In situ Raman observation of the crystallization in NaNO3–Na2SO4–H2O solution droplets

Several double salts have been detected in building materials and most of these salts are incongruently soluble compounds. In contrast to single salts, however, no systematic investigations of the crystallization behavior and deleterious effects of incongruently soluble double salts exist. To assess the damage potential of these salts, a systematic investigation of their highly complex behavior is desirable. This paper deals with the crystallization behavior of various solids in the ternary mixed NaNO₃–Na₂SO₄ system including the formation of the double salt darapskite, Na₃NO₃SO₄·H₂O. The crystallization sequence during droplet evaporation experiments at room conditions was determined using Raman and polarization microscopy. The basic idea of this research is to use deviations of the crystallization sequence of a salt or a mixed salt solution from the equilibrium pathway as an indicator to detect the degree of supersaturation. The observed crystallization pathway includes the formation of the metastable phases Na₂SO₄(III), Na₂SO₄(V) and darapskite. The experimental observations are discussed on the basis of the NaNO₃–Na₂SO₄–H₂O phase diagram and the results provide evidence for crystal growth from highly supersaturated solutions in both systems. If the crystals growing under these conditions are confined, these supersaturations result in substantial crystallization pressures.     

Solid-liquid Equilibria for the Quaternary NaCl–Na2SO4–Na2B4O7–H2O System at 348 K

正1 Introduction China has very abundant liquid mineral resources.Especially,the brine resources in the west of Sichuan Basin are pushed into the first place in China,whose K and B contents are unusually high.These rare liquid mineral resources have very good exploitation prospect(Lin,2001;2006).Generally speaking,phase equilibrium     

An Experimental Study on Picromerite Equilkibrium in the Five—Component Brine System K—Na—Mg—Cl—SO4—H2O

This paper presents the results of experiments on the physicochemical conditions for the formation of picaromerite in the five-component brine system K-Na-Mg-Cl-SO4-H2O and the process of isothermal evaporation-crystallization of picromerite from brines.The metastable phase fields of picromerite at 15,10 and 5℃and its stable equilibrium phase field at -5℃ have been established.In addition,the phase equilibrium relationships have also been established for other salt minerals.The lower limit of formation temperature of picromerite has been deduced on the basis of experi-mental results.The isothermal evaporation crystallization path of the invariant assemblage(point D) of picromerite,epsomite,sylvite and halite at 25,15,10 and 5℃ has been revealed.Furthermore,some controversial problems are approached concerning the 25℃“solar” diagram and the 25℃ metastable phase diagram of this system.     

Melt–Fluid and Fluid–Fluid Immiscibility in a Na2SO4–SiO2–H2O System and Implications for the Formation of Rare Earth Deposits

Liquid–liquid immiscibility has crucial influences on geological processes, such as magma degassing and formation of ore deposits. Sulfate, as an important component, associates with many kinds of deposits. Two types of immiscibility, including (i) fluid–melt immiscibility between an aqueous solution and a sulfate melt, and (ii) fluid–fluid immiscibility between two aqueous fluids with different sulfate concentrations, have been identified for sulfate–water systems. In this study, we investigated the immiscibility behaviors of a sulfate- and quartz-saturated Na2SO4–SiO2–H2O system at elevated temperature, to explore the phase relationships involving both types of immiscibility. The fluid–melt immiscibility appeared first when the Na2SO4–SiO2–H2O sample was heated to ~270°C, and then fluid–fluid immiscibility emerged while the sample was further heated to ~450°C. At this stage, the coexistence of one water-saturated sulfate melt and two aqueous fluids with distinct sulfate concentrations was observed. The three immiscible phases remain stable over a wide pressure–temperature range, and the appearance temperature of the fluid–fluid immiscibility increases with the increased pressure. Considering that sulfate components occur extensively in carbonatite-related deposits, the fluid–fluid immiscibility can result in significant sulfate fractionation and provides implications for understanding the formation of carbonatite-related rare earth deposits.     

Solid-liquid Equilibria for the System KBr–K2SO4–H2O at 348 K

正1 Introduction The underground brine resources distributing widely in Sichuan Basin,China have drawn worldwide attention due to their unusual element abundance and excellent quality.     

