The rate of water loss from olivine-hosted melt inclusions   总被引：1，自引：1，他引：0  

Yang Chen  Ariel Provost  Pierre Schiano  Nicolas Cluzel 《Contributions to Mineralogy and Petrology》2011,162(3):625-636

Diffusive water loss from olivine-hosted melt inclusions has been reported previously. This process must be considered when interpreting melt inclusion data. This study measured the rate of water loss from olivine-hosted melt inclusions during heating-stage experiments to test a previous diffusive reequilibration model and the hydrogen diffusion mechanism that controls the rate. Olivine-hosted melt inclusions were heated to a constant temperature in reduced Ar gas in a heating stage for a few hours, and unpolarized Fourier transform infrared spectra were repeatedly measured through the inclusions. Water loss occurred rapidly in the experiments. Within a few hours, the water absorbance at 3,500 cm⁻¹ wavenumber decreased by half. The observed water loss rate can be explained by the diffusive reequilibration model and hydrogen diffusion in olivine coupled with metal vacancy. The beginning of water loss was different in the low- and high-temperature experiments. At low temperatures (1,423 and 1,437 K), water loss did not occur in the initial 1 or 2 h. At high temperatures (1,471–1,561 K), water loss began immediately. The initial time period without water loss at low temperatures may be explained by a hydrogen fugacity barrier in the host olivine. At low temperatures, the internal pressure may be lower than the equilibrium pressure of melt inclusion and olivine, causing lower hydrogen fugacity in the melt inclusion than in the olivine, which will delay the water loss from the melt inclusion. The tested model and diffusivity were used to estimate the rate of water loss during homogenization experiments and magma eruption and cooling. For 1-h homogenization experiment, the model shows that large inclusions (50 μm radius) in large olivines (500 μm radius) are robust against water loss, while large or small inclusions (50–10 μm radius) in small olivines (150 μm radius) may suffer 30–100% water loss. For natural samples, the correlation between water concentration and melt inclusion and olivine sizes may be helpful to infer the initial water concentration, degree of diffusive reequilibration, and magma cooling rate.  相似文献   

Proposal for an International Molybdenum Isotope Measurement Standard and Data Representation     

Thomas F. Nägler  Ariel D. Anbar  Corey Archer  Tatiana Goldberg  Gwyneth W. Gordon  Nicolas D. Greber  Christopher Siebert  Yoshiki Sohrin  Derek Vance 《Geostandards and Geoanalytical Research》2014,38(2):149-151

Molybdenum isotopes are increasingly widely applied in Earth Sciences. They are primarily used to investigate the oxygenation of Earth's ocean and atmosphere. However, more and more fields of application are being developed, such as magmatic and hydrothermal processes, planetary sciences or the tracking of environmental pollution. Here, we present a proposal for a unifying presentation of Mo isotope ratios in the studies of mass‐dependent isotope fractionation. We suggest that the δ^98/95Mo of the NIST SRM 3134 be defined as +0.25‰. The rationale is that the vast majority of published data are presented relative to reference materials that are similar, but not identical, and that are all slightly lighter than NIST SRM 3134. Our proposed data presentation allows a direct first‐order comparison of almost all old data with future work while referring to an international measurement standard. In particular, canonical δ^98/95Mo values such as +2.3‰ for seawater and ?0.7‰ for marine Fe–Mn precipitates can be kept for discussion. As recent publications show that the ocean molybdenum isotope signature is homogeneous, the IAPSO ocean water standard or any other open ocean water sample is suggested as a secondary measurement standard, with a defined δ^98/95Mo value of +2.34 ± 0.10‰ (2s).  相似文献   

Selection and scaling of earthquake records in assessment of structures in low-to-moderate seismicity zones     

Ariel Catalán  Amadeo Benavent-Climent  Xavier Cahís 《Soil Dynamics and Earthquake Engineering》2010,30(1-2):40-49

