| 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. |
