R6: Plutonic rocks, volcanic rocks and subduction factory

[R6P-08] Petrological and geochemical features of High-Mg andesite, High-Mg orthopyroxene bearing andesite and dacite from the Choshi area, Chiba Prefecture, Japan

*Toshiro Takahashi¹, Akitaka Shibano², Jun-ichi Ohki³, Naoya Iwamoto⁴ (1. Niigata Univ, 2. Niigata Univ. Sci., 3. Natural History Museum and Institute, Chiba, 4. Choshi Geopark)

Keywords:high-Mg andesite, high-Mg orthopyroxene, slab melt, melt-mantle reaction

Early Miocene Ol basaltic andesite, Opx andesite, and Opx dacite lava are distributed in the Choshi area, Chiba Prefecture. Opx andesite and Opx dacite magma are thought to have been formed by the reaction between slab melt and mantle peridotite. On the other hand, the above model cannot explain the HFS element concentrations in Ol basaltic andesite. The generation of Ol basaltic andesite magma requires HFS elements enriched mantle material or their enrichment process.