Study On Fault Structure Characteristics Of Tumenjiang Drainage Area Since The Late Mesozoic

The Tumenjiang Drainage Area is located at the junction of China,Russia and North Korea in northeast China,at the junction of the eastern section of the northern margin of North China and the Ji-hei Fold Orogenic Belt,and the overlap of the paleoAsian tectonic domain and the coastal Pacific tectonic domain.The geological structure of this area is complex,which has been widely concerned by scholars at home and abroad.At present,the research on the deformation characteristics,kinematics characteristics,tectonic stress field and evolution law of fault structures in Tumenjiang Drainage Area is weak.This paper focuses on the geometry,kinematics and dynamics of the fault zone in the Tumenjiang Drainage Area,and investigates the structural traces of each fault zone in the field.observe and record the occurrence of a large number of ductile-brittle deformation structures(such as faults,joints,cleavage zones,etc.).The nature and scale,deformation characteristics,neotectonic movement,tectonic stress field and tectonic evolution of each fault zone are discussed.The ductile-brittle deformation structure in the Tumen River basin is mainly formed in the development stage of the foreshore-Pacific tectonic domain,in which NW-trending and NE-trending faults are the most developed,and the scale of faults is larger and mostly formed in the transition stage of the two major tectonic domains.the second is near SN and near EW faults.Most of the NW-trending faults were formed from the end of the late Mesozoic Triassic to the early Cretaceous,which are mainly characterized by thrust and left-lateral translation.Longjing-Baogelazi fault also developed normal fault structures in Yanji basin.The NE-trending faults represented by Dunhua-Mishan faults were mostly formed in the early Mesozoic Triassic,with large scale and multi-stage activity,thrusting in the early stage,strike-slip pull-apart and faulted basins formed in the late stage under the influence of plate subduction,the Cenozoic tectonic inversion and thrusting again,and fault slime can be seen in the fault zone.The near E-W-trending faults include not only the revival of paleo-faults before the late Mesozoic,but also the new faults formed by tectonic uplift in the Cenozoic,while most of the S-N-trending faults were formed in the stress extension stage of the early Cretaceous and experienced the process of changing from normal fault to sinistral thrusting.Since the study area entered the development stage of the foreshore-Pacific tectonic domain,the paleotectonic stress field has at least three stages of transformation,that is,from early Jurassic to Middle Jurassic,from early Jurassic to early late Cretaceous,from early late Jurassic to early late Cretaceous,it is dominated by NW-SE extensional stress.From late Cretaceous to Paleogene,the tectonic stress field returned to the compressional state of NW-SE direction again,and the compressional stress of NEE-SWW direction may have been derived locally.During the neotectonic period,the tectonic stress field changed from horizontal compressional stress to vertical stress,and most of the fault activities were inherited and distributed intermittently along paleofaults.The modern tectonic stress field is mainly compressed in the direction of nearly E-W,and the activity is weak.In recent years,most of the earthquakes are deep earthquakes.In this paper,the evolution of the Tumenjiang Drainage Area since the late Mesozoic is roughly divided into five stages.That is,the tectonic domain transformation stage from late Triassic to early early Jurassic,the intense compression stage from late early Jurassic to late Middle Jurassic,the transformation and extension stage from early late Jurassic to early late Cretaceous,the positive inversion stage from late Cretaceous to Paleogene and the neotectonic movement stage from Neogene to now.