The Yoron Hole: The Shallowest Hydrothermal System in the Okinawa Trough

During NT10-16 cruise with R/V NATSUSHIMA and ROV HYPER-DOLPHIN in 2010, a new hydrothermal vent community was discovered at the Yoron Hole, where is the shallowest hydrothermal system in the known hydrothermal site found in the Okinawa Trough. The maximum temperature of clear smoker fluid was 247 °C, which was slightly lower than the boiling temperature (275 °C) of the seawater at the water pressure of 560-m water depth (5.6 MPa). Hydrothermal chimneys are composed of barite, sphalerite, galena, pyrite, chalcopyrite, and tetrahedrite. Although crustaceans and polychaetes were found around the hydrothermal vent, the diversity and population density were lower than that of the Iheya North Knoll and the Izena Hole hydrothermal sites.