| Ordos basin is one of the mainly oil,gas and coal productive basin in China.The Dongsheng uranium metallogenic belt has been discovered which is a large in-situ leachable sandstone-type uranium deposit belt in the north of Ordos basin in recent 10 years.The studies of the metallogenic geological conditions,ore-forming environment,ore-controlling facers and deposits prospective of this area have been proved effectively by many investigation team and research departments.Owing to the fact that such deposits being deeply buried ones,the location prediction and analysis for such deposits become hard point in prospecting.With the purpose of in-depth studying metallogenesis of uranium deposit,discussing the characteristics of hydrogeochemistry and the condition of hydrodynamic in uranium mineralization,this paper was based on the theories of aqueous uranium deposit,approach hydrogeochemical and hydrodynamic condition of modern groundwater,and through hydrogeology and isotopic hydrogeology,computer software "MODFLOW" simulating hydrodynamic condition of groundwater,exploring the paleo-hydrogeology,paleo-hydrogeochemical,paleo-hydrodynamic condition and the paleo-ground-water metallogenesis of sandstone-type uranium mineralization.Zhiluo Formation has whole groundwater system with replenishment,runoff and drainage relations in north of Ordos basin in Mesozoic.The stability of the geological tectonic determine the characteristic of paleoground-water flow,namely paleoground-water flow direction from NW to SE.New tectonic movement changed regional geological structures,worked the transform of depositional systems,tectonic environment and paleohydrodynamic of the Zhiluo Formation in Dongsheng uranium metallogenic belt,and the accumulation and reformation processes of earlier interlayer oxidation zone and uranium deposit by later oxidationThe recharge of groundwater of Zhiluo Formation aquifer is located on the northwest of Gaotouyao and Hantaichuan area,and the northeast of Shenshangou area as lateral recharge.The main flow direction is NW to SE,contemporarily,later subordinate lateral flow direction from NE to SW,due to the upheaval of Dongsheng did not change the direction of the recharge of groundwater of Zhiluo Formation aquifer.The discharge areas are located on Wulanmulun River and the south of Hongjian lake,Chigai lake and Baga lake.The uranium metallogenic belt is located on the variant belt of hydrochemical types form Cl·SO4-Na to HCO3·Cl-Na.The mining area ground water located in the alkalescent reductive field because of the influence of the organic reducing materials.Continental basin was developed in the zhiluo and Yan'an Stage,salinity ranged from 8%0 to 14%o,belong to lacustrine facies aggradation circumstance.The inclusion formed in alkalescent environment,the pH value of paleoground-water is 9.88～10.05.It is concluded that the most Buried depth about 850m during geological evolution in mining area,the most buried temperature is 90.5℃.This paper separately restores various hydrogeological period such as the late Jurasic-early cretaceous period,the oligocene period,the Holocene Epoch-now period.The paleohydrodynamic model was preliminarily built up by using the software of Visual MODFLOW in Dongsheng area. The simulation results showed that hydrodynamic condition overall direction from the near north to south in the late Jurassic period to the eocene epoch which was advantageous to the formation and the transformation of uranium deposits in the Dongsheng uranium metallogenic belt.After the eocene epoch,northeast of the research area was denudated,simultaneously,the uranium deposit avoided destructing by protective ore action of organic matter in the mining area.Through these research and simulation of uranium mineralization paleo-hydrodynamic condition in dongsheng area,sandstone-type uranium deposit environment was more clear in the northeast of Ordos Basin and offered good deposit prospecting signatures of this type uranium deposits.
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