The behaviour of a building during an earthquake depends on many factors including the characteristics of the ground motion, the configuration and dynamic characteristics of the structure, the hysteretic behaviour of the structural components, the building's non-structural parts, and the local soil behaviour. When conducting seismic assessment studies, controlling the first factor involves selecting and scaling appropriate earthquake records. It is a common practice to scale the records to fit a target acceleration response S_a determined from a pre-determined spectrum or attenuation law. In doing so, two key-problems must be faced: (i) the value adopted for the “effective” period T₁,which lengthens as the structure enters the non-linear range, and (ii) the reliability of the reference value adopted for S_a(T₁). In this work, the influence of selecting appropriate values for these two parameters—T₁ and S_a(T₁)—on the response of the building is investigated from the study of two structures, of 4 and 8 stories. The study does not focus on evaluating a particular seismic code; rather, it uses a European attenuation model as the target spectrum. Non-linear dynamic response analyses are carried out to investigate the Collapse Prevention State of these structures subjected to records representative of a Performance-based Earthquake Engineering level characterized by 2% exceedence in 50 years with 2475 years of return time. The records are selected from a database of European earthquakes, and the failure of the structures is evaluated by statistical means. From the results of the analyses, it is proposed that in seismic assessment studies the reference period for scaling should be 1.1 times the fundamental period of the structure, and at least 30 records should be used to guarantee reliable results.  相似文献   

Impact of Biocides on Hydrogen Sulfide Production and Growth of Desulfovibrio vulgaris          下载免费PDF全文

Eitan Ben‐Dov  Ofir Zisman  Asher Brenner  Ariel Kushmaro 《洁净——土壤、空气、水》2016,44(10):1423-1427

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Galaxy groups in the 2dF Galaxy Redshift Survey: large-scale structure with groups     

Ariel Zandivarez  Manuel E. Merchán  Nelson D. Padilla 《Monthly notices of the Royal Astronomical Society》2003,344(1):247-256

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Determination of the linear mass power spectrum from the mass function of galaxy clusters     

Ariel G. Sánchez  Nelson D. Padilla  Diego G. Lambas † 《Monthly notices of the Royal Astronomical Society》2002,337(1):161-171

We develop a new method to determine the linear mass power spectrum using the mass function of galaxy clusters. We obtain the rms mass fluctuation  σ( M )  using the expression for the mass function in the Press & Schechter, Sheth, Mo & Tormen and Jenkins et al. formalisms. We apply different techniques to recover the adimensional power spectrum  Δ²( k )  from  σ( M )  namely the   k _eff  approximation, the singular value decomposition and the linear regularization method. The application of these techniques to the τCDM and ΛCDM GIF simulations shows a high efficiency in recovering the theoretical power spectrum over a wide range of scales. We compare our results with those derived from the power spectrum of the spatial distribution of the same sample of clusters in the simulations obtained by application of the classical Feldman, Kaiser & Peacock (FKP) method. We find that the mass function based method presented here can provide a very accurate estimate of the linear power spectrum, particularly for low values of k . This estimate is comparable to, or even better behaved than, the FKP solution.
The principal advantage of our method is that it allows the determination of the linear mass power spectrum using the joint information of objects of a wide range of masses without dealing with specific assumptions on the bias relative to the underlying mass distribution.  相似文献   

Cross-correlations of X-ray and optically selected clusters with near-infrared and optical galaxies     

Ariel G. Sánchez †  Diego G. Lambas †  Hans Böhringer  Peter Schuecker 《Monthly notices of the Royal Astronomical Society》2005,362(4):1225-1232

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Fe isotopic fractionation during mineral dissolution with and without bacteria     

Susan L. Brantley  Laura J. Liermann  Ariel Anbar  Jane Barling 《Geochimica et cosmochimica acta》2004,68(15):3189-3204

Fe released into solution is isotopically lighter (enriched in the lighter isotope) than hornblende starting material when dissolution occurs in the presence of the siderophore desferrioxamine mesylate (DFAM). In contrast, Fe released from goethite dissolving in the presence of DFAM is isotopically unchanged. Furthermore, Δ⁵⁶Fe_{solution-hornblende} for Fe released to solution in the presence of ligands varies with the affinity of the ligand for Fe. The extent of isotopic fractionation of Fe released from hornblende also increases when experiments are agitated continuously. The Fe isotope fractionation observed during hornblende dissolution with organic ligands is attributed predominantly to retention of ⁵⁶Fe in an altered surface layer, while the lack of isotopic fractionation during goethite dissolution in DFAM is consistent with the lack of an altered layer. When a siderophore-producing soil bacterium is added to the system (without added organic ligands), Fe released to solution from both hornblende and goethite differs isotopically from Fe in the bulk mineral: Δ⁵⁶Fe_{solution-starting material} = −0.56 ± 0.19 (hornblende) and −1.44 ± 0.16 (goethite). Increased isotopic fractionation is attributed in this case to the fact that as bacterial respiration depletes the system in oxygen and aqueous Fe is reduced, equilibration between aqueous ferrous and ferric iron creates a pool of isotopically heavy ferric iron that is assimilated by bacterial cells. Adsorption of isotopically heavy ferrous iron (Fe(II) enriched in the heavier isotope) or precipitation of isotopically heavy Fe minerals may also contribute to observed fractionations.To test whether these Fe isotope signatures are recorded in natural systems, we also investigated extractions of samples of soils from which the bacteria were isolated. These extractions show variability in the isotopic signatures of exchangeable Fe and Fe oxyhydroxide fractions from one soil sample to another, but exchangeable Fe is observed to be lighter than Fe in soil Fe oxyhydroxides and hornblende. This observation is consistent with isotopically light Fe-organic complexes in soil pore water derived from the Fe-silicate starting materials in the presence of growing microorganisms, as documented in experiments reported here. The contributions from phenomena including organic ligand-promoted nonstoichiometric dissolution of Fe silicates, uptake of ferric iron by organisms, adsorption of isotopically heavy ferrous iron, and precipitation of iron minerals should create complex isotopic signatures in soils. Better understanding of these processes and the timescales over which they contribute to fractionation is needed.  相似文献   

