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Name Alias(es): 
Iheya Small Ridge
Iheya Ridge
Vent Sites: 
Clam field (= Clam Site) (includes Calyptogena site and Pyramid chimney)
Noho (?) (= pNoho)
Maximum Temperature: 
Max Temperature Category: 
Location on map: 
National Jurisdiction: 
Maximum or Single Reported Depth (mbsl): 
Minimum Depth (mbsl): 
Tectonic setting: 
Full Spreading Rate (mm/a): 
Volcano Number (if applicable): 
Host Rock: 
basalt, high-K andesite, dacite, sediment
Deposit Type: 
Notes on Vent Field Description: 
Sakai field includes Clam, Hitoshi, and Noho (?) (direction: N to S & shallower to deeper); position in database and max temp 280 C at Hitoshi site 27°32.886'N, 126°59.371'E (Cruise Report NT15-13, 2015); maximum temperature 338 C for pNoho on ROV Hyper-Dolphin Dive 1772 in Miyazaki et al. (2017); for Clam site: Ishibashi et al. (2015): "temperature was recorded as 220 C in 1988. Venting was ceased in 1990, and since then, dive studies have not been conducted in this field"; Calyptogena site did not have shimmering water, Pyramid site 200 m N of Calyptogena had clear smokers 100-220 C;
Notes Relevant to Biology: 
Calyptogena okutanii, Neolepas-type scalpellid barnacles, tubeworms; fauna less abundant at Pyramid than Calyptogena
Year and How Discovered (if active, visual confirmation is listed first): 
1988 submersible Shinkai 2000; 1987 plume only
Discovery References (text): 
[Tanaka et al. (1989) Shinkai 2000 diving surveys in the east of Iheya Small Ridge of the central Okinawa Trough. JAMSTECR Deep-Sea Res. 267-281 (in Japanese with English abstract)];
(plume only) Ishibashi et al. (1988) Geochemical evidence for hydrothermal activity in the Okinawa Trough. Geochemical Journal 22: 107-114;
Other References (text): 
Ohta, S. and Kim, D. (2001) Submersible Observations of the Hydrothermal Vent Communities on the Iheya Ridge, Mid Okinawa Trough, Japan. J. Oceanogr. 57: 663-677;
Halbach et al., Econ. Geol., 88, 2210-2225, 1993;
Ishibashi, J., et al. (2015) Hydrothermal Activity in the Okinawa Trough Back-Arc Basin: Geological Background and Hydrothermal Mineralization. pp. 337-359 in Ishibashi, J. et al. (eds) Subseafloor Biosphere Linked to Hydrothermal Systems. Springer. doi:10.1007/978-4-431-54865-2_27;
R/V Natsushima & ROV Hyperdolphin Cruise Report NT15-13, 2015 Summer Tour of deep-sea hydrothermal ventfields in mid Okinawa Trough and investigation of their geochemical and (micro)biological diversity, July 27, 2015 from Kumamoto – August 6, 2015 to Kagoshima, Japan Agency f or Marine-Earth Science and Technology (JAMSTEC), (accessed on: 2019/03/20);
Miyazaki, J., et al. (2017) WHATS-3: An Improved Flow-Through Multi-bottle Fluid Sampler for Deep-Sea Geofluid Research. Front. Earth Sci., 5,;
Nakamura, K., et al. (2015) Water column imaging with multibeam echo-sounding in the mid-Okinawa Trough: Implications for distribution of deep-sea hydrothermal vent sites and the cause of acoustic water column anomaly. Geochem. J., 49,;