Alteration patterns of chromian spinels from La Cabaña peridotite, south-central Chile

La Cabaña peridotite is part of a dismembered ophiolite complex located within the metamorphic basement of the Coastal Cordillera of south-central Chile, and is the only location in Chile were Cr-spinels have been described so far. The La Cabaña peridotite is part of the Western Series unit, which c...

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Bibliographic Details
Published in:Mineralogy and petrology 2014-12, Vol.108 (6), p.819-836
Main Authors: Barra, Fernando, Gervilla, Fernando, Hernández, Elkin, Reich, Martin, Padrón-Navarta, José Alberto, González-Jiménez, José Maria
Format: Article
Language:English
Subjects:
Accessories
Alterations
Chromite
Chromium
Earth and Environmental Science
Earth Sciences
Fluid dynamics
Fluid flow
Geochemistry
Inorganic Chemistry
Mineralogy
Original Paper
Petrography
Rocks
Sciences of the Universe
Surface layer
Texture
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Summary:La Cabaña peridotite is part of a dismembered ophiolite complex located within the metamorphic basement of the Coastal Cordillera of south-central Chile, and is the only location in Chile were Cr-spinels have been described so far. The La Cabaña peridotite is part of the Western Series unit, which comprises meta-sedimentary rocks, metabasites, and serpentinized ultramafic rocks. This unit has been affected by greenschist-facies metamorphism with reported peak PT conditions of 7.0–9.3 kbar and 380°–420 °C. Within La Cabaña peridotite Cr-spinels are present in two localities: Lavanderos and Centinela Bajo. In Lavanderos, Cr-spinel occurs in small chromitite pods and as accessory/disseminated grains with a porous or spongy texture in serpentinite, whereas in Centinela Bajo Cr-spinel is present as accessory zoned grains in partly serpentinized dunites, and in chromitite blocks. All Cr-spinels display variable degrees of alteration to Fe 2+ -rich chromite with a variation trend of major elements from chromite to Fe 2+ -rich chromite similar to those observed in other locations, i.e., an increase in Fe 2 O 3 and FeO, a decrease in Al 2 O 3 and MgO. Cr 2 O 3 content increases from chromite to Fe 2+ -rich chromite in chromitite pods from Lavanderos and chromitite blocks from Centinela Bajo, but decreases in ferrian chromite zones in accessory grains from Centinela Bajo. The minor element (Ti, V, Zn, Ni) content is mostly low and does not exceed 0.4 wt.%, with the exception of MnO (
ISSN:0930-0708
1438-1168
DOI:10.1007/s00710-014-0335-5