| 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. |
