Two interrelated Neoproterozoic orogenic systems can be recognized between the Amazonian, West African and São Francisco/Congo cratons. The first is the Borborema Orogen and the Sergipano Fold Belt, on the northern margin of the São Francisco Craton. The second is the Tocantins Orogen, located between the Amazonian and São Francisco cratons that includes the Brasilia and Araguaia Fold Belts and the intervening Goiás Massif. (Figure 1).
The Brasília Fold Belt extends for over 1000 km along the western margin of the São Francisco Craton. It involves Archean basement as well as Meso- and Neoproterozoic clastic strata (Valeriano et al., 2004). Tectonic and metamorphic vergence is towards the cratonic area. Folds and thrusts in the orogen are overprinted by transcurrent faults (Fonseca et al., 1995, Seer, 1999; Valeriano, 1999). The Goiás Massif represents a complex crustal fragment, consisting of typical Archean TTG-greenstone terrains, large layered Mesoproterozoic mafic and ultramafic intrusions (Ferreira Filho et al., 1994), and Mesoproterozoic A-type granites (Pimentel et al. 1991, Pimentel et al., 1999).
The Borborema Province is part of a Brasiliano-Pan-African orogen that continued into Africa prior to Gondwana breakup. It consists of an array of E-W trending right-lateral strike-slip shear zones and a conjugate sinistral NE-SW trending set in northeastern Brazil (Caby et al., 1991). The shear zones cut across gneiss and migmatite complexes of the basement as well as supracrustal units represented by metamorphosed sedimentary and volcanic rocks. These give rise to linear, narrow fold belts. Syn-kinematic granitic magmatism intruded the orogen (Brito Neves, 1975; Neves and Vauchez, 1995, Weinberg et al., 2004). According to Vauchez et al. (1995) mylonitization developed between 600-570 Ma under high temperature conditions and was coeval with partial melting at shallow crustal levels.
The Sergipano Fold Belt is a frontal fold-thrust belt that defines the northern boundary of the São Francisco Craton in Brazil and continues into Africa, as the Oubanguide Fold Belt. This south-verging belt trends east-west and displays a triangle-shape metasedimentary wedge in map view (Davison and Santos, 1989; Silva, 1995).