Preliminary Nd isotopic data for the Anicuns-Itaberai sequence, associated orthogeneisses, and granite intrusions, Goias, Brazil

The Anicuns-Itaberai supracrustals are exposed along a ca. 90 km long N-S belt in the central-western part of Goias. Based on field and structural characteristics, previous studies have compared it to Archaean greenstone belt associations, (Barbosa 1987, Nunes 1990). Recent work by Pimentel et al. (1996, 2000a, b) have challenged this model and suggested a much younger age for these rocks. Granitoids exposed in the vicinities of Turvania and Choupana have TDM model ages between 0.94 and 1.13 Ga and yielded a Sm-Nd whole-rock isochron of 863±97 Ma with εND(T) of ca. +4 (Pimentel et al. 2000a). Metavolcanic rocks exposed to the southeast of the Anicuns-Itaberai sequence, in the vicinities of Pontalina, have also yielded a Neoproterozoic Sm-Nd isochron age (830±9 Ma) and εND(T) of +3.1 (Pimentel et al. 2000b). These rocks, therefore, are part of the Neoproterozoic Goias Magmatic Arc, raising the question wether the neighbouring Anicuns Sequence is also part of the juvenile arc. In this paper we present the first Sm-Nd isotopic data for supracrustal rocks of the northern part of the Anicuns-Itaberai Sequence as well as for associated regional gneisses, and intrusive granites and diorites (au)