Unnamed (west of the Middle Fork Chandalar River)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Pb; Zn
Other commodities Ag; Cu
Ore minerals chalcopyrite; galena; iron sulfides; sphalerite; tetrahedrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale PS
Quadrangle map, 1:63,360-scale A-2
Latitude 68.04
Longitude -147.82
Nearby scientific data Find additional scientific data near this location
Location and accuracy Site is at an elevation of about 3,750 ft. in a small drainage approximately 2 miles west of the Middle Fork Chandalar River and about 7 miles south of the confluence of Beaucoup Creek and Middle Fork Chandalar River (south-center sec. 19, T. 16 S., R. 19 E., of the Umiat Meridian). It is described as Area B on fig. 1 in Detra (1977). Location accurate within 1/4-mile radius.

Geologic setting

Geologic description

One of two mineralized areas with small outcrops within which lead-zinc-silver-(copper) mineralization is found (Detra, 1977). The mineralization is described as occurring in quartz veins in a chert breccia cap on limestone. Samples from the veins are reported to contain galena, sphalerite and chalcopyrite as well as iron sulfides. Exposures of mineralization are less than 3 meters in length and not much wider than the streams (approximately 1 to 2 meters) in which they are exposed. Two samples taken from the mineralized area returned analyses as high as 25 percent Zn, [more than] 2 percent Pb and 150 ppm Ag (Detra, 1977). The chert breccia cap which hosts the mineralization occurs locally at the top of the Skajit Limestone at an unconformity that has been interpreted as a paleokarst surface. The chert cap is overlain by yellow-weathering phyllitic siltstones, shales and sandstones, which in turn are overlain by black shales of the Hunt Fork Shale. The surrounding area is mapped as Devonian shale, sandstone and conglomerate with scattered bodies of mafic rocks of uncertain age (Detra, 1977).
Geologic map unit (-147.822777968996, 68.0396431233993)
Mineral deposit model Mississippi Valley Zn-Pb? (Cox and Singer, 1986; model 32a?).
Mineral deposit model number 32a?

Production and reserves

Workings or exploration
57 claims in two claim blocks located by Noranda and RAA in 1977.
Semi-quantitative spectrographic data (Detra, 1977) from rock samples from the area include: sample number 232RA - Ag (150 ppm), Ba (200 ppm), Cu (700 ppm), greater than 20,000 ppm Pb and Zn. Zn by wet chemical analysis - 250,000 ppm; sample number 232RB - Ag (30 ppm), Ba (300 ppm), Cu (150 ppm), Pb (15,000 ppm), greater than 20,000 ppm Zn. Zn by wet chemical analysis - 75,000 ppm (Detra, 1977, table 1).
Indication of production None

Additional comments

See also locations PS006 and PS008. Site is in an area thought to have potential for carbonate-hosted lead-zinc deposits (Menzie and others, 1985). The pH of the stream that cuts the mineralization is less than 4.5.

References