| 西藏甲玛—驱龙地区叶巴岩组构造学特征 |
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| 关键词:Jiama(Gyama)-Qulong area in Tibet Yeba tectonite group deformation kinematics dynamics |
| 基金项目:国家973项目(编号: 2011CB403103);地质调查项目(编号: 1212011221073; 1212011086057);“十一五”国家科技支撑计划项目(编号: 2006BAB01A04-4; 2006BAB01-05～06) |
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| Structural Features of Yeba Tectonite Group in Jiama(Gyama)-Qulong Area of Tibet |
| Based on field geological survey and oriented thin section observation, the authors studied deformation, kinematics and dynamics of the Yeba tectonite group, and reached the following conclusions: ① the previously named “Yeba group” is actually a tectonite group and should be called “Yeba tectonite group”, which consists of four lithologic sections and can be divided into two volcano-sedimentary cycles; ② macroscopically, from north to south, Yeba tectonite group shows an inclined anticlinorium and an inclined synclinorium whose axis trends northward; ③ Yeba tectonite group experienced two-stages of ductile deformation and multi-stage brittle-ductile deformation, and the C lithologic section experienced three-stages of foliation replacement and one stage of kink deformation at the superficial level, lying near the main napping plane of Jiama(Gyama)-Kajunguo thrust - gliding nappe tectonic system; ④ in Yeba tectonite group, kinematic direction of two-stages of ductile deformation is on the opposite: in the first stage, the upper layer shearing was from south to the north; in the second stage, the upper layer shearing was from north to south. The second ductile deformation and later multi-stage ductile-brittle deformation had multi-stage progressive deformation characteristics, and after southward nappe-fold lifting to the superficial level, Yeba tectonite group also experienced multi-stage brittle-ductile deformation, especially at the position near the main napping plane of Jiama(Gyama)-Kajunguo thrust-gliding nappe tectonic system; ⑤ the first stage ductile deformation of Yeba tectonite group occurred around 94~85 Ma, belonging to Late Cretaceous Turonian-Coniacian period and related to back-arc rift stretching that resulted from northward subduction of the Brahmaputra oceanic crust; the second stage ductile deformation and the later main brittle-ductile deformation occurred around 50 Ma in Eocene, related to Indo-Asia collision, and the post collision tectonism resulted in the superposition of multi-stage brittle-ductile deformation. |
| ZHONG Kang-hui,YAO Dan,Dorji,ZHENG Fan-shi,XU Chang-hao,HUANG Xiao-yu,LU Biao,LEI Bo,LIN Ji-qing,BAO Chun-hui,YAN Guo-qiang.2013.Structural Features of Yeba Tectonite Group in Jiama(Gyama)-Qulong Area of Tibet[J].Acta Geoscientica Sinica,34(1):75-86. |
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