Development Characteristics and Uranium Metallogenic Condition of the Upper Cretaceous Yaojia Formation and Qingshankou Formation in Kailu Depression of Songliao Basin
The uranium host layers in the southern part of Songliao Basin are mainly the Upper Cretaceous Yaojia Formation and Qingshankou Formation,both of which are red variegated and difficult to discriminate in the region.The unclear sequence framework restricts the expansion of exploration achievements.This paper conducted a comparative study on Yaojia Formation and Qingshankou Formation through core observation,seismic interface tracking,well logging,facies identification biological fossil assemblages,geochemical and heavy mineral analysis indicators,and preliminarily identified the stratigraphic division indicators of Yaojia Formation and Qingshankou Formation.The results show that the top of Qingshankou Formation is dominated by purple-red mudstone,and the lower part is purple-red,gray fine sandstone,argillaceous medium-coarse sandstone and thin-bedded purple-red mudstone.The seismic facies of Qingshankou Formation are characterized by poor continuity of reflection waves,small or medium amplitude,and the well logging curves are bell,finger,and box-shaped.CIA average is 57.16.And the petrochemical and heavy minerals are mainly ilmenite+garnet+barite+zircon.Yaojia Formation can be divided into two members,the lower member is dominated by brownish-red,brick-red,gray fine sandstone,medium sandstone and sandy conglomerate,and the upper member is composed of a set of gray-green,purple-red mudstone and gray-white siltstone,fine sandstone and medium sandstone.The seismic facies of Yaojia Formation are characterized by continuous reflection waves,high or high amplitude,low amplitude,and continuous reflection at the bottom,and the well logging curves are box,bell-shaped,and a small amount of finger-shaped,CIA average is 65.22,and the petrochemical and heavy minerals are the combination of weathering CIA mutation at the bottom,zircon+garnet+albite+anatase+ilmenite.On this basis,the uranium metallogenic conditions of Yaojia Formation and Qingshankou Formation are systematically analyzed and compared.The study shows that both have sufficient uranium source,which are mainly from the Middle and Cenozoic volcanic rocks and Hercynian and Yanshan granites in the southern margin of Songliao Basin.During Qingshankou-Yaojia period,the channel developed from south-west to north-east,and a typical sedimentary environment of alluvial fan-braided river-meandering river-delta-lake was formed from upstream to downstream.The ore-bearing gray sand bodies of Qingshankou Formation and Yaojia Formation are rich in reductant such as organic matter,carbonized plant detritum,pyrite,etc.,and their organic carbon content is 0.11%～0.56%,indicating that they all have good reducing properties.The oxidation zone of Yaojia Formation is mainly distributed in a planar manner.The mineralization potential of Yuliangbao-Qianjiadian and Jiamatu-Baokang is huge.The oxide zone of Qingshankou Formation is distributed in the form of a ring belt,and the mineralization potential of the Naiman,Tongliao-Qianjiadian and other sections is greater.
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