Updated on 2022/05/26

写真a

 
ARAI, Hiroyoshi
 
Affiliation
Affiliated organization, Waseda University Honjo Senior High School
Job title
Teacher (Affiliated Senior High School)

Research Institute

  • 2020
    -
    2022

    理工学術院総合研究所   兼任研究員

Education

  • 1998.04
    -
    2001.03

    Waseda University   Graduate School, Division of Science and Engineering   Mineral Industry and Materials Engineering  

  • 1996.04
    -
    1998.03

    Waseda University   Graduate School, Division of Science and Engineering   Mineral Industry and Materials Engineering  

  • 1992.04
    -
    1996.03

    Waseda Univeristy   Faculty of Education   Institute of Earth Science  

Degree

  • Waseda University   Doctor of Engineering

Research Experience

  • 2018.04
    -
     

    Waseda Research Institute for Science and Engineering

  • 2006.04
    -
    2018.03

    : Part-time lecturer at School of Education, Waseda University

  • 2006.04
    -
    2018.03

    : Visiting Researcher at Advanced Research Institute for Science and Engineering, Waseda University

  • 2014.04
    -
     

    Waseda University Honjo Senior High School

  • 2011.04
    -
    2014.03

    : Part-time lecturer at Waseda University Honjo Senior High School

  • 2006.04
    -
    2014.03

    : Part-time lecturer at Seikei High School

  • 2003.04
    -
    2006.03

    : Research associate at School of Education, Waseda University

  • 2002.04
    -
    2003.03

    : Part-time lecturer at School of Education, Waseda University

  • 2001.04
    -
    2003.03

    : Visiting Researcher at Advanced Research Institute for Science and Engineering, Waseda University

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Professional Memberships

  •  
     
     

    Japan Society of Earth Science Education

  •  
     
     

    American Geophysical Union

  •  
     
     

    Geological Society of America

  •  
     
     

    Japan Geoscience Union

  •  
     
     

    Geologycal Society of Jaan

 

Research Areas

  • Solid earth sciences

Research Interests

  • Geology, Structural geology

Papers

  • Low-angle structural boundaries in northern marginal area of the Kanto Mountains

    Takagi, Hideo, Arai, Hiroyoshi, Miyashita, Atsushi

    Jour. Geol. Soc. Japan   122 ( 7 ) 305 - 324  2016.07  [Refereed]

    DOI CiNii

  • Geological framework and fission track dating of pseudotachylyte of the Atotsugawa Fault, Magawa area, central Japan

    Hideo Takagi, Kosuke Tsutsui, Hiroyoshi Arai, Hideki Iwano, Tohru Danhara

    ISLAND ARC   22 ( 3 ) 318 - 337  2013.09  [Refereed]

     View Summary

    This paper describes newly discovered pseudotachylyte along the Atotsugawa Fault at the Magawa outcrop, where this fault divides Quaternary deposits in the SW from Triassic Hida granitic rocks to the NE. Within several meters of the fault surface, pseudotachylyte veins are found with a thickness of less than 10cm, but are displaced by fault brecciation. Zircon fission track dating of pseudotachylyte samples yields ages of 48.6-50.2 Ma (sample AT-A), 55.1 Ma (AT-A'-1) and 60.9 Ma (AT-D-1); the latter is similar to the fission track ages of 56.1-60.1 Ma for granitic protoliths. The results of fission track length analyses in zircon suggest that pseudotachylytes (AT-A and AT-D-1) and protolith granite are mostly annealed. Consequently, the pseudotachylyte (AT-A) reached the highest temperature during 48.6-50.2 Ma, thereby resetting the fission track system totally in zircon during faulting. Another pseudotachylyte (AT-A'-1) and its wall rock granite contain shortened tracks within zircon grains suggesting partial annealing. The age distribution pattern of the former also contains decomposed age after the normality test (Shapiro-Wilk test) in which the major age yields 52.5 Ma. Accordingly, these pseudotachylytes yield a peak age of about 50 Ma, whereas the peak ages of one pseudotachylyte (AT-D-1) and the protolith Hida granitic rocks are about 60 Ma, representing the thermal effects not caused by frictional heating but by intrusions of Late Cretaceous to Paleogene granitoids that are probably concealed below the exposed Triassic Hida granitic rocks. Such thermal effects did not affect the K-Ar muscovite age (149 Ma) for the protolith granite because of the higher closure temperature of this system. Using the new geochronological data, we can elucidate the cooling history of the Hida granitic rocks, and constrain the timing of the main pulse of pseudotachylyte generation along the Atotsugawa Fault at about 50 Ma.

