中国西北及周边地区上地幔密度异常驱动小尺度对流  

UPPER MANTLE CONVECTION BENEATH NORTHWEST CHINA AND ITS ADJACENT REGION DRIVEN BY DENSITY ANOMALY

作　　者：许萍[1] 傅容珊[1] 黄建平[1] 查显杰[1] 戴志阳[1] 

机构地区：[1]中国科学技术大学地球与空间科学学院中国科学院壳幔物质与环境实验室

出　　处：《地震学报》2006年第5期513-522,560,共10页Acta Seismologica Sinica

基　　金：中国科学院创新项目(KZCX3-SW-131);国家自然科学基金(40274033)资助.

摘　　要：假设地震层析成像提供的地震波速异常对应于上地幔物质的密度异常分布,而该密度异常直接源于上地幔热对流相应的温度扰动.在给定边界条件下,利用三维傅里叶变换,在波数域内求解控制流体行为的运动方程和连续性方程,得到上地幔小尺度对流流场.利用密度异常驱动上地幔小尺度对流的数学-物理模型,采用胥颐、刘福田等提供的地震层析成像数据计算得到了我国西北及周边地区上地幔对流模式.结果表明,对流流场的顶部在岩石圈较薄的盆地区域呈现上升发散流动特征,如塔里木盆地、柴达木盆地、哈萨克斯坦块体及准噶尔盆地;岩石圈较厚的山脉则对应了会聚下降的流动特征,如天山山脉、昆仑山山脉和祁连山山脉.同时,塔里木盆地处于拉张状态,驱动其上地幔物质南下向青藏高原北部西昆仑运动,以及北上向天山下部流动,这可能是天山隆升的原因之一.We assume that the density anomalies, which are transformed from seismic tomography data, are corresponding to temperature distribution in a convective mantle. We take density anomalies as the driving force for mantle convection and solve the basic equation with appointed boundary condition in a wave-number domain by using the FFT arithmetic. Using the physical model of upper mantle convection and the seismic tomography data supplied by Xu et al, we calculated upper mantle convection beneath northwest China and adjacent region. The flow patterns in the upper mantle show that there are upward and divergent flows in the basin regions, such as Tarim, Qaidam, Junggur and Kazakstan, where the lithosphere is thin. There are downward and convergent flows in the mountain regions, such as Tianshan, Kunlun and Qilian, where the lithosphere is thick. In addition, because of the divergent flow under the Tarim Basin the upper mantle material in this region is driven southward to the north part of Tibetan Plateau and northward to Tianshan Mountain. Maybe, it is one of the reasons for the recent uplift of the Tianshan Mountain.

关 键 词：地幔对流 西北及周边地区 地震层析成像 

分 类 号：P313.4[天文地球—固体地球物理学]