Explained by Jeanine M. Schmidt, Bruce M. Gamble, and Marti L. Miller
On the choice of deposit models
Paleozoic carbonate rocks that locally include platform carbonates in west-central Alaska are permissive for Kipushi-type deposits as defined by Cox and Bernstein (1986), because they were formed in an appropriate geologic setting (a continental platform or shelf with continental or passive margin rifting) and because they contain appropriate host rocks (dolostone, shale and shallow-water or platform carbonate rocks) for the deposit model. Although no occurrences of Kipushi deposits occur in this tract, it does host strata-bound Zn prospects in carbonate rocks (informally called the Reef Ridge district).
On the delineation of permissive tracts
This tract consists of areas underlain by Cambrian to Devonian shallow-water facies platform carbonate rocks of the Nixon Fork terrane (Patton and others, 1994). Locally, Pb and Zn anomalies are in stream-sediment and panned-concentrate samples in west-central Alaska. Sphalerite, chalcopyrite, cinnabar, pyrite and malachite were identified in some concentrates.
Important examples of this type of deposit
Examples of carbonate-hosted base-metal deposits (mainly Zn) occur in equivalent rocks in the Reef Ridge district in the Medfra quadrangle of west-central Alaska (Schmidt, 1997).
On the numerical estimates made
There are no tonnage and grade curves for Kipushi-type deposits; no quantitative estimates of the number of undiscovered deposits were attempted.
Cox, D.P., and Bernstein, L.R., 1986, Descriptive model of Kipushi Cu-Pb-Zn, in Cox, D.P., and Singer, D.A., eds., 1986, Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 227.
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.
Schmidt, J.M., 1997, Strata-bound carbonate-hosted Zn-Pb and Cu deposits of Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Economic Geology Special Volume, p. 90-119.