氯化物对方解石和白云石矿物溶解度的影响

借助PHREEQC软件,文章对方解石、白云石分别在无CO2和大气PCO2条件下NaCl、KCl、CaCl2和MgCl2溶液中的溶解度进行了模拟计算,结果显示:方解石在NaCl、KCl、和MgCl2溶液中以及白云石在NaCl、KCl溶液中的溶解度比纯水中大得多,其原因主要是盐效应。由于同离子效应,在CaCl2溶液中可降低方解石溶解度,而白云石在较高浓度CaCl2或MgCl2溶液中,虽发生同离子效应,其溶解度仍较纯水中有不同程度提高。模拟还显示,方解石在MgCl2溶液中以及白云石在CaCl2溶液中溶解时将分别发生白云石化和去白云石化反应,从而促使不全等溶解继续发生。在常规离子中,按方解石、白云石溶解度提高发挥作用的重要性排序为:阴离子中都是SO24->Cl-;对于方解石溶解,阳离子中Mg2+>Na+>K+>Ca2+;对于白云石溶解,当PCO2=0或PCO2=10-3.5bar且CaCl2浓度大约在1.5mol/L以下时,Na+>K+>Ca2+>Mg2+;当PCO2=10-3.5bar且CaCl2浓度大约在1.5mol/L以上时,Ca2+>Na+>K+>Mg2+。     

Ca2+含量对微粒释放的影响

通过批量试验和水平砂柱试验,以NaCl与CaCl2的混合溶液为研究对象,对Ca2+含量影响微粒释放的过程进行了研究,并提出了在不同浓度Ca2+存在情况下,混合溶液引起微粒释放的临界离子强度。研究结果表明:Ca2+不但不能引起微粒释放,而且对微粒释放过程具有明显而强烈的抑制作用,导致混合溶液引起微粒释放的浓度值急剧下降;Ca2+摩尔百分数为5%时,对应微粒释放的临界离子强度为0.02mol/L;Ca2+摩尔百分数为10%与20%时,对应微粒释放的临界离子强度分别为0.007mol/L与0.0005mol/L;Ca2+摩尔百分数为100%时,无微粒释放现象发生。上述临界离子强度值都远低于单一NaCl溶液引起微粒释放的临界盐浓度值0.06±0.005mol/L,且混合溶液中Ca2+含量越高,发生微粒释放的临界离子强度值越低,这一现象进一步验证了Ca2+对微粒释放的抑制作用。     

基于Pitzer模型预测Na-K-Ca-Mg-Cl-H2O溶液的密度

天然水体系的体积性质与压力、温度、组成的相关性(PVTx性质)研究在地球化学、盐湖化工等领域有广泛的应用。密度是卤水最基本的体积性质,不仅可以通过实验测定,还可以用理论模型进行预测。建立富钾卤水密度与组成、温度的关联模型有助于认识钾在复杂卤水中的富集、迁移规律。为了构建基于Pitzer离子相互作用模型的卤水密度预测方法,本文用高精度振荡管密度计测定了常压下KCl、CaCl₂纯盐溶液以及最高离子强度为11.8 mol·kg^-1的混合溶液在283~323 K下的密度,用所测得的密度通过Pitzer离子相互作用模型拟合得到多温下Pitzer单电解质参数和Pitzer混合参数。用Pitzer模型参数计算了Na-K-Ca-Mg-Cl-H₂O体系293~313 K的密度,计算密度值与实验值的相对偏差在±0.25%以内,计算的结果整体上要优于文献值,文献在计算中均未考虑Pitzer混合参数项。结果表明,K、Ca、Cl离子间的相互作用对于Na-K-Ca-Mg-Cl-H₂O溶液的密度有显著的影响,本文获得的Pitzer参数反映了这些离子间的相互作用,可用于计算含有K、Ca、Cl离子的复杂卤水密度的预测。     

