The Processes of the Moho Transition Zone and the Mechanism of Plate Spreading at Fast-Spreading Ridges: Insight from Off-Ridge Volcanism - TOMINAGA, MASAKO; KISHIMOTO, KIYOYUKI; ASADA, MIHO; KUMAGAI, HIDENORI; GESHI, NOBUO; UMINO, SUSUMU; KASAYA, TAKAFUMI; ISHIZUKA, OSAMU; GOTO, TADANORI; MIYASHITA, SUMIO (Annual Meeting of the Geological Society of Japan, 2010)