Harter Gulch Mine, Hot Springs Mining District, Yukon-Koyukuk Census Area, Alaska, USAi

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

Location: The site of the Harter Gulch placer mine is on the gulch at an elevation of about 700 feet, in the north half of section 17, T. 3 N., R. 16 W., of the Fairbanks Meridian. The site corresponds to location 31 of Cobb (1972), and roughly to the site for Harter Gulch, U.S. Bureau of Land Management MAS number 0020480017.
Geology: The Harter Gulch 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). The Harter Gulch mine lies just to the north of a regional thrust fault; bedrock in the gulch is Triassic strata. Little is published specifically about Harter Gulch. Wayland (1961) states that mining occurred there in the early days of the district, and that Richards, the principal operator, reportedly collected $90,000 worth of gold in one summer (equivalent to 4,350 ounces of refined gold at $20.67 per ounce). Wayland also states that the tailings in Harter Gulch contain significant quantities of gold and some cassiterite. Moxham (1954) tested the tailings for radioactivity, presumably with negative results. The placer gravels, which consist of angular phyllite and graywacke and some rounded sandstone, were not completely washed by the early prospectors, leaving more gold in the tailings than that found in other creeks. A cubic yard of these gravels averaged 0.84 pound of concentrate that yielded 0.27 pound of cassiterite and 0.017 ounce of gold per cubic yard (Thomas, 1957). Cobb (1981) reports that placer mining may have occurred in 1977.
Workings: No detailed information has been published about the mining techniques used on Harter Gulch, other than it was worked mainly by a man named Richards in the early days of mining (Wayland, 1961). Cobb (1981) reports that placer mining may have occurred in 1977.
Age: Quaternary.
Production: Wayland (1961) states that Richards reported recovering $90,000 worth of gold (at $20.67 per ounce) from Harter Gulch in one season. Cobb (1977) estimated production to the mid-1970's to equal approximately 5,000 ounces.

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:	TN094

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References