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2.
The hydrolysis of the Pd 2+ ion in HClO 4 solutions was examined at 25–70°C, and the thermodynamic constants of equilibrium K (1)0 and K (2)0were determined for the reactions Pd 2+ + H 2O = PdOH + + H + and Pd 2+ + 2H 2O = Pd(OH) 20 + 2H +, respectively. The values of log K (1)0 = −1.66 ± 0.5 (25°C) and −0.65 ± 0.25 (50°C) and log K (2)0 = −4.34 ± 0.3 (25°C) and −3.80 ± 0.3 (50°C) were derived using the solubility technique at 0.95 confidence level. The values of log K (1)0 = −1.9 ± 0.6 (25°C), −1.0 ± 0.4 (50°C), and −0.5 ± 0.3 (70°C) were obtained by spectrophotometric techniques. The palladium ion is significantly hydrolyzed at elevated temperatures (50–70°C) even in strongly acidic solutions (pH 1–1.5), and its hydrolysis is enhanced with increasing temperature. 相似文献
3.
The effect of sulfur on the sorption of gold by carbonaceous matter (CM) was investigated under hydrothermal conditions (200–400°C
and 1 kbar) using the autoclave-ampoule method. The model CM was represented by asphaltenes fractionated from the lignite
of the Pavlovskoe coal field. The source of gold was the walls of the Au container, which were dissolved in water under the
experimental conditions. Sulfur was added as finely ground pyrite (C-S-Fe-O-H-Au system) or elemental sulfur powder (C-S-O-H-Au
system). The contents of Au were measured by atomic absorption spectrometry with electrothermal atomization in quenched aqueous
solutions (WF), soluble organic fraction (SF), and insoluble residue (kerogen). The lowest Au concentration was detected in
the WF, −8.96 < log mAu < −6.32. The Au concentration is higher in the SF (−5.02 < log mAu < −4.34) and increases by more then an order of magnitude in the kerogen, −3.94 < log mAu < −2.33. The IR spectra of the experimental products showed that sulfur was accumulated in the kerogen, whereas no C-S
functional groups were observed in the SF. This is the reason for the negligible influence of sulfur in this system on Au
concentration in the SF. The maximum Au concentration was detected in the kerogen in the presence of pyrite, which was transformed
into pyrrhotite at 400°C. Thus, iron sulfides promote Au uptake by kerogen from ore-bearing hydrothermal fluids. 相似文献
5.
Vanadium has multiple oxidation states in silicate melts and minerals, a property that also promotes fractionation of its isotopes. As a result, vanadium isotopes vary during magmatic differentiation, and can be powerful indicators of redox processes at high temperatures if their partitioning behaviour can be determined. To quantify the partitioning and isotope fractionation factor of V between magnetite and melt, piston cylinder experiments were performed in which magnetite and a hydrous, haplogranitic melt were equilibrated at 800 °C and 0.5 GPa over a range of oxygen fugacities ( \({f_{{{\text{O}}_{\text{2}}}}}\)), bracketing those of terrestrial magmas. Magnetite is isotopically light with respect to the coexisting melt, a tendency ascribed to the VI-fold V 3+ and V 4+ in magnetite, and a mixture of IV- and VI-fold V 5+ and V 4+ in the melt. The magnitude of the fractionation factor systematically increases with increasing log \({f_{{{\text{O}}_{\text{2}}}}}\) relative to the Fayalite–Magnetite–Quartz buffer (FMQ), from ? 51V mag-gl = ? 0.63?±?0.09‰ at FMQ ? 1 to ? 0.92?±?0.11‰ (SD) at ≈?FMQ?+?5, reflecting constant V 3+/V 4+ in magnetite but increasing V 5+/V 4+ in the melt with increasing log \({f_{{{\text{O}}_{\text{2}}}}}\). These first mineral-melt measurements of V isotope fractionation factors underline the importance of both oxidation state and co-ordination environment in controlling isotopic fractionation. The fractionation factors determined experimentally are in excellent agreement with those needed to explain natural isotope variations in magmatic suites. Furthermore, these experiments provide a useful framework in which to interpret vanadium isotope variations in natural rocks and magnetites, and may be used as a potential fingerprint the redox state of the magma from which they crystallise. 相似文献
6.
