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Journal Articles

Micropores and mass transfer in the formation of myrmekites

Yuguchi, Takashi*; Yuasa, Haruka*; Izumino, Yuya*; Nakashima, Kazuo*; Sasao, Eiji; Nishiyama, Tadao*

American Mineralogist, 107(3), p.476 - 488, 2022/03

 Times Cited Count:1 Percentile:30.8(Geochemistry & Geophysics)

The methodology and interpretations in this study provide new insights into the mechanism of myrmekite formation in a granitic system. The presence of micropores in the myrmekites and this study clarified that the genesis of micropores is related to the formation of myrmekites in the Toki granite. The results led to an increased understanding of (1) an estimate of mass transfer between the reactant and product minerals, and the inflow and outflow of components with consideration of the volume change due to micropore formation, (2) the factor controlling the formation of micropores during myrmekitization, and (3) the sequential variations in the hydrothermal fluid chemistry during sub-solidus conditions. The micropores act as a migration pathway for hydrothermal fluid and thus enhance the mass transfer within a granitic body starting with the myrmekite formation and continuing through the present day and into the future.

Journal Articles

Mass transfer associated with chloritization in the hydrothermal alteration process of granitic pluton

Yuguchi, Takashi*; Matsuki, Takanobu*; Izumino, Yuya*; Sasao, Eiji; Nishiyama, Tadao*

American Mineralogist, 106(7), p.1128 - 1142, 2021/07

 Times Cited Count:3 Percentile:48.85(Geochemistry & Geophysics)

This study reveals the hydrothermal alteration processes in a pluton, with a focus on the mass transfer between minerals and hydrothermal fluid. Hydrothermal alteration of the Toki granite in Tono area, central Japan, progressed through the successive processes of chloritization, plagioclase alteration, and precipitation of a carbonate mineral. This paper describes the alteration process of hornblende chloritization, K-feldspar chloritization, and the formation of fracture-filling chlorite through petrography and mineral chemistry. Several types of chloritization reactions (including biotite chloritization) can be characterized by their reaction with the inflow of Al$$^{3+}$$, Fe$$^{2+}$$, Mn$$^{2+}$$, and Mg$$^{2+}$$ and the outflow of H$$_{4}$$SiO$$_{4}$$, Ca$$^{2+}$$, K$$^{+}$$+, and F$$^{-}$$. The reactions of chloritization and plagioclase alteration represent the sequential variations in fluid chemistry at temporal conditions from 68 Ma to 51 Ma as the temperature decreased from 350$$^{circ}$$C to 180$$^{circ}$$C.

Journal Articles

K-Ar geochronology for hydrothermal K-feldspar within plagioclase in a granitic pluton; Constraints on timing and thermal condition for hydrothermal alteration

Yuguchi, Takashi*; Yagi, Koshi*; Sasao, Eiji; Nishiyama, Tadao*

Heliyon (Internet), 7(4), p.e06750_1 - e06750_9, 2021/04

 Times Cited Count:1 Percentile:13.22(Multidisciplinary Sciences)

Our methodology and interpretations provide new insight for K-Ar geochronology in hydrothermal microcline within altered plagioclase in a granitic pluton. Our methodology employs a two-step separation process consisting of (1) plagioclase extraction from the rock sample and (2) separation of the hydrothermal microcline from the plagioclase, giving precise determination of microcline powders in K-Ar geochronology. This tighter constraint should provide the ability to better unravel thermal and age histories in granite subject to multi-step alteration processes and complex thermal histories.

Journal Articles

Crystallization processes of quartz in a granitic magma; Cathodoluminescence zonation pattern controlled by temperature and titanium diffusivity

Yuguchi, Takashi*; Ogita, Yasuhiro; Kato, Takenori*; Yokota, Rintaro*; Sasao, Eiji; Nishiyama, Tadao*

Journal of Asian Earth Sciences, 192, p.104289_1 - 104289_16, 2020/05

 Times Cited Count:5 Percentile:35.49(Geosciences, Multidisciplinary)

