共查询到20条相似文献，搜索用时 15 毫秒
1.
The solubility of pentatungstate of sodium (PTS) Na2W5O16 · H2O and sodium tungsten bronzes (STB) Na0.16WO3 in acid chloride solutions containing 0.026, 0.26, and 3.02m NaCl have been studied at 500°C, 1000 bar, given fO2 (Co-CoO, Ni-NiO, PTS-STB buffers), and constant NaCl/HCl ratio (Ta2O5-Na2Ta4O11 buffer). Depending on experimental conditions, the tungsten content in the solutions after experiments varied from 10−3 to 2 × 10−2 mol/kg H2O. Obtained data were used to calculate the formation constants of predominant tungsten complexes (VI, V): H3W3VIO123−, W3VO93−, [WVW4VIO16]3−, for reactions
|
$
\begin{gathered}
3H_2 WO_4^0 \leftrightarrow H_3 W_3 O_{12}^{3 - } + 3H^ + \log K_p = - 7.5 \pm 0.1, \hfill \\
3H_2 WO_4^0 \leftrightarrow W_3 O_9^{3 - } + 1.5H_2 O + 3H^ + + 0.75O_2 \log K_p = - 25.7 \pm 0.2, \hfill \\
5H_2 WO_4^0 \leftrightarrow \left[ {W^V W_4^{VI} O_{16} } \right]^{3 - } + 3H^ + + 3.5H_2 O + 0.25O_2 \log K_p = - 4.6 \pm 0.1 \hfill \\
\end{gathered}
$
\begin{gathered}
3H_2 WO_4^0 \leftrightarrow H_3 W_3 O_{12}^{3 - } + 3H^ + \log K_p = - 7.5 \pm 0.1, \hfill \\
3H_2 WO_4^0 \leftrightarrow W_3 O_9^{3 - } + 1.5H_2 O + 3H^ + + 0.75O_2 \log K_p = - 25.7 \pm 0.2, \hfill \\
5H_2 WO_4^0 \leftrightarrow \left[ {W^V W_4^{VI} O_{16} } \right]^{3 - } + 3H^ + + 3.5H_2 O + 0.25O_2 \log K_p = - 4.6 \pm 0.1 \hfill \\
\end{gathered}
相似文献
2.
We perform a statistical analysis of the properties of 170 rich clusters of galaxies. We confirm the existence of correlations
between the X-ray luminosity and temperature of the cluster intergalactic medium (IGM) and between the velocity dispersion
of the galaxies and the X-ray luminosity of the IGM. In addition, we have found a new anti-correlation between the optical
luminosity in Hα and the X-ray luminosity of the cluster IGM: log $
\left( {\frac{{L_{H\alpha } }}
{{L_ \odot }}} \right) = a - b\log \left( {\frac{{L_x }}
{{L_ \odot }}} \right)
$
\left( {\frac{{L_{H\alpha } }}
{{L_ \odot }}} \right) = a - b\log \left( {\frac{{L_x }}
{{L_ \odot }}} \right)
. Clusters form sequences with different values of a but similar values of b. 相似文献
3.
The paper considers some petrological and geochemical aspects of the formation of oceanic plagiogranites (OPG)—felsic intrusive
rocks, which were found in the plutonic complexes of modern mid-ocean ridges (MOR) and ophiolites of paleo-collisional zones.
