Ferguson Draw Mine, Hot Springs Mining District, Yukon-Koyukuk Census Area, Alaska, USAi

Regional Level Types
Ferguson Draw Mine	Mine
Hot Springs Mining District	Mining District
Yukon-Koyukuk Census Area	Census Area
Alaska	State
USA	Country

Location: The exact location of placer mining on Ferguson Draw is unknown. For this record, the site is at a sled-road crossing just upstream from its junction with Cache Creek, near the center of section 9, T. 3 N., R. 16 W., of the Fairbanks Meridian. The site corresponds to location 33 in Cobb (1972, 1977) and to location 8 in the Tanana quadrangle in Eberlein and others (1977). It also roughly corresponds to the site for Ferguson Draw, U.S. Bureau of Land Management MAS number 0020480131, but the MAS site is approximately 0.5 mile upstream.
Geology: The Ferguson Draw placer mine is one of a group of cassiterite- and gold-bearing placer deposits known as the Tofty tin belt, a 12-mile-long area that trends east-northeast, between Roughtop Mountain to the north and Hot Springs Dome to the south (Thomas, 1957). Roughtop Mountain and Hot Springs Dome respectively are underlain by Cretaceous (K-Ar age date of 92 +/- 5 Ma) and Tertiary (K-Ar age date of 62 +/- 3 Ma) granitic plutons (Chapman and others, 1982). The plutons intrude and contact metamorphose Mesozoic marine sedimentary strata, which also are cut by diverse faults, including regional-scale, east-northeast-striking, thrust faults (Reifenstuhl and others, 1998). A carbonatite sill(?) is in the Triassic section of these strata and there are exposures of serpentinized, Cretaceous(?) mafic and ultramafic rock, mainly on Serpentine Ridge. The gold- and tin-bearing creeks flow normal to the trend of the tin belt. They head in the plutonic, metamorphic, and mafic/ultramafic rocks of Roughtop Mountain and Serpentine Ridge, which probably are the source(s) of some of the metalliferous minerals in the placer deposits. Concentrations of gold diminish toward the south, probably due to dispersion (Thomas, 1957). Ferguson Draw is at the junction of two faults (Reifenstuhl and others, 1998). Bedrock in the creek consists of Triassic sedimentary rocks. The gravels in Ferguson Draw are thin or absent, and the gold is directly on the bedrock, often overlain by 40 feet of muck (Wayland, 1961). The gravels, when present, contain silicified phyllite, and well-traveled boulders of quartzite and quartz. Wayland reported that the ground contained 0.3-0.4 ounce of gold and 0.1 to 0.4 pound of cassiterite per square foot of bedrock. Upstream, the pay streak terminates abruptly at a bedrock bench. The gold recovered from Ferguson Draw was different from the gold at the head of Cache Creek (TN097). Gold from Ferguson Draw was characteristically fine and smooth, whereas the bulk of the gold from Cache Creek was bird-shot in size. The cassiterite mostly occurs as well-rounded to subangular particles that range in size from microscopic to several inches across. The larger sizes often are accompanied by vein quartz and tourmaline, as well as by fragments of sedimentary country rock. The smaller sizes generally are free of impurities (Thomas,1957).
Workings: Gold was discovered on Cache Creek (TN097) in 1909 and 1910, and prospecting began on Ferguson Draw about then. Subsequent mining presumably involved sinking shafts and underground workings.
Age: Quaternary.
Production: Wayland (1961) reported that the ground contained 0.3-0.4 ounce of gold and 0.1 to 0.4 pound of cassiterite per square foot of bedrock.

Commodities (Major) - Au; (Minor) - Sn
Development Status: Yes; small
Deposit Model: Placer Au(-Sn) (Cox and Singer, 1986; model 39a).

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Link to USGS - Alaska:	TN098

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References