New Chichagof Mining Syndicate Prospect, Chichagof District, Sitka Borough, Alaska, USA
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Location: This prospect is at an elevation of about 150 feet, about 0.4 mile east of the head of Pinta Bay. The prospect is 0.1 mile northwest of the center of sec. 21, T. 47 S., R. 57 E. It is location P-49 of Bittenbender and others (1999), location 21 of Cobb (1972, 1978), and MAS no. 0021140069 (U.S. Bureau of Land Management, 2002). The location is accurate.
Geology: Johnson and Karl (1985) map the rocks in the area of this prospect as Triassic(?) marble and greenstone, Cretaceous(?) phyllite, and a collage of metamorphosed Cretaceous and Cretaceous(?) sedimentary and volcanic rocks. The Triassic(?) and Cretaceous(?) rocks are separated by the Border Ranges Fault, a regional-scale, northwest-striking, steeply-dipping fault whose trace is at or near the prospect. The rocks are also cut by other northwest-striking faults, and by northeast-striking faults. Reed and Coats (1941) describe the prospect as a mineralized fault zone in sheared limestone, shale, greenstone schist, marble, and diorite. There also is an 8-foot-thick dike of unspecified composition. Quartz locally forms a vein up to 3 inches thick in the fault zone, and cements irregular breccia zones. The breccias constitute the ore, which reportedly carries free gold. The prospect was developed by 2 tunnels along the fault zone. One is about 795 feet long; the other, 85 feet higher, is about 145 feet long. Bittenbender and others (1999) report that the prospect was discovered in 1933 along a northeast-striking fault zone, and that the gold occurs in a quartz-carbonate-cemented, limestone breccia. A 110-foot section of mineralized quartz exposed in the underground workings averaged 0.24 ounce of gold per ton across a 4-foot mining width (Still and Weir, 1981). Numerous surface cuts expose mineralized quartz along a strike length of more than 500 feet. There is no record of production, but the extent of the workings suggests that some gold may have been produced. Isotopic studies indicate that the gold-quartz veins in coastal southern and southeastern Alaska are Eocene, about 50 Ma in age (Haeussler, 1995; Goldfarb, 1997; Goldfarb and others, 1997).
Workings: The prospect was developed by 2 tunnels along the fault zone. One is about 795 feet long; the other, 85 feet higher, is about 145 feet long (Cobb, 1978). Numerous surface cuts intermittently expose mineralized quartz along a strike length of more than 500 feet.
Age: Isotopic studies indicate that the gold-quartz veins in coastal southern and southeastern Alaska are Eocene, about 50 Ma in age (Haeussler and others, 1995; Goldfarb, 1997; Goldfarb and others, 1997).
Production: There is no record of production, but the extent of the workings suggests that some gold may have been produced.
Commodities (Major) - Au
Development Status: Undetermined.
Deposit Model: Low-sulfide gold-quartz veins (Cox and Singer, 1986; model 36a).
3 entries listed. 3 valid minerals.
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Bittenbender, P., Still, J.C., Maas, K., and McDonald, M., Jr., 1999, Mineral resources of the Chichagof and Baranof Islands area, southeast Alaska: Bureau of Land Management, BLM-Alaska Technical Report 19, 222 p. Cobb, E.H., 1972, Metallic mineral resources map of the Sitka quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-467, scale 1:250,000. Cobb, E.H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Sitka quadrangle: U.S. Geological Survey Open-File Report 78-450, 124 p. Goldfarb, R J., 1997, Metallogenic evolution of Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 4-34. Goldfarb, R.J., Miller, L.D., Leach, D.L., and Snee, L.W, 1997, Gold deposits in metamorphic rocks in Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 151-190. Haeussler, P J., Bradley, D., Goldfarb, R., Snee, L., and Taylor, C., 1995, Link between ridge subduction and gold mineralization in southern Alaska: Geology, v. 23, no. 11, p. 995-998. Johnson, B.R, and Karl, S.M., 1985, Geologic map of western Chichagof and Yakobi Islands, southeastern Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map 1-1506, 1 sheet, scale 1:125,000. Nelson, G.E., 1936, Report on New Chichagof Mining Syndicate, Pinta Bay, west coast of Chichagof Island, southeast Alaska: Unpublished report, 2 p. (Report held by the Mineral Information Center, Bureau of Land Management, Juneau, Alaska.) Racey, P.W., 1938, New Chichagof Mining Syndicate, Pinta Bay, Chichagof Island, Alaska: Alaska Territorial Dept. of Mines Miscellaneous Report 114-4, 4 p. Reed, J.C., and Coats, R.R., 1941, Geology and ore deposits of the Chichagof mining district, Alaska: U.S. Geological Survey Bulletin 929, 148 p. Roehm, J.C., 1936, Preliminary report of holdings of New Chichagof Mining Syndicate, Pinta Bay, Chichagof Island, July 3, 1936: Alaska Territorial Department of Mines, Property Examination 114-3, 3 p., 2 maps. Still, J.C., and Weir, K.R., 1981, Mineral land assessment of the west portion of western Chichagof Island, Alaska: U. S. Bureau of Mines Open-File Report 89-81, 168 p. U.S. Bureau of Land Management, 2002, Alaska mineral locations database report (Sitka quadrangle), July 2, 2002, 205 p. [http://imcg.wr.usgs.gov/dem.html]