Biased monitoring of fresh water-salt water mixing zone in coastal aquifers   总被引：2，自引：0，他引：2  

Shalev E  Lazar A  Wollman S  Kington S  Yechieli Y  Gvirtzman H 《Ground water》2009,47(1):49-56

In coastal aquifers, significant vertical hydraulic gradients are formed where fresh water and underlying salt water discharge together upward to the seafloor. Monitoring boreholes may act as "short circuits" along these vertical gradients, connecting between the higher and the lower hydraulic head zones. When a sea tide is introduced, the fluctuations of both the water table and the depth of the mixing zone are also biased due to this effect. This problem is intensified in places of long-screen monitoring boreholes, which are common in many places in the world. For example, all approximately 500 boreholes of the fresh water-salt water mixing zone in the coastal aquifer of Israel are installed with 10 to 50 m long screens. We present field measurements of these fluctuations, along with a three-dimensional numerical model. We find that the in-well fluctuation magnitude of the mixing zone is an order of magnitude larger than that in the porous media of the actual aquifer. The primary parameters that affect the magnitude of this bias are the anisotropy of the aquifer conductivity and the borehole hydraulic parameters. With no sea tide, borehole interference is higher for the anisotropic case because the vertical hydraulic gradients are high. When tides are introduced, the amplitude of the mixing zone fluctuation is higher for the isotropic case because the overall effective hydraulic conductivity is greater than the conductivity in the anisotropic case. In the aquifer, the fresh water-salt water mixing zone fluctuations are dampened, and tens of meters inland from the shoreline, the fluctuations are on the order of few centimeters.  相似文献   

The galaxy power spectrum: precision cosmology from large-scale structure?     

Ariel G. Sánchez  Shaun Cole 《Monthly notices of the Royal Astronomical Society》2008,385(2):830-840

Published galaxy power spectra from the two-degree field galaxy redshift survey (2dFGRS) and Sloan Digital Sky Survey (SDSS) are not in good agreement. We revisit this issue by analysing both the 2dFGRS and SDSS Data Release 5 (DR5) catalogues using essentially identical techniques. We confirm that the 2dFGRS exhibits relatively more large-scale power than the SDSS, or, equivalently, SDSS has more small-scale power. We demonstrate that this difference is due to the r -band selected SDSS catalogue being dominated by more strongly clustered red galaxies, which have a stronger scale-dependent bias. The power spectra of galaxies of the same rest-frame colours from the two surveys match well. If not accounted for, the difference between the SDSS and 2dFGRS power spectra causes a bias in the obtained constraints on cosmological parameters which is larger than the uncertainty with which they are determined. We also found that the correction developed by Cole et al. to model the distortion in the shape of the power spectrum due to non-linear evolution and scale-dependent bias is not able to reconcile the constraints obtained from the 2dFGRS and SDSS power spectra. Intriguingly, the model is able to describe the differences between the 2dFGRS and the much more strongly clustered Luminous Red Galaxy (LRG) sample, which exhibits greater non-linearities. This shows that more work is needed to understand the relation between the galaxy power spectrum and the linear perturbation theory prediction for the power spectrum of matter fluctuations. It is therefore important to accurately model these effects to get precise estimates of cosmological parameters from these power spectra and from future galaxy surveys like Pan-STARRS, or the Dark Energy Survey, which will use selection criteria similar to the one of SDSS.  相似文献