141 10 13078 https://digitalcollections.lakeheadu.ca/files/original/6b7449d2f9af1ec5e6f53ee6d8c5baca.jpg 2c0e97cd5e4c66ab582bb7096527dd4c 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 Lakehead University Collection Description An account of the resource Photographs from Lakehead University's history: people, events, and campus. 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/. Identifier An unambiguous reference to the resource within a given context UG6-C-I-9 Title A name given to the resource Biologist "milking" fish Subject The topic of the resource University Life People Description An account of the resource Biologist "milking" fish. Creator An entity primarily responsible for making the resource Lakehead University Format The file format, physical medium, or dimensions of the resource JPG Type The nature or genre of the resource Still image https://digitalcollections.lakeheadu.ca/files/original/0bd30364007f7db22f4dcab309cb21b8.jpg 383869f747ded35768b08b0b343fb0a9 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 Lakehead University Collection Description An account of the resource Photographs from Lakehead University's history: people, events, and campus. 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/. Identifier An unambiguous reference to the resource within a given context UG6-C-I-8 Title A name given to the resource Biologist "milking" fish Subject The topic of the resource University Life People Description An account of the resource Biologist "milking" fish. Creator An entity primarily responsible for making the resource Lakehead University Format The file format, physical medium, or dimensions of the resource JPG Type The nature or genre of the resource Still image https://digitalcollections.lakeheadu.ca/files/original/13685d4a4b8686899c142d06c720adef.jpg 7c881b95d5c10abd9561109223fdad66 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 Lakehead University Collection Description An account of the resource Photographs from Lakehead University's history: people, events, and campus. 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/. Identifier An unambiguous reference to the resource within a given context UG6-C-I-7 Title A name given to the resource Biology - Gwen O'Reilly Subject The topic of the resource University Life People Description An account of the resource Gwen O'Reilly Biology/Forestry, Agora Sept. 19, 1984, p. 6. Creator An entity primarily responsible for making the resource Lakehead University Date A point or period of time associated with an event in the lifecycle of the resource 1984-09-19 Format The file format, physical medium, or dimensions of the resource JPG Type The nature or genre of the resource Still image Coverage The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant Canada - Ontario - Thunder Bay https://digitalcollections.lakeheadu.ca/files/original/6f0a67c708e2a9584a155337849b5097.pdf e82d4e8665c057b693ce17e05520361b PDF Text Text Memo To Industry: // BIG GOVT. GRANTS NOW AVAILABLE FOR PLANTS IN NORTH.WEST ONTARIO U.S. A UNDER ITS NEW "EQUALIZATION OF INOUSTRIAL OPPORTUNITY PROGRAM" THE ONTARIO GOVERNMENT PROVIDES INTEREST-FREE, FORGIVABLE LOANS TO A MAXIMUM OF $500,000 FOR NEW OR EXPANDING INDUSTRIAL ENTERPRISES IN NORTH-WESTERN ONTARIO. THE GRANTS ARE BASED ON NEW BUILDINGS AND NEW EQUIPMENT AND RANGE FROM ONE-THIRD TO ONE-QUARTER OF THE TOTAL CAPITAL OUTLAY. MORE DETAILS ARE FOUND INSIDE THIS BROCHURE. NOW IS THE TIME TO INVESTIGATE FURTHER. NORTHWESTERN ONTARIO DEVELOPMENT COUNCIL 201 -202 NEWS CHRONICLE BUILDING PORT ARTHUR, ONTARIO. REPRINTED FROM THE DECEMBER, 1968, ISSUE OF TRADE AND COMMERCE MAGAZINE �Ill Production: • • stat1st1cs on northwestern • ontar10 The Land miles miles miles miles Forest Lands: Productive Forest Area ..... .............. 45,644 s·q. miles Non-Productive Forest Area ............ 5,133 sq. miles Principal Rivers: Nipigon, Albany, Winisk, English, Winnipeg, Rainy, Kaministiquia, Attawapiskat, Severn, Ogoki. Principal Lakes: Superior, Nipigon, Lake of the Woods, Rainy, Red, St. Joseph, Long, des Mille Lacs, Seul. The People: Population, 1968 . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233,000 Population, 1958 .......................... ••••••••••••••••••••• 196,000 Number of Cities: .... .. .. ....... .. ...... ....... .... ............. ... ... 2 Fort William, Port Arthur. Number of Towns . . . . . . . . . .. . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Kenora, Fort Frances, Dryden, Sioux Lookout, Geraldton, Keewatin, Rainy River. Number of Townships ..................................... :....... 27 Ignace, Jaffray and Mellick, Machin, Alberton, Atikokan, Atwood, Blue, Chapple, Dilke, Erno, La Vallee, McCrosson and Tovell, Morley and Patullo, Morson, Worthington, Conmee, Gillies, Longlac, Neebing, Nipigon, O'Connor, Oliver, Paipoonge, Red Lake, Schreiber, Shuniah, Terrace Bay. Number of Improvement Districts .......................... . 10 Balmertown, Barclay, Sioux Narrows, Kingsford, Beardmore, Dorion, Manitouwadge, Marathon, Nakina, Red Rock. Transportation: Railways-Main and branch lines of C.P .R. and C.N.R. traverse whole area with marshalling yards at Lakehead. Highways - Mileage totals approximately 5,400 miles, Queen's highways total 1,300 of which 1,100 miles are paved . Air Lines-Including Air Canada, TransAir Ltd., North Central Airlines, Northwestern Aviation Ltd., and Austin Airways Limited. Lake Shipping-Lakehead ports westerly terminus of deep waterway, greatest grain storage and shipping centre in the world. Twin ports handle up to 18 million tons of cargo annually. About three-quarters of this is composed of wheat and iron ore. 2 T & C RESEARCH DEPT. --- • Area: Kenora and Patricia ..................... 153,220 sq. Thunder Bay District .................... 52,471 sq. Rainy River District ........ ................ 7,276 sq. Total Area ............................................ 212,967 sq. Manufacturing .............. .. ............ 1967 $ 320,000,000 241,300,000 1957 259,829,000 Forest - based Industries .. .. ....... .. 1967 173,371,000 1957 Agriculture ..... ............................ 1967 9,200,000 4,530,000 1957 .. I M1n1ng ....................................... 1967 120,000,000 47,157,567 1957 Fishing ...................................... 1967 1,477,000 900,400 1957 Fur ................................ ............ 1967 927,000 1957 1,408,000 Construction (Value of Residential Building Permits) ............ 1967 8,834,000 1957 7,084,000 Construction (Value of NonResidential Building Permits) ......... ................ 1967 25,998,000 1957 13,083,000 Construction (Total value, all permits) ......................... 1967 34,832,000 20,167,000 1957 Number of Manufacturing Plants .. 1968 225 1958 not given PRINCIPAL TRADING AREAS OF NORTHWESTERN ONTARIO HUDSON BAY ARIAi FIATU ■ ID See Pages 6 and 7 Atikokan Balmertown-Red Lake Dryden Fort Frances Fort William Port Arthur Geraldton JAMES BAY Keewatin Kenora Longlac Nipigon Rainy River Sioux Lookout Business Activity Retail Trade . .. . .. . . . . . . . . . . . . . . . . . . . . . . .. . 1967 277,556,000 1957 171,414,000 Labour Income . .. . . . . . . . . . .. . .. . .. .. . . . . . 1967 280,860,000 1957 187,874,000 Average Personal Income ............. 1966 4,446 3,701 1961 Average Labour Income Per Capita 1967 3,901 1957 3,093 113.78 Average Weekly Wages and Salaries 1967 78.95 in Manufacturing 1957 Cheques Cleared Through Local Clearing Centres . . . .. . . . . . . . . 1967 1,360,395,000 725,225,000 1957 Cheques Cashed . . . .. . . . . . . . . . . . . .. . . . . . . 1967 1,564,454,250 1957 834,009,900 Motor Vehicle Registrations ........ . 1967 73,141 42,755 1957 Passenger Car Registrations . .. . . . . .. 1967 54,549 33,672 1957 Communications: Telephone in Service ...... ............ . 1967 1957 Number of Radio Stations ........... . 1968 1958 Number of Television Stations .... . 1968 1958 Number of Newspapers (Daily) .... . 1968 1958 Number of Newspapers (Weekly) .. 1968 1958 Education: Lakehead University-full time students ........................ . -part time students Teachers College Manpower Retraining Program ..... Confederation College-Full time students ....... .. ............... . . Part time students ....... ... . DENSITY OF POPULATION Areas shown in red ... 228,000 Areas shown in white ... 5.000 Total (Oecember1968) ••••••• 233,000 81,180 42,229 6 5 1 1 5 3 8 7 1968 1968 1968 1968 2,025 900 254 800 1968 1968 471 6 3 �$500,000 INCENTIVE GRANT AVAILABLE THE ONTARIO GOV'T WILL HELP BUILD YOUR NORTHWEST PLANT f In the first year of operation, the Ontario-sponsored industrial incentives program assisted new or expanding enterprises to the extent of more than $1 million. Ten concerns in Northwestern Ontario were aided to enlarge, to modernize, to create new jobs. LARGE-SCALE GRANTS ARE CONSIDERED FOR: I) Secondary manufacturing companies establishing new facilities or making approved additions. 2) Warehouses and other concerns of a closely related nature which have a direct relationship with secondary manufacturing . --- 3) Tourist developments which will effectively raise the occupancy levels of local establishments. THE NEW GRANT FORMULA WILL BE APPLIED AS FOLLOWS: 1) 33- 1/ 3 per cent of the first $250,000 of the approved capital cost of new build. ings and equipment. 2) 25 per cent of the balance of the approved cost of these facilities. .... ......., 3) The maximum grant will be limited to $500,000 . HERE IS HOW THE PROGRAM WORKS: At the end of the first year, one-tenth of the loan will be forgiven, a further onetenth of the loan at the end of the second year, and so on until the end of the fifth year. At the end of the sixth year, provided the company has performed satisfac. torily, the balance of the loan will be forgiven. Here is real opportunity for enterprising industry to locate in Central Canada, a resources-rich region with trans -continental roil, highway and air transport services and deep water ports to continental and overseas markets. It has low-cost electric power and natural gas, fine communities, an expanding university and a new college of applied arts and sciences. Great place to live. FOR MORE DETAILS ON THE INDUSTRY INCENTIVES PROGRAM, please contact the administering authority. ONTARIO DEVELOPMENT CORPORATION 950 Yonge Street Toronto 5, Ontario. ...,,--- -------- .. --- ~~~ NORTHWESTERN ONTARIO DEVELOPMENT COUNCIL 201 NEWS-CHRONICLE BUILDING, PORT ARTHUR, ONTARIO �STATISTICS ON MAJOR CITIES AND TOWNS IN NORTHWESTERN ONTARIO Grose Income of Population Population City or Town 1958 1968 1967 Groae Income of Trading Are a Population Trading Area Population 1957 1968 1958 To al Constr ction 1957 1967 164,446,536 110,669,204 149, 900, 000 88,307,000 301 124 178, 294, 032 $ $ $ 254,857 201,304 537,199,000 294, 830, 000 23,244,190 Kenora .................... 11, 107 10,256 29,489,760 16,693,000 59, 535 52,000 96,520,000 62,840,500 2,242,437 Fort France• •••...........• 9,620 8,854 16,300,000 10,200,000 Balmertown-Red Lake ....... 7,150 5,823 14,500,000 Dryden .................... 6,735 4,935 12,480,000 Atikokan ................... 6,178 6,430 11,250,000 7,250,000 6,700 6,600 12,750,000 8,000,000 3,021,975 Geraldton ...........•....•• 3,558 3,269 6,235,777 5,173,624 12,000 11,500 20,100,000 15,850,000 71,998 3,451 3,162 Sioux Lookout ..........•... Nipigon .................... Keewatin ................... 6,750,000 2,769 2,783 2,012 5,560,000 3,920,000 5,425,000 1,980 20, 150 6,500 3,250,000 3,985,000 10,300 54,000 37,500,000 4,300 8,500 2,970,000 17,800,000 12,200,000 5,300 14,320,000 49,000 92,500,000 1,235,011 69,900, 150 12,521,425 24,744,510 14,560,000 27 31 34,563,375 20,185,475 8,250,000 4,4ao,ooo 871,818 17,299,245 15,704,965 17,200,000 12,000,000 8 6 16,800,000 5,800,000 6,200,000 not given 784,815 236,638 3,974,919 2,119,366 16,000,000 8,900,000 11 6 26,300,000 14,888,457 6,000.000 3,600,000 2,778,766 1,278, 671 11,701,655 5,890,975 14,200,000 8,750,000 6 2 35,875, 750 13,500,000 9. 295,000 3,600,000 1, 773, 782 7,044,751 6,478, 525 8,120,000 3,560,000 4 3 45,380,000 37,700,000 7,920,000 4,750,000 500,000 3,157,870 not given 7,375,000 4,300,000 10 8 35,017,250 29,300,000 14,600,000 11,350,000 2,913,595 3,351,311 5,860,000 3,730,000 3 4 2,000,000 not given 750,000 not given 2,610,937 1,753,030 3,750,000 2,500,000 2 2 1,900,000 not given 500,000 not given 58,600 not given 1,939, 595 2,694,533 1,690,000 1,080,000 Nil 2 not given 1, 669, 535 1,074,401 2 1 645,837 625,037 3 2 10,800,000 I 146,800 5,420,000 not given 198,000 438,320 6,500,000 60,300,000 Longlac .................... 1,339 943 2,460,000 1,250,000 11,000 10,000 18,400,000 13,650,000 93, 150 Rainy River .......•....•.•. 1,087 1,290 2,500,000 1,350,000 3,000 3,500 8,000,000 900,000 150,000 60,000 Total Serviced Railways Fort William-Port Arthur .. 4,225 3,225 1,050 CPR and CNR Kenora •.•.......•.•..•.. 1, 115 400 50 ............ 150 125 25 Balmertown-Red Lake •.•.• 17 13 4 Dryden .......•.•..•.•..• 3,850 1,925 1,800 City or Town Fort Frances . Transportation Unoccupied Airports Truck Linea Nos. 11, llA, 17, 17Aand61 1 17 CPR Trans-Canada and Great River Road 2 (1 sea) CNR and DWP Nos. 11 & 71, us 11, 53 & 71 Nil C.P.R. Highways 88 3 Geraldton .... , .... , ...... 45 45 Sioux Lookout ......•.•... 6 unlimited unlimited Nipigon .................. 500 100 Keewatin ................. 103 18 Longlac ........ , ...... ... 50 Rainy River .............. 47 .. 40 --1,750,000 . .. . .. ... --- ... --- 50,000 Util Electricity ies Radio (Domiciled) Gas T.V. (Domiciled) T win City Gas Co, Ltd. Forest products, sulphate, iron ore, silver and precious metals. Sand, gravel, crushed rock, zinc. Grain and by-products, edible oils, malt, fish. CFPA, CJLX, CKPR 5 Kenora Hydro Electric Commiuion and Hydro Electric Power Commission of Ontario Northern Ontario Natural Gas Co. Ltd. Forest products; commercial fishing: minerals • gold, silver, nickel, copper, lead, zinc, molybdenum: kasolite (uranium) CJRL @ CBC Satellite Station 1 5 Public Utilities Commission Nil Forest products, commercial fishing, fur, gold, iron, copper, nickel, agricultural. CFOB CBC repeater Nos. 105, 125, 618 2 3 Hydro Electric Power Commission of Ontario Nil Forest products, commercial fishing, gold, silver, iron ore and other base metals. CBC Satellite Station CBC Satellite Station Trans-Canada #17 2 (l sea) 4 Dryden Hydro Electric Commission and Ontario Hydro Commission Twin City Gas Co. Forest products, commercial fishing, agricultural, crushed rock, gravel, etc., magnetite iron ore, nickel, gold, silver, copper, lead, cesium, molybdenite, zinc, lithium, soapstone, mineral gallium. CKDR CBC Satellite Station CNR Voyageur Highway #11 5 (4 eea) 2 Atikokan Hydro Electric Commission Twin City Gas Co. Ltd., and Atikokan Propane Iron ore, pulpwood, timber, gravel, fish and game. CBC Booster Station CBC Micro• wave, Nor-Video CNR No. 11 .. 2 Ontario Hydro Electric Commission Twin C:ity Gas Co. Ltd,, Natural resources, timber, precious and non precious minerals. CBC Low Power Relay CBC Satellite Station 50 CNR Transcontinental No.72 4 (3 sea) 1 Ontario Hydro Electric Commission 30 CNR and CPR Noa. 11 and 17 Trane-Canada .. l Nipigon Hydro Electric CommiBBion CPR Trane-Canada #17 21 Cl'IR Trana-Canada #11 -- 4 Ontario Hydro Electric CommiBBion 15 CNR Ontario #11 .. 2 Rainy River Public Utilities CommiHion 88 .. .. (Kenora) (Kenora) 130,000 20,000 25,000 Communication a Raw Materials Port Arthur Public Utilities Commission and Fort William Hydro Electric • Atikokan ................. --2,750,000 --- ... INFORMATION GENERAL Industrial Sites • Acreage 1957 1,170,760 28,400,000 12,000,000 23,799,921 18,595,352 $ 6,950 44,720,077 $ 181, 925, 250 8,400 $ 109,921,000 1957 $ $ 9,000,000 $ 1967 $ 247,166,327 48,500,000 1967 $ 1958 $ 93,295 23,800 1957 $ 1968 $ 109,511 Manufac~ring Payroll 1967 1957 1968 1967 Manufacturing Value 1967 Fort William-Port Arthur .... 28,800 Number of Industrial Plant• Retail Trade Volume Aseeesment Corp. of the Town of Kenora Nil Twin City Gas Co. Ltd, Nil Northern & Central Nil CKPR-TV Newaoanere Weeklies Dailies News Chronicle and Times Journal Canadian Uutiaet .. Kenora Daily Miner and News Fort Frances Daily Bulletin .. Fort France ■ Time• Red Lake District News .. Dryden Obeerver .. Atikokan .. Times Star Progre ■■ Forest products, gold, iron, molybdenite, fish, furs, water. .. .. Daily Bulletin Forest product• and minerals. .. .. .. Nipigon Gazette Forest products for pulp and paper, fish for processing and packaging, minerah. .. -. .. .. Wood and water. .. .. .. .. Limited aupply of timber, livestock. .- -. .- -· Rainy River Record 7 �Maior Proiects Underway FIRM COMMUNITY INVESTMENT CAPITAL International Nickel She bandowan 35,000,000 Ontario Hydro Northwest Ontario 26,500,000 Corporation of Port Arthur Port Arthur Ontario Hydro Northwest Ontario Lakehead Developers Lakehead Harbour Commission Shunish Port Arthur 2,000,000 3,500,000 Lakehead University Confederation College Port Arthur Fort William 3,000,000 600,000 Bell Telephone Company Aquativity Limited Municipality of Drtden Port Arthur Shipbuilding Co. Northwest Ontario Kenora Dryden Port Arthur Quetico Centre Lake Eva Arctic Enterprises Inc. Rainy River Colenso Lumber Co. Ontario Government B rayshaws Steel Limited Red Lake Highway Lakehead area Port Arthur Noralta Peat Products (Ontario) Limited Federal Government Barwick Kenora 9,500,000 20,000,000 10,000,000 2,000,000 200,000 5,000,000 100,000 350,000 15,000,000 750,000 300,000 700,000 REMARKS Development of new nickel mine. Transmission line to connect with Manitoba. First phase of 15-year urban renewal program. Linkup between northern & southern power systems. 15-store shopping complex. Major expansion of Keefer terminal cargo facility. University extension centre. Initial phase of new college construction program. Microwave system. New hotel on Lake of the Woods. Airport development. Conversion of bulk freighter to self-unloader. Final phase of $1 . 2 million expansion program. Building & equipment for new manufacturing plant. New saw and chipper mill. Lakehead expressway. Steel fabricating plant expansion. Peat moss processing plant. Building to house federal departments. I Maior Proiects Proposed FIRM COMMUNITY INVESTMENT CAPITAL Corporation of Fort William Superior Brick & Tile Co. Trans -Canada Pipelines Fort William Lakehead area Regional 14,100,000 300,000 70,000,000 Boise Cascade Corporation Trans-Canada Pi~lines Fort Frances area Rainy River area 12,000,000 Ontario-Minnesota Pulp & Paper Fort Frances Great Lakes Nickel Pardee 4,000,000 REMARKS Urban renewal program Brick-making plant 36-inch line traversing Northwest to Nipigon. Forest products plant Gas transmission line to serve Rainy River District. Plant improvement and anti-pollution program. Multi-million base metal mine development. � 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 Memo to Industry: advertising brochure Subject The topic of the resource Business and Industry Description An account of the resource Reprint of advertising from December 1968 Trade and Commerce Magazine, produced by the Northwestern Ontario Development Council. "Memo to Industry: Big Govt. Grants Now Available for Plants in Northwest Ontario." Creator An entity primarily responsible for making the resource Northwestern Ontario Development Council Date A point or period of time associated with an event in the lifecycle of the resource 1968 Format The file format, physical medium, or dimensions of the resource PDF Language A language of the resource English Type The nature or genre of the resource Text https://digitalcollections.lakeheadu.ca/files/original/48e51db0bb2e418314f7486dafcfffeb.mp3 6cb4b14d2ca8d5fbae9231cbc658a490 https://digitalcollections.lakeheadu.ca/files/original/69e8869a1ac2947d741f28b8c5ce31c2.mp3 da71513b3e620379221b167a2d9021c2 https://digitalcollections.lakeheadu.ca/files/original/9f17bb53191f22a079c4a7510425925b.mp3 a1e3c50cc379354da2e88d054a78d763 https://digitalcollections.lakeheadu.ca/files/original/ff2e04bad3230c43314465e9b43fcf30.mp3 e77faf496e85689e695d892eaa583460 https://digitalcollections.lakeheadu.ca/files/original/44613ca5d38eecfbbd89172f474c39cb.mp3 abe289d2bd46dbfc3a3edc7762c15e6d https://digitalcollections.lakeheadu.ca/files/original/25aedd586747948a9ff1b9162263fe47.mp3 1f7a1c3c7b2a622c6b85eb9b166833f9 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 Anishinaabemowik - Indigenous Languages Program Historical Documents Creator An entity primarily responsible for making the resource Faculty of Education, Native Language Instructors Program 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 Advanced Ojibwe: Audio Files Subject The topic of the resource Universities Indigenous Language Description An account of the resource Accompanying audio file for Advanced Ojibwe (Tom Beardy). There are six audio files: click on each to play or download in .mp3 format. Creator An entity primarily responsible for making the resource Native Language Instructor Program, Faculty of Education, Lakehead University Publisher An entity responsible for making the resource available Faculty of Education, Lakehead University Date A point or period of time associated with an event in the lifecycle of the resource 2001-07-01 Rights Information about rights held in and over the resource Faculty of Education, Lakehead University. The print version of this text and accompanying audio files are available at Lakehead University Libraries (Chancellor Paterson and Education Libraries) library.lakeheadu.ca This text has been scanned as part of the Anishinaabemowik - Indigenous Languages Program Historical Documents Digitization Project, Faculty of Education, Education Library (Thunder Bay Campus), Lakehead University. This work is licensed under a Creative Commons Attribution-NonCommercialNoDerivatives 4.0 International License. To view a copy of this license, visit https://creativecommons.org/licenses/by-nc-nd/4.0/ Please contact the Faculty of Education, Office of the Dean, Lakehead University, Thunder Bay, Ontario Canada for additional information or permissions. 807-343-8010 (ext. 8520) Format The file format, physical medium, or dimensions of the resource mp3 Language A language of the resource Ojibwe Type The nature or genre of the resource Audio https://digitalcollections.lakeheadu.ca/files/original/b753497c9dcb24ac5d8bf1b87daf24fa.pdf 92df58bde718fb3ae621adaaaee2e3c8 PDF Text Text Lakehead UNIVERSITY �Qreetings from LAKEHEAD UNIVERSITY Congratulations to you, our graduating class of 20251 Congratulations and Power to the Class of 2025 As you cross the stage at your convocation ceremony, I invtte you to reflect on this transformational moment. Your class is in the unique posttion of graduating into a world that is suffering from extremely negative uses of Power and Privilege. Power is used now to wage trade and armed wars. Power is used now to attack education, health, the press, and the arts. Power is used now to belttlle and demean individuals, groups, and countries. You are not simply walking across the stage to a roar of applause from your friends, family, and supporters; no, this milestone is much more profound. Crossing the stage and obtaining your hard-earned degree signifies stepping into the next phase of your bright and brilliant future. Whether your goal is to begin working in your chosen field or to continue your education by pursuing advanced studies, completing your degree at Lakehead University has bestowed upon you the gifts of choice and opportunity. From this moment forward, the key to unlocking your future is in your hands. I know that your journey from the first day of orientation to convocation was not easy. You have grown as a person, you have expanded your mind, built your skill sets, and you are well-prepared for what comes next. On behalf of our faculty and staff, and alongside your friends, family, and supporters, I offer my heartfelt congratulations. The entire Lakehead community is proud of all you have accomplished, and we are honoured to be part of your life's story. Dr. Gillian Siddall President and Vice-Chancellor Lakehead University However, class of 2025, you are in an equally unique position to counter these negative forces, and I have every confidence that you will. I join you in thanks for the power given to you by your support teams of family and friends. You are Empowered, and will continue to cultivate your partnerships of faculty and classmates. You are Empowered by your scholarship and abilities to find real solutions to real problems. You are Empowered by understanding the urgent need for truth and reconciliation, and by your active compassion for the demeaned. You are Empowered by your crucial involvements in education, health, the arts, and your love of Canada. You are ready and need not be afraid. Greetings. Congratulations. Thank you. Rita Shelton Deverell Chancellor Lakehead University �Thursday, May 29, 2025 - 9am ORDER OF PROCEEDINGS Graduate and Undergraduate Credentials to be Conferred: Faculty of Business Administration, Faculty of Engineering, Bora Laskin Faculty of Law Prelude Joe Petch Processional - Pomp and Circumstance by E. Elgar Joe Petch, Ted Vaillant, Damian Rivers-Moore, Erik Hongisto, Dr. Darlene Chepil-Reid The audience is asked to stand as the Academic Procession enters OCanada Robert Perrier Honour Song Elder Audrey DeRoy Invocation Elder Audrey DeRoy The Chancellor - "I hereby declare this Convocation open." Chancellor Rita Shelton Deverell Introduction of the Platform Party Dr. David Richards, Interim Provost & Vice-President (Academic) Greetings from Fort William First Nation Chief Michele Solomon, Fort William First Nation President's Address Dr. Gillian Siddall, President & Vice-Chancellor Conferring of the Honorary Degree Candidate Dr. Erin Pearson, Chair, Senate Honorary Degree Committee Chancellor Rita Shelton Deverell Dr. Gillian Siddall, President & Vice-Chancellor Convocation Address Dr. Jean Paul Gladu Message from the Class of 2025 Krish Khokhani Musical Interlude Ashley Belluz-Gerolami Presentation of the Candidates for the Conferring of Credentials and Medals/Awards Dr. Rhonda Koster, Deputy Provost and Vice Provost (Teaching & Leaming) Credentials Granted in Absentia Andrea Tarsitano, Vice-Provost (Students) & Registrar Message from the Alumni Association Paul Popo-Ola, President, Lakehead University Alumni Association Chancellor's Remarks & Closing "I hereby declare this Convocation closed." Chancellor Rita Shelton Deverell Recessional Jacob Wolframe The audience is asked to kindly wait until the graduates have exited the Auditorium and to then make their way to the Lakehead University campus for refreshments, photos, and conversation. Follow along as we acknowledge our graduates and this year's medal recipients. ~ �Lakehead UNIVERSITY The Arms of the University were granted by the Earl Marshal, the Duke of Norfolk, on June 20, 1959. The heraldic description is: Coat of Arms "Barry wavy of six Argent and Azure on a Chief Gules in front of a rising Sun issuant from the base of the Chief Or between two Candles enflamed proper each surmounted of an open Book also proper edged and bound Gold a Portcullis chained Sable" Crest "On a Wreath Or and Azure on Water Barry wavy Argent and Azure in front of a Rock growing therefrom a Pine Tree a Canoe paddled by an Indian Brave and Canadian Trapper." Motto Ad agusta per angusta Achievement through effort � https://digitalcollections.lakeheadu.ca/files/original/f637452a010d5d18f393fe53571396c2.pdf 3c5e4d5155f7099cae45275324808220 PDF Text Text ���� https://digitalcollections.lakeheadu.ca/files/original/d2e7b921e90ae43fb49420b387409f5e.pdf 6ba98768a3d39ee8f0359a8a3a3f11f2 PDF Text Text ���� https://digitalcollections.lakeheadu.ca/files/original/979a92d7f44b01fd51ac962abfcbad8f.pdf d7c85792f2a179adabb14f7241e42d90 PDF Text Text Lakehead UNIVERSITY �Qreetings from LAKEHEAD UNIVERSITY Congratulations to you, our graduating class of 2025! Congratulations and Power to the Class of 2025 ~ Your class is in the unique pos~ion of graduating into a world that is suffering from extremely negative uses of Power and Privilege. Power is used now to wage trade and armed wars. Power is used now to attack education, health, the press, and the arts. Power is used now to belittle and demean individuals, groups, and countries. you cross the stage at your convocation ceremony, I invite you to reflect on this transformational moment. You are not simply walking across the stage to a roar of applause from your friends, family, and supporters; no, this milestone is much more profound. Crossing the stage and obtaining your hard-earned degree signifies stepping into the next phase of your bright and brilliant future. Whether your goal is to begin working in your chosen field or to continue your education by pursuing advanced studies, completing your degree at Lakehead University has bestowed upon you the gifts of choice and opportunity. From this moment forward, the key to unlocking your future is in your hands. I know that your journey from the first day of orientation to convocation was not easy. You have grown as a person, you have expanded your mind, built your skill sets, and you are well-prepared for what comes next. On beha~ of our faculty and staff, and alongside your friends, family, and supporters, I offer my heartfelt congratulations. The entire Lakehead community is proud of all you have accomplished, and we are honoured to be part of your life's story. Dr. Gillian Siddall President and Vice-Chancellor Lakehead University However, class of 2025, you are in an equally unique position to counter these negative forces, and I have every confidence that you will. I join you in thanks for the power given to you by your support teams of family and friends. You are Empowered, and will continue to cultivate your partnerships of faculty and classmates. You are Empowered by your scholarship and abilities to find real solutions to real problems. You are Empowered by understanding the urgent need for truth and reconciliation, and by your active compassion for the demeaned. You are Empowered by your crucial involvements in education, health, the arts, and your love of Canada. You are ready and need not be afraid. Greetings. Congratulations. Thank you. Rita Shelton Deverell Chancellor Lakehead University �Thursday, June 5, 2025-11am ORDER OF PROCEEDINGS Graduate and Undergraduate Credentials to be Conferred: Faculty of Business Administration, Faculty of Education, Faculty of Engineering*, Faculty of Health and Behavioural Sciences, Faculty of Science and Environmental Studies*, Faculty of Social Sciences and Humanities *includes graduates from the Lakehead University-Georgian College Partnership Prelude Orillia Silver Band Processional - Pomp and Circumstance by E. Elgar Orillia Silver Band The audience is asked to stand as the Academic Procession begins OCanada Milli Kent Honour Song Honour Song by local Drum Group Invocation Elder Lorraine McRae The Chancellor - "I hereby declare this Convocation open." Chancellor Rita Shelton Deverell Introduction of the Platform Party Dr. David Richards, Interim Provost & Vice-President (Academic) Greetings from the Chief of the Chippewas of Rama First Nation Chief Ted Williams, Chippewas of Rama First Nation President's Address Dr. Gillian Siddall, President & Vice-Chancellor Recognition of the Recipients of the Emeritus Title Dr. David Richards, Interim Provost & Vice-President (Academic) Conferring of the Honorary Degree Candidate Brandon Rheal Amyot, Senate Honorary Degree Committee Chancellor Rita Shelton Deverell Dr. Gillian Siddall, President & Vice-Chancellor Convocation Address Dr. Ligaya Byrch Conferring of the Title of Fellow of the University Cathy Tuckwell, Chair of Lakehead University's Board of Governors Presentation of the Civitas Award Dr. Linda Rodenburg, Principal Message from the Class of 2025 Elizabeth Adams Presentation of the Candidates for the Conferring of Credentials and Medals/Awards Dr. Sonia Mastrangelo, Assistant Dean, Faculty of Education Credentials Granted in Absentia Andrea Tarsitano, Vice-Provost (Students) & Registrar Greetings from Georgian College Dr. Yael Katz, Vice President, Academic Message from the Alumni Association Paul Popo-Ola, President, Lakehead University Alumni Association Chancellor's Remarks & Closing Remarks "I hereby declare this Convocationn closed." Chancellor R~a Shelton Deverell Recessional Paul Connell The audience is asked to kindly wait until the graduates have exited the venue and to then make their way to the reception for refreshments, photos, and conversation. Follow along as we acknowledge our graduates and this year's medal recipients. ~ �Lakehead UNIVERSITY The Arms of the University were granted by the Earl Marshal, the Duke of Norfolk, on June 20, 1959. The heraldic description is: Coat of Arms "Barry wavy of six Argent and Azure on a Chief Gules in front of a rising Sun issuant from the base of the Chief Or between two Candles enflamed proper each surmounted of an open Book also proper edged and bound Gold a Portcullis chained Sable" Crest "On a Wreath Or and Azure on Water Barry wavy Argent and Azure in front of a Rock growing therefrom a Pine Tree a Canoe paddled by an Indian Brave and Canadian Trapper." Motto Ad agusta per angusta Achievement through effort � https://digitalcollections.lakeheadu.ca/files/original/92f143ce41d4983139f695a4266e2c66.pdf 648f5e88f9b18a9085d117ad4a060c51 PDF Text Text Graduating Class of 2025 Ceremony 1 - Thursday May 29, 2025 (9:00 am) Hello. We are delighted to welcome you, your families, and friends, as we celebrate your achievements at Lakehead University. Today we celebrate the success of your academic achievements! We are please to announce the following list of graduates from the following Faculties: • Faculty of Business Administration • Faculty of Engineering • Bora Laskin Faculty of Law ~ Faculty of Business Administration Master of Business Administration FARRISH, Allison Joanne Katherine FOURCAUDOT, Joseph Daniel ROONEY, Jared Reece VENERUZZO, Christian Dominic Honours Bachelor of Commerce BANJAW, Debora Daniel Business Economics *BELCAMINO, Marco Pasquale Marketing *BOARDMAN, Quinn Mary General Management Page | 1 �*BUSNIUK, Kassandra Mary Human Resources Management/Industrial Relations Minor in Marketing *BUSNIUK, Nicole Ann Human Resources Management/Industrial Relations Minor in Marketing *CARANGI, Isabella Angelina Finance *CARUSO, Carmine Accounting *CASE, Darci Faith Business Analytics and Information Systems Minor in Human Resources Management/Industrial Relations CHIODO, Ethan Joseph Finance CHONY, Evan Jakob Business Analytics and Information Systems *CHOWDHURY, Labwa Afifa Business Analytics and Information Systems *CIESLIK, Alec Henry Accounting COLLIER, Carla Dawn Accounting *FALLA, Jhon Jader Accounting *GHORI, Henilkumar Prakashbhai Accounting *GOODWIN, Chaneelia Human Resources Management/Industrial Relations Minor in Marketing *GOUNDREY, Alysha Lillian Marketing HANSON, Hunter McKenna Marie Accounting *HARDING, Nolan John Accounting *HEEREMA, Kevin Jackson Marketing Minor in Business Analytics and Information Systems Page | 2 �JACOBSON, Cassidy Yamile Marketing JONES, Jacob G Finance *KOZLOWSKI, Jessica Heather Accounting *LEBLANC, Kara Maureen Marketing *LEHTO, Noah Alexander Finance *LENARDON, Spencer Michael Human Resources Management/Industrial Relations MACCHI, Michael Xavier Finance MAKELA, Erik Paul Marketing Minor in Human Resources Management/Industrial Relations MENARD, Ewan Gregory McCrindle Marketing *OIKONEN, Damon William Thomas Finance OLOYA, Peter Onen Business Analytics and Information Systems PAQUETTE, Zachary Ian Accounting PONSINGH, Amos Jere Robert Finance RAMESH KUMAR, Rajeev Kannan Finance *REID, Laura Accounting *RIVARD, Kilee Elise Finance *ROMANELLO, Blake Paul Marketing *ROPPONEN, Jasmiina General Management Page | 3 �RYAN, Matthew James Michael Accounting *SADHWANI, Aarya Finance Minor in Business Analytics and Information Systems SHUKLA, Vibhuti Vishnubhai Vishnu International Business Minor in Marketing *SINGH, Chahatpreet Accounting Minor in Finance SINGH, Gauraang Business Analytics and Information Systems Minor in Finance SOUSA, Brandon Michael Accounting Minor in Finance *TETLOCK, Taylor Lee Human Resources Management/Industrial Relations Minor in Marketing TWEEDIE, Parker George Finance Minor in Economics WILLS, Amy Lee Finance Bachelor of Commerce 4 Year KEENE, Owen Reed Finance LIAO, Rongfei International Business Minor in Accounting LLOYD, Jared Sydney Marketing MACK, Joseph Jakob General Management MUSHTAQ MOHAMMED, Fathima Hafsa General Management OJAJUNI, Timilehin Moyosore International Business Minor in Marketing Page | 4 �OLATUNJI, Usman Olamilekan Finance PRADEEP, Adith Business Analytics and Information Systems WATTS, Gwendolyn Octavia Finance Minor in Human Resources Management/Industrial Relations XUN, Bo General Management Bachelor of Administration ADAMSON, Tristan James *AHMED, Saad BHATIA, Harshit Kumar BLACKWELL, Spencer David HAYES, Carter Nicolas MEENA, Ridhima *ROUKEMA, Alicia Ann *SAINNAWAP, Harvey Matthew SHI, Chong WILLISCROFT, Bryce Thomas Faculty of Engineering Doctor of Philosophy ABDELHAMED, Mostafa Civil Engineering Dissertation: Long Bolted HSS to HSS Connection for Modular Structures: A Solution for Indigenous Housing Challenges ABU MAHADY, Islam Electrical and Computer Engineering Dissertation: Improving Performance of NOMA & RSMA Systems with Improper Gaussian Signaling AL-CHALABI, Raghdah Civil Engineering Dissertation: Advancing Wind Load Assessment of Low-rise Buildings: CFD & Wind Tunnel Approaches Page | 5 �Master of Science CHAKMA, Soumik Environmental Engineering Thesis: Thesis: Water Decontamination Using Magnetic Biochar Produced from Biomass and Mineral Processing Waste CHINEDU, Nnaemeka Chemical Engineering EDIGA, Yashank Adithya Civil Engineering EKEH, Uchenna Francis Chemical Engineering GE, Mingyou Mechanical Engineering GHANOUNI, Farbod Mechanical Engineering Thesis: Noise Attenuation & Energy Harvesting Using Helmholtz Resonator Connected to Rectangular Cavity GHILDIYAL, Manan Civil Engineering HAAVE, Nikolas Mechanical Engineering Thesis: Estimating High-Pressure Hydrogen Storage Required to Refuel Heavy-Duty Vehicles HONG, Kang Electrical and Computer Engineering JAHADIHOSSEINI, Seyedreza Electrical and Computer Engineering JAYASUNDARA MUDIYANSELAGE, Nadun Eranda Medamarandawela Mechanical Engineering KAMRAN, Maham Mechanical Engineering Thesis: Computational Investigations of Integrated Vortex-Odor Dynamics in the Wake of Fish for Underwater Sensing KIRTHIPATI, Mohith Sai Varma Electrical and Computer Engineering KISHORE, Siddharth Electrical and Computer Engineering Thesis: Leveraging the Use of Liquid Metal Channels to Reconfigure Atennas' Impedance and Radiation Performance MALEKSABET, Zahra Mechanical Engineering Thesis: Aerodynamic and Flow Structure Analysis of Iced Wind Turbine Airfoil Page | 6 �MOJEDDI, Mohadeseh Environmental Engineering OKRAH, Gracious Korkor Environmental Engineering OMIYALE, Adedoyin Olufemi Civil Engineering OSAZUWA, Joseph Environmental Engineering PADHIARY, Swagat Environmental Engineering PAEZ, Juan Camilo Chemical Engineering Thesis: Demethylation of Sulfobutylated Kraft Lignin and its Application as PhenolFormaldehyde Adhesives PAN, Jiaqi Civil Engineering PATEL, Adilkumar Lalitkumar Electrical and Computer Engineering PATEL, Harsh Shaileshkumar Environmental Engineering PATEL, JEET KUMAR Civil Engineering PATEL, Maitri Brijeshkumar Electrical and Computer Engineering PATEL, Priyanshi Electrical and Computer Engineering RAGHURAMAN, Lithika Environmental Engineering RAMAZIFARAHANI, Aida Environmental Engineering SAMEEFAR, Mohsen Environmental Engineering SHAH, Aashray Axay Civil Engineering SHAIKH, Usama Zaheer Ahmed Civil Engineering SHAMS, Kimia Environmental Engineering Page | 7 �SHANMUGANATHAN, Annamalai Electrical and Computer Engineering SOLANKI, Rajankumar Yashvantbhai Civil Engineering SONY, Soumya Environmental Engineering SOUTHGATE, Jeffery Robert Electrical and Computer Engineering Thesis: Traveling Wave-Based Fault Location in Power Grids Using Neural Networks SUNDARALINGAM, Harish Electrical and Computer Engineering Thesis: Advancing Object Detection Models: An Investigation Focused on Small Object Detection in Complex Scenes SURESH, Tharrengini Electrical and Computer Engineering Thesis: Enhancing Semantic Segmentation: Architectural Innovations and Strategies for Label-efficient Learning TAYEBAN TAYEBA, Seyed Amirmohammad Mechanical Engineering VASILOPOULOS, Stephen Thomas Civil Engineering Thesis: Optimization of Tall Buildings Subjected to Wind Load Using Genetic Algorithm and Image-Based Machine Learning WANG, Shijing Electrical and Computer Engineering YADA, Nihal Electrical and Computer Engineering YANG, Kaiwen Electrical and Computer Engineering Thesis: A Novel Current Source Converter-Based Ultra-High-Power Offshore Wind Energy Conversion System ZONG, Haoyang Electrical and Computer Engineering Bachelor of Engineering ABITONA, Alyssa Carla Civil ADEDIJO, Temiloluwa Akintayo Mechanical Minor in Mathematics AHMED, Abdulrahman Saeed Ahmed Mechanical Page | 8 �AKOUM, Tamer Mechanical ALAJNAF, Abdulbary Naje Electrical *ALBAKHEET, Sofyan Electrical *ALLENDER, Rebecca Anne Mechanical Minor in Mathematics Co-operative Option AMEERDEEN, Bilal Electrical *ANABTAWI, Karam Mechanical BABAJIDE, Adelani Olasupo Mechanical Co-operative Option BALI, Akash Electrical *BEER, Aron Mechanical BELACHEW, Surafel Adera Mechanical BHATIA, Shubham Ranjit Mechanical BORBELY, Brendon Alexander Civil *BOYKO, Grant Alexander Shigeyuki Mechanical Co-operative Option *BULANKULAME, Maithri Mevinka Chemical Co-operative Option CAI, Jiayi Electrical CHAHAL, Ravinder Singh Electrical CHANDRA, Jason Leon Electrical Page | 9 �*CHAUDHARI, Charvin Civil *CHISHOLM, Maxwell Rowan Civil COULTER, Jill Aleksandra Przybylo Civil COX, Charles Brett Civil CURTIS, Christopher James Electrical *DE FRANCESCA, Fernando Branco Electrical *DOYLE, Zackary Patrick Civil *DRUMMOND, Elian Jean Civil DUONG, Chan Hung Software EASTERBROOK, Lucas Daniel Civil *EATON, Benjamin Lawrence Bouw Electrical EHIOGHAE, Goodness Enoma Electrical *EL HENAWY, Ahmed Mohamed Hanafi Hassan Mechanical *ELIGH, Matthew Patrick Mechanical *ELMEHRIKI, Nadine Civil FARAWI, Ahmad Wael Civil *FARRISH, Allison Joanne Katherine Mechanical *FELIX, Jesna Software Page | 10 �*FLEURY, Carter Andrew William Mechanical FOURCAUDOT, Joseph Daniel Electrical *FRANCIS, Kuruvila Mechanical Minor in Mathematics *FUNK, Ethan Civil *GAUDINO, Grace Catherine Mechanical GAZZOLA, Patric Thomas Electrical GIANG, Joshua Tuong Electrical *GJOKA, Ardaela Civil HALL, Michael Graham Electrical *HEROUX, Julien Leon Chemical *HOPKO, Andrew Gordon Peter Civil HOUNKANRIN, Agossa Laurens Civil *HUNCHAK, John Owen Hillman Mechanical HYSON, Conner John Electrical IBRAHIM, Mubashar Civil *ILOTT, Marlies Jamena Chemical IMAMVERDI, Amin Mechanical *ISSO, Ahmad Hannan Civil Page | 11 �ITURRALDE, Christia Leah Civil *KAMPHOF, Ethan Michael Mechanical *KASEKAMP, William Anthony Mechanical KAUSHAL, Abhishek Civil *KHOKHANI, Krish Manish Mechanical KIFORDU, Benedict Ifeanyinachukwu Mechanical *KNEZEVIC, Braydon Michael Software *KOCH, Scott Civil *KOETS, Owen Graham-Urquhart Civil *KOONAMA HENNADIGE, Uvindu Hashara Mechanical *KOVACIC, Nicole Sage Civil KOZHICHIRA, Jafrin George Mechanical Minor in Mathematics *LAHTI, Hanna Sarah Software *LARIVIERE, Gabriel Alain Mechanical LAWAL, Oluwasegun Emmanuel Electrical Co-operative Option LAWSON, Pablo Matias Mechanical Co-operative Option LECLAIR, Justin Eric Civil LEGGE, Kameron Austin Kenneth Electrical Page | 12 �LEUNG, Connor Civil LIU, Hongbo Civil LIU, Runfa Electrical *LLAMAS, Phoebe Gwyne Civil MADDESS, Shawn Samuel Benjamin Civil MARION, Jeremiah Mechanical MCCABE, Joseph David Sanderson Civil *MCRAE, Veronica Ann Civil Minor in Mathematics MEGHOWALIA, Rahul Mechanical MOFTAKHARI KAMRANI N, Amirali Civil NIELSEN, Michael Peter Electrical NIEMI, Saige Patricia Electrical ODIOH, Divine Favour Martins Favour Electrical OFNER, Craig Conrad Civil OPOKU, Michelle Civil ORLUKWU, Ebube Software *PACHOLCZAK, Amanda Isabel Chemical *PAQUETTE, Nycholas Daniel Electrical Co-operative Option Page | 13 �*PATEL, Charmish Arvindbhai Mechanical Co-operative Option Minor in Mathematics *PATEL, Milan Shamji Civil PATEL, Smit Kamleshkumar Mechanical *PHAM, Minh Tien Electrical *PORTEOUS, Bruce Henderson Mechanical Co-operative Option *PURI, Ritik Chemical RAMDASS, Kendell Civil *RATHOD, Harsh Mitesh Mechanical Minor in Mathematics ROLLER, Kilian Patrik Mechanical *ROONEY, Jared Reece Mechanical *SAAD, Mahmoud Medhat Mahmoud Hussein Mechanical SADEQ, Zaid Mohamad Civil SADLER, Griffin Wilson Electrical SALAH, Mohamud Mohamed Chemical *SAMUEL, Clifton George Software SANDHU, Harmanpreet Singh Civil *SEPA, Dejan Mechanical Page | 14 �*SHAAYA, Shahad Shahar Civil SHAH, Dhruval Harshilkumar Software SHEN, Jia-Wei Electrical SIDDIQUI, Muhammad Saad Chemical SIDHU, Gavin Mechanical SIMARD, Jonathan Eric Mechanical SINGH, Baldeep Mechanical Co-operative Option SINGH, Birendra Bahadur Civil *SINGH, Harmandeep Civil *SINGH, Shivdeep Civil SMITH, Darian Christopher Electrical SOLANO, Jonathan Marco Civil STRICKLAND, Matthew A Electrical STUPALO, Joseph Alexander Electrical TA, Ngoc My Duyen Chemical USSHER, Ebenezer O Civil *VADAPALLI, Nihita Mechanical Minor in Mathematics *VANDENHAAK, Matthew William Civil Page | 15 �*VENERUZZO, Christian Dominic Mechanical VIJH, Pratyaksh Mechanical *VREUGDENHIL, Joshua Anno Civil WALSH, Burke Daniel Mechanical WAYLAND, Jordan Cole Chemical WAYRYNEN, Maximilian Leo Civil *WEBB, Christopher Paul Mechanical *YOHANNES, Amanual Habtegebriel Civil *ZHOU, Jinjia Civil Diploma in Engineering Technology ADHIKARI, Apurva Civil AJAYI, Faramade Olamide Civil AWINI, Philip Wintima Software BARTEN, Charlie Benjamin Gary Electrical BOND, Paul David Electrical *CAZA, Christian Michel Civil DAVE, Harshi Mittal Chemical DOBSON, Tye Ian Electrical *DUONG, Chan Hung Software Page | 16 �*ELMEHRIKI, Nadine Civil FUNK, Isabella Grace Civil GRASLEY, Jamie Jordan Software *GUILERA, Eva Electrical HARRIS, Jackson James Mechanical *JAIN, Chaitanya Electrical *KUOPPA-AHO, Cory Andrew Allan Mechanical LAHTI, Hanna Sarah Software *LEVEQUE, Ryan Patrick Michael Mechanical *LONGHURST, Jeremy Daniel Civil MATHEW, Lois Elsa Software *MEANY, Joseph Malcolm Mechanical *MOLYNEAUX, Josiah Wayne Civil MOORE, Erikson Mechanical OGBONNA, Daniella Somtochukwu Electrical ORLUKWU, Ebube Software PATEL, Krish Kalpeshbhai Mechatronics PIASKOWSKI, Kalyn Grace Civil *PONKA, Benjamin Heikki Mechatronics Page | 17 �RAJA, Eugene Ethan Yohannan Mechanical RILEY, Lucas Tom Mechanical SANDBERG, Anders Kristopher Mechanical SINDREY, Connor Don Mechanical *TREMELLING, Mathew Thomas Civil UBA, Franca Noella Software VISINTIN, David Michael Mechanical WARYWODA, Lynden Patrick Mechanical Bora Laskin Faculty of Law Juris Doctor ABDULLE, Amal M ANDERSON, Nicholas Specialization in Aboriginal and Indigenous Law BAKSH, Bryanna Shana BALDASSINI, Josiah Diamante Specialization in Aboriginal and Indigenous Law *BAXTER, David George Specialization in Aboriginal and Indigenous Law BECK, Connor Douglas Wil Specialization in Aboriginal and Indigenous Law BERNIER, Stefanie Ann Specialization in Aboriginal and Indigenous Law BRUNT, Jenna Erin Specialization in Aboriginal and Indigenous Law BULA, Alexandra Maria Page | 18 �CHAPMAN, Jennifer June Specialization in Aboriginal and Indigenous Law COMPEAU, Gabrielle Marie Specialization in Aboriginal and Indigenous Law *COSTELLO, Caitlin Jane Woodley Specialization in Aboriginal and Indigenous Law DEMIANIUK, Cameron James DESCHEEMAEKER, Devyn Grace *DEW, Emmaleigh Irene Specialization in Aboriginal and Indigenous Law DOMSKI, Megan Kristen EGGETT, Jacob James Specialization in Aboriginal and Indigenous Law FAMULARI, Joseph Piero FANK, Alexandra Specialization in Aboriginal and Indigenous Law FANK, Daniel Joseph Mouro *FEDORUK, Lauren Nicole *FISHER, Simon Specialization in Aboriginal and Indigenous Law FLEMING, Eliza C GILL, Diljot Kaur Specialization in Aboriginal and Indigenous Law GUIDOLIN, Renato Justin Specialization in Aboriginal and Indigenous Law HAYES, Hailey Kendall HOOPER, Bradley Allen Specialization in Aboriginal and Indigenous Law HOSSEIN ZADEH, Aida Specialization in Aboriginal and Indigenous Law KENEFORD, Ella Clarice LATINA, Natasha *LAWSON-RIMMER, Kaitee Patricia MACKENZIE, Hunter Benjamin Page | 19 �MADIO, Nathan Joel MALLEY, Shaun Alexander Specialization in Aboriginal and Indigenous Law MCCARTNEY, Tiffany Leah MCKENZIE, Francine Faith Specialization in Aboriginal and Indigenous Law NEVRENCAN, Maiya Marie Zivka Specialization in Aboriginal and Indigenous Law OGDEN, Laura Kathleen ORFALI, Katherine PADDON, Andrew James PANCHBHAYA, Farah Salim PANJU, Zahra Fatema Mohamed Akbarali PERSIA, Cara Marie PLATANITIS, Joshua Michael Specialization in Aboriginal and Indigenous Law PRINGLE, Alvin Shane Specialization in Aboriginal and Indigenous Law *QUAN, Ethan Specialization in Aboriginal and Indigenous Law SALESKI, Alexa Margaret Specialization in Aboriginal and Indigenous Law SHARMA, Raman Specialization in Aboriginal and Indigenous Law SHAULE, Erika Hilja Specialization in Aboriginal and Indigenous Law SKYNNER, Sydney Caroline Specialization in Aboriginal and Indigenous Law SLESSOR, Emily Nicole Specialization in Aboriginal and Indigenous Law SORAMAKI, Samantha Vaughn Candice SPADE, Cassandra Neebin Lauren Specialization in Aboriginal and Indigenous Law Page | 20 �SPENCE, Tamara Helen *STEWART, Mason Donald SWEDAK, Grant Forsyth THIRUNAVUKARASU, Vaisnavi THOMPSON, Aundrea Leigh Specialization in Aboriginal and Indigenous Law VERBEEK, Johannes Herbertus Specialization in Aboriginal and Indigenous Law VIZI, Karlee M Page | 21 � https://digitalcollections.lakeheadu.ca/files/original/d3b62a6d3be3a36e9f71c7faa2b41970.pdf 6d8fb7027fc8169f19fe0d372aa2e92a PDF Text Text Graduating Class of 2025 Ceremony 2 - Thursday May 29, 2025 (2:00 pm) Hello. We are delighted to welcome you, your families, and friends, as we celebrate your achievements at Lakehead University. Today we celebrate the success of your academic achievements! We are please to announce the following list of graduates from the following Faculties: • Faculty of Education • Faculty of Health and Behavioural Sciences ~ Faculty of Education Master of Education ADDO, Solomon Educational Studies ADOKWU, Iveren Tseayo Educational Studies AJRI, Nilofar Educational Studies ALLEN, Deborah Ruth Education for Change Specialization in Social Justice Education AMANKWAH, Mavis Educational Studies BAI, Duning Educational Studies Page | 1 �BELLAVANCE, Jadyn Martina Education for Change Specialization in Indigenous Education CARRIERE, Caelan Ames Education for Change Specialization in Social Justice Education CHAUVIN GARANT, Hope Mae Marie Education for Change Specialization in Indigenous Education Thesis: In the Interest of Reconciliation in Education - Inclusive Indigenous Content and Modifications to the Ontario Social Studies and History Curriculum from 1998 to 2023 CHEN, Huiting Educational Studies CHENG, Ting Educational Studies CHU, Hui Educational Studies CLAYTON, Victor Andrei Education for Change Specialization in Social Justice Education DARKEY, Lucy Education for Change Specialization in Environmental and Sustainability Education DHILLON, Ramanpreet Kaur Educational Studies ERTL, Aryn Marissa Educational Studies GE, Yuqi Educational Studies GEHRS-WHYTE, Emma Education for Change Specialization in Social Justice Education and Environmental and Sustainability Education GUNAWARDANA, Denipitiyage Wathsala Lakmali Educational Studies GYASI, Stephen Educational Studies KAUR, Harleen Educational Studies Page | 2 �KOMOLAFE, Ranmilowo Education for Change Specialization in Social Justice Education KOSTROSKY-WAREHAM, Nicole Education for Change Specialization in Indigenous Education KRISHNA DEVI, Krishna Devi Educational Studies LALONDE, Debra Lynn Education for Change Specialization in Social Justice Education LEROUX, Sarah Education for Change Specialization in Indigenous Education and Environmental and Sustainability Education LIU, Mei Educational Studies MAUNULA, Alyssa Education for Change Specialization in Indigenous Education and Environmental and Sustainability Education MCINRUE, Erin Nicole Education for Change Specialization in Indigenous Education NA, Johnsy Educational Studies PAUCAR RESTREPO, Juliana Education for Change Specialization in Social Justice Education and Gender and Women’s Studies Thesis: Mapping my Latinx body in Canada: Challenging internalized anti-fat bias QI, Lin Educational Studies RAISA, Rawnak Rafa Educational Studies ROJAS URREA, Maria Del Mar Education for Change Specialization in Social Justice Education SCOTT, Neil Educational Studies SGAMBELLURI, Isabella Grace Educational Studies Page | 3 �SIDDIQ, Md Abu Bakar Education for Change Specialization in Social Justice Education SMITH, Sadie-Ellen Dell Educational Studies SUMANDEEP KAUR, Sumandeep Kaur Educational Studies SUN, Feihan Educational Studies TYAGI, Anita Education for Change Specialization in Social Justice Education WANG, Yingying Educational Studies XIE, Yonghong Educational Studies YANG, Tianrong Educational Studies ZHANG, XIAOMING Educational Studies ZHAO, Chang Education for Change Specialization in Social Justice Education Bachelor of Education – Professional Program *ANSARI, Ali Hassan *ANTON PARAMANAYAGAM, Karolina A *BENJAMIN, Ryan Asher *BLACKWELL, Amy Elizabeth *BOHONOS, Brenna Carol *BROWNING, Siobhan Eva May *BULLER, Cole Luke CALABRESE, Jacklyn Toni CARR, Erica Lynne CARRIGAN, Stephane Michel Page | 4 �*CHAGNON, Kaitlyn Marie CHARLTON, Cameron Issac *CODERRE, Grace Christine *COLE, Alexandria Laurinne *DAVENPORT, Andi Noel Marie DAVIS, Morgan Danielle *DECORTE, Aidyn Thomas Joseph DIPIETRO, Luke Anthony *DOWHOS, Nikolaos FEDORUK, Alexandria Johanna Maria *FINLEY, Malorie Ruth *FLETCHER, Carl *FORSYTH, Kit Nathaniel C *FORTNER, Olivia Claire *GARRETT, Larisa *GHAWALI, Sabina *GHAWALI, Sarina *GIBSON, Victoria Ashley *GILES, Renee Katelynn *GREEN, Brynn Elizabeth *HARDER, Alyssa Chelsea Helene *HISCOX, Emma Renee Victoria *HOUSTON, Rachel Lynn ISENOR, Ryan Taylor *JACKSON, Emily Elizabeht Anne *JACOBSON, Jenna Patricia *JAIN, Rachita *JOHNSON, Delaney Loryle Page | 5 �*KALYTA, Viktoria Madison KANDANCHATHA, Bhagyasree KATSIGIANNIS, Eva *KONTIO, Regan Alysa KUTOK, Jordan Alexandria *LAMPO, Tia Kristin *LEISHMAN, Abigail Rose Margaret LIM, Seongjun *LORUSSO, Gabriel Donovan *LOREY, Sarah Lisel MACDONALD, Madison *MACIAS, Vanessa Hope MALLON, Ryan John *MAROK, Jasmine Kaur *MCKAY, Jennifer *MIHALJEVIC, Makayla Nicole *MORTLEY, Enya Nicole *MURPHY, Joelle Michele *NICHOLL, Natasha Patricia *OWUSU-AFRIYIE, Vanessa PATTERSON, Eden Frances *PELTONEN, Kari Brian Walter *PEREIRA, Natalia Kathleen RAMDHARRY, Shalini Beverley *RAWN, Jenna Anne *REIBLING, Lauryn Jennifer *ROBBINS, Sydney Marion Ghislaine *ROJIK, Alexis Faith Page | 6 �*ROSS, Ryan Ronald Rejean *ROSS, Shannon Lois SCHMIDT, Mark D *SCHOALES, Sarah Angela *SEABY, Rebecca Anne *SHORTREED, Pasquel Grace Irene SIMPSON, Emma Zhoulin *SKRIPKARIUK, Nicole Jessica *STANLEY, Keaghan Iris *SWIFT, Hayley Joan TETREAULT, Vanessa TROY, Daniel *TYKOLIS-HORST, Mikayla *WALSH, Matthew *WELSH, Ryan Ramond *WHENT, Caitlyn Rochelle WILKINSON, Kyle Jacob *WISE, Izabella Sarah ZIVOLAK, Jacob Patrick Bachelor of Education Concurrent with the Faculty of Health and Behavioural Sciences BROCK, Elizabeth Kathleen Melody *DAROSA, Victoria Marie *GRIEVE, Sarah Erin *KOK, Abbie Jane *MARR, Daria Blaze NEWTON, Natalie Faith *POPOVIC, Tatyana Page | 7 �*TRAPPER, Taryn WALSH, Kaitlyn Elizabeth Bachelor of Education Concurrent with the Faculty of Science and Environmental Studies DAI, Yiran *JIANG, Shujing *LI, Haoran *TANG, Yufei *TRAER, Heidi Caroline *WANG, Zhenni *XING, Pei Zhi Bachelor of Education Concurrent with the Faculty of Social Sciences and Humanities *AIELLO, Baldino Jordan *ARELLA, Sarah Elizabeth BENNETT, Liadan *BJORKLUND, Tara CAMPBELL, Miranda CASASANTA, Isabella Victoria *CHASSE, Alyson Aisling Marie *CRONK, Julianna *FARIA, Julia Isabelle *FERGUSON, Kira Bettie *FERNANDES, Vanessa Pacheco *FORTIN, Maxime Nicholas *FREDRICKSON, Riley Elizabeth *GAUTHIER, Joshua *GEROLAMI, Ashley Alexandra Lynne Page | 8 �*GILCHRIST, Ashley Elizabeth HARRIS, Zachary Warren *HARTLEY, Katherine *JEWELL, Julianna Emily *LAMBERT, Brynne Vawn *LARRETT, Hailey Anastasia *LEHTO, MacKenzie Lea *LINDER, Ashley MACDOUGALL, Jessica Kayla MARTIN, Haley Alicia *MAYER, Jillian Amelia *MCGIRR, Juliet Elizabeth MIDWOOD, Andrew Frederick Donald MOYER, Samuel Dalton Arthur *PATTERSON, Justyne Rose Frances PETSNICK, Helene Ruth *PLANT, Shayleigh Marion ROBERTS, Skyler Montbrun SCHIRA, Shelby-Lin Annette SIMMONS, Bryanne Sarah SLUGGETT, Rachel Kate *SOBERING, Tyler Alexander ST JACQUES, Natalie Helanna *STROMNESS, Emily Anne *TASSONE, Sarah Katelyn *VISSER, Caitlan May Diploma in Technological Education *HULS, Shawn Oliver Page | 9 �*SAFAR, Justin Michael Indigenous Language Teacher Diploma NAKOOCHEE, Jane Dorothy Faculty of Health and Behavioural Sciences Doctor of Philosophy BENSON, Alycia Health Sciences Dissertation: A spirit-led journey to relational accountability – a visiting approach to understanding interconnections between substance use, healing pathways, and minobimaadiziwin: conversations with anishinabek Master of Health Sciences MENLAH, John Thesis: Housing Crisis and International Students' Health - A Case Study at Lakehead University Master of Public Health EDWARDS, Jaqueline Public Health Specialization in Social-Ecological Systems, Sustainability and Health GOBA, Rikki Michelle Public Health Specialization in Nursing GUTIERREZ, Raquel E Public Health Specialization in Social-Ecological Systems, Sustainability and Health HUDASEK, Josselyn Marie Public Health Specialization in Gerontology KLIMENKO, Maria Public Health Specialization in Social-Ecological Systems, Sustainability and Health LEAVENS, Cheryl Ann Public Health MAGSI, Madiha Public Health Page | 10 �PAUL, Bethany Public Health Specialization in Social-Ecological Systems, Sustainability and Health RAPOSO, Katie Teresa Public Health Specialization in Specialization in Indigenous and Northern Health TUTT, Jason Public Health Specialization in Epidemiology Master of Science CARUSO, Justin Ian Kinesiology WADHWA, Aaila Arora Kinesiology Master of Social Work JAGGER, Kimberly Noelle PANONTIN, Jenna Lee WILSON, Christine Margaret Thesis: The Apology Mosaic: Sexual Assault Survivors’ Experience in Receiving an Apology From the Perpetrator as a Form of Accountability Honours Bachelor of Arts *ADINEH, Shahla Psychology Specialized Honours *ALEXANDROV, Martin Psychology Specialized Honours Minor in Criminology *BENNARDO, Elizabeth Jane Psychology Minor in Criminology BOBYK-GOHEEN, Hope Evagayle Psychology Minor in Criminology *BOUCHARD, Beau Travis Psychology Specialized Honours *D SOUZA, Melinda Pamella Psychology Specialized Honours Minor in Aging and Health Page | 11 �*GOUVEIA, Jia-Li Psychology Specialized Honours Minor in English GREEN, Mikalea Sydney Marie Psychology *HALL, Kiera Sage Psychology Minor in Criminology HARGREAVES, Tessa-Lee Elizabeth Psychology *HOARD, Tanner Jarrell Psychology Specialized Honours Minor in Philosophy *JARVIS, Emily Joanne Psychology KELLY-SAMPLE, Haley Marie Psychology *KOK, Abbie Jane Psychology MARR, Daria Blaze Psychology *MCQUEEN, Mackenzie Faith Shirley Psychology Specialized Honours Minor in Philosophy *MCMENEMY, Jeffrey Psychology Specialized Honours *MELOCHE, Abbegayle Catherine Elaine Psychology MIRONSKY, Ilana Mary Psychology Minor in Criminology NWIZU, Ifeatu Psychology *NYSTROM, Levi Osiris Psychology and Gender and Women's Studies *PANETTA, Cheyenne Psychology Specialized Honours Minor in Criminology Page | 12 �POPOVIC, Tatyana Psychology RANTA-DIEGEL, Alexandria Tessa Mirjam Psychology STEPHENSON, Tiffany Alice Psychology Bachelor of Arts BONFIGLIO, Emily Riane Psychology *BOUKOURIS, Natasha Louise Psychology BROCK, Elizabeth Kathleen Melody Psychology CHARTERS, Richard James Psychology *GILLESPIE, Jasmine Evelyn Psychology GIVEN, Micheal John Psychology GRIEVE, Sarah Erin Psychology HATFIELD, Brooke Isabella Psychology JEWELL, Julianna Emily Psychology KATARIA, Ayush Psychology KUBER, Aaradhya Mahesh Psychology *LANTZ, Brittan Patricia Psychology MASSIE, Noah Psychology NEWTON, Natalie Faith Psychology TRAPPER, Taryn Psychology Page | 13 �Honours Bachelor of Kinesiology BASHARI, Paniz *BUCHAN, Julia Rose *CHOW, Harrison Grant *DAROSA, Victoria Marie *DEAGAZIO, Brianna Minor in Psychology *DORION, Victoria Ann DOWHOSZYA, Colton Richard John *GIANCOLA, Veronica Ruth GRAY, Hannah Michelle *GROSHEVA, Sofia Aleksandrovna HICKLIN, Olivia Peyton HOWELL, Morgan Blaze *JEDRUCH, Isabella Maria *JENSSON, Corissa Maxine *JOHNSTON, Emma Rae Minor in Aging and Health *JOY, Priya LEBANO, Noah Michael LINDSAY, Madison Kathleen *MAKIN, Samantha Anne Minor in Psychology *MARION, Fionnuala Minor in Indigenous Learning *MIGAY, Samuel Rudy Stuart *NELSON, MacKenzie Kate NICOL, Mackenzie Evelyn Page | 14 �*OPPEDISANO, Aiden McIntyre Minor in Mathematics ORIECUIA, Noah Johnathan PAVLETIC, Megan Hope Batista PETTINGER, Jessica Kathleen PRADHAN, Shreya *PYHTILA, Ethan Christopher *ROBINSON, Peter-Paul *RYDER-METHOT, Lana Minor in Aging and Health *SCHULZ, Sarah Katherine Minor in Criminology SHAH, Sanya Sheetal SKERRITT, Steve Strait WALSH, Kaitlyn Elizabeth WEBSTER, Aiden Alexander WHYNOT, Maren Lee *WILLIAMSON, Alleigh-Jane Elizabeth Bachelor of Kinesiology 4 Year GERULA, Erika HARGREAVES, Carter Roger QUEDENT, Michelle Leigh Dawn SCHMITT, Colton James Patrick Minor in English Honours Bachelor of Science *DASILVA, Aly Mya Psychology Minors in Criminology and Biology *HANLEY, Scarlett Rose Psychology Minor in Biology JAMEUS, Noah Nicholas Psychology Page | 15 �JOSEPH, Irine Psychology *KNOX, Brianna Psychology Specialized Honours MELGAR, Daniela Psychology *NAEEM, Muhammad Ahmad Psychology Specialized Honours PUGLIESE, Naleah Paige Psychology Minor in Criminology *SOORIYAKUMAR, Thanusan Psychology Specialized Honours *WHITE, Sydney Rae Psychology Minor in Biology Bachelor of Science *CORMIER, Kendall Gibson Psychology DOYLE, Owen Robert Psychology KNIGHT, Vincent Psychology STOVER, Tristan Rian Psychology Bachelor of Science in Nursing *ADENI, Oluwadamilola Oluwadara ADLER, Alexander Vladimir *AHMED, Fareedah Asabi *AKANNE, Nebechi Nwabuonu *AKANNE, Raluchi Nwadiuto ALBERTSON, Emma Grace ALLEN, Mikayla Justice ALVES, Victoria Madison Page | 16 �*AMANKONA, Prince Kwadwo ANVAR, Maryam AROWOSAFE, Aanuoluwa Gift ARPIN, Sydney Alyssa ARTHUR, Philip Kwakye *BADMUS-OREKAN, Taiwo BAPTISTE, Dominique Danielle BARNEY, Ryan David *BARNSLEY, Shannon Rae Marjorie *BIH, Marldel Awah BOLAND, Seth Claude BOND, Avery Makenna *BOULANGER, Anne Lucille BOWERS, Isabella Vittoria BRUGGEMAN, Victoria Amaya Diaz *CAHILL, Grace Michaela CAMBLY, Mackenzie Cora CAMERON, Sadie Anjolina Brooke Minor in Psychology *CHAHAL, Simrun CHAU, Maya CLEMENT, Sydney Shyanne COCCIMIGLIO, Noah Roberto *COOK, Alexander Philip John CROSS, Rhiannon Eva Rose DICKSON, Bryn Arianna Taylor *DOMINIC, Prince DORE, Fatoumata Teta Page | 17 �DROTAR, Isaac Christopher DUPUIS, Devan Alexander DUROJAIYE, Elizabeth Oluwatomisin *EDGAL, Omolua Stephanie EHIZOMWANGIE, Claudia Efia EKANEM, Daniel Ekong ENASHE, Addisu *EQUBEZGIE, Surafel Mebratu *EZIE, Sussan Akudo FARRELL, Sydney Lynn *FEIR, Michael Francis *FERNANDO, Shehan Mark FLOYDE, Jordyn *FOOTE, Hannah Grace FORBES, Spencer Andrew FREITAS, Abigail Nicole *FRYKAS-MONTGOMERY, Samantha Sue GADI, Jemima Charles *GANJOSA, Chaltu Abedi GEORGE, Betty Babu GIERTUGA, Dawson Joseph GINGERA, Hannah Elizabeth *GONZALEZ VALVERDE, Emily Victoria *GRANHOLM, Lukas William GRAVELLE, Payton Rae GREBTSOV, Dmitry GREBTSOVA, Liudmila Page | 18 �GREEN, Amber Rose Minor in Criminology GULUTZEN, Kelsey Sandra Minor in Aging and Health GUTHRIE, Emma Beatrice Irene GUTIERREZ, China Danielle Maglalang HAGARTY, Taya Elizabeth Marie HARBI, Nasro Aden *HARVEY, Paige Colleen HAYWARD, Stefanie HIGGINS, Samantha Doris Alyssa *HOANG, My Ngoc *HOEKSTRA, Tiffany Jacqueline *HOPF, Simone Minor in Psychology HOPKINS, Jendaya Carol Rose *HUNT, William James HUYLER, Naasson Zarrusho *IRVINE, Meaghan Rachel JAMES, Steffi Ann JANSEN, Morgan Carley Grace JAREMEY, Kailee Lynn JEON, Jaehyeon KAJORINNE, Kyra Veronica KAVCAR, Brittany Amber KIM, Thomas Dongchan KRUITWAGEN, Lindsay Claire *LACHIMEA, Ella Shea Marie LAI, Jasmine Boi Page | 19 �LAZINSKI, Abigail Marie LEHTO, Taylor Andrew Doran LENNSTROM, Laurisa Anne Celine LEONARD, Elise Kristin Paivi Minor in Psychology MA, Chong MADIMBU, Regina Tendaishe MAKSYMIU, Sydne Valerie MARCHAND, Sarah Emilee METANAD, Michelle Danille *MICELI, Tyler Alton MIGLIAZZA, Lucianna *MODHAVADIYA, Sanjay Punjabhai Punjabhai MOHAMMADI, Parsa MUIR, Jenny Marie NADEAU, Jayda Sarah Abigail NEBESKY, Isabelle Jean NEVES, Mercedes Castellani NGUYEN, Chau Phuc Minh *NOAH, Uduak Ema OGUNLANA, Oluwatobi Rebecca *OGUZIE, Sochima Raphael OKOKPUJIE, Akpotobore OKOLI, Stanley Chinweikpe OLAWUMI, Deborah Damilola Oluwatosin *ONOVIRAN, Salma Chinwe *ONYANGO, Linda Awiti ORMSTON, MacKenzie Reese Page | 20 �*OZERKEVICH, Rachael Amanda PAAVOLA, Haiden Maddox PACATANG, Angelica Cudiera *PARK, Siyoung *PATWARDHAN, Anuradha N *PEDERSEN, Kennedi Lynn PEREZ, Kurt Aaron Surbano POLLOCK, Brianna Marie *POLLOCK, Matthew Fowler PRESTIDGE, Paige Joan *PUENTES, Spencer Brady *RATTE, Melissa Kathryn ROBINSON, Josie Ann ROSS, Zachary Blaise RUDDERHAM, Julia Elizabeth Minor in Psychology SALDANHA, Deenal Sabeena SANAL, Ben Tom *SANDERSON, Robert Forest Beck SANNI, Aneezat *SCOCCHIA, Natalie *SCULLY, Katherine *SHEPHERD, Sarah Nathalie SINCLAIR, Jordyn Margrete *SIVER, Julia Elizabeth SMITH, Amanda Jayne Minor in Psychology SO, Hyerim SPEERS, Rhiannon Rose Page | 21 �STEIN, Astrid Kadjia Ann STEWART, Ewan Murray Angus STRICKLAND, Tiffiney Eunica Star *TANG, Tran Thuy My TANNAHILL, Tayla Faith *TAYLOR, Hannah Ruth *THIBOUTOT, Miera Elizabeth TRAN, Phuong Thi Minh *TROMBLEY, Kyle Jordan UMEH, Chizoba Loveth *VO, Hoai Thuong VOCA, Andrra *WAFULA, Grivinson Wanjala WARD, Mikaela Tatum Railyn WHITE, Kendaaz Jon Paul *WIITALA, Kiira Dawn *WILLIAMS, Camryn Alexandra WILSON, Mika Elisabeth WYVILLE, Cassandra Kathleen YOUNES, Selena Tilda *ZARETZKY, Zoe Amber Marie ZECHNER, Mylee Ann Rose Honours Bachelor of Social Work BEGALL, Mandy Lynn *CARTER, Elizabeth April CONWAY, Samantha Marie *DESBIENS, Alyssa Mae DOLISKA, Kayla Marie Page | 22 �*EDWARDS, Lisa Marie *GLOUSHER, Jillian Paige Concentration in Indigenous Learning GOODE, Tyler Patrick Minor in Indigenous Learning GOVIER, Keira Valerie *HEMINGWAY, Chloe Michelle *HILL, Ricki Anne HOOKE, Olivia Katherine Ann Minor in Political Science *ILLSON, Lindsey Dawn Minor in Psychology JOSHY, Aleena Mary KAPLANIS, Ashleigh Lauren Minor in History *KILGOUR, Hannah Bethany LANGTRY, Kelsey Grace LAPLANTE, Sarah Mariah LEACH, Denver Jerald Minor in Psychology *MAKI, Destiny Dawn SUNIL, Sayona SWANSON, Amy Morgan *WYMAN, Jennifer Dawn Gii Gashkatoon Gii Kendaaswin Mazina'igan: Indigenous Nurses Entry Program LYON, Nikita Page | 23 � https://digitalcollections.lakeheadu.ca/files/original/e78d6ce40d3846e28be4ccb9b7f31c65.pdf a84253c6c6d00888e51e160895f50aee PDF Text Text Graduating Class of 2025 Ceremony 3 - Friday May 30, 2025 (9:00 am) Hello. We are delighted to welcome you, your families, and friends, as we celebrate your achievements at Lakehead University. Today we celebrate the success of your academic achievements! We are please to announce the following list of graduates from the following Faculties: • Faculty of Natural Resources Management • Faculty of Science and Environmental Studies • Faculty of Social Sciences and Humanities ~ Faculty of Natural Resources Management Doctor of Philosophy LAVIGNE, Jonathan Forest Sciences Dissertation: Industrial Residuals in Land Reclamation - Enhancing Soil Recovery and Ecological Function in Disturbed Glacial Soils ONIRETI, Olaronke Omotayo Forest Sciences Dissertation: Interactive effects of photoperiod, soil moisture and carbon dioxide on ecophysiological traits of yellow birch (betula alleghaniensis) Master of Forest Management AMIHERE, Antoinette DANSOA, Josephine FOKUO, Tabitha GURUNG, Manisha Page | 1 �JEBAMONY KALAMARY, Mersha Jeslin JOHN KENNEDY, Celestina JUI, Homaira MEHDINASAB, Azamalsadat MANJALY, Bibin Paul NASIR, Turabi Master of Science in Forestry STARR, Sam Thesis: The Effect of Land Conversion from Forest to Agriculture on Soil Health Indicators in Rainy River, Ontario Honours Bachelor of Science in Environmental Management *CRIBBY, Katelyn Specialization in Wildlife Conservation and Management *DE LA MOTHE, Sam Michael Specialization in Wildlife Conservation and Management DEVERELL, Caden John Specialization in Wildlife Conservation and Management GATT, Sabrina Rose Specialization in Wildlife Conservation and Management *GIROUX, Luke Joseph Specialization in Wildlife Conservation and Management *GODDEN, Brooke Emily Specialization in Wildlife Conservation and Management MCCHRISTIE, Nathan Ryan Specialization in Wildlife Conservation and Management RANDALL, Eric Alexander Specialization in Wildlife Conservation and Management *THOMSON, Ethan Garret Rolf Specialization in Conservation Planning and Management Honours Bachelor of Science in Forestry *BILOSKI, Scotia Rae Specialization in Forest Health and Protection BOUGHN, Samuel Lorne Brown Specialization in Forest Health and Protection Page | 2 �CLARK, Taylor Specialization in Forest Management *DAVIDSON, Stephanie Ann Specialization in Forest Management *GILBERDS, Damien Bruce Lee Specialization in Forest Management JONES, Dorsey Atkin Specialization in Forest Products and Marketing KIM, Beom Specialization in Forest Health and Protection LEAR, Caden Matthew Specialization in Forest Health and Protection *MACEWEN, Wyatt William Specialization in Forest Health and Protection *PLOURDE, Sarah Mylene Specialization in Forest Management RAFIQ, Haider Jamal Specialization in Forest Management *SWINN, Madeline Specialization in Forest Health and Protection WU, Guyue Specialization in Forest Health and Protection YIN, Qingshan Specialization in Forest Products and Marketing Faculty of Science and Environmental Studies Doctor of Philosophy AFRA, Behrooz Biotechnology Dissertation: Flow Control of Low-Reynolds Number Airfoils Using Morphing Surface KAUR, Navneet Chemistry and Materials Science Dissertation: Photonic Sensor Based on Surface-Enhanced Raman Scattering for the Detection of Trace Chemicals MAO, Yang Chemistry and Materials Science Dissertation: Development of Small Molecules Targeting GPCRs (PAR2 & LPA1) for Potential Use in Cancer Diagnosis and Therapy Page | 3 �VARSHA, Varsha Chemistry and Materials Science Dissertation: Development of Mid-IR Laser Master of Arts AHMAD, Md Mustak Economics BILLO, Anwirin Joy Economics JAMES, Oowo Laura Economics KHAN, Mithun Economics MAHUVE, Heavenlight Economics TREHAN, Jasleen Economics Co-operative Option UMUTONIWASE, Nice Economics Master of Science BHOGARAJU, Vamsi Computer Science BOOMINATHAN, Arvind Chidambaram Computer Science Thesis: Integrating Multi-omics Data via Latent Space Construction for Breast & Bladder Cancer Analysis CHACKO, Renjith Eettickal Computer Science CHAKRAVARTY, Aniruddha Computer Science DUTTA, Anik Computer Science FAKHAR, Usman Computer Science Thesis: GraphSAGE-based Approach for Age-specific Multi-omics Biomarker Identification in Bladder GOPI, Rithika Computer Science Page | 4 �HATKAR, Tanmay Sunil Computer Science ISHAQUE, Samia Computer Science KAKIMOV, Rustem Computer Science Thesis: Upward Book Embeddings of DAGs: Constraint-Based Methods and Embeddability Analysis KOMPELLA YAJNA, Sai Santosh Computer Science KORUKONDA, Vivek Computer Science KOSHY, Jithin Reji Computer Science KUNDURU, Sai Asritha Computer Science KUSHAL, Kushal Computer Science LAUREIJS, Olivia Pauweliena Alde Archaeological Science Thesis: The radial wrist as a morphological and functional unit in extant African apes and humans LINGAREDDY, Nalini Gururaddi Computer Science LIU, Yanxu Computer Science NAGARAJAN THIRUPPATHI, Thanesh Computer Science NAMINENI, Sai Vishal Computer Science ORDOÑEZ AGUERO, Carlos Alberto Computer Science PALA, Gowthami Sai Sree Pooja Computer Science PAREKH, Aayush Nehal Computer Science PATHARE, Pooja Computer Science Page | 5 �RAMIGANI, Tharun Reddy Computer Science SEKAR, Tharun Computer Science SERRACIN MARTINEZ, Abel Computer Science SHAIK, Nethan Computer Science SHANKAR, Supprethaa Computer Science SHUBHAM, Shaksham Computer Science SINGH, Amandeep Computer Science SINGH, Jaspreet Computer Science SINGH, Sukhjeet Computer Science SINGH, Yuvraj Computer Science SIRASANAGANDLA, Vamsi Computer Science TOUGH, Georgina Biology Thesis: Investigating the use of paper mill residuals as agricultural soil amendments in Thunder Bay, Ontario VENKATRAMAN, Santosh Computer Science VINODH KUMAR, Tarun Computer Science WARNAKULASURIYA, Nimasha Computer Science YU, WEI Computer Science Honours Bachelor of Arts *BLAKELY, Joanna Geography Minor in History Page | 6 �*DOWLING, Meilan Anthropology HENDERSON, Amanda Mae Anthropology Minor in Sociology *MOOREY, Paige Raven Anthropology *PHILLIPS, Darion Economics and Political Science RAINFORD, Megan Elizabeth Anthropology *TRAER, Heidi Caroline Mathematics Bachelor of Arts *CALDER, Spencer Jason Economics and Political Science *GURBANLI, Ruhiyya Economics MASSIE, Dylan Paul Economics *TURPIN, Tyler Jordan Economics Honours Bachelor of Environmental Science *BROSSEAU, Marissa Krista Biology HARRIS, Paige Ellisa Biology MEYER, Rianna C Biology *WILSON, Natalie Theresa Biology Honours Bachelor of Environmental Studies *ESSEX, Keira Lyn Geography Page | 7 �Honours Bachelor of Science ARRIL, Beth Anna Biology *BHABA, Kartik Computer Science BHATT, Kshitij Kiran Computer Science *BLAGDEN, John Angelo Computer Science *BOSCH, Isabella Chiara Biology with Concentration in Neuroscience BRUNSON, Adaire Computer Science Co-operative Option *BUXTON, Adrien Applied Life Sciences *CANCADE, Alexis Bryn Biology *CHILAKALA, Sai Ajay Computer Science *CHUDASAMA, Drashtant Computer Science Co-operative Option *CLARA, Benjamin David Biology COATS, Cameron Angus Geology *COCEANCIC, Sandra Kirsten Biology with Concentration in Biodiversity and Conservation DEV, Gaurav Computer Science *DIGIUSEPPE, Matteo John Applied Life Sciences with Concentration in Biomedical Sciences *DOBSON, Jett Evan Physics with Concentration in Biomedical Physics *DOUGLAS, Aislyn Rose Lorraine Applied Life Sciences with Concentration in Biomedical Sciences Page | 8 �*GABRIELE, Jordan Ellis Anthropology *GILES, Garrett Raymond Computer Science GRAHAM, Kyle Bruce Computer Science Co-operative Option *HARDER, Mackenzie Renee Applied Life Sciences with Concentration in Biomedical Sciences *HASNAIN, Mahmood Shah Ashfaqul Computer Science Specialization in Game Programming Minor in Mathematics HUNNY, Fnu Computer Science *JACKSON, Parker Logan Computer Science Specialization in Game Programming JOHN, Isiah Sydney Geology *LAWSON, Benjamin John Chemistry with Concentration in Medical Sciences Minor in Biology *LE, Gia Hieu Computer Science Minor in Mathematics LE, Tam Minh Biology with Concentration in Neuroscience *LEHTO, Aiden Peter William Chemistry with Concentration in Medical Sciences *LELOND, Shanna Maria Biology *LOMBARDO, Claudia Emma Biology *LYONS-BARNEY, Isaac Computer Science *MARTIN, Emily Biology Page | 9 �*MCDONAGH, James William Xiang Computer Science Specialization in Game Programming MEMON, Samir Anwar Computer Science *MISHRA, Abhinav Computer Science *MOTIYANI, Harshkumar Kamleshbahai Mathematical Physics Minor in Mathematics *MURRAY, Bayze Telford Geology OLIVARES HERRERA, Malakai Nadya Biology with Concentration in Biodiversity and Conservation *ORIECUIA, Nicholas Matthew Biology and Chemistry *PALAHNUK, Emily Ann Biology with Concentration in Biodiversity and Conservation PAREIRA, Carron Computer Science Minor in Mathematics *PARKER, Emily MacKenzie Applied Life Sciences with Concentration in Biomedical Sciences *PARMAR, Shikha Shashi Computer Science *PATEL, Havan Mukeshkumar Computer Science *PATEL, Janviben Computer Science PATEL, Om Nileshkumar Computer Science *PRINCE, Taylor Aspen Biology and Chemistry PUTMAN, Daniel Robert Geology RAJALATHAN, Prishaa Kajalucksmi Applied Life Sciences with Concentration in Biomedical Sciences Page | 10 �RAYNOR, Hamish Pierson Hope Geoarchaeology RICHARDS, Grace Victoria Biology *ROBINSON, Marjorie Louise Jane Biology with Concentration in Biodiversity and Conservation *SANTAMARIA RODRIGUEZ, Emilio Daniel Computer Science *SHAW, Timothy Michael Computer Science Minor in Mathematics *SLAUBAUGH, Sierra Danielle Chemistry SONANI, Janvi Maheshbhai Computer Science *STEVENS, Lauren Marie Biology with Concentration in Neuroscience *STEWART, Jennah Eliza Anthropology *TANG, Yufei Mathematics *TAYLOR, Sarah Biology with Concentration in Plant Sciences *TRINH, Henry Cong Applied Life Sciences VAISHNAV, Gyan Computer Science *VARGAS RUIZ, Paulina Biology with Concentration in Neuroscience *VATAMANELU, Angelina Maria Biology with Concentration in Biodiversity and Conservation WEISE, Emily Darlene Chemistry WILLMORE, Ethan James Applied Life Sciences WRONOWSKI, Megan Ann Biology with Concentration in Animal Sciences Page | 11 �Bachelor of Science 4 Year AJITH, Anagha Applied Life Sciences with Concentration in Biomedical Sciences KAINEMBABAZI, Joanna Geology ZENIA, Shaheen Applied Life Sciences with Concentration in Biomedical Sciences Bachelor of Science AMBALIYA, Tanvi Rasikbhai Computer Science BARAIYA, Hirva Hiteshbhai Computer Science BEALS, Keelin Bryn General Program *CERVI, Dante Alexander General Program CORDONE, Amanda Kimberley General Program *DAI, Yiran Mathematics GHOJOGH, Aydin Computer Science GIGI, Gia Biology GILES, Garrett Raymond Mathematics HARRI, Cameron William Stanley General Program HRIDY, Redowana Rashid Computer Science JAIN, Angelena Sara Biology *JIANG, Shujing Mathematics KAHAR, Dhrumil Motilal Computer Science Page | 12 �KHAN, Tawhid Ashfaq Computer Science *KHOKHANI, Krish Manish Mathematics *LI, Haoran Mathematics MACLEAN, Guinevere Theodosia Physics *MCDONAGH, James William Xiang Mathematics MCTAVISH, Rachel Lynn Natural Science MISTRY, Kamal Balvant General Program O'HARE, Payton Colleen Natural Science PINTO, Royston Allwyn General Program POTLAPALLY, Abhinaya Computer Science *SCOTT, Emma-Lee Jane Clare Geography *SEMPLAY, Sunil Computer Science SUTHERLAND, Callie Frances General Program TAMRU, Abel Mickial Computer Science TOMS, Mariza Biology VORA, Chaitya Nishit Computer Science *WANG, Zhenni Mathematics *XING, Pei Zhi Mathematics Page | 13 �Gii Gashkatoon Gii Kendaaswin Mazina'igan: Indigenous STEM Access Program ARNAQJUAQ, Haily RILEY, Daneille Faculty of Social Sciences and Humanities Master of Arts APPIAH, Evangelina Social Justice Studies BOUCHARD, Jennifer Ann May Social Justice Studies CAMPBELL, John Farley History DUBE, Trista Mary Arlene Social Justice Studies GLEDHILL, Danielle Gloria Social Justice Studies GREENBERG, Shannon Social Justice Studies Specialization in Gender and Women’s Studies HELMER, Tiffany Rose English and Cultural Studies Specialization in Gender and Women’s Studies JOKINEN-PACKER, Nikos History KADOLPH, Mitchell Peter History KAKEGAMIC, Rachel History MANNING-MAYFIELD, Brianna Yvonne Social Justice Studies MENSAH, Beatrice Pokuaa Sociology Specialization in Social Justice Studies MIREAULT, Heather Social Justice Studies Page | 14 �MOK, Vivian Social Justice Studies MONTALBAN, Jocelyn Nicole Social Justice Studies NICHOLS, Jason Robert Paul History NOGARD, Hali History OVERSBY, Maya Mairead Social Justice Studies OWCA, Preston Jonathon Social Justice Studies ROGERS, Hilary Ann Social Justice Studies SABOURIN, Patrick Sociology Specialization in Social Justice Studies SAPKOTA, Dirgha Narayan English and Cultural Studies SHANTO, Arafat Alamgir History WILKINSON, Scott Sociology WINGROVE, Alyssa Jaimee English and Cultural Studies WOODS, Stefani Nadine Social Justice Studies Honours Bachelor of Arts ARELLA, Sarah Elizabeth English *ARIFIN, Katya Margaret English Minor in Indigenous Learning ARMSTRONG, Kirsten Elizabeth Political Science (Pre-Law) Minor in Criminology *BEEBE, Darrah Ashleigh Paige History Page | 15 �*BHOLA, Tristan Krishna Bhikam Political Science (Pre-Law) BJORKLUND, Tara French *BOARDMAN, Eve Adele Political Science (Pre-Law) BRITT, Brandon Joseph Political Science *EXCE, Ossman Danger Philosophy Minor in Indigenous Learning FERGUSON, Kira Bettie History FORTIN, Maxime Nicholas French *FREDRICKSON, Riley Elizabeth Gender and Women's Studies *GARCIA RODRIGUEZ, Gianella Political Science (Pre-Law) *GAUTHIER, Joshua French and History GRAHAM, Dawson August Grant History *HAMAR, Katerina Political Science (Pre-Law) *HARTLEY, Katherine Music JIANG, Yuxin History *JUTILA, Emma Lynn English LABONTE, Shantay Leena Political Science (Pre-Law) LAMBERT, Brynne Vawn English LARRETT, Hailey Anastasia History Minor in English Page | 16 �LEHTO, MacKenzie Lea English *LINDER, Ashley Sociology LISI, Orion English MACDOUGALL, Jessica Kayla English MARTIN, Haley Alicia History MAYER, Jillian Amelia English Minor in History MCGIRR, Juliet Elizabeth Sociology MIDWOOD, Andrew Frederick Donald History *NEILL, Franca Anne Political Science (Pre-Law) Minor in Gender and Women's Studies OLIVER, Carter Richard Douglas History and Political Science PAGE, Kristofer Connor History *PARKIN, Owen Gregory Political Science (Pre-Law) Minor in History PATTERSON, Justyne Rose Frances English *PFEIFER, Kendra Diane Political Science (Pre-Law) Minor in Sociology POILE, Zachery Joseph Political Science (Pre-Law) RICHARDSON, Cohen Political Science (Pre-Law) ROBERTS, Skyler English and History Page | 17 �*ROWAT, Andrew Kenneth Sociology and Gender and Women's Studies *RUSNAK, Eric Michael History and Philosophy SANTERRE, Nicole Gisele Political Science (Pre-Law) *SCHIRA, Shelby-Lin Annette Music SLUGGETT, Rachel Kate History SOBERING, Tyler Alexander English Minor in Philosophy SOLOMON, Michele Bernadette Indigenous Learning ST JACQUES, Natalie Helanna Music *TALBOT, Madison Grace Political Science and Gender and Women's Studies *TASSONE, Sarah Katelyn French Minor in History VISSER, Caitlan May History Minor in Psychology WESLEY, Erin Kelly English *WETENDORF, Joshua Nicholas History *WOOD, Olivia Justine History Minor in Philosophy *YAU SHENG, Chin Political Science Bachelor of Arts AIELLO, Baldino Jordan Sociology Page | 18 �*ANDRESEN, Matthew Ivar History *ANGUS, Alyssa Marcela Indigenous Learning ANSTEY, Lilya Erin Sociology BANNING, Izzabella General Program BENNETT, Liadan History BOLAND, Sylvia Anne Sociology BROWN, Ava-Mae Doris Political Science (Pre-Law) CAMPBELL, Madelyn Louise French CAMPBELL, Miranda Sociology *CARON, Alyssa Augustine Diane Political Science (Pre-Law) CARRASCO, Tait Josiah David Political Science (Pre-Law) *CLENDENNING, Calie Indigenous Learning *CLOWES, Danica Marie General Program CORY, Hayleigh Beth General Program *DELICATE, Adira Rachel History *DUGUAY, Ethan James General Program FARIA, Julia Isabelle French *FAYE, Robin Skya Indigenous Learning Page | 19 �FLEMING, Sheri Leah General Program FOREST, Anne Shiona General Program *GILBERT, Jade Visual Arts GILCHRIST, Ashley Elizabeth French GOODMAN, Josephine Mary Ann General Program HARDY, Cameron Anthony Sociology HOLFORD, Cicely Jacqueline General Program *HUNTER, Katherine Elizabeth Sociology KAKEPETUM, Darlene Lou General Program KARDACZ-FILOGRANA, Cassandra Sophia Elizabeth General Program KINGSTON, Dylan Tod General Program *MACLAURIN, Kyle Douglas Political Science (Pre-Law) *MACLEOD, Hailey Juila General Program MAO, Ruohui Sociology MARTYNYUK, Oskar-Arsen Arsen General Program MAWAKEESICK, Nancy General Program *MEGAN, Melissa General Program *MILLETTE, Emilie Josee General Program Page | 20 �*MYLLYMAA, Katia Joan Alexandra General Program NASH, Hannah Rae Political Science OBILAJA, Ifeoluwa Uzochgoziri General Program *OLSON, Paige Elizabeth Philosophy PLANT, Shayleigh Marion History RAD, Ezekia Indigenous Learning RENN, Noah Political Science RIPLEY, Tanisha General Program *ROBINSON, Gillian Enid Political Science (Pre-Law) SIMMONS, Bryanne Sarah History SKEAD, Wanda Indigenous Learning SOFEA, Jada Breeze Indigenous Learning STANTON, Grace Genevieve General Program STIENKE, Cassie Veronica General Program STROMNESS, Emily Anne Sociology *TALPADE, Simran Political Science (Pre-Law) TROULINOS, Haralambos Philosophy TURNER, Allison Karen French Page | 21 �UPADHYAY, Krushali General Program WALKOSKI-FAETZ, Taylor Lynn Gender and Women's Studies WILLIAMS, Jestina History Honours Bachelor of Fine Arts BEAUVAIS, Veritie Anna *CHASSE, Alyson Aisling Marie *GEROLAMI, Ashley Alexandra Lynne Minor in English *GILBERT, Sara Mae Marie *KIM, Alannah Narae Honours Bachelor of Music *CLARK, Sarah LEUTSCHAFT, Matthew Victor Johnathan *PICARD, Ailiin Vivien Honours Bachelor of Outdoor Recreation CASASANTA, Isabella Victoria *CRONK, Julianna *FERNANDES, Vanessa Pacheco HARRIS, Zachary Warren Minor in History *KELSO, Jared Bryan MACLEOD, Jillian Christina *MCTAVISH, Rachel Lynn MOYER, Samuel Dalton Arthur *PAUL, Cassandra Janine *PETSNICK, Helene Ruth SKINKLE, Jack Michael WALKOSKI-FAETZ, Taylor Lynn Page | 22 �Gii Gashkatoon Gii Kendaaswin Mazina'igan: Indigenous Transition Year Program ELLMAN-BIG GEORGE, Jason HANSEN, Augustina HARPER, Tessa KAABESTRA-WHITE, Ashlen KUSZNIER, Destiny LITTLEPOPLAR, Kayla MAWAGEESICK, Malakai MCKAY, Creedence MEEKIS, Breanne MEEKIS, Dunesheia MORRISEAU, Valen MOWEGEJICK, Raven SERGERIE-SUTHERLAND, Faybel STEVENSON, Ashley SUGANAQUEB, Jericho WILLOUGHBY, Athena YELLOWHEAD, Kyle Page | 23 � https://digitalcollections.lakeheadu.ca/files/original/0cf79f8e362372b2d127514a5612fac1.pdf 4601a55070a41c21899040b7f79890f7 PDF Text Text Graduating Class of 2025 Thursday June 5, 2025 (11:00 am) Hello. We are delighted to welcome you, your families, and friends, as we celebrate your achievements at Lakehead University. Today we celebrate the success of your academic achievements! We are please to announce the following list of graduates from the following Faculties: • Faculty of Business Administration • Faculty of Education • Faculty of Engineering* • Faculty of Health & Behavioural Sciences • Faculty of Science and Environmental Studies* • Faculty of Social Sciences and Humanities *includes graduates from the Lakehead University-Georgian College Partnership. ~ LAKEHEAD-GEORGIAN PARTNERSHIP FACULTY OF ENGINEERING Bachelor of Engineering ANNECCA, Ryan John Electrical BALACHANDRAN, Maathulan Latha Electrical BRANT, Parker James Electrical Page | 1 �DREW, Mitchell Joseph Delmar Electrical HASSAN, Mohammad Mohtasim Electrical JONAS, Krista Irene Electrical LANCIONE, Alyssa Kaley Electrical *O'LEARY, Tanner Dean Electrical TENOSO, Willy Rex Oliver Electrical FACULTY OF SCIENCE AND ENVIRONMENTAL STUDIES Honours Bachelor of Arts and Sciences *HESSER, Paula Marie Environmental Sustainability *HOEPP, Liam Eric Environmental Sustainability KIRBY, Bronwyn Annemiek Tiessinga Environmental Sustainability *MCELROY, Colleen Lily Environmental Sustainability NGUYEN, Danh Hiep Environmental Sustainability *SCHAT, Brin Fiona Prinzen Environmental Sustainability SHRUM, Matthew Robert Environmental Sustainability *SIMPSON, Cheyenne Rose Environmental Sustainability Bachelor of Arts and Sciences 4 Year BAKER, Jordyne Environmental Sustainability PRESSEY, Ethan John Environmental Sustainability Page | 2 �Honours Bachelor of Science *BECK, Preston Glenn Computer Science *BEREZHNOY, Michael Computer Science CUMMINS, John Computer Science FLORES, Xavier Christobal Computer Science *GOMBERG, Idan Computer Science *HAUTH, Corbin Anthony Applied Life Sciences *HILES, Connor Edwin Applied Life Sciences JOHNSTON, Lindsay Lorraine Applied Life Sciences *KAMAL, Yama Computer Science *KROPF, Desmond Lavon Computer Science LA CHANCE, Mystique Mary Applied Life Sciences LENTINI, Andreas Computer Science *MCELROY, Connor Stevens Computer Science MERDZIK, Dominik Tomasz Computer Science MILES, Tyler Harke Computer Science *MOLCZANSKI, Paul Jacob Computer Science *PALMER, Akeem Computer Science REDMOND, Colton Jessie Applied Life Sciences Page | 3 �*ROSANELLI, Michael Luca Computer Science *SOUVANLASY, Andrew Pachara Computer Science STEVENSON, Quinlan Monroe Computer Science VALENTINE, Rebecca Alexandria Applied Life Sciences *VAN, Tuany Computer Science Minor in Environmental Sustainability VAN WIERINGEN, William Gregory Computer Science *VEILLEUX, Christopher John Computer Science *WYER, Tyler Computer Science *ZHLEZNOV, Aleksandr Computer Science Bachelor of Science 4 Year OERTEL, Samantha Jean Angelikia Applied Life Sciences ORILLIA CAMPUS FACULTY OF BUSINESS ADMINISTRATION Honours Bachelor of Commerce ALEJANDRO, Ma Shane Angela Patane Business Administration *COLLINS, Noah Samuel Business Administration EAKINS, Daniel Reid Business Administration GONZALEZ CHACALTANA, Nicolas Alejandro Business Administration Minor in Finance Page | 4 �*GOWSELL, Owen Braden Paul Business Administration Minor in Finance HAMDAN, Hadi Business Administration Minor in Finance *HUMMEL, Sarah Ann Business Administration Minor in Finance HURLEY, Sarah Anne Business Administration MCLEAN, Matthew Jacob Business Administration *MIEBAI, Hephzibah Tarefegha Amira Business Administration Minor in Finance *NING, Xiaoying Business Administration *PATEL, Aaisha Dilawar Business Administration *RYAN, Emma Ann Business Administration Minor in Finance *SHEPPARD, Jack Gordon Donald Business Administration Minor in Finance *TOMAS, Rene Joseph Business Administration Minor in Finance Bachelor of Administration KHANANISHO, Samantha *PROTHMANN, Evangeline Victoria WONG, Trevor ZHOU, Siyu Management Page | 5 �FACULTY OF EDUCATION Master of Education BELLAND, Samantha Education for Change Specialization in Social Justice Education CERVO, Adrianna Ermelinda Education for Change Specialization in Indigenous Education DA SILVA, Nicoletta Teresa Sophia Educational Studies DE PASS, Shaenice Education for Change Specialization in Social Justice Education ELKHALIL, Sheema Educational Studies IAMPIERI, Shannon Esther Educational Studies JANISSE, Karly Education for Change Specialization in Social Justice Education KLOBUCAR, Rosemarie Educational Studies LO, Adrian Edward Educational Studies MCNISH, Shy-Anne Education for Change Specialization in Social Justice Education PALACIOS, Stephanie Education for Change Specialization in Social Justice Education SAPRA, Chirag Vishu Educational Studies SARGENT, Lindsay Michelle Education for Change Specialization in Environmental and Sustainability Education SEVERN, Melissa Caitlin Education for Change Specialization in Indigenous Education Page | 6 �THOMPSON, Tatiana Education for Change Specialization in Social Justice Education Thesis: Spaces of Possibility – Transmasculine Representation in Contemporary Media Bachelor of Education *AARTS, Hayley Maria *ADRIAN, Jessica Charis ALEXANDER, Stephanie *ALLIN, Justine Katherine *ANDRADE, Andrew Technological Education *ANJUM, Liala *ANTIC, Alexander *ARBID, Mariamna *ASGARI, Salomeh *ASHLEY, Adam Wilkinson Technological Education *ASIF, Anusha *ATKINS, Isobel Pearl *AUCOIN, Lauren Victoria AUDET, Ashton William Lee *AUSTIN, Jessica Margaret AZAM, Momil *BABCOCK, Lindsay Sharon *BADER, Emily Margaret BAGRI, Gurdeep Singh *BAHEERATHAN, Magisha *BAIANO, Zelda Eden *BAKER, Jessica M *BALAS, Deanne Louise *BALL, Katelyn Janine Page | 7 �*BARACH, Parker Shirleigh Skelding *BARTLETT, Jennifer Elizabeth BASIL, Diya BATOOL, Zahra *BECK, Jack Joseph *BELAIRE, Taryn Nicole *BELANGER, Barbara Lynn Technological Education *BELANGER, Brendan *BENGERT, Daniel Jacob *BENNETT, Vanessa Jo *BENVENUTO, Angelica Maria *BERNARD, Diandra Elaine *BERROA, Jaylen Marlis *BERTINATO, Mikayla Rose *BETTENCOURT, Darren *BIAMONTE, Sabrina Maria *BIEMANN, Sarah Theresia *BIGGS, Jade *BISHOP, Abigail Hardy *BLACK, Madison Victoria *BLOGG, Adrian Donald *BLY, Jessica Kathlena *BOURBON, Samantha Juliana *BOYD, Ashleigh Justine *BOZOLASCO, Bettina Maribel BRANCH, Nicole BRIERLEY, Hannah Frances Page | 8 �BROUILLARD, Taylor Ashton BROWN, Addisan *BROWN, Izabelle Eleanor *BROWN, MacKenzie Paige *BROWN, Sheridan Taylor *BRUSBY, Lauren Elizabeth *BUGAI, Olena *BULLOCK, Kelsey Grace *BURKE, Graydon Brian James *BURTON-VULOVIC, Margaret CADIEUX, Megan *CANNONS-HURLEY, Elizabeth Gwendolyn CARTER, Lara Grace Fisher *CASSAR, MacKenzie *CASTELLANO, Jennifer *CAVALLO, Julia *CEA-BERRY, Christina Marie CEKIC, Zeynep *CERDA, Emelyn Jeralee *CHERNISHENKO, Natasha Janine *CHINN, Lauren Delaney CINO, Alessandro Stefano *CIPRESSI, Alisa Nicole *COLASANTI, Esther Joanna *COOK, Esme Amelia COOMBS, Ethan Jose-Manuel *COVER, Alaina Rose *CRAIG, Lisa Melody Page | 9 �*DASILVA, Michael Paul DAVIDSON, Aidan William *DAWSON, Camryn June *DE JESUS, Mikaela Cidalia DE SILVA, Kaluhara Dewni Lakna *DEGEER, Allison Eve *DELABBIO, Sarah Jane *DELAIRE, Nicole Allyn *DELUCA, Patricia Amanda *DI TULLIO, Benjamin Joseph *DINSMORE, Jackalyn Eva *DIRVARIU, Francesca Ioana *DISTEFANO, Julia Gaspera *DMITRUK-COOK, Samuel Joel *DOBKO, Kevin Jaime *DOBSON, Sydney DONALD, Courtney Lorraine *DOSMAN, Sarah Michelle *DOUGHERTY, Lisa Donna Nicole *DOUCETTE, Rebecca *DOWLING, Joseph Tyler *DOYLE, Kobe Kaden DULAY, Anit *DURETTE, Michaela Ann *DWINNELL, Kristoffer Robert EDGAR, Blake William *EL-CHAMI, Rachel *ELLIOTT, Lauren Louise Page | 10 �ELSON, Calvin Mark *EROCHKO, Matthew John *ESPLANA, Elizabeth Ann *EVANS, Emily Catherine *EVANS, Natalie Catherine *FARID, Salma *FAZEKAS, Megan Paige *FEDERICO, Jaida *FIRTH, Nicholas James *FONTES, Paula Eduarda *FOSTER, Bethany Dianne *FRANCIS, Grace *FRANZIN, Joseph Jack FURYK, Sarah Elizabeth *GABRYS, Aura Marija *GALLIMORE, Tory Lynne *GALVEZ, Tran *GANTER, Bradley Peter GARD, Joseph Jack GARFORTH, Sasha Paige *GASCHO, Kyle Ian Scott *GATES, Ryley *GAUTHIER, Brooklyn Elizabeth *GEORGES, Joanna *GERRITSEN, Nashoba Johannes *GERVAIS, Alyse Michelle *GIBSON, Sarah Jordan *GIDGE, Luca Caroline Page | 11 �*GILL, Jasmeen Kaur *GIRARDO, Daniel Joseph Primo *GODDARD, Emma Rebekah *GOLDSWORTHY, Megan Ann *GORI, Jacqueline Marie *GRANGER, Simon Radford Hall *GRANT, Rory Samantha GRANT, Jennifer Leah *GREGORIO, Jessica Danielle Franco *GREGORIS, Meaghan Anne *GRIECO, Julia Francesca *GUTIERREZ, Justin Thomas *HAHN, Adam William *HALL, Haley Marie HARMANTAS, Alexander *HARRINGTON, Elizabeth Ellen *HARRISON, Martina Betty *HARTOG, Sierra Seantel *HAWKER, Kate Dianne *HAWKINS, Hunter Stewart *HELIOTIS, Vivian Kristina HELLYER, Hayden Miller HENDERSON, Rylee Frances *HILDRED, Emma Ainsley *HINKSMAN, Kate-Lynne Emma *HODGINS, Jacob W *HOEHNER, Anastasia Toula *HOLDSWORTH, Kyleigh Page | 12 �*HORLINGS, Mackenzie Madison *HUSKA, Dina *HUTTON-WALKER, Shianne Madison *ILES, Emma Noreen *JACK, Kassidy Lynne *JACKSON, Amanda Elizabeth JANSSEN, Camille Marie *JAREMKO, Holly Dawn *JAVANAINEN, Alana Kyra JOHANNINK, Paige Brittany *JOHN, Prashanth George JOHNS, James *JOHNSTON, Olivia Hope *JUHASZ, Adam Steven KAHLER, Connor Jacob *KANE, Danielle Amelia Rose *KEARNEY, Meaghan Catherine Loveday *KELL, Jennifer Ann *KELLY, Tracy Lyn *KENNEPOHL, Sophie Marie *KHAN, Marwah Ayub *KILEY, Kaci Loretta-Mae *KNUFF, Caelyn Sandrea *KOCH, Kevin Andrew *KRUL, Olivia Kimberley *LA PORTE, Kalanie Hilda Helene *LALANDE, Taliah Marie Lyn *LALONDE, Rachel Teresa Page | 13 �*LALONDE, Renee Claire *LANC, Greggory *LATKOLIK, Emily *LATOSKI, Lauryn Margaret *LAWSON, Erin Lynn *LECLAIR, Ashley LEBLANC, Gillian Grace *LEDSHAM, Megan Marlene *LEIS, Caitlin Dawn *LEONARD, Hannah Faith *LEONARD, Jordan Lee *LIMA, Megan Constance *LINHARES, Jacklyn Ponte *LINK, Kennedy LO, Dustin Lok Man *LUTZ, Caleb Jaiden *LYNCH, Emma Jane Charlotte *MABLEY, Holly Emma *MAC FARLANE, Doris Paige *MACINTYRE, Kendyl Elizabeth MACLAG, Christian Samuel *MACLEOD, Sean Elizabeth Jeanne *MANKOO, Parleen Kaur *MARAVI, Kendra Charlize *MARK, Hanna Mabel *MARSH, Anne Elizabeth MARTIN, Jane *MARTIN, Krista Lee Page | 14 �*MASTROPAOLO, David *MATTHEWS, Tobias Christopher *MAUCA, Jennifer Lee *MCAULEY, Kathleen Taylor *MCFADDEN, Shelby Lorraine *MCKEEGAN, Kathryn *MCLEAN, Evelyn MCNEIL, Alec Steele *MCPHEE, Riley Alan Fredrick MEDEIROS, Nicholas Anthony *MESCHINO, Matthew *MICALLEF, Ashlyn Marie *MICKOSKI, Thomas *MILLIGAN, Averie Lynn *MILNE, Thomas Edmund MacKenzie *MIRRLEES, Emma Elizabeth Ann *MISSEL, Amadore Karen *MLINAREVIC, Kristina *MOHAMMAD ZADEH YAGHCHI, Shahnaz *MOORE, Jessica Lynn *MORRIS, Shayna Rebecca *MORRIS, Stephanie Francoise *MORTLEY, Rachael Elizabeth *MULUGETA, Zacharias Soressa *MURRAY, Chelsea *MUSSMACHER, Natasha Paige NAVA, Arianna *NELLES, Bridget Page | 15 �*NG, Cheska Nicole *NIXON, Heather *NORTHEY, Tyne Emaleen *NYE-PETRONE, Tyrone Edward *O'FLAHERTY, Margaret Mary OBADA, Abdullah Ali *OKE, Lindsay Marie *OUELLETTE, Bethany Margaret *PACITTO, Midiana *PALUMBO, Martina Rose Cornelia *PANCZENKO, Nicholas Serhiy *PAOLUCCI, Michael Joseph *PARENT, Jacob Neil *PASCHKOWIAK, Christine Mary *PECCHIA, Domenic *PETERSON, Elizabeth Catherine *PHILLIPS, Lauren Julia *PIGEON, Bria Isabel *PILEGGI, Nicolai Fernando Technological Education *PITRE, Cole Ronald PITTARI, Anthony David *PLATER, Morgan Elizabeth *PONFERRADA, Kyla Jennelle *PONTONI, Lauren Melissa *POOLE, Janice Linda *POZZOBON, Victoria Nikole PREM, Aneeta Page | 16 �*PRIDMORE, Julia Sophie *PRINCE, Kathryn *PRZESIECKI, Evan Robert *PSIHOGIOS, Megan Kayla *PYKE, Jennifer Lynn *RAHEJA, Saniya *RAHMON, Nicholas Anthony *REDMOND, Isabella Christine *REYNOLDS, Sabrina Nicole *RICHARDS, Ashley Sarah Elizabeth *RIVAIT, Jasmyn Jaide *RIZZUTO, Paul *ROBERTS, Taylor Louise *ROCHA, Natasha Marie RODGER, Weston James Nathaniel ROGERS, Shane Michael *ROLEFF, Alicia Daila Anne *ROMEIRO, Ashley *ROSART MARTIN, Rachel Elise *ROSIELLO, Isabelle Carol Anne *RUTH, Kaitlyn Emma Kilburn *SAHIDSAHID, Taylor Maureen *SAWYER, Robyn Yvonne *SCARFONE, Michael *SCHIAVI, Aliya Rosanna *SCHINCAGLIA, Lola Adrianna SCHONEWILLE, Isaac Carson *SCHUCK, Danielle Catherine Page | 17 �*SCHULZ, Brittany Lynn *SEQUEIRA, Sabrina Marlene *SERRATORE, Alexander Patrick SHEI, Evan Yi-En *SHEARS, Simone Verna Technological Education *SHEPPARD, Sienna Lee *SHI, Ivy *SHOREMAN, Maggie *SILVA, Melanie *SIMARD, Sarah Anne *SIMAS, Michelle Melo *SIMON, Carson Emily Rachel *SINGH, Kumari Meenakshi *SKELLETT, Cooper Ireland Sanchez *SMEATON, Emerald Mary SMIT, Skylar Raymes *SMITH, Michelle Darlene Grace *SOLDIUK, Michelle *SOUSA, Krysta Manuela *SPADAFORA, Katarina Rosetta *SPAN, Willem Aaron *SPENCER, Abigail Rose *STAINTON, Marie *STANTON, Cassandra Marie *STEADMAN, Katherine Christine *STERLING, Kristen Lisa *STEWART, Sarah Alyse Page | 18 �*STONE, Blayne David *STRADER, Nicole Alison *STREET, Cory Damita Brown *STRIKWERDA, Lucas Andrew *TANSELLA, Selena Elizabeth *TANWAR, Prachi *TELFORD, Stephanie Anne *TENAGLIA, Daniela Christina *TERESO SAMPAIO, Catarina Susana *TERRY, Drew Paul *THANGTHONG, Joann Malyporn *THOMAS, Beena Annet Hans *THOMAS, Emma Caroline *THOMPSON, Coral Sandra *THOMPSON, Kendra Janine THOMPSON, Madeline Ann Spencer *THOMPSON, Mary Elizabeth *THOMSON, Laine Margaret *THORNTON, Erin Taylor *TITUS, Lucas Anthony *TRAM, Nancy *TUCKER, Tracey Anne *TUCKETT, Evan Robert William *TURNBULL, Taryn *VAN HULST, Marijke Irene *VAN RASSEL, Andrew John VAN VLAANDEREN, Cooper Dante *VANHOUCKE, Laura Jane Page | 19 �*VANMEER, Nicole Leslie *VANRY, Nicole Lauren *VASSILIADIS, Danae Adelia *VIEIRA, Vanessa VIGARS, Jack Ryan *WAGENAAR, Kristen Karlie *WALTON, Emily Lauren Blanche *WAREHAM, Matthew Jeffrey Ralph *WARFORD, Brianne Rose *WATSON, Kaiya Lynne *WEEL, Hannah Estel *WEIMAN, Sarah Victoria *WENZOWSKI, Emily Grace *WEST, Emma Elizabeth Ann *WHEELER, Dalton Robert *WHEELER, Janine Marie *WHITE, Kassidy Marie *WILKINS, Omega Michelle *WILSON, Hanna Leigh WINN, Justin Collins *WRIGHT, Taylor May *YALLEN, Norman *YANG, Chen *YI, Sandy See-Gar YOO, Duwon *YOUNG, Brett Garrett James *ZHANG, Jing Yi *ZIPPEL, MacKenzie Joy Page | 20 �Diploma in Technological Education BELIWICZ, Eliza Marie *BOYLE, Dana Lynn BUCKLEY, Mark Jason *ELLIOT, Shaun David *HARDING, Benjamin Brian *HARRISON, Jordyn R *HEFFERNAN, Daniel John Robert *HOVIUS, Melissa *LODGE, Ryan James MILLER, Daniel Sean *NEILSON, Blair Edward STEEVES, Jill Monique THURGOOD, Melanie Louise *VAN NIEKERK, Kevin Barry *WHITTAKER, Russell John FACULTY OF HEALTH AND BEHAVIOURAL SCIENCES Master of Social Work SMITH, Taylor Anne WRAY, Rebecca Mary WALSHAW, Madeleine Sophie Audrey Honours Bachelor of Arts *LALONDE, Julie Psychology Honours Bachelor of Social Work *BIENVENUE, Eunisse Minor in Sociology *BLANCHARD, Rebecca-Mae Marie *BLOOMER, Stephannie Nicole Page | 21 �*BONAVOTA, Vincenzo CHANT, Hannah Francis *CHURCHILL, Rebekah *CORBIERE, Carey Lynn Specialization in Gender and Women’s Studies Minor in Criminology *CROOKSTON, Ashleigh Mariah *DIMAKOS SHEVCHENKO, Dini *DOLSTRA, Connie Annette Minor in Psychology *EVE, Kathryn FARAGHER, Brooke *FERREIRA, Brian Conde *HENRY, Dawn Marie *HUDSON, Jordan Marie Georgette Minor in Criminology *LECLERC, Saige Elizabeth *LUCIANI, Victoria Gina Maria *MCCANN, Olivia Christine *MCCAW, Shelby Kaitlyn *MOYANO, April *POLKO, Robert Andrew Louis *SMITH, Ryan Patrick SPATARO, Shauna Lee *TRAVERS, Claire Margaret *TREMBLETT, Tiffany Kayla Minor in Sociology *VASINA, Anna Page | 22 �FACULTY OF SCIENCE AND ENVIRONMENTAL STUDIES Master of Science KOORNNEEF, Karen Lynn Biology Thesis: Wetlands as Filters of Heavy Metals - A Study in Temperate Fens of Central Ontario Honours Bachelor of Arts *CZECH, Genevieve Sara Gabrielle Anthropology Honours Bachelor of Arts and Sciences *DENOMME, Emma Carolyn Joan Environmental Sustainability DWINNELL, Kristoffer Robert Geography MOASE, Abbey Lauren Geography Minor in History *OLIVARES ESPINOSA, Tania Environmental Sustainability RATHOD, Vraj Environmental Sustainability TUCKER, Tracey Anne Environmental Sustainability *VEENSTRA, Jenna Rita-Maria Geography Minor in Indigenous Learning WEISS, Kirsten Marlene Environmental Sustainability Honours Bachelor of Science *GOULD, Allison Violet Applied Life Sciences Minor in Psychology PANDYA, Mugdha Haresh Applied Life Sciences SHANTZ, Jessica Davie Applied Life Sciences Minor in Psychology Page | 23 �SINGH, Gurleen Computer Science SREEDHARAPANICKER, Neeraja Applied Life Sciences Bachelor of Science 4 Year PANJABI, Phalguni Applied Life Sciences Bachelor of Science CHANNA, Gurtaj Singh General Program FUKSBRUMER, Jonathan General Program LIU, Xiaodai General Program KAUR, Lavinder General Program PATEL, Sonali Sureshkumar Applied Life Sciences PATEL, Vansh Dharmendra General Program ROBINSON, Hannah Kate General Program FACULTY OF SOCIAL SCIENCES AND HUMANITIES Honours Bachelor of Arts ADAMS, Elizabeth Dolorese Nadine English *BARRETT, Allan Douglas Political Science *DASILVA, Daniel Anthony Political Science DAVIES, Kaitlyn Alyssa English *DOOLITTLE, Kendra Jade English Minor in Indigenous Learning Page | 24 �FOSTER, Bethany Dianne English *GANTER, Bradley Peter History Minor in English *HARTLEY, Kaitlin Barbaralynne Political Science Minor in History *HOEHNER, Anastasia Toula English HORLINGS, Mackenzie Madison English KEMPER, Hailey Margaret English NYHOF, Kyle Political Science PETERSON, Elizabeth Catherine English SCOTT, Tyler Mitchel Political Science *SNOW, Ashley Political Science (Pre-Law) Minor in Criminology STEFANOVIC, Tayler Dianne Chantal English and History TREBBLE, Avery Madigan Sociology *VARANO, Vito History Bachelor of Arts AULD, Ryan David James History COOMBS, Ethan Jose-Manuel History CRIGHT, Kenzie Patricia General Program Fernandez-Sardina, Tai Alexander General Program Page | 25 �FORAGE, Aidan Alexander General Program FRETTER, Jayna Reese General Program GATES, Ryley English GIBSON, Sarah Jordan English GIRARDO, Daniel Joseph Primo History GIURIN, Anna Marina History JACK, Kassidy Lynne English *LEMBO, Lauren Anne General Program LILLY, Megan Christina Margaret English *MACKINLAY, Marguerite Grace History MCEACHERN, Alisa Ana Maria Sociology *MCGILL, Ryan James History NICHOLSON, Hunter Jade General Program ROMEO, Matthew Armando History *SPRUCE, Kerwood Allen General Program Honours Bachelor of Arts and Sciences ALLOUZ, Zahra Criminology *ARORA, Devansh Media, Film and Communications Minor in Writing Page | 26 �AUL, Sarah Criminology BASQUE, Vivian Criminology BECK, Jack Joseph Interdisciplinary Studies BELANGER, Brendan Interdisciplinary Studies *BIGGAR, Chloe Alyssa Criminology *BISHOP, Abigail Hardy Interdisciplinary Studies *BROWN, Carter Criminology Minor in Political Science BROWN, Izabelle Eleanor Interdisciplinary Studies CARTER, Lara Grace Fisher Interdisciplinary Studies with Concentration in Human Nature *CASSELLS, Ashley Erin Criminology Minor in Psychology CLEMENT, Joslyn Aubree Interdisciplinary Studies with Concentration in Social Justice *CONNELL, Amber Rose Criminology Minor in Psychology COUSINEAU-CARRICK, Wade John Interdisciplinary Studies DOYLE, Eric Thomas Leo Interdisciplinary Studies DURETTE, Michaela Ann Interdisciplinary Studies ESHIE, Selina Mary Criminology GAUTHIER, Brooklyn Elizabeth Interdisciplinary Studies Page | 27 �GLIDDON, Paisley Aleaha Criminology GOMEZ-ZAPATA, Isabela Media, Film and Communications Minor in Anthropology *GRATRIX, Kelly Lauren Interdisciplinary Studies GRAY, Ella Rose Interdisciplinary Studies *GRUNIG-BAYNTON, Hailey Lorraine Criminology Minor in Political Science HINKSMAN, Kate-Lynne Emma Interdisciplinary Studies with Concentration in Human Nature JARADAT, Kareem Othman Media, Film and Communications KNEESHAW, Nicole Jean Marie Criminology KREISEL, Wren Leutzinger Criminology LAKE, Sara Interdisciplinary Studies with Concentration in Social Justice LEBLANC, Gillian Grace Interdisciplinary Studies LEIGHTON, Danika Lynn Criminology LEIS, Caitlin Dawn Interdisciplinary Studies LUCK, Brittney L Criminology MACINTYRE, Kendyl Elizabeth Interdisciplinary Studies MEKALA, Rochanaa Criminology Minor in Psychology MORRIS, Stephanie Francoise Interdisciplinary Studies Page | 28 �OKUMURA, Shinowa Media, Film and Communications OTTAVIANI, Isabella Nicole Criminology *OUELLETTE, Bethany Margaret Interdisciplinary Studies PENA VILLARROEL, Juan Jose Criminology *PERRONS, Alexandria Lynn Criminology PISKUN, Andrew Jonathan Criminology PRAGNELL, Ethan Dwayne Criminology *PRICE, Kieran Douglas Criminology POOLE, Rachel Lynn Criminology RIVAIT, Jasmyn Jaide Interdisciplinary Studies REDDICK, Samantha Carrie Criminology *RUSSELL, Jaedyn Patricia Criminology Minor in Psychology SEQUEIRA, Sabrina Marlene Interdisciplinary Studies *SHEWFELT, Lindsey Ann Criminology SMIT, Skylar Raymes Interdisciplinary Studies *STREET, Cory Damita Brown Interdisciplinary Studies *STREETER, Shawn Kyle Media, Film and Communications SURUJBALI, McKayla Cianna Criminology Page | 29 �*TAYLOR, Christian David Criminology TEMPLE, Grace Marie Criminology *THOMAS, Emma Caroline Interdisciplinary Studies THOMPSON, Coral Sandra Interdisciplinary Studies TOMARIN, Jacob Media, Film and Communications *TOMS, Kassidy Mary Ellen Criminology WEST, Emma Elizabeth Ann English WHEELER, Dalton Robert Interdisciplinary Studies WHITE, Kassidy Marie Interdisciplinary Studies *WILLIAMS, Jessica R Criminology *WILSON, Keely Spencer Criminology Bachelor of Arts and Sciences 4 Year BOU-ZEID, Alexandra Joselyne Criminology Bachelor of Arts and Sciences AJILEYE, Adesuyi Babatunde Interdisciplinary Studies AMYOT, Brandon Rheal Interdisciplinary Studies BERROA, Jaylen Marlis Interdisciplinary Studies BLY, Jessica Kathlena Interdisciplinary Studies DOOLEY, Ayden Ross Interdisciplinary Studies Page | 30 �EVANS, Emily Catherine Interdisciplinary Studies *FERREIRA-LOPES, Ashley Interdisciplinary Studies HENDERSON, Rylee Frances Interdisciplinary Studies *HOLDSWORTH, Kyleigh Interdisciplinary Studies LALANDE, Taliah Marie Lyn Interdisciplinary Studies *LECLAIR, Ashley Interdisciplinary Studies *POLLOCK, Breanna Laurel Ann Interdisciplinary Studies *SPICER, Ryan Scott Interdisciplinary Studies TERRY, Drew Paul Interdisciplinary Studies THOMPSON, Mary Elizabeth Interdisciplinary Studies WALKER, Amanda Grace Interdisciplinary Studies ZIPPEL, MacKenzie Joy Interdisciplinary Studies Page | 31 � 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 Lakehead University Collection Description An account of the resource Photographs from Lakehead University's history: people, events, and campus. 