Unravelling the tectono-magmatic and metamorphic evolution of a Neoproterozoic terrane using allanite, titanite and zircon petrochronology

Abstract

Accretionary orogens exhibit a distinctive feature of abundant juvenile components (newly mantle-sourced) and discerning the origin of these components is imperative in order to understand the process of crustal formation. In ancient orogens, where only remnants of the original arc systems remain intact, the study of magmatic and metamorphic crustal processes can be hampered due to geological complexities resulting from multiphase events that may wipe out past information. However, combining petrographic and microstructural analysis with geochronological and geochemical data of different key accessory minerals provide a powerful tool to unravel various petrogenetic and geodynamic processes through time using constantly advancing in situ analytical techniques. This project aims to explore the tectono-magmatic and metamorphic processes associated with the evolution of an early Neoproterozoic terrane located in southern Brazil - The São Gabriel Terrane. The juvenile continental crust was formed in the context of the Western Gondwana assembly and displays well-preserved lithotectonic elements associated with an accretionary system. This geological setting will be used as a natural laboratory for investigating the subduction-accretion processes recorded by the magmatic arc rocks. By applying a coupled multi-mineral petrochronology approach involving zircon, titanite and allanite, we expect to elucidate the complex tectono-magmatic and metamorphic histories of crust generation and deformation during the early Neoproterozoic in southern Brazil. The interpretations derived from the integration of isotopic dates with elemental and isotopic tracers in these key accessory minerals will shed light on the importance of exploring beyond conventional geochronological and isotopic techniques to better understand complex crustal processes in ancient orogens.