3.3 GaSHRIMP U-Pb zircon age of a felsic metavolcanic rock from the Mundo Novo greenstone belt in the Sao Francisco craton, Bahia (NE Brazil)

Felsic metavolcanics associated with supracrustal rocks provide U-Pb zircon and Sm-Nd T-DM ages of approximately 3.3 Ga, which establish an Archean age of the Mundo Novo greenstone belt. A granodioritic gneiss from the Mairi complex, located on the eastern boundary of the Mundo Novo greenstone belt, exhibits a zircon evaporation minimum age of 3.04 Ga and a Nd model age of 3.2 Ga. These results constrain the occurrence of at least three major geological units in this area: the Archean Mundo Novo greenstone belt, the Archean Mairi gneisses, and the adjoining Paleoproterozoic (<2.1 Ga) Jacobina. sedimentary basin. The Jacobina basin follows the same trend as the Archean structure, extending southward to the Contendas-Mirante belt, in which a similar Archean-Paleoproterozoic association appears. We postulate that during the Paleoproterozoic in the eastern margin of the Gavi (a) over tildeo block, these Archean greenstone belts constituted a zone of weakness along which a late-stage orogenic sedimentary basin developed. (C) 2002 Elsevier Science Ltd. All rights reserved.