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1.
Dissociation constants of aqueous ion pairs HCl0 and HBr0 derived in the literature from vapor pressure and supercritical conductance measurements Quist and Marshall 1968b, Frantz and Marshall 1984 were used to calculate the standard partial molal thermodynamic properties of the species at 25°C and 1 bar. Regression of the data with the aid of revised Helgeson-Kirkham-Flowers equations of state Helgeson et al 1981, Tanger 1988, Shock et al 1989 resulted in a set of equations-of-state parameters that permits accurate calculation of the thermodynamic properties of the species at high temperatures and pressures. These properties and parameters reproduce generally within 0.1 log unit (with observed maximum deviation of 0.23 log unit) the log K values for HBr0 and HCl0 given by Quist and Marshall (1968b) and Frantz and Marshall (1984), respectively, at temperatures to 800°C and pressures to 5 kbar.  相似文献   

2.
Correlations among experimentally determined standard partial molal thermodynamic properties of inorganic aqueous species at 25 degrees C and 1 bar allow estimates of these properties for numerous monatomic cations and anions, polyatomic anions, oxyanions, acid oxyanions, neutral oxy-acid species, dissolved gases, and hydroxide complexes of metal cations. Combined with correlations among parameters in the revised Helgeson-Kirkham-Flowers (HKF) equation of state (Shock et al., 1992), these estimates permit predictions of standard partial molal volumes, heat capacities, and entropies, as well as apparent standard partial molal enthalpies and Gibbs free energies of formation to 1000 degrees C and 5 kb for hundreds of inorganic aqueous species of interest in geochemistry. Data and parameters for more than 300 inorganic aqueous species are presented. Close agreement between calculated and experimentally determined equilibrium constants for acid dissociation reactions and cation hydrolysis reactions supports the generality and validity of these predictive methods. These data facilitate the calculation of the speciation of major, minor, and trace elements in hydrothermal and metamorphic fluids throughout most of the crust of the Earth.  相似文献   

3.
Log–log correlation plots between the dissociation constants of known metal–chromate complexes and those of corresponding metal–sulfate complexes at 25 °C, 1 bar were used to derive the standard partial molal Gibbs free energies of formation of unknown metal–chromate complexes involving either (i) monovalent cations, divalent cations, and trivalent lanthanides or (ii) trivalent cations (excluding those of rare earth elements, REE) and tetravalent cations. For each of these two classes of ionic associations, empirical relationships between the standard partial molal volumes, isobaric heat capacities and entropies of known metal–chromate complexes and the corresponding thermodynamic properties of metal ions have been found. These data were utilized to evaluate the solute-characteristic parameters of the revised Helgeson–Kirkham–Flowers equation of state and to compute the thermodynamic properties of the dissociation reactions of metal–chromate complexes at high temperatures and pressures.  相似文献   

4.
The standard thermodynamic properties at 25°C, 1 bar (ΔG fo, ΔH fo, S o, C Po, V o, ω) and the coefficients of the revised Helgeson–Kirkham–Flowers equations of state were evaluated for several aqueous complexes formed by dissolved metals and either arsenate or arsenite ions. The guidelines of Shock and Helgeson (Geochim Cosmochim Acta 52:2009–2036, 1988) and Sverjensky et al. (Geochim Cosmochim Acta 61:1359–1412, 1997) were followed and corroborated with alternative approaches, whenever possible. The SUPCRT92 computer code was used to generate the log K of the destruction reactions of these metal–arsenate and metal–arsenite aqueous complexes at pressures and temperatures required by the EQ3/6 software package, version 7.2b. Apart from the AlAsO4o and FeAsO4o complexes, our log K at 25°C, 1 bar are in fair agreement with those of Whiting (MS Thesis, Colorado School of Mines, Golden, CO, 1992). Moreover, the equilibrium constants evaluated in this study are in good to fair agreement with those determined experimentally for the Ca–dihydroarsenate and Ca–hydroarsenate complexes at 40°C (Mironov et al., Russ J Inorg Chem 40:1690, 1995) and for Fe(III)–hydroarsenate complex at 25°C (Raposo et al., J Sol Chem 35:79–94, 2006), whereas the disagreement with the log K measured for the Ca–arsenate complex at 40°C (Mironov et al., Russ J Inorg Chem 40:1690, 1995) might be due to uncertainties in this measured value. The implications of aqueous complexing between dissolved metals and arsenate/arsenite ions were investigated for seawater, high-temperature geothermal liquids and acid mine drainage and aqueous solutions deriving from mixing of acid mine waters and surface waters. Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users.  相似文献   

