National mineral assessment tract AK-BR12 (Plutonic porphyry Au)

Tract AK-BR12
Geographic region Brooks Range, AK
Tract area 9,782sq km
Deposit type Plutonic porphyry Au
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
Proterozoic, Devonian or Cretaceous granitic plutons in the Brooks Range are permissive for plutonic porphyry Au as described by Hollister (1992). Although no deposits of this type are known, and petrologic and geochemical information on the plutons is limited or absent, the geologic setting and general rock types are appropriate for plutonic porphyry Au deposits. Numerous small occurrences of contact metasomatic skarns or disseminated and veinlet base metal mineralization are known in the area.
On the delineation of permissive tracts
This tract comprises all the Proterozoic, Devonian or Cretaceous granitic plutons in the Brooks Range, and includes all potential host rocks within 5 km of the plutons. The geochemical data from stream sediment samples show an anomalous Sn-W-Mo association in addition to the base metals Cu-Pb-Zn.
Important examples of this type of deposit
There are no known plutonic porphyry Au deposits in this tract
On the numerical estimates made
There is insufficient geologic or mineral deposit information to estimate the numbers of undiscovered mineral deposits in this tract.
References
Hollister, V.F., 1992, On a proposed plutonic porphyry gold deposit model: Nonrenewable resources, v. 1, no. 4, p. 293-302.

Geographic coverage

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