Unnamed (divide between Christy and Copeland creeks)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cr
Other commodities Ni; Pt
Ore minerals chromite; garnierite; pyrite
Gangue minerals serpentine

Geographic location

Quadrangle map, 1:250,000-scale HE
Quadrangle map, 1:63,360-scale A-6
Latitude 63.13
Longitude -149.75
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at an elevation of about 5,200 feet, about midway between the middle reaches of Christy and Copeland Creeks. the map site is about 1.3 mile north of VABM 5048 (Copeland), in the NE1/4 of sec. 1, T. 21 S., R. 12 W., of the Fairbanks Meridian. The location is accurate to within 0.5 mile. This is location 22 of Cobb (1978: OFR 78-1062), and location E-29 of Balen (1990: OFR 34-90).

Geologic setting

Geologic description

The country rocks in the area of this occurrence are a tectonically mixed assemblages of Upper Devonian serpentinite, basalt, chert, and gabbro. The occurrence consists of talus blocks of serpentinite(?) containing pods of massive chromite. The blocks occur in an area underlain by serpentinite altered to quartz-carbonate rock containing disseminated pyrite and stained with garnierite. Samples comprising 95% chromite contain 39.5% Cr2O3 and a chromium/iron ratio of 3.1:1, along with traces of platinum group metals (principally rhenium) and 1,000 ppm nickel (Hawley and others, 1969). The platinum values in eight samples were at the lower limit of detection (Balen, 1990: OFR 34-90).
Geologic map unit (-149.7522889101, 63.1295221403993)
Mineral deposit model Podiform chromite (Cox and Singer, 1986; model 8a)
Mineral deposit model number 8a
Age of mineralization Chromite probably was a magmatic segregation in Upper Devonian ultramafic intrusive rocks.
Alteration of deposit Serpentinization of ultramafic intrusive rocks. The serpentinite is altered to quartz-carbonate rock containing disseminated pyrite and stained with garnierite.

Production and reserves

Workings or exploration There has been surface sampling only. Samples comprising 95% chromite contain 39.5% Cr2O3 and a chromium/iron ratio of 3.1:1, along with traces of platinum group metals (principally rhenium) and 1,000 ppm nickel (Hawley and others, 1969). The platinum values in eight samples were at the lower limit of detection (Balen, 1990: OFR 34-90).
Indication of production None

References