Geochemical characteristics and geological significance of shaly rocks in Shanxi Formation of Suzhou Mining Area,Huaibei Coalfield

In order to study the geochemical characteristics and geological significance of shaly rock in Shanxi formation of Suzhou Mining Area,Huaibei Coalfield,the main and trace elements of shaly rock in the study area were tested and analyzed by X-ray fluorescence spectrum and ICP-MS.The results show that the content of SiO2 and Al2O3 in the argillaceous rocks in the study area is relatively high,with the average values of 62.67% and 21.36%,respectively.The elements of Sc,V,Cr,Ni,Zr, TH in shaly rocks of Shanxi Formation are relatively rich compared with those of Australia shale of post Archean,and the elements of Ba,Ta,Rb,Sr,Nb are deficient.The argillaceous rocks are rich in rare earth elements,the content is 242.4×10-6～302.9×10-6,LREE /HREE value is 8.87-10.01,the degree of heavy and light rare earth differentiation is large,δ EU value is 0.44-0.72,with obvious negative anomalies,δ CE value is 0.96-1.14,indicating no abnormality.The overall pattern of REE distribution curve is right dipping,similar to the element curve of Australian shale in post Archean,reflecting that the argillaceous rocks in the study area are mainly from the upper crust.The Al2O3/TiO2 and Cr/Zr values of argillaceous rocks in the study area are 22.77—29.47 and 0.22—0.40,respectively.Combined with the projection areas of samples in Th/Sc-Zr/Sc,TiO2-Ni,La/Th-Hf and La/Yb-REE diagrams,it shows that the material components of argillaceous rocks in the study area are mainly from felsic rocks in the upper crust.The discrimination maps of Th-Sc-Zr/10 and La-Th-Sc tectonic environments indicate that the source rocks of the argillaceous rocks in the study area are continental island arc tectonic environments.The Sr/Ba value of argillaceous rock in the study area is 0.41-0.54,reflecting the brackish water sedimentary environment.The Sr/Cu value is 3.96-4.89,indicating the warm and humid climate conditions,V/(V+Ni) value is 0.71-0.82,Ni/Co value is 1.94-3.55,and Cu /Zn value is 0.34-0.71,indicating that the sedimentary water is anaerobic and strongly restored to the original environment.These geochemical characteristics indicate that the Shanxi formation of Suzhou mining area in Huaibei coalfield formed in the river controlled delta environment,with warm and humid climate and brackish water body.