MEXT Grant-in-Aid for Scientiﬁc Research on Innovative Areas

Interaction and Coevolution of the Core and Mantle
Toward Integrated Deep Earth Science

International Symposium
FY2017 Annual General Meeting
March 26 - 29, 2018
Ehime University

Program
March, 26 (Mon)9:30-10:20

Reception

10:20-10:30 Opening address Taku Tsuchiya (Ehime Univ.)
Session 1 (Chairperson: Satoru Tanaka, Kenta Ueki)
10:30-11:00

Invited “Rheological weakening of orthopyroxene and the impacts on
asthenosphere rheology and the Lehmann seismic discontinuity”
Yanbin Wang (Univ. Chicago)

11:00-11:20“Development of New Technology for Geoneutrino Directional Measurement”
Hiroko Watanabe (Tohoku Univ.)

11:20-11:40“Construction of Stochastic Crustal Model for Geoneutrino Observation: Status and Outlook”
Sanshiro Enomoto (Univ. Tokyo)

11:40-12:00“Current status of neutrino oscillation tomography of the Earth”
Akimichi Taketa (Univ. Tokyo)

12:00-13:30 Break
13:30-14:30 Poster Session
Session 2 (Chairperson: Takashi Yoshino, Seiji Kamada)
14:30-15:00
Invited “Experimental evidence supporting a global melt layer at the base of the Earthʼ s
upper mantle”
Geeth Manthilake (UCA)
15:00-15:20“Determination of Intrinsic Attenuation in the Oceanic Mantle”
Nozomu Takeuchi (Univ. Tokyo)
15:20-15:40“The role of dense hydrous magnesium silicates (DHMS) in planet evolution”
Christine Houser (Tokyo Tech.)2

15:40-16:00“First principles investigation of the vibrational properties of hydrous wadsleyite and hydrous ringwoo
Jun Tsuchiya (Ehime Univ.)

16:00-16:20“He and Ar partitioning between liquid iron and molten silicateunder high pressure”
Zhihua Xiong (Ehime Univ.)

16:20-16:50 BreakSession 3 (Chairperson: Akio Suzuki, Zhihua Xiong)
16:50-17:20

Invited “Large volume presses for imaging, tomography and structural analysis at the PSICHE
beamline, synchrotron SOLEIL”
Nicolas Guignot (SOLEIL)

17:20-17:40“High Pressure Generation in a Kawai-type Multianvil Apparatus Equipped with SinteredDiamond Anvils”

Daisuke Yamazaki (Okayama Univ.)

17:40-18:00“High pressure generation up to 24 gigapascals using a D-DIA apparatus combined withjacketed anvils”

Tomohiro Ohuchi (Ehime Univ.)

18:00-18:20“Some recent progress in synthesis, characterization, and applications of NPD”
Tetsuo Irifune (Ehime Univ.)

19:00-21:00 Conference DinnerMarch, 27 (Tue)
Session 4 (Chairperson: Tetsuo Irifune, Masayuki Nishi)
9:00- 9:20

“Advancements in Ab Initio Mineral Physics”
Taku Tsuchiya (Ehime Univ.)
9:20- 9:40

“The role of minor elements in conductivity of mantle and core materials: new results in 2017”
Kenji Ohta (Tokyo Tech.)
9:40-10:00“Crystallographic-preferred orientation of MnGeO3 perovskite”
Yu Nishihara (Ehime Univ.)

10:00-10:20” Incorporation of nitrogen into the lower-mantle minerals under high pressure and hightemperature”

Hiroyuki Kagi (Univ. Tokyo)

10:20-10:50 Break3

Session 5 (Chairperson: M Satish-Kumar, Shinnosuke Aoyama)
10:50-11:20

Invited “Terrestrial magma ocean origin of the Moon”
Shun-ichiro Karato (Yale Univ.)

11:20-11:40“Zr isotope constraints on early Earth diﬀerentiation”
Tsuyoshi Iizuka (Univ. Tokyo)

11:40-12:00“Physical properties of volatile-bearing magmas in the Earthʼ s deep interior”
Akio Suzuki (Tohoku Univ.)

12:00-12:20“Origin of geochemical mantle components: Role of spreading ridge, subduction zone, andthermal evolution of mantle”
Jun-Ichi Kimura (JAMSTEC)

12:20-13:50 Break
13:50-14:50 Poster Session
Session 6 (Chairperson: Hidenori Terasaki, Hitoshi Gomi)
14:50-15:20

Invited “Earthʼ s Correlation Waveﬁeld and new Insights on Structure and Dynamics of the
Inner Core”

Hrvoje Tkalcic (ANU)
15:20-15:40“Ab-initio study of iron diﬀusion properties in Earthʼ s inner core”
Sebastian Ritterbex (Ehime Univ.)

15:40-16:00“Local strong slow S-wave anomalies at western edge of Paciﬁc LLSVP in the lowermost mantle”
Masayuki Obayashi (JAMSTEC)

16:00-16:20“Mobile broadband seismic observation in Thailand: Its present state and preliminary results”
Satoru Tanaka (JAMSTEC)

16:20-16:50 Break4

Session 7 (Chairperson: Katsuhiko Suzuki, Hideharu Kuwahara)
16:50-17:20
Invited “Computational models of magnetic ﬁeld generation in the Earth”
Andrew Jackson (ETH Zurich)
17:20-17:40“On penetration of compositional convection into a thermally stable stratiﬁed layer in the outer
core of the Earth”
Youhei Sasaki (Kyoto Univ.)
17:40-18:00“Melting experiments on Fe‒Si‒S alloys to core pressures”
Shigehiko Tateno (Tokyo Tech.)
18:00-18:20“Melting of iron to 290 gigapascals”
Ryosuke Sinmyo (Univ. Tokyo)
18:20-18:40“Core isotopic ﬂavors in OIB, without core entrainment”
John Hernlund (Tokyo Tech.)

March, 28 (Wed)Session 8 (Chairperson: Tetsu Kogiso, Norikatsu Akizawa)
9:00- 9:30

Invited “Shaping mantle volatile concentrations through early heterogeneities and long-term
cycling”
Sujoy Mukhopadhyay (UC Davis)
9:30- 9:50
“Stable isotopes as tools for exploring the deep Earth”
M Satish-Kumar (Nigata Univ.)
9:50-10:10“Determination of the noble gas partition coeﬃcients between metal-silicate melts”
Hirochika Sumino (Univ. Tokyo)
10:10-10:30“Siliconʼ s role in the evolution of the Earthʼ s core and mantle”
George Helﬀrich (Tokyo Tech.)

10:30-11:00 Break5

Session 9 (Chairperson: Taku Tsuchiya, Sebastian Ritterbex)
11:00-11:30
Invited “Thorium and uranium power plate tectonics, but not the geodynamo”
William F McDonough (Tohoku Univ.)
11:30-11:50“Tungsten isotopic heterogeneity in oceanic island basalts produced by core-mantle interaction”
Takashi Yoshino (Okayama Univ.)
11:50-12:10“Liquid metal-silicate partitioning of carbon in a magma ocean during the core formation ofterrestrial planets”
Hideharu Kuwahara (Ehime Univ.)

