Analysis Of Sedimentary Environment And Source Area Tectonic Background Of Changzhougou Formation And Chuanlinggou Formation In Xingcheng Area

In order to further understand the sedimentary environment and the tectonic background of provenance area of Changzhougou and Chuanlinggou Formations in Xingcheng area,based on the study of petrological characteristics of rock samples from Changzhougou Formation and Chuanlinggou Formation,combined with the methods of grain size analysis and geochemical data analysis,the sedimentary source characteristics of Changzhougou Formation and Chuanlinggou Formation in Xingcheng area were summarized,and then the tectonic background was studied and analyzed.Petrological study shows that the strata of Changzhougou Formation are in unconformity contact with the underlying Archean Suizhong granite,which can be divided into three sections.According to the QFL Trigonometric diagram,the sandstones of Changzhougou Formation are mainly feldspathic quartz sandstone and arkose,with grain sequence bedding and tabular cross bedding.The bottom of the sedimentary environment of Changzhougou Formation is fluvial sedimentary environment,the middle part is composited by two kind of sedimentary environments:littoral-shallow marin environment and delta front,the upper member is littoral-shallow marin environment,The Chuanlinggou Formation in the study area can be divided into two sections,which are a set of rock combination of mudstone,siltstone and sandstone interbedded,accompanied by volcanic tuff,indicating volcanic activities in the sedimentary process,and its sedimentary environment is the coastal and shallow marine environment.Geochemical studies were carried out on rock samples of Changzhougou Formation and Chuanlinggou Formation in the research area,and geochemical parameters were processed on the data of main elements,trace elements and rare earth elements.According to the ratio of Al₂O₃/?Ca O+Na₂O?to determine the rock composition,the average ratio of Al₂O₃/?Ca O+Na₂O?of rocks in the Changzhougou Formation in the study area is 110.3,and the average ratio of rock samples in the Chuanlinggou Formation is 105.0,indicating that the composition of rock samples in the Changzhougou Formation and Chuanlinggou Formation is relatively stable.The characteristics of rare earth elements in the sandstone samples of the Changzhougou Formation in the study area are similar to those of the rock samples of the Chuanlinggou Formation,both of which have a relatively high amount of rare earth elements and a relatively high La _N/Yb _N ratio.The difference lies in that the rock samples of the Chuanlinggou Formation show a more obvious negative Eu anomaly.Through the analysis of geochemical parameters such as major elements and trace elements,it can be seen that most of the rock samples of Changzhougou Formation in the study area are from relatively mature acid rocks,such as granites,experiencing moderate weathering;the characteristics of the source rocks of the Chuanlinggou Formation in the study area are similar to those of the Changzhougou Formation,and have medium to strong weathering.These results show that the tectonic background of the source area of Changzhougou Formation and Chuanlinggou Formation is relatively stable.The tectonic background of the provenance area of Changzhougou Formation and Chuanlinggou Formation is the passive continental margin.