The Relationship Between The Sedimentary Characteristics And Uranium Mineralization In Wukurqi Uranium Deposit At The Southern Margin Of Yili Basin

Yili basin is one of the important ore concentration area of sandstone-type uranium deposit in China.Wukurqi uranium deposit at the southern of Yili basin is an in-situ leachable sandstone type uranium deposit.In this paper,as the main layer of uranium containing in Wukurqi uranium deposit,Xishanyao Formation is the research object,combined with previous results,the existing data,by means of field investigation,drilling logging and sample analysis test,the sedimentary facies and the paleo geographical pattern of the target strata were analyzed,and then analyzed the relationship between sedimentary characteristics and Uranium mineralization.The main work,knowledge and results summarized as follows.1.By collecting the regional geological data,through a large number observation of cores and outcrops,and microscopic analysis,combined with the characteristics of lithology,sedimentary structures,vertical grain sequence etc.,the sedimentary facies analysis was carried out.The result of analysis shows that there are two types of sedimentary environment in Xishanyao Formation of the study area,including fan delta and fluvial facies.The fan delta was further divided into two sub units: fan delta plain and fan delta front.The fluvial facies was further divided into two sub units,the river bed and the river diffuse.2.According to the characteristics of drilling lithofacies,sedimentary structure and sedimentary sequence,the planar distribution of sedimentary facies map was mapped by using the method of dominant facies.The paleogeographical framework during the Xishanyao Period of the Middle Jurassic was: the Lower Xishanyao Formation of Middle Jurassic mainly deposited in fan delta environment,the Upper Xishanyao Formation deposited in the fluvial deposit environment.During the Xishanyao Formation sedimentary period,the southern area of the study area was the eroded area.The distributary channel of the fan delta plain and interdistributary bay of the fan delta plain developed stably in the central region,and the planar distribution of fan delta plain was nearly E-W trending.The underwater diversion Bay of delta front developed mainly on northern area.During the Upper Xishanyao Formation sedimentary period,the southern area of the study area was the eroded area too.In the central region,the meandering river sand body growth more stably,and the planar distribution of the meandering river was nearly E-W trending.There were some irregular mudflats developed in the river or between the rivers.The floodplain developed in the northern region.3.This paper focused on the analysis of the uranium source,lithology-lithofacies,groundwater dynamic,interlayer oxidation zone and the sedimentary micro-facies,and analyzed the relationship between these factors and Uranium mineralization.Study reveals that the uranium source of Wukurqi uranium deposit was taken from the erosion source area at the southern margin of Yili basin,and the amount of uranium supply controlled deposition rate and sediment thickness.The size and spatial distribution of uranium ore bodies were controlled by the thickness of the sand body and the plane distribution.The groundwater dynamics was influenced greatly by the sedimentary and tectonic features.The channel of sand body was the channel of groundwater,and the direction of channel sand body,to a great extent,determined the flow direction of groundwater with oxygen and Uranium.Interlayer oxidation zone affected by sedimentation,the planar distribution of innterlayer oxidation zone and sand body distribution were very similar,uranium ore bodies in space distribution characteristics was closely related with the development and distribution of relatedinterlayer oxidation zone.The analysis of realationship between sedimentary micro-facies and Uranium mineralization showed,that the ermeability of muddy intercalation was poor,so that the interlayer oxidation fluid flow slowed down or diverted,this changed the shape of the sand body,and controlled the development of the oxidation zone and uranium ore bodies.The change of sand body thickness,grain size and sedimentary environment caused by the abrupt change of sedimentary micro-facies were the main reason for the precipitation and enrichment of minerals.