Unnamed (north of Oskawalik River)

Occurrence, Inactive

Commodities and mineralogy

Main commodities As; Au
Other commodities Ag; Hg
Ore minerals pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale SM
Quadrangle map, 1:63,360-scale C-5
Latitude 61.69543
Longitude -157.75005
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence extends for about 0.6 mile along a northeast-trending ridge, north of the headwaters of the Oskawalik River. The coordinates are at about the center of the area which is at an elevation of about 1,500 feet in the NW1/4 sec. 35, T. 19 N., R. 47 W., of the Seward Meridian.

Geologic setting

Geologic description

This occurrence consist of an elongate, northeast-trending area of about 0.8 square mile. The rocks in the vicinity are altered and hornfelsed sandstone and shale of the Upper Cretaceous, Kuskokwim Group. The sedimentary rocks have been intruded by felsic dikes of at least two compositions. One is tan-colored, biotite granite porphyry; the other is bleached alaskite. Both strike N60E and average about 13 feet thick; they extend along strike for about 1,600 feet. The sedimentary rocks contains quartz, ferricrete, and sulfide-bearing breccia. In the southern part of the mineralized area, a conspicuous quartz vein about 10 feet thick and 320 feet long strikes N45E, nearly parallel to the felsic dikes. The mineralization occurs as goethite-rich quartz breccias in hornfels; pyrite-bearing, quartz veins; and quartz-carbonate stockworks near the dikes. Most of the mineralization is exposed only as rubble crop and float. Twelve grab samples of quartz veins and goethite-rich quartz breccia contained up to 83 parts per billion (ppb) gold, 470 parts per million (ppm) arsenic, 390 ppb mercury, and 300 ppb silver (T.K. Bundtzen, unpublished analytical data, 1998 and 1999).
Geologic map unit (-157.752429234907, 61.6947326856004)
Mineral deposit model Polymetallic vein? (Cox and Singer, 1986; model 22c).
Mineral deposit model number 22c?
Alteration of deposit Sericitic alteration in intrusive rocks; oxidation of breccia; hornfelsing of shale and sandstone.

Production and reserves

Workings or exploration The prospect was discovered and sampled in 1998 by government geologists.
Indication of production None
Reserve estimates None.

References

References

Reporters T.K. Bundtzen (Pacific Rim Geological Consulting, Inc.) and M.L. Miller (U.S. Geological Survey)
Last report date 5/8/2003