Quartz from a granitic pluton is found to have formed through sequential growth events under different mechanisms and crystallization temperatures, which can provide new insights into magmatic processes of granitic magmas that were eventually consolidified into plutons. The events were identified using (1) the description of crystal shape and occurrence, (2) the study of the internal structure with cathodoluminescence (CL), and (3) derivation of the crystallization temperatures based on TitaniQ thermometry. The magmatic quartz crystals from the Toki granite, central Japan, are characterized as having the following internal structures: oscillatory zonation, no-oscillatory zonation with luminescence graduation (gradational zonation), and heterogeneous CL. The quartz crystals with oscillatory zonation were formed in the temperature range of about 800 $$^{circ}$$C to below 700 $$^{circ}$$C, which is referred to as oscillatory zoning temperature (OZT) conditions. The CL zonation pattern was controlled by the temperature conditions and titanium diffusivity in the melt (magma). The crystallization process of quartz within the Toki granite reveals the cooling processes of the granitic pluton; the lithofacies with a high frequency of oscillatory-zoned quartz underwent slower cooling under the OZT conditions than those in other lithofacies.

Journal Articles

Role of micropores, mass transfer, and reaction rate in the hydrothermal alteration process of plagioclase in a granitic pluton

Yuguchi, Takashi*; Shobuzawa, Kaho*; Ogita, Yasuhiro*; Yagi, Koshi*; Ishibashi, Masayuki; Sasao, Eiji; Nishiyama, Tadao*

American Mineralogist, 104(4), p.536 - 556, 2019/04

 Times Cited Count:15 Percentile:71.24(Geochemistry & Geophysics)

This study describes the plagioclase alteration process with a focus on the role of micropores, mass transfer and reaction rate in the Toki granitic pluton, central Japan. The plagioclase alteration process involves albitization, K-feldspathization, and the formation of illite, calcite, fluorite and epidote. Such secondary minerals of hydrothermal origin in plagioclase within granitic rocks record the chemical characteristics of the hydrothermal fluid. Our results highlight (1) the nature of micropores such as distribution and volume in plagioclase, (2) the reaction nature of plagioclase alteration inferred by petrography and chemistry, (3) the physical conditions including alteration age and temperature, (4) the sequential variations of the fluid chemistry and (5) the mass transfer rate and reaction rate in the plagioclase alteration.

Journal Articles

Position-by-position cooling paths within the Toki granite, central Japan; Constraints and the relation with fracture population in a pluton

Yuguchi, Takashi*; Sueoka, Shigeru; Iwano, Hideki*; Izumino, Yuya*; Ishibashi, Masayuki; Danhara, Toru*; Sasao, Eiji; Hirata, Takafumi*; Nishiyama, Tadao*

Journal of Asian Earth Sciences, 169, p.47 - 66, 2019/01


 Times Cited Count:14 Percentile:64.27(Geosciences, Multidisciplinary)

This study presents position-by-position $$t-T$$ paths within a granitic pluton based on thermochronological data, and describes their constraints and their relationship with fracture frequency, as an example from the Toki granite, central Japan. The cooling paths have position-specific characteristics; a single $$t-T$$ path does not represent the cooling behavior of the entire pluton. Such position-specific $$t-T$$ paths enable us to evaluate three-dimensional thermal evolution within the granitic pluton, and thus can clarify the detailed formation history of the entire pluton after the incipient intrusion of the granitic magma into the shallow crust. This study reveals the relationship between position-specific $$t-T$$ paths and fracture frequency, and thus provides a criterion for evaluating the fracture population in terms of thermal stress.

Journal Articles

Spatial distribution of the apatite fission-track ages in the Toki granite, central Japan; Exhumation rate of a Cretaceous pluton emplaced in the East Asian continental margin

Yuguchi, Takashi*; Sueoka, Shigeru; Iwano, Hideki*; Danhara, Toru*; Ishibashi, Masayuki; Sasao, Eiji; Nishiyama, Tadao*

Island Arc, 26(6), p.e12219_1 - e12219_15, 2017/11

 Times Cited Count:11 Percentile:41.11(Geosciences, Multidisciplinary)

The spatial distribution of AFT age in the granitic body is a favorable key to reveal a cooling behavior of the whole pluton. The cooling behavior is attributable to the regional exhumation of the Toki granite related to the regional denudation of the Tono district. Combination of the AERs and AFT inverse model applying to the granite is a powerful procedure for evaluating the cooling and exhumation history of the granitic pluton and thus denudation history of the tectonic region that surrounded the rock body.

