Analytical procedures

Isotopic analyses performed at the Geochronology Laboratory of the University of Brasília followed the procedures described in Gioia and Pimentel (2000) and used a Finnigan MAT 262 mass spectrometer in static mode. Uncertainties regarding the Sm/Nd and 143Nd/144Nd ratios are considered to be better than ± 0.1% (1s) and 0.00001 (1s), respectively, based on the repeated analysis of international rock standards BCR-1 and BHVO-1. 143Nd/144Nd ratios were normalized to a 146Nd/144Nd ratio of 0.7219. Nd procedure blanks were less than 100pg. eNd (t) values were calculated for t = 600 Ma, taken as the average age of the peak of metamorphism during the Brasiliano Orogeny in this region (Heilbron, 1995; Trouw et al., 2000). TDM results follow the depleted-mantle model of DePaolo (1981).