掲載種別：研究論文（学術雑誌）  

DOI： 10.2138/am-2020-7284

DOI： 10.5026/jgeography.128.747

CiNii Article

掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s00531-019-01749-z

掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/ter.12355

掲載種別：研究論文（学術雑誌）  

Spatial growth patterns are natural recording media (NRMs) that preserve important historical information, which can be accessed and analyzed to reconstruct past environmental conditions and events. Here, we propose the Bayesian inversion method, which can reconstruct the evolution of target parameters from purely spatial data by extending data assimilation (DA), a method for integrating numerical simulations with time-series observations. Our method converts discrete spatial observation data to time-series data with the help of a law representing the NRM's time-evolution dynamics and Gaussian process regression, enabling us to directly compare the observations with a numerical simulation based on the DA framework. The method's effectiveness is demonstrated using a synthetic inversion problem, namely reconstructing the pressure-temperature-time (P-T-t) path of a metamorphic rock from chemical composition profiles of its zoned minerals. The proposed method is broadly applicable to a wide variety of NRMs.

DOI： 10.1103/PhysRevE.98.043311

掲載種別：研究論文（学術雑誌）  

<p>断層の内部構造に関し，この25年間における主として日本地質学会員の成果を中心にまとめた．脆性断層の研究において，野島断層掘削をきっかけに内部構造のみならず，断層の水理学的性質や摩擦の研究がさかんに行われ，断層研究における大きな転機となった．より深い脆性領域の断層岩内では圧力溶解クリープと，雲母類の塑性変形が報告され，そのダメージは結晶内歪を周囲の岩石に与えることなどが明らかになった．また脆性–塑性遷移領域に対しては応力や歪速度の条件を地質学的の評価しようとする試みが行われ，破壊開始過程や変形の空間的不均質が明らかにされている．さらに下部地殻では斜長石や輝石の転位クリープの一方で，変形中の細粒物質の生成による変形機構遷移の重要性が指摘されている．近年，下部地殻における破壊現象の痕跡が見つかっており，地震による応力集中が一つの可能性として考えられている．その理解には今後の研究が期待される．</p>

DOI： 10.5575/geosoc.2018.0004

CiNii Article

掲載種別：研究論文（学術雑誌）  

Devolatilization reactions during prograde metamorphism are a key control on the fluid distribution within subduction zones. Garnets in Mn-rich quartz schist within the Sanbagawa metamorphic belt of Japan are characterized by skeletal structures containing abundant quartz inclusions. Each quartz inclusion was angular-shaped, and showed random crystallographic orientations, suggesting that these quartz inclusions were trapped via grain boundary cracking during garnet growth. Such skeletal garnet within the quartz schist formed related to decarbonation reactions with a positive total volume change (Delta V-t > 0), whereas the euhedral garnet within the pelitic schists formed as a result of dehydration reaction with negative Delta V-t values. Coupled hydrological-chemical-mechanical processes during metamorphic devolatilization reactions were investigated by a distinct element method (DEM) numerical simulation on a foliated rock that contained reactive minerals and non-reactive matrix minerals. Negative Delta V-t reactions cause a decrease in fluid pressure and do not produce fractures within the matrix. In contrast, a fluid pressure increase positive Delta V-t reactions results in hydrofracturing of the matrix. This fracturing preferentially occurs along grain boundaries and causes episodic fluid pulses associated with the development of the fracture network. The precipitation of garnet within grain boundary fractures could explain the formation of the skeletal garnet. Our DEM model also suggests a strong influence of reaction-induced fracturing on anisotropic fluid flow, meaning that dominant fluid flow directions could easily change in response to changes in stress configuration and the magnitude of differential stress during prograde metamorphism within a subduction zone.

DOI： 10.1007/s00410-017-1393-6

掲載種別：研究論文（学術雑誌）  

To understand rheological weakening in the lower continental crust, we studied mylonites in the Paleoproterozoic Eidsfjord anorthosite, northern Norway. The zones of anorthositic mylonites range from a few millimeters to several meters thick, and include ultramylonites and protomylonites. They contain syn-kinematic metamorphic minerals, including Cl-bearing amphibole and scapolite. Thermodynamic analysis reveals that syn-deformational hydration reactions occurred at -600 degrees C and -700 MPa under CO2-bearing conditions. The protomylonites contain many fragmented plagioclase porphyroclasts. The fractures in porphyroclasts are filled with fine-grained plagioclase, suggesting that fracturing is a common mechanism of grain size reduction. The anorthite contents of fine-grained polygonal matrix plagioclase are different from those of porphyroclastic plagioclase, suggesting that the matrix grains nucleated and grew during syn-kinematic metamorphism. Plagioclase aggregates in the matrices of mylonites do not exhibit a distinct crystallographic preferred orientation, which implies that the dominant deformation mechanism was grain-size-sensitive creep. Consequently, in the lower crustal anorthositic mylonites, grain size reduction occurred via fracturing, rather than through dynamic. recrystallization, leading to grain-size-sensitive creep. The syn-kinematic recrystallization of minor phases at plagioclase grain boundaries may suppress the growth of plagioclase and contribute to the development of grain-size-sensitive creep. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jsg.2016.11.001

掲載種別：研究論文（学術雑誌）  

To clarify the processes that occur in hydrous basaltic magma chambers, we have undertaken detailed petrological and geochemical analyses of mafic and intermediate rocks from the Ikoma gabbroic complex, southwest Japan. The complex consists mainly of hornblende gabbros, hornblende gabbronorites, and hornblende leucogabbros. The hornblende leucogabbros are characterized by low TiO2 and high CaO contents, whereas the hornblende gabbronorites have high TiO2 and low CaO contents. The initial Sr-87/Sr-86 ratios (Sr-I) of the hornblende gabbronorites and hornblende gabbros are higher than those of the hornblende leucogabbros and plagioclase, and they may have resulted from a higher degree of assimilation of metasediments. The geochemical features of the hornblende leucogabbros and hornblende gabbronorites can be explained by accumulation of plagioclase and ilmenite, respectively, in a hybrid magma that formed by chemical interaction between mafic magma and metasediment, whereas the hornblende gabbros were produced by a high degree of crustal assimilation and fractional crystallization of this hybrid magma. As a result of the density differences between crystals and melt, the Ikoma gabbroic rocks formed by the accumulation of plagioclase in the middle of the magma chamber and by the accumulation of ilmenite in the bottom of the chamber. Taking into account the subsequent assimilation and fractional crystallization, our observations suggest an enriched mantle (Sr-I = similar to 0.7071) as the source material for the Ikoma gabbros.

DOI： 10.1007/s00710-016-0423-9

掲載種別：研究論文（学術雑誌）  

生駒断層帯において，白亜紀花崗岩類中に発達する露頭規模の断層群に対する構造地質学的解析を行った．断層群のスリップデータに基づく多重逆解法により求められた古応力場は，南北引張の正断層型であった．また，断層コアのガウジから分離したイライトのK-Ar年代は，45.2±1.0Ma（粒径0.2-0.4µm）および46.0±1.1Ma（粒径0.4-1.0µm）となった．各粒径区画におけるK-Ar年代値や低温イライトの含有率に有意な差が認められなかったため，母岩の黒雲母K-Ar年代を用いて砕屑性高温イライトの影響を考慮した結果，断層コア形成およびその後の熱水変質による年代として～45-30Maを得た．これらの結果は，生駒断層帯における白亜紀花崗岩類中に発達する露頭規模の断層群の形成が始新世後期〜漸新世前期の伸長テクトニクスに関連したものであることを示唆する．

DOI： 10.5575/geosoc.2015.0039

CiNii Article

掲載種別：研究論文（学術雑誌）  

We report newly obtained U-Pb SHRIMP ages of detrital zircons from metagreywackes in the Hiriyur Formation (Chitradurga Group, Dharwar Supergroup) from the central eastern part of the Chitradurga greenstone belt. U-Pb analyses yield three major Neoarchean age populations ranging from 2.70-2.54 Ga with some minor age population of Mesoarchean. The maximum age of deposition is constrained by the youngest detrital zircon population at 2546 Ma. This is the first report of the occurrence of supracrustal rocks less than 2.58 Ga in the central part of Chitradurga greenstone belt. Close evaluation of detrital ages with the published ages of surrounding igneous rocks suggest that the youngest detrital zircons might be derived from rocks of the Eastern Dharwar craton and the inferred docking of the western and eastern Dharwar cratons happened prior to the deposition of the Hiriyur Formation. The Chitradurga shear zone, dividing the Dharwar craton into western and eastern blocks, probably developed after the deposition. Furthermore, the lower intercept is interpreted as evidence for the Pan-African overprints in the study area.