Journal Articles

Zircon growth in a granitic pluton with specific mechanisms, crystallization temperatures and U-Pb ages; Implication to the "spatiotemporal" formation process of the Toki granite, central Japan

Yuguchi, Takashi*; Iwano, Hideki*; Kato, Takenori*; Sakata, Shuhei*; Hattori, Kentaro*; Hirata, Takafumi*; Sueoka, Shigeru; Danhara, Toru*; Ishibashi, Masayuki; Sasao, Eiji; et al.

Journal of Mineralogical and Petrological Sciences, 111(1), p.9 - 34, 2016/02

 Times Cited Count:17 Percentile:56.08(Mineralogy)

Zircon growth collected from a granitic pluton shows four (1st - 4th) events with specific mechanisms, crystallization temperatures and U-Pb ages, revealing the sequential formation process from intrusion through emplacement to crystallization / solidification. The events are recognized by: (1) internal structure of zircon based on the cathodoluminescence observation, (2) crystallization temperatures by the Ti-in-zircon thermometer in the internal structure and (3) U-Pb ages in the internal structure.

Journal Articles

Hydrothermal chloritization processes from biotite in the Toki granite, Central Japan; Temporal variations of the compositions of hydrothermal fluids associated with chloritization

Yuguchi, Takashi; Sasao, Eiji; Ishibashi, Masayuki; Nishiyama, Tadao*

American Mineralogist, 100(5-6), p.1134 - 1152, 2015/05

 Times Cited Count:27 Percentile:70.95(Geochemistry & Geophysics)

This paper describes the biotite chloritization process with a focus on mass transfer in the Toki granitic pluton, Central Japan, and also depicts the temporal variations in chemical characteristics of hydrothermal fluid associated with chloritization during the sub-solidus cooling of the pluton. Singular value decomposition (SVD) analysis results in chloritization reaction equations for eight mineral assemblages, leading to the quantitative assessment of mass transfer between the reactant and product minerals, and inflow and outflow of components through the hydrothermal fluid. The matrices for SVD analysis consist of arbitrary combinations of molar volume and closure component in the reactant and product minerals. The eight reactions represent the temporal variations of chemical characteristics of the hydrothermal fluid associated with chloritization: the progress of chloritization results in gradual increase of silicon, potassium and chlorine and gradual decrease of calcium and sodium in the hydrothermal fluid with temperature decrease. The biotite chloritization involves two essential formation processes: Formation Process 1, small volume decrease from biotite to chlorite and large inflow of metallic ions from the hydrothermal fluid, and Formation Process 2, large volume decrease and large outflow of metallic ions into hydrothermal fluid. Chlorite produced during Formation Process 1 dominates over that of Formation Process 2, resulting in the gradual decrease of metallic components in the hydrothermal fluid with chloritization progress. The combination of continuous reactions based on compositional variations in chlorite together with corresponding continuous Al$$^{IV}$$ variations gives an indication of the temporal variations in rates of decreasing and increasing concentration of chemical components in the hydrothermal fluid associated with chloritization.

Journal Articles

The Spatial variation of initial $$^{87}$$Sr/$$^{86}$$Sr ratios in the Toki granite, Central Japan; Implications for the intrusion and cooling processes of a granitic pluton

Yuguchi, Takashi; Tsuruta, Tadahiko; Hama, Katsuhiro; Nishiyama, Tadao*

Journal of Mineralogical and Petrological Sciences, 108(1), p.1 - 12, 2013/02

 Times Cited Count:12 Percentile:36.29(Mineralogy)

