National mineral assessment tract CR30 (Epithermal vein, quartz-alunite)

Tract CR30
Geographic region Central and Southern Rocky Mountains
Tract area 43,600sq km
Deposit type Epithermal vein, quartz-alunite
Deposit age Tertiary

Deposit model

Model code 25e
Model type descriptive
Title Descriptive model of epithermal quartz-alunite Au
Authors Byron R. Berger
URL https://pubs.usgs.gov/bul/b1693/html/bull0vxx.htm
Source https://pubs.er.usgs.gov/publication/b1693

Estimates

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

Estimators: Bartsch-Winkler, McLemore, Ludington, Wallace, Nash, Berger, Spanski

Rationale

Explained by Alan R. Wallace and Virginia McLemore
On the choice of deposit models
Quartz-alunite gold deposits are related to felsic volcanic and subvolcanic rocks, which are found in several volcanic fields in the State. We used the descriptive model of Berger (1986) and the grade-tonnage model of Mosier and Menzie (1986).
On the delineation of permissive tracts
Areas of felsic volcanic rocks, such as the Mogollon volcanic field, are extensive in New Mexico, and several occurrences of hypogene alunite and acid-sulfate alteration have been reported in these rocks. Therefore, all areas of felsic volcanic rocks are considered permissive for this deposit type.
Important examples of this type of deposit
Acid-sulfate alteration is present in the San Jose district, west of Truth or Consequences, and at Kline Mountain in the Black Range (V.T. McLemore, written commun., 1993). Native sulfur is present in the Valles caldera area, but an associated quartz-alunite assemblage is not reported.
On the numerical estimates made
The permissive tract of volcanic rocks is extensive, and acid-sulfate alteration is evident in at least two areas. Most districts in New Mexico have not been adequately explored at depth, and drilling and other exploration programs are needed to better evaluate the potential for undiscovered deposits (V.T. McLemore, written commun., 1993). For the 90th, 50th, 10th, 5th, and 1st percentiles, the team estimated 0, 0, 0, 2, and 4 or more deposits consistent with the grade and tonnage model for epithermal quartz-alunite gold deposits of Mosier and Menzie (1986).
References
Berger, B.R., 1986, Descriptive model of epithermal quartz-alunite Au, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 158.
Mosier, D.L., and Menzie, W.D., 1986, Grade and tonnage model of epithermal quartz-alunite Au, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 159-161.

Geographic coverage

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