Provenance of the Vazante Group: New U–Pb, Sm–Nd, Lu–Hf isotopic data and implications for the tectonic evolution of the Neoproterozoic Brasília Belt

Abstract

The Vazante Group show varied U–Pb provenance patterns along the basin. Zircon ages range from 936 to 3409Ma, but Paleo- and Mesoproterozoic terrains constitute the main sources of the original sediments. The youngest population (~930Ma) establishes the maximum depositional age of the group. Sm–Nd TDM data show the predominance of Paleoproterozoic ages (1.90–2.08Ga) and also indicate some input from younger sources in rocks of the Lapa Formation (1.67 to 2.0Ga) in the upper part of the group, whereas rocks of the Serra do Garrote Formation present the oldest model ages (2.03 to 2.76Ga). Hf isotopic compositions of the detrital zircons indicate that they were derived mainly from recycled Paleoproterozoic crust with a minor Mesoproteroic juvenile component. Terranes within the São Francisco Craton represent the main sources of detrital sediments of this group and reinforce the interpretation that it may be a passive margin sequence developed along the western margin of the original continent. However, the origin of Mesoproterozoic grains remains uncertain. Slightly younger Sm–Nd model ages in the Lapa Formation, however, are not entirely consistent with derivation solely from the craton and may indicate contribution from younger sources, such as the Neoproterozoic Goiás Magmatic Arc.