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• Geological Process of Island Arc Crust in the Ryukyu Islands

• Crustal Evolution of Central Dronning Maud Land, E. Antarctica

• Geological Process of Formation of Sapphirine-Bearing Gneisses

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Published Papers 【 display / non-display 】

• Low-pressure isobaric cooling metamorphic P–T paths from Botnnuten in the southern Lützow-Holm Complex, East Antarctica

  Sotaro Baba, Seira Ohshiro, Atsushi Kamei, Tomokazu Hokada, Ippei Kitano

  Mineralogy and Petrology     2024.06 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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• Zircon geochronology of high-grade metamorphic rocks from outcrops along the Prince Olav Coast, East Antarctica: Implications for multi-thermal events and regional correlations

  Kitano, I; Hokada, T; Baba, S; Kamei, A; Motoyoshi, Y; Nantasin, P; Setiawan, NI; Dashbaatar, DO; Toyoshima, T; Ishikawa, M; Katori, T; Nakano, N; Osanai, Y

  JOURNAL OF MINERALOGICAL AND PETROLOGICAL SCIENCES ( 一般社団法人　日本鉱物科学会 )  118 ( ANTARCTICA ) n/a - n/a   2023.05 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  <p>This paper reports laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U-Pb ages of a suite of high-grade metamorphic rocks collected from Sinnan Rocks, Akebono Rock, Niban Rock, Gobanme Rock, Tenmondai Rock, Akarui Point, Cape Omega, and Oku-iwa Rock along the Prince Olav Coast, in the Lützow-Holm Complex (LHC), East Antarctica. The dating results indicate that a newly detected ∼ 990 Ma metamorphism of garnet-sillimanite-biotite gneiss from Niban Rock. A thermal event at 931.7 ± 9.8 Ma is recorded in zircon from staurolite-bearing garnet-gedrite-biotite-chlorite gneiss in Akebono Rock. The metamorphic zircon grains in other analyzed samples provide Ediacaran to Cambrian ages. Their multi-growth textures and age populations are possibly interpreted to exhibit three metamorphic stages during >600-580, 580-550, and 550-500 Ma. Combined with previous reports, the metamorphic rocks in Cape Hinode, Niban-nishi Rock of Niban Rock, and Akebono Rock might have experienced earlier high-temperature metamorphism at ∼ 990-930 Ma without younger overprinting. Extensive high-grade metamorphism during ∼ 650-500 Ma is recorded from not only the granulite-facies zone in the west of the LHC but also the amphibolite-facies zone in its east. The main metamorphic episode in the LHC is likely to be subdivided into a preceding thermal event (either independent single metamorphic event or prograde stage) at pre-580 Ma, near-peak condition stage during 580-560 Ma, and subsequent retrograde stage after 550 Ma. In regional context this indicates that the assembly at the central Gondwana started with the collision of early and late Neoproterozoic terranes prior to 580 Ma, as a part of the East Africa-Antarctic Orogeny. Subsequent collisions took place among late Neoproterozoic igneous terrane, above terranes collided at pre-580 Ma, and Neoarchean terrane, which were probably driven by the Kuunga Orogeny.</p>

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• Counter-clockwise <i>P</i>-<i>T</i> history deduced from kyanite-bearing pelitic gneiss in Tenmondai Rock, Lutzow-Holm Complex, East Antarctica

  Baba, S; Nantasin, P; Kamei, A; Kitano, I; Section, YM; Setiawan, NI; Dashbaatar, DO; Hokada, T

  JOURNAL OF MINERALOGICAL AND PETROLOGICAL SCIENCES ( 一般社団法人　日本鉱物科学会 )  118 ( ANTARCTICA ) n/a - n/a   2023.04 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  <p>This paper first reports the counter-clockwise pressure-temperature (<i>P-T</i>) path for the Lützow-Holm Complex in East Antarctica. The metamorphic textures of kyanite-bearing pelitic gneisses from Tenmondai Rock including earlier spinel and ilmenite inclusions, geothermobarometric data, and pseudosection modeling indicate that the pressure increases prior to the peak metamorphic conditions at around 9 ± 0.5 kbar and 770-820 °C, followed by cooling to kyanite-stability field. We conclude that these gneisses underwent granulite-facies metamorphism with a counter-clockwise <i>P-T</i> path, but this contrasts with the widely recognized clockwise <i>P-T</i> path of the Lützow-Holm Complex basement rocks in general. One plausible hypothesis we proposed could be that this counter-clockwise <i>P-T</i> path originated from magmatism with late compression and the rocks of the different structural levels are juxtaposed, while acknowledging that this hypothesis conflicts with previous studies and that further work is needed to clarify these issues.</p>

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• Contrasting geological background based on the geochemistry of the mafic metamorphic rocks in central Dronning Maud Land

  Sotaro Baba , Masaaki Owada , Tomokazu Hokada , Tatsuro Adachi , Nobuhiko Nakano

  GEOLOGICAL MAGAZINE ( CAMBRIDGE UNIV PRESS )    2023.03 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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• Zircon geochronology and geochemistry of felsic gneisses from Harvey Nunatak, Napier Complex in East Antarctica.

