松辽盆地形成、发展与岩石圈动力学

根据区域构造环境、深部构造机制、火山活动的时间序列以及盆地几何学、运动学特征,分析了松辽盆地形成与发展的岩石圈动力学问题。提出古太平洋板块向欧亚大陆下俯冲引起热流上升,由此导致裂谷期前火山作用和岩石圈热与机械减薄,裂谷期上地壳伸展发育成裂谷盆地,火山活动减弱。随着陆缘陆块拼贴,俯冲带长距离后退,处于热异常的岩石圈开始向热平衡转化,盆地由伸展转化为坳陷。

A STUDY ON LITHOSPHERIC DYNAMICS OF THE ORIGIN AND EVOLUTION IN THE SONGLIAO BASIN

Two problems are discussed in this paper abaut the Songliao Basin in Mesozoic: the first is its dynamics of the origin, the second is how it transfers from rift to sag one.The Songliao Basin, located in the east part of Mongolia Block, developing on pre-Mesozoic basement. Its origin and evolution was controlled by lithospheric geodynamics of the continental margin of Northeast China. The evolution can be divided into different stages: prerift volcanism (Late Jurassic), synrift extension of lithosphere (the early period of Early Cretaceous) and postrift sagging (the remain period of Cretaceous).The Subduction of the Paleopacific Plate towards continent caused partial melting of the asthenosphere during Late Jurassic, which accumulated under the lithosphere and led to massive thermal thinning and doming of the lithosphere, and intensive volcanism.The Songliao rift basin occurred when the lithosphere began to stretch with increasing extensional stresses induced by the convection of melts and doming of the lithosphere at incipience of Cretaceous. The extension of the lithosphere also was due to the decceasing of tensile strenth of the thinned and heated lithosphere. Meanwhile the volcamism got little. The Songliao rift basin distributes in relay pattern.Then the sagging basin developed over rift region in postrift stage. The alteration from rifting to sagging contributed to a long distance withdrawing of the subduction zone since a crust block collide with the continent. The uniform volcanic activity from east part of Northeast China to Japan in Late Cretaceous reveals there was a long distance migration of the subduction zone to the east.