秦岭造山带二叠纪裂谷发育特征及演化

THE FEATURE AND EVOLUTION OF PERMIAN RIFT OFQINLING OROGENIC BELT

秦岭造山带地质历史的发展受华北和扬子两地块相对运动的制约，在二叠纪，由于南北两地块运动速度和旋转方向的变化，导致石炭纪开始的中秦岭裂陷作用更加强烈，形成完整的裂谷系统。裂陷中心位于甘肃岷县梅川至宕昌扎固一带，其两侧出现一系列大致平行的ＮＷ－ＳＥ向构造岩相带，分别代表裂谷斜坡和浅海陆棚沉积。沉积序列和地球化学资料反映了裂陷带海水不断加深和裂陷作用不断加强的过程。生物区系特征表明，裂谷对生物群有一定的隔离作用，古地磁资料亦为华北、扬子两地块的相对运动和中秦岭裂谷的发展演化提供了依据。裂谷活动持续到早三叠世，中三叠世拉丁期受早印支运动影响，中秦岭抬升成陆，裂谷最终消失。

The development of geologic history of Qinling orogenic belt was controlled by the relative motion of North China and Yangtze plates.Owing to changes of movment rate and rotatory direction of the two plates in Permian, Middle Qinling rifting at the beginning of Carboniferous were stronger and formed the rift system.The rift centre was situated in Meichuan, Minxian County to Zhagu, Dongchang area of Gansu Province, by two lateral sides of which there were a series of roughly parallel structure-rock facies belts running about NW-SE. They respectively represent rift slopes and shallow sea sheif.Sedimentary sequence and geochemical material suggest that the water was deeper and deeper and the rifting was stronger and stronger in the rift belt.The feature of biogeography shows that the rift plays the part of separating for fauna. Paleomagnetism data give some evidenoce for relative movment of North China and Yangtze plates and rift evolution of Middle Qinling area.The rift continued to Early Triassic and disappeared in Middle Triassic with finally closing of Qinling Sea resulting form influence of Indo-China movement and colliding of North China and Yangtze Plates.