Mike deposit, Maggie Creek Mining District, Eureka County, Nevada, USAi

Regional Level Types
Mike deposit	Deposit
Maggie Creek Mining District	Mining District
Eureka County	County
Nevada	State
USA	Country

Carlin-type gold mineralization is concentrated along the northwest-dipping Soap Creek fault, the northwest-striking, northeast-dipping Good Hope reverse fault, and the west-dipping Valley fault.

Mike is at the northwest end of a 3-mile (5-km) long belt of Carlin-type gold deposits aligned along the footwall of the northwest-striking, northeast-dipping Good Hope fault. Mike is subdivided into the West Mike deposit in the footwall of this apparent reverse fault and the Main Mike deposit along the fault and in the hanging wall. Contact-metamorphic, Carlin-type, and secondarily enriched mineral systems are hosted in variable hornfels after Silurian to Devonian carbonate and siliciclastic rocks of the Roberts Mountains Formation, Popovich Formation, and Rodeo Creek unit, and in mafic to intermediate dikes of at least 107 Ma age. Contact-metamorphic mineralization is coincident with potassium metasomatism dated at 111-107 Ma, and the formation of hornfels and local skarn. Mineralization typically consists of quartz-sulfide veins dominated by coarse-grained pyrite and iron-rich sphalerite with minor galena, chalcopyrite, and molybdenite. Quartz-carbonate veins hosting an arsenic-bismuth-lead-silver sulfosalt also occur throughout the deposit. At northwest West Mike, sphalerite-dominated, replacement-style base-metal mineralization is concentrated along the contact between the Rodeo Creek unit and the Popovich Formation.
West Mike gold mineralization is roughly flat-lying and stratiform, and segregated into upper and lower zones. The upper zone is 200 to 450 feet (60-135 m) thick, decarbonatized, oxidized, and grades 0.025 opt (0.86 g/t) gold. The lower zone has similar thickness, is partially oxidized, grades 0.080 opt (2.7 g/t), and is coincident with a 70- to 200-foot (21-60 m) thick dolomitic front at the base of decarbonatization. Gold at Main Mike grades an average 0.037 opt (1.2 g/t) and occurs in an oxidized and decarbonatized zone at the intersection of the Soap Creek and Good Hope faults. Sulfide-zone gold at the Mike deposit occurs in micron-size, arsenian pyrite rims coating euhedral, coarser-grained pyrite. Oxide-zone copper occurs in copper silicates, clays, arsenates, phosphates, oxides, and carbonates. Copper is sited in chalcocite and locally covellite in the top-of-sulfide zone and in sulfide lenses in overlying oxidized rock. Copper-bearing zones are typically decarbonatized, clay altered, alunite veined/replaced, and iron oxide stained. Oxide gold deposits at both Main Mike and the analogous Tusc, 4,000 feet (1,200 m) to the southeast, contain higher-grade (>0.05 opt [1.7 g/t]), flat-lying, bedding-discordant cores-possible supergene upgrades.
Mineralization is completely covered by postmineral volcaniclastic sediment of the Tertiary Carlin Formation.

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Link to USGS MRDS:	10310468

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