研究者詳細 - 道林　克禎

論文 - 道林　克禎

分割表示 176 件中 141 - 160 件目／全件表示 >>

Amphibolitization within the lower crust in the termination area of the Godzilla Megamullion, an oceanic core complex in the Parece Vela Basin 査読有り

Harigane, Y; Michibayashi, K; Ohara, Y

ISLAND ARC 19 巻 ( 4 ) 頁： 718 - 730 2010年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Island Arc

Gabbroic rocks and amphibolites were collected from the KR03-01-D10 dredge site located on the West Arm Rise of the Godzilla Megamullion, close to the Parece Vela Rift which appears to correspond to the termination area of a detachment fault, the Philippine Sea. The gabbroic rocks and amphibolites reveal the occurrence of a high hydrothermal activity in the lower crust close to a paleo-ridge. In the gabbroic rocks, plagioclase compositions of both porphyroclasts and matrix were transformed into sodium-rich compositions close to albite. Amphiboles are of secondary rather than igneous origin based on their microstructural occurrences. In the amphibolites, anorthite contents of porphyroclasts and matrix plagioclase are relatively lower than those of the gabbroic rocks, whereas the chemical compositions of amphibole within the amphibolites are similar to those of amphibole within the gabbroic rocks. Amphibolites represent the product of retrograde metamorphism associated with hydrothermal alteration of the gabbroic body by the reaction: clinopyroxene + calcic plagioclase + fluid → amphibole + sodic plagioclase. The estimated temperatures of the amphibolites derived from the amphibole thermobarometer and the gabbroic rocks derived from the hornblende-plagioclase geothermometer show ~700-950°C and 650-840°C, respectively. The hydrothermal alteration recorded in the gabbroic rocks possibly occurred under high-T conditions; the rocks were then metamorphosed to the amphibolites during a retrogressive stage. Our study indicates that amphibolitization took place with various degrees of deformation. It may imply that the hydrothermal activity increased as the Godzilla Megamullion developed as an oceanic core complex in the paleo-ridge. © 2010 Blackwell Publishing Asia Pty Ltd.

DOI： 10.1111/j.1440-1738.2010.00741.x

Spatial variations in antigorite fabric across a serpentinite subduction channel: Insights from the Ohmachi Seamount, Izu-Bonin frontal arc 査読有り Open Access

Hirauchi Ken-ichi, Michibayashi Katsuyoshi, Ueda Hayato, Katayama Ikuo

EARTH AND PLANETARY SCIENCE LETTERS 299 巻 ( 1-2 ) 頁： 196 - 206 2010年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Earth and Planetary Science Letters

We conducted a microstructural study of samples from a natural serpentinite shear zone in the Ohmachi Seamount, Izu-Bonin frontal arc. The serpentinite samples consist mainly of columnar antigorite grains that show marked variations in texture from two approximately orthogonal sets of grains (interpenetrating) to aligned (schistose) forms. Because the two types of grains have similar compositions, these textural differences are interpreted to reflect the existence of a strain gradient toward a plate interface in a subduction zone. The crystal-preferred orientation (CPO) of antigorite with interpenetrating texture is almost randomly oriented, whereas in the case of schistose texture the CPO shows a typical [010](001) pattern. We also found that with increasing intensity of schistosity, the polarization plane of Vs1 for antigorite grains becomes aligned parallel to the flow plane, consistent with a plane oriented normal to the maximum concentration of slow antigorite c-axes. This configuration results in seismic anisotropy that is approximately five times higher than that for olivine grains. These findings indicate that if a serpentinite layer on the plate interface attains large bulk shear strains (γ>~2), the resultant alignment of antigorite grains within the layer strongly influences the orientation and magnitude of seismic anisotropy in the mantle wedge, depending on the dip angle of the subducting slab. © 2010 Elsevier B.V.

