Caracterização petrográfica da intrusão alcalina ferragem 11, Grupiara, Minas Gerais

Abstract

The Alto Paranaíba Igneous Province (PIAP), located in the mesoregion of the same name, stands out for the abundant presence of volcanic and volcanoclastic rocks, predominantly between 80 and 90 million years old (Upper Cretaceous). Their mineralogical and geochemical compositions resemble rocks such as kimberlites, kamafugites and lamproites. The Grupiara region, the focus of this study, is home to seven intrusions recognized as part of the PIAP, present in units of the Brasília Fold Belt, such as the Araxá Group, the Goiandira Complex, the Monte Carmelo Granite Complex and the Estrela do Sul Granite Suite. One of these bodies, Ferragem 11, occurs as an intrusion in granitic rocks of the Monte Carmelo Complex and the Araxá Group, with an oval shape and a diameter of around 80 meters. Detailed petrographic analysis revealed the presence in the rock matrix of minerals such as olivine, clinopyroxene (Diopside), flogopite, perovskite, and suggests the possible existence of kalsilite. Macroscopically, clinopyroxene and olivine altered to serpentine and saponite were mainly identified as macrocrystals present in the samples. The studies indicate that the samples collected at Ferragem 11 exhibit mineralogical characteristics and chemical compositions compatible with the definition of kamafugitic rocks, strengthening the identification of these samples within this specific rock classification. This research contributes significantly to understanding the geological complexity of the region and reinforces the presence and nature of potassic alkaline mafic rocks in this region.