使用目前常用的两种红外吸收系数,对超高压榴辉岩中绿辉石的结构水含量分别进行了计算;结合最近的一些文献数据,对两种计算结果进行了对比分析;定量比较了两种方法的优劣,表明使用Bell等(AM,1995,80:465—474)的吸收系数会使得计算结果明显偏高(一倍左右),这会对理解水对地球内部物性和动力学的影响带来较大的不确定性。本文计算表明,使用Libowitzky和Rossman(AM,1997,82:1111-1115)的方法计算绿辉石中的水可能更加准确,相应的红外摩尔吸收系数应该为(13.43±0.12)ppm^-1·cm^2,即(7.47±0.0647)×10^4L/mol H2O·cm^-2。
Based on the two most widely used IR calibration coefficients and reported SIMS data for omphacitic clinopyroxene, a new molar absorption coefficient [13.43 ± 0.12 ppm^-1· cm^-2 or (7.47 ± 0.0647) × 10^4L/mol H2O·cm^2] is presented and the relationship between the determined results obtained by the IR and SIMS methods is quantitatively evaluated. The calibration coefficient was obtained by unpolarized IR spectra, but can be applied to polarized measurement, and also a statistically relevant mean unpolarized spectrum obtained from different omphacite grains in the same sample by the introduction of an orientation factor of 1/3.