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Great Lakes Tectonic Zone in Marquette Area, Michigan Implications for Archean Tectonics in North-Central United States

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Great Lakes Tectonic Zone in Marquette Area, Michigan Implications for Archean Tectonics in North-Central United States Great Lakes Tectonic Zone in Marquette Area, Michigan Implications for Archean Tectonics in North-Central United States U.S. GEOLOGICAL SURVEY BULLETIN 1904-E AVAILABILITY OF BOOKS AND MAPS OF THE U.S. GEOLOGICAL SURVEY Instructions on ordering publications of the U.S. Geological Survey, along with prices of the last offerings, are given in the cur­ rent-year issues of the monthly catalog "New Publications of the U.S. Geological Survey." Prices of available U.S. Geological Sur­ vey publications released prior to the current year are listed in the most recent annual "Price and Availability List." Publications that are listed in various U.S. Geological Survey catalogs (see back inside cover) but not listed in the most recent annual "Price and Availability List" are no longer available. Prices of reports released to the open files are given in the listing "U.S. Geological Survey Open-File Reports," updated month­ ly, which is for sale in microfiche from the U.S. Geological Survey, Books and Open-File Reports Section, Federal Center, Box 25425, Denver, CO 80225. Reports released through the NTIS may be obtained by writing to the National Technical Information Service, U.S. Department of Commerce, Springfield, VA 22161; please include NTIS report number with inquiry. Order U.S. Geological Survey publications by mail or over the counter from the offices given below. BY MAIL OVER THE COUNTER Books Books Professional Papers, Bulletins, Water-Supply Papers, Techniques of Water-Resources Investigations, Circulars, publications of general in­ Books of the U.S. Geological Survey are available over the terest (such as leaflets, pamphlets, booklets), single copies of Earthquakes counter at the following Geological Survey Public Inquiries Offices, all & Volcanoes, Preliminary Determination of Epicenters, and some mis­ of which are authorized agents of the Superintendent of Documents: cellaneous reports, including some of the foregoing series that have gone out of print at the Superintendent of Documents, are obtainable by mail from WASHINGTON, D.C.-Main Interior Bldg., 2600 corridor, 18th and CSts.,NW. U.S. Geological Survey, Books and Open-File Reports DENVER, Colorado-Federal Bldg., Rm. 169, 1961 Stout St. Federal Center, Box 25425 LOS ANGELES, California-Federal Eldg., Rm. 7638,300 N. Denver, CO 80225 Los Angeles St. MENLO PARK, California-Bldg. 3 (Stop 533), Rm. 3128, Subscriptions to periodicals (Earthquakes & Volcanoes and 345MiddlefieldRd. Preliminary Determination of Epicenters) can be obtained ONLY from RESTON, Virginia-503 National Center, Rm. 1C402,12201 the Sunrise Valley Dr. SALT LAKE CITY, Utah-Federal Bldg., Rm. 8105,125 Superintendent of Documents South State St. Government Printing Office SAN FRANCISCO, California-Customhouse, Rm. 504,555 Washington, D.C. 20402 Battery St. SPOKANE, Washington-U.S. Courthouse, Rm. 678, West (Check or money order must be payable to Superintendent of Docu­ 920 Riverside Ave.. ments.) ANCHORAGE, Alaska-Rm. 101.4230 University Dr. ANCHORAGE, Alaska-Federal Bldg, Rm. E-146, 701 C St. Maps For maps, address mail orders to U.S. Geological Survey, Map Distribution Maps Federal Center, Box 25286 Maps may be purchased over the counter at the U.S. Geologi­ Denver, CO 80225 cal Survey offices where books are sold (all addresses in above list) and at the following Geological Survey offices: Residents of Alaska may order maps from ROLLA, Missouri-1400 Independence Rd. Alaska Distribution Section, U.S. Geological Survey, DENVER, Colorado-Map Distribution, Bldg. 810, Federal New Federal Building - Box 12 Center 101 Twelfth Ave., Fairbanks, AK 99701 FAIRBANKS, Alaska-New Federal Bldg., 101 Twelfth Ave. Chapter E Great Lakes Tectonic Zone in Marquette Area, Michigan Implications for Archean Tectonics in North-Central United States By P.K. SIMS U.S. GEOLOGICAL SURVEY BULLETIN 1904 CONTRIBUTIONS TO PRECAMBRIAN GEOLOGY OF LAKE SUPERIOR REGION P.K. SIMS and LM.H. CARTER, Editors U.S. DEPARTMENT OF THE INTERIOR MANUEL LUJAN, JR., Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. UNITED STATES GOVERNMENT PRINTING OFFICE: 1991 For sale by the Books and Open-File Reports Section U.S. Geological Survey Federal Center Box 25425 Denver, CO 80225 Library of Congress Cataloging-in-Publication Data Sims, P.K. (Paul Kibler), 1918 Great Lakes Tectonic Zone in Marquette area, Michigan implications for Archean tectonics in north-central United States/by P.K. Sims. p. cm. (Contributions to Precambrian geology of Lake Superior region ; ch. E) (U.S. Geological Survey bulletin ; 1904-E) Includes bibliographical references. Supt. of Docs, no.: I 19.3:1904-E 1. Geology, Stratigraphic Archaean. 2. Geology Middle West. 3. Faults (Geology) Michigan Marquette Region. 