论海沟—岛弧—弧后盆地复合体系的形成机制

ON THE FORMATION MECHANISM OF TRENCH—ARC—BACKARC BASIC SYSTEM

海沟一岛孤一弧后盆地复合体系的成因与软流圈及岩石圈的流变性有关,以前者为主,并遵循流体运动的最小阻力原理。俯冲有两种类型:一是大洋岩石圈向大陆岩石圈的俯冲,二是大洋岩石圈之间的俯冲。弧后扩张及岛弧升高在时间上的滞后现象,也可以用此原理来说明。

The formfltion of trench-arc-backarc basin system is relative to the rheidity of asthenosphere and lithosphere,maily to the formet which proceeds according to the minimum resi stance princiwple for fluid motion.There are two types of subductjon: one is that oceanic crust undertrusted to continental crust; the other is that oceanic crust subducted oceanic one, The mechanisms of the two kinds are different.Formerly, because asthenosphere thinned near the continental margins,hence the change of boundary conditions would cause the energy to culmulate.When the energy rised to threshhold,the asthenosphere would pulse and drive the oceanic crust to downgo. In this way,the oceanic trench would be engenderd.Laterly,subduction occurred preferentially at local places, then conyexly curved trench would be formed along the subduction zone in the light of the minimum resistance principle because of plane convergence processes of asthenosphere and oceanic lithosphere.The back-arc spreading and retardation in time for arc uplifting can also be explained with this principle.