Geologia do granito Silvano associado ao Complexo Monte Carmelo, norte do distrito de Silvano, Patrocínio - MG

Abstract

This research focuses on the Brasília Belt, specifically its southern portion, characterized by an accumulation of nappes and sinistral tectonic compression, encompassing lithologies such as the Abadia dos Dourados Complex, Araxá Group, and the Monte Carmelo Complex (CMC). The study aims to enhance scientific knowledge of the local geological evolution, focusing on the CMC through facies mapping. The goal is to provide a detailed characterization of the granite body southeast of the CMC batholith, here referred to as the Silvano Granite (SG), using mapping, sample collection, and petrographic analysis. The Monte Carmelo Complex is an intrusive granite batholith associated with syntectonic and collisional magmatic events. The CMC is associated with the second magmatic event, followed by the last event, which produced S-type granites concurrently with the reworking of the region's rocks. The CMC features rocks that are compositionally classified as tonalite, granodiorite, syenogranite, and monzogranite. The SG rocks are hololeucocratic to leucocratic, with a phaneritic and inequigranular texture, ranging from fine to medium grain. The SG includes both metaluminous granites, characterized by I-type magma, and peraluminous granites, characterized as S-type. These granites were categorized into five distinct facies: S-type, A - Biotite-muscovite monzogranite/syenogranite facies, B - Muscovite-tourmaline monzogranite facies, and C - Garnet monzogranite facies; and an association of I-type facies, separated into: D.1 - Fine gray hornblende monzogranite facies and D.2 - Medium white hornblende monzogranite facies. The metaluminous granites are composed mainly of quartz, microcline, oligoclase, biotite, and hornblende, with opaque minerals as accessories, while the peraluminous granites consist of quartz, microcline, oligoclase, biotite, muscovite, and occasionally garnet or tourmaline. The Silvano Granite rocks formed in different tectonic environments, according to compositional variations and the arrangement of the bodies. The possible interpretation is that these bodies were subjected to regional tectonic stresses, resulting in their amalgamation. With the current data, it was not possible to determine the origin of the S-type granites in the Silvano Granite due to the lack of outcrops indicating contact structures with the surrounding rocks. Thus, further studies are necessary to identify the origin of the peraluminous bodies, which may be related to various bodies associated with the reworking of collisional granites, which led to the formation of S type granites, such as the Estrela do Sul Granite.