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 2025 Convocation Programmes Subject The topic of the resource Universities Description An account of the resource Programme and list of graduates for Convocations held May 29 and May 30, 2025. Creator An entity primarily responsible for making the resource Lakehead University Date A point or period of time associated with an event in the lifecycle of the resource 2025-05 Format The file format, physical medium, or dimensions of the resource PDF Language A language of the resource English Type The nature or genre of the resource Text https://digitalcollections.lakeheadu.ca/files/original/99c083bfbf57b97590b6050acae4bd4e.pdf f1d247daa107d03ceffc4ef05679054d PDF Text Text 71st Annual Meeting Proceedings Volume 71 Part 1 – Program and abstracts Mountain Iron, Minnesota, May 14-17, 2025 �71st Annual Meeting Institute on Lake Superior Geology Mountain Iron, Minnesota May 14-17, 2025 Meeting Co-Chairs Amy Radakovich, Allison Severson, Eric Nowariak, Stacy Saari, Aaron Hirsch Proceedings Volume 71 Part 1: Program and Abstracts Edited by Co-Chairs i �71st Institute on Lake Superior Geology Volume 71 consists of: Part 1: Program and Abstracts Part 2: Field Trip Guidebook Trip 1: Transect of the Quetico subprovince Trip 2: Drill Core from three Cu-Ni deposits of the Duluth Complex Trip 3: How do you make iron and/or manganese in Proterozoic Iron Formation? Trip 4: New Geological Insights into the genesis of iron ores at Lake Vermillion – Soudan Underground Mine State Park Trip 5: Neoarchean alkalic intrusions in the Wawa and Quetico subprovinces Trip 6: Unique Keweenawan inclusion (Colvin Creek) in the Duluth Complex Trip 7: Classic outcrops of Northeastern Minnesota Trip 8: Glacial Lake Norwood and the Koochiching Lobe Reference to material in Part 1 & 2 should follow the examples below: Authors, 2025, Title in Institute on Lake Superior Geology, 71st Annual Meeting, Mountain Iron, Minnesota, Part 1 - Abstracts and Program, v. 71, part 1, p. xx-xx. Authors, 2025, Field Trip title in Institute on Lake Superior Geology, 71st Annual Meetings, Mountain Iron, Minnesota, Part 2 – Field Trip Guidebook, v. 71, part 2, p. xx-xx. Proceedings Volume 71, Part 1: Program and Abstracts and Part 2: Field Trip Guidebook are published by the 71st Institute on Lake Superior Geology and distributed by the Institute Secretary: Peter Hollings Department of Geology Lakehead University Thunder Bay, ON P7B 5E1 CANADA peter.hollings@lakeheadu.ca Some figures in this volume were submitted by authors in color but are printed black and white. Full color imagery will appear in the digital version of the volume when it is available on-line at: http://www.lakesuperiorgeology.org ISSN 1042-99 ii �Table of Contents Table of Contents ..................................................................................................................................... iii Institutes on Lake Superior Geology, 1955-2025 .................................................................................... iv Sam Goldich and the Goldich Medal ...................................................................................................... vii Goldich Medal Guidelines ....................................................................................................................... ix Goldich Medalists .................................................................................................................................... xi Citation for the 2025 Goldich Medal Recipient ...................................................................................... xii Honoring the Pioneers of Lake Superior Geology ................................................................................. xiv Pioneers of Lake Superior Geology ....................................................................................................... xiv 2025 Citation for Robert Bell (1841-1917)............................................................................................. xv Eisenbrey Student Travel Awards ........................................................................................................... xx Joe Mancuso Student Research Awards ................................................................................................. xxi Doug Duskin Student Paper Awards ..................................................................................................... xxii Board of Directors ................................................................................................................................ xxiii 2025 ILSG Meeting Volunteers ........................................................................................................... xxiv 2025 ILSG Meeting Session Chairs ..................................................................................................... xxiv Field Trip Leaders and Guidebook Authors .......................................................................................... xxv Mine to Mountain Bike Mecca: ........................................................................................................... xxvi Report of the chairs of the 70th annual meeting .................................................................................. xxvii Donations to Support the Annual Meeting ........................................................................................... xxxi TECHNICAL PROGRAM ................................................................................................................ xxxiii ABSTRACTS........................................................................................................................................ xliii iii �Institutes on Lake Superior Geology, 1955-2025 # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Date 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 Place Minneapolis, Minnesota Houghton, Michigan East Lansing, Michigan Duluth, Minnesota Minneapolis, Minnesota Madison, Wisconsin Port Arthur, Ontario Houghton, Michigan Duluth, Minnesota Ishpeming, Michigan St. Paul, Minnesota Sault Ste. Marie, Michigan East Lansing, Michigan Superior, Wisconsin Oshkosh, Wisconsin Thunder Bay, Ontario Duluth, Minnesota Houghton, Michigan Madison, Wisconsin Sault Ste. Marie, Ontario Marquette, Michigan iv Chairs C.E. Dutton A.K. Snelgrove B.T. Sandefur R.W. Marsden G.M. Schwartz & C. Craddock E.N. Cameron E.G. Pye A.K. Snelgrove H. Lepp A.T. Broderick P.K. Sims & R.K. Hogberg R.W. White W.J. Hinze A.B. Dickas G.L. LaBerge M.W. Bartley & E. Mercy D.M. Davidson J. Kalliokoski M.E. Ostrom P.E. Giblin J.D. Hughes �# 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 Date 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Place St. Paul, Minnesota Thunder Bay, Ontario Milwaukee, Wisconsin Duluth, Minnesota Eau Claire, Wisconsin East Lansing, Michigan International Falls, Minnesota Houghton, Michigan Wausau, Wisconsin Kenora, Ontario Wisconsin Rapids, Wisconsin Wawa, Ontario Marquette, Michigan Duluth, Minnesota Thunder Bay, Ontario Eau Claire, Wisconsin Hurley, Wisconsin Eveleth, Minnesota Houghton, Michigan Marathon, Ontario Cable, Wisconsin Sudbury, Ontario Minneapolis, Minnesota Marquette, Michigan Thunder Bay, Ontario Madison, Wisconsin Kenora, Ontario Iron Mountain, Michigan Duluth, Minnesota Nipigon, Ontario Sault Ste. Marie, Ontario Lutsen, Minnesota Marquette, Michigan Ely, Minnesota International Falls, Minnesota 57 58 59 60 61 62 2011 2012 2013 2014 2015 2016 Ashland, Wisconsin Thunder Bay, Ontario Houghton, Michigan Hibbing, Minnesota Dryden, Ontario Duluth, Minnesota v Chairs M. Walton M.M. Kehlenbeck G. Mursky D.M. Davidson P.E. Myers W.C. Cambray D.L. Southwick T.J. Bornhorst G.L. LaBerge C.E. Blackburn J.K. Greenberg E.D. Frey & R.P. Sage J. S. Klasner J.C. Green M.M. Kehlenbeck P.E. Myers A.B. Dickas D.L. Southwick T.J. Bornhorst M.C. Smyk L.G. Woodruff R.P. Sage & W. Meyer J.D. Miller & M.A. Jirsa T.J. Bornhorst & R.S. Regis S.A. Kissin & P. Fralick M.G. Mudrey & Jr., B.A. Brown P. Hinz & R.C. Beard L. Woodruff & W.F. Cannon S. Hauck & M. Severson M. Smyk & P. Hollings A. Wilson & R. Sage L. Woodruff & J. Miller T.J. Bornhorst & J. Klasner J. Miller, G. Hudak, D. Peterson M. Jirsa, P. Hollings & T. Boerboom, P. Hinz & M.Smyk T. Fitz P. Hollings T.J. Bornhorst & A. Blaske J. Miller & M. Jirsa R. Cundari & P. Hinz J. Miller, C. Schardt & D. Peterson �# 63 Date 2017 Place Wawa, Ontario 64 2018 Iron Mountain, Michigan 65 66 2019 2020 Terrace Bay, Ontario Meeting cancelled 67 68 69 2021 2022 2023 Virtual meeting Sudbury, Ontario Eau Claire, Wisconsin 70 2024 Houghton, Michigan 71 2025 Mountain Iron, Minnesota vi Chairs A. Pace, A. Wilson & T.J. Bornhorst L. Woodruff, W. Cannon & E.K. Stewart P. Hollings & M.C. Smyk Cancelled by the COVID-19 pandemic M. Jirsa, M. Smyk & P. Hollings R.M. Easton & W. Bleeker R. Lodge, E.K. Stewart, & C. Ames T.J. Bornhorst, E. Vye, P. Cobin, & J. Degraff A. Radakovich, A. Severson, E. Nowariak, S. Saari, A.C. Hirsch �Sam Goldich and the Goldich Medal Sam Goldich received an A.B. from the University of Minnesota in 1929, a M.A. from Syracuse University in 1930, and a Ph.D. from the University of Minnesota in 1936. During World War II Sam worked for the U.S. Geological Survey in mineral exploration. In 1948, Sam returned to the University of Minnesota, and became Professor and Director of the Rock Analysis Laboratory the following year. He rejoined the U.S. Geological Survey in 1959 and was appointed as the first Branch Chief of the Branch of Isotope Geology. Sam returned to academia in 1964 when he went to Pennsylvania State University. He left PSU in 1965 and moved to the State University of New York at Stony Brook, where he stayed for 3 years. Restless yet again, he moved to Northern Illinois University in 1968 where he was a professor until his retirement in 1977. Sam’s final move was to Denver where he became an emeritus at the Colorado School of Mines. Sam died in 2000, less than a month before his 92nd birthday. In the late 1970s, Geological Society of America Special Paper 182, which included seminal geochronological studies by Sam Goldich and coworkers on the Archean rocks of the Minnesota River Valley, was nearing completion. At this time various ILSG regulars began discussing the possibility of recognizing Sam for his pioneering work on the resolution of age relationships and thus the geology of Precambrian rocks in the Lake Superior region. Three members, R.W. Ojakangas, J.O. Kalliokoski, and G.B. Morey, presented the idea to the ILSG Board of Directors in 1978. The Board approved the creation of an award, provided funding could be obtained. It was suggested that collecting one or two dollars at registration for a dedicated account would provide resources for striking the medal. A general request was made to the ILSG membership for donations and Sam himself offered a challenge grant to match the contributions. In total, $4,000 was collected and thus began the work of creating the Goldich Medal. The initial Goldich Award was presented to Sam by G.B. Morey in 1979 and consisted of a large paper proclamation. For the actual medal, G.B. Morey consulted with the foundry on production details, while Dick Ojakangas and Jorma Kalliokoski worked on the design of the award, suggesting that it be given for “outstanding contributions to the geology of the Lake Superior region.” Simultaneously, a committee of J.O. Kalliokoski, W.F. Cannon, M.M Kehlenbeck, G.B. Morey, and G. Mursky developed the Award Guidelines that were approved by the ILSG Board. By 1981 all the elements of the Goldich Award had come together, and the second recipient, Carl E. Dutton, Jr., received the Goldich Medal for 50 years of significant contributions to the understanding of the geology of the Lake Superior region. Since the beginning, the Awards Committee has consisted of individuals representing industry, government and academia, with each member of the Committee serving for three years. The medal is now awarded every year at the annual ILSG meeting. Reference: Morey, G.B. and Hanson, G.N. (editors). 1980. Selected studies of Archean gneisses and Lower Proterozoic rocks, southern Canadian Shield. Geological Society of America, Special Paper 182, 175 p. Prepared by various Goldich Medal Awardees, 2007 vii �Institute on Lake Superior Geology Goldich Medal viii �Goldich Medal Guidelines (Adopted by the Board of Directors, 1981; amended 1999) Preamble The Institute on Lake Superior Geology was born in 1955, as documented by the fact that the 27th annual meeting was held in 1981. The Institute’s continuing objectives are to deal with those aspects of geology that are related geographically to Lake Superior; to encourage the discussion of subjects and sponsoring field trips that will bring together geologists from academia, government surveys, and industry; and to maintain an informal but highly effective mode of operation. During the course of its existence, the membership of the Institute (that is, those geologists who indicate an interest in the objectives of the ILSG by attending) has become aware of the fact that certain of their colleagues have made particularly noteworthy and meritorious contributions to the understanding of Lake Superior geology and mineral deposits. The first award was made by ILSG to Sam Goldich in 1979 for his many contributions to the geology of the region extending over about 50 years. Subsequent medalists and this year’s recipient are listed in the table below. Award Guidelines 1) The medal shall be awarded annually by the ILSG Board of Directors to a geologist whose name is associated with a substantial interest in, and contribution to, the geology of the Lake Superior region. 2) The Board of Directors shall appoint the Goldich Medal Committee. The initial appointment will be of three members, one to serve for three years, one for two years, and one for one year. The member with the briefest incumbency shall be chair of the Nominating Committee. After the first year, the Board of Directors shall appoint at each spring meeting one new member who will serve for three years. In his/her third year this member shall be the chair. The Committee membership should reflect the main fields of interest and geographic distribution of ILSG membership. The out-going, senior member of the Board of Directors shall act as liaison between the Board and the Committee for a period of one year. 3) By the end of November, the Goldich Medal Committee shall make its recommendation to the Chair of the Board of Directors, who will then inform the Board of the nominee. 4) The Board of Directors normally will accept the nominee of the Committee, inform the medalist, and have one medal engraved appropriately for presentation at the next meeting of the Institute. 5) It is recommended that the Institute set aside annually from whatever sources, such funds as will be required to support the continuing costs of this award. Nominating Procedures ix �1) The deadline for nominations is November 1. Nominations shall be taken at any time by the Goldich Medal Committee. Committee members may themselves nominate candidates; however, Board members may not solicit for or support individual nominees. 2) Nominations must be in writing and supported by appropriate documentation such as letters of recommendation, lists of publications, curriculum vitas, and evidence of contributions to Lake Superior geology and to the Institute. 3) Nominations are not restricted to Institute attendees but are open to anyone who has worked on and contributed to the understanding of Lake Superior geology. Selection Guidelines 1) Nominees are to be evaluated on the basis of their contributions to Lake Superior geology (sensu lato) including: a) importance of relevant publications; b) promotion of discovery and utilization of natural resources; c) contributions to understanding of the natural history and environment of the region; d) generation of new ideas and concepts; and e) contributions to the training and education of geoscientists and the public. 2) Nominees are to be evaluated on their contributions to the Institute as demonstrated by attendance at Institute meetings, presentation of talks and posters, and service on Institute boards, committees, and field trips. 3) The relative weights given to each of the foregoing criteria must remain flexible and at the discretion of the Committee members. 4) There are several points to be considered by the Goldich Medal Committee: a) An attempt should be made to maintain a balance of medal recipients from each of the three estates—industry, academia, and government. b) It must be noted that industry geoscientists are at a disadvantage in that much of their work in not published. 5) Lake Superior has two sides, one the U.S., and the other Canada. This is undoubtedly one of the Institute’s great strengths and should be nurtured by equitable recognition of excellence in both countries. x �Goldich Medalists 1979 Samuel S. Goldich 1998 Zell Peterman 2016 Mark A. Jirsa 1980 not awarded 1999 Tsu-Ming Han 2017 Philip Fralick 1981 Carl E. Dutton, Jr 2000 John C. Green 2018 Val W. Chandler 1982 Ralph W. Marsden 2001 John S. Klasner 2019 Mark Severson 1983 Burton Boyum 2002 Ernest K. Lehmann 2020 not awarded 1984 Richard W. Ojakangas 2003 Klaus J. Schulz 2021 Alan MacTavish 1985 Paul K. Sims 2004 Paul Weiblen 2022 Terrence J. Boerboom 1986 G.B. Morey 2005 Mark Smyk 2023 Peter Hollings 1987 Henry H. Halls 2006 Michael G. Mudrey 2024 Suzanne W. Nicholson 1988 Walter S. White 2007 Joseph Mancuso 2025 Robert Michael Easton 1989 Jorma Kalliokoski 2008 Theodore J. Bornhorst 1990 Kenneth C. Card 2009 L. Gordon Medaris, Jr 1991 William Hinze 2010 William D. Addison & 1992 William F. Cannon 1993 Donald W. Davis 2011 Dean M. Rossell 1994 Cedric Iverson 2012 James D. Miller 1995 Gene La Berge 2013 Tom Waggoner 1996 David L. Southwick 2014 Laurel Woodruff 1997 Ronald P. Sage 2015 Rodney J. Ikola Gregory R. Brumpton 2025 GOLDICH MEDAL RECIPIENT Robert Micheal Easton Goldich Medal Committee Serving through the meeting year shown in parentheses. Dean Peterson (2022-2025) Big Rock Exploration, Industry Member (Committee Chair) Marcia Bjornerud (2023-2026) Lawrence University, Academic Member Robert Cundari (2025 - 2028) OGS, Government Member xi �Citation for the 2025 Goldich Medal Recipient Robert Michael Easton It is a great pleasure and honor to present the 2025 Goldich Medal to Dr. Robert Michael Easton, a highly respected senior scientist at the Ontario Geological Survey, in Sudbury, Ontario. Michael Easton, or ‘Mike’ as we know him, has been and is, without any doubt, among the leading and most productive geoscientists at the Geological Survey of Ontario (OGS) where he has spent much of his geological career (1982–2025). His curriculum vitae and publication list provide evidence for >600 publications and significant contributions — way too many to cite here. Even a short list of publications most relevant to the interests of the Institute and the geology of the Midcontinent Rift (MCR) spans four pages. The highlights include: • • • • a large number of peer-reviewed papers and reports; numerous extended abstracts in ILSG Proceedings volumes spanning the years from 1985 to 2023; meticulous editing of various ILSG Proceedings volumes; and the writing and editing of several comprehensive ILSG field trip guidebooks. In 2022, Mike co-lead and co-organized the 68th ILSG meeting in Sudbury, the first post-“peak COVID” meeting. We had proposed organizing this Sudbury meeting years earlier, an idea cooked up at another ILSG meeting in Terrace Bay, … but then COVID hit! It was a pleasure to organize this highly successful meeting with Mike, as one can always be 100% sure Mike will come through with everything. Although it was a joint effort, Mike took care of all the editing of both Proceedings volumes (Part I and II), and a fair bit of the local logistics. Born and raised in Ontario, Mike started his geology career with a BSc Honours degree (1976) at the University of Western Ontario, London, with a thesis titled "Geobotanical Studies in the Back River Volcanic Complex, NWT." He then moved on to the University of Hawaii, Honolulu, where he graduated (1978) with an MSc thesis on the "Stratigraphy and Petrology of the Hilina Formation: The oldest exposed lavas of Kilauea Volcano, Hawaii". In the late 1980s, I remember studying a treatise and guidebook on volcanology that was influential at the time, and this was authored by Mike Easton and his wife Monica (Easton & Easton, 1985)! Mike completed his graduate studies with a PhD from Memorial University (1982), in Newfoundland, with a thesis titled "Tectonic Significance of the Akaitcho Group, Wopmay Orogen, NWT." These studies brought him to the Slave craton of northern Canada, and its western active margin, the Paleoproterozoic Great Bear Magmatic Zone. His studies of these ancient terranes, sponsored in part by the Geological Survey of Canada, prepared him well for the complex geology of the Canadian Shield in Ontario. He then joined the OGS, where over the years he has taken on more and more senior roles but never gotten away from doing fieldwork. At the OGS, Mike has mentored and supervised numerous students and junior colleagues, including a good number of them working in areas along the northern xii �shore of Lake Superior. He has also taken on more and more editorial roles for various OGS publications, maps, and datasets. From 2002 to 2007, Mike was one of the scientific leads of the Lake Nipigon Geoscience Initiative (LNGI), and provided oversight on OGS mapping projects in the region. He was directly involved in some of the mapping, and particularly the geochronology sampling. He handled numerous publications for this large project and was a guest-editor on the final volume that published many of the LNGI results (Easton et al., 2007). Since then, Mike has been a frequent collaborator on other projects either directly or indirectly relevant to Lake Superior area geology. In the early 1990s, together with Terry Carter, Mike investigated the basement geology beneath the Paleozoic cover in SW Ontario (e.g., Easton & Carter, 1991, 1994, 1995), using geophysical data, and drill cores and cuttings, to locate the Grenville Front and the extension of the MCR in Ontario and into Michigan. Notably, they found that the Grenville Front was located some 100 km to the east of where previous interpretations had located it, and that metamorphosed equivalents of MCR rocks were likely present in the Grenville Front tectonic zone in Essex County. They were among the first to hypothesize that the final stages of MCR rifting and inversion were connected to the main tectonic phases of the Grenville orogeny. From 2002 to 2010, Mike was involved with the MCR digital data and publication collaboration between the OGS, the Minnesota Geological Survey, and the United States Geological Survey, specifically the compilation of Ontario geological, mineral deposit, geochemical, and geochronological data in GIS-compatible formats to allow incorporation into the USGS-led cross-border compilation for the Midcontinent Rift. In addition, also in 2010, he was a co-organizer and editor of four guidebooks for the 11th International Platinum Symposium (June 2010, Sudbury), a meeting that had a strong focus on the MCR, including a week-long field trip visiting deposits around Lake Superior. None of this would have ever happened without Mike’s efforts and contributions. Among his many other contributions to ILSG over the years, Mike also served (and still serves) as a board member for the Institute (2022-2025). After spending the last 53 summers doing fieldwork and research in the Grenville, the Southern Province, the Lake Superior area, or elsewhere in Ontario, Mike retired in March 2025. Given his outstanding accomplishments and amazing productivity over the years, either for the OGS or for various extra-curricular projects such as ILSG meetings, leading field trips, time-consuming editorial jobs, teaching as an adjunct professor, or supervising and mentoring many students (and never missing a beat!), it is a great honour to present Mike with the Goldich Medal Citation by: Wouter Bleeker, Senior Research Scientist, Geological Survey of Canada, Ottawa xiii �Honoring the Pioneers of Lake Superior Geology (Adopted by the Board of Directors, 2016) Preamble At the suggestion of Gene LaBerge, the 2016 executive board agreed to implement a program to recognize historic pioneers in the understanding of geology in the Lake Superior region. Beginning with the 2017 annual meeting, nominations will be accepted from the membership for geologists whose work was conducted primarily before the inception of the Institute in 1955. Biographical sketches of those pioneers will be presented at future annual meetings so that all may appreciate the value of their contributions. Selection of nominees will be decided in part by the organizing committee of each year's annual meeting, in consultation with the Board, to ensure equitable geographic representation in the selection process. Award Guidelines 1) Nominations from the membership will be submitted via the Institute web site and forwarded to the Chair of the next Annual Meeting. The nominations will be no more than half a page in length and will summarize the contribution of the nominee. 2) The Organizing Committee will select one or two individuals to be highlighted at the next Annual meeting and submit those names to the Board for approval. 3) The nominator will be requested to prepare a brief presentation to be given during the next annual meeting with a summary to be included in the Proceedings volume. 4) Unsuccessful nominations will be kept by the Secretary for two years and forwarded to the next meeting Chair; these nominations may be resubmitted at a later date. The Board will review this award every five years. Pioneers of Lake Superior Geology 2017 Douglass Houghton (1809-1845) 2018-20 not presented 2021 Newton Horace Winchell (1839-1914) 2022 Thomas Leslie Tanton (1890-1971) 2023 Thomas Benton Brooks (1836-1900) 2024 Roland Duer Irving (1847-1888) 2025 Robert Bell (1841-1917) xiv �2025 Citation for Robert Bell (1841-1917) Pioneer of Lake Superior Geology Robert Bell had a decided taste for the natural sciences, especially for geology. In 1856, at the age of 15, he secured a temporary position with the Geological Survey of Canada. He assisted Sir William Logan, the Survey’s Director, beginning an illustrious career with the GSC that would span half a century. While working summers for the Survey, Bell graduated in 1861 from McGill College and received the Governor General’s Medal. Two years later, after study at the University of Edinburgh, he joined the faculty of Queen’s College. All the while, he spent summers with the GSC and was made a permanent officer in 1869, named Assistant Director in 1877, Chief Geologist in 1890, and, finally, Acting Director in 1901. He also earned a medical degree in 1878 so that he was prepared for any mishap in the field. Bell is best-remembered for his extensive explorations in northern Quebec, Ontario, Manitoba and the eastern Arctic in the 1870s and 1880s. He mapped the rivers between Hudson Bay and Lake Superior and reconnoitred part of the route that would be adopted for the National Transcontinental Railway. In 1859, Bell assisted in mapping the north shore of Lake Huron and first visited the Lake Superior region in 1860, west of Sault Ste. Marie. His Report on the Geology of the Northwest Side of Lake Superior and of the Nipigon District was published in 1870. In 1870 and 1871, he continued to work north of Lake Superior. In 1872 and 1873, he assisted GSC Director Alfred Selwyn on a preliminary exploration westward from Lake Superior to Fort Garry (now Winnipeg). In 1876, Bell examined the eastern shore of Lake Superior, as well as the Garden River and Echo Lake areas and the northeastern shore of Georgian Bay. A reconnaissance survey was undertaken between Parry Sound and the Ottawa River. In 1881, Bell carried out additional surveys in the Hudson Bay basin and in the Lake Superior region. During 1883 and 1884, Bell continued work near Lake of the Woods. In 1887, he continued a survey, started in 1886, between the Montreal River and Lake Huron to clarify the nature of the Huronian, especially in connection with its mineral deposits. He served as a member of the Royal Commission on the Mineral Resources of Ontario from 1888 to 1889. Between 1888 and 1892, Bell mapped the Sudbury and French River areas. His 1890 paper, On Glacial Phenomena in Canada, was regarded as the most significant advance in Canadian glaciology since Logan’s first acceptance of glacial action in Canada in 1847. Bell was the first to recognize ice streaming in the Laurentide ice sheet and also noted the occurrence of diamonds in glacial drift from Ohio through Indiana, Michigan and Wisconsin, suggesting a possible provenance in Ontario. Of particular interest to the ILSG is Bell’s involvement on a Special Committee created in 1903 on the nomenclature and correlation of the Lake Superior region geology of the United States and Canada. Its findings led to the first joint report by geologists of the two countries. The Committee comprised C.R. Van Hise and C.K. Leith of the United States Geological Survey, A.O. Lane, State Geologist of Michigan; Robert Bell and Frank D. Adams of the GSC, and W.G. Miller, Provincial Geologist of Ontario. In August, 1904, the committee met in the Marquette district, and, during the six weeks following, visited the Gogebic, Mesabi, Vermilion, Rainy Lake, Lake of the Woods, Animikie, and xv �Huronian districts. As a result, both countries adopted a common stratigraphy and nomenclature that served as a basis for later iterations and our current stratigraphic framework. Bell also made field notes on flora and fauna, forests, climate, soil, indigenous people, ethnology and resources. He performed much of his field work without maps and had to do topographical surveys as he went along. It is estimated that Bell named over 3000 geographical features, prompting colleagues to call him the “Father of Canadian Place-Names”. Bell authored 32 GSC reports, 111 journal papers, 17 solo-authored geological maps, 46 other geological, topographical, and cadastral maps as senior author, and 38 maps as junior author. He gave numerous lectures to natural history, historical, and charitable societies. In 1865, at the age of 23, he was elected a fellow of the Geological Society of London. A chartermember of the Royal Society of Canada (1882), he became a fellow of the Royal Society of London in 1897. In 1903, he was made a companion of the Imperial Service Order and in 1906 was awarded both the Patron’s Medal of the Royal Geographical Society of London and the Cullum Geographical Medal of the American Geographical Society of New York. Bell retired from the GSC in 1908. His career exemplified the wide-ranging reconnaissance work performed by the government geologist in the late 19th century. He was a generalist who valued field work over more detailed, specialized study. Few could match Bell’s travels, eclectic interests, and length of service. As Ami (1927) memorialized, “Bell was especially fond of investigating and exploring regions hitherto untraversed. Pioneer work of this nature can scarcely be appreciated today, when newer and more up-to-date methods of examining a hitherto-unknown territory are employed.” Citation by: Mark Smyk (Lakehead University / Ontario Geological Survey (retired)) References Adams, F.D., Bell, R., Lane, A.C., Leith. C.K., Miller, W.G. and Van Hise, C.R. 1905. Report of International Committee on Lake Superior Geology; Journal of Geology, February-March, 1905; in Precambrian nomenclature; Ontario Bureau of Mines, Report for 1905, v.4, part 1, 1905, pp.269-277. Ami, H.M. 1927. Memorial of Robert Bell. Bulletin of the Geological Society of America, v.38, pp. 18-33; PLS. 1- https://archive.org/details/sim_geological-society-of-americabulletin_1927_38/page/n41/mode/2up?view=theater Brookes, I.A. 2016. All that glitters… The Scientific and Financial Ambitions of Robert Bell at the Geological Survey of Canada; Geoscience Canada, v. 43, pp. 147–158; http://www.dx.doi.org/10.12789/geocanj.2016.43.098. Waiser, W.A. 1998. Robert Bell. Dictionary of Canadian Biography, v. XIV (1911-1920), https://www.biographi.ca/en/bio/bell_robert_1841_1917_14E.html. xvi �In Memoriam James M. Franklin (November 9, 1942 – June 19, 2024) We note the passing, on June 19, 2024, of long-term member and former SEG President (2000) James (Jim) M. Franklin. Jim had a long and productive career in academia, government, and industry. He made landmark scientific contributions to our understanding of volcanogenic massive sulfide (VMS) deposits, black smokers and sea-floor massive sulfide (SMS) deposits, and the metallogeny of the Precambrian orogenic belts. Jim’s work with the Ontario Department of Mines in 1966 along the north shore of Lake Superior led to his PhD study of the Proterozoic geology and metallogeny of the Thunder Bay area. He was the first Professor of Economic Geology at Lakehead University (1970–1976) and was later named as a Fellow of Lakehead University in 2017 in recognition of his many contributions to that institution and to its fledgling Geology Department. He then spent more than 20 years at the Geological Survey of Canada where he led the marine minerals program and ongoing work on VMS deposits on land, such as at Sturgeon Lake. Late in his career at the GSC, he was Chief Scientist and responsible for the day-to-day scientific direction of the organization and helping to inform and educate politicians and bureaucrats on the importance of science to the economy and well-being of Canada. In 1998, after retiring from the GSC, he established Franklin Geosciences and had a highly successful career as a consultant and contributed to the discovery of mineral resources globally, while serving as a director and advisor to numerous companies and scientific organizations, including SEG. Jim was very generous with his time and provided guidance and mentorship to students and professionals alike. He received numerous recognitions for his contributions, including Fellow of the Royal Society of Canada, member of the Canadian Mining Hall of Fame, and recipient of the Logan Medal recipient the Geological Association of Canada and the R.A.F. Penrose Gold Medal from SEG. He supported ILSG as field trip leader, Proceedings editor and banquet speaker. xvii �In Memoriam Jorma “Joe” Kalliokosk (November 23, 1923 – June 3, 2024) Jorma “Joe” Kalliokoski passed away on June 3, 2024, at age 100. He was born in Harma, Finland on Nov 23, 1923. In 1931 his family moved to Sudbury, ON, and later to Timmins, ON. He graduated from Western University in London, ON, and later received his PhD from Princeton University. Joe started as a geologist with the Geological Survey of Canada and later worked for Newmont Exploration. He was hired by Princeton’s Department of Geology in 1956. In 1968, he moved to Michigan Tech as a Professor and Head of the Department of Geology and Geological Engineering, where he remained until his retirement in 1988. He was very proud of the department’s growth in research papers and in research funding during his tenure. During his long geology career, he had many travel adventures from the wilds of Canada, to remote areas of South America, and various locations in Europe. He had the ability to make new friends everywhere he went. Joe was a Fellow of SEG for a noteworthy 60 years, from 1958 to 2018. He served the Society in a number of volunteer positions, including SEG Councillor (1972–1974) and SEG President (1980). He served as Trustee of SEG Foundation, Associate Editor for Economic Geology, and Business Editor (1971–1977) and Director for the Economic Geology Publishing Company (PUBCO), the company that was established to publish the journal and later merged with SEG. Joe was also an active member and supporter of ILSG, serving as its Secretary-Treasurer and Chair of the Goldich Medal Committee. He delivered papers at ILSG on various topics, including unconformitytype Proterozoic uranium deposit potential in northern Michigan; the Jacobsville sandstone and tectonic activity; and new Precambrian geology mapping of the Upper Peninsula. He Chaired the 1972 meeting in Houghton and was awarded the Goldich Medal in 1989. xviii �In Memoriam James Alexander Grant (October 3, 1935 — October 3, 2024) James Alexander Grant died on October 3, 2024 – coincidentally also his birthday – at the age of 89. James “Jim” Grant was born in Inverness, Scotland, in 1935. After graduating from the University of Aberdeen, he left Scotland for Canada where he earned his M.S. at Queens University and then his Ph.D. at the California Institute of Technology (Caltech). After graduating from Caltech, Jim took a job in Minneapolis as a geology professor with the University of Minnesota. Jim and his family moved to Duluth in 1969 and he joined the geology department at the University of Minnesota-Duluth, where he would work with his beloved colleagues and students for the next 35 years. In the early 1970s, he helped launch UMD’s still-running geology summer field camp in Park City, Utah, bringing undergrad students out to the mountains for many years. Jim’s groundbreaking work in the 1980s on the isocon diagram is now used by geologists the world over. Over the course of his career, Jim made substantial contributions to the geology of the Lake Superior region. His seminal mapping of the Minnesota River Valley subprovince is still referenced today by the dozens who have since worked in the region. Jim taught hundreds of students over the course of his career who have gone on to contribute in many ways to the geology of the Lake Superior region. Among the most memorable experiences for his students were Jim’s metamorphic petrology trips through Michigan’s Upper Peninsula. xix �Eisenbrey Student Travel Awards The 1986 Board of Directors established the ILSG Student Travel Awards to support student participation at the annual meeting of the Institute. The name “Eisenbrey” was added to the award in 1998 to honor Edward H. Eisenbrey (1926-1985) and utilize substantial contributions made to the 1996 Institute meeting in his name. “Ned” Eisenbrey is credited with discovery of significant volcanogenic massive sulfide deposits in Wisconsin, but his scope was much broader - he has been described as having unique talents as an ore finder, geologist, and teacher. These awards are intended to help defray some of the direct travel costs of attending Institute meetings, and include a waiver of registration fees, but exclude expenses for meals, lodging, and field trip registration. The number of awards and value are determined by the annual Chair in consultation with the Secretary and Treasurer. Recipients will be announced at the end of the annual meeting. The following general criteria will be considered by the annual Chair, who is responsible for the selection: 1) The applicants must have active resident (undergraduate or graduate) student status at the time of the annual meeting of the Institute, certified by the department head. 2) Students who are the senior author on either an oral or poster paper will be given favored consideration. 3) It is desirable for two or more students to jointly request travel assistance. 4) In general, priority will be given to those in the Institute region who are farthest away from the meeting location. 5) Each travel award request shall be made in writing to the annual Chair, and should explain need, student and author status, and other significant details. Successful applicants will receive their awards during the meeting. xx �Joe Mancuso Student Research Awards The 2005 Board of Directors established the ILSG Student Research Fund with $10,000 US from the Institute’s general fund to encourage student research on the geology of the Lake Superior region. A minimum of two awards of $500 US each for research expenses (but not travel expenses) will be made each year. Students are expected to present their research orally or during a poster session at an ILSG meeting. The award winners will also be automatically eligible for the Eisenbrey Travel Awards. To allow the fund to grow, the Fund will receive one-half of any additional proceeds from each annual meeting, after all other commitments and expenses are covered. • The ILSG Board of Directors will be responsible for selecting a minimum of two awards each year. The ILSG Treasurer will issue the awards. • The ILSG Student Research Fund is available for undergraduate or graduate students working on geology in the Lake Superior region. • The applications are due to the ILSG Secretary by August 31st of each year. Awards will be made by October 1st of each year. • Names of the award recipients will be announced at the next annual meeting and posted on the ILSG website. • Details of the application process can be found on the ILSG web site. • The proposal will need to be signed by the researcher’s supervisor. The 2012 Board of Directors approved modification of the fund’s name, adding “Mancuso” to reflect the many contributions of Joseph Mancuso to the organization and sizeable donations made in his name. “Doc Joe,” as he was known by his students, taught geology for 36 years at Bowling Green State University, Ohio. He advised many graduate students in field-oriented research, and frequently brought them to Institute meetings. Joe was the 2007 Goldich Medalist. In fall 2024, the ILSG Board of Directors selected two students to be granted research funding of $500 each from the Joe Mancuso Student Research Fund. The awardees were: Zsuzsanna P. Allerton, University of Minnesota- Twin Cities Omar Khalil Droubi, University of Wisconsin - Madison xxi �Doug Duskin Student Paper Awards Each year, the Institute selects the best of student presentations and honors the presenters with a monetary award. Funding for the award is generated from registrations of the annual meeting, and from generous donations to the fund in honor of Doug Duskin—an exploration geologist and long- time friend of the Institute. The 2012 ILSG Board of Directors approved adding Doug’s name to the award to acknowledge his contributions and distribute those donations in a manner that would have pleased him. The Duskin Student Paper Committee is appointed by the Meeting Chair. Criteria for best student paper—last modified by the Board in 2001—follow: 1) The contribution must be demonstrably the work of the student. 2) The student must present the contribution in-person. 3) The Student Paper Committee shall decide how many awards to grant, and whether or not to give separate awards for poster vs. oral presentations. 4) In cases of multiple student authors, the award will be made to the senior author, or the award will be shared equally by all authors of the contribution. 5) The total amount of the awards is left to the discretion of the meeting Chair in conjunction with the Secretary, but typically is in the amount of about $500 US (increase approved by Board, 10/01). 6) The Secretary maintains, and will supply to the Committee, a form for the numerical ranking of presentations. This form was created and modified by Student Paper Committees over several years in an effort to reduce the difficulties that may arise from selection by raters of diverse background. The use of the form is not required but is left to the discretion of the Committee. 7) The names of award recipients shall be included as part of the annual Chair’s report that appears in the next volume of the Institute. Student papers will be noted on the Program. 2025 Student Paper Awards Committee Aaron Hirsch – Minnesota Geological Survey (Committee Chair) Carsyn Ames – Wisconsin Geological and Natural History Survey Paula Leier-Englehardt – HydroGeo Solutions LLC, Wisconsin Ross Salerno – United States Geological Survey Esther Stewart – Wisconsin Geological and Natural History Survey Nick Swanson-Hysell – University of Minnesota xxii �Board of Directors Amy Radakovich, Chair (2025-2028) - Minnesota Geological Survey Peter Hollings, Secretary (2019-2027) — Lakehead University Mark A. Jirsa, Treasurer (2022-2025) — Minnesota Geological Survey Mike Easton (2022-2025) — Ontario Geological Survey Carysn Ames (2023-2026) — Wisconsin Geological and Natural History Survey Theodore J. Bornhorst, (2024-2027) — Michigan Technological University Board members serve through the close of the meeting year shown in parentheses. xxiii �2025 ILSG Meeting Volunteers Angela Sipila - Mesabi Range Geological Society Henry Djerlev - Mesabi Range Geological Society Kim Berry - Mesabi Range Geological Society William Daniels - Mesabi Range Geological Society Ann Marie Prue - MN Department of Natural Resources 2025 ILSG Meeting Session Chairs Aaron Hirsch, Minnesota Geological Survey Robert Lodge, University of Wisconsin, Eau Claire Eric Nowariak, Minnesota Geological Survey Amy Radakovich, Minnesota Geological Survey Stacy Saari, Minnesota Department of Natural Resources, Lands and Minerals Allison Severson, Minnesota Geological Survey xxiv �Field Trip Leaders and Guidebook Authors Field trips have been the mainstay of the ILSG since its inception 71 years ago. We give special thanks to the field trip leaders and guidebook authors who volunteered their time and talent in carrying that tradition forward. Trip 1: Transect through the Quetico subprovince of northern Minnesota – Eric Nowariak (Minnesota Geological Survey), Mark Jirsa (Minnesota Geological Survey, retired) Trip 2: Drill Core from three Cu-Ni deposits of the Duluth Complex - Mark Severson (Natural Resources Research Institute, Teck Retired), Cullen Phillips (New Range Copper Nickel), Kevin Boerst (Twin Metals Minnesota) Trip 3: How do you make iron and/or manganese in Proterozoic Iron Formation? - Alex Steiner (Big Rock Exploration), Latisha Brengman (University of Minnesota, Duluth), Dean Peterson (Big Rock Exploration) Trip 4: New Geological Insights into the genesis of iron ores at Lake Vermillion – Soudan Underground Mine State Park - George J. Hudak (University of Minnesota, George Hudak Geosciences P.L.L.C.), Zsuzsanna P. Allerton (University of Minnesota), Annia Fayon (University of Minnesota) Trip 5: Neoarchean alkalic intrusions in the Wawa and Quetico subprovinces - Terry Boerboom (Minnesota Geological Survey, retired), Amy Radakovich (Minnesota Geological Survey) Trip 6: Unique Keweenawan inclusion (Colvin Creek) in the Duluth Complex - Mark Severson (Natural Resources Research Institute, Teck, retired), Allison Severson (Minnesota Geological Survey), Lauri Severson (Earth Science teacher, retired) Trip 7: Classic outcrops of Northeastern Minnesota - Dean M. Peterson (Big Rock Exploration), George J. Hudak (University of Minnesota, George Hudak Geosciences P.L.L.C.) Trip 8: Glacial Lake Norwood and the Koochiching Lobe - Phillip Larson (Vesterheim Geoscience PLC), Andrew Breckinridge (University of Wisconsin-Superior), Howard Mooers (University of Minnesota, Duluth) xxv �Mine to Mountain Bike Mecca: The story of the Redhead Mountain Bike Park Pete Kero PE, Senior Environmental Engineer Barr Engineering Co. Pete Kero, PE, is an environmental engineer and Vice President with Barr Engineering Co. He has over 30 years of experience in mine permitting, water management, reclamation, and repurposing across the United States. He was the visionary behind the award-winning Redhead Mountain Bike Park in Chisholm, Minnesota which repurposed several former iron mine pits and stockpiles into a destination-quality regional park for mountain biking, hiking, water recreation and all-terrain vehicles. The project has been featured by Outside Magazine, the Sierra Club and the nation-wide documentary film Biketown. Pete’s book Minescapes: Reclaiming Minnesota’s Mined Lands, which was published by the Minnesota Historical Society Press, won a 2024 Minnesota Book Award. This talk will describe the transformation of ten idled open pit iron ore mines in northeastern Minnesota into a world-class recreation destination for mountain biking, hiking and paddling. In addition to describing how and why the trails were built, the presentation will include technical details on sustainable trail design, the concept of intermediate recreational use, changes to mine pit fencing laws that allow for government-sanctioned recreational use of mine lands and the early results and benefits from the first 5 years of the park’s operation. xxvi �Report of the Chairs of the 70th Annual Meeting Theodore J. Bornhorst, Erika C. Vye and Patrice F. Cobin Houghton, Michigan The 70th Institute on Lake Superior Geology (ILSG) was held May 15 to 18, 2024 in Houghton, Michigan, with the meeting headquartered at the Memorial Union Building on the campus of Michigan Technological University. The meeting was sponsored by the A. E. Seaman Mineral Museum, the Great Lakes Research Center, and the Department of Geological and Mining Engineering and Sciences - all units of Michigan Technological University. The meeting was co-chaired by Ted Bornhorst (principal cochair), Erika Vye, Patrice Cobin, and Jim DeGraff; all co-chairs are affiliated with Michigan Technological University. In addition to being a co-chair Patrice Cobin and Julie Stark served as registrars for the 70th annual meeting. The institute was attended by a total of 182 participants of which 40 were students. The meeting consisted of two full days of technical sessions from Thursday morning 16th of May through Friday afternoon 17th of May, and two days for field trips, pre-and post-meeting. A total of 57 presentations were subdivided into 8 technical sessions; 6 technical sessions for 30 oral presentations (of which 5 were presented by students), and 2 poster technical sessions with a total of 27 poster presentations (of which 16 were presented by students). Three presentations were withdrawn. Since past meetings have not included a dedicated technical session for poster presentations, the chairs opted to include two poster sessions for the 70th meeting. We believe this facilitated more time for attendees to review the posters and facilitated interaction between the authors of posters and attendees. The technical sessions of the 70th annual meeting of ILSG were published in 2024 as Part 1 of Proceedings Volume 70 (111 pages). As is customary with ILSG meetings, the field trips were a highlight of the 70th ILSG. The meeting offered 7 field trips with 3 pre-meeting on Wednesday May 15, and 4 post-meeting trips on Saturday May 18. Overall, the field trips were well attended. There were 145 registrants for the 5 field trips that were able to be run. Demand for 4 of the trips exceeded capacity resulting in wait lists. Pre-meeting trip 1 was led by Ted Bornhorst (Michigan Tech) and focused on Mesoproterozoic “Midcontinent Rift-filling Strata and Native Copper Deposits of the Keweenaw Peninsula, Michigan.” Pre-meeting trip 2 was led by Tom Wright (Quincy Mine Hoist Association) and Jim DeGraff and Katherine Langfield (Michigan Tech) and focused on the “Mining History and Geology of the Quincy Mine, Keweenaw Peninsula Native Copper District, Michigan.” Pre-meeting trip 3 focusing on “Geoheritage of Buffalo Reef: Industrial Impact on Land, Culture, and Fish Sovereignty” was scheduled to be led by Erika Vye, Charlie Kerfoot (Michigan Tech), Stephanie Swart (Michigan Department of Environmental Quality), and Dione Price and Evelyn Ravindran (Keweenaw Bay Indian Community). However, the trip could not be run because of low water levels and shifting sediment impeding access to the harbor. xxvii �Post-meeting trip 4 was led by Jim DeGraff, Katherine Langfield, and Dan Lizzadro-McPherson (Michigan Tech) and focused on “Keweenaw Fault Geometry and Kinematics: Clues to Its Nature and Origin.” Post-meeting trip 5 was led by Matt Portfleet (Adventure Mining Company) and Ted Bornhorst (Michigan Tech) and focused on the “Adventure Mine, Ontonagon County, Michigan: Geology and History of a Native Copper Mine.” Post-meeting trip 6 led by Chad Deering (Michigan Tech) ventured outside of the Keweenaw rift to investigate “Southern Complex Granitoids, Gneisses, and Migmatites: New Data, Discoveries, and Perspectives.” Field trip 7 led by Stan Vitton and Mohammad Sadeghi (Michigan Technological University) was scheduled to investigate “Landslides in the Glacial Lake Ontonagon Sediments,” but had to be cancelled due to lack of registrations. Field trip guides were published in 2024 as Part 2 of the Proceedings Volume 70 (194 pages). Five Doug Duskin Best Student Paper Awards were given for student oral and poster presentations as judged by the 2024 Student Paper Awards Committee chaired by Stacy Saari (Minnesota Department of Natural Resources). Zsusanna Allerton was awarded the best oral presentation. The best graduate student poster presentation was awarded to Yirou Xu. The best undergraduate student poster presentation was awarded to Lyndsie Vickers. Alice Martin and Alexander Lawrence were awarded the runner-up for graduate student poster and for undergraduate student poster respectively. The 70th ILSG awarded 14 Student Travel and Participation Awards to help defray the cost of presentations of their research and participation in the ILSG professional meeting. The eligibility of costs, as designated by the Eisenbrey Award, were expanded for the 70th ILSG Student Travel and Participation Awards. We thank the donors for supporting the student awards. The awards were made possible by the generous financial support from our corporate sponsor Eagle Mine – Lundin Mining, the Geological Society of Minnesota, and 23 individual donors. The awardees were Zsuzsanna Allerton, Farhan Ahmed Bhuiyan, Andrea Paola Corredor Bravo, Kevin Mexia Duran, Trent Ediger, Alex Lawrence, Jordan Peterzon, Lucas Robarg, Daniel Shakked, Vlad Sheshnev, Demily Thibodeau-Bello, Adam Vanderkin, Lyndsie Vickers, and Yiruo Xu. There were 6 Michigan Tech students whose registration fees were waived because they volunteered with logistics for the meeting. The ILSG social and banquet was hosted at the Memorial Union Building on Thursday evening May 15. There were 120 people at the annual banquet. Ted Bornhorst served as master of ceremonies for the postbanquet program. After the introductions, Peter Hinz gave a short presentation about a geological excursion to Hawaii. Amy Radovich announced the location of the 2025 meeting as Mountain Iron. The program continued with ILSG awarding the prestigious Goldich Medal to Suzanne W. Nicholson (recently retired from the U.S. Geological Survey). Laurel Woodruff (U.S. Geological Survey and Goldich Medalist in 2014) provided the citation for Suzanne. The co-chairs and the A. E. Seaman Mineral Museum recognized Ted Bornhorst with a plaque for his distinguished service to ILSG. A highlight of the banquet was the keynote presentation by Robert Hazen (Carnegie Institution for Science), an internationally recognized and distinguished mineralogist. His thought-provoking presentation was on “Mineral Informatics: A New Frontier in Understanding Earth.” The keynote presentation ended the banquet program. Hazen’s presentation was made possible by joint funding between the 70th ILSG and the A. E. Seaman Mineral Museum of Michigan Tech. Hazen gave a second presentation on Friday evening for the general public and as a bonus for ILSG participants. This presentation was the A. E. xxviii �Seaman Mineral Museum’s 2024 Edith D. and E. Wm Heinrich Lecture titled “Mineral Evolution: A case study of a new natural law.” The first presentation of the technical sessions was given by Jim Miller (Goldich Medalist in 2012) who gave the citation for Roland Duer Irving as the 2024 Pioneer of Lake Superior Geology. Irving is the 5th person to be recognized for their contributions to Lake Superior Geology prior to the initiation of the ILSG. The Institute’s Board of Directors met on Thursday May 16, 2024 to discuss ILSG business and approve the 2025 meeting location. The meeting was attended by Ted Bornhorst (Board Chair), Carysn Ames, Mark Smyk, Peter Hollings (Secretary), and Mark Jirsa (Treasurer). Guests at the meeting were the meeting co-chairs Patrice Cobin, Erika Vye, and Jim DeGraff, and Amy Radakovich (Assistant Treasurer) and also the Chair of the proposed 2025 Mountain Iron meeting (approved by the board see below). Stacy Saari, Alli Severson, Eric Nowariak, and Aaron Hirsch were additional guests supporting the proposed Mountain Iron 71st ILSG. Institute’s Board of Directors meeting notes were taken by ILSG Secretary Hollings, which are as follows: Accepted report of the Chairs for the 69th ILSG, as published in the Proceedings volume, and minutes of last Board meeting, May, 2023 (Hollings). 2. Received, discussed, and accepted 2023-2024 ILSG Financial Summary (Jirsa). 3. Received, discussed, and accepted 2023-2024 report of the Secretary (Hollings). 4. Approved Ted Bornhorst as on-going ILSG Board member and Amy Radakovich as Chair. 5. Discussed and approved replacing Dorothy Campbell as the “member from government” on Goldich Committee (end of term 2024) with Robert Cundari. 6. Approved Mt Iron as the site for the 71st annual ILSG meeting. The meeting will be Chaired by Amy Radakovich and hosted by the Minnesota Geological Survey. 7. A number of future meeting locations were discussed. Peter Hinz has offered Kenora as a future site, while Mark Puumala has offered Thunder Bay. 8. The confusion over the appointment of the Board Chair was discussed and it was agreed we would follow the Constitution with the incoming Meeting Chair assuming the role of Board Chair. 9. It was agreed that the purchase of additional safety equipment would be postponed for now. 10. The Secretary agreed to revamp the boilerplate material for the volumes to make it easier for the organisers of subsequent meetings. Carsyn agreed to revamp the Eisenbrey and Mancuso award applications. Bornhorst agreed to rewrite the Eisenbrey award document for Board consideration. The allowable expenses will be broadened so the award will be more than travel. 11. Discussed and approved renewal of Pete Hollings as Institute Secretary (end of term 2027). This was later approved by a vote of the membership. 12. Hollings mentioned that the ILSG proceeding volumes standing order sales remain the same as the recent past with only 5 institutions receiving them plus one sent to GeoRef. 1. xxix �13. The co-Chairs would like to thank all those who helped make the 70th annual meeting a success such as judging student papers, chairing sessions, leading field trips, driving for field trips, staffing the registration desk, caring for the projectors, general logistics and more. A special thank you goes to Julie Stark, who played a key role in online and onsite registration. The 70th ILSG was a milestone for a professional organization, as noted by Pete Hollings in a recently published article on ILSG in the Lake Superior Magazine - “not a lot of groups hang around 70 years.” Forty years ago, Ted Bornhorst chaired the annual meeting and Board of Directors. At this time the board had serious concerns about the survival of the organization. We are happy to report that ILSG continues to thrive and has done so by being a small, but vibrant organization. We believe that the combination of collegial, friendly, and open discussion and exchange of ideas on geology of the Lake Superior region between government, industry, and academic geologists has played a major role in ILSG’s survival for 70 years. We strongly believe that field relations are the foundation of geologic interpretation. The depth, breadth, and quality of ILSG field trips is another reason ILSG continues to thrive. What makes ILSG field trips special is that trip leaders are open to debate on their interpretation of an outcrop. Open - but not competitive - discussion is a hallmark of both ILSG field trips and technical sessions. Lastly, meetings would not be possible without people willing to serve as chair or co-chair and people willing to organize the annual conference, to lead field trips, and to serve on local committees. Chairing an ILSG meeting involves personal time, extra work, and a bit of extra stress as attested to by anyone who has risen to this challenge in past years. One of us (Bornhorst) has been principal chair for 6 meetings over 41 years, from 1983 to 2024. He agreed to be Chair one last time to mentor Erika and Patty with the hope that one day, one or both of them, will chair a future annual meeting, contributing to the continuation of ILSG. We hope that ISLG survives for many decades and into the next century and beyond. We are gratified by the positive comments by participants and are happy to have served the Lake Superior geological community. We look forward to the 2025 Mountain Iron ILSG meeting when we can be much more relaxed! Respectfully submitted, Theodore (Ted) Bornhorst, Erika Vye, and Patrice (Patty) Cobin Co-chairs, 70th Institute on Lake Superior Geology xxx �Donations to Support the Annual Meeting of the Institute on Lake Superior Geology A special thank you to our individual contributors Roger Anderson Allan MacTavish Dave Dahl xxxi �Donations to Support Student Participation at the Annual Meeting of the Institute on Lake Superior Geology A special thank you to our individual contributors Kate Clover Jim and Isagel DeGraff Tom Erickson Tom Fitz Aaron Hirsch Paula Leier-Engelhardt Bob Mahin Vince and Susan Mathews Jim Miller Allison Severson Mark and Lauri Severson John Verhoeven Gerry White xxxii �TECHNICAL PROGRAM xxxiii �Wednesday May 14, 2025 All field trips begin and end at the Mountain Iron Community Center Pre-meeting Field Trips May 14, 2024 8:00 am - 5:00 pm PRE-MEETING FIELD TRIPS Trip 1: Transect through the Quetico subprovince of northern Minnesota – Eric Nowariak (Minnesota Geological Survey), Mark Jirsa (Minnesota Geological Survey, retired) Trip 2: Drill Core from three Cu-Ni deposits of the Duluth Complex - Mark Severson (Natural Resources Research Institute, Teck Retired), Cullen Phillips (New Range Copper Nickel), Kevin Boerst (Twin Metals Minnesota) Trip 3: How do you make iron and/or manganese in Proterozoic Iron Formation? - Alex Steiner (Big Rock Exploration), Latisha Brengman (University of Minnesota, Duluth), Dean Peterson (Big Rock Exploration) Trip 4: New Geological Insights into the genesis of iron ores at Lake Vermillion – Soudan Underground Mine State Park - George J. Hudak (University of Minnesota, George Hudak Geosciences P.L.L.C.), Zsuzsanna P. Allerton (University of Minnesota), Annia Fayon (University of Minnesota) Wednesday evening May 14, 2025 5:00 pm - 8:00 pm Registration (Mountain Iron Community Center) 6:00 pm - 8:00 pm Poster Setup and Viewing (Mountain Iron Community Center) 6:00 pm - 8:00 pm Welcoming Reception (Mountain Iron Community Center) * Denotes a student eligible for Best Student Paper Award. To be eligible students must have graduated no more than one month before the ILSG meeting, be first author, and present the paper at the meeting + Denotes author that will present the paper if different than the first author. Thursday - May 15, 2025 7:15 am – 12:00 pm 8:00 am. Registration (Mountain Iron Community Center) Opening remarks (Mountain Iron Community Center) Amy Radakovich, Allison Severson, Eric Nowariak, Stacy Saari, Aaron C. Hirsch Co-Chairs, 2025 ILSG xxxiv �TECHNICAL SESSION I – ORAL PRESENTATIONS Session Chair: Amy Radakovich 8:20 Mark SMYK Robert Bell - Pioneer of Lake Superior geology 8:40 William J. HINZE and Mark B. LONGACRE Revisiting Gravity and Magnetic Anomalies of the Baraboo Range 9:00 Huifang XU and Tianyu ZHOU Battle between the bands: competitive precipitations lead to bands in banded iron formations 9:20 Howard MOOERS, Mark SEVERSON, Peter JONGEWAARD, and Phillip LARSON US Steel Corporation / Ralph W. Marsden iron ore collection 9:40 Matt CARTER Updates on the Minnesota Department of Natural Resource’s Drill Core Library 10:00 END OF TECHNICAL SESSION I 10:00-10:20 COFFEE BREAK TECHNICAL SESSION II – ORAL PRESENTATIONS Session Chair: Stacy Saari 10:20 Alan AUBUT A Contrarian View: Thoughts on the Genesis of the Tamarack Ni-Cu Deposit 10:40Cory PALIEWICZ and Joyashish THAKURTA Lithogeochemical Characterization of Manganese Mineralization at the Cuyuna Range, Central Minnesota 11:00 Guy N. EVANS and William E. SEYFRIED JR. Experimental Reproduction of Acidic Mafic-Ultramafic Hydrothermal Fluids with Implications for Linking Seafloor Lithology to Ore Mineral Solubility and Novel Geochemical Trapping Mechanisms 11:20 Wyatt BAIN, James TOLLEY, and Peter HOLLINGS An overview of the geology, tectonic setting, and occurrence of sulphide mineralization in the Lac Des Iles Intrusive Suite 11:40 Thomas BUCHHOLZ, Alexander FALSTER, and William SIMMONS A complex F-rich alkalic pegmatite in the pyroxene syenites of the stettin complex, Wausau Complex, Marathon county, Wisconsin 12:00 END OF TECHNICAL SESSION II xxxv �12:00-1:30 LUNCH BREAK and ILSG BOARD OF DIRECTORS MEETING - Buffet lunch provided- TECHNICAL SESSION III- POSTER PRESENTATIONS Session Chair: Robert Lodge 1:30-3:00 AUTHORS PRESENT AT THEIR POSTERS 2:40-3:00 COFFEE BREAK 3:00 END OF TECHNICAL SESSION III TECHNICAL SESSION IV – ORAL PRESENTATIONS Session Chair: Allison Severson 3:00 James V. JONES, Ross SALERNO, William F. CANNON, and Pau O’SULLIVAN Geologic implications of detrital zircon U-Pb ages from Archean and Paleoproterozoic strata in central Minnesota and the Gogebic Range of Wisconsin and Michigan, USA 3:20 R. SALERNO, W.F. CANNON, A. SOUDERS, J.M. THOMPSON, and J. VERVOORT Constraining the timing of crustal exhumation following the Penokean orogeny using U-Pb, SmNd, and Lu-Hf geochronology and microstructural analysis 3:40 James DeGRAFF, Chad DEERING, and James JONES III The Archean Carney Lake gneiss complex in Michigan’s Upper Peninsula: Preliminary subdivisions with age constraints 4:00 *Omar Khalil DROUBI, Erik SCHOONOVER, Mona-Liza SIRBESCU, Joshua GARBER, and Chlo BONAMICI Geochronology of lithium mineralization in the Florence pegmatite field, WI, USA 4:20 END OF TECHNICAL SESSION IV xxxvi �Thursday evening May 15, 2024 5:30 pm RECEPTION AND CASH BAR (Mountain Iron Convention Center) 6:30 pm ANNUAL BANQUET (Mountain Iron Convention Center) 2025 Goldich Medal Recipient: Robert Michael Easton Banquet Speaker: Pete Kero, Mine to Mountain Bike Mecca: The story of the Redhead Mountain Bike Park Friday - May 16, 2025 8:15 INTRODUCTORY REMARKS AND UPDATES (Mountain Iron Community Center) Amy Radakovich, Allison Severson, Eric Nowariak, Stacy Saari, Aaron C. Hirsch; Co-Chairs, 2025 ILSG TECHNICAL SESSION V – ORAL PRESENTATIONS Session Chair: Aaron Hirsch 8:20 Wouter BLEEKER, Michael HAMILTON, and Sandra KAMO Paleoproterozoic mantle plume tracks shaping the southern margin of the Superior craton and the geology of the Lake Superior region 8:40 Max ROHRMAN Plume control on the initiation of Mid-Continent Rift breakup using Unconformities: Implications for the Tectono-magmatic evolution and mineral deposits 9:00 James TOLLEY, Pete HOLLINGS, Kevin MEXIA DURAN, and Myles HARDING Evaluating Ni in Olivine as a Prospectivity Indicator for Magmatic Ni-Cu-(PGE) Deposits: A Preliminary Study from the Midcontinent Rift System. 9:20 James TOLLEY, Jacob HANLEY, James CROWLEY, Sasha TSAY, Zoltan ZAJACZ, and Pete HOLLINGS A Porphyry in a Rift? Constraining the Petrogenesis of the Jogran Porphyry, Mamainse Point, Ontario, Canada: Insights from Zircon and Melt Inclusion Geochemistry 9:40 Nicholas SWANSON-HYSELL, Eben B. HODGIN, Tadesse ALEMU, Anthony FUENTES, Yiming ZHANG, Sarah SLOTZNICK, and Luke FAIRCHILD Midcontinent Rift extension ceased and the rift inverted due to the Grenvillian orogeny 10:00 END OF TECHNICAL SESSION V xxxvii �10:00-10:20 COFFEE BREAK – Sponsored by MRGS TECHNICAL SESSION VI – POSTER PRESENTATIONS Session Chair: Robert Lodge 10:00-11:30 AUTHORS PRESENT AT THEIR POSTERS 11:30 END OF TECHNICAL SESSION VI 11:30-1:00 LUNCH BREAK - Buffet lunch provided- TECHNICAL SESSION VII – ORAL PRESENTATIONS Session Chair: Eric Nowariak 1:00 Steven D.J. BAUMANN Pembine-Wausau Terrane as an Icelandic style island overthrust onto Archean basement, instead of an island arc or continental fragment accretion 1:20 Jiří1 ŽÁK, Filip TOMEK, Václav KACHLÍK, František VACEK, Martin SVOJTKA, and Lukáš ACKERMAN Broadly coeval but migrating deformation, plutonism and deposition in the northeastern Superior Province, Québec: evidence of hot accretionary orogeny and oroclinal folding in the late Archean? 1:40 Mark SMYK, Pete HOLLINGS, Riku METSARANTA, Robert CUNDARI, Stephen KISSIN, and Colleen KURCINKA Basaltic rocks of the Animikie Group in Ontario: Geochemical characteristics and tectonic significance 2:00 W. F. CANNON, M. Rebecca STOKES, Ross A. SALERNO Micromineralogy and textures in the Sudbury impact layer on the Mesabi Iron Range, Minnesota: record of processes in the proximal-distal ejecta transition zone 2:20 END OF TECHNICAL SESSION VII 2:20 COFFEE BREAK xxxviii �TECHNICAL SESSION VIII – ORAL PRESENTATIONS Session Chair: Amy Radakovich 2:40 J.D. VERHOEVEN and Tim ZOWADA Origin of magnetic black sand found on the south Shore of Lake Superior 3:00 Erika VYE and Daniel LIZZADRO-MCPHERSON Geospatial Learning Resources to Explore Relationships with Keweenaw Geology 3:20 Allan MACTAVISH, Peter HINZ, +George HUDAK, Phil LARSON, Allan AUBUT, Terry BOERBOOM, Vern CHILTON, Jim DeGRAFF, Tom ERICKSON, Barb FAULKNER, Isabel SERRANO, Larry and ZANKO An informal review of the ILSG field trip to Hawaii: January and February 2025 4:00 END OF TECHNICAL SESSION VIII 4:00 Presentation of Student Awards Best Student Paper Awards – Student award committee Student Travel/Participation Awards – Amy Radakovich MRGS Awards – Mark Severson 4:30 Concluding Remarks and Field Trips Amy Radakovich, Allison Severson, Eric Nowariak, Stacy Saari, Aaron C. Hirsch; Co-Chairs, 2025 ILSG END OF TECHNICAL SESSIONS OF THE 71st ANNUAL MEETING xxxix �Saturday May 17, 2025 Field trips begin and end at the Mountain Iron Community Center 8:00 am – 5:00 pm POST-MEETING FIELD TRIPS Trip 5: Neoarchean alkalic intrusions in the Wawa and Quetico subprovinces Terry Boerboom (Minnesota Geological Survey, retired); Amy Radakovich (Minnesota Geological Survey) Trip 6: Unique Keweenawan inclusion (Colvin Creek) in the Duluth Complex Mark Severson (Natural Resources Research Institute, Teck, retired); Allison Severson (Minnesota Geological Survey); Lauri Severson (Earth Science teacher, retired) Trip 7: Classic outcrops of Northeastern Minnesota Dean M. Peterson (Big Rock Exploration); George J. Hudak (University of Minnesota, George Hudak Geosciences P.L.L.C.) Trip 8: Glacial Lake Norwood and the Koochiching Lobe Phillip Larson (Vesterheim Geoscience PLC); Andrew Breckinridge (University of Wisconsin-Superior); Howard Mooers (University of Minnesota, Duluth) xl �POSTER PRESENTATIONS * Denotes a student eligible for Best Student Paper Award. To be eligible students must have graduated no more than one month before the ILSG meeting, be first author, and present the paper at the meeting + Denotes author that will present the paper if different than the first author. Numbered Posters and Abstracts are in sequential order 1. *Zsuzsanna ALLERTON, George HUDAK, Guy EVANS, Xinyuan ZHENG, and Christian TEYSSIER Geochemical analyses of banded iron formations and formerly mined iron ore in the Lake Vermilion-Soudan Underground Mine State Park, NE Minnesota 2. *Madelyn BANKS, Latisha BRENGMAN, Athena EYSTER Linking whole rock geochemical data with micro-scale mineral characterization of oxidation reactions in the Biwabik Iron Formation, MN, USA 3. Howard MOOERS, Mark SEVERSON, Peter JONGEWAARD, and Phillip LARSON US Steel Corporation / Ralph W. Marsden iron ore collection 4. *Sarah JAROZEWSKI, Paige DUFFY, Cole BARRÉ, Latisha BRENGMAN, and Athena EYSTER Mapping oxidation reactions in iron-rich rocks from northeast Minnesota, USA. 5. *Celia L. CORTOPASSI, Zsuzsanna P. ALLERTON, Joshua M. FEINBERG Alteration of magnetic mineralogy in the Giants Range Batholith by the Duluth Complex 6. *Samara GRIES, Robert W.D. LODGE, Sara HANEL, and Robert HOOPER Rare-element Geochemistry of the Eau Claire River Complex Pegmatites 7. *Linsey HULA and Dyanna CZECK Emplacement of the Mesoproterozoic Wausau Syenite Complex, Wisconsin 8. *Renee O. JEUTTER and Robert W.D. LODGE Geology and Geochemistry of the Mesoproterozoic Round Lake Intrusion and associated TiMineralization, Northern Wisconsin 9. *Bekah R. THOMPSON and Robert W.D. LODGE Ni-Cu-PGE Mineralization at the Mineral Lake Intrusive Complex, northern Wisconsin 10. *Lyndsie A. VICKERS and Robert W.D. LODGE Zircon Petrochronology of the Eau Claire Volcanic Complex in the Marshfield Terrane of the Penokean Orogen, Northcentral Wisconsin 11. *Andrew A. CASPER and Robert W.D. LODGE R Geology and Mineralization of the Plover Au Prospect, Marathon County, Wisconsin xli �12. William FITZPATRICK Textural and chemical analysis of sphalerite ores from the Highland Subdistrict, Upper Mississippi Valley Zinc-Lead District, Wisconsin 13. *Haley P. JOHANNESEN and Robert W.D. LODGE Geology and Geochemistry of the Ritche Creek Cu-Zn deposit, North central Wisconsin 14. *Aidan O. KWIATKOWSKI and Robert W.D. LODGE Zircon Petrochronology of Wisconsin’s Volcanogenic Massive Sulfide Deposits, Northcentral Wisconsin 15. Sara PEARSON, Nolan GAMET, Molly SHALIFOE, Ashley QUIGLEY, and Robert MAHIN Michigan Geological Survey’s Contributions to the USGS Earth MRI National Mine Waste Inventory Effort 16. Ashley K. QUIGLEY, Robert A. MAHIN, and Nolan G. GAMET Critical Mineral Potential of the Northern Margin of the Watersmeet Gneiss Dome, MI USA 17. *MaryElizabeth SHALIFOE and Peter VOICE Identifying Abandoned Mine Surficial Features Using Mask R-CNN, Upper Peninsula Michigan. 18. Sophie CHURCHLEY and Philip FRALICK Unusual early diagenetic structures in the Paleoproterozoic Gunflint Formation, Ontario, Canada 19. Gordon MEDARIS Jr. and Dave MALONE Post-Penokean and Pre-Yavapai Magmatism and Sedimentation in Central Wisconsin (Southern Lake Superior Region) 20. Esther K. STEWART, Michael TAPPA, Ann BAUER, Latisha BRENGMAN, and Anthony PRAVE Sedimentologic and geochemical evidence of marine incursion to the Oronto Group basin, southern Lake Superior region, at ca. 1.08 Ga 21. Carsyn AMES and Brad GOTTSCHALK High resolution thin-section scanning and metadata capture- WGNHS Data Preservation Project 2024 early efforts 22. Nate DANIELS, Grace MCELLISTREM, Raeann VOGEL, and Michael BRAUNAGEL Architecture of the Douglas Fault damage zone, northwest Wisconsin 23. Mark B. LONGACRE and William J. HINZE, William Geologic Interpretation of Filtered Gravity and Magnetic Anomalies of the Baraboo Range 24. Jack MALONE, David MALONE, Raymond ANDERSON, Ryan CLARK Refining the Age and Occurrence of Basement Rocks in Northwest Iowa: Implications for Precambrian Tectonics and Magmatic Evolution of the Laurentian Midcontinent xlii �ABSTRACTS xliii �Geochemical analyses of banded iron formations and formerly mined iron ore in the Lake Vermilion-Soudan Underground Mine State Park, NE Minnesota ALLERTON, Zsuzsanna1, HUDAK, George1,2,3, EVANS, Guy1, ZHENG, Xinyuan1, and TEYSSIER, Christian1 1 Earth & Environmental Sciences, University of Minnesota, Minneapolis, MN 55455, USA Earth and Environmental Sciences, University of Minnesota, Duluth, MN 55812, USA 3 George Hudak Geosciences P.L.L.C., Duluth, MN 55804, USA 2 The Lake Vermilion-Soudan Underground Mine State Park in northeastern Minnesota is known for its underground tours in the former iron mine that was operational between 1884-1962 (Klinger, 1960). The mine contains lenticular-shaped ore bodies enclosed in variably altered banded iron formations (BIFs) that were upgraded to massive hematite iron ore during replacement-style hydrothermal alteration (Gruner, 1926; Klinger, 1960; Thompson, 2015). The timing of ore mineralization is constrained to 1.8-1.6 Ga (Allerton, 2024b). The widely accepted simplified genetic model for these ore deposits involves hydrothermal fluids that leached silica from BIFs and concentrated iron as hematite. Here we utilize historic and recently acquired whole rock major, trace and rare earth element lithogeochemical analyses to perform mass balance evaluations via the isocon method (Grant, 2005) and iron stable isotope geochemistry to propose a new hydrothermal model to better constrain the transition from BIF to iron ore. Eight BIF and twelve ore samples from Thompson (2015) were utilized for this study. BIFs show varying degrees of alteration adjacent to the orebodies, whereas iron ore samples comprise massive hematite ± chlorite. Our data include eight additional samples; four least altered and two hematite-altered BIFs collected from surface outcrops, and two iron ore samples that are 1) high-grade hematite ore with primary phase microcrystalline hematite-martite (MCHMT) with minimal chlorite and 2) lower grade ore with abundant secondary quartz and microplaty hematite (MPH; Allerton, 2024b). The Fe isotope analysis incorporates variably deformed gabbroic rocks and chlorite schist adjacent to the ore bodies as well. Lithogeochemical analyses of 14 BIFs and 14 iron ore samples indicate inverse correlation between SiO2 and Fe2O3(total); BIF has high SiO2 and low Fe2O3(total) contents, whereas iron ore displays low in SiO2 and Fe2O3(total). Statistical evaluations suggest that high strength field elements (HFSE) are immobile and therefore have been selected for isocon analysis. Utilizing a HFSE ‘best fit’ isocon, the system shows almost complete SiO2-loss (99%) and 54% Fe2O3-loss from least altered BIF to high-grade ore (Fig. 1A), suggesting that greater loss of silica relative to iron has resulted in a net concentration of iron. Moreover, there is secondary quartz and MPH in the lower grade ore based on petrography, indicating the lower-grade ore postdates the high-grade ore. Isocon analysis shows SiO2-gain and continued Fe3O2-loss from high-grade to lower grade ore (Fig. 1B). The Fe stable isotope results attest to this by presenting higher δ56Fe values for BIFs that decrease from less to more altered BIF. MCH-MT in highgrade ore displays even lower δ56Fe values, and chlorite within fractures of high-grade ore shows similar values to secondary quartz and MPH in heterogeneous ore, suggestive of paragenesis of two different hematite phases and gangue minerals (Fig. 2). Our new hydrothermal model proposes continuous removal of Fe, entailing coeval Si mobilization and removal from BIF to high-grade MCH-MT ore and re-deposition into lower grade MPH ore. These hypotheses are supported by detailed analyses of lithogeochemistry, mineral textures, and Fe stable isotopes. 1 �Figure 1: A) Diagram displays major oxides of least altered BIF (x-axis) against MCH-MT ore (yaxis) and B) MCTMT ore (x-axis) against MPH ore (y-axis). Ratios show gains and losses are calculated based on the slope of HFSE best fit isocons. Figure 2: Diagram shows decreasing δ57Fe/ δ56Fe values of less and more BIFs, MCH-MT and MPH ore samples, and lithologies adjacent to the ore bodies in Soudan; foliated gabbro, gabbroderived schist, chlorite schist. Values are calibrated to BHVO-2 iron standard commonly used in Fe stable isotope geochemistry. REFERENCES Allerton, Z., Hudak, G., Teyssier, C., Fayon, A., Daniŝik, M., Courtney-Davies, L, and Larson, P., 2024b. Geochronology and geochemistry of hematite ore in northeastern Minnesota: Institute on Lake Superior Geology, Proceedings Volume 70, Part 1 – Program and Abstracts, p. 4-5. Grant, J.A., 2005. Isocon analysis: A brief review of the method and applications: Physics and Chemistry of the Earth, Parts A/B/C, v. 30, p. 997–1004, doi: 10.1016/j.pce.2004.11.003. Gruner, J. W., 1926. Hydrothermal alteration of iron ores of the Lake Superior type—a modified theory: Economic Geology, v. 32, p.121-130. Klinger, F.L., 1960. Geology and ore deposits of the Soudan mine, St. Louis County, Minnesota [thesis]. Thompson, A., 2015. A hydrothermal model for metasomatism of Neoarchean Algoma-Type banded iron formation to massive hematite ore at the Soudan Mine, NE Minnesota [thesis]. 2 �High resolution thin-section scanning and metadata capture- WGNHS Data Preservation Project 2024 early efforts AMES, Carsyn1 and GOTTSCHALK, Brad1 1 Wisconsin Geological and Natural History Survey, UW-Madison, 3817 Mineral Point Rd, Madison, WI 53704 USA The Wisconsin Geological and Natural History Survey (WGNHS) has recently undertaken an effort to scan approximately 3800 of the 4800 historical thin sections held in WGNHS collections as part of the USGS-National Geological and Geophysical Data Preservation Program (NGGDPP). This work builds upon a number of previous projects including: a 2011 NGGDPP project to inventory all thin sections in the WGNHS collections, an internal project to catalog fields notebooks and refine locations of recorded samples, a pilot study to develop a workflow for scanning and editing high resolution photos of thin sections, and a project to inventory and collect metadata from an extensive collection of samples donated to WGNHS by Gene LaBerge (UW-Oshkosh). Building on the lessons learned from these prior studies and methods outlined in Leung and Mcdonald (2023), we have developed a workflow to scan thin sections using a Plustek OpticFilm 8200i film scanner (Figures 1a and 1c) and SilverFastSE Plus software with settings shown in Figure 1b. Forty-eight-bit raw images are produced in both plane, non-polarized light and cross-polarized light (Figure 2). Images are edited post scanning in Adobe Lightroom to enhance the sharpness and exposure to better replicate what users see when viewing thin sections with a petrographic microscope. Scanning and editing images takes approximately 10 minutes per thin section. Photos are stored in TIFF format and are intended to be served on the WGNHS Dataviewer for public access. Thin sections included in this project capture a wide range of lithologies from several Wisconsin counties. Many samples represent some of the first efforts to survey the natural resources and map the geology of northern Wisconsin. The original data associated with the thin sections is archived in historic field notebooks archived at the WGNHS and includes documentation of geomorphology, bedrock and glacial geology, and magnetic susceptibilities of encountered bedrock units. Locations are recorded in Public Land Survey System (PLSS) notation. Samples with at least section level location information were included in this project; many of the locations given in the field notes can be narrowed down to quarter-section designation with certainty. In the initial phase of this ongoing project we have focused on scanning and entering metatdata for samples in and around Florence County, Wisconsin. Precambrian iron formation in this area was mined from 1880-1931 to produce some three million tons of hematite and limonite ore (Brown B., 2021). This project has focused on capturing lithological information from samples in this area, which is characterized by complex Precambrian stratigraphy and structure. Upon project completion, high resolution thin section images will be made publicly available online using the WGNHS Dataviewer. Additionally, all metadata will be uploaded to the USGS’s ReSciColl collection and the WGNHS internal database (Geobase). 3 �Figure 1: A) Plustek Optic Film 8200i scanner and acompyning film tray. B) Scanner settings to be used during the proposed project. Note the 600 ppi preset and further 7,200 ppi adjustable resolution. Thin sections are scanned in 48-bit HDR Raw C) Tray with card stock paper cut to better hold thin sections. Note the two slots on the right are fitted with linear polarizing screens that sandwich the thin sections. The polarized screens are oriented to cross polarize the light when scanning. Figure 2: High resolution thin section images scanned as part of the pilot project. A. and C. were scanned using plane, non-polarized light; B. and D. were scanned using cross polarized light. REFERENCES Brown, B., 2021. Florence Iron Mine: Historical Maps Showing Location of Surface Development, Regional Setting, and Underground Workings. Wisconsin Geological and Natural History Survey WOFR2018-03: 5. Leung, D. D.V., and Mcdonald, A.M., 2023. Picture-perfect petrography: affordable thin-section scanning for geoscientists in the digital era. The Canadian Journal of Mineralogy and Petrology, 61: 10451050. 4 �A Contrarian View: Thoughts on the Genesis of the Tamarack Ni-Cu Deposit. AUBUT, Alan1 1 Sibley Basin Group Ltd., PO Box 304, Nipigon, ON P0T 2J0.Canada The Tamarack Ni-Cu deposit has been attributed as being of intrusive origin (Goldner, 2021; Taranovic et al., 2018). There are many nickel deposits hosted by ultramafic bodies that display clear evidence of being the product of extrusive flows, often exhibiting the same key features used to invoke an intrusive origin (e.g. Arndt, 1975; Hill et al., 1995; Hubbert and Sparks, 1985; Marston et al.,1981). This includes the nickel deposits of the Kambalda district of Australia, Pechenga in the Kola Peninsula of western Russia, Raglan in northern Quebec and Thompson in northern Manitoba. All have been, or currently are, attributed to the intrusion of ultramafic sills (e.g. Bleeker, 1990; Marston et al., 1981; Melezhik et al., 1994). Key evidence in support of this model is that the ultramafic bodies typically exhibit at least some differentiation and are sub-concordant to the host sediments. This tendency to default to an intrusion model now includes the Tamarack deposit in Minnesota even though an extrusion model is more valid. The major komatiite hosted nickel deposits listed above share common features: 1) the nickel mineralisation is hosted by ultramafic rocks; 2) the sulphides are at the stratigraphic base of the host ultramafics; 3) the ultramafic rocks are hosted by, or in contact with, sulphidic and carbonaceous argillaceous rocks; 4) the ultramafic bodies are stratabound and generally conformable to the host lithology; and 5) they are hosted within extensional basins usually with a significant sedimentary component with Kambalda being the one exception. But there is a density “problem” in that ultramafic magmas are typically denser than the host rocks, especially when they are sedimentary. When rocks melt, they become about 10% less dense. In the case of ultramafic rocks, the average density is about 3.0 g/cc (Nisbet et al., 1993) while the crust has a density of 2.7 g/cc or less. To move upward from the mantle through the crust there must have been a mechanism other than buoyancy. “Overpressure” is a valid explanation (Sleep, 1974, 1992). Magma plumes in a mantle plume move upward due to buoyancy to the Mantle-Crust boundary. There it collects and then moves laterally thus creating extensional forces in the overlying crust. This accumulating magma would be constrained by the overlying lithostatic load and in doing so would build up overpressure. If the crust thins enough vertical fractures can form allowing the trapped magma to escape due to the built-up overpressure exceeding the lithostatic load. At surface the hot, dense ultramafic magma would then flow over, and into, deep water sediments where the magma would mechanically and thermally erode and assimilate sulphide rich sediments. Tamarack shows all the same characteristics as other Ni-Cu deposits associated with rift basins and features that are more easily explained by extrusive flow of komatiitic magma. As such the intrusive emplacement model currently favoured should be reviewed and serious consideration given to emplacement by extrusion of a high-density magma driven by overpressure. 5 �REFERENCES Arndt, N.T., 1975. Ultramafic rocks of Munro Township and their volcanic setting; Unpub. Ph.D. Thesis, Univ. Toronto. Bleeker, W., 1990. New Structural-Metamorphic constraints on Early Proterozoic oblique collision along the Thompson Nickel Belt, Manitoba, Canada; In Lewry, J.F. and Stauffer, M.R., eds., The Early Proterozoic Trans-Hudson Orogen of North America: Geological Association of Canada, Special Paper 37, p. 57-73. Goldner, B.D., 2011. Igneous Petrology of the Ni-Cu-PGE Mineralized Tamarack Intrusion; Unpub. M.Sc. Thesis, Univ. Minesota. Aitkin and Carlton Counties, Minnesota; Canadian Journal of Earth Sciences, 44, 1087-1110. Hill, R.E.T., Barnes, S.J., Gole, M.J. and Dowling, S.E., 1995. The volcanology of komatiites as deduced from field relationships in the Norseman-Wiluna greenstone belt, Western Australia; Lithos 34, p. 159-188. Huppert, H.E. and Sparks, R.S.J., 1985, Komatiites I: Eruption and Flow; Journal of Petrology, Vol. 26, Part 3, pp. 694-725. Marston, R.J., Groves, D.I., Hudson, D.R. and Ross, J.R., 1981, Nickel sulfide deposits in Western Australia: a review; Economic Geology, Vol. 76, pp. 1330-1363. Melezhik, V.A., Hudson-Edwards, K.A., Skuf'in, P.K and Nilsson, L.P., 1994a, Pechenga Area, Russia Part 1: geological setting and comparison with Pasvik, Norway; Transactions of Institution of Mining and Metallurgy (Sect. B: Applied Earth Science), Vol. 103, p B129-B145. Nisbet, E. G., Cheadle, M. J., Arndt, N. T., & Bickle, M. J. (1993). Constraining the potential temperature of the Archaean mantle: a review of the evidence from komatiites. Lithos, 30(3-4), 291-307. Sleep, N. H., 1974. Segregation of Magma in the Ascending Mantle. The Journal of Geology, 82(2), 131– 142. Sleep, N. H., 1992. Time Dependence of Kilauea Volcano Structure from Hotspots to Trench Due to Overpressure in the Asthenosphere. Journal of Geophysical Research: Solid Earth, 97(B8), 11773– 11782. Taranovic, V., Ripley, E.M., Li, C. and Shirey, S.B., 2018. S, O, and Re-Os Isotope Studies of the Tamarack Igneous Complex: Melt-Rock Interaction During the Early Stage of Midcontinent Rift Development; Economic Geology, v. 113, no. 5, pp. 1161-1179. 6 �An overview of the geology, tectonic setting, and occurrence of sulphide mineralization in the Lac Des Iles Intrusive Suite BAIN, Wyatt1, TOLLEY, James 2, and HOLLINGS, Peter 2 1 Department of Earth Sciences, Western University, 1151 Richmond St, London, ON N6A 5B7 Canada 2 Department of Geology, Lakehead University, 955 Oliver Road Thunder Bay, ON P7B 5E1 Canada The Lac des Iles (LDI) mafic-ultramafic complex hosts a world-class platinum group element (PGE) deposit and is spatially associated with a suite of mafic-ultramafic satellite intrusions (i.e. the LDI-intrusive suite; LDI-IS). The intrusions are hosted in the crystalline rocks of the Wabigoon subprovince, along its eastern contact with the sedimentary and volcanic rocks of the Quetico subprovince. Previous work identified textural and geochemical similarities between the LDI-IS and the mineralized rocks of the LDI complex that likely reflect a temporal and genetic association, and perhaps a similar degree of prospectivity for PGE mineralization (Stone et al., 2003). Here, we present an overview of the geology and setting of the LDI-IS, as well as new geochronology, isotopic data, and parental melt modelling. The LDI-IS (Tib Lake, Legris Lake, Wakinoo Lake, Demars Lake, Dog River, Taman Lake, and Buck Lake; Fig. 1a) are mostly leucogabbro to gabbronorite in composition but commonly include hornblende gabbro, hornblendite, and minor peridotite and pyroxenite. Zircon U-Pb ages for mineralized gabbro from the Buck Lake (2698.1 ± 1.6 Ma), Wakinoo Lake (2696.6 ± 0.8 Ma), Demars Lake (2694.1 ± 1.5 Ma), Legris Lake (2690.6 ± 0.8 Ma), Dog River (2689.9 ± 0.7 Ma), and Tib Lake (2685.9 ± 1.6 Ma) intrusions show a spatial trend of younging to the north and demonstrate a temporal association with the Lac des Iles Mine Block intrusion (2689.0±1.0 Ma; Stone, 2010; Fig 1 b). Trace element profiles for modelled parental melts are similar across most of the LDI-IS and are consistent with an arc setting and a common parental magma source reservoir. However, modelled REE profiles for some cyclic units in the Tib lake intrusion were more evolved and enriched in light rare earth elements. Similar patterns are reported in modelled parental melts from North LDI and are consistent with mixing between primitive and more evolved, siliceous magmas (Djon et al., 2017). Though magma mixing influenced the geochemical evolution of the Tib lake intrusion, cyclic units with more evolved signatures were not significantly mineralized. Whole rock εNdT values of gabbroic rocks from the LDI-IS and the Lac des Iles complex overlap with the tonalitic rocks of the Wabigoon subprovince in older intrusions and trend toward increasingly negative values in younger intrusions (Fig. 1c). This suggests assimilation of Wabigoon tonalite by LDI-IS parental magmas early in the formation of this magmatic system, and greater degrees of contamination by Quetico metasediment over time. Magmatic sulphides from the Legris Lake intrusion have δ34S values that overlap the mantle range but trend toward the composition of Wabigoon tonalite (Bain et al., 2023). This suggests that external S or Si addition from the tantalite drove sulphide saturation during its formation. However, a comparison of whole rock S/Se and Cu/Pd ratios of mineralized lithologies across the LDI-IS suggest that sulphide melt retention during emplacement was a more crucial control on the occurrence of PGE-bearing sulphide mineralization than the source of S or the timing of sulphide saturation. 7 �Figure 1: a. Regional geologic map showing locations of Thunder Bay, the Lac des Iles mine (in red), and the Lac des Iles intrusive suite (in blue). b. U-Pb ages for individual intrusions in the Lac des Iles intrusive suite. c. Whole-rock εNdT values for the LDI intrusive suite and host rock lithologies. North LDI and South LDI data from Brügmann et al. 1997 REFERENCES Bain, W.M., Hollings, P.N., Djon, M.L., Brzozowski, M.J., Layton-Matthews, D., Dobosz, A., and Stern, R.A., 2024. Geochemical evolution and parental magma of the Lake Legris mafic-ultramafic complex, Ontario. Mineralium Deposita 59:85-108 Brügmann, G.E., Reischmann, T., Naldrett, A.J., and Sutcliffe, R.H., 1997. Roots of an Archean volcanic arc complex: The Lac des Iles area in Ontario, Canada. Precambrian Research, 81: 223−239. Djon, M.L., Olivo, G.R., Miller, J.D., and Peck, D.C., 2017. Stratiform platinum-group element mineralization in the layered northern ultramafic center of the Lac des Iles Intrusive Complex, Ontario, Canada. Ore Geology Reviews, doi: 10.1016/j.oregeorev.2017.03.011. Stone, D., Lavigne, M.J., Schnieders, B., Scott, J., and Wagner, D., 2003. Regional geology of the Lac des Iles area. Ontario Geological Survey, Open File Report 6120: 15–25. Stone, D. 2010. Precambrian geology of the central Wabigoon Subprovince area, northwestern Ontario. Ontario Geological Survey, Open File Report 5422:1-130. 8 �Linking whole rock geochemical data with micro-scale mineral characterization of oxidation reactions in the Biwabik Iron Formation, MN, USA BANKS, Madelyn1, BRENGMAN, Latisha1, EYSTER, Athena2 1 Department of Earth and Environmental Sciences, University of Minnesota Duluth, Heller Hall, 1114 Kirby Drive, Duluth, MN 55812, USA 2 Department of Earth and Climate Sciences, Tufts University, Lane Hall, 2 North Hill Road, Medford, MA 02155, USA Oxidation and hydration reactions in iron-rich chemical sedimentary rocks are of critical interest because they signify post-depositional changes often linked to later weathering and fluid alteration. Evaluating oxidation and hydration reactions present in iron formations is therefore required to separate out depositional signals in mineralogical and geochemical data from those that link to post-depositional mineral reactions and enrichment processes (Geymond et al., 2022). The Biwabik iron formation is a part of a well-preserved, sub-greenschist lithologic assemblage containing three major meta-sedimentary formations known together as the Animike Group (e.g. Severson, 2009 and references therein). Previous work (e.g. Duncanson et al., 2024 and references therein) demonstrated the preservation of numerous mineral reactions in the Biwabik iron formation, making it an ideal location to test how mineral reactions link directly to whole rock geochemical signals. To evaluate the relative timing of different oxidation and hydration reactions and how they link to whole rock geochemical data, we integrate core, petrographic, and scanning electron microscope observations with whole rock digestion ICP-MS geochemical datasets from core LWD-99-01 (n = 60) of the Biwabik iron formation. Two key oxidation reactions identified in this work include (1) magnetite to hematite and (2) carbonate to magnetite. Mineral reactions are documented by cross-cutting relationships (Figure 1A-D). The mineral reaction of magnetite to hematite (possibly via the recrystallization of metastable maghemite, 2(αFe3O4) + H2O ↔ 3(γFe2O3) + H2); Geymond et al., 2023) is present in all four informal lithologic subunits of the Biwabik iron formation, occurring in 48% (n = 23) of samples (n = 48) across these units. The mineral reaction of carbonate to magnetite (3FeCO3 +H2O → Fe3O4 + 3CO2 + H2, Duncanson et al., 2024) is also present in all four informal lithologic subunits of the Biwabik Iron Formation, occurring in 77% (n = 37) of samples (n = 48) across these units. Based on 64 EDS point analyses of 4 representative samples from each subunit of the Biwabik iron formation, dominant carbonate minerals range from siderite at the base of the stratigraphy, to ankerite, dolomite, and calcite towards the top. Combined, carbonate compositional variability and zonation indicate element exchange during multiple generations of post-depositional fluid alteration, and cross-cutting relationships between carbonate-magnetite, and magnetite-hematite indicate post-depositional oxidation via fluid interaction with pre-existing reduced iron phases. Dissolution of carbonate may have created porosity providing pathways for oxidizing fluids, and further oxidation. Despite these later oxidation reactions, whole rock geochemical data preserves lithology specific signals of oxic vs. anoxic conditions, independent of the presence of the post-formational reactions outlined above. Lower stratigraphic units preserve oxic signals even with ferrous iron phases like siderite and greenalite preserved, while upper stratigraphic units preserve anoxic signals, despite the presence of hematite. Overall, bulk geochemical data from lithologic subunits of the Biwabik Iron Formation do not preserve clear signals associated with post-depositional mineral assemblage modification and oxidation documented by detailed petrographic work. 9 �Figure 1: LWD-99-01 reflected light photomicrographs documenting cross-cutting relationships between mineral phases. A. Upper Slaty sample MIR-17-15 carbonate granule cross-cut by euhedral magnetite (mag) in 20x. B. Lower Cherty sample MIR-19-14 carbonate granule (carb) cross-cut by euhedral magnetite (mag) in 5x. C. Upper Cherty sample MIR-19-15 magnetite crystal (mag) cross-cut by platy hematite (hem) in 20x. D. Lower Slaty sample U-05 magnetite crystals (mag) crosscut by platy hematite (hem) at the edge of a silicate granule in 10x. REFERENCES Duncanson, S., Brengman, L., Johnson, J., Eyster, A., Fournelle, J., Moy, A., 2024. Reconstructing diagenetic mineral reactions from silicified horizons of the Paleoproterozoic Biwabik Iron Formation, Minnesota. American Mineralogist, 109, 339-358. Geymond, U., Briolet, T,. Combaudon, V., Sissmann, O., Martinez, I., Duttine, M., Moretti, I., 2023. Reassessing the role of magnetite during natural hydrogen generation. Front. Earth Sci., 11, 1169356. Geymond, U., Ramanaidou, E., Lévy, D., Ouaya, A., Moretti, I., 2022. Can Weathering of Banded Iron Formations Generate Natural Hydrogen? Evidence from Australia, Brazil and South Africa. Minerals, 12, 163. Severson, M., Heine, J., Patelke, M., 2009. Geologic and Stratigraphic Controls of the Biwabik Iron Formation and the Aggregate Potential of the Mesabi Iron Range, Minnesota. University of Minnesota Duluth, Natural Resources Research Institute, Technical Report NRRI/TR- 2009/09, 173, 37 plates. 10 �Pembine-Wausau Terrane as an Icelandic style island overthrust onto Archean basement, instead of an island arc or continental fragment accretion BAUMANN, Steven D.J. Midwest Institute of Geosciences and Engineering Since at least the 1960s, we have thought of the Pembine-Wausau Terrane (PWT) as an island arc or continental fragment accretion, smashed between the Superior Craton to the north and the Marshfield Terrane to the south. We all have seen a fault zone appear on geologic maps of the border between the Upper Peninsula of Michigan and northeast Wisconsin called the Niagara Fault Zone (NFZ). There is only one major problem, no one has ever found the NFZ. It doesn’t outcrop anywhere, it does not appear in well records, nor clearly on gravity maps, or magnetic maps. Often where it is inferred it can be interpreted other ways. And the NFZ isn’t reflected in any smaller chronostratigraphically equivalent structures that do outcrop. I have found white unbaked quartzite pebbles (the Sturgeon Quartzite) north of the NFZ (fig. 1). The host rock of these pebbles according to maps, are metamorphic rocks that supposedly have an igneous protolith. I find that very hard to reconcile with present modeling. As I have looked at the highly deformed rocks of the Florence Wisconsin, Iron Mountain Michigan, and Norway Michigan areas, I have come to the conclusion that many rocks mapped as metaigneous, are in fact, metasedimentary. I have been working on a local cross section for several years with my observations. I am coming to the conclusion that the mafic rocks and metasediments to the north of where the NFZ has traditionally been mapped, are more or less continuous and correlative to the mafic and metasedimentary rocks to the south of it. Interpretation of the rocks is understandably very difficult as the rocks are highly metamorphosed and deformed. This work is preliminary. My interpretations could change. But this is where the evidence is leading me thus far. So, if the area that is mapped as the NFZ is not a fault zone, what is it? I see it as one of two possibilities. It could be more of a shear zone formed from a more lateral accretion of a volcanically active, partially rifted Archean sliver, similar in appearance to Baja California. Sheering would be hard to see expressed in the rocks, just as it is for other covered shear zones further north. The second possibility is that the PWT was originally an Icelandic style island on a spreading center that would eventually become subducted under the Superior Craton, similar to the East Pacific Rise, before subduction switched to the south as the Marshfield Terrane approached. Its suspected Archean basement could be explained by a thin skinned over thrusting of the PWT over a small sliver of Archean crust, while volcanism was ongoing. The age of the xenocryst zircons expected to be Archean are only 2,607+22 Ma (VanWyck and Johnson. 1997). This is similar to many Archean ages of the Superior Craton. It is still a possibility the Penokean was a continental fragment like the Marshfield Terrane, only far more incomplete and still covered with younger deposits, but this cannot be the default without understand the nature of the NFZ, if it even exists. The Archean basement of the PWT could also be some sort of an extension of nearly in situ Superior Craton, that hosted the PWT as it formed, or it was overridden by the PWT. I am currently favoring the second interpretation. In this case no NFZ is needed to explain anything observed, at least locally. Everything can be explained by dominantly ductile deformation, at least in the upper crust. This is really reflected in the rocks at Piers Gorge and in the local Michigamme Formation, which locally do not express any Penokean aged faults of any 11 �significance. It also would explain the contemporaneous crustal thinning to the east in the Sudbury area if we had a subducting rift. This is something that forearc extension and island arc accretion cannot explain on their own. This would also put the continental suture further south, at the Eau Claire Sheer Zone. Figure 1: Adapted from Baumann, 2021 REFERENCES Baumann, S.D.J., 2021. The Misunderstood Penokean Orogeny. Midwest Institute of Geosciences and Engineering, publication G-102021-1A VanWyck, N. and Johnson, C.M., 1997. Common lead, Sm-Nd, and U-Pb constraints on petrogenesis, crustal architecture, and tectonic setting of the Penokean orogeny (Paleoproterozoic) in Wisconsin. GSA Bulletin; July 1997; v. 109; no. 7; p. 799–808; 8 figures, 2 tables 12 �Paleoproterozoic mantle plume tracks shaping the southern margin of the Superior craton and the geology of the Lake Superior region BLEEKER, Wouter1, HAMILTON, Michael 2, and KAMO, Sandra 2 1 Geological Survey of Canada, 601 Booth Street, Ottawa, ON K1A 0E8, Canada; wouter.bleeker@canada.ca 2 Jack Satterly Geochronology Laboratory, Department of Earth Sciences, University of Toronto, 22 Ursula Franklin Street, Toronto, ON M5S 3B1, Canada All Archean cratons are fragments of late Archean “supercratons”, i.e. the larger landmasses to which these craton fragments trace their origin (Bleeker, 2023). At least two large independent supercratons, Superia and Sclavia, named after their well-preserved internal fragments, had formed by the late Archean and underwent progressive breakup during the early Paleoproterozoic, from ca. 2.2 Ga to 1.9 Ga. Based on well-populated apparent polar wander paths, these supercratons moved independently; hence, the mythical notion of a single, longlived, late Archean supercontinent “Kenorland” is incorrect, aside from being untestable. Craton fragments can be correlated and put back together again by matching distinctive basement geology, by correlating overlying pre-breakup basin stratigraphies, and by correlating remnants of pre- to syn-breakup large igneous provinces, particularly their dyke swarms (Bleeker and Ernst, 2006). Of all the dispersed Archean craton fragments, more than 10 trace their origin back to supercraton Superia, representing “nearest neighbour” fragments to the Superior: Karelia, Kola, Wyoming, Hearne, Kaapvaal, Pilbara, Yilgarn, Zimbabwe, North Atlantic craton, and possibly Dharwar. Kaapvaal-Pilbara joined a growing Superia late in the game, at ca. 2650 Ma, separating again ~600–700 Myr later, leaving the ancient Minnesota River Valley terrane behind. With a robust reconstruction of Superia, numerous other important insights follow, including that of ancient mantle plume tracks (Figure 1). Here we discuss evidence for two major plume tracks that shaped the southern margin of the Superior craton, the 2480-2440 Ma “Matachewan” plume track, and the 2125-2050 Ma “Marathon” plume track. Both these plume tracks started within Superia’s core, before crossing over to then-contiguous crust of “greater Karelia” and Kaapvaal, respectively. The Matachewan plume track was initiated in the Sudbury area with a suite of 2480-2472 Ma mafic layered intrusions emplaced at the base of the Huronian Supergroup. It then triggered the ca. 2461 Ma giant Matachewan dyke swarm, which converge to a magmatic centre well to the south. At ca. 2450 Ma, the plume crossed over to then-contiguous “greater Karelia” (Davey et al., 2020) where it spawned additional dyke swarms and a flare-up of large layered intrusions, some as young as 2440 Ma. The much younger Marathon plume was initiated at ca. 2125 Ma with a giant radiating mafic dyke swarm, the Marathon dykes, with a focal point in the eastern Lake Superior area. It then spawned progressively younger mafic dyke swarms to the southwest before crossing over to the contiguous Kaapvaal craton where it spawned carbonatites at 2060 Ma, and finally the emplacement of the Bushveld Complex at 2056 Ma, the long axis of which is aligned with the plume track (Figure 1). Both plume tracks show well-defined age progressions indicating plate velocities of ~1–5 cm/yr. SOME REFERENCES Bleeker, W., 2003. The late Archean record: a puzzle in ca. 35 pieces. Lithos 71(2-4): 99-134. Bleeker, W. and Ernst, R.E., 2006. Short-lived mantle generated magmatic events and their dyke swarms: The key unlocking Earth's palaeogeographic record back to 2.6 Ga. In: Hanski, E., Mertanen, S., 13 �Rämö, T., Vuollo, J. (Eds.) Dyke Swarms—Time Markers of Crustal Evolution, AA Balkema, Rotterdam, p. 3-26. Davey, S.C., Bleeker, W., Kamo, S.L., Vuollo, J., Ernst, R.E., and Cousens, B.L., 2020. Archean block rotation in Western Karelia: Resolving dyke swarm patterns in metacraton Karelia-Kola for a refined paleogeographic reconstruction of supercraton Superia. Lithos 368: 105553. Fiorentini, M.L., O’Neill, C., Giuliani, A., Choi, E., Maas, R., Pirajno, F., and Foley, S., 2020. Bushveld superplume drove Proterozoic magmatism and metallogenesis in Australia. Scientific Report 10(1): 19729. Figure 1. Paleogeographic reconstruction of late Archean–early Paleoproterozoic supercraton Superia, involving >10 of the better-known Archean craton fragments from around the world, with the wellpreserved Superior craton as its signature internal fragment. Vaalbara and several other cratons (e.g., Wyoming) formed a single, large, ancient superterrane that collided with the southern margin of growing Superia at ca. 2650 Ma. After a period of stasis, supercraton Superia underwent progressive rifting and breakup from ca. 2.2 Ga to 1.9 Ga. Selected Paleoproterozoic mafic magmatic events are shown, with a focus on two well-defined mantle plume tracks, the “Matachewan” plume track (bold grey arrow) and the “Marathon” plume track (bold purple arrow), both with clear age progression. The Marathon plume track, which initiated at 2125 Ma with a giant radiating dyke swarm, crossed over into the adjacent Kaapvaal craton where it culminated in the emplacement of the Bushveld Complex. The actively rifting Superia plate was likely at a stand-still at Bushveld time (ca. 2056 Ma), allowing the plume tail to erode and dramatically thin the Kaapvaal lithosphere and setting up the conditions for the emplacement of Earth’s largest mafic layered intrusive complex. Ponding of voluminous sublithospheric plume magma resulted in outflow to distal localities (dashed arrows), possibly as far as Karelia-Kola (e.g., Kevitsa, 2058 Ma) and the Yilgarn (e.g., Mount Weld, ca. 2060 Ma; cf. Fiorentini et al., 2020). 14 �A COMPLEX F-RICH ALKALIC PEGMATITE IN THE PYROXENE SYENITES OF THE STETTIN COMPLEX, WAUSAU COMPLEX, MARATHON COUNTY, WISCONSIN BUCHHOLZ, Thomas1, FALSTER, Alexander2, and SIMMONS2, William 1 1140 12th Street North, Wisconsin Rapids, Wisconsin 54494, 2MP2 Research Group, Maine Mineral and Gem Museum, PO Box 500, 99 Main Street, Bethel, Maine 04217, USA The Stettin Complex is the oldest (1565 +3-5 Ma, Van Wyck 1994) and most alkalic of the four intrusions that comprise the Wausau Syenite Complex, and is composed of various syenite phases. This abstract is an update to a study of this dike in ILSG 2024. The sub-horizontal pegmatite is weathered, mineralogically and texturally zoned, and includes numerous syenite screens. Thin 2-3 cm reaction zones are common at contacts, with small miaroles, scattered patches of abundant, tiny pink zircons, fergusonite-(Y), and other minerals. Small miarolitic cavities are common throughout the dike. Overall mineralogy is complex, typical for fractionated alkalic pegmatites. Pyroxenes are largely absent except for highly altered replacements and sparse unaltered remnants of hedenbergite. Early formed pyroxene(s) appear to have been destabilized by later oxidation, altering Fe2+-rich pyroxenes to quartz and smectite-group clays ± goethite with sparse remnants of hedenbergite, and allowing crystallization of more oxidized (Fe3+ rich) magnetite and arfvedsonite. Similar reactions may have altered early-crystallizing chevkinite(Ce) (or a similar LREE-Ti species) and possibly aeschynite-(Ce), to an unidentified Ti-Ce4+-Fe phase: relatively common soft, pale yellow to creamy to brown grains of varying morphologies typically containing high Ti-Ce-Fe contents with traces of other elements. Cerium is likely present as Ce4+ based on the absence of associated LREE3+ (La, Nd, Pr). Alteration under oxidizing conditions may have removed LREE3+, Si and other elements, leaving immobile Ti, Ce4+, minor Fe3+ and trace amounts of other elements. Fluorapatite occurs as abundant hexagonal prisms in intermediate zones of the dike; generally highly altered with elevated to very high LREE (Ce-dominant) and Si contents, while similar reddish crystals in pegmatite units near the lower contact show more typical very low LREE contents. This may be the result of alteration/partial replacement of fluorapatite by fluorbritholite as discussed by Betkowski et al (2016). Work also continues on a rare unidentified Ba-silicate mineral, where lack of Al precludes Ba-feldspars. Several small-volume units and isolated occurrences contain minerals not normally found in alkalic pegmatites, including cassiterite, Hf-enriched zircons (up to 5.5 wt.% HfO2, vs 1.48 wt. % HfO2 in pegmatite margin zircons), fluorcalciomicrolite (D-site occupancy Ta 1.05, Nb 0.65, Ti 0.30; Σ 2), tantalite-(Mn), and barite. Sphalerite in unweathered lower portions of the dike is notable in containing about 0.7 wt. % Indium. Later oxidizing conditions are evident in late crystallization of siderite (now goethite), and LREE fluocarbonates. Crystallization of fergusonite-(Y) (to date Nb-dominant, ≈Nb 1.96, Ta 0.04; Σ 2), being rich in MREE and HREE and lacking redox sensitive Ce, appears to have continued throughout dike crystallization. 