  Mami Takehara, Kenji Horie, Tomokazu Hokada, Sotaro Babs, Atsushi Kamei and Ippei Kitano

  Journal of Mineralogical and Petrological Sciences   118 ( S015 )   2023 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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• Monazite U-Th-Pb ages of the “unnamed nunatak (Nunatak 170224-3)“ east of Forfinger Point, Western Rayner Complex, Enderby Land, East Antarctica

  HOKADA Tomokazu, HOKADA Tomokazu, BABA Sotaro, KAMEI Atsushi, KITANO Ippei, KITANO Ippei

  極域科学シンポジウム(Web)  2021  -  2021 

• U-Pb zircon age of Grt-Bt gneiss in Akebono Rock, Prince Olav Coast, East Anatarctica

  馬場壮太郎, 堀江憲路, 外田智千, 竹原真美, 亀井淳志, 北野一平, 本吉洋一

  日本地質学会学術大会(Web)  2021  -  2021 

• Geologic nature and evolution of Western Rayner Complex, with reference to Point Widdows charnockite and its localized hydration process

  HOKADA Tomokazu, HOKADA Tomokazu, BABA Sotaro, KAMEI Atsushi, KITANO Ippei, MOTOYOSHI Yoichi, MOTOYOSHI Yoichi

  極域科学シンポジウム(Web)  2020  -  2020 

• Geochemical study on charnockites in Rundvagshetta, Luetzow-Holm Complex, Antarctica

  KAMEI Atsushi, AWATA Hikari, HOKADA Tomokazu, HOKADA Tomokazu, BABA Sotaro, KITANO Ippei, MOTOYOSHI Yoichi, MOTOYOSHI Yoichi

  極域科学シンポジウム(Web)  2020  -  2020 

• Cordierite megacrysts in felsic gneiss from Botunnuten in southern Luetzow-Holm Complex, East Antarctica

  BABA Sotaro, OHSHIRO Seira, HOKADA Tomokazu, HOKADA Tomokazu, KAMEI Atsushi, KITANO Ippei, MOTOYOSHI Yoichi, MOTOYOSHI Yoichi

  極域科学シンポジウム(Web)  2020  -  2020 

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Grant-in-Aid for Scientific Research 【 display / non-display 】

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• Study on supercontinent evolution based on Proterozoic magmatism recorded in East Antarctica

  Grant-in-Aid for Scientific Research(B)

  Project Year: 2018.04  -  2022.03 

  Direct: 13,000,000 (YEN)  Overheads: 16,900,000 (YEN)  Total: 3,900,000 (YEN)

• Systematization of formation tectonics of high-temperature metamorphic rock based on their P-T path

  Grant-in-Aid for Scientific Research(C)

  Project Year: 2015.04  -  2018.03 

  Investigator(s): BABA Sotaro, HOKADA Tomokazu, OSANAI Yasuhito 

  Direct: 3,200,000 (YEN)  Overheads: 4,160,000 (YEN)  Total: 960,000 (YEN)

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  We have examined the age of the metamorphism, and the tectonic setting of mafic rock protoliths based on whole rock chemical composition, for the metamorphic rocks constituting inland nunataks and coastal exposure of the central Droning Maud Land (CDML) in the East Antarctic. Combined the results of the metamorphic ages and the tectonic setting for metamorphic precursory rocks, metamorphic rocks with an isobaric cooling P-T path are due to heating just below in the back arc basin, and the metamorphic rocks showing an isothermal decompression P-T path are similar to the current accretionary prism, suggesting the possibility that it formed by changing from the arc - trench system to the collision zone. We will further attempt to systematize this result compared with the tectonic setting and the metamorphic process of high-temperature metamorphic rocks in other areas.

• Grant-in-Aid for Young Scientists(B)

  Project Year: 2004  -  2006 

  Direct: 2,400,000 (YEN)  Total: 2,400,000 (YEN)

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• 2023.12