Across-arc chemical variations in the basalts distributed in Southern Kyushu

In Southern Kyushu, the basalts which erupted at about 1Ma are distributed in across arc direction. From the volcanic front to the back-arc, these basalts vary from island-arc basalt through within-plate alkali basalt and within-plate tholeiite to island-arc basalt. This is not common in many island arcs and means that magma generation processes across in Southern Kyushu cannot be explained by the partial melting of the metasomatized mantle wedge source.