Generation and evolution of granitic magmas and tectonic implications: a contribution from Sr-Nd-Pb isotope geochemistry and in situ dating and geochemistry of zircon in granites from se Brazil

Abstract

The study of the granitic magmatism is fundamental to understanding the Neoproterozoic tectonic evolution in southeastern Brazil, particularly in view of the abundance and diversity of its products, and the potential to provide information about processes that occurred in the deep crust and mantle. Continuing systematic research developed by our group, this project proposes the re-evaluation of the crystallization ages of some of the major occurrences of granites of the Ribeira Belt and Socorro-Guaxupé Nappe, using in situ dating techniques (LA- MC-ICPMS and Shrimp), which allow to circumvent uncertainties and inaccuracies associated with heritage and loss of Pb, which appear frequently in analyzes by TIMS. In parallel, elemental geochemistry and isotopic (Sr-Nd-Pb-Hf) data will be obtained in whole rock and minerals (feldspar and zircon) of selected plutons, focusing "classic" granite occurrences that are still poor on this type of data (e.g., Socorro batholith; granites of São Roque Domain) and others whose tectonic meaning is still uncertain (e.g., granites of Embu and Costeiro domains). A fundamental aspect that integrates the studies in different tectonic domains addressed in this project is the comparison of "syn-orogenic" high-K calc-alkaline magmatism, which may have post-collisional character or be related to subduction processes, since the available data show that in the Três Córregos and Agudos Grandes batholiths (in the Apiaí Terrane), these granites (aged ~610 Ma), have isotopic signatures indicative of older sources (e.g., Nd TDM> 2.2 Ga), and seem to contrast both in age and in source compared to similar magmatism in the Socorro-Guaxupé Nappe (which would be older) and in the Costeiro Domain (where it seems to be younger). (AU)