Zircon U-Pb dates from the Taiheizan Complex Plutons in Akita Prefecture, NE Japan

Nakajima, Toru; Nagata, Mitsuhiro; Fukuda, Shoma; Sueoka, Shigeru

Chishitsugaku Zasshi (Internet), 129(1), p.503 - 507, 2023/11

https://doi.org/10.5575/geosoc.2023.0016

Zircon U-Pb dating was carried out on granitic rocks from plutons in the Taiheizan Complex in Akita Prefecture, NE Japan. Two granodiorites from the Main Intrusive Rocks yielded weighted mean 206Pb/238U dates of 103.41.0 Ma and 115.61.1 Ma (1SE). Three porphyrygranite from the Young Intrusive Rocks yielded weighted mean 206Pb/238U dates of 11.40.1 Ma, 4.70.1Ma, and 4.80.1 Ma (1SE). The older and younger dates can be interpreted as the ages of early and later stages of granitic intrusion at the sampling locations. The Pliocene U-Pb dates suggest that the Nibetsu Body in the Young Intrusive Rocks is one of the youngest granitic plutons currently exposed on Earth.

Annual report for research on geosphere stability for long-term isolation of radioactive waste in fiscal year 2022

Niwa, Masakazu; Shimada, Koji; Sueoka, Shigeru; Ishihara, Takanori; Ogawa, Hiroki; Hakoiwa, Hiroaki; Watanabe, Tsuyoshi; Nishiyama, Nariaki; Yokoyama, Tatsunori; Ogata, Manabu; et al.

JAEA-Research 2023-005, 78 Pages, 2023/10

JAEA-Research-2023-005.pdf:6.51MB

This annual report documents the progress of research and development (R&D) in the 1st fiscal year of the Japan Atomic Energy Agency 4th Medium- and Long-term Plan (fiscal years 2022-2028) to provide the scientific base for assessing geosphere stability for long-term isolation of high-level radioactive waste. The plan framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques. The current status of R&D activities with previous scientific and technological progress is summarized.

Background radiation monitoring via manned helicopter for application of technique of nuclear emergency response in the fiscal year 2021 (Contract research)

Futemma, Akira; Sanada, Yukihisa; Sasaki, Miyuki; Kawasaki, Yoshiharu*; Iwai, Takeyuki*; Hiraga, Shogo*; Haginoya, Masashi*; Matsunaga, Yuki*; Akutsu, Yuichiro*; Hokama, Tomonori; et al.

JAEA-Technology 2022-028, 127 Pages, 2023/02

JAEA-Technology-2022-028.pdf:15.21MB

A large amount of radioactive material was released by the nuclear disaster of Fukushima Daiichi Nuclear Power Station (FDNPS), Tokyo Electric Power Company, caused by the Great East Japan Earthquake and the following tsunami on March 11, 2011. After the nuclear disaster, airborne radiation monitoring via manned helicopter has been utilized to grasp rapidly and widely the distribution of the radioactive materials surrounding FDNPS. We prepare the data of background radiation dose, geomorphic characteristics and the controlled airspace surrounding nuclear facilities of the whole country in order to make effective use of the monitoring technique as a way of emergency radiation monitoring and supply the results during an accident of a facility. This report has summarized the knowledge noted above achieved by the aerial radiation monitoring around Ohi and Takahama nuclear power stations. In addition, the examination's progress aimed at introducing airborne radiation monitoring via an unmanned plane during a nuclear disaster and the technical issues are summarized in this report.

