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

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.

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

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.