DOI： 10.1016/j.epsl.2010.08.035

Uppermost mantle anisotropy beneath the southern Laurentian margin: Evidence from Knippa peridotite xenoliths, Texas 査読有り国際共著 Open Access

Satsukawa T., Michibayashi K., Raye U., Anthony E., Pulliam J., Stern R.

Geophysical Research Letters 37 巻 ( 20 ) 2010年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Geophysical Research Letters

Peridotite xenoliths from southern Texas consist of spinel lherzolite, harzburgite and minor dunite. Based on phase relations and temperature of equilibration, Knippa xenoliths come from the uppermost mantle, 40-70 km deep. Knippa xenoliths provide rare snapshots of upper mantle processes and compositions beneath south-central Laurentia. They preserve olivine a-axis fiber fabrics with a strong concentration of [100] and girdles of [010] and [001]. Assuming a lithospheric mantle having a horizontal flow direction parallel to fast directions, the mantle lithospheric fabric revealed by the xenoliths mostly explains the magnitude of observed shear-wave splitting observed along the southern margin of the Laurentian craton. © 2010 by the American Geophysical Union.

DOI： 10.1029/2010GL044538

Grain-size-sensitive deformation of upper greenschist- to lower amphibolite-facies metacherts from a low-P/high-T metamorphic belt 査読有り Open Access

Okudaira Takamoto T., Ogawa D., Michibayashi K.

Tectonophysics 492 巻 ( 1-4 ) 頁： 141 - 149 2010年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tectonophysics

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. © 2010 Elsevier B.V.

DOI： 10.1016/j.tecto.2010.06.002

Effect of grain growth on cation exchange between dunite and fluid: implications for chemical homogenization in the upper mantle 査読有り

Ohuchi, T; Nakamura, M; Michibayashi, K

CONTRIBUTIONS TO MINERALOGY AND PETROLOGY 160 巻 ( 3 ) 頁： 339 - 357 2010年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Contributions to Mineralogy and Petrology

The effect of grain growth on the cation exchange between synthesized forsterite aggregates (i. e., dunite) and nickel-rich aqueous fluid was evaluated experimentally at 1. 2 GPa and 1,200°C. The grain boundary (GB) migration caused nickel enrichment in the area swept by the GBs in a fashion similar to that reported for stable isotope exchange in the quartz aggregates. The progress of the grain growth resulted in an increase in the average nickel concentration in the dunites of up to ~80 times that was calculated for a system having stationary GBs. The overall diffusivity of the nickel along the wet GBs and interconnected fluid networks was found to be 6.5 × 10-19-6.7 × 10-18 m3/s, which is 4-5 orders of magnitude higher than the grain boundary diffusivity in the dry dunite. These results show that the grain growth rate is a fundamental factor in the evaluation of the time scale of chemical homogenization in the upper mantle. © 2010 Springer-Verlag.

DOI： 10.1007/s00410-009-0481-7

0.5GPa，800°Cにおけるメノウ中の石英多結晶体の結晶成長実験査読有り Open Access

井元恒, 道林克禎

静岡大学地球科学研究報告 37 巻 ( 0 ) 頁： 13 - 19 2010年7月

深海底から採取した蛇紋岩の弾性波速度測定：予察査読有り Open Access

新海優里, 渡辺了, 道林克禎, 針金由美子, 小原泰彦

静岡大学地球科学研究報告 37 巻 ( 0 ) 頁： 27 - 34 2010年7月

1GPa、800℃におけるフリント中の石英多結晶体の結晶成長実験査読有り Open Access

植田直彦, 道林克禎

静岡大学地球科学研究報告 37 巻 ( 37 ) 頁： 21-26 - 26 2010年7月

Exsolution of dolomite and application of calcite-dolomite solvus geothermometry in high-grade marbles: an example from Skallevikshalsen, East Antarctica 査読有り

Mizuochi, H; Satish-Kumar, M; Motoyoshi, Y; Michibayashi, K

JOURNAL OF METAMORPHIC GEOLOGY 28 巻 ( 5 ) 頁： 509 - 526 2010年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Metamorphic Geology

