ABSTRACT

Rear-earth abundances were determined precisely for twenty-four volcanoes of the Northeastern Japan Islands. The inclination of the pattern for lighter REE span was found to depend sensitively on the distance of the volcano from the volcanic front. The f_w value (residual liquid fraction) for the volcano situated near the volcanic front is about unity and decreases rapidly with the distance from the volcanic front. The rate of change of f_w is almost parallel with the rate of change in the volume of volcanic products with the distance from the volcanic front. Also it is emphatically noted that the relatively chondritic REE pattern not only actually emerges as a rather special case at the front but can be significant in consideration of possibly incipient magma. Moreover, it is suggested that there can be two kinds of sources of genetically different natures for apparently chondritic, initial melts.