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

在1988年4月至1992年3月的研究项目中，我们参加了多次考察，取得了如下丰硕成果：1988年4月至6月，“松恩”号和“海约”号科考船在冲绳海槽中部的Iheya凹陷和Izena洞发现了高温型热液丘。这些土丘位于日本专属经济区。在此之前，我们已于1986年在冲绳海槽中央地堑所在的利亚坳陷发现了活跃的热液丘。这是世界上首次在弧后盆地中发现活动热液喷口系统。然而，这些土丘是由无定形的沉淀物组成的，而且喷出的水的温度并不高。相反，1988年发现的土丘是由大量硫化物矿石和喷口生物群组成的，与洋中脊系统中发现的土丘相似。然后，潜水器回收了热液矿石和喷口生物群的样本……更多的是当年9月的“新海2000”。1989年4月至5月，通过潜水调查，在伊泽纳洞发现了一个黑烟和其他活跃的热液喷口系统。分析结果表明，热液丘样品由富含金银的黑子型矿石组成。热液喷口特有的生物群包括Caliptogena和细菌。它们可以用来了解地球上生物的起源。在1990-1991年的潜水调查中，还广泛发现了其他热液丘，如Iheya凹陷北部的Ensei Knoll。1991年6月，利用“天蝎”号无人潜航器在冲绳海槽东部边缘进行了潜水调查，以了解海槽的隆升机理和时间。1992年1月，“横须贺”号用多窄梁测量了南井-射户海沟的详细地形，了解了海沟运动与弧后形成的机理。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，冲绳坳陷处于大陆裂陷阶段。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