15 �REFERENCES Betkowski, Wladyslaw B., Harlov, Daniel E. and Rakovan, John F., 2016. Hydrothermal mineral replacement reactions for an apatite-monazite assemblage in alkali-rich fluids at 300-600° C and 100 MPa, American Mineralogist 101, 2620-2637. Van Wyck, N. 1994. The Wolf River A-type magmatic event in Wisconsin: U/Pb and Sm/Nd constraints on timing and petrogenesis (abstract): Institute on Lake Superior Geology, 40th Annual Meeting, Part 1, Program and Abstracts, 81-82. Aeschynite-(Ce) Albite Anorthoclase Barite Bavenite(?) Bertrandite Calcite Cassiterite Columbite-(Fe) Fayalite Fergusonite-(Y) Fluoro-arfvedsonite Fluorannite Fluorapatite Fluorite Fluorcalciomicrolite Fluorcalciopyrochlore Graphite Hedenbergite Ilmenite K-feldspar Kainosite-(Y) Magnetite Molybdenite Monazite-(Ce) Niocalite? Phenacite Quartz Siderite Sphalerite Thorite Titanite Zinnwaldite Zircon Zircon (metamict) (Ce,Ca,Fe,Th)(Ti,Nb)2(O,OH)6 NaAlSi3O8 (Na,K)AlSi3O8 BaSO4 Ca4Be2Al2Si9O26(OH)2 Be4(Si2O7)(OH)2 CaCO3 SnO2 Fe2+Nb2O6 Fe2+2SiO4 YNbO4 [Na][Na2][Fe2+4Fe3+]Si8O22F2 KFe2+3(Si3Al)O10F2 Ca5(PO4)3F CaF2 (Ca,Na)2(Ta,Nb)2O6F (Ca,Na)2(Nb, Ti)2O6F C CaFe2+Si2O6 Fe2+TiO3 KAlSi3O8 Ca2(Y,Ce)2(Si4O12)(CO3) · H2O Fe2+Fe3+2O4 MoS2 Ce(PO4) (Ca,Nb)4(Si2O7)(O,OH,F)2 Be2SiO4 SiO2 FeCO3 ZnS Th(SiO4) CaTi(SiO4)O KFe22+Al(Al2Si2O10)(OH)2 to KLi2Al(Si4O10)(F,OH)2 Zr(SiO4) Zr(SiO4) Table 1. Dike Mineralogy 16 Common Rock-forming Rock-forming Rare Rare Rare Common Uncommon Rare Rare Common Rock-forming Rock-forming Common Common Rare Rare Rare Uncommon Common Uncommon Rare Common Uncommon Common Rare Rare Rock forming Common Rare Rare Uncommon Uncommon Very common Common �Micromineralogy and textures in the Sudbury impact layer on the Mesabi Iron Range, Minnesota: record of processes in the proximal-distal ejecta transition zone CANNON, W. F., STOKES, M. Rebecca, SALERNO, Ross A. U.S. Geological Survey, Geology, Energy & Minerals Science Center, Mail Stop 954, Reston, VA 20192 The Sudbury Impact Layer (SIL) (1849 Ma), deposited here within hours of the giant meteor impact at Sudbury, Ontario, is known from drill core at four locations on the Mesabi Iron Range (Fig. 1) along a trajectory distance as great as 980 kilometers from the impact point. It records an instant of high energy deposition of about one meter of mixed ejecta and local bedrock within an otherwise quiescent sequence of siltstone and iron formation. Optical, scanning electron microscope, and Raman spectroscopy data provide details of the SIL that reveal some of the complexities of ejecta transport and deposition. Data presented here are from the Nashwauk occurrence where four drill holes provide continuous samples across the layer. Figure 1. Geologic map of the Mesabi Iron Range showing the four locations where the Sudbury Impact Layer (SIL) has been observed: Coleraine (Huber, et al., 2014; Nashwauk (Cannon, et al., 2017, this study); Eveleth (Addison, et al., 2005, this study); Erie (this study). The SIL on the Mesabi Iron Range consists of millimeter-scale ejecta particles expelled from the large crater near Sudbury, and coarser fragments, of sedimentary rocks, some greater than 3 cm diameter, which were derived locally. The ejecta can be subdivided into two categories: A- devitrified glass (Fig. 2), and B- millimeter-scale mineral grains and rock fragments displaying shock metamorphic features (Fig. 3). Figure 2. A-microtektite in matrix of coarse secondary dolomite. Original glass devitrified to K-mica. Vesicles are filled with dolomite. B-delicate bubble structures preserved in secondary dolomite. Bubble walls are mostly K-mica and chlorite. C-angular fragment of flattened vesicular glass, now mostly chlorite. D-rounded particle composed of fine K-mica. Spheres of vesicular glass and their fragments are common (Fig. 2A), including thinwalled hollow structures (Fig. 2B). They are now composed of micron-scale K-mica and chlorite. Irregularly shaped glass shards, mostly composed of chlorite, are also abundant (Fig. 2C). Many are larger than typical spherules and are probably far-flung bits of impact melt rather than broken spheres. Most are flattened into bedding. Also common are rounded grains composed of sub-micron K-mica with relict vesicles (Fig. 2D). These are distinct in having been 17 �sufficiently strong to have avoided flattening. Other glass particles are molded around them. They were likely droplets of melt with very uniform K-Al-Si composition. Quartz and feldspar grains with multiple sets of planar deformation features and zones of devitrified impact glass attest to the intense shock unique to meteor impacts. Small rock fragments with intense shock features are also common (Fig. 3). Figure 3. A-quartz with one well-developed set of planar deformation features and two weaker sets (red lines). B- intensely shocked quartz with “toasted” appearance and zones of devitrified glass. Ccathodoluminesence image of B showing complex shock-induced internal features. D-intensely shocked polycrystalline orthoquartzite fragment. Abundant glass spherules in the Nashwauk ejecta appear to be microtectites. Such particles are widely interpreted to form by condensation from impact vapor plumes above the atmosphere and can be distributed worldwide. At Nashwauk they are mixed with small rock and mineral particles from the outermost margins of the impact ejecta curtain. These were transported either (or both) on ballistic trajectories, or by intense impact-generated winds beyond the ejecta curtain. Many have strongly developed shock features attesting to their derivation by crater excavation near Sudbury. Notably missing from the SIL on the Mesabi Iron Range are accretionary lapilli, a hallmark of more proximal sites where ballistic ejecta and ground surges were the dominant transport mechanism for ejecta. The SIL at Nashwauk is very similar to that at the three other occurrences along the Mesabi Iron Range which, together, document a broad transition zone, between about 900 to 1000 kilometers from the impact point. Here the most distal ballistic ejecta persisted as millimeter-scale grains into a zone where ejecta plume material was becoming dominant. Along the Mesabi Iron Range ejecta was deposited in a shallow sea where fine-grained laminated silt and chert were being deposited, both before and after the impact. Strong impact-generated tsunamis reworked the ejecta and underlying sediments within hours or days of the impact to produce the intermixing of fine-grained ejecta particles with much coarser rip-up clasts from the pre-impact seabed. REFERENCES Addison, W.D., Brumpton, G.R., Vallini, D.A., McNaughton, Davis, D.W, Kissin, S.A., Fralick, P.W., and Hammond, A.L., 2005, Discovery of distal ejecta from the 1850 Ma Sudbury impact event. Geology, v. 33, p.193–196. doi: https://doi.org/10.1130/G21048.1 Cannon, W.F., Woodruff, L. J., Jirsa, M., and Everett, W, 2017, New observations on distal ejecta from the Sudbury impact in the central Mesabi Iron Range, northern Minnesota, Institute on Lake Superior Geology, v. 63, Proceedings Part 1, Program with abstracts, p. 19-20. Huber, M.S., McDonald, I. and Koeberl, C., 2014, Petrography and geochemistry of ejecta from the Sudbury impact event, Meteoritic and Planetary Science: v. 49. p. 17491768. https://doi.org/10.1111/maps.12352 Jirsa, Mark, Chandler, V.W., and Lively, R. S., 2005, Bedrock geologic map of the Mesabi Iron Range Minnesota, Minnesota Geological Survey Miscellaneous Map Series map M-163. 18 �Updates on the Minnesota Department of Natural Resource’s Drill Core Library CARTER, Matt1 1 Minnesota Department of Natural Resource, Division of Lands and Minerals, 1525 3rd Ave E, Hibbing, MN, 55746 USA The Minnesota Department of Natural Resource’s (DNR) Drill Core Library (DCL) in Hibbing, MN is the only state-owned facility for archiving drill cores and other geological materials from Minnesota. The DCL was first established in 1972 when Building 1 (B1) was constructed. It was expanded in 1979 when Building 2 (B2) was constructed. Building 3 was first constructed in 1989 and expanded in 1995 and 2009. The facility currently stores around 3.5 million linear feet of drill core and contains material and/or data for over 20,000 drillholes. In 2023, it was identified that original shelving units installed in B1 and B2 needed to be replaced, and other safety issues needed to be resolved. The DNR diligently prepared to move all drill cores and other noncore geological materials from B1 to replace the shelving units. This was accomplished by assessing materials for deaccession, creating a box index of its holdings, applying barcodes to over 38,000 drill core boxes, as well as inventorying and barcoding noncore materials. Boxes were moved box by box by hand onto roller tables to an intake station where tracking information and digital images were captured. Boxes were then palletized and placed into temporary storage, which involved 712 pallets and 40 storage containers. The captured digital images have created a new and accessible digital record for B1 cores. Once the original shelving units were removed from B1, the DNR upgraded its lighting, and a new racking system was installed. Reverse flow of materials to B1 is anticipated to be completed by the end of May. Similar preparation activities are being applied on materials in B2. Instead of placing materials into temporary storage, rack space will be freed up through deaccession activities and materials will be rearranged within B2 to create new egress space. Over 210,000 iron ore boxes will be repackaged and moved onto new rack units. Lighting upgrades have been implemented in portions of B2, with the remaining lights to be replaced later this year. The DCL remains partially open to visitors, but users should be aware that materials from B1 and B2 may be unavailable until the project is completed on or before June 30, 2026. The DCL is nearing its facility-wide storage capacity and there is very limited space to accept additional materials. The DNR is only accepting deliveries on a case-by-case basis, and it is expected that any materials turned over to the state will become public upon delivery. In 2017, recognizing that the DCL was rapidly filling up, the DNR designed and actively sought funding for a fourth building to double the facility-wide storage capacity and quadruple view room space. This project is shovel-ready, but construction remains on hold until funding is legislatively secured. 19 �20 �Geology and Mineralization of the Plover Au Prospect, Marathon County, Wisconsin CASPER, Andrew A.1, LODGE, Robert W.D.1 1 Department of Geology and Environmental Sciences, University of Wisconsin-Eau Claire, Eau Claire, WI 54701 USA The Plover Au Prospect, located in Marathon County, WI, is hosted in Paleoproterozoic metaandesites, schist, and felsic/mafic intrusive units of the Wausau Volcanic Complex (LaBerge & Myers, 1983). Gold prospects in this region are bound to the southeast and northwest by large faults within the Eau Claire Deformation zone and the Wolf River Batholith (Lynott et al, 2022) (Figure 1). Rocks have undergone potassic and sericite alteration, greenschist to amphibolite grade metamorphism, and multiple stages of deformation. Research on the formational history of gold mineralization, in combination with its geochemical footprint, is essential for establishing a regional geologic setting of gold-forming events. Previous mineral exploration on this area has focused on exploring high concentrations of gold (Au) within volcanic units and sulfide vein networks at the Reef Deposit (Figure 1). With its proximity to the larger Reef Deposit, a more complete understanding of the Plover Prospect can add to a better regional context to the Au mineralizing system and potentially improve mineral exploration models. For this study, two holes (PL-76-1 & PL-76-4), totaling ~1,180 linear feet of core were chosen based on their relative locations and lithologic variation to fully characterize the range of units hosting mineralization. Representative volcanic strata and intrusive rocks were sampled and characterized through petrographic and geochemical analyses. The Plover deposit is primarily composed of andesitic/basaltic volcanics and gabbro/diorite intrusive units deposited sequentially showing sharp and, in some cases, brecciated contacts with one another. Brittleductile deformation is indicated by zones of brecciation present within the volcanic units. These structures include vein networks containing boudins and vugs containing sulfides and calcitechlorite alteration. It is probable that multiple deformational events occurred due to veins crosscutting foliation locally, and variation in the internal composition of veins. Hydrothermal alteration is suggested based on the presence of potassic alteration within the basaltic foliation and sericite-chlorite alteration in layers. Pyrite, chalcopyrite and pyrrhotite occur within vein networks. Since high Au concentrations are typically present within massive/semi-massive sulfide veins which contain brittle to brittle-ductile deformation, this mineralization likely occurred after Penokean deformation and metamorphism that formed the primary structural fabric in the rocks. The Reef gold-copper deposit has been researched extensively by various exploration companies since the 1990’s (Lynott et al, 2022). The deposit is located <1 mi east of the Plover deposit and has shown significantly higher Au concentrations. The deposit has been broadly classified as orogenic in origin and is claimed to have produced shear hosted vein-type gold and copper occurrences. Gold/copper mineralization occurs within stacked and relatively thin zones of quartz-sulfide veins and lenses; and sericite alteration within vein selvage typically accompanies gold mineralization within these areas. The primary lithology between the two deposits is similar, however, the Reef deposits proximity to the Wolf River batholith potentially influenced the degree of deformation and sericite, talc, tremolite, and pyrrhotite alteration. Future research should focus on more detailed comparisons between the Reef and Plover gold systems to better constrain potential genetic links between them. 21 �Figure 1. The relative geographic locations of the Plover and Reef deposits in the Penokean Volcanic Belt (PVB), central Wisconsin. Plover Au prospect is bounded to the east by the Eau Claire fault zone and the Wolf River Batholith. Figure has been adapted from Dematties (2022) and Lynott et al, (2022). REFERENCES LaBerge, G.L., and Myers, P.E., 1983a, Precambrian geology of Marathon County, Wisconsin: Information Circular, v. 45. Lynott, J.S., and Dematties, T.A., 2022, An Evaluation of the Reef Gold-Copper Deposit, Marathon County, Wisconsin, USA, NI 43-101 Technical Report, 402p. DeMatties, T.A., 2022, Exploration-resource assessment of productive felsic volcanic centers in the paleoproterozoic penokean volcanic belt of northern Wisconsin, Michigan and East-central Minnesota, USA: Ore Geology Reviews, v. 141, p. 104489. 22 �Unusual early diagenetic structures in the Paleoproterozoic Gunflint Formation, Ontario, Canada CHURCHLEY, Sophie1, FRALICK, Philip2 1 Ontario Geological Survey, 435 James St S, Suite B002, ON P7E 6S7 Canada 2 Department of Geology, Lakehead University, 955 Oliver Road, Thunder Bay, ON P7B 5E1 Canada Newly identified microbial and diagenetic structures in the Gunflint Formation from the Thunder Bay area provide additional information to further our understanding of the environment in which these sediments were deposited and the diagenetic processes that affected them. Along the Current River, a horizon of carbonate lenses outcrop within a shale sequence. The structures are oblate in shape and range from approximately 0.5-1 m in diameter and 20-30 cm in height. Internally, the lenses are mostly calcite that displaces fine-grained siliciclastic laminae and preserves several interesting structures including cone-in-cone, inverted cuspate fenestrae and feather-like and braided fabrics. Some faces also display features that are more ‘fern-like’ in appearance and migrate up and across the surface of the oblate carbonate pods. We propose that these are oblate carbonate concretions formed via carbonate precipiation during diagenesis within a sequence of organic-rich laminated shales and siltstones. Several important features observed in the Gunflint Formation suggest that these structures formed via diagenetic processes including the similarities in stratigraphic placement within organic-rich shaley horizons and the light δ13Сcarb values recorded in the carbonate fraction. Cone-in-cone structures have been identified in both hand sample and thin section, displaying similarities to structures described from other locales (Figure 1A,B). Cone-in-cone structures occur in calcite-cemented sandstones or at the edges of disc-like to ellipsoidal concretions ranging in size from decimeters to meters long within shale beds in Erfoud, Morocco (Lugli et al. 2005). This stratigraphic positioning and size is consistent with what has been observed in the Gunflint Formation oblate concretions that host the cone-in-cone layers. Likewise, jagged ‘sawtoothed’ draping laminae that were identified in the Gunflint Formation are similar in appearance to those identified from cone-in-cone structure in the Devonian Middle Timan Formation in Russia (Figure 1C,D) (Shumilov 2020). The formation of cone-in-cone structure is still not well understood and numerous hypotheses have been proposed (see Lugli et al. 2005 and references therein). It is commonly associated with concretions and organic-rich sediments. The oblate carbonate horizons are located stratigraphically within a sequence of carbonaceous black shales near the base of the Upper Member of the Gunflint Formation with abundant evidence of microbially induced sedimentary structures (MISS) (Fischer and Fralick 2020). δ13Сcarb analyzed from the carbonate fraction in the Gunflint Formation samples displayed light values ranging from -12.29‰ to -0.17‰ with most values clustering near -10‰. These values are coincident with precipitation occurring in the zones of Fe, Mn, and/or sulfate reduction with relatively low rates of organic-carbonate oxidation and are consistent with ferruginous, reducing conditions (Mozley and Burns 1993). 23 �Figure 1. A. 1-3 cm scale cone-in-cone structure consisting of beige fibrous calicite draped by thin black siliciclastic films. B. Thin section close up of cone-in-cone structure from Permian carbonates in Thailand that is similar in appearance to those observed in the Gunflint Formation (see figure 3C; Chenrai et al. 2022). C. Hand sample of a carbonate-rich horizon displaying jagged ‘saw-toothed’ laminae near the top. D. Close-up image of similar jagged laminae from the Devonian Middle Timan Formation in Russia (see figure 9A; Shumilov 2020). At this location, the jagged laminae are associated with cone-in-cone structure. References Chenrai P., Assawincharoenkij T., Warren J., Sa-nguankaew S., Meepring S., Laitrakull K. and Cartwright I. (2022) The Occurrence of Bedding-Parallel Fibrous Calcite Veins in Permian Siliciclastic and Carbonate Rocks in Central Thailand. Front. Earth Sci. 9:781782. doi: 10.3389/feart.2021.781782. Fischer, S. and Fralick, P. (2020) Biological mats in siliciclastic sediments of the Paleoproterozoic Gunflint Formation, northwestern Ontario, Canada. Can. J. Earth Sci. 57: 947–953. Lugli, S., Reimold, W. and Koeberl, C. (2005). Silicified Cone-in-Cone Structures from Erfoud (Morocco): A Comparison with Impact-Generated Shatter Cones. doi: 10.1007/3-540-27548-7_3. Mozley, P.S. and Burns, S.J. (1993) Oxygen and carbon isotopic composition of marine carbonate concretions: an overview. Journal of Sedimentary Research 63, 73–83. Shumilov I.Kh. (2020) Сone-in-cone structure: New data. Litosfera, 20(1), 76-92. doi: 10.24930/16819004-2020-20-1-76-92. 24 �Alteration of magnetic mineralogy in the Giants Range Batholith by the Duluth Complex CORTOPASSI, Celia L., ALLERTON, Zsuzsanna P., FEINBERG, Joshua M. Department of Earth and Environmental Sciences, University of Minnesota, Suite 150, 116 Church St SE, Minneapolis MN 55455 During the Midcontinent Rift event (ca. 1.1 Ga) of the North American craton, the Duluth Complex (DC), a large mafic igneous intrusion, was emplaced into the Neoarchean Giants Range Batholith (GRB; ca. 2.7 Ga) in northeastern Minnesota, thermally altering the granitic country rock (Allison, 1925).The basal mineralized zone of the DC has been well-studied with regard to sulfide deposits, but the extent of alteration within the GRB footwall has not been as well constrained. Previous research has indicated the presence of sulfides at the DC-GRB contact, extending about hundred meters into the GRB (Steiner, 2014), and prior petrographic analysis has revealed textures consistent with contact metamorphism that diminish with distance from the contact (Pardi, 2024). This project seeks to define the magnitude of alteration within the GRB and to further characterize the orientation of the intrusion. This project utilizes a profile of 13 outcrop samples from the GRB that were collected systematically at distances between 100 and 4500 meters from the DC-GRB contact. We characterize changes in magnetic mineralogy as a function of distance from the DC-GRB contact using measured optical microscopy, electron microscopy, and magnetic properties (susceptibility and parameters calculated from hysteresis loops and backfield curves). These data reveal a distinguishable and consistent pattern in magnetic properties as a function of distance from the contact and distinct zones of textural alteration in oxide minerals (Figure 1). Patterns in smallscale magnetic properties broadly align with the large-scale trends seen in aeromagnetic data (Minnesota Geological Survey, n.d.), including changes in magnetic properties co-located with mapped faults (Jirsa et al., 2011). The orientation of the DC-GRB contact was examined using information from previously-drilled exploration drill holes (Minnesota Department of Health, n.d.) that penetrated through the DC and into the GRB. These observations, as well as outcrop measurements of modal layering and igneous foliation within the DC (Minnesota Geological Survey, 2023), constrain the orientation of the present-day DC-GRB contact to between 16-24° towards the east. The original depth of the modern day exposure of the DC-GRB remains unknown, as does any component of subsidence that occurred since the Midcontinent Rift event. Future work may include the collection of oriented samples for paleomagnetic studies, which would help constrain both the extent of thermal reheating of the GRB and postemplacement subsidence. Thermal modeling of the subsurface DC-GRB contact at various depths, alongside observed patterns in oxide mineral textures, could produce estimates of the extent of subsurface contact metamorphism. With these methods, we hope to better understand the conditions under which the DC was emplaced and accommodated, as well as estimate the thickness of Precambrian rock that has since been eroded away. 25 �Figure 1. A: Distribution of identified textures (A-E) as a function of distance from the DC-GRB contact. B: Measured magnetic properties as a function of distance from the DC-GRB contact. REFERENCES Allison, I. S.,1925. The Giants Range Batholith of Minnesota. The Journal of Geology, 33(5), 488–508. https://www.jstor.org/stable/30057863. Jirsa, M., Boerboom, T., Chandler, V. W., Mossler, J., Runkel, A., & Setterholm, D., 2011. S-21 Geologic Map of Minnesota-Bedrock Geology. https://conservancy.umn.edu/items/96de8d96-46ba441c-94ca-41080b4335be Minnesota Department of Health, n.d.. Minnesota Well Index (MWI). https://mnwellindex.web.health.state.mn.us/. Minnesota Geological Survey, n.d.. Collection of aeromagnetic data from Minnesota. https://doi.org/10.5066/P14LP38P. Minnesota Geological Survey, 2023. D-06, Structure Database. https://arcg.is/jfCLD. Pardi, L., 2024. Petrographic Analysis of the Giants Range Batholith in Northeastern Minnesota. Steiner, R. A., 2014. Genesis of sulfide mineralization within the granite footwall of the Maturi deposit of the South Kawishiwi intrusion, Duluth Complex, NE Minnesota. https://hdl.handle.net/11299/169376. 26 �Architecture of the Douglas Fault damage zone, northwest Wisconsin DANIELS, Nate, MCELLISTREM, Grace, VOGEL, Raeann, and BRAUNAGEL, Michael Department of Earth & Environmental Sciences, University of Minnesota Duluth, 1114 Kirby Drive Duluth, MN 55812 USA Major faults in the upper crust can be divided between the fault core, where most of the displacement is accommodated, and a surrounding damage zone (Faulkner et al., 2010). Fracturing in this damage zone occurs across a range of scales and intensity, varying from regularly spaced joint or deformation band sets to pervasive pulverization of the host rock. As such, fault damage zones can serve as fluid pathways, which control the migration of hydrothermal fluids and can alter the frictional strength of seismogenic fault systems. A number of processes are responsible for formation and evolution of a fault’s damage zone, including microfracturing within the process zone during fault propagation, localized wear along irregular fault surfaces, and volumetric changes associated with dynamic rupture propagation (Mitchell & Faulkner, 2009). As each process leaves a unique record in the fault system, the distribution and intensity of fault damage zones can provide insight into past fault activity and its relationship to fluid flow in the crust (Blenkinsop, 2008). This study presents preliminary observations of the fault-related damage surrounding the Douglas Fault from Amnicon and Pattison State Parks in northwestern Wisconsin. The Douglas Fault was activated during structural inversion of the Midcontinent Rift and previous work estimates its vertical displacement at ≳10 km (Grant, 1901; Cannon, 1994; Nicholson et al., 2006; Hodgin et al., 2024). At our study sites, the fault places basalts of the mid-continental rift Chengwatana volcanic group over post-rift siliciclastic sandstones of the Bayfield Group. Field and thin section observations along the fault system reveal pronounced damage zone asymmetry, with a hanging wall damage zone that is several times the width of the damage zone in the footwall. Chengwatana volcanics in the hanging wall are intensely fractured at the grain scale and cut by multiple generations of primarily calcite-filled opening mode veins. These veins and fractures broadly show two distinct orientations; one set striking generally NE to SW and the second characterized by NW to SE strikes. The damage-zone width is constrained by identifying changes in the slope of cumulative damage frequency plots, which shows high deformation frequency as a steep slope within an inner damage zone and less deformation decaying to background levels as a gentle slope in the outer damage zone of the Douglas Fault. Collectively, the full thickness of the hanging wall damage zone is >100 m (Grant, 1901). In contrast, sandstones of the Bayfield Group in the footwall exhibit lower frequency fracturing at the outcrop scale, no apparent grain-scale fracturing in thin section, and compressional deformation bands defined by porosity reduction. Bayfield sandstones in the footwall at these sites are also deformed by faultpropagation and drag folding that extend for tens of meters beyond the fault contact (Hodgin et al., 2024). Field and thin section scale observations of fault damage in both units are consistent with ultrasonic pulse velocities measured in samples collected from the fault zone with a Proceq Pundit Lab system. 27 �REFERENCES Blenkinsop, T.G., 2008. Relationships between faults, extension fracture and veins, and stress. Journal of Structural Geology, 30 (5), 622-632. Cannon, W.F., 1994. Closing of the Midcontinent Rift - A far-field effect of Grenvillian compression. Geology, 22 (2), 155-158. Faulkner, D.R., Jackson, C.A.L., Lunn, R.J., Schlische, R.W., Shipton, Z.K., Wibberley, C.A.J., and Withjack, M.O., 2010. A review of recent developments concerning the structure, mechanics and fluid flow properties of fault zones. Journal of Structural Geology, 32 (11), 1557-1575. Grant, U.S., 1901. Preliminary report on the copper-bearing rocks of Douglas County, Wisconsin (No. 3). Hodgin, E.B., Swanson-Hysell, N.L., Kylander-Clark, A.R.C., Turner, A.C., Stolper, D.A., Ibarra, D.E., Schmitz, M.D., Zhang, Y., Fairchild, L.M., and Fuentes, A.J., 2024. One billion years of stability in the North American midcontinent following two-stage Grenvillian structural inversion. Tectonics, 43 (9). Mitchell, T.M., and Faulkner, D.R., 2009. The nature and origin of off-fault damage surrounding strikeslip fault zones with a wide range of displacements: A field study from the Atacama fault system, northern Chile. Journal of Structural Geology, 31 (8), 802-816. Nicholson, S.W., Cannon, W.F., Woodruff, L.G., and Dicken, C., 2006. Bedrock geologic map of the Port Wing, Solon Springs, and parts of the Duluth and Sandstone 30’x60’ Quadrangles, US Geological Survey. 28 �The Archean Carney Lake gneiss complex in Michigan’s Upper Peninsula: Preliminary subdivisions with age constraints DeGRAFF, James1, DEERING, Chad1, and JONES III2, James 1 Department of Geological & Mining Engineering & Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 U.S.A. 2 U.S. Geological Survey, Alaska Science Center, 4210 University Drive, Anchorage, AK 99508 U.S.A. Much of the Precambrian bedrock in Michigan’s Upper Peninsula was last mapped at 1:24000 scale prior to modern tectonic concepts and advances in understanding related structural, magmatic, and metamorphic processes. A later decline in base and ferrous metal mining in the region reduced interest in commercial and scientific investigations, however recent concerns about the supply of critical minerals has renewed interest in developing an improved geologic framework for ore deposit exploration. The Archean Carney Lake gneiss complex (CLGC) and other granitegneiss complexes south of the Great Lakes tectonic zone are in the Minnesota River Valley subprovince of the southern Superior craton (Sims and Day, 1993). The CLGC, like the other complexes, is surrounded by Paleoproterozoic continental margin strata, partly older than and partly coeval with Penokean orogenesis (~1.85 Ga) that deformed the region (Schulz and Cannon, 2007). Bayley et al. (1966) describe the CLGC as predominantly felsic gneiss but with ~10% mafic inclusions and ~5% younger granodiorite and syenite intrusions by area. Mapping funded by the USGS Earth MRI program has revealed a wider variety of rocks than previously reported, differences in metamorphic grade, and new structural relationships (DeGraff et al., 2023). Felsic intrusions with little to no foliation are more abundant and varied than previously thought, ranging from granitic to tonalitic to locally syenitic. The original classification of gneiss based on mineralogy has been revised by also considering fabric characteristics. Consequently, we have identified an older EW-elongate core of thickly banded (≥2 cm) poly-deformed gneiss characterized by tightly folded banding, discordant banding across shear zones, and dismembered mafic pods (Fig. 1, area 1). Younger, less deformed, Archean rocks flank the older terrane, except on the north, and include the widespread felsic intrusions and thinly banded (≤1 cm), quartzo-feldspathic, gneissic rocks. The latter have quasi-planar, laterally continuous banding and local textures resembling cross-bedding and relict grains, suggesting derivation from a siliciclastic protolith. Boundaries between the older deformed gneiss terrane, the younger gneissic terrane with relict features, and areas with felsic intrusions are not yet well defined nor is their nature well understood. In addition to the above, at least four generations of mafic to ultramafic magmas have intruded the CLGC up to the late Mesoproterozoic. Our results, combined with those of others, indicate a long and complex tectonomagmatic history for the CLGC and adjacent rock units. The poly-deformed gneiss terrane includes rocks with inherited zircon cores dated at ca. 3750 Ma (Eoarchean) and recrystallized zircons and overgrowths dated at ca. 2750 Ma, the latter having formed during a Neoarchean thermal event (Ayuso et al., 2018). Neoarchean metamorphism of the Eoarchean gneiss, and perhaps much of its deformation, was accompanied by widespread felsic intrusions based on new zircon LA-ICPMS U-Pb dates ranging from ca. 2810 Ma to 2670 Ma (8 sites). Zircon trace-element analysis indicates that these magmas came from a hydrous oxidizing source and were contaminated while passing through a relatively thick crust, as is typical of magma generated during modern subduction. At the northern and eastern margins of the CLGC, relatively undeformed gneissic rocks were probably derived in part from siliciclastic protoliths of Neoarchean age. At the northern margin, 29 �however, NE-dipping beds of Paleoproterozoic Sturgeon Quartzite are parallel to well-defined layers of quartzo-feldspathic gneissic rocks along strike to the east. Field relationships and detrital zircon analysis suggest two scenarios: 1) a lateral facies change within Sturgeon Quartzite from meta-arkose on the east to meta-sandstone on the west, or 2) an onlapping relationship between younger quartzite and its parent Neoarchean meta-arkose. Figure 1: Preliminary subdivisions of the Archean Carney Lake gneiss complex (CLGC = 1, 2a, 2b, 3, Agu_clg). 1 = poly-deformed; 2 = metaigneous, 3 = meta-sedimentary; Agu_clg = undifferentiated; Xmrs = Paleoproterozoic Marquette Range Supergroup; Pz = Paleozoic clastic strata. Study area outlined in purple. REFERENCES Ayuso, R.A., Schulz, K.J., Cannon, W.F., Woodruff, L.G., Vazquez, J.A., Foley, N.K., and Jackson, J., 2018. New U-Pb zircon ages for rocks from the granite-gneiss terrane in northern Michigan: evidence for events at ~3750, 2750, and 1850 Ma. Institute on Lake Superior Geology, 64th Annual Meeting Proceedings, Part 1-Program and Abstracts, 64: 7-8. Bayley, R.W., Dutton, C.E., and Lamey, C.A., 1966. Geology of the Menominee Iron-Bearing District, Dickinson County, Michigan and Florence and Marinette Counties, Wisconsin. U.S. Geological Survey, Professional Paper 513: 1-96. DeGraff, J.M., Gannon, I.M., Deering, C.D., Smirnov, A.V., 2023. Bedrock geology of southeastern Dickinson County, Michigan: Vulcan 7.5’ quadrangle and adjacent parts of the Carney Lake, Cunard, Faithorn, Felch, Foster City, and Waucedah 7.5’ quadrangles. Michigan Geological Survey, Bedrock Geologic Map, 1:25,000 scale map sheet with explanatory text. Schulz, K.J. and Cannon, W.F., 2007. The Penokean orogeny in the Lake Superior region. Precambrian Research, 157: 4-25. Sims, P.K. and Day, W.C., 1993. Great Lakes tectonic zone – revisited. U.S. Geological Survey, Bulletin 1904-S: S1-S11. 30 �Geochronology of lithium mineralization in the Florence pegmatite field, WI, USA DROUBI, Omar Khalil1, SCHOONOVER, Erik2, SIRBESCU, Mona-Liza3, GARBER, Joshua2, BONAMICI, Chloë1 Department of Geoscience, University of Wisconsin-Madison, 1215 W. Dayton Street, Madison, Wisconsin, 53706, USA 2 Department of Geosciences, The Pennsylvania State University, University Park, PA, USA 3 Geology Department, Central Michigan University, 314 Brooks Hall, Mount Pleasant, MI 48859, USA 1 Global and national progression toward decreasing reliance on fossil fuels will correlate with increasing the supply of mineral resources that contain high concentrations of elements like lithium, copper, or rare earth elements– “critical minerals” deemed essential for building low-CO2 technologies. Lithium-cesium-tantalum (LCT) pegmatites are a significant component of global lithium production; despite their importance, the tectonomagmatic mechanisms by which these pegmatites form are not completely understood. The two main models for LCT pegmatite formation are 1) as late-stage fractionation products of nearby peraluminous granites (“fractionation origin”) (e.g., Černý, 1991) or 2) directly from partial melts of Li-bearing highgrade metamorphic rocks (“anatectic origin”) (e.g., Knoll et al., 2023; Koopmans et al., 2023). These models have implications for LCT pegmatite exploration (i.e., mapping outward from plutons or anatectic zones in mountain belts) and testing them requires precise age estimates for the pegmatites and their neighboring magmatic and metamorphic rocks. This study provides new age constraints for models of LCT pegmatite mineralization in Florence County, WI, USA. (Falster et al., 2005; Falster et al., 1996; Sirbescu et al., 2008) by applying LA-ICP-MS U-Pb geochronology and trace-element analysis to apatite crystallized within the LCT pegmatites and titanite in the proximal wall rock and a separate, non-mineralized granitic pegmatite located >1.8 km away (Figure 1). The Florence LCT pegmatites were emplaced <2.5 km south of the Niagara Fault Zone and are hypothesized to be fractionated products from the nearby Bush Lake granite (undated, but hypothesized ~1835 Ma; Sims et al., 1985) or anatectic melts of the wall rock, the metavolcanic/metasedimentary Quinnesec Fm. (~1866 Ma; Sims et al., 1985). These models suggest pegmatite emplacement is broadly bracketed in space and time by the end of the Penokean orogeny (~1835 Ma) and Yavapai arc accretion (~1750–1700 Ma) (Figure 1). The apatite grains from the King’s X and Animikie Red Ace LCT pegmatites have U-Pb dates of 1446 ± 6 [29] Ma and 1432 ± 4 [29] Ma, respectively. The targeted apatite grains, which nucleated in the pegmatite chilled margin at the wall rock contact, are interpreted as magmatic based on oscillatory cathodoluminescence zoning (Sirbescu et al., 2009). Xenoblastic titanite from the Quinnesec Fm., sampled at distances <1 cm to ~150 m from the pegmatites, have U-Pb ages of 1473 ± 7 [29] Ma (<1 cm), 1466 ± 7 [29] Ma (<5 m), 1436 ± 13 [29] Ma (60 m), and 1471 ± 8 [29] Ma (150 m), but euhedral titanite grains from the non-mineralized granitic pegmatite have a U-Pb age of 1811 ± 10 [36] Ma. Our data indicate that the Florence LCT pegmatites did not result from fractionation of the Bush Lake granite nor anatexis during the Penokean or Yavapai orogenies and are instead coeval with emplacement of the ~1476 Ma Wolf River batholith further south. A revised age model for lithium mineralization in northern WI suggests involvement of the Wolf River batholith or far-field influence of the Mesoproterozoic Pinware-Baraboo-Picuris orogeny. 31 �Figure 1. Conceptual cross section (not to scale) showing age constraints for the Florence pegmatite field. Hypothesized ages based on the following references: Bush Lake granite and Quinnesec Fm. (Sims et al., 1985), metagabbro (Guice et al., 2023). U-Pb dates reported as: date ± internal 2s [external uncertainty=2% of date]. REFERENCES Bradley, D.C., McCauley, A.D., and Stillings, L.M., (2017), Mineral-deposit model for lithium-cesiumtantalum pegmatites: U.S. Geological Survey Scientific Investigations Report 2010–5070–O, 48 p., https://doi.org/10.3133/sir20105070O. Černý, P., 1991, Rare-element Granitic Pegmatites. Part II: Regional to Global Environments and Petrogenesis: Geoscience Canada, v. 18, p. 68–81, Falster, A. U., Simmons, W.B., and Webber, K.L. (2005), Origin of the pegmatites in the Hoskin Lake pegmatite field, Florence Co., Wisconsin, in Crystallization Processes in Granitic Pegmatites, International Meeting in Cavoli, Elba Island, Italy, May 23–28, 2005, edited by F. Pezzotta, Mineral. Soc. of Am., Chantilly, Va. Falster, A. U.; Simmons, Wm. B.; and Webber, K. L. (1996) The Mineralogy and Geochemistry of the Animikie Red Ace Pegmatite, Florence County, Wisconsin. In Pandalai, S. G., ed., Recent Research Developments in Mineralogy, 7-67. Guice, G. L., Viete, D. R., Holder, R. M., & Roy, S. (2023). A c. 1900 Ma Tethyan-type ophiolite in the Penokean Orogen, Pembine, Wisconsin (USA): Insights from the volcanic stratigraphy. Precambrian Research, 399, 107223. Knoll, T., Huet, B., Schuster, R., Mali, H., Ntaflos, T., & Hauzenberger, C. (2023). Lithium pegmatite of anatectic origin-A case study from the Austroalpine Unit Pegmatite Province (Eastern European Alps): geological data and geochemical model. Ore geology reviews, 105298 Koopmans, L., Martins, T., Linnen, R., Gardiner, N.J., Breasley, C.M., Palin, R.M., Groat, L.A., Silva, D., and Robb, L.J., (2023). The formation of lithium-rich pegmatites through multi-stage melting. Geology. Sims, P. K., Peterman, Z. E., & Schulz, K. J. (1985). The Dunbar Gneiss-granitoid dome: Implications for early Proterozoic tectonic evolution of northern Wisconsin. Geological Society of America Bulletin, 96(9), 1101-1112. Sirbescu, M. L. C., Hartwick, E. E., & Student, J. J. (2008). Rapid crystallization of the Animikie Red Ace Pegmatite, Florence county, northeastern Wisconsin: inclusion microthermometry and conductivecooling modeling. Contributions to Mineralogy and Petrology, 156, 289-305. Sirbescu, M. L. C., Leatherman, M. A., Student, J. J., & Beehr, A. R. (2009). Apatite textures and compositions as records of crystallization processes in the Animikie Red Ace pegmatite dike, Wisconsin, USA. The Canadian Mineralogist, 47(4), 725-743. 32 �Experimental Reproduction of Acidic Mafic-Ultramafic Hydrothermal Fluids with Implications for Linking Seafloor Lithology to Ore Mineral Solubility and Novel Geochemical Trapping Mechanisms EVANS, Guy N.1 and SEYFRIED JR., William E.1 1 Department of Earth and Environmental Sciences, University of Minnesota, 116 Church St SE, Minneapolis, MN, 55455, United States Ultramafic-hosted seafloor massive sulfide (UM-SMS) deposits constitute a distinct class of CuZn-Co-Ni-Au-rich seafloor hydrothermal deposits (Fouquet et al., 2010). However, ultramafichosted volcanogenic massive sulfide (UM-VMS) deposits have been historically overlooked, in part because the formation of UM-VMS deposits differs from traditional VMS genetic models based on basalt-hosted SMS deposits (Pattern et al., 2022). Adding to this complexity, ultramafic-hosted seafloor hydrothermal fluids span nearly the full range of pH and metal concentrations observed at active seafloor hydrothermal vents, from highly acidic (pH= 2.8), metal-rich (Fe > 20 mmol/kg) fluids observed at Rainbow Hydrothermal Field (Douville et al., 2002), to alkaline (pH = 10.5), metal-poor (Fe < .02 mmol/kg) fluids observed at Lost City Hydrothermal Field (Kelley et al., 2005; Evans et al., 2024). Here, we present results from recent experiments conducted at the University of Minnesota that for the first time reproduce acidic hydrothermal fluids from mixed mafic-ultramafic source minerals. The observed acidity of these fluids results from temperature-dependent fluid-rock reactions and superimposed geochemical and physical processes. We further highlight the implications of these findings for UM-VMS deposit models, including novel geochemical trapping mechanisms potentially relevant in areas exhibiting significant ultramafic volcanic/intrusive rocks. Regional examples include the Newton Belt (northeast Minnesota), Shebandowan Belt (northwestern Ontario), and Kidd-Monroe assemblage (eastern Ontario and Quebec). REFERENCES Douville, E., et al., (2002). The rainbow vent fluids (36 14′ N, MAR): the influence of ultramafic rocks and phase separation on trace metal content in Mid-Atlantic Ridge hydrothermal fluids. Chemical Geology, 184(1-2), 37-48. Evans, G. N. et al. (2024). Transition metals in alkaline Lost City vent fluids are sufficient for early-life metabolisms. Geochimica et Cosmochimica Acta, 385, 61-73. Fouquet, Y. et al. (2010). Geodiversity of hydrothermal processes along the Mid‐Atlantic Ridge and ultramafic‐hosted mineralization: A new type of oceanic Cu‐Zn‐Co‐Au volcanogenic massive sulfide deposit. Diversity of hydrothermal systems on slow spreading ocean ridges, 188, 321-367. Kelley, D. S. et al. (2005). A serpentinite-hosted ecosystem: the Lost City hydrothermal field. Science, 307(5714), 1428-1434. Patten, C. G. et al. (2022). Ultramafic-hosted volcanogenic massive sulfide deposits: an overlooked subclass of VMS deposit forming in complex tectonic environments. Earth-Science Reviews, 224, 103891. 33 �34 �Textural and chemical analysis of sphalerite ores from the Highland Subdistrict, Upper Mississippi Valley Zinc-Lead District, Wisconsin FITZPATRICK, William1 1 Wisconsin Geological and Natural History Survey, 3817 Mineral Point Rd. Madison, WI, USA Lead + zinc ± barite ± copper deposits are widespread in Ordovician carbonate rocks of southwestern Wisconsin and the bordering areas of Illinois and Iowa, commonly referred to as the Upper Mississippi Valley zinc-lead district (UMVD). Sphalerite, the primary zinc ore mineral in the UMVD, is known from other mining districts to contain valuable byproduct commodities as trace elements such as gallium, germanium, cadmium and silver. Several previous studies have examined sphalerite from the UMVD, but focused on samples from the southern part of the district (Hall and Heyl, 1968, McLimans and others, 1980). Zinc ores from other areas of the UMVD have received less attention, and little is known of their textural character and trace element content. This study presents new trace element data and textural observations of sphalerite ores from the Highland Subdistrict, the northernmost mining center in the UMVD. Two hand-picked sphalerite concentrates and thirty-five bulk ore samples were analyzed by whole rock geochemical methods, complemented by 282 in situ electron microprobe analyses on six thin sections from a mix of vein and disseminated ores. Textures in the sphalerite ores were also documented through scanning electron microscopy with the aim of understanding mechanisms that localized sulfide mineralization. Sphalerite from the Highland Subdistrict is characterized by alternating sequences of lighter, honey-colored bands and darker, reddish-brown bands in both the disseminated and vein hosted ores (Fig. 1). Microprobe analysis shows that darker bands tend to localize elevated iron and lower cadmium relative to lighter bands (Fig. 1). Silver content is variable, but tends to be higher in lighter bands, especially in the cores of disseminated grains. Comparing results from the whole rock and microprobe analyses from the Highland Subdistrict to sphalerite analyzed elsewhere in the UMVD, iron and cadmium are within known ranges, but silver is enriched to a significant degree (Hall and Heyl, 1968). Gallium and germanium abundances were too low to be detected in microprobe analyses, but whole rock analysis indicates they are towards the low end of the range observed in sphalerite from the UMVD (Hall and Heyl, 1968). Scanning electron microscope observation discovered abundant, texturally early framboidal pyrite intergrown with marcasite that is enveloped by later sphalerite. Framboidal pyrite has a well-documented association with sulfate reducing bacteria (e.g. Maclean and others, 2008), indicating bacterial processes were likely important in creating a reservoir of reduced sulfur within the carbonate host rocks. This in turn may have acted as a chemical trap for metals in migrating connate brines to form the zinc deposits. REFERENCES Hall, W.E., and Heyl, A.V., 1968, Distribution of Minor Elements in Ore and Host Rock, IllinoisKentucky Fluorite District and Upper Mississippi Valley Zinc-Lead District. Economic Geology, 63, 655-670. Maclean, L., Tyliszczak, T., Gilbert, P., Zhou, D., Pray, T., Onstott, T., and Southam, G., 2008, A high resolution chemical and structural study of framboidal pyrite formed within a low-temperature bacterial biofilm. Geobiology, 6, 471-480. McLimans, R.K., Barnes, H.L., and Ohmoto, H., 1980, Sphalerite Stratigraphy of the Upper Mississippi Valley Zinc-Lead District, Southwest Wisconsin. Economic Geology, 75, 351-361. 35 �Figure 1. Plots of iron, cadmium and silver along linear traverses through banded sphalerite crystals from the Highland Subdistrict. Top panel shows scans of the thin sections analyzed and locations of the analyses. Note the concentrically zoned disseminated grain (left) vs vein (right). 36 �Rare-element Geochemistry of the Eau Claire River Complex Pegmatites GRIES, Samara1, LODGE, Robert W.D1, HANEL, Sara1,2, HOOPER, Robert1 1 Department of Geology and Environmental Sciences, University of Wisconsin-Eau Claire, Eau Claire, WI 54701 USA 2 Current Affiliation: Department of Earth and Environmental Sciences, University of Minnesota Twin Cities, Suite 150, 116 Church St. SE, Minneapolis, MN 55455 Minerals, such as monazite and xenotime, are an important source of rare earth (La, Ce, Nd) and high field strength (Th, Nb, Zr) elements which are essential for modern energy, communication, and military technologies. These critical minerals are often sourced in pegmatites and are important exploration targets worldwide (Haque et al, 2014). The Paleoproterozoic Eau Claire Volcanic Complex (ECVC) is intruded by granitic pegmatite dikes that postdate peak metamorphism (Lodge et al, 2023), indicating they are unrelated to Penokeanaged orogenic events. The ECVC pegmatites are highly fractionated, garnet bearing, and contain a high concentration U, Th, La, Ce, and other rare earth elements. Based on major and trace element associations, the pegmatites in the ECVC are classified as NYF family pegmatites that contain Nb>Ta, REE, U, Th, Zr and are A- to I- types with peralkaline relationship (Cerny and Ercit, 2005). This study collected bedrock samples from several locations across the ECVC (Little Falls, North Fork, Muskeg Creek) (Figure 1). The pegmatite dikes can range in size from a few meters to 100 m in width near the North Fork of the Eau Claire River. They mainly intrude foliated and metamorphosed Paleoproterozoic to Archean tonalites, amphibolites, and gneisses. Samples from these pegmatites were analyzed for whole rock and mineral chemistries. Whole rock chemistry was analyzed on XRF and ICPMS whereas mineral chemistry was determined using SEM-EDS. All three locations have quartz, feldspar, plagioclase, biotite, and muscovite. The main mineralogy of Little Falls samples are albite and muscovite. Trace mineralogy of the Little Falls samples include Fe- and Mn-garnet, samarskite, columbite, zircon, and xenotime. Muskeg Creek samples contains both orthoclase and albite with biotite instead of muscovite. Trace mineralogy of the Muskeg Creek samples includes xenotime, monazite, and barite. The North Fork samples mainly contain albite with minor orthoclase and biotite. Trace mineralogy of the pegmatites in the North Fork area include in Fe- and Mn-garnets, monazite, xenotime, and thorite. The pegmatites from the ECVC are all low in Ca and have trace minerals with rare earth elements. They all contain with albite with low quantities of orthoclase and almost no anorthite. The North Fork and Muskeg Creek samples have more barium-rich minerals than Little Falls, which may be the result of fractionation of feldspars and plagioclase (Yu et al, 2007). Ba-rich minerals can also be a product of hydrothermal activity (Hanor, 2000), but there is no evidence of syn- to post-hydrothermal alteration of the pegmatites. Mn-rich garnets at Little Falls and North Fork indicate a higher degree of fractionation relative to Fe-garnets at Muskeg Creek (Hernández-Filiberto et al, 2021). North Fork and Muskeg Creek also had the largest crystals reaching over 20 cm in size. The North Fork is enriched in the heavy rare earth elements, U, and Th. In comparison, Little Falls has more light rare earth elements. Muskeg is also enriched in light rare earth elements in addition to an increased enrichment of heavy rare earth minerals like Gd and Dy. All three locations contain other metals such as Nb, Zr, Hf. 37 �Figure 1. Bedrock geologic map of the Eau Claire Volcanic Complex with site locations. North Fork depicts a pink pegmatite intruding into a grey tonalite. Muskeg Creek depicts a 6 m pegmatite dike with zoning. Little Falls shows a 13 m pegmatite dike. Map from Mudrey & Brown (1982). REFERENCES Cerny, P., and Ercit,T., 2005. The classification of granitic pegmatites revisited. The Canadian Mineralogist, 43: 2005-2026. Hanor, J.S., 2000, Barite-celestine geochemistry and environments of formation. In Alpers, C.N., Jambor, J.L., Nordstrom, D.K., eds. Reviews in Mineralogy and Geochemistry, 40: p. 193-275 Haque, N., Hughes, A.., Lim, S., Vernon, C., 2014, Rare Earth Elements: Overview of Mining, Mineralogy, Uses, Sustainability, and Environmental Impact: Resources, 3, p. 614-635 Hernández-Filiberto, L., Roda-Robles, E., Simmons, W.B., Webber, K.L., 2021, Garnet as Indicator of Pegmatites from the Oxford Pegmatite Field (Maine, USA): Minerals, 11(8), 802 Lodge, RWD, Weber, EM, Hooper, RL, 2023, Precambrian Geology of the Eau Claire River Valley: Rediscovering the Eau Claire Volcanic Complex. in Lodge, RWD (Ed.), Institute on Lake Superior Geology Proceedings, 69th Annual Meeting, Eau Claire, Wisconsin, Part 2 – Field Trip Guidebooks. v.69, part 2, p.47-70. Mudrey, M.G., Jr., Brown, B. A., Greenberg, J. K., 1982, "Bedrock Geologic Map of Wisconsin." Wisconsin Geological and Natural History Survey, scale 1:1,000,000 Yu, J.-H., O’Reilly, S. Y., Zhao, L., Griffin, W. L., Zhang, M., Zhou, X., Jiang, S.-Y., Wang, S.-Y., Wang, R.-C., 2007, Origin and evolution of topaz-bearing granites from the Nanling Range, South China: a geochemical and Sr-Nd-Hf isotopic study: Minerology and Petrology, 90, p. 271-300 38 �Revisiting Gravity and Magnetic Anomalies of the Baraboo Range HINZE, William J.1 and LONGACRE, Mark B.2 1 Purdue University, 30 Brook Hollow Ln., West Lafayette, IN 47906 2 MBL, Inc., 51 Captain Perry Dr., Phippsburg, ME 04562 The efficacy of gravity and magnetic methods of geological exploration have increased greatly since they were first used to investigate the Baraboo Synclinorium of Wisconsin nearly 75 years ago (Ostenso, 1953; Hinze, 1959). These methods and their associated technology are used for the first time since then to investigate the geology of the Mesoproterozoic Baraboo Synclinorium, its regional basement, and to illustrate the importance of modern data sets and analysis and interpretation methods. The latter are the result of computers for analysis, interpretation, and presentation of anomalies that were unavailable when the geophysical methods were first applied to mapping the Synclinorium. Analysis and interpretation of current gravity and magnetic anomaly data sets (Figure 1) indicate that the negative gravity anomaly associated with the Baraboo Synclinorium is not unique to the Synclinorium but is the southern termination of the Wisconsin Gravity Minimum (WGM) that covers a large portion of central Wisconsin including the Wolf River Batholith (WRB). The WGM is derived largely from felsic plutons in the upper crust extending outward from the ~1.5 Ga WRB. The lower density of the plutons compared to the metamorphosed orogenic rocks of the upper crust is the likely source of the negative gravity anomaly. The Synclinorium, located along an east-northeast trending gravity and magnetic lineament within the Yavapai orogenic province, occurs in a syncline of largely felsic volcanic rocks (Figures 2 and 3), the Sauk Syncline, that was likely deformed along with the Baraboo Synclinorium by south and southeast-verging thrusting during the Mazatzal and Picuris-BarabooPinware Orogenic events. Variations in thrusting has led to significant differences in the eastern and western portions of the Baraboo Synclinorium. Key results of the gravity and magnetic anomaly data analysis of the Synclinorium include: (1) The Baraboo Synclinorium’s negative gravity anomaly originates in upper crustal Yavapai and Wolf River Batholith felsic plutons that are the source of the Wisconsin Gravity Minimum. (2) The Synclinorium occurs within a synclinal structure resulting from deformation related to generally south-verging, thin-skinned thrust faulting that also produced the Baraboo Synclinorium. (3) The structure of the eastern and western portions of the Baraboo Synclinorium differ likely as a result of variations in the direction and intensity of thrusting during the Mazatzal and PicurisBaraboo-Pinware Orogenies (~1.63-1.41 Ga). REFERENCES Hinze, W.J., 1959. A gravity investigation of the Baraboo Syncline region. The Journal of Geology, 67(4), 417-446. Ostenso, Ned, 1953. Magnetic studies of the Baraboo Syncline. Unpublished M.A. thesis, University of Wisconsin-Madison. 39 �Figure 1. Gravity and magnetic anomaly maps of the Baraboo Synclinorium. Reduced to pole (RTP) total magnetic intensity anomaly map (right) eliminates the effect of the inclined earth’s magnetic field on the induced magnetization of the crustal rocks and the vertical gradient Bouguer gravity anomaly map of the Baraboo Synclinorium region (left) minimizes the regional gravity anomaly. The boundaries of the counties are indicated and the outline of the boundary of the Baraboo Synclinorium is the dashed white line. The white line interior to the Synclinorium is the boundary of the Freedom Formation. Color coding of both figures is non-linear. Figure 2. Tilt derivative of the Bouguer gravity anomaly map of the Baraboo Synclinorium region showing the outline of the Sauk Syncline in thick dashed white lines interpreted from the gravity and magnetic anomaly maps. The outline of the Baraboo Synclinorium is the thin dashed white line. The white line interior to the Synclinorium is the boundary of the Freedom Formation. Color coding is non-linear. Figure 3. High pass 10-km RTP magnetic anomaly map of the Baraboo Synclinorium region showing the outline of the Sauk Syncline in thick dashed white line interpreted from the gravity and magnetic anomaly maps. The outline of the Baraboo Synclinorium is the thin dashed white line. The white line interior to the Synclinorium is the boundary of the Freedom Formation. Color coding is non-linear. 40 �Emplacement of the Mesoproterozoic Wausau Syenite Complex, Wisconsin HULA, Linsey1 and CZECK, Dyanna1 1 Department of Geosciences, University of Wisconsin Milwaukee, Lapham Hall, Room 366, 3209 N. Maryland Ave. Milwaukee, WI 53211 The Wausau Syenite Complex (WSC) in Marathon County, Wisconsin is an intrusive complex of granitoids emplaced approximately 1.5 Ga (Dewane and Van Schmus, 2007). It is traditionally considered part of a major anorogenic ferroan granite magmatic event that affected the southern margin of Laurentia circa 1.4 Ga. Recent studies have recognized a Laurentian-scale accretionary margin between 1520-1340 Ma (Fig. 1), including the Pinware Orogeny in the northeast, the Picuris Orogeny in the southwest, and the most recently attributed section, the Baraboo Orogeny centered in Wisconsin (Daniel et al., 2023). This new hypothesis provides intriguing opportunities to reconsider the origin and tectonic setting of WSC emplacement as well as other Mesoproterozoic granitoids in Wisconsin, including the larger 1.4 Ga Wolf River Batholith (Dewane and Van Schmus, 2007). This research project will use the orientation of magnetic fabrics within the WSC to better understand how the batholith was emplaced. Figure 1: Simplified geologic map of Precambrian crustal provinces including the Mesoproterozoic accretionary margin of the Picuris, Baraboo, and Pinware Orogenies. The 1.48-1.35 Ga ferroan granites, including the Wolf River Batholith, are highlighted in white and the ~1.5 Ga Wausau Syenite Complex is added. Modified from Medaris et al., 2021, originally based on (Whitmeyer and Karlstrom, 2007). The project will consist of an anisotropy of magnetic susceptibility (AMS) survey and thin section analysis of each granitoid within the WSC. With these data, the magmatic flow directions and any subsequent tectonic overprint can be determined, which can be used to constrain the location of the magmatic feeder and the tectonic environment of emplacement. For the purpose of this abstract, three possible outcomes are proposed: 41 �1. Radial magmatic fabrics are preserved, indicating that the WSC was emplaced and cooled prior to the Baraboo Orogeny, with deformation accommodated by the surrounding weaker country rock (Fig. 2A). 2. Magmatic fabrics show a preferential flow pattern parallel to the tectonic margin caused by differential stress from the Baraboo Orogeny, suggesting syntectonic emplacement (Fig. 2B). 3. Only solid-state deformation fabrics are present, implying that the WSC was emplaced before or at the onset of the Baraboo Orogeny and had fully cooled before significant deformation occurred (Fig. 2C). By focusing on these oldest known Mesoproterozoic ferroan granites in the region, we can learn about the timing and geometry of the earliest Baraboo orogenesis. This study will address the question of how these enigmatic granites fit into the overall tectonic history of the Great Lakes Region. Figure 1: Schematic diagram of the WSC showing three possible outcomes of the AMS study. A) Radial magmatic fabric. B) Magmatic fabric with preferential flow parallel to the tectonic boundary. C) Solid state fabric. REFERENCES Daniel, C.G., Indares, A., Medaris Jr., L.G., Aronoff, R., Malone, D., and Schwartz, J., 2023. Linking the Pinware, Baraboo, and Picuris orogens: Recognition of a trans-Laurentian ca. 1520–1340 Ma orogenic belt, in Whitmeyer, S.J., Williams, M.L., Kellett, D.A., and Tikoff, B. eds., Laurentia: Turning Points in the Evolution of a Continent, Geological Society of America, 175–190. Dewane, T.J., and Van Schmus, W.R., 2007. U–Pb geochronology of the Wolf River batholith, northcentral Wisconsin: Evidence for successive magmatism between 1484Ma and 1468Ma: Precambrian Research, 157, 215–234. Medaris, L.G., Singer, B.S., Jicha, B.R., Malone, D.H., Schwartz, J.J., Stewart, E.K., Van Lankvelt, A., Williams, M.L., and Reiners, P.W., 2021. Early Mesoproterozoic evolution of midcontinental Laurentia: Defining the geon 14 Baraboo orogeny: Geoscience Frontiers, 12, 101174. Whitmeyer, S.J., and Karlstrom, K.E., 2007. Tectonic model for the Proterozoic growth of North America: Geosphere, 3, 220–259. 42 �Mapping oxidation reactions in iron-rich rocks from northeast Minnesota, USA. JAROZEWSKI, Sarah1, DUFFY, Paige1, BARRÉ, Cole1, BRENGMAN1, Latisha, EYSTER2, Athena 1 Department of Earth and Environmental Sciences, University of Minnesota Duluth, Heller Hall, 1114 Kirby Drive, Duluth, MN 55812, USA 2 Department of Earth and Climate Sciences, Tufts University, Lane Hall, 2 North Hill Road, Medford, MA 02155, USA Aqueous alteration and post-depositional mineral assemblage modification in Precambrian terranes are ubiquitous, but clear accounting of the relative timing of oxidation reactions at the landscape scale is limited. Here we synthesize observations of oxidation and hydration reactions in three iron-rich lithologies in northeast Minnesota, the Soudan Iron Formation, the Cuyuna Iron Formation, and the Partridge River Intrusion of the Duluth complex to contribute to building a compiled relative mineral redox history for the landscape. The Soudan Iron Formation (~2.7 Ga) is a greenstone-hosted metamorphosed chemical sedimentary unit primarily composed of alternating bands of magnetite, hematite and microquartz affected by at least two Archean deformation events, and later fluid alteration (Thompson, 2015). The Soudan Iron Formation primarily consists of mm-scale bands of authigenic microquartz and iron oxides that preserve in outcrop samples distal to the ore zone, and within the ore horizon at Soudan underground mine. Reflected light petrography of oxides in outcrop samples reveals magnetite replacement by hematite (Figure 1A). Within ore zone samples, complete hematite replacement and large platy hematite is common, similar to previous observations (Thompson, 2015). Clear metamorphic minerals that could indicate high temperatures, pressures, and P-T-path histories are absent from the unit. The younger Cuyuna Iron Formation (~1.9 Ga) is part of an intensely folded metamorphosed sedimentary sequence deformed during the Penokean orogeny (Schmidt, R.G., 1963). Combining new observations and previous data from historic samples (Melcher et al., 1996), oxidation of magnetite is prevalent but limited in samples from the Gloria drill hole (Figure 1B). Metamorphic stilpnomelane is common in the Cuyuna iron formation in contrast to the Soudan Iron Formation. Documented differences in metamorphic silicate mineralogy between these two iron formations may indicate key differences in precursor phases, as both units were affected by significant metamorphic deformation events. Yet, for both, oxidation of magnetite and replacement by hematite indicate both iron formations are similarly affected by post-depositional fluid alteration and oxidation. The Partridge River Intrusion (PRI) is part of the layered series troctolitic intrusions that form the base of the Duluth complex (Tyson and Chang, 1984). In its present geometry, the magmatic layered series PRI now intersects the current land surface. Clear evidence of aqueous alteration in the first few hundred feet of drill core 17700 includes mineral transformation of biotite and olivine to hydrous ferric oxides and secondary iron silicates (Figure 1C). These replacement reactions are limited in scale, and primary igneous mineralogy is still preserved. Leveraging cross-temporal comparisons of current iron-rich bedrock outcrop exposures and drill cores in north-east Minnesota to identify formational vs. post-formational mineralogy will allow for landscape-scale mapping of oxidation reactions and their extent in the subsurface. 43 �Figure 1. Reflected light photomicrographs of the Soudan iron formation, Cuyuna Iron formation and back-scatter electron image (BSE) of the Patridge River Intrusion of the Duluth complex. (A) Magnetite is partially replaced by hematite in the Soudan iron formation. (B) Magnetite oxidation to hematite in the Cuyuna iron formation. (C) Back-scatter electron image of altered olivine in the Partridge River Intrusion from the UMTC EPMA lab, CHARFAC facility.. REFERENCES Melcher, F., Morey, G. B., McSwiggen, P. L., Cleland, J. M., & Brink, S. E. 1996. RI-46 Hydrothermal Systems in Manganese-Rich Iron-Formation Of the Cuyuna North Range, Minnesota: Geochemical and Mineralogical Study of the Gloria Drill Core. Report of Investigations 46, ISSN 0076-9177, 1 - 45. Schmidt, R. G. 1963. Geology and ore deposits of the Cuyuna North range, Minnesota. U.S. Geological Survey Professional Paper 407, p. 96. Taylor, Richard B., 1964. Geology of the Duluth Gabbro Complex near Duluth, Minnesota. Bulletin No. 44. Minnesota Geological Survey, University Digital Conservancy. Thompson, A. 2015. A hydrothermal model for metasomatism of neoarchean Algoma-Type banded iron formation to massive hematite ore at the Soudan Mine, NE Minnesota. University of Minnesota, Duluth. P. 1-59. Tyson, R. M., and Chang, L, L, Y. 1984. The Petrology and sulfide mineralization of the Partridge River Troctolite, Duluth Complex, Minnesota. Canadian Mineralogist, v. 22, p 23-38. 44 �Geology and Geochemistry of the Mesoproterozoic Round Lake Intrusion and associated Ti-Mineralization, Northern Wisconsin JEUTTER, Renee O.1, LODGE, Robert W.D.1 1 Department of Geology & Environmental Science, University of Wisconsin-Eau Claire, 105 Garfield Avenue, Eau Claire, WI 54701, USA Modern technology and renewable energy require large amounts of metals that are currently imported, and there is a tremendous effort to domesticate our mineral extraction and processing. Several of these critical minerals, such as Ti, are found in Wisconsin, but little data is available to guide future mineral exploration efforts. The Mesoproterozoic Mid-Continent Rift and its satellite intrusions are known to host Ti-Fe oxide mineralization and Ni-Cu-PGE magmatic sulfide deposits (Woodruff, 2020). During the development of the Mid-Continent Rift, there is a temporal evolution of occurrences of mineral deposits. The plateau stage typically created Ni-Cu-PGE sulfide deposits, layered Ti-Fe oxide deposits, and alkalic hosted U-Nb deposits. The Round Lake Intrusion, like other intrusions discovered through a strong aeromagnetic anomaly (Mudrey et al. 2003), is an example of a layered Ti-Fe oxide deposit. Anorthosite layers alternate with magnetite troctolite layers approximately every 100 ft. Fractional crystallization throughout the evolution of the magma created the alternating “layers” of plagioclase rich and plagioclase poor segments but has minimal additional differences in mineral composition and presence (Stuhr, 1976). This study describes the petrology and geochemistry of the Round Lake intrusion and Timineralization using historic drill cores stored at the Wisconsin Geological and Natural History Survey core repository. Two holes were relogged, totaling ~1787 feet, and representative samples were obtained of host intrusive phases and mineralization types. The intrusion was characterized via transmitted-light petrography and whole rock geochemistry was determined via WD-XRF. Mineral chemistry of the intrusion and mineralization was determined using SEDEDS. The intrusion segregated into layers: anorthosite, upper magnetite troctolite, middle magnetite troctolite, magnetite, and lower magnetite troctolite, crosscut by an intrusive gabbro dike (Stuhr, 1976). The main intrusion hosting mineralization magnetite-ilmenite rich troctolite, ranging from 35-60% intergrown magnetite-ilmenite and 5-20% coarse grained plagioclase laths (Figure 1). Movement and flow of magmas during emplacement are indicated trachytic flow textures of aligned plagioclase crystals. The anorthosite has 55-90% euhedral plagioclase, 10-15% magnetite, and 5-15% clinopyroxene. The magnetite-ilmenite rich troctolite and anorthosite are crosscut by fine-grained gabbroic dikes. Within the magnetite-ilmenite troctolite unit, magnetitetitanomagnetite and lesser ilmenite assumes interstitial growth between silicates (Figure 1). Apatite is variably present. Olivine is variably altered to iddingsite and serpentine strips of magnetite forming within fractures in the crystal. Both the Round Lake intrusion and Clam Lake intrusion are intrusions rich in magnetite associated with the Mid-Continent Rift, and both are likely to be hosts of Ti-Fe ± V deposits and are known to contain large amounts of titanomagnetite with approximately 1.5% V (Woodruff, 2020). Future work is recommended on the Round Lake Intrusion and Ti-mineralization to better constrain the layering and economic potential of Ti-mineralization. 45 �Figure 1: (A) Geologic map of Northwestern Wisconsin region surrounding the Round Lake Intrusion, Digitized from Stuhr (1976). (B) Image of Magnetite-Ilmenite rich troctolite core sample showing textures and magnetite matrix filling features. (C) Image from SEM showing major magnetite and olivine textures within a sample. Magnetite matrix filling texture and fracture filling within olivine fractures. REFERENCES Stuhr, S. W., 1976, Geology of the Round Lake Intrusion, Sawyer County, Wisconsin [Master’s Thesis]: Madison, University of Wisconsin, 148 p. Woodruff, L. G., Schulz, K. J., Nicholson, S. W., Dicken, C. L., 2020, Mineral Deposits of the Mesoproterozoic Midcontinent Rift system in the Lake Superior region – A space and time classification: Ore Geology Reviews, v. 126, p. 1-21. Mudrey Jr., M.G., Ervin, C.P., Olmsted, J.F., 2003, Middle Keweenawan Basin Evolution Inferred from Geophysical Analysis of a Strongly Magnetic Intrusion, Clam Lake, Wisconsin: Wisconsin Geological and Natural History Survey, Open-file Report 2003-04, 17 p. 46 �Geology and Geochemistry of the Ritche Creek Cu-Zn deposit, North central Wisconsin JOHANNESEN, Haley P. 1, LODGE, Robert W.D.1 1 Department of Geology and Environmental Sciences, University of Wisconsin-Eau Claire, Eau Claire, WI 54701 USA The Ritchie Creek deposit is a Volcanogenic Massive Sulfide (VMS) deposit located within the Paleoproterozoic Penokean Volcanic Belt (PVB) of northcentral Wisconsin (Figure 1). Mineral exploration efforts have demonstrated that the VMS mineralization at this site is concentrated on the western edge of a felsic volcanic center that is interpreted to have formed in a back arc or intra-arc rift environment within bimodal volcanic sequences (DeMatties, 1990). These interpretations were based on physical descriptions of units intersected in drill core and comparisons to other VMS deposits regionally and globally. Like many VMS deposits in the PVB, little research has been done at the Ritchie Creek prospect to link petrogenesis with largerscale VMS environments. This research aims to characterize and refine the geological and geochemical characteristics of the Ritchie Creek Cu-Zn deposit by re-examining historic drill core and representative volcanic stratigraphic units and provide a more comprehensive understanding of the tectonic environment that influenced mineralization. The study involved logging 1,000 linear feet of historic drill core from two holes and collecting 22 core samples from representative stratigraphic units for petrographic and geochemical characterization. The four sampled units include: (1) a medium grey, fine grained quartz mica schist with alternating coarse-grained quartz and K-feldspar bands and disseminated sulfides including pyrite and chalcopyrite, (2) a light green quartz mica schist, strongly altered by sericite and chlorite, containing disseminated chalcopyrite and pyrite, (3) an intermediate metafelsite unit, characterized by sericite and biotite, that grades into a rhyolitic tuff with angular felsic fragments, localized sulfide blebs, and quartz veins, and (4) a semi-massive to massive sulfide unit consists mainly of pyrite with minor chalcopyrite, in a sheared and brecciated matrix. Major and trace element geochemical data was generated via WD-XRF at the Material Science Center at the University of Wisconsin-Eau Claire. Major element geochemistry is highly variable because of varying degrees of hydrothermal alteration. Therefore, immobile trace elements are used to classify protoliths and discriminate tectonic settings. Least-altered volcanic strata were chemically classified as mafic volcanics (based on low Zr/Ti, high Cr), intermediate volcanics (based on elevated Zr/Ti), and felsic volcanics (based on high Zr/Ti). Mafic volcanic strata have high Zr, consistent with calc-alkalic magmatic affinities. Felsic volcanic strata are FII type felsic magmas and have low Nb and Y consistent with volcanic-arc felsic magmas. The quartz-sericite altered rocks have trace element chemistry consistent with the intermediate volcanic strata and alteration indices indicate a potassic-dominated alteration. These characteristics suggest an oceanic arc-backarc bimodal-mafic petrochemical association (Piercey, 2011) and provide a more comprehensive understanding of VMS mineralization in the PVB. 47 �(A) (B) Figure 1. (A) A regional map of the Ritche Creek VMS Deposit located in North Central Wisconsin. (B) A Cross-section view of the Ritche Creek VMS deposit, showing drill hole locations and stratigraphic units, faulting and alteration zones. This cross section focuses on (RC5) a drill holes that intersects significant sericite alteration and massive sulfide mineralization zones. REFERENCES DeMatties, T.A., (1990), The Ritchie Creek Main Zone: A Lower Proterozoic CopperGold Volcanogenic Massive Sulfide Deposit in Northern Wisconsin. Economic Geology Vol. 85, 1990, pp. DeMatties, T.A., (2018), Effects of paleoweathering and supergene activity on volcanogenic massive sulfide (VMS) mineralization in the Penokean Volcanic Belt, northern Wisconsin, Michigan and east- central Minnesota, USA: Implications for future exploration: Ore Geology Reviews, v. 95, p. 216–237. DeMatties, T.A., (2022), Exploration-resource assessment of productive felsic volcanic centers in the Paleoproterozoic Penokean Volcanic Belt of northern Wisconsin, Michigan, and east-central Minnesota, USA: Ore Geology Reviews, v. 141, p. 104489. Piercey SJ (2011) The setting, style, and role of magmatism in the formation of volcanogenic massive sulfide deposits. Mineralium Deposita 46:449-471. 48 �Geologic implications of detrital zircon U-Pb ages from Archean and Paleoproterozoic strata in central Minnesota and the Gogebic Range of Wisconsin and Michigan, USA JONES, James V.1, SALERNO, Ross2, CANNON, William F.2, and O’SULLIVAN, Paul4 1 U.S. Geological Survey, Anchorage, AK 99508, USA jvjones@usgs.gov U.S. Geological Survey, Reston, VA 20192, USA; 3 U.S. Geological Survey, Denver, CO 80225, USA 4 GeoSep Services LLC, Moscow, ID 83843, USA 2 Archean and Paleoproterozoic metasedimentary successions in the Lake Superior region of the northern United States record the assembly and breakup of southern Superia and the subsequent transition to long-lived accretionary orogenesis along the southern Laurentia margin. The successions are difficult to correlate for reasons that include contrasts in thickness, facies, and variable amounts of erosion, similarities in depositional environment through hundreds of millions of years of sedimentation, and variable overprinting by younger tectonic events. Detrital zircon U-Pb geochronology is useful for correlating siliciclastic strata and for identifying provenance patterns that reflect past tectonic and sedimentary interactions. We present new data for samples collected from ca. 2.6–1.8 Ga strata from across the Lake Superior region that provide key insights into regional correlations and local to global tectonic histories. In the eastern Gogebic Range of Michigan, Archean volcanic and volcaniclastic rocks are mapped in a fault-bounded panel between the Watersmeet gneiss dome to the southeast and Neoarchean Puritan batholith to the northwest. One new sample of Archean metagraywacke from within the supracrustal succession yielded only Neoarchean detrital zircon with age populations ranging from ca. 2740 to 2590 Ma, indicating derivation from nearby gneisses but not from older sources such as the early Paleoarchean Watersmeet gneiss. A younger succession of Paleoproterozoic metavolcanic and metasedimentary rocks near Lake Gogebic overlies the Archean gneisses and supracrustal rocks. One sample of fine- to medium-grained slate and metagraywacke from the Copps Formation yielded a mixture of Archean and Paleoproterozoic detrital zircon dates. Archean grains were minor and included age populations of ca. 2649 and 2553 Ma that match the nearby Neoarchean metagraywacke and gneiss domains. Paleoproterozoic grains defined a ca. 1846 Ma age peak and a maximum depositional age of ca. 1829 Ma. We also collected samples of the Paleoproterozoic Palms and Tyler Formations that overlie Archean domains in the western part of the Gogebic Range. Fine-grained gray quartzite of the Palms Formation yielded detrital zircon age populations ranging from ca. 2976 to 2458 Ma and a prominent peak at ca. 2675 Ma. The age spectrum indicates input and (or) recycling of Archean sources and an absence of coeval magmatic sources in the region. In contrast, fine-grained argillaceous sandstone of the overlying Tyler Formation contained mostly Paleoproterozoic detrital zircon with major age peaks at ca. 1863 and 1827 Ma together with minor older age populations ranging from ca. 2780 to 1953 Ma. In central Minnesota, new samples were collected from the Paleoproterozoic Denham and Little Falls Formations. The Denham Formation sample was collected on the northern side of the McGrath gneiss dome and consisted of fine-grained biotite argillite with 1-2 mm horizons of coarser sandstone. The sample yielded chiefly Archean detrital zircon with a dominant age population at ca. 2603 Ma and minor older populations ranging from ca. 3409 and 2789 Ma. Archean age populations match previously published data from nearby samples of basal arkose and dolomitic arkose from the same unit (Craddock et al., 2013). However, that basal arkose also contained a distinct ca. 2101 Ma age population that established a potential correlation between the Denham Formation and the East Branch Arkose of the Dickinson Group in Michigan. The 49 �Little Falls Formation sample of garnet-staurolite-biotite schist was collected from the southern side of the McGrath dome, and it predominately contained Paleoproterozoic detrital zircon that define a dominant unimodal age population at ca. 1846 Ma. The age spectrum for the Little Falls sample is nearly identical our data from the Copps Formation and is also like our Tyler Formation data and to previously published data for other parts of the upper Animikie Group. The marked difference in the proportion of Archean and Paleoproterozoic grains between the Little Falls and Denham Formations suggests a major change in provenance across their contact. The Denham Formation appears to have been derived from the underlying Archean gneiss dome with lesser contribution from older gneisses elsewhere in the region. Circa 2.1 Ga sources are rare in the region but are found locally to the east in Dickinson County, Michigan. The Paleoproterozoic age population that dominates the Little Falls Formation indicates derivation from the Wisconsin magmatic terrane that was approaching from the south (present coordinates) prior to collision that defines the Penokean orogenic cycle in the region. Additionally, our data indicate a maximum depositional age of ca. 1846 Ma for the Little Falls Formation that contrasts with the inferred ca. 2101 Ma age of the underlying Denham Formation reported by Craddock et al. (2013). Published observations suggest a gradational contact between schist of the Little Falls Formation and dolomitic marble of the underlying Denham Formation (Boerboom and Chandler in Bauer et al., 2022). Boerboom and Chandler (2022) noted a 1-meter graphitic/carbonaceous argillite at the base of the Little Falls Formation that could represent a hiatus and then a major change in depositional environment above the arkosic conglomerate and dolostone. We previously reported similar geologic and provenance patterns from the Dickinson Group approximately 600 km to the east in Michigan (Jones et al., 2024). In that area, the East Branch Arkose contains a similar distribution of DZ ages: a mixture of Archean detrital zircon and a distinctive ca. 2099 Ma age population interpreted to have been derived from local granitic sources. The overlying Solberg Schist is made up of biotite-staurolite schist that contains prominent ca. 1.86–1.84 Ga age populations together with minor ca 2.5 and 2.3 Ga age populations. More work is needed to better constrain the stratigraphic position of the depositional age and provenance shifts in both successions and to better understand the tectonic setting and significance of the subtle unconformities and pronounced shift in zircon sources. Preliminary observations and data suggest that the two successions are regionally similar but also distinct from surrounding strata. Thus, the Denham and Little Falls Formations may provide a distinctive and unique record of the transition from Superia rifting to Penokean orogenesis. REFERENCES Bauer, Emily J; Chandler, V.W.; Boerboom, Terrence J; Knaeble, Alan R; Nguyen, Maurice K; Lively, R. S.; Setterholm, Dale R; Steenberg, Julia R. (2022). C-52, Geologic Atlas of Aitkin County, Minnesota. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/253808. Craddock, J.P., Rainbird, R.H., Davis, W.J., Davidson, C., Vervoort, J.D., Konstantinou, A., Boerboom, T., Vorhies, S., Kerber, L., and Lundquist, B., 2013, Detrital zircon geochronology and provenance of the Paleoproterozoic Huron (~2.4-2.2 Ga) and Animikie (~2.2-1.8 Ga) basins, southern Superior Province: Journal of Geology, v. 121, p. 623–644, https://doi.org/10.1086/673265. Jones, J., Cannon, B., Drenth, B., and O’Sullivan, P., 2024, Geologic and tectonic implications of detrital zircon U-Pb age from the Dickinson Group in the western Upper Peninsula of Michigan, USA: Institute on Lake Superior Geology, “Institute on Lake Superior Geology: Proceedings, 2024,” Archives & Digital Collections at Lakehead University Library, accessed April 9, 2025, https://digitalcollections.lakeheadu.ca/items/show/10352. 50 �Zircon Petrochronology of Wisconsin’s Volcanogenic Massive Sulfide Deposits, Northcentral Wisconsin KWIATKOWSKI, Aidan O. 1, LODGE, Robert W.D.1 1 Department of Geology and Environmental Sciences, University of Wisconsin-Eau Claire, Eau Claire, WI 54701 USA Northern Wisconsin’s Paleoproterozoic Penokean Orogen, one of the classic Precambrian orogenic belts in North America, is known to host multiple volcanogenic massive sulfide (VMS) deposits which are important sources of Cu, Zn, Pb, Ag, and Au globally. Despite known large and potentially economic VMS deposits, limited outcrop exposure has hindered detailed reconstructions of the VMS-hosting environment to guide future exploration. Historic U-Pb geochronology indicates that volcanism occurred between 1889-1835 Ma (Sims et al. 1989) with the majority of VMS-hosting strata constrained between 1875-1873 Ma (Quigley 2016). Schultz & Cannon (2007) attribute the main VMS forming event ca. 1875 Ma to extension in a developing back arc basin, with a second later magmatic pulse around 1830 Ma being attributed to post-tectonic stitching plutons. However, a newer model by Zi et al. (2022) shows two VMS forming events around 1875 Ma and 1845 Ma suggesting a regime consisting of alternating compressional and extensional environments caused shifting subduction angles. Zircon petrochronology (U/Pb, Lu/Hf isotopic data and trace elements) can not only better constrain the timing of VMS formation but can also allow for a more complete understanding of the geological evolution and metallogeny of Wisconsin VMS deposits. This study sampled felsic igneous rocks from several VMS deposits to determine the timing and tectonic settings of VMS environments in the western Penokean Orogen. Samples were studied from the Flambeau, Eisenbrey, and Lynne deposits of the Ladysmith-Rhinelander Volcanic Belt (Figure 1a). Samples from the Flambeau and Eisenbrey deposits consist of felsic volcaniclastic units associated with sulfide mineralization and the sample from the Lynne deposits consists of a granodiorite which has intruded into the VMS deposit and volcanic strata. Samples were pulverized and heavy mineral separates were obtained by various magnetic and density separation techniques. The zircon mineral grains were imaged by cathodoluminescence prior to isotopic (U/Pb, Lu-Hf) and trace element analyses via LA-ICPMS at the Mineral Exploration Research Centre at Laurentian University, Sudbury, Ontario. U/Pb isotopic data constrains timing of magmatism. Trace elements and Lu-Hf data constrain the tectonic setting and crustal architecture. Preliminary results indicate two distinct VMS-forming magmatic events during the Penokean Orogeny that have similar tectonic and magmatic styles. All samples show a bimodal distribution of U/Pb ages centered on 1830-1835 Ma and 1870-1875 Ma (Figure 1). Trace element geochemistry of zircons reveals little petrogenetic difference between the magmatic events. Negative ƐHf(i) values, indicating interaction with Archean basement, is consistent amongst all samples and between magmatic events. The VMS-forming extensional event at ca. 1835 Ma contradicts the Schulz and Cannon (2007) model where collisional tectonics are dominant at this time. While the timing of VMS-formation more closely aligns with the Zi et al. (2022) model, the accordion-like tectonics cannot explain the lack of variation in magmatic setting or crustal architecture observed in our data. Therefore, additional data is needed to fully understand the tectonic and metallogenic significance of this younger extensional event. 51 �Figure 1. A) Generalized geologic map of the Penokean Orogen illustrating major tectonostratigraphic subdivisions and the location of sampled and major VMS occurrences. Figure modified from Schulz and Cannon (2007) and DeMatties (1994). Subdivisions of Pembine-Wausau terrane from DeMatties (1994, 2018). LRVC = Ladysmith-Rhinelander volcanic complex. B) U/Pb concordia diagram of older magmatic zircons. C) U/Pb concordia diagram of younger magmatic zircons interpreted to be crystallization age of sample. D) Weighted mean diagram distribution of ages and analyzed grains. Inset image shows frequency distribution of ages in samples. REFERENCES DeMatties TA (1994) Early Proterozoic volcanogenic massive sulfide deposits in Wisconsin: An overview. Econ Geol 89: 1122-1151. DeMatties TA (2018) Effects of paleoweathering and supergene activity on volcanogenic massive sulfide (VMS) mineralization in the Penokean Volcanic Belt, northern Wisconsin, Michigan and east-central Minnesota, USA: Implications for future exploration. Ore Geol Rev 95: 216-237. Quigley A (2016) Setting of the volcanogenic massive sulfide deposits in the Penokean Volcanic belt, Great Lakes region, USA. Colorado School of Mines, Masters Thesis. 95 p. Schulz KJ, Cannon WF (2007) The Penokean orogeny in the Lake Superior region. Precambrian Res 157: 4-25. Sims PK, Van Schmus WR, Schulz KJ, Peterman ZE (1989) Tectonostratigraphic evolution of the Early Proterozoic Wisconsin magmatic terranes of the Penokean orogen. Can J of Earth Sci 26: 2145-2158. Zi J-W, Sheppard S, Muhling JR, Rasmussen B (2021) Refining the Paleoproterozoic tectonothermal history of the Penokean Orogen: New U/Pb age constraints from the Pembine-Wausau terrane, Wisconsin, USA. Geol Soc Am Bull 134: 776-790. 52 �Geologic Interpretation of Filtered Gravity and Magnetic Anomalies of the Baraboo Range LONGACRE, Mark B.1 and HINZE, William J.2 1 MBL, Inc., 51 Captain Perry Dr., Phippsburg, ME 04562 Purdue University, 30 Brook Hollow Ln., West Lafayette, IN 47907 2 Investigations over the past decade have made significant advances in our geologic knowledge of the Mesoproterozoic Baraboo Synclinorium and adjacent region of south-central Wisconsin (e.g., Medaris, Jr. et al., 2021; Stewart et al., 2021; Marshak et al., 2023). To further the geologic information of this feature and nearby region we have filtered their gravity and magnetic anomaly maps to identify geologic formations and structures in the crystalline basement. The filtered maps isolate specific attributes of the anomaly fields which are useful in interpretation especially when combined with constraining geological information. These maps have identified a buried geologic structure to the east of and immediately adjacent to and along strike of the Sauk Syncline (Figures 1 and 2) which encompass the Baraboo Synclinorium. The buried structure is a near mirror image of the Sauk Syncline and thus is referred to as the Twin Syncline. Unlike the Sauk Syncline and the Baraboo Synclinorium the eastern structure is south rather than north of a geological lineament within the Yavapai orogenic province that marks the southern boundary of the Wisconsin Gravity Minimum. The Twin Syncline is notable in the magnetic anomaly map because of the positive anomaly associated with a magnetite-rich formation that is likely an extension of the lower portion of the Freedom Formation of the Baraboo Synclinorium. The elliptical trace of this anomaly and the steep gradients of the outer margin support the synclinal nature of the structure. We interpret this structure to be a result of south-verging thrusting with steeply dipping thrusts along the northern and southern margins of the Twin Syncline similar to the situation of the Sauk Syncline. This structure is not as tightly folded as the Baraboo Synclinorium suggesting that the thrusting to the east of Baraboo Synclinorium was less intense. The Syncline can be identified on the filtered maps as can other quartzite synclinoriums of the region by the subdued geophysical anomalies of the underlying felsic volcanic rocks because of their burial beneath the non-magnetic quartzite. The magnetic anomalies of the magnetic lower half of the Freedom Formation are also a useful marker for detailing the structure within the Baraboo Synclinorium and defining the limits of the Freedom Formation within it. Additionally, two parallel intrusives on strike with the Denzer Diorite that crops out along the southwestern margin of the Synclinorium extend northnortheasterly within the sub-quartzite basement across the western portion of the Synclinorium. They are associated with anticlines within the Synclinorium that may have resulted from differential deformation caused by variations in the rheology of the basement rocks. These and other interpretations of the filtered gravity and magnetic anomalies suggest that revisiting the studies of basement rocks of Wisconsin and adjacent regions is in order using the available improved analysis, interpretation, and presentation methods and modern data gravity and magnetic data sets. REFERENCES Marshak, S., Wilkerson, M.S., and DeFrates, J., 2023. Kinematic and tectonic implications of crenulation cleavage, kink bands, and mesoscopic folds in the Baraboo Syncline, Wisconsin (∼1.45 Ga Picuris Orogen). Journal of Structural Geology, 178, 105007. Medaris, Jr, L.G., Singer, B.S., Jicha, B.R., Malone, D.H., Schwartz, J.J., Stewart, E.K., Van Lankvelt, A., Williams, M.L., and Reiners, P.W., 2021. Early Mesoproterozoic evolution of midcontinental Laurentia: Defining the geon 14 Baraboo orogeny. Geoscience Frontiers,12(5), 101174, 17 p. 53 �Stewart, E.K., Brengman, L.A., and Stewart, E.D., 2021. Revised provenance, depositional environment, and maximum depositional age for the Baraboo (< ca. 1714 Ma) and Dake (< ca. 1630 Ma) Quartzites, Baraboo Hills, Wisconsin. The Journal of Geology, 129, 1-31. Figure 1. Total horizontal derivative of the RTP total magnetic anomaly map of south-central Wisconsin. The outlines of the Sauk (left) and Twin (right) Synclines are shown by the thin dashed white lines and the Baraboo Synclinorium by a dashed white line. The Baraboo Lineament of the Yavapai province is shown by the wide broadly dashed line. Color coding is non-linear. Figure 2. Tilt derivative of the Bouguer gravity anomaly map of south-central Wisconsin that emphasizes the short wavelength components. The outlines of the Sauk (left) and Twin (right) Synclines are shown by the dashed white lines and the Baraboo Synclinorium by a thin dashed white line. The Baraboo Lineament of the Yavapai province is shown by the wide broadly dashed line. Color coding is non-linear. 54 �An Informal Review of the ILSG Field Excursion to Hawaii, January – February, 2025 MACTAVISH, Allan1, HINZ, Peter1, HUDAK, George1, LARSON, Phil1, AUBUT, Allan1, BOERBOOM, Terry1, CHILTON, Vern1, DeGRAFF, Jim1, ERICKSON, Tom1, FAULKNER, Barb1, SERRANO, Isabel1, and ZANKO, Larry1 1 Members of the 2025 ILSG Field Trip to Hawaii, 2025 Between January 24, 2025 and February 5, 2025, twelve members of the Institute on Lake Superior Geology participated in a geological field excursion to investigate the geology of the island of Hawaii, with a focus on observing field relationships, outcrop characteristics and geomorphology to better understand the characteristics of modern basaltic volcanism in a hotspot environment. The field excursion was led by Allan MacTavish, Peter Hinz, George Hudak and Phil Larson. A new field trip guidebook and glossary of geological terms (MacTavish and Hudak, 2024) was prepared and utilized during the thirteen-day long trip. This presentation will review key features and take-aways from the excursion, which included investigations of five of the seven volcanoes associated with the island of Hawaii. Investigations took place via examinations of various outcrops, hikes through the Hawaiian wilderness, and a helicopter tour. Various eruption types, volcano types, coherent (lava flow) and volcaniclastic deposit types and features, different types of volcanic products and hydrothermal alteration facies, and observations of historical and cultural artifacts and natural phenomena will be discussed. Challenges and surprises associated with field studies of Hawaii will also be presented. REFERENCES MacTavish, A., and Hudak, G., 2024, The Volcanoes of the Island of Hawaii – Field Trip Guide: Institute on Lake Superior Geology Special Publication 3, 200 p. 55 �56 �Refining the Age and Occurrence of Basement Rocks in Northwest Iowa: Implications for Precambrian Tectonics and Magmatic Evolution of the Laurentian Midcontinent MALONE, Jack1, MALONE, David2, ANDERSON, Raymond1, CLARK, Ryan1 1 Iowa Geological Survey, University of Iowa, Iowa City, IA 52242 USA 2 Geography-Geology, Illinois State University, Normal, Illinois 61790 Precambrian basement rocks in northwest Iowa reveal an Archean and two Paleoproterozoic tectonic sutures (Figure 1; 1.9-1.8 Ga Trans-Hudson/Penokean and 1.8-1.7 Ga Yavapai; Bickford et al., 1986; Holm et al., 2007). Here we present four new U-Pb (LA-ICPMS) ages for drill cores of basement rocks along the Transcontinental Arch in northwest Iowa, USA (Figure 2). The cores are on repository at the Iowa Geological Survey. The Camp Quest migmatite gneiss was sampled at a depth of 1,078 ft from the Camp Quest D-21 core (W25498; z=38). The weighted mean and Concordia ages were both 1845 Ma, which is the first TransHudson/Penokean age recognized in Iowa. This core is located south of the Spirit Lake tectonic zone (SLTZ) which is interpreted as the suture between Yavapai terrane rocks to the south and Archean Superior province rocks to the north. Nine inherited zircons are mostly Archean in age and interpreted as xenocrysts, indicating Archean crust occurs at depth south of the SLTZ. Granite was also sampled at a depth of 660 ft from the Hawarden D-7 core (W27270; z=35). The zircon age spectrum reveals three age clusters at ~2895, ~2683, and ~1800 Ma. The older, inherited age clusters are consistent with ages of the Minnesota River Valley terrane and the greater Superior Province, respectively. The ~1800 Ma age is similar to the nearby 1803-1810 Ma Matlock “keratophyre” and the distant 1805 Ma Humboldt granite (northern Michigan), representing the initiation of north-directed Yavapai subduction and granitic melt production into Archean and previously accreted Trans-Hudson/Penokean rocks north of the SLTZ (Kilburg, 2024). Granodiorite was sampled at a depth of 915 ft from the Harris D-13 core (W27270; z=41). The weighted mean and Concordia ages are ~1780 Ma, suggesting that Yavapai rocks intrude older Trans-Hudson/Penokean or Archean rocks north of the SLTZ. A late-stage granitic dike was sampled at a depth of 1,611 ft from the Spencer BX-2 core (W16223; z=7), which is from a tabular noritic body within the Spencer intrusive complex just south of the SLTZ. The sampled interval yielded sparse zircons; however, the weighted mean age of 1238 Ma is the first Grenville age recognized in Iowa. This age suggests an obscure early Grenvillian thermal resetting or reactivation in the upper Midcontinent which postdates anorthositic/noritic magnetism concentrated along the SLTZ at Spencer. New complementary whole rock WDXRF major oxide and ICP-OES trace element geochemical analyses (n=163) from Precambrian units in northwest Iowa reveal a complex tectonic and crustal growth configuration. Intermediate to felsic intrusions are generally LREEenriched and have I-type volcanic arc-like trace element patterns. The origin of anorthositic to mafic-ultramafic occurrences are less straightforward but are characterized by slight to significant Ce, Sm, Eu, and Lu anomalies, indicating basaltic to mantle fractionation, differential partial melting at depth, and/or derivation from Fe-rich residual melts. These new results provide significant insight into the tectonomagmatic evolution of the southernmost Superior Province during the final assembly of the Laurentian craton. 57 �Figure 1: Geological map of Precambrian basement rocks in the northern midcontinent and northwest Iowa. Top: Red dots indicate previously published U-Pb ages and white dots are new (this study). Bottom: New geochronologic ages indicated with stars are CQ = Camp Quest, HW = Hawarden, HA = Harris, SP = Spencer. Figure 2: Weighted mean, probability density, and Concordia plots of newly dated Precambrian units in northwest Iowa. REFERENCES Bickford, M.E., Van Schmus, W.R., and Zeitz, I., 1986. Proterozoic history of the midcontinent region of North America. Geology, 14(6), 492-496. Holm, D.K., Anderson, R., Boerboom, T.J., Cannon, W.F., Chandler, V., Jirsa, M., Miller, J., Schneider, D.A., Schulz, K.J., & Van Schmus, W.R., 2007. Reinterpretation of Paleoproterozoic accretionary boundaries of the north-central United States based on a new aeromagnetic-geologic compilation. Precambrian Research, 157(1-4), 71–79. Kilburg, N., 2024. Age and petrogenesis of the Matlock ‘Keratophyre’ in northwest Iowa [M.S. Thesis]: Iowa City, University of Iowa, 129 p. 58 �Post-Penokean and Pre-Yavapai Magmatism and Sedimentation in Central Wisconsin (Southern Lake Superior Region) MEDARIS, Gordon Jr.1 and MALONE, Dave2 1 Dept. of Geoscience, University of Wisconsin-Madison, Madison, WI 53706 2 Dept. of Geography, Geology, and the Environment, Illinois State University, Normal, IL 61790 The principal Precambrian domains in Wisconsin are the Penokean Province, consisting of the Marshfield Terrane, Wausau-Pembine Terrane, and Craton margin, which include 2450-1770 Ma craton margin and foreland basin sediments and 1890-1830 Ma volcanic arc associations, 1760 Ma rhyolite and granite of the Yavapai Province, <1643 Ma quartzite of the Baraboo Interval, 1484-1468 Ma granitic rocks of the Wolf River batholith, and 1109-960 Ma igneous and sedimentary rocks of the Midcontinent Rift (Fig. 1). In addition to these five major domains, small outcrops of post-Penokean and preYavapai igneous and sedimentary rocks are scattered across central Wisconsin, which have been investigated in detail at Hamilton Mounds (Medaris et al., 2007), Biron Dam (Holm et al., 2020), and Brokaw (this report) (Fig. 1). Two sedimentary successions occur at Hamilton Mounds: an older arkose and a younger quartzite correlative with the Baraboo quartzite. The arkose is a gray, fine- to medium-grained, feldspathic sandstone (CIA = 59.0; Fig. 2). Detrital monazite in arkose yields a total Pb median age of 1850 Ma, with the youngest detrital grain at 1757 Ma, signifying post-Penokean deposition of the arkose. An upper age for the arkose is provided by the intrusion of 1762 ± 7 Ma granite (Yavapai), whose age is within error of the youngest detrital monazite grain. Muscovite in the younger quartzite yields a 40Ar/39Ar plateau age of 1470 ± 11 Ma, reflecting the widespread thermal effect of the Wolf River batholith throughout central and southern Wisconsin. At Biron Dam, trachybasaltic diabase dikes (Fig. 2) intruded Archean gneiss and Penokean tonalite, granodiorite, and granite. Zircon grains in three samples of diabase yield 207 Pb/206Pb ages within error of each other, with a weighted mean age of 1817 ± 2 Ma, which demonstrates post-Penokean and pre-Yavapai emplacement of the dikes. The diabase dikes have been metamorphosed under amphibolite-facies conditions; hornblende in metadiabase yields a 40 Ar/39Ar plateau age of 1672 ± Ma, possibly representing a Mazatzal influence. At Brokaw, polymictic conglomerate, feldspathic sandstone (CIA = 59.0; Fig. 2) and siltstone were intruded by rhyolite, which contains inherited zircon with ages between 2125 Ma and 3565 Ma. The sandstone contains detrital zircon with a 207Pb/206Pb median age of 1850 Ma and an age of 1810 Ma for the youngest subset of grains with overlapping errors, demonstrating post-Penokean deposition of the Brokaw sedimentary rocks. Primary structures and textures of the Brokaw igneous and sedimentary rocks have been preserved on the macroscopic scale, but such rocks have been pervasively recrystallized to greenschist-facies mineral assemblages on the microscopic scale, as seen for example in rhyolite, in which plagioclase was replaced by albite and epidote, and hornblende, by epidote (Fig. 3). The age of such recrystallization has not yet been determined, but is presumed to be related to the nearby Wolf river batholith. It is now recognized that igneous rocks were emplaced and sedimentary rocks were deposited over much of central Wisconsin in the interval 1817-1757 Ma after the Penokean orogeny, perhaps as a precursor to the Yavapai orogeny. 59 �Figure 2. Chemical compositions of Biron Dam diabase, Brokaw rhyolite and sandstone, and Hamilton Mounds sandstone in terms of Al (Al2O3), Ca* (CaO), N (Na2O), and K (K2O); CIA: Chemical Index of Alteration. Figure 1. Map of the major Precambrian geological units in the southern Lake Superior region. Star symbols: Brokaw (BK), Biron Dam (BD), and Hamilton Mounds (HM) localities; B: Baraboo Interval sedimentary rocks. Figure 3. Photomicrograph (crossed polarizers) of recrystallized Brokaw rhyolite; ab, albite; ep, epidote REFERENCES Medaris, L.G. Jr., Van Schmus, W.R., Loofboro, J., Stonier, P.J., Zhang, X., Holm, D.K., Singer, B.S., and Dott, R.H. Jr., 2007. Two Paleoproterozoic (Statherian) siliciclastic metasedimentary sequences in central Wisconsin. Precambrian Research, 157, 188-202. Holm, D., Medaris, L.G. Jr., McDannell, K.T., Schneider, D.A., Schulz, K., Singer, B.S., and Jicha, B.R., 2020. Growth, overprinting, and stabilization of Proterozoic Provinces in the southern Lake Superior region. Precambrian Research, 339, Article 105587. 60 �US Steel Corporation / Ralph W. Marsden iron ore collection MOOERS, Howard1, SEVERSON, Mark2, JONGEWAARD, Peter3, LARSON, Phillip4 1 Department of Earth and Environmental Sciences, University of Minnesota Duluth, Duluth, MN 55812 2 2122 W 22nd St., Duluth, MN 55811, USA 3 7009 Three Lake Rd., Canyon, MN 55717, USA 4 1613 14th Ave. East, Hibbing, MN 55746, USA By the time Ralph W. Marsden joined Oliver Iron Mining Division of US Steel Corporation (USSC) in 1951 he was already one of the World’s experts on iron ore. From 1953-1964 he managed the Geologic Investigations Unit in Duluth, MN. During this time, Ralph was one of the co-founders of the Institute on Lake Superior Geology in 1954. In 1964 Ralph was transferred to the Pittsburgh corporate office as Manager of Geologic Investigations, Iron Ore, however, Ralph wanted to return to Minnesota, and in 1967 he left USSC and moved to the University of Minnesota Duluth (UMD) Department of Geology as Professor and Head. USSC had an active, worldwide exploration program for iron ore from the 1920s into the 1960s, and a large number of the samples collected were housed in Duluth, MN. When USSC closed its Duluth, MN, office, this iron ore sample collection was to be discarded. Ralph “rescued” the collection of iron ore samples and moved them to the University of Minnesota Duluth. In 1986, Ralph died suddenly while attending the Geological Society of America Annual Meeting in San Antonio, TX. The collection of iron ore samples sat in a service tunnel at UMD for 40 years. This globally significant collection of iron ore samples was recently inventoried, photographed, and placed in storage containers that are readily accessible. The inventory of the 483 samples, complete with photographs, is cataloged on the University of Minnesota Digital Conservancy (https://hdl.handle.net/11299/265081). Many of these samples are from localities that are no longer accessible, are from closed mines, or are from areas of the World that simply cannot be visited because of political and social issues. This collection of iron ore samples dates from 1926 to the 1960s and has samples from 25 countries and 30 US states and Canadian provinces. The individual sample boxes are labeled, and many have great detail on the origin of the samples. Most of the samples are also individually labeled, with sample numbers and descriptions. There are photographs of the contents of each box, and where possible supporting documents are shown in the photos. For further information or to request access to samples contact the Department of Earth and Environmental Sciences, University of Minnesota Duluth or Howard Mooers (hmooers@d.umn.edu). 61 �Countries represented: USA, Angola, Australia, Brazil, Canada, Chile, Colombia, Congo, Costa Rica, Cuba, Gabon, Germany, Guatemala, Honduras, India, Ivory Coast, Liberia, Mexico, Nicaragua, Namibia, Portugal, South Africa, Sudan, Sweden, Venezuela. US States and Canadian Provinces represented: Alabama, Alberta, Arizona, British Columbia, California, Idaho, Illinois, Massachusetts, Michigan, Minnesota, Missouri, Montana, Nevada, New Jersey, New Mexico, New York, Newfoundland, North Carolina, North Dakota, Ontario, Oregon, Puerto Rico, Quebec, South Dakota, Utah, Virginia, Washington, Wisconsin, Wyoming. Figure 1. Example of samples from Liberia, West Africa, with supporting documentation. REFERENCES University Digital Conservancy, University of Minnesota Duluth, (2024). List of Samples for US Steel Corporation / Ralph W. Marsden Iron Ore Collection. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/266399. 62 �Lithogeochemical Characterization of Manganese Mineralization at the Cuyuna Range, Central Minnesota PALIEWICZ, Cory1, THAKURTA, Joyashish1 1 Natural Resources Research Institute (NRRI), University of Minnesota Duluth, 5013 Miller Trunk Hwy, Duluth, MN 55811 The Paleoproterozoic Cuyuna Range of central Minnesota contains elevated levels of manganese when compared to other Banded Iron Formations in the Lake Superior region. The total tonnage is estimated at 49 million metric tons at 7.84 percent Mn (Kilgore and Thomas, 1982). The Cuyuna Range consists of a Penokean fold-and-thrust belt divided into the Emily District, North Range, and South Range. These are separated by structural and stratigraphic discontinuities which make each area geologically distinct (Southwick et al., 1988; Morey, 1990). Although prior work has documented a variety of textural and sedimentary associations, this study will provide new lithogeochemical data to further characterize the manganese-bearing lithologies across the Cuyuna Range in support of ongoing research for manganese and other critical minerals in Minnesota as part of the USGS Earth MRI program. A total of 201 drill core samples were collected from 37 drill holes across the Emily District, North Range, South Range, and Glen Lake Sulfide Deposit (Figure 1). To date, all samples have been studied in hand-sample and sent for bulk geochemical analysis, 40 samples have been analyzed in thin section, and whole-rock geochemical results of 60 samples from 16 drill holes have been received from the USGS. Although lithologic features of both ironformations and non-iron-formations are variable across the range, the deposits also share many attributes. As such, we find it useful to texturally classify the collected samples into granular, banded, and irregular types while still recognizing the special characteristics of each individual mineral association. This study will present petrographic and whole-rock geochemical data, with particular emphasis on rocks from the Emily District, which from past studies is known to be mostenriched in Mn-content. In addition, Mn-bearing country rocks throughout the Cuyuna Range are also characterized and compared to historic drill logs and prior work (e.g., Morey et al., 1991, Dahl et al., 1992). In this way, new insights on lithological variation, manganese distribution, and other potential critical minerals at the Cuyuna Range may further be addressed and incorporated during the Earth MRI program. 