elsewhere give 1963). a date of 1,000 a 11100 million years (Lowdon fl The' olivine diabase dikes are displaced by the Murray' Fault' indicating late tectonic disturbance. At surface the fault has a vertical to steep southerly dip. .The vertical displacement of the fault is:6,000 stratigraphic feet,. south side up and the horizontal displacement measured on magnetic anomalies associated - with olivine diabase' dikes is 5,000 feet north•stde east. 1. Subsequently modified to 2,130± 80 million years; Tan Schmus, personal communication. �B ECONOMIC GEOLOOT Two types of ore deposit have aroused interest - the uranium— sulphide veins. Investigations into the. possible use of Bruce Limestone as a neutralizing agent in the Uranium mills and the use of Nipissing gabbro as road material were beth dropped at an early stage. The uranium deposits are found (Fig. 5) as quartz—pebble pyritic conglomerate beds in zones controlled by basement topography. In the Quirke syncline the relationship of the uraniferous conglomerates to granite—greenstone contact areas and valleyS over softer zones in the greenstone belt is clearly demonstrated by surface drilling and mining operations. At Pronto, bearing conglomerates and post-Huronian copper—bearing quartz- . . . . however, there is no clear relationship to basement geology which raises the possibility that there may be other economic uranium deposits underlain by granite. The ore—zones strike northwest—southeast and are controlled by basement structures. Original sedimentary structures preserved in the rocks indicate the zones are parallel to the depositional The Quirke zone (the largest in the area) is 32,000 feet long and•from 6000 to9 000 feet wide. The Nordic zone is 19,000 toot long and from 4,460 to 6,000 feet wide. The Pronto deposit and the unworked zones are of smaller dimensions. currents. The uraniferous quartz-pebble conglomerate and green arkose is characteristic of the Lower Mississagi Formation and has been used by Thomson (1962) as a marker horizon in tracing the Archean-Huroniafl boundary between Lake Timagami and Blind River. Locally where overlap brings Upper Mississagi into close proximity with the basement, arkose with thin, slightly radioactive pebble bands is found. The uranium—mineralization is thus associated with the basal beds of the Huronian and the distribution over a wide area suggests a syngenetic origin. The conglomerates consist of well-rounded, well sorted, quartz pebbles in a matrix of quartz, feldspar and sericito and have an I sequence I average pyrite content of 15 percent. Monazite and zircon are characteristic heavy minerals. Brannerito and uraninite are found in the matrix. Thucholite is found locally and may line fissures in the ore beds1 Th. ore—minerals are brannerite, uraninite and monazite. Roscoe has shown the uranium—thorium ratio (1:3) is comparable to that.of the basement. The lateral variation in the ore-mineral and uranium-thorium ratios as studies by Roscoe (1959) and D. Robertson (1962) are best explained by the relative stability of monazito during transportation. Locally, individual . conglomerate bands may assay as . . high as 20 lbs. or more U3O per ton, but over mining widths of the order of 9—30 feet average grade is 2-3 lbs. U30g per ton. _ I I �____ 9 with the ore conglomerate is generally greenish in colour and is crossbedded. It is probable that the conglomerate accumulated as placer deposits derived from weathered red-phase Algoman granite and that the uranium—bearing minerals were altered and redistributed during diagenesis, during the different periods of tectonic• stress, and definitely during the introduction of diabase. There is no evidence in the area mapped by the writer, of crosscutting uranium mineralization. Alternative theories include deposition from hydrothermal fluids derived from post—Huronian granite as suggested by Davidson (1957) and biogenic precipitation of uranium derived from weathered basement but transported in solution as proposed by Derry (1960). Although almost one billion dollars worth of uranium oxide have been extracted there are large drill—indicated reserves left. When marketing conditions for uranium improve, the Elliot Lake area should again be a major producer. By—products include small The arkose interbedded amounts of thorium and rare earths. The copper deposits of the north shore of Lake Huron have been known since the 1840's. These are normally veins of quartz, chalcopyrite, with or without pyrite, specularite, and carbonate. Favourable structural conditions occur near or in large differ— entiatéd Nipissing gabbro bodies (see Fig. 6). In the area under discussion the veins trend parallel to the major fold axes and to the Murray Fault. Contact metasomatic deposits are also found associated with the upper contacts of sill—like gabbro—bodies. Prospecting has been carried out and a few properties have shipped small tonnages of ore. The main producer in the area is the Pater mine at Spragge where 700 tons of 2.0 percent copper are hoisted a day and treated at the Pronto concentrator. At Pater, quartz, pyrrhotite, and chalcopyrite, are found in a shear zone slightly oblique to the Murray Fault and located in the metamorphic rocks of possible Huronian age. Epidiorite is thought to represent metamorphosed Nipissing gabbro. CONCLUSION The area is one of extreme importance in the long-range economy of the country in this nuclear age. The deposits of uranium and copper should continue to interest the prospector, mine; and the public. Elliot Lake area contains excellent The Blind River exposures of extremely interesting Precambrian rocks of diverse type. The area is readily accessible and is ideal for research prograames. r �I 10 SELECTED BIBLIOGRAPHY Abraham E.M. 19k3: Geology of Long and Spragge townships, Blind River uranium area, District of Algoma (prelim. map 1957: The north shore of Lake Huron from &ladstone to and report); Ontario Dept. Mines townships; j Spragge Royal Society P.R. 1953—2. The Proterozoic in Canada; of.Canada, Special Publications S No. 2,pp. 59—62. C.I.M.M. 1957: Mining, metallurgy and geology in the Algoma uranium area; (published for the Sixth Commonwealth Mining and Metallurgical Congress, 1957); Canadian Inst.. Mm. Met. W. H. The north shore of Lake Huron; Geol. Surv. Canada, 1925: Mem. 143. Collins,. Davidson C.F. 195G: 1958: . On the occurrence of uranium in ancient conglomerates; Economic Geol., Vol. 52, pp. 668 — 693. (Discussion in subsequent issues). Uranium in ancient conglomerates — a reply; Economic Geol.,.. Vol. 53, pp. 687 — Derry, D.R. 1960: I 889. Evidence on the origin of the Blind River uranium deposits; Economic Geol., Vol. 55, pp. 906 — 27. Fairbairn, F.W., Pinson W.H., and Hurley, P.M. Minezal awl rock ages at Sudbury - Blind River, 1960: Ontario; Geol. Assoc. Canada Proc., Vol. 12, pp. 41 — 6., Frarey M.J. l61a: 196lb: 1962: Dean Lake, District of Algoma; Geol. Surv. Canada, map No. 5—1961. Wakwekobi Lake, District of Algoma; Geol. Surv. Canada, map No. 6—1961. Bruce Mines, Ontario; Geol. Surv. Canada; map No, 32—1962. Logan, W.E. 1863:. Lowdon J. A. ]460: 1961: The Geology of Canada (with accdmpanying atlas). Age—determinationfl Geol. Surv. Canada, Rept. No. 1, Isotopic ages, Paper 60—17. Age—determinations; Geol. Sun. Canada, Rept. No. 2, Isotopic ages, Paper 61—17. I. I �U 11 Lowdon J.A. fl a]. 1*62: Ijedeterminations and geological 1963: Age—determinations and geological studies, Geol. Sun. Canada, Paper 62.17. studies; Geol. Surv. Canada, Paper 63—17. McDowell1 J.P. 1951: 1963: • sedimentary petrology of the Mississagi quartzite in the Blind River area; Ontario Dept. Mines, Geol. Circ., No. 6. A paleocurrent study of the Mississagi quartzite (Ph.D. Thesis, along the north shore of Lake Huron. John Hopkins University). The Pienaar Pd. l9&3: • Stratigraphy, petrology, and genesis of the Elliot Group, Blind River, Ontario; including the uraniferous conglomerate; Geo].. Surv. Canada,. Bull. 83. Robertson, D.S., and Steenland, W.C. The Blind River uranium ores and their origin; 1960: Economic Geol.,.Vol.. 55, pp. 659.— 694. Robertson, D.S. Thorium and uranium variations in the Blind River 1962: ores; Economic Geol., Vol. 57, pp. 1175 — 1184. Robertson, J.A. Geology of part of the Blind River area, Ontario; 1960: (M. 1961: Sc. Thesis Queen's.University, Kingston). Geology of Townships 143 and 144.; Ontario Dept. Mines, G.R.No.4. Geology of Townships 137. and 138; Ontario Dept. Mines, . 1962: l963a: l963b: l963c: 1963d: 1964: Roscoe S.M. 1*57: 1959: 0. R. No. 10. Geology of Townships 155, 156, 161, and 162; Ontario Dept. Mines, G. R. No. 13. Geology of the Iron Bridge area, Ontario; Ontario Dept. Mines, G.R. No. 17. Preliminary map of Township 149; Ontario Dept. Mines, P. 193. •• Preliminary map of Township 150; Ontario Dept. Mines, P. 192. Geology of Scarf e, Mack, Cobden, and Striker TownshJps; Ontario Dept. Mines, G.R. No. 20. Geology and uranium dipositsQuirke Lake — Elliot Lake, Blind River area, Ontario; Geol. Surv. . Canada, Paper 56—7. ratios in conglomerate and On thorium - uranium asseciated rocks near Blind River, Ontario; Economic Geol., Vol. 54, pp. 511 — 512. �1 12 Roscoe, S.M., and Steacy, H.R. 1958: On the geology and radioactive deposits of Blind River region; Atomic Energy of Canada Ltd., A. Conf0, l5/P/222. Schmus, W.R. Geochronology of the Blind River — Bruce Mines area, 1965: Ontario, Canada; Journ. Geol., Vol. 73, No. , pp. 755—780. Thomson, Jas. E. Extent of the Huronian system between Lake Timagami 1962: and Blind River, Ontario; j the Tectonics of the Canadian Shield; Royal Soc. Canada, Special Publications No. 4, pp. 76 — 89. Van Schmus,W.R0 Rb—Sr age determinations of the Nipissing diabase, 1963: north shore of Lake Huron, Ontario, Canada; Journ. of Geophysical Research, Vol. 68, No. 19, pp. 5589 — 5593. Wetherill, G.W., Davis, G.L., and Tilton, G.R. Age measurements on minerals from the Cutler 1960: batholith, Cutler, Ontario; Journ. of Geophysical Research, Vol. 65, No. 8, pp. 2461 — 2466. MAPS AND AtDENDA Geol Surv. Canada Ontario Dept. Mines Map Map Map Map Map ll8lA, Iron Bridge Area 5-1961, Dean Lake 6-1961, Wakwekobi Lake 32—1962, Lake George 3 2—1962, Bruce Mines I Geol. Report 17, Iron Bridge Area Map P303, Sault Ste. Marie Sheet Lake Sheet Map P304, Blind River — Vol. XLVIII, Part XI, 1939, Geology of the Flack Lake Area Elliot Beger, R. M. 1963: Geology of the Pater Mine, Blind River Area; (M.S. Thesis, Michigan College of Mining and Technology, Houghton). I I I I �13 DESCRIFflON OF STOPS Between Highway 17 a Highway 548 junction and Desbarats East of Saült Ste. Marie,Ontario Stop 1 Lorrain Formation. In this area Lorrain Formation are exposed as Li three members follows: of the 1/2 mile east of junction (22 miles east Of Sault Ste, Roadside outcrops of pink to buff—coloured, medium to coarse-grained quartzite of. the Lorrain Formation, member #3. In this vicinity, the member attains a thick- Marie) • ness of 2,000 feet. It is commonly feldspathic or pebbly (quartz and jasper) and characterized by large cross—beds. About 1/2 mill east i:s a series of outcrops, mostly of pinkish quartzose siltstone or fine—grained quartzite, in • • part spotted with hematite clots, of Lornin member f2. Some purplish layers nearby. The ouartzite is somewhat similar to host rock at• disseminated copper showings about 1.5 miles north of this locality. Large roadcut 1 mile to the east. Prominent display ef ripple marks in greyish si].tstone—quartzite, just above base of Lorraiü member #1. Successive bedding planes exhibit widely divergent ripple mark orientation. Shear the zone on south aide of road. Stops la and b are rigarded as optionil; stop Ic will be sufficiently long to permit taking of photographs. STOP 2 Proceed 7 miles east to second roadcut past Portlock side— road. The cut is in Oowganda Fonation, about 1,300 feet below the top of this unit which here i8 striking about N6OE and dipping 20 NW. Greywacke-argillité, making up the bulk of the rock, carries disoriented frapients of pink— grey silt none and sparser granitoid blasts. The oedimentary pieces are thought to represent an interbed disrupted by penecontemporaneous slide or slump. east to junction of Highway 17 and 112L1 Continue 3 miles Oranophyric Nipissing diabase is on Line sideread. side, and on the sideroad just north of the outcrops of Sparse conglomerate of the Bruce highway Centre south are Conglomerate Fermation and grey laminated limestone of the B"uce Limestone member of the .Espanola Formation. These sedimentary units are thin here, probably not exceeding 100 feet. The diabase is part ofa large sill which follows around the Bruce Mines anticline. Bruce Proceád one mile into Bruce Mines. This village is of flgj historical interest. It was the first settlement on the north share of Lake Huron1 established at the site of the earliest copper mining operation by the white man in mainland Canada. Mining was done sporadically for about 75 years, up to 1921. The depoSits consisted of quartz— �1 14 carbonate veins mineralized ih chalcopyrite, pyrite, specularite and bornite. Similar veins are widespread in the district, and will be seen at Stop 5. The classical work of Logan and Murray followed the discovery of Bruce Mines. Stop 4 From Bruce Mines continue east for about 15 miles to outcrops at the east end of the Thessalon by—pass. This is at the western margin of the Thessalon Formation, a volcanic assemblage previously classed as (a) Keewatin (Archean) or (b) Keweenawan, but now included in the Huronian. The formation consists mainly of uniform-looking, fine—grained metabasalt, commonly amygdaloidal, but generally lacking other volcanic features. As well as here at Thessalon, such volcanic rocks, correlated with the Thessalon Formation,occur in the Huronian sequence about 14 miles north of Bruce Mines and also about 9 miles northeast of Sault Ste. Marie; at this last area they have been named the Duncan Formation. In all three areas, thin sedimentary intercalations are found, including quartz— pebble conglomerate beds generally similar to the Elliot Lake uranium ore. At this stop, the metabasalt is exposed, and a few hundred feet to the north along Highway 129 are a few beds of feldspathic quartzite, probably iñterbeds. Hiy Three miles east on Highway 17, just east of Livingstone Creek0 Low roadcuts here of Archean gneiss, pre-Huronian basement. This basement rise extends southeastward for about 20 miles almost to Blind River. It is bounded on the north by the Murray Fault and passes under Lake Huron on the south. The basal Huronian contact is visible only at a few places, notably on small islands in Lake Huron south The regolith frequently mentioned in of this stop. descriptions of Elliot Lake district has not been recognized in this vicinity. An age determination using hornblende obtained at this stop, done in the G.S.C. laboratory, gave a figure of 2620 m.y., indicating the maximum age of the Huronian. Its minimum age, as determined by dating whole rock and mineral samples from the intrusive Nipissing diabase, is approximately 2150 m.y. STOP 5 Continuing terrane at eastward, Highway 17 soon leaves the basement Sowerby, where it crosses the concealed Murray Fault and traverses the Gowganda Formation for about 4 miles to this stop. At this stratigraphic level the formation is characterized by conglomeratic greywacke— argillite ("tillite") and a few low outcroos are visable along the road in this interval. At this stop a roadcut exposes a quartz stockwork in sparse greywacke conglomerate and feldspathic quartzite; chalcopyrite, specularite, siderite and calcite occur in the veins, which are quite typical of the numerous vein copper occurrences in this district. I Hiy Eastward, the highway continues to follow the Gowganda I I �15 Formation from about 20 miles, keeping close to the northeast side of the Mississagi River from the town of Iron Bridge on. At the large, right-angle bend in the river not far above its mouth, the highway recrosses the Murray Fault, crosses the narrow eastern extremity of the basement rocks seen at Stop 7, and follows feldspathic quartz— ite of the Lower Mississagi (Matinenda) Formation to the town of Blind River. From Blind River eastwards for 6 miles, the road follows ouartzites and argillites of the Middle Mississagi Formation to Algoma Mills. At Algoma Mills (Lake Lauzon) the Murray Fault crosses the road. From Lake Lauzon to Pronto subdivision (4 miles) the road lies in sparse i11ite ?) corglomerates, greywackes, etc. of the Gowganda Formation. The discovery locality for the Blind River uranium deposits is at Pronto Mine. From Pronto eastwards through Spragge to the junction of Highways 10 and 17 the road follows the Murray Fault. Undoubted Lower Huronian rocks lie north of the road for distances of 1/4 to 1 mile and to the south lie metamorphic rocks (mafic meta— volcanics, schists, and epidiorites) and the Cutler Batholith (probable age 1750 m.y.). At Spragge is the Pater Mine — the only producing copper mine on the north shore, From the junction of 10 and 17, follow l0 to Elliot Lake (l miles)0 The Murray Fault is crossed immediately north of Highway 17 and to the east of the road greenish arkoses of the Upper Mississagi can be seen resting on a local high in he granitic basement. Granitic rocks and gneisses cut by numerous diabase dikes are exposed in road cuts to Depot Lake, From Depot Lake to Buckles Mine the road follows the strike of Keewatin sediments, These are greywackes and lean iron formation. At Buckles the scarp Northwest of of the Lower Mississagi is clearly visible. Buckles the road follows a fault which displaces the Lower Mississagi. Elliot Lake Programme Sunday Stops for a.m. Transportation will leave the hotel at Stops the Elliot Lake trip will be marked on map 2032. 12, 13, 14 are on the road from Quirke Mine to Flack Lake They lie in the uppermost and the White River Road0 formations of the Cobalt Group — not exposed elsewhere in These stops will only be made if the Blind River area. time permits. Stop 6 Upper Mississagi Formation: well—bedded feldspathic Note cross—bedding, also bedding—plane quartzites. lineat ions0 �1 16 Stop 7 Stop S Uppermost beds of Upper Mississagi Formation, contact with Bruce Conglomerate. Bruce Conglomerate (characteristic composition, texture, weathering) reworked tillite? Nipissing diabase transgressive sill; texture, banding, alteration and metamorphism of country rock. Contact Bruce Conglomerate — Bruce Limestone. Bruce Limestone, bedding, composition, drag—folds, metamorphic minerals — idocrase, grossularite, wollastonite; thin sill of diabase west side of road. Gowganda Formation Tillite type sparse boulder greywacke conglomerate. composition, texture, striated boulders. Sb Stop9 Note Well bedded dense conglomerate + quartzite beds and lenses. Note composition, texture, boulder shapes, packing, graded bedding. Unconformity between Gowganda and Serpent formations (Denison Side Road). Stop 10 Panel side road to Serpent River and Quirke Lake. Location Outcrop of mines - Influence of Geology on Topography. Note delicate banding of Middle Mississagi conglomerate. (varying?) and rafted pebbles in more argillaceous Intersection of cleavage and bedding. sections. Stop 11 Return to Highway 105. Road largely over Espanola FormOutcrop at junction of Panel Road and road to ation. Quirke No. 2 shaft. Espanola, dolomitic mudstones, note siltstone dikes, intraformational breccia, bedding, weathering, other outcrop on road show mudcracks, ripple marks, ball structUres, etc. Stop 12 West of Quirke Mine road climbs up onto Archean basement After about three miles granite gives way to (granite). Keewatin massive and pillowed mafic Keewatin lavas. These become strongly shattered and a prominent valley North of represents the outcrop of the Flack Lake Fault. this fault is the Rawhide syncline of which only the north The upper units of the Cobalt Group limb is preserved. are well exposed along the highway which runs through some of the finest scenery in the district. Return to Elliot Lake for lunch which will be at 1 p.m. At lunch representatives of the mining companies will join the group and they will give brief descriptions of the geology and other features of interest at their operations. Following lunch the group will leave the hotel (2:30 p.m.) and proceed south on Highway 105. I I I �17 Stop 15 If time permits a brief stop will be made at Buckles Mine to discuss the influence of geology on scenery. Stop l Texaco gas station, junction of Highways 1O and 17. Staurolite-mica schists of the Spragge Group (believed meta—Ruronian); note twinning on some crystals, alteration to pinnite, and crude grading. Stop 17 3 1/2 miles west. Brief stop at Murray Fault. few localities where this fault is exposed. Stop l Pronto Mine. One of the This is the discovery area. Points of Interest 1. Albitization of feldspathic quartzites at junction of mine road and access trail. 2. Bedding, composition, colour, and texture of Lower Mississagi Formation and changes as ore—zone is approached. 3, Discovery 4. Pre-Huronian regolith and Archean - Huronian contact 5. Surface workings — the only excellent exposures of typical locality ore—conglomerates. 6. Note also hanging wall quartzites. Pronto Thrust Fault Formal termination of field trip. �• • • • •BRIDGE IRON :.::::::: 0 • • p's •• • :• ••• •. • • : • : • : ———————— : • • ••:•: x Cutler granite 0 ' 2 4 6 8 Scale of Miles I0 HI I + I Algoman granite ( )(I Keewatin greenstone Bruce group J.1 Cobalt group x LEGEND GENERAL GEOLOGY BLIND RIVER AREA FIG. 2 I �UNIT LITHOLOGY AGE MILLION YEARS CENOZOIC RECENT 8 Sand, gravel PLEISTOCENE GREAT UNCONFORMITY PRECAMBRIAN PROTEROZOIC KEWEENAWAN INTRUSIVE PENOKEAN INTRUSIVE NIPISSING INTRUSIVE Olivine diabase 1,190 Granite I,750 Quartz diabase 2,130 HURON IAN COBALT GROUP LORRAIN Quartzite Conglomerate, grey wacke G OWGAN DA UNCONFORMITY BRUCE GROUP SERPENT ESPANOLA BRUCE CONGLOMERATE UPPER MISSISSAGI MIDDLE MISSISSAGI -- Quartzite Limestone, greywacke Conglomerate Quartzite Argillite Conglomerate LOWER MISSISSAGI Argillife Quartzite, U—congIomerate Conglomerate Arkose + U—conglomerate UNCONFORMITY ARCHEAN ALGOMAN INTRUSIVE Granite K E E WAT I N Volcanic and sedimentary rocks FIG.3 TABLE OF FORMATIONS 2,500 �CM4 FIG. 4 ElO I 1000 Vertical Scale NI Limestone & Quartzite U—conglomerate A rgilIi te Conglomerate MIDDLE MJSSISSAGI Qu or tz I te NJ 13 PA -24 Z-5 - I UPPER MISSISSAGI Greywacke Bruce Limestone BRUCE CONGLOMERATE ESPANOLA SERPENT 2000 FEET Z-5-2 ———— —- LATERAL VARIATION IN BRUCE GROUP oI ———— MISSISSAGI LOWER �TWP. 143 .3 TWP. 144 SCHEMATIC NOR DIC CROSS—SECTION PAR DEE PECORS B — A-B-C ,-. 1—Base of Middle Mississogi Conglomerate TWP. 150 r$y FIG.5 HISKEY 0 LI] 6 Format! - Lower Miss, /ron Form a outcrop; magnetic ai Greei Gr H Cong/or 4 —1000 FEET —800 i—200 [—400 [—600 —0 2 Scale of Miles URANIUM DEPOSITS IN QUIRKE SYNCLINE ————————————— II I �FIG.6 — I, DISTRIBUTION OF COPPER DEPOSITS RELATIVE TO NIPISSING DIABASE ———————————— �U I SUDBURT NICKEL IRRUPTIVE TOUR Organized at the request of the Society of Economic Geologists and the Institute en Lake Superior Geology Prepared by Sudbury Field Trip Coittee: K. D. Card Ontario Department of Mines J. N. Holliway, International Nickel Co. of Canada, Ltd. P. Potapoff, Falconbridge Nickel Mines, Ltd. D. Rousell Laurentian University B. E. soucE International Nickel Co. of Canada Ltd. G. Thrail, international Nickel Co. of Canada, Ltd. J. S. Stevenson, McGill University (Leader) �1 2 TABLE OF CONTENTS Page Introduction Geology. • . Bibliography Tourlog. Geological . • , . . , . . . . . . • . . . . . 2 3 ,.,..... 9 , . 4 map, Sudbury Basin SUDBURY NICKEL IRRUPTIVE TOUR n I INTRODUCTION I Sudbury has been going f or a long time. To quote from Hewitt — "The first mine that was located in the Sudbury (1964) p. area was the Murray mine; it was discovered in l3 along the right of way during construction of the Canadian Pacific Railway. A gossan zone was observed in a rockcut (1) and copper mineralization was identified, The mine was opened in l9, and the ore From l4 to l9O was smelted and refined at Swansea in Wales, prospecting continued in the Sudbury area and during those first few years many of the major deposits of nickel—copper ore, including the Frood, Creighton, Stobie, and Copper Cliff mines, were discovered." Since that early period, many important discoveries have been made, and today we have l producing mines. These include in the South Range, from (see accompanying map for location): the west to the east; the Totten, Crean Hill, Ellen Pit, Creighton, Clarabelle, Murray, Frood—Stobie, Garson, Falconbridge, East, and Maclellan mines; and in the North Range, from west to east: Hardy, Boundary, Onaping, Levack, Fecunis and North mines. As active mines, but not producing at the moment, we have, in the South Range, the Copper Cliff North, Little Stobie, and Kirkwood mines, and in the North Range, the Coleman and Strathcona mines. As indicating the continued growth of mining in the Sudbury Basin area, it may be of interest to note that this past summer (1965) International Nickel opened No. 9 shaft at its Creighton mine. This shaft will go down to 7,150 feet, making it the deepest continuous mine shaft from surface in the Western Hemisphere, I (1) Although not marked as a stop on the accompanying sketch map, we will try to stop en route briefly at the Discovery cut and see ore in placeG I �3 GEOLOGY The nickel irruptive, because it contains the world's largest concentration of nickel sulfide ores, is for that very reason, unique in its geology, and all geological studies of The irruptive is a late it should be made with that in mind, Precambrian layered complex whose dominantly inward dipping members form a north—easterly trending ellipse 37 miles long by 17 miles wide. The rocks southeasterly outside the basin consist of a conformable series of steeply dipping, southward facing, volcanics and sediments intruded by Murray and Creighton granites and by the Sudbury gabbro. Elsewhere around the basin, the rocks consist of a complex of granites, gneisses and included basic rocks, The rocks outside the basin are cut by breccia zones, a fraction of an inch to a mile in width; this breccia is known as the Sudbury breccia, or more locally, the Frood breccia. The rocks inside the basin comprise the Whitewater series of gently dipping volcanic breccia and tuff, slate and groywacke (sandstone), The irruptive consists principally of micropegmatite These rocks are layered, (granophyre) and, below this, norite, but the layering is quite gross and requires detailed mapping with careful attention to the petrography to bring out the layering. The uppermost phase of the micropegmatite and therefore of the irruptive, is a quartzite breccia that is matrixed by irruptive derived igneous material, referred to by Stevenson (1963, p. 415) as pepper—and—salt micropegmatite. This breccia forms a layer between the more normal micropegmatite and the The border rock at the base of the overlying volcanic breccia, norite is the well—known quartz—diorite, the principal occur rences of whici are the tongues or dikes commonly known as the offsets, that extend outward from the norite, Primary features, structural and petrographic, of the irruptive are best studied in the North Range rocks. This is because the South Range rocks, in contrast to those of th North Range, have been subjected to extensive overthrusting and consequently, the primary layering and petrographic features have been considerably modified by dynamic metamorphism and recrystallization. With respect to the orebodies themselves, their occurrence has been very succinctly described by Hewitt (1964, p. 91) "The nickelcopper suiphide orebodies are found as follows: along the footwall contact of the norite in mineralized shear zones or in mineralized embayments of quartz diorite. These are called 0contact" or "marginal" deposits; Creighton, Falconbridge, Levack, Murray and Garson are of this type. Orebodies also are found in the quartz diorite offsets. The FroodStobie, Worthing ton, Victoria Nickel Offset, and Copper Cliff orebodies are of �I offset type. Three main types of ore are recognized: disseminated .sulphides largely in quartz diorite; massive sulphides along zones of shearing and brecciation; sulphide veins, and stringers in sheared and brecciated quartz diorite and country rock. The ore may lie in either the quartz diorite or the adjacent footwall country rocks. Both the Creighton and Falconbridge mines have been developed to depths greater than 6,500 feet. the • 'The principal pyrrhotite, ore minerals are pentlandite, nickeliferous chalcopyrite, cubanite, niccolite, gersdorffite, maucherite, and sperrylite. The average grade. of ore is about 2 percent nickel and 2 percent copper, but it varies from ore, body to orebody.' The principal ore—minerals are indeed those mentioned by Hewitt but it is interesting to note that Hawley (1962, p. 41) states that some 4.0 metallic minerals occur. • BIBLIOGRAPHY - SUDBURY BASIN GEOLOGY This rather comprehemsive post-1955 bibliography will show temporary studies of Basin geology. Pre-1955 referencea, including those to the important 'standard works' on Sudbury, may be found in the reference lists of several of the authors listed here. For easier reference, the material, in this bibli.— graphy has been arranged into several groups, and .within each group a chronological sequence has been followed. the great variety of disciplines that are being used in con- 1 •ICAL SURVEY OF CANADA Geological Survey of Canada (1958). Map 1063*, Sheet 41 N.E. Geological compilation, coloured, from near Sault Ste. Marie to near Cobalt Scale 1 in. to 8 miles. Siidbury, , Geological Survey of Canada, 11965) Sudbury, Ontario, aeromagnetic .:. sqr1e's, Mip 7067G. 2. I ONTARIO DEPAMWENT OF MINES . 2a. Thomson Vol. Annual Reuorts (1957) Geology of Sudbury LIV 11*56), 146. Jas. K. Basin: Pt. III, I . Howelt (19.57), Glowing avalanche deposits of the Sudury'Ba8In: Vol. LIV, Pt. III, (1956), 57—89. Williams Phemister, 'Vol. T. C., (1957) The Copper Cliff Rhyolit. LIT, Pt. III (1956), 91—116. Thomson, J. Pt. VI, (1958), Geology K. (1957,, 1—36. in Maim Np.: of .Falconbridge twp.: Vol. LIVI, 1 I .1 �______________, _____________ 5 2b. Geological Reports (1960), Uranium and thorium deposits at the base of the Huronian System in the district of Sudbury: No. 1, pp. 1—40. (1961), Maclellan and Scadding twps., district of Sudbury: No. 2, pp. 1—34. Card, K. D., (1965), Hyman and Drury townships: 2c, No. 34. Preliminary Reports Langford, F. F,, (1960), Geology of Levack twp. and the northern part of Dowling twp., District of Sudbury: 1960—5. Card, K. B., (1962), Geology of the Sudbury sewage tunnel: 2d. Preliminary Maps (Scale 1 in. 1/4 mile) Geology and compilation Jas. E. Thomson, (1953) p. 41 Lumsden twp. p. 42 Hanmer twp, p. p. p. p. 1962—63. issued 1960. 43 Dowling twp. 44 Balfour twp. 45 Rayside twp. 46 Fairbank twp. p. 52 Maclellan twp. Geology and compilation Jas, E. Thomson 1957—59 (issued 1960). p. 105 Espanola sheet, 1 in. = 2 mi. geological compilation by Jas. E. Thomson, (1961), (issued 1961). 1/4 mi., geology by K. B. Drury twp., scale 1 in, Card, et al, 1960, (1961), (issued 1962). p 134 1/4 mi., geology by p. 202 Denison twp., scale 1 in. K. D. Card et al. (issued 1962). p, 203 Graham twp., scale 1 in, — Card et al, (issued 1963). 1/4 ml., geology by K. D. p0 247 Waters twp., scale 1 in, Card et al, (issued 1964). 1/4 ml., geology by K. D. 1/4 ml,, geology by K. D. Foy twp., scale 1 in. Card etal, (issued 1965). p. 315 1/4 mi., geology by p. 316 Bowell twp., scale 1 in, K, D, Card et al, (issued 1965). �______________, ______________ __________ 1 6 2e. Miscellaneous Hewett, D. F., (1964), Rocks and minerals of Ontario: Circular No. 13. 3. Geol. SCIENTIFIC JOURNAL PUBLICATIONS Zietz, I. and Henderson, R. G. (1955), The Sudbury aeromagnetic Geophysics, Vol. XX, map as a test of interpretation methods: No. 2, pp. 307—317. Mamen, C. (1955) Nickel Rim Mines Ltd.: I Can. Mm. Journ., June. Lockhead, D. R. (1955), Falconbridge Ore Deposit, Canada: Geol., Vol. L, No. 1, 42—50. Econ. Mitchell, C. P. and Mutch, A. D. (1956), Geology of the Hardy District, Ont. Can. Inst. Mm. Met., Mine, Sudbury Vol. 49, February. Wilson, H.D.B., (1956), Structure of lopoliths: Bull. Geol. Soc. Am,, 67, 29—3OO, I Speers, E. C. (1957), Age relations of the common Sudbury breccia: Journ. Geol., vol. 65, 497—514. Thomson, J. E, (1957), Questionable Proterozoic rocks in the Sudbury— Espanola area: Roy. Soc. C. Special Pub. No. 2, Proterozoic in Canada. (1957), Recent geological studies in the Sudbury camp: Can. Mm. Journ. 7, 4, 109—12. Zurbrigg, H. F. et al. (1957), The Frood—Stobie mine in Structural geology of Canadian ore deposits: Can. Inst. Mm. Met., 343. Can. Mm. Journ. (1959) The Falconbridge Story — Geology: 116—127. Clarke, A. M. and Potapoff, P. (1959) Geology of McKim mine: Assoc. Can. Proc. 67—SO. Hamilton, W. (1960) Silicic differentiation of lopoliths: Geol. Congress, XXI Session, Part XIII, 59—67. Vol. (1960) Form of the Sudbury lopolith: 6, pt. 4, 427—447. Geol. Intern. Can. Mm., Stevenson, J. 5. (1961) Origin of quartzite at the base of the Whitewater series, Sudbury basin, Ont.: Intern. Geol. Congress, XXI Session, Part XXVI Supp. Vol. Sect. 1-21, 32—41. (1961) Recognition of the quartzite breccia in the Whitewater series, Sudbury basin, Ont.: I I I I Trans. Roy. Soc. Canada, Vol. LV, p. 57—66. I �7 Hood, P. J, (1961), Paleomagnetic study of the Sudbury basin: Jourri. Geoph. Res., Vol. 66, 1235—1241. Strangway, D, W. (1961), Magnetic properties of diabase dikes: Journ. Geoph. Res., Vol. 66, 3021—32. Hawley, J. E,, et al. (1961), Pseudo-eutectic intergrowths in arsenical ores from Sudbury: Can. Mm. 6, 555—575. Hawley, J. E. (1962), The Sudburyores: origin: their mineralogy and Can. Mm., Vol. 7, Pt. 1—207. Stevenson, J. S., (1963), The upper contact phase of the Sudbury micropegmatite: Can. Mm., Vol. 7, Ft. 3, 413—419. Thode, H. G. (1962), Sulfur isotope abundances in rocks of the Sudbury district and their geological significance: Geol., 57, 565—57g. Econ. Davis, T. E. and Slemmons, D. B. (1962), Observations on order— disorder relations on natural plagioclases, III Highly ordered plagioclases from the Sudbury intrusive: Norsk. Geol. Tidss., Vol. 42, Pt. 2, 561—577. Thomson, J, E. (1962), Extent of the Huronian system between Lake Timagami and Blind River, Ontario: Roy Soc. Canada, Special Pub. No. 4 Tectonics of the Canadian Shield, 76—9. Bucher (1963), Cryptoexplosion structures caused from without or within?, (astroblemes or geoblemes?); Am. Journ. Sc., Vol. 261, 597—649. Dietz, R. 5. (1963), Cryptoexplosion structures: Am. Journ. Sc., Vol. 261, discussion: Sopher, S. R. (1963), Paleomagnetic study of the Sudbury irruptive: Geol. Surv, Canada Bull. 4, 90. Kullerud, G. (1963), Thermal stability of pentlandite: Mm, 1, 353—366. Card, K. D. (1964), Metamorphism in the Agnew Lake area, Sudbury district, Ontario: 1011—1030, Geol, Soc. America, Bull., Vol. 7.5, Dietz, R. 5, (1964), Sudbury structure as an astrobleme: Geol,, Vol. 72, 412—434. Journ. Strangway, D, we (1964), Rock magnetism and dike classification: Journ. Geol. V. 72, 64—663. Kullerud, G, and Yoder, H. S., Jr. (1964), Sulfide—silicate reactions, Ann, Rept., Geophys. Lab. Yr. Bk. 62, 218—222. �1 8 Borchert, H. and Lamby, B. (1964), Mikroskopische untersuchungen an erzproben aus der Falconbridge-grube (Sudbury) und daraus resultierende genetische folgerungen: Zeits.fUr Erzbergbau u. Metall,, XVII, 645—653. Stevenson, J. S. (1964), Sudbury in Terms of Upper—Mantle Petrology: Geol. Soc. Am. Abstract in Sec. E., A.A.A.S., Montreal meeting 1964, p. 18. Hawley, J. E. (1965), Upside—down zoning at Frood, Sudbury: 1 Econ, Geol, 60, 529—575. A. J. and Kullerud, G. (1965), Sulfurization in nature: two examples: Geol, Soc. Am., Abst. p. 113. Naldrett, Simons, P. Y. and Dachille, F, (1965), Shock damage of minerals in shattercones: Geol. Soc. Am. Abst. p. 153. Vos, M. A. and Moorhouse, W, We (1965), Quartz diorites from the North Range, Sudbury: Can. Mm., Abst. in v. 8, pt. 3, Naldrett, A. J. and Kullerud, G. (1965), Investigations of the nickel—copper ores and adjacent rocks of the Sudbury district, Ontario: Geoph. Lab.. Wash. D. C., Year Book 64, pp. l77—188. Deals largely with Strahcona orebody. 4. I Pe 402. I I RADIOGENIC AGE DETERMINATIONS (Radiornetric dating) I Geological Survey of Canada, Age determinations (J. A. Lowdon et al.) and Geological studies, structural provinces etc. (C. H. Stockwell et al.) Paper 60—17 (1960) " " " " 61—17 (1961) 62—17 (1963) 63—17 (1963) 6—17 (1964). Massachusetts Inst. of Technology, Annual Progress Reports to U.S. Atomic Energy Commission 1958 to present, on variations in isotopic abundances of strontium, calcium and argon and related topics (variously refer to work on Sudbury specimens) particularly, "Re—examination of Rb—Sr whole — rock ages at Sudbury; Dec. 1964, 225-228. Davis, T. L. et al. (1957), The ages of rocks and minerals: 1 Carnegie Inst. Wash, Yr. Bk, Vol. 56, pp. 164—171. Wetherill, G. W. et al, (1957), Age measurements on rocks north of Lake Huron: Trans. Am. Geoph. Union, 38, 412. Fairbairn, H. W. et al. (1960), Mineral and rock ages at Sudbury— Blind River, Ont.: Geol0 Assoc. Can, Proc. Vol. 12, p. 41—66. I I �______________ 9. (1961), The relation of discordant Rb—Sr mineral and whole rock ages in an igneous rock to its ti of crystallization and to the time of subsequent Srö(/Sr metamorphism: Geochim, et Cosmochim. Acta, vol. 23, p. 135— 144. Faure, G, et al, (1964), Whole rock Rb—Sr age of norite and micro— pegmatite at Sudbury: Journ. Geol., 72, 4—54. Fairbairn, H. W., et al. (1965), Re—examination of Rb—Sr whole—rock Geol. Assoc, Canada Proc. 16, 45—101. ages at Sudbury: Slawson, W. F. and Russell, R. D. (1965), Age of major minera1 izations in Ontario: Geol, Soc. Am, Abst. p. 156. 5. GUIDE BOOKS Guide Book for Field Trip No. 7 (1953), Sudbury area, in conjunction with joint annual meeting in Toronto, one of Geol, Soc. Am. and Geol, Assoc. Canada (by Sudbury geologists). Geological Field Trip. Guide Book Sudbury area (1957): Sixth Commonwealth Mm. and Met, Congress, Sudbury, Ontario, (by congress committee at Sudbury.) TOUR LOG With respect to this particular tour, we thought that, because of the very close relation between the ore-bodiesiand the irruptive and therefore because of the fundamental importance of the irruptive, we might take advantage of the detailed studies that are currently being made of the irruptive and would restrict our tour, in the time that is available, to the irruptive itself, The briefing and discussion on Saturday evening at Laurentian University and the stops on Sunday, have therefore been arranged with this specific objective in mind. We will Copper Cliff and en route Copper Cliff reach our first stop by driving from Sudbury through to near the Copper Cliff North and Clarabelle mines, we will have several views, no stops, of Inco's Smelter. Copper Cliff offset, Clarabelle Road, STOP 1 This is a type locaflty for the quartz—diorite phase of the norite, Ore specimens from nearby mines will be provided here, �I 10 We will drive from Stop 1 east to the Levack highway, thence north 1—1/2 miles to the Discovery Cut at the Murray Mine, stop here briefly and return south along the highway to Regent St0 in Sudbury and then along Frood Road, driving by the Frood and Stobie Mines, joining Highway 69 and thence to Stop 2. I STOP 2 South Range norite, both the fresh ?tbrowh_blacktt norite 1e widespread, altered "green norite", From here we will continue northward along Highway 69, across the norite and into the micropegmatite, Stop 3. STOP 3 Typical South Range, foliated micropegmatite0 1 1 From Stop 3 we will drive north along 69 over a hill of black Onaping tuff into the farmlands of the Chelmsford valley underlain by Onwatin slate and the Chelmsford sandstone0 We will continue through Val Caron and Hanmer to the turn-off, to the right of the Ella (Capreol LakeWest Bay road, one mile south of Capreol. We will drive along this road for about 3 miles to Stop 4, 1/2 north of the Ella Lake campground. Stops 4 and 5 will be concerned with the North Range phase of the irrupt ive. STOP 4 North Range Norite, I This is on the township line between Norman and Capreol townships. We will wallcwestward along this line and in doing so will cross several members of the irruptive, which here trends north0 Stop 4a: Stop outcrops along the road are of lower gray norite0 I westward across the slough, a fine—grained, sharp textured norite, overlying the medium-grained gray norite, outcrops on the hillside0 4b: Stop 4c: outcrops of fine-grained mafic phase of the last, on the same hillside0 Stop 4d: farther west up the hillside, outcrops of pink norite. the last of the outcrops on this line are of the lowermost member of the micropegmatite, a coarse—grained, salmon— coloured member0 Stop I I 4e: Return to buses for trail lunch in Ella Lake campgrounds, and drive back along Ella Lake road to C. N, Railway crossing; this is Stop 5. I I �STOP 5 North Range Micropegmatite. Walk westward along the railway. Stop 5a: outcrop along railway of upper micropegmatite, a fine to medium gray member. Stop 5b: farther west on railway, outcrop of breccia at top of micropegmatite. From here we will walk along the railway a short distance, to a tote—road of the new hydro line (incidentally, one of the new E.H,V. lines of the Ontario Hydro), then northwards to Stop 5c. En route, most of the outcrops on left (west) side of the road are of Onaping volcanic breccia. Stop 5c: about l000'north along tote—road on the south side to study outcrops of breccia and the uppermost phases of the irrupt lye. Stop 5d: continue along tote—road for a short distance to look at other outcrops of the irruptive and the breccia. Return via tote-road and railway to bus, drive back along Ella Lake road to Highway 69, turn south on 69 then left on the GarsonFalconbridge road, route 545 to Stop 6 which is l/2mile south of the junction of 545 with 541. STOP 6 Typical South Range, foliated micropegmatite. From this stop we will drive south over South Range norite, turn left, geologically at the footwall, and continue in footwall greenstone, to Falconbridge townsite, where we will have a chance to drive by the Falconbridge Smelter and be able to see in the distance towards the east, the headframes of the Falconbridge and the East mines. Ore specimens from nearby mines will be provided From Falconbridge we will return and drive southwesterly here. past the Garson mine and back to Sudbury. �LEGEND SOUTH MANNE BOOTS 54542 ACTIVE MINE M)NE PR000CINO FAA LT S FOOTWAIS ROCKS TOTTEN OOARTZITE BRECCIA IWSERE MAPPED TO DATE) ONOPING TOFF LNICKEL J SANDSTONE ONWATIN OLATE CSELMSPOKO MORITE MICROPEOMOTITE ± o • iJIllhlIll _______ O DI 2 S KILOMETERS 4 NIL ES S 2 540 IS aaaaaaaaaaa )ALWNBRIDGE cv • MACLENNAN SUDBURY BASIN GEOLOGICAL MAP I — — �PREVIOUS ANNUAL MEETINGS of INSTITUTE ON LAKE SUPERIOR GEOLOGY First 1955 Minneapolis, Minnesota University of Minnesota Second 1956 Houghton, Michigan Michigan College of Mining and Technology Third 1957 East Lansing, Michigan Michigan State University Fourth l95 Duluth, Minnesota University of Minnesota, Duluth Fifth 1959 Minneapolis, Minnesota University of Minnesota Sixth 1960 Madison, Wisconsin Geology Department, University of Wisconsin and Wisconsin Geological and Natural History Survey Seventh 1961 Port Arthur, Ontario Canadian Institute of Mining and Metallurgy, Lakehead Branch, and Ontario Department of Mines. Eighth 1962 Houghton, Michigan Michigan College of Mining and Technology Ninth 1963 Duluth, Minnesota University of Minnesota, Duluth Tenth 1964 Ishpeming, Michigan Mining Companies: Inland Steel, Cleveland—Cliffs Iron, Jones and Laughlin, North Range Eleventh 1965 St. Paul, Minnesota Minnesota Geological Survey and University of Minnesota �Zn, Cu, Ag, Pb, Au in massive iron sulphide deposits in Archaean volcanic rocks Al Fe deposits in Archaean iron formation A2 0 Cu, Pb, Zn, Au quartz veins associated with Proterozoic gabbro Cl areas of abundant Au deposits (see abstract) Geological Survey of Canada By S. M. Roscoe, reproduced by permission of C2 Cu disseminated in sodic porphyry C3 Mo, Li, Be in Kenoran pegmatites C4 Cu-Mo, Pb-Zn veins Dl uraninite in pyritic Huronian quartz pebble conglomerate -F D2 Ag-Co-As bearing calcite veins associated with Nipissing diabase D3 Bi Cu, Cu-Au 'veins' with gabbro-anorthosite Ni, Cu-Nj with ultrabasic rocks and gabbro sedimentary rocks Keweenawan volcanic and B2 Cu veins assocjated with gabbro—peridotite B3 F2 El Zn-Pb-Cu-Ag-pyrite deposits in Animikean volcanic rocks ZOO miles B4 asbestos in Archaean ultrabasic rocks 100 chalcopyrite in breccia zones F3 Fl chalcocite, native copper in pitchblende veins associated with Keweenawan diabase dykes F4 U, Fe, apatite Zn-Pb, Pb-Ag veins Nb, alkalic syenite F5 E2 Ni-Cu-Pt associated with Hudsonian gabbro METALLOGENIC STUDY, SAULT STEMARIE TO CHIBOUGAMAU PRINCIPAL TYPES OF MINERAL DEPOSITS, THEIR GEOLOGICAL ASSOCIATIONS AND AGES II — ——————————————————r �(see abstract) By W. R. Farrand, J. H. Zumberge, and J. Parker — — — — — — — — — — — — — — — — I_I DnNIvMEmlC CHART ir rI -II — — � 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, 1966 Description An account of the resource Institute on Lake Superior Geology. Michigan Technological University, Sault Ste. Marie, Michigan. May 6-7, 1966. 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 1966 Contributor An entity responsible for making contributions to the resource Larry L. Babcock L.O. Bacon W.A. Longacre A. Stevens Alexander C. Brown John W. Trammell Joseph P. Dobell W.R. Farrand J.H. Zumberge J. Parker Bevan M. French P.E. Giblin John C. Green Tsu-Ming Han E. Wm. Heinrich Richard W. Vian William J. Hinze Norbert W. O'Hara James W. Trow Harold J. Lawson W.O. Mackasey A.M. Johnson A.S. MacLaren Louis Moyd Richard W. Ojakangas Willard P. Puffett S.M. Roscoe A.P. Ruotsala G.J. Koons S.C. Nordeng John Q. St. Clair Kenneth Segerstrom Terrence J. Smith A.K. Snelgrove Kiril Spiroff G.G. Suffel Walter M. Tovell C.F.M Lewis R.E. Deane M.E. Volin Richard J. Wold Ned A. Ostenso Grant M. Young Paul W. Zimmer 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/37cabe0e7ea7bfdd9ba9dcbc494adb36.pdf cd719f14ad23652fa7736dc1061d666b PDF Text Text Eleventh Annual Institute on Lake Superior Geology May 6-8, 1965 University of Minnesota St. Paul Minnesota �11thAnnual AnnualInstitute Institute on lith Superior Geology Geology Lake Superior Sponsored by: 3ponsored Minnesota Minnesota Geological Survey of Minnesota Minnesota University of and The Twin The Twin City Geologists Wicons,i GIoccaj ad Na1ur Hiry 9igj 3811 M;rior pci,,t flc. Madj5Qfl, WI 63; i �r7j ch§Technical Technical tlJI Sessions n I I I., > (TZR .----- a '-- ST PAUL CAMPUS CAMPUS 1 J �COMMITTEES Local Committee Local Hogberg General Chairmen - P. K. K. Sims and R. R. K. Hogberg Program Program Arrangements Social P. P. K. K. Sims Sims Judy Holmes Keith Knobloch I(nobloch CnarLes Matsch Cnarles Jane Titcomb Jane Titcomb Sarah Tufford Sarah D. y.;. Lindgren Lindgren D. W. George Austin George R. R. K. K. Hogberg Hogberg Field Field Trip t. K. R. K. Hogberg Hogberg D. D. H. H. Yardley Yardley Institute Secretary Secretary Institute D. H. Hase, D. Hase, State State University Universityof of Iowa Iowa Institute Eoard Board of Directors Institute M. M. W. W. Bartley, M. M. W. W. J3artley Bartley & & Associates, Associates, Port Port Arthur, Ontario A. A. T. T. Broderick, Broderick,Inland InlandSteel SteelCompany, Company, Istipeming, Ishpeming, Michigan Michigan D. H. Hase, State University of Iowa, Iowa City, Iowa D. H. Hase, State University of Iowa, Iowa Iowa H. Lepp, Lepp, Macalester MacaLester College, College, St. Paul, Paul, Minnesota Minnesota H. A. A. K. K. Sneigrove, Snelgrove, Michigan Michigan Technological Technological University, University, Houghton, Houghton, Michigan �11th Annual Institute on 11th Annual Institute on Lake SuperiorGeo1o~ Geolo_ Lake Superior May May 66 -- 8, 8~ 1965 PRO GRAM PROGRAM Thursd, Thursday?May May 66 8:00 - 9:20 a.m. a.m, Registration and coffee coffee hour9 hour 9 2nd floor floor of of Student Student Center, center, St. Paul Paul Campus st. Campus Technical sessions,9 2nd Technical sessions 2nd floor, f1oor~ Green Hall 8:45 -- 9:00 9:00 Business Meeting...........D. Hase, Secretary, Meeting ••••••••••• D. H. H. Hase~ Secretary, conducting Session II Co-chairmen: and Ralph John W. W. Gruner and Marsden 9:00 Progressive contact metamorphism of the Biwabik Iron-formation on on the 9:20 9:40 10:00 10:45 11:05 11:25 12:15 Nesabi ,........Bevan M. French Mesabi range, range, Minnesota....................... Minnesota •••••••••••••••••••••••••••••••• Bevan M. The distribution of manganese in the Biwabik Iron-formation, Minnesota.••••••••••• Minnesota Henry Lepp . . . . . . . . . • ~ ••••••••• ..•...... .. .e ••.• •.•.• •.•.• •. c •. •• •.•.•.•.•.•.•.• .• •. .~ .••• •• ••.• •.Henry Some aspects of of iron-formations in Australia and South Africa.. . . . •. . . . . ........ . . , . . , . . . . . . . . •. . . . . . . . . . . . . .Gene Africa •••••••••••••••••••••••••••••••••••••••••••••••• • Gene L. L. LaBerge Coffee break Structure and and lithology of of the metamorphosed Biwabik Biwabik Iron-formation, Iron-formation, Dunka River area, area, Eastern Mesabi district, district, Minnesota••• Minnesota. . Bil1 Bonnichsen Structural control control of of the Mount Mount Wright-Mount Wright-Mount Reed Reed iron iron deposits, Structural .Bill J. Clarke Quebec •••••••.••••••.••••••••••••••••••••••• • • • • • •.•. •• Peter J. Quebec...... . ........ .... . . . . . . . . . . . . . . . . . .o ........ . •.Peter Petrology of the silicate iron-formation in the Republic mine area, area, Marquette County, County, Michigan............Tsu—Ming Michigan•••••••••••• Tsu-Ming Ban Han and and James James W. W. Villar Villar Luncheon, Student Center, Luncheon, Center~ 2nd floor, floor, North Star star Ballroom Ballroom Session II II Co—chairmen: Co-chairmen: 1:30 1:55 2:15 2:35 2:35 2:50 3:35 3:35 3:55 3:55 4:15 4:15 George M. M. Schwartz and James Neilson Tectonics of the Keweenawan basin, basin~ western Lake Superior Superior S. White region. . . . . . . . . . . . . . . . . . . .. .o .• ,• • region ••••••••••••••••••••• • Walter S. . •. •. •. •. •. •. •. •. •. •. •. •. •. •. •. •. •. •. •. •. •. •. •. .WaJ.ter of western western Lake Lake Superior...........Richard Superior•••••••••• Richard J. J. Wold An aeromagnetic survey of The Sauble geophysical geophysical anomaly, anomaly, Lake Lake County, County, Michigan.....................G..HowardJ. Michigan••••••• o • • • • • • • • • • • • • • • ~ • • Howard J. Meyer Meyer and and WilliamJ. William J. Hinze Hinze Contributions of rock rock physics physics to to geology•••••••••••••••Robert geology..,...........Robert J. J. Willard Coffee break Geological analysis and remedial action action in in an open pit rock slide. slide ••••••••••••••••••••••••••••••••••••••••••••••• D. H. H. Yardley rock . . .. . . . . . . . . . . . . . . . . . . . ,. . . . . . . . . . . . . . . . . . . . . .D. Measurement of in-situ stresses in in aa St. st. Cloud quarry-quarry--aa Measurement progress progress report. report •••••••••••••••••••••••••••••••••••••• . ......... .... •. .... .. . . ..... ..... .. . Charles Char1es Fairhurst Fairhurst An example of statistical analysis and possible interpretation and interpretation of of Hill, Skanee quadrangle, quadrangle, Upper structural data from Arvon Hill, Peninsula, Michigan ••••••••••••••••••••••••••••••••••••• J. D. Juilland Peninsula, Michigan. . . . . . . . . . . . . . . . . . . . . .. . . . . . . . .. . . . . . J • 1 �Thursday9 May Thursday, May 66 (continued) ~continued) Annual Annual Banquet Twins Motor Motor Motel Motel 1975 University Avenue (University at at Prior) Prior) 6:00 6:00 p.m. p.m. 7:00 Social Hour Social Dinner Address: Professor Campbell Campbell Craddock Craddock will will speak speak on on 'Geologic QfGeologic Professor structure of West West Antarctica,' Antarctica, 'I a summation summation of six six structure austral austral seasons seasons of field work work illustrated illustratedwith withmany many of field colored pictures. pictures. fine colored Friday, May May 77 Friday, Co—chairmen: Co-chairmen: 9:00 9:00 9:20 9:40 Session III III Carl E. E. Dutton Dutton and and H. H. L. L. James Stratigraphy, structure, structure~ and and granitic granitic rocks rocks in in the the Marenisco—Watersmeet Marenisco-Watersmeet, Stratigraphy, E0 Fritts'~ Fritts area, area, Michigan. Michigan•••••••••••••••••••••••••••••••••••••• .. .. .. .. ... .. .. ... .., .. .. .. .. . . •.. . Crawford E. Ages of mafic dikes near Granite Falls, near Granite Gilbert N. N. Hanson Minnesota •••••••••••••••••••••••• Glen R. Hixmnelberg, Himmelberg~ Gilbert structure and stratigraphy stratigraphy of of the the Knife Knife Lake Group Group east east of of Ely, Ely, Structure and a •a•a•a. Minnesota...... Minne sota •••••••••• ••••• ••• • •,John John C. C. Green . . . ~. •••••••••••••••.•••• . . . . . .. . . . .... .. . . . . e ••e a. ••a.•. a•a. Coffee break Spiroff,. Keweenaw fault, Houghtori Houghton County, Michigan •••••••••••••••••• Kiril Spiroff~ Keweenaw fault, County, Michigan.... ... .. s... •• .lCii'il The sedimentology sedimentology of the the Precambrian Precambrian Rove Rove Formation Formation in in , B. Morey Morey --northeastern northeastern Minnesota.., Minnesota••••••••••••••••••••••••••••••••••••• G. B. ~ .. . . . .. . .. . .. .. .. ... .. ... . ... . .G. Petrology Petrology of the the Amberg Precambrian Precambrian crystalline crystalline complex, complex, .Dennis northeastern northeastern Wisconsin...,.... Wisconsin••••••••••••••••••••••••••••••• Dennis p. P. Rebello ....... Sedimentation of Middle Precambrian quartzites quartzites in in Sedimentation of R;chard W. OJ'akangas~ W. Ojakangas Finland. F;nland ..•,•.•.•.•.•.•.•.•.•$• •. ., •. •. •. •. •. •.•..• •. •. .0 .• •. •. ••,• •• •, •. •, •..• •. •. •. ." ..Richard • •. •• 1'\ Luncheon, Center, 2nd floor, Luncheon, Student Center, floor, North Star Ballroom Minnesota........,.,........,..GlenR. . 10:00 10:40 11:00 11:00 11:20 11:40 •.•,.,...• .... ..I. 12:15 Co-chairmen: 1:30 1:50 Session IV G. A. A. Thiel Thiel and and Don Don Lindgren Lindgren G. A study on the the hydrology hydrology of of potholes potholesin inMinnesota••••• Minnesota.....George Schwartz A study on George M.M.Schwartz -~' Geology of the the Fillmore County district iron ores, L. Bleifuss southeastern southeastern Minnesota..,. Minnesota•••••••••••••••••••••••••••••••••• R, L. ...... ... . .... .......... . ,. ,R, Organic geochemistry geochemistry of of Rossburg Rossburg peat peat bog, bog, Aitkin Aitkin County, County, F. M. M. Swain, Swain, Mykola Mykola Nalinowsky, Malinowsky, and and David David Nelson Minnesota•••••••••••••• Minnesota.............F. Preliminary Prelimina:ry results results of of geochemicaT geochemical prospecting prospecting north north of of the the Marqu~tte ••••••••••••••••••••••• Kenneth Segerstrom Marquette iron iron range, range, Michigan Michigan......................Kenneth Coffee Coffee break break Protoclastic borders borders of of the the felsite felsite near near Bergland, Bergland, Protoc1as;ic Michigan..........0.........Joseph Michizan •••••••••••••••••••••• Joseph P. P. Dobell Dobell and and Robert W. W. Leonardson Some aspects aspects of of the the pegmatites pegmatites in in the the Feich Felch district, district, Dickinson Dickinson Some •••••••••••••••••••••••••••••••••••• Geoffrey W. W. Mathews Mathews County, Michigan County, Miehigan...................................Geoffrey . 2:10 2:10 2:30 2::30 2:50 3: 20 3: 3:40 3:40 2 2 �Friday9 May Friday? May 77 (continued) (continued) 7:30 —- 9:Lk5 9:45 p.m. U. S. S. Bureau of Mines, Mines, Research Research Center, Center, Fort Tour of U. Bus will leave at 7:30 Snelling. 7:30 p.m. p.m. from Student Student Snelling. Center, st. St. Paul Campus with an intermediate stop center, at Twins Motor Motel and and will will return return to to the the same same at locations. Saturday, May 8 Saturday? 8:00 a.rn. to 8:00 a.m. to 6:00 6:00 p.m. p.m. Field trip trip to to St. st. Cloud Cloud district. district. Buses will depart Field from and and return return to to the the Student Student Center, Center, St. St. Paul Paul campus. campus. from Field trip willinclude include tour tourofofthe theCold ColdSpring Spring Granite Granite Field trip will CompanyO s finishing visits Companys finishingplant plantandand visitstotothree three"granite: 'granite' quarries. Participants will will be be provided provided with with aa guideguidehats are hard book and. and lunch. clothes and and are advised. advised. lunch. Field clothes Authors and and Technical Technical Session Session Chairmen Chairmen BLEIFUSS, R. L...........Mines BLEIFUSS, R. L••••••••••• Mines Experiment Experiment Station, Station, University University of of Minnesota, Minnesota, Minneapolis Minneapolis BONNICHSEN, BILL....0...Department BONNICHSEN, BILL ••••• o • • • Department of of Geology Geology and and Geophysics, Geophysics, University of Minnesota, Minne sota, Minneapolis Minneapolis ~X ,. CLARKE, PETER PETER JJ.........Department CLARKE, •••••••••• Department of of Natural Natural Resources, Resources, Province Province of of Quebec, Quebec, Quebec, Canada Quebec, Geophysics, University CRADDOCK, CAMPBELL •••••••.Department Department of Geology and and Geophysics, University of of CAMPBELL..... Minnesota, Minneapolis Minneapolis DOBELL, JOSEPH DOBELL, JOSEPH P....... P•••••••••.Department Department of of Geology Geology and and Geological Geological Engineering, Engineering, Michigan Technological Technological University, University, Houghton, Houghton, Michigan Michigan Michigan " DUTTON,CARL CARLE...........U. E••••••••••• U. S. S. Geological Geological Survey, Survey, Madison, Madison, Wisconsin Wisconsin ADUTTON, FAIRHURST, CHARLES•••••••.School School of of Mineral Mineral and and Metallurgical Engineering, FAIRHURST, CHARLES..... University of Minnesota, Minnesota, Minneapolis Minneapolis FRENCH, BEVAN M •••••••••• Theoretical Division, Goddard Space Space Flight Flight Center, Center, M..........Theoretical Greenbelt, Maryland Greenbelt, Maryland )(FRITTS, CRAWFORD E••.•••• E......U. XFRITTS, CRAWFORD U. S. S. Geological Geological Survey, Survey, Denver, Denver, Colorado Colorado GREEN, GREEN, JOHN C............Department C•••••••• o • • • Department of of Geology, Geology, University University of of Minnesota, Minnesota, Duluth Duluth GRUNER, JOHN JOHN W.o W..........Professor and GRUNER, ••••••••• Professor Emeritus, Emeritus, Department Department of Geology and University of of Minnesota, Minnesota, Minneapolis Minneapolis Geophysics, Geophysics, University Company, Ishpeming, HAN, TSU-MING Cleveland-Cliffs Iron Comp2ny, Ishpeming, Michigan TSU-MING,•••••••••••• . . . . .,. . . Cleveland—Cliffs HAN, .. Institut HANSON, GILBERT GILBERTN.l'l •••••••• Institut fur Kristallographie und Petrographie, Petrographie, HANSON, ... Sonneggstrasse, Zurich, Switzerland Sonneggstrasse, Zurich, S\\I:Ltzerland / Geology, University University of j('HASE, D. H••••• , •••• o • • • • Department of Geology, of Iowa, Iowa, Iowa Iowa City, City, XHASE, D. k~ Iowa HIMMELBERG, HThIMELBERG, ..Departm.nt GLE:J R.. R••••••• Departm,mt of of Gtology Gt~ology and and Geophysics, Geophysics, University of GIE Mirmesota, Minneapolis Minl!~apol:'Ls Minnesota, HINZE, XNZE, ~ 'V': , (, '. ,;lJ \ !~'~i\.. Geology, Michigan University, 7J '" WILLIAM ~f.[LLI.AM J.........Department J ••••••••• Department of of Geology, Michigan StateState University, ~t ~i~\ j/l>';'>:: East Lansing, Michigan J3 ,f �P .,~N·".I' ,'vV' () AHOGBERG, .J( HOGBERG~ R.R.K............Minnesota K••••••••••••Minnesota Geological Geological Survey, Survey, University University of of Minnesota, Minnesota, JAMES, JAMES~ Minneapolis H. L•••••••••••••• G0010gical Survey, Survey, Minneipolis MiQDo~polis L............U.D.S.S.Goological JUflL.A1D, J. JUILLAND, J. D..........Michigan D••••••••.•• Michigan Technological Technological University, University, Houghton, Houghton, Michigan Michigan ,.;zLaBERGE, LaBERGE, GENE L•••••••••• National Research Council Council of of Canada, Canada, Geological Geological L.........NationaJ. Survey of Canada, Canada, ottawa, Ottawa, Ontario LEDNP1RDSON, ROBERT W.. LEONARDSON, ROBERT W••••• Department of of Geology Geology and and Geological Geological Engineering, Engineering, . .Department Michigan Technological Technological University9 University, Houghton, Houghton, Michigan Michigan Michigan LEPP, HENRy•••••••••••••• HENRY.............Department Paul LEPP, Department of of Geology, Geology, Macalester College, College, St. st. Paul LINIJGREN, DONALD DONPLD W W.......Lindgren & Lehmann, Lehmann, Inc., Inc., Wayzata, Wayzata, Minnesota LINDGREN, ••••••• Lindgren & MALINOWSKY, MYKOLA••••••• Department of of Geology Geology and and Geophysics, University University of of MALINOWSKY, MYKOLA.......Department Minnesota, Minnesota, Minneapolis MARSDEN, RALPH W ••••••••• U.S.S.Steel Steel Corporation, iJuluth Duluth W...,....U. Corporation, MATHEWS, GEOFFREY W Reserve University, University, •••••• Department of Geology, Western Reserve W......Department Geology, Western Cleveland, Ohio Ohio of Geology, Geology, Michigan Michigan State University, MEYER, HOWARD HOWARD J...........Department J •••••••••• Department of University, East Lansing, Lansing, Michigan MOREY, G. DepartmentofofGeology Geologyand and Geophysics, Geophysics, University University of of MOREY, G. B•••••••••••••• B............Department Minnesota, Minneapolis Minnesota, NEILSON, JAMES. JAMES•••••••••••Michigan Technological University, University, Houghton, Houghton, Michigan Michigan ... ... . . . .Michigan Technological NELSON, DAVID •••••••••••• Department of of Geology Geology and and Geophysics, Geophysics, University University of NELSON, DAVID...........Department Minnesota, Minneapolis OJAKANGAS, OJAKANGAS, RICHARD RICHARD W.....Department W••••• Department of of Geology, Geology, University University of of Minnesota, Minnesota, Duluth REBELLO, DENNIS REBELLO, DENNIS P.......Department P•••••••• Department of of Geology, Geology, Western Western Reserve Reserve University, University, Cleveland, Ohio Cleveland, SCHWARTZ, GEORGE M M......Professor and SCHWARTZ, GEORGE ••••••• Professor Emeritus, Emeritus, Department Department of Geology and Geophysics, University of of Minnesota, Minnesota, Minneapolis Minneapolis Geophysics, University SEGERSTROM, KENNETH......U. SEGERSTROM, KENNETH •••••• U. S. S. Geological Survey, Survey, Denver, Colorado Colorado P. K•••••••••••••••Minnesota K..,..0.......Minnesota Geological Geological Survey, Survey, University University of of Minnesota, Minnesota, J i~ SIMS, P. / Minneapolis SPIROFF, KfltIL...........Department KIRIL ••••••••••• Department of Geology and and Geological Geological Engineering, Engineering, SPIROFF, Michigan University, Houghton, Houghton, Michigan Michigan Michigan Technological Technological University, SWAIN, SWAIN, F. F. M•••••••••••••• Department of of Geology Geology and and Geophysics, Geophysics, University University of of Minnesota, Minnesota, Minneapolis Minneapolis THIEL, G. A•••••••••••••• A.............Professor THIEL, G. Professor Emeritus, Emeritus, Department Department of of Geology and Geophysics, University of of Minnesota, rfLnnesota, Minneapolis Minneapolis Geophysics, University VILLAR, JAMES W W.........Cleveland—Cliffs VILLAR, Jfu~ES •••••••••• Cleveland-Cliffs Iron Iron Company, Company, Ishpeming, Ishpeming, Michigan Michigan WHITE, WALTER WALTER S.........U. S•••••••••• U. S. S. Geological Geological Survey, Survey, Beltaville, Beltsville, Maryland WHITE, WILLARD, ... .U. S. Bureau Bureau of Mines, Mines, Minneapolis Minneapolis 'WILLARD, ROBERT ROBERT J.... J •••••••• U. S. 4 L. �'/WOLD, RICHARD J J........,.Department WOLDt RICHARD •••••••••• Department of of Geology, Geology, The The University University of of Wisconsin, Wisconsin, Madison, Wisconsin Madison, YARDLEY, D, H.....,......School YARDLEY, D. H•••••••••••• School of Mineral and and Metallurgical Engineering, Engineering 9 University of University of Minnesota, Minnesota, Minneapolis 55 �GEOLOGYOF OF THE THE FILLMORE DISTRICT GEOLOGY FILLMORE COUNTY COUNTY DISTRICT IRON ORES,SOUTHEASTERN SOUTHEASTERN MINNESOTA MINNESOTA IRON ORES, R. L. L. Bleifuss Bleifuss R. Station Mines Experiment Station */ University of Minnesota, Minnesota, Minneapolis— MinneapolisIron ores have been known to exist in southeastern southeastern Minnesota Minnesota since the the earliest earliest geological reconnaissance of the area by the since 9 Owen's Owen s survey survey in in 1852. The development of the the Fillmore County district was stimulated stimulated by by the the demands demands for for iron iron ores ores during during World World War II, II, and initial ore shipments shipments were made in in 1943. 