Porphyry copper deposit in Alaska, United States

Names and other identifiers

Tract name Alaska Peninsula and Aleutian Islands (003pCu5006)
Site status deposit

Geographic location

Country United States
State or province Alaska
Geographic location -160.6753, 55.6298
Geologic map unit -160.6753, 55.6298
Nearby data

Geologic information

Deposit type Porphyry copper
Age (Ma) 6.4Ma
Age determination method Re-Os molybdenite
Age range 6.4 Ma
Age reference Singer and others (2008); Wilkins (2011)
Minerals apatite, biotite, chalcocite, chalcopyrite, chlorite, chrysocolla, covellite, cuprite, epidote, fluorite, goethite/limonite, hematite, kaolinite, magnetite, molybdenite, pyrite, rhodochrosite, rutile, sericite
Associated rocks dacite porphyry, hornfels, quartz diorite porphyry, andesite, carbonaceous shale, sandstone, volcaniclastic sedimentary rocks
Tectonic setting mixed
Stratigraphic age Miocene

Commodity and development information

Development status Prospect
Major commodities Cu, Mo
Minor commodities Ag, Au, Pb, Sb, Zn
Tonnage (Mt) 159Mt
Cu grade (%) 0.372%
Mo grade (%) 0.018%
Au grade (g/t) 0.05g/t
Contained copper 591,000t
Gold-Moly ratio 3

Reference information

Comments Associated with a quartz diorite pluton that cuts Paleocene- to Eocene-age sedimentary rock of the Tolstoy Formation; the stock and Mo mineralization have been dated at 6 million years (Wilson and others, 1996; Wilkins, 2011). The alteration consists of a barren, potassically-altered core zone, an intermediate zone characterized by pervasive quartz and sericite, and a propylitic outer zone. In 1975, the resource was estimated to be 126 million tons with a grade of 0.403 percent copper and 0.025percent molybdenum; there was said to be potential for an additional 49 million tons of chalcocite-enriched ore. In 2013, the resource was estimated to be 173 million metric tons with a grade of 0.088 g/t Au, 0.35% copper, and 0.02% molybdenum (based on 49 drill holes totaling 9,177 m).
Study area name United States
References U.S. Geological Survey (2014a); Wilkins (2011); Wilson and others (1996); Farrow and Arseneau (2013); Nokleberg and others (1987); Young and others (1997); Singer and others (2008)
Site reference U.S. Geological Survey National Mineral Resource Assessment Team (2002)