激光探针等离子体质谱用于锆石Pb-Pb定年的分析和校正方法的进一步探讨  

Further discussion on analytical methology and calibration strategiesfor Pb-Pb isotope analyses of zircon by LP-ICPMS

作　　者：徐平[1,2] 关鸿[1,2] 孙敏[1,2] 袁超 周新华[1,2] J.Malpas[1,2] 

机构地区：[1]中国科学院地质研究所 [2]香港大学地球科学系

出　　处：《地球化学》1999年第2期136-144,共9页Geochimica

基　　金：香港大学研究和会议资助;香港研究资助局;国家自然科学基金

摘　　要：激光探针等离子体质谱可对锆石进行快速准确的Ｐｂ－Ｐｂ同位素定年。本文进一步探讨了该方法应用中的几个问题。对不同样品采用不同的聚焦方式可以对Ｕ／Ｐｂ分异有一定的控制作用。在一定的条件下，不连续和连续采样模式都可以得到较高精度和准确度的结果。连续采样模式还可以得到同位素计数的深度剖面。不同的测量滞留时间会影响测量结果的精度。２０ｍｓ为适合锆石２０７Ｐｂ／２０８Ｐｂ分析的最佳测量滞留时间。在对测定结果进行校正时，可以采用玻璃标样ＮＩＳＴ６１０和钻石标样两种不同的校正方法。Laser probe-inductively coupled plasma mass spectrometry (LP-ICPMS) provides a rapid,precise and accurate technique for Pb-Pb zircon chronology. Different conditions affect massfractionation during laser ablation. Fixed-focus-mode and active-focus-mode, focus-mode anddefocus-mode, time-average mode (single point method) and time-resolved mode (depth pro-filing method), are compared. Both time-average mode and time-resolved mode can give rel-atively high precise, accurate results, and depth profile can only be obtained by time-resolvedmode. Comparing the results of time-resolved mode using different dwell time, it is found that20 ms is the best dwell time with highest precision and accuracy. It is shown that both NIST610and Zircon Standard give satisfactory calibration results for zircon 207Pb/206Pb isotopic age.Therefore, time resolved mode with dwell time of 20 ms is preferred for zircon analysis.

关 键 词：激光探针 等离子体质谱 锆石 地质年代学 铅-铅 

分 类 号：P578.941[天文地球—矿物学] P597[天文地球—地质学]