Alteration mineralogy and pathfinder element inventory of the McArthur River unconformity-related uranium deposit, Canada

The chemical compositions, modal mineralogy, and textural variability of interstitial minerals in sandstones of the Athabasca Group strata in the vicinity of the McArthur River unconformity-related uranium deposit were characterized using a combination of short wave infrared spectroscopy (SWIR), lithogeochemistry, scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and laser ablation mass spectrometry (LA-ICP-MS) to determine the residence sites of pathfinder trace elements. The importance of integrating in-situ mineral chemistry with whole-rock analyses resides in the possibility to establish the mineralogical and paragenetic context of geochemical signatures in defining the footprint of the deposit. Located in the Athabasca Basin, Saskatchewan, Canada, the deposit is situated below ~550 m of quartz arenitic sandstones that are strongly silicified between depths of approximately 200-400 m. The silicified layer exhibits significant control on the distribution of alteration minerals, and appears to have restricted both the primary and secondary dispersion of pathfinder trace elements, which include U, radiogenic Pb isotopes, V, Ni, Co, Cu, Mo, As, Zn, and REEs. Diagenetic background sandstones contain assemblages of illite, dickite, aluminum-phosphate-sulfate (APS) minerals, apatite, and Fe-Ti oxide minerals. Altered sandstones contain assemblages of Al-Mg chlorite (sudoite), alkali-deficient dravite, APS minerals, kaolinite, illite, and oxide minerals. Throughout the sandstones, APS minerals account for the majority of the Sr and LREE concentrations, whereas late pre-ore chlorite, containing up to 0.1 wt.% Ni, accounts for the majority of Ni concentrations. Cobalt, Cu, Mo, and Zn occur predominantly in cryptic sub-micron sulfide and sulfarsenide inclusions in clay mineral aggregates and in association with paragenetically-late Fe-Ti oxides. Uranium occurs predominantly in cryptic micro-inclusions associated with pyrite in late-stage quartz overgrowths, and with paragenetically late Fe-Ti oxide micro-inclusions in kaolinite. Additionally, up to 0.2 wt.% U is cryptically distributed in post-ore Fe-oxide veins. Early diagenetic apatite, monazite and apatite inclusions in detrital quartz, and detrital zircon also contribute significant U and HREE to samples analyzed with an aggressive leach such as Aqua Regia. Detailed LA-ICP-MS chemical mapping of interstitial assemblages, detrital grains, and cements provides new insights into the distribution and inventory of pathfinder elements in the footprint of the McArthur River uranium deposit.

Grain size, morphometry and mineralogy of airborne input in the Canary basin: evidence of iron particle retention in the mixed layer

[EN]Aeolian dust plays an important role in climate and ocean processes. Particularly, Saharan dust deposition is of importance in the Canary Current due to its content of iron minerals, which are fertilizers of the ocean. In this work, dust particles are characterized mainly by granulometry, morphometry and mineralogy, using image processing and scanning northern Mauritania and the Western Sahara. The concentration of terrigenous material was measured in three environments: the atmosphere (300 m above sea level), the mixed layer at 10 m depth, and 150 m depth. Samples were collected before and during the dust events, thus allowing the effect of Saharan dust inputs in the water column to be assessed. The dominant grain size was coarse silt

Grain size, morphometry and mineralogy of airborne input in the Canary basin: evidence of iron particle retention in the mixed layer

[EN] Aeolian dust plays an important role in climate and ocean processes. Particularly, Saharan dust deposition is of importance in the Canary Current due to its content of iron minerals, which are fertilizers of the ocean. In this work, dust particles are characterized mainly by granulometry, morphometry and mineralogy, using image processing and scanning northern Mauritania and the Western Sahara. The concentration of terrigenous material was measured in three environments: the atmosphere (300 m above sea level), the mixed layer at 10 m depth, and 150 m depth. Samples were collected before and during the dust events, thus allowing the effect of Saharan dust inputs in the water column to be assessed.

