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首页> 外文期刊>Contributions to Mineralogy and Petrology >Electrical conductivity of dry and hydrous NaAlSi_3O_8 glasses and liquids at high pressures
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Electrical conductivity of dry and hydrous NaAlSi_3O_8 glasses and liquids at high pressures

机译：干燥和含水NaAlSi_3O_8玻璃和液体在高压下的电导率

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摘要

We report the first study of electrical conductivities of silicate melts at very high pressures (up to 10 GPa) and temperatures (up to 2,173 K). Impedance spectroscopy was applied to dry and hydrous albite (NaAlSi_3O_8) glasses and liquids (with 0.02-5.7 wt% H_2O) at 473-1,773 K and 0.9-1.8 GPa in a piston-cylinder apparatus, using a coaxial cylindrical setup. Measurements were also taken at 473-2,173 K and 6-10 GPa in two multianvil presses, using simple plate geometry. The electrical conductivity of albite melts is found to increase with temperature and water content but to decrease with pressure. However, at 6 GPa, conductivity increases rapidly with temperature above 1,773 K, so that at temperatures beyond 2,200 K, conductivity may actually increase with pressure. Moreover, the effect of water in enhancing conductivity appears to be more pronounced at 6 GPa than at 1.8 GPa. These observations suggest that smaller fractions of partial melt than previously assumed may be sufficient to explain anomalously high conductivities, such as in the asthenosphere. For dry melt at 1.8 GPa, the activation energy at T > 1,073 K is higher than that at T < 1,073 K, and the inflection point coincides with the rheological glass transition. Upon heating at 6-10 GPa, dry albite glass often shows a conductivity depression starting from ～ 1,173 K (due to crystallization), followed by rapid conductivity enhancement when temperature approaches the albite liquidus. For hydrous melts at 0.9-1.8 GPa, the activation energies for conductivity at > 1,373 K are lower than those at <973 K, with a complex transition pattern in between. Electrical conductivity and previously reported Na diffusivity in albite melt are consistent with the Nernsl-Einstein relation, suggesting the dominance of Na transport for electrical conduction in albite melts.
机译：我们报道了硅酸盐熔体在非常高的压力（高达10 GPa）和温度（高达2,173 K）下的电导率的首次研究。使用同轴圆柱体设置，在活塞缸设备中以473-1,773 K和0.9-1.8 GPa的阻抗将光谱应用于干燥的含水钠长石（NaAlSi_3O_8）玻璃和液体（具有0.02-5.7 wt％H_2O）。还使用简单的板几何结构在两台多砧压力机中以473-2,173 K和6-10 GPa进行了测量。发现钠长石熔体的电导率随温度和水含量而增加，但随压力而降低。但是，在6 GPa时，电导率随温度超过1773 K迅速增加，因此，在温度超过2200 K时，电导率实际上可能随压力而增加。此外，水在提高电导率方面的效果在6 GPa时比在1.8 GPa时更为明显。这些观察结果表明，比先前假设的部分熔融少的部分可能足以解释异常高的电导率，例如在软流圈中。对于1.8 GPa的干熔体，T> 1,073 K时的活化能高于T <1,073 K时的活化能，并且拐点与流变玻璃化转变相吻合。在加热到6-10 GPa时，干燥的钠长石玻璃经常会出现电导率下降的现象，起于〜1,173 K（由于结晶），然后当温度接近钠长石液相线时，电导率会迅速提高。对于0.9-1.8 GPa的水熔体，电导率在> 1,373 K时的活化能低于<973 K在电导率下的活化能，并且两者之间具有复杂的过渡模式。钠长石熔体中的电导率和先前报道的Na扩散率与Nernsl-Einstein关系一致，表明钠转运在钠长石熔体中占主导地位。

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