Picric Hill

Occurrence, Undetermined

Commodities and mineralogy

Main commodities Au; Cu
Ore minerals chalcopyrite; magnetite; pyrite

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale B-4
Latitude 63.3179
Longitude -145.8634
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Picric Hill occurrence is at an elevation of about 5,250 feet on a ridge between headwater tributaries of Ann Creek. It is about 2.1 miles north-northeast of the junction of the North and West Forks of Rainy Creek and about 0.6 mile north-northeast of the center of section 32, T. 18 S., R. 10 E.

Geologic setting

Geologic description

This occurrence was first identified and sampled by Bittenbender and others (2007) in 2002. As of 2007 there is no indication of industry work on it.
The rocks in the area are mainly olivine-rich basalt (picrite) of probable Triassic age (Rose, 1965; Nokleberg and others, 1992 [MF]; 1992 [Open-File]; Bittenbender and others, 2007). The occurrence is in a band of interfingering skarn and sulfides that is exposed for 44 feet along strike and is 5-11 feet thick. The wall rock of the band is altered felsic intrusive rock. The band is highly fractured and locally brecciated. The skarn consists mainly of fine- to medium-grained massive garnet with minor epidote and actinolite. The sulfides are mainly pyrite with about a third chalcopyrite and some magnetite. The sulfides generally occur in the interstices of euhedral garnet . Bittenbender and Gensler (2003) collected three, 5 to 6 foot samples across the skarn. The highest gold value was only 37 parts per billion and the highest copper value was 1,205 parts per million (ppm). A select sample of float contained 2,750 ppm copper.
Geologic map unit (-145.865656936516, 63.3174841046899)
Mineral deposit model Band of copper skarn associated with a basalt.
Age of mineralization Source of skarn mineralization is probably the Triassic basalt (picrite) in the area.
Alteration of deposit Mineralization in an altered band of felsic intrusive rocks.

Production and reserves

Workings or exploration This occurrence was first identified and sampled by Bittenbender and others (2007) in 2002. As of then, there was no indication of industry work on it.
Indication of production None
Reserve estimates None.
Production notes None.

References

References

Bittenbender, P.E., and Gensler, E.G., 2003, Mineral investigations in the Delta River Mining District, east-central Alaska, 2001-2002: U. S. Bureau of Land Management- Alaska, Open-File Report 91, 82 p.
Bittenbender, P.E., Bean, K.W., Kurtak, J.M., and Deininger, James Jr., 2007, Mineral assessment of the Delta River Mining District area, east-central, Alaska: U.S. Bureau of Land Management, Alaska Technical Report 57, 675 p.
Reporters D.J. Grybeck (Contractor, USGS)
Last report date 5/13/2012