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1.
Melchor González-Dávila J. Magdalena Santana-Casiano Frank J. Millero 《Aquatic Geochemistry》2007,13(4):339-355
The thermodynamic stability constants for the hydrolysis and formation of mercury (Hg2+) chloride complexes
have been used to calculate the activity coefficients for Hg(OH)
n
(2–n)+ and HgCl
n
(2–n)+ complexes using the Pitzer specific interaction model. These values have been used to determine the Pitzer parameters for
the hydroxide and chloro complexes and C
ML). The values of and have been determined for the neutral complexes (Hg(OH)2 and HgCl2). The resultant parameters yield calculated values for the measured values of log to ±0.01 from I = 0.1 to 3 m at 25°C. Since the activity coefficients of and are in reasonable agreement with the values for Pb(II), we have estimated the effect of temperature on the chloride constants
for Hg(II) from 0 to 300°C and I = 0–6 m using the Pitzer parameters for complexes. The resulting parameters can be used to examine the speciation of Hg(II) with Cl− in natural waters over a wide range of conditions. 相似文献
2.
Interaction of freshly precipitated silica gel with aqueous solutions was studied at laboratory batch experiments under ambient
and near neutral pH-conditions. The overall process showed excellent reversibility: gel growth could be considered as an opposite
process to dissolution and a linear rate law could be applied to experimental data. Depending on the used rate law form, the
resulting rate constants were sensitive to errors in parameters/variables such as gel surface area, equilibrium constants,
Si-fluxes, and reaction quotients. The application of an Integrated Exponential Model appeared to be the best approach for
dissolution data evaluation. It yielded the rate constants k
dissol ∼ (4.50 ± 0.68) × 10−12 and k
growth ∼ (2.58 ± 0.39) × 10−9 mol m−2 s−1 for zero ionic strength. In contrast, a Differential Model gave best results for growth data modeling. It yielded the rate
constants k
dissol ∼ (1.14 ± 0.44) × 10−11 and k
growth ∼ (6.08 ± 2.37) × 10−9 mol m−2 s−1 for higher ionic strength (I ∼ 0.04 to 0.11 mol L−1). The found silica gel solubility at zero ionic strength was somewhat lower than the generally accepted value. Based on the
and standard Gibbs free energy of silica gel formation was calculated as and −850,318 ± 20 J mol−1, respectively. Activation energies for silica gel dissolution and growth were determined as and respectively. An universal value for growth of any silica polymorph, is not consistent with the value for silica gel growth, which questions the hypothesis about one unique activated complex
controlling the silica polymorph growth. 相似文献
3.
Frank J. Millero Abzar Mirzaliyev Javid Safarov Fen Huang Mareva Chanson Astan Shahverdiyev Egon Hassel 《Aquatic Geochemistry》2008,14(4):289-299
The density ρ of Caspian Sea waters was measured as a function of temperature (273.15–343.15) K at conductivity salinities
of 7.8 and 11.3 using the Anton-Paar Densitometer. Measurements were also made on one of the samples (S = 11.38) diluted with water as a function of temperature (T = 273.15–338.15 K) and salinity (2.5–11.3). These latter results have been used to develop an equation of state for the Caspian
Sea (σ = ±0.007 kg m−3)
where ρ0 is the density of water and the parameters A, B and C are given by
Measurements of the density of artificial Caspian Sea water at 298.15 K agree to ± 0.012 kg m−3 with the real samples. These results indicate that the composition of Caspian Sea waters must be close to earlier measurements
of the major components. Model calculations based on this composition yield densities that agree with the measured values
to ± 0.012 kg m−3. The new density measurements are higher than earlier measurements. This may be related to a higher concentration of dissolved
organic carbon found in the present samples (500 μM) which is much higher than the values in ocean waters (~65 μM). 相似文献
4.