Based on the multi-equilibrium clinopyroxene-orthopyroxene-amphibole-plagioclase geothermobarometry, typical OPG found in
gabbros and peridotites were formed at temperatures of 820–850°C and pressure of 2–2.5 kbar. Close temperature estimates (825
± 50°C) were obtained from literature data on Ti content in zircon, with allowance for lowered TiO2 activity in the rock. Under these P-T parameters, OPG can be generated only in the presence of fluid of water activity $
\left( {a_{H_2 O} } \right)
$
\left( {a_{H_2 O} } \right)
close to 0.9. OPG and associated recrystallized gabbroids contain high-temperature hornblende with significant Cl content
(0.5–2 wt %). In addition, the plagiogranites are characterized by particular geochemical features such as extremely high
Na2O/K2O (up to 135), sharp LREE enrichment ((Ce/Yb)cn and (La/Sm)cn up to 10 and 4, respectively), and elevated 87Sr/86Sr ratio relative to DMM. All these facts point to the key role of hydrothermal fluid, the seawater derivative, in the OPG
formation. The fluid with $
a_{H_2 O} = 0.9
$
a_{H_2 O} = 0.9
(approximately 28 wt % NaCl) could be produced from seawater due to hydration reactions at the higher lower temperature horizons
of oceanic crust in the course of its percolation to the OPG generation areas. The formation of plagiogranites in the MOR
oceanic core complexes possibly reflects the fundamental feature of oceanic accretion: practically simultaneous (at the geological
time scale) proceeding of exogenic (neptunic) and endogenous (plutonic) processes. 相似文献
4.
The data of the bottom “summit” surface were used for compiling the schematic structural-neotectonic map and map of the main
neotectonic structural elements. Their comparison with the schematic paleogeographic maps of the lithophysical complexes for
four periods (K2-$
_{1 - 2}
$
_{1 - 2}
, $
\rlap{--} P_3
$
\rlap{--} P_3
-N11, N11–2, and N13-N2) reveals that the largest part of the considered area was characterized by either a continental or relatively shallow-sea
environment, except for the western areas occupied at that time by the relatively deep trough with its axis located substantially
westward of the neotectonic Deryugin Basin and the Staritskii Trough. In the Late Pliocene, the deep paleotrough ($
\rlap{--} P_3
$
\rlap{--} P_3
-N22) and Deryugin Basin were likely occupied by shelf settings with continuing sedimentation. The paleogeographic environments
of the area for the period from the terminal Pliocene to the late Riss (Taz) Glaciation (Q26; MIS6) are unknown so far. The most complete Quaternary section recovered by Core LV 28-34-2 consists of six units; the odd
(1, 3, and 5) and even (2, 4, and 6) among them correspond to the warm and cold marine isotopic stages, respectively. Judging
from the benthic foraminiferal assemblages, the water depths during cold periods were shallower as compared with the warm
stages, which is explained by the respective ascending and descending bottom movements and, partially, by the eustatic sea
level fluctuations. In the Late Pleistocene-Holocene (∼17 ka), the bottom of the Deryugin Basin and the summit part of the
Institut Okeanologii Rise subsided with average rates of 8 and 3 cm/year, respectively. 相似文献
5.
A new version of the STRUCTON (2009) computer model is proposed for the simulation of the molecular mass distributions (MMD)
characterizing the diversity of anions in silicate melts depending on their polymerization and temperature. In contrast to
earlier versions, the new version of the model accounts for disproportionation reactions of Q
n
species and makes use of their proportions in the statistical simulations of the origin of real Si-O complexes. The new potentialities
of the STRUCTON program package are illustrated by its application to studying the structural-chemical characteristics of
melts in the Na2O-SiO2 system along its liquidus line, including the points of eutectics and phase transitions at 0.333 ≤ $
N_{SiO_2 }
$
N_{SiO_2 }
< 0.500. This problem is solved with the use of a temperature-composition dependence of polymerization constants K
p
Na in the Toop-Samis approximation. The variations in K
p
Na were proved to be as large as three orders of magnitude due to both the temperature effect at a constant composition and
the composition effect at a constant temperature. The results of the MMD simulations on the liquidus show that the concentration
of the SiO44− ion strongly decreases, and the proportion of chain species increases compared to those at a stochastic distribution. The
concentration of the Si2O76− anion reaches its maximum (∼42%) at 40 mol % in the liquid, i.e., the composition of Na6Si2O7. At $
N_{SiO_2 }
$
N_{SiO_2 }
> 0.40, this ion dominates over the SiO44− monomer. More silicic melts with $
N_{SiO_2 }
$
N_{SiO_2 }
≥ 0.45, are dominated by (Si
n
O3n
)3n− ring species, and the concentrations of these species are related as (Si3O9)6− > (Si4O12)8− > (Si5O15)10−. The maximum concentration of these flat rings also occurs near the composition of stoichiometric metasilicate with Si/O
= 0.333. The comparison of the dependence of the average size of anions i
av and the average number of their species on depolymerization indicates that a change in the proportion of Q
n
species in melt at decreasing temperature results in structural restyling and an increase in the average size of Si-O complexes.
