Electrical conductivity anisotropy of deformed talc rocks and serpentinites at 3 GPa
Electrical conductivity anisotropy of deformed talc rocks and serpentinites at 3 GPa
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DOI：
10.1016/j.pepi.2011.06.012
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发表时间：
2011-09-01
影响因子：
2.3
通讯作者：
Katayama, Ikuo
中科院分区：
文献类型：
--
作者：
Guo, Xinzhuan;Yoshino, Takashi;Katayama, Ikuo
利用Kawai型多砧压力机，在500-1000 K、3 GPa的温度范围内，研究了天然滑石岩和蛇纹岩变形后的电导率各向异性。用阻抗分析仪在10（-3）-10（6）Hz沿着3个方向测量样品的电导率：平行于定向矿物线理的方向（x方向）、垂直于叶理面上线理的方向（y方向）和垂直于叶理的方向（z方向）。对于这两种岩石类型，平行于x和z方向的电导率分别最高和最低。滑石岩和蛇纹岩的电导率至少比以前的报告低两个数量级。蛇纹岩的电导率高于滑石岩。在相同的氧缓冲条件下，滑石岩的电导率各向异性强于蛇纹岩。蛇纹岩的电导率和各向异性随氧逸度的增大而增大。滑石的活化焓在x方向最低（0.59 eV），在z方向最高（0.68 eV）。蛇纹岩在不同方向上的激活能谱显示出相似的值：对于使用Mo和Ni电极的实验，分别为约0.74 eV和0.68 eV。两种岩石类型的阻抗谱显示存在两个传导路径：晶粒内部和晶界传导。晶界导电降低了总电导率。含水矿物的电导率对氢浓度和氢迁移率有很强的依赖性。的传导机制可能是质子迁移通过外在的空缺来自于存在的三价铁垂直于c轴的晶体和通过间隙机制平行于c轴。在温暖和寒冷的俯冲带中，高导电体（类似于10（-15）S/m）不能用滑石或蛇纹岩的存在来解释。在俯冲带中的电导率各向异性将是不明显的小（在一个顺序内），除非我们考虑其他良好排列的高导电相。(C)2011 Elsevier B. V.保留所有权利。
The electrical conductivity anisotropy of deformed natural talc rocks and serpentinites was investigated using a Kawai-type multi-anvil press in the temperature range of 500-1000 K at 3 GPa. The electrical conductivities of the samples were measured by an impedance analyzer with a frequency range of 10(-3)-10(6) Hz along three sample directions: the direction parallel to the lineation of oriented minerals (x direction), the direction perpendicular to the lineation on the foliation plane (y direction), and the direction perpendicular to the foliation (z direction). For both rock types, electrical conductivities parallel to the x and the z directions were the highest and the lowest, respectively. Electrical conductivities of talc rocks and serpentinites were at least two orders of magnitude lower than previous reports. Electrical conductivities of the serpentinites were higher than those of the talc rocks. Electrical conductivity anisotropy for the talc rocks was stronger than that for the serpentinites at the same oxygen buffer condition. Electrical conductivity and its anisotropy of the serpentinites become higher with higher oxygen fugacity. The activation enthalpy of talc rocks was the lowest (0.59 eV) in the x direction and highest (0.68 eV) in the z direction. The activation enthalpies of the serpentinites in different directions show similar values: about 0.74 eV and 0.68 eV for the experiments using Mo and Ni electrodes, respectively. Impedance spectra for both rock types show the presence of two conduction paths: grain interior and grain boundary conductions. The total electrical conductivities were reduced by grain boundary conduction. Electrical conductivities of hydrous minerals show strong dependence on hydrogen concentration and hydrogen mobility. The conduction mechanism probably was proton migration through extrinsic vacancies derived from a presence of ferric iron perpendicular to the c axis of the crystals and through interstitial mechanisms parallel to the c axis. In both warm and cold subduction zones, high electrical conductors (similar to 10(-15) S/m) cannot be explained by the presence of talc or serpentinites. The electrical conductivity anisotropy in a subduction zone would be inconspicuously small (within one order) unless we consider other well aligned high conductive phases. (C) 2011 Elsevier B.V. All rights reserved.