Features of the heavy rare-earth elements in seawater

抄録

The rare earth element (REE) abundances in twenty-one seawater samples around the Japanese Islands have been precisely determined by the isotope dilution method. Besides Ce anomaly, REE patterns of the seawater samples show a zigzag feature reflecting the lanthanide tetrad effect, which is considered to be associated with the filling of 4f electron orbitals. Particularly, the third and the fourth tetrads, zigzags in Gd-Dy-Er and Er-Yb-Lu spans, are clearly observed. Furthermore, most of the REE patterns shown here demonstrate a straight line for La-Nd-Sm-Eu and a discontinuity between Eu and Gd. The degree of the third tetrad effect becomes larger with the increase of the discontinuity between Eu and Gd.