Sm-Nd isotope systematics and REE data for leucotroctolites and their amphibolitized equivalents of the Niquelandia Complex upper layered series, central Brazil: further constraints for the timing of magmatism and high-grade metamorphism

The Barro Alto, Niquelindia, and Cana Brava Complexes are major Proterozoic layered intrusions in central Brazil that were affected by high-grade metamorphism with associated ductile deformation during the Neoproterozoic (770-795 Ma). Recent studies recognized that the Niquelandia Complex comprises two petrologically distinct and tectonically juxtaposed magmatic systems: a younger Upper Layered Series to the west and an older Lower Layered Series to the east. Previous geochronological studies on Lower Series rocks suggested a Paleoproterozoic (ca 2.0 Ga) age for the Lower Series magmatic event, New trace element data matched with Sm-Nd isotope data for Upper Series samples yielded well-constrained and original geochronological information, The 1.35 Ga age of the Upper Series magmatism reported in this paper indicates a much younger age of the Upper Series compared with the Lower Series, The tectonic contact between these two distinct magmatic systems is now raised to the category of a major Paleo-Mesoproterozoic crustal discontinuity. (C) 2000 Elsevier Science Ltd. All rights reserved.