Trace element abundances in the Quaternary volcanic rocks of the Norikura volcanic chain, central Honshu, Japan

抄録

Abundances of 16 trace elements including rare earths are determined by the instrumental neutron activation analysis for the Quaternary volcanic rocks of central Honshu, Japan. There is no systematic lateral variation along the Norikura volcanic chain except for the older part of Ontake volcano and Ueno volcano. The across-arc variation along the transverse through Yatsugatake-Norikura-Hakusan volcanoes does not reveal a regular increase in the incompatible element abundances away from the volcanic front. Based on the incompatible element abundances normalized to SiO₂ = 50%, volcanoes in central Honshu are grouped into three, that is, Myoko and Kurohime (MK & KH), Yatsugatake (YT) and Norikura volcanic chain and Hakusan (NVC & HK) in increasing order. This variation can be explained by the difference in degree of partial melting and of the local enrichment of K and Rb in Myoko and Kurohime volcanoes.