SEDIMENT GEOCHEMISTRY FROM 13°N EAST PACIFIC RISE HYDROTHERMAL FIELD

Element analyses have been carried out on the sediment cores from East Pacific Rise 13°N. Sediments are rich in Fe and Mn, with Fe contents from 8.5% to 13.8% in E271 and 6% to 13% in E272, Mn contents from 1.7% to 3.17% and from 6% to 13% respectively, which indicates important sedimentation influences of hydrothermal plume at a distance of 25~45 km west of EPR 13°N hydrothermal field. Carbonates also occupy an important component, with E271 from 5.9% to 27.57% and E272 from 6.67% to 38.20%. A few foraminifer fossils were found in the sediment cores. These sediments are rich in Cu, Pb and Zn which are fallout from hydrothermal plume with iron oxides. Cu/Fe, Pb/Fe and Zn/Fe ratios are lower than those in vent particles. Pb performs short transport distance or only minor Pb transports with iron oxides particles. Sediments are rich in Li, Mo and Ni as well. Further, plume supplies V to underlying sediment by scavenging from seawater. Ti and Al have a good correlation, with Ti/Al ratio nearly at 0.05. U content of the cores is similar to that of the pelagic sediments.