PETROLOGY, GEOCHEMISTRY AND MONAZITE U-Th-Pb AGES OF WEST ÁGUA RASA PALEOPROTEROZOIC POST-COLLISIONAL METAGRANITES FROM SOUTHERN SÃO FRANCISCO CRATON – BRAZIL

Petrologia, geoquímica e idades U-Th-Pb de monazitas dos metagranitos paleoproterozoicos pós-colisionais Água Rasa, oeste do Cráton do São Francisco Meridional

Abstract

During the transition of Rhyacian to Orosirian periods a collision between the Archean Divinópolis and Campo Belo metamorphic complexes occurred in southern São Francisco Craton (SFC) followed by the collapse of the orogen. In the same region, the Statherian period is marked by a huge intraplate magmatic event that is represented in the area by the Para de Minas dyke swarm. Peraluminous granitoid occurrences are reported in the region of Formiga and Itapecerica (Minas Gerais – Brazil), surrounding high metamorphic grade khondalitic paragneisses and banded iron formations. To contribute to the understanding of the tectonic context of the southern SFC during the Paleoproterozoic era, these granitic rocks are studied based on petrographic, geochemical, and monazite U-Th-Pb geochronological analyzes. They were characterized as S-type (metasedimentary origin) peraluminous metamonzogranites, with crustal geochemical signature, and genesis related to anatexis in syn- to post-collisional environment. The geochronological results yielded two groups of Orosirian (~1,90 Ga) and Statherian (~1,78 Ga) ages. These results are related, respectively, to the collapse of the Rhyacian-Orosirian orogen and to the regional warming, associated with the Avanavero-Xiong’er LIP that is represented in the area by the Pará de Minas dyke swarm.