Diorites of the High-K Calc-Alkalic Association: Geochemistry and Sm-Nd Data and Implications for the Evolution of the Borborema Province, Northeast Brazil

Abstract

Accretion of exotic terranes during the Cariris Velhos (late Mesoproterozoic to early Neoproterozoic) and Brasiliano (late Neoproterozoic) events has been proposed as an important process of continental growth in Borborema province, northeastern Brazil. If this hypothesis holds true, it is reasonable to assume that the roots of these accreted blocks have variable chemical and isotopic compositions. Here, we investigate this possibility using lithospheric-derived high-K calc-alkalic diorites. These rocks are widespread throughout the province and occur in areas proposed to represent distinct tectonic terranes. The similar geochemical and Sm-Nd isotopic signatures of the diorites (T DM from 1.7 to 2.0 Ga), except for one pluton, impose serious limitations to the terrane accretion model in Borborema province. On the contrary, these data strongly suggest that a large portion of the province is underlain by a LILE-enriched metasomatized lithospheric mantle formed around 2.0 Ga.

Early to Late Paleoproterozoic magmatism in NE Brazil: The Alto Moxotó Terrane and its tectonic implications for the Pre-West Gondwana assembly

“…1.0 Ga (Santos et al, 2010) and followed by collage during the Brasiliano orogeny (0.6 Ga). However, Mariano et al, 2001;Neves, 2003;Neves et al, 2006 andGuimarães et al, 2012 have contested the existence of the Cariris Velhos orogeny and the model of tectonic accretion of terranes. These authors suggest instead, an intracontinental tectonic model for the Borborema Province evolution.…”

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

“…Furthermore, UePb analysis of detrital zircons from metasedimentary sequences show Paleoproterozoic age peaks in several samples (Santos et al, 2004;Neves et al, 2006Neves et al, , 2009Van Schmus et al, 2003Araújo et al, 2012;Guimarães et al, 2012), indicating that Paleoproterozoic rocks were an important, if not dominant, source for the detritus. Finally, the presence of xenocristic zircons in Brasiliano granitoids and SmeNd model ages much older than their crystallization ages (Ferreira et al, 1998;Fetter et al, 2000;Mariano et al, 2001;Da Silva Filho et al, 2002;Hollanda et al, 2003;Guimarães et al, 2004;Rodrigues and Brito Neves, 2008;Van Schmus et al, 2008Neves et al, 2008) suggest that Paleoproterozoic rocks occur extensively in the deep crust. All these lines of evidence confirm the Paleoproterozoic, particularly the 2.2e2.0 b.y.…”

Quantificação da deformação finita nos Metagranitoides Cariris Velhos na região de Alagoa Grande (PB)

“…Esta assinatura isotópica de Nd provavelmente reflete um período de acreção crustal relacionado ao "Evento Cariris Velhos" (Brito . Este evento é interpretado por alguns autores como um ciclo orogenéti-co completo, com geração de rochas e metamorfismo (Brito Neves et al, 2001a), enquanto para outros o metamorfismo é de idade brasiliana Mariano et al, 2001;.…”