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地质论评  2003 

副矿物的电子探针化学定年方法原理及应用

Keywords: 矿物电子探针化学定年方法铀铅钍放射性锆石同位素

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Abstract:

化学定年方法是利用电子探针分析副矿物中的U、Th、Pb含量而进行定年的一种新方法。基本原理是,假设可以忽赂矿物韧始铅,封闭体系中矿物的总铅含量代表U―Th衰变形成的放射性成因铅含量,即:Pb总=^238U(e^λ238r-1)^235U(e^λ235r―1)^232Th(e^λ232r―1),该方法可利用的副矿物包括:锆石、独居石、褐帘石、碘纪矿、铀石、钍石、晶质铀矿等。本文以华南西华山岩体漂塘花岗岩中的锆石为例,对该方法进行了尝试性的研究。分析结果计算表明,两颗锆石的平均年龄分别为143.9Ma和143Ma,与前人通过同位素方法获得的年龄基本相符。结果还显示,锆石颗粒从中心到边缘的年龄呈现从老到新的趋势。

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