Study On Distribution Characteristics Of High Radioactivity Anomaly In D Area Of Southern Margin Of Ordos Basin

Under the idea of "coal and uranium exploration",in order to make full use of coal resources exploration data,provide data support for the subsequent uranium resources exploration,the paper make full use of the region D coalfield exploration geological data,test results and logging data.The distribution characteristics of high radioactivity anomalies in zone D were studied with Zhiluo Group as the object.On the basis of data collection and collation,the logging response characteristics are studied,and the occurrence horizons of radioactive anomalies are determined by combining stratigraphic division and correlation.Based on the study of logging response characteristics of the target layer,the thickness of each borehole anomaly layer is determined.The spatial distribution of the target layer is analyzed according to the sedimentary structure characteristics of Zhiluo Formation.Based on the analysis of the test results of samples,the relationship between the radioactivity logging value and uranium content was studied and the prediction model of uranium content was constructed.The uranium content of each abnormal borehole was estimated,and the "point,line and plane" characteristics of the radioactive anomaly were studied.Finally,the influencing factors of uranium content distribution in this area are discussed.The study shows that the radioactive anomaly layer in sandstone has the characteristics of high natural gamma ray,low compensation density and low resistivity,so the lithology can be better identified and the conventional mudstone and the radioactive anomaly layer can be distinguished effectively by using the relevant chartThe thickness of the strata in the lower member of Zhiluo Formation in the study area is relatively stable,with the characteristics of sand and mud,and the top and bottom microstructures are high in the east and low in the west,forming a tectonic slope zone in the east of the study area.The lower sub-member of Zhiluo Formation is nested braided river deposit and the upper sub-member is meandering river deposit.There is a close correlation between the natural gamma values measured by different natural gamma logging instruments and the quantitative gamma logging values.The methods for estimating uranium content using natural gamma include indirect estimation and direct estimation.Based on the logging data of coal field,the single project uranium content and uranium content of the lower and lower sub members of Zhiluo Formation in the study area are calculated,and the uranium content per square meter is predicted.The radioactive anomaly layers are mainly located at the top and bottom of the medium and fine sandstone with good physical properties in the lower member of Zhiluo Formation,and the lower sub member is more widely distributed than the upper sub member.The radioactive anomaly layers are mainly located in the eastern structural slope belt of this area.The medium and fine sandstone in the lower member of Zhiluo Formation provides a good channel for the migration of Uranium-rich ionized water.Reductive gas may increase the radioactive anomaly in the tectonic slope belt,and the lithofacies combination in the lower member of Zhiluo Formation is conducive to uranium enrichment.