Description
U.S.G.S./Placer Dome
Commodities
PrimaryGold, Silver
TertiaryMercury, Arsenic, Antimony
Commodity typeM
Deposit
Deposit typeDISSEMINATED; SEDIMENT-HOSTED
Model173: Sediment-hosted Au
Deposit sizeL
Orebody formIrregular; gold is localized where limestone was faulted, brecciated and folded along margin of Tertiary intrusive, gold is micron-to sub-micron-size.
Ore controlGold is localized where limestone was faulted, brecciated and folded along the margin of a Tertiary intrusive.
Materials
Ore mineralsGold, Pyrite
GangueHematite, Goethite, Quartz, Clay
Geology
Host rockLimestone,Siltstone,Sandstone · "Roberts Mountain limestone", "Wenban Limestone"
Associated rockPorphyry,Quartz Monzonite,Andesite,Rhyolite · "Mill Canyon quartz monzonite stock", "Caetano Tuff"
StructureThe deposit occurs within the Cortez Window in the Roberts Mountain Thrust., The deposit lies within the Cortez Window of the Roberts Mountain Thrust (Cortez Range).
Tectonic settingBasin and Range
AlterationHost rocks have been decalcified, silicified, leached, bleached, argillized, and oxidized. This phase of low grade hydrothermal alteration occurred after intrusion of the porphyry sill, and removed most of the carbon. A decalcification halo extends into the host rock surrounding the mineralized area. Mineralization is associated with silicification.
Economic & production
Development statusProducer
Production years1969-1976, 1981-1983, 1988-1993
First production1969
Last production1993
Discovery year1966
Identification
Deposit ID10310410
MRDS IDM232243
Alternate namesCortez Joint Venture Gold Mine, Cortez Leach Operation, Cortez Mine, Garrison Mine
RegionNA
Data scoreA
Coordinates40.19158, -116.62593
References
Roberts, R.J. et al, (1967) Geology and Mineral Deposits of Eureka Co. Nev., N.B.M. Bull. 64Wells J.D., Stoiser, L.R., and Elliot, J.E., (1969) Geology and Geochemistry of the Cortez Gold Deposit, Economic Geology v. 64, p. 526Stager, H.K., (1977) Geology and Mineral Deposits of Lander Co., N.B. of M. Bull. 88Division of Mine Inspection, Dec. 1983, Directory of Nevada Mine Operations Active in Calendar Year 1983.NBMG, 1983, Map 84, Active Mines and Oil Fields.NBMG, 1983, Active Mines and Oil Fields, Map 84.Bentz, J. and Smith, P., 1982, Field Examination Report, July 12, 1982.Metal Market Consultants, Inc., 1987, Gold Situation MapNevada Dept. of Minerals, 1993.95-2.Geological Society of Nevada 1997 Spring Field Trip: Geology and Ore Deposits of Northeastern Nevada, Special Publication No. 25Long, K.R., DeYoung, J.H., Jr., and Ludington, S.D., 1998, Database of significant deposits of gold, silver, copper, lead, and zinc in the United States; Part A, Database description and analysis; part B, Digital database: U.S. Geological Survey Open-File Report 98-206, 33 p., one 3.5 inch diskette.Geology and Ore Deposits of the American Cordillera, Field Trip Guidebook Compendium of the April 1995 Geological Society of NevadaSymposium; 501 p.Gulf Resources 1971-1974, Placer Development 1975-1984 Annual Reports.