American River Placers

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

Information leading to the delineation of this focus area

Basis for focus area Outline of placer localities in MRDS with PGE production listed by Peterson (1994); localities may not be exact.
Identified resources Historical production of gold and PGE.
Production Folsom placer produced about 5,000 oz PGE.
Status Past placer mining.
Estimated resources Unknown.
Geologic maps Bartow and Helley (1979), scale 1:62,500.
Geophysical data Inadequate aeromagnetic and aeroradiometric coverage.
Favorable rocks and structures Gravels in or along the American River and near the lower contacts of the Laguna and Mehrten Formations.
Deposits Folsom placer (MRDS dep_id: 10103627).
Evidence from mineral occurrences MRDS.
Geochemical evidence No data.
Geophysical evidence Unknown.
Evidence from other sources None.
Comments Reworking of historical tailings, especially if coupled with mercury cleanup, could provide potential PGE resources if technology and economic incentives warranted the effort.
Cover thickness and description Surface alluvial/tailings deposits.
Authors Jane M. Hammarstrom, Erica Key.
New data needs Updated geologic mapping, lidar, 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.
Digital elevation data needs Lidar complete for northern half of focus area, in progress for southern half.