氯化铵浸取纤蛇纹石动力学研究

较低的矿物溶解率和反应剂的不可循环利用是CO2矿物封存发展的两大难题。针对这些问题,本文提出了一种新的以可循环的NH4Cl溶液作为中间媒介的CO2矿物封存工艺,并系统地研究了蛇纹石在氯化铵溶液中的液-固两相的反应动力学。实验研究发现:(1)纤蛇纹石的浸取符合Elovich模型,浸取过程基本在1h左右完成,在100℃、5mol/L氯化铵溶液中,纤蛇纹石的浸取率达到12.67%;(2)温度对纤蛇纹石初始反应速率的影响显著,温度越高,反应速率越快;(3)当氯化铵浓度在1~5mol/L范围内变化时,它对镁离子浸取率的影响不明显,反应速率随着浓度的升高而有所增加;(4)本实验反应表现出来的活化能大小为129.56kJ/mol。      

(斜长石 + 黑云母 + 石英 ) NaCl(NaHCO3) H2O 矿物蚀变与金矿化反应研究 : 450～ 250 ℃和 50 MPa

采用（斜长石＋黑云母＋石英）这三种单矿物组合与1mol/L NaCl或0．5mol/L NaCl 0.5mol/L NaHCO3溶液在450－250℃和50MPa条件下反应7d。实验表明，反应后流体pH值发生了变化，NaCl介质向酸性变化，N aCl NaHCO3介质向中性转化。溶液中K,Ca,Mg,Fe和Au量也随之发生变化。矿物表面发生溶解和离子置换等反应。斜长石表面形成钠长石反应边，黑云母变色，石英重结晶，反应器皿金管中的金被溶解后在金管壁和黑云母表面重结晶，黑云母周边出现红色Fe2O3，在450℃的NaCl介质中，金含量可达1070μg/g，但随温度下降迅速减低，在NaCl NaHCO3介质中，金含量较低，显著，金的活化迁移和富集与Cl,pH,Fe^3 /Fe^2 密切相关，这中金起到示踪作用，显示出金在水／岩反应中的原电池效应。     

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。     

CO_2-H_2O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（fCO2=70.79MPa）、酸性（pH=3.71）、还原性（fO2=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（fCO2=0.80MPa、fO2=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。     

雪玉洞岩溶地下水、地表水Ca2+、Mg2+、Sr2+变化特征研究

通过2011年对重庆丰都雪玉洞洞内滴水和地下河河水,上覆岩层中出露的表层岩溶泉水和雪玉洞附近龙河河水等不同类型水中Ca2+、Mg2+、Sr2+浓度及Mg/Ca、Sr/Ca值的研究,发现不同水的Ca2+、Mg2+、Sr2+随外界降水条件的改变而出现明显变化。表层岩溶泉水Ca2+变化能够敏感反应外界降水条件改变,滴水对外界降雨的反应滞后接近1个月,地下河Ca2+可以反应雨季和旱季的变化,地表河水Ca2+全年比较稳定,但是对特殊干旱天气有显著响应。2011年不同类型水的Mg2+、Sr2+全年变化趋势基本一致,在降水较多的3、5、10月呈低值,在其他降水较少的月份浓度相对较高。各离子的这种变化特征主要是受到稀释效应、CO2效应以及所在地层的岩性的影响。雪玉洞不同类型水的Mg/Ca、Sr/Ca值呈现出滴水>地表河>地下河>表层岩溶泉的特点,反映出不同类型水在含水介质中滞留时间的长短,并且Mg/Ca、Sr/Ca值在降水较多的月份降低,在降水较少的月份升高;受碳酸钙的前期沉淀和运移路径差异的影响,不同类型水的Mg/Ca、Sr/Ca值变化稍有不同。因此,不同类型水的离子变化及其比值对外界降水条件变化的响应特征和时间的不同,决定了在利用元素及其比值反映外界环境变化时也要区别对待。      

