Abstract: Teleseismic receiver functions(RFs)migration method has been used to image the spatial variation of the converters in the crust and upper mantle along the north Hi-Climb broadband seismic array in the western Qinghai-Tibet Plateau.Results of RFs migration image show the crustal structure under Bangong-Nujiang Suture(BNS)takes on opposite underthrust form,i.e.,the Lhasa block exhibits northward overthrust and underthrust of upper crust and lower crust,respectively,the Qiangtang block southward overthrust and underthrust of upper crust and lower crust,respectively.The above underthrust form means Lasha and Qiangtang blocks may have complex assembly process.Combined with petrology achievements from previous researchers,terrain assembly model has been constructed based on the opposite underthrust form under BNS.Terrain assembly model illustrates that oceanized crust of the New-Tethys north ocean basin has been subducted southward beneath the Lasha block since the closure of the ocean basin and the continental collision of Lhasa and Qiangtang blocks.Since the continental collision of the Indian and Eurasian Plates at 60～50Ma ago,the lower crust of Lasha block however has been subducted northward and may have made the southward subduction plate delaminated,and then Indian Plate subducted beneath the Qiangtang block.

Key words: crustal structure, receiver function, Bangong-Nujiang Suture(BNS), Lhasa block, Qiangtang block

摘要： 利用远震接收函数偏移成像方法获得青藏高原西部Hi-Climb项目剖面北段地壳结构转换波成像。结果显示班公-怒江缝合带下方拉萨地体上地壳向N仰冲,下地壳向N俯冲,而羌塘地块上地壳向S仰冲,下地壳向S俯冲,可能意味着青藏高原西部拉萨地块和羌塘地块具有复杂的拼合过程。结合前人的岩石学研究成果,建立了新特提斯北洋盆洋壳S向俯冲、距今60～50Ma印度板块与欧亚板块碰撞后,拉萨地块的下地壳向羌塘地块下俯冲,而后印度板块俯冲到羌塘地块下方的地块拼合模式。

关键词: 地壳结构, 接收函数, 班公-怒江缝合带, 拉萨地块, 羌塘地块