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Journal Articles

Thermochronology of hydrothermal alteration zones in the Kii Peninsula, southwest Japan; An Attempt for detecting the thermal anomalies and implications to the regional exhumation history

Sueoka, Shigeru; Iwano, Hideki*; Danhara, Toru*; Niwa, Masakazu; Kanno, Mizuho; Kohn, B. P.*; Kawamura, Makoto; Yokoyama, Tatsunori; Kagami, Saya; Ogita, Yasuhiro; et al.

Earth, Planets and Space (Internet), 75(1), p.177_1 - 177_24, 2023/12

Fluid-inclusion and thermochronometric analyses have been applied to hydrothermal alteration zones and their host rocks outcropping in the Hongu area of the Kii Peninsula, southwestern Japan in an attempt to detect thermal anomalies related to hydrothermal events and quantify the thermal effects on the host rocks. Hydrothermal events at ca 150 deg. C and ca 200 deg. C were identified by fluid-inclusion microthermometry of quartz veins in the alteration zones. For the host rocks and alteration zones, in the youngest population zircon yielded U-Pb dates ranging between ca 74.7-59.2 Ma, fission-track dates of ca 27.2-16.6 Ma, and (U-Th)/He single-grain dates of ca 23.6-8.7 Ma. Apatite yielded pooled fission-track ages of ca 14.9-9.0 Ma. The zircon U-Pb dates constrain the maximum depositional ages of the sedimentary samples. However, the fission-track and (U-Th)/He dates show no clear trend as a function of distance from the alteration zones. Hence, no thermal anomaly was detected in the surrounding host rocks based on the thermochronometric data patterns. The fission-track and (U-Th)/He dates are rather thought to record regional thermal and exhumation histories rather than a direct thermal imprint of fluid flow, probably because the duration of such activity was too short or because fluid flow occurred before regional cooling events and were later thermally overprinted. Apatite fission-track ages of ca 10 Ma may reflect regional mountain uplift and exhumation related to the obduction of the SW Japan lithospheric sliver onto the Shikoku Basin, or the rapid subduction of the Philippine Sea slab associated with the clockwise rotation of the Southwest Japan Arc.

Journal Articles

Exhumation history of the Kurobe area, Hida Range, based on solidification ages and depths of the Pliocene-Quaternary plutons

Sueoka, Shigeru; Kawakami, Tetsuo*; Suzuki, Kota*; Kagami, Saya; Yokoyama, Tatsunori; Shibazaki, Bunichiro*; Nagata, Mitsuhiro; Yamazaki, Ayu*; Higashino, Fumiko*; King, G. E.*; et al.

Fisshion, Torakku Nyusureta, (36), p.1 - 3, 2023/12

no abstracts in English

Journal Articles

Examination of the wet analysis for the (U-Th)/He method; Attempt to determine the contents of parent nuclides based on the calibration curve method

Fukuda, Shoma; Kagami, Saya

Fisshion, Torakku Nyusureta, (36), p.14 - 18, 2023/12

For the determination of parent nuclides in the (U-Th)/He method, the isotope dilution method using U and Th isotope spikes is commonly employed worldwide, and much knowledge has been accumulated. On the other hand, the possession and use of these spikes are strictly restricted, which makes the application of the isotope dilution method itself difficult. After the complete dissolution of apatite and zircon by the wet method, we have therefore attempted to verify the calibration curve method for measuring the concentration of the parent nuclides. Durango apatite and Fish Canyon Tuff zircon, which are well-known as the age standard samples for the fission track method, were used as analytical samples. In this presentation, we will introduce some of the results of the determination of parent nuclides (U, Th, Sm) in each mineral sample based on the calibration curve method as well as results of evaluating the suitable internal standards (Bi, Tl) to determine the contents of parent nuclides.

JAEA Reports

Research plan on geosphere stability for long-term isolation of radioactive waste (Scientific program for fiscal year 2023)

Niwa, Masakazu; Shimada, Koji; Sueoka, Shigeru; Fujita, Natsuko; Yokoyama, Tatsunori; Ogita, Yasuhiro; Fukuda, Shoma; Nakajima, Toru; Kagami, Saya; Ogata, Manabu; et al.

JAEA-Review 2023-017, 27 Pages, 2023/10

JAEA-Review-2023-017.pdf:0.94MB

This report is a plan of research and development (R&D) on geosphere stability for long-term isolation of high-level radioactive waste (HLW) in Japan Atomic Energy Agency (JAEA), in fiscal year 2023. The objectives and contents in fiscal year 2023 are described in detail based on the JAEA 4th Medium- and Long-term Plan (fiscal years 2022-2028). In addition, the background of this research is described from the necessity and the significance for site investigation and safety assessment, and the past progress. 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.

