Deformational structures of the northern portion of the footwall of the Guacha Corral shear zone, Sierras de Córdoba

Abstract

The northern part of the footwall of the Guacha Corral shear zone in Sierra de Comechingones is dominated by a migmatic sequence classified as metasedimentary and mafic metatexites. The contacts between both lithologies are generally transitional and are characterized by different morphologies depending on the percent of melt. The results obtained from the structural analysis of migmatites allow us to determine a progressive succession of non-coaxial and compressive deformational events in the study area. The main deformational event would be linked to the occurrence of partial melting processes that generated migmatization in the footwall at conditions of 650-700 °C and 0.5 a 0.6 GPa. Anatexis would have occurred simultaneously with ductile mylonitization at amphibolite facies along the Guacha Corral shear zone in the hanging wall during the Famatinian Orogeny. In the footwall, this shear zone generated a textural and mineralogical reworking of the migmatic rocks, expressed as narrow shear belts with compressive and inverse kinematics. Dynamic metamorphism within this zone occurred under greenschist facies conditions (400-450 °C and 0.2-0.4 GPa). The progressive cooling of footwall rocks from ~700 °C at 475 Ma to ~500 °C at 400 Ma, integrated with petro-structural study allowed us to document a long history of deformation activity related to the Guacha Corral shear zone in this portion of Sierras Pampeanas.