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地幔过渡带间断面的形态能够提供地幔动力学状态的重要信息.本文利用密集流动台阵观测获得的地震波形记录,采用高分辨的地壳-上地幔速度结构成像结果作为接收函数共转换点叠加的速度模型,获得了华北克拉通地区地幔过渡带410km间断面和660km间断面深度的空间分布.结果揭示华北克拉通410km间断面和660km间断面结构的空间变化显著,存在多处间断面深度异常.地幔过渡带的结构特征以南北重力梯度带为界分为东西两部分;410km间断面变深(420～430km)的区域主要分布在华北克拉通东部,660km间断面变浅(642～655km)的区域出现在华北克拉通西北部;在华北克拉通东南部,660km间断面显著加深.本文分析认为,停滞在地幔过渡带的太平洋俯冲板块、厚度剧烈变化的克拉通岩石圈以及它们与周围地幔的相互作用,导致华北克拉通下存在活跃的地幔流动体系,造成过渡带间断面形态的高度不均匀.本文推测了两种可能的地幔过程:在克拉通根厚度显著变化的区域发生减压熔融,或者边界驱动的对流引起地幔物质沿着厚的克拉通根向上流动;或者是停滞在地幔过渡带的俯冲板块部分沉入下地幔,同时导致被排出的下地幔物质上升.
The morphology of the mantle transitional zone can provide important information on the dynamic state of the mantle.Using the record of seismic waveforms obtained from intensive mobile array observations, the high resolution crustal-upper mantle velocity imaging results are used as the co-conversion point for the receiver function Velocity model was used to obtain the spatial distribution of 410 km section and 660 km section depth in the mantle transitional zone of North China Craton.The results revealed that there is significant spatial variation in the structures of 410 km section and 660 km section in North China Craton and there are many inter-section depth anomalies. The structural features of the mantle transitional zone are divided into east and west parts by the north-south gravity gradient zone, and the areas of 410km deepening (420 ~ 430km) are mainly distributed in the eastern part of North China Craton, with a shallow section of 660km (642 ~ 655km) The area appears in the northwestern part of North China Cratonic, and the 660km section deepens significantly in the southeastern part of North China Craton.This paper analyzes that the Pacific subduction plate in the mantle transitional zone, the craton rock with drastically varying thickness, and their interaction with the surrounding mantle Interaction, resulting in the existence of an active mantle flow system under the North China Craton, resulting in a transitional zone intercept This paper suggests two possible mantle processes: depressurization and melting occurs in areas where the thickness of cratonic roots vary significantly, or boundary-driven convection causes the mantle material to flow up along the thick carat roots; or Part of the subducting plateau that has stagnated in the mantle transitional zone sinks into the lower mantle and at the same time causes the drained lower mantle material to rise.