The Gogebic iron range: a sample of the northern margin of the Penokean fold and thrust belt / W.F.Cannon et al. - Washington: U.S. Geological Survey, 2008. - v, 44 p. - (U.S. Geological survey. Professional paper; 1730). - Ref.: p.40-44. - ISBN-13 978-1-4113-1917-2  Место хранения:   018 | Институт нефтегазовой геологии и геофизики им. А.А.Трофимука | Новосибирск | Библиотека

Оглавление / Contents

Abstract ........................................................ 1 Introduction .................................................... 2 General Geology ................................................. 4 Neoarchean Rocks ............................................. 4 Paleoproterozoic Rocks ....................................... 4 Chocolay Group ............................................ 6 Sunday Quartzite ....................................... 6 Bad River Dolomite ..................................... 6 Menominee Group ........................................... 8 Palms Formation ........................................ 8 Ironwood Iron-Formation ................................ 8 Relation between the Ironwood Iron-Formation and the Emperor Volcanic Complex ........................... 9 Stratigraphic Relations in the Menominee Group and Emperor Volcanic Complex .............................. 10 Baraga Group ............................................. 11 Copps Formation ....................................... 12 Tyler Formation ....................................... 12 Pabst Member .......................................... 12 Age and Correlation of the Marquette Range Supergroup .... 13 Stratigraphic Correlations within the Marquette Range Supergroup ...................................... 13 Absolute Age of the Marquette Range Supergroup ........ 14 Paleoproterozoic Intrusive Rocks ......................... 15 Mesoproterozoic Rocks ....................................... 19 Structural Geology ............................................. 19 Mesoproterozoic Structures .................................. 19 Atkins Lake-Marenisco Fault .............................. 21 Paleoproterozoic Structures ................................. 22 Central Gogebic Iron Range ............................... 23 Eastern Gogebic Iron Range ............................... 24 Extensional Phase ..................................... 24 Contractional Phase ................................... 25 Summary of Eastern Gogebic Iron Range Structure ....... 27 Western Gogebic Iron Range ............................... 27 Economic Geology ............................................... 31 Natural Iron Ores ........................................... 31 Taconite .................................................... 33 Synopsis ....................................................... 34 Sedimentation of the Marquette Range Supergroup ............. 34 Environmental Setting of Deposition ...................... 34 Chocolay Group ........................................ 34 Menominee Group ....................................... 34 Baraga Group .......................................... 35 Tectonic Setting of Deposition ........................... 35 Chocolay Group ........................................ 35 Menominee Group ....................................... 35 Baraga Group .......................................... 36 Volcanism ............................................. 36 Penokean Deformation ........................................ 38 Acknowledgments ................................................ 40 References Cited ............................................... 40 Plates (In pocket) 1. Geologic maps of the Gogebic iron range. Figures 1. Generalized geologic map of the upper Great Lakes region, U.S. and Canada ............................................. 3 2. Schematic stratigraphic section along approximately 150 km of the Gogebic iron range ................................... 5 3. Geologic map of part of the eastern Gogebic Range ........... 7 3-4.Photographs showing 4. Stromatolites in Bad River Dolomite ......................... 8 5. Examples of typical rocks types of the Emperor Volcanic Complex .................................................... 10 6. Schematic longitudinal section of part of the central Gogebic iron range ......................................... 13 7. Geochemical discrimination diagrams showing the subalkaline tholeiitic character of the mafic rocks from the Emperor Volcanic Complex and diabase near Atkins Lake ....................................................... 14 8. Chondrite-normalized rare earth element plot and primitive-mantle-normalized multi-element plot for mafic rocks from the Emperor Volcanic Complex and diabase near Atkins Lake ................................................ 18 9. Block diagram illustrating the geometric relationship between Neoarchean, Paleoproterozoic and Mesoproterozoic rocks in the central part of the Gogebic iron range ........ 22 10. Photomicrographs of rocks from the Atkins Lake-Marenisco fault zone on the north side of the Marengo River .......... 23 11. Schematic block diagram illustrating the geometry of fault sets in the central Gogebic iron range ............... 25 12. Diagram illustrating the restoration of the Paleoproterozoic geometry of the Presque Isle trough constructed by compensating for the Mesoproterozoic northward rotation ......................................... 27 13. Small scale recumbent fold in Ironwood Iron-Formation in NEH, sec. 24, T.44 N., R.4W ................................ 30 14. Schematic block diagram showing the relation of natural ores to the stratigraphy and structure of the central Gogebic iron range ......................................... 32 15. Primitive-mantle-normalized multi-element plot showing the compositional similarity of mafic rocks from the Emperor Volcanic Complex and diabase near Atkins Lake with basalts of the Hemlock Formation and Badwater Greenstone ................................................. 37 16. Tectonic discrimination diagrams showing the within-plate affinity of the mafic rocks of the Emperor Volcanic Complex and diabase from near Atkins Lake .................. 38 17. Primitive-mantle-normalized multi-element plot showing the compositional similarity of rift-related Late Silurian to Early Devonian basalts from the northern Appalachians and the mafic rocks from the Emperor Volcanic Complex and diabase near Atkins Lake .............. 39 Tables 1. Whole-rock chemical analyses of Paleoproterozoic mafic rocks from the Emperor Volcanic Complex and diabase near Atkins Lake ............................................... 16 2. Sequence of tectonic events in the Gogebic iron range ...... 20