盐类溶解动力学的数学模型和热力学函数

总结了研究盐类溶解动力学的方法和数学模型。采用C语言编写了自动寻优的单线形法，实现了含4个参数的通用程序，并例举了研究实例。另外讨论了热力学函数的处理，也例举了研究实例。     

Crystal-chemical and energetic systematics of wadeite-type phases A2BSi3O9 (A = K, Cs; B = Si, Ti, Zr)

Wadeite K₂ZrSi₃O₉ and its analogues K₂TiSi₃O₉ and Cs₂ZrSi₃O₉, synthesized by high-temperature solid-state sintering, have been investigated using powder X-ray diffraction coupled with Rietveld analysis and high-temperature oxide melt solution calorimetry. The crystal chemistry and energetics of these phases, together with K₂Si^VISi₃ ^IVO₉, a high-pressure wadeite analogue containing both tetrahedral and octahedral Si, are discussed in term of ionic substitutions. As the size of the octahedral framework cation increases, Si⁴⁺ → Ti⁴⁺ → Zr⁴⁺, the cell parameter c increases at a much higher rate than a. In contrast, increasing the interstitial alkali cation size (K⁺ → Cs⁺) results in a higher rate of increase in a compared with c. This behavior can be attributed to framework distortion around the interstitial cation. The enthalpies of formation from the constituent oxides (ΔH_f,ox⁰) and from the elements (ΔH_f,el⁰) have been determined from drop-solution calorimetry into 2PbO·B₂O₃ solvent at 975 K. The obtained values (in kJ/mol) are as follows: ΔH_f,ox⁰ (K₂TiSi₃O₉) = −355.8 ± 3.0, ΔH_f,el⁰ (K₂TiSi₃O₉) = −4395.1 ± 4.8, ΔH_f,ox⁰ (K₂ZrSi₃O₉) = −374.3 ± 3.3, ΔH_f,el⁰ (K₂ZrSi₃O₉) = −4569.9 ± 5.0, ΔH_f,ox⁰ (Cs₂ZrSi₃O₉) = −396.6 ± 4.4, and ΔH_f,el⁰ (Cs₂ZrSi₃O₉) = −4575.0 ± 5.5. The enthalpies of formation for K₂Si^VISi₃ ^IVO₉ were calculated from its drop-solution enthalpy of an earlier study (Akaogi et al. 2004), and the obtained ΔH_f,ox⁰ (K₂SiSi₃O₉) = −319.7 ± 3.4 and ΔH_f,el⁰ (K₂SiSi₃O₉) = −4288.7 ± 5.1 kJ/mol. With increasing the size of the octahedral framework cation or of the interstitial alkali cation, the formation enthalpies become more exothermic. This trend is consistent with the general behavior of increasing energetic stability with decreasing ionic potential (z/r) seen in many oxide and silicate systems. Further, increasing the size of the octahedral framework cation appears to induce more rapid increase in stability than increasing the interstitial alkali cation size, suggesting that framework cations play a more dominant role in wadeite stability.     

Thermodynamics and fluid dynamics of effusive subglacial eruptions

We consider the thermodynamic and fluid dynamic processes that occur during subglacial effusive eruptions. Subglacial eruptions typically generate catastrophic floods (jökulhlaups) due to melting of ice by lava and generation of a large water cavity. We consider the heat transfer from basaltic and rhyolitic lava eruptions to the ice for typical ranges of magma discharge and geometry of subglacial lavas in Iceland. Our analysis shows that the heat flux out of cooling lava is large enough to sustain vigorous natural convection in the surrounding meltwater. In subglacial eruptions the temperature difference driving convection is in the range 10–100??°C. Average temperature of the meltwater must exceed 4??°C and is usually substantially greater. We calculate melting rates of the walls of the ice cavity in the range 1–40?m/day, indicating that large subglacial lakes can form rapidly as observed in the 1918 eruption of Katla and the 1996 eruption of Gjálp fissure in Vatnajökull. The volume changes associated with subglacial eruptions can cause large pressure changes in the developing ice cavity. These pressure changes can be much larger than those associated with variation of bedrock and glacier surface topography. Previous models of water-cavity stability based on hydrostatic and equilibrium conditions may not be applicable to water cavities produced rapidly in volcanic eruptions. Energy released by cooling of basaltic lava at the temperature of 1200??°C results in a volume deficiency due to volume difference between ice and water, provided that heat exchange efficiency is greater than approximately 80%. A negative pressure change inhibits escape of water, allowing large cavities to build up. Rhyolitic eruptions and basaltic eruptions, with less than approximately 80% heat exchange efficiency, cause positive pressure changes promoting continual escape of meltwater. The pressure changes in the water cavity can cause surface deformation of the ice. Laboratory experiments were carried out to investigate the development of a water cavity by melting ice from a finite source area at its base. The results confirm that the water cavity develops by convective heat transfer.     

