Produção Nacional
THE NEOPROTEROZOIC GOIÁS MAGMATIC ARC, CENTRAL BRAZIL: A REVIEW AND NEW Sm-Nd ISOTOPIC DATA
2000; Sociedade Brasileira de Geologia; Volume: 30; Issue: 1 Linguagem: Inglês
10.5327/rbg.v30i1.754
ISSN2317-4889
AutoresMárcio Martins Pimentel, Reinhardt A. Fuck, Simone Maria Costa Lima Gioia,
Tópico(s)Geochemistry and Elemental Analysis
ResumoIn this study we review the main characteristics and geochronological/isotopic data of metaigneous rocks of the juvenile Neoproterozoic Goias Magmatic Arc in central Brazil. Some new Sm-Nd isotopic data are also presented for both the southern (Arenopolis) and northern (Mara Rosa) sections of the arc. In the south, granitoids of the Choupana-Turvania area yielded a Sm-Nd whole-rock isochron age of 863 ± 97 Ma and a Nd (T) of +4.1. T model ages vary between 0.94 and 1.13 Ga. Metavolcanic rocks in the Pontalina region have a Sm-Nd whole-rock isochron age of 762 ± 77 Ma and a Nd (T) of+2.9. T DM values are between 0.96 and 1.10 Ga. In the northern section of the Goias Arc, mylonitic gneisses of the Serra Azul ridge, an important N30E snear zone, were investigated and have a Sm-Nd isochron age of 3058 ± 120 Ma and initial a Nd value of ca. +2.1. This data suggests that the Serra Azul ridge might represent either a mylonitized fragment of the Archaean terranes exposed just to the south, or the sialic basement of the Araguaia Belt supracrustals, along the eastern margin of the Amazon Craton. The geochronological data available so far indicate a long history of arc formation and amalgamation on the western margin of the Sao Francisco- Congo continent during the Neoproterozoic. The history of convergence of continental masses is partially coeval with the fragmentation of Rodinia, indicating that the western margin (present geographic reference) of that continent occupied a peripheral setting in the Rodinia supercontinent.
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