流体包裹体的氧逸度计算公式及其应用

FORMULAE FOR CALCULATING OXYGEN FUGACITIES OF FLUID INCLUSIONS AND THEIR APPLICATIONS

目前，某些研究者推出几种流体包裹体的氧逸度计算公式和相应的图表。由于这些图表精确度较低，在详细的研究和对比时不能应用。此外，对于导出的这些分步计算公式，因不能直接计算也造成了实际应用的不便。我们根据流体包裹体中含O2组分参加的化学反应，利用热力学原理，推导出只含T、p和x三种参数而直接计算氧逸度的公式。由化学分析包裹体中各组分的摩尔分数，再由其他方法获得包裹体形成温度和压力，代入公式可直接计算出形成条件时的氧逸度值，这比用图表要精确很多，比其他分步计算方法也方便得多。

At present several formulae for calculating oxygen fugacities on the basis of fluid inclusion da-ta and corresponding diagrams and tables have been proposed by some researchers. Because thesediagrams and tables are low in precision and accuracy, they could not be used for detailed study andcomparison. Moreover, the formulae derived are used in step-by-step calculations and there are nostraight forward formulae available, which would bring about much inconvenience in practice.On the basis of the chemical reaction with O2 involved and the thermodynamic principle, wehave derived the specific formulae for calculating oxygen fugacities with only three parameters, i.e., T, p and x.By substituting the mole fraction of each component in fluid inclusions and the formation tem-perature and pressure of the inclusions by chemical analysis and other approaches respectively intothe formulae, the oxygen fugacities of fluid inclusions can be directly calculated. The results ob-tained in this way are more accurate than those obtairied by diagrams. The approach is more conve-nient than other step-by-step calculating methods.