The Carrancas Nappe System in the southern margin of the Brasilia Orogen: sedimentary provenance and tectonic setting.

Abstract

The southern margin of the Brasília Orogen is characterized by an ediacaran nappe system formed during the collision between the São Francisco and Paranapanema paleocontinentes. In this nappe system the superior alocthons were laterally transported to the southern margin of the São Francisco Craton (Socorro-Guaxupé Nappe and Andrelandia Nappe System), while the inferior alocthons were transported directly against the craton (Lima Duarte Nappe and Carrancas Nappe System). Metassedimentary and metamafic units of the Carrancas Nappe System and the Biotita Schist Unit from the Andrelandia Nappe System front are the study objects of this project.Isotopic and geochemical signatures and the geochronological study will be the main tools in the sedimentary provenance and the tectonic setting during the sedimentation approaches. The objectives will be accomplished by isotopic and elemental geochemistry in total rock analyses, by trace element geochemistry in situ in detrital zircon and detrital plagioclase, and by U-Pb system analyses and the concentration of Hf isotopes in zircon. The analyses will be realized by X-ray fluorescence, by ICP MS and LA-MC-ICP MS.