【作者】 王多君；

【导师】 李和平；

【作者基本信息】 中国科学院研究生院（地球化学研究所） ， 地球化学， 2004， 博士

【摘要】 电导率是重要的地球物理参数。模拟地球内部条件下的矿物、岩石电导率测量是了解地球内部物质组成及物理化学性质的有效手段，同时，还可以为野外大地电磁测量结果的解释提供依据。在YJ—紧装式六面顶压机上，对原有的矿物、岩石电性测量系统进行了进一步的改进：建立了一套以Solartron 1260阻抗／增益—相位分析仪为测试仪器，使用Mo电极和Mo盾来控制样品氧逸度的测量系统，该系统的氧逸度环境为Mo—MoO₂，接近IW缓冲对。石英（人造水晶）、橄榄石、纯橄榄岩、辉石岩、二辉橄榄岩、巨晶辉石的电导率测量是在新的测量系统下获得的，而辉长岩的电导率测量是基于LCR仪为测量仪器的测试系统下获得的。 在压力为1—3GPa、温度为675K—1600K、频率为10⁸—0.1Hz、氧逸度为Mo—MoO₂的条件下，对不同方向石英（人造水晶）的电学性质进行了研究。复阻抗平面上出现了反映样品本身性质的阻抗弧和反映样品与电极之间扩散的直线。石英的电导率随温度增加而增加，随压力的变化比较微弱。石英的导电机制主要为离子导电，载流子可能为碱金属离子和氢离子，这些碱金属离子和氢离子主要在平行于光轴的通道中运动。在相同的温度和压力条件下，α石英的电导率和c轴的夹角有关，石英的电导率随着夹角的增大而减小，表现出了强烈的各向异性。对各个方向石英在发生了相变前后的电导率进行了研究，发现α石英转变为β石英后，电导率并没有突变，仍然随着温度的增加而增加。 在压力为1—2GPa、温度为563-1173K、频率为12—10⁵Hz的条件下研究了辉长岩的阻抗。结果发现辉长岩复阻抗的实部随频率的增加而减小，而虚部随频率增加先增大后减小；相角随频率增加而减小。在复阻抗平面上出现了反映颗粒内部的阻抗弧，该阻抗弧出现在高频段。实验室获得辉长岩在地壳的压力和温度（1.0GPa和893K）条件下的电导率值为1.77×^-4S／m，而高导层的电导率值为0.01—0.1S／m，二者相差了2—3个数量级，推断辉长岩不能在下地壳形成高导层。 在压力为3.0GPa、温度为1299—1600K、频率为10⁶—0.1Hz、氧逸度为Mo—MoO₂条件下，对不同颗粒粒度的橄榄石电导率进行了测量。在复阻抗平面上均出现了反映颗粒内部电响应的阻抗弧，这些阻抗弧随着温度的增加而减小。而反映颗粒边界导电机制的阻抗弧并不明显，两种阻抗弧出现在不同的频率范围内，反映颗粒内部导电机制的阻抗弧出现在频率较高的范围内，而反映颗粒边界导电机制的阻抗弧出现在频率相对低的范围内。不同粒度橄榄石在3.OGPa条件下的电导率随着温度的增加而增加，它们的激化烩介于1.03一2.lleV之间。 在压力为l一3GPa、温度为1282一z544K、频率为0.1一lo6Hz、氧逸度为Mo一MoOZ的条件下，对纯橄榄岩的电导率进行了测量。在复阻抗平面上出现了反映颗粒内部电响应和颗粒边界电响应的阻抗弧。反映颗粒内部导电的阻抗弧出现在较高的频率段，随着温度的增加，这些阻抗弧逐渐收缩。颗粒边界的阻抗弧出现在相对低的频率段。纯橄榄岩的电导率随着温度增加而增加，随压力变化比较微弱。对颗粒边界的电导率研究表明，颗粒边界的电导率高于颗粒内部的电导率，总电导率则小于颗粒内部和颗粒边界的电导率，颗粒边界并没有增强总电导率。纯橄榄岩的激化能为1 .62ev，而激化体积为o.67c扩/mol，指前因子为5125/m。利用实验所获得的拟合参数，建立了地球内部200一400km处的电导率模型，并同地球物理模型进行了对比，在温度和氧逸度的合理波动范围内，实验室电导率模型和地球物理模型吻合的很好。 在压力为z一ZGPa、温度为1228一r584K、频率为0.2一106Hz、氧逸度为Mo一MoO:条件下，测量了天然和热压辉石岩、热压巨晶辉石、二辉橄榄岩的电导率。结果发现，在复阻抗平面上出现了反映颗粒内部电响应和颗粒边界电响应的阻抗弧，反映颗粒内部导电的阻抗弧出现在较高的频率段，随着温度的增加，这些阻抗弧逐渐收缩。颗粒边界的阻抗弧出现在相对低的频率段。辉石岩、二辉橄榄岩、巨晶辉石电导率随着温度增加而增加，随压力变化比较微弱。天然辉石岩和热压辉石岩颗粒边界的电导率高于它们各自颗粒内部的电导率，而总电导率则小于颗粒内部和颗粒边界的电导率，颗粒边界并没有增强总电导率。辉石岩一二辉橄榄岩一纯橄榄岩的电导率依次减小，这可能是与它们的铁含量有关。天然辉石岩的电导率与热压辉石岩的电导率的差异可能与样品中的水（氢）含量的不同有关。更多还原

