内蒙古西胡里吐盆地构造-水文地质演化与砂岩型铀成矿作用

西胡里吐盆地为一个早白垩世断陷盆地,受沉积后断裂错动的影响而裂解为3个次级亚盆地。在断裂的导通作用下,盆地发育完整的地下水补给、径流、排泄体系,构成了明显的水文地质分区和不同的水文地球化学环境,为铀的迁移与富集成矿创造了良好条件。盆地构造水文地质演化经历了断陷成盆期的开放旋回、沉积与成岩作用期的封闭旋回和后生改造期的径流旋回等3个阶段。其中,后生改造期的径流型古水文地质演化阶段是砂岩型铀成矿作用的主要时期。

Tectonic and hydrogeological evolution and its relation to sandstone-type uranium ore- formation in Xihulitu basin, Inner Mongolia

The Xihulitu basin is an Early Cretaceous down-faulted basin.It was disintegrated into three sub-basins(blocks) by the post-depositional fault displacement.Owing to the connection resulting from the fault structure,a complete groundwater recharge-run off-discharge system was developed leading to the formation of apparent hydrogeologic zonation and different geochemical environments,and creating favourable conditions for the uranium migration,concentration and ore-formation.The tectonic-hydrogeologic evolution of the basin includes the following three stages:(1)the open cycle of down-faulted basin formation;(2)the close cycle sedimentation and diagenesis,and (3) the run-off cycle of epigenetic reworking.Of them,the paleohydrogeologic evolution of epigenetic reworking run-off stage is the main period for the formation of sandstone-type uranium deposit.