东北地区拉布达林盆地的构造特征及早白垩世变形序列

Structural Features and Lower Cretaceous Deformation Sequence of Labudalin Basin in Northeast China

拉布达林盆地为内蒙—大兴安岭古生代碰撞造山带之上的中生代断陷盆地,主要发育下白垩统和第四系。拉布达林盆地的构造特征复杂,主要发育NE向、NEE向和NW向构造,其中NE向构造主要为一系列NE向犁式正断层及其与之相伴的同向正断层组合,NEE向构造具有剪切正断层的性质,NE向和NEE向断层都是形成于塔木兰沟组—伊列克得组沉积时期的控陷断层,它们是形成于同一应力场具有不同力学性质的构造。NW向断层形成较晚,切割了NE向和NEE向断层,具有左行走滑的特征。在大磨拐河组沉积时期经历了较大规模的挤压作用,不仅使部分早期NE向控陷正断层发生正反转作用,而且形成断层转折褶皱和断层传播褶皱。依据反射地震资料及相关地质资料,确定拉布达林盆地在早白垩世经历了3期变形作用,即塔木兰沟组—伊列克得组沉积时期的NW-SE向的伸展作用、大磨拐河组沉积时期的NW-SE向挤压作用和伊敏组沉积时期的近EW向伸展作用。

The Labudalin basin is a Mesozoic unsymmetrical fauh depression basin located in the Paleozoic orogenic belt in Inner Mongolia-Da Hinggan Ling area. The Lower Cretaceous and Quaternary depositional systems are well developed in the basin. Structural features of Labudalin basin are very complex. There are three groups of structures in NE direction, NEE direction and NW direction, respectively. The NE-trending structures are mainly a series of listric normal faults and associated normal faults in the same direction. The NEE-trending structures are shear-normal faults. The NE- and NEE-trending faults were formed in the same stress field during the depositional periods of Tamulangou Formation-Yiliekede Formation and have different characteristics. The NW-trending faults are late sinistral strike-slip normal faults cutting the NE- and NEE-trending faults. The Labudalin basin experienced three times of deformation during the Lower Cretaceous： （1） The NW-NE extension from the Tamulangou Formation depositional period to the Yiliekede Formation depositional period; （2） The NW-NE compression in the Damoguaihe Formation depositional period; （3） The nearly EW extension in the Yimin Formation depositional period.