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Holbrook and McGuire Group 1

Minor podiform chromite deposit, 5 of 20 in Calaveras county (in California)

Sections of this page: [Geologic] - [Economic] - [Reference]

Geologic Information
CountryUnited States
State or provinceCalifornia
Geographic location:37°57'15"N, 120°33'33"W
(-120.559167, 37.954167)
Geographic context: (click for info)
Deposit typeminor podiform chromite
Model typeMinor Podiform
Deposit formlenses, clots, streaks
Deposit texturenearly massive
Ore typeUnknown
Age of depositPermian (280±3 m.y. 206Pb/238U, 282±3 m.y. 207Pb/235U)
Age (m.y.)281million years
Area of deposit122sq m
Ore body length61m
Ore body width2m
Host rock typeserpentine
Host rock length30000
Host rock width6000
Ophiolite zonetectonite
Deposits < 10kmpodiform chromite
Rocks within 5kmserpentine
pillow basalt
basalt pyroclastics
quartz diorite
Geologic map unit-120.559166666667, 37.9541666666667
Nearby scientific dataFind additional scientific data near this location
Economic Information
Tonnage0.0024million metric tons
Mine depth6.1m
Ore depth0m
Cr2O3 grade20percent
Reference information
CommentsProduction of several hundred t of low-grade ore (about 20% Cr2O3). Maximum size of orebody indicates 2,400 t of ore. Tuolumne ophiolitic melange. Calaveras County.
Rogers, T.H., 1966, Geologic map of California, San Jose sheet: California Division of Mines and Geology, scale 1:250,000.
Cater, F.W., Jr., 1948, Chromite deposits of Calaveras and Amador counties, California, in Geological investigations of chromite in California, Part 3--Sierra Nevada: California Division of Mines Bulletin 134, pt. 3, ch. 2, 60 p.
Saleeby, J.B., 1982, Polygenetic ophiolite belt of the California Sierra Nevada--Geochronological and tectonostratigraphic development: Journal of Geophysical Research, v. 87, no. B3, p. 1803-1824.
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