Potential Of Sandstone-type Uranium Mineralization In The Northwest Margin Of The Badanjilin Basin

The northwestern margin of the Badanjilin Basin has the same geological background,similar geological features,and ore-bearing horizons as the Suhaitu Depression,which contains the Tamusu uranium deposit,and good uranium mineralization clues have been identified,indicating the possibility of uranium resources.The field geological survey discovered visible traces of oxidation fluid and thermal fluid transformation in the study area’s sandstone.Previously,uranium exploration in the basin’s northwestern margin focused primarily on the study of basic geological conditions of uranium mineralization,ignoring the effect of oxidation fluid and thermal fluid on uranium mineralization.In this paper,on the basis of field geological investigations and secondary interpretation of boreholes,the geochemical characteristics of oxidizing fluid and thermal fluid activities at the northwest edge of the basin were systematically studied through microscopic identification,elemental geochemical analysis,and fluid inclusion analysis,and the geological conditions of uranium mineralization in the study area were systematically sorted out in terms of uranium geology and sedimentary petrology,and the above comprehensive information on uranium mineralization was compared with typical sandstone type uranium deposits to explore the uranium mineralization potential of the study area and select favorable areas for uranium mineralization.The main insights gained are as follows.(1)Microscopic identification identified that the types of alteration in the lower Cretaceous strata in the sag of the study area include carbonatization,ferritization,hematization and clayization,indicating that there is oxidation fluid transformation activity in the sandstone of this layer.The hydrothermal altered minerals calcite and gypsum can be seen in the lower Cretaceous sandstone in the study area,indicating that the sandstone in this layer has undergone the transformation of thermal fluid activity.(2)Elemental geochemical analyses show that the U enrichment in the sandstones of the Sairhena area and the Lujing Depression is correlated with Ba and REE,indicating that the modification of medium and low-temperature hydrothermal fluids favored uranium mineralization.In contrast,the uranium-rich rocks in the Sairhena area are significantly enriched in Y and HREE,reflecting their modification by deep hydrothermal fluids.The above evidence suggests that thermal fluid modification activity is becoming more pronounced from the center of the basin depression towards the margin,which may be influenced by the tectonic activity of the Arjin Left Slip Fault.(3)Through a comprehensive study of uranium metallogenic geological conditions,oxidation fluid,and thermal fluid activity characteristics,it is found that the structure,sedimentary facies,oxidation-reduction conditions,and ore-bearing horizon of the study area are similar to that of the Tamu uranium deposit,and the uranium-rich sandstones have undergone a thermal fluid transformation after interlayer oxidation,which reflects that the study area has great uranium metallogenic potential.In addition,based on the spatial matching of the various metallogenic elements,and taking into account the location of the uranium mineralization at Saierhena,two uranium anomalies in the Lujing Depression,and16 radioactive anomalies in the oil and coal fields,the following favorable uranium mineralization areas in the study area were selected: fan-delta sands in the Lower Cretaceous strata of the Lujing Depression that have been modified by peroxide fluids and low to medium temperature thermal fluids;fluvial sands in the Suhongtu Formation of the Jianguoying Depression that has been modified by peroxide fluids and low to medium temperature thermal fluids;and fan-delta sands in the Bayingobi Formation of the western slope of Kuanzihu where the Saierhena area is located.