Descriptive and Geoenvironmental Model for Cobalt-Copper-Gold Deposits in Metasedimentary Rocks
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Descriptive and Geoenvironmental Model for Cobalt-Copper-Gold Deposits in Metasedimentary Rocks 1 cm Scientific Investigations Report 2010–5070–G U.S. Department of the Interior U.S. Geological Survey COVER. Upper left, Blacktail open pit in the Blackbird district, central Idaho, U.S.A.; view looking approximately northwest (bulldozer for scale in bottom center). Upper right, Skuterud open pit in the Modum district, southern Norway; view looking south (wooden fence on left is about 1.5 meters high). Middle left, South Idaho underground mine in the Blackbird district, showing stratabound lenses and discordant veins of Cu-rich sulfide in dark argillite wall rock. Middle right, hand sample from the Sunshine open pit in the Blackbird district, showing layers of granoblastic cobaltite with a matrix of white quartz and dark green chlorite. Lower left, underground photo of the Skuterud mine showing pink secondary erythrite (a hydrated cobalt arsenate mineral). Lower right, water sampling of acid mine drainage in the Blackbird district, view looking approximately east. Descriptive and Geoenvironmental Model for Cobalt-Copper-Gold Deposits in Metasedimentary Rocks Edited by John F. Slack Chapter G of Mineral Deposit Models for Resource Assessment Scientific Investigations Report 2010–5070–G U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior SALLY JEWELL, Secretary U.S. Geological Survey Suzette M. Kimball, Acting Director U.S. Geological Survey, Reston, Virginia: 2013 For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1–888–ASK–USGS. For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprod To order this and other USGS information products, visit http://store.usgs.gov Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. Suggested citation: Slack, J.F., ed., 2013, Descriptive and geoenvironmental model for cobalt-copper-gold deposits in metasedimentary rocks (ver. 1.1, March 14, 2014): U.S. Geological Survey Scientific Investigations Report 2010–5070–G, 218 p., http://dx.doi.org/10.3133/sir20105070g. ISSN 2328–0328 (online) iii Acknowledgments This report benefited greatly from field guidance and discussions in the Blackbird district with Art Bookstrom and Tom Nash, both now retired from the USGS. We also thank Terje Bjerkgård and Jan Sverre Sandstad of the Geological Survey of Norway in Trondheim for lead- ing an informative geological tour of the Modum district in Norway, and for providing esti- mated production data (tonnage and cobalt grade) for the Skuterud mine; thanks also to Arne Bjørlykke of the University of Oslo for helpful information on the Modum district. Discussions with Murray Hitzman of the Colorado School of Mines (Golden), Mark Barton of the Univer- sity of Arizona (Tucson), and Robin Goad of Fortune Minerals Ltd. (London, Ontario, Canada) have been helpful. Appreciation is also extended to Xiaolin Wang of Nanjing University in China and I-Ming Chou of the USGS for translating parts of several articles in Chinese, Eric Morrissey of the USGS for drafting many of the illustrations, and Pasi Eilu of the Geological- Survey of Finland for providing grade and tonnage data for deposits in Finland and figure 4–3; Matts Willdén (Wiking Mineral AB) and Matti Talikka (Dragon Mining Oy) supplied results of recent exploration on the Gladhammer deposit of Sweden and deposits in the Kuusamo belt of Finland, respectively. Special thanks to Greg Hahn and Jerry Zieg for detailed and helpful reviews of this report, and to Murray Hitzman and Art Bookstrom for comments on an early draft; these colleagues do not agree with all of the interpretations and conclusions presented herein, and are not responsible for any errors or shortcomings that may remain. Finally, we are especially indebted to Richard Goldfarb of the USGS for a comprehensive and incisive review that greatly improved and focused the final version. v Contents 1. Introduction References Cited............................................................................................................................................7 2. Deposit Type and Associated Commodities Name and Synonyms...................................................................................................................................13 Brief Description ..........................................................................................................................................13 Associated Deposit Types ..........................................................................................................................13 Primary and Byproduct Commodities .......................................................................................................13 Trace Constituents .......................................................................................................................................13 Example Deposits.........................................................................................................................................13 Tonnage-Grade Variations ..........................................................................................................................13 References Cited..........................................................................................................................................17 3. Historical Evolution of Descriptive and Genetic Knowledge and Concepts References Cited..........................................................................................................................................26 4. Regional Environment Geotectonic Environment ...........................................................................................................................33 Temporal (Secular) Relations .....................................................................................................................39 Duration of Mineralizing Processes .........................................................................................................39 Relations to Structures ...............................................................................................................................40 Relations to Igneous Rocks ........................................................................................................................40 Relations to Sedimentary Rocks ...............................................................................................................43 Relations to Metamorphic Rocks ..............................................................................................................44 References Cited..........................................................................................................................................44 5. Physical Description of Deposits Geology and Dimensions in Plan View .....................................................................................................53 Blackbird District, USA ......................................................................................................................53 Modum District, Norway....................................................................................................................53 NICO Deposit, Canada .......................................................................................................................55 Werner Lake Deposit, Canada ..........................................................................................................55 Kuusamo Schist Belt, Finland ...........................................................................................................58 Size of Hydrothermal System Relative to Extent of Economically Mineralized Rock .......................58 Vertical Extent ..............................................................................................................................................58 Form and (or) Shape ....................................................................................................................................60 Host Rocks ....................................................................................................................................................60 Structural Setting(s) and Controls ............................................................................................................60 Remote Sensing ...........................................................................................................................................60 References Cited..........................................................................................................................................60 6. Geophysical Characteristics Magnetic Signature .....................................................................................................................................67 vi Gravity Signature .........................................................................................................................................70 Electrical Signature .....................................................................................................................................71