Timing and sources of granite magmatism in the Ribeira Belt, SE Brazil: Insights from zircon in situ U–Pb dating and Hf isotope geochemistry in granites from the São Roque Domain

SHRIMP U-Pb zircon dating of Neoproterozoic granites from the easternmost São Roque Domain, Ribeira Belt

“…A contribution from contemporaneous mafic magmatism is evident in some occurrences, as scattered mafic synplutonic dykes and mafic microgranular enclaves. Often more evident are evidences of contamination by assimilation of metasedimentary rocks, which may appear as xenoliths or strongly modified mica-rich enclaves (Janasi et al, 2016).…”

“…Source: Janasi et al (2016); modified from Campos Neto et al (2010). AçD: Açungui Domain; CFT: Cabo Frio Terrane; CT: Curitiba Terrane; ET: Embu Terrane; Go: Goiás Magmatic Arc; LAM: Luiz Alves Microplate; OcT: Ocidental Terrane; OrT: Oriental Terrane; PT: Paraná Terrain; SBB: South Brasília Belt; SGN: Socorro-Guaxupé Nappe; SRD: São Roque Domain.…”

“…Equally important, however, is that the spatial resolution of ~20 µm allows to avoid sites of loss of lead (e.g., fractures, inclusions of other minerals or areas subject to post-magmatic textural modification) and also, in a number of cases, circumvent small inherited zircon nuclei which, if included in the analysis, would result in ages greater than the true age of magmatic crystallization. One of our recent systematic dating programs (Janasi et al, 2016) revealed that the age of the high-K calc-alkaline (HKCA) magmatism, which formed the most voluminous plutons intruding the low-to medium-grade meta-volcano-sedimentary sequences of São Roque Domain (SRD), seems confined to a small interval (~605-595 Ma), which is ~30 Ma younger than previously admitted for these rocks, on the basis of U-Pb TIMS dating (Töpfner, 1996). This discrepancy was tentatively attributed to inadvertent inclusion of small inherited nuclei in the multigrain zircon fractions used in the TIMS analyses.…”

“…Voluminous granitic magmatism comprising a wide variety of types (Campos Neto et al, 1983) is present in the easternmost part of SRD, east of the area studied by Janasi et al (2016). Previous work by Ragatky (1998) and Ragatky et al (2013) brought important information on the petrography and geochemistry of these granites, which include, along with porphyritic biotite granites that are very similar to the typical HKCA granites from the central SRD (e.g., the Morro Azul and Imbiruçu granites), several elongated plutons with widely varied composition, from tonalites (Morro do Pão suite) to leucogranites (Serra dos Índios suite).…”

Modelagem termodinâmica de fusão parcial e metamorfismo em condições de fácies granulito: exemplo do complexo Itatins, SP

“…This tectonic province extends for about 3000 km along the Brazilian east coast, running alongside the eastern borders of the São Francisco and Paranapanema Cratons, the latter is now completely covered by the Parana Basin (Heilbron et al, 2004;Mantovani & Brito Neves, 2005). The Ribeira Belt displays NE-SW structural trend and includes several terranes with ages that range from Archean to Neoproterozoic with widespread Ediacaran arc-related to post-collision granitoids emplaced across the belt Campanha & Sadowski, 1999;Janasi et al, 2001Janasi et al, , 2015Campanha et al, 2008Campanha et al, , 2015Campanha et al, , 2016Siga Jr et al, 2009, 2011a, 2011bVlach et al, 2011;Alves et al, 2013Alves et al, , 2016Henrique-Pinto et al, 2015). Its central part is segmented by a crustal-scale transcurrent shear-zone system (Faleiros et al, 2011 and references therein) that is related to the accretion and dispersion of tectonostratigraphic terranes.…”