Unnamed (ridge between the middle and east forks in Broxson Gulch)

Prospects, Active

Commodities and mineralogy

Main commodities Ag; Au; Co; Cu; Ni
Other commodities Pd; Pt
Ore minerals chalcopyrite; magnetite; marcasite; pentlandite; pyrite; pyrrhotite
Gangue minerals serpentine

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale B-5
Latitude 63.3485
Longitude -146.0481
Nearby scientific data Find additional scientific data near this location
Location and accuracy This location represents several prospects at about 4,800 feet in elevation on the east side of the ridge between the locally named middle and east forks of the stream(s) in Broxson Gulch (Rose, 1965, figure 2). It is at the southeast corner of section 17, T. 18 S., R. 9 E., Fairbanks Meridian. The site corresponds to locality 18 on figure 2 of Rose (1965), locality 19 of MacKevett and Holloway (1977), and locality 50 in table 2 of Nokleberg and others (1991).

Geologic setting

Geologic description

This deposit consists of sulfide lenses along the contact between peridotite and sheared serpentinized olivine cumulate, layered units of an Upper Triassic ultramafic intrusive complex (Rose, 1965, figure 2; Nokleberg and others, 1991). The deposit was discovered by Rose (1965), who described six lenses of massive sulfide in an area having a radius of 100 feet. The largest lens was 3 feet thick by 6 feet long. The massive sulfides are mainly marcasite, but chalcopyrite, pyrrhotite, pentlandite, and probably magnetite are also present. The marcasite is probably a retrograde product of pyrrhotite.
The occurrence was also sampled by Nokleberg and others (1991). Their samples 79IL030A-D of massive pyrrhotite containing disseminated chalcopyrite and pyrite assayed as much as 2 percent copper, 1,000 parts per million (ppm) cobalt, and 2,000 ppm nickel (locality 50, table 2). Foley (1992) collected massive sulfide samples assaying as much as 13 ppm silver, 416 parts per billion (ppb) gold, 137 ppb palladium, 2.4 percent copper, 0.66 percent nickel, and 0.08 percent cobalt.
Geologic map unit (-146.050365509892, 63.3480815866485)
Mineral deposit model Ni-Cu-PGE in differentiated mafic-ultramafic sill.
Age of mineralization Late Triassic, the age of the host rock.
Alteration of deposit Some of the peridotite and olivine cumulate is serpentinized, mainly near their contacts, but it mostly is relatively unaltered (Rose, 1965).

Production and reserves

Workings or exploration
The massive sulfide lenses in the Broxson Gulch area assay as much as 13 parts per million silver, 416 parts per billion (ppb) gold, 137 ppb palladium, 137 ppb platinum, 2.4 percent copper, 0.66 percent nickel, and 0.08 percent copper (Foley, 1992).
The occurrence is on active MAN Resources claims.
Indication of production None

References