Unnamed (west side of Broxson Gulch)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Asbestos
Other commodities Cu; Pb; Zn
Ore minerals chrysotile
Gangue minerals serpentine

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale B-5
Latitude 63.3155
Longitude -146.1672
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at an elevation of 3,500 feet at the mouth of an east-flowing tributary to the stream(s) in Broxson Gulch, approximately in the center of the NW1/4 section 35, T. 18 S., R. 8 E., Fairbanks Meridian. The occurrence corresponds to locality 17 of MacKevett and Holloway (1977), locality 33 in figure 4 of Cobb (1979 [OFR 79-238]), and locality 3 on figure 3 of Rose (1966 [ADMM GR 20]).

Geologic setting

Geologic description

This record describes two mineral localities: asbestos in dunite, and base metals in slate near the dunite.
The asbestos deposit is in an Upper Triassic serpentinized dunite sill that can be followed for more than 5 miles (Rose, 1966 [ADMM GR 20, figure 3]). The dunite is part of the informally named Eureka ultramafic complex that occupies strands of the Broxson Gulch thrust fault (Nokleberg and others, 1991; W.T. Ellis, unpublished data, 1996). The deposit consists of chrysotile asbestos in the dunite. Rose (1966 [ADMM GR 20, p. 20]) reported 0.25-inch veinlets of chrysotile in bedrock at the site and found prospectors' samples of larger veins nearby.
Paleozoic slate near the dunite is marked by gossan that carries anomalous amounts of copper, lead, and zinc (MacKevett and Holloway, 1977, p. 37, locality 17).
Geologic map unit (-146.169464018488, 63.315078486535)
Mineral deposit model Serpentinite-hosted asbestos (Cox and Singer,1986; model 8d). The base metal-bearing gossan in slate may be a sedimentary-exhalative deposit.
Mineral deposit model number 8d
Age of mineralization The dunite host of chrysotile is of Late Triassic age; the chrysotile may have formed during Cretaceous faulting and regional metamorphism (Nokleberg and others, 1991). The base metal-bearing gossan in slate is Paleozoic or younger.

Production and reserves

Workings or exploration The occurrence is on active MAN Resources claims.
Indication of production None