12:10-13:40 BreakSession 10 (Chairperson: Hisayoshi Shimizu, Sunil K. Roy)
13:40-14:10
Invited “Chemical Stratiﬁcation and Magnetic Field Generation”
Laneuville Matthieu (Tokyo Tech.)
14:10-14:30“Spatiotemporal variations of core-mantle coupling revealed by geomagnetic ﬁeld data (FY2017)”
Masaki Matsushima (Tokyo Tech.)
14:30-14:50“Highly precise 182W/184Wisotopic compositions of terrestrial samples”
Katsuhiko Suzuki (JAMSTEC)

14:50-15:20 Comments and Discussion

6Core time
Odd-number presentations: 13:30-14:30, March, 26
Even-number presentations: 13:50-14:50, March, 27
P01“The eﬀects of ferromagnetism and interstitial hydrogen on the equation of states of hcp

and dhcp FeHx”
Hitoshi Gomi (Okayama Univ.)
P02“Grain growth kinetics of lower-mantle materials: Implications for the grain size evolution

and the rheology”
Tomoaki Kubo (Kyusyu Univ.)
P03“Diﬀusion mechanisms of creep and grain growth of two-phase polymineralic rocks:

Implications for rheology of the lowermost mantle”
Atsuro Okamoto (Univ. Tokyo)
P04“Experimental study on transport properties of liquid iron-silicon alloy at and above theouter core conditions”
Kohei Miyanishi (Osaka Univ.)
P05“Microstructures of experimentally deformed carbon steels”

Yozora Sakoda (Hiroshima Univ.)
P06“Deformation of bridgmanite and post-spinel two-layered sample under lower mantle

conditions with DT-Cup apparatus”
Fang Xu (IMPMC)
P07“Toward development of ultrasonic measurement technique under whole lower mantle

conditions”
Yuji Higo (JASRI)
P08“Searching for multi light elements in iron-silicate-water system using high pressure andhigh temperature experiments: Implications for the Earthʼ s evolution”
Riko Iizuka-Oku (Univ. Tokyo)
P09“Melting experiments of hydrous peridotite under the top of the lower mantle conditions”

Ayano Nakajima (Tohoku Univ.)
P10“Al substitution mechanism in anhydrous bridgmanite as a function of Al content”

Masamichi Noda (Ehime Univ.)
P11“Structures of basaltic glass under high pressure by in-situ X-ray and neutron diﬀraction

investigations”
Tomonori Ohashi (Tohoku Univ.)
P12“Density measurement of metals at high temperatures using newly designed furnace”

Hidenori Terasaki (Osaka Univ.)
P13“Silicate melt viscosities at high pressure:Experimental results and its implications”

Longjian Xie (Osaka Univ.)

7

P14

“Melting of Al-rich phase D up to the uppermost lower mantle and transportation of H2O tothe deep Earth”

Chaowen Xu (Ehime Univ.)
P15“A recent application of NPD anvils to EXAFS spectroscopy: element-selective elastic

properties of Fe-Ni and Fe-Pt Invar alloys”
Naoki Ishimatsu (Hiroshima Univ.)
P16“Thermal equations of state of MgSiO4H2 phase H”

Masayuki Nishi (Ehime Univ.)
P17“High pressure generation using double-stage diamond anvil technique: problems andequations of state of rhenium”
Takeshi Sakai (Ehime Univ.)
P18“Multiple sulfur isotopes of Archean oceanic crust and granitoids: Implication for the

anomalous sulfur budget in the mantle”
Shinnosuke Aoyama (Niigata Univ.)
P19“Crystallization of metasomatic sulﬁde melt, and recrystallization of crystalline sulﬁdesconstrained by sub-μm-scale investigations for PGE-bearing sulﬁde inclusion in Tahitian
harzburgite xenolith”
Norikatsu Akizawa (Univ. Tokyo)
P20“Quantitative isotope imaging methods using secondary ion mass spectrometry”

Shoichi Itoh (Kyoto Univ.)
P21“Behavior of highly siderophile elements in mantle peridotite and its bearing on theprimitive mantle composition”
Tetsu Kogiso
P22“Seismic scatterers in the lower mantle near subduction”

Satoshi Kaneshima (Kyusyu Univ.)
P23“Observation of multipathing at the western edge of the Paciﬁc Large Low-Velocity

Provinc”
Sunil K. Roy (Univ. Tokyo)
P24“Examination of local geomagnetic jerks using wavelet analysis”

Hisayoshi Shimizu (Univ. Tokyo)
P25“The evaluation of the chemical variation in a single granitic rock suite revealed by grid

sampling toward improving the accuracy of geoneutrino ﬂux”
Kazuki Minami (Univ. Tokyo)
P26“The new database for composition of the basement rocks of Japanese islands withaccurate location information for geo-neutrino modeling”
Kenta Ueki (JAMSTEC)

8

P27

“Eﬀects of iron on the lattice thermal conductivity of lower mantle minerals evaluated by

Ab initio anharmonic lattice dynamics simulations”
Haruhiko Dekura (Ehime Univ.)
P28“The dependence of mantle convection in super-Earths on the planetary mass”

Takehiro Miyagoshi (JAMSTEC)
P29“Basic features of the kinematic dynamo action associated with top-down type convection

in a rotating spherical shell”
Hinami Taniguchi (Kyushu Univ.)
P30“Normal mode splitting functions for CMB sensitive modes”

Naoki Suda (Hiroshima Univ.)
P31“Bayesian Inference of 3-D Lithology Distribution Using a Seismic Tomography Model:

Eﬀects of Lithology Mixture”
Nozomu Takeuchi (Univ. Tokyo)

9Oral Session10

S1-1 Invited
Rheological weakening of orthopyroxene and the impacts on asthenosphererheology and the Lehmann seismic discontinuity
Feng Shi1, Tony Yu1, and Yanbin Wang1
1

Center for Advanced Radiation Sources, The University of Chicago(wang@cars.uchicago.edu)

Pyroxenes, with roughly equal amounts of orthopyroxene and clinopyroxene, mayconstitute up to 40% by volume in the upper mantle, second only to olivine, and should
impose significant influences on the rheological behavior of the asthenospheric mantle.
Here we report high-pressure, high-temperature deformation experiments on polycrystalline
orthoenstatite (OEn). Natural crystals with an average composition of En89Fs10Wo1 (where
En=MgSiO3, Fs=FeSiO3, and Wo=CaSiO3) with ~4 wt% Al2O3 were hand-picked from a
fresh, coarse-grained spinel lherzolite specimen (Damaping, China), disaggregated andground into powders with grain size ~25-35 m.
crystals were about 20-30 ppm by weight.

FTIR showed that water contents of the

The powders were sintered at 3 GPa and 1273 K

for 4 h, to form polycrystalline “rocks” 1.2 mm in diameter and 1.2 mm in length.

Creepexperiments were conducted in the D-DIA apparatus at beamline 13-BM-D of the Advanced
Photon Source, Argonne, National Laboratory, at temperatures of 1273-1473 K and pressures
up to 8 GPa, with strain rates between 4×10-6 and 4×10-5 s-1.

Ni foils were attached to thesamples as strain markers and to help constrain oxygen fugacity.

