SIT04-01

会場:106

時間:5 月 27 日 15:15-15:30

高圧下の純粋剪断変形場におけるアンチゴライトの脱水反応と AE 挙動
Flow behaviors and AE activities during syndeformational antigorite dehydration at highpressures
岩里 拓弥 1 ; 久保 友明 1∗ ; 肥後 祐司 2 ; 加藤 工 1 ; 金嶋 聰 1 ; 上原 誠一郎 1 ; 丹下 慶範 2
IWASATO, Takuya1 ; KUBO, Tomoaki1∗ ; HIGO, Yuji2 ; KATO, Takumi1 ; KANESHIMA, Satoshi1 ;UEHARA, Seiichiro1 ; TANGE, Yoshinori2
1
1

九州大・理, 2 JASRI
Kyushu Univ., 2 JASRIIntermediate-depth earthquakes are seismic activities in Wadati-Benioff zone at depths from 60 km to 300 km, where subducting plates deform plastically rather than brittle failure. To understand the shear instability mechanisms above ˜2 GPa, there havebeen some acoustic emission (AE) measurements with multi-anvil apparatus (e.g., Jung et al., 2009; Gasc et al., 2011). However
in previous studies, the relationships among dehydration, plastic flow and shear instability were unclear because quantitative
flow data, reaction kinetics, and AE activities could not be obtained simultaneously. To conduct quantitative and simultaneous
measurements of these processes, we have carried out syndeformational antigorite dehydration experiments at high pressure.
High-pressure deformation experiments were conducted at 1-8 GPa, 300-1050 K, and strain rates of 3.4-7.4 x 10-5 s-1 in pure
shear using a 1500-ton uniaxial press (SPEED Mk. II) with a D-DIA type guide block installed at BL-04B1, SPring-8. 50 keV
monochromatic X-ray were used to measure reaction kinetics and stress-strain data. To monitor shear instabilities by detecting
AEs, six piezoelectric devices were positioned between first and second stage anvils of MA 6-6 type system. AE waveforms
were recorded in trigger mode using six-channel 8-bit digital oscilloscopes at a sampling rate of 50 MHz, and were analyzed todetermine 3D AE source location and AE magnitude. We used three kinds of starting materials (1.7 mm in diameter and 2.7
mm in length) of polycrystalline antigorite (Atg) , fine-grained forsterite (Fo) polycrystal, and two-phase mixtures of Atg and
San Carlos olivine (10%, 30%, and 50%Atg). The starting sample was first compressed at room temperature, then heated atconstant load, and finally deformed with constant strain-rate mode. In some experiments, dehydration occurred during heating
or deformation. Microstructures of recovered samples were preliminarily observed by optical microscopy.
Many AE events of relatively large amplitude were observed from Fo sample during cold compression stage at lower than 2
GPa. In contrast, almost no AEs were observed from Atg and 10-50% Atg samples during cold compression and heating stages.
Optical microscopic observations of recovered Atg samples from each stage revealed that some faults are generated during cold
compression stage, and fault slipping occurred during the heating stage. Creep behaviors of Atg samples during the deformation
stage indicate that flow stress reached steady state at the sample strain of more than 10%, and no stress drops were observed
until the final strain of 30-40%. These flow behaviors and flow strengths are almost similar to the previous study (Hilairet et al.,2007). Few AEs were recorded and additional faults were not observed from recovered sample during the deformation stage. We
observed dehydration of Atg and 10-50% Atg samples when increasing temperature from 673K to 1000K during deformation,
however we did not observe AEs during the syndeformational dehydration stage. Faults were absent in fully dehydrated samples.
Although more detailed microstructural observations are needed, these results suggest that syndeformational dehydration do notenhance shear instability of antigorite in pure shear at high pressure .

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SIT04-02

会場:106

時間:5 月 27 日 15:30-15:45

多結晶体の非弾性の実験的研究と上部マントル地震波構造への応用
Experimental study on polycrystal anelasticty with implications for upper mantle seismic
structure
武井 康子 1∗ ; 山内 初希 1
TAKEI, Yasuko1∗ ; YAMAUCHI, Hatsuki1
1
1

東京大学 地震研究所
Earthquake Research Institute, Univ. of Tokyo

Rock anelasticity causes dispersion and attenuation of seismic waves. Therefore, for the quantitative interpretation of seismic
low velocity and/or low Q regions in the upper mantle, understanding of rock anelasticity is necessary. Recent experimental
studies have shown that anelasticity of polycrystalline materials is subject to the Maxwell frequency fM scaling: Q−1 (f/fM ).
However, the applicability of this scaling to the seismic waves has not been guaranteed because experimental frequencies normalized to fM of the laboratory samples are usually much lower than the seismic frequencies normalized to fM in the upper
mantle (106 ≤ f/fM ≤ 109 ). In this study, by using polycrystalline organic borneol as an analogue to mantle rock, we measured
anelasticity up to f/fM ∼= 108 and found that the Maxwell frequency scaling is not fully applicable at f/fM >104 . A closer
examination of our data showed that each of the relaxation spectra obtained under various temperature, grain size, and chemicalcomposition can be represented by the superposition of a background dissipation which is subject to the Maxwell frequency
scaling and a peak dissipation which is always centered at f/fM = 103 . Significant increases of the peak amplitude and widthwith increasing temperature, grain size, and impurity (dyphenylamine) content result in failure of the Maxwell frequency scalingat f/fM >104 , where the peak dissipation dominates over the background dissipation. To quantitatively estimate the dispersion
and attenuation of seismic waves, it is important to understand the behavior of the peak dissipation.
The addition of impurity (diphenylamine) to borneol significantly reduces the melting (solidus) temperature from Tmelt = 477
K to Tmelt = 316 K. Therefore, we have speculated that the observed variation of the peak dissipation with impurity and temperature can be scaled by the normalized temperature T/Tmelt , such that the peak amplitude and width increase with increasing
T/Tmelt . The significant broadening of the peak observed near (but below) the solidus temperature (T/Tmelt = 0.93) means thatseismic velocity and Q are considerably lowered even without melt and has important implications for upper mantle seismic
structure. We further investigated the detailed behavior of the peak dissipation at near solidus temperatures (0.88 ≤ T/Tmelt ≤1.01), and found that the peak amplitude saturates at about T/Tmelt = 0.95, but that the peak width continuously increases up to
the supersolidus temperature T/Tmelt = 1.01. The obtained result was formulated in terms of the two nondimensional parameters
f/fM and T/Tmelt and preliminarily applied to the seismic waves in the upper mantle. The result shows that low V and low Q
occur at near solidus temperatures even without melt. At the onset of melting, seismic wave velocity shows a discrete reduction
due to the poroelastic effect of melt, but the seismic attenuation does not show a discontinuous change.

