MODE OF ELEMENT OCCURRENCE IN SURFACE SEDIMENTS FROM EAST PACIFIC RISE NEAR 13°N AND THE EQUATOR

In order to assess the influence of seafloor hydrothermal activity on element occurrence in sediments, we carried out sequential extraction procedures and whole-rock analysis for the surface sediments(17A-EPR-TVG1, 17A-EPR-TVG5) collected from East Pacific Rise near 13°N and the equator, and discussed mode of element occurrence of Al,Ca,Fe,Mn,Ti,Ba,Zn,Cu,Sr,V,Mo,U and rare earth elements (REE).XRD results indicate that the primary mineral phase of 17A-EPR-TVG1 is pyrite and 17A-EPR-TVG5 sample has calcite as its main mineral. Elements except Ca and Sr of 17A-EPR-TVG1 which were greatly affected by hydrothermal activity mainly occur in the residual phase and ferromanganese oxide phase. However, elements except Al,Ba and Ti of 17A-EPR-TVG5 which is characteristic of normal deep ocean sediment mainly concentrate in carbonate phase and ferromanganese oxide phase. The sequential extraction results indicate that, the shale-normalized REE distribution pattern of the REEs in the sediments exhibits a positive Eu anomaly in all the four phases of 17A-EPR-TVG1,while the negative Ce anomaly occurs in the four phases of 17A-EPR-TVG5. We come to the conclusion that the sea water and hydrothermal fluid participated in the formation of the sediments.