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. Gravimetric and magnetic data profiles that crossed the Sergipano Belt from south to north were modeled jointly by the direct method to provide a 2D view of the crust framework. 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's 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 Paleo-Plate under the Pernambuco-Alagoas Superterrane, sutured in the Shear Zone of São Miguel do Aleixo. 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 backarc 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, Coruripe River Domains and the crust north of the Palmeira dos Índios Shear Zone. These terrains are separated by shear zones with evident expression in gravimetric and magnetic data. However, the existence of Neoproterozoic metasedimentary supracrustal rocks partially covering the domains and zones and borderline 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 gravimetric, magnetic, and geological data Accepted manuscript -Uncorrected pre-proof This is a PDF file containing an unedited and non-definitive version of a manuscript that has been accepted for publication by the Journal of the Geological Survey of Brazil -JGSB, which serves to provide early visibility of the article. Being an uncorrected preproof version, errors may appear during the production process (language review, formatting and proof review), and these can affect the final content of the article and all legal disclaimers (https://jgsb.cprm.gov.br/index.php/journal/6).

Gamma-ray spectrometry, magnetic and gravity signatures of Archean nuclei of the Borborema Province, Northeastern Brazil

“…The northern limit of the crustal block is correlated with the Mocambo and São Miguel do Aleixo shear zones (see figure 3 in Oliveira et al 2023a). From regional gravity maps (Figure 4), it is possible to infer that this nucleus is located in the intermediate part of a regional anomaly associated with the boundary between the São Francisco Craton and the Sergipano Belt (Oliveira and Medeiros 2018;Oliveira et al 2023a). According to the gravity modeling of Oliveira et al (2023a), this crustal block (density around 2,900 kg/m 3 ; see figures 5 and 7 in Oliveira et al 2023a) dips northwards and is juxtaposed against the upper low-angle interface of the São Francisco Craton.…”

“…The total magnetic gradient map (Figure 14C) shows that Archean rocks have a strong magnetization, likely caused by a relative enrichment in magnetic minerals (Profile P-Q in Figure 14E). The interpretation of Oliveira et al (2023a) of the magnetic signature of this nucleus (better known as Itabaiana-Simão Dias Dome; e.g., D'el-Rey Silva 1995) suggests that this crustal block continues to the northeast beneath the sedimentary rocks of the Sergipe-Alagoas Basin. The northern limit of the crustal block is correlated with the Mocambo and São Miguel do Aleixo shear zones (see figure 3 in Oliveira et al 2023a).…”

“…The interpretation of Oliveira et al (2023a) of the magnetic signature of this nucleus (better known as Itabaiana-Simão Dias Dome; e.g., D'el-Rey Silva 1995) suggests that this crustal block continues to the northeast beneath the sedimentary rocks of the Sergipe-Alagoas Basin. The northern limit of the crustal block is correlated with the Mocambo and São Miguel do Aleixo shear zones (see figure 3 in Oliveira et al 2023a). From regional gravity maps (Figure 4), it is possible to infer that this nucleus is located in the intermediate part of a regional anomaly associated with the boundary between the São Francisco Craton and the Sergipano Belt (Oliveira and Medeiros 2018;Oliveira et al 2023a).…”

“…From regional gravity maps (Figure 4), it is possible to infer that this nucleus is located in the intermediate part of a regional anomaly associated with the boundary between the São Francisco Craton and the Sergipano Belt (Oliveira and Medeiros 2018;Oliveira et al 2023a). According to the gravity modeling of Oliveira et al (2023a), this crustal block (density around 2,900 kg/m 3 ; see figures 5 and 7 in Oliveira et al 2023a) dips northwards and is juxtaposed against the upper low-angle interface of the São Francisco Craton. In the residual Bouguer gravity map (Figure 14D), Archean units are correlated with a positive anomaly with an amplitude of 5 mGal and a wavelength of 40 km (see also Profile P-Q in Figure 14E).…”

Editorial: message from the Editor-in-Chief

“…This first issue of 2023 mainly contains the Special Session on the Borborema Province from northeastern Brazil. Oliveira et al (2023) integrate geology and geophysics to investigate the deep structure of the Sergipe Belt. In-depth reviews on lithostratigraphy are presented for the North (Pinéo et al 2023) and Transversal Zone (Santos et al 2023) domains and also for the Mesozoic basins that cover the province (Morais et al 2023).…”