63 �Drill Hole Sampled Figure 1: Regional geologic map of the Cuyuna Range showing approximate drill hole locations sampled for this study. Modified from Southwick et al., 1988 and Cleland et al., 1996. REFERENCES Dahl, L.J., Brink, S.E., Blake, R.L., Tuzinski, P.A., and Adamson, N.R., 1992, Site characterization of Minnesota manganese deposits to evaluate the potential for in-situ leach mining: Littleton, Colorado, Society for Mining, Metallurgy and Exploration, Inc. Preprint 92-243, 31 p. Cleland, J.M., Morey, G.B., and McSwiggen, P.L., 1996, Significance of tourmaline-rich rocks in the North Range Group of the Cuyuna Iron Range, east-central Minnesota: Economic Geology, v. 91, no. 7, p. 1282-1291 Kilgore, C.C., and Thomas, P.R., 1982, Manganese availability-Domestic: U.S. Bureau of Mines Information Circular 8889, 14 p. Morey, G.B., 1990, Geology and manganese resources of the Cuyuna iron range, east-central Minnesota: Minnesota Geological Survey Information Circular 32, 28 p. Morey, G.B., D.L. Southwick, and S.P. Schottler, 1991, “Manganiferous Zones in Early Proterozoic Iron Formation in the Emily District, Cuyuna Range, East Central Minnesota.” Minnesota Geological Survey Report of Investigations 39. 42 pp. Southwick, D.L., Morey, G.B., and McSwiggen, P.L., 1988, Geologic map (scale 1:250,000) of the Penokean orogen, central and eastern Minnesota, and accompanying text: Minnesota Geological Survey Report of Investigations 37, 25 p., 1 pl. 64 �Michigan Geological Survey’s Contributions to the USGS Earth MRI National Mine Waste Inventory Effort PEARSON, Sara1, GAMET, Nolan2, SHALIFOE, Molly 1, QUIGLEY, Ashley2, and MAHIN, Robert2 1 Michigan Geological Survey, Western Michigan University, 5272 W. Michigan Ave. Kalamazoo, MI 49009 2 Michigan Geological Survey, Western Michigan University, 416 Avenue C Gwinn, MI 49841 In the mid-19th century, the discovery of rich copper and iron deposits in Michigan’s Upper Peninsula (U.P.) led to intense mining, resulting in hundreds of abandoned mine waste sites. Both published and unpublished geological literature suggests that some of these legacy mine waste sites have the potential to host critical minerals, such as manganese and graphite, that were previously overlooked during production. The Michigan Geological Survey (MGS) is contributing to the United States Geological Survey’s (USGS) national effort to build a comprehensive national inventory of mine wastes, their compositions, and potential critical minerals. The MGS team has completed an inventory and submitted 120 mine waste sites from 6 counties across the western U.P. to the USGS for a final review and inclusion in the national mine waste database (Figure 1). These 120 sites are further subdivided into 216 individual mine waste features that met the minimum 2,000m2 size requirement. Finalized point and polygon layers for each mine site were accompanied by corresponding geology, resource, and reference attribute tables. The process consisted of creating an ArcGIS Pro project, adding all available mine-related state and federal datasets, LiDAR-derived DEMs (digital elevation models), published maps, and an ArcGIS geodatabase template containing feature classes and related attribute tables required by the USGS. Initial mine waste inventory work focused on searching for and digitizing mine waste features throughout the western U.P that exceeded the 2,000m2 size requirement. The MGS team originally located and digitized 441 mine waste features by utilizing LiDAR-derived, 1-meter DEMs, 2024 ESRI areal imagery, and published geologic maps. This process is depicted by a simplified workflow shown in Figure 2. The mine waste features were then filtered based on their size. Those smaller than 2,000m2 were omitted from the master dataset. Corresponding attribute tables were then populated with data from publicly available literature, websites, state and federal datasets, and information archived in the state’s drill core repositories. The final databases will ultimately comprise the most up-to-date record of the volume, tonnage, grade, and mineralogy of Michigan’s legacy mine waste sites. Future MGS work within the scope of the Earth MRI Mine Waste Cooperative Agreement is a mine waste characterization effort, which aims to sample and evaluate nonfuel mine waste sites that potentially contain critical minerals. This project will begin in 2025 and continue through 2026. 65 �Figure 1. Map displaying all mine waste features inventoried and submitted to the USGS for the fiscal year 2023 Priority 1 funding represented as purple points and polygons. Figure 2. Simplified process to locate and digitize the mine waste features using ArcGIS Pro coupled with online sources. A.) ESRI imagery (Esri, 2024); B.) Bedrock geology of central Dickinson County, MI (James and others, 1961); C.) 1-m QL2 LiDAR DEM model; D.) Digitization of mine waste features. REFERENCES Esri, 2024, World imagery: Esri, https://services.arcgisonline.com/ArcGIS/rest/services/ World_Imagery/MapServer. James, H.L., Clark, L.D., Lamey, C.A., and Pettijohn, F.J., 1961, Geology of central Dickinson County, Michigan, U.S. Geological Survey, Professional Paper 310, 1:24,000. 66 �Critical Mineral Potential of the Northern Margin of the Watersmeet Gneiss Dome, MI USA QUIGLEY, Ashley K.1, MAHIN, Robert A. 1, and GAMET, Nolan G. 1 1 Michigan Geological Survey, Western Michigan University, 416 Avenue C Gwinn, MI 49841 Precambrian gneisses and schists on the northern margin of the Watersmeet Dome in Michigan have been shown to be unusually enriched in rare earth elements, fluorite and incompatible elements including U, Th, Hf, and Zr (Barovich et al., 1991; Sims, 1990). The area is within two Earth Mapping Resources Initiative (EMRI) critical mineral focus areas for IOCG/IOA and magmatic REE deposits (Dicken and others, 2022). To further assess the potential for critical minerals, the Michigan Geological Survey (MGS) is conducting detailed geologic mapping and sampling, as well as collecting geophysical and geochronological data. The project area is roughly 36 square kilometers on the border of Gogebic and Ontonagon Counties and 10 kilometers northwest of the town of Watersmeet, MI. Field work began in July of 2024 with a projected completion date in early 2026. During the 2024 field season, the MGS mapped, described and recorded 620 outcrops in the project area using ArcGIS Field Maps and submitted 124 samples for whole rock and trace element geochemistry. An RS-230 BGO gamma-ray spectrometer was used to take over 600 total gamma (K/U/Th) measurements from outcrop. Additionally, a drone-borne, high resolution magnetic survey was flown over areas where permission was granted by landowners. Preliminary field observations include the presence of fluorite in outcrop spatially associated with magnetic and gamma count anomalies. The results of the lithogeochemistry show a strong spatial correlation between fluorine, uranium, thorium, and total REEs. When rare earth element concentrations were converted to industry standard rare earth oxides (REOs), 14 samples had total rare earth oxide (TREO) values greater than 1,000 ppm (Hellman and Duncan, 2018). Geophysical, analytical, and field data also identified an anomalous magnetic high approximately 500m x 300m associated with previously undescribed REE-bearing, magnetic, fine-grained schists. In 1982, Rocky Mountain Energy (RME) conducted exploration drilling for uranium based on anomalous gamma radiation in outcrop. A reexamination of the core found chalcopyrite in close association with fluorite. The presence of anomalous F, Cu, U, REE and magnetite is suggestive of an IOA/IOCG footprint (Hitzman, 2000). This will be investigated using IOCG discrimination diagrams such as Montreuil and others (2013). Barovich et al. (1991) observed that the elevated REEs, fluorite and incompatible elements were tied to a gneiss and schist unit with an interpreted Paleoproterozoic age between 1.9 and 1.7 Ga, much younger than the Archean aged rock units that make up most of the Watersmeet gneiss dome. Because of the apparent link between rock age and critical minerals, confirming existing ages with modern U-Pb dating techniques, as well as adding ages from new locations, is an important piece of this study. Five samples were submitted for U-Pb geochronology of zircon grains. Results are pending. 67 �REFERENCES Barovich, K.M., Patchett, P.J., Peterman, Z.E., and Sims, P.K., 1991. Neodymium Isotopic Evidence for Early Proterozoic Units in the Watersmeet Gneiss Dome, Northern Michigan. U.S. Geological Survey Bulletin 1904-G: G1-G7. Dicken, C.L., Woodruff, L.G., Hammarstrom, J.M., and Crocker, K.E., 2022, GIS, supplemental data table, and references for focus areas of potential domestic resources of critical minerals and related commodities in the United States and Puerto Rico (ver. 2.0, April 2024): U.S. Geological Survey data release, https://doi.org/10.5066/P9DIZ9N8. Hellman, P.L. and Duncan, R.K., 2018, Evaluating Rare Earth Element Deposits. ASEG Extended Abstracts. 2018. 1. 10.1071/ASEG2018abT4_3E. Hitzman, M.W., 2000, Iron oxide-Cu-Au deposit: What, where, when, and why, in Porter, T.M., ed., Hydrothermal iron oxide copper-gold and related deposits a global perspective: Adelaide, Australian Mineral Foundation, p.9–26. Montreuil J-F., Corriveau L., Grunsky E., 2013. Compositional data analysis of IOCG systems, Great Bear magmatic zone, Canada: To each alteration types its own geochemical signature. Geochem. Explor. Environ. Anal. 13:219–247. Sims, P.K., 1990, Geologic map of Precambrian rocks, Marenisco, Thayer, and Watersmeet 15-minute quadrangles, Gogebic and Ontonagon counties, Michigan, and Vilas County, Wisconsin: U.S. Geological Survey Miscellaneous Investigations Series Map I-2093, scale 1:62,500. 68 �Plume control on the initiation of Mid-Continent Rift breakup using Unconformities: Implications for the Tectono-magmatic evolution and mineral deposits ROHRMAN, Max1 1 DECAN Geosolutions, PO Box 131148, Houston, TX 77219 Regional unconformities from the stratigraphic record interpreted on existing Multi Channel Seismic (MCS) data obtained by Grant Norpac/Argonne (red numbered) and the GLIMPCE program (red lettered) (Figure 1A), are used for temporal and spatial control on MidContinent Rift (MCR) evolution. This allows identification of key events in the evolution of the rift, whereas potential field data, seismic refraction and Rayleigh waves, help constrain spatial and quantitative constraints. Based on magmatic stage definition, two regional unconformities were interpreted from MCS data: MU (Magmatic Unconformity), at the top of the Main stage (~ 1100 – 1089 Ma), signaling the end of major flood basalt magmatism, and BU (Breakup Unconformity) representing the Latent stage (~ 1104 – 1100 Ma). The latter is observed as a sequence at Mamainse Point (Figure 1), rather than an unconformity, stressing the importance of spatial control on events. Magmatic crustal thicknesses and lower crustal seismic velocities obtained from MCS and refraction data (Shay and Trehu, 1993) are used to constrain relative importance of important parameters in melt production, such as: potential temperature, active mantle upwelling and lithospheric thinning. Together, these data suggest that the MCR originated from an earlier NW-SE pre- or proto-rift (blue, Figure 2A) recognized from outcrop (Figure 1A) and MCS, further reconstructed by aligning Archean granitic blocks such as White Ridge (WR), Grand Marais (GM) and Wawa-Abitibi (purple, WA) from gravity lows (Figure 1B, 2A). The area was affected by a plume constrained by a Rayleigh Wave Low Velocity Anomaly (RWLVA) (Foster et al., 2020) (Figure 1A). This generated uplift in central Lake Superior focused on a region around the Coldwell Complex (Figure 1A). Subsequently, Earlystage (~ 1110 - 1104 Ma) magmatism in the proto-rift generated by NE-SW extension along strike slip faults such as the Thiel Fault (TF) (Figure 1A), in the central and eastern arm of the MCR. By the end of the Early-stage, the plume was deeply embedded in the lithosphere and initiated the start of a thick N-S crustal ridge or proto-hotspot track in central Lake Superior during the late Early- to Latent stage (Figure 2B,C). After a break in activity recorded by the Breakup Unconformity (BU), the plume moved relatively southward during the Main-stage and possibly influenced stress re-orientation to N-S (Figure 2D). This locked the eastern arm and locally, new thick oceanic crust formed along the syncline in central Lake Superior, generating the western rift arm. However, magmatism and breakup terminated shortly after as a result of Grenvillian compression, evidenced by the Magmatic Unconformity (MU). During the Main stage, active upwelling and anomalously thick oceanic crust formation was highest on the crustal ridge (black dash-dot line, Figure 2D), measured at line A, just north of the WA block (purple arrow, Figure 2D) and decreasing toward line C (purple arrow). Further west, at St Croix, upwelling rates approach unity and no oceanic crust formation took place. Pulsing and waning of the plume stem/conduit through time (Figure 2) is recorded in the unconformities, suggesting a drop in potential temperature and upwelling rate around BU time (Latent stage) (Figure 2C). 69 �Figure 1: A. Geological map with seismic lines (red). Numbering refers to onshore geological sections. B. Gravity map. Abbreviations: MB Marquette Basin, KP Keweenaw Peninsula, HVB High Velocity Body. Figure 2: Tectono-magmatic evolution. South shore (between yellow cubes) is mobile, North shore is kept fixed. EPC Early Plume center, LPC Latent Plume Center, MPC Main Plume Center. REFERENCES Foster, A., Darbyshire, F., and Schaeffer, A., 2020. Anisotropic structure of the central North American Craton surrounding the Mid-Continent Rift: evidence from Rayleigh waves. Precambrian Research, 342: 105662. Shay, J., and Trehu, A., 1993. Crustal structure of the central graben of the Midcontinent Rift beneath Lake Superior. Tectonophysics, 225: 301-335. 70 �Constraining the timing of crustal exhumation following the Penokean orogeny using U-Pb, Sm-Nd, and Lu-Hf geochronology and microstructural analysis SALERNO, R.,1 CANNON, W.F.,1 SOUDERS, A.,2 THOMPSON, J. M.,2 VERVOORT, J.,3 1 U.S. Geological Survey, Reston, VA 20192, 2U.S. Geological Survey, Denver, CO 80225, 3Washington State University, Pullman, WA 99164. Precambrian terranes in the Lake Superior region have complex igneous, metamorphic, and deformational histories spanning the Eoarchean to the Neoproterozoic. In this sequence, the Penokean orogeny (1880–1830 Ma) is the first collisional event in a long-lived subduction system on Laurentia’s southern margin, marking a transition in the style of Laurentian assembly from the amalgamation of disparate Archean cratons to growth by accretion of juvenile arcs. The metamorphic and structural history of the corridor of Archean gneiss domes south of Lake Superior is typically attributed to the Penokean orogeny. However, recent 40Ar/39Ar geochronology calls this relationship into question as ~1760 Ma cooling ages across the region indicate the deformation and metamorphism coincident with dome uplift is markedly younger (Schneider et al., 2004; Tinkham and Marshak, 2004; Holm et al., 2005; Schulz and Cannon, 2007). To correctly distinguish the effects of the Penokean orogeny and more accurately reconstruct the Paleoproterozoic tectonic history of the Upper Midwest, we present new U-Pb, Sm-Nd, and LuHf geochronology and microstructural analyses for a suite of metamorphosed and deformed rocks within and adjacent to several gneiss domes (Fig. 1). Titanite U-Pb ages and trace element compositions reflect Archean metamorphism at 2550 ± 46 Ma (2SE), and variable degrees of recrystallization in the Paleoproterozoic (Fig. 2). Apatite and monazite U-Pb ages, along with garnet Lu-Hf ages of metamorphosed supracrustal rocks directly outside of domes, record the onset of peak conditions by 1837 ± 7 Ma that continued beyond the end of the Penokean orogeny until 1782 ± 15 Ma. The garnet Sm-Nd ages of several samples are ~70 Ma younger than the Lu-Hf ages, reflecting a period of cooling and exhumation between 1752 ± 10 and 1738 ± 9 Ma. This exhumation interval overlaps with the U-Pb ages of synkinematic titanite at 1713 ± 32 Ma and the 1750 ± 6 Ma Lu-Hf age of re-equilibrated pre-kinematic garnets. U-Pb ages of apatite in one sample reflect much later reheating of the system at 1592 ± 26 Ma. These data show that deformation and metamorphism related to the uplift of gneiss domes in the Lake Superior region can only be partially linked to tectonic events between 1880–1830 Ma. Peak metamorphic conditions lasting until 1782 Ma indicate the persistence of thick orogenic crust well after the end of the Penokean orogeny—perhaps supported by continued convergence or an unrecognized collisional event along the margin. Exhumation beginning at 1752 Ma coincided with subduction farther south during the Yavapai orogeny (1760-1720 Ma), whereas uplift may be related to crustal extension above the downgoing slab, aided in part by gravitational forces acting on overthickened crust. Extension during this time would also have played a role in the generation and spatial accommodation of Yavapai-age granite intrusions across the region (e.g., East-Central Minnesota batholith). The youngest apatite U-Pb age at 1592 Ma likely represents distal thermal effects of the Mazatzal orogeny (1650–1600 Ma) farther south. These data reveal the gneiss dome structures in the Upper Midwest are the result of a protracted history including several Paleoproterozoic metamorphic, deformational, and uplift events spanning more than 70 m.y.. 71 �Figure 1: Left, geologic map showing gneiss domes in northern Michigan with geochronology sample sites. Cities shown – Marquette (M), Watersmeet (W), Republic (R), and Hardwood (H). Modified from Tinkham and Marshak (2004). Figure 2: Right, ages at 2SE precision. Vertical bars represent the timing of the Sacred Heart (S), Penokean (P), Yavapai (Y), and Mazatzal (M) orogenies. Hatched fields represent durations of metamorphic prograde and cooling intervals. Sm-Nd ages of UPMI 10 23 and UPMI 8 23 have high uncertainties from mineral inclusions that could not be removed prior to analyses and therefore are not used to define the duration of the cooling interval. Diagrams below show the Archean-Mesoproterozoic tectonic evolution of southern Laurentia. Yellow star shows study area location. REFERENCES Holm. D., Van Schmus, W., MacNeill, L., Boerboom, T., Schweitzer, D., Schneider, D., 2005, U-Pb zircon geochronology of Paleoproterozoic plutons from the northern mid-continent, USA: Evidence for subduction flip and continued convergence after geon 18 Penokean orogenesis: Geol. Soc. Am. Bull. 117, 259-275. Schneider. S., Holm. D., O’Boyle. C., Hamilton. M., Jercinovic. M., 2004, Paleoproterozoic development of a gneiss dome corridor in the southern Lake Superior region, USA: GSA Special Paper 380, 339357. Schulz. K., Cannon. W., 2007, The Penokean orogeny in the Lake Superior Region: Precambrian Research, 157, 4-5. Tinkham. D., Marshak. S., 2004, Precambrian dome and keel structure in the Penokean orogenic belt of northern Michigan, USA: GSA Special Paper 380, 321-338. 72 �Identifying Abandoned Mine Surficial Features Using Mask R-CNN, Upper Peninsula Michigan. SHALIFOE, MaryElizabeth1, VOICE, Peter1 1 Department of Geological and Environmental Sciences and Michigan Geological Survey, Western Michigan University, 1903 W Michigan Ave, Kalamazoo MI, 49008-5241, USA From the 1840s to the 1980s, iron, and copper mining in Michigan's Upper Peninsula thrived, leaving behind numerous surficial features from the early underground mining practices. Even today the Eagle Mine located in Marquette County is still active Mining both copper and nickel. Today's demand for rare earth minerals has sparked interest in exploring locations near these primary ores including the tailing piles (Demas A., 2023). Mapping old mine features using optical satellite imagery is challenging in Michigan's Upper Peninsula due to dense vegetation and snow cover – instead we need to use techniques that allow us to see through this cover. This study aims to assess the performance of object detection Deep Learning Models (DLMs) in mapping potential mine features using high-resolution terrain data (LIDAR-derived 1meter Digital Elevation Models) produced through the 3D Elevation Program. Dickinson County was chosen as the study area due to its rich history of 52 known abandoned mines within the East Menominee Iron Range (Figure 1). This study targeted various features, such as prospect pits, open pits, lateral ditches, and waste piles, resulting in a total of 946 identified features used for training the DLMs. The object detection methods available within ArcGIS software were evaluated including Feature Classifier, Faster R-CNN, and Mask R-CNN. Our initial evaluation has shown that Mask R-CNN performed better than the other methods, due to the Mask R-CNN method that enables pixel-level segmentation in addition to object detection (Maxwell A. E., et al., 2020. Our ongoing work is focused on the refinement of the model parameters to better locate surface features related to historic mining. Once the model is completed, it will be tested on various locations in northern Michigan within the mining ranges of the Marquette Iron Range, Menominee Iron Range, Gogebic Iron Range, and the Copper Ranges within Ontonagon and through the Keweenaw. This will then be ground-truthed, by going out into the field to verify the locations of the features or using historical topographic maps to verify the existence of features that may be inaccessible. REFERENCES Department of Environment, Great Lakes, and Energy, (2024) EGLE Geowebface; mining and minerals, State of Michigan, https://www.egle.state.mi.us/geowebface/#btnToolNavInfo Demas A. (2023). Bipartisan Infrastructure Law Funds Geologic Mapping in Michigan, by Bipartisan Infrastructure Law Investments, USGS, https://www.usgs.gov/special-topics/bipartisaninfrastructure-law-investments/news/bipartisan-infrastructure-law-funds-6 Maxwell, A. E., Pourmohammadi, P., & Poyner, J. D. (2020). Mapping the Topographic Features of Mining-Related Valley Fills Using Mask R-CNN Deep Learning and Digital Elevation Data. Remote Sensing, 12(3), 547. https://doi.org/10.3390/rs12030547 73 �Figure 1: Study Area in Dickinson County, showing the distribution of underground mines (Department of Environment, Great Lakes, and Energy, 2024). Figure 2: Mine Features located near East Central Vulcan Mine in Dickinson County, DEM sourced USGS TNM, 2016. (Department of Environment, Great Lakes, and Energy, 2024). 74 �Basaltic rocks of the Animikie Group in Ontario: Geochemical characteristics and tectonic significance SMYK, Mark1,3, HOLLINGS, Pete1, METSARANTA, Riku2, CUNDARI, Robert3, KISSIN, Stephen1 and KURCINKA, Colleen3 1 Department of Geology, Lakehead University, 955 Oliver Road, Thunder Bay, ON P7B 5E1 Canada 2 Ontario Geological Survey, Ministry of Mines, 933 Ramsey Lake Road, Sudbury, ON P3E 6B5 Canada 3 Ontario Geological Survey, Ministry of Mines, 435 James St. South, Thunder Bay, ON P7E 6S7 Canada The Paleoproterozoic Animikie Group in Ontario records a history of continental sedimentation and minor volcanism on the southern margin of the Superior Craton between ca. 1.88 Ga and 1.82 Ga. Both the chemical sedimentary rock-dominated Gunflint Formation and overlying, siliciclastic sedimentary rock-dominated Rove Formation contain significant intervals of tuffs and basalt flows. Copper-bearing amygdaloidal basalts were noted in Crooks and Blake townships (Coleman 1900); basalt flows and tuffs were identified by Gill (1925) and Goodwin (1960) in the Mink Mountain area, and by Tanton (1931) in Oliver Township. Tanton (1936) mapped “Rove basalt” in Devon Township. In 2022, a 774 m diamond drill hole (DDH ST-2201), completed by Metal Energy Corp. in Hartington Township, provided a complete section from Rove Formation into Archean basement. New geochemical, petrographic and stratigraphic data gleaned from this drill core and recent field work have provided insights into the nature of the basaltic rocks. The lowermost volcanic unit occurs in the middle of the Gunflint Formation, exposed near Mink Mountain; its base is ~53 m above Archean basement. Approximately 21 m thick, it consists of several distinctive, typically massive, locally pillowed, vesicular/spherulitic basalt flows. An isolated outcrop of amygdaloidal basalt in Oliver Township, approximately 40 km northeast of Mink Mountain, shares similar petrographic characteristics, stratigraphic position and geochemistry. Limited geochemical data gleaned from amygdaloidal basalts in Crooks Township are similar to those of the aforementioned Gunflint lavas. Further work is required to elucidate the nature and stratigraphic position of these flows. Basaltic flows, exposed on top of Rove shales and wackes in Devon Township (Cundari, 2010) had recently been considered part of the Mesoproterozoic Midcontinent Rift, based mainly on a Keweenawan reversed paleomagnetic mean direction and equivocal stratigraphic constraints (Cundari et al., 2012). However, a mafic interval, approximately 510 m above Archean basement and ~4 m thick, occurs within DDH ST-22-01 and displays a variolitic, chilled basal contact and spherulitic, vesicle-like features, similar to those displayed by the lowermost Devon flows. Similar trace element geochemistry further supports the contention that the mafic rocks intersected in drilling may be correlative with the Devon basalts and with other, similar rocks exposed in an isolated outcrop in Hardwick Township, ~30 km northwest of the Devon basalts. The Gunflint basalts are characterized by moderate La/SmCN ratios (~1.9 to 3.9), negative Nb-Ta and Ti anomalies and relatively flat Gd/YbCN ratios (~1.3 to 1.7). The Devon basalts are characterized by moderate La/SmCN ratios (~2.8 to 3.5), negative Nb and Ti anomalies and moderate Gd/YbCN ratios (~3.0-3.6). In a Penokean tectonic context, the Gunflint basalts may represent limited back-arc volcanism (cf. Kissin and Fralick, 1994), contemporaneous with the older phase of volcanism in the Pembine domain of the Pembine-Wausau terrane (PWT; ca. 1875 Ma, Zi et al. 2022). The Devon basalts may represent relatively deeply sourced, crustally contaminated, OIB-like magmas generated after ca. 1840 Ma, at the same time as renewed volcanism in the PWT. 75 �REFERENCES Coleman, A.P. 1900. Copper and iron regions of Ontario; in Ninth Report of the Bureau of Mines, 1900; Ontario Bureau of Mines, Annual Report, pp.143-191. Cundari, R. 2010. Geology and Geochemistry of the Devon volcanics, south of Thunder Bay, Ontario; unpublished HBSc. thesis, Lakehead University, Thunder Bay, 68p. Cundari R., Piispa, E., Smirnov, A.V., Pesonen, L.J., Hollings P. and Smyk, M. 2012. Geochemistry and paleomagnetism of the Devon township basalt, Ontario, Canada; in Mertanen, S., Pesonen, L. J. and Sangchan, P. (eds.). Supercontinent Symposium 2012 – Programme and Abstracts; Geological Survey of Finland, Espoo, Finland, p.30-31. Gill, J. E. 1925. Gunflint iron-bearing formation; Geological Survey of Canada, Summary Report 1924, pt.C, pp.28-88; https://doi.org/10.4095/103167. Goodwin, A.M. 1960. Gunflint iron formation of the Whitefish Lake area; Ontario Department of Mines, Annual Report, vol.69, pt.7, pp.41-63. Kissin, S.A. and Fralick, P.W. 1994. Early Proterozoic volcanics of the Animikie Group, Ontario and Michigan, and their tectonic significance; 40th annual Institute on Lake Superior Geology, Houghton, MI, Proceedings, vol.40, pp.18-19. Tanton, T.L. 1936. Pigeon River area, Thunder Bay District; Geological Survey of Canada, Map 354A, sheet 1, scale 1:63 360; https://doi.org/10.4095/107549. Tanton, T. L. 1931. Fort William and Port Arthur, and Thunder Cape map areas, Thunder Bay District, Ontario; Geological Survey of Canada, Memoir, 167, 222. https://doi.org/10.4095/100799. Zi, J.-W., Sheppard, S., Muhling, J.R. and Rasmussen, B. 2021. Refining the Paleoproterozoic tectonothermal history of the Penokean Orogen: New U-Pb age constraints from the PembineWausau terrane, Wisconsin, USA; GSA Bulletin; March/April 2022; v. 134; no. 3/4; p. 776–790; https://doi.org/10.1130/B36114.1; 8 figures; 1 supplemental file. published online 1 July 2021. 76 �Sedimentologic and geochemical evidence of marine incursion to the Oronto Group basin, southern Lake Superior region, at ca. 1.08 Ga STEWART, Esther K.1, 2, TAPPA, Michael 1, BAUER, Ann1, BRENGMAN, Latisha3, and PRAVE, Anthony 4 1 Department of Geoscience, University of Wisconsin-Madison, Madison, Wisconsin 53705 2 Wisconsin Geological and Natural History Survey, University of Wisconsin-Madison Division of Extension, Madison, Wisconsin 53705 3 Department of Earth and Environmental Sciences, University of Minnesota-Duluth, Duluth, Minnesota 55812 4 School of Earth and Environmental Sciences, University of St. Andrews KY16 9TS, Scotland/UK The late Mesoproterozoic Oronto Group (Copper Harbor Conglomerate, Nonesuch, and Freda Formations), Wisconsin and Michigan, preserves a continuous record of depositional environment and related microbial habitat. Over three kilometers of siliciclastic sediments with minor authigenic, molar tooth calcite record physical and biogeochemical processes acting within the Oronto Group basin at the time of deposition and early diagenesis. Combined sedimentologic and geochemical evidence motivates reevaluation and refinement of evolving depositional conditions (Stewart, 2025). Sedimentary facies indicate a shallow marine, tidal influence on deposition, requiring marine incursion to the Laurentian interior at ca. 1.08 Ga (Stewart et al., 2024). The degree of marine connectivity is investigated using C, O, and Rb-Sr isotope compositions of calcite microspar in molar tooth structures and carbonate laminae of the Nonesuch Formation. Molar tooth structures and laminae were milled from thick sections, and one split of sample powder was analyzed for C and O isotopes while the other underwent a multistep chemical separation process to isolate Rb-Sr isotopes from calcite. Carbon isotope (δ13C) values (-3.9 to -2.0‰) of earliest diagenetic calcite reflect organic matter remineralization driven by in situ microbial carbon cycling (e.g. Gilleaudeau and Kah, 2013). Values of δ18O (-6.7 to -3.6‰) measured in the calcite microspar of molar tooth structures overlap the isotopic signature of marine carbonates from other late Mesoproterozoic evaporative marine basins (e.g. Kah, 2000). The 87Sr/86Sr of least-altered calcite (~0.7068 to 0.7069) reflects marine mixing with continental runoff. Combined, these data reflect deposition within a restricted-marine epeiric setting. In addition to isotopic evidence for marine connectivity, conditions of salinity, redox, and productivity are evaluated using whole rock geochemistry of fine-grained siliciclastics and rare earth element + yttrium (REY) distributions of calcite microspar. Whole rock geochemistry was compiled from published sources and new data was collected from two cores in Wisconsin. Calcite REY distributions were analyzed from aliquots of the same sample material processed for Rb-Sr isotopes. Shale geochemistry, including Mo and U enrichment and stratigraphic trends in proxies for detrital input (Zr, Al), redox (S, TOC) and productivity (Ba, P) reveal deposition within an oxidized basin with a deep, fluctuating chemocline and expansion of anoxic and euxinic conditions during maximum flooding and base level lowstand. REY distributions of calcite microspar preserve an early diagenetic estuarine signal characterized by muted, positive La and Y/Ho anomalies and heavy REE enrichment. Shale geochemistry and carbonate REY distributions bring into focus the prevalence of particle shuttling between the water column and shallow sediments that likely enhanced and focused nutrient P bioavailability, analogous to modern estuarine nutrient cycling. Collectively, these data provide a richer understanding of late Mesoproterozoic environmental conditions that influenced early eukaryote ecology. 77 �Figure 1: Images from core (A, C-D, F) and thin section (B, E) of the Nonesuch Formation highlighting sedimentary structures indicative of tidal influence and molar tooth calcite microspar targeted for geochemistry. A & C: photos and line drawings showing close association of fine-grained sandstone (light color) and shale (dark color). Note mud drapes on bi-directional ripple laminae (red arrows, A), flame structures (red arrow, C), and structureless mud layers indicative of fluid mud deposits. B: Photomicrograph (cross-polarized light) showing bedding deflecting around molar tooth structure (arrow) and brittle deformation of molar tooth structures (1 displaced from 2). D: molar tooth structure (MT) cross-cutting carbonate-rich layers (CR) in drill core. E: Photomicrograph (plane-polarized light) highlighting characteristic molar tooth microspar texture. F: Core photo showing ~2 cm diameter mud ball with subangular rhyolite clast at its core. Scale bars are 1 cm unless otherwise noted. REFERENCES Gilleaudeau, G. J., and Kah, L. C., 2013. Carbon isotope records in a Mesoproterozoic epicratonic sea: carbon cycling in a low-oxygen world. Precambrian Research, 228, 85-101. Kah, L. C., 2000. Depositional δ18O signatures in Proterozoic dolostones: constraints on seawater chemistry and early diagenesis. SEPM Special Publication 67, 346 – 360. Stewart, E. K., Bauer, A. M., and Prave, A. R., 2024. End-Mesoproterozoic (ca. 1.08 Ga) epeiric seaway of the Nonesuch Formation, Wisconsin and Michigan, USA. Geological Society of America Bulletin, 136, 7-8, 2940-2960. https://doi.org/10.1130/B37060.1 Stewart, E.K., 2025. Sedimentologic and geochemical markers of marine incursion to the interior Laurentian Oronto Group basin at ca. 1.08 Ga. Ph.D. dissertation, University of WisconsinMadison. 78 �Midcontinent Rift extension ceased and the rift inverted due to the Grenvillian orogeny 1 2 3 SWANSON-HYSELL, Nicholas , HODGIN, Eben B. , ALEMU, Tadesse , FUENTES, 4 2 5 4 Anthony , ZHANG, Yiming , SLOTZNICK, Sarah and FAIRCHILD, Luke 1 Department of Earth and Environmental Sciences, University of Minnesota, Minneapolis, MN, USA Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI, USA 3 Department of Geology and Environmental Science, University of Wisconsin, Eau Claire, WI, USA 4 Department of Earth and Planetary Science, University of California, Berkeley, CA, USA 5 Department of Earth Sciences, Dartmouth College, Hanover, NH, USA 2 The cessation of rifting within the Midcontinent Rift was a key event in the evolution of the Lake Superior region. If rifting had continued and led to the formation of an ocean basin, the subsequent geologic and paleogeographic history would have been profoundly different. In a 1994 paper, Bill Cannon used emerging geochronology from the Midcontinent Rift and the Grenville orogen to conclude that the closing of the Midcontinent Rift was a far-field effect of compression associated with the Grenvillian orogeny (Cannon, 1994). An alternative proposal was put forward by Stein et al. (2014) who proposed that the Midcontinent Rift is an abandoned rift segment associated with successful rifting along Laurentia’s margin. In this contribution, we leverage improved chronostratigraphy within the volcanics and sedimentary rocks of the Midcontinent Rift (e.g. Fairchild et al., 2017; Hodgin et al., 2024) combined with rich new records of metamorphic chronology associated with the Grenvillian orogeny (reviewed in Swanson-Hysell et al., 2023) to revisit this question and gain fresh insight. The transition from active rift extension to post-rift thermal subsidence is recorded by the Brownstone Falls angular unconformity in northern Wisconsin. The thinning of the Copper Harbor Conglomerate from >2,200 m thick on the Keweenaw Peninsula of Michigan to pinching out against the unconformity implies topographic relief at the onset of post-rift sedimentation that is comparable to that in the modern-day East African rift. The end of active extension (ca. 1090 to 1085 Ma) is coincident with early prograde metamorphism associated with the Grenvillian orogeny, whose metamorphic imprint extends from the Blue Ridge inliers of the eastern US up through the Grenville Province of eastern Canada. This timing is consistent with the onset of continent-continent collision resulting in the cessation of extension in the rift. Figure 1: The start and end of Midcontinent Rift extension compared with U-Pb dates from Grenville Province metamorphic chronometers (blue diamonds: zircon; red pentagons: monazite). The rift developed during an interval of tectonic quiescence on the margin. Extension ceased with the onset of the Grenvillian orogeny and the rift contractionally inverted during the peak of the Ottawan stage. 79 �Following the end of Midcontinent Rift extension, deposition of the Oronto Group continued until ca. 1045 Ma (Hodgin et al., 2024; Fuentes et al, in review). This deposition resulted from post-rift thermal subsidence prior to contractional deformation associated with the Grenvillian orogeny propagating into the continental interior. Paleomagnetic records from the Oronto Group, including recently published data from the Nonesuch Formation (Slotznick et al., 2024) and new unpublished data from the upper Freda Formation, reveal that Laurentia’s plate motion dramatically slowed coincident with the onset of Grenvillian orogenesis. Preceding rapid motion was associated with ocean basin closure leading up to continent-continent collision that changed the force balance and slowed the plate. Oronto Group deposition ended when contractional deformation associated with the Grenvillian orogeny propagated into the Midcontinent. This deformation occurred in two phases with major exhumation occurring during the peak of the Ottawan phase of the Grenvillian orogeny and a second more minor phase of ca. 1000 to 980 Ma contraction associated with the Rigolet phase (Hodgin et al., 2024). This final interval of contraction is associated with the ca. 990 Ma deposition of the Jacobsville-Bayfield Group (Hodgin et al., 2022; Alemu et al., 2023). Following 130 Myr of tectonic excitement from ca. 1110 to 980 Ma, stability returned to Laurentia’s Midcontinent region. While the comings and goings of inland seas and the occasional impact crater have left their mark on the geological record, there has been only very minor tectonism over the past billion years. REFERENCES Alemu, T.B., Hodgin, E.B., and Swanson-Hysell, N.L., 2023. Grooving in the midcontinent: A tectonic origin for the mysterious striations of L’Anse Bay, Michigan, USA. Geosphere, 19(5), 1291–1299. Cannon, W.F., 1994. Closing of the Midcontinent Rift—A far-field effect of Grenvillian compression. Geology, 22(2), 155–158. Fairchild, L.M., Swanson-Hysell, N.L., Ramezani, J., Sprain, C.J., and Bowring, S.A., 2017. The end of Midcontinent Rift magmatism and the paleogeography of Laurentia. Lithosphere, 9(1), 117–133. Hodgin, E.B., Swanson-Hysell, N.L., DeGraff, J.M., Kylander-Clark, A.R.C., Schmitz, M.D., Turner, A.C., Zhang, Y., and Stolper, D.A., 2022. Final inversion of the Midcontinent Rift during the Rigolet Phase of the Grenvillian orogeny. Geology, 50(5), 547–551. Hodgin, E.B., Swanson-Hysell, N.L., Kylander-Clark, A.R.C., Turner, A.C., Stolper, D.A., Ibarra, D.E., Schmitz, M.D., Zhang, Y., Fairchild, L.M., and Fuentes, A.J., 2024. One billion years of stability in the North American Midcontinent following two-stage Grenvillian structural inversion. Tectonics, 43(9). Slotznick, S.P., Swanson-Hysell, N.L., Zhang, Y., Clayton, K.E., Wellman, C.H., Tosca, N.J., and Strother, P.K., 2024. Reconstructing the paleoenvironment of an oxygenated Mesoproterozoic shoreline and its record of life. Geological Society of America Bulletin, 136(3–4), 1628–1642. Stein, C.A., Stein, S., Merino, M., Keller, R.G., Flesch, L.M., and Jurdy, D.M., 2014. Was the Midcontinent Rift part of a successful seafloor-spreading episode? Geophysical Research Letters, 41(5), 1465–1470. Swanson-Hysell, N.L., Rivers, T., and van der Lee, S., 2023. The late Mesoproterozoic to early Neoproterozoic Grenvillian orogeny and the assembly of Rodinia: Turning point in the tectonic evolution of Laurentia. In: Whitmeyer, S.J., Kellett, D.A., Tikoff, B., and Williams, M.L. (Eds.), Laurentia: Turning Points in the Evolution of a Continent. Geological Society of America Memoir 220, 337–356. 80 �Ni-Cu-PGE Mineralization at the Mineral Lake Intrusive Complex, northern Wisconsin THOMPSON, Bekah R. 1, LODGE, Robert W.D.1 1 Department of Geology & Environmental Science, University of Wisconsin-Eau Claire, 105 Garfield Avenue, Eau Claire, WI 54701, USA The Mineral Lake Intrusive Complex (MLIC), near Mellen, Wisconsin, is a 1.1 Ga layered and differentiated mafic intrusive complex within the Mesoproterozoic Mid-Continent Rift in the Lake Superior region (Siefert et al., 1992). This intrusive complex hosts Ni-Cu-PGE mineralization discovered in the 1960’s via electromagnetic geophysical surveys and at least 16 drill holes were completed (Bakheit, 1981). With an increase in demand for domestic critical minerals to supply metals for energy, communication, and military infrastructure, underexplored prospects like the Mineral Lake Ni-Cu-PGE prospect are increasingly important. This project aims to describe the mineralogy of the sulfide inclusions and the host intrusion geochemistry to better understand the geological characteristics of PGE-mineralization within the MLIC. Two drill holes were re-logged (WIS-12 and WIS-11), totaling ~950 linear feet of core, and sixteen samples were collected from representative intrusive phases and mineralization types. Micron-scale PGE-bearing mineral phases are described using the SEM-EDS. Whole rock geochemistry of the MLIC was completed via X-ray Fluorescence (WD-XRF). Silicate and sulfide mineralogy was determined by transmitted and reflected light petrography. Mineralization is hosted in either medium-grained, equigranular olivine gabbro, olivine norite and troctolite phases of the intrusion and are found as mm-scale sulfide segregations composing 1-10% of the rock. Weak foliation and alteration along fractures are observed along brittle-ductile shears resulting in serpentinization of olivine. Contacts between intrusive phases are generally gradational over a few centimeters. Sulfide inclusions contain varying amounts of chalcopyrite, pyrrhotite, and pentlandite and are not obviously correlated with any specific intrusive phase. Graphite, both fracture-associated and matrix-associated, were observed in the Troctolite and Olivine norite phases. Sulfide inclusions are comprised of primarily pyrrhotite with variable amounts of chalcopyrite and pentlandite. Analysis on the SEM-EDS has shown PGE mineralization is commonly hosted as micron-scale inclusions within pyrrhotite and pentlandite. These PGEbearing mineral phases include rhenium-bearing molybdenite (Mo,Re)S2, padmaite (PdBiSe) (found within silicates), argentopentlandite Ag(Fe,Ni)8S8 , sperrylite (PtAs2), rhenite (ReS2), naldrettite (Pd2Sb). PGE minerals are typically ~5 microns. Notably large, 30-micron sperrylite (PtAs2) grains and 25-micron rhenite (ReS2) grains were observed (Figures 1C and 1D). PGE’s are most abundant hosted in sulfide minerals whereas the notable critical elements (Bi, Mo, Sb, Te, Ob, Se) tend to be hosted in the silicates. These results are comparable to other conduit-type and contact-type MCR intrusions, although the age of the MLIC is coeval with contact-type mineralization. Dunka road of the Duluth complex is a contact type Ni-Cu-PGE sulfide deposit. Phases include norite-hosted disseminated sulfides, troctolite-hosted disseminated sulfides, PGE-rich disseminated sulfides, and chalcopyrite rich disseminated sulfides (Theriault and Barnes, 1998). Since the MLIC is a large, differentiated intrusion that is coeval with other contact-type mineralization in the MCR, future exploration efforts and research should focus on the lower parts of the intrusion where dense sulfides may accumulate. 81 �Figure 1. (A) Regional map of Mineral Lake area. Map modified from Cannon and Ottke (1999). Inset map from Mudrey & Brown (1982). (B) Rhenium-bearing molybdenite (Mo,Re)S2 (white) under SEMEDS, (C) Rhenite (ReS2) (white) under SEM-EDS, (D) Sperrylite (PtAs2) under SEM-EDS (white). REFERENCES Bakheit, A.K., 1981. Petrography of Cu-Ni mineralization in the Mineral Lake area, Ashland County, Wisconsin. Unpublished M.S. thesis, University of Wisconsin-Madison. Cannon, W.F. and Ottke, D., 1999. Preliminary digital geologic map of the Penokean (Early Proterozoic) continental margin in northern Michigan and Wisconsin (No. 99-547). The Geological Survey of America. Middlemost EAK (1994) Naming materials in the magma/igneous rocks system. Earth Sci Rev 37:215– 224. doi:10.1016/0012-8252(94)90029-9 Siefert, K.E., Peterman, Z.E., Thieben, S.E. 1992. Possible crustal contamination of the Midcontinent Rift igneous rocks: examples from the Mineral Lake intrusions, Wisconsin. Canadian Journal of Earth Science, 29. 1140-1153. Thériault, R.D., Barnes, S.-J., 1998. Compositional variations in Cu-Ni-PGE sulfides of the Dunka Road deposit, Duluth complex, Minnesota: the importance of combined assimilation and magmatic processes. Can. Mineral. 36, 869–886 82 �A Porphyry in a Rift? Constraining the Petrogenesis of the Jogran Porphyry, Mamainse Point, Ontario, Canada: Insights from Zircon and Melt Inclusion Geochemistry. TOLLEY, James1, HANLEY, Jacob2, CROWLEY, James3, TSAY Sasha4, ZAJACZ Zoltan4, and HOLLINGS, Pete1 1 Department of Geology, Lakehead University, 955 Oliver Road, Thunder Bay, ON, P7B 5E1, Canada. Department of Geology, Saint Mary’s University, 923 Robie Street, Halifax, Nova Scotia, B3L 2Y5, Canada. 3 Isotope Geology Lab, Department of Geosciences, Boise State University, 1910 University Drive, Boise, Idaho, 83725-1535, USA. 4 Department of Earth Sciences, University of Geneva, Rue des Maraichers 13, Geneva, 1205, Switzerland. 2 The Jogran quartz-monzonite porphyry, located near Mamainse Point, Ontario, Canada, on the northeastern shoulder of the ~1.1 Ga Midcontinent Rift System (MRS), hosts unique porphyrystyle Cu-(Mo) mineralization in an intra-plate, rift-related large igneous province setting (Perelló et al., 2020). Combining high precision zircon geochronology with zircon and melt inclusion (MI) geochemistry refines the timing of emplacement and offers constraints on the crystallization temperature, oxygen fugacity (fO2), and melt composition (including ore metal tenor) during the magmatic evolution of the deposit. A new high precision 206Pb/238U zircon age of 1090.90 ± 1.27 Ma (CA-TIMS) constrains the formation of the Jogran porphyry to the waning of the main Rift Stage (1102-1090 Ma) and synchronous with the transition to the Late-Rift stage (1090-1083 Ma), as defined by Woodruff et al., (2020). Zircon geothermometry (Crisp et al., 2023) and oxybarometry (Loucks et al., 2020) suggest crystallisation conditions of 900-670 °C and a fO2 range of ∆FMQ = -1.3 to +0.6. As temperatures decrease, ΔFMQ values increase along a trend subparallel to the SO₂-H₂S buffer. The presence of sulfide inclusions in zircon, confirms sulfide saturation during crystallization. The analysed zircon crystals are zoned. They display an increase in [Yb/Gd]n ratios (1220) and concomitant depletion in Th/U (1.0-0.4) in the rims relative to the cores ([Yb/Gd]n = <12; [Th/U] = >1). This zonation infers that the parental magma underwent a single stage of fractionation and crystallisation upon emplacement. Melt inclusions (MIs) range in composition from 65-70 wt.% SiO₂ with 5.5-8.3 wt.% K₂O and K₂O/Na₂O ratios of ~1.5-3.5, suggesting the parental melt was alkalic to shoshonitic. Low Cs concentrations, coupled with high Rb, Ba, and Nb, in MIs indicate minimal crystal fractionation of a near-primitive, mantle-derived composition. In contrast, whole-rock data show lower alkali contents (4.0 wt.% K2O) and have a subalkalic affinity, suggesting crustal contamination or alteration obscured the primitive magmatic signature. A new, precise U-Pb zircon age constrains the felsic magmatism and porphyry-style mineralization at Jogran to the period of maximum lithospheric weakening/crustal thinning during the shift from extensional tectonics to thermal subsidence in the late stages of the MRS. This study suggests that early partitioning of metals and sulfur into magmatic fluids played a key role in ore formation. However, the conditions required remain ambiguous, as the tectonic environment at Jogran differs markedly from the subduction-related settings upon which most porphyry models are based. Porphyry deposits are increasingly recognised across a broader range of tectonic settings (e.g., southeast China [Richards, 2021]; and central Europe [Drew, 2006]). Jogran highlights the potential for porphyry-style mineralisation in non-subduction tectonic contexts and underscores the need to better understand metallogenic pathways beyond the traditional subduction models. 83 �Quartz-Feldspar Porphyry (K-Ar) 1 Tribag Breccia (K-Ar) 2 Mamainse Point Rhyolites (Rb-Sr) 3 Mamainse Point Volcanics (U-Pb) 4 Mamainse Point Tuff (U-Pb) 5 Jogran Porphyry Error bars represent the reported uncertainties in respective studies. Satellite Mineralisation (Re-Os) 6 Porphyry Stock Mineralisation (Re-Os) 6 References 1 Norman and Sawkins (1985) 2 Roscoe (1965) 3 Van Schmus (1971) 4 Davies et al. (1995) 5 Swanson-Hysell et al. (2014) 6 Perelló et al. (2020) Figure 1: New U-Pb zircon age (1090.90 ± 1.27 Ma) for the Jogran porphyry (diamond), published age data (circles) and MRS stages defined by Woodruff et al., (2020) – Early (green), 1109–1104 Ma; Latent (orange), 1104–1098 Ma; Main (blue), 1098–1090 Ma; and Late (purple), 1090–1083 Ma. REFERENCES Drew, L.J. (2005). A tectonic model for the spatial occurrence of porphyry copper and polymetallic vein deposits - Applications to central Europe: U.S. Geological Survey Scientific Investigations Report 2005-5272. Crisp, L. J., Berry, A. J., Burnham, A. D., Miller, L. A. & Newville, M. (2023). The Ti-in-zircon thermometer revised: The effect of pressure on the Ti site in zircon. Geochimica et Cosmochimica Acta 360, 241–258. Loucks, R. R., Fiorentini, M. L. & Henríquez, G. J. (2020). New magmatic oxybarometer using trace elements in zircon. Journal of Petrology, 61, egaa034. Perelló, J., Sillitoe, R. H. & Creaser, R. A. (2020). Mesoproterozoic porphyry copper mineralization at Mamainse Point, Ontario, Canada in the context of Midcontinent rift metallogeny. Ore Geology Reviews, 127, 103831. Richards, J.P, (2021). Porphyry copper deposit formation in arcs: What are the odds? Geosphere, 18, 130– 155. Woodruff, L. G., Schulz, K. J., Nicholson, S. W., and Dicken, C. L. (2020). Mineral deposits of the Mesoproterozoic Midcontinent Rift system in the Lake Superior region - A space and time classification. Ore Geology Reviews, 126, 103716. 84 �Evaluating Ni in Olivine as a Prospectivity Indicator for Magmatic Ni-Cu-(PGE) Deposits: A Preliminary Study from the Midcontinent Rift System. TOLLEY, James1, HOLLINGS, Pete1, MEXIA DURAN, Kevin1 and HARDING, Myles1 1 Department of Geology, Lakehead University, 955 Oliver Road, Thunder Bay, ON P7B 5E1, Canada. Nickel content of olivine [(Mg,Fe)2SiO4] can serve as an important petrogenetic marker in mafic igneous systems. Nickel’s concentration in olivine is controlled by several factors, including: (1) the Ni content of the parental magma; (2) the partition coefficient of Ni between olivine and the silicate melt; and (3) variable parameters such as temperature, pressure and fO2 of the melt (Li et al., 2007). More recently, Ni content in olivine has been studied as a potential fertility indicator for magmatic Ni-Cu sulfide deposits as well as providing information about the original composition of the magma. Olivine crystallizing from sulfide-saturated magmas will exhibit lower Ni contents relative to olivine crystallized from sulfide-undersaturated melts. This premise was assessed by Barnes et al. (2023) across Ni-Cu-(PGE) deposits globally, but there was a notable paucity of olivine data from Ni-Cu deposits within the Midcontinent Rift System (MRS). This study presents 700 new electron probe microanalyses (EPMA) of Ni and other major elements in olivine from five magmatic Ni-Cu-(PGE) deposits in the MRS: Sunday Lake, Steepledge, Escape, Current and Hele. These data have been integrated with published datasets from the mineralised Seagull, Eagle and East Eagle intrusions to produce the first regional-scale dataset of olivine chemistry from the MRS. Curation of this data aims to assess: (1) the deposit scale variability of olivine chemistry across the MRS; (2) the utility of Ni in olivine as a regional prospectivity indicator for Ni-Cu deposits within the MRS; and (3) the implications for primary melt evolution across the MRS. Preliminary results show that olivine forsterite (Fo) contents (i.e., 100*Mg/[Mg+Fetotal], mol %) range from Fo72.5-85 across most intrusions, except for the Hele intrusion, which has a much wider range (Fo44.0-82.5; Fig. 1). Across the entire dataset, Ni concentrations in olivine vary significantly (600-2500 ppm) and generally increase with higher Fo values. The range of Ni in olivine values can be vary up to 1000 ppm from a single deposit, over a narrow Fo range (e.g., Current Intrusion – Fo79.7-81.7). Furthermore, concentric zoning between Mg-rich cores relative to the Mg-depleted rims is frequently observed – most notably at Eagle East, where an average core analysis displays Fo80 vs. average rim value of Fo77. This preliminary compilation of olivine compositions across the MRS both reveals the variability of olivine compositions within a single intrusive complex and highlights fractionation trends regionally. The integration of the MRS data with the global compilation of Barnes et al. (2023) highlights the similarities between the signatures of unmineralized and mineralized intrusions and that there is no universal evidence for consistent Ni depletion in olivine from mineralised deposits. Placing the MRS olivine data within the context of other Ni-Cu-(PGE) systems may elucidate previously unrecognized potential within the MRS, and similarly these data can contribute to the global understanding of magmatic processes that culminate in economically viable deposits. 85 �Figure 1: Ni concentrations (ppm) in olivine as a function of forsterite content (Fo#) from a suite of maficultramafic Ni-Cu intrusions located in the Midcontinent Rift System. Grey field denotes the global array of ‘barren’ intrusions as defined by Barnes et al. (2023). Published datasets comprise: (1) Eagle and East Eagle Intrusion – Ding et al. (2010); (2) Seagull Intrusion – Heggie (2005); (3) Coldwell, Two Duck Gabbro – Good (1992); (4) Coldwell, Eastern Gabbro – Shaw (1997). REFERENCES Barnes, S. J., Yao, Z. S., Mao, Y. J., Jesus, A. P., Yang, S., Taranovic, V., & Maier, W. D. (2023). Nickel in olivine as an exploration indicator for magmatic Ni-Cu sulfide deposits: A data review and reevaluation. American Mineralogist, 108, 1-17. Ding, X., Li, C., Ripley, E. M., Rossell, D., & Kamo, S. (2010). The Eagle and East Eagle sulfide ore‐ bearing mafic‐ultramafic intrusions in the Midcontinent Rift System, upper Michigan: Geochronology and petrologic evolution. Geochemistry, Geophysics, Geosystems, 11(3). Good, D.J. (1992). Genesis of copper-precious metal sulphide deposits in the Port Coldwell Alkalic Complex, Ontario; unpublished Ph.D. thesis, McMaster University, Hamilton, Ontario, 203p. Heggie, G.J. (2005). Whole rock geochemistry, mineral chemistry, petrology and Pt, Pd mineralization of the Seagull Intrusion, northwestern Ontario. Unpublished M.Sc. thesis, Lakehead University, Thunder Bay, Ontario, 156. Li, C., Naldrett, A. J. & Ripley, E. M. (2007). Controls on the Fo and Ni Contents of Olivine in Sulfidebearing Mafic/Ultramafic Intrusions: Principles, Modeling, and Examples from Voisey’s Bay. Earth Science Frontiers 14, 177–183. Shaw, C. S. (1997). The petrology of the layered gabbro intrusion, eastern gabbro, Coldwell alkaline complex, Northwestern Ontario, Canada: evidence for multiple phases of intrusion in a ring dyke. Lithos, 40(2-4), 243-259. 86 �Origin of magnetic black sand found on the south Shore of Lake Superior Verhoeven, J.D1., and Zowada, Tim2 1 Iowa State University, Emeritus Prof., Iowa State University, Levering MI 49755, jver@iastate.edu, 2 Custom Knifemaker, Boyne Falls, MI, timzowada@gmail.com Many of the beaches on the shores of Lake Superior contain black sand which is magnetic. This sand can be smelted into iron using the ancient bloomery process which produces small chunks of iron called blooms. They consist of iron containing a low level of carbon. The chunk of iron is filled with cavities containing remnant slag produced in the smelting process. Recent experiments [1] have shown that often but not always the resultant iron of the blooms contain significantly levels of Ti and that one of the microconstituents in the slag is the mineral ulvöspinel. The authors of [1] had assumed that the magnetic black sand came from erosion of banded hematite-magnetite iron formations (BIF) which are the source of the iron mined in the Lake Superior region. Finding Ti in some of the blooms shows that there is likely an alternate source of the iron in the black sands, namely the Fe–Ti oxide-bearing ultramafic intrusions (OUIs) deposited in the lake bottom from the 1.1Ga Midcontinent Rift (MCR) that runs through the lake region. This talk presents a comparison of the composition of the ulvöspinel constituent found in bloom slags of black sand smelts with the composition of the ulvöspinel constituents found in a recent study [2] of drillings from the Coldwell Complex region located at the north central region of Lake Superior which contain Fe-Ti magnetite-ilmenite intergrow deposits from the MCR. The results present strong evidence that the some of the magnetic black sand on Lake Superior’s shores comes from source rocks of MCR deposits in the Coldwell Complex and some from BIF deposits in the lake bottom. Additional evidence that the Fe-Ti source rock is the Coldwell Complex is that the location of the black sand used in the study is in the same region of the south shore of Lake Superior near White Fish Point where yooperlite rocks have been found. Literature data [3] shows that the source rock of the yooperlite is the Coldwell Complex. REFERENCES 1 Zowada T., Straszheim W., Chumbley S. and Verhoeven. J.D., 2025. A study of the carbon distribution and alloy composition of iron blooms made from two different batches of black sand collected from Lake Superior, accepted for publication in JMMA. 2 Brzozowski M.J., Samson I.M., Gagnon J.E., Linnen R.L. and Good D.J., 2021. Effects of fluid-induced oxidation on the composition of Fe–Ti oxides in the Eastern Gabbro, Coldwell Complex, Canada: implications for the application of Fe–Ti oxides to petrogenesis and mineral exploration, Mineralium Deposita 56, 601–618. 3 Laughlin, R. and Carlson A., 1987. A new find of fluorescent sodalite, Mineral News 34, no 5. 87 �88 �Zircon Petrochronology of the Eau Claire Volcanic Complex in the Marshfield Terrane of the Penokean Orogen, Northcentral Wisconsin VICKERS, Lyndsie A.1, LODGE, Robert W.D.1 1 Department of Geology and Environmental Sciences, University of Wisconsin-Eau Claire, Eau Claire, WI 54701 USA The Eau Claire Volcanic Complex (ECVC) serves as a type locality for Penokean-age magmatism and volcanism associated with the Marshfield terrane in the Penokean Orogeny (Figure 1A). This volcanic event is central to tectonic models that describe the collision of the Pembine-Wausau oceanic arc terrane and Archean crustal fragments of the Marshfield terrane with the southern margin of the Superior Craton (Shultz and Cannon 2007). A defining feature of these models is the proposed "double" subduction zone system, which is thought to have overprinted the Archean Marshfield terrane with younger Penokean volcanism and magmatism during ocean closure. Newer tectonic models suggesting accordion-like tectonics (Zi et al, 2022) still rely on historic interpretations of the ECVC where only physical outcrop descriptions in the literature (Myers et al, 1980). Despite its significance, the ECVC has remained understudied due to extensive Paleozoic and Quaternary cover which obscures outcrops and little mineral exploration and drilling. To address these challenges, this study focused on remote outcrops of the ECVC along the Eau Claire River in Wisconsin, aiming to better constrain tectonic models and clarify terrane boundaries in the southern Penokean Orogen. Field mapping yielded samples that were processed to isolate zircon grains for U/Pb radiometric dating and petrochronological analyses. These zircons were analyzed using a Laser Ablation Inductively Coupled Plasma Mass Spectrometer (LA-ICP-MS) at Laurentian University, providing the only modern geochronological and petrochronological data (U/Pb, Lu/Hf, zircon trace elements) from this region in the orogen. The results challenge long-standing interpretations of the area’s stratigraphy. Rocks previously classified as Paleoproterozoic volcanic units have Archean U/Pb ages and are now redefined as part of an Archean greenstone belt, significantly altering the geological narrative of the region. This study confirmed the presence of Paleoproterozoic intrusions (Figure 1C), but Lu-Hf isotopic analyses revealed that magmas did not have isotopic inheritance from the Archean basement (Figure 1D). This suggests the Paleoproterozoic magmas are in structural contact with Archean rocks. Additionally, Paleoproterozoic metasedimentary samples exhibited a diverse array of sedimentary sources (Figure 1-B), including Penokean, Marshfield, and a 2.2 Ga provenance, hinting at potential links to the Chocolay and Huronian groups which are continental rift assemblages formed during the breakup of an Archean supercontinent (Shultz & Cannon, 2007). As the first comprehensive petrochronological dataset from the Penokean Orogen, this study not only redefines the age and origin of key outcrops but also shows the complexity of the region’s tectonic and magmatic evolution. The discovery of previously unrecognized Archean basement rocks necessitates a reassessment of regional stratigraphy, particularly for classic outcrops historically attributed to Paleoproterozoic activity. Furthermore, the potential connection between the Marshfield terrane’s sedimentary sources and those of the Superior Craton’s rift assemblages raises questions about the terrane’s origins, suggesting it may represent a southernmost fragment of the Superior Craton. 89 �Figure 1: (A) Geologic map of the North Fork of the Eau Claire River adapted from Brown (1988). (B) Histogram displaying the distribution of zircon ages from a metasedimentary sample (C) Weighted mean diagram for intrusive sample showing a uniform range of zircon 207Pb/206Pb ages. Grey bars represent outliers and were excluded from age calculation. (D) ƐHf(i) versus 207Pb/206Pb age comparing ECVC intrusion to other Penokean intrusions in the Marshfield Terrane (Weber et al., 2023). REFERENCES Brown, B.A., 1988. Bedrock Geology Map of Wisconsin (Regional Map Series: West-Central Sheet), University of Wisconsin-Extension Geological and Natural History Survey, Scale: 1:250,000. Schulz K.J., Cannon W.F., 2007. The Penokean orogeny in the Lake Superior region. Precambrian Research 157:4-25. Weber, E.M., Lodge, R.W.D., Marsh, J.H., 2023. U/Pb geochronology and zircon petrochronology of Paleoproterozoic magmas from the Marshfield terrane, Penokean Orogen, Wisconsin. Institute on Lake Superior Geology Proceedings, 69th Annual Meeting, Eau Claire, Wisconsin, Part 1-Program and Abstracts, p. 97-98. Zi, J.W., Sheppard, S., Muhling, J.R., and Rasmussen, B., 2021. Refining the Paleoproterozoic Tectonothermal History of the Penokean Orogen: New U-Pb Age Constraints from the PembineWausau terrane, Wisconsin, USA: GSA Bulletin, v. 134, p. 776–790. Myers, P. E., Cummings, M. L., and Wurdinger, S. R., 1980. Precambrian geology of the Chippewa Valley, Wisconsin, Institute of Lake Superior Geology 26th Annual Meeting, Eau Claire, Wisconsin, Field Trip Guidebook 1, 123 p 90 �Geospatial Learning Resources to Explore Relationships with Keweenaw Geology VYE, Erika1, and LIZZADRO-MCPHERSON, Daniel2 1 Great Lakes Research Center, Michigan Technological University, 1400 Townsend Drive, Houghton, MI, 49931, United States 2 Geospatial Research Facility, Michigan Technological University, 1400 Townsend Drive, Houghton, MI, 49931, United States The globally significant geologic processes and features of the Keweenaw have fostered relationships with land and water for millennia. We have created three geospatial, digital resources that express the deep relationships between the underpinning geology and the scientific, educational, cultural, economic, and aesthetic significance of publicly accessible geosites in the Keweenaw region. These geospatial resources serve as living databases that will evolve over time in order to support formal and informal learners in understanding the fundamental role geology plays in our varied relationships with land and water. All resources are hosted and shared publicly on the Geospatial Research Facilities’ Enterprise Geospatial Research Portal at Michigan Technological University. 1) The Keweenaw Coastal Geoheritage StoryMap was created as a teaching and learning resource for local K-12 educators to explore the rock types of the Keweenaw at geosites along the shores of Lake Superior (Fig. 1). This resource: a) provides an overview of the main lithologies in the Keweenaw region, b) shares where federal, state, local government, and nonprofit organizations are working to preserve the rich geologic landscape and fragile wetlands of the Keweenaw, and c) provides a virtual learning experience to explore over 30 geologically significant sites along Lake Superior (Lizzadro-McPherson & Vye, 2023). 2) The Keweenaw Geoheritage Geoatlas is a knowledge directed exploration geospatial data hub that integrates physiographic landscape-wide feature coverages with a variety of downloadable GIS datasets. The repository of maps and data articulate the geoheritage of the region; the data hub supports educators, students, the scientific community, local tourist entities, land use planners, and the broader public in learning more about specific geosites in the Keweenaw region (Cowling, et al., 2024). 3) The Keweenaw Geoheritage geodatabase and web-viewer provide an innovative way of exploring the relationships between the bedrock geology and how this influences current and future education, conservation, and sustainable economic development initiatives in the Keweenaw region (Fig. 2). Each site expresses: a) a brief description of how the site contributes to the rich geoheritage of the Keweenaw, b) a 360-photo, and c) a description of the scientific (specific to the geologic phenomena), educational, cultural, economic, and aesthetic significance of the site (Lizzadro-McPherson & Vye, 2024). These resources are intended to support the co-stewardship of cultural heritage, restoration of legacy mining sites, conservation issues, and the development of sustainable economic opportunities based on the region’s globally significant geologic underpinnings. Further, they serve as the foundation for an evolving community participatory geoheritage mapping project in the Keweenaw. Through innovative, interactive geospatial resources we aspire to engage the broader public in sharing and exploring their relationships with the Keweenaw landscape (e.g. stories, valued geosites, photos, and curiosities). 91 �REFERENCES Cowling, R., Lizzadro-McPherson, D.J., Verissimo, L. & Vye, E.C. (2023). Keweenaw Geoheritage Geoatlas. DOI: 10.13140/RG.2.2.30945.28005 Lizzadro-McPherson, D.J., and Vye, E.C. (2024). Keweenaw Geoheritage Geodatabase. Michigan State Geological Survey; U.S. Geological Survey, National Cooperative Geologic Mapping Program (Award #G23AC00285 FY23). Lizzadro-McPherson, D. J. & Vye, E.C. (2023). Keweenaw Coastal Geoheritage StoryMap. DOI: 10.13140/RG.2.2.12680.74242 Fig. 1: Keweenaw Coastal Geoheritage StoryMap Fig. 2: Keweenaw Geoheritage Viewer 92 �Battle between the bands: competitive precipitations lead to bands in banded iron formations Xu, Huifang, and Zhou, Tianyu Department of Geoscience, University of Wisconsin–Madison, Madison, WI 53706, USA Banded iron formations (BIFs) are massive chemical deposits composed of alternating layers of chert and iron-rich minerals (such as hematite, magnetite and siderite), with three scales of bandings: microbands, mesobands (1 mm - 10 cm) and macrobands. Their abundance in the Archaean/early Proterozoic era and their absence thereafter suggest that chemical conditions and iron transport pathways on the early Earth surface were different from those after 1.7 billion years ago. Thermodynamic calculations show that Fe-silicate metal complex can be generated by hydrothermal leaching of low-Al oceanic crustal rocks such as komatiites, which suggest that the presence of low-Al ultramafic rocks (for example, komatiitic rocks) in the early oceanic crust were the reason for both the formation of BIFs and their abundance in the Archaean/early Proterozoic era (Wang et al., 2009). This is consistent with the findings that the ages of komatiites are correlated strongly, at the 99% confidence level, with the ages of BIFs (Isley and Abbott, 1999). We used the PHREEQC geochemical modeling package was used to test the chemical reactions that may have led to the banding pattern in the BIFs based on competitive precipitation of ferrihydrite (precursor of hematite and magnetite) and silica gel (precursor of chert) (Zhou et al., 2024). After aqueous ferrous silicate decomposition in O2-sufficient condition (pO2 ≥ 10-4), the faster Fe2+ oxidation and precipitation rate led to Fe-rich layer preceding Si-rich layer with ferrihydrite and amorphous silica as the precursor to the hematite and quartz, respectively. Episodic Fe(H3SiO4)2 input resulted in successive cycles of layering (Fig. 1). O2-deficient environments (pO2 < 10-4) results in jaspilite (no bands). The kinetic model also works well for the formation of siderite bands under O2-deficient environments when pCO2 is high. In summary, the precipitation process model proposed in this study offers an alternative abiotic explanation for the formation of distinct bands within the BIFs. 93 �Figure 1: Schematic depositional model of felsic volcanism associated BIF-like Iron Formations under different surface oxygen levels in a shallow hot spring lake (O2-deficient: pO2 < 10-4; O2-sufficient: pO2 ≥ 10-4). When the O2 level is high, the mix of aerobic lake water and Fe(H3SiO4)2-bearing spring fluid leads to the ferrihydrite-rich layer and amorphous silica-rich layer precipitating successively. But ferrihydrite and silica coprecipitate when O2 is deficient and there is no layering. The ferrihydrite-rich layer would convert to hematite-rich layer and amorphous silica-rich layer transforms into Si-rich layer. The surface water level is regulated by precipitation, evaporation and seepage from surrounding rock without visible inflow or outflow. DOI:10.1016/j.chemgeo.2024.122091) REFERENCES Isley, A. E. & Abbott, D. H., 1999. Plume-related mafic volcanism and the deposition of banded iron formation. J. Geophys. Res. 44, 15461-15477. Wang Y., Xu, H., Merino, E., and Konishi, H., 2009. Generation of banded iron formations by internal dynamics and leaching of oceanic crust. Nature Geoscience, 2, 781-784. Zhou, T., Hill, T., Roden, E. E., and Xu, H., 2024. The Felsic Volcanism Associated BIF-like Iron Formations: Their Origin and Implication for BIFs. Chemical Geology, 656, 122091. 94 �Broadly coeval but migrating deformation, plutonism and deposition in the northeastern Superior Province, Québec: evidence of hot accretionary orogeny and oroclinal folding in the late Archean? ŽÁK, Jiří1, TOMEK, Filip 1, 2, KACHLÍK, Václav 1, VACEK, František 1, 3 SVOJTKA, Martin 2, and ACKERMAN, Lukáš 2 1 Institute of Geology and Paleontology, Faculty of Science, Charles University, Albertov 6, Prague, 12843, Czech Republic 2 Institute of Geology of the Czech Academy of Sciences, Rozvojová 269, Prague, 16500, Czech Republic 3 Czech Geological Survey, Klárov 3, Prague, 11821, Czech Republic The James Bay Road in Québec provides a unique crustal-scale transect across several principal lithotectonic belts of the northeastern Superior Province. From north to south, these belts are Bienville (plutonic), La Grande (ʽgrayʼ gneisses, metaplutonic), Opinaca–Némiscau (metasedimentary), and Opatica (mostly volcano-plutonic). This assemblage has been controversially interpreted to record non-plate vertical tectonics driven by mantle plume activity or as resulting from the step-wise accretion of these belts to the northerly proto-cratonic core. We present here new structural and anisotropy of magnetic susceptibility (AMS) data from all the units along the James Bay Road transect. The data indicate a multistage fabric evolution: (1) an early fabric F1 is preserved only in isolated domains across the La Grande and Opinaca belts and is at a high angle to boundaries between the individual belts; (2) the F2 fabric seems to record a progressive reorientation (folding) towards an E–W direction; (3) the regionally dominant F3 fabric indicates regional NNE–SSW shortening across all units and is coeval with pluton emplacement and anatexis; (4) the last major ductile event is represented by localized dextral shear zones. The AMS indicates that magnetic foliations in general match well the mesoscopic foliations, whereas magnetic lineations vary from steeply plunging to subhorizontal, interpreted as recording a transition from vertical stretching during folding to horizontal stretching during shearing. The latter interpretation is further supported by a more detailed analysis of the ca. 2712–2697 Ma Radisson pluton, which is a syntectonic intrusion at the Bienville–La Grande boundary. Its magmatic to solid-state fabrics analyzed through the AMS also suggest a strain evolution from vertical magma stretching during regional shortening overprinted by later dextral shearing. In conjunction with the previously published U–Pb geochronology, the structural data suggest a short time span and north-to-south migration of plutonism, deposition, and contractional/transpressional deformation, altogether favoring a modern-style plate tectonics operating in the NE Superior Province in the late Archean. Furthermore, the relict F1 and F2 fabrics overprinted by F3 are interpreted as being compatible with changing block/microplate convergence vectors and crustal-scale folding of the outboard La Grande and Opinaca–Némiscau belts. In conclusion, the northeastern Superior Province may have been assembled as large, hot accretionary supra-subduction orogen, oroclinally folded, and finally dextrally sheared. Were this interpretation correct, a key question arises what was the geodynamic cause and mode of the oroclinal folding, whether with or without hard collision, taking the Alaskan terrane wreck or Mongolian orocline as prime examples, respectively. 95 � https://digitalcollections.lakeheadu.ca/files/original/772524cda5601210f7360a628832f9e3.pdf ed3bb63e47c2b1557a98f43e22c97dfb PDF Text Text Volume 71, Part 2 71st ANNUAL MEETING Mountain Iron, Minnesota, May 14-17, 2025 PART 2—Field Trip Guidebook �Meeting Co-Chairs Amy Radakovich, Allison Severson, Eric Nowariak, Stacy Saari, Aaron Hirsch Special thanks to field trip leaders: Zsuzsanna Allerton Terry Boerboom Kevin Boerst Latisha Brengman Annia Fayon George Hudak Mark Jirsa Phil Larson Dean Peterson Cullen Phillips Laurie Severson Mark Severson Alex Steiner i �71st Institute on Lake Superior Geology Volume 71 consists of: Field Trip 1 – Transect of the Quetico Subprovince ................................................................................... 1 Field Trip 2 – Drill Core from three Cu-Ni Deposits of the Duluth Complex .......................................... 15 Field Trip 3 – How Do You Make Iron and/or Manganese Ores in Proterozoic Iron Formation?............ 46 Field Trip 4 – New Geological Insights into the Genesis of Iron Ores at Lake Vermilion – Soudan Underground Mine State Park..................................................................................................................... 74 Field Trip 5 – Neoarchean Alkalic Intrusions in the Wawa and Quetico Subprovinces ......................... 108 Field Trip 6 – Unique Keweenawan Inclusion (Colvin Creek) in the Duluth Complex ......................... 136 Field Trip 7 – Classic Outcrops of Northeastern Minnesota ................................................................... 151 Field Trip 8 – Glacial Lake Norwood and the Koochiching Lobe…. ..................................................... 188 ii �Trip 1 – Quetico FIELD TRIP 1 Transect of the Quetico Subprovince Eric Nowariak1 and Mark Jirsa (retired)1 1 Minnesota Geological Survey, College of Science and Engineering, University of Minnesota, 2609 Territorial Road, St. Paul, MN 55114 Introduction This trip will examine exposures of the metasedimentary, migmatitic, and intrusive rocks of the Neoarchean Quetico subprovince from north of Mountain Iron to near Crane Lake and along part of the Echo Trail. It will attempt to “unpack” the primary components of deposition, magmatism, deformation, and metamorphism that likely spanned 40 million years (~2700-2660 Ma). The latter is based in part on newly acquired geochronologic analyses (Jirsa and others, 2020; Salerno, 2017). The trip will also address the challenge of creating meaningful geologic maps of this and similarly complex terranes, and the apparent lithologic and temporal link between Quetico metasediments and those associated with successor basins in the region. Figure 1-1. Complex migmatite exposed at field trip stop # 3. 1 �Trip 1 – Quetico Figure 1-2. Geologic Map of Central St. Louis County. This draft version of the St Louis County Precambrian bedrock map (superceded by Jirsa, 2020) portrays parts of the Neoarchean Wawa and Quetico subprovinces of Superior Province, and the approximate location of field trip stops. Wawa subprovince colors: greens=volcanic and volcaniclastic rocks; blues=metasedimentary rocks (primarily metagraywacke); reds=iron-formation; pinks=granitoid rocks; yellows=epiclastic and volcaniclastic sedimentary rocks. Quetico subprovince is labeled: BS=biotite schist (metagraywacke); SM=schist-rich migmatite; GM=granite-rich migmatite; TM=tonalite-rich migmatite. Pale pink Lac La Croix granite is more magnetic, darker pink is less so. Bold line marks the approximate boundary between subprovinces—a fault in some places, an inferred unconformity in others. 2 �Trip 1 – Quetico GEOLOGIC SETTING The Quetico is one of a number of east-trending, largely metasedimentary subprovinces in the Superior Province. It is bounded on the south by the Wawa volcanoplutonic subprovince, and on the north by the Wabigoon subprovince. It consists of schist derived from turbiditic sedimentary rocks and a complex suite of granitic intrusions and associated migmatite. In northeastern Minnesota, the subprovince displays a roughly symmetrical distribution of metasedimentary rocks on the north and south, that grade irregularly through zones of schist-rich migmatite, to a central axial zone composed largely of polyphase granitoid migmatite and younger granite. To some extent, metamorphic grade mimics this symmetry, with generally higher grade rocks in the central axis and lower grade near the bounding volcanoplutonic subprovinces. The accretionary prism model of Williams (1990) implies deposition of sediment shed from the craton to the north, and the subducting island arc to the south by submarine fans and abyssal turbidites. The Rainy Lake-Seine River Fault zone at the southern margin of the Wabigoon subprovince is thought to mimic the subduction front. The southern boundary against the Wawa subprovince is interpreted as an unconformity in some locales, and a fault in others. DEPOSITIONAL HISTORY Timing of deposition of the clastic sedimentary rocks of the Quetico subprovince in Minnesota has been constrained by populations of the youngest detrital zircons at 2690 +/- 12 Ma (Salerno, 2017). Similarly, geochronologic studies of the Quetico metasedimentary sequences in Canada has been constrained to 2698 Ma near Atikokan, ON (Davis and others, 1990) and <2690 according to Zaleski and others (1999) near the Manitowage Greenstone Belt of the Wawa subprovince. Zaleski and others (1999) also proved deposition of graywacke units within the Manitowage Greenstone Belt were contemporaneous, if not genetically related. A similar temporal and possible genetic link between the metasedimentary rocks of the Lake Vermilion formation and turbiditic metasediments of the Quetico in Northern Minnesota, wherein immature, volcaniclastic rocks of the Lake Vermilion formation gave way to silicic, clastic sedimentation observed in the Quetico subprovince as the basin evolved from alluvial fan deposits to a deep-water, active margin depocenter as the Quetico basin developed (Davis and others, 1990). In addition to Neoarchean zircons, small populations of older zircons including Mesoarchean zircons have also been recognized (Salerno, 2017; Davis and others, 1990). Probable sources of these older zircons have identified from multiple terranes in the southern Superior province and a proximal source for the sediments is inferred. The composition of the Quetico metasedimentary rocks suggests the source region was shedding sediment from a mixture of sialic plutonic terranes and lesser juvenile volcanic terranes. In addition to the clastic metasedimentary rocks that dominate the bulk of the Quetico subprovince, thin, discontinuous amphibolitic layers are found interbedded in many areas; likely representing volcanoclastic deposits and rare flows from active volcanism occurring near the margins of the subprovince. VERMILION GRANITIC COMPLEX The migmatitic and plutonic rocks in the axial zone are known collectively in Minnesota as the Vermilion Granitic Complex (Southwick and Sims, 1980). Southwick and Ojakangas (1979) subdivided migmatite for mapping purposes as schist-rich and granite-rich components, depending on the ratio of paleosome to neosome. Subsequent mapping by Jirsa (2011) and Jirsa and others (2014), applied the same terms, based instead on the extent to which the predominant fabric in the rock is controlled by neosome vs. paleosome and further distinguished units based on neosome composition. In this nomenclatural system, schist-rich migmatite is schist containing intrusions of granitoid neosome as both delaminating and crosscutting bodies; granite-rich migmatite is neosome with inclusions of paleosome. These can be equated generally with the terms metatexite (low degree of partial melting) and diatexite (nearly complete fusion), respectively, of Sawyer, (2008). Field relationships within the complex (Southwick, 1991) indicate that earliest granitoid phases are leucogranite, tonalite, granodiorite, and trondhjemite, which make up the leucosome of a broad area of migmatite across the western portion of the Vermilion Granitic Complex. For this field trip guide, these granitoids, broadly of TTG affinity, are referred to as “neosome 1”. The 3 �Trip 1 – Quetico migmatite is interlayered at all scales with paleosomes of biotite schist, paragneiss, orthogneiss, and amphibolite and often carries an internal fabric similar to the paleosome. Salerno (2017) obtained a discordant U-Pb zircon age of a granodiorite phase of neosome 1 at 2684 +/- 23 Ma. The migmatite is cut by poorly to non-foliated dikes, sills, and irregular masses of two mica leucogranite with accessory garnet, and a slightly younger biotite granite and pegmatite that contain minor magnetite. The presence of magnetite within the granitic rocks related pegmatites has proved to be an important mapping tool as these intrusive bodies create conspicuous aeromagnetic anomalies (Fig. 3b). The latter forms a large granitic mass, known as the Lac La Croix granite nearest the US/Canadian border, and apophosial intrusions that flare and pinch westward, producing aeromagnetic anomalies that highlight broad fold structures. These intrusive “fingers” generally decrease in thickness and continuity westward, suggesting that the western portion of the complex may represent the roof- or floor-zone of the batholith cored by massive granite. For simplicity within this field guide, the leucogranitic and granitic rocks of the Lac La Croix granite are referred to as “neosome 2” and represents the youngest granitic intrusive units of the Vermilion Granitic Complex. Geochronologic analyses of leucogranite and granite of the Lac La Croix granite has dated the crystallization of this unit with U-Pb zircon ages of 2658.71 +/- 0.47 Ma and 2668 +/10 Ma (Jirsa and others, 2014; Salerno, 2017). a b Figure 1-3. Maps of the Crane Lake and Brule Narrows 30’X60’ quadrangles (US and Canada) illustrating the connections between attributes of structure, lithology, topography, and magnetite content in this area of abundant near-surface bedrock. (a) 30m lidar land surface topographic grid; low areas darker. Topography defines major fold structures, and massive granitic vs. foliated orthogneissic and schistose bedrock. Prominent NNW-trending linear low areas are fault and fracture systems, many of which are occupied by rivers and lakes (named). (b) First vertical derivative map of aeromagnetic data. Magnetic highs (lighter colored) typically are more granitic; lows, more schist-rich. Like the topographic map, the magnetic data identify folds and faults. Linear, NW-trending highs are normally polarized diabase dikes of the Paleoproterozic Kenora-Kabetogama dike swarm. Linear lows are coincident with topographic lows, implying oxidation by meteoric, or more likely hydrothermal fluids along fractures. Some field evidence indicates that rock adjacent to fractures is chemically weathered, and hence more easily eroded. The subparallelism of dikes with fractures may indicate that oxidizing hydrothermal fluids were temporally related to dike emplacement. Neosome 1 and neosome 2 are readily distinguished in the field based on mineralogy and textural characteristics described above. Day and Weiblen (1986) used simple geochemical plots and CIPW normative mineralogy to visualize these differences (Fig. 1-4). Both plutonic suites are characterized as calc-alkaline, metaluminous to weakly peraluminous, magnesian granitoids. Neosome 1 tonalitetrondhjemite-granodiorite intrusions are inferred to have been sourced from partial melting of mafic crust. 4 �Trip 1 – Quetico Geochemical evidence indicates that the early neosome 2 migmatite was derived from partial melting of a metasedimentary protolith (Day and Weiblen, 1986). Southwick (1991) and Day and Weiblen (1986) suggested that the younger Lac La Croix-type granite of neosome 2 may represent further distillation of granitic liquid from partial melting of the combined older migmatite and metasedimentary rocks. Figure 1-4. From Day and Weiblen (1986). (A) CIPW normative mineralogy for Vermilion Granitic Complex. Q – quartz; Pl – albite+anorthite; Or – orthoclase. “Early Plutonic Suite” is equivalent to neosome 1 of this guidebook. (B) AFM diagram of same data (Irvine and Baragar, 1971). DEFORMATION AND METAMORPHIC HISTORY The Quetico subprovince has undergone a complex deformation history over a relatively contracted tectonic history between deposition of sediments ca. 2690 Ma and intrusion of the Lac La Croix Granite related pegmatite dikes ca. 2658 Ma. As summarized by Bauer and others (2011), three main phases of deformation have been recognized. D1 produced tight to isoclinal, recumbant folds plunging to the southwest and locally overturned to the southeast and produced a weak, bedding parallel axial planar foliation. Hinges of these recumbent folds are rare, and recognition of this event are often limited to overturned bedding and bedding-parallel foliation that is crenulated by subsequent deformational events. This event may locally have produced recumbent folds over a broad region (Bauer, 1985; Poulsen and others, 1980). It occurred shortly after deposition and involved burial to produce metamorphic conditions of moderate pressure and temperature (Valli and others, 2004). Fralick and others (2006) suggested D1 deformation was contemporaneous with development of the Quetico basin as an accretionary wedge. D2 deformation was synchronous with peak regional metamorphism to upper greenschist facies in the Wabigoon subprovince and amphibolite facies in the adjacent Quetico subprovince, and produced the dominant structural grain observed in the Minnesota segment of the Quetico subprovince. Folding associated with D2 deformation produced tight to isoclinal upright folds that plunge to the E-NE 10-30°. The intrusion of neosome 1 occurred slightly prior to or contemporaneous with D2 as veins of neosome 1 are commonly folded and occupy gently to moderately plunging D2 related fold hinges. Peak metamorphism presumed to be contemporaneous with D2 deformation within the Vermilion Granitic Complex has been dated by U-Pb monazite geochronology by Salerno (2017) and has constrained to ca. 2675 Ma. Continued contractional and transpressional deformation during D3 has been noted as ductile, eastnortheast trending transpressional shear zones and coaxial refolds of D2 related structures. Folding associated with D3 deformation is better developed near plutons of the Lac La Croix granite and related granitoids, suggesting early stages of neosome 2 intrusions were contemporaneous with deformation or used these structures as conduits (Bauer and others, 1992). D2-D3 is interpreted to be a result of the accretion of the Quetico subprovince to the Wabigoon subprovince to the north. Metamorphic indicator minerals within the Vermilion Granitic Complex including garnet, sillimanite, and locally cordierite have been well documented (Day, 1990; Tabor, 1988; Salerno, 2017). Limited thermobarometric studies have determined peak metamorphism reached amphibolite facies in the axial core of the Minnesota segment of the Quetico subprovince and upper greenschist facies along the northern margin of the subprovince, with garnet-biotite thermometry revealing metamorphic temperatures between 500-600°C and 430-475°C, 5 �Trip 1 – Quetico respectively (Bauer and others, 1992; Salerno, 2017). It is unknown whether the intrusion of the Lac La Croix granite and other neosome 2 intrusions produced a significant metamorphic overprint, however Tabor (1988) recognized kyanite in metamorphic assemblages of the Quetico subprovince along its northern boundary along the Rainy Lake-Seine Fault; which may represent an earlier, relatively higher pressure metamorphic regime prior to intrusion of the Lac La Croix granite. Subsequent deformation including brittle-ductile faulting with associated planar fabrics developed locally near fault zones and minor open folds reorienting existing structures has been ascribed to continued contraction post-dating metamorphism and major plutonism has been ascribed to D4 deformation. One of the most prominent and through-going features of the Quetico subprovince in Minnesota is the Vermilion Fault—a northwest-trending structure that truncates metamorphic zones and folds that are apparent on aeromagnetic maps is likely a product of late D3 and/or D4 deformation. Based largely on geophysical maps, dextral offset along this fault is on the order of 40 km. The fault can be traced from the extreme NW corner of the state for some 250 miles southeastward to near Ely, Minnesota. There it appears to veer to the northeast, manifest as a complexly splayed, post-metamorphic thrust-system known collectively as the Burntside Lake Fault. A summary of the deformational and metamorphic features observed in the Minnesota segment of the Quetico subprovince is shown in Table 1-1 below. Event General Features Associated Fabrics Metamorphic Features Timing Source(s) D1 Recumbant folds Bedding parallel foliation N/A ca. 2690 Ma Fralick and others (2006), Bauer (1985) D2 Upright to inclined tight to isoclinal folds, axes plunge to the northeast and southwest Axial planar cleavage, strong hinge-parallel lineation Upper greenschist to amphibolite facies ca. 2675 Ma Bauer and others (1992) and references therein, Salerno (2017) D3 Upright tight to isoclinal folds – coaxial to D2 folding, east-northeast trending shear zones Axial planar cleavage, strong hinge-parallel lineation, shear fabrics proximal to fault zones Amphibolite Facies 2675-2668 Ma Bauer and others (1992) and references therein, Jirsa (2014) D4 Brittle-ductile faulting, broad folding Planar fabrics proximal to shear zones Hydrothermal alteration along fault zones </=2668 Ma Bauer and others (1992), Recent unpublished mapping Table 1-1. Summary of deformational and metamorphic features observed in the Quetico subprovince within Minnesota. CONSIDERATIONS FOR GEOLOGIC MAPPING Complex geologic terranes recording multiple, interdependent geologic processes including sedimentation, multiple phases of deformation, and diverse polyphase intrusive histories like that of the Quetico subprovince represent a unique challenge in creating meaningful, consistent geologic maps and map units. Multiple attempts to properly portray the complicated geology of the Minnesota segment of the Quetico subprovince have used varied approaches, which have proved to require the incorporation field observation, petrography, aeromagnetic and gravity anomalies, LiDAR and aerial photography, and magnetic susceptibility measurements. Early iterations of geologic maps in the area focused on the proportional differences between the paleosomatic and neosomatic components of the migmatitic rocks within the subprovince to distinguish geologic units (Southwick and Ojakangas, 1979), while other authors have decided to incorporate the textural, compositional, and petrophysical characteristics of paleosomes and neosomes to further distinguish coherent map units (Jirsa, 2011; Jirsa and others, 2014). In addition to traditional field observations, thousands of magnetic susceptibility measurements recorded for units across the subprovince have been used to varied effect (Chandler and Lively, 2014). While petrophysical characteristics of the host 6 �Trip 1 – Quetico rocks are not sufficient to determine many units, the extent and morphology of some distinct units, namely late magnetite bearing granites and pegmatites, have been found to correlate with higher magnetic susceptibilities and resultant aeromagnetic anomalies (Fig. 1-3b). The structural complexities observed in this trip are preserved from the outcrop to map-scale. Many map-scale structures are discernable in aeromagnetic derivative maps and have been used in conjunction with the magnetic characteristics described above to outline geometric and temporal relationships between deformation and intrusive intervals where outcrop exposure is insufficient. Careful observations at individual outcrops has been found to be beneficial in comparison to regional lithologic mapping. Many geologic structures may be more readily identified by field checking and correlating the roughness and patterns of exposed outcrops using lidar and aerial photos. Recognition of post-intrusive faults visible in LiDAR derived maps and as linear magnetic lows in aeromagnetic maps have also helped reconcile locales where map patterns would be otherwise difficult to align with the known structural character of the area. FIELD TRIP STOP DESCRIPTIONS It should be noted that this trip derives from several years of field work to produce two geologic maps of the western-most exposed portions of the Quetico subprovince in Minnesota (Jirsa, 2011; Jirsa and others, 2014); and refinement by more recent field work to create maps of St. Louis and Koochiching Counties (Jirsa and others, 2020; Nowariak and others, in preparation). Mapping focused largely on structural and magnetic attributes that could yield a “meaningful” geologic map of this very complex terrane, and little analytical work was conducted; though ongoing work in Koochiching county has begun to tackle this. As a result, this field trip lacks details of metamorphism, petrology, and geochemisty. Instead, the focus was largely structural, in an attempt to reconcile prominent geophysical anomalies and topographic trends with field observations. The associated maps incorporate structural data, field relationships, and thousands of magnetic susceptibility measurements to ascertain the connections between lithology and magnetite content. Because glacial sediments are thin to absent in much of the area, mapping was also influenced by 10-meter (and subsequent 1-meter, for more recent mapping) LiDAR imagery (Fig. 1-3a). Mapping in the Quetico subprovince on which this field trip is based was supported by grants from the U.S. Geological Survey STATEMAP element of the National Geologic Mapping program, and by the Minnesota Environmental and Natural Resources Trust Fund. NOTE: All locations are denoted in UTM coordinates, NAD 83, Zone 15N STOP 1 – Feldspathic graywacke of the Lake Vermilion Formation Location: 526342E/5288565N, (47.74991°, 92.64856°), Highway 53 Northbound, 0.4 miles north of Heino Road (County 467) Description: This stop examines the feldspathic metasedimentary and meta-volcanogenic sediments of the Lake Vermilion formation, formally part of the Wawa Subprovince. Here, the Lake Vermilion formation is composed of feldspathic graywackes and tuffaceous slates and wackes. The stratigraphy Figure 1-5. Pavement exposure of laminated feldspathic metagraywacke of the Lake Vermilion generally tops to the north and is folded, with locally formation. well-developed axial planar cleavage and thin shear bands. This stop serves as a reference in comparing the composition and character of the metasedimentary 7 �Trip 1 – Quetico rocks of the uppermost units of the Wawa subprovince and the metasedimentary rocks of the Quetico subprovince. Directions: From the Mountain Iron Community Center, head east on highway 169 and turn north onto highway 53, continue north 20 miles and pull-off on the right side of the highway. STOP 2 – Alkalic and Lamprophyric Intrusive Rocks, Gheen Pluton Area Location: 515162E/5306034N (47.74992°, -92.64856°) (2a); 514380E/5306809N (-92.80754°, 47.91444°) (2c); Highway 53, ~6.5 miles northwest of Cook, MN Description: This series of outcrops examines exposures of alkalic granitoids and lamprophyric rocks intruded into metasediments of the Quetico Subprovince. Stop 2a (515162E/5306034N): This outcrop preserves outstanding porphyritic textures within pyroxene syenite and syenodiorite of the Gheen Pluton (Fig. 1-6). Evidence for multiple phases of intrusion and magma mingling are observed throughout. Very coarse phenocrysts exhibit compositional zoning and local magmaticflow features. The main phase of syenite and syenodiorite contains inclusions of, and is cross-cut by medium grained, amphibole-phyric gabbro and pyroxenite. Late aplitic and pegmatitic dikes represent the youngest intrusive components of the Figure 1-6. Porphyritic syenodiorite with abundant outcrop. Chloritic slickensides are apparent on feldspar phenocrysts at stop 2a. fracture faces, locally. Stop 2b (514530E/5306605N): This outcrop of the west side of the highway, USE CAUTION WHEN CROSSING THE ROAD. Here, pyroxene-biotite phyric lamprophyric rocks are exposed (Fig. 1-7). Beyond the dominant biotite and pyroxene, the mineralogy includes prismatic hornblende, feldspar, apatite, and trace chalcopyrite. Limited work to characterize these rocks has determined they are best described as augite bearing kersantites and spessartites (Le Bas, 2007). The mineralogy and texture vary within the a b Figure 1-7. Representative examples of lamprophyric rocks exposed at stops 2b-2d. (a) Biotite-pyroxene bearing kersantite with inclusions of wallrock. (b) Pyroxene-hornblende phyric spessartite with plagioclase dominated groundmass. Blocky, prismatic pyroxene dominates the modal mineralogy here. 8 �Trip 1 – Quetico outcrop at multiple scales, where complex structural and intrusive relationships juxtapose and include multiple mineralogic and lithologic phases. Stop 2c (514380E/5306809N): This outcrop, on the east side of the highway, is composed of similar lamprophyric rocks as stop 2b, but include blocks of lamprophyric rocks of varied composition and the schist wall-rock. The schist here is commonly altered and is cross-cut by small dikes and veinlets of lamprophyric mineralogy. Schist inclusions become more abundant to the north. Stop 2d (514262/5306920): Continuing to the north from stop 2c, the dominant lithology transitions to well foliated biotite-muscovite schist cross-cut by sulfide bearing quartz veins and discontinuous dikes and veinlets of lamproid parallel to and cross-cutting foliation. Directions: From the Stop 1, continue north along highway 53, continue north ~14 miles and pull-off on the side of the highway. STOP 3 – Polyphase, granitoid rich migmatite Location: 512642E/5316320N, (48.00005°, -92.83053°), Highway 53, ~2.5 miles north of Gheen Corner Figure 1-8. Multiphase migmatite at stop 3 showing representative intrusive relationships between the host biotite schist (dark-grey to black), tonalitic neosome 1 (grey),and granitic neosome 2 (tan-pink). Schist preserves crude structural grain. 9 �Trip 1 – Quetico Description: This extensive roadcut exhibits the complex features common throughout much of the migmatitic core of the Quetico subprovince. Here, we will observe and discuss the structural and intrusive relationships and geophysical properties between the metasedimentary quartz-biotite schist paleosome, early granodioritic and tonalitic neosome 1 intrusions, and granitic neosome 2 intrusions. The complexity observed here begs the question of how to create coherent geologic maps in similarly complex regions across the central Quetico Subprovince. Stop 3a (512642E/5316320N) Here, paleosomes of biotite schist have been strongly recrystallized and exhibit a granoblastic texture with faint foliation defined by biotite orientation. Multiple phases of neosome intrusions, both mafic and felsic, include lenses and irregular, blobby bodies of biotite-hornblende granodiorite ascribed to neosome 1 affinity. All units are cross-cut by pink, coarse-grained biotite granite and syenogranite with abundant pegmatitic veins and segregations. The intrusive relationships seen here generally apply to the regional evolution of magmatic rocks within the Vermilion Granitic Complex and Quetico Subprovince, at large. Stop 3b (512645E/5316400N) The agmatic migmatite here includes mafic and silicic paleosome blocks which are disaggregated by the intrusion of both neosome 1 and neosome 2 (Fig. 1-8). Although intrusive phases of the migmatite dominate the outcrop, the structural grain of the paleosomes is preserved as relict bedding and faint foliations. One may note that the paleosomes of differing compositions are difficult to distinguish on the outcrop. Silicic, quartz-biotite schist paleosomes are strongly recrystallized and exhibit an almost massive granular texture. Mafic paleosomes are locally present and are characterized by poorly foliated hornblende (+/- pyroxene) bearing assemblages along with coarsened biotite. Mafic paleosomes seen here may represent thin layers of primary, mafic protoliths or may be restitic components of in-situ melting of the migmatitic host rock. The exposure here is representative of many of the outcrops within the migmatitic core of the Quetico subprovince and highlights the difficulty of creating meaningful geologic maps in the region. How would you map this outcrop? Stop 3c (512644E/4135316N) Small, biotite-pyroxene lamproid intrusion, similar to those inspected at stop 2. Here, acicular, prismatic pyroxene is supported in potassium feldspar-rich segregations (Fig. 1-9). Chalcopyrite is present in trace amounts. Stop 3d (512645E/5316450N) Throughout the core of the Quetico Subprovince, migmatites are locally associated with pyroxenite and pyroxene-hornblende rich gabbroic dikes. Here, a set of pyroxenite dikes with sheared, biotite rich margins crosscut the biotite schist and neosome 1 wallrock and have mutually cross-cutting relationships with granitic neosome 2 intrusions. Stop 3e (512612E/5316833N) On the northern end of the roadcut, the complex multi-stage migmatite gives way to bedded biotite schist with graded beds and crosscutting dikes of late neosome 2 granite and Figure 1-9. Acicular, prismatic pyroxene within pegmatite. Beds here are stratigraphically facing up, potassium feldspar-rich matrix at stop 3c. This small based on fining upward sequences in graded beds, intrusion is similar to alkalic rocks observed at stop 2. and dip 45 to the south-southeast. Directions: From stop 2, continue north along highway 53, continue north ~6.5 miles and pull-off on the right side of the highway. 10 �Trip 1 – Quetico STOP 4 – Schist and schist-rich rich migmatite near Myrtle Lake Location: 523750E/5324590N, (-92.68116°, 48.07414°), Highway 23, ~7.5 miles east of Orr Description: Here, quartz-feldsparbiotite schists and schist-rich migmatite of the Quetico subprovince are exposed. This outcrop preserves moderately dipping beds (30° to the E-SE) of turbiditic metasedimentary rocks with graded beds. Though obscured by metamorphism, bedding here is interpreted to be upright with graded beds observed as decimeter scale, subtle, rhythmic changes in the amount of micaceous minerals. The base of individual beds is marked by coarse grained sandy layers, which transition to biotite rich schist marking the top of the beds. Fine grains of garnet are present locally in beds Figure 1-10. Biotite schist with faint, relict bedding intruded by with appropriate composition. The schist is boudinaged and lit-par-lit dikelets of tonalitic neosome 1. intruded by boudinaged dikes and veins up to 1 meter thick and lit-par-lit injections of tonalitic and granitic neosome 1 (Fig. 1-10). Rare dikes of coarse-grained to pegmatitic, pink, granitic neosome 2 crosscut bedding and dominant fabric of the outcrop and mark the latest intrusive event. Directions: From stop 3, continue north on Highway 53 to the town of Orr and make a right turn on OrrBuyck Road (Highway 23) and continue 7.5 miles east to the roadcut. LUNCH AND STOP 5 – Vermilion Falls ***No Hammers*** Location: 531860E/5345460N, (48.26155°, -92.57072°), Picnic area off Vermilion Falls Rd (USFS 491) Description: This picturesque waterfall cuts through quartz-plagioclase-biotite schist and schist rich migmatite. Both upstream and downstream of the falls, the Vermilion River runs parallel to the dominant regional fabric defined by the orientation of the underlying bedded and foliated metasedimentary rocks and generally foliation parallel intrusions of neosome 1 before draining into Crane Lake. Vermilion Falls occupies a N-NW trending, post-metamorphic and post-intrusive fracture and fault zone orthogonal to the dominant internal fabric of the Precambrian bedrock (Fig. 1-3, Fig. 1-11). These fracture and fault networks are ubiquitous throughout the Vermilion Granitic Complex and the Quetico Subprovince and strongly influence the surface topography and outcrop exposure in the area. Little is known about the timing and relative offsets along these fault zones, though correlation of map units on either side of these features suggests only minor relative motion. Near the upper portion of the falls, tonalitic neosome 1 dikes and sills delaminate the schist along bedding and sub-parallel foliation planes and occupy mesoscopic fold hinges. Downstream, tonalitic neosome 1 dikes are discordant and cross-cut the dominant fabric in the rock. 11 �Trip 1 – Quetico Figure 1-11. Geologic map of the Vermilion Falls area, after Jirsa and others (2011) draped over LiDAR hillshade. NW trending, post-metamorphic and post-intrusive fractures and faults have been highlighted with dashed lines. "GM" - granite rich migmatite, "SM” – schist rich migmatite, “LLC” – Lac La Croix granite, “TTG” – tonalitetrondhjemite-granodiorite gneiss. Directions: From Stop 4, continue east on Orr-Buyck Road (Highway 23) for 8.5 miles, continue straight along Crane Lake Road (Highway 24) at the village of Buyck for 9.5 miles, turn left onto Vermilion Falls Road (USFS 491) for 5.6 miles, turn left onto single-lane access road to turnaround at the picnic area. STOP 6 – Echo Lake Quarry Location: 549810E/5324630N, (48.07300°, -92.33132°), Quarry off USFS 200 Description: NOTE: This is an active quarry, permission to access this site needs to be granted from the quarry operator prior to visiting. The photogenic exposures at this dimension stone quarry include washed, glacially scoured outcrops and fresh blast faces of taxitic, red-pink to pinkish grey granitic gneiss and granite with abundant mafic inclusions (Fig. 1-12). This unit is mapped as a gneissic phase of the Lac La Croix of the Vermilion Granitic Complex, temporally related to neosome 2 seen at other stops (Jirsa, 2011). Gneissic layering here is chaotic and boundaries between gneissic phases are diffuse. Abundant mafic inclusions and schlieren ranging from a few centimeters to multiple meters in size and are randomly oriented. Mafic inclusions are delaminated along planar features and have diffuse, fringed boundaries. Increases in the abundance of biotite and 12 �Trip 1 – Quetico hornblende on the margins of mafic inclusions represent restitic rinds developed during assimilation and interaction with the host granitic melt. Directions: From Stop 5, return to Crane Lake Road (Highway 24) along Vermilion Falls Road (USFS 491) and turn right. Continue southward on Crane Lake Road (Highway 24) for 5.5 miles and turn left onto Echo Trail. Continue along Echo Trail for 8.3 miles and turn right onto USFS 200 for 5 miles. Turn Left onto unnamed forest road near Gustafson Lake. RETURN TO MOUNTAIN IRON COMMUNITY CENTER Figure 1-12. Gneissic granitoid with partially digested amphibolite inclusion. Directions: From Stop 6, return to Echo Trail via USFS 200 and turn left on Crane Lake Road. Continue south on Crane Lake Road/Orr-Buyck Road to the town of Orr. Turn left onto Highway 53 and continue 44.1 miles to the Highway 169 exit ramp. Turn left onto Enterprise Drive. 