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Journal Articles

Simultaneous determination of zircon crystallisation age and temperature; Common thermal evolution of mafic magmatic enclaves and host granites in the Kurobegawa granite, central Japan

Yuguchi, Takashi*; Yamazaki, Hayato*; Ishibashi, Kozue*; Sakata, Shuhei*; Yokoyama, Tatsunori; Suzuki, Satoshi*; Ogita, Yasuhiro; Sando, Kazusa*; Imura, Takumi*; Ono, Takeshi*

Journal of Asian Earth Sciences, 226, p.105075_1 - 105075_9, 2022/04

Simultaneous determination of the U-Pb age of zircon and concentration of titanium in a single analysis spot, using inductively coupled plasma mass spectrometry with laser ablation sample introduction, produces paired age and temperature data of zircon crystallisation, potentially revealing time-temperature ($$t-T$$) histories for evolved magma. The Kurobegawa granite, central Japan, contains abundant mafic magmatic enclaves (MMEs). We applied this method to evaluate MMEs and their host (enclosing) granites. Cooling behaviour common to both MMEs and host rocks was found between 1.5 and 0.5 Ma. Rapid cooling from the zircon crystallisation temperature to the closure temperature of biotite K-Ar system was within $$sim$$1 million year. Combining the obtained $$t-T$$ paths of MMEs and host rocks with petrological information can provide insights into magma chamber processes. This suggests that MME flotation, migration, and spread through the magma chamber ceased at 1.5-0.5 Ma, indicating the emplacement age of the Kurobegawa granitic pluton, as no large-scale reheating episodes have occurred since then.

Journal Articles

Permeability measurement for macro-fractured granite using water including clay

Nara, Yoshitaka*; Kato, Masaji*; Sato, Tsutomu*; Kono, Masanori*; Sato, Toshinori

Proceedings of 5th ISRM Young Scholars' Symposium on Rock Mechanics and International Symposium on Rock Engineering for Innovative Future (YSRM 2019 and REIF 2019) (USB Flash Drive), 6 Pages, 2019/12

It is important to understand the long-term migration of radionuclides considering carious rock engineering projects such as the geological disposal of radioactive wastes. The network of fractures and pores in a rock mass can play important roles as the pathway of the fluid flow of rock. Usually groundwater contains fine-grained minerals such as clays. It is probable that the accumulation of the fine-grained minerals occurs in a fracture if the groundwater flows in a fracture in a rock. In this study, we have conducted the permeability measurement using water including clays. Specifically, we used a macro-fractured granite as a rock sample, and investigated the change of the permeability under the flow of the water including clays. It was shown that the hydraulic conductivity decreased with elapsed time.

Journal Articles

Enhancement of permeability activated by supercritical fluid flow through granite

Nohara, Tsuyoshi; Uno, Masaoki*; Tsuchiya, Noriyoshi*

Geofluids, 2019, p.6053815_1 - 6053815_16, 2019/08

 Times Cited Count:1 Percentile:0.02(Geochemistry & Geophysics)

Amphibole-plagioclase thermometry was applied to estimate the temperature of a glassy vein as approximately 700. The results of observations of the rock core revealed that of supercritical fluid flow was microfracture filling with hornblende and plagioclase. The current high permeability was recognized to be microfracture network. A high-angle fracture of chlorite filling in combination with an open fracture was recognized as characteristics of a high-permeability type.

Journal Articles

Precipitation of minerals on rock kept in water with different calcium ion concentrations

Nara, Yoshitaka*; Kuwatani, Ryuta*; Kono, Masanori*; Sato, Toshinori; Kashiwaya, Koki*

Zairyo, 67(7), p.730 - 737, 2018/07

Information of confining ability of rock is important for the geological disposal of radioactive wastes. To maintain or improve the confining ability of rocks, it is important to seal pores and cracks. In this study, we investigated the precipitation of minerals on the rock surface. As rock samples, we used Berea sandstone and Toki granite in this study. It was shown that precipitation occurred on the surface of rock specimens kept in calcium hydroxide solution for 1 month if the concentration was high. Specifically, if the concentration of calcium hydroxide solution was higher than 300 mg/l, the precipitation occurred obviously. After keeping rock specimens in calcium hydroxide solution, the weight of the rock samples increased and the concentration of calcium ion decreased by the precipitation. It is considered that the calcium ion in water was used for the precipitation on rock surfaces. Since the precipitation has been recognized for rock surfaces, it is possible to seal pores and cracks in rocks. Therefore, it is also possible to keep or decrease the permeability of rocks by the precipitation of calcium compounds.