The thermal stability of sideronatrite and its decomposition products in the system Na2O–Fe2O3–SO2–H2O

The thermal stability of sideronatrite, ideally Na₂Fe³⁺(SO₄)₂(OH)·3(H₂O), and its decomposition products were investigated by combining thermogravimetric and differential thermal analysis, in situ high-temperature X-ray powder diffraction (HT-XRPD) and Fourier transform infrared spectroscopy (HT-FTIR). The data show that for increasing temperature there are four main dehydration/transformation steps in sideronatrite: (a) between 30 and 40 °C sideronatrite transforms into metasideronatrite after the loss of two water molecules; both XRD and FTIR suggest that this transformation occurs via minor adjustments in the building block. (b) between 120 and 300 °C metasideronatrite transforms into metasideronatrite II, a still poorly characterized phase with possible orthorhombic symmetry, consequently to the loss of an additional water molecule; X-ray diffraction data suggest that metasideronatrite disappears from the assemblage above 175 °C. (c) between 315 and 415 °C metasideronatrite II transforms into the anhydrous Na₃Fe(SO₄)₃ compound. This step occurs via the loss of hydroxyl groups that involves the breakdown of the [Fe³⁺(SO₄)₂(OH)] _∞ ^2? chains and the formation of an intermediate transient amorphous phase precursor of Na₃Fe(SO₄)₃. (d) for T > 500 °C, the Na₃Fe(SO₄)₃ compound is replaced by the Na-sulfate thenardite, Na₂SO₄, plus Fe-oxides, according to the Na₃Fe³⁺(SO₄)₃ → 3/2 Na₂(SO₄) + 1/2 Fe₂O₃ + SO_x reaction products. The Na–Fe sulfate disappears around 540 °C. For higher temperatures, the Na-sulfates decomposes and only hematite survives in the final product. The understanding of the thermal behavior of minerals such as sideronatrite and related sulfates is important both from an environmental point of view, due to the presence of these phases in evaporitic deposits, soils and sediments including extraterrestrial occurrences, and from the technological point of view, due to the use of these materials in many industrial applications.     

Phlogopite Formation in the Orthopyroxene–Garnet System in the Presence of H2O–KCl Fluid in Application to the Processes of Mantle Metasomatism

Doklady Earth Sciences - The results of experimental studies are presented for reactions in the orthopyroxene–garnet–phlogopite system in the presence of H2O–KCl fluid at...     

Experimental evidence for the coexistence of two liquids in the H2O-SiO2-NaF-Na2SO4 System at T = 700°C and P = 2 kbar

The phase state of fluid in the H₂O-NaF-Na₂SO₄ system in the presence of silicates (quartz and albite) was experimentally explored using the method of synthetic fluid inclusions in quartz at 700°C and pressures of 1 and 2 kbar. Parallel experiments were conducted under identical conditions with either two silicates (quartz and albite) or quartz only. The presence of albite affects heterogeneous fluid equilibria both at different pressures and at different solution compositions. This indicates high solubilities of silicates in a saltwater fluid containing NaF and Na₂SO₄. The absence of inclusions homogenizing to a gas phase in the experimental products provides compelling evidence that liquid-liquid rather than liquid-vapor equilibria are characteristic of the H₂O-SiO₂-NaF-Na₂SO₄ and H₂O-SiO₂-NaF-Na₂SO₄-NaAlSi₃O₂ systems in the heterogeneous region. It can be concluded that critical equilibria in saturated solutions can exist in these systems. In addition, it was shown that the phase diagrams of these systems are complicated by the formation of immiscible liquids in the presence of vapor. This allowed us to conclude that there are two critical curves describing equilibria with two different salts. Fluids containing two salts (NaF and Na₂SO₄) are similar to fluids containing only one of these salts: (a) two liquids are in equilibrium under the parameters of the upper heterogeneous region, (b) each of them can in turn undergo unmixing at decreasing temperature and pressure, and (c) owing to chemical interaction between silicate and fluid components, a glassy phase can be formed and trapped in inclusions.     