Geochemistry and mineralogy of a silica chimney from an inactive seafloor hydrothermal field (East Pacific Rise, 18°S)

An inactive vent field comprised of dead chimneys was discovered on the ultrafast East Pacific Rise (EPR) at 18°S during the research campaign NAUDUR with the R/V Le Nadir in December 1993. One of these chimneys was sampled, studied and found to be largely composed of silica-mineralized bacterial-like filaments. The filaments are inferred to be the result of microbial activity leading to silica (± Fe-oxyhydroxide) precipitation. The chimney grew from the most external layer (precipitated 226 ± 4 yr. B.P.) towards the central chimney conduit. Hydrothermal activity ceased 154 ± 13 yr. B.P. and the chimney conduit was completely sealed. Mixing between an end-member hydrothermal fluid and seawater explains the Sr–Nd isotopic composition of the chimney. Seawater was the major source of Sr to the chimney, whereas the dominant Nd source was the local mid-ocean ridge basalt (MORB) leached by the hydrothermal fluids. The mixing scenarios point to a dynamic hydrothermal system with fluctuating fluid compositions. The proportion of seawater within the venting fluid responsible for the precipitation of the silica chimney layers varied between 94 and 85%. Pb-isotope data indicates that all of the Pb in the chimney was derived from the underlying MORB. The precipitation temperatures of the chimney layers varied between 55 and 71 °C, and were a function of the seawater/end-member hydrothermal fluid mixing ratio. δ30Si correlates with the temperature of precipitation implying that temperature is one of the major controls of the Si-isotope composition of the chimney. Concentrations of elements across the chimney wall were a function of this mixing ratio and the composition of the end-member hydrothermal fluid. The inward growth of the chimney wall and accompanying decrease in wall permeability resulted in an inward decrease in the seawater/hydrothermal fluid mixing ratio, which in turn exerted a control on the concentrations of the elements supplied mainly by the hydrothermal fluids. The silica chimney is significantly enriched in U, likely a result of bacterial concentration of U from the seawater-dominated vent fluid. The chimney is poor in rare earth elements (REE). It inherited its REE distribution patterns from the parent end-member hydrothermal fluids. The dilution of the hydrothermal fluid with over 85% seawater could not obliterate the particular REE features (positive Eu anomaly) of the hydrothermal fluids.

Mineralogy and Geochemistry of Phosporite Deposits from Tropic Seamount (NE Tropical Atlantic Ocean)

Marine phosphorite deposits can form in a variety of environments, and despite of similar P contents, their mineralogy can change substantially. Seamount phosphorites are increasingly recognized for their P resources and are known to concentrate rare earth elements (REEs) and yttrium (Y) during early diagenetic formation, much more than continental-margin phosphorite deposits. Their importance is increasing in terms of economic potential but have always been studied for paleoenvironmental reconstruction purposes. The Canary Island Seamount Province (CISP) has been extensively studied for its Fe-Mn crusts and nodules deposits, but to date there has not been any systematic study on the phosphorite substrate rocks. This study aims at characterizing the mineralogy and geochemistry of the Tropic seamount phosphorites and offer insights into their mechanisms of formation. The Tropic seamount is a guyot that presents a variety of depositional environments. Two types of phosphorite slabs were identified: (1) a massive facies with oxic enrichments of Mn, Cr, Co, Ni and Cu located on the summit edges and flanks, and (2) a complex facies with suboxic-to-anoxic enrichments of U and V observed on the phosphorites located on the summit of the guyot. Both phosphorite types experienced advanced phosphatization (P2O5 between 24 and 31 wt.%, 3-4 wt.% of F). Differences in uptake of rare earth elements + yttrium (REY) and variations in mineralogy (e.g., presence of foraminifera vs. rounded glauconite grains, carbonate fragments or bioclasts) between the two types, allow phosphorites that formed in upwelling, nutrient-rich and oxic-suboxic environments to be distinguished from those which formed in suboxic-anoxic organic-poor environments. A potential combined ore deposit (Fe-Mn crusts + phosphorites) with high REY contents, like the seamount phosphorites analyzed in this study (ΣREY=870 μg/g on average), could help supply the resources needed for green-tech and high-tech applications.

