斜向聚合及弧后伸展作用对中国台湾北部-琉球地区的构造影响——砂箱模型实验的启示

Oblique Convergence and Back-arc Extension in China Northern Taiwan–Ryukyu Area:Insights from Sandbox Modeling

中国台湾造山带位于欧亚板块和菲律宾海板块交界处,由于两板块斜向聚合作用,使得中国台湾造山带构造极其复杂并具有分段性:南部尚处于碰撞造山初期,而北部已处于碰撞后期,构造环境已从挤压转变为张裂。前人利用三维砂箱模型对造山带进行研究时,主要关注于斜向聚合作用对造山带的影响,较少考虑到冲绳海槽张裂作用。本文在前人基础上通过添加砂纸带机器模拟张裂作用,探讨挤压-张裂同时作用下砂体的变形模式,解释中国台湾造山带北部—琉球地区的构造现象。通过分析实验图像和粒子图像测量(PIV)数据,并与地震剖面、GPS速度场测量和古地磁数据进行对比后认为:中国台湾岛北部顺时针旋转主要与斜向汇聚作用有关;宜兰平原东西至东北—西南向的运动,及南北有别的运动模式主要与冲绳海槽张裂作用有关;琉球地区形貌主要受控于俯冲的菲律宾海板块形状,在斜向聚合作用下造成地层褶皱和挤压。之后在由东向西发展的弧后伸展作用下,形成冲绳海槽东宽西窄的凹陷区及一系列正断层,并伴随琉球岛弧的顺时针旋转。

The complex and segmented China Taiwan orogenic belt is located on the convergent boundary between the Eurasian Plate and the Philippine Sea Plate.The southern part of the orogen is in the early stages of collision,while the northern part is in the last stage due to the oblique convergence,with the changing of tectonic setting from compression to extension.Previous studies of sandbox modeling in China Taiwan are more concentrated on the effect of arc-continent collision and basement high but only a few noted the effect of the opening of Okinawa Trough.Our 3D experiments aim to better understand the structure and tectonic evolution of the China northern Taiwan–Ryukyu area by adding a sandpaper machine composed of motor,bearing,and sandpaper that could move freely during the experiment to simulate the opening of the Okinawa Trough.By analyzing experimental images and Particle Image Velocimetry(PIV),and comparing it with seismic profiles,GPS,and paleomagnetic data,the results show that clockwise rotation of China northern Taiwan is mainly related to the oblique convergence.The opposite movement of the Philippine Sea Plate and the different movement patterns between north and south of Ilan plain are mainly related to the opening of Okinawa Trough.The morphology of Ryukyu area is mainly controlled by the shape of the subducted Philippine Sea Plate,which also causes strata fold.The Okinawa Trough opens from east to west causing the clockwise rotation of the Ryukyu arc,which also leads the west to be narrower than the east.