Polarization effects at grain-boundaries

晶界处的极化效应

• 批准号: 33831276
• 负责人: Dr. Heinrich Brasse
• 金额: --
• 依托单位: Institut für Angewandte Geowissenschaften (AGW)
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2007
• 资助国家: 德国
• 起止时间: 2006-12-31 至 2010-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/33831276?language=en
• 关键词: Polarization; effects; grain; boundaries

The electrical conductivity of partially molten rocks mainly depends on the interconnectivity of the melt phase. Different electrical conductivity mechanisms dominate in melts and minerals. If an electrical field is applied to a partially molten rock, polarizations should occur at meltmineral-interfaces due to different charge carriers in melts (ions) and crystals (electrons). This polarization will significantly influence the scaling behavior of electrical conductivity experiments. Within this project we want to test the following hypothesis: "The complex electrical conductivity of partially molten rock is significantly influenced by polarization effects at melt-mineral interfaces" and discuss the consequences of polarizations at the melt-mineral interface a) for the interpretation of laboratory experiments and b) for the inversion and interpretation of field observations. The qualitative and quantitative understanding of polarization effects on the electrical conductivity of partially molten systems should give us a deeper insight into the scaling behaviour of systems where polarization effects at meltmineral-interfaces occur. At low frequencies (direct current - DC experiments) the polarization will significantly contribute to the observed overall resistivity. At higher frequencies-such as in laboratory experiments - this polarization is usually overprinted by electrode polarizations. One consequence might be that the deduced melt portions to explain observed conductivity anomalies are underestimated while neglecting polarization effects. Therefore, a consequence, the existing magnetotelluric data for the Andes, in Tibet, or in the Pyrenees need to be re-evaluated while taking polarization effects at melt-mineral-interfaces into account.

部分熔融岩石的电导率主要取决于熔体相之间的相互连通性。不同的导电机制在熔体和矿物中占主导地位。如果电场作用于部分熔融的岩石，由于熔体(离子)和晶体(电子)中载流子的不同，熔体-矿物界面应发生极化。这种极化将显著影响电导率实验的定标行为。在这个项目中，我们想要检验以下假设：“部分熔岩的复杂电导率受到熔体-矿物界面极化效应的显著影响”，并讨论熔体-矿物界面极化的后果a)用于解释实验室实验，b)用于反演和解释野外观测。定性和定量地了解极化对部分熔融体系电导率的影响，将使我们更深入地了解在熔体-矿物界面发生极化效应的体系的标度行为。在低频下(直流电-直流电实验)，极化对观测到的总电阻率有很大影响。在更高的频率下--例如在实验室实验中--这种极化通常被电极极化所覆盖。一个后果可能是，用来解释观测到的电导率异常的熔体部分被低估了，而忽略了极化效应。因此，现有的安第斯山脉、西藏或比利牛斯山脉的大地电磁数据需要重新评估，同时考虑熔体-矿物-界面的极化效应。