Location: For this record, the site of the Sullivan Creek placer mine is on the creek at Tofty, at the north-central boundary of section 18, T. 3 N., R. 16 W., of the Fairbanks Meridian. The site represents at least a mile of placer workings on Sullivan Creek near Tofty (Cobb, 1972, location 30). This site very roughly corresponds with the site for Tofty tin belt, U.S. Bureau of Land Management MAS number 0020480032. The site for Sullivan Creek, MAS number 0020480005, is approximately 0.5 mile to the east.
Geology: The Sullivan 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 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 Sullivan Creek placer mine is on the trace of a northwest-trending fault with small relative right-lateral displacement, and approximately 0.5 mile north of a regional thrust fault (Reifenstuhl and others, 1998). Bedrock in Sullivan Creek comprises Triassic clastic sedimentary strata. The principal pay streak was the Sullivan bench placer, approximately 2,000 feet east of the present course of Sullivan Creek (Wayland, 1961). The bedrock of the placer operations has been described as graphitic phyllite containing oxidized pyrite (Wayland, 1961), and phyllite containing quartz stringers and pyrite (Mertie, 1934). The thickness of overburden ranges from 30 to 70 feet and the gravels are 10 to 35 feet thick (Eakin,1913). The gold was concentrated in the lower 2 to 3 feet of the gravels and in fractures in shattered bedrock. The overburden contains the remains of Quaternary mammoth, bison, and horses (Heiner and others, 1968). Eakin (1915) described the bench placer deposits as elliptical in plan view. The centers of these deposits were very rich and graded outward to leaner ground. For example, one mine produced $200,000 worth of gold from 5,000 square feet (gold at $20.67 per ounce) (Eakin, 1915). Cassiterite occurs with the gold throughout the area. Hess (1912) reported that the pebbles are very smooth. This was confirmed by Eakin (1913), who described pans worth $10-$15 in gold (at $20.67 per ounce), and containing as much as a half-pound of cassiterite. Other heavy minerals in the concentrates included pyrite, ilmenite, picotite, magnetite, native copper, zircon, monazite, aeschynite, and xenotime (Waters, 1934), as well as chromite, galena, and arsenopyrite (Wayland, 1961). The sources of the chromite, picotite, magnetite, and ilmenite probably are the serpentinized mafic and ultramafic rocks. Cobb (1977) summarized mining activity on Sullivan Creek to 1975. Mining began on the benches in 1907 and continued into the 1940's. Initially, only the gold was kept, but by about 1918 the cassiterite became an important byproduct. In 1951, L. McGee bought the Cleary Hill Mines, Inc., mining claims and equipment and began mining (Williams, 1951). By 1956, Sullivan Creek had produced 58,136 ounces of gold, 5,463 ounces of silver, and 215,445 pounds of cassiterite concentrate, which was between 1/3 and 1/2 of the total production of placer deposits in the Tofty tin belt (Thomas, 1957). It appears that far more cassiterite might have been recovered if different sluicing techniques had been employed (Wayland, 1961). Placer mining was underway in 1967, with over a dozen claimblocks or working groups on the creek (Heiner and others, 1968). More recent mining has included drifting on Sullivan bench by Burgess Mining in 1985 (Bundtzen and others, 1986). As of 1988, Shoreham Resources was preparing to mine on the bench (Green and others, 1989), and they mined it in 1991. Their operation recovered 1,746 ounces of gold, 324 ounces of silver, and 6,800 lbs of tin metal as cassiterite (Bundtzen and others, 1992). Harold Bergman spent part of 1990 working a cut (Swainbank and others, 1991). Bundtzen and others (1996) reported that Cassiterite Placers, Inc., worked Sullivan Bench in 1995.
Workings: Sullivan Creek was originally drift mined, and accounted for most of the early output of placer gold in the Tofty district (Brooks, 1909; Hess, 1912). By the early 1920's hydraulic plants were being used. Much of the land was bought up by Alaska Gold Dredging Company, and in 1929 they conducted an extensive drilling program of the Sullivan bench. The results were not satisfactory and the land was passed on to miners, who sold their holdings to Cleary Hill Mines in 1931. By 1934, Cleary Hill Mines was using hydraulic giants to strip land and was mining alternate summers, apparently until 1941 (Wayland, 1961). In 1951, L. McGee bought the Cleary Hill Mines claims and equipment and began mining (Williams, 1951). Placer mining was underway in 1967, with over a dozen claimblocks or working groups on the creek (Heiner and others, 1968). In 1991, Shorham Resources operated an open-cut placer mine on Sullivan Creek. The company stripped 310,000 cubic yards of overburden and sluiced 104,000 cubic yards of pay. Recovery was 1,746 ounces of gold, 324 ounces of silver, and 6,800 pounds of tin metal as cassiterite.
Age: Quaternary.
Production: Thomas (1957) reported that 58,136 ounces of gold, 5,463 ounces of silver, and 215,445 pounds of cassiterite concentrate (averaging 60% tin), were recovered from Sullivan Creek through 1956. There has been significant mining since then, but more up-to-date production estimates are not available.

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

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Mineral List

9 valid minerals.