Star Group; Tonopah; Rex Prospect, Chandalar Mining District, Yukon-Koyukuk Census Area, Alaska, USAi

Regional Level Types
Star Group; Tonopah; Rex Prospect	Prospect
Chandalar Mining District	Mining District
Yukon-Koyukuk Census Area	Census Area
Alaska	State
USA	Country

See also: Summit prospect (CH041), Mikado mine(CH045), Little Squaw mine (CH040).
Location: The Star prospect is located at an elevation of about 5,000 ft just south of St. Marys Peak (as shown on fig. 2 in Chipp, 1970); it is about 1 mile east of the Mikado mine (CH045) and 4 1/4 miles south of Squaw Lake (SE1/4 sec. 4, T. 31 N., R. 3 W., of the Fairbanks Meridian). The Tonopah claim is the easternmost claim on the Star prospect and is described as being just west of Big Creek and the upper airstrip. The location is accurate within a 1/4-mile radius.
Geology: The Star claim group (including the Tonopah claim) covers one of the four principal auriferous quartz vein systems in the Chandalar area. The vein system of the Star group, like the other vein systems in the area, is localized along steeply-dipping, northwest-trending normal faults in Devonian quartz-muscovite schist, phyllite, and quartzite, intruded by Devonian mafic sills and dikes (Chipp, 1970). In general, the veins in this area are less than 10 feet thick and are discontinuous, pinching out within a few hundred feet or less. The veins are composed principally of white crystalline to microcrystalline quartz, and their sulfide content is generally less than 5 percent. The principal sulfides in relative order of abundance are arsenopyrite, galena, sphalerite, and pyrite. Scorodite and limonite commonly are oxidation products. The quartz veins exhibit evidence of shearing, indicating that they were emplaced before or during fault movement. Major structural features in the area include large-scale northeast-trending anticlines and synclines, northeast-trending thrusts, and the northwest-trending, high-angle cross faults. The fault zone on which the Star group is located lies between the Mikado and Summit faults (Chipp, 1970). A prospect pit on the property exposed a 6-foot-wide, partly vuggy quartz vein containing visible arsenopyrite and scorodite. The vein trends approximately N70W and dips 70 to 90 degrees northeast. A grab sample assayed 11 ppm Au. Another pit exposed vuggy, brown-stained quartz containing phyllite inclusions and minor arsenopyrite. On the Tonopah claim (west of the airstrip on upper Big Creek) trenching has exposed a 50-foot-wide fracture zone containing numerous east-west-trending, vuggy, iron-stained quartz-filled fractures 2
Workings: The Star prospect has been prospected by a 10-foot shaft on the Star No. 2 claim and by several pits and trenches on the Star No. 1 and 3 claims.
Age: Middle Cretaceous(?) based on arguments by Dillon (1982) that the age of emplacement of the gold-bearing quartz veins of the Koyukuk and Chandalar districts was between the Neocomian metamorphism of the Devonian host rocks and their erosional unroofing and cooling in Albian time.
Alteration: Oxidation of sulfides in the quartz veins.

Commodities (Major) - Ag, Au
Development Status: Undetermined
Deposit Model: Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a)

Other Databases

Link to USGS - Alaska:	CH042

Other Regions, Features and Areas containing this locality

References