Won - North; Stockwork Zone; Standoff Ridge Prospect, Innoko District, Yukon-Koyukuk Borough, Alaska, USA
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Location: The Won - North prospect is situated on a north-facing slope near the summit of a north-south trending ridgeline at an elevation of 2,300 feet (701 m) in Section 12, T. 23 S., R. 16 E., of the Kateel River Meridian. Mineralization in the Standoff Ridge Zone of the Won - North prospect is about 2.1 miles (3.4 km) North of the Won - South prospect (MD024). Location is accurate; the reporter visited the site in 1984.
Geology: The Won - North prospect is the northern-most group of silver-tin prospects that have been referred to by Burleigh (1992; BMOF 85-92) as the 'Won' deposit. Mineralization occurs as moderately dipping breccia vein structures in thermally altered rocks of the Upper Cretaceous Kuskokwim Group. The Stockwork zone consists of stockwork quartz veining and crosscutting tourmaline breccias that can be traced on the surface for about 1,000 feet (300 m) by 250 feet (76 m). Small 0.5 to 2 inch (1.2 to 5.0 cm) thick quartz veinlets occur often, with a density of 30 per foot (0.3 m). The Standoff Ridge Zone is a series of four or more north 25 degrees west -trending vein structures that can be traced for about 1,500 feet (457 m). Arsenopyrite and cassiterite are the dominant ore minerals found in the various zones. Age of mineralization is inferred to be Late Cretaceous-Early Tertiary, based on ages of nearby plutonic rocks (Bundtzen and Miller, 1997). Anaconda Mineral Company drilled the property in 1984 and encountered up to 0.14 percent tin and 4.6 ounces/ton silver over narrow, sheeted veins up to six feet (1.8 m) wide.
Workings: The U.S. Geological Survey AMRAP program of the Medfra quadrangle (King and others, 1980, 1983; Patton and others, 1980) reported anomalous values of arsenic, bismuth, tin, silver, tungsten, and lead in stream sediment and pan concentrate samples from streams draining the project area. Duval Corporation and Anaconda Minerals Company followed up on these anomalies and found the Won-North prospect. In 1984, Anaconda Minerals company drilled the Standoff Ridge zone, and encountered up to 0.14 percent tin and 4.6 ounces/ton silver over narrow, sheeted veins up to 6 feet (1.8 m) wide. Online Exploration Services Inc., Anchorage, Alaska, has continued exploration at the Won-North prospect in recent years.
Age: Late Cretaceous-early Tertiary, inferred based on ages of nearby plutonic rocks (Bundtzen and Miller, 1997).
Alteration: Axinite and sericite.
Reserves: No reserves were calculated from the drill program.
Commodities (Major) - Ag, Sn; (Minor) - As, Cu, Pb, Sb, Zn
Development Status: No
Deposit Model: Tin-polymetallic (Cox and singer, 1986; model no. 20b)
Mineral List
8 entries listed. 6 valid minerals.
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References
Burleigh, R.E., 1992, Tin mineralization at the Won prospect, west-central Alaska: U.S. Bureau of Mines Open-File Report 85-92, 21 p. Bundtzen, T.K., and Miller, M.L., 1997, Precious metals associated with Late Cretaceous-early Tertiary igneous rocks of southwestern Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 242-286. Patton, W.W. Jr., Moll, E.J., Dutro, J.T., Jr., Silberman, M.L., and Chapman, R.M., 1980, Preliminary geologic map of the Medfra quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-811, one sheet at 1:250,000 scale.