Abstract

ANZIL, Patricia A  and  MARTINO, Roberto D. Petrography and geochemistry of the anphibolites from La Cocha Hill, Sierra Chica, Córdoba, Argentina. Rev. Asoc. Geol. Argent. [online]. 2012, vol.69, n.2, pp.263-274. ISSN 0004-4822.

In the Sierra Chica of Córdoba (Argentina), two lithological varieties of amphibolites associated with the La Cocha ultramafic body, crops out two kilometer south of the Bosque Alegre Astronomical Observatory. These varieties include non-pyroxene amphibolite composed of hornblende, plagioclase, titanite and opaque minerals, situated in the core of the ultramafic body folded structure. The second group is pyroxene amphibolites comprising hornblende, plagioclase, orthopyroxene (En), clino-pyroxene (Di) and accessories including opaque minerals, apatite, more rarely titanite and zircon. This group appears in the ultramafic country rock represented by garnet sillimanite gneisses. Whole rock chemical study was conduct with the objective to determine the protolith of amphibolites product of metamorphism. Two pyroxene amphibolites are classifed as tholeiitic series and rare earth elements diagrams suggest that parental magma may be N-MORB setting. Also, non-pyroxene amphibolites could belong to an N-type MORB, with low contents of light rare earth elements, probably suggesting that their parental melt has originate from a depleted mantle.

Keywords : Amphibolite; Metamorphism; Geochemistry; La Cocha; Sierra Chica.

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