DEGEO - Departamento de Geologia

URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/8

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Assunto: search.filters.subject.Trace elements

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Agora exibindo 1 - 9 de 9
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    Amphimedon viridis marine sponge as metal bioindicator for Al, Ba, Cr, Fe and Mn.
    (2022) Moreira, Ronan Pereira Garcias; Krohling, Werther; Ferreira Júnior, Paulo Dias; Abreu, Adriana Trópia de; Nalini Júnior, Hermínio Arias; Schmitt, Elisângela Flávia Pimentel; Coutinho, Silvia Cruz Goes; Endringer, Denise Coutinho
    BACKGROUND: Bivalves, oysters, and mussels are accepted as biological indicators for marine pollutants. Heavy metals biomonitoring on the environment was this study objective using A. viridis compared with Perna perna (mollusk bivalve). The area studied included Ilha Pituã in Vila Velha – ES and Ilha do Boi and Camburi Garden Beach in Vitoria - ES. METHODS: The sample collection comprised seawater, mussel (P. perna) and sponge (A. viridis). Al, As, Ba, Cr, Cu, Fe, Pb, Mn, K, Ti and Zn were analyzed using ICP OES. RESULTS For metal studied Al, Ba, Cr, Fe and Mn presented greater accumulation in A. viridis than in P. perna. The metal concentrations detected in seawater, sponge, and mussel could be related using PCA with 79.26% total variance demonstrating that A. viridis bioaccumulated more metals than P. perna. CONCLUSION: Sponge metal accumulation reflected not only spatial metal variation but also seasonal changes.
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    Trace-element composition of pyrite and its implications for hydrothermal process within the Mesoproterozoic metasedimentary sequences of the São Francisco Craton, northeastern Brazil.
    (2022) Melo, Marilane Gonzaga de; Moreira, Éder Carlos; Simplicio, Fábio; Queiroga, Gláucia Nascimento; D’Agostim, Letícia Garcia; Castro, Marco Paulo de
    A distribuição de elementos traço em pirita é documentada pela primeira vez em veios de quartzo hospedados em sequências metassedimentares mesoproterozoicas da Formação Tombador, Cráton São Francisco, Nordeste do Brasil. Neste estudo, aná- lises de microssonda eletrônica (EPMA) foram utilizadas para determinar as composições de elementos traço em pirita nesses veios de quartzo hidrotermal. Três variedades de pirita foram distinguidas e interpretadas com base em relações petrográficas e padrões de elementos traço. A pirita preexistente (Py1 ), derivada do quartzito hospedeiro, é pobre em Ni, com concentrações variando de 600 a 6.100 ppm. A pirita alongada sintectônica (Py2 ) tem composição de elementos traço similar à de Py1 , com concentrações de Ni entre 830 e 7.870 ppm. Em contraste, a pirita euédrica a subédrica hidrotermal (Py3 ), possivelmente pós- -tectônica, contém teores mais elevados de Ni (7.970 – 26.120 ppm). Rochas máficas e/ou metassedimentares do Supergrupo Espinhaço foram provavelmente a fonte de Ni para esse evento de fluxo de fluido. A geração de fluidos está relacionada à des- volatilização da base da crosta espessada, com migração de fluidos por estruturas preexistentes. Várias zonas de cisalhamento e dobras de tendência NNW em larga escala foram desenvolvidas durante a inversão da bacia Espinhaço, como resultado do evento orogênico Brasiliano de 0,6 Ga. O movimento do fluido regional através da crosta nesse momento é suportado por vários veios mineralizados e depósitos hidrotermais no Cráton São Francisco e cinturões neoproterozoicos adjacentes.
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    A cathodoluminescence-assisted LA‑ICP‑MS study of topaz from different geological settings.
    (2018) Araújo, Teodoro Gauzzi Rodrigues de; Graça, Leonardo Martins
    In this study, the crystallization dynamics and the fingerprints of two topaz crystals from the Ouro Preto region (Brazil), two from the Eastern Brazilian Pegmatite Province (EBPP), one from the Western part of the United States (US) and one from Pakistan were characterized. The combination of scanning electron microscope-cathodoluminescence (SEM-CL) and laser ablation inductively coupled plasma mass spectrometry (LA‑ICP‑MS) data allowed for the characterization of these samples. Samples from the Ouro Preto region showed primary crystallization and recrystallization processes, which were demonstrated by a CL-heterogeneous core and CL-homogeneous rims in the SEM-CL images. Their fingerprint was composed of Ca, Ti, V, Cr, Mn, Fe, Cu and Zn. Samples from the EBPP showed both dark and CL-homogeneous SEM-CL images, implying slow and late-stage crystallization, typical of pegmatites. Their fingerprints were composed of Li, Nb, LREE, Ta and W, and of Ti, Nb and HREE. A sample from a Western part of the US displayed CL-heterogeneity with growth and resorption events and well-preserved growth zones, which were noticeable through the SEM-CL images. Its fingerprint was composed of Li, Ti, V, Mn, Nb, LREE, Ta and W. A sample from Pakistan showed an evident metamorphic recrystallization process, which was visible by the incipient and CL-homogeneous luminescence given by the SEM-CL images. Its fingerprint was composed of Ca, Cr, V, Zn, LREE, HREE and W.