The spatial variation in initial $$^{87}$$Sr/$$^{86}$$Sr ratios (SrI) in the Toki granite, Central Japan, shows heterogeneity ranging from 0.708942 to 0.710069, which provides information on formation processes of plutons. The Toki granite has three mineralogy-based rock facies: muscovite-biotite granite (MBG), hornblende-biotite granite (HBG) and biotite granite (BG). Large SrI values were found to be distributed at the western margin (west MBG) and the lithologically central region (central BG), while small SrI values were found at the northeast margin (northeast MBG). Regions with high and low Sr concentrations were also found in the Toki granite. In the Sr-rich samples, SrI (0.708942-0.709789) increases with 100/Sr (0.7-1.5). This geochemical trend extends towards the country sedimentary rocks of the Mino Terrane, which can be interpreted to result from assimilation and fractional crystallization (AFC) between the original granitic magma and the Mino sedimentary rocks. The SrI values in the Sr-rich regions show a correlation with the Alumina Saturation Index (ASI). In particular, the west MBG, with large SrI values, is classified as a peraluminous granitoid, suggesting that the western margin of the pluton was strongly affected by assimilation during the intrusion process. The Sr-poor samples are present both in the central BG, with large SrI values, and in the northeast MBG, with small SrI values. The Sr-poor samples have small ASI and large differentiation indices, indicating that the central BG and the northeast MBG were generated either by different AFC process with different amounts of contaminants or by the intrusion and fractionation of different source magma with different SrI values. Overall, the geochemical spatial variations found in the Toki granite can be explained by various degrees of assimilation and fractional crystallization in the magma chamber and/or multi-stage intrusions with different degrees of crystallization of plural source magmas.

Journal Articles

Three-dimensional fracture distribution in relation to local cooling in a granitic body; An Example from the Toki granitic pluton, Central Japan

Yuguchi, Takashi; Tagami, Masahiko*; Tsuruta, Tadahiko; Nishiyama, Tadao*

Engineering Geology, 149-150, p.35 - 46, 2012/11

 Times Cited Count:10 Percentile:42.48(Engineering, Geological)

This paper describes the spatial distribution of fractures in the Toki granitic pluton, Central Japan and their evaluation with respect to the pluton's cooling behavior. Three-dimensional frequency distributions of entire fractures, based on borehole television data collected from 19 boreholes, shows that (1) the central region of the granite has a high fracture frequency and (2) fracture frequency decreases with decreasing elevation (datum is mean sea level), with the exception of the west side of the body. The development of sub-solidus reaction features was measured at two neighboring positions, and the difference was divided by the distance between the two positions. The resulting quantity is here defined as "local cooling rate". We observed a significant correlation between the distribution patterns of entire fracture frequency and local cooling rate; the region with a high local cooling rate corresponds to the region with a high frequency of entire fractures, and vice versa. This correlation indicates that fracture genesis can be explained by "local cooling rate", combined with the concept of thermal stress. Thus, the three dimensional pattern of local cooling rate is a potential diagnostic tool for quantifying the distribution of fracture frequency.

Journal Articles

Thermochronology and the three-dimensional cooling pattern of a granitic pluton; An Example from the Toki granite, Central Japan

Yuguchi, Takashi; Amano, Kenji; Tsuruta, Tadahiko; Danhara, Toru*; Nishiyama, Tadao*

Contributions to Mineralogy and Petrology, 162(5), p.1063 - 1077, 2011/11

 Times Cited Count:23 Percentile:58.1(Geochemistry & Geophysics)

Journal Articles

Three-dimensional cooling pattern of a granitic pluton, 2; The Study of deuteric sub-solidus reactions in the Toki granite, Central Japan

Yuguchi, Takashi; Tsuruta, Tadahiko; Nishiyama, Tadao*

Journal of Mineralogical and Petrological Sciences, 106(3), p.130 - 141, 2011/06

 Times Cited Count:17 Percentile:46.43(Mineralogy)

Petrographical studies examining the development and variations of sub-solidus reactions recorded in the Toki granite represent the three-dimensional cooling pattern of this zoned pluton in Central Japan. Samples collected from 19 boreholes in the Toki granite show characteristics indicative of spatial variations in the extent of sub-solidus reactions. Exsolution coarsening has produced microperthite including albite-rich lamellae in this pluton, while deuteric coarsening has resulted in patchperthite, myrmekite, and the reaction rim. The extent of deuteric coarsening reactions can be evaluated by the width and spacing of albite-rich patch in patchperthite, and by the thickness of myrmekite and the reaction rim. The width, spacing and thickness of these textural features increase systematically with elevation and also increase gradually in the horizontal inward in the western part but not in the eastern part of the pluton. The systematic variations in textural development indicate that the Toki granite cooled effectively from the roof and from the western margin during the deuteric coarsening stage. The deuteric coarsening may have occurred at temperatures below 500$$^{circ}$$C based on ternary feldspar thermometry.

