红河-哀牢山剪切带角闪岩中角闪石变形特征及地震波各向异性  

Deformation Characteristics and Seismic Wave Anisotropy of Amphibole in Amphibolite from Red River-Ailao Shan Shear Zone

作　　者：刘建华[1] 曹淑云[1] 周丁奎 李俊瑜 程雪梅 Liu Jianhua;Cao Shuyun;Zhou Dingkui;Li Junyu;Cheng Xuemei(State Key Laboratory of Geological Processes and Mineral Resources,School of Earth Sciences,China University of Geosciences,Wuhan 430074,China)

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室地球科学学院,湖北武汉430074

出　　处：《地球科学》2019年第5期1716-1733,共18页Earth Science

基　　金：国家自然科学项目(Nos.41722207;41472188);国家重点研发计划项目(No.2017YFC0602401)

摘　　要：角闪岩作为中下地壳的重要物质组成,其岩石和矿物的变形行为及力学强度表现直接制约着中下地壳力学属性与状态,因此开展对其中重要组成矿物角闪石的变形行为和地震波各向异性研究,具有重要地质意义.以红河-哀牢山剪切带中出露的变形角闪岩中角闪石为研究对象,其中显微构造分析表明,变形角闪岩分别呈现出粗、中粒条带状糜棱岩和细粒条带状超糜棱岩.分别对这3种变形岩石中的角闪石矿物颗粒进行了EBSD晶格优选定向分析和地震波各向异性计算,结果表明3种变形角闪岩中的角闪石呈现出不同取向及典型晶质塑性变形特征,(100)[001]主要滑移系发育,同时发育不同程度的(010)[001]和(110)[001]次级滑移系.我们认为在剪切变形过程中,角闪石双晶滑移和解理面滑移共同作用致使角闪石细粒化.从粗粒到细粒条带状角闪石,随着角闪石颗粒粒度减小,角闪石中AV_p也有逐渐变小的趋势,表明角闪石变形行为、形态优选定向及晶格优选定向共同影响着地震波各向异性.Amphibolite is an important component in middle to lower crustal rocks, and the deformation behavior and mechanical strength of rocks and minerals in it control the mechanical properties and state of middle to lower crustal rocks directly, so it's quite meaningful to study amphibole's deformation behavior and seismic anisotropy. we took deformed amphibolite from Red River-Ailao Shan shear zone as our studying object. Microstructure analysis of amphibolite shows three types of mylonites:coarse-grained banded mylonite, medium-grained banded mylonite and fine-grained banded ultramylonite. we carried out EBSD crystal preferred orientation analysis and seismic anisotropy calculation of three types of amphibole respectively. Results show that these three types of amphiboles have different initial orientations and typical crystal plastic deformation,(100)[001] is the dominant slip system, furthermore, two secondary slip systems (010)[001] and (110)[001] are also developed. It is concluded that in the process of shear deformation amphibole's twin slip and cleavage plane slip contribute to the grain size reduction together. As amphibole's grain size become finer from coarse-grained banded mylonite to fine-grained banded ultramylonite, AVps of amphiboles also tend to be smaller, it indicates that amphibole's deformation behavior, shape preferred orientation and crystal preferred orientation affect its seismic wave anisotropy together.

关 键 词：角闪石变形 细粒化 EBSD晶格优选定向 地震波各向异性 角闪石变形机制 构造地质 

分 类 号：P54[天文地球—构造地质学]