Cache Creek Mine, Hot Springs Mining District, Yukon-Koyukuk Census Area, Alaska, USAi

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

Location: The site of the Cache Creek placer mine is at the junction of Cache Creek and Ferguson Draw (TN098), just south of the center of section 9, T. 3 N., R. 16 W., of the Fairbanks Meridian. The location is probably accurate within half a mile. The site corresponds to location 33 of Cobb (1972), and roughly to the site for Gold Basin Creek, U.S. Bureau of Land Management MAS number 0020480020.
Geology: The Cache Creek 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 rocks, mainly on Serpentine Ridge. The gold- and cassiterite-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 Cache Creek placer area is low-lying, with little exposed bedrock. Most of the area is covered by Quaternary loess and alluvium. The deposit is on the trace of a thrust fault that separates Triassic and Cretaceous rocks, and just south of a northwest-trending fault that offsets the thrust (Reifenstuhl and others, 1998). Farther upstream, the creek flows across carbonatite and another fault. The stream gravels in the mined area consist mainly of angular to subangular fragments of phyllite and graywacke, but also contain fragments of biotite granite, weathered monzonite, metadiorite, and serpentinized gabbro (Wayland, 1961). Mining in the Cache Creek area began during the winter of 1908-09 (Ellsworth, 1910), and by 1910 steam hoists were being used. The pay gravel was at an average depth of about 50 feet; it was about 10 feet thick, and rested on bedrock. The gold was concentrated at the bedrock/gravel interface. Waters (1934) reported that pan concentrates of the placer deposit contained, in addition to gold and cassiterite, magnetite, pyrite, ilmenite, barite, picotite, and aeschynite. Pebbles of cassiterite also contain tourmaline (Wayland, 1961). Through 1956, the U.S. Bureau of Mines reported that approximately 3,650 ounces of gold, 409 ounces of silver, and 5,155 pounds of cassiterite concentrate were removed from Cache Creek (Thomas, 1957). Otto Hovely drift mined on Cache Creek around 1951 (Williams, 1951). Active claims in 1967 on Cache Creek, with mining on some or all of the claims, were held by Benson, Lincoln Quartz Nos. 1 and 2, McGee, McLaughlin, and Strandberg Mines, Inc. (Heiner and others, 1968). More recent activity included mining by Shoreham Resources, Ltd., which in 1989 opened a large-scale placer operation for gold and cassiterite ('tin'), recovering 2,190 ounces of gold and 14,000 pounds of byproduct tin. In that season, the company reported that the recoverable reserves were raised from 63,000 to 74,500 ounces of gold (Bundtzen and others, 1990). The following year, it reported recovery of 1,074 ounces of gold, 208 ounces of silver and 2,600 pounds of tin from 26,000 cubic yards of processed pay (Swainbank and others, 1991). Cassiterite Placers, Inc., mined on Cache Creek during the 1990s (T.K. Bundtzen, oral commun., 2000). Quartz veins and stringers that have small amounts of cassiterite have been identified in the area (TN092), and veins containing a little gold and silver are associated with the granite of Hot Springs Dome (TN103). Such lode deposits probably are the source(s) of some of the metalliferous minerals in this placer deposit.
Workings: Mining in the Cache Creek area began in 1908-09, and by 1910 steam hoists were being used. The pay gravel was at a depth of approximately 50 feet, with limited water supplies for sluicing (Eakin, 1913). Reports of cassiterite ('tin') recovery were sporadic, owing to sub-economic conditions. According to Ellsworth and Davenport (1913), the cassiterite was abundant, while Mertie (1934) reported that it was not. Little is published about mining on Cache Creek between 1917 and 1937. Mining appears to have taken place on a much smaller scale from 1937 to at least 1940. Otto Hovely drift mined on Cache Creek around 1951 (Williams, 1951). Active claims in 1967 on Cache Creek, with mining on some or all of the claims, were held by Benson, Lincoln Quartz Nos. 1 and 2, McGee, McLaughlin, and Strandberg Mines, Inc. (Heiner and others, 1968). More recent activity on Cache Creek included mining by Shoreham Resources, Ltd. In 1989, the company opened a large-scale placer operation for gold and tin, stripping 192,000 cubic yards of overburden, sluicing 26,000 cubic yards of gravel, and recovering 2,190 ounces of gold and 14,000 pounds of byproduct tin. In that season, the company reported that the recoverable reserves were raised from 63,000 to 74,500 ounces of gold (Bundtzen and others, 1990). They hydraulic mined the overburden and sluiced the ore to a containment zone using a completely enclosed system, recycling 100 percent of the mine-process water (Bundtzen and others, 1990). In 1990, the company reported recovery of 1,074 ounces of gold, 208 ounces of silver, and 2,600 pounds of tin from 26,000 cubic yards of processed pay (Swainbank and others, 1991). In 1990, Harold Bergman also worked Cache Creek. Cassiterite Placers, Inc., worked Cache Creek during the 1990's (T.K. Bundtzen, oral commun., 2000).
Age: Quaternary.
Production: The U.S. Bureau of Mines reported that approximately 3,650 ounces of gold, 409 ounces of silver, and 5,155 pounds of cassiterite ('tin') concentrate were removed from Cache Creek through 1956 (Thomas, 1957). This figure is thought to be conservative. Recent mining activity on Cache Creek included mining by Shoreham Resources, Ltd. In 1989, the company opened a large-scale placer operation for gold and tin, recovering 2,190 ounces of gold and 14,000 pounds of byproduct tin. In that season, the company reported that the recoverable reserves were raised from 63,000 to 74,500 ounces of gold (Bundtzen and others, 1990). The following year, it reported recovery of 1,074 ounces of gold, 208 ounces of silver and 2,600 pounds of tin from 26,000 cubic yards of processed pay (Swainbank and others, 1991). Cassiterite Placers, Inc., was also active on Cache Creek in the 1990s (T.K. Bundtzen, oral commun., 2000), but estimates of its production are not available.

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

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Link to USGS - Alaska:	TN097

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References