High-temperature and high-pressure equation of state for the hexagonal phase in the system NaAlSiO4 – MgAl2O4

Thermal equation of state of an Al-rich phase with Na_1.13Mg_1.51Al_4.47Si_1.62O₁₂ composition has been derived from in situ X-ray diffraction experiments using synchrotron radiation and a multianvil apparatus at pressures up to 24 GPa and temperatures up to 1,900 K. The Al-rich phase exhibited a hexagonal symmetry throughout the present pressure–temperature conditions and the refined unit-cell parameters at ambient condition were: a=8.729(1) Å, c=2.7695(5) Å, V ₀=182.77(6) Å³ (Z=1; formula weight=420.78 g/mol), yielding the zero-pressure density ρ₀=3.823(1) g/cm³ . A least-square fitting of the pressure-volume-temperature data based on Anderson’s pressure scale of gold (Anderson et al. in J Appl Phys 65:1534–543, 1989) to high-temperature Birch-Murnaghan equation of state yielded the isothermal bulk modulus K ₀=176(2) GPa, its pressure derivative K ₀ ^′ =4.9(3), temperature derivative (?K _T /?T) _P =?0.030(3) GPa K^?1 and thermal expansivity α(T)=3.36(6)×10^?5+7.2(1.9)×10^?9 T, while those values of K ₀=181.7(4) GPa, (?K _T /?T) _P =?0.020(2) GPa K^?1 and α(T)=3.28(7)×10^?5+3.0(9)×10^?9 T were obtained when K ₀ ^′ was assumed to be 4.0. The estimated bulk density of subducting MORB becomes denser with increasing depth as compared with earlier estimates (Ono et al. in Phys Chem Miner 29:527–531 2002; Vanpeteghem et al. in Phys Earth Planet Inter 138:223–230 2003; Guignot and Andrault in Phys Earth Planet Inter 143–44:107–128 2004), although the difference is insignificant (<0.6%) when the proportions of the hexagonal phase in the MORB compositions (～20%) are taken into account.     

Equation of state and pressure-induced structural changes in mirabilite (Na2SO4·10H2O) determined from ab initio density functional theory calculations

We have carried out ab initio calculations using density functional theory to determine the bulk elastic properties of mirabilite, Na₂SO₄·10H₂O, and to obtain information on structural trends caused by the application of high pressure up to ~60 GPa. We have found that there are substantial isosymmetric discontinuous structural re-organisations at ~7.7 and ~20 GPa caused by changes in the manner in which the sodium cations are coordinated by water molecules. The low-pressure and intermediate-pressure phases both have sodium in sixfold coordination but in the high-pressure phase the coordination changes from sixfold to sevenfold. These coordination changes force a re-arrangement of the hydrogen-bond network in the crystal. The trend is towards a reduction in the number of hydrogen bonds donated to the sulphate group (from twelve down to six over the range 0–60 GPa) and an increase in hydrogen bonding amongst the Na-coordinated water molecules and the two interstitial water molecules. Ultimately, we observe proton transfers from the interstitial waters (forming OH^? ions) to two of the Na-coordinated waters (forming a pair of H₃O⁺ ions). The equation of state in the athermal limit of the low-pressure phase of mirabilite, parameterised by fitting an integrated form of the third-order Birch-Murnaghan expression to the calculated energy as a function of unit-cell volume, yields the zero-pressure unit-cell volume, V ₀ = 1468.6(9) ų, the incompressibility, K ₀ = 22.21(9) GPa, and the first pressure derivative K ₀′ = (?K/?P)₀ = 5.6(1).     

CH4-H2O体系流体包裹体拉曼光谱定量分析和计算方法

CH4—H2O体系流体包裹体研究对含油气盆地流体分析和成矿流体研究都有重要的意义。本文详细介绍了H2O、CH4和CH4—H2O体系的拉曼光谱特征及分子作用,分析了CH4—H2O体系热力学特征,同时对CH4—H2O体系流体包裹体拉曼光谱定量分析和计算的方法及步骤进行了叙述。利用人工合成流体包裹体建立甲烷浓度与拉曼特征峰面积比值之间的校正曲线是实现CH4—H2O体系流体包裹体定量分析的基础。盐度对包裹体定量分析的影响最为显著,在恒定甲烷浓度下,甲烷与水的拉曼峰面积比值随着盐度增加而减少。对于流体包裹体封闭体系,随温度升高,液相甲烷浓度增大。校正曲线必须包含对温度和盐度的校正。石英主矿物性质和方位对甲烷浓度定量分析的影响可以忽略。实验研究表明,原位拉曼光谱技术是准确获取流体包裹体中甲烷水合物生成条件的一种有效方法。因此,基于拉曼光谱分析和显微测温分析结果,采用热力学模型可以定量计算CH4—H2O体系流体包裹体的相关参数。     

