Unnamed (on headwater tributary to Porcupine Creek)

Occurrence, Probably inactive

Commodities and mineralogy

Main commodities Ag; Au
Other commodities Cu
Ore minerals pyrite

Geographic location

Quadrangle map, 1:250,000-scale SK
Quadrangle map, 1:63,360-scale B-4
Latitude 59.33
Longitude -136.28
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at an elevation of approximately 3,500 feet on the east side of an unnamed headwater tributary to Porcupine Creek near the divide to Cottonwood Creek. It is in the the SW1/4, section 23, T. 29 S., R. 54 E. of the Copper River Meridian. It is shown as location 146 by Still and others (1987) and as site R by Gilbert and Redman (1989) who informally referred to it as the 'Porcupine Roof Pendant'.

Geologic setting

Geologic description

According to Still and others (1991), this occurrence is a mineralized, 400 foot by 1,000 foot, roof pendant surrounded by diorite. The pendant consists of metamorphosed slate and limestone that form bands of garnet and diopside at some locations. Samples from the pendant contained up to 0.068 ppm gold, 1.1 ppm silver, 192 ppm zinc, and 230 ppm copper (Gilbert and others, 1991), and a sample of gossan rubble with 20% pyrite collected 500 feet below the pendant contained 6.33 ppm gold, 18.2 ppm silver, and 515 ppm copper (Still and others, 1991). The metamorphosed slate and limestone are of probable Paleozoic age (MacKevett and others, 1974). The bands of garnet and diopside and the mineralization are probably due to to contact metasomatism by the surrounding Cretaceous diorite (MacKevett and others, 1974).
Geologic map unit (-136.281866214515, 59.3296576383794)
Mineral deposit model Based on limited information, this is probably a skarn related occurrence (Cox and Singer, 1986; model 18b? or 18c?).
Mineral deposit model number 18b? or 18c?
Age of mineralization Probably Cretaceous or younger based on the age of the surrounding diorite (MacKevett and others, 1974).
Alteration of deposit Development of calc-silicate minerals.

Production and reserves

Indication of production None

References

MRDS Number 10308252

References

Reporters T.C. Crafford (T. Crafford & Associates, Anchorage)
Last report date 2/4/2001