东构造结那木拉断裂带上新世以来强烈活动的年代学证据

为揭示东喜马拉雅构造结那木拉断裂带上新世以来强烈活动特征,对采集自那木拉断裂带的三件基岩样品进行黑云母40Ar/39Ar、 磷灰石裂变径迹两种热年代学方法测年;并利用"Pecube"软件对测得年龄数据及断裂带两侧已发表年龄数据进行定量模拟计算.测试结果显示黑云母40 Ar/39 Ar年龄范围为4.44±0.71 Ma～...

The strong activities of the Namula fault zone in the eastern Himalayan syntaxis since Pliocene, constraints from thermochronological data

To reveal the strong activities of the Namula fault zone in the eastern Himalayan syntaxis since Pliocene, this paper reports biotite ⁴⁰Ar/³⁹Ar and apatite fission track ages of 3 rock samples from the Namula fault zone, and quantitatively interpret these ages and the published ages from the adjacent areas, using a modeling code "Pecube". Biotite ⁴⁰Ar/³⁹Ar ages range from 4.44±0.71 Ma to 3.45±0.24 Ma, and apatite fission track ages range from 3.7±0.4 Ma to 1.8±0.2 Ma. The ages and simulation results show that, prior to ~3 Ma the highest exhumation rate had been located in the south of the Namula fault zone and was about 2.5 km/Ma, and the Namula fault zone had a motion feature of normal fault; Since ~3 Ma the highest exhumation rate have been located in the north of the Namula fault zone and was about 1.3 km/Ma, and the Namula fault zone had a motion feature of thrust fault. The evolution of the Namula fault zone''s motion, probably have resulted from the south to north migration of the fast crust exhumation area in the eastern Himalayan syntaxis since ~8 Ma.