The contents and speciation of nitrogen, carbon, and hydrogen were determined in basalt–basaltic andesite melts in equilibrium with liquid Fe alloys at 1.5 Gpa, 1400°C, and oxygen fugacity ( fO 2) 1.4–1.9 log units below that of the Fe–FeO buffer (Δlog fO 2(IW) =–1.4 …–1.9). Experiments were carried out on a piston- cylinder type apparatus using welded Pt capsules in the presence of excess С (graphite). Starting mixture consisted of natural ferrobasaltic glass and silicon nitride (Si 3N 4) as nitrogen source in the system. Experimental quench products representing glasses with spherical inclusions of iron alloy were analyzed using electron microprobe, Raman, and IR spectroscopy. With increase of Si 3N 4 in the starting mixture and, respectively, decrease of fO 2, silicate melt forming during experiments became depleted in FeO and enriched in SiO 2. It was established that the nitrogen content in the glasses increases from 0.13 to 0.44 wt % with decrease of Δlog fO 2(IW) from–1.4 to–1.9, whereas C content in the first approximation remains constant within 1.18–1.13 wt %, while the total water content (ОН – + Н 2О) determined by IR spectroscopy decreases from 4.91 to 1.20 wt %. The N (0.13–0.48 wt %) and C (0.75–2.26 wt %) contents determined in the Fe alloy show no clear correlation with fO 2. The IR and Raman spectroscopic study of the glasses indicates the formation of molecules and complexes with bonds N–H (NH 3, NH 2 ?, NH 2 +, NH 4 +), Н–О (Н 2О, OH –), С–Н (СН 4) as well as N 2 and Н 2 molecules in silicate melts. IR spectra also reveal the presence of complexes with С=О, С–N bonds and СО 2 molecules. Obtained data are compared with results of previous studies on the solubility and speciation of N, С, and Н in the model FeO–Na 2O–SiO 2–Al 2O 3 melts in equilibrium with liquid iron alloys at 1.5 GPa (1400°C) and 4 GPa (1550°C) (Kadik et al., 2011, 2015). 相似文献
7.
Recently in China, soil–cement is widely used to improve the soft ground in the highway construction engineering. Literature
studies are mainly investigating the mechanical properties of the soil–cement, while its properties of the electrical resistivity
are not well addressed. In this paper, the properties of the electrical resistivity of the reconstituted soil-cement and the
in situ soil–cement columns are investigated. The test results show that the electrical resistivity of the soil–cement increases
with the increase in the cement-mixing ratio and curing time, whereas it decreases with the increase in the water content,
degree of saturation and water–cement ratio. A simple equation is proposed to predict the electrical resistivity of soil–cement
under the condition of the specified curing time and water–cement ratio. It is found that the electrical resistivity has a
good relationship with the unconfined compression strength and blow count of SPT. It is expected that the electrical resistivity
method can be widely used for checking/controlling the quality of soil–cement in practice. 相似文献
8.
The paper presents results of experiments aimed at diamond synthesis in the Fe–C–S system at 5.3–5.5 GPa and temperatures of 1300–1370°C and detailed data on the microtextures of the experimental samples and the composition of the accompanying phases (Fe 3C and Fe 7C 3 carbides, graphite, and FeS). It is demonstrated that diamond can be synthesized after temperatures at which carbides are formed are overcome and can crystallize within the temperature range of 1300°C (temperature of the peritectic reaction melt + diamond = Fe 7C 3) to 1370°C (of thermodynamically stable graphite) under the appearance experimental pressure. The possible involvement of natural metal- and sulfur-bearing compounds in the origin of natural diamond is discussed. 相似文献
10.
The composition of a reduced C–O–H fluid was studied by the method of chromatography–mass spectrometry under the conditions of 6.3 GPa, 1300–1400°C, and fO 2 typical of the base of the subcratonic lithosphere. Fluids containing water (4.4–96.3 rel. %), methane (37.6–0.06 rel. %), and variable concentrations of ethane, propane, and butane were obtained in experiments. With increasing fO 2, the proportion of the CH 4/C 2H 6 peak areas on chromatograms first increases and then decreases, whereas the CH 4/C 3H 8 and CH 4/C 4H 10 ratios continually decrease. The new data show that ethane and heavier HCs may be more stable to oxidation, than previously thought. Therefore, when reduced fluids pass the “redox-front,” carbon is not completely released from the fluid and may be involved in diamond formation. 相似文献
11.
Parts of the Fe–C–N system were studied in experiments at 7.8 GPa and 1350°C. It was shown that the admixture of nitrogen extends considerably the domain of melt stability in the system at temperatures close to the Fe–Fe 3C eutectic temperatures. Nitrogen solubility in cementite in equilibrium with the nitrogen- rich melt is below the detection limit of the EMPA technique applied. The metal melt is the only nitrogen concentrator (up to 4 wt % of N) in the range of compositions considered. The data obtained permit the conclusion that, in the case of complete dissolution of carbon and nitrogen, which might occur in the enriched mantle, native iron at ~250 km depth should either be completely molten or consist of a melt and carbide of iron. 相似文献
14.