DOI： 10.1007/s12594-016-0372-2

掲載種別：研究論文（学術雑誌）  

本論では,大阪層群に挟まるテフラ層のSEM-EDS分析による火山ガラスの主成分元素組成,および大阪層群と琵琶湖高島沖コア試料に挟まるテフラ層のICP-AES分析による火山ガラスの微量成分元素組成を明らかにした.本論では,火山ガラスの形状・重鉱物組成・粒子組成の組み合わせからテフラタイプを区分し,それと主成分元素組成から近畿地方に降下・堆積したテフラを5つのグループ,1)アルカリ岩質テフラグループ,2)高カリウムテフラグループ,3)中間カリウムテフラグループ,4)低カリウムテフラグループ,5)高シリカ・扁平型火山ガラステフラグループに区分した.また,Y-Sr/Y図,La/Y-Fe/(Fe+Mg)mol%図,MgO-Ba図を用いて,それらの微量成分元素組成における特徴を明らかにした.本論で対象としたテフラ層のうち給源が既知のテフラ層は,これまで指摘されていた伊豆・箱根地域,東北地域,山陰地域,中部九州と南部九州を給源とするテフラ層の岩石化学的特徴と整合的である.さらに本論において明らかになったアダカイト質テフラおよび低カリウムテフラグループの堆積時期は,それぞれ山陰地域の火山,伊豆・箱根地域の火山の爆発的噴火活動と対応する.

CiNii Article

掲載種別：研究論文（学術雑誌）  

The mechanism of shear zone formation in lower crustal, relatively dry rocks is still poorly understood. We have studied the high-temperature deformation of the Hasvik gabbro (northern Norway) which commences by fracturing. The 10-20 mu m wide fractures show little displacement. The fine-grained plagioclase and orthopyroxene in the fractures lack a crystallographic preferred orientation (CPO) or a systematic crystallographic orientation with respect to the host grains. Fractures grade into narrow shear zones, which are composed of fine (10-20 mu m), equant grains of recrystallized plagioclase, amphibole, and pyroxene. Recrystallized plagioclase and pyroxene have compositions different from the magmatic grains, suggesting that they have formed by nucleation and growth. Based on conventional plagioclase-amphibole thermobarometry, the shear zones have formed at temperatures and pressures of 700-750 degrees C and 0.5-0.6GPa. The observed primary minerals cut by fractures suggest high-temperature fracturing in the absence of high pore pressures, which implies a high strength of the lower crustal gabbros and high stresses at fracturing. The shear zones are characterized by the lack of CPO and a small grain size, suggesting that the mechanism of deformation of the fine-grained plagioclase and orthopyroxene has been grain boundary sliding accommodated by diffusive mass transfer. The amphibole grains have strong CPOs, which most likely result from oriented growth and/or rigid body rotations during deformation. The process that initiated the fracturing and subsequent viscous creep in the Hasvik gabbro may have resulted from a process of coseismic loading followed by creep during decaying stress in the lower crust.

DOI： 10.1002/2014JB011708

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

The chemical compositions of fly ash particles emitted in Northeast Asia were studied to better understand the long-range transportation of atmospheric pollutants. We examined the compositions of spheroidal carbonaceous particles (SCPs), a type of fly ash from several to similar to 20 mu m in diameter found in surface sediments in or near the main industrial cities of Japan, China, South Korea, and Taiwan. SCPs from different countries were found to vary; SCPs from Japan and South Korea were characterized by low Ti/Si and high S/Si ratios, whereas SCPs in China exhibited high Ti/Si and low S/Si ratios and particles from Taiwan showed high Ti/Si and S/Si ratios. We also examined the SCPs found in remote islands in the Sea of Japan, at least 100 km from any industrial city. On the basis of their chemical compositions, these SCPs were classified as Japan and Korea, China, and Taiwan types using discriminant analysis. The results indicated that 30-50% of the particles found in these islands were assigned to the China type, suggesting that most of these SCPs were probably transported from Chinese industrial regions to these islands. It implies that even large particulate pollutants of similar to 10 mu m, such as SCPs, could be transported long distances of similar to 1000 km. (C) 2014 The Authors. Published by Elsevier Ltd.

DOI： 10.1016/j.atmosenv.2014.06.048

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

球状炭化粒子（SCPs）は，産業活動での化石燃料燃焼によって発生するフライアッシュ粒子の一つである．球状炭化粒子は，主に炭素からなり，そのため長期にわたって堆積物中に保存される．それゆえ堆積物中の球状炭化粒子は，環境汚染の程度や歴史を明らかにするために用いられる．球状炭化粒子は，空間的および時間的な大気汚染，あるいは堆積物コアの年代指標として用いられ，さらには越境汚染の評価（例えば，非工業地域で検出される汚染物質の発生源の特定）に用いることができる．堆積物中の球状炭化粒子含有量および形態，粒径，化学組成などの各特徴は，過去および現在における大気汚染に関する有用な情報を提供する．本総説では，その分析法と活用法について，特に過去約10年間の日本での研究成果を中心に概説する．

DOI： 10.5575/geosoc.2014.0035

CiNii Article

掲載種別：研究論文（学術雑誌）  

We report here on a study of three deformed granitoids: two mylonites and an ultramylonite from the inner ductile shear zone of the Ryoke metamorphic belt, SW Japan. Monophase layers composed of quartz, plagioclase or K-feldspar are present in all samples. The plagioclase-rich layers consist of grains 6-10 mu m in size, and sometimes include patchy K-feldspar and quartz, indicating solution-precipitation. In the mylonite, the fine-grained plagioclase is mainly An(23-25) and, the composition of plagioclase porphyroclast is An(21-39) without any significant maximum. The An compositions together with textural observations indicate that fine-grained plagioclase nucleated from solution with mass transfer during deformation. In the ultramylonite, fine-grained plagioclase is widely changed to be An(15-37), indicating that the grain-size-reduction process includes fracturing of original plagioclase porphyroclasts in addition to the solution-precipitation process, which results in the composition concentrated around An(30). In all samples, the crystallographic orientations of fine-grained plagioclases are almost random and do not correlate with neighbouring porphyroclasts. Grain-size-sensitive creep occurred during rock deformation subsequent to the process of solution-precipitation that involved mass transfer via fluids. (c) 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jsg.2013.03.006

掲載種別：研究論文（学術雑誌）  

To clarify the relationship between the transport distance of spheroidal carbonaceous particles (SCPs) and particle size, we investigated the spatial distribution of SCP sizes in swimming pool deposits in the central Osaka Plain, central Japan. Median particle size of SCPs generally decreases with distance (0 to similar to 20 km) downwind from the local coastal industrial area where SCP sources are distributed widely. This suggests that most SCPs found in the study area are derived from the industrial area. Samples with &gt;40 % of particles &gt;20 mu m were predominantly collected within 2 km of the industrial area, while samples with &gt;40 % of particles &lt;10 mu m were mostly collected over 10 km from the industrial area. Based on the results of our study and previous studies, we conclude that a higher proportion of particles of size &gt;20 mu m indicates that the origin of SCPs is within a few kilometres upwind of the sample site, whereas the presence of higher proportion of particles &lt;10 mu m indicates that their source is generally further than 10 km upwind. However, other factors may affect the size distribution of SCPs at a given location (e. g. fuel type, quality of the particle precipitator and topography of the terrain). Pool deposits provide more suitable samples than lake sediments for investigating atmospheric precipitation.

