Precise zircon U-Pb (TIMS) dating of dioritic rocks and implications for the age of the Graciosa province of A-type granites and syenites, southern Brazil - Vlach, Silvio Roberto Farias; Siga Júnior, Oswaldo; Gualda, Guilherme Augusto Rosa; Basei, Miguel Angelo Stipp; Hyppolito, Thais Nogueira; Vilalva, Frederico Castro Jobim (Symposium on Magmatism, Crustal Evolution and Metallogenesis of the Amazonian Craton, 2006)