SIT07-01

日本地球惑星科学連合2016年大会

物性物理学の観点から説明される地球の内部構造
The Earth’s internal structure explained from a viewpoint of the condensed matter physics*唐澤 信司1*Shinji Karasawa1
1.宮城工業高等専門学校 名誉教授
1.Miyagi National College of Technology Professor emeritus​ 地球の深さの増加に応じて物質に及ぼす圧力が増加します。外部から圧力を受けると物質のサイズは縮小
し、凝集力のポテンシャルエネルギーは大きくなります。物質は低いエネルギーの状態になる時に低下する分のエネルギーを放出します。ところで、隕石が地表に衝突する際には衝突により圧縮された物質は収縮して発熱しますが、その熱は直後の膨張で吸収されてしまいます。隕石が衝突するとクレーターを作りますが、衝突の周辺の地域の地面が溶融していた形跡はありません。ちなみに、地球の中心部の定常温度は最高で7000℃であり、0.63 eV の電子状態に相当します。地球の中心部の温度をそのような状態にするのは衝突のエネル
ギーではなくて、集積した物質の性質によるとして説明できます。
地球の地下深くなるほど電子軌道間の相互作用が大きくなり、より低いエネルギーの状態が可能になります。熱運動により隣接原子を交換して置かれた状況に適した物質になることが可能であれば物質はその変化をします。物質はエネルギーが低い状態になる時に、前後の差のエネルギーによって発熱します。その熱はマントルを経由して地殻に放出されます。熱の移動に伴って物質も移動するのでマントル対流が起こります。その対流は海のプレートの下のマントルの方が大陸の地殻の下より放熱が盛んであるので、海底に湧き出します。
地球の深い内部の物質の性質は次のようになります。地球内部の高い圧力で物質の電子軌道がオーバーラップ
すると、同じエネルギーレベルに複数の電子軌道が存在する縮重状態になります。縮重した電子状態は電気伝導性と流動性を持ち、その物質は液体金属のような性質を示します。それが地球内部の外核の状態です。ところが物質の縮重状態の電子のエネルギーレベルは原子の配置の対称性を低くすると分裂して、さらに低いエネ
ルギーの電子状態が得られるというヤーン・テラー効果があります。そのヤーン・テラー効果によって横波を伝える固体の状態になったのが地球の中心部の内核の状態です。
このように集まった物質の電子状態を考慮して次の事柄を説明しました。 (1)マントル対流の熱源、(2)海のプレートが沈み込む付近の火山の熱源、(3)地球の外殻の液体の状態、(4)地球の内核の固体の状態、 (5)太陽系の形成、及び(6) 地球型惑星の形成。詳しくは以下のWebsite をご覧ください。
(https://www.youtube.com/watch?v=Wi5G2F_pDXM&feature=youtu.be )キーワード：マントル対流、外核、内核、断熱圧縮、縮重電子状態、ヤーン・テラー効果
Keywords: Mantle convection, Outer core, Inner core, Adiabatic compression, Degenerated state ofelectron, Jahn-Teller-Effect©2016. Japan Geoscience Union. All Right Reserved.

- SIT07-01 -SIT07-02

日本地球惑星科学連合2016年大会

低粘性層を有する月の深部構造：月の潮汐応答に関する最新の測地学的係数に基づいて修正された制
約条件
The deep lunar interior with a low-viscosity zone: Revised constraints from recent
geodetic parameters on the tidal response of the Moon
*原田 雄司1,2、ホーセンス サンダー3、松本 晃治4、エン 建国5、平 勁松6、野田 寛大4、春山 純一7*Yuji Harada1,2, Sander Goossens3, Koji Matsumoto4, Jianguo Yan5, Jinsong Ping6, Hirotomo Noda4,
Junichi Haruyama7
1.澳門科技大学太空科学研究所、2.東京大学地震研究所、3.メリーランド大学ボルチモア郡校宇宙科学技術研
究探査センター、4.自然科学研究機構国立天文台、5.武漢大学測絵遥感信息工程国家重点実験室、6.中国科学院国家天文台、7.宇宙航空研究開発機構宇宙科学研究所
1.SSI, MUST, 2.ERI, UT, 3.CRESST, UMBC, 4.NAOJ, NINS, 5.LIESMARS, WHU, 6.NAOC, CAS, 7.ISAS, JAXA
We revisit the constraints on the deep lunar interior with a possible low-viscosity zone at thecore-mantle boundary obtained from our previous forward modeling of the tidal response of the Moon,by comparing a numerical model with several tidal parameters that have been improved or are newly
determined by recent geodetic observations and analyses from GRAIL (gravity), LRO (shape), and LLR(rotation). Our results are in principle consistent with the latest data and lead to a thicker
low-viscosity layer (with an outer radius of about 540 to 560 km, which is much larger than that ofabout 500 km in our earlier investigation) which reaches just below or inside the place where many
seismic nests of deep moonquakes are located.
キーワード：粘性、月、内部、潮汐、ラブ数、クオリティ係数
Keywords: viscosity, Moon, interior, tide, Love number, quality factor©2016. Japan Geoscience Union. All Right Reserved.

