The Congonhas-Itaverava Shear Zone in the Southern São Francisco Craton: Implications for the Rhyacian Amalgamation in the Minas-Bahia Orogen

Three main strike-slip shear zones define the boundaries of Archean-to-Paleoproterozoic terranes comprising the Mineiro Belt and the Minas Block at the southeastern edge of the Archean Sao Francisco Protocontinent. These terranes accommodated the accretionary and collisional phases of the Rhyacian Minas-Bahia orogen. The related structural and shear sense indicators provide evidence of a dominant oblique dextral movement. However, the confined puzzle-like regional geometry of the terranes suggests a complex kinematic history with recurrent activity along the suture zones that have been reactivated during a long tectonic history until the consolidation of the Sao Francisco Craton in the late Cambrian. Analyzing the aeromagnetic data surveyed by the Companhia de Desenvolvimento Economico de Minas Gerais (Codemig, 2001) and applying the Phase-Preserving Dynamic Range (PPDRC) technique, followed by Magnetic Vector Inversion (MVI), it was possible to individualize three main magnetic regions separated by shear zones. Six structural domains were discriminated based on the structural data, including photo-lineaments, magnetic anomalies, and field data. The age of crystallization of the quartz-diorite plutonic body of the Alto Maranhao Suite is coeval with intruding aplitic veins filling shear fractures associated with the Congonhas-Itaverava shear zone attesting its contemporary emplacement during the amalgamation of the Mineiro Belt against the Minas Block.