JAEA Reports

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.

Journal Articles

LA-ICPMS U-Pb dating of zircon in paleotsunami deposits from Miyazaki plain, southwest Japan

Watanabe, Takahiro; Kagami, Saya; Yokoyama, Tatsunori; Niwa, Masakazu

Chigaku Zasshi, 132(4), p.353 - 361, 2023/08

U-Pb dating of detrital zircons in paleotsunami deposits from the 1662 CE Kanbun-Hyuganada sea earthquake, Miyazaki plain on the Pacific coast of southwest Japan, was performed by a laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-ICPMS) system at Tono Geoscience Center, Japan Atomic Energy Agency. Twenty-five zircon grains were separated from the paleotsunami deposits by chemical abrasion and analyzed by the LA-ICPMS. U-Pb ages of the detrital zircons showed from ca. 14 Ma to 2405 Ma, and the age spectrum revealed high relative probability values around ca. 100 Ma and 2000 Ma. Detrital zircons with the age of ca. 100 Ma in the 1662 CE paleotsunami deposits could be partly originated from the Shimanto supergroup in southwest Japan. Moreover, the age spectrum of detrital zircons with Precambrian grains from the paleotsunami deposits was similar with those of fore-arc sandstones from central Kyushu Island.

Journal Articles

Zircon U-Pb-Hf Isotopes and Whole-rock Geochemistry of Rhyolite and Tuff from the Harachiyama Formation, North Kitakami Mountains, NE Japan

Harada, Takuya*; Nagata, Mitsuhiro; Ogita, Yasuhiro; Kagami, Saya; Yokoyama, Tatsunori

Chigaku Zasshi, 132(1), p.57 - 65, 2023/02

The Harachiyama Formation is Lower Cretaceous volcanic rocks, distributed in the eastern margin of the Kitakami Mountains in northeastern Japan. We performed whole-rock chemical analysis, zircon U-Pb dating and Hf isotope analysis from the Harachiyama Formation to constrain the formation age and discuss the origin of magma. The lava and tuff samples of the Harachiyama Formation from the Omoto and Tsukue areas support island-arc rhyolitic rocks (SiO$$_{2}$$ content $$>$$ 70%), and yielded the weighted mean U-Pb ages of 127.8 $$pm$$ 3.4 Ma and 129.2 $$pm$$ 2.6 Ma (2$$sigma$$), respectively. Eighteen zircon grains from two samples, dated between 141.6 Ma and 123.9 Ma, yielded positive $$varepsilon$$Hf(t) values between +5.0 and +8.7. These ages and values are consistent with those of the Kitakami Granititods reported in previous studies. Therefore, it is suggested that the Harachiyama Formation have the same magmatic origin as the Kitakami Granitoid.

Journal Articles

An Experiment of complete dissolution of zircon crystals by high-temperature and pressure acid digestion for the (U-Th)/He method

Fukuda, Shoma; Kagami, Saya

Fisshion, Torakku Nyusureta, (35), p.11 - 14, 2022/12

In this study, we firstly attempted the wet-chemical analyses at Tono Geoscience Center based on a high-temperature and pressure acid digestion for determination of U-Th contents in zircon crystals. In the beginning, zircon crystals were annealed at 900 degrees Celsius for 48 hours to recover radiation damages, and annealed zircons were transferred and sunk into 29 M HF, and finally zircons were digested at 220 degrees Celsius for 70 hours. To verify that zircons were digested completely, Zr contents in zircons were measured as major elements by using ICP-MS (Agilent 7700x) based on the calibration curve method. As a result, theoretical values for Zr contents were obtained, these experimental conditions are thus valid for zircon digestion. Now, we are considering to perform these analyses in the clean booth and to select more appropriate analyses instruments and conditions for decreasing a blank level, which contributes to improve the determination of U-Th contents for zircon (U-Th)/He dating.

