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Trinidad

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

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

Geologic Information

Other names	La Trinidad
Country	United States
State or province	California
Geographic location:	35°21'47"N, 120°41'12"W (-120.686667, 35.363056)
Geographic context:	(click for info)
Deposit type	minor podiform chromite
Model type	Banded Podiform
Deposit form	irregular pods, stringers
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
Area of deposit	2295sq m
Ore body length	85m
Ore body width	27m
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	-120.686666666667, 35.3630555555556
Nearby scientific data	Find additional scientific data near this location

Economic Information

Discovery date	1918
Startup date	1918
Tonnage	0.005087	million metric tons
Ore depth	0	m
Cr₂O₃ grade	46	percent
Rh grade	0.005	g/t
Ir grade	0.042	g/t
Ru grade	0.09	g/t
Pd grade	0.0005	g/t
Pt grade	0.005	g/t
Fe %	14.39	percent
Cr:Fe ratio	2.18

Reference information

Comments	Production 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.
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. http://link.springer.com/article/10.1007/s00410-008-0300-6 Jennings, C.W., 1958, Geologic map of California, San Luis Obispo sheet: California Division of Mines and Geology, scale 1:250,000. http://ngmdb.usgs.gov/ngm-bin/ILView.pl?sid=328_1.sid&vtype=b 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. http://archive.org/details/geo22logicalinvest134calirich 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. http://pubs.er.usgs.gov/publication/ofr85442 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. http://specialpapers.gsapubs.org/content/438/1.full.pdf+html

Comments

Production 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.

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.

http://link.springer.com/article/10.1007/s00410-008-0300-6

Jennings, C.W., 1958, Geologic map of California, San Luis Obispo sheet: California Division of Mines and Geology, scale 1:250,000.

http://ngmdb.usgs.gov/ngm-bin/ILView.pl?sid=328_1.sid&vtype=b

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.

http://archive.org/details/geo22logicalinvest134calirich

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.

http://pubs.er.usgs.gov/publication/ofr85442

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.

http://specialpapers.gsapubs.org/content/438/1.full.pdf+html

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