使用SHRIMP测定锆石铀-铅年龄的选点技巧  

Techniques for Choosing Target Points during SHRIMP Dating of Zircon U-Pb Ages

作　　者：刘建辉[1] 刘敦一[1] 张玉海[1] 杨之青[1] 

机构地区：[1]中国地质科学院地质研究所,北京离子探针中心,北京100037

出　　处：《岩矿测试》2011年第3期265-268,共4页Rock and Mineral Analysis

基　　金：中国地质科学院地质所基本科研业务费资助(J1006)

摘　　要：应用离子探针SHRIMP测定锆石铀-铅年龄时,锆石选点至关重要,它将直接影响实验结果的可靠性和准确性。透射光、反射光图像及阴极发光图像是锆石选点的重要依据,透射光和反射光图像反映了锆石表面及内部裂隙、包体的发育程度;阴极发光图像可以提供锆石成因类型及相应岩体经历的演化历史等信息。文章归纳了单一成因锆石、核边类型锆石、单一成因的年轻锆石选点的技巧,包括:在测定锆石铀-铅年龄之前,根据透反射光图像及阴极发光图像,研究锆石的显微结构,初步判断锆石的成因;在进行锆石测年选点过程中,根据阴极发光图像确定需要分析的锆石及分析位置,选择其中比较干净的位置进行测试,避开裂纹或包裹体等杂质,确定最佳的分析位置;在测定具有单一成因、铀含量很低的年轻锆石时,选择在阴极发光较暗的位置进行测试,有利于得到误差小、精度更高的数据年龄。When dating Zircon U-Pb ages by SHRIMP,choosing the target points of zircon is very important as they directly affects the reliability and accuracy of the results.Some preliminary work needs to be conducted,including taking photographs of reflected and transmitted light,and performing cathodoluminescence.Images of the first two reflect the development of fractures and inclusions.The cathodoluminescence images provide information on genesis and evolution histories of the host rocks.The techniques of choosing target points were summarized for single genesis zircon,core-mantle type zircon and young age single genesis zircon.The photographs of reflected and transmitted light and cathodoluminescence images were used to study the micro-struction and the genesis of zircon before U-Pb dating.When choosing the target points of zircon,the cathodoluminescence images are used to choose the approximate points with clean surface,no fractures and inclusions.The darker area was chosen for single genesis and low U content zircon with young age from cathodoluminescence images in order to obtain smaller error and higher precision dating data.

关 键 词：离子探针 锆石 铀-铅年龄 阴极发光 选点技巧 

分 类 号：P597.3[天文地球—地球化学]