Calcite-dolomite solvus geothermometry is a versatile method for the estimation of metamorphic temperature because of its simplicity. However, in medium- to high-grade metamorphic rocks the accuracy of estimating temperature by the integration of unmixed dolomite and calcite is hampered by the heterogeneous distribution of unmixed dolomite, difficulties in distinguishing between preexisting and exsolved dolomite and demarcating grain boundaries. In this study, it is shown that calcite-dolomite solvus thermometry can be applied to calcite inclusions in forsterite and spinel for the estimation of peak metamorphic temperature in granulite facies marbles from Skallevikshalsen, East Antarctica. The marbles are comprised of a granoblastic mineral assemblage of calcite + dolomite + forsterite + diopside + spinel + phlogopite ± apatite, characteristic of granulite facies metamorphic conditions. Forsterite, spinel and apatite frequently contain 'negative crystal' inclusions of carbonates that display homogeneously distributed dolomite lamellae. On the basis of narrow ranges of temperature (850-870 °C) recorded from carbonate inclusions compared with the range from matrix carbonate it is regarded that the inclusion carbonates represent a closed system. Furthermore, this estimate is consistent with dolomite-graphite carbon isotope geothermometry, and is considered to be the best estimate of peak metamorphic temperature for this region. Matrix calcite records different stages of retrograde metamorphism and re-equilibration of calcite that continued until Mg diffusion ceased at ∼460 °C. Electron backscattered diffraction (EBSD) results together with morphological features of unmixed coarse tabular dolomite suggest anisotropic diffusion and mineral growth are influenced by crystallographic orientation. Identification of sub-grain boundaries and formation of fine-grained unmixing in calcite rims suggest the presence of grain boundary fluids in the late retrograde stages of metamorphic evolution. These results, thus, demonstrate the usefulness of carbonate inclusion geothermometry in estimating the peak metamorphic temperatures of high-grade terranes and the application of EBSD in understanding the unmixing behaviour of minerals with solid solutions. © 2010 Blackwell Publishing Ltd.

DOI： 10.1111/j.1525-1314.2010.00877.x

Two Contrasting Fabric Patterns of Olivine Observed in Garnet and Spinel Peridotite from a Mantle-derived Ultramafic Mass Enclosed in Felsic Granulite, the Moldanubian Zone, Czech Republic 査読有り Open Access

Kamei Akira, Obata Masaaki, Michibayashi Katsuyoshi, Hirajima Takao, Svojtka Martin

JOURNAL OF PETROLOGY 51 巻 ( 1-2 ) 頁： 101 - 123 2010年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Petrology

The Mohelno peridotite is a medium-sized ultramafic body (2 km×4 km in size) enclosed in the Gföhl granulites in the eastern part of the BohemianMassif. It consists mainly of coarse spinel peridotite (harzburgite and dunite); garnet peridotite occurs only in the sheared and deformed margins of the body. To decipher the origin and history of this mantle-derived peridotite, we determined the mineral chemistry by electron microprobe analysis and olivine fabric patterns by the electron backscattered diffraction method for each rock type.We found two distinct types of olivine fabric (crystal-preferred orientation; CPO) in the peridotite, which can be correlated with the mineralogy and thermal history of each. The olivine CPO in coarse-grained spinel peridotite shows a strong concentration of [100] slightly oblique to the lineation and [010] and [001] girdles normal to the lineation (which is the so-called {0kl}[100] pattern typical of medium-temperature deformation). Olivine in coarse-grained garnet peridotite, on the other hand, shows a strong concentration of [010] normal to the foliation and a concentration of [100] parallel to the lineation (which is the so-called (010)[100] pattern typical of high-temperature deformation). These fabric patterns become diffuse as the grain size is reduced for each mineralogical type.We interpret the development of these contrasting fabric patterns and mineralogical types based on the pressure-temperature history of each rock type determined by applying published geothermometers and geobarometers to the constituent minerals. Starting from a high-temperature (>1200°C) spinel peridotite, during exhumation and cooling in contact with surrounding granulites, the marginal part of the body was transformed to garnet peridotite, whereas the interior remained in the spinel-peridotite facies because cooling was slower inside the body. Because of the slow cooling and continuous deformation in the interior of the body, the original high-temperature fabric pattern in the spinel peridotite was converted to a lower-temperature type.The high-temperature fabric was preserved only at the margin of the body where cooling was more rapid. Reduction of grain size that occurred during later, low-temperature, deformation partly obliterated the high-temperature fabric patterns for both garnet and spinel peridotites. The initial rapid cooling at high temperatures associated with deformation probably occurred after the mantle peridotite was emplaced within the crustal granulites, which implies that the spinel- to garnet-peridotite transformation took place in the continental crust. © The Author 2010. Published by Oxford University Press.

