SPOT, Yonaguni Knoll IV

Southernmost Part of Okinawa Trough; westernmost vent field within Japanese waters; "20 active hydrothermal vents are aligned along an elongated depression and fluid circulation occurs within accumulated terrigenous sediments"; Inagaki et al. (2006): "The hydrothermal field is characterized by two active black smoker vents (Tiger and Lion chimneys), with vent fluid temperatures up to 323°C"; known for liquid CO2; Lee (1999): " Seven out of the 68 identified volcanoes have shown an active hydrothermal venting from the high-frequency EK500 records"; Gamo et al. (2010) clarified the hydrocasts SPOT-1 through SPOT-5, with SPOT-5 being the closest; see maps in Okino et al. (2002) and Hongo et al. (2007); Okino et al. (2002): "Station SPOT-5 (Fig.3) showed the highest light transmission anomaly up to ~5% within 300 m above the seafloor."; 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.";