Structural Features of Yeba Tectonite Group in Jiama (Gyama)-Qulong Area of Tibet
详细信息
- 责任者：Zhong Kanghui (Chengdu University of technology ; Chengdu 610059 ; China) ; Yao Dan
- 刊名：Acta Geoscientica Sinica
- 出版年：2013
- 卷期：34(1)
- 关键词：构造变形 ; tectonic deformation ; 西藏 ; Tibet
- 页码：p.75-86
- 图表：illus., 3 tables, 17 refs.
- 分类号：0300
- issnNo：ISSN1006-3021
- isbnNo：CN11-3474/P
摘要
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.
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