Journal Articles

Estimation of thermal/denudation histories in the Tanigawa-dake area based on thermochronological methods

Minami, Saki*; Sueoka, Shigeru; Fukuda, Shoma; Nagata, Mitsuhiro; Kohn, B. P.*; Yokoyama, Tatsunori; Kagami, Saya; Kajita, Yuya*; Tagami, Takahiro*

Fisshion, Torakku Nyusureta, (35), p.22 - 26, 2022/12

no abstracts in English

JAEA Reports

Research plan on geosphere stability for long-term isolation of radioactive waste (Scientific program for fiscal year 2022)

Sasao, Eiji; Ishimaru, Tsuneari; Niwa, Masakazu; Shimada, Akiomi; Shimada, Koji; Watanabe, Takahiro; Sueoka, Shigeru; Yokoyama, Tatsunori; Fujita, Natsuko; Ogita, Yasuhiro; et al.

JAEA-Review 2022-022, 29 Pages, 2022/09

JAEA-Review-2022-022.pdf:0.97MB

This report is a plan of research and development (R&D) on geosphere stability for long-term isolation of high-level radioactive waste (HLW) in Japan Atomic Energy Agency (JAEA), in fiscal year 2022. The objectives and contents in fiscal year 2022 are described in detail based on the JAEA 4th Medium- and Long-term Plan (fiscal years 2022-2028). In addition, the background of this research is described from the necessity and the significance for site investigation and safety assessment, and the past progress. 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

Journal Articles

Solidification pressures and ages recorded in mafic microgranular enclaves and their host granite; An Example of the world's youngest Kurobegawa granite

Suzuki, Kota*; Kawakami, Tetsuo*; Sueoka, Shigeru; Yamazaki, Ayu*; Kagami, Saya; Yokoyama, Tatsunori; Tagami, Takahiro*

Island Arc, 31(1), p.e12462_1 - e12462_15, 2022/09

 Times Cited Count:1 Percentile:37.23(Geosciences, Multidisciplinary)

Journal Articles

Geochemical and heavy mineral signatures of marine incursions by a paleotsunami on the Miyazaki plain along the Nankai-Suruga trough, the Pacific coast of southwest Japan

Watanabe, Takahiro; Kagami, Saya; Niwa, Masakazu

Marine Geology, 444, p.106704_1 - 106704_13, 2022/02

 Times Cited Count:2 Percentile:32.67(Geosciences, Multidisciplinary)

Miyazaki plain on the Pacific coast of southwest Japan along the Nankai-Suruga trough was also affected by marine incursion by the past interplate earthquakes and tsunami. Notably, paleotsunami deposits were found on the area and important clues to reconstruct the past marine incursion by earthquakes and tsunami. However, geochemical and heavy mineral analyses on the area were not enough to characterize the deposits. Therefore, quantification analyses with high-time resolution by portable energy dispersive X-ray fluorescence spectrometry (portable XRF), scanning by X-ray analytical microscope (XGT), statistical analyses for chemical components, and heavy mineral analyses were performed for the paleotsunami deposits of the Kanbun Hyuganada earthquake with the age of 1662 CE from the south Miyazaki plain in this study. Based on our research, we summarized as follows: (1) increases in the titanium normalized values of S, Ca, Fe and Sr, and depletions of Si, K, and Rb were observed in the deposits, (2) Zr accumulations and heavy minerals such as zircon were found in the deposits caused by possible high energy tsunami, and (3) cluster analyses of the geochemical data from the core by portable XRF distinguished the paleotsunami deposits on the Miyazaki plain.

Journal Articles

Two pulse intrusive events of the Pliocene Tanigawa-dake granites revealed from zircon U-Pb dating

Minami, Saki*; Nagata, Mitsuhiro; Sueoka, Shigeru; Fukuda, Shoma; Kajita, Yuya*; Ogita, Yasuhiro; Kagami, Saya; Yokoyama, Tatsunori; Tagami, Takahiro*

Earth, Planets and Space (Internet), 73(1), p.231_1 - 231_7, 2021/12

 Times Cited Count:1 Percentile:8.69(Geosciences, Multidisciplinary)

Journal Articles

Estimation of denudation history of the Kitakami Mountains based on apatite fission-track thermochronology

Kajita, Yuya*; Sueoka, Shigeru; Fukuda, Shoma; Yokoyama, Tatsunori; Kagami, Saya; Nagata, Mitsuhiro; Tagami, Takahiro*

