中生代东亚大陆边缘构造演化

MESOZOIC TECTONIC EVOLUTION OF CONTINENTAL MARGIN IN EAST ASIA

根据东亚陆缘增生带生物古地理、放射虫时代研究的进展并结合同位素年代及东亚地区火山活动、构造演化探讨了中生代东亚大陆与古太平洋板块之间的运动学关系及俯冲带后退特征。中、晚三叠世那丹哈达岭、美浓等地体还位于北纬１２°以内及赤道附近，晚侏罗世到达中高纬度。东亚活动大陆边缘开始于中侏罗世末，在此之前属转换大陆边缘。洋壳板块向大陆下俯冲之后，由于地体拼贴引起俯冲带快速、长距离后退。

The main problem to be discussed is the tectonic evolution of the East Asian continental margin and the retreat of subduction zone in Mesozoic, based on isotopic age, volcanism and the study advances in paleobiogeography, radiolarians and paleomagnetism. The terranes of Mino, Nadanhada and others were located in near the equator in middle and late Triassic determined by paleobiogeography and paleomagnetism, but in late Jurassic they had reached the mid to high latitude. The oldest tectonic melanges in the accretionary belt occurred in late Jurassic, 169Ma is the diagenetic age of the pillow basalt in Nadanhada Terrane, and the massive volcanism took place in late Jurassic on the East Asia. According to above facts, we come to the conclusion that the active continental margin began at the end of mid Jurassic, before that it was a transform continental margin. After the subduction of the oceanic plate, the subduction zone started a quick and long distance retreating to the east due to the colliding of terranes with continent, which caused that volcanic activities migrated to the east and got newer, and the East Asian continent got far away from the active continental margin.