D″层的地震地质特征及其地球动力学意义  

Seismic Geological Characteristics and Geodynamic Significances of the Core-Mantle Transition Zone(D″ Layer)

作　　者：李江海[1,2] 范庆凯 吴桐雯 LI Jianghai;FAN Qingkai;WU Tongwen(MOE Key Laboratory of Orogenic Belts and Crustal Evolution,School of Earth and Space Sciences,Peking University,Beijing 100871,China;Institute of Oil and Gas,Peking University,Beijing 100871,China)

机构地区：[1]北京大学地球与空间科学学院,造山带与地壳演化教育部重点实验室,北京100871 [2]北京大学石油与天然气研究中心,北京100871

出　　处：《大地构造与成矿学》2018年第6期955-964,共10页Geotectonica et Metallogenia

基　　金：科技部重大专项(2016ZX05033002);国家重点研发课题(2016YFC0503301)联合资助.

摘　　要：地震层析成像和高温高压实验的研究进展,不断加深对地幔底部的D″层的地质认识,包括D″层精细结构及其物质组成。本文在回顾该领域研究进展的基础上,探讨D″层的化学、矿物组成、内部结构,与板片俯冲的动力学关系,板片墓地向地幔柱生成带的转变,以及D″层对地幔对流模式的制约。全球D″层的分布具强烈的横向不均一性,布里基曼石向后钙钛矿的相变成是D″层边界的重要标志。LLSVPs(large low shear velocity provinces)边缘是全球重要热点——大岩浆岩省(LIP)的起源地,其边缘和内部大尺度不均匀性的研究,对于认识地幔演化及成分具有重要意义。LLSVPs与地幔深部俯冲板片具有密切的构造关系和成因联系,对认识地球地幔模型具有关键意义。修正后的双层地幔对流模式能较合理解释目前的下地幔研究进展,上、下双层地幔对流之间,涉及了超级地幔柱和板片俯冲的有效沟通和物质循环。The progress in seismic tomography and high temperature and high pressure experiments is deepening the geological understanding of the D″ layer at the bottom of the mantle, including its fine structure and material composition. This paper provides, from the perspective of tectonics, a comprehensive review of literatures related to the topics including the chemical and mineral compositions and internal structure of the D″ layer, the relationship between the D″ layer and slab subduction, and the manner how the plate cemetery will turn into mantle plume. We also explore the restriction of the D″ layer on the convection model and the new geodynamic model. The global distribution of the D″ layer has a strong transverse heterogeneity while the phase transition of perovskite to post-perovskite delineates the boundary of the D″ layer. Edges of large low shear velocity provinces(LLSVPs) are considered as provenances of supper plumes and large igneous provinces(LIPs). It is believed that studies on the large scale inhomogeneity outside and inside of the LLSVPs are important to the understanding in the compositional evolution of the mantle. LLSVPs are closely related to the deep subduction plate into the mantle, and are of great significance to the understanding of the mantle convection model. The modified two-layer mantle convection model can reasonably explain the new results obtained from the current researches on the lower mantle. Convection between the upper and lower mantle involves the effective communication and material cycle between supper plumes and plate subduction.

关 键 词：下地幔底部 D″层结构与组成 布里基曼石和后钙钛矿 地幔对流模式 

分 类 号：P542[天文地球—构造地质学]