Graphite Creek Mine, Port Clarence District, Nome Borough, Alaska, USA
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Geology: Flake graphite occurs as disseminations and high-grade tabular lenses within amphibolite facies metasedimentary rocks (Coats, 1944). The metamorphic rocks are primarily biotite-quartz schist with some sillimanite and garnet (Sainsbury, 1972). Small granitic plugs, dikes, and sills locally intrude the metamorphic rocks. The graphite-bearing schists are sharply bound to the north by the recently active Kigluaik fault, the principal fault along which late Cenozoic uplift of the Kigluaik Mountains has taken place (Hudson and Plafker, 1978). The graphite-bearing schists strike approximately parallel to the mountain front and dip north between 25 and 65 degrees. They form a zone along the mountain front that is 200 to 400 feet thick and possibly 20,000 feet long (Hudson, 1981; also see Christophosen Creek locality to the west and Graphite Creek locality to the east). To the south, the graphite-bearing schists are in conformable contact with other amphibolite facies metasedimentary rocks. The latter appear to be feldspathic and contain much less graphite. The graphite-bearing schists make up two general sequences; (1) a heterogeneous sequence of garnet-sillimanite-biotite-quartz schist with disseminated graphite and graphite-rich lenses, and (2) a more evenly layered biotite-quartz schist with disseminated graphite. The latter contains disseminated pyrrhotite and commonly weathers orange. West of Graphite Creek a 30 foot-long pit exposes a garnet-bearing schist with disseminated graphite and graphite-rich lenses. A 13-foot section here contained 3 feet of garnet -bearing schist with graphite and a 3.5 foot thick high-grade graphite lense with quartz stringers. A sample of the garnet-bearing schist contained 12% graphite of which 80% was coarser than 30 mesh per inch and a sample of the graphite-rich material contained 59% graphite of which 83% was coarser than 30 mesh per inch (Coats, 1944). A 25-foot thick zone containing disseminated graphite and a 3-foot wide high-grade lense is exposed on the east side of Graphite Creek. Twenty foot of this section is estimated to contain 10% disseminated graphite. This zone has been traced eastward on the surface for a distance of 480 feet and where it is well exposed, a 3- to 4-foot wide high-grade lense is present (Coats, 1944).
Workings: Surface pits, including one 30-feet long from which 50 tons of high-grade material were recovered, are present. Exploration activity in the general area took place as recently as 1994 (Swainbank and others, 1995).
Age: The metamorphism that has developed coarse graphite in these rocks is Late Jurassic to Early Cretaceous in age.
Alteration: Some shearing and deformation of graphite-rich lenses has accompanied faulting and oxidation of disseminated pyrrhotite has led to orange-staining of graphite-bearing rocks but other types of alteration are not identified.
Production: Most of the graphite shipments reported for the Alaska Graphite Company may have come from this locality. These shipments include 35 tons (1907) and 100 tons (1916 or 1917) of hand-sorted, high-grade material (Mertie, 1918; Harrington, 1919; Coats, 1944). Coats (1944) reports that about 50 tons were recovered in 1916 from the 30-foot long pit on the west side of Graphite Creek.
Reserves: The few miles of strike between the area of the Christophosen Creek deposit and the Graphite Creek deposit to the east has been estimated to contain 65,000 tons averaging about 60% graphite (Coats, 1944). This zone has also been estimated to contain, overall, more than 10 million tons of 10% or more graphite (Weiss, 1973).
Commodities (Major) - Graphite
Development Status: Yes, small
Deposit Model: Flake graphite in disseminations and tabular lenses within amphibolite facies me
11 entries listed. 8 valid minerals.
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Coats, R.R., 1944, Graphite deposits on the north side of the Kigluaik Mountains, Seward Peninsula, Alaska: U.S. Geological Survey Open-File Report 10, 8 p. Cobb, E.H., 1975, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Teller quadrangle, Alaska: U.S. Geological Survey Open-File Report 75-587, 130 p. Cobb, E.H., and Sainsbury, C.L., 1972, Metallic mineral resources map of the Teller quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-426, 1 sheet, scale 1:250,000. Hudson, T.L., 1981, Preliminary notes on the Kigluaik graphite deposits, Seward Peninsula, Alaska: Anchorage, Alaska, Anaconda Minerals Company internal memorandum (Report held by Cook Inlet Region, Inc., Anchorage, Alaska). Hudson, T.L., and Plafker, George, 1978, Kigluaik and Bendeleben faults, Seward Peninsula, in Johnson, K. M., ed., The United States Geological Survey in Alaska--Accomplishments during 1977: U.S. Geological Survey Circular 772-B, p. B47-B50. Harrington, G.L., 1919, Graphite mining in Seward Peninsula: U.S. Geological Survey Bulletin 692-G, p. 363-367. Mertie, J.B., Jr., 1918, Lode mining and prospecting on Seward Peninsula: U.S. Geological Survey Bulletin 662-H, p. 425-449. Sainsbury, C.L., 1972, Geologic map of the Teller quadrangle, Seward Peninsula, Alaska: U.S. Geological Survey Map I-685, 4 p., 1 sheet, scale 1:250,000. Swainbank, R.C., Bundtzen, T.K., Clough, A.H., Henning, M.W., and Hansen E.W., 1995, Alaska's mineral industry 1994: Alaska Division of Geological and Geophysical Surveys Special Report 49, 77 p. Weiss, P.L., 1973, Graphite: U.S. Geological Survey Professional Paper 820, p. 277-283.