13 �Trip 1 – Quetico REFERENCES Bauer, R.L., 1985, Correlation of early recumbent and younger upright folding across the boundary between an Archean gneiss belt and greenstone terrane, northeastern Minnesota: Geology, v. 13, p. 657-660. Bauer, R.L., Czeck, D.M., Hudleston, P.J., and Tickoff, B., 2011, Structural geology of the subprovince boundaries in the Archean Superior Province of northern Minnesota and adjacent Ontario: Geological Society of America Field Guide 24, p. 203-241. Bauer, R.L., Hudleston, P.J., and Southwick, D.L., 1992, Deformation across the western Quetico subprovince and adjacent boundary regions in Minnesota: Canadian Journal of Earth Sciences, v. 29, p. 2087-2103. Chandler, V.W., and Lively, 2014, Rock Properties Database; Minnesota Geological Survey web-accessible file data (http://www.mngs.umn.edu/). Davis, D.W., Pezzutto, F. and Ojakangas, R.W., 1990. The age and provenance of metasedimentary rocks in the Quetico Subprovince, Ontario, from single zircon analyses: implications for Archean sedimentation and tectonics in the Superior Province. Earth and Planetary Science Letters, 99(3), pp.195-205. Day, W.C., 1990, Bedrock geologic map of the Rainy Lake area, northern Minnesota: U.S. Geological Survey Miscellaneous Investigations Series I-1927, scale 1:50,000. Day, W.C. and Weiblen, P.W., 1986. Origin of late Archean granite: geochemical evidence from the Vermilion Granitic Complex of northern Minnesota. Contributions to Mineralogy and Petrology, 93(3), pp.283-296. Fralick, P., Purdon, R.H., and Davis, D.W., 2006, Neoarchean trans-subprovince sediment transport in southwestern Superior Province: sedimentalogical, geochemical, and geochronological evidence: Canadian Journal of Earth Sciences, v.43, p. 1055-1070. Jirsa, M.A., 2011, Bedrock geology of the Crane Lake and Brule Narrows 30’X60’ quadrangles, northern Minnesota: Minnesota Geological Survey, Miscellaneous Map M-192, scale 1:100,000. Jirsa, M.S., Block, A.R., Boerboom, Chandler, V.W., and Peterson, D.M., 2020, Bedrock geology of St. Louis County, Minnesota: Minnesota Geological Survey County Geologic Atlas C-51, Part A, Plate 2—Bedrock Geology; scale 1:200,000. [contains ancillary digital files including geophysics and geochronology] Jirsa, M.A., Boerboon, T.J., and Chandler, V.W., 2014, Bedrock geology of the International Falls-Little Fork 30’X60’ quadrangles, northern Minnesota: Minnesota Geological Survey Miscellaneous Map M-197, scale 1:100,000. Le Bas, M., 2007. Igneous rock classification revisited 4: Lamprophyres. Geology Today, 23(5), pp.167-168. Poulsen, K.H., Borradaile, G.J., and Kehlenbeck, M.M. 1980. An inverted Archean succession at Rainy Lake, Ontario: Canadian Journal of Earth Sciences, v. 17, p. 1358-1369 Salerno, R.A., 2017. Neoarchean Deposition, Metamorphism, And Intrusion In Rapid Succession, Vermilion Granitic Complex, Superior Province Of Northern Minnesota. Master's thesis, University of Minnesota – Duluth. Sawyer, E.W., 2008. Atlas of migmatites (Vol. 9). NRC Research press. Southwick, D.L., 1991, On the genesis of Archean granite through two-stage melting of the Quetico accretionary prism at a transpressional plate boundary: Geological Society of America Bulletin v. 103, p. 1385-1394. Southwick, D.L., and Ojakangas, R.W., 1979, Geologic map of Minnesota, International Falls sheet: Minnesota Geological Survey, scale 1:250,000. Southwick, D.L., and Sims, P.K., 1980, The Vermilion Granitic Complex—A new name for old rocks in northern Minnesota: U.S. Geological Survey Professional Paper 1124A, p. A1-A11. Tabor, J.R., 1988, Deformational and metamorphic history of Archean rocks in the Rainy Lake District, Northern Minnesota, [Ph.D. thesis]: Minneapolis, University of Minnesota, 224 p. Valli, F., Guillot, S., and Hattori, K.H., 2004, Source and tectono-metamorphic evolution of mafic and pelitic metasedimentary rocks from the central Quetico metasedimentary belt, Archean Superior Province of Canada: Precambrian Research, v. 132, p. 155-177. Williams, H.R., 1990, Subprovince accretion tectonics in the south-central Superior Province: Canadian Journal of Earth Sciences, v. 27, p. 571-581. Zaleski, E., van Breemen, O. and Peterson, V.L., 1999. Geological evolution of the Manitouwadge greenstone belt and Wawa-Quetico subprovince boundary, Superior Province, Ontario, constrained by U-Pb zircon dates of supracrustal and plutonic rocks. Canadian Journal of Earth Sciences, 36(6), pp.945-966. 14 �Trip 2 – Cu-Ni Duluth Complex FIELD TRIP 2 Drill Core from three Cu-Ni Deposits of the Duluth Complex Mark Severson1,2 (retired), Cullen Phillips3, and Kevin Boerst4 1 (1988–2012) Natural Resources Research Institute, University of Minnesota, Duluth, 5013 Miller Trunk Hwy, Duluth, MN 55811 2 (2013–2018) Previously Teck American, then Teck Resources Unlimited, now NewRange (joint venture between Teck and PolyMet Mining Inc.) 3 NewRange Copper Nickel, 6500 Kensington Dr., Hoyt Lakes, MN 55750 4 Twin Metals Minnesota, 400 Miners Drive East, P.O. Box 329, Ely, MN 55731 Diagram from Peterson (2010) modified from plots of Eckstrand and Hulbert (2007). This guidebook is modified and updated from a guidebook published in 2016 for the 62nd Institute on Lake Superior Geology (pdf). Severson, M., Ware, A., Boerst, K., and Geerts, S., 2016, Cu-Ni-PGE Deposits of the Duluth Complex. Proceedings of the Institute on Lake Superior Geology, Volume 62, Part 2-Field Trip Guidebook, Trip 3, P. 27-78 15 �Trip 2 – Cu-Ni Duluth Complex INTRODUCTION The Duluth Complex, located in northeastern Minnesota, is a series of tholeiitic intrusions of Keweenawan age (1.1 billion years ago) that formed with coeval flood basalts along a portion of the Midcontinent Rift. The Midcontinent Rift system developed during crustal extension during the Mesoproterozoic era and is traceable in a broad arc that begins in northeastern Kansas extending northward through the axis of Lake Superior and then southeastward into Michigan. The Duluth Complex and associated Keweenawan intrusions constitute one of the largest mafic complexes in the world. These rocks cover an arcuate area over 3,000 square miles (5,000 square kilometers) extending from the city of Duluth northward 170 miles (275 km) to the Canadian border. The northwest, convex edge of the complex defines its basal contact, which dips to the southeast towards the rift. Along this contact the complex is successively underlain by Neoarchean granites (Giants Range granitic rocks) and greenstones (Vermilion District) to the north, and Paleoproterozoic sediments (Virginia Formation and Biwabik Iron Formation) to the south. Roof rocks to the Duluth Complex consist of Mesoproterozoic intrusive and volcanic rocks of the Beaver Bay Complex and North Shore Volcanic Group, respectively. Once recognized as a single large lopolithic intrusion, the complex has since been established to be collectively comprised of numerous smaller subintrusions (Figure 2-1) that were episodically emplaced into the base of a comagmatic volcanic edifice between 1108 and 1098 million years ago. Figure 2-1. Generalized geologic map of northeastern Minnesota (modified from Miller et al., 2002). 16 �Trip 2 – Cu-Ni Duluth Complex The Duluth Complex hosts several known large low-grade disseminated Cu-Ni occurrences (Figure 2-2), all of which are located within the basal portions of the Partridge River (PRI), Bathtub (BTI) and South Kawishiwi (SKI) sub-intrusions. A cursory study by Listerud and Meineke (1977) estimated 4.4 billion tons of material averaging 0.66% Cu and 0.20% Ni, using a 0.5% Cu cutoff, in at least nine deposits. Five of these Cu-Ni deposits have recent NI 43-101 reports that estimate a combined mineral inventory well over that amount using lower cutoff values. Known resources (Measured and Indicated, and Inferred) for several of the deposits in Duluth Complex are shown in Table 2-1. Copper-to-nickel ratios generally range from 3:1 to 4:1. Primary mineralization is magmatic. Sulfur source is probably both local (from the footwall sediments) and magmatic. Sulfur isotope studies indicate that most of the sulfur was derived from the Virginia Formation. Most of the mineralization is in the basal portions of these intrusions but there are also local disseminated zones higher in the intrusions. The latter tend to be much more discontinuous except for continuous mineralized horizons, termed “Magenta” style mineralization, that are present at NorthMet and Mesaba, and to a lesser degree, at South Filson Creek. The mineralization styles at each of the Cu-Ni deposits are varied. The general geology and mineralization of the Partridge River, Bathtub, and South Kawishiwi intrusions, as well as the deposits that they host, are presented below. Figure 2-2. Distribution of Cu-NiPGE deposits (in red) and potential titaniumenriched ultramafic pipes (OUIs in blue) in the Partridge River, Bathtub, and South Kawishiwi intrusions. Note that the Mesaba deposit is mostly contained in the Bathtub intrusion. 17 �Trip 2 – Cu-Ni Duluth Complex Table 2-1. Known Resources for the Various Duluth Complex Cu-Ni-PGE Deposits at various Cut-Offs. Average values for Co and Ag are available for some of the deposits but are not shown in the table. Deposit Tons (st) millions Cu % Ni % Pd ppb Pt ppb Au ppb Maturi – Measured and Indicated 1,233 0.58 0.19 334 147 80 0.30% Cu Twin Metals Minnesota 43-101 AMEC Oct-14 Maturi – Inferred 563 0.49 0.16 305 134 68 0.30% Cu Twin Metals Minnesota 43-101 AMEC Oct-14 Birch Lake – Indicated 100 0.52 0.16 515 235 115 0.30% Cu Twin Metals Minnesota 43-101 AMEC Oct-15 Birch Lake – Inferred 239 0.46 0.15 370 180 87 0.30% Cu Twin Metals Minnesota 43-101 AMEC Oct-14 480 0.43 0.16 0.30% Cu Twin Metals Minnesota 43-101 AMEC Oct-14 425 0.41 0.14 0.20% Cu Encampment Resources Non 43101 Amax 1979 NorthMet – Measured and indicated 702 Open Pit 0.25 0.07 234 67 34 0.20% Cu New Range Cu-Ni 43-101F1 M3/HRC Dec-22 NorthMet – 441 Open Pit 0.25 0.07 243 67 34 0.20% Cu /New Range Cu-Ni 43-101F1 M3/HRC Dec-22 Mesaba – Measured and Indicated 2,207 Open Pit 0.43 0.10 97 34 25 NSR $12/ton New Range Cu-Ni 43-101F1 IMC/JDS Nov-22 Mesaba – Inferred 1,423 Open Pit 0.37 0.09 143 43 26 NSR $12/ton New Range Cu-Ni 43-101F1 IMC/JDS Nov -22 Spruce Road – Inferred Serpentine Inferred Cut-Off Company Source Partridge River intrusion The Partridge River intrusion (PRI) is exposed in an arc-shaped area ~10x20 miles (16x32 km) that extends from the southern edge of the Mesaba deposit on the northeast to the Water Hen deposit on the southwest as shown in Figure 2-2. Footwall rocks include the Virginia Formation and very locally the Biwabik Iron Formation. The basal stratigraphic section (Figure 2-3) was first described by Severson and Hauck (1990) and is briefly summarized below. Unit I (PR1) The lowest troctolitic unit of the PRI consists of intermixed troctolite and augite troctolite that locally grade to olivine gabbro. Most of the unit is sulfide-bearing with a PGE-bearing horizon at the top (Red Horizon of Geerts, 1991, 1994). Unique to PR1 are extreme variations in modal mineral percentage and average grain size. Due to this heterogeneous texture, numerous internal contacts divide PR1 into several subunits that are probably related to continuous magma replenishment. Hornfels inclusions of the Virginia Formation are most commonly present within PR1. Near the basal contact the intrusive rocks of PR1 have undergone silica contamination and norite and gabbronorite are often the dominant rock type in the bottom zone. Unit II (PR2) This unit is characterized by sulfide-poor, texturally-homogenous, troctolite that locally grades to augite troctolite and leucotroctolite. PR2 grades downward into a persistent ultramafic horizon(s) defined by melatroctolite, with local peridotite zones, that generally exhibits a sharp contact with PR1. 18 �Trip 2 – Cu-Ni Duluth Complex Figure 2-3. Stratigraphy of the Partridge River intrusion at the Mesaba, NorthMet, Wetlegs, and Wyman Creek deposits (note that the Bathtub intrusion is denoted by the BT-series units in the lower right corner). From Severson and Hauck (2008). Unit III (PR3) Unit III is the most distinctive “marker bed” of the PRI at the NorthMet, Wetlegs, and southern Mesaba deposits. This unit is fine-grained and is characterized by leucotroctolite that locally grades to troctolite and augite troctolite. In all cases, the rock presents a mottled appearance due to the presence of very coarse-grained (>2 cm) olivine oikocrysts that are irregularly distributed throughout the rock. This mottled-texture and fine-grained nature make PR3 unique relative to all the other units of the PRI. PR3 exhibits variable thicknesses at each of the Cu-Ni deposits and pinches out to the west of Wetlegs and to the southeast of Mesaba. The extreme thickness range for PR3 and its physical attributes (poikilitic) have suggested to several geologists that it may be associated with an earlier Anorthositic Series intrusive phase. In this scenario, PR3 may have been intruded earliest along the Virginia Formation-North Shore Volcanic contact and was later underplated by PR1 and PR2 in an early-formed magma chamber subject to continuous magma replenishment. Unit IV (PR4) Unit IV of the PRI is characterized by thick intervals of texturally-homogeneous troctolite and/or augite troctolite. In many areas, PR4 grades upward into a persistent zone of augite-rich augite troctolite and olivine gabbro, which in turn, grades upward into leucotroctolite that is characteristic of PR5. At its base, PR4 has a semi-persistent ultramafic horizon that contains one or more melatroctolite and/or peridotite layers. In some areas a thin semi-massive oxide layer containing very fine-grained chromium titanomagnetite is present immediately above the upper contact of PR3. Unit V (PR5) Unit V is generally an easily recognizable unit in that it is characterized by thick intervals of texturally-homogeneous, medium- to coarse-grained leucotroctolite (dominantly anorthositic troctolite). Another feature that aids in distinguishing PR5 is a highly gradational bottom contact into augite troctolite at the top of PR4. The upper contact of PR5 is sharp against one or more ultramafic horizons that mark the base of the overlying PR6. 19 �Trip 2 – Cu-Ni Duluth Complex Unit VI (PR6) Leucotroctolite (anorthositic troctolite to troctolitic anorthosite) is the most common rock type in PR6. However, near equal amounts of troctolite and augite troctolite are more common in some drill holes at Mesaba. Overall, PR6 becomes more heterogeneous, consisting of multiple rock types, toward the southern and eastern margins of the Mesaba deposit. The base of PR6 is usually marked by a fairly persistent ultramafic horizon. Unit VII (PR7) This unit consists almost wholly of homogeneous leucotroctolite at the NorthMet deposit, but it is characterized by a potpourri of rock types at Mesaba with leucotroctolite being slightly more common. Overall, PR7 becomes more heterogeneous, consisting of multiple rock types, toward the southern and eastern margin of the Mesaba deposit. PR7 contains a basal ultramafic horizon(s) in most drill holes. Unit VIII (PR8) The uppermost PRI unit that has been drilled at Mesaba is referred to as PR8 that consists of a multitude of rock types with no consistent pattern except that leucotroctolite is slightly more dominant. PR3-like inclusions are excessively common to this unit. Oxide-bearing Ultramafic Intrusions (OUIs) Several plug-like, late-stage, oxide-bearing ultramafic intrusions have been delineated in the PRI, the Bathtub intrusion (BTI), and elsewhere within the Duluth Complex (Figure 2-4). The OUIs are intrusive into all units of the PRI and BTI and range in size from large bodies (>200 feet thick, >60 meters thick) to small bodies/lenses (<30 feet thick, <9 meters thick). Rock types are characterized by coarse- to very coarse-grained peridotite and dunite to pegmatitic clinopyroxenite and locally minor orthopyroxenite. These rock types contain varying amounts of ilmenite and titanomagnetite ranging from 5% to massive oxide zones (>80% oxides). The OUIs are in sharp contact with the surrounding troctolitic rocks and are clearly younger. In almost all instances the OUIs are spatially arranged along linear trends suggesting that structural control was important to their genesis. Two of the OUIs are currently being evaluated for their titanium potential and include: 1. Longnose with a NI 43-101 inferred resource of 65.3 million tonnes of 16.4 TiO2; and 2. Titac with a NI 43-101 inferred resource of 45.1 million tonnes of 15% TiO2 (Farrow, 2012). A third OUI, Skibo, is being evaluated for its high-grade Cu-Ni-PGE potential where two vein stockwork zones have been identified by historic drill holes (Inco – up to 6.42% Ni in a 1 foot-thick massive sulfide and other intervals in the hole) and recent drilling by Encampment Minerals (Green Bridge Metals press release, Feb. 6, 2024 at www.greenbridgemetals. com). NorthMet Deposit (NewRange Copper Nickel) The NorthMet deposit is located in the PRI as shown in Figures 2-2 and 2-5. This deposit was initially drilled by United States Steel Corporation (USSC) at what they called the Dunka Road deposit. More recent drilling was conducted by PolyMet Mining Incorporated at the now renamed NorthMet deposit that is being developed by NewRange Copper Nickel (Glencore and Teck joint venture). The geology of the deposit consists of seven igneous units, originally defined by Severson and Hauck (1990) as shown in Figure 2-6. 20 �Trip 2 – Cu-Ni Duluth Complex Mineralization Trends at NorthMet Two open pits are currently planned at the NorthMet deposit - an East Pit and a West Pit (shown in Figure 2-7). The majority of economic mineralization at NorthMet occurs in three scenarios: 1. All of Unit I is mineralized at the East Pit (see cross-section in Figure 2-8); 2. mostly the upper portion of Unit I is the best mineralized in the West Pit (see cross-section in Figure 2-9) and the bottom portions of Unit I will not be mined; and 3. the cross-cutting Magenta Zone (Figs. 2-9 and 2-10) is located well above the basal contact. Grades are generally highest at the top of Unit I and decrease going down hole. However, there are exceptions, and the middle of Unit I contains the highest grades in the center of the deposit. PGE-enriched zones at NorthMet Geerts (1991, 1994) found that the top of Unit I often hosts a PGE-bearing zone that he referred to as the Red Horizon (also referred to as Red Zone) which was determined to be approximately 10 meters thick with an average of 0.57% Cu and 986 ppb Pt+Pd. Geerts also found two more PGE-bearing zones within Unit I referred to as Orange and Yellow horizons. All three of these horizons are positioned beneath ultramafic layers suggesting that they are the result of recharge events and magma mixing whereby a new influx of primitive, PGE-bearing magma was injected into the chamber creating Figure 2-4. Distribution of the Oxide-bearing Ultramafic the ultramafic layers (crystal settling) before Intrusions (OUIs) within the Partridge River, Western mixing with the resident magma (sulfideMargin and Boulder Lake intrusions. Note the linear bearing) and forming the PGE-enriched zones arrangement of OUI along various trends. beneath them. The continuity of these three PGE-bearing zones in more recent PolyMet/NewRange drilled holes is unknown and the three zones are not specifically mentioned in any NI 43-101 reports or field trip guidebooks. It is important to note that the Red Horizon/Zone has been documented to be present at the top of PR1 at Mesaba (Severson and Hauck, 2003). Mineralized Magenta Zone at NorthMet In addition to the Red Horizon, at the top of PR1, there is another PGE-bearing horizon that has been referred to as the Magenta Horizon (or Magenta Zone). This zone is unique in that it crosses several lithologic contacts and progressively downcuts through Units 6, 5, 4, and 3 in a northerly direction (Figure 2-10). The total resource volume of the Magenta zone relative to the rest of the deposit has not been documented in any NI 43-101 reports. Initially, Geerts (1991, 1994) found the Magenta Zone in six holes wherein it averaged about 0.72% Cu and 1,488 ppb Pd+Pt in an over 8 meters thick zone. Cu:Ni ratios in the Magenta Zone are reported to be 3.9-4.1:1. More recent drilling by PolyMet and NewRange has documented the presence of the PGE-enriched Magenta Zone in additional drill holes that are positioned in 21 �Trip 2 – Cu-Ni Duluth Complex the western half of the deposit as shown in Figure 2-8. The Magenta Zone is also present in the PRI along the southern edge of Mesaba deposit to the east where it is referred to as the PRU zone by NewRange CuNi. Figure 2-5. Location and geology of the NorthMet deposit relative to the nearby Mesaba deposit. Modified from combined maps of Miller and Severson (2005) and Severson and Miller (2005). Mesaba Deposit and the Bathtub intrusion (NewRange Copper Nickel) In 1990, the Natural Resources Research Institute (NRRI) was the first to define and describe the igneous stratigraphy of the PRI (Severson and Hauck, 1990). This same stratigraphy was documented to be present in portions of the Mesaba deposit in 1995 (then referred to as the Babbitt deposit). However, this stratigraphy applied to only the deep drill holes along the extreme southern portion of Mesaba and all 22 �Trip 2 – Cu-Ni Duluth Complex Figure 2-6. Igneous stratigraphic section recognized by NewRange Copper Nickel at their NorthMet deposit (not that these same units are also present along the southern margin of the Mesaba deposit where they are referred to as PR1, PR2, PR3 etc.) 23 �Trip 2 – Cu-Ni Duluth Complex Figure 2-7. Geologic map of the NorthMet deposit showing outlines of the two planned open pits. The location of the mineralized Magenta zone is present in the southern half of the West Pit. Figure 2-8. Cross-section illustrating mineralization trends in NorthMet’s East Pit. Note that all of Unit I is mineralized down to the footwall Virginia Formation. 24 �Trip 2 – Cu-Ni Duluth Complex Figure 2-9. Cross-section illustrating mineralization trends in NorthMet’s West Pit. Note that the top portion of Unit I will be mined as it exhibits the best mineralization. Note also that the Magenta mineralized zone is present in a downcutting relationship in Units 5, 4, and 3. Figure 2-10. Typical cross-section at NorthMet (facing east) showing mineralized zones and modeled units. The “Upper Zone Mineralization” in this diagram is also referred to as the Magenta zone. Note how this zone progressively transects downward into the lower geologic units in a northerly direction. 25 �Trip 2 – Cu-Ni Duluth Complex Figure 2-11. Geologic map (circa 2015) showing distribution of major igneous units in the Bathtub intrusion (BTI) and adjacent Partridge River intrusion (PRI) of the Mesaba deposit. attempts to carry this stratigraphy to the north into the majority of Mesaba were not conclusive. Through several iterative follow-up logging campaigns by the NRRI, the Bathtub intrusion (BTI) was finally recognized as a separate intrusion (Severson and Hauck, 2008). A geologic map of the Mesaba deposit showing the geologic units (per the igneous stratigraphy) is shown in Figure 2-11. At least five criterions, listed below and discussed in Severson and Hauck (2008), were initially used to help separate the PRI from the newly named BTI: 1. Abrupt terminus of the PR3 Unit (major marker bed in the PRI) northward into the BTI at the Mesaba deposit 2. Thicker sections of heterogeneous-textured rock in the BTI relative to the adjacent PRI 3. Lack of PGE-enrichment at the top of a specific unit in the BTI (BT1 Unit) relative to PGEenrichment at the top of a similar unit (PR1) in the adjacent PRI 4. The best mineralization at Mesaba is near the base of the BTI (base of the BT1 unit) where it is characterized by high Cu grades associated with pyrrhotite- and cubanite-rich zones. In contrast, the best mineralization at the majority of the NorthMet deposit is present at the top of the PR1 unit where it is associated with chalcopyrite-rich zones 5. Use of a hornfels-rich zone, termed the Hidden Rise, was used to help separate the BTI from the PRI. The current igneous stratigraphy of the Bathtub intrusion, as defined by the NRRI, is summarized in Figure 2-12, and is described in the sections below. 26 �Trip 2 – Cu-Ni Duluth Complex Figure 2-12. Stratigraphic section at the Mesaba deposit showing the relationships between major units (and their corresponding subunits) in the BTI and PRI. Modified from Severson and Hauk (2008). BT1 Unit The lowest unit of the BTI consists of intermixed troctolite and augite troctolite with localized leucotroctolite zones. Unique to BT1 are extreme variations in modal mineral percentage and average grain size; both change rapidly over zones that vary from a few feet to tens of feet thick. Due to this heterogeneous texture, numerous internal contacts subdivide the BT1 into several subunits that often cannot be correlated from drill hole to drill hole. Thus, BT1 is a mixture of various troctolitic subunits that are probably related to continuous magma replenishment. Most of this unit is sulfide bearing. Hornfels inclusions of Virginia Formation are common within the BT1 Unit, especially closer to the basal contact. The BT1 Unit has been further subdivided into several internal subunits based on the dominant presence of one rock type over other rock types. Contacts between these rock types vary from highly gradational to abrupt with locally measurable sharp contacts. The various subunits of the BT1 Unit, and hornfels-rich zones in the BT1, are presented in Figure 2-12 and some are briefly discussed below. • BT1-c – At the base of the BT1 unit there is significant silica contamination of the magma, due to assimilation of the footwall rocks, and orthopyroxene rather than olivine crystallized to produce noritic rocks. Thus, rock types that dominate in the BT1-c subunit range from norite to gabbro norite; especially near either the basal contact or surrounding common hornfels inclusions. Overall, the BT1-c subunit spatially occurs as a rind or coating along the basal contact of the BTI where it ranges anywhere from a foot-thick to over 650 feet-thick. • “The Rise” – along the extreme northern edge of the entire Mesaba deposit, the basal contact of the BTI rises steeply toward the surface. However, in one area, called “The Rise,” the basal contact actually subcrops at the surface and then drops off again in a northerly direction beneath the South Kawishiwi intrusion (see Figure 2-11 for location); A pyrrhotite-rich and graphite-rich unit within the Virginia Formation in “the Rise” has been informally termed the Bdd Po or BDPO unit. • The “Hidden Rise” – the “Hidden Rise” unit is a loosely-defined zone situated along the crest of the Local Boy anticline (Figures 2-11, 2-12 and 2-13) wherein scattered hornfels inclusions, and associated noritic rocks, are fairly common. Like the BT1-c unit, the Hidden Rise shows evidence 27 �Trip 2 – Cu-Ni Duluth Complex of mixing and contamination with the Virginia Formation. This unit is indicative of strong magma contamination and assimilation of what once may have been a magma chamber wall initially separating the BTI and PRI. Thus, the Hidden Rise is used to both define this hornfelsbearing zone and to artistically, and conveniently, divide the BTI from the PRI. Figure 2-23. Projected distribution of the Hidden Rise at Mesaba relative to structural features. The projected location of the shaft and drifts of the Local Boy ore zone are shown in red. The southern edge of the Hidden Rise is approximated due to a paucity of drill holes. BT4 Unit The uppermost unit of the Bathtub intrusion is referred to as the BT4 Unit. It was originally correlated with PR4 of the PRI. However, BT4 is distinctly different from PR4 in that the BT4 Unit is heterogeneous-textured at all scales (though less heterogeneous than BT1 overall), composed of many alternating rock types, and is locally sulfide-bearing. The BT4 Unit appears to grade into thicker, more homogenous troctolitic packages toward the extreme east of the deposit. The BT4 Unit has been further subdivided into several more internal subunits based on the dominant presence of one rock type over other rock types. All these various subdivisions of the BT4 Unit are shown Figure 2-12 and are discussed below. • “± Picrite – the base of the BT4 is defined by a semi-persistent ultramafic layer and/or package, consisting of melatroctolite to peridotite ± troctolitic beds that is referred to as the "± Picrite.” The "± Picrite is present in about 60% of the drill holes in the Bathtub Intrusion and acts as a local horizon that defines the BT1-BT4 contact; however, in many instances the "± Picrite is absent and the BT1-BT4 contact is arbitrarily chosen based on its presence in nearby drill holes. 28 �Trip 2 – Cu-Ni Duluth Complex • Bathtub Layered Interval (BTLI) – this subunit designates zones (see Figures 2-12 and 2-14) where ultramafic layers are extremely common within the BT4 Unit. The ultramafic layers may represent repetitious cyclic layers and can be correlated in drill holes as an overall rock package. The inclination of internal contacts and modal bedding associated with the ultramafic layers are highly variable, ranging from 5° to 80° (even within a single drill hole). Individual ultramafic beds cannot be traced with certainty between drill holes; however, correlations of packages of the BTLI can be traced. This dichotomy for individual ultramafic beds indicates that the bedding relationships are extremely complex in the third dimension and may be related to rapid pinch-out of individual beds. In addition, the BTLI package fades out to the north with increased distance away from the Hidden Rise. If the Hidden Rise represents a magma chamber wall, the BTLI may have crystallized against it via either a static crystallization method or by current-driven crystal settling against the wall. Figure 2-34. Spatial distribution of the BTLI (in solid green hatch) relative to Bathtub syncline and the Hidden Rise (cross-hatched zone). This map is circa 2015 and changes have been made by NewRange Copper Nickel based on newer information. 29 �Trip 2 – Cu-Ni Duluth Complex Footwall Rocks The footwall rock types at both the NorthMet and Mesaba deposits consist mainly of the Virginia Formation, Biwabik Iron Formation (BIF), and very locally the Pokegama Quartzite. All are Paleoproterozoic in age (approximately 1.9-1.8 billion years ago) and collectively comprise the Animikie Group. The rock types of the Virginia Formation and BIF have undergone metamorphism and partial melting that was produced during emplacement of the Duluth Complex. The metamorphic variants of the footwall rocks are schematically portrayed in Figure 2-15 but are not discussed individually herein. Figure 2-45. General Relationships of the Metamorphosed Footwall Rocks beneath the Duluth Complex at the Mesaba, NorthMet, Wetlegs, and Serpentine Deposits. See Severson and Hauck (2008) for more information. Structural Features There are several prominent structural features at Mesaba that were important to formation of the BTI and possibly to mineralization trends. These major features are shown in Figure 2-16 and discussed below (features such as the Rise and the Hidden Rise have been discussed previously). Local Boy anticline and Bathtub syncline The most prominent structural features at the Mesaba deposit are a pair of east-west trending parallel folds, defined by contouring the top of the footwall Biwabik Iron Formation (Figure 2-17), that are informally referred to as the Local Boy anticline and Bathtub syncline. Both of these folds probably exerted strong controls on the style of emplacement of the BTI and its basal contact mimics the form of the anticline and syncline. The trend of the Hidden Rise, the possible wall once separating the BTI and PRI, also correlates with these two fold axes. The structural history regarding the Local Boy anticline and Bathtub syncline appears to be extremely complicated and long lived. Grano Fault Along the far eastern edge of the Mesaba deposit is the north-trending Grano Fault (Fig. 2-16), so named for the abundant and sometimes voluminous amounts of associated late granitoid lenses and OUIs that are associated with the fault zone (Severson, 1994). Both types of late intrusive lenses are interpreted to be steeply oriented and to have been injected along subsidiary fault zones parallel to, and immediately west of the Grano Fault. These late intrusives cross-cut the troctolitic rocks and thus, demonstrate that the 30 �Trip 2 – Cu-Ni Duluth Complex Figure 2-56. Major structural features at the Mesaba deposit. Note the orange-outlined zone to the immediate west of the Grano Fault is a zone wherein late stage subvertical lenses of granitoid and OUI (cyan outlines) commonly cross-cut the troctolitic rocks of the PRI and BTI. OUI (outlined in cyan) are also common along the inferred trace of the South Minnamax Fault. Figure 2-67. Contoured top of the footwall beneath the Mesaba deposit relative to sea level. The contour interval is 100 feet. Note that the contoured lines in this map are derived from Severson and others (1994) and do not take into account any of the more recent drill holes; however, the overall trends would remain basically the same. 31 �Trip 2 – Cu-Ni Duluth Complex fault was active during and after emplacement of the PRI, BTI and SKI. The Grano Fault is thought to be a primary feeder structure for the BTI and possibly the massive sulfides at the Local Boy ore zone (Severson and Hauck, 2008). South Minnamax Fault The South Minnamax Fault is an east-west trending fault along the extreme southern edge of the Mesaba deposit. Several OUIs occur at the surface along the trend of the fault (Figure 2-16). Displacement of the fault, based on correlations and projections of units between only six drill holes, is generally 100200 feet (30-61 meters), but in one area a displacement of over 400 feet (122 meters) is indicated. Mineralization The Mesaba deposit is characterized by disseminated sulfide mineralization that occurs most commonly as fine- to coarse-grained, intercumulus disseminations of chalcopyrite, cubanite, pentlandite, and pyrrhotite. The most important continually mineralized zone at Mesaba is a basal zone with disseminated sulfides that is present within all or portions of the BT1 unit, and locally in the bottom of the BT4 unit (Figure 2-18). This zone commonly ranges between 200 and 600 ft (61 to 183 m) in thickness. Higher in the intrusive package, often overlapping the BT1-BT4 unit boundary, are thinner, secondary zones of erratic and discontinuous, disseminated sulfide mineralization referred to as “cloud zones.” Increased sulfide contents with depth are obvious in drill core and are manifested mainly by increasing amounts of pyrrhotite and cubanite. This dramatic increase in pyrrhotite and cubanite with depth appears to be related to contamination from the footwall rocks and has been classified as occurring mainly in the basal contaminated BT1-c unit but there are exceptions. Talnakhite [Cu9(Fe,Ni)8S16] is present in numerous holes coincident with the axis of the Bathtub syncline (and north of the Hidden Rise), as well as, in the massive sulfides at Local Boy, as shown in Figure 2-19. Talnakhite occurs as exsolution lamellae with chalcopyrite and cubanite. Talnakhite is difficult to distinguish from chalcopyrite in freshly drilled core. However, talnakhite tarnishes rapidly, sometimes within 10-15 minutes depending on the relative humidity, to a purplish brown or peacock blue similar to bornite (orange-brown color in polished sections). Figure 2-78. Typical cross-section at the Mesaba deposit showing mineralization throughout most of BT1 and in portions of BT4. Note the discontinuous “cloud zone” occurrences in the upper portions of the BT4 unit. 32 �Trip 2 – Cu-Ni Duluth Complex Figure 2-89. Distribution of holes that contain significant amounts of Talnakhite based on tarnished relationships observed on drill core. This map is circa 2015. Note that the Local Boy ore zone, shown in lower right red ovoid, also contains significant talnakhite. Massive Sulfides at the Local Boy Ore Zone of the Mesaba Deposit Cu-rich massive sulfides near the basal contact of the Complex are locally present at the Mesaba deposit in a small zone referred to as the Local Boy ore zone. In 1976, AMAX Inc. completed a 1,700foot-deep exploratory shaft (Minnamax shaft), and in 1977, completed four drifts (A, B, C, and D; Figures 2-20 and 2-21). Underground Fan drilling (217 holes) was completed in 1978 to further define the massive sulfide distribution. Potential ore resources for Local Boy are presented in Table 2-2; high PGE values (up to 11 ppm Pd and up to 8 ppm Pt) are locally present in the ore. Sulfide minerals include pyrrhotite, pentlandite, chalcopyrite, talnakhite, cubanite, maucherite (nickel arsenide), sphalerite, bornite, late mackinawite, chalcocite, covellite, godlevskite, and native silver (Severson and Barnes, 1991). Table 2-2. Grade/tonnage data for Cu and Ni in the Local Boy ore zone. These values are for geologic resources, not mineable ore. From Severson and Barnes, 1991. The Local Boy ore zone is also situated over the Local Boy anticline. The majority of massive sulfide ore zones, hosted mainly by the Virginia Formation (Severson and Barnes, 1991), are broadly 33 �Trip 2 – Cu-Ni Duluth Complex coincident with the axis of the anticline. The contoured top of the BIF in the Local Boy area is shown in Figure 2-20 (left). Similar anticline geometries are also present for the basal contact as shown in Figure 220 (right). All the data indicate that an EW-trending anticline is the major structural feature present within the footwall rocks of the Local Boy area. Figure 2-20. Contoured top of the Biwabik Iron Formation at Local Boy (left) and the contoured top of the basal contact between the Virginia Formation and the intrusive rocks at Local Boy (right). Mineralization Trends in the Massive Sulfide at the Local Boy Ore Zone The vast majority of massive sulfides at Local Boy are contained within the Paleoproterozoic Virginia Formation. Even though the massive sulfides straddle the basal contact, most of the massive sulfides are associated with either hornfelsed sedimentary inclusions above the contact or with footwall rocks below the contact while the interfingering intrusive rocks (mostly norite) are relatively barren of massive sulfides (Severson and Barnes, 1991). This suggests that the massive sulfide ores were not formed in this area by the gravitational settling of sulfides, but rather, the ores formed by injection of an immiscible sulfide melt into structurally prepared areas within the footwall rocks along the Local Boy anticline in a vein-like setting. A similar mechanism is proposed for the Norilsk-Talnakh deposits in Russia. Even though the basal contact of the Complex with the Virginia Formation is highly undulatory, the massive sulfides exhibit a definite top and bottom. Figure 2-21 is an attempt to show, in plan view, where massive sulfide zones are present. Also shown in the figure are the different massive sulfide types (ranging from pyrrhotite-dominant to Cu-rich) relative to structural features. The relationships shown in Figure 2-21 indicate that the massive sulfides show a progressive change in an east-to-west direction from Cu-poor massive sulfides to Cu-rich massive sulfides in the vicinity of the Local Boy anticline. These relationships suggest that the injected immiscible sulfide melt underwent fractional crystallization and progressively became more Cu and PGE enriched as it moved through the footwall rocks in an east-to-west direction. 34 �Trip 2 – Cu-Ni Duluth Complex Figure 2-29. Potential distribution of semi- massive to massive sulfide types (Cu-poor versus Cu-rich) at the Local Boy ore zone (left); and an isopach map of cumulative thickness of the massive sulfides (right). Note that the massive sulfides are not present as a continuous blanket, but rather, as one or more stacked disjointed/separated multiple horizons near the basal contact. A possible feeder vent for the sulfide injection event may have been the Grano Fault, which was repeatedly reactivated during emplacement of the Complex. Other data that indicates that the Grano Fault was a potential feeder vent include: 1) the massive sulfides are more common, and thicker (Figure 2-21 right), close to the Grano Fault (feeder) and along the axis of the Local Boy anticline (structurally-prepared site); 2) the VirgSill, at the base of the Virginia Formation, rarely contains significant amounts of disseminated sulfides – except near the Grano Fault; and 3) the Biwabik Iron Formation rarely contains sulfides – except near the Grano Fault. In summary, the massive sulfides at the Local Boy ore zone are interpreted to be structurally controlled in that they are situated along the axis of the Local Boy anticline. The massive sulfides are Curich (5-25% Cu) and are almost exclusively hosted by the Virginia Formation. Sulfide textures suggest that the massive sulfides were injected as an immiscible sulfide melt into the footwall rocks. The overall pattern of sulfide types and PGE contents suggest that the sulfides formed via a process of fractional crystallization of an immiscible sulfide melt as it migrated into the footwall rocks. The Grano Fault is inferred to represent the potential feeder zone in this scenario. 35 �Trip 2 – Cu-Ni Duluth Complex Wetlegs Deposit The Wetlegs deposit (Figures 2-2 and 2-3) was drilled by Bear Creek (13 holes) and Exxon (12 holes). Exxon determined that there were 38 million tons of material at a 0.57% Cu equivalent (files at DNR) but details regarding their cursory calculations are unknown. Most of the igneous units that are present at NorthMet are also present at Wetlegs except: Unit II thins down to a single ultramafic horizon positioned immediately below Unit III (Figure 2-3), and Unit I contains abundant ultramafic layers that are referred to as the Wetlegs Layered interval (Miller and others, 2002). The top of Unit I (aka Red Horizon of the NorthMet deposit) contains scattered anomalous concentrations of PGEs up to 3,132 ppb Pd+Pt (Severson and Hauck, 2003). The Magenta Zone is also present at Wetlegs, but is only known in one drill hole (A4-11) with up to 6,072 ppb Pd+Pt. No work has been conducted on this property since 1998. Wyman Creek Deposit (Encampment Minerals) The Wyman Creek deposit (Figures 2-2 and 2-3) is located at a turning point in the basal contact of the PRI – the contact trends northeast to the east of Wyman Creek and then exhibits a drastic change to a north-south orientation to the south of the deposit. This area was initially drilled by Bear Creek, followed by more extensive drilling (21 holes) by United States Steel Corp. (USSC), and very limited drilling by Exxon. USSC determined (literally a back-of-the-envelope calculation) an open pit potential of 14 million tons of material containing 0.30% Cu and 0.18% Ni (Severson and Heine, 2007). South Kawishiwi intrusion The South Kawishiwi intrusion (SKI) is exposed in an arc-shaped area ~5x20 square miles (8x32 square km) that extends from the Serpentine deposit on the southwest to the Spruce Road deposit on the northeast as shown in Figure 2-2. Footwall rocks include the Virginia Formation, Biwabik Iron Formation, and granitic rocks of the Neoarchean Giants Range granitic complex; the latter is the dominant footwall rock type. The basal stratigraphic section (shown in Figure 2-22) is known in detail from studies of historic drill core (Severson, 1994; Zanko and others, 1994) and is divided into 17 different units that are present over a strike-length of 19 miles (31 kilometers). Figure 2-102. Generalized igneous stratigraphy of the basal zone of the SKI (Severson, 1994). The Lowermost units are BAN = Basal Augite Troctolite and Norite; BH = Basal Heterogeneous; U3 = Ultramafic 3; PEG = Pegmatitic unit of Foose (1984); U2 = Ultramafic 2; U1 = Ultramafic 1; AT-T = Anorthositic Troctolite to Troctolite; UW = Up dip Wedge; Main AGT = Main Augite Troctolite; AN-G Group = Anorthositic Series inclusion with internal gabbroic lenses. 36 �Trip 2 – Cu-Ni Duluth Complex The lowermost units are unevenly distributed along the strike-length of the intrusion in a compartmentalized fashion, suggesting a complicated intrusive history. The stratigraphy, as defined by Severson (1994), has been documented to be present in all the holes drilled recently by Twin Metals Minnesota (TMM) at the Birch Lake and Maturi deposits but it has since been simplified by TMM. According to Severson and Hauck (2008), a few salient features of the SKI include: • • • • • The vast majority of sulfide mineralization is confined to the BH, BAN, and U3 units - all of these are collectively referred to as BMZ by TMM at the Maturi deposit). The PEG unit, though not particularly mineralized except locally, is also included in the BMZ by TMM Major marker beds include three horizons that contain abundant ultramafic layers (U1, U2 and U3) and a pegmatite-bearing unit (PEG unit – originally recognized by Foose, 1984). The U3 unit is unique in that it contains several massive oxide pods (titanomagnetite-rich and locally Cr-bearing) as well as recognizable inclusions of bedded Biwabik Iron Formation. The spatial correspondence between the U3 unit and footwall iron-formation suggests that most of the massive oxide pods are iron-rich “restite” produced by assimilation and a high degree of partial melting of the iron-formation. This relationship is the most prevalent at Birch Lake The U3 unit contains the vast majority of high PGE values; however, high PGE values are locally present in the overlying PEG unit. High PGE values are also present well above the base of the SKI at the South Filson Creek deposit A large inclusion of anorthosite of formidable size (3,500 feet thick) is present at Maturi and was referred to as the AN-G Group by Severson (1994). Peterson (2001) suggested that the high PGE contents within the BMZ unit (beneath the inclusion) formed as a result of confined turbulent magma flow, and thus an increased R-factor, beneath a “pillar” of anorthosite. Peterson (2001) further hypothesized that a portion of a Nickel Lake Macrodike, which served as a feeder to the nearby Bald Eagle intrusion, may have projected beneath the Maturi deposit and also served as a feeder to the SKI Four of the Cu-Ni deposits within the SKI historically held by TMM are shown in Figure 2-23. These four deposits and others within the SKI are discussed in the following sub-sections. The information given for each of the deposits is based on various NI 43-101 reports, field trip guidebooks (Patelke and others, 2009; and Severson and others, 2016), various NRRI reports, oral presentations at professional meetings, and personal knowledge. Maturi Deposit (Twin Metals Minerals) The very first exploration drill hole in search of Cu-Ni deposits in the Duluth Complex was cored in the Maturi deposit by Fred S. Childers (prospector) and Roger V. Whiteside (investor) in 1951. Eventually, the International Nickel Company (Inco) picked up the property and outlined a sizeable, but low grade, Cu-Ni deposit. A shaft was sunk on the property during 1966 to 1967 to collect material for metallurgical tests. Inco took their bulk sample from pyrrhotite-rich material, which is more prevalent near the basal contact, and decided the grade was too low to support an underground mine. Three other companies (Bear Creek, Duval and Newmont) put down several scattered drill holes on the periphery of the deposit and intersected good mineralization at great depth but also determined it was too low grade to support an underground mine. 37 �Trip 2 – Cu-Ni Duluth Complex Figure 2-113. Twin Metals Minnesota (TMM) deposits and Resource Classification. Mineralization at Maturi, and an extension referred to as Maturi SW, is present in the lower portion of the South Kawishiwi intrusion (SKI) in what TMM refers to as the Basal Mineralized Zone (BMZ). Note that the BMZ collectively consists of the PEG, U3, BH and BAN units of Severson (1994). While the Severson units are recognized by TMM at Maturi they are not consistently present throughout the deposit and for simplicity-sake TMM combined them into the BMZ unit. In 2008, Dean Peterson from Duluth Metals (the original company from which TMM was created) theorized that the initial SKI magmas at Maturi were intruded as sulfide-bearing, crystal-laden (olivine- and plagioclase-rich), crystal slurries. Based on this new interpretation, TMM combined Severson’s (1994) basal units into the BMZ unit that they believed originated by physical sorting of the crystal slurries (possibly top down) and by melting of the footwall granitic rocks (bottom up) to create the heterogeneous lithologies and textures of the BMZ as is shown in Figure 2-24. Mineralization at the Maturi deposit consists of a tabular sheet of disseminated Cu-Ni-Fe sulfides that averages 215 feet thick (65 meters) with a range of 5 to 865 feet thick (1.5 to 260 meters) with the thickest range towards the north end of the deposit. Dips of the BMZ vary from 35 to 55 degrees with a N60E plunge along the contact. Higher grades are concentrated in the upper 100 feet (30 meters) of a zone that has been traced laterally by drilling for approximately 2.2 miles (3.5 km) and open at depth. While mineralization is mostly restricted to the BMZ, exceptions are locally present in the overlying PEG unit and in the footwall granitic rock. TMM reports that mineralization within the footwall granite occurs in appr38 �Trip 2 – Cu-Ni Duluth Complex Figure 2-124. Simplified crystal-liquid slurry model for the SKI in the Maturi area. oximately one-quarter of the holes drilled to date with about 80% of these holes showing mineralization in the overlying BMZ that continues directly downward into the footwall mineralization with little or no breaks. Mineralization typically consists of 1-5% disseminated chalcopyrite, talnakhite, cubanite, pyrrhotite, and pentlandite. Bornite, covellite, and millerite occur in subordinate amounts. Better grades of Cu, Ni and PGE are associated with more mafic units located near the top of the BMZ. Modeling of the ore deposits by Duluth Metals, TMM, and AMEC indicated that the mineralization at Maturi can be characterized by several distinct patterns as shown in Figure 2-25. Figure 2-135. Mineralization trends of the BMZ and adjacent rocks within the Maturi area. 39 �Trip 2 – Cu-Ni Duluth Complex The three stages of mineralization within Maturi’s BMZ zone include: • Stage 1 Mineralization (S1, with top and bottom zones): barren to very low-grade mineralization showing low variability. • Stage 2 Mineralization (S2, with top and bottom zones): moderate grade mineralized intervals showing low variability. Cu:Ni ratios are 3.0 to 3.2:1. Cu-sulfides are the dominant sulfide but pyrrhotite becomes increasingly present with depth. Cubanite and pentlandite decrease in abundance with depth. Normalized chalcopyrite/chalcopyrite+cubanite ratios are approximately 0.61 to 0.65 (Hoffmann and others, 2015). • Stage 3 Mineralization (S3): higher grade mineralized intervals that are commonly bounded by low grade selvages and, interestingly, contains ultramafic units (aka U3 unit of Severson, 1994). Cu:Ni ratios are 3.0 to 3.2:1. Cu-sulfides are the dominant sulfide. Normalized chalcopyrite/chalcopyrite+cubanite ratios are approximately 0.58 to 0.67 (Hoffmann and others, 2015). Birch Lake Deposit (Twin Metals Minerals) The Birch Lake deposit lies to the south of Maturi (Figures 2-2 and 2-23), with mineralization also hosted at the bottom of the SKI. The area was first drilled by Duval in the 1970s but remained dormant until high PGE values were found in drill hole Du-15 by state agencies in the mid-1980s (Sabelin and Iwasaki, 1985). This discovery marked the start of serious PGE exploration in the Duluth Complex. Ernest Lehmann formed several joint ventures, the last known as Franconia Minerals LLC or Beaver Bay Joint Venture, and several holes were drilled on the property intermittently during 1988 through 2010. TMM acquired the property in 2011 and drilled 30 holes from 2011 to 2012. A total of 114 holes have been drilled at Birch Lake (excluding 154 wedge holes that were drilled mainly to obtain material for metallurgical testing). The geology is very similar to Maturi except for the common occurrence of more (and often thicker) ultramafic layers, assimilated BIF inclusions, and discontinuous oxide-rich horizons/pods that are inferred to represent BIF “restites”, all of which are present in the U3 unit. The continuity of these U3 rock types is extremely heterogeneous in 3D as revealed by wedge drilling. Mineralization is associated with what TMM also refers to as the BMZ which consists of the U3, BH, and BAN units of Severson (1994). The BMZ averages about 100 feet thick (30 meters) but is as thick as 515 feet (157 meters). The main footwall unit at Birch Lake is the Neoarchean Giants Range granitic complex, but Paleoproterozoic rocks are exposed at the surface in the Dunka Pit mine located <1 km to the southwest. The four inferred mineralization types at Birch Lake in the BMZ and GRB are shown in Figure 2-26 (non-mineralized material below the GRB_M is identified as GRB_B for barren footwall rocks). Figure 2-26. Igneous stratigraphy according to mineralization trends at Birch Lake. 40 �Trip 2 – Cu-Ni Duluth Complex Mineralization trends at Birch Lake are very similar to Maturi, with four inferred types: 1. Melatroctolite / BL_MT Unit (similar to S3 at Maturi and U3 unit of Severson): an upper melatroctolite to mafic troctolite unit that hosts the highest grade mineralization and is correlative across the deposit. The top and bottom of this unit are typically based on high Mg contents with values generally greater than 6% Mg. The Cu:Ni ratio is about 3.3. The base of the BL_MT unit is gradational downward into the BL_T unit. Almost all of the significant Cu-Ni and precious metal mineralization is hosted by this unit but the total volume, or percentage of the mineral resource, has not been published 2. Troctolite / BL_T Unit (similar to S1 at Maturi and BH and BAN units of Severson): a lower troctolitic unit with lower grades that is also correlative across the deposit. Mg contents are in the 3.5-4.5% range. Locally the top of BL_T is more mineralized and there are small, mineralized zones near the base 3. Basal Hybrid Zone / BL_HX: a basal hybrid rock sequence, with localized oxide-rich layers, that shows similarities to both BL_T and underlying metasomatized Giants Range granitic rocks. This hybrid sequence is marked by an abrupt increase in P and erratic Sr, Ba, Mg, and V concentrations. Iron ranges from 2% Fe to upwards of 45% Fe (largely because of assimilated BIF inclusions) 4. Mineralized GRB / GRB_M: consists locally of mineralized Giants Range granitic rocks as well as locally mineralized Virginia Formation and BIF. Average grade is about 0.28% Cu and 0.16% Ni with a Cu:Ni ratio of about 2.3. Local massive sulfide bodies are present and contribute significantly to the average grade The thickness of the four units is quite variable, but the stratigraphic succession does not vary across the deposit. Any one or more of the units, however, can be missing locally from a specific drill hole. Geologic modeling indicated that there is a sinuous, channel-like body of persistent and higher Cu grades that traverse the length of the deposit and follows the thickest portion of the BL_MT unit as shown in Figure 2-27. The origin of the channel is not well understood but it may be related to a magma conduit. Spruce Road Deposit (Twin Metals Minerals) The Spruce Road deposit lies to the northeast of Maturi (Figures 2-2 and 2-23). Mineralization is also present at the base of the SKI. It was at this deposit that the first good indications of Cu-Ni mineralization were uncovered while constructing a forest access road in 1948. From 1954 to 1971, Inco drilled the deposit on 200-foot centers (61 meters) for a total of 232 holes (the vast majority of which are no longer preserved after they were destroyed in a fire at Sudbury, Ontario). In 1997, Inco’s subsidiary, American Copper and Figure 2-147. Birch Lake magma channel superimposed on average copper grade base map. 41 �Trip 2 – Cu-Ni Duluth Complex Nickel Company (ACNC), joint ventured the property with Wallbridge Mineral Company Limited (from which Duluth Metals was eventually created). Wallbridge eventually drilled two holes on the property during 1999 to 2000 in search of high-grade footwall veins but failed to find significant mineralization in the footwall rocks. In 2002, Franconia Minerals Corp. entered into an agreement with Beaver Bay Joint Venture to acquire the Spruce Road and Maturi properties from ACNC but conducted no work. TMM acquired the property in 2011 and drilled 57 drill holes totaling 65,635.5 ft between September 2012 and January 2014 and a prefeasibility study technical report was issued on the TMM project in August 2014. The geology at Spruce Road is vastly different than at either Maturi or Birch Lake. Publiclypreserved core from historic drill holes are extremely limited for this deposit in that only six Inco holes are preserved along with two Wallbridge holes. From this limited data, Severson (1994) determined that most of the igneous units that typify the SKI elsewhere are not present at Spruce Road. Rather, the mineralization appears to be present in a much thicker BH unit (also referred to as the BMZ unit by TMM) consisting of a heterogeneous mix of troctolitic rocks with common hornfelsed inclusions of basalt (North Shore Volcanic Group). Also present are extremely localized noritic rocks associated with hornfelsed sedimentary rocks (Virginia Formation and Biwabik Iron Formation) and at the basal contact with the Giants Range granitic complex. The U3 unit and massive oxide zones are also locally present. Mineralization does not appear to correlate with any specific igneous lithology and there are no known marker horizons. Historic drill logs indicate that there may be an igneous mega-breccia unit that is referred to as “Spruce Road breccia.” South Filson Creek Deposit (Encampment Minerals) The South Filson Creek deposit, located to the east of Spruce Road, as previously presented in Figure 2-2, was initially drilled by the Hanna Mining Company (23 holes) in the late 1960s. There, the CuNi mineralization is hosted by troctolitic rocks (AT&T unit of Severson, 1994), both in outcrop and in the tops of several drill holes situated well above the basal contact. In 1987, encouraging high PGE values (>1.0 ppm) were reported in these “cloud” zone sulfides by Steve Hauck of the NRRI. A subsequent study of the PGE mineralization (Kuhns and others, 1990) indicated that the PGE were concentrated by a latestage hydrothermal event that concentrated the PGE in extremely fine, discontinuous, microscopic veinlets that were inferred to be associated with a NE-trending fault zone. Encampment Minerals drilled an additional 27 holes on the property, but results are largely unknown. Serpentine Deposit (Encampment Minerals) The Serpentine deposit, shown in Figure 2-26, is located to the north of the Mesaba deposit. The deposit was initially discovered by Bear Creek Mining Company in 1967 as part of a follow-up drilling campaign of an airborne electromagnetic conductor (Kulas, 1979). The name “Serpentine” was chosen for this deposit due to the presence of a sinuous-trending massive sulfide located at the base of the SKI. When the next owner, Amax, began working on the deposit, they calculated that the deposit contained 250 million tons of resources (not NI 43-101 compliant) grading 0.41% Cu, 0.14% Ni and 1.96% S at a 0.20% copper cut-off, with a higher-grade portion of over 7 million tons, at a 0.60% copper cut-off, with a grade of 0.88% Cu, 0.30% Ni and 5.67% S (Kulas, 1979, Zanko and others, 1994). The presence of such voluminous pyrrhotite-rich massive to semi-massive sulfide at the basal contact at Serpentine makes this an unusual deposit (Figure 2-29). There, the massive sulfide is closely related to the BDPO which provided a local sulfur source. Empirical evidence in drill core is evidenced by partially melted BDPO (present in the footwall and in inclusions) that transitions upwards and downwards into massive sulfide near the basal contact. The massive sulfide is also located close to the projected location of the Grano Fault that may have played a role in its origin. Another feature that may be related to the Grano Fault at Serpentine is a northerly-trending zone wherein subvertical olivine-rich ultramafic dikes were emp42 �Trip 2 – Cu-Ni Duluth Complex -laced in the troctolitic host rocks while the host rocks were still solidifying. Encampment Minerals drilled eight holes at the Serpentine deposit, but no data are known regarding their results. Figure 2-168. Location of the Serpentine deposit in relation to the Mesaba deposit. Note drill holes posted in red are holes that intersected massive sulfides at or slightly above the basal contact (larger red dots intersected significantly more and thicker massive sulfide zones). Figure 2-159. Trend of BDPO unit relative to basal massive sulfide mineralization at the Serpentine deposit (from Zanko and others, 1994). 43 �Trip 2 – Cu-Ni Duluth Complex Field Trip Stops Drill core will be displayed at NewRange’s Babbitt core facility, for both the NorthMet and Mesaba deposits, and at Twin Metals Ely office for the Maturi deposit. Cross-sections displaying the geology will be posted, as well as Cu-Ni-PGE grades, for the appropriate holes. At this point in time, the core displayed will be determined by the companies. NewRange core facility: 578810 / 5284970, (47.71330°, -91.94930°) Twin Metals Ely office: 585230 / 5306550, (47.90661°, -91.85949°) References Barber, J., Parker, H., Frost, D., Hartley, J., White, T., Martin, C., Sterrett, R., Poeck, J., Eggleston, T., Gormely, L., Allard, S., Annavarapu, S., Radue, T.,Malgensini, M and Pierce, M., 2014:, Twin Metals Minnesota Project, Ely, Minnesota, USA: NI 43-101 Technical Report on Pre-feasibility Study prepared by AMEC E&C Services, Inc. for Duluth Metals Limited, October 2014, Project 176916. Bennett, A., Dempers, N., Neff, D., Radue, P.E., Roth, D., Schwering, R., Tahija, L., Uble, J.S. and Welhener, H.E., 2022, NorthMet Copper-Nickel Project, Feasibility Update National Instrument 43-101F1 prepared for PolyMet Minerals Corp. by M3 Engineering and Technology Corp., Project M3-PN220283, Dec. 30th, 2022, 248 p. Eckstrand, 0.R., and Hulbert, L.J., 2007, Magmatic Nickel-Copper-Platinum Group Element Deposits; in Goodfellow,W.D., ed., Mineral Deposits of Canada: A synthesis of Major Types, District Metallogeny, The Evolution of Geological Provinces, and Exploration Methods: Geological Association of Canada, Mineral Deposits Division, Special Publication No.5, p. 205-222. Farrow, D, and Johnson, M, 2011, January 2012 National Instrument 43-101 Technical Report on the Titac Ilmenite Exploration Project, Minnesota, USA. SRK Consulting (Canada) Inc. SRK Project Number 2CC031.004. Cardero Resources Corp. Farrow, D, and Johnson, M, 2012, January 2012 National Instrument 43-101 Technical Report on the Longnose Ilmenite Exploration Project, Minnesota, USA. SRK Consulting (Canada) Inc. SRK Project Number 2CC031.004. Cardero Resources Corp. Foose, M., 1984, Logs and correlation of drill holes within the South Kawishiwi intrusion, Duluth Complex, northeastern Minnesota: United States Geological Survey, Open-file Report 84-14 Geerts, S.D., 1991, Geology, stratigraphy, and mineralization of the Dunka Road Cu-Ni prospect, northeastern Minnesota: Natural Resources Research Institute, University of Minnesota Duluth, Duluth, MN, Technical Report NRRI/TR-91/14, 63 p. Geerts, S.D., 1994, Petrography and geochemistry of a platinum group element-bearing horizon in the Dunka Road prospect, (Keweenawan) Duluth Complex, northeastern Minnesota: University of Minnesota Duluth, Unpublished M.S. thesis, 100 p. Kuhns, M.P, Hauck, S.A, and Barnes, R.J, 1990, Origin and occurrence of platinum group elements, gold and silver, in the South Filson Creek copper-nickel deposit, Lake County, Minnesota: Natural Resources Research Institute, University of Minnesota Duluth, Duluth, MN, Technical Report NRRI/GMIN-TR-89-15, 60 p. Kulas, J.E., 1979, Serpentine Reserve – Minnamax project: unpublished AMAX Company report on file at the Minnesota Department of Natural Resources, Lands and Minerals Division, Hibbing, MN, 5 p. Listerud, W.H., and Meineke, D.G., 1977, Mineral resources of a portion of the Duluth Complex and adjacent rocks in St. Louis and Lake Counties, northeastern Minnesota: Minnesota Department of Natural Resources, Div. of Minerals, Hibbing, MN, Report 93, 49 p. Miller, J.D., Jr., Green, J.C., Severson, M.J., Chandler, V.W., and Peterson, D.M., 2001, Geologic Map of the Duluth Complex and Related Rocks: Minnesota Geological Survey, Miscellaneous Map Series, Map M-119. Miller, J.D., Jr., Green, J.C., Severson, M.J., Chandler, V.W., Hauck, S.A., Peterson, D.M., and Wahl, T.E., 2002, Geology and mineral potential of the Duluth Complex and related rocks of northern Minnesota: Minnesota Geological Survey, Report of Investigations RI-58, 207 p. Miller, J.D., and Severson, M.J., 2005, Bedrock Geology of the Babbitt Southwest Quadrangle, St. Louis County. Minnesota: Minnesota Geological Survey, University of Minnesota, Miscellaneous Map Series, M-161. 44 �Trip 2 – Cu-Ni Duluth Complex Patelke, R, Peterson, D, Severson, M, Jefferson, T, and Lehmann, E., 2009, Cu-Ni-PGE Deposits of the Duluth Complex, Geology and Development; 55th Annual Institute on Lake Superior Geology, Ely, MN, Part 2 Field Trip Guidebook, p. 1-80. Peterson, D.M., 2001, Development of a conceptual model of Cu-Ni-PGE mineralization in a portion of the South Kawishiwi Intrusion, Duluth Complex, Minnesota: Laurentian University – Society of Economic Geologists, Second Annual PGE Workshop, Sudbury, Ontario. Peterson, D.M., 2010, The Nokomis Cu-Ni-PGE Deposit, Minnesota. Prospectors and Developers Association of Canada. Annual Meeting, Powerpoint presentation. Sabelin, T., and Iwasaki, I., 1985, Metallurgical evaluation of chromium-bearing drill core samples from the Duluth Complex (Contract report of Minnesota Department of Natural Resources, Division of Minerals): Minerals Resources Research Center, University of Minnesota, Minneapolis, MN, 58 p. Sabelin, T., and Iwasaki, I., 1986, Evaluation of platinum group metal occurrence in Duval 15 drill core from the Duluth Complex: Internal report, Minerals Resources Research Center, University of Minnesota, Minneapolis, MN, 23 p. Severson, M.J., 1994, Igneous stratigraphy of the South Kawishiwi intrusion: Duluth Complex, northeastern Minnesota: Natural Resources Research Institute, University of Minnesota Duluth, Duluth, MN, Technical Report NRRI/TR-93/34, 210 p. Severson, M.J. and Barnes, R.J., 1991, Geology, mineralization and geostatistics of the Minnamax/Babbitt Cu-Ni deposit (Local Boy area), Minnesota, Part II: Mineralization and geostatistics: Natural Resources Research Institute, University of Minnesota, Duluth, Technical Report, NRRI/TR-91/13b, 216 p. Severson, M.J. and Hauck, S.A., 1990, Geology, geochemistry, and stratigraphy of a portion of the Partridge River intrusion: Natural Resources Research Institute, University of Minnesota Duluth, Duluth, MN, Technical Report NRRI/GMIN-TR-99-11, 236 p. Severson, M.J. and Hauck, S.A., 1997, Igneous stratigraphy and mineralization in the basal portion of the Partridge River intrusion, Duluth Complex, Allen Quadrangle, Minnesota: Natural Resources Research Institute, University of Minnesota Duluth, Technical Report NRRI/TR-97/19, 102 p. Severson, M.J. and Hauck, S.A., 2003, Platinum group elements (PGEs) and platinum group minerals (PGMs in the Duluth Complex, Natural Resources Research Institute, University of Minnesota Duluth, Technical Report NRRI/TR-2003/37. 296 p. Severson, M.J. and Hauck, S.A., 2008, Finish Logging of Duluth Complex Drill Core (And a Reinterpretation of the Geology at the Mesaba (Babbitt) Deposit): Natural Resources Research Institute, University of Minnesota Duluth, Duluth, MN Technical Report NRRI/TR-2008/17, 68 p. + 94 plates. Severson, M.J. and Heine, J.J., 2007, Data compilation of United States Steel Corporation (USSC) exploration records in Minnesota; Natural Resources Research Institute, University of Minnesota Duluth, Duluth, MN, Technical Report NRRI/TR-2007/25, 98 p. Severson, M.J. and Miller, J.D., 2005, Bedrock Geology of the Babbitt Quadrangle, St. Louis County. Minnesota: Minnesota Geological Survey, University of Minnesota, Miscellaneous Map Series, M=159. Severson, M.J., Patelke, R.L., Hauck, S.A., and Zanko, L.M., 1994, The Babbitt copper-nickel deposit, Part B: Structural datums: Natural Resources Research Institute, University of Minnesota Duluth, Duluth, MN, Technical Report NRRI/TR-94/21b, 48 p. Severson, M, Ware, A, Boerst, K, and Peterson, D, 2016, Cu-Ni-PGE Deposits of the Duluth Complex, Geology and Development; 62nd Annual Institute on Lake Superior Geology, Duluth, MN, Part 2 Field Trip Guidebook, p, 27-78. Welhener, H. and Crowie, S.T., 2022, NI 43-101F1 Technical Report on Mesaba Project, Mineral Resource Statement prepared for PolyMet Mining Corp. by Independent Mining Consultants, Inc. and JDS Energy and Mining, Inc., November 2022 Zanko, L.M., Severson, M.J., and Ripley, E.M., 1994, Geology and mineralization of the Serpentine copper-nickel deposit, Duluth Complex, Minnesota: Natural Resources Research Institute, University of Minnesota Duluth, Duluth, MN, Technical Report NRRI/GMIN-TR93-52, 90 p. 45 �Trip 3 – Proterozoic Fe & Mn Formations FIELD TRIP 3 How Do You Make Iron and/or Manganese Ores in Proterozoic Iron Formation? Dean Peterson1, Alex Steiner1, and Latisha Brengman2 1 Big Rock Exploration, 2505 W. Superior St., Duluth, MN 55806 Earth and Environmental Sciences, Swenson College of Science and Engineering, University of Minnesota, Duluth, 1114 Kirby Dr., Heller Hall 229, Duluth, MN 55812 2 Introduction Iron formations are among the most important rocks for our modern industrial world. Their extraordinary iron content facilitates the manufacture of steel, while their manganese content is of crucial importance as a steel-alloy product and a critical component of battery technologies. Fueling modern technology requires efficient production of iron resources, exploration of manganese resources, and determination of enrichment processes that lead to ore formation. This field trip will explore ore-formation processes that turn otherwise uneconomic iron formations into valuable resources of iron and manganese. The trip may include an optional stop at the Hibbing Core Library where participants will examine drill core of the Biwabik taconite ores. Participants will explore sedimentary features, diagenetic reactions, and weathering reactions that contribute to iron grade and iron distribution within ore-horizons of the Biwabik. We will then travel to the North Star Manganese/Electric Metals core logging facility in Emily, MN to look at four recent (2023 drilling) drillholes where we will discuss the formation and subsequent redistribution of manganese within the Emily Iron Formation. Participants will have the opportunity to observe highgrade manganese oxide drill core, primary iron-manganese carbonate facies iron formation, and breccia horizons possibly associated with the 1.85 Ga. Sudbury impact. The trip will then proceed to the Mary Ellen mine, a former natural ore pit, where the oxidation and weathering of the Biwabik was central to ore formation and early mining efforts on the range. Participants can observe primary features such as stromatolites and sedimentary structures as well as oxidation-weathering features. If time allows, we will wrap up the trip at the Biwabik outcrops in Virginia near the new Highway 53 bridge over the historic Rouchleau natural ore (hematite) mine before heading back to Mountain Iron. Regional Geologic Setting To gain a true understanding of the geology and origin of the high-grade Paleoproterozoic iron and manganese resources of the Mesabi and Cuyuna Ranges of northern Minnesota (Fig. 3-1), it is best to start with an understanding of the regional-scale geologic setting and its contained ferrous mineral resources. These Paleoproterozoic iron ranges include several categories of marine chemocline mineral systems outlined in recent USGS publications (Schulz et al., 2017 and Hofstra and Kreiner, 2020). These categories include: 1) Superior-iron deposits (Mesabi Iron Range and the Emily District of the Cuyuna Iron Range) and 2) Algoma-type iron-manganese deposits (Cuyuna North and South Iron Ranges). Superior Type Iron Resources of the Mesabi Iron Range Superior type iron formation resources of Minnesota are exemplified by the long-standing mining of iron resources of the Biwabik Iron Formation along the length of the Mesabi Iron Range. The Mesabi Iron Range is largely located in St. Louis and Itasca counties and has been the most important iron ore district in the United States since ~1900. The Mesabi Iron Range is 120 miles long, averages one to two miles wide, and is comprised of rocks of the Paleoproterozoic Animikie Group. The Animikie Group on 46 �Trip 3 – Proterozoic Fe & Mn Formations the Mesabi Iron Range consists of three major conformable formations: Pokegama Formation at the base; Biwabik Iron Formation in the middle; and the overlying Virginia Formation. On the Mesabi Iron Range, these three formations generally dip gently to the southeast at angles of 3-15 degrees. Figure 3-1. Location map of identified ferrous mineral resources in Minnesota. Since the early 20th century, the Biwabik Iron Formation has been subdivided into four informal members referred to as (from bottom to top): Lower Cherty member, Lower Slaty member, Upper Cherty member, and Upper Slaty member (Wolff, 1917). The cherty members are typically characterized by a granular (sand-sized) texture and thick-bedding (beds ≥ several inches thick); whereas the slaty members are typically fine-grained (mud-sized) and thin-bedded (≤1 cm thick beds). The cherty members are largely composed of chert and iron oxides (with zones rich in iron silicate minerals), while the slaty members are composed of iron silicates and iron carbonates with local chert beds. Both cherty and slaty iron-formation 47 �Trip 3 – Proterozoic Fe & Mn Formations types are interlayered at all scales, but one rock type or the other predominates in each of the four informal members, and they are so-named for this dominance Severson et. al. (2009). Leached and iron enriched direct ores (or natural ores) were the first materials mined, with the first shipments beginning in 1892, from strongly oxidized pockets along fault and fracture zones and the blanket oxidation of the iron formation at the surface. Taconite, which is the material that is mined today using magnetic separation methods, constitutes most of the iron formation and pertains to the hard, non-oxidized portions of the iron-formation. Production has been dominantly controlled by vertically integrated steelmakers since 1901, and therefore the mining and utilization of these ores have been dictated largely by US ironmaking capacity and demand. Taconite typically contains 30-35% iron and 40-50% SiO2, plus other components (Morey, 1992). The Biwabik Iron Formation is around 175-300 feet thick in the extreme eastern end of the Mesabi Iron Range at Dunka Pit, 730-780 feet thick in the central Mesabi Iron Range/Virginia Horn area near Eveleth, around 500 feet thick in the western Mesabi Iron Range near Coleraine, and eventually exhibits a “nebulous ending about 15 miles southwest of Grand Rapids” (Marsden et al., 1968) on the extreme western end of the Mesabi Iron Range. Maps of currently active taconite mining operations on the Mesabi Iron Range are presented in Figure 3-2 and compiled grade/tonnage ore reserve calculations for these operations are given in Table 3-1. Table 3-1. Reported grade/tonnage of active taconite mines. operations. Geology of the Cuyuna Iron Range The Cuyuna iron range is about 160 km west-southwest of Duluth in Aitkin, Cass, Crow Wing, and Morrison Counties (Fig. 3-1). It is part of an Early Proterozoic geologic terrane which occupies much of east-central Minnesota. The Cuyuna iron range is traditionally divided into three districts, the Emily district, the North range, and the South range (Fig. 3-3). The Emily district extends from the Mississippi River northward through Crow Wing County and into southern Cass County and comprises an area of about 1,165 square kilometers. Although exploration drilling has been extensive in the Emily district, mining never commenced. The North range, a much smaller area about 19 km long and 8 km wide, is near the cities of Crosby and Ironton in Crow Wing County. 48 �Trip 3 – Proterozoic Fe & Mn Formations Figure 3-2. Bedrock geology and iron mining features of the Mesabi Iron Range. 49 �Trip 3 – Proterozoic Fe & Mn Formations Figure 3-3. Bedrock geologic map of the Cuyuna Iron Range of Minnesota, illustrating the locations of the Emily District, North Range, and South Range. Since their discovery in 1904, it has been recognized that the iron-formations and associated ore deposits of the Cuyuna iron range in east-central Minnesota contained appreciable quantities of manganese, and large quantities of manganese were extracted as ferromanganese ores from several mines on the North range from 1911 to 1984. The presence of this manganese resource sets the Cuyuna range apart from other iron-mining districts of the Lake Superior region. Although relatively small, the North range was the principal site of mining activity (Fig. 3-4), which had largely ceased by 1970. The South range, where one small open pit and only a few underground mines were operated, in the 1910s and 20s, comprises an area of northeast-trending, generally parallel belts of iron-formation extending from near Randall in Morrison County northeast for about 100 km. In addition to the three named districts, numerous linear magnetic anomalies occur east of the range proper, and may indicate other, but currently poorly defined, beds of iron-formation. Three major insights regarding the geology of the Cuyuna range have emerged from the geologic mapping (Schmidt, 1963) and associated studies which utilized geophysical and drilling data (Southwick et al., 1988). First, there is clear evidence that iron sedimentation occurred at several different times and under varying geological conditions. This observation invalidates the stratigraphic premises of Morey (1978). Major iron-formations are associated stratigraphically with volcanic rocks in the South range, with black shale, argillite and rare volcanic rocks in the North range, and with shallow-water deposits of sandstone and siltstone in the Emily district. 50 �Trip 3 – Proterozoic Fe & Mn Formations Figure 3-4. Bedrock geology and open pit Fe-Mn mine map of the North Range of the Cuyuna Iron Range. Second, the iron-rich strata of the Emily district are correlative with the Biwabik Iron Formation of the Mesabi Range, as inferred by Marsden (1972) and Morey (1978). However, they and the other sedimentary rocks of the well-known Animikie Group occur above a major deformed unconformity that cuts across previously deformed, somewhat older sedimentary and volcanic rocks of the North range. There, a prominent iron-rich unit named the Trommald Formation, as well as several other units beneath the unconformity, forms part of a locally twice-deformed sequence. Therefore, the rocks of the North range and the Emily district cannot be correlative but are separate stratigraphic entities. Because the stratigraphic succession of folded sedimentary rocks on the North range comprises a distinct stratigraphic entity, Southwick et al., (1988) referred to it informally as the North Range group with the understanding that a formal name may be justified later. As defined by Schmidt (1963), the stratigraphic sequence in the North range consists of a quartz-rich lower sedimentary unit named the Mahnomen Formation, a middle iron- and locally manganese-rich sequence assigned to the Trommald Formation, and an upper greywacke shale interval called the Rabbit Lake Formation. Third, Southwick et al., (1988) recognized several geophysically defined structural discontinuities in the southern part of the Cuyuna iron range, within and southeast of the South range. These discontinuities are marked by demonstrable contrasts in metamorphic grade, by differing structural styles, and by different lithic components. One of the most pronounced of these, the Serpent Lake structural discontinuity, passes along the south edge of the North range. This discontinuity is interpreted as a tectonic boundary, probably involving major thrust faults between slices of folded rocks. Thus, it seems certain that the iron-rich strata of the South range are not correlative with either the Trommald Formation of the North range or the ironrich strata of the Emily district. The fact that iron-formation occurs within three different stratigraphic and structural contexts in the Cuyuna iron range is of considerable importance to the ultimate development of manganese resources. Since we now recognize that the Emily district, the North range, and the South range are separate entities, we can no longer develop regional syntheses that extrapolate mineralogical and structural attributes from one entity to another. 51 �Trip 3 – Proterozoic Fe & Mn Formations Cuyuna Iron Range Manganese Resources Several attempts have been made over the last 70 years to estimate the size of the manganese resources of the Cuyuna iron range. For example, Lewis (1951) estimated that 455 million metric tons of manganiferous iron-formation containing from 2 to 10 percent manganese were available to open-pit mining to a depth of 45 meters. Dorr et al., (1973) used that estimate to establish that the Cuyuna range contains approximately 46 percent of known manganese resources in the United States. US Steel geologist Richard Strong (1959) estimated iron and manganese resources from several well-drilled deposits in the Emily District and Beltrame et al., (1981) estimated a minimum of 170 million metric tons of manganiferous rock with an average grade of 10.46 weight percent manganese. All historic grade/tonnage estimates (Lewis, 1951, Strong, 1959, and Beltrame et al., 1981) should be considered with a certain amount of skepticism for at least two reasons. First, the manganese data used to make these estimates were, for the most part, by-products of data that were acquired originally by various mining companies as they explored for iron. Second, the various estimates were prepared for different reasons at different times, using different databases and different methodologies. Therefore, the results of these estimates are neither comparable, nor do they necessarily reflect the actual resource. A table listing the grade and tonnage from properties that Strong (1959) and Beltrami et al. (1981) estimated manganese resources is given in Table 3-2 and a location map of these properties is presented in Figure 3-5. Table 3-2. Manganese grade and tonnage estimates from reports by Strong (1959) and Beltrame et al. (1981). 52 �Trip 3 – Proterozoic Fe & Mn Formations Despite their problematic nature, the estimates of Lewis (1951) and Beltrame et al., (1981) do show that the Cuyuna range contains a large, but low- to moderate-grade manganese resources remaining. This large size, combined with the fact that the manganese deposits are in an established mining district, makes the Cuyuna range an ideal place to study geological and technological factors needed to evaluate this and other sedimentary manganese deposits in the United States. Especially important are studies of the geologic habit of the manganese and the controls on its distribution and subsequent concentration into deposits of minable size. Figure 3-5. Bedrock geology and location map of properties outlined in reports by Strong (1959) and Beltrame et al. (1981) that includes manganese grade-tonnage estimates. Labeled parcels correlate with the MAP ID column in Table 3-2 and are those with an estimated resource greater than 100,000,000 pounds of manganese metal. 53 �Trip 3 – Proterozoic Fe & Mn Formations Penokean Orogeny The Penokean orogeny began at about 1880 Ma when an oceanic arc, the Paleoproterozoic Pembine–Wausau terrane, collided with the southern margin of the Archean Superior (Laurentia) craton marking the end of a period of south-directed subduction. The docking of the buoyant craton to the arc resulted in a subduction jump to the south and development of back-arc extension both in the initial arc and adjacent craton margin to the north. Synchronous extension and subsidence of the Laurentia craton resulted in the development of broad shallow seas overlapping the Archean craton. The classic Superior-type banded iron-formations of the Lake Superior District, including those in the Marquette, Gogebic, Mesabi, and Gunflint Iron Ranges, formed in that sea. The newly established subduction zone caused continued arc volcanism until about 1850 Ma when a fragment of Archean crust, now the basement of the Marshfield terrane, arrived at the subduction zone. The convergence of Archean blocks of the Superior and Marshfield cratons resulted in the major contractional phase of the Penokean orogeny. Rocks of the Pembine–Wausau arc were thrust northward onto the Superior craton causing subsidence of a foreland basin in which sedimentation began at about 1850 Ma in the south (Baraga Group rocks) and 1835 Ma in the north (Rove Formation). A thick succession of arc-derived turbidites constitutes most of the foreland basin-fill along with lesser volcanic rocks. In the southern fold and thrust belt, tectonic thickening resulted in high-grade metamorphism of the sediments by 1830 Ma. At this same time, a suite of post-tectonic plutons intruded the deformed sedimentary sequence and accreted arc terranes marking the end of the Penokean orogeny. A regional geologic map of the Penokean orogen, modified from Schulz and Cannon (2007), is given in Figure 3-5. Figure 3-5. Generalized geologic map of the Penokean orogen. Abbreviations: ECMB - East-central Minnesota batholith; EPSZ - Eau Pleine shear zone; MD - Malmo discontinuity; NFZ - Niagara fault zone. Modified from Schulz and Cannon, 2007. The Penokean deformation in Minnesota includes a southern intensely and complexly deformed series of thrust panels (Cuyuna North, Cuyuna South, Moose Lake, McGrath-Little Falls panels) that gives way northward to progressively more weakly and simply deformed rocks (Emily District) across a belt 54 �Trip 3 – Proterozoic Fe & Mn Formations about 100 km wide. Farther north strata in the Mesabi and Gunflint Iron Ranges are essentially undeformed (Holst, 1991). It should be noted that the “more weakly and simply deformed rocks” of the Emily District have been shortened ~250% into a series of shallowly east-plunging anticlines and synclines. Substantial progress has been made in deciphering the structure of the poorly exposed rocks of the Minnesota foreland through the use of aeromagnetic and gravity data and drillhole information. Southwick and Morey (1991) and Southwick et al. (1988) have presented syntheses of this information. The complex thrust panels on the south, like comparable structures in Michigan, appear to be thinskinned slices without Archean basement. However, as in Michigan, this area of thin-skinned thrusting is also the area where Archean-cored gneiss domes developed during post orogenic collapse of the Penokean orogen (Holm and Lux, 1996; Schneider et al., 2004). Farther north, basement-cover relations are not well known except for the Mesabi Range where Paleoproterozoic strata are mostly nearly flat lying above an undisturbed unconformity with Archean basement rocks. A schematic north-south geologic cross section of the Penokean orogeny in Minnesota, modified from Southwick and Morey (1991) is presented in Figure 3-6. Figure 3-6. Schematic diagram illustrating the interpreted tectonic setting of the Penokean orogen in Minnesota. A) continental margin sedimentation, and B) thin-skinned thrusting and deformation related to the Penokean orogeny. Modified from Southwick & Morey, 1991. Post Penokean Weathering and Erosion Perhaps the most important component in the formation of the high-grade iron and manganese ores on the Mesabi and Cuyuna ranges is the vast amount of time (measured in hundreds of millions of years) upon which the newly-formed and uplifted Penokean mountains of the southern Laurentia craton weathered and eroded. As plate tectonic forces moved Laurentia across the globe to its current position on planet Earth, there were long periods of time when it resided within the tropical weathering zone (+30° to -30° latitude) near the Earth’s equator. It is believed that the supergene enrichment of iron (to >60 wt.% elemental Fe) and manganese (to >50 wt.% elemental Mn) on the Mesabi and Cuyuna largely formed during the protracted periods of time that the area resided within the tropical weathering zone. A paleogeographic reconstruction of the location of Laurentia on planet Earth is given in Figure 3-7. 55 �Trip 3 – Proterozoic Fe & Mn Formations Figure 3-7. Paleogeographic reconstruction of the Laurentia craton from the Paleoproterozoic to present times. FIELD TRIP STOPS Four field trip stops have been selected to showcase selected geological features associated with supergene weathering of primary Paleoproterozoic Superior-type iron formation into high-grade of Fe and Mn ores. The locations of the field trip stops are shown in Figure 3-8 and briefly described below. 1) DNR drillcore library in Hibbing: Drillcore review of unoxidized Biwabik Iron Formation, 2) Emily deposit core shed: Drillcore review of high-grade supergene Mn ores, primary Mn-Fe carbonate-facies iron formation, Overlying Sudbury Impact breccias & accretionary lapilli? 3) Mary Ellen Mine: Walk into a historic natural-ore (hematite) open pit iron mine, sampling of the classic Mary Ellen stromatolites, and 4) Large roadcut of the partially oxidized Biwabik Iron Formation adjacent to the historic naturalore Rouchleau Mine Complex. Stop 1: DNR Drillcore Library, Hibbing Minnesota Longitude/Latitude: 47.432412°N, -92.941811E UTM NAD 83 Zone 15N: 504388E, 5253220N At our first stop on this field trip, we will examine sections of two different drill cores of the Biwabik iron formation to directly compare depositional features to post-depositional features. The Drill Core Library is maintained by the Minnesota Department of Natural Resources, Lands and Minerals Division, and provides direct access for visitors to examine publicly owned geologic materials and exploration data. This incredible 56 �Trip 3 – Proterozoic Fe & Mn Formations Figure 3-8. Location map of field trip stops and the collar location of the two drill holes looked at Stop 1. repository contains over 7,000 mineral exploration cores, 1,500 roadway and bridge foundation cores, and 500 cores collected during scientific, governmental, and academic research, and their curation activities support researchers, exploration geologists, and engineers from around the world. Depositional features and mineralogy in Precambrian chemical sedimentary rocks like iron formations have long been of interest to the scientific community as they may record information about Earth’s early surface conditions. However, recovering data that links to depositional conditions requires the reconstruction of post-depositional mineral reactions and quantification of geochemical exchange. For this reason, the original mineralogy and geochemistry of iron formations has been the subject of numerous investigations. Critical early investigations recognized the mineral greenalite - postulating its authigenic origin as a “chemical oceanic precipitate”, and hypothesizing its role in forming the iron ore deposits in Minnesota, USA (Irving, 1886; Irving and Van Hise, 1892; Leith, 1903; Van Hise and Leith, 1911; Aldrich 1929; Gruner, 1946; Tyler, 1949; James, 1954; White, 1954; Goodwin, 1956; Gundarson and Schwartz, 1962; LaBerge; 1964). Key initial evidence for a primary or early origin for greenalite in the Superior craton included: (1) its abundance in low temperature, well-preserved assemblages, and comparative absence in metamorphosed iron formations in the same region (LaBerge, 1964); (2) the existence of submicroscopic 57 �Trip 3 – Proterozoic Fe & Mn Formations greenalite in the cores of circular to elliptical sand-sized grains as either the main mineral phase, <0.05 mm spherules, or as dusty nano-scale (submicroscopic) particles (Goodwin, 1956); intergranular relationships between phases where greenalite is crosscut by other phases in the same sample; (LaBerge, 1964; French, 1973; Klein and Fink, 1976), and even distribution throughout primary bedding (LaBerge, 1964). Recent mineralogical investigations (e.g, Duncanson et al., 2024, Muhling et al., 2025 and references therein) highlight that the earliest forming minerals in iron formation are commonly found within silica-cemented horizons, where abundant chert cement silicified the sediments at or near the sediment water interface. Such silica-cemented horizons preserve incomplete reactions and allow for identification of direct mineral relationships and local element exchange. Common mineral reactions observed in the Biwabik iron formation include the transformation of greenalite to minnesotaite, minnesotatite to stilpnomelane, greenalite to magnetite, siderite to magnetite, and magnetite to hematite. Of the mineral reactions that commonly occur in iron formation, transformations of Fe2+-containing silicates like greenalite to mixed valence state minerals like magnetite and further oxidation of magnetite to hematite, contributed to formation of iron ores in the Biwabik. To illustrate some of the many post-depositional reactions that occur in iron formations worldwide, we will examine a small section of two drill cores, MGS 8 from the western end of the Mesabi iron range, and LWD-99-01 from near the Virigina horn area (see Figure 3-8 for locations). LWD-99-01 clearly preserves depositional features, while MGS-8 documents abundant post-depositional oxidation throughout. Stop 2: North Star Manganese Inc Drillcore Shed, Emily Minnesota Longitude/Latitude: 46.753571°N, -93.973496E UTM NAD 83 Zone 15N: 425650E, 5178240N Historic exploration and drilling in the 1940’s and 1950’s by Pickands Mather and US Steel identified iron and manganese-bearing mineralization within the Emily Iron Formation. US Steel developed but did not implement a preliminary mine plan for mining of the Emily Deposit. Following approximately 50 years of inactivity, Cooperative Mineral Resources (subsidiary of Crow Wing Power) pursued a pilot mining operation using pressurized water that was ultimately unsuccessful. As a follow up investigation into the outcomes of pilot mining, a small-scale drill program was accomplished in 2010-2012. A drilling program was designed and executed by Big Rock Exploration, LLC, in 2022-2023. A total of 29 drill holes were completed to extend mineralization and refine the previous resource estimates. A total of 13,107 feet of drilling was completed for this program. Data collected for this project includes lithological, structural, geotechnical, geochemical and geophysical data from the drill core. Through interpretation of legacy, recent and new drilling data, Big Rock Exploration identified coherent zones of high-grade manganese mineralization (30 to ≥40 wt.% Mn) over a 1.25-kilometer strike length. Mineralization is comprised of horizons of secondary manganese oxide minerals, as well as locally present primary iron-manganese carbonate mineralization. An ore deposit model has been developed that incorporates the oxidation of primary thin-bedded manganese-iron carbonates into massive manganese oxide through early folding and prolonged periods of weathering, oxidation, and erosion. This ore deposit model and associated geological model have been used to support an updated and expanded mineral resource estimate (Table 3-3) for the Emily Deposit that was completed and published by Forte Dynamics (Hulse et al., 2024) on May 24, 2024. We’ll first begin the review of important geological features revealed in the four Emily Mn deposit drillholes on display in the core shed by elucidating our current understanding of the geology and structure for the whole Cuyuna Iron Range and then focus specifically on the stratigraphy and ore-forming processes at Emily through a series of figures and descriptive text written into a technical report (Steiner et al., 2024) and orally presented at the 2024 ILSG conference (Peterson and Steiner, 2024). 58 �Trip 3 – Proterozoic Fe & Mn Formations Table 3-3. Mineral resource estimate for the Emily Manganese deposit. Figure 3-9. Continent-scale initial condition framework of Paleoproterozoic iron formations of Minnesota. Initial Conditions Deposition of Paleoproterozoic iron formations of the Lake Superior district all owe their origins to the ~2.4 – 2.1 Ga. rifting of the Wyoming Province craton off of the southern Superior Province craton (Figure 3-9). This rifting set the stage for the development of environments of deposition conducive to the formation of thick sequences of both Algoma- and Superior-type iron formations (Figure 3-10). During the Penokean orogeny (see Figure 3-6) these variable environments of iron formation deposition were transposed northwestward via thin-skinned tectonics into a fold & thrust belt (Cuyuna North and South range thrust panels) over a series of thrust-front folds (Emily District) that was bounded by a basal decollement. Outcomes of the Penokean orogeny in the Cuyuna Range of central Minnesota are shown in an idealized cross sectional view Figure 3-11 and how ~1.8 billion years of erosion has left it today in Figure 3-12. 59 �Trip 3 – Proterozoic Fe & Mn Formations Figure 3-10. Schematic model for the variable environments of deposition of Paleoproterozoic iron formations of the Cuyuna and Mesabi ranges of Minnesota. Figure 3-11. Idealized cross section of Minnesota’s Penokean Mountains of central Minnesota approximately 1.83 billion years ago. Figure 3-12. Schematic representation of the results of deep weathering and erosion of the Penokean Mountains in central Minnesota. 60 �Trip 3 – Proterozoic Fe & Mn Formations Geologic Maps Geologic maps are the foundation upon which geologists interpret Earth processes and depict on a piece of paper the final outcomes of such processes in plan form. As such, the authors have added annotated bedrock geology map of the Cuyuna Range in Figure 3-13 and more specifically for the Emily District of the Cuyuna Range in Figure 3-14. Figure 3-13. Annotated bedrock geologic map of a portion of the Cuyuna Range, central Minnesota. Clipped from the map of Peterson (2022). Figure 3-14. Annotated bedrock geologic map of the Emily District, Cuyuna Range, central Minnesota. Modified after Peterson, 2022. 61 �Trip 3 – Proterozoic Fe & Mn Formations Figure 3-15. Schematic stratigraphic section through the Emily Manganese deposit, after Peterson & Steiner, 2024. Stratigraphy Relogging of historic drill core and logging of new core drilled during the 2023 exploration drilling program has led to the identification of a predictable stratigraphic sequence at the Emily Deposit (Fig. 315). The four formations recognized at the Emily Deposit include three units of the Paleoproterozoic Animikie Basin unconformably overlain by Quaternary glacial drift. Descriptions of these stratigraphic units from the oldest to youngest are given below: 1. Pokegama Formation – White-grey, tan, or cream-colored indurated argillite and quartzite. The Pokegama formation at the Emily deposit is typically a clayey siltstone, though mudstones and quartz-arenites are common. Bedding is quite variable ranging from massive siltstones and quartzarenites to thick, medium, and thin bedded or even finely laminated clayey-siltstones and mudstones. The Pokegama formation does not host significant manganese mineralization but when observed manganese minerals occur in trace amounts in veinlets or as small patches with iron oxides. 2. Emily Iron Formation – See below for subdivision descriptions. 3. Virginia Formation – Grey-brown in color, red when oxidized, fine-grained, well bedded clastic sediments commonly forming turbidite sequences. Fine-scale bedding, graded beds, and sandy lenses are common. Thin horizons of lean iron formation (subunit Pvif) composed of ferruginous chert occur locally. The basal 20-40 feet is characterized by highly disrupted and fragmented turbidite clasts sed in a poorly sorted massive matrix. This horizon has been hypothesized to be landslides associated with the Sudbury Impact. 4. Glacial Overburden – Unconsolidated glacial material including well sorted sands, lacustrine clays, and unsorted glacial till. The preservation of earthy hematite and saprolitic materials immediately below the basal angular unconformity indicates that overlying Laurentide ice sheet was not eroding its base in the immediate deposit area. Composition of the overburden is inferred from drill returns during tri-cone drilling. Emily Iron Formation is further divided into five sub-units. Criteria for subunit designation requires that a given interval be sufficiently distinctive in petrologic character to be easily identified, and laterally extensive enough to be intercepted in multiple boreholes. Distinctive petrologic characteristics may be texture (e.g., banded or granular iron formation, composition (e.g., chert, carbonate), or unique 62 �Trip 3 – Proterozoic Fe & Mn Formations characteristics such as stromatolites. The subdivisions of the Emily Iron Formation are as follows from bottom to top: 1. Peif1 – This unit is located as the base of the Emily Iron Formation lies conformably atop the Pokegama quartzite. The base is commonly cherty or stromatolitic before giving way to grain stones. The majority of the unit is a red-brown to black, granular iron formation (GIF) or ferruginous quartzose sandstone. The upper part (above the Peif1r marker, see below) is granular iron formation composed of silicious, hematitic granules that range from <1 to 2mm in size. Granular iron formation is weakly bedded. The lower part of Peif1 (below the Peif1r marker horizon) contains abundant quartzose sands cemented by iron oxides giving the rock a purple appearance. Sands are composed of well-rounded fine-grained quartz and are interbedded with granular iron formation. Manganese oxide mineralization is most intense within the Peif1 unit. Manganese oxides occur in multiple styles including massive Mn-oxide that replaces all original textures (may be within a bed or cross bedding), interstitial to grains (replacing the original iron cement?), and as veinlets. The most intense manganese oxide mineralization within Peif1 occurs adjacent to (above and below) the Peif1r marker horizon, though mineralization may occur throughout the unit. The lower Peif1 commonly exhibits a pock-mark texture when strongly mineralized. A thin stromatolite horizon (Peifbs) typically occurs at the base of Peif1. 2. Peif1r – This unit is located within the Peif1 unit. Usually <3m thick, the Peif1r is composed of finegrained hematite-chert banded iron formation. The base of the Peif1r hosts distinctive digitate stromatolites. 3. Peif2 – This unit lies conformably atop Peif1, usually gradually transitioning from granular iron formation (Peif1) to banded iron formation (Peif2) over a meter. The Peif2 is characterized by finegrained well-bedded banded iron formation though the composition of the iron formation is variable. The most common composition for Peif2 is a hematite-chert banded iron formation, though this appears to be a secondary, altered composition. The primary composition is iron-manganese carbonate facies type iron formation. The carbonate facies are cream to greenish and gradually becomes red with increased oxidation. Fresh carbonate facies contain much more manganese than oxidized material, with the manganese found in rhodochrosite. This represents a very different manganese host than the oxide mineralization found in the granular iron formation units (Peif1 and Peif3). 4. Peif3 – Peif3 is characterized by interbedded medium to fine grained GIF and fine grained, narrow BIF lenses. This unit lies conformably atop Peif2 where the contact is a graduation from BIF to GIF dominant facies. Both GIF and BIF are weakly to moderately strongly bedded and silicious in composition. Peif3 is commonly mineralized manganese oxides, only subordinate in manganese endowment to Peif1. 5. Peif4 – White to grey, massive chert with mottled patches of iron-oxides. The sharp basal contact with the underlying Peif3 is often “sheared” possibly from bedding parallel slip. Some parts of the massive chert contain faint outlines of granules while most is simply massive white chert. The mottled iron oxides include large irregular pods and stringers, sometimes reaching a meter in width. Manganese is rarely found within the oxide pods. 6. Peif5 – Well-bedded banded iron formation consisting of 2-5cm beds of chert and iron oxide in gradational contact with the underlying Peif4 massive chert. This unit is the least spatially consistent, due to a lack of drillhole intercepts and difficulty identifying it as a result of intense oxidation. Supergene Enrichment of Manganese The unique manganese endowment of the Emily Iron Formation is attributed to the primary deposition of Mn-carbonates in a shallow water environment (Figures 3-10, 3-16 and 3-17). However, 63 �Trip 3 – Proterozoic Fe & Mn Formations subsequent weathering, erosion, and oxidation has redistributed much of the manganese from the carbonate unit to other areas. The majority of the manganese mineralized material at the Emily deposit is composed of manganese oxides including manganite, jacobsite, and cryptolomene/hollandite. However, these phases are not the stable manganese phase predicted by geochemical modelling of early oceans (Mitra et al., 2022). Instead, manganese carbonates are the predicted stable phase. Therefore, the manganese oxide minerals that constitute the majority of the orebody must have formed at a later stage. The tectonics during and immediately after deposition of the Animikie basin sediments provide a plausible explanation for the extremely high-grade manganese oxide formation. Figure 3-16. Carbonate facies iron formation where the gradual oxidation of primary carbonates can be observed from left to right. Note the increasingly hematite rich BIF from left to right. Primary silicate and carbonate minerals in iron formations are well documented to be unstable under oxidizing, near surface conditions. For example, the formation of direct ship ores of the Biwabik Iron Formation on the Mesabi Iron Range has been ascribed to deep weathering of primary Fe-minerals (e.g., greenalite and siderite) over hundreds of millions or a billion years. The direct ship ores were composed of hematite and goethite. The Emily Iron Formation, having been deposited contemporaneously with the Biwabik Iron Formation, would have endured at least as much weathering over that period. The weathering and subsequent supergene enrichment of manganese is related to the hydrogeologic and geochemical interaction between interbedded banded (BIF) and granular (GIF) iron formation. Manganese in the Emily Figure 3-17. Emily deposit drill core that seemingly documents that the oxidation of carbonate-facies (rhodochrosite-siderite-chert) BIF generates classic thin-bedded hematite-jasper BIF as well as being the primary source of Mn3+ that forms the massive manganese oxide zones in permeable GIF horizons. 64 �Trip 3 – Proterozoic Fe & Mn Formations Iron Formation was originally co-precipitated with iron carbonate minerals (rhodochrosite MnCO3 and siderite FeCO3) within the banded iron formation lithotype (Peif2 subunit). Primary carbonates are observed at various stages of oxidation in several boreholes (e.g., NSC-23005). Like the Biwabik Iron Formation, the Emily Iron Formation underwent a protracted period of weathering and oxidation. Exposure of carbonate facies iron formation to oxidizing waters over that period is hypothesized to be the causative mechanism for supergene manganese enrichment at the Emily deposit. Oxidized meteoric water percolating through the carbonate iron formation reacts with and dissolves the carbonates, liberating manganese from rhodochrosite and converting siderite to hematite. The restite lithology appears very similar to hematiterich banded iron formation (Fig. 3-17). The now manganese enriched waters redistribute manganese downslope to other subunits of the Emily Iron formation. The second important litho-type, granular iron formation, is recognized as the primary manganeseoxide ore hosts at the Emily Deposit. Granular iron formation is composed of granules of varying compositions (e.g., Fe-silicate, chert, Fe-carbonates) with pore space found between the granules. That pore space creates permeability that drives fluid flow through the granular iron formation thereby moving and redepositing manganese from the enriched waters leaving the carbonate facies banded iron formation. The observations from drillcore logging at Emily indicate that manganese oxides are not found in significant concentrations within the banded iron formations, but manganese oxides are abundant in the granular iron formation. The migration of manganese-rich waters from the banded iron formation into the granular units is the primary redistribution mechanism for manganese. Once manganese enriched waters enter the granular units, it is unclear by what mechanism the precipitation of manganese occurs. However, manganese oxide minerals are observed in the interstices between granules indicate direct precipitation from the pore fluids. It is unclear whether this interstitial manganese is the result of filling otherwise empty pore space if it is the result of replacement of prior GIF matrix. Additionally, pock marked textures in manganese-rich units suggest that granules may be replaced by the manganese-rich fluids, though the mechanism by which this may occur is unclear due to a lack of mineralogical constraints. Stratigraphic and Structural Controls on the Distribution of Secondary Manganese The compression associated with the Penokean Orogen uplifted the rocks Emily deposit. Folding and subsequent uplift of these originally shallow water subaqueous rocks into the Penokean mountains has important hydrogeological implications by greatly lowering the water table and exposing the Emily Iron Formation to oxidizing meteoric waters. The Emily deposit is on the northernmost anticline of the Penokean fold and thrust belt, specifically within a parasitic syncline along the norther limb of the larger anticline. The structural geometry established during the Penokean provides a hydrogeologic “slope” that meteoric waters can migrate down under the influence of gravity. In particular, the parasitic syncline that hosts the Emily Deposit (see Figure 3-14), likely acted like a funnel or gutter that focused fluid flow through the rocks that now constitute the deposit. A schematic stepwise ore genesis model for the Emily deposit is presented in Figure 3-18. On a deposit scale and within this structural setting, the two major litho-types play an important role in the movement of fluids due to their contrasting hydrogeological characteristics. In particular, the Peif1r stromatolite horizon represents an aquitard that seemingly focused fluid along its margins. The focusing of fluids along these margin manifests as exceptionally high Mn-grades (often massive manganese oxides) at the upper and lower contacts with flanks GIF of Peif1. Similarly, but to a lesser extent, the basal contact with the Pokegama formation and the contact between Peif2 and Peif3 represent areas of contrasting hydrogeologic characteristics that may concentrate mineralizing fluids. Both areas are observed to host massive manganese oxide mineralization, supporting such a relationship. 