SIT03-01

会場:106

時間:5 月 25 日 14:15-14:30

Synthesize of boron-doped diamond cylinder as a heater in Multi-anvil apparatus
Synthesize of boron-doped diamond cylinder as a heater in Multi-anvil apparatus
XIE, Longjian1∗ ; YONEDA, Akira1 ; ITO, Eiji1
XIE, Longjian1∗ ; YONEDA, Akira1 ; ITO, Eiji1
1
1

ISEI, Okayama University
ISEI, Okayama University

Diamond is the hardest known material in the world. It is the first time to report synthesize of semi-conductor boron-doped
diamond cylinder in the Kawai-type multi-anvil apparatus at 15 GPa and 2100o C. The dimension of the cylinder is 2.6 mm outer
diameter, 1.5 mm inner diameter and 3.35 mm length. SEM image shows that the grain size of diamond is about 1 micrometer.
Those cylinders have been used for extremely high temperature generation (˜3000o C) in a large sample volume (˜0.1mm3 )in the Kawai apparatus; the sample volume is ˜1000 times larger than that in diamond anvil cell. High X ray transparency ofboron-doped diamond is optimum as well for in-situ synchrotron X ray analysis. Although there have been several reports onboron-doped graphite heater, the present study is the first report on pure boron-doped diamond heater in Kawai-type apparatus.
The reversibility of the heater was confirmed well through three times of repeated cycle of heating and cooling. The borondoped diamond heater with 3 wt.% boron shows metallic behavior, i.e. increasing resistance with increasing temperature. This
electrical characteristic is beneficial for stably generating temperature as high as 2700o C; the heating for higher temperature wasfailed because of failure of electrode. Therefore, succeeding optimization is required for higher temperature generation with thisnew heating element. Boron-doped diamond heater is more advantageous than B-doped graphite heater, because it is free fromcomplicated power-temperature relationship and pressure drop associated with graphite to diamond conversion.

キーワード: diamond synthesize, B-doped diamond heater, ultrahigh temperature, Multi-anvil apparatus
Keywords: diamond synthesize, B-doped diamond heater, ultrahigh temperature, Multi-anvil apparatus

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SIT03-02

会場:106

時間:5 月 25 日 14:30-14:45

Electrical conductivity of San Carlos clinopyroxene as a function of water content
Electrical conductivity of San Carlos clinopyroxene as a function of water content
ZHAO, Chengcheng1∗ ; YOSHINO, Takashi1
ZHAO, Chengcheng1∗ ; YOSHINO, Takashi1
11

Institute for Study of the Earth Interior, Okayama University, Misasa, Tottori, 682-0193, Japan.
Institute for Study of the Earth Interior, Okayama University, Misasa, Tottori, 682-0193, Japan.

The high conductive region (50-100 km) obtained from magnetotelluric data at Southern East Pacific Rise has been interpretedby the high electrical conductivity of hydrous olivine. Though the fact that water could enhance the electrical conductivity orders of magnitude, the conductivity enhanced by hydrous olivine and orthopyroxene seems to be insufficient to account for thisanomaly convincingly. Clinopyroxene, one of the main constituent minerals in the upper mantle, could be a possible candidate
to raise the conductivity in this region because water tends to partition into this phase rather than olivine and orthopyroxene. In
this study, we measured the electrical conductivity of clinopyroxene as a function of temperature and water content under the
P-T condition corresponding to the conductivity anomaly region in the upper mantle.
Clinopyroxene aggregates with water contents ranging from ∼0 to 2000 wt. ppm were synthesized from Scan Carlos clinopyroxene powder at 1270-1370 K and 1.5 GPa in a piston cylinder apparatus. The double capsule technique was used to realize
the Ni-NiO buffer. The electrical conductivity measurements were performed at the same pressure and temperatures from 600 to
1200 K at the same oxygen fugacity, using a DIA-type apparatus. The water content of the sample both before and after electricalconductivity were determined by FTIR using Paterson calibration.
The electrical conductivity increases with increasing water content. Two conductive mechanisms were identified, i.e. proton
conduction and hopping conduction. For hopping conduction, the activation energy is ∼1.44 eV. For proton conduction, theactivation energy differs by water content. At low water content, the activation energy is 1.28-1.36 eV; while at high watercontent, the activation energy is ∼0.92 eV. All these data were fitted using the formula σ=σ h0 exp(-Hh /kT)+σ p0 Cw r exp(-Hp /kT).
Compared with the electrical conductivity of olivine (Yoshino et al., 2006) and orthopyroxene (Zhang et al., 2012) under thesame oxygen fugacity, electrical conductivity of hydrous clinopyroxene is comparable to those of the other major constitute minerals. To estimate electrical conductivity beneath the oceanic lithosphere as a function of water content, the Hashin-Shtrikman
lower and upper bounds were used, and water-partitioning coefficients among olivine, orthopyroxene and clinopyroxene werealso assumed. The model showed no obvious advantage to explain the high conductive anomaly. Thus, the conductivity anomaly
predicted near the mid-ocean ridge cannot be originated from hydrated mantle. The conductivity anomaly region beneath theoceanic lithosphere should be explained by a presence of other conductive agents such as partial melt.

Yoshino et al. (2006), Nature 443, 973-976.
Zhang et al. (2012), EPSL 357-358, 11-20.

キーワード: clinopyroxene, electrical conductivity, water content, conductivity anomaly region, oceanic lithosphere
Keywords: clinopyroxene, electrical conductivity, water content, conductivity anomaly region, oceanic lithosphere

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SIT03-03

会場:106

時間:5 月 25 日 14:45-15:00

Defect chemistry and diffusion in hydrous forsterite
Defect chemistry and diffusion in hydrous forsterite
FEI, Hongzhan1∗ ; KATSURA, Tomoo2
FEI, Hongzhan1∗ ; KATSURA, Tomoo2
1

Institute for Study of the Earth Interior, Okayama University, Misasa, Tottori, 682-0193, Japan, 2 Bayerisches Geoinstitut, University of Bayreuth, 95447, Bayreuth, Germany
1
Institute for Study of the Earth Interior, Okayama University, Misasa, Tottori, 682-0193, Japan, 2 Bayerisches Geoinstitut, University of Bayreuth, 95447, Bayreuth, Germany
The mass transport of olivine, which reflects the flow in the Earth’s upper mantle, is controlled by the diffusion of structuralelements. On the other hand, the diffusivity of an ion in the crystal is dominated by the motion of point defects of the corresponding sites. It is thus necessary to know the diffusivities of elements in olivine in the view of defect chemistry so as to investigate
the behaviors in the upper mantle conditions.
Fei et al. (2013, 2014) systematically measured silicon and oxygen self-diffusion coefficients (D Si and D O , respectively) iniron-free forsterite as functions of water contents, showing that D Si ∝C H2O 0.32(7) , D O ∝C H2O 0.05(6) . These water-content exponents are much smaller than that expected on the basis of the assumption that self-diffusion coefficient of a chemical species is
simply proportional to its defect density. Therefore, a new defect chemistry model is required to explain the above relationships.
Silicon diffusion:
The D Si should be proportional to the density of silicon defects, namely, D Si ∝[VSi ””]. On the other hand, Si4+ is tightly
surrounded by four-coordinated O2− , and therefore, migration of Si4+ should be enhanced if a surrounding O2− is missing. We
can expect that a certain proportion of VSi ”” is associated with VO •• due to their excess charges with the opposite signs. As
a result, Si migration is probably dominated by VO •• -associated VSi ””. D Si is thus also proportional to [VO •• ] and wehave,
D Si ∝ [VSi ””] × [VO •• ].
Under the charge neutrality condition of [(OH)O • ] = 2[VM g ”] in hydrous forsterite, we have [VSi ””] ∝ (f H2O )2/3 and [VO•• ] ∝ (f H2O )−1/3 . Therefore,
D Si ∝ [VSi ””] ×[VO •• ] ∝ (f H2O )1/3 ,which agrees well with the experimental results: D Si ∝ (C H2O )0.32(7) (Fei et al., 2013).
Oxygen diffusion:
In hydrous olivine/forsterite, hydrogen exists as hydroxyl, (OH)− . Oxygen ions could diffuse either by hopping of O2− without H+ or by hopping of O in (OH)− . Because H+-associated O has a lower Coulomb force due to the excess charge by H+ , thehopping probability of (OH)− should be higher than that of O2− . Thus, the O diffusion should be dominated by O2− of (OH)− .
As a result, we have,
D O ∝ [VO ] × ([O2− ]hopping + [(OH)− ]hopping ) ≈ [VO •• ] × [(OH)− ]hopping .
There are mainly three types of (OH)- in hydrous olivine/forsterite: (a) (OH)O • associated with VM g ”; (b) (OH)O • associated with VSi ””; (c) (OH)O • un-associated with any cation vacancies. The un-associated (OH)O • should have much higher
mobility than VSi ”” or VM g ” associated ones due to the Coulomb force and therefore the O diffusion is probably dominated byun-associated (OH)O • . Thus,
D O ∝ [VO •• ] × [(OH)− ]hopping ≈ [VO •• ] × [(OH)O • ]un−associated .
Under the charge neutrality condition of [(OH)O • ] = 2[VM g ”], we have [VO •• ] ∝ (f H2O )−1/3 and [(OH)O • ]un−associated∝ (f H2O )1/3 . Therefore,
D O ∝ [VO •• ] × [(OH)O • ]un−associated ∝ (f H2O )0 .
This model suggests that D O is independent from C H2O , which agrees well with the experimental results, D O ∝ C H2O 0.05(6)(Fei et al., 2014).
Fei et al. (2013), Nature 498, 213-215.
Fei et al. (2014), JGR 119, 7598-7606.
キーワード: defect chemistry, self-diffusion coefficient, silicon, oxygen, water content, forsterite
Keywords: defect chemistry, self-diffusion coefficient, silicon, oxygen, water content, forsterite