1943. Cumulative tons, iron-ore million tons, iron—ore production production through through 1964 1964 has has been been about about 6t 6 million Reserves and current current production production is is about about -t million tons per per year. year. Reserves and carried on on the the tax tax rolls rolls in in 1964 1964 are are in in excess excess of of 2* million million tons. tons. 2t The iron ores lie on Paleozoic limestones ranging ranging in in age age from from the Middle Ordovician to to Middle Devonian. Devonian. The commercial ore bodies are restricted restricted to to two two dolomitic limestone limestone units: units: the the Middle Middle Ordovician Ordovician The Galena Formation, Formation, and and the Middle Devonian Devonian Cedar Cedar Valley Valley Formation. Formation. The iron ores, ores, and the widespread iron-rich weathering residuum residuum which which is is developed on nearly all of the formations formations in the the area, area, has has been been Member, of the Cretaceous Windrow ~Tlndrow assigned to the lower, lower, Iron Hill Member, Formation. Formation. The clays, sands, sands, and gravels gravels overlying overlying The unconsolidated unconsolidated clays, the the ores are assigned to the upper, upper, or or 0Ostrander same strander Member Member of of the the same formation. Previous investigators have postulated that the the ores ores in in the the district originated by intensive chemical chemical weathering, which which resulted resulted in the widespread replacement of certain certain favorable favorable dolomitic dolomitic limelimepaper on the stone by iron. iron. In the most recent paper on the area, area, stone bedrock units by In the postulated Sloan (1964) (1964) agrees agrees with the the Cretaceous Cretaceous age of the iron ores postulated by previous workers, workers, and further emphasizes the the importance importance of of humid, humid, temperate, to to sub..tropical sub-tropical climatic that prevailed prevailed in in the the temperate, climatic conditions that area during the time of the transgression of the Cretaceous seas seas over Minnesota. The present study has produced evidence that the the ores ores are are siderite-rich beds that originated originated during during the the related to primary siderjte-rjch transgression of of the the Devonian Devonian seas. seas. The uniform thickness, thickness, chemical chemical transgression composition, and physical characteristics of of the the ore are preclude preclude their their composition, formation by by the the surficial surficial weathering of of aa normal normal dolomitic dolomitic limestone limestone formation without an an intermediate intermediate concentration concentration step. step. The author believes that the the physical-chemical phy"sical-chemical conditions required required to precipitate precipitate relatively pure pure siderite siderite in in an an otherwise otherwise normal normal carbonate carbonate environment environment relatively during the the Devonian. Devonian. This would require a euxinic were present during environment in an estuary or bay with limited mixing of of normal normal marine marine waters. The by streams streams draining draining a The iron iron was wastrffilsported transported in in solution by low-lying coastal plain under arid arid or or semi-arid semi-arid climatic climatic conditions. conditions. ~/Work done on of the theMinnesota Minnesota Geological Geological Survey Survey on behalf of — Work done 66 �The ultimate ultimate source of the drainage The source of iron iron was was the the normal normal sediments sediments of drainage basin; no basin; no specific iron-rich iron-rich source source beds beds are are required. required. The ores are not necessarily dependent upon unique Cretaceous climatic conditions, conditions 9 and the advisability of placing them within the Formation is is dubious. dubious. the Windrow Formation 77 �*/ STRUCTURE AND AND LITHOLOGY LITHOLOGI OF STRUCTURE OFTHE THEMETJ\MORPHOSED METAMORPHOSED BIWABIK BIWABIK IRON— IRONFORMATION, FORMATION, DUNKA DUNKA RIVER AREA, AREA, EASTERN MESABI MESABI DISTRICT, DISTRICT,MINNESOTA MINNESOTA- Bill Bonnichsen Bill Bonnichsen Department of Geology Geology and and Geophysics Department University of of Minnesota, Minnesota, Minneapolis Minneapolis A three-mile—long three-mile-long belt of of metamorphosed metamorphosed Biwabik Biwabik Iron-formation Iron-formationA in the Dunka River area, Babbitt, Minnesota, Minnesota, at area, near Babbitt, at the eastern eastern end of the Mesabi Range, is being developed developed by Erie Erie Mining Company Company as as aa Range, is taconite property. property. age, rests with profound The The Biwabik Biwabik Iron-formation, Iron-formation, Animikian Animikian in age, profound on granitic granitic rocks rocks of of the the Giants Giants Range Range batholith batholith and and is unconformity on unconformity overlain Formation. The Pokegama Pokegama Quartzite, Quartzite, overlairi conformably conformably by by the the Virginia Virginia Formation. which lies immediately immediately below the the Biwabik Biwabik Iron-formation Iron-formation in in other other parts parts these of the Mesabi range, virtually absent absent at at Dunka Dunka River. River. All of these range, is virtually older rocks have been intruded and thermally metamorphosed by the Keweenawan Duluth Duluth Gabbro Gabbro Complex. Complex. The iron—formation iron-formation and other other PreKeweenawan cambrian rocks are covered locally by as much as 100 feet of as much as 100 feet of glacial is drift. iron—formation ranges in thickness from At Dunka Dunka River, River, the iron-formation from 175 to 300 feet, to feet, and varies as as much as 100 feet in in aa short short distance distance much as 100 feet horizontally horizontally as aa result resultofofboth bothdepositionaJ. depositionaland and structurally— structurallyinduced thinning and induced and thickening. The Lower Lower Slaty, thickening. The LowerCherty, Cherty, Lower Slaty, Upper Cherty, and Upper Cherty, and Upper Upper Slaty Slaty Members Members of of the the Biwabik Biwabik Iron-formation Iron-formation are recognizable recognizable at at Dunka and, except except for for aa markedly markedly thinned thinned are Dunka River River and, Lower Lower Cherty Cherty Member, Member, the the formation formation is is similar similar in in thickness thickness and and stra— stratigraphy to to other other localities in in the the Eastern Eastern Mesabi district. district. AA persistent persistent 55- to 15-foot diabase sill, sill, believed to to be be part part of of the the Duluth Gabbro Complex, Complex, occurs occurs throughout throughout the the property property at at the the same same stratigraphic position stratigraphic position in in the the Upper Upper Slaty Slaty Member. Member. The minerals minerals of of the the Biwabik Biwabik Iron-formation—-quartz, Iron-formation--quartz,magfletite, magnetite, The fayalite, ferrohypersthene, ferrohypersthene,hedenbergite, hedenbergite,hornblende, hornblende, cummingtonite, fayalite, curniiiingtonite, and lesser amounts of diopside, diopside, actinolite, actinolite, andradite, andradite, calcite, calcite, and and pyrrhotite--are characteristic of of a high temperature metamrophic metamrophic environment. The mineralogy and paragenesis are similar similar to to that that at at environment. the the Reserve Reserve Mining Company Company (Gundersen (Gundersen and and the Peter Mitchell mine of the 1962). Quartz is the most abundant mineral in in the the iron— ironSchwartz, 1962). Quartz is formation, formation, and grains grains developed in relatively pure layers are are as as much as as 55 to 10 mm. in diameter. diameter. Magnetite, Magnetite, the the second second most most abundant abundant mm. in mineral, mineral, has haR been coarsened by the the metamorphism; its its grain-size grain-size varies varies considerably from from layer to in general, general, increases increases northward northward considerably to layer but, but, in through the property. property. The taconite shows shows reI.iograde reh'ograde metamorphism metamorphism with hydrous iron—silioat,e forn-thg at the expense iron-si1icateLr1itxer] miner-a] ~s fOl"lJli ng at expense of ofanhydrous anhydrous varieties. *1 ~/Work — Work done partly on on behalf of of the the Minnesota Geological Geological Survey Survey done 8 �The Biwabik Biwabik Iron-formation Iron—formationand andoverlying overlying Virginia Virginia Formation The Formation 0 SE. strike N. 25—35°E. and dip 15-35° The outcrop belt strike N. 25-35°E. and 15-35 SE. The outcrop belt of these these rocks is truncated at angle by the at a slight angle the intrusive intrusive Duluth Gabbro Gabbro Complex9 and in the northern part of the area both formations are Complex, Southward9 the iron-formation extends cut out completely. completely. Southward, extends uninteruninterruptedly down-dip beneath the overriding gabbro and Virginia FormaFormation and can can be be mined mined for for some some distance below the the outcrop by open-pit methods. the structure is superficially Although the superficially simple, simple, the the iron-formairon-formalocally faulted and and folded folded and and is is pervasively pervasively jointed. jointed. A few tion is locally steeplydipping steeply-dipping faults that strike northward and northwestward cut and displace the formation; do not exceed a few formation; maximum displacements do ofwhich whichare arerelated related to to the tens of feet. Small-scale folds, folds, some some of the northward-trending faults, faults, produce local flattening of the the beds and and belt. Two of systematic joints, subwidening of the outcrop outcrop belt. Two sets sets of systematic joints, subparallel to parallel to the major fault sets, sets, and many other joints joints occur throughthroughout the rocks at at Dunka Dunka River, River. The north— north- and northwest-trending faults and appear to regional and systematic systematicjoint joint sets sets appear to be be related related to regional stress patterns; stress patterns; most most of the other other structures stnlctures are are probably probably related to to emplacementofof the the gabbro. emplacement gabbro. 99 �STRUCTURAL CONTROLOF OFTHE TI MOUNT STRUCTURAL CONTROL MOUNT WRIGHT lrJRIGHT -MOUNT REED REED IRON IRON DEPOSITS, DEPOSITS,QUEBEC QUEBEC Peter J. Clarke J. Clarke Department of of Natural Natural Resources, Province Province of of Quebec, Quebec, Quebec, Quebec, Canada The Mount Wright Wright -- Mount Reed district, district, located located about about midway midwaySchefferville in northern Quebec, Quebec, has between Seven Islands and Scheffervifle proven to iron ore. ore. to be be an important source of concentrating grade iron The district contains the southern extension of of the the Labrador Labrador Trough, Trough, which has been deformed and and metamorphosed by the Grenville Grenville Orogeny. Orogeny. by the it is underlain by Proterozoic Proterozoje metasediments, metasediments, including gneisses, It gneisses, marble, quartzite, quartzite, iron-formation iron-formation and and aluminous aluminous schists, which rest rest marble, on a basement of remetamorphosed remetamorphosed granulite granulite and and gneiss. gneiss. Acidic and and basic intrusions are common common in in the the gneisses gneisses below below and and above above the the iron-formation respectively. The Proterozoic Proterozoic metasediments change change in in sedimentary sedimentary facies facies from near-shore deposits in the the northwest northwest to to deeper deeper water water deposits in in the the southeast. southeast. Their structural structural style style varies varies in in different different parts parts of absence of of folds folds of of the the district, district, depending on the presence or or absence depending on the presence two structural trends (northeast two (northeast to to east east and and northwest northwest to to north). north). In a part of the district relative simple simple folds of only one one trend trend dominate; in another part cross dominate; cross folds folds are are developed, and and folds folds of of both trends are are about equally equally abundant. abundant. Much of of the the valuable valuable oxideoxidefades facies iron—formation iron-formation occurs in in the the cross-.folded cross-folded zone, zone, and and the the important iron deposits lie in structural basins separated by domes of older iroD deposits lie in structural basins gneiss. \~ere Wherethe thecross-folds cross—foldsare arespaced spacedrelatively relatively uniformly, uniformly, iron gneiss. are repeated repeated at atabout aboutfour—mile four-mile intervals on a rough rough grid deposits are intervals on with axes with axes trending northeast northeast to east east and and northwest to north. north. 10 �PROTOCLASTIC BORDERSOF OFTHE THE FELSITE PROTOCLASTIC BORDERS NEAR BERGLAND, NEAR BERGLAND, MICHIGAN MICHIG.Ai~ Joseph P. Dobell and Robert W. Joseph W. Leonardson of Geology Geology arid and Geological Michigan Geological Engineering, Michigan Technological University, Houghton, Houghton, Michigan Michigan Technological University, Department rock located located along the north side An intrusive side An intrusive mass massofoffelsitic felsitic rock of Gogebic Lake near Bergland, Michigan, shows Bergland, Upper Michigan, showsdistinctly distinctly protoclastic borders at protoclastic at contacts contacts with basalt and and sandstone which indicates that the rock was at least partially solidified at at the time of emplacement. Zones showing protoclastic structure vary in width from from one to four four feet, feet, and grade away from contacts to a directionless fine fine grained felsite. felsite. The The most conspicuous features of these border zones are are aa distinct distinct banding banding resembling resembling flow flow (fluxion) (fluxion) structure or zones structure or banding, and and aa granular texture texture which which gives the the weathered sedimentary banding, sandstone or a granule conglomrock the appearance of a very coarse sandstone erate. erate. 11 �MEASUREMENT IN-SITU STRESSES SAINT MEASUREMENT OFOFIN-SITU STRESSES IN INAA SAINTCLOUD CLOUDQUARRY QUARRY A PROGRESS A PROGRESS REPORT REPORT Charles Fairhurst Charles School of Mineral School of Mineral and and Metallurgical Metallurgical Engineering Engineering University of Minnesota Minneapolis Minnesota99 Minneapolis The phenomenon is well well known known to to quarry quarry workers The phenomenon of of rock rock Iipressure;Q 'pressure is workers and often results in effects such such as undesired fracturing of blocks during quarrying. Modification Modification of of quarrying quarrying procedures procedures appears appears to to affect affect the the incidence incidence of of pressure pressure effects. effects. The paper paper describes describes surface surface strain strain gauge gauge and and borehole borehole deformation deformation measurements now now in in progress progress in in aa Saint Saint Cloud Cloud quarry quarry to to determine determine the the measurements magnitude and and orientation orientation of of the the stresses stresses considered considered to to be be responsible responsible magnitude for the pressure pressure effects. effects. The The geology geology of of the the area area is is briefly briefly described. Preliminary results results from from one one quarry quarry suggest suggest that that subsubstantial (4000 lb. (lateral) stresses stresses exist stantial (4000 lb. per sq. sq. in.) in.) horizontal horizontal (lateral) in the the directions directions suspected suspected by by the the workmen. workmen. Further Further tests, tests, which will be be discussed, discussed 9 are are planned planned to to determine determine whether the the stresses stresses are are regional regional (i.e. (i.e. externally externally developed) developed) or or residual (i.e. (i.e. internally internally developed, developed 9 for for example example during during cooling). cooling). residual Hast Hast (1958) (1958) has measured measured high high horizontal horizontal stresses stresses in in underground underground mines in in Scandinavia. Scandinavia. The major major axes axes of of the the stress stress ellipsoids ellipsoids at at various points points appear appear to to be directed directed towards towards the the center center of of earthearthquake activity in Scandinavia. Scandinavia. He He suggests regional suggeststhat that similar regional stresses may stresses may be expected expected in the the Great GreatLakes Lakes region region of ofNorth NorthAmerica. America. The possibility that the Ule stresses stressesmay may be be residual residual isissuggested suggested by by The possibility that the fact fact that thatpressure pressure effects effectsare aremost most serious serious in in the the finer-grained finer-grained the rocks. 12 �PROGRESSIVE CONTACT OF THE THE BIWABIK CONTACT METAMORPHISM METAMORPHISM OF BH1ABIK IRON-FORMATION ON ON THE THE MESABI IRON-FORMATION HESABI RANGE, RANGE, MINNESOTA MINNESOTA Bevan Bevan M. M. French Theoretical Division, Division, NASA, NASA, Goddard Space Flight Center, Center, Greenbelt, Greenbelt, Maryland Flight The Biwabik Iron-formation, on on the the Mesabi range range in in northern northern Biwabjk Iron—formation, Minnesota, is is the the middle middle unit unit of of the the three-fold three-fold Animikie Animikie Group Group of of Minnesota, Middle Precambrian Precambrian age. age. On the the eastern eastern end end of of the the range, range, the the Middle Animikian rocks have been intrusive Duluth Duluth Animikian been metamorphosed metamorphosed by the intrusive Complex; mineralogical changes changes in in the the sediments, sediments, particularly particularly Gabbro Complex; in the iron-formation, appear appear related related to to the the gabbro. gabbro. From From the the data of of the present present study, study, four four metamorphic zones zones may may be distinguished within the Biwabik Iron-formation by changes changes in in mineralogy along along the the strike strike of of the the formation formation toward toward the the gabbro gabbro contact: contact: (1) unaltered taconite taconite extends from the the western limit of (1) unaltered of the the Mesabi range range approximately approximately to to the the town town of of Aurora. Aurora. It It is is composed composed of of Mesabi quartz, magnetite, magnetite, hematite, hematite, siderite, quartz, siderite, ankerite, ankerite, talc, and and the the iron iron Of silicates chamosite, chamosite, greerialite, greenalite, minnesotaite, stilpnomelane. Of minnesotaite, and stilpnomelane. these, only quartz, quartz, hematite, hematite, chamosite, chamosite, greenalite, greenalite, siderite, siderte, and and these, some are considered considered primary. primary. The textures of of the the other other some magnetite are minerals indicate indicate aa secondary secondary origin, origin, possibly possibly through through diagenesis diagenesis or low-grade metamorphism prior to intrusion intrusion of the Duluth Gabbro Gabbro Complex. Complex. (2) (2) transitional taconite contains the same mineralogy but exhibits extensive extensive replacement replacement by by quartz quartz and and ankerite. ankerite. Incipient exhibits metamorphic changes changes in in this this zone zone are are the the partial partial reduction reduction of of hematite hematite metamorphic to magnetite and the appearance of clinozoisite clinozoisite in in the underlying underlying Pokegama Pokegama Formation. Formation. (3) (3) moderately metamorphosed taconite taconite is is characterized by development of the iron-rich amphibole amphibole grunerite grunerite and and by by the the disappearance disappearance Calcite appears from of original original iron iron carbonates carbonates and and silicates. silicates. of reaction of of ankerite ankerite and and quartz quartz to to form form grunerite. grunerite. (4) taconite, within two miles of the Duluth (4) highly metamorphosed taconite, Gabbro contact, Gabbro contact, is is completely completely recrystallized recrystallized to to aa metamorphic metamorphic fabric fabric and is composed chiefly of quartz, quartz, iron amphiboles, amphiboles, iron and iron pyroxenes, pyroxenes, magnetite, and rare and calcite. calcite. Small veins and and pegmatites pegmatites magnetite, arid rare fayalite fayalite and this zone zone may represent introduction of reported from from this represent. minor intl"odnction of material from the gabbro. gabbro. The following mineralogical mineralogical changes changesoccur occuralong alongthe the strike strike of The following of the iron-formation iron-formation toward toward the gabbro gabbro contact: contact: (a) (a) partial partialreduction reductionof ofhematite hematite to tomagnetite magnetite (in the Pokegama Pokegama Formation) Formation) (b) development of clinozoisite (in (c) formation formation of grunerite (c) 13 13 �(d) (d) (e) (e) (f) (f) (g) (g) appearance of iron-rich clinopyroxene appearance clinopyroxene (hedenbergite) (hedenbergite) disappearance of hematite appearance of ferrohypersthene appearance of graphite (from organic matter). All the changes, changes, which represent the complete complete transition from from unmetamorphosed to highly metamorphosed taconite, taconite~ occur within a a horizontal distance of of about about two two miles miles near near Mesaba. Mesaba. iron-formation Compositions of the carbonate minerals in the iron—formation by combining combining refractive refractive index index measurements measurements with with X-ray X-ray were determined by diffraction data to obtain values for for the Ca, Ca~ Fe, Fe~ and Mg components. components. In unaltered taconite, taconite~ siderite siderite compositions compositions approximate approximateCa5F'e75Mg20; Ca5Fe7y~gzo; at ankerite compositions same material compositions from from the the same material are are quite uniform at calcites that approximately Ca53Fe24Mg2j. Ca53FeZ4MgZ3. The The calcites that appear appear in in the themetameta- morphosed taconite are andand Mg—poor, morphosed taconite areFe-rich Fe-rich Mg-poor~ approximating approximatingCa9Fe10Mg1. CaB9Feld1g1. No definite change in siderite siderite or No definite change in or ankerite ankerite compositions compositions is noted along the the strike of BiwabikFormation; Formation;there there is is no indicanoted along of the the Biwabik tion of progressive progressive removal removal of of iron from from the the carbonate carbonate with increasing increasing metamorphism. By contrast, contrast~ calcites from the metamorphosed taconite increase in Ca, Ca, becoming becoming virtually virtually pure pure CaCO3 CaCO) near near the the gabbro. gabbro. The present study indicates that metamorphism of the Biwabik Iron-formation by the the Duluth Gabbro Complex was largely Isochemical i"'o~hemical and was was characterized by progressive progressive loss loss of 0fH20 H20 ;:r1d COZ. characterized chiefly by CO2. There is no indication that the original mineralogy consisted cons~sted only magnetite, or that large quantities of other components of quartz and aDd magnetite, components were introduced introduced into into the the sediments sediments from fro!ll the the gabbro, gabbro, as as has has been been proposed (Gundersen (Gundersen and and Schwartz, Schwartz, 1962). 196Z). 14 l4 �STRATIGRAPHY,STRUCTURE, STRUCTURE,fu~D ANDGRANITIC GRANITICROCK~/IN R0CK1IN THE STRATIGRAPHY, THE MARENISC0-WATERSMEE AREA, }\1ARENISCO-WATERSMEET AREA, MICHIGAN—' MICHIGAN- Crawford CrawfordE.E.Fritts Fritts Survey, Denver, S. Geological Survey, Denver, Colorado U. S. detailed mapping mapping near near Lake Lake Gogebic, Gogebic, Michigan, Michigan, reconnaissance, reconnaissance, Recent detailed Recent the Marenisco-Watersmeet area recorded by the and review of data from the Michigan Michigan Geological Geological Survey Survey since since 1900 have have led led to to reinterpretation reinterpretation of of regional stratigraphy stratigraphy and and structure. structure. The Tyler Slate of the the Gogebic regional an east—plunging east-plunging anticline anticline west west of of the the Range wraps around the nose of an lake and conformably conformably underlies aa thick thick sequence sequence of of south-dipping south-dipping metametalake and volcanic and metasedimentary rocks, rocks, which apparently underlies the the Michigamme Slate Slate (fig. (fig. 1, 1, on page). North North of Cup Cup Lake, Lake, graded graded Michigamme on next page). bedding in in quartzite formerly fornlerly interpreted interpreted as as folded folded and and overturned overturned of the the Marenisco Marenisco Range Range indicates that rocks there actually strata of are are right right side side up. up. Similarly, Similarly, near near Kakabika Kakabika Falls, Falls? pillow pillow structures structures metavolcanjc rocks indicate that strata in metavolcanic strata of the Turtle Range also also are right side up. up. The The principal structurebetween betweenMarenisco Marenisco and and principal structure Water&neet, therefore, is is aa south-dipping south-dipping monocline. monocline. Although Although Watersmeet, therefore, diamond-drill data indicate indicate aasynclinal synclinalflexure flexurenear nearBanner BannerLake, Lake, field evidence at present present does does not not require require tight tight folding field evidence at folding or largefor scale there. However, large throw throw accounts accounts for scale faulting there. However,a afault fault of large MarenisCo, and it westward disappearance the westward disappearance of of the Tyler Slate near Marenisco, is possible that that other other faults faults will will be be found found farther farther east east as as mapping mapping is continues. Rocks formerly formerly mapped mapped as as Presque Presque Isle Isle Granite Granite include include at at least least Banded gneiss three of different ages. ages. Banded gneiss three distinctive distinctive lithologic units of and a younger younger equigranular equigranular granite granite unconforinably unconformably overlain overlain by by the the Tyler Slate Slate west west of of Lake Lake Gogebic Gogebic probably probably are are pre-Animikie pre-Animikie in in age. age. Tyler Well granitic to to quartz foliated, well well lineated, lineated, biotite.-rich, biotite-rich, granitic Well foliated, monzonitic gneiss gneiss intrudes rocks rocks stratigraphically stratigraphically above above the the Tyler Tyler south and east of and probably probably is is post-Aniinikie post-Animikie in in age. age. of Marenisco Marenisco and In the Marenisco-Watersmeet area, the metamorphic grade of Animikie area, Animikie strata, in in general, general, increases southeastward toward the center of a strata, in part, part, by by the the post—Animikie post-Animikie gneiss. gneiss. It It is is broad zone zone underlain, underlain, in likely, therefore, that the the metamorphism metamorphism accompanied accompanied and and perhaps perhaps likely, therefore, of this this gneiss. gneiss. followed emplacement emplacement of ~/Work done in cooperation — Work done in cooperation with the Geological Survey Division with of the Conservation the Hichigan Michigan Department of Conservation 15 �Yondoto Falls 1]] ----~ 1]] I o 0 I I I I 2 3 4 5MILES 5 MILES I I I I I EXPLANAT I EXPLANAT zz zz «« i~ ~ Jacobsville Sandstone Jacobsville Sandstone UNCONFORMI TV UNCONFORMITY cr cr 0l0l } ::;:::;: «« 00 uu w crcr o0 0..0 ON a N zz nI Rocks Rocks near Cup Cup Lake Lake Interlayered amphibolite, Interloyered amphibolite, metogroywacke metagraywacke, phyllitic phyllilic schist, and and porphyritic schisl, parphyrilic metotuff metatuff; minor minor conglameralic quarlzite parI conglomerotic quortzite in lower part ~ cr Ol ::; « 0 u uJ w cr aa.. Keweenawan Series Keweenawan Un/CONFORM/TV UNCONFORMITY Tyler Slate Siale Graywacke.slote overlying thin Graywacke-slale thin basal basal conglomerate conglomerate £INCONFORM/ TV UNCONFORMITY Gronitic to Quartz quartz monzonitic nonzonitic gneiss Granitic to gneiss u-,,:;.~ ~, Granite Michigarnme Michigamme Slate Slate FT-T'T'll U:i±.IJ Metamorphosed pillow lavas lovos and and luffs tufts Metamorphosed pillow ~ Metatuffs Metatuffs and and metasedimentary metasedimentary rocks racks Stratigraphic Straligraphic position position uncertain; uncerlain; possibly possibly younger lhan thon pre—Animikie younger pre-Animikle granite rzJI!llJ Banded gneiss gneiss Rocks Rocks near Bonner Banner Lake Lake -1".&, phyilitic schist and and other athermetasedimentory metasedimentary phyllitiC schist rocks, undivided; undivided, may racks, may also also include include metatuff metatuff lean iron -- fa formation ~, lean r ";',0 ti an" carbonaceous slate slale • , carbonaceous Figure II. Preliminary geologicmap mapofofthe the Marenisco Marenisco —Wotersmeet area,Mlchillan, Michigan,showinll showingtentative tentative interpretation interpretation -Watersmeet area, Preliminary geologic of strotigraphy andstructure structurebybyC.C.E.E.Fritts, Frifts, 1965, of stratigraphy and 1965. �STRUCTUREAND ANDSTRATIGRAPHY STRATIGRAPHYOF OFTHE ThE KNIFE LAKE STRUCTURE LAKE GROUP GROUP EAST OF ~ HINNESOTJl:/ EAST OF ELY ELY9 MflESOTA/ John C. Green Green John C. Department of of Geology Geo1or Minnesota, Duluth University of Minnesota~ In the Gabbro Lake quadrangle just east of Ely, Lake 1.5-minute 15-minute quadrangle Ely~ Minnesota~ Precambrian Precambrian Knife Knife Lake Lake rocks rocks occur occur in in two two belts. belts. The The Minnesota, southern belt~ composed of of schist, schist, gneiss, gneiss 9 and and migmatite, is derived belt, composed from graywacke, graywacke 9 conglomerate, conglomerate 9 and and arkose, arkose~ and and is is intruded intruded and and metametathe Giants Giants Range Range batholith batholith of of .Algoman Algoman age. age. It is faulted morphosed by by the against the the basal basal part part of of the the older but but lower-grade lower-grade Ely Greenstone Greenstone against on the north north side side of of the the belt, belt, along along the the major major North North Kawishiwi Kawishiwi fault. fault. on The northern and and wider belt has been metamorphosed only to the the chlorite zone, zone. its Its contact contact with the the underlying Ely Ely Greenstone Greenstone is is with a basal conglomerate. mostly faulted, faulted, but locally conformable ~nth conglomerate. Above this this are, are, successivelY9 successively, 0-2,500 0—2,500 feet feet of of mixed mixed felsic felsic tuff and and Above elastic sediments, feetofofchloritic chloritic clastic elastic sediments, clastic sediments, 1,500_LI.,.5OO 1,500-4~500 feet sediments, mafic volcanic volcanic unit unit 0-2,250 0-2,250 feet feet thick, thick, and a thick thick a predominantly mafic sequence felsic volcanic volcanic rocks, rocks, mainly pyroclastic, pyroclastic, as as much as sequence of felsic 8,000 feet feet thick. thick. Within Within this this unit unit near near Fall Fall Lake Lake is is aa.500-foot 500-foot bed of of siliceous siliceous limestone limestone and and chert chert conglomerate. conglomerate. The felsic felsic bed volcanic rocks interfinger with mafic volcanics similar to Ely volcanic rocks with mafic volcanics to Greenstone northwest of Fall Lake, Lake, and are faulted against mafic Greenstone volcanics and sediments of unknown correlation in the northwest and north-central north—central borders borders of of the the area. area. Knife Lake time in in this this area area evidently evidently was one one of of great great crustal crustal disturbance, disturbance, with rapid erosion of the older greenstones and the rocks rocks that intrude intrude them~ them, and and extensive extensive volc&~ic volcanic activity, activity, probably mostly underwater. An active, active, island arc type of environment is envisioned. This This activity activity culminated culminated in in the batholithic intrusions intrusions and extensive faulting of the Algoman and Algoman orogeny. orogeny. *1 ~/work — Work done done ononbehalf behalf of theof Minnesota the Hinnesota GeologicalGeological Survey 16 16 Survey �PETROLOGY OF IRON-FORMATION IN THE THE REPUBLIC IlEPUBLIC PETROLOGY OFTHE THE SILICATE IRON-FORMATION MINE AREA, AREA,IVL4RQUETTE M.ARQUETTE COUNTY, COUNTY, MICHIGAN MICHIGAN Tsu-Ming Hanand and James JamesW. W.Villar Villar Tsu-Hing Han Cleveland-Cliffs Iron Iron Company, Company, Ishpeming, Michigan Michigan Cleveland—Cliffs The iron-rich metasediments at at the the Republic mine mine can can be be subsub- divided into four four lithologic lithologic types types according according to to major major mineraJ. mineral constituents. stituents. These include aa quartz-specular hematite-muscovite conglomeratic the Goodrich FOTI~ation Formation and and three conglomeratic member at the base of the lithologic types within the Negaunee Iron-formation, Iron-formation, which normally and major major reflect a close close relationship between stratigraphic stratigraphic position and mineral assemblage. assemblage. In In descending descending stratigraphic stratigraphic order order the the mineral mineral assemblages generally are: are: quartz-specular quartz-specular hematite, hematite, quartz-magnetite, quartz-magnetite, and quartz-grunerite-magnetite. The type type characterized by the and latter assemblage, assemblage, the subject subject of this study, study, is as much as 500 SOO feet thick and commonly contains a series of sill-like amphibolites. and commonly contains a series of sill-like amphibolites. The rock is typically banded as a result of compositional variations in in the the ratios ratios of of quartz, quartz, magnetite, magnetite, and and grunerite. grunerite. variations Bands Bands with with oolites oolites of of quartz-magnetite, quartz-magnetite, quartz-grunerite-magnetite, quartz-grunerite-magnetite, Locally, carbonate occurs as a and grunerite-magnetite are are common. common. Locally, major constituent of of some some bands. bands. Five generations generations of minerals are are recognized: recognized: (1) (1) scattered scattered Five grains of original elastic clastic quartz and and fine-grained fine-grained magnetite, magnetite, (2) (2) quartz, magnetite, grunerite, garnet, calcite, hornblende, and quartz, magnetite, grunerite, garnet, calcite, hornblende, pyroxene, during regional regional metamorphism, metamorphism, (3) stilpnomelane, pyroxene, formed formed during minnesotaite, hornblende, hornblende, and calcite, minnesotaite, calcite, formed during retrograde metamorphism, (4) (4) quartz-calcite, quartz-hematite, quartZ-hematite, and and an an unidentified unidentified brownish green silicate, silicate, formed as fracture fracture fillings subsequent subsequent to metamorphism, and and (5) (S) martite and hematite, hematite, formed formed from from magnetite magnetite and grunerite during supergene supergene oxidation. oxidation. Paragenetic studies studies indicate indicate that that grunerite grunerite formed, formed, at least least in part, at the expense of magnetite and quartz during metamorphism part, in the Republic mine mine area. area. This is indicated by the following observations: observations: (1) growth of gTIlnerite porphyroblasts in in nearly nearly pure pure magnetite magnetite (1) grunerite porphyroblasts bands, bands, (2) presence presence of magnetite-quartz remnants (2) remnants within within grunerite grunerite bands, bands, (3) (3) magnetite grains within grunerite bands exhibit irregular or subrounded crystal outlines in contrast to subhedral and euhedral ruagnetite in in assemblages assemblages lacking lacking grunerite, magnetite grunerite, (4) common common development development of thin grunerite grunerite layers between (4) magnetite and and quartz bands, bands, and and (S) (5) growth of grunerite along the borders of magnetite-rich veinlets that that cut cut quartz quartz bands. bands. This reaction is further substantiated substantiated by determinations of ferric ferric and ferrous ferrous iron contents of the iron—formation, iron-formation, which reveal 17 17 �the quantities of magnetite and an inverse relationship between the grunerite. This does does not not preclude preclude the the participation participation of of other other reactants reactants This such iron silicates silicates in in the the development development of of such as as carbonates and layered iron grunerite. grunerite. 18 18 �AGES MAFIC DIKES NEAR NEAR GRANITE GRANITE FALLS9 FAIJLS, MINNESOTkMINNESOTk~/ AGES OF OF MAFIC Glen and Gilbert Gilbert N. Glen R. R. Himnielberg Himmelberg and N. Hanson Hanson Department of Geology and and Geophysics University of Minnesota, Minnesota9 Minneapolis, Minneapolis9 Minnesota Precambrian rocks exposed in the Minnesota River valley near Granite Falls9 Falls, Minnesota consist of interlayered metamorphic rocks iiitruded by numerous numerous mafic dikes. intruded by dikes. Existing structures structures in in the the metametamorphic rocks rocks resulted resulted from from dynamothern-ial dynamothermal metamorphism metamorphism about 2.6 billion years years ago. ago. AA later 1.8 b.y. b.y. thermal event is reflected in potassi~~-argon potassium-argon and rubidium-strontium ages of biotite from the metamorphic rocks. rocks. The dikes can be divided petrographically into into tholeiitic diabase, hornblende hornblende andesit.e, andesite, and olivine olivine diabase. diabase. Older tholeiitic several varieties of hornblende diabase dikes are cross-cut by several andesite dikes. dikes. In addition, addition, shear shear zones, zones, which by field evidence could have formed during the late stages stages of of the the 2.6 2.6 b.y. b.y. event, event, cross-cut cross-cut the the tholeiitic tholeiitic diabase diabase but but are are cut cut by by hornblende hornblende andesite andesite dikes, dikes. One of the hornblende andesite dikes is intruded by a 1.8 b.y. granitic b.y. granitic body. body. The relative age of the olivine diabase with respect to the other dikes was not not determined determined in in the the field. field. In In this this study, study, a potassium-argon potassium-argon determination on on hornblende hornblende from from the the metamorphosed metamorphosed country rock rock gives an an age age of of 2.8 b.y., b.y., which which indicates that the hornblende was not not affected affected by by the the 1.8 1.8 b.y. b.y. thermal event. Hornblende from a tholeiitic diabase dike gives an age of 2.0 2.0 b.y.; b.y.; four four of of the the varieties varieties of of hornblende hornblende andesite andesite dikes dikes age gave concordant biotite and and hornblende potassium—argon potassium-argon ages ages of of 1.7 1.7 —1.8 b.y. b.y. the 2.0 2.0 b.y. b.y. age age is is real, real, the the shearing occurred between between 2.0 2.0 If the If, however, however, this 2.0 b.y. and 1.8 boY, ago. If, b.y. value reflects reflects the the ago. loss of argon at 1.8 b.y., b.y., the intrusion of the tholeiitic diabase and the the shearing could have taken and taken place place at at the the close close of of the the 2.6 2.6 b.y. b.y. metamorphic metamorphic event. event. ~/Work done done on on behalf of the the Minnesota Geological Geological Survey -'Work 19 19 �AI EXAMPLE OF STATISTICAL AN EXAJ.\I!.J'LE OF STATISTICAL A1\ALYSIS ANALYSIS AND AND POSSIBLE POSSIBLE INTERPRETATION INTERPRETATION OF STRUCTURAL HILL, SKANEE STRUCTURAL DATA DATA FROM FROM ARVON ARVON HILL, SKMJEEQUADRANGLE, QUADRANGLE, UPPER UPPER PENINSULA, PENINSULA, MICHIGAN MICHIGAN J. D. D. Juilland 1912-B Woodman Drive Drive Houghton, Michigan Skanee quadrangle, quadrangle, Upper Peninsula of Arvon Hill is located in Skanee Michigan, about about 13 l miles northeast Michigan, northeast of of L'anse. L 9 anse. Regionally, the area is underlain by Lower Precambrian metamorphic rocks, rocks, which which are are overlain overlain unconformably unconformably by by .Animikian Animikian metasediments. Younger glacial deposits are virtually absent except along the the flanks flanks of the the hill. hill. Five major types of rocks have been recognized in the Argon Hill area, namely, quartzite (Ajibik), gneiss, migmatite, migmatite, area, (Ajibik), aniphibolite amphibolite gneiss, granitic rock, rock, and and dioritic dioritic rock. rock. The last four rock rock types types form form the the Lower Precambrian or Archean basement; the quartzite occurs on the the basement; the flanks of of the the hill. hill. An An anticlinal structure structure is is inferred inferred from from the the distribution of the rock rock units. units. Foliations, joints were Foliations, lineations, lineations, and and joints were recorded recorded and and plotted plotted on on Schmidt nets nets for statistical analysis. analysis. Structural data data from from the the for statistical Lower Precambrian Precambrian rocks rocks were Lower were separated from those of the theAnimikian Animikian rocks. The The present-day present-day structure observed observed in the rocks was analyzed analyzed first. The Thelimbs limbsofofthe the quartzite quartzite were then rotated rotated back to horizontal. first. were then back to for the The The same same amount amount of rotation for the underlying underlying rocks rocks was used, used, thus position before rotating all structures to their theirassumed assumed position before folding folding of all structures the quartzite. These new sets sets of of readings readings were were plotted, plotted, contoured, contoured, and interpreted as as the the pre—quartzite pre-quartzite structure. structure. As indicated indicated by by BadgleyQs Badgleys Joints were were analyzed analyzed separately. separately. As Joints 'triangle of of intersection, intersection,Ii the \'triangle the joint joint system system in in the the Lower Lower Precambrian Precambrian rocks resulted two periods of stress, rocks resulted from two stress, whereas the joint joint system in the quartzite is the result result of of only only one one period, period, the the second. second. It is concluded that at least two two periods of folding affected affected the the area as a result of forces forces from from approximately approximately the the same same direction. direction. 20 �SOME IRON-FORMATIONS IN AUSTRALIA AUSTRALIA AND AND SOUTH SOUTH AFRICA AFRICA SOME ASPECTS ASPECTS OF OF IRON-FORMATIONS Gene L. L. LaBerge Gene LaBerge Postdoctoral Fellow Fellow National Research Research Council Council of of Canada Canada Canada, Ottawa Geological Survey of Canada~ The extent of Proterozoic iron-formations in the the Hamersley only recently. The Range of Western Australia has has been been recognized recognized only Range, which covers about 40,000 square miles miles,1 probably Hamersley Range~ contains more exposed exposed iron-formation iron-formation than than any any equivalent area in the the world. Three banded iron-formations having an aggregate thickness of more more than than 31500 ,5OO feet feet and, and, probably, probably~ aa total total of of more more than than 80,000 80 1000 feet sediments occur occur in in the the area. area. feet of Proterozoic sediments In South Africa, Africa, aa more more or less continuous belt of Proterozoic iron-formation that is part of the Transvaal System extends for for more than 800 miles. miles. The iron—formation iron-formation is locally more than 5,000 feet thick, thick, but is generally 800—2,000 feet 800-2 1 000 feet feet thick. thick. A A brief account account of of the the general general Proterozoic Proterozoic stratigraphy and and the stratigraphy of the iron-formations from from each each area area will will be be presented presented to to show how they differ from the stratigraphy stratigraphy of the Lake Superior iron—formations region. Layers of altered pyroclastic rocks rocks in the the iron-formations indicate indicate that that there there was was volcanic volcanic activity activity during during much much of of the the time time the iron—formations iron-formations in in each each area area were were being being deposited. deposited. the Certain features iron—formations in Western Australia features of the iron-formations and and South Africa Africa are are very very similar to to those those in in iron-formations iron-formations in in the Lake Superior region, others—-notably the occurrence of region, but others--notably crocidolite crocidoflte asbestos asbestos and and the the virtual virtual absence absence of of granules--are granules——are distinctly distinctly different. There is more similarity between Australian and South African iron-formations than there is between iron-formation of either with the Lake Superior area ~nth Superior region. region. 21 �THE IN THE THE DISTRIBUTION DISTRIBUTION OF OFMANGANESE MANGANESE IN THE BIWABIK IRON-FORMATION, BIWABIK IRON- FORt\1ATION, MINNESOTA MINNESOTA Lepp Henry Lepp Department of Geology, st. Paul Geology, Macalester College, St. The weighted mean mean Mn Mn content content of of the the Biwabik Biwabik Iron.-formation Iron-formation based on 948 individual samples samples is is 0.48 0.48 per per cent. cent. This represents represents an enrichment of about about 4.8 4.8 times times the the mean mean crustal crustal abundance abundance (Clarke) (Clarke) of this this element. element. The Biwabik shows a mean Mn/Fe ratio of 0.016 as compared to a crustal average of 0.022 for this ratio, ratio, thus indicating a slight geochemical separation separation of of Mn Mn and and Fe. Fe. Samples of iron-formation that have been oxidized without appreciable leaching or iron enrichment have considerably lower Mn/Fe ratios ratios than than do unoxidized taconites. taconites. Core samples of ores (enriched oxidized taconites containing containing more more than than 40 40 per per cent cent Fe) Fe) show only a slightly slightly lower lower mean mean Mn/Fe Mn/Fe ratio ratio than than unaltered unaltered taconite, taconite, but their mode and median for this ratio The ratio are much lower. lower. The sideritic iron—formation contain the most manganese sideritic sections of the iron-formation and the goethite-rich oxidized sections sections contain contain the the least. least. There appears appears to to be be no no significant significant variation variation in in the the Mn content content There of the Biwabik laterally if only only unoxidized samples samples are are considered. considered. There is, is, however, however, a significant significant difference between the the four four members; members; the means in in per per cent cent Mn Mn are are as as follows: follows: Lower Cherty Cherty -- 0.67, Lower Lower Slaty -. Slaty - 0.44, Upper Cherty Cherty -- 0.34, Upper Slaty Slaty - 0.29. In an attempt variations in in the the Mn content content aa attempt to to show the local variations trend surface surface was computed for an an area area with closely closely spaced spaced holes. holes. The trend surface f(TJ,V,W) ) accounts for 52 per cent surface (%Mn (%Mn == Xn = f(U,V,W) of the sum sum of of squares. squares. Deviations from from the trend surface surface cut cut across across thus suggesting of the variability the formation formation thus suggesting that some some of variabilitymay may be be the secondary oxidation planes. due to due to secondary oxidation and and leaching leaching along along joint joint planes. ) 22 �SOME ASPECTS SOME ASPECTSOF OFTHE THEPEGMATITES PEGNATITESIN IN THE THE FELCH FELCH DISTRICT DISTRICT,9 DICKINSON DICKINSON COUNTY, COUNTY, MICHIGAN HICHIGAN Geoffrey W. Geoffrey W. Mathews Mathews Department of Geology Department Geology University, Cleveland, Cleveland, Ohio Western Reserve University, cut the the pre-Animikian Numerous simple, simple, unzoned un zoned pegTnatites pegmatites cut units in in the the Feich Felch district. district. Size and shape shape of of the the metamorphic units pegmatites vary from small small sinuous sinuous bodies in the the Mill Pond Granite Gneiss to to large large irregular irregular masses masses in in the the Solbert Solbert Schist. Schist. to subdivide the the pegmatites into meaningful In an attempt attempt to groups, pegmatites groups, the Be, Be, Mo, Mo, and and Ti contents of twenty unclustered pegmatites were determined determined spectrographically. spectrographically. Ratios of the concentrations of of these these elements elements provide provide aa basis basis for for separating separating the the pegmatites pegmatites into into two two distinct distinct groups. groups. AA similar similar analysis analysis was run on the granite granite dikes and samples of of the the granite granite gneiss gneiss in in the the Feich Felch district. district. Seven of and samples the pegmatites (Group II pegmatites), pegmatites), characterized by a relatively relatively high Ti:Be+Mo ratio, ratio, plot in in the the same same area area of of aa relative-percent relative-percent triangle diagram as the Group the granite granite dikes dikes and and the the granite granite gneiss. gneiss. Group comprisingthe the remaining remainingthirteen thirteen of the II pegmatites, comprising the pegmatites pegmatites and characterized by by a relatively relatively low low Ti:Be+Mo ratio, ratio, plot plot in in aa distinctly different different region region on on the the diagram. diagram. Correlation coefficients coefficients Be—Mo, Be-Ti, Be-Ti9 and Mo-Ti Mo—Ti also emphasize the difference between between Be-Mo, the two groups. groups. Group II pegmatites and the the granite dikes and gneiss show small small positive positive correlations between Be Be and Mo Mo and relatively show large negative correlations between Be-Ti and and Mo-Ti. Ho-Ti. Group II II pegpegmatites have a large positive correlation between Be-Mo and small small correlations between Be-Ti and Mo-Ti, positive and and negative negative respectively. respectively. Mo-Ti, positive There appears to to be be no simple simple relation relation between geographical geographical loca.tion, size, size, shape, shape, or or host host rock rock unit unit and and the the two two groups groups of of location, pegmatites. The strikes strikes of of bodies bodies within within the the different different groups, groups, however, are divergent. divergent. Strikes of Grou.p Group II pegmatites are are confined confined however, are 0 E., to the range N. 80° E., whereas the the strikes of Group II to N. 300 30 0 E. E. -- N. 80 peginatites are seemingly haphazard. pegmatites are haphazard. It is suggested suggested that the in the the Felch the two two groups groups of pegmatites in district district represent represent either either (1) (1) different different parental parental sources, sources, or or (2) (2) intrusion at at different stages stages of of the the progressive progressive differentiation differentiation of of intrusion a single parent magma under different different tectonic tectonic controls. controls. 23 23 �LAKE COUNTY, THE SAUBLE SAUBLE GEOPHYSICAL GEOPHYSICAL ANOMALY, ANOMALY, LAKE COUNTY, MICHIGAN MICHIGAN THE Howard J. J. Meyer and Howard and William J. J. Hinze of Geology, State University, Geology, Michigan Michigan State University, Lansing, Michigan Michigan East Lansing, Department Department A detailed gravity and magnetic survey was conducted of the A Sauble anomaly of Lake County, County, Michigan. This outstanding outstanding anomaly anomaly is a circular magnetic and gravity high having residual maximum and 22 22 milligals milligals respectively. respectively. The The comcomamplitudes of 1,130 gammas and bined gravity gravity and and magnetic lnagnetic analysis analysis method method utilizing utilizing Poisson's equation was applied applied to to the the residual residual anomalies, anomalies. An idealized idealized case case was employed employed to to check check the accuracy accuracy of of the the combined combined analysis analysis method. method. form, size, The composition, composition, form, size, and depth of the anomalous body were studied further by depth determinations and by fitting idealized cases to the observed anomaly anomaly profiles. profiles. It was concluded that that the the anolnalous body body is is a very basic Precambrian intrusive stock. The anomalous The the body and the the Precambrian surface in this elevation of the top of the area is about 8,000 to 99000 feet below 9,000 feet below sea sea level. level. 24 �THE THE SEDINENTOLOGY SEDIMENTOLOGY OF THE THEPRECAMBRIAN PRECAMBRIAN ROVE ROVE FOPUATION FORMATION NORTHEASTERN MINNESOTA-! MINNESOTA~/ IN NORTHEASTERN G. B. Moray Morey G. B. Department of Geology Geology and and Geophysics9 Geophysics, University of Minnesota9 Minnesota, Minneapolis The Middle Middle Precambrian Rove Formation, the upper part of the the The Formation, the Aninikie Group, Group, is estimated to to be at least 3,200 feet thick, Animikie thick, and is and the is exposed between northwestern Cook County, County, Minnesota Minnesota and Thunder Bay is aa sequence sequence of of gra~~acke, grayacke, Bay district, district, Ontario. Ontario. It is argillite, locally abundant argillite, abundant intraformational intraformational conglomerate, conglomerate, quartzite, quartzite, and carbonate carbonate rocks. rocks. This sequence was deposited some some time between 2.0 b.y. b.y. ago in a northeast-trending basin, b.y. and 1.7 b.y. basin, the the conconfiguration of which which was was probably controlled by a pre-existing pre—existing figuration structural structural grain. grain. Detailed mapping in the South Lake 7*-minute 7i-minute quadrangle, quadrangle, combined with a field and laboratory study study of approximately 150 other scattered stratigraphic stratigraphic sections provide provide aa basis basis for for the the recognition of four informal lithologic units. units. From oldest to to youngest these these are: are: (1) lower argillite, (1) argillite, 400 feet thick; (2) (2) transition transition beds beds of of inter— interbedded argillite and graywacke, grayacke, 70 argillite and 70 -- 100 feet feet thick; thick:; (3) (3) thin-bedded graywacke, gra~Nacke, as much as as 2,000 feet thick; thick; and (4) (4) upper graywacke— gra~Nacke­ quartzite, at least 700 feet quartzite, feet thick. thick. It is concluded that the argillite argillite and and associated associated graywackegraywackesandstone and and graywacke-siltstone graywacke-siltstone units units were were deposited deposited in in moderately sandstone deep, quiet quiet water water which which was was probably probably marine. marine. Repeated sedimentation sedimentation deep, units one to three feet thick indicate indicate sediment sediment transport and and deposition A sedimentation unit reconstructed deposition by by turbidity turbidity currents. currents. A from composite sections sections consists of (1) (1) a basal conglomeratic gray— graywacke, (2) wacke, (2) aa structureless structure1ess unit unit that that grades grades indistinctly indistinctly into into (3) (3) a graywacke that that is is overlain overlain by by (4) (4) aa laminated laminated graywacke, graywacke, graded grayvJacke by (5) (5) small-scale cross-bedding, or or (6) (6) conwhich may be modified by torted one or several torted bedding. bedding. Any Anyone several of these may be absent, absent, but the argillite. unit unit is is always always overlain overlain by by (7) (7) an argillite. Post-depositional Post-deposition31 soft-sediment soft-sediment structures structures such such as as load load casts, casts, flame structures, clastic dikes, dikes, bed pull-aparts, pull-aparts, overfolds, overfolds, and flame structures, clastic micro-faults micro—faults indicate indicate rapid rapid deposition of of Rove sediments, sediments, active active bottom currents, and post-depositional post-depositional deformation. deformation. A A detailed analysis analysis of of paleocurrent directional indicators indicators such such as groove casts, casts, flute flute casts9 casts, dendritic dendritic ridges, ridges, as grain lineations, lineations, groove and and cross-bedding show that the turbidity currents had a southerly southerly trend perpendicular perpendicular to to the the axis ~xis of of the the Rove Rove basin. basin. However, ripple ripple marks, winnowed lag deposits at at the the tops tops of many graywacke graywacke beds9 beds, and festoon-type festoon-type cross-bedding show that the the turbidities were later modified by by bottom currents currents that that trended trended southwesterly southwesterly parallel parallel to to the axis of the the basin. basin. —'Work ~/Work *1 done the Minnesota Geological Survey Survey done on behalf of the 25 �The heavy minerals of of the the Rove Rove are are characterized characterized by by epidote— epidotegroup minerals, sphene, and tourmaline~ minerals, apatite, apatite, sphene, tourmaline, and are typical of pre-Middle Precambrian igneous rocks now exposed north of the present outcrop area of the Rove Formation. Formation. Thin section and and X-ray analyses of 200 200 samples show that the the angular, poorly sorted grains of elastic graywackes consist of angular, clastic quartz and plagioclase (niü_An25) embedded plagioclase (AnlO-An25) embedded in in an an argillaceous argillaceous matrix matrix that now consists of quartz, chlorite, chlorite, and and muscovite. muscovite. The finefinegrained, fissile fissile argillite argillite and mudstone have have the the same grained, srone mineralogy and micro-textures micro-textures as as the the graywacke. graywacke. to pre-Keweenawan tilting removed an unknown Erosion subsequent subsequent to the formation formation prior to the the deposition of Lower Keweenawan amount of the sedimentary rocks. rocks. The intrusion of Middle Keweenawan igneous rocks sedimentary Rove Formation to to a variety of caused local metamorphism of the Rove mineral, assemblages now now assigned assigned to to the pyroxene- and mineral assemblages and hornblende— hornblendehornfels facies, hornfels facies, but but the the remainder remainderisisessentially essentiallyunnieta.morphosed. unmetamorphosed. 26 26 �SEDIMENTATION OFOFMIDDLE FINLAND SEDflVIENTATION MIDDLEPRECAMBRIAN PRECJMBRIANQUARTZITES QUJRTZITES IN IN FINLAND Richard W. W. Ojakangas Department Departmentof of Geology, Geology,University University of Minnesota, Minnesota, Duluth quartzites, metamorphosed 1,800 m.y. m.y. ago, The Jatulian quartzites, ago, were studied in in eastern, eastern, central, central, and and northern northern Finland Finland to to decipher decipher the the studied sedimentary history of the the original original sandstones. sandstones. Erosional remnants remnants thick, indicate an initial of the formation, formation, several hundred meters thick, distribution over over an an area area of of about about 400,000 400,000 km2. km2. The quartzites at at some localities localities are are completely completely recrystallized~ recrystallized; at at other other localities localities some they are are sheared sheared but but retain retain sedimentary sedimentary characteristics. characteristics. Most Most of of the quartzites were formed under the under conditions conditions of of the the amphibolite amphibolite facies, facies, with the degree of metamorphism increasing from east to west. west. The sandstones sandstones were mainly clayey orthoquartzites, orthoquartzites, clayey subsubarkoses, arkoses, and and clayey clayey arkoses. arkoses. The clayey matrix has been recrystallized into Zircon is is the the only abundant nonopaque nonopaque detrital heavy into mica. mica. Zircon mineral; mineral~ most other heavy minerals were formed formed during during metamorphism. metamorphism. The source rocks were mainly granitic with indeterminate proporproportions of granites and and gneisses. gneisses. Zircon varieties indicate derivation from both para- and ortho-gneisses. Large parts of the formation are mineralogically and tex~urally evidently detritus on on the the are texturally mature; mature; evidently weathered, vegetation-free vegetation-free landmass, as well as as similar similar sediment sediment landmass, as supplied by by streams streams from from the the east, east, was was reworked reworked by by wind wind and and then then by by supplied the shallow shallow sea. sea. Clay was probably carried carried into the sea sea vuth with quartz sand, sand, separated separated there there by by wave wave and and current current action, action, and and then again again mixed mixed with with sand sand prior prior to to burial. burial. Carbonates and shales shales were deposited deposited upon the sandstones. upon the sandstones. Analysis of of cross-bedding indicates that the the major paleocurrent Analysis movement in the Jatulian Sea was toward the west-northwest, with a prominent current current movement movement toward toward the the south-southwest. south-southwest. secondary but prominent secondary One of these currents probably moved parallel to the shoreline shoreline and the other other normal normal to to it. it. The The sea sea probably probably transgressed transgressed eastward eastward upon upon the a stable, stable, low-lying low-lying landmass. landmass. 27 �PETROLOGYOF OFTHE THE AMBERG M'ERG PRECPJYRIAN PETROLOGY PRECAMBRIAN CRYSTALLINE CRYSTALLINE COMPLEX, NORThEASTERN NORTHEASTERN WISCONSIN WISCONSIN COMPLEX, Dennis P. Rebello P. Rebello Department of Geology Western Reserve University, University, Cleveland, Cleveland, Ohio Reconnaissance study study of of parts of of northeastern Wisconsin by J. A. A. Cain and Quinnesec J. and others has resulted resulted in in recognition recognition of the Quinnesec Formation, pink mberg AmbergGranite, Granite,and andgray grayAniberg Amberg Granite. Granite. Detailed Formation, mapping of approximately approximately 100 square square miles during the summer summer of 1964 has has resulted resulted in in the the identification identification of of an an additional additionalunit, unit, the the.Amberg Amberg addition, diabase and basalt dikes were found found Granodiorite. In addition, cutting the the granitic granitic units. units. The Quinnesec Formation Formation include include greenstones greenstones and and meta-basalts, meta-basalts, which contain contain plagioclase plagioclase and and hornblende hornblende and and minor minor amounts amounts of of chlorite, chlorite, epidote, epidote, and and quartz. quartz. The unit is is exposed exposed along along the the north north and and northnortheastern boundaries of this area area and and in in aa small small triangular patch patch south south of of Amberg. Amberg. The major part part of of the the area is underlain by the the pink Amberg niberg The Granite, which is Granite, is circular circular in in outline. outline. The rocks rocks are are fresh, fresh, massive, massive, coarse-grained coarse-grained pink pink granites. granites. Locally they they have aa rapakivi rapakivi tex±ure. texture. Xenoliths of Quinnesec Formation and gray Amberg _~berg Granite are are not microcline-perthite, sodic uncommon. The rocks are are composed of microcline-perthite, sodic oligoclase, quartz, biotite, and and hornblende. hornblende. Minor Minor shear shear zones zones are are present. Lineation and foliation are are poorly poorly developed. developed. The The unit unit intrudes the the gray gray J3mberg Amberg Granite, and the the Granite, Amberg Amberg Granodiorite, and Quinne sec Formation. Formation. Quinnesec The gray gray Amberg is exposed exposed in the center center of of the the area area Pmberg Granite is and is almost surrounded surrounded by by the the pink pink unit. unit. It consists consists of of fresh, fresh, massive, massive, medium- to fine-grained gray gray granites granites composed composed of of orthoclaseorthoclaseperthite, oligoclase—sodic oligoclase-sodic andesine, andesine, quartz, quartz, biotite, biotite, and and hornblende. hornblende. The rnberg Amberg Granodiorite Granodiorite covers covers most most of of the the southeastern southeastern part part of of The the area. area. It is is coarse-grained, coarse-grained, altered, altered, and and has abundant abundant xenoliths xenoliths of the Quinnesec Formation. Formation. Shear zones and mafic schlieren schlieren are are common throughout the unit. The rocks consist of orthoclase—perthite, orthoclase-perthite, oligoclase—andesine, quartz, biotite, oligoclase-andesine, biotite, and ffild hornblende. hornblende. Modal analyses analyses and and chemical chemical analyses analyses for for alkalies alkalies suggest suggest that that the the granitic units units represent represent independent independent intrusions. intrusions. Field Field and and petrographic petrographic data data point point to to aa m.agmatic magmatic origin for for the the granites. granites. 28 �A STUDY ON ON THE THE HYDROLOGY MINNESOTA~I A STUDY HYDROLOGYOF OFPOTHOLES POTHOLES IN IN MINNESOTA- M. Schwartz Schwartz George M. Professor Emeritus, Department of Geology Professor Emeritus, Department University of of Minnesota, Minnesota, Minneapolis study of of the hydrology of potholes (ponds) (ponds) in Minnesota by A A study the writer and and associates associates has has been been carried carried out out since since 1962. 1962. Potholes and adjacent adjacent lakes were selected selected in in various parts of the state state to and to represent as as many different topographic and geologic situations situations as as represent practical. Detailed Detailed observations observations were were made made on on 39 39 potholes and and lakes lakes and limited observations on about about 60 60 others. others. The field field work included sinking sinking test holes adjacent to shore shore to determine the the character character of of the the soil soil and and the the depth depth of of the the water water table, table, observing the the water (and (and ice) ice) levels levels in in the the ponds, ponds 9 collecting collecting bottom bottom observing sediments, the bottom sediments according sediments, and classifying samples of the to soil soil type. type. Limited X-ray X-ray and and pollen pollen studies studies of of selected selected samples samples also made. made. Cross-sections Cross-sections and and graphs graphs were prepared prepared of of all all were also pertinent pertinent data. data. Tentative results results and and conclusions conclusions include include the the following: following: 1. The glacial deposits adjacent to the water are extremely 1. are reasonably permeable as variable lithologically, but but most. most are as shown shown by movement of water out of of test test holes. holes. 2. No consistent consistent relation relation exists exists between the open open water surface surface 2. No and the the groundwater surface surface except except in in the the Anoka Anoka Sand Sand Plain. Plain. 3. Most of the the ponds and and lakes show show a similar similar pattern pattern of of 3. fluctuation of of the the water water levels levels throughout throughout the the year. year. Li. 4. With few exceptions, al'e exceptions, the water levels in the ponds are determined mainly mainly by by the the relation relation of of precipitation precipitation to to evapotranspiration. evapotranspiration. 5. In highly permeable soil, soil, such such as as in in the the Anoka Anoka Sand Sand Plain, Plain, 5. the surfaces coincide and fluctuate the open water and groundwater surfaces fluctuate together by movement of water water from one one to to the the other as required by Li, 4, above. 6. 6. Most lakes and potholes do not contribute significant significant quantities of water water to to underground underground storage. storage. The bottoms of potholes normally consist of silt, 7. silt, clay, clay, and 7. organic matter. 8. S. In ponds ponds that that lose lose water water by by seepage, seepage, the the water water level level rises rises during the the spring spring break-up and periods periods of heavy rains, rains, then then declines declines far beyond possible possible loss loss by by evapotranspiration evapotranspiration and and continues continues to to far freeze—up; collapse of the ice occurs in severe decline after the freeze-up; cases of loss loss of of water. water. In contrast, remain relatively relatively contrast, most ponds remain stable while covered covered by by ice. ice. — Funds to :/Funds to start start the program were made available in 1962 by the the Minnesota State State Soil Soil Conservation. Conservation. Supervision of the project project and and funds were were provided by the Department of Agricultural additional funds Engineering. 29 �PRELIMINARY RESULTS OF GEOCHEMICAL GEOCHEMICAL PROSPECTING PROSPECTING PRFJJIMINARY RESULTS OF NORTH NORTH OF OF THE THE MARQUETTE MARQUETTE IRON IRON RANGE9 RANGE? MICHIGAN MICHIGAN Kenneth Segerstroni Kenneth Segerstrom Survey, Denver? Denver, Colorado U. S. Geological U. Geological Survey? Colorado material Geochemical prospecting by means of sampling of surficial material has been conducted in Marquette County during the past two field field seasons. More than 600 samples samples have been collected and and chemically chemically analyzed for for their their total total heavy-metals heavy-met~_s content. content. Many of the samples samples were also analyzed analyzed for copper, copper? lead, lead? zinc, zinc, and manganese, manganese? and and some some samples were examined examined spectrographically for for cobalt? cobalt, nickel, nickel, and other other elements. elements. AA few few were assayed assayed for for gold gold and and silver. silver. Preliminary results resultshave have encouraged encouraged the the continuance continuance of ofsampling sampling Preliminary in so-called Northern 11Northern Range, Range?:1 just justnorth northofofthe theDead Dead River River in the so-called discouragedits its continuance in the the Southern storage and have continuance in 11Southern storage basin, and have discouraged Range," between between the the Dead Range," Dead River and and the the Marquette Iron Range. Range. In the the Northern Range Range good good results have been been obtained obtained on on the the lee lee side, side, Northern glacially speaking, of ridges ridgesofof resistant pre-Animikiegraywacke graywacke speaking, of resistant pre—.Animikie and volcanic volcanic rocks rocks which whichlie lie on on the the limbs limbs and and crest crest of an an anticlinoriuni. anticlinorium. and The ridges ridges are are bordered to the north and and south south by synclinal synclinal valleys underlain by by poorly ridges tend tend poorlyresistant resistant slate. The The stoss stoss side side of ridges to have have a thick till cover and the valleys are deeply filled ~nth with to glaciofluvial sand. glaciofluvial sand. Soils underlain by the sand do the till and the sand not not show show concentrations concentrations of of heavy heavy metals. metals. The best results are are obtained where the cover of of surficial surficial materials materials (chiefly (chiefly glacial) glacial) colluviun derived is thin, thin, and and where where there there are are abundant abundant adrnixtures admixtures of of colluviu..m is from from the the bedrock bedrock ridges. ridges. Anomalous copper and and lead or zinc, Anomalous concentrations concentrations ol' of copper zinc, of of the the order of hundreds of parts per million, million, have shown up in samples samples taken in Nt N sec. sec. 30, 30, T. T. 49 49 N., N., R. R. 27 27 W. W. In that area area of of no no mines mines or or prospects, the exposed bedrock locally contains fine—grained prospects, fine-grained disseminated pyrite and galena. galena. In In the same same township, township, lesser anomalies anomalies that that are are likewise likewise apparently unrelated unrelated to to known known sulfide sulfide SE- sec. deposits have shown up in SEt sec. 21, 21, NW sec. sec. 27, 27, &3- sec. 26, 26, and N'vJt NT4 sec. sec. 36. 36. NWt 30 st �KEWEENAWFAULT, FAULT, HOUGHTON COUNTY, MICHIGAN KE"WEENAW HOUGHTON COUNTY, MICHIGAN Kiril Kiril Spiroff Michigan Michigan Technological Technological University, Universitys Houghton, Michigan wifl describe a few of the geologically The talk will geologically interesting interesting features found found associated with the features the Keweenaw Fault in Houghton County, Michigan. 31 31 �__________ _______ ORGANIC GEOCHEMISTRYOF OF ROSSBURG,llEAT ROSSBURGPEAT BOG, ORGA1'HC GEOCHEMISTRY BOG 9 AITKIN COUNTY, COUNTY 9MINNESOTA—' MINNESOTA- F. M. M. Swain 9 Mykola Swain, Mykola MalinowskY9 Malinowsky, and and David Nelson of Geology Geology and and Geophysics, Geophysics, Department of of Minnesota Minneapolis University of Minnesota,9 Minneapolis sees. 18 and and 19, 19~ Rossburg peat bog occupies about 600 acres in secs. T. 47 N., R. R. 25 W. W. and sec. T. sec. 24, T. 47 47 N., N. 9 R. R. 26 26 W., W., Aitkin Aitkin County, County, Minnesota. Minnesota. Coarse-detritus, Coarse-detritus 9 reddish brown Sphagnum moss peat exbends extends to depths of of from from 12 12 to to 19 19 feet feet and and is is underlain underlain by by fine-detritus, fine-detritus 9 to dark brown to black copropel, coprope1 9 and and sapropel-peat sapropel-peat to to depths of of 22 22 feet feet or more. more. Below the peat lies slightly slightly calcareous calcareous and and organic organic clay clay to depths of 27 feet to feet or or more, beneath beneath which which lies lies sand. sand. Moisture content content of the peat peat is is 85-90%; 85-90%; that of of the the underlying clay 50-68%, 50-68%9 and and of of the the sand sand 34%. 