Investigating assembly timing of Ediacaran Serra dos ?Orgaos batholith-Hints on prolonged magmatism at Ribeira belt, SE Brazil

摘要

The Pan-African/Brasiliano orogeny, result of the West-Gondwana assembly from the Neoproterozoic to Ordo-vician, had produced the Ribeira and Aracuai belts at the edges of the Sa similar to o Francisco and Congo cratonic margins. In the central Ribeira belt, the docking of accretionary systems to the reworked continental margin of the Sa similar to o Francisco paleoplate culminated in a complex Ediacaran granite production event. Syn-to late-collisional I-and S-type granites and hybrid granitoids intruded the reworked margins and accreted continental masses, as well as the Tonian to Ediacaran juvenile magmatic arcs represented by the Serra da Prata and Rio Negro Complexes. The Serra dos ' Orga similar to os batholith is the main intrusion emplaced at the juvenile crust, forming an elongated NE-SW trending tabular body that crops out in the highland region of Rio de Janeiro State, Southeast Brazil. Geochemical and geochronological data in addition to field and petrological evidence was gathered to explore the assembly timing of the SOB granitic end-member. Zircon U-Pb SHRIMP and LA-ICP-MS geochronological data yield a prolonged emplacement timelapse for the studied granites and, along with published U-Pb ages of the SOB granodioritic end-member, enable the characterization of the Serra dos ' Orga similar to os as a composite batholith. The wide time interval of heat input inside intermediate crust is consistent with a prolonged, slow-cooling hot orogenic belt model for the Aracuai-Ribeira Orogenic System.