Basement inliers of the Araçuaí-West Congo orogen: key pieces for understanding the evolution of the São Francisco-Congo paleocontinent

Abstract

The Araçuaí-West Congo orogen is a confined orogen, formed by the inversion of a gulf of the São Francisco-Congo paleocontinent during the Neoproterozoic assembly of Gondwana. In this convergent process, fragments of the gulf's continental margin were tectonically dismembered and involved in the growing orogenic pile, and these domains are now exposed by the erosion as basement inliers within the orogen. These basement assemblages (i.e. rocks older than 1.8 Ga) occupy almost 30% of the orogen and occur in various domains along its external zone , amid Meso-to Neoproterozoic metaigneous and metasedimentary rocks. The main recognized basement domains are named Itarantim, Gavião, Porteirinha, Guanhães, Gouveia, Quadrilátero Ferrífero, Mantiqueira and Juiz de Fora (South America), and Kimezian (Africa). They comprise Archean gneisses, granitoids and metavolcanosedimentary sequences and various Rhyacian-Orosirian plutonics and supracrustal units, whose history trace back to the Minas-Bahia orogeny, event responsible for the assembly of the São Francisco-Congo paleocontinent. In this paper we present a detailed and unprecedented review of literature that aims to condensate the state-of-the-art of the geological knowledge about each of these basement inliers and, based on that, to discuss and propose paleogeographic scenarios for the Minas-Bahia orogeny. Due to the confined nature of the Araçuaí orogen, all their basement inliers correspond to fragments of the São Francisco-Congo paleocontinent reworked during the Neoproterozoic Brasiliano orogeny. In the context of the Rhyacian-Orosirian Minas-Bahia orogeny, Guanhães, Gouveia, Porteirinha and Gavião domains are understood as parts of the continents involved in the collision, while the Mantiqueira, Kimezian, Juiz de Fora and Itarantim domains mostly record magmatic arcs, formed in various environments. This review revealed that the density of geological information available for each basement inlier is very uneven, and that there are many gaps for further investigation in all the domains.