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Mityaev A. S. Safonov O. G. Reutsky V. N. Izokh O. P. Varlamov D. A. Kozlovskii V. M. van Reenen D. D. Aranovich L. Y. 《Doklady Earth Sciences》2020,492(1):342-345
Doklady Earth Sciences - Data on the carbon and oxygen isotopic composition of carbonates from the rocks of the Giyani greenstone belt, Kaapvaal craton, South Africa are presented. This belt is... 相似文献
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Pertsev A. N. Bortnikov N. S. Prokofiev V. Yu. Aranovich L. Ya. Ageeva O. A. Beltenev V. E. Zhilicheva O. M. Kovalchuk E. V. 《Doklady Earth Sciences》2018,480(1):661-665
New data on local mineral associations and the microheterogeneity of minerals and fluid inclusions in gabbro were obtained for the gabbro–peridotite oceanic core complex with a long-lived detachment fault controlling the hydrothermal activity. It is assumed that the hydrothermal hydrogen-bearing fluid with a NaCl content of >30 wt % is formed in the seawater/harzburgite (~1/5) reaction of serpentinization. The brine residual after serpentinization interacted with gabbro at the final stages of crystallization of an intrusion and assimilated some components (K, REEs, and Ba) from the residual melt. The interaction was resulted in metamorphic transformations of gabbro at decreasing temperature below 500°C. The reaction of the decomposition of magmatic titanomagnetite with the transition of iron reduced to Fe2+ into newly formed chlorinebearing amphibole at 540–450°C and logf(O2) from–20 to–24 is shown.
相似文献5.
H2O activity in concentrated NaCl solutions at high pressures and temperatures measured by the brucite-periclase equilibrium 总被引：1，自引：0，他引：1
H2O activities in concentrated NaCl solutions were measured in the ranges 600°–900° C and 2–15 kbar and at NaCl concentrations
up to halite saturation by depression of the brucite (Mg(OH)2) – periclase (MgO) dehydration equilibrium. Experiments were made in internally heated Ar pressure apparatus at 2 and 4.2
kbar and in 1.91-cm-diameter piston-cylinder apparatus with NaCl pressure medium at 4.2, 7, 10 and 15 kbar. Fluid compositions
in equilibrium with brucite and periclase were reversed to closures of less than 2 mol% by measuring weight changes after
drying of punctured Pt capsules. Brucite-periclase equilibrium in the binary system was redetermined using coarsely crystalline
synthetic brucite and periclase to inhibit back-reaction in quenching. These data lead to a linear expression for the standard
Gibbs free energy of the brucite dehydration reaction in the experimental temperature range: ΔG° (±120J)=73418–134.95T(K). Using this function as a baseline, the experimental dehydration points in the system MgO−H2O−NaCl lead to a simple systematic relationship of high-temperature H2O activity in NaCl solution. At low pressure and low fluid densities near 2 kbar the H2O activity is closely approximated by its mole fraction. At pressures of 10 kbar and greater, with fluid densities approaching
those of condensed H2O, the H2O activity becomes nearly equal to the square of its mole fraction. Isobaric halite saturation points terminating the univariant
brucite-periclase curves were determined at each experimental pressure. The five temperature-composition points in the system
NaCl−H2O are in close agreement with the halite saturation curves (liquidus curves) given by existing data from differential thermal
analysis to 6 kbar. Solubility of MgO in the vapor phase near halite saturation is much less than one mole percent and could
not have influenced our determinations. Activity concentration relations in the experimental P-T range may be retrieved for the binary system H2O-NaCl from our brucite-periclase data and from halite liquidus data with minor extrapolation. At two kbar, solutions closely
approach an ideal gas mixture, whereas at 10 kbar and above the solutions closely approximate an ideal fused salt mixture,
where the activities of H2O and NaCl correspond to an ideal activity formulation. This profound pressure-induced change of state may be characterized
by the activity (a) – concentration (X) expression: a
H
2O=X
H
2O/(1+αX
NaCl), and a
NaCl=(1+α)(1+α)[X
NaCl/(1+αX
NaCl)](1+α). The parameter α is determined by regression of the brucite-periclase H2O activity data: α=exp[A–B/ϱH
2O ]-CP/T, where A=4.226, B=2.9605, C=164.984, and P is in kbar, T is in Kelvins, and ϱH
2O is the density of H2O at given P and T in g/cm3. These formulas reproduce both the H2O activity data and the NaCl activity data with a standard deviation of ±0.010. The thermodynamic behavior of concentrated NaCl solutions at
high temperature and pressure is thus much simpler than portrayed by extended Debye-Hückel theory. The low H2O activity at high pressures in concentrated supercritical NaCl solutions (or hydrosaline melts) indicates that such solutions
should be feasible as chemically active fluids capable of coexisting with solid rocks and silicate liquids (and a CO2-rich vapor) in many processes of deep crustal and upper mantle metamorphism and metasomatism.