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SIT03-04

会場:106

時間:5 月 25 日 15:00-15:15

D/H exchange in wadsleyite and ringwoodite: Implications for electrical conductivity
D/H exchange in wadsleyite and ringwoodite: Implications for electrical conductivity
SUN, Wei1∗ ; YOSHINO, Takashi1 ; SAKAMOTO, Naoya2 ; YURIMOTO, Hisayoshi2SUN, Wei1∗ ; YOSHINO, Takashi1 ; SAKAMOTO, Naoya2 ; YURIMOTO, Hisayoshi2
1

ISEI, Okayama University, Misasa, Tottori 682-0193, Japan, 2 Division of Earth and Planetary Sciences, Hokkaido University,
Sapporo, Hokkaido 060-0810, Japan
1
ISEI, Okayama University, Misasa, Tottori 682-0193, Japan, 2 Division of Earth and Planetary Sciences, Hokkaido University,
Sapporo, Hokkaido 060-0810, Japan
Wadsleyite and ringwoodite, which are main constituent minerals of the mantle transition zone, can incorporate large amountof hydrogen in their structure (up to a few wt % H2O). A knowledge of hydrogen self-diffusion in these minerals and its
relationship with their electrical conductivity is critical to estimate the real amount of water present in the transition zone.
Although only the hydrogen incorporation experiments in wadsleyite was performed using polycrystalline samples, the obtained
diffusion coefficients cannot rule out the influence of grain boundary diffusion (Hae et al. 2006). Therefore, we have to investigatehydrogen lattice self-diffusion of wadsleyite and ringwoodite using single crystal at high pressure.
To estimate proton conduction from hydrogen self-diffusion, large single crystals (>1mm) of hydrogen (H) and deuterium(D)-doped wadsleyite and ringwoodite were synthesized respectively at high pressure and high temperature in Kawai-type multianvil apparatus.
We applied H/D exchange method to determine hydrogen self-diffusion coefficients because this method (Du Frane et al.
2012) has advantage to distinguish between incorporation and self-diffusion, and provides more accurate hydrogen diffusion
coefficients contributing to proton conduction than traditional incorporation method (Kohlstedt and Mackwell, 1998, Demouchy
and Mackwell, 2003, Hae et al. 2006).
After determination of crystallographic orientation, a pair of H and D-doped wadsleyite or ringwoodite crystals aligned tothe same axis was placed together in gold capsule. The polished surfaces were tightly contacted each other. The inter-diffusion
experiments were conducted at different temperatures (900-1300K) and the same pressure as synthesis condition. H/D interdiffusion profiles were obtained by SIMS in Hokkaido University.
Hydrogen volume diffusion coefficients in wadsleyite determined from each single crystal pair are ˜1 order of magnitude lower
than those obtained from polycrystal wadsleyite (Hae et al. 2006). The hydrogen self-diffusion coefficients in ringwoodite arecharacterized by lower enthalpy and hydrogen mobility than wadsleyite at the temperature of transition zone.
Electrical conductivities of wadslyite and ringwoodite estimated from the present diffusion coefficients based on the NernstEinstein relation. Our model suggests that hydrogen makes significant contributions to wadsleyite but insignificant contributions
to ringwoodite due to large contribution of hopping conduction at the transition zone condition. Our proton conductivity valuesof wadsleyite are similar with those of Yoshino et al. [2012] at the transition zone condition but values of ringwoodite are lower
especially at high water content. This model suggests that global average concentration of hydrogen in the transition zone of is
˜1000 wt ppm H2O.

キーワード: hydrogen, diffusion, wadsleyite, conductivity, ringwoodite
Keywords: hydrogen, diffusion, wadsleyite, conductivity, ringwoodite

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SIT03-05

会場:106

時間:5 月 25 日 15:15-15:30

広帯域海底地震観測によるソサエティ・ホットスポット下のマントル遷移層構造の推定
Thickness of the mantle transition zone beneath the Society hotspot
末次 大輔 1∗ ; 杉岡 裕子 1 ; 一瀬 建日 2 ; 伊藤 亜妃 1 ; 塩原 肇 2
SUETSUGU, Daisuke1∗ ; SUGIOKA, Hiroko1 ; ISSE, Takehi2 ; ITO, Aki1 ; SHIOBARA, Hajime2
1
1

海洋研究開発機構, 2 東京大学地震研究所
Japan Agency for Marine-Earth Science and Technology, 2 Earthquake Research Institute, the University of Tokyo

We have conducted a seafloor geophysical observation from 2009 to 2010 near
the Society hotspot. The observation network was composed of nine sets ofbroadband seismographs and electro-magnetometers, and two differential pressure gauges. In this presentation we show the
mantle transition zone (MTZ) structure obtained with a receiver function method using the broadband seismograms. We employed a common-conversion point (CCP) stacking technique to map the MTZ thickness. A preliminary result indicates an areaof a thin MTZ 200 km to the south of the Society hotspot (thinner than global average by 20-30 km). The lateral dimension of
the thin MTZ area is about 200 km. There is another area of the thin MTZ 300 km EES to the hotspot. The thin MTZ areas areroughly correlated with slow P-velocities in the MTZ in the P-wave tomograms (Obayashi et al., 2014). They may represent hot
mantle plumes ascending from the lower mantle.
キーワード: ホットスポット, 海底地震観測, レシーバー関数, 仏領ポリネシア
Keywords: hotspot, ocean bottom seismograph, receiver function, French Polynesia

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SIT03-06

会場:106

時間:5 月 25 日 15:30-15:45

リサイクルしたエクロジャイトを含むハワイプルームの実験的研究： 第１部 プ
ルームのポテンシャル温度について
Experimental Study on the Hawaiian Plume with Recycled Eclogite: Part-1: Constraints
on potential temperature
高橋 栄一 1∗ ; 高 珊 1
TAKAHASHI, Eiichi1∗ ; GAO, Shan1
1
1

東京工業大学大学院理工学研究科地球惑星科学専攻
Magma Factory, Earth and Planetary Sciences, Tokyo Institute of Technology

Potential mantle temperatures (PMT) of plumes are thought to be significantly higher than shallow asthenosphere (200˜300C).
Excess PMT of the plume is very important in calculating the plume flux among the heat budget of the Earth dynamics (e.g.,
Sleep, 1990). In order to produce large amount of tholeiite magma in the shield building stage at the base of old Pacific plate,potential temperature of the Hawaiian plume is considered to be at least 300C higher than asthenosphere judging from theperidotite dry solidus at 3 GPa, base of the oceanic plate (e.g., Watson & McKenzie, 1991).
If large amount of recycled eclogite component is involved in the genesis of LIP magmas (e.g., Hawaii hot spot: Hauri, 1996;
Takahashi & Nakajima, 2002, Sobolev et al., 2007, Columbia River flood basalt: Takahashi et al., 1998), PMT of the plumes
which have been estimated based on peridotite dry solidus alone should be largely in error. For example, Takahashi et al.(1998)
concluded that temperature of the initial emplacement stage of the Yellowstone plume may be only 100C higher than normal
asthenosphere, based on melting study of the Columbia River basalts. In order to evaluate the role of recycled eclogite in magma
genesis of Hawaiian plume, we carried out hig-P and high-T melting experiments. Chemistry of the recycled eclogite will be
discussed in Part 2.
High-pressure melting experiments were carried out under dry and hydrous conditions with layered eclogite/peridotite starting
materials. Spinel lherzolite KLB-1 (Takahashi 1986) was employed as peridotite component in this study. Two basalt components
were tested as recycled crust component: 1) Columbia River basalt (CRB72-180, Takahashi et al., 1998) which is relatively
enriched in K, Ti and LREE (K2O?1wt%, TiO2=3.15wt%), N-type MORB (NAM-7, Yasuda et al., 1994) (for REE patterns,
see Fig.1 of Gao et al. this conference, Part 2 of this work). The 2.85GPa experiments (corresponding to about 80km depth
which is the top most horizon of the Hawaiian plume head) were carried out with Boyd-England type piston-cylinder apparatus at(1460˜1540C for dry experiments; 1400˜1500C for hydrous experiments), The 5GPa experiments (corresponding to about 150km
depth on the plume axis) were conducted by Kawai-type multi-anvil apparatus (1550˜1650C for dry experiments; 1350˜1550C
for hydrous experiments).
Melts formed by reactive melting of dry eclogite and peridotite changes dramatically in the temperature range across the solidusof peridotite KLB-1 from basalt (below dry solidus) to picrite (20-40C above dry solidus). Basaltic melts are not saturated witholivine both at 2.85 and 5 GPa and therefore they are separated by peridotite matrix by Opx film. Chemical reaction between
the basalt melt and the peridotite matrix proceeds only slowly by solid-diffusion across the Opx film. In hydrous experiments,
solidus of peridotite decreases significantly and therefore the reaction between hydrous melt and the partially molten peridotite
matrix proceeds at temperatures below peridotite dry solidus.
Based on present experiments, we propose that potential temperature of the Hawaii plume may be only 100-150C above that ofnormal asthenosphere. Tholeiite magma in the shield building stage may be formed slightly under hydrous condition near the drysolid of peridotite (1450-1500C at about 3 GPa). Chemical distinction between Hawaiian shields (e.g., Mauna Loa and Kilauea)
might correspond with difference in mixing ratio or degree of the chemical reaction between the recycled eclogite blocks and theambient peridotite.
Potential mantle temperature in other mantle plume (OIB, flood basalt, etc) will be discussed in the light of present experiments.
Our model predicts lower plume temperatures than most previous estimates. Plume flux may be related to the amount of entrained
eclogite than potential temperature.

