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Sueoka, Shigeru; Kawakami, Tetsuo*; Suzuki, Kota*; Kagami, Saya; Yokoyama, Tatsunori; Shibazaki, Bunichiro*; Nagata, Mitsuhiro; Yamazaki, Ayu*; Higashino, Fumiko*; King, G. E.*; et al.
Fuisshon, Torakku Nyusureta, (36), p.1 - 3, 2023/12
no abstracts in English
Sueoka, Shigeru; Kawakami, Tetsuo*; Suzuki, Kota*; Kagami, Saya; Yokoyama, Tatsunori; Shibazaki, Bunichiro*; Nagata, Mitsuhiro; Yamazaki, Ayu*; Higashino, Fumiko*; King, G. E.*; et al.
no journal, ,
Minami, Saki*; Sueoka, Shigeru; Fukuda, Shoma; Nagata, Mitsuhiro; Kohn, B. P.*; Yokoyama, Tatsunori; Kagami, Saya; Kawakami, Tetsuo*; Higashino, Fumiko*; Abe, Noriaki; et al.
no journal, ,
Nakajima, Toru; Niki, Sota*; Kudo, Shumpei*; Kawakami, Tetsuo*; Higashino, Fumiko*; Hirata, Takafumi*; Sakai, Harutaka*
no journal, ,
no abstracts in English
Minami, Saki*; Sueoka, Shigeru; Fukuda, Shoma; Malatesta, L.*; Kawakami, Tetsuo*; Higashino, Fumiko*; Kajita, Yuya*; Tagami, Takahiro*
no journal, ,
Nakajima, Toru; Niki, Sota*; Kudo, Shumpei*; Kawakami, Tetsuo*; Higashino, Fumiko*; Hirata, Takafumi*; Sakai, Harutaka*
no journal, ,
The orthogneisses widely distributed in the Himalayas are thought to be originated from granites intruded during the early Paleozoic Bhimphedian orogeny on the northeastern margin of Gondwana, although details are not clear due to the poor of metamorphic minerals such as garnet. In this study, we focus on the internal microstructure and inclusions of zircons in orthogneisses in the Central Himalaya and attempt to decipher the early Paleozoic magma-fluid activity, which was overprinted by high-temperature metamorphism accompanied with Cenozoic Himalayan orogeny. In this study, the internal microstructure of the zircon was divided from the inside into 1) the inner-core, 2) the outer-core, 3) the dark annulus, and 4) the metamorphic rim based on optical microscope and cathodoluminescence (CL) observation. Each of these domains is cut by the more outer domain. 1) the inner-core shows oscillatory or sector zoning in the CL image, with U-Pb date of 
1000 Ma. 2) the outer-core shows an oscillatory zoning in the CL image, with U-Pb date between 510 and 460 Ma. In addition to mineral inclusions such as quartz and biotite, the outer-core encloses primary fluid inclusions of medium-salinity and polyphase mineral inclusions. Euhedral quartz, K-feldspar, chalcopyrite, fluorite, sphalerite, and native bismuth occur in some of the polyphase inclusions, indicating that the outer-core crystallized from a highly differentiated S-type granitic melt. 3) The dark annulus is recognized in the CL image as a dark annular domain, rich in P, Y, REE, and U, with U-Pb date of 490-440 Ma. The dark annulus is rich in mineral inclusions such as xenotime, monazite, and thorite, as well as high-salinity primary fluid inclusions. These internal microstructures and low Gd/Yb ratio of the dark annulus suggest the garnet breakdown and zircon dissolution-reprecipitation accompanied with high-salinity fluid influx during late stage of magmatism.
Sueoka, Shigeru; Kawakami, Tetsuo*; Suzuki, Kota*; Kagami, Saya; Yokoyama, Tatsunori; Nagata, Mitsuhiro; Yamazaki, Ayu*; Higashino, Fumiko*; King, G. E.*; Tsukamoto, Sumiko*; et al.
no journal, ,
Young plutons of 10-0.8 Ma, including the world's youngest Kurobegawa pluton, are exposed in the Kurobe area of the Hida Range, central Japan, indicating rapid rock uplift and exhumation in the Quaternary. However, reconstructing the exhumation history has been challenging because interpretations of the thermochronologic data are difficult due to the complicated, recent and active thermal history/structure. Here we are determining the exhumation history by estimating formation depths and ages of the young plutons based on Al-in-Hb geobarometry and zircon U-Pb geochronometry, respectively. At JpGU2021, we reported the preliminary results based on three datapoints from the ~5 Ma plutons and one datum from the ~0.8 Ma pluton, suggesting the three following interpretations: (1) formation depths of ~5 Ma and ~0.8 Ma plutons were estimated to be ~6-9 km, which indicates an increase of the exhumation rate after ~0.8 Ma, (2) mean exhumation rate since ~0.8 Ma was computed at 8-10 mm/yr in the Baba-dani area, (3) the formation depths are uniform in the E-W direction, disagreeing with the eastward tilting model. As of January 2022, we have obtained 14 datapoints in total: five from the ~5 Ma plutons, two from the ~2-1 Ma plutons, five from the ~0.8 Ma plutons, and two from the 65 Ma plutons. These additional data are basically consistent with the previous data, reinforcing the three interpretations above. Recently, new uplift models of the Kurobe area were proposed, in addition to the eastward tilting model. Ito et al. (2021) suggested that the Kurobegawa pluton is a resurgent pluton of the Jiigatake caldera and was uplifted by the resurgence. Kawasaki (2021) proposed that displacements related to the E-W compression are localized along the Kurobe area due to the high geothermal gradient caused by presence of thermal fluid interstratified layers. We are planning to discuss consistency between our data and these two models.
Minami, Saki*; Sueoka, Shigeru; Fukuda, Shoma; Malatesta, L.*; Kohn, B. P.*; Kawakami, Tetsuo*; Higashino, Fumiko*; Kajita, Yuya*; Tagami, Takahiro*
no journal, ,
