大庆长垣构造演化特征及对砂岩型铀矿成矿的控制作用

Tectonic Evolution and Control Effect on Sandstone-Type Uranium Mineralization in Changqi Placantieline

大庆长垣的形成主要受三个构造期次的影响,即早白垩世嫩江组末期、晚白垩世明水组末期和早第三纪末期。三个构造运动期分别呈现了隆起雏型、形成大庆长垣的整体背斜及背斜整体隆升加高并遭受剥蚀形成剥蚀天窗。该构造运动造就了该区多个有利铀成矿条件,一是使背斜顶部遭受剥蚀形成的构造天窗,有利于含铀含氧水渗入地下岩层;二是改变了地层产状,使地下水从滞流状态变为循环状态;三是改善了地层和岩石的物理性质,增加了岩层的渗透性;四是产生了新断裂或激活了早期断层,是深部还原性烃类流体上升的通道。因此,大庆长垣东西两翼应是寻找铀矿的有利部位,其中东翼更为有利。

The formation of Daqing Placantieline was controlled by three tectonic episodes, i.e. the end of Nen- jiang Formation in Early Cretaceous and the end of Mingshui Formation in late Cretaceous as well as the end of early Tertiary Period. These three tectonic episodes present diversified geological feature including uplift proto- type, overall anticline and denudation window formed by anticline uplift and erosion. The tectonic movements re- suited in several favorable conditions for uranium mineralization： 1 ） the top of anticline denuded by tectonic movements and formation of denudation window. Denudation window is helpful for uranium-oxygen water flowing into underground rock formations; 2） tectonic movements altered the attitude of stratum so that groundwater con- verted from stagnant state to circulatory state; 3 ） tectonic movements improved the physical properties and in- creased permeability of the rock; 4） tectonic movements produced new faults or activated the early faults, which are the pathways of deep reducing hydrocarbon fluids lifting up. Therefore, the east and west limbs of Daqing Pla- cantieline should be the favorable parts for exploring the uranium, the eastern part of Daqing Placanticline is more advantageous.