Permalink : http://hdl.handle.net/2115/36736

Abundances of trace elements including REE were determined for 22 Late Tertiary (Late Miocene to Pliocene) volcanic rocks from southwest Hokkaido. Geochemical features of the Late Tertiary volcanic rocks show that LIL elements, K2O and Th, increase at a given SiO2 content across the arc from the Pacific to the Japan Sea side, being similarly to those of the Quaternary volcanic rocks in the same region. However, the Late Tertiary volcanic rocks are higher in Hf/Yb ratios than the Quaternary rocks. This geochemical feature suggests that the former rocks may have derived from a more enriched source mantle than the source material of the latter ones.