Fractionation of yttrium (Y) and the rare earth elements (REEs) begins in riverine systems and continues in estuaries and the ocean. Models of yttrium and rare earth (YREE) distributions in seawater must therefore consider the fractionation of these elements in both marine and riverine systems. In this work we develop a coupled riverine/marine fractionation model for dissolved rare earths and yttrium, and apply this model to calculations of marine YREE fractionation for a simple two-box (riverine/marine) geochemical system. Shale-normalized YREE concentrations in seawater can be expressed in terms of fractionation factors (
ij
) appropriate to riverine environments (
) and seawater (
):
where
and
are input-normalized total metal concentrations in seawater and
is the ratio of total dissolved Y in riverwater before
and after
commencement of riverine metal scavenging processes. The fractionation factors (
ij
) are calculated relative to the reference element, yttrium, and reflect a balance between solution and surface complexation of the rare earths and yttrium. 相似文献
5.
The chemical potential of oxygen (µO2) in equilibrium with magnesiowüstite solid solution (Mg, Fe)O and metallic Fe has been determined by gas-mixing experiments at 1,473 K supplemented by solid-cell EMF experiments at lower temperatures. The results give:
where IW refers to the Fe-"FeO" equilibrium. The previous work of Srecec et al. (1987) and Wiser and Wood (1991) agree well with this equation, as does that of Hahn and Muan (1962) when their reported compositions are corrected to a new calibration curve for lattice parameter vs. composition. The amount of Fe3+ in the magnesiowüstite solid solution in equilibrium with Fe metal was determined by Mössbauer spectroscopy on selected samples. These data were combined with literature data from gravimetric studies and fitted to a semi-empirical equation:
These results were then used to reassess the activity-composition relations in (Mg, Fe)2SiO4 olivine solid solutions at 1,400 K, from the partitioning of Mg and Fe2+ between olivine and magnesiowüstite in equilibrium with metallic Fe experimentally determined by Wiser and Wood (1991). The olivine solid solution is constrained to be nearly symmetric with
, with a probable uncertainty of less than ±0.5 kJ/mol (one standard deviation). The results also provide a useful constraint on the free energy of formation of Mg2SiO4.Editorial responsibility: B. Collins 相似文献
6.
We present a theoretical model for diffusive daughter isotope loss in radiochronological systems with increasing temperature.
It complements previous thermochronological models, which focused on cooling, and allows for testing opening and resetting
of radiochronometers during heating. The opening and resetting temperatures are, respectively,
where R is the gas constant, E and D
0 are the activation energy and the pre-exponential factor of the Arrhenius law for diffusion of the daughter isotope, a the half-size of the system (radius for sphere and cylinder and half-thickness for plane sheet) and τ the heating time constant, related to the heating rate by
For opening and resetting thresholds corresponding to 1 and 99% loss of daughter isotope, respectively, the retention parameters
for sphere, cylinder and plane sheet geometries are A
op = 1.14 × 105, 5.07 × 104 and 1.27 × 104 and A
rs = 2.40, 1.37 and 0.561. According to this model, the opening and resetting temperatures are significantly different for most
radiochronometers and are, respectively, lower and higher than the closure temperature.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
7.
The solubility of calcite in H2O was measured at 6–16 kbar, 500–800 °C, using a piston-cylinder apparatus. The solubility was determined by the weight loss of a single crystal and by direct analysis of the quench fluid. Calcite dissolves congruently in the pressure (P) and temperature (T) range of this study. At 10 kbar, calcite solubility increases with increasing temperature from 0.016±0.005 molal at 500 °C to 0.057±0.022 molal at 750 °C. The experiments reveal evidence for hydrous melting of calcite between 750 and 800 °C. Solubilities show only a slight increase with increasing P over the range investigated. Comparison with work at low P demonstrates that the P dependence of calcite solubility is large between 1 and 6 kbar, increasing at 500 °C from 1.8×10–5 molal at 1 kbar to 6.4×10–3 molal at 6 kbar. The experimental results are described by:
where T is in Kelvin and
H2O is the density of pure water in g/cm3. The equation is applicable at 1–20 kbar and 400–800 °C, where calcite and H2O stably coexist. Extrapolated thermodynamic data for
indicates that the dominant dissolved carbon species is CO2,aq at all experimental conditions. The results require that equilibrium constant for the reaction:
increases by several orders of magnitude between 1 and 6 kbar, and also rises with isobaric T increase. Published thermodynamic data for aqueous species fail to predict this behavior. The increase in calcite solubility with P and T demonstrates that there is a strong potential for calcite precipitation during cooling and decompression of water-rich metamorphic fluids sourced in the middle to lower crust.Editorial responsibility: T.L. Grove 相似文献
8.
