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鄂尔多斯块体及周边区域的深部构造研究对于了解华北克拉通与其周边地带形成、发展和克拉通破坏具有怎样的壳、幔结构和深层动力学过程具有重要的意义.本文利用北京大学和中国地震局在华北克拉通西部地区布设的共32台宽频带地震仪记录的远震体波资料,组成一条近南北向的观测剖面,由北至南依次穿过阴山造山带、河套盆地、鄂尔多斯块体、渭河盆地、秦岭造山带和大巴山系.计算各台站的P波接收函数,利用倾斜叠加(H-κ)方法得到了研究区域地壳厚度和泊松比;利用Kirchhoff偏移成像方法得到了研究区域下方Moho面的形态.研究结果表明,阴山造山带地壳厚度为42~44km,地壳结构稳定,泊松比约为0.27,推测该区域的造山运动是深部物质上涌导致.河套盆地内Moho面抬升,可认为是岩石圈物质上涌导致.鄂尔多斯块体内平均地壳厚度41.2km,泊松比0.27,Moho面从北至南平缓有平缓抬升的趋势,从最北端的43.5km到最南端的39km.鄂尔多斯块体北部在20km深度处存在低速层,块体内部36°N~37°N区域内出现Moho面小规模下沉,这对鄂尔多斯块体地壳结构单一、完整、未遭到破坏的观点提出了挑战.渭河盆地内Moho面隆起,最浅达到30km,推测是青藏高原地壳上地幔物质向东挤出并上涌所造成的.秦岭造山带地壳厚度约38.5km,Moho面平稳.位于扬子板块北缘的大巴山系地壳厚度达到54.5km,明显大于华北克拉通的地壳厚度.
The study of the deep structure of the Ordos block and the surrounding area is of great significance for understanding the formation and development of the North China Craton and the crustal crust, the mantle structure and the deep dynamic process of the craton.This paper uses Peking University and China Earthquake Administration The teleseismic body-wave data recorded by a total of 32 broadband seismographs distributed in the western part of North China Craton made up a nearly north-south observation section, which successively crossed the Yinshan orogenic belt, the Hetao Basin and the Ordos block from north to south, Weihe Basin, Qinling orogenic belt and Dabashan system.The P-wave receiver function of each station was calculated, and the crustal thickness and Poisson’s ratio of the study area were obtained by the method of slope-superposition (H-κ). The Kirchhoff migration imaging method was used to obtain the P wave reception function under the study area Moho surface.The results show that the crustal thickness of the Yinshan orogenic belt is 42 ~ 44km, the crustal structure is stable and the Poisson’s ratio is about 0.27, suggesting that the orogeny is caused by the upwelling of Moho in the Hetao Basin, Which can be considered as the upwelling of the lithosphere.The average crustal thickness in the Ordos block is 41.2km with a Poisson’s ratio of 0.27 and the Moho surface extends from north to Nanping There is a gentle upward trend, ranging from 43.5km in the northernmost part to 39km in the southernmost part.Low velocity layers exist in the north of Erdos block at a depth of 20km, and small Moho subsidences occur in the region of 36 ° N ~ 37 ° N within the block , Which poses a challenge to the single, complete and unbroken crustal structure of the Ordos block.Moho surface in the Weihe basin rises up to a depth of 30km, presumably that the crust and upper mantle material in the Qinghai-Tibet Plateau are squeezed eastward and upwelling The Crustal thickness of the Qinling orogenic belt is about 38.5km with a stable Moho surface.The crust of the Daba Mountains, located in the northern margin of the Yangtze Plate, has a thickness of 54.5km, which is obviously larger than the crustal thickness of North China Craton.