中国东部大别苏鲁造山带壳内低速高导异常成因探究  

Study on the origins of low-velocity and high-conductivity anomalies in the crust of Dabie-Sulu orogenic belt,eastern China

作　　者：余阳 张宝华[1,3] 刘永刚 YU Yang;ZHANG BaoHua;LIU YongGang(CAS Key Laboratory of High-Temperature and High-Pressure Study of the Earth’s Interior,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,China;University of Chinese Academy of Sciences,Beijing 100049,China;Key Laboratory of Big Data in Geosciences and Deep Earth Resources of Zhejiang Province,School of Earth Sciences,Zhejiang University,Hangzhou 310027,China)

机构地区：[1]中国科学院地球化学研究所,地球内部物质高温高压院重点实验室,贵阳550081 [2]中国科学院大学,北京100049 [3]浙江大学地球科学学院,浙江省地学大数据与地球深部资源重点实验室,杭州310027

出　　处：《地球物理学进展》2021年第6期2371-2391,共21页Progress in Geophysics

基　　金：中国科学院前沿科学研究计划从0到1原始创新项目(ZDBS-LY-DQC015);国家自然科学基金(41973056,41773056)联合资助。

摘　　要：地震学和大地电磁研究表明,中国东部大别苏鲁造山带壳内广泛存在低速高导异常.本文首次较系统地梳理了前人针对大别苏鲁造山带开展的地震学和大地电磁观测结果以及岩石矿物波速和电导率的高温高压实验结果,建立了岩石波速、电导率随深度变化的模型,探究了大别苏鲁造山带壳内低速高导异常的可能成因以及形成的基本条件.大别苏鲁造山带壳内低速高导的成因复杂多样,主要有:含水矿物模型、部分熔融模型、高电导矿物模型、各向异性模型、含盐流体模型和名义无水矿物模型等.我们认为普遍低热流的大别造山带中下地壳的低速异常层和高导异常可能与波速各向异性明显的成岩矿物有关,高导异常可能与电性各向异性明显的成岩矿物有关.普遍高热流的苏鲁造山带中上地壳的低速异常可能与含水矿物脱水熔融和波速各向异性较大的成岩矿物有关,下地壳的低速异常可能是高压变质岩中角闪岩相退变质作用的结果;而下地壳的高导异常可能与含水矿物脱水以及名义无水矿物中的结构水有关.以上结论对于我们深入认识大别苏鲁造山带壳内物质组成、地质作用以及地球内部动力学过程具有重要意义.Seismological and magnetotelluric studies indicate that there are widespread low-velocity and high-conductivity anomalies in the crust of the Dabie-Sulu orogenic belt,eastern China.This paper systematically summarises the seismological and magnetotelluric observation results of the Dabie-Sulu orogenic belt,as well as the experimental results of wave velocity and electrical conductivity of rocks and minerals under high temperature and pressure.Taking the temperature of the Dabie-Sulu orogenic belt into account,the models of rock wave velocity and conductivity changing with depth are established.In this way,the possible causes and basic conditions for the formation of low-velocity and high-conductivity anomalies in the Dabie-Sulu orogenic belt are discussed in detail.The origins of low velocity and high conductivity in the crust of the Dabie-Sulu orogenic belt are complex and diverse,mainly including hydrous minerals model,partial melting model,high-conductivity mineral model,anisotropic model,saline fluid model and nominal anhydrous mineral model.We think that the low-velocity anomalies in the middle and lower crust of the Dabie orogenic belt with low heat flow may be related to the diagenetic minerals with obvious anisotropy of wave velocity,and the high-conductivity anomalies may be related to the diagenetic minerals with obvious anisotropy of electrical property.The low-velocity anomalies in the middle and upper crust of the Sulu orogenic belt with high heat flow may be related to the dehydration and melting of hydrous minerals and diagenetic minerals with high-velocity anisotropy;the low-velocity anomalies in the lower crust may be the result of amphibolite facies retrograde metamorphism in the high-pressure metamorphic rocks;and the high-conductivity anomalies in the lower crust may be related to dehydration of hydrous minerals and structural water in nominal anhydrous minerals.Finally,we point out the problems of the current research and prospects of future research.These conclusions are of great significanc

关 键 词：大别苏鲁造山带 低速高导异常 高温高压实验 波速 电导率 

分 类 号：P315[天文地球—地震学]