- SIT07-02 -SIT07-03

日本地球惑星科学連合2016年大会

Seafloor subsidence and mantle dynamics
Seafloor subsidence and mantle dynamics*Adam Claudia1、King S1、Rabinowicz M2、Vidal Valerie3、Jalobeanu A4、吉田 晶樹5*Claudia Adam1, S King1, M Rabinowicz2, Valerie Vidal 3, A Jalobeanu4, Masaki Yoshida51.Virginia Polytechnic Institute and State University、2.GET, Observatoire Midi-Pyrénées,
Toulouse、3.Laboratoire de Physique, ENS Lyon、4.Bayes Map Solutions, LLC, Castro Valley, CA、5.独立行政法人海洋研究開発機構

地球深部ダイナミクス研究分野

1.Virginia Polytechnic Institute and State University, 2.GET, Observatoire Midi-Pyrénées, Toulouse,
3.Laboratoire de Physique, ENS Lyon, 4.Bayes Map Solutions, LLC, Castro Valley, CA, 5.Department of
Deep Earth Structure and Dynamics Research, Japan Agency for Marine–Earth Science and Technology(JAMSTEC)
The subsidence of seafloor is generally considered as a passive phenomenon related to the
conductive cooling of the lithosphere since its creation at mid-oceanic ridges. Recent alternative
theories suggest that the mantle dynamics plays an important role in the structure and depth of theoceanic lithosphere. However, the link between mantle dynamics and seafloor subsidence has still tobe quantitatively assessed. Here we provide a statistic study of the subsidence parameters(subsidence rate and ridge depth) for all the oceans. These parameters are retrieved through thepositive outliers method, a classical method used in signal processing. We also model the mantle
convection pattern from the S40RTS tomography model. The density anomalies derived from this model
are used to compute the instantaneous flow in a global 3D spherical geometry, and the induced
dynamic topography.
The variations of the mid-oceanic ridge depths are well recovered by the modeled dynamic
topography. The systematic fit of the bathymetry allows the recovery of the subsidence rate, fromwhich we derive the effective thermal conductivity, keff. This parameter ranges between 1 and 7 Wm-1
K-1. We show that departures from the keff=3 Wm-1K-1 standard value are systematically related tomantle convection and not to the lithospheric structure. Regions characterized by keff>3 Wm-1K-1 areassociated with the uplift of mantle plumes. Regions characterized by keff<3 Wm-1K-1 are related tolarge scale mantle downwellings such as the Australia-Antarctic Discordance (ADD) or the return
flow from the South Pacific Superswell to the East Pacific rise. This demonstrates that the mantle
dynamics plays a major role in the shaping of the oceanic seafloor. In particular, the parameters
generally considered to quantify the lithosphere structure, such as the thermal conductivity, are
not only representative of this structure but also incorporate signals from the mantle convection
occurring beneath the lithosphere.

©2016. Japan Geoscience Union. All Right Reserved.

- SIT07-03 -SIT07-04

日本地球惑星科学連合2016年大会

Effect of along-trench slab dimension on subduction-induced upper mantle flow: Insightsfrom 3-D laboratory models*Vincent Strak1,2, Wouter Pieter Schellart11.Monash University, 2.Earthquake Research InstituteThree-dimensional self-evolving subduction models with various along-trench dimensions have been
quantitatively analysed in the laboratory by means of a stereoscopic Particle Image Velocimetry(sPIV) technique. The purpose was (1) to provide information on the pattern of the upper mantle
flow induced by subduction, particularly focusing on the location and magnitude of upwellings
around the lateral slab edges and in the mantle wedge, (2) to study the evolution of mantle
upwellings in terms of location and magnitude, and (3) to study the effect of along-trench slab
dimension on upwelling location and magnitude. The model results show that 4 types of upwelling are
generated by subduction in a Newtonian upper mantle. One of these upwellings occurs laterally awayfrom the sub-slab domain and could potentially trigger decompression melting, thereby explaining
the occurrence of a certain type of intraplate volcanism. Two other significant upwellings areobserved in the mantle wedge. The tested along-trench slab dimensions were comparable to slabs ofnarrow (e.g., Calabria) to wider (e.g., Tonga-Kermadec-Hikurangi) subduction zones. The results
indicate that both the location and magnitude of the upwelling occurring laterally away from thesub-slab domain are affected by the along-trench slab dimension, with wider slabs producing fasterand more focused upwellings that are located closer to the lateral slab edges. The models also seem
to show that the along-trench slab dimension controls the intensity of upwellings in the mantle
wedge.
Keywords: Subduction, Mantle flow, Upwellings©2016. Japan Geoscience Union. All Right Reserved.

- SIT07-04 -SIT07-05

日本地球惑星科学連合2016年大会

Seismic structure and dynamics beneath eastern Tibet: Insight into large earthquakes andTengchong volcano*Lei Jianshe1, Dapeng Zhao2
1.Key Laboratory of Crustal Dynamics, Institute of Crustal Dynamics, China Earthquake
Administration, 2.Department of Geophysics, Tohoku University
We review recent studies of seismic tomography and earthquake sequences, and discuss theirimplications for seismotectonics and mantle dynamics beneath eastern Tibet. The crustal structuresin the source areas of the 2008 Ms 8.0 Wenchuan and the 2013 Ms 7.0 Lushan earthquakes are similarand exhibit prominent low-velocity (low-V) and high-Poisson's ratio anomalies in the source areas,indicating that in addition to compositional variations, fluid-filled rock matrices exist in theLongmenshan fault zone, which may have influenced the nucleation of the two earthquakes.
Significant low-V anomalies are revealed between the Wenchuan and Lushan mainshocks, which may
explain why their aftershock zones extend northward and southward, respectively. The relocatedaftershocks of the 2011 Ms 5.8 Yingjiang and the 2014 Ms 6.5 Ludian earthquakes show a
conjugate-shaped distribution, which may explain why the two moderate-sized earthquakes caused
heavy damage. The large earthquakes in eastern Tibet are located at boundaries of low- or
high-velocity anomalies in the upper mantle. The structural heterogeneities in the crust and upper
mantle are associated with hot and wet upwelling and corner flows in the big mantle wedge above thesubducting Indian slab beneath eastern Tibet, as well as slab dehydration, which affect theseismogenesis in the region.
Keywords: Seismci structure, Mantle dynamics, Eastern Tibet, Large earthquake, Tengchong volcano©2016. Japan Geoscience Union. All Right Reserved.

