Buckhorn Mine, Buckhorn Mining District, Eureka County, Nevada, USAi

Regional Level Types
Buckhorn Mine	Mine
Buckhorn Mining District	Mining District
Eureka County	County
Nevada	State
USA	Country

A gold property owned by COMINCO. Started 1984 to 1993. Earlier mining from glory holes and an adit from 1908.
Structure: A system of parallel normal faults strikes N10W and controls mineralization. Displacements are less than a few hundred feet. Roberts Mountains Thrust

Alteration: Argillization of basaltic andesite host rock is the main alteration. Underlying and overlying sediments are silicified. The upper two-thirds (100 ft.) of the mineralized zone is oxidized, the lower third is pyritic. The oxidation of the upper portion is believed to be hypogene, not supergene. In the oxide zone, white kaolinite-rich rocks are found at the center surrounded by purple montmorillonite-rich rocks in peripheral locations. The change in color typically marks the edge of the possible ore zone. Major elements introduced during alteration include Si, Al, K, and Ti. Major elements depleted in altered rocks are Mg, Ca, Na, Mn.

Commodity: Commodity Info: AG:AU ratio is 15:1. gold recovery is 67%. Ore Materials: gold Gangue Materials: quartz, kaolinite, montmorillonite, adularia, jarosite, goethite, pyrite, sericite, calcite, gypsum, plagioclase. native gold within skeletal limonite after pyrite and marcasite

Deposit: Ore occurs as three lenses (North Buckhorn, Junkyard, Glory Hole) along a zone 3000 feet long and 100-1000 feet wide. Barren areas between ore lenses typically contain less than 50 ppb gold.

Deposit type: Epithermal vein, Comstock

Development: The first claims were staked in 1908. In 1910, Buckhorn Mines Co. was organized and a mill was constructed in 1913. This cyanide plant operated 1914-1916, processing oxidized ore mined by glory hole method. Pardners Mines Corp. reopened the mine and operated a flotation mill 1935-1937 to treat sulfide ore. From 1938 to 1978 production was limited to working of the dumps. In 1978, Bar Resources Ltd. attempted to process oxide ore from an open pit, but failed due to mining and treatment problems caused by high clay content of the ore. Bethlehem Copper Corp. acquired an interest in the property in 1979. Cominco American's involvement began in 1980 with the purchase of Bethlehem copper. During 1980, Bethlehem blocked out a potentially bulk-mineable orebody in the area of the 1978 Bar Resources pit. A feasibility study was initiated in March 1983. Construction began in September and gold was poured in June 1984. Total capital costs for Cominco American mine development were $12 million. Production costs were $200/oz gold.

Geology: See Wells and Elliot (1969) USGS open-file report for geochemical and geologic maps of the mine area. Basaltic andesite flows are about 400 ft. thick as determined from resistivity measurements. Beneath the Tertiary rocks are either the cherty Fourmile Canyon Formation, or carbonates of the lower plate assemblage. Extensions of the Jurassic Mill Canyon stock may be present at depth. Rhyolite plugs and flows (15.3, 0.4 ma) exposed four miles southwest of the mine area may be related to hydrothermal system responsible for Au mineralization at Buckhorn.

Ore(s): High angle normal faults acted as conduits for hypogene hydrothermal fluids while subsidiary fracture systems increased permeability in the basalts allowing the development of stockwork mineralization. Overlying graben fill sediments may have locally acted as an impermeable cap rock.

Other Databases

Link to USGS MRDS:	10310544
Link to USGS MRDS:	10107309

Other Regions, Features and Areas containing this locality

References