Geochemical evolution of granites from the Achala batholith of the Sierras Pampeanas, Argentina

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Abstract
The Achala batholith is a post-orogenic intrusion of probable Silurian age exposed in the Sierra de Cordoba in the eastern Sierras Pampeanas of central Argentina (31°6′S to 32°2′S; 64°29′W to 65°7′W). The batholith was emplaced into late Precambrian amphibolite- and granulite-facies metamorphic rocks. Five comagmatic granitoid facies, all monzogranite in composition, have been recognized. Geochemical data suggest these granitoids formed by a magmatic differentiation process that began with porphyritic and fine-grained facies B, C, and D, and ended with leucogranite facies A. Biotite-apatite enclaves that are interpreted as cumulates and tonalitic nodules occur in facies B. Less abundant rock types are quartz-muscovite greisens, feldspathic episyenites, pegmatites, and aplites. The granitoids have S-type chemical affinities and are consistent with a within-plate granite tectonic setting.

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