National mineral assessment tract AK-WC24 (Cu (Au) skarn)

Tract AK-WC24
Geographic region West Central, AK
Tract area 7,891sq km
Deposit type Cu (Au) skarn
Deposit age Mesozoic - Tertiary

Rationale

Explained by Marti L. Miller and Bruce M. Gamble
On the choice of deposit models
In the southeastern part of west-central Alaska, carbonate rocks and units containing carbonate rocks, which have been intruded by Late Cretaceous or Tertiary plutons, may host deposits that fit the Cu-(Au) skarn model of Cox and Theodore (1986) and Theodore and others (1991). The Nixon Fork skarn deposit lies within this tract.
On the delineation of permissive tracts
The permissive tract for skarn deposits in west-central Alaska encompasses an area of carbonate rocks in the southeastern part of the region. This area is a continuation of the permissive area in southwestern Alaska, and is delineated by Cambrian to Devonian carbonate rocks of the Farewell terrane (Decker and others, 1994) and by carbonate-bearing rocks of the Minchumina terrane (Patton and others, 1994)
Important examples of this type of deposit
The Nixon Fork deposit (Bundtzen and others, 1996; Swanson, 1996), which lies within this tract, has reported reserves of about 117,000 tons containing 1.32 ounce/ton gold (Northern Miner, 1995).
On the numerical estimates made
Insufficient data exist to estimate the expected number of undiscovered Cu-(Au) skarn deposits for this tract.
References
Bundtzen, T.K., Swainbank, R.C., Clough, A.H., Henning, M.W., and Charlie, K.M., 1996, Alaska’s Mineral Industry, 1995: Alaska Division of Geological and Geophysical Surveys Special Report 50, 72 p.
Cox, D.P., and Theodore, T.G., 1986, Descriptive model of Cu skarn deposits, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 86.
Decker, John, Bergman, S.C., Blodgett, R.B., Box S.E., Bundtzen, T.K., Clough, J.G., Coonrad, W.L., Gilbert. W.G., Miller, M.L., Murphy, J.M., Robinson, M.S., and Wallace, W.K., 1994, Geology of southwestern Alaska, in Plafker, G., and Berg, H.C., eds., The geology of Alaska: Boulder, Colorado, Geological Society of America, The Geology of North America, v. G1, p. 285-310.
Northern Miner, 1995, v. 81, no. 36, November 6, 1995, p. 1-2.
Patton, W.W., Jr., Box, S.E., Moll-Stalcup, E.J., and Miller, T.P., 1994, Geology of west-central Alaska, in Plafker, George, and Berg, H.C., eds., The Geology of Alaska: Boulder, Colorado, Geological Society of America, The Geology of North America, v. G-1, p. 241-269.
Patton, W.W., Jr., Moll, E.J., Dutro, J.T., Silberman, M.L., and Chapman, R.M., 1980, Preliminary geologic map of Medfra quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-811-A, 1 sheet, scale 1:250,000.
Swanson, Mel, 1996, Nixon Fork mine [abs], in Alaska mining-no longer just a dream: Alaska Miners Association, Abstracts, 1996 Annual Convention, Nov. 6-8, 1996, Anchorage, Alaska, p. 30-31.
Theodore, T.G., Orris, G.J., Hammarstrom, J.M., and Bliss, J.D., 1991, Gold-bearing skarns, U.S. Geological Bulletin 1930, 61 p.

Geographic coverage

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