Paleoproterozoic greenstone-granite belts in Northern Brazil and the former Guyana Shield - West African Craton province

Abstract

The mainly meta-volcano-sedimentary Vila Nova Group and associated granites constitute separate belts, which form part of a large paleoproterozoic (mainly rhyacian) province in the Guyana Shield of which northern Brazil forms a part, and the West African Craton. In Brazil the southwestern Serra do Ipitinga and Serra Tumucumaque-Serra do Navio belts have no obvious geometrical extensions in the Guyanas or Venezuela, and may represent deposits formed at penecontemporaneous passive continental margins and ocean floor spreading centres. To the Northeast the Serra Lombarda-Tartarugalzinho and Oiapoque belts are continuations of Guianese belts. In the former the igneous rocks have geochemical characteristics of suprasubduction environments. Belts in the Guyana Shield and West African Craton have many similar features. The megaprovince evolved in a number of stages, which may have started at about 2.3 Ga, and continued with diminished activity after 2.11 Ga. Both major juvenile additions and (possibly minor) reworking of earlier crust contributed to the growth of the province. The major transcurrent deformation, responsible for the present structure of the belts, probably occurred during the later stages of evolution of the province, but metamorphism and deformation are registered even in the oldest rocks.Palavras-chave: terrenos paleoproterozóicos de greenstones e granitos; Escudo das Guianas; Norte brasileiro; Craton Oeste-Africano. RESUMOO Grupo Vila Nova, predominantemente meta-vulcanossedimentar e os granitos associados constituem cinturões que formam parte de uma grande província paleoproterozóica (predominantemente riaciana) localizada no Escudo Guianense do qual o Norte brasileiro faz parte, e no Craton Oeste-Africano. No Brasil identificam-se ambientes tectônicos diferenciados para os diferentes cinturões. No sudoeste da província os cinturões da Serra de Ipitinga, e da Serra de Tumucumaque ao Serra do Navio não encontram extensões geometricamente claras nas Guianas e Venezuela, e talvez representem depósitos penecontemporâneos formados em margens continentais passivas e bacias oceânicas. Seguindo para nordeste, os cinturões da Serra Lombarda até Tartarugalzinho e Oiapoque são continuações de cinturões presentes nas Guianas. Naquele, as características geoquímicas, tanto das rochas máficas metavulcânicas como das félsicas plutônicas posteriores, apontam para origens em zonas de supra-subducção. Os cinturões guianenses e oeste-africanos apresentam muitas feições e características semelhantes. A evolução da megaprovíncia ocorreu por etapas, desde talvez 2,3 Ga com atividade em diminuição depois de 2,11 Ga. Adições crustais, tanto juvenis quanto por retrabalhamento de crosta antiga, contribuíram para o crescimento da megaprovíncia. É provável que a deformação maior de transcorrência, responsável pela estrutura atual dos cinturões, ocorresse em fase tardia da evolução, embora mesmo as unidades mais antigas sejam deformadas e metamorfizadas.

Paleoproterozoic evolution of the Guiana Shield in Suriname: A revised model

“…Whatever the position and fate of the Archean continents, the main phase of the Trans-Amazonian Orogeny starts at its earliest around 2.26 Ga with the formation of tholeiïtic gabbros of mid-oceanic ridge or back-arc-basin origin in the Île de Cayenne in French Guiana, on the basis of recent zircon U–Pb dates and Sm–Nd data (Vanderhaeghe et al, 1998; Delor et al, 2003a,b) and in the Ipitinga greenstone in Amapá (McReath & Faraco, 2006). This early event has not yet been recognised with certainty in Suriname, but the tholeiïtic metabasalts of the Paramaka Formation might belong to the same stage of oceanic crust formation.…”

Geochemistry and U–Pb zircon ages of plutonic rocks from the Algodões granite-greenstone terrane, Troia Massif, northern Borborema Province, Brazil: Implications for Paleoproterozoic subduction-accretion processes

“…1A), for example, the Eburnean-Birimian greenstone belts of the West African Craton (e.g., Abouchami et al, 1990;Hirdes and Davis, 2002;Baratoux et al, 2011;Kock et al, 2011), Paleoproterozoic greenstone sequences in the Guyana Shield (Amazonian Craton) (e.g., Vanderhaeghe et al, 1998;Rosa-Costa, 2006;McReath and Faraco, 2006), metavolcano-sedimentary sequences of São Luis Craton (e.g., Klein et al, 2005Klein et al, , 2008, and the Rio Itapicuru and Rio Capim greenstone belts in the northern São Franscico Craton (e.g., Silva et al, 2001;Mello et al, 2006;Costa et al, 2011;Oliveira et al, 2011). Tectonic evolution for most of these greenstone terranes starts with early oceanic/back-arc basin development at 2260e2230 Ma (e.g., Abouchami et al, 1990;Silva et al, 2001;Baratoux et al, 2011;Nyame et al, 2013), followed by widespread calc-alkaline/TTG volcanism/plutonism at~2190e2120 Ma, and final continental collision and metamorphism at ca.…”

40Ar–39Ar geochronology across Archean and Paleoproterozoic terranes from southeastern Guiana Shield (north of Amazonian Craton, Brazil): Evidence for contrasting cooling histories

“…The supracrustal sequences are constituted mainly of mafic metavolcanics rocks, but a large supracrustal belt, which marks the boundary between the Amapá Block and the Carecuru Domain, also comprises meta-sedimentary rocks, composing the Ipitinga Group. In this belt, a whole-rock Sm-Nd isochron furnished an age at 2267 ± 66 Ma (McReath and Faraco, 2006). Several granite plutons, one of them dated at about 2.10 Ga, cross-cut the calc-alkaline granitoids and supracrustal belts (Rosa-Costa et al, 2006).…”