| Project/Area Number |
12640442
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Geology
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| Research Institution | Nagoya University |
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Principal Investigator |
SUZUKI Kazuhiro Nagoya Univ., Center for Chronological Research, Professor, 年代測定総合研究センター, 教授 (90111624)
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| Co-Investigator(Kenkyū-buntansha) |
TAKEUCHI Makoto Nagoya Univ., Graduate School of Environmental Studies, Associate Professor, 大学院・環境学研究科, 助教授 (80273217)
ENAMI Masaki Nagoya Univ., Graduate School of Environmental Studies, Professor, 大学院・環境学研究科, 教授 (20168793)
ADACHI Mamoru Nagoya Univ., Museum, Professor, 博物館, 教授 (10113094)
TSUKADA Kazuhiro Nagoya Univ., Museum, Assistant Professor, 博物館, 助手 (80303600)
KATO Takenori Nagoya Univ., Center for Chronological Research, Professor, 年代測定総合研究センター, 助手 (90293688)
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| Project Period (FY) |
2000 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥4,300,000 (Direct Cost: ¥4,300,000)
Fiscal Year 2001: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2000: ¥3,300,000 (Direct Cost: ¥3,300,000)
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| Keywords | CHIME dating / Monazite / Korean Peninsula / Metamorphic rocks / Geochronology / Higo metamorphic belt / Denudation history / Gyonggi massif / 変成帯の削剥上昇 / CHIME ages / Permian / Korean Peninsula / Japanese Islands / Gyeonggi Massif / Precambrian / Hida belt / Higo belt |
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| Research Abstract |
Basement rocks in the Japanese Islands and the eastern margin of Asian continent were correlated on the basis of the CHIME dating of accessory monazite and zircon and the XRF analyzes of whole-rock composition. The main results are as follows.
(1) Tonalitic clasts in Usuginu conglomerate of the South Kitakami terrane show 258-247 zircon and monazite ages which are are consistent with the Late Permian fossil age. If these ages are taken as representing emplacement ages of the source granitoids, rapid denudation of the source areas must have occurred. Granitoids in the Sikhote-Alin area show CHIME monazite ages of around 250 Ma, and appear to be a likely source ofclasts in the Usuginu conglomerate.
(2) Quartzofeldspathic veins in the sillimanite-grade Ryoke paragneiss in the Otowa-Honguusann area, Aichi Prefecture are classified into deformed and ndeformed veins. Deformed veins show boudinage structure, and give CHIME monazite ages of 95-90 Ma. Undeformed veins are discordant with a clear-
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cut boundary, and give 86-77 Ma monazite age. The ages coupled with the deformation pattern of veins suggest that the metamorphic rocks in the area had been uplifted from the ductile deformation condition to the brittle deformation conditions during the period of 90-86 Ma.
(3) CHIME dating of granitoids in southeastern China disclosed that the middle to late Jurassic granites are prominent throughout the inland area including Huangshan and Wugongshan, whereas the middle Cretaceous granites are distributed mainly in the coastal region.
(4) A granite clast from the Tsukiyozawa conglomerate shows 178+/-3 Ma CHIME monazite ages. This is the first authenticated document to unveil the existence of the Jurassic granitoid from the Jurassic intraformational conglomerate in the Mino terrane, and provides a clearer clue to the Mesozoic source rock for clastic rocks of the terrane.
(5) The Sosan granite gneiss shows 1.72 Ga CHIME zircon age. It has long been considered to be a intrusion emplaced into paragneisses in the G^onggi massif. The CHIME dating, however, show monazite and zircon in the paragneiss are much younger that in the Sosan granite gneiss. The paragneisses were folded together with leucogranite veins which give CHIME monazite and zircon ages of c. 250 Ma. This suggests an intense Late Permian metamorphism in Korean Peninsula.
(6) Monazite grains in Higo metamorphic rocks are in textural equilibrium with the peak metamorphic mineral assemblage, and are oriented parallel to a strong mineral foliation developed during peak metamorphism. All monazite grains yield CHIME ages of 110-120 Ma. On the basis of the petrographic evidence the monazite ages are interpreted as representing the time of metamorphism and deformation. This conclusion is contrary to studies which suggest that the Higo gneiss formed during the Permian-triassic. Less
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