U-Pb ages of zircons from metamorphic rocks in the upper sequence of the Hidaka metamorphic belt, Hokkaido, Japan; Identification of two metamorphic events and implications for regional tectonics

Takahashi, Yutaka*; Mikoshiba, Masumi*; Shimura, Toshiaki*; Nagata, Mitsuhiro; Iwano, Hideki*; Danhara, Toru*; Hirata, Takafumi*

Island Arc, 30(1), p.e12393_1 - e12393_15, 2021/01

https://doi.org/10.1111/iar.12393

The Hidaka metamorphic belt is an excellent example of island-arc-type crust, and in this belt the metamorphic grade increases westwards from unmetamorphosed sediment up to the granulite facies. The metamorphic age of the belt had previously been considered to be ca. 55 Ma. However, zircons from the granulites in the lower sequence have given U-Pb ages of ca. 21-19 Ma and a preliminary report on zircons from pelitic gneiss in the upper sequence gave a U-Pb age of ca. 40 Ma. In this paper we provide new U-Pb ages for zircons from the pelitic gneisses in the upper sequence in order to assess the metamorphic age and also the maximum depositional age of the sedimentary protolith. The weighted mean Pb/U ages and 2 sigma errors for zircons from biotite gneiss in the central area of the belt are 39.6 0.9 Ma for metamorphic overgrowth rims and 53.1 0.9 Ma for the youngest inherited detrital cores. The ages of zircons from cordierite-biotite gneiss in the southern area are 35.9 0.7 Ma for overgrowth rims and 46.5 2.8 Ma for the youngest detrital cores. These results indicate that the metamorphism of the upper sequence took place at ca. 40-36 Ma, and that the sedimentary protolith was deposited after ca. 53-47 Ma. These metamorphic ages are consistent with the reported ages of ca. 37-36 Ma plutonic rocks in the upper sequence, but contrast with the ca. 21-19 Ma ages of metamorphic and plutonic rocks in the lower sequence. Therefore, we conclude, that the upper and lower metamorphic sequences developed independently but became coupled before ca. 19 Ma as a result of dextral reverse tectonic movements, as indicated by the intrusion of ca. 19-18 Ma magmas, possibly generated in the lower sequence, into the upper sequence.

Periodic safety review of the experimental fast reactor JOYO; Review of the activity for safety

Maeda, Yukimoto; Kashimura, Yoichi; Suzuki, Toshiaki; Isozaki, Kazunori; Hoshiba, Hideaki; Kitamura, Ryoichi; Nakano, Tomoyuki; Takamatsu, Misao; Sekine, Takashi

JNC TN9440 2005-001, 540 Pages, 2005/02

JNC-TN9440-2005-001.pdf:8.35MB

Periodic safety review (Review of the activity for safety) which consisted of "Comprehensive evaluation of operation experience" and "Incorporation of the latest technical knowledge" was carried out up to January 2005.

Comparison of dosimetry by the realistic patient head phantom and by the patient's brain, and the JCDS calculation; A Clinical dosimetry study

Endo, Kiyoshi*; Matsumura, Akira*; Yamamoto, Tetsuya*; Nose, Tadao*; Yamamoto, Kazuyoshi; Kumada, Hiroaki; Kishi, Toshiaki; Torii, Yoshiya; Kashimura, Takanori*; Otake, Shinichi*

Research and Development in Neutron Capture Therapy, p.425 - 430, 2002/09

Using the Rapid Prototyping Technique, we produced a realistic phantom as a formative model of a patient head. This realistic phantom will contribute to verification of our planning system. However, cross-correlation among the calculations using the JAERI Computational Dosimetry System (JCDS), the realistic phantom, and the in vivo measurements were not fully completed because of the difficulty involved in modeling a post-surgical brain and a thermal neutron shield. The experimental simulation technique using the realistic phantom is a useful tool for more reliable dose planning for the intraoperative BNCT.

Development of advanced reprocessing system using high selective and controllable precipitants

Noda, Kyoko*; Takao, Koichiro*; Sugiyama, Yuichi*; Harada, Masayuki*; Nogami, Masanobu*; Maruyama, Koichi*; Takahashi, Hiroaki*; Kim, S.-Y.; Sato, Makoto; Mineo, Hideaki; et al.

no journal, , 

We have been developing an advanced reprocessing system for spent FBR fuels based on precipitation method using pyrrolidone derivatives. In previous investigation, N-cyclohexyl-2-pyrrolidone (NCP) is used as a precipitant, which is able to precipitate selectively UO ions in HNO solution, and a process consisting of two separation steps; selective U precipitation step and U-Pu co-precipitation step, was developed. In order to make the process more effective and more economical, we are now studying precipitation of U and Pu with other pyrrolidone derivatives. The outline of the study and main results obtained until now are shown in this presentation.

Science seminar activities in JAEA-Kansai for science outreach promotion

Nishimura, Akihiko; Asai, Toshiki; Hoshiya, Taiji; Kimura, Toyoaki; Uchikoshi, Katsumi; Matsuda, Toshiaki

no journal, , 

Science seminar activities by JAEA-Kansai have been progressed since 2002 up to now for high school students. The outline of the activities has been summarized.

Development of advanced reprocessing system using high selective and controllable precipitants, 2; Precipitation behavior of Pu by novel pyrrolidone derivatives

Kim, S.-Y.; Kawata, Yoshihisa; Morita, Yasuji; Nogami, Masanobu*; Harada, Masayuki*; Ikeda, Yasuhisa*; Kikuchi, Toshiaki*; Nishimura, Kenji*

no journal, , 

A reprocessing system for spent FBR fuels based on the two precipitation processes has been proposed. In this system, first only U(VI) species are precipitated using pyrrolidone derivatives (NRP) with low hydrophobicity and donicity, and secondly residual U(VI) and Pu(IV, VI) are precipitated simultaneously using pyrrolidone derivative with high precipitation ability. It is important to control precipitation of Pu(IV), and recent advances on precipitation behavior of Pu(IV, VI) by using novel pyrrolidone derivatives will be introduced in this presentation. Precipitation tests using mixed solutions of U(VI) and Pu(IV) showed that N-n-butyl-2-pyrrolidone (NBP) is the most appropriate precipitant for the first precipitation step and N-neopenthyl-2-pyrrolidone (NNpP) is the most appropriate precipitant for the second step.

Solvent extraction of heavy actinides (III) with HDEHP

Takayama, Reona*; Oe, Kazuhiro*; Komori, Yukiko*; Fujisawa, Hiroyuki*; Kuriyama, Ai*; Kikutani, Yuki*; Kikunaga, Hidetoshi*; Kasamatsu, Yoshitaka*; Yoshimura, Takashi*; Takahashi, Naruto*; et al.

no journal, , 

The extraction behavior of trivalent actinides (Am, Cm, Cf, Es, and Fm) into di(2-ethylhexyl)phosphoric acid, HDEHP, in benzene from HNO was studied together with lanthanides. The extraction constants, values, of lanthanides, Am, Cm, Cf, and Es were determined by a batch method using stable lanthanide isotopes and radiotracers of Am, Cm, Cf, and Es, respectively, while that of Fm was measured with Fm which was produced in the U(O,4n) reaction and was on-line supplied by a gas-jet method at the AVF cyclotron of RCNP, Osaka University. The values were determined by the slope analysis for the variation of the distribution ratio as a function of the concentration of HDEHP. We found that the of Fm is smaller than that of Dy in spite of the similar ionic radii while those of other actinides are almost the same as those of each lanthanide with a similar ionic radius.