Geology and Petrogenic Evolution of Itatiaia Alkaline Massif, MG-RJ

Abstract

This project, which will be developed in the Mineralogy and Petrology Post-Graduate Program of Geosciences' Institute - USP, aims the systematic study of the Itatiaia alkaline massive, seeking the refinement of its geology, also petrologic and petrogenetic evolution models. The massif has a wide textural and mineralogical variety, and shows a concentric structure, with an outside part, predominantly composed by unsaturated rocks, syenite and nepheline syenite, and an inner part composed by saturated and supersaturated rocks, quartz syenite, quartz syenite and a small granite body. Also occur magmatic breccias, dikes, both felsic as mafic, and mylonites. To reach the proposed objectives, the project provides, for the revaluation of the complex geology and detail mapping, meticulous petrographic studies, chemical analyzes of the main mineral phases and, possibly, some rare mineral, with electron microprobe and LA-ICPMS; chemical analyzes of major petrographic types, including major, minor and trace elements; isotopic analysis of Sr, Nd, and Pb, and geochronological determinations by Ar/Ar in mineral and, if it´s possible, U/Pb zircon SHRIMP. This examined information, which will be studied together, is fundamental to approaches about the nature of primordial magma generated in the mantle, and igneous processes involved in the evolution of these rocks. Also, it´s contribute with information about the nature of mantle region where these magmas were generated regarding the geochemical signature, ratio of partial melting age and Sm/Nd (CHUR/DM), and geodynamic models of magmatism in the Cabo Frio Magmatic Lineament.