Big River

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Ag; Au; Mo; Pb; Zn
Ore minerals chalcopyrite; molybdenite; pyrite; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale AF
Quadrangle map, 1:63,360-scale C-6
Latitude 58.68
Longitude -153.87
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site is northeast of the Big River on an unnamed tributary in sec. 26, T. 17 S., R. 28 E. (Church and others, 1992, sheet 1, locality 11). The location is accurate to within 1/2 mile.

Geologic setting

Geologic description

At this site quartz-sulfide veins and disseminated sulfides occur in an altered Tertiary plug exposed in a creek drainage. Pyrite, chalcopyrite, sphalerite, and molybdenite are present in quartz veins up to 6 centimeters in width. Metal values run to greater than 20,000 ppm copper, and up to 2000 ppm zinc, 200 ppm lead, 200 ppm silver, 200 ppm cobalt, 100 ppm molybdenite, and 1.1 ppm gold (Church and others, 1994, table 15). Bedrock in this general area consists of sedimentary units of the Kaguyak Formation (Late Cretaceous) and sill-like and crosscutting Tertiary intrusive bodies of tonalite and granodiorite.
This site occurs within a broad zone of geochemical anomalies located southwest of Fourpeaked Mountain and northeast of the mouth of Big River. Within this zone many silt samples are anomalous in arsenic, cobalt, copper, lead, and zinc (Church and others, 1994). Panned concentrates contain arsenopyrite, barite, chalcopyrite, pyrite, scheelite, sphalerite, and wulfenite. The site is also within a smaller zone of silts which are anomalous in boron, molybdenum, and tungsten.
Geologic map unit (-153.872068567919, 58.6793252752865)
Mineral deposit model Polymetallic vein, concealed porphyry copper or porphyry copper-molybdenum (Cox and Singer, 1986; models 22c, 17, 21a).
Mineral deposit model number 22c, 17, 21a
Age of mineralization The mineralization is associated with a small Late Tertiary stock.
Alteration of deposit The intrusive rock at this site exhibits argillic and quartz-sericite alteration associated with abundant quartz veining.

Production and reserves

Workings or exploration Samples were collected and analyzed by the U.S. Geological Survey.
Indication of production None

Additional comments

Site is located in Katmai National Park.

References

MRDS Number A106171
Reporters S.H. Pilcher (Anchorage)
Last report date 8/11/1998