Mineralogical and chemical characteristics of volcanic rocks from the eastern part of Izu peninsula

Abstract

Basalt to basaltic andesite formed by monogenetic volcanoes is distributed along the vents extending from NW to SE direction in the eastern part of the Izu Peninsula. Among the volcanic group along the vent indicated by Koyama & Umino (1991), three volcanoes groups, 1) IT group (0 to 4 ka), 2) KT group (10 to 20 ka) 3) KW group (20 to 40 ka), were selected, and chemistry of rock and its constituent minerals in each group were examined. In particular, we investigated the relationship between chemical changes of zonal structure observed in phenocryst minerals and magma composition.