The electrical structure of the São Francisco craton margin and the Araçuaí Orogen: Implications for the amalgamation of West Gondwana

The geodynamic evolution of the Araçuaí Orogen remains debated between purely intracontinental models and subduction-driven continental collisions. This study investigates the deep electrical structure of this collision zone through three-dimensional (3D) inversion of magnetotelluric (MT) data from 16 stations along a 202 km transect. The phase tensor analysis revealed dominant 3D effects, indicated by elevated skew angles, justifying the inversion methodology. The final conductivity model images a complex lithosphere marked by the juxtaposition of two distinct lithospheric-scale geoelectric domains. The western portion is dominated by a deep resistive feature (R1), which is tectonically inferred as the Archean to Paleoproterozoic lithosphere of the São Francisco Craton potentially acting as the lower plate. Adjacent to this, a prominent Steep Lithospheric Conductor (SLC), C1, dips eastward, presenting a spatial correlation with the surface traces of the Neoproterozoic paleosuture. To the east, an expressive resistive block (R2) is observed, whose geometry and spatial coincidence suggest it represents the possible roots of the Rio Doce Magmatic Arc emplaced on a thickened Neoproterozoic lithosphere (R3, inferred upper plate). Complementing existing regional geophysical studies, this work presents the first 3D resistivity model specifically along this transect, providing new geophysical constraints for this key segment of West Gondwana. The results reinforce the existence of an older, reworked lithosphere juxtaposed against a younger orogenic lithosphere. Furthermore, a modeled deep conductive anomaly in the mantle beneath the suture favors interpretations of post-collisional mantle upwelling, although a metasomatized mantle or inherited conductive fabrics represent valid alternative sources for this high conductivity.