DOI： 10.1007/s11270-013-1580-7

掲載種別：研究論文（学術雑誌）  

We evaluate a temperature-dependent coefficient for grain-boundary diffusion in quartz aggregates using grain size data from a contact aureole, based on the coupling of a numerical model for the temperature-time history of the contact aureole with a model for the kinetics of diffusion-controlled grain growth. The metachert samples were collected from the contact aureole of the Hanase-Bessho quartz diorite at Hanase Pass, Kyoto, Japan. The quartz grain sizes vary systematically with distance from the quartz diorite. We calculated the temperature-time history using a one-dimensional thermal model, validated by peak metamorphic temperature estimates that are based on the degree of graphitization of carbonaceous material in metapelites, as characterized by Raman microspectroscopy. To minimize the sum of the squares of the errors between the measured and calculated grain sizes, based on the normal grain growth law together with the temperature-time history, we estimated the activation energy and pre-exponential factor in the alpha-quartz field to be 208 kJ/mol and 1.1 x 10(-8) m(2)/s, respectively, assuming a grain-boundary width of 1 nm. The grain-boundary diffusion rates for temperatures in the greenschist and amphibolite facies are similar to those determined in natural or laboratory grain-coarsening experiments, but differ significantly from those determined in tracer diffusion experiments. During grain-size-sensitive deformation, "effective" grain-boundary diffusion rates may be intermediate between the rates of diffusion along and across the grain boundary, and would be higher than the grain-boundary diffusion rates estimated by grain-coarsening experiments, and lower than those by tracer diffusion experiments.

DOI： 10.2138/am.2013.4308

掲載種別：研究論文（学術雑誌）  

Spheroidal carbonaceous particles (SCPs) are produced by the high-temperature combustion of fossil fuels and are emitted to the atmosphere. We examined the surface morphology and the chemical composition of SCPs in samples of surface sediment from five industrial cities each of Japan and China, using scanning electron microscopy with energy dispersive spectroscopy (EDS). There exists a relationship between surface morphology and the chemical composition of SCPs in China, but not for SCPs in Japan. The chemical compositions of SCPs differ between Japan and China: those in Japan are S-rich, whereas those in China are Ti-rich. The results suggest that EDS can be used to identify China-derived SCPs in East Asian countries such as Japan, South Korea, and Taiwan.

DOI： 10.1007/s11270-012-1232-3

掲載種別：研究論文（学術雑誌）  

The electrical conductivity of fluid-bearing quartzite was determined as function of temperature and fluid fraction at 1 GPa in order to assess the origin of the high conductivity anomalies observed in the middle to lower crustal levels. Dihedral angles of quartz-fluid-quartz determined from recovered samples were below 60, suggesting that fluid forms an interconnected network through the quartz aggregate. The electrical conductivity of quartzite increases with increasing temperature, which can be approximately expressed by Arrhenius equation. The apparent activation enthalpy decreases from 0.70 to 0.25 eV with increasing fluid fraction in volume from 0.00043 to 0.32. The electrical conductivity (sigma) of the fluid-bearing quartzite increased with fluid fraction (phi) proportionally to a power law (sigma proportional to phi(0.56-0.71)) within the temperature range of 900-1000K. The electrical conductivity of the aqueous fluid-bearing quartzite with the maximum fluid fraction (0.32) was found to be about three orders of magnitude higher than that of dry quartzite at 1000 K. However, its electrical conductivity was definitely lower than the geophysically observed values of high-conductivity anomalies, even if the quartzite contained large fluid fractions (0.32). The present results suggest that fluid-bearing quartzite is unable to account for the high-conductivity anomalies in terms of fluid fraction. A significant amount of other ionic species, such as Na, Cl, and Al in aqueous fluid, in addition to silica phases dissolved in fluid, is required to increase conductivity. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.pepi.2012.03.007

掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.tecto.2012.01.033

掲載種別：研究論文（学術雑誌）  

Microstructural analyses of mylonites next to the Median Tectonic Line (MTL), SW Japan, reveal a transition in the dominant deformation mechanism of quartz from grain-size-insensitive dislocation creep to grain-size-sensitive grain-boundary sliding (GBS). The transition occurred under greenschist-facies conditions (similar to 300-400 degrees C) during grain-size reduction by dynamic recrystallization. The stereologically corrected grain size for the transition is approximately 4.3 mu m. At the boundary between the fields of dislocation creep and GBS, as calculated from creep constitutive relations, the differential stress and strain rate for this corrected grain size are estimated to be similar to 280 MPa and 1.2 x 10(-11) s(-1) for 300 degrees C, and similar to 110 MPa and 1.0 x 10(-10) s(-1) for 400 degrees C. The strain rates estimated for the mylonites next to the MTL are much higher than those estimated for the surrounding metamorphic rocks (similar to 10(-14) s(-1)), and the displacement rates calculated based on the thickness of high-strain mylonites and their strain rates are comparable with the average slip rates of the most active intraplate faults in Japan. These inferences suggest that the high-strain mylonite zones next to the MTL are the exhumed downward extension of a seismogenic fault in the ductile region. The zones were highly localized (&lt;10 m) and experienced very high strain rates (10(-11) to 10(-10) s(-1)).

DOI： 10.1029/2011JB008799

掲載種別：研究論文（学術雑誌）  

Three basic minerals, biotite, chlorite and amphibole, were mineralogically and chemically examined to specify primary host phase(s) of As in the aquifer sediments and verify the formation mechanism of As contaminated groundwater of Sonareaon, Bangladesh, where the highest As contaminated groundwater appears in actively recharging zones. Among those minerals, only the chlorite included As by mu-XRF analysis. Fe-rich and tritoctahedral nature indicated this chlorite termed chatnosite. The chlorite was weathered to form eoethite on the cleavage, however, the eoethite did not host the As. Combining with the saturation of goethite in the groundwater (Itai et al., 2008), in situ chemical weathering of the chlorite promoted by accelerated aerobic water infiltration is suggested to be the first stage of formation of the As contaminated groundwater of the Holocene aquifer. This study implies the importance of aerobic aquifer condition to promote the As release via decomposition of As-bearing detrital mineral(s) as the formation mechanism of As contaminated groundwater in the Ganges-Bramaptra-Meghna river basin.

DOI： 10.2343/geochemj.2.0208

掲載種別：研究論文（学術雑誌）  

Spheroidal carbonaceous particles (SCPs) are produced by the high-temperature combustion of fossil fuels and emitted in to the atmosphere. The distribution and concentration of SCPs in sediments have been used as a proxy for the distribution of pollutants emitted to the atmosphere. However, the effect on the distribution of SCPs due to industrial activity at nearby industrial cities is yet to be quantified. To clarify the origin of SCPs of similar to 20 mu m in size that are preserved in sediments, we evaluated the abundance, surface morphology, and chemical composition of SCPs in sediment core samples recovered from industrial cities in Japan (Tokyo, Osaka, and Nagasaki) and China (Beijing), with the cities being located at least similar to 500 km away from each other. Vertical profiles of SCP concentration in sediment cores from the Japanese cities and Beijing are different, reflecting the contrasting industrial histories of the two countries. The SCPs from different cities show contrasting morphological and chemical characteristics, suggesting that similar to 20 mu m SCPs in sediments from the industrial cities could represent the local combustion history in detail, as the influx of local SCPs is dominant at such sites.

