华北克拉通橄榄岩包体的显微构造、含水量与地震波性质

项目名称： 华北克拉通橄榄岩包体的显微构造、含水量与地震波性质

项目编号： No.40872144

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 生物科学

项目作者： 王勤

作者单位： 南京大学

项目金额： 45万元

中文摘要： 华北克拉通是研究大陆岩石圈形成与演化的热点地区。对华北克拉通上地幔橄榄岩包体进行显微构造、含水量和地震波性质的综合研究不仅为解释上地幔塑性变形和地震波各向异性提供可靠依据，而且可以追溯大陆岩石圈的变形历史，促进对华北克拉通岩石圈减薄机制的研究。本项目的主要内容包括：（1）使用电子背散射（EBSD）技术测量高温高压下橄榄岩的显微组构，并根据矿物的晶格优选定向计算岩石的波速和各向异性；（2）将计算结果与高温高压下的实测波速和各向异性对比，定量研究温度、压力、岩石成分、显微构造和折返过程对岩石地震波性质的影响；（3）使用傅立叶变换红外光谱仪测量橄榄石、斜方辉石和单斜辉石的结构水含量，探讨含水量对岩石显微构造，尤其是橄榄石组构发育的影响，以及上地幔含水量不均一性对华北克拉通岩石圈强度的影响；（4）根据地震观测结果，建立华北克拉通的地壳－上地幔成分模型，研究岩石圈减薄的时空分布规律和减薄机制。

中文关键词： 橄榄岩；含水量；地震波各向异性；显微构造；华北克拉通

英文摘要： The North China Craton (NCC) is an ideal place to explore the formation and evolution of the continental lithosphere due to its reactivation/destruction since the Mesozoic. An integrated study of microstructure, water content and seismic properties of peridotite xenoliths from the NCC will not only give important constraints on interpretation of ductile deformation mechanisms and seismic anisotropy of the upper mantle, but also provide new insights into the deformation history of the continental lithosphere and the lithospheric thinning of the NCC. This project includes three parts: (1) Study microstucture of peridotite xenoliths using the electron backscatter diffraction (EBSD) technique, and calculate seismic velocities and anisotropy based on the lattice-preferred orientations of major constituent minerals; (2) Measure seismic velocities of peridotites at high pressure and high temperature, and compare the results with calculated values to obtain relationships between the seismic properties of peridotites and the controlling factors (such as temperature, pressure, compositions, microstructure and exhumation process, etc); (3) Measure water contents of olivine, orthopyroxene and clinopyroxene using the FTIR spectrometer, investigate the role of water in the microstructure development of peridotites, especially olivine fabrics, and the effect of heterogonous water distribution on the lithospheric strength of the NCC; (4) Combined with seismic observations, set up a crust-mantle composition model of the NCC, and discuss the lithospheric thinning mechanisms of the NCC.

英文关键词： peridotite; water content; seismic anisotropy; microstructure; North China craton