Insights on the evolution of the interference zone between the Southern Brasília and the Central Ribeira orogens, SE Brazil: Implications from new U-Pb ages of late- to post-collisional granitoids

Abstract

In southeastern Brazil, the Mantiqueira Province, formed during the Brasiliano-Pan-African Orogenic Cycle, records a complex and diachronous evolution. Contextually, the Southern Brasília (SBO) and Central Ribeira (CRO) orogens developed between the Ediacaran and Cambrian. The boundary between these orogens, and the overprinting of the older SBO by the younger CRO, remains a topic of debate, particularly in the Socorro Nappe, which spans the border region of Rio de Janeiro, Minas Gerais and São Paulo states. To contribute to this debate and to improve understanding of the tectono-magmatic evolution, this study presents field observations, petrographic data and new U-Pb zircon ages (LA-SF-ICP-MS) for four granitoids interpreted as crystallization ages: the Getulândia (608.5 ± 7.1 Ma), Capivara (602.4 ± 12 Ma and 604.1 ± 6.9 Ma) and the porphyritic Serra do Lagarto and Maromba granites (589.8 ± 8.4 Ma and 573.9 ± 4.4 Ma, respectively). Combined with published data, two petrographically and geochronologically similar groups are proposed: an older group (ca. 610-600 Ma), interpreted as late-tectonic, and a younger group (ca. 595-570 Ma), interpreted as post-tectonic relative to the evolution of the SBO. These granitoids, locally affected by shear zones and metamorphism linked to the CRO, define an extensive late- to post-collisional magmatic province from Getulândia (RJ) to Apiaí (SP). It is proposed that they were emplaced during the orogenic collapse of the SBO, later overprinted by CRO events, supporting the interpretation that the study area, which lies within the Socorro Nappe, is tectonically associated with the Paranapanema paleocontinent, and located within the interference zone between the two orogens.