| Project/Area Number |
63440006
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
Stratigraphy/Paleontology
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| Research Institution | University of the Ryukyus |
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Principal Investigator |
KIMURA Masaaki University of the Ryukyus, College of Science, associate professor, 理学部, 助教授 (20112443)
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| Co-Investigator(Kenkyū-buntansha) |
UYEDA Seiya Tokai University, Department of Marine Science, Professor, 海洋学部, 教授 (60011459)
YAMAZATO Kiyoshi University of the Ryukyus, College of Science, 理学部, 教授 (80044973)
KATO Yuzo University of the Ryukyus, College of Science, Professor, 理学部, 教授 (70004372)
OOMORI Tamotsu University of the Ryukyus, College of Science, Associate professor, 理学部, 助教授 (00045022)
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| Project Period (FY) |
1988 – 1991
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| Keywords | Okinawa Trough / Backare basin / Hydrothermal ore / Hydrothermal biota / Black smoker / Ryukyu Arc / Vent system / Rift system |
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| Research Abstract |
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
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