Evolução do conhecimento do Membro Rodeio Velho da Bacia do Camaquã, RS

Abstract

The Rodeio Velho Member, belonging to the Camaquã Basin, representes the latest magmatic event ocurred during the formation of this geological unity. The rocks of this subunity occurs in the midwest region of Sul-rio-grandense Shield and they are characterized by lava flows, shallow intrusions and piroclastics deposits with basic to intermediary composition. This magmatism is associated to distensive post-collisional events related to the latest phases of Brasiliano/Pan-African Cycle, corresponding to a neoproterozoic age. The rocks from Rodeio Velho Member are controversially classificated as tholeitic to moderately alkaline affinity or subalkaline to alkaline affinity. Generally, the informations about Rodeio Velho Member are meager and presentes differences in various aspects. With the purpose of review the rocks that occurs in this unity, a compilation of the stratigraphic, geochemistry, isotopic, petrographic, tectonics and geochronologics previous studies of the Rodeio Velho Member was realized, aiming at the discussion and interpretation of the information described by the authors who studied this magmatism. From the petrographic data acquired, it is suggested in this work that the magmatism of the Rincão da Tigra region, described by several authors as belonging to the Rodeio Velho member of the Guaritas Alogrupo, is related to the magmatism of the Hilário Formation It is also suggested more detailed studies in the belonging regions of Rodeio Velho Member.