Behaviors of Mn and Fe in hydrothermal lpumes and diffused flows at the Suiyo Sea Mt., Izu-Bonin arc

We studied for hydrothermal plumes and diffused flows at the Suiyo Sea Mount in the Izu-Bonin arc by using in situ Mn-Fe analyzers (GAMOS). GAMOS-II (Geochemical Anomalies MOnitoring system) is an in-situ chemical analyzer used to detect manganese and/or iron anomalies in neutrally buoyant plumes and to map distributions in bottom seawater over vent fields. During NT 01-09 (SHINKAI 2000 / NATSUSHIMA, JAMSTEC) and KR 01-15 (KAIREI, JAMSETC) cruises, GAMOS-II measurements were conducted for plume observation. Manganese, iron concentrations and temperature anomalies were observed in the caldera of the Suiyo seamount . Three maxima in temperature were detected at 1,080 m, 1,200 m and 1,280 m. But only one peak was observed for iron and manganese. Shallow plum at 1,080 m has a lower Metal /heat ration compared to deeper plume. GAMOS-IV was designed for stand-alone operation of up to one month. GAMOS-IV was deployed on seafloor for long term observation of manganese concentration and water temperature in hydrothermal diffused flow using ROV HAKUYO 2000 in August, 2001 and manned submersible SHINKAI 2000 in September, 2001 and 2002. Anomalies of manganese concentration (- 4,000 nM) and water temperature (- 6.0°C) were observed coincidentally. The Mn/ŸOT ratio observed at this diffused flow were almost same with high temperature fluid in the seamount and uniform throughout each two deployments. This indicates that the diffused flow in the Suiyo seamount had single source fluid same as the high temperature fluid.