连续测定方解石和白云石中碳、氧同位素比值的方法及其意义

本文提出了利用方解石和白云石二者的不同活性,在不同的温度条件下,在同一份碳酸盐岩样品中,连续测定碳、氧同位素比值的新方法。测定结果精度高,能用于判定白云石的成因,具有实用价值。

The Successive Determination of Carbon and Oxygen Isotopes in Calcite and Dolomite: Its Method and Significance

The phosphoric acid method estahlished by J. M. McCrea in 1950 is generally used to determine the carbon and oxygen isotopic ratios in carbonate minerals. Nevertheless, that method requires the experimenter to select highly pure individual minerals.The method suggested by the authors is based on J.M. McCrea's technique. Using the different activities of calcite and dolomite at d iffereat temperatures and under different reaction conditions, one can collect CO_2 gas step by step from the same sample containing both of the two minerals and then determine carbon and oxygen isotopic ratios separately. Through the experiment on method conditions and the determining of natural carbonate samples, it is thought that the determination is highly precise and can be used to judge the origin of dolomite. The method is of practical significance. Furthermore, the method has the advantage of determining carbon and oxygen isotopic ratios of the two minerals simultaneously and separately, and rendering it unnecessary to choose and separate individual minerals. The method is easy to use with low production cost and can spare a lot of time and energy.