- SIT07-05 -SIT07-06

日本地球惑星科学連合2016年大会

Transformational Faulting as a Deep-Focus Earthquake Mechanism: Correlating In-Situ
Acoustic Emission Locations at High P-T with Post-Mortem Fault Imaging Using Synchrotron
X-Ray Microtomography in Controlled Deformation Experiments*Yanbin Wang1, Lupei Zhu2, Feng Shi1, Tony Yu1, Mark L Rivers1, Alexandre Schubnel3, Nadege Hilairet4, Fabrice Brunet5
1.Center for Advanced Radiation Sources, University of Chicago, Chicago, IL, USA, 2.Department ofEarth Sciences, St. Louis University, St. Louis, MO, USA, 3.Laboratoire de Géologie, CNRS UMR 8538,
Ecole Normale Supérieure, Paris, France, 4.Université des Sciences et Technologies de Lille, Lille,
France, 5.CNRS-ISTerre, Université de Grenoble, Grenoble, France
One of the possible mechanisms responsible for deep-focus earthquakes occurring at depths below 350
km is faulting induced or triggered by phase transformation from metastable olivine to its
high-pressure phases (wadsleyite and ringwoodite, both are related to the general spinel structure)in the mantle transition zone. We have studied transformational faulting from olivine to spinel in
Mg2GeO4, a close analog of the silicate olivine (Mg,Fe)2SiO4, using a high-pressure deformation
apparatus in conjunction with in-situ acoustic emission (AE) monitoring [1]. Synchrotron X-ray
microtomography (XMT) [2] was used to image the samples recovered from high-pressure deformation
experiments, with spatial resolution of ~0.005 mm. In this study, we establish spatial correlations
between AE events observed during in-situ deformation experiments and faults imaged by XMT
post-mortem. The nature of high-pressure experiments limits the sample size to the order of 2 mm inlinear dimensions, and the acoustic system we used has a maximum sampling rate of 50 MHz (i.e., 20
ns between adjacent sampling points), which limits spatial resolution of AE locations to about 0.3
mm. This makes it difficult to locate AE events accurately. A well-developed double-difference
cross-correlation (CC) algorithm (hypoDD –[3]) developed for seismological studies has beensuccessfully adapted in the analysis of AE locations, improving AE allocation spatial resolution bya factor of ~10. This algorithm also helps separate events with various waveforms, which are
related to different fault planes and faulting directions. The CC algorithm classifies AE events
into various groups. Events within each group share common characteristics and may be consideredoccurring within the same faulting mechanism. These groups of events display excellent correlations
with faults imaged by XMT, with two major groups of AE events correlating well with two conjugatedfaults in XMT images. Furthermore, time sequence of AE events can be examined to investigate
details of formation of macroscopic faults from the micro AE events. These results help understandthe dynamic process of transformational faulting.
References:[1] A. Schubnel et al., Deep-Focus Earthquake Analogs Recorded at High Pressure and Temperature in
the Laboratory. Science 341, 1377 (2013).
[2] M. L. Rivers, Y. Wang. (2006), Recent developments in microtomography at GeoSoilEnviroCARS, in:Developments in X-Ray Tomography V, U. Bonse (ed.), Proc. SPIE vol. 6318, pp. 63180J-63180J-15[3] F. Waldhauser, W. L. Ellsworth, A Double-Difference Earthquake Location Algorithm: Method andApplication to the Northern Hayward Fault, California. Bulletin of the Seismological Society ofAmerica 90, 1353 (2000).
Keywords: Deep-focus earthquakes, High P-T deformation, Acoustic emission, Synchrotron x-ray
diffraction and imaging, Earthquake mechanisms©2016. Japan Geoscience Union. All Right Reserved.