The average number of anion species thereby decreases compared to that in a stochastic MMD. The results presented in this
publication direct the progress in the thermodynamic theory of silicate melts to a new avenue that makes use of the capabilities
and advantages of the ion-polymer model, the theory of associated solutions, spectroscopic data, and the experimental study
of variations in oxide activities depending on composition and temperature. 相似文献
6.
Solubility curves of water-hydrogen fluid were studied using a high-pressure gas apparatus at a pressure of 200 MPa under
variable fluid composition in haplogranite (Ab
39
Or
32
Qtz
29, 950°C), Na-disilicate (Na2Si2O5, 950°C), and albite melts (1200°C). The mole fraction of hydrogen in experiments was controlled directly by Ar-H2 mixtures using a specially designed cell with a Shaw membrane. $
X_{H_2 }^{Ar - H_2 }
$
X_{H_2 }^{Ar - H_2 }
ranged from 0 to 1. In some experiments with haplogranite and Na-disilicate melts under oxidizing conditions, in order to
increase the accuracy of experimental parameters, the fugacities of oxygen and hydrogen were controlled using the double-capsule
technique and the solid-phase buffer mixtures Ni-NiO (NNO) and Co-CoO (CCO). The addition of H2 to the H2O-saturated systems ($
X_{H_2 }^{H_2 O - H_2 }
$
X_{H_2 }^{H_2 O - H_2 }
≥ 0.012) results in the appearance of a distinct maximum on the solubility curves at $
X_{H_2 }^{H_2 O - H_2 }
$
X_{H_2 }^{H_2 O - H_2 }
= 0.05–0.07 (H2 mole fractions were calculated for real H2O-H2 mixtures of real gases), and the maximum content of H2O-H2 fluid increases relative to the H2O-saturated melts by 1.51 wt % for haplogranite melt at $
X_{H_2 }
$
X_{H_2 }
= 0.063, 2.68 wt % for albite melt at $
X_{H_2 }
$
X_{H_2 }
= 0.066, and 3.54 wt % for Na-disilicate melt at $
X_{H_2 }
$
X_{H_2 }
= 0.067. A further increase in H2 content in the gas mixture decreases the solubility of H2O-H2 fluid in the melts, and under pure H2 pressure, the contents of fluid components are 0.08 wt % in haplogranite melt and 0.06 wt % in albite melt. The 1H NMR study of aluminosilicate and Na-silicate glasses obtained under the pressure of H2O and H2O-H2 fluids suggests different mechanisms of the dissolution of H2O and H2O-H2 fluids in magmatic melts. In addition to the spectra of dissolved water fluid, the spectra of quenched glasses synthesized
under H2O-H2 fluid pressure exhibited a narrow line of molecular hydrogen with a width at half height of 1.8–2.0 kHz at $
X_{H_2 }
$
X_{H_2 }
≥ 0.653 for albite and $
X_{H_2 }
$
X_{H_2 }
≥ 0.063 for Na-disilicate and two lines at $
X_{H_2 }
$
X_{H_2 }
≥ 0.063 for the haplogranite composition. 相似文献
7.
