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Irabu Knoll

Name Alias(es): 
Yaeyama Graben
East Yaeyama Graben
Maximum Temperature: 
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National Jurisdiction: 
Maximum or Single Reported Depth (mbsl): 
Minimum Depth (mbsl): 
Tectonic setting: 
Full Spreading Rate (mm/a): 
Volcano Number (if applicable): 
Host Rock: 
Deposit Type: 
Notes on Vent Field Description: 
southern Okinawa Trough; note: S. Petersen distinguishes northern and southwestern volcanoes at eastern end of Yaeyama Graben; Yaeyama Central Graben trends east-west and is located south of Miyako Seamount and north of Miyako Island; Matsumoto et al. (2001): "The area was surveyed by R/V YOKOSUKA and DSV SHINKAI 6500 in July-August 2000 (Lequios Cruise: Cruise ID=YK00-06 Leg2) after the succession of the previous l'Atalante cruise in 1996 in the SPOT Area (east of Taiwan). ... Two active hydrothermal sites were newly located through 10 dives in the study area. One is located in the SPOT area and the other on the axial zone of the Okinawa Trough off the northern coast of Miyako Island. Maximum temperature was 170.DEG.C. in the former case and 150.DEG.C. in the latter case. Both sites are characterised by active chimneys associated with sulphide deposits and chemosynthetic communities."; Okino et al. (2015): AUV Urashima dives 181 and 184 in 2014, "In dive 181 and 184, we confirmed three known hydrothermal vents"
Notes Relevant to Biology: 
dense actinian assemblage (KATSURA et al., 1986)
Year and How Discovered (if active, visual confirmation is listed first): 
2000 submersible Shinkai 6500; 1986 seafloor photos did not confirm activity
Discovery References (text): 
Matsumoto et al. (2001) Volcanic and hydrothermal activities and possible "segmentation" of the axial rifting in the westernmost part of the Okinawa Trough. Preliminary results from the YOKOSUKA/SHINKAI 6500 Lequios Cruise. JAMSTEC Journal of Deep Sea Research 19: 95-107
(photos only) [KATSURA T., et al. (1986) Geological and geophysical characteristics of the southwestern Okinawa Trough and adjacent area. Report of Hydrographic Researches, 21, 21-47 (In Japanese with English abstract)].
Other References (text): 
Okino, K. et al. (2015) Preliminary report of AUV URASHIMA dives at Tarama and Irabu hydrothermal fields. Japan Geosience Union Meeting 2015, abstract SCG64-09.