造山带沉积盆地与大陆动力学

Sedimentary basinsin orogenic belt and continental geodynamics

造山带原型盆地恢复是地质学研究的重要内容,是板块构造研究的难点与前沿,对于理解造山带演化及其大陆动力学具有重要意义。本文从原型盆地恢复的方法出发,评述了前人根据碎屑组成、元素地球化学和碎屑单矿物年代学来进行原型盆地恢复的原理、方法和效果。基于喜马拉雅造山带沉积盆地的实践,提出造山带原型盆地恢复的五个要素:盆地顶底界面、古地理环境、物源分析、构造分析和盆地外围研究。详细介绍了新特提斯洋俯冲、印度-亚洲大陆碰撞以及后碰撞阶段的沉积盆地的地质特征,包括印度北缘被动大陆边缘盆地、日喀则弧前盆地、雅鲁藏布海沟盆地、林周弧后-弧背叠合盆地、桑单林同碰撞盆地,以及后碰撞阶段的冈仁波齐盆地、柳区盆地和札达-吉隆裂谷盆地。基于沉积盆地研究反演了喜马拉雅大洋俯冲-大陆碰撞的演化过程,探讨了沉积盆地与大陆动力学之间的耦合关系。

Prototype restoration of sedimentary basins in orogenic belts,one of the most challenging tasks in earth sciences,is crucial for understanding the evolution of orogenic belts and continents geodynamics.This paper first reviews the traditional methods of restoration of prototype basins in orogenic belts with focus on their principles and methods to reconstruct the tectonic setting of the sedimentary basin based on clastic composition,elemental geochemistry,and single-mineral geochemistry.Based on our assessment of sedimentary basins in the Himalayan-Tibetan Plateau,five major elements for the restoration of orogenic prototype basins are proposed.These include the tectonostratigraphic boundaries of the sedimentary basin,paleogeographic analysis,provenance analysis,structure geological analysis and basin-related terrane analysis.Considering the Himalayan orogenic belt as an example,this paper analyzes in detail the geological characteristics of the relevant basins in three tectonic stages of the Neo-Tethys oceanic subduction,the India-Asia collision and the post-collision.This is followed by a discussion on the geodynamics of the orogenic belt as reflected by the sedimentary basins,including the northern Indian passive continent margin basin,the Xigaze forearc basin,the Yarlung Zangbo trench basin,the Linzhou backarc-foreland composite basin,the Sangdanlin syn-collision basin,and the post-collision Gangrinboche basin,the Liuqu basin and the Zhada-Gyirong rift basin.The evolution process of the Himalayan orogenic belt is proposed based on the analysis of the sedimentary basins,and the relationships between the sedimentary basins and continental geodynamics are further addressed.