DEGEO - Departamento de Geologia
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/8
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Resultados da Pesquisa
Item Adsorption of gaseous elemental mercury on soils : influence of chemical and/or mineralogical characteristics.(2019) Montoya, Juan Andres; Lena, Jorge Carvalho de; Windmoeller, Claudia CarvalhinhoGaseous elemental Hg is stable enough to be transported over long distances. Some of the most important sources of Hg in the atmosphere are artisanal gold mining activities and forest fires. Both of these sources are particularly prevalent in the Amazonia region. Information regarding the capacity of soils for retaining Hg transported by the atmosphere is very important for understanding the metal cycle in the environment. The aim of this work was to study gaseous elemental Hg adsorption in soils with different physical and chemical characteristics. For this purpose, soils from different regions in Brazil and Colombia influenced or possibly influenced by gold mining activities and forest fires were studied. Hg adsorption tests were conducted by exposing soil samples to a gaseous elemental Hg atmosphere for 144 h. The total Hg concentration (THg) and Hg oxidation states were monitored using a direct Hg analyzer. Sample characterization analyses were performed. THg values obtained before the adsorption tests were 43–413 and 144–590 µg kg−1 for grain size fractions below 2 and 0.063 mm, respectively. The predominant species found was Hg2+, with abundance levels from 68% to 99%. The results show a wide range of enhanced Hg retention capacities among the samples, ranging from 13 to 2236 times the initial concentration, and the speciation results demonstrate a decrease in the oxidized species range, from 21% to 78%. The statistical analysis indicated the importance of Mn-bearing minerals for the processes of adsorption/oxidation of gaseous elemental Hg in soils. These results contribute to the elucidation of the processes that occur with Hg at the soil/atmosphere interface and may help to explain the high concentrations of Hg found in Amazonian soils where no gold mining activities are practiced.Item Application of multivariate statistic of U, Th and Pb concentrations and Pb Isotopic signatures in the assessment of geogenic and anthropogenic sources in a U-mineralized area.(2019) Vecchia, Adriana Monica Dalla; Lena, Jorge Carvalho de; Ladeira, Ana Cláudia QueirozThis work presents a Principal Component Analysis (PCA) study using Pbi- sotope signatures and U, Th and Pb concentrations from groundwater, sedi- ments and rocks (granites and orthogneisses) of the Complex of Lagoa Real (Bahia, Brazil). This area is naturally enriched in U and Th, with the occur- rence of Pb derived from the radioactive decay of the elements (238U, 235U and 232Th) in the form of their stable isotopes 206Pb, 207Pb and 208Pb in addition to the natural isotope 204Pb. Sampling was carried out in the rainy season (De- cember to January) and the points were selected according to regional hy- drology and geology. Thirty samples were analyzed: 12 of groundwater (AP) and 18 of sediments (S). The results show that the use of isotopic ratios allows discrimination between geogenic and anthropogenic samples. This informa- tion is not obtained using only the analysis of concentration data. Statistically, the isotopic data of Pb stand out as an efficient tool in the characterization of sources in the scenario investigated, allowing an effective environmental monitoring and a better management of the mining activities.Item Assessment of the molecular structure of an intermediate member of the triplite-zwieselite mineral series : a raman and infrared study.