2019-09-062019-09-062012-04-11BARRETO, Carla Joana Santos. Vulcanismo félsico paleoproterozóico do Grupo Iricoumé, NW do Pará, domínio Erepecuru-Trombetas, Província Amazônia Central: petrografia, geoquímica e geocronologia Pb-Pb em zircão e Sm-Nd em rocha total. Orientador: Jean Michel Lafon. 2012. 112 f. Dissertação (Mestrado em Geologia e Geoquímica) – Instituto de Geociências, Universidade Federal do Pará, Belém, 2012. Disponível em: http://repositorio.ufpa.br/jspui/handle/2011/11631. Acesso em: .https://repositorio.ufpa.br/handle/2011/11631The Iricoumé Group is part of the Orosirian large volcano-plutonic event in the Amazonian Craton, which comprises pyroclastic volcanic rocks with well-preserved textures and structures. The study area is located in the southwestern part of the Erepecuru-Trombetas Domain in the Guyana Shield. This area is bounded by the Paleozoic cover of the Amazonas Basin to the south and by basement rocks to the north. Petrographical studies allowed the distinction of a dominant pyroclastic volcanism (ignimbrites, reoignimbrites, lapilli-tuff related to surge and fall co-ignimbrites), and subordinate hypabissal (spessartitic lamprophyres, trachyte, rhyolite) and effusive (andesitic lava flows). Pyroclastic rocks display features indicative of pyroclastic deposition at high temperatures, suggesting generation in caldera environments. Zircon Pb-Pb ages of 1888 ± 2.5 Ma e 1889 ± 2 Ma obtained in trachytic ignimbrites from the Iricoumé Group confirm that most rocks belong to this group. On the other hand, a zircon age of 1992 ± 3 Ma obtained in a trachyandesite sample allowed the identification of a subordinate late Orosirian volcanism, already identified to the South of the Amazonas Basin, in the Tapajós Domain. Less differentiated pyroclastic rocks (compositions trachyte and dacite) have metaluminous signature, Sr positive anomalies and weak to absent negative Eu anomalies, while the more differentiated pyroclastic rocks (compositions rhyolites) have slightly peraluminous signature, strong negative Sr, P and Ti anomalies, and moderate negative Eu anomalies. Hypabissal rocks display metaluminous to peraluminous characters, strong negative Sr, Ti and P anomalies in trachyte and rhyolite, and positive Sr anomalies for the lamprophyre. In addition, these hypabissal rocks show weak to absent negative Eu anomalies. The geochemical characteristics of these rocks suggest formation in a post-collisional tectonic setting. This interpretation is accepted for volcanoplutonic associations from other domains of the central portion of the Amazonian Craton. The trachyandesites display metaluminous character with positive Sr anomalies and absent Eu anomalies, as well as an affinity with a volcanic arc setting, suggesting that these rocks were formed in subduction-related geodynamic setting. Sm-Nd results yielded Nd values between - 3.04 and +2,35 and TDM ages ranging from 1.98 Ga to 2.39 Ga, which indicate dominantly Rhyacian to Siderian crustal sources for the parental magmas without Archean crustal contributions. These new results constitute additional evidence for the large extension of the Iricoumé volcanism and for the correlate volcanic rocks in the central portion of the Amazonian Craton, reinforcing the hypothesis of the presence of a large Felsic Igneous Province (SLIP), as already described by some authors.Acesso AbertoGeocronologia Pb-PbOrosirianoCráton AmazônicoPetrografiaDissertaçãoCNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIASGEOCRONOLOGIA E GEOQUÍMICA ISOTÓPICAGEOQUÍMICA E PETROLOGIA