俯冲板片形貌特征和活动大陆边缘演化体制的关系

当大洋板块向大陆板块下俯冲时，上覆板块的边缘可以以沟—弧—盆体制发育，也可以不发育弧后拉伸盆地．为什么同属上覆板块边缘但可以这二种完全不同的体制演化是现代地球科学研究的一个热点．本文在查阅大量最新文献的基础上认为造成这二种不同演化体制除了与俯冲作用的年代学特征有关外还可能主要与俯冲板片的形貌不同所导致局部地幔对流方式不一有关．由于俯冲的倾角，俯冲达到的最大深度以及俯冲板片在６７０ｋｍ上下地幔过渡带处保存的形态等因素不同，造成仰冲板块边缘之下软流圈对流方式不一．从而，造成弧体近陆一侧是否将发生岩石圈拉伸的动力学过程．

RELATIONSHIP BETWEEN THE MORPHOLOGY OF SUBDUCTED SLABS AND THE TECTONIC EVOLUTION IN THE ACTIVE CONTINENTAL MARGINS

When the oceanic plate subducts into the continental plate,the tectonic evolution of overlapping plate can be in the forms of two types;(1)the Trench-arc-basin (TAB) system which is characterized by the occurrence of back arc spreading. (2)the Trench-arc (TA) system which is characterized by the absence of back arc speading. The problem that why the active continental margin can be evolved in the wholly different two systems is one of the most debating focuses in the moden geosciences. By analyzing the latest research achievements,the present authors illustrate that the geodynamics to cause the difference is mainly related to the difference of the mantle convection which is derived from the morphology of subdected slabs. Owing to the difference on the subductting angles and the deformational styles of slabs accumulated at the 670km transition zone,the mantle convection initiated by the slab subduction between the triangle zone which is bounded by the relative brittle lithosphere and subducted slabs is different. Thus possibly causing the two types of tectonic systems in the active continental margin.