琼东南盆地岩石圈伸展模拟探讨——以测线1为例

LITHOSPHERIC STRETCHING MODELING OF QIONGDONGNAN BASIN:BASED ON LINE 1

在挠曲悬臂梁模型的基础上,利用二维正、反演相结合的方法,对琼东南盆地近垂直于盆地走向、过陆架、陆坡的测线1岩石圈不同圈层的伸展因子进行计算。其中,上地壳伸展因子是通过统计地震剖面上断层水平伸展量获得,介于1.678~2.238之间;全地壳伸展因子则采用拉伸前后地壳厚度之比的方法,分布在1.251~2.468之间;岩石圈伸展因子利用剖面二维反演回剥和正演伸展模拟得到的,分布在1.062~2.647之间。沿剖面方向不同圈层的伸展因子综合对比分析表明,琼东南盆地岩石圈发生了随深度变化的伸展,但并非简单的随深度增加,而可能与岩石圈不同层次的流变学特征及伸展前岩石圈流变性的不均匀性有关。

In order to better understand the lithospheric extension process of the Qiongdongnan Basin, lithospheric stretching factors were calculated along the Line 1 which across both the continental shelf and slope. Upper-crust stretching factors were calculated by summing heaves measured on seismically imaged faults, varying from 1. 678-2. 238. Whole crust stretching factors changed from 1. 251- 2. 468, derived from crustal-thinning constrained by seismic reflection and gravity inversion. Litho- sphere stretching factors were determined from the combination of the two-dimensional flexural-canti- lever forward and reverse modeling, ranging from 1. 062-2. 647. The results indicate that the depth dependent model is likely optional in the Qiongdongnan Basin. But the stretch factors are not simply increasing with depth, but also related to rheological features and the anisotropy of lithosphere before stretching.