Alpha Mine, Kantishna District, Denali Borough, Alaska, USA
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Location: The Alpha mine (Cobb, 1980 [OFR 80-363]) is on the south flank of Alpha Ridge above Eldorado Creek. It is about 4000 feet due west of Iron Dome. The mine workings are at an elevation of about 3000 feet and are in the SW1/4SE1/4 sec. 15, T. 16 S., R. 18 W., Fairbanks Meridian. The location is accurate within 500 feet. The mine is location 9 of Bundtzen, Smith, and Tosdal (1976) and Bundtzen (1981), 14 and 15 of Thornsberry, McKee, and Salisbury (1984), D of Hawley and Associates (1978), and 3 of Cobb (1972 [MF 366]) and MacKevett and Holloway (1977).
Geology: The fault-controlled Alpha vein system strikes NE and dips steeply. It cuts tan-weathering quartz-mica schist of Birch Creek type (Bundtzen, 1981). The fault can be traced southwest along strike for about 1000 feet. It appears to continue about 1500 feet east-northeast. The fault may be the continuation of a fault which offsets a calcareous schist unit about 500 feet (Hawley and Associates, 1978, fig. 4.1-A(1)). The fault zone is as much as 25 feet wide and individual veins are up to 10 or more feet thick. In about 1922, a shallow shaft exposed an eight- or nine-foot-thick zone containing three quartz veins, each about a foot thick. A representative sample of hand-cobbed material assayed 266.3 ounces of silver per ton (Davis, 1923, p. 131). The workings were largely caved when Wells visited the property in 1931; he reported that a foot-thick galena-rich vein assayed 0.01 ounce of gold per ton, 346 ounces of silver per ton and 5.46 percent lead (Wells, 1933, p. 375-376). The mineralogy is typical of quartz-siderite polymetallic veins in the Kantishna Hills area (MM091). The veins mainly comprise arsenopyrite, pyrite, galena, jamesonite, stibnite, and sphalerite, along with lesser amounts of boulangerite and tetrahedrite, in a siderite-rich quartz gangue. Extensive near-surface limonite appears to be derived from siderite as well as from the sulfide minerals. The veins are probably Eocene, roughly contemporaneous with the eruption of the Teklanika Volcanics in the Mt. McKinley area (Gilbert, Ferrill, and Turner, 1976).
Workings: The Alpha mine was developed before 1923 by a 120-foot-long drift adit and a 20-foot shaft (Davis, 1923). About 10 tons of selected, high-grade ore was shipped in 1921; ore was also shipped in 1923. Although the ore was rich, the mine was not profitable, owing to high shipping costs (Brooks, 1925). The mine was inactive when visited by Wells in 1931 (Wells, 1933). Sometime later, a bulldozer trail was cut to the mine and there was some bulldozer trenching. Claims were never patented; in 1983, they were held as the Virginia City 1 and 2 by James Fuksa. Samples collected in the 1970s and 1980s tend to confirm the high-grade nature of the vein. A sample collected by Bundtzen (1981, table 9) assayed about 83 ounces of silver per ton, about 18 percent lead and nearly 3 percent zinc. Samples collected by McKee (in Thornsberry, McKee, and Salisbury, 1984, v. 2, location 14) assayed as much as 48 ounces of silver per ton and 15 percent or more combined lead and zinc. Antimony content locally exceeded 9 percent. Samples collected by Bundtzen contained up to 75 ppm tungsten, and one contained 20 ppm uranium. Soil samples collected as much as 1000 feet southwest of the mine workings were significantly enriched in lead, zinc, and silver (Hawley and Associates, 1978, samples nos. 47-49, table 4.1-1(A)).
Age: The veins are probably Eocene, about contemporaneous with eruption of the Teklanika volcanics of the Mt. McKinley area (Gilbert, Ferrill, and Turner, 1976), (also see record MM091).
Alteration: Silicification; iron-oxide alteration.
Production: Probably a total of about 25 tons, including 10 tons of ore shipped in 1921 that assayed more than 200 ounces of silver per ton.
Commodities (Major) - Ag; (Minor) - Au, Cu, Pb, Sb, Zn
Development Status: Yes; small
Deposit Model: Polymetallic veins (Cox and Singer, 1986; model 22c).
12 entries listed. 11 valid minerals.
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Brooks, A.H., 1925, Alaska's mineral resources and production, 1923: U.S. Geological Survey Bulletin 773-A, p. 3-52. Bundtzen, T.K., 1981, Geology and mineral deposits of the Kantishna Hills, Mt. McKinley quadrangle, Alaska: M. S. Thesis, University of Alaska, College, Alaska, 238 p. Bundtzen, T.K., Smith, T.E., and Tosdal, R.M., 1976, Progress report--Geology and mineral deposits of the Kantishna Hills: Alaska Division of Geological and Geophysical Surveys Open-File Report AOF-98, 80 p., 2 sheets, scale 1:63,360. Cobb, E. H., 1972, Metallic mineral resources map of the Mount McKinley quadrangle, Alaska: U. S. Geological Survey Miscellaneous Field Studies Map MF-366, 1 sheet, scale 1:250,000. Cobb, E.H., 1980, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Mount McKinley quadrangle, Alaska: U. S. Geological Survey Open-File Report 80-363, 150 p. Cox, D.P., and Singer, D.A., eds., 1986, Mineral deposit models: U.S. Geological Survey Bulletin 1693, 379 p. Davis, J. A., 1923, The Kantishna region, Alaska, in Stewart, B. D., Annual Report of the Mine Inspector to the Governor of Alaska, 1922: Alaska Division of Geological and Geophysical Surveys AR-1922. Gilbert, W. G., Ferrell, V. M., and Turner, D. L., 1976, The Teklanika Formation: a new middle Tertiary formation in the central Alaska Range: Alaska Division of Geological and Geophysical Surveys Geological Report 47, 16 p. Hawley, C. C. and Associates, Inc, 1978, Mineral appraisal of lands adjacent to Mt. McKinley National Park, Alaska: U. S. Bureau of Mines Open-File Report 24-78, 275 p. (paged by sections). MacKevett, E.M., Jr., and Holloway, C.D., 1977, Map showing metalliferous and selected non-metalliferous mineral deposits in the eastern part of southern Alaska: U.S. Geological Survey Open-File Report 77-169-A, 99 p., 1 sheet, scale 1:1,000,000. Thornsberry, V. V., McKee, C. J., and Salisbury, W. G., eds, 1984, 1983 Mineral Resource Studies: Kantishna Hills and Dunkle Mine Areas, Denali National Park and Preserve, Alaska: U. S. Bureau of Mines Open-File Report 129-84. 3 Volumes: v. 1, Text; v. 2, Appendices; v. 3, Maps. Prepared by Salisbury & Dietz, Inc., Spokane, WA. Wells, F. G., 1933, Lode deposits of Eureka and vicinity, Kantishna district, Alaska: U. S. Geological Survey Bulletin 849-F, p. 335-379.