Large-scale fluid circulation in shear zones from the Southern Ribeira Belt

Abstract

This Project has the objective of quantifying the large-scale fluid flow along shear zones from the southern Ribeira Belt by means of microthermometric and laser Raman microspectroscopic analyses of fluid inclusions hosted in syntectonic veins. Veins collected in a known structural context (e.g., filling extensional fractures, shear fractures or hosted in metamorphic foliations) will be studied, which will allow establishing their temporal relationships with regional structures and deformational phases. The fluid inclusion studies will be preceded by macroscopic and microscopic petrography where the vein geometries, structures, and internal microstructures will be described. The petrographic work aims to identify veins with preserved growth microstructures that can be attributed to different opening and filling mechanisms and are expected to preserve primary fluid inclusions that should record parameters related to the formation of the veins. It is also intended to identify veins dominated by deformational microstructures that can host reequilibrated fluid inclusions and record the conditions acting during deformation along the shear zones. The microthermometry and Raman spectroscopy analyses in fluid inclusions will allow characterizing the compositions and conditions of pressure and temperature of entrapment of primary, pseudo secondary, secondary and reequilibrated fluid inclusions, in order to quantify the metamorphic trajectories associated with fluid regimes. This work will use available double-polished sections from samples collected from previous work and samples to be collected from fieldwork during this project.