キーワード: ハワイプルーム, リサイクルエクロジャイト, マグマ生成, ポテンシャル温度
Keywords: Hawaiian plume, recycled eclogite, magma genesis, potential temperature

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SIT03-07

会場:106

時間:5 月 25 日 15:45-16:00

リサイクルしたエクロジャイトを含むハワイプルームの実験的研究：第 2 部 リサ
イクル成分の地球化学的特徴
Experimental Study on the Hawaiian Plume with Recycled Eclogite: Part 2, Constraints
on Chemistry of Recycled Component
高 珊 1∗ ; 高橋 栄一 1 ; 木村 純一 2 ; 鈴木 敏弘 1
GAO, Shan1∗ ; TAKAHASHI, Eiichi1 ; KIMURA, Jun-ichi2 ; SUZUKI, Toshihiro1
1

東京工業大学大学院理工学研究科地球惑星科学専攻, 2 海洋研究開発機構・地球内部物質循環研究分野
Earth & Planetary Sciences, Tokyo Institute of Technology, 2 Department of Solid Earth Geochemistry,Japan Agency for MarineEarth Science and Technology
1Introduction: It is believed that recycled oceanic crust is involved in the magma genesis of the Hawaiian mantle plume (e.g.,
Hauri et al., 1996; Takahashi & Nakajima., 2002; Sobolev et al., 2007). Takahashi & Nakajima (2002) proposed that magma
produced near the axis of the plume head may be mixtures of two types of melts 1) basaltic andesite melt formed by meltingof eclogite and 2) picritic melts formed by the reactive melting of eclogite and peridotite. However, geochemical feature ofrecycled oceanic crust component is still under disputed. A sequence of high-T high-P experiments were conducted to figure out
constrains of such recycled component. Experimental details are shown in Part 1 of this presentation.
Phase and major elements features:
1) Anhydrous conditions: (CRB: 1460˜1540C, 3h for 2.85GPa; N-MORB or CRB: 1550˜1650C for 5GPa):
When peridotite remained subsolidus, molten basalt was separated from peridotite by thin Opx band formed by the chemical
reaction between Si-rich partial melt of eclogite and olivine in the peridotite matrix, therefore the chemical reaction between
basalt and peridotite layers proceeded only by solid diffusion. As peridotite reached its solidus between 1520C˜1540C, fullymolten basalt melt and melt pockets from peridotite layer linked, judging from sharp changes in MgO and FeO/MgO ratio. Extensive chemical mass transport took place by chemical diffusion and liquid percolation. However, Si-content remained nearly
constant even at temperatures above solidus.
2) Hydrous conditions: 1400C˜1500C, 2.85GPa 3h
In wet experiments (with 1wt% H2 O in peridotite layer originally), extraction of water took place from peridotite layer into
basaltic melt (water was detected by FT-IR), giving little influence to the melting process of peridotite. On the other hand, in
wet experiments (with 5wt% H2 O in peridotite layer), basalt started melting even at 1400?C. At 1480C and 1500C, melting process of both layers enhanced the chemical exchange of both sides. H2 O promotes melting of only basalt layer under low water
concentration, while it enhances melting and chemical interaction between both layers leading to formation of Si-poor melts inbasalt.
In the case 5GPa, 1wt% H2 O, coexisted hydrous vapor and hydrous silicate melt generated under temperature 1350˜1450C(about 200C below peridotite dry solidus). Ti, K, P are enriched in the hydrous vapor.
REE features.
Rare earth element patterns: Columbia River basalt is enriched in LREE than N-MORB, run products of this study turned out
to have a similar pattern (Fig.1, normalized patttern by CI chondrite) with their starting material (basalt). Since REE elements
prefer to stay in the melt, increasing degree of partial melting will lower the whole REE elements abundance in the melt. REE
abundance of lava from Kilauea and Mauna Loa is also plotted in this diagram, showing sharp decline of HREE components
in these shield stage lava. Garnet (the key component of eclogite) is the only known mineral that prefers heavy REE. Althoughgarnet together with Cpx are the residual phase at 2.85 and 5 GPa experiments, REE patterns of Kilauea and Mauna Loa are far
more depleted in HREE than melts produced by our experiments. .
Discussion: In an upwelling mantle plume with recycled oceanic basalt components, both tholeiitic magma and alkali component could be obtained from hybrid melting of basalt and peridotite. H2 O promotes the melting process and generate more mafic
melts. Very depleted HEE pattern of Hawaiian tholeiite might be explained by percolation of partial melt in vertically elongatedeclogite blobs in the center of the plume (chromatographic effect). Enriched signature in K , Ti, and LREE in the Hawaiian
tholeiite might indicate that source of recycled component in the Hawaiian plume is not NMORB but is more enriched in theseincompatible elements (see Fig.1).

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SIT03-07

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時間:5 月 25 日 15:45-16:00

キーワード: ハワイプルーム, マグマ生成, リサイクルしたエクロジャイト, 化学組成, 希土類元素
Keywords: Hawaii plume, magma genesis, recyled eclogite, chemistry, REE

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SIT03-08

会場:106

時間:5 月 25 日 16:15-16:30

High-pressure and high-temperature polymorphism in the CaCO3 at pressures to 30 GPa
High-pressure and high-temperature polymorphism in the CaCO3 at pressures to 30 GPa
LITASOV, Konstantin1∗ ; SHATSKIY, Anton1 ; SHARYGIN, Igor1 ; CHANYSHEV, Artem2 ; GAVRYUSHKIN, Pavel2 ;BEKHTENOVA, Altyna2
LITASOV, Konstantin1∗ ; SHATSKIY, Anton1 ; SHARYGIN, Igor1 ; CHANYSHEV, Artem2 ; GAVRYUSHKIN, Pavel2 ;BEKHTENOVA, Altyna2
1
1

VS Sobolev Institute of Geology and Mineralogy, Novosibirsk, Russia, 2 Novosibirsk State University, Novosibirsk, Russia
VS Sobolev Institute of Geology and Mineralogy, Novosibirsk, Russia, 2 Novosibirsk State University, Novosibirsk, Russia

We determined phase transitions in CaCO3 at pressures up to 30 GPa and high-temperatures using in situ X-ray diffraction
and synchrotron radiation. In additional to geological importance this investigation has crystal-chemical and fundamental aspect
as in this region enigmatic phase transitions from aragonite to disordered calcite or other phases takes place. The degree oforientational disorder in calcite drastically grow in the narrow temperature range of 1200-1230 K (at 1 bar) producing fully
disordered phase (by orientation of CO3 triangles) (Ishizawa et al., 2013). Despite of such apparent significance, there is just a
few works where this phase transition was investigated by X-ray diffraction at high pressures (Suito et al., 2001). The results
are not unequivocal, because disordered calcite was determined by only common similarity of diffraction patterns, whereas unit
cell parameters were not determined. By the same reason the compressibility of disordered calcite is also unknown. The lackof the experimental results is explained by grain growth and disordering phase transitions in CaCO3 at temperatures close to themelting point and as a result difficulties in getting relatively high quality diffraction patterns with amount of peaks enough forunit cell parameters determination. In present experiments we observed transition of aragonite to presumably disordered calcite
phase at 1 and 3 GPa and 1273-1473 K, however at 5 and 8 GPa and higher temperature we observed transition to new phase,
which we tentatively named disordered aragonite. At 14 GPa we did not observe transition of aragonite in the experiment to 1900
K, however at 20 GPa and at 31 GPa transition from aragonite to new phase(s) was observed at 1773 and 1373 K, respectively.
The structures of the new phases will be refined based on diffraction data and subsequent ab initio computations.
キーワード: high pressure, calcium carbonate, phase transition, aragonite, X-ray diffraction
Keywords: high pressure, calcium carbonate, phase transition, aragonite, X-ray diffraction

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SIT03-09

会場:106

時間:5 月 25 日 16:30-16:45

High-pressure decomposition of FeTiO3, MgTiO3 and ZnTiO3 perovskites
High-pressure decomposition of FeTiO3, MgTiO3 and ZnTiO3 perovskites
赤荻 正樹 1∗ ; 阿部 航平 1 ; 石井 貴之 1 ; 糀谷 浩 1 ; 遊佐 斉 2
AKAOGI, Masaki1∗ ; ABE, Kohei1 ; ISHII, Takayuki1 ; KOJITANI, Hiroshi1 ; YUSA, Hitoshi211