Hydrous pyrolysis of New Albany and Phosphoria Shales: production kinetics of carboxylic acids and light hydrocarbons and interactions between the inorganic and organic chemical systems

Hydrous pyrolysis in flexible gold-bag autoclaves was used to study the production of carboxylic acids and light hydrocarbons from two marine type IIb source rocks (New Albany and Phosphoria Shales). Kerogen pyrolysis produced significant amounts of the monocarboxylic acids (acetic > propionic > butyric). The gases were dominated by CO₂ and methane, in that order, and progressively smaller amounts of the alkanes (ethane > propane > butane > pentane). Kinetic analyses of production rates for the New Albany Shale suggest mean activation energies (E) of 51-54 kcal/mol for both the light hydrocarbons and acids. Pressure had little effect on measured production rates for either shale over the pressure range investigated. Chemical thermodynamic speciation modeling suggests that in these experiments metal-organic acid anion complexation had little impact on aluminum speciation/solubility, but was important with respect to the alkaline earths.     

Complex formation of Cm(III) with formate studied by time-resolved laser fluorescence spectroscopy

Pore waters of natural clays, which are investigated as potential host rock formations for high-level nuclear waste, are known to contain large amounts of low-molecular weight organic compounds. These small organic ligands might impact the aqueous geochemistry of the stored radionuclides and, thus, their migration behavior. In the present work, the complexation of Cm(III) with formate in aqueous NaCl solution is investigated by time-resolved laser fluorescence spectroscopy (TRLFS) as a function of the ionic strength (0.5–3.0 mol/kg), the ligand concentration (0–0.2 mol/kg) and the temperature (20–90 °C). The Cm(III) speciation is determined by deconvolution of the emission spectra. The obtained distribution of Cm(III) species is used to calculate the conditional stability constants (log K′(T)) at a given temperature and ionic strength which are extrapolated to zero ionic strength by using the specific ion interaction theory (SIT). Thus, the thermodynamic log K⁰_n(T) values for the formation of [Cm(Form)_n]⁽³⁻ⁿ⁾⁺ (n = 1, 2) and the ion interaction coefficients (ε(i,k)) for [Cm(Form)_n]⁽³⁻ⁿ⁾⁺ (n = 1, 2) with Cl⁻ are obtained. The log K⁰₁(T) (2.11 (20 °C)–2.49 (90 °C)) and log K⁰₂(T) values (1.17 (30 °C–2.01 (90 °C)) increase continuously with increasing temperature. The log K⁰_n(T) values are used to derive the standard reaction enthalpies and entropies (Δ_rH⁰_m, Δ_rS⁰_m) of the respective complexation reactions according to the Van’t Hoff equation. In all cases, positive Δ_rH⁰_m and Δ_rS⁰_m values are obtained. Thus, both complexation steps are endothermic and entropy-driven.     

