Unnamed Prospect (ARDF - TN087; west side of Sullivan Creek), Hot Springs Mining District, Yukon-Koyukuk Census Area, Alaska, USAi

Regional Level Types
Unnamed Prospect (ARDF - TN087; west side of Sullivan Creek)	- not defined -
Hot Springs Mining District	Mining District
Yukon-Koyukuk Census Area	Census Area
Alaska	State
USA	Country

Location: This lode prospect is at an elevation of about 700 feet on the west side of Sullivan Creek, about 1 mile upstream from old Tofty and 100 feet above the valley floor (Mertie, 1934). The site is in the northeast quarter of section 12, T. 3 N., R. 17 W., of the Fairbanks Meridian. The location is accurate within 3,000 feet.
Geology: The Sullivan Creek lode prospect is north 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. The Tofty tin belt lies along a regional-scale, east-northeast-striking thrust fault which juxtaposes Triassic argillite, sandstone and shale to the northwest over Cretaceous sandstone, siltstone, and shale to the southeast (Reifenstuhl and others, 1998). Carbonatite sills(?) are in the Triassic sedimentary rocks at the head of Idaho Gulch, and similar bodies occur throughout most of the Tofty tin belt. Loess, generally 4 feet thick, and colluvial gravel, usually 2 to 4 feet thick, blanket most of the local area. Sullivan Creek follows the trace of a northwest-trending, high-angle fault. On the west side of Sullivan Creek, about 1 mile upstream from old Tofty and 100 feet above the valley floor, are several shallow prospects pits in slate (Mertie, 1934). At the bottom of the prospect pits the slate is much sheared and contorted, and contains masses of crumbly and honeycombed white quartz. This quartz is iron-stained and encloses irregular pieces of slate ranging from less than one sixteenth of an inch to at least one inch in diameter (Mertie, 1934). In places, these slate inclusions are almost completely altered to sericite. About 100 yards downstream from these pits is massive, gray quartzite that is cut by an intricate network of iron-stained, whitish, glassy quartz stringers. The quartzite bordering some of these stringers is intensely silicified, and contains a few arsenopyrite crystals (Mertie, 1934). The arsenopyrite in the quartzite is about one inch from the quartz stringers. Mertie also described pyrite-bearing quartz and quartz stringers honeycombed with calcite along Sullivan Creek about 2 miles upstream from old Tofty. At one site, a sharply angular block of iron-stained, whitish, glassy quartz, enclosed in highly sheared wallrock, contains abundant pyrite.
Workings: Several shallow prospects pits are on the west side of Sullivan Creek about 1 mile upstream from old Tofty and 100 feet above the valley floor (Mertie, 1934).
Alteration: Sericitization and silicification.

Commodities (Major) - As
Development Status: None
Deposit Model: Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a), Polymetallic vei

Other Databases

Link to USGS - Alaska:	TN087

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References