%0 Journal Article
%T Sr and Nd isotopic characteristics of 1.77-1.58 Ga rift-related granites and volcanics of the Goi¨¢s tin province, central Brazil
%A PIMENTEL M¨¢RCIO M.
%A BOTELHO NILSON F.
%J Anais da Academia Brasileira de Ci¨ºncias
%D 2001
%I Academia Brasileira de Ci¨ºncias
%X Supracrustal rocks of the Ara¨ª Group, together with coeval A-type granites represent a ca. 1.77-1.58 Ga old continental rift in Brazil. Two granite families are identified: the older (1.77 Ga) group forms small undeformed plutons, and the younger granites (ca. 1.58 Ga) constitute larger, deformed plutons. Sr-Nd isotopic data for these rocks indicate that the magmatism is mostly product of re-melting of Paleoproterozoic sialic crust. Initial Sr ratios for both granite families are ca 0.726 and 0.720. Most TDM model ages are between 2.58 and 1.80 Ga. epsilonND(T) values are between +3.6 and -11.9. Ara¨ª volcanics are bimodal, with basalts and dacites/rhyolites interlayered with continental sediments. The felsic volcanics show Nd isotopic characteristics which are very similar to the granites, and are also interpreted as reworking of Paleoproterozoic crust. Detrital sediments of the Ara¨ª Group revealed T DM model ages between 2.4 and 2.16 Ga, indicating that they are the product of erosion of Paleoproterozoic crust. The data indicate that the Ara¨ª rift system was established on crust that had just become stable after the Paleoproterozoic orogeny.
%K Sr-Nd isotopes
%K Paleoproterozoic
%K tin granites
%K Transamazonian
%U http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652001000200010