ABSTRACT

Seeing from the theory advanced by MASUDA and MATSUI (1966), the tholeiite having a slightly upward convex, chondrite-normalized lanthanide pattern shows an apparent uniform enrichment of all the lanthanides. This enrichment factor is understood, at least partially, to have been brought about by the partial melting of the upper mantle material. The alkali olivine basalt having a logarithmically linear lanthanide pattern does not show a substantially high, uniform enrichment of lanthanides. It is inferred that the tholeiite and the alkali olivine basalt are derived from quite different source materials. The presence of two different types of source materials for magmas is considered to be natural in light of the model presented by us.