キーワード: 非弾性, 地震波減衰, 上部マントル
Keywords: anelasticity, seismic attenuation, upper mantle

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SIT04-03

会場:106

時間:5 月 28 日 12:00-12:15

Rheological transition during large strain deformation of melting and crystallizing metapelites
Rheological transition during large strain deformation of melting and crystallizing metapelites
MAINPRICE, David1∗
MAINPRICE, David1∗
1
1

Geosciences Montpellier, CNRS-UMR 5243, Universite de Montpellier , 34095 Montpellier, France
Geosciences Montpellier, CNRS-UMR 5243, Universite de Montpellier , 34095 Montpellier, France

Torsion experiments (strain-rate =3 x 10−4 s−1 ) were performed to investigate the large strain (γ 15) rheology on quartzmuscovite aggregate as analogue to pelitic rocks undergoing melting and crystallization during deformation at 300 MPa confining pressure and 750 ℃ temperature. Microstructures reveal four distinct but gradational stages of crystal-melt interactions
during deformation ; (a) solid state deformation, (b) initiation and domination of partial melting, (c) simultaneous partial melting
and crystallization, and (d) domination of crystallization. The microstructural stages are linked to the rheology of the deforming
samples. Partial melting starts at relatively low finite shear strains (γ=1 to 3) showing approximately 60% strain softening. At
γ=4 to 10 the partially molten bulk material shows a steady state flow at low stress. Further crystallization of new crystals at theexpense of melt between γ = 10 and 15 causes weak strain hardening until the material fails by developing brittle fractures. The
stress exponent (n), calculated at γ = 1, 5, and 10, increases from ∼ 3 to ∼ 43, indicating a transition from power to power law
breakdown or exponential flow of the bulk system. Hydrostatic experiments for equivalent times and conditions of the torsion
experiments were also conducted to evaluate the reaction kinetics and microstructures under static conditions. The new experimental data establish that partially molten rock does not flow according to a constant strain rate-dependent power law (steadystate) rheology. The rheological transition from strain rate sensitive to strain rate insensitive flow is interpreted as a function ofmelt-crystal ratio, their mutual interactions, and the evolution of microstructures in the partially molten rock. EBSD measurements reveal weak crystal preferred orientations, which are different for each mineral.
キーワード: Rheology, Deformation, Melting, Crystallization, Crystal preferred orientation, Localization
Keywords: Rheology, Deformation, Melting, Crystallization, Crystal preferred orientation, Localization

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SIT04-04

会場:106

時間:5 月 28 日 12:15-12:30

海洋プレート最上部マントル構造はマントルダイヤピルで形成される
The uppermost mantle structure in the oceanic plate induced by mantle diapir
道林 克禎 1∗ ; 尾上 彩佳 1 ; Mainprice David2 ; 小田島 庸浩 1
MICHIBAYASHI, Katsuyoshi1∗ ; ONOUE, Ayaka1 ; MAINPRICE, David2 ; ODASHIMA, Norihiro1
1
1

静岡大学・理・地球科学, 2 モンペリエ大学
Institute of Geosciences, Shizuoka University, Japan, 2 Geosciences Montpellier, Universite de Montpellier, FranceThis study presents results of microstructural analyses and crystallographic preferred orientations (CPOs) in order to clarify
characteristics of harzburgite in the Samail and Hilti mantle sections. The Samail peridotites of seven samples were collectedin the Maqsad area across the mantle diapir. The Hilti peridotites of thirteen samples were collected in the zone of the high-T
deformation near the paleo-Moho in the mantle section. Thus, we studied twenty samples in Oman ophiolite. Olivine CPOs
in the Samail samples are characterized by slightly strong point maximum of [010] and weak girdle distributions of [100] and[001]. Olivine CPOs in the Hilti samples are characterized by two types of the distributions: one type shows slightly strong point
maximum of [010] and weak girdle distributions of [100] and [001], and the other type is slightly strong point maximum of [010]and weak point distributions of [100] and [001]. The olivine fabrics have been used to be represented by fabric intencities of eachaxis such as pfJ so far. However, pfJ does not necessarily reflect olivine fabrics of their whole axes and it strongly depends on astereographic distribution. Moreover, AG-type has various patterns of distributions in both a-axis and c-axis, so that it is difficult
to classify AG-type by any previous methods. In this study, we prefer to classify olivine CPO patterns using Vp-Flinn diagram.
It shows that both Samail and Hilti samples are almost identical each other and in the VP-Flinn diagram that olivine fabrics could
be classified into three types: 1) A-type like fabric, 2) AG-type like fabric and 3) low Vp anisotropy AG-type like fabric. Grainboundaries have different characteristics between them; the Samail samples showed regular grain boundaries, whereas the Hilti
samples showed irregular grain boundaries. It is likely that the temperature in the Oman ophiolite would have been the highest
in the mantle diaper beneath the ridge axis and therefore its solidus line could be deeper as moving away from the ridge axis.
Therefore, the difference of grain boundary geometries may result from a temperature change in the vicinity of the mantle diapir
from vertical flow to subhorizontal flow. The olivine grain sizes are almost constant regardless of their CPO patterns and arein the same range between 0.6 and 2.1 mm in both the Samail and the Hilti samples. It shows that the Hilti samples may haveexperienced only a small horizontal strain that is not enough to change olivine CPOs except a weak grain size reduction due todynamic recrystallization. As a consequence, the olivine CPOs could have been formed in the mantle diapir and preserved evenin the horizontal structure away from the mantle diapir. The olivine fabric could have been formed by melt effects like MORB in
the mantle diaper or diffusion creep.
Keywords: olivine fabrics, lithosphere, uppermost mantle, mantle diapir

