Goldfield District

Region West, Southwest
Mineral systems
Deposit types
Other minerals

Information leading to the delineation of this focus area

Basis for focus area Outline of Goldfield district.
Identified resources Identified resources of gold and silver. Historical production of copper, gold, and silver.
Production Goldfield district (1903-1945): 4.2 million oz Au at 18.55g/t Au, 1.5 million oz Ag, and 3,800 tons Cu.
Status Past mining; current exploration.
Estimated resources Mineral resource estimates for 3 deposits in the Goldfield district are: Gemfield: Measured+Indicated 17.02 metric tonnes with 1.05 g/t Au, 3.37 g/t Ag; Goldfield Main: Measured+Indicated 8.55 metric tonnes with 1.53 g/t Au, 421,000 oz Ag; McMahon Ridge: Measured+Indicated 5.51 metric tonnes with 1.34 g/t Au, 238,000 oz Ag (Anderson and others, 2012).
Geologic maps Ashley (1975), scale 1:24,000; Crafford (2010), scale 1:500,000; Albers and Stewart (1965), scale 1:200,000; Cornwall (1967), scale 1:200,000.
Geophysical data Partly Rank 1 to 2 (50%) aeromagnetic coverage and inadequate aeroradiometric coverage.
Favorable rocks and structures Production at Goldfield was derived from a small proportion of numerous silicified, sub-linear fissures, or ledges, within an area of altered Miocene volcanic and pre-Tertiary rocks.
Deposits Goldfield District (MRDS dep_id: 10310328) compiles information from the many individual mines.
Evidence from mineral occurrences MRDS.
Geochemical evidence Ashley (1990) analyzed 3 drill core in the Goldfield district. Mineralized ledge (silicified rock) is comprised of microcrystalline quartz that replaced andesites and rhyolites, and internal breccias with multiple generations of clasts encrusted and replaced by Au, pyrite, and a large number of Cu-As-Sb-Au-Ag-Bi-Sn-Te-Se minerals (for example, enargite-luzonite, famatinite, goldfieldite, bismuthinite, and calaverite), minor sphalerite, galena, and chalcopyrite, alunite, kaolinite, dickite, and pyrophyllite (Vikre and others, 2005).
Geophysical evidence Blakely and others (2007).
Evidence from other sources Unknown.
Comments Ledges are flanked by broad selvages of altered andesite consisting of proximal to distal quartz±alunite±kaolinite+pyrite, quartz+kaolinite+K-mica+pyrite, montmorillonite+pyrite, and, calcite+chlorite±, respectively (Vikre and others, 2005).
Cover thickness and description Exposed to hundreds of meters in depth.
Authors Albert H. Hofstra, Peter G. Vikre.
New data needs Geologic mapping, geophysics.
Geologic mapping and modeling needs Updated geologic mapping.
Geophysical survey and modeling needs High-resolution, Rank 1 aeromagnetic and aeroradiometric surveys.
Digital elevation data needs Lidar inadequate.