Efeitos de diferentes tamanhos de palmares nos indicadores tecnicos do nado crawl em esforços maximos de 50 e 100m

Universidade Estadual de Campinas . Faculdade de Educação Física

Limiar ventilatorio e comportamento do sinal eletromiografico durante exercicio incremental no cicloergometro

Universidade Estadual de Campinas . Faculdade de Educação Física

Avaliação isocinetica de joelho em jogadores de futebol categoria sub-20

Universidade Estadual de Campinas . Faculdade de Educação Física

Mineralogia de um latossolo vermelho distrófico submetido a diferentes manejos por 24 anos

Atualmente, procuram-se sistemas de manejo que preservem ou melhorem as qualidades do solo, tanto mineralógicas como orgânicas, priorizando maior produtividade. Este trabalho teve como objetivo verificar qualitativamente, por meio das técnicas de fluorescência de raios X, difração de raios X e infravermelho com transformada de Fourier, os efeitos provocados pela utilização dos manejos: plantio convencional, preparo mínimo e plantio direto, por 24 anos, na mineralogia de um Latossolo Vermelho distrófico de Ponta Grossa, PR. Não foram observadas mudanças significativas na mineralogia do Latossolo estudado, por meio das técnicas utilizadas, quanto aos diferentes manejos durante os anos de sua aplicação. Pôde-se verificar, qualitativamente, a presença dos minerais gibbsita, caulinita, haloisita, montmorilonita, hematita, rutilo, anatásio, goethita e quartzo.

Crianças nascidas após emprego de técnica de fertilização assistida

OBJETIVO: Caracterizar mulheres e recém-nascidos que foram submetidos ao processo de reprodução assistids. MÉTODO: Estudo descritivo, retrospectivo para coleta de dados e prospectivo para análise, em mulheres submetidas a duas diferentes técnicas de reprodução assistida no Centro de Reprodução Humana do Hospital Israelita Albert Einstein no período de janeiro de 1995 a Dezembro de 2003. Foram selecionados todos os casos de sucesso e término do parto que ocorreram na Instituição no período. RESULTADOS: no período analisado, ocorreram 2448 procedimentos, sendo 439 de fertilização in vitro e 2009 de injeção intracitoplasmática de esperma. A taxa de sucesso variou de 25 a 30%. Não houve diferenças significativas entre os dois métodos estudados quanto aos resultados perinatais. Maior morbidade foi observada entre os nascimentos múltiplos em relação aos únicos. CONCLUSÕES: as técnicas de reprodução assistida não interferiram nos resultados perinatais. A prematuridade foi o fator determinante de maior morbimortalidade entre os múltiplos

Sorption aspects for unconsolidated materials of the Sao Carlos region (SP), Brazil

The transport of liquid and gaseous pollutants through porous geological media depends on the physical and chemical characteristics of the unconsolidated material, rocks and water associated with the characteristics of the pollutants. Of these characteristics, the sorption aspect is of fundamental importance and is a function of the mineral proportions, pH, Eh and void aspects encountered in the porous media. In the Sao Carlos region, located in the eastern-central part of the 9 ate of Sao Paulo, Brazil, there are basically two types of unconsolidated materials: the first is a residual from sandstones cemented with fines and the secondarily composed of claystones, siltstones and conglomerates from the Cretaceous Period that constitute the Itaqueri Formation; the second is a sandy sediment of the Tertiary Period. These geological conditions are found in areas where chemical products are disposed of characterized as either diffuse or point pollutions sources. Because of this situation, a study was developed to evaluate the sorption aspects of some inorganic cations that are frequently found in these sources, in varied concentrations. Taken into consideration were their physical/chemical properties, such as: specific weight, grain size, mineralogy, cationic exchange capacity, pH, hydraulic conductivity. Batch tests were run using solutions of KCl, ZnCl(2) and CuCl center dot H(2)O at three different pH values, and then with a combined solution (KCl + ZnCl(2) + CuCl center dot H(2)O), also at three different pH values.

