National mineral assessment tract SB07 (Porphyry Cu)

Tract SB07
Geographic region Southern Basin and Range
Tract area 4,680sq km
Deposit type Porphyry Cu
Deposit age Mesozoic

Deposit model

Model code 17
Model type descriptive
Title Descriptive model of porphyry Cu
Authors Dennis P. Cox
URL https://pubs.usgs.gov/bul/b1693/html/bull9ik5.htm
Source https://pubs.er.usgs.gov/publication/b1693

Estimates

Confidence Number of
deposits
90% 0
50% 0
10% 1
5% 1
1% 2

P(none): 0.9

Estimators: DCox, Ludington

Rationale

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.
References
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.

Geographic coverage

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