Sierra Nevada foothills orogenic Au

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

Information leading to the delineation of this focus area

Basis for focus area Map of California showing locations of gold districts from Clark (1970a). Correlation of the Klamath Mountains and Sierra Nevada from Irwin (2003).
Identified resources Historical production of gold and tungsten.
Production The Grass Valley district produced over 17 million ounces of gold. The Idaho-Maryland mine (sporadic mining between 1862 and 1954) produced 2,383,000 oz Au from 5,546,000 tons of ore for an average grade of 0.43 oz/ton. When Au mining ended, the government subsidized W production from 1954 to 1957 (Pease, 2009).
Status Past mining, current exploration.
Estimated resources Unknown.
Geologic maps Jennings and others (2010), scale 1:750,000.
Geophysical data Inadequate Rank 3, 4, and 5 aeromagnetic coverage and Rank 5 aeroradiometric coverage.
Favorable rocks and structures Northern Sierra terrane, Calaveras Complex, Jura-Triassic arc belt, Jurassic accretionary arc sequence. Variable rocks include diorite, granite, greenstone, schist, slate, serpentinite.
Deposits Grass Valley district (MRDS dep_id: 60000011) (Idaho-Maryland mine).
Evidence from mineral occurrences MRDS; Clark (1970a).
Geochemical evidence Common As-bearing pyrite and arsenopyrite are associated with Au ore. Various telluride minerals can be ore or are associated with Au ore.
Geophysical evidence Unknown.
Evidence from other sources Goldfarb and others (2017).
Comments Calaverite (or gold telluride) was discovered in the Sierra Nevada foothills in 1861 and was named after Calaveras County.
Cover thickness and description Mineralization may extend from the surface to great depths.
Authors Ryan D. Taylor.
New data needs Geophysics, geologic mapping.
Geologic mapping and modeling needs Detailed geologic mapping.
Geophysical survey and modeling needs High resolution aeromagnetic and aeroradiometric coverage.
Digital elevation data needs Lidar inadequate.