Explained by Dennis P. Cox
On the choice of deposit models
The association of base- and precious-metal vein and replacement deposits with Mesozoic plutons suggests a favorable environment for porphyry copper deposits. No well defined examples are known, but alteration and mineralization that strongly resembles a porphyry system was described by Longwell and others (1965) around a Cretaceous pluton at Crescent Peak.
On the delineation of permissive tracts
High-level plutons and their sedimentary and volcanic country rocks are permissive for porphyry copper deposits. The permissive tract includes a 10 km-wide area around all Mesozoic plutons.
On the numerical estimates made
We estimate that there is a 10 percent chance that the Crescent Peak prospect has sufficient tonnage and grade to be classed as a deposit consistent with the grade and tonnage model of Singer and others (1986). For the 90th, 50th, 10th, 5th, and 1st percentiles, the team estimated 0, 0, 1, 1, and 2 or more deposits consistent with that model.
Singer, D.A., Mosier, D.L., and Cox, D.P., 1986, Grade-tonnage model of porphyry copper, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 77-81.
Longwell, C.R., Pampeyan, B.B., and Roberts, R.J., 1965, Geology and mineral deposits of Clark County, Nevada: Nevada Bureau of Mines and Geology Bulletin 62, 218 p.