    DOI

  • Identification of the Unchanging Reference Component of Compositional Data from the Properties of the Coefficient of Variation

    Tohru Ohta, Hiroyoshi Arai, Atsushi Noda

    MATHEMATICAL GEOSCIENCES   43 ( 4 ) 421 - 434  2011.05  [Refereed]

     View Summary

    In analyses of compositional data, it is important to select a suitable unchanging component as a reference to detect the behavior of a single variable in isolation. This paper introduces two tests for detecting the unchanging component, based on a new approach that utilizes the coefficient of variation of component ratios. That is, the coefficient of variation of a compositional ratio is subject to change when the unchanging component is switched between the denominator and numerator, and the coefficient of variation tends to be small when the unchanging component occurs as the denominator against any arbitrary components (Test 1). In addition, the ratio of the component pair that gives the lowest coefficient of variation is most likely to represent the two unchanging components (Test 2). However, Tests 1 and 2 are not necessary and sufficient conditions for uniquely finding the unchanging component. To verify the effectiveness of the tests, 500 artificial datasets were analyzed and the results suggest that the tests are able to identify the unchanging component, although Test 1 underperforms when the dataset includes a component with skewness greater than 0.5, and Test 2 fails when the dataset includes components with a correlation coefficient greater than 0.75. These defects can be overcome by interpreting the two test results in a complementary manner. The proposed tests provide powerful yet simple criteria for identifying the unchanging component in compositional data; however, the reliability of this approach needs to be assessed in further studies.

    DOI

  • Circular statistics for the analysis of directional geological data

    Arai Hiroyoshi

    Jour. Geol. Soc. Japan   117 ( 10 ) 547 - 564  2011  [Refereed]

    Authorship:Lead author, Corresponding author

     View Summary

    Geological data such as the strike of bedding, paleocurrent directions, paleomagnetic directions, and the trend of mineral lineations are directional data defined by an angle from a reference direction. The main characteristic of such data is circularity in any reference direction (i.e. 0°=360°), which creates problems when analyzing the data statistically. In this regard, only directional statistics are adequate for dealing with directional data. This paper introduces the fundamental theory of circular statistics, a form of directional statistics that is restricted to data on a circumference, and presents practical methods with which to analyze circular data, including their graphical representation, descriptive statistics, the characteristics of circular uniform and von Mises distributions, tests of goodness-of-fit, and single- and multi-sample statistical tests. In addition, statistical software is considered with which to analyze circular data.

    DOI CiNii

  • Petrological and mineralogical characterizationsofjadeite-bearing rocksfrom the Mikabu greenstones in the Shimonita area, Kanto Mountains, Central Japan

    Hiroyoshi Arai, Atsushi Miyashita, Katsuyuki Tanabe, Mamoru Murata

    Japanese Magazine of Mineralogical and Petrological Sciences   40 ( 6 ) 177 - 194  2011  [Refereed]

    Authorship:Lead author

     View Summary

    Jadeite-bearing meta-basalt occur within a greenstone complex at the southern margin of the Mikabu greenstones in the Shimonita area, northern Kanto Mountains, Central Japan. The greenstone complex shows a block-in-matrix structure consisting of small, sporadically occurring greenstone blocks (jadeite-bearing meta-basaltic lavas, jadeite-free pargasite rocks, and jadeite-free garnet-epidote rocks) embedded within a matrix of actinolite rocks. The complex has been interpreted as a tectonic meá lange composed of allochthonous metamorphic blocks within the Mikabu greenstones. However, both the greenstone blocks and actinolite rocks preserve original igneous or pyroclastic textures without the deformation structures commonly seen in tectonic melanges. The concentrations of high field strength (HFS) elements within the jadeite-bearing lavas indicate that these rocks are alkali basalts derived from oceanic island basalt (OIB). The composition of these lavas is similar to that of OIB blocks in the Mikabu greenstones in Shikoku, western Japan. The whole-rock chemical composition of the lavas reveals higher Na2O concentrations (max. 10.1 wt%) than in unmetamorphosed Hawaiian OIB alkali basalts. The actinolite rocks of the matrix show a pyroclastic texture and contain relic Ca-pyroxenes. The concentrations of HFS elements and pyroxene chemistry of the actinolite rocks indicate an origin from tholeiitic MORB, similar in composition to typical Mikabu greenstones in the Kanto Mountains and Shikoku. These observations strongly suggest that the greenstone complex is not a tectonic melange comprising allochthonous meta-morphic rocks within a matrix of Mikabu greenstones, but that the entire complex consists of Mikabu greenstones. Therefore, the complex was subjected to Sanbagawa metamorphism after a Na-enrichment event
    jadeite grew in Na-rich blocks during the metamorphism. © 2011, Japan Association of Mineralogical Sciences. All rights reserved.

    DOI CiNii

  • Miocene dextral movement of Tanakura Shear Zone: Evidence from the Western Marginal Fault, Hanawa Town, Northeast Japan

    Dohta Awaji, Ryota Sugimoto, Hiroyoshi Arai, Kenta Kobayashi, Hideo Takagi

    ISLAND ARC   19 ( 4 ) 561 - 564  2010.12  [Refereed]

    DOI

  • Majoritic garnet: A new approach to pressure estimation of shock events in meteorites and the encapsulation of sub-lithospheric inclusions in diamond

    Kenneth D. Collerson, Quentin Williams, Balz S. Kamber, Soichi Omori, Hiroyoshi Arai, Eiji Ohtani

    GEOCHIMICA ET COSMOCHIMICA ACTA   74 ( 20 ) 5939 - 5957  2010.10  [Refereed]