Yongliang Xiong 《Aquatic Geochemistry》2008,14(3):223-238
Solubility experiments were conducted for the dissolution reaction of brucite, Mg(OH)2 (cr):
Experiments were conducted from undersaturation in deionized (DI) water and 0.010–4.4 m NaCl solutions at 22.5°C. In addition,
brucite solubility was measured from supersaturation in an experiment in which brucite was precipitated via dropwise addition
of 0.10 m NaOH into a 0.10 m MgCl2 solution also at 22.5°C. The attainment of the reversal in equilibrium was demonstrated in this study. The solubility constant
at 22.5°C at infinite dilution calculated from the experimental results from the direction of supersaturation by using the
specific interaction theory (SIT) is: with a corresponding value of 17.0 ± 0.2 (2σ) when extrapolated to 25°C. The dimensionless standard chemical potential (μ°/RT)
of brucite derived from the solubility data in 0.010 m to 4.4 m NaCl solutions from undersaturation extrapolated to 25°C is
−335.76 ± 0.45 (2σ), with the corresponding Gibbs free energy of formation of brucite, , being −832.3 ± 1.1 (2σ) kJ mol−1. In combination with the auxiliary thermodynamic data, the is calculated to be 17.1 ± 0.2 (2σ), based on the above Gibbs free energy of formation for brucite. This study recommends
an average value of 17.05 ± 0.2 in logarithmic unit as solubility constant of brucite at 25°C, according to the values from
both supersaturation and undersaturation.
Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the
United States Department of Energy’s National Nuclear Security Administration under Contract DE-AC04-94AL85000. 相似文献
9.
The objective of this study was to describe the proton promoted disproportion of synthetic manganite (γ-MnOOH) and to characterise
the resulting phase transformations. The solution and remaining solid phase after disproportionation was analysed by techniques
including atomic absorbance spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy
(SEM). In suspensions with pH between 5 and 7, −log[H+] was monitored for 17 months and equilibrium constants were determined at 9, 12 and 17 months of reaction time for the following
reaction (25 °C, 0.1 M (Na)NO3):
The formed MnO2 ages with time and the equilibrium constant for a metastable phase (ramsdellite or nsutite) as well as the most stable phase,
pyrolusite (β-MnO2), was determined. Furthermore, combined pH and pe (Eh) measurements were performed to study the equilibrium;
Real-time AFM measurements of the dissolution showed shrinkage of the length of the manganite needles with time (2 hours).
After 1 week SEM images showed that this decreased length also was followed by a reduced thickness of the manganite needles.
From the SEM images the morphology of the formed Mn(IV) oxides was studied. At pH 2.6, pyrolusite (β-MnO2) and MnCl2 were found in the XRD patterns. Throughout the pH range there were indications of ramsdellite (MnO1.97) in the XRD patterns, which coincided with the existence of a fraction of needle shaped crystals with smaller dimensions
(compared to manganite) in the SEM images. These observations together with the long term dissolution experiments suggest
that the dissolution of manganite initially forms a ramsdellite or nsutite phase that over time rearranges to form pyrolusite. 相似文献
10.