5.
热水溶液地球化学   总被引：8，自引：0，他引：8  
曾贻善 《地学前缘》1996,3(3):89-95
概述了热水溶液地球化学的主要研究内容和近年来在实验和理论研究方面的进展，包括高温高压下水的热力学性质、状态方程式、介电常数、电导率和电离平衡；ＮａＣｌ－ＣＯ２－Ｈ２Ｏ体系及其边界体系（ＮａＣｌ－Ｈ２Ｏ和ＣＯ２－Ｈ２Ｏ）的相关系、热力学性质和状态方程式，特别是利用人工流体包裹体技术和分子动力学模拟取得的新成果；高温高压电解质稀水溶液的电导测定；以ＨＫＦ模型为基础，热水溶液中不同物种的标准偏摩尔热力学性质和高温高压有关物理化学参数的估算；热水溶液中的物种形成（热液流体中的矿物溶解度测定、电势测量和谱学研究）；水和热水溶液结构的红外和拉曼谱学研究；水和热水溶液的传输性质（粘度和导热系数）。  相似文献   

6.
This article presents methods for predicting the standard partial molar Gibbs energy (standard chemical potential) and related derivative properties of aqueous hydroxy and aminoderivatives of (alkyl)benzenes over a wide range of temperatures and pressures. A thorough literature overview was conducted for collecting all available experimental data resulting from phase equilibrium, calorimetric and volumetric measurements that allow calculation of the thermodynamic properties of hydration. New experimental values are presented for solubility in water of isomeric toluidines and for the partial molal volume of phenol and cresols at high temperatures. Building upon the acquired database several prediction schemes were developed and tested for calculating the standard thermodynamic properties (and namely the Gibbs energy of hydration) of aqueous alkylphenols and alkylanilines as a function of temperature and pressure. First, a simple group contribution method was proposed for estimations at 298.15 K and 0.1 MPa using the simultaneous treatment of all available data on hydration properties at near ambient conditions. Second, this group contribution method allowed re-adjustment of the parameters of the Helgeson-Kirkham-Flowers model (HKF) using a new procedure proposed recently by Plyasunov and Shock [Plyasunov, A.V., Shock, E.L., 2001b. Correlation strategy for determining the parameters of the revised Helgeson-Kirkham-Flowers model for aqueous nonelectrolytes. Geochim. Cosmochim. Acta65, 3879-3900]. Third, using the Sedlbauer-O’Connell-Wood equation of state for aqueous species (SOCW), group contributions were determined for predictions at high temperatures and pressures by simultaneous correlation of all available thermodynamic data on hydration properties. The latter method was constrained by the group contributions at 298.15 K and 0.1 MPa making both group contribution schemes consistent at near ambient conditions. The calculations from the HKF and SOCW equations of state and those from the simple thermodynamic integration of the data at 298.15 K and 0.1 MPa were compared for several alkylphenols and alkylanilines. Equilibrium constants for hydration reactions obtained from the three approaches are in very good agreement at temperatures to at least 400 K. At higher temperatures we assess the accuracy of different predictive schemes and their associated uncertainties. The reliable predictions of the standard chemical potentials to at least 573 K and 100 MPa are possible by the group contribution method using the SOCW equation of state.  相似文献   