(2014) Frost, Ray Leslie; Xi, Yunfei; López, Andrés; Moreira, Viviane Amaral; Cipriano, Ricardo Augusto Scholz; Lima, Rosa Malena Fernandes; Gandini, Antônio LucianoThe mineral series triplite-zwieselite with theoretical formula (Mn2þ)2(PO4)(F)-(Fe2þ)2(PO4)(F) from the El Criolo granitic pegmatite, located in the Eastern Pampean Ranges of Cordoba Province, was studied using electron microprobe, thermogravimetry, and Raman and infrared spec- troscopy. The analysis of the mineral provided a formula of (Fe1.00, Mn0.85, Ca0.08, Mg0.06)P2.00(PO4)1.00(F0.80, OH0.20)P1.00. An intense Raman band at 981cm1 with a shoulder at 977cm1 is assigned to the PO3 4 n1 symmetric stretching mode. The observation of two bands for the phosphate symmetric stretching mode offers support for the concept that the phosphate units in the structure of triplite-zwieselite are not equivalent. Low-intensity Raman bands at 1012, 1036, 1071, 1087, and 1127 cm1 are assigned to the PO3 4 n3 antisymmetric stretching modes. A set of Raman bands at 572, 604, 639, and 684 cm1 are attributed to the PO3 4 n4 out-of-plane bending modes. A single intense Raman band is found at 3508 cm1 and is assigned to the stretching vibration of hydroxyl units. Infrared bands are observed at 3018, 3125, and 3358 cm1 and are attributed to water stretching vibrations. Supplemental materials are available for this article. Go to the publisher’s online edition of Spectroscopy Letters to view the supplemental file.Item Dois séculos de viagens motivadas pelo (re)conhecimento da geodiversidade : bases metodológicas e teóricas para inventariação, qualificação e quantificação de valores da geodiversidade relevantes ao desenvolvimento do geoturismo no Caminho dos Diamantes (Estrada Real, Minas Gerais, Brasil).(2018) Paula, Suzana Fernandes de; Castro, Paulo de Tarso Amorim; Castro, Paulo de Tarso Amorim; Pires, Maria do Carmo; Azevedo, Úrsula Ruchkys de; Machado, Maria Marcia Magela; Nolasco, Marjorie CseköDesde 2003 o Instituto Estrada Real gere um produto que tem por finalidade organizar, fomentar e gerenciar ações e infraestrutura para o desenvolvimento de possiblidades turísticas em quatro caminhos distintos que compões a Estrada Real, no sudeste brasileiro. O presente trabalho busca propor uma nova abordagem àquelas que já são utilizadas no referido produto: o geoturismo. O recorte dado aos estudos foi o segmento do Caminho dos Diamantes, que liga os municípios de Ouro Preto e Diamantina, em Minas Gerais Foram consultadas bibliografias e relatos de viajantes naturalistas do século XIX que percorreram a região e que corroboram com o entendimento de que o patrimônio geomineiro sempre foi um atrativo para aqueles municípios, visto a toponímia deste lugares que, em sua maioria, remetem à aspectos da geodiversidade. Sendo assim, utilizando de metodologias capazes de qualificar, quantificar, dimensionar e comparar geossítios, foi possível estabelecer parâmetros que apontam as prioridades no desenvolvimento de atividades de interesses geoturísticos nos municípios que fazem parte deste produto turístico já consolidado. A partir das informações, cálculos, mapas e sistematização de todos os produtos obtidos, foi possível estabelecer uma forma de dar visibilidade e demonstrar a viabilidade d desenvolvimento do geoturismo no Caminho dos Diamantes já que se trata de uma abordagem pouco utilizada ou desconhecida.Item Protocolo de avaliação e inventariação de lugares de interesse geológico e mineiro : bases para um turismo científico e aplicação em um circuito geológico e mineiro urbano (Ouro Preto) - MG.(2013) Paula, Suzana Fernandes de; Castro, Paulo de Tarso Amorim; Castro, Paulo de Tarso Amorim; Costa, Adivane Terezinha; Azevedo, Úrsula Ruchkys deEm função da sua história e dos recursos que possui, Ouro Preto, localizada ao Sul do Quadrilatero Ferrífero, é uma das mais importantes províncias minerais do Brasil e foi o cenário da descoberta do ouro e da nucleação dos primeiros centros urbanos brasileiros afastados da zona litorânea. A descoberta do ouro na região ao final do século XVII, representou um marco da interiorização e urbanização do Brasil. Estes trabalhos resultaram em uma intensa modificação da paisagem, com a remoção de grandes volumes de rochas, escavação de minas e construção de aquedutos. Com o final do ciclo do ouro, as minas foram abandonadas resultando em um importante acervo arqueológico representado por aquedutos, sarilhos, galerias subterrâneas, ruínas de mundéus, barragens para retenção de água para as atividades mineiras e diversas edificações. Quanto ao patrimônio mineiro, os registros da mineração de ouro a partir do século XVIII na região das minas são de grande importância e proporciona o desenvolvimento estudos e trabalhos condizentes com a divulgação do patrimônio geológico e mineiro, para turistas e moradores locais, valorizando e envolvendo as comunidades para o significado deste patrimônio. A Geomorfologia Antropogênica tem como objeto de estudo as geoformas produzidas