Explained by Dennis P. Cox, Steve Ludington, and Michael F. Diggles

On the choice of deposit models

Cyprus massive-sulfide deposits are associated with basaltic submarine volcanic rocks in ophiolite sequences. Ophiolites are widespread in the Klamath Mountains and one Cyprus-type deposit, and several prospects are known (Koski and Derkey, 1981).

On the delineation of permissive tracts

Submarine basalts and associated ultramafic rocks ranging in age from Permian through Jurassic are widespread in the Klamath terrane. All sedimentary and volcanic rocks of these ages as well as the eastern part of the Josephine Peridotite were delineated as permissive for Cyprus-type deposits.

Important examples of this type of deposit

The Turner Albright deposit contains three million metric tons of massive sulfide ore averaging 1.46 percent copper, 3.33 percent zinc, 15 grams per metric ton silver, and 3.7 grams per metric ton gold (Kuhns and Baitis, 1987).

On the numerical estimates made

Because of the presence of one known deposit, and 2 significant prospects, the estimators decided that there is an even chance of an equal number of undiscovered deposits (3), and that belief guided our estimate. For the 90th, 50th, 10th, 5th, and 1st percentiles, the team estimated 0, 3, 4, 5, and 6 or more undiscovered deposits consistent with the grade and tonnage model of Singer and Mosier (1986).

References

Koski, R.A., and Derkey, R.E., 1981, Massive sulfide deposits in ocean-crust and island-arc terranes in southwestern Oregon: Oregon Geology, v. 43, no. 9, p. 119-125.

Kuhns, R.J., and Baitis, H.W., 1987, Preliminary study of the Turner Albright Zn-Cu-Ag-Au-Co massive sulfide deposit, Josephine County, Oregon: Economic Geology, v. 82, no. 5, p. 1362-1376.

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.