DOI： 10.1007/s12665-011-0907-1

掲載種別：研究論文（学術雑誌）  

 In the Ryoke belt formed at the eastern margin of East Asia during mid-Creataceous time, the most important geological record is that of felsic igneous activity, which may have been caused by the subduction of a young (hot) oceanic lithosphere. The mantle-derived arc magmas formed due to subduction of the hot lithosphere underplated the lower crust. Continuous underplating of the mantle-derived magmas resulted in partial melting of the lower crustal mafic to intermediate rocks to produce granite magmas. The granite magmas rose and were emplaced at a mid-crustal depth. They caused thermal perturbation around rocks of the Jurassic accretionary complex (Mino–Tamba belt) and formed the resultant low-pressure/high-temperature regional contact metamorphism (Ryoke metamorphism). At the time of Ryoke metamorphism, during subduction of a hot oceanic lithosphere with high obliquity, a low-angle detachment fault formed at the forearc region of the mid-Cretaceous SW Japan arc. Following this event, subduction of an inactive oceanic ridge or a very hot oceanic lithosphere with low obliquity occurred; a compressional stress regime occurred at the forearc region, forming granite mylonites and large-scale upright folds associated with crustal displacement along the detachment fault. After this event, the angle of subduction decreased gradually; the location of the felsic igneous activity moved toward the continent.

DOI： 10.5026/jgeography.120.452

CiNii Article

掲載種別：研究論文（学術雑誌）  

To identify the dominant deformation mechanism in continental middle crust at an arc-trench system, we used an SEM-EBSD system to measure the lattice-preferred orientations of quartz grains in fine-grained metachert from the low-grade (chlorite and chlorite-biotite zones) part of the low-P/high-T Ryoke metamorphic belt, SW Japan. Quartz c-axis fabrics show no distinct patterns related to dislocation creep, although the strain magnitudes estimated based on deformed radiolarian fossils are high enough that a distinct fabric might be expected to have formed during deformation. Fabric intensities are very low, indicating a random distribution of quartz c-axes. Quartz grains are equant in shape and polygonal, and free of intracrystalline plasticity. These observations suggest that the dominant deformation mechanism in the metacherts was grain-size-sensitive flow (diffusion creep accompanied by grain-boundary sliding) rather than dislocation creep, possibly reflecting the relatively low strain rate or low flow stress compared with that in high-strain zones. The development of grain-size-sensitive flow in metamorphic tectonites at mid-crustal conditions would result in a significant decrease of the rocks strength of the continental middle crust. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tecto.2010.06.002

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

Spheroidal carbonaceous particles (SCPs) are produced by the high-temperature combustion of fossil fuels and are emitted to the atmosphere. Previous studies are divided regarding whether SCPs derived from the combustion of various fossil fuels can be identified based on their surface morphologies and chemical compositions. In this study, we examined the surface morphology and chemical composition of SCPs in sediment core samples collected from Osaka Bay, Japan, with the aim of evaluating the usefulness of SCPs morphology in identifying their origin. Scanning electron microscope (SEM) observations reveal three distinct surface morphologies: (1) smooth, (2) rough and irregular, and (3) convoluted and layered. According to a morphological classification scheme proposed previously, the former two morphologies correspond to coal-derived carbon particles, whereas the latter corresponds to oil-derived carbon particles. In terms of the chemical compositions of the particles with different morphologies, as analyzed by energy-dispersive spectroscopy, linear discriminant analysis reveals that the two fuel types can be distinguished. An overall success rate of &gt;90% of reference of morphologically classified material correctly assigned to two groups that are chemically different each other, indicating a relationship between surface morphology and chemical composition. This result suggests that morphological characterization based on conventional SEM observations is useful in identifying the source fuel of SCPs.

DOI： 10.1007/s12665-009-0154-x

掲載種別：研究論文（学術雑誌）  

The strain geometry of a Cretaceous low-P/high-T metamorphosed accretionary complex in SW Japan is one of the key geological constraints in understanding the Cretaceous tectonics of the forearc region at the eastern margin of Eurasia. We studied the strain geometry of upper greenschist to lower amphibolite facies metamorphic rocks from the mid-Cretaceous low-P/high-T Ryoke metamorphic belt, which during the mid-Cretaceous were located at mid-crustal depths close to the volcanic front. Strain analysis focused on deformed radiolarian fossils in metachert and sandstone/chert clasts within metapelite. The maximum stretching direction (X-direction) of the strain ellipsoid of the schistosity-forming deformation at the peak metamorphism is oriented E-W, and the XY-plane of the strain ellipsoid developed parallel to schistosity. The metachert and metapelite exhibit plane strain to general flattening strain that probably largely resulted from the schistosity-forming deformation. Based on the results of the previous strain analyses and this study, it reveals that the schistosity-forming deformation occurred under bedding-normal shortening, resulting in general flattening strain throughout the Ryoke metamorphic belt. The X-direction of the strain ellipsoid of the schistosity-forming deformation is oriented parallel to the length of the Ryoke metamorphic belt throughout the SW Japan arc. The schistosity formed parallel to bedding planes that developed horizontally in non-metamorphosed accretionary complexes of SW Japan, indicating horizontal XY-plane of the strain ellipsoid. These observations indicate the occurrence of horizontal shear deformation within the middle crust (similar to 15 km depth) at the time of the low-P/high-T metamorphism. The deep-seated horizontal shear zone and the shallower incipient Median Tectonic Line (MTL) fault system could result in a crustal-scale detachment fault in the forearc region of the mid-Cretaceous SW Japan arc. After the formation of the detachment, the left-lateral pull-apart forearc basins, Onogawalzumi Group distributed on the north side of the MTL and the southern marginal mylonite zone might be formed by the sinistral movement along the detachment fault. (C) 2008 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jseaes.2008.11.015

DOI： 10.1016/j.apgeochem.2008.12.034

Mineralogy and oxygen isotope ratios of <0.1μm authigenic clay minerals were determined for the nine volcanic ash layers in the sediment column from 580 to 1255 meters below sea floor at ODP Site 808 in the Nankai Trough. Seven of 9 samples comprise of monomineralic smectite, and 2 samples from 922.2 and 998.6 mbsf comprise of R=1 illite-smectite mixed-layered clay minerals. Assuming that oxygen isotope compositions of the clay minerals are equilibrated with those of the coexisting porewater, of which composition is the same as that of sea water, formation temperature of the clay minerals was estimated to be ca 50℃ regardless of burial depth. It means that the smectite was formed most actively when the temperature of sediments rose at ca 50℃ during burial, and no distinctive change of oxygen isotope composition occurred after its formation. Three samples from 775.6, 812.3 and 1253.8 mbsf gave the high formation temperature of ca 75℃, probably due to the simultaneous formation of clinoptilolite and/or analcime. R = 1 illite-smectite mixed-layered clay minerals may be formed at the same temperature as smectite but under different condition(s) of water/rock ratio and/or porewater chemistry.

