National mineral assessment tract AK-BR03 (Cyprus massive sulfide)

Tract AK-BR03
Geographic region Brooks Range, AK
Tract area 12,189sq km
Deposit type Cyprus massive sulfide
Deposit age Jurassic

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
Altered basalts with pyrite and locally high copper values may suggest submarine hydrothermal activity, and the area is permissive for Cyprus massive sulfide deposits as defined by Singer (1986).
On the delineation of permissive tracts
This tract contains all the known mafic rocks of Proterozoic(?), Paleozoic, or Mesozoic age except the Brooks Range mafic-ultramafic complexes (Murchey and Harris, 1985; Pallister and others, 1989).
Important examples of this type of deposit
No Cyprus-type deposits are known in the area, although the Kivivik Creek Cu prospect may be of this type (Schmidt and Allegro, 1980).
On the numerical estimates made
No estimates of the number of undiscovered deposits have been attempted.
References
Murchey, B.L., and Harris, A.G., 1985, Devonian to Jurassic sedimentary rocks in the Angayucham Mountains of Alaska: possible sea mount or oceanic plateau deposits [abs]: EOS, Transactions of the American Geophysical Union, v. 66, no. 46, p. 1102.
Pallister, J.S., Budahn, J.R., and Murchey, B.L., 1989, Pillow basalts of the Angayucham terrane: oceanic plateau and island crust accreted to the Brooks Range: Journal of Geophysical Research, v. 94, no. B11, p. 15,901-15,923.
Singer, D.A., 1986, Descriptive model of Cyprus massive sulfide, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 131.
Schmidt, J.M., and Allegro, G.L., 1980, Mineral occurrences and indicators in the Baird Mountains quadrangle, Alaska: USGS Miscellaneous Field Studies Map MF1992, 1 plate, scale 1:250,000, 19 p.

Geographic coverage

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