学習院大学理学部化学科, 2 物質材料研究機構
Department of Chemistry, Gakushuin University, 2 National Institute of Materials Science

It is generally accepted that transition of MgSiO3 -rich perovskite (bridgmanite) to CaIrO3 -type postperosvkite is responsible
for formation of D layer in the lowermost mantle. Since discovery of the perovskite-postperovskite transition in MgSiO3 ,numerous studies have been made to clarify high-pressure transitions of ABX3 perovskites. FeTiO3 and MgTiO3 are endmembersof natural ilmenite, and ZnTiO3 is an analogue for these compounds. Previous studies revealed that at 15-20 GPa range FeTiO3and MgTiO3 ilmenites transform to perovskites, which are recovered as LiNbO3 -type phases at ambient conditions. In contrast
to many perovskite-type oxides including MgSiO3 perovskite, FeTiO3 and MgTiO3 perovskites do not transform to CaIrO3 -type
postperovskite but decompose into two-phase assemblages. However, the transition behaviors of these perovskites are still incontroversy, and little has been known on phase transition of ZnTiO3 .
We have examined high-pressure transitions in ZnTiO3 and MgTiO3 to about 25 GPa and those of FeTiO3 to about 33 GPausing multianvil apparatus. Pressure was calibrated against press-load using pressure-fixed points at room temperature including
GaP and Zr. The pressure was further corrected at high temperature using transition boundaries including dissociation of pyrope
into Mg-rich perovskite + corundum. Quenched samples were examined by powder X-ray diffractometers and a scanning electron
microscope with an energy-dispersive X-ray spectrometer. Some in-situ X-ray observations on ZnTiO3 phases have also been
made using a diamond anvil cell with synchrotron X-ray diffraction method.
The results by quench and in-situ experiments on ZnTiO3 indicate that at 1200 o C ZnTiO3 ilmenite transforms to perovskite
at 10 GPa, which dissociates into rocksalt-type ZnO + baddeleyite-type TiO2 at 22 GPa. On release of pressure, perovskite-type
ZnTiO3 , rocksalt-type ZnO and baddeleyite-type TiO2 are converted into LiNbO3 -type, wurtzite-type and α PbO2 -type phases,
respectively. MgTiO3 perovskite decomposes into MgO + baddeleyite-type TiO2 at 20 GPa and 1400 o C. FeTiO3 perovskite
dissociates first into CaTi2 O4 -type Fe2 TiO4 + TiO2 phase at about 28 GPa. At about 30 GPa, this assemblage further changes
into Fe3 Ti2 O7 phase + TiO2 phase below about 1100 o C, above which CaTi2 O4 -type Fe2 TiO4 + FeTi2 O5 phase were synthesized.
These two assemblages have not yet been found in the previous studies. Combination of our results on ZnTiO3 , MgTiO3 andFeTiO3 with those of other titanate perovskites suggests that transition pressure of titanate perovskite increases with tolerance
factor or ionic radius of divalent cation. It is also indicated that all the titanate perovskites studied dissociate into two-phaseassemblages which are denser than hypothetical CaIrO3 -type postperovskites. This is consistent with the previously suggested
tendency that ABX3 perovskites with relatively ionic B-X bonds do not transform to postperovskites.
キーワード: ペロブスカイト, チタン酸塩, 高圧実験, ポストペロブスカイト
Keywords: perovskite, titanate, high pressure experiment, postperovskite

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SIT03-10

会場:106

時間:5 月 25 日 16:45-17:00

Phase relations of MgSiO3-Al2O3 system in Earth’s lower mantle
Phase relations of MgSiO3-Al2O3 system in Earth’s lower mantle
LIU, Zhaodong1∗ ; IRIFUNE, Tetsuo1 ; NISHI, Masayuki1 ; TANGE, Yoshinori2 ; ARIMOTO, Takeshi1 ;SHINMEI, Toru1
LIU, Zhaodong1∗ ; IRIFUNE, Tetsuo1 ; NISHI, Masayuki1 ; TANGE, Yoshinori2 ; ARIMOTO, Takeshi1 ;SHINMEI, Toru1
11

Geodynamics Research Center (GRC), Ehime University, 2 Spring-8, Japan Synchrotron Radiation Institute
Geodynamics Research Center (GRC), Ehime University, 2 Spring-8, Japan Synchrotron Radiation Institute

Abstract
Aluminum oxide (Al2 O3 ) is present in about 4˜5 mol% for the Earth’s mantle compositions, e.g., pyrolite, piclogite andchondrite (Ringwood, 1966; Sun, 1982; Anderson, 1989; Irifune et al. 1986, 2007). In the Earth’s uppermost parts of lower
mantle conditions, the Al2 O3 is accommodated mainly in bridgmanite (Irifune 1994), which is the most abundant mineral phasein this region (Ringwood 1975). The MgSiO3 -Al2 O3 system is a basis system to understand lower mantle phase equilibria in amore complex composition. Phase relations of MgSiO3 -Al2 O3 system have since been extensively studied using the multi-anvil
apparatus with tungsten carbide anvils from upper mantle to the uppermost parts of lower mantle conditions (Irifune 1986, 1996;
Kubo et al. 2000; Hirose et al. 2001; Akaogi et al. 2002), and also further constructed by theoretical calculation (Panero et al.
2006; Tsuchiya et al. 2008). The phase relation of MgSiO3 -Al2 O3 , especially toward the Al2 O3 -rich side, in the lower mantle
conditions is still relatively limited. Recent technique development of sintered diamond anvils in multi-anvils apparatus allow us
to achieve the high pressures and high temperatures conditions of Earth’s middle lower mantle(Tange et al. 2008, 2009; Irifune etal. 2010; Ito et al. 2010; Nishi et al. 2013; Yamazaki et al. 2014). Here, we further extend the phase relations of MgSiO3 -Al2 O3system between 31 GPa and 45 GPa at 2000 K using multi-anvil apparatus with sintered diamond anvils. Aluminum oxide
solubility in bridgmanite is increasing with increasing pressure and temperature. These results can further confirmed previous
experimental studies on the same system and pyrolite composition (Irifune et al. 1994, 1996, 2010), and the entire inventory of
Al2 O3 in pyrolite can be accommodated in bridgmanite in Earth’s lower mantle.
キーワード: Aluminum oxide, bridgmanite, lower mantle, sintered diamond technique, phase relation
Keywords: Aluminum oxide, bridgmanite, lower mantle, sintered diamond technique, phase relation

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SIT03-11

会場:106

時間:5 月 25 日 17:00-17:15

First principles study on the phase stability and elasticity of potassium-host hexagonal
aluminous phases
First principles study on the phase stability and elasticity of potassium-host hexagonal
aluminous phases
河合 研志 1∗ ; 土屋 卓久 2
KAWAI, Kenji1∗ ; TSUCHIYA, Taku2
1

Department of Earth Science and Astronomy, Graduate School of Arts and Sciences, University of Tokyo, 2 Geodynamics
Research Center, Ehime University
1
Department of Earth Science and Astronomy, Graduate School of Arts and Sciences, University of Tokyo, 2 Geodynamics
Research Center, Ehime University
In order to understand the fate of the potassium-bearing phase subducted into the deep Earth’s interior, we have studied thehigh-pressure stability and elasticity of KMg2Al5SiO12 hexagonal aluminous phase (K-Hex) by means of the density functional
computation method. The K-Hex phase is found to be mechanically stable up to 150 GPa and also energetically more stable
than the calcium-ferrite (K-CF) type structure up to 150 GPa. In addition, calculations indicate that when the spinel composition
coexists with the K-hollandite (K-Hol) phase, the K-Hex phase becomes more stable than the K-Hol phase at pressures above
˜27 GPa. This suggests that the hexagonal aluminous phase be a potential host of the incompatible large-ion elements such as
potassium in the lower mantle, especially in the subducted basaltic Mg and Al rich composition. Finally, seismic velocities of
the K-Hex phase are found slower than Mg-perovskite (pv) in the lower mantle pressures, while its density is larger than Mg-pv
over 70 GPa.
キーワード: High pressure, Pottasium, Lower mantle, Aluminous phase
Keywords: High pressure, Pottasium, Lower mantle, Aluminous phase

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SIT03-12

会場:106

時間:5 月 25 日 17:15-17:30

Effect of Al content on electrical conductivity of bridgmanite
Effect of Al content on electrical conductivity of bridgmanite
芳野 極 1∗ ; 鎌田 誠司 2 ; 大谷 栄治 2 ; 平尾 直久 3
YOSHINO, Takashi1∗ ; KAMADA, Seiji2 ; OHTANI, Eiji2 ; HIRAO, Naohisa3
1
1