     View Summary

    A means for estimating pressures in natural samples based on both the coupled substitution (Na+)([1+]) + Si-[VI]([4+]) = (M)([2+]) (Al + Cr)([3+]), and the classic pyroxene-stoichiometry majorite-substitution into garnet at high-pressure, is derived for garnets with majoritic chemistry. The technique is based on a compilation of experimental data for different bulk compositions. It is compositionally and thermally robust and can be used to estimate pressures experienced by natural materials during formation of majoritic garnet. In addition, it can be used either retrospectively, or in new experimental studies to establish the pressures of crystallization of reaction products, and determine if disequilibrium is recorded by the chemistries of majoritic garnets. Pressures are calculated based on majoritic chemistries in chondritic meteorites and diamond inclusions. Majoritic garnets associated with Mg perovskite in shocked L chondrites (n = 4) yield uniform pressures of 23.8 +/- 0.2 GPa that are slightly higher than pressures recorded by majoritic garnet in shock-derived melt veins in L chondrites (22.4 +/- 0.6 GPa; n = 5). Similar pressures are also exhibited by shock-derived majoritic garnets in H chondrites (22.2 +/- 1.1 GPa; n = 3). Diamond inclusions with eclogitic and peridotitic majoritic garnet chemistries exhibit mean pressures of 10.7 +/- 2.7 GPa (n = 30) and 8.3 +/- 1.6 GPa (n = 15) respectively, consistent with a sub-lithospheric origin. However, pressures defined by majoritic diamond inclusions from Jagersfontein (22.3 +/- 0.8 GPa and 16.9 +/- 1 GPa), Monastery (15.7 +/- 7 GPa) and Kankan (15.5 +/- 0.2 GPa) show that these inclusions originated from the mantle transition zone. Thus, this new single-phase method for pressure estimation has unmatched potential to map the depth of formation of garnets with majoritic chemistries that occur as diamond inclusions in all parageneses except those that include Ca silicate perovskite. The derived pressures confirm the sub-lithospheric origin of eclogitic majoritic diamond inclusions, and thus provide a more comprehensive picture of the important role of storage of oceanic lithosphere in the transition zone. (C) 2010 Elsevier Ltd. All rights reserved.

    DOI

  • A function for the R programming language to recast garnet analyses into end-members: Revision and porting of Muhling and Griffin's method

    Hiroyoshi Arai

    COMPUTERS & GEOSCIENCES   36 ( 3 ) 406 - 409  2010.03  [Refereed]

    DOI

  • Comparison of petrofabrics with composite magnetic fabrics of S-C mylonite in paramagnetic granite

    Takaaki Ono, Yukinobu Hosomi, Hiroyoshi Arai, Hideo Takagi

    JOURNAL OF STRUCTURAL GEOLOGY   32 ( 1 ) 2 - 14  2010.01  [Refereed]

     View Summary

    An anisotropy of magnetic susceptibility (AMS) analysis was conducted for a typical S-C mylonite in a small-scale ductile shear zone derived from Late Cretaceous magnetite-free granite in the Ryoke Belt, Teshima Island, southwest Japan. In such mylonites, paramagnetic minerals such as biotite and hornblende, which define foliations, are assumed to control the AMS. Accordingly, we attempted to measure the orientations of both minerals to correlate the S-C-C' fabric to the AMS using techniques of microscopic and back-scattered electron (BSE) image analyses. A measured magnetic fabric of the S-C mylonite that is expressed by a K(min) normal plane (K(max)-K(int) plane) approximated S foliation, K(max) orientation coincided well with the orientations of mean resultant vectors for long axes of biotite and minor hornblende, whereas K(max) did not coincide well with those of the mean resultant vectors for long axes of the brighter domain (aggregates of biotite and minor hornblende) from the binary BSE image. These results show that the magnetic fabric fairly reflects the shape preferred orientation of individual grains of paramagnetic monoclinic minerals, especially biotite, which forms the S-C-C fabric. (C) 2009 Elsevier Ltd. All rights reserved.

    DOI

  • Excavation history of the Sanbagawa belt deduced from the Aoiwa Conglomerate, Kanto Mountains

    Takagi Hideo, Arai Hiroyoshi, Iwasaki Ichiro, Takahashi Masaki

    Jour. Geol. Soc. Japan   115 ( 5 ) IX - X  2009  [Refereed]

    DOI CiNii

  • K-Ar ages of metamorphic clasts from the Miocene Aoiwa Conglomerate, Hiki Hills, Central Japan: Implications for exhumation history of source rocks

    Arai Hiroyoshi, Takagi Hideo, Iwasaki Ichiro, Asahara Yoshihiro, Takahashi Masaki

    Jour. Geol. Soc. Japan   115 ( 5 ) 223 - 241  2009  [Refereed]