Journal Articles

Application of transient pulse method to permeability measurement for clay

Kato, Masaji*; Nara, Yoshitaka*; Okazaki, Yuki*; Kono, Masanori*; Sato, Toshinori; Sato, Tsutomu*; Takahashi, Manabu*

Zairyo, 67(3), p.318 - 323, 2018/03

To ensure the safe geological disposal of radioactive wastes, it is important to determine the permeability of clays. The transient pulse test is suitable to apply to the low permeability materials, because it takes relatively short term to determine the permeability. Usually we increase the upstream pore pressure in the measurement with the transient pulse test. However, it is impossible to determine the permeability of clay in this procedure because of the increase of pore pressure. Therefore, the transient pulse test has never been applied to the determination of permeability of clays. In this study, we tried to apply the transient pulse test to a clay obtained in Mizunami Underground Research Laboratory to determine the permeability with decreasing the downstream pore pressure. It was clarified that the transient pulse test with decreasing downstream pore pressure is appropriate from the measurements of granite and sandstone. It was shown that the permeability of a clay was determined by the transient pulse test with decreasing the downstream pore pressure, which agreed with the permeability determined from the falling head test. The measurement time of the transient pulse test is much shorter than that of the falling head test. It is concluded that the transient pulse test is appropriate for the determination of the permeability of clays.

Journal Articles

Comparative modeling of an in situ diffusion experiment in granite at the Grimsel Test Site

Soler, J. M.*; Landa, J.*; Havlova, V.*; Tachi, Yukio; Ebina, Takanori*; Sardini, P.*; Siitari-Kauppi, M.*; Eikenberg, J.*; Martin, A. J.*

Journal of Contaminant Hydrology, 179, p.89 - 101, 2015/08

 Times Cited Count:30 Percentile:84.43(Environmental Sciences)

Matrix diffusion is a key process for radionuclide retention in crystalline rocks. An in-situ diffusion experiment in granite matrix was performed at the Grimsel Test Site (Switzerland). Several tracers (HTO, Na$$^{+}$$, Cs$$^{+}$$) were circulated through a borehole and the decrease in tracer concentrations was monitored for 2.5 years. Then, the borehole section was overcored and the tracer profiles in the rock were analyzed. Transport distances in the rock were 20 cm for HTO, 10 cm for Na$$^{+}$$ and 1 cm for Cs$$^{+}$$. The dataset was analyzed with diffusion-sorption models by different teams using different codes, with the goal of obtaining effective diffusivities (De) and rock capacity factors. There was a rather good agreement between the values from different teams, implied that De and capacity factors in the borehole damaged zone are larger than those in the bulk rock. However, HTO seems to display large discrepancies between measured and modeled results.

Journal Articles

Influences of humid substances, alkaline conditions and colloids on radionuclide migration in natural barrier

Mukai, Masayuki; Ueda, Masato; Inada, Daisuke; Yukawa, Kazuhiko; Maeda, Toshikatsu; Iida, Yoshihisa

Proceedings of International Symposium NUCEF 2005, p.219 - 224, 2005/08

For better quantitative understanding of radionuclide migration for safety assessment of geologic disposal, JAERI has been conducting experimental and modeling studies on influences of humic substances, highly alkaline conditions and colloids on sorptive and diffusional behavior of TRU in geologic materials. In the absence of fulvic acid, one of humic substances, diffusion of Am through a tuff sample was not detected. By adding fulvic acid, Am was detected in the downstream cell, which indicates the diffusion through the sample. Highly alkaline conditions arisen from cementitious materials may spread by altering chemical and physical properties of geologic materials. Through-diffusion experiments of alkaline species in granite showed that the effective diffusion coefficient of Ca$$^{2+}$$ and OH$$^{-}$$ in a cement-equilibrated aqueous solution were found to be higher by almost two orders of magnitude than Na$$^{+}$$ and OH$$^{-}$$ in a NaOH solution. Radionuclide migration can be enhanced by colloids, and thus a calculation code describing the effect of colloids on radionuclide migration has been required.

