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Minor podiform chromite deposit, 22 of 30 in Placer county (in California)
Sections of this page: [Geologic] - [Economic] - [Reference]
| Other names | Blue Bird |
|---|---|
| Country | United States |
| State or province | California |
| Geographic location: | 39°2'20"N,
120°45'36"W (-120.76, 39.038889) |
| Geographic context: | (click for info) |
| Deposit type | minor podiform chromite |
| Model type | Minor Podiform |
| Deposit form | lenses, pods, stringers |
| Deposit texture | coarse-grained massive, disseminated |
| Ore type | Unknown |
| Age of deposit | pre-Early Devonian-Jurassic (388±17 Ma U-Pb zircon from felsic igneous rocks; 174 Ma K-Ar white mica from blueschists) |
| Age (m.y.) | 388million years |
| Area of deposit | 74.42sq m |
| Ore body length | 122m |
| Ore body width | 0.61m |
| Mineralogy | chromite uvarovite |
| Host rock type | dunite |
| Host rock length | 134000 |
| Host rock width | 7000 |
| Paleotectonic setting | suprasubduction |
| Ophiolite zone | tectonite |
| Deposits < 10km | podiform chromite |
| Rocks within 5km | dunite serpentine harzburgite or lherzolite diabase dikes albitite gabbro slate graywacke conglomerate mudstone quartzite chert mudflow breccia rhyolite tuff sandstone alluvium |
| Geologic map unit | -120.76, 39.0388888888889 |
| Nearby scientific data | Find additional scientific data near this location |
| Discovery date | 1880s | |
|---|---|---|
| Startup date | 1880s | |
| Tonnage | 0.000411 | million metric tons |
| Mine depth | 26 | m |
| Ore depth | 0 | m |
| Cr2O3 grade | 35 | percent |
| Rh grade | 0.004 | g/t |
| Ir grade | 0.04 | g/t |
| Ru grade | 0.15 | g/t |
| Pd grade | 0 | g/t |
| Pt grade | 0 | g/t |
| Fe % | 12 | percent |
| Cr:Fe ratio | 2.4 |
| Comments | Analysis <0.001 ppm Pd, <0.01 ppm Pt. Cr/Fe 2.27 to 2.53. Feather River Belt. Placer County. |
|---|---|
| References | Burnett, J.L., and Jennings, C.W., 1962, Geologic map of California, Chico sheet: California Division of Mines and Geology, scale 1:250,000. Mayfield, J.D., and Day, H.W., 2000, Ultramafic rocks in the Feather River Belt, northern Sierra Nevada, California, in Brooks, E.R., and Dida, L.T., eds., Field guide to the geology and tectonics of the northern Sierra Nevada, National Association of Geoscience Teachers Far-Western Section Fall Conference 2000: California Division of Mines and Geology Special Publication 122, p. 1-15. Rynearson, G.A., 1951, Chromite deposits in the northern Sierra Nevada, California (Placer, Nevada, Sierra, Yuba, Butte, and Plumas counties), in Geological investigations of chromite in California, Part 3--Sierra Nevada: California Division of Mines Bulletin 134, pt. 3, ch. 5, 321 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. Ehrenberg, S.N., 1975, Feather River ultramafic body, northern Sierra Nevada, California: Geological Society of America Bulletin, v. 86, p. 1235-1243. |