    Authorship:Lead author

     View Summary

    The exhumation of high-P/T metamorphic rocks plays a key role in the rearrangement of the geotectonic framework in arc-trench systems. The deposition of clasts of exhumed rocks constrains the timing of exhumation and the denudation history. We obtained the K-Ar ages of clasts from the Miocene Aoiwa Conglomerate, Hiki Hills, eastern Kanto Mountains. The Aoiwa Conglomerate is an unsorted breccia (maximum clast diameter up to ca. 3 m) composed of clasts of high-P/T metamorphic rocks (greenstones and crystalline schists), granitic rocks, low-P/T metamorphic rocks (mafic to felsic plutono-metamorphic rocks), and sedimentary rocks.The clasts of high-P/T metamorphic rocks were previously considered to have been derived from the Sanbagawa metamorphic rocks, which have been exposed nearby since the Miocene. However, schist clasts yield K-Ar phengite ages of 127.2-121.0 and 98.4-80.7 Ma, significantly older than ages obtained for the Sanbagawa metamorphic rocks in the Kanto Mountains, although the mineral assemblage and metamorphic grade of clasts are similar.Clasts of granitic rocks and low-P/T metamorphic rocks yield K-Ar hornblende ages of 131.5-114.0 Ma and phengite ages of 97.8-88.9 Ma, significantly older than ages obtained for Ryoke granites in the Kanto Mountains. In addition, a tonalite mylonite clast yields a lower 87Sr/86Sr initial ratio (0.70510-0.70520 or 0.70498-0.70505) than that of the Ryoke granites.Based on the results of K-Ar dating and a detailed petrologic study of the clasts, we conclude that the schist clasts were derived from an older unit within the Sanbagawa metamorphic rocks and that granitic and mafic metamorphic clasts were derived from the paleo-Ryoke terrane, which previously overlaid the Sanbagawa metamorphic rocks and today occurs only as sporadic allochthonous rocks. The Aoiwa Conglomerate was probably deposited in association with denudation of the paleo-Ryoke and uppermost Sanbagawa terranes. Deposition was accelerated during exhumation of Sanbagawa metamorphic rocks during the Middle Miocene.

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  • Application of GPS loggers in geological surveys

    Arai Hiroyoshi, Omori Soichi, Miyashita Atsushi

    Jour. Geol. Soc. Japan   115 ( 10 ) 552 - 557  2009  [Refereed]

    Authorship:Lead author, Corresponding author

     View Summary

    Geological information is of little value in the absence of location data regarding the site where the observation was made. Topographic maps have traditionally been used for this purpose; however, this role has now been taken over by GPS receivers. The past decade has seen the development of compact and inexpensive GPS receivers, the so-called GPS loggers, which sequentially record positional data every 1–15 seconds. Such data can be linked with, for example, image files taken by a digital camera, using common time-stamp data. The geographic coordinates (latitude and longitude) of the site where the image was taken are embedded within the image file as metadata (i.e., a geotag). This paper introduces a geotagging system designed for use with a GPS logger and digital camera, and examines the accuracy and precision of positioning by GPS logger, as well as its application in geological surveys.

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  • Clockwise 180 degrees rotation of slip direction in a superficial nappe pile emplaced upon a high-P/T type metamorphic terrane in central Japan

    Hiroyoshi Arai, Kenta Kobayashi, Hideo Takagi

    GONDWANA RESEARCH   13 ( 3 ) 319 - 330  2008.04  [Refereed]

    Authorship:Lead author, Corresponding author

     View Summary

    Understanding the exhumation process of deep-seated material within subduction zones is important in comprehending the tectonic evolution of active margins. The deformation and slip history of superficial nappe pile emplaced upon high-P/T type metamorphic rocks can reveal the intimate relationship between deformation and transitions in paleo-stress that most likely arose from changes in the direction of plate convergence and exhumation of the metamorphic terrane. The Kinshozan-Atokura nappe pile emplaced upon the high-P/T type Sanbagawa (=Sambagawa) metamorphic rocks is the remnant of a pre-existing terrane located between paired metamorphic terranes along the Median Tectonic Line (MTL) of central Japan. Intra- and inter-nappe structures record the state of paleo-stress during metamorphism and exhumation of the Sanbagawa terrane. The following tectonic evolution of the nappes is inferred from a combined structural analysis of the basal fault of the nappes and their internal structures. The relative slip direction along the hanging wall rotated clockwise by 180 degrees, from S to N, in association with a series of major tectonic changes from MTL-normal contraction to MTL-parallel strike-slip and finally MTL-normal extension. This clockwise rotation of the slip direction can be attributed to changes in the plate-induced regional stress state and associated exhumation of the deep-seated Sanbagawa terrane from the Late Cretaceous (Coniacian) to the Middle Miocene. (C) 2007 International Association for Gondwana Research. Published by Elsevier B.V All rights reserved.

    DOI

  • Statistical empirical index of chemical weathering in igneous rocks: A new tool for evaluating the degree of weathering

    Tohru Ohta, Hiroyoshi Arai

    CHEMICAL GEOLOGY   240 ( 3-4 ) 280 - 297  2007.06  [Refereed]

