超高压变质岩单斜辉石中石英出溶体的形成机制及其构造物理意义

项目名称： 超高压变质岩单斜辉石中石英出溶体的形成机制及其构造物理意义

项目编号： No.41272080

项目类型： 面上项目

立项/批准年度： 2013

项目学科： 天文学、地球科学

项目作者： 徐海军

作者单位： 中国地质大学（武汉）

项目金额： 86万元

中文摘要： 单斜辉石中发育定向石英棒状体的显微结构在超高压变质岩区广泛发现，有些还伴生有定向钙质角闪石。目前还不清楚其成因机制和动力学过程，对其是否能作为超高压变质的可靠识别标志还存在很大争议。我们拟采用电子背散射衍射、扫描电镜和电子探针等多种微区测试分析手段，分析天然单斜辉石中石英棒状体的显微拓扑结构及其与主晶的结晶学取向关系，研究其与全岩化学组成以及单斜辉石Ca-Eskola含量的关系；并选择典型天然样品，粉碎后开展化学平衡的高温高压实验岩石学研究，查明石英棒状体完全溶解进入辉石的平衡温压条件。同时，模拟天然榴辉岩化学体系的初始样品，开展2-12GPa、600-1200℃范围的高温高压实验，研究单斜辉石中硅含量随温度、压力和含水量的变化关系。在此基础上结合前人研究成果，探讨这种显微结构的形成机制、关键控制因素和动力学过程，解析其所指示的构造物理条件以及能否作为超高压变质作用的可靠识别标志。

中文关键词： 超高压变质作用；单斜辉石；石英出溶体；电子背散射衍射；拓扑结构

英文摘要： In recent years an increasing number of ultrahigh pressure (UHP) metamorphic localities have been described where clinopyroxene contains oriented needles or rods of quartz, in part coexisting with calcic amphibole, phlogopite or phengite. However, there is still heated debate on its mechanism and dynamic process, expecially on whether it can be used as UHP-indicators. In this project, we plan to combine qualitative research and quantitative study on such microstructure in natural rocks, to reveal the detailed microstructure, crystallographic orientation and chemistry of quartz rod from clinopyroxene. The main methods and techniques include the electron backscatter diffraction (EBSD), electron probe micro-analyzer (EPMA) and transmission electron microscope (TEM). Then, the representative samples will be selected and prepared for high pressure and high temperature experiments using multianvil apparatus to reveal the P-T condition of the pre-exist super silicpyroxene. In order to understand the pressure implications of silica exsolution from clinopyroxene in UHP metamorphic rocks, experiments will be conducted in the P-T range of 2-12GPa and 600-1200℃ using bulk compositions close to natural eclogites collected from Dabie-Sulu region. Then, we will integrate exsolution microstructure and chemical analyses in natur

英文关键词： ultrahigh pressure metamorphism；clinopyroxene；quartz exsolution；EBSD；topotaxy