Synchrotron x-ray

diffraction and imaging were used to measure stress and strain, respectively, during
deformation.

Up to 4.5 GPa, the quasi-steady-state stress-strain data can be fitted quite wellwith a power-law rheology yielding stress exponent n=3.85 and an activation volume V*=13
cm3/mol.

Electron backscattered diffraction (EBSD) was used to quantify crystallographic

preferred orientation (CPO) development after creep.

The (100) poles are generally alignedwith the shortening (axial) direction, while the (001) poles tend to be normal to that direction.
This suggests that the dominant slip system is [001](100), consistent with previous studies.
Within this pressure range, OEn is significantly weaker than olivine. Model calculations
show that, between ~50 and ~150 km depths, effective viscosity of an upper mantle with
20-40% OEn plus olivine is at least one order of magnitude lower than that of a 100% olivine
upper mantle.

Therefore, the presence of pyroxenes cannot be ignored when modeling11mantle viscosity profiles. More importantly, above 4.5 GPa, OEn exhibits an unexpectedpressure-induced rheological weakening, with a strongly negative apparent activation volume.
This high-temperature rheological weakening occurs at pressures 2-3 GPa lower than theelastic weakening in OEn observed at room temperature [1].

EBSD on samples recoveredfrom above 6 GPa reveals that (001) poles form additional well-defined maxima
perpendicular to the axial direction, suggesting new slip directions in the (001) plane.

Wepostulate that the new “slip directions” are activated when OEn is compressed close to ahigh-pressure structure under differential stress. The high-pressure structure can be either
high-pressure clinoenstatite (C2/c) [2], or another monoclinic phase (P21/c) recently
discovered [3, 4].

The latter is structurally closely related to OEn (Pbca) by losing mirror

planes in (001), resulting in twinning.

The pressure-induced rheological weakening above

4.5 GPa may be due to an incipient response prior to the transition and is expected to haveprofound impact on the nature of the asthenosphere.

The high-pressure phase transition in

OEn, together with weakened pre-transition rheology, may also be a main contributor to theLehmann seismic discontinuity.
References[1] Kung et al., In situ measurements of sound velocities and densities across theorthopyroxene → high-pressure clinopyroxene transition in MgSiO3 at high pressure. Phys.
Earth Planet. Int., 147, 27 (2004).
[2] Angel et al., Stability of high-density clinoenstatite at upper-mantle pressures. Nature,
358, 322 (1992).
[3] Zhang et al., A new high-pressure phase transition in natural Fe-bearing orthoenstatite.
Am. Min., 97, 1070 (2012).
[4] Dera et al., Metastable high-pressure transformations of orthoferrosilite Fs82. Phys. Earth
Planet. Int., 221, 15 (2013).

12

S1-2
Development of New Technology for Geoneutrino Directional Measurement
Hiroko Watanabe1
1Research Center for Neutrino Science, Tohoku University (hiroko@awa.tohoku.ac.jp)
Neutrino is an elusive particle and it can penetrate even astronomical objects. Whileneutrino experiments continue to explore the neutrino propertied, e.g. oscillation nature ofneutrino flavor transformation, mass-square differences and mixing angles, we have began toutilize neutrino as a tool to look into the Earth. Anti-neutrinos emitted from radioactive
isotopes, geo-neutrinos, bring unique and direct information of the Earth’s interior and thermal
dynamics.
KamLAND, Kamioka Liquid-scintillator Anti-neutrino Detector, has 1 kton ultra pureliquid scintillator. They reported the first experimental study of geo-neutrino in 2005 [1].
Later the geo-neutrino signals were used to estimate the Earth’s radiogenic heat production andconstrain the composition models of the bulk silicate Earth [2]. Following the Fukusima
reactor accident in March 2011, the entire Japanese nuclear reactor industry has been subjected
to a protected shutdown. This unexpected situation allows us to improve the sensitivity for
geo-neutrinos [3].
The liquid scintillator detectors have the sensitivity for measuring total amount of
geo-neutrinos from the Earth’s crust and mantle. However, we do not have the technology to
track the direction of incoming geo-neutrinos at present due to the high miss-identification in aneutrino’s track reconstruction. The direction-sensitive detector can map out the U and Th
distribution inside the Earth and this technic is also applicable to resolving crust versus mantle
contributions. Recent progress in studying this this new technology confirmed that a signify
improvement is possible in neutrino tracking identification with a combination of 6Li-loaded
liquid scintillator and imaging detector. We developed prototype detector to measure 3D
image of scintillation light and study the methodology for the image reconstruction. We will
present recent status of our prototype detector and achievement of dark noise reduction of
pixelated detector.
[1] T. Araki et al., Nature 436, 499 (2005)[2] A. Gando et al., Nature Geosci. 4, 647 (2011)[3] A. Gando et al., Phye. Rev. D 88, 033001 (2013)

13

S1-3
Construction of Stochastic Crustal Model for Geoneutrino Observation:
Status and Outlook
Sanshiro Enomoto1, Nozomu Takeuchi2, Kenta Ueki3, and Tsuyoshi Iizuka4
1

Kavli-IPMU, University of Tokyo / University of Washington (sanshiro@uw.edu)
2
3

Earthquake Research Institute, University of TokyoJapan Agency for Marine-Earth Science and Technology
4

University of Tokyo

Geoneutrino observation with KamLAND is expected to provide unique insights about
Earth’s deep chemical composition and thermal dynamics, but for this, proper description of
U and Th distributions in the Japan crust is essential. Despite several attempts in the past, nomodel is satisfactory in terms of objective and quantitative description.
We approached this problem with Bayesian inference of 3D lithology from seismic
tomography data, combined with a new rock composition model that removes all biases
existed in past treatments, and constructed a truly probabilistic crustal model for the first time
(Takeuchi et al, submitted). However, there remains a difficulty on modeling geological
special correlations, resulting in a large error in the final flux calculation. Also, if
uncertainties and biases exist in the input data of our calculations, such as errors in the
tomography model and bias on collecting rock samples, those are not properly propagated to
the final results.
In order to understand special correlations, we are investigating ~10 cm to ~1 km scale
compositional structure, which is usually not discussed in past studies, by systematicallycollecting rock samples out of a single granite unit. We are also developing a method toevaluate tomography model uncertainties and effects of finite resolutions. For rock samplingbiases, statistical methods are being explored to detect the possible bias.
Currently the error of our model prediction is large at ~70%, while the KamLAND
geoneutrino observation error has been being reduced and is now at 18%. Depending on the
results of the geological correlation structure that we are investigating, we expect that the
final model errors could be reduced to a level comparable to the geoneutrino observation
errors.

14

S1-4
Current status of neutrino oscillation tomography of the Earth
Akimichi Taketa1, Carsten Rott2
1

Earthquake Research Institute, University of Tokyo, Tokyo, Japan (taketa@eri.u-tokyo.ac.jp)
2

SungKungKwan University, Suwon, Korea

We report the current status of neutrino oscillation tomography.
Next generation large neutrino detectors (Hyper-Kamiokande, IceCube-gen2, ORCA,
BIKAL NERPA) are under construction or proposed,and they have capability to measure theaverage chemical composition of the core and mantle.
The sensitivity estimations of those detector will be reported.The preliminarily result of
neutrino oscillation tomography using existing detector is also reported.

