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Ajo

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Porphyry copper deposit in Arizona, United States

Names and other identifiers

GMRAP ID 74
Alternate names New Cornelia
Tract name Western Mexican Basin and Range and Laramide Southwest (003pCu3006x)
Site status deposit

Geographic location

Country United States
State or province Arizona
Geographic location -112.865277778, 32.356944444
Geologic map unit -112.865277778, 32.356944444
Nearby data
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Geologic information

Deposit type Porphyry copper
Age (Ma) 63Ma
Age determination method unknown
Age range 63 Ma
Age reference Singer and others (2008)
Minerals albite, alunite, anhydrite/gypsum, biotite, barite, bornite, brochantite, carbonate, chalcocite, chalcopyrite, chlorite, chrysocolla, covellite, cuprite, epidote, gold, hematite/specularite, ilmenite, jarosite, magnetite, malachite, molybdenite, pyrite, sericite, shattuckite, sphalerite, tetrahedrite/tennantite
Associated rocks andesite dike, andesite porphyry dike, quartz diorite, quartz monzonite, quartz monzonite porphyry, pegmatite, rhyolite, gneiss, andesite flow, andesite breccia, fanglomerate, tuff
Tectonic setting continental margin
Stratigraphic age Paleocene

Commodity and development information

Development status Occurrence
Major commodities Cu
Tonnage (Mt) 742Mt
Cu grade (%) 0.576%
Mo grade (%) 0.0089%
Au grade (g/t) 0.16g/t
Ag grade (g/t) 1.7g/t
Contained copper 4,270,000t
Gold-Moly ratio 18

Reference information

Comments Exposed.
Study area name United States
References Cox, Force and others (2006); Dixon (1966); Gilluly (1946); Long (1995); McDowell (1971); Niemuth (1994); Trischka (1938); Wilkinson and others (1999); Singer and others (2008); Singer and others (2005)
Site reference U.S. Geological Survey National Mineral Resource Assessment Team (2002)
Cox, D.P., Force, E.R., Wilkinson, W.H., More, S.W., Rivera, J.S., and Wooden, J.L., 2006, The Ajo mining district, Pima County, Arizona—Evidence for middle Cenozoic detachment faulting, plutonism, volcanism, and hydrothermal alteration: U.S. Geological Survey Professional Paper 1733, 46 p., scale 1:24,000. (Also available at http://pubs.usgs.gov/pp/pp1733/.)
Dixon, D.W., 1966, Geology of the New Cornelia mine, Ajo, Arizona, in Titley, S.R., and Hicks, C.L., eds., Geology of the porphyry copper deposits, southwestern North America: Tucson, University of Arizona Press, p. 123–132.
Gilluly, James, 1946, The Ajo mining district, Arizona: U.S. Geological Survey Professional Paper 209, 112 p. (Also available at http://pubs.usgs.gov/pp/0209/report.pdf.)
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.
McDowell, F.W., 1971, K-Ar ages of igneous rocks from the Western United States: Isochron/West, no. 11, 41 p.
Niemuth, N.J., 1994, The primary copper industry of Arizona, 1992: Arizona Department of Mines and Mineral Resources Special Report 20, 58 p. (Also available at http://mines.az.gov/DigitalLibrary/ADMMR_Reprints/CopperReports/cu1992SR20.pdf.)Singer, D.A., Berger, V.I., and Moring, B.C., 2005, Porphyry copper deposits of the world—Database, map, and grade and tonnage models: U.S. Geological Survey Open-file Report 2005-1060, [9] p. and digital data, accessed December 31, 2013, at http://pubs.usgs.gov/of/2005/1060/.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/.
Trischka, C., 1938, Bisbee district: Arizona Bureau of Mines, Geological Series, Bulletin 145, p. 32–41.
Wilkinson, W.H., More, S.W., Rivera, J.S., and Mortensen, J.K., 1999, Geological and structural evolution of the Ajo copper deposit, Pima Co., AZ [abs.]: Society for Mining, Metallurgy, and Exploration (SME) 1999 Annual Meeting: Denver, Colorado, Technical Program with Abstracts, p. 31.