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 having 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 by the distribution of known deposits, and by the outcrop area of inferred permissive host rocks.
Important examples of this type of deposit
The Cleary Hill, Hi-Yu, and Ryan Lode mines may be examples of gold-antimony veins in the Fairbanks area, although these mines have also been classified as low-sulfide gold-quartz veins (Berger, 1986).
On the numerical estimates made
The expected tonnage and grade of the majority of the gold-bearing veins in the Fairbanks area probably most closely fit the distribution curves for the low-sulfide Au-qtz model (Berger, 1986), and several deposits in the east-central Alaska area, such as the Cleary Hill, Hi-Yu, and Ryan Lode mines, have been included in the that model. We estimated that the number of undiscovered deposits that would fit the grade and tonnage curves for Au-Sb deposits (Berger, 1993) would be approximately one fourth of the number of low-sulfide Au-quartz veins for the same area (see tract AK-EC08). The minimum number of undiscovered deposits, consistent with the grade and tonnage curves of (Berger, 1993) is:
Percentile 90 50 10 5 1
Estimated number of deposits 1 3 5 8 12
Berger, B.R., 1986c, 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.