Unnamed (south of Arrigetch Creek)

Occurrences, Inactive

Commodities and mineralogy

Main commodities Ag; Cu; Pb; Sn; Zn
Other commodities As; Bi; F; W
Ore minerals chacopyrite; sphalerite
Gangue minerals calc-silicate minerals; magnetite

Geographic location

Quadrangle map, 1:250,000-scale SP
Quadrangle map, 1:63,360-scale B-3
Latitude 67.4303
Longitude -154.0242
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site includes several occurrences that extend east for several miles along the east-trending contact of a granite. The area is about 5.8 miles southwest of the mouth of Arrigetch Creek. The coordinates are for the approximate center of the area in sec. 5, T. 23 N., R. 22 E. The location is accurate. The site corresponds to localities 33 through 35 of Grybeck and Nelson (1981).

Geologic setting

Geologic description

This site consists of three contact-metamorphic, skarn deposits adjacent to Devonian granite (Grybeck and Nelson, 1981). At one locality several skarn bodies up to 700 m long and 70 m thick at a granite-carbonate contact contain lenses and pods of magnetite, and minor disseminated chalcopyrite, sphalerite and unspecified tungsten minerals. At another locality, heterogeneous contact-metamorphic rocks include fluorite-magnetite rock, quartz-epidote skarn, epidote-garnet skarn and sphalerite-epidote skarn. Selected samples contained up to 150 parts per million (ppm) silver, 1000 ppm bismuth, and more than 1 percent each of tin, lead, and zinc. A brief reconnaissance of a granite-phyllite contact revealed several tactite pods less than 5 meters wide. The most prominent consists of magnetite with copper staining. Grab samples contained up to 1000 ppm each of arsenic, copper, tin, and zinc. These occurrences probably are similar in origin to other Devonian contact-metamorphic deposits in nearby areas of the Brooks Range (Newberry and others, 1986).
Kurtak and others (2002) collected several samples of mineralized skarn and thin quartz veins for about a mile along the north side of the Devonian granite. Their samples contained up to 3,042 ppm copper, 269 ppm cobalt, and 1,080 ppm tin.
Geologic map unit (-154.027007586753, 67.4298086195236)
Mineral deposit model Skarn (Cox and Singer, 1986; model 14b).
Mineral deposit model number 14b
Age of mineralization Devonian; related to the intrusion of Devonian pluton.
Alteration of deposit Calc-silicate minerals in skarn and related contact metamorphic rocks adjacent to Devonian granite.

Production and reserves

Workings or exploration The sites were briefly visited and sampled during regional geologic mapping by the USGS in the late 1970s and again visited and sampled by the Bureau of Land Management in about 2000.
Indication of production None
Reserve estimates None.
Production notes None.

Additional comments

Located in the heart of a notable scenic part of the Gates of the Arctic National Park.

References

MRDS Number A011922

References

Kurtak, J.M., Klieforth, R.F., Clark, J.M., and Maclean, E.A., 2002, Mineral investigations in the Koyukuk mining district, northern Alaska: Final Report: U.S. Bureau of Land Management Technical Report 50, 2 vols., 845 p.
Newberry, R.J., Dillon, J.T., and Adams, D.D., 1986, Regionally metamorphosed calc-silicate-hosted deposits of the Brooks Range, northern Alaska: Economic Geology, v. 81, p. 1728-1752.
Reporters S.W. Nelson (Anchorage, Alaska); D.J. Grybeck (Contractor, USGS)
Last report date 2/1/2011