DOI： 10.14934/chikyukagaku.43.1

CiNii Article

出羽丘陵は，東北日本が強い東西圧縮応力場におかれた鮮新世前期から逆断層や褶曲構造を形成しながら隆起を開始し，更新世中期にかけて全域が陸化したと考えられている．この隆起運動に関連した変形構造は，出羽丘陵成立過程の構造運動の実態を明らかにするために重要なデータとなるだけでなく，脆性領域の変形機構や変形様式を理解するための格好の素材を提供している．この見学旅行では，出羽丘陵西縁部に存在する北由利衝上断層群および中央部に位置する鳥田目断層群に伴われる変形構造を観察し，その運動像や変形条件について考察する．

DOI： 10.5575/geosoc.114.s75

CiNii Article

CiNii Article

掲載種別：研究論文（学術雑誌）  

出羽丘陵は，東北日本が強い東西圧縮応力場におかれた鮮新世前期から逆断層や褶曲構造を形成しながら隆起を開始し，更新世中期にかけて全域が陸化したと考えられている．この隆起運動に関連した変形構造は，出羽丘陵成立過程の構造運動の実態を明らかにするために重要なデータとなるだけでなく，脆性領域の変形機構や変形様式を理解するための格好の素材を提供している．この見学旅行では，出羽丘陵西縁部に存在する北由利衝上断層群および中央部に位置する鳥田目断層群に伴われる変形構造を観察し，その運動像や変形条件について考察する．

DOI： 10.5575/geosoc.114.S75

CiNii Article

掲載種別：研究論文（学術雑誌）  

To clarify the deformation history of rocks formed within an arc-trench system, we studied the strain geometry and strain path of upper greenschist to lower amphibolite facies metamorphic rocks of contrasting lithologies (i.e., metapelite and metachert) from a metamorphosed accretionary complex (the Cretaceous low-pressure/high-temperature Ryoke metamorphic belt, SW Japan). Strain analysis focused on deformed radiolarian fossils in the metachert and pebbles in the metapelite. The metachert records flattening strain, whereas the samples of metapelite record flattening (non-folded samples) and constrictional strains (folded samples). The samples that plot in the flattening field may record strain related mainly to the schistosity-forming deformation, whereas the samples that plot in the constriction field may record the total tectonic strain of both the schistosity-forming deformation and late-stage upright folding. The fold structures observed in the layered metachert are distinct from those in the metapelite; it is likely that they mainly formed during accretion. The preservation of primary fold structures in the metachert may reflect lower strain than that in the metapelites for the period during and after the main metamorphism event. The present results demonstrate that the geometries and strain paths of different lithologies differ over a small area; consequently, in using strain analysis to constrain tectonic models, strain analysis must be undertaken in conjunction with a clear distinction of the deformation phases recorded in different lithologies. (C) 2007 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jsg.2007.09.008

掲載種別：研究論文（学術雑誌）  

The Kibaran Supergroup, a &gt;= 13000-km-long belt of metasedimentary and igneous rocks in the southeastern Congo, is in a critical location between the Congo Craton (sensu stricto) and the Tanzania-Bangweulu Block. Understanding its tectonic evolution will shed much-needed light on the amalgamation history of sub-Saharan Africa. This study presents U-Pb SHRIMP age data for 150 detrital zircons from four metasedimentary formations of the Nzilo Group, the middle lithostratigraphic unit within the Kibaran Supergroup in Katanga Province. These samples yielded dates between 3214 +/- 7 and 1329 +/- 32 Ma. Prismatic Mesoproterozoic detrital zircons (dated at 1499 +/- 49 to 1329 +/- 32 Ma, with a peak at 1380 Ma) occur in all samples and are inferred to be derived from the Mitwaba orthogneisses, which intrude the Kiaora Group, the oldest lithostratigraphic unit of the Kibaran Supergroup. More than three-quarters of the zircon population is composed of recycled grains, yielding dates between and Ma, with 2434 +/- 5 1696 +/- 18 peaks at 2050 and 1850 Ma. These peaks overlap with the timing of geological events in the adjacent Paleoproterozoic Bangweulu Block, including the Ubendian-Usagaran belts. Archean zircons were not found in the oldest Nzilo units and are restricted to the youngest Nzilo rocks, where they form only a minor component (&lt;6%) of the zircons recovered. The Archean zircons are inferred to be derived from the unroofing of successively older crust in the East African lithosphere. U-Pb data support field observations and indicate that the Nzilo Group sediments postdate the similar to 1.38-Ga Kibaran syn-D-1 igneous rocks and received some detritus from them. The lithostratigraphic and geochronological data, coupled with the regional geology, indicate that a substantial portion of the Nzilo Group detritus came from interbasinal reworking of the underlying Kiaora Group and its associated 1.38-Ga orthogneisses, with a significant contribution from the Tanzania-Bangweulu Block. The data support a previously proposed subductional model for the Kibaran belt and constrain the paleotectonic environment during the deposition of the Nzilo Group.

DOI： 10.1086/509270

掲載種別：研究論文（学術雑誌）  

Granitic mylonites from an upper greenschist facies mylonite zone in the Ryoke metamorphic belt, SW Japan show three types of microstructure with increasing mylonitization: (1) mylonite, (2) banded mylonite and (3) banded ultramylonite. The banded mylonites and ultramylonites include bands of quartz, biotite, K-feldspar, plagioclase &gt; K-feldspar (&gt;quartz + biotite) and K-feldspar &gt; plagioclase &gt; quartz. The inequality sign indicates abundance in modal proportion within a band. Microstructural and textural investigations by cathodoluminescence (CL), scanning electron microscopy (SEM) and electron back-scatter diffraction (EBSD) show that the microstructural changes from mylonites to banded ultramylonites have occurred through fracturing of plagioclase porphyroclasts, K-feldspar replacement by myrmekite, K-feldspar precipitation in fractures and tails and dislocation creep of quartz and K-feldspar. Development of the banded structure was promoted by high mobility via solution transfer of K-feldspar. Clear spatial distribution of constituent minerals in polyphase feldspar-rich bands, instead of homogeneous mixing of them, indicates that the grain boundary sliding was not the dominant deformation process. (c) 2007 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jsg.2007.02.008

近畿中央部の初瀬深成複合岩体は，主に片麻状黒雲母花崗閃緑岩とそれと同時形成の苦鉄質岩類から構成されており，E－W方向とNW－SE方向の2つのシンフォームによって特徴づけられるベースン構造を形成している．花崗閃緑岩の片麻状構造は，主に黒雲母クロットの形態定向配列によって定義され，マグマ流～亜マグマ流によって形成されている．花崗閃緑岩中の角閃石の化学組成から，花崗閃緑岩マグマの定置深度は，およそ20 kmと見積もられる．花崗閃緑岩中には，高温の塑性変形組織が見出されている．マグマ流～亜マグマ流による変形と高温塑性変形の最大伸長方向が一致しており，これらの変形作用は花崗閃緑岩の定置に関連して，マグマの固結後に温度の低下とともに連続して生じたと推測される．E－W方向のシンフォーム構造は，領家変成帯中に広く認められるD3期鉛直褶曲構造と平行であることから，片麻状黒雲母花崗閃緑岩は，領家変成帯の鉛直褶曲時の広域応力場において定置したと考えられる．<br>

