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  

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

作　　者：涂继耀[1,2] 季建清 钟大赉[3] 孙东霞[4] 周晶 TU Jiyao;JI Jianqing;ZHONG Dalai;SUN Dongxia;ZHOU Jing(Laboratory of Orogenic Belts and Crustal Evolution,School of Earth and Space Sciences,Peking University,Beijing 100871,China;Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China)

机构地区：[1]北京大学地球与空间科学学院造山带与地壳演化教育部重点实验室,北京100871 [2]中国地震局地球物理研究所,北京100081 [3]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029 [4]中国地质科学院地质力学研究所,北京100081

出　　处：《地质力学学报》2021年第4期679-690,共12页Journal of Geomechanics

基　　金：国家自然科学基金项目(41603055);中国地震局地球物理研究所基本科研业务费专项(DQJB20X10)。

摘　　要：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^(40)Ar/^(39)Ar、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~3.45±0.24 Ma,磷灰石裂变径迹年龄范围为3.7±0.4 Ma~1.8±0.2 Ma。年龄数据及其模拟计算结果表明,约3 Ma以前那木拉断裂带南侧地壳隆升最快,隆升速率约2.5 km/Ma,断裂带以正断层运动特征为主;约3 Ma以来那木拉断裂带北侧地壳隆升最快,约为1.3 km/Ma,断裂带以逆断层运动特征为主。那木拉断裂带运动特征变化可能与约8 Ma以来东喜马拉雅构造结快速地壳隆升剥露区域由南向北逐渐迁移有关。To reveal the strong activities of the Namula fault zone in the eastern Himalayan syntaxis since Pliocene,this paper reports biotite^(40)Ar/^(39)Ar 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^(40)Ar/^(39)Ar 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.

关 键 词：那木拉断裂带 东喜马拉雅构造结 黑云母^(40)Ar/^(39)Ar 磷灰石裂变径迹 

分 类 号：P546[天文地球—构造地质学]