34%. Ignition loss ranges from 67.6% clay to 96.5% in the the peat and from 11.0% 11.0% to to 15.5% 15.5% in in the the clay clay and and sand. sand. pH values increase increase gradually from from 4.0 at at the surface surface of of the the peat peat to to the peat and are about 6.8—7.0 7.2 at the base of the 6.8-7.0 in the clay and sand. Eh values gradually decrease from from +420 mv at the the surface surface of of sand. Eh my at my at 28 feet the peat to -20 mv feet in in the sand; sand; in in general, general 9 Eh values values are are negative below below 16 16 feet feet in in the the peat. peat. negative Kjeldahl nitrogen K.jeldahl nitrogen averages averages about about 1% i% in the upper 33 feet of the peat, 2.8%; it decreases peat 9 below which it increases to between 1.8% and 2.8%; abruptly to 0.5% or less in in the the underlying underlying clay. clay. Protein amino amino acids show distribution consistent with with variations in type of peat and nitrogen nitrogen content. content. Basic Basic amino amino acids occur throughout the the peat peat and and indicate prevailingly prevailingly acid acid conditions conditions in in the the history history of of the the bog. bog. Total carbohydrates average about about 100 mg/gm expressed as as glucose glucose equivalent in Sphagnum peat, peat, but decrease to 50-70 mg/gm mg/gm in in copropelic coprope1ic peat. peat. Glucose Glucose and and arabinose arabinose are are the the predominant predominant mononaccharides. mononaccharides. aromatic hydrocarbons and hydrated phenols increase Saturated and aromatic in total amount from 2x10—4 mnount from 2xlO- 4 g/g gig at at the the surface surface of of the the moss moss peat peat to to 4 4x104 gig ',4x10g/g at 44 feet, feet, below below which which a decrease decrease occurs to base of moss peat. Absorption Absorption spectra spectra of chromatographic chromatographic fractions fractions show show that that 2-naphthol 2-naphthol is is an an important important hydrocarbon hydrocarbon constituent constituent of of the the moss moss peat. peat. It It is 4_s suggested suggested totohave haveformed formed either either froma protein—naphthylamine a protein-naphthylamine from by by Bucherer Bucherer reaction: reaction: NH3 (NH4)2 4 ,OH ;' .: "',-" :.:-, NH 22 i: ~ .' ~, ;:;..-~ +H 0 2 or from from aa plant-growth plant—growth accelerator (auxin) (auxin) such as naphthyiacetic naphthylacetic acid: acid: CH2 COOH CH 2 CO OH ~:; .......... ~/Work Work i ...-., :1 "1 :1 b~~aif~of 1 done partly partly on behalf of the the Minnesota Geological Geological Survey Survey done 32 32 �Beta-carotene Beta-caroteneasas observed observedininUV-visible UV-visiblespectra spectraisis aa significant componentofofthe thecopropelic copropelicpeat peatbut but is is nearly absent component absent from from the overoverlying moss It isisinterpreted originating from moss peat. It interpretedasas originating fromphytoplankton phytoplankton whenthere therewas wasa alake lakein in the the area. Pheophytini!:a from when area. Pheophytin from chlorophyll relationship to to facies fades of of the the peat. peat. shows a similar relationship Carbonyl-group compounds observed in IR spectra are are quantitatively more important in the moss peat than in in the underlying lake peat. peat. The organic analyses aid aid in in understanding the developmental the deposits deposits and in evaluation of them history of the them as as commercial commercial of plant nutrients sources of nutrientsand and peat peatchemicals. chemicals. sources 33 �TECTONICS OF THE THEKEWEENAWAN KEWEENAWAN BAS~N, TECTONICS OF BASN, WESTERN LAKE SUPERIOR REGION-SI REGION~/ WESTERN LAKE SUPERIOR ~valter S. S. White ~Jhite Walter U. S. Geological Geological Survey, Survey, Beltsville, Maryland U. S. Beltaville, Maryland The subsurface of the thewestern western Lake Lake Superior Superior region region The subsurface structure structure of has been analyzed by combining surface surface geologic, geologic, aeromagnetic, gravity, and paleomagnetic paleomagnetic data. data. Surface attitudes and and map map patterns patterns gravity, and suggest that the Keweenawan sedimentary rocks have the general the upper Keweenawan form of a lens thickening to southeast, away from aa featheredge featheredge to the the southeast, along the shore of of Lake Lake Superior. Superior. Graphic subtraction subtraction of the Minnesota shore the assumed gravitational effect of this sedimentary lens from the Bouguer anomalies anomalies of of the the region region leaves leaves aa residual residual anomaly anomaly due due primarily to to the the mafic mafic lavas lavas and and intrusives. intrusives. When residual maps for various assumed thicknesses of the sedimentary sedimentary rocks are compared with the the aeromagnetic aeromagnetic maps, maps, the the patterns patterns more more or or less less coincide coincide when when with the thickness thickness of sedimentary sedimentary rocks rocks under the the Bayfield Peninsula Peninsula is is the The analysis leads to recognition assumed assumed to to be be at at least least 25,000 25,000 feet. feet. of the following stages stages in in the the tectonic tectonic history history of of the the region: region: (1) Accumulation, Accumulation, during during middle middle Keweenawan Keweenawan time, time, of a thick thick (1) series of lava flows and and mafic intrusives intrusives in in two two basins basins or or troughs, troughs, separated separated by a positive positive area area that that trends trends more more or or less less north-south north-south across the Bayfield. Peninsula, Wisconsin, Wisconsin, in which which the lavas Bayfield Peninsula, lavas are are thin or or absent. absent. (2) Evolution Evolution of of the the present present Lake Lake Superior basin, basin, with with axis axis (2) trending northeast, late Keweenawan Keweenawan time. time. northeast, during late the Ashland syndilne (J) syncline and the major faults (3) Development of the Keweenaw, Lake Owen) Owen) still later in of the region (Douglass, (Douglass, Keweenaw, Keweenawan time. time. the Duluth Gabbro Complex is a sheet of fairly uniform If the Duluth Gabbro thickness dipping to to the the southeast under Lake Superior, Superior, the the combined combined thickness of gabbro should attain a maximum somewhere somewhere gabbro plus lavas should under under the the lake. lake. The gravity maximum is actually about 10 miles northwest of the Minnesota shore shore of the lake, lake, suggesting that that the gabbro pinches out out beneath beneath the the lavas lavas somewhere somewhere near near the the shore. shore. ~/Published with the permission of of the Director, U. S. S. Geological Geological — Published with Director, U. Survey Survey 34 34 �CONTRIBUTIONS CONTRIBUTIONS OF ROCK ROCK PHYSICS PHYSICS TO TOGEOLOGY GEOLOGY Robert J. J. Willard Robert Willard u. S. S. Bureau of Mines, Mines, Minneapolis Minneapolis U. Laboratory Laborato~ study study of rock rock behavior behavior can be a useful guide to to understanding understanding of of rock rock behavior behavior in in the the field. field. A goal of of rock rock physics physics A goal research at the the Bureau of Mines Mines Minneapolis Center is the identificaidentification, tion, classification, classification, and definition of rock and mineral properties that influence behavior behavior under under laboratory-imposed laboratory-imposed stresses. stresses. AA signifisignifithe current research effort involves petrographic petrographic analysis analysis cant part of the of rock fabric fabric in in core core samples. samples. material can can be be regarded regarded as as having having some some degree degree of of Most rock rock material Most fabric anisotropy, anisotropy, as expressed by population parameters of mineral species, species, aa tangible end-product end-product of of geologic geologic history. history. Such parameters of compositional anisotropy may at times be reflected in the mechanical response stresses. response of laboratory specimens to artifically-created stresses. example, tensile failure For example, failure studies in such rocks as granite and gneiss show show definite of fracture fracture path characteristics characteristics definite correlation of with fabric anisotropism, as expressed in in feldspar, feldspar, amphibole, amphibole, mica, and quartz. quartz. Similarly, Similarly, field correlation exists for for rocks having rift, grain, grain, bedding, bedding, or other planar features, features, resulting in fracture rift, fracture patterns patterns which which are are used used to to advantage advantagebybyquarr3nnen. quarrymen. Shear failure, failure, on the other hand, hand, is not necessarily related related to fabric anisotropy. anisotropy. Inclusion of fabric study can supplement supplement fabric anisotropism in field field study correlation of of deformed deformed and/or and/or fractured fractured rock rock material material with stresses correlation to which it has been subjected during its geologic history. history. Such Such fabric study study can can be facilitated facilitated by by petrographic petrographic work without without use use of of fabric Thus, by making thin sections normal to to core axes a U—stage. U-stage. Thus, a drilled from field-oriented rock in in three, three, mutually-perpendicular directions, a three-dimensional three-dimensional picture picture is is obtained obtained of of fabric fabric directions, a anisotropy such such as, as, e.g., e.g., foliation. foliation. Rock physics is using this anisotropy approach in the the testing testing of an oriented block from the the St. approach st. Cloud area to correlate fabric fabric anisotropy anisotropy with with field field anisotropy. anisotropy. 35 35 �AN AEROMAGNETIC AEROMAGNETIC SURVEY SURVEY OF WESTERN \,oJESTERN LJ\KE LAKE SUPERIOR J\N Richard J.J. Wold Wold Department of of Geology, Geology, The University of Wisconsin, Wisconsin, Madison, Madison, Wisconsin In March 1964, over the the l96'4, an an aeromagnetic aeromagnetic survey survey was was conducted over western half half of of Lake Lake Superior, SUperior, covering covering the the area area westward westward from from the the tip tip of of the the Keweenaw Keweenaw peninsula peninsula to to Duluth, Duluth, Minnesota. Minnesota. The survey survey concon7,500 miles miles of north-south flight flight lines spaced at six-mile sisted of 7,500 intervals. A intervalS. A digital recording proton precession magnetometer system system installed in in aa Navy Navy P2V-5 (Neptune) (Neptune) aircraft, aircraft, flown flown 3,000 feet feet above above sea level, in the survey. survey. level, was used in The results results of the survey survey indicate indicate aa very very flat flat magnetic magnetic character character over the the major major portion portion of of Lake Lake Superior. Superior. Several known geologic features are are traced traced by the anomalies: the the Keweenaw, Keweenaw, Douglas, Douglas, the magnetic anomalies: and Lake Owen faults, faults, and and the the Gogebic Gogebic and and Marquette Marquette iron iron ranges. ranges. The existence of the the Isle Royal fault appears to be confirmed, confirmed, and possibly it it extends extends as as far far east east as as Superior Superior Shoals. Shoals. The The existence existence possibly questionable;9 however, however, a fault may be of a North Shore fault is questionable present south south of of Isle Isle St. st. Ignace. Ignace. present Western Lake Superior appears to be underlain by by aa syncline, syncline, bounded on the north and south south by major fault systems, systems, which continues continues southeasterly into into the the eastern eastern half half of of Lake Lake Superior. Superior. southeasterly 36 36 �GEOLOGICAL GEOLOGICAL ANALYSIS AND AND REMEDIAL REMEDIAL ACTION ACTION IN AN AN OPEN OPEN PIT PITROCK ROCK SLIDE SLIDE D. H. H. Yard.ley Yardley D. School of of Mineral Mineral and and Metallurgical Metallurgical Engineering9 Engineering, School University of ofMinnesota, Minnesota, Minneapolis Minneapolis Tworock rockslides slides in the wall of an Two thesame same 't<Tall an open open pit pitininiron—formation iron-formation were studied to to determine determinethe thecause causeofofthe the slope slope failures, failures, and were studied and to propose remedialmeasures measurestotoprevent preventfurther further failures. failures. propose remedial The upperslide slide zone zone is is about The upper about 200 200 feet higher higher in in elevation elevationarid and LOO feet feet west of the lower one. one. 400 Although the the immediate immediate cause cause of of Although the the rock rock failures failures was was mining mining activity, activity, the the real real cause cause of of the the instabilinstability is the the presence of geologic structural structural defects. defects. is o SE. A iron—formationstrikes strikes N.35°E. The iron-formation N.J5°E. and and dips l2 system of of 12°SE. A system near—vertical joints near-vertical joints cuts the strata; strata; the most prominent set set strikes strikes A 50- to N.145°W,, N.45°W., parallel to the pit wall and and to to the the ore-trough. ore-trough. A o 100-foot thick fault zone that strikes N.5O°E. and dips 25—3O°SE lOO-foot strikes N.50 E. 25-JO oSE crosses the upper slide slide area area and and the the top top of of the the lower lower one. one. the upper upper slide slide is is aa J-foot 3—foot chloritic chioritic "green 'green shale shale The base of the layer. and permeable permeable to to water, the material material is is layer. iNhere Where it is fraculred fractured and water, the physically weak weak and and tends tends to to ttsqueeze "squeeze out.,J is stratistratiphysically out. This layer is graphically above above the the lower lower slide slide area. area. The chronology chronology of of the the slope slope failures and check check surveys surveys also also support support the the conclusion conclusion that that the the two two failures and slides are are not not expressions expressions of a single deep-seated cause cause and and thus thus slides single deep-seated could be treated treated independently. independently. j Remedial action action for for the the lower lower unstable unstable zone zone consisted consisted of of changing changing Remedial the sequence so so as to to decrease the the ratio ratio of of weight to to potential the mining sequence failure failure plane plane area. area. The upper slide slide area constituted an an unusual problem problem because economic considerations required haulage over rock-fill and over the economic unstable zone zone where all the elements creating instability instability still still The remedial the slide rock and exLsted. existed. The remedial design involved removal removal of the installation of post-tensioned post-tensioned cables cables in in rock rock back—fill. back-fill. The system system il is designed designed to to provide provide lateral lateral restraint restraint to to the the 'squeezing' 'I squeezing layer, layer, is increased frictional frictional resistance resistance at at the the back-fill back-fill bench bench interface, interface, and increased shear shear resistance within the back-fill by placing it in compression. This is believed to be the first designed use of postcompression. tensioned rock—fill rock-fill for for control control of of aa potential potential slide slide zone. zone. 37 37 � https://digitalcollections.lakeheadu.ca/files/original/5c09d2e9390894b4e68e13c6d3cb7f62.pdf 0bdef7544f3da876e9226dffa2551051 PDF Text Text FID TRIP GUIDE ST. CLOUD GRANITE DISTRICT CENTRAL MINNESOTA by R. K. Hogberg Minnesota Geological Survey University of Minnesota prepared for 11th ANNIJIiL INSTITUTE ON LANE SUPPRIOR GEOLOGY St. Paul, Minnesota, May 8, 1965 conducted by The Twin City Geologists �CONTENTS Page Introduction. . . Production ...... •••••••• •••a•••S5 2 ,.................. .•... •.•.....a• 2 •••••• •• a history. • . . , • , • • a Research by the General 3 a..••aa•aea•a 3 a•aaaaaaa•a•aaa•aaaaaaaaa a•aaaa•aaaaaaaaa••a 6 aaaaa 7 . . a i . a a •i• a a a a a a a a a a a a a •. a . a a 8 .....,.... 8 St. Cloud Gray Granodiorite. . a • a a a a • a as a. a a a a $ • • a. a a.. e.• a a as.. a 9 St. 9 geology. . . a a a • . a a • a . a a a • a • a • Rocklle C rysta].. quarry. . .. . a • a gray quarry. a a a a a a a a a a a a aaoaaa••aaaaaaa•aa •aaaaaa Shiely—Petters aggregate quarry. . • . • . •aaa•a.aaaaa aaaaaaaa• Introduction. • a • a a • a • a a • a a a a a . • a a a a a a a a a a • a a a • • • • • • • Cloud Red Granite. • • • • • as a a • a a a a a a a a a a • a aa • • a Quartz latite porphyry. •. . . . a • • ..•aa a . .aaaaaaaa•a a .' a a a a a a a a . • . a a a a • • a a . . a • a 10 Basalt and granite References cited. . .. a 10 a a a • a a •a a •a•. 12 aaaaaaaaaaaaaaaaaaaaaa 1 aa•aaaaaa•.aaaaa..••aaaaa• •a$• ILLUSTRATIONS Route of field trip, a • a. a a a a a a a a a a a a a a a a • a . a a a • Figure 1—-Generalized geologic section St. Cloud district.55555..... ii �ROCKVILLE ROUTE OF FIELD TRIP (Modified from Minnesota Highway Dept. Map) Scale ]:lLlóO �INTRODUCTION The purpose of this field trip is primarily to see the quarrying and processing operations of granite dimension stone in the St. Cloud district of central Minnesota. The Cold Spring Company will host the tour of their plant at Cold Spring. Leaders for the field trip will be I H. Yardley and R. K. Hogberg. Production History Quarrying began in the St. Cloud district in 1868, near the site of the present town of Sauk Rapids. The first salable products were rough From the late l880s until the late dimension stones and paving blocks. l92Os the sale of dimension stone rose steadily and reached a peak of $4,281,700 annually in 192:3. The major demand was for dimension stones obtained from St. Cloud Red, St. Cloud Gray, and Rockville granites.' From 1929 until the end of World War II sales were depressed and reached a low of $396,800 in 1943. The processing plants for dimension stone have decreased in number and increased in size since the early 190QU5 At present (1965) there are about 20 small granite processing plants, whereas in 1915 a record of 89 finishing plants were operated in Minnesota. However, due to consolidations and increased automation three of the plants-—two of which are located in the St. Cloud district——account for nearly all of the sales. One of the largest such plants in the world——that of the Cold Spring Granite Company—is our first stop. The 'hard' dimension stone industry of Minnesota has centered in the St. Cloud district. Those commercial quarries outside of the district—— in the Minnesota River valley and near Lake MUle Lacs—-are operated by St. Cloud—] ased firms. 2 �Sales of granite in the State in the decade 1952-1962 averaged The Rockville and the St. Cloud Gray "granites" about $3,327,000 annually. constitute most of the present sales from the St. Cloud district. Research by the Industry In recent years research by the industry has been largely confined The results have been quite success- to the field of product development. ful, have and resulted in the development of many new uses of dimension "granites in building construction. Among the new uses are: (1) precast monolithic wall units composed of a regular mosaic of 'granite blocks or, 'granit&' chips, in random arrangement, both set in a cement base; (2) floor tiles or patio-type pavements composed of granitic slabs with split or broken joints; "tumble stone," and built-up veneer (3) walls of split face ashlar or (4) various types of window unit facings composed veneer. granite Granite facings, the bread and butter of the industry, are specified in larger and thinner units than previously; as quarry of now result, the a blocks must be extremely large and free of fractures. GENERAL GEOLOGY The available geologic data on the St. Cloud district obtained by Margaret Skillman Woyski in 1945 and 1946. in a Ph.D. dissertation in 1946 and the largely Her work resulted a published paper in the Bulletin of the Geological Society of America in 1949. (Minn. was In 1961, Goldich and others Geol. Survey Bull. 41) published K/Ar and Rb/Sr ages on rocks of district and reviewed the current state of knowledge of the geology of the region. As a result of expansion of old quarries and opening of new quarries—- especially the Shiely—Petters "aggregate" quarry——excellent exposures are now available to observe the geologic relationships of the district. 3 �The commercial rock t,pes of the district have been given informal names such as St. Cloud Red, St. Cloud Gray9 Rockville, etc. These names have been used in the published literature (Woyski, l9149; Goldich and In addition, each of the others, 1961) and are now well established. companies has assigned many trade names to the dimension stones they sell. Figure 1 Generalized Geologic Section - (millions of years) 0.01 to 0.035 Quaternary Cenozoic Character and Distribution Age System and Period Era St. Cloud District Stratified drift; sandy and clayey till ——unconforrnity— 90 Upper Mesozoic Cretaceous Small vpockets of sandy, clayey, shaly and less commonly lignitic sedi— ments I i—unconformity— (basalt and granite porphyry dikes) Penokean Middle I Intrusive Rocks Precambrian l,62l'0 Younger granites (St. Cloud Red, Rockville, Crystal Gray, and quartz latite dikes) I 1,780 Older granodiorite and related rocks (St. Cloud Gray Granodio rite) —-unconformity— Thomson Formation (slate, graywacke and schist) Inim±kie Group The rocks that have been quarried for dimension stone in the St. Cloud district are igneous rocks of intermediate and felsic composition that are Penokean (post—Animikian' in age (Goldich and others, 1961, p. 101—122). They intrude pelitic sedimentary rocks, now metamorphosed to medium—grade schists, and apparently were emplaced subsequent to the peak of deformation in the Penokean orogeny. The intrusive rocks distinguished by Woyski (19249) 4 �can be grouped according to age relations observed in the field into three classes: and (3) (1) basalt older granodiorite and related rocks, (2) younger granites, and granite porphyry dikes. Within the district, the older intrusive rocks are represented by the St. Cloud Gray Granodiorite. This rock underlies a roughly circular area at least three miles in diameter that lies south of St. Cloud. The rock has been dated by the K/Ar method at 1.78 b.y. (Goldich and others, 1961, p. 104). The younger granites comprise several types of intrusive rocks of intermediate to felsic composition. The major facies that were distinguished by Woyski (1949) are the St. Cloud Red Granite, Rockville Porphyritic Granite, and quartz latite porphyry. The St. Cloud Red Granite is a coarse-grained augite—hornblende granite. The Rockville Porphyritic Granite is a fine— to medium—grained microcline-quartz monzonite. The quartz latite porphyry has phenocrysts of hornblende and plagioclase in a felsitic groundmassQ All the rocks of this group are altered to some degree by late-stage deuteric and hydrothermal solutions. The sequence of alteration as recognized by Skillman (1946) was albitization, formation of chlorite—epidote—calcite, arid silicification. The late intrusive rocks include basaltic dikes and granite porphyry dikes that dominantly occupy N. 50° E.-trending fractures in the older rocks. Preliminary results on K/Ar dating of hornblende (G. N. Hanson, oral communication, 1965) from a basaltic dike from the Diamond Pink quarry, three and one—half miles southeast of St. Cloud, indicate that the dikes are somewhat younger than the Penokean rocks dated by Goldich and others (1961) but older than Keweenawan. The St. Cloud district was a positive area from late Middle Precambrian to late Cretaceous time. In the early Cretaceous(?) 5 (Sloan, 1964) a thick �kaolinitic regolith was developed on the bedrock surface. Reworking of the regolith by the late Cretaceous sea resulted in the relatively thin succession of sandy, clayey and shaly sediments found in isolated pockets throughout the district. Pleistocene drift consisting of sandy and clayey till and stratified silts, sands, and gravels mantles the irregular Precanthrian rock surface. The greatest thickness of drift known in the district is a north-trending sandy moraine that crosses highway 213 between Rockville and Cold Spring. Quarries in the older granodiorite and younger granites are located in a swampy area within and south of St. Cloud, where highs'' on the undulating Middle Precambrian bedrock surface form low knobby outcrops and lows are filled by a thin mantle of glacial outwash materials. of younger granites that protrude from the glacial outwash sands Outcrops and gravels in the valley of the Sauk River and its tributaries are the sites of several other quarries. ROCKVILLE QIL4RRY Cold Spring Granite Company The Rockville quarry, within the Rockvifle Porphyritic Granite, has been the largest producer of dimension stone in Minnesota for many years. The relatively wide spacings of the joints and the general consistency of color, grain-size, and texture enable the operators to meet the demand for quarry blocks of consistent quality. The shape and limits of the quarry are governed by two steeply-dipping intersecting N. 550 across spacing 350/4,50 W. and The spacing between fractures ranges from 25 to 55 feet. E. N. 50_100 fracture sets, which strike respectively N. E.-trending fracture that dips the quarry. A 600_700 A NW cuts diagonally sheeting that dips gently to the southwest has a that ranges from 5 feet near the top to 30 feet near the bottom of the quarry. 6 �The quarry is located within a belt of outcrops of the Rockville that extends from St. Cloud southwestward to Richmond. The Rockville crosscuts the St. Cloud Gray Granodiorite and has irregular contact with the St. Cloud Red Granite to the north and east of the quarry. Inclusions of schistose material are quite abundant in the Rockville within the upper part of the quarry. The Rockville is a pink to reddish—gray porphyritic microcline quartz The potassic feldspar is pert.hitic and forms large crystals monzonite. The groundmass is fine— to medium-grained and is 1-6 cm. in length. composed of about equal quantities of gray quartz and white plagioclase (andesine-oligoclase) and contains about 10 percent biotite. Easily recognized accessory minerals are hornblende, plagioclase and magnetite. Myrmekitic quartz, replacement rims of early plagioclase, and some pyrite- bearing epidote veinlets are thought to represent late stage deuteric and hydrothermal late— stage activity. Aplite dikelets commonly less than 5 cm. wide fill fractures. CRYSTAL GRAY GRANITE QUARRY Cold Spring Granite Company The Crystal Gray quarry, which is 100-150 feet east of the Sauk River, was opened about 25 years ago by the Pyramid Quarry Company. It was purchased about 10 years ago by the Cold Spring Company who has operated it since that time. The quarry was completely flooded by overflow of the Sauk River in early April, 1965. The quarry is bounded on the north and south by vertical fractures that strike N. )45 ). and on the east and west by vertical fractures that strike N. 45° . A fracture set that strikes N. NE., and a five-foot basalt dike that strikes N. cross the quarry diagonally. 80° W. and and dips 80° 60° E. and dips 80° NW., The fractures have a 5- 7 to 30—foot separation. �The sheeting fractures have approximately a 5-foot separation in the upper part and a greater separation in the lower part of the quarry. A prominent sheeting fracture which is 20-35 feet below the quarry rim strikes N. W. 40 and dips 100_iSo SW. towards the Sauk River. The Crystal Gray is a porphyritic quartz monzonite that has somewhat smaller phenocrysts than the Rockville. It is a distinctively purplish to greenish-gray facies of the younger granites and quarry. average is known only at this The pinkish-gray potassic feldspar phenocrysts are perthitic and 10 mm. in length. The medium—grained groundmass consists of approximately 30 percent opalescent quartz, 30 percent greenish-gray plagioclase (andesine to oligoclase), and 10 percent biotite. accessory minerals are magnetite, plagioclase, and The hornblende. Crystal Gray appears to have had a crystallization history similar to the Rockville. to Observable Skiliman (1946) suggests that the gray coloring is due the almost complete assimulation of xenoliths of St. Cloud Gray Granodiorite. Alteration is strong along fractures in the rock, and is indicated by the presence of pyrite, chlorite, and reddish feldspars. On the west side of the quarry, bedrock is overlain by 5—10 feet of stratified glacial drift. On the east side the bedrock capping consists of about J feet of kaolinite-rich regolith, about 10 feet of Cretaceous sandy shale and clay, and a 3— 5-foot layer of sand and gravel. SHIY-PETTERS AGGREGATE QUARRY Introduction The Shiely—Petters quarry was opened in 19499 after the operating company abandoned an attempt to use nearby waste rock, from former quarry operations, for production of aggregate. from Approximately half the production the plant is sold for railroad ballast; the remainder is shipped to markets that require high—grade aggregate. 8 The quarry is approximately 850 �9 50 about of consists and granite, augite—hornblende red to pink grained coarse— a is It quarry. the of wall west the in Gray Cloud St. the in and wall north the along monzonite quartz microcline with associated stringers dike-like and masses irregular small as seen be can Red Cloud St. The Granite Red Cloud St. Gray. Cloud St. the in veinlets surround that halos alteration greenish-black mottled to red to pink in resulted granites, younger the from emanated which alteration, hydrothermal stage late A 1946). (Skiliman, granites younger the by metasomation of degree the reflect to thought is rock the in feldspar potassic and quartz of quantity chalcopyrite. and pyrite, magnetite—illmenite, are minerals accessory The identifiable Easily feldspar. potassic pink percent 10 arid quartz, gray or blue percent 15 augite, and hornblende percent 15 oligoclase), (andesine- plagioclase bluish-gray percent 50 granodiorite, hornblende augite fine—grained to The inclusions. biotite-rich approdmately of consisting medium- a is rock unaltered and hornblende black to gray dark abundant quarry. contains and altered, somewhat pinkish-gray, is it Commonly the of ends west and east the in exposed is Gray Cloud St. The Granodiorite Gray Cloud St. quarry. the of part lower the in feet 25 about to increases spacing the surface; the near feet five about of intervals at spaced is sheeting The NE. 70° dips and W. 800 N. strike fractures sheeting respectively, east and north, northwest9 trend that sets fracture steeply-dipping three stops. previous the at examined quarries the in those to addition In to contrast in fractured, intensely are quarry the within rocks The deep. feet 140—60 is it direction; north-south a in wide feet 300—450 and direction east—west an in long feet �percent perthitic potassic feldspar9 30 percent quartz9 10 percent white plagioclase (andesine—oligoclase), and 10 percent biotite. Easily identifiable accessory minerals are hornblende, magnetite, and hematite. The crystallization history probably was similar to that of other fades of the younger granites. Skiliman (1946) suggests that the St. Cloud Red differs from the other younger granites mainly in having incorporated substantial quantities of the earlier-crystallized St. Cloud Gray Granodiorite. She attributes the pronouncedly red color to intense alteration by late-stage hydrothermal solutions. The sequence of hydrothermal alteration as recognized by Skillman (1946) was albitization, formation of chlorite-epidote—calcite, and silicification. The intense albitization of potassic feldspars released iron as hematite. A less intense alteration marked by chlorite-epidote-calcite is shown by irregularly colored green rocks that are adjacent to closely spaced fractures. Quartz Latite Porphyry Quartz latite porphyry is exposed as massive rock units in the north wall of the quarry. is Skiliman (1946, p. 81) says the quartz latite porphyry later than the St. Cloud Gray and St. Cloud Red. Phenocrysts of hornblende and bluish—gray plagioclase occur in a dark pink felsitic groundmass. Potassic feldspar and quartz in the rocks are thought to have been introduced by late—stage deuteric solutions. Basalt and Granite Porphyry Dikes The late intrusive rocks exposed in the quarry consist of basaltic dikes and granite porphyry; minor pegmatite, quartz veins, and chloriteepidote—calcite veinlets cut the rocks. The basaltic dikes range in width from 1 to 50 feet and average about 5 feet. They occupy three joint sets: 10 (1) N. 35°—50° W., 70°—80° NE., �a in set are 11 s. groundmas granulitic and these, of some of aggregates and hornblende, biotite, oligoclase, quartz, feldspar, potassic perthitic of consist phenocrysts The fractures. post-basalt the fill dikelets porphyry granite narrow Very andesine). (zoned plagioclase and olivine, and uralite augite, of mixtures various of consist cores the plagioclase; and magnetite, glass, basaltic of proportions equal approximately of composed margins chilled have They amphiboles. bluish-green and plagioclase sodic of amounts anomalous containing rock acidic more to basalt normal a from composition NE. trend and gypsum some contacts. 75o_900 E.9 50°—70° N. (3) W. The 35°_L()° N. hematite-stained are dikes massive; conjugate wall the to 600 joints jointing columnar horizontal rudimentary have NW. in vary dikes 70°_80° dip and contain that zones mylonitized are fractures Post-basalt and Most some and NW., 70°—90° E., loO_200 N. (2) �REFERENCES CITED Goldich, S. S., Nier, A. 0., Baadsgaard, H., Hoffman, J. H, and Krueger, H. W., 1961, The Precambrian geology and geochronology of Minnesota: Minn. Geol. Survey Bull. 41, l93 p. Skiliman, Margaret W., 1946, Intrusives of central Minnesota: Unpublished Ph.D. Thesis, Univ. of Minnesota, 211 p. Sloan, R. E., 1964, The Cretaceous System in Minnesota: Minn Geol. Survey Rept. mv. 5, 64 p. Woyski, Margaret S., 1949, Intrusives of central Minnesota: America Bull., v. 60, no. 6, p. 12 999—1016. Geol. Soc. � 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, 1965 Description An account of the resource Institute on Lake Superior Geology. University of Minnesota, St. Paul, Minnesota. May 6-8, 1965. 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 1965 Contributor An entity responsible for making contributions to the resource R.L. Bleifuss Bill Bonnichsen Peter J. Clarke Joseph P. Dobell Robert W. Leonardson Charles Fairhurst Bevan M. French Crawford E. Fritts John C. Green Tsu-Ming Han James W. Villar Glen R. Himmelberg Gilbert N. Hanson J.D. Juilland Gene L. LaBerge Henry Lepp Geoffrey W. Mathews Howard J. Meyer William J. Hinze G.B. Morey Richard W. Ojakangas Dennis P. Rebello George M. Schwartz Kenneth Segerstrom Kiril Spiroff F.M. Swain Mykola Malinowsky David Nelson Walter S. White Robert J. Willard Richard J. Wold D.H. Yardley 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/da466cb83dd892048eea446819b1c3c8.pdf f302183e88d2b2ae53f079a2cc2d4694 PDF Text Text Tenth Annual institute on Lake Superior Geology t a —,1 ISHPEMING, MICHIGAN MAY 6-7-8-9, 1964 ��PROGRAM & INT)EX Wednesday May 6 1:00 - 2:00 PM ES.T. REGISTRATION at the Mather Inn Two concurrent field trips to the Republic and Empire 2:00 PM (Hard hats and glasses required, Field clothes Mines respectively. reconmended. Ladies must wear slacks and low heels) At the Republic Mine, the upper (stratigraphically) 500 feet of the This ore consists Negaunee Iron formation is mined by open pit methods. of alternating bands of quartz and coarsely crystalline specularite with In this area, the lower part of the minor magnetite and silicates. Negaunee consists of coarse iron silicates and magnetite. The Negaunee is overlain unconformably by the Goodrich quartzite which is in part rich enough to be mined also. The metamorphic grade is believed to be In the plant, this ore is high, possibly above the sillinianite isograd. crushed and ground to liberation by standard techniques and the iron is concentrated by flotation. The final cleaner flo,v.t after regrinding is made after conditioning the pulp at the boiling point. The concentrate is then filtered, balled and fired in a grate-kiln. The annual capacity of this operation is 3,000,000 long tons of pellets. A the Empire Mine, a 900 foot section in the lower part of the Negaunee Iron Formation is mined by open pit metho!s. The ore consists of thin, even-bedded alternating layers and mixta of fine.-grained quartz, magnetite, iron carbonate and iron silicates. The area is in the chlorite zone of metamorphism. This ore is crushed to nine inches and then the magnetic portions are reduced to about 95 7. — 500 mesh in two stages of autogenous milling. The magnetite is concentrated on drums and in tank-type hydroclassifiers. The filtered concentrate is balled and than fired in a grate-kiln. The annual plant capacity is 1,200,000 long tons of pellets. 7:00 - 9:00 PM REGISTRATION at the Mather Inn. Thursday, May 7 10:00 I4 E.S,Tb REGISTRATION at the Butler Theatre,Main St. ,Ishp. 8:00 8:30 - 9:00 AM BUSIIIESS ETING 9:00 - 11:45 AM TECHNICAL SESSION Chairman: C.E. Dutton AEan(!NETICSURT:y OF THE MARQUETTE IRON RANGE, REPUBLIC TROUGH, p. 1 AN-- 3. E, Case ADOANT AREAS, MIC Mm STRUCTURES IN THE IATERN PART OF THE MARQUETTE SYNCLINORIUM p. 3 —-3. E. Gair STRATIGPAPHY OF ANI1IKIE (Formerly Huronian) ROCKS EAST OF TEAL p. 5 TAKE, NEGAUN'E, MICHIGAN-- C. E. Fritts ThIND 'fi.FACE ANALYS OF TRACE ELEMENTS IN PEGMATITES IN MARp. 9 QUETTF C)UNTY, MICHIGAN,-- S.C. Nordeng and A. K. Snelgrove SOE SEDINENTARY INTERPRETATIONS OF GRANULE SIZE DISTRIBUTIONS p.11 IN THE LAKE SUPERIOR IRON FORMATIONS.-- J. T. Mengel, Jr. II �Thursday, May 7, coat. THE POSSIBLE ROLE OF LIFE IN THE FORMATION OF THE GUNFLINT IRON FORMATION, PORT ARTHUR REGION.-- WW, Moorhouse 12:00 - 1:15 1:30 — 5:13 M LUNCH at the Mather Inn. ?MTc11NICAL St!SI0N Chairman: D.W. Lindgren STRUCTTA1.. E ONTARIO C.OGY OF THE SKIBI LAKE IRON PROPERTY, NORTHWESTERN GEOL:f OF : AND THE ICA$ ANCIENI STI p.17 FL'E AREA, WISCONSIN—MICN.—— C.E. Duton p.21 PINE VER (BREAIATER) QUA:ri; 'COMERA QUART2L'i, FLORENCE COU?TY, WSCON.--T.H.N;.!sen.p.23 1M CHANNELS AND THEIR EFFECT ON MINE PLANNING AND GRADE CONTR(iL AT THE WHITE C.O. Ensign, Jr. THE UQJE OCCURRENCE ATIKOIAN, (Y:TARIO, -- M. PINE MINE, MICHIGAN.-- J.W. Tranmiell and p.26 OF HEMATITE AT CANADIAN CHARLESON LTD., p.27 W. Bartley LANDS LiYNG AND RIVER EROSION AT V!CTORIA GENERATING STATION, ONTONACON COUNTY, MICHIGAN.-- 3. M. Neilson ORIGIN OF THE TIGERTON ANORTHOSITE.--L. N. Weis RAPAKIVI-TYPE GRANITES OF THE AMBERG AREA, WISCONSIN.--J.A.CAIN ARVON SLATE DEPOSITS, BARAGA COUNTY, MICHIGAN.-- Kiril Spiroff 6:00 PM p.13 SOCIAL HOUR, p.30 p.31 p.32 p.33 Mather Inn 7:00 PM ANNUAL DINNER, featuring a talk on EXPLORATION--FROM ANOMALIES TO ZANZIBAR by R.H. Pemberton, Director, Exploration Division of the Aero Service Corporation. Mr. Pemberton will also shoi a new Aero Service movie titled "PATHFINDERS". Friday, May 8 8:45 - 11:45 AM EIS.T. TECHNICAL ESS,_Chairman: E. N. Cameron MICHIGAN TECH'S METHOD OF TEACHING MINERALOGY.--Kirtl Spiroff PETROGRAPHIC ANALYSIS OF MESABI NON-MAGNETIC TACONITE USING THE POINT COUNTER.-- R.E, Lubker PREPARATION OF MINERAL SPECIMENS FOR ELECTRON MICROSCOPY.-V. L. Doane ALTERED SPODUMENE OF THE LITHIUM PEGMATITE DEPOSITS OF THE GEORGIA LAKE AREA, ONTARIO.-- E. G. Pye and V. G. Mime CLAY ALTERATION AND OTHER COORDINATED GEOCHEMICAL STUDIES IN THE UPPER MISSISSIPPI VALLEY ZINC DISTRICT.--A PROGRESS REPORT.4A.V. Heyl, 3. M. Hosterman, W.E. Hall, 3. C. Green CURRENT INVESTIGATIONS OP THE PRECAMBRIAN ELY GREENSTONE IN NORTHERN MINNESOTA.-- 3. C. Cree* 12:00 - 1:15 PM LUNCH at the Mather Inn. III p.34 p,40 p.41. p.42 p.46 p.48 �Friday, May 8, cent. 1:30 - 5:15 PM TECHNICAL SESSION Chairman: W. C. Kelly GEOLOGIC AEROMAGNETIC INTERPRETATION OF PART OF ONTARIO LYING NORTH OF LAKE SUPERIOR.-- A. S. MacLaren and S. Duffel PRESENTATION OF A REGIONAL AEROMAGNETIC MAP OF WISCONSIN.-- R. Patenaude A METHOD FOR COMPUTING THE MAGNETIZATION OF DIKES WITH EXAMPLES OF ITS APPLICATION TO DIKES NORTH OF COVINGTON, MICHIGAN.-- G. VanVoorhis and L. 0. Bacon THE APPLICATION OF RADIO FIELD INTENSITY MEASUREMENTS TO MAPPING PRECAMBRIAN GEOLOGICAL FEATURES.-- C. E. Kerman and Fl. 3. Hinze INVESTIGATION OF THE THICKNESS OF THE JACOBSVILLE SANDSTONE BY SEISMIC REFLECTION METHODS --A PROGRESS REPORT.-- L. 0. Bacon THE APPLICATION OF INDUCED POLARIZATION PROBING TECHNIQUES UNDERGROUND: MICHIGAN NATIVE COPPER DISTRICT.-- AU. Schillinger THE AGE OF THE DULUTH GABBRO AND THE ENDION SILL BY THE WHOLE-ROCK Rb-Sr METHOD.-- G. Faure and P. M. Hurley THE PENOKEAN FOLD BELT NORTH OF LAKE HURON.-- G, C. Suffel Saturday, May 9 7:30 AM - 6:00 PM MAIUUETTE RANGE FIELD TRIP conducted by S. E. Gair of the U. S. Geological Survey. See the guidebook for details. Lunch will be provided en route. 8:00 AM A second field trip to the Republic Mine. 1:15 PM A second field trip to the Empire Mine. IV p.56 p.57 p.58 p.6O p.63 �AUTHORS AND TECHNICAL SESSION CHAIRNEN L, 0. BACON3 Professor of Geophysic8, Michigan Technological University, Hough ton, Michigan M. W. BARTLEY, General Mgr. Cliffs of Canada and Consulting Geologist, Port Arthur, Ontario M. R. BROCK, U.S.G.S., Denver, Colorado J. A. CAIN, Ass't. Professor of Geology, Western Reserve University, Cleveland, Ohio Madison, E. N. CAMERON, Professor of Geology, University of Wisconsin, Wisconsin. J. E. CASE, Geophysicist, U.S.G.S., Denver, Colorado Michigan V. L. DOANE, Research Engineer, Institute of Mineral Research, Technological University, Houghton, Michigan S. DUFFEL, Geologist, Geological Survey of Canada, Ottawa C. E. DUTTON, Geologist, U.S.G.S., Madison, Wisconsin Pine, Michigan C. 0. ENSIGN, Jr., Chief Geologist, Copper Range Co., White Columbus, Ohio G. FAURE, Ass't. Professor of Geology, Ohio State University, C. E. FRITTS, Geologist, U.S.G.S., Denver, Colorado J. E. GAIR, Geologist, U.S.G.S., Denver, Colorado of Minnesota Duluth J. C. GREEN, Ass't. Professor of Geology University Geological Survey, Duluth, Minnesota and Geologist, Minnesota W. E. HALL, U.S.G.S., Washington, D. C. A. V. HEYL, U.S.G.S., Beltsville, Maryland University, East W. 3. HINZE, Assoc. Professor of Geology, Michigan State Lansing, Michigan 3. M. HOSTERNAN, U.S.G.S., Beltaville, Maryland P. Massachusetts InM. }iURLEY, Department of Geology and Geophysics, W, C. KELLY, Professor C. KERMAN, Geophysicist, California Oil Co., New Orleans, Louisiana stitute of Technology, Cambridge, Massachusetts. of Geology, University of Michigan, Ann Arbor, Mich. V �P, A. LINDBERG, Geological Engineer, Anaconda American Brass Co. Ltd, Britannia Beach, British Columbia D. W. LINDGREN, President, Lindgren & Lehmann, Inc. 1ayzata, Minnesota R. E. LUBI(ER, Research Geologist, U. S. Bureau of Mines, Minneapolis, Minnesota A. S. MACLAREN, Geologist, Geophysics Division, Geological Survey of Canada, Ottaia J. T. MEGEL, Jr., Assoc. Professor of Geology, Wisconsin State College, Superior, Wisconsin V. C. MILNE, Geologist, Ontario Department of Mines, Toronto, Ontario W, W. MOORHOUSE, Professor of Geology, University of Toronto, Toronto, Ontario 3. M. NEILSON, Professor of Geological Engineering, Michigan Technological University, Houghton, Michigan T. H. NILSEN, Teaching Assistant & Graduate Student in Geology, University of Wisconsin, Madison, Wisconsin S. C. NORDENG, Assoc. Professor of Geology, Michigan Technological University, Houghton, Michigan R. PATENAUDE, Graduate Student & Research Assistant in Geology, University of Wisconsin, Madison, Wisconsin E. G. PYE, Resident Geologist, Ontario Dept. of Mines, Port Arthur, Ontario A. W. SCHILLINGER, Resident Geologist, Calumet & Hecla, Inc., Calumet, Mich. A. K. SNELGROVE, Professor and Head, Department of Geology and Geological Engineering, Michigan Technological University, Houghton, Michigan K. SPIROFF, Professor of Mineralogy, Michigan Technological University, Houghton, Michigan G. C. SUFFEL, Professor of Economic Geology, University of Western Ontario, London, Ontario 3. W. TRAMMELL, Staff Geologist, White Pine Copper Co., White Pine, Mich. C. VANVOORHIS, Graduate Student in Geophysics, Michigan Technological University, Roughton, Michigan L. W. WEIS, Ass't. Professor of Geology, Lawrence College, Appleton, Wiscons in. VI �51 ItO 04 027 4 046 AC -v r 320L1/ ,3 7/ Sc 30 / / 4 2? ci 1 / ( / // PAGE NUMBER& AREA INDEX 7,/ 7) I, �.AROMAGNETIC SURVEY OF THE MARQUETTE IRON RANGE1 REPUBLIC TROUGH1 AND ADJACENT REA. MICHIGAN J. E. Case Aeromagnetic surveys have been conducted by the U. S. Geological Survey over the Marquette iron range, Republic trough, Gwinn district, and adjacent areas on the Northern Peninsula of Michigan. The aeromagnetic surveys were flown at 500 feet above the ground along lines spaced at intervals of one-quarter mile in the western part of the area and at intervals ranging from one to three miles in the eastern part. The resulting aeromagnetic map is characterized by six groups of anomalies or anomaly patterns. (1) In the central, western, and southwestern parts of the area, iron-formation in the Animikie Series is shown by magnetic highs ranging from 2,000 to 25,000 gammas in amplitude. The pattern of magnetic highs over iron-formation generally outlines the west-trending synclinorium along the Marquette iron range, the northwest-trending Republic trough, and the belts of Animikie rocks south and west of the Republic trough. In a few places, especially in the Ish peming-Negaunee area, large magnetic lows are associated with Negaunee Iron-Formation, indicating that strong inverse remanent magnetization is Iron-formation in the Gwinn district does not yield recogdominant. Serpentinized peridotite in the (2) nizable aeromagnetic anomalies. pre—Animikie basement northwest of Ishpeming gives rise to an aeromagThe basement of gneiss and granite is (3) netic high of 7,000 gammas. characterized by a pattern of discontinuous highs and lows of low to moderate amplitude; the anomalies are generally less than 500 gammas. Intrusive greenstone in the basement gneiss is associated in some (4) places with distinct magnetic highs of moderate amplitude, 500 gammas, or more, but in other places it is apparently only weakly magnetic. Westward-trending reversely magnetized diabase dikes of Keweenawan (5) age are shown by prominent elongate magnetic lows of moderate to high amplitude. The lows are most abundant north of the Marquette iron range In the eastern part of the area, between (6) in T. 48, 49, and 50 N. Laughing Fish Point and Grand Portal Point, where Precambrian rocks are covered by as much as 2,000 feet of lower Paleozoic sedimentary rocks, large magnetic highs and lows with relatively flat magnetic gradients predominate. From the aeromagnetic data, vast areas can be eliminated as poHowever, tential sites for prospecting for magnetic iron-formation. the Gwinn dissome iron deposits of commercial grade, such as those in trict, may not be sufficiently magnetic to cause detectable aeromagnetic anomalies. Conversely, serpentinized peridotites can cause ano1 �maiies as large as those associated with some magnetic iron-formation. As expected, magnetic anomalies are generally of higher amplitude over magnetite-rich iron-formation than over hematite-rich iron-formation. Measurements of magnetic properties of iron-formation indicate that remanent magnetization may be of much greater importance than induced magnetization. Remanent magnetization must be evaluated if quantitative calculations based on aeromagnetic data are to be attempted. 2 �STRUCTURES IN THE EASTERN PART OF THE MARQUETTE SYNCLINORIUM Jacob E. Gair The U. S. Geological Survey and the Michigan Department of Conservation began in 1957 a cooperative program of remapping the Marquette district, ;using new 7 1/2-minute quadrangle sheets as base maps. The district comprises 12 such quadrangles and is about 600 square miles in area. Mapping has been completed in the Marquette and Sands quadrangles at the east end of the district and is now being done in the adjoining Negunee and Palmer quadrangles on the iest. About 125 square miles has been mapped to date. The westward—plunging Marquette synclinorium contains principally middle Precambrian metasedimentary rocks which formerly were considered Ruronian, but which are now placed in the Animikie Series by the U.S. The synclinorium is bordered by broad basement Geological Survey. areas of lower Precambrian mafic metavolcanic rocks and gneiss. The middle Precambrian (Animikie) formations in the mapped area are conformable Mesnard Quartzite, Kona Dolomite, and Wewe Slate separated by an erosional unconformity from an overlying conformable sequence of Ajibik Quartzite, Siaxno Slate, and Negaunee Iron-Formation. The most comprehensive result of the mapping has been a better definition of major structures in the eastern part of the synclinorium. The major synclinal axis in the Marquette and Sands quadrangles crosses the central parts of secs. 5 and 6, T. 47 N., R. 25 U. Considering the entire synclinorium as a first-order fold, the north limb is comparatively straight and only slightly affected by second—order folds, but along the south side a series of large westward-plunging second-order folds occurs en echelon to the southwest, between the eastern end of the synclinorium The noses of some of these folds are sliced and offset, and and Palmer. some limbs are thinned or eliminated by faults trending mainly westward or southwestward. The "outlier" of middle Precambrian rocks in the Palmer area has long been attributed to downfaulting from the main part of the synclinorium along such a fault, but the structural relationship of the rocks near Palmer to the overall fold pattern of the synclinorium remained obscure. Mapping northeast and east of Palmer shows the Palmer rocks to be a downfaulted segment of a large west-plunging syncline, at This synleast part of whose north limb was removed by the faulting. dine evidently is the southwesternmost in the series of second-order en echelon folds. The eastward-plunging syncline at the easterninost end of the synclinorium is an exception to the generally westward-plunging folds and 3 �reflects cross folding of Mesnard Quartzite and Kona Dolomite near the line between secs. 1 and 2, T. 47 N., R. 25 N. The major westward-trending faults are located in the principal Faults axial region of the synclinorium and along the south margin. in the latter area are indicated by brecciated and silicified zones, the local absence of lowest Animikie beds, and by southward dips of higher beds toward the basement. No such direct evidence of faulting is known aloog the north margin where, however, rocks close to the basal AnimIkie contact locally display strong vertical shearing and lineation. Furthermore, top directions in steeply north-dipping basement metavolcanic rocks point north, whereas tops in the vertical or steeply south-dipping Animikie rocks point south. Deep faulting beneath the north margin is postulated to explain both this unusual Itback_to_backtl relationship and the shearing. Cleavage in Animikie rocks in the eastern part of the synclinorium conforms closely to foliation and layering of probable early Precambrian age in basement rocks north and south of the synclinorium. On a regional scale the axis of the synclinorium also parallels the trend These facts of foliation-layering in the gneiss and the greenstone. controlled by suggest that the development of the synclinorium was earlier basement structures. 4 �STRATIGRAPHY OF ANIMIKIE (FORRLY HURONIAN) ROCKS EAST OF TEAL LAKE, NEGAUNEE, MICHIGAN Crawford E. Fritts 'ork done in cooperation with the Geological Survey Division of the Michigan Department of Conservation Detailed mapping in 1963 in and near the quartzite ridges known locally as the Makwa Hills (secs. 31, 32, 33, T. 48 N., R. 26 U.) east of Teal Lake, Negaunee, Michigan, has shed new light on at least two controversial aspects of the stratigraphy of rocks of Animikie (form(1) The Mesnard Quarterly Huronian) age in the Marquette District. zite, Mona Dolomite, and Wewe Slate of early Animikie age are distinctive mappable formations that represent a valid stratigraphic sequence. They are not "...more or less lateral equivalents of a single time unit..." as suggested by Tyler and Twenhofel (1952, p. 12). Facies changes within the Kona Dolomite, however, are recognized. (2) The Ajibik Quartzite, Siamo Slate, and Negaunee Iron-Formation of middle Animikie age represent a second sequence of time-stratigraphic units separated from underlying formations by an angular unconformity, The unconformity, which was confirmed during the recent mapping. first recognized by A. E. Seaman sometime prior to August 1904 (Van Hise and others, 1905, p. 90, 91), was not recognized by Tyler and Twenhofel. The controversy over the existence of the unconformity at the base of the Ajibik Quartzite arose mainly because Seaman's map of the Makwa Hills (Van Hise and Leith, 1911, p1. 19) shows parts of east-trending The quartzites in two distinct stratigraphic positions as Ajibik. southern unit, which is overlain conformably by the Siamo Slate, cuts across underlying formations with marked angular discordance along the southern side of the Makwa Hills, especially near the western edge of sec. 32 north of County Road 492 east of route U.S. 41. This quartzite still is recognized as Ajibik. On the other hand, the northern unit, which is exposed south of the Mesnard Quartzite in a roadcut on U.S. 41, is part of a sequence of interbedded slates and quartzites that conformably overlies the Mesnard. The conformable relationship near the roadcut was emphasized by Tyler and Twenhofel (1952, p. 24-26), but they continued to call the northern unit Ajibik. Apparently they overlooked the angular discordance displayed at the base of the typical Ajibik Quartzite in sec. 32. The quartzite exposed near U.S. 41 above the Mesnard now is recognized as the lowest of three quartzites interbedded with four slates above the Mesriard but overlain unconforinably by the Ajibik. Collectively, six of the seven interbedded slates and quartzites above the Mesnard are believed to be the near-shore equivalent of the Mona Dolomite. The uppermost slate is interpreted as 5 �Wewe (?) Slate (table 1), because there is no evidence that the uppermost slate was overlain by more rocks of Kona age before erosion in post-Wewe, pre-Ajibik time. The basin in cihich formations of early Animikie age in the Marquette District were deposited may not have extended much farther west or northwest than the present Makwa Hills. The Mesnard Quartzite pinches out less than half a mile west of the above-mentioned roadcut. This fact, together with the westward facies change in the Kona Dolomite from largely chemical sedimentary rocks to predominantly clastic sedimentary rocks, suggests that a shoreline existed in early Animikie It is not known, time near the western end of the present Makwa Hills. however, whether this shorline represented the edge of a major landmass or merely a local high on the basin floor in the vicinity of the Marquette District. References cited Tyler, S. A., and Twenhofel, W. H., 1952, Sedimentation and stratigraphy of the Huronian of Upper Michigan: Am. Jour. Sci., V. 250, no. 1 and 2, p. 1—27, 118—151. Van Hise, C. R., Adams, F. D., Bell, Robert, Lane, A. C., Leith, C.K., and Miller, W. G., 1905, Report of the special committee for the Lake Superior region: Jour. Geology, v. 13, no. 2, P. 89-104. Van Hise, C. R., and Leith, C. K., 1911, The geology of the Lake Superior region: U. S. Geol. Survey Mon. 52, 641 p. 6 �Table 1. Stratigraphic section in and near the Makwa Hills, Negaunee, Michigan. Age Formation Stratigraphic or lithologic unit Approximate Thickness (feet) Negaunee Iron—formation 1500-:- Iron—Formation Siamo Slate Slate with subordinate quartzite 1500—1800 6 w Ajibik Quartzite (vitreous) 75—150 __________________________________________________ Quartzite Slate with minor conglomerate 0—100 UNCONFORMITY Wewe(?) Slate Kona Dolomite (near-shore facies) 175-:- Slate Upper quartzite (vitreous to cherty) 50-175 Upper slate 50—150 Middle quartzite (vitreous to cherty) 100—200 Middle Slate 75-300 Lower quartzite (vitreous to cherty) 50-250 Lower slate 0-250 Quartzite 0—250 - Mesnard Quartzite (vitreous) Slate and thin-bedded quartzite 0-100 Quartz-pebble conglomerate 0-50 UNCONFORMITY - ".4 Metavolcanic and metasedimentary rocks, undivided 7 �T 47N T 48 N — .-- [000 0 1000 FEET MILE Underground cone workings IRON-FORMATION MAPPED WITH THE AID OF SUBSURFACE DATA OBTAINED FROM THE CLEVELAND-CLIFFS IRON COMPANY NEGAUNEE 1963 C. E. FRITTS BY OF THE NEGAUNEE 7/2' QUADRANGLE, MICHIGAN BEDROCK GEOLOGY OF THE SOUTHWESTERN PART L 0 ________ 0 -ii S Si 0 UNCONFORMITY Metovolcanic, metasedimentary, and intrusive rocks, undivided L Whte, Slate Sod, Conglomerate Quartzite Mesnard Quartzite H Ku Slate Kona Dolomite Ku, ,ndivided Upper quartzite Wh tn Upper slate Middle quartuite Whte, Middle slate Lower quartzite White, Lower slate Wewe (?) as, Conglomerotic slate UNCONFORMITY Quartz ite Ajibik Quortzite Siamo Slate Negaunee Iron--Formation Intrusive Metodiabase Li EXPLANATION a- cc 0 Lii cu cc co z �TREND SURFACE ANALYSIS OF TRACE ELENTS IN PEGNATITES IN MARQUETTE COUNTY, MICHIGAN Stephen C. Nordeng and A. K. Sneigrove This study is a test of the application of trend surface analysis to semi-quantitative spectrographic trace element analyses made on 33 samples from pegmatites from Marquette County. The and V. elements used were: Pb, Zn, Cr, Li, Ga, Ti, Sr, Ba, Ti, Be, V was found to be most closely associated with Ga, Ti with Be, Sr is most closely associated with Ba, Ti and Li with and Zn with Pb. Sr, and Cr with Li. The order of average intensity of trace elements from greatest to This ranking least is: Ti, Pb, V, Ga, Ba, Sr, Li, Cr, Be, Zn, and Ti. is similar to that of the abundance of the same elements in the lithosphere as a whole. Trend surfaces for the sample localities were run using the lithNumbers were ology of the country rock of the pegmatites as a model. assigned to Huronian, northern part of "Northern Complex', etc. A second model was based on the distance of the sample locality from the nearest Huronian contact on the assumption that this distance is related to depth beneath the surface at the time of pegmatite formation. Comparison of the trace element trend surfaces with the two models shows that depth of emplacement may have been a major controlling factor in the amount of a given trace element present. The greatest number of elements are present in pegmatites in the Lake Michigarmne and Big Bay areas. Used for purposes of prediction, the trend surfaces show that very large traces or greater quantities of Ti, Li, Sr, Ba, Ga, V, and Ti would have the most probability of occurring in pegmatites in the southeast part of the "Southern Complex" and in the northern part of the Zn, Pb, and Cr "Northern Complex," in the Big Bay-Huron Mountain area. Zn shows should decrease to the southeast in the "Southern Complex". Cr increases in the increase in the direction of Presque Isle Point. Lake Michigamitte and Big Bay areas. Pb increases away from the Dead River Basin in the "Northern Complex" and shows a slight decrease to the south in the "Southern Complex." Ba, Sr, Li, Cr, and Be increase, and the other elements decrease, in the Republic Area. 9 �This investigation is being extended to some 7,000 pieces of similar data available in Marquette and Baraga Counties from six other types of petrographic associations. These are described on the bases of geologic and geographic occurrence in Progress Report No. 10 of the Michigan GeoStrategic Minerals Investigations in Marquette and Barlogical Survey: aga Counties 1943 by A. K. Snelgrove, W. A. Seaman, and V. L. Ayres, 1944. 10 �SOME SEDIMENTARY INTERPRETATIONS OF GRANULE SIZE DISTRIBUTIONS IN THE LAKE SUPERIOR IRON FORNATIONS J. T. Mengel The size distribution of the iron-rich granules in the chert matrix of the thicker bedded types of Lake Superior iron formation were studied using standard sedimentary petrographic equipment and procedures to obtain objective data for the interpretation of sedimentary conditions. Size determinations were made on 250 randomly chosen grains in each of 108 thin sections selected to illustrate the granule texture clearly, to include as wide a range of grain sizes as possible, and to give an inclusive coverage of the Lake Superior iron formations. Limited materials representing the iron formations of the Beicher Islands and the Labrador Trough were measured for comparison and found to be similar to the American material. Granules occur in strata which exhibit graded bedding and cross bedding, and their association with chart and carbonate pebbles, f raginents of algal structures, oolites and, rarely, with detrital quartz, bear out their behavior as particulate detritus during sedimentation, and permit their interpretation as a special type of sand. The granules have a mean grain size toward the coarse end of the medium sand size range, moderately good to good sorting, a nearly symmetrical, mesokurtic, grain size distribution which is skewed toward an excess of fine material. Plots of mean size against standard deviation indicate that the granules accumulated in a tectonically stable environment which had a low rate of deposition and in which a considerable amount of re-working Oolites, associated with granules at a few horizons, have took place. approximately the same size parameters as do the granules, but typically are slightly coarser and better sorted. Moderately well sorted detrital quartz of fine to coarse sand If it is assumed that the granules and the size is locally present. quartz were deposited from the same current it is possible to estimate the specific gravity of the granules at the time of deposition, using the relationship: 0 A - 0B = 1/1.5 (Log2 - Log2D) where 0 is the mean grain size in phi units, D is the density of the 11 �mineral minus the density of water, and 1.5 is a constant for the sand size range (c.f. McIntyre, 1959, Jour. GeolQ, pp. 278—301.) Granule specific gravities appear to average about that of opal (i.e. about 2.0). The large grain size and low density of the granules would favor their selective transport and explain their sedimentary segregation from detrital quartz and aluminous material. Much additional quantitative work on granule size, shape, and packing parameters is needed to give a firm basis for chemical interpretations of the origin of iron formations. 12 �THE POSSIBLE ROLE OF LIFE IN THE FORMATION OF THE GUNFLINT IRON FORMATION. PORT ARTHUR REGION W. W. Moorhouse Organic remains have been recognized for many years in the Gunflint formation in Ontario and Minnesota. Examination of several hundred thin sections from various units of the Gunf lint has indicated that fossils and fossil-like structures are even more abundant than hitherto suspected, and has suggested that life may have had a profound effect on the conditions of sedimentation. The following structures have been recognized as organic or possibly organic in nature: Algal concretions, first recognized many years ago, and widely 1. distributed in the Port Arthur area. Anthraxolite, as seams and pockets, mostly associated with 2. algal structures; carbonaceous matter in argillites, tuffs, calcareous less convincing are brownish layers, and on stylolitic surfaces; (bituminous?) stains in chert and carbonate. Spherical structures, composed of carbonate, or carbonate 3. and greenalite, some of which are 30 to 40 microns in diameter (Fig. b), others up to .2 mm. (Fig. a), in calcareous layers and in shaly greenalite beds between lenses of taconite. A few have a complicated structure (Fig. c) or unusual forms (Fig. d), and are surely organic. Spherulitic structures (Fig. e), composed of chert ot car4. bonate, found in thinly bedded chert-carbonate rocks. Filaments, 20 to 30 microns wide, rarely preserved in greena5. lite (Fig. f) or taconites (Fig. g), may be algal filaments. Others, 1 to 3 microns thick, may represent bacterial chains or mycelia of fungi. Sponge spicules have been tentatively identified from one 6. outcrop of limestone in Port Arthur (Fig. i). Spots of greenalite in chert—greenalite granules, in one 7. specimen (Fig. k) are enclosed in carbonate showing a radiating structure (although the carbonate noi extinguishes as a unit). Possibly such structures are due to organisms. 13 �8. possibly A variety of larger, more complicated structures (Fig. j) organic. Having regard for the great age (possibly 2000 m.y.) and coinplicated replacement history of these rocks, the number of delicate structures preserved is surprising. It is tempting to assign a much more important role to the activity of organisms than has been the case hitherto. The following functions may have been performed by the life of the Animikie: As urged by some authorities for over forty years, organisms 1. may have been one of the most important agents of deposition of iron (iron bacteria, fungi, algae), of carbonate (algae and other primitive plants), and of silica. Organic growth and decay controlled the pH and Eh of the 2. waters in which deposition of iron, silica, and carbonate took place. Thus, at the same time, in adjacent environments, oxides, carbonates, silicates, and suiphides of iron were deposited, due to a variety of local environments, modulated by the proliferation or decay of organisms. Algal filaments and sea—weeds on the sea floor acted as 3. binders for the accumulating silicate, oxide, and carbonate granules. They stabilized these fragments in drifts or windrows, producing the characteristic wavy bedding of taconites. Abundant growth of phytoplankton in sheltered bays may have 4. produced stagnant areas where the thinly and evenly bedded chertcarbonate sections accumulated. The waxing and waning of these planktonic swamps with the seasons would conveniently explain the alternation of chert and carbonate layers. The growth of algal reefs may have brough added complica5. tion to local environments, by introducing barriers, and forming isolated lagoons. In conclusion, there are indications here of a population explosion of primitive plants, in particular those capable of precipThis may have been an important if not major factor in itating iron. making the Proterozoic the most prolific period of sedimentary iron ore deposition. Illustration: Organic or pseudo-organic structures from the Gunf lint iron formation. The horizontal bar beneath each sketch represents 0.1 mm. a) Spherical structure (carbonate) enclosed in greenalite. 14 �b) Spherical structure (carbonate), irnbedded in chert, in a carbonate layer. c) Complex "colony" of spherical structures. d) Spore—like structure, same thin-section as c. a) Spherulitic structure in chart, brecciated chert-carbonate rock. f) Filaments (with reproductive cyst?), in greenalite. g) Twisted filaments, outlined by greenalite, in chert; dark areas are parts of greenalite granules; from taconite. h) Filaments in algal chert; black spots are hematite dust. i) Suspected sponge spicules, from limestone. j) Spherical structure (organic?) of carbonate and greenalite(black). k) Chert—greenalite granule, containing circular spots of greenalite; some of the greenalite enclosed in carbonate showing radiating structure. 15 ��STRUCTURAL GEOLOGY OF THE SKIBI LAKE IRON PROPERTY NORTHWESTERN ONTARIO Paul A. Lindberg The Skibi Lake iron property, owned by Anaconda Iron Ore (Ontario) Ltd., is located in northwestern Ontario about 70 miles north of the town of Geraldton, Bands of Archean iron formation and schist outcrop intermittently along an eastwest strike length of over 20 miles and probably represent an eastward extension of the St. Joaeph Lake iron formations. These metasediments have been isoclinally folded and metamorphosed, faulted and secondarily folded, and intruded by granitic rocks, commonly pegmatite. According to Kindle (1931, Part IV, Vol. XL, Report on Ontario Dept. of Mines) they are included in the MarAnn. shall Lake series of Coutchiching (?) age. Potassium-argon age dating by Goldich et al (1961, Bull. 41, Minnesota Geol. Survey) revealed ages of 2.60 b.y. for the quartz biotite schist and 2.54 b.y. for the intruding peginatite. The bulk of the tectonic deformation of this area was completed following the widespread granitic intrusions of the Algoman orogeny. Late Precambrian diabase dikes cut the region causing local disruptions. The iron formations are magnetite and quartz-rich horizons and are in general of two related types. The most important is composed of banded magnetite and quartz with small amounts of amphibole and biotite, and commonly has a grade of 25-307. iron. The other type consists of cyclic layers of magnetite, schist and often quartz and ranges in grade from 10-30% iron. Garnet and mafic minerals are often concentrated at the interfaces between schist and iron formation. Any chert which may have been present initially is now completely recrystallized to quartz. The enclosing schist is composed of quartz, feldspars and biotite with lesser amounts of garnet and muscovite. Pre-pegmatite amphibolite dikes are sometimes encountered, and later intrusions were comprised of pegmatite, granite and granodiorite. The older horizon of iron formation was followed by ± 2000 feet of barren sediments before another horizon of iron was deposited under similar geologic conditions to the first. This latter formation is dominantly composed of a basal iron-bearing band and an upper higher grade band, separated by a layer of schist. The upper band varies from 10 to perhaps 80 feet in thickness across the district and constitutes the economically important strata from which the ore zones were later formed. Further deposition of barren sediments was followed by layers of volcanic rocks which now lie to the north. 