Electrical Conductivity of NaCl-Bearing Aqueous Fluids to 900°C and 5GPa
Electrical Conductivity of NaCl-Bearing Aqueous Fluids to 900°C and 5GPa
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DOI：
10.1029/2018jb016658
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发表时间：
2019-02-01
影响因子：
3.9
通讯作者：
Keppler, Hans
中科院分区：
文献类型：
--
作者：
Guo, Haihao;Keppler, Hans
在活塞-气缸装置中测量了含有0.01、0.1和1 M NaCl的含水流体的电导率，测量温度高达900 ℃和5GPa。电导率一般随NaCl浓度的增加而增加，而压力和温度的影响更为复杂。在1-2GPa下，温度对电导率的影响很小，而在较高压力下，电导率随温度而增加。压力也能提高导电性，但仅在300-400摄氏度以上。这种效应可能是由于响应于增加的介电常数而增强的离子解离。然而，在较低的温度下，电导率随着压力而降低，可能是由于流体粘度的增加。测量的NaCl-H2O流体的电导率高达900 ℃和5GPa的再现（R-2=0.953），其中log σ =-0.919-872.5/T+7.61 log +0.852 logc+log（0），其中σ是以S/m为单位的电导率，T是以K为单位的温度，c是以wt%为单位的NaCl浓度，是在给定压力和温度下纯水的密度（g/cm（3）），（0）是无限稀释时NaCl在水中的摩尔电导率（Scm（2）mol（-1）），（0）= 1，573 - 1，212 + 537，062/T-208，122，721/T-2。我们用我们的数据来模拟俯冲板上方地幔楔的电导率升高。我们发现，由于强大的电导率增强，在大多数情况下，小于一个体积百分比的含水流体具有中等盐度是足以解释所观察到的电导率异常。
The electrical conductivity of aqueous fluids containing 0.01, 0.1, and 1M NaCl was measured in a piston-cylinder apparatus up to 900 degrees C and 5GPa. The conductivity generally increases with NaCl concentration, while the pressure and temperature effects are more complex. At 1-2GPa, the effect of temperature on conductivity is small, while at higher pressures, conductivity increases with temperature. Pressure also enhances conductivity, but only above 300-400 degrees C. This effect may be due to enhanced ion dissociation in response to an increasing dielectric constant. However, at lower temperatures, conductivity decreases with pressure, probably due to an increase in fluid viscosity. The measured conductivities of NaCl-H2O fluids up to 900 degrees C and 5GPa are reproduced (R-2=0.953) by a numerical model with log sigma=-0.919-872.5/T+7.61 log +0.852 logc+log(0), where sigma is the conductivity in S/m, T is temperature in K, c is NaCl concentration in wt%, is the density of pure water (in g/cm(3)) at given pressure and temperature, and (0) is the molar conductivity of NaCl in water at infinite dilution (in Scm(2)mol(-1)), (0)=1,573-1,212 +537,062/T-208,122,721/T-2. We use our data to model the elevated electrical conductivity in the mantle wedge above subducted slabs. We find that due to the strong conductivity enhancement, in most cases less than one volume percent of aqueous fluid with moderate salinity is sufficient to explain the observed conductivity anomalies.