GEOLOGY AND PETROLOGY OF THE S-TYPE MAGMATISM OF THE ESTRELA DO SUL SUITE, SOUTHERN BRASÍLIA BELT

Geology and petrography of the S-type magmatism of the Estrela do Sul Granitic Suite, Southern Brasília Belt

Abstract

The Neoproterozoic granitic rocks of the Estrela do Sul Suite outcrop near the city of the same name, being mainly
exposed along the bed of the Bagagem River. The igneous bodies are located in the western portion of Minas Gerais State, in the Alto Paranaíba region, within the southern sector of the Brasília Belt, occurring east of the erosional escarpments of the Peripheral Depression Geomorphological Unit. The magmatic suite rocks intrude lithologies of the metavolcanosedimentary sequence of the Araxá Group and generally form plutonic bodies with circular to elliptical shapes, covering an area of approximately 21 km². The suite is represented by three stocks named as follows: the main Estrela stock and the smaller Limeira and Itambé bodies. These bodies are dominantly monzogranitic, with rare and local syenogranitic compositions, showing equigranular to inequigranular textures, ranging from fine- to coarse-grained, hololeucocratic, isotropic to weakly anisotropic. Eight distinct facies are recognized, composed of variable proportions of microcline, oligoclase, quartz, and aluminous minerals such as biotite, muscovite, garnet, and tourmaline. Locally, aplitic and pegmatitic rocks occur, representing late magmatic phases, one of the most prominent of which is known as the Limeira pegmatite. The granitic magmatism, characteristic of S-type suites, is related to crustal melting during the evolution of the Brasília Orogenic Belt.