Christmas and Enterprise Prospect (Whitney claims), Lemesurier Island, Chichagof District, Skagway-Hoonah-Angoon Borough, Alaska, USA
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Location: The prospect is about 50 feet above sea level near the southernmost point on Lemesurier Island, about 0. 2 mile west of triangulation station Gail. It is located accurately within about 0.1 mile. It is location 61 of Cobb (1972).
Geology: Molybdenum and copper occur in contact-type deposits in marble of Paleozoic age that has been intruded by a granitic pluton of probable Cretaceous age (Knopf, 1912, p. 17; Buddington, 1926, p. 55-56; Reed, 1938). At the Whitney claims, a thirty-foot-wide zone along a contact between marble and granitic rock is mainly garnet-pyroxene tactite. A 78-foot adit driven in about 1916, started in tactite, cut through banded hornfels and quartzite, and ended in 'diorite' (Smith, 1942, p. 176) Molybdenite occurs as fracture coatings and as disseminations in the tactite. Hornfels is developed locally and contains chalcopyrite. Local molybdenite-lined vugs or pockets in the tactite contain as much as several percent molybdenum.
Workings: Surface exposures of molybdenite and chalcopyrite were explored in a 78-foot-long tunnel and 25-foot-crosscut, that were driven in about 1916. The occurrence was first reported by Knopf (1912), and subsequently described in resource summaries by Brooks (1918, 1919, 1921), Kaufman (1958), Berg and Cobb (1967) and Cobb (1972). The site was also noted by Buddington (1926, p. 55-56) and Buddington and Chapin (1929, p. 329-330). It was visited by Reed (1938). Smith (1942, p. 176-177) summarized developments and also reported that Reed believed the prospect deserved more work.
Age: Cretaceous or younger.
Alteration: Development of hornfels and tactite.
Production: Small test shipments made.
Commodities (Major) - Mo; (Minor) - Cu
Development Status: No
Deposit Model: Contact metasomatic deposit, molybdenum skarn.
4 entries listed. 4 valid minerals.
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Berg, H.C., and Cobb, E.H., 1967, Metalliferous lode deposits of Alaska: U.S. Geological Survey Bulletin 1246, 254 p. Brooks, A.H., 1918, Mineral resources of Alaska, 1916: U.S. Geological Survey Bulletin 662, 469 p. Brooks, A.H., 1919, Alaska's mineral supplies: U.S. Geological Survey Bulletin 666-P, p 89-102. Brooks, A.H., 1921, The future of Alaska mining, in Martin, G.C., and others, Mineral resources of Alaska, 1917: U.S. Geological Survey Bulletin 714-A, p. 5-57. Buddington, A.F., 1926, Mineral investigations in southeastern Alaska: U.S. Geological Survey Bulletin 783, p. 41-62. Buddington, A.F., and Chapin, Theodore, 1929, Geology and mineral deposits of southeastern Alaska: U.S. Geological Survey Bulletin 800, 398 p. Cobb, E.H., 1972, Metallic mineral resources map of the Mount Fairweather quadrangle, AK: U.S. Geological Survey Miscellaneous Field Study Map MF-436, 1 sheet, scale 1:250,000. Kaufman, A., 1958, Southeastern Alaska's Mineral industry: U.S. Bureau of Mines Information Circular 7844, 37 p. Knopf, Adolph, 1912, The Sitka mining district, Alaska: U.S. Geological Survey Bulletin 504, 32 p. Reed, J.C., 1938, Some mineral deposits of Glacier Bay and vicinity, Alaska: Economic Geology, v. 33, p. 52-80. Smith, P.S., 1942, Occurrences of molybdenum in Alaska: U.S. Geological Survey Bulletin 926-C, p. 161-210.