| Basis for focus area |
The focus area consists of the Hahns Peak polymetallic prospect inferred to be part of a Climax-type porphyry system. Since these systems commonly occur in clusters, a 15 km buffer was applied to Hahns Peak (latitude 40.8430, longitude -106.9298) to encompass undiscovered occurrences in adjacent areas. |
| Identified resources |
Identified resources of gold, lead, silver, and zinc. Historical production of gold, silver, lead, and zinc. |
| Production |
Unknown. |
| Status |
Past mining. |
| Estimated resources |
Modest placer gold (10,000-25,000 oz), plus small amounts of Ag-Cu-Pb-Zn ore. A large tonnage of very low grade resource contains 1.3 million tons at a grade of 0.58 oz/t Ag, 0.5% Pb, and 0.2% Zn, and a larger zone contains 710 million tons at a grade of 0.29 oz/t Ag, 0.1% Pb, and 0.06% Zn (Young and Segerstrom, 1973). |
| Geologic maps |
Segerstrom and others (1972), scale 1:24,000. |
| Geophysical data |
Inadequate aeromagnetic and aeroradiometric coverage. |
| Favorable rocks and structures |
Dacite, quartz latite, and rhyolite intrusive porphyry of Hahns Peak. Breccia pipe in a porphyry. A Miocene (~11 Ma) porphyry stock, and related dikes and sills, intrudes and domes Precambrian to Miocene rocks. The stock has been intensely altered, brecciated, and mineralized. |
| Deposits |
Hahns Peak district (MRDS dep_id: 10311069), Royal Flush, Tom Thumb mines. |
| Evidence from mineral occurrences |
MRDS. |
| Geochemical evidence |
Rock and stream sediment samples contain anomalous abundances of Sb, As, Pb, Mo, Ag, and Zn. Samples from Farewell Mountain district, east of Hahns Peak, have anomalously high abundances of As, Bi, Sn, W, and Zn (Bankey and others, 2000). Molybdenite is a favorable host for Re, although no Re data are known for Hahns Peak. A zone of breccia just southeast of Hahns Peak contains highly anomalous values of Ag, Pb, and Zn, plus anomalous Cu and Mo. Breccia fragments contain molybdenite veinlets. |
| Geophysical evidence |
Inadequate Rank 4-5 aeromagnetic and aeroradiometric data. |
| Evidence from other sources |
State-wide trend of similar occurrences. |
| Comments |
Gold (placer), Ag, Pb, Zn, Cu, and Mo. May be underlain by Mo porphyry; REE, W, and Sn are potential byproducts with potentially low concentrations of Re. Silicified fragments of porphyry with stockwork veins of silica, pyrite, and molybdenite are present in both an early phase of quartz latite porphyry and in the breccia cone sheet. These fragments suggest the presence of a stockwork molybdenite deposit at depth beneath Hahns Peak (Casaceli, 1983). Presence of Ga, Ge, and In inferred from the mineral system/deposit type table (Hofstra and Kreiner, 2020). |
| Cover thickness and description |
Shallow polymetallic mineralization and possible porphyry at depth. |
| Authors |
Albert H. Hofstra, Joshua M. Rosera. |
| New data needs |
1:24,000 scale geological mapping, geochemical sampling for pathfinder elements, geophysics. |
| Geologic mapping and modeling needs |
Need 1:24,000 scale geological mapping at Meaden Peak, Elkhorn Mountain, West Fork Lake, and Shield Mountain quadrangles. |
| Geophysical survey and modeling needs |
High resolution Rank 1 aeromagnetic and aeroradiometric surveys. |
| Digital elevation data needs |
Limited amount of adequate lidar, but rest of focus area in progress. |
