Surprize Mine, Battle Mountain Mining District, Lander County, Nevada, USAi

Regional Level Types
Surprize Mine	Mine
Battle Mountain Mining District	Mining District
Lander County	County
Nevada	State
USA	Country

Sec 28 T32N R44E Copper. Open pit Battle Mountain Gold Co.
Structure: Numerous regional scale thrust faults are present in the mine area, in particular along the contact between the Harmony and Battle Formations The NNE-striking Copper King fault zone and the WNW-striking Surprise fault.

Alteration: Alteration that has affected all rocks in the mine area are strong silicification, prograde garnet+diopside skarn that has been partially replaced by a retrograde assemblage of chlorite, quartz, calcite, and minor epidote.

Commodity: Ore Materials: Free gold, auriferous pyrite, chalcopyrite, chrysocolla, malachite, azurite, tenorite, limonite, hematite Gangue Materials: Chlorite, quartz, calcite, epidote, garnet, diopside, iron oxides, clay minerals, goethite

Deposit: The Bailey Day deposit formed as a vein associated with a fault zone in a sandstone bed bounded by bedding-plane fault. Ore is associated with disseminated and fracture controlled oxidized pyrite in garnet skarn of the Harmony Formation and in lens-shaped calc-silicate horizons of the Battle Formation adjacent to mineralized structures. Ore at the Labrador and Surprise orebodies is principally localized along 2 faults: the NNE-striking Copper King fault zone and the WNW-striking Surprise fault. Most of the Bailey Day ore came from a sandstone bed bounded by bedding-plane faults and impregnated with secondary copper minerals. Model name could also be gold-or copper-bearing skarn. There are two other types of gold deposits. The gold-bearing skarns which may be related to mid-Oligocene intrusive activity and an example of this type is the Labrador deposit, which occurs in the northeast portion of Copper Basin. The other type is a silica-pyrite body with a lack of skarn and calc-silicate assemblage minerals. This deposit type develops in calcareous siltstones and sandstones of the Harmony Formation (Schmidt et al., 1988). The Surprise deposit ore primarily occurs within the Harmony Formation. It consists of strongly oxidized and retrograde altered garnet skarn developed within interbedded limestone, calcareous siltstone and sandstone. Two main faults have acted as conduits: the Copper King fault zone strikes northeast and dips 70-80? east; the Surprise fault strikes west-northwest and dips 85? north. Both faults show post-mineral offset (Schmidt et al., 1988). The Labrador deposit ore occurs in the garnet skarn of the Harmony Formation and also in the calc-silicate and siliceous hornfels of the lower Battle Formation. North-northeast and west-northwest high-angle normal faults localize mineralization (Schmidt et al., 1988)

Deposit type: Skarn Au

Development: Underground production occurred in 1937, 1938, 1941, 1945, 1947, and 1954. The open pit operated from 1987 to 1993. Exploration for precious metals by numerous companies at the site of the historic copper mines began in the district in the 1980s, and through 1986, 114 drill holes had been completed in the Surprise mine area indicating an in place gold resource of 150,000 ounces. Pre-mining stripping began in April, 1987, involving about 2 million tons of overburden. Production of mill grade ore began in August 1987. In 1988, plans for a heap leach facility were postponed for at least one year. Gold recovery using heap leaching was expected to average about 60%. Mill grade ore was be treated at the Fortitude mill.

Geology: A quartz-feldspar porphyry dike in the pit is cut by garnet+pyroxene veinlets. This dike has characteristics of other Tertiary dikes in the area.

Ore(s): There is strong structural and lithologic control of ore formation, being affected by WNW-trending high angle normal faults, the Surprise fault, and location of calcareous sediments.

Other Databases

Link to USGS MRDS:	10310304
Link to USGS MRDS:	10044055

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