17 �Large scale tectonic folding resulted from steady compression directed from the north and south. With very little apparent faulting a huge isoclinal fold developed much like the folds formed when a rug is The present orientation of the axial planes of these pushed together. folds is vertical at the west end of the district with a steady flattening towards the east where north dips as low as 200 are observed. At this point the apex of the isoclinal fold appears to have over-reached it's crustal support and a large fault block dropped several thousand feet forming the present Two Mile ore zone. Widespread faulting of the district was followed by pegmatitic intrusions along zones of weakness. The economically potential ore zones are the result of thickening of higher grade iron bands by isoclinal folding. The Briarcliffe ore zone is a tight Z—type fold where the limb of the regional isoclinal fold is in turn "isoclinally drag-folded" to yield widths of up to 500 feet of 25-30% iron. The Two Mile ore zone represents the fold nose of the regional isoclinal anticline. 18 �2 3 TWO MILE' o ORE ZONEf 5coIe " 4 SKETCH MAP OF SKIBI LAKE IRON PROPERTY SHOWING MAJOR STRUCTURAL ELEMENTS. FIGH TWO HORIZONS OF IRON FORMATION AND ENCLOSING SCHIST APPEAR TO BE ISOCLINALLY FOLDED ORE ZONES ARE THE RESULT OF FOLDING OF GOOD GRADE NARROW ACROSS THE PROPERTY. IRON FORMATION BANDS TO MANY TIMES THEIR ORIGINAL THICKNESSES. BRIARCLIFFE IS ON THE NORTH LIMB AND TWO MILE APPEARS TO BE THE DOWN-FAULTED ANTICLINAL NOSE. MAP SHOWING DETAIL OF EAS1 FIG. 2 (RIGHT) END OF BRIARCLIFFE ORE ZONE. THE UNFOLC ED IRON BAND AT® IS GREATLY INCREASED BY FOLDING IN THE ISOCLINAL ANTICLINOR- IUM" AT®. NOTE THE OBSERVED HABIT OF THE PEGMATITE DIKES AND SILLS TO WRAP — _\// fZ ..—.—'.-.— AROUND FOLD NOSES. '-'(/ ..••'___'i' ± ': ( i'. ., .j.. (,0' . FIG.3(LEFT) SKETCH FROM PHOTOGRAPH SHOWING NATURE OF ISOCLINALLY FOLDED IRON FORMATION AS SHOWN IN FIGURE 2. VIEW IS LOOKING TO THE NORTHEAST IN THE DIRECTION OF THE FOLD PLUNGES. FROM STRUCTURAL GEOLOGY OF THE SKIBI LAKE IRON PROPERTY, NORTHWESTERN ONTARIO' TENTH ANNUAL INSTITUTE ON LAKE SUPERIOR GEOLOGY, '9 964 PAUL A. LINOBERG �SOUTH NORTH PRE- PEGMATITE FAULT TRACES..\ —— -—— BELIEVED TO BE THE EASTWARD EXTENSION OF THE ISOCLINAL ANTICLINE AS SEEN IN THE BRIARCLIFFE AREA - I I I -,. -. OF SECONDARY — .— — —. — \ ZONE —.— -.---—-.—. •-• — 7 -- 2 ± 5000' \ FOLDING -,-- _5.rfoci r-_; --- - — - - - — -—— SCH 1ST . 0 1000' 0000 I I I \/s GNEISS , s,..SI — .5/ I., 3000 "GRANITIZED SCHIST" PEG M AT IT E Vert. £ .4orz. .5tIe 'O 2(.o40 VIEW LOOKING EAST SHOWING PROBABLE DEVELOPMENT OF THE TWO MILE ORE ZONE AS FIG. 4 THE DOWN-FAULTED ANTICLINALLY FOLDED IRON FORMATION FOLD NOSE. THE FAULT TRACE IS INTRUDED BY PEGMATITE DIKES PARALLEL TO DRAGGED SELVAGES OF IRON FORMATION. NOTE THE TWO AGES OF FOLDING: (I) ISOCLINAL FOLDING TRACEABLE FOR SCORES OF MILES WITH A PERSISTENT EASTERLY PLUNGE, (2) SECONDARY FOLDING OF LOCAL IMPORTANCE WHICH EXHIBITS OPEN FOLDS, WARPS AND CONTORTED BEDS. PEGMATITE INTRUSIOJ FOLLOWED THE LATTER. DIAGRAMATIC CROSS SECTION OF THE BRIARCLIFFE AREA SHOWING INFERRED AXIS OF MAJOR ISOCLINAL FOLD. TWO HORIZONS OF IRON FORMATION APPEAR TO BE PRESENT. THE OLDER IS LOWER IN GRADE, BUT GEOLOGICALLY SIMILAR TO THE YOUNGER, AND IS SEPARATED FROM IT STRATIGRAPHICALLY BY LESS THAN 2000. NOTE THE UNFOLDED SOUTHERLY LIMBS IN BOTH FIGURES AND THE ISOCLINALLY OVERFOLDED' NORTHERN ELEMENTS WHICH ARE OF ECONOMIC FIG 5 IMPORTANCE. FROM STRUCTURAL GEOLOGY OF THE SKIBI LAKE IRON PROPERTY, NORTHWESTERN ONTARIO", TENTH ANNUAL INSTITUTE ON LAKE SUPERIOR GEOLOGY, 20 1964 PAUL A. LINDBERG ��cut by granite from a granite granite in the Precambrian in dikes and pegmatites, which are probably offshoots Similar pluton in the southwestern part of the area. nearby Aurora-Niagara area is probably late middle age. The Florence area is divided into four blocks by faults of northwesterly trend whose southwest sides are relatively upthrown. The northernmost block is principally a northwestward-plunging major syndine containing the sequence from Michigamme Slate to post-Riverton strata, but most of the southwest limb is missing because of faulting and erosion. The synclinal structure, with widely deverging limbs, extends northwestward into and characterizes the geology of southern Iron County, Michigan; only Badwater Greenstone and Michigamme Slate continue southeastward along the syncline to its termination at a The adshort distance within southern Dickinson County, Michigan. jacent block on the southwest is mainly a vertical to steeply southward-dipping homocline of Michigamme Slate, but the west end is modified by southeastward-plunging folds of the Michigarnme to postRiverton sequence. This block is not known to continue northwestward beyond the Florence area; eastward to the end of the district it continues as a homocline of Michigamine and pre-Michiganime formations of middle Precambrian age. The next block is apparently also a homocline of Michigamme Slate with vertical to steep southerly inclination and top to the south; this block, like the one previously mentioned, exThe tends eastward only and also contains pre-Michigamme strata. southernmost block is underlain by the Quinnesec Formation of early Precambrian age, and the top is northward; this block extends eastward and in part probably northwestward. Metamorphism of the Precambrian rocks in the Florence area is mainly at chlorite grade along the central part of the plunging major Continuity syncline, and rises to garnet grade to north and south. of isograds appears to have been affected by faulting. 22 �GEOLOGY OF THE PINE RIVER (BREAIATER) QUARTZITE CONGLOMERATE AND THE KEYES LAKE QUARTZITE FLORENCE COUNTY, WISCONSIN T. H. Nilsen Setting: The Pine River (formerly Break'iater) and Keyes Lake units are informally designated members of the Michigamme Slate in the Baraga Group of the Animikie Series of the Middle Precambrian. They crop out in separate fault blocks as resistant northwest_southeast-trending Because they occur ridges in northeastern Florence County, Wisconsin. as steeply dipping homoclines, it is impossible to judge their original extent; also the lateral boundaries are generally vague due to lack of outcrop. They appear to be anomalous local lenticular quartzrich bodies within the more typical dark Michigamme slates, graywackes and basic volcanics. Pine River: The Pine River quartzite conglomerate crops out near the Pine River Reservoir five miles south of Florence and consists of a lower conglomerate, middle cross—stratified quartzite and pebbly quartzite, and an upper conglomerate, each of which thins to the northwest from a maximum total thickness of 600 feet to 150 feet in a distance of three miles. The underlying stratigraphic sequence indicates an upward gradational change from a reducing to an oxidizing depositional environment, i.e. from amphibolite and graphitic-pyritiC slate to grun— eritic quartz wacke to specularite-rich conglomerate. The strike of the homocline is northwest-southeast with a dip of about 700 to the southwest; the top of the unit everywhere faces southwest. The conglomerates consist of elongate pebbles of white and blue— gray recrystallized chert, interstratified chert and specularite, mosaic quartzite, and rounded strained vitreous quartz (probably vein quartz) in a fine granular quartzitic matrix that contains variable amounts of specularite, magnetite or martite, sericite and muscovite, biotite, chlorite, garnet, and locally grunerite and chloritoid. The middle unit is more quartzose and has small-scale inclined and festoon cross—strata that increase in abundance to the east • To the extreme northwest this 23 �unit is present in minor amounts as thin lenses of parallel-stratified quartzite within the conglomerate. Structural deformation along pairs of symmetrical shear planes produced elongation of pebbles parallel to the intersection of the shear planes, or the direction of tectonic elongation. Brief petrofabric study of orientation of quartz c-axes within pebbles suggests a deformationproduced fabric that has been considerably modified. Translation gliding within the quartz grains is suggested as the mechanism of elongation, with associated small faults, quartz-filled tension fractures, foliation Metaand lineation on the foliation also explained by the shear planes. morphism is at garnet grade, and it is suggested that it followed deformation, although a few strained and rolled garnets indicate some postKyanite was found in one thin section, metamorphic deformation as well. as well as coarse blades in quartz veins associated with coarsely crystalline specularite. Eighty percent of the 97 paleocurrent measurements indicate currents flowing toward the southeast quadrant. The postulated depositional environment was a shallow marine basin close to a local tectonically active source area that contributed coarse debris in two pulses, with transgression and regression of the sea possible contributing factors in the distribution of the sediment. Outcrops of apparently laterally equivalent chert breccias with magnetite and gruneritic iron formation to the southeast indicate a less energetic and possibly deeper water environment. Keyes Lake: The Keyes Lake quartzite crops out as a vertically-dipping, northwest-southeast striking homocline about two miles southwest of Florence. It is bounded on the north by a major fault and grades laterally into The iron—rich rocks of the Little Commonwealth area to the southeast. unit consists of horizontally—stratified quartzites, profusely cross— stratified quartzites and finer quartzose phyllites that can be traced for variable distances parallel to the strike. Thin persistent conglomeratic zones containing pebbles of rounded red and white vitreous vein quartz, fine quartzite and/or chert, and rare interstratified chert and specularite found in the northwest become finer, thinner, and apparently discontinous to the southeast. The quartzite consists of rounded vitreous quartz clasts suspended in a finer, granular quartz-sericite matrix with scattered zircons and magnetite—martite. Rare outcrops of units below this quartzite consist of hematitic quartzose phyllite and sericitic quattzose phyllite that grade upward into the quartzite. A variety of probably conformable rocks overlie it, such as chioritic-graphitic slate, chioritic slate with chert lenses or pebbles, and graywacke. Outcrop width narrows from 3000 feet to 250 feet in the southeast, The and the abundant cross-stratification has inclinations up to 650. 24 �cross-strata are of the inclined and festoon varieties with 89 percent of 144 paleocurrent measurements indicating current directions toward the southeast quadrant. Rare ripple markings confirm this pattern. The quartzite is extensively sheared, but the prominent foliation has a constant orientation regardless of the strike of the bedding. The unit has been subjected to chlorite grade metamorphism, but due to its composition the quartzite is not a good indicator of grade. The presence of chioritic, magnetitic, stilpnomelane-bearing rocks in one area overlying the quartzite that also contain grunerite and garnet suggests a local higher grade. This unit is postulated to have been deposited in a shallow marine basin that became somewhat shallower to the southeast before grading into deeper water deposits of the Little Commonwealth area, which contains a sedimentary breccia interpreted by Johnson (1958) to represent slumping along a surface of steep initial dip. Possibly the breccia is a result of intraforTnational Itripupfl in the postulated area of shallower water. Synthesis: The two quartzitic members were probably never coextensive, but may represent deposition in different areas along the same Precambrian coast line, or possibly under basically similar conditions at different Brief investigation of other quartzites in the Michigamme Slate times. indicates dissimilarity in composition, texture and stratigraphic features from the Keyes Lake and Pine River members. 25 ���( A ( A * A A, —f— j— *A A 'A/NY /VEAP S TEEPECCk x X LA kE X ON T,4 R/. AE'EA Kr 'vo -LEGE/VD - 0r '/ac,o/ 5/t,'i. D,r/,cri 0/ f)P/r( /P/ /ma/,/Q A.e05 0/ C0,ug/i-cj/rnj / Locci/,on 0/ ,4QP0O/I/ V14p - SCALL: /,'th '/ii'/ — KfY �HEMA TI r - . /,vG RA VEZ- A �AT VICTORIA VICTORIA GENERATING GENERATING STATION, LANDSLIDING AND AND RIVER EROSION AT STATION, COUNTY MICHIGAN ONTONAGON COUNTY. ONTONAGON MICHIGAN J. N. J. M•..Neilson Neilson River bank River bank erosion erosion and and massive massive slides slides of of Ontonagort Ontonagon clay clay long long have plagued the Upper Peninsula Power Company at its Victoria have plagued the Upper Peninsula Pover Company at its Victoria Generating Station Station on West Branch Generating on the the West Branch of of the the Ontonagon Ontonagon River River in in Ontonagon County, Michigan. generating Water ponded ponded by Victoria Dam Water by the the Victoria Dam is is conducted conducted to to the the generating approximately station turbines through a 6000-foot wood stave pipeline station turbines through a 6000-foot wood stave pipeline approximately Normally the ten feet feet in diameter. Normally ten the entire entire flow flow of of the the river river passes passes through the pipeline but during spring run—off, the excess through the pipeline but during spring run-off, the excess flow flow (est(est­ imated at at 10,000 10,000 c.f.s.) c.f.s.) is is diverted diverted through through the river channel. imated the river channel. Over Over run—off water water has period of of nearly 35 years, the the run-off has eroded eroded the the boulder, boulder, aa period sand, and and clay clay banks banks to point where where the sand, to aa point the power po~~er substation substation is is threatened. threatened. under Various river—training schemes and revettment systems are Various river-training schemes and revettment systems are under study study in an an effort effort to in to check further further erosion. erosion. Landsliding is Landsliding is aa problem problem of of more more immediate immediate concern. concern. AA particpartic­ of the ularly damaging slide occurred shortly after commencement ularly damaging slide occurred shortly after commencement of the The slide mass of river erosion erosion study. study. The slide involved involved aa mass of clay clay 250 250 feet feet wide 'Jide It effectually effectually dammed dammed the the tailrace and 1000 feet and feet long. long. It tailrace and and this this naturally resulted naturally resulted in in reduction reduction of of the the effective effective head head and and aa major major and and Several remedial measures costly curtailment costly curtailment in in power power output. output. Several remedial meaSures were were One solution was to considered. One solution was to restore restore the the tailrace tailrace section section by by digdig­ ging through the toe of the slide; another was to excavate a new ging through the toe of the slide; another WaS to excavate a new secsec­ Study of tion around around the tion the toe toe through through aa wooded wooded area. area. Study of air air photos photos and and had been been built examination of examination of the the site site revealed revealed that that the the power power station station had built It was decided to construct a new on an abandoned abandoned meander. meander. It waS decided to construct a new tailrace tailrace in the the bed bed of of the the old old meander meander channel channel with with a drag-line and in a drag-line and dozer dozer and and Although future this proved proved to be a this to be a simple simple and and practical practical remedy. remedy. Although future slides may may be be expected expected in in the the area, area, it is unlikely unlikely that slides it is that any any further further damage will will be damage be caused caused to to the the installation. installation. 30 30 �ORIGIN OF THE TIGERTON ANORTHOSITE Leonard W. Weis occupies about about 200 200 square square miles miles in in western western anorthosite occupies The Tigerton ariorthosite It is Shawano County, Wisconsin. It is a hornblende anorthosite anorthosite of of igneous igneous origin. The plagioclase is is generally high andesine or low low labradorite, labradorite, with occasional grains low andesine or high labradorite. labradorite. Accessory Accessory minmin­ grains low erals include hornblende, magnetite, magnetite, ilmenite, erals include hornblende, ilmenite, sphene, chlorite, biotite, biotite, In places places the rock is is crushed, crushed, in places it shows a pyroxene, epidote. epidote. In the rock It is is surrounded surrounded and and cut cut by the Bowler granite non-diagnostic foliation. foliation. It which is is considered an an independent independent unit. unit. Structurally, the the anorthosite anorthosite occurs as at least occurs least two two roof roof pendants pendants in in the the granite. granite. The country country rock rock was probably a series of metasediments, but invaded by the the anorthosite was the evidence is the is scanty. scanty. Igneous origin for Igneous for the the anorthosite is stated, inter inter alia, alia, because of the optical character of the plagioclase, the characteristics of of the optical of the plagioclase, of the the ore minerals, the textural relations, and several minor features. are minerals, the relations, features. PostPost­ formational metamorphism metamorphism certainly occurred, formational occurred, explaining at least least in in part The possibility of the formation of an inde­ inde the crushing and foliation. the and foliation. The possibility of the formation of an pendent anorthosite magma has been demonstrated demonstrated by Yoder Yoder && Tilley Tilley (1962) (1962) and the the Tigerton anorthosite is and is an example of the emplacement of such aa magma. 31 31 ��BA1AGA COUNTY. COUNTY, MICHIGAN DEPOSITS, BARAGA THE ARVON t:'HE ARVON SLATE DEPOSITS. Kiril Spiroff In the the Arvon Arvon slate slate quarry quarry area) area, the the stratigraphic In stratigraphic succession is pure, massive, massive, vitreous quartzite, as quartzite, probably probably Ajibik, Ajibik, as follous: follois: aa pure, which is is the the oldest oldest rock rock exposed; exposed; a thin thin quartz quartz con3lcrnerate; con3l8merate; aa reddish to black quartzite; aa thin thin cherty cherty carbonate carbonate member; menber; gray gray to variegated slate; slate; black satiny slate, to slate, and, and, lastly, lastly, pyritic black slate. 8 late. Three small pits pits in the uere worked from Three the black satiny slate ~7ere from 1872 to to 1890) 1890, during during which time time 50,000 squares squares of roofing slate 1872 worth 188,000 188,000 iere uere produced. produced. These These deposits deposits are are probably probably not not of of commercial value today. today. 33 33 �MICHIGAN TEACHING MINERALOGY MINERALOGY MICHIGAN TECH'S TECH'SMETHOD THO OFOFTEACHING Kiril Kiril Spiroff Spiroff The technique ~f identification which which is is taught taught The technique of megascopic megascopic mineral mineral identification at Michigan Tech differs fr~m that of most schools in that it puts greater at Michigan Tech differs from that of most schools in that it puts greater stress on the use of cleavage and/or crystal form whenever these features stre&s on the use of cleavage and/or crystal form whenever these features are in the the unknown unknown mineral. mineral. are present in Michigan Tech's system system starts starts with with the the placing placing of of the the unknown unknown min­ Michigan Tech's mineral into one of three classes as shown in Plate 1. This shows that the the eral into one of three classes as shown in Plate 1. This shows that specimen Can be: be: specimen can 1. A cleavage fragxnent,or fragment,or 1. A cleavage 2. A or 2. A crystal. crystal, or 3. 3. Massive, that is, is, fine—grained fine-grained so so that that neither neither crystals crystals nor n~r Massive, that cleavages can be be observed. observed. cleavages can 1. Cleavage Fra_gments Fragments 1. Cleavage Cleavage a mineral possesses due due to to its its atomic atomic arrangearrange­ Cleavage is is aa property property a mineral possesses ment and is recognized by the greater amount of light which is reflected ment and is recognized by the greater amount of light which is reflected area from from cleavage cleavage planes. planes. Cleavage Cleavage may may be considered considered from from per unit area three aspects: number, perfection, and angular relations (Plate 2). In three aspects: number, perfection, and angular relatior1s (Plate 2). In number there can Can be one, two, two, three, three, four four or six separate separate cleavages. cleavages. In types, from perfect+toto distinct -. In perfection perfection we we recognize recognize seven types, perfect-Egistinct_. 6 0 0 In angular relations we deal with and measure only 60 , 75 and 90 In angular relations we deal and and 90 75 angles. The student starts starts with large simple simple fragments fragments and and works works toward toward The student with large smaller, less less perfect fragments. fragments. , The is held held in in the the right right hand hand and and turned turned until until aa light light The specimen is flash from from aa mineral mineral cleavage cleavage plane plane is is observed. observed. Then Then the the specimen specimen is is rotated to to the the next flash flash by by using using the the wrist, not the the fingers. fingers. The The wrist, not amount is noted as as well as the the cleavage cleavage perfection. perfection. If this amount of rotation is veil as If this is the eyes eyes will observe the patterns produced produced by by the the is done done objectively, objectively, the number of relations. After After practice, practice, the the of cleavages cleavages and their angular relations. angles 60°, 75°, 75 0 , and and 90° 90 0 can can be be easily easily distinguished. distinguished. angles 600, At this this point, point, the the identity identity of of many many minerals minerals will will have have been been estabestab­ lished. For example, a mineral showing showing four four perfect perfect cleavages cleavages and and having having example, a vitreous luster aa vitreous luster is is Fluorite. 2. 2. Crystals If shows crystal crystal faces, faces, it it is is pigeon—holed pigeon-holed into into the the If the the specimen shows system by the the study study of of the the geometry geometry of of those those faces. faces. proper crystal system The first studied with the the unaided eye eye or or with with The unknown crystal is first the hand lens. the lens. The planes planes of of the the observed observed crystal crystal faces, faces, if if they they are are incomplete, are extended extended mentally mentally until until they they intersect intersect so so that that the the corn— com­ incomplete, are 34 �crystal form form is is visualized. visualized. plete crystal The and rotated around around an an imaginary imaginary The crystal is is held held vertically and axis and the axis the angles of repetition repetition are are observed0 observed. If If the the faces faces are are rere­ peated every 90°or 90 0 0r four times during one revolution, revolution, the the crystal pospos­ sesses a four—fold sesses four-fold symmetry. symmetry. If the crystal itself every If the crystal face face repeats repeats itself every 600, or six 60°, six times times during during aa complete co~plete revolution, revolution, it it has has aa six—fold six-fold symmetry, If the crystal face symmetry. face repeats repeats itself itself every every 1200, 120°, or three or three times during aa complete revolution, revolution, it it has has aa three—fold three-fold symmetry. symmetry. times these symmetries, symmetries, minerals Can be into the the various various Using Using these minerals can be classified into systems shown in in Plate Plate 3. 3. This takes takes care of one—half one-half of of the the systems, systems, but all all crystals crystals do do not possess aa four, four, three three or or six—fold six-fold symmetry. symmetry. In In crystals crystals which which lack lack these is sought. sought. A prism consists consists of of two two or or more more these symmetries, symmetries, a prism is A prism planes extended, will intersect intersect and have the the same Same angular angular planes which, which, if extended, relationship to relaticnship to some some other other plane. plane. The prism prism is is held held vertically, vertically, and and by using using the the principles principles shown shown in in Plate Plate 4, 4, it it can Can be be classified classified into into the the by proper system. If the complete If the complete crystal form cannot be visualized and classified in the next is to to construct construct an accurate picture of aa in this this way, way, the next step step is the unknown unkno'Jn mineral by by working from from theoretical theoretical axes axes perfect crystal of the and Miller indices. and indices. Orthographic Orthographic and and Clinographic Clinographic projections projections are are used. used. The unknown crystal is sketched as architects architects sketch sketch aa building: building: by by dra'Jing view. A side view view is is also also helpful. helpful. After After the the dra'iing aa plan plan and and front view, A side proper system system has has been determined determined and and an an accurate accurate sketch sketch has has been been drawn, forms characteristic of the the system can be be studied. studied. drawn, the forms advanced stage stage in in the the course, course, atomic atomic arrangement arrangement is is disdis· At aa more advanced cussed and the the use of of XX rays rays is is expained. expained. 3. 3. Massive Specime.a Specime~~ If the unknown mineral is is megascopically massive, the the usual usual If the methods of identification identification are are used used as as outlined outlined in in Plate Plate 5. 5. The basic System is is to to basic objective of Michigan Tech's Tech's Mineralogical System train the student to observe the physical properties of minerals in in aa train the student to systematic cleavages and and crystal forms, forms, and and to to systematic way, way, perticularly their cleavages seen on on paper in in aa neat neat and and orderly orderly fashion. fashion. When put what has been seen this the mineral is is usually aa this has has been done, done, the identification of the simple matter of correlating his simple his findings findings with any any standard standard mineralogy text or mineral table. table. 35 35 �I 22 CRYSTAL CRYSTAL I CLEAVAGE CLEAVAGE FRAGMENT FRAGMENT 33 NEITHER NEITHE R MASSIVE MASSIVE PLATE I C~PLATEI CLEAVAGE CLEAVAGE I,L2,3,4, 2, 3, 4, 6. 6. I,I, NUMBER 2,PERFECTION 2, PERFECTION PERF 4+ ++ PERF ++ PERF PERF PERF DIST ++ DIST DIST DfST DIST - MUSCOVITE MUSCOVITE GRAPHITE CALCITE GAL E NA GALENA ORTHOCLASE'" ENARGITE ORTHOCLASE"C" ENARG ITE ORTHOCLASE "S" "B" COSAlTITE COBALTITE ORTHOCLASE WERNERITE APATITE CASSITERITE 3, ANGULAR ANGULAR RELATIONS RELATIONS PATTERNS I 22 3 44 6 PYRITE ARSENOPYR I TE ARSENOPYRITE TANTALITE TANTAllTE 750 6O 60~ 75°.. 9Qo 90~ PRODUCED PRODUCED PLATY PLATY FIBROUS FISROUS~~? ~ A BRICKS BRICKS T/7./ HOMB RMAi?f PLATE PLATE 22 �____ CRYSTALLOGRAPHY CRYSTALLOGRAPHY 3 3 ATOMS ATOMS 2 2 AXIS I PLANES PL ANES I HAND LENSE HAND LENSE X-RAY EQUIPMENT X-RAY EQUIPMENT DRAWING DRAWING MUST SKETCH MUST SKETCH CRYSTAL CRYSTAL TETRAGONAL TETRAGONAL ONE ONLY ONLY FOUR-FOLD ONE FOUR- FOLD:J SYMMETRY SYMMETRY HEXAGONAL HEXA GONAl ONEONLY ONLYSIXSIX-FOLD ONE FOLD 00 SYMMETRY SYMMETRY TRIGONAL TRI GONAl ONE ONLY ONLY THREE-FOLD ONE A SYMMETRY 6 SYMMETRY © ISOMETRiC ISOMETRIC MORE THAN ONE MORE ONE FOUR-FOLD SYMMETRY FOUR-FOLD SYMMETRY MORE THAN THREE-FOLD SYMMETRY SYMMETRY MORE THAN ONE ONE THREE-FOLD COMBINATION OF OF FOUR COMBINATION FOUR AND AND THREE THREE FOLD FOLD SYMME SYMMETRY PLATE PLATE 33 @ �IN CRYSTALS WHICHLACK LACK0 ElD.A 0 SYMMETRY IN CRYSTALS WHICH SYMMETRY FOR AA PRISM FOR PRISM LOOK MORE PLANES A PRISM PRISM IS TWO OR OR MORE PLANES IF IF EXTENDED IS TWO WILL SAME ANGULAR AND HAVE AND HAVE THE THE SAME ANGULAR INTERSECT RELATIONSHIP TO SOME TO SOME OTHER OTHER HOLD PRISM PLANE. VERTICAL VERTICAL ORTHORHOMBIC ACROSS TOP IS IS STRAIGHT e @@ MONO CLINIC MONOCLINIC TOP ill SLANTS m TRICLINIC TRIC LINIC TOP IS IS CROOKED PLATE 4 PLATE 4 m �MASSIVE MASSIVE LACKS CLEAVAGE LACKS CLEAVAGE OR OR ITS ITS TOO TOO FINE FINE TO TO SEE SEE CRYSTALCRYSTAL­ LINE HABIT LUSTER=APPEARANCE L USTE R =APPEARANCEOFOFMINERAL MINERAL SURFACE SURFACE IN IN LIGHT CAUSED LIGHT CAUSED BY BY ABSORPTION ABSORPTION AND AND REFLECTED REFRACTION MINERAL TYPE VITREOUS RESINOUS RESINOUS ADAMANTINE N N WATER CORUNDUM SPHALERITE COPPER I.1.33 33 1.77 2.5 METALLIC METALLIC HARDNESS = =MINERALS HARDNESS MINERALS ABILITY ABILITY TO TO SCRATCH SOME OTHER STUDENT EROSION----- KNIFE-—STUDENT EROSION KNIFE --- ABRAID ABRAID OR OR SUBSTANCE FEEL --— FEEL --- SOUND--SOUND--­ SPECIFIC GRAVITY= MINERALS SPECIFIC GRAVITY = MINERALSWEIGHT WEIGHT IN AIR IN AIR AN EQUAL COMPAIREDTO TO THE THE WEIGHT COMPAIRED WEIGHT OF OF AN EQUAL VOLUME VOLUME OF OF LUSTER OF OF THE THE MINERALS. WATER. USUALLY ASSOCIATE WATER. USUALLY ASSOCIATE GRAVITY GRAVITY WITH WITH THE THE LUSTER MINERALS. COLOR IFIF IT HAS IT HAS AA DEFINITE DEFINITE AST TA ST E E OF SOLUBLE MINERALS. OF SOLUBLE MINERALS. STREAK ODOR FINE FINE POWDER. POWDER. WHEN SCRATCHED WHEN SCRATCHED FRACTURE AND TENACITY CONCHOIDAL. SECTILE. ELASTIC. FRACTURE AND TENACITY CONCHOIDAL.SECTILE.ELASTIC. CHEMICALS HCL MAGNETITE PYRRHOTITE. MAGNETISM MAGNETITE PYRRHOTITE. HCL ASSOCIATION II "KIN FOLKS' IIKIN FOLKS PRESSURE TEMPERATURE PRESSURE TEMPERATURE TIME TIME PLATE 55 PLATE �PETROGRAPHIC ANALYSIS ANALYSIS OF PETROGRAPHIC OF MESABI MESABINON1IAGNETIC NONMAGNETIC TACONITE TACONITE USING THE THE POINT COUNTER R. R. E. E. Lubker Lubker this study was the application of the the pointpoint­ The objective of this counting method to to samples samples of of West lvest Mesabi Mesabi noninagnetic nonmagnetic taconites taconites for for were a quantitative mineral analysis. quantititive analysis. Samples Samples used used \'1ere a screen screen fraction fraction of of each of 159 composites, which were taken in a sampling area extending each of 159 composites, 'tlhich Here area Samples were were split for 50 30 miles along for along the the range. range. Samples split in in aa microsplitter, microsplitter, briquetted with aa cold-setting cold-setting plastic, plastic, polished polished on briquet ted with on aa leather leather lap lap with \7ith chromium oxide, and counted with an electronic point counter. chromium OXide, and ~.,ith electronic counter. Weight-percent of Weight-percent of each each mineral mineral was was calculated calculated from from the the modal modal analysis by using a standardized density value, and the iron-bearing analysis by using a value, iron-bearing minerals ~'lere were multiplied by their minerals their respective respective iron iron factors. factors. For For each each sample, these calculated iron values were added to give total count Fe. F. sample, these calculated iron values were added to give total count The count analysis was compared with the chemical Fe analysis and an The count analysis was compared with the chemical Fe analysis and an arbitrary limit limit of of 2~ 2 percent arbitrary percent difference difference of of count count Fe Fe from from chemical chemical Fe Fe Ninety-one çercent of the samples fell within was established. Ninety-one rercent of the samples fell within this Has this limit; the the failure failure of of those which did did not, not, after after several several recounts, limit; those l;hich recounts, can can be attributed to adverse physical characteristics and mnera1 be attributed to adverse physical characteristics and mineral assoasso­ cia t ion. ciation. 40 40 �~PARATION PREPARATION MINERAL SPECIMENS SPECIMENS OF MINERAL FOR ELECTRON ELECTRON MICROSCOPY MICROSCOPY Virginia Doane Virginia L.L.Doane In the for examination by electron the preparation preparation of of specimen mounts mounts for microscopy, two microscopy, t~o limitations are imposed, imposed, due to to the the fact fact that that the the mass inof the electron electron is is so so small small that that its its movement movement can canbebeimpeded impededbybyinf infin­ itesimal limitations are (1) (1) the the specimen specimen itesimal amounts amountS of matter. These limitations thin and (2) (2) the the examination examination must be be conducted conducted in in an an ulul­ must be ultra thin tra high vacuum. vacuum. With these limitations l~ith limitations in in mind, four four classes classes of of specimen specimen mounts mounts (1) suspensions suspensions of microscopic and can be examined: (1) and submicroscopic submicroscopic solids, (2) ultra thin sections, (3) solids, (2) ultra thin sections, (3) surface films films and deposits and and (4) replic~s replicas ~hich which reproduce the surface (4) surface structure. structure. This paper describes the This the preparation of of these these four four types types of of specspec­ imen mounto mounts and and is is illustrated by the electron microscopic study of imen nuclei formed by by the the direct direct reduction reduction of of hematite. hematite. 41 41 �ALTERED SPODUMENE SPODUMENEOFOFTHE THELITHIUM LITHIUM PEGMATITE PEGNATITE DEPOSITS ALTERED AREA, ONTARIO OF THE THE GEORGIA GEORGIA LAKE LAKE AREA. mrrARIO E. G. G. pye Pye and and V. V. G. G. Milne Mime E. Because of alteration, alteration, some of the spodumene in certain lithium lithium pegniatite bodies of Archean Archeart age age in in the the Georgia Georgia Lake Lake area has low pegmatite bodies of low lithia lithia In several cases it and high iron contents and is not marketable. and and is not marketable. it dede­ tracts appreciably from the values values of the deposits containing it and tracts and is of considerable economic significance, is significance. There are two types of altered altered In one, the spodumene has been altered to a granular—texured spodumene. one, the granular-texured aggregate of of muscovite, muscovite, in the other, other, it has has been sericitized and renaggregate ren­ dered dark green green to to black. black. l4uscovitized spodumene spodumene is is associated associated with with cogenetic cogenetic aplite aplite and and Muscovitized muscovite—quartz veins and replacement units of saccaroidal albite muscovite-quartz saccaroidal albite or or Sericitized spodumene post— of muscovite-albite intergrowths. intergrowths. Sericitized spodumene is is post­ pegniatite in in age age and and is is believed believed to to be be related related in in space space and and time time to pegmatite Proterozoic diabase intrusives. intrusives. 42 42 �Chemical Analyses Analyaes of of Spodumene Spdumene Crystals Chemical Crystals Georgia Lake Georgia Lake Area Area (Analyses Nos. Nos. 1-5 1-5 by by the Laboratories Branch, (Analyses the Laboratories Branch, Ontario Ontario Department of Mines) Department of Mines) !I I I No.1 I ! A1203 A1 20 3 No.2 Altered Altered Spoduinenesi Spodumenesl No.3 No.3 No.4 No.4 No.5 No.5 Muscovites Muscovites II No.6 No.6 No.7 No.7 1 45.21 45.21 48.76 48.76 i , Si02 Si0 2 \ Unaltered Spodumenes i 60.85 60.85 62.70 I 62.70 i 61.44 61.44 48.84 48.84 27.60 27.27 I I 29.06 29.78 29.78 28.23 28.23 I 33.40 33.40 29.91 29.91 1.53 1.22 1.22 1.50 1.50 4.59 4.59 2.78 2.78 4.24 4.24 2.00 2.00 0.41 0.41 - 0.33 0.33 1.58 1.58 2.63 2.63 i i 49.57 49.57 I I Fe203 Fe203 0.29 0.29 FeO 0.44 0.31 0.33 2.19 2.19 1.56 1.56 CaO - 0.34 0.28 0.28 - 0.40 0.40 MgO 0.32 0.22 0.22 0.16 0.16 .00 2.73 2.73 Li203 0 Li 2 3 6.62 5,33 5.33 5.63 5.63 0.43 0.43 0.15 0.15 - K20 KzO 0.23 0.16 0.16 0.33 0.33 8.99 8.99 6.50 6.50 10.71 10.71 6.83 6.83 Na20 Na 0 2 H20 O H2 0.24 0.24 0.17 0.17 0.12 0.12 0.20 0.20 0.16 0.16 0.42 0.42 2.31 2.31 - — 3.95 3.95 4.60 4.60 ­- .- 0.94 0.94 - 5,26 5.26 - — i I- F F - L.O.I. L.O.I. I Totals I 97.79 I I No. 1. No.1. No. 2. No.2. No. 3. No.3. No. No. 4. 4~ No. 5. No.5. No. 6. No.6. No. 7. No.7. ~ -•••— ••— • 1.20 1.20 I- - I i . . -- I ! 0.65 0.65 0.70 5.73 99.27 99.27 100.66 100.66 i •! — I 98.68 98.68 l I , — — I - I 98.95 98.95 deposit, Jean No. 11 deposit, Jean Lake Lake Lithium Lithium Mines Mines zone, Nania Creek Mines North zone, Nama Creek Mines Ltd. Ltd. zone, Nama Nama Creek North zone, Creek Mines Mines Ltd. Ltd. 1 deposit, Jean Lake No. 1 deposit, Jean Lake Lithium Lithium Mines Mines Mines Ltd. zone, Mama North zone, Nama Creek Mines Ltd. No. 11 Muscovite No. 11 (Dana, (Dana, 1909). 1909). Muscovite No. Muscovite No. 16 16 (Dana, (Dana, 1909). 1909). 43 43 Ltde Ltd. Ltd. Ltd. ­ - - — 00e99 (aOO.99 : 1 I - — ­ ­ — 100.02 100.02 �VERTICAL DYKE DYIE NO. NO. I I LUN ECHO LUN ECHO I I I I II I ~ 11 I I LEGEND f////J I.§:'>...'l§§l DIABASE DIABASE [LU] METASEDIMENTS METASEDIMENTS [[[[] LITHIUM LITHIUM , I"::,"~::::;' I I )~";\ ~III ,z~ :0.~2~1 I~ 21.0 . " , n'''j ~~~~ Il II: \L 1,IL1J 1,1: J 1'1 ~~ O<.J..'1 2.57 % 21.0 feetL;2 ~~,. L-314 L-31B I I I I I I I _0.42% "'.J L-'" a.57% Li200 r-- L-3IA I LIMITED MINES GOLD L-I S.E. S.E. 4900 4900NN SECTION SECTION _0 2 LI 0 I (150/, S I pod I I' ° (20 ~II I II 29 1 • I N.W. I I I 1 I S~ . I (1501. I I 545 .. " I I 120 N.W. '1° feet III 2~ 1°1 • Spod.) Jli , '/ . PEGMATITE PEGMATITE SYMBOLS SYMBOLS CORE CORE 0 o L-I L-I SAMPLE SAMPLE DIAMOND DIAMOND QRILL QRILL GEOLOGICAL -- -- -- GEOLOGICAL HOLE BOUNDARY WITH WITH NUMBER NUMBER (ASSUMED) SCALE SCALE —— 00 1__ 40 '0 OF OF 40 40 I I FEET FEET 80 80 I I 20 120 I I -­ �______ NORTHWEST NORTHWEST _ SOUTHEAST I~ -- ------,'''' IV­ t I':',' --4------------'<-----~""-, I~ ,".; ~- I~ I) "v l'r '---~---------~-------'.., 1-') \ "'.' ~) :-----~--------~._________h, )-~, "''''''' _---_....... L 120 (20 0/0) % '\ J.... 1'\;-_ II ',\, , ,')' _~~''-,..1., ~), I 4 . 0 FEE T " ~J lJ ~--------___;,... ," ,II (,I , ,- ~-- I' ,".; ," ''.I ~~ _ _ _ _ _ _- - - - - - l l [ _ _ - - - - - - - ,"ty-( ,-, J) ~',,' (i ,''' 1'\.,'-- I)' 1......." -'_ _ I~ :;'::; IS~, '! " ::: <.,'1')') , _ "" _ _ _ _ _ _ _~------,'v-I--.:.-~,~) "I '"'J V "r __, _ ........' ,\' I,J-!'..r- /-',- '" ,'\r "x...­ \".;-­ _ _ _ _~_-----___,___--__:__~,:~"'~~,., r 4 '''i -- ~.______-----~I~t _ T- _ ,,", ' \ N,., " ~--_____,,~I"-t--'"'-I~--------".----f'\,.'------ --\- ') "-v !'I '" (~-:---...n; l'-...v tI-,) ,v ~___\'___-----------":~--" " I) ,'\.'N ''\., ""- . ; - - - - - ­ " '" ) ''\., ,-----_~-------------ll[___...,' - '''-:t':--,I.J':-------''',~----" I ........ " 1,1 '''-..',., I'\., 't------..:~---- ,'I N _ _- - - - - ­ 1 _ _----\-_L'20 (15 0/0) __ ~~~:j} I ~~-~~--- " "'-r--:,\,"', ~ 10 ~~: FEET , ~? t:::;": ---\- ,0__ \' ,~, :; --------'<-----,~I;), _ / NC-36 I~' -,:,'-~-----I'f-------- ","\( rI ",'" -----'r---:::--"-:-l"i'--~\,___--:--------­ ,~ II ,~.... r --f : , //. _-/. - /. _ /--/ __/.. /_." , ,y ','~ / -- .. ,"..; ' , PEG MATI TE P EGMATITE _ ""1 " "w'-----­ I"I - - I, -,." ~; ,~' I'" ~;----,~-," (] ," "" ~) ) ,l\--~' I~ .... ~~' I ~ ~ ", --;)~'" ~ METASEDfMENTS METASEDFMENTS _ ~ N _ _ (_"'--\--;-- . . . . -~ ''\. I~ " :>-.'-1 "--,,,-, ,~ ,::. II II 1"1, ~~ " - - - - - - < - __ 1'1 ,\ ,. II "r ,',< ~) --------".-" '-' I' ~' ,;' ,,-'<------­ I " "-'- D BAS E DII AABASE o /.7 " '\.' LEGEND " ,')-----­ ," ~~~'r-;---- ' - - - - - - \ --,'+-,\"---­ S S SY YM MB B 00 L S --- Ij ,) L.-- ~--- -- AI "'-' ' ~ .. lJ ----,'\ / ,~) ,)---------..:1.--- 41 - - - - - - - - ­ - /"-'2. ' I I . 0 FEE T / ---l\,___--IJ U 0/0) ~o,;'~-,~:?/~.~·-.l::~;:'--b~,:-------_. I Q/o L ' 2 0 (20 / N ....' I I - - - - \ - - I'-,'.....; _ I l , KI t' A ( \'~').- ,", ,", - N C - 49-t\" ' - " ,\., , '"-I- N - - ­ N --1\0-.., - - ­ - - , '" G E 0 LOG ALB 0 U N DAR Y , ''\..,lJ, S S'lJ M E D GEOLOGAL BOUNDARY,' ASSUMED NC-36 1DIAMOND NC-36 DIAMOND DRILL DRILL HOLE HOLE WITH WITH NUMBER NUMBER SPODUMENE ESTIMATED ((20%) 2 0 0/0) S POD U MEN E CONTENTS CON TEN TIE S TIM ATE D , 80 80 SCALE OF SCALE OF FEET FEET o0 80 80 160 160 240 240 T Fig. ? ��in the the outer outer fringe fringe of of the aureole and migration of the in the aureole the elements toward the ore zone. the zone. However, HOvlever) the the proportionate volumes volumea and and contents of the the with those those of of th8 the inner alter~tion alteration aureole leached zone as c.Dmpared c)mpared with aureole and and ore zone zone suggest suggest that that much much of of the the aluminum, aluminum, irou, irci silica, ore silica) titanium, titanium) and and by the the ore-bearing ore-bearing solutiono solution3 from from sources sources other manganese were ~lere ad-1ed ad1ed by than leaehed outer part. than the the narrow leached Other studies in in progress of of samples samples from from the the Thompson-Teniperly Thompson-Temperly include: mine include: (1) (1) X-ray diffraction analyses which indicate indicate that that an an abundant abundant gray cobaltian iron iron sulfide sulfide from from the the mine is is pyrite pyrite with ~lith micro-intergrowths of probable cobaltite. (2) (2) Calcite grew in four successive crystal habits; scalenohedral scalenohedral forms predominate predominate in stages, rhombohedral forms forms in earlier stages, forms in later stages. stages. These habits can be easily traced, traced, in in the the same same mine depositional order, order, not not only only ininthe theThonipsori-Temperly Thompson-Temperly mine they are are well developed, developed, but but throughout throughout the the 3,000 3,000 where they square miles of the the district. district. By contrast, preliminary studies by Philip studies Philip Bethke and Paul Barton on thin thin composcompos­ itional layering itional layering in sphalerite have shown that although this this layering be correlated with confidence throughout the layering can be the Thompson ore body, body, attempts attempts to to trace trace it it even even to to nearby nearby mines mines are, as as yet, yet, inconclusive. are, (3) (3) measurements of thermoluminescence suggest aa Preliminary measurements distinct variation between the distinct the reaction reaction of of barren barren and and alal­ tered rock to to heating. heating. (4) (4) Semiquantitative spectrographic spectrographic analyses analyses of of compositional compositional variations in in minerals of the the altered altered zone, zone, and and quantitative quantitative determinations of the determinations the amounts amounts of calcite and dolomite by aa combination of X-ray diffraction and other geochemical tests. tests. E. Hall and Irving (5) W. E. Irving Friedman's work on on fluid fluid inclusions inclusions (5) from ore ore minerals minerals in the from the district shows ShO\lS that the the mineralizing solutions were highly concentrated sodium-calcium chloride solutions were brines similar to connate waters found today in deep to found today in deep wells wells Temperature in the Illinois basin. basin. Temperature studies studies by by Darrell Darrell Pinckney in Pinckney in the the inclusions inclusions from from the the Thompson-Tentperly Thompson-Temperly mine mine Eugene Roseboom is are in progress. Eugene Roseboom is studying studying the the copper copper H. T. T. Shacklette mineralogy. H. Shacklette has has made made aa district—wide district-wide geo— geo­ botanical study of minor-element variations botanical study of minor-element variations in in the the vegetation. vegetation. 47 47 ��_______ MA PPED NOT -I: MAPPED - —— 77 - LEGEND - Duluth Gabb,o Cornpiee PRELIMINARY SKETCH MAP Li OF THE ELY GREENSTONE in the GABBRO LAKE QUADRANGLE n MINNESOTA Gonts Rang. batbohth (Algoman) kntfe Lax. Group Dact. Porphyry I L liar S ntiflfl) Ely Gr..nstone Iphirulitic mefab010ht conglomerate SCALE ----:c- /2 I 2 miles 49 iron formation 3 4 trend fault of Strata �I', * 0 U V 4 U 'I, E N 0 .5 2 50 - -J A- 1' ��PRESENTATION PRESENTATION OF OF AAREGIONAL REGIONALAEROMAGNETIC AEROMAGNETIC MAP MAP OF OF WISCONSIN WISCONSIN Robert Patenaude Robert Patenaude aeromagnetic map map of Wisconsin Wisconsin is The aeromagnetic is most distinctive in the northwest quadrent of the state by virtue of aa strongly northwest quadrant strongly developed developed northeast—southwest lineation in the contours. northeast-southwest lineation in the contours. The The positive positive magmagnetic zones netic zones appear to coincide in in location location with the the mid-continent gravity high and with Huronian iron iron formation and its its metamorphosed metamorphosed The Gogebic iron range in particular is equivalent. is marked by aa strong positive positive magnetic anomaly. strong anomaly. In the the north north central central part part of of the the state state In anomalies extends to the east and northeast anomalies extends to Wausau. Another group of positive magnetic the vicinity of Eau the Eau Claire. Claiye. A relatively A relatively central Wisconsin Wisconsin central southeast part of of southeast stronger and more a zone of positive from the the vicinity of of anomalies anomalies occurs occurs in in undisturbed undisturbed magnetic magnetic pattern pattern extends extends from from east east to to the the southwest portion of of the the state. state. In In the the Wisconsin the the magnetic pattern pattern again again becomes becomes irregular. irregular. 52 52 �A METHOD FOR COMPUTING THE MAGNETIZATION OF DIKES A METHOD FOR COMPUTING THE NAGNETIZATION OF DIKES WITH WITHEXAMPLES EXAMPLES OF ITS OF ITSAPPLICATION APPLICATIONTO TODIKES DIKESNORTH NORTHOF OFCOVINGTON COVINGTON Gerald Gerald Van Van Voorhis Voorhis and and Lloyal Lloyal Bacon Bacon When interpreting vfuen interpreting the the data data from from aa magnetic magnetic survey, survey, it it is is often often helpful to be able to compute the magnetic anomaly for various helpful to be able to compute the magnetic anomaly for various geogeoBecause of of the magnetic logic structures. logic structures. Because the difficulty difficulty in in computing computing the the magnetic effect of of three-dimensional three—dimensional bodies, bodies, most most computations computations are effect are limited limited to to One of the most frequently encountered the two—dimensional the two-dimensional case. case. One of the most frequently encountered twotwoSince the dimensional structures dimensional structures is is the the dike. dike. Since the depth depth extent extent of of aa dike dike is not not usually usually known, known, and and the magnetic effect effect of of the bottom surface is the magnetic the bottom surface is is small if the depth is large, it is often assumed in making calculations small if the depth is large, it is often assumed in making calculations that the the dike dike extends extends to that to infinity. infinity. inA A formula formula for for computing computing the the magnetic magnetic anomaly anomaly of of aa dike dike of of inf infinFrom Figure 1 it is seen that ite depth extent is given in Figure 1, ite depth extent is given in Figure 1, From Figure I it is seen that the effects of of the magnetization are the effects the dike's dike's dip dip and and magnetization are contained contained in in the the Generally these factors will be unknown. constants 01 C1 and constants and C2. C2 • Generally ~hese factors will be unknown. On On the the otherhand, the variables L L and otherhand, the variables and ~ depend depend only only on on the the depth depth of of burial burial If the the magnetic magnetic anomaly and width width of and of the the dike dike and and are are usually usually known. knotm. If anomaly of the dike has been measured, C1 and C2 can be determined of the dike has been measured, Cl and Cz can be determined by by least least If the dip of of the dike is magnetization in squares. If squares. the dip the dike is known, known, the the magnetization in the the plane plane normal normal to to its its strike strike can can then then be be computed. computed. Frequently, the Frequently, the depth depth of of burial burial of of the the dike dike is is known, knotm, but but its its The available geologic information. width is width is not not known lcnown from from available geologic information. The width width can can Figure 2 be be determined determined from from the the measured measured magnetic magnetic anomaly. anomaly. Figure 2 is is aa plot plot of the the anomaly anomaly and and the the corresponding corresponding L L and and I terms of terms for for aa specific specific term has even symmetry The L L term dike. The dike. term has has odd odd and and the the t term has even symmetry about about the the If the dike anomaly is folded about the center of center of the the dike. dike. If the dike anomaly is folded about the center center as as shown on on Figure Figure 3 3 and and the sum and difference of of the sho~m the sum and difference the resulting resulting curves curves plotted, the the sum sum curve curve will will equal equal ZC2~ 2C2 and plotted, and the the difference difference curve curve will will The maxima and minima of the L term and the points equal 2C1L. equal 2C I L. The maxima and minima of the L term and the points of of at the same distance, distance, r, maximum slope maximum slope of of the the i term term fall fall at the same r, from from the the If aa semicircle semicircle of of radius radius rr is center of of the center the dike. dike. If is drawn drawn as as shown shown on on Figure 3, Figure 3, the the intersection intersection of of the the semicircle semicircle with with the the depth depth of of burial burial plane will will define plane define the the edges edges of of the the dike. dike. analysis of the The above The above techniques techniques have have been been applied applied to to the the analysis of the In one case, oriented samples measured anomalies of known dikes. measured anomalies of knotm dikes. In one case, oriented samples of of check on the least the dike dike had had been been studied studied previously previously and and provided provided a a check the on the least In that that case case the computed results results checked checked with square calculation. calculation. In square the computed with the measured measured values values to the to within within the the error error of of measurement. measurement. 53 53 �mag. mag. north north ) A ! si - ----- 8B / / i, .,e /' I I / c ~,,/ I ~o/ -i <:</ / / I / \ L I 8 8 0 C1L+ C2 anomaly = anomaly c L = 22Iog(R1/R2) log (R 1 / R ) 2 mag. north '\,..---- ~ = 22(Ø1CØ2) (0 1(+) ~~\ ) A Hsini 2 A= Hn sln i +Z Z Slnl sin i cos I COSI + .J.- Z z Z sin sini -H sin I cosi cos I B = Z -Hsini B n 1- r----··------,-------- -- .-_. I I component component in-no. ---------vertical vertical I I total field - - -- I i C1 Cl I - ---------- ------------------, C2 --r--------- ---- -------------------l----- --------..-- ------------------r I A I h or z ant a I horizontal un - B I B II I A A sin B cos I sin s _f~~~_L_:_~~~~ __~B c~_~_~_~_~~~ J_~~~_s_~ sS'lnn sS - ~~~~_I __ J Ltota_1 Figure 1. Figure 1. I i + Geometry, notation, notation, and and formula forrnua for for infinite Geometry, infinite dike. dike. 54 S4 I �fI anomaly I = C L ÷ C2 > 4J .. , (I) C .-' C uU "—— . , .... fIIII" ......... ..... __ - - - ,,-..... • I •• • • I \ ' · .... ~C2~ , ,, +-' OJ . ',I . 'I cC (J) cn a o \' " E E I ".- " ,_ ....\.. ... -- --- ---- ~ -1-- C, LL C1 i I Figure Fig ure 2. 2. Illustration Illustrat ion symmetry of 0 f sym met r y used used for for dike di ke width width determination determination. sum = ..~sum i 2C2 I >, I +-' 4. If) c OJ +-' c U u +-' C) OJ C C ,- , - -' \ f- difference = difference .. ... .... 2 C 1 LL = 2C1 \ 01 0a — folded ""--f"-fold ed anomaly an oma Iy E E I I I -S , Figure 3. 3. Anomaly folding to to obtain Figure Anomaly folding obtain terms. terms. 55 55 sum sum and and difference difference 't ' is , �THE APPLICATION OF OF RADIO RADIOFIELD FIELDINTENSITY INTENSITY MEASUREMENTS TO TO THE MEASUREMENTS MAPPING PRECAMBRIAN GEOLOGICAL NAPPING PRECAMBRIAN GEOLOGICAL FEATURES FEATURES Charles E. Kerman Kerman and and William William J. J. Hinze Hinze Charles E. intensity of of radio radio waves waves received received from from A.N. A.M. broadeasting broadeasting The intensity The stations is a function of many factors including the and stations is including the electrical electrical and magnetic properties of the the underlying earth earth formations. formations. In In areas areas where the effects effects of of the the earth earth formations formations are are great great enough enough to to override override where the the other factors or the other factors can be eliminated~ the the factors factors eliminated, the radio field intensity method can be utilized for detecting changes in in these these field intensity method can be utilized for detecting changes physical properties. These These physical physical properties properties may may be be related related to to spe. spe cific geological formations formations and and structures, structures, therefore therefore this this method method is is cific geological potentially applicable applicable to to geological geological mapping. mapping. A radio field field intensity intensity survey survey was lIas conducted conducted in in the the Marquette, Marquette, A radio Iron areaS of of the the Northern PeninPeninIron Mountain, Mountain, Ironwood~ Ironwood, and Keweenaw areaB sula the applicability of this this method to to sula of of Michigan Michigan to to determine determine the mapping Precambrian Precambrian geological geological features features in in the the Lake Lake Superior Superior region. region. mapping Measurements were made from from aa vehic'e vehicle utilizing utilizing continuous continuous recording recording techniques. Correlation of of radio radio field field intensity intensity variations variations with with known geology 3eology indicates indicates that that this this method method offers offers promise promise as as an an econonieconomical and and rapid rapid method of of geological geological mapping mapping particularly particularly for for tracing tracing and extending known known faults, faults, contacts, contacts, and and formations formations where where cultural cultural and topographical topographical effects effects are are not not severe severe and and the the glacial glacial drift drift is is thin. thin. 56 �INVESTIGATION OF THE THICKNESS OF THE THE JACOBSVILLE SANDSTONE SAZ!DSTONE BY SEISMIC REFLECTION --A BY REFLECTION METHODS METHODS -A PROGRESS PROGRESS REPORT REPORT Lloyal 0. L10ya1 O. Bacon Bacon The area just just east and south of the the Keweenaw KeHeenal'1 fault fault has aa very section of Jacobsville sandstone of Cambrian (Ozarkian?) age. thick section (Ozarkian?) age. Previous gravity work by the author indicated indicated a throw throl-l of the the Keweenaw Keloleenaw fault of of the the order order of 10,000 feet, feet, with an indication that fault that a parallel fault existed existed to to the the east east and and the the possibility of at at least one major fault A seismic lecnearly normal to to the the strike strike of of the the Keweenaw Keweenaw fault. fault. A seismic ref reflection program was instituted to to check check the the gravity gravity interpretation. interpretation. Seismic reflections reflections can be obtained from within or at the the base of the the sedimentary section if appropriate care is is used in shot lolowith the use of multiple geophones mixing. cation and nith geophones and signal mixing. The seismic seismic evidence substantiates substantiates previous estimates estimates of of about about 10,000 feet feet throw throw for for the the Keweenaw Keweenaw fault; fault; honever, however, the the limited data 10,000 limited data does not substantiate the presence of a cross fault near obtained does Limestone Mountain as as interpreted interpreted from from gravity gravity data. data. 57 57 �OF INDUCED THE APPLICATION OF INDUCED POLARIZATION POLARIZATIONPROBING PROBINGTECHNIQUES TECHNIQUESUNDERGROUND; UNDERGROUND; MICHIGAN NATIVE MICHIGAN NATIVE COPPER COPPER DISTRICT A. W. Schillinger Schillinger Exploration drilling with a success factor factor (discovery (discovery ratio) ratio) of of only 347 did not not initially prove prove entirely satisfactory in the search 34% did for native native copper copper mineralization mineralization in the footwall of the Amyg— for the footwall the Osceola Amygdaloid workings. Mining experience proved the oreshoots to to be more continuous than drilling results results indicated, indicated, but additional fill-in fill-in drilling was ~7as impractical. An auxiliary exploration tool was needed. needed. At the the request of Calumet && Hecla, Inc., Inc., the the Geophysics Department Department of of Michigan Technology University evaluated evaluated the the measurable electrical electrical properties of native copper copper mineralization and recommended recommended that that their their efforts be be directed to efforts to developing an induced polarization method adaptable to able to drill hole probing techniques. techniques. As developed by the the University, the the apparatus apparatus consists of of aa semisemirigid coiled probe and a power supply/instrument case easily easily transported transported A standard and operated by one and one man. man. A standard AM (3 (3 electrode) electrode) logging logging configconfigresulting in in a uration is used with aa spacing spacing of of 2' 2' -- 4' 4 tt -- ,::"_ resulting a sampsampling radius of 5'±. ling 5'+. Readings Readings are are generally generally taken taken at at two-foot two-foot interintervals in in the the hole. hole.- The three probe electrodes are are sponge-covered, sponge-covered, nonnonpolarizing lead/lead oxide types and the remote current electrode electrode is is wire gauze. gauze. AA constant constant current current of of 5, 5, 10, 10, or or 20 20 ma. mao of of alternately alternately rerePotential readings versed polarity is is pulsed pulsed at at 3.5 3.5 sec. sec. intervals. intervals. Potential readings are are During the taken during during the the "on" ont cycle taken cycle for for resistivity resistivity determinations. determinations. During the "off" cycle, cycle, after after aa 10 10 ms. ms. delay, delay, the the I.P. I,P. potential is "off" is sampled for for a data is is computed computed in 10 ms. ms. interval and 10 and recorded. recorded. Field Field data in the the office office and both resistivity values (ohm-feet) (ohm-feet) and "S" liS" values (mv/v) (mv/v) are are plotted together on semi-log semi-log paper. paper. The The interpretation interpretation of of the the probe probe results results consists consists of of (1) plotting plotting aa lithologic lithologic log log based based on the the calculated resistivity, (1) resistivity, and (2) delimiting, delimiting, on on aa semi-quantitative semi-quantitative basis, basis, anomalous anomalous zones (2) zones based on inspection of the the "S" "s" values and their corresponding resistivity resistivity Amygdaloid, averaging values. The Osceola Amygdaloid, averaging 30 30 feet feet in in true true thickness, thickness, consists of hanging-wall, hanging—wall, intermediate, consists intermediate, and footwall foot~7all amygdaloidal amygdaloidal zones zones of low resistivity separated by one or more "bars" or sills of high of low resistivity separated by one or more "bars" or sills of high resistivity footwall-type footwall-type basaltic basaltic trap. trap. Comparing Comparing aa large large number number of of lithologic resistivity resistivity logs logs with with the lithologic the corresponding core logs logs showed showed that that remarkably good correlation was obtainable and amygdaloid-trap contacts contacts Based could frequently be picked picked to could frequently be to +.5' +.5' from from resistivity resistivity logs logs alone. a10n~. Based on resistivity data, it was now possible to make up geologic logs of on resistivity data, it was now possible to make up geologic logs of long steel steel holes holes to augment or even replace replace the long to augment the time-consuming, time-consuming, only Based on partially satisfactory partially satisfactory sludge sludge logging logging procedures. procedures. Based on laboratory laboratory data and empirical observations in mining areas, a threshold data and empirical observations in mining areas, a threshold "S" "s" value value 58 58 �diagnostic induced of 30 30 mv/v mv/v tlaS was established established as as the of diagnostic of the lower lower limit limit of induced Above 30 mv/v polarization effects in mineralized anygdaloidal vein. polarization effects in mineralized anygdaloidal vein. Above 30 mv/v 50 mv/v); "fair" anomalous zones were designated anomalous zones were designated "slight" "slight" (30 (30 — 50 mvlv); "fair" mv/v) and "very good" (plus 200 200 mvlv) mv/v); "good" 100 mvlv); (50 (50 - 100 "good" (100 (100 -- 200 and "very good" (plus 200 grade values to No attempt has been made to mv/v). No attempt has been made to assign mvlv). assign absolute absolute grade values to better are concorresponding "S" values, although two points "fair" or better corresponding IISI1 values, although t",o points "fair" or are considered ore sidered ore from from aa development development standpoint. standpoint. M steel holes aggregating Since 1956, Since 1956, 876 876 diamond diamond drill drill and and lcng long steel holes aggregating workings. Of the 47,000 feet have been drilled in the Osceola mine uorkings. 47,000 feet have been drilled in the Osceola mine Of the probed witch the I.P. 914 footwall footwall zones zones penetrated, penetrated, 316 316 have have been been probed 914 with the I.P. The success factor anomalies. The equipment yielding yielding 203 or better better anomalies. equipment 203 "fair" "fair ll or success factor drilling oniy to 727. for (discovery ratio) has increased from 34% for (discovery ratio) has increased from 34% for drilling only to 72% for Forty—six probe results were checked drilling and drilling and probing probing combined. combined. Forty-six probe results \Jere checked the interpretations were by by subsequent subsequent drifting drifting or or crosscutting crosscutting and and the interpretations \~ere Incorrect results consisted of found to of the found to be be correct correct 787. 78% of the time. time. Incorrect results consisted of all or of the interthe probe probe not not detecting the detecting copper copper mineralization mineralization at at all or However, of the interin no of an anomaly. preter underestimating preter underestimating the the significance significance of an anomaly. However, in no case was Case was aa false false anomaly anomaly found. found. the discovery ratio two- The use The use of of the the I.P. I.P. probe probe has has increased increased the discovery ratio tworadius of exploration holes fold by by greatly greatly increasing increasing the the sampling sampling radius fold of exploration holes footwall ore than drill results and has has proven proven a and a greater greater continuity continuity of of footwall ore than drill results be employed In addition, long steel drilling can now now be alone indicate. alone indicate. In addition, long steel drilling can employed be plotted more accurwith more more confidence confidence inasmuch with inasmuch as as contacts contacts can can be plotted more accur the necessity of saving sludge ately and and ore ore zones ately zones delineated delineated without without the necessity of structures, saving sludge favorable maxHowever, in samples. However, samples. in the the search search for for ore ore and and favorable structures, maxbe realized if geofrom the use of the probe can only imum results imum results from the use of the probe can only be realized if geointerpretation of the data and its logical reasoning reasoning is logical is applied applied in in the the interpretation of the data and its subsequent use subsequent use on on geologic geologic plans plans and and sections. sections. M 59 59 ��Table 11 Table Analytical Data Analytical Data for for Duluth Duluth Gabbro Gabbro M.I.T. H.l.T. Sample Sample Rock Type Rock Type 4364 4364 4361 4361 4363 4363 4365 4365 4362 4362 Granophyre Granophyre Granophyre Granophyre Granophyre Granophyre Granophyre Granophyre Anorthositic Anorthositic Gabbro Gabbro Gabbro, Layered Gabbro, Layered Series Series Gabbro Gabbro 4366 4366 1231 1231 j"sr::l r86 sr871 'Sr ~ Rb87 87 Rb SrS6 . S"rB"6' 2.62(2 2.62(2~ 0.7408 0.740B 0.7218 0.721B 0.7146 0.7146 0.7114 0.7114 0.7087 0.7087 1.07(2) 1.07(2) 0.63 0.63 0.42 0.42 0.23 0.23 0.7049(3) 0.7049(3) 0.07 0.07 0.7065(2) 0.7065(2) 0.06 0.06 Table Table 22 Analytical Data Analytical Data for for Endion Endion Sill Sill Granophyre Granophyre Granophyre Granophyre Intermed. Rock Rock Intermed. Diabase Diabase 4373 4373 4372 4372 4371 4371 4369 4369 0.7839 0.7B39 0.7402 0.7402 0.7163 0.7163 0.7136 (2) 0.7136(2) 5.22 5.22 2.29(2) 2.29(2) 0.78 0.78 0.55 0.55 All All Sr87/Sr86 SrB7 /Sr B6 ratios ratios have have been been corrected corrected for for fractionation fractionation by by normalizing normalizing to to Sr86/Sr88 Sr B6 /Sr B8 = 1194. = 0. 0.1194. Numbers in brackets indicate Numbers in brackets indicate the the number number of of measurements measurements made. made. 61 61 �0.780 FIGURE I I 0.760 87 S/7 Sr -86 86 Sr 0.74 0 0.740 0 o DULUTH 0.720 0.7 20 V 00 T97:,I.O0t 0.07 B.Y. [ST~7]=,,1.00±0.07 B.Y. 0/ ,0 8. GABBRO ". 86 Sr 0 0.7 0 Ol.......-_ _----L. 0.700 1.0 ± 0.0009 0.0009 = 0.7052 0.7052 ± 0 ....l.....-_ _- - - l ----l...... 2.0 87 Rbi Sf6 Rb/Sr 86 I I I 3.0 4.0 ----I..._-J 5.0 I 0 o 0.780 0.780 FIGURE FIGURE / 22 0.760 0.760 87 Sr87 Sr 86 Sr96 Sr 0.740 0.740 o0 ENDION SILL ENDION SILL 0.7 20 0.720 /0 o o0.700 .700 T T ,0 • I..08 08 z ±0.05 ± 0.05 B.Y. B. Y. 0.7050±0.0009 [~:~: 0.7050 ± O. 0009 .L....-_ _----I.. 1.0 ---L... 2.0 R8;s~6 Rb8Sr 82 ....J.....- 3.0 .L.....-_ _----J..._---" 4.0 5.0 �� https://digitalcollections.lakeheadu.ca/files/original/df3cc93218f5673f9364658638861275.pdf 0819b5112b00282b9e5c563c678b7086 PDF Text Text THE CLEVELAND-CLIFFS IRON COMPANY PAPER ON The Marquette Mineral District Michigan 1964 Presented to the Conference on Lake Superior Geology National Science Foundation Summer Conference Sponsored by Michigan Technological University BY BURTON H. BOVUM CHIEF GEOLOGIST ISHPEMING. MICHIGAN �17 17 THE MARQUETTE THE MARQUETTE MINERAL MINERAL DISTRICT, DISTRICT, MICHIGAN MICHIGAN by by Burton Burton H. H. Boyum, Boyum, Chief Chief Geologist Geologist Mining Department Mining Department The Cleveland-Cliffs The Cleveland-Cliffs Iron Iron Company Company Ishpeming, Michigan Ishpeming, Michigan General Sett General Setting The Marquette Marquette Mineral Mineral District District of is situated The of Michigan Michigan is situated in in Marquette Marquette It was the first Countyand andthe theeast east central central part County part of of Barage Barage County. County. It was the first of of the the Lake Superior iron iron districts Lake Superior districts to tobe be discovered discoveredand and mined; mined; and and iron iron mining mining There has continues to to be be the the major major mining activity to to this this date, continues mining activity date. There has also also been been Figure 11 shows some production some production of of gold. gold. Figure shows the the outlined outlined location location of of the the Negaunee Negaunee Geographically, the iron-formation, the iron-formation, the principal principal host host rock rock for for the the iron iron ore, ore. Geographically, the Marquette Marquette District District is is located locatedon onaa topographic topographichighland highland rising risingsome some600 600to to1200 1200 above Lake Lake Superior Superior (mean feet above feet (mean sea sea level level elevation elevation+602 +602 feet). feet). The The average average 1400 feet. feet. ground elevation near near the ground elevation the mines mines at atIshpeming Ishpeming and and Negaunee Negaunee is is ++ 1400 feet. Locally, 1875 feet. Firetower Hill area rises Firetower Hill in in the the Tilden Tilden Mine Mine area rises to to ++1875 Locally, the the is rugged, with numerous lakes and swamps. The watershed topography topography is rugged, with numerous lakes and swamps. drains both both to toLake LakeSuperior Superiorand andLake Lake Michigan Michigan from from the the Marquette Marquette high­ high drains By tradition, tradition, in the Lake Superior Region, the topographic highs land. By in the Lake Superior Region, the topographic highs in in which most ofofthe theiron irondistricts districts are are found foundare are called called "ranges"; Iranges; hence which most hence the the designation, the the Marquette MarquetteIron IronRange. Range. The The three three principal principal cities cities are are designation, Marquette (County seat and port), Ishpeming and Negaunee. Forest Marquette (County seat and port), Ishpeming and Negaunee. Forest products, products, education (Northern (Northern Michigan Michigan University) University) and and tourism tourism augment in the education augment mining mining in the area's economic activity. area's economic activity. Historical Setting Historical Setting The first miners in in the the region region may may have have been the the pre~historic prehistoric Indian The first miners Indian 1961). We We know know copper miners miners some some 3800 (Drier and and DuTemple, DuTemple, 1961). copper 3800 years years ago (Drier that the French explorers, Brule and Grenoble, visited the Upper Peninsula that the French explorers, Brule and Grenoble, visited the Upper Peninsula in 1E>22. 