基底非均一性对琼东南盆地新生代构造变形差异的影响: 来自物理模拟实验的启示

琼东南盆地位于南海北部大陆边缘西北部，是新生代形成的北东向伸展盆地，其断裂走向、次级凹陷分布方向、构造样式等在东西部表现出明显差异。文章采用构造解析与构造物理模拟相结合的方式，探究先存的中生代构造几何形态及基底性质差异对琼东南盆地东西部构造差异性演化的控制作用。实验结果表明：（1）先存构造薄弱带几何边界分布方向与区域伸展方向共同控制了琼东南盆地主要断裂的走向以及断裂构造样式。由于先存构造薄弱带边界方向存在东西差异，在早期NW向拉伸阶段（Tg-T80）盆地断裂系统在东西部就已表现出明显的分段特征。西部由于垂向拉伸产生一组NEE向断裂；东部由于斜向拉伸，发育至少两组方向的断裂，一组与应力方向垂直（NEE向），另一组沿着构造薄弱带分布（WE向）。后期断裂活动继承和改造了这一时期的断裂，使断裂系统更加复杂。先存构造薄弱带几何形态变化是导致琼东南盆地东西部构造差异性发育的主控因素。（2）基底强度差异性对上覆构造的断裂数量以及地貌起伏特征有一定影响。琼东南盆地在东西部的断裂走向及构造样式上的差异性受基底强弱、先存构造形态及构造应力方向的共同控制。

The Influence of Basement Heterogeneity on Cenozoic TectonicDeformation Difference in Qiongdongnan Basin : Insights from Analogue Models

Qiongdongnan Basin, located in the northwest of the northern continental margin of the South China Sea, is a NNE extensional basin formed in the Cenozoic era. The fault trend, distribution direction of secondary depressions and tectonic styles show obvious differences between the eastern and the western zones. In this work, the influence of the orientation of the preexisting structure and basement properties of the Mesozoic structures on the tectonic evolution of Qiongdongnan basin is discussed by using physical simulation experiments. The experimental results indicate that:（1）the pre-existing structural orientation and the regional extension direction jointly control the fault strikes and structural styles of the rift basin. As a result, the fault system of Qiongdongnan Basin shows segmentation between the western and eastern zones. The differences of fault systems between the western and eastern zone have been formed during the first-rift stage（Tg-T80）, while the later fault systems inherited and reformed from the first-rift stage. The pre-existing structure is the main controlling factor leading to the differential development of the eastern and western structures in the Qiongdongnan Basin. （2）the difference of basement strength has a great influence on the number of faults and the characteristics of topographical relief. The tectonic differential evolution between the eastern and western zones of Qiongdongnan Basin controlled by the basement strength, pre-existing structural orientation and stress direction.