Geologia e geocronologia do Complexo Marceleza: vestígios de um arco magmático cordilherano do Terreno Paraíba do Sul, no limite entre os estados do RJ e MG

• Autor(a) principal: Corrales, Felipe.
• Data de Publicação: 2015
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/7130
• topic: Western Godwana; Ribeira Belt; Marceleza Suite; Geochronology; Magmatic arc; Paraíba do Sul Terrain; Godwana Ocidental; Faixa Ribeira; Suite Marceleza; Geocronologia; Arco magmático cordilherano; Terreno Paraíba do Sul; CNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIA

The purpose of this study is to characterize the basic to intermediate rocks of the Marceleza Complex through petrography, lithogeochemistry and geochronology. The rocks of the Marceleza complex are inserted in the Ribeira Belt, at the northwest portion of the State of Rio de Janeiro and at the border of the Minas Gerais State. The Marceleza Complex is represented by metamorphosed gabbros, diorites and monzonites that intruded the Paleoproterozoic orthogneisses (Quirino Complex) of the Paraíba do Sul/Embú Terraine. Metamorphic parageneses of the country rocks display conditions of the upper amphibolite to granulite facies. Petrographic and geochemical data suggest that these igneous rocks belonged to calcalkaline to shoshonitic series. They were tentatively subdivided into three calcalkaline groups, one with medium potassium signature and two with high potassium characteristics, and one with shoshonitic signature. The major, minor and trace elements including the REE confirm this subdivision. The REE spidergrams and other tectonic discriminant diagrams strongly suggest that these rocks were generated in magmatic arc setings. LA-MC-ICPMS U-Pb analyses performed in zircons of these rocks provided crystallization ages of between ca. 618 and 500 Ma, with a high grade metamorphic overprint of ca. 582-572 Ma. In the recent years, at least three new magmatic arcs were described in the Neoproterozoic orogenic belt in southeastern Brazil. These magmatic arcs are located in the Oriental Terrain of the belt. They show geochemical signatures and geochronological consistent with a more primitive tectonic setting, evolving from an intra-oceanic environment to cordilleran environment. On the other hand, the occurrence of other magmatic arcs over the Ocidental Terrain, as the Serra da Bolívia Complex, point to cordilleran settings, with significant Paleoproterozoic basement contribution. Moreover, the Serra da Bolívia Complex has been cited in the literature as correlate to the magmatic arc of Socorro and Galiléia/Rio Doce located at the southern of the Ribeira belt and Araçuaí belt respectively. The new data presented indicate strong similarity between the rocks of Marceleza Complex with rocks related to Serra da Bolivia Complex. The location of this new association, south of the previously described Rio Doce and Serra da Bolivia Arcs strongly favours the correlation of the cordilleran arcs located at the Embú and Socorro terranes. Finally, as these rocks have a strategic position in the more occidental cordilleran arcs of the Araçuaí-Ribeira orogenic system, the new data contribute to the tectonic evolution of the western segment of the Gondwana Supercontinent