     View Summary

    Chemical weathering indices are useful tools in characterizing weathering profiles and determining the extent of weathering. However, the predictive performance of the conventional indices is critically dependent on the composition of the unweathered parent rock. To overcome this limitation, the present paper introduces an alternative statistical empirical index of chemical weathering that is extracted by the principal component analysis (PCA) of a large dataset derived from unweathered igneous rocks and their weathering profiles. The PCA analysis yields two principal components (PC1 and PC2), which capture 39.23% and 35.17% of total variability, respectively. The extent of weathering is reflected by variation along PC1, primarily due to the loss of Na2O and CaO during weathering. In contrast, PC2 is the direction along which the projections of unweathered felsic, intermediate and mafic igneous rocks appear to be best discriminated; therefore, PC1 and PC2 represent independent latent variables that correspond to the extent of weathering and the chemistry of the unweathered parent rock. Subsequently, PC1 and PC2 were then mapped onto a ternary diagram (MFW diagram). The M and F vertices characterize mafic and felsic rock source, respectively, while the W vertex identifies the degree of weathering of these sources, independent of the chemistry of the unweathered parent rock.
    The W index has a number of significant properties that are not found in conventional weathering indices. First, the W index is sensitive to chemical changes that occur during weathering because it is based on eight major oxides, whereas most conventional indices are defined by between two and four oxides. Second, the W index provides robust results even for highly weathered sesquioxide-rich samples. Third, the W index is applicable to a wide range of felsic, intermediate and mafic igneous rock types. Finally, the MFW diagram is expected to facilitate provenance analysis of sedimentary rocks by identifying their weathering trends and thereby enabling a backward estimate of the composition of the unweathered source rock. (C) 2007 Elsevier B.V. All rights reserved.

    DOI

  • Problems in compositional data analysis and their solutions

    Ohta Tohru, Arai Hiroyoshi

    Jour. Geol. Soc. Japan   112 ( 3 ) 173 - 187  2006  [Refereed]

     View Summary

    Compositional data, represented as percent or parts per million, are subject to the constant-sum constraint that precludes compositional data from much of statistical analysis. Despite this constraint, a theory for statistically rigorous treatment of compositional data is currently under intense development. This paper reviews the utility of two main procedures for compositional data analysis, which will be termed "logratio analysis" and "simplicial analysis". Logratio analysis is a way to map compositional data from a simplex space to a Euclidean real space by transforming compositional data into logarithms of component ratios. This bijectional mapping allows the transformed data to be analyzed by many traditional statistical methods available in real space. On the other hand, simplicial analysis introduces proper classes of parametric distribution, translation operation, scalar multiplication operation, identity unit and metric function within the simplex space. These definitions permit the simplex space to be reviewed as a metric space and compositional data as an Abelian group. Moreover, simplicial analysis provides statistical methodologies for compositional data, which are analogous to those for data sets associated with real space. A brief overview of the constant-sum constraint is followed by mathematical descriptions of logratio and simplicial analyses. Practical analyses of real data sets based on logratio and simplicial analyses are provided to illustrate their potential and to encourage their use.

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  • Computer program for assessing the immobile variables in compositional data, based on Woronow-Love-Schedl method

    Arai Hiroyoshi, Ohta Tohru

    Jour. Geol. Soc. Japan   112 ( 6 ) 430 - 435  2006  [Refereed]

    Authorship:Lead author, Corresponding author

     View Summary

    The Woronow-Love-Schedl method is a logratio-based statistical assessment for detecting immobile variables in compositional data. The method was designed in order to address the constant-sum constraint. This method is effective, but difficult to apply without special statistical software. A computer program to process the method for open source statistical environment 'R' was developed. This program enables a user to assess the immobile variables in given data set. Care must be taken, however, because the program just gives some statistical information about the candidates for immobile variables. Hence, additional geological evidence is necessary for a definite decision about immobility.

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  • Note on zero and missing values in compositional data

    Arai Hiroyoshi, Ohta Tohru

    Jour. Geol. Soc. Japan   112 ( 7 ) 439 - 451  2006  [Refereed]

    Authorship:Lead author, Corresponding author

     View Summary

    In the field of geology, compositional data, such as petrochemical compositions, faunal compositions and modal compositions of sandstones, are common. This type of data contains an awkward mathematical problem known as constant-sum constraint. To resolve this problem, logratio and simplicial analyses have been developed in the last two decades. However, zero and missing values are common in practical compositional data, which are troublesome for logratio or simplicial analysis because neither logarithm nor geometric mean can take zeros. In this context, many authors have suggested nonparametric replacement methods of zero and missing values to overcome this problem. We review these nonparametric methods, additive replacement and multiplicative replacement, with their merits and limitations, after showing types and nature of zeros: rounded zeros stemmed from a detection limit of apparatus and essential (or true) zeros designating nothing. Zero replacement, however, may create outliers of data vectors and would lead us to erroneous conclusions. For this reason, we also review how to assess the outlier: by atypicality indices of data vectors and by confidence regions of a population. To disseminate statistically rigorous replacement and outlier detection, computer programs for open source statistical environment 'R', which replace zeros in a given data set and calculate atypicality indices, were developed.

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  • Restoration of exotic terranes along the Median Tectonic Line, Japanese islands: Overview

    Hideo Takagi, Hiroyoshi Arai

    Gondwana Research   6 ( 4 ) 657 - 668  2003  [Refereed]