Partitioning of more than 35 elements between coexisting phases in the apatite (Apt)–carbonate (Carb)–H2O system was studied experimentally at P = 0.5 GPa and T = 1200°C for estimation of the efficiency of fluid transport during the formation of carbonatite in platform alkaline intrusions. The interphase partition coefficients of elements (D) range from n × 10–2 to 100 and higher, which provides evidence for their effective fractionation in the system. The following elements were distinguished: (1) Apt-compatible (REE, Y, Th, Cu, and W), which are concentrated in apatite; (2) hydrophile (Na, K, Mg, Ba, S, Mn, Pb, U, W, and Re), which are preferably distributed into fluid or the carbonate melt. The high hydrophilicity of alkali metals controls the alkaline character of postmagmatic fluids and related metasomatic rocks, whereas the high D(Fl/Apt) and D(Fl/LCarb) for S, Zr, W, Re, and U show their high potential in relation to U–W–Re mineralization. 相似文献
15.
Doklady Earth Sciences - The issue of the stability of carbonate matter (CaCO3) in subduction zones under reduced conditions remains topical. In addition, carbonates may be one of the key sources... 相似文献
16.
Uraninite solubility in 0.001–2.0 m HCl solutions was experimentally studied at 500°C, 1000 bar, and hydrogen fugacity corresponding to the Ni/NiO buffer. It
was shown that the following U(IV) species dominate in the aqueous solution: U(OH) 40, U(OH) 2Cl 20, and UOH Cl 30 Using the results of uraninite solubility measurement, the Gibbs free energies of U(IV) species at 500°C and 1000 bar were
calculated (kJ/mol): −9865.55 for UO 2(aq), −1374.57 for U(OH) 2 Cl 20, and −1265.49 for UOH Cl 30, and the equilibrium constants of uraninite dissolution in water and aqueous HCl solutions were estimated: UO 2(cr) = UO 2(aq), p K
0 = 6.64; UO 2(cr) + 2HCl 0 = U(OH) 2 Cl 20, p K
2 = 3.56; and UO 2(cr) + 3HCl 0 = UOHcl 30 + H 2O, p K
3 = 3.05. The value p K
1 ≈ 5.0 was obtained as a first approximation for the equilibrium UO 2(cr) + H 2O + HCl 0 = U(OH) 3Cl 0. The constant of the reaction UO 2(cr) + 4HCl 0 = UCl 40 + 2H 2O (p K
4 = 7.02) was calculated taking into account the ionization constants of U Cl 40 and U(OH) 40, obtained by extrapolation from 25 to 500°C at 1000 bar using the BR model. Intense dissolution and redeposition of gold
(material of experimental capsules) was observed in our experiments. The analysis and modeling of this phenomenon suggested
that the UO 2 + x
/UO 2 redox pair oxidized Au(cr) to Au +(aq), which was then reduced under the influence of stronger reducers. 相似文献
18.
Large-scale melting of the Earth’s early mantle under the effect of global impact processes was accompanied by the generation of volatiles, which concentration was mainly controlled by the interaction of main N, C, O, and H gas-forming elements with silicate and metallic melts at low oxygen fugacity ( fO 2), which predominated during metallic segregation and self-oxidation of magma ocean. The paper considers the application of Raman and IR (infrared) Fourier spectroscopy for revealing the mechanisms of simultaneous dissolution and relative contents of N, C, O, and H in glasses, which represent the quench products of reduced model FeO–Na 2O–Al 2O 3–SiO 2 melts after experiments at 4 GPa, 1550°C, and fO 2 1.5–3 orders of magnitude below the oxygen fugacity of the iron—wustite buffer equilibrium ( fO 2( IW)). Such fO 2 values correspond to those inferred for the origin and evolution of magma ocean. It was established that the silicate melt contains complexes with N–H bonds (NH 3, NH 2 + , NH 2 - ), N 2, H 2, and CH 4 molecules, as well as oxidized hydrogen species (OH – hydroxyl and molecular water H 2O). Spectral characteristics of the glasses indicate significant influence of fO 2 on the N–C–O–H proportion in the melt. They are expressed in a sharp decrease of NH 2 + , NH 2 - (O–NH 2), OH –, H 2O, and CH 4 and simultaneous increase of NH 2 - (≡Si–NH 2) and NH 3 with decreasing fO 2. As a result, NH 3 molecules become the dominant nitrogen compounds among N–C–H components in the melt at fO 2 two orders of magnitude below fO 2( IW), whereas molecular СН 4 prevails at higher fO 2. The noteworthy feature of the redox reactions in the melt is stability of the ОН – groups and molecular water, in spite of the sufficiently low fO 2. Our study shows that the composition of reduced magmatic gases transferred to the planet surface has been significantly modified under conditions of self-oxidation of mantle and magma ocean. 相似文献
19.
