Cambrian orogeny in the Ribeira Belt (SE Brazil) and correlations within West Gondwana: ties that bind underwater

Abstract

A 530–490 Ma tectono-metamorphic event, the Búzios orogeny, is recognized within the Ribeira Belt, along the coast of SE Brazil. Tectonic evolution started with a Late Neoproterozoic marine basin and volcanic activity at c. 610 Ma. The rocks in this basin were affected by high-grade metamorphism at c. 530 Ma, coeval with deformational phases D1–D2, which generated compressive low-angle tectonic structures with top-to-NW tectonic transport. Large recumbent folds with NW–SE axes parallel to the main stretching lineation formed during D3 as the Cabo Frio tectonic domain, the focus of this study, collided with the Oriental terrane to the NW. D4 sub-vertical shear zones are limited in extent. A new U–Pb age of 501±6 Ma is reported for zircon from an amphibolite-facies shear zone related to either D3 or D4. Post-tectonic 440 Ma pegmatites mark the final stage of tectono-magmatic activity. The Cabo Frio tectonic domain has African affinities and is exotic to the Ribeira Belt. Middle Cambrian deformational and metamorphic ages are also reported from the ‘Angolan’ Pan-African belt, the southern Kaoko and Damara belts in Namibia, and the Cuchilla Dionisio–Punta Del Este terrane in Uruguay. The occurrence of Cambrian metamorphic rocks along the present African and South American coastlines shows that Mesozoic rifting closely follows Palaeozoic sutures of West Gondwana.

The tectonic significance of the Cabo Frio Tectonic Domain in the SE Brazilian margin: a Paleoproterozoic through Cretaceous saga of a reworked continental margin

“…520 Ma onto the Ribeira Orogen. Schmitt et al (2008b) agreed that the CFTD has African affinities, but proposed that it was amalgamated into the Ribeira belt due to a westward subduction preceding continental collision. Campos Neto Schmitt et al 2009a,b;Tupinambá et al 2009;Geraldes et al 2009;Almeida et al 2009 and Peternel et al (in prep).…”

“…1). Considering this and since it is largely covered by post-Jurassic sedimentary/volcanic deposits, it has been regarded by several authors as an exotic terrane (Rosier 1957(Rosier , 1965Fonseca et al 2012;Campos Neto 2000;Heilbron et al 2000Heilbron et al , 2008Schmitt et al 2008b;Brito Neves et al 2014). One of the main reasons is that it is the only terrane that contains a Cambrian tectonometamorphic event (Buzios Orogeny; Schmitt et al 2004), with a contrasting evolution in comparison to the adjacent Neoproterozoic Oriental Terrane (Ribeira Orogen).…”

Tectonic breccia of the Cabo Frio area, State of Rio de Janeiro, Brazil, intruded by Early Cretaceous mafic dyke: evidence of the Pan-African brittle tectonism?

“…The mafic gneiss is made up mainly of amphibolite and intercalated by the granitic gneiss. It is called the São Mateus Unit (Schmitt et al, 2008a).…”

Batólito Serra das Araras: um exemplo de magmatismo granítico peraluminoso sintectônico do Ediacarano, região sudoeste do estado do Rio de Janeiro

“…550-520 Ma (Fernandes et al, 2015), cuja evolução iniciou-se em um ambiente extensional em ca. 606 Ma, representada por idades Sm-Nd de rochas vulcânicas com assinatura geoquímica de N-MORB e E-MORB (Schmitt et al, 2004(Schmitt et al, , 2008.…”