65 �Trip 3 – Proterozoic Fe & Mn Formations Figure 3-18. Emily deposit Mn-Oxide ore deposit model that incorporates stratigraphy, permeability, processes, and time, after Peterson & Steiner, 2024. Drillholes on Display Four drillholes from the 2023 exploration program at Emily will be on display for the 2025 ILSG field trip. These holes include: 1) NSC-23002A - high-grade Mn-oxide ores at the bedrock interface in Peif1, 2) NSC-23004 - an almost complete stratigraphic section through the Emily IF, 3) NSC-23005 - Peif2 with carbonate facies IF and Sudbury Impact breccias in unit Pvf, and 4) NSC-23050 – The Western-most drillhole, nearly complete section of the Emily IF. A detailed bedrock geology and drillhole location map of North Star Manganese Inc’s Emily Project is presented in Figure 3-19, and striplogs of the four holes on display are given in Figures 3-20, 3-21, 3-22, and 3-23. 66 �Trip 3 – Proterozoic Fe & Mn Formations Figure 3-19. Detailed bedrock geology and drillhole location map of North Star Manganese Inc’s Emily project. Note that the collar location of the four drillholes on display are highlighted by the small yellow circles. Modified after Steiner et al., 2024. 67 �Trip 3 – Proterozoic Fe & Mn Formations Figure 3-20. Striplog for drillhole NSC-23002A. Figure 3-21. Striplog for drillhole NSC-23004. 68 �Trip 3 – Proterozoic Fe & Mn Formations Figure 3-22. Striplog for drillhole NSC-23005. Figure 3-23. Striplog for drillhole NSC-23050. 69 �Trip 3 – Proterozoic Fe & Mn Formations Stop 3: Mary Ellen Mine, Biwabik Minnesota Longitude/Latitude: 47.527677°N, -92.366645E UTM NAD 83 Zone 15N: 547675E, 5264000N The historic natural ore Mary Ellen mine (Figure 3-24) near Biwabik is probably most well-known today as the source of Mary Ellen Jasper, a world-class type-locality of Precambrian stromatolites. Rocks and polished slabs of stromatolites from the Mary Ellen mine can be found in natural history museums throughout the world, and you’ll get to find and take-home pieces yourself during this field trip. According to several annual mining directories, the Stanley Iron Mining Company operated the Mary Ellen Mine between 1924 and 1928, with stockpile shipments occurring in 1929 and 1930. It actively mined the property again between 1948 and 1951. Beginning in 1952, the Pioneer Mining Company worked the mine, continuing to do so through 1961. The Pittsburgh Pacific Company operated it for one final year, in 1962. Its cumulative output of natural ore was 4,574,973 long tons, again according to an annual mining directory. An interesting quote from the 2015 book titled: Stromatolites Ancient, Beautiful and EarthAltering, by Bruce Stinchcomb & Bob Leis copied below strongly hints that some oxidation-related processes that formed the high-grade earthy hematitic iron ores were similar to those outlined for the highgrade manganese oxide ores at Emily. The quote is as follows, "In the early days of iron mining in Minnesota, the location of stromatolite material would indicate that an iron rich vein was close. The Mary Ellen Stromatolite material could be as much as 15 feet thick and would have to be removed before mining could commence. To the miners this material was considered a nuisance and a waste product." Figure 3-24. Simplified bedrock geology and iron mine map of the Mary Ellen mine area. 70 �Trip 3 – Proterozoic Fe & Mn Formations Stop 4: Rouchleau Mine Complex Bridge, Virginia Minnesota Longitude/Latitude: 47.516178 °N, -92.518663 E UTM NAD 83 Zone 15N: 536240 E, 5262640 N The Thomas Rukavina Memorial Bridge carries U.S. 53 over the Rouchleau Mine pit connecting Virginia, Minnesota with other cities to the south. U.S. 53 continues through Virginia to International Falls and Canada; International Falls is about 100 miles (160 km) north of Virginia. The bridge, opened in 2017, was named after Tom Rukavina in 2021 following his death in 2019. Rukavina was a state legislator from the Iron Range. At 204 feet tall, it is the tallest bridge in Minnesota. This bridge carries a traffic volume of about 22,200 cars per day, making it one of the most-traveled highway segments on the Iron Range. The bridge also features a bike lane and pedestrian walkway (the Mesabi Trail) that leads to trails connecting Gilbert and Virginia. In 1960, the state of Minnesota and the mining companies in the area came to an agreement that allowed the construction of U.S. 53 across lands held by the mining company without the state paying anything for the land. The agreement stipulated that after 1987, the state would be responsible for the costs involved with moving the roadway to allow for mining after given advance notice by the mining companies. The two owners of the land notified MnDOT of their intent to mine the site in 2010 which gave the state until 2017 to move the roadway. Cliffs Natural Resources, which had a nearby active mine, hoped to begin mining the site by 2017. After evaluating several more expensive options that involved longer bridges or routing US 53 across an active mine pit, an alignment was selected that resulted in the highest bridge in Minnesota. A route on level ground away from the mining formation was identified as too disruptive to development patterns in the area. The entire project estimated to cost $220 million with $159 million for construction of the bridge and diverted roadway. The bridge crosses the Rouchleau Mine pit.[9] The water filled pit also serves as Virginia's water supply. The final cost was $230 million with $30 million coming from the federal government and the remaining from the state. To prevent the need to move the bridge in the future, the state purchased the mineral rights for the land beneath roadway for $15 million. References Aftabi, A., Atapour, H., Mohseni, S., and Babaki, A., 2021, Geochemical discrimination among different types of banded iron formations (BIFs): A comparative review, Ore Geology Reviews, Volume 136. Aldrich, H. R., 1929, The geology of the Gogebic Iron Range of Wisconsin: Wisconsin Geol. Survey Bull. 21, 279 p. Beltrame, R.J., Holtzman, R.C., and Wahl, T.E., 1981, Manganese resources of the Cuyuna range, east-central Minnesota: Minnesota Geological Survey Report of Investigations 24, 22 p. Berg, T., Peterson, D.M., and Sweet, G., 2022, The Emily Manganese Deposit, Crow Wing County, Minnesota: A mineral resource evaluation for North Star Manganese Inc, Big Rock Exploration technical report BRE-TR2022-02, 33 pages, 3 appendices. Dorr, J.VN., II, Crittenden, M.D., Jr., and Worl, RG., 1973, Manganese, in Probst, D.A., and Pratt, W.P., eds., United States Mineral Resources: U.S. Geological Survey Professional Paper 820, p. 385-399. Duncanson S and 5 coauthors (2024) Reconstructing diagenetic mineral reactions from silicified horizons of the Paleoproterozoic Biwabik Iron Formation, Minnesota. American Mineralogist 109: 339-358, doi: 10.2138/am2022-8776. Goodwin, A.M., 1956, Facies relations in the Gunflint iron-formation: Ecox. GEOL., v. 51, p. 565-595. Gruner, 1946, Mineralogy and geology of the Mesabi range: Iron Range Resources and Rehabilitation, St. Paul, Minn., 127 p. Gunderson, J. N., and Schwartz, G. M., 1962, The geology of the metamorphosed Biwabik iron-formation, Eastern Mesabi District, Minnesota: Minnesota Geol. Survey Bull. 43, 139 p. Hofstra, A.H., and Kreiner, D.C., Systems-Deposits-Commodities-Critical Minerals Table for the Earth Mapping Resource Initiative: U.S. Geological Survey Open-File Report 2020-1042, 24 p. Holm, D.K., Lux, D.R., 1996, Core complex model proposed for gneiss dome development during collapse of the Paleoproterozoic Penokean orogen, Minnesota, Geology 24, 343–346. 71 �Trip 3 – Proterozoic Fe & Mn Formations Holst, T.B., 1991, The Penokean orogeny in Minnesota and Upper Michigan, U.S. Geological Survey Bulletin 1904D, 10 pages. Hulse, D.E., Irons, A., and Malhotra, D., 2024, Electric Metals (USA) Limited Emily Manganese Project, NI 43-101 Technical Report, Project No. 219001, Forte Dynamics, 89 pages. Irving, R. D., 1886, Origin of the ferruginous schists and iron ores of the Lake Superior region: Am. Jour. Sci., v. 32 p, 255-272. Irving and Van Hise, C. R., 1892, The Penokee iron-bearing series of Michigan and Wisconsin: U.S. Geol. Survey Mon. 19, 534 p. James, H. L., 1954. Sedimentary facies of iron-formation. Economic Geology, 49(3), 235–293. Klein, C., and Fink, R.P., 1976, Petrology of the Sokoman Iron Formation in the Howells River area, at the western edge of the Labrador trough: Economic Geology, v. 71, p. 453–487. LaBerge, G.L., 1964, Development of magnetite in iron-formations of the Lake Superior Region: Econ. Geol., V. 59, p. 1313-1342. Leith, C. K., 1903, The Mesabi iron-bearing district of Minnesota: U.S. Geol. Sur. Mono. 43, 316 p. Lewis, W.E., 1951, Relationship of the Cuyuna manganiferous resources to others in the United States, in Geology of the Cuyuna Range Mining Geology Symposium, 3rd, Hibbing, Minnesota, Proceedings: Minneapolis, University of Minnesota, Center for Continuation Study, p. 30-43. Marsden, R.W., 1972, Cuyuna district, in Sims, P.K., and Morey, G.B., eds., Geology of Minnesota: A centennial volume: Minnesota Geological Survey, p. 227-239. Marsden, R.W., Emanuelson, J.W., Owens, J.S., Walker, N.E., and Werner, R.F., 1968, The Mesabi Iron Range, Minnesota, in Ridge, J.D. (ed.), Ore Deposits of the United States, 1933-1967: New York, American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc., The Grafton-Sales Volume, v. 1, p. 518-537. Mitra, Kaushik, Eleanor L. Moreland, Greg J. Ledingham, and Jeffrey G. Catalano, 2023, Formation of manganese oxides on early Mars due to active halogen cycling, Nature Geoscience 16, no. 2, p. 133-139. Morey, G.B., 1978, Lower and Middle Precambrian stratigraphic nomenclature for east-central Minnesota: Minnesota Geological Survey Report of Investigations 21, 52 p., 1 pIate. Morey, G.B., 1992, Chemical composition of the eastern Biwabik Iron Formation (Early Proterozoic), Mesabi Iron Range, Minnesota: Economic Geology, v. 87, p. 1649-1658. Muhling, J., Brengman, L., & Johnson, J. Greenalite (2025, June issue): Cryptic mineral of ancient ferruginous oceans. Elements: Greenalite - Tiny crystal with a big story, Elements (in press). Peterson, D.M., 2022, Bedrock geology and manganese mineral resource assessment map of the Emily Manganese Deposit, Big Rock Exploration map BRE-MAP-2022-02, 1:50,000 scale. Peterson, D.M., and Steiner, A., 2024, The geology, history, and ore deposit model of the high-grade Emily Manganese Deposit, Cuyuna Range, Minnesota: Oral presentation, Institute on Lake Superior Geology conference, Houghton, Michigan. Schmidt, R.G., 1963, Geology and ore deposits of Cuyuna North range, Minnesota: U.S. Geological Survey Professional Paper 407, 96 p. Schneider, D.A., Holm, D.K., O’Boyle, C., Hamilton, M., Jercinovic, M., 2004, Paleoproterozoic development of a gneiss dome corridor in the southern Lake Superior region, U.S.A. In: Whitney, D.L., Teyssier, C., Siddoway, C.S. (Eds.), Gneiss Domes in Orogeny. Geol. Soc. Am. Spec. Pap. 380, pp. 339–357. Schulz, K.J. and Cannon, W.F., 2007, The Penokean orogeny in the Lake Superior region, Precambrian Research, 157, p. 4–25. Schulz, K.J., DeYoung, J.H., Jr., Seal, R.R., II, and Bradley, D.C., eds., 2017, Critical mineral resources of the United States - Economic and environmental geology and prospects for future supply: U.S. Geological Survey Professional Paper 1802, 797 p., https://doi.org/10.3133/pp1802. Severson, M.J., Heine, J.J., and Patelke, M.M., 2009, Geologic and Stratigraphic Controls of the Biwabik Iron Formation and the Aggregate Potential of the Mesabi Iron Range, Minnesota: University of Minnesota Duluth, Natural Resources Research Institute, Technical Report NRRI/TR- 2009/09, 173 p. + 37 plates. Southwick, D.L. and Morey, G.B., 1991, Tectonic imbrication and foredeep development in the Penokean orogen, east-central Minnesota; an interpretation based on regional geophysics and results of test drilling, U.S. Geological Survey Bulletin 1904-C, pp. C1–C17. Southwick, D.L., Morey, G.B., and McSwiggen, P.L., 1988, Geologic map (scale 1:250,000) of the Penokean orogen, central and eastern Minnesota, and accompanying text: Minnesota Geological Survey Report of Investigations 37, 25 p., 1 pIate. 72 �Trip 3 – Proterozoic Fe & Mn Formations Steiner, A., Peterson, D.M., Berg, E., Solie, J., Larson, M., Schaefbauer, E., and Sweet, G., 2024, The North Star Emily Manganese Deposit: Observations, Interpretations, and Recommendations Following the Initial 2023 Drilling Campaign, Big Rock Exploration Technical Report BRE-TR-2023-01, 47 pages, 4 appendices, 1 plate. Strong, R., 1959, Report on Geological Investigation of the Cuyuna District, Minnesota, 1949-1959, US Steel Internal Report, 318 pages. Tyler, S.A., 1949, Development of Lake Superior soft iron ores from metamorphosed information: Geol. Soc. Am. Bull., v. 60, p. 1101-1024. Van Hise, C. R., and Leith, C. K., 1911, Geology of the Lake Superior region. U.S. Geol. Survey Mon. 52, 641 p. White, D. A., 1954, The stratigraphy and structure of the Mesabi Range, Minnesota: Minnesota Geol. Survey Bull. 38, 92 p. Wolff, J.E., 1917, Recent geologic developments on the Mesabi Iron Range, Minnesota: American Institute of Mining and Metallurgical Engineers, Transactions, v. 56, p. 229-257. 73 �Trip 4 – Soudan FIELD TRIP 4 New Geological Insights into the Genesis of Iron Ores at Lake Vermilion – Soudan Underground Mine State Park George J. Hudak1,2,3, Zsuzsanna P. Allerton1, and Annia Fayon1 1 Department of Earth and Environmental Sciences, University of Minnesota Twin Cities, 116 Church Street SE, Minneapolis, MN 55455 2 Department of Earth and Environmental Sciences, University of Minnesota Duluth, 1114 Kirby Drive, Duluth, MN 55812 3 George Hudak Geosciences P.L.L.C., Duluth, MN 55804 Introduction The Vermilion District of northeastern Minnesota contains one of the classic greenstone belts in the United States. The district comprises the southwestern part of the Wawa-Abitibi Terrane (Stott et al., 2007; Stott and Mueller, 2009) which encompasses Neoarchean metavolcanic, metasedimentary, and metaintrusive rocks that extend northeastward through northwestern Ontario and Quebec (Figure 4-1). In Canada, this terrane hosts numerous volcanogenic massive sulfide deposits (e.g. Winston Lake, Geco, Noranda), gold-rich volcanogenic massive sulfide deposits (Horne (Noranda camp), Bousquet 2 – LaRonde 1, LaRonde-Penna; Mercier-Langevin et al., 2010), as well as a large number of lode (orogenic) gold deposits (for example, in the Hemlo, Timmins, and Kirkland Lake camps). The Vermilion District is known for its numerous, previously mined massive hematitic iron ore deposits (including the Pioneer Mine in Ely and the Soudan Mine in Soudan) which locally occur within regional extensive Algoma-type banded iron formations cut by Neoarchean shear zones. To date, no volcanogenic massive sulfide, gold-rich volcanogenic massive sulfide, or lode gold deposits have been discovered in the Vermilion District, although several studies (Peterson and Jirsa, 1999; Peterson, 2001; Hudak et al., 2002a; Peterson and Patelke, 2003; Hoffman, 2007; Hudak et al., 2007; Hudak et al., 2012; Lodge et al., 2013; Lodge et at., 2015; Thompson, 2015) have indicated that evidence for volcanic, hydrothermal, and structural processes associated with these types of mineral deposits is present throughout the Vermilion District. The Vermilion District’s iron ore mining heritage is currently preserved at Lake Vermilion / Soudan Underground Mine State Park located near Soudan, Minnesota as well as within several historic mines west of and within Ely, Minnesota. The Soudan mine operated from 1882 until December, 1962 and produced approximately 15.5 tons of hematic iron ore. With the donation of land and infrastructure associated with the former Oliver Iron Mining Division’s Soudan Mine by United States Steel to the State of Minnesota in 1965, Soudan Underground Mine State Park was established. This state park currently preserves the historical surface and underground workings from, as well as the wilderness adjacent to, Minnesota’s oldest iron ore mine, the Soudan Mine. The mine previously hosted several underground physics laboratories, including: 1) Soudan 1 (23rd level) which studied neutrino decay; 2) Soudan 2 (27th level), also to study neutrino decay; and 3) the MINOS (Main Injector Neutrino Oscillation Search) lab, which was built on the 27th level adjacent to Soudan 1 and studied the decay of neutrinos within the earth as they passed from Fermilab to Soudan. This popular tourist site continues to be the focus of a wide variety of research related to geology, geochemistry, hydrogeology, biology, biochemistry and physics. Lake Vermilion/Soudan Underground Mine State Park is Minnesota’s newest state park. In 2008, Minnesota State Legislature set aside $20 million in bonding authority to buy, plan, and develop the park, which is located immediately east of the former Soudan Underground Mine State Park. Lake Vermilion/Soudan Underground Mine State Park was established in June 2010 after over 3,000 acres land was purchased from U. S. Steel Corporation (Bakst, 2013). At the present time, considerable development 74 �Trip 4 – Soudan Figure 4-1. Regional geology of the Lake Superior region illustrating the wide variety of mineral deposit types (modified from Hudak and Peterson, 2014; D.M. Peterson, personal communication, 2013). has taken place in the eastern part of the park, including the establishment of trails, roads, and campsites. The park boasts a rich natural and human history, including a wide variety of ~2.7 billion year old rocks that were formed by a wide variety of genetic process, abundant wildlife, as well as archaeological evidence for human habitation dating back over 6,000 years. Additionally, considerable evidence for recent (within the past 140 years) mineral exploration efforts can be readily identified in the park. Since the late 1990’s considerable geological research has been conducted in the region between Tower, MN (in the west) to Ely, MN (in the east) within the Vermilion District. Much of this research has been conducted to better understand the stratigraphy, structural geology, and economic geology of the belt. This research is summarized in several recent Institute on Lake Superior Geology (ILSG) field trips (Hudak et al., 2004; Jirsa et al., 2004; Peterson and Patelke, 2003; Larson and Mooers, 2009; Peterson et al., 2009a; Jirsa and Hillman, 2009; Peterson et al., 2009b), as well as in a few recent journal publications (Lodge et al., 2013; Lodge et al., 2015). In 2010 and 2011, students and faculty from the University of Minnesota Duluth Precambrian Research Center conducted new, 1:5000 scale mapping of this park and several maps and reports were produced (Radakovich et al., 2010; Vallowe et al., 2010; Heim et al., 2011; Baumgardner et al., 2013; Hudak et al., 2016; Peterson et al., 2016). These findings are summarized in Hudak et al., 2014. In addition, geologists from the Natural Resources Research Institute (NRRI), the Minnesota Geological Survey (MGS), and the University of Wisconsin Eau Claire produced a 1:10000-scale map of the park as well as a project report and accompanying spatial databases (Peterson et al., 2016; Hudak et al., 2016). Over the past several years, students and faculty from the University of Minnesota Twin Cities Advanced Field Camp have refined the geological map in an area approximately one-half mile east of the Soudan Mine headframe. 75 �Trip 4 – Soudan The results of these studies have provided a solid foundation for geological research that is currently taking place in Lake Vermilion/Soudan Underground Mine State Park (e.g.). Recent masters and doctoral studies from the University of Minnesota Duluth (Thompson, 2015) and the University of Minnesota Twin Cities (Allerton, in prep.; Allerton et al., 2024a; Allerton et al., 2024b; Allerton et al., in review) have focused their research on understanding the absolute age of massive hematite mineralization at the Soudan Mine. This is a problem that has baffled geoscientists for over a century (e.g. Gruner, 1926; Klinger, 1960). In addition, students and faculty from the University of Minnesota Twin Cities Advanced Field Camp have conducted more recent geological mapping (1:5000 scale) in an area approximately one-half mile east of the Soudan Mine headframe for the past several years. This mapping has led to minor reinterpretations of the geology in the central part of Lake Vermilion/Soudan Underground Mine State Park that was depicted by Peterson et al. (2016). Recently, a grant from the Leaonardt Foundation was awarded to one of the co-authors (Fayon) to develop a new trail in the park that will focus on public education related to the ancient geology and geological processes that have taken place in the park. K-12 teachers are playing a major role in developing the curriculum and lessons that will be part of this trail project. The goals of this field guide are to illustrate to field trip participants the wide variety of geological processes that have taken place within Lake Vermilion/Soudan Underground Mine State Park. Morning field trip stops will focus on understanding the stratigraphy, structure, hydrothermal alteration and mineralization closely associated with the Soudan iron orebodies. The afternoon will focus on observing both geological features of the massive hematite orebodies, as well as recent advances in our geochemical and geochronological understanding of these iron ore deposits in the Montana stope, located on the 27th level of the Soudan Mine. Figure 4-2. Simplified correlation map of Neoarchean assemblages in Minnesota and northwestern Ontario (after Peterson et al., 2001; Hudak and Peterson, 2014). Inset map illustrates location of the Wawa-Abitibi Terrane in Minnesota and northwestern Ontario (Stott et al., 2007). The Leach Lake structural discontinuity is illustrated in red. The red star symbols indicate location of Lake Vermilion State Park. 76 �Trip 4 – Soudan Regional Geologic Setting A simplified regional geological map of the Neoarchean terranes of northeastern Minnesota and adjacent Ontario is presented in Figure 4-2. Supracrustal rocks in the Vermilion district consist of volcanicdominated stratigraphic sequences of the Wawa Abitibi Terrane within the Superior Province of the Canadian Shield. Rocks of the Wawa Abitibi Terrane in northern Minnesota are divided based on stratigraphic and structural setting into: (1) the Soudan belt, to the south, and (2) the Newton belt, to the north (Jirsa et al., 1992; Southwick et al., 1998). The boundary between these contrasting structural panels can be traced geophysically across the width of Minnesota and was informally designated the Leech Lake structural discontinuity (Jirsa et al., 1992). In the region west and north of Lake Vermilion/Soudan Underground Mine State Park, the Leech Lake structural discontinuity occurs along the Mud Creek shear zone (Hudleston et al., 1988), small segments of the Vermilion and Wolf Lake faults (Sims and Southwick, 1985), and the Bear River fault (Jirsa et al., 1992). The Soudan belt (Figure 4-3) contains large, broad generally east-west trending folds involving calc-alkalic and tholeiitic volcanic strata overlain by, and locally interlayered with, turbiditic rocks. In contrast, the Newton belt consists of elongate, northeast-trending, and mostly northward-younging volcanic and volcaniclastic sequences. Volcanic rocks of the Newton belt differ from those of the Soudan belt in containing locally abundant komatiite/basaltic komatiite flows and peridotite sills. The two belts are faultbounded, and the relationships between stratigraphic units within each belt are largely conformable (although faults obscure contacts locally). In its eastern extension, the Soudan belt is continuous with the Saganagons assemblage in Ontario and terminates against the Saganaga pluton and Northern Light Gneiss. The Newton belt extends discontinuously eastward into the Shebandowan District of Ontario to form the Greenwater and Burchell assemblages. Intrusive rocks in both belts vary from gabbroic and felsic porphyries demonstrably related to volcanism, to large plutons emplaced post-tectonically. Both districts contain unconformable, Timiskaming-type sequences composed of calc-alkalic volcanic rocks, conglomerates, and finer grained sedimentary rocks. Lithostratigraphic units in the western Vermilion district (Table 4-1) include: (1) the Lower member, Soudan Iron-Formation member, and Upper member (Upper Ely) of the Ely Greenstone Formation, the Lake Vermilion Formation (including the informally named Britt and Gafvert Lake sequences), and the Knife Lake Group of the Soudan belt; (2) the Bass Lake sequence (Peterson and Jirsa, 1999) and the Newton Lake Formation of the Newton belt; and, (3) syn- to post-tectonic granitoid intrusions of the Giants Range batholith, and a suite of post-tectonic alkalic stocks and plutons. Contacts between the different units are typically conformable, although considerable overlap in time and space is documented between volcanic and sedimentary sequences (Southwick, 1993). Regional chronostratigraphic correlations between the Vermilion district, the Wawa Greenstone (northwestern Ontario) and the Abitibi greenstone belt (eastern Ontario and Quebec) are indicated in Figure 4-4. Geochronological information for supracrustal and intrusive lithologies in the Vermilion District is relatively sparse (Figure 4-4). Peterson et al. (2001) obtained a U-Pb zircon age date of 2722 ± 0.9 Ma from a quartz-phyric rhyolite dome in the Fivemile Lake Sequence of the Lower Member of the Ely Greenstone Formation. Lodge et al. (2013) obtained a U-Pb zircon date of 2689.7 ± 0.8 Ma for a Gafvert Lake Sequence dacitic tuff breccia that occurs approximately 2m north of the contact with the Soudan Iron-Formation member of the Ely Greenstone Formation. As well, Lodge et al. (2013) obtained detrital zircon dates ranging from 2680-2690 Ma from greywackes that comprise the Lake Vermilion Formation. This date confirms the source of the detritus in the Lake Vermilion Formation was derived locally from the volcaniclastic rocks comprising the Gafvert Lake Sequence. Jirsa et al. (2012) obtained a U-Pb age of 2690.7 ± 0.6 Ma for synvolcanic intrusions that cross-cut volcaniclastic rocks that comprise the Knife Lake Group. The upper part of the Knife Lake Group includes conglomerates which contain clasts derived from Table 4-1. Lithostratigraphic units within the western Vermilion District (modified after Peterson and Jirsa, 1999; Peterson et al., 2009; Hudak et al., 2012). 77 �Trip 4 – Soudan Intrusive Rocks Late Intrusions Plutons and stocks of syenite, monzonite, diorite, and lamprophyre. A U-Pb zircon age date of a non-foliated feldspar porphyry intrusion in the Newton belt is 2683 ± 1.4 Ma (Peterson et al., 2001). Vermilion Granitic Complex Granite, schist, amphibolite, and schist-rich migmatite Giants Range Batholith Granite, granodiorite, monzodiorite, and schist-rich migmatite. U-Pb zircon dates indicate a crystallization age ranging from 2640-2777Ma (Allerton et al., 2024a). Supracrustal Rocks Newton Belt Newton Lake Formation Tholeiitic and komatiitic basalt lava flows, intrusions, and clastic strata (deep subaqueous?) Bass Lake Sequence Tholeiitic basalt lava flows, iron-formation, and felsic porphyries (deep subaqueuous) Soudan Belt Knife Lake Group Graywacke, slate, conglomerate, and sheared equivalents Lake Vermilion Formation Graywacke, slate, dacitic tuff, minor conglomerate. Detrital zircons from planar bedded, normal-graded resedimented volcaniclastic rocks have UPb age dates of 2680-2690 Ma (Lodge et al., 2013; subaerial to subaquous) Gafvert Lake Sequence Dacitic to rhyodacitic tuff, lapilli-tuff, tuff-breccia, and iron-formation. Basal dacite tuff-breccia deposits in Lake Vermilion State Park have UPb age date of 2689.7 ± 0.8 Ma (Lodge et al., 2013; subaerial to subaqeous) Britt Sequence Tholeiitic basalt lava flows (deep subaqueous?) Upper Member – Ely Greenstone Tholeiitic basalt lava flows and iron-formation (deep subaqueous?) Soudan Member – Ely Greenstone Oxide-facies iron formation with intercollated basalt lava flows and felsic volcaniclastic rocks (deep subaqueous) Lower Member – Ely Greenstone Calc-alkaline and tholeiitic basalt-rhyolite lava flows, tuffs, epiclastic rocks, and minor iron-formation (shallow- to deep subaqueous) Central Basalt Sequence Calc-alkaline to tholeiitic sparsely amygdaloidal basalt and minor basaltic andesite lava flows with MORB-like or back arc basin-like chemical affinities within 100-200 meters of the overlying Soudan Member iron-formation; FII- and FIIIa-type felsic volcanic and volcaniclastic rocks (transition from shallow- to deep water environment) Fivemile Lake Sequence Calc-alkaline to transitional moderately to highly vesicular basalt and andesite lava flows and volcaniclastic rocks with arc-like chemical affinities: FI-, FII-, and FIV-type felsic volcanic and volcaniclastic rocks. Rhyolite dome at near Fivemile Lake has U-Pb age date of 2722.6 ± 0.9 Ma (Peterson et al., 2001). Epithermal-like zinc stringer mineralization is present near Fivemile Lake (Hudak et al., 2002a; interpreted as shallow subaqueous environment). Eagles Nest Sequence Algoma-type iron formation, basalt-andesite lava flows, hydrothermal exhalites, felsic tuffs. 78 �Trip 4 – Soudan Figure 4-3. Generalized geology of the Soudan belt in the vicinity of the Tower-Soudan anticline (modified after Peterson, 2001; Hudak et al., 2014; Hudak and Peterson, 2014). Locations, ages, and sources of U-Pb ages dates within the district are noted in the callout boxes. Generalized lithologies for each of the groups, formations or sequences are also noted. The outline of the Lake Vermilion section of Lake Vermilion/Soudan Underground Mine State Park is shown in green. 79 �Trip 4 – Soudan Figure 4-4. Regional chronostratigraphic correlations between the Vermilion district (Minnesota), the Wawa greenstone belt (northwestern Ontario), and the Abitibi greenstone belt (eastern Ontario and Quebec; after Ayer et al., 2010). the Saganaga Tonalite, which has been dated by Driese et al. (2011) at 2690.83 ± 0.26 Ma. Peterson et al. (2001) also dated a non-foliated feldspar porphyry intruded into Newton Belt strata at 2683.1 +1/-4 Ma. This date provides a minimum age for the regional D2 deformation event that is described below. Structural Geology The structural geology of the Vermilion District has been well described by Peterson et al. (2009). Periods of generally N-S directed compression resulted in three major regional deformation events in the Neoarchean terranes of northern Minnesota. The earliest deformation event (D1) produced broad, locally recumbent folds within the Soudan belt and major fault zones throughout the region. In the Newton belt, D1 was accommodated by thrust imbrication of large crustal blocks, resulting in mainly northward stratigraphic facing. Field relationships indicate that uplift, faulting, and the deposition of Timiskamingtype clastic sedimentary sequences in local fault-bounded basins occurred late in D1 deformation (Jirsa, 2000). A large, map-scale structure related to D1 deformation in the western Vermilion District is the Tower-Soudan Anticline, which is a west-plunging anticline within which the axis and plunge changes orientation along strike from nearly vertical in basalts to shallow NE plunging in the western sedimentary rocks. Axial-planar cleavage associated with this early fold typically is lacking, although Bauer (1985), Hooper and Ojakangas (1971), Hudleston (1976), and Jirsa et al. (1992) have described early cleavage (S1) locally. A second deformation event (D2) associated with synchronous regional metamorphism resulted in foliation development and structures exhibiting dominantly dextral asymmetry. D2 is constrained in the Vermilion District to the time period 2674 to 2685 Ma (Boerboom and Zartman, 1993), and between about 2680 and 2685 Ma in the Shebandowan (Corfu and Stott, 1998). Because D2 deformation affected all the supracrustal rocks in the area and is reasonably constrained by geochronology, the regional foliation (S2) can be used in the field to temporally relate other structural, intrusive, and deformation events. The relationship between S2 fabric and shear structures indicates that most shearing occurred relatively late in the D2 event. Major shearing that produced the Mud Creek and related shear zones is attributed to the late stages of D2 dextral transpression (Peterson, 2001; Hudak et al., 2004; Peterson et al., 2009). 80 �Trip 4 – Soudan The third deformation event (D3) is believed to be associated with the juxtaposition of the Wawa Abitibi and Quetico terranes (Peterson and Patelke, 2003). Structures associated with D3 include abundant NE- and NW-trending faults that dissect the stratigraphic assemblages and include the NE-trending Waasa and Camp Rivard faults east of the Soudan Mine area, and the WNW-trending, crustal-scale Vermilion and related faults that form the Wawa-Quetico Subprovince boundary. Geology of Lake Vermilion/Soudan Underground Mine State Park Lake Vermilion State Park contains a variety of supracrustal and intrusive lithological units (Figure 4-5). Supracrustal rocks that can be observed in the park include the Lower Member of the Ely Greenstone Formation (both the Fivemile Lake and Central Basalt Sequences), the Soudan Member of the Ely Greenstone Formation, and the Gafvert Lake Sequence of the Lake Vermilion Formation. Additionally, a wide variety of syn- and post-volcanic mafic and felsic intrusive rocks and several varieties of sheared rocks crop out in the park (Peterson and Patelke, 2003; Radakovich et al., 2010; Heim et al., 2011; Hudak et al., 2016; Peterson et al., 2016). These various lithologies are described below. Lithology Supracrustal rocks in Lake Vermilion/Soudan Underground Mine State Park were described by Hudak et al. (2016) based on lithological types rather than lithostratigraphic members and/or formations. Their lithological descriptions are included below. A summary of mafic supracrustal rocks that occur within the park include: • undivided mafic volcanic rocks, including gray-green to green massive basalt, pillow basalt, basalt tuff, bedded scoria tuff and lapilli-tuff, and foliated basalt rocks • massive basalt comprising green to dark green, aphyric to sparsely plagioclase-phyric basalt • • • • pillow basalt, including gray-green to green bun, mattress, and lobe morphologies using the pillow lava classification of Dimroth et al., (1978) basalt tuff, including green, massive to bedded, aphyric to sparsely plagioclase-phyric tuff. bedded scoria tuff and lapilli-tuff, composed of green, thin- to very thick-bedded, poorly-sorted, typically poorly-graded tuff and lapilli-tuff containing up to 65% <1-20cm scoria lapilli foliated basaltic rocks, made up of green, fine-grained, moderately to strongly foliated basalt comprising anastomosing bands of chlorite-rich phyllite separating domains of less deformed basalt Felsic volcanic rocks within the park include: • • • • epiclastic, intermediate-felsic volcanic-derived sedimentary rocks, composed of light gray to brownish gray polymict volcaniclastic matrix-supported conglomerates and sandstones containing clasts of felsic volcanic and volcanic strata, oxide facies iron formation, and chertrich iron formation. laminated felsic tuff, made up of white to dark gray, laminated- to very thinly bedded, aphyric to sparsely quartz- ± plagioclase-phyric dacite to rhyolite tuff. felsic tuff breccia, comprising light gray, very thickly bedded to massive, matrix-supported quartz- and plagioclase-phyric polymict dacite to rhyodacite tuff breccia containing 10-20% 110 cm quartz and plagioclase-phyric coherent dacite lapilli and blocks, 5-7% lens-shaped quartz- and plagioclase-phyric pumice lapilli up to 3 cm in diameter, 1% light- to dark-gray chert lapilli up to 3 cm in diameter, and 1-3% 0.5-5.0cm diameter black to dark gray to red magnetite-rich, hematite-rich, or jasper-rich banded iron formation lapilli. massive felsic lava flows composed of light gray to greenish gray, fine-grained, massive, aphyric to quartz-phyric rhyodacite to rhyolite lava flows. 81 �Trip 4 – Soudan Figure 4-5. Geologic map of Lake Vermilion/Soudan Underground Mine State Park (after Peterson et al., 2016). Detailed maps showing locations of field trip stops are provided in Figure 4-8, and optional stops are shown in Figure 4-12. 82 �Trip 4 – Soudan Figure 4-6. Regional stratigraphic correlations across the Vermilion District (after Hudak et al., 2012; Hudak et al., 2014; Hudak and Peterson, 2014). The sections are hung on the base of the Soudan Member of the Ely Greenstone Formation 83 �Trip 4 – Soudan • felsic tuff, made up of gray to tan, fine-grained, aphyric to quartz ± plagioclase-phyric rhyodacite to rhyolite tuff. Clastic sedimentary rocks within the park include: • graywacke-slate, made up of light gray, fine- to medium-grained, thin- to medium-bedded graywacke containing up to 3% <1-2mm quartz and plagioclase grains that are interbedded with dark gray, laminated to thin-bedded mudstone/slate. • graphitic argillite, composed of dark gray to black, laminated to thin-bedded graphite-bearing argillite Chemical sedimentary rocks that occur in the park include: • oxide-facies iron formation, made up of black (magnetite-rich), dark gray (magnetite- and/or hematite-rich, red (jasper-rich or hematite-rich), or gray (chert-rich) laminated to medium-bedded, planar bedded to chaotically soft-sediment folded, banded iron formation. Hydrothermal alteration of the oxide-facies iron formations has resulted in the genesis of the massive hematite ores that make up the numerous iron ore lenses of the Soudan Mine (Gruner, 1926; Klinger, 1960; Thompson, 2015; Allerton, 2024a, 2024b). • chert-rich iron formation, composed of light gray to black laminated to very thin bedded chert that is locally interbedded with subordinate laminated to very thin bedded oxide facies iron formation Both mafic and felsic intrusive rocks have been identified in the park. Mafic intrusive rocks include: • lamprophyre intrusions, including 1) massive gray-green intrusions containing scoria, chert and granite clasts within a fine- to medium-grained groundmass composed of up to 85% acicular amphibole; and 2) black, fine-grained massive hornblende-plagioclase-bearing intrusions containing up to 15% fine-grained hornblende needles and local rounded granite blocks greater than 25cm in diameter in a fine-grained gray-black to red groundmass (Peterson and Patelke, 2003). Felsic intrusive rocks in the park include: • diorite, comprising gray to gray-green, fine- to medium-grained, plagioclase- and hornblendephyric equigranular diorite (actinolite pseudomorphs of hornblende are common) • granodiorite, made up of whitish-pink to green-gray, medium-grained granodiorite and hornblende granodiorite that locally contains xenoliths of oxide-facied banded iron formation, chert, felsic epiclastic rocks, and mafic volcanic and volcaniclastic rocks • feldspar porphyry, composed of white to whitish-pink, medium-grained, holocrystalline dacite with 5-12% 1-4mm subhedral to euhedral tabular plagioclase feldspar phenocrysts, and locally, 2-5% 13mm dark green actinolite pseudomorphs of hornblende (Radakovich et al., 2010) • quartz feldspar porphyry, characterized by white to whitish-pink, light gray to pale green-gray porphyritic dacite and rhyodacite that contains 20-25% 1-5mm diameter subhedral to euhedral plagioclase feldspar phenocrysts and 5-15% 1-3mm diameter subhedral to euhedral pale gray to gray-blue quartz phenocrysts Sheared rocks that crop out in Lake Vermilion/Soudan Underground Mine State Park include: • chlorite-dominant schist, composed of dark green very fine- to fine-grained chlorite phyllite and schist (Peterson and Patelke, 2003) • sericite-dominant schist, made up of pale yellow to yellow-gray to yellow-green very fine- to finegrained sericite-bearing phyllite and schist (Peterson and Patelke, 2003) • green mica (fuchsite)-dominant schist, comprising pale yellow to yellow gray, very fine- to finegrained sericite-bearing phyllite that contains up to 20% emerald green disseminated porphyroblasts of green mica that are up to 5mm in length • Schist ‘n’ BIF, an enigmatic unit made up of interlayered chlorite-dominant phyllite and schists and sericite-dominant phyllites and schists that contain lens-shaped clasts of oxide facies iron formation ranging from 1mm – 1 meter in length 84 �Trip 4 – Soudan Stratigraphic correlations across the central part of the Vermilion district are illustrated in Figure 4-6 (Hudak et al., 2012). Structure Three distinctive types of fault zones have been identified during geological mapping within Lake Vermilion/Soudan Underground Mine State Park. These structures include: • • • Synvolcanic fault zones (D0), which formed at the time of volcanism associated with the genesis of the volcanic rocks in the State Park, and which possess higher concentrations of synvolcanic hydrothermal alteration mineral assemblages proximal to the synvolcanic structures (see Gibson et al. (1999) and Hudak et al. (2014) for a detailed explanation of synvolcanic fault zones). Two potential synvolcanic fault zones have been described in the north-central part of the former Lake Vermilion State Park by Hudak et al. (2014); Shear zones that are associated with the regional D2 deformation, and are characterized by linear zones of sheared rocks including chlorite-dominant schist, sericite-dominant schist, fuchsite (green mica)-dominant schist, and schist ‘n’ BIF. The Mine Trend and Murray shear zones (Peterson and Patelke, 2003; Peterson et al., 2016; Table 4-2) are examples of D2associated shear zones within the bounds of Lake Vermilion/Soudan Underground Mine State Park. Late faults are characterized by brittle deformation and associated offset of adjacent lithological units. Within Lake Vermilion/Soudan Underground Mine State Park, these D3associated structures are commonly expressed as northwest- to northeast-trending, minor displacement (generally less than one meter) brittle faults that offset sedimentary bedding and / or contacts between adjacent lithological units (D3-associated faults are clearly evident at field trip stop 1). Table 4-2. Calculated displacements among the Mine Trend and Murray Shear zones (Peterson and Patelke, 2003). Ranges of values were calculated geometrically by using the average plunges of lineations associated with the shear zones, and two measured lines of possible correlative stratigraphy offset by the bounding shear zones. See Peterson and Patelke (2003) for further details. Measurements of other planar (e.g. bedding orientation, orientations of geological contacts, foliation measurements) and linear (e.g. mineral lineations, glacial striations) geological structures were recorded during field mapping, and are included on the new geologic map of Lake Vermilion/Soudan Underground Mine State Park (Peterson et al., 2016; see Figure 4-5). Geochronology Geochronological information for supracrustal and intrusive lithologies in the Vermilion District is relatively sparse (refer back to Figure 4-4). Peterson et al. (2001) obtained a U-Pb zircon age date of 2722 ± 0.9 Ma from a quartz-phyric rhyolite dome in the Fivemile Lake Sequence of the Lower Member of the Ely Greenstone Formation. Allerton et al. (2024a) obtained a crystallization age of 2708 ± 25 Ma for the Purvis Pluton, which intrudes the Eagles Nest Succession of the Lower Ely Member and has been interpreted as a synvolcanic intrusion (Peterson, 2001). The age of the Upper Member of the Ely Greenstone formation is currently unknown. Jirsa (2016) obtained an age of 2715.74 ± 0.50 Ma for a felsic volcanic 85 �Trip 4 – Soudan unit within the Newton Lake Formation (Boerboom, T. J., 2020). Lodge et al. (2013) obtained a U-Pb zircon date of 2689.7 ± 0.8 Ma for a Gafvert Lake Sequence dacitic tuff breccia that occurs approximately 2 meters north of the contact with the Soudan Iron-Formation member of the Ely Greenstone Formation. As well, Lodge et al. (2013) obtained detrital zircon dates ranging from 2680-2690 Ma from greywackes that comprise the Lake Vermilion Formation. This date confirms the source of the detritus in the Lake Vermilion Formation was derived locally from the volcaniclastic rocks comprising the Gafvert Lake Sequence. The age of the orebodies at the Soudan Mine has eluded geologists for nearly a century. The genesis of the massive hematite orebodies was previously interpreted to be syn- or post-depositional to the formation of the Soudan Member of the Lower Ely Greenstone Formation (Gruner, 1926; Klinger, 1960; Thompson, 2015). Gruner (1926) believed the ores could be as young as the Mesoproterozoic Duluth Complex. Klinger (1960) found abundant evidence for post-iron formation depositional genesis of the massive hematite ores, but he could not determine a specific date for mineralization and concluded the orebodies were formed along with or after shear zones that are spatially associated with the ores. Thompson (2015) speculated based on geological, structural, and lithogeochemical data, that the ores were formed during the D2 deformation, but could not determine a specific date for the massive hematite mineralization. Recent U/Pb and (U-Th)/He radiometric dating of hematite by Allerton (2024b) suggests the massive hematite orebodies at Soudan formed during Paleoproterozoic time (1640.8 ± 47.2 Ma – 1740.4 ± 72.5 Ma) and have been overprinted by a Mesoproterozoic hydrothermal event at approximately 1100 Ma (1093.1 ± 16.4 Ma). Terminology Used for This Field Trip The terminology used on this field trip will be consistent with the terminology used by Hudak et al. (2014) for their “Walk in the Park” ILSG field trip and is described below. All stop locations for this field trip are given in Universal Transverse Mercator (UTM) coordinates, Zone 15N, using the North American Datum of 1983 (NAD83) as well as latitude/longitude. Section subdivisions read from smallest to largest quarter (e.g., “NW, SE” should be read “NW quarter of the SE quarter”). A geologic map with stop locations is given in Figure 4-8. A map of optional field trip stops is given in Figure 4-12. It is important to note the terminology utilized in this field trip guide for: 1) volcaniclastic rocks; and 2) bedding characteristics. Use of consistent terminology is required to facilitate consistent and accurate describe these geological features. Volcaniclastic rocks contain abundant volcanic material irrespective of their origin or depositional environment (Fisher, 1966). Such rocks can form directly from volcanic eruptions (whether subaerial or subaqueous), resedimentation of non-lithified volcanic deposits (for example, resedimentation of pyroclasts prior to lithification), or weathering and resedimentation of pre-existing lithified volcanic rocks. Primary (juvenile) volcaniclastic particles result directly from eruptive processes, and are of three types: • • • Pyroclasts, which form by explosive fragmentation of magma into particles (including ash, highly vesiculated glass (pumice, scoria), crystals and crystal fragments, and lithic fragments); Hydroclasts, which form by explosive interaction with external water (via phreatic (steam only) and/or phreatomagmatic (steam and magma) explosions) or by non-explosive quenching and granulation of lava (for example, the formation of hyaloclastite fragments on the margins of submarine lava flows or intrusions into wet sediments); and Autoclasts, which form by frictional breakage of moving viscous lava flows (for example, to form carapace breccias on the margins of subaerial lava flows). Based on these different types of fragmentation, four types of primary volcaniclastic deposits have been identified by White and Houghton (2006): 86 �Trip 4 – Soudan • • • • Pyroclastic deposits, which are generated from volcanic plumes and jets or pyroclastic density currents as particles first come to rest. Deposition mechanisms associated with these processes include suspension settling, traction, or en masse freezing; Autoclastic deposits, which are generated during effusive volcanism when lava cools and fragments as a result of thermal processes, or recently cooled lava breaks during flow. Deposition for these types of rocks is under the influence of continued lava flowage; Hyaloclastite deposits, which are generated during effusive volcanism when magma or flowing lava is chilled and fragmented due to contact with water. Deposition of such deposits is is influenced by the continued emplacement of the lava in the presence of water, and the thicknesses of the hyaloclastite deposits can be dictated by the temperature of the magma, the effusion rate, and the distance from the volcanic vent (Cas and Wright, 1987; Gibson et al., 1999; Newkirk et al., 2001); and Peperite deposits, which are generated when magma intrudes into unconsolidated clastic material and mingles with (generally wet) debris to form a volcaniclastic deposit (McPhie et al., 1993). Deposition of peperite deposits takes place essentially in-situ. Secondary volcaniclastic particles are known as epiclasts: • Epiclasts are lithic clasts and/or crystals derived from physical weathering and erosion of preexisting lithified rocks. Epiclasts are volcaniclasts when the pre-existing rocks are volcanic. The terminology for volcaniclastic rocks has historically been somewhat confusing because many different classification schemes have been developed (for example Fisher, 1961; Fisher 1966; Schmid, 1981; Cas and Wright, 1987; McPhie et al., 1993; White and Houghton, 2006), and different classification schemes are preferentially used in different parts of the world. As a result, the terminology relating to volcaniclastic rocks is commonly misused or misinterpreted. Four classification schemes that have been used most in the recent geological literature include: • • • • Fisher (1961, 1966) – Classification based on particle size, particle formation, or particle fragmentation mechanism; Schmid (1981) – Particle type within the deposit; Cas and Wright (1987) – Mode of fragmentation and deposition; and McPhie et al. (1993) – Transport and deposition mechanisms. According to R. V. Fisher (1998), the difficulties with volcaniclastic rock classification can be understood because “volcaniclastic rocks are essentially igneous on the way up and sedimentary on the way down”. In fact, Fisher’s thesis advisor, when observing the volcaniclastic rocks that were the focus of his thesis studies, indicated that they were “the ugliest and most undistinguished rocks I’ve seen in my 30 years of petrology!” Classification is also especially difficult in ancient volcaniclastic rocks because key aspects of classification can be obscured by subsequent hydrothermal alteration, metamorphism and/or structural deformation (e.g. particle type, particle size) or because genetic processes cannot be ascertained unambiguously (e.g. transport and deposition mechanism, fragmentation mechanisms). For this field trip guidebook, we will utilize Fisher’s (1966) classification (Figure 4-7) for volcaniclastic rocks. This classification scheme is based on the relative proportions of ash-sized material (< 2mm), lapilli-sized material (2-64mm), and blocks/bomb sized material (>64mm) in the rock. Both Gibson et al. (1999) and Mueller and White (2004) suggest that this classification be used for field-based rock classification (mapping, diamond drill core logging, petrography) of ancient volcaniclastic deposits for the following reasons: 87 �Trip 4 – Soudan • • • The classification scheme is “field-user friendly” because it accommodates both the historically important pyroclastic rock names and enables comparison at both the hand sample and thin section scale (Mueller and White, 2004); It is a Wentworth-based scale, and thus enables comparison of volcaniclastic deposits to sedimentary deposits; and Rock classification does not require knowledge of the specific transport mechanism or depositional processes involved with the genesis of the deposit. More recently, White and Houghton (2006) have developed a modified version of Fisher’s (1966) volcaniclastic classification scheme (Figure 4-7). The scheme is essentially equivalent to the Fisher (1966) scheme, with the exception that the lapill-tuff field in the White and Houghton (2006) classification comprises the lapilli-tuff and lapillistone fields of Fisher’s (1966). Figure 4-7. Volcaniclastic rock classification schemes of Fisher (1966) and White and Houghton (2006). This field trip guidebook will classify volcaniclastic rocks using Fisher’s (1966) classification scheme. Specific terms for bedding thicknesses are also used in this guidebook. The terminology for bedding thickness has been adopted from McPhie et al. (1993) and includes: • • • • • • Laminated Very thinly bedded Thinly bedded Medium bedded Thickly bedded Very thickly bedded <1 centimeters thick 1-3 centimeters thick 3-10 centimeters thick 10-30 centimeters thick 30-100 centimeters thick >100 centimeters thick 88 �Trip 4 – Soudan FIELD TRIP OVERVIEW NOTE: This field trip will require hiking along trails and through the bush in Lake Vermilion/ Soudan Underground State Park and includes observations on the 27th level of the Soudan Mine. Hiking boots and safety eyewear are strongly encouraged as traverses in the park may encounter slippery conditions and vegetation which can cause eye injuries. Field trip participants should plan to wear a jacket and gloves while underground as the temperatures in this location are typically around 50°F (10°C). Upon arriving at Lake Vermilion/Soudan Underground Mine State Park, we will park in the main parking lot located near the Park Manager’s office. After a coffee break, we will strap on our hiking boots and spend the remainder of the morning making field trip stops in the central part of Lake Vermilion/Soudan Underground Mine State Park along a more-or-less north-south traverse. These field trip stops (Figure 4-8) will illustrate the stratigraphy, structural, and hydrothermal alteration features associated with the massive hematite ores at the Soudan Mine. We will then head back to the visitor center and have lunch overlooking one of the original Soudan Mine ore pits. After lunch, we plan to continue the field trip by going underground. We will proceed to the mine shaft and travel 2341 feet underground to the 27th Level of the Soudan Mine. We will board a train (converted ore cars) and travel west for approximately three-quarters of a mile to the Montana Stope, the last active part of the mine. At this point we will climb vertically approximately 30 feet using a very tight spiral staircase. One in the Montana Stope, we will observe the massive hematite ore, the transitional region of non-ore iron formation, and will observe massive chlorite-rich schists associated with approximately east-west-trending D2-associated shear zones. Here we plan to discuss recent geological research that has been conducted to determine the absolute age of the massive hematite ores that reside there (Allerton et al., 2024a, 2024b; Allerton et al., in review). At the end of the tour we will proceed back down to the 27th level drift, board the train, and head back east through the drift to the shaft station where we will proceed back to the surface. Field trip participants may not be able to access the 27th level of the Soudan Mine due to flooding that occurred during summer, 2024. Should this happen, afternoon field trip stops will investigate outcrops that illustrate the rarely exposed geological contact between the Soudan Member iron formation and Gafvert Lake Sequence tuffs, lapilli-tuff and tuff-breccias, Gafvert Lake Sequence tuffs and lapilli-tuffs, and subvolcanic intrusive rocks related to the Gafvert Lake Sequence that occur in the northeastern part of Lake Vermilion/Soudan Underground Mine State Park. Descriptions of these outcrops are included in a section below called “Optional Outcrop Stops” which have been taken from a recent ILSG field trip titled “Field Trip 2 - A Walk in the Park: Neoarchean Geology of Lake Vermilion State Park” (Hudak et al., 2014). Following the completion of the field trip, we will board the vehicles and proceed back to the Mountain Iron Community Center, where the field trip will end. FIELD TRIP From the Mountain Iron Community Center, proceed 0.2west on Enterprise Drive S to Emerald Avenue. Turn north on Emerald Avenue and go 0.05 miles to Highway 169. Turn east on Hwy 160 and proceed 1.5 miles to the turn off for Hwy 169/Hwy 53N. Take Hwy169/Hwy53 approximately 6.1 miles, bear right, and continue north on Hwy1/169 toward Ely. Continue north/northeast on Hwy 1/169 for approximately 23.75 miles to the first turn-off to Soudan (this will be Main Street and you will see an ore car and a sign for the Soudan Mine at the intersection). Proceed north for 0.4 miles on Main Street, turn right, and continue on Main Street for approximately 0.9 miles until it intersects 1st Ave./Stuntz Bay Road. Turn north on 1st Ave/Stuntz Bay Road and proceed for approximately 0.4 miles until you see the dirt road (McKinley Park Road) that is the east entrance to the Soudan Mine. Turn west on the dirt road, go about 0.05 miles, and park near the Lake Vermilion/Soudan Underground Mine State Park Manager’s office. Here 89 �Trip 4 – Soudan we will check in with the Manager. Turn left (south) on the dirt road and follow it around the old mine infrastructure, parking near the intersection of McKinley Park Road and Stuntz Bay Road (approximately 0.1 miles). From our vehicles parked at the intersection of Mckinley Park Road and Stuntz Bay Road, we will walk north approximately 175 meters up 1st Ave/Township Highway 4598 to field trip stop 1. Please walk against traffic as we proceed to and from this location. Stop 1: Soudan Member Banded Iron Formation Longitude/Latitude: 47.820074°N, -92.2365908°E UTM NAD 83 Zone 15N: 557144E, 5296585N (NOTE: From Peterson et al., 2009A; Hudak and Peterson, 2014) The Soudan Member of the Ely Greenstone Formation is dominantly composed of laminated to thinly bedded Algoma-type oxide facies banded iron-formation, with subordinate, locally interstratified, sparsely amygdaloidal massive to pillowed basalt lava flows and resedimented felsic tuff deposits. Regionally, the stratigraphic thickness of the Soudan Member of the Ely Greenstone Formation varies from 50-3,000 meters, with an average stratigraphic thickness of approximately 700 meters (Peterson et al., 2009). Within Lake Vermilion State Park, the Soudan Member ranges in stratigraphic thickness from approximately 300 – 680 meters in thickness. Individual horizons of oxide-facies iron formation range from approximately 70-345 meters thick, whereas the Soudan basalt lava flow units range from approximately 60-300 meters in thickness. This classic exposure of the Soudan member of the Ely Greenstone Formation lies on the north limb of the Tower-Soudan anticline approximately 75 meters north of the stratigraphic contact with the Lower member of the Ely Greenstone. The outcrop displays two generations of tight folding in delicate laminae of chert (creamy white), chert-hematite jasper (red), and magnetite-chert (black to silver-colored). The second generation of folds (F2) is tectonic in origin, having subvertical axial surfaces that trend east, and steeply plunging axes. Most display Z-asymmetry. The earlier folds (F0-1) appear to have been sharply refolded to produce complex interference patterns. Lundy (1985) studied folding at this locality and concluded that some of the apparent interference structures are the product of early-formed sheath folds that did not involve refolding by D2. The F1 structures are predominantly intrafolial, and exhibit a great variety of styles and orientations; implying they formed by layer-parallel, soft-sediment slumping (Fig. 49). Lundy’s mapping of this outcrop is an interesting demonstration of how unraveling details at a single outcrop that led to recognition that D1 deformation was not systematic here, but likely the result of soft sediment folding. It is interesting to observe the rhythmic microlaminae (1 mm or so thick) in various cherty beds exposed here and speculate about the paleoenvironment - that is, whether these represent daily heating/cooling, tidal, climatic, annual, or some other repetitive influence (e.g. waxing/waning of a hydrothermal system) in the depositional environment. What is known about units of iron-formation in the Ely Greenstone, of which there are many, is that deposition occurred in deep water (below wave base) during periods of relative volcanic and tectonic quiescence by the slow subaqueous precipitation of chemical sediments. The deep excavations in this area are the early workings of the Soudan iron mine, the first in Minnesota. The mine produced about 16 mt of high-grade hematite ore (60-63 percent ironconverted to a park. Although some early production came from open pits, most of the ore was extracted from underground workings that began here in 1900, and which now can be visited on guided tours. The mine previously housed several underground physics research facilities. These include Soudan 1 (23rd level) which studied neutrino decay; 2) Soudan 2 (27th level), also to study neutrino decay; and 3) the MINOS (Main Injector 90 �Trip 4 – Soudan Figure 4-8. Geologic map of the central part of Lake Vermilion/Soudan Underground Mine State Park (after Peterson et al., 2016) illustrating locations of field trip stops. See Figure 4-5 for the description of map units. 91 �Trip 4 – Soudan Figure 4-9. Outcrop map showing bedding trajectories and multiple generations of folds and faults (from Lundy, 1985). F1 folds are non-systematic and include both nappe- and sheath fold geometries. Neutrino Oscillation Search) lab, which was built on the 27th level adjacent to Soudan 1 and studied the decay of neutrinos within the earth as they passed from Fermilab to Soudan. Follow the field trip leaders south along First Avenue/Township Highway 4598 to the blacktop-paved Mesabi Trail. Turn to the east and walk along the paved Mesabi trail for approximately 800m. There, turn north and proceed up the unpaved trail approximately 350 meters, where the trail intersects another trail that goes northeast. Turn right and proceed northeast along the trail for about 90 meters. We will then head into the bush and hike approximately 200 meters northeast to field trip stop 2. Stop 2: Soudan Member Basalt Pillow Lavas Longitude/Latitude: 47.82544775°N, -92.22434651°E UTM NAD 83 Zone 15N: 558055E, 5297191N Detailed mapping in the park by Peterson and Jirsa (1999), Peterson and Patelke (2003), Hoffman (2007), Radakovich et al. (2010), Vallowe et al. (2010), Heim et al. (2011), and Baumgardner et al. (2013) has shown that the Soudan member is dominantly composed of oxide facies iron formation horizons that are locally interlayered with massive and pillowed mafic lava flows and associated volcaniclastic rocks (e.g. pillow breccias). Basalt lava flows associated with the Soudan Member of the Lower Ely Greenstone Formation are characterized by a medium green to dark green color. They are typically aphyric- to sparsely plagioclase ± pyroxene (now actinolite)-phyric. Plagioclase phenocrysts vary from subhedral to euhedral tabular in morphology, are typically less than or equal to 1mm in length and are locally present in abundances up to 3%. Locally, 5-7% dark green actinolite pseudomorphs of pyroxene phenocrysts may be present. Where amygdaloidal, the unit contains up to 7% oval to round, light gray quartz-filled amygdules ranging from <1-4mm in diameter. At this outcrop we will observe well-preserved 0.5-2m long, aphyric- to sparsely plagioclasephyric, massive- to sparsely amygdaloidal bun- and mattress-shaped pillow lavas. These pillows dip steeply to the north and strike approximately east-west. Interpillow hyaloclastite is locally well-preserved and is 92 �Trip 4 – Soudan composed of <1-5mm chlorite-rich cuspate shards that are pseudomorphs of original volcanic glass formed by quenching of the mafic magma by water. These pillow lavas share many characteristics with the underlying Central Basalt Sequence mafic lava flows that comprise the uppermost part of the Lower Ely Member of the Ely Greenstone Formation. Such characteristics include exceptional preservation of primary volcanic textures, medium- to dark green color, sparsely plagioclase ± pyroxene-phyric, and low vesicularity. Based on these features, the Soudan Member pillow basalts at this location and are interpreted to have formed in a “deep water” (e.g. below wave based) volcanic environment. Proceed approximately 200 meters southwest to the northeast-southwest trending trail. Walk approximately 90 meters southwest to intersect the main north-south trail that intersects the Mesabi Trail. Walk approximately 350 meters south back to the paved Mesabi Trail. Turn to the east and follow the field trip leaders through the bush for about 140 meters to field trip stop 3. Stop 3: Soudan Member Oxide Facies Banded Iron Formation Longitude/Latitude: 47.82139974°N, -92.225809591°E UTM NAD 83 Zone 15N: 557990E, 5296775N Within Lake Vermilion/Soudan Underground Mine State Park, the Soudan Member oxide-facies banded iron-formation is generally planar laminated to medium-bedded, with black magnetite-rich horizons, light gray to black chert horizons, red to blueish-black hematite-rich horizons, and red jasper horizons defining the bedding. Locally, very tight, chaotically oriented folds, resulting from syndepositional soft sediment deformation and subsequent tectonic deformation, are present. As indicated above, these iron formation deposits are locally intimately interbedded with basalt lava flows such that mapping individual iron-formation and basalt horizons is often impossible at 1:5000 scale (Peterson and Patelke, 2003; Hudak and Peterson, 2014; Hudak et al., 2016). This outcrop is composed of slightly- to moderately hematite-altered Soudan member oxide facies banded iron formation. The rock varies from locally non-magnetic to slightly magnetic due to alteration of magnetite to hematite/martite. Such alteration is common in areas within a few hundred meters of massive hematite ore and is commonly found in close proximity to D2-associated shear zones. The closest previously mined massive hematite orebody was located approximately 250 meters west-southwest of this location in an existing mine pit. D2-associated shear zones have been identified approximately 25 meters north and south of this outcrop. Here, the oxide-facies banded iron formation comprises interlayered planar horizons of gray oxiderich (hematite ± magnetite), red jasper-rich, and pale white (silica (chert)-rich that are laminated, thinly bedded, and locally medium bedded. Bedding orientations generally strike more or less east-west, although locally contorted layers may vary significantly in strike direction. Dips are generally steep (>75°) to the north, although locally dips may be steep to the south. Follow the field trip leaders southwest for about 85 meters to field trip stop 4. Stop 4: Mine Trend Shear Zone “Schist ‘n’ BIF” Longitude/Latitude: 47.82126659°N, -92.22607876°E UTM NAD 83 Zone 15N: 557725E, 5296740N The “Schist ‘n’ BIF” units at this location (Figure 4-10) are composed of sheared rocks comprising chlorite schist that are interlayered with, and locally contain fragments of red, jasper-rich banded iron formation and light gray to white chert. The chlorite schist is fine-grained (<1 mm) with a tan (chloriteankerite) to green (chlorite-rich) weathered surface. Common minerals include chlorite, ankerite, sericite, 93 �Trip 4 – Soudan Figure 4-10. Photographs of outcrop exposures at Stop 4. A) Image is showing the southern face of the “Schist ‘n’ BIF” unit. The greenish tan rock is chlorite schist, and the red and white layers are banded iron formation. B) This image is north of image A and is the near horizontal exposure of the “Shist ‘n’ BIF” outcrop. The dark red inset in this figure is the location of the photographic in Figure 4-10C. C) This image shows a sigma clast of banded iron formation enclosed by chorite schist. Although the banded iron formation pieces are locally broken off, the clast can be traced, and a sketch of the clast is shown in Figure 4-10D). D) Sketch of a somewhat intact banded iron formation clast (dark pink) surrounded by silicates and other chert fragments (light pink) and enclosed by green and tan chlorite ± ankerite schist. and siderite. Banded iron formation fragments occur as clasts or thin bedded layers between foliation planes of the schist. The foliation here strikes east-west and dips near-vertically. The previously mentioned D2 associated shearing has a dextral or right lateral sense of shear that is approximately east-west trending on a regional scale, although locally sinistral shear sense indicators are present locally. This outcrop is located southwest of the previously visited oxide facies banded iron formation. The construction of a new paved road in 2020 exposed the now southern face of the unit (Figure 4-10A), providing access to three planes for structural measurements. The shear plane (Figure 4-10B) contains banded iron formation/chert clasts that serve as kinematic indicators and are located conveniently under our feet due to the dip of the schist layers. Outcrop-scale kinematic indicators of sigma and delta clasts (Figures 4-10C and 4-10D) trend mostly east-west with dextral sense of shear, mimicking regional deformation trends. Follow the field trip leaders and walk west-southwest for approximately 800 meters along the paved Mesabi back to First Avenue/Township Highway 4598. We will then proceed back to the vehicles and head to the 94 �Trip 4 – Soudan main parking lot for the Soudan Mine. We will eat lunch at the Soudan Mine visitors’ center (bathrooms are available in the visitors’ center). Stop 5: Soudan Underground Mine Shaft Longitude/Latitude: 47.82126659°N, -92.22607876°E UTM NAD 83 Zone 15N: 556765E, 5296536N Following lunch, we will watch a short video, pick up hard hats from state park staff, and proceed to the Soudan Mine shaft. Make sure to bring a jacket and gloves underground as the temperature there is approximately 50°F (10°C). Once in the cages, we will travel 2341 feet underground to the 27th Level of the Soudan Mine. After exiting the cage we will board a train (converted ore cars) and travel west for approximately three-quarters of a mile to the Montana Stope, the last active part of the mine. It is important for everyone’s safety to stay in the train car for the duration of the trip, and to not raise your hands while traveling in the train car. At this point we will exit the train, and after a short walk, climb vertically approximately 30 feet using a very tight spiral staircase to the Montana Stope. The Montana Stope is the last active part of the Soudan Mine. Thompson (2015) conducted detailed mapping of the Montana ore zone (Figure 4-11) and noted the presence of several rock types, including: • • • • • • • Chlorite-dominant schist, which locally replaces sericite-dominant schist proximal to the ore (unit 5c) Chlorite + sericite schist, which locally replaces sericite-dominant schist (unit 5cs) Sericite-dominant schist composed of sericite + paragonite ± pyrophyllite that has a mylonitic texture and occurs intermediate to ore breccia zones (unit 5s) Sericite-dominant schist that is locally silicified and occurs in well foliated zones at the margins of ore bodies that locally contain disseminated iron-rich chlorite domains (unit 5sc) Hematite ore, predominantly composed of specular hematite with microplaty hematite occurring locally within fractures and vugs (unit 4o) Hematite ore breccia, composed of hematite-rich banded iron formation and brecciated massive hematite ore with abundant milky “bull” quartz and disseminated sulfides (pyrite ± chalcopyrite; unit Fbx) Hematite-jasper banded iron formation, which retains many of its primary sedimentary textures and represents an intermediate rock between fresh Soudan Member oxide facies banded iron formation and the altered hematite-rich iron ore (unit 4a) The absolute age and geological processes associated with the genesis of the Soudan (and other Vermilion district) massive hematite ores have baffled geoscientists for over a century (e.g. Gruner, 1926; Klinger, 1960). Gruner (1926) proposed that massive hematite mineralization occurred after deposition and lithification of the Soudan Member oxide facies banded iron formation and proposed that the mineralization occurred resulted from alteration of the original banded iron formation by ascending upwelling hydrothermal solutions that oxidized most of the iron, dissolved quartz, and precipitated secondary carbonates and sulfides. He did not specify an exact age for this mineralization process. Klinger (1960) noted the close association of massive hematite ore zones at the Soudan Mine to faults (shear zones) within the mine. He states that “the orebodies occur in the iron formation and their dimensions are controlled by its structure”. He also noted that the massive hematite ores showed little evidence of deformation and concluded that “a second generation of hematite appears to post-date structural movements which occurred after the main ore-forming period. These movements, and later hematite, are 95 �Trip 4 – Soudan Figure 4-11. Geological map of the Montana stope (modified from Thompson, 2015). both later in time than a sericite rock that has been dated at 1.67 billion years by the A40/K40 method”. He also indicated that “at least some of the hematite is younger than 1.67 billion years” and concluded that the ores were “post-Huronian to pre-Keewenawan” in age. Recent masters and doctoral studies from the University of Minnesota Duluth (Thompson, 2015) and the University of Minnesota Twin Cities (Allerton, in prep.; Allerton et al., 2024a; Allerton et al., 2024b; Allerton et al., in review) have focused their research on understanding the absolute age of massive hematite mineralization at the Soudan Mine. Based on detailed mapping, petrographic studies, and lithogeochemical studies, Thompson (2015) suggested that the massive hematite ores at Soudan were formed from a multi-stage process involving alteration of the original oxide-facies banded iron formation by a fluid-dominated synvolcanic sea-floor hydrothermal system followed by interaction with hydrothermal metamorphic fluids associated with the subduction of strata within the Vermilion district. Therefore, his model for the genesis of the Soudan massive hematite ores suggests a Neoarchean age ranging from the time of the original deposition of the oxide-facies banded iron formations (~2720 Ma) to the time spanning the D2 deformation (2674-2685 Ma (Boerboom and Zartman, 1993) which is likely associated transpression and the development of the D2 shear zones in which the ores occur. New research (Allerton et al., in review) utilizing petrographic observations and electron microprobe analyses shows that the massive hematite ore can be divided further into two distinct ore 96 �Trip 4 – Soudan textures comprising: 1) homogenous microcrystalline hematite-martite; and 2) heterogenous microcrystalline hematite. The fine-grained microcrystalline hematite-martite (martite comprises hematite pseudomorph replacing magnetite) locally contains minute vug spaces and larger fractures that are filled by microplaty hematite and silicates. The heterogeneous ore contains a minor amount of metallic and/or earthy microcrystalline hematite, but is predominantly composed of coarser-grained microplaty hematite and silicates. Microcrystalline hematite-martite predates microplaty hematite and silicates based on crosscutting relationships. U-Pb radiometric dating of hematite was used to establish the timing of ore mineralization at ca. 1.8-1.6 Ga. Our new model for the genesis of Soudan massive ore suggests that hydrothermal alteration related to mineralization is coeval with orogenic events generated by Proterozoic terrain accretion and associated magmatism. Additional geochemical analyses involving mass-balance calculations and Fe stable iron isotopes indicate that the upgrade of BIF to hematite ore was a two-stage process. Dense microcrystalline hematitemartite matrix yielding a homogeneous texture was produced during the first stage. The second stage resulted in the formation of a heterogeneous texture containing microplaty hematite and silicates in larger vugs and fractures in the microcrystalline hematite-martite ore. At the end of this stop, we will proceed back to the 27th level drift using another tight spiral staircase. We will board the train and proceed east back to the shaft station where we will board the cages and return to the surface. At the surface, we will reboard the vehicles and proceed back to the Mountain Iron Community Center via the directions below. From our parking spot at Soudan Mine, proceed down the hill on McKinley Park Road for approximately 0.4 miles to the intersection with Main Street. Turn south and drive for approximately 0.4 miles to the intersection with Hwy 1/169. Turn west and Hwy 1/169 and drive for about 23.7 miles and merge onto Hwy 53/169 South. Follow Hwy 1/169 the intersection with Hwy 53/Hwy 169. Merge on to Hwy 169 south and proceed for 1.5 miles to Emerald Avenue. Turn south and proceed on Emerald Avenue for approximately 0.1 mile. Turn east and proceed for approximately 0.2 miles back to the Mountain Iron Community Center. OPTIONAL OUTCROPS The following field trip stop descriptions have been taken from the 2014 ILSG Field Trip 2 “A Walk in the Park – Neoarchean Geology of Lake Vermilion State Park” (Hudak et al., 2014). A map showing the locations of the optional field trip stops is shown in Figure 4-12. From the original parking spot near the Manager’s office at Soudan Mine, proceed approximately 0.2 miles south on Stuntz Bay Road/1st Avenue to the intersection with Jasper Street. Go southeast on Jasper Street for about -.5 miles to the intersection of Hwy 1/169. Proceed east on Hwy 1/169 for 0.75miles to Vermilion Park Drive (this is the eastern entrance to Lake Vermilion/Soudan Underground Mine State Park and allows access to campsite near Cable Bay). Turn north on to Vermilion Park drive and proceed for 2.9 miles to Old Hwy 169. Turn west (left) on to Old Hwy 169 and follow it for 0.8 miles to Vermilion Ridge Road. Turn west on Vermilion Ridge Road and proceed for approximately 0.5 miles. Turn right and park near the restroom east of Cable Bay. We will depart the vehicles here and walk across the street to the Crosscut Trail. walk southeast along the Crosscut Trail for about 2200 meters. We will then take a short hike (approximately 30 meters) up the hill to Stop 6o. 97 �Trip 4 – Soudan Figure 4-12. Geologic map of the northeastern part of Lake Vermilion/Soudan Underground Mine State Park (after Peterson et al., 2016) illustrating locations of optional field trip stops. See Figure 4-5 for the description of map units. 98 �Trip 4 – Soudan Stop 6o (Optional)” Contact” Between Soudan Member Banded Iron Formation and Gafvert Lake Sequence Rhyodacite Polymict Lapilli-tuff/Tuff-breccia Longitude/Latitude: 47.834710°N, -92.211647°E UTM NAD 83 Zone 15N: 558,995E / 5,298,230N Here we will see one of the few places where the nature of the contact between the Soudan IronFormation Member oxide facies iron-formation and the overlying dacitic to rhyodacitic volcaniclastic rocks associated within the informally named Gafvert Lake Sequence can be observed (Figure 4-13). The Gafvert Lake Sequence (mapped as the “Upper Sequence” by Peterson and Patelke, 2003; Radakovich et al., 2010: and Heim et al., 2011) comprises dacitic to rhyodacitic volcaniclastic and epiclastic rocks that are locally interbedded with Algoma-type banded iron-formation and chert deposits. This sequence is part of the Lake Vermilion Formation. Within Lake Vermilion State Park, the overall stratigraphic thickness of the Gafvert Lake Sequence is up to approximately 1300 meters thick, with individual felsic volcaniclastic deposits having stratigraphic thicknesses ranging from approximately 75 – 400 meters thick, and individual Algomatype oxide facies banded iron formations and associated massive- to bedded chert deposits ranging from 25-250 meters and up to 175 meters in stratigraphic thickness, respectively. Northwest of the Soudan Mine, the Gafvert Lake Sequence is locally interlayered with, and overlain by, greywacke deposits associated with the Lake Vermilion Formation. Within Lake Vermilion State Park, several lithofacies comprise the Gafvert Lake Sequence. The basal member of this sequence comprises massive, very-thickly bedded, quartz- and plagioclase-phyric polymict dacitic to rhyodacitic tuff, lapilli-tuff, and tuff-breccia deposits. These light gray, non-sorted, nongraded, matrix-supported deposits contain 3-8% 1-2mm (rare 3mm) pale gray anhedral to subhedral quartz phenocrysts, 10-15% <1-2mm subhedral to euhedral tabular plagioclase phenocrysts, and a wide variety of lapilli- to block-sized clasts including: 1) 10-20% 1-10 cm quartz- and plagioclase-phyric coherent dacite to rhyodacite lapilli and blocks; 2) 5-7% <3cm diameter pale gray-green lens-shaped, locally quartz- and plagioclase-phyric pumice lapilli; 3) up to 1% dark gray to light gray angular chert lapilli ranging from 0.53cm in diameter; and 4) 1-3% 0.5-5cm dark gray to black to red magnetite-rich, hematite-rich, or jasperrich banded iron formation lapilli. These deposits are overlain by, and interbedded with, light gray, matrixsupported, non-sorted and non-graded quartz- and plagioclase-phyric dacitic to rhyodacitic tuff deposits (Figure 4-14) which contain 10-25% 1-3mm subhedral to euhedral tabular plagioclase phenocrysts, 1-3% 1-3mm subhedral to anhedral, commonly broken, quartz phenocrysts, as well as 10-15% subangular quartzand plagioclase-phyric coherent dacite to rhyodacite lapilli and up to 5% locally quartz- and plagioclasephyric pumice lapilli. Spectacular felsic epiclastic deposits comprising polymict volcaniclastic conglomerates and lithic sandstones are also present in the Gafvert Lake Sequence and crop out west of Lake Vermilion State Park in Stunz Bay (Radakovich et al., 2010). Based on regional mapping, Sims and Southwick (1980), Southwick (1993), and Southwick et al. (1998) have suggested that the contact between the underlying Soudan Iron-Formation Member of the Ely Greenstone Formation and the overlying Lake Vermilion Formation is locally an unconformity. Geochronological work in the Vermilion District (Peterson et al., 2001. Lodge et al., 2013), combined with detailed field mapping in the limited number of locations where the contact between the Soudan IronFormation Member and the Lake Vermilion Formation occurs, bears out this interpretation. Based on field relationships recognized by Radakovich et al. (2010), Lodge et al. (2013) collected a sample of the basal part of the Gafvert Lake polymict dacite- to rhyodacite lapilli-tuff / tuff-breccia deposits that occur at this outcrop in order to determine the age of volcanism of the Gafvert Lake Sequence relative to the ages of the Lower and Soudan Iron-Formation members of the Ely Greenstone Formation. Zircons from the sample of polymict rhyodacite tuff-breccia from this outcrop approximately 2m north of the contact with the Soudan Iron-Formation Member at this field trip stop produced a high precision U-Pb date of 2689.7 ±0.8 Ma using 99 �Trip 4 – Soudan Figure 4-13. Detailed (1:5000 scale) map (after Hudak et al., 2014) illustrating the disconformable contact between the Soudan Member Algoma-type banded iron-formation (unit S4a) and the Gafvert Lake Sequence quartz- and plagioclase-phyric polymict dacite-rhyodacite tuff-breccia / lapilli-tuff deposits (unit US2eh). We will start our investigation where Stop 6o is indicated, and traverse along the bedding and are locally folded. path indicated by the red dashed line over a series of outcrops. We will assemble on the two-track trail where indicated by the star symbol before proceeding to Stop 7o. Figure 4-14. Quartz- and plagioclase-phyric polymict dacite-rhyodacite tuff-breccia / lapilli-tuff from the Gafvert Lake Sequence. A) Typical appearance of very thickly bedded quartz- and plagioclase-phyric polymict daciterhyodacite lapilli-tuff. B) Close-up of unit illustrating tannish-white subhedral to euhedral tabular plagioclase phenocrysts, gray to gray-blue anhedral quartz phenocrysts, and 1cm diameter angular accidental fragment composed of jasper-rich banded iron formation. 100 �Trip 4 – Soudan hermal ionization mass spectrometry (Lodge et al., 2013). Given that the basal Gafvert Lake Sequence deposits contain angular intraclasts of chert and banded iron formation, and that there appears to be no intense structural fabric in either the Soudan Iron-Formation Member or the Gafvert Lake volcaniclastic rocks, Lodge et al. (2013) interpreted the contact here to represent a disconformity, a type of unconformity characterized by strata that are essentially parallel on either side of the erosional or non-depositional surface. Several outcrops occur at this location (refer back to Figure 4-13). The largest part of the outcrop, which extends east up the hill, is composed of laminated to medium bedded Soudan Iron-Formation Member. Alternating magnetite-rich horizons, chert horizons, and jasper horizons display planar bedding and are locally folded. Moving toward the northwest part of this outcrop, we observe a small break in the outcrop exposure. This break occurs directly above the contact between the Soudan Member iron formation (to the south) and the Gafvert Lake volcaniclastic rocks (to the north). In this area, note the lack of deformation in both lithological units. The lack of structural deformation at this contact, as well as geochronological data obtained from the Gafvert Lake volcaniclastic rocks near this contact (Lodge et al., 2013), supports the interpretation of a disconformity. Moving to the northwest, we observe the basal several meters of the Gafvert Lake Succession volcaniclastic rocks. Here, the rock is composed of a very thickly bedded quartz- and plagioclase-phyric polymict dacite-rhyodacite tuff-breccia / lapilli-tuff. The rock is characterized by up to 5% 1-3mm diameter subhedral to euhedral gray to blue-gray quartz phenocrysts and locally, 5-10% subhedral to euhedral light gray to tan tabular plagioclase phenocrysts set in a fine-grained quartzo-felspathic matrix that is locally sericite altered. Accidental fragments comprising laplli-sized light gray to grayish black angular to subangular chert, gray to dark gray subangular to angular banded iron formation (Figure 4-14), and rare angular to subangular reddish brown jasper fragments are present. As well, juvenile fragments comprising lapilli- to locally block-sized pumice are present. Lapilli- to block-sized accessory fragments of quartz- and plagioclase-phyric coherent dacite and rhyodacite are also present, in abundances up to 5%. As we move northwest then north down the hill, we will traverse several outcrops composed of Gafvert Lake Sequence tuff-breccia and lapilli-tuff deposits. We will traverse northwest then north down the hill (as shown in Figure 4-13) for about 80 meters back to the Crosscut Trail. We will then head northeast along the Crosscut Trail for approximately 900 meters. We will then traverse southeast through the bush for about 45 meters to Stop 7o. Stop 7o (Optional): Gafvert Lake Sequence Tuffs and Lapilli -tuffs Longitude/Latitude: 47.838875°N, -92.202496°E UTM NAD 83 Zone 15N: 559,675E / 5,298,700N We will stop here to observe several small outcrops of the Gafvert Lake Sequence tuffs and lapillituffs. These deposits comprise very thickly bedded, light gray, quartz- and plagioclase-phyric dacitic to rhyodacitic tuffs and lapilli-tuffs. The light gray recrystallized matrix generally contains 10-15% <1-2mm subhedral to euhedral tabular plagioclase phenocrysts which locally appear to be broken, as well as 3-8% <1-2mm pale gray anhedral, locally broken, anhedral to subhedral quartz phenocrysts. Various types of lapilli may be observed, including: 1) 10-20% 1-3cm diameter quartz- and plagioclase-phyric coherent dacite to rhyodacite lapilli; 2) 5-7% <3cm diameter pale gray green, lens-shaped, locally quartz- and plagioclase-phyric pumice lapilli; 3) <1mm dark gray to light gray angular chert lapilli ranging from 0.53cm in diameter; and 4) 1-3% 0.5-5cm dark gray to black magnetite-rich banded iron formation lapilli. We will traverse northwest for about 45 meters back to the Crosscut Trail. We will then proceed northeast along the Crosscut Trail for approximately 750 meters, then turn north for about 35 meters to Stop 8o. 101 �Trip 4 – Soudan Stop 8o (Optional): Quartz- ± Plagioclase-phyric Rhyodacite Sill (informally named the Gafvert Lake Intrusive Complex) Longitude/Latitude: 47.843117°N, -92.197887°E UTM NAD 83 Zone 15N: 560,015E / 5,299,175N At this location we will observe a spectacular light gray, massive, quartz- ± plagioclase-phyric coherent rhyodacite which, based on regional mapping (Peterson and Jirsa, 1999; Peterson, 2001; Hudak et al., 2002b; Heim et al., 2011) comprises a sill-dike complex that extends from the northern extents of Lake Vermilion State Park over 20km eastward to Mitchell Lake. This intrusion is most prevalent in the vicinity of Gafvert Lake, where it comprises several sills and dikes that intrude into the thickest section of Gafvert Lake Sequence volcaniclastic rocks. Based on the distribution of sills and dikes, coherent-facies Gafvert Lake Sequence deposits, and an abundance of coarse polymict breccias in this region, Peterson (2001) has interpreted this area to be the remnants of a stratovolcano that produced the Gafvert Lake Sequence dacitic to rhyodacitic volcaniclastic rocks. For this reason, this unique quartz-feldspar porphyry intrusion has been informally named the Gafvert Lake Intrusive Complex (GLIC). Lithogeochemical work recently completed at the University of Wisconsin Eau Claire (Schwierske et al., 2014; Figure 4-15) indicates that the GLIC and Gafvert Lake volcaniclastic rocks have very similar major, trace and rare earth element characteristics suggesting that they may be genetically related. However, geochronological studies will need to be performed to determine unambiguously if the GLIC and Gafvert Lake volcaniclastic rocks are indeed genetically related. The GLIC comprises light gray, massive, quartz ± plagioclase-phyric coherent rhyodacite. The light gray aphanitic groundmass contains 3-7% gray to light blue subhedral rounded to euhedral square quartz phenocrysts that range from 3-10mm in diameter, and 2-10% pale gray to tan, subhedral to euhedral tabular plagioclase phenocrysts ranging from 1-4mm in length. A variety of xenoliths may be found in this intrusion, including: 1) brown mudstone lapilli; 2) green to gray-green massive and/or amygdaloidal basalt lapilli; and 3) light gray aphyric coherent rhyodacite lapilli. In the field, the presence of large 5mm-10mm diameter gray to blue gray quartz phenocrysts distinguishes the GLIC from other quartz-feldspar-porphyry intrusions in the Vermilion District. 102 �Trip 4 – Soudan Figure 4-15. Chemical classification of various lithologies within Lake Vermilion State Park (Schwierske et al., 2014) using the immobile element classification scheme of Winchester and Floyd (1977). Open triangles represent samples from a quartz- ± plagioclase-phyric rhyodacite/dacite sill in the northeastern part of Lake Vermilion State Park. The black squares, large black diamonds, and small black diamonds represent various Gafvert Lake Succession volcaniclastic and epiclastic rock units. We will return to the Crosscut Trail and proceed northeast on the trail back to the vehicles. Upon loading the vehicles, we will return to the Mountain Iron Community Center. Travel east on Vermilion Ridge Road for approximately 0.5 miles to the intersection with Old Highway 169. Turn right (south) and continue east on Old Highway 169 for 0.8 miles. Turn south at the intersection with Vermilion Park Drive and proceed south for 2.9 miles to the intersection with Hwy 1/169. Turn west and Hwy 1/169 and drive for about 25.4 miles and merge onto Hwy 53/169 South. Follow Hwy 1/169 the intersection with Hwy 53/Hwy 169. Merge on to Hwy 169 south and proceed for 1.5 miles to Emerald Avenue. Turn south and proceed on Emerald Avenue for approximately 0.1 mile. Turn east and proceed for approximately 0.2 miles back to the Mountain Iron Community Center. END OF FIELD TRIP 103 �Trip 4 – Soudan Acknowledgements The authors would like to thank Jim Essig (Manager, Lake Vermilion/Soudan Underground Mine State Park), James Pointer (former Interpretive Supervisor, Lake Vermilion/Soudan Underground Mine State Park), and Jim DeVries (Assistant Manager, Lake Vermilion/Soudan Underground Mine State Park) for their assistance over the past two decades while the authors have conducted research, teaching, and numerous field trips within the park. References Allerton, Z., in prep., Thermal and Hydrothermal Effects of Proterozoic Events in the Archean Terrain of Northeastern Minnesota: unpublished Ph. D. dissertation, University of Minnesota Twin Cities. Allerton, Z., Hudak, G., Teyssier, C., Fayon, A., Daniŝik, M., Courtney-Davies, L, and Larson, P., 2024b, Geochronology campaign in northeastern Minnesota: Institute on Lake Superior Geology, Proceedings Volume 70, Part 1 – Program and Abstracts, p. 2-3. Allerton, Z., Hudak, G., Teyssier, C., Fayon, A., Daniŝik, M., Courtney-Davies, L, and Larson, P., 2024b, Geochronology and geochemistry of hematite ore in northeastern Minnesota: Institute on Lake Superior Geology, Proceedings Volume 70, Part 1 – Program and Abstracts, p. 4-5. Allerton, Z. P., Courtney-Davies, L., Daniŝik, M., Hudak, G. J., Teyssier, C., Mitchell, J. T., and Larson, P., in review, Hematite double-dating defines Proterozoic mineralization and thermal history of Archean banded iron formations, NE Minnesota, USA: submitted to Geology. Ayer, J. A., Goutier, J., Thurston, P. C., Dube, B., and Kamber, B. 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W., 1926, Hydrothermal alteration of iron ores of the Lake Superior type – a modified theory: Economic Geology, v. 32, p. 121-130. Heim, N., Scott, H., Kilduff, R., Rahtz, C., Vial, A., Young, S., Mahr, C., and Hudak, G., 2011, Preliminary bedrock geology map of the eastern part of Lake Vermilion State Park, St. Louis County, NE Minnesota: Precambrian Research Center Map Series Map PRC/Map – 2010-01, 1:5000 scale. Hoffman, A. T., 2007. Lithostratigraphy, Hydrothermal Alteration, and Lithogeochemistry of Neoarchean Rocks in the Lower and Soudan Members of the Ely Greenstone Formation, Vermilion District, NE Minnesota: Implications for Volcanogenic Massive Sulfide Deposits: unpublished M. S. thesis, University of Minnesota – Duluth, 295 p. Hooper, P., and Ojakangas, R., 1971, Multiple deformation in the Vermilion District, Minnesota: Canadian Journal of Earth Sciences, v. 8, p. 423-434. Hudak, G. J., Heine, J., Hocker, S. M., and Hauck, S., 2002b, Geological mapping of the Needleboy Lake – Sixmile Lake area, northeastern Minnesota: a summary of volcanogenic massive sulfide potential: Natural Resources Research Institute Report of Investigation NRRI/RI-2002/14, 15 p. Hudak, G.J., Heine, J., Jirsa, M.A., and Peterson, D.M., 2004, Field Trip 1 - Volcanic stratigraphy, hydrothermal alteration, and VMS potential of the Lower Ely Greenstone, Fivemile Lake to Sixmile Lake area: 50th Annual Meeting, Institute on Lake Superior Geology, Proceedings Volume 50, Part 2 – Field Trip Guidebook, p. 1-45. Hudak, G. J., Heine, J., Lodge, R. W. D., and Jansen, A., 2012, Recent developments understanding the volcanic, magmatic, tectonic, and metallogenic evolution of the Ely Greenstone Formation, Vermilion District, NE Minnesota: Geological Association of Canada – Mineralogical Association of Canada, Abstracts and Program, v. 35, p. 59. Hudak, G. J., Heine, J., Newkirk, T., Odette, J., and Hauck, S., 2002a, Comparative geology, stratigraphy, and lithogeochemistry of the Fivemile Lake, Quartz Hill, and Skeleton Lake VMS occurrences, Vermilion district, NE Minnesota: A report to the Minerals Coordinating Committee, DNR, Minerals Division, State of Minnesota: Natural Resources Research Institute Technical Report NRRI/TR-2002/03, 390 pages. Hudak, G. J., Hoffman, A. T., Peterson, D. M., and Heine, J., 2007, Recent developments understanding the volcanic, magmatic, tectonic, and metallogenic evolution of the Ely Greenstone Formation, Vermilion District, NE Minnesota: 53rd Annual Meeting, Institute on Lake Superior Geology, Proceedings Volume 53, Part 1 – Program and Abstracts, p. 42-43. Hudak, G. J., and Peterson, D. M., 2014, Non-Ferrous Mineralization Associated with the Wawa-Abitibi Terrane and Duluth Complex Cu-Ni-PGM Deposits, Northeastern Minnesota: Society of Economic Geologists, Guidebook Series, v. 47, 150 p. Hudak, G. J., Peterson, D. M., Radakovich, A, Pignotta, G., Schwierske, K., and the students from the 20120-2013 Precambrian Research Center Field Camp, 2016, Bedrock Geology of Lake Vermilion/Soudan Underground Mine State Park: Natural Resources Research Institute Technical Report NRRI/TR-2016-20, 23 p. Hudak, G. J., Radakovich, A., Pignotta, G., and Schwierske, K., 2014, Field Trip 2 – A Walk in the Park – Neoarchean Geology of Lake Vermilion State Park: Institute on Lake Superior Geology, Proceedings Volume 60, Part 2 – Field Trip Guidebook, p. 37-75. Hudleston, P. J., Schultz-Ela, D., and Southwick, D. L., 1988, Transpression in an Archean greenstone belt, northern Minnesota: Canadian Journal of Earth Sciences, v. 25, p. 1060-1068. Hudleston, P.J., 1976, Early deformational history of Archean rocks in the Vermilion district, north-eastern Minnesota: Canadian Journal of Earth Sciences, v. 13, p. 579-592. Jansen, A. C., Hudak, G. J., Heine, J. J., and Peterson, D. M., 1999, Lithogeochemical evaluation of Neoarchean mafic volcanic rocks comprising the footwall to the Soudan Member of the Ely Greenstone Formation, northeastern Minnesota: 55th Annual Meeting, Institute on Lake Superior Geology, Proceedings Volume 55, Part 1 – Program and Abstracts, p. 46-47. Jirsa, M. A., 2000. The Midway sequence: a Timiskaming-type pull-apart basin deposit in the western Wawa Subprovince, Minnesota: Canadian Journal of Earth Sciences, v. 37, p. 1-15. Jirsa, M.A., 2016, Preliminary geologic maps of Lake and St. Louis counties, northeastern Minnesota: Minnesota Geological Survey Open File Report OFR 16-4, https://conservancy.umn.edu/items/a68ec090-cf02-463a-8fcbe3c05926d80e. Jirsa, M. A., Boerboom, T. J., Green, J. C., Miller, J. D., Morey, G. B., Ojakangas, R. W., and Peterson, D. M., 2004, Field Trip 5 – Classic outcrops of northeastern Minnesota: 50th Annual Meeting, Institute on Lake Superior Geology, Proceedings Volume 50, Part 2 – Field Trip Guidebook, p. 129-169. 105 �Trip 4 – Soudan Jirsa, M., and Hillman, M., 2009, Field Trip 4 – Pioneer Mine (Miners Lake) Canoe Excursion: 55th Annual Meeting, Institute on Lake Superior Geology, Proceedings Volume 55, Part 2 – Field Trip Guidebook, p. 110115. Jirsa, M. A., Starns, E. C., and Schmitz, M. D., 2012, Bedrock geologic map of the 2006 Cavity Lake forest fire area, Boundary Waters Canoe Area Wilderness, northeastern Minnesota: Minnesota Geological Survey Miscellaneous Map M-193, 1:24,000 scale. Jirsa, M.A., Southwick, D.L., and Boerboom, T.J., 1992, Structural evolution of Archean rocks in the western Wawa subprovince, Minnesota: refolding of precleavage nappes during D2 transpression: Canadian Journal of Earth Sciences 29:2146-2155. Klinger, F. L., 1960, Geology and ore deposits of the Soudan Mine, St. Louis County, Minnesota: unpublished Ph. D. dissertation, University of Wisconsin, Madison, 96 p. Larson, P., and Mooers, H., 2009, Field Trip 2 – Glacial geology of the Vermilion Moraine: 55th Annual Meeting, Institute on Lake Superior Geology, Proceedings Volume 55, Part 2 – Field Trip Guidebook, p. 81-99. Lodge, R.W.D., Gibson, H. L., Stott, G. M., Franklin, J. M., and Hudak, G. J., 2015, Geodynamic setting, crustal architecture, and VMS metallogeny of ca 2720 Ma greenstone belt assemblages of the northern Wawa Subprovince, Superior Province, Canadian Journal of Earth Sciences, v. 52, p. 196 – 214. Lodge, R. W. D., Gibson, H. L., Stott, G. M., Hudak, G. J., Jirsa, M. A., and Hamilton, M. A., 2013, New U-Pb geochronology from the Timiskaming-type assemblages in the Shebandowan and Vermilion greenstone belts, Wawa Subprovince, Superior Craton: Implications for the Neoarchean development of the southwestern Superior Province: Precambrian Research, v. 235, p. 264-277. Lundy, J. R., 1985, Clues to structural history in the minor folds of the Soudan Iron Formation, northeastern Minnesota: Unpublished M. S. thesis, University of Minnesota, Minneapolis, 144 p. McPhie, J., Doyle, M., and Allen, R., 1993, Volcanic Textures: A Guide to the Interpretation of Textures in Volcanic Rocks: CODES Key Centre, University of Tasmania, Hobart, Tasmania, 198 p. Mercier-Langevin, P., Hannington, M. D., Dubé, B., and Bécu, V., 2010, The gold content of volcanogenic massive sulfide deposits: Mineralium Deposita, v. 46, p. 509-539. Mueller, W. U., and White, J. D. L., 2004, 4.2 – Terminology of Volcanic and Volcaniclastic Rocks: in Eriksson, P. G., Altermann, W., Nelson, D. R., Mueller, W. U., and Catuneanu, O., (eds.), The Precambrian Earth: Tempos and Events: Developments in Precambrian Geology, v. 12, Elsevier, Amsterdam, p. 273-277. Newkirk, T., Hudak, G. J., and Hauck, S. A., 2001, Preliminary lava flow morphology studies at the Five Mile Lake VMS prospect, Vermilion District, NE Minnesota: Implications for volcanic processes, volcanic paleoenvironments, and VMS exploration [abstract/poster]: Geological Society of America Abstracts and Programs V. 33, No. 6. Peterson, D. M., 2001, Development of Archean lode-gold and massive sulfide deposit exploration models using geographic information system applications: targeting mineral exploration in northeastern Minnesota from analysis of analog Canadian mining camps: unpublished Ph. D. dissertation, University of Minnesota, Duluth, Minnesota, 503 p. Peterson, D. M., Gallup, C., Jirsa, M. A., and Davis, D. W., 2001, Correlation of Archean assemblages across the U.S.- Canadian border: Phase I geochronology: 47th Annual Meeting, Institute on Lake Superior Geology, Proceedings Volume 47, Part 1 – Programs and Abstracts, p. 77-78. Peterson, D.M., Hudak, G.J., Radakovich, A., Pignotta, G., and Schwierske, K., 2016, Geologic Map of Lake Vermilion/Soudan Underground Mine State Park: Precambrian Research Center Map PRC/Map-2016-01, 1:10,000 scale. Peterson, D. M., and Jirsa, M.A., 1999, Bedrock geologic map and mineral exploration data, western Vermilion district, St. Louis and Lake Counties, northeastern Minnesota: MGS Miscellaneous Map M-98, scale 1:48,000. Peterson, D., Jirsa, M., and Hudak, G., 2009a, Field Trip 7 – Architecture of an Archean Greenstone Belt: Stratigraphy, Structure, Mineralization: 55th Annual Meeting, Institute on Lake Superior Geology, Proceedings Volume 55, Part 2 – Field Trip Guidebook, p. 178-215. Peterson, D. M., and Patelke, R. L., 2003, National Underground Science and Engineering Laboratory (NUSEL): Geological site investigation for the Soudan Mine, northeastern Minnesota: Natural Resources Research Institute Technical Report NRRI/TR-2003/29, 88 p.a Peterson, D. M., and Patelke, R. L., 2004, Field Trip 7 – Economic geology of Archean gold occurrences in the Vermilion District, northeast of Soudan, Minnesota: 50th Annual Meeting, Institute on Lake Superior Geology, Proceedings Volume 50, Part 2 – Field Trip Guidebook, p. 200-226. 106 �Trip 4 – Soudan Peterson, D. M., Pointer, J., and Marshak, M., 2009b, Field Trip 3 – Soudan Iron Mine and Physics Lab Tour: 55th Annual Meeting, Institute on Lake Superior Geology, Proceedings Volume 55, Part 2 – Field Trip Guidebook, p. 100-109. Radakovich, A. L., Parent, C. T., Partridge, M. E., Ritts, A. D., Pierce, R., and Hudak, G. J., 2010, Reconnaissance bedrock geological map of the northern part of Soudan Underground Mine State Park and the northwestern part of Lake Vermilion State Park, St. Louis County, Minnesota: Precambrian Research Center Map Series Map PRC/Map – 2010-04, 1:5000 scale. Schmid, R., 1981, Descriptive nomenclature and classification of pyroclastic deposits and fragments; recommendations of the IUGS subcommission on the systematics of igneous rocks: Geology, v. 9, p. 41-43. Schwierske, K.L., Pignotta, G. S., and Hudak, G. J., 2014, The 2.7 billion year old Mt. St. Helens of northern Minnesota: Petrography, geochemistry, and economic significance of the Neoarchean Gafvert Lake Sequence: 60th Annual Meeting, Institute on Lake Superior Geology, Proceedings Volume 60, Part 1 – Programs and Abstracts, p. 113-114. Sims, P. K., and Southwick, D. L., 1985, Geologic map of Archean rocks, western Vermilion district, northern Minnesota: U. S. Geological Survey, Miscellaneous Investigations Map I-1527, scale 1:48,000. Southwick, D. L., (compiler), 1993, Bedrock geologic map of the Soudan-Bigfork area, northern Minnesota: Minnesota Geological Survey, Miscellaneous Map M-79, scale 1:100,000. Southwick, D. L., Boerboom, T. J., and Jirsa, M. A., 1998, Geologic setting and descriptive geochemistry of Archean supracrustal and hypabyssal rocks, Soudan-Bigfork area, northern Minnesota: implications for metallic mineral exploration: Minnesota Geological Survey, Report of Investigations 51, 69 p. Stott, G., Corkery, T., Leclair, A., Boily, M., and Percival, J., 2007, A revised terrane map for the Superior Province as interpreted from Aeromagnetic Data: 53rd Annual Meeting, Institute on Lake Superior Geology, Proceedings Volume 53, Part 1 – Program and Abstracts, p. 74-76. Stott, G. and Mueller, W., 2009, Superior Province: The nature and evolution of the Archean continental lithosphere: Precambrian Research, v. 168, p. 1-3. Thompson, A., 2015, A Hydrothermal Model for Metasomatism, of Neoarchean Algoma-Type Banded Iron Formation to Massive Hematite Ore at the Soudan Mine, NE Minnesota: unpublished M. S. Thesis, University of Minnesota Duluth, 59 p. Vallowe, A. M., Thalhamer, E. J., Rhoades, D. L., and Peterson, D. M., 2010, Surface and subsurface geologic maps of the Soudan Underground Mine State Park, St. Louis County, northeastern, Minnesota: Precambrian Research Center Map Series Map PRC/Map – 2010-01, 1:2500 and 1:5000 scale. White, J. D. L., and Houghton, B. F., 2006, Primary volcaniclastic rocks: Geology, v. 34, no. 8, p. 677-680. Winchester, J. A., and Floyd, P. A., 1977, Geochemical discrimination of different magma series and the differentiation products using immobile elements: Chemical Geology, v. 20, p. 325-343. 107 �Trip 5 – Alkalic plutons FIELD TRIP 5 Neoarchean Alkalic Intrusions in the Wawa and Quetico Subprovinces Terry Boerboom (retired)1 and Amy Radakovich1 1 Minnesota Geological Survey, College of Science and Engineering, University of Minnesota, 2609 Territorial Road, St. Paul, MN 55114 This field trip will visit several alkalic intrusions that have been mapped from a combination of outcrop, drilling, and geophysical data. Refer to Figure 5-1 for the pluton names and generalized regional geology. The stop descriptions are very brief, but a more thorough description of each pluton (as well as others not visited on this trip) are contained in the introductory text. These plutons were emplaced mainly into the Lake Vermilion Formation which is composed of volcanogenic sedimentary rocks sourced from Gafvert Lk rhyodacite tuff (2689.7±0.8 Ma) and also likely from felsic tuffs at the south limb of the Britt structure (2689.6±0.5 Ma). The Linden pluton has an age of 2681.00±0.29 Ma, and the Lost Lake pluton an age of 2675.1±0.5 (Boerboom et al., 2022). These ages are slightly older than the large Shannon Lake granite (2674±5 and 2674±27; Boerboom and Zartman 1993), and straddle two ages obtained on the Britt granodiorite (2681±4 and 2685±4 Ma; Boerboom and Zartman 1993). The Idington pluton is intruded by the Shannon Lake granite, consistent with the aforementioned age dates. The suite of alkalic plutons we will visit are located mainly in the Wawa subprovince but one (Gheen) is in the Quetico subprovince and will include the Side Lake, Morcom, Linden, Gheen, Idington, and Lost Lake plutons (Figure 5-1). All of these intrusions are similar in mineralogy with varied ratios of perthitic to antiperthitic feldspar and Na-plagioclase, hence are divided into those that are more syenitic vs. monzodioritic. All contain Na-rich aegirine/aegirine-augite with variable proportions of primary and secondary-deuteric hornblende, titanite, biotite, and minor oxides and apatite. Textures vary from uniformly medium-coarse grained to strongly and coarsely porphyritic, and they typically exhibit a flow-foliation defined by feldspar and subprismatic pyroxene and/or hornblende. All except the Linden are multi-phase with variations from ultramafic pyroxenite/hornblendite to intermediate syenite/monzodiorite, with relatively minor late-phase felsic phases; where multi-phase they generally show complex and conflicting intrusive relationships between the various phases. The following discussion, modified from Minnesota Geological Survey Report of Investigations 43 (Boerboom, 1994), covers the plutons we will visit as well as others that we will not visit. Note that some of the ideas presented in this report may have been modified or discredited based on newer geochronological data. 108 �Trip 5 – Alkalic plutons ALKALIC PLUTONS OF NORTHEASTERN MINNESOTA Minnesota Geological Survey Report of Investigations 43 By T. Boerboom ABSTRACT A series of alkalic plutons in northeastern Minnesota intrude metamorphosed sedimentary and volcanic rocks in the Wawa and Quetico subprovinces of the Archean Superior Province. The plutons generally fall into one of three categories-a syenitic clan, a monzodioritic clan, and a granitic clan. The main rock phases of the syenitic and monzodioritic clans are strongly porphyritic, coarse-grained, green and pink, quartz-poor syenite and diorite. Na-rich pyroxene is the predominant mafic mineral in these intrusions, and titanite is prominent in hand sample. Some of the syenitic intrusions contain melanite garnet, and at least one contains the feldspathoids nepheline and cancrinite. The granitic intrusions consist of variably porphyritic, coarse-grained, pink granite and monzonite, with hornblende as the dominant mafic mineral. Whereas these granitic plutons tend to be uniform in texture and composition, the syenite and monzodiorite plutons are characterized by abrupt internal variations in rock type ranging from dark-colored pyroxenite to light-pink leucocratic granite, syenite, and trondhjemite. The alkalic plutons range in size from 1.5 to 60 mi2 (3.9 – 155 km2) are oval to amoeboid in shape and elongate to the northeast, and are eroded to middle and upper levels. All of the alkalic plutons produce positive aeromagnetic anomalies; outcrops, although limited, confirm that these anomalies reflect the shapes of the plutons. Several unexposed plutons, whose shapes are inferred from aeromagnetic data, have been verified by test drilling. Field relationships show that these plutons are post-tectonic. Although chemical data are not available for all of the plutons, those with analyses plot as alkalic in terms of Na2O + K2O vs SiO2, but as mainly calc-alkalic on an AFM diagram. The syenitic and monzodioritic clans are generally neither nepheline-normative to neither quartz- nor nepheline-normative, with the exception of minor leucocratic phases. All are characterized by steep REE patterns and exceptionally high concentrations of Ba and Sr. INTRODUCTION Recent mapping in northern and northeastern Minnesota, including the Koochiching-ItascaBeltrami County area (Jirsa and Boerboom, 1990) and western St. Louis County (Jirsa and others, 1991), has delineated several previously unrecognized subalkalic to alkalic plutons. This report summarizes the lithological and intrusive relationships of several of these alkalic intrusions and briefly summarizes their geochemical characteristics. Some plutons in this group, such as the Snowbank and Kekekabic stocks and the Daisy Bay and Dead River plutons have been previously described (Geldon, 1972; Sims and Mudrey, 1972) and are not included in this report. Others (Coon Lake, Linden, Lost Lake plutons) have been briefly described in the literature (Sims and others, 1970, 1972; Sims and Mudrey, 1972), but are detailed here, as are others which have no published information or were unknown (Fig. 5-1A). Alkalic rock complexes similar to these are well known in Ontario (for example Sage, 1988a, 1988b, 1988c), but few have been described from Minnesota. Several other small alkalic plutons are inferred from aeromagnetic data, but are not exposed or have not been drilled (Jirsa and others, 1991). 