高温高压下中下地壳物质电学性质实验研究

Experimental study on electrical conductivity (EC) of earth's interior materials at high temperature and high pressure are critical for constraining the explanation of field geophysical observation and for building up material compositions profile and structure of the lithosphere. In this study, EC of hydrous minerals (serpentine, talc and gypsum ), and dry and liquid-saturated eclogites are measured at high temperature and high pressure, and the influences of temperature, pressure, frequency and other factors on the measured EC were evaluated. Also the impedance spectroscopy method was used to pursue the specific microscopic mechanism of electron conduction. The EC of serpentine rises abruptly to reach a high value at high temperature and high pressure, through which a highly conductive layers ( HCL) commonly occurring in the mid-lower continental crust may be formed. However, dehydration of talc at high temperature and high pressure does not elevate EC rapidly, and therefore a HCL can not be formed by talc dehydration. The discrepancies above are most probably due to the content of structural water, the content and connectivity of free water after dehydration and the dehydration rate at high temperature and high pressure between serpentine and talc. Based on high sensitivity of EC changes to the existence and content of free water in system studied, a new method to dynamically monitor dehydration process of hydrous mineral is established with EC. A dynamic monitoring of gypsum dehydration, as an example, is successfully carried out with the method. The EC of dry eclogites at conditions equivalent to the mid-lower crust is too low to explain the crustal HCL genesis. The EC of eclogites saturated with saline solution reaches the range of EC in the global mid-lower crustal HCL, howerer is still too much low to reach the EC of HCL at the depth of 20~50 km in the Dabieshan orogen area. Thus eclogites could not be the main type of rocks at such depths in the area.

在高温高压下测定中下地壳典型岩石在干的和在各种盐水熔液饱和下的电导率，测定含高导相岩石的电导率，探讨电导率与其影响因素之间的关系，据此来讨论中下地壳高导层的可能成因，建立电导率与温度之间的函数关系，并与其它方法建立的地壳岩石结构和物质组成模型相互补充，通过实验手段为通过地球物理方法建立的地壳模型赋予物质内容。