Evaluation of suitability of zircon as standard materials based on thermal history; Example of the Wassogatake Formation in Ishikawa Prefecture

Nagata, Mitsuhiro; Nakajima, Toru; Fukuda, Shoma; Sueoka, Shigeru; Yagi, Koshi*; Yokoyama, Tatsunori

Fisshion, Torakku Nyusureta, (36), p.9 - 13, 2023/00

Zircon U-Pb and fission track (FT) dating and moonstone (sanidine) K-Ar dating of the Wassogatake Formation in the southern part of Hakusan City, Ishikawa Prefecture were carried out as part of the search for zircon standard materials for dating. The weighted average U-Pb dates obtained from the three samples are ca. 21.9-21.7 Ma, overlapping within the uncertainty range. Zircon FT and moonstone K-Ar dates were obtained younger ages from some samples. In addition, the track lengths of the three samples are short. Based on the above results, the zircons of the Wassogatake Formation are effective for the high closure temperature dating method (e.g., U-Pb dating), but are not suitable for the low closure temperature dating method (e.g., FT dating).

Evaluation of potential age standards for zircon (U-Th)/He thermochronometry; Results from further chronometric investigations

Fukuda, Shoma; Kohn, B. P.*; Sueoka, Shigeru; Danhara, Toru*; Iwano, Hideki*; Tagami, Takahiro*

Fisshion, Torakku Nyusureta, (35), p.7 - 10, 2022/12

In order to establish the age standard of zircon (U-Th)/He method, we performed zircon (U-Th)/He (hereinafter, ZHe) dating on 4 zircon samples. In this presentation, the Nohi rhyolite and the Mt. Wasso moonstone rhyolite as domestic samples, and Mt. Dromedary and OD-3 were also adopted as age standard zircons of fission-track and U-Pb methods. Consequently, regarding the ZHe age of the Nohi rhyolite indicated younger, which possibly reflected secondary heating, while ones of the others indicated consistent with previous thermochronometric data. Integrated with previously obtained ZHe data about 7 samples, the Utaosa rhyolite in the previous study showed a small age dispersion in grain ages, which infers a suitable candidate for the ZHe age standard. As future prospects, we are planning to conduct geochemical analyses and structure observations of these zircons for exploring the causal factors in age dispersions.

Thermochronological data in the Kitakami Mountains and their interpretation

Kajita, Yuya*; Sueoka, Shigeru; Fukuda, Shoma; Tagami, Takahiro*

Fisshion, Torakku Nyusureta, (35), p.19 - 21, 2022/12

no abstracts in English

Weinberg operator contribution to the -odd nuclear force in the quark model

Yamanaka, Nodoka*; Oka, Makoto

Physical Review D, 106(7), p.075021_1 - 075021_15, 2022/10

https://doi.org/10.1103/PhysRevD.106.075021

The contribution of the violating three-gluon interaction, proposed by Weinberg, to the short-range -odd nuclear force is evaluated in the nonrelativistic quark model. We first show that the naive leading contribution generated by the quark exchange process vanishes at sufficiently short distance within the resonating group method, by considering the one-loop level gluon exchange -odd interquark potential induced by the Weinberg operator with massive quarks and gluons. We then estimate the true leading contribution by evaluating the gluonic correction to the -odd interquark potential in the closure approximation. It is found that the resulting irreducible -odd nuclear force is comparable to that generated by the chiral rotation of the -even short-range nuclear force, where the -odd mass calculated with QCD sum rules is used as input. The explicit calculation of the electric dipole moment (EDM) of the He nucleus yields MeV. The total EDM, accounting for the intrinsic nucleon EDM, the pion-exchange and the short- range -odd nuclear force, is MeV, with the dominant effect coming from the intrinsic nucleon EDM.

U-Pb zircon dates from the Utaosa Rhyolite of the Teragi Group

Nagata, Mitsuhiro; Fukuda, Shoma; Sueoka, Shigeru; Nakajima, Toru; Kajita, Yuya*; Minami, Saki*; Okamoto, Akira*; Tagami, Takahiro*

Fisshion, Torakku Nyusureta, (35), p.15 - 18, 2022/09

We performed U-Pb dating on zircons from the Utaosa Rhyolite of the Teragi Group as part of the search for standard materials for dating of zircons. Previous studies about Utaosa Rhyolite have reported ca. 2.30-2.77 Ma zircon fission track, zircon (U-Th)/He, and biotite K-Ar ages. U-Pb dating was carried out on the multi-collector inductively coupled plasma mass spectrometer with a laser ablation system. The weighted mean U-Pb ages of 2.650.16 Ma and 2.660.15 Ma were obtained from two samples. These ages are consistent with the ages from the previous studies. Therefore the results show that zircons from the Utaosa Rhyolite may be effective as a standard material.