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    The fingerprint of imperial topaz from Ouro Preto region (Minas Gerais state, Brazil) based on cathodoluminescence properties and composition
    (2017) Araújo, Teodoro Gauzzi Rodrigues de; Graça, Leonardo Martins; Lagoeiro, Leonardo Evangelista; Mendes, Isolda Maria de Castro; Queiroga, Gláucia Nascimento
    A study of the cathodoluminescence (CL) properties of imperial topaz from Ouro Preto region (Minas Gerais state, Brazil) and its relation with trace-element composition was conducted, using scanning electron microscope cathodoluminescence (SEM-CL), optical microscope cathodoluminescence (OM-CL), cathodoluminescence-spectrometry (CL-spectrometry), electron microprobe analysis (EMPA), laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) and Raman spectrometry. Each analytical technique allowed characterization of the imperial topaz fingerprint. SEM-CL panchromatic images show different crystal growth and resorption events in imperial topaz crystals. Colour CL images indicate only blue to violet emissions. The CL-spectra indicate a broad emission band with low intensity peak at ∼417 nm and a broad emission band with high intensity and major peaks at 685, 698, 711 and 733 nm. The EMPA indicates high OH content, in which the OH/(OH + F) ratio ranges between 0.35–0.43 (0.72 ≤ OH ≤ 0.86 apfu). High Cu and Zn concentrations (LA-ICP-MS) were measured in the high luminescence areas of SEM-CL images, suggesting both elements as CL-activators in imperial topaz. Raman and CL-spectra indicate high Cr concentrations, corroborated by EMPA and LA-ICP-MS results. The high Cr caused strong luminescence intensities that enabled their superimposition over the OH stretching mode (∼3650 cm–1) of topaz in all Raman spectra. Among trace elements, the concentrations of Ti, V, Cr, Mn, Fe, Cu, Zn, Ga and Ge provide the fingerprint of imperial topaz.
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    U-Pb geochronology of Paraná volcanics combined with trace element geochemistry of the zircon crystals and zircon Hf isotope data.
    (2019) Hartmann, Leo Afraneo; Baggio, Sergio Benjamin; Brückmann, Matheus Philipe; Knijnik, Daniel Barbosa; Lana, Cristiano de Carvalho; Massonne, Hans-Joachim; Opitz, Joachim; Pinto, Viter Magalhães; Sato, Kei; Tassinari, Colombo Celso Gaeta; Arena, Karine da Rosa
    The Paraná volcanic province is a window into mantle and crustal processes in the Cretaceous. The variability and complexity of this province can be determined through the study of minerals. An integrated study of zircon from Paraná lavas (one high-Ti basalt, one low-Ti andesite, one high-Ti rhyodacite and one high-Ti andesite sill) was achieved using backscattered electron imaging, sensitive high resolution ion microprobe (SHRIMP-IIe) for U-Pb geochronology, and laser ablation inductively coupled mass spectrometer (LA-ICPMS) to determine the Lu- Hf isotopes and the trace-element compositions. U-Pb-Hf and trace-element data indicate that zircon crystallized from the magma at approximately 134 Ma. This South American large igneous province originated from the mantle and was contaminated by crust either in the mantle or during ascent and crystallization of magma. Contaminant continental crust had Precambrian age. Trace elements point to a new compositional field for zircon, different from other types of provinces. Examination of volcanic zircon improves our understanding of age and contamination of the Paraná volcanics.
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    Geochemistry of muscovite from pegmatites of the Eastern Brazilian pegmatite province : a clue to petrogenesis and mineralization potential.
    (2007) Viana, Rúbia Ribeiro; Evangelista, Hanna Jordt; Stern, Willem B.
