Estrutura geoelétrica da crosta superior revelada por dados magnetotelúricos 2d na bacia do Jaibaras, NW do Ceará

Abstract

We have presented a magnetotelluric survey at 14 sites at Jaibaras Paleozoic Basin which is located in the northeastern part of Ceará, in municipalities of Mucambo and Pacujá. Basin structures were subjected to reactivation, influenced by Transbraziliano Lineament among others. In previous works, the reactivation of the so-called Sobral Pedro II lineament with gravity anomalies was interpreted as graben. The geological setting of this basin is still unknown, especially due to lack of detailed geophysical work. As well there were no direct geological information’s. With an integration of geological and geophysical data, 14 magnetotelluric sites was performed in order to understand the geoelectrical structure of the area, as an interpretation of two-dimensional MT section. Firstly, time series processing was preformed and 1-D inversion. After TE+TM mode inversion was done. The aim was to highlight crustal structure in the regional context with the help of geoelectrical inversion. It was possible to highlight shallow structures and delimitate between the geoelectrical units (horizontal structures) and contrasts between the vertical facies (vertical structures). MT section shows us that part of the Jaibaras rift was delimited with high-resistivity values which denote sub vertical structures, shear zones that are dipping in Jaibaras rift, part of the Transbrasiliano Lineament (Sobral-Pedro II shear zone). Other important lineaments have been identified such as Café-Ipueiras fault. Post-tectonic Mucambo granite and sediments of Parnaíba Basin looks clearly mapped. Two dimensional MT section presents a geoelectrical/geological interpretation of the upper part of the crust in that region.