Sr and Nd isotopic characteristics of 1.77-1.58 Ga rift-related granites and volcanics of the Goias tin province, Central Brazil

Citation
Mm. Pimentel et Nf. Botelho, Sr and Nd isotopic characteristics of 1.77-1.58 Ga rift-related granites and volcanics of the Goias tin province, Central Brazil, AN AC BRASI, 73(2), 2001, pp. 263-276
Citations number
23
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Multidisciplinary
Journal title
ANAIS DA ACADEMIA BRASILEIRA DE CIENCIAS
ISSN journal
0001-3765 → ACNP
Volume
73
Issue
2
Year of publication
2001
Pages
263 - 276
Database
ISI
SICI code
0001-3765(200106)73:2<263:SANICO>2.0.ZU;2-S
Abstract
Supracrustal rocks of the Ami Group, together with coeval A-type granites r epresent a ca. 1.77-1.58 Ga old continental rift in Brazil. Two granite fam ilies are identified: the older (1.77 Ga) group forms small undeformed plut ons, and the younger granites (ca. 1.58 Ga) constitute larger, deformed plu tons. Sr:Nd isotopic data for these rocks indicate that the magmatism is mostly p roduct of re-melting of Paleoproterozoic sialic crust. Initial Sr ratios fo r both granite families are ca 0.726 and 0.720. Most TDM model ages are bet ween 2.58 and 1.80 Ga. epsilon (Nd)(T) values are between +3.6 and -11.9. A rai volcanics are bimodal, with basalts and dacites/rhyolites interlayered with continental sediments. The felsic volcanics show Nd isotopic character istics which are very similar to the granites, and are also interpreted as reworking of Paleoproterozoic crust. Detrital sediments of the Arai Group revealed T-DM model ages between 2.4 a nd 2.16 Ga, indicating that they are the product of erosion of Paleoprotero zoic crust. The data indicate that the Arai rift system was established on crust that h ad just become stable after the Paleoproterozoic orogeny.