109 �Trip 5 – Alkalic plutons Characteristics of the Alkalic Rock Suite The alkalic intrusions fall into three general categories – a syenitic group comprising the Coon Lake, Linden, Gheen, and Baudette plutons; a monzodioritic group including the Side Lake, Morcom, Idington, and Cook plutons; and a granitoid group containing the Bello Lake, Stingy Lake, and Rice River plutons (Fig. 5-1). Although most classify into one of the three clans, the many phases in each pluton (Table 5-1) produce considerable overlap. The syenitic and monzodioritic intrusions consist mainly of medium- to coarse-grained, porphyritic, pink and green syenite and monzodiorite, whereas the granitoid intrusions are typically medium-grained, variably porphyritic, pink quartz monzonite or granodiorite. The syenite and especially the monzodiorite plutons contain multiple erratic melanocratic to felsic phases with aegirineaugite as the predominant mafic mineral, whereas the granitoid plutons generally lack multiple phases, are more uniform in texture, and contain mainly hornblende as the mafic phase. Most of the alkalic plutons intrude metamorphosed volcanic and sedimentary rocks in the western Wawa subprovince, but some are within the Quetico subprovince (Card and Ciesielski, 1986; Fig. 5-1A). All were emplaced in the latest stages of the last major regional deformational event (Jirsa and others, 1992) or after it. Several of the alkalic plutons are cut by northwest-trending Late Proterozoic diabase dikes of the KenoraKabetogama swarm, which have been dated al 2,125 Ma (Rb-Sr; Beck, 1988) [NOTE: more recent U-Pb geochron ages of ca. 2067 -2070 Ma (Chamberlain and others, 2015; Schmitz and others 2006; Wirth and others , 1995). The plutons are exposed at various levels, and many, such as the Gheen, Side Lake, and Lost Lake, are exposed close to their roof zones. All of the alkalic plutons produce positive aeromagnetic anomalies which generally conform to the pluton shape (Fig. 5-1B). The major-element geochemistry of the alkalic plutonic rocks varies greatly as a result of their diverse mineralogy. However, except for minor proportions of felsic differentiates, they are low in SiO2 (49-62 wt. % for syenites, 47 to 58 wt. % for monzodiorites, 61-70 wt. % for granites; Table 5-2), and are mostly metaluminous to weakly peralkalic in composition (Fig. 5-2). The syenitic and monzodioritic rocks are generally quartz-free to nepheline-normative, whereas the granite from the Bello Lake pluton is mostly quartz-normative (Fig. 5-3). Except for one of the granites and a leucocratic differentiate of the Idington pluton, all plot as alkalic in terms of Na20 + K20 vs Si02, but as calc-alkalic to weakly alkalic on an AFM diagram. In all the plutons, Ba and Sr are in general highly enriched, but vary between the different phases. However, the Coon Lake pluton although slightly enriched, is surprisingly low in Ba and Sr, considering its extremely alkalic composition. The Linden pluton is extremely enriched in Ba and Sr, with Ba values of up to 13,000 ppm and Sr values up to 8,100 ppm reported from company drill cores. Chondrite-normalized REE patterns for the syenites and monzodiorites are fairly consistent, with moderately steep slopes and negligible Eu anomalies (Fig. 5 6). No REE data are available for any of the granitoid plutons. Table 5-1 (next page). Modal analyses of alkalic plutonic rocks; results in volume percent. Linden analyses from Sims and others (1972, p. 161); samples with KIB and CD prefixes from drill cores, all others from outcrops. Pyroxene includes aegirine to augite; n, points counted; est, estimate 110 �Trip 5 – Alkalic plutons Sample Quartz K-feldspar Plagioclase Pyroxene Hornblende Biotite Muscovite Chlorite Epidote Apatite Sphene Opaques Calcite, Fl* Nepheline Cancrinite Melanite n KIB-7 20 43 32 2 1 tr tr tr 2 est Bello Lake Coon Lake KIB-39 KIB-40 DL-61 KIB-6 3 32 46 50 79 53 40 9 tr 8 5 2 1 8 1 tr tr tr 1 tr tr tr tr tr tr 1 tr tr tr 3 3 tr tr tr 33 15 2 2 2 est est 1143 est Gheen Idington Linden C027 C029 C551X C552B C650 C561A Gnw7A Msw2A Gnw7-2 tr 41 2 tr 8 61 26 3 tr 3 77.6 56.2 37.1 21 7 29 55 32 88 1.9 5.6 0.4 12 31 49 16.8 25.9 57.1 46 19 8 6 7 5 7 4.1 0.4 4 4 1 1 tr tr 2 3 2 5 2 2 1368 1114 989 2 Fl* 1157 tr tr 2 2 tr 999 1 1 1 0.8 2.9 1.1 3.7 3.4 2.7 2.3 946 Side Lake satellites Morcom Stingy Rice R. Cook Side Lake Linden L-Sat Sample Gnw-7B CD-4 1242 C706B C533A C534A C543A C564A C603A CD-7** CD-7 CD-9 CD-17 CD-19 Quartz 26 13 K-feldspar 56.3 28 31 tr 13 2 28 1 29 7 20 22 30 Plagioclase 0.9 52 30 65 47 33 55 44 20 54 55 47 43 67 Pyroxene 27.1 16 17 22 26 30 47 21 5 Hypersthene 14 8 Hornblende 2 34 16 9 3 8 8 3 6 Biotite 9 7 4 1 3 20 1 7 10 1 Muscovite 1 14 3 1 1 4 Chlorite Epidote 5 1 1 1 2 183 Apatite 5.2 1 tr tr 2 2 1 1 0.5 tr Sphene 1.5 2 2 I 1 1 0.5 1 0.5 tr Opaques 1 1 tr 0.5 tr Calcite 1 n 1166 1151 est 976 1188 947 1115 1137 988 1152 836 960 est * Fluorite in sample C552B; ** Poikilitic and non-poikilitic phases, sample CD-7; L-Sat is intrusion beween Linden and Gheen 111 �Trip 5 – Alkalic plutons Figure 1-1. 112 �Trip 5 – Alkalic plutons SYENITIC PLUTONS Most of the syenitic plutons are northwest of the other plutons (Fig. 5-1A). The Gheen and Baudette plutons are within the Quetico subprovince, the Coon Lake pluton is in the Wawa subprovince, and the Linden pluton straddles the subprovince border. These plutons are distinguished by a preponderance of K-rich perthite, typically as trachytic, blocky phenocrysts in an aegirine-rich groundmass, or an amphibole-rich groundmass in the case of the Gheen pluton. . The Gheen and Linden plutons contain quartz, chlorite, apatite, epidote, titanite, opaque oxides, and pyrite as ubiquitous but generally minor constituents. The Coon Lake pluton differs from all others in that it contains substantial nepheline and cancrinite; the Baudette pluton lacks both feldspathoids and quartz. Melanite garnet is present in the Coon Lake and Baudette plutons, and in some phases of the Linden. A distinctive phase of spotted monzodiorite with centimeter-size poikilitic feldspar enclosing pyroxene, hornblende, plagioclase, biotite, and sphene is present in both the Linden and Gheen plutons and in plutons of the monzodiorite clan. Although the Gheen and parts of the Linden plutons are texturally similar to rocks of the monzodiorite clan, they differ by having phenocrysts of pink perthite instead of gray antiperthite. Trachytic fabric in the syenitic intrusions conforms to the pluton edges and dips steeply toward the pluton centers. However, outcrops are generally limited to the pluton borders, and the Baudette and Linden satellite intrusions are seen only in drill core. Aeromagnetic signatures correspond with intrusion shapes, whether it be a consistent oval like the Baudette, Coon Lake, and Linden plutons, or irregular and amoeboid like the Gheen and Linden satellite plutons (Fig. 5-l B). Coon Lake Pluton The Coon Lake pluton (Fig. 5-l; Jirsa, 1990; Jirsa and Boerboom, 1990) is a 48-mi2 subcircular pluton which intrudes mafic to felsic volcanic rocks metamorphosed to greenschist grade. A narrow aureole of amphibolite-grade metamorphism accompanied pluton emplacement. The pluton has a strongly magnetic border and internal lithological zonation is indicated by a circular, weakly positive magnetic anomaly within the pluton. Its north and northeast edges are exposed in scattered outcrops, and a single 10-foot-long vertical drill core was obtained from the pluton center (Boerboom and others, 1989). The main rock type in the exposed and cored portions of the Coon Lake pluton is pink to gray, medium- to very coarse grained, slightly to strongly porphyritic nepheline syenite, 50-79% microperthite, 15-33% nepheline {Ne76-80) 2-5% aegirine (Ac23Wo18En7Fs52), and as much as 9% plagioclase, 2% cancrinite, and 3% melanite, together with accessory sphene, apatite , biotite, magnetite, muscovite , and zircon (Tables 5-1 and 5-3, Fig. 5-7). Minor proportions of pyroxenite occur in ill-defined dikelets. String- and braid-textured microperthite forms rectangular crystals with minor inclusions of aegirine, sphene, cancrinite, and nepheline. Nepheline is typically anhedral but locally euhedral, up to 2 mm in size, and ranges from fresh to moderately altered to an unknown fibrous mineral of low birefringence. Prismatic, grass- green aegirine formed early in the crystallization sequence and is trachytic. Plagioclase and cancrinite are interstitial, the latter as colorless, highly birefringent fibrous grains. Melanite garnet forms subhedral, dark-brown grains up to 1 cm across with inclusions of aegirine and altered feldspar. In places the syenite consists of trachytic, purplishbrown, rectangular perthite crystals up to 7 cm in length, with minor nepheline, melanite, biotite, and aegirine. A syenite dike that cuts mafic volcanic rocks outboard of the main pluton contains an estimated 1% scolecite and a trace of blue corundum. Netlike anastomosing veinlets of white nepheline parallel to the vertical trachytic fabric of the feldspar in drill core from the center of the pluton imply that a late influx of volatiles affected the magnetic signature of the pluton's interior. 113 �Trip 5 – Alkalic plutons Table 5-2. Major- and select minor-element geochemical analyses of alkalic rocks [Major elements in wt% oxides, minor elements in ppm, blank – nod determined. See Boerboom 1994 for more information. Bello Lake Coon Lake Gheen Morcom Sample KIB-7 KIB-40 SiO2 Al2O3 CaO MgO Na2O K2O Fe2O3t FeO Fe2O3c MnO TiO2 P2O5 LOI Total Rb Sr Y Zr Nb Ba Ni Cu Zn Cs La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf V Cr Li B 69.7 15.7 1.87 0.51 5.67 3.51 1.84 0.4 1.4 0.04 0.2 0.09 0.7 100.2 165 1210 <10 90 <10 1340 63.9 17.4 2.16 1.28 6.13 4.47 3.32 1 2.21 0.07 0.35 0.18 0.77 100.4 135 1340 41 303 14 1470 F KIB39 60.2 17.2 3.55 1.85 6.3 4.4 3.94 1 2.83 0.08 0.42 0.32 1 99.8 129 2180 17 253 14 1970 KIB-6 CLP-1 I-561A DL-61 C029 C027 12, IC-2 CD-7 57.7 17.8 5.45 0.42 5.75 5.8 2.71 0.3 2.38 0.07 0.26 0.11 2.77 99.6 100 3700 81 64 15 2530 62.3 18.9 0.33 0.35 5.32 9.3 2.18 1.6 0.76 0.05 0.18 0.02 0.85 100.1 246 1300 <10 118 24 676 8 8.7 70.3 9 17.5 33 60.3 22.4 1.69 0.28 7.1 4.13 2.54 1.7 1.78 175 ppm 0.19 <10 ppm 1.31 100.1 132 806 10 404 27 500 <l 9.8 46.3 3 79.3 130 12.8 39.7 5.5 1.45 3.9 0.5 2.6 0.49 1.4 0.5 1.4 0.19 9 45 29 74 41 55.65 21.88 1.65 1.01 8.12 7.28 3.67 6.08 5 0.08 0.44 0.08 0.37 100.38 100 926 2 119 49.2 9.52 12.3 10.5 1.51 2.4 10.2 49.65 9.27 13.08 8.89 2.38 1.71 11.76 58.5 l5.4 5.01 3.58 5.9 3.8 5.22 0.16 0.88 0.33 2.39 99.5 60 290 14 84 13 697 94 40.8 80.1 2 20.8 46 0.56 0.89 0.06 1.99 99.93 79 1470 <10 0.1 0.48 0.29 1.08 99.7 215 7 16 30 4.5 27 58 56 14.1 6.48 2.55 3.57 6.56 6.19 3.2 1.66 0.12 0.71 1.03 1.85 99.9 120 2520 47 331 24 3710 78 5.5 84.5 1 130 328 33 5.1 1.21 186 34.7 9.3 24 5.7 1.9 0.4 2.3 0.7 0.65 0.1 4 2.3 0.2 8 1.7 0.2 3 11 39 <10 67 <10 <10 630 <10 <10 160 850 11.2 8.18 11 1.7 0.4 <0.5 22 26 36 <10 0.2 <0.1 4 20 10 18 30 114 Cs �Trip 5 – Alkalic plutons Idington Sample C552B SiO2 Al2O3 CaO MgO Na2O K2O Fe2O3t FeO Fe2O3c MnO TiO2 P2O5 LOI Total Rb Sr y Zr Nb Ba Ni Cu Zn Cs La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf V Cr Li B F 74.5 14.8 0.08 0.09 8.8 1.08 0.51 0.03 0.03 0.02 0.16 100.1 97 43 <10 36 30 81 <1 1.5 28.6 7 5.9 10 <5 0.2 0.2 <0.5 <0.2 <0.1 2 <10 4 <10 20 10, IC2- 11, IC-2 47.27 6.99 20.49 9.18 1.91 0.89 9.15 5.44 3.1 0.3 0.67 1.62 1.33 99.28 50.27 7.61 13.87 7.92 2.41 3.63 10.68 7.04 2.86 0.2 1.51 1.46 0.84 99.91 Linden L’ndn Sat Side Lk-Sat Side Lake Cook C650A C551X 8, IC-2 MN-10 CD-4-92 C564A 1242 C706B CD-19 48.3 7.24 16.6 9.58 2.12 1.23 IO.IO 6 3.43 0.19 1 1.25 0.77 98.6 59 772 37 262 15 817 76 185 125 9 164 348 41.4 171 27.9 6.99 18.2 2 8.8 1.46 3.2 0.3 2.6 0.32 7.6 256 140 231 14 2900 54 13.1 8.16 4.56 4.24 3.86 7.05 3.3 3.38 0.13 0.96 0.75 1.23 98.5 57 1770 26 181 9 1830 64 54.9 120 1 134 278 30.8 124 19.2 5.14 11.8 1.3 6.4 1.01 1.9 0.2 1.6 0.22 5 148 120 76 14 1400 60.21 16.28 4.76 2.21 3.78 6.32 4.29 1.62 2.49 0.08 0.56 0.23 0.73 99.76 57.1 10.2 10.1 4.43 2.64 6.52 6.51 2.83 3.36 0.15 0.64 1.07 62.2 15 4.09 1.62 6.57 4.73 3.98 1.4 2.42 0.09 0.48 0.24 0.54 99.9 94 510 10 246 14 2290 52.2 11.7 9.89 7.08 4.04 2.22 10.3 55.2 14.6 7.38 6.89 3.42 2.95 7.93 0.19 0.81 0.45 1.08 100.2 67 1080 <10 102 21 985 57 108 128 2 50.6 101 0.14 0.77 0.39 0.23 100.2 60 1030 20 30 10 1220 53.5 15.4 7.68 6.25 3.79 2.21 8.37 5.7 2.04 0.15 0.76 0.39 0.47 99.3 31 1190 20 82 2 1530 61 20.4 108 1 43.2 88 11.3 48.8 9.3 2.81 6.4 0.8 4.1 0.73 1.8 0.2 1.6 0.23 2.2 208 180 26 <10 680 53.6 17.7 7.59 3.26 5.4 1.79 7.07 2.6 4.18 0.13 0.71 0.36 1.54 99.5 39 1950 <10 110 15 882 99.1 164 2924 3574 406 183 28.1 6.62 16.6 46 8.9 2.4 0.6 1.53 0.262 115 1.4 0.2 4 210 80 84 <10 �Trip 5 – Alkalic plutons Figure 5-3. Modal (A) and normative (B) compositions of the alkalic plutonic rocks. Compositional fields from Streckeisen (1973), except “P” corner, which consists of albite and anorthite, used here to emphasize variations in K content. Q, quartz; F, feldspathoids; A, alkali feldspars; P, plagioclase. Circled symbols are feldspathoidal, not quartz. Figure 5-4. Geochemical discrimination diagrams. (A) Alkalic versus subalkalic discrimination diagram; modified from Irvine and Baragar (1971). (B) AFM diagram for the alkalic plutonic rocks; modified from Barker and Arth (1976). Figure 5-5. Harker diagrams for the alkalic plutonic 116 rocks, in wt % oxides recalculated to no loss on ignition. �Trip 5 – Alkalic plutons Figure 5-6. Chondrite-normalized rare-earth-element patterns for the alkalic plutonic rocks for which analyses are available. Figure 5-7. Pyroxene compositions from the Coon Like and Linden plutons. Pyroxene compositions from Poohbah Lake (Sage, 1988a) and compositions of pure aegirine (Deer and others, 1966, p. 107) shown for comparison. 117 �Trip 5 – Alkalic plutons Table 5-3. Microprobe analyses of minerals from the Coon Lake and Linden plutons. [Linden results from Sims and others (1972). Chemical analyses in weight percent oxides. Cancrinite totals low due to abundance of volatiles. Table is continued on next page. Biotite Aegirine Coon Lake Linden Coon Lake Sphene Linden Coon Lake Linden SiO2 51.49 51.62 51.8 53 46.85 37.16 35.69 44 43 30.01 30.65 31 TiO2 0.58 0.54 0.48 0.5 2.13 2.66 3.13 0.5 0.5 37.17 34.62 31 Al2O3 1.35 1.34 1.38 1 2.5 13.96 12.34 11 13 0.55 0.57 3.5 FeO 25.43 25.36 25.74 14.8 16.97 21.02 18.42 18 14 2.06 2.34 3 MnO 0.33 0.41 0.44 0.31 1.13 1.11 0.01 0.06 MgO 1.96 2.00 1.85 8.6 8.17 9.32 10.03 0.02 0.02 CaO 6.74 6.92 6.29 18.8 17.85 0 0.01 26.51 25.44 29 Na2O 9.74 9.51 9.88 3.5 2.49 0.14 0.22 1 1 0.29 0.33 3.3 K2O 0.00 0 0.00 0.5 0.5 9.21 9.34 10.5 11.5 0.01 0.01 Cr203 0.00 0.02 0.00 nd 0.01 0 0.00 0 Total 97.62 97.70 97.85 99.84 94.60 90.28 96.62 94.04 100.80 100.7 Number of cations based on 6 oxygen 14 99.0 16.2 99.20 Number of cations based on 24 oxygen Si 2.1 2.1 2.1 2.02 1.88 6.31 6.33 6.96 6.71 4.89 5.11 4.91 Ti 0.02 0.02 0.01 0.01 0.06 0.34 0.42 0.06 0.06 4.55 4.34 3.69 Al 0.06 0.06 0.07 0.04 0.12 2.79 2.58 2.05 2.39 0.11 0.11 0.65 Fe 0.87 0.86 0.87 0.47 0.57 2.98 2.73 2.38 1.83 0.28 0.33 0.40 Mn 0.01 0.01 O.D2 0 0.01 0.16 0.17 0.00 0.01 Mg 0.12 0.12 0.11 0.49 0.49 2.36 2.65 3.3 3.77 0.01 0.01 Ca 0.29 0.3 0.27 0.77 0.77 0 0.00 0.00 0.00 4.63 4.54 4.92 Na 0.77 0.75 0.78 0.26 0.19 0.05 0.08 0.31 0.3 0.09 0.11 1.01 K 0 0 0 0.02 0,03 1.99 2.1I 2.12 2.29 0.00 0.00 Cr 0 0 0 0.00 0.00 0.00 0.00 0.00 0.00 118 �Trip 5 – Alkalic plutons Table 5-3 continued Exsolved albite Perthite Nepheline Coon Lake Linden Cancrinite Coon Lake Coon Lake SiO2 72.37 63.422 66.725 67.493 66.235 61.5 46.153 46.641 48.068 46.297 45.345 37.455 37.613 37.472 Al2O3 19.868 15.347 17.527 18.889 18.612 19 33.061 34.701 35.152 34.217 33.123 28.053 26.956 28.416 BaO 0.000 0.000 0.132 0.000 0.104 0.000 0.000 0.000 0.028 0.000 0.122 0 0 CaO 0.031 0.000 0.018 0.001 0.000 0.5 0.084 0.076 0.116 0.102 0.484 5.583 5.432 5.348 Na2O 10.58 0.646 3.055 3.785 0.716 1.5 15.947 14.848 13.198 15.917 13.574 18.776 18.468 18.201 K 2O 1.268 12.139 12.521 12.016 15.932 15.8 6.186 6.211 5.877 6.133 6.068 0.04 0.052 0.206 Total 104.118 91.553 99.977 102.185 101.598 99.8 101.43 102.476 102.412 102.693 98.594 90.029 88.52 89.643 Number of cations based on 8 oxygen Number of cations based on 32 oxygen No. of cations based on 12 O Si 3.03 3.13 3.04 3 3.01 2.92 8.67 8.62 8.79 8.59 8.70 3.02 3.08 3.02 Al 0.98 0.89 0.94 0.99 1 1.06 7.33 7.56 7.58 7.48 7.49 2.67 2.6 2.7 Ba 0 0 0.01 0 0.01 0 0 0 0.01 0 0.01 0 0 Ca 0 0 0 0 0 0.03 0.02 0.02 0.02 0.02 0.10 0.48 0.48 0.46 Na 0.86 0.06 0.27 0.33 0.06 0.14 5.81 5.32 4.68 5.72 5.05 2.94 ·2.93 2.85 K 0,07 0.76 0.73 0.68 0.92 0.96 1.48 1.46 1.37 1.45 1.49 0 0.01 0.02 119 �Trip 5 – Alkalic plutons Linden Pluton The Linden pluton [2681.00±0.29 Ma] and its smaller satellite to the east intrude mafic to felsic volcaniclastic and sedimentary rocks that are metamorphosed to the sillimanite grade at the north edge of the pluton and to chlorite grade at the southern edge. A narrow amphibolite-grade metamorphic aureole surrounds the pluton (Jirsa and others, 1992), as is evident in drill core LF-1 (Fig. 5-1). In this core, thin syenitic dikelets cut biotite-amphibole schist that has centimeter-thick green bands dominated by bright-green sodic amphibole and brown bands dominated by biotite. The country rock here is of sillimanite grade, and the aureole along the north edge of the Linden pluton may reflect retrogression. Sims and others (1972), who describe amphibolite-grade contact metamorphism of mafic volcanic rocks adjacent to the western margin of the pluton, suggest that the foliation at a high angle to the regional fabric is the result of forcible pluton emplacement. The Linden pluton is roughly 54 mi2 in size and elongate to the northwest, whereas the satellitic intrusion is about 4.5 mi2 in size and elongate to the northeast (Fig. 5-1). Exposures are limited to the pluton edges, but ten drill cores from the pluton were obtained by various private and governmental agencies. Records of these cores and the cores themselves are on file at the Minnesota Department of Natural Resources, Division of minerals in Hibbing. A summary of the cores is given in Table 5-4. The LP-series of drill cores were subsequently examined by Himmelberg (1973), and thin sections from these cores were briefly reexamined in conjunction with this report. The LP-series descriptions are directly from company logs, and the OB­ series descriptions are from the Minnesota Department of Natural Resources, Division of Minerals (Martin and others, 1988). The target of company drilling is not known, but complete metals analyses, together with Na, K, Al, Ca, Ba, and Sr abundances, were obtained by the explorationists. The satellite intrusion is not exposed, but one short drill core was obtained by the Minnesota Geological Survey (Meints and others, 1993). The main Linden pluton is generally uniform in composition within the exposed portions and in the drill cores. The typical phase consists of trachytic, variably porphyritic, salmon-pink and greenish-black, medium-to coarse-grained aegirine-augite syenite with conspicuous dark-brown sphene and centimeter-scale elliptical pyroxenite clots. As reported by Sims and others (1972), and confirmed here, the dominant minerals of the syenite are braidtextured perthite and dark-green aegirine-augite (Ac7Wo41En26Fs25, Table 5-3 and Fig. 5-7), with variable but lesser amounts of plagioclase, sphene, apatite, biotite, hornblende, magnetite, and epidote. Modal analyses and compositions of selected minerals are summarized in Tables 51 and 5-3. Complete descriptions of exposures are given in Sims and others (1972), and the drill cores are summarized in Table 5-4. Textures in the groundmass of drill holes CD-13 (Meints and others, 1993) and LF-2 are suggestive of cataclasis, yet other features in these cores, such as tabular plagioclase, blocky pseudomorphic biotite and epidote (presumably after pyroxene), and euhedral diamond-shaped sphene, show no evidence of brittle deformation. Thus the granoblastic fabric of the groundmass is most likely the result of plastic flow deformation of a viscous, mostly crystallized magma, in conjunction with late deuteric fluids. Drill hole CD-4 in the Linden satellite also contains zones of moderately sheared syenite characterized by rounded, rolled feldspar phenocrysts, suggestions of C­ S fabric, and streaky pink and gray segregations. Shear bands <I inch to 10 feet thick are foliated parallel to the trachytic fabric of unsheared portions, and the mineralogy of the sheared rock in thin section is identical to that of the undeformed portions (Table 5-1). As is the case in the Linden pluton proper, the annealed texture implies that deformation occurred in a hot, 120 �Trip 5 – Alkalic plutons semiplastic state, under near-magmatic temperatures. These submagmatic deformation features are also present in the Idington and Coon Lake plutons. Gheen Pluton The Gheen pluton, some 3 miles east of the Linden pluton, intrudes sillimanite-grade metasedimentary rocks. It is currently exposed at a high level, and its magnetic signature conforms to the long, sinuous, northeast­ elongate shape deduced from scattered outcrops along the length of the body. Local trachytic fabric defined by tabular perthite phenocrysts is steep and subconformable to the pluton contacts and the pluton shape at both map and outcrop scale is subcordant to the schistosity of the host supracrustal rocks. The pluton is chiefly mesocratic, pink and dark-green, porphyritic syenite and ranges to dark-greenish-black, coarse-grained pyroxenite and leucocratic, pink, coarse­ grained alkalifeldspar syenite. Conflicting internal intrusive relationships are common, with melanocratic phases occurring both as inclusions and as dikes in the porphyritic phase. However, pink leucosyenite dikelets cross all other phases. Mesocratic syenite phases contain 1- to 3-cm tabular perthite phenocrysts in a groundmass of fibrous amphibole, euhedral sphene, blocky oxides, stubby prismatic apatite, and minor calcite and epidote. Trace amounts of dark-green pyroxene are present, but most has been deuterically altered to bright-green fibrous amphibole. Calcite occurs both in irregular veinlets with amphibole and as magmatic, interstitial grains against sharp comers of feldspar phenocrysts. The melanocratic monzodiorite phase consists predominantly of relict pale-green pyroxene up to 2.5 mm across and lesser amounts of sericitized plagioclase, finegrained, euhedral sphene, and apatite. The pyroxene is variably replaced by euhedral, pale-green hornblende. Biotite occurs as brown books within hornblende, and is slightly altered to chlorite. Unaltered microperthite occupies a late anhedral interstitial position. Sills of pink, leucocratic, coarse-grained syenite up to 10 feet wide emanate from the Gheen pluton and cut adjacent metasedimentary rocks. This phase is characterized by irregular microcline phenocrysts in a seriate groundmass of macroscopically identified, pink microcline, fine-grained biotite, and minor white albite. Local planar miariolitic cavities lined with K-feldspar crystals are consistent with the interpretation that the pluton is exposed at a high level. The Gheen pluton differs from the other alkalic intrusions by its pervasive deuteric alteration and relatively abundant chalcopyrite. Modal analyses of the melanocratic and porphyritic mesocratic phases are listed in Table 5-1 and shown on Figure 5-3. 121 �Trip 5 – Alkalic plutons Table 5-4. Descriptions of cores from the Linden pluton; Dominant lithology in bold type. Drill Description Hole Pink, slightly porphyritic, medium-grained homogeneous leuco alkalifeldspar syenite. Trachytic foliation defined by aligned mafic minerals. LF-2 Feldspar varies from coarse blocky phenocrysts with recrystallized edges to granoblastic groundmass. LF-3 LF-4 LF-5 Dark-gray, slightly porphyritic, fine- to medium-grained heterogeneous poikilitic syenite to monzonite. Poikilitic feldspar encloses pyroxene, biotite, and sphene. Weak trachytic fabric defined by aligned pyroxenes and feldspar oikocrysts. Feldspathic dikelets and aegirine veinlets. Light-grayish-white, medium-grained, granular to hypidiomorphic hornblende monzonite with 1-cm mafic segregations. Deuteric pyroxene alteration. Light-pinkish-gray, medium- to coarse-grained, moderately porphyritic syenite; 2- to 4-cm mafic segregations of slightly porphyritic, euhedral aegirine in groundmass of feldspar, hornblende, sphene, etc. Mineralogy Perthite, biotite, muscovite, aegerine, melanite, sphene, calcite, epidote, oxides, pyrite. Microperthite that grades to antiperthite, pyroxene, biotite, sphene, apatite Perthite, antiperthite, hornblende-biotite-oxide clusters after pyroxene, epidote, sphene, apatite, calcite in brittle veinlets. Perthite, aegirine, sphene, apatite, oxides, hornblende, biotite, chlorite. Perthite, aegirine-augite, biotite, sphene, apatite, oxides. Red-stained perthite, fine granular plagioclase, stilpnomelane after biotite, chlorite after hornblende or pyroxene, leucoxene after sphene. Very coarse feldspar, 7-80% aegirine, sphene. Not described. OB-207 Pinkish-gray, coarse-grained, trachytic, aegirine syenite. OB-212 Coarse-grained, green and pink, trachytic syenite. Deuteric alteration of mafic minerals. LP-1 Pink, coarse-grained syenite with erratic distribution of mafic minerals. Contains a 1-foot-wide dike of melasyenite (biotite pyroxene-carbonate). LP-2 Upper 20 feet, leucosyenite with 75-90° dipping trachytic fabric; rest is pink and green mesocratic syenite with biotite segregations. Not described CD-13 Pink and green, coarse-grained, weakly trachytic syenite with annealed cataclastic texture. Microperthite phenocrysts, pyroxene altered to tabular clusters of biotite plus epidote. Foliated matrix of fine-grained plagioclase. Microperthite, plagioclase, biotite, epidote, melanite, sphene, sericite. CD--4 Linden Satellite Gray, coarse-grained, trachytic, porphyritic syenite with narrow pink and green, fine-grained shear bands. Granoblastic-recrystallized texture in shear bands grades into unsheared rock, contains rolled feldspar phenocrysts. Sheared portions of same mineralogy as unsheared. In unsheared portion, tabular perthite rimmed by granular plagioclase, zoned euhedral aegirine-augite rimmed by pale-green fibrous amphibole. Apatite, chlorite, sphene, allanite, oxides. 122 �Trip 5 – Alkalic plutons Baudette pluton, Lake of the Woods County The Baudette pluton is not exposed, but is seen in a drill core obtained by the Minnesota Geological Survey (hole 1986-CUSMAP-1; Mills and others, 1987). It is located 8 miles south of the town of Baudette, in Lake of the Woods County, and intrudes felsic schists. As judged from geophysical data, the pluton is approximately 1 mile long and half a mile wide, but the best resolution of available geophysics is only 1:250,000 (USGS data in Chandler, 1991). The core consists of coarse-grained, green and pink, porphyritic garnet-biotite syenite. Trachytoid phenocrysts of pink perthite up to 2 cm long with irregular granular borders are in a groundmass of green biotite, melanite garnet, plagioclase, lesser epidote, sphene, and aegirine­ augite, and accessory apatite and zircon or monazite. The brownish-yellow melanite varies from small euhedral crystals to large granular masses enclosed within coarser green biotite. The biotite varies greatly in grain size from fine-grained mats to medium-grained books with a decussate intergrown fabric. MONZODIORITE CLAN The monzodioritic group includes the Side Lake, Morcom, Idington, Lost Lake, and Cook plutons, as well as the Daisy Bay pluton (Sims and Mudrey, 1972), which is shown on Figure 5-1 but not discussed here. All are within the Wawa subprovince, adjacent to the north edge of the Shannon Lake granite phase of the Giants Range batholith (Jirsa and others, 1991). These plutons tend to be irregular in shape and elongate to the northeast, parallel to the regional D2 fabric (Jirsa and others, 1992) of the supracrustal country rocks. The rock is largely pink and green porphyritic monzodiorite, but varies erratically to dark-green pyroxenite and pink granite, granodiorite, and Na-rich trondhjemite. The pyroxenite tends to occur in small irregular pods and segregations, whereas the felsic differentiates occur in thin, straight dikes and in larger segregations. In addition, the monzodiorite group contains minor dark-green poikilitic phases in which antiperthite is grown over pyroxene, sphene, apatite, and hornblende. Porphyritic phases typically have strong trachytoid fabrics, defined by aligned feldspar phenocrysts that are subconformable to the borders but more erratic in the centers of the intrusions. The typical porphyritic phase is characterized by coarse, blocky, pink to gray phenocrysts of Na-rich antiperthite in a groundrnass of predominantly fine-grained euhedral aegirine-augite, along with sphene, perthite, polygonal plagioclase, lesser proportions of hornblende, biotite, apatite, epidote, chlorite, opaque oxides, and rare quartz. Feldspar phenocrysts are typically antiperthitic, but range from albitic plagioclase to strongly perthitic K-feldspar. The normative composition is commonly midway between the K-rich and Na-rich end members in contrast to the compositions implied by point counting, because of difficulties in properly quantifying modal abundances of the strongly exsolved feldspars (Fig. 5-3B). Idington Pluton The Idington pluton is located in west-central St. Louis County near the former village of Idington. Its irregular horseshoe shape, roughly 8 mi2 in size, is elongate to the northeast (Fig. 5-1). Trachytic foliations are predominantly northeast-oriented, subcordant to the pluton boundary, and dip generally more than 70°. However, exposures are limited to central parts of the pluton, where trachytic fabrics are less likely to conform to the pluton shape. The pluton has a rather irregular magnetic anomaly (Fig. 5-1), but the magnetic pattern has been somewhat obscured by a 150-foot-wide, strongly magnetic diabase dike and possibly by late north-trending brittle faults. No contact relationships with country rocks were observed, except at the southwestern edge of the pluton, where it is intruded by the 2,674-Ma Shannon Lake granite of the Giants Range batholith (Jirsa and others, 1991; Boerboom and Zartman, 1993). 123 �Trip 5 – Alkalic plutons Rock types in the Idington pluton are consistent in mineralogy but extremely erratic in modal proportions. Mesocratic, porphyritic pyroxene monzonite predominates, but dark-green aegirine-augite pyroxenite is common, and a small proportion of pink, sodic leucotrondhjemite occurs in aplopegmatite dikes 1 to 10 cm wide in the heart of the pluton. A mappable segregation of leucotrondhjemite exposed at the pluton's northeast corner contains minor flat-lying vuggy fractures lined with purple fluorite and a dark brown translucent tetragonal mineral tentatively identified as zircon or cassiterite. Modal analyses from four samples of the Idington pluton (porphyritic phase-C.551.X, pyroxenite phase­ C.650.A, and two felsic differentiates-C.552.B and C.561.A) are listed in Table 51. In the porphyritic phase, feldspar phenocrysts are mostly gray, rectangular, 1- to 4- cm crystals of coarsely exsolved antiperthite, but small intergrown polygonal grains of plagioclase and perthite also are abundant in the groundmass. Aegirine-augite crystals are prismatic, weakly pleochroic, and zoned with darker green rims. Apatite inclusions are common near the edges of pyroxene crystals. Euhedral, dark-brown sphene is prominent in hand sample and is microscopically associated with biotite. Melanocratic diorite is medium to coarse grained, with trachytically aligned aegirine-augite prisms in a groundmass dominated by fresh, zoned, anhedral plagioclase. Hornblende in this phase occurs as dark-green patches of secondary origin within pyroxene and as larger subpoikilitic grains with inclusions of apatite, pyroxene, and plagioclase. Green biotite forms clusters of euhedral blocky grains aligned parallel to the trachytic fabric. Sphene is mostly euhedral, but locally is subpoikilitic-anhedral and partially encloses pyroxene and other mafic minerals. Accessory minerals include allanite and secondary chlorite, calcite, and epidote. The leucocratic differentiate contains albitic feldspar as large as 40 cm across, which is characterized by graphic Intergrowths with quartz. Aplitic parts of the leuco-phase contain radial-plumose sheaves of albite as long as 3 cm. The erratic distribution between phases, which typifies exposures of this intrusion, can be documented on an outcrop scale to have formed by filter-pressing of a mafic liquid out of a feldsparphenocryst slurry. The groundmass in the porphyry is identical to the melanocratic pyroxenite, which occurs as irregular amoeboid to net-vein segregations as large as several feet. However, at the southwestern end of the pluton, cumulus modal layering is also present in the form of melanocratic layers tens of centimeters thick interlayered with mesocratic, porphyritic diorite. This diorite itself shows layering by changes in phenocryst size and abundance and trachytoid foliation parallel to layering. The layering and trachytic fabric have been drag-folded into widely spaced, crosscutting ductile shear bands, which lack cleavage or schistosity, but instead have an annealed, granoblastic habit similar to that in the Linden pluton. Pink granite pegmatite dikelets (Shannon Lake granite?) commonly occupy these shear planes. In these bands, elliptical deformed relict feldspar phenocrysts are recrystallized into granoblastic aggregates, and the pyroxenes have been replaced by bright-green hornblende. The annealed textures and lack of through-going fabric development imply that ductile deformation, recrystallization, and annealment, caused by self-induced strain during emplacement or the last vestiges of regional deformation, occurred while the rock was still hot. In a series of exposures along Highway 53 at the south edge of the Idington pluton a sharp line of demarcation exists whereby outcrops of Shannon Lake granite have inclusions only of Idington monzodiorite north of an east-west line, and those south of it have inclusions only of granodiorite derived from the Britt pluton, an early, D2-deformed intrusion (Jirsa and others, 1991, 1992). This implies that the earlier intrusive contact of the Idington pluton into the Britt granodiorite was overprinted but preserved by upward stoping of the Shannon Lake granite (Boerboom and Zartman, 1993). Side Lake Pluton The long, arcuate Side Lake pluton, roughly 27 mi2 in dimension, extends eastward from Side Lake in western St. Louis County. The pluton crops out only at its very western and eastern limits. Two exposed satellitic plugs off the eastern tip of the main pluton (Fig. 5-1) are identical in mineralogy to, and 124 �Trip 5 – Alkalic plutons conterminous with, the eastern end of the Side Lake pluton. These satellites have complex intrusive relationships with the country rocks, and are described in a separate section below. The main pluton intrudes metamorphosed basaltic volcanic and felsic sedimentary rocks along most of its length. It is just north of the Shannon Lake granite, but intrusive relationships with the granite are unknown because of lack of exposure. Crosscutting Proterozoic diabase dikes have lowered the magnetism along their length, in contrast to the Idington pluton, where the diabase dikes have enhanced the magnetism. Rocks from the exposures of the Side Lake pluton range from mesocratic biotite-hyperstheneclinopyroxene diorite on the west to hornblende monzodiorite on the east Trachytic fabrics in most outcrops are generally conformable to the margins of the pluton. Segregations of melanocratic pyroxenite to hornblendite occur throughout the intrusion, but are more abundant to the west, where they occur as irregular dikelets, segregations, and small inclusions in mesocratic diorite. In addition, dikes of diorite and pyroxenite up to 150 feet wide, which emanate from the western margin of the pluton, are parallel to the pluton boundary and intrude metabasaltic rocks. These dikes are clearly discordant to the regional metamorphic fabric in the intruded basalts; some of them contain wispy felsic stringers parallel to their walls produced by flow segregation. Thin, straight, late-stage pink granitic to syenitic dikelets are common within and adjacent to the pluton. Mesocratic, medium-grained, pinkish-gray diorite, which predominates at the western end, contains 5-10% tiny euhedral grains of pleochroic pale-pink to green hypersthene, and at least 20% euhedral, palegreen clinopyroxene with light-colored rims. These pyroxenes range in size from less than 1 to 3 mm; the hypersthene is generally finer grained, and the clinopyroxene is variably phenocrystic. Plagioclase is the predominant feldspar. A sample from the pluton 200 feet from the western contact contains strongly zoned, subhedral, trachytic plagioclase, with fuzzy grain boundaries. Another thin section 500 feet from the contact has fine-grained granoblastic plagioclase, orthoclase, and quartz between larger augite phenocrysts. Apatite is abundant as fine-grained euhedral prismatic grains included within pyroxene and feldspar. Oxides occur both within augite as wormy blebs of apparent secondary origin and as scattered blocky, fine-grained crystals. Sphene is rare or lacking at the western end. Brown biotite is a generally minor component at the western end of the pluton, but in some outcrops composes up to 5% of the rock. It locally forms vertically oriented poikilitic plates that are up to 2 cm long and oriented parallel to the trachytic fabric of the monzodiorite. The eastern outcrops consist of moderately heterogeneous, medium- to coarse-grained, pink and green pyroxene-hornblende monzodiorite. Here moderately developed trachytic foliation plunges 2030° to the souL'1west, down the axis of the pluton. Fine-grained, centimeter-sized, angular cognate xenoliths of mafic monzodiorite, in addition to dark-green mafic stringers, are common. Side Lake Pluton Satellites Two small plugs are exposed northeast of the Side Lake pluton. One, about 1/4 mile east of the Side Lake pluton, is round and 3/4 mile in diameter. It consists of medium- to coarse-grained, trachytic, weakly porphyritic, green and pink hornblende-pyroxene monzodiorite. Subhedral 5-mm orange-white antiperthite and scattered 2-mm aegirine-augite phenocrysts are set in a fine-grained groundmass of green prismatic pyroxene, fine-grained anhedral feldspar of unknown composition, minor hornblende, and brownish-green biotite mostly replaced by chlorite. Apatite, biotite, opaques (oxides and pyrite), and sphene each compose about 1% (Table 5-1). Clots and irregular segregations of pyroxenite are common, as are late dikelets of pink syenite up to 10 cm wide which cut across trachytic fabrics. The trachytic fabric is locally variable and inconsistent in orientation, but generally has a shallow southwest plunge toward the main Side Lake pluton. The next satellite is a horseshoe-shaped body, 0.75 mi2 in size, located 1.5 miles east of the Side Lake pluton (Fig. 5-1). Its linear trachytic fabrics are subconformable to the edges of the plug, and again plunge shallowly southwest toward the Side Lake pluton. This small intrusion is highly varied in 125 �Trip 5 – Alkalic plutons texture and mafic content, but dark-green poikilitic diorite and white leucocratic monzodiorite with small inclusions of pyroxenite predominate. The poikilitic diorite has 1-cm, oval-shaped antiperthitic to perthitic poikilitic feldspar with inclusions of aegirine-augite, biotite, sphene, and apatite. The long axes of the poikilitic feldspars and prismatic pyroxenes are parallel and define a primary trachytic fabric. The dark poikilitic phase is sharply cut by sills of the white monzodiorite. However at one location, the two rocks are commingled in a pillow-like fashion that suggests mixing of immiscible liquids. Thus the field relationships, as well as mineralogy, indicate that the dark poikilitic and leucocratic phases are comagmatic. Relationship of Satellitic Intrusions to the Side Lake Pluton Their similar lithological and textural attributes and aligned trachytic fabrics imply that the Side Lake pluton and the two satellites are derived from a common source at depth to the west. Further evidence of comagmatism is the presence of numerous thin anastamosing sills of white monzodiorite, identical to the white phase in the small plugs, which are parallel to the schistosity of the surrounding metasedimentary country rocks and intercalated with them. The intercalated monzodiorite and schist define a mappable unit along a discrete zone (dashed area on Fig. 5-1 that links the two satellitic plugs to the Side Lake pluton. This zone continues past the eastern satellite for at least 2.5 miles, where it merges back into a magnetic anomaly interpreted as another alkalic intrusion (Jirsa and others, 1991). At the intersection of Highway 73 and the Sturgeon River east of the Side Lake pluton, the intercalated monzodiorite and metasedirnentary rocks are transected by a late, north-trending brittle shear zone, which has minimal offset but has reduced the rocks to a fine-grained cataclasite. Morcom Pluton [Thin section CD-7] The Morcom pluton is just north of the Side Lake pluton and may be related to it at depth, because a large positive gravity anomaly underlies the area between the two. The Morcom pluton, which intrudes metasedimentary rocks, has a bulbous shape with a long narrow appendage to the east (Fig. 5-1). Scattered outcrops exist at the eastern limit of the pluton, and a drill core was obtained from the western end, near the north side. Trachytic foliation near the southeast edge dips 80°N, and at the eastern tip plunges 40°SW. In the drill core the foliation dips 40-45°, presumably toward the pluton center. Rock types are similar in the Morcom pluton, the eastern Side Lake pluton and its satellites, and the Idington pluton. However, the major-element geochemistry of the Morcom is very similar to that of the Linden pluton (Fig. 5-5). The drill core consists of multiphase, medium-grained, weakly porphyritic biotite-hornblende-pyroxene monzodiorite, with a trachytoid foliation defined by alignment of plagioclase phenocrysts and prismatic mafic minerals. Dark-green, poikilitic monzodiorite occurs in the core as 15-cm inclusions or layers; small miariolitic cavities lined with fine-grained crystalline biotite, pyroxene, and pyrite are also present. Late brittle slickensided faults and fractures, oriented obliquely to foliation, locally transect the core. Feldspar compositions vary from clean plagioclase with narrow twin lamellae to untwinned plagioclase, and from antiperthite to perthite, the latter confined to anhedral grains in the groundmass. Euhedral, light-green, aegirine-augite has hornblende rims and alteration patches; hornblende is also present as subhedral to prismatic, brownish- to bluish-green grains with patchy color zonation and rare deuteric overgrowths of colorless actinolite. Biotite is dark green and pleochroic, and is associated with hornblende. Accessory minerals include sphene, allanite, apatite, epidote, calcite, and minor secondary oxides within pyroxene. The nonpoikilitic and poikilitic phases have similar mineralogy (Table 5-1). Exposures at the eastern tip of the pluton consist of pink to gray, medium-grained monzodiorite with abundant 5- to 10-cm, elongate xenoliths of foliated felsic to pelitic schist, together with cognate xenoliths of fine-grained melanocratic monzodiorite. Some of the intrusive-breccia xenoliths are themselves an intrusive breccia. Pink monzonitic dikelets are abundant and cut all the earlier intrusive phases and xenoliths. The monzodiorite contains scattered sericitized plagioclase phenocrysts in a fine­ grained groundmass consisting of up to 5% quartz intergrown with granular K-feldspar and plagioclase, 126 �Trip 5 – Alkalic plutons along with hornblende, actinolite, sphene, chlorite, apatite, and minor oxides and secondary calcite. Melanocratic clots are of similar mineralogy but with a higher proportion of mafic minerals. Elsewhere at the eastern terminus, the rock lacks xenolithic inclusions but is still heterogeneous and cut by late, pink felsic differentiates. This inclusion­ free monzodiorite has a trachytic fabric defined by aligned feldspars and mafic clots, and is similar in mineralogy to the core from the western end of the pluton. Lost Lake Pluton (2675.1±0.5 Ma) The Lost Lake pluton, the "pluton southwest of Lost Lake" of Sims and Mudrey (1972), was described as a circular pluton composed of heterogeneous syenite with a local, conspicuously porphyritic facies, a pegmatitic facies with miariolitic cavities, and small bodies of pyroxene­ biotite lamprophyre. They noted that the borders of the pluton tend to be quartzose and contain small angular inclusions of metagraywacke and slate of the Lake Vermilion Formation. Based on detailed remapping, the authors have redefined the shape of the pluton as a long, sinuous and bulbous, northeast-trending body that is 1 mile or less wide but approximately 9 mi2 in size. The eastern tip of the pluton lies 1/4 mile south of Lost Lake, and the western terminus is just south of Angora on State Highway 53, about half a mile north of the Idington pluton (Fig. 5-1). The uniform magnetic signature of the pluton has been lowered locally by late, north-south, brittle faults which have minimal offset. The western end of the Lost Lake pluton is not exposed and its shape is inferred from aeromagnetic data, whereas the central portion is well exposed, and scattered outcrops exist over the eastern end, mainly adjacent to more resistant crosscutting Proterozoic diabase dikes. Two mappable intrusions of quartz monzonite 1/4 mile in diameter occur adjacent to the main body (Jirsa and others, 1991). These small plugs are similar in composition to leucocratic dikes within the main pluton, and are related to the pluton. Subvertical trachytic fabric, which is defined by both phenocrysts and elongate poikilitic feldspar, strikes generally northeast, subparallel to the length of the intrusion. The small, separate bodies of pink monzonite also possess a northeast-oriented trachytic fabric, defined by orbicular clots of biotite, disseminated biotite, or aligned feldspar crystals. The Lost Lake pluton is mineralogically similar to the Idington and eastern Side Lake plutons, but contains a higher proportion of pink leucocratic phases. The main rock types range from pink and green, porphyritic monzodiorite to dark-green, poikilitic biotite-pyroxene monzodiorite to pink monzonite, syenite, and quartz monzonite. Pyroxenite occurs in small segregations, in the same fashion as in the Idington pluton. In general, the poikilitic and porphyritic phases are earliest and are cut by the pink rock varieties. Small dikes of pink granitic pegmatite cut all other rock types, but it is unclear whether these dikes are related to the pluton or are from an external source, such as the Shannon Lake granite of the Giants Range batholith. The pink monzodiorite and syenite differentiates are medium grained, equigranular to weakly porphyritic, and commonly aplitic to pegmatitic, with pyroxene, hornblende, and biotite as the predominant mafic phases. The two small felsic plugs of quartz monzonite to granodiorite contain a mafic mineral assemblage of varied proportions of biotite, chlorite, and hornblende, and up to 30% quartz. The margins of these plugs contain abundant inclusions of felsic volcanic country rocks up to 15 feet across which were clearly deformed prior to incorporation, and small dikes emanating from these plugs cut across fold axes in the supracrustal rocks. One of the plugs contains a unique medium-grained, pink, orbicular granodiorite with trachytically aligned discs of black, concentrically foliated biotite that are as much as 0.5 cm thick and 5 cm long. The biotite orbs which contain intergrown sphene, apatite, plagioclase, quartz, and magnetite, compose as much as 15% of the rock. The orbicular rock grades into a non-orbicular phase with the same proportion of biotite, but as medium-grained, uniformly disseminated flakes. In addition to the typical phases, related rocks in the small plugs include coarse-grained, dark-green biotite-hornblende lamprophyre; green poikilitic monzodiorite; and pink monzonitic pegmatite. 127 �Trip 5 – Alkalic plutons Cook Pluton The Cook pluton (Cook Airport pluton on Southwick, 1993), 1 mile south of the town of Cook (Fig. 5-1), is inferred from aeromagnetic data to be 1.5 mi2 in size, elongate to the east. No outcrops of this pluton are known, but a drill hole in the western margin of the pluton recovered core of uniformly coarse-grained, peppery, dark-greenish-black and light-green, epidote-altered hornblende-biotite diorite. Strong trachytic foliation, which is defined by tabular plagioclase and mafic minerals, dips 50° from horizontal. One fine-grained cognate xenolith, 1 cm x 3 cm in size, is present near the bottom of the 10-foot core. The rock has a primary hypidiomorphic-granular texture, but pervasive, small euhedral crystals of secondary epidote are overprinted on all primary minerals, preferentially in the cores of plagioclase, and as fine-grained granular masses in biotite. Pale-green hornblende is rimmed by green biotite, and zoned plagioclase is clean and well-twinned, despite the pervasive epidote alteration. Accessory minerals include apatite, sphene, oxides, calcite, and interstitial orthoclase. Scattered late, brittle fractures which dip as much as 20° from horizontal are lined with coarse, lineated chlorite, pinkaltered feldspar, and a crust of epidote and white carbonate. The pristine trachytic igneous texture and lack of metamorphic fabric indicate that the pervasive epidotization is the result of deuteric alteration, rather than regional metamorphism. GRANITOID PLUTONS The granitoid group includes the Stingy Lake, Rice River, and Bello Lake plutons, all within the Wawa subprovince. These plutons tend to be oval in shape and elongate to the northeast. Rocks in this group are characterized by substantial quantities of quartz and are vaguely to strongly porphyritic and trachytic. Hornblende is the predominant mafic phase, along with biotite and rare pyroxene. These plutons are considered part of the alkalic group on the basis of their similarity to the other alkalic plutons in size, shape, high Ba and Sr content, magnetic signature, and trachytic fabric. Stingy Lake Pluton The Stingy Lake pluton is a 9 mi 2 circular pluton located 3 miles south of Sturgeon Lake, adjacent to the Giants Range granite, and is inferred to intrude mafic volcanic rocks (Fig. 5-1). Although unexposed, its round shape is well defined by its aeromagnetic anomaly (magnetic rim and nonmagnetic core). A 10-foot drill core was obtained from the northwest side of the pluton (Meints and others, 1993). The intrusion is cut by two Proterozoic diabase dikes. The rock in the core is uniformly coarse-grained, porphyritic, pink granodiorite to quartz monzodiorite. Tabular phenocrysts of string-and-braid microperthite up to 7 mm long, together with weakly zoned plagioclase up to 2 mm long having narrow twin lamellae and weakly sericitized cores, define the 45°-dipping trachytoid foliation. The perthite contains small blocky plagioclase inclusions, and the areas between abutting perthite grains are also stuffed with small blocky plagioclase grains. Lightgray anhedral interstitial quartz with shadowy extinction has been recrystallized into coarse polycrystalline aggregates. Hornblende is mostly altered to green biotite, epidote, and granular oxides; however, fresh, dark-green, euhedral hornblende is locally preserved within quartz and feldspar. Accessory minerals include blocky primary oxides, sphene, zircon, and apatite (Table 5-1). Late closely spaced, vertical brittle fractures lined with epidote and chlorite are pervasive in the 10-foot core. Rice River Pluton The Rice River pluton, about 5 miles west of Cook, intrudes metamorphosed sedimentary rocks. It is inferred to be approximately 15 mi2 in size, although its magnetic signature (Fig. 5-1B) of magnetic rim and nonmagnetic core is irregular and overprinted at the western edge by a north­ trending Proterozoic diabase dike. A drill hole in the magnetic eastern rim of the pluton recovered core of gray, coarse-grained, porphyritic quartz monzonite to monzodiorite. Steeply inclined trachytic foliation is 128 �Trip 5 – Alkalic plutons defined by euhedral, strongly zoned, 1- to 2-cm perthite phenocrysts and small elliptical melanocratic clots that are fine-grained cognate xenoliths. Groundmass to the phenocrysts consists of 3- to 6-mm subhedral microcline, zoned plagioclase, hornblende, and anhedral interstitial quartz; the phenocrysts are rimmed by fine-grained plagioclase and myrmekitic quartz-feldspar intergrowths. Plagioclase grains are heavily sericitized, preferentially in the cores. Hornblende is weakly zoned and slightly altered to biotite, chlorite, and opaques. Euhedral sphene, allanite rimmed by epidote, and secondary calcite occur in minor proportions. Scattered chlorite-pyrite veinlets dip 5-10° from horizontal and occupy brittle fractures; some have slickensides that dip shallowly in the fracture planes. Bello Lake Pluton The Bello Lake pluton (Jirsa, 1990; Jirsa and Boerboom, 1990) is just southwest of the Coon Lake pluton. It is approximately 60 mi2 in size, elongate to the northeast parallel to the regional strike of the mafic to felsic supracrustal rocks that it intrudes. The Bello Lake pluton is unexposed, but three 10-foot drill cores were obtained by the Minnesota Geological Survey, two near the western end, and one near the eastern end of the pluton (Fig. 5-1). The intrusion is magnetically quiet relative to the mafic volcanic rocks around it, but the pluton margins are strongly magnetic locally. As judged from the cores, the Bello Lake pluton is uniform in color and texture, but moderately variable in composition, ranging from pyroxene monzonite to hornblende granite. The pyroxenebearing phase occurs close to the pluton margin, whereas the hornblende monzonite occurs near the center of the pluton at its western end, and the hornblende granite is near the eastern end of the pluton. Data are insufficient to properly judge spatial variation of rock types, but the observed distribution suggests that the pluton may be zoned from a pyroxene-bearing phase at the rim, to a more differentiated, quartz-bearing phase near the center. Pyroxene monzodiorite near the pluton border (KIB-39; Table 5-1) is green and pink, medium grained, and seriate in texture with a strong trachytic fabric defined by rectangular, zoned plagioclase and subhedral, weakly uralitized augite crystals. Accessory oxides, sphene, hornblende, chlorite, biotite, and apatite all formed late in the crystallization sequence, and tend to occur together. Green and pink, medium-grained, slightly porphyritic hornblende monzonite (KIB-40; Table 5-1) on the western side of the pluton contains subhedral-prismatic hornblende and small phenocrysts of grayish-pink, blocky microperthite in an allotriomorphic-granular to weakly seriate groundmass of plagioclase, perthite, and minor quartz. This rock is similar to the pyroxene monzodiorite in hole KIB-39, except that hornblende occupies the position of pyroxene. Hornblende granite from the eastern part of the pluton (drill hole KIB-7; Table 5-1) is characterized by strongly zoned, blocky plagioclase with sericitized cores surrounded by poikilitic microperthite. Myrmekitic feldspar-quartz intergrowths occur along perthite-plagioclase grain boundaries. Quartz is coarse and anhedral interstitial, and hornblende forms dark-green, irregular grains with abundant tiny quartz inclusions near the edges and granular oxide inclusions in the cores. Accessory green biotite, epidote, and chlorite are associated with hornblende as alteration products, and blocky apatite crystals are associated with mafic phases. PETROGENETIC AND GEOCHRONOLOGICAL STUDIES Arth and Hanson (1975), using data on major, trace, and rare earth elements, and isotopic data from the Linden pluton, concluded that the magma formed from 5 to 10% partial melting of a mixed eclogite and garnet peridotite source at mantle depth. Stern and others (1989) believe that the Linden originated by partial melting of a LILE­ enriched mantle peridotite at shallow depths under hydrous conditions created by mantle metasomatism from rapid subduction of oceanic 129 �Trip 5 – Alkalic plutons lithosphere. However, they have lumped the Linden pluton in with the "sanukatoid suite," a very broad suite of rocks of variable size, timing, and associations throughout the Superior Province. The age of D2 deformation of t h e supracrustal rocks at the southern edge of the area from Cook to Side Lake (Jirsa and others, 1991) was bracketed by U-Pb zircon geochronology to between 2,685 and 2,669 Ma (Boerboom and Zartman, 1993). The alkalic plutons lack significant D 2 fabrics, and thus could not have been emplaced until approximately 2,669 Ma. [NOTE: This has been discredited by the new ages of 2681.00±0.29 Ma on the Linden and 2675.1±0.05 Ma on the Lost Lake plutons – Boerboom and others, 2022] The Idington pluton is intruded by a granite pegmatite inferred to have originated from the Shannon Lake granite, which was dated by Boerboom and Zartman (1993) at 2,674 ± 5, or a minimum of 2,669. Catanzaro and Hanson (1971) obtained a discordant Pb207/Pb206 age of 2,740 ± 10 Ma on sphene f r o m the Linden pluton. Prince and Hanson (1972) obtained a similar age of 2,740 Ma, based on a Rb/Sr isochron through apatite and two whole-rock samples. These older ages on the Linden pluton relative to the younger age implied for the ldington pluton indicate that the syenitic rocks may be slightly older than the monzodioritic group, or that pluton emplacement may have progressed from north to south. Clearly, modern high-precision U-Pb zircon dates on the alkalic plutons are needed. [NOTE: Recent age of 207Pb/206Pb 2681.00±0.29 Ma (Boerboom and others, 2022)] CONCLUSIONS The alkalic intrusions in northern Minnesota can be generally subdivided into a syenitic group, a monzodioritic group, and a granitoid group. The syenitic plutons are somewhat north of the monzodioritic intrusions, whereas the granitoid plutons are interspersed with the monzodiorites. Although these groups differ in mineralogy, they are all similar in terms of size, texture, map pattern, geochemistry (e.g., high Ba and Sr), aeromagnetic signature, and timing of emplacement All of the alkalic plutons have porphyritic textures, and the syenitic and monzodioritic plutons typically contain abrupt phase transitions from predominantly mesocratic, porphyritic rocks to dark-green pyroxenites and pink felsic differentiates. The granitoid plutons are more uniform in composition and texture. The plutons are eroded to various levels. The northeastward-elongation and en-echelon map pattern of the Gheen and Lost Lake plutons and the eastern Side Lake pluton and its satellites indicate exposure at high levels, whereas the broad, rounded map shapes of the Linden, Coon Lake, and Bello Lake plutons indicate a deeper level of erosion. The map patterns of the relatively well exposed Side Lake, Idington, and Lost Lake plutons indicate a similar style of emplacement, in which the plutons have penetrated the supracrustal rocks to different levels. The Side Lake pluton plunges to the west, as indicated by the deeper level of erosion at the western end of the pluton and the west-plunging linear trachytic fabrics in the Side Lake satellites. This westward plunge may be either a primary emplacement feature or the result of tilting of the pluton prior to unroofing. Several other plutons of alkalic affinity are suggested by the aeromagnetic data, but they are not exposed and their existence has not been verified by drilling. ACKNOWLEDGMENTS Field work and geochemical analyses for this project were funded by the Minerals Diversification Program administered by the Minerals .Coordinating Committee for the Minnesota Legislature. The Minerals Division of the Minnesota Natural Resources Research Institute (also supported by the Minerals Diversification Program) coordinated the analytical work for several of the geochemical samples. 130 �Trip 5 – Alkalic plutons FIELD TRIP STOPS These stop descriptions are brief – see introductory section for more detail about the individual plutons. Directions: To stop 1: Drive west on Highway 169 to Highway 5 at Chisholm • go ~15 miles north on Hwy. 5 to road 915/McCarthy Beach road the •go west on McCarthy Beach road between Side and Sturgeon Lakes, this turns into Link Lake trail—stay on for a total of ~7 miles to small trail (491988, 5283636) • walk SW on trail ~ 1000’ / 300m and go W-SW to ridge where there are some peeled outcrops. Work your way back NE along top of ridge for more outcrop back to road. Stop 1. (NAD83: 491723, 5283344) (47.70606°, -93.10680°) Side Lake pluton – multiphase Side Lake Pluton ultramafic to felsic. NEXT: Head back east on Link Lake Trail • at about one mile turn left on Beatrice Lake road at sharp bend in trail. • Take Beatrice Lake road ~1.7 miles to intersection with Snake Trail and turn right. • Follow Snake Trail ~2.5 miles to Hwy. 5. • Go right/south on Hwy. 5 for ~1.8 miles. • Go left on Hwy. 65/Perch Lake road for 1.7 miles then • take a left / north on Dean Forest Road (268). • Follow Dean Forest Road (276) ~4.6 miles through a series of jogs to a small road on the right / south (Mud Hole Road # 276). • Drive ~500 feet and park next to knob on the west side of the road (504781, 5284935), go up on outcrop knob to east. Multiple peels. Stop 2. (NAD83: 504781, 5284935) (47.71778°, -92.93625°) Roof zone of Side Lake Pluton. Many dikes of multiphase monzonitic rocks cut high-grade garnet-staurolite-sillimanite bearing metasedimentary rocks of the Lake Vermilion Formation. Some dikes may be unrelated tonalite. One smaller outcrop near road along south edge of knob has 3-5 x 7-15 cm mafic enclaves in quartz tonalite to monzonite. This lies in what is interpreted as the roof zone of the Side Lake Pluton. NEXT: Go back to road # 276 • turn right / east and drive ~3.4 miles to Highway 73. • Turn left / north on Hwy 73 for 4 miles to Hwy. 22 • turn left / west for 3 miles to road 931. • Turn left / south on 931 for 0.5 miles to crest of small hill, outcrop in the east side of road. Stop 3. ***Private Property please be respectful*** (NAD83: 504882, 5290921) (47.77164°, -92.93484°) Morcom Pluton – Monzdioritic intrusive breccia of widely variable grain size bearing many inclusions of different phases of itself that range from intermediate-porphyritic to ultramafic. One thin section was made from this outcrop and in it the mafic phase is dominantly hornblende, in contrast to samples from other parts of the pluton which contain abundant green Na-pyroxene in addition to hornblende. Sphene, magnetite, and apatite are also relatively abundant. This pluton is not well exposed with only a few outcrops in this vicinity on the east end and a drill hole on the west end; extent outlined via aeromag data. NEXT: Head back east to Hwy. 73 • turn left / north for 5 miles to Highway 1 • Turn left / west on Hwy. 1 for 3.4 miles to large outcrop ridge and find a safe place to park... Stop 4. Linden Pluton (NAD83: 504222, 5301045) (47.86273°, -92.94355°) (2681.00±0.29 Ma) Brownish-pink medium- to coarse-grained, strongly foliated, moderately porphyritic pyroxene syenite. Tabular crystals of gray perthite and prismatic dark green pyroxene phenocryst are surrounded by a pink groundmass composed mainly of fine granular albitic plagioclase. The foliation (and weak subvertical lineation), interpreted as magmatic, is defined by the phenocrysts of microcline and 131 �Trip 5 – Alkalic plutons pyroxene, and dips steeply to the northwest parallel to the pluton margin. The syenite also contains cm-scale ellipsoidal ultramafic pyroxenite enclaves that are flattened parallel to the main foliation. Dominantly composed of perthitic alkali feldspar, albitic plagioclase, and dark-green prismatic aegirine-augite (Ac7Wo41En26Fs25, Table 5-3 and Fig. 5-7), with lesser amounts of sphene, apatite, biotite, hornblende, magnetite, and epidote. Relatively coarse reddish-brown titanite/sphene is readily visible in hand sample. Plagioclase is generally restricted to the groundmass as very fine-grained granoblastic grains. In thin section the pyroxene is very fresh, bright green, sub-euhedral, and weakly zoned with roundish lighter green cores. Sphene forms small euhedral crystals, apatite forms thick irregular to subprismatic crystals, and minor proportions of biotite form strongly pleochroic light brown to deep brownish-green irregular books commonly intergrown with or included in pyroxene. Strongly aligned perthitic orthoclase forms blocky-rectangular crystals up to 7mm in length that are commonly Carlsbadtwinned. The groundmass matrix between the orthoclase and pyroxene is composed of fine-grained granoblastic feldspar that appears to have undergone brittle deformation; however within this granulated matrix are pristine pyroxene, sphene, and apatite crystals that show no evidence of shearing or rotation. This coupled with the apparent lack of shear bands on the outcrop implies that the granulation of the groundmass may have occurred during emplacement by semi-plastic deformation during upward flowage of the magma. Just north of the highway at the lowermost east end of this outcrop is an old adit that goes straight into the hillside; not sure as to when or why this was made. NEXT: Head back east on Hwy. 1 to Hwy. 73 • turn left / north for 5.2 miles to Highway 53. • Hang a right (go SW) on Hwy. 53 for 2 miles to where there are outcrops on the northeast side of the road. There is a driveway adjacent to this outcrop (on the north end) that would be a good place to park. Stop 5. ************WATCH OUT FOR TRAFFIC THIS IS A BUSY ROAD************ Gheen Pluton (NAD83: 515162, 5306034) (47.90745°, -92.79711°) The Gheen pluton is a spectacular example of multi-phase magma mingling textures. Strongly and coarsely porphyritic pyroxene syenite grades into, is cut by, and has inclusions of, medium-grained dark green hornblende gabbro to pyroxenite. Pink aplite and pegmatite forms the latest phase as small dikes that cross the other phases, and seems to have preferentially permeated the more mafic phases. Bluish chloritic slickenside surfaces look similar to those in the Linden pluton. The phenocrysts in the porphyritic phase at this stop are composed of braid-textured perthite to antiperthite in a matrix of bluish-green hornblende and prismatic actinolitic amphibole, abundant sphene, magnetite, and apatite, and anhedral to subpoikilitic saussuritized plagioclase. The aphyric mafic phases are composed varied combinations of pale green augite magmatic hornblende, secondary actinolitic amphibole, biotite, and accessory sphene, apatite, magnetite, and calcite. NEXT: Continue southeast on Hwy. 53 for about 14 miles, through the town of Cook, to County Road 467. • Turn left / east for 0.6 miles then veer right to stay on 467. Continue on 467 to railroad crossing; from there go another 0.75 miles to Forest Road 258D • Either drive or walk south on this road for 0.5 mile to an outcrop on the left / east in an overgrown clearcut, next to a logging trail that goes east. Stop 6. Idington Pluton (NAD83: 529108, 5287200) (47.73752°, -92.61175°) 132 �Trip 5 – Alkalic plutons The Idington (eye-ding-ton) pluton as not been dated, but it is intruded by the 2,674-Ma Shannon Lake granite along the southwestern margin of the pluton. This pluton is characterized by its coarsely porphyritic character as dramatically shown at this stop, and the phenocrysts are typically aligned by magmatic flow (trachytoid) in a crystal mush. In places the phenocrysts are randomly oriented, and in others oriented in a circular fashion that implies they were caught in an eddy. The mafic matrix is composed dominantly of aegirine or aegirine-augite and commonly has been squeezed out (i.e. filter-pressed) of the crystal mush to form small to large (10’s of meters) zones of an ultramafic phase. White ‘aplite’ dikes and some larger segregations cut the syenite and pyroxenite phases; these are interpreted as late residual differentiated melts that were squirted around through the semi-solid pluton. Very fine, delicate compositional zonation is visible in some of the phenocrysts here at this stop, where the rock is properly weathered. For a more thorough description of the pluton as a whole refer to the appropriate section of the introduction. The strikingly porphyritic syenite at this stop is typical of the Idington pluton although the phenocrysts are larger than normal. The phenocrysts are composed of perthite / antiperthite and NEXT: Go back north to the main road (467) and head east for 2.25 miles then follow road around bend to north (turns into County road 381) • Continue on 381 for 2.75 miles to Highway 1 • Turn right / east on Hwy. 1 for 3.25 miles to County Road 361 • Turn left / north and drive 1.5 miles to a small flat outcrop in the east ditch. There are also outcrops along the road on the way here one can stop at. Stop 7. Lost Lake Pluton (NAD83: 537263, 5293105) (47.79023°, -92.50248°) 2675.1±0.5 Ma The Lost Lake pluton is an irregularly-shaped intrusion that elongate to the east-northeast. The small outcrop in the road ditch shows mafic pyroxene-rich enclaves in pink syenitic phase. Outcrops nearby in the woods to the east demonstrate many different phases ranging from uniform pink to coarsely porphyritic to dark green and ultramafic. The ultramafic phases/enclaves in the road ditch outcrop are composed primarily of deep green (in thin section) aegirine as small equant to subprismatic crystals, a lesser proportion of larger blocky to subpoikitic biotite, and accessory sphene and apatite in a groundmass of poikilitic calcite (it fizzes) and minor sodic plagioclase. The pink portion is composed of allotriomorphic-granular mosaic of anhedral sodic plagioclase, perthite to antiperthite (commonly poikilitic), prismatic green aegirine, apatite, biotite, and interstitial calcite. At this stop we also will display some drill core from the Lost Lake pluton which demonstrates the multiple phases and diversity within this unit. NEXT: End of trip. Go back south to Highway 1 then east to Highway 169, then south back to Mountain Iron. Thank you for attending. 133 �Trip 5 – Alkalic plutons REFERENCES CITED Arth, J.G., and Hanson, G.N., 1975, Geochemistry and origin of the early Precambrian crust of northeastern Minnesota: Geochimica et Cosmochimica Acta, v. 39, p. 325-362. Barker, J.G., and Arth, J.G., 1976, Generation of trondhjemite-tonalite liquids and Archean bimodal trondhjemite-basalt suites, Geology, v. 4, p. 596-600. Beck, J.W., 1988, Implications for Early Proterozoic tectonics and the origin of continental flood basalts, based on combined trace element and neodymium/strontium isotopic studies of mafic igneous rocks of the Penokean Lake Superior belt, Minnesota, Wisconsin, and Michigan: Unpublished Ph.D. dissertation, University of Minnesota, Minneapolis. Boerboom, T.J., Jirsa, M.A., Southwick, D.L., Meints, J.P., and Campbell, F.K., 1989, Scientific core drilling in parts of Koochiching, Itasca, and Beltrami Counties, north-central Minnesota, 1987-1989: Summary of lithological, geochemical, and geophysical results: Minnesota Geological Survey Information Circular 26, 159 p. Boerboom, T.J., and Zartman, R.E., 1993, Geology, geochemistry, and geochronology of the central Giants Range Batholith, northeastern Minnesota: Canadian Journal of Earth Sciences, v. 30, p. 2510-2522. Boerboom, T.J., Block, Amy Radakovich, Jirsa, M.A., Chandler, V.W., and Peterson, D.M., 2022, Bedrock Geology, pl. 2 of Jirsa, M.A., project manager, Geologic Atlas of Lake County, Minnesota: Minnesota Geological Survey County Atlas C-54, pt. A, 6 pls., scale 1:200,000 Card, K.D., and Ciesielski, A., 1986, DNAG #1. Subdivisions of the Superior Province of the Canadian Shield: Geoscience Canada, v. 13, p. 5-13. Catanzaro, E.J., and Hanson, G.N., 1971, U-Pb ages for sphene in northeastern Minnesota-northwestern Ontario: Canadian Journal of Earth Sciences, v. 8, p. 1319-1324. Chamberlain, K.R., Boerboom, T.J, and Bleeker, W., 2015: 2070 Ma dyke of southern Superior Province: a test of the radiating dyke model for the Kenora-Kabetogama/Fort Frances swarm, in Reconstruction of supercontinents back to 2.7 Ga using the large igneous province (LIP) record: with implications for mineral deposit targeting, hydrocarbon resource exploration, and earth system evolution; Supercontinent.org report number A194, 9 p. Chandler, V.W., 1991, Aeromagnetic map of Minnesota: Minnesota Geological Survey State Map Series S-17, scale 1:500,000. Deer, W.A., Howie, R.A., and Zussman, J, 1966, An introduction to the rock-forming minerals: London, Longman Group Limited, 528 p. Geldon, A.L., 1972, Petrology of the larnprophyre pluton near Dead River, in Sims, P.K., and Morey, G.B., eds., Geology of Minnesota: A centennial volume: Minnesota Geological Survey, p. 153-159. Himmelberg, G.R., 1973, Geologic descriptions of drill core from greenstone belts in northeastern Minnesota: Minnesota Geological Survey Open-File Report Irvine, T.N., and Baragar, W.R.A., 1971, A guide to the chemical classification of the common volcanic rocks: Canadian Journal of Earth Sciences, v. 8, p. 523-548. Jirsa, M.A., 1990, Bedrock geologic map of northeastern Itasca County, Minnesota: Minnesota Geological Survey Miscellaneous Map M-68, scale 1:48,000. Jirsa, M.A., and Boerboom, T.J., 1990, Bedrock geologic map of parts of Koochiching, Itasca, and Beltrami Counties, north-central Minnesota: Minnesota Geological Survey Miscellaneous Map series M-67, scale 1:250,000 / Jirsa, M.A., Boerboom, T.J., Chandler, V.W., and McSwiggen, P.L., 1991, Bedrock geologic map of the Cook to Side Lake area, St. Louis and Itasca Counties, Minnesota: Minnesota Geological Survey Miscellaneous Map Series M-75, scale 1:48,000. Jirsa, M.A., Southwick, D.L., and Boerboom, T.J., 1992, Structural evolution of Archean rocks in the western Wawa subprovince Minnesota: Refolding of pre­ cleavage nappes during D2 transpression: Canadian Journal of Earth Sciences, v. 29, p. 2146-2155. Martin, D.P., Meyer, G.N., Lawler, T.L., Chandler, V.W., and Malmquist, K.L., 1988, Regional survey of buried glacial drift geochemistry over Archean terrane in northern Minnesota: Minnesota Department of Natural Resources, Division of Minerals Report 252, V. 1, 74 p.; V. 2, 386 p. Meints, J.P., Jirsa, M.A., Chandler, V.W., and Miller, J.D., Jr., 1993, Scientific core drilling in parts of Itasca, St. Louis, and Lake Counties, northeastern Minnesota, 1989-1991: Summary of lithologic, geochemical, and geophysical results: Minnesota Geological Survey Information Circular 37, 159 p. 134 �Trip 5 – Alkalic plutons Mills, SJ., Southwick, D.L., and Meyer, G.N., 1987, Scientific core drilling in north-central Minnesota: Summary of 1986 lithologic and geochemical results: Minnesota Geological Survey Information Circular 24, 48 p. Prince, L.A., and Hanson, G.N., 1972, Rb-Sr isochron ages for the Giants Range granite, northeastern Minnesota: Geological Society of America Memoir 135, p. 217-225. Ruotsala, A.P., and Tufford, S.P., 1965, Chemical analyses of igneous rocks: Minnesota Geological Survey Information Circular 2, 87 p. Sage, R.P., 1988a, Geology of carbonatite-alkalic rock complexes in Ontario: ·Poohbah Lake alkalic rock complex, district of Rainy River: Ontario Geological Survey Study 48, 68 p. Sage, R.P., 1988b, Geology of carbonatite-alkalic rock complexes in Ontario: Sturgeon Narrows and Squaw Lake alkalic rock complexes, district of Thunder Bay: Ontario Geological Survey Study 49, 117 p. Sage, R.P., 1988c, Geology of carbonatite-alkalic rock complexes in Ontario: Wapikopa Lake alkalic rock complex, district of Kenora: Ontario Geological Survey Study 52, 63 p. Schmitz, M.D., Bowring, S.A., Southwick, D.L., Boerboom, T.J., and Wirth, K.R., 2006, High-precision U-Pb geochronology in the Minnesota River Valley subprovince and its bearing on the Neoarchean to Paleoproterozoic evolution of the southern Superior Province: Geological Society of America Bulletin, v. 118, p. 82-93. Sims, P.K., and Mudrey, M.G., Jr., 1972, Syenitic plutons and associated lamprophyres: in Sims, P.K., and Morey, G.B., eds., Geology of Minnesota: A centennial volume: Minnesota Geological Survey, p. 140-152. Sims, P.K., Morey, G.B., Ojakangas, R.W., and Viswanathan, S., 1970, Geologic map of Minnesota, Hibbing Sheet: Minnesota Geological Survey, scale 1:250,000. Sims, P.K., Sinclair, D., and Mudrey, M.G., Jr., 1972, Linden pluton: in Sims, P.K., and Morey, G.B., eds., Geology of Minnesota: A centennial volume: Minnesota Geological Survey, p. 160-162. Southwick, D.L., 1993, Geologic map of Archean bedrock, Soudan to Bigfork area, northern Minnesota: Minnesota Geological Survey Miscellaneous Map Series M-79, scale 1:100,000. Stern, R.A., Hanson, G.N., and Shirey, S.B., 1989, Petrogenesis of mantle-derived LILE-enriched Archean monzodiorites and trachyandesites (sanukitoids, in southwestern Superior Province: Canadian Journal of Earth Sciences, v. 26, p. 1688-1712. Streckeisen, A.L., 1973, Plutonic rocks: Classification and nomenclature recommended by the IUGS Subcommission on the Systematics of Igneous Rocks: Geotimes, v. 18, no. 10, p. 26-30. Wirth, K.R., Vervoort, J.D., and Heaman, L.M., 1995, Nd isotopic constraints on mantle and crustal contributions to 2.08 Ga diabase dykes of the southern Superior Province (abstract), Program & Abstracts for the Third International Dyke Conference, Sept. 4-8, 1995, Jerusalem, Israel, A. Agnon, G. Baer, 84, 1995. 135 �Trip 6 – Colvin Creek FIELD TRIP 6 Unique Keweenawan Inclusion (Colvin Creek) in the Duluth Complex Mark Severson (retired)1,2, Allison Severson3 and Laurie Severson (retired)4 1 (1988–2012) Natural Resources Research Institute, University of Minnesota, Duluth, 5013 Miller Trunk Hwy, Duluth, MN 55811 2 (2013–2018) Previously Teck American, then Teck Resources Unlimited, now NewRange (joint venture between Teck and PolyMet Mining Inc.) 3 Minnesota Geological Survey, College of Science and Engineering, University of Minnesota, 2609 Territorial Road, St. Paul, MN 55114 4 Earth Science Teacher, Woodland Middle School, ISD 709, Duluth, MN 55811 In memory of Richard Patelke 1957-2011 “Well, it ain’t my truck” 136 �Trip 6 – Colvin Creek INTRODUCTION Magnetic basalt inclusions within the Duluth Complex were first described by Bonnichsen (1974). Most of that description pertained to limited outcrops in what is now informally referred to as the South Colvin Creek Hornfels (Fig.6-1). Later, Tyson (1976) looked at four basalt inclusions including three nonmagnetic basalt inclusions in railroad cuts to the north, as well as the South Colvin Creek Hornfels. He concluded that the South Colvin Creek Hornfels was different and theorized that the magnetic basalts were derived from weathered and oxidized basalt flows, correlative with the North Shore Volcanic Group, and metamorphosed by the Duluth Complex. This field trip will visit the North Colvin Creek Hornfels (NCCH), shown in Figure 6-1, which is better exposed, contains several internal mappable units, and was first described by Severson and Hauck (1990). There they found a unique very fine-grained and cross-bedded unit, of gabbroic composition, within the inclusion. They initially theorized that the NCCH was formed as a result of magmatic currents (a concept they no longer support). It was also theorized that the cross-bedded unit represents a portion of a shear zone (Ojakangas and Holst, pers. com., sited in Patelke (1996)). This theory is also no longer deemed viable. Lastly, Patelke (1996) mapped and described the NCCH in more detail and proposed that it was an inclusion containing both metavolcanic and metasedimentary rocks that can be correlated with the North Shore Volcanic Group. This field trip will visit the NCCH which is referred to simply as the Colvin Creek Inclusion for the remainder of this guide. The thesis by Patelke (1996) is the source of almost all of this guide. GEOLOGIC SETTING The Colvin Creek inclusion is a large inclusion (2,500 X 800 meters), associated with a magnetic high, that has been rotated to a near vertical position and exhibits stratigraphic tops to the northwest as defined by pipe amygdules, sheeted amygdules, local convoluted flow bases and flow tops, and crossbedding. Patelke (1996) subdivided the inclusion into five major mappable units that include: two granoblastic, fine-grained metavolcanic units; two gabbroic sill units that bound the inclusion on the north and south; and a 350-meter-thick, cross-bedded, granoblastic, fine-grained metasedimentary unit of gabbroic composition. Overall, the inclusion strikes about N60°E with dips of 70-90° to the northwest. The entire inclusion has been metamorphosed to pyroxene grade facies and rotated to a subvertical position by the Duluth Complex. According to Miller and Severson (2005), the Colvin Creek inclusion is situated near the bottom of a “heterogeneous upper troctolitic cumulate” of the Partridge River intrusion (PRI). Geochemical work by Patelke (1996) indicate that metamorphism of the magnetic metabasalt units was isochemical and that they are probably equivalent to intermediate olivine tholeiites of the North Shore Volcanic Group (NSVG). The metasedimentary rocks are more problematic in that they are not analogous to any of the interflow sandstones of the NSVG as described by Jirsa (1980, 1984). At about 350 meters thick they are as thick as the total measured section of the NSVG interflow sedimentary rocks and show: no rock fragments; NO quartz, no conglomeratic horizons, and no intercalated volcanic rocks. Patelke (1996) suggested that the cross-bedded rocks were most likely deposited in a restricted basin as an eolian sediment that was derived from a strictly basaltic terrain – thus no quartz. Similar inclusions of crossbedded sediments with a gabbroic composition have been found at six locations within the Duluth Complex (i.e., geologic maps of the Babbitt SE and Babbitt SW quadrangles). Patelke (1996) thought that the informal “Phantom Lake sandstone,” an inclusion in the Whyte Quadrangle to the north of Two Harbors, was the most similar to the sediments in the Colvin Creek inclusion. While Patelke (1996) felt that these two units were similar, he concluded that neither of them can be strictly correlated with any other of the interflow sandstones in the Keweenawan system. 137 �Trip 6 – Colvin Creek Figure 6-1. Generalized geologic map of a portion of the Partridge River intrusion showing locations of the Colvin Creek Hornfels inclusions (gray) relative to the known Cu-Ni deposits. Base map from Miller and others (2001). GEOLOGY OF THE COLVIN CREEK INCLUSION Patelke (1996) mapped six major units associated with the Northern Colvin Creek Hornfels inclusion (exposed in Sections 27, 28, 33, and 34, T.59N., R.13W.). These units are briefly described below, and their distribution is shown in the geology map of Figure 6-2. The six units are, from south to north (also stratigraphically younging to the north) labeled as: MCC, AMG, AA, XBB, and GOG. These names are acronyms for field textures observed by Severson and Hauck (1990), and while these are not appropriate rock names, Patelke (1996) retained them in his thesis. MCC (Massive Colvin Creek unit) The MCC unit is a plagioclase-augite-oxide (titanomagnetite>ilmenite) rock, with local orthopyroxene and/or olivine, that under Phinney’s classification system (1972) is an oxide-bearing gabbro to augite troctolite. The MCC displays a massive, fine- to medium-grained texture similar to the units that stratigraphically overlie it but also shows primary decussate igneous texture. It is variably ophitic, and locally porphyritic. Granoblastic triple point junctions are reasonably well developed where the feldspar is 138 �Trip 6 – Colvin Creek Figure 6-2. Geology of the Northern Colvin Creek inclusion from Patelke, 1996. equant. Locally, there are ovoid clots of granular plagioclase that could be interpreted as amygdule infillings. The bottom contact of the MCC unit is not exposed. The upper contact with the AMG unit consists of rock types attributable to both MCC and AMG units within a 3-meter zone. For this reason, Patelke (1996) suggests that the MCC was injected sill-like and was mixed into the AMG while both were in a plastic state. Unfortunately, this particular exposure will not be visited during this trip. AMG (Amygdaloidal Gabbro unit) The AMG is stratigraphically above the MCC unit and is interpreted to be a subaerial metavolcanic unit with recrystallized amygdules. The rock is classed as an oxide melagabbro to augite troctolite. In the vast majority of the exposures, it is fine- to medium-grained and composed of plagioclase, augite, and oxide (titanomagnetite>ilmenite) with local orthopyroxene and poikilitic olivine. The AMG unit shows a persistent fine-grained, polygonal-granoblastic, sugary texture. In a few instances this texture is interrupted by clusters of plagioclase and by rounded to amoeboidal clot-like segregations of augite; both of which are lengthened parallel to the overall strike of bedding. These layers of pyroxene-rich segregations are interpreted to be recrystallized amygdules within relict volcanic flowtops. In areas of outcrop with common pyroxene-rich layers, the spacing of layers indicates flow thicknesses of 0.5 to 3.5 meters. The upper contact with the AA unit is exposed in only one outcrop (Fig. 6-3 - not visited this trip) wherein a black pyroxenemagnetite rich convoluted flowtop of the AMG is overlain by the base of a flow in the AA unit. 139 �Trip 6 – Colvin Creek Figure 6-3. Contact between the AMG (bottom, dark) and AA (top, light) units. The dark portion of the image is related to increased pyroxene and oxide content and interpreted to be a rubbly flow top that is abruptly overlain by the AA unit. MGC (Medium-Grained Gabbro unit) The MGC is a sill of very limited extent in the SW end of the Colvin Creek inclusion (Fig. 6-2). The rock is a medium- to coarse-grained orthopyroxene-bearing anorthositic gabbro according to the classification system of Phinney (1972). The sill crosscuts only the AMG unit, exhibits apparent chilled margins, and is estimated to be about two meters thick. Exposures of this unit will not be visited. AA (Amoeboidal Augite unit) The AA unit overlies the AMG unit and is also a fine- to medium-grained, massive, granoblastic magnetic basalt unit. At the outcrop scale, the AA is distinguished from the AMG by increased amounts pyroxene-filled avoids (amygdules) and by elongate pyroxene segregations that are interpreted as recrystallized pipe amygdules. Petrographically, the AA and AMG are very similar. Mineralogy consists of plagioclase, diopsidic augite, and titanomagnetite>ilmenite with local orthopyroxene (a major constituent in one outcrop). Plagioclase has a bimodal grain distribution consisting of fine-grained equant to stubby grains (0.25-1 mm) and patchy distributed laths (2-7 mm). The modal layering within this unit is defined by pyroxene stringers and ovoid clots that are interpreted to define both lava flow bases and amygdaloidal tops. Individual flows range from 0.5 to several meters thick. Elongate pyroxene masses lying perpendicular to strike are thought to be recrystallized pipe amygdules near the flow base (Fig. 6-4). 140 �Trip 6 – Colvin Creek Figure 6-4. Two flow units in the AA unit. Base of a single flow (6 inches to left of hammer head) with recrystallized, coalescing upward-trending pipe vesicles. Black wavy lines in extreme upper right of photo is the base of a third lava flow. The location of this outcrop is not documented. “Pyroxene interval” At the very top of the AA unit is a 0-2 meter thick, black, melagabbro unit, or “pyroxene interval” as mapped by Patelke (1996) in a few scattered outcrops. This unit consists of fine- to coarse-grained ferrosalite pyroxene and plagioclase. At one locality this unit contains: 1-10% brown garnet, 2-5% ilmenite>>titanomagnetite, and trace amounts of cordierite and hercynite. At one exposure (Fig. 6-5 – to be visited), there are several “veins” of potassium feldspar masses (up to 20-40 cm long by 1-10 cm wide), or tension gashes according to Patelke (1996). These “veins” are perpendicular to, and truncated by, the upper contact with the overlying XBB unit. The base of the XBB unit often exhibits a trough-like morphology downwards towards these feldspar masses. At several locations where this “pyroxene interval” is present, Patelke (1996) thought that there was some evidence of left-lateral tectonic movement. The tension gashes are one of his lines of evidence. Overall, Patelke (1996) thought that the “pyroxene interval” represents a deeply weathered flow top or soil developed on the AA unit and the effects of faulting are secondary. 141 �Trip 6 – Colvin Creek At another outcrop along the contact between the AA and XBB units (Stop 5 - to be visited), the “pyroxene interval” is absent. In its place are several sigmoidal-shaped pyroxene-rich lenses. Patelke (1996) thought that these lenses were developed along a bedding parallel fault. Figure 6-5. “Pyroxene Interval” (bottom 2/3rds of photo) between the AA and XBB units. Note convolute contact and k-spar-filled “tension gashes” as described by Patelke (1996). Figure 6-6. Typical cross-bedding exhibited by the XBB unit in a flat-laying outcrop. 142 �Trip 6 – Colvin Creek XBB (Cross-Bedded Belt) To the north of, and overlying the magnetic basalt units, is the Cross-Bedded Belt unit of roughly gabbroic composition. The rock is composed of fine-grained (1mm average) plagioclase-diopsideorthopyroxene-titanomagnetite>ilmenite with minor amount of orthopyroxene, hematite, hercynite, and geikielite. The rock exhibits beautiful bedding, cross-bedding (Fig. 6-6), density graded modal layering, and concave upward cross-beds along with scour and fill structures. Throughout the unit are localized minor biotite. There are several intervals, 0.5-3.0 meters thick, that are located near the base of the XBB that contain poikiloblastic pyroxene, up to several inches long (Fig. 6-7) that appear to have grown along bedding planes. The density graded modal layering consists of oxide- and pyroxene-rich basal layers grading upward into plagioclase-rich layers. Grain size for any individual mineral (1 mm) remains constant throughout the bed thickness. Angles of bedding and cross-bedding change over short distances in most outcrops. In some areas, the bedding exhibits a weak convolution or deformation (Fig. 6-7); possibly due to either soft sediment deformation and/or partial melting by the Duluth Complex. GOG (Gabbro-Olivine Gabbro unit) A gabbro to olivine gabbro unit, labelled as GOG, bounds the Colvin Creek inclusion at its upper (northwest) contact. The GOG was classed as a unit of the inclusion because it contains contact parallel layering (as does the inclusion) and shares strike-length and general tabular form with the other units of the inclusion. The GOG is medium to coarse-grained and composed of plagioclase (37-72%), augite (9-42%), olivine (0-23%), ilmenite (3-12%), and titanomagnetite (2-8%). The GOG unit is best exposed at the northwest end of the Colvin Creek inclusion where four contact-parallel zones were described by Severson and Hauck (1990) and by Patelke (1996). These zones (Fig. 6-2) are: A. weakly modally layered granular-textured augite troctolite zone with a plagioclase foliation B. phenocryst-rich gabbroic zone with anorthositic inclusions up to 5 inches across; C. a zone of heterogeneous gabbroic rocks with local inch-scale layering and cross-bedding (Fig. 6-8) indicative of magmatic currents; and D. a zone of anorthositic gabbro grading upward to gabbro with olivine gabbro interbeds. The trend of all of these zones parallel the contact trends of the underlying Colvin Creek inclusion. Unfortunately, this unit is too far away to bushwhack to Figure 6-7. Poikiloblastic pyroxene (black squares) in XBB unit. Note strange gain access and convolutions of bedding. visit during this trip. 143 �Trip 6 – Colvin Creek Common Characteristics of Colvin Creek Hornfels Listed below are characteristics common to all rock types of the Colvin Creek Hornfels: • All of the units are strongly magnetic and microscopically exhibit polygonal/granoblastic triple point junctions • Thin veins and later pods of pyroxene and/or massive magnetite are locally common. They are arranged in both parallel sets and discontinuous cross-cutting stringers • Thin, brown hornblende and/or orthopyroxene rims around titanomagnetite are commonly seen in thin-section • Sericitized plagioclase is seldom seen • Olivine, where present, is usually fresh and never serpentinized • Biotite is generally absent except in the XBB just above the “pyroxene interval” • The titanomagnetite is titanium-rich and the ilmenites are magnesium-rich. Figure 6-8. Rhythmic layering in GOG unit (subzone C) consisting of alternating olivine-rich and olivinepoor layers. Upper massive gabbro (hammer) truncates bed sets. FIELD TRIP STOPS Access starting from Mountain Iron will be heading south on Highway 53 through Virginia. Shortly after crossing the Tony Rukavina Bridge, over the Rouchleau Mine, turn and head east on Road 135 through the towns of Gilbert, Biwabik, and Aurora. Within Aurora, turn right at the stop sign and head south on CSAH 100, cross the railroad tracks, proceed to a stop sign and turn left on CSAH 110. Proceed to Hoyt Lakes on this highway. Within Hoyt Lakes continue straight through two stop signs and head out of town on Highway 110 (also called Skibo Vista Road). for about 4 miles. Just after passing the Bird Lake Recreation area, turn left onto road UT9235 (also called 569/Skibo Rd). Proceed down this road about 2.7 miles, cross the railroad tracks and continue east for another 1.9 miles. Turn left (north) on forest road 113 (yellow “share the road” sign at this intersection). Go 5.9 miles north on 113 to an unmarked logging road (another yellow ”share the road” sign at this intersection). Turn left on unmarked logging road (Figure 69) and head west about 1.5 miles depending on road conditions. Turn vehicles around, park as best as possible, and walk about 0.2 miles to the west (through an old beaver pond) to the first stop. Locations of the trip stops are shown in Figures 6-9 and 6-10. 144 �Trip 6 – Colvin Creek Figure 6-9. Access to Colvin Creek hornfels area and trip stops via remote logging road. Figure 6-10. Field trip stops (black dots) relative to mapped geology (modified from Patelke, 1996). 145 �Trip 6 – Colvin Creek Stop 1: MCC (Massive Colvin Creek unit) (NAD83: 577246E/5268002N) (47.56084°, -91.97315°) The MCC unit at this exposure is enigmatic. The rock is massive, lacks modal layering and regular concentrations of minerals. It is classed as a gabbro to augite troctolite composed of plagioclase, augite, orthopyroxene, olivine, and oxide (titanomagnetite>ilmenite). It is fine- to medium-grained with granoblastic triple point junctions. Locally, there are clots of granular plagioclase that could be interpreted as amygdule infillings, as in the overlying basaltic units. However, the MCC also displays primary decussate igneous textures, is variably ophitic, and locally porphyritic. For this reason, the distinction between the MCC and overlying AMG are often unclear. Patelke (1996) felt that the portions of the MCC were injected sill-like into the base of the inclusion while they were both in a plastic state. Directions: Continue down the road for about 2 minutes to a flagged trail off to the north. Follow the trail for another 5 minutes to Stop 2. Stop 2: AMG (Amygdaloidal Gabbro unit) (NAD83: 577230E/5268130N) (47.56199°, -91.97334°) At first glance, the AMG unit at this exposure is similar to the previous stop in that it consists mostly of massive, fine- to medium-grained “oxide gabbro.” However, within this exposure are several localized dark-gray, very fine-grained internal patches of basalt, that contain unquestionable plagioclasefilled amygdules. These patches exhibit gradational contacts with the surrounding medium-grained “oxide gabbro.” Thus, both fine-grained basalt and medium grained “gabbro” are present here (best seen after peeling a large area of the exposure). It is unknown whether these basalt patches represent true inclusions or are remnant unmetamorphosed patches in a rock that has undergone various degrees of partial melting to produce the “gabbroic” portions. Directions: Return to fork in flagged trail and continue north a few minutes to Stop 3. Stop 3: AA (Amoeboidal Augite unit) (NAD83: 577094E/5268083N) (47.56159°, -91.97515°) The AA unit overlies the AMG unit and is also a fine- to medium-grained, massive, granoblastic magnetic basalt unit. At the outcrop scale, the AA is similar to the AMG except for zones that contain common pyroxene-filled ovoids (recrystallized amygdules) and by pyroxene-rich horizons that are interpreted as sheeted amygdules and/or flow tops. Petrographically, the AA and AMG are very similar. Mineralogy consists of plagioclase, diopsidic augite, and titanomagnetite>ilmenite. Several basalt flows can be distinguished in portions of this outcrop based on massive flows grading upward (northward) into amygdule-rich basalt that in turn grades into pyroxene-rich flow tops. Individual flows range from over several meters to less than one meter thick. Note the presence of a cluster of coarse-grained pyroxene with minor K-spar (similar features will be seen at stop 6). Directions: Return to road and proceed further west for about 1-2 minutes to another flagged trail leading to the north. The Stop 4 exposure is about 100 feet north of the road on this trail. Stop 4: XBB Unit (Cross-Bedded Belt) (NAD83: 577065E/5268019N) (47.56101°, -91.97555°) To the north of, and overlying the magnetic basalt units, is the Cross-Bedded Belt unit of roughly gabbroic composition. This is the first of several exposures of the XBB unit that will be viewed during this trip. The rock is composed of fine-grained (1mm average) plagioclase-diopside-orthopyroxenetitanomagnetite>ilmenite. The rock exhibits beautiful bedding, cross-bedding, density graded modal layering, and concave upward cross-beds along with scour and fill structures. Note that NO quartz has ever been noted in this unit! 146 �Trip 6 – Colvin Creek There appears to be small-scale convolutions in the bedding trends that may be related to either soft-sediment slump or folding during intrusion of the Duluth Complex and subsequent rotation of the Colvin Creek inclusion. The location of this exposure along a curved mapped contact (Fig. 6-9) suggests that there is a small open fold between the AA and XBB units as suggested by Patelke (1996). Directions: Return to the road and head 3 minutes to the west to Stop 5 (about 50 feet north of the road). Stop 5: Contact of XBB and AA units (below photo) (NAD83: 576907E/5267935N) (47.56028°, 91.97767°) Both the AA and XBB units are present in this exposure. At the southern end of the exposure is a massive basalt unit that grades upward (northward) into a rock that contains abundant pyroxene-filled amygdules, which in turn, contains several pyroxene-rich lenses that represent sheeted amygdules and flow tops. Several flows are defined in the outcrop and the contact with the XBB unit is well defined (see Fig. 6-11). The overlying XBB unit consists of a fine-grained gabbroic rock with bedding planes similar to the previous stop but actual cross-bedding is not as striking. In regard to the contact between the two units, the intervening “pyroxene interval” is largely absent except for thin irregular pyroxene-rich lenses that display sigmoidal shapes. Patelke (1996) thought that sigmoidal-shaped pyroxene-rich lenses were developed along a bedding parallel fault with left-lateral movement. At the extreme north end of the exposure is an irregular, cross-cutting, massive oxide vein up to 3 inches wide. Figure 6-11. Contact between AA (left) and XBB (right) units with very poorly defined “pyroxene interval” in the contact zone. Note sigmoidal shapes of pyroxene layers at the contact. To the left of the contact (not in photo) are 2-3 trough-shaped zones (less than 2x3 feet) that contain bedded sediments similar to the XBB unit. Whether these zones are sedimentary interbeds or enfolded patches is unknown. 147 �Trip 6 – Colvin Creek Directions: Return to the road and proceed further west for about 10 minutes to Stop 6 on the southern edge of the road. On the way to Stop 6 there are numerous pavement road-crop exposures that consist mostly of massive magnetic basalt with local amygdules. Stop 6: AA (Amoeboidal Augite Unit) (NAD83: 576560E/5267549N) (47.55684°, -91.98234°) This outcrop is situated about 2,000 feet down the road from Stop 5 and serves more as a rest and regrouping stop. At this locale, the unit is massive and grades upwards (toward the road) into typical amygdaloidal basalt. Directions: Proceed down the road 350 feet and follow a flagged trail through the woods for about 840 feet westward (10 minutes). Stop 7: Contact of XBB & underlying AA unit (NAD83: 576259E/5267482N) (47.55628°, -91.98636°) This is the best exposure of “pyroxene interval” along the contact (see Figure 6-5 and description in text). Perpendicular to the contact, and wholly within the “pyroxene interval,” are at several “vein-like” potassium feldspar veins (up to 20-40 cm long by 1-4 cm wide) and a mass about 4 ft long by 1.5 ft wide. Patelke (1996) felt that the veins are tension gashes formed by lateral movement along the contact. The contact between the XBB and “pyroxene interval” exhibits some folding (soft-sediment?) with small-scale V-shaped troughs projecting downward into the “pyroxene interval.” Some of these troughs exhibit truncated bedding of the XBB against the “pyroxene interval” At one of the “V’s”, biotite, garnet and cordierite have been identified by Patelke (1996). At the extreme east end of the exposure, it appears that a bed of the XBB is folded(?) downward into the “pyroxene interval.” Patelke (1996) thought that the “pyroxene interval” represents a deeply weathered flow top or soil developed on the AA unit. Directions: At the west end of the Stop 7 exposure proceed northward for short distances (<100 feet) to several outstanding outcrops of the XBB unit of Stop 8. Stop 8: XBB Unit (Cross-Bedded Belt) (NAD83: 576248E/5267546N) (47.55685°, -91.98649°) Numerous exposures of beautifully cross-bedded XBB unit are present on the top of this hill. The rock is a very fine-grained granoblastic rock with a general modal composition of oxide-bearing anorthositic gabbro to gabbroic anorthosite. It is composed of plagioclase, diopsitic augite, and various iron-titanium-manganese oxides making up to 8-15% of the rock, NO quartz has ever been documented. As shown in Figures 6-6, 6-7 and 6-11, the rock is bedded and cross-bedded, exhibits density graded modal layering, concave upward cross beds, and scour and fill features. Some of the cross-beds show an unusually high angle of repose over very short distances possibly related to the environment of deposit (aeolian). 148 �Trip 6 – Colvin Creek Figure 6-12. Classic exposure of the XBB unit. Bedding tops to the north (right). Directions: Return to Stop 7 and proceed west for about 5 minutes to large exposures of the XBB and AA units. Note that between stops 8 and 9 is a glacial erratic of the GOG unit with stupendous inch-scale layering. This erratic is a good example of the GOG unit (otherwise inaccessible on this field trip). Stop 9: AA (Amoeboidal Augite Unit) (NAD83: 576167E/5267425N) (47.55578°, -91.98759°) After crossing over a large outcrop of the XBB unit, proceed southward a short distancer to a large tip over exposure (uprooted and wind-fallen tree) of the AA unit consisting of multiple basalt flows with ropey tops. This outcrop is present near the upper contact of the unit and small exposures of the XBB are present to the north and west. Pipe vesicles are present in one small area of the AA unit. Also present is a very small exposure of the “pyroxene interval.” Directions: Return to vehicles. Return to Mountain Iron Community Center (47.51869°, -92.58997°). References Bonnichsen, B., 1972, Southern Part of the Duluth Complex. In: Sims, P.K. and Morey, G.B. (eds), Geology of Minnesota – A Centennial Volume, Minnesota Geological Survey, p. 361-388. Jirsa, M.A., 1980, The Petrology and Tectonic Significance of Interflow Sediments in the North Shore Volcanic Group, Northeastern Minnesota, unpublished M.S. Thesis, University of Minnesota Duluth, 125 pages. Jirsa, M.A., 1984, Interflow Sedimentary Rocks in the Keweenawan North Shore Volcanic Group, Northeastern Minnesota: Minnesota Geological Survey, Report of Investigations 30, 20 p. 149 �Trip 6 – Colvin Creek Miller, J.D., Green, J.C., Severson, M.J., Chandler, V.W., and Peterson, D.M., 2001, Geological map of the Duluth Complex and related rocks, Northeastern Minnesota; Minnesota Geological Survey, Miscellaneous Map M119, scale 1:200,000. Miller, J.D., Jr. and Severson, M.J., 2002, Geology of the Duluth Complex in Miller, J.D., Jr., Green, J.C., Severson, M.J., Chandler, V.W., Hauck, S.A., Peterson, D.M., and Wahl, T.E., 2002a, Geology and mineral potential of the Duluth Complex and related rocks of northeastern Minnesota: Minnesota Geological Survey Report of Investigations RI-58, p. 106-143. Miller, J.D., Jr. and Severson, M.J., 2004, Geology and Mineralization of the Western Contact of the Duluth Complex, Partridge River and South Kawishiwi intrusions, Northeastern Minnesota: Institute on Lake Superior Geology, 50th Annual Meeting, Duluth, MN, Part II: Field Trip Guidebook, p. 227-258. Miller, J.D., Jr. and Severson, M.J., 2005, Patelke, R.L., 1996, The Colvin Creek Body, A Metavolcanic and Metasedimentary Mafic Inclusion in the Keweenawan Duluth Complex, northeastern Minnesota: unpublished M.S. Thesis, University of Minnesota, 232 p. Phinney, W.C., 1972, Duluth Complex, history and nomenclature, in Sims, P. K., and Morey, G. B., eds., Geology of Minnesota: A Centennial Volume: Minn. Geol. Survey, pp. 333-334. Severson, M.J., and Hauck, S.A., 1990, Geology, geochemistry, and stratigraphy of a portion of the Partridge River intrusion: Natural Resources Research Institute, University of Minnesota-Duluth, Technical Report, NRRI/GMIN-TR-89-11, 236p. (with plates). Tyson, R. M., 1976, Hornfelsed Basalts in the Duluth Complex: unpublished M.S. Thesis, Cornell University, Ithaca, New York, 85 p. 150 �Trip 7 – Classic Outcrops FIELD TRIP 7 Classic Outcrops of Northeastern Minnesota Dean M. Peterson1 and George J. Hudak2,3 1 Big Rock Exploration, 2505 W. Superior St., Duluth, MN 55806 George Hudak Geosciences P.L.L.C., Duluth, MN 55804 3 Department of Earth and Environmental Sciences, University of Minnesota Twin Cities, 116 Church Street SE, Minneapolis, MN 55455 2 Introduction This field trip will investigate a wide variety of Neoarchean, Paleoproterozoic and Mesoproterozoic rocks that illustrate the diversity of Precambrian rocks in northeastern Minnesota. The field trip is an updated version of “Field Trip 5 – Classic Outcrops of Northeastern Minnesota” that was run during the 50th Annual Meeting of the Institute on Lake Superior Geology that took place in Duluth, Minnesota during May, 2004. As such, several of the field trip stop descriptions in this guidebook are derived from this earlier field trip guide, with updates based on recent geological studies. Generalized Stratigraphy of Northeastern Minnesota Neoarchean Vermilion District Supracrustal rocks in the Vermilion district consist of volcanic-dominated stratigraphic sequences of the Wawa-Abitibi Terrane within the Superior Province of the Canadian Shield. Rocks of the WawaAbitibi Terrane in northern Minnesota are divided on the basis of stratigraphic and structural setting into: (1) the Soudan belt, to the south, and (2) the Newton belt, to the north (Jirsa et al., 1992; Southwick et al., 1998). The boundary between these contrasting structural panels can be traced geophysically across the width of Minnesota and was informally designated the Leech Lake structural discontinuity (Jirsa et al., 1992). In the region west and north of the Lake Vermilion State Park, the Leech Lake structural discontinuity occurs along the Mud Creek shear zone (Hudleston et al., 1988), small segments of the Vermilion and Wolf Lake faults (Sims and Southwick, 1985), and the Bear River fault (Jirsa et al., 1992). A simplified regional geological map of the Neo-Archean terranes of northeastern Minnesota and adjacent Ontario is presented in Figure 7-1. The Soudan belt (Figures 7-1 and 7-2) contains large, broad folds involving calc-alkalic and tholeiitic volcanic strata overlain by, and locally interdigitated with, turbiditic rocks. In contrast, the Newton belt consists of elongate, northeast-trending, and mostly northward-younging volcanic and volcaniclastic sequences. Volcanic rocks of the Newton belt differ from those of the Soudan belt in containing locally abundant komatiitic flows and peridotitic sills. The two belts are fault-bounded, and the relationships between stratigraphic units within each belt are largely conformable (although faults obscure contacts locally). In its eastern extension, the Soudan belt is continuous with the Saganagons assemblage in Ontario and terminates against the Saganaga pluton and Northern Light Gneiss. The Newton belt extends discontinuously eastward into the Shebandowan District of Ontario to form the Greenwater and Burchell assemblages. Intrusive rocks in both belts vary from gabbroic and felsic porphyries demonstrably related to volcanism, to large plutons emplaced post-tectonically. Both districts contain unconformable, Timiskaming-type sequences composed of calc-alkalic volcanic rocks, conglomerates, and finer grained sedimentary rocks. Lithostratigraphic units in the western Vermilion district (Table 7-1) include: (1) the Lower member, Soudan Iron-Formation member, and Upper member (Upper Ely) of the Ely Greenstone 151 �Trip 7 – Classic Outcrops Figure 7-1. Simplified correlation map of Neoarchean assemblages in Minnesota and northwestern Ontario (after Peterson et al., 2001). Inset map illustrates location of the Wawa-Abitibi Terrane in Minnesota and northwestern Ontario (Stott et al., 2007). The Leach Lake structural discontinuity is illustrated in red. Figure 7-2. Generalized geology and geochronology of the Vermilion District in the vicinity of the Tower-Soudan anticline (modified after Peterson, 2001; Hudak et al., 2014). 