地下水中氯化钠对某新型释氧材料性能的影响

释氧化合物应用于地下水有机污染原位修复技术具有广阔的应用前景,然而地下水中各离子组分对释氧化合物性能的影响却鲜有文献提及。本研究建立了一套地下水流模拟装置,以含有热解改性含油污泥残渣的新型释氧材料(Modified Oxygen Releasing Compound,简称MORC)作为研究对象,采用Na Cl溶液和去离子水作为对照组,探讨Na Cl对MORC释氧性能的影响,并采用扫描电镜对MORC表面矿物结构进行表征。研究结果表明:Na Cl对MORC释氧具有显著的促进作用,当Na Cl溶液浓度为1 000 mg/L、3 000 mg/L时,其促进释氧率分别为12.91%和14.13%。MORC释氧过程中产生的矿物沉淀逐渐在MORC表面沉积,导致材料表面释氧孔道堵塞是影响MORC释氧的重要限制因素。     

溶出珊瑚砂中Ca~(2+)、Mg~(2+)的动力学实验研究及其影响因素

通过改变固液比、摇床转速、珊瑚砂粒径、温度、溶液pH值及溶液含盐量等参数,对珊瑚砂在水溶液中溶出Ca~(2+)、Mg~(2+)进行了实验,以探讨溶出过程中的动力学规律和影响因素。实验结果表明,珊瑚砂中Ca~(2+)、Mg~(2+)溶出量随反应时间逐渐增大;摇床转速越快、固液比越大、温度越高、溶液pH值越低,Ca~(2+)、Mg~(2+)溶出量越大;当珊瑚砂粒径为2.36~4.75 mm、溶液含盐量为100 mg/L时,Ca~(2+)、Mg~(2+)溶出量最大。统计分析表明,摇床转速、温度及溶液p H值均对珊瑚砂溶出有显著影响,但溶液p H值影响最大。珊瑚砂在水中的溶出过程符合收缩核内扩散模型,表明控制整个溶出过程反应速率的决定因素是内扩散速率;在15~40℃时,珊瑚砂在纯水中溶出Ca~(2+)、Mg~(2+)的活化能分别为78.07和74.91 k J/mol。     

Experiments on the phase transition calcite+wollastonite+ +epidote=grossular-andraditess+CO2+H2O

The reaction 2 epidote+2 calcite+3 wollastonite3 grossular-andradite_ss+ 2 CO₂+1 H₂O has been explored by hydrothermal experiments at a total fluid pressure of 1000 bars. For a grossular-andradite_ss of andradite ₂₅ composition, the isobaric univariant curve passes through the points 458°C: X_CO2=0.00; 521°C: X_CO2=0.026; 523°C: X_CO2=0.052; 526°C: 0.088; 528°C: X_CO2=0.104. This curve intersects the isobaric univariant curve of the reaction calcite+quartz+[H₂O] wollastonite+CO₂+[H₂O] at the isobaric invariant point around 528°C and X_CO2=0.12. At higher values of X_CO2, this reaction is replaced by another one, namely: 2 epidote+5 calcite+3 quartz3 grossular-andradite_ss+5 CO₂+ 1 H₂O. It is demonstrated that both the reactions do actually take place during the metamorphism of calcareous rocks. The petrologic significance of contrasted sequence of reactions within this system observed by various workers is also discussed.     

The stability of annite+quartz: reversed experimental data for the reaction 2 annite+3 quartz=2 sanidine+3 fayalite +2 H2O