岡山大学地球物質科学研究センター, 2 東北大学, 3 高輝度光科学研究センター
Institute for Study of the Earth’s Interior, Okayama Univ., 2 Tohoku Univ., 3 JASRIElectrical conductivity is one of useful methods to prove temperature, structure and composition of the Earth’s deep interior.
Interpretation of electrical conductivity in the Earth has been done by comparison between conductivities obtained from geophysical observations and conductivities measured in the laboratory. Because bridgmanite is believed to be a dominant constituent
mineral in the lower mantle, knowledge of electric conduction for bridgmanite to constrain the conductivity profile of the lower
mantle. Xu et al. (1998) reported that Al incorporation to bridgmanite enhance the electron hopping conduction. Although there
is a large variation of Al content in bridgmanite under the lower mantle, electrical conductivity of aluminous bridgmanite havenot been measured as a function of Al content.
In this study, Impedance spectroscopy measurements were performed at 26 or 28 GPa and up to 2000 K in a Kawai-type
multi-anvil apparatus in order to investigate effect of aluminium content on electrical conductivity of bridgmanite. The starting
materials were synthetic orthopyroxene (Mg0.9 , Fe0.1 )SiO3 powders with various amounts of aluminium (Al2 O3 = 3, 6 and 10wt.%). Electrical conductivity of aluminous bridgmanite increases with increasing Al content. At temperatures below 1700 K, theactivation enthalpies of these samples are around 0.4 eV, which is consistent with that reported by Shankland et al. (1993), who
measured the conductivity of quenched perovskite. At higher temperatures (>1800 K) corresponding to temperature conditionsof the uppermost lower mantle, the conductivity of samples with relatively lower Al content abruptly increases with temperatureand the resultant activation enthalpy is around 1 eV, which is consistent with that reported by Dobson (2003). At temperatures below about 1700 K, small polaron (electron hole hopping between ferrous and ferric iron sites) conduction with activation energyof 0.4 eV is considered as a dominant conduction mechanism of aluminous bridgemanite. At higher temperatures, a different
conduction mechanism dominates with more than1 eV of activation enthalpy.
To estimate ferric iron content in bridgmanite, synchrotron Mossbauer spectroscopy was performed at SPring-8 BL10XU. The
ferric iron contents of all samples are estimated to be more than 60 % against total iron content. Proportion of ferric iron in A
site tends to increase with increasing Al contents. Thus, increase of ferric iron content due to Al incorporation into bridgmanite
can induce enhancement of conductivity. At high temperatures above 1800 K, the dominant conduction mechanism can change
extrinsic oxygen ionic conduction when Al2 O3 content is low. Xu and McCammon (2002) reported evidence that in aluminous
perovskite with Mg#90, ionic conduction characterized by high activation energy (1.5 eV) becomes significant above 1700 K
dependent on Al content. This is most likely due to the presence of oxygen vacancies, which charge-balance Al and ferric ironsubstituting onto the B site (Brodholt 2000; Lauterbach et al. 2000). The present results suggest that the electrical conductivityof a region at the top of the earth’s lower mantle could be sensitive to amount of Al content in bridgmanite. On the other hand,when Al content in bridgmanite is low, the lower mantle conductivity will be more sensitive to temperature due to the extrinsic
oxygen ionic conduction.
References
Brodholt, J.P., Nature 407, 620?622, 2000.
Dobson, D., 2003. Phys. Earth Planet. Inter. 139, 55-64, 2003.
Lauterbach, S., C. A. McCammon, P. van Aken, F. Langenhorst, F. Seifert, Contrib. Mineral. Petrol., 138, 17? 26, 2000.
Shankland, T.J., Peyronneau, J., Poirier, J.-P., Nature 366, 453?455, 1993.
Xu, Y., McCammon, C., Poe, B.T., Science282, 922?924, 1998.
Xu, Y., C. McCammon, J. Geophys. Res., 107, 2251, 2002.
キーワード: ブリッジマナイト, 下部マントル, 電気伝導度, メスバウア分光, Al, 電子ホッピング
Keywords: bridgmanite, lower mantle, electrical conductivity, Mosbauer spectrocopy, Al, electron hopping

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SIT03-13

会場:106

時間:5 月 25 日 17:30-17:45

下部マントルにおける鉄のスピン転移の統一像に向けて
Toward the unified image of the spin transition of iron in the lower mantle
藤野 清志 1∗ ; 入舩 徹男 1
FUJINO, Kiyoshi1∗ ; IRIFUNE, Tetsuo1
1
1

愛媛大学地球深部ダイナミクス研究センター
Geodynamics Research Center, Ehime University

The pressure-induced spin transition of iron in the lower mantle minerals deeply affects the structures and physical propertiesof the lower mantle minerals, and there by the dynamics of the lower mantle. So far, many experimental and theoretical studies
have been carried out to clarify the spin transition of iron in the lower mantle minerals. However, there is still a controversy about
the existence and the pressure dependence of the spin transition of iron in Mg-perovskite (Pv) and post-Mg-perovskite (PPv) at
the lower mantle conditions. Pv and PPv in the lower mantle are considered to involve both Fe2+ and Fe3+ , and Al as minor
elements. Until recently, the controversy had been mainly about the spin transition of Fe2+ . Now, the spin transition of Fe2+ in
Pv and PPv seems to be settling down in the direction that Fe2+ in both Pv and PPv remains high spin (HS) at the dodecahedral
site (A site) at the lower mantle conditions (Hsu et al., 2011; Yu et al., 2012).
On the other hand, with the spin transition of Fe3+ there are still large discrepancies among the reports, particularly related to
the Al content involved in Pv and PPv. Some experimental results indicate that Fe3+ becomes low spin (LS) at the octahedral
site (B site) in Al-bearing Pv (above ca. 70 GPa) and PPv (whole stability region) (Catalli et al., 2011; Fujino et al., 2012, 2013),
while other experimental results indicate that Fe3+ coexisting with Fe2+ at the A site prefers to occupy the A site and remains
HS even at high pressure (Mao et al., 2014; Dorfman et al., 2014). Meanwhile first-principles calculations indicate that Fe3+
remains HS at the A site in Al-bearing Pv and PPv (Hsu et al., 2012).
In the presentation, the possible explanations to resolve the above discrepancies among the previous reports to obtain theunified image of the spin transition of iron in the lower mantle minerals are proposed.

キーワード: 鉄のスピン転移, ３価鉄, Mg-ぺロブスカイト, ポスト Mg-ぺロブスカイト, Al 量, 陽イオン交換反応
Keywords: spin transition of iron, ferric iron, Mg-perovskite, post-Mg-perovskite, Al content, cation exchange reaction

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SIT03-14

会場:106

時間:5 月 25 日 17:45-18:00

西太平洋沈み込み帯の深部構造と異方性
Deep structure and seismic anisotropy of the Western-Pacific subduction zones
趙 大鵬 1∗ ; Wei Wei1
ZHAO, Dapeng1∗ ; WEI, Wei1
1
1

東北大学大学院理学研究科
Tohoku University, Department of Geophysics

We determined high-resolution P and S wave tomography and 3-D P-wave azimuthal anisotropy of the Western-Pacific subduction zones by inverting a large number of P and S wave arrival-time data of local and regional earthquakes. Our results
show some differences between P and S wave images for the stagnant Pacific slab in the mantle transition zone (MTZ) beneath
NE Asia. The stagnant slab looks thicker in the P wave image than that in the S wave image, which may reflects the effects
of both hydration and lower temperature in the MTZ, though differences in the resolution of P and S wave tomography may
also have some effects. The Changbai and other intraplate volcanoes in NE Asia are caused by hot and wet upwelling in the
big mantle wedge above the stagnant Pacific slab in the MTZ. Our P-wave anisotropy tomography shows that the fast velocity
direction (FVD) in the subducting Philippine Sea plate beneath the Ryukyu arc is NE-SW (trench parallel), which is consistent
with the spreading direction of the West Philippine Basin during its initial opening stage, suggesting that it may reflect the fossil
anisotropy. A striking variation of the FVD with depth is revealed in the subducting Pacific slab beneath the NE Japan arc, which
may be caused by slab dehydration that changed elastic properties of the slab with depth. The FVD in the mantle wedge beneaththe NE Japan and Ryukyu arcs is trench normal, which reflects subduction-induced convection. Beneath the Kuril and Izu-Boninarcs where oblique subduction occurs, the FVD in the mantle wedge is nearly normal to the moving direction of the downgoing
Pacific plate, suggesting that the oblique subduction together with the complex slab morphology have disturbed the mantle flow.
キーワード: 沈み込み帯, 地震波トモグラフィー, 異方性, スラブ, 地震
Keywords: Subduction zones, Seismic tomography, Anisotropy, Slab, Earthquakes

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SIT03-15

会場:106

時間:5 月 26 日 09:00-09:15

Archean lithosphere in time and space: geophysical evidence on lateral and vertical heterogeneity in Siberia
Archean lithosphere in time and space: geophysical evidence on lateral and vertical heterogeneity in Siberia
ARTEMIEVA, Irina1∗ ; HERCEG, Matija1 ; CHEREPANOVA, Yulia1 ; THYBO, Hans1
ARTEMIEVA, Irina1∗ ; HERCEG, Matija1 ; CHEREPANOVA, Yulia1 ; THYBO, Hans1
1
1

IGN, University of Copenhagen
IGN, University of Copenhagen

We present geophysical models for Precambrian cratons, including the structure of the crust and the lithospheric mantle, and thethermal structure of the Precambrian lithosphere based on surface heat flow data. A particular focus is on thermo-compositional
heterogeneity of the lithospheric mantle. It is modelled as a non-thermal part of upper mantle seismic velocity heterogeneity
based on a joint analysis of thermal and seismic tomography data, and as lithosphere density heterogeneity as constrained byfree-board and satellite gravity data. The results are compared with xenolith data from the Siberian kimberlite provinces.
An analysis of surface heat flow indicates that many Precambrian cratons (particularly Siberia) are characterized by extremely
low surface heat flow (<25-30 mW/m2), which is in apparent contradiction with a worldwide compilation of cratonic xenolith
P-T arrays. In regions with very low heat flow, the depth extent of the lithospheric keels locally may reach the depth of 300-350km.
An analysis of temperature-corrected seismic velocity structure indicates strong vertical and lateral heterogeneity of the cratonic lithospheric mantle. The lateral extent of depleted lithospheric keels diminishes with depth and, below a 150-200 km depth,
is significantly smaller than geological boundaries of the cratons. In the Siberian craton, Proterozoic sutures and intracratonic
basins are manifested by an increase in mantle density as compared to light and strongly depleted lithospheric mantle of theArchean nuclei.
We demonstrate that density structure of the cratonic lithosphere is well correlated with crustal structure and surface tectonics.
The analysis of lithosphere seismic velocity and density structure allows for speculations on processes which formed and modified the Archean lithosphere.

