天山及邻区Vening Meinesz均衡重力异常特征及其动力学意义

本文基于Vening Meinesz区域均衡模型，通过试验不同参数计算Vening Meinesz均衡补偿深度，将其与CRUST1.0模型给出的莫霍面深度进行拟合，得到适应于天山及邻区的平均补偿深度、"地区性指标"以及区域补偿半径.结合地球重力场模型EIGEN-6C4与地形数据，利用球冠体积分方法进行地形效应、沉积层效应计算和均衡校正，得到了研究区的Vening Meinesz均衡重力异常.结果显示天山及邻区的均衡重力异常幅值在-110~120 mGal之间，表明了天山及周边盆地岩石圈所处于的均衡状态，同时揭示了研究区的壳幔密度分布特征.天山、塔里木盆地、准噶尔盆地等块体的地壳垂向形变可能部分地由均衡调整引起，且均衡调整趋势与地面形变测量结果相契合.通过对均衡重力异常成因的解释，从地壳均衡角度分析了该地区复杂的构造背景及其新生代以来的演化历程.

Characteristics of Vening Meinesz isostatic gravity anomalies in Tien Shan and surroundings and its dynamic significances

Based on the Vening-Meinesz regional isostatic model, we calculate the Vening-Meinesz isostatic compensation depth by adopting different parameters, and fit it with CRUST1.0 Moho depth to obtain mean compensation depth, "degree of regionality" and regional compensation radius around the Tien Shan Mountains. With the Earth's gravitational field model EIGEN-6C4 and the terrain data, we use the sphere-cap integral method to calculate gravity effects of topography, sedimentary layer and isostatic correction, then obtain the Vening-Meinesz isostatic gravity anomalies in the study area. The isostatic anomaly varies between -110 mGal and 120 mGal, demonstrating the isostatic status of the lithosphere in the Tien Shan Mountains and neighboring basins. Moreover, the isostatic anomalies delineate features of the lithospheric density distribution in the study area. Crustal deformations in the Tien Shan Mountains, Tarim Basin and Junggar Basin may be partly generated by the isostatic adjustment, and their trend is consistent with the ground deformation measurements. Through investigation of causes for isostatic anomaly variations, the complex tectonic setting of this area and its evolution history since the Cenozoic are analyzed from the perspective of isostasy.