A comparison of the critical impeller speed for solids suspension in a bench-scale and a pilot-scale mechanical flotation cell

This paper compares the critical impeller speed results for 6 L Denver and Wemco bench-scale flotation cells with findings from a study by Van der Westhuizen and Deglon [Van der Westhuizen, A.P., Deglon, D.A., 2007. Evaluation of solids suspension in a pilot-scale mechanical flotation cell: the critical impeller speed. Minerals Engineering 20,233-240; Van der Westhuizen, A.P., Deglon, D.A., 2008. Solids suspension in a pilot scale mechanical flotation cell: a critical impeller speed correlation. Minerals Engineering 21, 621-629] conducted in a 125 L Batequip flotation cell. Understanding solids suspension has become increasingly important due to dramatic increases in flotation cell sizes. The critical impeller speed is commonly used to indicate the effectiveness of solids suspension. The minerals used in this study were apatite, quartz and hematite. The critical impeller speed was found to be strongly dependent on particle size, solids density and air flow rate, with solids concentration having a lesser influence. Liquid viscosity was found to have a negligible effect. The general Zwietering-type critical impeller speed correlation developed by Van der Westhuizen and Deglon [Van der Westhuizen, A.P., Deglon, D.A., 2008. Solids suspension in a pilot scale mechanical flotation cell: a critical impeller speed correlation. Minerals Engineering 21, 621-629] was found to be applicable to all three flotation machines. The exponents for particle size, solids concentration and liquid viscosity were equivalent for all three cells. The exponent for solids density was found to be less significant than that obtained by the previous authors, and to be consistent with values reported in the general literature for stirred tanks. Finally, a new dimensionless critical impeller speed correlation is proposed where the particle size is divided by the impeller diameter. This modified equation generally predicts the experimental measurements well, with most predictions within 10% of the experimental. (C) 2009 Elsevier Ltd. All rights reserved.

Separation of silica from bauxite via froth flotation

This paper reports an innovative development: concentrating gibbsite via reverse froth flotation in order to obtain a metallurgical-grade bauxite concentrate. Tailings from an industrial plant have undergone attrition scrubbing and desliming; the quartz silica contained in the tailings has undergone flotation. Starch was used as a depressant, and ether-amine as the cationic collector. Optimum pH is around 10.0. In pilot plant scale, a metallurgical-grade concentrate was obtained by assaying 42.3% available alumina with an alumina/insoluble silica mass ratio of 11.1. It contained the gibbsite and the iron and titanium bearing minerals. The concentrate was further upgraded by magnetic separation, leading to 54.0% available alumina, with an alumina/insoluble silica mass ratio of 12.6 at an overall available alumina recovery of 69.3% in the final concentrate (non-magnetic product). (C) 2008 Elsevier Ltd. All rights reserved.

Structural ceramics made with clay and steel dust pollutants

Electric arc furnace steel dust is a by-product of the steelmaking process and contains high amounts of the iron and zinc and significant amounts of lead, chromium, and cadmium. Metal recycling however, is not always economically feasible, especially due to the complex mineralogical composition of this material. In this study an application of this material is presented. Ceramics were produced with clay and variable amounts of steel dust. The bulk material was fired between 800 and 1100 degrees C. The influence of the composition and the processing temperature on the mechanical strength, linear shrinkage, water absorption, apparent density and bending strength and metal leaching of the ceramic samples was investigated. A blend of clay with up to 20% dust yielded ceramics with limited metal contamination risk and may thus be used for structural ceramics production. (C) 2011 Elsevier B.V. All rights reserved.

Montmorillonite as a component of polysulfone nanocomposite membranes

Nanocomposite membranes containing polysulfone (PSI) and sodium montmorillonite from Wyoming (MMT) were prepared by a combination of solution dispersion and the immersion step of the wet-phase inversion method. The purpose was to study the MMT addition with contents of 0.5 and 3.0 mass% MMT in the preparation of nanocomposite membranes by means of morphology, thermal, mechanical and hydrophilic properties of nanocomposite membranes and to compare these properties to the pure PSf membrane ones. Small-angle X-ray diffraction patterns revealed the formation of intercalated clay mineral layers in the PSf matrix and TEM images also presented an exfoliated structure. A good dispersion of the clay mineral particles was detected by SEM images. Tensile tests showed that both elongation at break and tensile strength of the nanocomposites were improved in comparison to the pristine PSf. The thermal stability of the nanocomposite membranes, evaluated by onset and final temperatures of degradation, was also enhanced. The hydrophilicity of the nanocomposite membranes, determined by water contact angle measurements, was higher; therefore, the MMT addition was useful to produce more hydrophilic membranes. (C) 2009 Elsevier B.V. All rights reserved.