|Quadrangle map, 1:250,000-scale||KC|
|Quadrangle map, 1:63,360-scale||A-5|
|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 descriptionThe 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.|
|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|
Berg, H.C., 1972, Geologic map of Annette Island, Alaska: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-684, 8 p., 1 sheet, scale 1:63,360.
|Reporters||H.C. Berg, USGS|
|Last report date||7/6/1999|