National mineral assessment tract AK-EC07 (Low-sulfide Au-quartz veins)

Tract AK-EC07
Geographic region East Central, AK
Tract area 74,586sq km
Deposit type Low-sulfide Au-quartz veins
Deposit age Cretaceous - Tertiary

Estimates

Confidence Number of
deposits
90% 2
50% 8
10% 15
5% 20
1% 30

Estimators: Grybeck, Cox, Light, Lee, Phillips

Rationale

Explained by Donald Grybeck, Thomas D. Light, William J. Keith, Dennis P. Cox, Gregory K. Lee, and Jeffrey D. Phillips
On the choice of deposit models
The metamorphic rocks of the Yukon-Tanana Upland outside the Fairbanks area are permissive for low-sulfide Au-quartz veins as described by Berger (1986), because the geology and tectonic setting are similar to the Fairbanks area, which hosts numerous low-sulfide Au-quartz veins.
On the delineation of permissive tracts
The major constraint as well as the main evidence for undiscovered low-sulfide Au-quartz vein deposits is the widespread occurrence of placer gold deposits and the presence of favorable host rocks.
Important examples of this type of deposit
No good examples occur outside the Fairbanks area, but the Fairbanks deposits serve as excellent examples of what might be found elsewhere in similar rocks in east-central Alaska.
On the numerical estimates made
Additional deposits similar to those in the Fairbanks area are expected to occur outside the Fairbanks area. Using the mean size and grade projections of Bliss (1986), the estimated minimum number of undiscovered low-sulfide Au-quartz veins in the Yukon-Tanana Upland is:
Percentile 90 50 10 5 1
Estimated number of deposits 2 8 15 20 30
References
Berger, B.R., 1986, Descriptive model of low-sulfide Au-quartz veins, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 239.
Bliss, J.D., 1986, Grade and tonnage model of low-sulfide Au-quartz veins, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 239-243.

Geographic coverage

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