Explained by Stephen E. Box and Arthur A. Bookstrom
On the choice of deposit models
Cyprus massive-sulfide deposits are massive, stratabound Cu-, Zn-, and Fe- sulfide deposits deposited with submarine basalts in ophiolite sequences (Singer, 1986). Recent work in modern ocean basins has identified active modern analogues in hydrothermal vents associated with modern mid-ocean ridge spreading centers (Koski and others, 1994). Widespread ophiolite fragments in the Baker terrane of northeastern Oregon are thought to be remnants of Phanerozoic oceanic plate crust accreted to the edge of the Proterozoic continent (Brooks and Vallier, 1978).
On the delineation of permissive tracts
The Baker terrane is composed of a melange of crustal fragments of ocean basin and island arc origin in a highly deformed argillaceous matrix (Brooks and Vallier, 1978). Large and small fragments of ophiolite sequences occur widely throughout the terrane. The entire terrane as shown by Walker and MacLeod (1991) was considered permissive for Cyprus deposits.
Important examples of this type of deposit
No known examples of this type of deposit are known from the Baker terrane, but some prospects are considered to have characteristics that could be indicative of this deposit type.
On the numerical estimates made
Although there are no deposits known, the estimators judged there was still some potential for undiscovered deposits. The exploration for them has not been thorough, and the potential exploration area is quite large. For the 90th, 50th, 10th, 5th, and 1st percentiles, the team estimated 0, 0, 0, 0, 1 or more undiscovered deposits consistent with the grade and tonnage model of Singer and Mosier (1986) .
Brooks, H.C., and Vallier, T.L., 1978, Mesozoic rocks and tectonic evolution of eastern Oregon and western Idaho, in David G. Howell and Kristin A. McDougall, eds., Mesozoic paleogeography of the western United States: Pacific section, Society of Economic Paleontologists and Mineralogists, Pacific Coast Paleogeography Symposium 2, p. 133-146.
Koski, R.A., Jonasson, I.R., Kadko, D.C., Smith, V.K., and Wong, F.L., Compositions, growth mechanisms, and temporal relations of hydrothermal sulfide-sulfate-silica chimneys at the northern Cleft segment, Juan de Fuca Ridge: Journal of Geophysical Research, v. 99, p. 4813-4832.
Singer, D.A., 1986, Descriptive 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.
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.
Walker, G.W., and MacLeod, N.S., 1991, Geologic map of Oregon: U.S. Geological Survey, 2 sheets, scale 1:500,000.