CH4-H2O体系流体包裹体均一过程激光拉曼光谱定量分析

对南黄海盆地二叠纪地层中某石英脉中的CH4-H2O体系流体包裹体均一过程进行了激光拉曼光谱定量分析。利用甲烷与水的拉曼峰面积比值计算不同温度下流体包裹体中水溶液相中甲烷的浓度,除了在100℃附近出现最小值,随温度增加甲烷浓度呈指数增大。包裹体在214℃完全均一,均一时甲烷的浓度为0·1347mol/L。同时利用甲烷的拉曼特征对流体包裹体均一过程的内压变化作了分析。压力变化可以分为三个区间:19~100℃,随温度升高压力增大;100~150℃压力随温度升高减小;150℃之后压力迅速增大。均一温度下的内压为21·92MPa。流体包裹体内压的变化主要是由甲烷溶解行为和封闭体系的热力学特征决定的。实验表明激光拉曼光技术可以作为定量分析含甲烷流体包裹体的一种有效方法。     

磷灰石结构中[SO_4]、[SiO_4]四面体的喇曼谱学特点

磷灰石是重要的生物材料矿物。天然磷石晶体结构中［ＰＯ４］３－能广泛地被［ＳｉＯ４］、［ＳＯ４］类质同象取代,形成含硅硫磷灰石以至硅硫磷灰石［１］。据报道,在合成羟磷灰石中引入部分Ｓ、Ｓｉ离子将提高其抗蚀性能,因此［ＳｉＯ４］与［ＳＯ４］对［ＰＯ４］的四面体替换是磷灰石晶体化学研究的重要内容［２～４］。振动光谱（包括喇曼与红外光谱）是研究晶体结构络阴离子行为的主要手段之一。对磷灰石中磷氧四面体振动谱学特点的研究,无论是理论计算还是实验结果均已十分成熟［５,６］,但对其结构中硫氧、硅氧四面体的喇曼光…     

原位低温拉曼光谱技术在人工合成CaCl_2-H_2O和MgCl_2-H_2O体系流体包裹体分析中的应用Ⅰ:低温拉曼光谱研究

利用原位低温拉曼光谱分析技术,对在设定的实验条件下合成的CaCl2-H2O体系和MgCl2-H2O体系的流体包裹体进行分析研究,结果表明低温下CaCl2水溶液和MgCl2水溶液形成的盐水合物具有各自不同的特征拉曼光谱,通过测定特征光谱,能够简易直接的鉴定这些物质,进而确定盐水体系包裹体的成分.因此,原位低温拉曼光谱技术,能够有效地测定Ca2+和Mg2+这两种盐水体系包裹体流体中常见,但显微测温过程难以观察和判别的二价阳离子.实践表明,原位低温拉曼光谱分析技术是对传统的流体包裹体显微测温技术的一个十分有效的补充,在包裹体研究领域会得到越来越广泛的应用.     

二氧化碳—水体系的拉曼光谱研究

研究了使用石英管熔融封闭法分别在酸性、中性以及碱性条件下,采用ＣａＣＯ３或Ｎａ２ＣＯ３与ＨＣｌ反应制备不同浓度的ＣＯ２标准系列,并对气相、液相中的ＣＯ２进行拉曼光谱研究,得出了定量分析气相ＣＯ２所遵循的规律,即ＣＯ２的浓度与拉曼位移（１３８８．９ｃｍ－１）强度呈线性相关,为定量分析流体包裹体中ＣＯ２的含量奠定了基础。     

