摘要
当前,增生型造山带和碰撞型造山带的研究均取得了丰富的成果和创新性认识。二者过渡期间常常发生陆壳俯冲。然而,该俯冲具有什么样的构造变形特点,并如何影响造山带演化过程,长期未受到足够的关注。基于此,文中选择曾发生了陆壳俯冲的两个新生代时期的造山带(中国台湾造山带和雅鲁藏布江造山带)和一个中生代时期的造山带(羌塘造山带)开展研究,以期阐明陆壳俯冲的独特构造变形特征以及和造山过程的交互作用。研究发现,陆壳俯冲常常在造山带形成双层结构,上部为一套由史密斯地层组成的逆冲叠瓦扇构造体系,下部为一套具“岩块-基质”结构特征的俯冲杂岩。双层结构的上下部分物质组成相似,均以斜坡相-海底扇相沉积为主,也有陆棚相沉积。因此,由于构造变形时间相近,双层结构应是由同一套被动陆缘物质俯冲形成的深浅不同的构造体系。研究认为,在陆壳俯冲过程中,早期的斜坡-海底扇俯冲是形成双层结构的主要因素。后续的陆棚俯冲则对碰撞作用的发生起到了主导作用,从而使应变逐渐向克拉通内部扩展,形成前陆褶皱-冲断带。随着碰撞作用的持续,双层结构常常遭到构造破坏,深部的俯冲杂岩因此得以剥露至浅表。因此,文章的研究强调了陆壳俯冲和深俯冲物质的折返在造山带演化中的重要意义。
At present,the study of accretionary orogenic belts and collisional orogenic belts has achieved numerous insights and improvements.However,continental subduction,which often occurs during the oceanic and continental transition,has not received enough attention for a long time,such as what kind of structural deformation characteristics it has and how it affects the evolution of the orogenic belt.This paper studied two Cenozoic orogenic belts(the Taiwan orogenic belt and the Yarlung Zangbo River orogenic belt)and one Mesozoic orogenic belt(the Qiangtang orogenic belt)in order to clarify the unique structural deformation characteristics of continental subduction and its interaction with orogenic processes.It is found that the subduction of continental crust often forms a double-layer structure in the orogenic belt.The upper part is a set of thrust imbricate composed of Smith strata,and the lower part is a set of subduction complexes with a“blocks in the matrix”structure.The upper and lower parts of the double-layer structure are similar,mainly slope facies-submarine fan facies rocks and little shelf facies rocks.Due to the similar deformation time,the double-layer structure should be a structural system formed in different depths by the subduction of the same passive continental margin.We suppose that the subduction of the slope-submarine fan is the main factor for the formation of the double-layer structure.The subsequent continental shelf subduction could induce the collision and thus lead to strain’s gradual propagation to the craton’s interior,resulting in the foreland fold-thrust.Also,the double-layer structure is often destroyed during the collision,so the deeply underplated continental subduction complex can be exhumed to the shallow level.Therefore,this study also emphasizes the importance of continental subduction and the exhumation of subducted crustal rocks in the evolution of orogenic belts.
作者
王根厚
李典
梁晓
唐宇
WANG Genhou;LI Dian;LIANG Xiao;TANG Yu(School of Geosciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China;School of Earth Science,Chengdu University of Technology,Chengdu 610059,Sichuan,China)
出处
《地质力学学报》
CSCD
北大核心
2022年第5期705-727,共23页
Journal of Geomechanics
基金
国家自然科学基金面上项目(42172259)。
关键词
双层结构
造山带
陆缘俯冲
羌塘造山带
雅鲁藏布江造山带
中国台湾造山带
double-layer structure
orogens
continental subduction
Qiangtang orogenic belt
Yarlung Zangbo River orogenic belt
Taiwan orogenic belt