122. They voyageurs. in Theywere werefollowed followedby byfur fur traders, traders, missionaries and voyageurs. In 1668 Father Jacques Marquette and Father Claude Dablon established In 1668 Father Jacques Marquette and Father Claude Dablon established the the believed that that Father Father Marquette Marquette visited It is n-ission at at Sault mission Sault Ste. Ste. Marie Marie (Soo). (Soo). It is believed visited site of and used used aa campsite campsite at the site of the the City City of of Marquette Marquette in in 1670 1670 and and 1671 1671 and at His name was given to the city, county and iron range Lighthouse Point, Lighthouse Point, His name was given to the city, county and iron range in in �18 honor of of his his early early work work here, here, as honor as well well as as his his extensive extensive efforts efforts in in other other parts parts of of He assisted assisted Fathers the north north central central states. states. He the FathersAllouez Allouezand andDablon Dablon in in making making the the first map in 1672 in Paris. Paris. Sporadic first map of of the the Lake Lake Superior Superior Region, Region, published published in 1672 in Sporadic fur fur trading marked marked the the next next 170 170 years years in in this this vicinity. trading vicinity. Michigan became became aa State Dr. Douglass the first first State Michigan State in in 1837. 1837. Dr. Douglas s Houghton, Houghton, the State Geologist, convinced the State State Legislature Legislature that Geologist, convinced the that the the Federal FederalLand LandSubdivision Subdivision The Indian Indian Treaty Treaty of Survey should should have have geological geological mapping as an Survey mapping as an adjunct. adjunct. The of LaPointe, 1842, LaPointe, 1842, opened opened the the Upper Upper Peninsula Peninsula to to the the white white men. men. On OnSeptember September 19, 1844, Survey Party Party under 19, 1844, a a Government Government Survey under Mr. Mr. William William A. A. Burt Burtwas was running running Shaft the east line of Section 1, T. 47 N. and R. 27 W. (Mather Mine the east line of Section 1, T. 47 N. and R. 27 W. (Mather Mine nBt! property). AA younger Jacob, noted erratic property). younger brother brother of of Douglass Douglass Houghton, Houghton, Jacob, noted erratic They sought sought the the cause cause and and found, found, as compass behavior. compass behavior. They as recorded recorded by by Douglass Douglass Houghton, rrSpathose "Spathoseand andmagnetite magnetiteores oresabounding. abounding." Later, in Houghton, rr Later, in 1846, 1846, Burt Burt wrote: ItrrItmay wrote: maybe bereasonably reasonablyinferred inferredthat thatnot notmore morethan thanone-seventh one-seventh of of the the of Iron Iron ore ore beds beds were were seen Township lines; number number of seen during during the the survey survey of of the Township lines; mines be subdivided with care care in in reference district of ofTownships Townships be this district and if and if this subdivided with reference to to mines If this view minerals, six times as many more will probably be found. and minerals, six times as many more will probably be found. If this view of of the Iron the Northern Northern Peninsula Peninsula of of Michigan Michiganbebecorrect, correct, itit far the Iron region region of of the far excels excels any other other portion States in qualities of its any portion of of the the United United States in the the abundance abundance and and good good qualities of its Iron ores. ores."rr Iron Word of ore discovery discovery spread state and and elsewhere elsewhere Word of the the iron ore spread through through the the state group of ofmen men from from Jackson, Jackson, Michigan, Michigan, formed formed In 1845 that winter. during that winter. In 1845 aa group The treasurer, Philo Everett, and his associthe Jackson Jackson Mining Mining Company. Company. The treasurer, Philo Everett, and his as sod­ the story is ates, reached reached Teal ates, Teal Lake Lake in in June. June. The story is told told that that the the Indian Indian chief, chief, stump sick, showed them the high grade hard ore under the Marji-Ge Marji-Gesick, showed them the hard under the stump of of a a ore pine tree. tree. By By 1846, 1846, there there were were 106 106 mining mining companies. companies. The fallen pine fallen The first first ore the Soo Soo Locks Locks opened opened 7, 1852. barrels on July 7. shipped consisted shipped consisted of of six six barrels 1852. After the June, 1855, in June, 1855, Lake Lake Superior Superior iron iron mining mining boomed boomed -- a tribute tribute to to the the farsighted farsighted vision of vision of Douglass Douglass Houghton. Houghton. Since much much ofofthe theore ore was wasfound foundatatorornear near surface, surface, the Since the early early mines mines were were As the mines went deeper, worked by open pit methods, as shown in Figure 2. worked by open pit methods, as sho\VTI in Figure 2. As the mines went deeper, skip roads roads were were used bring the the ore oretotosurface. surface. By By 1880, 1880, most most of inclined skip inclined used to to bring of the ore was was produced produced from from underground underground workings. the ore workings. Early methods were were open open by top-slicing stoping, room-and-pillar stoping, and square-sets, followed stoping, room-and-pillar stoping, and square-sets, by top-slicing Large scale Sub-level caving caving was was used used where where conditions permitted. Large in 1890. Sub-level in conditions permitted. scale illustrates a sub-level stoping Figure 3 block caving was was introduced in 1950. introduced in 1950. Figure 3 illustrates a sub-level stoping scene. scene. Emphasis in Emphasis in mining mmmgwas wasplaced placedononthe the high high grade grade direct direct shipping shipping ores. ores. the 1880t5 several attempts attempts were However, in However, in the 1880's several were made made to to use use concentrating concentrating plants. plants. It produced Edison built a magnetic separator at Humboldt in 1888. Thomas Edison built a magnetic separator at Humboldt in 1888. It produced Thomas World War War grade concentrate burned in 893 tons of of high grade concentrate before before it it burned in 1889. 1889. After After World II, the mining companies worked on developing economic processes of con II, the mining companies worked on developing economic processes of con­ �• • 19 19 centrating grade Negaunee Negauneeiron-formation, iron-formation, also also called centrating the the low low grade called jaspertr ffjasper rr or or The first commercial plant, opened in 1954, was the Humboldt ttaconite. rttaconite. The first commercial plant, opened in 1954, was the Humboldt Mine of of The The Cleveland-Cliffs Cleveland-Cliffs Iron Iron Company Companyand andFord Ford Motor Motor Company. Company. The Mine The Repuolic Mine was opened in 1956, and the Empire Mine in 1963; both partnerRepuolic Mine was opened in 1956, and the Empire Mine in 1963; both partner­ ships of ships of various various steel steel companies companies and and Cleveland-Cliffs. Cleveland-Cliffs. All All three three open open pit pit properties produce grade pellets. properties produce high high grade pellets. II The Marquette Marquette Iron Iron Range Rangeisis made made up upofofthree three districts districts (see The (see Figure Figure 4). 4). From 1852 through 1963, the iron ore production from these districts was: From 1852 through 1963, the iron are production from thes e districts was: Principal Principal district district Cascade district Cas cade district Gwinndistrict district Gwinn 291,323,507 291,323,507 17,895,700 17,895,700 785, 260 12, 12,785,260 Total Total 322, 004,467 long 322,004,467 long tons tons Of the the total total of of291 291million milliontons tonsproduced produced from from the part of of the the Range, Range, Of the principal principal part 4,266,858 long tons were from the Bijiki iron-formation, and the balance was 4,266,858 long tons were from the Bijiki iron-formation, and the balance was from the Negaunee iron-formation. from the Negaunee iron-formation. Concentration was was accomplished Concentration accomplishedononthe the Bijiki Bijiki iron-formation iron-formation by by using using total heavy media media process the Ohio OhioMine. Mine. From From 1952 the heavy the process at at the 1952 to to 1960, 1960, a a total of of pit operations. 745, 620 long tons of concentrate was produced from several open 745,620 long tons of concentrate was produced from several open pit operations. Local Not all all Marquette Marquette Range Range ores Not ores were wereshipped shippedtotothe the blast blast furnaces. furnaces. Local charcoal furnaces, furnaces, used used from from 1857 charcoal 1857 through through 1893, 1893, produced produced an an estimated estimated one one and aa half million million and tons tons of of pig pig iron. iron. Sett Geologic Geologic Setting The principal principal rock rock units units are are Precambrian The Precambrian in in age. age. Structurally, Structurally, they they are are al, to the Southern Province of the great Canadian Shield (Leech et assigned to the Southern Province of the great Canadian Shield (Leech et aI, assigned Probably they were subjected the major major orogenies orogenies of of the theKenoran Kenoran and and 1963), Probably 1963). they were subjected to to the Penokean (Hudsonian, Stockwell, 1962), as well as more local deformation, Penokean (Hudsonian, Stockwell, 1962), as well as more local deformation. which the found was was called The thick sedimentary sedimentary series series in The thick in which the iron iron ore ore is is found called next century. by Whitney in 1857, and the term was used for the Huronian by Whitney in 1857, and the term was used for the next century. (1958)pointed pointedout outthat thatthe theseries series differs differs considerably James (l958) considerably from from the the type type section of the Huronian of Ontario and is more firmly correlated with section of the Huronian of Ontario and is more firmly correlated with the the Animikie series series of Animikie of northeastern northeastern Minnesota; Minnesota; therefore, therefore, the theUnited United States States GeolGeol­ Goldich, et al (1961) dated the Animikie ogical Survey uses the term Animikie. ogical Survey uses the term Animikie. Goldich, et al (I96l) dated the Animikie practice, Stockwell as middle Precambrian in as middle Precambrian in age. age. By ByCanadian Canadian practice, Stockwell(1962) (1962) would would term Animikie as Lower Proterozoic. term Animikie as Lower Proterozoic • �20 The found in in aa long long westward westward plunging plunging synclinorium The Animikie Animikie series series isis found which County line, the south south line, the which opens openstoto the the west west (see (see Figure Figure 4). Near the Barage County limb syncline has has been been folded folded into a lesser lesserdownfold downfold called called the the limb of the the major syncline The sedimentary sedimentary series series continues Republic Trough. The continues into into Baraga, Baraga, Dickinson Dickinson Republic Trough. and Iron Counties. Older and (Archean) rocks rocks are are found found to to the the north north of Older (Archean) of the the syn~ syn clinorium, To To the south is clinorium. granite complex, complex, thought thought to to be be related related to to the the is aa granite folding of against the the older rock to the the north. north. of the the synclinorium synclinorium against rock buttres buttresss to to the Cascade Range, immediately The Cascade immediately to the southeast southeast of of the the Marquette Marquette synsyn­ clinorium, is considered considered to to be be aa faulted faulted segment segment of of the the main main structure. structure. The clinorium, is or Swanzy Swanzy area, Negaunee, and Dead Gwinn area, some some 20 20 miles miles southeast southeast of of Negaunee, and the the Dead Gwinn or of the the Marquette Marquette Range, Range,are are separate separate basins, River area, basins, area, a few miles north of entire district to contain contain rocks rocks of of the the Animikie Animikie series. thought to thought series. The The entire district has has been been intruded by rocks of Keweenawan age. Cambrian and Ordovician sandstones intruded rocks of Keweenawan age. Cambria.n and Ordovician sandstones district was and limestones limestones are and are found found to to the the south south and and southeast, southeast. The The district was glaciated glaciated extensively. extensively. Stratigraphic Column Stratigraphic Column A schematic schematic summary summary of the stratigraphic A of the stratigraphic column column is is shown shown as as the the legend legend This column is aa modification the most on Figure Figure 4. on 4. This column is modification of of the most recent recent work work by by the the United States States Geological Geological Survey, Survey, together together with United with data data from from the the mining mining companiest companies I drill hole undergroundand andsurface surfaceexposure exposureinformation. information. Figure Figure 44 is drill hole and and underground is aa plan map map indicating indicating the the principal principal Animikie and older older rock plan Animikie and rock units units which which make make up up the Marquette synclinorium and environs, Figures 5 and 6 illustrate spatial the Marquette synclinorium and environs. Figures 5 and 6 illustrate spatial relations of relations of the the principal principal rock rockunits units in inthe thevicinity vicinityofofNegaunee Negaunee and and Ishpeming. Ishpeming. Figure 77 indicates the relative Figure indicates the relative thicknesses thicknesses of of the the stratigraphic stratigraphic units units from from east east reflect several to west west in to in the the synclinorium. synclinorium. Variations Variations reflect several features features such such as as the the extent of of primary primary sedimentation and later later erosion. extent sedimentation and erosion. Apparently Apparently the the locus locus of of the sedimentation westerly as the sedimentation moved moved westerly as the the younger younger ro.cks rocks were were being being deposited. deposited. Pre-Animikie Pre-Animikie Basement Basement Complex Complex Both Monographs Monographs 28 28 and and 52 52describe describe the and Kitchi Kitchi schists Both the Mona Mona and schists which which They were were intruded were called metasediments and were called Keewatin Keewatin metasediments and metavolcanics, metavolcanics. They intruded by flLaurentian by Laurentian"granites, granites.now nowrepresented representedby by granites granites and and gneisses. gneisses. Recent detailed detailed mapping mapping by bythe the U. U.S. Survey (Gair (Gair et et aI, al, 1963, Recent S. Geological Geological Survey 1963, et seq.) that the the Mona Monaschist schist consists consists of of schistose schistose and and massive massive meta­ meta et seq.) has has found found that basalt, actinolitic and chioritic schists, ellipsoidal greenstone, chioritic slate basalt, actinolitic and chloritic schists, ellipsoidal greenstone, chloritic slate and felsite. felsite, This This thick thick series series isis intruded and intruded by by tonalite tonalite and and granodiorite, granodiorite, with with �21 some monzonite, monzonite, quartz The dikes dikes and and sills sills cutting some quartz monzonite monzonite and and granite. granite. The cutting the the Mona schist felsic porphyry, porphyry, frequently frequently weathering weathering to to aa pale pale pink pink color. color. Mona schist are are felsic A the Animikie A widespread widespread unconformity unconformityseparates separatesall all these these rocks rocks from from the Animikie series. series. Animikie Series Animikie Series Chocolay Group Group Chocolay Three formations Three formations make make up up the the Chocolay Chocolay Group Group of of lower lower Animikie Animikie sediments. sediments. The basal basal unit unit is is the the Mesnard quartzite, which is aa vitreous, The Mesnard quartzite, which is vitreous, medium-grained, medium-grained, thin to to thick thick bedded beddedquartzite, quartzite, locally locally brecciated, brecciated, with thin with cross-bedding cross-bedding and and ripple marks. ripple marks. Near NearEnchantment Enchantment Lake, Lake, about about 44 miles miles southwest southwest of of Marquette, Marquette, the basal basal portion is made of conglomerate, conglomerate, graywacke, graywacke, arkose, arkose, and the portion is made up up of and sericitic slates sericitic slates and and quartzites quartzitesalthough although not not all all of of these these types types are arefound found in in the the same location. same locaUon. The Kona Konadolomite dolomiteoverlies overlies the the Mesnard Mesnard formation formation and and is is the The the thickest thickest and and most extensive most extensive member member of of the the Chocolay Chocolay Group Group in in the the area area between between Marquette Marquette and and It is is principally Negaunee, It Negaunee. principally a a light-colored light-colored fine fine to to medium-grained medium-grained massive massive Locally itit has has thin thinlaminated laminatedchert chertlayers, layers, sericitic sericitic slate, dolomite. Locally dolomite. slate, quartzites quartzites In places places the is extensively and laminated laminated siltite. siltite. In and the dolomite dolomite is extensively silicified. silicified. Recent Recent mapping (Fritts, 1964) identifies some quartzitic areas as Kona, rather mapping (Fritts, 1964) identifies some quartzitic areas as Kona, rather than than describes the Mesnard as as mapped earlier. Gair Mesnard mapped earlier. Gair et et al al (1961) (1961) describes the silicification silicification of of rSilicified Kona Konadolomite dolomite most most typically typically consists consists the Kona dolomite as as follows: the Kona dolomite follows: rrSilicified laminations are are of thick thick laminated laminated masses masses of fine-grained quartz quartz (chert). of of fine-grained (chert). The The laminations reddish or variations in reddish or bluish bluish black black to to white, white, depending depending on on variations in minor minor amounts amounts of of Massive siliceous rock consisting different iron iron oxides from layer layer to different oxides from to layer. layer. Massive siliceous rock consisting of of fragments of white chert chert in in aa reddish-brown hematitic cherty fragments of white reddish-brown hematitic cherty matrix matrix apparently apparently resulted from resulted from post-brecciation post-brecciation silicification silicificationof of the the dolomitic dolomitic portion portion of of laminated laminated Thin sections sections of cherty dolomite. cherty dolomite. Thin of silicified silicified dolomite dolomite generally generally show show aa fine-gràined fine-grained mosaic of cherty quartz quartz with small loose loose clusters mosaic of cherty with small clusters of of very very fine-grained fine- grained carbonate carbonate Not only only the the dolomitic dolomitic portions portions of have been been silicified silicified but particles. rr Not particles. of the the Kona Kona have but the slates slatesand andquartzites quartziteshave havebeen beenimpregnated impregnated and and cut cutby bynumerous numerous also the also quartz veins. Another distinctive the Kona Kona is the presence presence of Another distinctive feature of of the is the of the the algal structures, occur widely although they they are are not which occur widely throughout throughout the the Kona Kona although not confined confined to to any any given given Algal structures are locally associated with olites, which confirms horizon. horizon. Algal structures are locally associated with O'~lites, which confirms their shallow-water their shallow-water origin origin (Gair, (Gair, 1962, 1962, oral oralcommunication). communication). The uppermost uppermost member Group is is the slate, which The member of of the the Chocolay Chocolay Group the Wewe Wewe slate, which has an has an estimated estimated maximum maximum thickness thickness of of nearly nearly 900 900 feet, feet. It It is is aa gray gray to to greenishgreenish­ gray, laminated to massive slate, with interbeds of impure dark quartzite. gray, laminated to massive slate, with interbeds of impure dark quartzite. A A �22 Elsewhere, the is brecciated conglomerate is conglomerate is found found locally. locally. Elsewhere, the Wewe Wewe is brecciated and and imim­ In places places the the rock has textures pregnated with with quartz quartz and and specular specular hematite. pregnated hematite. In rock has textures which suggest suggest the the presence presence of of volcanic volcanic and andpyroclastic pyroclastic materials materials (Gair, which (Gair. 1962, 1962, oral communication). oral communication). Seaman (1944) (1944) assigned assigned the to the Seaman the Wewe Wewe to the upper upper Kona; Kona; Boyum Boyum (1954, (1954, 1963) 1963) followed the the same same practice. practice. This followed This report report reflects reflects the the recent recentTi. U. S. Geological Geological Survey mappingand andre-instates re-instates the as aa distinct Survey mapping the Wewe Wewe as distinct formation. formation. Menominee Group Menominee Group The MenomineeGroup Groupisis named namedfor for the the Menominee Menomineedistrict district of The Menominee of southern southern James (1958) assigned this name to the middle Animikie Dickinson County. Dickinson County. James (1958) assigned this name to the middle Animikie rocks rocks of of the the Marquette Marquette Range Range comprising comprising the the Ajibik, Ajibik, Siamo Siamoand andNegaunee Negaunee There appears to be an erosional disconformity between formations. formations. There appears to be an erosional dis conformity between the the Chocolay and and Menominee Menominee Groups. Groups. Chocolay The Ajibik Ajibikquartzite quartzite isis vitreous, vitreous, medium-grained, The medium- grained, thin thinto tothick thickbedded, bedded, with some some sericitic sericitic to to chloritic chloritic slate. with slate. AAbasal basalconglomerate conglomerate is is found found in in Section 6, T. T. 47 Section 6, 47 N., N., R. R. 25 25 W., W., and and elsewhere. elsewhere. The Siamo Siamo slate slate formation formation contains laminated to to massive massive dark The contains laminated dark gray gray and and gray-green slates, argillites, graygreen slates, argillites,graywacke graywacke and and impure impure quartzite. quartzite. CharacterCharacter­ istically, the istically, the slates slates weather weather brownish brownish or or reddish. reddish. Tyler and (1952)described described the the Goose Goose Lake Lake iron-formation, iron-formation, Tyler and Twenhofel Twenhofel (1952) Its thickness which is aa magnetic which is magnetic member member of of the the Siamo Siamo formstion. formstion. Its thickness is is estimated estimated It extends for some the strike strike west at 50 at 50 to to 100 100 feet. feet. It extends for some distance distance along along the west and and northnorth­ The iron-formation is laminated, west of Goose Lake (Gair and Wier, 1964). west of Goose Lake (Gair and Wier, 1964). The iron-formation is laminated, The iron-formation iron-formation at magnetic, cherty, cherty, chloritic magnetic, chloritic and and sideritic. sideritic. The at the the St. St. to be be Goose 27 W. is though Lawrence pit in Section 5, 5, T. Lawrence pit in Section T. 47 47 N. N. ,, R 27 W.,, is though to Goose Lake, Lake, also. also. The Palmer gneiss The Palmer gneiss was was described described in in detail detail by by Lamey Lamey (1935). (1935). He He concon­ cluded that the the Palmer Palmer gneiss cluded that gneiss represented representedmetamorphosed metamorphosed (Animikie) (Animikie) sedisedi­ ments, formations, and ments, principally principally the the Ajibik Ajibik and and Siamo Siamo formations, and locally locally the the Mesnard Mesnard Monographs 28 and 52 describe the Palmer gneiss as and Kona Kona formations. formations. Monographs 28 and 52 describe the Palmer gneiss as and aa belt belt of of Laurentian Laurentian rocks, rocks, with withthe thecomment comment that thatT'phases "phases of of it it look look like like metameta­ Future mapping may clarify these relationships. morphosed sediments. morphosed sediments." Future mapping may clarify these relationships. The Negaunee Negauneeiron-formation iron-formation isis the the most The most important important and and interesting interesting member of of the the entire entire column, column, as as itit is member is the the host host rock rock for for most most of of the the iron iron ores. ores. In general, general, itit isis similar In similartotoother otherAnimikie Animikie iron-formations iron-formations of of the the Lake Lake Superior Superior The maximum maximum stratigraphic stratigraphic thickness Region. Region. The thickness is is attained attained in in the the NegauneeNegaunee­ Ishpeming area where where itit exceeds 000 feet, feet, not including the the intrusive intrusive masses. masses. Ishpeming area exceeds 2, 2,000 not including It It is is remarkable remarkable also also for for its its relative relativelack lackof ofargillaceous argillaceous and and arenaceous arenaceous facies. facies. �23 The in this this summary. sum.m.ary. The lithology lithologyisis discussed discussed in in m.ore more detail detail later later in Baraga Group Baraga Group The Baraga Baraga Group Group consists consists of major members: The of two two m.ajor m.em.bers: the theGoodrich Goodrich and and the the The Goodrich Goodrichform.ation formation isis principally principally quartzite, quartzite, with Michigamme form.ations. formations. The Michigam.m.e with In m.ost most localities, localities, there interbedded argillites argillites and interbedded and conglomerates. conglom.erates. In there is is aa basal basal conglomerate m.ade made up up of of fragm.ents fragments of iron-formation. The conglom.erate of the the Negaunee Negaunee iron-form.ation. Negaunee-Goodrich contact contact isis reported reported to angular discordance, Negaunee-Goodrich to have have up up to to 150 150 angular discordance, but com.m.only commonlythere there isis little little noticeable but noticeable discordance. discordance. Overlying the the Goodrich Goodrichquartzite quartzite isis the the thickest thickest member Overlying m.em.ber of of the the entire entire Animikie Series, the exceeds 5,000 Anim.ikie Series, the Michigamme Michigam.m.e formation form.ation which which probably probably exceeds 5,000 feet. feet. It is is distinctive also in It distinctive also in its its areal areal extent, extent, not not only only in in the the Marquette Marquette District, District, but but over much of the the central central part over m.uch of part of of the the Upper Upper Peninsula. Peninsula. Near the the base base of formation isis aa thin sub-member, Near of the the Michigamme Michigam.m.e form.ation thin magnetic m.agnetic sub-m.em.ber, termed the term.ed the Greenwood Greenwood formation form.ationby bySwanson Swanson and and Zinn Zinn (1930). (1930). Most Most of of the the The Clarksburg pyroclastics Michigamme is slate, argillite and graywacke. Michigam.m.e is slate, argillite and graywacke. The Clarksburg pyroclastics are found are found in in the the lower lower portion portion of of the the Michigamme Michigam.m.e where where they they occupy occupy an an The Bijiki ironasymmetrical position in the synclinorium (see Figure 4). asym.m.etrical position in the syncli norium. (see Figure 4). The Bijiki iron­ formation is the middle form.ation is found found above above the m.iddle member m.em.ber of of the the Michigamme. Michigam.m.e. It It extends extends from north north of Humboldt, at at the the Bessie Bessie Mine, from. of Hum.boldt, Mine, to to west west of of Three Three Lakes. Lakes. Over Over million tons tons of of iron iron ore from mines 44 m.illion ore have have been been produced produced from. m.ines in in the the Bijiki. Bijiki. the U.S.G.S. Harold Jam.es James (1958) Harold (1958) in in the U.S.G.S. Professional Professional Paper Paper 314-C, 314-C, the Paint describes the Paint River River Group Group that that overlies overlies the the Michigamme Michigam.m.e formation. form.ation. the southwest southwest of the Marquette Marquette Mineral These rocks are These are found found to the of the Mineral District. District. In In the past, past, som.e some geologist iron-formation with the geologist have have correlated correlated the the Bijiki Bijiki iron-form.ation with the River-Crystal Falls iron-formation of Riverton iron-form.ation of the the Iron Iron River-Crystal Fallsiron irondistricts. districts. This This would m.ean mean that that part part of formation would would be be in in the the Paint Paint River would of the the Michigamme Michigam.m.e form.ation River Group. Group. Granite is Granite is the the principal principal rock rocktype type along along the the south southlimb lim.bof ofthe the Animikie Anim.ikie There are thought to be both pre-Animikie and post-Animikie synclinorium. synclinorium.. There are thought to be both pre-Anim.ikie and post-Anim.ikie Goldich determ.ined determined an an age age of of 1,900 1,900 m.illion million years years on granites. Goldich granites. on one one sample sam.ple south of of Republic, Republic, and and 1,600 1, 600m.illion millionyears years on onanother. another. Some south Som.e students students believe believe that aa portion the granite-appearing that portion of of the granite-appearing rocks rocks were were formed form.ed by by granitization granitization of of sediments. pre - existing Animikie pre-existing Anim.ikie sedim.ents. Seaman (1944) suggested periods Seam.an (1944) suggested periods of of orogeny orogeny following following Michigamme Michigam.m.e time tim.e which he called the Sibley and Superior or Republic, preceding Keweenawan which he called the Sibley and Superior or Republic, preceding Keweenawan This would correspond to time. This tim.e. would correspond to the the Penokean Penokean (Goldich (Goldich et et al, aI, 1961) 1961) and and may m.ay be the be the time tim.e of of the the post-Animikie post-Anim.ikie granites granites and and the the deformation deform.ation of of the the Marquette Marquette Range synclinorium.. synclinorium. Range �I I 24 intrusive masses found within the has been been made Reference has Reference made above aboveto to the the intrusive masses found within the but are These intrusives Negaunee Negaunee iron-formation. iron-formation. These intrusives are are irregular irregular in in shape, shape, but are rather than as diorite They are described as as metadiabse metadiabse rather often sill-like. often sill-like. They are best best described than as diorite Locally, the sills have been publications. greenstone, as used in earlier or greenstone, as used in earlier publications. Locally, the sills have been of recognized primary differences in used as as horizon markers in used horizon markers in the the absence absence of recognized primary differences in these intrusives may be has been It has the Negaunee. It been suggested suggested that that the the age age of of these intrusives may be Possibly they might be related to the Clarksburg or or Keweenawan. Keweenawan. Possibly either Clarksburg either they might be related to the of these sillIt has also been suggested that that one one or or more more of Penokean orogeny. Penokean orogeny. It has also been suggested these sill­ indicate that bulk of the structural features like masses is extrusive, but the like masses is extrusive, but the bulk of the structural featull!es indicate that of some 700 feet. A They reach maximum thickness they are are intrusive. intrusive. They reach aa maximum thickness of some 700 feet. A of 400 400 feet. general average average would order of general would be be of of the the order feet. both the pre-Animikie and other intrusives intrusives are Various other are found found cutting cutting both the pre-Animikie and fine-grained mafic and andfelsic felsic dikes, dikes, others are Animikierocks. rocks. Some are fine-grained mafic Animikie Some are others are metapyroxenite and metagabbro. Some dikes medium toto coarse-grained coarse-grained meta-pyroxenite and metagabbro. Some dikes are medium are Locally they may be inversely and texture. fresh diabases, both in compoiti.on fresh diabases, both in composItion and texture. Locally they may be inversely polarized magnetically. polarized magnetically. sandstone are found south of Marquette. Exposures of Exposures of Jacobsville Jacobsville Cambrian Cambrian sandstone are found south of Marquette. friable sandstone with some conglomerate Typically, the Jacobsville is reddish, Typically, the Jacobsville is reddish, friable sandstone with some conglomerate are found, too, in the Gwinn and reddish reddish shale. shale. Some and Some sandstones sandstones exposures exposures are found, too, in the Gwinn the Ordovician rocks. Through all Still further District. Still further south south is is the the onlap onlap of of the Ordovician rocks. Through all of the recent Quaternary surficial material of the the district, district, variable of variable amounts amoun~s of the recent Quaternary surficial material of glacial glacial origin. are found, are found, principally principally of origin. (see Figure 4) has been compared to The column column in in the the Gwinn District (see Figure 4) has been compared to The Gwinn District Allen (1914): the principal synclinorium, and the principal synclinorium, and is is summarized summarized as as follows follows from from Allen (1914): Ordovician Ordovician Cambrian Cambrian Paleozoic Paleozoic Keweenawan Keweenawan Late Late Baraga Baraga j s:: n:l ..... 1-4 ~n:l uU Q) Middle Middle 1-4 O-i Early Early Menominee Menominee Limestones and sandstone Limestones and sandstone Intrusives Intrusives Princeton Series Princeton Series Ferruginous slate, cherty Ferruginous slate, cherty quartzite and graywacke quartzite and graywacke conglomerate conglomerate Gwinn Series Gwinn Series Dark gray slate, graywacke Dark gray slate, graywacke Iron-formation Iron-formation Dark gray to graphitic slate Dark gray to graphitic slate arkose and conglomerate arkose and conglomerate Granite, greenstone Granite, greenstone �• • 25 25 Some geologist geologist have have considered considered the the iron-formation iron-formation in District Some in the the Gwinn Gwinn District the Michigamme formation. as correlative to the Bijiki iron-formation in as correlative to the Bijiki iron-formation in the Michigamme formation. Metamorphic Metamorphic Zones Zones Studies have have been been made made on the metamorphic Studies on the metamorphic zones zones in in the the Upper Upper Peninsula. Peninsula. The area Particularly noteworthy Particularly noteworthy is is the the study study of of James James(1955). (1955). The area around around Republic Republic and the Republic Trough is shown on his maps to be of the highest intensity, and the Republic Trough is shown on his maps to be of the highest intensity, in in metamorphic intensity the the sillimanite sillimanite zone. zone. The The metamorphic intensity in in the the balance balance of of the the Marquette Marquette The Ishpeming-Negaunee Ishpeming-Negaunee extremity extremity of Iron Range Rangedecreases decreases to to the the east. east. The Iron of the the The metamorphic isograd6 cross producing district is in the chlorite zone. producing district is in the chlorite zone. The metamorphic isograds cross the the This suggests geologic structures structures at angles in in many areas. This geologic at high high angles many areas. suggests that that the the metameta­ morphism isis post-structure. post-structure. morphism Of considerable considerable interest interest is Of is the the paper paper by by James Jamesand andClayton Clayton (1962) (1962) relating relating mineral formation temperatures to their oxygen isotope fractionization. mineral formation temperatures to their oxygen isotope fractionization. Some Some samples from from the Range were were tested, tested, specifically samples the Marquette Marquette Range specifically from from the the Athens Athens They tentatively tentatively conclude: and Greenwood Greenwood Mines Mines and and the the Republic Republic district. district. They and conclude: (1) on on the the basis basis of of internal internal consistency and consistent consistent relations (1) consistency and relations to to the the mineralogic mineralogic evidence of metamorphic zoning, the isotopic data yields at least a fair evidence of metamorphic zoning, the isotopic data yields at least a fair approxapprox­ imation of of temperatures temperatures of imation of metamorphism metamorphism through through the the garnet garnet zones; zones; (2) (2) the the 2000 temperature of metamorphism for the chlorite zone reaches zpproximately temperature of metamorphism for the chlorite zone reaches zpproximately 200 0 that of and that of the the biotite biotite zone that of C. , that C., zone approximately approximately 275° 275 0 C. C.,, and of the the garnet garnet zone zone 0 (3) the approximately 3350°C. approximately 50 C. ;; (3) the rocks rocks in in the the staurolite staurolite and and sillimanite sillimanite zones zones (upper part part of amphibolite facies facies and and amphibolite amphibolite facies, facies, respectively) (upper of the the epidote epidote amphibolite respectively) 0 the present and the 350°C. were formed at temperatures were formed at temperatures above above 350 C., and present isotopic isotopic composition composition of the oxygen of these rocks is due to retrograde equilibration during temperature of the oxygen of these rocks is due to retrograde equilibration during temperature , decline. decline. Nome nc1atur e Nomen.clature From the until 1949 little From the time time of of the the publication publication of of Monograph Monograph 52 52 in in 1911 1911 until 1949 little change occurred in the petrographic nomenclature of the Marquette Mineral change occurred in the petrographic nomenclature of the Marquette Mineral that time, District. At District. At that time, The The Cleveland-Cliffs Cleveland-Cliffs Iron IronCompany Company undertook undertook aa sweepsweep­ ing revision revision of of many many ofofits its rock rock names. names, Numerous ing Numerous old old or or ambiguous ambiguous terms terms names had replaced with with modern modern or or more more precise were replaced were precise terms. terms. Various Various names had been been past; at used for the iron-formation iron-formation in used for the in the the past; at this this time, time, the the term termrtjrofl rtiron formationt'r -formation rr of des description was adopted adoptedasas the the sole sole name. name. A was A uniform uniform system system of cription was was effected effected also.. also �I 26 I rrsoft ore jaspertr previously used were The terms terms "hard 'hard ore The ore jasper" jasper rr and and rrsoft ore jasper rr previously used were and Republic Mine are Our beneficiating beneficiating plants eliminated. Our eliminated. plants at at the the Humboldt Humboldt and Republic Mine are processing rtjasper or taconitetT; sometimes referred referred to to in in the the press press as sometimes as processing ttjasper fY or rrtaconite"; ,iron_formationrrr is is preferred. however, the however, the expression expression "iron-formation preferred. Primary Primary Iron-Formation Iron-Formation I Sedimentary Facies of Iron- The summary summary of The of James James (1954) (1954) on on the the Sedimentary Facies of Iron­ sulphide, silicate and Formation emphasized emphasized the the four four facies: fades: carbonate, Formation carbonate, sulphide, silicate and Boyum_AndersonHan (1955) (1955)Primary PrimaryFeatures Other references references are are Boyum-Anderson-Han oxide. Other oxide. Features Relationship and Anderson-Han (1956) The of the the Negaunee Iron-FormatiOn and Anderson-Han (1956) The Relationship of Negaunee Iron-Formation; and Secondary Oxidation to the Concentrating of Diagenesis, Diagenesis, Metamorphism of Metamorphism and Secondary Oxidation to the Concentrating of the the Marquette Range. The Characteristics of Iron-Formation of Characteristics of the the Negaunee Negaunee Iron-Formation Marquette Range. The of been the principal primary constituent carbonate facies carbonate facies is is thought thought to to have have been the principal primary constituent of remnant Plate 1-A the Negaunee iron..formation, Plate the Negaunee iron-formation. I-A illustrates illustrates an anunoxidized unoxidized remnant James (1954 pages 258 et seq.), iron-formation. of typical typical cherty of cherty carbonate carbonate iron-formation. James (1954 pages 258 et seq.), oxide fades (as hematite) in the upper advances arguments arguments for for the advances the primary primary oxide facies (as hematite) in the upper The summary summary byStone and Qimberlidge part of iron-formation. The part of the the Negaunee Negaunee iron-formation. by S tone and Glmberlidge suggests that both hematite and magnetite (1964) on on the the Groveland Groveland Mine (1964) Mine geology geology suggests that both hematite and magnetite he believes is (1962) has has found found some some magnetite were primary. primary. Han were Han (1962) magnetite which which he believes is places in iron-formation. primary oxide facies in in several primary oxide facies several places in the the Negaunee Negaunee iron-formation. sulphides and and silicates silicates from the Marquette Specific illustrations illustrations of primary sulphides Specific of primary from the Marquette Range are are not Range not readily readily available. available. I chioritic clastic iron-formation Plate I-B Plate I-B illustrates illustrates the the magnetitic magnetitic chloritic clastic iron-formation Tilden Mine in the southeast portion of the found at the Empire Mine and the found at the Empire Mine and the Tilden Mine in the southeast portion of the found on the Cascade Range. Cla.stic iron-formation iron-formation is is also Marquette Range. Marquette Range. Clastic also found on the Cascade Range. southeast of the synclinorium. This suggests suggests aa source This source to to the the southeast of the synclinorium. Alteration of the Iron-Formation Iron-Formation Alteration of the iron-formation has been by oxidation and The principal principal alteration alteration of The of the the iron-formation has been by oxidation and The average iron content of primary enrichment under enrichment under varying varying conditions. conditions. The average iron content of primary The average altered Negaunee ironironformation approximates iron-formation approximates 26% 26%. dried. dried. The average altered Negaunee iron­ Locally in in the the Negaunee area, the dried. Locally formation approximates Fe, dried. formation approximates 31% 31% Fe, Negaunee area, the A general increase in porosity is higher, higher, reaching reaching about about 35%, average is average 35%. A general increase in porosity accompanies the accompanies the alteration. alteration. frequently characterized enrichment has has occurred, occurred, it Where enrichment it is is most most frequently characterized iron oxides, primarily hematite and replacement of of the the primary primary chert by replacement chert by by iron oxides, primarily hematite and I �27 greater part goethite, and goethite, and locally locally magnetite. :magnetite. The The greater part of of this this alteration alteration has has been been volume-for-volume replace:ment replacement as as very very little volu:me-for-volu:me little slumping slu:mping has has been been noted. noted. In In numerous instances instances it from the nu:merous it is is possible possible to to follow follow the the primary pri:mary bedding bedding fro:m the ironiron­ The ore ore contacts formation into into the the ore. for:mation ore. The contacts frequently frequently cut cut the the bedding bedding at at high high angles. angles. The folding folding of of the the Marquette Marquette Range The Range synclinorium synclinoriu:m was was accompanied acco:mpanied by by the development of a strong joint system which increased the permeability the develop:ment of a strong joint syste:m which increased the per:meability of of Exploration and and :mining mining in in recent recent years the iron-formation. the iron-for:mation. Exploration years have have indicated indicated that both both oxidation oxidation and and enrich:ment enrichment extend extend toto far far greater greater depths that depths than than thought thought Numerous drill drill holes holes have have cut cut rich rich ore ore grade earlier. Nu:merous earlier. grade material :material to to depths depths of of term trorerr oretr isis used over 5, 000 feet feet fro:m from the the present present land over 5, 000 land surface. surface. The The ter:m used here here as as meaning high and does does not not neces necessarily imply an an econo:mic economic profit :meaning high iron iron content content and sarily i:mply profit hole on the Range was drilled drilled as the term is customarily. The the ter:m is defined custo:marily. The deepest hole on the Range was size, and and encountered encountered oxidation and enrichinch) size, depth of 365 feet, feet, NX NX (3 to aa depth of 6, 6,365 (3 inch) oxidation and enrich­ During late late Preca:mbrian Precambrian ti:me time when the alteration alteration may nay the bottom. ment to :ment to the botto:m. During when the have occurred, occurred, the greater. have the depth depth of of this this alteration alteration was was undoubtedly undoubtedly greater. Some parts parts of contain considerable considerable silicates silicates such So:me of the the Negaunee Negaunee contain such as as sericite, grunerite-cummingtonite, hornblende and garnet in the higher sericite, grunerite-cu:m:mingtonite, hornblende and garnet in the higher meta:meta­ morphis zones minnesotaite, :morphis zones (such (such as as at at Humboldt Hu:mboldt and and Republic); Republic); and and :minnesotaite, stilpnomelane and and chlorite chlorite in stilpno:melane in the the diagenetic diagenetic or or lower lower metamorphic :meta:morphic zones zones (such as as at at E:mpire). Empire). According or all all of of these these silicates silicates are (such According to to one one view, view, many :many or are derived by by the the :meta:morphis:m metamorphismofofearlier earlier pri:mary primary silicates. silicates. Others derived Others believe believe that that these silicates silicates are these are the the result result of of the the reaction reaction of of earlier earlier iron iron minerals :minerals (carbonate (carbonate and/or the silica and/ or oxides) oxides) and and the silica of of the the chert chert under under metamorphic :meta:morphic conditions. conditions. Plate I-C of the the silicates. silicates. Plate Plate I-C shows shows the the development develop:ment of Plate I-D I-D is is aa polished polished slab slab are photoof :magnetite magnetite carbonate carbonate silicate silicate iron-formation. of iron-for:mation. Plates Plates I-E I-E and and F Fare photo­ micrographs of the portions portions rich :micrographs of the the slab slab showing showing the rich and and lean lean in in magnetite, :magnetite. Ore Ore Occurrences Occurrences There There are four four general general types types of of ore orewhich which have have been been produced produced and and shipped are shipped They are: from the Marquette Iron fro:m the Marquette Iron Range. They are: High grade grade direct direct shipping shipping rrsoftu rrsoft tr ores, ores. High grade grade direct direct shipping "hardtttr ores, ores, High shipping "hard Siliceous ores, Siliceous ores, Concentrates and agglomerates (pellets) Concentrates and agglo:merates (pellets) from fro:m low low grade grade iron-formations. iron-for:mations. Traditionally in in the the Lake Lake Superior Superior Region, Region, the the direct direct shipping Traditionally shipping ores ores have have Recently, the direct natural (moisture aa base base iron iron content content of of 51.5% 51. 5% natural (:moisture included). included). Recently, the direct �1 J 28 28 I the competition of averaged 54% Fe, natural-, reflectingores ores have shipping have aof shipping ores have averaged 54% paid Fe, natural, reflecting competition for the hard lump the which premium is the foreign foreign ores. ores. AA premium Thea the isTheir paid average for the hard lump ores which have content is 61. 5%. iron inch -8 inch. range of +2 size size range of +2 inch -8 inch. Their average iron content 61. 5%. of The small isshipments specialty grade, constitutes siliceous type type of of ore, ore, aa specialty from siliceous grade, constitutes small shipments of which averages 38% Fe. The pellets range richer iron_formation richer iron-formation which averages 38% Fe. The pellets range from natural. 61 to to 65% Fe, natural. 61 65% Fe, between rrsoftrt For For made a distinction many years the miners have made a distinction between earthy many years the miners havesoft rrsoft" ores are porous, friable, "hard" ores. In generals the ores and and r'hard" ores ores. In general, the soft ores are porous, and martite friable, (locally earthy chiefly of hematite, semi_plastic and are made up to and to semi-plastic and are made upamounts of hematite, and martitechert, (locally of goethite unreplaced and with minor chiefly of still magnetite) The other still magnetite) and with minor amounts goethite, unreplaced chert, and through P). (see Plate III - M (mica, chlorite) locally silicates with low locally silicates (mica, chlorite) (see hard, Plate dense, III - M compact, through P). The other hard ores which are hard, extreme dense compact ext reme are are the the hard ores which are dense, compact, with low magnetite martite, The iron minerals are porosity. These ores form porosity. The iron minerals are magnetite, martite, T).dense compact specularite (see Plate III - Q through hematite, and would fall hematite, and specularite (see Plate III -ofQhigh through T).oreThese form grade minedores amount A substantial the lump "semi-hard" the lump product. product. A substantial amount of high grade oreasmined would fall Terms such these two end types. somewhere in between tonnageS of rr somewhere in between these two end orebodies, types. Terms such as "semi-hard substantial Locally in the soft been used. have been used. Locally in the soft orebodies, appearance have substantial tonnages of macroscopic found which are similar in "hard" ores have been "hard" ores have been found which are similar in in macroscopic appearance Plate III. of the hard ore mines, as shown to the the hard hard ores ores of to the hard ore mines. as shown in Plate III. Soft Ores Ores Soft total production of the Marquette Iron Range, per cent of the Seventy per gradeRange, direct Seventy cent of the total production the of Marquette been the high Iron and Gwinn Districts, has of including the Cascade in the basal including the Cascade and Gwinn Districts, has for been the high theofmost part,grade direct The ores occurred, shipping type of soft ore. be asinthick as shipping type of soft ore.iron_formation. The ores occurred, the most the basal Thesefor deposits maypart, of the Negaunee portion The lateral extent. portion of the Negaunee iron-formation. These deposits may be as thick as the bedding, and have considerable Z60 feet, feet, normal normal to 260 to the bedding, and have considerable lateral extent.bounded The and in fault structures found in the synclineS orebodies are generally north-south section lookorebodies are generally found in the synclines and in fault structures bounded along at least one side. Figure 6 is a by basic dikes Negaunee showing a by basic dikes along at least one side.side Figure is a of north-south section look­ of the6 City through the eastern ing west west passing passing through ing theineastern side of the City of Negaunee showing a this vicinity. variety of ore occurrences variety of ore occurrences in this vicinity. which are chimneys of Locally the soft ores are found in "ore pipes" of the ironLocally the soft ores are found incutting "ore pipes" which are chimneys of the stratification distance vertically, ore extending some and are ore extending some distance vertically, cutting the stratification of the iron­ ZOO to 300 feet across generals these ore pipes are In general, formation. In iron_formation. formation. theseofore are dikes 200 to cutting 300 feet and are theacross twopipes or more at the intersection localized phosphorus content localized at the intersection of two or more the iron-formation. alsodikes by itscutting low type of ore has been characterized This This type of ore has been characterized also by its low phosphorus content ground." and by "heavy "heavy ground. and by It the large intrusive sills The other major type of soft ore occurs on some sills of the The other major type of soft ore occurs on soft the large intrusive These ores were part of the iron_formation. near the upper distribution near the upper part of soft were some of the The ore is ores of irregular in the theiron-formation. Ishpeming area. These first to to be be exploited exploited in locality in which first theand Ishpeming area. The ore is of irregular distribution its thickness. The principal as to its occurrence both of the Ishpeming toward the axis both as to its occurrence and its the principal locality in which souths.of The orebodieS were found is to thicknes these these orebodies were found is to the south of Ishpeming toward the axis of the I I I I I I I �29 29 Marquette Range Range synclinorium. synclinorium. We Marquette We do do not not have have any any mines mines operating operating in in this this type of of are ore occurrence occurrence at type at this this time, time, although although around around the the turn turn of of the the century century It is is interesting this was an important important ore ore source. this was an source. It interesting to t01 note note that that these these soft soft structural ores, lying sheets, are ores, lying on on the the metadiabase metadiabase sheets, are limited limitedby by the the same same structural In general, general, the controls as controls as the the ore ore lying lying on on the the footwall footwall contact. contact. In the ores ores were were high in in iron high iron content content and and low low in in phosphorus phosphorus and and sulphur. sulphur. A sizable sizable tonnage of soft soft ore ore in A tonnage of in Ngaunee Negaunee is isimpregnated impregnatedwith with gypsum. gypsum. The gypsiferous ores analyses range 2 to Sulfur analyses Sulfur range from from0.0.2 to over over 3. 3. 0%. The gypsiferous ores occur occur at at cutting across the bedding of definite elevations (near the present sea level) definite elevations (near the present sea level) cutting across the bedding of iron formation. the ironthe Ores Hard Ores The hard hard ores of the the total total production The ores amount amount to to 20% 20% of production to to date. date. Most Most of of them are found in the uppermost portion of the Negaunee iron-formation and them are found in the uppermost portion of the Negaunee iron-formation and ores were immediately below the Goodrich formation contact. immediately below the Goodrich formation contact. The The ores were made made up up hematite, and of hard, hard, compact of compact to to specular specular hematite, andmagnetite magnetite(see (seePlate PlateIll). III). AccesAcces­ the ore may include include garnet garnet and sory minerals may and tourmaline. tourmaline. The The footwall footwall of of the ore iron-formation of !jaspilite?! may be be unoxidized unoxidized iron-formation, iron-formation, oxidized may oxidized iron-formation of the the" jaspilite" hanging wall wall may may consist consist of type, or the intrusive intrusive sills. sills. The type, or one one of of the The hanging of material material less commonly of the the Goodrich Goodrichformation, formation, oxidized oxidized iron-formation iron-formation or or - less commonly -­ of The orebodies orebodies are are frequently material. The intrusive material. intrusive frequently related related to to intrusive intrusive dikes. dikes. features are noted in the hard ores as well as in Replacement features are noted in the hard ores as well as in the Replacement the soft soft ores. ores. are frequently related to The outlines hard orebodies The outlines of hard orebodies are frequently related to structural structural features features as folds, folds, faults faultsand anddikes. dikes.Some Some hard hard ores ores are are also such as such also found found locally locally the soft soft orebodies. orebodies. near the base of of the theNegaunee Negaunee iron-formation, iron-formation, as near the base as aa part part of of the basal Goodrich material consists consists of conglomerates, argillites, The basal The Goodrich material of conglomerates, argillites, Locally a conglomerate may contain a sufficient slates and quartzites. slates and quartzites. Locally a conglomerate may contain a sufficient amount amount of ore, ore, either or the the matrix matrix material, of either in in the the form form of of pebbles pebbles or material, to to be be merchantable merchantable The intrusives intrusives which cut the the hard hard ore for mining. for mining. The which cut ore are are quite quite frequently frequently confused confused Both materials are fine-grained and highly with the the argillite argillite of with of the the Goodrich. Good'rich. Both materials are fine-grained and highly altered, making altered, making identification identification difficult. difficult. Presently there there are hard ore Presently are two two active active hard ore properties properties in in the the Range: Range: the the Cliffs Cliffs Shaft and andthe theChampicm ChampionMines. Mines. Former Former major now Shaft major hard hard ore ore properties, properties, now include the the Lake Lake Superior Superior Hard Hard Ore, inactive, include inactive, Ore, Humboldt, Humboldt, Republic, Republic, Michigamme Michigamme The Cliffs Shaft Mine structure is a westerly and Greenwood Mines. and Greenwood Mines. The Cliffs Shaft Mine structure is a westerlyplunging plunging The Greenwood syncline, having syncline, having a a cross-fold cross-foldunder underthe thetown town of of Ishpeming. Ishpeming. The Greenwood and Champion ChampionMines, Mines,by bycontrast, contrast, are and are located located on on the the south south limb limb of of the the synsyn­ These hard orebodies have a definite westward plunge and extend clinorium. clinorium. These hard orebodies have a definite westward plunge and extend At Republic Republic Mine Mine the the ores ores some distance distance below below the the present present land some land surface. surface. At were mined some 4, 4,000 feet along along the the plunge, plunge, or or 2,800 2,800 feet feet vertically. were mined some 000 feet vertically. �30 Concnetrating Ores Concnetrating Ores properties in Michigan was the the modern beneficiating The first of grade concentrates producing high in The first of the property modern beneficiating properties Michiganspecularitic was the has been This Humboldt Mine. consists of the The crude ore Humboldt Mine. This property has been producing high grade concentrates Concentration is and peUets since 1960. since 1954, Negaunee. since 1954, and pellets since 1960. consists of the specularitic theThe topcrude of theore iron-formation at production magnetic cherty having started magnetic cherty ironformation at the top of the Negaunee. Concentration is Mine is similar, Republic The and specularitic flotation. by froth the specularitic by froth flotation. The Republic Mine is similar, having started production L illustrate 1956. Plates II- K and Both Humboldt and Republic of pellets pellets in crude the ores. of iniron-formations 1956. Plates II· K and L illustrate specularitic and specularitic which are the magnetitic iron- formations whichofare magnetitic thegrade crudeores. ores. Both Humboldt and Republic high formerly producers were formerly Mines were Mines producers of high grade ores. silicate cherty ironmagnetitic carbonate mining a Concentration is iron-formation. The Empire Mine The Empire Mine is mining a magnetitic carbonate silicate cherty iron­ of the Negaunee lower section I, and J H, formation in the lower and Plates II-G, formation in theseparation. section of the Negaunee iron·formation. Concentration Plates I-D, E and F, is by is by magnetic magnetic separation. Plates I-D, E and F, and Plates II-G, H, I, and J illustrate some of this crude ore. illustrate some of this crude ore. Genesis of the_High Grade Ores Genesis of the High Grade Ores on the origin of the high grade universal agreement There has been no also, regarddifference in opinion, There are There has beenIron no universal agreement on the ongm of the high Range. opposed hard ores as grade the Marqiette ores of enrichment of the ores of the Marquette Iron Range. There are difference in opinion, also, regard­ timing of the and the ing both the method and discussed first. ing both the method the timing of the enrichment of the hard ores as opposed The soft ores are to the the soft ores. The to soft ores. soft ores are discussed first. Soft Ores hypotheses of the origin of the soft to most are common Certain features Soft Ores ores: ores: Certain features are common to most hypotheses of the origin of the soft iron-formation was important in permitting Fracturing of the silica and 1. iron-formation, to remove primary 1. Fracturing of the ironformation was important in permitting oxidize the access for water to of the silica. to remove silica and much access for water to oxidize the primary ironformation, the iron which replaced to transport to transport the iron which replaced much of the silica. solutions that removed presumably by the same have been The silica was silica 2. remnants of theby removed 2. The silica was removed presumably the same carried solutions that Inasmuch as no to the carried the iron. Inasmuch as no remnants that it was it is assumed carried the iron. Marquette of the removed silica have been Range, identified on the identified on the Marquette Range, it is assumed that it was carried to the ancient surface. ancient surface. and Bijiki ironfound only in the Negaunee The orebodies are altered and en3. mayNegaunee have been in the column 3. The orebodies are found only in the and iron­ found has been formations. Other rock types tonnage of high grade soft oreBijiki formations. Other rock types in the column may have been altered and en­ but no significant riched locally, numbers. riched locally, but geologic no significant tonnage of high grade soft ore has been found other in any of the in any of the other geologic numbers. the and on found lying on the Siamo footwallThese orebodies are less The soft uopen_facinght structures. 4, or 4. The soft orebodies are found lying on the Siamo footwall and on the in trough-like" metadiabase sheets metadiabase sheets in "trough-like" or "open-facing 11 structures. These less — �• • 31 31 permeable members members may may be be folded foldedandlor and/or faulted, faulted, but but appear appear to to act act as as "bottom" 'bottom" permeable surfaces. surfaces. major structural 5. The major structural controls controls of of folding, folding, faulting faulting and and most most intrusives intrusives Some intrusives and, according to to some some observers, were pre-ore. were pre - ore. Some intrusives are post-ore and, observers, faulting and and possibly possibly some some of of the the folding folding are are post-ore. some faulting post-ore. Few of of the the deeper deeper major Few major orebodies orebodies extend extend to to ledge ledge surface surface up up the the dip dip or up or up the the pitch, pitch, but but the the oxidation oxidation of of the the iron-formation iron-formation adjacent adjacent to to the the orebodies orebodies definitely does definitely does extend extend to to ledge. ledge. 6. Any hypotheses must must account account for for the 7. Any hypotheses the circulation circulationof ofa. a. hydraulic hydraulic system which extends to to depths depths of of over over 6, 000feet feet from from present present surface. system which extends 6, 000 surface. Most soft soft ores ores contain amounts of of clay clay mineral mineral assemblages 8. Most contain varying varying amounts assemblages that temperatures higher that indicate indicate temperatures higher than than normal normal ground-water ground-water temperatures. temperatures. The relations relations of these clay minerals to The of these clay minerals to the the iron iron minerals minerals is is not not conclusive. conclusive. They are are not They not established established as as definitely definitely contemporaneous. contemporaneous. Cold Water Origin Cold Water Origin Monograph28 28reviewed reviewedthe thevariolJ.s varioiis ideas ideas of of soft soft ore Monograph ore origin origin and and advanced advanced agent of of oxidation, oxidation, solution solution of of silica, silica, and the basic basic cold the cold water water hypothesis. hypothesis. The The agent and The iron which replaced introduction of of iron iron was was oxygen-bearing oxygen-bearing ground-waters. ground-waters. The iron which replaced introduction In 1935, the silica silica was the was derived derived from from other other portions portions of of the the iron-formation. iron-formation. In 1935, C. C. K. K. Leith et Leith et al al (pages (pages 2424- 26), 26), modified modified the the hypothesis hypothesis by by proposing proposing that that the the chemical chemical activity of the circulating circulating ground-waters activity of the ground-waters had had been been increased increased by by heating heating due due to to They also observed that oxidation is found Keweenawan lavas and intrusives. Keweenawan lavas and intrusives. They also observed that oxidation is found at at greater depth be expected expected of of normal normal ground-water ground-water circulation greater depth than than would would be circulation even even under under mountainous mountainous conditions. conditions. Hydrothermal Origin Hydrothermal Origin In 1926, J. W. In 1926, J. W. Gruner Gruner proposed proposed aa hydrothermal hydrothermal origin origin for for Vermilion Vermilion Iron Iron In 1929 he extended extended this this hypothesis hypothesis to to the Range ores. ores. In Range 1929 he the formation formation of of high high grade grade Gruner's hypothesis stressed the ores throughout the Lake Lake Superior Superior region. ores throughout the region. Gruner's hypothesis stressed the The thermal conditions would greater dissolving hot water water on on silica. silica. The thermal conditions would greater dissolving power power of of hot Objections were were raised raised to stimulate hydraulic stimulate hydraulic circulation. circulation. Objections to the the idea idea that that these these waters were juvenile on the basis that most of the Lake Superior intrusives waters were juvenile on the basis that most of the Lake Superior intrusives were were his "modified theory' basic and and therefore thereforerelatively relatively"dry". 