The tectonic evolution of the Neoproterozoic Brasilia Belt, central Brazil: a geochronological and isotopic approach

The Brasilia Belt is one of the most complete Neoproterozoic orogens in western Gondwana. Rapid progress on the understanding of the tectonic evolution of the belt was achieved due to new U-Pb data, combined with Sm-Nd and Lu-Hf analyses. The evolution of the Brasilia orogen happened over a long period of time (900 - 600 Ma) involving subduction, magmatism and terrain accretion, as a result of the consumption of the Goias oceanic lithosphere. Provenance studies, based on U-Pb zircon data, indicate that the sedimentary rock units record different tectonic settings and stages of the evolution of the orogen. The Paranoa and Canastra groups represent passive margin sequences derived from the erosion of the Sao Francisco Craton. The Araxa and Ibia groups, however, have dominant Neoproterozoic detrital zircon populations, as -young as 650 Ma, suggesting derivation from the Goias Magmatic Arc. The Goias Magmatic Arc represents a composite arc terrain, formed by the accretion of older (ca. 0.9 - 0.8 Ga) intraoceanic island arc(s), followed by more evolved continental arcs. It extends for several thousand kilometers, from SW Goias, through NE Brazil and into Africa. Metamorphism took place between 650 - 630 Ma reflecting final closure of the Goias Ocean and continental collision.