The experiments of the dissolution kinetics of fluorite were performed in aqueous HCl solutions over the temperature range
of 25–100 °C using a flow-through experimental apparatus. With a constant input of aqueous HCl solution through the reactor,
output concentrations of the dissolved species Ca, F, Cl vary with flow rate, as well as with the surface compositions. Measured
output concentrations of dissolved species and the pH can be used to determine a rate law for fluorite dissolution. Fluorite
dissolution rates are found to be pH dependent. Usually, dissolution rates of fluorite decreases with increasing dissolved
Ca in the output solution at 25 and 100 °C. Dissolution rate can be expressed as
where k is the rate constant and α is the order with respect to the hydrogen ion activity vs. the activity of dissolved Ca. The α was obtained from kinetic experiments. For the fluorite sample passed through 18–35 mesh, α =1.198 at 100 °C and k = 10−0.983, while fluorite dissolved in HCl–H2O solution at pH 2.57 of input solution. Adsorption of a proton and Cl−1onto the fluorite surface, surface cation exchange and the formation of the surface complex Ca(F, Cl)2 and/or (H2x, Ca1−x)(F, Cl)2 control dissolution rates. Investigation of the fluorite surface before and after dissolution by using X-ray photoelectron
spectroscopy (XPS) indicate that surface modifications affect reaction rates. 相似文献
| (1a) |
11.
The diffusion of water in a peralkaline and a peraluminous rhyolitic melt was investigated at temperatures of 714–1,493 K
and pressures of 100 and 500 MPa. At temperatures below 923 K dehydration experiments were performed on glasses containing
about 2 wt% H2O
t
in cold seal pressure vessels. At high temperatures diffusion couples of water-poor (<0.5 wt% H2O
t
) and water-rich (~2 wt% H2O
t
) melts were run in an internally heated gas pressure vessel. Argon was the pressure medium in both cases. Concentration profiles
of hydrous species (OH groups and H2O molecules) were measured along the diffusion direction using near-infrared (NIR) microspectroscopy. The bulk water diffusivity
() was derived from profiles of total water () using a modified Boltzmann-Matano method as well as using fittings assuming a functional relationship between and Both methods consistently indicate that is proportional to in this range of water contents for both bulk compositions, in agreement with previous work on metaluminous rhyolite. The
water diffusivity in the peraluminous melts agrees very well with data for metaluminous rhyolites implying that an excess
of Al2O3 with respect to alkalis does not affect water diffusion. On the other hand, water diffusion is faster by roughly a factor
of two in the peralkaline melt compared to the metaluminous melt. The following expression for the water diffusivity in the
peralkaline rhyolite as a function of temperature and pressure was obtained by least-squares fitting:
where is the water diffusivity at 1 wt% H2O
t
in m2/s, T is the temperature in K and P is the pressure in MPa. The above equation reproduces the experimental data (14 runs in total) with a standard fit error
of 0.15 log units. It can be employed to model degassing of peralkaline melts at water contents up to 2 wt%. 相似文献
12.
Yongjun Jiang Cheng Zhang Daoxian Yuan Gui Zhang Raosheng He 《Hydrogeology Journal》2008,16(4):727-735
The impact of land-use change on the quality of groundwater in the Xiaotjiang watershed, China was assessed for the period
1982–2004. Groundwater samples were collected from 30 monitoring points across the watershed, and were representative of the
various changes, determined by remote sensing and geographical information systems. The results indicate that 610 km2 (60% of the total watershed area) were subject to land-use change during the period. The most important changes were the
conversion of 135 km2 of forested land to cultivated land, and 211 km2 of unused land to cultivated land. The main impact was ascribed to diffuse pollution from fertilizers applied to newly cultivated
land, and from building development. Overall the groundwater pH value was significantly increased, as were the concentrations
of ions , , , , and Cl− in groundwater whilst the concentrations of Ca2+ and declined. More precisely, in the regions where forested land and unused land were converted into cultivated land, the pH
value and the concentrations of Mg2+, , , , , Cl− increased whilst the concentrations of Ca2+ and declined. However in the region where cultivated land was converted into construction land, the pH value and the concentrations
of Ca2+, Mg2+, , , , , , Cl− increased.
