The Serra da Serpentina Group: a back-arc basin related to the Paleoproterozoic Minas-Bahia orogeny?

Abstract

In the Rhyacian and Orosirian periods, Archean crustal fragments and Paleoproterozoic magmatic arcs were amalgamated into the São Francisco-Congo Paleocontinent during the Minas-Bahia orogeny. In the foreland terranes of the orogen, a BIF-bearing metasedimentary sequence including the Serra da Serpentina Group and its correlates is extensively exposed but still poorly characterized. A geochemical study undertaken in the basal succession of Serra da Serpentina Group comprising schists, phyllites, and quartzites of the Meloso Formation, delineates the characteristics of the sediment source and constrain the tectonic environment and crustal evolution of the Serra da Serpentina basin. Trace and REE geochemistry studies reveal that clastic sediments of the Meloso Formation comprise mantle and upper crustal-derived source components. The meta-ultramafic Serro-Alvorada de Minas Suite, the Minas-Bahia magmatic rocks, and the Archean TTG terranes are the main potential source rocks for the Meloso basin infilling, as also suggested by the detrital zircon age spectra.Our results suggest the opening of a back-arc basin stretching along the Mantiqueira magmatic arc in response to the Minas-Bahia Orogen during the Rhyacian-Orosirian. The Serra da Serpentina Group was deposited in this environment associated with crustal thinning and local development of submarine volcanism. This assembly shares similarities with the upper Minas Supergroup that comprises the Piracicaba and Sabará groups, suggesting a cogenetic sedimentation.