National mineral assessment tract GB03 (Skarn Cu)

Tract GB03
Geographic region Great Basin
Tract area 43,400sq km
Deposit type Skarn Cu
Deposit age Tertiary

Deposit model

Model code 18b
Model type descriptive
Title Descriptive model of Cu skarn deposits
Authors Dennis P. Cox and Ted G. Theodore
URL https://pubs.usgs.gov/bul/b1693/html/bull7nxq.htm
Source https://pubs.er.usgs.gov/publication/b1693

Estimates

Confidence Number of
deposits
90% 0
50% 1
10% 2
5% 4
1% 6

Estimators: Stoeser, Nutt, Ludington

Rationale

Explained by Douglas B. Stoeser
On the choice of deposit models
The model used here follows Einaudi and others (1981) and Cox and Singer (1986) that distinguish two types of copper skarns, those related to porphyry copper deposits and those related to other intrusions. Here the latter model type is considered.
On the delineation of permissive tracts
The basis for the tract delineation is areas where epizonal calc-alkaline granitic stocks intrude carbonate rocks. Thus, the permissive tract has the same geographic boundaries as the one for skarn-related porphyry copper deposits and other types of skarns.
Important examples of this type of deposit
There are no significant examples of this type of deposit in Utah. Seven minor occurrences of this type are listed in Reid (1991) for western Utah, but most are part of polymetallic replacement districts, and it is not clear whether all are actually copper skarns.
On the numerical estimates made
Although no significant deposits of this type are known for Utah, minor deposits occur in western Utah and the region is permissive in terms of the overall geological environment. Large parts of the permissive tract are covered, and, for the 90th, 50th, 10th, 5th, and 1st percentiles, the team estimated 0, 1, 2, 4, and 6 deposits consistent with the grade and tonnage model for Cu skarn deposits of Cox and Theodore (1968).
References
Cox, D.P., and Theodore, T.G., 1986, Descriptive model of Cu skarn deposits, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 86-89.
Einaudi, M.T., Meinert, L.D., and Newberry, R.J., 1981, Skarn deposits, in Skinner, B.J., ed., Economic Geology Seventy-Fifth Anniversary Volume, 1905–1980: Lancaster, Pennsylvania, Economic Geology Publishing Company, p. 317-392.
Reid, J.E., 1991, Skarn occurrences in Utah and the potential for associated gold mineralization: Utah Geological Survey Contract Report 91-13, 49 p.

Geographic coverage

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