15

S2-1 Invited
Experimental evidence supporting a global melt layer at the base of the
Earth’s upper mantle

G. Manthilake1, D. Freitas1, F. Schiavi1, J. Chantel2, N. Bolfan-Casanova1, M.A. Bouhifd1, D.
Andrault1

1.

Université Clermont Auvergne, CNRS, IRD, OPGC, Laboratoire Magmas et Volcans, F63000 Clermont-Ferrand, France (geeth.manthilake@uca.fr)
2.

Department of Earth, Environmental and Planetary Sciences, Case Western Reserve
University, Cleveland, OH 44106, USA

The low velocity layer (LVL) atop the 410-km discontinuity has been widely
attributed to dehydration melting. In this study, we experimentally reproduced the wadsleyiteto-olivine phase transformation in the upwelling mantle across the 410-km discontinuity andinvestigated in-situ the sound wave velocity during partial melting of hydrous peridotite. Ourseismic velocity model indicates that the globally observed negative Vs anomaly (-4 %) canbe explained by a 0.7 % melt fraction in peridotite at the base of the upper mantle. The
produced melt is richer in FeO (~ 33 wt. %) and H2O (~16.5 wt. %) and its density isdetermined to be 3.56-3.74 g.cm-3. The water content of this gravitationally stable melt in the
LVL corresponds to a total water content in the mantle transition zone (MTZ) of 0.22 ± 0.02
wt. %. Such values agree with estimations based on magneto-telluric observations.

16

S2-2
Determination of Intrinsic Attenuation in the Oceanic Mantle
Nozomu Takeuchi1, Hitoshi Kawakatsu1, Hajime Shiobara1, Takehi Isse1, Hiroko Sugioka2,
Aki Ito3, and Hisashi Utada1
1

Earthquake Research Institute, University of Tokyo (takeuchi@eri.u-tokyo.ac.jp)
23

Graduate School of Science, Kobe University

Japan Agency for Marine-Earth Science and Technology

Quantitative

characterization

of

the

physicalproperties

of

the

oceanic

lithosphere-asthenosphere system (LAS) is indispensable to our understanding of plate
tectonics.

P and S waves traveling through the oceanic LAS are known to have ananomalous feature of long lasting high frequency waves. A large number recordings of the2011 Tohoku earthquake aftershocks by broadband ocean bottom seismometer arrays
deployed in the NW Pacific provided an unprecedented opportunity to quantitatively separate
the intrinsic (anelastic) and extrinsic (scattering) attenuation effects on seismic wave
propagation in the pure-oceanic paths and to directly infer thermo-mechanical properties ofthe oceanic LAS.
In this study, we simulated energy transportation of higher frequency seismic waves (~3Hz) in scattering media and compared the simulated and observed envelopes.

The envelopes

observed in the NW Pacific are characterized by larger amplitudes especially in S andquasi-exponential amplitude decay with distance.

We showed that such features can be

explained if and only if we have high intrinsic Q in the lithosphere and low intrinsic Q in theasthenosphere.
The strong intrinsic attenuation in the asthenosphere obtained in this study (~3 Hz) is
comparable to that constrained at lower frequency (~100 s) by surface waves and suggests
frequency-independent anelasticity, while that in the lithosphere is frequency dependent.
This difference in frequency dependence indicates that the strong and broad peak dissipation
recently observed in the laboratory exists only in the asthenosphere and sheds new light onwhat distinguishes the asthenosphere from the lithosphere.

17

S2-3
The role of dense hydrous magnesium silicates (DHMS) in planet evolution
Christine Houser1, Cayman Unterborn2
1

Earth-Life Science Institute, Tokyo Institute of Technology (chouser@elsi.jp)
2

School of Earth and Space Exploration, Arizona State University

As terrestrial planets cool, the stability field of hydrous minerals at high pressure andtemperature expands such that terrestrial planets may desiccate with age.

We explore

scenarios for planets in the neighborhood of Earth in terms of size and composition todetermine the fate of surface water as the planet ages. Plate tectonics is the dominanttectonics on Earth and a consistent source of the rock-water chemistry thought to be promote
the stability of life. As hydrated oceanic crust and mantle are recycled back into the Earth, aseries of dehydration reactions returns most of that water back to the surface. However,under conditions that may exist in the core of the coldest sinking oceanic lithosphere today,
Dense Hydrous Magnesium Silicates (DHMS) may be stable into the transition zone andlower mantle. We quantify the extent to which increasing the Mg/Si ratio, cooling the upper
mantle, and increasing a planet’s Al content will increase a planet's capacity to draw water
down and store it in the mantle based on what is currently known regarding DHMS stability.
Once water can be transported into the lower mantle, oceans of water can be efficiently
drained within billions of years.

For example, using lower bounds of water transport to themantle for Earth, our surface ocean would drain in 4 billion years.

18

S2-4
First principles investigation of the vibrational properties of hydrous
wadsleyite and hydrous ringwoodite
Jun Tsuchiya1,21

Geodynamics Research Center, Ehime University (junt@ehime-u.ac.jp)
2

Earth-Life Science Institute, Tokyo Institute of Technology

Wadsleyite and ringwoodite are the primary constituent minerals in the Earth's transitionzone. Since these minerals are able to retain up to about 3 wt% H2O in the crystal structures,
these phases are known to be the most important water reservoir in the Earth. There have been
large numbers of reports about the structure, stability, and physical properties of hydrous
wadsleyite and ringwoodite. The vibrational measurements such as FTIR and Raman are themost commonly used for investigating the OH defects in these minerals.
In the case of hydrous wadsleyite, there are major and minor doublets of OH stretching bands,
the former exist around 3300 cm-1 with d/dP~-10 cm-1 and the latter around 3600 cm-1 withalmost no pressure dependence. There is a broad consensus that main absorption band isinterpreted as the OH stretching modes existing in the M3 vacancy. On the other hand, theminor OH band is not well constrained so far. Since the stable hydrogen defects are usually lessmobile in wadsleyite crystal, the determination of minor and metastable hydrogen defects are
more important for investigating the transport properties including the electrical conductivity
and the deformation properties.
Hydrous ringwoodite, on the other hand, shows very broad OH stretching band around 3200
cm-1 at ambient conditions and there is no consensus about the structural explanation of theseOH bands nor its high capacity of water storage.
Here I investigated the structural and vibrational properties of hydrous wadsleyite andhydrous ringwoodite using first principles techniques using several different hydrogen defects
structures in order to clarify the minor metastable hydrogen positions in wadsleyite and also toshed light on the stability of hydrogen defects in hydrous ringwoodite.