Journal Articles

Three-dimensional cooling pattern of a granitic pluton, 1; The Study of exsolution sub-solidus reactions in the Toki granite, Central Japan

Yuguchi, Takashi; Tsuruta, Tadahiko; Nishiyama, Tadao*

Journal of Mineralogical and Petrological Sciences, 106(2), p.61 - 78, 2011/04

 Times Cited Count:18 Percentile:49.26(Mineralogy)

Journal Articles

Zoning of rock facies and chemical composition in the Toki granitic body, Central Japan

Yuguchi, Takashi; Tsuruta, Tadahiko; Nishiyama, Tadao*

Ganseki Kobutsu Kagaku, 39(2), p.50 - 70, 2010/03

JAEA Reports

Development of the JAERI Computational Dosimetry System (JCDS) for boron neutron capture therapy (Cooperative research)

Kumada, Hiroaki; Yamamoto, Kazuyoshi; Torii, Yoshiya; Matsumura, Akira*; Yamamoto, Tetsuya*; Nose, Tadao*; Nakagawa, Yoshinobu*; Kageji, Teruyoshi*; Uchiyama, Junzo

JAERI-Tech 2003-002, 49 Pages, 2003/03


no abstracts in English

JAEA Reports

Production of a faithful realistic phantom to human head and thermal neutron flux measurement on the brain surface (Cooperative research)

Yamamoto, Kazuyoshi; Kumada, Hiroaki; Kishi, Toshiaki; Torii, Yoshiya; Endo, Kiyoshi*; Yamamoto, Tetsuya*; Matsumura, Akira*; Uchiyama, Junzo; Nose, Tadao*

JAERI-Tech 2002-092, 23 Pages, 2002/12


Thermal neutron flux is determined using the gold wires in current BNCT irradiation, so evaluation of arbitrary points after the irradiation is limited in the quantity of these detectors. In order to make up for the weakness, dose estimation of a patient is simulated by a computational dose calculation supporting system. In another way without computer simulation, a medical irradiation condition can be replicate experimentally using of realistic phantom which was produced from CT images by rapid prototyping technique. This phantom was irradiated at a same JRR-4 neutron beam as clinical irradiation condition of the patient and the thermal neutron distribution on the brain surface was measured in detail. This experimental evaluation technique using a realistic phantom is applicable to in vitro cell irradiation experiments for radiation biological effects as well as in-phantom experiments for dosimetry under the nearly medical irradiation condition of patient.

Journal Articles

Outline of simulation code fact for analysis of ventilation system on criticality accident

Tsubata, Yasuhiro; Tashiro, Shinsuke; Koike, Tadao; Abe, Hitoshi*; Watanabe, Koji; Uchiyama, Gunzo

Transactions of the American Nuclear Society, 87, p.60 - 61, 2002/11

no abstracts in English

Journal Articles

Development of ITER-CS model coil terminal assembling by using indium wires

Takahashi, Yoshikazu; Kato, Takashi; Nunoya, Yoshihiko; Ando, Toshinari; Nishijima, Gen; Nakajima, Hideo; Hiyama, Tadao; Sugimoto, Makoto; Isono, Takaaki; Koizumi, Norikiyo; et al.

Fusion Engineering and Design, 58-59, p.93 - 97, 2001/11

 Times Cited Count:9 Percentile:56.28(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Evaluation of critial current performance of 13 T-46 kA steel-jacketed Nb$$_{3}$$Al conductor

Koizumi, Norikiyo; Azuma, Katsunori*; Tsuchiya, Yoshinori; Matsui, Kunihiro; Takahashi, Yoshikazu; Nakajima, Hideo; Nishijima, Gen; Nunoya, Yoshihiko; Ando, Toshinari; Isono, Takaaki; et al.

Fusion Engineering and Design, 58-59, p.1 - 5, 2001/11

 Times Cited Count:2 Percentile:19.75(Nuclear Science & Technology)

no abstracts in English

94 (Records 1-20 displayed on this page)