| The Manglai sandstone type uranium deposit is located in the Tabei Sag in the southwestern part of the Manite Depression in the central eastern part of the Erlian Basin.It is located in the central axis of the ancient valley uranium mineralization belt,and the orebodies are developed on North and south sides of the river valley.It is a typical object for studying the genesis of ancient valley sandstone type uranium deposits.Previous researchers have conducted some basic geological and genetic research on the northern ore body of this uranium deposit,and gained some important understanding.However,research on some oreforming elements,such as favorable sedimentary facies zones,structural backgrounds,sources of ore-forming materials,fluid environments,and ore genesis,is not yet in-depth and systematic.Based on systematic basic geological investigation,mineralogy analysis and element geochemical analysis,this paper comprehensively studies and discusses the climatic conditions,tectonic background,favorable sedimentary facies belt for mineralization,material sources and genesis of the Manglai sandstone type uranium deposit.The main insights gained in the paper are as follows:(1)Manglai sandstone type uranium deposit is a typical sandstone type uranium deposit in Tabei sub sag,southwest of Manite depression,Erlian basin.The ore body mainly occurs in the gray sand body at the bottom of the upper section of the Saihan Formation in tabular form.The favorable ore bearing sedimentary facies are composed of a set of channel sand bodies under the braided river sedimentary system.The sand body is thick in the west and thin in the east.(2)the ore-bearing sandstone is yellow oxidized sandstone and gray reduced sandstone,which are relatively loose,Granular fillers can be seen on the surface,mainly medium to coarse particles,and calcareous cementation can be seen locally.Uranium ore is mostly gray,gray black and black,and there are many gravel particles on the surface of the ore.Under the microscope,quartz,feldspar,mica,pyrite,clay minerals,rock debris,etc.are often associated with uranium ore,and the multiple ring structure of pyrite can reflect the fluid transformation in this area.(3)The occurrence state of uranium is mainly independent uranium minerals,adsorbed uranium and uranium bearing minerals.Independent uranium minerals are mainly pitchblende and uranium ore,often near pyrite and quartz;The adsorbed uranium is mainly composed of adsorbed carbon chips,and the uranium content in different parts of the same carbon chip is different;The most common uranium bearing mineral in the Manglai area is phospermuranite.,which also contains some titanium uranium ore and uranium thorite.(4)Spider web of trace elements in different types of sandstones are similar,indicating that they share the same source characteristics.Among them,Mo and Cs have the highest correlation with uranium and can be used as preliminary indicator elements for U.The distribution curve of rare earth elements show that the region has obvious δEu negative anomaly,And the fractionation of light and heavy rare earth elements is also significant,Indicating the presence of fluid transformation in the region.(5)The comprehensive constraints of climate,tectonic background,material sources,favorable sedimentary facies zones,and redox conditions,the mineralization process of the Manglai sandstone type uranium deposit can be divided into pre enrichment period,mineralization period,and preservation period;The formation of uranium minerals is not only closely related to the reduction media such as pyrite and carbon chips,but also has a greater impact on the enrichment of uranium ores due to the fluid transformation.The types of uranium minerals in the southern and northern mining areas are the same,but the uranium element content in the southern part is higher than that in the northern part,which may be related to the differences in the north-south bidirectional uranium supply in the depression and the imbalance of fluid interaction. |
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