19

S2-5
He and Ar partitioning between liquid iron and molten silicate
under high pressure
Zhihua Xiong1, Taku Tsuchiya11

Geodynamics Research Center, Ehime University, Matsuyama, Japan(xiong.zhihua.us@ehime-u.ac.jp)

The Earth’s core has been suggested as a potential reservoir of noble gases, which can remove thedifficulties of their long-term maintenance in the mantle. The fundamental process controlling noble
gas sequestering into the core is their partitioning between liquid iron and molten silicate.
Unfortunately, limited measurements have only been conducted so far. Experiments conducted by
Matsuda et al. [1995] up to 10 GPa showed that the partitioning coefficients of noble gases decrease
with pressure, denying the core to be a noble gas reservoir. In contrast, Bouhifd et al. [2013] reported
that the helium partitioning coefficient becomes more constant (~10-2) at P > 10 GPa, suggesting thatsome helium could be dissolved into the core. However, it is unclear whether this tendency isapplicable to other noble gases.

Here we investigate the helium and argon partitioning between liquid iron and molten silicate
using the ab initio molecular dynamics method combined with thermodynamics integration
technique [Taniuchi and Tsuchiya, 2018]. The partitioning coefficients are computed from the
Gibbs free energy changes associated with their exchange reactions. Although more detailed
studies on several factors including temperature, pressure, and composition are required, ourresults in the moment suggest possible partitioning of helium and argon into liquid metal athigh pressure. We will try to explain the behaviors from the electronic and structural points of
view.

20

S3-1 Invited
Large volume presses for imaging, tomography and structural analysis at
the PSICHE beamline, synchrotron SOLEIL
Nicolas Guignot1, Geeth Manthilake2, Eglantine Boulard3, Andrew King1, Alisha N. Clark3,4,
Denis Andrault2, Longjian Xie5, Daisuke Yamazaki5, Akira Yoneda5, Jean-Philippe Perrillat6,
Yann Le Godec3, Guillaume Morard3, Alain Prat7, and Jean-Paul Itié1
1

Synchrotron SOLEIL (guignot@synchrotron-soleil.fr)
2

Laboratoire Magmas et Volcans, OPGC
34IMPMC, Sorbonne Université

Department of Earth and Planetary Sciences Northwestern University Technological
Institute
5

Institute for Planetary Materials, Okayama University
6

LGLTPE, UCBL Lyon 1
7

Institut Néel

The PSICHE beamline (synchrotron SOLEIL, France) is focused on the determination ofvarious materials physical properties in-situ at high pressure – high temperature (HP-HT), e.g.
thermoelastic properties, viscosity, electrical or thermal conductivity but also phase transitions
and structural studies. Imaging, tomography and X-ray diffraction techniques have been
specifically designed for large volume presses (Multi-anvil and Paris-Edinburg) operated inwhite and pink beam modes, focused in the vertical direction for a very high flux or parallel.
We present here the different setups and recent experiments and developments to illustrate thepossibilities of the beamline.
Our first station is the multi-anvil (MA) apparatus that has proven to be invaluable forexperiments where an excellent control over pressure and temperature conditions and a large
sample volume are required. Our setup consists of -1/ a 1200 tons load capacity MA presswith a (100) DIA compression module - 2/ a CAESAR (combined angle- andenergy-dispersive structural analysis and refinement, Wang et al. 2004) XRD setup, which is
the ideal tool when accurate structural measurements are required, especially in the case of
liquids and amorphous materials -3/ a high resolution imaging system, with framerates up to 2
kHz full-frame and beam sizes up to 10x4 mm2 (HxV). This latter mode is illustrated withrecent results obtained on viscosity measurements of forsterite and diopside liquid21

compositions up to 30 GPa.
The second setup consists of a couple of Paris-Edinburg presses, one with rotational anvils(rotoPEc, Philippe et al. 2016) used to perform full or partial 3D reconstructions of samples at
HP-HT conditions. These tools have been used for example to measure the density of liquids
and amorphous materials in combination with the CAESAR system. We will also show ourvery recent efforts to provide a station ready for ultra-fast tomography, opening up the way
for time resolved 3D imaging at HP-HT.
References
Y. Wang et al., A new technique for angle-dispersive powder diffraction using anenergy-dispersive setup and synchrotron radiation (2004), J. Appl. Cryst., 37, 947–956
J. Philippe et al., Novel portable press for synchrotron time-resolved 3-D micro-imagining
under extreme conditions (2016), AIP Conference Proceedings, 1741, 30002

22

S3-2
High Pressure Generation in a Kawai-type Multianvil Apparatus Equippedwith Sintered Diamond Anvils
Daisuke Yamazaki
Okayama University (dy@misasa.okayama-u.ac.jp)
The Kawai-type multianvil apparatus (KMA) has been widely employed to clarify the
structure and state of the deep Earth [1]. One of important advantage of the KMA over the
diamond anvil cell (DAC) is the capability to compress a large volume sample (>1 mm3) in an
octahedral pressure medium under a quasihydrostatic environment owing to squeezing by eight
cubic anvils [2]. Moreover, homogeneous and stable heating for sample can be done byadopting an internal heating system, which makes it possible to measure physical and chemical
properties of minerals under high pressure and temperature conditions. However, in theconventional KMA, in which tungsten carbide (WC) is used as second stage anvils, theattainable pressure has been limited to ~50 GPa [3]. To extend the pressure range in KMA, theexperimental technique for high pressure experiments have been developed using sintereddiamond anvil [4].
In this study, the pressure generation tests were conducted in a large volume press (SPEED
mk.II) at BL04B1, SPring-8 synchrotron facility. In the experiments, Cr-doped MgO withoctahedral edge length of 4.1 mm and BN+TiB2 which is high transparency for X-ray were used
for pressure medium and heater, respectively, for Kawai-type cell assembly. Soft fired
pyrophyllite was prepared for gasket. Temperature was monitored by W97%Re3%-W75%Re25%
thermocouple whose junction was located in the heater. Before experiment, the sintered starting
material of the mixture of Mg0.9Fe0.1SiO3+5wt % Al2O3 bridgmanite was prepared. Sample wasalso mixed with gold in the ration of 1/6 in weight for the standard to estimate the pressure [5](Tsuchiya, 2003). During compression in the experiments, sample was frequently pre-heated to
800-1100 K at every 5-10 GPa for the relaxation of stress stored in the cell assembly to reduce
the probability of “blow out”.
The generated pressure finally reached to 120 GPa with press load of 13 MN at an ambient
temperature after pre-heating at 800K. Then sample was heated again up to 1673 K to try toobserve the phase transition from bridgmanite to post-perovskite. The obtained diffraction
pattern under sufficient heating condition was completely indexed as bridgmanite, indicating
the stability field of bridgmanite with the composition of Mg0.9Fe0.1SiO3+5wt % Al2O3. The
present result is consistent with previous study in MgSiO3 (Tateno et. al., 2009) because of alarge pressure drop occurred down to 105 GPa in this study. They reported the phase boundary
to be 110 GPa at ~1673 K. As a conclusion, the effect of 10 mol % of iron component and 5
wt % of Al2O3 is less than 5 GPa on phase boundary shift in pressure.
References[1] E. Ito, “Theory and practice-multianvil cells and high-pressure experimental methods”
Ed: G. Schubert, B. Romanowicz, A. Dziewonski, (Elsevier B.V) pp. 197–230 (2007). [2] N.
Kawai and S. Endo, Rev. Sci. Instrum. 4, 425 (1970). [3] T. Kunimoto et al., High Press. Res.
36, 97 (2016). [4] D. Yamazaki et al., Phys. Earth Planet. Inter. 228, 262 (2014). [5] T. Tsuchiya,
J. Geophy. Res., 108, 2003JB002446 (2003).

