Analysis Of Metallogenic Conditions Of Sandstone-type Uranium Deposits In Northwest Area Of Songliao Basin

Songliao Basin is one of China's main exploration basins for sandstone-type uranium deposits,and Qianjiadian and Baolongshan uranium deposit are discovered in the south of the basin.The research area is located in the northwest of Songliao Basin.Although the degree of uranium geological prospecting in the study area is relatively low,however,a series of significant uranium mineralized and anomaly occurrences(belts)have been found successively.Through field exploration,documentation of drill holes and core observation,combined with studies on petrological characteristics under indoor microscopes,this paper systematically discussed the tectonic characteristics,sedimentary environment and uranium metallogenesis in the study area.Based on these researches,the paper demonstrated the metallogenic conditions of sandstone-type uranium deposits in the study area.According to the current datum of field exploration?drilling and drill core,analysing characteristics of dynamic mechanism and tectonic evolution in the Songliao Basin,the paper considered that tectonic evolution of the basin has experienced Fracture-fault period(T-K1d),thermal precipitation depression period(K2q-K2n),squeezing atrophy period(K2s-K2m)and incompetent fold period(E-Q),which controls three stages,concluding formation of uranium source body,formation of uranium-rich sedimentary formation and formation of uranium deposit.The discovered uranium mineralized layer is mainly formed in the depression and atrophy stage in the basin.According to abnormal occurrence characteristics of uranium in the study area,combining formation characteristics of lithology in each position can infer that main prospecting target stratum of Heping and Taikang area is Mingshui formation in the south of the research area and Yaojia ? Qingshankou and Mingshui formation is the main prospecting target stratum in the Nehe and Fulaerji area of in the north of the research area.Observing petrological characteristics of sandstone samples from target stratum by microscopes,according to the data obtained to carry out Folk's sandstone classification and mapping of provenanc tectonic attributes of Dickinson,which indicates the type of sandstone in the target stratum is mainly lithic sandstone and lithic arkose and the tectonic attributes are mainly the recycled orogen,and secondly,are the transitional island arc and the cut pattern island arc.Thus,sedimentary source of target stratum may be mainly provided by the uplifted zone of basin margin in the Songliao Basin.According to sedimentary facies analyses,this paper thinked that the alluvial fan facies,fan delta facies,delta facies,meandering river facies and shore-shallow lake subfacies are mainly developed in the study area,and developed several of obvious mud-sand-mud sedimentary formation,which creates favorably depositional environment of mineralization for the study area.By systematically analysing uranium metallogenic condition,such as uranium source,geologic climate,hydrology and epigenetic alteration,and combined with tectonic evolution,analysis of sedimentary facies from target stratum,position of bearing ore sandstone and study on petrological characteristics,this paper deemed that the northwestward of Songliao Basin possesses preferably prospecting potential of sandstone-type uranium deposits.