DOI： 10.1093/petrology/egp092

深海底から採取した蛇紋岩の弾性波速度測定:予察査読有り Open Access

新海優里, 渡辺了, 道林克禎, 針金由美子, 小原泰彦, 小原泰彦

静岡大学地球科学研究報告 ( 37 ) 2010年

Trench-parallel anisotropy produced by serpentine deformation in the hydrated mantle wedge 査読有り

Katayama Ikuo, Hirauchi Ken-ichi, Michibayashi Katsuyoshi, Ando Jun-ichi

NATURE 461 巻 ( 7267 ) 頁： 1114-U209 2009年10月

Rock seismic anisotropy of the low-velocity zone beneath the volcanic front in the mantle wedge 査読有り Open Access

Michibayashi Katsuyoshi, Oohara Tatsuya, Satsukawa Takako, Ishimaru Satoko, Arai Shoji, Okrugin Victor M.

GEOPHYSICAL RESEARCH LETTERS 36 巻 ( 12 ) 2009年6月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Geophysical Research Letters

Peridotite xenoliths derived from the low velocity zone beneath the Avacha frontal volcano, Kamchatka, preserve a-axis slip fabrics, comparable with those in xenoliths from the back-arc region of the NE Japan. Although low-velocity zones are commonly attributed to zones of partially melted mantle, migration of the melt does not erase the existing olivine fabrics and related Scismic anisotropics. These anisotropics may counteract the anisotropics associated with c-axis slip fabrics, if they exist, along the slab or in the high-pressure zone. Copyright 2009 by the American Geophysical Union.

DOI： 10.1029/2009GL038527

Peridotites from a ductile shear zone within back-arc lithospheric mantle, southern Mariana Trench: Results of a Shinkai 6500 dive 査読有り国際共著

Michibayashi K., Ohara Y., Stern R. J., Fryer P., Kimura J. -I., Tasaka M., Ishii T.

GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS 10 巻 ( 5 ) 2009年5月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Geochemistry, Geophysics, Geosystems

[1] Two N-S fault zones in the southern Mariana fore arc record at least 20 km of left-lateral displacement. We examined the eastward facing slope of one of the fault zones (the West Santa Rosa Bank fault) from 6469 to 5957 m water depth using the submersible Shinkai 6500 (YK06-12 Dive 973) as part of a cruise by the R/V Yokosuka in 2006. The dive recovered residual but still partly fertile lherzolite, residual lherzolite, and dunite; the samples show mylonitic, porphyroclastic, and coarse, moderately deformed secondary textures. Crystal-preferred orientations of olivine within the peridotites show a typical [100](010) pattern, with the fabric intensity decreasing from rocks with coarse secondary texture to mylonites. The sampled peridotites therefore represent a ductile shear zone within the lithospheric mantle of the overriding plate. Peridotites were probably exposed in association with a tear in the subducting slab, previously inferred from bathymetry and seismicity. Furthermore, although the dive site is located in the fore arc close to the Mariana Trench, spinel compositions within the sampled peridotites are comparable to those from the Mariana Trough back arc, suggesting that back-arc basin mantle is exposed along the West Santa Rosa Bank fault. © 2009 by the American Geophysical Union.

