Unnamed (east side of upper Specimen Creek)

Prospect, Active

Commodities and mineralogy

Main commodities Ag; Au; Cu
Ore minerals chalcopyrite; pyrite
Gangue minerals actinolite; epidote; magnetite

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale B-5
Latitude 63.3199
Longitude -146.0284
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is at an elevation of about 5,050 feet on the south flank of a ridge at the head of an unnamed east fork of Specimen Creek. The prospect is about 2,000 feet south of the center of section 28, T. 18 S., R. 9 E., Fairbanks Meridian. The location corresponds to locality 15 on figure 2 of Rose (1965), locality 21 of MacKevett and Holloway (1977), locality 41 of Cobb (1979 [OFR 79-238]), and locality 57 in table 2 of Nokleberg and others (1991).

Geologic setting

Geologic description

The rock at this prospect has been described either as amphibole 'serpentinite' by Rose (1965) or as metabasalt of the Nikolai Greenstone of Late Triassic age by Nokleberg and others (1991, locality 57). A thin section examined by Rose was composed mainly of olivine and amphibole with minor amounts of epidote, pyrite, and chalcopyrite. He also identified actinolite and glaucophane.
The deposit consists of a copper-bearing shear zone that trends about N35 E. Rose (1965) noted that irregular pods of dark- and light-colored rock were present along this zone and that quartz was present in the lighter colored rock. W.T. Ellis (unpublished data, 1996) interpreted the mineralized zone to be magnetite-bearing skarn associated with the contact of the lighter colored felsic intrusive rock . A 4-foot sample collected by Rose (1965) assayed 0.09 ounce of gold per ton, 1.18 ounces of silver per ton, 0.75 percent copper, and a trace of nickel. Nokleberg and others (1991, table 2) collected samples that assayed as much as 0.75 percent copper 1.05 ounces of silver per ton, and 0.8 ounce of gold per ton.
Geologic map unit (-146.030662684481, 63.3194809667023)
Mineral deposit model Copper skarn? (Cox and Singer, 1986; model 18b?).
Mineral deposit model number 18b?
Age of mineralization Epigenetic mineralization in a shear zone in the Upper Triassic host rock is possibly Cretaceous, the age of faulting and regional metamorphism. If the mineralization is skarn related to the felsic intrusion, it could be of Late Cretaceous to Early Tertiary age.
Alteration of deposit Silicification, along with magnetite-amphiobole alteration of the host rock.

Production and reserves

Workings or exploration The deposit was discovered by Rose (1965 ). The area is on active claims of MAN Resources.
Indication of production None