【Abstract】 Electrical conductivity is an important geophysical parameter. Measurements of the electrical conductivity of minerals and rocks from the Earth’s interior provide a powerful tool for probing physical and chemical properties and composition of the deep earth, and help us to interpret magnetotelluric data. A new measurement system for electrical conductivity in an YJ-3000t press fitted with a wedge-type cubic anvil was set up on the basis of the old one. A solartron 1260 impedance/Gain phase analyzer was used in the new system; Mo electrodes and a Mo shield were also used to keep oxygen fugacity close to the Mo-MoO2, which is similar to that of iron-wustite (IW). The high accuracy of electrical conductivity measurement could be reached with this new system, and oxygen fugacity could be well controlled.Electrical conductivities of quartz, olivine, dunite, Iherzolite, pyroxenite, and megaaugite were measured by virtue of the new system; whereas, the electrical conductivity of gabbro was measured by means of the old one.An interesting outgrowth of the present study is the measurement of the complex impedance of a series of quartz plates with different orientations. Measurements were made over the frequency range 0.1 tol06 Hz at 1-3 GPa and 600 -1600 K. The complex impedance plot displays one arc and one straight line at each temperature; they correspond to different conduction process or mechanism at different range of frequency, and have different relaxation time, respectively. The high-frequency arc represents bulk properties of the sample. The straight line is characteristic of diffusional processes at the sample-electrode interface. The phase angle displays a strong dependence on frequency; the impedance magnitude decreases with frequency. The electrical conductivity of quartz increases with temperature, but pressure has weak effect on the electrical conductivity. Conductivity mechanism of a -quartz is ionic, and alkali and hydrogen ions moving in channels parallel to the c-axis are the predominant current carriers. The electrical conductivity of quartz decreases with increasing angle to c axis at the same temperature and pressure due to decreasing of the channel size. There is no sudden change in the conductivity at the transition point.The complex impedance of gabbro was determined at 1-2 GPa and 593 - 1173 K, over a frequency range 12 to l5 Hz. The real part of the complex impedance decreases with frequency; the imaginary part of the complex impedance increases with frequency to the maximum, and then decreases with frequency; and phase angle decreases with frequency increasing. The grain interior arc occurs at highest frequency range. The electrical conductivity value of the gabbro is 1.77X l0-4S/m at 1.0 GPa and 893 K, which is 2-3 orders magnitude lower than that of high conductivity layer in the lower crust, so gabbro could not form the high conductivity layer.The polycrystalline olivine compacts were synthesized at 130 MPa and 1473 K for 2.5 hours. The complex electrical impedance of polycrystalline olivine compacts was determined at 3 GPa and 1273-1573 K, and at the fo2 of Mo-MoO2 over a frequency range 0.1 to 106Hz. The arcs representing grain interior conduction mechanisms appear on all complex impedance plots, and occur at high frequency rang and contract with temperature. However, those arcs representing grain boundary and occurring at low frequency range were observed only in a small number of experimental runs. The phase angles display a strong dependence on frequency; the impedance magnitudes decrease across the entire frequency spectrum. The activation enthalpies lie in the range of 1.03-2.11eV.The complex electrical properties of dunite were measured over the frequency range from 0.1-106Hz, at 1-3 GPa and 1282-1544K, and at the fo2 of Mo-MoO2. Complex plane plots show separate effects of grain interior and grain boundary conductivity. Grain interior transport controls the response above ~100 Hz, whereas grain boundary transport dominates between ~100 and 0.1 Hz. The electr更多还原