bem como aquelas modificadas pelas atividades humanas. Em regiões mineiras, como o Quadrilátero Ferrífero em Minas Gerais, a mineração tem sido o principal atividade antrópica a afetar e modificar a paisagem. A partir das premissas da geoconservação são analisados pontos em que são evidentes as ações antrópicas na modificação da paisagem: tanto pela mineração quanto pela instalação de infraestrutura urbana que subsidiava as pessoas que nela trabalhava. Esses pontos integram um roteiro turístico urbano Ouro Preto de base científica e educativa. A difusão de informações sobre a realidade geológica que fazemos parte ainda é deficiente, dificultando seu entendimento pela grande maioria das pessoas, por isso, foi elaborado, no Departamento de Geologia da Universidade Federal de Ouro Preto, o Protocolo de Avaliação e Inventariação de Lugares de Interesse Geológico e Mineiro. Esta metodologia baseia-se na descrição e quantificação de aspectos e variáveis relativas aos geossítios selecionados possibilitando a identificação, qualificação e comparação entres determinadas localidades e/ou variáveis.Item Tectonic control of erosion in the southern Central Andes.(2018) Val, Pedro Fonseca de Almeida e; Venerdini, Agostina L.; Ouimet, William; Alvarado, Patricia; Hoke, Gregory D.Landscape evolution modeling and global compilations of exhumation data indicate that a wetter climate, mainly through orographic rainfall, can govern the spatial distribution of erosion rates and crustal strain across an orogenic wedge. However, detecting this link is not straightforward since these relationships can be modulated by tectonic forcing and/or obscured by heavy-tailed frequencies of catchment discharge. This study combines new and published along-strike average rates of catchment erosion constrained by 10Be and river-gauge data in the Central Andes between 28◦S and 36◦S. These data reveal a nearly identical latitudinal pattern in erosion rates on both sides of the range, reaching a maximum of 0.27 mm/a near 34◦S. Collectively, data on topographic and fluvial relief, variability of rainfall and discharge, and crustal seismicity suggest that the along-strike pattern of erosion rates in the southern Central Andes is largely independent of climate, but closely relates to the N–S distribution of shallow crustal seismicity and diachronous surface uplift. The consistently high erosion rates on either side of the orogen near 34◦S imply that climate plays a secondary role in the mass flux through an orogenic wedge where the perturbation to base level is similar on both sides.Item Regional landscape response to thrust belt dynamics : the Iglesia basin, Argentina.(2018) Ruetenik, Gregory A.; Hoke, Gregory D.; Moucha, Robert; Val, Pedro Fonseca de Almeida eIntermontane basins are often the result of regionally variable uplift in tectonic settings. Wedge-top basins, a type of intermontane basin, form along thrust faults within a fold and thrust belt, and provide an ideal environment to study the regional fluvial and surface response to local variations in rock uplift. This study simulates the formation and evolution of an intermontane basin using a landscape evolution model. The modelling results demonstrate that large trunk streams maintain connectivity during basin formation for two reasons: (1) their stream power is enhanced by the capture of smaller streams, enabling them to incise through the uplifting downstream region, and (2) they acquire increased sediment yield to completely infill the upstream accommodation space rather than forming an endorhic basin. During active deformation of the fold-and-thrust belt, both channel slope and erosion rates are reduced upstream of the intermontane basin and these changes propagate as a wave of low erosion into the uplands. For a uniform background uplift rate in a landscape previously at steady state, this reduced rate of erosion results in a net surface uplift upstream of the basin. Following the eventual breach of the basin’s bounding structural barrier, a wave of high erosion propagates through the basin and increases the channel slope. This onset of increased erosion can be delayed by up to several million years relative to the onset of downstream uplift. Observed paleoerosion rates in paired wedge-top and foreland basin sequences, and presentday stream profiles in the Argentine Precordillera support our modelling results. Our results may be extrapolated to other foreland systems, and are potentially identifed using low-temperature thermochronometers in addition to paleoerosion rates.Item The changing course of the Amazon River in the Neogene : center stage for Neotropical diversification.