长乐-南澳韧性剪切带走滑特征探讨

THE STRIKE-SLIP MOVEMENT OF THE CHANGLE-NAN'AO DUCTILE SHEAR ZONE, SOUTHEASTERN CHINA

长乐-南澳韧性剪切带可能是在碰撞造山缝合带基础上发育的,其走滑特性严格受闽台微大陆与闽浙中生代火山弧碰撞过程中碰撞动力学的制约。岩石韧性组构和糜棱岩变形的微构造研究表明,碰撞前期走滑为左行。在早垩世晚期(100-120Ma)的主碰撞期和以伸展作用为主的碰撞后期,该带以右行为主,这种右行走滑一直持续至今。发育韧性剪切带的闽台微大陆(或称平潭-东山带)原始位置可能比现今更靠南,这是属于几百公里的漂移位移而不是剪切位移。

The Changle-Nan'ao ductile shear zone might develop from the collision suture zone. The strike-slip movement was strictly controlled by dynamics of collision between the Fujian-Taiwan microcontinent and the Fujian-Zhejiang Mesozoic volcanic arc. Analyses of the ductile fabrics and mylonitic microstructure suggest that strike - slip was sinistral in the early stage of collision. It became dominantly dextral in the late Early Cretaceous main-collision stage (120 - 100 Ma B. P. ). The dextral strike-slip movement continue in the late collision stage with extension as the dominant process and even up to now. The Fujian-Taiwan microcontinent (or called the Pingtan-Dongshan belt) where the ductile shear zone developed might be originally located to the south of the present position, which was altributed to a few hundred kilometers of drift rather than shear displacement.