Reversals for the reaction 2 annite+3 quartz=2 sanidine+3 fayalite+2 H₂O have been experimentally determined in cold-seal pressure vessels at pressures of 2, 3, 4 and 5?kbar, limiting annite +quartz stability towards higher temperatures. The equilibrium passes through the temperature intervals 500–540°?C (2?kbar), 550–570°?C (3?kbar), 570–590°?C (4?kbar) and 590–610°?C (5?kbar). Starting materials for most experiments were mixtures of synthetic annite +fayalite+sanidine+quartz and in some runs annite+quartz alone. Microprobe analyses of the reacted mixtures showed that the annites deviate slightly from their ideal Si/Al ratio (Si per formula unit ranges between 2.85 and 2.92, Al^VI between 0.06 and 0.15). As determined by Mössbauer spectroscopy, the Fe³⁺ content of annite in the assemblage annite+fayalite +sanidine+quartz is around 5–7%. The experimental data were used to extract the thermodynamic standard state enthalpy and entropy of annite as follows: H ⁰ _f,?Ann =?5125.896±8.319 [kJ/mol] and S ⁰ _Ann=432.62±8.89 [J/mol/K] (consistent with the Holland and Powell 1990 data set), and H ⁰ _f,Ann =?5130.971±7.939 [kJ/mol] and S ⁰ _Ann=424.02±8.39 [J/mol/K] (consistent with the TWEEQ data base, Berman 1991). The preceeding values are close to the standard state properties derived from hydrogen sensor data of the redox reaction annite=sanidine+magnetite+H ₂ (Dachs 1994). The experimental half-reversal of Eugster and Wones (1962) on the annite +quartz breakdown reaction could not be reproduced experimentally (formation of annite from sanidine+fayalite+quartz at 540°?C/1.035?kbar/magnetite-iron buffer) and probable reasons for this discrepancy remain unclear. The extracted thermodynamic standard state properties of annite were used to calculate annite and annite+quartz stabilities for pressures between 2 and 5?kbar.     

Experimental determination of the reaction dolomite + 2 coesite = diopside + 2 CO2 to 6 GPa

 The carbonation reaction CaMg(CO₃)₂ (dolomite)+2SiO₂ (coesite)=CaMgSi₂O₆ (diopside)+2 CO₂ (vapor) has been determined experimentally between 3.5 and 6 GPa in a multiple-anvil, solid-media apparatus. This reaction, a candidate for carbonation of eclogites (garnet+clinopyroxene) in the Earth’s mantle, lies at higher pressure for a given temperature than do the carbonation reactions for peridotites (olivine+orthopyroxene±clinopyroxene). A depth interval may exist within the Earth’s mantle under either ‘normal’ or ‘subduction’ thermal regimes where carbonated peridotite could coexist with carbonate-free, CO₂-bearing eclogite. Received: 25 May 1994/Accepted: 13 June 1995     

Die Reaktion Phlogopit + Calcit + Quarz = Tremolit + Kalifeldspat + H2O + C2O

Hydrothermal experiments with mixtures of synthetic minerals have shown the reversibility of the reaction 5 phlogopite + 6 calcite + 24 quartz = 3 tremolite + 5 K-feldspar + 2 H₂O + 6 CO₂. In an isobaric T – diagram the equilibrium curve reaches a maximum at = 0,75. The P, T-values for this maximum are: 2 kb-523°; 4 kb-585°; 6 kb-625°; P±5%, T±10° C. These results give a first approximation of the P, T conditions responsible for a similar mineral reaction which has been recorded from natural metamorphic assemblages.

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Herrn Prof. H. G. F. Winkler danke ich für anregende Diskussionen, desgleichen Herrn Dr. D. Puhan für wichtige Hinweise und Mitteilung seiner exp. Daten. Herrn Prof. V. Trommsdorff und Herrn P. H. Thompson bin ich für petrographische Angaben zu Dank verpflichtet. Der Aufbau der Hydrothermalanlage und die Finanzierung der laufenden Untersuchungen wurde aus den Mitteln des Fonds zur Förderung der wissenschaftlichen Forschung ermöglicht. Für diese Unterstützung gilt daher mein besonderer Dank.     

