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《Chinese Journal of Geophysics》 2016-04
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Crust structure of the Qinling orogenic and the region on its north and south margins from teleseismic receiver function

SI Xiang;TENG Ji-Wen;LIU You-Shan;MA Xue-Ying;QIAO Yong-Hu;DONG Xing-Peng;SONG Peng-Han;Institute of Geology and Geophysics,Chinese Academy of Sciences;University of Chinese Academy of Sciences;Strategic Research Center of Oil & Gas Resources,Ministry of Land & Resources;  
Qinling-Daba orogenic belt is located between North China craton and the Yangtze craton in an EW narrow zone.As an important part of the central orogenic belt,it is a uniquecomplex typical continental orogenic belt.Studying its crust structure plays an important role for understanding and discussing the interaction among Mainland China blocks.From March 2013 to November 2014,one seismic profile was deployed crossing the North China craton,Qinling-Daba orogenic belt,and the Yangtze craton,which covered about 900 km from Yanchuan to Fulin and included 70 mobile stations.5638 teleseismic P wave receiver functions were extracted from the waveforms.H-κauto-searching stacking and CCP stacking methods were used to study the crust structure beneath the Qinling orogenic belt and the adjacent north and south zones.Crustal thickness along the profile was obtained by H-κand CCP stacking methods.The average crust velocity ratio VP/VS(κ)beneath each station along the profile was gained by using receiver function H-κstacking method and then the Poisson′s ratio was calculated.The Poisson′s ratio has obvious regional distribution characteristic.Through the CCP stacking methods,the tectonic zone along the profile may be recognized and analyzed.The results indicated,(1)About the crustal thickness:Crustal thickness along Daba mountain is the thickest,which is around 47~51km.While going to the Qinling the thickness becomes thinner,which is around 37~46km.The Weihe basin reaches the thinnest(around 35km)at 34°N.On the north side of profile,i.e.,the south Erdos basin,the crust thickness fluctuates slowly,mostly about 44 km.The thickness of the Sichuan basin northeast margin becomes thinner slowly heading south,mostly about 42~48km.(2)About the Poisson′s ratio:The Poisson′s ratio of Qinling orogenic belt is significantly lower than that of southern and northern area.Qinling′s Poisson′s ratio is less than 0.26,which means that its main crust components are acidic rocks,and its felsic upper crust is thicker than its mafic lower crust.There isn′t high Poisson′s ratio in Qinling orogenic belt,this shows that there is no extensive partial fusion.(3)About tectonic zone:The boundary between Qinling-Daba orogenic belt and the Yangtze craton is not in the Mianlue structure zone,it should migrate southward to the northeast margin of the Sichuan Basin.North China craton and Yangtze craton is located in the north and south side of Qinling-Daba orogenic belt.They subducted respectively southward and northward with steep and moderate dip along the Qinling-Daba orogenic belt,which made Qinling-Daba orogenic belt an extending outward uplift asymmetric geometry sector model.There is an interface near 33°N between Qinling and Daba Mountain,their regional crustal thickness and Poisson′s ratio have different characteristics.
【Fund】: 国家自然科学基金项目(90914012)资助
【CateGory Index】: P315.2
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