Relationship Between NW-Trending Faults Of Luxi Block And Tan-Lu Fault Zone

In this paper,the NW trending faults of the Luxi Block and the Tan-Lu fault zone are taken as the research objects,and the relationship between these NW trending faults and the Tan-Lu fault zone is studied.The geometry,kinematics and geochronology of the NW faults are determined by using the methods of field work,balanced section restoration and fission track dating,and the relationship between the NW faults and the Tan-Lu fault zone is revealed by comparing with the characteristics.The geometric characteristics show that the fault dip angle of NW trending is relatively small in the Luxi Block,ranging from 50 ° to 70 °.Fault breccia,cataclastic rock,fault gouge,scratch,step and so on are developed in the fault zone.The NW trending faults in the Luxi Block can be divided into large basion-controlled faults,such as Taishan-Tongyedian,Xintai-duozhuang,Mengshan faults,and non-basion-controlled faults such as Ganlin,Nishan and Jiushan faults,which are arranged roughly in parallel on the plane and ladder-shaped in profile.The four main faults in the Yishu section of the Tan-Lu fault zone are nearly parallel on the plane and horst and graben in profile.The angle between the NW trending faults and the Tan-Lu fault zone in plane is 36°for the Nanxinzhuang fault and larger than 47°for the other faults,indicating that the Tan-Lu fault zone is left-lateral,and hinding the NW-trending faults of the Luxi Block are derived from the Tan-Lu fault zone.The kinematics study of the Luxi Block shows that the compression amount before the Late Jurassic-Early Cretaceousis 6.3 km,and the NW thrust faults are formed in the Luxi Block.In the Late Jurassic-Early Cretaceous the extension value is 3.4 km,the Paleogene extension is 9.8 km and the Neogene is 1.4 km.In addition to the Qi-Guang fault,Taishan-Tongyedian,Xintai-Duozhuang,Mengshan and Wensi faults were inversed from reverse faults to normal faults at the end of Triassic,and the activity rate of the faults reached the maximum in Paleogene.And the tectonic activity migrated from south to north.In theLate Triassic of the Tan-Lu fault zone,the left-lateral strike-slip occurred,with a strike-slip of300~430km and a vertical activity rate of 0.909km/m,the Jurassic the Luxi Block was compressed and the left-lateral strike-slip of Tan-Lu fault was still carried out,the Early Cretaceous strike-slip value of Tan-Lu fault was about 100 km,while in Late Cretaceous Tan-Lu fault is in extension.In the Early Cretaceous,the cutting depth is 40 km,the vertical activity rate is 0.1896 km/Ma.In the Eocene of the 43 Ma,The Tan-Lu act from left-lateral to right-lateral and the Eocene to Early Pleistocene its strike-slip value is 50 km,and the cutting depth is 80 km,with the vertical activity rate of 0.4094 km/Ma.Through the comparison of the two,it can be seen that both of them were compressed in Late Triassic,the extension of NW fault in Late Jurassic and Early Cretaceous was normal fault activity.The strike-slip activity of Tan-Lu fault zone weakened in Paleogene,and the peak value of NW trending fault in the Luxi Block.In the Neogene,the NW trending faults commonly stopped,and the activity of the Tan-Lu fault zone was relatively strong.The kinematic relationship shows that the extensional activity NW trending faults in the Luxi Block was a derivative fault of the Tan-Lu fault zone since the late Mesozoic which is related to the strike-slip activity of the Tan-Lu fault zone.The results of apatite fission track test show that the age distribution of NW non-basion-controlled faults samples in the Luxi Block is 184 Ma,99~74Ma,66~43Ma,25 Ma,and the distribution of the basion-controlled faults ages is 141~126Ma,80 Ma,61~32Ma,25 Ma,and the fault activity time has the law of South early North late.The time of activity of the Tan-Lu fault zone is 224~201Ma,162~143Ma,136~71Ma,54 Ma,32~28Ma,13 Ma,8Ma.It can be seen that after the late three ages,the activities of the two movements are basically synchronous.The NW fault is derived from the Tan Lu fault zone.The Late Triassic-Early Jurassic collision between Yangtze Plate and North China Plate formed the Tan-Lu fault zone,and the NW thrust fault formed in the Luxi Block in the mean time.In the middle and Late Jurassic,the Izanaqi plate subducted under the Eurasian plate at high speed,and the strong left-lateral strike-slip activity occurred again in the Tan-Lu fault zone,which led to the normal fault activity of the NW fault in the Luxi Block,as it's R'and T faults.and the Early Cretaceous Izanaqi plate subducted to the Eurasian continent with NNW direction.The Luxi Block is extensional in NE-SW direction,except Ganlin and Nishan fault,the other faults are developed into normal faults.In the Late Cretaceous,there was a left-lateral activity in the Tan-Lu fault zone due to the reduction of the subduction rate of the Pacific Plate,which may have caused the NW faults activity.Due to the left-lateral activity of the Tan-Lu fault zone and the right-lateral activity of the Lan-Liao fault zone,the SW direction tectonic escape occurred in the Luxi Block and the NW normal fault reacted.After the Eocene about 43 Ma,the Pacific Plate NWW subducted under the Eurasian Plate,the Tan-Lu fault occurred dextral strike-slip Neogene,and the NW faults activity of Luxi Block ceased.