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RELAÇÕES ISOTÓPICAS Rb-Sr E Sm-Nd E IDADES DO MAGMATISMO GRANÍTICO BRASILIANO DA REGIÃO LESTE DO CINTURÃO DOM FELICIANO NO RIO GRANDE DO SUL: EVIDÊNCIAS DE RETRABALHAMENTO DE CROSTA CONTINENTAL PALEOPROTEROZÓICA

1999; Sociedade Brasileira de Geologia; Volume: 29; Issue: 2 Linguagem: Inglês

10.25249/0375-7536.199929227232

ISSN

2177-4382

Autores

José Carlos Frantz, Nilson Francisquini Botelho, Márcio Martins Pimentel, Alan Potrel, Edinei Koester, Roberto Santos Teixeira,

Tópico(s)

Geography and Environmental Studies

Resumo

The granitoids belonging to the brasiliano cycle from the eastern region at the Dom feliciano Belt in the Rio Grande do Sul state have had Rb-Sr data that indicated bodies which were intruded between 800 and 585Ma. The TDM ages are suggesting the participation of an older source in their generation. This source could be represented by a long period enriched mantle, much than would be expected during the evolution of the magmatic arcs, or could be represented by the interaction between an older continental crust and mantle during a continental collision regime. The tectonic evolution of this area, the existence of a long period of time between the granitic intrusions associated to the tangential regime and to the transpressive regime ones, the isotopic relations between Sr and Nd and the very low negative values of ENdt are suggesting a strong participation of an older continental crust. This older continental crust, may be constituted by gneissic protoliths of paleoproterozoic ages and generated during the evolution of the Transamazonic Cycle, has participated in the formation of the sources of the granitic magmatism of this part of the belt. The variations of the TDM ages and of the Nd ratios in the calc-alkaline granitoids are suggesting different proportions of mixture between an older continental crust and mantle or different homogenization grades in the magmas sources. For the peraluminous granites, that have be resulted from continental crustal melt, there are indications of different sources to the different bodies.

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