Résumé L’impact des changements de l’utilisation du territoire sur la qualité de l’eau souterraine dans le bassin versant de Xiaojiang, en Chine, a été évalué de 1982 à 2004. Des échantillons d’eau souterraine ont été récoltés à partir de 30 points d’observation éparpillés sur le bassin, représentant les divers changements déterminés par télédétection et système d’information géographique. Les résultats indiquent que 610 km2 (soit 60% de la surface du bassin) ont été sujets à des modifications de l’utilisation du territoire sur cette période. Les changements les plus importants furent la conversion de 135 km2 de forêt et 211 km2 de terres inutilisées en terres cultivées. Le principal impact est attribué à la pollution diffuse des engrais utilisés en agriculture et pour les batiments. De manière générale le pH de l’eau souterraine a augmenté significativement, ainsi que les concentrations des ions , , , , et Cl−, tandis que les concentration en Ca2+ et ont diminué. Plus précisément dans les régions transformées en terres cultivées, la valeur du pH et les concentrations en Mg2+, , , , , Cl− ont augmenté tandis que les concentrations en Ca2+ et ont diminué. Toutefois dans les régions cultivées converties en zones de construction, le pH et les concentrations en Ca2+, Mg2+, , , , , , Cl− ont augmenté.
Resumen El impacto del cambio en uso de la tierra en la calidad del agua en la cuenca Xiaojiang, China fue evaluado para el periodo 1982–2004. Muestras de agua subterránea fueron tomadas de 30 puntos de monitoreo a través de la cuenca, y fueron representativas de los múltiples cambios, determinados por sensores remotos y sistemas de información geográfica. Los resultados indican que 610 km2 (60% del área total de la cuenca) estaban sujetos a cambios de uso de la tierra durante el periodo estudiado. Los cambios más importantes fueron la conversión de 135 km2 de bosques a tierra cultivada, y 211 km2 de tierra sin uso (ociosa) a tierra cultivada. El impacto principal fue causado por contaminación difusa de fertilizantes aplicados a la tierra recientemente cultivada, y a desarrollo de construcciones. En general el pH en agua subterránea creció significantemente, al igual que las concentraciones de los iones , , , , y Cl− en agua subterránea mientras que las concentraciones de Ca2+ y decrecieron. Mas precisamente, en las regiones donde bosque y tierra ociosa fueron convertidas en tierra cultivada, el valor de pH y las concentraciones de Mg2+, , , , , Cl− crecieron mientras las concentraciones de Ca2+ y decrecieron. Sin embargo en la región donde tierra cultivada fue convertida en construcciones, el valor de pH y las concentraciones de Ca2+, Mg2+, , , , , , Cl− crecieron.相似文献
13.
A modified cross-twinning growth mechanism is put forward to explain the anomalous morphology of a spinel multiple-twin from Sri Lanka, flattened crosswise the twin
planes. Cross-twinning in spinel was found also in other specimens from Pegu (Myanmar), and the results were published in
a previous paper. This particular type of twinning is derived from the combination of cyclic
twinning with lamellar
twinning, so that these samples may be thought of as partial fivelings (cubic cyclic {111} twins with five components sharing a common <110> pseudo-fivefold axis). In the present paper, the sample
from Sri Lanka has been suitably cut with the aim of focusing the study on the cross-twinning region. The transformation matrices
that link the orientation states of each couple of twin components have been determined by means of White Beam Synchrotron
Radiation Topography. They showed that the specimen is made up of four twin components (A, B, C and D), with three twin planes:
and They also showed that the cross-twinned individuals (B and D) actually are not twinned to each other, and that a simple crystallographic
relationship holds between them. X-ray diffraction topography by conventional source allowed to image the crossing-region
and to determine that the cross-twinned individuals are in contact through a semi-coherent boundary, with twinning dislocations contributing to relieve the coherency strains. Electron probe microanalyses with wave dispersive spectroscopy showed that
the chemical composition is almost homogeneous, at least within the spatial resolution limit of this technique. The similar
growth features observed in the spinel sample from Sri Lanka and in those from Myanmar are interpreted as growth marks, indicators of a similar origin: in both cases they are found in impure dolomitic marbles. In particular, the specimen from
Sri Lanka results from the interaction of thermal and metasomatic effects due to contact metamorphism. An unusual stepped
morphology of the face close to the twin boundary, possibly due to corrosion and re-growth processes acted preferentially at a re-entrant corner by metasomatic
fluids, is interpreted as indicator of a metasomatic event that succeeded to the crystal growth, the latter occurred by thermal
effect.
