高温高压下角闪片麻岩的电导率研究

摘要

在1.0 GPa压力、343～962 K温度和0.1～106Hz频率的条件下,使用Solartron 1260阻抗-增益/相位分析仪对含角闪石的片麻岩从平行和垂直面理两个不同方向分别进行了电阻抗的测定,并且进一步分析了片麻岩的微观导电机制.高温高压实验结果表明:片麻岩的复阻抗对温度、频率表现出明显的依赖性.片麻岩的电导率在平行和垂直面理两个方向表现出明显的各向异性,平行面理方向的电导率远大于垂直面理方向.二者的导电机制分别在～799 K和～881 K发生了变化,这一变化可能与角闪石的脱水相关.片麻岩中角闪石的脱水作用可使电导率增大.低温阶段,二者的激化焓分别为0.31 eV和0.56 eV,高温阶段分别高达2.24 eV和4.21 eV.实验室模型与大地电磁测深结果的对比表明,实验结果为地球内部高导层的形成提供可能的实验证据.%We conducted electrical impedance spectra measurements parallel and perpendicular to foliation in dry gneiss at 1.0 GPa and 343～962 K within the frequency range of 0. 1～106 Hz using a 1260 impedance analyzer. The high temperature and pressure experimental results indicate that impedance spectrum strongly depends upon the variation of frequency and temperature. The electrical conductivity of gneiss is remarkably anisotropic, the electrical conductivity parallel to foliation shows the highest value. Dehydration may alter the conduction mechanisms and enhance the electrical conductivity of gneiss. The activation enthalpies of gneiss derived are about 0. 31 eV and 0. 56 eV at low temperature ranges, in contrast, the activation enthalpies with values of 2. 24 eV and 4. 21 eV are obtained at high temperature ranges,respectively. A comparison between experimental results with data derived from electromagnetic soundings indicates that the dehydration of amphibole-bearing gneiss may provide an alternativeexplanation for high-conductivity layer.