榴辉岩中石英出溶体的拉曼光谱学研究及其构造意义

Raman Spectrum Study on Quartz Exsolution in Omphacite from Eclogite and Its Tectonic Significances

利用拉曼光谱学和费氏台方法对若干地区超高压榴辉岩中柯石英和榴辉岩中石英出溶体的超显微构造特征进行了研究 .研究结果表明 ,石榴石 (或绿辉石 )中柯石英向石英相变是一个连续变化过程 .绿辉石中石英出溶体和主晶具有一定的晶体学拓扑关系 ,即石英出溶体长轴有两个展布方向 :平行于绿辉石 ( 10 0 )裂理面和平行于绿辉石 ( - 10 1)面 .目前 ,部分学者推断榴辉岩绿辉石中石英出溶体可作为超高压变质作用的标志 .笔者认为 ,棒状定向石英在绿辉石中出溶的温压条件和出溶机理尚未查明 .因此 ,需加强过量二氧化硅单斜辉石出溶机理的超高压实验研究 ,从而为证实石英出溶体作为超高压标志提供实验定量约束 .

The studies on ultra-microstructure characteristic of quartz exsolution in eclogite and coesite in UHP eclogite of several localities are done with the appliance of laser Raman spectroscopy and U-stage. Research results show that the phase transformation of coesite-quartz in garnet and/or omphacite is a continuous process. Topological relationships are present between quartz exsolution in omphacite and its host mineral which shows orientations of two long axes of quartz exsolution parallel to (100) and (-101) of omphacite. At present, some of scholars suggest that the quartz exsolution in omphacite of eclogite is the evidence of UHP metamorphism. However, temperature and pressure condition and the exsolution mechanism of oriented needlelike quartz in omphacite still remain unclear. Therefore further study should be enhanced on experimental study on exsolution mechanism of super-silicate clinopyroxene, which could provide experimental quantitative constraint on quartz exsolution as UHP indicator.