Hydrogen-alkali exchange between silicate melts and two-phase aqueous mixtures: an experimental investigation
Hydrogen-alkali exchange between silicate melts and two-phase aqueous mixtures: an experimental investigation
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DOI：
10.1007/s004100050298
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发表时间：
1997-07
影响因子：
3.5
通讯作者：
Thomas J. Williams;P. Candela;P. Piccoli
中科院分区：
文献类型：
--
作者：
Thomas J. Williams;P. Candela;P. Piccoli
在高硅流纹岩熔体+低盐度水蒸气+水盐盐水三相体系中，研究了岩浆-热液体系在800℃和100 MPa、850℃和50 MPa条件下氢、钾、钠的交换平衡。水蒸气+卤水混合物和硅酸盐熔体之间的氢钠交换的kaqm /meltH、NaandKaqm/meltH、k与水蒸气+卤水混合物中总氯化物浓度成反比（ΣCl），表明低盐度水蒸气中HCl/NaCl和HCl/KCl高于高盐度卤水。蒸汽/熔体和卤水/熔体交换的平衡常数由kaqm /meltH、NaandKaqm/meltH、kvs .在pandt上的水混合物中水蒸气相对于卤水的比例（Faqv）的回归提取，以ΣCl的函数表示。在研究的压力范围内，没有观察到压力对经验确定的交换常数的显著影响。模型平衡常数为：Kaqv/meltH，Na（蒸气/熔体）在100 MPa（800℃）时=26（±1.3），在50 MPa（850℃）时= 19（±7.0）；Kaqv/meltH，K在100 MPa（800℃）时=14（±1.1），在50 MPa（850℃）时= 24（±12）；Kaqb/meltH,b（盐水/熔体）在100 MPa（800℃）时= 1.6（±0.7），在50 MPa（850℃）时= 3.9（±2.3）；kaqb /meltH，在100 MPa（800℃）下K=2.7（±1.2），在50 MPa（850℃）下K= 3.8（±2.3）。用kaqv /meltH、KandKaqb/meltH、kk的值计算了水溶液和卤水中KCl/HCl作为熔融铝饱和指数（ASI：摩尔Al2O3/(K2O+Na2O+CaO)）和压力的函数。模型对数KCl/HCl值表明，熔体ASI从过铝质（ASI = 1.04）到中度铝质（ASI = 1.01）的变化使水蒸气的冷却路径（在温度-对数KCl/HCl空间中）向红柱石+白云母+ k -长石反应点转移。
Experiments were performed in the three-phase system high-silica rhyolite melt + low-salinity aqueous vapor + hydrosaline brine, to investigate the exchange equilibria for hydrogen, potassium, and sodium in magmatic-hydrothermal systems at 800 °C and 100 MPa, and 850 °C and 50 MPa. TheKaqm/meltH,NaandKaqm/meltH,Kfor hydrogen-sodium exchange between a vapor + brine mixture and a silicate melt are inversely proportional to the total chloride concentration (ΣCl) in the vapor + brine mixture indicating that HCl/NaCl and HCl/KCl are higher in the low-salinity aqueous vapor relative to high-salinity brine. The equilibrium constants for vapor/melt and brine/melt exchange were extracted from regressions ofKaqm/meltH,NaandKaqm/meltH,Kversus the proportion of aqueous vapor relative to brine in the aqueous mixture (Faqv) atPandT, expressed as a function of ΣCl. No significant pressure effect on the empirically determined exchange constants was observed for the range of pressures investigated. Model equilibrium constants are:Kaqv/meltH,Na(vapor/melt)=26(±1.3) at 100 MPa (800 °C), and 19( ± 7.0) at 50 MPa (850 °C);Kaqv/meltH,K=14(±1.1) at 100 MPa (800 °C), and 24(±12) at 50 MPa (850 °C);Kaqb/meltH,b(brine/melt)= 1.6(±0.7) at 100 MPa (800 °C), and 3.9(±2.3) at 50 MPa (850 °C); andKaqb/meltH,K=2.7(±1.2) at 100 MPa (800 °C) and 3.8(±2.3) at 50 MPa (850 °C). Values forKaqv/meltH,KandKaqb/meltH,Kwere used to calculate KCl/HCl in the aqueous vapor and brine as a function of melt aluminum saturation index (ASI: molar Al2O3/(K2O+Na2O+CaO) and pressure. The model log KCl/HCl values show that a change in melt ASI from peraluminous (ASI = 1.04) to moderately metaluminous (ASI = 1.01) shifts the cooling pathway (in temperature-log KCl/HCl space) of the aqueous vapor toward the andalusite+muscovite+K-feldspar reaction point.