San Juan tungsten veins

Region West, Rocky Mountains
Mineral systems
Deposit types
Critical minerals
Other minerals

Information leading to the delineation of this focus area

Basis for focus area USMIN W site CO00048, Ftr_ID Mr00030 is the polygon for the San Juan area W. The Colorado Geological Survey updated this focus area, based on Cement Creek (the outline from the USMIN W publication) and added the Eureka district to the east as well as some other areas to the south. These areas generally had a higher concentration of past W producers taken from MRDS. There are other producers/occurrences nearby to the west and the north not included in this polygon.
Identified resources Indicated resources for tungsten. Historical production of antimony, fluorite, manganese, and tungsten.
Production Minor production.
Status Past mining.
Estimated resources 1956 Inferred reserves 700 metric tons W.
Geologic maps Horton and others (2017), scale 1:500,000; Luedke and Burbank (1987, 2000), scale 1:24,000; Burbank and Luedke (1964, 1966), scale 1:24,000.
Geophysical data Inadequate aeromagnetic and aeroradiometric coverage.
Favorable rocks and structures A down-fault block, more or less circular and about 8 miles in diameter, is situated in the Silverton area. This fault block has been called the Silverton caldera. Stocks of monzonite and diorite have been intruded into a ring-fault zone. Known W deposits are adjacent to or within the caldera or occur in or near igneous stocks or vein systems (Belser, 1956).
Deposits Over 40 mines, prospect, and properties have been described (see Belser, 1956). The area provided by the USMIN program contains all or a portion of the following mining districts: Animas, Eureka, Cement Creek, Animas Forks, Mineral Point, Poughkeepsie, Upper Uncompahgre, Red Mountain, Camp Bird, Imogene Basin, Sneffels, Upper San Miguel, Telluride, Iron Springs, and Ophir (USMIN Site_ID: CO00048).
Evidence from mineral occurrences MRDS; USMIN (W); Belser (1956).
Geochemical evidence Manganese is associated with polymetallic fissure veins (for example, King Group mine) and possibly by supergene enrichment (for example, see MRDS Fairview record; dep_id: 10018491). There is a manganese-fluorite association. Fluorite mines are also associated with polymetallic Ag-Au-Pb-Zn mineralization.
Geophysical evidence Subdued magnetic anomalies indicate extensive alteration in Silverton Caldera.
Evidence from other sources No data.
Comments The known W deposits are adjacent to or within the caldera or occur in or near igneous stocks or strong vein systems. The ore mineral hübnerite is often associated with fluorite. A small amount of scheelite occurs in some veins.
Cover thickness and description Deposits associated with volcanic rocks. Potentially variably buried.
Authors Jane M. Hammarstrom, Joshua M. Rosera, Michael K. O'Keeffe.
New data needs Report containing data/GIS compilation of historical data and description of deposits.
Geologic mapping and modeling needs No mapping needed.
Geophysical survey and modeling needs EM being flown, rank 3 aeromagnetic.
Digital elevation data needs Lidar in progress or complete.