7.
A critical evaluation has been made of the thermodynamic properties reported in the literature for 43 organic iodine compounds in the solid, liquid, or ideal gas state. These compounds include aliphatic, cyclic and aromatic iodides, iodophenols, iodocarboxylic acids, and acetyl and benzoyl iodides. The evaluation has been made on the basis of carbon number systematics and group additivity relations, which also allowed to provide estimates of the thermodynamic properties of those compounds for which no experimental data were available. Standard molal thermodynamic properties at 25 °C and 1 bar and heat capacity coefficients are reported for 13 crystalline, 29 liquid, and 39 ideal gas organic iodine compounds, which can be used to calculate the corresponding properties as a function of temperature and pressure. Values derived for the standard molal Gibbs energy of formation at 25 °C and 1 bar of these crystalline, liquid, and ideal gas organic iodine compounds have subsequently been combined with either solubility measurements or gas/water partition coefficients to obtain values for the standard partial molal Gibbs energies of formation at 25 °C and 1 bar of 32 aqueous organic iodine compounds. The thermodynamic properties of organic iodine compounds calculated in the present study can be used together with those for aqueous inorganic iodine species to predict the organic/inorganic speciation of iodine in marine sediments and petroleum systems, or in the near- and far-field of nuclear waste repositories.  相似文献   

8.
Optical absorption spectra of Fe(II), Co(II), Ni(II) and Cu(II) have been measured in aqueous solutions of up to 5 m NaCl at temperatures from 25°C to 300°C and at water-saturated vapor pressures. Ni and Co complexes exhibited a change from octahedral to tetrahedral coordination, this occurring at both higher temperatures and Cl? concentrations. Similar transitions to lower coordination number are predicted for Cu and Fe but were not directly observed because of interference with water overtone bands. The coordination changes in response to ligand type and concentration, pressure and temperature. Formation of lower coordination complexes is attributed to the decreased dielectric constant of the solvent, the predominance of electrostatic forces and a decrease in the octahedral site preference energy at elevated temperatures. Our data suggest that lower coordination complexes with lower or neutral formal charge, will result in minerals having a higher solubility. The molecular properties and changes in coordination of these complexes are important in determining the transport and deposition of hydrothermal minerals.  相似文献   

9.
The solubility of amorphous silica was obtained in aqueous sodium nitrate solutions up to six molal and at temperatures from 25 to 300°C. It was expected that solubilities in aqueous sodium chloride solutions would be similar. At 25°C, the solubility of amorphous silica is lowered from that in water to 0.00086 m in 6.12 m sodium nitrate, or a decrease of 60%. At 300°C, the corresponding decrease is only 27% from a solubility of 0.0269 m in H2O. From the change in solubility with temperature at a given constant molality of sodium nitrate, the molal heat of solution over the range, 100 to 300°C, increases from + 2.93 kcal mol?1 in water to + 3.64 kcal mol?1 in 6m sodium nitrate. The value approaches a constant of +3.8 kcal mol?1 as sodium nitrate approaches saturation at 10.8 molal.  相似文献   

10.
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11.
An internally consistent thermodynamic database has been compiled for the Ag-Se (?II, 0, +IV)-S (?II, +VI)-Cl-O-H system on the basis of published experimental data. This database is fit for predicting the chemical properties of species over a broad interval of temperatures (0–600°C) and pressures (1–3000 bar). The stability constant of the hydroselenide silver complexes [AgHSeaq] and [Ag(HSe) 2 ? ] has been estimated. A thermodynamic model of the effect of Se on the transport properties of Ag-bearing hydrothermal fluid has been developed. Selenium has been found to be a good precipitant even if its concentration in the fluid is five orders lower than the sulfur concentration. When the temperature falls, the role of selenium as a precipitant becomes increasingly important. It has also been shown that the effect of hydroselenide complexes on Ag behavior in natural hydrothermal fluids may be ignored.  相似文献   

