Geochemical Characteristics And Geological Significance Of Lower Cretaceous Bayingebi Formation In Balongwula Area Section Of Bayingebi Basin

In recent years,with the advancement of the selection process of clay rock geological repository sites in China,the Tamusu area in Inner Mongolia is one of the preselected areas,on the basis of studying and consulting a large number of previous literature,through the field survey and sampling in the study area,this paper is based on the important horizon perspective of high-level radioactive waste geological repository location,The samples of Bayingebi Formation in Balongwula mountain were studied from the perspective of element geochemical,petrology,paleosedimentary environment and provenance,the main contents and conclusions are as follows:The lithology of samples from Bayingebi formation of Early Cretaceous in Balongwula mountain area is mainly composed of shale,mudstone,argillaceous siltstone,yellowish-brown calcareous sandy conglomerate and argillaceous dolomite,with a small amount of carbonaceous shale and occasional plant debris.The shale facies can be divided into massive shale,parallel laminar shale and non-parallel laminar shale.According to the analysis of scanning electron microscope,there are four kinds of clay minerals in the area,which are illite(I),kaolinite(k),chlorite(c),Illite/Smectite(I / S).The clay minerals are generally higher,and the relative content of illite Montmorillonite Mixed Layer is the highest,followed by kaolinite,illite is lower,and chlorite is the lowest.Through the analysis of the contents of trace elements Li,Sr,Ni,Ga,Sr /Ba,Th /U,Ni / Co,V /(V + Ni),U / Th and Ceanom,It can be inferred that the study area of balongwula mountain(Sifang mountain)has a dry wet alternate sedimentary climate,a fresh water to salt water to fresh water sedimentary environment,an oxygen poor to sub oxygen rich environment,and partially reduced environment,paleoclimate,paleosalinity and oxidation-reduction environment are consistent in the vertical evolution trend,which has a good corresponding relationship,there is a short period of dry and cold reduction salt lake environment in the warm and humid oxidation environment.Major elements in the study area are rich in Si,Al,Ca and Fe;trace elements such as Rb,Th,U and La are relatively rich;light rare earth elements are rich,heavy rare earth elements are deficient,?Eu shows obvious negative anomaly,?Ce has positive anomaly indicates that the provenance of the samples in the study area is mainly felsic rocks,granitic,with diversity of provenance,and La/Th–Hf,La/Sc–Co/Th,REE–La/Yb,Hf–Co–Th discrimination the diagram also reflects similar provenance characteristics.The correlation between ?Ce and?Eu,?Ce and ?REE,CIA and Th /U,Th / Sc is not obvious,which reflects that the REE values of the samples are directly controlled by the material composition of the source area.The tectonic background of the source area is mainly characterized by continental island arc,accompanied by oceanic island arc and active continental margin.