'dry'. In basic In 1937, 1937, he he published published his "modified th eory ll which proposes that the ore-forming fluids were principally meteoric waters which proposes that the ore-forming fluids were principally meteoric waters which had hadbeen beenheated heatedby byigneous igneousemanations. emanations. He also0 that which He conceded conceded als that not not all all of of Gruner explained the observed the introduced iron came from these emanations. the introduced iron carne from these emanations. Gruner explained the observed differences in in resultant resultant ore differences ore types types as as being being related related to to differences differences in in primary primary ironiron­ formation, structural formation, structural conditions, conditions, temperatures temperatures of of the the water, water, and and relative relative quantities quantities of of emanations. emanations . �32 Summary on Soft Ore Ore Genesis Summary on Soft Genesis dissimilar. Aside from The theories theories of Gruner are are not The of Leith Leith and and Gruner not too too dissimilar. Aside from is almost the same, the Gruner's "emanations," the ore-forming process Gruner's "emanations," the ore-forming process is almost the same, the The geometry of the soft orebodies differences being only aa matter matter of differences being only of degree. degree. The geometry of the soft orebodies complicated plumbingH of the hydraulic systems. is significant in stressing stressing the is significant in the complicated "plumbing" of the hydraulic systems. Some the "open" "open' side structural traps. Many of of the the orebodies orebodies are are found Many found on on the side of of structural traps. Some surface. have no no apparent apparent relationship relationship to have to the the present present surface. Recent microscopic work by also. Recent microscopic work by The mineralogy The mineralogy may may be be significant significant also. in the the soft soft ores, ores, as shown in Plate Tsu-Ming Han has has found found appreciable appreciable martite martite in TsuMing Han as shown in Plate soft orebodies are essentially The semi-hard 0 and III. a III. and P. P. The semi-hardores oresfound found in in the the soft orebodies are essentially contains traces traces to appreciable martite, some some of which contains up of equigranular martite, made up made of equigranular of which to appreciable martitization was contemporaneous remnants, Han magnetite remnants. magnetite Hansuggests suggeststhat that the the martitization was contemporaneous the soft with the soft ore are formation. formation. clay minerals suggest temperature Lastly, as Lastly, as pointed pointed out out above, above, some some of of the the clay minerals suggest temperature The writer noted dickite and chrome higher than those of normal ground-waters. higher than those of normal ground- waters. The writer noted dickite and chrome in 1945, as described by Gruner (1946). nontronite in in the ores in nontronite the Marquette Marquette Range Range ores 1945, as described by Gruner (1946). (non-definitive), (l96Q)describes describes dickite, dickite, kaolinite The paper paper by Bailey and The by Bailey and Tyler Tyler (196P:L kaolinite (non-definitive), clinochrysotile, muscovite, lizardite, lizardite, clinochrysotile, nacrite, talc, nacrite, talc, pyrophyllite, pyrophyllite, 1M 1M and and 2M1 2M 1 muscovite, trioctahedral chlorite, dioctahedral and trioAl-serpentine, dioctahedral AI-serpentine, dioctahedral and and trioctahedral chlorite, dioctahedral and trio­ and regular inter stratifications of ctahedral montmorillonite, skite, and regular inter stratifications ctahedral montmorillonite, palygor palygorskite, of non-clay minerals apatite, alunite, chloritemontmorill0flite, as chlorite-montmorillonite, as well well as as the t'he non-clay minerals apatite, alunite, and Tyler state on pages 155 and rhodochrosite. Bailey gypsum, clacite, clacite, and gypsum, and rhodochrosite. Bailey and Tyler state on pages 155 and by field data and 156, "In "In summary, summary, both 156, both the the synthesis synthesis data and the the evidence evidence provided provided by- field in the world suggest that the clay relationships for for similar relationships similar clays clays elsewhere elsewhere in the world suggest that the clay is primarily the result of hydromineral assemblage iron ores mineral assemblage in in the the Michigan Michigan iron ores is primarily the result of hydro­ intimate association of the clay minerals with the . The intimate . . thermal activity. thermal activity. The association of the clay minerals with the differences may also extend to the origin of the ore ore suggests these differences iron are iron suggests that that these may also extend to the origin of the ore itself.''II itself. chlorite zone of metaAs noted As noted earlier, earlier, the the soft soft ores ores are are found found in in the the chlorite zone of meta­ morphism. morphism. Hard Ores Hard Ores the soft ores. There may be two hard ores ores are are more more complex The hard The complex than than the soft ores. There may be two Significant features are: origin and and times times of formation. or more more modes or modes of of origin of formation. Significant features are: 1. formation. 2. 2. under less under less 200 feet of the Negaunee ironThe hard upper 200 The hard ores ores are are found found in in the the upper feet of the Negaunee iron­ the Goodrich contact. Most commonly, the hard ore is at Most commonly, the hard ore is at the Goodrich contact. such as anticlinal flexures, The hard The hard ores ores are are in in 'closed" ilclosedll structures, structures, such as anticlinal flexures, permeable rocks. permeable rocks. �33 33 3. Common ly, the adjacent to ore is is the the "oxide"oxide­ 3. Commonly, the iron-formation iron-formation adjacent to the the ore facies" jaspilite, the reddish, pinkish pinkish banded banded chert the miners miners once once called called facies" -- jaspilite, the reddish, chert the "hard "hard ore ore jasper." jasper." 4. Hard ores tend to little to to no no Hard ores tend to have have equigranular equigranular iron iron minerals, minerals, little porosity, few vugs vugs and and no porosity, few no botryoidal botryoidal textures. textures. The magnetite magnetite ores ores are masses in 5. The are commonly commonly in ln discontinuous discontinuous masses in specularitic iron-formation specularitic iron- formation and and ore, ore. The The chert chert associated associated with with magnetite magnetite ore ore is gray In some some areas areas magnetite is gray rather rather than than reddish. reddish. In magnetite orebodies orebodies and and magnetitic magnetitic iron-formation traversed by by quartz quartz veins veins containing containing tourmaline, very coarse coarse iron-formation are are traversed tourmaline, very specularite and crystalline siderite specularite and crystalline siderite with with minor minor pyrite, pyrite, sphalerite sphalerite and and chalcopyrite. chalcopyrite. Frequently the 6. Frequently the hard hard ores ores extend extend down down into into the the iron-formation iron-formation as as "droppers,"" appearing "droppers, appearing to to have have been been formed formed by by replacing replacing the the iron-formation. iron- formation. Locally, at contact, some 7. Locally, at the the Goodrich Goodrich contact, some massive massive hard hard ore ore contains contains detrital quartz which suggests that the original iron minerals may have detrital quartz which suggests that the original iron minerals may have had had a a similar detrital similar detrital origin. origin. Above the the hard hard ores ores and 8. Above and at at the the base base of of the the Goodrich, Goodrich, one one finds finds conglomerates of conglomerates of varying varying thickness. thickness. The The conglomerate conglomerate may may contain contain much much detrital detrital chert or chert or quartz, quartz, and and some some ore ore fragments fragments that that appear appear to to have have been been ore ore at at the the time time of deposition. deposition. of Dynamic metamorphism metamorphism has has been been responsible responsible for 9. Dynamic for the the formation formation of of the the specular hematite in the ores and adjacent iron-formation. specular hematite in the ores and adjacent iron-formation. 10. 10. No hard hard ore ore is in the the Bijiki Bijiki iron-formation. No is found found in iron-formation. Hypotheses of of Hard Hard Ore Ore Origin Hypotheses Origin Monograph 52, 52, pages pages 278278-279, Monograph 279, outlines outlines a a possible possible origin origin and and time time sequence sequence upper portion portion of iron-formation was The upper of ore ore formation. of formation. The of the the Negaunee Negaunee iron-formation was exposed exposed to weathering weathering and and concentration concentration (mechanical (mechanical classification?) classification?) to to to produce produce an an iron iron Burial by rich product. rich product. Burial by the the Goodrich Goodrich and and later later formations formations followed. followed. After After the the deposition of of the the Michigamme Michigamme formation, formation, the deposition the Animikie Animikie sediments sediments were were folded, folded, The metamorphism metamorphism associated associated with with the the structural structural deformafaulted and faulted and intruded. intruded. The deforma­ tion formed formed the the hard hard ores ores from tion from the the weathered weathered ores. ores. re-exposed the iron-formaPost-Keweenawan erosion re-exposed Post-Keweenawan the Negaunee Negaunee and andBijiki Bijiki iron-forma­ They were altered by ground-waters to form the soft ores, as outlined They were altered by ground-waters to form the soft ores, as outlined ores were earlier. Since the the soft soft ores were formed formed after after the the dynamic dynamic metamorphism, metamorphism, they they do not not display display the the specular specular hematite hematite and the hard hard ore. do and other other features features of of the ore. tions, tions. �J.' 34 I I The objection concept centers on on the the trweathered_surfaceu "weathered-surfacer! origin ongln objection to to this this concept for the hard necessary to to postulate postulate some some introduction introduction of of iron for all of the hard ores. It It is necessary to explain both of many many hard orebodies. orebodies. to explain both the the geometry geometry and and detailed detailed features features of This introduction of of iron must have have been been accomplished accomplished before or during during metameta­ This introduction iron must before or morphism. morphism. The school of of thought thought would much of The hydrothermal school wouldascribe ascribe much of the the hard ores to replacement of the iron-formation by high high temperature solutions. to temperature solutions. An Alternate Time Time Sequence Sequence The by the mining mlnlng companies, companies, and and the The continuing continuingresearch research each year year by mapping by Geological Survey, add materially to to our our informainforma­ current mapping by the the U. U. S. S. Geological Survey, add tion More age-dating age -dating will will be be done done to to tion on on the the geology geology ofofthe the Marquette MarquetteRange. Range. More help time - sequences of of ore-formation. The The writer that aa help establish establish time-sequences writer believes that better understanding of the Clarksburg Clarksburg better understanding of the the relationship relationship of of the the metadiabases, metadiabases, the pyroclastics and the Penokean Penokean orogeny pyroclastics and orogeny will willalter alter the the classic classic time-sequence. This understand the the effects effectsof ofKeweenawan Keweenawan vulcanism. vulcanism. This will help us understand Other Ores of of Economic Economic Interest Other Interest Numerous gold, silver and and lead lead prospects prospects have have been been noted noted north north of of Numerous gold, silver Ishpeming The age of the is Ishpeming inin the the Pre-Animikie Pre-Animikie series. series. The age of the mineralization is thought M. Broderick Broderick(1945) (l945) who who described des cribed thought to to be be post-middle post-middle Animikie Animikie by by T. T. M. the gold occurrence occurrence at at the the Ropes Ropes Gold Gold Mine. Mine. AAtotal totalofof$703, $703,000 000 was was the major gold recovered this operation operation during during the the period periodof of1883 1883 to to 1897. 1897. recovered from this Significant amounts iron­ Significant amounts of of uranium uranium oxide oxide have have been been detected detected in in the the ironformation on the Marquette Marquette Range Range and and in in the the Gwinn Gwinn District. rich formation on District. ThoriumThorium-rich monazite noted in Goodrich quartzite and conglomerate conglomerate of of the the monazite has has been noted in the Goodrich quartzite and Cascade District, Cascade Vickers (1956). (l956). District, as as described described by Vickers Acknowledgment Grateful acknowledgment acknowledgment is Grateful is made colleagues in in The The made to to the the writer's writerts colleagues Cleveland-Cliffs Iron Company, Cleveland-Cliffs Company and and Laughlin Laughlin Company, Inland Inland Steel Steel Company and Jones Jones and Steel Corporation, and Steel and their their managements, for assistance assistance in in preparing preparing this managements, for summary. The summary. The writer writerparticularly particularlyappreciates appreciatesthe thecooperation cooperationand and contributions contributions by the the U. by U. S. S. Geological Geological Survey Survey and and the the Michigan Michigan Geological Geological Survey. Survey. Special I ~ II I I I I I I I I J J J �35 thanks are are due to Dr. Dr. Jacob thanks due to Jacob Gair. Gair. SELECTED SELECTED B]BLIOGRAPHY BIBLIOGRAPHY Adler, Joseph Adler, Joseph L., L., (1935), (1935), "Stratigraphic "StratigraphicZones Zones in inthe theNegaunee Negaunee Iron-Formation Iron-Formation of Marquette Marquette County, County, Michigan" Michigan" The The Journal Jburnal of of of Geology, Geology, Vol. Vol. XLIII, XLIII, pp. 113-132 pp. "Correlation and and Structure Structure of of the the Precambrian Precambrian Forma­ FormaR. C. (1914), "Correlation Allen, R. C.,, (l914), tions of Iron Bearing Bearing District tions of the the Gwinn Gwinn Iron Districtof ofMichigan" Michigan" Journal JournalofofGeology, Geology, Vol. XXII, pp. 560573 Vol. XXII, pp. 560=573 Anderson, Anderson, G. G. J. J. and andHan, Han, Tsu-Ming, Tsu-Ming,(1956), (l956), "The "TheRelationship Relationship of of Diagenesis, Diagenesis, Metamorphism, and to the the Concentrating Concentrating Character­ CharacterMetamorphism, and Secondary Secondary Oxidation Oxidation to istics of the Negaunee Iron-Formation of the Marquette Range" istics of the Negaunee Iron-Formation of the Marquette Range" Geological Geological Exploration pp. 63-69, 63-69, Institute Exploration (MCM&T) (MCM&T) pp. Institute on on Lake Lake Superior SuperiorGeology Geology "Mineral Notes (1940), "Mineral Ayres, V. Ayres, V. L. L.,, (l940), Notes from from the the Michigan Michigan Iron Iron Country" Country" The American American Mineralogist, Mineralogist, pp. The pp. 432-434 432-434 S. W. and Bailey, S. Bailey, and Tyler, Tyler, S. S. A., A., (1960), (l960), "Clay "Clay Minerals Minerals Associated Associated with with the the Geology, Vol. Vol. 55, Superior Iron Iron Ores " Economic Lake Superior Ores" Economic Geology, 55, pp. pp. 150-175 150-175 Boyum, Burton Burton H., H., (1945), Boyum, (1945), "Geological "Geological Exploration Exploration on on the the Marquette Marquette Range" Range" Mining CongressJournal, Journal, pp. Mining Congress pp. 29-33, 29-33, 36 36 Boyum, Burton Burton H., H., (1954), the Marquette Marquette Iron Iron Range~' Range' Boyum, (l954), "The "The Geology Geology of of the Fourth Mining GeologySymposium, Symposium,University University of of Minnesota, Minnesota, pp. pp. 3-8 Fourth Mining Geology 3-8 G. J.., "Primary Features Anderson, G. Boyum, B. B. H. Boyum, H.,, Anderson, J., and and Han, Han, T-M, T-M, (1955), (l955), "Primary Features of the the Negaunee Iron-Formation" Fifth of Negaunee Iron-Formation" FifthMining MiningGeology Geology Symposium, Symposium, University University of of Minnesota Minnesota Geology of of the the Marquette Marquette Iron Boyum, Burton Boyum~ Burton H. H. (1962), (1962), "The Geology Iron Range" Range" Geology of the the Lake Lake Superior Superior Region, Geology of Region, Michigan Michigan College College of ofMining Mining and Technology, Technology, pp. pp. 41-50 and 41-50 Broderick, Broderick, T. T.M. M.(1945) (l945)"Geology "Geologyof ofthe theRopes Ropes Gold Gold Mine, Mine, Marquette MarquetteCounty, County, Michigan" Economic EconomicGeology, Geology, VoL Vol. XL, XL, pp. Michigan" pp. 115-128 115-128 Southern Complex Complex of Dickey, R. MM (1938) Dickey, (l938) "The "The Ford Ford River River Granite Granite of of the the Southern of Michigan" Journal Geology, Vol. 1-335 Michigan" Journal of of Geology, VoL 46, 46, pp. pp. 32 321335 (1961) rrprehistoric "Prehistoric Copper Drier, R. R. W. W. and DuTemple, DuTemple, 0. Drier, O. J. J. (l961) Copper Mining Mining in in the the Lake Lake Superior Region", published published privately privately Huronian) Rocks of Animikie Animikie (formerly (formerly Huronian) Fritts, C. E. Fritts, E. (1964) (l964) "Stratigraphy of Rocks of Teal Lake, Negaunee, Michigan" Transactions, Tenth Annual East East of Teal Lake, Negaunee, Michigan" Transactions, Tenth Annual Instituteon onLake Lake Superior Superior Geology Geology Institute J. E., Thaden, R. E., and Jones, Gair, Gair, J. E., Thaden, R. E., and Jones, B. B. F. F.(1961) (1961) "Folds "Folds and and Faults Faults in in the Eastern Eastern Part Partof ofthe theMarquette MarquetteIron IronRange, Range, Michigan" Michigan" Geological Geological Survey Research, Research, pp. Survey pp. 76-78 76-78 Gair, J. and Jones, B.B.F. F. (1961) "Silicification Gair, J. E., E.,Thaden, Thaden,R. R.E., E., and Jones, (1961) "Silicificationof of the the Kona Dolomite Dolomiteininthe theEastern Eastern Part Part of Kona of the the Marquette Marquette Iron Iron Range, Range, Michigan" Geological GeologicalSurvey SurveyResearch, Research, pp. Michigan" pp. 78-80 78-80 Gair, J.J. E.E.(1964) Gair, (1964) Structures Structuresin inthe theEastern EasternPart Partofofthe theMarquette MarquetteSynclinorium" SynClinorium" Transactions, Tenth Annual Institute on Lake Superior Geology Transactions, Tenth Annual Institute on Lake Superior Geology �36 36 Gair, J. (1964) uGeologic Gair, J. E. E. and andWier, Wier,K. K.L.L. (1964) "Geologicand andMagnetic Magnetic Survey Survey of of a a File, U.S.G.S. Part of Part of the the Palmer Palmer Quad., Quad., Michigan' Michigan" Open Open File, U. S. G. S. Goldich, S. S. S., S., and Goldich, and Nier. Nier, Baadsgaard, Baadsgaard,Hoffman Hoffmanand andKrueger Krueger(1961) (1961) II'The The Precambrian PrecambrianGeology Geology and andGeochronology Geochronology of of Minnesotat Minnesota" Bulletin 41, Bulletin 41, Minnesota Minnesota Geologica.l Geological Survey Survey Hydrothermal Leaching Leachingofof IIron Ores of (1937) "Hydrothermal John W. , (1937) Gruner, John Gruner, W., ron Ores of the the Modified Theory" Theory" Economic Economic Geology, A Modified Superior Type - A Lake Superior Lake Geology, Vol. XXXII, pp. 121-130 (1946) "Dickite and Chromium Silicate J, W. (1946) Gruner, J. "Dickite and Chromium Silicateininthe the Iron Iron Ores Ores of of Marquette and and Gogebic Gogebic Ranges, Ranges, Michigan' the Marquette Michigan" America.n American Mineralogist, Mineralogist, Vol. 31, 31, p. Vol. p. 195 195 Han, Tsu-Ming (1962) 'Diagenetic Han, Tsu-Ming (1962) "Diagenetic Replacement Replacement in in Ore Ore of of the the Empire EmpireMine Mine of Northern Northern Michigan, Michigan, and of and Its I ts Effect Effect on onMetallurgical MetallurgicalConcentration" Concentration" Paper presented Paper presented at at Institute Instituteon onLake LakeSuperior SuperiorGeology Geology Upper Huronian Sedimentation in Portion of Hase, D. Hase, D. H. H. (1957) (1957) "Upper Huronian Sedimentation in aa Portion of Trough, Michigan" Journal ofGeology, Geology,pp. pp.561561574 Marquette Trough, Marquette Journal of 574 from Ishpeming ((Covers Covers from! shpeming to to Champion) Harold L. Soft Iron Iron Ores Ores of Michigan" James, L. (1953) (1953) "Origin "Originof of the the Soft of Michigan" James, Harold pp. 726-'728 Vol. 48, Economic Geology, Vol. 48, pp. 726-728 "Sedimentary Facies of Iron-Formation" Harold L. James, Harold L. (1954) ( 1954) "Sedimentary Facies of I ron-Formation" 235293 Geology, Vol. Economic Economic Vol. 49, 49, pp. pp. 235-293 James, Harold PreJames, Harold L. L. (1955) (19 55) "Zones "Zonesof of Regional Regional Metarrorphism MetanV:::!t"phism in in the the Pre­ Michigan' Bulletin, Geological Society Cambrian of Northern Cambrian of Michigan" Bulletin, Geological Society of of Vol. 66, 66, pp. pp. 1455-1487 America, Vol. America, James, Harold ofPre-Keweenawan Pre-Keweenawan Rocks James, Harold L. L. (1958) (1958) "Stratigraphy "Stratigraphy of Rocks in in of Northern Michigan" Professional Paper 314-C (44 pp) parts of Northern Michigan" Professional Paper 314-C (44 pp) U. S. U. S. Geological Geological Survey Survey Isotope James, Harold L. and Clayton, James, Harold L. and Clayton, R. R. N. N. (1962) (l962) 'Oxygen "Oxygen Isotope in Metamorphosed ron Formations Formations of fractionation in fractionation Metamorphosed II ron of the the Lake Lake Superior Region and in Other IronRich Rocks' Buddington Superior Region and in Other Iron-Rich Rocks" Buddington Volume, Volume, Geological Society Society ofofAmerica, America, pp. Geological pp. 217-239 217- 239 Lamey, Carl "The Palmer Lamey, Carl A. A. (1935) (935) "The Palmer Gneiss' Gneiss" Bulletin, Bulletin, Geological Geological Society Society 46, pp. pp. 1137-1162 l1371162 of America, Vol. of Vol. 46, Lamey, Carl 'Republic Granite Granite or orBasement Basement Complex" Complex" Lamey, Carl A. A. (1937) (1937) 'IRepublic Journal of Geology, Vol. XLV, pp. 387510 Journal of Geology, VoL XLV, pp. 387-510 Leech, G. G. B., C. H. H. and and Wanless, Wanless, R. R. K. Leech, B., Lowdon, Lowdon, J. J. A., A., Stockwell, Stockwell, C. K. Paper 63l7, (1963) "Age Determinations and Geologic Studies (1963) "Age Determinations and Geologic Studies" Paper 63-17, Geological Survey Survey of of Canada Canada Geological (1931) "Secondary 'Secondary Concentration Concentration of Lake Superior Superior Iron Iron Ores" Ores" C. K. Leith, C. Leith, K. (1931) of Lake Economic, Vol. 26, VoL 26, pp. pp. 274-288 274-288 C. K., K., Jund, Jund, R. R. J. J. and and Leith, Leith,A.A,(1935) (1935) PreCambrian Rocks Leith, C. Leith, l!Pre-Cambrian Rocks of of 184 (34pp) USGS Paper the Lake Superior Region" Professional the Lake Superior Region" Profession2.l Paper 184 (34pp) USGS Oxidation to to the the Origin The Relation Mann, Virgil Mann, Virgil I. 1. (1953) (1953) t: The Relation of of Oxidation Origin of of Soft Soft Iron Iron pp. 25l281 Vol. 48, of Michigan' Economic Geology, Ores 'l Ores of Michigan Economic Geology, Vol. 48, pp. 251-281 Stephen (1942) (1942)"Iron "Iron Ranges Ranges of of the the Lake Lake Superior Superior Di.strict District"li Royce, Stephen Royce, Ore Deposits Deposits as as Related Related to to Structur2.l Structural Features Features edited Ore edited by by W. H. Newhouse, pp. 54-63 W. H. Newhouse, pp. 54- 63 2icGeoiar, Economic Geology, �37 37 Snelgrove, A. K., K., Seaman, Seaman, W. A., andAyers, Snelgrove, A. and Ayers, V. V. L. L. (1944) (1944) Minerals Investigations Baraga Strategic Minerals Investigations in in Marquette Marquette and and Baraga Counties, 1943" Progress Report Number Ten, Michigan Counties, 1943" Progress Report Number Ten, Michigan Geological Geological Survey Survey (69 (69 pp) pp) Stockwell, Stockwell, C. C. H. H.(1962) (1962)HA riA Tectonic Tectonic Map Map of of the the Canadian Canadian Shield" Shield rl Shield" Special pp. 6-15 pp. 6-15 in in "The rlThe Tectonics Tectonics of of the the Canadian Canadian Shield" Special Publication No. 4, The Publication No.4, The Royal Royal Society Society of of Canada Canada Stone, John Stone, John G. G. and and Cumberlidge, Cumberlidge, John JohnT. T.(1964) (1964)"Geology "Geology of of the the Groveland Orebody, Groveland Orebody, Iron Iron Mountain, Mountain, Michigan" Michigan" A.I. A;r. M. M. E. E. 0. and Zinn, Justin (1930) "Report on a Portion Swanson C. Swanson, O. and Zinn, Justin (1930) "Report on a Portion of of the the Marquette Range Range Covered Covered by by the the Michigan Michigan Geological Geological Survey Survey in 1929" Geological Survey Survey (Mimeographed in 1929" Michigan Michigan Geological (Mimeographed -- 15 15 pp) Swanson, C, Swanson, C. 0. O.(1933) (1933)"Geology "Geology of ofthe the Marquette MarquetteRange" Range "Guidebook Guidebook 27 27 Lake Superior Superior Region, Region, International Congress, Lake International Geological Geological Congres s, pp. pp. 10-21 10-21 Tyler, Superior Soft Ores from Tyler, S. S. A. A.(1949) (1949) "Development II Development of of Lake Lake Superior Soft Ores from MetamorphosedIron-Formation Iron-Formation'" Bulletin, Metamorphosed Bulletin, Geological Geological Society Society of America, America, Vol. of Vol. 60, 60, pp. pp. 1101-1124 1101-1124 Tyler, S. StratiTyler, S. A. A. and andTwenhofel, Twenhofel, W. W. H. H. (1952) (1952) "Sedimentation "Sedimentation and and Stratigraphy of the Huronian of Upper Michigan" American Journal graphy of the Huronian of Upper Michigan" American Journal of of Science, Vol. Science, Vol. 250, 250, pp. pp. 1-27, 1-27, 118-151 118-151 Hise, C. Lake Van VanHise, C. R. R. and and Leith, Leith, C. C. K. K. (1911) (1911) "The "The Geology Geology of of the the Lake Superior Region" Monograph Monograph52, 52, U. U. S. S. Geological Geological Survey Survey (641 (641 pp) pp) R. C. Vickers, R. C. (1956) (1956) "Geology "Geology and and Monazite Monazite Content Content of of the the Goodrich Goodrich Quartzite, Palmer Quartzite, Palmer Area, Area,Marquette MarquetteCounty, County, Michigan" Michigan" U.S. Survey, Bulletin U. S. Geological Geological Survey, Bulletin 1030-F 1030-F Zinn, Justin of the the Portion Zinn, Justin (1931) (1931) "Geology "Geology of Portion of of the the Marquette Marquette Range Range between and Lake Lake Michigamme between Humboldt Humboldt and Michigamme Covered Covered by by the the Michigan Geological Survey Survey in Michigan Geological in 1930" 1930" Michigan Michigan Geological Geological Survey (Mimeographed Survey (Mimeographed -- 18 pp) pp) , �xj 1.a. 0 C-,. Cl) CD CD C,) 0 CD () CD I..'. JQ 0 C-,. C) I-i U) P II CD '-a. C)CD C)CD CD Cl) CD0 ,. 0 CD H0 I1 PC) CD pJ. 1rJ �Figure 2 - North Jackson Mine No. I Pit, 1860 �MARQUETTE IRON RANGE, MICHIGAN THE CLEVELAND-CLIFFS IRON COMPANY — + DEER L AKE 4 + JN A C- II5 14 Il I BUSH 4 J6, 9 7 r LOG LAKE 4 JiGLASS c II 4( 120 30 I '3 8 '5 48 29 'tAKE 26 29 / %L N LDM/NE 4K LAKE' ,,1 7 ——-.7_ — \35 32 36 34 SPRUCE &NW HEARILAKEJ 4430• —-' 8);q 10 I 2 ---1h 'CE Jj7y(LAE (/ '3 '4 15 18 4731 4( '—'{20 22.- 21 .. 20 24 .. -- LEGEND 34 tAlla lU1U111Ul I 8 1 7 ° 6 2I 35 TY '-" & lUc I 9' SANDSTONE, CONGLOMERATE DIABASE KEWEENAWAN INTRSOIVES, LAVA FLOWS, SANDSTONES S RA N IT ES BASIC MET/I— ISNEOSS 4 PAINT RIVER MOSTLY INTRUSIVE FOUND IN THE SOUTHWEST SF THE MARQUETTE RANGE GROUP BA RAG A MICHIGAMME GROUP l4 23 22 3 MI DDLE '5 I 46 '30 46 20 22 2R 26 28 ..I PEN LASE HEAD II :1 35 36 y rE 33 5805 29 27 IL 89.So• 32 - CLARKSBURS PYROCLASTICS GREENWOOD MAGNETIC MEMBER GOODRICH QUARTZITE, ARSILLITE, CONGLOMERATE NEGAUNEE IHON FORMUTION MENOMINEE PRE — CAMBRIAN (OIUMS-AJIBIIY GROUP 24 UPPER ARGILLITE, SRUYWACKE RIJIKI IRON FORMATION MIDDLE ARSILLITE, URUYWUCKE LOWER ARGILLITE, SLATE, SRAYWACKE 0 tRANT 33 JACOBS VILLE CAMBRIAN LATE •- j, LAKE 32 RECENT GLACIAL DEPOSITS QUATERNARY PAL EOZ OIC I 5 34 OF THE GEOLOGIC ;: h': 3V 3' PRINCIPAL DISTRICT COLUMN MODIFIED FROM U.S. GEOLOGICAL SURVEY ,• 25 26 27 0 CHOCO LAY UNDIFFERENTIATED IN URSILLITE, SRAYWACIYE CONTAINS SGSSE LAKE SLATE AJI 81 K QUARTZITE — T4IINTGTHICK WEWE GRAY SLATE — LOCALLY QUARTZTES , CONSLSMERATE KONG DOLOMITE — M'NOR QUARYZIYESILT!YE MESNARD IR SNFORMAT ISN QSARTZITE CONGLOMERATE, GRAYWACKE, ARKOSE FELSITE PORPHYRY EARLY WESTERN PSRTIONI SI AMO GROUP MONA MUD 20 TONALITE, GRANODIORITE SCHISTS, METASEDIMENTS, SNEISOES GREENSTONE, MASSIVE — ELLIPSOIDAL FELSITE, METABASALT 8 6 7\REI 48 26 E 1421 —-- 23 22 LL 2/ a :)uN -:S jACR DAM 26 25 26 27 '3 24 23 21 PETrICOATK 32 _r CKY E ROUND ALAKE 'I6 8 5 18 5 FIGURE 4 25 41 S7J I \ \\ AROUETr H I I • 5 l5 29 �MAR QUE TIE IRON RANGE MICHIGAN GENERAL IZED CROSS SECTION Nrn-S ONE MILE EAST OF WEST LINE OF R.26W FIGURE 6 LOOKING WEST S N TRACY MINE NEGAUNEE - MAAS ilpgu- /964- �FIGURE 7 GRAPH SHOWING RELATIVE THICKNESSES OF ANIMIKIE SEDIMENTS ON THE MARQUETTE RANGE LOOKING NORTH HUMBOLDT M I C HI GAM ME ENCHANTMENT LAKE ISHPEMING 3 m SW of Marquette EROSION 7,, / / / // U /// / / / / / / / // / 9 0 0 (9 (1) /7 4 — — LLJ— zl / / / — = (9 2 i: —--- 7 — —0—— — — 7 —- F- — — / / / — 7 7 —_ GO° 7 0. 0 0 (9 U U z * WEWE / 7 77 7 V / V 0 / / / (0 / c, I I / / / 4) / / I, I/ / 1/ z— / // 4 0 0 / 7 (9, / V V V 0 ,0 -J ,,,0 7- 'N I0 — KONA I —— — — +- ___(I)_ w -7 84S4L, — SLAMO — AJI8IK -I--I 400 400 FEET 800 200 Vertical Scale SEcT,0 UNDI FFERENTLATED Dl STRIBUTION Horizontal 8000 Scale - — 000 8000 FEET 6000 2 ' 24000 �t C') p with magnetite - che rt carbonate - silicate Chert-silicate containino carbonate and rnagnetie Magnetite lan-dna alternating Magnetite lamina alternating with magnetite-chertcarbonate -silicate Silicate -chert containing some carbonate Magnetite lamina alternating with silicate-carbonate Silicate -carbonate granules, various shades; chert, white D. Magnesium iron carbonate t '1 Thin section ZGUX Athens Mine A. Cherty Carbonate I-Fm. 0 n 0 0rt- Polished slab of Inn-Formation Natural scale S g roundmas s E. and F. Pol.Sec. lCUX B. Mag. Chloritic Ciastic I-Fm. C. Mag. Urunetitic Cherty I-Fm. Thin section i O X Empire Mine Thin section IGUX Republic Mine Coarse magnetite and quartz Grunetite, gray; chert, dusty granules with chioritic white: magnetite. black 1 0 I: CD �oi U) H I 0 C whitish gray; chert and quartz, dark gray Martite, white; magnetite, H. Same - Pol. Sec. 100X G. Martitic Cherty Clastic I-Fm. Natural size Cherty Goethitic I-Fm. Natural size Martite, white; goethite, gray; chert, dark gray; and pits, black J. Same - Pal. Sec. bOX I. gray; chert, dark gray Cherty I-Fm. Pal. Sec. 100X Hematite, white; magnetite, L. Magnetitic Specularitic K. Specularitic Cherty I-Fm. Pal. Sec. 100X - Hematite, white; chert, black U) oQ 0 0 0 (L çi �';! AAf fl grey. As N. 500x Hematite, white; and gangue and pores, dark A ;, soft hematite. Hematite white. Pci. sac. lOOx. i. Nather : : t: . e * .a: +1* ? •• Ø ''S — — —— — Pol. sec. bOx P. Mather hard rnartitic ore. K. Cliffs-Shaft Magnetite. Magnetite, greyih white; Martite, white; pore, black, hematite, white; gangue Pol. sec. lOOx. dark grey, and pit black. Fob. sec. lOOx I T. As S. Fob. sec. lOOx Hematite, greyish white; martite, white, gangue, dark grey. 0. Mather soft martitic ore. Q. Cliffs—Shaft hard hematite S. Cliffs—Shaft ore conglomerate. Hematite, white; and Martite, white, chert, Natural size. Magnetite, greyish white. dark Fob. sec. lOOx Hematite, greyish white. • V V I 0 0 CD p �GEOLOGY OF NEGAUNEE IRON FORMATION EMPIRE MINE AREA AND CASCADE DISTRICT 1000 000 2000 l0O0 GENERALIZED CROSS SECTION MINE AREA, SEC. 19, 47-26 E-W X-SEC. A-A' LOOKING NORTH EMPIRE 400 4?0 800 +1600 PM 0 0.01-1. 9 + 200 + 800 --(i_— 2 21122 201121 22 23 LEGEND I! GOODRICH QUARTZITE UNOX. IRON FORMATION OX. IRON DIORITE LOWER MIDDLE ANIMIKIAN E1 METASEDIMENTS OX. IRON FORMATION ARGILLITE ————-————-——-—-—--—————___._____.L0_____________ 30 EMPIRE INTRUSIVE P7 ROCLA ST IC CLASTIC SIAMO—AJIBIK FORMATION 28 CONC. PLANT 32 LATT MiNE 27 �OF GEOLOGY THE REPUBLIC MINE AREA PA ....\ 'A \\. f; r . ::..•1I. 55 N PIT GENERALIZED CROSS SECTION LdOKING A—A' N— E -dole'4t0 000 S 6 Ef FL AN AT tN Metasnd imentn I4ichipamnme Formation Nicacmoan, parmetiferoas aod amphibalitic nchints tdoadrick Formafian Qnartzites, metapraymacken and mica schists Negaannn Iron—Format Ion Coeplameratic iron tormatiar Spmcalar hematite — mapnotite cherty iron—formation Silicate iron—formation AJitik Formation lgnmaan Ojartzites, metapraymackas. feldnpathic pmmisnnn and mica nchintn ('I) *.ImtadioniteS & knph,bolites ftntly nralitic nub fepabi ic Camplen Pnrphynitin and epnipraenlar oraniton mith ainphitol iten. At leant in part represents pranitizod sediments Faa It Contact (appronimate) Strike and dip of tnddinp S Strike and dip of foliation tnrike and dip of jointing tntcrop area OPhIL, 19t3 - 4 3 — ���������������������THE CLEVELAND-CLIFFS IRON COMPANY O)MARQUETTE IRON RANGE, MICHIGAN GEOLOGIC COLUMN OF THE PRINCIPAL DISTRICT MODIFIED FROM U.S. GEOLOGICAL SURVEY RECENT GLACIAL DEPOSITS SANDSTONE, CONGLOMERATE S NA N IT ES BASIC META— IGNEOUS MOSTLY INTRUSIVE MARQUETTE RANGE FOUND IN THE SOUTHWEST OF THE UPPER ARUILLITE, URAYWUCKE BIJIKI IRON FORMATION MIDDLE ARUILLITE, GRAYWACKE CLURKSBURG PYROCLASTICU GREENWOOD MAGNETIC MEMBER LOWER ARSILLITE, SLATE, URAYWACKE QUARTZITE, ARUILLITE, CONGLOMERATE IRON FORMATION ISIAMO—AJIBIK UNDIFFERENTIATED ARGILLITE, GRAYWACKE SLATE — CONTAIN SAUUSELAK E IN WESTERN IR ONFORMAT ION QUARTZITE — THINTOTHICIIB EBBED GRAY SLATE — I. OCALLY QUARTZflEG DOLOMITE — ONOR 000RTZITE , CONGLOMEBAT SIL1IlE QUARTZ lIE CONGLOMERATE, GRAYWACKE, ARKOSE FELSITE PORPHYRY TONALITE, URANODIORITE GCHIDTU, METASEDIMENTS, GNEISSES GREENUTONE, MASSIVE — ELLIPSOIDAL FELSITE, METABASALT FIGURE 4 � 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, 1964 Description An account of the resource Institute on Lake Superior Geology. Ishpeming, Michigan. May 6-9, 1964. 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 1964 Contributor An entity responsible for making contributions to the resource J.E. Case Jacob E. Gair Crawford E. Fritts Stephen C. Nordeng A.K. Snelgrove J.T. Mengel W.W. Moorhouse Paul A. Lindberg Carl E. Dutton T.H. Nilsen John W. Trammell Chester O. Ensign Jr. M.W. Bartley J.M. Neilson Leonard W. Weis J. Allan Cain Kiril Spiroff R.E. Lubker Virginia L. Doane E.G. Pye V.G. Milne A.V. Heyl J.W. Hosterman W.E. Hall M.R. Brock John C. Green A.S. MacLaren S. Duffell Robert Patenaude Gerald Van Voorhis Lloyal Bacon Charles E. Karman William J. Hinze A.W. Schillinger G. Haure P.M. Hurley G.G. Stuffel 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/7338fb743a085a3636f695617419003d.pdf 469cd2492591ee36bab1d297d7b4d2d0 PDF Text Text �NINTH ANNUAL INSTITUTE ON LAKE SUPERIOR GEOLOGY University of Minnesota, Duluth May 2-3, 1963 PROGRAM Thursday Morning - May 2, 1963 Science Auditorium, University of Minnesota, Duluth 9:00 General Meeting of the Institute ............ Chairman, H. Lepp Secretary, D. H. Hase SESSION I Co—chairmen: J. C. Green, J. S. Owens 9:30 D. W. Pollock S. C. Nordeng: PRELIMINARY INVESTIGATION OF A PORTION OF THE NORTHERN COMPLEX, BARAGA Co., MICH. 9:55 George Moerlein: STRUCTURE AND STRATIGRAPHY OF THE KEWEENAWAN IN NORTHWESTERN MICHIGAN 10:20 lO:+5 11:10 BURIED EXTENSION OF THE KEWEENAWAN Isidore Zeitz & P. K. Sims: BASIN IN MINNESOTA - A GEOPHYSICAL STUDY P. K. Sims & Isidore Zeitz: GEOLOGIC INTERPRETATION OF AERO— MAGNETIC ANOMALIES OVER PRE-KEWEENAWAN ROCKS IN CENTRAL MINNESOTA THE APPLICATION OF S. C. Nordeng, C. 0. Ensign & M. E. Volin: TREND SURFACE ANALYSIS TO THE WHITE PINE COPPER DISTRICT GENERAL DISCUSSION 11:35 12:00 LUNCH — MAIN BALLROOM, KIRBY STUDENT CENTER SESSION II Co-Chairmen: F. D. Effinger, T. E. Stephenson STRUCTURE WITHIN THE DULUTH GABBRO COMPLEX IN THE 2:00 W. C. Phinney: 2:25 C. N. Hanson, W. C. Phinney & P. W. Gast: THE THERMAL EFFECT OF THE DULUTH GABBRO UPON THE SNOWBANK GRANITE GABBRO LAKE AND GREENWOOD LAKE QUADRANGLES, MINNESOTA �* Hf 2:50 THE RELATIONSHIPS BETWEEN THE DULUTH GABBRO AND DIKES AW SILLS NEAR HOVLAND, MINNESOTA N. W. Jones: COFFEE BREAK 3:15 3:145 :1O G. FORMATION, THE STRATIGRAPHY AND STRUCTURE OF THE ROVE B. Morey: GUNFLINT LAKE AREA, MINNESOTA STRUCTURES OF CONCRETIONS IN THE THOMSON FORMATION, CARLTON AND PINE COUNTIES, MINNESOTA Paul Wieblen: GENERAL DISCUSSION 14:35 6:30 THEL/ DINNER - MAIN BALLROOM, KIRBY STUDENT CENTER Dr. R. L. Heller, Director, Earth Science Project; Head, Department of Geology, University of Minnesota, Duluth Speaker: EARTH SCIENCE AND THE SECONDARY SCHOOL CURRICULUM Topic: Friday Morning, May 3, 1963 SESSION III Co-Chairmen: C. Tychsen, I. L. Reid P. R. E. Hessevick: REFINEMENT OF THE 9:00 R. L. Blake, T. Z. Zoltai 9:25 G. L. Laberge: CARBONATE MINERALS IN THE IRON FORMATION AND THEIR SIGNIFICANCE 9:50 R. E. Randolph: SUSCEPTIBILITY MEASUREMENTS CF EMPIRE MINE MAGNETIC MATERIAL & HEMATITE CRYSTAL STRUCTURE COFFEE BREAK 10:15 Hoppin, J. C. Palmquist & L. 0. Williams: CONTROL BY PRECAMBRIAN BASEMENT STRUCTURE ON THE LOCATION OF THE TENSLEEP - BEAVER CREEK FAULT, BIGHORN MOUNTAINS, WYOMING 10:145 R. A. 11:10 C. M. Gallick: CLAY MINERALOGY OF THE DECORAH SHALE, MINNESOTA 11:35 M. A. Rogers: BIOGEOCHEMISTRY OF MINNESOTA LAKES: 12:00 LUNCH - MAIN BALLROOM, KIRBY STUDENT CENTER CARBOHYDRATES �SESSION IV R. W. Marsden Chairman: 2:00 J. H. Zumberge & 14. R. Farrand: LAKE SUPERIOR CORES AND BOTTOM TOPOGRAPHY ORIENTED LAKES IN NORTHERN ALASKA 2:25 C. E. Carson: 25O 0. M. 'hwartz: 3:15 THE SUBDIVISIONS OF THE BTWABT}( FORNATTON ON THE EASTERN MESABI GENERAL DISCUSSION Saturday, May , 7:30 - Hotel 1963 Duluth FIELD TRIP TO THE MESABI IRON RANGE Field trip leaders: F. D. Effinger, Pickands Mather & Company J. 14. EmanuelsOfl, Reserve Mining Company C. L. Iverson, Oliver Iron Mining Division Richard Strong, Oliver Iron Mining Division �1 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2—3, 1963 Institute on Lake Superior Geology REFINEMENT OF THE HEMATITE CRYSTAL STRUCTURE R. L. Blake.Y, T. Z. Zo1taiY, and R. E. Hessevick!" The crystal structure of hematite has been refined as an initial phase of studies involving atomic positions and vacancies in hematite during reduction to magnetite. Three—dimensiofll diffraction intenItieD were collected and automated on a spherical single crystal of hematite with both manual Buerger single crystal diffractometer. The structure has been refined with R factor of 7.1 pera least squares program and the final structure gave an cent. The structure model of Pauling and Hendricks has been confirmed with essentially no change in the iron coordinates and approximately a 5 percent change in the oxygen coordinates. The interatomic distances and bond angles were also calculated. TMinneapolis Metallurgy Research Center, Bureau of Mines 2! Department of Geology g Geophysics, University of Minnesota �2 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2-3, 1963 Institute on Lake Superior Geology ORIENTED LAKES IN NORTHERN ALASKA C. E. Carson University of Minnesota, Duluth Study of numerous thaw-lakes in the permafrost of the Arctic Coastal Plain has revealed that basin shape and orientation is controlled by winddriven waves and currents with associated thermal effects. The lakes range in size from mere puddles to basins 8 or 9 miles long, and all possess a similar basin morphology. This morphology consists of wide sub-littoral shelves and bars on the east and west sides, with the deeper central basin extending uninterrupted to the north and south ends. The ba- sins are elongated in a north-south direction, and have length-width ratios ranging from 1 to 5.1. Few basins are over 8 feet deep. In the Point Barrow area, most basins taper toward the north. Analysis of wind data from the Barrow weather station has revealed that summer winds are bimodal, being either easterly or westerly, average some 15 m.p.h., and are remarkably steady from one direction for several days at a time. orientation. Their average directions are nearly perpendicular to the axes of Investigation has shown that wind-driven wave action on the east and west sides, and the presence of circulation cells in the north and south ends, has produced the characteristic basin morphology; therefore, orientation. �3 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2-3, 1963 Institute on Lake Superior Geology CLAY MINERALOGY OF THE DECORAH SHALE, MINNESOTA Cyril M. Gallick University of Minnesota, Minneapolis The Middle Ordovician Decorah Shale is exposed sporadically in a 20-. mile wide band, extending from St. Paul to the southwestern corner of Houston It is a green-gray or less commonly a blue-gray shale that contains County. thin (generally 0.1 to 0.2 foot) interbeds and lenses of limestone and co- quina. The limestone layers are widely separated in the basal 10 to 20 feet, but increase in number irregularly upwards. In the middle of the formation, there are two or more zones, 3 to 5 feet thick, which contain limestone beds separated by less than O.i feet of shale; near the top, the limestone beds A few of the uppermost beds are become thicker and more widely separated. The formation is 89 feet thick at St. Paul and thins one to two feet thick. progressively to 25 feet at the Minnesota-Iowa border. The minerals in the grade size less than 1/512 mm were determined with "illite" (a 10 layered silicate with inter— the X—ray diffactometer to be: layers of a lL mineral), kaolinite, orthoclase, and calcite. Where all minerals are present, peak intensities indicate that orthoclase and illite predominate. The material sized greater than 1/512 mm is mostly fossil hash and At St. Paul, illite and orthoclase are present throughrare quartz grains. out the formation, apparently in constant proportions; kaolinite and calcite are sparse in the basal part but occur in significant amounts in the middle and upper part of the section. At Rochester, the basal shale contains illite or-thoclase, and calcite in proportions similar to that in the upper part of the St. Paul section and sparse kaolinite; the middle shales consist entirely of illite; beds in the upper part contain either kaolinite or orthoclase or both, but apparently only in minor amounts. The orthoclase in the Decorah Shale has been presumed to be the result of authigenesis. All illite (001) peaks on the diffractometer from the St. Paul section and from the basal part of the Rochester section are very asymmetrical, extending from 9.BA to slightly more than lLR, possibly indicating a considerIn the middle and able amount of interlayer 1L4X mineral in the structure. upper parts of the Rochester section, the illite (001) peaks are nearly symmetrical. analysis of a shale which had been weathered for possibly more This peak than five years showed only a change of the illite (001) peak. much more asympeak, broader and was lower in relation to the (002) illite X-ray metrical than that of any other shale analyzed. little more than l7R. It extended from 9.8k to a �L. UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on May 2-3, 1963 Lake Superior Geology THE THERMAL METAMORPHIC EFFECT OF THE DULUTH GABBRO UPON THE SNOWBANK GRANITE G. N. Hanson, W. C. Phinney, and P. W. Gast University of Minnesota, Minneapolis, Minnesota The effect of the thermal metamorphism of the 1.0 billion-year Duluth Gabbro on the 2.5 billion-year Snowbank Granite can be seen in the changes of the Rb-Sr ages of the biotites and the changes in the degree of triclinof the potassium feldspar in the granite. tion zones parallel the granite-gabbro contact. icity In both cases, the transi- Biotites from the granite within 2.0 kilometers of the contact (map distance) have Rb-Sr ages of less than 1.2 billion years. At distances greater than 2.0 kilometers, the successive biotite ages increase regularly to 2.55 billion years. The change in the ages exhibited by the biotite is shown to result from the loss of radiogenic strontium from the biotite strucThe mechanism for this loss is assumed to be either recrystallization ture. of the biotite structure or volunie diffusion of the radiogenic strontium out By a trial and error process of fitting theoretical of the structure. curves to the data, an activation energy of about 50 kilocalories for recrystallization by a zero—order rate process and an activation energy of 85 kilocalories for volume diffusion are proposed. Potassium feldspars at distances greater than 2.0 kilometers from the contact are maximum mirocline (maximum triclinicity) as determined by mea— Within 2.0 kilometers surement of the 131-131 spacing by x-ray diffraction. of the contact, the potassium feldspars are primarily orthoclase (monoclinic feldspar) except for several samples near the contact which show mixed orthoclase and microcline. The albite content of the potassium feldspar tends to be only a function of the facies of the stock and ranges from 0r59—0r96. The above data raise several questions which as yet are unanswered: (1) Why is microcline the potassium feldspar at distances greater than 2.0 kilometers? Could this be explained by regional metamorphism of the stock during the Algoman orogeny about 2.5 billion years ago? (2) Why did the potassium feldspar within 2.0 kilometers of the contact change to orthoclase upon thermal metamorphism by the gabbro and then not revert back to microcline upon cooling? Could this be a result of a lowering of water pressure in the stock at the time of the intrusion of the gabbro? �5 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2-3, 1963 CONTROL BY PRECAMBRIAN BASEMENT STRUCTURE OF THE LOCATION OF WYOMING THE TENSLEEP-BEAVER CREEK FAULT, BIGHORN MOUNTAINS, Richard A. Hoppin - University of Iowa, Iowa City, Iowa John C. Palniquist - Monmouth College, Monmouth, Illinois Lyman 0. Williams - The California Company, Pensacola, Florida angic fdnlt, The Tensleep—Beaver Creek Fault (Laramide in age) is a high The north side 32 miles in length, trending E-W across the Bighorn Mountains. The fault has moved up a maximum of 1350' in the axial portion of the range. presently known is a major transcurrent fracture but is the only such feature this trend, has that crosses the whole range. Why the fault formed and has the eastern 12 miles been a puzzle. This investigation was restricted to The Precambrian rocks were exalong which the Precambrian rocks are exposed. might have been reamined to see if there was any structural anisotropy that sponsible for the localization of the fault. One is best developed near the and dips 500 This foliation varies from N.80°E. to N.80°W. in strike fault. Several zones of pervasive foliation up to 300 feet wide were mapto 70°N. is less well deAs one goes north away from the fault, the foliation ped. in width are preveloped although local zones of a few inches to five feet shear surfaces; In the field, the foliation looks like closely spaced sent. for occahowever, thin sections indicate complete recrystallization except Later, pegmatitic masses cut this sional deformed relict plagioclase augen. In the fault zone, these foliated rocks, and the sedimentary foliation. quartz cementation are rocks, are brecciated and crushed. Quartz veins and 50 feet wide. characteristic. The crushed zone is only about Two strong foliations were discovered. This The second foliation trends N.50°-65°W. and dips 60° to 70°NE. foliation is dominant to the north of the fault but is absent near the fault. This fabthe fault. It is also the main foliation in the Horn area south of plagioric is also completely recrystallized with only a few relict deformed mylonitizatiofl arid quartz veining have clases. Later, zones of crushing, straight A particularly strong cataclastic zone is followed by a this trend. This same zone conportion of the valley of the North Fork of Powder River. is probably responsible for a small detinues southeast into the fault and flection of the fault. It seems reasonable, therefore, that the Tensleep-Beaver Creek fault was formed along an E-W zone of pervasive foliation and deflected in one area along another zone of northwesterly foliation. These foliations were formed under deep-seated conditions of plastic deformation followed by reLaramide took place at crystallization. The later deformation during the shallow depth and was of a brittle nature. �6 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2—3, 1963 Institute on Lake Superior Geology THE RELATIONSHIPS BETWEEN THE DULUTH GABBRO AND THE DIKES AND SILLS NEAR HOVLAND, MINNESOTA Norris W. Jones University of Minnesota, Minneapolis, Minnesota It is tentatively concluded from onissan'e go1ogic inepping in the vicinity of Hovland, Cook County, that the Duluth gabbro complex does not exand othtend as far eastward as Lake Superior, as suggested earlier by Grout ers (1959). Instead, the gabbro appears to terminate at the Brule River. The mafic rocks along the shore that previously were called Duluth gabbro are the lower part of the Hovland diabase sill. Three other diabase or gabbro units are recognized in the area. Petrographic and x-ray studies show systematic changes in the Hoviand sill. Silica, alkalis, and iron gradually increa3e upward from the base. is present As in the Skaergaard intrusion of East Greenland, an olivine gap and the two pyroxene boundary is crossed. The compositional changes are in- ferred to indicate that the sill formed by crystal fractionation. The relations of the intrusive units in the area can be explained as the result of emplacement of Logan intrusives, followed by intrusion of the Duluth gabbro ccinplex. The Logan intrusives were emplaced along a dominant- ly northeast—trending fracture system, whereas the Duluth gabbro complex in this area strikes essentially east-west. The Hoviand area represents the intersection of these two malor structural trends. �7 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute May 2-3, 1963 on Lake Superior Geology CARBONATE MINERALS IN THE IRON-FORMATION AND THEIR SIGNIFICANCE Gene L LaBerge University of Wisconsin, Madison, Wisconsin To allow more rapid identification, a staining technique was used in studying the carbonate minerals in the iron-formation. The procedure is outlined in an to simp- article by Warne in the Jour, of Sed. lifying the identification of the carbonate species, the stain showed beauti- Pet., March, 1962. In addition fully the relationship of the various carbonates to one another, and the association of particular carbonate species with certain other minerals. Some generalizations to which there certainly are many exceptions which may be made, are as follows: Most of the siderite is primary material. The ex- tremely fine-grained carbonate which comprises up to 75 per cent of some slaty layers in the iron-formation is almost certainly primary. ial is siderite and/or very iron-rich ankerite. This mater- Textures indicate that the siderite granules, which are not uncommon, are probably primary. Unques- tionably, secondary siderite is not common. In contrast, most of the ankerite, ferroandolomite, and dary. dolomite are secon- Much of this secondary carbonate is probably a byproduct of the de- composition of the iron-rich ankerite to form magnetite, with which it is usually associated. However, primary ankeritic carbonate in both the slaty material and in granules does occur. �8 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2-3, 1963 Institute on Lake Superior Geology STRUCTURE AND STRATIGRAPHY OF THE UPPER KEWEENAWAN ROCKS IN NORTHWESTERN WISCONSIN George Moerlein Bear Creek Mining Company, Anchorage, Alaska Between the summer of 1955 and the winter of 1960, Bear Creek Mining Company explored the western tip of the Lake Superior Syncline in quest of possible copper-bearing Nonesuch formation. The area covered includes por- tions of Ashland, Bayfield, Douglas, Washburn, and Burnett Counties, Wisconsin. Field mapping, extensive magnetic and gravity surveys, some refraction seismic work, and diamond drilling each played a part in outlining the geology of the area. The normal sequence of Keweenawan sediments, Copper Harbour, Nonesuch, and Freda formations was recognized, and the tratigraphy of each formation will be discussed. The structure of the area is essentially that shown on the 1948 edition of the Geologic Map of Wisconsin, a northeast plunging syncline. however, is locally complicated by faults of major Evidence importance. will be presented which indicates that the formation of the Lake Superior Syncline, at least in Wisconsin, began in an time. This, very late Keweenaw- �9 UNIVERSITY OF MINNESOTA, DULUTH of Geology Department May 2-3, 1963 Institute on Lake Superior Geology THE STRATIGRAPHY AND STRUCTURE OF THE ROVE FORMATION, GUNFLINT LAKE AREA, MINNESOTA G. B. Morey University of Minnesota, Minneapolis, Minnesota in the South Lake Quadrang1. near Gunf lint Lake in Cook County, was completed in 1962. The area is on the north limb of the Lake Superior structural basin; accordingly, the strata Geologic mapping of Animikie Group rocks strike eastward and dip consistently five to 15 degrees south, except adjacent to the Duluth Complex where the dips increase to as much as 65 degrees. The Rove Formation overlies the Gunflint Iron Formation, apparently conformably, and is truncated by the Duluth Complex; approximately 1,800 feet of The formation consists of two recognizable lithologic units. Rove are exposed. The lower unit, about 400 feet thick, consists mainly of a black, very finegrained, thin-bedded or fissile argillite with abundant graphitic or carbonaceous material and pyrrhotite, interbedded with lesser amounts of gray, mediumThe grained, massive graywacke. Calcareous concretions are locally abundant. argillites, grayupper unit, about 1,400 feet thick, consists of interbedded wackes, and quartzites; the latter two rock types become more abundant upward in the section. Graded bedding, sole marks, intraforrnational argillite fragments, convolute and small-scale cross-laminations and clastic dikes suggest a subaqueous flow origin for much of the upper unit. A south-southwestward movement of material is suggested by many of these structures. The Animikie Group rocks contain several east-trending sill-like bodies, mainly of diabasic gabbro, which range from less than 100 to more than The sedimentary rocks adjacent to the sills are 1,000 feet in thickness. metamorphosed to mineral assemblages. characteristic of the horr1blende-hornfels facies. The sills are correlated with the Logan Intrusives; they are older than and are truncated by the Duluth Complex. �10 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2-3, 1963 THE APPLICATION OF TREND SURFACE ANALYSIS TO THE WHITE PINE COPPER DISTRICT S. C. Nordeng1, C. 0. Ensign, Jr.2, M. E. Volin3 Over one hundred sets of drill hole data were taken from the files of the White Pine Company and coded on IBM cards. The section was divided into upper and lower halves and linear, quadratic and cubic surfaces of best fit were computed for each half for average copper percentage, thickness, and ounces of silver per ton, utilizing a taped multiple regression program on a medium speed digital computer. The linear surface for the upper half accounted for one-half or better of the departures from the mean and showed slight improvement for higher order surfaces, suggesting that the trends of the quantities under consideration are essentially planar in nature. The best fit was found for copper, The surfaces show an increase in thickness to the the poorest for silver. north and northeast, and in copper content to the southeast. The lower section showed macimum improvement in the sum of squares for the cubic model for both percent copper and thickness. Maps of the cubic surfaces successfully predict the location of a known ore body for which Departures of observed values from com no data was entered in the program. puted values for the lower half are interpreted as resulting from relative thickening and thinning of the upper part of the lower section which is relatively barren, and the lower part of the lower section in which most of the ore is found. 1 Department of Geology and Geological Engineering, Michigan College of Mining and Technology, Houghton, Michigan. 2 Chief Geologist, Copper Range Company, White Pine, Michigan Institute of Mineral Research, Michigan College of Mining and Technology, Houghton, Michigan �U UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2—3, 1963 STRUCTURE WITHIN THE DULUTH GABBRO COMPLEX, GABBRO LAKE AND GREENWOOD LAKE QUADRANGLES, LAKE COUNTY, MINNESOTA William C. Phinney University of Minnesota, Minneapolis, Minnesota Mapping and petrologic studies of the Duluth gabbro complex in the Gabbro Lake and Greenwood Lake quadrangles during the summers of 1961 and 1962 have indicated a complex series of gabbroic intrusions associated with antiform and basin-like structures. A major intrusion in the southeast quarter of the Gabbro Lake quadrangle and the north-central part of the Greenwood Lake quadrangle is roughly elliptical in plan, has a long axis of at least nine miles, and is inferred to be cone-shaped. It intrudes anorthositic gabbro and concentric layers that dip nearly vertical at the border and nearly horizontal at the center. Regular variation in mineral assemblages from olivine rich at the border to pyroxene-rich at the center indicate a normal differenNumerous smaller gabbroic intrusions as well as zones of tiation sequence. intrusions have been mapped. has Olivine gabbro with well defined layers having graded olivine concentrations in rhythmic succession forms a broad, shallow basin in the southwest quarter of the Gabbro Lake quadrangle. Within the basin, there are many anorthosite lenses that contain numerous one- to two—inch patches of olivine, apThe eastern boundary of parently concentrated from the interstitial fluid. the basin is in sharp contact (apparently intrusive) with the anorthositic The relative ages gabbro intruded by the cone-like intrusive mentioned above. of the cone-like gãbbro intrusion and basin-shaped gabbro intrusion are not known. Southeast of Gãbbro Lake, a marker zone in the gabbro can be traced around an antiformal structure that is elongated subparallel to the basal contact of the gabbro and has an anorthositic gabbro core. In the same area, a very coarse-grained pyroxene- and ilmenite-magnetite-rich dike, that is as much as one-fourth mile wide, can be traced for several miles. �12 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2-3, 1963 Institute on Lake Superior Geology PRELIMINARY INVESTIGATION OF A PORTION OF THE NORTHERN COMPLEX, BARAGA COUNTY, MICHIGAN D. W. Pollock and S. C. Nordeng Michigan College of Mining and Technology, Houghton, Michigan During the summer of 1962, the writers initiated a study of a portion Some results of the "Northern Complex" which lies in Baraga County, Michigan. of this study are reported herein. (1) amphiboSeveral lithologic groups have been mapped. These are: plagioclase—rich gneis— lite; (2) greenstone; (3) rnesocratic gneisses and (4) varieties. ses. Each of these groups can be subdivided into more specific The groups occur in definite belts and the following gradations were observed in the field: greenstone chiorite-plagioclase gneiss amphibolite mesocratic gneiss plagioclase-rich gneisses A thin "infolded" belt of Michigamme (?) phyllite has been located west of Clear Lake in Sec. 14, R 49 N, R 32 W. The broad structural trend is an arc, convex to the west. In detail, the structure is more complex. Poles to foliation (llsdiagrams) were plotted, but with poor results. The most useful approach was to outline the structure on the basis of vertical foliation trends. The origin of the foliation reMesoscopic linemains in doubt as the origin of the rocks is not yet known. ation is only feebly developed. Investigation is continuing. of some of the many problems raised during this study �13 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2-3, 1963 SUSCEPTIBILITY MEASUREMENTS OF EMPIRE MINE MAGNETIC MATERIAL E. Richard Randolph Cleveland Cliffs Iron Company, Ishpeming, Michigan The Negaunee Iron-Formation at the Empire Mine on the Marquette Range in Michigan consists, briefly, of magnetic cherty iron-formation, magnetic cherty carbonate iron-formation, magnetic cherty silicate iron-formation and a hanging wall member containing many large clastic facies interbedded with the precipitate iron—formation. The common criterion for grading ore at the mine is on the basis of per cent weight recovery. The ore type which presents the greatest problem in grade control is the clastic facies of the iron-formation which can vary It is very difficult to distinguish in weight recovery from 10% to tl1%. macroscopic means. Close orrich, moderate and poor der magnetometer surveying is an aid to localizing large zones, but a more definitive procedure is desirable for day-to-day control. It was suggested that susceptibility measurements on the cuttings from blast hole drilling might indicate the grade of the ore in that hole more cheaply and reliably than crude Fe analyses or streamlined Davis tube testing. clastic ore material by Susceptibility is the ratio of the intensity of magnetization acquired by a substance to the strength of the magnetizing field acting on the In a rock containing magnetite as the principal magnetizable constitbody. uent, susceptibility is, for practical purposes, the measure of the amount of magnetite present. Because per cent weight recovery of magnetite is the criterion for the cut-off s between rock, lean ore and ore in the hanging wall clastic zone, a program relating susceptibility measurements to per cent weight recovery was started. The conclusions are as predicted: measurements show a broad range of values for the general area but within a limited area correlate sufficiently well to offer a rapid, cheap, reliable method for sampling blast hole cuttings for grade control. �l&1 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2—3, 1963 Institute on Lake Superior Geology BIOGEOCHEMISTRY OF MINNESOTA LAKES: CARBOHYDRATES M. A. Rogers University of Minnesota, Minneapolis Fossil carbohydrates have been found in trypical sedimentary rocks; carbonaceous organic rocks such as peat, coal and lignite; fossilized wood; insect remains; modern lake sediments; modern and ancient marine sediments; and in lake waters. Carbohydrate materials were studied in the aquatic plants, lake waters and lake sediments of two eutrophic-alkalitrOphiC lakes of central Minnesota. Both free sedimentary sugars and sugars liberated on hydrolysis were recovered. Glucose, galactose, xylose and arabinose are the dominant sugars in order of decreasing abundance in aquatic plants of the two lakes. Maxima and minima in these sugars, as well as in the content of cellulose and hemicellulose, show little relation to season of collection and appear to be characteristic of individual plant species. Acid hydrolysis of lake bottom sediments recovered the eight sugars, arabinose, xylose, galactose, glucuronic acid, glucose, rhamnose, mannose and ribose, in concentrations ranging from 19.1 to 0.1 mg/gm of dry wt. sedThe variety and amount of these sugars is believed to demonstrate iment. the importance of microorganisms in altering the carbohydrate fraction prior to stabilization and preservation within the sediment. Acid hydrolysis of lake sediments from a deep core from Blue Lake, Minnesota, recovered in order of decreasing abundance the eight sugars, xylose, glucose, arabinose, galactose, mannose, rhamnose, ribose and glucuronic acid. A natural stability series for carbohydrates in the lacustrine envifairly stable: xylose, glucose, rhamnose, arabinose; moderateronment is: galactose; very unstable: ribose, mannose; fairly unstable: ly stable: glucoronic acid. �15 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2—3, 1963 GEOLOGIC INTERPRETATION OF AEROMAGNETIC ANOMALIES OVER PRE- KEWEENAWAN ROCKS IN CENTRAL MINNESOTA P. K. Sims, Minnesota Geological Survey, Minneapolis, Minnesota Isidore Zietz, U. S. Geological Survey, Washington, D. C. in An aeroinagnetic survey completed by the U. S. Geological Survey of 1961 has clarified our knowledge of the Pre-Keweenawan rocks in an area about 3,000 square miles in central Minnesota, extending from the latitude in of Little Falls, in Morrison County, south to the vicinity of Gaylord, of the anomalies In the northern part of the area, sources Sibley County. units have have been identified from scattered outcrops and separate rock been extended, based on geologic considerations and magnetic data. The aeromagnetic data indicate that the igneous rocks of the Penokean orogeny (Woyski, 19L19), which have been quarried extensively for building monumental stone in a broad area centered at St. Cloud, extend in the and eastward beneath oversubsurface south at least to latitude L5°l5' N. Northwestward from St. Cloud, lapping upper Keweenawan sedimentary rocks. and schist appears to be the dominant bedrock. In the southern part of the area, outcrops are lacking and interpretation of the magnetic patterns is more equivocal. Except for an anomaly at above igneous rocks of Lake Washington in Meeker County, which probably is mafic composition, interpretation of the magnetic anomalies intermediate or of the baseis not attempted. South of Hutchinson, a change in the trendmarked discontiby the magnetic pattern, suggests a ment rock, as indicated nuity, possibly a fault or an unconformity, in the Pre-Keweenawan rocks at this latitude. �16 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geo1gy May 2-3, 1963 STRUCTURES OF CONCRETIONS IN THE THOMSON FORMATION CARLTON AND PINE COUNTIES, MINNESOTA Paul Weiblen University of Minnesota, Minneapolis, Minnesota Calcareous concretions in the Thomson Formation found in the vicinity of Carlton are of two types. The concretions in graywacke and graywacke—iate beds consist of massive calcite, are ellipsoidal, and lack a distinctive internal Those in structure other than bedding, which conforms to the enclosing rock. finer-grained slate beds are zoned; they contain an inner core of slaty mater— ial, surrounded by well—crystallized calcite or by quartz with sutured grain The outer zone has a pseudo cone-in-cone structure, defined by boundaries. bands of slaty material. The calcite in both types of concretions replaces quartz and feldspar. The zoned concretions on the limbs of folds in the slate and graywacke succession are rotated out of the plane of bedding. The c axis of the calcite in the pseudo cone-in-cone structures is oriented parallel to the direction of maximum compression and a cleavage, which is well developed, parallels shear These features afford a promising means for further study of directions. structural relations in the formation. Remnants of concretions are found in the more intensely metamorphosed phases of the Thomson Formation southwest of Carlton, in phyllite, metagraywacke, and mica schist. Quartz has replaced the calcite in phyllite. Well—zoned concretions occur in the metagraywacke. The outer zones of these consist principally of hornblende, garnet, quartz, and andesine; the cores contain mainly epidote, quartz and andesine. Sections of the cores show that they are deformed into boudins. They also contain characteristic S-shaped structures formed by shearing and defined by heavy mineral concentrations. These similarStructures similar to these occur in the slate and phyllite. the concretions can be ities indicate that further sampling may show that Formation. used as stratigraphic marker beds in the Thomson Remnant calcite is found in the concretions in the mica schist, metagraywacke and phyllite. The (211) spacing of the calcite ranges from 3.04 angstrorns in the slate to 3.02 angstroms in the schists, indicating the occurrence of relatively pure calcite (less than 5 percent Fe,Mg) throughout the entire formation. Plagioclase coexisting with calcite ranges from An5 in the slate and graywacke to An40 in the mica scist and metagraywacke. It has been found that radiographs afford a practical method for studying the internal structures of the concretions. Fluorescence excited by electron bombardment provides a mean of distinguishing calcite from dolomite. �17 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2-3, 1963 Institute on Lake Superior Geology BURIED EXTENSION OF THE KEWEENAWAN BASIN IN MINNESOTA GEOPHYSICAL STUDY A Isidore Zietz, U. S. Geological Survey, Washington, D.C. P. K. Sims, Minnesota Geological Survey, Minneapolis, Minnesota Approximately 30,000 linear traverse miles have been flown eromagnet— ically by the U. S. Geological Survey across the "mid—continent gravity high". This is, perhaps, the most oustanding gravity feature in the United States, extending from near Lake Superior in a southwesterly direction to the Sauna basin in Kansas. Coupled with the gravity measurements and meager drill hole records, the aeromagnetic data strongly, if not unequivocally, imply the existence of a several-mile-thick accumulation of Keweenawan lava flows, extending uninterruptedly for 800 miles, f tanked by Pre-Cambrian sandstones which locally may be more than a mile thick. Total thicknesses of lava flows and neighboring sandstone can be estimated from the gravity data, whereas the aeromagnetic data supply the details of the configuration of the upper surface of the flows. In Minnesota, the magnetic data clearly outline the Twin Cities artesian basin, an elliptical trough 60 miles long in a northeast direction and 30 to 35 miles wide. basin and north of latitude LL°35' N., At the eastern margin of the the magnetic data suggest that the basin is bounded by a narrow northeast-trending horst of mafic volcanic rocks, probably elevated at least 1,000 feet above the adjacent rocks. The horst is the basement manifestation of the Fiudson-Afton anticline, a northeast-trending Paleozoic fold. In southern Minnesota, south of latitude L44°l5' N., the mafic lavas are at considerable depths, but the surface of the flows rises to within 1,500 feet at the Iowa border. �18 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2—3, 1963 LAKE SUPERIOR CORES AND BOTTOM TOPOGRAPHY James H. Zumberge and William R. Farrand University of Michigan and Columbia University to Cores were recovered from eleven drill holes in water depths of 500 drilling 1,130 feet in Lake Superior in 1961 and 1962. A shipboard, rotary and to lorig was used to penetrate the unconsolidated Pleistocene sediments The sediments were recovered by gravity and piston cate the bedrock surface. coring -- continuously in the upper 30 feet and intermittently below that depth. reaching bedThe longest core penetrated 686 feet of sediments without sediments rock, and it shows at least four alternations of glaciolacuStrifle The other cores penetrated only 7 to 156 feet and the varved), red lacustypical sequence was gray, lacustrine clay (lower part trifle clay (some varved), and red clay till. Below the till, well—washed and red, clayey till. red and sand (outwash?) was found in three holes, and in four other holes white (Cambrian?) sandstone was reached. drill A sub-bottom depth recorder was used in combination with the topography. Near logs for the interpretation of stratigraphy and sub-bottom broad bedrock valthe Minnesota coast, more than 700 feet of drift lies in a valleyIn the eastern part of the basin, strong north-south trending ley. modified stream and-ridge topography appears to be a submerged, glacially system, rather thinly covered with glacial drift. Also, the possibility of strong east—west faults between Keweenaw Peninsula and Sault Ste. Marie is indicated. � https://digitalcollections.lakeheadu.ca/files/original/5a175e5c561d413faf02a1b640ea415e.pdf c174ae149f6d8beb5546748ab48f1a3a PDF Text Text Field Trip "Stratigraphy of the.Biwabik Iron Formation 11 Sponsored by the Lake Superior Geology Club Duluth, Minnesota May 4, 1965 �,, ~~ G>,._ /<I AUBURN ~t-«~ 1-/19 19/11. G' . G'-'9 ~ )'1- ~ 0 '9</ ~ O,s- +-~ ~ -v~ ~,o -v~~ <? INDEX MAP OF THE MESABI DISTRICT , MINNESOTA �FOREWORD Gentle reader, take heed, the field trip which you are about to take - not a polished affair with textbook illustrations and trip leaders able to J ve glib expla.ne.tions for everything you are going to see. o the gene al objectives for which the Lake Superior Geology In keeping with stitute was or- g nized, that is, to present preliminary r e sults of investigation in new areas of geologic interest, the leaders of this trip plan t o show you their approach tp subdivic1:1.ng the Biwabik iron formation beyond the basic fourfold subdivision ~rst proposed by J. F. Wolff in 1917. That the problem of further subdivision i ls difficult can be accepted si nce such authoritie s as Gruner, Grout and Broderick, E te , Schwartz and Gunderson have all come up with systems that many individuals use but which do not appear to be generally acceptable to all 'rorkers in the ield. In such a situation we may expect considerable discussion and disagreement i th any system proposed. ~Y emerge, Perhaps in the anticipated clash of opinions the truth. but don't count on i t. In any event the trip should be instructive " o both you and the leaders, and perhaps even entertaining to the philosophers rong you contemplati ng the state Of geol ogic knO'£o7ledge concerning this 1 the ,randfather of all iron for-mations. . A secondary but highly interesting part of this trip \d.ll be the 1ppo1~unity to observe the changes vmich take place in unoxidized iron formation rom the Eveleth area eastward almost to the contact of the Duluth Gabbro. T~~s spect of the trip should be of particular interest to students of metamorphism and those less c,o ncerned with the local problems of iron formation stratigraphy. lble controversy exists even in this area, the individualists among you vTontt I q.ave to accept any of our leaders' statements since the rocks themselves \-Till be tvailable for identification and collection. Due to the unexpectedly large number of people participating in this trip, we are antici pating some difficulty in maintaining our schedule of arrivals and departures f rom each stop. ~orn blows . compensation. Please return to the buses promptly a fter the I f you are left i n the pit don •t panic, apply for unempl oyment �The field trip will start at 7: 50 A.M. at Hotel Duluth and proceed rectly to the Auburn Mine property outside of Virginia . Upon completion of tq.e one stop at Auburn , the buses ldll ta.k.e us to the Erie property and proceed through four stops in various parts of the pit. Two stops are planned in the I REf Serve property to complete the program for the day. The buses will return to Duluth via Aurora and deposit passengers at the beginning point. Passengers 'rushing to remain on the Range should make private arrangements for transportation ftam the Reserve property or possibly from Aurora. It is anticipated that we ,dll finish the trip around 6:00 P.M. Lunch ~dll be served at the third stop in the Erie pit and rest stops are planned on ent ering the Erie property and leaving the Reserve property. Please read, consider and observe the regulations on the following page to which ~rJ have agreed in order that we can gain entrance to the various properties. �ruiruuTIONS: Through t he courtesy of the Oliver Iron Mining Division, United States Steel Corporation , Pickands Mather & Co., and the Reserve Mining Company, we have beFn granted permission to enter, inspect and collect small specimens on their rebpective properties. t~ In return for this privilege, we have agreed to abide by following regtuations which apply not only to visitors but also to all company pe~sonnel. l. pits. Safety hats and goggles will be worn at all times while in the various You will be issued such equipment at the first stop. This equipment is charged out to the Lake Superior Geology Club and we will have to pay for it if it is not returned at the end of the trip . 