We present detailed petrographic observations, modal compositions of phenocrysts, and wholerock major and trace element data (Ba, Rb, Nb, Sr, Zr, and Y) for volcanic rocks of the Kuju Volcanic Group (KVG), northeast Kyushu Island, southwest Japan Arc.We classified these volcanic rocks into three groups based on the mineral assemblage and modal abundance of phenocrysts: (1) a group containing 2.9 vol.% olivine and lacking hornblende (Ol-g); (2) a group containing hornblende (Hbl-g); and (3) a group containing 2.0 vol.% orthopyroxene with a small amount of olivine (1.3 vol.%) and lacking hornblende (Opx-g).In addition, based on the characteristics of plagioclase (Pl) and clinopyroxene (Cpx) phenocrysts, Hbl-g can be subdivided into three types: samples containing abundant Pl with dusty cores are defined as Hbl-g1, whereas those poor in Pl with dusty cores are divided into Cpx-rich Hbl-g2 and Cpx-
Yamanaka et al. (Thu,) studied this question.