Caracterização faciológica das rochas da porção central da suíte granítica estrela do sul na mesorregião do Triângulo Mineiro e Alto Paranaíba - MG

Abstract

The petrogenetic studies related to the Neoproterozoic magmatic granite in the western portion of Minas Gerais in the Triângulo Mineiro, have been developing with advanced scientific works, studies of details and updated maps. Theres no bibliography of the association of lithofacies and faciological studies about the research area, becausa they generally involve large scale mappings. The Neoproterozoic Ediacaran magmatism represented by the Estrela do Sul Granitic Suite, located in the regions of Estrela do Sul, Cascalho Rico and Monte Carmelo in the western region of Minas Gerais state, is geologically inserted in the Tocantins Province in the southern portion of the Brasilian Belt. The Estrela do Sul Granite Suite it’s composed by seven (7) syn-tectonic granitic intrusive bodies, mainly in the Araxá Group, being the focus of this study. The central body located in the municipality of Estrela do Sul, in the north-central sector of the homonymous sheet. As a result of this research it was observed that this intrusion has an elliptical shape, N-S direction, outcropping in the form of blocks, crags and boulders composing elongated hills, monzogranite petrographic composition, equi to unequigranular texture, fine to medium grained, light gray, deformed at the edges, composed of quartz, microcline, plagioclase (oligoclase/albite), primary and secondary muscovite, biotite garnet, zircon, tourmaline, monazite, apatite, rutile, with magnetite and ilmenite as opaques. It’s possible to identify abundant pegmatitic facies rich in tourmaline and quartz in the northeastern setting of the body, identified as tourmalinites. From the geological surveys and petrographic characterization, it was possible to observe that the facies of the central body that composes the Estrela do Sul Granitic Suite is divided into three (3) distinct facies named by their coverage, the first two dominant ones named by 1. Biotite-Muscovite Medium Monzogranite, followed by 2. Muscovite-Tourmaline Medium Monzogranite. The facies one (1) and two (2) together constitute the largest extension of the area of occurrence, covering the region SE, East-Central, NE and NW, respectively, and the subordinate facies covering the southwestern portion, called facies 3. Muscovite-Biotite Thin Monzogranite. Generally classified as a two-mica granite due to muscovite and biotite, both of primary origin, which together with the presence of garnet and tourmaline concentrations, characterize its strong aluminous character compatible with the classification of peraluminous granite type that suggests a magma resulting probably from reworking of the Mesoproterozoic crust or originated by crustal fusion of the bedrock.