| Basis for focus area |
Tungsten skarn areas eastern California. Includes Atolia mining district and Pine Creek area. |
| Identified resources |
Historical production of copper, gold, lead, tungsten, and zinc. |
| Production |
Strawberry mine (1943-1984): 5429 metric tons WO3 (Werner and others, 2014); Cerro Gordo: Total recorded production about 4.4 million oz Ag, 37,000 tons Pb, 12,000 tons Zn, with byproduct production of 2,000 oz Au and 300 ton Cu (Merriam, 1963); Darwin district: over 8,409,580 oz Ag, 126,209,848 lbs Pb, 66,907,584 lbs Zn, 1,700,451 lbs Cu, and 6,715 oz Au (Hall and MacKevett, 1962). Atolia district (1906-1939): Approximately 821,000 units of tungsten trioxide (WO3), equivalent to 13,683 tons of concentrates containing 60% WO3 produced from the district (Lemmon and Dorr, 1940). About 54% of the total production has come from the Union mine, which has been developed to a depth of 1,021 feet. Little Sister mine (1916-18, 1937-1941, and 1948): 140,000 metric tons grading on average 0.35% WO3 for calculated production of 470 metric tons W (Bateman, 1956). |
| Status |
Past mining. |
| Estimated resources |
Tungsten Hills-Pine Creek area: Estimate ranges between 100,000 and 200,000 tons reserve containing 40,000 to 80,000 units of WO3 (Bateman and others, 1950). Atolia district: Mill tailings contain an appreciable reserve, and are now being re-treated. "The Atolia district is not exhausted, but the easily discovered and richest [lode] ore bodies have probably been mined. Future production can be expected from the extension of present ore bodies in depth, new ore shoots in known veins, and ore shoots in veins yet to be discovered" (Lemmon and Dorr, 1940). |
| Geologic maps |
Hall and MacKevett (1962, plate 1), scale 1:48,000; Jennings and others (2010), scale 1:750,000; Lemmon and Dorr (1940), scale 1:4,800; Kerr (1946), scale 1:317,000 [Pine Creek, Nevada area]. |
| Geophysical data |
Partly adequate (5%) aeromagnetic coverage. Inadequate aeroradiometric coverage. |
| Favorable rocks and structures |
Cerro Gordo: Silver-Pb ores formed as 1) massive low silica pipe-like replacement and fissure filling bodies formed in marble at the intersection of northerly and northwesterly fracture sets and 2) replacement of marble and infilling of fractures by both low silica and high silica ore solutions. Zinc ores deposited as supergene precipitates. Darwin district: Ore bodies occur as structurally controlled replacement and fissure filling deposits within a contact metamorphic calc-silicate aureole developed within Keeler Canyon Formation limestones surrounding the intrusive Darwin quartz monzonite stock. Atolia district: High-grade scheelite ore, with a quartz-carbonate gangue, has been mined in the Atolia mining district from steeply dipping fissure veins of Miocene age. A minor quantity of scheelite has been taken from placers. The country rock is quartz monzonite probably of late Jurassic age. Tungsten Hills-Pine Creek area: Metasedimentary roof pendants enclosed in intrusive plutonic rocks; deposits are of the contact-metamorphic type. |
| Deposits |
Cerro Gordo (MRDS dep_id: 10310600), Darwin district (MRDS dep_id: 10310607), Strawberry mine (MRDS dep_id: 10115441; USMIN Site ID: CA00057), Paradox No. 1 mine (MRDS dep_id: 10292369), Paradox No. 3 mine (MRDS dep_id: 10213689), Union mine (MRDS dep_id: 10040725), Little Sister mine (MRDS dep_id: 10008716; USMIN Site ID: CA00042), Aeroplane mine (MRDS dep_id: 10008556), Jackrabbit mine (MRDS dep_id: 10285228), Round Valley mine (MRDS dep_id: 10008560). |
| Evidence from mineral occurrences |
MRDS; USMIN. |
| Geochemical evidence |
Scheelite is the only ore mineral in the Atolia district and occurs in veins and stream placers. |
| Geophysical evidence |
Unknown. |
| Evidence from other sources |
Unknown. |
| Comments |
Atolia district: High-grade scheelite ore, with a quartz-carbonate gangue, has been mined in the Atolia mining district from steeply dipping fissure veins of Miocene age. A minor quantity of scheelite has been taken from placers. Alluvium contains a large quantity of scheelite, although in uneven quantities. The presence of Au might make it possible to extract W as a byproduct. Tungsten Hills-Pine Creek area: The deposits are of the contact-metamorphic type and scheelite (CaWO4) is the only tungsten-bearing mineral. Mining, with a few exceptions, is confined to two areas, the Deep Canyon area and the belt along the northern margin of the Round Valley pendant. In the Deep Canyon area the deposits are contained in small bodies of metamorphosed sedimentary rock that are completely enclosed in plutonic intrusive rocks. The deposits that have been explored at depth show a downward decrease in scheelite content and in the degree of additive metamorphism. These relationships suggest that the metamorphic rocks in this area are inclusions. The more intense mineralization and metamorphism in their upper parts are probably due to the imperviousness of the capping igneous rock which impeded the movement of upward-moving solutions and caused the deposition of new minerals. Two of the deposits are still partly covered by the igneous rock enclosing them. The mines along the northern contact of the Round Valley pendant, a somewhat larger body of metamorphosed sedimentary rocks, do not show any such relation between depth and degree of metamorphism and mineralization. The additive metamorphism and amount of tungsten minerals are most noticeable at the contact of the pendant with granite and diminish with distance from the granite. Other areas: Approximately 94% of California's Pb production and 28% of California's Zn production has come from Pb-Ag-Zn deposits in the western Basin and Range province, which includes the Death Valley region and most of Inyo County. Most California deposits lie in a mineralized belt trending northwest-southeast and extending from the Inyo Mountains to the Nopah Range. The bulk of production comes from three leading mining districts within this trend; the Cerro Gordo District in the southern Inyo Mountains, the Darwin District, and the Tecopa District at the south end of the Nopah Range east of Death Valley. The Darwin District ranks first in mineral production, followed by the Cerro Gordo and Tecopa districts. |
| Cover thickness and description |
Exposed at the surface, may extend to some depth. |
| Authors |
Erica Key. |
| New data needs |
Updated geologic mapping, lidar, geochemistry, aeromagnetic and aeroradiometric surveys. |
| Geologic mapping and modeling needs |
Needs updated geologic mapping. |
| Geophysical survey and modeling needs |
High-resolution, Rank 1 aeromagnetic and aeroradiometric surveys. |
| Digital elevation data needs |
Lidar inadequate. |