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SIT04-05

会場:106

時間:5 月 28 日 12:30-12:45

島弧の沈み込み量の推定
Supply rate of continental materials by subduction of island arcs
市川 浩樹 1∗ ; 河合 研志 3 ; 山本 伸次 3 ; 亀山 真典 1
ICHIKAWA, Hiroki1∗ ; KAWAI, Kenji3 ; YAMAMOTO, Shinji3 ; KAMEYAMA, Masanori1
1

愛媛大学 地球深部ダイナミクス研究センター, 2 東京工業大学 地球生命研究所, 3 東京大学 総合文化研究科
Geodynamics Research Center, Ehime University, 2 Earth-Life Science Institute, Tokyo Institute of Technology, 3 Graduate
School of Arts and Sciences, The University of Tokyo1

Evolution of life on the Earth is strongly related to the oceans and the continents, both of which are unique to the Earth.
Continental materials contain a large amount of incompatible and radiogenic elements, which may affect terrestrial thermal
history and chemical evolution, as well as the Earth’s surface environment. Geological studies have revealed that continental
materials subduct from the Earth’s surface via the following three mechanisms: tectonic erosion, sediment subduction, anddirect subduction of immature oceanic arcs, which are found, for example, in the western Pacific. In the first two processes, thecontinental materials are conveyed through subduction channels of thickness of 2-3km just above the subducting slabs. Here,in order to estimate the supply rate of continental materials of oceanic arcs to the deep mantle, we have conducted numericalsimulations of subduction of arcs based on the finite element method, using relevant rheology models. The results show that the
subduction rate highly depends on temperature profiles of the subducting slabs and the size of the arcs.
キーワード: 大陸地殻, 島弧, マントル, 沈み込み, レオロジー
Keywords: continental crust, island arc, mantle, subduction, rheology

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SIT04-06

会場:106

時間:5 月 28 日 14:15-14:30

Anisotropic viscosity of olivine aggregates: A laboratory, field, and numerical approach
Anisotropic viscosity of olivine aggregates: A laboratory, field, and numerical approach
Hansen Lars N.1∗ ; CONRAD Clinton2 ; WARREN Jessica3 ; KOHLSTEDT David4
HANSEN, Lars N.1∗ ; CONRAD, Clinton2 ; WARREN, Jessica3 ; KOHLSTEDT, David4
1
1

University of Oxford, 2 University of Hawaii, 3 Stanford University, 4 University of Minnesota
University of Oxford, 2 University of Hawaii, 3 Stanford University, 4 University of Minnesota

Shearing of mantle rocks within Earth’s lithosphere and asthenosphere causes mantle minerals, particularly olivine, to develop
crystallographic textures that can be detected seismically. In laboratory studies, such crystallographic textures have also been
associated with dependence of the viscosity of a mineral on the orientation of an applied stress. This anisotropic viscosity
may affect tectonic plate motions and the stability of the lithospheric base, but it is highly dependent on 1) the rate of fabricdevelopment and 2) the poorly constrained viscosity tensor, which relates the stress applied to an olivine crystal of known
orientation to the resulting strain-rate.
Here we constrain the importance of viscous anisotropy in the upper mantle using deformation experiments conducted in a
gas-medium apparatus. Olivine aggregates were deformed at a temperature of 1200 ⁰ C and a confining pressure of 300 MPa.
One set of samples was initially deformed in torsion and subsequently deformed in tension. A second set of samples was initiallydeformed in tension and subsequently deformed in torsion. Torsion experiments reached a maximum shear strain of ˜20. This
combination of strain paths allowed us to quantify the effect of evolving crystallographic texture on multiple components of theviscosity tensor.
We developed a micromechanical model that allows estimation of the complete viscosity tensor based on a measured texture
and a single-crystal viscosity tensor. We then used the laboratory-derived mechanical data in conjunction with this model to invert
for the values of the single-crystal viscosity tensor. We developed a second, independent model of olivine textural developmentthat takes into account the strength of individual slip systems yet is stable to high strains. We calibrate this texture modelthrough comparison to the strengths and shapes of measured textures in experimental samples. Together, these two calibrated
models allow us to constrain both the rate of texture development in an arbitrary deformation geometry and also the resulting
macroscopic viscosity tensor. Our results indicate that olivine textural development can yield viscosities that vary by over anorder of magnitude depending on the orientation of the applied stress relative to the dominant crystallographic texture.
We tested our mechanical and textural evolution model through comparison to natural peridotite shear zones exposed in theJosephine Peridotite. We find that (1) the natural textural development is well approximated by our numerical model and (2) asignificant portion of the strain localization can be attributed to the development of viscous anisotropy.
キーワード: rheology, olivine, crystallographic preferred orientation, viscosity, rock deformation, shear zones
Keywords: rheology, olivine, crystallographic preferred orientation, viscosity, rock deformation, shear zones

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SIT04-07

会場:106

時間:5 月 28 日 14:30-14:45

含水かんらん石多結晶体の変形と組織発達
Evolution of the rheological and microstructural properties of olivine aggregates duringdislocation creep under hydrous
田阪 美樹 1∗ ; Zimmerman Mark1 ; Kohlstedt David1
TASAKA, Miki1∗ ; ZIMMERMAN, Mark1 ; KOHLSTEDT, David1
1
1