12.
Estimation of equation of state parameters for Sn++ and calculation of the thermodynamic properties of other aqueous species and dissociation constants for various stannous and stannic complexes as a function of temperature permit prediction of the high temperature solution chemistry of tin and calculation of the solubility of cassiterite in hydrothermal solutions. The results of these calculations indicate that in the absence of appreciable chloride and fluoride concentrations, Sn(OH)20 and Sn(OH)40 are the predominant tin species in H2O up to 350°C at ~2 $?pH $?7.5. The calculations also indicate that chloride complexes of Sn++ predominate by several orders of magnitude over their fluoride and hydroxide counterparts in 1–3 molal (m) NaCl solutions, except in the presence of geologically unrealistic concentrations of fluoride or a pH greater than ~3.5 at 250°C or ~5.0 at 350°C. At higher pH values, most of the tin in solution is present as hydroxide complexes, even at concentrations of NaCl as high as 3 m. Calculated values of the solubility of cassiterite at high temperatures compare favorably with experimental data reported in the literature. Depending on the fugacity of oxygen and solution composition, the solubility of cassiterite in hydrothermal solutions may exceed 100 ppm under geologically realistic conditions.  相似文献   

13.
Stability and solubility of arsenopyrite, FeAsS, in crustal fluids   总被引：3，自引：0，他引：3  
The stability and solubility of natural arsenopyrite (FeAsS) in pure water and moderately acid to slightly basic aqueous solutions buffered or not with H2 and/or H2S were studied at temperatures from 300 to 450°C and pressures from 100 to 1000 bar. The solubilities of FeAsS in pure water and dilute HCl/NaOH solutions without buffering are consistent with the formation of the As(OH)30(aq) species and precipitation of magnetite. At more acid pH (pH ≤2), arsenopyrite dissolves either stoichiometrically or with formation of the As-FeAsS assemblage. In H2S-rich and H2-rich aqueous solutions, arsenopyrite dissolution results in the formation of pyrrhotite (±pyrite) and iron arsenide(s), respectively, which form stable assemblages with arsenopyrite.Arsenic concentrations measured in equilibrium with FeAsS in slightly acid to neutral aqueous solutions with H2 and H2S fugacities buffered by the pyrite-pyrrhotite-magnetite assemblage are 0.0006 ± 0.0002, 0.0055 ± 0.0010, 0.07 ± 0.01, and 0.32 ± 0.03 mol/kg H2O at 300°C/400 bar, 350°C/500 bar, 400°C/500 bar, and 450°C/500 bar, respectively. These values were combined with the available thermodynamic data on As(OH)30(aq) (Pokrovski et al., 1996) to derive the Gibbs free energy of FeAsS at each corresponding temperature and pressure. Extrapolation of these values to 25°C and 1 bar, using the available heat capacity and entropy data for FeAsS (Pashinkin et al., 1989), yields a value of −141.6 ± 6.0 kJ/mol for the standard Gibbs free energy of formation of arsenopyrite. This value implies a higher stability of FeAsS in hydrothermal environments than was widely assumed.Calculations carried out using the new thermodynamic properties of FeAsS demonstrate that this mineral controls As transport and deposition by high-temperature (>∼300°C) crustal fluids during the formation of magmatic-hydrothermal Sn-W-Cu-(Au) deposits. The equilibrium between As-bearing pyrite and the fluid is likely to account for the As concentrations measured in modern high- and moderate-temperature (150 ≤ T ≤ 350°C) hydrothermal systems. Calculations indicate that the local dissolution of arsenopyrite creates more reducing conditions than in the bulk fluid, which is likely to be an effective mechanism for precipitating gold from hydrothermal solutions. This could be a possible explanation for the gold-arsenopyrite association commonly observed in many hydrothermal gold deposits.  相似文献   

14.
Calculation of the thermodynamic properties of biomolecules at high temperatures and pressures is fundamental to understanding the biogeochemistry of hydrothermal systems. Ample evidence indicates that hyperthermophilic microbes interact chemically with their mineralogical environment in these systems. Nevertheless, little is known about the thermodynamic properties of the biomolecules involved in such processes. Recent advances in theoretical biogeochemistry make it possible to calculate these properties using the limited experimental data available in the literature, together with correlation and group additivity algorithms, reference model compounds, and the revised HKF equations of state. This approach permits calculation of the standard molal thermodynamic properties of the 120 common protonated and deprotonated nucleotides and their constituent nucleic-acid bases and nucleosides as a function of temperature and pressure. The requisite equations of state parameters can be calculated from experimental standard molal heat capacities, volumes, and compressibilities reported in the literature for nucleic-acid bases and nucleosides. Because no calorimetric or densimetric data are available for the nucleotides, experimental heats of reaction taken from the literature were used together with correlation and group additivity algorithms to generate provisional values of the corresponding equations of state parameters for the nucleotides. The thermodynamic properties and revised HKF equations of state parameters generated in the present study can be used to carry out comprehensive mass transfer and Gibbs energy calculations to describe and quantify the chemical interaction of minerals and microbes in hydrothermal systems.  相似文献   