Journal Articles

Contribution of the surface diffusion on mass transfer of Ba$$^{2+}$$ in granite matrix

Yamaguchi, Tetsuji; Nakayama, Shinichi; Kawada, Chiharu*

Genshiryoku Bakkuendo Kenkyu, 9(1), p.61 - 66, 2002/09

The effective diffusivity (${it D}$$$_{e}$$) and distribution ratio (${it K}$$$_{d}$$) of $$^{133}$$Ba$$^{2+}$$ in Inada granite have been determined by the through-diffusion method. Experiments were performed in triplicate for 10$$^{-1}$$, 1 and 10 mol m$$^{-3}$$ BaCl$$_{2}$$ solutions at 25$$^{circ}$$C. The ${it D}$$$_{e}$$ value obtained at a BaCl$$_{2}$$ concentration of 10 mol m$$^{-3}$$, agreed to the estimated value based on the pore diffusion model. The lower BaCl$$_{2}$$ concentrations yielded higher ${it D}$$$_{e}$$ values and higher ${it K}$$$_{d}$$ values. The variation in ${it D}$$$_{e}$$ was neither due to the speciation of barium in the solutions nor due to variation in physical properties of the pore structure in the rock. Contribution of diffusion in sorbed state should be responsible for the variation in ${it D}$$$_{e}$$.

Journal Articles

Chraracterization of iron hydroxides in a weathered rock surface by visible microspectroscopy

Nagano, Tetsushi; Isobe, Hiroshi*; Nakashima, Satoru*; Ashizaki, Midori*

Applied Spectroscopy, 56(5), p.651 - 657, 2002/05

 Times Cited Count:8 Percentile:46.34(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Present status of the study on radionuclide diffusion in barrier materials

Yamaguchi, Tetsuji; Nakayama, Shinichi

JAERI-Conf 2002-004, p.325 - 332, 2002/03

When long-lived radionuclides are transported by groundwater through fractures in the rock mass surrounding a radioactive waste repository, their diffusion into pores in the rock matrix and ensuing sorption onto mineral surfaces are expected to retard their transport along the pathways. We have characterized the pore structure of the Japanese Inada biotite granite and confirmed that Fick's diffusion law can be applied to the transport of aqueous species in granite. Effective diffusivity was determined by the through-diffusion method for cationic, anionic and actinide complex species to explore the mechanism of diffusion of the aqueous species. The results of this study enable us to provide a scientifically sound basis for radionuclide diffusion in granite for performance assessment of geological disposal. Future studies should emphasize understanding the diffusion mechanisms in low-permeability engineered barrier materials, data acquisition on long-term degradation of the materials and quantifying uncertainties associated with long-term mass transport analysis.

Journal Articles

Migration behavior of cesium in fresh and fractured granite

*; *;

Oyo Chishitsu, 32(2), p.55 - 63, 1991/06

no abstracts in English

Journal Articles

The Pore structure of granite as the migration pathways of dissolved species

*; ; Nagano, Tetsushi; *

Kozan Chishitsu, 39(6), p.349 - 354, 1989/00

no abstracts in English

Journal Articles

Measurement of diffusion and sorption of radionuclides in rocks

; ; *;

Journal of Nuclear Science and Technology, 22(10), p.833 - 840, 1985/00

 Times Cited Count:3 Percentile:47.62(Nuclear Science & Technology)

no abstracts in English

Oral presentation

Study of permeable structure distribution and hydrogeological structure model of granitic rocks; Features of the permeable structures deduced from the wall surface geological data of the Mizunami Underground Research Laboratory

Nohara, Tsuyoshi; Takeuchi, Ryuji; Sakai, Toshihiro

no journal, , 

Focusing on the characteristics of the faults and fractures of the MIU, based on analysis of existing data and on geological investigations, we examined the geological and hydrological features of the deep underground granitic rocks in the site scale. As a result, main permeable structures of granitic rocks can be associated with the old structures formed with the faulting and/or hydrothermal activity in geological times. Furthermore, we examined the distribution of the major permeable structures, based on the distribution of the geological structures.

Oral presentation

Is a fracture in Toki granite a trace of high temperature fluid in the past?

Nohara, Tsuyoshi; Tsuchiya, Noriyoshi*

no journal, , 

A trace of a high-temperature fluid in the Toki granite is investigated using pre-existing boring core of MIU. Fractures filled with secondary formed biotite and pores filled with quarts are recognized. It is considered that these filling minerals are traces of a high-temperature fluid in the past.

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