摘要
名义上无水矿物(NAMs)的结构水研究是认识超高压变质作用(UHPM)过程中流体活动规律的重要手段,并对板块汇聚边缘大陆动力学及水的深部地球循环有重要意义。本文采用傅立叶变换红外光谱(非偏振光)研究了中国大陆科学钻探(CCSD)主孔岩心及其周围地表榴辉岩中副矿物—金红石中的结构水。所有测试样品都在3285 cm^(-1)和3295 cm^(-1)附近产生尖锐的吸收峰,证实“水”以结构羟基(OH^-)的形式赋存于金红石晶格之中。采用最新标定的摩尔吸收系数[38000 L/(mol·cm^2)]计算表明,金红石结构水含量在324×10^(-6)~523×10^(-6)范围内,远较前人有关金红石结构水含量的计算结果为低。同时,结构水分布不均一性在不同样品之间和颗粒内部都有明显表现,指示超高压变质过程中有限的流体活动和快速的板块俯冲—折返过程。
The research of structural water in nominally anhydrous minerals (NAMs) is significant for understand of the fluid flow activity in ultra-high pressure metamorphism, the geodynamics in convergent continental margins and the water recycling in mantle. This study focus on the structural hydroxyl concentrations of rutile in eclogites from main-hole of the Chinese Continental Scientific Drilling project (CCSD) and its areas nearby emp light. The rutile grains all exhib oying microscope Fourier infrared spectroscopy(FTIR) with unpolarized t a single sharp band at near 3285 cm^-1 or 3295 cm^-1, which is the structural hydroxyl (OH^- ) absorption band, indicating water is structurally incorporated in rutiles. Calculating with the molar absorption coefficient [38000 L/(mol. cm^2)] of Maldener et al. (2001) shows that the "water" contents in rutiles are 324 to 523 × 10^- 6, which is greatly lower than the previous researcher's result calculated with the molar absorption coefficient[3270 L/(mol · cm^2)]of Hammer et al. , (1991). Theinhomogenous distribution of OH^- in rutile is shown not only in different samples but also in the different micro-areas in the same grain, indicating that the fluid flow activity in ultra-high pressure metamorphism is limited and slabe subduction and exhumation are quick.
出处
《地质论评》
CAS
CSCD
北大核心
2007年第2期267-272,共6页
Geological Review
基金
国家自然科学基金重大项目(编号40399142)
中国科学院同位素年代学和地球化学实验室合作基金项目(编号GIGIso-0504)
国家重大基础研究973项目(编号2003C13716501)的成果