2. Picture taking of equipment is discouraged in all active pits and all pictures forbidden on the Reserve property. at the entrance to the Reserve property. for the fun of it . Arrangements will be made to check cameras Please do not try t o outwit these regulations You may make it difficult for future geologists to enter these interesting areas . 3. Please use caution when approaching rock walls . The talus slopes are notoriously unstable footing and rock slides from the walls above are not uncommon in the spring. While the purists among you will want to remove specimens from the living rock, let us remind you that \dth taconite, it ' s going to take a lot of hammering. We have a long, tO'\.lgh day ahead of us, so save your strength. also applies to potential mountain goats climbing up rock faces. Thi s You may endanger yorrself and other people as well as delay the trip , so stay off high faces. 4. Please use discretion wnen hammering on rocks near other people . Taconite is tough and hard. at high speed. Sharp chips have a tendency to fly in all directions The safety goggles supplied you are not just a bureaucratic detail. Us~ them at all times and make your arm on Minnesota taconite. sure they are on people near you before you t est It is reported to have an average crushing stkength of 55,000 pounds per square inch . �Ea ster n Biwabi k Str atigraphy f rom Gunderson a nd Schwartz .Minnes ota Geological Survey Bulletin 43 -~ z;~a ~ ~~ !I ~~! ;- s ~ -'C-Q; ~ ..~ ~ GENERALIZED COLUMNAR SECTION OF THE BIWABIK IRON-FORMATION ~ ~ -~ ~ ~ £ r: ~-:! == j -!!cri ~ ~ ? ! -0f:i!..._ou E~ ~ r ~ s o ~ ~ -- J: j IN THE EASTERN MESABI DISTRIC T, MINNESOTA i? 1-- - -- - - --------=---,--.,-,--- - - - -- - - - - - - - - l 6 i ·~· ~:g 32: c.5 Descnption of Submembe rs ;; .:...: w - Q (Notations cO - Jf ~ J I B {!6) (eo~t} and (we!:> I) refer to orcas near the easter n and western drill holes) calcite marble,. minor diop side, wollastonite , id oc ro s e, andradit e and quartz j """-;;;;ered (di'op/;ide) chert taconite locally wilh hornblende, hedenberq ite and some cummingtonite a nd oc tmol•te /ami'n aled (ferrohyperslhene - moqnel i le) c;uarl.t ! aconite with hedcnberqite c >~ w (l_ (l_ ::J taconite {west) I /:::,vy laminated (oclinoh'le-moqnefite) chert taconite 1-:---:-::::--fV ··-·tonile ond minor hedenbc rgi te -' (/) cr laminated (cummin91onite - mognetite) chert and loyoli te (east) and (421 "' .D :> <I 0 (71 E 161 F (201 with abundant granule struc tures and locolly w ith quart zfilled seplorio s tructures; m inor magneti te, c ufT'ming tonite and o ttinolite shaly bedded (cumminqtonite-maqnetite) quartz laconile hedenocrgite (cost); locally abundant w•l h minor andradite cumminglanite (west} quartz taconite (ea st) and mol/led (andradite) quartz obundonl magne ltl e - bearing granules throughout G (251 wavy layered (actinolite? -maqnetite) quartz taconite f---:1 J wit~ cumminc;~- quartz taconite r----t--__ond H locally liOl local ly with foyoli te (eas t) taconite (west) with with minor hedenberq:itei and cummingtonite (wes t) .,--+ - - (Sl (l6 ) " ' alq~l (moqnetile) quorlz toconife with abundant magnetite- r ich granules ond "---: ebblcs; conglomcrolic fabric throuc;~houl; minor hematite r---+-_ granule (maqneltle) quartz facomle with obundonl magneti te - rich pebbles ~top and thic kly layered (magnel!le) quoriL tocomle near bottom >- K (351 L (301 near wavy layered (silicole moqnelite) quartz taconite with abundant moQne tite· rich granules ond ptbblcs ; silicates ore actinolite ond ferrahyperslh ene (east) ond cummingtamte (we st) 9 1- cr w I u wavy layered (st'licote-magnett~e) silicate-quartz taconite with abundant mag netite-rich granules ncar bollom; silic.o tes with magnetite ore ferrohypersthcne and hor nblende (e o:o t) and cumming toni te and actinoli te (wes t); silicates wi th quartz ore fcrrohypers thene (cost) ond c umminqtonite (west) cr w (l_ (l_ ::J layered (maqnelt~e) loyolite-quorlz /acon/tc with fcrrohypersthene layered (maqnel/te) cumminqtom~e-quar tz tacom~e (wes t) M (201 N 41 0 (17) foyalde -quartz tacomle tocomle (westli minor with ferrohyp ersthene (eosl) and {eas t) and cumminqlomle-quorlz mac;~ne t ite bedded granule (magnetite) quortz - loyolile tacomle with some fcrrohypers thene and minor cummingtoniti! (cost) to quartz -cumminqtom~e focamle with · moogranules (west} ~et ite -beoring r: sholy quortz- foyoli!e tocomle cumminqlontle taconite 10 foyoltle tocomle (easJI and sholy quorlz- to cummingtont~e tocom~e (west); minor moonetite '!!aceous grophite -sikcote-quortz laconlle with abundant ferrohypersthene and minor foyolite, biotite, olmondilc ond pyrrhotite (eosl) and traces of pyrite, pyrhotit e and cummingtonite (wes t) . layered (magnetJ/e) loyolite -quortz taconite with m inor cumminQtonite ered (moqneflle) quorl.l taconite with minor cummingtonite throuq:hout, and hedenbcrgitc and some l oj!alite (east) ljr;;nule (magnetite) quartz taconite 1---+---+-- --flj r-minor f-,---:-:-:-i(/ (;;ered and granule 'j -, locotly, with minor cummingtonite throuqhout, ond foyolitc least) (moqnetJ~e) cummingtom~e-quorlz taconite with hedenberqite ond some fayolite (cos t) ~rlz f-;-;---;-o;;-( FIGU!\1': 5. - taconite with minor hedenbcrgite and cummingtonitei clastic quartz p ebble zone locally at bose Generalized columnar section or the Biwabik iron-[ormation. };j �sw - sw 28-58 - 1 7 S E -S W 1 7-58-17 ·. N W - NW 20-58 - 1 7 .r. - I . I 1/ v ~I , - ------ -- - ---- ---/+-- ---- / / : I I SW-N W ) 20 - 58-1 7 I I S E - NW 2 0-58 - 1 7 I G E O LOG I C M AP OF AUBU R N M I NE N SC ALE } . 1" - ·4 00' a. 0 --+--· ---- ~----· -·-· -·t--· --+--1 I I I l_ __ L E GE ND GEOLOGIC C O N TA CT S ( A PPRcJX I MA T F) ~ O VE R DU R OEN ____ ...,. CRE ST OF BA NK ..- ___ _... T OE O F B ANK �STRATIGRAPHIC S~UENCE IN THE BIWABIK IRON FORMATION AUBURN mNE 'lhickness in feet 1 UJ PER CHERTY MEMBER 16. 2 Jaspery, conglomeratic and algal chert (G and 15 . 14 13. 12 . + 10. submember I) 10 (est . ) Covered interval 10 (est.) Nodular hematitic chert beds interbedded with laminated hematite-silicate- magnetite beds 48 +'l Laminated hematite- silicate-magnetite beds with subordinate jaspery chert beds and lenses 31 Jaspery, conglomeratic chert beds interbedded with subordinate laminated hematite-silicate~magnetite beds 28 Cherty taconite ld th thin irregular ma.gneti te beds, magnetite mottles and disseminated magnetite 16 143 SIM'Y MEMBER ll. s 3 Laminated silicate magnetite tacom. t e with subordinate silicate chert lenses Laminated non- magnetic silicate taconite, fissile in part. 6 ' of fissile "intermediate slate" at bottom (G and S submember Q) lOl 37 ---:l::-:38=- LOWER CHERTY MEMBER I 9. Cherty taconite with irregular magnet ite beds . Upper 10 ' dark·~ colored silicate rich beds instead of magnetite beds , making base of lower slaty somewhat indefinite . 37 Mottled silicate- magnetite chert with chert "pebbles" and abundant coarse granules. ll Cherty taconite with thick (l"!) magnetite beds and mottles 84 has 8. 7 6. 5. Mottled cherty taconite vlith thin, very irregular magnetite ~ds. u Thick jaspery chert beds interbedded w1 th varying proportions of thin, regular laminated magnetite-hematite- silicatecarbonate beds . 66 �l Thickness in f'eetl CIIER1'I' MEMBER (Cont'd) 4. Thick hematitic chert beds with subordinate la.minated zones. Some clastic sand grains near bottom. Much carbonate. 8 Jaspery, conglomeratic and algal chert w1 th subordinate laminated zones. Sand grains common. 4 2. Massive chloritic (or hematitic) sandstone 8 1. Jaspery, conglomeratic and algal chert 4 3. 236 Total thickness exposed mGAMA ,.. QUARTZITJt~ 517 Base not exposed 1. Units 15 and 16 measured on bank between truck road and railroad near entrance to pit. Units l - 5 measured on SW bank, at SE end of' pit. Remainder measured above railroacl. 2. Unit numbers correspond to numbers pa.inted on the walls of' the Auburn Mine and are not intended to be a new stratigraphic system. 3. The lower slaty-upper cherty contact is not well-marked and disagreement exists as to its position. �__..... ...--- ERIE MINING CO MPANY / MAP OF ? PLANT AND PIT / / / I AREAS LEGEND I COARSE CRUSHER 2 FINE CRUSHER ,3~ CONCENTRATOR 1)PELLET PLANT , §\LOADING POCKET • 6 STOCKPILE 7' GENERAL SHOPS ' ,\ WEST PIT BIWABIK IRON FORMATION VIRGINIA FORMATION ::," 1;- 1 {! { DULUTH GABBRO �STOPS AT ERIE PITS Stor. At this stop, we have the base of the iron formation in the West Pit. The gama quartzite and the basal algal layer and conglomerate can be found in the roa • The alternating chert and argillaceous layers of submember V are exposed in the outer op. ' Fok The bank at the south edge of the pit is the Lower Slaty material P&Q. The r efore, the widt h of the pit here is the entire Lower Cherty member. 1 Sto J 2. This stop shows the upper part of the Lower Cherty ore horizon. The submember R can be seen along the top of the bank. It is greenish in color and !contains much minnesotaite and greenalite. Iead D irectly below this is the wavy bedded submember R. This is more noti ~ eable toward t he west, (containing abundant granular jasper). J The mottled submember S is below this layer. This submember occupies most of the lower part of the bank. It also contains much jasper as well as the con J. picuous pink to red carbonate mottles. J StoR 3. At the east end of the cut, we find the even bedded (U) and the alternating ma~sive and slaty submember (V). The massive layers consist almost entirely of ryedium grained green silicates . Some granular jasper and flinty black chert occ j rs. Minor amounts of sulfides are present. I Proceeding westward, we encounter the lower wavy bedded submember (T) and the mottled submember (S). Here the mottles consist of fine grained sili ~ ates instead of the carbonates seen in Stop 2. StoJ 4, This stop is in the upper part of the Lower Cherty member and shows submembers R & S . It correlates with Stop 2. The effects of the gabbro to the sou~heast are quite apparent. At the extreme east end there are abundant sulfides and Jvery coarse grained dark green silicates. Proceeding westward along the cut the grain size decreases and buff colored silicates (ferrocummingtonite) begin to app~ ar. The cut immediately to the south is in the Lower Slaty horizon (P). This :::t~::::u~ ;~~: ::~::::h::8 :les:;here Sto~ and shows recrystallization. Small 5. At this stop, units 0 through K can be observed. Representative blocks of e t ch subunit are marked. Locally abundant coarse grained silicates and some sulftdes occur. A few blocks show portions of jet-pierced holes. Some septaria are !e vident. �STJ ATIGRAPHY OF THE BIWABIK IRON FORMATION AT THE ERIE MINING CO. Pr oda~l:n~eo:::~ation ,.. A. Calcite - marble layer. B. Lean quartz and silicate as irregular zones and layers. U:PP+r c. s..a t y (3 - 16) (10- 35) & D. Laminated zones of magnetite and silicate interlayered with thinner chert layers. (30 - 50) E. Massive granular chert with disseminated magnetite and occasional magnetite-silicate layers. Septaria. (5 - 10) F. Similar to C. & D. but the chert contains much disseminated magnetite and granular jasper. (25 - 35) G. Massive with much disseminated granular magnetite and jasper. Locally concentrated into irregular granular layering. Conspicuous carbonate or silicate mottles. (15 - 20) H. Similar to above except more abundant granular layering. Layering becomes more laminated toward bottom. ( 10) I. Algal structures and conglomerates. J. Granular. Similar to G. & H. but more abundant disseminated granular magnetite. Carbonate - silicate mottles are very con• spicuous. (5 - 15) ;..!, h (3 - 10) Upple r K. Cherty Thin, irregular and discontinuous magnetite layers having distinct boundaries separated by thicker massive layers of lean chertsilicate. The diabase sill is within this unit. (28 - 48) L. Moderately thick layers of laminated magnetite and silicate separated by equally thick layers of chert with much disseminated magnetite. ( 30 - 40) M. Thin, well defined magnetite layers similar to K. with more magnetite occurring as granular layers and disseminated magnetite (20 - 45) N. Not recognized. o. Alt ernating laminated magnetite - silicate zones and chert layers. Similar to L., but with increasing disseminated granular magnetite in the chert toward the bottom. Conglomerate near base • ( 15 - 3 5) 'l �-2- Pilobable Correlation to Gunderson L~er P. Massive granular silicate unit with vague layering. (75 - 90) Sl/a ty Q. Black, moderately laminated argillite. R. Upper unit is massive with granular silicates in a chert • silicate matrix. Lower unit is similar to above with scattered tnirt layers of magnetite and disseminated granules. (20 - 35) s. Irregular zones and mottles of dense and granular magnetite. Much disseminated magnetite in the massive chert. Abundant carbonate or silicate mottles. (15 - 35) L wer Ta Cherty I . u~ v. (5-45) = L lern?ed, st/1!- Thin irregular layers and granular concentrations of magnetite within thicker massive chert layers. Occasional mottles. (20 - 35) Magnetite occurs in even bedded iaminated zones wfth s~lica~e and argillite and/ or as even bedded concentrations of granules iri the chert. (15 - 30) Thick laminated zones of hematite, magnetite, silicate and argillite alternating with massive granular chert layers. Conglomerate, algal and/ or slate usually occur at the base of this member. (6 - 30) �RESER 'E ' B BABBRlY~ A MONHESOTA LAKE SUPER UOR PNST i'V'Uli'E Of EOLOGY fiElD fRIP MAY 4B ~923 NERAt.: RESER VE MiNING COMPAN~ ~OLUCY DOES NOV PERMIT POSSEIIION OF CAMERAS ON VHE OPERVYa Oft PLEAS£ CHECK YOUR CAMERA WITH PLANT PROTECTION AV VHE MAIN GAV Eo i: PLEASE AVOID SVANDtNG 'tOO CLOSE UNKS ON VOP OF VHE WALL~ 0 YHE NOR'ti'H AND SOUTH WALL o MAKE CLOSE INSPECTION OF THE WALLS ll..ARGt VACON II 'II'[ UN ADDI T ION NAZAROOU~o AYO»O CLRMB ING ON VHE MUC PILES AS THE RE IS A POSSIBILITY or DtSLODGING CHUNKS VACON VV'Eo APPROXIMATELY 85 FEET OF ijpp R CHERTY AND 35 THE BAlE OF VHE NORTH WALL VO THE VOP OF THE YHE ~LWTH GABBRO LSE EN LY VHUS REGUON ABOWV 3 OUVH WALLo TH A FEW ~~NORED FEET TO VHE $0UVH UN VH t EXHUBtV~ EPRE~ENVr O FEEV OF ijpPER St.ATY ARE STRATA AREA o GENER£L L ~ CoN E- A HIGHER DEGREE OF METAMORPHISM THAN STOP No o 2 WH i CH MULE$ VO VHE WE~To ~GNEVITE AND QUARTZ ARE VKE PREDOMI NANT MU NERALSo H DEN8ERGtTE 1 FAYAL ITE, ACV tNOLIVE, FE RROHYPERSV HoWEVER, COARSE GRA U N~ Of NE AND HORNBLE NDE ARE COMMON c UNT BLACK HiSINGERI TE CAN 8E SEE N IN YH£ NORTH WAL lo IT tS ONE OF THE LAST StLICA~ E Tp FORM IN V~E BIWABIK HRON f ORMATION AND CUVI THROUGH ALL PREVIOUS MINERAL ASSEMBLAGE o ~NOERSEN AND SCHWARTZ AVVRUBUVE VHE roRMAVtON ~ OtNBERGIVE 8 FERROHYP£RSVHEN£~ ~EGMAYHTE WEINSo EiSENV4AllY OEFLY ~r Ywo COM~OSED CF HORNBLENDE AND CU VYPES OF VEI NS ARE Q~ARVZ AND ~UNK or MEDIUM fO COARSE GRA INED M~NavONI E~UOENV I TO fHE IN VHtl AREAo ALKAL I FELDSPAR o tNJEC~tON OF THE AC IDIC VE INS fHE MAFIC VEINS CON IIV HORNBlENDEo 2: W[ ARE ABOUV NORVHEA~V 3 WALLo Ml E VO fHE WE@V OF SVO~ Noo ~e A MONOCL WNAL FOLD II VID NV IN �I ~rD NERALLY FINER GRAt MAGNET IV~ SI ZE II PREVALENT I N THIS AREA Q MN ADDITION vo QUARVZ CUMMINGVONRTE, ACVINOLUTE AND ANDRADIVE ARE COMMON MONERALSo OTHER F A URES VO NOTE IN VHOS AREA ARE THE £LG L ZONE &NO A SMALL DIABA E DUKE I ~ICH TRENDS SE-NWo ,,6oo FEET A LARGER DIABASE DIKE ABOUT 35 FE WtD£ OCCURS APPROXIMATELY W SV AL ONG THE PIT CENTER LINE FROM fHE EA T END 'LSO VRENDI SE-NWo or VHE PITo TH~S DIKE � 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, 1963 Description An account of the resource Institute on Lake Superior Geology. University of Minnestota, Duluth, Minnesota, May 2-3, 1963 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 1963 Contributor An entity responsible for making contributions to the resource R.L. Blake T.Z. Zoltai R.E. Hessevick C.E. Carson Cyrill M. Gallick G.N. Hanson P.W. Gast Richard A. Hoppin John C. Palmquist Lyman O. Williams Norris W. Jones Gene L. LaBerge George Moerlein G.B. Morey S.C. Nordeng C.O. Ensign M.E. Volin William C. Phinney D.W. Pollock E. Richard Randolph M.A. Rogers P.K. Sims Isidore Zietz Paul Weiblen James H. Zumberge William R. Farrand 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/7d87a2792037d451dbf6e8c0ff55ab06.pdf c174ae149f6d8beb5546748ab48f1a3a PDF Text Text Field Trip "Stratigraphy of the.Biwabik Iron Formation 11 Sponsored by the Lake Superior Geology Club Duluth, Minnesota May 4, 1965 �,, ~~ G>,._ /<I AUBURN ~t-«~ 1-/19 19/11. G' . G'-'9 ~ )'1- ~ 0 '9</ ~ O,s- +-~ ~ -v~ ~,o -v~~ <? INDEX MAP OF THE MESABI DISTRICT , MINNESOTA �FOREWORD Gentle reader, take heed, the field trip which you are about to take - not a polished affair with textbook illustrations and trip leaders able to J ve glib expla.ne.tions for everything you are going to see. o the gene al objectives for which the Lake Superior Geology In keeping with stitute was or- g nized, that is, to present preliminary r e sults of investigation in new areas of geologic interest, the leaders of this trip plan t o show you their approach tp subdivic1:1.ng the Biwabik iron formation beyond the basic fourfold subdivision ~rst proposed by J. F. Wolff in 1917. That the problem of further subdivision i ls difficult can be accepted si nce such authoritie s as Gruner, Grout and Broderick, E te , Schwartz and Gunderson have all come up with systems that many individuals use but which do not appear to be generally acceptable to all 'rorkers in the ield. In such a situation we may expect considerable discussion and disagreement i th any system proposed. ~Y emerge, Perhaps in the anticipated clash of opinions the truth. but don't count on i t. In any event the trip should be instructive " o both you and the leaders, and perhaps even entertaining to the philosophers rong you contemplati ng the state Of geol ogic knO'£o7ledge concerning this 1 the ,randfather of all iron for-mations. . A secondary but highly interesting part of this trip \d.ll be the 1ppo1~unity to observe the changes vmich take place in unoxidized iron formation rom the Eveleth area eastward almost to the contact of the Duluth Gabbro. T~~s spect of the trip should be of particular interest to students of metamorphism and those less c,o ncerned with the local problems of iron formation stratigraphy. lble controversy exists even in this area, the individualists among you vTontt I q.ave to accept any of our leaders' statements since the rocks themselves \-Till be tvailable for identification and collection. Due to the unexpectedly large number of people participating in this trip, we are antici pating some difficulty in maintaining our schedule of arrivals and departures f rom each stop. ~orn blows . compensation. Please return to the buses promptly a fter the I f you are left i n the pit don •t panic, apply for unempl oyment �The field trip will start at 7: 50 A.M. at Hotel Duluth and proceed rectly to the Auburn Mine property outside of Virginia . Upon completion of tq.e one stop at Auburn , the buses ldll ta.k.e us to the Erie property and proceed through four stops in various parts of the pit. Two stops are planned in the I REf Serve property to complete the program for the day. The buses will return to Duluth via Aurora and deposit passengers at the beginning point. Passengers 'rushing to remain on the Range should make private arrangements for transportation ftam the Reserve property or possibly from Aurora. It is anticipated that we ,dll finish the trip around 6:00 P.M. Lunch ~dll be served at the third stop in the Erie pit and rest stops are planned on ent ering the Erie property and leaving the Reserve property. Please read, consider and observe the regulations on the following page to which ~rJ have agreed in order that we can gain entrance to the various properties. �ruiruuTIONS: Through t he courtesy of the Oliver Iron Mining Division, United States Steel Corporation , Pickands Mather & Co., and the Reserve Mining Company, we have beFn granted permission to enter, inspect and collect small specimens on their rebpective properties. t~ In return for this privilege, we have agreed to abide by following regtuations which apply not only to visitors but also to all company pe~sonnel. l. pits. Safety hats and goggles will be worn at all times while in the various You will be issued such equipment at the first stop. This equipment is charged out to the Lake Superior Geology Club and we will have to pay for it if it is not returned at the end of the trip . 2. Picture taking of equipment is discouraged in all active pits and all pictures forbidden on the Reserve property. at the entrance to the Reserve property. for the fun of it . Arrangements will be made to check cameras Please do not try t o outwit these regulations You may make it difficult for future geologists to enter these interesting areas . 3. Please use caution when approaching rock walls . The talus slopes are notoriously unstable footing and rock slides from the walls above are not uncommon in the spring. While the purists among you will want to remove specimens from the living rock, let us remind you that \dth taconite, it ' s going to take a lot of hammering. We have a long, tO'\.lgh day ahead of us, so save your strength. also applies to potential mountain goats climbing up rock faces. Thi s You may endanger yorrself and other people as well as delay the trip , so stay off high faces. 4. Please use discretion wnen hammering on rocks near other people . Taconite is tough and hard. at high speed. Sharp chips have a tendency to fly in all directions The safety goggles supplied you are not just a bureaucratic detail. Us~ them at all times and make your arm on Minnesota taconite. sure they are on people near you before you t est It is reported to have an average crushing stkength of 55,000 pounds per square inch . �Ea ster n Biwabi k Str atigraphy f rom Gunderson a nd Schwartz .Minnes ota Geological Survey Bulletin 43 -~ z;~a ~ ~~ !I ~~! ;- s ~ -'C-Q; ~ ..~ ~ GENERALIZED COLUMNAR SECTION OF THE BIWABIK IRON-FORMATION ~ ~ -~ ~ ~ £ r: ~-:! == j -!!cri ~ ~ ? ! -0f:i!..._ou E~ ~ r ~ s o ~ ~ -- J: j IN THE EASTERN MESABI DISTRIC T, MINNESOTA i? 1-- - -- - - --------=---,--.,-,--- - - - -- - - - - - - - - l 6 i ·~· ~:g 32: c.5 Descnption of Submembe rs ;; .:...: w - Q (Notations cO - Jf ~ J I B {!6) (eo~t} and (we!:> I) refer to orcas near the easter n and western drill holes) calcite marble,. minor diop side, wollastonite , id oc ro s e, andradit e and quartz j """-;;;;ered (di'op/;ide) chert taconite locally wilh hornblende, hedenberq ite and some cummingtonite a nd oc tmol•te /ami'n aled (ferrohyperslhene - moqnel i le) c;uarl.t ! aconite with hedcnberqite c >~ w (l_ (l_ ::J taconite {west) I /:::,vy laminated (oclinoh'le-moqnefite) chert taconite 1-:---:-::::--fV ··-·tonile ond minor hedenbc rgi te -' (/) cr laminated (cummin91onite - mognetite) chert and loyoli te (east) and (421 "' .D :> <I 0 (71 E 161 F (201 with abundant granule struc tures and locolly w ith quart zfilled seplorio s tructures; m inor magneti te, c ufT'ming tonite and o ttinolite shaly bedded (cumminqtonite-maqnetite) quartz laconile hedenocrgite (cost); locally abundant w•l h minor andradite cumminglanite (west} quartz taconite (ea st) and mol/led (andradite) quartz obundonl magne ltl e - bearing granules throughout G (251 wavy layered (actinolite? -maqnetite) quartz taconite f---:1 J wit~ cumminc;~- quartz taconite r----t--__ond H locally liOl local ly with foyoli te (eas t) taconite (west) with with minor hedenberq:itei and cummingtonite (wes t) .,--+ - - (Sl (l6 ) " ' alq~l (moqnetile) quorlz toconife with abundant magnetite- r ich granules ond "---: ebblcs; conglomcrolic fabric throuc;~houl; minor hematite r---+-_ granule (maqneltle) quartz facomle with obundonl magneti te - rich pebbles ~top and thic kly layered (magnel!le) quoriL tocomle near bottom >- K (351 L (301 near wavy layered (silicole moqnelite) quartz taconite with abundant moQne tite· rich granules ond ptbblcs ; silicates ore actinolite ond ferrahyperslh ene (east) ond cummingtamte (we st) 9 1- cr w I u wavy layered (st'licote-magnett~e) silicate-quartz taconite with abundant mag netite-rich granules ncar bollom; silic.o tes with magnetite ore ferrohypersthcne and hor nblende (e o:o t) and cumming toni te and actinoli te (wes t); silicates wi th quartz ore fcrrohypers thene (cost) ond c umminqtonite (west) cr w (l_ (l_ ::J layered (maqnelt~e) loyolite-quorlz /acon/tc with fcrrohypersthene layered (maqnel/te) cumminqtom~e-quar tz tacom~e (wes t) M (201 N 41 0 (17) foyalde -quartz tacomle tocomle (westli minor with ferrohyp ersthene (eosl) and {eas t) and cumminqlomle-quorlz mac;~ne t ite bedded granule (magnetite) quortz - loyolile tacomle with some fcrrohypers thene and minor cummingtoniti! (cost) to quartz -cumminqtom~e focamle with · moogranules (west} ~et ite -beoring r: sholy quortz- foyoli!e tocomle cumminqlontle taconite 10 foyoltle tocomle (easJI and sholy quorlz- to cummingtont~e tocom~e (west); minor moonetite '!!aceous grophite -sikcote-quortz laconlle with abundant ferrohypersthene and minor foyolite, biotite, olmondilc ond pyrrhotite (eosl) and traces of pyrite, pyrhotit e and cummingtonite (wes t) . layered (magnetJ/e) loyolite -quortz taconite with m inor cumminQtonite ered (moqneflle) quorl.l taconite with minor cummingtonite throuq:hout, and hedenbcrgitc and some l oj!alite (east) ljr;;nule (magnetite) quartz taconite 1---+---+-- --flj r-minor f-,---:-:-:-i(/ (;;ered and granule 'j -, locotly, with minor cummingtonite throuqhout, ond foyolitc least) (moqnetJ~e) cummingtom~e-quorlz taconite with hedenberqite ond some fayolite (cos t) ~rlz f-;-;---;-o;;-( FIGU!\1': 5. - taconite with minor hedenbcrgite and cummingtonitei clastic quartz p ebble zone locally at bose Generalized columnar section or the Biwabik iron-[ormation. };j �sw - sw 28-58 - 1 7 S E -S W 1 7-58-17 ·. N W - NW 20-58 - 1 7 .r. - I . I 1/ v ~I , - ------ -- - ---- ---/+-- ---- / / : I I SW-N W ) 20 - 58-1 7 I I S E - NW 2 0-58 - 1 7 I G E O LOG I C M AP OF AUBU R N M I NE N SC ALE } . 1" - ·4 00' a. 0 --+--· ---- ~----· -·-· -·t--· --+--1 I I I l_ __ L E GE ND GEOLOGIC C O N TA CT S ( A PPRcJX I MA T F) ~ O VE R DU R OEN ____ ...,. CRE ST OF BA NK ..- ___ _... T OE O F B ANK �STRATIGRAPHIC S~UENCE IN THE BIWABIK IRON FORMATION AUBURN mNE 'lhickness in feet 1 UJ PER CHERTY MEMBER 16. 2 Jaspery, conglomeratic and algal chert (G and 15 . 14 13. 12 . + 10. submember I) 10 (est . ) Covered interval 10 (est.) Nodular hematitic chert beds interbedded with laminated hematite-silicate- magnetite beds 48 +'l Laminated hematite- silicate-magnetite beds with subordinate jaspery chert beds and lenses 31 Jaspery, conglomeratic chert beds interbedded with subordinate laminated hematite-silicate~magnetite beds 28 Cherty taconite ld th thin irregular ma.gneti te beds, magnetite mottles and disseminated magnetite 16 143 SIM'Y MEMBER ll. s 3 Laminated silicate magnetite tacom. t e with subordinate silicate chert lenses Laminated non- magnetic silicate taconite, fissile in part. 6 ' of fissile "intermediate slate" at bottom (G and S submember Q) lOl 37 ---:l::-:38=- LOWER CHERTY MEMBER I 9. Cherty taconite with irregular magnet ite beds . Upper 10 ' dark·~ colored silicate rich beds instead of magnetite beds , making base of lower slaty somewhat indefinite . 37 Mottled silicate- magnetite chert with chert "pebbles" and abundant coarse granules. ll Cherty taconite with thick (l"!) magnetite beds and mottles 84 has 8. 7 6. 5. Mottled cherty taconite vlith thin, very irregular magnetite ~ds. u Thick jaspery chert beds interbedded w1 th varying proportions of thin, regular laminated magnetite-hematite- silicatecarbonate beds . 66 �l Thickness in f'eetl CIIER1'I' MEMBER (Cont'd) 4. Thick hematitic chert beds with subordinate la.minated zones. Some clastic sand grains near bottom. Much carbonate. 8 Jaspery, conglomeratic and algal chert w1 th subordinate laminated zones. Sand grains common. 4 2. Massive chloritic (or hematitic) sandstone 8 1. Jaspery, conglomeratic and algal chert 4 3. 236 Total thickness exposed mGAMA ,.. QUARTZITJt~ 517 Base not exposed 1. Units 15 and 16 measured on bank between truck road and railroad near entrance to pit. Units l - 5 measured on SW bank, at SE end of' pit. Remainder measured above railroacl. 2. Unit numbers correspond to numbers pa.inted on the walls of' the Auburn Mine and are not intended to be a new stratigraphic system. 3. The lower slaty-upper cherty contact is not well-marked and disagreement exists as to its position. �__..... ...--- ERIE MINING CO MPANY / MAP OF ? PLANT AND PIT / / / I AREAS LEGEND I COARSE CRUSHER 2 FINE CRUSHER ,3~ CONCENTRATOR 1)PELLET PLANT , §\LOADING POCKET • 6 STOCKPILE 7' GENERAL SHOPS ' ,\ WEST PIT BIWABIK IRON FORMATION VIRGINIA FORMATION ::," 1;- 1 {! { DULUTH GABBRO �STOPS AT ERIE PITS Stor. At this stop, we have the base of the iron formation in the West Pit. The gama quartzite and the basal algal layer and conglomerate can be found in the roa • The alternating chert and argillaceous layers of submember V are exposed in the outer op. ' Fok The bank at the south edge of the pit is the Lower Slaty material P&Q. The r efore, the widt h of the pit here is the entire Lower Cherty member. 1 Sto J 2. This stop shows the upper part of the Lower Cherty ore horizon. The submember R can be seen along the top of the bank. It is greenish in color and !contains much minnesotaite and greenalite. Iead D irectly below this is the wavy bedded submember R. This is more noti ~ eable toward t he west, (containing abundant granular jasper). J The mottled submember S is below this layer. This submember occupies most of the lower part of the bank. It also contains much jasper as well as the con J. picuous pink to red carbonate mottles. J StoR 3. At the east end of the cut, we find the even bedded (U) and the alternating ma~sive and slaty submember (V). The massive layers consist almost entirely of ryedium grained green silicates . Some granular jasper and flinty black chert occ j rs. Minor amounts of sulfides are present. I Proceeding westward, we encounter the lower wavy bedded submember (T) and the mottled submember (S). Here the mottles consist of fine grained sili ~ ates instead of the carbonates seen in Stop 2. StoJ 4, This stop is in the upper part of the Lower Cherty member and shows submembers R & S . It correlates with Stop 2. The effects of the gabbro to the sou~heast are quite apparent. At the extreme east end there are abundant sulfides and Jvery coarse grained dark green silicates. Proceeding westward along the cut the grain size decreases and buff colored silicates (ferrocummingtonite) begin to app~ ar. The cut immediately to the south is in the Lower Slaty horizon (P). This :::t~::::u~ ;~~: ::~::::h::8 :les:;here Sto~ and shows recrystallization. Small 5. At this stop, units 0 through K can be observed. Representative blocks of e t ch subunit are marked. Locally abundant coarse grained silicates and some sulftdes occur. A few blocks show portions of jet-pierced holes. Some septaria are !e vident. �STJ ATIGRAPHY OF THE BIWABIK IRON FORMATION AT THE ERIE MINING CO. Pr oda~l:n~eo:::~ation ,.. A. Calcite - marble layer. B. Lean quartz and silicate as irregular zones and layers. U:PP+r c. s..a t y (3 - 16) (10- 35) & D. Laminated zones of magnetite and silicate interlayered with thinner chert layers. (30 - 50) E. Massive granular chert with disseminated magnetite and occasional magnetite-silicate layers. Septaria. (5 - 10) F. Similar to C. & D. but the chert contains much disseminated magnetite and granular jasper. (25 - 35) G. Massive with much disseminated granular magnetite and jasper. Locally concentrated into irregular granular layering. Conspicuous carbonate or silicate mottles. (15 - 20) H. Similar to above except more abundant granular layering. Layering becomes more laminated toward bottom. ( 10) I. Algal structures and conglomerates. J. Granular. Similar to G. & H. but more abundant disseminated granular magnetite. Carbonate - silicate mottles are very con• spicuous. (5 - 15) ;..!, h (3 - 10) Upple r K. Cherty Thin, irregular and discontinuous magnetite layers having distinct boundaries separated by thicker massive layers of lean chertsilicate. The diabase sill is within this unit. (28 - 48) L. Moderately thick layers of laminated magnetite and silicate separated by equally thick layers of chert with much disseminated magnetite. ( 30 - 40) M. Thin, well defined magnetite layers similar to K. with more magnetite occurring as granular layers and disseminated magnetite (20 - 45) N. Not recognized. o. Alt ernating laminated magnetite - silicate zones and chert layers. Similar to L., but with increasing disseminated granular magnetite in the chert toward the bottom. Conglomerate near base • ( 15 - 3 5) 'l �-2- Pilobable Correlation to Gunderson L~er P. Massive granular silicate unit with vague layering. (75 - 90) Sl/a ty Q. Black, moderately laminated argillite. R. Upper unit is massive with granular silicates in a chert • silicate matrix. Lower unit is similar to above with scattered tnirt layers of magnetite and disseminated granules. (20 - 35) s. Irregular zones and mottles of dense and granular magnetite. Much disseminated magnetite in the massive chert. Abundant carbonate or silicate mottles. (15 - 35) L wer Ta Cherty I . u~ v. (5-45) = L lern?ed, st/1!- Thin irregular layers and granular concentrations of magnetite within thicker massive chert layers. Occasional mottles. (20 - 35) Magnetite occurs in even bedded iaminated zones wfth s~lica~e and argillite and/ or as even bedded concentrations of granules iri the chert. (15 - 30) Thick laminated zones of hematite, magnetite, silicate and argillite alternating with massive granular chert layers. Conglomerate, algal and/ or slate usually occur at the base of this member. (6 - 30) �RESER 'E ' B BABBRlY~ A MONHESOTA LAKE SUPER UOR PNST i'V'Uli'E Of EOLOGY fiElD fRIP MAY 4B ~923 NERAt.: RESER VE MiNING COMPAN~ ~OLUCY DOES NOV PERMIT POSSEIIION OF CAMERAS ON VHE OPERVYa Oft PLEAS£ CHECK YOUR CAMERA WITH PLANT PROTECTION AV VHE MAIN GAV Eo i: PLEASE AVOID SVANDtNG 'tOO CLOSE UNKS ON VOP OF VHE WALL~ 0 YHE NOR'ti'H AND SOUTH WALL o MAKE CLOSE INSPECTION OF THE WALLS ll..ARGt VACON II 'II'[ UN ADDI T ION NAZAROOU~o AYO»O CLRMB ING ON VHE MUC PILES AS THE RE IS A POSSIBILITY or DtSLODGING CHUNKS VACON VV'Eo APPROXIMATELY 85 FEET OF ijpp R CHERTY AND 35 THE BAlE OF VHE NORTH WALL VO THE VOP OF THE YHE ~LWTH GABBRO LSE EN LY VHUS REGUON ABOWV 3 OUVH WALLo TH A FEW ~~NORED FEET TO VHE $0UVH UN VH t EXHUBtV~ EPRE~ENVr O FEEV OF ijpPER St.ATY ARE STRATA AREA o GENER£L L ~ CoN E- A HIGHER DEGREE OF METAMORPHISM THAN STOP No o 2 WH i CH MULE$ VO VHE WE~To ~GNEVITE AND QUARTZ ARE VKE PREDOMI NANT MU NERALSo H DEN8ERGtTE 1 FAYAL ITE, ACV tNOLIVE, FE RROHYPERSV HoWEVER, COARSE GRA U N~ Of NE AND HORNBLE NDE ARE COMMON c UNT BLACK HiSINGERI TE CAN 8E SEE N IN YH£ NORTH WAL lo IT tS ONE OF THE LAST StLICA~ E Tp FORM IN V~E BIWABIK HRON f ORMATION AND CUVI THROUGH ALL PREVIOUS MINERAL ASSEMBLAGE o ~NOERSEN AND SCHWARTZ AVVRUBUVE VHE roRMAVtON ~ OtNBERGIVE 8 FERROHYP£RSVHEN£~ ~EGMAYHTE WEINSo EiSENV4AllY OEFLY ~r Ywo COM~OSED CF HORNBLENDE AND CU VYPES OF VEI NS ARE Q~ARVZ AND ~UNK or MEDIUM fO COARSE GRA INED M~NavONI E~UOENV I TO fHE IN VHtl AREAo ALKAL I FELDSPAR o tNJEC~tON OF THE AC IDIC VE INS fHE MAFIC VEINS CON IIV HORNBlENDEo 2: W[ ARE ABOUV NORVHEA~V 3 WALLo Ml E VO fHE WE@V OF SVO~ Noo ~e A MONOCL WNAL FOLD II VID NV IN �I ~rD NERALLY FINER GRAt MAGNET IV~ SI ZE II PREVALENT I N THIS AREA Q MN ADDITION vo QUARVZ CUMMINGVONRTE, ACVINOLUTE AND ANDRADIVE ARE COMMON MONERALSo OTHER F A URES VO NOTE IN VHOS AREA ARE THE £LG L ZONE &NO A SMALL DIABA E DUKE I ~ICH TRENDS SE-NWo ,,6oo FEET A LARGER DIABASE DIKE ABOUT 35 FE WtD£ OCCURS APPROXIMATELY W SV AL ONG THE PIT CENTER LINE FROM fHE EA T END 'LSO VRENDI SE-NWo or VHE PITo TH~S DIKE � https://digitalcollections.lakeheadu.ca/files/original/535d7f6dfe72cecce1a31043297745d9.pdf 469cd2492591ee36bab1d297d7b4d2d0 PDF Text Text �NINTH ANNUAL INSTITUTE ON LAKE SUPERIOR GEOLOGY University of Minnesota, Duluth May 2-3, 1963 PROGRAM Thursday Morning - May 2, 1963 Science Auditorium, University of Minnesota, Duluth 9:00 General Meeting of the Institute ............ Chairman, H. Lepp Secretary, D. H. Hase SESSION I Co—chairmen: J. C. Green, J. S. Owens 9:30 D. W. Pollock S. C. Nordeng: PRELIMINARY INVESTIGATION OF A PORTION OF THE NORTHERN COMPLEX, BARAGA Co., MICH. 9:55 George Moerlein: STRUCTURE AND STRATIGRAPHY OF THE KEWEENAWAN IN NORTHWESTERN MICHIGAN 10:20 lO:+5 11:10 BURIED EXTENSION OF THE KEWEENAWAN Isidore Zeitz & P. K. Sims: BASIN IN MINNESOTA - A GEOPHYSICAL STUDY P. K. Sims & Isidore Zeitz: GEOLOGIC INTERPRETATION OF AERO— MAGNETIC ANOMALIES OVER PRE-KEWEENAWAN ROCKS IN CENTRAL MINNESOTA THE APPLICATION OF S. C. Nordeng, C. 0. Ensign & M. E. Volin: TREND SURFACE ANALYSIS TO THE WHITE PINE COPPER DISTRICT GENERAL DISCUSSION 11:35 12:00 LUNCH — MAIN BALLROOM, KIRBY STUDENT CENTER SESSION II Co-Chairmen: F. D. Effinger, T. E. Stephenson STRUCTURE WITHIN THE DULUTH GABBRO COMPLEX IN THE 2:00 W. C. Phinney: 2:25 C. N. Hanson, W. C. Phinney & P. W. Gast: THE THERMAL EFFECT OF THE DULUTH GABBRO UPON THE SNOWBANK GRANITE GABBRO LAKE AND GREENWOOD LAKE QUADRANGLES, MINNESOTA �* Hf 2:50 THE RELATIONSHIPS BETWEEN THE DULUTH GABBRO AND DIKES AW SILLS NEAR HOVLAND, MINNESOTA N. W. Jones: COFFEE BREAK 3:15 3:145 :1O G. FORMATION, THE STRATIGRAPHY AND STRUCTURE OF THE ROVE B. Morey: GUNFLINT LAKE AREA, MINNESOTA STRUCTURES OF CONCRETIONS IN THE THOMSON FORMATION, CARLTON AND PINE COUNTIES, MINNESOTA Paul Wieblen: GENERAL DISCUSSION 14:35 6:30 THEL/ DINNER - MAIN BALLROOM, KIRBY STUDENT CENTER Dr. R. L. Heller, Director, Earth Science Project; Head, Department of Geology, University of Minnesota, Duluth Speaker: EARTH SCIENCE AND THE SECONDARY SCHOOL CURRICULUM Topic: Friday Morning, May 3, 1963 SESSION III Co-Chairmen: C. Tychsen, I. L. Reid P. R. E. Hessevick: REFINEMENT OF THE 9:00 R. L. Blake, T. Z. Zoltai 9:25 G. L. Laberge: CARBONATE MINERALS IN THE IRON FORMATION AND THEIR SIGNIFICANCE 9:50 R. E. Randolph: SUSCEPTIBILITY MEASUREMENTS CF EMPIRE MINE MAGNETIC MATERIAL & HEMATITE CRYSTAL STRUCTURE COFFEE BREAK 10:15 Hoppin, J. C. Palmquist & L. 0. Williams: CONTROL BY PRECAMBRIAN BASEMENT STRUCTURE ON THE LOCATION OF THE TENSLEEP - BEAVER CREEK FAULT, BIGHORN MOUNTAINS, WYOMING 10:145 R. A. 11:10 C. M. Gallick: CLAY MINERALOGY OF THE DECORAH SHALE, MINNESOTA 11:35 M. A. Rogers: BIOGEOCHEMISTRY OF MINNESOTA LAKES: 12:00 LUNCH - MAIN BALLROOM, KIRBY STUDENT CENTER CARBOHYDRATES �SESSION IV R. W. Marsden Chairman: 2:00 J. H. Zumberge & 14. R. Farrand: LAKE SUPERIOR CORES AND BOTTOM TOPOGRAPHY ORIENTED LAKES IN NORTHERN ALASKA 2:25 C. E. Carson: 25O 0. M. 'hwartz: 3:15 THE SUBDIVISIONS OF THE BTWABT}( FORNATTON ON THE EASTERN MESABI GENERAL DISCUSSION Saturday, May , 7:30 - Hotel 1963 Duluth FIELD TRIP TO THE MESABI IRON RANGE Field trip leaders: F. D. Effinger, Pickands Mather & Company J. 14. EmanuelsOfl, Reserve Mining Company C. L. Iverson, Oliver Iron Mining Division Richard Strong, Oliver Iron Mining Division �1 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2—3, 1963 Institute on Lake Superior Geology REFINEMENT OF THE HEMATITE CRYSTAL STRUCTURE R. L. Blake.Y, T. Z. Zo1taiY, and R. E. Hessevick!" The crystal structure of hematite has been refined as an initial phase of studies involving atomic positions and vacancies in hematite during reduction to magnetite. Three—dimensiofll diffraction intenItieD were collected and automated on a spherical single crystal of hematite with both manual Buerger single crystal diffractometer. The structure has been refined with R factor of 7.1 pera least squares program and the final structure gave an cent. The structure model of Pauling and Hendricks has been confirmed with essentially no change in the iron coordinates and approximately a 5 percent change in the oxygen coordinates. The interatomic distances and bond angles were also calculated. TMinneapolis Metallurgy Research Center, Bureau of Mines 2! Department of Geology g Geophysics, University of Minnesota �2 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2-3, 1963 Institute on Lake Superior Geology ORIENTED LAKES IN NORTHERN ALASKA C. E. Carson University of Minnesota, Duluth Study of numerous thaw-lakes in the permafrost of the Arctic Coastal Plain has revealed that basin shape and orientation is controlled by winddriven waves and currents with associated thermal effects. The lakes range in size from mere puddles to basins 8 or 9 miles long, and all possess a similar basin morphology. This morphology consists of wide sub-littoral shelves and bars on the east and west sides, with the deeper central basin extending uninterrupted to the north and south ends. The ba- sins are elongated in a north-south direction, and have length-width ratios ranging from 1 to 5.1. Few basins are over 8 feet deep. In the Point Barrow area, most basins taper toward the north. Analysis of wind data from the Barrow weather station has revealed that summer winds are bimodal, being either easterly or westerly, average some 15 m.p.h., and are remarkably steady from one direction for several days at a time. orientation. Their average directions are nearly perpendicular to the axes of Investigation has shown that wind-driven wave action on the east and west sides, and the presence of circulation cells in the north and south ends, has produced the characteristic basin morphology; therefore, orientation. �3 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2-3, 1963 Institute on Lake Superior Geology CLAY MINERALOGY OF THE DECORAH SHALE, MINNESOTA Cyril M. Gallick University of Minnesota, Minneapolis The Middle Ordovician Decorah Shale is exposed sporadically in a 20-. mile wide band, extending from St. Paul to the southwestern corner of Houston It is a green-gray or less commonly a blue-gray shale that contains County. thin (generally 0.1 to 0.2 foot) interbeds and lenses of limestone and co- quina. The limestone layers are widely separated in the basal 10 to 20 feet, but increase in number irregularly upwards. In the middle of the formation, there are two or more zones, 3 to 5 feet thick, which contain limestone beds separated by less than O.i feet of shale; near the top, the limestone beds A few of the uppermost beds are become thicker and more widely separated. The formation is 89 feet thick at St. Paul and thins one to two feet thick. progressively to 25 feet at the Minnesota-Iowa border. The minerals in the grade size less than 1/512 mm were determined with "illite" (a 10 layered silicate with inter— the X—ray diffactometer to be: layers of a lL mineral), kaolinite, orthoclase, and calcite. Where all minerals are present, peak intensities indicate that orthoclase and illite predominate. The material sized greater than 1/512 mm is mostly fossil hash and At St. Paul, illite and orthoclase are present throughrare quartz grains. out the formation, apparently in constant proportions; kaolinite and calcite are sparse in the basal part but occur in significant amounts in the middle and upper part of the section. At Rochester, the basal shale contains illite or-thoclase, and calcite in proportions similar to that in the upper part of the St. Paul section and sparse kaolinite; the middle shales consist entirely of illite; beds in the upper part contain either kaolinite or orthoclase or both, but apparently only in minor amounts. The orthoclase in the Decorah Shale has been presumed to be the result of authigenesis. All illite (001) peaks on the diffractometer from the St. Paul section and from the basal part of the Rochester section are very asymmetrical, extending from 9.BA to slightly more than lLR, possibly indicating a considerIn the middle and able amount of interlayer 1L4X mineral in the structure. upper parts of the Rochester section, the illite (001) peaks are nearly symmetrical. analysis of a shale which had been weathered for possibly more This peak than five years showed only a change of the illite (001) peak. much more asympeak, broader and was lower in relation to the (002) illite X-ray metrical than that of any other shale analyzed. little more than l7R. It extended from 9.8k to a �L. UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on May 2-3, 1963 Lake Superior Geology THE THERMAL METAMORPHIC EFFECT OF THE DULUTH GABBRO UPON THE SNOWBANK GRANITE G. N. Hanson, W. C. Phinney, and P. W. Gast University of Minnesota, Minneapolis, Minnesota The effect of the thermal metamorphism of the 1.0 billion-year Duluth Gabbro on the 2.5 billion-year Snowbank Granite can be seen in the changes of the Rb-Sr ages of the biotites and the changes in the degree of triclinof the potassium feldspar in the granite. tion zones parallel the granite-gabbro contact. icity In both cases, the transi- Biotites from the granite within 2.0 kilometers of the contact (map distance) have Rb-Sr ages of less than 1.2 billion years. At distances greater than 2.0 kilometers, the successive biotite ages increase regularly to 2.55 billion years. The change in the ages exhibited by the biotite is shown to result from the loss of radiogenic strontium from the biotite strucThe mechanism for this loss is assumed to be either recrystallization ture. of the biotite structure or volunie diffusion of the radiogenic strontium out By a trial and error process of fitting theoretical of the structure. curves to the data, an activation energy of about 50 kilocalories for recrystallization by a zero—order rate process and an activation energy of 85 kilocalories for volume diffusion are proposed. Potassium feldspars at distances greater than 2.0 kilometers from the contact are maximum mirocline (maximum triclinicity) as determined by mea— Within 2.0 kilometers surement of the 131-131 spacing by x-ray diffraction. of the contact, the potassium feldspars are primarily orthoclase (monoclinic feldspar) except for several samples near the contact which show mixed orthoclase and microcline. The albite content of the potassium feldspar tends to be only a function of the facies of the stock and ranges from 0r59—0r96. The above data raise several questions which as yet are unanswered: (1) Why is microcline the potassium feldspar at distances greater than 2.0 kilometers? Could this be explained by regional metamorphism of the stock during the Algoman orogeny about 2.5 billion years ago? (2) Why did the potassium feldspar within 2.0 kilometers of the contact change to orthoclase upon thermal metamorphism by the gabbro and then not revert back to microcline upon cooling? Could this be a result of a lowering of water pressure in the stock at the time of the intrusion of the gabbro? �5 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2-3, 1963 CONTROL BY PRECAMBRIAN BASEMENT STRUCTURE OF THE LOCATION OF WYOMING THE TENSLEEP-BEAVER CREEK FAULT, BIGHORN MOUNTAINS, Richard A. Hoppin - University of Iowa, Iowa City, Iowa John C. Palniquist - Monmouth College, Monmouth, Illinois Lyman 0. Williams - The California Company, Pensacola, Florida angic fdnlt, The Tensleep—Beaver Creek Fault (Laramide in age) is a high The north side 32 miles in length, trending E-W across the Bighorn Mountains. The fault has moved up a maximum of 1350' in the axial portion of the range. presently known is a major transcurrent fracture but is the only such feature this trend, has that crosses the whole range. Why the fault formed and has the eastern 12 miles been a puzzle. This investigation was restricted to The Precambrian rocks were exalong which the Precambrian rocks are exposed. might have been reamined to see if there was any structural anisotropy that sponsible for the localization of the fault. One is best developed near the and dips 500 This foliation varies from N.80°E. to N.80°W. in strike fault. Several zones of pervasive foliation up to 300 feet wide were mapto 70°N. is less well deAs one goes north away from the fault, the foliation ped. in width are preveloped although local zones of a few inches to five feet shear surfaces; In the field, the foliation looks like closely spaced sent. for occahowever, thin sections indicate complete recrystallization except Later, pegmatitic masses cut this sional deformed relict plagioclase augen. In the fault zone, these foliated rocks, and the sedimentary foliation. quartz cementation are rocks, are brecciated and crushed. Quartz veins and 50 feet wide. characteristic. The crushed zone is only about Two strong foliations were discovered. This The second foliation trends N.50°-65°W. and dips 60° to 70°NE. foliation is dominant to the north of the fault but is absent near the fault. This fabthe fault. It is also the main foliation in the Horn area south of plagioric is also completely recrystallized with only a few relict deformed mylonitizatiofl arid quartz veining have clases. Later, zones of crushing, straight A particularly strong cataclastic zone is followed by a this trend. This same zone conportion of the valley of the North Fork of Powder River. is probably responsible for a small detinues southeast into the fault and flection of the fault. It seems reasonable, therefore, that the Tensleep-Beaver Creek fault was formed along an E-W zone of pervasive foliation and deflected in one area along another zone of northwesterly foliation. These foliations were formed under deep-seated conditions of plastic deformation followed by reLaramide took place at crystallization. The later deformation during the shallow depth and was of a brittle nature. �6 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2—3, 1963 Institute on Lake Superior Geology THE RELATIONSHIPS BETWEEN THE DULUTH GABBRO AND THE DIKES AND SILLS NEAR HOVLAND, MINNESOTA Norris W. Jones University of Minnesota, Minneapolis, Minnesota It is tentatively concluded from onissan'e go1ogic inepping in the vicinity of Hovland, Cook County, that the Duluth gabbro complex does not exand othtend as far eastward as Lake Superior, as suggested earlier by Grout ers (1959). Instead, the gabbro appears to terminate at the Brule River. The mafic rocks along the shore that previously were called Duluth gabbro are the lower part of the Hovland diabase sill. Three other diabase or gabbro units are recognized in the area. Petrographic and x-ray studies show systematic changes in the Hoviand sill. Silica, alkalis, and iron gradually increa3e upward from the base. is present As in the Skaergaard intrusion of East Greenland, an olivine gap and the two pyroxene boundary is crossed. The compositional changes are in- ferred to indicate that the sill formed by crystal fractionation. The relations of the intrusive units in the area can be explained as the result of emplacement of Logan intrusives, followed by intrusion of the Duluth gabbro ccinplex. The Logan intrusives were emplaced along a dominant- ly northeast—trending fracture system, whereas the Duluth gabbro complex in this area strikes essentially east-west. The Hoviand area represents the intersection of these two malor structural trends. �7 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute May 2-3, 1963 on Lake Superior Geology CARBONATE MINERALS IN THE IRON-FORMATION AND THEIR SIGNIFICANCE Gene L LaBerge University of Wisconsin, Madison, Wisconsin To allow more rapid identification, a staining technique was used in studying the carbonate minerals in the iron-formation. The procedure is outlined in an to simp- article by Warne in the Jour, of Sed. lifying the identification of the carbonate species, the stain showed beauti- Pet., March, 1962. In addition fully the relationship of the various carbonates to one another, and the association of particular carbonate species with certain other minerals. Some generalizations to which there certainly are many exceptions which may be made, are as follows: Most of the siderite is primary material. The ex- tremely fine-grained carbonate which comprises up to 75 per cent of some slaty layers in the iron-formation is almost certainly primary. ial is siderite and/or very iron-rich ankerite. This mater- Textures indicate that the siderite granules, which are not uncommon, are probably primary. Unques- tionably, secondary siderite is not common. In contrast, most of the ankerite, ferroandolomite, and dary. dolomite are secon- Much of this secondary carbonate is probably a byproduct of the de- composition of the iron-rich ankerite to form magnetite, with which it is usually associated. However, primary ankeritic carbonate in both the slaty material and in granules does occur. �8 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2-3, 1963 Institute on Lake Superior Geology STRUCTURE AND STRATIGRAPHY OF THE UPPER KEWEENAWAN ROCKS IN NORTHWESTERN WISCONSIN George Moerlein Bear Creek Mining Company, Anchorage, Alaska Between the summer of 1955 and the winter of 1960, Bear Creek Mining Company explored the western tip of the Lake Superior Syncline in quest of possible copper-bearing Nonesuch formation. The area covered includes por- tions of Ashland, Bayfield, Douglas, Washburn, and Burnett Counties, Wisconsin. Field mapping, extensive magnetic and gravity surveys, some refraction seismic work, and diamond drilling each played a part in outlining the geology of the area. The normal sequence of Keweenawan sediments, Copper Harbour, Nonesuch, and Freda formations was recognized, and the tratigraphy of each formation will be discussed. The structure of the area is essentially that shown on the 1948 edition of the Geologic Map of Wisconsin, a northeast plunging syncline. however, is locally complicated by faults of major Evidence importance. will be presented which indicates that the formation of the Lake Superior Syncline, at least in Wisconsin, began in an time. This, very late Keweenaw- �9 UNIVERSITY OF MINNESOTA, DULUTH of Geology Department May 2-3, 1963 Institute on Lake Superior Geology THE STRATIGRAPHY AND STRUCTURE OF THE ROVE FORMATION, GUNFLINT LAKE AREA, MINNESOTA G. B. Morey University of Minnesota, Minneapolis, Minnesota in the South Lake Quadrang1. near Gunf lint Lake in Cook County, was completed in 1962. The area is on the north limb of the Lake Superior structural basin; accordingly, the strata Geologic mapping of Animikie Group rocks strike eastward and dip consistently five to 15 degrees south, except adjacent to the Duluth Complex where the dips increase to as much as 65 degrees. The Rove Formation overlies the Gunflint Iron Formation, apparently conformably, and is truncated by the Duluth Complex; approximately 1,800 feet of The formation consists of two recognizable lithologic units. Rove are exposed. The lower unit, about 400 feet thick, consists mainly of a black, very finegrained, thin-bedded or fissile argillite with abundant graphitic or carbonaceous material and pyrrhotite, interbedded with lesser amounts of gray, mediumThe grained, massive graywacke. Calcareous concretions are locally abundant. argillites, grayupper unit, about 1,400 feet thick, consists of interbedded wackes, and quartzites; the latter two rock types become more abundant upward in the section. Graded bedding, sole marks, intraforrnational argillite fragments, convolute and small-scale cross-laminations and clastic dikes suggest a subaqueous flow origin for much of the upper unit. A south-southwestward movement of material is suggested by many of these structures. The Animikie Group rocks contain several east-trending sill-like bodies, mainly of diabasic gabbro, which range from less than 100 to more than The sedimentary rocks adjacent to the sills are 1,000 feet in thickness. metamorphosed to mineral assemblages. characteristic of the horr1blende-hornfels facies. The sills are correlated with the Logan Intrusives; they are older than and are truncated by the Duluth Complex. �10 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2-3, 1963 THE APPLICATION OF TREND SURFACE ANALYSIS TO THE WHITE PINE COPPER DISTRICT S. C. Nordeng1, C. 0. Ensign, Jr.2, M. E. Volin3 Over one hundred sets of drill hole data were taken from the files of the White Pine Company and coded on IBM cards. The section was divided into upper and lower halves and linear, quadratic and cubic surfaces of best fit were computed for each half for average copper percentage, thickness, and ounces of silver per ton, utilizing a taped multiple regression program on a medium speed digital computer. The linear surface for the upper half accounted for one-half or better of the departures from the mean and showed slight improvement for higher order surfaces, suggesting that the trends of the quantities under consideration are essentially planar in nature. The best fit was found for copper, The surfaces show an increase in thickness to the the poorest for silver. north and northeast, and in copper content to the southeast. The lower section showed macimum improvement in the sum of squares for the cubic model for both percent copper and thickness. Maps of the cubic surfaces successfully predict the location of a known ore body for which Departures of observed values from com no data was entered in the program. puted values for the lower half are interpreted as resulting from relative thickening and thinning of the upper part of the lower section which is relatively barren, and the lower part of the lower section in which most of the ore is found. 1 Department of Geology and Geological Engineering, Michigan College of Mining and Technology, Houghton, Michigan. 