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伊平屋北部热液区(Iheya North hydrothermal field)位于冲绳海槽中部地区。综合大洋钻探计划(IODP)331航次于2010年9月1日至10月4日在该区钻探了5个站位(C0013～C0017):C0016站位位于North Big Chimney(NBC)地区活跃的热液烟囱和硫化物—硫酸盐丘状体上;在C0013、C0014、C0015、C0016站位发现了异常高热流值;在热液补给区C0017站位,实现最大钻探深度达到海底下151 m。在活跃的丘状热液喷口处的C0016站位,尽管取芯率只有4.7%,但首次在现代海底获得黑矿型(Kuroko-type)、富闪锌矿的黑色矿石样品。其他4个站位岩芯主要为具有不同热液蚀变和矿化程度(沸石相到绿片岩相)的互层状半深海和火山碎屑沉积物,及火山角砾和浮岩砾屑。钻孔中不规则的地温梯度剖面变化揭示出地下流体的横向运移趋势。现场数据表明,岩芯孔隙水和气体组成在垂向和横向上变化较大。海底作用主要包括通过相态分离而形成高盐水和富气体的流体,矿物蚀变释放Ca而吸附Mg和Na,高温下K释放而低温吸收,硬石膏形成,有机质的微生物氧化和甲烷利用硫酸盐的厌氧氧化,微生物作用下甲烷形成等。船上研究未证实研究区存在活跃的深部生物圈,细胞丰度明显低于以前的ODP/IODP在陆架边缘的钻探站位。
The Iheya North hydrothermal field is located in the central Okinawa Trough. The Integrated Ocean Drilling Program (IODP) voyage 331 drilled 5 stations (C0013-C0017) in the area from September 1 to October 4, 2010: active site C0016 at North Big Chimney (NBC) Liquid chimneys and sulphide-sulphate mounds; abnormally high heat flow values were found at stations C0013, C0014, C0015 and C0016; and at the station C0017 in the hydrothermal recharge zone, the maximum drilling depth reached 151 m below seafloor. At station C0016 at the moulting hydrothermal vents, Kuroko-type, black ore-rich black ore samples were obtained for the first time on modern seafloor, despite a coring rate of only 4.7%. The other four core stations are mainly interbedded semi-deep sea and volcaniclastic sediments with volcanic hydrothermal alteration and mineralization (zeolite facies to greenschist facies), volcanic breccias and pumice gravels. Irregular geothermal gradient profile changes in boreholes reveal the tendency of underground fluids to migrate laterally. Field data show that core pore water and gas composition vary greatly in both vertical and horizontal directions. Submarine effects mainly include the formation of high-saltwater and gas-rich fluids by phase separation, the alteration of Ca and Mg by mineral alteration, the release of K at high temperature, the absorption of low temperature, the formation of anhydrite, the microbial oxidation of organic matter and the utilization of sulphate Anaerobic oxidation, methane formation under the action of microorganisms and the like. The on-board study did not confirm the presence of an active deep biosphere in the study area, with a significantly lower abundance of cells than the previous ODP / IODP drilling site at the edge of the shelf.