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中缅边界那邦变质基性岩出露于东缅著名的 Mogok带的东缘。那邦基性麻粒岩经历了早期麻粒岩相、晚期角闪岩相的两期变质作用的改造。早期变质作用的矿物石榴石和单斜辉石的 40 Ar/ 39Ar激光微区等时线年龄是 74.44± 1.44 Ma;石榴石和单斜辉石的 40 Ar/ 39Ar年龄谱图和等时线年龄均显示两组年龄 :74～ 76 Ma和 2 3～ 2 4Ma。晚期变质作用矿物角闪石的K- Ar法得出 2 3Ma,角闪石和斜长石的 40 Ar/ 39Ar年龄谱图和等时线年龄均显示 2 3～ 2 4Ma的变质年龄。综合这些结果 ,可以确定那邦基性麻粒岩的早期麻粒岩相变质作用的年龄是 74～ 77Ma,可能与新特提斯洋壳俯冲事件有关 ;晚期角闪岩相变质作用的年龄是 2 3～ 2 4Ma,与区内喜山期以来陆内块体响应两大陆会聚作用发生的大型走滑事件有关。那邦基性麻粒岩是世界上最年轻的麻粒岩相岩石之一 ,而且 ,两期变质作用年龄的确定对揭示区内与变质作用相关的地质事件具有重要意义。
The metamorphic basement rocks on the Sino-Burmese border exposed the eastern margin of the famous Mogok belt in Eastern Burma. The Bunchi sexual granulite underwent two phases metamorphism of early granulite facies and late amphibolite facies. The 40 Ar / 39Ar laser micro-area isochron age of the early metamorphic mineral garnets and clinopyroxenes is 74.44 ± 1.44 Ma. The 40Ar / 39Ar ages and isochron ages of garnet and clinopyroxene are shown Two groups of age: 74 ~ 76 Ma and 23 ~ 24Ma. The K-Ar method of amphibole in the late metamorphism gave 2 3Ma. The 40 Ar / 39Ar ages and the isochron ages of amphiboles and plagioclase all showed metamorphic age of 23 ~ 24 Ma. Based on these results, we can confirm that the age of the early granulite facies metamorphism of the Bonyitic granulites is 74 ~ 77Ma, which may be related to the subduction of the Neos Tethyan oceanic crust. The age of late amphibolite facies metamorphism 2 3 ~ 2 4Ma, which is related to the large-scale strike-slip event in which the intracontinental block responses to the convergence of the two continents since the Himalayan period in the area. Nabukitic granulite is one of the youngest granulite facies rocks in the world. Moreover, determining the age of two metamorphism plays an important role in revealing the geological events related to metamorphism in the area.