缅甸Sagaing走滑断裂及对睡宝盆地构造演化的控制和影响

Evolution of the Sagaing Strike-slip Fault and Its Control of Shwebo Basin Structural Evolution,Myanmar

在研究Sagaing走滑断裂的形成和发展的基础上将其分为2个阶段:第一阶段古新世—早始新世洋陆俯冲造成了缅甸板块与欧亚板块的分离,使缅甸板块加速向北漂移,Sagaing断裂开始形成;第二阶段始新世以来发生陆陆俯冲,印度板块的北东部首次开始碰撞缅甸板块。这次A型俯冲使得缅甸板块沿Sagaing走滑断裂向北继续漂移,最大的右行走滑位移达450 km。在Sagaing走滑断裂的控制下,睡宝盆地亦呈现2期构造特征:中新世,缅甸盆地内经历拉张和断裂,安德曼海(Andaman)打开,并且弧后扩张中心向南迁移,睡宝盆地即呈现拉张的构造环境;上新世—更新世,由于缅甸板块向北运动碰撞到亚洲板块的喜马拉雅断裂,受到阻挡,构造反转。睡宝盆地受挤压和扭压导致一系列的逆断层、花状构造,最终形成以南北向右行走滑为主、叠加东西向扭压的应力背景。

The formation and development of the Sagaing strip-slip fault can be classified into two main stages.The first stage is from Paleocene to Early Eocene,and oceanic plate subduction occurred along the west edge of the Burma plate.Paleocene oblique subduction has detached the Burma plate from the Eurasian plate,and the Sagaing fault began forming.The second stage is during Eocene,and the northeastern Indian and Burma plates collided,resulting in the coupling of these two plates and also accelerating the northward movement of the Burma plate along the Sagaing strip-slip.The dextral strike-slip displacement distance of Sagaing fault is up to 450 km.Controlled by the evolution of Sagaing fault,the Shwebo subbasin presents two stages of structural features.During Miocene,the Burma basin was in tensional stress,the Andaman Sea opened,back-arc spreading center drove to south because of the India coupling with western Myanmar.From Early Pliocene to Pleistocene,collision of the Burma plate and Himalayan resulted in southwest-northeast transpressional forces that produced reverse faults.Therefore,by squeezing and twist-compression of the Shwebo subbasin a series of reverse faults and ＂flower＂ structures are developed,and ultimately in south-north trend Sagaing dextral strike-slip compression stress and west-east trend transpressional environment formed.