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

2022; Volume: 6; Issue: 1 Linguagem: Inglês

10.29396/jgsb.2023.v6.n1.1

2595-1939

Roberto Gusmão de Oliveira, Nitzschia Regina Rodrigues Domingos, Walter E. Medeiros,

Geological formations and processes

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 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.Deep crustal structure of the Sergipano Belt, NE-Brazil, revealed by integrated modeling of gravity, magnetic, and geological data Pernambuco-Alagoas Superterrane.In turn, with the use of a magnetotelluric profile of direction NE-SW, which crossed the Tucano Basin in an oblique angle, Corrêa-Gomes et al. ( 2022) interpreted the geoelectric section image as being the interaction between two crustal blocks, the most resistive to NE representing the crust of the Pernambuco-Alagoas Block and the least resistive to SW representing the São Francisco Craton.The interface between the two blocks, with dip to the southwest, was interpreted as a suture produced by the indentation of the NE Block in the SW Block during a Brasiliano collision.In this context, this study presents the results of direct 2.5D joint forward modeling of gravity and magnetic data, in integration with the available geological knowledge, of two N-S oriented profiles that cross the eastern portion of the Sergipano Belt (Figure 1).The objective was to build sets of density and magnetic susceptibility models that help the understanding of the deep crustal structure of the Sergipano Belt crust resulting from the collision of the São Francisco Craton with the Pernambuco-Alagoas Superterrane, in the region located between the Tucano and Sergipe-Alagoas basins.The geological interpretation of geophysical models for the understanding of regional tectonic frameworks is a task that requires the ability to understand the limitations that geophysical data impose on the interpreter and the expertise of integrating geophysical and geological data.In this study, the modeling was linked and supported by the use of geological data.It is a fact that geophysical models can offer only a frozen view of the final events that have acted in the tectonic environment under study.However, there is no other way to access deep information beyond the use and modeling of geophysical data.Therefore, the method used and the results of this work were able to produce an adequate and geologically coherent view of the deep crustal structure of the Sergipano Belt to the depth of the Moho discontinuity resulting from the collision between the São Francisco Craton and the Pernambuco-Alagoas Superterrane at the end of the Neoproterozoic.