| Basis for focus area |
Polymetallic sulfide veins, fissures, and replacement deposits occur through the La Plata area. Mineralization is spatially associated with Laramide alkaline to calc-alkaline porphyries. Past mining targeted precious metals, with some base metal production. Focus area drawn around La Plata mountains, and encloses historical mines. |
| Identified resources |
Historical production of copper, gold, lead, and silver. |
| Production |
District production estimates include, approximately: 5 metric tons Au, >50 tons Ag, >120 tons Cu, and >320 tons Pb. |
| Status |
Past mining, current exploration by Metallic Minerals. |
| Estimated resources |
Unknown. |
| Geologic maps |
Eckel (1949), scale 1:31,680; Kirkham and others (2000), scale 1:24,000. |
| Geophysical data |
Inadequate aeromagnetic and aeroradiometric coverage. |
| Favorable rocks and structures |
La Plata dome, pre-mineral faults, and in places carbonate unites near intrusive contacts. |
| Deposits |
La Plata district (MRDS dep_id: 60000378); numerous mines listed in MRDS, area includes the La Plata, California, and Oro Fino districts (Burnell, 2015). |
| Evidence from mineral occurrences |
MRDS. |
| Geochemical evidence |
Alkaline porphyry (Allard stock) contains anomalously high Bi and Te in mineralized areas (Werle and others, 1984). Occurrence of tellurides has been documented (for example, Galbraith, 1941; Eckel, 1949), and is consistent with similar telluride occurrences in the region. Arsenic and antimony-bearing sulfosalts are reported to occur along a "ruby silver belt" that cross the northern portion of the historical mining district (Eckel, 1949). Sphalerite is described as the second most common sulfide after pyrite. Detailed mineralogical discussion in Eckel (1949). |
| Geophysical evidence |
Unknown. |
| Evidence from other sources |
Unknown. |
| Comments |
Likely a small resource for Zn and Te, but included because sphalerite is a prominent sulfide mineral throughout the area. Critical commodities of PGE, Ga, Ge, and In inferred from the mineral system/deposit type table (Hofstra and Kreiner, 2020). |
| Cover thickness and description |
No cover. |
| Authors |
Joshua M. Rosera. |
| New data needs |
Geologic mapping, geochemical characterization of historical ore material. |
| Geologic mapping and modeling needs |
At least three quadrangles would need to be mapped at 1:24,000 scale including: Monument Hill, Rampart Hills, and Thomson Park. |
| Geophysical survey and modeling needs |
None requested at this time. |
| Digital elevation data needs |
Lidar is adequate. |
