秦岭—大别造山带北部中新生代逆冲推覆构造期次及时空迁移规律

秦岭—大别造山带北部中新生代逆冲推覆作用可分出5个期次:印支期(T2-T3)、燕山早期(J2末-J3)、燕山晚期(K1末)、燕山末期(K2末)和喜马拉雅早期(E末)。本区中-新生代逆冲推覆构造具有明显的时空迁移特征,主要体现在同一期次断裂在不同区域内规模和强度明显不同,并具有穿时迁移演化特征;不同期次断裂在规模和强度及其地球动力学机制上也明显不同。印支期逆冲推覆构造具有东强西弱、东断西褶的构造迁移规律;燕山早期具有由东向西由早到晚穿时迁移演化特征;燕山晚期和燕山末期具有东弱西强的构造特征。前4期逆冲推覆构造规模和强度大,而古近纪末期规模和强度相对较小。前3期具有从南向北规模和强度递减的趋势,后2期表现出北强南弱特征。反映出中生代造山作用由早到晚、由东向西、由南向北的时空变化规律。中生代逆冲推覆构造是在扬子、华北两板块由东向西呈剪刀差式穿时碰撞、陆内俯冲断离和山脉隆升与伸展坍塌的地球动力学背景下形成的。古近纪末期逆冲构造形成机制与印度板块向欧亚板块之下俯冲的远程效应有关。

EPOCHS AND SPACE-TIME MIGRATING OF MESO-CENOZOIC THRUST-NAPPE TECTONICS IN THE NORTH QINLING-DABIE OROGEN

The Meso-Cenozoic thrust-nappe tectonics in north part of the Qinling-Dabie orogen could be divided into five epochs,namely,Indosinian (T₂-T₃),Early Yanshanian (the last stage of J₂-J₃),Late Yanshanian (the last stage of K₁),Terminal Yanshanian (the last stage of K₂) and Early Himalayaian (the last stage of E) ones.The Meso-Cenozoic thrust-nappe tectonics in the area had an outstanding feature of space-time migration,which mainly embodied that the faults in the same epoch were obviously varied in scale and strength in varied regions and had a feature of diachronous migration evolution.The faults in varied epochs were clearly varied in scale,strength and geodynamic mechanism.The thrust-nappe tectonics in Indosinian epoch had a regularity of tectonic transport which was stronger in the east,weakened in the west,faulted in the east and folded in the west.The Early Yanshanian thrusting had a feature of diachronous migration evolution from the early period to the late period and from the east to the west.The Late and Terminal Yanshanian thrustings had tectonic feature which was weakened in the east and stronger in the west.The thrustings in the former four epochs were stronger in strength and larger in scale,but the scale and strength of thrust nappe tectonics in the Paleogene were weakened.The former three epochs had a tendency of progressive decreasing in scale and strength from the south to the north,but the latter two epochs were stronger in the north and weakened in the south,which showed that the Mesozoic orogeny had space time migration from the early period to the late period,from the east to the west,or from the south to the north.The Meso-Cenozoic thrust-nappe tectonics formed in a geodynamic background of diachronous collision between the Yangtze and the North China plates from the east to the west,and subduction and break-off of subducted plate in the intracontinent and mountains uplifting,extension and collapse.The formation mechanism of thrust tectonics in the Paleogene was supposed to be related to a far-field effect caused by collision between the Indian and the Eurasian plates.