- SIT07-06 -SIT07-07

日本地球惑星科学連合2016年大会

Behavior of basalt-carbonate melts at high pressures
Behavior of basalt-carbonate melts at high pressures*Kono Yoshio1、Ohfuji Hiroaki2、Stagno Vincenzo2、Kenney-Benson Curtis1、Wang Yanbin3、Shen Guoyin1*Yoshio Kono1, Hiroaki Ohfuji2, Vincenzo Stagno2, Curtis Kenney-Benson1, Yanbin Wang3, Guoyin Shen1
1.Carnegie Institution of Washington、2.Ehime University、3.The University of Chicago
1.Carnegie Institution of Washington, 2.Ehime University, 3.The University of Chicago
Knowledge of the occurrence and mobility of carbonate-rich melts in the Earth’s mantle is importantfor understanding the deep carbon cycle and related geochemical and geophysical processes.
Recently, Kono et al. (2014) find that viscosities of carbonate melts are surprisingly low, in therange of 0.006-0.010 Pa s, which are ~2 to 3 orders of magnitude lower than those of basaltic meltsin the upper mantle. As a result, the mobility of carbonate melts (defined as the ratio of
melt-solid density contrast to melt viscosity) is ~2 to 3 orders of magnitude higher than that ofbasaltic melts. Such high mobility of carbonate melts may have significant influence on several
magmatic processes, such as fast melt migration and effective melt extraction beneath mid-ocean
ridges. However, the behaviour of carbonate-rich silicate melt may be complex, as demonstrated in
the reported immiscible behaviour of silicate-carbonate melts. To predict potential implications ofcarbonate-rich silicate melt as they migrate up in the upper mantle, the stability should be
investigated at those pressures. Here we investigate behavior of basalt-dolomite melts with 20-61
vol.% dolomite compositions at high pressures to 7.3GPa by using newly developed X-ray phase
contrast imaging technique in Paris-Edinburgh cell at beamline 16BMB, HPCAT, in the Advanced Photon
Source. We find that basalt plus 32-61 vol.% dolomite becomes single melt at pressure >~5.5 GPa,
while it separates into silicate-dominant melt plus CO2 at lower pressures. The abrupt change ofstability of carbonate-rich silicate melt may play a role of paramount importance in migration
velocity of upwelling carbonate-silicate magmas due to separation of carbonate component fromsilicate melt, with 2-3 orders of magnitude difference of viscosity between basalt and carbonate
melts.
Reference
Kono, Y., C. Kenney-Benson, D. Hummer, H. Ohfuji, C. Park, G. Shen, Y. Wang, A. Kavner, and C. E.
Manning (2014), Ultralow viscosity of carbonate melts at high pressures, Nature Communications, 5, 5091.
キーワード：carbonate、melt、high pressure
Keywords: carbonate, melt, high pressure©2016. Japan Geoscience Union. All Right Reserved.

- SIT07-07 -SIT07-08

日本地球惑星科学連合2016年大会

沈み込むスラブの構造と運動学的観測から見た滞留スラブの形成と進化
Stagnant slab formation and evolution inferred from kinematic and geometrical observationsof the subduction zone
*中久喜 伴益1*Tomoeki Nakakuki1
1.広島大学大学院理学研究科地球惑星システム学専攻
1.Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima
University
Seismic tomography revealed variable slab structure in the mantle transition zone (e.g., Fukao etal., 2009). Numerical modeling that incorporates phase transition at the 660 km depth and trenchmigration succeeded to simulate formation and avalanche of the stagnant slab (Christensen, 1996;
Torii and Yoshioka, 2007; Nakakuki et al., 2010). Mechanisms to control structure of the transitionzone slab are still controversial (e.g., Karato et al., 2001; King et al., 2015), since we have notsufficiently understood relationship of the slab dynamics with tectonic features in the actual
subduction zone (cf. Billen, 2010). In this study, subduction zone geometric and kinematic
observations are analyzed aiming to construct a scenario for the stagnant slab formation andevolution. The data, which are compiled by Lallemand et al. (2005) and (2008), include absolute
motions of the subducting plate, the overriding plate and the trench based on a global plate motion
model (SB04) constructed by Steinburger et al. (2004), slab depths, and slab dip angles.
Important observations connected to the stagnant slab dynamics are summarized as follows. (1) Mostof upper mantle slabs are retreating with the velocity larger than 1 [cm/yr]. (2) In the subduction
zone with the slab penetrating at the depth between 660 to 1200 km, trench motion is advance (e.g.,
Mariana, Java) or retreat with the slower velocity (< 1 [cm/yr], e.g., north Kuril) than that in
the subduction zone with the upper slab. (3) Back-arc extension often occurs in the subduction zone
in which the maximum slab depth is 660 km (e.g., Tonga). (4) Dip angles of the upper and lower
mantle slabs become steeper with the age. (5) Stagnant slabs are classified into 2 types. (i) The
first type has young age (< 60 [Ma]), slow subducting plate motion (the slab descending motion
occur as if the plate peeled and fell off from the surface (e.g., New Hebrides). (ii) The second
type has old age (> 100 [Ma]) and dip angles obviously shallower (< ~50 [deg], e.g., south Kuril,
Japan) than those of the slab penetrating into the lower mantle.
These results indicate important relationship of the slab dip angle and trench migration to theslab structure varying with the sinking depth. The following scenario emerges as a possible
explanation for the stagnant slab mechanics. (1) A relatively young slab with shallow dip angle andtrench retreat collides to the 660 km phase transition. (2) The slab start stagnates at 660 km, andthe slab rollback is further enhanced. (3) When the dip angle of the stagnating slab is shallow,
the slab retains the stagnation at the 660 km after the trench retreat is declined. (4) When the
dip angle is steepened and/or the trench advance is generated owing to increase of subducting plateage or collision of the continent, the slab penetrates into the lower mantle.
キーワード：滞留スラブ、マントル遷移層、プレート運動、沈み込み帯
Keywords: stagnant slab, mantle transition zone, plate kinematics, subduction zone

©2016. Japan Geoscience Union. All Right Reserved.

