National mineral assessment tract AK-WC28 (Sedex Zn-Pb)

Tract AK-WC28
Geographic region West Central, AK
Tract area 3,918sq km
Deposit type Sedex Zn-Pb
Deposit age Paleozoic


Explained by Marti L. Miller, Bruce M. Gamble, and Jeanine M. Schmidt
On the choice of deposit models
The presence of siltstone, shale, chert, and carbonate rocks that were deposited in a deep-water environment suggests the possibility of sedex deposits as described by Briskey (1986). Bedded barite deposits may form distal to sedex occurrences. The presence of a bedded barite deposit in possibly correlative rocks in the continuation of this tract to the south supports the selection of this model type.
On the delineation of permissive tracts
This tract includes parts of the Nixon Fork and Minchumina terranes (Patton and others, 1994), both of which locally contain deep-water facies consisting of siltstone, shale, chert, and carbonate rocks.
Important examples of this type of deposit
No examples of sedex deposits are known in this tract, but the Gagaryah barite deposit (Bundtzen and Gilbert, 1991), in similar rocks in the Lime Hills quadrangle of southwestern Alaska, may be related to sedex mineralization.
On the numerical estimates made
No attempt was made to estimate the number of undiscovered Sedex Zn-Pb deposits in this tract.
Briskey, J.A., 1986, Descriptive model of sedimentary exhalative Zn-Pb, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 211-212.
Bundtzen, T.K., and Gilbert, W.G., 1991, Geology and geochemistry of the Gagaryah barite deposit, western Alaska Range, Alaska, in, Reger, R.D., ed., Short Notes on Alaskan Geology 1991: Alaska Division of Geological and Geophysical Surveys Professional Report 111, p. 9-20.
Patton, W.W., Jr., Box, S.E., Moll-Stalcup, E.J., and Miller, T.P., 1994, Geology of west-central Alaska, in Plafker, George, and Berg, H.C., eds., The Geology of Alaska: Boulder, Colorado, Geological Society of America, The Geology of North America, v. G-1, p. 241-269.

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