Descripción geoquímica y geocronológica de secuencias volcánicas neógenas de Trasarco, en el extremo oriental de la Cadena Volcánica Transversal del Quevar (Noroeste de Argentina)

I.A. PETRINOVIC, J. MITJAVILA, J.G. VIRAMONTE, J. MARTÍ, R. BECCHIO, M. ARNOSIO, F. COLOMBO

Abstract


New geochronological data (34) and 39 new geochemical analyses have been made in the Neogene backarc volcanic sequences in the “El Quevar Transversal Volcanic Chain” defined by Viramonte et al (1984a). This chain starts at the present N-S arc with WNW-ESE trend. New volcanic centres have been recognised and analysed at the eastern end of this chain. The different pulses from each volcanic centre (Aguas Calientes, Acay, El Morro - Organullo and Tocomar) are petrographically and geochemically homogeneous. This suggests that the magma chambers related in each volcano, were geochemically homogeneous and did not have crystal enriched sectors. The Acay eruptive centre is an exception of this assumption; a compositionally differentiated magmatic chamber could be inferred. The isotopic composition of the Aguas Calientes emission centre has a crust signature in its origin, related with melts generated by crustal fussion. The geochronological determinations show volcanic pulses at 17-19 Ma, 13-12 Ma, 10 Ma, 7-6 Ma, 1-0.5 Ma in this region of the Central Andes.

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