相似文献
| Rosa Anna FregolaEmail: |
14.
The standard enthalpies of formation of FeS (troilite), FeS2 (pyrite), Co0.9342S, Co3S4 (linnaeite), Co9S8 (cobalt pentlandite), CoS2 (cattierite), CuS (covellite), and Cu2S (chalcocite) have been determined by high temperature direct reaction calorimetry at temperatures between 700 K and 1021 K. The following results are reported: $$\Delta {\rm H}_{f,FeS}^{tr} = - 102.59 \pm 0.20kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,FeS}^{py} = - 171.64 \pm 0.93kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,Co_{0.934} S} = - 99.42 \pm 1.52kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,Co_9 S_8 }^{ptl} = - 885.66 \pm 16.83kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,Co_3 S_4 }^{In} = - 347.47 \pm 7.27kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,CoS_2 }^{ct} = - 150.94 \pm 4.85kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,Cu_2 S}^{cc} = - 80.21 \pm 1.51kJ mol^{ - 1} ,$$ and $$\Delta {\rm H}_{f,CuS}^{cv} = - 53.14 \pm 2.28kJ mol^{ - 1} ,$$ The enthalpy of formation of CuFeS2 (chalcopyrite) from (CuS+FeS) and from (Cu+FeS2) was determined by solution calorimetry in a liquid Ni0.60S0.40 melt at 1100 K. The results of these measurements were combined with the standard enthalpies of formation of CuS, FeS, and FeS2, to calculate the standard enthalpy of formation of CuFeS2. We found \(\Delta {\rm H}_{f,CuFeS_2 }^{ccp} = - 194.93 \pm 4.84kJ mol^{ - 1}\) . Our results are compared with earlier data given in the literature; generally the agreement is good and our values agree with previous estimates within the uncertainties present in both. 相似文献
15.
The activity of silica in kimberlites,revisited 总被引：1，自引：1，他引：0
Robert W. Luth 《Contributions to Mineralogy and Petrology》2009,158(2):283-294
The activity of silica in a silicate liquid in equilibrium with olivine and orthopyroxene decreases with increasing pressure. In contrast, the activity of silica in
an unbuffered silicate liquid changes little with pressure. Although the implications of these pressure dependencies have
been considered by previous authors in terms of inferring pressures of origin of magmas, less consideration has been given
to the implications of these dependencies on the evolution of the magma en route to the surface, or to the mantle through
which the magma passes. In this paper, a combination of Schreinemakers’ analysis in isothermal section and calculated reactions in space is used to (a) rationalize the absence of orthopyroxene xenocrysts in kimberlites and the relative abundance of olivine
“megacrysts” therein, (b) propose another reason for the paucity of xenocrystic mantle-derived carbonates in kimberlites,
(c) explain why clinopyroxene is much less reactive in the kimberlite melt than is orthopyroxene, and (d) explore the implications
of the relative stabilities of olivine, orthopyroxene, and clinopyroxene in kimberlitic magma for the mantle through which
the magma transits.
相似文献
| Robert W. LuthEmail: |
16.
