National mineral assessment tract AK-EC21 (Sedex Zn-Pb)

Tract AK-EC21
Geographic region East Central, AK
Tract area 23,298sq km
Deposit type Sedex Zn-Pb
Deposit age Paleozoic


Explained by Jeanine M. Schmidt and Thomas D. Light
On the choice of deposit models
This tract contains dark, fine-grained, restricted or deep water marine sedimentary rocks similar to Paleozoic rocks that host several large sediment-hosted Zn-Pb (Briskey, 1986) and barite deposits in the adjacent Yukon Territory of Canada (Schmidt, 1997).
On the delineation of permissive tracts
The tract delineates the occurrence of dark-gray to black Paleozoic marine shales and some metamorphic rocks (graphitic schists etc.) inferred to be the equivalent of fine-grained marine sedimentary rocks (Dover, 1994). Many metasedimentary rocks of the Yukon-Tanana upland are Paleozoic, inferred to have been deposited on continental crust (Dover, 1994), and contain phyllites and argillites that could contain shale-hosted massive sulfide deposits.
Important examples of this type of deposit
Prospects include Derwent Creek, Hard Luck Creek, Lead Creek, and Grayling (Doyon Ltd., 1986).
On the numerical estimates made
Due to the lack of detailed geologic information and mineral deposit data, no attempt was made to estimate the number of undiscovered sedex deposits.
Briskey, J.A., 1986c, 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.
Dover, J.A., 1994, Geology of part of east-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 p. 153-204.
Doyon, Ltd., 1986, Mines, prospects, and geochemical anomalies on Doyon, Ltd., regional overselection lands, Alaska, vol., 1, Blocks 1-8: Doyon Report 86-01A, Doyon, Ltd., Fairbanks, Alaska, 150 p.
Schmidt, J.M., 1997, Shale-hosted Zn-Pb-Ag and barite deposits of Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 35-65.

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