Resumo

MONTENEGRO, Teresita; ORTIZ SUAREZ, Ariel  e  MARTINEZ, Amancay. Age and geochemestry of El Puesto lamprophyre, Las Aguadas, San Luis. Rev. Asoc. Geol. Argent. [online]. 2010, vol.67, n.2, pp.266-271. ISSN 0004-4822.

The lamprophyre from El Puesto, sierra de San Luis, is a minette, calc-alkaline rock-type. It is a dyke that intrudes metamorphic rocks from Complejo Metamórfico Las Aguadas and igneous rocks from Rodeo Viejo tonalitic pluton. Its texture is porphyritic with phlogopite and apatite, and minor proportions of amphibole and rutile. K-feldspar, apatite, rutile, hematite, carbonates, sphene, quartz and altered clinopyroxene form the groundmass. High SiO₂, K₂O, ligth rare earths, Ba, Sr, Zr y Hf contents are the geochemical characteristics, and negative Nb anomaly is present. Enrichment in Si, K, Ba and ligth rare earths contents, higher than calc-alkaline lamprophyres, could be caused by a major degree of crustal contamination. A K-Ar age on phlogopite phenocrysts yield 408 ± 6 Ma, relating the lamprophyre intrusion with the latest famatinian magmatism cycle of Sierras Pampeanas.

Palavras-chave : Minette; Calc-alkaline lamprophyre; Post-orogenic plutonism; Late Famatinian cycle; Sierra de San Luis.

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