| 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 |
Small byproduct PGE production. |
| Status |
Past placer mining. |
| Estimated resources |
Unknown. |
| Geologic maps |
Wagner and Saucedo (1987), scale 1:250,000. |
| Geophysical data |
Inadequate Rank 3-5 aeromagnetic and rank 5 radiometric data. |
| Favorable rocks and structures |
Gold occurs as native element, or electrum, sometimes with Pt alloys in beds of active streams and at or near the base of terrace gravels generally from 25 to 400 ft above the stream beds along the Trinity River and its tributaries. Gold and PGE also occur in older gravels (Miocene) that are generally tilted and preserved in downfaulted basins. (Silberman and others, 1994). |
| Deposits |
Klamath River mine (MRDS dep_id: 10115107), Weitchpec Bar (MRDS dep_id: 10038022). |
| 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 |
Klamath River mine: Average of 2 PGM grains from the Klamath River mine yielded 26.04% Pt, 72.15% Os, and 1.165% Au (Logan, 1919); Weitchpec Bar placer: Ferorplatinum, cooperite, sperrylite, rhodian sperrylite identified by electron microprobe and x-ray (Peterson, 1994). |
| 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 inadequate. |
