Accretion tectonics in Western Gondwana highlighted by the aeromagnetic signature of the Sergipano Belt, NE Brazil

Abstract

Identification of suture zones in Precambrian orogens can be a major problem due to later reworking and/or erosion. Interpretation of aerogeophysical data is a useful tool to the understanding of the structure and evolution of old fold belts. In this study, we use aeromagnetic data to identify domain boundaries in the Sergipano Belt (SB), a Neoproterozoic orogen developed on the northern border of the São Francisco Craton (SFC), NE Brazil. The SB was formed due to convergence between the SFC and the Pernambuco-Alagoas Superterrane during the Brasiliano Orogeny, culminating in the assembly of West Gondwana. Total Magnetic Intensity (TMI) and tilt derivative maps provided the delimitation of magnetic domains corresponding to main lithological units of the Sergipano Belt and its basement and the definition of first to fourth order lineaments. Matched filter and Euler deconvolution results allowed to observe the magnetic behavior of both domains and lineaments in depth. The data suggest that the Marancó and Poço Redondo domains are two distinct lithotectonic units and that the Jirau do Ponciano dome, extreme NE of the Sergipano Belt, is likely a structural window of the São Francisco paleoplate reworked basement. Interpretation of these results combined with existent geological data allowed to highlight at least two possible terrane boundaries in the northern margin of the São Francisco Craton, represented by the São Miguel do Aleixo and Belo Monte-Jeremoabo shear zones, and the definition of the High-Intensity Magnetic Zone, which comprises a ca. 10 km wide and 140 km long corridor of mafic and ultramafic rocks, and represents the main suture zone within the SB. The data imply that the Sergipano Belt evolved as an accretionary orogen during West Gondwana assembly.