(2018) Albert, James S.; Val, Pedro Fonseca de Almeida e; Hoorn, CarinaWe review geological evidence on the origin of the modern transcontinental Amazon River, and the paleogeographic history of riverine connections among the principal sedimentary basins of northern South America through the Neogene. Data are reviewed from new geochronological datasets using radiogenic and stable isotopes, and from traditional geochronological methods, including sedimentology, structural mapping, sonic and seismic logging, and biostratigraphy. The modern Amazon River and the continental-scale Amazon drainage basin were assembled during the late Miocene and Pliocene, via some of the largest purported river capture events in Earth history. Andean sediments are first recorded in the Amazon Fan at about 10.1-9.4 Ma, with a large increase in sedimentation at about 4.5 Ma. The transcontinental Amazon River therefore formed over a period of about 4.9-5.6 million years, by means of several river capture events. The origins of the modern Amazon River are hypothesized to be linked with that of mega-wetland landscapes of tropical South America (e.g. várzeas, pantanals, seasonally flooded savannahs). Mega-wetlands have persisted over about 10% northern South America under different configurations for >15 million years. Although the paleogeographic reconstructions presented are simplistic and coarse-grained, they are offered to inspire the collection and analysis of new sedimentological and geochronological datasets.Item Indirect quantitative-qualitative pedologic geomorphic characterization in sub-basin of 7th order of the middle São Francisco watershed – northern Minas Gerais state.(2019) Teixeira, Marcílio Baltazar; Martins Júnior, Paulo Pereira; Camargo, Pedro Luiz Teixeira de; Silva, Samuel Tarso daThe characterization presented in this study aims to identify and map the different types of pedogeomorphic units found in a 7th order, the Pandeiros river basin, in the upper São Francisco River (1st order basin), located in the North of Minas Gerais State. A general panoramic view of the geodiversity is presented, since the Pedogeomorphic Maps allow a visualization of the spatial distribution of the main pedogeomorphic classes, providing important information for various purposes, such as teaching, research and land-use planning. These Maps are relevant specifically for the territorial planning, even without providing data of the local use and occupation because they have strategic information for the understanding and evaluation of the landscape dynamics in region, offering subsidies to the understandings of the processes, phenomena and behaviors of the physical environment related to the different forms of interference of human actions. The Maps also provide support for environmental assessments that have been applied to identify, characterize and monitor trends in environmental aspects.Item Uso das imagens de sensores remotos para análise crítica da degradação do cerrado no Alto Médio São Francisco – Minas Gerais.(2018) Teixeira, Marcílio Baltazar; Camargo, Pedro Luiz Teixeira de; Martins Júnior, Paulo PereiraEste estudo busca compreender os níveis de progressão temporal da degradação do Cerrado em uma área localizada no Alto Médio São Francisco, no norte de Minas Gerais, durante um período aproximado de 40 anos, precisamente nos anos de 1975, 1984, 1993, 2003, 2009 e 2011. Por meio da utilização das técnicas de Processamento Digital de Imagens (PDI), foram desenvolvidos mapas temáticos em que podem ser percebidos os variados níveis de degradação do Cerrado. Assim, percebendo-se a complexidade do uso e da ocupação dos solos da região e simpliicando-se o entendimento da evolução do processo da degradação, a localidade estudada foi classiicada em seis temas fundamentais, que representam aspectos que podem ser encontrados em campo: Cerrado, plantações antrópicas, solo exposto, mata ciliar, água e “outros aspectos”. A partir dos estudos realizados, constatou-se a preocupante evolução da deterioração do Cerrado na área de interesse.