DOI： 10.5575/geosoc.113.249

CiNii Article

掲載種別：研究論文（学術雑誌）  

The Cretaceous low-pressure/high-temperature Ryoke Metamorphic Belt contains abundant Ryoke and San-yo Granitoids that intruded to various crustal depths during or after formation of the belt. To clarify the tectono-metamorphic history of the belt, it is necessary to evaluate the thermal effects of the intrusion of the different types of granitoids. The geology of Kasado-jima Island, SW Japan, consists of metasedimentary rocks, massive biotite granite, and migmatitic biotite tonalite. The granite and tonalite occur in the central and southern areas of the island, respectively. Within the central area, granite intrudes metasedimentary rocks and cuts across bedding-parallel schistosity within the metapelites; this indicates that intrusion of the granite postdates Ryoke metamorphism. In contrast, tonalite in the southern area was emplaced parallel to the schistosity. On the basis of the field occurrences and petrographic characteristics of these granitoids, we correlate the biotite tonalite and biotite granite with the Older Ryoke and San-yo Granitoids, respectively. Based on the paragenesis of schistosity-forming minerals within metapelites, we identify two mineral zones in the island: the biotite and cordierite zones. The biotite zone is characterized by a mineral assemblage of muscovite + biotite ± garnet, and the cordierite zone is characterized by the assemblage muscovite + biotite + K-feldspar + cordierite or garnet. On the basis of mineral chemistry, we estimate peak metamorphic conditions for the biotite and cordierite zones to be ∼ 470 °C (reference pressure: 200 MPa) and ∼ 550 °C at 250 MPa, respectively. In the central part of the island, a contact aureole adjacent to the biotite granite is identified by the occurrence of randomly oriented muscovite and very large dendritic cordierite porphyroblasts. These randomly oriented porphyroblasts may have formed under a high degree of supersaturation associated with the thermal perturbation of the shallow intrusion of the biotite granite into cooler crust. In the southern area, most metamorphic minerals are of similar size, and their long axes are aligned to form a schistosity; this indicates a small degree of thermal perturbation and/or a high strain rate. These observations indicate that the biotite tonalite on Kasado-jima Island, as a deep-seated granitoid, was related to regional low-pressure/high-temperature metamorphism.

DOI： 10.2465/jmps.101.240

CiNii Article

掲載種別：研究論文（学術雑誌）  

Nahcolite (NaHCO₃) has been found in fluid inclusions in quartz veins hosted by the Ryoke metamorphic rocks in Kasado-Jima (Island), Yamaguchi Prefecture, Japan. The inclusions are classified into three types: type 1 containing vapor +/− liquid of the H₂O-NaCl-CO₂-CH₄ system, type 2 of H₂O-NaCl fluids and type 3 with nahcolite solid. Salinities of the nahcolite-bearing fluids are lower than 4 wt% NaCl eq. Extremely large volume fractions of nahcolite solids, occupying more than 50% of total inclusion volume, and various fluid compositions are indicative of their origin as accidentally trapped ones while the fluids were immiscible below the nahcolite melting temperature (270 °C). A thermodynamic calculation of the nahcolite stability and a phase analysis of the fluids show log<i>a</i>_Na⁺ = 7.4 − pH as the minimum activity at P = 100 MPa and T = 270 °C where the neutral pH = 5.6. Hence, it can be concluded that the original (prior to immiscible state) liquids might have contained high Na⁺ and low Cl⁻ yielded by an interaction of a low-salinity fluid and Na-bearing minerals such as plagioclase in the host metamorphic rocks below the fractures now occupied by quartz if nahcolite precipitated from boiling fluids.

DOI： 10.2465/jmps.101.254

CiNii Article

掲載種別：研究論文（学術雑誌）  

Five representative key regions from the NE-SW-trending Mesoproterozoic Kibaride belt of SE Congo are described. Although the present database is still insufficient for a definitive reconstruction of the tectonic setting, available data suggest that the investigated areas experienced a similar geological history. The Kibaran Supergroup comprises four major lithostratigraphic units in SE Congo. The Kiaora Group is the oldest unit. It starts with a basal conglomerate which is overlain by siliciclastic rocks deposited in fluviatile and possibly lacustrine environments. The conglomerate is overlain by abundant metapelites (predominantly black schist) with calc-silicate, volcano-sedimentary rocks and minor metachert deposited in shallow marine environments. These units are cut by 1.38 Ga granitoids. The overlying Nzilo Group is composed of coarse-grained, siliciclastic metasedimentary rocks including metaconglomerates, quartzites and minor metapelites and metamorphosed ironstones. Frequent herringbone and wavy ripples suggest tidal flat deposition. The maximum depositional age of this group is given by the 1.38 Ga granitoids on which it rests disconformably and by detrital zircons from a quartzite which yields a concordant age of 1360 +/- 27 Ma. The above two groups are separated by a disconformity along with the matrix-supported Kataba Conglomerate occurs at the base of the Nzilo Group. Higher in the succession, the Hakansson Group is essentially pelitic with minor quartzites. At the top of the succession, the Lubudi Group is made of (stromatolitic) carbonates, black schists and minor black quartzites and is inferred to record shallow marine deposition. All these metasedimentary rocks were deposited before the emplacement of ca. 1.0-0.95 Ga tin granites and are older than 1.08 Ga, which is the age of the climax of Kibaran deformation in the Mitwaba area.
Two major deformational events have been recognized in the study areas. The earliest (D(1)) is characterized by ENE-trending asymmetric folds and thrusts showing N to NNW transport directions. These structures occur in the Kiaora Group and predate the deposition of the Nzilo, Hakansson and Lubudi Groups. The second deformation (D(2)) marks the climax of the Kibaran orogeny and affects all sedimentary units. It is defined by NW-verging mesoscopic and macroscopic isoclinal folds (F(2)) and reverse faults parallel to D(2) planar fabrics. M(2) metamorphism is characterized by medium-pressure/medium-temperature (MP/MT) mineral parageneses, with preliminary data indicating peak P-T conditions between 740-780 degrees C and 6-6.5 Kb. U-Pb dating of metamorphic zircon in older orthogneisses in the Mitwaba region tentatively constrains the timing of M(2) metamorphism at 1079 +/- 14 Ma.
The Kiaora Group was intruded by widespread arc-related gabbro-diorite and ca. 1.38 Ga syn-D(1) calcalkaline and strongly peraluminous granitic plutons similar to those documented in the Lachlan and Hercynian belts. Late to post-kinematic granites and related pegmatites and greisens hosting tin-group ore deposits were emplaced at similar to 1.0-0.95 Ga and exhibit geochemical similarities with SE Asian collisional granites. The Kibaran orogenic system was active between similar to 1.4-1.38 (accretionary stage) and similar to 1.0-0.95 Ga (continental collision and post-orogenic exhumation), but the Kiaora Group sedimentary rocks were deposited prior to 1.4-1.38 Ga, which is the igneous crystallization age for the syn-D(1) Kibaran orthogneisses intruding them. Sedimentological data broadly indicate that the Kiaora Group was deposited in shallow marine environments, during the rift-drift stage of the evolving Kibaran basin while the post-D(1) Nzilo Group was deposited in an intra-arc environment, although more modern data are required before a definite conclusion can be reached. Available structural, sedimentological, geochronological and petrological data support a convergent margin setting for the Kibaride belt and are inconsistent with an intracontinental, rift model. (c) 2006 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jafrearsci.2006.01.017

掲載種別：研究論文（学術雑誌）  

Mesoproterozoic supracrustal rocks in the Kibaride belt (southeast Congo) were intruded by mafic-intermediate plutonic rocks. These igneous rocks were affected by greenschist- to amphibolite-facies metamorphism during the Mesoproterozoic Kibaran orogenesis. U-Pb single zircon dating of the Mitwaba mafic-intermediate plutonic rocks yields an emplacement age of 1.38 Ga. The compositions of the Mitwaba mafic-intermediate plutonic rocks range from gabbro to diorite and show the following elemental concentrations: SiO2: 49-58 wt %, TiO2: 0.53-0.92 wt %, Al2O3: 13.1-18.68 wt %, Zr: 45-142 ppm, Y: 13-43 ppm. Mg no. 40-66 indicates variable degrees of fractionation of the magmas. The rocks are marked by high and variable Th/Ta (3-14), La/Nb (2-5) and low Ce/Pb (0.3-12.8) and Ti/V (10-19). Chondrite-normalized REE patterns exhibit enrichment in LREE relative to HREE ((La/Yb)(N) = 2.9-5.8). Primordial mantle-normalized spider diagrams show negative slopes with gradual decrease from LIL to HFS elements and are marked by Nb and Ti negative anomalies. Immobile trace-element contents indicate a continental arc setting for these mafic-intermediate igneous rocks. They are inferred to have originated from a mantle wedge enriched by fluid from a subducting slab, with possibly an additional contribution from subducted sediments. Low, sub-chondritic Nb/Ta ratios in these mafic rocks support this interpretation. A model involving underplating of mafic-intermediate arc magma into the crust, triggering partial melting of Mitwaba group metasedimentary rocks during the accretionary stage of the Kibaran orogeny, is proposed to explain the coeval emplacement of mafic-intermediate arc magmas and peraluminous S-type granitoids in the Kibaride belt of central Africa.

