Lithospheric boundaries of the São Francisco paleocontinental block revealed by multiple frequency seismic tomography

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ID: 325949
2026
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Abstract
Summary The São Francisco Paleocontinental block (SFPB) and the Congo Paleocontinental block (CPB) composed, prior to the Atlantic opening in the Cretaceous, the São Francisco-Congo Paleocontinent (SFCP). The SFCP was one of the landmasses involved in the Neoproterozoic Brasiliano-Pan African Orogeny and the assembly of Western Gondwana. Both the SFPB and CPB underwent reworking during the amalgamation of Western Gondwana, forming the orogenic belts that surround the preserved portions of the SFPB and CPB that are known today as the São Francisco and Congo cratons. Although the crustal portions in the outermost areas of these paleocontinents are no longer visible in the surface due to this reworking, the limits of these paleocontinents remain relatively intact at subcrustal depths. The objectives of this study are to delimit the SFPB and to image the structures beneath the Araçuaí belt at mantle lithosphere depths. We present the results of our study which were obtained by the multiple-frequency seismic tomography method for the SFPB and adjacent structures between depths of 68 and 587 km. Data were obtained by processing broadband seismograms recorded between 11-August-2023 and 31-July-2024 for P and PKIKP phases. The processed database comprised 9 254 residuals, which were added to the database of a previous regional study resulting in 97 150 traveltime delays. Checkerboard resolution tests using patterns with horizontal dimensions of 390×390 km reveal very good recovery between depths of 68 and 226 km, although the sharp vertical transition between the checkerboard layers is not fully recovered between the depths of 316 and 384 km. The checkerboard pattern with horizontal dimensions of 312×312 km reveals that the best recovery is observed in the southern and eastern portions of the São Francisco craton (SFCr) and in the Borborema province (BP) between depths of 68 and 226 km. Our results show a high-velocity anomaly with roughly NE-SW trend that extends from the Paranapanema block (PaBl), through the entire extension of the SFCr up to the southern BP. This anomaly contains two major segmentations, one in the southern Brasilia belt, marking the division of the PaBl with the SFPB, and the other dividing the eastern and western arms of the SFPB with a roughly NW-SE trend, interpreted as the Paramirim aulacogen. We also observe a high-velocity anomaly beneath the Araçuaí belt (ArBe) that dips with a SE direction. This anomaly starts at the northern end of the Abre Campo suture at a depth of 136 km, deepens to the south, and is interpreted as the foundered cratonic lithosphere that originated from the delamination of the SFCr due to the passage of the Trindade plume. To reinforce our interpretation, we tested several synthetic models with geometries that were based on our results and previous studies in the area. The synthetic model which presents the most resemblance to the real data model contains a high-velocity anomaly beneath the Araçuaí belt between depths of 226 and 384 km. A strong low-velocity anomaly beneath the Ribeira Belt is interpreted as material rising from the Nazca Slab dehydration.
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Authors Guilherme Manno Penna Crepaldi Affonso, Marcelo Peres Rocha, Tiago Jalowitzki, Fernando Flecha Alkmim, Reinhardt A. Fuck, Aderson Farias do Nascimento, Jordi Julià, Karin Sigloch, Guust Nolet, Eduardo Alexandre Santos de Menezes, Estevão Tadeu, Giuliano Sant’Anna Marotta
Journal geophysical journal international
Year 2026
DOI
10.1093/gji/ggag340
URL
https://doi.org/10.1093/gji/ggag340
Keywords Keywords not found

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