东亚大汇聚与中-新生代地球表层系统演变

MESO-CENOZOIC EVOLUTION OF EARTH SURFACE SYSTEM UNDER THE EAST ASIAN TECTONIC SUPERCONVERGENCE

东亚长期处于古亚洲洋、特提斯洋和古太平洋三大构造域的大汇聚构造背景之下。印支运动后,东亚东缘形成了统一的被动大陆边缘,随着晚三叠世古太平洋板块俯冲的启动,东亚东缘的被动大陆边缘转化为主动大陆边缘,发育了与俯冲相关的蛇绿岩、I型花岗岩。晚三叠世—中侏罗世,古太平洋俯冲带持续向西迁移,板块俯冲产生的挤压应力影响到了东亚内部,发生广泛构造变形,构造体制从受E—W向特提斯构造域和古亚洲洋构造域控制逐渐向受NE向的古太平洋构造域控制转变。晚侏罗世—早白垩世早期(160~135 Ma),古太平洋板块继续西进,东亚被挤压-走滑的应力场控制,安第斯型主动大陆边缘和华北东部高原最终形成,发育少量的埃达克岩。早白垩世晚期(135~90 Ma),古太平洋俯冲带向东后撤,东亚陆缘由挤压-走滑应力场转变为拉张-走滑应力场,安第斯型大陆边缘被破坏,华北东部高原开始垮塌,伴随大量的埃达克岩、变质核杂岩的出现。在晚白垩世,随着俯冲带的后撤,东亚内部伸展作用减弱。新生代东亚发生了巨型的地形倒转,印度板块与欧亚板块碰撞最终导致中国西部的青藏高原隆升,相反,中国东部渤海湾盆地和海区的盆地群形成;构造-盆地-岩浆带体现出自西向东迁移的特征,盆地群起始时代主要在古近纪,形成了新生代西高东低的台阶式地貌格局。在新近纪盆地群由断陷转为快速拗陷,同时东亚内部的伸展构造主要受青藏高原隆起制约。

East Asia has suffered for a long duration under the superconvergence system of the Paleo-Asian, Tethyan and Paleo-Pacific tectonic domains. The Indosinian Movement for the first time made an unified passive continental margin in East Asia. The intrusion of ophiolites and I-type granites associated with the subduction of the Paleo-Pacific Plate in Late Triassic suggests a transition from passive to active continen- tal margins. In the process of the westward migration of the Paleo-Pacific Subduction Zone, the sinistral transpressional stress field dominated the intraplate deformation during the period from Late Triassic to Middle Jurassic. The E-W-trending structural system controlled by Tethys and Paleo-Asian oceans started changing to the N-E-trending structural system caused by the Paleo-Pacific Ocean subduction. The contin- uously westward migration of the subduction zones resulted in the transpressional stress field in East Asia marked by the emergence of the Eastern North China Plateau and the formation of the Andean-type of ac- tive continental margin from Late Jurassic to Early Cretaceous （160~135 Ma）, accompanied by the devel- opment of a small amount of adakites. In Late Cretaceous （135~90 Ma）, due to the eastward retreat of the Paleo-Pacific Subduction Zone, the regional stress field was changed from sinistral transpression to transtension. Since a large amount of late-stage adakites and metamorphic core complexes was developed, the Andean-type of active continental margin was destroyed and the Eastern North China Plateau started to collapse. In Late Cretaceous, the extension in East Asia gradually decreased eastward with the retreat of the Paleo-Pacific subduction zones. Futhermore, a significant topographic inversion took place in Cenozoic resulted from a rapid uplift of the Tibet Plateau owing to the India-Eurasian collision and the formation of the Bohai Bay Basin and other basins in the East Asian continental margin. The inversion has a remarkable eastward migration of deformation, basin formation and magmatism. Meanwhile, the basins mainly devel- oped in Paleogene which caused the formation of the three-stepping topography with dropping altitude eastward. In Neogene, most of the basins underwent rapid subsidence under the control of faulting, as well as the intracontinental extension in East Asia, which also made substantial contribution to the uplif- ting of the Tibet Plateau.