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

Names and other identifiers

Tract name Northern Rocky Mountains (003pCu9004)
Site status deposit

Geographic location

Country United States
State or province Montana
Geographic location -112.511111111, 46.017222222
Geologic map unit -112.511111111, 46.017222222
Nearby data

Geologic information

Deposit type Porphyry copper
Deposit subtype Cu-Mo
Age (Ma) 60Ma
Age determination method unknown
Age range 64–57 Ma
Age reference Singer and others (2008)
Minerals alunite, anhydrite/gypsum, azurite/malachite, biotite, bornite, cerussite, chalcocite/digenite, chalcopyrite, chlorite, copper, covellite, cuprite/tenorite, enargite, fluorite, galena, goethite/limonite, hematite/specularite, jarosite, kaolinite, magnetite, molybdenite, powellite, pyrite, pyrophyllite, rhodochrosite, sericite, siderite, smithsonite/hydrozincite, sphalerite, tetrahedrite/tennantite, wad/psilomelane
Associated rocks breccia, jasper, quartz porphyry, granodiorite, gneiss, schist, aplite, pegmatite, quartz monzonite, rhyolite
Tectonic setting continental margin
Stratigraphic age Paleocene

Commodity and development information

Development status Producer
Major commodities Cu
Tonnage (Mt) 5,220Mt
Cu grade (%) 0.673%
Mo grade (%) 0.028%
Au grade (g/t) 0.042g/t
Ag grade (g/t) 8.6g/t
Contained copper 35,100,000t
Gold-Moly ratio 1.5

Reference information

Study area name United States
References Bartos (1989); Long (1992); Meyer and others (1968); Miller (1978); Tooker (1990); Singer and others (2008)
Site reference U.S. Geological Survey National Mineral Resource Assessment Team (2002)
Bartos, P.J., 1989, Prograde and retrograde base metal lode deposits and their relationship to underlying porphyry copper deposits: Economic Geology, v. 84, p. 1671–1683. (Also available at, K.R., 1992, Reserves and production data for selected ore deposits in the United States found in the files of the Anaconda Copper Company: U.S. Geological Survey Open-File Report 92-002, 21 p. (Also available at
Meyer, Charles, Shea, E.P., Goddard, C.C., Jr., Zeihen, L.G., Guilbert, J.M., Miller, R.N., McAleer, J.F., Brox, G.B., Ingersoll, R.G., Jr., Burns, G.J., and Wigal, T., 1968, Ore deposits at Butte, Montana, in Ridge, J.D., ed., Ore deposits of the United States, 1933–1967: New York, American Institute of Mining and Metallurgical Engineers, v. 2, p. 1373–1427.
Miller, R.N., ed., 1978, Guidebook for the Butte field meeting of the Society of Economic Geologists (2d ed.): Society of Economic Geologists meeting, Butte, Mont., August 18–21, 1973, 234 p.
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, E.W., 1990, Gold in the Butte district, Montana, in Shaw, D.R., and Ashley, R.P., eds., Gold in porphyry copper systems: U.S. Geological Survey Bulletin 1857-E, p. E17–E27. (Also available at