ミネソタ大学
University of Minnesota

Since hydrogen plays an important role in dynamic processes in the mantle, we conducted high-strain torsion experiments on
Fe-bearing olivine aggregates under hydrous conditions. Most of the samples deformed homogeneously to total shear strains of
up to γ ≈ 5. We deformed samples to high enough strain that a steady-state microstructure was achieved, in order to investigate
the evolution of the rheological and microstructural properties. The stress exponent of n ≈ 3 and the grain size exponent of p
≈ 0 determined from the fitting of strain rate, stress, and grain size data indicates that these samples deformed by dislocation
creep. Fourier transform infrared (FTIR) measurements of an imbedded olivine single crystal demonstrated that our samples
were saturated with hydrogen during the deformation experiments. The crystallographic preferred orientation (CPO) of theolivine aggregates changed as a function of strain due to competition among the three slip systems (010)[100], (100)[001], and(001)[100]. The observed strain weakening that occurs early in each experiment is to geometrical softening associated with
development of a CPO, which reduces the stress by 36% in constant strain rate experiments. The evolution of the rheologicaland microstructural properties observed in our experiments is important for understanding dynamic evolution of Earth’s mantle
under hydrous conditions.
Keywords: olivine, deformation, high-strain torsion experiment, hydrous conditions, mantle

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SIT04-08

会場:106

時間:5 月 28 日 14:45-15:00

オリビン多結晶体の合成と高温クリープ実験
Synthesis and deformation experiments on polycrystalline olivine
谷部 功将 1∗ ; 平賀 岳彦 1
YABE, Kosuke1∗ ; HIRAGA, Takehiko1
1
1

東京大学地震研究所
Earthquake Research Institute, The University of Tokyo

マントル対流やアセノスフェアの成因を理解する上で、上部マントルの流動特性を決定することは非常に重要である。
これまで、天然で産出したオリビンから作製されたオリビン多結晶体を用いて高温変形実験により、オリビン多結晶体の流動特性に対する温度、粒径、応力依存性や水やメルトによる効果が調べられ、上部マントルの理解が進んできた(Karato et al 1986, Hirth and Kohlstedt 1995, Hirth and Kohlstedt 2003)。しかしながら、Faul and Jackson (2007) が、試薬からゾル・ゲル法で人工的に合成したオリビン多結晶体が天然由来のオリビンよりも粘性率にして 1 ˜2 桁固いことを報告
し、オリビン多結晶体の流動則が確立されていないことが明らかになった。そこで、本研究では第三の手法を用いてオ
リビン多結晶体の合成を行い、変形実験によってその流動特性を調べた。また、先行研究の固さの違いの原因と推測される、微量な不純物を含んだオリビン多結晶体の合成と変形実験を行い、添加物が流動特性に与える影響を調べた。
試料作製には、高純度かつ細粒 (<100 nm) の試薬を用いて細粒な鉱物粉末を合成し、それを真空で焼結するという手法を用いた (Koizumi et al 2010)。その中で、鉄源としての原料粉の種類の最適化と、酸素分圧制御手法の開発をおこなった。添加物を含まない試料と、0.1wt%の Al2O3、CaO、NiO、TiO2 をそれぞれ含む試料を作製した。それぞれについて
変形実験を行ったところ、拡散クリープ条件下では添加物による大きな流動特性の変化は見られなかった。また、本研究の試料の固さは Faul and Jackson (2007) の人工的に合成されたオリビン多結晶体の固さと一致した。したがって、本研
究で添加した不純物以外にオリビン多結晶体の流動特性を大きく変化させる化学種が存在することが示唆される。

キーワード: オリビン多結晶体の合成, 高温変形実験
Keywords: Synthesis of polycrystalline olivine, High-temperature deformation experiments

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SIT04-09

会場:106

時間:5 月 28 日 15:00-15:15

In situ deformation of eclogite at high pressure and temperature
In situ deformation of eclogite at high pressure and temperature
FARLA, Robert1∗ ; ROSENTHAL, Anja1 ; PETITGIRARD, Sylvain1 ; BOLLINGER, Caroline1 ;KAWAZOE, Takaaki1 ; FROST, Daniel1
FARLA, Robert1∗ ; ROSENTHAL, Anja1 ; PETITGIRARD, Sylvain1 ; BOLLINGER, Caroline1 ;KAWAZOE, Takaaki1 ; FROST, Daniel111Bayerisches Geoinstitut, Universitat Bayreuth, Universitats str. 30, 95447 Bayreuth, Germany
Bayerisches Geoinstitut, Universitat Bayreuth, Universitats str. 30, 95447 Bayreuth, Germany

Little is known about the physical behaviour of heterogeneous, rheological contrasting rocks in the Earth’s mantle and theirimpact on mantle processes. Understanding of the stress/strain partitioning, microstructural evolution, and seismic signatures inbimineralic eclogites provide crucial information for transport modeling of these dense materials into and out of the deep Earth.
For example, heterogeneity in the peridotite-dominated mantle may develop via a variety of processes such as entrainment andmixing of discrete eclogite bodies from subducted slabs or from detachment of deep continental roots into the convecting mantle.
Exhumed eclogitic bodies are characterized by intense foliation and strain localization and strong shape- and crystallographic
preferred orientations. In this preliminary study we used synchrotron X-ray diffraction at the ID06 beamline at ESRF to estimate
the stresses in situ on a deforming bimineralic eclogite (˜40% garnet and ˜60% clinopyroxene) and a dunite (100% olivine)
at 5 GPa and a range of temperatures (1473 - 1673 K), i.e. at subsolidus conditions. The starting material was prepared asa residual eclogite after extraction of ˜46 wt% melt from GA2 eclogite (Spandler et al. , 2008, J Petrology 49, 771-795) andwas pre-sintered at 5 GPa and 1673 K using a multi anvil apparatus. The run products yield well-equilibrated sub-/euhedral
crystals of garnet and tabular crystals of clinopyroxene with average grain sizes of <30 µm. Coesite was present only as multiple
small, rounded inclusions in garnet. The compressive deformation experiments were carried out at constant strain rates of 10−6
to 10−5 s−1 to axial strains of 5 to 30% on a stack comprising the pre-sintered bimineralic eclogite sample above a pure San
Carlos olivine sample (as a reference). The cylindrical samples have dimensions of 1.2 mm in diameter by 1.5 mm in lengthand are separated by metal foils (e.g. Re) acting as strain markers visible in radiographic images. The deviatoric stresses aretransmitted via hard alumina pistons above and below the sample stack. Furthermore, the samples are surrounded by a boron
nitride sleeve and graphite resistance heater and the cubic pressure medium is made of boron epoxy, which is transparent tosynchrotron X-rays. We expect results on the strength partitioning between garnet and pyroxene in a residual bimineralic eclogite
and between the eclogite and the dunite deformed under conditions applicable to the upper mantle. Complementary information
on crystallographic preferred orientation development of garnet and clinopyroxene in eclogite, and of olivine in dunite will giveinsight into the deformation mechanisms and interpretation of fast seismic wave propagation directions and anisotropy relative
to the prevalent stress direction. The data will be compared against natural field and seismic observations and offer insight into
deep crustal seismic reflectors seen in regions of intense deformation.
キーワード: two-phase deformation, eclogite rheology, in situ X-ray diffraction, mantle heterogeneity
Keywords: two-phase deformation, eclogite rheology, in situ X-ray diffraction, mantle heterogeneity

