Geochemistry of Lavas and Ejecta of the 1986 Eruption of Izu-Oshima Volcano

Abstract

Major and trace element compositions and ⁸⁷Sr/⁸⁶Sr ratios were determined for 3 lavas and 2 scorias of the 1986 eruption of Izu-Oshima volcano. The magma from A crater has similar chemical and Sr isotopic compositions to magmas which flowed out many times in the post-caldera stage of Oshima volcano. While, magmas from B and C craters have different chemical compositions from the magma from A crater, in spite of similar Sr isotopic compositions. REE pattern, Sr/Ca-Ba/Ca systematics and other trace element distribution pattern indicate that the magma of B and C lavas are fractional crystallization products of the magma of A lava.