Explained by D.P. Cox, Steve Ludington, B.R. Berger, M.G. Sherlock, and D.A. Singer, (USGS); and J.V. Tingley (Nevada Bureau of Mines and Geology)
On the delineation of permissive tracts
The Roberts Mountains and Golconda allochthons are believed to contain remnants of closed oceanic basins. Parts of these assemblages that contain volcanic rocks form a tract permissive for Cyprus massive sulfide deposits. Parts of the Golconda allochthon include thick pillow basalt units, chert, and turbidite, as well as scattered bodies of serpentine indicating an oceanic depositional environment (Jones and Jones, 1990). The Roberts Mountains assemblage contains chert, argillite, and greenstone that also suggest an oceanic environment permissive for Cyprus-type deposits, but the eastern part of the Roberts Mountains allochthon that is composed chiefly of shales of the Vinini Formation is considered less favorable.
Rationale for Numerical Estimates
Our estimate is based on the broad extent of the permissive area, and on the presence of one known deposit and one occurrence that might belong to this model. For the 90th, 50th, 10th, 5th, and 1st percentiles, the team estimated 1, 2, 5, 7, and 8 or more deposits that are comparable in grade and tonnage to the Cyprus massive sulfide model of Singer and Mosier (1986).
Jones, A.E., and Jones, D.L., 1991, Paleogeographic significance of subterranes of the Golconda allocthon, northern Nevada, in Raines, G.L., Lisle, R.E., Schafer, R.W., and Wilkinson, W.H., eds., Geology and ore deposits of the Great Basin—Symposium proceedings: Reno, Geological Society of Nevada, p. 21–23.
Rye, R.O., Roberts, R.J., Snyder, W.S., Lahusen, G.L., and Motica, J.E., 1984, Textural and isotopic studies of the Big Mike cupriferous volcanogenic massive sulfide deposit, Pershing County, Nevada: Economic Geology, v. 79, no. 1, p. 124-140.
Singer, D.A., and Mosier, D.L., 1986, Grade-tonnage model of Cyprus massive sulfide, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p.131-135.