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SIT04-10

会場:106

時間:5 月 28 日 15:15-15:30

上部マントルの流動を支配する粒界すべり
Grain boundary sliding as the major deformation mechanism of olivine in Earth’s upper
mantle大内 智博 1∗ ; 川添 貴章 2 ; 肥後 祐司 3 ; 舟越 賢一 4 ; 鈴木 昭夫 5 ; 亀卦川 卓美 6 ; 入舩 徹男 1
OHUCHI, Tomohiro1∗ ; KAWAZOE, Takaaki2 ; HIGO, Yuji3 ; FUNAKOSHI, Ken-ichi4 ; SUZUKI, Akio5 ;KIKEGAWA, Takumi6 ; IRIFUNE, Tetsuo1
1

愛媛大学地球深部ダイナミクス研究センター, 2 バイロイト大学地球科学研究所, 3 高輝度光科学研究センター, 4 総合科学研究機構, 5 東北大学大学院地学専攻, 6 高エネルギー加速器研究機構
1
Geodynamics Research Center, Ehime University, 2 Bayerisches Geoinstitut, University of Bayreuth, 3 Japan Synchrotron Radiation Institute, 4 Research Center for Neutron Science and Technology, 5 Graduate School of Science, Tohoku University, 6 HighEnergy Accelerator Research Organization

Anisotropic propagation of seismic waves have been observed in the Earth’s upper mantle, which is attributed to the crystallographic preferred orientation of olivine associated with mantle dynamics. The most likely deformation mechanism of olivinethat explains the observed seismic anisotropy has been considered to be dislocation creep (e.g., Karato et al, 1986). Diffusion
creep may also partly contribute to the deformation of olivine in the upper mantle, while another possible mechanism, grainboundary sliding, has been thought to play only minor roles in some limited circumstances such as in melt-bearing rocks or finegrained rocks (Hirth and Kohlstedt, 1995; Hiraga et al., 2010). Hansen et al. (2011) proposed that the dislocation-accommodated
grain boundary sliding (DisGBS) may dominate the upper mantle flow, based on deformation experiments for olivine at a pressure of 0.3 GPa and temperatures to 1523 K. Development of crystallographic preferred orientation (CPO) of olivine through
DisGBS-controlled creep is so significant (Hansen et al., 2012) that this would be a potentially important deformation mechanism
controlling the upper mantle flow. Nevertheless, most of experimental investigations on the deformation mechanism of olivine
have been limited to the pressures below 0.5 GPa, which are lower than those in the actual upper mantle.
We conducted uniaxial deformation experiments on olivine aggregates with a composition of Mg1.8 Fe0.2 SiO4 at pressures
1.5-6.7 GPa and at temperatures 1273-1473 K with strain rates of 0.3-7.2∗10−5 s−1 using a deformation-DIA apparatus. The
averaged values of stress exponent, activation energy, and activation volume were obtained to be 3.0, 423 kJ/mol, and 17.7
cm3 /mol, respectively. The obtained parameters supports the deformation of water-poor olivine controlled by DisGBS. A significant water-fugacity dependency of creep strength of olivine on water fugacity was observed, and the water fugacity exponent was
obtained to be 1.25. The dependency of creep strength of olivine controlled by DisGBS on pressure is weak due to competingthe pressure-hardening effect of activation volume and the pressure-softening effect of water fugacity. Because creep strengthof olivine controlled by the grain boundary sliding is insensitive to pressure, the estimated viscosity of water-poor olivine isindependent of depth and is in a range of 1020 -1021.5 Pa s throughout the upper mantle, which is consistent with geophysicallyobserved viscosity profiles. Viscosity of the deep upper mantle would be overestimated by ˜10-104 times if we assume the conventional dislocation creep mechanism for water-poor olivine.
Keywords: grain boundary sliding, olivine, upper mantle, pressure, water, viscosity

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SIT04-11

会場:106

時間:5 月 28 日 15:30-15:45

拡散クリープにおける１粒子スケールから複数粒子スケールでの変形
Observations of grain- to multi-grain-scale deformation of mineral aggregates deformedby diffusion creep
丸山 玄太 1 ; 平賀 岳彦 1∗
MARUYAMA, Genta1 ; HIRAGA, Takehiko1∗
1
1

東京大学
The University of Tokyo

We deformed cylindrical polycrystalline samples of synthesized forsterite + diopside and anorthite mineral aggregates at its
diffusion creep regime. We polished the lateral side of the sample where we imposed grooves parallel to the compression axisof the sample using a focused ion beam. These marker lines allow us to observe fine-scale deformation of the sample. Afterthe high temperature one atmosphere compression creep experiment, we observed the sample surface with marker lines underscanning electron microscope.
Strains of bulk sample and of the marker line exhibited the similar values indicating that the similar deformation proceededboth at bulk and surface regions of the samples. Grain rotation, which was identified by misfits of the markers at grain boundaries
and rotation of intra-granular markers, were frequently observed in all the samples. No distortion of the markers within the grains
was found indicating the absence of intragranular deformation process such as a glide of dislocations; however, in the samples
deformed at high stress (˜300 MPa), curved intra-granular markers were observed, which is consistent with dislocation activity athigh stress condition. The changes in grain configuration were also observed elsewhere in the samples demonstrating significant
operation of grain boundary sliding which produced grain switching. Grain rotations were controlled by the orientation of longflat crystallography-controlled grain boundaries with respect to the compressional direction. Such grain rotation resulted in asignificant development of crystallographic preferred orientation in the samples.