23

S3-3
High pressure generation up to 24 gigapascals using a D-DIA apparatus
combined with jacketed anvils
Tomohiro Ohuchi1
1

Geodynamics Research Center, Ehime Univ. (ohuchi@sci.ehime-u.ac.jp)

Rheological properties of high-pressure polymorphs of olivine are important tounderstand the cause of seismic anisotropy, viscosity structure, deep-focus earthquakes in the
deeper part of the Earth’s mantle. Three types of deformation apparatus, namely, the D-DIA
type (Wang et al., 2003), the rotational Drickamer apparatus (RDA: Yamazaki and Karato,2001), and the Kawai-type apparatus for triaxial deformation (KATD: Nishihara, 2008) havebeen developed to deform high-pressure polymorphs of olivine. Although recent studies byGirard et al. (2015) and Tsujino et al. (2016) succeeded to deform bridgmanite at lower
mantle pressures and temperatures using a RDA and a KATD respectively, in-situ D-DIA
experiments are still limited to the conditions of lower part of the mantle transition zone
(Kawazoe et al., 2016). The main cause disturbing further pressure generation using an in-situ
D-DIA apparatus is relatively low toughness of the x-ray transparent anvils made fromsintered diamond or cubic BN. In the geometry of cubic-type multianvil apparatus, theavailable press load needs to be low (usually < 0.6 MN) to avoid the breakage of the x-raytransparent anvils. The advantages of D-DIA apparatus are as follows: i) compatible withacoustic emission monitoring (i.e., many transducers are available) and ii) temperature can bemonitored by using a thermocouple. To explore the quantitative deformation experiments atlower mantle conditions, we adopted the ‘jacketed’ 6-6 type anvils (Yamada et al., 2016) and
optimized the cell assembly using preformed gaskets (e.g., Kawazoe et al., 2010). Combining
these techniques, I succeeded to generate 24 GPa at room temperatures using a D-DIA
apparatus (in the case of truncation edge length = 3 mm). Pressures higher than 20 GPa arealso available using the ‘jacketed’ x-ray transparent anvils. Optimization of the design of‘jacketed’ x-ray transparent anvil and cell assembly would lead to quantitative deformation
experiments at lower mantle conditions in near future.

24

S3-4
Some recent progress in synthesis, characterization, and applications of
NPD
Tetsuo IRIFUNE1
1

Geodynamics Research Center, Ehime Univ. (irifune@dpc.ehime-u.ac.jp)

We have been working to use ultrahard nano-polycrystalline diamond (NPD) developed byourselves for advanced studies in deep Earth and related sciences, in collaboration with the
GRC members and users of NPD via the PRIUS cooperative research program. Applications to
the Kawai-type multianvil apparatus (KMA) using NPD cubes as the second-stage anvils havebeen limited to about 90 GPa, but its advantages in both higher pressure generation and in situ
X-ray observations over the commercially available sintered diamond have been demonstrated.
New development of the earlier 6-8-2 system using NPD as the third-stage anvils is currently
being pursued for static generation of multi-megabar regime in the KMA.
In addition to the very successful applications to X-ray absorption studies under pressureusing the polycrystalline nature of NPD, new technologies in diamond anvil cell (DAC) havebeen developed. These include rotational DAC for deformation studies, double-stage DAC forhigher pressure generation, large DAC for neutron diffraction and X-ray Raman studies,
electrode-deposited DAC for electric resistance measurements, a mortar-pestle system forcrushing ultrahard materials, etc.
Synthesis of NPD with various grain size and fine structures has also been attempted byusing different types of carbon sources and varying pressure and temperature conditions in
KMA. Some mechanical tests, such as elastic properties and strength, have also been made onsuch NPD samples.

Preliminary results on synthesis of the NPD samples with various grain

sizes and their compressional behaviours will be reported in this talk.

25

S4-1
Advancements in Ab Initio Mineral Physics
Taku Tsuchiya11

Geodynamics Research Center, Ehime University (tsuchiya.taku.mg@ehime-u.ac.jp)

Recent progress in theoretical mineral physics (TMP) based on the density functional
quantum mechanical theory has been dramatic in conjunction with the advancement ofcomputer technologies. It is now possible to predict high-P,T equation of state, phase stability,
and thermoelasticity of complex minerals quantitatively with uncertainties that arecomparable to or even smaller than those attached in experimental data. The technique is now
routinely applied not only for theoretical backup to experiments but also for guide toexperiments [1]. Our next grand challenges include new technical developments for high-P,Tthermochemical properties, such as elemental partitioning of both solid and liquid phases [2],and transport properties, such as thermal/electrical conductivity [3,4], and atomic diffusivity[5], within both usual and correlated systems. Chemical partitioning, which we can accessusing the ab initio thermodynamic integration molecular dynamics method [6], allows us tolink mineral physics to geochemistry. lattice thermal conductivity, which is calculated basedon the harmonic and anharmonic lattice dynamics theories and Boltzmann's transport
equation, is on the other hand a key to clarifying thermal properties of the deep mantle andcore. In this talk I will report recent activities in the Ehime Univ. TMP group.
[1] M. Nishi, Y. Kuwayama, J. Tsuchiya, T. Tsuchiya, Nature 547, 205 (2017)[2] Z. Xiong, T. Tsuchiya, T. Taniuchi, under review[3] H. Dekura, T. Tsuchiya, Phys. Rev. B 95, 184303 (2017).
[4] S. Ohmura, T. Tsuchiya, H. Ichikawa, under review[5] S. Ritterbex, T. Harada, T. Tsuchiya, Icarus 305, 350 (2018)[6] T. Taniuchi, T. Tsuchiya, J. Phys. Cond. Mat. 30, 114003 (2018)

26

S4-2
The role of minor elements in conductivity of mantle and core materials:
new results in 2017
Kenji Ohta1
1

Department of Earth and Planetary Sciences, Tokyo Institute of Technology(k-ohta@geo.titech.ac.jp)

Knowledge about transport properties of Earth-forming minerals is important tounderstand the evolution and the dynamics of solid Earth. State-of-the-art high-pressuretechniques enable us to replicate the Earth's internal conditions, and to reveal various physicalproperties of minerals at the conditions of the Earth’s interior. In this fiscal year, we mainly
performed the following three studies: (1) Lattice thermal conductivity measurements onhydrous wadsleyite and ringwoodite at the pressures corresponding to the mantle transition
zone, (2) Thermal conductivity measurements on Fe, Al-bearing bridgmanite and (Mg,Fe)O at
the lower mantle pressures, (3) Electrical resistivity measurements on Fe-Si-S alloy and Fe-H
alloy. These experimental studies revealed the role of minor elements (hydrogen, iron,aluminum, and sulfur) in the electrical and thermal conductivity of mantle and core materials
under high pressure, which would provide for more reliable estimates of electrical andthermal conductivity of deep Earth.

