摘要
运用电子探针和显微Fourier变换红外光谱技术,对新疆西天山3个榴辉岩样品中的石榴石进行了详细的主量元素和结构水分析。结果显示,石榴石发育以核部富锰铝榴石组分、边部富镁铝榴石组分进变质作用的成分环带。石榴石中OH^(-1)分布也具有规律:核部→边缘,其结构水OH^(-1)逐步增加,即从核部的89～239ppm增加到边部的367～658ppm;与石榴石边部相比,石榴石的核部含有较低的OH^(-1),却含有较高的H_2O和Mn含量。这表明,在蓝片岩向榴辉岩进变质作用过程中,含水矿物脱水反应而释放出大量的分子水,这部分水促进了高压变质反应,形成榴辉岩相矿物,石榴石核部的结晶就是在富水和Mn的条件下进行的。随着高压变质作用的继续,石榴石核部的分子水逐步失水而进入石榴石晶格,形成结构水。因此,在高压变质作用过程中,OH^(-1)演化实际上是一个由内部不平衡逐步向平衡转变过程。
The main elements and hydroxyl within garnets of eclogites from the west Tianshan were examined using electron microprobe and Fourier infrared spectroscopy. As a result, the garnets show zoning composition： that is spessartite in the core and pyrope in the rim. Our data show that the hydroxyl component decrease gradually from rim （about 367 - 658ppm） to core （about 89 - 239ppm）, where contains relative high Mn concentrations. It imply that large amount of aqueous fluids were released by the dehydration reactions during the transition from blueschist to eclogite. The hydrous components participate in the high-pressure metamorphism and formation of eclogitic minerals. The core of garnet crystallized at the rich Mn and water concentration conditions. The part of water at core of garnet is preserved as OH in the garnet with high-pressure metamorphism.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2006年第5期1380-1386,共7页
Acta Petrologica Sinica
基金
国家重点基础研究发展规划项目(2001CB409803)
国家自然科学基金项目(40572028
40421202)
中国科学院"百人计划"资助。
关键词
水
分布
石榴石
榴辉岩
西天山
Water, Distribution, Garnet, Eclogite, The west Tianshan
