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Minor podiform chromite deposit, 7 of 13 in San Luis Obispo county (in California)
Sections of this page: [Geologic] - [Economic] - [Reference]
| Other names | Safety |
|---|---|
| Country | United States |
| State or province | California |
| Geographic location: | 35°21'35"N,
120°40'14"W (-120.670556, 35.359722) |
| Geographic context: | (click for info) |
| Deposit type | minor podiform chromite |
| Model type | Banded Podiform |
| Deposit form | irregular zone |
| Deposit texture | massive, disseminated |
| Ore type | Metallurgical |
| Age of deposit | Middle Jurassic (163.3±1.1 Ma, U-Pb apatite-feldspar isochron in gabbro) |
| Age (m.y.) | 163million years |
| Mineralogy | chromite |
| Host rock type | serpentinized dunite |
| Host rock length | 20000 |
| Host rock width | 4250 |
| Paleotectonic setting | suprasubduction |
| Ophiolite zone | transition |
| Deposits < 10km | podiform chromite |
| Rocks within 5km | serpentine dunite wehrlite harzburgite sandstone conglomerate shale schist basalt diabase |
| Geologic map unit | -120.670555555556, 35.3597222222222 |
| Nearby scientific data | Find additional scientific data near this location |
| Discovery date | 1870 | |
|---|---|---|
| Startup date | 1870 | |
| Tonnage | 0.003 | million metric tons |
| Ore depth | 0 | m |
| Cr2O3 grade | 53 | percent |
| Cr % | 37.93 | percent |
| Fe % | 12.02 | percent |
| Cr:Fe ratio | 3.16 | |
| Al2O3 % | 12.61 | percent |
| Si2O2 % | 0.9 | percent |
| Comments | Production from 1870 to 1917 unknown, but reported to be large. Production from 1918 to 1944 was 2,100 t ore (Walker and Griggs, 1953). Chromite ore analyses range from 47-88% chromite, 53.87-54.85% Cr2O3. Estimated total tonnage of 3,000 t. Analysis 55.42% Cr2O3, 12.61% Al2O3, 8.10% Fe2O3, 8.19% FeO, 13.70% MgO, 0.16% MnO, 0.16% CaO, 0.13% TiO2, 0.90% SiO2, 37.93% Cr, 12.02% Fe, 3.16 Cr/Fe, 48.1% Cr2O3 in ore, 87% chromite in ore (Stevens, 1944). San Luis Obispo County. |
|---|---|
| References | 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. 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. Jennings, C.W., 1958, Geologic map of California, San Luis Obispo sheet: California Division of Mines and Geology, scale 1:250,000. 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. Stevens, R.E., 1944, Composition of some chromites of the Western Hemisphere: The American Mineralogist, v. 29, nos. 1 and 2, 34 p. |