     View Summary

    This paper reviews recent progress on the geotectonic evolution of exotic Paleozoic terranes in Southwest Japan, namely the Paleo-Ryoke and Kurosegawa terranes. The Paleo-Ryoke Terrane is composed mainly of Permian granitic rocks with hornfels, mid-Cretaceous high-grade metamorphic rocks associated with granitic rocks, and Upper Cretaceous sedimentary cover. They form nappe structures on the Sambagawa metamorphic rocks. The Permian granitic rocks are correlative with granitic clasts in Permian conglomerates in the South Kitakami Terrane, whereas the mid-Cretaceous rocks are correlative with those in the Abukuma Terrane. This correlation suggests that the elements of Northeast Japan to the northeast of the Tanakura Tectonic Line were connected in between the paired metamorphic belt along the Median Tectonic Line, Southwest Japan. The Kurosegawa Terrane is composed of various Paleozoic rocks with serpentinite and occurs as disrupted bodies bounded by faults in the middle part of the Jurassic Chichibu Terrane accretionary complex. It is correlated with the South Kitakami Terrane in Northeast Japan. The constituents of both terranes are considered to have been originally distributed more closely and overlay the Jurassic accretionary terrane as nappes. The current sporadic occurrence of these terranes can possibly be attributed to the difference in erosion level and later stage depression or transtension along strike-slip faults. The constituents of both exotic terranes, especially the Ordovician granite in the Kurosegawa-South Kitakami Terrane and the Permian granite in the Paleo-Ryoke Terrane provide a significant key to reconstructing these exotic terranes by correlating them with Paleozoic granitoids in the eastern Asia continent.

    DOI

  • 関東山地の跡倉・金勝山ナップと中央構造線

    小林健太, 新井宏嘉

    日本地質学会第109年学術大会見学旅行案内書     87 - 108  2002  [Refereed]

  • Paleostress-field analysis by en-echelon veins in the Atokura Formation, Kanto Mountains, central Japan

    Arai Hiroyoshi

    Jour. Geol. Soc. Japan   108 ( 9 ) 575 - 590  2002  [Refereed]

     View Summary

    En-echelon veins hosted by sandstone and mudstone of the Atokura Formation were examined to clarify the paleostress field in that formation which constitutes the Atokura Nappe in a northern part of the Kanto Mountains. The veins are morphologically classified into two groups:1) a similar fold type with smoothly curved limbs, the vein tips pinch out and are not linked to any other fractures (type A) and, 2) a chevron fold type, the vein tips linked to joints formed before the vein opening (type B). The two types show a different texture and assemblage of infilling minerals. The type A consists mostly of fibrous to polygonal quartz and chlorite with lesser amounts of calcite and albite, whereas the type B of polygonal to prismatic calcite and quartz with lesser amounts of plagioclase and chlorite. Regardless of the vein type, morphology of the en-echelon sigmoidal veins is represented by a similar fold, but that of bridges is close to a parallel fold. The presence of undulatory extinction and subgrains in the fibrous quartz and pressure-solution cleavage in the bridges, which are considered to have simultaneously formed, indicates that the en-echelon veins were formed in a brittle-ductile shear zone. According to the paleostress analysis with conjugate sets of type-A vein arrays, the maximum (σ_1) principal stress axis is inferred to have been oriented in the NW-SE to NNE-SSW direction and horizontal, intermediate (σ_2) principal stress axis vertical, and minimum (σ_3) principal stress axis in the NE-SW to WNW-ESE direction and horizontal. The veining could have occurred during the formation of E-W trending open upright folds of the Upper Cretaceous Atokura Formation.

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  • Provenance of the Atokura Formation, Kanto Mountains, central Japan(Geotectonic evolution of the Paleo-Ryoke and Kurosegawa Terranes)

    Arai Hiroyoshi, Murakami Shinjiro, Takagi Hideo

    The memoirs of the Geological Society of Japan   ( 56 ) 123 - 136  2000  [Refereed]

    Authorship:Lead author, Corresponding author

     View Summary

    The Upper Cretaceous Atokura Formation constitutes the Atokura Nappe overlying the Mikabu Unit of the Sambagawa Belt. Framework mode of sandstones, modal composition of heavy minerals, and chemical composition of detrital garnets from the Atokura Formation were investigated. Detritus in the Atokura Formation are characterized by fragments of granitic rocks, hornfels, acidic to intermediate volcanic rocks, while those derived from rocks of accretionary complex such as chert, limestone, and greenstones are rather rare. Sandstone compositions plotted on a Qm-F-Lt diagram show dominant provenance types of the basement uplift, and subsidiary of dissected arc and transitional continental. Composition of heavy minerals is characterized by epidote, biotite, titanite, garnet, and muscovite. The chemistry of detrital garnets implies that low to intermediate P/T metamorphic rocks, plutonic rocks and calcareous metamorphic rocks were present in the provenance, while high P/T metamorphic rocks such as the Sambagawa metamorphic rocks was not exposed. Detrital high-Mg garnets whose source rocks have not been found in present Japanese Island are contained in sandstones, and might have been derived from Precambrian basement of the Asian Continent. Most of detritus in the Atokura Formation probably originated from Permian and mid-Cretaceous plutono-metamorphic complex of the Atokura and Kinshozan Nappes. Correlatives of the Lower Cretaceous in the Kitakami Mountains and the Siluro-Devonian in the Kurosegawa Belt are possible sources of acidic to intermediate volcanic clasts. The Paleo-Ryoke Terrane has been constructed of the source of these detritus.

