Large hydrothermal deposit found off coast of Iheya Island

Large hydrothermal deposit found off coast of Iheya Island

Iheya north sea hill, where the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) found the largest hydrothermal deposit ever found near Okinawa.

July 27, 2014 Ryukyu Shimpo

The Japan Agency for Marine-Earth Science and Technology (JAMSTEC) announced on July 26 that there is possibly presence of a hydrothermal deposit under the sea off the coast of Iheya Island. JAMSTEC speculates that this hydrothermal deposit is the largest one of those ever found near Okinawa. The location of the hydrothermal deposit is at North Knoll, Iheya Ridge, about 150 kilometers off the coast northwest of Naha. The survey results suggest the deposits span a wide area in three locations in the sea knoll. There is a possibility that the hydrothermal deposits include seabed resources such as lead and zinc.

The survey was carried out during the period from July 14 to 26 using the deep sea drilling vessel Chikyu, which is 210 meters long and weighs 56,752 tons. JAMSTEC carried out the survey using Logging While Drilling (LWD) technique, which is able to analyze viscosity and composition of geological formation. They drilled between 150 and 350 meters below the seabed at six locations of three hydrothermal deposits. They also collected minerals at two locations of six drilling places. JAMSTEC speculates this hydrothermal deposit spans about five kilometers from north to south and around 3-3.5 kilometers from east to west. The nature of the materials collected at six different locations is similar.

On July 26, at Nakagusuku Port, JAMSTEC's deep sea drilling vessel Chikyu came to an anchor.

Ken Takai, a researcher of JAMSTEC said, “We can almost prove the presence of a hydrothermal deposit in an area stretching from east to west. However, we need to do further research because the number of drilling points is not enough. We want to continue working on it into next year. He added, “The data acquired by the logging-while drilling (LWD) systems was almost the same as that of the actual minerals collected by drilling. The LWD is a cutting edge technology that will have a major impact on the development of hydrothermal deposit-searching.”

(English translation by T&CT)

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