Misheguk Mountain--west

Occurrence, Inactive

Commodities and mineralogy

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

Geographic location

Quadrangle map, 1:250,000-scale MU
Quadrangle map, 1:63,360-scale A-4
Latitude 68.25
Longitude -161.06
Nearby scientific data Find additional scientific data near this location
Location and accuracy Location plotted is midway between localities 229 and 231 of Degenhart and others (1978, fig. 8); about 1 mi (1.6 km) northeast of Misheguk Mountain summit; located to within 1 mi (1.6 km).

Geologic setting

Geologic description

Chromite, along with a greenish mineral tentatively identified as garnierite, occurs in discontinuous bands less than an inch (25.4 mm) wide, small pods, and disseminations in part of a large serpentinized dunite-peridotite body. Misheguk Mountain is part of an ultramafic body approximately 32 miles long in a northeastern direction and about 13 miles wide. It is part of an ophiolite complex composed of a central core of the serpentinized ultramafic and gabbroic rocks flanked on three sides by mafic volcanic and intrusive rocks of Jurassic, Triassic, and(or) Permian age.
Geologic map unit (-161.062976462421, 68.2493904780539)
Mineral deposit model Lode; podiform chromite
Mineral deposit model number 8a
Age of mineralization Jurassic?

Production and reserves

Workings or exploration Assay values of 4.3% Cr and 0.22% Ni were obtained by the U.S. Bureau of Mines (Degenhart and others, 1978, p. 126, 232-40, 491) over a 50 ft. sample length. Also, chromite pods in dunite and pyroxenite contained up to 0.123 troy oz/st (4200 ppb) Pt, 0.137 troy oz/st (4700 ppb) Pd, 140 ppb Ir, 45 ppb Os, 360 ppb Rh, 98 ppb Ru, and 14 ppb Au. Plagioclase peridotite containing accessory pyrrhotite assayed up to 0.004 troy oz/st Pd and 0.005 troy oz/st Pt, and dunite contained 0.001 troy oz/st (42 ppb) Pt, 22 ppb Pd, 1 ppb Ir, and 6 ppb Rh. Sperrylite and argentite were identified by Scanning Electron Microscope analysis of a PGE-rich iron-rich chromian spinel sample.
Indication of production None
Reserve estimates Chromium reserve estimates include 117,000-349,000 st Cr2O3 in 9 low-grade banded zones in dunite with associated peridotite, pyroxenite, and gabbro; the largest of these zones contains between 78,000 and 261,000 st Cr2O3. At least 30 additional unmeasured chromite occurrences plus chromite and PGE placer potential are present (Degenhart and others, 1978, p. 232-240, 491).

Additional comments

Additional work is required to test the entire ultramafic body for significant occurrences of chromium, nickel, asbestos, and platinum.
See MAS/MILS Sequence number 0020190022 (USBM, 1995).

References