Fisshion, Torakku Nyusureta, (34), p.14 - 16, 2021/12

For reconstructing the uplift/denudation history of the fore-arc side of the NE Japan Arc on geologic timescales, U-Pb dating and apatite fission-track (AFT) thermochronometry were applied to granitoids in Kitakami mountains. In addition, U-Pb dating for the Jodogahama rhyolite at the easternmost Kitakami mountains was also carried out to estimate the timing of volcanism and its thermal effect. Consequently, U-Pb ages of 122.7 Ma and 117.3 Ma for 2 samples of the Cretaceous granites and AFT ages ranging from 156.8 Ma to 70.3 Ma of 15 samples were obtained. Concerning the Jodogahama rhyolite, U-Pb age of 44.3 Ma was obtained. Integrated AFT data of this study and previous ones in Kitakami mountains, the trend of ages shows younging toward west. Although such age trend can be explained by volcanism of the Jodogahama reflecting the migration of a paleo-volcanic front, all AFT ages exhibited significantly older than U-Pb data of the Jodogahama and the thermal inverse modeling based on track length distributions provided slow cooling patterns. These observations did not supported the reheating of volcanism as a cause of age trend. As future prospects, we are planning to improve the reliability of age data based on additional analyses and apply an ultra low-temperature thermochronometer, e.g., ESR method.

Journal Articles

Estimation of intrusion ages in the Miocene-Pliocene granodiorite around the Tanigawa-dake based on zircon U-Pb dating

Minami, Saki*; Nagata, Mitsuhiro; Sueoka, Shigeru; Fukuda, Shoma; Kajita, Yuya*; Ogita, Yasuhiro; Yokoyama, Tatsunori; Kagami, Saya; Tagami, Takahiro*

Fisshion, Torakku Nyusureta, (34), p.4 - 8, 2021/12

This study employed U-Pb dating for determining the intrusive age of young (several Ma) granitoids in Tanigawa-dake area, where rapid and intense uplift/denudation has probably occurred in Japan. As results, U-Pb age of 109 Ma for the Cretaceous granodiorite and 3.95-3.19 Ma about 3 samples of the Pliocene granodiorites were obtained. These U-Pb ages showed consistent with previously reported ages based on thermochronometers having lower closure temperatures such as K-Ar or zircon fission-track methods. All previous data indicated younger ages than U-Pb ones in this study. Therefore, our U-Pb data can be interpreted as intrusive ages of young granitoids, inferring multiple events possibly occurred at least twice and contributed to the formation in young granitoids in the Tanigawa-dake area.

Journal Articles

Simultaneous determination of insoluble fluoride-forming and high field-strength element abundances in rock samples by ICP-QMS through isotope dilution-internal standardisation

Kagami, Saya; Yokoyama, Tetsuya*

Geostandards and Geoanalytical Research, 45(4), p.679 - 699, 2021/12

AA2020-0580.pdf:1.27MB

 Times Cited Count:2 Percentile:22.73(Geochemistry & Geophysics)

We developed a new method for the determination of the mass fractions of insoluble fluoride-forming elements (IFFEs) and high field strength elements (HFSEs) in rock samples by ICP-QMS. Unlike conventional methods in which the two elemental groups were measured separately using two solutions prepared from distinct sample aliquots, the new technique prepares a solution by acid digestion from a single sample aliquot, then divide the solution into two fractions that are dedicated to the measurement of IFFEs and HFSEs, respectively. The problem regarding the incorporation of IFFEs/HFSEs into insoluble fluorides during HF digestion was overcome by adjusting the Ca-Al-Mg composition of the sample before acid digestion. The acceptable compositional range was Ca/(Ca+Al) $$<$$ 0.43 and Mg/(Mg+Al) $$<$$ 0.40 when the sample was decomposed on a hot plate, while more restricted condition of Ca/(Ca+Al) $$<$$ 0.40, Mg/(Mg+Al) $$<$$ 0.40, and Al/(Mg+Ca) $$<$$ 1.7 was required for the digestion under high pressure and temperature using Teflon bomb. This method achieved the repeatabilities of $$<$$ 4% for most IFFEs and HFSEs, and yielded the mass fractions of most IFFEs and HFSEs that were consistent with the data obtained by conventional methods within $$pm$$5%. The method is applicable not only to precious samples but also to heterogeneous samples containing accessory minerals enriched in IFFEs/HFSEs.

JAEA Reports

Annual report for research on geosphere stability for long-term isolation of radioactive waste in fiscal year 2020

Ishimaru, Tsuneari; Ogata, Nobuhisa; Kokubu, Yoko; Shimada, Koji; Niwa, Masakazu; Shimada, Akiomi; Watanabe, Takahiro; Sueoka, Shigeru; Yokoyama, Tatsunori; Fujita, Natsuko; et al.

JAEA-Research 2021-007, 65 Pages, 2021/10

JAEA-Research-2021-007.pdf:4.21MB

This annual report documents the progress of research and development (R&D) in the 6th fiscal year during the JAEA 3rd Mid- and Long-term Plan (fiscal years 2015-2021) to provide the scientific base for assessing geosphere stability for long-term isolation of the high-level radioactive waste. The planned 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.

