Results 1 - 10 of 820
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[en] This paper aims at presenting a standardized methodology for analysis of free silica by X-ray diffraction developed by FUNDACENTRO Jorge Duprat Figueiredo Institution of Safety and Medicine Work through the adaptation of updated international methods, applicable to this purpose. (author)
[pt]O presente trabalho tem por objetivo apresentar metodologia padronizada para analise de silica por difracao de raios X, desenvolvida pela FUNDACENTRO a partir da adaptacao de metodos internacionais modernos, aplicaceis a essa finalidade. (autor)
[en] Experiments for measurement of time taken to reach thermal equilibrium in Spodumene crystals - 2mm to 5,4mm thick - in the temperature range 1000 to 2500C are described. The measurements indicate a linear relationship between time and thickenes for heating as well as for cooling. Difference in thermal equilibrium time for heating and for cooling is about of 20 seconds. (author)
[pt]Descricao de experimentos de medida de tempo para o equilibrio termico em cristais de espodumenio, com espessura de 2mm atr 5,4mm, na faixa de temperatura de 1000C a 2500C. Os tempos para o equilibrio termico mostram uma correlacao linear com a espessura tanto para o aquecimento, como para esfriamento. A diferenca nos tempos para o equilibrio termico e para o aquecimento e esfriamento e da ordem de 20 segundos. (autor)
[en] Complete text of publication follows. The Konder massif is represented a pipe-like mantle body that intruded the Archean crystalled basement of Aldan Shield. The rounded dunite body of 5.5 km in diameter is bordered with a pyroxenite zone about 150-200 m of width. This dome-like structure was probably formed because of diapiric intrusion of solid and hot dunite-pyroxenite body. With the purpose to study both geomagnetic zonality and features of formation of the Konder massif, we investigated magnetic properties of dunite for more than 150 samples, selected on three radial profiles under corners approximately 120 deg to each other. An attempt to establish statistical connection between magnetic susceptibility χ, remanent magnetization In of dunite and distance of sampling points from contact with pyroxenite ring has been undertaken. Magnetic susceptibility values χ for three profiles depend on distance and have multiextreme character (the contact dunite-pyroxenite is accepted as zero point). The first from the pyroxenite ring maximum reaches the greatest value (∼ 0.01 unit SI). Further, with increase of distance from periphery of the dunite massif, amplitudes of extremes naturally decrease. Variations of remanent magnetization of dunite In are in an antiphase with spatial changes of magnetic susceptibility χ, that is minimum of In corresponds to maximum of χ. The mineral grain size varies from fine to medium and large from periphery of dunite core to its center. It is possible to interpret process of its emplacement as a combination of rolling and extrusion. We observed thin structure of conjugate deformation bands in zones of minimum values of χ, magnitoaccoustic emission and coercive force Hc for 'massive' dunites. The 'massive dunites' characterize high density of defects ρ (plastically deformed zones), because Hc ∼ √ρ. Thus, variations of magnetic properties of rock are an indicator of localization of plastic deformation at different hierarchy levels.
[en] Thermogravimetric, differential thermal analysis, Infrared spectroscopy, chemical analysis, powder X-ray diffraction, and physical properties were performed to characterize ninavite silica rocks. The results indicate that such rocks posses a high silica content, low bulk density and high porosity. As a results of such characterization, ninavite was considered of great industrial importance. It has been used to fraction te heavy crude oil into their simple components. (authors). 17 refs., 5 figs., 3 tabs
[en] Precise and accurate estimates of silicate mineral weathering rates are crucial when setting policy targets for long-term forest sustainability, critical load calculations and assessing consequences of proposed geo-engineering solutions to climate change. In this paper, we scrutinize 394 individual silicate mineral weathering estimates from 82 sites on three continents. We show that within-site differences of several hundred per cent arise when different methods are used to estimate weathering rates, mainly as a result of uncertainties related to input data rather than conceptually different views of the weathering process. While different methods tend to rank sites congruently from high to low weathering rates, large within-site differences in estimated weathering rate suggest that policies relying on quantitative estimates based upon a single method may have undesirable outcomes. We recommend the use of at least three independent estimates when making management decisions related to silicate mineral weathering rates. (letter)
[en] The Xinyang and Jilin meteorites were investigated using Moessbauer spectroscopy. In addition to troilites and silicates, the Jilin meteorite contains taenite and kamacite, while the Xinyang meteorite contains kamacite only. The Moessbauer data of these two meteorites confirm them as ordinary H chondrites. The Moessbauer parameters can be interpreted by a model based on the cooling history of these meteorites. (orig.)
[en] Two members of the pyroxene family, the germanate-type LiFeGe2O6 and the titanate-type LiFeTi2O6, are prepared for the first time via non-conventional one-step mechanosynthesis. The evolution of the as-prepared materials in the course of mechanosynthesis and their structural state on the long-range and local atomic scales are characterized by X-ray diffraction and 57Fe Mössbauer spectroscopy, respectively. Both, the nanocrystalline nature of LiFeGe2O6 and the nanoglassy state of LiFeTi2O6 are revealed.
[en] Complete text of publication follows. At the University of Liverpool microwaves have been employed as an alternative to conventional heating in palaeointensity determinations in an effort to reduce thermo-chemical alteration. There has been some confusion within the literature as to how much heating occurs, what the source of the heating is and how magnetic reorientation occurs. We address these issues through experiments that show conclusively that a sample of basalt may be demagnetized without significant heating through interaction with the magnetic component of the microwave field. It is shown that previous theoretical studies have failed to take into account the high dielectric loss exhibited by pyroxene and plagioclase feldspar, the main constituents of basalt. By innovative design of the microwave cavity we show how the electric field in the vicinity of the sample can be minimized, and that this in turn eliminates substantial heating. Perturbation theory is developed to characterise the fields within the cavity and their interaction with various materials leading to a fuller understanding of the physical processes underlying microwave demagnetization.
[en] A new type of glass-ceramics obtained via original glass powder, sintering have been obtained from Canary Islands basalts. The original basaltic rock for this experiment was an alkalin basalt from the El Hierro Island. Different additions of partially stabilized zirconia have been tested in original glass and in pyroxene (diopside) glass-ceramic matrices. Likewise, uniaxial and isostatic pressing processings were used. In the final products different properties such as: density, microhardness and stress critical factor (K sub(IC)) and phase composition and microstructural characteristics (by XRD and SEM/EDX) were determined. (author)
[en] Two new types of REE-rich mineral associations have been discovered at Kvanefjeld in the northern of the Ilimaussaq alkaline complex. Type 1 consists of ussingite veins intersecting lujavrite and containing 5-7% nacareniobsite-(Ce) and 2-4% steenstrupine-(Ce); the adjacent altered lujavrite contains up to 10-12% nacareniobsite-(Ce). Type 2 consists of cavernous sodalite-rich veinlets and vugs inlujavrite containing 5-8% vitusite-(Ce). The chemical compositions and unit cell parameters of REE minerals are given. Nacareniobsite-(e) and vitusite-(Ce) were considered to be extremely rare minerals in the Ilimaussaq complex. Nacareniobsite-(Ce) is now known to be of more widespread occurrence in some hyper-agpatic rocks of the Ilimaussaq complex, and vitusite-(Ce) is known to be the precursor of the widespread occurrence of the yellow pseudomorphs termed erikite. (au)