Mapeamento geológico e petrografia de migmatitos da Zona Interna da Faixa Brasília, Cascalho Rico - MG

Abstract

Migmatites are rocks generated from partial melting during medium-to-high-grade metamorphism in the lower-than-average crust region on continents. The geological mapping and petrography of these rocks are important for the recognition of the processes that are associated with the transfer of mass between the layers (lower, middle and upper) of the continental crust. The study of migmatites becomes possible with the exhumation of rocks in syn and post orogenic events. During partial melting, the rocks are kept at specific pressure and temperature conditions, which can be recognized through the characterization of first and second order features and petrography of the migmatites. The migmatites of the internal zone of the Brasilia Belt, in the center-southeast of the Tocantins Province, occur in the middle of a Belt of Orthogneisses and Granulites juxtaposed to the Araxá Group. Despite the various occurrences of migmatites associated with these portions of the Southern Brasília Belt, the characterization of partial melting processes in these rocks still represents a large gap in knowledge. This work brings as its main debate the characterization of partial melting in the migmatites of the region of Cascalho Rico, MG. For this, a regional geological mapping was carried out with a focus on the description of mafic granulites that develop migmatitic structures. The analysis of the migmatites was focused on the identification of the first and second order morphologies, in addition to the petrography in transmitted and reflected light, which allowed the definition of textures related to the partial melting process. In this context, it was possible to characterize the reactions that led to partial melting and estimate the pressure and temperature conditions that occurred in the process.