CO2-H2O流体不混溶对Au溶解度的影响——以贵州省贞丰县水银洞金矿床为例

运用热力学原理和方法,研究了CO2-H2O流体不混溶作用对Au的溶解度的影响。结果表明,贵州水银洞金矿床的成矿流体是一种富含挥发分( fCO 2=70.79MPa)、酸性(pH=3.71)、还原性(fO 2=0.50×10-36MPa)、中温(267℃)、具有超压(180MPa)性质的含Au(a∑Au=3.744×10-8mol/L)流体。当超压流体的封闭层——炭质页岩因断裂作用而被破坏时,热液体系的压力发生骤降(28.50～35.30MPa),CO2-H2O流体发生不混溶作用,并有大量CO2溢出。CO2的流失可使成矿溶液的CO2逸度和O2逸度降低(fCO 2=0.80MPa、fO 2= 2.512×10-42MPa),酸碱度升高(pH=4.32),同时伴随温度的下降(224℃),成矿热液中Au溶解度的降低(a∑Au=3.790×10-9mol/L),从而快速沉淀下来成矿。     

Determining Fluid Compositions in the H2O-NaCl-CaCl2 System with Cryogenic Raman Spectroscopy: Application to Natural Fluid Inclusions

Previous cryogenic Raman spectroscopic analysis of H₂O-NaCl-CaCl₂ solutions has identified the Raman peaks of various hydrates of NaCl and CaCl₂,and established a linear relationship between Raman band intensity of the hydrates and the composition of the solution(NaCl/（NaCl+CaCl₂） molar ratio,or X_NaC1) using synthetic fluids,which created the opportunity to quantitatively determine the solute composition of aqueous fluid inclusions with cryogenic Raman spectroscopy.This paper aims to test the feasibility of this newly established method with natural fluid inclusions.Twenty-five fluid inclusions in quartz from various occurrences which show a high degree of freezing during the cooling processes were carefully chosen for cryogenic Raman analysis.X_NaCl was calculated using their spectra and an equation established in a previous study.These inclusions were then analyzed with the thermal decrepitation-SEM-EDS method.The X_NaCl values estimated from the two methods show a 1:1 correlation,indicating that the new,non-destructive cryogenic Raman spectroscopic analysis method can indeed be used for fluid inclusion compositional study.     

硫酸盐三氧同位素测试制样新技术——Ag2SO4热解法

氧同位素能有效地示踪硫酸盐起源及其形成环境,随着硫酸盐中氧同位素质量不相关分馏现象的陆续发现,三氧同位素的研究已成为热点与前沿.笔者研究了硫酸盐三氧同位素(16O、17O、18O)测试制样的最新技术--Ag2SO4热解法.基本原理是:Ag2SO4在1050℃下热解为O2和SO2,其中O2产额可达(45±7)%,SO2产额接近100%,收集两种气体送作质谱分析可测得δ17O、δ18O和δ34S值.本方法的特殊要求是所有硫酸盐样品都必须转化为Ag2SO4,笔者详细介绍了水样、土样、石膏样品、BaSO4样品的处理方法与步骤.Ag2SO4热解法不再使用传统方法中的氟化试剂,安全可靠、价廉,顺应了环保意识和以人为本的原则.技术先进:适用性强,具有很大的推广应用价值.     

小秦岭地区花岗岩体中CO2—H2O包裹体的找矿意义

小秦岭地区与金矿成因有关的燕山期文峪花岗岩及其派生石英脉中发育了非常丰富的ＣＯ２－Ｈ２Ｏ包裹体,其流体为富含ＣＯ２的低盐度（＜１０％ＮａＣｌ）流体,这与含金石英脉内的包裹体类型及金矿成矿流体性质上十分相似。与金矿成因无关的华山岩体内包裹体类型则为水溶液包裹体,流体性质为贫ＣＯ２的低盐度流体。与金矿有关,但其周围矿化很差的娘娘山岩体内ＣＯ２－Ｈ２Ｏ包裹体数量很少。因此,ＣＯ２－Ｈ２Ｏ包裹体可以作为与金矿成因有关的花岗岩体关联程度的判别标志,而ＣＯ２－Ｈ２Ｏ包裹体的丰度可以作为金矿床品位和规模评价及成矿前景展望的依据