キーワード: craton, lithospheric mantle, density, lithosphere thickness, depletion, metasomatism
Keywords: craton, lithospheric mantle, density, lithosphere thickness, depletion, metasomatism

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SIT03-16

会場:106

時間:5 月 26 日 09:15-09:30

慣性変化法によるマントルの熱対流シミュレーション
Variable inertia method: A novel numerical method for mantle convection simulation
竹山 浩介 1∗ ; 斎藤 貴之 2 ; 牧野 淳一郎 3
TAKEYAMA, Kosuke1∗ ; SAITOH, Takayuki2 ; MAKINO, Junichiro3
1
1

東京工業大学, 2 地球生命研究所, 3 理化学研究所 計算科学研究機構
Tokyo Institute of Technology, 2 Earth-Life Science Institite, 3 RIKEN AICS

地球のマントル対流を理解することは非常に重要であり、近年では三次元の数値シミュレーションが盛んに行われている。ほとんど全てのマントル対流のシミュレーションでは、非弾性近似、または（拡張）ブジネスク近似が使われてきた。この方法は陰解法であり、CFL 条件に制限されない長い時間ステップを可能にする、という利点がある。その反面、これにより導出される行列は計算に悪条件であり、特に粘性の空間変化が大きい場合への対応が極めて困難である。
また、この行列を解くためには、計算ステップごとにメモリ間のグローバルな通信を必要とし、近年の大規模な並列計算機に向かない。そこで、我々はマントル対流を陽解法で解くための新たな方法を考案した。
近年、太陽の熱対流を解くため、Rempel (2005) により音速抑制法が提案された。従来、太陽の対流では非圧縮性近似が使われてきたが、それは結果的に陰解法となる。音速抑制法は、その名が示すように、連続の式に変更を加えることで音速を抑制し、物理的な CFL 条件から制約されるよりも長い時間ステップを可能にする方法である。Hotta et al.(2012)
では、これにより、マッハ数が 0.7 未満では流れの基本的性質は変わらない事を示した。また、音速抑制法を使うことにより、太陽の超高解像度シミュレーションに成功した。（Hotta et al. 2014, 2015）
マントルでは、マッハ数だけではなく、レイノルズ数も非常に小さいので、これら２つのパラメータを独立に変化させることが可能な方法（慣性変化法）を考案した。まず、我々はレイノルズ数とマッハ数が１よりも小さい範囲では、流れの性質は変わらない事に注目し、慣性項に粘性依存の係数を乗じる定式化をした。さらに、熱伝導率と粘性を同時にスケーリングし、対流の特徴が変わらない定式化を行った。これら２つの定式化により、マッハ数とレイノルズ数を独立に変化させる事が可能であり、理論的にはこれらのパラメータが１より小さい範囲では対流の性質は変わらない事が予想される。
結果、慣性変化法によりレイノルズ数・マッハ数を１近くにしても、熱対流の性質は変わらなかった。また、粘性が５桁以上変化する場合においても計算可能である事が確認できた。慣性変化法により、CFL 条件や von-Neumann 条件から制限される時間ステップを緩和することができるため、非常に速い計算時間でシミュレーションを行う事ができる。さらに、この方法は陽解法であるため、近年の大規模な並列計算機に適しており、将来的に、非常に高解像度のマントル対流シミュレーションを行えることが期待される。
キーワード: マントル対流, 数値シミュレーション
Keywords: mantle convection, numerical simulation

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SIT03-17

会場:106

時間:5 月 26 日 09:30-09:45

物性の空間変化と強い圧縮性を持つ流体中の熱対流に関する線形解析: スーパー地
球のマントル対流に関する考察
Linear analysis on the onset of thermal convection of highly compressible fluids withvariable physical properties
亀山 真典 1∗KAMEYAMA, Masanori1∗
1
1

愛媛大学地球深部ダイナミクス研究センター
Geodynamics Research Center, Ehime University

A series of linear analysis was performed on the onset of thermal convection in a highly compressible fluid with variable physical properties, in order to study the fundamental nature of mantle convection of massive super-Earths in the presence of strong
adiabatic compression. We consider the temporal evolution (growth or decay) of an infinitesimal perturbation superimposed
to a highly compressible fluid which is in a hydrostatic (motionless) and conductive state in a basally-heated horizontal layer.
As a model of spatial variations in physical properties, we employed an exponential dependence of thermodynamic properties(thermal expansivity and reference density), together with the spatial variations in transport properties (thermal conductivity andviscosity). The linearized equations for conservation of mass, momentum and internal (thermal) energy are numerically solved
for the critical Rayleigh number as well as the vertical profiles of eigenfunctions for infinitesimal perturbations. The above calculations are repeatedly carried out by systematically varying (i) the dissipation number which measures the effect of adiabatic
compression, (ii) the temperature at the top surface and (iii) the magnitude of spatial variations in physical properties of themodeled fluid.
By first analyzing the roles of thermodynamic properties, we found that the onset of thermal convection is strongly affected by
the adiabatic compression, through the modulation of the static stability of thermal stratification in the fluid layer. For sufficiently
strong adiabatic compression where a very thick “stratosphere” of stable stratification develops in the layer, for example, the critical Rayleigh number explosively increases with the dissipation number. The explosive changes in the critical Rayleigh number
are associated with drastic decreases in the length scales of perturbations both in vertical and horizontal directions. In addition,
when the effect of adiabatic compression is extremely strong so that the thermal stratification becomes stable in the entire layer,
no perturbation is allowed to grow with time regardless of the Rayleigh number and/or the horizontal wavelength.
We also found that the critical states of thermal convection are greatly altered by introducing the depth-dependence in thermal conductivity: the increase in thermal conductivity counteracts the decrease in thermal expansivity with depth by raising theadiabatic temperature change and, hence, enhancing the stability of thermal stratification. In particular, for the cases where a“stratosphere” occurs at the mid-depth of the fluid layer owing to the moderate depth-dependence both in thermal expansivity
and conductivity, we observed discontinuous changes in the structures of incipient flows with the dissipation number, dependingon the concentration of flows either in the upper and lower “tropospheres”. Our findings suggest that a delicate interplay between
the depth-dependent thermal expansivity and conductivity is of crucial importance in understanding the dynamic nature of the
mantle convection of massive super-Earths.
キーワード: スーパー地球, マントル対流, 断熱圧縮, 熱膨張率, 熱伝導率
Keywords: super-Earths, mantle convection, adiabatic compression, thermal expansivity, thermal conductivity

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SIT03-18

会場:106

時間:5 月 26 日 09:45-10:00

Post-perovskite phase boundary of Fe- and Al-bearing MgSiO3
Post-perovskite phase boundary of Fe- and Al-bearing MgSiO3
WANG, Xianlong1∗ ; TSUCHIYA, Taku1
WANG, Xianlong1∗ ; TSUCHIYA, Taku1
1
1

GRC, Ehime University; ELSI, Tokyo Institute of Technology
GRC, Ehime University; ELSI, Tokyo Institute of Technology

The post-perovskite (PPv) phase transition of MgSiO3 bridgmanite (Br) [1,2,3] occurs in the pressure (P) and temperature (T)conditions corresponding to the Earth’s D? layer. Therefore, MgSiO3 PPv is believed to be a key mineral to understanding theseismological properties in this layer. However, to date, it is still a challenging subject to determine the phase transition boundary
preciously in the geophysically relevant Fe and Al-bearing compositions. Based on the first-principles methods combined with
the internally consistent LSDA+U method and the lattice dynamics approach, the high-P and high-T thermodynamics of the
MgSiO3 phases are directly calculated with incorporation of 6.25 mol% of Fe2+ , Fe3+ Fe3+ , Fe3+ Al3+ , and Al3+ Al3+ [4,5].
Using calculated free energies, we determine the PPv phase boundaries for Fe and Al-bearing compositions. Our results showthat at 2500 K, the Fe3+ Al3+ and Fe3+ Fe3+ incorporations span coexisting domains between Br and PPv significantly withlowering the transition pressure, in contrast to the Fe2+ - and Al3+ Al3+ -bearing cases.
References:[1] M. Murakami, K. Hirose, K. Kawamura, N. Sata, and Y. Ohishi, Science 304, 855 (2004).
[2] A. Oganov, and S. Ono, Nature 430, 445 (2004).
[3] T. Tsuchiya, J. Tsuchiya, K. Umemoto, and R. M. Wentzcovitch, Earth. Planet. Sci. Lett. 224, 241 (2004).
[4] J. Tsuchiya, and T. Tsuchiya, Proc. Natl. Acad. Sci. USA 105, 19160 (2008).
[5] A. Metsue, and T. Tsuchiya, Geophys. J. Int. 190, 310 (2012).