Mineral-specific IR absorption coefficients were calculated for natural and synthetic olivine, SiO2 polymorphs, and GeO2 with specific isolated OH point defects using quantitative data from independent techniques such as proton–proton scattering,
confocal Raman spectroscopy, and secondary ion mass spectrometry. Moreover, we present a routine to detect OH traces in anisotropic
minerals using Raman spectroscopy combined with the “Comparator Technique”. In case of olivine and the SiO2 system, it turns out that the magnitude of ε for one structure is independent of the type of OH point defect and therewith
the peak position (quartz ε = 89,000 ± 15,000
\textl \textmol\textH2\textO-1 \textcm-2\text{l}\,\text{mol}_{{\text{H}_2}\text{O}}^{-1}\,\text{cm}^{-2}), but it varies as a function of structure (coesite ε = 214,000 ± 14,000
\textl \textmol\textH2\textO-1 \textcm-2\text{l}\,\text{mol}_{{\text{H}_2}\text{O}}^{-1}\,\text{cm}^{-2}; stishovite ε = 485,000 ± 109,000
\textl \textmol\textH2\textO-1 \textcm-2\text{l}\,\text{mol}_{{\text{H}_2}\text{O}}^{-1}\,\text{cm}^{-2}). Evaluation of data from this study confirms that not using mineral-specific IR calibrations for the OH quantification in
nominally anhydrous minerals leads to inaccurate estimations of OH concentrations, which constitute the basis for modeling
the Earth’s deep water cycle. 相似文献
8.
Sogdianite, a double-ring silicate of composition
( \textZr0. 7 6 \textTi0. 3 84 + \textFe0. 7 33 + \textAl0.13 )\Upsigma = 2 ( \square 1. 1 5 \textNa0. 8 5 )\Upsigma = 2 \textK[\textLi 3 \textSi 1 2 \textO 30 ] ( {\text{Zr}}_{0. 7 6} {\text{Ti}}_{0. 3 8}^{4 + } {\text{Fe}}_{0. 7 3}^{3 + } {\text{Al}}_{0.13} )_{\Upsigma = 2} \left( {\square_{ 1. 1 5} {\text{Na}}_{0. 8 5} } \right)_{\Upsigma = 2} {\text{K}}[{\text{Li}}_{ 3} {\text{Si}}_{ 1 2} {\text{O}}_{ 30} ] from Dara-i-Pioz, Tadjikistan, was studied by the combined application of 57Fe M?ssbauer spectroscopy and electronic structure calculations. The M?ssbauer spectrum confirms published microprobe and
X-ray single-crystal diffraction results that indicate that Fe3+ is located at the octahedral A-site and that no Fe2+ is present. Both the measured and calculated quadrupole splitting, ΔE
Q, for Fe3+ are virtually 0 mm s−1. Such a value is unusually small for a silicate and it is the same as the ΔE
Q value for Fe3+ in structurally related sugilite. This result is traced back to the nearly regular octahedral coordination geometry corresponding
to a very symmetric electric field gradient around Fe3+. A crystal chemical interpretation for the regular octahedral geometry and the resulting low ΔE
Q value for Fe3+ in the M?ssbauer spectrum of sogdianite is that structural strain is largely “taken up” by weak Li–O bonds permitting highly
distorted LiO4 tetrahedra. Weak Li–O bonding allows the edge-shared more strongly bonded Fe3+O6 octahedra to remain regular in geometry. This may be a typical property for all double-ring silicates with tetrahedrally
coordinated Li. 相似文献
9.
The redox state of the continental lithospheric mantle of the Baikal-Mongolia region 总被引：1，自引：0，他引：1
L. P. Nikitina A. G. Goncharov A. K. Saltykova M. S. Babushkina 《Geochemistry International》2010,48(1):15-40
The thermal and redox state of the upper mantle beneath the Baikal-Mongolia region was estimated on the basis of the investigation
of the chemical composition (including iron oxidation state) of major minerals (olivine, orthopyroxene, clinopyroxene, and
spinel) in spinel and garnet-spinel peridotite xenoliths from the Cenozoic alkali basalts of the volcanic fields of the Dariganga
Plateau, Tariat Depression, and Vitim Plateau. At temperatures of 1030–1500°C and pressures of 29–47 kbar, the Δlog$
f_{O_2 }
$
f_{O_2 }
values relative to the FMQ buffer (calculated using the olivine-spinel oxygen barometer) range from −0.9 to −1.7 for the
xenoliths of the Dariganga Plateau, from −0.9 to −1.8 for the Tariat Depression, and from −0.8 to −0.1 for the Vitim Plateau.
