National mineral assessment tract AK-BR06 (Kipushi Cu-Pb-Zn)

Tract AK-BR06
Geographic region Brooks Range, AK
Tract area 32,935sq km
Deposit type Kipushi Cu-Pb-Zn
Deposit age Early Paleozoic


Explained by Jeanine M. Schmidt, Karen D. Kelley, Richard I. Grauch, Byron R. Berger, John W. Cady, Gregory T. Spanski, James E. Kilburn.
On the choice of deposit models
Kipushi-type deposits (Cox and Bernstein, 1986) containing Cu, Co, and minor Zn, such as the Ruby Creek and Omar deposits, are known from two separate carbonate areas within this tract in the Brooks Range. The entire tract is permissive for Kipushi-type deposits because it has the appropriate geologic setting (a continental platform or shelf with continental or passive margin rifting) and host rocks (dolostone, shale and shallow-water or platform carbonate rocks) for the deposit model.
On the delineation of permissive tracts
This tract outlines all pre-Mississippian carbonate rocks in the Brooks Range, including very shallow water, platform, slope and deeper water facies of Late Proterozoic(?) through Devonian age. These rocks include the Katakturuk Dolostone, Nanook Limestone, Baird Group carbonates, Eli, Kougurourok, and Skajit Limestones, their metamorphosed equivalents, and various marbles of uncertain age and affinity. Where the environment of deposition is not known or indeterminate, thick carbonate rocks of possible shelf, slope, or deeper-water-facies are included. Minor mafic rocks and / or rapid facies changes into deeper-water sedimentary rocks suggest that extensional tectonism affected these host rocks during Proterozoic (?), Ordovician (?), late Devonian (?) and/or Mississippian time.
Important examples of this type of deposit
The Ruby Creek (Hitzman, 1983, 1986; Bernstein and Cox, 1986), Omar (Folger and Schmidt, 1986; Folger, 1988), Pardners Hill and Aurora Mountain deposits, hosted by Ordovician (?) and Silurian to Devonian carbonate rocks, are examples of Kipushi type deposits.
On the numerical estimates made
There are no tonnage and grade curves for Kipushi-type deposits; no attempt was made to estimate the number of undiscovered deposits.
Bernstein, L.R., and Cox, D.P., 1986, Geology and sulfide mineralogy of the Number One ore-body, Ruby Creek copper deposit, Alaska: Economic Geology, v. 81, p. 1675-1689.
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.
Folger, P.F., 1988, The geology and mineralization at the Omar prospect, Baird Mountains Quadrangle, Alaska: unpublished MSc. thesis, Missoula, MT, University of Montana, 152p.
Folger, P.F., and Schmidt, J.M., 1986, Geology of the carbonate-hosted Omar copper prospect, Baird Mountains, Alaska: Economic Geology, v. 81, no. 7, p. 1690-1695. Abstract reprinted in Tailleur, I.L., and Weimer, P, eds., 1987, v. 1, p. 286, Alaskan North Slope Geology: SEPM Pacific Section, Bakersfield, CA, Book 50, 2 volumes, 874 p..
Hitzman, M.W., 1983, Geology of the Cosmos Hills and its relationship to the Ruby Creek copper-cobalt deposit: Stanford, California, Stanford University, PhD, dissertation, 266 p.
Hitzman, M. W., 1986, Geology of the Ruby Creek copper deposit, southwestern Brooks Range, Alaska: Economic Geology, V. 81, p. 1644-1674.
Schmidt, J.M., 1997b, 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.

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