Crustal evolution of the South American Platform, based on Nd isotopic systematics on granitoid rocks

A comprehensive interpretation of the crustal evolution of the South Americ an Platform is made, based on several hundred Sm-Nd determinations from gra nitoid rocks of Brazil and part of the neighbouring countries. The histogra m of the T-DM model ages indicates small amounts of continental crust older than 3.3 Ga surviving within Archean terrains formed between 3.1 and 2.7 G a. The main period of crust formation was between 2.2 and 2.0 Ga, correspon ding to the Transamazonian orogenic cycle, and accretion of juvenile materi al continued until Neoproterozoic times, but at much slower-rates. The Transbrasiliano megasuture separates a large northwestern continental m ass, including the Amazonian and Sao Luis cratons, from a southeastern mass , formed by a collage of cratonic fragments, of which the Sao Francisco and Rio de La Plata are the largest, which took part in the agglutination of t he West Gondwana supercontinent in the Neoproterozoic. On both continental masses, crustal evolution was,similar between 3.0 and 1.7 Ga, suggesting th at they were possibly contiguous, within a Paleoproterozoic supercontinent.