Yellow Hill

Occurrences, Undetermined

Commodities and mineralogy

Main commodities Cr
Other commodities Platinum-group metals; chrysotile asbestos
Ore minerals chromite; chrysotile; magnetite

Geographic location

Quadrangle map, 1:250,000-scale KC
Quadrangle map, 1:63,360-scale A-5
Latitude 55.106
Longitude -131.574
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site consists of two occurrences near Yellow Hill, in sections 16 and 17, T. 78 S., R. 92 E., of the Copper River Meridian. One is at an elevation of about 300 feet, about 0.3 mile north-northeast of the top of Yellow Hill; the other is at an elevation of about 200 feet, about 0.45 mile northwest of the top of the hill. The coordinates are for the approximate midpoint between the occurrences. The site corresponds to loc. 22 in Berg (1972 [I 684]), loc. 149 in Elliott and others (1978), and loc. 49a, b in Karl (1992). The location is accurate within about 0.1 mile.

Geologic setting

Geologic description

The country rocks in the area of this site are hornblende gabbro and partly serpentinized dunite, probably of Cretaceous age (Berg, 1972). The occurrences consist of sparse, thin veinlets, and disseminated grains, of magnetite and chromite in massive dunite that also contains abundant thin seams of chrysotile (Berg, 1972, loc. 22; Karl, 1992, loc. 49a, b). Samples of the dunite contained up to 150 ppm Co, 2000 ppm Cr, and 150 ppm Ni; and one sample yielded a value of 0.029 Pt (Berg, 1972; Karl, 1992). Most samples of dunite from the Yellow Hill area, however, showed no Pt content above the lowest limit of detection. A sample of gabbro contained 0.015 ppm Pt (Karl, 1992, loc. 49b).
Geologic map unit (-131.575677880625, 55.1056573334039)
Mineral deposit model Alaskan PGE (Cox and Singer, 1986; model 9).
Mineral deposit model number 9
Age of mineralization Oxide minerals probably are magmatic segregations of Cretaceous age.
Alteration of deposit Serpentinization of dunite.

Production and reserves

Workings or exploration Samples of the dunite contained up to 150 ppm Co, 2000 ppm Cr, and 150 ppm Ni; and one sample yielded a value of 0.029 Pt (Berg, 1972; Karl, 1992). Most samples of dunite from the Yellow Hill area, however, showed no Pt content above the lowest limit of detection. A sample of gabbro contained 0.015 ppm Pt (Karl, 1992, loc. 49b).
Indication of production None

References