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Kirwin

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Porphyry copper (Cu-Mo) deposit in Wyoming, United States

Names and other identifiers

GMRAP ID 28
Alternate names Kerwin/Bald Mtn.
Tract name Northern Rocky Mountains (003pCu9004)
Site status deposit

Geographic location

Country United States
State or province Wyoming
Geographic location -109.288049015, 43.870973424
Geologic map unit -109.288049015, 43.870973424
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Geologic information

Deposit type Porphyry copper
Deposit subtype Cu-Mo
Age (Ma) 40Ma
Age determination method unknown
Age range 40 Ma
Age reference Singer and others (2008)
Minerals anglesite, azurite/malachite, biotite, chalcocite/digenite, chalcopyrite, chlorite, copper, covellite, cuprite, epidote, galena, goethite/limonite, gold, hematite/specularite, kaolinite/illite, magnetite, molybdenite, montmorillonite, opal, pyrite, sericite, stephanite, tetrahedrite
Associated rocks diorite, diorite porphyry, quartz monzonite, rhyolite tuff, granodiorite, limestone, andesite, andesite porphyry, andesite breccia, granodiorite, tuff
Tectonic setting continental margin
Stratigraphic age Eocene

Commodity and development information

Development status Occurrence
Major commodities Cu
Tonnage (Mt) 118Mt
Cu grade (%) 0.76%
Mo grade (%) 0.02%
Au grade (g/t) 0.03g/t
Ag grade (g/t) 1.5g/t
Contained copper 900,000t
Gold-Moly ratio 2

Reference information

Comments 0.25 oz/ton Au, 11.8 oz/ton Ag.
Study area name United States
References Hausel (1989); Hausel (1993); Long (1995); Schassberger (1972); Singer and others (2008)
Site reference U.S. Geological Survey National Mineral Resource Assessment Team (2002)
Hausel, D.W., 1989, The geology of Wyoming’s precious metal lode and placer deposits: Laramie, Wyo., Geological Survey of Wyoming Bulletin 68, 248 p.
Hausel, D.W., 1993, Metal and gemstone deposits of Wyoming, in Snoke, A.W., Steidtmann, J.R., and Roberts, S.M., eds., Geology of Wyoming: Laramie, Wyo. Geological Survey of Wyoming Memoir 5, p. 816–835.
Long, K.R., 1995, Production and reserves of Cordilleran (Alaska to Chile) porphyry copper deposits, in Pierce, F.W., and Bolm, J.G., eds., Porphyry copper deposits of the American Cordillera: Tucson, Arizona Geological Society Digest 20, p. 35–68.
Schassberger, H.T., 1972, A K-Ar age of a quartz monzonite dike in the Kerwin mining district, Park County, Wyoming: Isochron/West, no. 4, p. 31.
Singer, D.A., Berger, V.I., and Moring, B.C., 2008, Porphyry copper deposits of the world—Database and grade and tonnage models, 2008: U.S. Geological Survey Open-File Report 2008-1155, [45] p. and digital data, accessed December 31, 2013, at http://pubs.usgs.gov/of/2008/1155/.