Cenozoic Tectonic Evolution Of Datong Basin, Northeastern Margin Of Ordos Block

Datong basin is a Cenozoic rift located in the central part of North China Craton. It has experienced strong and persistent rifting since late Miocene. The shallow-level extension is analyzed from the kinematics of boundary faults and tectonic stress field inversion, and the deep process is analyzed from Cenozoic basalts evolution. Based on the striation data of boundary faults, the tectonic stress field controlling Datong basin’s forming is inversed:ai is vertical,σ2 and σ3 is horizontal, the strike of σ3 is about 150°. This is the normal fault stress field of NW extending which differs from strike-slip fault stress field of NE compressing in North China region. In terms of the evolution of Cenozoic basalts, the proportion of alkaline basalts declines, the Yb content of alkaline basalts in the basin rises, which implie continuous thinning of the lithosphere. What’s more, the Dayukou basalt’s K-Ar age of 0.68±0.13Ma is first obtained in this article. The formation of the tectonic stress field is related to the mantle activity that results in the eruption of basalts. The tectonic stress field difference between Datong basin and Eastern North China block corresponds with their lithosphere thickness variations. Accordingly, author proposed the formation and evolution model of Datong basin:since 10-8 Ma, the asthenosphere upwells continuously, the mantle activity transfer the heat to the crust, the NW extending tectonic stress field of certain strength is formed in the upper crust, the tectonic stress field controls the formation and evolution of Datong basin. This process may be related to the far-field effect of India-Eurasia collision and Pacific-Eurasia collision. All these research provide a new basis for building the Cenozoic kinematics and dynamatics model of the Shanxi Rift system.