U-Pb SHRIMP age determinations for the Iporanga formation, SE Brazil:: implications for the tectonic evolution of the Ribeira belt - Campanha, Ginaldo Ademar da Cruz; Basei, Miguel Angelo Stipp; Tassinari, Colombo Celso Gaeta; Nutman, Allen; Faleiros, Frederico Meira (International Gondwana Symposium, 2005)