中非Doba盆地反转构造特征及成因机制

Inversion structural characteristics and genetic mechanism of Doba Basin in Central Africa

为了查明中非裂谷系伸展盆地反转构造特征及形成机制,结合中非裂谷系区域构造背景,以Doba盆地地震资料为基础,优选典型剖面进行断裂解释,定量计算生长断层在不同时期的反转率,并恢复盆地的构造演化过程,基于地幔对流理论对盆地反转构造成因进行探讨。结果表明,Doba盆地是多期次叠加型伸展反转盆地,盆内反转构造类型分为单断型、双断型和复合“Y”字型,并以断层上盘发育的掀斜断块、反转背斜、断背斜为其主要构造表现形式。Doba盆地在早白垩世阿尔布期和晚白垩世桑顿期反转作用较强,渐新世末期较弱,高反转率区域为中央坳陷。Doba盆地的构造演化分为7个阶段,早白垩世贝利阿斯期阿普特期裂陷作用最强,晚白垩世桑顿期反转作用最强。地幔对流反转是Doba盆地形成3期叠加裂陷反转构造的主控因素。

In order to find out the inversion structural characteristics and formation mechanism of the extensionalbasins in the Central African rift system,combined with the regional tectonic background of the Central African rift system,based on the seismic data of the Doba Basin,the typical profiles were selected for fault interpretation,and the inversion rates of the growth fault in different periods were quantitatively calculated.The tectonic evolution process of the basin was restored,and the genesis of the inversion structure of the basin was discussed based on the mantle convection theory.The results show that Doba Basin is a multistage superimposed extensional inversion basin,the inversion structures in the basin can be divided into single fault type,double fault type and compound“Y”type,and the main structural manifestations are the tilted fault block,inversion anticline and fault anticline developed in the upper wall of the fault.The inversion of Doba Basin is strong in the Early Cretaceous Albian period and Late Cretaceous Santonian period,but weak in the Late Oligocene,and the region with high inversion rate is the central depression.The tectonicevolution of Doba Basin can be divided into seven stages,with the strongest rifting during the Berriasian-Aptian in the Early Cretaceous and the strongest inversion during the Santonian in the Late Cretaceous.Mantle convective inversion is the main controlling factor for the formation of three-stage superimposed rift-inversion structure in Doba Basin.