The oxygen fugacity of peridotites from all of the areas is, in general, lower than that of the WM buffer. Oxygen fugacity
is usually below the CCO and EMOD/G buffers in the peridotites of the Dariganga Plateau and the Tariat Depression and higher
than these buffers in the peridotites of the Vitim Plateau. The T-PΔlog$
f_{O_2 }
$
f_{O_2 }
relationships in the xenoliths suggest the existence of spatial heterogeneity in the thermal and redox state of the upper
mantle of the Baikal-Mongolia region. This heterogeneity is probably related to the influence of the plume that was responsible
for the Late Mesozoic-Cenozoic intraplate magmatism of this region and reflects the different distance of the respective mantle
domains from the plume head. The C-O-H fluids in equilibrium with the upper mantle peridotites are composed mainly of water
and carbon dioxide. The mantle of the Dariganga Plateau and the Tariat Depression (Δlog$
f_{O_2 }
$
f_{O_2 }
< −0.9) is characterized by the dominance of H2O, whereas CO2-rich fluids are characteristic of the more oxidized mantle of the Vitim Plateau (Δlog$
f_{O_2 }
$
f_{O_2 }
is mostly higher than −0.8). 相似文献
10.
The present work aims in discussing a principle that distinguishes between elastic parameters sets, $ \{ \Upphi \} \equiv \{ K_{0} , \, K^{\prime}, \, V_{0} ,\ldots\}
11.
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
12.
Relative humidity (
P\textH 2 \textO P_{{{\text{H}}_{ 2} {\text{O}}}} , partial pressure of water)-dependent dehydration and accompanying phase transitions in NAT-topology zeolites (natrolite,
scolecite, and mesolite) were studied under controlled temperature and known
P\textH 2 \textO P_{{{\text{H}}_{ 2} {\text{O}}}} conditions by in situ diffuse-reflectance infrared Fourier transform spectroscopy and parallel X-ray powder diffraction.
Dehydration was characterized by the disappearance of internal H2O vibrational modes. The loss of H2O molecules caused a sequence of structural transitions in which the host framework transformation path was coupled primarily
via the thermal motion of guest Na+/Ca2+ cations and H2O molecules. The observation of different interactions of H2O molecules and Na+/Ca2+ cations with host aluminosilicate frameworks under high- and low-
P\textH 2 \textO P_{{{\text{H}}_{ 2} {\text{O}}}} conditions indicated the development of different local strain fields, arising from cation–H2O interactions in NAT-type channels. These strain fields influence the Si–O/Al–O bond strength and tilting angles within and
between tetrahedra as the dehydration temperature is approached. The newly observed infrared bands (at 2,139 cm−1 in natrolite, 2,276 cm−1 in scolecite, and 2,176 and 2,259 cm−1 in mesolite) result from strong cation–H2O–Al–Si framework interactions in NAT-type channels, and these bands can be used to evaluate the energetic evolution of Na+/Ca2+ cations before and after phase transitions, especially for scolecite and mesolite. The 2,176 and 2,259 cm−1 absorption bands in mesolite also appear to be related to Na+/Ca2+ order–disorder that occur when mesolite loses its Ow4 H2O molecules. 相似文献
13.
Li diffusion in zircon 总被引：2，自引：2，他引：0
Diffusion of Li under anhydrous conditions at 1 atm and under fluid-present elevated pressure (1.0–1.2 GPa) conditions has
been measured in natural zircon. The source of diffusant for 1-atm experiments was ground natural spodumene, which was sealed
under vacuum in silica glass capsules with polished slabs of zircon. An experiment using a Dy-bearing source was also conducted
to evaluate possible rate-limiting effects on Li diffusion of slow-diffusing REE+3 that might provide charge balance. Diffusion experiments performed in the presence of H2O–CO2 fluid were run in a piston–cylinder apparatus, using a source consisting of a powdered mixture of spodumene, quartz and zircon
with oxalic acid added to produce H2O–CO2 fluid. Nuclear reaction analysis (NRA) with the resonant nuclear reaction 7Li(p,γ)8Be was used to measure diffusion profiles for the experiments. The following Arrhenius parameters were obtained for Li diffusion
normal to the c-axis over the temperature range 703–1.151°C at 1 atm for experiments run with the spodumene source:
|