Fabrica magnética y emplazamiento del plutón Alpa Corral (Sierras de Córdoba, Argentina).

Resumen

Nearly circular in outcrop, the Alpa Corral pluton is one of the post-tectonic monzogranitic plutons of the Sierras Pampeanas, in Córdoba (Argentina). This pluton intrudes the Early Paleozoic basement of the Sierras Pampeanas during Late Oevonian times. This concentrically zoned pluton is made up by inequigranular to porphyritic monzogranites, distributed in two units: a internal unit formed by coarse to porphyritic granite and a external unit represented by inequigranular leucogranite. Bulk magnetic susceptibility (K) shows bimodal distribution, reflecting magnetite-rich granites for the internal unit and magnetite-poor to paramagnetic granites within external unit. Microstructural evidence indicates that magnetic fabrics are entirely magmatic in origin and reflect the internal magma dynamics. From structural and Anisotropy of Magnetic Susceptibility measurements, the internal structure of this pluton has been inferred. According to the AMS and structural data from the country rocks, the emplacement of the Alpa Corral pluton took place after the vanishement of the compresional stress field responsible for the main structures recorded in the country rocks. However, some control by a far field stress can be deduced from the NNW-SSE alignment of the post-tectonic plutons of the Sierras Pampeanas. This suggests that granite emplacement was controlfed by a set of early master fractures related to the extensional collapse in this sector of the Sierras Pampeanas.