Unnamed (near Caribou Mountain)

Occurrences, Inactive

Commodities and mineralogy

Main commodities Cr
Other commodities Co; Ni; PGE
Ore minerals chromite

Geographic location

Quadrangle map, 1:250,000-scale BT
Quadrangle map, 1:63,360-scale B-2
Latitude 66.4126
Longitude -150.6308
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site includes several similar occurrences along the ridge which extends northeast from the summit of Caribou Mountain. The coordinates are of one occurrence approximately at the center of these occurrences; it is near hill 2355 at an elevation of about 2,300 feet, about 0.25 mile south-southwest of the center of section 6, T. 15 N., R. 14 W., of the Fairbanks Meridian. The other occurrences extend to about 0.8 mile northeast and 1.5 miles southwest. The location is accurate.

Geologic setting

Geologic description

This site consists of ten chromite occurrences in Jurassic or older, dunite and pyroxene-peridotite of the Caribou Mountain ultramafic complex (Foley and McDermott, 1983). The chromite occurs as massive chromitite in alternating layers of dunite and pyroxene-peridotite; as wispy concentrations of disseminated chromite in dunite; and as disseminated and massive chromite in dunite. The chromite deposits are small and discontinuous (Foley and McDermott, 1983). Samples of the occurrences contain up to 20 percent chromium but the mean is less than 2 percent. Chromium analyses vary erratically as is typical of podiform chromite deposits (Foley and McDermott, 1983). Samples also contain cobalt, copper and nickel values typical of ultramafic rocks, consistent with the apparent absence of sulfide minerals (Foley and McDermott, 1983). The platinum group elements are generally low, although one high-grade chromite sample contains 377 ppb Pd and 1,337 ppb Pt (Foley, 1992).
The ultramafic, mafic volcanic and intrusive rocks, and associated chert in this area are thought to represent a dismembered ophiolite assemblage (Foley and McDermott, 1983). The mafic-ultramafic components are mainly interlayered dunite and pyroxene-peridotite, with subordinate gabbro, pyroxenite, serpentinite, and chromitite. Individual layers may range from tens to thousands of feet thick. The richest chromite deposits are in the dunite. Although chromite is ubiquitous in the dunite and pyroxene-peridotite, it seldom exceeds 1 or 2 percent of the rock.
Geologic map unit (-150.633439252681, 66.4121413093711)
Mineral deposit model Podiform chromite (Cox and Singer, 1986; model 8a).
Mineral deposit model number 8a
Age of mineralization The chromite is a normal primary constituent of the ultramafic rocks which are Jurassic or older.
Alteration of deposit Some serpentinization of the ultramafics.

Production and reserves

Workings or exploration Only surface sampling and mapping.
Indication of production None
Reserve estimates Foley (1992) estimates that there are 1,800 to 2,200 million tons of chromic oxide in three deposits. Seven other unmeasured or minor chromite occurrences were noted.

Additional comments

See also Upper Kanuti (BT012) and Lower Kanuti (BT014).