Magmatismo pós-colisional na região de Caçapava do Sul, RS: petrologia do Granito Santo Ferreira

Abstract

The Sul-Rio-Grande Shield is marked by the widespread occurrence of granitic rocks associated with the Brasiliano Cycle. The western portion of the shield, a locality of the study area, has numerous granitic intrusions, such as the Santo Ferreira Granite and the Caçapava do Sul Granitic Complex. These are associated with the same geotectonic formation event, being late to the Brasilian Orogenesis. They are sub-alkaline geochemical signature rocks, equigranular with reddish color, which have very similar textures and structures. Located southeast of the Caçapava do Sul Granitic Complex and 20 km from the urban area of this municipality, the study area is located on the Granite Santo Ferreira. The Santo Ferreira Granite is composed of three distinct petrographic facies due to their mineralogical variability: the biotite-granitoid facies comprises monzogranites to quartz-monzonites; leucogranitic facies, sienogranitic to monzogranitic rocks; and the transitional facies, in turn, presents intermediate characteristics. In general, the Santo Ferreira Granite belongs to the high-K calcium-alkaline series, with peraluminous character and ETR pattern similar to the Caçapava do Sul Granitic Complex. The geological, petrographic and geochemical characteristics allowed a better understanding of the genesis of the Granite. Santo Ferreira, suggesting a formation from the same parental magma of the Caçapava do Sul Granitic Complex by mineral fractionation processes, considering the behavior of the larger elements and trace