Received: 1 September 1995 / Accepted: 24 March 1996 相似文献
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Exchange-mineral equilibria with Al and Fe3+ aqueous chloride solutions (aq.), Andr + AlCl aq 3 = FeCl aq 3 + Gros, (1) Psc + AlCl aq 3 = FeCl aq 3 + Czo, (2) were studied under the following experimental conditions: 500°;C and 580°;C and 1 and 2 kbar, respectively, with an overall concentration of metals in the aqueous solutions of about 0.5 M and pH 3. The mixing functions of the components in garnet and epidote were calculated from the experimental data. Thermodynamic treatment of experimental evidence for reaction (1) led to the conclusion that, within the accuracy of experiment, garnet in the andradite-grossularite series was an ideal solid solution. However, epidote solid solution markedly departed from the ideal, as was shown by concentration and pressure-temperature (PT) dependencies of Gibbs's molar excess energies and by mixing-volume concentration dependence. 相似文献
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In the period up to about 1965 the stations of the Soviet seismic network distributed throughout the regions of the U.S.S.R. had increased in number to in excess of one hundred. In order that the data provided by such stations could be applied to the study of the earth's structure rather than merely regional problems, and to the determination of the seismic character of the territory of the U.S.S.R. as a whole, it became necessary to institute the Unified System of Seismic Observations (USSO) of the U.S.S.R. The standardization of data and organization of the stations into a system of base and regional stations and also into zonal networks, covering specific seismic zones of the U.S.S.R., has been effected within the USSO. Currently the USSO consists of 215 stations mostly equipped with high-sensitivity instruments with magnifications of 20–50,000 and dynamic ranges of 35–40 dB. To exploit the large volume of observational data obtained through the system it is necessary to devise a programme for the transmission, processing and storage of data on the necessary scale. In the present paper we describe the methods which have been adopted and those which are in the course of development for such a programme in the U.S.S.R. 相似文献
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H2O activities in supercritical fluids in the system KCl-H2O-(MgO) were measured at pressures of 1, 2, 4, 7, 10 and 15 kbar by numerous reversals of vapor compositions in equilibrium
with brucite and periclase. Measurements spanned the range 550–900 °C. A change of state of solute KCl occurs as pressures
increase above 2 kbar, by which H2O activity becomes very low and, at pressures of 4 kbar and above, nearly coincident with the square of the mole fraction
(x
H2O). The effect undoubtedly results primarily from ionic dissociation as H2O density (ρH2O) approaches 1 gm/cm3, and is more pronounced than in the NaCl-H2O system at the same P-T-X conditions. Six values of solute KCl activity were yielded by terminal points of the isobaric brucite-periclase T-x
H2O curves where sylvite saturation occurs. The H2O mole fraction of the isobaric invariant assemblage brucite-periclase-sylvite-fluid is near 0.52 at all pressures, and the
corresponding temperatures span only 100 °C between 1 and 15 kbar. This remarkable convergence of the isobaric equilibrium
curves reflects the great influence of pressure on lowering of both KCl and H2O activities. The H2O and KCl activities can be expressed by the formulas: a
H2O = γH2O[x
H2O+(1 + (1 + α)x
KCl)], and a
KCL = γKCl[(1 + α)x
KCl/(x
H2O +(1 + α)x
KCl)](1 + α), where α is a degree of dissociation parameter which increases from zero at the lowest pressures to near one at high pressures
and the γ's are activity coefficients based on an empirical regular solution parameter W: ln γi = (1 − xi)2W. Least squares fitting of our H2O and KCl activity data evaluates the parameters: α = exp(4.166 −2.709/ρH2O) − 212.1P/T, and W = (−589.6 − 23.10P) /T, with ρH2O in gm/cm3, P in kbar and T in K. The standard deviation from the measured activities is only ± 0.014. The equations define isobaric liquidus curves,
which are in perfect agreement with previous DTA liquidus measurements at 0.5–2 kbar, but which depart progressively from
their extrapolation to higher pressures because of the pressure-induced dissociation effect. The great similarity of the NaCl-H2O and KCl-H2O systems suggests that H2O activities in the ternary NaCl-KCl-H2O system can be described with reasonable accuracy by assuming proportionality between the binary systems. This assumption
was verified by a few reconnaissance measurements at 10 kbar of the brucite-periclase equilibrium with a Na/(Na + K) ratio
of 0.5 and of the saturation temperature for Na/(Na + K) of 0.35 and 0.50. At that pressure the brucite-periclase curves reach
a lowest x
H2O of 0.45 and a temperature of 587 °C before salt saturation occurs, values considerably lower than in either binary. This
double-salt eutectic effect may have a significant application to natural polyionic hypersaline solutions in the deep crust
and upper mantle in that higher solute concentrations and very low H2O activities may be realized in complex solutions before salt saturation occurs. Concentrated salt solutions seem, from this
standpoint, and also because of high mechanical mobility and alkali-exchanging potential, feasible as metasomatic fluids for
a variety of deep-crust and upper mantle processes.
Received: 9 August 1996 / Accepted: 15 November 1996 相似文献
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R. G. Berman L. Ya Aranovich D. R. M. Pattison 《Contributions to Mineralogy and Petrology》1995,119(1):30-42
The garnet (Grt)-clinopyroxene (Cpx) Fe-Mg exchange thermometer has been re-evaluated through analysis of phase equilibrium
experiments defining the Fe-Mg exchange between Grt and Cpx, Grt and Ol (Ol=Olivine), and Cpx and Ol, together with thermophysical
and other phase equilibrium constraints on solid solution and individual end-member properties. Results show that all data
are mutually compatible if the heterogeneity range of Grt and Cpx in run products previously obtained by Pattison and Newton
(PN) are accounted for in assessing equilibrium Grt-Cpx compositions. Derived mixing properties are in good agreement with
results from numerous recent phase equilibrium studies. Application of the newly calibrated thermometer to a number of amphibolite
to granulite facies terrains indicates temperatures between 70 and 200 ° C above PN’s thermometer, and general compatibility
with independent temperature estimates.
Received: 3 September 1993 / Accepted: 16 June 1994 相似文献