摘要
The southern São Francisco Paleocontinent(SFP)comprises Archean nuclei and Paleoproterozoic complexes encompassing magmatic arcs juxtaposed during a Rhyacian to Orosirian orogenic event.The Juiz de Fora Complex(JFC)represents an imbricated thrust system that comprises orthogranulites with a wide compositional range formed in an intra-oceanic setting during the Siderian to the Orosirian and later accreted to the southeastern margin of the SFP.Here we report new petrological,geochemical,whole-rock Nd and Sr data,as well as zircon U–Pb ages from felsic and mafic orthogranulites from the JFC.The new data is combined with a regional compilation that enables an evaluation of the interaction between magmatism and orogenetic episodes in the context of the consolidation of São Francisco Paleocontinent during the Rhyacian–Orosirian.Pre collisional Island Arc tholeiites(IAT),Tonalites-Tron dhjemites-Granodiorites(TTGs)and sanukitoid magmatism occurred from 2200 Ma to 2085 Ma.This was followed by post-collisional magmatism,which is represented by hybrid granitoids coeval with the emplacement of E-MORB basic rocks.Crustal signatures for the Rhyacian to Orosirian evolution are highlighted by the dominance of negativeεNd(t)associated with Meso-to Neoarchean Nd TDMmodel ages as well as inherited zircon grains from the hybrid granitoids.The JFC is extensively highlighted in the literature as a primitive intra-oceanic arc,but here we propose the reworking or recycling of ancient crustal segments within the mature arc stage of the JFC,suggesting a Mesoarchean crustal source involved in the JFC evolution.
基金
the Rio de Janeiro State University and the Faculty of Geology(FGEL)for all the support from the LGPA and LAGIR labs
FAPERJ,CNPq and CAPES,and joint projects with CPRM and Petrobras,are thanked for the financial support。
