东海地区壳体构造演化及其盆地形成机制探讨

CRUSTOBODY EVOLUTION AND MECHANISM OF BASIN FORMATION OF THE EAST CHINA SEA

本文引用最近的地震、钻探、海底拖网采样及其它地质资料，通过综合研究与分析，证实东海地区的壳体属薄化陆壳型壳体，其构造演化经历了地槽阶段（Ｐｔ－Ｄ＿２）、地台阶段（Ｄ＿３－Ｔ＿２）和地连阶段（Ｔ＿３－Ｑ）。其中，前两个阶段与东亚壳体东南地区的构造演化基本一致，进入地洼阶段后逐步薄化。东海盆地的形成与“菲律宾海板块俯冲”无关，而与地幔蠕动流所产生的拖拽型拉张应力场和地洼造山带所具拉伸趋势而形成的伸展型拉张应力场有关。

The East China Sea is lcoated in the middle portion of the East Asia continental margin crustobody,belonging to the thinned continental crust type according to its present tectonic setting and its thinned thickness.The crustobody in the East China sea is composed of three structural layers,i.e.the mantle rock. simatic and sialic structural layers,and the crust of it now thins eastward from 30km to 20km.The crustobody of the East China Sea is trending NNE,and can be divided into three zones,i.e.the western continental shelf,continental shelf basin and Okinawa Trough from west to east.It has been experienced the geosynclinal stage(Pt-p(z1)),platform stage(p(z2)-T2)and diwa stage(T3-Q).The diwa stage consists of the initial-mobility period(T3-J1),the maximum-mobility period(J2-E2)and the residual-mobility period(E3-Q).During the former two stages,the crustobody evolution of the East China Sea was generally in accordance with the southeastern region of the East Asia crustobody,and it has gradually been thinned.The study suggests that the formation of the East China Sea basin is not related to'the subduction of the Philippines Sea Plate'.but to the mantle creep current.The directly related stress field includes the drag tensile one resulted from the mantle creep current(horizontal creep flow)and the extension tensile one produced by the extension of the diwa orogenic belt.