Paleoproterozoic accretionary and collisional processes and the build-up of the Borborema Province (NE Brazil): Geochronological and geochemical evidence from the Central Domain

Abstract

a b s t r a c tSeveral Brasiliano-Pan-African belts consist of large areas of reworked Paleoproterozoic rocks. Characterization of these rocks is needed to place better controls on Precambrian paleogeographic reconstructions. The Borborema Province, northeastern Brazil, occupies a central position in West Gondwana configuration, and knowledge of its geological evolution is crucial to infer relationships between Paleoproterozoic units in South America and Africa. Here, we report UePb ages, major-and trace-elements analyses and SmeNd isotopic data for orthogneisses in the eastern portion of Central Domain. The dominant basement units in the study area are banded gneisses of intermediate composition and relatively juvenile character, and migmatitic gneisses of granitic composition with Archean Nd T DM model ages. One sample of the banded gneiss yielded a weighted 207 Pb/ 206 Pb age of 2096 ± 23 Ma and an upper intercept age of 2044 ± 27 Ma, which we interpret, respectively, as ages of crystallization and metamorphism. Two large units of migmatitic gneiss in the southern and central parts of the area gave ages of, respectively, 2057 ± 20 Ma and 2055 ± 23 Ma; an orthoamphibolite associated with the latter yielded crystallization age of 2042 ± 11 Ma and metamorphic age of 1996 ± 13 Ma. All these rocks have geochemical signatures typical of subduction zone-related magmas. Combined with evidence provided by previous studies, we suggest that the evolution of the study area starts with island arc construction around 2.2 Ga, leading to an expressive volcanic arc edifice by 2.13 e2.10 Ga. By 2.06 Ga, the crust had evolved enough to become intruded by magmas formed at the mantle wedge of the now largely continental magmatic arc, which continued to be intruded by mantle melts until at least 2.04 Ga. An augen gneiss in the northern part of the area, with an age of 2109 ± 15 Ma, and a migmatitic gneiss with a much older age (2183 ± 9 Ma), both of which have geochemical characteristics akin to intraplate magmas, suggest that crustal reworking also took place. The 1981 ± 23 Ma age of a small body of peraluminous felsic gneiss may be related to regional metamorphism and syncollisional magmatism at c. 2.0e1.98 Ga.

Geological and isotopic characteristics of granites from the Western Pernambuco-Alagoas Domain: implications for the crustal evolution of the Neoproterozoic Borborema Province

“…In one of them, the Borborema Province is considered the product of an accretionary event involving the collage of several allochthonous terrains Santos et al 2004). The other model suggests an intra-plate setting in which reworking of pre-existing Archean-Paleoproterozoic crust and deposition of Proterozoic volcano-sedimentary sequences took place in an intra-continental environment (Neves 2003;Neves et al 2014;. A new model proposed by Ganade de Araújo et al (2014), based on some aspects of the mentioned ones, suggests that the Borborema Province underwent two major collisional events, one between 620 and 610 Ma and another between 590 and 580 Ma.…”

Geocronologia e aspectos estruturais e petrológicos do Pluton Bravo, Domínio Central da Província Borborema, Nordeste do Brasil: um granito transalcalino precoce no estágio pós-colisional da Orogênese Brasiliana

“…É composto predominantemente por ortognaisses, além de sequências supracrustais geralmente migmatizadas. Na área de estudo, os termos ortoderivados correspondem a gnaisses de composição intermediária a ácida e rochas metamáficas associados ao Complexo Cabaceiras (idade de 2055 Ma -Lages e Marinho 2012; Neves et al 2015) e augen gnaisses de composição sienogranítica a monzogranítica, representados pelo Ortognaisses São Joãozinho (idade de 2109 Ma -Lages e Marinho 2012; Neves et al 2015) (Fig. 2).…”

“…2). As idades-modelo T DM para essas rochas variam entre 3,3 e 2,5 Ga, indicando a presença de crosta arqueana retrabalhada Lages 2012;Lages e Marinho 2012;Neves et al 2015). Esses dados contrastam com as idades-modelo T DM obtidas para o terreno Alto Pajeú, que mostram valores caracterís-ticos entre 1,0 e 2,0 Ga (Rodrigues e Brito-Neves 2008).…”

“…1), próximo ao limite do terreno Alto Pajeú, e foi alojado em ortognaisses graníticos de alto grau metamórfico do Complexo Cabaceiras. O quimismo da rocha encaixante remete a granitos, granodioritos e tonalitos (subordinados), cálcio-alcalinos de médio K com características de arco vulcânico Neves et al 2015).…”

“…Regionalmente, tais litologias, que incluem componentes graníticas a granodioríticas e, em menor parte, tonalíticas, estão presentes no Complexo Cabaceiras, encaixante do pluton, que possui características anidras, portando, em parte, paragêneses de fácies granulito. Dentre essas paragêneses minerais pode-se citar forsterita-hercinita-diopsídio metacarbonatos (Carmona 2006;Marinho et al 2008;Ventura Santos et al 2013;Santos et al 2013;Lages 2012) e granada granulito charnoquítico mesopertítico (Neves et al 2015;Lages 2012).…”