Geochemical characteristics and geological significance of major elements of surface sediments from Changjiang River Estuary

Major elements(SiO2,Al2O3,Fe2O3,MgO,CaO,Na2O,K2O,P2O5,TiO2,MnO,TOC and CaCO3)of 187surface sediments from Changjiang River Estuary have been tested to analyze the spatial distribution character and geological significance.The results indicate that the major element oxides are mainly composed of SiO2,Al2O3,Fe2O3,MgO,CaO,Na2O,K2O and TiO2,which account for 91.59%. SiO2has the highest content in this area with the average content up to 62.43%.Al2O3has the second highest content of 11.16%.R-factor analysis indicates that the major element oxides of surface sediments can be classified into three groups:the first group includes SiO2,Al2O3,Fe2O3,MgO,P2O5,TiO2and MnO;the second group includes CaO,K2O,CaCO3and TOC and the third one includes Na2O,which possibly represent the terrigenous sediment,the mixture of marine biologic sediment and terrigenous sediment,as well as the marine chemical sediment.Similar spatial distribution of Al2O3/Na2O and CIA indicates that the materials are mainly derived from Changjiang River and accumulated in the estuary and its southern area,especially in the west of 123.5°E area.The main driving force is Min-Zhe Coastal Current in the study area.