Baultoff

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

Names and other identifiers

GMRAP ID 11
Tract name Eastern Alaska Range and Wrangell Mountains (003pCu5002)
Site status deposit

Geographic location

Country United States
State or province Alaska
Geographic location -141.211944444, 62.110555556
Geologic map unit -141.211944444, 62.110555556
Nearby data

Geologic information

Deposit type Porphyry copper
Deposit subtype Cu-Mo
Age (Ma) 111Ma
Age determination method K-Ar
Age range 111 ±3.6 Ma (Inferred from age of Klein Creek pluton.)
Age reference Richter, Lanphere, and Matson (1975)
Minerals actinolite, albite, anhydrite, chalcopyrite, chlorite, pyrite, sericite
Associated rocks granodiorite porphyry, quartz diorite porphyry, quartz porphyry, andesite, basalt, diorite, granodiorite, quartz monzonite
Tectonic setting continental margin
Stratigraphic age Cretaceous

Commodity and development information

Development status Prospect
Major commodities Cu
Minor commodities Ag, Au, Mo
Tonnage (Mt) 140Mt
Cu grade (%) 0.2%
Mo grade (%) 0.01%
Au grade (g/t) 0.01g/t
Contained copper 280,000t
Gold-Moly ratio 1

Reference information

Comments Disseminated pyrite and chalcopyrite occur in hornblende diorite and quartz porphyry of the mid-Cretaceous-age Klein Creek pluton. The deposit is estimated to contain 160 million tons with an average grade of 0.20 percent copper and very low amounts of molybdenum. A 400- by 1,000-meter central altered zone is characterized by albite, chlorite, sericite and late anhydrite veins; it is within a 2,000- by 3,000-meter outer zone marked by abundant sericite and pyrite. Surface exploration and some diamond drilling.
Study area name United States
References U.S. Geological Survey (2014a); Hollister (1978); Nokleberg and others (1987); Nokleberg and others (1995); Richter, Singer and Cox (1975); Young and others (1997); Richter, Lanphere, and Matson (1975); Singer and others (2008)
Site reference U.S. Geological Survey National Mineral Resource Assessment Team (2002)
Hollister, V.F., 1978, Geology of the porphyry copper deposits of the western hemisphere: New York, American Institute of Mining and Metallurgical Engineers, 219 p.
Nokleberg, W.J., Bundtzen, T.K., Berg, H.C., Brew, D.A., Grybeck, D., Robinson, M.S., Smith, T.E., and Yeend, W., 1987, Significant metalliferous lode deposits and placer districts of Alaska: U.S. Geological Survey Bulletin 1786, 104 p. (Also available at http://pubs.usgs.gov/bul/1786/report.pdf.)
Nokleberg, W.I., Bundtzen, T.K., Brew, D.A., and Plafker, G., 1995, Metallogenesis and tectonics of porphyry copper and molybdenum (gold, silver) and granitoid-hosted gold deposits of Alaska, in Schroeter, T.G., ed., Porphyry deposits of the northwestern Cordillera of North America: Canadian Institute of Mining, Metallurgy and Petroleum Special Volume 46, p. 103–141.
Richter, D.H., Singer, D.A., and Cox, D.P., 1975, Mineral resources map of the Nabesna quadrangle, Alaska: U.S. Geological Miscellaneous Field Studies Map 655-K, scale 1:250,000. (Also available at http://ngmdb.usgs.gov/Prodesc/proddesc_3780.htm.)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/.U.S. Geological Survey, 2014a, Alaska Resource Data File (ARDF): U.S. Geological Survey database, accessed February 5, 2014, at http://mrdata.usgs.gov/ardf/.
Young, L.E., St. George,P., and Bouley, B.A., 1997,Porphyry copper deposits in relation to the magmatic history and palinspastic restoration of Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral deposits of Alaska: Economic Geology Monograph 9, p. 306–333.