Unnamed (on Cape Kumlik)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Ag; Au; Mo
Ore minerals chalcopyrite; molybdenite; pyrite
Gangue minerals quartz; barite

Geographic location

Quadrangle map, 1:250,000-scale SW
Quadrangle map, 1:63,360-scale C-5
Latitude 56.63
Longitude -157.48
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is located on the east coast of the mainland between Kujulik and Aniakchak Bays. The map site is about 1 mile inland from the easternmost tip of Cape Kumlik (MacKevett and Holloway, 1977, localities 3 and 7; Cox and others, 1981, locality 1). The site location is accurate to within 1/2 mile.

Geologic setting

Geologic description

At this site a quartz diorite stock has intruded volcanic rocks of the Oligocene and Eocene Meshik Formation (Detterman and others, 1981). The occurrence is marked by a large color anomaly covering about 1 section. Chalcopyrite and pyrite occur in quartz(?) veinlets and as disseminations in both the intrusive and in the surrounding volcanic rocks (Hedderly-Smith, 1977). Barite has been noted in many stream-sediment samples.
Numerous rock-chip samples collected by Bear Creek Mining Company returned copper values in the 400 ppm to 1000 ppm range and several contained 1000 ppm to 2000 ppm copper (Hedderly-Smith, 1977). The highest value was 5600 ppm copper from a sample of the mineralized intrusive. Molybdenum and silver were indicated as low-order anomalies. Gold was detected in the 0.07ppm 0.31 ppm range. The higher gold values generally coincided with the higher copper values. Of 7 rock samples collected here in 1978 by the U.S. Geological Survey, only 1 contained strongly anomalous values in copper (2200 ppm) (Yount and others, 1978). Cox and others (1981) estimate a small tonnage of low grade mineralization.
The rocks at the center of the mineralized area exhibit potassic alteration (Hedderly-Smith, 1977). Quartz-sericite alteration and silicification occur to the east, south, and west of the central area in both intrusive and volcanic rocks. An outer zone of propylitization is present.
Geologic map unit (-157.482046048963, 56.6292440990955)
Mineral deposit model Porphyry copper (Cox and Singer, 1986, model 17)
Mineral deposit model number 17
Age of mineralization Tertiary.
Alteration of deposit The rocks exhibit a zoned alteration pattern, with a central potassic core grading outward to quartz-sericite and silicification, and to peripheral propylitization.

Production and reserves

Workings or exploration Resource Associates of Alaska did a stream-sediment geochemical survey in 1975 (Hedderly-Smith, 1977). Bear Creek Mining Company geochemically sampled and mapped the occurrence in 1977 (Hedderly-Smith, 1977). Most samples returned copper values in the 400 to 1000 ppm range. One sample of mineralized intrusive contained 5600 ppm copper. Low order molybdenum and silver anomalies were also detected. The U.S. Geological Survey (Yount and others, 1978) took 7 samples in 1978. The highest copper value obtained was 2200 ppm.
Indication of production None
Reserve estimates This occurrence is estimated to have a small tonnage of low grade (Cox and others, 1981).

Additional comments

This site is located on land selected by the Koniag Native Corporation.

References