27

S4-3
Crystallographic-preferred orientation of MnGeO3 perovskite
Yu Nishihara1, Simon Hunt2, David Dobson2, and Yuji Higo3
1

Geodynamics Research Center, Ehime University, GRC (yunishi@sci.ehime-u.ac.jp)
2
3

University College London

Japan Synchrotron Radiation Research Institute

Efficiency of material and heat transport in the Earth is largely influenced by flow patternin the mantle. Flow direction at around the 660 km discontinuity is one of the key to understandthe flow pattern of the whole mantle. Recently, Tsujino et al. (2016) determined shear induced
crystallographic-preferred orientation (CPO) of (Mg,Fe)SiO3 bridgmanite (Brd), which is themost abundant mineral in the lower mantle, based on high-pressure and high-temperature
deformation experiments. They showed that seismic anisotropy in the uppermost lower mantle
near subducting slab is reasonably explained by horizontal flow of mantle material. However,Tsujino et al.’s (2016) study consists of very limited number of experimental data due todifficulty in conducting experiments under the lower mantle pressure and temperature
condition, and further studies are desirable to assess their conclusion. In this study, we haveconducted high-pressure and high-temperature deformation experiments on MnGeO3perovskite (Pv) which is an analog material of Brd and determined its deformation-induced
CPO.
A sintered aggregate of MnGeO3-Pv was synthesized from MnGeO3-Opx and adopted asa starting material of deformation experiments. Deformation experiments were conducted using
D111-type deformation device installed at PF-AR, KEK and DT-Cup at UCL. The DT-Cup,developed by Hunt et al. (2014), is a modified Kawai-type multi-anvil apparatus by which wellcontrolled deformation experiments at pressures higher than 15 GPa can be conducted bydriving two second-stage anvils using differential actuators. The D111-type apparatus is an
improved version of DT-Cup which can be used under higher press load. Pressure andtemperature conditions of experiments were 16 GPa and 1200-1300ºC, and strain rates were4.5−13.9 × 10−5 s−1 in shear deformation and 3.7 × 10−5 s−1 in uniaxial compression. The CPOof recovered samples were determined using MAUD software by analyzing 2-dimensional
diffraction pattern taken with monochromatic X-ray (50 keV) at SPring-8, BL04B1.
Three recovered samples from shear deformation experiments consistently showed CPO

28

pattern with [010] aligned parallel to shear direction, and [100] and [001] weakly aligned subparallel to shear plane normal. In a uniaxial compression experiment, [100] strongly aligned
parallel to compression direction. These results suggest that dominant slip system of MnGeO3Pv is [010](100) under the studied conditions. This slip system differs from the dominant slip
system of Brd reported by Tsujino et al. (2016), [001](100), whereas Ferre et al. (2007) reported
that [010](100) is one of the easiest slip system in MgSiO3-Pv based on first principles
calculation. If [010](100) is assumed to be the dominant slip system in Brd, the resultant seismic
anisotropy for VP and VS is almost identical to that for the [001](100) dominant case. Therefore,
present results also suggest predominance of horizontal flow in the uppermost lower mantle
near subducting slab as Tsujino et al. (2016) concluded.
Hunt et al. (2014) Rev. Sci. Inst., 85, 085103.
Tsujino et al. (2016) Nature, 539, 81-84.

29

S4-4
Incorporation of nitrogen into the lower-mantle minerals under highpressure and high temperature
Ko Fukuyama1, *Hiroyuki Kagi1, Toru Inoue2,3, Toru Shinmei3, Sho Kakizawa3,
Naoto Takahata4, Yuji Sano4 (*presenting author)
1

Geochemical Research Center, Graduate School of Science, The University of Tokyo(ko.fukuyama@eqchem.s.u-tokyo.ac.jp)
2

Department of Earth and Planetary Systems Science, Hiroshima University
3
4

Geodynamics Research Center, Ehime University

Atmosphere and Ocean Research Institute, The University of Tokyo

Nitrogen occupies about 80% of the Earth 's atmosphere and it is suggested that nitrogen had
an impact on the climate in the early Earth (e.g. Goldblatt et al., 2009). Thus, nitrogen is avery important volatile element in discussing the early Earth evolution process and origin of
the life. However, we still cannot fully understand the behavior of nitrogen especially in the
deep Earth. For example, nitrogen is depleted compared to other volatile elements in deep
mantle (Marty et al., 2012). This is so-called "Missing" nitrogen, which is an important
subject in earth science.
In this study, we compared nitrogen incorporation into lower-mantle minerals (bridgmanite,
periclase and stishovite) by high-temperature high-pressure experiment using multi-anvil
apparatus installed at Geodynamics Research Center, Ehime University under the conditionsof 27 GPa and 1600 ̊C-1900 ̊C. In these experiments, we used Fe-FeO buffer in order toreproduce the redox state of the lower mantle. Two types of starting materials: a powder
mixture of SiO2 (quartz) and MgO and a powder mixture of SiO2, MgO, Al2O3 and Mg(OH)2
were used for starting materials. Nitrogen in recovered samples was analyzed using
NanoSIMS installed at Atmosphere and Ocean Research Institute.
A series of experimental results revealed that stishovite and periclase can incorporate more
nitrogen than bridgmanite. This suggests that periclase, the major mineral in the lower mantle,
may be a nitrogen reservoir. Furthermore, the results suggest that stishovite, which is formedby the transition of the SiO2-rich oceanic crustal sedimentary rocks transported to the lower30

mantle via subducting slabs, can incorporate more nitrogen than bridgmanite (20 ppm
nitrogen solubility reported by Yoshioka et al. (2016)). Our study suggests that nitrogen
would continue to be supplied to the lower mantle via subducting slabs since approximate 4billion years ago when the plate tectonics had begun, forming a “Hidden” nitrogen reservoir
in the lower mantle.

31

S5-1 Invited
Terrestrial magma ocean origin of the Moon
Shun-ichiro Karato1, Natsuki Hosono2, , Junichiro Makino3, and Takayuki R. Saitoh4
1

Yale University, Department of Geology & Geophysics (shun-ichiro.karato@yale.edu)
2

JAMSTEC
3

4

RIKEN

ELSI, Tokyo Institute of Technology

Any viable model for the origin of the Moon must explain both the chemical and mechanicalcharacteristics of the Earth-Moon system. The classic model of oblique giant impact explains
the large angular momentum and the lack of a large Fe-rich core in the Moon, but it isdifficult to explain the similarity in the isotopic compositions without violating the angularmomentum constraint. In most of previous studies, they tried to solve this dilemma by
modifying the mechanical conditions of collision. However, these models did not givesatisfactory explanation because they could explain both chemical and mechanical aspects of
the Moon-Earth system only in a very small fraction of the parameter space, and in manycases, the validity of the models for the angular momentum has been questioned. Moreover,none of the previous models explain a higher FeO content of the Moon than Earth.
Furthermore, in all previous models, they used a numerical method (SPH (Smoothed Particle
Hydrodynamics)) that contains a serious physical problem in treating a density discontinuity.
In this study, we propose a new model to explain both chemical and mechanical aspects of theMoon-Earth system using (i) a new equation of state of silicate melts, and (ii) a modified SPH
code where a density discontinuity can be treated correctly. A key to this model is an
assumption that the proto-Earth to which a giant impact occurred was covered by a magma
ocean. Since the melts and the solids follow completely different equation of state (Jing andKarato, 2011), the degree of heating is much higher for melts and as a consequence, amajority of the materials ejected by a giant impact to form the Moon is from the magma
ocean of the proto-Earth. This model provides a natural explanation of the similarities in theisotopic composition and the difference in FeO content between the Moon and Earth with theangular momentum constraint being satisfied.

