ABSTRACT

Abundances of trace elements including rare earth elements (REE) were determined by instrumental neutron activation analysis for twenty three Tertiary volcanic rocks of northeast Japan. Positive correlations were confirmed in the following couples of elements: Hf-La, K-La, Th-La and Fe-Sc. Unlike Quaternary volcanic rocks, Tertiary volcanic rocks show no definite correlation between the inclination of REE patterns and the distance of sampling sites from the estimated volcanic front of the Tertiary. The presence of low alkali tholeiites with relatively flat REE patterns in the Japan Sea side suggests that Tertiary volcanism is qualitatively different from Quaternary one.