北京密云放马峪基性岩墙群LA-MC-ICP-MS锆石U-Pb年龄及其意义

Constraint from LA-MC-ICP-MS zircon U-Pb dating of mafic dyke swarms in Miyun County of Beijing and its geological implications

摘要: 太古宙基性岩墙群在北京密云地区广泛分布，其年代学研究一直备受关注，多年来取得了一些数据，但对太古宙变质片麻岩控制作用未做论述。利用LA-MC-ICP-MS U-Pb同位素测定技术，测得放马峪石榴辉石岩中锆石的年龄为2497±15Ma，此年龄被解释为区内变质片麻岩成岩年龄应早于基性岩墙群成岩年龄，其为研究区内太古宙片麻岩成岩年龄提供了重要的参考数据。

Abstract: Archaean ultrabasic dyke swarms in Miyun District of Beijing are widely distributed and chronological researches on these swarms have attracted much attention and obtained many data. Nevertheless, the control of Archean metamorphic gneiss has been rarely discussed. In this study, U-Pb LA-MC-ICP-MS technology was used to obtain the age of 2497±15Ma. This shows that the diagenetic age of the metamorphic gneiss should be earlier than that of the mafic dyke swarms. The result obtained by the authors provides important reference data for the formation age of Archean gneiss in the study area.