Grubstake Creek Mine, Chistochina Mining District, Valdez-Cordova Census Area, Alaska, USAi

Regional Level Types
Grubstake Creek Mine	Mine
Chistochina Mining District	Mining District
Valdez-Cordova Census Area	Census Area
Alaska	State
USA	Country

See also Slope Creek (GU020). The placer in upper Grubstake Creek probably overlies a disseminated lode gold deposit (GU019).
Location: Grubstake Creek (Cobb, 1979 [OF 79-1247 p. 11-12] flows west and joins Ahtell Creek about 2 miles south of the Dome. The creek was mainly mined in a section of its canyon about 0.8 to 1.2 miles above its mouth. Grubstake Creek is locality 10 of Richter (1966), locality 17 of Richter and Matson (1972), and locality 16 of MacKevett and Holloway (1977). The location is accurate to within 500 feet; it is in the SE1/4SW1/4, section 26, T. 12 N., R. 7 E., Copper River Meridian.
Geology: The rocks along Grubstake Creek consist of granitic rocks of the Pennsylvanian to Permian, Ahtell pluton and altered volcanics and minor sedimentary rocks of the Pennsylvanian to Permian,Tetelna Formation. Jurassic diorite forms small bodies that intrude the volcanic section and possibly the Ahtell pluton. Richter and Matson (1968) proposed that the source of the placer was the Jurassic diorite; earlier Richter (1966) had assumed that the source was the Permian, Ahtell intrusive. The placer deposit consisted of poorly sorted gravels with occasional boulders. The discovery of an economic placer was made in 1934. The gravel section reported then was more than 16 feet thick and bedrock had not been reached (Moffit, 1936, p. 139-141). The country rock was volcanic and limestone with Permian fossils. Native gold was accompanied by significant amounts of native copper and native silver. The native metals found in the placer, are rough and some are dendritic, indicating a local source. Ilmenite was found in concentrates, and magnetite occurred locally in flattened slabs more than 1 foot across. Moffit (1937, p. 106-107) later reported that sheared diorite was encountered in bedrock under the placer.
Workings: Gold was found in sub-economic concentrations early in the history of the district. An economic deposit was found in 1934 and was mined on at least a small scale until World War II (Moffit, 1936, 1937,1938; Smith, 1942; Moffit, 1942; Thorne, 1946). It was subsequently worked on a small scale after the war.
Age: Holocene placer .
Alteration: Rocks nearby have iron-stained, pyrite-rich zones and and there is local hydrothermal alteration of the Ahtell pluton and its wall rocks.
Production: Placer deposits in Grubstake and Slope Creeks (GU007) have been mined intermittently since 1934. The total gold production from both creeks is probably less than $30,000 (about 857 ounces) (Richter and Matson, 1968).

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

Other Databases

Link to USGS - Alaska:	GU017

Other Regions, Features and Areas containing this locality

References