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首页> 外文期刊>Contributions to Mineralogy and Petrology >Quartz, albite and diopside solubilities in H2O–NaCl and H2O–CO2 fluids at 0.5–0.9 GPa
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Quartz, albite and diopside solubilities in H2O–NaCl and H2O–CO2 fluids at 0.5–0.9 GPa

机译：0.5–0.9 GPa的H2 O–NaCl和H2 O–CO2 流体中的石英，钠长石和透辉石溶解度

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The solubility of quartz and incongruent dissolution ('apparent solubility') of albite and diopside in H2O–NaCl and H2O–CO2 fluids have been determined at pressures up to 0.9 GPa (9 kbar) and temperatures of 500–900 °C. Solubilities of quartz and albite decrease with increasing salt concentration [X(NaCl)](salt-out effect), whereas the solubility of diopside increases with increasing X(NaCl)(salt-in effect). Quartz solubilities in the systems H2O–NaCl and H2O–CO2 are very similar and are proportional to X(H2O)2. Quartz solubility in NaCl-rich brines does not change with pressure under the P–T conditions of our experiments. At 0.9 GPa and 800 °C, albite solubility in pure water is higher (~100 g/kg H2O) than that of quartz (~74 g/kg H2O), but at NaCl concentrations >6 mol% these solubilities are very similar. Albite dissolution is slightly incongruent; formation and composition of secondary and quench phases (paragonite, Na-margarite, amorphous quench spheres) indicate that the solution is enriched in SiO2 and Na2SiO3. As fluid composition changes from H2O towards more CO2-rich fluids or NaCl-rich brines, the solubilities of albite and quartz decrease by about one order of magnitude, but are still measurable at X(H2O)<0.5. A thermodynamic analysis of new quartz solubility data for H2O–CO2 fluids at 0.9 GPa indicates that complexing is dominated by SiO2.4H2O for water-rich fluids, but for X(H2O)<0.7 the mean solvation number decreases to ≤3. This speciation is similar to that reported previously for lower pressures, and is in agreement with recent high P–T spectroscopic data for the system H2O–SiO2. For dissolution of quartz in both H2O–CO2 and H2O–NaCl fluids, the molecular proportions of silica to water are almost the same at any X(H2O). Assuming similar non-ideal water-salt interactions irrespective of whether the water is in the fluid or is complexed with silica, then the speciation of silica appears to be similar in both H2O–CO2 and H2O–NaCl fluids under the experimental conditions. We conclude that the speciation of silica in both H2O–CO2 and H2O–NaCl fluids at 0.9 GPa and 800 °C is comparable, is dominated by Si(OH)4·2H2O and/or hydrated species with lower hydration numbers, and is also comparable to that proposed for lower P–T conditions.
机译：在高达0.9 GPa的压力下确定了石英的溶解度以及钠辉石和透辉石在H2 O–NaCl和H2 O–CO2 流体中的不一致溶解（表观溶解度）。 9 kbar）和500–900°C的温度。石英和钠长石的溶解度随盐浓度[X（NaCl）]的增加而降低（盐析效应），而透辉石的溶解度随X（NaCl）的增加（盐析效应）而增加。 H2 O–NaCl和H2 O–CO2 系统中的石英溶解度非常相似，并且与X（H2 O）2 成比例。在我们实验的PT条件下，富含NaCl的盐水中的石英溶解度不会随压力而变化。在0.9 GPa和800°C的温度下，钠长石在纯水中的溶解度（〜100 g / kg H2 O）高于石英（〜74 g / kg H2 O），但在NaCl浓度下> 6 mol％时，这些溶解度非常相似。阿尔比特解散略有不一致；次生相和淬火相（方钠石，钠-玛格丽特，非晶态淬火球）的形成和组成表明该溶液富含SiO2 和Na2 SiO3 。随着流体成分从H2O变为更多的富含CO2的流体或富含NaCl的盐水，钠长石和石英的溶解度降低了大约一个数量级，但在X（H2 < /sub>O)<0.5。对H2 O–CO2 流体在0.9 GPa时新的石英溶解度数据进行热力学分析表明，对于富水流体，络合作用以SiO2 .4H2 O为主，但当X（H2 O）<0.7时，平均溶剂化数降至≤3。这种形态与先前报道的较低压力的形态相似，并且与H2 O-SiO2 系统最近的高P–T光谱数据一致。为了使石英溶解在H2 O–CO2 和H2 O–NaCl流体中，在任何X（H2 O处，二氧化硅与水的分子比例几乎相同）。假设无论水是在流体中还是与二氧化硅络合，非理想的水盐相互作用都类似，那么H2 O–CO2 和H2 < / sub> O–NaCl流体在实验条件下。我们得出的结论是，在0.9 GPa和800°C的H2 O–CO2 和H2 O–NaCl流体中，二氧化硅的形态具有可比性，主要受Si（OH）4 < / sub>·2H2 O和/或水合数较低的水合物质，也可与较低P–T条件下的水合物质相比。

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  • 来源
    《Contributions to Mineralogy and Petrology》 |2001年第1期|95-108|共14页
  • 作者

    Kirill Shmulovich; Colin Graham; Bruce Yardley;

  • 作者单位

    Department of Geology and Geophysics University of Edinburgh West Mains Road Edinburgh EH9 3JW UK;

    Department of Geology and Geophysics University of Edinburgh West Mains Road Edinburgh EH9 3JW UK;

    School of Earth Sciences University of Leeds Leeds LS2 9JT UK;

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