中国西部大陆岩石圈的有效弹性厚度研究

中国西部是地球上陆地隆升最显著的地区, 有世界上新构造运动最强烈的青藏高原、规模巨大的左行走滑位移的阿尔金断裂系和中亚地区最大的板块内部造山带———天山褶皱造山带.作为印度板块与欧亚板块相互碰撞的会聚带, 本区是研究岩石圈动力学的有利场所.主要运用重力资料和地形资料来研究中国西部地区显著上地壳结构和其上地幔变形之间的关系.依据岩石圈流变学的理论, 在空间域采用垂直和水平受力的多个变刚度的三维有限差分方法来计算弹性板的有效弹性厚度.模拟结果显示中国西部地区的岩石圈有效弹性厚度存在明显的横向不均匀性, 从6~10 km的造山带区域的有效弹性厚度变到大于60 km的古陆区域的有效弹性厚度.青藏高原地区的岩石圈有效弹性厚度平均为30 km, 塔里木盆地的有效弹性厚度为40~50 km, 南、北天山的岩石圈有效弹性厚度分别为10~15 km和30 km左右, 阿尔金断裂在东经90°以西部分的岩石圈有效弹性厚度要小于90°以东部分. 

Effective Elastic Thickness of Continental Lithosphere in Western China

Western China has the most spectacular tectonic features on the continental Earth. It possesses the world highest plateau (Tibet), the world largest intra-continental strike-slip fault (Altyn Tagh) and the world highest intra-continental mountain belt (Tienshan Mountains). As the convergence belt between India plate and Europe plate, this region is a good place for the study of lithosphere dynamics. In this paper, the authors use gravity data and topography data to demonstrate the correlation of these conspicuous upper crustal structures with the deformation of the upper mantle lithosphere in China. we compute the effective elastic thickness of the elastic plate using three-dimensional finite difference in space domain according to the rheology of the continental lithosphere. This model considers the variation of the mechanical strength in vertical and horizontal orientation. The modeling results show that the effective elastic thickness of the lithosphere in China varies significantly from elastic thickness of 6-10 km in highly deformed mountain belts to over 60 km in stable platform areas. The effective elastic thickness of Tibet, Tarim, southern Tienshan and northern Tienshan are separately 30, 40-50, 10-15 and 30 km. While the effective elastic thickness in the western portion of the Altyn Tagh fault (west of 90°E) is less than that in the eastern portion.