申珂玮,
王多君^,,
刘涛
中国科学院大学地球与行星科学学院, 北京 100049

基金项目: 国家自然科学基金项目（91958216，41874104）和中央高校基本科研业务费专项资金资助


详细信息

作者简介: 申珂玮, 女, 博士研究生, 主要从事矿物电学性质研究.E-mail:shenkewei15@mails.ucas.ac.cn

通讯作者: 王多君, 男, 教授, 主要从事矿物物理研究.E-mail:duojunwang@ucas.edu.cn

中图分类号: P315

收稿日期:2020-01-04
修回日期:2020-03-27
上线日期:2020-09-05

Electrical conductivity of amphibolite at high temperature and high pressure and its geophysical implications

SHEN KeWei,
WANG DuoJun^,,
LIU Tao
College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China



More Information

Corresponding author: WANG DuoJun,E-mail:duojunwang@ucas.edu.cn

MSC: P315

--> Received Date: 04 January 2020
Revised Date: 27 March 2020
Available Online: 05 September 2020


摘要
摘要:中下地壳和俯冲带区域的高电导率异常（0.01~1 S·m^-1）可能与地球内部的特定物质及其变化有关.斜长角闪岩是中下地壳以及俯冲带区域的重要组成之一，高温高压下斜长角闪岩的电导率研究对认识电导率异常具有重要意义.本研究采用交流阻抗谱法，在0.5，1.0，1.5 GPa和473~1073 K条件下测量了天然斜长角闪岩样品的复阻抗，实验结果表明压力对斜长角闪岩的电导率影响非常小，而温度对于电导率影响非常显著，其电导率在1073 K可以达到10^-0.5 S·m^-1；实验获得的活化能值为52.21 kJ·mol^-1，推断其导电机制可能为小极化子传导（Fe²⁺的氧化）主导.结合本实验获得的结果与大陆岩石圈和俯冲带的温度结构，我们计算得到相应的电性结构剖面，并与三种不同构造背景下的大陆岩石圈（克拉通、大陆裂谷和活动造山带）和俯冲带区域的电磁剖面结构进行了对比研究，结果发现斜长角闪岩可以解释大陆裂谷和活动造山带构造背景下的莫霍面附近的高电导率异常现象，同时可能是导致较热的俯冲带区域（例如卡斯卡迪地区）高电导率异常现象的原因.
关键词: 斜长角闪岩/
电导率/
压力/
中下地壳/
俯冲带

Abstract:High electrical conductivity anomalies (0.01~1 S·m^-1) at continental middle-lower crust as well as subduction zones at different depths detected by Magnetotelluric (MT) are often associated with certain chemical compositions and their changes. Amphibolite is one of the most important components of the continental lower crust and subduction regions. The study of electrical conductivity of amphibolite at different pressures and temperatures is important to provide reasonable explanation for the high electrical conductivity anomalies in subduction zone. In this study, we measured the complex impedances of natural amphibolite at 0.5, 1.0 and 1.5 GPa and 473~1073 K. Our results indicated that pressure has a very weak effect on the electrical conductivity of amphibolite, while temperature strongly influences conductivity of amphibolite. The electrical conductivity of amphibolite is increased to 10^-0.5 S·m^-1 at 1073 K. The activation energy derived is 52.21 kJ·mol^-1, implying that the conduction mechanism was small polaron conduction (the electron hopping between Fe²⁺ and Fe³⁺). By combining our experimental results with geothermal models, we construct the conductivity models and compare the electrical structure profiles of the continental lithosphere from three different tectonic settings and subduction zones. We conclude that the electrical conductivity of amphibolite could be responsible for the anomalous high conductivities of lower crust beneath continental rifts and mobile orogenic belts and the hot subduction zone.
Key words:Amphibolite/
Electrical conductivity/
Pressure/
Middle-lower crust/
Subduction zone



PDF全文下载地址:

http://www.geophy.cn/data/article/export-pdf?id=dqwlxb_15579