GENESIS OF NEOPROTEROZOIC GRANITOID MAGMATISM IN THE EASTERN ARAÇUAÍ FOLD BELT, EASTERN BRAZIL: FIELD, GEOCHEMICAL AND SR ND ISOTOPIC EVIDENCE.

JOIL JOSÉ CELINO, NILSON FRANCISQUINI BOTELHO, MÁRCIO MARTINS PIMENTEL

Resumo


The Neoproterozoic granitoid magmatism of the Araçuaí Fold Belt (AFB) is an important element for the discussion of the evolution of this belt and its relationships with the African counterpart, the West Congo Belt. In the eastern part of the AFB, four different granitoid suites were recognized. The Nanuque Suite (NQS) comprises syn-tectonic peraluminous cordierite-bearing monzogranites. The São Paulinho Suite (SPS) consists of Th-rich peraluminous two mica or biotite- only granitoids. Calc-alkalic granitoids with magmatic epidote were grouped into the Itagimirim Suite (ITS) and post-tectonic charnockitic rocks were grouped into the Salomão Suite (SLS). Sm-Nd mineral isochron and Rb-Sr isochron yielded ages of respectively 761 Ma and 714 Ma for the Nanuque and São Paulinho suites. The general Sr-Nd isotopic characteristics of the granitoid suites and some country rocks indicate that the parental magmas were mostly the product of melting of the Paraíba do Sul metasediments. The chronological and genetic evolution of the Neoproterozoic plutonism can be envisaged in a model of east-dipping subduction zone, followed by a continental collision between the Brasiliano/Pan-African São Francisco (Brazil) and Congo (Africa) cratons and final episodes of uplift and collapse.

Palavras-chave


Granites; Petrogenesis; Geochemistry; Isotopes; Neoproterozoic.

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