- SIT07-08 -SIT07-09

日本地球惑星科学連合2016年大会

クロミタイトの微細構造に保存されたマントル遷移層における変形
Messengers from the deep: Fossil wadsleyite-chromite microstructures from the Mantle
Transition Zone
*佐津川 貴子1、Griffin William2、Piazolo Sandra2、O'Reilly Suzanne2*Takako Satsukawa1, William L Griffin2, Sandra Piazolo2, Suzanne Y O'Reilly2
1.京都大学大学院理学研究科地球惑星科学専攻地球物理学教室、2.CCFS&GEMOC, Department of Earth andPlanetary Sciences, Macquarie University
1.Department of Geophysics, Division of Earth and Planetary Sciences, Kyoto University,
2.CCFS&GEMOC, Department of Earth and Planetary Sciences, Macquarie University
Investigations of the Mantle Transition Zone (MTZ; 410-660 km deep) by deformation experiments andgeophysical methods suggest that the MTZ has distinct rheological properties, but their exact cause
is still unclear due to the lack of natural samples. Here we present the first direct evidence forcrystal-plastic deformation by dislocation creep in the MTZ using a chromitite from the Luobusa
peridotite (E. Tibet). Chromite grains show exsolution of diopside and SiO2, suggesting previous
equilibration in the MTZ. Electron backscattered diffraction (EBSD) analysis reveals that olivine
grains co-existing with exsolved phases inside chromite grains and occurring on chromite grainboundaries have a single pronounced crystallographic preferred orientation (CPO). This suggeststhat olivine preserves the CPO of a high-pressure polymorph (wadsleyite) before the high-pressurepolymorph of chromite began to invert and exsolve. Chromite also shows a significant CPO. Thus, thefine-grained high-pressure phases were deformed by dislocation creep in the MTZ. Grain growth ininverted chromite produced an equilibrated microstructure during exhumation to the surface, masking
at first sight its MTZ deformation history. These unique observations provide a window into thedeep Earth, and constraints for interpreting geophysical signals and their geodynamic implications
in a geologically robust context.
キーワード：マントル遷移層、クロミタイト、かんらん石、結晶方位定向配列、EBSD、微細構造
Keywords: Mantle transition zone, chromitite, olivine, CPO, EBSD, microstructure©2016. Japan Geoscience Union. All Right Reserved.

- SIT07-09 -SIT07-10

日本地球惑星科学連合2016年大会

Mantle transition zone beneath a normal seafloor in the northwestern Pacific: Electricalconductivity, seismic discontinuity, and water content
Mantle transition zone beneath a normal seafloor in the northwestern Pacific: Electricalconductivity, seismic discontinuity, and water content*松野 哲男1、末次 大輔2、歌田 久司1、馬場 聖至1、多田 訓子2、清水 久芳1、塩原 肇1、一瀬 建日1、杉岡
裕子3、伊藤 亜妃2*Tetsuo Matsuno1, Daisuke Suetsugu2, Hisashi Utada1, Kiyoshi Baba1, Noriko Tada2, Hisayoshi Shimizu1, Hajime Shiobara1, Takehi Isse1, Hiroko Sugioka3, Aki Ito2
1.東京大学地震研究所、2.海洋研究開発機構、3.神戸大学
1.Earthquake Research Institute, The University of Tokyo, 2.Japan Agency for Marine-Earth Scienceand Technology, 3.Kobe University
We conducted a joint electromagnetic (EM) and seismic experiment to probe the mantle structure
below a normal seafloor around the Shatsky Rise in the northwestern Pacific. Specifically for theinvestigation of the mantle transition zone (MTZ) structure, we deployed our state-of-the-art
instruments in two arrays to the north and south of the Shatsky Rise for 5 years from 2010 to 2015.
Here we report the result of analyses of EM and seismic data obtained in the joint experiment aswell as in previous studies. From the EM data analysis, a 1-D profile of electrical conductivity
was obtained for two observational arrays. The thickness of the MTZ was also obtained by the P-wave
receiver function analysis, from which temperature profiles in the MTZ below two arrays were thenestimated. We found that the northern array provides EM and seismic data with much higher quality
than the southern array, and therefore meaningful estimation of MTZ water content is possible forthe northern array. We estimated water content based on profiles of electrical conductivity andtemperature obtained by our geophysical observation and electrical conductivities of dry and wet
MTZ minerals (wadsleyite and ringwoodite) obtained by mineral physics. The result of the forward
modeling study indicated that the upper limit of water content below the northern array is 0.5 wt.%
or 0.05 wt.%, depending on different results of laboratory experiments for water effects onelectrical conductivities. The lower limit of water content was not constrained by our data.

©2016. Japan Geoscience Union. All Right Reserved.

- SIT07-10 -SIT07-11

日本地球惑星科学連合2016年大会

H-D inter-diffusion in Fe-free wadsleyite: implication for multiple hydrogen mechanism*Wei Sun1, Takashi Yoshino1, Naoya Sakamoto2, Hisayoshi Yurimoto3
1.Research Group of Physics of the Earth's Interior at the Institute for Study of the Earth's
Interior, Okayama University, 2.Isotope Imaging Laboratory, Creative Research Institution, Hokkaido
University, 3.Department of Natural History Sciences, Hokkaido University
It has been proposed that concentration and speciation of water-derived species in minerals may
adjust in response to changes of points defect condition [Demouchy and Mackwell, 2006], To lift
the veil of Fe effect on hydrogen diffusion and isotopic differentiation, a sets of H-Dinter-diffusion experiments were conducted in Fe-free wadsleyite single crystal couples at various
temperatures, 16 GPa and compared with our former study on Fe-bearing wadsleyite. Distinguish withsymmetric profiles in Fe-bearing condition, H-D inter-diffusion in Fe-free wadsleyite revealed
evidently asymmetric properties and it indicates deuterium diffuses about 1 order faster thanhydrogen in Fe-free wadsleyite. Both magnitude and anisotropy of H-D inter-diffusion in Fe-free
condition are largely different with Fe-bearing condition, which strongly demonstrated a multiplehydrogen mechanism proposed by Karato (2013) association with free proton migration in interstitialsites. Simulation model suggests free proton migration in interstitial sites dominates the hydrogen
diffusion in Fe-free condition and asymmetric properties might owe to the distinguished jumping
probabilities from Mg sites to interstitial sites between hydrogen and deuterium.
Keywords: inter-diffusion, wadsleyite, asymmetric, multiple©2016. Japan Geoscience Union. All Right Reserved.

