Geology
Host rockLimestone,Siltstone,Sandstone · "Roberts Mountain Formation", "Wenban Limestone"
Associated rockPorphyry,Quartz Monzonite,Andesite,Rhyolite · "Mill Canyon quartz monzonite stock", "Caetano Tuff"
StructureThe deposit lies within the Cortez Window of the Roberts Mountain Thrust (Cortez Range)., The deposit occurs within the Cortez Window in the Roberts Mountain Thrust.
Tectonic settingThe upper portion of the Devonian carbonate sequence beneath the Roberts Mountains thrust hosts the Cortez Hills deposit.
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. Pervasive oxidation and marble development are key alteration types associated with gold deposition
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 pRobert C. Hays, Jr., 2003, The Cortez Hills Deposit, a recent discovery in an historic mining district, Lander County, Nevada, abstract for Geological Society of Nevada talk given in spring 2004.