DOI： 10.1029/2008GC002197

P- and S-wave velocities of the lowermost crustal rocks from the Kohistan arc: Implications for seismic Moho discontinuity attributed to abundant garnet 査読有り Open Access

Kono Yoshio, Ishikawa Masahiro, Harigane Yumiko, Michibayashi Katsuyoshi, Arima Makoto

TECTONOPHYSICS 467 巻 ( 1-4 ) 頁： 44 - 54 2009年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tectonophysics

P- (Vp) and S-wave (Vs) velocities of garnet-free (two-pyroxene granulite) and garnet-bearing (garnet granulite and garnet pyroxenite) lowermost crustal rocks collected from the Kohistan arc, northern Pakistan, were measured at 0.1-1.0 GPa and 25-400 °C. Garnet granulite had higher Vp (+ 0.31 km/s) and Vs (+ 0.27 km/s) than two-pyroxene granulite. Although Vp and Vs increased with increasing volume percent of garnet, plagioclase-free garnet pyroxenite showed significantly higher Vp and Vs than plagioclase-rich garnet granulite mainly due to the low Vp and Vs of plagioclase. In contrast, we observed two quasi-linear relationships between Vp (Vs) and SiO2 content for the garnet-bearing and garnet-free rocks. The garnet-bearing rocks had relatively higher Vp and Vs and stronger SiO2 dependences than the garnet-free rocks. The stronger SiO2 dependences of Vp and Vs in the garnet-bearing rocks suggest that the garnet formation in mafic to ultramafic rocks (e.g., pyroxenite and hornblendite), having relatively lower SiO2, leads to more pronounced increases in Vp and Vs than that of relatively felsic rocks (e.g., felsic-to-mafic granulite). Indeed, the Vp and Vs of the garnet pyroxenite were significantly higher than those of garnet granulite but comparable to those of dunite. The significantly high Vp and Vs of the garnet pyroxenite yielded high reflection coefficients between the garnet granulite and garnet pyroxenite of up to 0.13 for P-waves and 0.14 for S-waves, comparable to values expected for Moho reflection. Thus the lithological boundary between plagioclase-rich garnet granulite and plagioclase-free garnet pyroxenite in the lowermost crust of the Kohistan arc corresponds to the seismic Moho discontinuity. © 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tecto.2008.12.010

結晶方位配列と亜結晶粒回転軸によるかんらん石すべり系の推定～秋田県男鹿半島一の目潟火山かんらん岩捕獲岩を例として～ Open Access

佐津川貴子, 道林克禎

地質学雑誌 115 巻 ( 6 ) 頁： 288 - 291 2009年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本地質学会

In this study of peridotite xenoliths from Ichinomegata volcano, Oga peninsula, NE Japan, we used electron backscattered diffraction to assess the validity of two methods of identifying the olivine slip system that operated during deformation. The xenoliths are harzburgite in composition and contain a distinct foliation and lineation defined by aligned spinel and pyroxene grains. Using the first method, the dominant slip system in olivine was estimated based on the crystallographic preferred orientation (CPO) of olivine with respect to the foliation and lineation. The second method was based on an analysis of subgrain rotation: given that intracrystalline subgrain boundaries were observed within several olivine grains, we measured the misorientation angles across these boundaries to define sets of slip planes, slip directions, and rotation axes. The olivine slip systems estimated using the two methods are essentially identical. The CPO pattern provides an important constraint on the dominant slip system that operated during deformation, whereas the analysis of subgrain rotation yields the slip system responsible for the development of individual subgrain boundaries composed of edge dislocations. The two methods are therefore complementary.

