CAJ | 학술논문

盆地的形成是深部过程的浅部响应，其中不同尺度拉张因子的变化能够反映岩石圈的伸展特征。运用基于弹性梁模型和挠曲均衡原理的2D构造模拟软件对横穿南海东北部地区的两条地震-地质剖面进行模拟，计算上地壳、全地壳和岩石圈尺度拉张因子。结果表明，南海东北部岩石圈伸展存在横向非均质性和深度相关的伸展现象：(1)不同坳陷中心的拉张因子从陆架-陆坡-海盆区有变大的趋势；(2)三种尺度的拉张因子之间存在明显差异，并且这种岩石圈深度相关的伸展现象在陆架和陆坡地区表现不同：陆架范围内上地壳和全地壳尺度的拉张因子在数值上相近，而在陆坡向洋壳方向，岩石圈、全地壳尺度拉张因子在数值上比上地壳尺度拉张因子大的差别趋势越来越明显。分析认为南海东北部岩石圈深度相关的伸展模式与海底扩张早期温度较高且黏滞性较小的下地壳在陆坡向海盆方向的流动性大于陆架地区有关。南海东北部伸展盆地的形成经历了岩石圈在陆内裂谷阶段均匀伸展以及大陆边缘裂谷阶段深度相关的伸展作用过程。
분지적형성시심부과정적천부향응，기중불동척도랍장인자적변화능구반영암석권적신전특정。운용기우탄성량모형화뇨곡균형원리적2D구조모의연건대횡천남해동북부지구적량조지진-지질부면진행모의，계산상지각、전지각화암석권척도랍장인자。결과표명，남해동북부암석권신전존재횡향비균질성화심도상관적신전현상：(1)불동요함중심적랍장인자종륙가-륙파-해분구유변대적추세；(2)삼충척도적랍장인자지간존재명현차이，병차저충암석권심도상관적신전현상재륙가화륙파지구표현불동：륙가범위내상지각화전지각척도적랍장인자재수치상상근，이재륙파향양각방향，암석권、전지각척도랍장인자재수치상비상지각척도랍장인자대적차별추세월래월명현。분석인위남해동북부암석권심도상관적신전모식여해저확장조기온도교고차점체성교소적하지각재륙파향해분방향적류동성대우륙가지구유관。남해동북부신전분지적형성경력료암석권재륙내렬곡계단균균신전이급대륙변연렬곡계단심도상관적신전작용과정。
The formation of basin is the shallow response of the deep geological process, of which different scales of extension factors can reflect the characters of lithospheric extension. 2D structural simulation softwares based on the flexure isostasy model and flexural cantilever mode were utilized to model two interpreted seismic profiles across the northeastern South China Sea. The calculated extension factors of the upper crust, whole crust and lithosphere indicate the lateral heterogeneity and depth-dependence of lithospheric extension in the northeastern South China Sea. (1) The extension factors gradually increase from uplift zone to depression, and the centers of which demonstrate an increasing tendency southward from the shelf, to slope, and to deep sea basin area. (2) Three scales of extension factors are significantly different from each other. (3) The depth-dependence of lithospheric extension varies is vary from the shelf to the slope area:the differences between the upper crust and whole crust in the slope area are more obvious than that in the shelf zone. We infer that the differentiated lithospheric extension process is result from the differentiated flowing of the lower crust between the shelf and the slope area during the early sea-floor spreading period, where the lower crust is characterized by high temperature and lower viscosity. The extension basins in the northeastern South China Sea have experienced the uniform lithospheric stretching in the stage of intracontinental rift, and the depth-dependence of lithospheric stretching in the stage of continental margin rift. They become more complex because of the presumable anomalous post-rifting subsidence and the remnant Mesozoic subducted oceanic lithosphere.