GEOLOGY OF GRANITE CASCALHO RICO, A SIN-COLLISIONAL STOCK IN THE SOUTHERN PORTION OF THE BRASILIA BELT

Geology of the Cascalho Rico granite, a sin-collisional stock in the southern portion of the Brasília Belt

Abstract

The stocks of the Cascalho Rico Granitic Suite are located in the western portion of the state of Minas Gerais, exposed in the Triângulo Mineiro region, within the Alto Paranaíba. The suite is composed of three small Neoproterozoic granitic bodies intrusive into metasedimentary rocks of the Araxá Group, as well as orthogneisses and paragneisses of the Anápolis–Itauçu Complex, in the southern segment of the Brasília Belt. The exposed area of the largest stock, described in this study, the Cascalho Rico Granite, comprises syeno- to monzogranitic rocks distributed over approximately 30 km², exhibiting an irregular geometry. Contacts between the suite rocks and the host lithologies are abrupt against migmatitic orthogneisses and partially diffuse against migmatitic paragneisses of the Anápolis–Itauçu Complex. The body is predominantly composed of three main facies: Gray Equigranular Monzogranite, Pink Equigranular Monzogranite, and White Monzogranite, which display equigranular to inequigranular textures and fine- to medium-grained sizes. The rocks generally exhibit a weak foliation, as well as incipient mylonitic foliation in the contact zones with the host rocks. The essential mineralogy consists of quartz, K-feldspar, oligoclase, and biotite ± muscovite. Aplitic and pegmatitic rocks occur locally as late intrusive igneous phases. The magmatism is syn-collisional, S-type, and is associated with the main regional deformational phase, linked to the metamorphic peak, involving partial melting of metasedimentary rocks. This process is consistent with paramigmatitic rocks of the Anápolis–Itauçu Complex as possible protoliths, related to the evolution of the Brasília Orogenic Belt.

Keywords: Petrography; Mapping; Cascalho Rico Granitic Suite; Brasília Belt