【摘要】 从微观尺度研究结构水的分布状态可以为超高压变质岩的形成环境、构造演化动力学过程提供重要的依据.为探讨大别山地区超高压变质岩中"名义上无水矿物"(nominal anhydrous minerals,NAMs)结构水的分布特征、赋存状态与超微结构缺陷的关系,对大别山石马地区榴辉岩中的柯石英进行了傅立叶变换红外光谱(FTIR)分析和第一性原理计算.FTIR研究表明柯石英主要吸收峰为(Ⅰ)3 561~3 580cm-1、(Ⅱ)3 433~3 462cm-1和(Ⅲ)3 412~3 425cm-1;柯石英颗粒结构水含量为15×10-6~52×10-6,平均值是32×10-6.第一性原理理论计算得到了柯石英(4H)Si和(AlH)Si复合缺陷超晶胞模型(2×1×1)的形成能分别是-4.92eV和-3.10eV;含氢缺陷模型计算结果得到3 526cm-1和3 198cm-1的拉曼峰与柯石英的合成实验结果基本符合.FTIR分析表明石马地区柯石英结构水含量具有不均一性;模拟计算得到(4H)Si复合缺陷模型比(AlH)Si有更低的复合缺陷形成能,有更加稳定的结构,柯石英结构水中(OH)4Si氢结合机制是优先模式,为实验研究提供理论依据.更多还原

【Abstract】 The study of the distribution of structural water at microscopic scale can provide important evidences for the formation environment and tectonic evolution dynamics of UHP metamorphic rocks.In order to investigate the distribution characteristics and the relationship between occurrence state and microstructure defects of "nominal anhydrous minerals"(NAMs)structure water in ultrahigh pressure metamorphic rocks from Dabie Mountains,the NAMs such as coesite in eclogites of the Shima area from Dabie Mountains were studied by FTIR analysis and first-principle calculations.FTIR studies show that the main absorption peaks of coesite are(Ⅰ)3 561-3 580 cm-1,(Ⅱ)3 433-3 462 cm-1 and(Ⅲ)3 412-3 425 cm-1 respectively.The structural water content of the coesites in Shima is 15×10-6-52×10-6,with an average of 32×10-6.The vacancy formation energies of the(4 H)Siand(AlH)Sicomplex defect coesite supercells(2×1×1)calculated by the first principle are-4.92 eV and-3.10 eV respectively.The Raman peaks at 3 526 and 3 198 cm-1 in the hydrogen-containing defect models of coesite are consistent with the experimental results.The vacancy defect formation energy of the(4 H)Sicomplex defect model is lower,which is the more stable structure than(AlH)Si.Moreover,the(OH)4Si hydrogen bonding mechanism is a preferential model,which provides the theoretical basis for the experimental research.更多还原