Low-temperature thermochronology of active arc-arc collision zone, South Fossa Magna region, central Japan

Sueoka, Shigeru; Kobayashi, Yumi*; Fukuda, Shoma; Kohn, B. P.*; Yokoyama, Tatsunori; Sano, Naomi*; Hasebe, Noriko*; Tamura, Akihiro*; Morishita, Tomoaki*; Tagami, Takahiro*

Tectonophysics, 828, p.229231_1 - 229231_17, 2022/04

https://doi.org/10.1016/j.tecto.2022.229231

The South Fossa Magna zone, central Japan, has been an active collision zone between the Honshu Arc and the Izu-Bonin Arc since the middle Miocene and provides an excellent setting for reconstructing the earliest stages of continent formation. Multi-system geo-thermochronometry was applied to different domains of the South Fossa Magna zone, together with some previously published data, to reveal mountain formation processes, i.e., vertical crustal movements. Nine granitic samples yielded zircon U-Pb ages of 10.2-5.8 Ma ( = 2), apatite (U-Th)/He (AHe) ages of 42.8-2.6 Ma ( = 7), and apatite fission-track (AFT) ages of 44.1-3.0 Ma ( = 9). Thermal history inversion modeling based on the AHe and AFT data suggested rapid cooling events confined within the study region at 6-2 Ma. The Kanto Mountains may have undergone a domal uplift in association with their collision with the Tanzawa Block at 5 Ma. However, this uplift may have slowed down following the migration of the plate boundary and late Pliocene termination of the Tanzawa collision. The Minobu Mountains and possibly adjacent mountains may have been uplifted by the motional change of the Philippine Sea plate at 3 Ma. Therefore, the mountain formation in the South Fossa Magna zone was mainly controlled by collisions of the Tanzawa and Izu Blocks and motional change of the Philippine Sea plate. Earlier collisions of the Kushigatayama Block at 13 Ma and Misaka Block at 10 Ma appeared to have had little effect on mountain formation. Together with a 90 deg. clockwise rotation of the Kanto Mountains at 12-6 Ma, these observations suggest that horizontal deformation predominated during the earlier stage of arc-arc collision, and vertical movements due to buoyancy resulting from crustal shortening and thickening developed at a later stage.

Radiation monitoring using manned helicopter around the Nuclear Power Station in the fiscal year 2020 (Contract research)

Futemma, Akira; Sanada, Yukihisa; Ishizaki, Azusa; Kawasaki, Yoshiharu*; Iwai, Takeyuki*; Hiraga, Shogo*; Sato, Kazuhiko*; Haginoya, Masashi*; Matsunaga, Yuki*; Kikuchi, Hikaru*; et al.

JAEA-Technology 2021-029, 132 Pages, 2022/02

JAEA-Technology-2021-029.pdf:24.58MB

By the nuclear disaster of Fukushima Daiichi Nuclear Power Station (FDNPS), Tokyo Electric Power Company (TEPCO), caused by the Great East Japan Earthquake and the following tsunami on March 11, 2011, a large amount of radioactive material was released from the FDNPS. After the nuclear disaster, airborne radiation monitoring using manned helicopter has been conducted around FDNPS. The results of the airborne radiation monitoring and the evaluation for temporal change of dose rate in the fiscal 2020 were summarized in this report. Analysis considering topographical effects was applied to the result of the airborne monitoring to improve the accuracy of conventional method. In addition, technique for discriminating gamma rays from the ground and those from the airborne Rn-progenies was also utilized to evaluate their effect on airborne radiation monitoring.