ABSTRACT

The lanthanides, La, Ce, Nd, Sm, Eu, Gd, Dy, Er and Yb were determined quantitatively for six basalts of Japan by the use of isotope dilution method. It is suggested that the high-alumina olivine basalt was a primary liquid-type material, the primary tholeiite was a primary solid-type material, and the alkali olivine basalt which was supposed to be primary was a secondary liquid-type material. This observation is in agreement with the consequence from the analysis of the relationship between thorium and uranium concentrations. The original depths for the aforementioned three magmas were estimated to be 200, 150 and 220 km, respectively, from the relative enrichment of lanthanides. A genetically close connection was corroborated for tholeiite and high-alumina basalt.