| Basis for focus area |
The Eocene Lowland Creek Volcanic field is a northeast-aligned series of caldera complexes and diatremes that cuts the mineralized Late Cretaceous Boulder batholith. Past mining produced Au and sapphires from placer deposits and Au, Ag, Cu, Pb, and Zn from epithermal quartz veins. Some veins have not been fully explored or developed along strike and at depth (Korzeb and Scarberry, 2020). |
| Identified resources |
Identified gold and silver resources; historical gold and silver production. |
| Production |
Tuxedo mine (1920-1950): unknown amount of Ag and lesser Au; Flume Gulch mine (1903-??): unknown amount of Ag and Au as early as 1903; Ruby mine (1885-1912): Ag and Au worth around $90 million in today's dollars; Montana Tunnels: produced Au and Ag worth around $2.3 billion in today's dollars. |
| Status |
Past mining. |
| Estimated resources |
The Ruby Mine has a resource estimated at 12,500 tons of ore that has 0.5 oz/t Au and 20 oz/t Ag. The Tuxedo mine sits on an estimated 6 million tons of Au- and Ag-bearing breccia that forms a 2-mile-long northeast-trending ridge. |
| Geologic maps |
Scarberry and others (2019), scale 1:100,000. |
| Geophysical data |
Inadequate Rank 3 to 4 aeromagnetic and Rank 4 aeroradiometric coverage. |
| Favorable rocks and structures |
Northeast-striking faults and veins at contact between the volcanic field with the Boulder batholith. Mineralization in vent walls, northeast-striking dikes, veins, and diatreme breccias. |
| Deposits |
Tuxedo mine (MRDS dep_id: 10010814), Flume Gulch mine, Ruby mine, Montana Tunnels mine. |
| Evidence from mineral occurrences |
MRDS. |
| Geochemical evidence |
A chip sample from a vein at the Tuxedo mine assayed 0.9% Pb, 1.2% Zn, 8.0 oz Ag and 0.02 oz Au per ton (Geach, 1972). |
| Geophysical evidence |
Unknown. |
| Evidence from other sources |
Unknown. |
| Comments |
Tellurides and fluorite reported in a few MRDS records for Au-Ag mines in this focus area. All other critical commodities are inferred to be enriched based on the mineral system/deposit type table (Hofstra and Kreiner, 2020). |
| Cover thickness and description |
Exposed at the surface, with the main workings in the Tuxedo mine about 80 feet in depth (Geach, 1972). |
| Authors |
Kaleb C. Scarberry. |
| New data needs |
Geochemistry, geologic mapping, trace element analysis of epithermal vents and related veins. |
| Geologic mapping and modeling needs |
Targeted 1:24,000 scale mapping and mine-site mapping would be beneficial. |
| Geophysical survey and modeling needs |
High resolution aeromagnetic and aeroradiometric coverage. |
| Digital elevation data needs |
Lidar complete for some parts; incomplete for others. |