Fe–Mg diffusion in olivine II: point defect chemistry,change of diffusion mechanisms and a model for calculation of diffusion coefficients in natural olivine

Analysis of existing data and models on point defects in pure (Fe,Mg)-olivine (Phys Chem Miner 10:27–37,1983; Phys Chem Miner 29:680–694, 2002) shows that it is necessary to consider thermodynamic non-ideality of mixing to adequately describe the concentration of point defects over the range of measurement. In spite of different sources of uncertainties, the concentrations of vacancies in octahedral sites in (Fe,Mg)-olivine are on the order of 10⁻⁴ per atomic formula unit at 1,000–1,200 °C according to both the studies. We provide the first explicit plots of vacancy concentrations in olivine as a function of temperature and oxygen fugacity according to the two models. It is found that in contrast to absolute concentrations at ∼1,100 °C and dependence on fO₂, there is considerable uncertainty in our knowledge of temperature dependence of vacancy concentrations. This needs to be considered in discussing the transport properties such as diffusion coefficients. Moreover, these defect models in pure (Fe,Mg)-olivine need to be extended by considering aliovalent impurities such as Al, Cr to describe the behavior of natural olivine. We have developed such a formulation, and used it to analyze the considerable database of diffusion coefficients in olivine from Dohmen et al. (Phys Chem Miner this volume, 2007) (Part - I) and older data in the literature. The analysis documents unequivocally for the first time a change of diffusion mechanism in a silicate mineral—from the transition metal extrinsic (TaMED) to the purely extrinsic (PED) domain, at fO₂ below 10⁻¹⁰  Pa, and consequently, temperatures below 900 °C. The change of diffusion mechanism manifests itself in a change in fO₂ dependence of diffusivity and a slight change in activation energy of diffusion—the activation energy increases at lower temperatures. These are consistent with the predictions of Chakraborty (J Geophys Res 102(B6):12317–12331, 1997). Defect formation enthalpies in the TaMED regime (distinct from intrinsic defect formation) lie between −66 and + 15 kJ/mol and migration energies of octahedral cations in olivine are most likely ∼ 260 kJ/mol, consistent with previous inferences (Phys Chem 207:147–162, 1998). Plots are shown for diffusion at various constant fO₂ as well as along fO₂ buffers, to highlight the difference in behavior between the two. Considering all the diffusion data and constraints from the point defect models, (Fe–Mg) diffusion in olivine along [001] is best described by the Master equations: (1) At oxygen fugacities greater than 10⁻¹⁰ Pa:

安徽月山矿成矿流体中铜,金的迁移形式和沉淀的物理化学条件

文章基于矿床地质特征和地球化学热力学理论,计算和讨论了安微月山矽卡岩－热液型铜,金矿田成矿流体中成矿物质的迁移形式和沉淀的物理化学条件,两类矿床的主要成矿阶段,成矿流体中铜主要以氯络合物ＣｕＣｌ、ＣｕＣｌ２＾－、ＣｕＣｌ＾２－３,ＣｕＣｌＯＨ,金主要以硫的络合物Ａｕ２（ＨＳ）２Ｓ＾２－,Ａｕ（ＨＳ）２＾－,ＡｕＨＳ、ＡｕＨ３ＳｉＯ４等形式进行迁移,成矿流体中铜沉淀的主要物化条件是降温及氯离子浓度的     

白云石形成过程中的热力学与动力学基础及白云岩形成环境划分

CaMg(CO3)2在现代海水中是过饱和的,但是前人的研究发现在实验室标准状态下(25℃,1atm)无法从海水中直接沉淀出白云石,所以,白云石的形成不是一个单纯的热力学问题,而是一个动力学问题。依据白云石形成的热力学和动力学特征,将白云岩的形成环境划分为表生成岩环境与埋藏成岩环境。表生成岩环境按白云岩发育位置又分为:潮坪-澙湖蒸发环境、环礁潜流面与深?粱肪场B癫爻裳腋萘魈褰胩逑?的方式又分为:与裂缝相关的埋藏成岩、与缝合线相关的埋藏成岩、与岩溶相关的埋藏成岩和与渗透回流相关的浅埋藏成岩。分别对所划分的各成岩环境进行了详细的岩石学与地球化学特征分析与讨论。     

岩石中固定铵的矿床地球化学

讨论了各种地质流体介质中的铵（氨）的有关的一些热力学实验和推导，汇总了固定铵在在矿物学，岩石学及矿床勘探的有关研究成果，最后探讨了固定铵的矿床地球化学研究中的关键问题及在中国地区应用的可能性。