Soda Creek Prospects, McGrath District, Yukon-Koyukuk Borough, Alaska, USA
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Location: The Soda Creek prospects are located on a north facing slope near the top of an east-west trending ridgeline south of Soda Creek in the Medfra B-3 quadrangle in Section 2, T. 25 S., R. 23 E., of the Kateel River Meridian, at an elevation of 2,250 feet (686 m). Location is precisely known; reporter visited the property in 1993.
Geology: Two small carbonate hosted zinc/lead deposits approximately 1,500 feet (457 m) apart are structurally controlled along fractures and solution breccia zones in an interbedded carbonate unit that is probably equivalent to the Paradise Creek Formation of Dutro and Patton (1982). The South Soda Creek prospect consists of a linear zone up to 3 feet (0.9 m) wide and up to 30 feet (9.1 m) long in strongly mineralized rubble that is largely composed of solution breccias of several types (Schmidt, 1997). The North Soda Creek deposit consists of smithsonite-bearing gossan in a 2,000 square foot area on a steep, north-facing dip slope. The smithsonite appears to be introduced along a 10 foot (3 m) thick brecciated zone in massive micrite limestone. Mineralization does not extend laterally for more than 200 feet (61 m). Solution breccias occur at both prospecting sites. Rocks hosting the mineralization are inferred to be Late Silurian in age, based on fossils at the site; however, the specific age of the mineralization is unknown. From 1976 to1982, surface sampling and limited trenching was completed on the property. One grab sample at the South Soda Creek prospect contained 26.6 percent zinc and 0.11 percent lead. Other grab samples contained from 370 ppm to 18.10 percent zinc, 2 to 35 ppm cadmium, and 7 to 250 ppm lead. At the North Soda Creek showing, a channel sample along a 37 foot (11.2 m) long trench yielded 0.50 percent zinc, but no lead or cadmium (Schmidt, 1997).
Workings: The Soda Creek prospects were discovered by WGM Inc. and Patino Ltd. during exploration for base metals in the late 1970s (Schmidt, 1997). From 1976 to1982, surface sampling and limited trenching was completed on the property. Intermittant exploration work was continued by Pasminco Ltd. until about 1989 (Schmidt, 1997). One grab sample at the South Soda Creek prospect contained 26.6 percent zinc and 0.11 percent lead. Other grab samples contained from 370 ppm to 18.10 percent zinc, 2-to-35 ppm cadmium, and 7-to-250 ppm lead. At the North Soda Creek showing, a channel sample along a 37 foot (11.2 m) long trench yielded 0.50 percent zinc, but no lead or cadmium (Schmidt, 1997).
Age: Host is inferred to be Late Silurian in age, based on fossils at site; however, the age of the mineralization is unknown.
Alteration: White dolomite; secondary carbonate solution breccias.
Commodities (Major) - Zn; (Minor) - Pb
Development Status: No
Deposit Model: Southeast Missouri Lead-Zinc (Cox and Singer, 1986; model no. 32a)
3 entries listed. 2 valid minerals.
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Anderson, G.M., and Macqueen, R.W., 1988, Mississippi Valley Type lead-zinc deposits, in Roberts, R.G., and Sheahan, P.A., eds., Ore deposit models: Geoscience Canada Reprint Series 3, Ottawa, Canada, p. 79-90. Dutro, J.T. Jr., and Patton,W.W. Jr., 1982, New Paleozoic formations in the northern Kuskokwim Mountains, west-central Alaska: U.S. Geological Survey Bulletin 1529-H, p. H13-H22. Fisher, D.G., and Juilliand, J.D., 1986, Mineral deposit types and their characteristics: U.S. Bureau of Land Management Technical Reference 3031-1, 153 p. 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. Schmidt, J.M., 1997, Shale-hosted Zn-Pb-Ag and barite deposits of Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral deposits of Alaska, 1997: Economic Geology Monograph 9, p. 35-65.