National mineral assessment tract AK-EC16 (Polymetallic replacement)

Tract AK-EC16
Geographic region East Central, AK
Tract area 27,331sq km
Deposit type Polymetallic replacement
Deposit age Cretaceous - Tertiary

Rationale

Explained by Jeanine M. Schmidt and Thomas D. Light
On the choice of deposit models
Numerous small occurrences of contact metasomatic skarns or disseminated and veinlet base metal mineralization associated with felsic plutons are known in east-central Alaska. Petrologic and geochemical information on the plutons is limited, but the geology is permissive for several types of mineral deposits, including polymetallic replacement deposits as described by Morris (1986).
On the delineation of permissive tracts
This tract is defined by Paleozoic carbonate rocks of the Yukon-Tanana terrane. Paleozoic metamorphic rocks that contain minor marble units of unknown origin, such as biotite gneiss and amphibolite (PzpCb of Foster, 1976), have not been included in this tract. In the Eagle and Charley River quadrangles geologically favorable units include the limestones of the Tindir Group, the Funnel Creek Limestone, the Hillard Limestone, and the Calico Bluff Formation. The western portion of this tract includes the Paleozoic limestones of the Quail, Amy Creek, Schwatka, and other minor units.
Important examples of this type of deposit
There are no known examples of polymetallic replacement deposits in this tract.
On the numerical estimates made
There is insufficient geologic information to estimate the number of undiscovered polymetallic replacement deposits in this tract.
References
Foster, H.L., 1976, Geologic map of the Eagle quadrangle, Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map I-922, scale 1:250,000.
Morris, H.T., 1986, Descriptive model of polymetallic replacement deposits, in Cox, D.P., and Singer, D.A., eds., 1986, Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 99.

Geographic coverage

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