研究生知识库

高温高压下矿物、岩石的电导率不仅可以为反演地球内部的物质组成、结构构造和演化过程提供约束，而且是了解矿物的微观晶格结构和缺陷、电子和离子的迁移，透视地球深部宏观结构和矿物晶格微观结构的重要窗口。橄榄石是上地幔最主要的矿物，因此橄榄石在高温高压下的电导率是构建上地幔电导率模型的重要组成部分。本实验借助于YJ–3000t高压设备和Solartron–1260阻抗/增益?相位分析仪，在1～3 GPa和723～1273 K的条件下原位测量了含不同含量FeS的橄榄石电导率。取得了一些成果：1. 利用交流阻抗谱法，在频率范围为10-1～106 Hz，测量含0 wt.%、5 wt.%、10 wt.%、15 wt.%和20 wt.% FeS的橄榄石在1 GPa和723～1273 K的温度压力范围内的电导率。在实验温度、压力范围内，纯橄榄石电导率为10-6～10-2 S/m，含FeS的橄榄石电导率为10-2～101 S/m，对比纯的和含FeS的橄榄石电导率可知，少量的FeS对橄榄石的电导率具有显著的影响。在实验温度范围，样品的电导率随着温度的升高而增大，但是纯橄榄石对温度的依懒性强于含硫化亚铁的橄榄石。样品的电导率符合Arrhenius关系式，对电导率数据进行线性拟合，获得纯橄榄石的活化焓大于1 eV，而含FeS的橄榄石的活化焓小于1 eV。2. 为了研究压力对含FeS的橄榄石电导率的影响，我们利用交流阻抗谱法在1～3 GPa、723～1273 K的温度压力条件下测量了纯橄榄石和含15 wt.% FeS橄榄石的复阻抗谱。结果表明，纯的和含15 wt.% FeS的橄榄石电导率对压力的变化做出相反的响应，随着压力的升高，纯橄榄石电导率微弱的降低，而含15 wt.% FeS的橄榄石电导率显著的增加。含15 wt.% FeS的橄榄石电导率对温度、压力的效应以及实验获得的活化焓可知，15 wt.% FeS在橄榄石中形成了相互连通的网络，主导着橄榄石的导电过程，并且可以推测压力的升高可以增强高导相在硅酸盐基质中的连通性，不能完全连通的少量高导相，随着压力的增加可能会形成相互连通的网络。

Electrical conductivity of mineral rocks under high temperature and pressure can not only provide constraints for inversion of material composition, structure and evolution process of the earth's interior, but also provide an important window for understanding the micro-lattice structure and defects of minerals, migration of electrons and ions, and perspective of macro-structure and mineral lattice microstructures in the deep part of the earth. Olivine is the most important mineral in the upper mantle. The electrical conductivity of olivine at high temperature and high pressure is an important part of building the electrical conductivity model of the upper mantle. In this present work, the electrical conductivity of olivine with different content of FeS were measured in situ at 1–3 GPa and 723–1273 K by the help of YJ–3000t high voltage equipment and Solartron–1260 impedance/gain-phase analyzer. Some achievements mainly include:1. Electrical conductivity of olivine containing 0 wt.%, 5 wt.%, 10 wt.%, 15 wt.% and 20 wt.% FeS at range of 1 GPa and 723–1273 K was measured by AC impedance spectroscopy in the frequency range of 10-1–106 Hz. Under the experimental temperature and pressure range, the electrical conductivity of pure olivine is 10-6–10-2 S/m, and that of FeS–bearing olivine is 10-2–101 S/m, we know a small amount of ferrous sulfide has a significant effect on the electrical conductivity of olivine by comparing the electrical conductivity of pure olivine and FeS–bearing olivine. In the experimental temperature range, the electrical conductivity increases with the increase of temperature, but the laziness of pure olivine to temperature is stronger than that of FeS–bearing olivine. Experimental results show that all of the electrical conductivities of samples satisfy the Arrhenius relation. By linear fitting of the electrical conductivity data yields an activation enthalpy of pure olivine greater than 1 eV, while an activation enthalpy of FeS–bearing olivine is less than 1 eV. 2. In order to study the effect of pressure on the electrical conductivity of FeS –bearing olivine, the complex impedance spectra of pure olivine and 15 wt.% FeS–bearing olivine were measured by AC impedance spectroscopy at 1–3 GPa and 723–1273 K. The results show that pressure has different effects on the conductivity of pure olivine and 15 wt.% FeS–bearing olivine. With the increase of pressure, the electrical conductivity of pure olivine decreases slightly, while that of 15 wt.% FeS–bearing olivine increases significantly. Based on the experimental results including the Arrhenius parameters, it is proposed that 15 wt.% FeS can form an interconnected network in olivine, which dominates the conduction process of olivine, the increase of pressure can enhance the connectivity of high conductivity phases in silicate matrix, and therefore a small number of high conductivity phases cannot be completely connected, but with the increase of pressure, a interconnected network may be formed.