Hetta Mountain Prospects, Hetta Mountain, Prince of Wales Island, Ketchikan District, Prince of Wales-Outer Ketchikan Borough, Alaska, USA
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Location: These prospects are at an elevation of about 2,800 feet near the summit of Hetta Mountain; they are in the NW1/4 section 14, T. 77 S., R. 85 E.
Geology: The Hetta Mountain prospects are on 14 patented claims. The workings, all of which date from before WW I, consist of three short adits and several trenches (Wright and Wright,1908; Wright, 1915; Herreid and others, 1978; Maas and others, 1991, 1995). The rocks in the vicinity consist of a faulted-bounded block of Late Proterozoic or Cambrian marble of the Wales Group that is surrounded by Cretaceous, albite-epidote hornfels and garnet-bearing hornblende hornfels. The metamorphic rocks are cut by several granitic dikes, and the marble is locally altered to skarn. In one adit, a shear zone about 80 feet thick in marble contains diopside-garnet skarn with veinlets and blebs of chalcopyrite. In another adit, three short, en echelon pods of massive pyrite, pyrrhotite, and chalcopyrite replace marble along a porphyritic diorite dike (Herreid and others, 1978). A grab sample of rich ore contained 2.2 percent copper, 0.74 percent zinc, 12.3 ounces of silver per ton, 0.10 ounce of gold per ton, 600 parts per million (ppm) molybdenum, 750 ppm cobalt, and 22 ppm lead. Maas and others (1991) collected 15 samples from the prospects. Several had insignificant metal values, but the best contained 4.17 percent copper, 43.8 ppm silver, and 0.572 ppm gold. Wright and Wright (1908) show several additional prospects along the trail from the head of Copper Harbor to Hetta Mountain. At one, at an elevation of about 1,380 feet, a small mass of chalcopyrite is exposed in a 30-foot tunnel.
Workings: The Hetta Mountain prospects are on 14 patented claims. The workings, all of which date from before WW I, consist of three short adits and several trenches.
Age: Probably Cretaceous.
Alteration: Locally, skarn is developed in marble.
Commodities (Major) - Ag, Au, Cu, Fe, Zn; (Minor) - Co, Mo, Pb
Development Status: None
Deposit Model: Copper skarn (Singer and Cox, 1987; model 18b).
6 entries listed. 5 valid minerals.
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Cobb, E. H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Craig quadrangle, Alaska: U.S. Geological Survey Open-File Report 78-869, 262 p. Glavinovich, P.S., 1987, Sealaska Corporation Minerals Breifing Book, December 1987: Sealaska Corporation, 40 p. and plates. (Unpublished report held by Sealaska Corporation, Juneau, Alaska). Hedderly-Smith, D.A., 1997, Results of 1996 reconnaissance sampling at Hetta Lake-Sealaska minerals reconnaissance project: Sealaska Corporation, 17 p.with addendum. (Unpublished report held by the Sealaska Corporation, Juneau, Alaska.) Hedderly-Smith, D.A., 1999, Inventory of metallic mineral prospects, showings and anomalies on Sealaska lands, 1988 through 1998: Sealaska Corporation, Juneau, Alaska, 217 p. (internal report held by Sealaska Corporation, Juneau, Alaska). Herreid, Gordon, Bundtzen, T.K., and Turner, D.L., 1978, Geology and geochemistry of the Craig A-2 quadrangle, Prince of Wales Island, southeastern Alaska: Alaska Division of Geological and Geophysical Surveys Geologic Report 48, 49 p. Maas, K.M., Bittenbender, P E., and Still, J.C., 1995, Mineral investigations in the Ketchikan mining district, southeastern Alaska: U.S. Bureau of Mines Open-File Report 11-95, 606 p. Maas, K.M., Still, J. C., Clough, A. H., and Oliver, L. K., 1991, Mineral investigations in the Ketchikan mining district, Alaska, 1990: Southern Prince of Wales Island and vicinity--Preliminary sample location maps and descriptions: U.S. Bureau of Mines Open-File Report 33-91, 139 p. Wright, C.W., 1915, Geology and ore deposits of Copper Mountain and Kasaan Peninsula, Alaska: U.S. Geological Survey Professional Paper 87, 110 p. Wright, F.E., and Wright, C.W., 1908, The Ketchikan and Wrangell mining districts, Alaska: U.S. Geological Survey Bulletin 347, 210 p.