|Quadrangle map, 1:250,000-scale||HG|
|Quadrangle map, 1:63,360-scale||D-6|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||Fox Gulch is a west headwater tributary to Platinum Creek (HG014). Its confluence with Platinum Creek is about 1 mile upstream of the mouth of Platinum Creek on Salmon River. The map site is at the approximate midpoint of the placer workings. It is included in locality 12 of Cobb (1972 [MF 362]; 1980 [OF 80-909]).|
Fox Gulch is where platinum was first discovered in the Salmon River area (1926). It has been placer mined for about 0.4 mile upstream from its junction with Platinum Creek. The headwaters of Fox Gulch are in dunite of the Red Mountain ultramafic pluton, and it also flows across border zone clinopyroxenite and hornblende-bearing rocks. In the area of mining, however, the bedrock is part of an assemblage that includes sheared argillite, graywacke, and mafic to intermediate, fine-grained igneous rocks that are difficult to identify because of their decomposed character where exposed in mining cuts (Mertie, 1940). These strata are included in a regional sedimentary and volcanic assemblage that ranges in age from Paleozoic to Mesozoic (Hoare and Coonrad, 1978).
Gravels in lower Fox Gulch are up to 12 feet thick, but they thin upstream.The gravels are coarse, subangular, and locally derived and contain boulders averaging 8 to 12 inches in diameter. The average width of the pay streak was 75 feet and it extended at least 2,600 feet upstream from the mouth of Fox Gulch. Platinum was concentrated in the lower few feet of gravel, on bedrock, and in fractures in bedrock. Chromite is common in the heavy-mineral concentrates and some chromite grains are intergrown with PGM. The U. S. Bureau of Mines collected 4 samples from the present drainage. These samples contained 0.0009 to 0.0378 ounce of PGM per cubic yard (Fechner, 1988, p. 80) The highest grade sample was from unmined material in the upper part of the gulch. One sample of tailings in Fox Gulch contained 0.0121 ounce of PGM per cubic yard (Fechner, 1988). Microprobe analyses of PGM grains from these samples showed 1.3 to 1.9 percent Rh, 0.7 to 1.0 percent Ru, 37.7 to 48.6 percent Pt, 26.7 to 41.3 percent Ir, 9.8 to 13.4 percent Os, and 4.1 to 8.4 percent Fe. PGM-bearing phases that were identified in these samples included iron-platinum alloy containing 8 to 30 percent Fe; iron-platinum alloy with minor osmiridium inclusions; and hollingsworthite, irarsite, iridarsenite, iridium, sperrylite, and platarsite (Fechner, 1988, p. 80). The mean of 26 analyses of PGMs (recalculated to exclude impurities) recovered during mining from Fox Gulch and Platinum Creek above Squirrel Creek was 63.71% Pt, 28.01% Ir, 5.39% Os, 0.47% Ru, 1.82% Rh, 0.23% Pd, and 0.37% Au. Six samples from Fox Gulch, recalculated free of impurities, averaged 50.56 percent Pt, 39.14 percent Ir, 7.74 percent Os, 0.71 percent Ru, 1.62 percent Rh, 0.14 percent Pd, and 0.09 percent Au (Mertie, 1976). Fechner (1988) estimates that there are 160,000 cubic yards of tailings on Fox Gulch that contain 0.012 ounce of PGM per cubic yard and 20,000 cubic yards of unmined material that contain 0.02 ounce of PGM per cubic yard.
|Geologic map unit||(-161.752227006074, 58.9192158079387)|
|Mineral deposit model||Placer PGE-Au (Cox and Singer, 1986; model 39b)|
|Mineral deposit model number||39b|
|Age of mineralization||Quaternary.|
|Workings or exploration||Placer tailings are present along about 1/2 mile of lower Fox Gulch. Small-scale mining took place as early as 1927 and continued intermittently until 1934, when the Goodnews Bay Mining Company started larger-scale dragline operations in the area (Mertie, 1940). The deposit was worked out by WWII. Mining was continuous from Fox Gulch downstream into Platinum Creek.|
|Indication of production||Yes; small|
|Reserve estimates||Fechner (1988) estimates that there are 160,000 cubic yards of tailings on Fox Gulch that contain 0.012 ounce of PGM per cubic yard and 20,000 cubic yards of unmined material that contain 0.02 ounce of PGM per cubic yard.|
|Production notes||If 0.02 ounce of PGM per cubic yard were recovered from 160,000 yards of pay, Fox Gulch produced 3,200 ounces of PGM.|
|MRDS Number||A013213; M045373|
Alaska Earth Sciences, 2000, The Goodnews Bay ultramafic complexes: Unpublished data, http://aes.alaska.com/UMAF/FIGURES/page4.html
Cobb, E.H., 1972, Metallic mineral resources map of the Hagemeister Island quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-362, 1 sheet, scale 1:250,000.
Cobb, E.H., 1980, Summaries of data and lists of references to metallic and selected nonmetallic mineral deposits in fifteen quadrangles in southwestern and west-central Alaska: U.S. Geological Survey Open-File Report 80-909, 103 p.
Hoare, J.M., and Coonrad, W.L., 1978, Geologic map of the Goodnews and Hagemeister Island quadrangles region, southwestern Alaska: U.S. Geological Survey Open-File Report 78-9-B, 2 sheets, scale 1:250,000.
Mertie, J.B., Jr., 1940, The Goodnews platinum deposits, Alaska: U.S. Geological Survey Bulletin 918, 97 p.
|Reporters||Travis L. Hudson|
|Last report date||3/18/2001|