Neoarchean And Paleoproterozoic Granitoids Marginal To The Jeceaba-bom Sucesso Lineament (se Border Of The Southern Sao Francisco Craton): Genesis And Tectonic Evolution

摘要

The sialic crust of the southern Sao Francisco craton along the Jeceaba-Bom Sucesso lineament, central-southern part of Minas Gerais (Brazil), encompasses, among other rock types, Neoarchean and Paleoproterozoic granitoids. These granitoids, according to their petrographic, lithogeochemical and geochrono-logic characteristics, were grouped into two Neoarchean suites (Samambaia-Bom Sucesso and Salto Paraopeba-Babilonia) and three Paleoproterozoic suites (Cassiterita-Tabuoes, Ritapolis and Sao Tiago). Varied processes and tectonic environments were involved in the genesis of these suites. In particular, the lithogeochemistry of the (Archean and Paleoproterozoic) TTG-type granitoids indicates an origin by partial melting of hydrated basaltic crust in a subduction environment. In the Neoarchean, between 2780 and 2703 Ma, a dominant TTG granitoid genesis related to an active continental margin was followed by another granite genesis related to crustal anatexis processes at 2612-2550 Ma. In the Paleoproterozoic, the generation ofTTG and granites s.s. occurred at three distinct times: 2162,2127 and 1887 Ma. This fact, plus the rock-type diversity produced by this granite genesis, indicates that the continental margin of the southern portion of the Sao Francisco craton was affected by more than one consumption episode of oceanic crust, involving different island arc segments, and the late Neoarchean consolidate continent. A Paleoproterozoic tectonic evolution in three stages is proposed in this work.