鄂尔多斯西缘北段的地壳结构和块体间变形关系

Crustal structure and deformation between different blocks in the northern part of the western margin of Ordos

本文对喜马拉雅计划二期部分台站的远震波形数据进行接收函数提取,利用接收函数共转换点叠加方法获得阿拉善地块、鄂尔多斯地块以及银川—河套盆地下方0~80 km深度的速度间断面结构.结果表明:鄂尔多斯地块成层性好,地壳厚度为38~42 km,康拉德界面为18~22 km,阿拉善地区的Moho面深度为38~45 km.河套盆地地壳厚度约52 km,银川断陷盆地和贺兰山下方的Moho面最深为~55 km.鄂尔多斯西缘构造边界下方Moho面变化明显,且黄河断裂为深大断裂直接切割莫霍界面.根据本文的间断面成像结果我们进一步确定阿拉善地块与鄂尔多斯地块分属不同的大地构造单元.与此同时,我们推测贺兰山以西70~80 km范围内和鄂尔多斯地块西缘北段存在地壳增厚变形的可能.

Probing the velocity interface structure of the crust is crucial to understand the interaction between the Alxa block and Ordos block.We obtained the image of Moho and intracrustal discontinuities structure beneath the research area by using 3-D Common Conversion Point(CCP)stacking technique with the P-wave receiver function extracted by teleseismic waveform,which is recorded from China Array seismic experiment during 2013—2015.The stations nearly evenly covered Alxa,Ordos and Yinchuan-Hetao basin blocks in north China.Our results show that the Moho and Conrad discontinuity in Ordos is 38~42 km and 18~22 km,respectively.The crustal thickness of Alxa block is 38~45 km,the Moho lies at a depth of^52 km beneath the Hetao basin.The deepest Moho depth is^55 km,located around Helan Shan.Combining our results with the previous research from different aspects,we further confirmed that the Alxa block and the Ordos block belong to different terrestrial tectonic units.At the same time,we conjecture the existence of crustal thickening in the west of Helan Shan and the western margin of Ordos.