R7: Petrology, Mineralogy and Economic geology (Joint Session with Society of Resource Geology)

[R7-05] Ancient melting event recorded in fore-arc peridotite

*Norikatsu Akizawa¹, Akira Ishikawa², Ryo Fujita², Teruaki Ishii³ (1. AORI, Univ. Tokyo, 2. Tokyo Tech., 3. Shizuoka Univ.)

Keywords:Fore-arc peridotite, Re–Os isotope, Boninite, Ancient mantle melting, Izu-Ogasawara-Mariana Trench

A melting-age model using Os isotopes and Yb has estimated that the source of boninite is heterogeneous, with the contribution of a mantle melted in Archean. In this study, in order to better understand the actual condition of mantle heterogeneity in terms of melting timing of the forearc mantle, bulk chemical composition and Re-Os isotope of peridotites collected in the forearc region of the Izu-Ogasawara-Mariana Trench were analyzed. The forearc mantle was found to be heterogeneous with respect to melting timing. However, we could not detect melting events back to Archean.