Unnamed (lower Broxson Gulch)

Occurrence, Undetermined

Commodities and mineralogy

Main commodities Au; Cu; Ni
Ore minerals chalcopyrite; gold; malachite; pentlandite; pyrite; pyrrhotite

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale B-5
Latitude 63.3018
Longitude -146.0826
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at an elevation of about 4,150 feet, about 2.1 mile northeast of the junction of the two forks of Broxton Gulch that diverge just about its mouth. The occurrence is about 0.6 mile northeast of the center of section 6, T. 19 S., R. 9 E.

Geologic setting

Geologic description

Rose (1965) first described this occurrences in altered limestone with copper staining and serpentine. Nokleberg and others (1992 [OF]; 1992 {MF]) assigns the ultramafic rocks to the Triassic. Bittenbender and others (2007) describes the deposit as being in bleached white limestone with epidote and garnet. Sporadic small pods and lenses, generally about a foot in size, of semi-massive sulfides occur for about 500 feet along the contact of limestone and oxidized ultramafic rocks. The sulfides are mostly pyrrhotite, chalcopyrite, and pyrite, with some pentlandite. One sample contained 1.97 percent copper but most contained less than 0.5 percent. The highest gold value was 27 parts per billion; the highest nickel value was 2,180 parts per million but most samples contained much less. Bittenbender and others (2007) classify the deposit as a skarn.
Geologic map unit (-146.084861768658, 63.3013794441389)
Mineral deposit model Copper-nickel skarn.
Age of mineralization Triassic or younger based on the age of the host rock.
Alteration of deposit Mineralized skarn developed at limestone-serpentine contact.

Production and reserves

Workings or exploration Only brief examination and sampling by state and federal geologists.
Indication of production None
Reserve estimates None.
Production notes None.

References

References

Reporters W.T. Ellis (Alaska Earth Sciences), C.C. Hawley (Hawley Resource Group), and W.J. Nokleberg (USGS); D.J. Grybeck (Contractor, USGS)
Last report date 5/13/2012