Paleomagnetic Constraints On The Tectonicresponse Of The Eastern Part Of The West-Qinlingto The Eastward Spreading Process Of The Tibetanplateau

In order to explore the deformation characteristics of various parts of the West-Qinling at the "cross-tectonics" hub during the eastward extension of the Qinghai-Tibet Plateau,in the Early Cretaceous and Neogene deposits in Zhouqu,Wudu,Chengxian and Fengxian Carried out detailed paleomagnetic research.Obtained the Early Cretaceous paleomagnetic poles in Zhouqu and Chengxian areas(Zhouqu 82.7°N,282.7°E,?95=9.1°;Chengxian 72.2°N,227.2°E,?95=9.3°),and Wudu area recently Jigu geomagnetic pole(65.8°N,205.9°E,?95=12.8°).Comparing them with the paleomagnetic poles of North China in the same period shows that:(1)the Zhouqu Early Cretaceous paleomagnetic pole has rotated 15.5±5.7°counterclockwise relative to the North China reference pole;(2)Chengxian Early Cretaceous The paleomagnetic pole is consistent with the North China reference pole;(3)The Wudu Neogene paleomagnetic pole has a clockwise rotation of 23.7±3.5° relative to the North China reference pole.Combining the results published by predecessors,we believe that the evolution process of the northeastward expansion of the Qinghai-Tibet Plateau controlled the tectonic evolution of the Western Qinling since the Cretaceous,but different regions exhibited different tectonic activity characteristics.The area on the northwest side shows that the block rotates clockwise in situ,and the fault separating the block appears as a left-slip,which is consistent with the dynamic mechanism of the northeastern marin of the Qinghai-Tibet Plateau;the main body of the southwest side is controlled by Songpan-Garze Northeast Squeezing and thrusting,and shifting and shifting under the action of northeast-trending secondary faults,accompanied by dragging deformation near the fault,resulting in counterclockwise rotation of local tectonic trails;the eastern part is formed by early strike-slip faults and the Pull-apart Basin is formed in the east.The squeezing stress was reformed,the boundary fault occurred structural flip,and the weak deformation in the basin was characterized.