The Influence of Redox Reactions on the Uptake of Dissolved Ce by Suspended Fe and Mn Oxide Particles 总被引：1，自引：0，他引：1
Laboratory experiments were conducted to evaluate the partitioning ofrare earth elements (REE) between solution and suspended
particles. Becauseof their strong tendency to complex, the REE can be used to study a varietyof marine processes and in particular
particle scavenging. In this study, anemphasis was placed on examining abiotic redox processes that influence theuptake of
dissolved Ce by particles. Batch sorption experiments wereconducted with REE and synthetic mineral phases over the range of
pH4–9. The solutions varied in ionic strength between 0 and 0.7 M andconsisted of individual solutes (NaNO3, NaCl, andNa2SO4), ionic mixtures that duplicate theseawater composition, and natural seawater. The uptake of REE from solutionwas also studied
at a Pt electrode coated with
using cyclic voltametry.
Experimental results are consistent with uptake of dissolved Ce onto
occurring by a combination of oxidativescavenging and surface complexation. The contribution of oxidativescavenging to the
removal of Ce from solution is most pronounced at acidicpH, where the strictly trivalent REE exhibit little propensity for
sorptiononto
. Sorption of dissolved Ce onto FeOOH occursin a manner analogous to that of the other strictly trivalent REE and nocontribution
from oxidative scavenging is observed on this mineral phase atlow pH. Our work also substantiates the hypothesis that anions
in solution,particularly
and Cl-, aswell as those adsorbed on the surface of the particles, influence the extentof Ce uptake by
.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
Sylvie Demouchy Stephen J. Mackwell David L. Kohlstedt 《Contributions to Mineralogy and Petrology》2007,154(3):279-289
Interdiffusion of Fe and Mg in (Mg,Fe)O has been investigated experimentally under hydrous conditions. Single crystals of
MgO in contact with (Mg0.73Fe0.27)O were annealed hydrothermally at 300 MPa between 1,000 and 1,250°C and using a Ni–NiO buffer. After electron microprobe
analyses, the dependence of the interdiffusivity on Fe concentration was determined using a Boltzmann–Matano analysis. For
a water fugacity of ∼300 MPa, the Fe–Mg interdiffusion coefficient in Fe
x
Mg1−x
O with 0.01 ≤ x ≤ 0.25 can be described by with and C = −80 ± 10 kJ mol−1. For x = 0.1 and at 1,000°C, Fe–Mg interdiffusion is a factor of ∼4 faster under hydrous than under anhydrous conditions. This enhanced
rate of interdiffusion is attributed to an increased concentration of metal vacancies resulting from the incorporation of
hydrogen. Such water-induced enhancement of kinetics may have important implications for the rheological properties of the
lower mantle.
相似文献
| Sylvie DemouchyEmail: |
18.
Equations of state of Plagioclase Feldspars 总被引：2，自引：1，他引：1
The volume variation with pressure of seven intermediate plagioclase feldspars has been determined by high-pressure single-crystal X-ray diffraction. The bulk moduli of plagioclases for a 3rd-order Birch-Murnaghan EoS can be described by the following pair of equations:
with
for plagioclase with X
An
<20 and
for X
An
>35. These parameters can also be used in a Murnaghan EoS to describe the volume variation of plagioclase feldspars up to pressures of 3 GPa. For a Murnaghan EoS with
, the values of the bulk moduli can be described by a single equation,
, with a small loss in the accuracy of the predicted volumes up to pressures of 3 GPa.Editorial responsibility: T.L. GroveAn erratum to this article can be found at 相似文献
19.
Three independent Pb isotope homogenizing processes operating on large volumes of rock material during limited intervals in the Phanerozoic have been used to define a unique evolutionary curve for rock and ore lead isotopic compositions of the southern Massif Central, France. The model is
|
相似文献
20.
Kurt Leinenweber Alexandra Navrotsky Paul McMillan Eiji Ito 《Physics and Chemistry of Minerals》1989,16(8):799-808
The enthalpies of transition at T= 298 K between zinc metasilicate assemblages, measured by molten oxide solution calorimetry, are:
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