4. Faults (Geology) Great Lakes Region. I. Title. II. Series. III. Series: U.S. Geological Survey bulletin ; 1904-E QE75.B9 no. 1904-E [QE653.3] 557.3 s dc20 90-13956 [551.7'12] CIP CONTENTS Abstract El Introduction El Acknowledgments E2 Geologic setting E2 Archean greenstone-granite terrane E3 Granitoid rocks E3 Structure E3 Late-tectonic conglomerate E7 Archean gneiss terrane E7 Gneiss and associated granitoid rocks E7 Structure E8 Great Lakes tectonic zone E8 Mylonite E9 Interpretation E9 Kinematic analysis E13 Evolution E13 Concluding remarks E14 References cited E15 FIGURES 1. Geologic map of part of the Marquette I°x2° quadrangle E4 2. Quartz-alkali feldspar-plagioclase diagram for granitoid rocks of Archean greenstone-granite terrane E7 3. Quartz-alkali feldspar-plagioclase diagram for granitoid rocks of Archean gneiss terrane E8 4. Equal-area projection of poles to foliation, lineations, and fold hinges in gneisses of Archean gneiss terrane E9 5. Structure map of southwestern part of Sands 71/2-minute quadrangle showing Great Lakes tectonic zone E10 6. Isometric diagram illustrating geometry and deformational elements of Great Lakes tectonic zone Ell 7. Equal-area projection of poles to foliation, stretching lineation, and fold hinges in Great Lakes tectonic zone Ell 8. Simplified tectonic map of Lake Superior region showing Great Lakes tectonic zone and adjacent Archean terranes E12 TABLES 1. Approximate modes of granitoid rocks in Archean greenstone-granite terrane E6 2. Approximate modes of granitoid rocks in Archean gneiss terrane E8 Contents III CONTRIBUTIONS TO PRECAMBRIAN GEOLOGY OF LAKE SUPERIOR REGION Great Lakes Tectonic Zone in Marquette Area, Michigan Implications for Archean Tectonics in North-Central United States By P.K. Sims Abstract As a whole, the GLTZ is characterized by systematic angular bends that alternately trend west-northwestward, as in The Great Lakes tectonic zone (GLTZ) is an Archean the Marquette area, and northeastward. This zigzag pattern crustal boundary of subcontinental length that separates a probably reflects original irregularities in the continental greenstone-granite terrane (southern part of Superior province margin (Superior province) composed of greenstone-granite of Canadian Shield) on the north from a partly older gneiss crust. Late Archean convergence along this margin resulted in terrane on the south. It is generally interpreted as a paleosuture a variable trajectory of stress into the greenstone-granite crust resulting from continent-continent collision. The tectonic zone and probably in along-strike diachroneity of orogeny. The is covered at imost places in the Lake Superior region by major deformation resulted from oblique compression at Proterozoic rocks or Pleistocene glacial deposits, and its promontories, which acted as buttresses against which position and characteristics previously have been determined compressive stress was directed into the crust. In addition to mainly by geophysical data. Geologic mapping in the Mar­ the dominant foliation, major brittle-ductile to brittle strike-slip quette, Michigan area provides for the first time direct obser­ faults, such as the Vermilion fault system in northern vations of the structure. Minnesota and the Quetico and Rainy Lake-Seine River faults In the Marquette area, the GLTZ is characterized by a in southern Ontario, resulted from a more brittle continuum of zone of mylonite (orthomylonite) that has been superposed on the transcurrent shear caused by collision along the GLTZ. previously deformed rocks of both the Archean greenstone- granite terrane and the Archean gneiss terrane. Foliation in the mylonite strikes about N. 60° W. and dips steeply southwest, presumably subparallel to the boundary between the greenstone-granite and gneiss terranes. A pronounced INTRODUCTION stretching lineation and tight fold hinges plunge about 45° S. 45° E. The attitude of the stretching lineation (line of tectonic The Great Lakes tectonic zone (GLTZ) is an Archean transport) together with asymmetric structures indicative of crustal boundary more than 1,000 km long that separates a movement sense indicates that collision at this locality was greenstone-granite terrane (southern part of Superior prov­ oblique, resulting in dextral-thrust shear along the boundary, ince) on the north from a gneiss terrane on the south (Sims northwestward vergence, and probable overriding of the and others, 1980; Sims and Peterman, 1981; Peterman, greenstone-granite terrane by the gneiss terrane. Transmittal of 1979). It is covered throughout most of the Great Lakes the dextral shear stress across a large area of the greenstone- region by younger Proterozoic rocks or Pleistocene glacial granite crust (Superior province) to the north may have been responsible for the nearly east-west foliation, upright folds, and deposits, but recently it has been delineated and studied in northwest- to east-west-trending dextral faults and shear zones outcrop in an area south of Marquette, Mich. (fig. 1). at least as far north as the Quetico fault, in southern Ontario, The boundary was first recognized in Minnesota a distance of about 250 kilometers. (Sims and Morey, 1973; Morey and Sims, 1976) from regional geologic relations, which indicated that the two basement terranes had different geologic histories and Manuscript approved for publication June 26, 1990.
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