UnB - Instituto de Geociências - Produção Científica
RESUMOS/ABSTRACTS de artigos publicados em revistas com corpo editorial

Neoproterozoic crustal accretion in central Brazil 

Pimentel M.M.
Fuck R.A. 

Geology(1992), 20(4): 375-379. 
Key words: geochronology; crustal accretion; mantle; Neoproterozoic; Brazil; Tocantins Structural Province 

Abstract

Recent geochronological studies have demonstrated the existence of several Neoproterozoic orthogneiss and metavolcanic arc suites (ca. 900 to 600 Ma) in the southern part of the Tocantins province. Nd and Sr isotopic characteristics of these metamorphic suites are primitive: initial 87Sr/86Sr ratios vary from c.0.7024 to c.0.7042 and initial Nd values are positive, varying between +0.2 and +6.9. The most primitive initial Sr and Nd isotopic compositions are very similar to model depleted-mantle compositions at the time of formation of the original magmas. The mantle-like characteristics of these arc suites in western Goias contradict previous ensialic evolution models for the Tocantins province and reveal that crustal accretion processes were important in large areas of central Brazil during Neo-proterozoic time.