キーワード: First-principles method, internally consistent LSDA+U, post-perovskite, phase transition
Keywords: First-principles method, internally consistent LSDA+U, post-perovskite, phase transition

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SIT03-19

会場:106

時間:5 月 26 日 10:00-10:15

太平洋 LLSVP 西端の S 波速度構造についての新たな制限
New constraints on S-wave velocity structure near the western edge of the Pacific LLSVP
田中 聡 1∗ ; 川勝 均 2
TANAKA, Satoru1∗ ; KAWAKATSU, Hitoshi2
1
1

海洋研究開発機構, 2 東京大学地震研究所
JAMSTEC, 2 ERI, Univ. Tokyo

S-wave velocity structure near the edge of the Pacific Large-Low Shear Velocity Province (LLSVP) has been examined bymany researchers (e.g., He et al., 2006; He and Wen, 2009; Takeuchi et al., 2008; Idehara et al., 2013). They have mainly usedthe differential travel times of ScS-S observed by global or local broadband networks (e.g., IRIS GSN, F-net, CNDSN and soon). Here we add the new data of ScS-S and S-SKS travel time data obtained by NECESSArray and a temporal broadband ocean
bottom seismograph network in the Philippine Sea by the Stagnant Slab Project (SSP-BBOBS) (Shiobara et al., 2005).
ScS-S anomalies observed by NECESSArray in conjunction with those by F-net, which covers the region beneath the eastern
Micronesia, are roughly explained by the existing 3D S-wave models. However, S-SKS anomalies, which are affected by S-waves
propagated near the base of the mantle beneath the western Micronesia and the north of New Britain Island, suddenly changes
from positive in the eastern area to almost zero or slightly negative in the western, whereas all the models predict large positive
anomalies without significant changes. To confirm this S-SKS observation, we further examined ScS-S anomalies observed by
the SSP-BBOBS. Some data indicate nearly zero in the corresponding area although the data are scattered and still sparsely
distributed. Since a low velocity anomaly beneath the New Guinea Island are confirmed by Takeuchi et al. (2008) and Idehara etal. (2013), our observation suggests that the Pacific LLSVP is separated beneath the north of New Britain Islands. The models
of 3D mantle structure are possibly insufficient near the western edge of the Pacific LLSVP.
Acknowledgements. The authors are grateful to the participants of NECESSArray and SP-BBOBS projects and the staffs of
IRIS and F-net for providing valuable data.

キーワード: 大規模 S 波速度低速体, 太平洋, S 波速度構造, 下部マントル
Keywords: LLSVP, Pacific, S-wave velocity structure, lower mantle

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SIT03-20

会場:106

時間:5 月 26 日 10:15-10:30

ダイナモモデルから推測されるコア-マントル境界下の安定成層の起源
On the origin of a stably stratified layer below the CMB inferred from dynamo models
高橋 太 1∗
TAKAHASHI, Futoshi1∗
11

九州大学理学研究院地球惑星科学部門
Department of Earth and Planetary Sciences, Kyushu University

The geodynamo is powered by the two agents, thermal and compositional buoyancy. The former is fueled by secular coolingof the Earth and/or latent heat upon solidification of the inner core, while the latter is by release of the light elements at the innercore boundary with inner core growth. Since these two buoyancy sources should behave differently due to the vast difference of
their diffusivity based on the molecular values, double diffusive convection would occur in the Earth’s core.
Apart from double diffusive convection, it is inferred from seismic observations that there is a thin stably stratified layer ofO(100) km below the core-mantle boundary. However, it is not well constrained whether the origin of stable stratification isthermal or compositional. Here we investigate effects of a stable layer on dynamo action driven by double diffusive convection.
Stably stratified layer is imposed by giving a sub-adiabatic temperature gradient. Thickness of the stable layer is assumed tobe 10 % of the core radius. It is found that strength of the dynamo-generated magnetic field is significantly reduced by thethin stable layer in case of dipolar dynamos. On the other hand, the magnetic field is strengthened with the stable layer in caseof weak multi-polar dynamos, consistent with a previous study. We discuss mechanisms responsible for such a difference andimplications for the origin of the stably stratified layer.

キーワード: ダイナモ, コア, 安定成層, 二重拡散対流
Keywords: dynamo, core, stable stratification, double diffusive convection

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SIT03-21

会場:106

時間:5 月 26 日 10:30-10:45

地球深部コアにおける磁気ロスビー波
Magnetic Rossby waves in the Earth’s core
堀 久美子 1∗ ; Jones Chris1 ; Teed Rob3
HORI, Kumiko1∗ ; JONES, Chris1 ; TEED, Rob3
1

リーズ大学応用数理学科, 2 名古屋大学太陽地球環境研究所, 3 ケンブリッジ大学応用数理理論物理学科
Department of Applied Mathematics, University of Leeds, UK, 2 STEL, Nagoya University, 3 DAMTP, University of Cambridge,
UK

1

Magnetohydrodynamic waves in rapidly rotating planetary cores can produce several secular variations of the planetary magnetic field. Some axisymmetric modes, including the torsional Alfven waves, are thought to be responsible for certain observed
features of the Earth’s core dynamics and the geomagnetic variation. It is, on the other hand, possible for other waves to lead tothe nonaxisymmetric variations. A potential candidate is the magnetic Rossby wave, which migrates in the azimuthal direction
along the internal toroidal field. This can be related to the westward drift of the geomagnetic field, which has been observed in
the Atlantic hemisphere for the past hundred years. Though the drift has commonly been believed to reflect advection due tolarge-scale lateral flows beneath the top of the core, propagation of the waves excited within the core may also account for it.
This was originally proposed by Hide (1966), who showed that a slow mode of magnetic Rossby waves, sometimes called a slow
MC-Rossby mode, could propagate westward on timescales of hundreds years.
To investigate whether this mode can be relevant in the Earth’s core, we extend Hide’s linear theory to quasi-geostrophic cylinders and explore nonlinear dynamo simulations in rotating spherical shells. By performing tempo-spatial spectral analyses, we
identify slow MC-Rossby waves that propagate at the correct speed, given by the Alfven and Rossby speeds, with respect to themean zonal flow. The result indicates that this mode could be excited in the planetary fluid core and that the wave propagation
may indeed play a role in the magnetic drift. Taking geomagnetic drift speeds, the theory suggests the internal toroidal field of
about 10 mT at the mid core radius. This could give a framework for inferring the physical properties in the fluid core, in termsof nonaxisymmetric waves.

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SIT03-22

会場:106

時間:5 月 26 日 11:00-11:15

第一原理計算による地球外核条件下における液体鉄合金の研究
Liquid iron alloys with light elements at outer core conditions by first-principles calculation
梅本 幸一郎 1∗ ; 廣瀬 敬 2
UMEMOTO, Koichiro1∗ ; HIROSE, Kei2
11

東京工業大学地球生命研究所, 2 東京工業大学地球生命研究所, 海洋研究開発機構
Earth-Life Science Institute, Tokyo Institute of Technology, 2 ELSI, TITECH; OELE, JAMSTEC

Since the density of the outer core deduced from seismic data is about 10% lower than that of pure iron at core pressures andtemperatures (P-T), it is widely believed that the outer core includes one or more light elements. Although intensive experimental
and theoretical studies have been performed so far, the light element in the core has not yet been identified. Comparison of thedensity and sound velocity of liquid iron alloys with observations, such as the PREM, is a promising way to determine the species
and quantity of light alloying component(s) in the outer core. Here we report the results of a first-principles molecular dynamics
study on liquid iron alloyed with different concentrations of light elements, in order to clarify the effects of their impurities on
the liquid density and sound velocity under outer core P-T conditions. We also discuss validity of empirical Birch’s law between
density and sound velocity in liquid iron alloys.
キーワード: 外核, 液体鉄合金, 第一原理計算
Keywords: outer core, liquid iron alloys, first principles

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SIT03-23

会場:106

時間:5 月 26 日 11:15-11:30

高圧下における液体 Fe-C 合金の音速測定
Sound velocity measurements of liquid Fe-C alloy under high pressure
中島 陽一 1∗ ; 今田 沙織 2 ; 廣瀬 敬 2 ; 駒林 鉄也 3 ; 小澤 春香 4 ; 舘野 繁彦 2 ; 桑山 靖弘 5 ; 筒井 智嗣 6 ;Baron Alfred1
NAKAJIMA, Yoichi1∗ ; IMADA, Saori2 ; HIROSE, Kei2 ; KOMABAYASHI, Tetsuya3 ; OZAWA, Haruka4 ;TATENO, Shigehiko2 ; KUWAYAMA, Yasuhiro5 ; TSUTSUI, Satoshi6 ; BARON, Alfred1
1

