鄂尔多斯盆地后期改造与砂岩型铀成矿关系

Relationship Between Late Reformation and Formation of Sandstone-type Uranium Ore in Ordos Basin

依据鄂尔多斯盆地中新生代地层接触关系、沉积建造、构造变形、主要构造变动事件及同位素测年等资料,对盆地后期改造期次、类型及分布进行了分析。盆地改造作用发生于晚侏罗世以来,可分为晚侏罗世、早白垩世、早白垩世末—古新世、始新世—中新世及中新世末—现今5个阶段,改造形式包括抬升剥蚀、冲断褶皱、叠合埋藏、断陷分隔及热力改造等,并且在空间上有明显的不均一性。盆地后期改造与砂岩型铀成矿的关系密切。提出了晚侏罗世以来多期抬升剥蚀期控制着砂岩型铀成矿作用的发生形成,构造抬升(掀斜)区控制着铀矿的空间展布,而冲断褶皱、叠合埋藏、断陷分隔等改造作用使含矿层变形破坏、深埋或与地下水补给区分割,对铀成矿作用不利。

The stages, types, distribution features of late reformation in Ordos Basin are researched based on contact relation, sedimentary formation, tectonic deformation, main tectonic events and isotopic ages. The reformation of the basin occurred in the late Jurassic and later epoches, and can be divided into 5 phase, they are late Jurassic, early Cretaceous, early Cretaceous end time-Paleocene epoch, Eocene epoch-Miocene epoch and Miocene epoch - present phases. The reformation types are uplifting and weathering, thrust fold, fault depression, deep burial with superimposition, and thermodynamic reforming, and their spacial distributions are uniformity. Relationship between the late reformation and Sandstone-type uranium deposits are analyzed. This paper put forward that multi-stage uplifting and weathering since late Jurassic Epoch controlled the formation of Sandston-type Uranium deposits; uplifting tilting area controlled the spacial distribution of Sandstone-type Uranium deposits; but thrust fold, fault depression, deep burial with superimposition is unfavorable to metallogenetic of sandstone-type uramium deposits, because they change the form, depth of ore-bearing layers and local groundwater discharge.