The Analysis Of Uranium Metallogenic Prospect In Shiwandashan Basin

Shiwandashan basin is so far the only known Uranium-productive basin which uranium deposits are found in Jurassic strata.Predecessors' have plenty of the existing researches on the basin oil and gas resources,meanwhile uranium resources research is less and the research level is not high.On the basis of large amounts of information collected,summarize and analysis predecessors' research results systematically,combining with the field geological work in this paper and indoor analysis,conclude the uranium metallogenic geologic features and reservoir characteristics of Shiwandashan basin systematically;exampled Fulong-phoenix mountain and Xintang two section,analyze the sedimentary of basin,element geochemical characteristics and petrological characteristics,compared with typical uranium-producing basin in the North at the same time,comprehensive the above analysis,the results are as follows:(1)The tectonic activity at Shiwandashan basin is frequent and lots of fracture is advantageous to the migration of the oxygen uranium containing water and the deep hydrothermal fluid;A large number of magmatic rocks are exposed in the Surrounding,that under the weathering can provide source of ore-forming materials for basin continuously;Basin basement are Marine strata and Cap is given priority to the lacustrine facies.(2)The petrography features on two section show that the rock debris consists of feldspar,quartz and lithic,and much of quartz and debris come from the granite rock surrounding the basin;Sandstone classification triangle shows that the source material of basin is complex.According to the comparison of sedimentary characteristics on two Section grouping,the sedimentary environment is relatively close,more for shore shallow lake and delta plain sedimentary facies,and the metallogenic conditions must satisfy(1)the sandstone and mudstone is interbed(2)The thickest degree and the ratio of the sandstone and mudstone should reach a certain value.Element geochemical characteristics show that the U content of strata and granite in the study area is relatively higher than crustal abundance,so formation can provide uranium source,but given priority to with granite.The ratio of characteristic elements parameters and the ?Eu and the ?Ce anomaly show that the sedimentary environment of basin is given priority to with oxidation environment from the devonian to the Jurassic,in which both reductive environment.(3)According to the regional stratigraphic lithology,facies and ancient climate characteristics etc,the known and presumably uranium reservoirs in basin are mainly composed of Jurassic strata,including Banba and Pingdong group of Triassic,the three sections of Xinlong group of Cretaceous and Neogene.The formation lithology aboved is given priority to with light color layer,rich in reducing medium at the same time;the anomalies of Gamma is higher and the porosity of Sandstone is better.(4)Compared with typical uranium-producing basin and typical ore deposit in the north shows that Shiwandashan basin has metallogenic favorable conditions: tectonic fracture,abundant uranium source,good uranium reservoir and plenty of reducing medium.Comprehensive study shows that the mineralization types of uranium are hydrothermal superimposed transformation and interlayer oxidation zone in Shiwandashan basin.(5)Concluded that there is a close relationship between uranium mineralization and strata,lithology,the original source of uranium is the granite which surrounded the basin and the part of the basement lithology.But the special geological features of basin(syncline mountains)and the strong bond between calcite and mudstone have become obstacles to mineralization of uranium persistently.So divided the research area into the prospecting prospect areas of uranium deposit which is hydrothermal superimposed transformation of Xintang;the prospecting prospect areas of uranium deposit which is interlayer oxidation zone of Phoenix mountain;The prospecting prospect areas of uranium deposit which is interlayer oxidation zone of Nabo-Guitai eventually.