Glenn; Glen; Swisher Prospect, Kantishna District, Denali Borough, Alaska, USA
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Location: The Glenn (sometimes called Glen or Swisher) prospect (Cobb, 1980 [OFR 80-363]) is at altitude of about 4200 feet on the south side of Glacier Peak, within 1000 feet of hilltop 4310. It is near the middle of the S1/2 SE1/4 of section 35, T. 15 S., R. 17 W., Fairbanks Meridian. The location is accurate within 500 feet. The prospect is location 17 of Cobb (1972 [MF 366]), and is included in location 13 of MacKevett and Holloway (1977). It corresponds to number 47 of Bundtzen, Smith, and Tosdal (1976), 216 of Hawley and Associates (1978), 52 of Bundtzen (1981), and 70 of Thornsberry, McKee, and Salisbury (1984).
Geology: The country rock at the Glenn prospect is micaceous quartz schist of the upper Precambrian Birch Creek Schist, near the rest of the Kantishna antiform (MM091) (Bundtzen, 1981). The schist strikes north and dips 20-40 W. The prospect is about 500 feet north of a fault that strikes WNW and juxtaposes Spruce Creek lithologies (to the south) against Birch Creek Schist (Thornsberry, McKee, and Salisbury, 1984, fig. K-2). The deposit is a sulfide-bearing quartz vein that locally contains potassium feldspar. The vein is 4 to 10 feet thick, strikes N80W and is nearly vertical. The ore minerals include arsenopyrite, galena, boulangerite, jamesonite, stibnite, sphalerite, and, tentatively, tetrahedrite; free gold occurs locally (Capps, 1919, p. 100; Bundtzen, 1981; Thornsberry, McKee, and Salisbury, 1984). The sulfides are partly oxidized to scorodite, stibiconite, goethite, and jarosite. The vein was explored by two adits. A sample from the upper dump assayed 8.54 ounces of silver per ton, 0.03 ounce of gold per ton, 0.086 percent copper, 3.4 percent lead, 0.480 percent zinc, 2.05 percent antimony, and 2.05 percent arsenic. Ore from the lower dump assayed 23.08 ounces of silver per ton, 0.05 ounce of gold per ton, 0.093 percent copper, 6.55 percent lead, 1.00 percent zinc, and less than 1 percent each of arsenic and antimony.
Workings: The Glenn prospect was explored between 1906 and 1909 by a group led by Tom Lloyd, an early local landowner. The exploration consisted chiefly of two adits. The portal of the lower tunnel is at an elevation of about 4050 feet; the upper portal is at about 4250 feet (Wells, 1933, p. 373). The tunnels were caved when Capps (1919) visited the property in 1916. By 1931, the property was controlled by Lee Swisher, but no more underground work was done (Wells, 1933). Bundtzen, Smith, and Tosdal (1976), Hawley and Associates (1978), and Thornsberry, McKee, and Salisbury (1984) mapped the site or collected rock and soil samples.
Age: The deposit is assumed to be Eocene (see record MM091).
Alteration: Silicicification and introduction of potassium feldspar. Oxidation of iron, arsenic, and antimony minerals.
Commodities (Major) - Ag, Au; (Minor) - Pb, Sb, Zn
Development Status: Undetermined.
Deposit Model: Polymetallic vein (Cox and Singer, 1986; model 22c).
14 entries listed. 12 valid minerals.
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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. Capps, S. R., 1919, The Kantishna region, Alaska: U. S. Geological Survey Bulletin 687, 116 p. 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. 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.