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Porphyry copper deposit in Washington, United States

Names and other identifiers

GMRAP ID 23
Alternate names Earl
Tract name Cascade Arc (003pCu9014)
Site status deposit

Geographic location

Country United States
State or province Washington
Geographic location -122.080833333, 46.356388889
Geologic map unit -122.080833333, 46.356388889
Nearby data
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Geologic information

Deposit type Porphyry copper
Age (Ma) 16Ma
Age determination method unknown
Age range 17–16 Ma
Age reference Singer and others (2008)
Minerals arsenopyrite, azurite/malachite, biotite, bornite, chalcopyrite, chlorite, chrysocolla, copper, covellite, epidote, galena, goethite/limonite, kaolinite, magnetite, molybdenite, pyrite, Sb-mineral, sericite, sphalerite, tourmaline
Associated rocks andesite dike, breccia, dacite dike, quartz porphyry dike, volcanic rocks, volcaniclastic rocks, granodiorite, quartz diorite, quartz monzonite
Tectonic setting continental margin
Stratigraphic age Miocene

Commodity and development information

Development status Occurrence
Major commodities Cu
Tonnage (Mt) 523Mt
Cu grade (%) 0.36%
Mo grade (%) 0.011%
Au grade (g/t) 0.24g/t
Ag grade (g/t) 1.6g/t
Contained copper 1,900,000t
Gold-Moly ratio 22

Reference information

Study area name United States
References Chaffee (1994); Derkey and others (1990); Lasmanis (1995); Singer and others (2008)
Site reference U.S. Geological Survey National Mineral Resource Assessment Team (2002)
Chaffee, M.A., 1994, Data for four drill holes, Mount Margaret copper-molybdenum-gold deposit, Skamania County, Washington: U.S. Geological survey Open-File Report 94-2-A, 10 p. (Also available at http://pubs.er.usgs.gov/publication/ofr942A.)Derkey, R.E., Joseph, N.L., and Lasmanis, Raymond, 1990, Metal mines of Washington—Preliminary report: Washington Division of Geology and Earth Resources Open File Report 90-18, 577 p. (Also available at http://panoramagem.com/News/2013/ger_ofr90-18_metal_mines_pt1.pdf, http://panoramagem.com/News/2013/ger_ofr90-18_metal_mines_pt2_1.pdf, http://panoramagem.com/News/2013/ger_ofr90-18_metal_mines_pt2_2.pdf, and http://panoramagem.com/News/2013/ger_ofr90-18_metal_mines_pt2_3.pdf.)
Lasmanis, Raymond, 1995, Regional geological and tectonic setting of porphyry deposits in Washington State, 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. 77–102.
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/.