Proveniência das rochas metassedimentares dos diferentes terrenos tectono-estratigráficos da Faixa Ribeira Central, com base em dados U-Pb e Lu-Hf obtidos em grãos de zircão detríticos

Abstract

This work involves the use of U-Pb and Lu-Hf methodologies, applied to detrital zircon crystals, to understand provenance in Neoproterozoic metasedimentary associations from different domains of the Central Ribeira Belt in Southeastern Brazil. The following groups are evaluated: a) São Fidélis from the Coastal Domain, b) Bom Jesus de Itabapoana from the Cambuci Domain, c) Paraíba do Sul, and d) Raposos from the Juiz de Fora Domain. The São Fidélis Group presents sources with ages between ca. 3.3 Ga and 2.5 Ga, associated with granitoids present in the São Francisco and Congo paleoplates, and robust contributions from the Paleoproterozoic and Mesoproterozoic. Contributions from the Rhyacian-Orosirian between 2.2 and 2.0 Ga suggest events recorded in the São Francisco Craton (SFC) corresponding to the development of magmatic arcs, and ages around 1.9 Ga are attributed to orthogneisses from the basement of the Cabo Frio Terrane, the last to join the other terranes of the Central Ribeira Belt. Detrital contributions from the late Paleoproterozoic and Mesoproterozoic, around 1.7 and 1.5 Ga, with a juvenile signature, would be related to extensive anorogenic episodes in the SFC. It presents crystals with ages between 1.5 and 1.0 Ga, common in the corresponding terrains on the African side. Neoproterozoic ages obtained in detrital zircon grains around 900 Ma with a high Th/U ratio indicate extensional magmatism in the SFC, and contributions between 898-823 and 794-620 Ma are related to Neoproterozoic juvenile magmatic arcs of the Eastern Terrane (Serra da Prata and Rio Negro). Regarding the Bom Jesus de Itabapoana Group, the obtained data present crustal signature populations, concentrated in the Neoproterozoic, in age intervals 206Pb/208U around 553-609 Ma, around 615-638 Ma, around 640-699 Ma, and around 728-778 Ma. Data from the Paraíba do Sul Group indicate Archean contribution, with ages between 3220 and 2560 Ma, and Paleoproterozoic sources. with a main mode at 2.1 Ga. This siliciclastic metasedimentary sequence shows contributions related to the Paleoproterozoic-Archean basement itself. Neoproterozoic ages were obtained in grains with recrystallization textures compatible with the development of magmatic arc systems in the Ribeira and Araçuaí belts. Regarding the Raposos Group, the collected data indicate Archean sources, with ages between 3378 Ma and 2514 Ma, and Paleoproterozoic sources with ages ranging from 2383 to 1624 Ma. In the sector of increasing metamorphic conditions towards the top of the tectonic stack (Central Sector), contributions of older ages are restricted. The source areas for these intervals, with juvenile and crustal signatures, would be associated with the Juiz de Fora and Mantiqueira complexes and the Archean paleoplates. The supracrustal rocks of the Western (Raposos Group) and Paraíba do Sul (Paraíba do Sul Group) terrains, with documented basement associations, indicate a significant contribution from the Paleoproterozoic around 2.1-2.2 Ga.