Post-Collisional Magmatism and Crust-Mantle Interaction during Gondwana Assembly: Insights from the Araçuaí Orogen, Southeastern Brazil

The Várzea Alegre Intrusive Complex (VAIC),in the Araçuaí orogen, Brazil, represents a significant example of post-collisional magmatism, characterized by a complex interplay between mantle and crustal sources. This study aims to investigate the petrogenesis of VAIC rocks and evaluate the contributions of different magmatic sources to the system. U-Pb geochronological and Lu-Hf isotopic analyses of zircon grains (LA-ICP-MS), and lithogeochemical analyses of mafic, charnockitic, and granitic rock samples, were conducted. The U-Pb results revealed crystallization ages ranging from 510 to 484 Ma, suggesting a sequence of magmatic events, including late-stage intrusive pulses. The Lu-Hf analyses indicated substantial variations in 176 Hf/ 177 Hf ratios and ε Hf values (-10 to +15), pointing to a mix of enriched and depleted mantle components, as well as Neoproterozoic and pre-Neoproterozoic crustal sources. These findings highlight the influence of delamination processes and crustal assimilation. The results suggest that VAIC magmatism is intrinsically linked to mantle and crustal dynamics during the post-collisional phase of the Araçuaí orogen, reflecting a multi-source interaction characterized by the coexistence of multiple magmatic pulses and processes of mingling and assimilation-fractional crystallization. These results not only deepen our understanding of VAIC petrogenesis but also underscore the significance of mantle-crust interactions in generating post-collisional magmas, inviting further exploration of how these dynamics contribute to the compositional and isotopic diversity observed in Araçuaí orogen rocks.