152 �Trip 7 – Classic Outcrops Formation, the Lake Vermilion Formation (including the informally named Britt and Gafvert Lake sequences), and the Knife Lake Group of the Soudan belt; (2) the Bass Lake sequence (Peterson and Jirsa, 1999, Peterson, 2001) and the Newton Lake Formation of the Newton belt; and, (3) syn- to post-tectonic granitoid intrusions of the Giants Range batholith, and a suite of post-tectonic alkalic stocks and plutons. Contacts between the different units are typically conformable, although considerable overlap in time and space is documented between volcanic and sedimentary sequences (Southwick, 1993). Regional chronostratigraphic correlations between the Wawa Greenstone (northwestern Ontario) and the Abitibi greenstone belt (eastern Ontario and Quebec) are indicated in Figure 7-3. Geochronological information for supracrustal and intrusive lithologies in the Vermilion District is relatively sparse (Figure 7-3). Peterson et al. (2001) obtained a U-Pb zircon age of 2722 ± 0.9 Ma from a quartz-phyric rhyolite dome in the Fivemile Lake Sequence of the Lower Member of the Ely Greenstone Formation. Allerton et al. (2024a) obtained a crystallization age of 2708 ± 25 Ma for the Purvis Pluton, which intrudes the Eagles Nest Succession of the Lower Ely Member, and has been interpreted as a synvolcanic intrusion (Peterson, 2001). The age of the Upper Member of the Ely Greenstone formation is currently unknown. Jirsa (2016) obtained an age of 2715.74 ± 0.50 Ma for a felsic volcanic unit within the Newton Lake Formation (Boerboom, T. J., 2020). Lodge et al. (2013) obtained a U-Pb zircon age of 2689.7 ± 0.8 Ma for a Gafvert Lake Sequence dacitic tuff breccia that occurs approximately 2m north of the contact with the Soudan Iron-Formation member of the Ely Greenstone Formation. As well, Lodge et al. (2013) obtained detrital zircon ages ranging from 2680-2690 Ma from greywackes that comprise the Lake Vermilion formation. These dates confirm the source of the detritus in the Lake Vermilion Formation was derived locally from the volcaniclastic rocks comprising the Gafvert Lake Sequence. Figure 7-3. Regional chronostratigraphic correlations between the Vermilion district (Minnesota), the Wawa greenstone belt (northwestern Ontario), and the Abitibi greenstone belt (eastern Ontario and Quebec; after Ayer, 2010). Table 7-1. Lithostratigraphic units within the western Vermilion District (modified after Peterson and Jirsa, 1999; Peterson et al., 2009; Hudak et al., 2012). 153 �Trip 7 – Classic Outcrops Intrusive Rocks Late Intrusions Plutons and stocks of syenite, monzonite, diorite, and lamprophyre. A U-Pb zircon age date of a non-foliated feldspar porphyry intrusion in the Newton belt is 2683 ± 1.4 Ma (Peterson et al., 2001). Vermilion Granitic Complex Granite, schist, amphibolite, and schist-rich migmatite Giants Range Batholith Granite, granodiorite, monzodiorite, and schist-rich migmatite. U-Pb zircon dates indicate a crystallization age ranging from 2640-2777Ma (Allerton et al., 2024a). Supracrustal Rocks Newton Belt Newton Lake Formation Tholeiitic and komatiitic basalt lava flows, intrusions, and clastic strata (deep subaqueous?) Bass Lake Sequence Tholeiitic basalt lava flows, iron-formation, and felsic porphyries (deep subaqueous) Soudan Belt Knife Lake Group Graywacke, slate, conglomerate, and sheared equivalents Lake Vermilion Formation Graywacke, slate, dacitic tuff, minor conglomerate. Detrital zircons from planar bedded, normal-graded resedimented volcaniclastic rocks have UPb age dates of 2680-2690 Ma (Lodge et al., 2013; subaerial to subaqueous) Gafvert Lake Sequence Dacitic to rhyodacitic tuff, lapilli-tuff, tuff-breccia, and iron-formation. Basal dacite tuff-breccia deposits in Lake Vermilion State Park have UPb age date of 2689.7 ± 0.8 Ma (Lodge et al., 2013; subaerial to subaqueous) Britt Sequence Tholeiitic basalt lava flows (deep subaqueous?) Upper Member – Ely Greenstone Tholeiitic basalt lava flows and iron-formation (deep subaqueous?) Soudan Member – Ely Greenstone Oxide-facies iron formation with intercalated basalt lava flows and felsic volcaniclastic rocks (deep subaqueous) Lower Member – Ely Greenstone Calc-alkaline and tholeiitic basalt-rhyolite lava flows, tuffs, epiclastic rocks, and minor iron-formation (shallow- to deep subaqueous) Central Basalt Sequence Calc-alkaline to tholeiitic sparsely amygdaloidal basalt and minor basaltic andesite lava flows with MORB-like or back arc basin-like chemical affinities within 100-200 meters of the overlying Soudan Member iron-formation; FII- and FIIIa-type felsic volcanic and volcaniclastic rocks (transition from shallow- to deep water environment) Fivemile Lake Sequence Calc-alkaline to transitional moderately to highly vesicular basalt and andesite lava flows and volcaniclastic rocks with arc-like chemical affinities: FI-, FII-, and FIV-type felsic volcanic and volcaniclastic rocks. Rhyolite dome at near Fivemile Lake has U-Pb age date of 2722.6 ± 0.9 Ma (Peterson et al., 2001). Epithermal-like zinc stringer mineralization is present near Fivemile Lake (Hudak et al., 2002a; interpreted as shallow subaqueous environment). Eagles Nest Sequence Algoma-type iron formation, basalt-andesite lava flows, hydrothermal exhalites, felsic tuffs. 154 �Trip 7 – Classic Outcrops The upper part of the Knife Lake Group includes conglomerates which contain clasts derived from the Saganaga Tonalite, which has been dated by Driese et al. (2011) at 2690.83 ± 0.26 Ma. Jirsa et al. (2012) obtained a U-Pb age of 2690.7 ± 0.6 Ma for synvolcanic intrusions that cross-cut volcaniclastic rocks that comprise the Knife Lake Group. Peterson et al. (2001) also dated a non-foliated feldspar porphyry intruded into Newton Belt strata at 2683.1 +1/-4 Ma. This date provides a minimum age for the regional D2 deformation event that is described below. The age of the orebodies at the Soudan Mine were previously interpreted to be syn- or postdepositional to the precipitation of the Soudan Member of the Lower Ely Greenstone Formation (Gruner, 1926; Klinger, 1960; Thompson, 2015). Recent U/Pb and (U-Th)/He radiometric dating by Allerton (2024b) suggest the massive hematite orebodies at Soudan formed during Paleoproterozoic time (1640.8 ± 47.2 Ma – 1740.4 ± 72.5 Ma) and have been overprinted by a Mesoproterozoic hydrothermal event at approximately 1100 Ma (1093.1 ± 16.4 Ma). Structural Geology The structural geology of the Vermilion District has been well described by Peterson et al. (2009) and is reproduced below. Periods of generally N-S directed compression resulted in three major regional deformation events in the Neoarchean terranes of northern Minnesota. The earliest deformation event (D1) produced broad, locally recumbent folds within the Soudan belt and major fault zones throughout the region. In the Newton belt, D1 was accommodated by thrust imbrication of large crustal blocks, resulting in mainly northward stratigraphic facing. Field relationships indicate that uplift, faulting, and the deposition of Timiskamingtype clastic sedimentary sequences in local fault- bounded basins occurred late in D1 deformation (Jirsa, 2000). A large, map-scale structure related to D1 deformation in the western Vermilion District is the Tower-Soudan Anticline, which is a west-plunging anticline within which the axis and plunge changes orientation along strike from nearly vertical in basalts to shallow NE plunging in the western sedimentary rocks (Figure 7-2). Axial-planar cleavage associated with this early fold typically is lacking, although Bauer (1985), Hooper and Ojakangas (1971), Hudleston (1976), and Jirsa et al. (1992) have described early cleavage (S1) locally. A second deformation event (D2) associated with synchronous regional metamorphism resulted in foliation development and structures having largely dextral asymmetry. D2 is constrained in the Vermilion District to the time period 2674 to 2685 Ma (Boerboom and Zartman, 1993), and between about 2680 and 2685 Ma in the Shebandowan (Corfu and Stott, 1998). Because D2 deformation affected all of the supracrustal rocks in the area and is reasonably constrained by geochronology, the regional foliation (S2) can be used in the field to temporally relate other structural, intrusive, and deformation events. The relationship between S2 fabric and shear structures indicates that most shearing occurred relatively late in the D2 event. Major shearing that produced the Mud Creek and related shear zones is attributed to the late stages of D2 dextral transpression. Structures related to the third deformation event (D3), which led to juxtaposition of the Wawa Abitibi and Quetico terranes (Peterson and Patelke, 2003) include abundant NE- and NW-trending faults that dissect the stratigraphic assemblages. Named structures related to D3 include the NE-trending Waasa and Camp Rivard faults east of the Soudan Mine area, and the WNW-trending, crustal-scale Vermilion and related faults that form the Wawa-Quetico Subprovince boundary. Paleoproterozoic Superior Type Iron Resources of the Mesabi Iron Range Superior type iron formation resources of Minnesota are exemplified by the long-standing mining of iron resources of the Biwabik Iron Formation along the length of the Mesabi Iron Range. The Mesabi Iron Range is largely located in St. Louis and Itasca counties and has been the most important iron ore district in the United States since ~1900. The Mesabi Iron Range is 120 miles long, averages one to two miles wide, and is comprised of rocks of the Paleoproterozoic Animikie Group. The Animikie Group on 155 �Trip 7 – Classic Outcrops the Mesabi Iron Range consists of three major conformable formations: Pokegama Formation at the base; Biwabik Iron Formation in the middle; and the overlying Virginia Formation. On the Mesabi Iron Range, these three formations generally dip gently to the southeast at angles of 3-15 degrees. Since the early 20th century, the Biwabik Iron Formation has been subdivided into four informal members referred to as (from bottom to top): Lower Cherty member, Lower Slaty member, Upper Cherty member, and Upper Slaty member (Wolff, 1917). The cherty members are typically characterized by a granular (sand-sized) texture and thick-bedding (beds ≥ several inches thick); whereas the slaty members are typically fine-grained (mud-sized) and thin-bedded (≤1 cm thick beds). The cherty members are largely composed of chert and iron oxides (with zones rich in iron silicate minerals), while the slaty members are composed of iron silicates and iron carbonates with local chert beds. Both cherty and slaty iron-formation types are interlayered at all scales, but one rock type or the other predominates in each of the four informal members, and they are so-named for this dominance Severson et. al. (2009). Leached and iron enriched direct ores (or natural ores) were the first materials mined, with the first shipments beginning in 1892, from strongly oxidized pockets along fault and fracture zones and the blanket oxidation of the iron formation at the surface. Taconite, which is the material that is mined today using magnetic separation methods, constitutes most of the iron formation and pertains to the hard, non-oxidized portions of the iron-formation. Production has been dominantly controlled by vertically integrated steelmakers since 1901, and therefore the mining and utilization of these ores have been dictated largely by US ironmaking capacity and demand. The taconite typically contains 30-35% iron and 40-50% SiO2, plus other components (Morey, 1992). The Biwabik Iron Formation is around 175-300 feet thick in the extreme eastern end of the Mesabi Iron Range at Dunka Pit, 730-780 feet thick in the central Mesabi Iron Range/Virginia Horn area near Eveleth, around 500 feet thick in the western Mesabi Iron Range near Coleraine, and eventually exhibits a “nebulous ending about 15 miles southwest of Grand Rapids” (Marsden et al., 1968) on the extreme western end of the Mesabi Iron Range. Maps of currently active taconite mining operations on the Mesabi Iron Range are presented in Figure 7-4. Mesoproterozoic Duluth Complex The Duluth Complex and associated intrusions of Keweenawan age (~1.1 billion years) in northeastern Minnesota constitute one of the largest mafic intrusive complexes in the world, second only to the Bushveld Complex of South Africa (Miller et al., 2002). These rocks cover a 2,200 square mile (5,700 square km) arcuate area associated with the two strongest gravity anomalies (+50 and +70 milligals) in North America, implying intrusive roots over 8 miles (13 km) deep (Allen and others, 1997). The comagmatic flood basalts and intrusive rocks underlying much of northeastern Minnesota were emplaced during development of the Mesoproterozoic Midcontinent rift, which can be traced geophysically from exposures in the Lake Superior region along a 1250 mile (2,000 km) long, segmented, arcuate path to Kansas and Lower Michigan. The Duluth Complex is defined as the more or less continuous mass of mafic to felsic plutonic rocks that extends for >170 miles (275 km) in an arcuate fashion from Duluth nearly to Grand Portage (Figure 7-5). It is bounded by a footwall of Paleoproterozoic sedimentary rocks and Archean granite-greenstone terranes (Peterson and Severson, 2002), and a hanging wall largely of comagmatic, rift-related flood basalts and hypabyssal intrusions of the Beaver Bay Complex. In genetic terms, the Duluth Complex is composed of multiple discrete intrusions of mafic to felsic tholeiitic magmas that were episodically emplaced into the base of a volcanic edifice between 1108 and 1098 Ma. The geology of the Duluth Complex and adjacent areas has been described in two major publications by the Minnesota Geological Survey (MGS). These include a 1:200,000 scale regional bedrock geological map of northeastern Minnesota (Miller et al., 2001), and a comprehensive written description of the geology depicted on this map (Miller et al., 2002), commonly referred to as the “bible” by geologists working on Duluth Complex geology. Within the nearly continuous mass of intrusive igneous rock forming the Duluth Complex, four general rock series are distinguished on the basis of age, dominant lithology, internal structure, and structural position within the complex. 156 �Trip 7 – Classic Outcrops Figure 7-4. Bedrock geology and iron mining features of the Mesabi Iron Range. Felsic series—Massive granophyric granite and smaller amounts of intermediate rock that occur as a semicontinuous mass of intrusions strung along the eastern and central roof zone of the complex, that were emplaced during early-stage magmatism (~1108 Ma). Early gabbro series—Layered sequences of dominantly gabbroic rocks that occur along the northeastern contact of the Duluth Complex, emplaced during early-stage magmatism (~1108 Ma). 157 �Trip 7 – Classic Outcrops Anorthositic series—Structurally complex suite of foliated, but rarely layered, plagioclase-rich gabbroic anorthosite emplaced throughout the complex during main stage magmatism (~1099 Ma). Layered series—Suite of stratiform troctolitic intrusions that comprises at least 11 variably differentiated mafic layered intrusions that occur mostly along the base of the Duluth Complex. These intrusions were emplaced shortly after the Anorthositic series (~1099 Ma). South Kawishiwi Intrusion The South Kawishiwi intrusion (SKI), together with the similar sized Partridge River intrusion (PRI) immediately to the south, are most renowned for hosting the largest tonnage of Cu-Ni sulfide mineralization in the world (Naldrett, 1997). The realization that the SKI hosts vast quantities of Cu-Ni mineralization over 50 years ago has led to the publication of numerous geologic maps, (Green et al., 1966, Bonnichsen, 1974, Foose and Cooper, 1974, Miller et al., 2001, Peterson, 2002e, f, Peterson et al., 2004, Peterson, 2006b, Peterson et al., 2006), articles (Bonnichsen et al., 1980, Weiblen and Morey, 1980, Ripley, 1986, Chandler and Ferderer, 1989, Lee and Ripley, 1996, Hauck et al., 1997, Peterson, 2001b) theses (Weiblen, 1965, Vislova, 2003, Marma, 2003, Gal, 2008, White, 2010), and reports (Phinney, 1969, Phinney, 1972, Listerude and Meineke, 1977, Morey and Cooper, 1977, Foose, 1984, Dahlberg, 1987, Figure 7-5. Geologic map of northeastern Minnesota. 158 �Trip 7 – Classic Outcrops Dahlberg et al., 1989, Kuhns et al., 1990, Severson, 1994, Zanko et al., 1994, Hauck et al., 1997, Peterson, 1997, Peterson, 2001c, Miller et al., 2002, Peterson, 2002d, Patelke, 2003, Severson and Hauck, 2003). The SKI is shallow dipping (~20º to the east-southeast) sill-like intrusion dominantly composed of troctolitic cumulates that are exposed in an 8 x 32-km arcuate band along the northwestern margin of the Duluth Complex. Footwall rocks include the Paleoproterozoic Virginia Formation in the Serpentine and Dunka Pit deposits, the Paleoproterozoic Biwabik Iron Formation in the Dunka Pit and Birch Lake deposits, and the Archean Giants Range batholith from the northern Birch Lake deposit north to the Spruce Road deposit. The presence of shallow-dipping Biwabik Iron Formation inclusions as far north as the Spruce Road deposit indicates that the majority of Paleoproterozoic units were assimilated and removed from the footwall during emplacement of the SKI, leaving the Giants Range batholith as the dominant footwall rock type. Alternately, the Virginia and Biwabik Iron Formations may simply have been largely eroded prior to the development of the Mid-Continent Rift. Also present as inclusions in the SKI are mafic volcanic hornfels (North Shore Volcanic Group), quartz sandstone hornfels (either the Puckwunge or Nopeming sandstones), and anorthosite (of the Anorthosite series). Anorthositic series rocks about the SKI on the northeast – and enclose an interpreted SKI feeder dike (the NLM) that extends farther northeast – the PRI forms the southern sidewall of the SKI, and the BEI and Anorthositic series rocks overlie the SKI to the east. On the regional Duluth Complex map of Miller et al. (2001), the SKI is subdivided into five major map units. These are, from the base upward, 1. Heterogeneous sulfide-bearing troctolite, gabbro, and norite with localized hornfels inclusions, 2. A thick unit of subophitic to ophitic augite troctolite, 3. Discontinuous and localized layers of poikilitic leucotroctolite, 4. A thick homogeneous sequence of ophitic troctolite, and 5. A thick uppermost sequence of homogeneous troctolite that contains numerous anorthositic layers. Severson (1994) and Zanko et al. (1994) further subdivided the SKI into 17 different lithostratigraphic units that are present in over 180 drill holes over a strike length of 31 kilometers. Sulfide mineralization is confined to the BH, BAN, UW, and U3 units near the base of the intrusion, and to a lesser extent the U1, U2, and PEG units. Major marker horizons that are correlated in drill holes include three horizons with abundant cyclic ultramafic layers (U1, U2, and U3 units) and a pegmatite-bearing unit (PEG unit) that was initially recognized by Foose (1984). The understanding of the significance of a large anorthositic inclusion, originally intersected in six deep drill holes east of the Maturi deposit, and its role in magma dynamics of the SKI has been a key feature in the development of an exploration model for Duluth Metals Limited’s Maturi Extension deposit (Peterson, 2001c). Terminology It is important to note the terminology utilized in this field trip guide for: 1) volcaniclastic rocks; 2) bedding characteristics; and 3) description and unit coding of outcrops in the Duluth Complex. Use of consistent terminology is required in order to accurately describe these geological features. Volcaniclastic rocks contain abundant volcanic material irrespective of their origin or depositional environment. Such rocks can be formed directly from volcanic eruptions (whether subaerial or subaqueous), result from resedimentation of non-lithified volcanic deposits (for example, resedimentation of pyroclasts prior to lithification), or result from weathering and resedimentation of pre-existing lithified volcanic rocks. Primary (juvenile) volcaniclastic particles result directly from eruptive processes, and are of three types: • Pyroclasts, which form by explosive fragmentation of magma into particles (including ash, highly vesiculated glass (pumice, scoria), crystals and crystal fragments, and lithic fragments); 159 �Trip 7 – Classic Outcrops • • Hydroclasts, which form by explosive interaction with external water (via phreatic (steam only) and/or phreatomagmatic (steam and magma) explosions) or by non-explosive quenching and granulation of lava (for example, the formation of hyaloclastite fragments on the margins of submarine lava flows or intrusions into wet sediments); and Autoclasts, which form by frictional breakage of moving viscous lava flows (for example, to form carapace breccias on the margins of subaerial lava flows). Based on these different types of fragmentation, four types of primary volcaniclastic deposits have been identified by White and Houghton (2006): • • • • Pyroclastic deposits, which are generated from volcanic plumes and jets or pyroclastic density currents as particles first come to rest. Deposition mechanisms associated with these processes include suspension settling, traction, or en masse freezing; Autoclastic deposits, which are generated during effusive volcanism when lava cools and fragments as a result of thermal processes, or recently cooled lava breaks during flow. Deposition for these types of rocks is under the influence of continued lava flowage; Hyaloclastite deposits, which are generated during effusive volcanism when magma or flowing lava is chilled and fragmented due to contact with water. Deposition of such deposits is is influenced by the continued emplacement of the lava in the presence of water, and the thicknesses of the hyaloclastite deposits can be dictated by the temperature of the magma, the effusion rate, and the distance from the volcanic vent (Cas and Wright, 1987; Gibson et al., 1999; Newkirk et al., 2001a, 2001b); and Peperite deposits, which are generated when magma intrudes into unconsolidated clastic material and mingles with (generally wet) debris to form a volcaniclastic deposit (McPhie et al., 1993). Deposition of peperite deposits takes place essentially in-situ. Secondary volcaniclastic particles are known as epiclasts: • Epiclasts are lithic clasts and/or crystals derived from physical weathering and erosion of preexisting rocks. Epiclasts are volcaniclasts when the pre-existing rocks are volcanic. The terminology for volcaniclastic rocks has historically been somewhat confusing because many different classification schemes have been developed (for example Fisher, 1961; Fisher 1966; Schmid, 1981; Cas and Wright, 1987; McPhie et al., 1993; White and Houghton, 2006), and different classification schemes are preferentially used in different parts of the world. As a result, the terminology relating to volcaniclastic rocks is commonly misused or misinterpreted. Four classification schemes that have been used most in the recent geological literature include: • • • • Fisher (1961, 1966) – Classification based on particle size, particle formation, or particle fragmentation mechanism; Schmid (1981) – Particle type within the deposit; Cas and Wright (1987) – Mode of fragmentation and deposition; and McPhie et al. (1993) – Transport and deposition mechanisms. According to R. V. Fisher (1998), the difficulties with volcaniclastic rock classification can be understood because “volcaniclastic rocks are essentially igneous on the way up and sedimentary on the way down”. In fact, Fisher’s thesis advisor, when observing the volcaniclastic rocks that were the focus of his thesis studies, indicated that they were “the ugliest and most undistinguished rocks I’ve seen in my 30 years of petrology!” Also, classification is especially difficult in ancient volcaniclastic rocks because key aspects 160 �Trip 7 – Classic Outcrops of classification can be obscured by subsequent metamorphism and/or structural deformation (e.g. particle type, particle size) or because genetic processes cannot be ascertained unambiguously (e.g. transport and deposition mechanism, fragmentation mechanisms). For this field trip guidebook, we will utilize Fisher’s (1966) classification (Figure 7-6) for volcaniclastic rocks. This classification scheme is based on the relative proportions of ash-sized material (< 2mm), lapilli-sized material (2-64mm), and blocks/bomb sized material (>64mm) in the rock. Both Gibson et al. (1999) and Mueller and White (2004) suggest that this classification be used for field-based rock classification (mapping, diamond drill core logging, petrography) of ancient volcaniclastic deposits for the following reasons: • • • The classification scheme is “field-user friendly” because it accommodates both the historically important pyroclastic rock names and enables comparison at both the hand sample and thin section scale (Mueller and White, 2004); It is a Wentworth-based scale, and thus enables comparison of volcaniclastic deposits to sedimentary deposits; and Rock classification does not require knowledge of the specific transport mechanism or depositional processes involved with the genesis of the deposit. Figure 7-6. Volcaniclastic rock classification schemes of Fisher (1966) and White and Houghton (2006). This field trip guidebook will classify volcaniclastic rocks using Fisher’s (1966) classification scheme. More recently, White and Houghton (2006) have developed a modified version of Fisher’s (1966) volcaniclastic classification scheme (Figure 7-6). The scheme is essentially equivalent to the Fisher (1966) scheme, with the exception that the lapill-tuff field in the White and Houghton (2006) classification comprises the lapilli-tuff and lapillistone fields of Fisher’s (1966). Specific terms for bedding thicknesses are also used in this guidebook. The terminology for bedding thickness has been adopted from McPhie et al. (1993) and includes: • • • • Laminated Very thinly bedded Thinly bedded Medium bedded <1 centimeters thick 1-3 centimeters thick 3-10 centimeters thick 10-30 centimeters thick 161 �Trip 7 – Classic Outcrops • • Thickly bedded Very thickly bedded 30-100 centimeters thick >100 centimeters thick Figure 7-7. The classification scheme used to describe and code mafic intrusive rocks within the Duluth Complex, modified after Phinney, 1972. Classification of outcrops and map units within the Duluth Complex have relied on the early work of William Phinney (Green et al., 1966; Phinney 1969, and Phinney, 1972) and is given in Figure 7-7. 162 �Trip 7 – Classic Outcrops FIELD TRIP STOPS Table 7-2. Simplified description of the twenty-field trip stops presented in this guidebook. Also included are the coordinates (UTM, Nad83, Zone 15N and Lat-Long), mileage along the route to the stop, and the age of features that will be observed and discussed on the outcrops. Stop 1: Laurentian Divide at Confusion Hill Longitude/Latitude: 47.51868699°N, -92.58996713E UTM NAD 83 Zone 15N: 530870E, 5262888N Exposed near this wayside and in road cuts on both sides of the highway is an array of variably layered intrusions having both tonalitic (white) and dioritic (black) compositions. A cursory look shows intrusive relationships that conclusively demonstrate that diorite was emplaced into tonalite at one locality, and at another, tonalite was emplaced into diorite. In detail, all compositions intermediate between the two end members are also present locally. Although the dioritic component is abundant here, the bulk of the mapped unit is tonalitic. Emplacement of this unit, now known as the Lookout Mountain tonalite, probably involved some degree of magma mingling. Dikes of tonalite that cut the adjacent high-grade supracrustal rocks of the Minntac sequence contain metamorphic fabrics, yet little evidence of metamorphic origin can be seen in the interior of the body, implying it is syntectonic with respect to D2 deformation. U-Pb zircon dates (Boerboom and Zartman, 1993) of two components of the batholith exposed to the north bracket the age of D2 deformation between about 2674 and 2682 Ma. Exposures at Confusion Hill are a small part of the Giants Range batholith, which forms the core bedrock of the Laurentian (drainage) divide. The batholith is a 40-mile wide belt of intrusions that can be traced on geophysical maps and outcrop east to the Mesoproterozoic Duluth Complex, and west beyond the western border of Minnesota. It separates Archean supracrustal sequences in the Virginia horn from those of the Tower-Soudan area - making stratigraphic correlation between the two districts speculative. Return to bus. 163 �Trip 7 – Classic Outcrops Figure 7-7. Simplified bedrock geology map overlain by the field trip stops and traveled route. Stop 2: Pike River Dam Greywackes Longitude/Latitude: 47.57736062°N, -92.54367719E UTM NAD 83 Zone 15N: 534317E, 5269428N This glacially scoured outcrop exposes a nearly perfect cross-section of straight-bedded, variably graded, feldspathic graywacke and black slate. The feldspar-rich, dacitic composition of sandy textured beds is presumed to represent derivation from the Gafvert Lake felsic volcanic sequence exposed to the east in the Soudan area. Regionally, a series of outcrops from Gafvert Lake westward shows an irregular transition from proximal, possibly subaerial deposition on the east, to distal submarine turbiditic fan deposition to the west. The beds contain numerous "soft-sediment" deformation features including load structures, flames, intrafolial slump folds, and possibly some of the cross-stratal faulting. Bedding is nearly vertical, and graded beds indicate stratigraphic younging to the south. This topping direction, and the presence of a weak D2 cleavage that is left of bedding, indicate westward structural facing in the cleavage; consistent with a position on the south limb of a large, south-overturned, regional, D1 fold structure—the western extension of the Tower–Soudan Anticline. Northeast-trending kink bands, fault zones, and raised quartz veins traversing the outcrop. One of the truly classic outcrops of greywacke of the Lake Vermilion Formation is beautifully exposed at this stop. Prior to about the 1950s, no depositional mechanism could satisfactorily explain the coincidence in graywacke of; 1) coarse sand derived from a source many kilometers distant and having an altered clayey matrix; 2) interbedded black slate; and 3) the lack of evidence for reworking in shallow water (indicative of deposition below wave base). This was changed when the concept of turbidity currents was introduced to the geological profession by Kuenen and Migliorini (1950). Despite widespread publication on turbidites in more modern geologic settings through the 1950s and 1960s, the facies model was not 164 �Trip 7 – Classic Outcrops refined and applied to Archean and Proterozoic strata in the Lake Superior region until somewhat later (Morey, 1965; Ojakangas, 1966). Return to bus. Stop 3: Gafvert Lake Sequence Volcaniclastic Rocks Longitude/Latitude: 47.80135914°N, -92.28615141E UTM NAD 83 Zone 15N: 553454E, 5294469N This relatively new roadcut (approximately 15 years old) exposes rhyodacitic to dacitic composition Gafvert Lake Sequence lapilli tuffs and tuff breccias. The deposits have tentatively been interpreted to represent mass flow units produced by slumping of volcanic and volcaniclastic material from the Gafvert Lake volcano into an adjacent, probably submarine basin. Close inspection of the unit indicates the presence of a variety of lapilli and blocks including: 1) subrounded to subangular plagioclase ± quartz-phyric coherent dacite to rhyodacite; 2) subrounded to subangular pumice; 3) angular carbonate-rich fragments; 4) angular chert fragments; and 5) local subangular to angular massive sulfide fragments. Locally, abundant (up to 10%) <1mm euhedral pyrite cubes are disseminated in the matrix. The presence of both carbonate and massive sulfide fragments, as well as plagioclase- and quartz phyric coherent rhyodacite to dacite lapilli, may suggest the slumps are derived from a Gafvert Lake sequence subaqueous lava dome that was affected by local hydrothermal alteration and the deposition of chemical exhalates (e.g. carbonate, chert and massive sulfide fragments). Structurally, this outcrop occurs on the southern margin of an east-southeast – west-northwest trending D2-associated structure that extends from Pike Bay (northwest) to south of Putnam Lake (southeast). Here one can observe a strong, steeply dipping E-NE foliation and a well-developed lineation that plunges approximately 70° E. Return to bus. Stop 4: Soudan Member Banded Iron Formation Longitude/Latitude: 47.820074°N, -92.2365908E UTM NAD 83 Zone 15N: 557144E, 5296585N (NOTE: Modified from Peterson et al., 2009 and Hudak and Peterson, 2014.) This classic exposure of the Soudan iron-formation member of the Ely Greenstone Formation lies on the north limb of the Tower-Soudan anticline approximately 75 meters north of the stratigraphic top of the volcanic sequences known collectively as the Lower member of the Ely Greenstone. The outcrop displays two generations of tight folding in delicate laminae of chert (creamy white), chert-hematite jasper (red), and magnetite-chert (black to silver-colored). The second generation of folds (F2) is tectonic in origin, having subvertical axial surfaces that trend east, and steeply plunging axes. Most display Z-asymmetry. The earlier folds (F0-1) appear to have been sharply refolded to produce complex interference patterns. Lundy (1985) studied folding at this locality and concluded that some of the apparent interference structures are the product of early-formed sheath folds that did not involve refolding by D2. The F1 structures are predominantly intrafolial and exhibit a great variety of style and orientation; implying they formed by layerparallel, soft-sediment slumping (Fig. 7-8). Lundy’s mapping of this outcrop is an interesting demonstration of unraveling details at a single outcrop that led to recognition that D1 deformation was not systematic here, but likely soft sediment. Furthermore, it is a microcosm of regional-scale deformation. 165 �Trip 7 – Classic Outcrops It is interesting to observe the rhythmic microlaminae (1 mm or so thick) in various cherty beds exposed here and speculate about the paleoenvironment—that is, whether these represent daily heating/cooling, tidal, climatic, annual, or some other repetitive influence (e.g waxing/waning of a hydrothermal system) in the depositional environment. What is known about units of iron-formation in the Ely Greenstone, of which there are many, is that deposition occurred in deep water (below wave base) during periods of relative volcanic and tectonic quiescence by the slow subaqueous “rain” of chemical precipitates. The deep excavations in this area are the early workings of the Soudan iron mine, the first in Minnesota. The mine produced about 16 mt of high-grade hematite ore (60-63 percent iron converted to a park. Most of the production came from underground workings that began here in 1900, and which now can be visited on guided tours. The mine previously housed several underground physics research facilities. These include Soudan 1 (23rd level) which studied neutrino decay; 2) Soudan 2 (27th level), also to study neutrino decay; and 3) the MINOS (Main Injector Neutrino Oscillation Search) lab, which was built on the 27th level adjacent to Soudan 1 and studied the decay of neutrinos within the earth as they passed from Fermilab to Soudan (Peterson et al., 2009b). Figure 7-8. Outcrop map showing bedding trajectories and multiple generations of folds and faults (from Lundy, 1985). F1 folds are non-systematic and include both nappe- and sheath fold geometries. Return to bus. Stop 5: Murray Shear Zone Along Hwy 1/169 Longitude/Latitude: 47.81809993°N, -92.20694376E UTM NAD 83 Zone 15N: 559366E, 5296388N A series of roadcuts along Highway 169 expose a transect through the northern edge of the Murray Shear Zone, which is one of the most striking Neoarchean structural features in the Tower-Soudan area 166 �Trip 7 – Classic Outcrops (Peterson and Patelke, 2003). This series of outcrops perfectly display a classic feature of Neoarchean ductile (shear zone) structures - strain partitioning (Figure 7-9). A close look at these outcrops also gives one hints of broader economic geology implications via the presence of carbonate alteration of the chlorite schists. The carbonate (ankerite and/or ferro-dolomite) strain hardens the ductile deformed schistose rocks and allows for subsequent brittle deformation (and perhaps orogenic gold mineralization in cross-cutting quartz-ankerite-sulfide veins. On the larger scale, the D2 Murray shear zone transposes rocks 3-5 km eastwards in the zone bounded by its northern and southern strain partitioned boundaries. The overall geometry of this panel of Figure 7-9. Scanned image of the field sheet used to map outcrop OC-567. On the right are digital photographs of outcrop OC-567: A) the overall outcrop view looking WNW; B) view to the north of steeply east plunging, lineated and rod-shaped pillowed andesite (rock hammer 68cm for scale); and C) close-up view of rock sample S-604, taken from the west side of the outcrop (bright zone on the left side of picture A). Data from Peterson & Patelke, 2003. 167 �Trip 7 – Classic Outcrops rocks is like the geometry of “wedge-shaped shear zones” described in detail by Ramsey and Huber (1987). Peterson’s mapping and collection of structural data in the Murray shear zone panel is largely confined to a series of outcrops along the northern edge of the zone. Field observations of these outcrops indicate that the strain symmetry along this boundary is largely constrictional, with a dominant steeply east-dipping, elongate and rod-shaped structural fabric. A stereonet projection of planar and linear structural features within the Murray panel is shown in Figure 7-10. The mean value of the strike and dip of planar features is 282°/82°, and the trend and plunge of linear features has a mean orientation of 87°/71°. The overall mapscale internal geometry of the Murray panel clearly shows dextral asymmetry, with a strong sigmoidal wrapping of iron-formation (see field trip geologic maps) to the northeast. Figure 7-10. Stereonet projections of foliation, shear fabrics, and linear features from the Murray shear zone. An estimate of the amount of displacement of the rocks within the panel of rocks bounded by the Murray shear zone is given in Table 7-3. These values were calculated geometrically by using the average plunge of measured lineations (71°) and two measured lines of possible correlative stratigraphy offset by the bounding shear zones. The calculated total displacement values (net slip) are quite large (up to 13.8 km, or 43,000 feet of net slip), but the displaced rocks would still fall within the range of depth generally associated with greenschist facies metamorphism. Table 7-3. Calculated displacement along the Murray shear zone Strike Slip Lineation Plunge Dip Slip Net Slip 71° 4.5 13.1 13.8 71° 3.0 8.7 9.2 Return to bus. 168 �Trip 7 – Classic Outcrops Stop 6: Lower Ely Member (Central Basalt) Sheet and Pillowed Flows Longitude/Latitude: 47.8306566°N, -92.17157352E UTM NAD 83 Zone 15N: 561999E, 5297811N (NOTE: Modified from Field Trips of Hudak et al., 2004, 2014; Peterson et al., 2005, 2009). This classic outcrop has been visited during field trips associated with the 2004, 2009 and 2014 ILSG conferences (Hudak et al., 2004; Peterson et al., 2009; Hudak et al., 2014). This is a no-hammer outcrop, as the preservation of the delicate textures here rivals those observed in other classic Neoarchean camps in the Superior Province containing well-preserved volcanic textures such as Noranda, Quebec and Timmins, Ontario. The description and figure below have been modified from Peterson et al. (2009) and Hudak et al. (2014). The Central Basalt sequence (Peterson and Patelke, 2003, Peterson, 2005) comprises a steeply north-dipping (75°- vertical), north-facing sequence of sparsely amygdaloidal pillowed and massive lava flows of basalt andesite to basalt composition that are believed to be correlative with the tholeiitic Armstrong Lake volcanic sequence mapped in the Eagles Nest quadrangle (Jirsa et al., 2001), approximately 11km to the east. Hudak et al. (2007), Jansen et al. (2009), and Hudak et al. (2012) have shown that the lowermost sections of the Central Basalt Sequence are composed of submarine basaltic andesite to basalt lava flows that have rare earth element lithogeochemical patterns similar to mafic rocks in oceanic volcanic arcs. However, locally, submarine basalt lava flows that occur within 50-200m stratigraphically below the contact between the Central Basalt Sequence and the overlying Soudan Member of the Ely Greenstone Formation illustrate MORB-like or back-arc basin-like lithogeochemical patterns. This change in rare earth element characteristics may be interpreted to indicate a change from an oceanic arc to back-arc environment immediately prior to the deposition of the Soudan Member. Relative to massive and pillowed basalt and andesite flows in the Fivemile Lake sequence, Central Basalt sequence lava flows are notably less amygdaloidal, and lack multiple pillow rind structures. In addition, the Central Basalt sequence lacks the thick sequences of scoria-rich basalt-andesite lapilli tuffs that are commonly interstratified with lava flows in the Fivemile Lake sequence. These characteristics of the Central Basalt sequence indicate eruption and deposition in a deeper submarine environment than the stratigraphically older Fivemile Lake sequence and suggest overall increasing water depth during the temporal development of the Lower Ely. Deepening of the water column could be accommodated by extensional tectonics and normal faulting associated with the development of the proposed back-arc environment. At this stop, the outcrop comprises two east-southeast striking massive basalt flows, ranging from at least five to nine meters in thickness, that are separated by a ten-meter-thick flow unit comprising pillows and pillow lobes (Fig. 7-11). All three lava flows at this vicinity illustrate tholeiitic, MORB-like lithogeochemistries (Hudak et al., 2007). Flow 1, at the southern part of the outcrop, is composed of a pale- to dark green, faintly feldspar-phyric (~10% 0.5-1 mm laths), sparsely amygdaloidal, basalt sheet flow that locally exhibits tortoise-shell jointing formed in response to contraction during cooling. The uppermost 10-40 cm of the coherent part of Flow 1 is generally silicified and epidotized. Petrographic observations indicate that this section of the flow also contains up to 70% <0.1 cm round spherulites. An irregular contact occurs between the coherent basalt flow and an overlying one- to two-meter-thick unit of dark green, exceptionally well-preserved perlitic in-situ hyaloclastite and associated self-peperite (c.f. Batiza and White, 2000). The hyaloclastite formed from non-explosive fracturing of the basalt glass developed on the flow top due to quenching by water, whereas the perlite formed following deposition by hydration of volcanic glass. An irregular contact occurs between the hyaloclastite and Flow 2, which is composed of north-facing mattress- to bun- shaped pillow lavas and pillow lobes with numerous “neck and knob” structures. Individual Pillow structures have well developed perlitic hyaloclastite margins that range from 1-4 cm in 169 �Trip 7 – Classic Outcrops Figure 7-11. Detailed geological map of sheet flows, pillow lavas, and associated hyaloclastite deposits at Field Trip 3, Stop 1 (after Hudak et al., 2014; Hudak and Peterson, 2014). width. Pillow buds indicate propagation from east to west, suggesting the volcanic vent was located east of this location. The coherent pillows and lobes are overlain by up to 2.5 meters of hyaloclastite breccia that contains 20-40% subrounded to subangular pale gray green basalt lapilli in a jigsaw puzzle-fit dark green perlitic hyaloclastite matrix. The upper contact of Flow 2 and the overlying basalt sheet flow (Flow 3) is irregular, and is marked by thin (1-8 cm thick), sheet- like basalt fragments that are up to 1.6 meters in length. These fragments locally appear to be isoclinally folded about an east-west-trending fold hinge. Although the genesis of this structure is currently not well understood, it may be due to syneruptive deformation of either thin slabs of hot, basal flow margin crust from the overlying flow, or thin injections of basalt magma into the hyaloclastite from either the underlying pillows or the overlying sheet flow. Flow 170 �Trip 7 – Classic Outcrops 3 comprises an at least ten-meter-thick pale green-gray, slightly feldspar-phyric, sparsely amygdaloidal sheet flow. Steep, NNE-trending west dipping D3 joints are well developed in this unit, as are lens-shaped psuedo-pillows that are up to 50 cm in diameter. Return to the bus by walking back down the hill. Stop 7: Mud Creek Shear Zone Longitude/Latitude: 47.87440908°N, -92.14025702E UTM NAD 83 Zone 15N: 585753E, 5309482N This outcrop shows highly strained rocks in the Mud Creek shear zone. The rock type is a quartziron carbonate-sericite schist, having quartz and tourmaline knots, abundant pyrite, and trace amounts of gold. Its protolith is unknown, because of the intense deformation, but could be any of several rock types in the region, including quartzofeldspathic porphyry, basaltic metavolcanic rocks, or graywacke. The shear fabric trends east-northeast, and lineations plunge at shallow angles to the east. Development of this shear zone, which occupies most of the valley of Mud Creek, is a product of largely dextral transpressive deformation that has been partitioned into discrete zones, presumably late in D2 deformation. It is generally believed that gold-bearing mineralization was introduced during these later deformation events, and the Mud Creek shear zone and environs have attracted considerable attention as a gold target (Peterson, 2001, Peterson and Patelke, 2004a, 2004b). The Mud Creek shear is a broad, anastomosing zone that forms the boundary between rocks of the Ely Greenstone and Lake Vermilion Formation on the south, and volcanic and iron formation-bearing rocks known informally as the Bass Lake sequence on the north. The Bass Lake rocks may be equivalent to parts of the Newton Lake Formation exposed north of Ely, but a complex series of faults in the intervening area makes this correlation speculative. Return to bus. Stop 8: Newton Lake Formation Variolitic Pillow Lavas and Hyaloclastite Longitude/Latitude: 47.93291301°N, -91.85191152E UTM NAD 83 Zone 15N: 585753E, 5309482N (NOTE: Modified from Field Trip Stop 5-16 (Jirsa et al., 2004), and Field Trip Stop ET-1 (Peterson et al., 2009)). The Neoarchean Newton Lake Formation is composed primarily of tholeiitic and komatiitic pillowed mafic lava, diabasic gabbro, differentiated mafic-ultramafic sills, intermediate-mafic pyroclastic rocks and siliceous marble with minor felsic-intermediate volcaniclastic rocks and lava flows. This formation is approximately 2,350 m thick. The unit overlies the Knife Lake Group in central part of the Vermilion district and the Lake Vermilion Formation in western part of Vermilion district (USGS National Geologic Map Database, https://ngmdb.usgs.gov/Geolex/UnitRefs/NewtonLakeRefs_9525.html). The Newton Lake Formation differs from the Ely Greenstone Formation in that the former contains a high proportion of mafic-ultramafic sills and lava flows, abundant diabasic sills and rare iron-formation. Lava flows in the Newton Lake Formation typically have larger MgO and incompatible element contents than those of the Ely Greenstone Formation, and some are classified as komatiites and komatiitic basalt (Schulz, 1980; Jirsa et al., 2004; Grotte and Hudak, 2014). The Newton Lake Formation (and possibly equivalent Bass Lake sequence) appears to be younger than the Lower Ely Member (~2723 MA; Peterson et al., 2001) with an age date of ~2715 MA (Jirsa, 2016) and was previously interpreted to be the youngest Archean supracrustal sequence in the Vermilion district until the Gafvert Lake Sequence was dated at 171 �Trip 7 – Classic Outcrops approximately 2689 MA (Lodge et al., 2013). Rocks having nearly identical composition and stratigraphic/structural setting occur in Itasca County some 80 kilometers to the west (Jirsa, 1990; Jirsa et al., 2004). A sequence of exceptionally well-preserved steeply-dipping, south-topping, lower greenschist facies metamorphosed Newton Lake Formation variolitic pillow lavas is exposed along a series of outcrops located on the west side of the road approximately one-half mile north of CR-88 on the Echo Trail. Variolites are defined as “a spherulite-like radiating aggregate composed of feathery, needle-like crystals of plagioclase and pyroxene that occur in mafic volcanic rocks (typically basalt). Variolites may result from devitrification but are commonly believed to be formed in subaqueous rocks by quench-induced crystallization (Cas and Wright, 1987, p. 420). According to Arndt and Fowler (2004), variolites result from either magma mingling or blotchy alteration, or they are a type of plagioclase spherulite. A generalized cross-section through these pillows from a detailed field and petrographic study of this outcrop (Grotte and Hudak, 2014) is presented in Figure 7-12A. Pillows vary from “bun-” to “mattress” shaped (Dimroth et al., 1978) and range from <1 to >2.5 meters in diameter. Pillow shapes, as well as the local occurrence of quartz-filled vacuoles within individual pillows, indicate younging directions to the south. Pillow cores tend to be dark green to pale yellow-green in color depending upon the abundance of secondary epidote alteration. The pillow cores commonly contain massive, globular variolites with local <1cm diameter spherical variolites., and are locally variolitic (Figure 7-12B). Pillow selveges are well preserved and commonly contain concentric zones globular to spherical Figure 7-12. Summary of field and petrographic observations of Newton Lake Formation variolitic pillow lavas at this location (from Grotte and Hudak, 2014). A) Generalized cross-section through a Newton Lake Formation pillow lava at this location. B) Outcrop photo of the margin of a pillow lava at this location noting the transition from well-preserved interpillow hyaloclastite into a variolitic pillow selvege. C) Thin section scan illustrating the well preserved cuspate, angular shards comprising the interpillow hyaloclastite. Dark spherical shapes on the right half of the photo are variolites. 172 �Trip 7 – Classic Outcrops variolites that mimic individual pillow shapes. Interpillow hyaloclastite is extremely well preserved and is composed of jigsaw-puzzle-fit angular cuspate shards that were originally glass but are now composed of fine-grained alteration minerals (Figure 7-12C). Petrographic observations (Grotte and Hudak, 2014) indicate that variolites in this exceptional exposure of Newton Lake Formation pillow lavas are dominantly composed of rounded to oval, radiating plagioclase spherulites with rare, axiolitic plagioclase spherulites locally present. The presence of needlelike to acicular skeletal plagioclase crystals and absence of phenocrysts suggest that the pillow lava flows at this location erupted at temperatures above the liquidus and experienced relatively large degrees of undercooling before undergoing rapid crystallization on the Neoarchean seafloor. As indicated in Jirsa et al. (2004), the Newton Lake is separated from the Ely Greenstone to the south by a complex zone of faulting (Shagawa Lake and Sibley faults) developed within sedimentary rocks of the Knife Lake Group. Although relatively undeformed conglomerate and sedimentary rocks of the Knife Lake Group are exposed just a few miles to the east, they are typically so sheared and altered in this area as to obscure lithologic and sedimentary interpretations. Return to bus Stop 9: Giants Range Batholith Longitude/Latitude: 47.81587746°N, -91.79083789E UTM NAD 83 Zone 15N: 590518E, 5296544N (NOTE: Modified from Hudak and Peterson, 2014). Footwall rocks to the northern part of the South Kawishiwi Intrusion are part of the Neoarchean Giants Range batholith (GRB). At this exposure along Highway 1, the GRB consists of porphyritic hornblende quartz monzonite that contains distinctive 1-2cm diameter potassium feldspar phenocrysts. One may also observe a distinctive foliation represented by alignment of black to dark green amphiboles and locally dark brown biotite. The massive nature of this unit creates an excellent footwall for Duluth Complex-associated intrusions and associated Cu-Ni-PGE deposits as the GRB lacks bedding and thus rare (if ever) gets incorporated into the mineralized zone as barren xenoliths. Additionally, melting of the GRB beneath longlived magma channels (Peterson and Boerst, 2013) at the base of the Maturi deposit has contaminated the South Kawishiwi intrusion, inducing additional sulfide immiscibility and the genesis of Ni- and Co-rich massive sulfide bodies. Return to bus Stop 10: Maturi SW Roadcuts of BH and U3 Units Longitude/Latitude: 47.78505228°N, -91.79056387E UTM NAD 83 Zone 15N: 590592E, 5293118N Classic roadside exposures of heterogeneous sulfide-bearing troctolite and layered melatroctolite of Severson’s (1994) Basal Heterogeneous (BH) and Ultramafic 3 (U3) units of the SKI. A large core-stone is well exposed in the weakly saprolitic heterogeneous troctolite outcrop. Several small xenoliths of finegrained troctolite can be observed on top of the outcrop and are interpreted as Stage 1 chilled margin autoliths (Peterson and Boerst, 2013). Within the exposure of the overlying U3 layered melatroctolite, olivine layers strike 17° and dip steeply 51° to the ESE. The steep dip is apparently associated with two 173 �Trip 7 – Classic Outcrops defined north-south trending faults east of these exposures. Recent drilling by Twin Metals Minnesota in this area has led to the definition of the Maturi SW deposit. Return to bus Stop 11: SKI Magmatic Slurry Igneous Breccia Longitude/Latitude: 47.780584°N, -91.79273111E UTM NAD 83 Zone 15N: 590437E, 5292619N At this stop, we’ll examine perhaps the best exposure of Severson’s (1994) BH unit in the whole of the SKI. The heterogeneous troctolitic rocks at this stop are generally poorly mineralized and thus lack a gossanous saprolitic weathering profile which lets one see the true nature of the heterogeneity within the troctolite. We believe that all geologists who log drill core within the Cu-Ni-PGE deposits of the Duluth Complex (or who attempt to model such deposits for mine planning purposes) should be required to spend several days examining the rocks within the area around both Stops 10 and 11. All participants should imagine a drill core cutting this exposure and how they would interpret the geology of that core without first examining this outcrop. Such thoughts are why the Precambrian Research Center’s field camp had for many years its students complete a 1:5,000-scale bedrock geology map of this area. Return to bus Stop 12: Main AGT Longitude/Latitude: 47.81303067°N, -91.73468023E UTM NAD 83 Zone 15N: 594727E, 5296295N Recent road cut along the south side of Minnesota Highway #1 of massive, extremely homogeneous augite troctolite of the Main AGT unit of Severson (1994). Troctolite of the Main AGT unit differs from the Middle and Upper SKI troctolite in two distinctive ways: 1) ophitic augite crystals are black, distinctly associated with Fe-Ti oxides + apatite, and occur as high-density ophitic crystals from 1 to 3 inches in diameter. In the Middle and Upper SKI, ophitic augite crystals are brown, not associated with Fe-Ti oxides, and occur as large (up to 15 inches) low-density grains; and 2) The Main AGT is never layered. Geologists at Duluth Metals interpret the units’ homogeneity and lack of layering as evidence that the Main AGT magma lacked phenocrysts of olivine and plagioclase and represents the end product of topdown and bottom-up solidification of a basaltic liquid. We currently interpret the Main AGT as the solidification of much of the “carrier liquid” of the underlying sulfide-bearing BMZ magmatic slurry. Return to bus Stop 13: Spruce Road Bulk Sample Site/Discovery Burrow Pit Longitude/Latitude: 47.83271644°N, -91.67864227E UTM NAD 83 Zone 15N: 598885E, 5298553N Beginning in the late 1940s, the U.S. Forest Service utilized locally derived glacial tills and weathered bedrock gossans as road building materials during the construction of the Spruce Road. As we take a short hike into one of these borrow pits, we will walk by the 1973 INCO bulk sample site in the Spruce Road deposit and visit several outcrops with fresh Cu-Ni sulfide minerals. This short stop will examine the bottom of an old borrow pit where participants can walk on and sample sulfide-bearing 174 �Trip 7 – Classic Outcrops troctolite gossans. Please note the friable nature of the rocks in the weakly saprolitic exposure and look for rounded core-stones where weathering over the eons was less intense. Return to bus Stop 14: Nickel Lake Macrodike Longitude/Latitude: 47.83079527°N, -91.63760896E UTM NAD 83 Zone 15N: 601959E, 5298393N The Nickel Lake Macrodike (NLM) is a northwest to southwest-trending, steeply dipping, asymmetric troctolitic and gabbroic intrusion interpreted to be a feeder dike for the northern portions of the SKI. The macrodike is interpreted to be located within a major rift-parallel normal fault (down to the southeast) now obscured by intrusion of NLM igneous rocks. Regional southward tilting (based on the deep level of erosion of the northern Bald Eagle Intrusion directly east of this area) leads to the interpretation that the southwest end of the NLM (near Omaday Lake) is structurally higher than the northeastern portion of the dike, and represents the location where magma flow changed from dike-like to sill-like, as it exited Figure 7-13. Bedrock geology map of the southwestern end of the Nickel Lake Macrodike. 175 �Trip 7 – Classic Outcrops the dike – thus the magma velocity slowed – and entered the growing SKI magma chamber. Excellent potential exists for Ni-Cu rich massive sulfide at the basal contact where the dike enters the SKI (Section 31, T62N, R10W). The 6.5km long by 1.0 km wide macrodike is composed of three main units: 1) inclusion-rich, locally sulfide-bearing, heterogeneous troctolite (unit Mpth) along the northwestern margin; 2) layered troctolite, melatroctolite, and dunite (unit Mltmt) along the southeastern margin; and 3) a late, cross-cutting, coarse-grained to pegmatitic oxide-rich, olivine-gabbro to melagabbro (unit Mxog) traversing generally through the center. Small (< 1m) to large (hundreds of meters long) xenoliths include Mesoproterozoic Anorthositic Series wall rocks (unit Mai) and North Shore Volcanic Group basalts (unit Mhb), and Paleoproterozoic Biwabik Iron Formation (unit Pifs) and Virginia Formation (unit Pvf). For this field trip we are simply going to take some walks in the bush, mostly along logging roads and snowmobile trails as time allows and look at numerous outcrops of the NML and adjacent rocks and discuss geology as we see it. Numerous detailed bedrock geology maps, reports, and presentations of the NLM and adjacent areas have been published over the last couple of decades (Peterson, 2002a, 2002b, 2002c, 2006a, 2006b, 2006c, 2008, Peterson and Albers, 2007) and a compilation of detailed geologic mapping data for the southwestern NLM is given in Figure 7-13. Return to bus Stop 15: Remnant Saprolite, Middle SKI Longitude/Latitude: 47.77089981°N, -91.66297244E UTM NAD 83 Zone 15N: 600176E, 5291703N A short field trip stop to examine locally layered troctolitic rocks of the Upper SKI of Peterson and Boerst (2013). This outcrops in this area epitomizes the “Sea of Troctolite” that occurs throughout the vast majority of the SKI (Middle and Upper SKI of Peterson and Boerst, 2013). Careful attention will be given to an outcrop next to the bus where spheroidal weathering of the troctolite is forming rounded core stones of troctolite, which we’ll see once again at stop 18. Return to bus Stop 16: Anorthosite Series Roadcut Longitude/Latitude:: 47.75915521°N, -91.64719916E UTM NAD 83 Zone 15N: 601381E, 5290418N Large, glacially polished roadside outcrop of the gabbroic and troctolitic anorthosites of the Anorthositic Series of the Duluth Complex. At this location these anorthositic rocks form the eastern sidewall of the SKI and are cut by a series of northeast-striking valleys. The valleys were interpreted by geologists of Duluth Metals Limited as steeply west-dipping reverse faults that were formed by emplacement of the SKI immediately to the west. Approximately 2.5 km to the southwest of this roadcut Cold Spring Granite Company quarries a large gabbroic anorthosite xenolith similar to this stop in their Mesabi Black quarry. Return to bus 176 �Trip 7 – Classic Outcrops Stop 17: Bald Eagle Intrusion Longitude/Latitude: 47.7385175°N, -91.6405279E UTM NAD 83 Zone 15N: 601921E, 5288133N A quick stop to observe a roadside outcrop of troctolite of the Bald Eagle Intrusion (BEI). The BEI is a large (4.5 to 16.5 km x 31 km) troctolitic to gabbroic body that was emplaced partially within Anorthositic series rocks, the SKI, and the Greenwood Lake Intrusion (see BEI on Figure 7-7). Weiblen (1965) mapped the well-exposed northern portion of the intrusion and showed that it is funnel-shaped and consists of an outer zone of troctolite and an inner zone of olivine gabbro. In the poorly exposed southwestern portions of the intrusion, field mapping by Green et al., (1966) and Foose and Cooper (1978) showed the BEI and SKI in direct conformable contact. Steep foliation and modal layering (Weiblen, 1965, Green et al., 1966) integrated with a distinct gravity anomaly over the northern BEI imply that the northern part of this intrusion is funnel shaped and necks down to a steep feeder dike. Weiblen and Morey (1980) interpreted the limited cryptic variation (Weiblen, 1965), the steep dip of lamination and layering, and adcumulate nature of the BEI as indicative of its being an open conduit to higher intrusions and perhaps volcanic flows. Petrologic observations and geophysical interpretations (Chandler, 1990, Chandler and Ferderer, 1989) suggest that the BEI and SKI were emplaced by successive overplating of magmas from a common feeder centered on the northern BEI and extending along the trace of the NLM that links the BEI and SKI. In a related analogy, Cartwright and Møller-Hansen (2006) have shown that interconnected sill complexes transect the middle to upper crust over a vertical distance of 8-12 km offshore of Norway. The geometry of the gravity and magnetic anomalies of the BEI, as well as the overall Midcontinent Rift is very similar to the pattern of the seismic reflections profiles of active ridge systems (Vislova, 2003). In detail, the geophysical expressions of the BEI have the same shape and dimensions as the “bulls’ eye” pattern of low velocity seismic reflection anomalies along the East Pacific Rise. These anomalies are interpreted to define regions of melt concentrations, i.e., active magma chambers. These data suggest that the BEI could be a “frozen” dynamic magma chamber (Weiblen et al., 2005, Peterson and Hauck, 2005). Eight exploration holes drilled by Duluth Metals Limited in 2011 revealed several new distinct features of the BEI. All of these holes encountered chromitite layers within horizontally layered troctolites with many of the chromitite horizons occurring as “rip up” clasts within troctolites. Duluth Metals Limited’s hole LOD-06, drilled 12km SSW of this field trip stop, encountered flowing gas at a depth of 1,778 feet. The gas was analyzed and found to contain >10% helium. This is the site where Pulsar is currently exploring with the aim of producing helium gas. Return to bus Stop 18: Vermilion Moraine Longitude/Latitude: 47.6918526°N, -91.81063993E UTM NAD 83 Zone 15N: 589247E,5282737N In common with most of the high latitude regions of North America, northeastern Minnesota was repeatedly glaciated during the ice ages of the Pleistocene Epoch. Glaciogenic sediments and landforms in this 2025 ILSG field trip area are associated with the Rainy Lobe of the Laurentide ice sheet. While there are a number of possible definitions of what constitutes the Rainy Lobe – sedimentological, textural, compositional, and association with particular geomorphic features – a definition rooted in glacial dynamics perhaps works best. In this sense, the Rainy Lobe refers to that portion of the Laurentide ice sheet lying northwest of Lake Superior (occupied by the Superior Lobe), and east of the Winnipeg Basin and Red River Valley (occupied by the Red River Lobe). In common, Rainy Lobe landforms and glaciogenic sediments 177 �Trip 7 – Classic Outcrops reflect a general northeast to southwest ice flow direction, and a Labradoran (northeastern) sediment provenance. In common with much the Canadian Shield, glacial erosion has nearly completely stripped preglacial regolith from bedrock north of the Laurentian Divide. However, preglacial saprolites are a common occurrence underlying glaciogenic sediments in central and western Minnesota; the nearest such occurrences are exposed in open pit mines of the Mesabi Range, on the south flank of the Giant’s Range. Approximately 12,400 years ago, the retreating Rainy Lobe made a last stand in northern Minnesota to form the West-Northwest to East-Southeast trending Vermilion Moraine. This stop includes a quick walk over the end of the Vermilion Moraine and a view to the south over a glacial lake plain (Fig. 7-14). Return to bus Figure 7-14. Annotated lidar digital elevation model showing glaciogenic landforms in the stop 18 area. Stop 19: Contaminated Basal SKI, Dunka Pit Area Longitude/Latitude: 47.69423099°N, -91.85803438E UTM NAD 83 Zone 15N: 585687E, 5282948N The recently permitted extension of Cliffs Natural Resources Northshore mine required the rerouting of St. Louis County Road 623 to the north. The building of the new road resulted in the exposure of rocks of the ~1.85 Ga. Biwabik Iron Formation and the 1.1 Ga. South Kawishiwi intrusion. This short stop will include the examination of three new roadside outcrop areas, including: 1) Metamorphosed Biwabik Iron Formation, 2) Sulfide-poor gabbroic rocks, and 3) Sulfide-rich (pyrrhotite-dominant) 178 �Trip 7 – Classic Outcrops contaminated noritic rocks. Geochemical analyses of rock samples from these three outcrop areas (completed by Duluth Metals in 2012) are given in Table 7-4. Table 7-4. Geochemical analyses of rock samples taken from the roadside outcrops of Stop 19. Sample ID DMR0446 DMR0447 DMR0164 DMR0165 DMR0448 DMR0449 DMR0450 DMR0451 Rock Type Iron Formation Iron Formation Olivine Gabbro Biotitic Gabbro Sulfidic Norite Sulfidic Norite Sulfidic Norite Sulfidic Norite Outcrop # 1 1 2 2 3 3 3 3 Cu (ppm) 4 0 357 218 3960 2630 4380 4270 Ni (ppm) 0 0 82 87 1230 761 1030 1120 Co (ppm) 2 13 44 53 191 117 168 183 Pt (ppb) 5 1 1 1 9 20 6 16 Pd (ppb) 1 3 1 2 53 40 58 60 Au (ppb) 1 1 1 1 18 15 23 23 S (%) -0.01 -0.01 0.02 -0.01 2.61 1.62 1.58 1.79 SiO2 (%) 51.35 38.71 48.14 47.28 42.67 51.62 41.25 43.53 Al2O3 (%) 0.25 0.45 15.21 15.06 15.02 17.56 13.81 13.71 Fe2O3 (%) 40.11 55.01 15.64 16.35 21.04 11.98 22.12 21.34 CaO (%) 6.07 3.33 7.87 8.00 7.51 5.39 6.29 6.90 MgO (%) 1.93 1.52 4.93 5.47 7.15 5.13 6.01 6.97 Na2O (%)t 0.06 0.06 2.90 2.62 2.25 2.72 1.99 2.34 K2O (%) 0.01 0.01 1.12 1.10 0.68 2.54 0.56 0.63 Cr2O3 (%) -0.01 -0.01 0.02 0.01 0.02 0.03 0.02 0.02 TiO2 (%) -0.01 0.05 3.12 3.47 1.77 0.76 1.90 2.31 MnO (%) 0.97 0.51 0.19 0.20 0.16 0.08 0.14 0.18 P2O5 (%) 0.06 0.07 0.43 0.34 0.23 0.05 0.26 0.26 -0.95 -1.37 0.05 -0.09 1.25 1.80 5.13 1.02 LOI (%) Photographs of the Biwabik Iron Formation (outcrop #1) and sulfidic norite of the South Kawishiwi intrusion (outcrop #3) are presented in Figure 7-15. 179 �Trip 7 – Classic Outcrops Figure 7-15. Field photographs of roadside outcrops of stop 5. (A) outcrop of the Biwabik Iron Formation, (B) closeup shot of bedding in granular iron formation (GIF), (C) rusty weathering and gossanous outcrop of the basal mineralized zone of the South Kawishiwi intrusion, and (D) pyrrhotite-rich norite. Return to bus Stop 20: Giants Range Batholith Migmatite/Pyroxenite-Lamprophyre Dike Longitude/Latitude: 47.68689429°N, -92.05199159E UTM NAD 83 Zone 15N: 571144E, 5281936N This field trip ends where we began, within the Neoarchean Giants Range Batholith. This roadside outcrop of the Embarrass tonalite, an early phase of the GRB that was first mapped by Griffin and Morey (1969) and later remapped by Terry Boerboom in 2015. The outcrop, as mapped by Terry Boerboom, consists of intermixed migmatitic biotite-schist and tonalitic gneiss crosscut by a lamprophyre/pyroxenite dike. Approximately 4-miles to the west of this outcrop the Embarrass Tonalite was originally dated by UPb zircon at 2718 ± 67 Ma by Peterman in Southwick (1994). This data has been superseded by a second U-Pb zircon age of 2687 ± 0.6 Ma by Jirsa (2016). RETURN TO MOUNTAIN IRON COMMUNITY CENTER 180 �Trip 7 – Classic Outcrops Acknowledgements Characterizing and evaluating the detailed geology of northeastern Minnesota has been a team effort involving former NRRI geologists, former and current Minnesota Geological Survey geologists and geophysicists, personnel from the Minnesota Department of Natural Resources and students and faculty from the Precambrian Research Center Field Camp, the University of Minnesota Duluth, the University of Minnesota Twin Cities, and the University of Wisconsin Eau Claire. Their efforts are appreciated. As well, permission to map private properties that was granted by local landowners and mineral exploration/mining companies is much appreciated. The authors would like to thank Jim Essig (Manager, Lake Vermilion / Soudan Underground Mine State Park) and James Pointer (Interpretive Supervisor, Lake Vermilion / Soudan Underground Mine State Park) from the MDNR for their support, assistance, and guidance while planning and conducting detailed geological mapping by the NRRI geologists during the DUSEL project and PRC students and faculty in Lake Vermilion State Park in 2010 and 2011. Funding from the Minerals Coordinating Committee, the University of Minnesota Permanent University Trust Fund, the National Science Foundation, the University of Minnesota Duluth Undergraduate Research Opportunities Program, the University of Minnesota Duluth Graduate School, The University of Wisconsin Oshkosh StudentFaculty Research Program, and many mineral exploration companies also enabled geological research in northeastern Minnesota. 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Peterson, D.M., Pointer, J., and Marshak, M., 2009b, Field Trip 3 – Soudan Iron Mine and Physics Lab Tour: 55th Annual Meeting, Institute on Lake Superior Geology, Proceedings Volume 55, Part 2 – Field Trip Guidebook, p. 100-109. Peterson, D.M. and Severson, M.J., 2002, Chapter 4, Archean and Paleoproterozoic rocks forming the footwall of the Duluth Complex, in Geology and mineral potential of the Duluth Complex and related intrusions of northeastern Minnesota, Minnesota Geological Survey, Report of Investigations 58, pp. 76-93. Phinney, W.C., 1969, The Duluth Complex in the Gabbro Lake quadrangle, Minnesota: Minnesota Geological Survey, Report of Investigations 9, 20 p. Phinney, W.C., 1972, Duluth Complex, history and nomenclature, in Sims, P. K., and Morey, G. B., eds., Geology of Minnesota: A Centennial Volume: Minn. Geol. Survey, pp. 333-334. Phinney, W.C., 1972, Northwestern part of Duluth Complex, in Sims, P.K., and Morey, G.B., eds., Geology of Minnesota: A centennial volume: Minnesota Geological Survey, p. 335-345. Ramsey, J.G., and Huber, M.I., 1987, The Techniques of Modern Structural Geology, Academic Press Inc. (London) Ltd. Ripley, E.M., 1986, Origin and concentration mechanisms of copper and nickel in Duluth Complex sulfide zones – a dilemma: Economic Geology, v. 81, p. 974-978. Schmid, R., 1981, Descriptive nomenclature and classification of pyroclastic deposits and fragments; recommendations of the IUGS subcommission on the systematics of igneous rocks: Geology, v. 9, p. 41-43. Schulz, K.J., 1980, The magmatic evolution of the Vermilion greenstone belt, NE Minnesota: Precambrian Research 11:215-245. Severson, M.J., 1994, Igneous stratigraphy of the South Kawishiwi intrusion, Duluth Complex, northeastern Minnesota: University of Minnesota Duluth, Natural Resources Research Institute, Technical Report NRRI/TR93/34, 210 p., 15 plates. Severson, M.J., and Hauck, S.A., 2003, Platinum-group elements (PGEs) and platinum-group minerals (PGMs) in the Duluth Complex: University of Minnesota Duluth, Natural Resources Research Institute, Technical Report, NRRI/TR-2003/37, 296 p., 1 CD. Severson, M.J., Heine, J.J., and Patelke, M.M., 2009, Geologic and Stratigraphic Controls of the Biwabik Iron Formation and the Aggregate Potential of the Mesabi Iron Range, Minnesota: University of Minnesota Duluth, Natural Resources Research Institute, Technical Report NRRI/TR- 2009/09, 173 p. + 37 plates. Sims, P. K., and Southwick, D. L., 1985, Geologic map of Archean rocks, western Vermilion district, northern Minnesota: U. S. Geological Survey, Miscellaneous Investigations Map I-1527, scale 1:48,000. Southwick, D. L., (compiler), 1993, Bedrock geologic map of the Soudan-Bigfork area, northern Minnesota: Minnesota Geological Survey, Miscellaneous Map M-79, scale 1:100,000. Southwick, D. L., Boerboom, T. J., and Jirsa, M. A., 1998, Geologic setting and descriptive geochemistry of Archean supracrustal and hypabyssal rocks, Soudan-Bigfork area, northern Minnesota: implications for metallic mineral exploration: Minnesota Geological Survey, Report of Investigations 51, 69 p. Stott, G., Corkery, T., Leclair, A., Boily, M., and Percival, J., 2007, A revised terrane map for the Superior Province as interpreted from Aeromagnetic Data: 53rd Annual Meeting, Institute on Lake Superior Geology, Proceedings Volume 53, Part 1 – Program and Abstracts, p. 74-76. Thompson, A., 2015, A hydrothermal model for metasomatism of Neoarchean Algoma-type banded iron formation to massive hematite ore at the Soudan Mine, NE Minnesota: unpublished M. S., thesis, University of Minnesota Duluth, 59 p. Vislova, T., 2003, Petrology of the Bald Eagle intrusion and associated rocks and its relevance to crystallization in dynamic magma chambers in the Midcontinent Rift: Unpublished Ph.D. Thesis, University of Minnesota. 186 �Trip 7 – Classic Outcrops Weiblen, P.W., 1965, A funnel-shaped, gabbro-troctolite intrusion in the Duluth Complex, Lake County Minnesota: Unpublished Ph.D. Thesis, University of Minnesota, 161 p. Weiblen, P.W., Morey, G. B., 1980, A summary of the stratigraphy, petrology, and structure of the Duluth Complex: American Journal of Science, vol. 280A, Part I, p 88-133. Weiblen, P.W., Peterson, D.M., and Vislova, T., 2005, Implications of Midcontinent Rift and oceanic ridges analogies and 3-D interpretations of the subsurface structure of the Bald Eagle intrusion in the Duluth Complex and the East Pacific Rise: Institute on Lake Superior Geology, 51st Annual Meeting, Sault Ste Marie, Ontario, v. 51, 3 p. White, C., 2010, The Nokomis Deposit, a Masters of Geology thesis: University of Minnesota, Duluth. White, J. D. L., and Houghton, B. F., 2006, Primary volcaniclastic rocks: Geology, v. 34, no. 8, p. 677-680. Wolff, J.F., 1917, Recent geologic developments on the Mesabi range, Minnesota: American Institute of Mining and Metallurgical Engineers Transactions, v. 56, p. 142-169. Zanko, L.M., Severson, M.J., and Ripley, E.M., 1994, Geology and mineralization of the Serpentine copper-nickel deposit: University of Minnesota Duluth, Natural Resources Research Institute, Technical Report NRRI/TR93/52, 90 p., 3 pls. 187 �Trip 8 – Glacial FIELD TRIP 8 Glacial Lake Norwood and the Koochiching Lobe Phil Larson1, Andrew Breckinridge2, and Howard Mooers3 1 Vesterheim Geoscience PLC Natural Sciences Department, University of Wisconsin Superior, 202 Barstow Hall, Superior, WI 54880 3 Department of Earth and Environmental Sciences, University of Minnesota Duluth, 1114 Kirby Drive, Duluth, MN 55812 2 Introduction The region north of the Giants Range is draped by sediment deposited during the final retreat of the Laurentide ice sheet from northeastern Minnesota. These sediments record the retreat of the Rainy Lobe ice margin to the northeast, the formation of Glacial Lake Norwood (GLN), two successive advances of the Koochiching Lobe from the northwest, and the opening of a western outlet of GLN and its succession by Glacial Lake Agassiz, all over the span of a few thousand years. Historically, the Quaternary geology of this region has received scant attention. However, recent work integrating varve chronology, high resolution LiDAR digital terrain models, till geochemistry, rotasonic drilling, and mapping has resulted in substantially improved and nuanced understanding of the sedimentary processes active, and the sequence of events, during deglaciation. A key finding is that GLN was of significantly longer duration than previously believed, and consequently a stronger control on sediment and landform distribution in the region. Within the footprint of GLN, there is scant evidence for preservation of glacigenic sediments predating the Late Wisconsinan. Interbedded till and glaciolacustrine sediment thicknesses up to 70 m thick preserve evidence of extremely high sedimentation rates in a dynamic sediment system. High rates of sediment delivery by the Koochiching Lobe and analogues from the west served as the dominant sediment source, while intense reworking by wave action in GLN was a dominant control on sediment distribution. Historical Background The earliest formal studies of glacial deposits in northeastern Minnesota were conducted by Upham (1894) who identified a series of moraines across Minnesota. He identified the Vermillion moraine as the 12th moraine in the deglaciation sequence, although he did not define its entire length. Elftman (1898) suggested two lobes for the northeastern portion of Minnesota because of observed till differences and provenances; he named these the Superior and Rainy lobes; the Rainy lobe referring to the ice flowing from the Rainy River areaWinchell (1899) compiled Upham, Elftman, and his own observations into a map of large portions of northeastern Minnesota and description of the surficial deposits. Winchell (1900) described evidence for glacial lakes in Minnesota, including naming Glacial Lake Norwood. Notably, he did not recognize the full extent of Glacial Lake Norwood, assigning portions of the Norwood basin to other glacial lakes. Leverett (1932), based mostly on the work of his predecessors, proposed that northeastern Minnesota was glaciated by three separate lobes of ice. He recognized that the earliest drift in the area was the result of ice flowing from the Patrician [Labradoran] ice center located in the Hudson Bay Lowlands between the Keewatin and Labradorean ice accumulation centers. 188 �Trip 8 – Glacial Figure 8-1. Extent of Glacial Lake Norwood (light green-blue). The lack of modern lakes (blue) in the GLN basin highlight area of significant glaciolacustrine sediment thickness. Major Rainy lobe recessional moraines (brown lines). Proglacial Lake Northofnashwauk is the high-level (elev. >1500’) proglacial lake predating GLN dammed by the St. Louis sublobe. Modern understanding of the surficial geology of northeastern Minnesota began with Wright Wright (1956), who was the first to conduct systematic fieldwork in the area between the border lakes and Lake Superior. Wright and Watts (1969) reconstructed the postglacial vegetational history of northeastern Minnesota, and established the first regional deglaciation chronology, including use of radiocarbon dates to establish absolute ages to deglaciation. These early efforts were summarized in the comprehensive general glacial geologic framework of Minnesota Wright (1972). The United States Geological Survey conducted a comprehensive study of surficial geology and groundwater availability on the Mesabi Iron Range. An initial map (Cotter, Young, and Winter 1964) was later followed by additional publications on the glaciation sequence (Winter 1971) glacial sediment composition (Winter, Cotter, and Young 1973), and groundwater hydrology in glacial drift-hosted aquifers (Winter 1973). Hobbs (1983) provided the first comprehensive account of Glacial Lake Norwood’s extent and history. At that time, he rechristened GLN as Glacial Lake Koochiching, not recognizing the continuity with Winchell’s (1900) definition of GLN. In this respect he was hampered by the paucity of well-defined strandlines for the upper levels of GLN in the rocky meltout till underlying much of the southern portion of the basin. He also posited a late, lower elevation outlet for Glacial Lake Koochiching southward along the Prairie River; recent (2012) LiDAR elevation data (MNDNR 2012) combined with a better defined isostatic rebound reconstruction (Breckenridge 2015) suggest the existence of a southern outlet to GLN untenable. Significantly, Hobbs recognized that Glacial Lake Norwood expanded westward, ultimately establishing an outlet via the McIntosh Channel into Glacial Lake Climax. Continued retreat of the Red River lobe ice margin resulted in coalescence of Glacial Lake Climax and GLN into Glacial Lake Agassiz at the Herman level at 13.9±0.3 cal kyr BP (Lepper et al. 2007). 189 �Trip 8 – Glacial Björck (1990) expanded Wright and Watts (1969) pioneering work by collecting radiocarbon dates north of the Giants Range. He obtained basal radiocarbon dates from Sabin Lake (located in the outflow to GLN) of 10,230±230 and 10,320±170 14C kyr BP. Bjorck’s oldest date was 12,100±150 14C kyr BP from Heikkila Lake, located within the Big Rice moraine. Lowell et al. (2009) reported a radiocarbon date from north of the Vermilion moraine of 12,000±85 14C kyr BP, assigning a minimum age to the Vermilion phase and the moraines to the south of 13.9±0.2 cal kyr BP. These dates establish that Glacial Lake Norwood and drainage through the Embarrass Gap persisted long after the Laurentide ice sheet margin retreated from the Vermilion moraine. Johnson et al. (2016) assigned the glacigenic deposits in northeastern Minnesota to a formal statewide lithostratigraphic framework. Essentially all the aforementioned published work was opened to critical re-examination and revision upon release of 1m resolution LiDAR-derived digital terrain models in the spring of 2012 (MDNR 2012). This data provides resolution orders of magnitude greater than previous topographic models, allowing for vastly improved recognition of some classes of glacigenic landforms, and recognition for the first time of entire new classes of landforms. These advances allowed for significant refinement in mapping of glacial landforms, interpretation of sediment-landform relationships, and development of deglaciation process models. Breckenridge (2015) mapped glacial lake strandlines and developed an isostatic rebound model for much of northern Minnesota, including much of the Glacial Lake Norwood basin, demonstrating the previously unrecognized widespread extent of both Glacial Lake Norwood and the early, high levels of Glacial Lake Agassiz. Bauer et al. (2022) published a surficial geologic map and Quaternary stratigraphic interpretation of much of the GLN basin, relying primarily on the lithostratigraphic mapping approach favored by the Minnesota Geological Survey, but also incorporating landform interpretation based on the 2012 LiDAR data. Glacial History Northeastern Minnesota was continuously covered by ice from the earliest Late Wisconsin ice advance approximately 28 kyr bp until about 11 kyr bp by the Rainy lobe of the Laurentide ice sheet (Clayton and Moran 1982); (Mooers and Lehr 1997)). Although the Glacial Lake Norwood basin was subjected to multiple glacial cycles, the vast majority of glacigenic sediment was deposited during the last retreat of the Laurentide ice sheet during the Late Wisconsinan (<15 kyr bp). The Pleistocene stratigraphic record therefore principally reflects retreat of the ice sheet, and is composed of glacigenic sediment deposited at or near the ice margin. Bedrock Geology and Preglacial Regolith The GLN basin underlain by greenstone (metavolcanic and metasedimentary rocks) and granitoids of the ~2.7 Ga Wawa-Shebandowan Subprovince. The craton was intruded by mafic intrusives of the 2076 Ma Kenora-Kabetogama dike swarm (Southwick and Halls 1987; Buchan, Halls, and Mortensen 1996), while contact relationships indicate the Archean craton was peneplained by the time arenites, ironformation, greywacke, and argillite of ~1.85 Ga Animikie Basin were deposited to the south. Minor mafic dikes related to the 1.1 Ga Midcontinent Rift are known to intrude the Archean craton north of the Giants Range; it is probable that additional similar intrusives have yet to be recognized or mapped. Subsequent to cessation of the Midcontinent Rift, Precambrian bedrock in the GLN basin was subject to a nearly 1 billion year period of chemical weathering and saprolite formation. Saprolite formation was preferentially, but not necessarily, focused along joints, faults, and less weathering-resistant lithologies, forming deep linear weathering pendants beneath a more widespread blanket of saprolite. Commencement of glaciation at the beginning of the Pleistocene ~3 Ma subjected the Superior craton to significant physical erosion for the first time in nearly a billion years. Successive glacial cycles 190 �Trip 8 – Glacial preferentially eroded unconsolidated saprolite, removing first the extensive saprolite blanket, and then excavating saprolite from deep weathering pendants. To the southwest of the GLN basin (central Minnesota), the preglacial saprolite is largely intact beneath Pleistocene glacigenic sediment. To the northeast (northwestern Ontario), preglacial saprolite has been essentially completely removed. Here, the rugged ‘glacially sculpted’ shield terrain characteristic of this region is better explained as the unweathered bedrock surface forming the base of the preglacial saprolite; bedrock has undergone relatively little actual glacial weathering. In the GLN basin proper, preglacial saprolite removal by glacial erosion is incomplete, leaving patchy remnants of unconsolidated preglacial saprolite on the bedrock surface. Saprolite is occasionally intercepted in boreholes. Saprolite and incipient pendant weathering have been encountered associated with joints and fractures as deep as 100 m. Pre-Late Wisconsinan The overlying preglacial saprolite was removed by repeated cycles of erosion and deposition during the Pleistocene. Saprolite eroded as the ice sheet grew (relative early in a glacial cycle) was transported to the margin. The remnant saprolite was blanketed by glacigenic sediment as the ice margin receded (late in the glacial cycle. Subsequent glacial cycles removed both the older glacigenic sediment and additional saprolite. Winter (1971) and Winter, Cotter, and Young (1973) described a dark-colored, sandy-silty calcareous till in exposures in open pit mines on the Mesabi Iron Range. Since this till, where present, occurred immediately above bedrock, they referred to it as the “basal till”. Stark (1977) and (Lehr and Hobbs 1992) described occurrences of Winter’s basal till in exposures in the Dunka Mine. The matrix of Winter’s basal till is calcareous, and the pebble fraction contains carbonate clasts in addition to the granitic and metamorphic lithologies typical of Rainy lobe tills. A northeast-southwest pebble fabric in Winter’s basal till strongly supports a northeastern provenance for this till, indicating the carbonate in pebbles and till matrix is derived from Paleozoic carbonates in the Hudson Bay Lowlands (HBL). A distinctive greywacke lithology (Prest, Donaldson, and Mooers 2000) associated with carbonate-bearing tills has been recovered from glacigenic sediments north of the Giants Range (this author), indicating older carbonatebearing glacigenic sediment was actively reworked during the last retreat of the Laurentide ice sheet. Additional occurrences of this calcareous basal till have been intercepted in boreholes elsewhere in the GLN basin, indicating patchy remnants of preglacial saprolite and older (carbonate-bearing) glacigenic sediment are present beneath the relatively continuous blanket of glacigenic sediment deposited between ca. 15 kyr bp and 10 kyr bp during the last retreat of the Laurentide ice sheet. Post-Last Glacial Maximum – Rainy Lobe Recession of the Laurentide ice sheet margin following its last glacial maximum extent at ca. 20 kyr bp was characterized by rapid melting of ice during summer months followed by stabilization and minor re-advance during the winter. This process formed a series of small, annual recessional moraines, spaced 25-75 m apart, reflecting the long-term retreat rate of the ice sheet. To a significant degree, glacigenic sediment deposited by the Rainy lobe of the Laurentide ice sheet during retreat of its margin from the southwest to northeast is the oldest Pleistocene sediment preserved in the GLN basin. Post-LGM Rainy lobe sediments are typically comprised predominantly of sediment eroded locally from Archean greenstone and granitoid lithologies; this results in significant lithologic and geochemical compositional variability(Larson, 2004; Larson & Mooers, 2004). Lodgment tills are commonly ~2 m thick, while sand and gravel deposited in subaqueous recessional moraines commonly form sharp-crested ridges 5-40 m thick. Distal glaciolacustrine sand and silt commonly drapes older basal lodgment tills and recessional moraines. 191 �Trip 8 – Glacial This process of gradual ice margin retreat was punctuated by surges, episodes of major re-advance and stagnation. These surges resulted in deposition of moraines significantly broader and thicker than annual recessional moraines. The surges may not reflect re-advance of the ice sheet as a whole, but were likely restricted to sectors of the ice margin on the order of 100s of km. They may therefore not be a direct physical reflection of climate fluctuations, but rather reflect internal ice sheet dynamics. Most of the area exposed by ice margin retreat from the Giants Range was inundated in proglacial lakes, successively by Glacial Lake Nashwauk, Glacial Lake Norwood, and finally by Glacial Lake Agassiz. The extended interval between ice margin retreat, lake drainage, and establishment of terrestrial vegetation over most of this area significantly hinders the ability to establish a precise deglaciation chronology (compare Björck (1990)). Allen Phase The oldest major surge-stagnation moraine recognized in the GLN basin is the Allen moraine, which forms a WNW-ESE trending belt of stagnation topography (ice-walled lake plains, meltout tills, etc.), passing through the Embarrass Gap. Ice flow during the Allen phase was generally toward the SSW (bearing 190°). Ice margin retreat from the Allen moraine and opening of meltwater drainage through the Embarrass Gap was the event that by definition resulted in formation of Glacial Lake Norwood. Further ice margin recession and deposition of annual recessional moraines suggests about 150 years before the next major surge-stagnation event. Big Rice and Wahlsten Phases The second major surge-stagnation moraine recognized in the GLN basin is the Big Rice moraine, a W-E trending belt of thick meltout till and stagnation topography. Ice flow during the Big Rice phase was generally toward the SSW (bearing 190°). The third major moraine recognized in the TMM AOI is the Wahlsten moraine, an E-W trending belt of thick meltout till and stagnant ice topography. Ice flow during the Wampus phase was generally toward the S (bearing 180-190°), reflecting a significant reorientation in ice flow of the Laurentide ice sheet. Annual recessional moraines associated with the Wampus and Wahlsten phases consist of both subaqueous moraines composed of sand, gravel, and meltout tills deposited in Glacial Lake Norwood, and subaerial moraines predominantly composed of meltout tills. Vermilion Phase The fourth and final major moraine recognized in the GLN basin is the Vermilion moraine, a 40 m high, 1-2 km wide, WNW-ESE trending belt of thicker meltout till, stagnant ice topography, and subaqueous debris flow fans. Ice flow during the Vermilion phase was generally toward the SSW (bearing 195-205°). The Vermilion moraine truncates the eastern extent of the Wahlsten moraine, reflecting a further significant reorientation in ice flow of the Laurentide ice sheet. The next moraine formed by a major surgestagnation event lies >100 km to the northeast, suggesting an interval of >1000 years of gradual ice margin retreat after the Vermilion phase. Glacial Lake Norwood Retreat of the Rainy lobe margin north of the continental height of land at the Giants Ridge dramatically changed the character of sedimentation associated with the Laurentide ice sheet. South of the divide, meltwater generally flowed downslope away from the margin, depositing outwash in channels and as outwash plains with intervening rolling plains of subglacial lodgment till or moraines composed of hummocky supraglacial meltout till. Immediately upon marginal retreat north of the divide, ponding of meltwater against the ice sheet formed the first of a nearly continuous succession of proglacial lakes. Glacial 192 �Trip 8 – Glacial meltwater and other precipitation ponded against the ice sheet overflowed to the south through a series of successively lower outlets over the height of land, a process that continued until final collapse of the ice sheet in Hudson Bay. Initially, a series of ephemeral lakes formed in stagnant ice north of the divide. These lakes were dammed in part by the advance of the St. Louis Sublobe into the Glacial Lake Upham I basin (see Knaeble et al. (2005) and Larson et al. (2014)) Associated strandlines and meltwater channels are only poorly defined, and meltwater likely drained southward through stagnant Rainy lobe ice karst and St. Louis sublobe ice. Once the active Rainy lobe ice margin receded to the Allen moraine, a stable, relatively long-lived meltwater outlet was established through the Embarrass Gap. By definition, the first proglacial lake located north of the Laurentian Divide that drained through the Embarrass Gap is referred to as Glacial Lake Norwood. Three well-developed outlets to Glacial Lake Norwood are recognized, corresponding to relatively stable, long-lived lake levels. These are herein referred to as Glacial Lakes Norwood I, II, and III, corresponding to successively older and lower lake levels. The initial stable lake level (Glacial Lake Norwood I) was controlled by an outlet channel with a modern floor elevation of about 450 m amsl. This channel was bounded by the Giants Range ridge to the south, and the Allen moraine to the north. The Allen moraine at this location is a major recessional moraine, approximately 500 m wide with in excess of 15 m of vertical relief above the meltwater channel. The ice-cored Allen moraine formed an effective barrier to meltwater drainage blocking most of the Embarrass Gap until after the ice sheet margin retreated from the Vermilion moraine, a time interval of 100s to 1000s of years. Incision of the Glacial Lake Norwood I outlet was inhibited during this time interval in part because the channel was graded to its downstream inlet into Glacial Lake Upham II; only after drainage of this lake was further significant erosion and channel incision in the Embarrass Gap initiated (Larson and Mooers 2009). Gradual collapse of the Allen moraine due to ice melt led to resulted in an episode of collapse and downcutting of the moraine dam, and establishment of a second, lower stable outlet level for Glacial Lake Norwood II in the Embarrass Gap at a modern floor elevation of about 443 m amsl. Paleoislands of outwash and esker sediment located in Glacial Lake Norwood considerable distances north of the Vermilion moraine display well-developed shoreline features corresponding to this outlet, indicating that the downcutting episode occurred well after ice margin retreat from the Vermilion moraine, and that Glacial Lake Norwood II stood at this stable lake level for a relatively long time interval. A second collapse and downcutting episode through the Big Rice moraine led to establishment of the third, and final, lower stable outlet level corresponding to Glacial Lake Norwood III in the Embarrass Gap. An outlet with a modern floor elevation of about 433 m amsl corresponds to a second, lower welldeveloped strandline on esker and outwash paleoislands to the north. During its relatively long history, Glacial Lake Norwood expanded along the receding ice margin to form a lake that ultimately extended ~400 km E-W and in excess of 100 km N-S. The lake experienced two major ice re-advances into its western arm, evidenced by thick (>70 m) accumulations of glaciolacustrine sediment and till. The large fetch of the lake resulted in vigorous wave erosion along its shoreline and the considerable fraction of the lakebed situated above wave base. Final drainage of Glacial Lake Norwood III occurred when a western outlet (the McIntosh spillway) flowing into an early (Herman) level of Glacial Lake Agassiz formed in the vicinity of Trail, MN, 260 km to the west of the Embarrass Gap. 193 �Trip 8 – Glacial Figure 8-2. Outline of maximum extent of Glacial Lake Norwood in northern Minnesota. The lake extended over 350 km from east to west. The final outflow was westward into Glacial Lake Climax near Trail, MN. Glacial Lake Norwood sediments generally consist of gravels and sands in littoral (shallow) environments, reflecting local reworking of till and outwash by wave action, and silt and clay in benthic environments, reflecting settling of suspended fine-grained sediment from the water column. In general, Glacial Lake Norwood sediment sequences fine upward, reflecting diminished wave erosion and the increasing distance of the primary sediment source (the receding ice margin). Koochiching Lobe Subsequent to retreat of the Rainy lobe from the Vermilion moraine, Koochiching lobe (KL) ice re-advanced into the Glacial Lake Norwood basin, this time from the west and the Red River lobe (Meyer, 1993). In marked contrast to the sandy-textured till and glaciofluvial sediment associated with the Rainy lobe, KL diamicton is calcareous, and distinctly finer grained than Rainy lobe till; these sediments are placed in the Blackduck Formation in the MGS lithostratigraphic framework (Johnson et al., 2016). Based on rotosonic drilling, diamictons associated with at least two distinct advances into the GLN basin are present in the field trip area, separated by fine-grained glaciolacustrine sediment. The genesis of these diamictons – till or subaqueous debris flow – are enigmatic; fine-grained lacustrine sediment may grade upward into normally consolidated diamicton, which may grade upward into overconsolidated diamicton of similar composition. The Koochiching lobe advances overran older Rainy lobe landforms, including the Vermilion moraine. There is little evidence for erosion and entrainment of older glacigenic sediment by the KL, and no well-defined moraines or other landforms define the limits of the advances. Sediment was deposited from suspended sediment plumes or debris flows in the proglacial GLN, or as subglacial lodgment till. Although KL ice thickness is unknown, it was sufficiently thick relative to the depth of GLN to preclude development of a calving margin. 194 �Trip 8 – Glacial The majority of sediment shed by the advancing Koochiching lobe was deposited as glaciolacustrine sediment in GLN, and subject to a high degree of reworking in the lacustrine environment. Bedrock highs – shallow areas in GLN – are typically devoid of either older Rainy lobe or KL sediments. In places, a thin boulder lag containing limestone and dolomite clasts attests to the former presence of KL diamicton. In contrast, thicknesses of up to 70 m of till and glaciolacustrine sediment have been reported in intervening bedrock lows. Two distinct till compositions attesting to two distinct source areas have been reported in KL sediments. The younger, overlapping KL till bears greater similarity to calcareous Red River and Des Moines lobe tills elsewhere in Minnesota. In contrast, an older KL till is characterized by a distinctly higher Na2O content, similar to tills exposed at surface in Hubbard and Wadena Counties. Even as the Laurentide ice sheet margin was broadly retreating from Minnesota, both from the Red River Valley and from the Arrowhead, the advances of the Koochiching lobe into the GLN served to block development of meltwater outlets to the north and west. Ultimately, stagnation and wasting of the KL led to westward propagation of GLN until development of the McIntosh spillway. The massive sediment accumulations associated with the KL – up to 70 m in places as previously noted – were deposited over a time interval on the order of 1000 years. Description of Field Trip Stops Stop 1: Glacial Lake Norwood strandline 498550E/5283740N (UTM Zone 15, NAD83) (47.70704, -93.0193) Side Lake 7.5’ USGS Quadrangle This site is located on the uppermost relatively well-developed beach associated with Glacial Lake Norwood. A well-developed boulder lag and wave-cut notch attest to a relatively long-lived stable lake at this level characterized by energetic wave action. To the south, ice collapse pits in the subaqueous deposited Big Rice moraine evidence long lived stagnant ice along this moraine trend. Locally, the Big Rice and other moraines served as ice-cored dams preventing southern outflow. Stop 2: Gravel pit in minor Rainy lobe recessional moraine 498480E/5294980N (UTM Zone 15, NAD83) (47.80817, -93.0203014) Bear River 7.5’ USGS Quadrangle Here a small, sharp-crested subaqueous deposited recessional moraine has been developed into a gravel pit. The flanks of the moraine are draped by fine-grained glaciolacustrine sediment deposited in Glacial Lake Norwood. 195 �Trip 8 – Glacial Stop 3: Gravel pit in large Rainy lobe recessional moraine 495260E/5302290N (UTM Zone 15, NAD83) (47.8739285, -93.0633884) Bear River 7.5’ USGS Quadrangle This gravel pit is developed in a large subaqueous ice marginal fan(?) deposited at the margin of the retreating Rainy lobe. The fan was of sufficient height that its surface was above the GLN wave base, precluding deposition of finer-grained glaciolacustrine sediment. The presence of limestone and dolomite boulders on the fan surface indicate that this area was overrun by Koochiching lobe ice. Stop 4: Wave-washed bedrock high 492880E/5301180N (UTM Zone 15, NAD83) (47.8639194, -93.095198) Bear River 7.5’ USGS Quadrangle This wave-scoured bedrock high evidences the intensity of wave action in Glacial Lake Norwood. Rainy lobe sediment has been almost completely washed away, no Koochiching lobe sediment is preserved, and no glaciolacustrine sediment has been deposited. The very large boulder – a Rainy lobe erratic - attests to the ‘minimum’ particle size of this ‘boulder lag’. Stop 5: Glacial striae and grooves 489180E/5304010N (UTM Zone 15, NAD83) (47.8893303, -93.1447397) Rauch 7.5’ USGS Quadrangle Glacial striae and grooves on outcrop on either side of the road at this stop preserve evidence of ice flow directions for both the Rainy lobe (bearing 190° and 205°) and the later Koochiching lobe (bearing 140°). This indicates that Rainy lobe sediment was largely stripped from bedrock highs by wave action in Glacial Lake Norwood prior to advance of the Koochiching lobe from the west. 196 �Trip 8 – Glacial Stop 6: Borrow pit in reworked calcareous Koochiching lobe drift 490750E/5305460N (UTM Zone 15, NAD83) (47.9024009, -93.1237689) Silverdale 7.5’ USGS Quadrangle This small borrow pit on the margin of a wave-scoured bedrock high contains abundant carbonate pebbles and cobbles. These originated from calcareous Koochiching lobe till deposited on the bedrock high and later eroded by wave action. Stop 7: Slumping Koochiching lobe till and Glacial Lake Norwood 491460E/5311020N (UTM Zone 15, NAD83) (47.9524357, -93.114379) Silverdale 7.5’ USGS Quadrangle This site exposes a sequence of interbedded Koochiching lobe diamicton (till and debris flows(?)) and fine-grained glaciolacustrine sediment adjacent to the Littlefork River. The slope, already prone to slumping by stream erosion at the toe, was further destabilized by construction of the road. In the near vicinity to the southwest, an exploration rotosonic borehole intercepted around 70 m of such sediment. Stop 8: Samuelson Park 492580E/5310600N (UTM Zone 15, NAD83) (47.9459716, -93.0993661) Silverdale 7.5’ USGS Quadrangle Bedrock underlying the small waterfall in the Littlefork River has been striated by the Rainy lobe (bearing 196°). In the upstream direction, boulders eroded from the basal Rainy lobe lodgment till are visible in the stream bed and banks. Such bedrock and boulder lags serve as knickpoints defining the bed of the Littlefork River; steep and commonly slumping slopes adjacent to the river attest to the significant erosion of Koochiching lobe and Glacial Lake Norwood sediment during the Holocene. 197 �Trip 8 – Glacial Stop 9: Embarrass Gap 9A: 551980/5270340N (UTM Zone 15, NAD83) (47.583892, -92.3087077) 9B: 552150/5272700N (UTM Zone 15, NAD83) (47.6056089, -92.3061663) 9C: 552760/5272950N (UTM Zone 15, NAD83) (47.6078088, -92.2980211) Biwabik 7.5’ USGS Quadrangle These three stops are in the three successive major outlet channels for Glacial Lake Norwood. Stop 9A (elevation 450 m) is in a meltwater channel developed at the margin of the Rainy lobe, perhaps against an active ice margin. Stops 9B (elevation 443 m) and 9C (elevation 433 m) are two successively lower major outlets formed as the ice-cored Allen moraine collapsed over a time interval on the order of 1000 years. The outlet at 9C served as the stable outlet to Glacial Lake Norwood until opening of its final lower outlet to the west, through the McIntosh spillway in the vicinity of Trail, Minnesota. 198 �Trip 8 – Glacial REFERENCES Bauer, Emily J., Mark A. Jirsa, Amy Radakovich Block, Terrence J. Boerboom, Val W. Chandler, Dean M Peterson, Kaleb G. Wagner, Elizabeth L. McDonald, Jennifer M. Dengler, Gary N. Meyer, and Jacqueline D. Hamilton. 2022. “Geologic Atlas of St. Louis County, Minnesota.” Minnesota Geological Survey County Atlas Series C–51. Björck, Svante. 1990. “Late Wisconsin History North of the Giants Range, Northern Minnesota, Inferred from Complex Stratigraphy.” Quaternary Research 33:18–36. Breckenridge, Andrew J. 2015. “The Tintah-Campbell Gap and Implications for Glacial Lake Agassiz Drainage during the Younger Dryas Cold Interval.” Quaternary Science Reviews 117:124–34. https://doi.org/10.1016/j.quascirev.2015.04.009. Buchan, Kenneth L., Henry C. Halls, and James K. 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Hobbs, Carrie E. Jennings, Alan R. Knaeble, Barbara A. Lusardi, and Gary N. Meyer. 2016. “Quaternary Lithostratigraphic Units of Minnesota.” Minnesota Geological Survey Report of Investigations 68:262. Knaeble, Alan R., Gary N. Meyer, Lisa M. Marlow, Phillip C. Larson, and Howard D. Mooers. 2005. “Deposits and Landforms in the Region Glaciated by the St. Louis Sublobe.” In Field Trip Guidebook for Selected Geology in Minnesota and Wisconsin, edited by Lori Robinson, Guidebook, 40–79. Minneapolis: Minnesota Geological Survey. Larson, Phillip C., Alan R. Knaeble, Howard D. Mooers, and Lisa M. Marlow. 2014. “The St. Louis Sublobe and Glacial Lake Upham.” Institute on Lake Superior Geology Field Trip Guidebook 60:102–18. Larson, Phillip C., and Howard D. Mooers. 2009. “Glacial Geology of the Vermilion Moraine.” Institute on Lake Superior Geology Field Trip Guidebook 55 (2): 81–99. Lehr, James D., and Howard C. Hobbs. 1992. “Glacial Geology of the Laurentian Divide Area, St. Louis and Lake Counties, Minnesota.” Minnesota Geological Survey Guidebook 18:82. Lepper, Kenneth, Timothy G. Fisher, Irka Hajdas, and Thomas V. Lowell. 2007. “Ages for the Big Stone Moraine and the Oldest Beaches of Glacial Lake Agassiz : Implications for Deglaciation Chronology.” Geology 35 (7): 667–70. https://doi.org/10.1130/G23665A.1. Leverett, Frank. 1932. “Quaternary Geology of Minnesota and Parts of Adjacent States.” USGS Professional Paper 161:149. 199 �Trip 8 – Glacial Lowell, Thomas V., Timothy G. Fisher, Irka Hajdas, K. Glover, Henry M. Loope, and T. Henry. 2009. “Radiocarbon Deglaciation Chronology of the Thunder Bay, Ontario Area and Implications for Ice Sheet Retreat Patterns.” Quaternary Science Reviews 28 (17–18): 1597–1607. https://doi.org/10.1016/j.quascirev.2009.02.025. 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Upham, Warren. 1894. “Preliminary Report of the Field Work during 1893 in Northeastern Minnesota, Chiefly Relating to the Glacial Drift.” Geological and Natural History Survey of Minnesota Annual Report 22:18–86. Winchell, Newton H. 1899. “The Geology of the North Part of St. Louis County.” Geological and Natural History Survey of Minnesota 4:222–65. ———. 1900. “Glacial Lakes of Minnesota.” Geological Society of America Bulletin 12:109–28. Winter, Thomas C. 1971. “Sequence of Glaciation in the Mesabi-Vermilion Iron Range Area, Northeastern Minnesota.” USGS Professional Paper 750–C:C82–88. ———. 1973. “Hydrogeology of Glacial Drift, Mesabi Iron Range, Northeastern Minnesota.” USGS Water Supply Paper 2029-A:31. Winter, Thomas C., Ralph D. Cotter, and H.L. Young. 1973. “Petrography and Stratigraphy of Glacial Drift, Iron Range Area, Northeastern Minnesota.” USGS Bulletin 1331–C:50. Wright, Herbert E. 1956. “Sequence of Glaciation in Eastern Minnesota.” Geological Society of America Guidebook 3:1–24. ———. 1972. “Quaternary History of Minnesota.” In Geology of Minnesota: A Centennial Volume, edited by Paul K. Sims and G.B. Morey, 515–47. St. Paul, Minnesota. Wright, Herbert E., and William A. Watts. 1969. “Glacial and Vegetational History of Northeastern Minnesota.” Minnesota Geological Survey Special Publication 11. 200 � 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/. 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