キーワード: 拡散クリープ, 鉱物
Keywords: diffusion creep, mineral

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SIT04-12

会場:106

時間:5 月 28 日 15:45-16:00

高圧下でのフォルステライト反応帯の組織と成長カイネティクス
Microstructure and growth-kinetics of forsterite reaction rim under high pressure
西原 遊 1∗ ; 丸山 玄太 2NISHIHARA, Yu1∗ ; MARUYAMA, Genta2
1
1

愛媛大学地球深部ダイナミクス研究センター, 2 東京大学地震研究所
Geodynamics Research Center, Ehime University, 2 Earthquake Research Institute, University of Tokyo

Since many transport properties, such as rheology, highly depend on grain-size of the constituent materials, knowledge ofgrain-growth is important for accurate understanding of dynamics in the Earth’s mantle. Tasaka and Hiraga (2013) showed thatgrain-growth in forsterite-enstatite two-phase system is rate-limited by growth of secondary phase through Mg-O grain-boundary
diffusion in primary phase. In this study, we have experimentally studied growth-kinetics of forsterite (Mg2 SiO4 ) reaction rim
at deep upper mantle conditions which is controlled by Mg-O grain-boundary diffusion in forsterite. Based on the experimental
results, depth dependence of grain-growth in the upper mantle is discussed.
Experiments were carried out using multi-anvil apparatus installed at GRC, Ehime University, Japan. The starting materials,
MgO (single crystal) and MgSiO3 (powder or aggregate), were packed in Pt capsule. The annealing experiments were conducted
at pressure of 3.0-11.1 GPa and temperature of 1473-1873 K for duration of 0-780 min. Recovered samples were analyzed by
SEM or FE-SEM for microstructural observation and by FT-IR to examine water content.
Water content in MgO single crystal in the recovered samples was relatively low and 6.9 wt ppm H2 O at the maximum. The Pt
marker, which was originally placed at MgO-MgSiO3 boundary, was always on MgO-Mg2 SiO4 boundary indicating that Mg-O
diffusion in Mg2 SiO4 is the rate-limiting process in the rim growth. MgSiO3 inclusions were found in Mg2 SiO4 grains suggesting
the grain-boundary diffusion is rate-limiting. Based on the analysis using equation for reaction-rim growth rate-limited by grainboundary diffusion (Gardes and Heinrich, 2011), the activation energy and the activation volume were determined to be 375
kJ/mol and -2.1 cm3 /mol, respectively. Although reason for the small negative value of the activation volume is not quite clear,this may be due to successive structural change of grain-boundary. The results suggest that the grain-growth in the Earth’s upper
mantle is faster at deeper part.
キーワード: 上部マントル, 原子拡散, カンラン石, フォルステライト, 粒成長, レオロジー
Keywords: Upper mantle, Element diffusion, Olivine, Forsterite, Grain-growth, Rheology

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SIT04-13

会場:106

時間:5 月 28 日 16:15-16:30

In situ creep strength measurement on ringwoodite up to 1700 K at 17-18 GPa using a
deformation-DIA apparatus
In situ creep strength measurement on ringwoodite up to 1700 K at 17-18 GPa using a
deformation-DIA apparatus
KAWAZOE, Takaaki1∗ ; NISHIHARA, Yu2 ; OHUCHI, Tomohiro2 ; MARUYAMA, Genta3 ; HIGO, Yuji4 ;FUNAKOSHI, Ken-ichi5 ; IRIFUNE, Tetsuo2
KAWAZOE, Takaaki1∗ ; NISHIHARA, Yu2 ; OHUCHI, Tomohiro2 ; MARUYAMA, Genta3 ; HIGO, Yuji4 ;FUNAKOSHI, Ken-ichi5 ; IRIFUNE, Tetsuo2
1

Bayerisches Geoinstitut, University of Bayreuth, Bayreuth D-95440, Germany, 2 Geodynamics Research Center, Ehime University, Ehime 790-8577, Japan, 3 Earthquake Research Institute, University of Tokyo 113-0032, Japan, 4 Japan Synchrotron
Research Institute, Hyogo 679-5198, Japan, 5 Research Center for Neutron Science and Technology, Ibaraki 319-1906, Japan
1
Bayerisches Geoinstitut, University of Bayreuth, Bayreuth D-95440, Germany, 2 Geodynamics Research Center, Ehime University, Ehime 790-8577, Japan, 3 Earthquake Research Institute, University of Tokyo 113-0032, Japan, 4 Japan Synchrotron
Research Institute, Hyogo 679-5198, Japan, 5 Research Center for Neutron Science and Technology, Ibaraki 319-1906, Japan
Deformation experiments on polycrystalline (Mg0.9 ,Fe0.1 )2 SiO4 ringwoodite have been conducted in uniaxial geometry up to
strains of 15.5 % at 17.3-17.9 GPa, 1500-1700 K and strain rates of 3.46-3.59 × 10−5 s−1 using a deformation-DIA apparatus
at the synchrotron facility SPring-8. Stress magnitude was measured from azimuthal dependence of three diffraction peaks ofringwoodite (220, 311 and 400) by two-dimensional X-ray diffraction. Strain was calculated from X-ray radiographs of strain
markers. Stress magnitude of ringwoodite at steady-state deformation, i.e. creep strength, was 400 MPa at 1500 K. The creep
strength decreased to 130 MPa with increasing temperature to 1700 K. The creep strengths of this study are lower than those (4-6GPa) observed at 3-10 GPa and room temperature using a deformation-DIA apparatus (Nishiyama et al., 2005) and those (1.7-2.8
GPa) determined at 21-23 GPa and 1800 K using a rotational Drickamer apparatus (Hustoft et al., 2013; Miyagi et al., 2014).
Further deformation experiments and subsequent sample analyses should be performed to determine flow laws of ringwoodite
and in turn to discuss viscosity at the lower part of the mantle transition zone.
キーワード: ringwoodite, creep strength, stress, strain, deformation-DIA apparatus, synchrotron X-ray
Keywords: ringwoodite, creep strength, stress, strain, deformation-DIA apparatus, synchrotron X-ray

