卫星重力资料揭示的新疆天山地区构造动力学状态

利用最新的地球重力场模型，计算了新疆及邻近地区的自由空气重力异常、大地水准面扰动异常、地壳和上地幔平均密度异常以及地幔对流引起的岩石层底界面粘滞应力场分布．根据计算结果，对新疆天山地区的构造动力学特征进行了分析和推断，认为天山处于地幔对流形成的挤压沉降环境中，在南北不对称的挤压应力作用下快速隆升，挤压应力场中心在天山以南．这种应力场特征有利于塔里木板块向天山之下俯冲的观点．天山南北两侧的准噶尔盆地南缘和塔里木盆地北缘，是地壳内质量缺失区，是由于南北两侧地壳向天山下挤压而弯曲造成的．中国天山东段的深部密度分布特征与中段和西段的不同，可能是地幔对流分布的东西向差异造成的． 

DYNAMIC FEATURES OF THE TIANSHAN OROGEN DEDUCED FROM SATELLITIC GRAVITY DATA

The latest geopotential model, EGM96, was employed to compute the free air gravity anomaly, geoidal separation, the average density anomalies of the crust and the uppermost mantle, and the distribution pattern of the viscous stress exerted by mantle convection over Xinjiang and its neighboring areas. Based on these results and other data, we try to interpret the geodynamical features of the Tianshan orogen. Our research suggests that the Tianshan orogen is in a tectonic setting of compressive settling, driven by mantle convection. Under the effection of the compressive stress field, asymmetric in north south direction, the Tianshan orogen upheaved quickly. The center of compressive stress field is in the south of the Tianshan, and the characteristic of stress field is favorable for the view point that the Tarim plat subducts beneath the Tianshan. The southern margin of the Juggar basin and the northern margin of the Tarim basin are two areas where the crust is of mass deficiency. We attribute the mass deficiency to the fact that the crust in both north and south the Tianshan is bend downwards under the compressive stress. Our research also indicates that the density distribution patterns in the deep of the eastern Tianshan are different from those in the middle and western Tianshan. It may be explained as the results from the east west oriented distinction of the mantle convection.