- SIT07-11 -SIT07-12

日本地球惑星科学連合2016年大会

High-pressure phase relations in the system MgCr2O4-Mg2SiO4 with implications to ultra-highpressure chromitites in ophiolites
High-pressure phase relations in the system MgCr2O4-Mg2SiO4 with implications to ultra-highpressure chromitites in ophiolites*赤荻 正樹1、姉川 由輝1、河原 愛理1、石井 貴之1、糀谷 浩1*Masaki Akaogi1, Yuki Anegawa 1, Airi Kawahara1, Takayuki Ishii1, Hiroshi Kojitani1
1.学習院大学理学部化学科
1.Department of Chemistry, Faculty of Science, Gakushuin University
Podiform chromitites which are enveloped by dunite are commonly found in harzburgite in ophiolites.
It is interpreted that the podiform chromitites were formed through reaction between harzburgite
and melt at a shallow upper mantle level. However, some podiform chromitites recently found in
Luobusa ophiolites, Tibet, were interpreted to be derived from the deep mantle, because thechromitites contained diamond and coesite as inclusions. Yamamoto et al. (2009) and Arai (2013)
suggested that the chromitites originally consisted of calcium-ferrite (CF) structured phase in the
deep mantle and that they transformed to spinel-structured chomites during upwelling.
We have recently determined phase relations in MgCr2O4 at pressure up to 28 GPa and temperature to1600 oC. Magnesium chromite (MgCr2O4) with the spinel structure first transforms to a two-phaseassemblage of modified ludwigite (mLd)-type Mg2Cr2O5 + corundum-type Cr2O3 at 13-15 GPa, and the twophases combine into a calcium-titanate (CT) phase at 16-20 GPa (Ishii et al., 2015). Because
chromite minerals in natural podiform chromitites are enveloped in olivine crystals, we haveextended our experimental study to the system MgCr2O4-Mg2SiO4 to examine phase relations and mutual
solubilities in the high-pressure phases.
High-pressure high-temperature experiments were performed in composition of 50mol%MgCr2O4.50mol%Mg2
SiO4 up to 26 GPa at 1600 oC using a Kawai-type mulitianvil apparatus. Phase identification of thesynthesized samples were made using micro-focus and powder X-ray diffractometers. Composition
analysis was performed using a scanning electron microscope with an energy-dispersive X-ray
spectrometer. At pressure below about 14 GPa, Mg2SiO4 forsterite coexists with MgCr2O4-rich spinel.
At 14-19 GPa, a three-phase assemblages, mLd + garnet (Gt) + wadsleyite (Wd) becomes stable. This
assemblage changes into MgCr2O4-rich CT + ringwoodite at about 20 GPa, which further changes into
an assemblage of MgSiO3-rich bridgmanite (perovskite) + CT + periclase at about 23 GPa. The mLd
composition was close to Mg2Cr2O5, while Gt has a middle composition between Mg4Si4O12 and Mg3Cr2Si3O12. Solubility of Mg2SiO4 component in CT increases with pressure to about 20 mol% at 26 GPa. These
results implies that, when podiform chromitites are subducted into the deep mantle, MgCr2O4 spineland forsterite react to form mLd + Gt at 14-19 GPa which corresponds to pressure range of the upper
part of the mantle transition zone. Also, if CT phase containing substantial Mg2SiO4 component goes
upward from the deep mantle, it decomposes into the assemblage containing mLd + Gt at 14-19 GPa. To
the best of our knowledge, mLd + Gt in association with chromite have not yet been found in thenatural chromitites. Therefore, we suggest that possible occurrence of mLd and/or Gt coexistingwith chromite is an important indicator which shows that the chromitites were derived from thedepth at least upper-part of the transition zone.
キーワード：high pressure 、chromitite、phase relation
Keywords: high pressure , chromitite, phase relation©2016. Japan Geoscience Union. All Right Reserved.

- SIT07-12 -SIT07-13

日本地球惑星科学連合2016年大会

Boron doped diamond heater in the Kawai-type apparatus*Longjian Xie1, Akira Yoneda1, Eiji Ito1
1.Institute for Study of the Earth Interior , Okayama University
Boron doped diamond (BDD) heater has attracted special attention because of its high melting point
and X-ray transparency. In the previous studies, graphite boron composite (GBC) was usually used asa precursor of BDD. In the present study, we firstly investigated the application ofpre-synthesized BDD cylinder and BDD powder as cylindrical heaters in the Kawai-type apparatus at
15 GPa. BDD with 0.5 and 3.0 wt % was synthesized at 15 GPa and 2100 oC. The BDD powders were
grinded from BDD blocks by using Nano Polycrystalline Diamond mortar at GRC, Ehime Univ.; SEM image
showed that the grain size of diamond is about 1 μm. Both kinds of heaters showed good stability
and high reproducibility. The BDD heater with 0.5 wt % boron (resistivity:~0.001Ω.m at 1500 oC)
showed semi-conductive behavior, i.e. decreasing resistance with increasing temperature. However,the BDD heater with 3.0 wt % boron showed lower resistivity (about 0.00016 Ω.m at 1500 oC) andmetallic behavior, i.e. increasing resistance with increasing temperature. This electricalcharacteristic enables us to adjust the boron concentration of BDD to get the desired resistivity.
We succeeded to generate temperature about 3500 oC by using small heater (1.5 mm outer diameter, 1
mm inner diameter, 6 mm length) with TiC electrode. Temperature higher than 1800 oC was estimatedby input power according to its temperature–power relationship. The pressure generation efficiency
by assembly using BDD heater was checked by in-situ X ray experiments at SPring-8. Compared withassembly using GBC heater, the use of BDD heater has lower efficiency of pressure generation in the
beginning stage of compression, while has higher efficiency in the later stage. It is obvious thatthe BDD heater is more advantageous than GBC heater, because it is free from the complicatedtemperature–power relationship and pressure drop associated with graphite to diamond conversion.
Keywords: Diamond synthesize, Boron doped diamond heater, Ultrahigh temperature, Multi-anvil
apparatus©2016. Japan Geoscience Union. All Right Reserved.