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SIT04-14

会場:106

時間:5 月 28 日 16:30-16:45

Si and O self-diffusion in stishovite
Si and O self-diffusion in stishovite
XU, Fang1∗ ; YAMAZAKI, Daisuke1 ; SAKAMOTO, Naoya2 ; YURIMOTO, Hisayoshi2
XU, Fang1∗ ; YAMAZAKI, Daisuke1 ; SAKAMOTO, Naoya2 ; YURIMOTO, Hisayoshi2
1
1

ISEI, Okayama University, 2 Isotope Imaging Laboratory, Hokkaido University
ISEI, Okayama University, 2 Isotope Imaging Laboratory, Hokkaido University

Seismological studies revealed the seismic reflectors in the lower mantle at the depth from 900 to 1850 km (e.g., Kaneshima
and Hellfrich, 1999; Niu et al., 2001; Castle and Creager, 1999). These reflectors are interpreted as pieces of subducted ancient
oceanic crust (Kaneshima and Hellfrich, 1999), indicating the high viscous oceanic crust to inhibit the deformation duringsubduction and further mixing with the lower mantle. At lower mantle depth, stishovite is as much as 20 % in the basaltic
composition and 40 % in the sedimental rocks (Irifune and Ringwood, 1993; Ono et al., 2001; Irifune et al., 1994). Therefore,
the viscosity of stishovite may be one of the key parameter to constrain the viscosity of the ancient oceanic crust in the lower
mantle. Viscosity of solid is thought to be controlled by diffusion of the constituting elements. To know the viscosity of stishovite,thus, diffusivity of Si and O was studied by means of high pressure experiments in this study.
Single crystals of stishovite (˜500 µm in size) were synthesized at 12 GPa in a Kawai-type high pressure apparatus by slowcooling method (Shatskiy et al., 2010). The polished {110} surfaces were coated with ˜150 nm 29 Si and 18 O enriched SiO2
layer in a high-vacuum thermal evaporator. The coated crystals were again compressed at 14-21.5 GPa and 1673-2073 K in
the Kawai-type apparatus for diffusion. The recovered samples were measured by secondary ion mass spectroscopy (SIMS) to
obtain diffusion profiles by the depth profile method. The obtained profiles were fitted to semi-infinite diffusion model and thefitting results were ∆ E , ∆ V and logD0 to be 178.6±4.4 kJ/mol, 6.0±0.2 cm3 /mol and -12.9±0.14 m2 /s, respectively, for Si
diffusion, and 262.7 kJ/mol, 5.0±1.6 cm3 /mol and -10.1 m2 /s, respectively, for O diffusion, where ∆ E , ∆ V and D0 are theactivation enthalpy, activation volume and pre-exponential factor, respectively.
Our results show that Si diffusion in stishovite is slower than O under mantle conditions and hence the deformation of stishovite
is controlled by Si diffusion. The diffusivity of Si in stishovite is ˜3 orders of magnitude smaller than that in wadsleyite and garnet(Shimojuku et al., 2009, 2013), ˜4 orders of magnitude smaller than that in ringwoodite (Shimojuku et al., 2009) and perovskite(Yamazaki et al., 2000). We can conclude that stishovite is the hardest mineral among the main mantle minerals. The survivalof the subducted slab observed as seismic reflector at the lower mantle might be supported by the significantly high viscousstishovite.
キーワード: stishovite, diffusion, viscosity, subducted oceanic crust
Keywords: stishovite, diffusion, viscosity, subducted oceanic crust

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SIT04-15

会場:106

時間:5 月 28 日 16:45-17:00

Development of a rotational Drickamer apparatus (RDA)
Development of a rotational Drickamer apparatus (RDA)
KARATO, Shun-ichiro1∗
KARATO, Shun-ichiro1∗
1
1

Yale University, Department of Geology & Geophysics
Yale University, Department of Geology & Geophysics

Many major developments in the study of deformation of Earth materials occurred based on the developments of new techniques. They include the contributions from UCLA lab (Griggs) based on the development of a solid-medium deformation
apparatus, and the contributions from ANU lab (Paterson) based on the development of a high-resolution (but low pressure)
deformation apparatus. Surprisingly (or embarrassingly), there was a large hiatus in the development of new technology between
˜1980 and ˜2000 and until very recently reliable experimental results on rheological properties were limited to ˜0.3 GPa (˜10 km).
Recognizing this, a group of scientists in USA started a serious effort of developing new techniques of quantitative deformation
experiments. The developments include the design and operation of new types of deformation apparatus and the developmentof synchrotron-based techniques of measuring stress and strain. In this presentation, I will review the development of RDA(rotational Drickamer apparatus) and a theory of stress measurements performed in my lab. The advantage of RDA include (i)the capability of conducting high-P (and T) deformation experiments (compared to D-DIA), and (ii) the capability of large-strain
deformation experiments. A brief description of RDA deformation experiments and some recent results will be presented including the results of deformation of a mixture of bridgmanite + ferro-periclase at the lower mantle conditions.

