流体包裹体Rb-Sr等时线定年的可靠性  

Comment on the reliability of Rb Sr isochrone dating by using fluid inclusion in minerals

作　　者：姚海涛[1] 郑海飞[1] 

机构地区：[1]北京大学地质学系,北京100871

出　　处：《地球化学》2001年第6期507-511,共5页Geochimica

基　　金：国家自然科学基金重点资助项目(40032010)

摘　　要：通过对Rb-Sr等时线原理应用的必要条件及流体包裹体样品的成因特点的分析,认为是否可以用流体包裹体Rb-Sr定年在理论上尚需解决以下问题:(1)因矿物中常有不同期次、不同成因的流体包裹体存在,必须保证所选择的各流体包裹体样品具有相同的初始Sr同位素比值;(2)流体包裹体中Rb与Sr的分异机理以及分异程度问题,即流体中Rb与Sr之间是否存在分异和分异程度是否可以达到Sr同位素分析的精度要求。已有的流体包裹体的Rb-Sr等时线年龄研究资料和数据的分析检验结果普遍存在以下问题:等时线图上数据点分散;拟合年龄较老;等时线拟合品质参数MSWD偏大,可靠性低。It is shown that most of the isochrone dating by fluid inclusions in minerals have the same problems, such as the data points dispersing, the higher value of MSWD and the elder age which could be a mixing age. Based on the principle of isochrone dating and the forming characteristics of magma rock and fluid inclusion, the following problems should be solved for the method: (1) it mustbe sure that all the samples have same initial Sr composition, and (2) the differentiation and its mechanism between Rb and Sr, that is, whether the differenceof 87Rb/86Sr ratio is comparable to the error of 87Sr/86Sr ratio.

关 键 词：流体包裹体 Rb-Sr等时线定年 可靠性 铷同位素 锶同位素 分异机理 

分 类 号：P597[天文地球—地球化学]