| Basis for focus area |
Polymetallic (Cu-Ag-Au-Pb-Sn) vein and breccia deposits mostly in Oligocene rhyolite, a mined Ag(-Sn) deposit in Oligocene rhyolite, elevated Ag and Sn concentrations in rhyolite (presumably Oligocene) and cassiterite in Au placers. Tin production (cassiterite) from mines on Majuba Hill; placer cassiterite in Rosebud Canyon and Rabbit Hole, north and northwest of Majuba Hill; stannite in drill hole cuttings from the Trinity Silver mine; elevated Sn concentrations in altered rhyolite, Trinity Silver mine and Trinity Range south of Majuba Hill. |
| Identified resources |
Indicated resources of lead, silver, and zinc. Historical production of copper, gold, lead, silver, tin, and zinc. |
| Production |
Majuba Hill area mines (1906-1951): total production as compiled was approximately 2.8 million lbs Cu, 184,000 oz Ag, 885,800 lbs Pb, 106,000 lbs Zn, and 21,000 lbs Sn (Stevens, 1971); Rabbit Hole-Rosebud Canyon placer mines (1870s-1940s): estimated >10,000 oz Au, small amounts of cassiterite, cinnabar, scheelite were recovered; Rosebud gold mine (1908-1947): 3,775 oz Au, 116,772 oz Ag, minor Cu and Pb; Rosebud gold mine (1997-2000): ~0.39 Moz Au, 1.25 Moz Ag; Trinity silver mine (1987-1989): ~0.6 Moz Ag. |
| Status |
Past mining. Mines are inactive; episodic exploration has taken place at Majuba Hills area, Rosebud gold mine, and Trinity silver mine since the 1970s. |
| Estimated resources |
Trinity Oxide Ag deposit: Inferred 6.43 million tons, grade 1.134 oz/t Ag, contained metal 7,287,000 oz Ag; Trinity Ag-Pb-Zn sulfide deposit: Inferred 19.79 million tons, grade 1.07 g/t Ag, 0.217% Pb, 0.354% Zn, contained metal 21,165,000 oz Ag, 85,957,000 lbs Pb, 140,253,000 lbs Zn (Pennington and Martin, 2013). |
| Geologic maps |
Johnson (1977, plates 1 and 4), scale 1:250,000 and 1:48.000, respectively; MacKenzie and Bookstrom (1976), scale ~1:12,000. |
| Geophysical data |
Inadequate aeromagnetic and aeroradiometric coverage. |
| Favorable rocks and structures |
Late Oligocene rhyolite domes, flows, and subvolcanic intrusions in Mesozoic argillite and siltstone. |
| Deposits |
Majuba Hill mine (MRDS dep_id: 10042468), Trinity Silver mine (MRDS dep_id: 10042483), Esther mine (MRDS dep_id: 10042473), Rabbit Hole placers (MRDS dep_id: 10042453), Rosebud gold mine (MRDS dep_id: 10310434). |
| Evidence from mineral occurrences |
MRDS. |
| Geochemical evidence |
Elevated Sn concentrations in altered rhyolites; elevated Sn concentrations in Trinity mine ores and mineralized rocks, Trinity Range south of Majuba Hill; cassiterite in Au placer deposits, Kamma Mountains. |
| Geophysical evidence |
Unknown. |
| Evidence from other sources |
Pennington and Martin (2013). |
| Comments |
The area of the Trinity Silver mine could represent what was at the surface above the Majuba Hill intrusive complex. Sanidine in rhyolite and hydrothermal sericite from the ore zone were dated by 40Ar/39Ar at 26.02±0.14 Ma and 26.829±0.059 Ma, respectively. The sericite age is older than the host rocks, which is likely the result of recoil (John and Muntean, 2006). |
| Cover thickness and description |
Surface exposures but vein systems mined underground. |
| Authors |
Peter G. Vikre. |
| New data needs |
Mapping, petrography, biogeochemistry, geochronology, geophysics. |
| 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 (GeoDAWN). |
