Granites and the geodynamic history of the neoproterozoic Brasilia belt, central Brazil: a review

Recent field and geochronological studies have demonstrated the importance of granitic magmatism in the evolution of the Neoproterozoic Brasilia Belt, in Central Brazil. This is an orogenic belt developed in response to the convergence between the Amazon, Sao Francisco-Congo and Parana continental blocks. The presence of Neoproterozoic juvenile are rocks and syn-collisional peraluminous granites challenged previous intracontinental evolution models for the belt. The granitoid intrusions reviewed in this paper record the different stages of evolution of the orogen and their field and isotopic characteristics can be used to reconstruct the tectonic history of the belt. The main field and isotopic characteristics of four granite suites associated with the Brasilia Belt are reviewed: (i) 1.77-1.58 Ga old rift related A-type granite intrusions, (ii) ca. 0.8-0.7 syn-collisional granitoids, (iii) are metatonalites and metagranodiorites (ca. 0.9 to 0.63 Ga), and (iv) bimodal post-orogenic suite ranging in age from ca. 0.59 to 0.48 Ga. These rocks suggest that during most of the Neoproterozoic the western margin of the Sao Francisco continent faced a large oceanic basin, where subduction and oceanic lithosphere consumption started at ca. 0.9 Ga, roughly coeval with the initial stages of the break up of Rodinia. Final ocean closure happened at ca. 0.63-0.60 Ga with crustal thickening, uplift and erosion. Post-orogenic extension-related magmatism took place between ca. 0.6 and 0.5 Ga and was partially contemporaneous with the deposition of the Paraguay and Tucavaca sedimentary successions, resulting from the rifting event related to the break up of Laurentia from southwestern Gondwana. (C) 1999 Elsevier Science B.V. All rights reserved.