同位素地质年龄测定技术及应用  

Isotope Geochronology: Technique and Application

作　　者：陈文[1] 万渝生[2] 李华芹 张宗清[1] 戴橦谟[4] 施泽恩[4] 孙敬博[1] 

机构地区：[1]同位素热年代学实验室大陆构造与动力学国家重点实验室中国地质科学院地质研究所,北京100037 [2]北京离子探针中心中国地质科学院地质研究所,北京100037 [3]武汉地质矿产研究所,武汉430205 [4]中国科学院广州地球化学研究所,广州510640

出　　处：《地质学报》2011年第11期1917-1947,共31页Acta Geologica Sinica

基　　金：国家重点基础研究发展计划项目(编号2007CB411306;2009CB421001);中国地质调查局项目(编号1212010660212;1212011120293);公益性行业专项经费(编号200911043-13)资助成果

摘　　要：同位素地质年代学是地球科学、物理学、化学和技术科学相互交叉发展起来的一门新兴学科,是地球系统科学中一个年轻而充满活力的分支学科。它根据放射性同位素衰变规律确定地质体形成和地质事件发生的时代,以研究地球和行星物质的形成历史和演化规律。本文对几种常用的精度比较高的同位素测年方法从理论、实验技术、应用范围、使用的注意事项等方面予以简要总结和介绍,期望为地质同行们提供有益的参考。所涉及的同位素测年方法主要有U-Pb法、Ar-Ar法、Rb-Sr法、Sm-Nd法、Re-Os法、(U-Th)/He法等。①U-Pb法:是最早用来测定地质年龄的放射性方法之一,也是国内目前最重要的同位素测年方法。近10年来,近乎完美的锆石微区U-Pb年龄测定技术的引进对我国的地质科学研究起到了巨大的推动作用,并且其应用领域仍在进一步扩展中。②Ar-Ar法:已经成为同位素地质年代学研究最主要的方法之一。该方法具有以下特点:a.测量的时间域较宽,最老可到3800 Ma(月岩年龄),最年轻可测到千年级(意大利维苏威火山喷发年龄);b.测量对象广泛,原则上,所有的含钾矿物、岩石都可以用作Ar-Ar法同位素测年,甚至含有微量钾盐包裹体的非钾矿物如石英、闪锌矿等也有成功测定出Ar-Ar年龄的报道;c.独特的分步加热技术和内部组分的Ar同位素相关图处理技术不仅可以获得高精度的年龄,还可以揭示被测定对象所经历的多期地质演化信息;d.和激光技术配套可以直接在岩石光片上寻找待测矿物进行微区(几十微米—几百微米)Ar-Ar测年,从而能够获得变质岩P-T-t轨迹研究中最精确的时间信息;e.应用领域广泛,几乎所有的地质学分支学科中都有应用;f.是矿床年代学研究的最主要的技术手段;g.是同位素热年代学研究的支柱技术。Ar-Ar法测年也有其局限性:首先是分析技术复杂导致其�Isotope geochronology is a newly developed interdisciplinary science which combines geoscience,physics,chemistry and technical sciences,and is a young and energetic branch of earth science.The decay of radioactive isotopes is used to determine the formation age of geological body and the age of geological events,with aiming to study the formation history and evolution of earth and planetary materials.This paper presents brief introduction and summary of relative high-precise isotope dating methods in terms of theory,experiment techniques,application scope,precautions for use,in hope of providing a useful reference to geologist.Main isotope dating methods involved s are U-Pb,Ar-Ar,Rb-Sr,Sm-Nd,Re-Os and（U-Th）/He methods.（1）U-Pb method： It is one of the earliest radioactive methods for determination of geological age as well as the most important isotope dating method in China so far.In the past 10 years,the introduction of zircon U-Pb dating technique has played a significant role in promoting geological research in China,and its application is expanding.（2）Ar-Ar method： Ar-Ar dating has become one of the most important methods of isotope geochronology.The characteristics of this method are as follows： ① Wide time-domain measurements,with the oldest age up to 3.8Ga（the age of lunar rocks） and the youngest one in a scale of millennium age（the eruption age of Mount Vesuvius,Italy）;② A wide range of measurement objects.In principle,all the k-bearing minerals and rocks can be used for Ar-Ar isotopic dating,even there are reports on the successful determination of Ar-Ar ages from non-potassium minerals such as quartz and sphalerite which contain trace amounts of kainitite inclusions;③ Unique step heating technique and Ar isotope correlation diagram of internal components can not only obtain high-precision age but unfold multi-stage geological evolution of the object;④ Combined with laser technique,it can be used to determine Ar-Ar age by searching microzonation directly on polished sect

关 键 词：同位素地质年代学 分析测试技术 地质应用 U-PB法 AR-AR法 Rb-Sr法 Sm-Nd法 Re-Os法 (U-Th)/He法 

分 类 号：P597.3[天文地球—地球化学]