    Single crystals of muscovite (N = 143) from different zones of selected granitic pegmatites belonging to two wellknown gem-producing districts of the Eastern Brazilian Pegmatite Province (northern Araçuai and western Governador Valadares in Minas Gerais) were analyzed for major, minor and trace elements. Structural formulae display considerable (Fe+Mg) variation within the octahedral site, coupled with tetrahedral Si-Al substitution (Tschermak substitution – phengite component). Tetrahedral Si varies from 3.06 to 3.21 and AlVI from 1.71 to 1.90 apfu. Trace elements in muscovite are significant indicators for the economic potential of pegmatites as well as for the differentiation degree and origin of the magma. Muscovite with higher Li and B contents is characteristic for gem-tourmaline-bearing pegmatites. Lower concentrations in K/Rb, Ti and Mg and higher F contents are found in muscovites from higher differentiated zones within the pegmatite. In comparison with anatectic pegmatites, relatively low K/Rb ratios of muscovite from the studied pegmatites are indicative of derivation by fractional crystallization of granite magma. Zn, Ga and Y, elements rarely analyzed in micas, tend to increase with decreasing K/Rb ratios, showing them to be good indicators of the fractionation degree of magmas.
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    Evaluation of the mineral exploration influence on sediment composition in the Gualaxo do Norte River Basin (MG-Brazil) based on geochemical and stratigraphic data.
    (2012) Rodrigues, Aline Sueli de Lima; Malafaia, Guilherme; Costa, Adivane Terezinha; Nalini Júnior, Hermínio Arias
    The aim of this study was to investigate the influence of mining on the geochemical composition of the alluvial sediments of the Gualaxo do Norte River Basin, located in the eastern-southeastern portion of the Quadrila ´tero Ferrı´fero (Minas Gerais State, Brazil). The analysis of the sedimentological succession was carried out using 16 stratigraphic sections (cutbanks and alluvial terraces) and analysis of 111 sediment samples for major- and trace-elements by ICP-OES. The stratigraphic analysis revealed the deposition history of the collected sediments. Anomalous concentrations of certain elements such as As and Pb were found, which are associated with stratigraphic facies with evidences of gold artisanal mining, and Fe anomalies associated with iron ore mining. The classification of the sections was possible by means of principal component analysis. From the sediment characteristics, three groups were identified: (1) those influenced by iron ore mining and gold artisanal mining; (2) those influenced by iron ore mining and (3) those with no influence of human activities.
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    Valores de background geoquímico e suas implicações ambientais.
    (2009) Rodrigues, Aline Sueli de Lima; Nalini Júnior, Hermínio Arias
    O estabelecimento de valores de background geoquímico como medida relativa para distinguir concentrações naturais de um elemento (geogênica e/ou biogênica) e a influência das atividades antrópicas nestas concentrações representa um dos assuntos mais importantes das ciências ambientais recentes. A relação entre as alterações naturais e as proporcionadas pela ação antrópica nas espécies químicas é uma questão que envolve implicações importantes nas áreas da geologia, toxicologia e biologia, entre outros campos do conhecimento. Isto é especialmente importante, quando interpretações geoquímicas de elementos tóxicos são requeridas. Assim, o objetivo principal desse artigo é apresentar e discutir as razões pelas quais o estabelecimento de valores de background geoquímico tem implicações nos estudos ambientais. Ao longo desse artigo, são apresentados alguns conceitos de background geoquímico e os principais métodos utilizados para avaliar a concentração background de elementos químicos (métodos direto e indireto). Além disso, são destacados alguns exemplos de estudos desenvolvidos no Brasil. Estudos envolvendo o estabelecimento de valores de background geoquímico são importantes porque permitem avaliar riscos potenciais de contaminação e identificar concentrações naturais de elementos-traço de uma determinada área.
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    Distribuição, fracionamento e mobilidade de elementos-traço em sedimentos superficiais.
    (2007) Pereira, Janice Cardoso; Silva, Aline Kelly Guimarães; Nalini Júnior, Hermínio Arias; Silva, Érica Pacheco; Lena, Jorge Carvalho de
    The gold and iron mining activities in the Velhas River yield considerable amounts of suspended solids as well as metals to the hydrological system of the region. The risks were assessed by sequential extraction procedures. They were carried out in sediment samples, aiming to evaluate the presence of Co, Cr, Cu, Ni, Zn and As. Although being at high levels in some parts of the river (e.g. As 527 mg g-1 and Cr 475 mg g-1) they are associated with the residual fraction. Mobility factors were also calculated and show that these species are enriched along the river, e.g. for As 0.02 at the spring and 0.33 at the high course of the river.