地质科技通报 (Jul 2021)
Constraints of the sequence stratigraphic structure of uranium-bearing series on mineralization in Qianjiadian uranium deposit, Songliao Basin
Abstract
Understanding the stratigraphic structure of uranium-bearing rock series in sandstone-type uranium deposits and its constraints on uranium mineralization is the basis of understanding the uranium metallogenic regularity and mineralization. In this paper, the sequence stratigraphic structure of the uranium-bearing series in Qianjiadian uranium deposit, southwest Songliao Basin, is studied based on seismic, well logging, core analysis and test data. The relationship between stratigraphic structure and uranium mineralization is discussed. It is found that the Yaojia Formation in Qianjiadian area is a complete third-order sequence. The bottom boundary of Yaojia Formation is a regional unconformity and the bottom part of Yaojia Formation is composed of mud conglomerate and sandstone with mud pebble. The top boundary of Yaojia Formation is a parallel unconformity, and the top part of Yaojia Formation comprise mauve mixed with gray mudstone. The initial flooding surface and the largest flooding surface have been recognized internally, which is divided into low system tract, transgressive system tract and high system tract. The low system tract distributes in a small area with an average thickness of about 40 meters, showing a long and narrow north-east distribution. The transgressive system tract and the high system tract continuously overlap, and the distribution area extends southwest to the Baxian Tube-Kailu County area, and the overall direction is still north-east. The average formation thickness in the study area is 85m and 75m respectively. The uranium mineralization of the Yaojia Formation in the study area is restrained by the sequence stratigraphic structure, and the uranium mineralization of the different small sequence groups from the bottom to the top gradually weakens in the vertical direction. On the plane, the distribution characteristics of uranium mineralization are different in different system tracts. The uranium mineralization in the low system tract mainly develops in the area of QianⅣ-QianⅤ.The ore bodies are plate-like and lenticular in shape, and are distributed in a north-east strike strip. Uranium mineralization in transgressive system tract in the Qian Ⅱ, Qian Ⅳ and Qian Ⅴ is irregular arc-shaped and the ore bodies are "roll-like", which is classical interlayer oxidation zone uranium mineralization. The uranium mineralization in high system tract mainly develops in Qian III and sporadic distribution in the south, and it is speculated that there is further prospecting space to the south. The study results can provide a basis for prospecting in the study area, and a basis for the study of uranium metallogenic model and process.
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