Interpretação gravimétrica e magnética da estrutura crustal entre a Província Borborema Meridional Oeste e o Norte do Cráton São Francisco

Abstract

The Southern Borborema Province and the Northern São Francisco Craton experienced major tectonic events in the Neoproterozoic Era and their tectonic history is still not completely clarified due to insufficient geotectonic and geophysical studies. This work aims investigating the main boundaries of the crustal blocks between the Southern Borborema Province and the Northern São Francisco Craton for the reconstruction of the tectonic history of this area. Gravimetric, magnetic, geoid anomaly and elevation data were used to accomplish the objectives. The lateral extensions of the sources were determined through magnetic field transformations and the depths were estimated by integrating geoid anomaly and topography data as well as by An-Euler method. The obtained source depths of less than 1 km and more than 5 km with structural index 1 to 3 are present in the São Francisco Craton as in the Borborema cross section and west of the Sergipano belt. The obtained crustal thickness shows a crustal thinning in the Riacho do Pontal belt with 37.25 km in relation to the north of the São Francisco Craton, with values ranging from 41.6 km, these results are in accordance with seismic data. These results were used as a priori information, in the direct crustal 3D modeling to obtain the density contrast distribution in the subsurface. The lithosphere-asthenosphere interface (LAB) results revealed culminating values in the north of the craton reaching 216.0 km. In relation to the Pernambuco-Alagoas domains and the Sergipe belt, LAB values reach 203.0 to 207.0 km thick. The results of the interpreted geophysical maps reveal geological structures marked by lineaments with preferential direction NE-SW, consistent with the features originating from the Brasiliano orogenic event, as well as the contact boundary between the craton and the Borborema Meridional Province, and the boundary between the Pernambuco-Alagoas domains and the belt: Sergipano and Riacho do Pontal. The suture zone was identified from high magnetic signatures.