摘要
羟基矿物内部存在两种位于不同结构位置上的氧原子硅氧四面体氧和羟基氧，二者之间的Ｏ同位素分馏可能比任何共生矿物对都大，是一种潜在的单矿物同位素地质温度计。单矿物同位素地质温度计较矿物对同位素地质温度计有很多优点。准确测量矿物中羟基的Ｏ同位素组成是建立单矿物同位素地质温度计的关键。本文介绍了一种精确测量白云母、高岭石矿物中羟基的Ｏ同位素组成的新方法火焰加热真空脱水氟化法。δ１８ＯＯＨ的分析精度达到０３‰，羟基氧的提取率达到９９％～１００％。实验证明羟基矿物在高温真空脱水过程中不存在Ｏ同位素动力学分馏，羟基水与石英玻璃之间没有发生Ｏ同位素交换。
The internal oxygen isotope fractionation between silicon oxygen tetrahedra and hydroxyl groups of hydrosilicates may be greater than that between any other coexisting minerals in the same temperature range The temperature dependency of the internal oxygen isotope fractionation is also much greater Such fractionation is considered to be a potential single mineralgeothermometer, which has more advantages than the isotope geothermometer of coexisting minerals The accurate measurement of the oxygen isotope composition of hydroxyl groups is the key of setting up the single mineral geothermometer A new method of accurate analysis of the oxygen isotope composition of hydroxyl groups is reported in this paper Samples were heated by fire flame under vacuum up to 1400℃,and the water extracted from hydroxyl bearing minerals was immediately frozen in a nickel tube with liquid nitrogen Then water samples reacted with BrF 5 to liberate O 2 for isotopic analysis The analytical reproducibility of the δ 18 O OH is in the range of 0 3‰ The yield of water during extraction is in the range from 99% to 100% The experimental results show that there occurs no isotopic dynamic fractionation during dehydroxylation of the examined kaolinite and muscovite,nor oxygen isotope exchange between quartz glasses and water extracted from hydroxyl groups.
基金
国家自然科学基金
关键词
羟基O同位素
白云母矿物
高岭石矿物
oxygen isotope of hydroxyl groups heating by fire flame single mineral thermometers