2 Chief Geologist, Copper Range Company, White Pine, Michigan Institute of Mineral Research, Michigan College of Mining and Technology, Houghton, Michigan �U UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2—3, 1963 STRUCTURE WITHIN THE DULUTH GABBRO COMPLEX, GABBRO LAKE AND GREENWOOD LAKE QUADRANGLES, LAKE COUNTY, MINNESOTA William C. Phinney University of Minnesota, Minneapolis, Minnesota Mapping and petrologic studies of the Duluth gabbro complex in the Gabbro Lake and Greenwood Lake quadrangles during the summers of 1961 and 1962 have indicated a complex series of gabbroic intrusions associated with antiform and basin-like structures. A major intrusion in the southeast quarter of the Gabbro Lake quadrangle and the north-central part of the Greenwood Lake quadrangle is roughly elliptical in plan, has a long axis of at least nine miles, and is inferred to be cone-shaped. It intrudes anorthositic gabbro and concentric layers that dip nearly vertical at the border and nearly horizontal at the center. Regular variation in mineral assemblages from olivine rich at the border to pyroxene-rich at the center indicate a normal differenNumerous smaller gabbroic intrusions as well as zones of tiation sequence. intrusions have been mapped. has Olivine gabbro with well defined layers having graded olivine concentrations in rhythmic succession forms a broad, shallow basin in the southwest quarter of the Gabbro Lake quadrangle. Within the basin, there are many anorthosite lenses that contain numerous one- to two—inch patches of olivine, apThe eastern boundary of parently concentrated from the interstitial fluid. the basin is in sharp contact (apparently intrusive) with the anorthositic The relative ages gabbro intruded by the cone-like intrusive mentioned above. of the cone-like gãbbro intrusion and basin-shaped gabbro intrusion are not known. Southeast of Gãbbro Lake, a marker zone in the gabbro can be traced around an antiformal structure that is elongated subparallel to the basal contact of the gabbro and has an anorthositic gabbro core. In the same area, a very coarse-grained pyroxene- and ilmenite-magnetite-rich dike, that is as much as one-fourth mile wide, can be traced for several miles. �12 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2-3, 1963 Institute on Lake Superior Geology PRELIMINARY INVESTIGATION OF A PORTION OF THE NORTHERN COMPLEX, BARAGA COUNTY, MICHIGAN D. W. Pollock and S. C. Nordeng Michigan College of Mining and Technology, Houghton, Michigan During the summer of 1962, the writers initiated a study of a portion Some results of the "Northern Complex" which lies in Baraga County, Michigan. of this study are reported herein. (1) amphiboSeveral lithologic groups have been mapped. These are: plagioclase—rich gneis— lite; (2) greenstone; (3) rnesocratic gneisses and (4) varieties. ses. Each of these groups can be subdivided into more specific The groups occur in definite belts and the following gradations were observed in the field: greenstone chiorite-plagioclase gneiss amphibolite mesocratic gneiss plagioclase-rich gneisses A thin "infolded" belt of Michigamme (?) phyllite has been located west of Clear Lake in Sec. 14, R 49 N, R 32 W. The broad structural trend is an arc, convex to the west. In detail, the structure is more complex. Poles to foliation (llsdiagrams) were plotted, but with poor results. The most useful approach was to outline the structure on the basis of vertical foliation trends. The origin of the foliation reMesoscopic linemains in doubt as the origin of the rocks is not yet known. ation is only feebly developed. Investigation is continuing. of some of the many problems raised during this study �13 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2-3, 1963 SUSCEPTIBILITY MEASUREMENTS OF EMPIRE MINE MAGNETIC MATERIAL E. Richard Randolph Cleveland Cliffs Iron Company, Ishpeming, Michigan The Negaunee Iron-Formation at the Empire Mine on the Marquette Range in Michigan consists, briefly, of magnetic cherty iron-formation, magnetic cherty carbonate iron-formation, magnetic cherty silicate iron-formation and a hanging wall member containing many large clastic facies interbedded with the precipitate iron—formation. The common criterion for grading ore at the mine is on the basis of per cent weight recovery. The ore type which presents the greatest problem in grade control is the clastic facies of the iron-formation which can vary It is very difficult to distinguish in weight recovery from 10% to tl1%. macroscopic means. Close orrich, moderate and poor der magnetometer surveying is an aid to localizing large zones, but a more definitive procedure is desirable for day-to-day control. It was suggested that susceptibility measurements on the cuttings from blast hole drilling might indicate the grade of the ore in that hole more cheaply and reliably than crude Fe analyses or streamlined Davis tube testing. clastic ore material by Susceptibility is the ratio of the intensity of magnetization acquired by a substance to the strength of the magnetizing field acting on the In a rock containing magnetite as the principal magnetizable constitbody. uent, susceptibility is, for practical purposes, the measure of the amount of magnetite present. Because per cent weight recovery of magnetite is the criterion for the cut-off s between rock, lean ore and ore in the hanging wall clastic zone, a program relating susceptibility measurements to per cent weight recovery was started. The conclusions are as predicted: measurements show a broad range of values for the general area but within a limited area correlate sufficiently well to offer a rapid, cheap, reliable method for sampling blast hole cuttings for grade control. �l&1 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2—3, 1963 Institute on Lake Superior Geology BIOGEOCHEMISTRY OF MINNESOTA LAKES: CARBOHYDRATES M. A. Rogers University of Minnesota, Minneapolis Fossil carbohydrates have been found in trypical sedimentary rocks; carbonaceous organic rocks such as peat, coal and lignite; fossilized wood; insect remains; modern lake sediments; modern and ancient marine sediments; and in lake waters. Carbohydrate materials were studied in the aquatic plants, lake waters and lake sediments of two eutrophic-alkalitrOphiC lakes of central Minnesota. Both free sedimentary sugars and sugars liberated on hydrolysis were recovered. Glucose, galactose, xylose and arabinose are the dominant sugars in order of decreasing abundance in aquatic plants of the two lakes. Maxima and minima in these sugars, as well as in the content of cellulose and hemicellulose, show little relation to season of collection and appear to be characteristic of individual plant species. Acid hydrolysis of lake bottom sediments recovered the eight sugars, arabinose, xylose, galactose, glucuronic acid, glucose, rhamnose, mannose and ribose, in concentrations ranging from 19.1 to 0.1 mg/gm of dry wt. sedThe variety and amount of these sugars is believed to demonstrate iment. the importance of microorganisms in altering the carbohydrate fraction prior to stabilization and preservation within the sediment. Acid hydrolysis of lake sediments from a deep core from Blue Lake, Minnesota, recovered in order of decreasing abundance the eight sugars, xylose, glucose, arabinose, galactose, mannose, rhamnose, ribose and glucuronic acid. A natural stability series for carbohydrates in the lacustrine envifairly stable: xylose, glucose, rhamnose, arabinose; moderateronment is: galactose; very unstable: ribose, mannose; fairly unstable: ly stable: glucoronic acid. �15 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2—3, 1963 GEOLOGIC INTERPRETATION OF AEROMAGNETIC ANOMALIES OVER PRE- KEWEENAWAN ROCKS IN CENTRAL MINNESOTA P. K. Sims, Minnesota Geological Survey, Minneapolis, Minnesota Isidore Zietz, U. S. Geological Survey, Washington, D. C. in An aeroinagnetic survey completed by the U. S. Geological Survey of 1961 has clarified our knowledge of the Pre-Keweenawan rocks in an area about 3,000 square miles in central Minnesota, extending from the latitude in of Little Falls, in Morrison County, south to the vicinity of Gaylord, of the anomalies In the northern part of the area, sources Sibley County. units have have been identified from scattered outcrops and separate rock been extended, based on geologic considerations and magnetic data. The aeromagnetic data indicate that the igneous rocks of the Penokean orogeny (Woyski, 19L19), which have been quarried extensively for building monumental stone in a broad area centered at St. Cloud, extend in the and eastward beneath oversubsurface south at least to latitude L5°l5' N. Northwestward from St. Cloud, lapping upper Keweenawan sedimentary rocks. and schist appears to be the dominant bedrock. In the southern part of the area, outcrops are lacking and interpretation of the magnetic patterns is more equivocal. Except for an anomaly at above igneous rocks of Lake Washington in Meeker County, which probably is mafic composition, interpretation of the magnetic anomalies intermediate or of the baseis not attempted. South of Hutchinson, a change in the trendmarked discontiby the magnetic pattern, suggests a ment rock, as indicated nuity, possibly a fault or an unconformity, in the Pre-Keweenawan rocks at this latitude. �16 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geo1gy May 2-3, 1963 STRUCTURES OF CONCRETIONS IN THE THOMSON FORMATION CARLTON AND PINE COUNTIES, MINNESOTA Paul Weiblen University of Minnesota, Minneapolis, Minnesota Calcareous concretions in the Thomson Formation found in the vicinity of Carlton are of two types. The concretions in graywacke and graywacke—iate beds consist of massive calcite, are ellipsoidal, and lack a distinctive internal Those in structure other than bedding, which conforms to the enclosing rock. finer-grained slate beds are zoned; they contain an inner core of slaty mater— ial, surrounded by well—crystallized calcite or by quartz with sutured grain The outer zone has a pseudo cone-in-cone structure, defined by boundaries. bands of slaty material. The calcite in both types of concretions replaces quartz and feldspar. The zoned concretions on the limbs of folds in the slate and graywacke succession are rotated out of the plane of bedding. The c axis of the calcite in the pseudo cone-in-cone structures is oriented parallel to the direction of maximum compression and a cleavage, which is well developed, parallels shear These features afford a promising means for further study of directions. structural relations in the formation. Remnants of concretions are found in the more intensely metamorphosed phases of the Thomson Formation southwest of Carlton, in phyllite, metagraywacke, and mica schist. Quartz has replaced the calcite in phyllite. Well—zoned concretions occur in the metagraywacke. The outer zones of these consist principally of hornblende, garnet, quartz, and andesine; the cores contain mainly epidote, quartz and andesine. Sections of the cores show that they are deformed into boudins. They also contain characteristic S-shaped structures formed by shearing and defined by heavy mineral concentrations. These similarStructures similar to these occur in the slate and phyllite. the concretions can be ities indicate that further sampling may show that Formation. used as stratigraphic marker beds in the Thomson Remnant calcite is found in the concretions in the mica schist, metagraywacke and phyllite. The (211) spacing of the calcite ranges from 3.04 angstrorns in the slate to 3.02 angstroms in the schists, indicating the occurrence of relatively pure calcite (less than 5 percent Fe,Mg) throughout the entire formation. Plagioclase coexisting with calcite ranges from An5 in the slate and graywacke to An40 in the mica scist and metagraywacke. It has been found that radiographs afford a practical method for studying the internal structures of the concretions. Fluorescence excited by electron bombardment provides a mean of distinguishing calcite from dolomite. �17 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2-3, 1963 Institute on Lake Superior Geology BURIED EXTENSION OF THE KEWEENAWAN BASIN IN MINNESOTA GEOPHYSICAL STUDY A Isidore Zietz, U. S. Geological Survey, Washington, D.C. P. K. Sims, Minnesota Geological Survey, Minneapolis, Minnesota Approximately 30,000 linear traverse miles have been flown eromagnet— ically by the U. S. Geological Survey across the "mid—continent gravity high". This is, perhaps, the most oustanding gravity feature in the United States, extending from near Lake Superior in a southwesterly direction to the Sauna basin in Kansas. Coupled with the gravity measurements and meager drill hole records, the aeromagnetic data strongly, if not unequivocally, imply the existence of a several-mile-thick accumulation of Keweenawan lava flows, extending uninterruptedly for 800 miles, f tanked by Pre-Cambrian sandstones which locally may be more than a mile thick. Total thicknesses of lava flows and neighboring sandstone can be estimated from the gravity data, whereas the aeromagnetic data supply the details of the configuration of the upper surface of the flows. In Minnesota, the magnetic data clearly outline the Twin Cities artesian basin, an elliptical trough 60 miles long in a northeast direction and 30 to 35 miles wide. basin and north of latitude LL°35' N., At the eastern margin of the the magnetic data suggest that the basin is bounded by a narrow northeast-trending horst of mafic volcanic rocks, probably elevated at least 1,000 feet above the adjacent rocks. The horst is the basement manifestation of the Fiudson-Afton anticline, a northeast-trending Paleozoic fold. In southern Minnesota, south of latitude L44°l5' N., the mafic lavas are at considerable depths, but the surface of the flows rises to within 1,500 feet at the Iowa border. �18 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2—3, 1963 LAKE SUPERIOR CORES AND BOTTOM TOPOGRAPHY James H. Zumberge and William R. Farrand University of Michigan and Columbia University to Cores were recovered from eleven drill holes in water depths of 500 drilling 1,130 feet in Lake Superior in 1961 and 1962. A shipboard, rotary and to lorig was used to penetrate the unconsolidated Pleistocene sediments The sediments were recovered by gravity and piston cate the bedrock surface. coring -- continuously in the upper 30 feet and intermittently below that depth. reaching bedThe longest core penetrated 686 feet of sediments without sediments rock, and it shows at least four alternations of glaciolacuStrifle The other cores penetrated only 7 to 156 feet and the varved), red lacustypical sequence was gray, lacustrine clay (lower part trifle clay (some varved), and red clay till. Below the till, well—washed and red, clayey till. red and sand (outwash?) was found in three holes, and in four other holes white (Cambrian?) sandstone was reached. drill A sub-bottom depth recorder was used in combination with the topography. Near logs for the interpretation of stratigraphy and sub-bottom broad bedrock valthe Minnesota coast, more than 700 feet of drift lies in a valleyIn the eastern part of the basin, strong north-south trending ley. modified stream and-ridge topography appears to be a submerged, glacially system, rather thinly covered with glacial drift. Also, the possibility of strong east—west faults between Keweenaw Peninsula and Sault Ste. Marie is indicated. � 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, 1963 Description An account of the resource Institute on Lake Superior Geology. University of Minnestota, Duluth, Minnesota, May 2-3, 1963 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 1963 Contributor An entity responsible for making contributions to the resource R.L. Blake T.Z. Zoltai R.E. Hessevick C.E. Carson Cyrill M. Gallick G.N. Hanson P.W. Gast Richard A. Hoppin John C. Palmquist Lyman O. Williams Norris W. Jones Gene L. LaBerge George Moerlein G.B. Morey S.C. Nordeng C.O. Ensign M.E. Volin William C. Phinney D.W. Pollock E. Richard Randolph M.A. Rogers P.K. Sims Isidore Zietz Paul Weiblen James H. Zumberge William R. Farrand 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/238d4ac647a23bdc878175ce30cd2492.pdf bed7e5202588fbfe694e67fe18680f19 PDF Text Text 8th ANNUM MEETING a fitute on Lake Superior Geoióy o, I cC I';' L11 12, 1962 rI 1t; scy - tti 't1 : -. Sponsored by • Department of Geology & Geological rtngineenng in Cooperation with The Institute of Extension Service t . . n 'ucrngan Coiiege ot Minmg & Technology �!LOARD OF DIRECTORS Dr. E. N. Crneron, Madson, Wisconsin Dr. W. I... C. Greer, Port Arthur, Ontario Dr. Iienry, Lepp, Duluth, Minnesota Dr. G. M. Schwartz, Minneapolis, Minnesota Dr. A. K. Sneigrove, Houghton, Michigaz. STEERING COMMIT'IE1' Dr. M W. Bartley, Port Arthur, Ontario Dr. W. L. Daoist, State Geologist, Lansing, Michigan Dr. C. E. Dutton, U.S. eological Survey, Madison, WiScnsin Dr. J. P. Dobell, Michigan Tech., Houghton, Micbigan Mr. R.obert Edwards, InIandSteelCornpany, Iron River, Michigan Iowa Dr. D. H. Hase, T.iveisity of Iowa, Iowa Dr. R., L. HeUr, Duluth Branch, University of Minnesota, Duluth, Minnesota Dr. H. L James, University of Minnesota, Minneaplis, Minnesota Dr. E. G. Pye, Ontario Department of Mines, Port Arthur, Ontario Dr. P. Tychsen, Wisconsin State College, Superior, Wisconsin Dr. 3. Zinn, Mithigan Stat University, East Lansing, Michigan Dr. J. H. Zumberge, University of Michigan, Ann Arbor, Michigan �EIGHTH ANNUAL MEETING OF THE INSTITUTE ON LKE SUPERIOR GEOLOGY May 10, 11, and 12 1961 Co.!Chairmen: A. K. Snelgroie an4 J. P. Dobell PRQGRAM civil-Geology Auditorium THURSDAY, MAY 10 8:30 Reg.itration Memorial Union Building 9:30 Address of Welcome President 3, R. Van Pelt Biness Session Henry L,epp Chairman - J. P. Dobell 10:30 Current Geological Research i the Palmer Area of the Marquette District, Michigan Jugtin Zinn 11:00 Geological Surveys Pikes Peak Area, Baraga Countr, Michigan Kiril Spiroff 11:30 Petrology of a Pec.mbrian Piuton 3. liai Cain near Pembine, Wiacon1sin 12 - 1:30 Luitch Chairman - L. 0. Bacon 1:30 Geophysical Evidence for the Presence of Kewee-nawan Volcanics in the Area of Upper Michigan be tween Marquette and SuIt Ste. Marie R. W. Patenaude 2:00 Application øf the High Speed Digital Computer to Gravity and Magnetic Analysea R. L. Coon and Peter Wolfe �THU± DAY, MAY 10 2:30 3-3:15 3:15 3:4 Magnetic Investigatios in Iowa A Preliminary Report D. H. Rase Coffee Break Extension of the Normal Distribution to Filtering of TwoDimensional (St.zface) Gravity and Magnetic Data Th Optimum Dip Needle Reading W. W. Johnson* and S. A. Finnegan W. 3. Hinze Method 4:15 Geophysical Investig-ation of a Diabase Dike near L'Ane, R. J. Reuss Michigan FRIDAY, MAY l1 Chairman - M. W. Bartley 9:30 A Regional Verticel Iiitensity Map of the Southern Peninsula of W. J. Hirize. Michigan 19:00 Diagenetic Replacement in Ore of the Empire Mine of Northern Michigan, and Its Effect on Tsu-Ming Han Metallurgical Concentration Footwall Mixeralization of the Osceola Amygdaloid in the Michigan Copper District R. Weege* 1:1:OQ. Induced Polarizatioi Logging in the Search for Native Copper in the Osceola Footwall Zones L. 0. Bacon 11:30 Preliminary Investigation or Late T. VT. Page* Wisconsin Drift North of Lake and 10:30 Superior 1Z 1:30 Lunch and A. Scliihinger D. R. Lindsay �FRIDAY, MAY11 Chairman - J M Neilson 1:30 Precipitation Chromatography in Geo-hemica1 Exploration S. D. Spain 2:00 The Water Prob1em of the Mining. Industry Qf the Upper Peninsula, S. H. Butler Michigan 2:30 Iron Ores of Bthar and Orissa, A. K. Sneigrove India 3:00 Mineral Exploration in the East Glare District of ireland R. W. .Schultz 330 Magne.tite Analysis of Magnetic P. D. Shandley 4:00 Sustptibility - An Investigation of the Remanent Magnetization of the Covi.ngton Dike Indicates speaket C. G Eufe �AUTHORS Page No. L. 0. Bacon C. G. Bufe J. H. Butler J. A. Cain Department of Physics, Michigan Tech., 1 Houghton, Michigan University of Michigan, Ann Arbor, Michigan Geography Departrnent, Michigan Tech., Houghton, Michigan Department of Geology, 2 4 5 Western Reserve University, Cleveland, Ohio R. L. Coons S. A. Finnegan Madison, Wisconsin Michigan Tech., Houghton, Tsu-Ming Han The Cleveland-Cliffs Iron Company, Ishpeming, Michigan 7 D. H. Hase Department of Geology, University of Iowa, Iowa City, Iowa Department of Geology, Mjchigan State University, East Lansing, Michigan Michigan Tech., Houghton, Michigan Lakehead College of Arts, Science and 8 W. J. Hinze W. W. Johnson D. R. Lindsay T. W. Page R. W Patenaude R. J. Reuse A. Schilhinger R. W. Schultz P. D. Shandley A. K. Sneigrove L D. Spain K. Spiroff 6 Michigan Technology, Port Arthur, Ontario Lakehead College of Arts, Science and Technology, Port Arthur, Ontario University of Wisconsin, Madison, Wisconsin Michigan Tech., Houghton, Michigan.. Geology Department, Calurnet & Hecla Incorporated, Ca,lumet, Michigan Michigan Tech., Houghton, Michigan Department of Physics, Michigan Tech., Houghton, Michigan Department of Geology aid Geological Engineering, Michigan Tech., Houghton, Michigan Department of Chemistry and Chemical Engineering, Michigan. Tech., Houghton, Michigan Department of Geology and Geological Engineering, Michigan Tech., Houghton, ii 9- 10 11 12 12 14 15 22 16 18 19 20 21 Michigan R. Weege Geology Depart-ient, a1umet & Hecla Incorporated, Calurnet, Michigan Peter Wolfe Madison, Wisconsin Justin Zinn Department of Geology, Michigan State University East Lansing, Michigan 22 6 23 �I INDUCED POLARIZATION LOGGING TN THE SEARCH FOR NATIVE COPPER IN THE OS EOLA FOOTWALL ZONES L. 0. Bacon A prograzn in cooperation with Calurnet and Hecla, Inc., has been. carried out. to adopt e induced polarization rnetrnd to under- ground logging of exploratory holes. The paper discusses equipment, logging techniques, interpretational methods and results. 7 7 / �AN INVESTIGATION OF THE REMANENT MAGNETIZATION OF THE COVINOTON DIKE C. G. Bufe The irwestigation of the remanent magnetization of the C.ovington dike near Watton, Michigan, was begun in September of 1960, and in the course of tha investigation oriented cores were taken froxi the dike and country rock on both sides., thin sections an4 magnetic samples were prepared fron the cores•, a spimer magnetometer was built and used to determine the direction of remannt magnetization, of 'the cores, several of the cores wer partly demagnetized to check their magnetic stability, and the, vertical magnetic anomaly recorded over the dike analyzed. The results f the investigation indicate the following: 1. The dir eCtios of magnetization of the samples ar fairly cons istnt, with mean declination of 1340, inclination of 86 degrees, with a four degree radius of conidenc.e at the 95 percent level. This corresponds to a noxth magnetic pole position of 530 N., 95°W. 2. The intensity of magnetization varies greatly between adjacent samples, even betweert sampl.e.s from the same. core. The intensity is less than the average rear the .suth contact o the dike and. near the center. The- average intensity of magnetization is 4. 35 x 103c g. s emu/cc 3. 60-cycle a. c. partial demagitetization at a peak field of 500 oesteds slightly increases t1 intensity of mnagnetization of samples fro•m near the contact, but reduces the intens ity of the interior samples to about one half oE. their initial value. The 4gher perentages of chlorite and deute.ric hornbiende near the contact indicate late stage oxidation reactions which may have produced a magnetic tonstituent of high coercive force. The percentage of magnetite is the same near the contact as near te oenter of the dike. 4 As theY demagnetizing field strength is irtcreased the directions ot rnagnetization of the- çors converge. After demagnetization at a peak 60- ytte field of 500 'oersted-s, the inean inclinatIon of the samples is -82° and the mean �3 declination is 55°, with a four degree radius at the 95 per" cent confidence level. The results of demagnetization are based upon the data from four s ampies. 5. The difficulties encountered in the intrpretation of the anomaly over the covington dike indicate that care nwt be taken in terpreting vertical field anomaijes over bodies with revere ed remanent magnetization by us e of formulas such as Cook's (1950) which are based on the assumption that there are no anomalous polarization effects present. �4 THE WATER PROBLEMS OF THE MINING INDUSTRY OF THE UPE R PENINSULA OF MICHIGAN J. H Butler The irreversible trend to-ai-d etr action of lcw er-'grade metallic mineral deposits, as localized, high-grade deposits become depleted t13ruh incre acing oneurnption, involves large-s cal&, highly me.chanized mining and mineral processing operations. Such operations normally have very high energy and water requiremet. Year by years the availability of vtater for mineral industries becomes of greater signfficace as growing 7cr:uiation -nd intensification of ecwmIc activity throughout the nation bring about competition for existing water resources Despite the very favvrable hydologic environment of Mihigans Upper PennsuIa, water "probi.em&' appear to be developing 'th respect to the mini and processing of low-grade .ron ore deposits on the Marquette Iron ange. The situation t one plant is éamined and water availability for future regional desrolopment of the Marquette Iron Range is considred. Implications are drawn far the future ot low-grade mineral ecploitation in the subhumid areas of the country. �PETROLOGY OF APRECAMBRIANPLUTON NEARPEMBINE, WISCONSIN A. Cain rock units have been mapped within some 350 square miles of the Precambrian grariiti and metamorphic complex ci northeastern Wiscorisin. The r1ative age-relationships among these units are suggested, primarily from a study of enoliths, as follows: Nine Youngest: Diabase dikes Amberg Granite Newingham Granodiorite }Ioskin Lake Granite Metagabro sills TwIe Foot Fall Quartz Diorite Marinette Quartz Diorite Bitite gneiss Oldest: Quinnesec Formation Structural, modal, and specific gravity data are presented for the Newingham Granodierite to illustrate their behavior within, this terrane. The results of structural analysis are somewhat inconclusive but suggest a ioughly coicentric foliation pattern for the 40 square mile pluton. Data derived from 5 spcimens of Newingham Granodiorite are used tc illustrate the geographic variabilit {br means of trend surface analysis) of quartz percentage, feldspar percentage feldspar ratio potash feldspar/ plagioc1ase) color index, and specific gravity within the mass. Correation coefficie4ts are given for each of the 10 pairs of variates t indicate degrees of assQciation. From thi quantitative analysis, feldspar ratio is Seen to be the one variate which does not conform to "expected" patterns of behavior. �6 APPLICATIONS OF THE HIGH SPEED DIGITAL COMPUTER TO GRAVITY AND MAGNETIC ANALYSIS R. L. Coons and Peter Wolfe Niflety prcent of the time spent in geophysical interpretation is taken up by manipnlating numbers leaving only about ten percent of the time for geologic interpretation of the results. Until the advent of the high speed digital cnputer certain analysis techniques were. t costly or time consuming to perform by hand. The proper applications of computer tecb iques to data reduction and analysis allow the geophysicist to reverse th above procedure spending ten percent of his time on arithmetic and ninety percent of his time on interpretation. Pgrams eoped to date in magnetic and gravity analysis clearly demonatrate sorn of the advantages in using the computer. Magnetic readings •can be electronically recorded on paper tape, fed into a coxnpixter, corrected for drift and. diurnal ariations, and plots of total intensity, second derivatives, and downward continuation, made by the computer.. This eliminates all erors that are normally introduced in recopying nd manipulating the data by hand. The resulting maps o the analysis can be pibtted and in certain cases even contoured by the computer. Gravity readings are cirift corrected by hand along with the s1ireyers notes.. These operatiotis could be. pefo:rmed by the computer but this gives the interpreter a chance to examine the reliability of the data. The computer then calculates the Bouguer Anomalies using several density asumptions, plots profiles, checks før errors, performs least square surface analysis, and plots the residual maps. SeraI types of resdil analysis are thus quickly obtained leaving more time for geologic Interpretation of the results. �7 DIAGENETIC REPLACEMENT IN ORE OF THE EMPIRE MINE OF NORTHERN MICHIGAN AND ITS EFFECT ON METALLURGICAL CONCENTRATION Tsu-Ming Han This paper describes the texture, mineralogical, and chemical criteria of diagenetic enrichment of the low grade irpn-forxation at the new Empire Mine near Palmer, Michigan, and the influence of the diagenetic changes upon nietallurgical response of the ctude ore to benefication. At the Empire Mine, in Section 19, 47-26, the iron-formation is involved in a secondary fold of the. Marquette syclinorium. The strike changes from N-S at the north side of the section to E-W in the southern oart of the section. Dips also change from W to NW to N as the formation swings around the fold. In general the dips average about 300. On the basis of mineral ratio, and mineral assemblage, the iron-formation may be classified into five lithological types: (a) interbedded complex (which includes magnetite -bearing g reywacke, magnetite -hematitic che rt with clastics, and the other four lithological types), (b) magnetite-carbonateche rt, (c) magnetite-silicate - chert-carbonate, (d) magnetite-chertcarbonate, and (e) magnetite -bearing chert- carbonate. Laboratory data revealed that the iron content among the abovementioned nonclastic rocks is fairly uniform averaging 32% in type (c) to 36% in type (c). The ma.gnetite content varies considerably averaging 20% in type (e) to more than 42% in type (b). The iron uni.t recovery averages 44% in type (e) to 88% in type (b). Such variations are, in a large part, attributed to the differential diagenetic enrichment of rn-agnetite in the different lithological types. The following criteria, involving the formation of the mineral magnetite, support the contention that diagenesis has played an important role in the geologic history of the Empire ore: (a) more or less the same mineral assemblage but different mineral ratios; (b) more than one generation of magnetite; (c) cut-off and replacement of carbonate-chert by magnetite larnina; (d) evenly distributed magnetite; and (e) lack of correlation of metallurgical concentration results between samples from the same lithologic horizons. �8 MAGNETIC INVESTIGATIONS IN IOWA D. H. Hase In 1961, vertical intensity magnetic measurements were made in evera1 areas for the Iowa Geological Survey as the initial phase of a project to map the etitir state magnetically. Ground and airborned magnetometer su.veys of the state are currently in progress. The magnetic anomalies are attributed to changes in the lithológy and/or configuration of the Precambrian cyrstaUine basement rocks. The Vincennes anomally is probably due to a body of feldspathized gneiss r diorite which is a few square miles in extent, has a maximum relief of a few hundred feet, and is about 2900 feet below the surface, The Manson anomaly is attributed to somewhat feldspath.ized, znagnetiterich, biotite and augen gneiss. Relief owing to erosion and perhaps partly to faulting in the vicinity of the main anomaly may be of the order of 1000 to 1500 feet along a northeast-trending buried ridge. Large gravity and magnetic anomalies in the Adair area are apparently related to rather shallow, basic igneous rocks. Departures from the smoothed profiles define the Thurman-Redfield and other basement structural ZOne8. A magnetic high without a corresponding gravity high near Greenfield is attributed to ferruginous schists in the base.rnent rocks, - �9 OPTIMUM DIP NEEDLE READING METHOD Wm. J. Hinze A good deal of the confusion surrounding the use arid interpretation of ip needle observation originates from the method by which the instrument s read. The selectjon of the.optimum reading method is dependent on four criteria: accuracy, reliability, simplicity, and rapidity. These are all important; however, their relative importance varIes dependIng or.the requirement and conditions of the survey. Various reading methods are va1uated with respect to these criteria with the aide of a laboratory investigation employing controlled magnetic fields. The optimum readIng method varieS, with the survey, but the reading method based on the arithmetic mean of the second, twice the third, and the fourth reversals of the oscillating dip needle is most universally acceptable. �10 A REGIONAL MAGNETIC MAP OF THE SOUTHERN PENINSULA OF MICHIGAN Wm, J. Hinze A regional vertical magnetic intensity map is presented of the Southern pninsula of Michigan. It is based on a peninsulawide ground magnetic survey with observations made on a six mile interval plus detailed observations in local areas. This map which primarily reflects lithological and structural variations in the Precambrian basement rocks and their depth beneath the surface shows a strong relationship to the trend of sedimentary structures of the Michigan basin and Precambrian trends of Wisconsin and the Northern Peninsula extrapolated into the basin. The magnetic map and the regional gravity map also show a marked resemblance in many areas. In particular the Michigan Gravity High correlates with a major positive magnetic anomaly. �11 EXTENSION OF THE NORMAL DISTRIBUTION TO FITRING OF TWO DIMENSIONAL (SURFACE) GRAVITY AND MAGNETIC DATA W. W. Johnson amd S. A. Finnegan The normal distribution curve has been successfully used in filtering one dimensional (profile) data. This method has been extended to two dimensional measurements of potential fields, both as a smoothing function and as a high-pass filter. The method involves the use of weights determined by different processes operating on a normal curve of revolution. of this method are shown applied to remove regional trends gravity anomalies yielded by a buried spherical body and a buried Results from infinite vertical sheet. �12 r _____ PRELIMINARY INVESTIGATIONS OF LATE WISCONSIN DRIFT NORTH OF LAKE SUPERIOR .T. W. Page and D. R. Lindsay Problems of late Wisconsin chronology have been studied for the past fl years in the Lake Superior region of Minnesota and adjacent States. Work of a similar nature has been carried Qut on the Canadian side of the Lake but has been local and disconnected. Investigations of a regional nature and correlation of new findings with presently known data will help to complete the Canadian picture and pO5Sibly aid in solving some of the admitted problems remaining on the American side. As aioffshoot of work presently in progress and supported by the Geological Survey of Canada, some new data and correlations are presented. The Rainey lobe of Patrician ice is believed to have developed at least two systems within the area discussed after retreat from the Ver' million moraine in Minnesota. They are believed to be post Two Creeks in age. Retreat to and beyond the Hartman-Kaiashk moraine allowed development of Lake Johnson in the Steeprock area and a similar lake in the Wabigoon basin. Outlets to both lakes were blocked by ice to the west during their early history. '—morainal The Nipigon and Dog Lake moraines are both considered younger than the Hartman-Kaiashk moraine and may represent the positions of an ice front during the life of Lake Duluth. While definite conclusions cannot be drawn at present it appears that a large area in northeastern Minnesota was free of ice from Two Creeks time n and was closely followed by disappearance of the ice from adjoining areas in Ontario. A study of plant geography lends further credance to this hypothesis. retreat After of the ice from the Nipigon moraine a later front developed some 30 miles east of Lake Nipigon and trended in a southeaster- ly direction to the White River area. The presence of extensive outwash plains and varved clays east of Lake Nipigon suggest a greatly expanded and possible connection with Lake Ojibway. forerunner of this lake Final retreatof the ice over the continental divide impounded the stages of Lake Ojibway which at this time drained through the Pic early �13 -vr system to the Lake Superior basin. Lake Agassiz II has yet been dtermined. No definite eastern outlet for throughout the area await continuThis and more complete detail of vnt5 vestigat10. �14 GEOPHYSICAL EVIDENCE FOR THE PRESENCE OF KEWEENAWAN VOLCANICS IN THE AREA OF UPPER. MICHIGAN BET WEEN MARQUETTE AND SAULT ST MARIE R. W. Paten.aude During five days in August, 1961, 1100 data miles were flown with an Elsec proton precession magnetometer in the area of Paleozoic sediments between Marquette and Sault Ste. Marie. The magnetic data suggests that the area between Grand Island and Sault Ste. Marie is undr1ain by Keweenawan type volcanics. The magnetic pattern is believed to reflect the influence of therrno- remanent magnetization in the volcanics. �15 GEOPHYSICAL INVESTIGATION OF A DIABASE DIKE NEAR LTANSE, MICHIGAN R. J. Reuss The purpose of the investigation was to determine the relative age of the reversely magnetized, fresh dabase dikes that occur in the area near L'Anse, Michigan. The dike investigated trended from an area of late Huronian slates into an area overlain by red sandstones of Cambrian or late Precambrian age. A magnetometer survey was run across the dike at several places in an attempt to determine whether or not the dike penetrated the sandstone, or was overlain by it. The results of the survey seem to indicate that the dike is overlain by the sandstone, and is therefore of an earlier geological age. �16 GEOCHEMICAL AND GEOPHYSICAL PROSPECTING FOR COPPER, LEAD, AND ZINC IN THE EAST GLARE AREA OF IRELAND RichardW. Schultz The rocks in this area are predominantly lower Carbonilerous limesstoneS and si-tales, underlain by Upper Devonian shales and sandstones. The najor structural feature is a large, shallow, south westerly trending syndilne. The nearest exposure of post-Carboriiferous intrusive rocks lies over one hundred miles from this area. On the north limb of the syndlirie, in an area containing numerous minor folds, re several small base metal suiphide deposits which had been mined in the last century. A small, but geologically significant chalcopyrite replacement deposit has been discovered recently by means of the induced polarization method. The two basic typcs of suiphide deposits found in the area arc: (1) fracture-filling calcite-suiphide lodes with minor walirock replacernrt in competent limestone, and (2) replacement deposits in shaly limestone controlled by upfolded irnpernneable barrier rocks. High pH of stream and ground water throughout the area inhibits the of heavy metals and renders them practically immbile. For that rason, as well as poor drainage conditions in general, stream water and sediment sampling was found to be ineffective. Also, blind deposits could not be expected to have secondary chemical dispersion haloes associated with them. However, glacial erosion has caused strong and clearly discerni ble physical dispersion of metals from subouteropping deposits and, therefore, a method of reconnaissance soil sampling was adopted to search specifically for glacial dispersion patterns. Experimental work showed solubility that all of the known deposits could have been found by geochemical float tr?cing, and several new anomalies have been discqvered. variable-frequency induced polarization method was used in and detailed geophysical prospecting. It was found to be effective in detecting even relatively small amounts of disseminated suiphides and, therefore, to be more sensitive than other electrical methods. Its main disadvantage is poor resolution and geometric definition of anomalies, making The reconnaissance it difficult to spot drill holes. The vertical-coil electromagnetic technique was found to be unsatismost reconnaissance work as it does not respond well to dis- factory for �r 17 :inatd suiphide rruineralization. Howeier, ii has been effective in disrfl1flg flat-lyingblack shale beds coiitaining primary pyrite which give riSe CO strong induced polarization anomalies. Self-potential measurements provided an additional means of recognizing the troublesome pyritic shale. �18 M\GNETITE ANALYSIS BY MAGNETIC SUSCEPTIBILITY P. D. Shandley A transistorized magnetic susceptibility meter which utilizes the balanced transformer principle is described. The instrument has been used to determine the percent magnetite in ores. The results of this• method of analysis are comparable to the results obtained by magnetic separation and cheniical analysis. �19 IRON ORES OF BIHAR AND ORISSA, INDIA A. K, Sneigrove While visiting the University of Sind, Hyderabad, West Pakistan, in 1961-62, as Fuibright Lecturer in Geology, the speaker made a brief tour of the Tata Iron and steel empire of Northeast India. The Iron Ore Series, containing an estimated 8 billion tons of good grade wrkable ore in Bihar and Orissa produced 6,670,000 in 1960. Rocks of the Iron Ore Series range from shales and quartzites to coarsegrained clastics and are associated with pyroclastics, only slightly metamorphosed. The well layered major deposits occur chiefly along ridges. Generally soft, friable and powdered varieties together form the major part of a deposit, and hard, compact varieties are found mostly in the top portions. Depths are about 300 feet. Properties of varieties generally available in one- deposit are hard 33%, soft 16%, lateritic 9%, biscuity or flaky friable 33%, blude dust 10%. Principal minerals are hematite, magnetite, rnartite, and occasionally also lirnonite and goethite, together with some hydrous iron silicates such as greenlite and chamosite. Quality, origin structure, alterations, and development planning, treatment, and economics will also be discussed.. The author is indebted to Tata Iron and Steel Corpor3tion for much information and many courtesies.. �r•__ 20 THE USE OF PRECIPITATION CHROMATOGRAPHY IN GEOCHW CAL PROSPECTING J. D. Spain The use of agar gel columns containing arnmonium sulfide precipitant for mineral identifications and trace element determination will be described. (Spain1 J. D.., AnaL Chern. 32; 1622-1624 (1960), Spain, J. D.,, Ludernan, F. L., and Sneigrove, A. K.,, Econ. Geology, in press). Sensitivity studies showed cobalt, zinc, lead, bismuth, antimony, and to be determined in solutions containing 20 ppm or less. Iron, cadmium, copp'r, and arsenic were determined in solutions containing less than 300 ppm. All analyses involved the standard amrnonium sulfide column with the metal irons applied in 6 M HC1 søluton. In preliminary studies to determine accuracy of qualitative identification, 80 synthetic unknowns composed of tin, three component mixtures of the previously mentioned ions were analysed. iron, lead, cadmium. and cobalt were identified correctly in all unknowns. arsenic. antimony1 and tin gave any extensive difficulty, these having been determiiied with less than 80% accuracy. Only Sixty one mineral samples were analysed by this method and the results were compared with those obtained from the emission spectrograph. It was found that the major metallic constituents of miner als can be det erznined with a high degree of accuracy. How in most cases the minor con- stituents were missed. It'was concluded thatin special cases the method would be a useful field tool. The more recently developed technique of filter paper precipitation chromatography will be described and its advantages over the agar gel technique will be discussed. These advantages include. stability..bf:the precipitation media, speed of chrornatograrn development, quantitative as well as qualitative results in a permanent form, and inexpensive, portable apparatus. �2.] GEOLOGICAL SURVEY, PIKES PEAK AREA, BARAGA COUNTY, MICHIGAN. Kiril Spiroff Unusually high geiger counter readings were detected in outcrops on the west side of Huron Bay, ten miles east of L'Anse, in Barag& County, Michigan. The area was investigated by trenching and diamond drilling. Surface mapping and ir1ormation from three diamond drill holes yields the following geological column (from top to bottom): andstone, iron formationu, quartzite, conglomerate, and granite. The study fills a gap in our knowledge of the Precambrian area of Michigan's Upper Peninsula. It did not reveal any deposits of economic sigrificance. �22 FPOTWI4LL MNERALIZATION I THE OSGEOLA AMYGDALOID MICHIGAN NATIVE COPPER DISTRICT R. J. Weege and A. W. Schillinger Conventional underground mapping methods and diamond drilling are being applied in a study to determine the nature of the copper ore occurrences r.car the footwall of the Osceola amygdaloid. A description is given of the character of the airiygdaloid and the types and location of native physical copper mineralization and associated alteration. Work to date suggests that the footwail ore is formed independently from the hanging-wall ore and tha.t localization at the footwall is caused by impermeable barriers. The barrier concept as advanced by earlier writers to explain the concentration of solutions in the ore body as a whole is carried one step further and is found to be equally as applica!ble for the localization of smaller oreshoots within the Osceola ore body. �________ r 23 CURRENT GEOLOGICAL RESEARCH IN THE PALMER AREA, MARQUETTE DISTRICT, MICHIGAN J. Zinn r Palmer area is structuraUy a distinct syncline containing jirnikean rocks and is separated from the main Marquette synclinorium by the prominent Volunteer Fault. Exposures of the Negaunee iron formation in this area show variations not characteristic of this formation s seen elsewhere. The lower horizons at the Negaunee contain various proportions of clastic debris and some lenses of conglomerate material. 1dso, this fôrrriation rests on Ajibic quartzite locally without the normally intervening Siamo slate. Currently, these sedimentational problems are being investigated by Robert Henny. The investigation to date appears to show that the Negaunee was a near shore deposit in this area, that the chert layers in the formation rapidly solidified into durable beds and that the iron precipitated in trivalent condition. iron forination was deposited continuously with the clastics even in the conglomerate horizons. The implications of .ch deposition encourage speculation as to rate of deposition an. other sedimentary problems concerned with Lake Superior type formations. The Several other problems in the Palmer area deserve attention. Some of these are the extent and nature of the Volunteer Fault, the Eastern limits of the Palmer syricline and the pyroclastics in the iron formation. It is understood that research on some of these problems is being done at the University of Wisconsin. � 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, 1962 Description An account of the resource Institute on Lake Superior Geology. Michigan College of Mining & Technology, Houghton, Michigan. May 10-12, 1962 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 1962 Contributor An entity responsible for making contributions to the resource L.O. Bacon C.G. Bufe J.H. Butler J.A. Cain R.L. Coons S.A. Finnegan Tsu-Ming Han D.H. Hase W.J. Hinze W.W. Johnson D.R. Lindsay T.W. Page R.W. Patenaude R.J. Reuss A. Schillinger R.W. Schultz P.D. Shandley A.K. Snelgrove J.D. Spain K. Spiroff R. Weege Peter Wolfe Justin Zinn 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/44f7124d14f12414cf6d4607d9d50899.pdf 596272a38cfdcea234c5d67d1589e6f5 PDF Text Text -&IXTH ANNUAL MEETING INSTITUTE O LAKE SUPERIOR GEOLOGY • APRIL 27th 29th, 1961 SNYSORED13' I tKEFJEAD BRANCH - C NLWJ \N [WI ITUTr OF MENING & METALLURGY 1 EL- — ON'IAfl-iO-DFI-TAhTMI \T OF MINLS PORT EIThJR& FORtW4LE1 \F ONTARIO �SIXTH ANNUAL MEEfl'ING OF TE OF lAKE SUPERIOR GEOLOGY iNSflTflE April 2?, 28 and 29, 1961 PRcOHAM. Provl.ncial Rooms Prince Arhm' Hotel Thurs4ay, April 27 Chairman E• 8,30 A.M. 9.30 10.30 11.00 11,20 1l.O G . SE$SION I Abàtract Na. Pye Page. No. Registration and Social Hour Address of Welcne WL.CS Greer Business Session .Henry Lepp Glimpses of the XXI Injernational a Geó1ogca1 Congress -s A. ic. Snelgrove Geocheidcal Anomalies in Forest Floor Material I Progres Report D.fl Trd1ey The Petrology of the Ge4o Nine R.C..Ee 'ay An Investigation of Sçme GoldQüartz Veins . , V.. Oja iS 18 12 Institute Luncheon 12.30 PJ. SESSION II Co.iChairmen 2.00 PN 2.30 3.00 .3O .O0 Henry Lepp, A. K. .Snelgrova Sublacustrine Topography of Eastern Lake Supe'ior Jack Parker Recent Contributions to the Late and Recent Geological History of Lake Superior John }. Zwnberge Ve1octy and Isotropy Stwltes of Pre cambrian Lameflar Forination2 (to be Dreserred by G, Secor) D. W, 4erritt (o'fee and biscuits (no charge) Granitic Rocks of the Pembine Area, Northeast Wisconsin - J. Allen Cain Tectni Analysis of Some Precambrian Rocks, Horn Area, Bighorn Mountains, John C. Palmquist Wyoming Lithology of the Seine Series in the Vicinity of Crilly, Ontario W. L. Young Friday, April 28 Co-Chairman 6 13 19 SESSION III Henry Lepp, Gerald Anderson 9.OQ A.N, Types of Iron Formation in Western Ontario 9.30 Geology of the Nakina Iron Froperty, 3.0,00 30 ar4 Their Sign ficanc 0. G. Suffel OntariQ W T. Swensen Geology of East Lake St. Joseph Iron Formation A, T. Avison and J. .F. Wbite 4 16 17 3. �Friday, April Abstract No. SESSI0N III 8 Page NQ, 10.30 A,M. 100 Coffea and b±scuit?s charge) The. Erce Lake Iron Formation, Red Lake Mining Division, Ontario •. M. We Eartiey Some PetrQgraphic and Chemical FeatureE 11.30 3 of the 0iinlirtt Iron Range, Pt Arth Area W. W. Mooz'ehouee Institute Cobaiien -' (no Luncheon 12.30 P.M. Trevor Page, R. V. Oja 2.00 P .N. Rem nent 2.30 in recambrian Banded W. A • Gross and D W. Strangway The Use of the Dp Need'e wi1b Specia3. gnctsm and Orgin of Hard Hematite Iron Fortnation Reference to Magnetic Taconite Exp1oraiion — william J. Hne Manganese in the Menonirise Iron Rang€i, Niàhigau (to be presented by gaul Zirnmer) Paul Zimner and G icnatra 3,30 Corfee and bisc4ts (no I 20 Iron The Distribution of Manganese in Sedimentary Iron FoririatjQna and Associated Rocks — ffnry Lepp The Thterpolat±on Parabola Applied t 5e002x1 Deriatve. Interpret&tion — Lloyal 0. Bacon 00 8 charge) Rep1aoment Texture in Negaunee Formation E. L. Beutner I.30 7 b 9 2 �UTHORS Geologist, Ungac; Iran Ores Mxtrea]. A. T. Avison Geologist, Geco Nines 'Manitouwadge K. Abe]. Lloy]. College of Mining and Technology, Houghton, Michigan Michigan 0. Bacon W. Bartley B. L. Beutner R.C.E. gray j Allen Cain . Re Gross Abstract 'a No. UI Consulting Geologist, Port Arthtr Chief Geo1ogist Jones & Laughlin StOl Corporation, Pittsburgh. Pa. Chief Geologist, GecoMines, Deprtment of Geology, Northwestern University, Evanstn, flhlnois 6 Geology, 7 Assistant Professor, Department of University of Toronto Department of Geoipr, Michigan State Univerglty, East Lansing, Michigan C. Kustra Nie1gan College of Mining arid D. W. Merritt Tehnology, Hôüghton, Michigan Associate Professor of Geo)!igy, Univezsiy of Minnesota, Duluth Geologist, The CaliforuiC. Can7 in New Orleans, Louisiana W. W. oorehouse Professox' Department of Geology University of Toronto Consulting Geologist, Port Arthur Ray V. Oa Geologist, Geco Mines, Manitouwadge V. T. Onodera Jo, O Palmquif .Departmont of Geology3 State Univeri.ty of Iowa, Iowa City Michigan College of Mining and Jack Parker Technology, Houghton, Michigan A. K, Sneigrova Professor, Michigan College of G 0. Suffel Aasociate Frofessor Department of W. T, Swensen D• Strangway F. White D0 H. Yadley 1 U, L. Young P J. W0 Zer H. Z'umberge 3 Manitouwadge U. J. Hinze Henry Lepp 2 8 20 9 10 11 12 13 ilL Mining and Technology Houghton Geology, University of Western Ontario, London Asdstant Vice President, The Anaconda 16 17 oIiipany (Canada) Lirnit,e, TorontG Geophysicist, Bear Creek Research 7 Mining Company, Denver, Colorado Ltd., .. Geologist, teep Rock Mines 1 Steep Rock Lake Engineer" Associate Professor of 1ining ing, University of Minnesota, MinneapoliS 18 — Ass±stant Profes sor, Department of neology, Carieon College, Ottawa District Geologist, The M. A, Hanna company, Iron River, Michigan professor, Department University of Michigan, n Arbor of Geo1o 19 20 21 -• �:i. GEOLOGY 0? THE EAST LAKE ST. JEPH ThCI WOPY A, T, Avison and J, F White Magnetite iron formaton occurs in a belt of meta. morphosed Keewatin#ype se&Lments at the east end of Lake at. Josepk in N th-centval Ontario. Two major hwiz ens and nuirm smaller lenseà of iror formation re interbeddéd with a series of quarbz''biotite schists and tLc chlorite and anetifrous schists near the north áomtait of an igieoiis mass of granite and gatbro, The two major h'izone vary betweo 3.O and 1180 feet wide at 8tU' face and are believed to be made up of closely interfthgered lenee rathex than widespread regiilez' beda. �2 THE ThTERPOLPTION PAR&BOL& APPLIED TO S CO DEIVATIVE IEPREL'AT ION Lloyal 0. Eacon • • Numerical second derjvatLe forpuIation is derived for one dimensional (profile) arid tWQ ditnensioua3. (surface) data. Coiu' parison with other methods of second derivative calcjlattrn is px'e.. sented for several minezal exploration areas �THE BRUCE LP1KE IRON FORMATION, RED LAKE MINING DD1ISION, ONTARIO M. W Bartley The history of exploration for treatable iron 'ormation at ruce Lake, Red Lake Mining Divi3ion,, Ontario is described a1cng with a brief review of the general ratigraphy and strueturee The Keewatin..'t37pe iron fonnation has been deliz:ieated by geological nd geophysicai riapping, and diamond drilling has outlined two stthstanr tial iron. çre deposits from which a des±rable peflstized product can be dx'ved. ( �RPLkCEMENT TEXTURE IN NEGAUNEE IRON FORMATION E L. Beutner Studies and Qb5ercations which were iade during th past fifteen years in the curse of field mapping, exploration drilling and mining in a portion of the Marquette Range south of Negaunee, Michigan, point up sonie interesting relations between charatsrstica of the iron romation, geological structure and the localization of soft irn ore deposits Evidence here seems to indicate that much of the. iron forination had undergone oxidation before ore forming processes were actIve and possibly before completion of iiastrophisn, Secondary oxidation, leaching, replacement and sometimes actual inioval of both iron and silica occurred in some zoneLs which had been strongly fractured through folding or faulting ar4 along the contacts between the von formation and in— trsive ocka. Where waters circulated through such disturbed areas they 1et their mark in a distinctive spotty or "leopard" texture which is superirrrposed on the norma]. straight bedded iron formation. Tha avenues of circulation nay be traced from the present surfae through steeply dipping fault zones to the lower thin bedded part if the iron formation where the soft ore bodies are localized. The fact that the hanging wall iron formatibn of many of the ore deposit exhibits the porous "leopard" texture suggests that the game solutions which were responsible f leaching and repaoement in the iron forxna.. tiori may also have brought about nearly completu removal f silida and enr±c}ent o.t iron in e1eted structm'a). situatjox to form the high grade ires, I �THE PPROLCY OF THE QECO MINE R,CE. Mo'e Bray, LK. Abel, V.T. OnQ4e'r. detailed petrographic studies o the rocks with the Geco cop zinc ore deposit at Maz4touwadge,. Ontario, thafl waE previousIy possible have establJshed the sedi. meritary Qrigin of the grey gneiss, The variations in the quartz. ass ociated muacevlte schist and in the horn.fel are escrbed, The intrusive quartz dirites and pegrnatjtea are also described.: The rntainorphic minerals connected with the re zone are discussed. �6 PREGAMBRIAN GRANITIC COMPLEX OF NORTHEASTERN WISCONSIN J. Allan Cain From an area oX soiie 350 square miJes mapped within th Wiconsin Pre canbrian Qorriplex, a rock..uriit was selected for more de ta structural and modal analysis. This unit the Newingham Granite lies jirmiediately 3djacent to the town of Pembin, is .sci$ O square miles in area1 and has intrusive contacts wi±h greenstone, bjotite neiss and horriilende gneies. Nodal data from 70 specimens- for quartz o1or index, feldspax ratio (potash. feldspar/plagioclase), and total feldspa', as well as spific gravity, were analyzed. on..orthoginal polynoird.aJ analycts was used — via 1.3. 650 - to compute linear and quadra tic trexid!..surface8 and deviations for each variable. A comparison of these results with those *tained by lthitten from his similar £tudy of the "older granite" of Dneal (Ireland) indicates the potenttal petrogenetie significance of trend—srn'face analysis. I �7 REMA.NENT MAGNETISM AND THE ORIGIN OF HAiti) HEMATITES IN PRECAMBRIAN BANDET) IRON FOIThIATION W. H, Gross and D W. Str.ngway Because hematite is a mineral with a high degree of znagnetio stabiUty t was considered possib]e that a study of the reman t maget. ierrx of hematite ore bodies In. iron forration 4ght add to a knowledge of their origin. To test this possibility, a number of ,riented spLmens an iron were collected from two hard hematite ore bodis that ocem' formation near. Fort Gouraud, Mauritania. Or of these ore bodies is an elongated ens of hard hematite which occurs in a steep plunging "S' shaped fold. The lens is roughly con cordant 'with the trend of the bedding of the surrounding iron formatiofl. and it is known to extend to a depth of at least .7S0 feetbeiow the present surface without any detectable change in physical or chemical properttee. It was found that the principal directions of remanerit magnetizatoii must have been formed in the hematite whefl the. beds were essentially flat. This is interpreted to mean. that' the bulk of 'the hematite in the ore is either syngenetio and was formed as an Iron rich horizon during sedimen" taton or it was formed by leaching of the flat-lying iron formation. The steep inclination of the magnetization in the beds when. they have been "unfolded" to the flat position suggests that the ore was formed in the Precambrian when the earth's magnetic pole w:as located in Northweatei Africa, magnetic direction on one of the limbs A Second rather is thought to indicate the Lormation of secondary hematite that was formed either by reworking of the primary hematite or by introduction. of hema-. tite into the ore zone at the time of folding. If the ore Is essentially syngenitic, prospecting for additional ore bodies of this type at Fort Qouraud should be governed by a knowledge of the primary features in the oigina. basin of deposition. A second ore body is composed primarily of soft hematite that has a hard hematite capping.. The soft ore is relatively shallow in depth ar4 .s discordant 'wth the bedding in the underlying iron formation, The magnetic dixections in the hard hematite capping were lagely random but hae some preference towards the present magnetic north. These results suggest that this type of hard In re].ati'ly modern times. fii was formed by leaching It is concluded that the hematite ores at Forb Gotiraud have had a complex and multiple origin. �8 USE OF T} DIP NLE T}E WITH SPECIAL REFERENCE TO MkGNETIC TACONITE William J, PLORAT ION Rinze The dip needle, crie of the oldest of geophysical explora. tion instruments, is skill beig used as an ecploratiori tool particu larly in the arch for magnetic taconite ores0 However, the highly distorted magnetic fields associated with these ores oten produce misleading dip needle anomalies due to the interaction of intensIty and inclination effects0 tase histories and a laboratory investiga-' magnetic fields illustrate the profound. effect that both of these magnetic yariables have on dp needle. readings • Results of a laboratory investigation indicate that large negative normal settings nay be used to subordinate the effect of inclination over high ±ntensit ranges thus forcing the dip needle to give a clearer picture of the rnagnetic character and distribution of the rock formations. The period of oscilJation of the swinging dip needle, which decreases as the vertical magnetic intensity increases 3fld as the inclination decreases, can also be used as an aid to the successful geological interpretation tioia employing controlled of dp needle tnoaliea. Studies indicate that temperature, orientatior, and leveling variations normally encountered in field operation of the dip needle result in negligible errtx*s and a stuclT of dip ieedle reading method indicates that the optimum, reading method varies the requiremezts and conditions of the surveys but that the reading rrthod based on the ritnetic meanof the second, twice wit l i the and the fourth reversals third, most universaU I acceptable. f the oscillating dip needle �9 TH DISTRIBUTION OF MP3ANESE IN SEDINENTARY IRON FORMAT IONS AND ASSOCIATED ROCKS Henry Ipp The average Mn:Fe ratio f Precambr.an iron formations is O.O3! which is essentially the same as that of the average crystal. line rock (' .028) from which these formations were derived • Post Pre. cambrian iron formations, on the. other hand, have an average Nn:Fe indicatIng a pronounced geochemical separation of iron and ianganese as compared to the crutal average. The difference in Mri:Fe of the two age groups of iron sediments nay be due to differences in depositional eivfroninents ( dizing. environment favors the separation o! Mn and Fe, rbonate fie]d does not) ratio of 0.007, ratios en.ces In the nature of their source rocks, or to differ. In Precambrian Iron fornmtions, the oxide horizons have considerably lower' Mn:e ratios than the c'bonate..silicate horizons. There appeai's to be a correlation between Mn:Fe ratio and CQ2 content, The distribution of Nn:Fe ratios for analyses from the Quyuna range 18 bimodal • The rorinangan.U'eroua sections of this iron tr ratio of an show lower than norma'. MzuFe ratios whereas the reverse s for the manganiferous horizons, The average iralu of the Mn:Fe iron formation nay provide an indication of whether or formatIon nt sedimentary manganese deposits can be expected in the same sedi. ment1ary sequence, �10 VELOCITY AMISCIrR0PY STUDIES OF PFECAMBRIAN WLLAR FOR1ATIONS Donald W Merritt A prelimnary field investigation was made of seismic wave velocity arilsotropy in lameilar formations. Results of the shallow seismic refraction surveys in seven different localities on Precambrian metasdimentary and inetaigneous rocks cornprising eight different lithQlogies inciudin schist, granite gneiss, banded iron formatiO, slate and per±dotie altered to serperitiriite show that velocity anisotropy is meaurable in the Zi4d and nay be useful in delineating structural orientation in buried fonna.. tions, Sei'mic vave velocities in steeply dipping formations characterized by beddiig, jointing, cleavage or fractures were foufld to be faster in the directjon parallel to the fractures than perpendicular to theni The ratias between the seirrd.c wave veio'' cities parallel to and perpendicular to these feat1res approached values of two to one, I �SE PETRORAFHIC AND CHEMICAL FEATURES OF THE GUNFLINT IRON RANGE PORT ARTHUR AREA W. W. Moorehouse be results of about 100 spectrochemical analysss of iron fømtion and asociated argillites from the Gunflint and Mesabi ranges are suzmnarized and compared with simiLar ana1yes of ancient and recent marine and non'-marine sediments of varioi typese The results of these analyses are consistent with a marine or bracki3h-.water environment of depo8ition of these iron fcrrmation. The significance of various characteristic textures of the several facies Qf the Gunflint is revieied. The granules ai4 other features of the taconites, as well as their field oharcteris-* tics are indicatIve ef active or tebu1et conditions of depos±ti5n. The variations oftei encountered ri the mineralogy f the taconites point to the mixing of the products of local regimes of varying h and pH. The influence of diageriesis and itamorphism in modifying the mineralogy and texture is discussed. It is voncluded that they have not seriously disturbed the aigriificaxzt environmental criteria. The petrog2'aphic features of the other main facie3 of the Gunflirit are corzsidered, it is concluded that these result from variations in depth, turbulence and organic content in the environ-' merit of sedimentation. Textural and compostiona1 features bearing on the role of volcanic contributions to the accumulation. of the sediments of the Gunflint cQnclude the discussion. I �32 ANVESTIGATIONOFSO GQQUARTZVEIT R V Oja ijwestigation was conducted ort 30 o' 70 ore-. and non!ore.'bearing quartz veins in one section of one of the gold -jnes of the PorQupine Camp, Qntario. Although all 70 veins had been exposed and developed by underground headings, not all con-u This tamed gold in qu'antities'suiTtcierrt to make ore Since both orend non-.ore-beqring quartz veins were identical in appearance in iamond drill interectionD and in the underground eXpQsm'eB, the perpleirg decision, "Should the vein be develope4 further?' zearly always h.d to be faced. This research, therefore5 sought to establish a means Qf distnguishg between ore- and non-.ore-.bearing quartz veins by petrographic, dcrepitation and spectrographic techniques klthoigh it was discovered that ore-.bearing quartz contains more liquid in.. clusiorts and decrepttates 11$ to 3i% more than the non-.ore-.bearing çucrtz, sp much overlap exists in the results of these observationa categorized with as'surance. so that no single secirnen Sir.ilarly, no conclualve differences were revealed by spectrographic cnbe irrve stigation. After reconsiderIng the methods of quartz vein formation the gold, and gold introduction, it is concluded that, apart there need be no major d. erences in the chemical or piysical pro" perties of the ore— and non.orebearing quartz veins considered in this iigation, �33. TECTONIC ANALYSIS OF SOME PRECAMBRIAN ROCKS, i IGORN MOU1TAINS WYOMING Johii C, Palinquist A Laramide blocls"like uplift of the Precambrian basement. resulted in the formation of a faulted mountain. niasa cveririg approxi.. rnatély 27 equare miles, extending southward from the centraL Bighorn unit. The core of this uplift contains complexly folded, £oliated hihgrade metamorphic. rocks Precambrian rock types include pegmatite, anphibolite, calc—siUcate rock, fldspathic rotk, btotite shist, marble, banded ironstonø, quartzite, varieties of garietiferous rock and amphibole' rQC1S in addition to the predominant gneiss. Schistosity, inineraJ_0g1. cl and lithological. layering are conformable throughon the complex with c±oss—cutting pegmattes being the çuly exception. These rocks are believd to have originated from reginaJ. metamorphism and later alkali meta.somai4,vi of supracrustal. rocks. Alkali inetasomatism, apparently a post-tectonte event arid perhaps a late stage of the regional rnetamorp1iism, culmirated in pegmatitizatot.. The staurolite'. quartz s'ubfacea of the almandinei.amph±bolit,e facies is iidioaied. The internal structure of the metamorphic rocks is dominated by a complex anticline plunging to the norrorthwest. Foliation, lineation, reiaton of minor folds and distribution o mapped uiits all point to the existence oi' this fold, but the preoise g&ometryof the fold is elucidated ory after a study involving methods of st&tistical analysis and tectonic profile construction, This study reveals a closed, slightly overturned cyiindric4 anticline dth. planar limbs, Measured lirieatiori cqrrespo4s to the axial line as determined from statistical analysis ot foliation data, and is, there'.. fore, b.Uneation, Sediinentary..covez' structures are believed to result from passive draping cver active basement blocks. The blocks are bounded. by the Horn and Tensleep faults, The attitude of the Horn fault parallels foliation weas the Tensleep fault appears to be a rejuvenated Pre. cambriaxt fault, These relatiàns demonstrate that the strictural grain of the basement may influence later deformation. I �SISBIACUSTRINE TQPCXRAP}1T OF EASTERN LAKE SUPERIOR Jack Parker Interpretation of recent echosoiinding taken by the IJ,S. Lake Survey indicates that the Lake Superior basin has been ice out of relatively soft rocks,. and that inoraines excavated on the south shore hold the water at its present level, Long, nà'rw vaUeys, as much as 700 feet belcw sea level, exteid as in a northau"south directions rrruch as So by inils ros±on of hard arid soft Dock8 and the general liiiiits of lavas, sandstones, and glacial drift, the 4irection of ice mcvernent and. the major faults. Differential shear zones pern.tts mapping of I Of �GLflSES OF T} XXI I1'TERNATIONLGECLOGICAL CONGRESS A. K. Sneigrove A travelogue of the Copenhagen Congress in August, 1960, by one of N.tQhigan Tech's official professional delegates. In additiou to attending the meetings, the speaker yiited the Western Noegian Fjord oouxxbry, and participated in geological exeureicns, in the 0810 area &td in the rnird.ng cezitera of outbern Norway �T!?ES OF IRON FOR1ATION IN WE$TERN ONTARIO AND THEIR ORIGINAL ENVIRONMENT G. G, SiiffeJ. A detailed study of published literature mentioning or describing sedinnta7 iron formation in Western Ontario has con. firnied that there are four types aufficiently different n character and lithologic arid structural envfroruiient that they can be readily distinguished. The Patricia and Port Arthur Mining Div±sions provide a north.south section across the Superior province in Canada. It is suggested that the iron forniations were deposited. in enornents compatible with those supposed to occur during a sequence of geo. synclinal sedinntatioi with the development of jsland arcs. It seems conceivable that the IIars hail Lake series and related rocjcs of Coutchiching type represent ancient shelf deposits, the oldest rocks in the Province The Keewatin type in almost cer-. ainy lagoonal marine, the iron. proba'bly originating i'rc volcanic emanations, The Windigo1an or imniskaming in closely associated with producte of mechanical erosion of eugeosync3.inal rocks. The origin of the iron may have varied with time and. place. The Animikie formations are imiogeosynclinal, blQnging to a new arid uncompleted cycle, Although this area is upposed to represent one of the original continental nucleil, considerable evidence suggests that still older land masses exited, as yet unrecognized. I •1 �TYPES OF IRON FOINATION IN WESTERN ONTARIO AND THEIR ORIQINAL ENVIRONME G. G, SuXfel A detailed study of published literature mgntionirzg or de3cribing sedirnentar-y iron formation in Western. Ontario has con- firmed that there are four types sufficiently different in oharacter and lithologic and structural environment that they can be readily distinguished. The Patricia and Port Arthur Mining Divisions provide a orthisouth section across the Superior province in Canada It is suggested that the iron forT1ations were deposited in erivirormients conpatible with those supposed to occur during a sequence of ge° syciinal sedimentatin with the development of island arcs. It seems conceivable that the Marshall Lake series and related rooks o Coutchiching type represent ancient shelf deposits, the oldest rocks in the Province, The Keewatin type is almost er tainy lagoonai. marine, the iron probably originating from volcanic eirxiations. The WindigoTzan or Tirniskaming type is closely associated -ith products of mechanical erosion of eugosynolinal rocks. The of the iron may have varied with time and place. The Ariimikie formations are iniogeosynciinal, belonging to a new and uncompleted origin cycle. Although this area s suppoed to represent one of the original continental nucleii, considerable evidence suggests that still older land masses existed, as yt unrecognized, I �17 GEOLOGY OF THE NAKINA IRON PROPEIY1 ONTARIO W, T, eisen The Anaconda Ccmpany, through its wholly ned aub sidiary The Anaconda oinpany (Canada) Ltd., has investigated optioned arid partially developed a large tonnage of iron ore amenable to magnetic cocentration0 The reserves are located in north centra1 Ontario and ccur within a twenty.'two mile belt b!' layered arid intricately fo)ded metamorphic rocks close to the north contact of an igneous complex of gz'anite aid pegmatite. There are two main ore deposits.0 Bx'iarclil'fe. is a steep to vrtially dipping body 100 to 500 feet wide and over a mU long. The Tw Nile deposit is flat dipping and confined to an open, asymretric syricline; it is approximately a in:tle wide and 2S0 to 1400 feet thick. On Its flat easterly punge it i aaucer1ike shape and is emanable to open-pltting for an east-west distance in of several thousand feet. Its further extension has been mdi" cated for at leaat three nd.la by xrgnetometer wor1 in conjunobion with diamond drill tests. �18 GEOCHEMICAL ANOMALIES IN FOREST FLOOR MATEEIAIS A PRGRESS REPORT fl H. Yardley Geochemical investigations of forest duff (htunus layer) near ZLy, Minnesota demonstrate that CNi inineralizai. tion in wder13ring gabbro is rZLected by the Ci-Ni content of the forest. duff. The anomalous pattern is more erratic than the pattern in the underlying till but does identify a target zones 8anpLing of forest duff is faster than soil sampling but further simplification of both analybtl arid sanp].ing methods appears neceasary before recommending the method for gerra1 app), cation.. �1, ITHOLOGY OFT}SINE StIES LLYrARI W. L. Yowig The .&tho].ogy of the Seine Series is diused arid the three princ±paL fac.e-s are suggested. Petrologic and geocheincal analyses ef the matrjx of the Seine "Conglomerate" compare favol2rably with the nearby Keewatin. lavas, suggesting a volcanic matrix for the Seine "Conglomerate". Lack or sedimentary features within the matrix: suggests a non.sedimentaz'y origin. It is postulated that the natrlx was a voLcsc flow or glowing-avalanche-'tuff which picked up and ircor.. porated boulcers while it was being laid down, and must, therefore, be thought of as a volcanto r?.ther than a sediment. If the Seine is to be used as a mrke'formation, then, it is impprtant to recogzize that the lithpogy may change from a "boulder conglomerate" to a "sericite..ohlorite 5Chi5t" in a short distance. Near Crilly the Series dips under the Keewatin volcariic6 At Nine center the Series is intruded by the Bad Vermillion granite, It was concluded that the Seine Series is of Keewatin age. I �20 MA.NQANESE NThERALIZATICN IN THE CANNON IRON NINES, IRON RWRaCRThL FALLS DISTRICT ,KECHTG P. W. Zier arid C. R, Kutra Nngane.sa occurs in only one mine in this area in quantities large enough and with gzade high enough to make & manganiferous iron ore product. This paper describes the mineralogy of this mangantferous ore body. The primary manganese mineral s hausmannite accompanied by such mzinezls as manganite, pyrolusite, rhodochrosite, braunite, ar4 rhodordte, as well as email amounts of i.ydrohauannite and maanese'ich sussexith. Other minerals occurring with the manganese mineraii. zation besides the ate, limonite, and goetbite are calnite, siderite, gypsum, qimtz pyrite, chalcopyrite, native copper, chrome, montmorilionite, and other clay minerals such as kaolinite and auxite, Although rrjanr of the above minerals strongly suggest hrth'othermal waters, no firal conclusions are drawn at this time as it is felt ean be made0 ( much more rork must be done before 4euch. concLusione �21 PROPOSED CORING IN LAKE SUPERIOR James I-1 Zumberge Shallow btton cores arid fathometer records óbtained from Lake Superior in 1953 provide the basis for seleothig sites for a coring program in 1961. Cores will be obtaix4 fz'oni several locations in the western, central and eastern parts or the basin through the use of a rotary drilling rig mounted on a ship aquipped to drill in water 1300. feet deep0 Fathometer records frQm a previous cruise reveal areas where more than 60 feet of laoustrine sècthnent occur above denser ntteria1, Glacial till gives the sa fathometer signal as Pro-. c'.mbrian bdrock, A core retrieved from a depth of 612 feet, 13 miles east of Grand Marais orf the Minnesota shore, contained 105 lamin-' ated couplets of alternating light and dark silty clay layers with an average combined thickness of 8.5 mm. The lighter layer con-. tains more carbonate than the darker layer, but is almost devoid of pdflen. Highest pollen concentration occurs in the darker layer&0 Other material found includes frosted sand grains, agnetc spherules, arid diatoms5 Laboratory analyis of the cores in which all of these eleineats are iwrestigatad should provide the basis for the geological history of the lake since its origin. � 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, 1961 Description An account of the resource Institute on Lake Superior Geology, Lakehead Branch - Canadian Institute of Mining & Metallurgy, Port Arthur, Ontario. April 27-29, 1961 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 1961 Contributor An entity responsible for making contributions to the resource A.T. Avison M.K. Abel Lloyal O. Bacon M.W. Bartley B.L Beutner R.C.E. Bray J. Allen Cain W.H. Gross W.J. Hinze C. Kustra Henry Lepp D.W. Merritt W.W. Moorehouse Ray V. Oja V.T. Onodera J.C. Palmquist Jack Parker A.K. Snelgrove G.G. Suffel W.T. Swensen D. Strangway J.F. White D.H. Yardley P.W. Zimmer J.H. Zumberge Format The file format, physical medium, or dimensions of the resource PDF Language A language of the resource English