DOI： 10.1017/S0016756804009951

掲載種別：研究論文（学術雑誌）  

領家変成帯中の近畿中央部飛鳥地域に分布する苦鉄質岩は，領家古期 花崗岩類に対して層状に産している．苦鉄質岩のほとんどは，コアもリムもほぼ均一な化学組成を示す半自形～他形の斜長石と角閃石からなる．また，斜長石－角閃石温度計を用いて平衡温度を計算するとおよそ500－600℃となることから，これらの苦鉄質岩は角閃岩相の変成作用を被った変成岩であると考えられる．一部の苦鉄質岩に認められる面構造とマグマ期－亜マグマ期に形成された花崗岩類の片麻状構造が斜交関係にあることから，両者は同じ変形作用を被っておらず，苦鉄質岩の面構造は，少なくとも花崗岩類との接触以前に形成されたと判断される．これらのことから，苦鉄質岩は花崗岩質マグマの定置以前に角閃岩相の変成作用を被った後，花崗岩質マグマに捕獲されたと結論づけられる．<br>

DOI： 10.5575/geosoc.111.141

CiNii Article

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（大学，研究機関等紀要）   共著区分：単著  

掲載種別：研究論文（学術雑誌）   共著区分：単著  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（大学，研究機関等紀要）  

掲載種別：研究論文（大学，研究機関等紀要）  

共著区分：単著  

掲載種別：研究論文（大学，研究機関等紀要）  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）   共著区分：単著  

掲載種別：研究論文（学術雑誌）   共著区分：単著  

掲載種別：研究論文（大学，研究機関等紀要）  

掲載種別：研究論文（大学，研究機関等紀要）   共著区分：単著  

掲載種別：研究論文（学術雑誌）   共著区分：単著  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（大学，研究機関等紀要）  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（大学，研究機関等紀要）  

掲載種別：研究論文（学術雑誌）  

著書種別：学術書  

著書種別：学術書  

著書種別：学術書  

著書種別：学術書  

著書種別：学術書  

著書種別：学術書  

掲載種別：記事・総説・解説・論説等（学術雑誌）  

CiNii Article

会議種別：口頭発表（一般）  

開催地：千葉  

会議種別：口頭発表（一般）  

開催地：千葉  

会議種別：口頭発表（一般）  

開催地：日本  

会議種別：口頭発表（一般）  

開催地：Japan  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

開催地：東京  

<p>大陸地殻の主要構成鉱物である石英について、結晶構造水や流体包有物として含まれる水は、石英の塑性変形を促進させることが知られている。しかし、天然の石英中の水の形態や含水量、およびこれらと塑性変形との関係性ついて不明な点が多い。そこで本研究では、阿武隈山地東縁から採取した異なる変形様式を示す割山花崗岩に含まれる石英について、赤外分光法を用いて水の分析を行った。</p><p>　分析試料は1. ほぼ原岩、2. 弱変形、3. 強変形試料、の3種を用いた。1.のほぼ原岩試料では、偏光顕微鏡下において、領域によっては石英の粒界でバルジングが起こっており、10 µm程度の粒子が一つまたは数個生成しているが、全体の組織としては大方原岩の状態を保持している。2.の弱変形試料では、試料は弱い面構造を示し、ホスト石英粒子の近傍に、バルジングや亜粒界回転によって生成した動的再結晶粒子が最大数百µmの領域で見られる。長石類もポーフィロクラストとなっている。3.の強変形試料では、強い面構造を示し、石英領域は100 µm程度のホスト粒子とその内部に発達した10 µm程度の若干の亜粒子が見られる領域もあるが、ほぼ動的再結晶が完了しており、細粒石英粒子が基質を占める。</p><p>　上記のような3種の変形度を示す試料について、赤外分光法面分析を用いて、石英含水量の2次元分布を測定した。試料の厚みは100 µm前後で、十分なシグナルを示す赤外スペクトルが測定でき、かつ偏光顕微鏡下で試料の微細構造も観察できる。面分析領域は最大400 x 400 µm、空間分解能=アパーチャーサイズは最小25 x 25 µmで分析を行った。ほぼ原岩試料は石英一粒子内部、弱変形試料はホスト石英粒子と動的再結晶石英領域、強変形試料は動的再結晶石英領域を分析した。</p><p>　分析結果を以下に述べる。ほぼ原岩試料の石英粒内の赤外スペクトルは波数2800-3800 cm^-1に幅広い吸収帯を示し、流体包有物として分子状の水が含まれている。含水量は不均質で、一つの粒内で、数十wt ppm H₂O から1500 wt ppmまで幅広く変化する。弱変形試料では、ホスト石英粒子内部の含水量はほぼ原岩試料と同様に不均質であった。一方、動的再結晶領域は強変形試料と共に分子状の水の吸収帯を示し、含水量は200-350 wt ppm、平均250 wt ppmとほぼ均質であった（下図）。このような水は動的再結晶石英粒内と粒界に存在していると考えられる。</p><p>　以上の分析結果は、Fukuda et al. (2012)で見られた、長石の溶解-沈殿機構による細粒化が起こる際、ホスト粒子（150-2200 wt ppm）からの水の放出と、含水量が均質な細粒長石領域の生成（150-300 wt ppm）とよく似た結果となった。一方、Fukuda and Shimizu (2019)の三波川変成岩中の石英集合体領域で見られた含水量分布とは相反する。Fukuda and Shimizu (2019)では、石英粒径が150 µmから30 µmへと減少するに従って、含水量は40 wt ppmから300 wt ppmへと増加した。これは石英の粒界の面積が相対的に増加し、粒界により多くの水が保持されていることを示唆する。三波川変成岩中の石英の場合では、動的再結晶による細粒化が起きたのか、元々粒径が異なるのかは不明であるが、粒界がより多くの水のリザーバーになっている。一方、本研究での割山花崗岩の場合では、ホスト粒子よりも低い含水量が細粒石英領域の粒内、粒界に含まれており、水はホスト石英粒子の動的再結晶時に放出されたことを示唆する。</p><p></p><p>引用文献</p><p>Fukuda J., Okudaira T., Satsukawa T., Michibayashi K. (2012) Solution-precipitation of K-feldspar in deformed granitoids and its relationship to the distribution of water. Tectonophysics, vol. 532-535, pp. 175–185</p><p>Fukuda J. and Shimizu I. (2019) Water distribution in quartz schists of the Sanbagawa Metamorphic Belt, Japan: Infrared spectroscopic mapping and comparison of the calibrations proposed for determining water contents. Earth, Planets and Space, vol. 71:136, pp. 1–14</p>

