江汉盆地幕式构造运动及其演化特征

对江汉盆地的不整合面、断裂活动和火成岩成因及分布规模的研究表明,江汉盆地在白垩-第三纪时期主要经历了五期较大规模的构造运动,发育五期不整合面,据此将盆地白垩-第三纪的构造演化划分为四个裂陷幕和一个拗陷沉降期五个演化阶段。自老而新各裂陷幕断裂活动主方向表现为自北西向北北东、北东、北东东顺时针有序偏转的特点;岩浆岩由碱性玄武岩变化为石英拉斑玄武岩、再变为以橄榄拉斑为主、最后变为以石英拉斑为主的玄武岩,反映构造演化的幕式特点和断裂活动强弱的变化。沉积中心在不同构造幕发生了明显的变化。在构造I幕时期,盆地中、西部发育3个沉降中心;在构造Ⅱ幕时期,沉降中心位于盆地西南部;在构造Ⅲ幕时期,盆地没有统一的沉降中心;在构造Ⅳ幕时期,沉降中心移至盆地中心。多期构造运动的叠合,形成了盆地内复杂的构造格局。

Episodic tectonic movement and evolutional character in Jianghan basin.

Study of genesis and spreading size of unconformity, fault action and igneous rock in Jianghan basin showed that Jianghan basin went through mainly five large-scale tectonic movements in Cretaceous to Tertiary epoch and developed five un-conformable surface. For that reason, the Cretaceous-Tertiary tectonic movement is divided into four episodic rifting periods and one depression period. The main direction of fault activity for individual episodic rifting sequenced from old to new showed the character of sequential clockwise rotation from NW to NNE, NE and NEE; Igneous rocks changed from alkalin basalt to quartz tholei-ite basalt,then to olivine tholeiite basalt and finally to quartz tholeiite basalt sequentially, which reflects the episodic character of tectonic evolution and the change in power of fault activities. The important variations occurred in depocenters of different tectonic episodes. In the period of tectonic episode I , three deposition centers developed in the west of the basin; in the period of tectonic episode II , the depression center was located in the southwest of the basin; in the period of tectonic episode III , there was no uniform depression center in the basin; in the period of tectonic episode IV, the depression center shifted into the center of the basin, so the complex structural framework has been formed in the basin because of the stack of multiple period of tectonic movements.