15.
The authors’ database (which includes data from more than 17500 publications on fluid and melt inclusions in minerals) was used to generalize information on the principal physicochemical parameters of natural mineral-forming fluids (temperature, pressure, density, salinity of aqueous solutions, and the gas composition of the fluids). For 21 minerals, data are reported on the frequency of occurrence of the homogenization temperatures of fluid inclusions in various temperature ranges, which make it possible to reveal temperature ranges most favorable for the crystallization of these minerals. Data on 5260 determinations were used to evaluate the frequency of occurrence of certain temperature and pressure ranges of natural fluids within the temperature intervals of 20–1200°C and 1–12000 bar. Within these intervals, frequencies of occurrence were evaluated for water-dominated and water-poor or water-free fluid inclusions in minerals. The former are predominant at temperatures below 600°C and pressures below 4000 bar, whereas the latter dominate at temperatures of 600–1200°C and pressures of 4000-12000 bar. Illustrative examples are presented for visually discernible magmatic water that exists as an individual high-density phase in melt inclusions in minerals from various rocks sampled worldwide (in the Caucasus, Italy, Slovakia, United States, Uzbekistan, New Zealand, Chile, and others). Attention is drawn to the fact that extensive data testify to fairly high (>1000–1500 bar) pressures during hydrothermal mineral-forming processes. These pressures are much higher not only than the hydrostatic but also the lithostatic pressures of the overlying rocks. Data on more than 18000 determinations are used to evaluate the frequency of occurrence of certain temperature and salinity ranges of mineral-forming fluids within the intervals of 20–1000°C and 0–80 wt % equiv. NaCl and certain temperature and density ranges of these fluids at 20–1000°C and 0.01–1.90 g/cm3. Information is presented on the gas analysis methods most commonly applied to natural fluids in studying fluid inclusions in minerals in 1965–2007. The average composition of the gaseous phase of natural inclusions is calculated based on more than 3000 Raman spectroscopic analyses (the most frequently used method for analyzing individual inclusions).  相似文献   

16.
<正>To determine compositions,homogenization pressures and isopleths of CO2-H2O-NaCl fluid inclusions,an improved activity-fugacity model is developed to calculate CO2solubility in aqueous NaCl solutions.The model can predict the solubility of CO2in aqueous NaCl solutions from 273 K to 723 K,from1 bar to 1500 bar and from 0 to 4.5 mol kg-1of NaCl,within or close to experimental uncertainties.The average deviation between the solubility predicted by  相似文献   

17.
Available experimental data on the solubility of Nb2O5 and the stability constants for particles of an aqueous solution in the Nb–O–H–F system were processed. As a result, a set of thermodynamic properties for 25°C and 1 bar was obtained, in addition to the equation parameters for the HKF model (Helgeson–Kirkham–Flowers) for hydroxo and hydroxofluoride niobium complexes. F– ion is the most important factor governing the concentration of dissolved Nb: neutral hydroxo complex Nb(OH)5(aq) is formed at a low HF concentration, whereas an increase in HF results in an increase in the first Nb(OH)4F(aq) and second Nb(OH)3F2(aq) fluoride complexes. The Nb(OH)5F– oxofluoride anion determines oxide solubility in alkali F-bearing fluids. Neutralization of acidic fluoride solution can be the main factor leading to niobium deposition.  相似文献   

