西非下刚果盆地、加蓬盆地裂陷期构造特征对比研究

Comparison of structural characters in rifting stage between Lower Congo Basin and Gabon Basin in West Africa

为研究下刚果盆地和加蓬盆地盐下构造特征的差异性,指导其盐下勘探,通过不同构造位置的地震、地质剖面分析,对比两盆地裂陷期构造特征的异同。研究结果表明两者均经历了裂谷期、过渡期和漂移期三大构造演化阶段。在裂陷期,两者构造格局相同,但构造规模和隆坳格局有一定的差异性。下刚果盆地内裂谷盆地隆坳特征更为明显,加蓬盆地外裂谷盆地隆坳格局更加清楚。裂陷期的有利勘探区带,下刚果盆地主要集中在内裂谷盆地,加蓬盆地则主要集中在外裂谷盆地。裂谷作用的起始时间、转换断层和基底性质差异可能是造成两者异同的主要原因。

The structural characteristics of the Lower Congo and Gabon basins in rifting stage are analyzed based on the interpretation of the seismic and geological profiles to compare the pre-salt structures between two basins and to guide the pre-salt exploration. The results show that both basins experienced three stages of tectonic evolution: rifting period, transitional period and drifting period. In the rifting stage, the two basins have the same structural framework, but the structural scale and patterns of uplift-depression are different. In the Lower Congo Basin, the depression-uplift structure is more obvious in the inner rift-basins, while in Gabon Basin, it is more explicit in outer rift-basins. So in Lower Congo Basin, the favorable exploration area may be in inner rift-basins and in Gabon basin the exploration potential may be in outer rift-basins. The differences in starting time of the rift, the transform faults and the characters of the basement may be the reasons leading to the differentiation between the two basins in rifting period.