锆石U-Pb年龄不一致原因浅析

Preliminary Analysis of Discordant Reason of Zircon U-Pb Dating

单颗粒锆石U -Pb法是当前最重要的一种同位素定年方法 ,但由于放射成因铅的不同程度丢失而导致获得不一致的年龄数据。本文讨论了导致年龄数据不一致主要因素是由蜕晶化作用、重结晶作用、扩散作用和增生作用过程中产生的放射成因铅丢失 ,并提出为了获得具有明确地质意义的年龄数据 ,必须采用各种手段尽可能选择新鲜、结晶完好、成因单一的锆石作为测试对象。在定年方法中 ,应首选能进行微区分析的离子探针质谱法和激光探针—等离子质谱法。

At present,single grain zircon U-Pb dating is the most important isotopic dating method in the world.But the partial pb-lose in Zircon lead to discordant age-data.The major reason which makes the inconsistency of age-data is the partial Pb-lose during the course of metamictization,recrystallization proliferation and multiplication.For obtaining definite geological age-data,it is necessary to choose as possible as unweathered,well-crystallized and single genesis zircon.In isotopic dating methods,the ion probe MS or laser probe ICP-MS should first of all selected,becouse they can satisfactorily perform micro-yegion al analysis.