National mineral assessment tract AK-BR19 (Zn-Pb skarn)

Tract AK-BR19
Geographic region Brooks Range, AK
Tract area 9,782sq km
Deposit type Zn-Pb skarn
Deposit age Cretaceous

Rationale

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
Numerous small occurrences of contact metasomatic skarns or disseminated and veinlet base metal mineralization near plutons are known in the Brooks Range (Newberry and others, 1986). Petrologic and geochemical information on the plutons is limited or absent, but numerous mineral deposit types may occur, including Zn-Pb skarn deposits (Cox, 1986).
On the delineation of permissive tracts
This tract comprises all the known or inferred Proterozoic, Devonian or Cretaceous granitic plutons in the Brooks Range, and includes all potential host rocks within 5 km of the plutons. These tracts contain variable amounts of carbonate rocks of ?Proterozoic to Paleozoic age which are likely hosts for skarn mineralization. The timing and grade of metamorphism of the carbonate rocks, and their lithologies are not known in enough detail to differentiate areas of higher or lower favorability. The geochemical data from stream sediment samples show anomalous levels of Sn, W, and/or Mo in addition to the base metals Cu-Pb-Zn. There is very little, if any, gold associated with the intrusions.
Important examples of this type of deposit
No Zn-Pb skarn deposits are known in this tract.
On the numerical estimates made
There is insufficient information to estimate the numbers of undiscovered Zn-Pb skarn deposits in this tract.
References
Cox, D.P., 1986, Descriptive model of Zn-Pb skarn deposits, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 90.
Newberry, R.J., Dillon, J.T., and Adams, D.D., 1986, Regionally metamorphosed, calc-silicate-hosted deposits of the Brooks Range, Northern Alaska: Economic Geology, v. 81, p. 1728 - 1752.

Geographic coverage

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