南海西部晚渐新世主要断裂活动特征及与红河断裂之关系

南海的形成演化是众多被动型边缘海中最复杂的,而南海西部的断裂带构造活动特征又是南海中最复杂的构造之一。本文针对前人提出的红河断裂带出莺歌海盆地后的东延、南延以及东南延问题,通过晚渐新世-早中新世琼东南盆地受到南北向挤压的区域应力场分析,认为这期的应力主要来自南海西部近南北向断裂带的右旋剪切活动,结合红河断裂带的构造运动特征,提出晚渐新世末南海西部发生断裂构造置换,红河断裂带17°30′N以南近SN走向部分被南海西缘断裂带所置换,并且构造活动特征与北部红河断裂带明显不同,南海西部晚渐新世前后两个时期不同的断裂构造活动特征反映了印度板块与欧亚板块碰撞造成的两种不同影响效应。

RELATIONSHIP ON THE MOVEMENT CHARACTERISTICS OF THE MAIN FAULT AND RED RIVER FAULT IN WESTERN SOUTH CHINA SEA AT LATE OLIGOCENE

Among numerous passive marginal seas,the South China Sea is one of the most complicated in formation and evolution processes,especially the activity characteristics of the structural belt in the western South China Sea.According to the latest interpretation of seismic profile and the analysis on the regional compressive stress field which controlled the Southeast Hainan basin from late Oligocene to Miocene,the author points out that the existed views that Red River Fault Zone elongated eastward,southward and southeastward after extending out of Yinggehai basin has much contradictory.In addition,in combination with characteristics of tectonic movement of the Red River Fault Zone,we argue that the strain of this stage was caused by the dextral shearing of the S-N direction fault zone in the west of South China Sea,where fault structure replacement took place in the late Oligocene,and the S-N direction segment of the Red River Fault Zone south of 17°30'N was partly replaced by the structural fracture belt of western South China Sea,which was of evidently difference in characteristics of tectonic movement compared with the Red River Fault Zone.Two effectors of the collision between India plate and Eurasia plate are reflected by the fault structure movement in western South China Sea at the two periods,that is,before the Late Oligocene,its main effect is to the west of the west fault zone of the South China Sea,resulting in Indo-China peninsula southward extrusion;after the Late Oligocene,its main effect derived from the west of the west fault zone of the South China Sea,performance of the mainland mantle material creeping south-easterly direction.