Research and analyses of hydrothermal smokers, biota and ores in the Okinawa Trough.

在1988年4月至1992年3月的研究计划中，我们参加了多次研究航行，并取得了以下成果。1988年4 ~ 6月，日本“索内”号和“海洋”号考察船在冲绳海槽中部的伊平谷坳陷和出泉洞发现了高温型热液土丘。这些土丘位于日本专属经济区内。在此之前，我们已于1986年在冲绳海槽中央地堑的黎亚坳陷发现了活动热液土丘。这是在世界弧后盆地中首次发现活动热液喷口系统。土丘由无定形沉淀物组成，喷出水的温度不高。相反，1988年发现的土丘由块状硫化物矿和喷口生物群组成，与大洋中脊系统中发现的丘体相似。然后，通过潜水器回收热液矿石和喷口生物样品 ...更多信息 2000年9月的“SHINKAI 2000”1989年4 ~ 5月在伊泽纳洞潜水调查中发现了黑烟囱和其他活动热液喷口系统。分析结果表明，热液土丘样品由产金、银的黑矿型矿石组成。还发现了特定的热液喷口生物群，包括Caliptogena和细菌。他们可以知道地球上生物的起源。1990 ~ 1991年的潜水调查，在伊平谷凹陷以北的延世穹丘等地发现了热液土丘。1991年6月，为了解冲绳海槽的破裂机制和破裂时间，在冲绳海槽东缘进行了“蝎子号”潜水调查。1992年1月，“横须贺”号在南海诸岛海沟进行了多波束地形测量，了解了海沟运动与弧后构造的关系。相反，最近的研究表明，冲绳海槽具有典型的大陆地壳。这些证据表明冲绳海槽处于大陆裂谷阶段。少

During this research program from April 1988 to March 1992, we attended to many research cruises and got fruitful results as follows. High temperature type of hydrothermal mounds were discovered at the Iheya Depression and the Izena Hole in the middle Okinawa Trough by research ships Sonne and Kaiyo between April and June 1988. The mounds are located in Japanese Exclusive Economic Zone. Before that, we had already discovered active hydrothermal mounds at the lheya Depression where is the central graben of the Okinawa Trough in 1986. It was the first finding of the active hydrothermal vent system in the world backarc basins. The mounds, however, are composed of amorphous precipitates and the temperature of, venting water is not so high. On the contrary, the mounds discovered in 1988 are composed of massive sulfide ore and vent biota, which were similar to those found in the mid-oceanic ridge systems. And then, samples of hydrothermal ore and vent biota were recovered by the submersible … More "SHINKAI 2000" in September of the year. A black smoker and other active hydrothermal vent systems were discovered at the Izena Hole during April to May in 1989 by the diving surveys. Analytical results show that samples from hydrothermal mounds are composed of Kuroko type ore producing tich gold and silver. Specific hydrothemal vent biota including Caliptogena and bacteria were also recovered. They are available to know origin of living things on the earth. And then other hydrothermal mounds has been found in wide such as the Ensei Knoll north of the Iheya Depression by the diving surveys during 1990-1991. The diving survey with the chartered, unmanned submersible "Scorpion" were carried out at the eastern margin of the Okinawa Trough to understand the mechanism and stating time of rifting of the trough in June 1991. Detailed topography were surveyed with multi-narrow beams at the Nansei-shoto Trench by "Yokosuka" in January 1992, knowing mechanism relating between trench movement and backarc formations. On the contrary, recent studies show that the Okinawa Trough has a typical continental crust. All these evidence suggests that the OkinawaTrough is in continental rifting stage. Less