Commodities
PrimaryGold, Silver
TertiaryTungsten, Arsenic, Antimony, Thallium, Mercury, Molybdenum, Fluorine-Fluorite, Manganese
Commodity typeB
Deposit
Deposit typedisseminations; veins; sheeted zones
Model104: Hot-spring Au-Ag
Deposit sizeS
Orebody formtabular
Ore controlThere is a ring fracture zone associated with a buried caldera. Gold deposition is controlled by high-angle fractures, particularly the NW-trending sets. Fractures were reactivated by NW-trending strike-slip faulting.
Materials
Ore mineralsGold, Electrum, Pyrite, Quartz, Adularia, Sericite, Hematite, Limonite, Alunite, Jarosite, Illite, Montmorillonite, Kaolinite, Fluorite, Realgar, Scorodite
GangueClay
Geology
Host rockAsh-Flow Tuff,Rhyolite · Mount Jefferson Caldera
Associated rockGranite,Metasedimentary Rock · Shoshone granite pluton
StructureNorthwest-striking faults and joints; a WNW-trending paleotopographic high, may represent the margin of buried caldera located SW of Round Mountain., Ore deposits are localized by a NW-trending lineament.
AlterationPropylitization and argillization of host rocks are intense. Adularia replacement of K-feldspars and plagioclase is associated with ore. Plagioclase and groundmass are replaced with quartz and sericite. Within propylitically altered rock, biotite is partially or wholly altered to chlorite. Groundmass is altered to chlorite +/- clay +/- carbonate+/- epidote. Plagioclase phenocrysts are altered to sericite (illite) as small points, clots, and veinlets along cleavage planes. Argillically altered rock contains no unaltered biotite or plagioclase, both phases being altered to clay (illite, montmorillonite, kaolinite) and sericite. Groundmass is entirely composed of fine-grained clays and sericite. Quartz-adularia silicification is widespread along the veins. Degree of silicification, sericite + argillic alteration increases with (higher) elevation. Fine-grained secondary quartz has replaced original plagioclase feldspars, occurs as clots in the groundmass, and as hairline veinlets that lace the rock.
Economic & production
Development statusProducer
Production years1910-1942; 1950-1964
First production1910
Last production1960
Discovery year1910
Identification
Deposit ID10310493
RegionNA
Data scoreB
Coordinates38.77255, -117.05165
References
Giancola, 1998Harding 2004cKinross Gold Corp., 2004aKleinhampl and Ziony, 1984Nevada Bureau of Mines and Geology, 1999, 2000, 2001, 2003.Nevada Star Resources Corp. Annual Report, 2004Tingley, 1998United States Bureau of Land Management, 1978kUnited States Bureau of Mines, 1995United States Geological Survey, 1971a.Nevada Star Resource Corp. press release, 7/2/2003Nevada Star Resource Corp. website, Dec. 2005, http://www.nevadastar.com/s/GoldHillProject.asp