A drilling campaign in Okinawa Trough, back arc hydrothermal systems

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Author(s): Kumagai, Hidenori; Ishibashi, Jun-Ichiro; Nozaki, Tatsuo; Takai, Ken; Nagase, Toshiro; Maeda, Lena; Kubo, Yusuke
Chikyu SIP Cruises On-board Members Scientific Team
Author Affiliation(s): Primary:
Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
Kyushu University, Japan
Tohoku University, Japan
Volume Title: AGU 2018 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2018; American Geophysical Union 2018 fall meeting, Washington, DC, Dec. 10-14, 2018. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Following IODP Expedition 331 in 2010, a series of scientific drilling in a back-arc hydrothermal systems was performed in Okinawa Trough, Western Pacific. The series targeted 1) to bound the sub-seafloor hydrothermal reservoir at Iheya-North Knoll, 2) to obtain typical lithology of sediment layers ores impregnating, 3) in-situ measurement of physicochemical properties of mineralization parts and ores, in order to provide the key information to assemble a future exploration apparatus and to formulate a model of ore-formation. To overwhelm the low recovery of the core under largely heterogeneous formations under alteration and sulfide mineralization, we widely applied to logging operations, especially Logging-while-Drilling (LWD) apparatus, in the areas of Iheya-North Knoll and of Iheya Minor Ridge. Further, another memory-type apparatus applied to the drilling at Izena Hole. Further, an ambitious coring operation was performed using hydraulic piston-coring system with every five meters or shorter, even for the subseafloor orebodies in Izena Hole. The above described strategy was quite successful, then, the series of drilling resulted in; 1) a km-scale reservoir provides common high temperature fluids for three vent-concentrated sites on Iheya-North Knoll, 2) simultaneous progress of sulfide mineralization were found associating with multiply layered reservoir beneath Iheya-North Knoll, 3) distinct textures suggesting rather slow precipitations of sulfide minerals were found at sub-seafloor ore-body in Izena-Hole contrasting to the rapid precipitation found in the mound-derived ore-bodies. Although detailed modeling of the sulfide mineralization in sediment layers penetrated through this drilling campaign is yet to be done, it is suggested that the wide-variation for sulfide mineralization processes occurs in the submarine hydrothermal deposits.
Year of Publication: 2018
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Drilling; Expedition 331; Hydrothermal conditions; Integrated Ocean Drilling Program; International cooperation; Metal ores; Mineral resources; North Pacific; Northwest Pacific; Okinawa Trough; Pacific Ocean; Well-logging; West Pacific
Coordinates: N274700 N274800 E1265500 E1265300
Record ID: 2019050475
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