Manned submersible studies have delineated a large and actively growing Kuroko-type volcanogenic massive sulfide deposit 400 kilometers south of Tokyo in Myojin Knell submarine caldera, The sulfide body is Located on the caldera floor at a depth of 1210 to 1360 meters, has an area of 400 by 400 by 30 meters, and is notably rich in gold and silver. The discovery of a Large Kuroko-type polymetallic sulfide deposit in this are-front caldera raises the possibility that the numerous unexplored submarine silicic calderas elsewhere might have similar deposits.