DOI： 10.5575/geosoc.115.288

Hydration due to high-T brittle failure within in situ oceanic crust, 30°N Mid-Atlantic Ridge 査読有り Open Access

Michibayashi K., Hirose T., Nozaka T., Harigane Y., Escartin J., Delius H., Linek M., Ohara Y.

Earth and Planetary Science Letters 275 巻 ( 3-4 ) 頁： 348 - 354 2008年11月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Earth and Planetary Science Letters

Analysis of an in situ fault zone within the Atlantis Massif oceanic core complex (Mid-Atlantic Ridge) provides clues to the relevant deformation mechanisms and their temporal evolution within oceanic crust. IODP EXP304/305 drilled a succession of gabbroic lithologies to a final depth of 1415 m below the sea floor (mbsf), with very high recovery rates of up to 100% (generally ∼ 80%). We identified an intra-crustal fault zone between 720 and 780 mbsf in a section of massive gabbro, olivine gabbro, oxide gabbro units, and minor diabase intrusions. Of particular interest is the section between 744 and 750 mbsf, which unfortunately was marked by low recovery rates (17%). Electrical borehole-wall images show a 1-m-thick zone of east-dipping fractures within this interval, which is otherwise dominated by N-S dipping structures. Despite the high fracture density in this section, the hole walls are smooth, with rare breakouts, suggesting that the low recovery rate was due to a change in lithology rather than well conditions. The recovered rocks include ultracataclasite and possibly incohesive fault gouge that formed in the upper amphibolite regime, with mostly amphibole infill. Logging data suggest that the gabbroic rocks in this interval are rich in hydrous phases, consistent with increased amounts of amphibole found in the core. Equilibration temperature conditions of about 640 °C were obtained for plagioclase clasts and aluminous actinolite, assuming a pressure of 200 MPa. The permeability of the fault zone is in the range of 10- 19 to 10- 17 m2. Although the permeability appears to be high within the fault zone relative to other parts of the section, it is no higher than that in typical lower crustal material. As a consequence, because brittle failure occurred at high temperatures, the fault zone was subsequently completely sealed by hydrous minerals, thereby preventing further fluid circulation and preserving water in the crust. © 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.epsl.2008.08.033

Shearing within lower crust during progressive retrogression: Structural analysis of gabbroic rocks from the Godzilla Mullion, an oceanic core complex in the Parece Vela backarc basin 査読有り Open Access

Harigane Y., Michibayashi K., Ohara Y.

Tectonophysics 457 巻 ( 3-4 ) 頁： 183 - 196 2008年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tectonophysics

Microstructural and petrological analyses of gabbroic rocks sampled from the Godzilla Mullion, located along the Parece Vela Basin spreading ridge (Parece Vela Rift), Philippine Sea, reveal the development of a ductile shear zone in the lower crust. The shear zone is interpreted to represent a detachment fault within an oceanic core complex. Microstructures indicative of intense deformation, characterized by porphyroclastic textures consisting dominantly of coarse plagioclase porphyroclasts and lesser clinopyroxene porphyroclasts in a fine-grained matrix, are observed within samples of gabbroic rocks dredged near the breakaway area of the Godzilla Mullion (dredge site D6). Samples are classified into three types based upon the grain-size of fine-grained plagioclase in the matrix: coarse (80-130 μm), medium (25 μm), and fine (∼ 10 μm). Although the chemical composition of plagioclase porphyroclasts is consistently An 40-50 among all sample types, the compositions of fine grains in the matrix vary with decreasing grain-size, being An 40-50 for the coarse-type, An 30-40 for the medium-type, and An 5-30 for the fine-type. This finding implies that the composition of fine-grained plagioclase in the matrix is related to the following retrograde reaction that occurred during deformation: clinopyroxene + plagioclase + Fe-Ti oxide + fluid → hornblende + plagioclase. Plagioclase crystal-preferred orientations also show a gradual change with grain-size, varying from a (010)[100] pattern for the coarse-type, (010)[100] and (001)[100] patterns for the medium-type, and a weak (001)[100] pattern or random orientations for the fine-type. These patterns are interpreted to result from a change in the deformation mechanism of plagioclase from dislocation creep to grain-size-sensitive creep with decreasing temperature, thereby leading to strain softening and localization during cooling. Although secondary amphibole occurs ubiquitously within all samples, the chemical composition of amphibole varies from pargasitic hornblende (i.e. brown hornblende) to actinolite (i.e. green hornblende) within each of the sample types. However, amphibole in the coarse-type shows no evidence of deformation, whereas brown hornblende in the medium- and fine-types is plastically deformed. As a consequence, we argue that the microstructural development of the gabbroic rocks occurred during uplift-related cooling of the gabbro body and that a primary shear zone developed near the breakaway area at depth under anhydrous conditions at high temperatures above 850 °C; the shear zone subsequently evolved during progressive retrogression in association with hydration of the shear zone, possibly resulting in the development of the detachment fault that gave rise to the Godzilla Mullion. © 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tecto.2008.06.009

