National mineral assessment tract AK-SW04 (Epithermal vein, generic)

Tract AK-SW04
Geographic region Southwestern, AK
Tract area 24,282sq km
Deposit type Epithermal vein, generic
Deposit age Cenozoic

Rationale

Explained by Frederic H. Wilson, Stanley E. Church, Richard W. Saltus, Lawrence J. Drew, and W. David Menzie.
On the choice of deposit models
Epithermal vein deposit models in the conterminous US have been divided into several types based largely on the underlying basement rocks (Cox and Singer, 1986). For the most part, information about Alaska is inadequate to classify individual epithermal gold vein types. Therefore, we have combined deposit models for Creede epithermal veins (Mosier and others, 1986b), Comstock epithermal veins (Mosier and others, 1986c), Sado epithermal veins (Mosier and others, 1986a), and epithermal quartz-alunite gold (Berger, 1986) into a generic epithermal vein model. We evaluated the permissive area for undiscovered deposits of all types of epithermal veins based on this generic model, which includes gold and/or silver veins associated with intermediate to felsic volcanic rocks similar to those described by Panteleyev (1987).
The mineral resource assessment of the Katmai 1:250,000 scale quadrangle (Church and others, 1992) was used to infer the possibility of the epithermal vein deposits in the Eocene and Oligocene volcanic rocks in this tract.
On the delineation of permissive tracts
This tract consists of Tertiary volcanic and shallow intrusive rocks (Detterman and Reed, 1980; Nelson and others, 1983) permissive for epithermal vein deposits. Isolated gold and silver stream-sediment geochemical anomalies, in addition to other metals, and placer gold in drainages west and north of Sugarloaf Mountain (see Church and Bennett, 1989, cited in Church and others, 1992) suggest that this tract is similar to other tracts of Tertiary volcanic rock on the Alaska Peninsula and is permissive for epithermal gold veins.
Important examples of this type of deposit
None known.
On the numerical estimates made
No estimates of the number of undiscovered deposits were made for this tract.
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.
Church, S.E., Riehle, J.R., Magoon, L.B., and Campbell, D.L., 1992, Mineral and energy resource assessment maps of the Mount Katmai, Naknek, and western Afognak quadrangles, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2021-F, 22 p., scale 1:250,000
Cox, D.P., and Singer, D.A., eds., 1986, Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 130.
Detterman, R.L., and Reed, B.L., 1980, Stratigraphy, structure, and economic geology of the Iliamna quadrangle, Alaska: U.S. Geological Survey Bulletin 1368-B, 86 p., scale 1:250,000.
Mosier, D.L., Berger, B.R., and Singer, D.A., 1986a, Descriptive model of Comstock epithermal veins, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 154.
Mosier, D.L., Sato, Takeo, Page, N.J., Singer, D.A., and Berger, B.R., 1986b, Descriptive model of Creede epithermal veins, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 145.
Mosier, D.L., Singer, D.A., and Berger, B.R., 1986c, Descriptive model of Comstock epithermal veins, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 150.
Nelson, W.H., Carlson, Christine, and Case, J.E., 1983, Geologic map of the Lake Clark quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1114-A, scale 1:250,000.
Panteleyev, Andrejs, 1987, A Canadian cordilleran model for epithermal gold-silver deposits, in Roberts, R.G., and Sheahan, P.A., Ore Deposit Models: Geoscience Canada Reprint Series 3, p. 31-43.

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