Formation, Transformation and Evolution of Lower Continental Crust: Investigating the Southern Brasília Orogen

Abstract

Timescales, over which high-grade metamorphism occurs, are required in order to fully integrate petrological data into tectonic frameworks. In the absence of geochronological constraints, the shape of a P-T path does not necessarily indicate the tectonic setting of metamorphism. Zircon, monazite and titanite are common accessory phases in many rock types, including the ones underwent high-grade metamorphic conditions. They are minerals that carry U-Th-Pb and due to the contrast of closure temperatures for the geochronological systems formed by these elements in each one of them, it is possible to constrain the P-T-t paths of high-grade rocks. Further, the study of trace element composition of these phases can also be used to reveal the growth and temperature of formation, as well as which of these phases are in chemical equilibrium with major phases used in thermobarometric calculations. The Lu-Hf isotopic system in zircon provides insights into the time-integrated chemical differentiation of crust and mantle, being a powerful toll to integrate igneous and metamorphic processes. All of this is enhanced by the use of in situ analysis, such as LA-ICP-MS and SHRIMP, which allows the connection and determination the age of different stages of mineral growth with high spatial resolution, connecting it with a determined stage of igneous or metamorphic history. The project will be carried out at Curtin University, Perth, Australia, under supervision of Prof. Ian Fitzsimons, which is an expert in petrology, geochronology and their application to tectonics. This approach will be used as the backbone to investigate the connection between the genesis, deformation and exhumation of granulite, charnockite and migmatite from the Socorro-Guaxupé Nappe and its infrastructure, in Southern Brasília Orogen, Minas Gerais, Brazil.