南大西洋两岸被动大陆边缘构造分段性特征及其成因探讨

Characteristics and genesis of structural segmentation of the passive continental margins of the South Atlantic

南大西洋两岸被动大陆边缘盆地群是全球油气最富集的地区之一,也是当今世界油气勘探的热点.随着油气勘探的推进,地震及重力、磁法资料不断积累,为两岸构造分段性及盆地群发育规律研究提供了依据.从南大西洋区域构造背景着手,筛选盆地群地球物理与地质剖面,并将地壳尺度与盆地尺度的剖面相结合,沿着洋底转换断裂带编制了4条跨南大西洋两岸盆地的构造长剖面,分别位于南大西洋北部、中部及南部.同一盆地不同尺度的剖面对比表明,板块运动和地壳减薄方式决定了陆架、陆坡结构,控制了盆地发育并使地层发育处于重力作用的背景.4条构造长剖面间的对比直观显示出南大西洋两岸盆地群构造特征的分段性差异,但同时它们又具有相似的构造演化阶段,且两岸盆地具有明显共轭关系.南大西洋由南向北张开,根据主要构造特征,依次形成了3段被动大陆边缘4类盆地即南段岩浆型盆地、中段盐构造型盆地、中段泥构造型盆地、赤道段转换型盆地.

The basin group on the passive continental margins of the South Atlantic is one of the regions with the most abundant oil and gas resources in the world,and it is also a hot spot of oil and gas exploration in the world today.With the advancement of oil and gas exploration,the accumulation of seismic,gravity and magnetic data provides a basis for the study on the structural segmentation and the development law of the basins on the two sides of the South Atlantic.Starting from the tectonic setting of the South Atlantic region,and after screening the geophysical and geological sections of the basin group,and combining the crustal scale with the basin-scale sections,four long structural sections across the basins have been mapped along the transform faults,which are located in the northern,central and southern parts of the South Atlantic.The comparison of the sections at different scales in a same basin shows that plate movement and crustal thinning modes determine the structures of continental shelves and continental slopes,control the development of basins and make the formation development on the background of gravity.The comparison among the four long structural sections shows a segmental difference in the tectonic features of the basins on both sides of the South Atlantic,but they have similar tectonic evolution stages,and the basins on two sides have an obvious conjugate relationship.The South Atlantic is open from south to north,and according to the primary structural features,three segments of passive continental margins and four types of basins are divided,namely the southern magmatic basin,the central salt-structural basin,the central mud-structural basin,and the equatorial transformed basin.