Magnetotelluric imaging of the southeastern Borborema province, NE Brazil

Abstract

In the present work we propose a geoelectric model of the crust and upper mantle in the SE portion of Borborema province, northeast Brazil. Magnetotelluric data were collected at 25 stations obtained from a linear profile deployed perpendicularly to the main structures in the SE portion of the study region. The data were collected and processed with modern instrumentation and modeled with the most advanced techniques currently available for studies of electromagnetic induction within the Earth. For the quantitative analysis an inversion of two-dimensional (2D) resistivity curves and phase in two orthogonal directions (TE and TM) was performed. The analysis suggests that the lithosphere under the Sergipana belt and Pernambuco-Alagoas complex, the SE portion of the profile, and the Alto Moxotó terrain, the NW portion, are geoelectrically different within the middle and lower crust with a well marked discontinuity in the region of the Jatobá basin and the Pernambuco lineament. The data support the conclusion that the crust of the Sergipana Belt and the Pernambuco-Alagoas complex was significantly stretched in the Cretaceous during the opening of the South Atlantic Ocean. Apparently, the Alto Moxotó terrain worked as a region of higher resistance to stretching, causing the crustal thinning to be larger in the SE portion of the profile subdomains. The behavior was favored by the deep lithospheric structure, a shear zone (Pernambuco lineament).