Título:	Modelagem geológica e geoquímica da Gruta do Tamboril
Autor(es):	Ribeiro, Tulio Gabriel Ramos
Orientador(es):	Santos, Roberto Ventura
Assunto:	Paleoclimatologia Hidrogeologia Hidrologia Cavernas Minas Gerais (Estado)
Data de publicação:	29-Jun-2020
Data de defesa:	5-Abr-2019
Referência:	RIBEIRO, Tulio Gabriel Ramos. Modelagem geológica e geoquímica da Gruta do Tamboril. 2019. 100 f.. Dissertação (Mestrado em Geologia) — Universidade de Brasília, Brasília, 2019.
Abstract:	Processes related to the epikarst and cave environment can significantly affect the signature of proxies in speleothems, which may generate uncertainties about paleoclimate and hydrology. In order to reduce paleoclimatic data uncertainties in the central region of Brazil, this study aims to present geological modeling of the Tamboril Cave, Unaí-MG, as well as the hydrogeochemical characterization of this cave. To understand the components of the percolation system, the area of the hill to which the cave was developed was mapped with focus on bedding and structural distribuition. It was also done 3D modeling positioning of the Tamboril Cave in the karst system. The cave was monthly monitored between September 2016 and December 2018 with the collection of rock, soil, rainwater, drips, lake and air samples. Measurements of drip rate, pH and electrical conductivity were performed at the time of collection and measurements of CO2 concentration, temperature and relative humidity of the air during the entire monitoring period. The water samples were separated in aliquots for analysis of δ 13CDIC, δ 18O and δD, concentration of metals (Ca, Mg and Sr) and 87Sr/86Sr. Analyzes of δ 13C and 87Sr/86Sr were made for host rock while for soil sample, total chemistry and 87Sr/86Sr analysis were performed. Through the modeling of the Tamboril Hill and Cave, it was interpreted that the main type of flow is seasonal through tension joints, being less influenced by diffuse flow from the soil. The isotopic composition of dissolved inorganic carbon in water is in phase with δ 13C values of the atmospheric CO2 of the cave. This variability is in anti-phase with the CO2 concentration. However, values of δ 18O and δD in general do not present such typical seasonal variability, and are homogenized and close to the average value of the local rainwater. The mean distribution values of the 87Sr/86Sr ratio ranged from 0.72131 for the monitoring point 6B and 0.72553 for lake water. It was observed that the difference between the mean values of the points has an inverse relation with the drip rate, and less radiogenic values are recorded for points with a higher drip rate and vice versa. On the other hand, the seasonal variability of the values shows an increase in the 87Sr/86Sr ratio with an increase in flow and vice versa. 6 In relation to the cation variability (Ca2+, Mg2+ and Sr2+ ) it was found that (1) preferential leaching, (2) dilution, (3) prior CaCO3 precipitation may have influenced the water chemistry. The Tamboril Cave displays a system of percolation of water in the epikarst controlled mainly by joints. The 87Sr/ 86Sr is influenced by the degree of interaction with the variable host rocks and soil, but coupled with residence time. Values of δ 13C of water and cave air seasonally co-varied and are controlled by advection of external air during the dry season and diffusion of CO2 from the soil during the rainy season. Dilution, preferential leaching and prior aragonite/calcite precipitation are the main controlling processes inducing variation in Ca, Mg and Sr concentrations at the monitored sites.
Unidade Acadêmica:	Instituto de Geociências (IG)
Informações adicionais:	Dissertação (mestrado)—Universidade de Brasília, Instituto de Geociências, Programa de Pós-Graduação em Geologia, 2019.
Programa de pós-graduação:	Programa de Pós-Graduação em Geologia
Licença:	A concessão da licença deste item refere-se ao termo de autorização impresso assinado pelo autor com as seguintes condições: Na qualidade de titular dos direitos de autor da publicação, autorizo a Universidade de Brasília e o IBICT a disponibilizar por meio dos sites www.bce.unb.br, www.ibict.br, http://hercules.vtls.com/cgi-bin/ndltd/chameleon?lng=pt&skin=ndltd sem ressarcimento dos direitos autorais, de acordo com a Lei nº 9610/98, o texto integral da obra disponibilizada, conforme permissões assinaladas, para fins de leitura, impressão e/ou download, a título de divulgação da produção científica brasileira, a partir desta data.
Agência financiadora:	CAPES
Aparece nas coleções:	Teses, dissertações e produtos pós-doutorado

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