ELEMENTAL OCCURRENCE PHASES OF SURFACE SEDIMENTS FROM THE EAST PHILIPPINE SEA

To understand the elemental occurrence phases of different surface sediments from the East Philippine Sea, chemical extraction method has been utilized to extract surface sediments with or without new-type ferromanganese crusts step by step and elements in each phase were measured. The occurrence phases of metallic elements and rare earth elements (REE) of different surface sediments are coherent as a whole, indicating that surface sediments of the studied area were formed in similar geologic and oceanic conditions. Among the metallic elements, Fe mainly concentrates in the residual phase, while Mn, Cu, Co and Ni mainly concentrate in the ferromanganese oxide phase. The REEs also concentrate in these two phases. The carbonate phase, ferromanganese oxide phase and organic phase preferentially adsorb or complexation reacts with the heavy REEs, causing the relative enrichment of the heavy REE and the passive Ce-anomaly. The residual phase preferentially adsorbs the light REE, leading to the relative enrichment of the light REE and the positive Ce-anomaly. The volcanic materials make the residual phase of surface sediments show positive Eu-anomaly character. Meanwhile, there are some differences between different surface sediments, too, which may be correlated with the local environment, that is, with or without ferromanganese crust growth.