Sifangtai formation of the Upper Cretaceous is one of the main horizons for uranium exploration in the northern part of Songliao basin.The uranium mineralization is mainly controlled by the sedimentary system of the Upper Cretaceous meandering river delta.Uranium deposits are mainly enriched in the bottom sandstone layer,mostly in plate-like and lens shaped shapes.The size of the ore body is closely related to the size and number of layers of the sand body,the larger the sand body size is,the larger the ore body size is.Conversely,the smaller the size of ore body is.However,the development of sand bodies at the bottom of the Upper Cretaceous Sifangtai formation in Meilisi area of the western overlying zone of Songliao basin is not yet clear,in this article controlled source audio-frequency magnetotelluric(CSAMT)was used to invert the resistivity section of the study area with the Occam algorithm.Combined with the resistivity characteristics of rocks in various layers of the study area,the structure of the cap rock was analyzed,especially the spatial distribution characteristics of the Cretaceous Sifangtai formation in the target layer for ore exploration.At the same time,the characteristics of basement undulation,as well as strike,dip,and depth of the fault were also inferred.The research showed that the river facies sand bodies of the Sifangtai formation in the study area are mainly distributed in the southeastern part of the study area,mostly in a lens shape,showing a gradually pinching feature from southeast to northwest,with a thickness generally not exceeding 180 meters.The achievements of this measurement provided a basis for the deployment of featured drilling engineering.
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