Interpretation of deep earth structures from electromagnetic data requires the constraint from the electrical conductivity of various minerals experimentally measured at high temperature and high pressure. However, the combination of these measured conductivities of different minerals always fails to match the conductivities of the multiphase rocks under in-situ conditions. To investigate the effect of ion segregation at grain boundaries on bulk conductivity, we measured the electrical conductivities of quartz, albite, and orthoclase single-phase aggregates, as well as those of two multiphase aggregates made up of the three minerals at both ambient pressure and 1 GPa over a range of temperatures. The electrical conductivities of the multiphase aggregates were an order of magnitude higher and the activation enthalpies were lower than those of the three single-phase aggregates. A significant dependence of conductivity on grain size was identified in the multiphase aggregates but not in the single-phase aggregates. The interdiffusion of alkali ions between orthoclase and albite initiated grain boundary ionic conduction, which enhanced the bulk conductivity of the multiphase aggregates to 20 S/m at 1073 K. This conduction mechanism might explain the electrical conductivity anomalies of the active shear zone in the crust.

从电磁数据解释深部地球结构需要受到高温高压下实验测量的各种矿物的电导率的约束。然而，这些测量的不同矿物的电导率的组合总是无法与原位条件下多相岩石的电导率相匹配。为了研究晶界离子偏析对体电导率的影响，我们测量了石英、钠长石和正长石单相聚集体的电导率，以及由三种矿物组成的两种多相聚集体在环境压力和压力下的电导率。在一定温度范围内为 1 GPa。多相聚集体的电导率比三个单相聚集体高一个数量级，活化焓低。在多相聚集体中但在单相聚集体中没有发现电导率对晶粒尺寸的显着依赖性。正长石和钠长石之间碱离子的相互扩散引发了晶界离子传导，使多相聚集体在 1073 K 时的体电导率提高到 20 S/m。这种传导机制可能解释了地壳活动剪切带的电导率异常.