- SIT07-13 -SIT07-14

日本地球惑星科学連合2016年大会

CO2 レーザー加熱ダイヤモンドアンビルセルを用いた下部マントル条件下における MgO-MgSiO3 系の溶融関係
Melting relations in the MgO-MgSiO3 system under the lower mantle condition using a CO2
laser heated diamond anvil cell
*大西 里佳1、桑山 靖弘2、井上 徹2*Satoka Ohnishi1, Yasuhiro Kuwayama2, Toru Inoue2
1.愛媛大学大学院理工学研究科、2.愛媛大学地球深部ダイナミクス研究センター
1.Graduate School of Science and Engineering, Ehime University, 2.Geodynamics Research Center,
Ehime University
Seismological observations of the ultralow-velocity zones (ULVZs) suggest the presence of partial
melts above the core-mantle boundary (CMB). Knowledge of the melting relations in the lower mantle
is a key to understand the chemical differentiation at the base of the mantle. While melting
relations of mantle materials at relatively low pressure (below 30 GPa) have been extensively
studied using a multi-anvil apparatus (e.g. Ito et al., 2004 Phy. Earth Planet. Inter.), themelting experiments at higher pressures are still limited. Only in a few model rock compositions,such as peridotite and mid-oceanic ridge basalt (MORB), the experiments were conducted under the
CMB conditions using a laser-heated diamond anvil cell (LHDAC) (e.g. Fiquet et al., 2010 Science,
Andrault et al., 2014 Science). Since chemical heterogeneity of both major elements (Mg, Si, Fe,
Al...) and minor ones (e.g. alkalis and volatiles) should have a large effect on the melting
behavior, the melting phase diagrams as a function of composition are fundamental to understand thenature of the ULVZs. For melting relations in a binary system MgO-MgSiO3, which is a major
component in the lower mantle, the experiment up to only 26 GPa was performed (Liebske and Frost,2012 Earth Planet. Sci. Lett.). So, further studies at higher pressure corresponding to the deep
lower mantle condition are required. In this study, we determined the melting relations in the
MgO-MgSiO3 system above 30 GPa using a LHDAC. Glasses of several different compositions in the
MgO-MgSiO3 system (from 37 to 45 mol% SiO2) were used as the starting materials. A CO2 laser heating
system was used to heat the sample directly. The recovered samples were polished and analyzed by adualbeam focused ion beam (FIB) and a field emission scanning electron microscope (FE-SEM),
respectively. The eutectic compositions and the liquidus phases were determined on the basis ofchemical and textural analysis of the quenched samples. Our results show that the eutectic
composition at 30 GPa is about 44 mol% SiO2 and it becomes about 40 mol% at 50 GPa. Above 50 GPa,
it is predicted to become relatively constant, consistent with the previous result by Liebske andFrost (2012). From these results, MgO-rich melt layer may be generated by partial melting of thebulk mantle, such as pyrolite composition (i.e. 42 mol% SiO2), at the base of the mantle.
The present result should provide basic information for better understanding on the melting
relations at deep mantle conditions.

©2016. Japan Geoscience Union. All Right Reserved.

- SIT07-14 -SIT07-15

日本地球惑星科学連合2016年大会

Ｘ線非弾性散乱による下部マントル物質のフォノン物性
Phonon properties of the lower mantle minerals by inelastic x-ray scattering*福井 宏之1、米田 明2、芳野 極2、バロン アルフレッド3*Hiroshi Fukui1, Akira Yoneda2, Takashi Yoshino2, Alfred Q.R. Baron3
1.兵庫県立大学大学院物質理学研究科、2.岡山大学地球物質科学研究センター、3.理化学研究所放射光科学総合研究センター
1.Graduate School of Material Science, University of Hyogo, 2.Institute for Study of the Earth's
Interior, Okayama Univeristy, 3.RIKEN SPring-8 Center
Inelastic x-ray scattering is a useful technique to obtain phonon properties of lower mantle
minerals with single crystal samples. We would like to discuss what kind of information can bederived from IXS spectra and how to do it with treating bridgmanite and ferropericlase as examples.
キーワード：下部マントル、フォノン、Ｘ線非弾性散乱
Keywords: lower mantle , phonon, inelastic x-ray scattering©2016. Japan Geoscience Union. All Right Reserved.

