Fluid flow, deformation and tectonic significance of regional shear zones from the southern Ribeira Belt

Abstract

This project aims to investigate the transcurrent shear system that cut the southern portion of the Ribeira Belt (SE Brazil) by means of three main approaches: (a) fluid flow quantification and identification of related seismically activated process by means of the study of fluid inclusions (petrography, microthermometry, laser Raman spectroscopy and trace element analysis by LA-Q-ICP-MS) present in sintectonic hydrothermal veins; (b) quantification of the deformational and thermal history of the regional shear zones by means of structural analysis and qualitative and quantitative microstructural analyses involving the geometry of structures in the field, correlation between optical microstructures and deformation mechanisms and quantifications of textures and crystallographic preferred orientation using the MEV-EBSD system; (c) investigation of the tectonic significance of the regional shear zones by means of determination of thermochronological ages using isotopic methods with high to low closure temperatures (U-Pb in zircon and monazite, Ar-Ar in hornblende, muscovite and biotite) and integration and complementation of available petrochronological data and detrital zircon U-Pb ages of tectonostratigraphic terranes bounded by regional shear zones, which will provide data to evaluate if each terrane had a distinct evolutive history relative to neighboring terranes and were juxtaposed along suture zones or post-orogenic collage lateral scape zones, or if they represent autochthonous or para-autochthonous units. (AU)