Unnamed (near Weyahok River)

Occurrences, Inactive

Commodities and mineralogy

Main commodities Ag; Cu; Pb; Zn
Other commodities Sb
Ore minerals chalcopyrite; galena; pyrite; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale SP
Quadrangle map, 1:63,360-scale D-5
Latitude 67.86
Longitude -155.28
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site represents roughly circular area of about 30 square miles centered at about the midpoint of the Weyahok River, a headwater tributary to the Alatna River. The coordinates are for the approximate center of the area, which is mostly in sec. 4, T. 28 N., R. 16 E., of the Kateel River Meridian. Includes localities 1-4 of Grybeck and Nelson (1981) and is accurate to within 2000 ft.

Geologic setting

Geologic description

The site consists of a sprinkling of small occurrences of epigenetic quartz veins, lenses, and breccia zones less than 3 feet thick that contain various combinations of galena, sphalerite, chalcopyrite, and pyrite. The occurrences are in an area of about 30 square miles in an otherwise monotonous sequence of feldspathic sandstone of the Hunt Fork Shale (Nelson and Grybeck, 1980; Grybeck and Nelson, 1981). Assays of the sulfide-bearing samples show up to 100 ppm Ag and 200 ppm Sb. Fieldwork (S.W. Nelson and D. Grybeck, unpublished data, 1977-1980), and geochemical sampling (Cathrall and others, 1981) suggest that many additional such deposits may occur in this area. All the occurrences found to date are small and discontinuous and there is no obvious sign of any large deposit within the area.
There are two theories about the origin of the deposits: (1) Grybeck and others, 1985) cite geochemical evidence that they may be related to a buried felsic intrusion; (2) Schmidt and Werdon (1993) and Schmidt (1997) believe that they are related to post-depositional dewatering of the sedimentary rock section and are similar in origin to other sedimentary-rock hosted mineral occurrences in the Brooks Range.
Geologic map unit (-155.282826760497, 67.8595038466441)
Mineral deposit model Polymetallic vein (Cox and Singer, 1986; model 22c). (See also Schmidt and Werdon, 1993, p. 143.).
Mineral deposit model number 22c

Production and reserves

Workings or exploration The site is defined by a few short traverses and spot stations by USGS in late 1970s, and since closed to exploration.
Indication of production None

Additional comments

The area is within the Gates of the Arctic National Park and Wilderness and has been closed to prospecting since 1981.


MRDS Number AO11931; AO11932


Reporters S.W. Nelson (Anchorage, Alaska)
Last report date 9/16/1999