剪切变形下地幔矿物岩石电导率测量的新方法  

A new method to measure the electrical conductivity of mantle minerals and rocks under shear deformation

作　　者：张宝华[1,2] 

机构地区：[1]冈山大学地球物质科学研究所 [2]地球内部物质高温高压实验室,中国科学院地球化学研究所,贵阳550002

出　　处：《地球物理学进展》2013年第5期2467-2474,共8页Progress in Geophysics

基　　金：国家自然科学基金(41303048);日本文部省杰出研究中心项目共同资助

摘　　要：本文中简要介绍了如何利用DIA型大压机同时在剪切变形和高温高压下测量地幔矿物岩石电导率的新方法.首先阐述了DIA型大压机的工作原理和剪切变形实验的步骤,然后选择了两个典型的实例分别从样品合成、实验组装、微组织结构观察等方面简要介绍了剪切变形下电导率测量的流程和最新进展,最后探讨了新结果在地球物理学方面的一些应用及存在的技术问题.目前实验研究表明:含一定量磁铁矿的蛇纹石在剪切变形下不可能在俯冲板块的表面形成相互连接的高导层,因而磁铁矿假说不能解释俯冲带的高电导率异常;此外,发现剪切应力能够诱发熔体在含部分熔融的橄榄岩颗粒边界的重新分布,从而熔体能够形成相互连接的各向异性网络,并导致与大地电磁观测结果相一致的高电导率各向异性.In this paper, a new method was briefly introduced to measure the electrical conductivity of mantle minerals and rocks by using the DIA-type apparatus simultaneously under the shear deformation and high- temperature and high-pressure. Firstly, the principle of the DIA-type apparatus and the experimental procedures of shear deformation were outlined. Secondly, two typical examples were used to display the work flow and recent advances in conductivity measurement under shear deformation in the light of sample synthesis, cell assembly, microstruetural observations and so on. Finally, the author discussed the geophysical implications of the present new results and pointed out some technical matters which need more improvements in future. The present experimental results show that the intereonnection of magnetite in serpentinites by shear deformation is not expected as an origin of high conductivity anomaly occasionally observed at the slab interface in the mantle wedge. On the other hand, it is found that shear stress can induce the redistribution of melt in partially molten peridotite and form an anisotropically well-interconnected network under shear, which is most likely to explain the high anisotropic conductivity anomalies observed by MT surveys at the top of the asthenosphere.

关 键 词：剪切变形 电导率 高温高压 各向异性 矿物 岩石 

分 类 号：P311[天文地球—固体地球物理学] P319[天文地球—地球物理学]