2005 Fiscal Year Final Research Report Summary
The evolution of deeply subducted carbonates and the formation of microdiamonds
| Project/Area Number |
15204050
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Petrology/Mineralogy/Science of ore deposit
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| Research Institution | Waseda University |
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Principal Investigator |
OGASAWARA Yoshihide Waseda University, School of Education, Professor (70160736)
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| Project Period (FY) |
2003 – 2005
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| Keywords | UHP metamorphic rock / microdiamond / deep continental subduction / carbonate / dolomite / intraslab UHP metasomatism |
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| Research Abstract |
This study revealed the evidence for the aqueous fluid recycling in the continental materials during deep subduction to form UHP metamorphic rocks and for the metasomatism under UHP conditions. Intraslab UHP metasomatism model was proposed to explain these processes occurred in natural UHP metamorphic rocks. Multicomponent aqueous fluid released from subducted silicate rocks had been infiltrated into carbonate layers and had led to strong metasomatism. During such a metasomatism process, abundant microdiamond could form in carbonate rocks, particularly dolomite marble. Several components could be solved in recycled aqueous fluids under UHP conditions ; TiO2 was one of the representative one. In the Kokchetav UHP metamorphic rocks, Ti-clinohumite occurs in diamond-free UHP dolomitic marble, and the origin of TiO2 in clinohumite could be a solved component in aqueous fluid indicating high H2O activity. This suggest that diamond could be unstable under very high H2O activity even in carbo
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nate rocks and carbon could dissolve into fluid phase. Diopside in this rock contains over 850ppm of H2O as hydroxyl on the basis of micro-FT-IR study. This also means diamond-free dolomitic marble could form under very high H2O activity conditions. Diopside in this marble does not contain K2O-bearing exsolved phases contrary to diamond-bearing dolomite marble. Not only the bulk K2O composition, the solubility of K2O in aqueous fluid under UHP conditions might control the presence of exsolved lamellae in diopside, and probably, K2O had been completely leached out into fluid phase in this rock.
K2O-bearing tourmaline had been discovered in tourmaline-K-feldspar-quartz rock, and could be a new mineral because no such high-K2O compositions were reported in tourmaline. The occurrence of this tourmaline also indicates the high activity of volatile components in such rocks and the possibility of aqueous fluid as a carrier for these volatile components.
All these results described above strongly suggest the importance of the role of aqueous fluid during UHP metamorphism and lead to the proposed model of“Intraslab UHP metasomatism". Less
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[Journal Article] Discovery of coesite from Indus Suture Zone(ISZ),Ladakh,India:Evidence for deep subduction2004
Author(s)
Sachan, H.K., Mukherjee, B.K., Ogasawara, Y., Maruyaya, S., Ishida, H., Muko, A., and Yoshioka, N.
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Journal Title
European Journal of Mineralogy 16
Pages: 235-240
Description
「研究成果報告書概要(和文)」より
Peer Reviewed
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[Journal Article] N. Discovery of coesite from Indus Suture Zone(ISZ), Ladakh, India : Evidence for deep subduction.2004
Author(s)
Sachan, H. K., Mukherjee, B. K., Ogasawara, Y., Maruyaya, S., Ishida, H., Muko, A., Yoshioka
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Journal Title
European Journal of Mineralogy 16(reviewed paper)
Pages: 235-240
Description
「研究成果報告書概要(欧文)」より
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[Journal Article] Oxygen,carbon and strontium isotope geochemistry of diamond-bearing carbonate rocks from Kumdy-kol,Kokchetav Massif,Kazakhstan2003
Author(s)
Ohta, M., Mock, T., Ogasawara, Y., and Rumble, D.
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Journal Title
Description
「研究成果報告書概要(和文)」より
Peer Reviewed
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[Presentation] FTIR Study of Microdiamonds From Farnet-Biotite Gneisses of the Kokchetav Massif, Kazakhstan2005
Author(s)
Kikuchi, M., Kagi, H. Ogasawara. Y., Dobrzhinetskaya, L.
Organizer
Eos, Transactions, AGU, 86 F2004.
Place of Presentation
San Francisco, USA.
Year and Date
20051200
Description
「研究成果報告書概要(欧文)」より
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[Presentation] Petrology of UHP calcite marble from the Kokchetav Massif2004
Author(s)
Aoki, K, Kikuchi, M., Adachi, T., and Ogasawara, Y.
Organizer
Eos, Transactions, AGU, 85 F1655
Place of Presentation
San Francisco,USA
Year and Date
20041200
Description
「研究成果報告書概要(和文)」より
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[Presentation] Petrology of UHP calcite marble from the Kokchetav Massif.2004
Author(s)
Aoki, K, Kikuchi, M., Adachi, T., Ogasawara, Y.
Organizer
Eos, Transactions, AGU, 85 F1655.
Place of Presentation
San Francisco, USA.
Year and Date
20041200
Description
「研究成果報告書概要(欧文)」より
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[Presentation] SIMS carbon isotope study of microdiamond in UHP dolomite marble from the Kokchetav Massif2003
Author(s)
Imamura, K., Ogasawara, Y., Yurimoto, Y., and Kusakabe, A.
Organizer
Eos, Transactions, AGU, 84, F1532
Place of Presentation
San Francisco,USA
Year and Date
20031200
Description
「研究成果報告書概要(和文)」より
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[Presentation] SIMS carbon isotope study of microdiamond in UHP dolomite marble from the Kokchetav Massif.2003
Author(s)
Imamura, K., Ogasawara, Y., Yurimoto, Y., Kusakabe, A.
Organizer
Eos, Transactions, AGU, 84, F1532.
Place of Presentation
San Francisco, USA.
Year and Date
20031200
Description
「研究成果報告書概要(欧文)」より
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