Undoped ZnO phosphor with high luminescence efficiency grown by thermal oxidation 査読有り国際共著

Xiao Zhiyan, Okada Morihro, Han Gui, Ichimiya Masayoshi, Michibayashi Katsuyoshi, Itoh Tadashi, Neo Yoichiro, Aoki Toru, Mimura Hidenori

JOURNAL OF APPLIED PHYSICS 104 巻 ( 7 ) 2008年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Applied Physics

Various ZnO morphologies with hexagonal cross sections were fabricated by a thermal oxidation method. Depending on the growth temperature, the lateral lengths of the hexagonal cross section varied from several hundred nanometers to the micrometer order. Comparing the cathodoluminescence (CL) of the synthesized ZnO to that of commercial ZnO:Zn phosphor revealed that a strong luminescence can be realized in undoped ZnO by fabricating one-dimensional structures. Specifically, in the micropyramid and towerlike structures, the CL intensity is locally concentrated near the hexagonal boundary. The enhanced green emission in these structures can be qualitatively explained by whispering gallery resonance modes produced in the hexagonal microcavity. © 2008 American Institute of Physics.

DOI： 10.1063/1.2990050

B-type olivine fabrics developed in the fore-arc side of the mantle wedge along a subducting slab 査読有り Open Access

Tasaka, M; Michibayashi, K; Mainprice, D

EARTH AND PLANETARY SCIENCE LETTERS 272 巻 ( 3-4 ) 頁： 747 - 757 2008年8月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Earth and Planetary Science Letters

B-type olivine fabrics are pervasive within highly depleted dunites of the small-sized Imono peridotite body located within the subduction-type Sanbagawa metamorphic belt of the southwest Japan arc. The dunites contain various microstructures, ranging from porphyroclastic to fine-grained intensely sheared textures. The Mg/(Mg + Fe) atomic ratios (Fo number) of olivine within these dunites are consistently around 0.9, as are the Cr/(Cr + Al) atomic ratios (Cr number) of chromian spinel, suggesting their evolution from a highly depleted magma (boninite). These data provide strong thermal constraints on the formation of the highly depleted dunites, as their formation requires hot, hydrous, shallow mantle (> 1250 °C at < 30 km depth) in the mantle wedge. Because the Sanbagawa metamorphic belt finally entrained these peridotites during progressive retrogression, B-type olivine fabrics probably developed in the fore-arc side of the subduction zone, above or along the subducting slab, possibly in association with dehydration fluids derived from the slab. The previously documented small magnitude of S-wave splitting can be explained by the seismic properties of B-type peridotites within an anisotropic layer of approximately several kilometers in thickness, oriented by flow parallel to the subducting slab, under maximum temperatures of 880-1030 °C depending on the flow stress. These findings indicate that such a B-type layer could constitute a dominant source of seismic S- and P-wave anisotropy in mantle wedge regions. © 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.epsl.2008.06.014

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