RARE EARTH ELEMENT GEOCHEMISTRY OF Co-RICH CRUST IN THE MID -PACIFIC AND SOUTH CHINA SEA

The rare-earth element (REE) concentrations of Co-rich crust from the Central Pacific Ocean and South China Sea were determined using chemical-digest ICP-MS method. This paper discusses the REE abundance, distribution features in different layers,and REE participation patterns of Co-rich crust. Our research results indicate that:(1) The REE concentrations in Co-rich crusts of the Central Pacific and South China Sea are distinctively high, and REE content varies between 1380×10^-6~2360×10^-6, 10~100 times higher than the REE concentration of crusts from water sediment and seawater. (2) The REE participation patterns of research area and other sea area are similar. The TREE is relatively enriched and the HREE is in relative depletion. (3) Content of Ce and ∑Ce/∑Y is decreasing along the growth layer of the Co-rich crust (from bottom to top). (4) Different sea areas have great differences in REE concentrations of Co-rich crusts. REEs in Co-rich crust are the highest in the Hawaiian Islands, and the lowest in the South China Sea, with those of the Mid-Pacific seamounts in between.The rare earth element distribution characters indicate that ocean environment for Co-rich crust growth is different from each other in different seamounts.