【摘要】 地壳或岩石圈尺度内伸展因子随深度变化特征对于理解岩石圈演化有重要的指示意义.我们利用南海北部大陆边缘琼东南盆地区深反射地震剖面的地壳分层模型,计算了沿剖面上地壳与全地壳的伸展因子.结果表明:琼东南盆地区具有明显的地壳尺度内伸展的深度相关性(上地壳尺度伸展因子变化范围为1.0～2.0,全地壳尺度的伸展因子变化范围为1.2～2.5);琼东南盆地各构造单元内的上地壳与全地壳伸展具有明显的非均一性(长昌凹陷上地壳尺度伸展最大,乐东陵水凹陷其次,松南—宝岛凹陷最小;长昌凹陷和松南宝岛凹陷的地壳尺度伸展因子较乐东陵水凹陷大)与各向异性(南东北西剖面较之北东南西向剖面地壳伸展因子大).这些结果预示着琼东南盆地区地壳伸展优势方向为北西向,盆地区东四部的伸展过程或伸展机制可能差异较大拟或存在太平洋岩石圈俯冲角空间差异或地幔岩浆产出时空差异.结合研究区相关研究成果,推断地壳伸展因子的深度相关性可能是共轭大陆边缘低角度拆离控制的简单剪切系统内伴随地幔挤出的动力学现象.更多还原

【Abstract】 The depth-dependence of crustal extension factor is considered as an important indicator to understand lithosphere evolution.We used the crustal layering model to estimate extension factors both of upper crust and whole crust along the deep seismic profiles carried out in the Qiongdongnan basin areas, northern continental margin, South China Sea.The results demonstrate the obvious depth-dependence of extension factor within crust (the factor ranges within 1.0～2.0 for the upper crust and 1.2～2.5 for the whole crust);the spatially lateral heterogeneity of crustal extension factors and anisotropy (the extension factors in NW-SE larger than in NE-SW indicating the dominant extension direction of NW).These results suggest the predominating extension direction in the northern continental margin of South China Sea and different extension processes occurred in the western and eastern portions of the studied area and/ or different mechanisms controlling the extension.Integrating the related geological, geophysical and geochemistry dataset, we infer that the depth-dependence of crustal extension factor and probably simultaneous occurrence of mantle exhumation are resulted from large-scale lithosphere extension in South China controlled by low-angle detachment as simple-shear model.更多还原