LA-ICP-MS测定锡石U-Pb同位素年龄时两种普通铅扣除方法的原理及适用性比较

The comparison of the principle and applicability between two methods of deducting the initial common lead for in situ LA-ICP-MS U-Pb isotope dating of cassiterite

摘要: 根据近年来激光烧蚀电感耦合等离子体质谱仪锡石微区原位U-Pb同位素定年的实验结果, 结合相关资料, 对实验过程中普通铅扣除的2种主要方法, 即谐和图法和等时线法的原理、效果、优点和局限性进行了深入的比较。研究成果表明, 2种主要方法各有不同的优点及局限性。在实际工作中, 要想获得比较准确的测试结果, 需要根据具体矿物样品的年龄范围、总的U和Pb含量、普通铅相对含量、测年精度要求等因素, 灵活地选择普通铅扣除的方法。

Abstract: For the purpose of deducting the initial common lead of in situ LA-ICP-MS U-Pb isotope dating of cassiterite, this pa-per has discussed the theory, effect, advantages and limitations of concordia and isochron methods and the basic principles for selecting a suitable method in experiment based mainly on the authors' studies, combined with recently reported related references. The results show that the two methods have different advantages and limitations in deducting the initial common lead of in situ LA-ICP-MS UPb isotope dating of cassiterite. In practical work, it is very important to choose an appropriate method according to the age range of cassiterite, total U, Pb content, common lead relative content and dating accuracy requirement of the samples.