Explained by Dennis P. Cox
On the choice of deposit models
Alunite alteration occurs in the Alunite district near Las Vegas, in Tertiary andesites. Although production from the associated gold deposits was very small (Longwell and others, 1965), and no districts as defined by the grade and tonnage model of Mosier and Menzie (1986) are known, the coexistence of epithermal mineralization and hydrothermal alteration in volcanic rocks indicates that the area is permissive for undiscovered quartz-alunite districts.
On the delineation of permissive tracts
All Tertiary volcanic rocks and their extensions under less than 1 km of cover are permissive.
On the numerical estimates made
Based on the broad area of covered Tertiary volcanic rocks permissive for this deposit type, and the presence of known deposits to the west, in rocks of the same age in California, the team estimated, for the 90th, 50th, 10th, 5th, and 1st percentiles, 0, 1, 2, 4, and 5 or more deposits consistent with the grade and tonnage model of Mosier and Menzie (1986).
Mosier, D.L., and Menzie, W.D., 1986, Grade-tonnage model of epithermal quartz-alunite veins, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 159-161.
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.