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North Knoll, Iheya Ridge

Name Alias(es): 
North Iheya Ridge
Iheya North
Iheya North Original
Vent Sites: 
Iheya North Original [contains North Big Chimney (= NBC, C0016), South Big Chimney (= SBC)]
Iheya North Natsu (contains Yarigatake Chimney)
Iheya North Aki (contains Ikinari Chimney, Furikaeri Chimney, Table Mountain, Kagamimochi)
Maximum Temperature: 
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
Deposit Type: 
Notes on Vent Field Description: 
position in database is for NBC at Iheya North Original; for assessment after the 2010 IODP drilling, see Kawagucci et al. (2013) and Nakajima et al. (2015); on cruise KY14-01 with ROV Hyper-dolphin in 2014, two new vent clusters - Iheya North Natsu and Iheya North Aki - were confirmed south of the Iheya North Original field. Here, we call these 'vent clusters' rather than creating new 'vent fields' in this database because the cruise report says: "These three hydrothermal fields likely had common [sub-seafloor] hydrothermal fluid sources such as sub-seafloor hydrothermal fluid reservoir and whole hydrothermal fluid flow paths. This implied that Iheya North Original, Natsu and Aki fields comprised one gigantic hydrothermal system (>3 km horizontal extension at the seafloor events)."; Ikinari Chimney at 317 C was boiling in 2014: "was the highest temperature of hydrothermal fluid ever recorded in the Iheya North Knoll."; Neptune Minerals Plc, 21 Feb. 2007, applications by Neptune Minerals Japan Kabushiki Kaisha: "Neptune's applications also cover the Minami-Ensei Knoll and Iheya North areas, both of which contain known SMS mineralisation."; JAMSTEC YouTube video, accessed 23 Apr. 2015:
Notes Relevant to Biology: 
Yamamoto et al. (1999): "... included some obligate species of chemosynthetic communities, Vestimentifera, Bathymodiolus and Calyptogena, which have chemosynthetic symbiont bacteria. Many of other species (two limpets, Provanna sp., three species of Polynoidae and Alvinocaris sp.) were thought to be obligate to chemosynthetic communities"; cruise KY14-01: two types of mussels with "huge" biomass near Kagamimochi; for megabenthos including the galatheid crab Shinkaia crosnieri after the 2010 IODP drilling, see Nakajima et al. (2015)
Year and How Discovered (if active, visual confirmation is listed first): 
1995 deep tow survey
Discovery References (text): 
[Chiba et al. (1996) Seafloor hydrothermal systems at North Knoll, Iheya Ridge, Okinawa Trough. JAMSTEC Journal of Deep Sea Research 12: 211-219].
Other References (text): 
Yamamoto et al. (1999) Chemosynthetic community at North Knoll, Iheya Ridge, Okinawa Trough. JAMSTEC J DSR 15: 19-24
Kataoka et al. (2000) Topography and fluid geochemistry of the Iheya North Knoll seafloor hydrothermal system in the Okinawa Trough. JAMSTEC Journal of Deep Sea Research 16: 1-7
Yamanaka, T. and Sakata, S. (2004) Abundance and distribution of fatty acids in hydrothermal vent sediments of the western Pacific Ocean. Org. Geochem. 35: 573-582.
Masaki, Y. et al (2011). Hydrothermal regime of the Iheya-North hydrothermal field inferred from surface heat flow data and IODP Expedition 331 drilling results. Poster abstract B51G-0478 presented at the American Geophysical Union 2011 fall meeting, December 5–9, 2011, San Francisco, CA.
Kawagucci S., et al. (2013), Post-drilling changes in fluid discharge pattern, mineral deposition, and fluid chemistry in the Iheya North hydrothermal field, Okinawa Trough, Geochem. Geophys. Geosyst., 14, 4774–4790, doi:10.1002/2013GC004895.
cruise KY14-01 report, available from JAMSTEC GODAC database
Nakajima R, Yamamoto H, Kawagucci S, Takaya Y, Nozaki T, et al. (2015) Post-Drilling Changes in Seabed Landscape and Megabenthos in a Deep-Sea Hydrothermal System, the Iheya North Field, Okinawa Trough. PLoS ONE 10(4): e0123095. doi:10.1371/journal.pone.0123095.