National mineral assessment tract AK-WC01 (Besshi massive sulfide)

Tract AK-WC01
Geographic region West Central, AK
Tract area 37,919sq km
Deposit type Besshi massive sulfide
Deposit age Paleozoic

Rationale

Explained by Bruce M. Gamble, Robert G. Eppinger, John W. Cady, Stanley E. Church, Byron R. Berger, Gregory T. Spanski
On the choice of deposit models
The presence of marine metasedimentary and mafic metavolcanic lithologies indicates that this area may be permissive for Besshi massive sulfide deposits as described by Cox (1986).
On the delineation of permissive tracts
This tract includes all of the Nome Group, including high-grade equivalents, containing in part mafic metavolcanic rocks (Casadepaga Schist) and metasedimentary rocks (Solomon Schist, mixed unit) (Till and others, 1986). Anomalously high concentrations of elements in stream-sediment and panned-concentrate samples include As, Sb, Au, Cu, Pb, Zn, Ag, Ni, Co, Ba, and Mn (Gamble and Till, 1993). This is a speculative tract.
Important examples of this type of deposit
No Besshi massive sulfide deposits are known in this tract.
On the numerical estimates made
No estimate of the number of undiscovered deposits was attempted.
References
Cox, D.P., 1986, Descriptive model of Besshi massive sulfide, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 136.
Gamble, B.M., and Till, A.B., 1993, Maps showing metallic mineral resources of the Bendeleben and Solomon quadrangles, western Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF 1838-D, 3 sheets, scale 1:250,000, 22 p.
Till, A.B., Dumoulin, J.A., Gamble, B.M., Kaufman, D.S., and Carroll, P.I., 1986, Preliminary geologic maps and fossil data, Solomon, Bendeleben, and southern Kotzebue quadrangles, Seward Peninsula, Alaska: U.S. Geological Survey Open-File Report 86‑276, 62 p., scale 1:250,000.

Geographic coverage

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