Deep crustal structure of the Sergipano Belt, NE-Brazil, revealed by integrated modeling of gravity, magnetic, and geological data

Abstract

The Sergipano Belt is located in the Southern Subprovince of Borborema Province in the Northeast of Brazil. Its tectonic framework was consolidated in the Pan-African-Brasiliano Orogeny at the end of the Neoproterozoic. The most recent geological models indicate that its evolution occurred over a complete Wilson Cycle. Gravity and magnetic data profiles that crossed the Sergipano Belt from south to north were modeled jointly by the forward method to provide a 2D view of the deep crustal structure. The modeling process was linked and supported by the use of geological data and models. The result revealed the deep structure of the crust and identified the geometry of the main geological domains to the depth of Moho discontinuity. The folds and thrusts toward the São Francisco Craton are a persistent and deep feature in the Southern crust of the Sergipano Belt. The general tectonic context of the models is compatible with the subduction and collision of the São Francisco Paleoplate under the Pernambuco-Alagoas Superterrane, sutured in the São Miguel do Aleixo Shear Zone. The presence of dense blocks at the base of the crust was interpreted as layers of ophiolites placed by obduction. The metasediments of the Vaza Barris and Macururé domains are tabular bodies with thicknesses lower than 5 km, which dip horizontally or at a low angle on the flanks of the shear zones. Small vertical bodies of lower density within the Macururé Domain have a correlation with granitic intrusions. In the Canindé Domain there is a dense layer in the lower crust that was interpreted as the relicts of the oceanic crust that based a back-arc basin. The granitic bodies modeled north of the Canindé Domain and correlated with the Serra do Catu batholith in Pernambuco-Alagoas Superterrane, may be the record of subduction of this crust to the north. The data and models revealed geophysical differences between the Jirau do Ponciano and Rio Coruripe domains, and the crust north of the Palmeira dos Índios Shear Zone. These terranes are separated by shear zones with evident expression in gravity and magnetic data. However, the existence of Neoproterozoic metasedimentary supracrustal rocks partially covering both the domains and zones and the boundary shear indicates that the junction among these blocks occurred before the deposition of Neoproterozoic sediments.