Sierra Nevada foothills 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 MRDS records of copper, manganese, and zinc production in Sierra Nevada foothills region and Peterson (1984). Selected metavolcanic units from California geologic map known to host VMS deposits within the Foothill Metamorphic Belt.
Identified resources Historical production of copper, gold, lead, manganese, silver, and zinc Identified resources of zinc (Giroux and O'Connor, 2018).
Production Total production during 1942-1946 from Foothill Copper-Lead-Zinc belt is approximately 21.7M lbs Cu, 1.5M lbs Pb, 35.4 M lbs Zn, 14,500 troy oz Au, 552,000 troy oz Ag from 945,000 tons of ore (Martin, 1988). Taliaferro (1943) reports that that production from even the best of the investigated deposits was less than 300 tons of ore. ~175 locations in California total have produced 263,000 short tons pre-1957 (Davis, 1957); historical mines produced 1,000-2,000 tons (Davis, 1957).
Status Past mining; active exploration by Blue Moon Mining at the Blue Moon zinc deposit.
Estimated resources Blue Moon mine Inferred resources: 7.79 M tons @ 8.07% ZnEq cutoff (4.95% Zn and lesser Cu, Ag, Au, Pb cutoffs) (Giroux and O'Connor, 2018).
Geologic maps Matthews and Burnett (1965), scale 1:250,000; Wagner and others (1981), scale 1:250,000; Wagner and others (1991), scale 1:250,000; Saucedo and Wagner (1992); scale 1:250,000; Jennings and others (2010), scale 1:750,000; California Geological Survey Regional Geologic Maps and Geologic Atlas of California, scales 1:250:000.
Geophysical data Adequate Rank 2 aeromagnetic and aeroradiometric coverage.
Favorable rocks and structures Metasedimentary and metavolcanic rocks of the Foothills Metamorphic belt of approximate Jurassic age.
Deposits Foster Mountain (MRDS dep_id: 1003144), Blue Jay, Thomas Mountain, Fort Seward, Hale Creek, Fort Baker, Linser, Keller, 50, Thomas, Camp 9; See Bradley and others (1918) for hundreds of occurrences and historical production (too many to list). Penn, American Eagle, Big Bend, Quail Hill, Blue Moon, Green Mountain and many other mines with polymetallic metal production; see Martin (1988).
Evidence from mineral occurrences MRDS; Bradley and others (1918); Martin (1988).
Geochemical evidence Mn, Fe, Cu, Zn, and Ba.
Geophysical evidence Unknown.
Evidence from other sources Unknown.
Comments Extensive mining district of Kuroko-type VMS deposits stretching for over 200 miles along the Sierra Nevada foothills area. Deposits were of medium to small size in tonnage but supported base metal mining in the late 1800s and early 1900s.
Cover thickness and description Most deposits exposed at the surface and show evidence of surface oxidation.
Authors Laurel G. Woodruff, Catherine Wesoloski, David Reioux, Ben Parrish.
New data needs Updated geologic mapping, geochemistry, aeromagnetic and radiometric surveys.
Geologic mapping and modeling needs Updated geologic mapping.
Geophysical survey and modeling needs High-resolution, Rank 1 aeromagnetic and aeroradiometric surveys.
Digital elevation data needs Partial coverage, mostly from wildfires; needs full coverage.