首页> 外文OA文献 >An Experimental Study of Water and Carbon Dioxide Solubilities in Mid-Ocean Ridge Basaltic Liquids. Part I: Calibration and Solubility Models
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An Experimental Study of Water and Carbon Dioxide Solubilities in Mid-Ocean Ridge Basaltic Liquids. Part I: Calibration and Solubility Models

机译:在海洋中脊玄武质液体中水和二氧化碳溶解度的实验研究。第一部分:校正和溶解度模型

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摘要

Experiments were conducted to determine the solubilities of H_2O and CO_2 and the nature of their mixing behavior in basaltic liquid at pressures and temperature relevant to seqfloor eruption. Mid-ocean ridge basaltic (MORB) liquid was equilibrated at 1200°C with pure H_2O at pressures of 176–717 bar and H_2O—CO_2 vapor at pressures up to 980 bar. Concentrations and speciation of H_2O and CO_2 dissolved in the quenched glasses were measured using IR spectroscopy. Molar absorptivities for the 4500 cm^(−1) band of hydroxyl groups and the 5200 and 1630 cm^(−1) bands of molecular water are 0⋅67±0⋅03, 0⋅62±0⋅07, and 25±3 l/mol-cm, respectively. These and previously determined molar absorptivities for a range of silicate melt compositions correlate positively and linearly with the concentration of tetrahedral cations (Si+Al).udThe speciation of water in glass quenched from vapor-saturated basaltic melt is similar to that determined by Silver & Stolper (Journal of Petrology 30, 667–709, 1989) in albitic glass and can be fitted by their regular ternary solution model using the coefficients for albitic glasses. Concentrations of molecular water measured in the quenched basaltic glasses are proportional to fH_2O in all samples regardless of the composition of the vapor, demonstrating that the activity of molecular water in basaltic melts follows Henry's law at these pressures. A best fit to our data and existing higher-pressure water solubility data (Khitarov et al., Geochemistry 5, 479–492, 1959; Hamilton et al., Journal of Petrology 5, 21–39, 1964), assuming Henrian behavior for molecular water and that the dependence of molecular water content on total water content can be described by the regular solution model, gives estimates for the V^(o,m)_(H2O) of 12±1 cm^3/mol and for the 1-bar water solubility of 0⋅11 wt%.udConcentrations of CO_2 dissolved as carbonate in the melt for pure CO_2-saturated and mixed H_2O-CO_2-saturated experiments are a simple function of f_(CO2). These results suggest Henrian behavior for the activity of carbonate in basaltic melt and do not support the widely held view that water significantly enhances the solution of carbon dioxide in basaltic melts. Using a ΔV^(o,m)_r of 23 cm^3/mol (Pan et al., Geochimica et Cosmochimica Acta 55, 1587–1595, 1991), the solubility of carbonate in the melt at 1 bar and 1200°C is 0⋅5 p.p.m. Our revised determination of CO_2 solubility is ∼20% higher than that reported by Stolper & Holloway (Earth and Planetary Science Letters 87, 397–408, 1988).
机译:进行实验以确定H_2O和CO_2的溶解度及其在玄武岩液中与喷发有关的压力和温度下混合行为的性质。中海洋脊玄武岩(MORB)液体在1200°C下用纯H_2O在176-717 bar的压力下平衡,而H_2O-CO_2蒸汽在980 bar的压力下平衡。使用红外光谱法测量了淬火玻璃中溶解的H_2O和CO_2的浓度和形态。 4500 cm ^(-1)羟基带和5200和1630 cm ^(-1)分子水带的摩尔吸收率是0⋅67±0⋅03、0⋅62±0⋅07和25±分别为3 l / mol-cm。这些和先前确定的对于一系列硅酸盐熔体组成的摩尔吸光度与四面体阳离子(Si + Al)的浓度呈线性正相关。 ud由蒸气饱和的玄武质熔体淬火后的玻璃中水的形态与银测定的相似。 &Stolper(Journal of Petrology 30,667–709,1989)运用于太空玻璃中,并且可以通过其常规三元解模型使用太空玻璃系数进行拟合。在淬火的玄武岩玻璃中测得的分子水浓度与所有样品中的fH_2O成正比,而与蒸气的成分无关,这表明玄武质熔体中的分子水活度在这些压力下均遵循亨利定律。假设Henrian行为为H,则最适合我们的数据和现有的高压水溶性数据(Khitarov等,地球化学5,479–492,1959; Hamilton等,岩石学杂志5,21–39,1964)。分子水以及分子水含量对总水含量的依赖性可以通过常规溶液模型来描述,其估算的V ^(o,m)_(H2O)为12±1 cm ^ 3 / mol, 1-bar的水溶性为0⋅11wt%。 ud对于纯CO_2饱和和H_2O-CO_2饱和混合实验,熔体中溶解为碳酸盐的CO_2浓度是f_(CO2)的简单函数。这些结果表明Henrian对玄武质熔体中碳酸盐活性的行为,并不支持人们普遍认为水显着增强玄武质熔体中二氧化碳的溶液的观点。使用23 cm ^ 3 / mol的ΔV^(o,m)_r(Pan等人,Geochimica et Cosmochimica Acta 55,1587-1595,1991),碳酸盐在1 bar和1200°C下在熔体中的溶解度是0⋅5ppm我们修订的CO_2溶解度测定比Stolper&Holloway(地球与行星科学快报87,397-408,1988)报道的测定高约20%。

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