Aeromagnetic anomaly analysis of Ordos and adjacent regions and its tectonic implications
鄂尔多斯及邻区航磁异常特征及其大地构造意义

Affiliated to the North China Craton(NCC),the Ordos massif contacts with the Qinling-Qilian orogenic belt to the south,with complicated geological features around as a result of episodic tectonics.By applying the upward continuation,vertical derivation of different orders,and a new method for delineating magnetic boundaries to the aeromagnetic data,as well as taking into account the earthquake data,here we present the characteristics of aeromagnetic anomalies of field sources at different depths and their tectonic implications.Our results show that the basement of the Ordos is rigid on the whole but is still heterogeneous.The east of the Ordos massif in NCC is a relatively weak zone with approximately NS trending suffered from subsequent tectonic alternation.The ductile lower crustal material flows along two weak zones of the Qinling and Qilian orogenic belt coevally with the thickening and shortening of the crust in Qinghai-Tibet Plateau,as well as the anticlockwise rotation of the Ordos massif due to the intensive compressional stress in NE direction derived from the India-Eurasia collision.The diverse tectonic features mentioned above in and along the margins of the Ordos massif represent the tectonic responses of the crustal blocks of different rigidity to the boundary forces,that resulted in prominently different geological features.The tectonic deformation in and around the Ordos massif is characterized by inheritance and superimposition.