Unnamed Prospect (ARDF - TE042; on Tin Creek; tributary to Lost River), Port Clarence District, Nome Borough, Alaska, USA
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Geology: The headwaters of Tin Creek are in an area where a small stock of biotite granite, the Tin Creek stock (Sainsbury, 1969; Hudson and Arth, 1983) intrudes Orovician limestone and dolomite. The Tin Creek stock covers a 1,000 by 2,000 foot area on the crest of the rounded hill between Tin Creek and its northern tributary. The south contact of the stock is irregular and includes granite offshoots, dikes, and apophyses in the bordering carbonate rocks. Two types of mineralization are present in the carbonate country rocks on the south flank of the Tin Creek stock: (1) laminar magnetite-fluorite- idocrase skarn (wrigglite) with helvite, and (2) fluorite-diaspore-white mica veins and replacements that contain chrysoberyl. The laminar skarn forms replacement veins along fractures in limestone and larger irregular bodies adjacent to granite intrusions. The fluorite-diaspore-white mica-chrysoberyl veins, from less than an inch up to a few feet wide, are scattered through limestone and localized along borders to granite dikes. They contain cassiterite, stannite, and other sulfide minerals in places. Oxidation of the sulfide-bearing veins has produced gossanous materials at the surface. The helvite-bearing skarn is reported to carry up to 0.45% BeO (Sainsbury, 1969, p. 80). Three samples of beryllium-bearing veins contained 0.13 to 1.11% BeO (Sainsbury, 1963, p. 13). Samples of skarn from this area contained 1,020 to 4,500 ppm tin and more than 20,000 ppm fluorine; one of these samples contained 175 ppb gold (Hudson, 1983).
Workings: A few surface pits and trenches are present in the area.
Age: The age of the mineralization is assumed to be related to the development of tin systems in the Lost River area and therefore Late Cretaceous, the age of the tin-mineralizing granites there (Hudson and Arth, 1983).
Alteration: Calc-silicate, magnetite, and fluorite replacement of limestone
Reserves: Not defined
Commodities (Major) - Be, Sn, fluorite
Development Status: None
Deposit Model: Veins and tactite in limestone intruded by granite. Tin skarn model (14b) of co
7 entries listed. 6 valid minerals.
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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., 1983, Interim report on the Lost River district, Seward Peninsula, Alaska: Anchorage, Alaska, Anaconda Minerals Company internal report (Report held by Cook Inlet Region, Inc., Anchorage, Alaska). Hudson, T.L., and Arth, J. G., 1983, Tin granites of Seward Peninsula, Alaska: Geological Society of America Bulletin, v. 94, p. 768-790. Sainsbury, C.L., 1963, Beryllium deposits of the western Seward Peninsula, Alaska: U.S. Geological Survey Circular 479, 18 p. Sainsbury, C.L., 1969, Geology and ore deposits of the central York Mountains, western Seward Peninsula, Alaska: U.S. Geological Survey Bulletin 1287, 101 p.