中国大陆科学钻探主孔超高压榴辉岩中绿辉石结构水研究

本文利用傅立叶（Fourier）变换红外光谱技术对CCSD主孔100～3100米深度范围榴辉岩中的绿辉石结构水含量进行了原位分析。结果表明，所有绿辉石都舍有一定的以OH形式存在的结构水，其含量范围为45～784ppm，平均为235ppm。不同榴辉岩绿辉石之间的结构水含量差别较大，而且呈现出明显的空间分布不均一性。相关性分析显示，绿辉石的结构水含量与全岩的Mgo、TFeO、Al2O3，含量成正相关，与NaO成反相关，与绿辉石的NaO、TFeO含量成负相关，与榴辉岩的峰期变质条件无关；与其它类型榴辉岩相比，多硅白云母榴辉岩中绿辉石的结构水含量较高，平均为339ppm。由此推测，超高压榴辉岩绿辉石中所残留的结构水含量很可能与其峰期结构水含量、矿物化学成分和岩石矿物组成有关。

Study of hydroxyl content of omphacite in UHP-eclogite from the main hole of Chinese Continental Scientific Drilling Project

The hydroxyl contents of omphacite in eclogite from the depths of 100m to 3100m of the main hole of Chinese Continental Scientific Drilling Project (CCSD) were analyzed in-situ, using the method of Fourier transform infrared spectroscopy ( FTIR). The results indicate that all the omphacite grains contain a trace amount of structural water as hydroxyl with a range from 45ppm to 784ppm, and the average of 235ppm. The water content of omphacite from eclogite samples is different from each other, showing obviously heterogeneity in the space. The correlation analysis demonstrates that the hydroxyl content of omphacite is correlated positively with the MgO, TFeO and Al2 O3 contents, and negatively with the Na2 O content of the whole rock and the Na2 O and TFeO contents of omphacite, but is not related with the peak metamorphic conditions. Omphacite in phengite eclogite contains more hydroxyl with an average of 339ppm as compared with other types of eclogites. It can be inferred that the hydroxyl content now remained in omphacite may be related to its structurally-bound water content at the peak metamorphism, the mineral composition and the mineral assemblage of the eclogite.