North central California massive sulfide

Region West, Northwest
Mineral systems
Deposit types
Critical minerals
Other minerals

Information leading to the delineation of this focus area

Basis for focus area Permissive tracts PC15 and PC16 for Massive sulfide, Kuroko-type deposits polygons extracted and merged from the 1995 National Assessment (U.S. Geological Survey National Mineral Resource Assessment Team, 2002). Also tracts PC14 and PC14a in Box and others (1996).
Identified resources Historical production of copper, gold, silver, and zinc.
Production Iron Mountain: produced 197,951,738 lbs Cu by the end of 1919; major Cu production between 1925 and 1947; 2,600,000 tons of gossan contained 8.3 oz/t Au and 0.073 oz/t Ag (Kinkel and others, 1956); Balaklala (1915-1919): 5351,171 short tons @0.031 oz/t Au, 1 oz/t Ag, 3.05% Cu (Kinkel and others, 1956); Mammoth (1905-1925): 3,311,145 tons Cu ore, averaged 3.99% Cu, 4.2% Zn, 2.24 oz/t Au and 0.038 oz/t Ag; and 84,000 tons Zn ore, averaged 21.1% Zn, 2.4% Cu. 5.79 oz/t Ag, and 0.078 oz/t Au (Lydon and O'Brien, 1974).
Status Past mining. Iron Mountain is a Superfund site.
Estimated resources Unknown.
Geologic maps Fraticelli and others (2012), scale 1:100,000; Kinkel and Albers (1951), scale 1:5,800; Hollister and Evans (1965), scale 1:24,000.
Geophysical data Inadequate aeromagnetic and aeroradiometric data.
Favorable rocks and structures The focus area is based on the extent of the Devonian Copley Greenstone and Balaklala Rhyolite, host rocks for deposits in the West Shasta district (Kinkel and others, 1956; Albers and Bain, 1985). Eastern part of the area is based on the extent of the Triassic Dekkas Andesite and Bully Hill Rhyolite, host rocks for the Kuroko-type massive sulfide deposits in the East Shasta district (Albers and Robertson, 1961).
Deposits West Shasta district: Iron Mountain mine (MRDS dep_id: 10077593), Mammoth (MRDS dep_id: 10310642), Balaklala mine (MRDS dep_id: 10077587); East Shasta district: Afterthought (MRDS dep_id: 10077520), Bully Hill-Rising Star (MRDS dep_id: 10262643).
Evidence from mineral occurrences MRDS.
Geochemical evidence VMS deposits enriched in Fe, Cu, Zn, Ba, Pb, As, Hg, Sn, Ag, and Au. Streambed sediments have anomalous Cu, Zn, Pb, As, Ag, Au, Hg, and Ba (Silberman and others, 1994).
Geophysical evidence Unknown.
Evidence from other sources Bismuth, Ga, and Zn occurrences.
Comments The West Shasta District, in the Klamath Mountains, has been an important mineral producer in the past. The Iron Mountain mine is one of the larger examples of volcanogenic massive sulfide deposits in the United States, and has produced nearly 11 metric tons of gold. The East Shasta district produced less than 700,000 metric tons of ore, mainly from two massive sulfide deposits, the Afterthought and Bully Hill-Rising Star.
Cover thickness and description Mineralization exposed at the surface; mining was underground.
Authors Allen K. Andersen, Deborah A. Briggs.
New data needs Updated geologic mapping, geochemistry, aeromagnetic and aeroradiometric surveys.
Geologic mapping and modeling needs Updated geologic mapping.
Geophysical survey and modeling needs High resolution, Rank 1 aeromagnetic and aeroradiometric surveys would be useful in delineating serpentine, ultramafics, but unclear if a new geophysical survey would be effective.
Digital elevation data needs Lidar partial coverage, mostly from wildfires; needs full coverage.