Explained by Jeanine M. Schmidt and Bruce M. Gamble
On the choice of deposit models
Paleozoic platform carbonate rocks in south-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 are known in this tract, correlative rocks in west-central Alaska host numerous strata-bound Zn prospects (informally called the Reef Ridge district) in carbonate rocks.
On the delineation of permissive tracts
This tract consists of areas locally underlain by Cambrian to Devonian shallow-water facies platform carbonate rocks of the Nixon Fork and Minchumina terranes (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 occur in equivalent rocks in the informally named 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., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 90-119.