Tracing the continental margins of the Southern Ribeira belt, Brazil: Provenance and connections of post-Rodinia fragments

Abstract

The reconstruction of ancient continental margins encompassed in continent–continent collision is a complex task. The continental blocks generally record a multiphase evolution with interaction of tectonic settings, plate polarities, basins and their depositional architecture.The Ribeira belt (Southeast-Southern Brazil) resulted from the juxtaposition of several crustal blocks during the Brasiliano/Pan-African tectonic events (800–490 Ma) leading to the amalgamation of Western Gondwana. In this context, a series of pre-Brasiliano blocks underwent variable rates of tectonic reworking, including fragments derived from Rodinia.Some of the metasedimentary strata of the Southern Ribeira belt are representative of Late Meso- to Neoproterozoic basins which bordered these pre-Brasiliano continental fragments, such as the Capiru Group.The Capiru Group (Late Meso- to Neoproterozoic) is a low-grade metasedimentary unit that crops out on the Curitiba microplate and records passive to active continental margin stages.In this work we show new provenance data (U-Pb geochronology of detrital zircon) of the Capiru Group and compare them to the other chrono-correlative continental margin units of the region (Lajeado and lower Itaiacoca groups).Through the evolution of Capiru, Lajeado, and Itaiacoca groups we show that the post-Rodinia continental margins of the Southern Ribeira belt show similar Paleoproterozoic contributions (2,000 – 2,185 Ma) and slightly different Mesoproterozoic populations, suggesting distinct paleogeographic contexts: the Capiru Group was deposited on the Northern margin of the Curitiba-Angola block, with Mesoproterozoic “exotic” contribution (1,508 – 1,100 Ma). On the other hand, the Lajeado and Itaiacoca groups were deposited on the East-Southeastern margin of the Paranapanema continental block.