National mineral assessment tract SB04 (Skarn Cu)

Tract SB04
Geographic region Southern Basin and Range
Tract area 20,900sq km
Deposit type Skarn Cu
Deposit age Laramide

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% 0
10% 1
5% 2
1% 3

P(none): 0.9

Estimators: Wallace, Ludington

Rationale

Explained by Steve Ludington
On the choice of deposit models
In southwestern New Mexico, copper-rich skarn deposits occur in carbonate rocks adjacent to Laramide intermediate to felsic intrusive rocks that are not related to known porphyry copper deposits.
On the delineation of permissive tracts
Skarn deposits form where intermediate to felsic intrusive rocks, which are the principal sources of the metals, are emplaced into carbonate rocks. Therefore, the permissive tract for Laramide copper skarn deposits is that broad area where Laramide intrusive rocks are coincident with carbonate units. This permissive tract occurs in southwestern New Mexico and is contiguous with the Arizona porphyry copper province.
Important examples of this type of deposit
The most important copper skarn deposit in southwestern New Mexico is the Continental mine (Richter and Lawrence, 1983).
On the numerical estimates made
Whereas the permissive area is relatively small, and there is only one known deposit, the team emphasized the substantial area (>50 percent of the tract) of covered permissive rocks. In addition, the area has yielded significant production from porphyry copper and polymetallic deposits of Laramide age. For the 90th, 50th, 10th, 5th, and 1st percentiles, the team estimated 0, 0, 1, 2, and 3 or more deposits consistent with the grade and tonnage model for copper skarns of Jones and Menzie (1986).
References cited
Jones, G.M., and Menzie, W.D., 1986, Grade and tonnage model for Cu skarns, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 86-89.
Richter, D.H., and Lawrence, V.A., 1978, Mineral deposit map of the Silver City 1° x 2° quadrangle, New Mexico-Arizona: U.S. Geological Survey Miscellaneous Field Investigations Map I-1310-B, scale 1:250,000.

Geographic coverage

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