Journal Articles

Local tephra as an age-determination tool; Example of 2.3 ka Yakedake volcano tephra in Nagano Prefecture, central Japan

Kojima, Satoru*; Kagami, Saya; Yokoyama, Tatsunori; Kariya, Yoshihiko*; Katayama, Yoshikazu*; Nishio, Gaku*

Proceedings of 5th International Workshop on Rock Mechanics and Engineering Geology in Volcanic Fields (RMEGV 2021) (Internet), 6 Pages, 2021/09

A local tephra embedded in a hand-auger boring core drilled at near-shore of Kinugasanoike Pond about 4.6 km NE of Mt.Yakedake, one of the most active volcanoes in central Japan, is composed mainly of several kinds of volcanic glass shards (microlite-bearing, blocky, fluted and micro-vesicular types) with minor amounts of crystal minerals including quartz, plagioclase, hornblende, biotite, and pyroxene. Plant remains recovered from the horizon 10 cm below the tephra layer yield $$^{14}$$C ages of 2,331-2,295 (19.2% probability distribution) and 2,270-2,155 (76.2% probability distribution) cal yrs BP. We measured major element compositions of 241 individual glass shards using Electron Probe Micro Analyzer. They are plotted on the SiO$$_{2}$$-K$$_{2}$$O, SiO$$_{2}$$-Na$$_{2}$$O+K$$_{2}$$O, and FeO$$^{ast}$$-K$$_{2}$$O diagrams in a region different from those of major regional tephras distributed in central Japan. The clast and chemical compositions coincide with those of a tephra embedded in the Nakao pyroclastic flow deposits distributed about 2 km NNW of Mt. Yakedake dated as around 2,300 cal yrs BP. The tephra could be used as a local marker of 2,300 cal yrs BP in the southern part of Northern Japan Alps.

JAEA Reports

Analytical method for chemical compositions of volcanic glasses in Tono Geoscience Center; Quantitative measurements of Major Elements by using EPMA and Minor Elements by LA-ICP-MS

Kagami, Saya; Yokoyama, Tatsunori; Umeda, Koji*

JAEA-Testing 2021-001, 49 Pages, 2021/08

JAEA-Testing-2021-001.pdf:3.86MB

To make a contribution to safety assessment for geological disposal of high level radioactive and/or TRU waste, we need to assess long-term stability of geological environment and predict long-term changes of geotectonic events that will occur in the future, especially for Quaternary period ($$sim$$ 2.6 million years ago-present). In the most case, we investigate chronological data of geological events by radiometric dating. When some geological samples have no objects to which radiometric dating method can be applied (e.g., zircon, biotite, wood fragments and plant residues), we can use tephrochronology, which is geological dating method using each layer of tephra (erupted volcanic ash), for dating of geological layers. This chronological method is essential in Japan, where volcanism is very active. Tephra is usually characterized by petrographic characteristics and/or chemical composition (mainly major elements) of volcanic glasses and/or minerals in tephra. In Tono Geoscience Center (Japan Atomic Energy Agency), we develop an analytical technique of chemical composition including trace elements of volcanic glasses for detailed tephra identification. In this paper, we report a sample preparation procedure and analytical methods of chemical compositions of individual volcanic glass shards by using an electron probe microanalyzer and a laser ablation-inductively coupled plasma-mass spectrometer.

JAEA Reports

Research plan on geosphere stability for long-term isolation of radioactive waste (Scientific program for fiscal year 2021)

Ishimaru, Tsuneari; Kokubu, Yoko; Shimada, Koji; Shimada, Akiomi; Niwa, Masakazu; Watanabe, Takahiro; Sueoka, Shigeru; Yokoyama, Tatsunori; Fujita, Natsuko; Ogita, Yasuhiro; et al.

JAEA-Review 2021-012, 48 Pages, 2021/08

JAEA-Review-2021-012.pdf:1.64MB

This report is a plan of research and development (R&D) on geosphere stability for long-term isolation of high-level radioactive waste (HLW) in Japan Atomic Energy Agency (JAEA), in fiscal year 2021. The objectives and contents in fiscal year 2021 are described in detail based on the JAEA 3rd Medium- and Long-term Plan (fiscal years 2015-2021). In addition, the background of this research is described from the necessity and the significance for site investigation and safety assessment, and the past progress. 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.

51 (Records 1-20 displayed on this page)