FEATURES OF THE HEAVY RARE-EARTH ELEMENTS IN SEAWATER

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 pat-terns of the seawater samples show a zigzag feature reflecting the lanthanide tetrad effect, which is con-sidered 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. © 1990, GEOCHEMICAL SOCIETY OF JAPAN. All rights reserved.