The Research Of Sedimentary Environment And Uranium Mineralization In The Ailegemiao Area In Erlian Basin

The Erlian Basin is regarded as one of the ten largest energy basins in China.After more than 30 years of continuous investigation,a number of large and medium-sized mudstone and sandstone-type uranium deposits have been discovered and proved successively by Geological Department CNNC in Erlian Basin.With the further studies in recent years,uranium mineralization has been discovered in the Ailegemiao area of Erlian Basin.Base on field profile observation,borehole core observation,single-hole Sedimentary phase profile analysis,profile sedimentation ratio,Sedimentary phase plane distribution analysis,research on target layer sedimentary environment and sedimentary system,this paper discussed uranium metallogenic regularity.Above research work will point out the direction for further exploration in Ailegemiao area.The paper achieves the following key contents:1.Through the analysis of sedimentary environment characteristics in the study area,it shows that The Tengger Formation develops typical gravity flow deposits of fan delta in steep slope zone of fault depression,and braided river delta may also be developed in gentle slope zone of fault depression;alluvial fan,fan delta,braided river,Braided River Delta and lacustrine depositional system can be seen in the lower part of Saihan Formation.The braided river and braided river delta systems are main uranium-producing systems,the fan delta system is secondary.Alluvial fan deposits are mainly developed in the upper part of Saihan Formation,characterized by large area of red alluvial fan-flooding plain deposits,and braided river deposits are developed in the eastern part of Saihan Formation.2.According to the classification and statistics of uranium ore bodies in the study area,uranium mineralization in Tengger Formation is mainly located near the oxidation front and form phreatic-interlayer oxidation zone type uranium deposits.The host strata lithology is mainly gray medium sandstone,fine sandstone and argillaceous fine sandstone,rich in organic matter and pyrite.The uranium mineralization in the lower part of Saihan Formation is generally sandstone-type ore body,which is deeper and thicker than mudstone-type ore body,even lower grade.Uranium mineralization occurs in braided channel sandstone of braided river plain subfacies,swampy mudstone,siltstone or lignite in the lower part of Saihan Formation.Uranium mineralization in the upper part of Saihan Formation is mainly controlled by the oxidation surface of paleophreatic water,followed by superimposition of phreatic-interlayer oxidation and secondary reduction.The occurrence of ore body is gentle,mainly layered and plate,a few lenticular.3.There are abundant uranium-rich granite bodies around the study area,large areas of radioactive anomalies and halos exist on the surface,the ore-bearing bed is rich in uranium,which provides the main uranium source for later mineralization.Ore bodies of Tengger Formation are mainly distributed in fan delta of steep slope zone of fault depression.The main ore bodies in the lower part of Saihan Formation are mainly distributed on the side of Braided River Delta near the front of the delta.The main ore bodies in the upper part of Saihan Formation are located in the ancient meandering valley.4.The main prospecting site of the upper part of the Saihan Formation is in the center of the basin.The main prospecting lower part of the Saihan Formation and the Tengge Formation are at the edge of the basin.it is considered that the western Wulanchabu depression has good mineralization conditions.The lower part of the Saihan Formation and the Tengge Formation are both the target horizons for uranium ore prospecting.In recent years,the uranium mineralization information of the Tengger Formation has been discovered in the Ailegemiao area,which has a metallogenic prospect.