National mineral assessment tract AK-EC08 (Low-sulfide Au-quartz veins)

Tract AK-EC08
Geographic region East Central, AK
Tract area 1,721sq km
Deposit type Low-sulfide Au-quartz veins
Deposit age Cretaceous - Tertiary

Estimates

Confidence Number of
deposits
90% 5
50% 12
10% 20
5% 30
1% 50

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 lode gold deposits in the Fairbanks district occur in a variety of host rocks that include felsic to intermediate plutonic stocks and various types of schist units. The deposits have some of the characteristics of low-sulfide Au-qtz veins (Berger, 1986), polymetallic veins (Cox, 1986), simple antimony veins (Bliss and Orris, 1986), and Au-Sb veins (Berger, 1992), but are much richer in Sb than most of the polymetallic veins in that model. Locally, the Fairbanks Au-quartz veins grade into simple Sb veins with a much higher gold content than is normal for the simple antimony model. Some of these veins could be classified as low-sulfide Au-quartz veins, but locally have a much higher sulfide and sulfosalt content than Berger’s (1986) model.
On the delineation of permissive tracts
This tract was defined mainly by the distribution of known deposits.
Important examples of this type of deposit
The most important deposits of this type in this tract are the Cleary Hill and Hi-Yu mines in the Cleary Hill area, and the numerous mines and deposits in the Ester Dome area.
On the numerical estimates made
The expected tonnage and grade of these gold-bearing veins in the Fairbanks area probably most closely fit the distribution curves for the low-sulfide Au-qtz model of Bliss (1986), with an average orebody size of 30,000 tonnes and an average grade of 16 grams of gold per ton. The estimated minimum number of undiscovered low-sulfide Au-quartz deposits is:
Percentile 90 50 10 5 1
Estimated number of deposits 5 12 20 30 50
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.
Berger, V.I., 1993, Descriptive, and grade-tonnage model for gold-antimony deposits: U.S. Geological Survey Open-File Report 93-194, 24 p.
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.
Bliss, J.D., and Orris, G.J., 1986, Descriptive model of simple Sb deposits, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 183-184.
Cox, D.P., 1986c, Descriptive Model of polymetallic veins, in Cox, D.P., and Singer, D.A., eds., Mineral Deposit Models: U.S. Geological Survey Bulletin 1693, p. 125.

Geographic coverage

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