The CK16-01/Expedition 908 was conducted at the active hydrothermal field in the Iheya-North Knoll and Noho in Okinawa trough Japan by D/V Chikyu in Feb-Mar 2016. This expedition drilled hydrothermal fields recently discovered in the Iheya Small Ridge (Noho site: as reported in the JOGMEC news release on December 4, 2014) using LWD and geothermal tools. The purpose of this study in 2016 are to establish the origin and development model of deep water hydrothermal deposit, and to examine continuity of reservoir and mineral deposits in this area. The project was a part of "Scientific Research on Genesis of Marine Resources" for "Next-generation Technology for Ocean Resources Exploration," of the Cross-ministerial Strategic Innovation Promotion Program (SIP). LWD was conducted at 3 sites in Iheya-North Knoll and at 4 site in Noho. The gamma ray, various resistivities, and high resolution resistivity borehole image allows us to understand the futures of hydrothermal sediments. Real-time annular pressure and temperature allow us to analyze dynamic thermal formation fluid flow. The cores were acquired and quick measurement and analysis were carried out by onboard scientists. Monitoring devices were successfully installed at active hydrothermal field in Iheya and Noho to record temperature, pressure and flow rate of the hot fluid, and to observe its process of deposits.
The sub seafloor hydrothermal fluid reservoir at the Iheya North Knoll was surveyed in the IODP expedition 331 in 2010 by the deep sea drilling vessel (D/V) Chikyu (Takai et al., 2011, 2012). The results from the core samples indicated the possible existence of enormous sub seafloor hydrothermal fluid reservoirs that were much more expansive that expected from the extension of seafloor hydrothermal activities. "Scientific Research on Genesis of Marine Resources" for "Next-generation Technology for Ocean Resources Exploration," of the Cross-ministerial Strategic Innovation Promotion Program (SIP) had started for more detail exploration inse 2014. Measurement with LWD, core analysis, and installation of monitoring device were completed successfully in CK14-04/Expedition 907 (Takai et al., 2015; Sanada et al., 2015). Six wells with natural gamma ray, resistivity, annular temperature, and annular pressure with LWD shows us vertical and horizontal mapping of deposit.