下刚果盆地中段挤压带盐底辟构造形成演化分析--基于物理及离散元模拟

Analysis of Formation and Evolution of Salt Diapir in the Contractional Domain of Central Lower Congo Basin Based on Analogue and Discrete Element Modeling

基于下刚果盆地中段实际地震剖面,结合物理模拟及离散元数值模拟方法,研究西非安哥拉被动大陆边缘下刚果盆地中段挤压带盐底辟构造的成因机制及演化过程,理解被动大陆边缘重力失稳构造的深层驱动机制,分析挤压作用下底辟构造间迷你盆地沉积中心的迁移与底辟作用的关系。结果表明,下刚果盆地中段挤压带的盐底辟构造演化过程与应力条件密不可分,早期主要受重力扩张作用控制,后期受挤压作用控制。依据物理模拟实验、离散元模拟实验结果与实际地震剖面解释结果的对比,可将盐底辟构造的演化过程分为3个阶段:1)早期伸展再活化底辟阶段;2)中期被动底辟阶段;3)晚期挤压主动底辟阶段。盐底辟构造间迷你盆地的沉积中心向同期活动强烈的底辟构造迁移。

Based on the seismic profile,analogue modeling and discrete element modeling method were carried out to study the deep genetic mechanism of the gravity instability structure and evolution process of the salt diapirs in the contractional zone of central Lower Congo Basin in the passive continental margin of Angola in West Africa.The effect of salt diapir activity on the migration of the sedimentary center of the mini-basin between the diapirs was further studied.The results show that the evolution process of salt diapirs in the contractional domain of central Lower Congo Basin is related to the stress conditions.In the early stage,it was mainly controlled by the effect of gravity spreading,and in the later stage,it was controlled by the effect of squeezing.According to the comparison between the results of analogue modeling and discrete element modeling and the seismic sections,the evolution process of salt diapir can be divided into the following three stages:1)The early stage,the extended reactive diapir stage;2)The mid stage,the passive diapir stage;3)The late stage,squeezed active diapir stage.The sedimentary center of the mini-basin between the salt diapirs migrated to the diapirs with strong activities during the same period.