The southern Ribeira Belt in Western Gondwana: a record of a long-lived continental margin and terrane collage

Abstract

The Ribeira Belt is an ENE-trending orogen in southeastern South America associated with the Neoproterozoic and Early Cambrian assembly of Western Gondwana. Its final configuration results from the amalgamation of several Statherian to Neoproterozoic continental margin tectonostratigraphic terranes. This contribution provides a revision of the southern Ribeira Belt, encompassing the São Roque, Apiaí, Embu, Costeiro, Curitiba, and Paranaguá terranes, bounded by branches of long-lived Tonian–Ediacaran shear zone systems. An initial Statherian rifting (1750 Ma) associated with anorogenic magmatism and sedimentation is followed by Calymmian to Ectasian (1600–1200 Ma) large carbonate platforms as well turbiditic volcanosedimentary successions, including both passive and active continental margins, and possible island arc collision, making up the Apiaí and São Roque composite terranes. The Tonian is represented by the Embu Terrane accretion and orogenesis at 850–760 Ma. The Brasiliano orogeny in the terranes north of the Lancinha–Cubatão shear zone is mainly represented by 630–600 Ma granitic magmatism associated with a Barrovian metamorphism, related to a tectonic scenario evolving from subduction to oblique collisional and final post-collisional stabilization. Terranes south of the Lancinha-Cubatão shear zone display evidence of an early Ediacaran suture zone, including a high-grade complex, ultramafic suites, a paired low-P and high-P belt corresponding to a back-arc basin, and an accretionary wedge, with a metamorphic collisional peak between 590 and 585 Ma. Terrane dispersion along strike-slip shear zones occurred after 590 Ma, resulting in the final configuration of the southern Ribeira Belt, associated with anorogenic A-type granitic magmatism and pull-apart continental sedimentary and volcanic basins. The deformation in this final period may reflect a far-field stress related to continental collisions that proceed south and southeast as the docking of the Costeiro (Oriental) and Paranaguá terranes, and later the Cabo Frio Terrane collision, as well the southernmost Dom Feliciano and Kaoko final collisional process, until the upper Cambrian (500–490 Ma).