The phase state of fluid in the system H 3BO 3–NaF–SiO 2–H 2O was studied at 350–800 °C and 1–2 kbar by the method of synthetic fluid inclusions. The increase in the solubility of quartz and the high reciprocal solubility of H 3BO 3 and NaF in water fluid at high temperatures are due to the formation of complexes containing B, F, Si, and Na. At 800 °C and 2 kbar, both liquid and gas immiscible phases (viscous silicate-water-salt liquid and three water fluids with different contents of B and F) are dispersed within each other. The Raman spectra of aqueous solutions and viscous liquid show not only a peak of [B(OH) 3] 0 but also peaks of complexes [B(OH) 4] –, polyborates [B 4O 5(OH) 4] 2–, [B 3O 3(OH) 4] –, and [B 5O 6(OH) 4] –, and/or fluoroborates [B 3F 6O 3] 3–, [BF 2(OH) 2] –, [BF 3(OH)] –, and [BF 4] –. The high viscosity of nonfreezing fluid is due to the polymerization of complexes of polyborates and fluorine-substituted polyborates containing Si and Na. Solutions in fluid inclusions belong to P–Q type complicated by a metastable or stable immiscibility region. Metastable fluid equilibria transform into stable ones owing to the formation of new complexes at 800 ºC and 2 kbar as a result of the interaction of quartz with B-F-containing fluid. At high concentrations of F and B in natural fluids, complexes containing B, F, Si, and alkaline metals and silicate-water-salt dispersed phases might be produced and concentrate many elements, including ore-forming ones. Their transformation into vitreous masses or viscous liquids (gels, jellies) during cooling and the subsequent crystallization of these products at low temperatures (300–400 °C) should lead to the release of fluid enriched in the above elements. 相似文献
20.
Oxygen isotope fractionations in laboratory systems have been determined between chlorite and water at 170–350°C. In one series of experiments, the Northrop-Clayton partial exchange method was used where three (sometimes four) isotopically different waters were reacted with chlorite [(∑Fe)/∑Fe+Mg = 0.483] for four durations (132–3282 h) at 350°C and 250 b. The percents of exchange determined for the four times from shortest to longest are 4.4, 6.5, 8.0, and 11.9. The fractionations calculated from the Northrop and Clayton (1966) method are in modest agreement for the four run durations: 0.13, 0.26, −0.46, and −0.55 per mil. Errors associated with each of these fractionations are quite large (e.g., ±1.2 per mil for the longest run). The value determined for the longest run of ∼20 weeks is the most reliable of the group and compares very closely with a value of ∼ −0.7 per mil estimated by Wenner and Taylor (1971) based on natural chlorites. Good agreement is also observed with the estimates, −1.2 and −1.3‰ calculated at 350°C for chlorite compositions with [(∑Fe)/∑Fe+Mg] = 0.313 and 0.444, respectively, from equations given by Savin and Lee (1988) based on their empirical bond-type method.Additional fractionation data have been estimated from hydrothermal granite-fluid experiments where chlorite formed from biotite. Detailed thin section, scanning electron microscope (SEM), x-ray diffraction (XRD), and electron microprobe analyses demonstrate that biotite is altered exclusively to chlorite in 13 granite-fluid experiments conducted at the following conditions: T = 170–300°C, P = vapor saturation − 200 b, salinity = H 2O, 0.1 and 1 m NaCl, fluid/biotite mass ratios = 3−44, run durations = 122−772 h. The amount of chlorite, quantified through point counting and XRD, increased with increasing temperature, salinity, and time. The isotope compositions of chlorite were calculated from mass balance and compared to the final measured δ 18O of the fluids. The 10 3ln α values averaged 0.14, 0.8 and 2.9 per mil for 300°, 250°, and 200°C, respectively. A least-squares regression model of the combined data set (all T’s) gives the following expression for fractionation: 1000 ln α chl-w=2.693 (10 9/T 3)−6.342 (10 6/T 2)+2.969 (10 3/T) The curve described by this equation is in very good agreement with empirical curves given by Wenner and Taylor 1971, Savin and Lee 1988 and Zheng (1993). 相似文献
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