摘要
本文论证了各类变质岩的全岩 Rb-Sr 等时线所反映的岩石初始或叠加变质变形年龄。角闪岩相的锆石 U-Pb 一致线和 Sm-Nd 等时线则因原岩(火成或沉积成因)的差别分别反映生成年龄或变质变形年龄,实际是受原生水控制。Sm-Nd 等时线年龄偏低,还与低温动力变质中水的加入有关。由于本区2450Ma 的数据出现频率很高,反映了太古宙与元古宙间的主要地质事件,结合双山子群、朱丈子群中发育可供洲际对比的绿岩带,故二者统归太古宙新太古代晚期(2450—2650Ma)。
In isotopic dating this paper emphasizes the role of fluids in isotopic rehomo-genization during metamorphism.Sedimentary metamorphic rocks are abundant inconnate water and the dating of clastic zircon yields,in most cases,the age ofmetamorphism and deformation.In some cases the Sm-Nd isochron ages of igneousrocks are also relatively low.All this may be related to the incorporation of mixedwater during low-temperature diaphthoresis.It is concluded,based on the availableU-Pb ages,Rb-Sr isochron ages and Sm-Nd ages(including the whole-rock isochronand mortal ages)in conjunction of the geochronology data of global greenstones,thatthe Shuangshaazi and Zhuzhangzi groups should be Late Neoarchaean in age,rangingfrom 2450 to 2650 Ma.
出处
《地球化学》
CAS
CSCD
北大核心
1993年第4期373-378,共6页
Geochimica
关键词
变质岩
同位素年龄
双山子群
地层
Shuaugshanzi Group
Zhuzhangzi Group
age determination
Late
