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; pyrite; sphalerite; tetrahedrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale PS
Quadrangle map, 1:63,360-scale A-2
Latitude 68.05
Longitude -147.81
Nearby scientific data Find additional scientific data near this location
Location and accuracy Site is at an elevation of about 3,800 ft. in the upper part of a small drainage approximately 2 miles west of the Middle Fork Chandalar River and about 6 miles south of the confluence of Beaucoup Creek and Middle Fork Chandalar River (SE1/4 sec. 18, T. 16 S., R. 19 E., of the Umiat Meridian). 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). Sphalerite, galena and pyrite are found in crosscutting veins in a chert breccia with quartz veins. Samples from the veins are reported to contain galena, sphalerite and chalcopyrite as well as iron sulfides. An analysis of mineralized material returned a value of 34 percent Zn and 70 ppm Ag (Detra, 1977). 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. The mineralization is described as occurring in a chert cap at an unconformable paleokarst surface at the top of the Devonian Skajit Limestone at the base of a 1,200-meter-thick Frasnian fine clastic marine sequence (Dutro, 1978). This marine sequence grades upward from basal black shales and dark laminated limestones through cycles of fine clastics and into reef limestones. The clastics contain volcaniclastics and mafic volcanic rocks. The overlying clastics are yellow-weathering phyllitic shales and sandstones, which in turn are overlain by black shales of the Hunt Fork Shale. This is purportedly the only carbonate-hosted prospect in Alaska genetically linked to a karst or paleokarst event (Schmidt, 1997). The surrounding area is mapped as Devonian shale, sandstone and conglomerate with scattered bodies of mafic rocks of uncertain age.
Geologic map unit (-147.812778396123, 68.0496437125057)
Mineral deposit model Mississippi Valley Zn-Pb? (Cox and Singer, 1986; model 32a?).
Mineral deposit model number 32a?

Production and reserves

Workings or exploration Two blocks of claims staked in 1977 (19 by Noranda, 6 by RAA). Semi-quantitative spectrographic data for sample 76ARR46 (Detra, 1977, Table 1): Ag (70 ppm), Cu (1,000 ppm), Pb (3,000 ppm), Sb (700 ppm), Zn (greater than 20,000 ppm); Zn by wet chemical analysis (340,000 ppm).
Indication of production None

Additional comments

See also locations PS007 and PS008. Area has potential for stratabound lead-zinc deposits.

References