Copper Mountain

Prospect, Probably inactive

Commodities and mineralogy

Main commodities Cu; Pb
Other commodities Ag; Au
Ore minerals azurite; bornite; chalcopyrite; galena; malachite; pyrite
Gangue minerals calcite; mica; quartz

Geographic location

Quadrangle map, 1:250,000-scale NM
Quadrangle map, 1:63,360-scale D-1
Latitude 64.8719
Longitude -165.2089
Nearby scientific data Find additional scientific data near this location
Location and accuracy The occurrence is on the south side of hill 1690, on the divide between Copper Creek and Dickens Creek. This hill was called Copper Mountain by Cathcart (1922, figure 15). It is locality 7 of Hummel (1962 [MF 242]) and was included with other nearby prospects in locality 16 of Cobb (1972 [MF-463], 1978 [OFR 78-93]).

Geologic setting

Geologic description

The Copper Mountain prospect appears to be the most significant of the several copper prospects in this area (NM051, NM053, this prospect, NM055, NM056, and NM115). As reported by Smith (1908), blocks of marble are malachite stained, and hand-picked material contained 15 percent copper, 20 percent lead, rather high silver, and low gold. Bornite, galena, chalcopyrite, and copper carbonates were present in shallow workings that included a 10 foot shaft and an incline. The workings were caved or flooded in 1920 (Cathcart, 1922). Cathcart (1922) describes the mineralization here as sulfide-bearing, silica-rich layers in bleached marble. Some small quartz veinlets and muscovite are parallel to layers in the host metacarbonate rock. This prospect appears to have similarities to several other copper-bearing deposits in the eastern Teller quadrangle (for example, the Ward mine, Hudson, 1998, TE071) and in the western Solomon quadrangle (for example, the Wheeler mine, Hudson, 1999, SO172).
The country rocks here are interlayered pelitic schist and marble that is part of the Nome Group derived from Proterozoic to early Paleozoic protoliths (Thurston, 1985, figure 3A; Till and Dumoulin, 1994). The Nome Group underwent regional blueschist facies metamorphism in the Late Jurassic or Early Cretaceous (Sainsbury, Coleman, and Kachadoorian, 1970; Forbes and others, 1984; Thurston, 1985; Armstrong and others, 1986; Hannula and McWilliams, 1995). The blueschist facies rocks were recrystallized to greenschist facies or higher metamorphic grades in conjunction with regional extension, crustal melting, and magmatism in the mid-Cretaceous (Hudson and Arth, 1983; Miller and Hudson, 1991; Miller and others, 1992; Dumitru and others, 1995; Hannula and others, 1995; Hudson, 1994; Amato and others, 1994; Amato and Wright, 1997, 1998). Lode gold mineralization on Seward Peninsula is mostly related to the higher temperature metamorphism in the mid-Cretaceous (Apodoca, 1994; Ford, 1993 (thesis); Ford and Snee, 1996; Goldfarb and others, 1997). The relation of the Copper Mountain deposit to the lode gold deposits is uncertain. A mid-Cretaceous age for the stratabound copper deposits is possible, but Copper Mountain could have also formed in late Proterozoic synchronous with emplacement of some orthogneiss or in the early Paleozoic in relation to other plutonism.
Geologic map unit (-165.211525667105, 64.8711435785935)
Mineral deposit model Carbonate-hosted, sulfide-bearing silica-rich rock.
Age of mineralization Late Proterozoic, early Paleozoic, or mid-Cretaceous.
Alteration of deposit Development of silica-rich layers, formation of white mica, bleaching of marble, and oxidation.

Production and reserves

Workings or exploration Explored by pits, trenches, a shallow shaft, and an incline; these were caved or water-filled by 1920.
Indication of production None

References

MRDS Number A012792

References

Apodoca, L.E., 1994, Genesis of lode gold deposits of the Rock Creek area, Nome mining district, Seward Peninsula, Alaska: Boulder, Colorado, University of Colorado, Ph.D. dissertation, 208 p.
Armstrong, R.L., Harakal, J.E., Forbes, R.B., Evans, B.W., and Thurston, S.P., 1986, Rb-Sr and K-Ar study of metamorphic rocks of the Seward Peninsula and southern Brooks Range, Alaska, in Evans, B.W., and Brown, E.H., eds., Blueschists and eclogites: Geological Society of America Memoir 164, p. 184-203.
Ford, R.C., 1993, Geology, geochemistry, and age of gold lodes at Bluff and Mt. Distin, Seward Peninsula, Alaska: Golden, Colorado School of Mines, Ph.D. dissertation, 302 p.
Ford, R.C., and Snee, L.W., 1996, 40Ar/39Ar thermochronology of white mica from the Nome district, Alaska--The first ages of lode sources to placer gold deposits in the Seward Peninsula: Economic Geology, v. 91, p. 213-220.
Goldfarb, R.J., Miller, L.D., Leach, D.L., and Snee, L.W, 1997, Gold deposits in metamorphic rocks in Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 151-190.
Hannula, K.A., and McWilliams, M.O., 1995, Reconsideration of the age of blueschist facies metamorphism on the Seward Peninusla, Alaska, based on phengite 40Ar/39Ar results: Journal of Metamorphic Geology, v. 13, p. 125-139.
Hannula, K.A., Miller, E.L., Dumitru, T.A., Lee, Jeffrey, and Rubin, C.M., 1995, Structural and metamorphic relations in the southwest Seward Peninsula, Alaska; Crustal extension and the unroofing of blueschists: Geological Society of America Bulletin, v. 107, p. 536-553.
Hudson, T.L., 1994, Crustal melting events in Alaska, in Plafker, G., and Berg, H. C., eds., The Geology of Alaska: Geological Society of America, DNAG, The Geology of North America, Vol. G-1, p. 657-670.
Hudson, T.L., and Arth, J. G., 1983, Tin granites of Seward Peninsula, Alaska: Geological Society of America Bulletin, v. 94, p. 768-790.
Miller, E.L., Calvert, A.T., and Little, T.A., 1992, Strain-collapsed metamorphic isograds in a sillimanite gneiss dome, Seward Peninsula, Alaska: Geology, v. 20, p. 487-490.
Thurston, S.P., 1985, Structure, petrology, and metamorphic history of the Nome Group blueschist terrane, Salmon Lake area, Seward Peninsula, Alaska: Geological Society of America Bulletin, v. 96, p. 600-617.
Till, A.B., and Dumoulin, J.A, 1994, Geology of Seward Peninsula and St. Lawrence Island, in Plafker, G., and Berg, H.C., eds., The Geology of Alaska: Geological Society of America, DNAG, The Geology of North America, v. G-1, p. 141-152.
Reporters C.C. Hawley and Travis L. Hudson
Last report date 10/22/1999