2019-09-092019-09-092018-12-27SOUZA, Thiago Pereiras de. Influência do rio amazonas nos sedimentos de fundo do rio Xingu: evidências mineralógicas e geoquímicas. Orientador: Nils Edvin Asp Neto. Coorientador: José Francisco Berrêdo Reis da Silva. 2018. 96 f. Dissertação (Mestrado em Geologia e Geoquímica) – Instituto de Geociências, Universidade Federal do Pará, Belém, 2018. Disponível em: http://repositorio.ufpa.br/jspui/handle/2011/11701. Acesso em:.https://repositorio.ufpa.br/handle/2011/11701The Xingu River is an important tributary of the Amazon River in terms of water discharge, mainly due to its unique morphology and diversified sedimentary dynamics. Hydrodynamic studies record the effect of the tide on the lower Amazon River and its spread on tributaries such as the Xingu and Tapajós rivers, both classified as tidal rivers. These studies support the hypothesis that the Amazon river is a regulating agent in sediment transport and deposition in these environments, acting as a sediment source. In view of this, this work proposed to determine the possible influence area of the Amazon river in the low Xingu river through granulometric, mineralogical and geochemical analysis. The collection points of the bottom sediments obeyed an extensive sampling network that covered 109 transverse and longitudinal collection points of the main and secondary channels of the Xingu River. The granulometric determination was performed with a laser particle analyzer. The mineralogical analyzes consisted of X-ray diffraction data (total sample and clay fraction) and petrographic description of heavy minerals. The total chemical analyzes were performed in total sample for quantification of major elements, traces and rare earth by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that the sediments of the Amazon and Xingu rivers have varying levels of sand, silt and clay and extreme textural variability. The heterogeneity of the textural composition is attributed essentially to the hydrodynamic deposition conditions of the sediments. The mineralogical analysis verified the presence of compositional trends related to clay minerals and heavy minerals, with the association between kaolinite and ultra - stable minerals for samples upstream of the Xingu river and high levels of smectite and unstable minerals for samples from the confluence region between the Xingu and Amazonas , similar to the samples of the Amazon River. Further, the analyzes suggest that the banks of the Xingu estuary act as a third possible source of sediment. Despite the diversity of textured compositions, the sediments of the two rivers did not show significant variations of major elements, traces and rare earths along the sampling stations, but the chemical alteration indexes (CIA) indicated different weather conditions in the sediment source area of the Amazon and Xingu rivers. The statistical treatment of the larger elements, traces and rare earths by PCoA and PERMANOVA, confirmed the differentiation of two large groups of samples of the Amazon River, with similarity to samples from the confluence region with the Xingu River and samples upstream of the Xingu River, corroborating patterns already indicated by the granulometric and mineralogical distribution. According to the analyzes, the influence of the Amazon River on the composition of the bottom sediments of the Xingu River was evident in the entire confluence area with the Amazon River.Acesso AbertoSedimentos (Geologia)MineralogiaGeoquímicaDissertaçãoCNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIASGEOLOGIA MARINHA E COSTEIRAGEOLOGIA