理化学研究所放射光科学総合研究センター, 2 東京工業大学地球生命研究所, 3 エジンバラ大学地球科学科, 4 独立行政法
人海洋研究開発機構, 5 愛媛大学球深部ダイナミクス研究センター, 6 独立行政法人高輝度光科学研究センター
1
RIKEN, SPring-8 Center, 2 Earth-life science institute, Tokyo Institute of Technology, 3 School of GeoSciences, The Universityof Edinburgh, 4 Japan Agency for Marine-Earth Science and Technology, 5 Geodynamics Research Center (GRC), Ehime University, 6 Japan Synchrotron Radiation Research InstituteThe liquid Earth’s outer core consists predominantly of iron with c.a. 10 wt.% lighter elements, such as hydrogen, carbon,
oxygen, silicon, and sulfur. Other terrestrial planets such as Mars, Mercury and Venus are also similar to the Earth in that they
have a central metallic core, which are considered to be at least partially molten. Popular models for those planetary cores alsofavor the existence of lighter elements. The nature of the light elements is important for understanding the acient core formation
processes and the present core structure and dynamics in terrestrial planets, which are still not well understood. The seismic wave
speed is the primary information on the Earth’s core. The sound velocity of liquid Fe alloying with light-elements is therefore
key to constrain the lighter component in the Earth’s core and will be referenced for the future survey of other planets. Recently
we have developed the techniques for inelastic X-ray scattering (IXS) measurements combined with diamond-anvil cell (DAC)
experiments at the SPring-8 synchrotron facility, in order to investigate sound velocities of liquid Fe alloying with light-elements
under high pressure and high temperature conditions relevant to planetary cores. We determined sound velocities of liquid Fe-C
alloy up to 70 GPa. We will discuss the effect of carbon on sound velocity of liquid iron and on planetary cores.
Keywords: sound velocity, light element in the core, liquid iron carbide, high pressure

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SIT03-24

会場:106

時間:5 月 26 日 11:30-11:45

コア圧力下における Fe-FeS 系の融解実験
Melting experiments in the system Fe-FeS at core pressures
森 祐子 1∗ ; 舘野 繁彦 2 ; 廣瀬 敬 2 ; MORARD Guillaume3 ; 大石 泰生 4
MORI, Yuko1∗ ; TATENO, Shigehiko2 ; HIROSE, Kei2 ; MORARD, Guillaume3 ; OHISHI, Yasuo4
1

東京工業大学 地球惑星科学専攻, 2 東京工業大学 地球生命研究所, 3 IMPMC, Universite Pierre-et-Marie-Curie, 4 高輝度光科学研究センター
1
Dept. of Earth & Planetary Sciences, Tokyo Institute of Technology, 2 Earth-Life Science Institute, Tokyo Institute of Technology, 3 IMPMC, Universite Pierre-et-Marie-Curie, 4 Japan Synchrotron Radiation Research InstituteJ

Most of the Earth’s core is iron and nickel alloy. However, the density of the core acquired from Preliminary reference Earthmodel (PREM) is smaller than that of pure iron. The amount of deficit is 6-10 wt % at the outer core and 1-3 wt % at the innercore. To explain this deficit, the core might contain one or more light elements (H, C, N, O, Si, S).
S is depleted in the crust and mantle compared to other volatile elements (Poirier ,1994). Moreover, iron meteorites contain
S (Chabot, 2004), thus we focus on S. In order to discuss the composition of the core, the phase diagram is important. The
bulk core composition must be Fe-rich side at inner core boundary (ICB) because the outer core incorporates larger amounts oflight element than the inner core. Fe-FeS phase diagram is determined by X-ray diffraction (XRD) pattern (e.g. Morard et al.
2008) or chemical analysis of recovered sample (e.g. Kamada et al. 2012). However, no accurate determination of the eutectic
composition has been obtained by XRD. On the other hand, constraining by chemical analysis has not been done using sample
recovered from core pressure. Thus, we examine Fe-S phase diagram at higher pressure.
High pressure and temperature (P-T) conditions were generated in a laser-heated diamond-anvil cell. We used Fe-7.5, 13.5
wt.% S foil as a starting material. Angle-dispersive in situ X-ray diffraction (XRD) measurements at high P-T were conducted
at BL10XU, SPring-8. The textural and chemical characterizations of recovered samples were made with a field-emission-type
scanning electron-microprobe (FE-SEM) equipped with energy dispersive x-ray spectrometry (EDS) and with a field-emissiontype electron probe microanalyzer (FE-EPMA). Cross sections of samples were carefully examined by combining a focused Ga
ion beam (FIB) with FE-SEM.
From quantitative analysis, we observed the trend that the amount of S in melt decreases and that the amount of S in the solid
Fe increases with increasing pressure.
Obseving the sample using Fe-7.5 wt % S by SEM, we can see the 3 textures; melt, solid Fe, subsolidus phase. Melt includes
more S than solid Fe. The content of S in liquid is between 12.5 and 10.4 wt. % in the range of 38-138 GPa. The eutectic composition is expected to have S than molten iron. Moreover, according to the experiment using S rich starting material, the texture ofrecovered sample contain melt ,Fe3S, subsolidus phase. The S content in melt is larger than that in eutectic composition.Using
both of S-rich and S-poor starting material, we can constrain the eutectic composition.
Assuming that the negative pressure dependence of S content in melt is retained up to ICB pressure, the content of S in liquid
Fe at ICB pressure is lower than 10 wt %. The S amount required to explain core density deficit (CDD) is 11.9-13.9 wt.% atouter core and 6-6.6 wt. % at inner core (Sata et al. 2010) . In this condition, the S content of eutectic composition is more than
11.9 wt.%. However, this value is great comparing to the eutectic composition expected from this study. Therefore, S is not the
only light element inthe Earth’s core.
キーワード: 高温高圧, 融解実験, 地球核, 軽元素, 密度欠損
Keywords: High pressure and temperature, melting experiments, the Earth’s core, light element, core density deficit

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SIT03-25

会場:106

時間:5 月 26 日 11:45-12:00

ε鉄の粒成長と内核のダイナミクス
Inner core dynamics inferred from grain growth of epsilon-iron山崎 大輔 1∗ ; 辻野 典秀 1 ; 米田 明 1 ; 芳野 極 1 ; 肥後 祐司 2
YAMAZAKI, Daisuke1∗ ; TSUJINO, Noriyoshi1 ; YONEDA, Akira1 ; YOSHINO, Takashi1 ; HIGO, Yuji2
1
1

岡山大学, 2 高輝度光科学研究センター
Okayama Univ., 2 JASRI

The inner core is thought to be composed of Fe-Ni alloy with hcp structure based on the high pressure experiments (Tateno
et al., 2012) and hence the physical properties of hcp iron (epsilon-iron) are keys for understanding the dynamics of the innercore. Recent seismic observations suggest the variation in grain size in the inner core (Monnereau et al., 2010). It is importantto understand the variation in grain size for constraints of the dynamics of the inner core because grain size is controlled by thegrowth rate and growth rate gives us information on time scale of the inner core growth and/or deformation. In this study, we
experimentally determine the grain growth rate of epsilon-iron to understand the dynamics of inner core.
epsilon-iron is only stable at high pressure and it is unquenchable to an ambient condition. Therefore, in this study, we conduct
in situ high pressure experiments to determine the grain growth rate of epsilon-iron. We prepared polycrystalline iron of starting
material by multi-directional forging (MDF) on highly purity iron rod to avoid oxidation during sintering. In the high pressure
experiment, the starting materials was compressed in a Kawai-type high pressure apparatus equipped with sintered diamondanvils with 1.0 truncated edge length at BL04B1, SPring-8. At the pressure of 50-60 GPa, sample was heated for several hours
to determine the grain growth rates. Grain growth can be detected by the reduction of number of diffraction spots on the twodimensional detector with monochromatic X-ray (Offerman et al., 2002) with annealing time.
In the experiments, we observed the reduction of the number of diffracted spots, meaning that grain growth occurs during
annealing experiments. For example, the number of diffraction spots reduced to 50 % after annealing at 1300 K for two hours.
By extrapolating the present data, we may constrain the translation dynamics of the inner core (Alboussiere et al., 2010) incomparison with seismic observation.
Monnereau, M., Calvet, M., Margerin, L., Souriau, A. (2010) Lopsided growth of earth’s inner core, Science, 328, 1014-1017.
Alboussiere, T., Deguen, R., Melzani, M. (2010) Melting-induced stratification above the earth’s inner core due to convective
translation, Nature, 466, 744-747.
Offerman, S. E., van Dijk, N. H., Sietsma, J., Grigull, S., Lauridsen, E. M., Margulies, L., Poulsen, H. F., Rekveldt, M., vander Zwaag, S. (2002) Grain nucleation and growth during phase transformations, Science, 298, 1003-1005.
Tateno, S., Hirose, K., Komabayashi, T., Ozawa, H., Ohishi, Y. (2012) The structure of Fe-Ni alloy in earth’s inner core,
Geophy. Res. Lett., 39, L12305.

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