Trinity County Placers

Region West, Northwest
States
Mineral systems
Deposit types
Commodities
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 Four deposits listed had small byproduct PGE production of a few ounces per year.
Status Past placer mining.
Estimated resources Unknown.
Geologic maps Irwin (2010), scale 1:50,000; Fraticelli and others (2012), scale 1:250,000.
Geophysical data Inadequate aeromagnetic and aeroradiometric coverage.
Favorable rocks and structures Uplifted beach terraces.
Deposits Corona De Oro mine (MRDS dep_id: 10038045), Hammer Property (MRDS dep_id: 10109530), Hawkins Bar (MRDS dep_id: 10038040), Valdor Dredge (MRDS dep_id: 10038041).
Evidence from mineral occurrences MRDS; other MRDS sites in and near this focus area are described as Au-PGE placers, but the presence of PGE is not substantiated at all localities.
Geochemical evidence Hasseman and others (1992) analyzed rock samples from the Hayfork 1:100,000 quadrangle that included samples with ppm levels of PGE. These could represent source materials for the PGE placers. A 0.75 g Pt nugget was found in the South Fork of the Trinity River that was 79.9% iridosmine with the rest Pt (Snetsinger, 1971).
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 in progress over much of the focus area.