The mechanism of the reaction 1 tremolite+3 calcite+2 quartz =5 diopside+3 CO2+1 H2O: results of powder experiments

The mechanism of the reaction 1 tremolite +3 calcite+2 quartz=5 diopside+3 CO₂+1 H₂O was investigated at 2 and 5 kb, , using powder experiments lasting from 14 to 170 days. Because experiments were at high ratios of fluid to solids, the study identified the mechanism under surface-control conditions and thus establishes which reactant surface determines the kinetics. To achieve a diopside nucleation rate high enough to gain detectable reaction in the time of experimentation, the equilibrium boundary had to be overstepped by 30°–60° C at 5 kb. Experiments in which diopside successfully nucleated show that the reaction proceeds by a dissolution-crystallization mechanism. Experimentally-produced textures are presented in a series of SEM images and demonstrate that diopside nucleates and grows topotactically exclusively on tremolite. The mechanism of the forward reaction is modeled by a simplified scheme consisting of three processes, each comprising formation, transport and incorporation of 1) the Ca-, 2) the Mg-, and 3) the Si-bearing species in the fluid in response to dissolution of the reactants and crystallization of diopside. Using the dependence of the overall-reaction rate on the surface area of the reactants, it was experimentally determined that process 2) (dissolution of tremolite, transport of the Mg-bearing species in the fluid and crystallization of diopside) will be rate-limiting in most cases where metamorphism occurs in an internally controlled system. Due to the experimental design chosen, the dissolution of tremolite at the beginning of process 2) is rate-limiting in the experiments. The magnitude of the probable temperature-overstep necessary to achieve a significant nucleation rate during metamorphism is discussed on the basis of the experimental evidence and a simple nucleation rate model.     

Experimental investigation of the mechanism of the reaction: 1 tremolite+11 dolomite ⇌ 8 forsterite+13 calcite+9 CO2+1H2O

Stoichiometric mixtures of tremolite and dolomite were heated to 50° C above equilibrium temperatures to form forsterite and calcite. The pressure of the CO₂-H₂O fluid was 5 Kb and \(X_{{\text{CO}}_{\text{2}} }\) varied from 0.1 to 0.6. The extent of the conversion was determined by the amount of CO₂ produced. The resulting mixtures of unreacted tremolite and dolomite and of newly-formed forsterite and calcite were examined with a scanning electron microscope. All tremolite and dolomite grains showed obvious signs of dissolution. At fluid compositions with \(X_{{\text{CO}}_{\text{2}} }\) less than about 0.4, the forsterite and calcite crystals are randomly distributed throughout the charges, indicating that surfaces of the reactants are not a controlling factor with respect to the sites of nucleation of the products. A change is observed when \(X_{{\text{CO}}_{\text{2}} }\) is greater than about 0.4; the forsterite and calcite crystals now nucleate and grow at the surface of the dolomite grains, thus indicating a change in mechanism at medium CO₂ concentrations. As the reaction progresses, the dolomite grains become more and more surrounded by forsterite and calcite, finally forming armoured relics of dolomite. Under experimental conditions this characteristic texture can only be formed if the CO₂-concentration is greater than about 40 mole %. These findings make it possible to estimate the CO₂-concentration from the texture of the dolomite+tremolite+forsterite+calcite assemblage. The results suggest a dissolution-precipitation mechanism for the reaction investigated. In a simplified form it consists of the following 4 steps:

1. Dissolution of the reactants tremolite and dolomite.
2. Diffusion of the dissolved constituents in the fluid.
3. Heterogeneous nucleation of the product minerals.
4. Growth of forsterite and calcite from the fluid.

Two possible explanations are discussed for the development of the amoured texture at \(X_{{\text{CO}}_{\text{2}} }\) above 0.4. The first is based upon the assumption that dolomite has a lower rate of dissolution than tremolite at high \(X_{{\text{CO}}_{\text{2}} }\) values resulting in preferential calcite and forsterite nucleation and growth on the dolomite surface. An alternative explanation is the formation of a raised CO₂ concentration around the dolomite grains at high \(X_{{\text{CO}}_{\text{2}} }\) values, leading to product precipitation on the dolomite crystals.     

