电子探针化学测年技术及其在地学中的应用

CHEMICAL DATING TECHNIQUE ON THE ELECTRON PROBE MICRO ANALYSES AND ITS APPLICATION TO EARTH SCIENCE

主要对电子探针化学测年技术的基本原理及其相关技术作一介绍。并以其在地学中的具体应用 ,如对独居石、锆石的化学测年 ,证明它是一种分析快速、测试容易的技术 ,与传统的同位素法测得的年龄具可比性。此项技术对矿石的来源、不同矿物的不同环带、不同世代的成分演化乃至时间演化均可进行分析 ,并可使年龄数据点与成分数据严格对应 ,而且测试所需的样品量少 ,可进行单颗粒的测定。因此 ,当某些岩体的被测矿物有捕虏体成因、岩浆成因、地幔成因等各种来源时 ,可分别求出某单一事件的年龄。另外 ,利用碎屑独居石的 w( Pb O) /w( Th O*2 )比值来确定碎屑岩的源岩是一种新的方法 。

This paper mainly introduces the basic theory, age calculation and application of chemical dating technique using Electron Probe Micro Analyses (EPMA) and so on. Many concrete examples of its application to earth science, for instance, the chemical dating of monazite and zircon analysis on EPMA have proved it's a kind of fast, easy analyzing technique. The age data can be comparable with those of the isotope dating technique. However, it can respectively analyze the source of minerals, the different zones of various minerals, the component and time evolving of their different secula. And the age data strictly correspond with the points of the component. It needs a small amount of sample and can analyze the single grain. Hence, for the minerals to be analyzed in some rocks, when there are all sorts of genesis with xenolith, magma, mantle and so on in them,the age of a certain single event can be respectively got.The ratio of w (PbO)/ w (ThO * 2) of detrital monazite is a new measure for the provenance analysis of clastic rocks. All these above suggest it's a kind of age dating technique with many developing prospects. At the same time, the authors also point out its limitation.