Idade U-Pb shrimp de zircão de Suítes Gnaisses Greníticos da Serra dos Órgãos e do Rio de Janeiro: implicações para a (560 ma) colagem brasiliano/pan-africana

Abstract

Recent systematic geological mapping at a scale of 1:400,00 scale revealed that the State of Rio de Janeiro State is na important field-laboratory to test the connections of the Costeiro Domain of the Ribeira Belt (former Rio Doce Orogen) and the Aracuai Orogen. The regional geological mapping was supported by zircon U-Pb SHRIMP geochronological data of three synorogenic, thrust-related key plutons, namely the pre- to syn-collisional Serra dos Orgaos Batholith and the syn-collisional Corcovado and Pao de Acucar gneissic granites (Rio de Janeiro Suite). These plutons have a chemical and tectonic signatures akin to the Australian I-and S-type continental arc granitoids. The Serra dos Orgaos Batholith yielded a crystallization age of 569 ± 6 Ma, whereas the syncollisional Pao de Acucar and Corcovado gneissic granites ages of 559 ± 4 Ma and 560 ± 7 Ma, respectively. The new data, supported by the integration of the geochronological data on the Aracuai Orogen magmatism in Espirito Santo and Minas Gerais states, cast new lights on the regional Neoproterozoic (Brasiliano) evolution. Similar late Precambrian ages, spanning from ca. 580-560 Ma, recently obtained on similar syn-collisional plutons from the northern segment of the Aracuai Orogen, highlights the synchronous development of the collisional event in Costeiro Domain of Rio de Janeiro State and in the northern domain of the Aracuai Orogen and, accordingly, the synchronicity of the Neoproterozoic orogenic collage in both domains. As far as the Pan-African connections are related, the age of the collisional peak in the western African orogens (West Congo, Kaoko, Damara, Gariep and Saldania) are also synchronous with the ca. 560 Ma Brasiliano collisional event. However, the data do not confirm previous correlation of this segment with the adjacent southwestern Paranapiacaba Orogen (Ribeira Belt), owing to the much older collisional climax ( ca. 630 Ma) dated on the latter.