Geochemical investigation of submarine hydrothermal systems.

Hydrothermal activity of Loihi Seamount，Hawaii，was researched by using R/V Hakuho Maru(KH85-4)in September1985。We established several basic techniques for locating submarine hydrothermal system：a CTD towing method for detecting temperature anomalies，and a method for mapping hydorthermal plumes from water column distributions of dissolved methane.Taking into account the importance of simultaneous measurements of many trace vetals in seawater，We purchased an ICP spectroscopy and have improved and utilized since then.From 1986，the survey target was focussed on the submarine hydrothermal activity in the Okinawa Trough。In July 1986，hydrothermal mounds(subsurface tempetature：40°C)issuing warm water were discovered at the Natsushima-84 Knoll in the middle Okinawa Trough by the submersible“SHINKAI 2000”(JAMSTEC)。The shimmering water samples were proved to have high methane and^3He/^4He values，characteristic of hydrothermal origin.In May 1987，the KH87-2cruise of R/V Hakuh…More o Maru was dedicated to the geochemical studies in the Okinawa Trough。A revised CTD towing system for surveying hydrothermal activity，a piston corer with heat flow measuring probes，and a transponder navigating system were employed in addition to usual equipments.In1988，the last year of the project，techiques so far developed were all concentrated on the Okinawa Trough surveys during the cruises：R/VCchofu Maru(Magasaki Marine Observatory)，R/V Sonne(West Germany，M/V Maru)。Massive sulfide deposits with the emanation of hot fluids(&gt；130°C)were discovered at the Izena Cauldron，about20miles south of the Natsushima-84Knoll.Water column anomalies of CH_4，MN，TCO_2，^3He，ets.Were also found there.The following areas were also surveyed by utilizing the same experimental techniques：Escanaba Trough in the Gorda Ridge spreading center，back-arc volcanism in the North Fiji Basin，fore-arc volcanism in the Izu-Bonin area，and plate boundaries in the Sagami Bay clam colony and in the eastern Japan Sea，etc.Less

Hydrothermal activity of Loihi Seamount, Hawaii, was researched by using R/V Hakuho Maru (KH85-4) in September 1985. We established several basic techniques for locating submarine hydrothermal system: a CTD towing method for detecting temperature anomalies, and a method for mapping hydorthermal plumes from water column distributions of dissolved methane. Taking into account the importance of simultaneous measurements of many trace vetals in seawater, We purchased an ICP spectroscopy and have improved and utilized since then.From 1986, the survey target was focussed on the submarine hydrothermal activity in the Okinawa Trough. In July 1986, hydrothermal mounds (subsurface tempetature: 40゜C) issuing warm water were discovered at the Natsushima-84 Knoll in the middle Okinawa Trough by the submersible "SHINKAI 2000" (JAMSTEC). The shimmering water samples were proved to have high methane and ^3He/^4He values, characteristic of hydrothermal origin.In May 1987, the KH87-2 cruise of R/V Hakuh … More o Maru was dedicated to the geochemical studies in the Okinawa Trough. A revised CTD towing system for surveying hydrothermal activity, a piston corer with heat flow measuring probes, and a transponder navigating system were employed in addition to usual equipments.In 1988, the last year of the project, techiques so far developed were all concentrated on the Okinawa Trough surveys during the cruises: R/VCchofu Maru (Magasaki Marine Observatory) , R/V Sonne (West Germany) , M/V Kaiko Maru No.5 (DELP) , R/V Tansei Maru, and "SHINKAI 2000". Massive sulfide deposits with the emanation of hot fluids (>130゜C) were discovered at the Izena Cauldron, about 20 miles south of the Natsushima-84 Knoll. Water column anomalies of CH_4, MN, TCO_2, ^3He, ets. were also found there.The following areas were also surveyed by utilizing the same experimental techniques: Escanaba Trough in the Gorda Ridge spreading center, back-arc volcanism in the North Fiji Basin, fore-arc volcanism in the Izu-Bonin area, and plate boundaries in the Sagami Bay clam colony and in the eastern Japan Sea, etc. Less