Unnamed (west of Aniak River)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Cu; Hg; Pb; Sb; Zn
Other commodities Au
Gangue minerals quartz; tourmaline

Geographic location

Quadrangle map, 1:250,000-scale BH
Quadrangle map, 1:63,360-scale C-1
Latitude 60.72
Longitude -159.12
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at an elevation of about 1800 feet, approximately 2.3 miles west-northwest of hill 3127 ('Obvious'). The map site is on the northwest-trending ridge, in the SW1/4 of sec. 4, T. 7 N., R. 56 W., of the Seward Meridian. The site corresponds to locality 8 of Frost (1990, fig. 1). The location is probably accurate to within 1 or 2 miles.

Geologic setting

Geologic description

Quartz and tourmaline variably replace plagioclase porphyry at this occurrence (Frost, 1990, p. C4). Incipient alteration includes tourmaline replacement of plagioclase phenocrysts and quartz replacement of groundmass. More-extensively altered rocks are granular aggregates of fine-grained quartz and clumps of tourmaline. Some rocks are made up of alternating quartz-rich and tourmaline-rich layers. The altered rocks weather as bright red, vegetation-free areas. Rock samples contain up to 70 ppm Ag, 2,000 ppm As, greater than 2,000 ppm B, 500 ppm Cu, 7,000 ppm Pb, 7,000 ppm Sb, 1,000 ppm Zn, and 4.4 ppm Hg (Frost, 1990; Frost and others, 1992). Gold was detected at 0.10 ppm in one sample. The occurrence is at least 100 meters above the base of the Kipchuk volcanic field, a large area of Upper Cretaceous andesite, basalt, tuff, and local rhyolite in the uplands between the Kipchuk and Aniak River drainages (Box and others, 1993).
Geologic map unit (-159.122271621104, 60.7192748178615)
Mineral deposit model Polymetallic veins (Cox and Singer, 1986; model 22c).
Mineral deposit model number 22c
Age of mineralization Post-Late Cretaceous. Quartz and tourmaline replace volcanic rocks of the Kipchuk volcanic field that locally yield 69 to 71 Ma K/Ar ages (Box and others, 1993).
Alteration of deposit Quartz and tourmaline replacement, oxidation.

Production and reserves

Workings or exploration Reconnaissance surface observation and geochemical sampling has occurred at this site.
Indication of production None

References

MRDS Number 10307258
Reporters Travis L. Hudson
Last report date 3/24/2001