Abstract

SATO, Ana María; LLAMBIAS, Eduardo J.  and  BASEI, Miguel A.. Deformation and age of the early post-orogenic monzonitic-granitic pluton and dykes of West of the Sierra de San Luis. Ser. correl. geol. [online]. 2006, vol.21, n.1, pp.105-132. ISSN 1666-9479.

The Río del Molle Plutonic Complex is the oldest post-orogenic igneous unit present at the western Famatinian orogenic axis in the Sierra de San Luis. Conventional U-Pb analyses of zircon from a quartz monzodiorite of the El Molle pluton yielded 417 Ma. This is interpreted as the crystallization age of the pluton and confirms the early character of the Río del Molle Plutonic Complex within the post-orogenic group. The complex is composed of (in order of decreasing age of intrusion) three contemporaneous plutons (El Molle, Barroso, Villa de la Quebrada), a NW longitudinal dyke swarm, ring dykes and sheeted-like dyke swarm. Monzonitic and granitic series of rocks were identified within the whole complex. They are related to two mingling processes between, at least, three end-members, and also mixing. Meso- and micro-structural evidences of solid-state flow superimposed on magmatic flow are preserved in deformed igneous rocks, as well as several criteria suggest submagmatic flow. This means that melts appears to have been present during the complex deformation at early stages (Late Silurian) of late- to post-orogenic phase of the Famatinian cycle.

Keywords : Monzonite; Mingling; Deformation; Post-orogenic Magmatism; U-Pb age; Sierras Pampeanas; San Luis.

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