珠江口盆地珠一坳陷裂后期断裂作用：迁移、转换及其动力学
Post-Rift Faulting Migration, Transition and Dynamics in Zhu Ⅰ Depression, Pearl River Mouth Basin

珠江口盆地裂后期断裂作用对新近系油气成藏具有重要影响，但人们对其发育特征及动力学演化规律的认识一直不够.利用钻井约束的高精度三维及二维地震资料对珠一坳陷裂后期断裂的几何学与运动学特征进行了分析，结果表明珠一坳陷裂后期存在南海期和东沙期两期断裂作用，从南海期断裂作用到东沙期断裂作用，断裂的几何学、运动学特征以及动力学机制均发生了转换.南海期断裂作用具有从南向北迁移的特征；而东沙期断裂具有由东向西迁移的特征.两期断裂都以伸展为主，其中东沙期断裂具有微弱扭性特征.南海期断裂区域伸展方向为NNE10°～15°，东沙期为NNE20°～25°，区域伸展方向发生了5°～10°的顺时针偏转.南海期断裂作用发生于南海同扩张期，可能与南海扩张期间北部陆缘残留的伸展作用有关.东沙期断裂作用形成于南海后扩张期的东沙运动，该时期区域主应力轴σ2方向与吕宋岛弧和欧亚大陆的挤压碰撞方向一致.东沙期断裂特征进一步证实了东沙运动是中中新世以来吕宋岛弧与欧亚大陆碰撞的结果.研究结果对整个南海地区裂后期南海运动与东沙运动的进一步认识具有重要意义.
Post-rift fault plays an important role in hydrocarbon accumulation of the Neogene in Pearl River Mouth basin, but understanding of the features and dynamics evolution is to be enhanced in this paper, post-rift fault system in Zhu Ⅰ depression is studied by geometric and kinematic analysis methods using high quality 3D seismic reflection data. The analysis reveals two episodes of faulting in the post-rift stage, namely, Nanhai-phase faulting and Dongsha-phase faulting. Transition of fault geometry and kinematics from Nanhai-phase to Dongsha-phase indicates a change of dynamics. Both Nanhai-phase faulting and Dongsha-phase faulting have migration. The former migrates from south to north, and the latter migrates from east to west. The two periods of faulting are both extensional faults, with a slight component of shear in Dongsha-phase. Regional extensional direction transforms from NNE10°-15° in Nanhai-phase faulting to NNE20°-25° in Dongsha-phase faulting, with 5°-10° clockwise rotation. The Nanhai-phase faulting is related to the remaining extension in the northern margin of SCS. The Dongsha-phase faults formed after the cease of the sea-floor spreading of SCS. Coincidently, direction of the regional intermediate principal strain (σ2) during the Dongsha-phase faulting is consistent with the collision direction between the Luzon arc and the Eurasian plate. This feature of the Dongsha-phase faulting in Zhu Ⅰ depression confirms the conclusion that Dongsha movement is the result of the collision between the Luzon arc and the Eurasian plate since Middle Miocene. This study is significant for better understanding of Nanhai movement and Dongsha movement