DOI： 10.14863/geosocabst.2022.0_50

DOI： 10.14863/geosocabst.2022.0_310

DOI： 10.14863/geosocabst.2022.0_309

<p>To clarify the relationship between the strain and the activity of slip systems in quartz, we analyzed crystallographic and shape preferred orientation of sheared quartz phenocrysts in a granitic porphyry in the Ryoke belt, Awaji Island, SW Japan. In general, slip systems, i.e., basal <<i>a</i>>, rhomb <<i>a</i>> and prism <<i>a</i>> slip systems,are the active slip systems under the upper crustal condition, and the activity of slip systems has been considered to be temperature-dependent (Passchier and Trouw 2005; Law 2014). It has been proposed that basal and prism may operate readily at lower and higher temperature conditions. However, based on the detailed textural analysis of CPOs of experimentally deformed Black Hills Quartzite, Kilian and Heilbronner (2017) suggested that the texture transition is not as a result of the temperature-dependent activity of different slip systems but as a result of different texture forming processes depending on stress and/or strain. Textures with peripheral [c] axes are often observed in rocks deformed under low-grade conditions cannot attribute to the activity of basal slip system, and proposed oriented nucleation and growth a new process to form textures with peripheral [c] axes. Furthermore, with increasing strain, dislocation glide involving prism and rhomb slip leads to a high density of [c] axes in the center of the pole figure.</p><p>In this study, we analyzed the deformed granitic porphyry samples with different strain, which has been reported by Kano and Takagi (2013), and measured the shape preferred orientation of quartz grains by calculating aspect ratio from the long and short axis of grains are those of fitted ellipse to grain shape using ImageJ software to reveal the strain magnitude. Quartz CPOs was measured by U-stage equipped with an optical microscope to infer the operative slip systems. Based on the crystallographic- and shape-preferred orientation of sheared quartz phenocrysts in a granitic porphyry, we will discuss the effect of strain on the activity of slip system in deforming quartz.</p><p>References: Kano H, Takagi H (2013) J Geol Soc Japan 119:776–793. Kilian R, Heilbronner R (2017) Solid Earth 8:1095–1117. Law RD (2014) J Struct Geol 66:129–161. Passchier CW, Trouw RAJ (2005) Microtectonics.</p>

DOI： 10.14863/geosocabst.2021.0_276

<p></p>

DOI： 10.14863/geosocabst.2019.0_548

CiNii Article

<p></p>

DOI： 10.14863/geosocabst.2019.0_201

CiNii Article

<p></p>

DOI： 10.14863/geosocabst.2019.0_496

CiNii Article

<p></p>

DOI： 10.14863/geosocabst.2019.0_6

CiNii Article

<p></p>

DOI： 10.14863/geosocabst.2019.0_531

CiNii Article

【災害のためプログラム中止】 平成30年北海道胆振東部地震により学術大会のプログラムが大幅に中止となりました．中止となったプログラムの講演要旨については，著者のプライオリティ保護の見地からJ-STAGEに公開し，引用可能とします．ただし，学術大会においては専門家による議論には供されていませんので「災害のためプログラム中止」との文言を付記します．（日本地質学会行事委員会）

DOI： 10.14863/geosocabst.2018.0_221

CiNii Article

【災害のためプログラム中止】 平成30年北海道胆振東部地震により学術大会のプログラムが大幅に中止となりました．中止となったプログラムの講演要旨については，著者のプライオリティ保護の見地からJ-STAGEに公開し，引用可能とします．ただし，学術大会においては専門家による議論には供されていませんので「災害のためプログラム中止」との文言を付記します．（日本地質学会行事委員会）

DOI： 10.14863/geosocabst.2018.0_228

CiNii Article

【台風のためプログラム中止】 台風18号により学術大会の一部プログラムが中止となりました．中止となったプログラムの講演要旨については，著者のプライオリティ保護の見地から今回に限りJ-STAGEに公開し，引用可能とします．ただし，学術大会においては専門家による議論には供されていませんので「台風のためプログラム中止」との文言を付記します．（日本地質学会行事委員会）

DOI： 10.14863/geosocabst.2017.0_339

CiNii Article

DOI： 10.14863/geosocabst.2017.0_471

CiNii Article

DOI： 10.14863/geosocabst.2016.0_147

CiNii Article

DOI： 10.14863/geosocabst.2016.0_145

CiNii Article

DOI： 10.14863/geosocabst.2015.0_395

CiNii Article

DOI： 10.14863/geosocabst.2014.0_568

CiNii Article

DOI： 10.14863/geosocabst.2014.0_547

CiNii Article

DOI： 10.14863/geosocabst.2014.0_229

CiNii Article

DOI： 10.14863/geosocabst.2013.0_421

CiNii Article

DOI： 10.14863/geosocabst.2013.0_536

CiNii Article

インド南部太古代ダールワール岩体の片麻岩体-片岩帯の地質関係と変成作用について再検討をおこなった。

DOI： 10.14824/jakoka.2013.0_205

CiNii Article

DOI： 10.14863/geosocabst.2012.0_421

CiNii Article

DOI： 10.14863/geosocabst.2012.0_253

CiNii Article

DOI： 10.14863/geosocabst.2012.0_533

CiNii Article

DOI： 10.14863/geosocabst.2012.0_22

CiNii Article

DOI： 10.14863/geosocabst.2011.0.202.0

CiNii Article

DOI： 10.14863/geosocabst.2011.0.403.0

CiNii Article

DOI： 10.14863/geosocabst.2011.0.163.0

CiNii Article

DOI： 10.14863/geosocabst.2010.0.488.0

CiNii Article

DOI： 10.14863/geosocabst.2010.0.517.0

CiNii Article

DOI： 10.14863/geosocabst.2010.0.446.0

CiNii Article

バングラデシュ・ショナルガオ地域のヒ素汚染地下水帯水層堆積物中の黒雲母と緑泥石を，SPring-8においてマイクロビーム蛍光エックス線分析を用いて分析を行った。 黒雲母には，ヒ素はごく微量にしか含まれていなかったが，緑泥石中には普遍的にヒ素が分布していることを確認した。ヒ素を主成分とする硫ヒ鉄鉱などとのX線強度の比較から，濃度は数十～数百ppmと推定される。一方，ヒ素を含む緑泥石にはサブミクロンオーダーの大きさ針鉄鉱が含まれていることが確認された。現段階では，ヒ素の全量が緑泥石中にあるのか，針鉄鉱にも含まれているのかは明らかでない。しかし，定説で原因物質とされている風化生成物であるヒ素を吸着した酸水酸化鉄ではなく，砕屑性の緑泥石がヒ素の担体として重要であることは明らかである。このことは，ヒ素汚染地下水の形成機構を説明する上で，定説の見直しをせまるものである。

DOI： 10.14862/geochemproc.56.0.98.0

CiNii Article

DOI： 10.14863/geosocabst.2009.0.206.0

CiNii Article

CiNii Article

DOI： 10.14863/geosocabst.2008.0.434.0

CiNii Article

DOI： 10.14863/geosocabst.2008.0.151.0

CiNii Article

DOI： 10.14863/geosocabst.2008.0.512.0

CiNii Article

CiNii Article

CiNii Article

DOI： 10.14863/geosocabst.2007.0.581.0

CiNii Article

DOI： 10.14863/geosocabst.2007.0.246.0

CiNii Article

DOI： 10.14863/geosocabst.2006.0_208_2

CiNii Article

DOI： 10.14863/geosocabst.2005.0_121_2

CiNii Article

DOI： 10.14863/geosocabst.2005.0_156_1

CiNii Article

種別：査読等 

種別：査読等 

種別：査読等 

種別：査読等 

種別：査読等 

種別：査読等 

種別：査読等 

種別：査読等