キーワード: high pressure, deformation experiments, synchrotron facility, lower mantle, RDA
Keywords: high pressure, deformation experiments, synchrotron facility, lower mantle, RDA

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SIT04-16

会場:106

時間:5 月 28 日 17:00-17:15

Dislocation mobility in ringwoodite as a function of temperature and water content
Dislocation mobility in ringwoodite as a function of temperature and water content
FEI, Hongzhan1∗ ; YAMAZAKI, Daisuke1 ; OHFUJI, Hiroaki2 ; YAMAMOTO, Takafumi3
FEI, Hongzhan1∗ ; YAMAZAKI, Daisuke1 ; OHFUJI, Hiroaki2 ; YAMAMOTO, Takafumi3
1

Institute for Study of the Earth Interior, Okayama University, Misasa, Tottori, 682-0193, Japan, 2 Geodynamics Research Center,
Ehime University, Matsuyama, 790-8577, Japan, 3 Department of Earth and Planetary Systems Science, Hiroshima University,
Hiroshima, 739-8526, Japan
1
Institute for Study of the Earth Interior, Okayama University, Misasa, Tottori, 682-0193, Japan, 2 Geodynamics Research Center,
Ehime University, Matsuyama, 790-8577, Japan, 3 Department of Earth and Planetary Systems Science, Hiroshima University,
Hiroshima, 739-8526, Japan
Ringwoodite is the dominant mineral in the lower part of the Earth’s mantle transition zone from 520 to 670 km depth.
Understanding the creep properties of ringwoodite is thus essential to know the geodynamical process at this depth. Dislocation
creep, which could cause seismic anisotropy and non-Newtonian viscosity, is an important creep mechanism for high temperatureplastic deformation of minerals. Since the dislocation creep rate is controlled by the mobility of dislocations, we measured thedislocation mobility in ringwoodite single crystals as a function of temperature and water content under the mantle transitionzone conditions.
The ringwoodite single crystals were synthesized from natural olivine at 1800 K and 22 GPa in a multi-anvil apparatus. The
crystals were deformed after synthesization by increasing the load to create high density dislocations. The deformed crystals
were surrounded by CsCl and annealed at 22 GPa, 1600-2000 K for dislocation recovery. The water contents in the crystals were
measured by Fourier transform infrared, the dislocation densities before and after recovery were determined by transmission
electron microscopy, and the dislocation mobility were calculated from the dislocation densities and annealing durations.
The activation enthalpy for dislocation mobility is 360±90 kJ/mol. This value is much lower than that for Si diffusion (480±90kJ/mol), but similar to that for O diffusion (370±80 kJ/mol) (Shimojuku et al., 2009). It is probably because the dislocation
movement in ringwoodite is controlled by both Si and O due to their similar diffusion rates (less than 0.5 orders of magnitudedifference, Shimojuku et al., 2009). Temporary results suggest that the water content exponent for the dislocation mobility
in ringwoodite is about 1.1(±0.9). Namely, in contrast with olivine (Fei et al., 2013; 2014), water may have large effect on
ringwoodite rheology. But more experimental data are required for precise determination of the water content exponent.
Shimojuku et al. (2009), EPSL 284, 103-112.
Fei et al. (2013), Nature 498, 213-215.
Fei et al. (2014), JGR 119, 7598-7606.

キーワード: ringwoodite, dislocation mobility, recovery, water content
Keywords: ringwoodite, dislocation mobility, recovery, water content

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SIT04-17

会場:106

時間:5 月 28 日 17:15-17:30

ブリッジマナイトのその場応力-歪同時測定のための予備的変形実験
Preliminary deformation experiments for in-situ stress-strain measurements of bridgmanite
辻野 典秀 1∗ ; 山崎 大輔 1 ; 芳野 極 1 ; 櫻井 萌 2 ; XU Fang1 ; 肥後 祐司 3
TSUJINO, Noriyoshi1∗ ; YAMAZAKI, Daisuke1 ; YOSHINO, Takashi1 ; SAKURAI, Moe2 ; XU, Fang1 ;HIGO, Yuji31
1

岡山大学 地球物質科学研究センター, 2 東京工業大学
ISEI, Okayama Univ., 2 Tokyo Institute of Tech., 3 JASRI

地球惑星科学専攻, 3 高輝度光科学研究センター

In order to discuss mantle dynamics in the Earth’s interior, knowledge of viscosity of the Earth’s lower mantle, which is thehighest of the whole mantle, is important. Viscosity models of the Earth’s lower mantle were reported by geophysical observations. However, observation values of viscosity have large variety (2˜3 order magnitude). Although determination of viscosityof lower mantle minerals by high pressure experiments is needed to understand mantle dynamics, stress-strain relationship forbridgmanite, which are principal minerals of the Earth’s lower mantle, are not reported due to difficulty of high pressure deformation experiments. In this study, we tried in-situ stress-strain measurements of Mg-Pv at 27 GPa.
In-situ uniaxial deformation experiments were conducted using MADONNA, which is D-DIA apparatus, as Kawai-type apparatus at SPring-8 BL04B1. Experimental conditions are 27.3 GPa, 1473 K estimated by equation of state on bridgmanite(Katsura et al., 2009). WC anvils with slit or corn (5o ) to take tomography and 2D X-ray diffraction, was used along X-ray path.
Two-dimensional X?ray diffraction patterns were taken for 300 s using CCD detector. To calculate the stress magnitude from the
X?ray diffraction data, we used a model of stress-lattice strain relationship (Singh et al. 1998),
dhkl (ψ)= d0hkl [1+(1-3cos2ψ) σ/6 Ghkl ] (1)where dhkl is the d-spacing measured as a function of azimuth angle ψ, d0hkl is the d-spacing under the hydrostatic pressure,Ghkl is the appropriate shear modulus for a given hkl, and σ is the uniaxial stress. Pressure and stress were estimated using
bridgmanite (111) diffraction peak at deformation experiments. X?ray radiographies of the strain markers was taken using an
imaging system composed of a YAG crystal and a CCD camera with an exposure time of 10 s.
Uniaxial tension stress and strain of Mg-Pv at 27.3 GPa, 1473 K were estimated as ˜1.3 GPa and ˜4 % during doformation
by differential ram. We confirmed deformation experiments at the lower mantle pressure conditions can be conducted by WC
anvils. We will perform additional deformation experiments with large strain.

キーワード: ブリッジマナイト, その場観察, 変形実験, 下部マントル
Keywords: Bridgmanite, In-situ measurements, deformation experiments, The Earth’s lower mantle

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