后碰撞伸展环境下的盆地特征与成盆机制

与造山带结合,动态、系统地探讨伸展盆地的成盆机制是大陆动力学研究的新思路。本文以后碰撞环境下的伸展盆地为对象,与其它类型伸展盆地相区别,尝试探讨其大陆构造属性和成盆机制。后碰撞伸展盆地一般平行于造山带展布,受相邻活动造山带控制,形成于造山带后碰撞构造环境。盆地的转换、叠合过程与相邻造山带的演化密切相关,表现为动态的耦合关系,即由前陆盆地与主碰撞造山带相耦合,发展为伸展盆地与后碰撞造山带相耦合。其成盆机制实质是地壳缩短增厚后的去"山根"作用,拆沉作用造成加厚地壳减薄,并诱发基性岩浆活动,在地表形成裂谷或断陷,接受河湖相沉积。

Characteristic and Dynamical Mechanism of Post Collision Extensional Basins

Combined with the orogenic belt, study on the dynamical mechanisms of extensional basins systematically is a new approach of continental dynamics research. This paper choose extensional basin in post collision stage for the object, and distinguish it from other types of extensional basin, and attempt to explore its continental structural properties. Paralleling to the spread of orogenic belt, the post collision extensional basin is preliminarily defined as a kind of hinterland extensional basin which controlled by the adjacent orogenic belt, and formed in the post-collision tectonic setting of orogenic evolution. The progress of basin conversion and super implosion is closely related to the evolution of the coupled orogenic belt, that is, it sequel from foreland basin coupled with the syncollision orogenic belt into extensional basins coupled with the post-collision orogenic belt. The essential mechanism of this kind of basin is removing mountain root after the crustal shortening and thickening effect. The thickened crust thinning is caused by delamination mainly. The delaminations of lower crust bring out mafic magmatism, and formed the rift and fault—depression on surface, which filled with fluvial facies sediments.