Structural interplay between plutons during the construction of a batholith (Cerro Aspero batholith, Sierras de Córdoba, Argentina)

Abstract

Magnetic fabric patterns and microstructures of granitic rocks provide evidence of structural modifications as a result of the coalescence of two plutons, Alpa Corral and Talita, during the construction of a large granitic batholith, Cerro Aspero, in the Sierras Pampeanas of Córdoba (Argentina). The Alpa Corral granite is a small and nearly circular pluton, while the larger Talita pluton displays a marked N-S elongation. The NW quadrangle of the Alpa Corral pluton underwent a deformation resulting in foliation trajectories that outline a crescent moon pattern whose inner arc is concordant with the Alpa Corral/Talita contact. The highest values for the magnetic susceptibility and its anisotropy are concentrated in the coalescence zone between both plutons. The magmatic and sub-magmatic nature of the microstructures demonstrates that such a deformation was caused by the southward overriding of the largest Talita pluton while the Alpa Corral pluton was not yet fully crystallized. Rb-Sr geochronology indicates that this process took place 369±9 Ma ago, long after the Famatinian (Ordovician to Early Devonian) deformation of the country rocks, which confirms a synmagmatic, rather than a regional, deformational event. © 2006 Elsevier Ltd. All rights reserved.