四国中央部柳野デイサイトの全岩化学組成

Abstract

Whole rock major and trace element compositions of the two samples from the Yanagino dacite in central part of Shikoku were determined by XRF and INAA. One sample have similar composition with those previously reported by Umehara et al. (1991). The other sample have more evolved composition with higher SiO₂. content. Both samples are peraluminous and show REE pattern with enriched-LREE, flat -HREE, and negative Eu anomaly. These characteristics are osculate with those of S-type granite of Outer zone granitic rocks of SW Japan. However their alkali content and some of the trace elements composition are clearly differ from those of granodiorites in the Uwajima pluton, a neighboring S-type granite of Outer zone granitic rocks. To correlate Yanagino dacite to other Middle Miocene igneous rock series in SW Japan, more precise radiometric dating is indispensable.