Two possible hydrothermal vents in the northern Okinawa Trough

As the Okinawa Trough is a back-are basin in early spreading, modern submar ine hydrothermal activity and minerallization have many characteristics whi ch have aroused wide attention. Up to now three well-known hydrothermal ven ting areas are all located in the middle part of the trough, During two cru ise investigations to map and sample the seafloor numbers of Calyptogena sp , shells were dredged at two sites in the northern trough with comparativel y thicker crust and numerous submarine volcanoes. Based on the fact that Ca lyptogena sp, is only observed around the hydrothermal vents and lives on h ydrothermal activities, it is predicted that there is the possibility of mo dern hydrothermal activities in the northern part of the trough. In this no te, the shell is carefully characterized and the sample locations with poss ible hydrothermal activity are given. it Is pointed out that the research o f biogenic fossils to trace hydrothermal activity changes in venting time, strength fluctuations, evolution In chemical compositions and so on should be stressed in the future in addition to the study of the ecological charac teristics of hydrothermal organisms.