Explained by Stephen E. Box and Arthur A. Bookstrom
On the choice of deposit models
Kuroko massive sulfide deposits are stratabound accumulations of massive Fe-sulfides with subordinate (but economically significant) layers and lenses of Cu, Zn, and Pb sulfide minerals (Singer, 1986). These are deposited on the seafloor around hydrothermal vents associated with felsic and intermediate volcanic rocks in and around island-arc volcanic complexes. The Quesnellia terrane in northeastern Washington is considered to be an accreted island-arc terrane (Mortimer, 1986).
On the delineation of permissive tracts
All of the Permian through Jurassic rocks of the Quesnellia terrane are considered permissive for kuroko massive sulfide deposits (Stoffel and others, 1991). The Quesnellia terrane in northeastern Washington consists of Permian through Jurassic arc volcanic rocks and associated sedimentary rocks (Mortimer, 1986).
Important examples of this type of deposit
Although no known Kuroko massive sulfide deposits are known from this terrane in Washington, there are known deposits in the Quesnellia terrane in British Columbia to the north.
On the numerical estimates made
The lack of known deposits or prospects of massive sulfide deposits in northeastern Washington led the team to give a very low estimate for the occurrence of an undiscovered deposit here. For the 90th, 50th, 10th, 5th, and 1st percentiles, the team estimated 0, 0, 0, 0, and 1 or more kuroko deposits consistent with the grade and tonnage model of Singer and Mosier (1986).
Mortimer, N., 1986, Late Triassic, arc-related potassic igneous rocks in the North American Cordillera: Geology, v. 14, p. 1035-1038.
Singer, D.A., 1986, Descriptive model of kuroko massive sulfide, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 189.
Singer, D.A., and Mosier, D.L., 1986, Grade and tonnage model of kuroko deposits, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 190-197.