莺歌海盆地构造演化与强烈沉降机制的分析和模拟

The Analysis and Analogue Modeling of the Tectonic Evolution and Strong Subsidence in the Yinggehai Basin

莺歌海盆地新生代发生了快速沉降,盆内充填了最厚达17km的沉积,根据模拟实验,印支地块或之上刚性地块的存在对莺歌海盆地的强烈沉降具有重要的贡献,可能是造成莺歌海盆地裂陷期强烈沉降的重要原因之一.结合地质分析和物理模拟实验,莺歌海盆地的演化大致可以分为以下4个主要阶段:早期(42Ma以前)主要受到南海北部陆缘(主要是北部湾盆地)裂解造成的右旋转换伸展作用的影响,但影响范围较小,主要为莺歌海盆地西北部和东部边界.42～21Ma期间,主要受控于印支地块左行走滑和顺时针旋转作用的影响,莺歌海盆地在此期间发育了主体裂陷体系,东侧受到右旋转换伸展应力场的叠加影响而导致沉降加强;21～10.4Ma期间,受印支地块逐渐减弱直至停止的左行走滑作用的影响,盆地西北部在21～15.5Ma期间发生局部反转褶皱,但盆地整体进入以热沉降为主的时期;10.4Ma以后,盆地受华南地块沿红河断裂右旋走滑作用和5Ma以后新一期热事件的影响.

During Eocene period, rapid subsidence occurred in the Yinggehai basin where more than 17 km of sedimentary cover has been accumulated. According to the analogue modeling experiments, the rigid massif on the Indochina block could be one of the most important factors contributing to the strong subsidence and high sedimentation rate of the basin. Combined the geological analysis with analogue modeling experiments, the evolution of the Yinggehai basin could be divided into four main stages： （1） Before 42 Ma, controlled by the southeastward extension of the Beibu Gulf basin on the northern continental margin, the Yinggehai basin experienced dextral pull-apart. Bounded by NS-trending Yingxi fault, the transtensional areas mainly are the northwest part and along the eastern boundary of the basin. （2） From 42 to 21 Ma, the development of the main rift body in Yinggehai basin was mainly controlled by the southward slip and clockwise rotation of the Indochina block along the Red River fault zone, and the sedimentation was strengthened due to the sinistral transtension. In the east, the subsidence is deepened due to the dextral transtension. （3） From 21 to 10. 4 Ma, the sinistral movement of the Indochina block slowed down to still. From 21 to 15.5 Ma, the northwest part of the basin began to inverse locally because of post-rift thermal subsidence of the whole basin. （4） From 10. 4 Ma to present, the basin was affected by the dextral movement of the South China block along the Red River fault zone and thermal accident in a new phase at 5Ma.