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Minor podiform chromite deposit, 6 of 13 in San Luis Obispo county (in California)

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

Geologic Information
Other namesLa Trinidad
CountryUnited States
State or provinceCalifornia
Geographic location:35°21'47"N, 120°41'12"W
(-120.686667, 35.363056)
Geographic context: (click for info)
Deposit typeminor podiform chromite
Model typeBanded Podiform
Deposit formirregular pods, stringers
Deposit texturemassive, disseminated
Ore typeMetallurgical
Age of depositMiddle Jurassic (163.3±1.1 Ma, U-Pb apatite-feldspar isochron in gabbro)
Age (m.y.)163million years
Area of deposit2295sq m
Ore body length85m
Ore body width27m
Host rock typeserpentinized dunite
Host rock length20000
Host rock width4250
Paleotectonic settingsuprasubduction
Ophiolite zonetransition
Deposits < 10kmpodiform chromite
Rocks within 5kmserpentine
Geologic map unit-120.686666666667, 35.3630555555556
Nearby scientific dataFind additional scientific data near this location
Economic Information
Discovery date1918
Startup date1918
Tonnage0.005087million metric tons
Ore depth0m
Cr2O3 grade46percent
Rh grade0.005g/t
Ir grade0.042g/t
Ru grade0.09g/t
Pd grade0.0005g/t
Pt grade0.005g/t
Fe %14.39percent
Cr:Fe ratio2.18
Reference information
CommentsProduction 5,087 t ore. No reported grade, but analysis of crude ore was 18% chromite, 45.78% Cr2O3. Analysis 0.034-0.05 ppm Ir, <0.1-0.18 ppm Ru, 0.004-0.006 ppm Rh, <0.001-0.001 ppm Pd, <0.01-0.01 ppm Pt. San Luis Obispo County.
Choi, S.H., Shervais, J.W., and Mukasa, S.B., 2008, Supra-subduction and abyssal mantle peridotites of the Coast Range ophiolite, California: Contributions to Mineralogy and Petrology, v. 156, p. 551-576.
Jennings, C.W., 1958, Geologic map of California, San Luis Obispo sheet: California Division of Mines and Geology, scale 1:250,000.
Walker, G.W., and Griggs, A.B., 1953, Chromite deposits of the southern Coast Ranges of California, in Geological investigations of chromite in California, Part 2--Coast Ranges: California Division of Mines Bulletin 134, pt. 2, ch. 2, 88 p.
Carlson, C.A., Wilson, S.A., Carlson, R.R., Bradley, L., Cornell, J., Gent, C., Gass, W., Groeneboer, H., Haffty, J., Haubert, A., Love, A., McDade, J.M., Moore, R., Riley, L., Moring, B.C., Singer, D.A., and Page, N. J, 1985, Analyses for platinum group elements in samples from podiform chromite deposits, California and Oregon: U.S. Geological Survey Open-File Report 85-442, 15 p.
Hopson, C.A., Mattinson, J.M., Pessagno, E.A., Jr., and Luyendyk, B.P., 2008, California Coast Range ophiolite--Composite Middle and Late Jurassic oceanic lithosphere: Geological Society of America Special Paper 438, p. 1-101.
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