18.
Copper transport and deposition in highly saline hydrothermal fluids are controlled by the stability of copper(I) complexes with ligands such as chloride and hydrosulphide. However, our understanding of the behavior of copper(I)-chloride complexes at elevated temperatures and in highly saline brines is limited by the conditions of existing experimental studies where the maximum chloride concentration is 2 m. This paper presents the results of a study of copper(I)-chloride complexes at much higher chloride concentrations, 1.5 m to 9.1 m, using a UV spectrophotometric method. The UV spectra of copper(I)-bearing LiCl solutions were measured at temperatures between 100 °C and 250 °C at vapor-saturated pressures and quantitative interpretation of the spectra shows that CuCl2−, CuCl32−, and CuCl43− were present in the experimental solutions. The fitted logarithms of formation constants (log K) for CuCl2− are in good agreement with the previous results of solubility experiments reported by Xiao et al. (1998) and Liu et al. (2001). The log K values for CuCl32− also agree with those of Liu et al. (2001) and theoretical estimates of Sverjensky et al. (1997). This study presents the first experimentally determined formation constants for CuCl43−, at temperatures greater than 25 °C, and indicates that this complex predominates at chloride concentrations greater than 5 m. Based on the new log K values generated from this study, the calculated chalcopyrite solubility in NaCl solutions indicates that in addition to cooling, fluid mixing (dilution of saline fluids) may be an important factor controlling the deposition of copper minerals from hydrothermal solutions.  相似文献   

19.
The solubility of the high grade pelite assemblage albite+K-feldspar+andalusite+quartz at 650 °C and 2 kbar was determined in aqueous solutions over a total chloride range of 0.01–3 mCltot using rapid-quench hydrothermal technique. The concentration of Na, K, Si, and Al was determined in the fluid phase after quench. The K/Na ratio was determined by approaching the equilibrium from below and above. It is 0.34 at low chloride concentrations and decreases slightly to 0.31 with increasing total chloride. Silica and aluminum concentrations were determined only from undersaturation. The silica solubility is found to be independent of chloride concentration and is 0.13 molal. Aluminum is nearly independent of chloride concentration decreasing only slightly from 0.0015 to 0.0007 molal. Comparison of the experimental data with thermodynamic model calculations demonstrates that the silica concentrations are well predicted, while significant differences exist between individual databases for Al speciation and its total concentration. Al concentrations are underestimated by up to 10 to 15 orders of magnitude using the SUPCRT92 database. Predicted K/Na ratios are underestimated by up to 30%. The best predictions achieved for this simplified high-grade pelite assemblage are those using the SUPCRT92 database with revised thermodynamic data for feldspars and K- and Na-species (J. Phys. Chem. Ref. Data 24 (1995) 1401) and additional Al-species (Am. J. Sci. 295 (1995) 1255; Geochim. Cosmochim. Acta 61 (1997) 2175). The use of ideal mixing for neutral complexes in combination with the extended Debye–Hückel activity model for the charged species yields the most compatible speciation model.  相似文献   

20.
Interaction between oil and hydrothermal solutions of different compositions was experimentally studied in a wide range of temperature (260–490°C) and pressures (8–150 MPa). This study was based on a new technique involving simultaneous occurrence of water-hydrocarbon interaction and growth of quartz, calcite, and fluorite crystals with fluid inclusions from the same solution. Fluid inclusions were studied to characterize the behavior of oil and aqueous solutions at elevated and high temperatures and pressures. It was shown that, owing to interaction with hydrothermal solutions, oil is intensely removed from the source rock and accumulated in the frontal part of hydrothermal convective flow. During this process, the oil is partially transformed into hydrocarbons, light oil, semiliquid and solid bitumens. At temperatures of 300–350°C and pressures of 50–100 MPa, oil and its fractionation products migrate in hydrothermal solution mainly in a drop-liquid state. At higher temperatures (360–395°C), when the oil/water ratio in the initial mixture is no higher than 1/70–1/35, liquid and gaseous hydrocarbons are completely dissolved in hydrothermal solutions forming a complex homogenous water-hydrocarbon fluid. The fluid can exist and migrate in this state, but it becomes heterogeneous with decreasing P-T parameters. Under favourable structural and lithological conditions, this can lead to the formation of displaced oil-and-gas deposits, with oil enriched in light components. The experiments unambiguously confirmed the concept that bitumen inclusions in minerals can serve as indicators of hydrocarbon migration paths in the Earth’s crust.  相似文献   

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