横过西昆仑和塔里木结合带的山隆盆降机制动力学模拟

最近的地震探测表明，在西昆仑和塔里木结合带有岩石圈根存在。据此，本文提出地壳均衡与岩石圈根拖曳共同作用导致“山隆盆降”的动力学机制假说。利用新近中英合作完成的有限元粘弹塑构造数据模拟技术FEVPLIB，模拟研究了青藏高原西部横过西昆仑和塔里木结合带剖面的这一动力学深化过程。这种模式既能解释高原隆升，又能解释边缘沉积盆地的成因。模拟结果表明，两个大陆碰撞到一起，当岩石圈根一旦形成以后，造山水平挤压力主要来源于岩石圈根的向下拖曳，而印度板块向北挤压沦为次要因素。

Modelling of the Evolution of Collision Mountain Range across the Contact Zone between West Kunlun and Tarim

Evidence for the existence of a massive deep-seated lithospheric root beneath the contact zone between West Kunlun and Tarim has recently been recognized on the basis of deep seismic reflection and broadband seismic exploration. It is explained as follows: the convergence of Indian Plate and Asian Plate caused crustal thickening and associated isostatic uplift of the mountain range; to accommodate the lithospheric convergence, the cool topmost mantle (subcrustal lithosphere) should also have thickened and sinked downwards when it was subducted into the underlying mantle. The tectonic finite element computer package FEVPLIB (Zhang and Bott, 2000) was used to model the evolution of collision mountain range across the contact zone. The finite element grid used was 1000 km long and extended to the depth of 650 km. The western Kunlun thrust belt (WKTB) dipping southward was centered at the submountain region of West Kunlun. The stress distribution for five stages of sinking of the lithospheric root was modeled. The results show that there are two opposing stress systems along the contact zone. The surface loading of the mountain and the associated root of thickened crust produced horizontal deviatoric tension in the strong upper crust in the south of the WKTB (90 MPa at Stage 4). In contrast, the deep and dense lithospheric root and its associated downflexing of the surface produced horizontal compressive deviatoric stress in the strong upper crust in the north of the WKTB (100 MPa at Stage 4). It is concluded that the sinking lithospheric root produced a collision pull force which developed West Kunlun mountain range, and surface downflexure formed by the root down pull may have given rise to Tarim Basin.