Experimentelle Untersuchung der Reaktion Dolomit + Kalifeldspat + H2O ⇌ Phlogopit + Calcit + CO2

The equilibrium curve for the reaction 3 dolomite + 1 K-feldspar + 1 H₂O=1 phlogopite + 3 calcite + 3 CO₂ was determined experimentally at a total gas pressure of 2000 bars using two different methods.

1. In the first case water alone was added to the reactants. The CO₂ component of the gas phase was producted solely by the reaction under favourable P-T conditions. This manner of carrying out the reaction is called the “water method”. With this method sufficient time must be allowed for the gas phase to attain a constant composition (see Fig. 1). Reverse reactions were carried out using reaction products of the forward reaction.
2. In the second case silver oxalate + water were added to the reactants. Breakdown of the silver oxalate leads to formation of a CO₂-H₂O gasphase of definite composition. At constant temperature and gas pressure the \(X_{{\text{CO}}_{\text{2}} } \) determines whether the reaction products will be phlogopite + calcite or dolomite + K-feldspar. In this case it is not necessary to wait for equilibrium to be attained. This method is abbreviated the “oxalate method”. Reactants for reverse reactions are not identical with the products of the forward reaction.

At high temperatures the results of the two different methods agree well (see Tables 1 and 2). Equilibrium was attained in one case at 490° C and \(X_{{\text{CO}}_{\text{2}} } \) of approximately 0.77, and in the other case at 520° C and \(X_{{\text{CO}}_{\text{2}} } \) of 0.90. At lower temperatures there are considerable differences in the results. With the water method an \(X_{{\text{CO}}_{\text{2}} } \) of about 0.25 was reached at 450° C. With the oxalate method dolomite K-feldspar and water still react with each other at even higher \(X_{{\text{CO}}_{\text{2}} } \) values. Phlogopite, calcite and CO₂ are formed together with metastable talc. There are no criteria to indicate which of the methods is the correct one at lower temperatures and in Fig. 2, therefore, both equilibrium curves are plotted.     

Die Reaktion 2 Zoisit+1 CO2 ⇌ 3 Anorthit+1 Calcit+1 H2O

The equilibrium conditions of the following reaction 2 zoisite +1 CO₂?3 anorthite+1 calcite+1 H₂O 2 Ca₂Al₃[O/OH/SiO₄/Si₂O₇]+1 CO₂?3 CaAl₂Si₂O₈+1 CaCO₃+1 H₂O have been determined experimentally at total pressures of P _j= 2000 bars, P _f =5000 bars, and P _f =7000 bars. Owing to the vertical position of the equilibrium curves in isobaric T- \(X_{{\text{CO}}_{\text{2}} }\) diagrams, the composition of the binary H₂O-CO₂ fluid phase coexisting with zoisite is independent of temperature in the temperature interval investigated. According to our experiments, orthorhombic zoisite is only stable in equilibrium with a fluid phase at a concentration of CO₂ which is less than, respectively, ca. 2 Mol% CO₂ at P _f =2000 bars, ea. 6 Mol% at P _f =5000 bars, and ca. 10 Mol% at P _f =7000 bars. Thus, the fluid phase coexisting with zoisite is rich in H₂O. While this is independent of temperature the experimental data demonstrate that the influence of pressure cannot be neglected: With increasing pressure the concentration of CO₂ of the fluid phase coexisting with zoisite can rise a little. The position of the reaction studied, which is independent of temperature and exhibits small values of \(X_{{\text{CO}}_{\text{2}} }\) ,leads to two important petrogenetic conclusions:

1. The occurrence of zoisite is an indicator for a CO₂-poor and H₂O-rich fluid composition during metamorphism of marly calcsilicates.
2. If the concentration of CO₂ of the fluid phase coexisting with zoisite exceeds the equilibrium value of \(X_{{\text{CO}}_{\text{2}} }\) calcite+anorthite+H₂O is formed from zoisite+CO₂. Thus, a considerable increase in the anorthite-content of plagioelase is possible.