    CiNii

  • Geotectonic development of the Atokura Nappe:Restoration of the overfold in the Shimonita area,Kanto Mountains

    Arai Hiroyoshi, Takagi Hideo

    Jour. Geol. Soc. Japan   104 ( 12 ) 861 - 876  1998  [Refereed]

    Authorship:Lead author, Corresponding author

    DOI CiNii

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Books and Other Publications

  • 日本の地質構造100選

    日本地質学会構造地質部会編( Part: Contributor)

    朝倉書店  2012 ISBN: 9784254162738

Research Projects

  • NA

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Encouragement of Scientists

    Project Year :

    2022.04
    -
    2023.03
     

  • NA

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Encouragement of Scientists

    Project Year :

    2021.04
    -
    2022.03
     

  • NA

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Encouragement of Scientists

    Project Year :

    2019
     
     
     

    ARAI Hiroyoshi

  • NA

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Encouragement of Scientists

    Project Year :

    2018
     
     
     

Presentations

  • 関東山地,跡倉ナップの内部構造−跡倉層の横臥褶曲−

    日本地質学会第103年学術大会 

  • 跡倉ナップの変形

    構造地質研究会1996冬の例会 

  • 関東山地,跡倉層の砂岩組成と地質構造

    日本地質学会第104年学術大会 

  • 九州−四国西部に認められる南部北上帯−阿武隈帯構成要素

    日本地質学会第104年学術大会 

  • 跡倉・金勝山ナップの構造発達史

    日本地質学会第105年学術大会 

  • Tectonic evolution of the Atokura Nappe, Kanto Mountains, central Japan.

    The first joint meeting of Japanese and Korean structure and tectonic research group 

  • 跡倉ナップに累重する金勝山ナップの運動像

    日本地質学会第107年学術大会 

  • Tectonic evolution of the Japanese Islands:Evidence from the Paleo-Ryoke and Kurosegawa Terranes.

    The third joint meeting of Japanese and Korean structure and tectonic research groups 

  • New model of the restoration of Paleo-Ryoke-Kurosegawa Terrane along the Median Tectonic Line, Japanese Islands.

  • 雁行脈の三次元形態

    日本地質学会第110年学術大会 

  • 棚倉破砕帯西縁断層のガウジ帯

    日本地質学会第110年学術大会 

  • 砕屑岩の変形からみた断層帯の規模評価

    日本地質学会第111年学術大会 

  • 関東山地北西部,内山断層に伴う堆積岩中の断層帯構造

    日本地質学会第111年学術大会 

  • 関東山地下仁田地域ヒスイ輝石岩体の地質構造と岩石学

    日本地質学会第111年学術大会 

  • ポイントカウント法におけるデータ処理の問題点と是正法

    日本地質学会第112年学術大会 

  • アイチソン幾何学に基づく砂岩モード組成のトレンド解析

    日本地質学会第112年学術大会 

  • 埼玉県比企丘陵周辺の中新統青岩礫岩中の変成岩およびマイロナイト礫のK-Ar年代とその意義

    日本地質学会第113年学術大会 

  • 白亜紀花崗岩に伴われる暗色貫入岩−徐冷型シュードタキライトの可能性−

    日本地質学会構造地質部会2006年度例会 

  • Statistical empirical index of chemical weathering: A new tool for evaluating the weathering intensity and paleoclimate.

    2nd International Symposium of the IGCP Project No. 507 

  • 領家花崗岩類に伴われる暗色貫入岩−徐冷型シュードタキライトの可能性−

    日本地質学会第114年学術大会 

  • 統計学的経験則に基づく岩石風化の指標開発ならびに古気候解析への応用

    日本地質学会第114年学術大会 

  • 関東山地三波川帯の年代学から見た日本地質構造発達史

    日本地球惑星科学連合2009年大会 

  • 鉱物化学組成の統計学的分類:ランダムフォレスト法による鉱物相の同定

    日本地球惑星科学連合2010年大会 

  • ランダムフォレストによる統計学的鉱物同定法:解析条件の最適化

    日本地質学会第117年学術大会 

  • 関東山地三波川帯のユニット境界構造と年代値:埼玉県長瀞町本野上露頭の解析

    日本地質学会第119年学術大会 

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Specific Research

  • フィールドワークを基軸とした自然環境教育の教材開発とその実践

    2020  

     View Summary

     本研究は,自然現象を観察・測定・記録し,自然現象のしくみを読み解く能力を養うための効果的な教材開発と実践を目的として行った.この目的を達成するため,研究者勤務地のキャンパスに広がる雑木林と丘陵の環境を活用した自然環境教育の教材を開発し,担当する選択授業において実践した.具体的には,スケッチの描き方,双眼鏡の使い方と野鳥観察,地図投影法,地形断面図の作成,ルートマップ作成,地形図読図の実地訓練,水準測量実習とデータ処理,どんぐりの形状計測と統計処理などである.これらの教材を実践した結果,授業開始当初と年度末とで生徒のスケッチ技術,計測技術,考察力に大きな進歩が見られた.

  • キャンパスの自然環境を活用した気象環境調査の教材化

    2020  

     View Summary

     本研究は,早稲田大学本庄キャンパスにおける気温・湿度の測定を通して自然観測の方法とデータ解析方法を学習する教材を開発し,その実践のため本庄高等学院の卒論テーマとして高校生1名を指導しながら遂行した.気温・湿度の観測にはデータロガーを用い,ラジエーションシールドはプラスチック製の植木鉢皿で自作した.観測点は針葉樹林,広葉樹林,グラウンド等を選定し,10月中旬〜11月上旬にかけて観測した.観測の結果,林地がクールアイランドとして機能し,そこから冷気のにじみ出し現象が起こっていることが推察された.今後も継続して観測することで,クールアイランド効果をより明確に示すデータが得られるものと期待される.

