花岗岩锆石U-Pb年龄与全岩Rb-Sr等时线年龄对比研究及其地球化学意义  

Comparison between the Zircon U-Pb Ages and the Whole-Rock Rb-Sr Ages of Granite Plutons and Its Geochemical Implication

作　　者：吴俊奇[1] 章邦桐[1] 凌洪飞[1] 陈培荣[1] 

机构地区：[1]南京大学内生金属矿床成矿机制研究国家重点实验室及地球科学系,南京210093

出　　处：《高校地质学报》2007年第2期272-281,共10页Geological Journal of China Universities

基　　金：国家自然科学基金资助项目(批准号40372036;40221301)

摘　　要：对国内外32个花岗岩体的锆石U-Pb年龄与全岩Rb-Sr等时线年龄之间差值(Δt)进行的频数统计分析表明:Δt呈对称正态分布(偏度系数CSK=0.36;峰度系数CKU=2.99);年龄差(Δt)既呈正值又有负值,其均值为2.08Ma;相对年龄差(Rt)小于5%。采用最小二乘法计算,花岗岩体锆石U-Pb年龄(tZr)对全岩Rb-Sr等时线年龄(tRb)拟合出相关系数很高(r=0.998),回归系数接近l(α=1.003)的线性回归方程(tRb=1.003tZr+1.258)。这些统计特征表明,从总体来看,花岗岩体的Rb-Sr等时线定年测定结果与锆石U-Pb定年测定结果是一致的,花岗岩全岩Rb-Sr等时线定年方法是成熟、可信的,同时也为花岗岩锆石U-Pb年龄代表结晶年龄而不代表花岗岩侵位年龄提供了依据。The frequency analysis of age difference （△t） between the results of zircon U-Pb dating and whole rock Rb-Sr dating for 32 granite plutons shows that the △t displays a symmetrical normal distribution （skewness Csk=0.36; kurtosis Cku=2.99） in the histogram. The △t is both positive and negative, with a mean of 2.08 Ma, and the percentage of age difference is less than 5% （absolute value）. Using least squares regression procedure, a best regression equation with high correlation coefficient （r=0.998） and regression coefficient close to 1 （a=1.003） is fitted to the points of the zircon U-Pb ages and the whole rock Rb-Sr ages for 32 granite plutons. These statistic characteristics indicate that the zircon U-Pb dating ages are corresponding with the whole-rock Rb-Sr isochron ages for granites as a whole. The whole-rock Rb-Sr isochron dating method for granites is mature and reliable, the zircon U-Pb age cannot represent the emplacement ages of granites, but the crystallization age.

关 键 词：花岗岩锆石U-PB年龄 花岗岩全岩Rb-Sr等时线年龄 花岗岩侵位年龄 对称正态分布 线性回归方程 

分 类 号：P588.121[天文地球—岩石学] P597[天文地球—地质学]