- SIT07-15 -SIT07-16

日本地球惑星科学連合2016年大会

大陸の離合集散を含む3次元マントル対流と物質循環
Three-dimensional mantle convection and material cycling with continental dispersal andcoalescence*柳 竜之介1、吉田 晶樹2*Ryunosuke Yanagi1, Masaki Yoshida2
1.東京工業大学、2.JAMSTEC
1.Tokyo Institute of Technology, 2.JAMSTEC
The Earth is unique among the solar terrestrial planets, having the continents and the abundantliquid water on its surface. In this study, we have developed a three-dimensional mantle convection
model that incorporates these two features into the numerical program, and investigate how theflow-temperature field and water distribution occur under the circumstances of continental
dispersal and coalescence. In this numerical simulation of 3-D spherical mantle convection,
supercontinent is introduced in the model set up in order to study how continental dispersal andcoalescence happens and affect the structures of the interior. In addition, water is also
introduced, considering water solubility of mantle rocks. The results show that water istransported to broader regions effectively once continental dispersal occurred, due to enhanced
flow velocity associated with increased horizontal temperature gradient partly with the blanketing
effect beneath the supercontinent. This process distributes the water in a spatially wide region asa “migrating entrance” of water into the mantle. Once the water subducts with the cold down-goingflow and reaches CMB (core mantle boundary), then it horizontally spreads to be heated up. In somecase, dehydration of Phase H may occur to generate a fluid that migrates upward and hydrate theoverlying mantle, which occurs near the boundary between the cold continental domain and the warmer
oceanic domain, yet within the hydrated cold domain beneath the (super)continent region. Thismechanism, together with the near-surface process described above, may create a hydrous domain
beneath the continental region where a rather uniform hydration may prevail. Therefore, theeffective redistribution with a global scale structure can be created simultaneously. Such amechanism could be important to account for the observed geochemical mantle hemispheres.
キーワード：大陸の離合集散、物質循環
Keywords: continental dispersal and coalescence, material cycling©2016. Japan Geoscience Union. All Right Reserved.

- SIT07-16 -SIT07-17

日本地球惑星科学連合2016年大会

2次元軸対称モデルによるスーパー地球マントル内上昇プルームの数値シミュレーション
Numerical simulations on the upwelling plumes in the mantle of super-Earths in 2-D
axisymmetric geometry*亀山 真典1*Masanori Kameyama1
1.国立大学法人愛媛大学地球深部ダイナミクス研究センター
1.Geodynamics Research Center, Ehime University
We carried out numerical simulations on the upwelling plumes in the mantle of the Earth and that ofsuper-Earths. The objects of our study are (1) to confirm the validity of our program which is
newly developed for this study by comparing our numerical results with those of earlier studies on
the upwelling plumes in the Earth's mantle and (2) to examine the effects of temperature-dependent
viscosity and internal heating rate on upwelling plumes in the mantle of super-Earths. In thisstudy, we consider a major upwelling plume at the center of 2-D axisymmetric model. We have carriedout two series of numerical simulations. In a first series, we calculated thermal convection in an
incompressible Boussinesq fluid under the conditions identical to those in earlier studies. In asecond series, we performed simulations under the conditions for the mantle of super-Earths using
the truncated anelastic liquid approximation (TALA).
In the first series of our simulations, we obtained the results similar to earlier ones, such as
the increase in the heat flow at the top and bottom boundaries in proportion to Ra13, demonstrating
the validity of the numerical simulation in this study. Furthermore, the second series of our studyof the mantle of super-Earths showed that (1) temperature-dependence of viscosity tends to reduce
plume heat transport, and (2) the variation of compressibility does not affect the detail of theloss of plume heat flux during their ascent. We also found that heat can flow downward into thecore when the chondritic rate of internal heating is present in the mantle of super-Earths,
demonstrating significant effects of the internal heating rate on the convection and thermal statein the mantle of super-Earths.
キーワード：スーパー地球、マントル対流、内部発熱
Keywords: super-Earths, mantle convection, internal heating©2016. Japan Geoscience Union. All Right Reserved.

- SIT07-17 -SIT07-18

日本地球惑星科学連合2016年大会

第一原理計算による高圧下における固体鉄水素合金の研究
First-principles study of solid iron-hydrogen alloys under high pressure*梅本 幸一郎1、廣瀬 敬1*Koichiro Umemoto1, Kei Hirose1
1.東京工業大学地球生命研究所
1.Earth-Life Science Institute, Tokyo Institute of Technology
Hydrogen and iron are two of major constituents of the Earth and planetary interiors. The crystal
structure of solid FeHx is one of the most fundamental information in order to understandproperties of planetary cores. Recently, hydrogen-rich phases, FeH2 and FeH3, were experimentally
synthesized [1]. The crystal structure of FeH3 was clarified by comparing experimental compression
curve with calculated one. On the other hand, the structure of FeH2 remains unclear. It is mainly
because the hydrogen positions are quite difficult to be determined by x-ray diffraction
measurements. Ref. 1 proposed the crystal structure of FeH2, but it is less consistent with its
experimental compression curve. Here we report the results of first-principles calculations on FeH2
. We find the new hydrogen positions which lead to more stable structure than proposed by Ref. 1
and reproduces experimental compression curve very well. Our new structure will be essential for
constraining the amount of hydrogen in iron alloys.
[1] C. M. Pépin, A. Dewaele, G. Geneste, P. Loubeyre, and M. Mezouar, Phys. Rev. Lett. 113, 265504(2014).
キーワード：鉄水素合金、第一原理計算、高圧における結晶構造
Keywords: Iron-hydrogen alloys, First principles, Crystal structure at high pressure©2016. Japan Geoscience Union. All Right Reserved.

- SIT07-18 -