摘要
郯庐断裂带起源于华北克拉通与扬子板块的汇聚过程中已被多数学者所认同。该断裂带的起源机制,涉及到这两个大陆板块的汇聚方式。可是,对于这一重要问题却长期存在着不同的认识。本文依据郯庐断裂带内部及其两侧前陆上构造与年代学研究成果,综合分析该断裂带的起源机制。郯庐断裂带内部残留的起源期构造为左行走滑韧性剪切带,所获得的白云母40Ar/39Ar同位素年龄为239~217 Ma。华北克拉通边缘的徐淮弧形逆冲-推覆构造,及九江地区扬子板块上的弧形褶皱带,分别为苏鲁造山带、大别造山带点碰撞的产物。郯庐断裂带西侧的华北克拉通边缘,在汇聚过程中呈现为刚性陆块的特征,没有出现大规模的牵引弯曲现象。而东侧的扬子板块前陆构造,在汇聚过程中却明显出现了大规模的牵引弯曲现象。断裂带东侧的张八岭隆起北段,出露了扬子板块上中地壳韧性拆离带,其中所获得的白云母40Ar/39Ar同位素年龄为245~218 Ma,其滑动方向受控于郯庐断裂带起源期的左行走滑运动。这一系列构造与年代学信息,表明郯庐断裂带起源于华北克拉通与扬子板块的汇聚过程中,代表了这两个大陆的斜向汇聚边界。该断裂带起源期的活动时限,与大别、苏鲁造山带内大陆深俯冲时间相吻合。在大别造山带北部的华北克拉通,原始应存在着向南的突出体(嵌入体),从而导致嵌入式碰撞与嵌入体边界的大陆斜向汇聚(起源期郯庐断裂带),符合嵌入式碰撞导致板片撕裂模式。
It has been widely accepted that the Tan-Lu fault zone originated during the convergence of the North China Craton and Yangtze Plate.Origination of the fault zone deals with the convergence mode of the two continental plates.However,this important issue remains controversial for a long time.On the basis of structural and geochronological results from the Tan-Lu fault zone and surrounding foreland regions,origination of the fault zone is analyzed comprehensively in this paper.Origination structures remained within the fault zone are sinistral ductile shear zones,and muscovite40Ar/39Ar ages from the shear zones range from 239 Ma to 217 Ma.The Xu-Huai arcuate thrust-nappes in the margin of the North China Craton and the arcuate fold belts around Jiujiang in the Yangtze Plate result from the point collision at the Sulu and Dabie orogens respectively.The margin of the North China Craton to the west of the fault zone shows a feature of rigid continental block during the convergence without large-scale dragging and bending phenomena.In contrast,foreland structures of the Yangtze Plate to the east of the fault zone display large-scale dragging and bending phenomena related to the convergence.A mid-crustal ductile décollement zone of the Yangtze plate is exposed in the northern Zhangbaling uplift belt to the east of the Tan-Lu fault zone.It gives muscovite40Ar/39Ar ages of 245~218 Ma,and shows kinematics controlled by sinistral motion along the fault zone.The structural and geochronological information suggests that the Tan-Lu fault zone originated during the convergence of the North China Craton and Yangtze Plate,and represents an oblique convergent boundary of the two continents.The activity time of the origination is synchronous with the continental subduction in the Dabie and Sulu orogens.The North China Craton had a southward promontory(indenter)in front of the Dabie Orogen originally,resulting in indentation during the collision and the oblique convergence along the indenter boundary(initial Tan-Lu fault zone).The
作者
陆元超
朱光
尹浩
张帅
牛漫兰
LU Yuanchao;ZHU Guang;YIN Hao;ZHANG Shuai;NIU Manlan(School of Resource and Environmental Engineering,Hefei University of Technology,Hefei,Anhui 230009,China)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2022年第10期3410-3425,共16页
Acta Geologica Sinica
基金
国家自然科学基金项目(编号41830213)资助的成果。
关键词
郯庐断裂带起源
左行平移
大陆斜向汇聚
前陆变形
嵌入式碰撞
三叠纪
origination of the Tan-Lu fault zone
sinistral displacement
continental oblique convergence
foreland deformation
indentation-type collision
Triassic