  • キャンパスの自然環境を活用した気象環境調査の教材化

    2019  

     View Summary

     本研究は,最近低価格化が進んでいる温湿度データロガーを多数用いて本庄キャンパスの環境データ(気温・湿度)を観測し,その結果を用いて等値線マップを作成する教材開発を目的として実施した.まず,比較的低価格で入手しやすい2機種について,その性能差を検証して本研究の目的に合ったデータロガーを選定した.また,導入した同一機種(12台)を等しい環境下で作動させて器差を測定した.センサーを日射や風雨から守るためのラジエーションシールドは,ホームセンターで入手できる材料を用いて自作し,シールドが測定値に与える影響,耐久性について検証中である.

  • 三波川変成岩のユニット境界に見られる変形構造の解析とその教材化

    2017  

     View Summary

    昨年度からの継続・発展研究課題として,埼玉県長瀞町本野上の露頭における三波川変成岩類の変形構造解析を行い,露頭図への情報追加,露頭スケール変形構造の記録,変形岩の研磨標本および定方位薄片の作製を実施した.今年度は岩石変形構造の教材化により重きをおき,露頭スケールの構造から薄片スケールの構造に至るまで,変形構造が観察スケールによってどのように変化して見えるのかを高校生向けに解説した掲示パネルの制作も試みた.これらの成果は次年度の選択地学授業での教材として使用する予定である.

  • 三波川変成岩のユニット境界に見られる変形構造の解析

    2016  

     View Summary

    三波川変成岩の上昇過程を解明する手がかりとして,埼玉県長瀞町本野上において詳細な変形構造解析を行った.本野上露頭では,変成度の異なる岩体が断層で接するユニット境界が認められ,この断層に沿ってカタクレーサイト帯が発達している.ユニット境界の変形構造に加え,ユニット内部の延性変形も合わせて構造解析を行い,ユニットの接合前,接合時,接合後の変形がほぼ一定の応力場で形成されたことがわかった.本野上露頭の片理面およびユニット境界面はアンチフォームを形成しているため,地質構造の観察や地質図学の実習の場として適している.この教材化の目的のため,露頭の詳細な構造マップも作成した.

  • ランダムフォレスト法による鉱物化学組成の解析

    2014  

     View Summary

    鉱物化学組成から統計学的に鉱物相を判別することを試みた.化学組成データはDeer et al.のRock-forming mineralsシリーズから鉱物85族3763個の分析値を入力した.判別には機械学習の一種であるランダムフォレスト法を採用し,SiO2,TiO2など42成分の重量%値と合計値を用いた.解析の結果,判別に大きく寄与する変量はSiO2,ZrO2,TiO2,Al2O3,FeO,MnO,MgO,CaO,Na2O,K2O,P2O5などの主要成分であった.これら成分に限定して判別した場合の誤判別率は約5%である.本研究により,鉱物相は化学組成だけで十分判別できることが確認された.

  • 雁行脈の三次元的形態の解明

    2003  

     View Summary

     関東山地北縁部,上部白亜系跡倉層のタービダイトに発達する雁行脈の形態を三次元的に解析した.その結果,1つの鉱物脈(主脈)から雁行脈へと移り変わる形態が明らかになった.このような形態は断層や節理においてしばしば観察されるが,これまで考えられていたような主断裂から雁行配列する断裂群へとその回転角が徐々に増加するようなものではなく,主脈と雁行脈との漸移部で雁行脈の回転角が最大となることが明らかになった.このような産状はこれまで報告されていなかった.この形態は,母岩の岩相に強く依存し,砂岩泥岩互層の砂岩部では単一の脈,泥岩部では雁行脈が発達する.すなわち,脈の形態は岩相の違いによるコンピテンシーに依存していることになる.また,単一脈はほとんど方解石で形成されるのに対し,雁行脈は方解石のほか石英および緑泥石を多く含む.脈面積は単一脈ではほぼ一定であるのに対し,雁行脈では層理面に近づくにつれ徐々にその面積が減少する.個々の雁行脈の回転角から求めた剪断歪も,層理面に近づくにつれて減少する.雁行脈部での脈面積および剪断歪の減少,ブリッジ中の劈開の発達,脈構成鉱物中の石英および緑泥石の増加などから考えると,単一脈部と雁行脈部とでは歪の解消様式が異なっていたことが推察される.すなわち,単一脈部ではより脆性的な変形により,ほぼ脈に沿った変位のみで歪を解消したのに対し,雁行脈部ではより延性的な変形により,母岩中の石英などの圧力溶解による劈開形成および雁行脈の回転・成長によって歪を解消したものと考えられる.さらに,石英や方解石の脈鉱物に,結晶塑性変形による微細構造が観察されることから,これらの脈が脆性-延性遷移領域における剪断帯で形成されたものであると結論できる.

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Committee Memberships

  • 2016.05
    -
    2018.05

    一般社団法人日本地質学会  代議員(全国区)