32

S5-2
Zr isotope constraints on early Earth differentiation
Tsuyoshi Iizuka1, Keita Itano1, and Shinji Yamamoto2
1

University of Tokyo (iizuka@eps.s.u-tokyo.ac.jp)
2

Yokohama National University

The radionuclide 92Nb decays to 92Zr with a half-life of 37 Ma [1]. Because Nb and Zr canfractionate from each other during partial melting of the mantle and mineral crystallization as
well as metal-silicate differentiation, Nb-Zr isotope systematics can potentially placechronological constraints on early planetary differentiation. Considering the initial abundanceof 92Nb in the solar system (92Nb/93Nb = 1.7 ×10-5), yet, the possible Zr isotopic variation on
the Earth would be highly restricted [2]. For instance, even a 4.53 Ga reservoir having a
Nb/Zr ratio four times higher than that of CHUR is expected to display a 92Zr anomaly of only
+10 ppm. Such reservoir with an elevated Nb/Zr ratio might be formed if Fe-Ti oxide andsulfide minerals presented as a liquidus phase during differentiation on the infant Earth.
Here we report our search for a Zr isotopic vestige of early Earth differentiation using ancientterrestrial zircons. Zirconium isotopic ratios in single zircon grains were measured using
MC-ICP-MS with the desolvating nebulization technique, which allows us to achieve
analytical precision of ±<10 ppm. So far, the high-precision Zr isotopic analysis has been
applied to detrital zircons with ages up to 4.3 Ga from the Jack Hills in the Yilgarn Craton,
Western Australia and igneous zircons from the 4.0–3.6 Ga orthogneisses in the Acasta Gneiss
Complex, northwestern Canada. These Acasta rock samples were previously studied
for zircon Lu–Hf isotope systematics and the results indicated that their magmatic sources
contained Hadean crustal components [3]. Our Zr isotopic data for the Jack Hills and Acasta
zircons display no resovable 92Zr anomalies at the level of analytical precision. By combining
the Hf isotopic data for these zircon grain, we indicate the development of a 4.5 Ga enriched
reservoir on the Earth that had a Lu/Hf of 0.07 and a Nb/Zr less than 0.4. Such reservoir could
form via fractional crystallization processes within the shallow or upper mantle.
[1] Holden (1990) Pure Appl. Chem. 62, 941–958. [2] Iizuka et al. (2016) Earth Planet. Sci.
Lett. 439, 172–181. [3] Iizuka et al. (2009) Chem. Geol. 259, 230–239.

33

S5-3
Physical properties of volatile-bearing magmas in the Earth’s deep interior
Akio SUZUKI
Department of Earth Science, Graduate School of Science, Tohoku University(akio.suzuki.c5@tohoku.ac.jp)
Viscosity of magma is an important property, which controls the mobility in the Earth’s
interior. Therefore, it is important to measure the viscosity of silicate melt at high pressure.
Magma is formed by melting of rocks. To reduce the melting temperature of rocks, thevolatile components such as H2O and CO2 are necessary. Therefore, we investigated the effectof volatile components on the viscosity of magma at high pressure. The viscosity wasmeasured by the falling sphere method using the synchrotron X-ray radiography. Cell
assembly and experimental techniques have been described elsewhere (e.g., Suzuki et al.,2002 PCM).
The structure of magma (silicate melt) is characterized by the network of TO4-terrahedra(T is the network forming cation such as Si and Al). This study shows that the viscosity ofpolymerized melts is significantly reduced by the volatile component at high pressure.
However, we observed that the effect of H2O and CO2 on the viscosity of depolymerized
melts was very small. Recently, Sakamaki (2017) suggested that the density of melt at deep
interior was little reduced by volatile components. Melting experiments have shown that thecomposition of melts formed by the melting of mantle rocks become basic to ultrabasic withincreasing pressure. The structure of such melts is depolymerizd. We have shown that theviscosity of depolymerized melts increased with increasing pressure. Although the melting
temperature of rocks is reduced by the volatile elements at high pressure, the density and theviscosity of melt is not reduced. Therefore, it is implied that the mobility of magma in the
deep Earth’s interior is not affected by volatile components.

34

S5-4
Origin of geochemical mantle components: Role of spreading ridge,
subduction zone, and thermal evolution of mantle
Jun-Ichi Kimura1, James B. Gill2, Peter E. van Keken3, Susanne Skora4, Hiroshi Kawabata5
1

Dept. Solid Earth Geochemistry, JAMSTEC (jkimura@jamstec.go.jp)
2

Dept. Earth and Planetary Sciences, UC Santa Cruz
3

4

D.T.M., Carnegie Institution for Science

Institute of Geochemistry and Petrology, ETH Zurich
5

Research and Education Faculty, Kochi University

We explore the element redistribution at mid-ocean ridges (MOR) and subduction zones (SZ)
using a numerical model to evaluate the roles of decompression melting at MOR and fluxed
melting at SZ of the mantle in Earth’s geochemical cycle, with focus on the formation of thedepleted and enriched mantle components. Our model uses a trace element mass balance basedon an internally consistent thermodynamic-petrologic computation to explain the compositionof MOR basalt (MORB) and SZ magmas and their residual mantles and slab components.
Model results for MORB-like basalts from 3.5 to 0 Ga indicate a high mantle potential
temperature (Tp) of 1650–1500°C during 3.5–1.5 Ga before decreasing gradually to ~1300°C
today. The source mantle composition changed from primitive (PM) to depleted as Tp
decreased, but this source mantle is variable with an early depleted reservoir (EDR) mantle
periodically present. We examine a two-stage Sr-Nd-Hf-Pb isotopic evolution of mantle
residues from melting of PM or EDR at MORs. At high-Tp (3.5–1.5 Ga), the MOR process
formed extremely depleted DMM. This event coincided with formation of the majority of thecontinental crust (CC), the sub-continental lithospheric mantle (SCLM), and the enriched
mantle components EM1, EM2, and HIMU formed from the slab components at the Archean
to early Proterozoic high-Tp SZs and stored in the lowermost mantle now found in ocean island
basalts (OIBs) through plume upwelling. During cooler mantle conditions (1.5–0 Ga), the MOR
process formed most of the modern ocean basin DMM. Changes in the mode of mantle
convection from vigorous deep mantle recharge before ~1.5 Ga to less vigorous afterwards issuggested to explain the thermochemical mantle evolution. These EM and DM components
appear to form large domains forming N-S hemispheric lower mantle EM and E-W hemispheric
upper mantle DM structures, respectively. Mantle convection appears to be sluggish for thesemantle components perhaps due to density stratification of the source materials.

35

S6-1 Invited
Earth’s Correlation Wavefield and new Insights on Structure and Dynamics
of the Inner Core
Hrvoje Tkalčić
1

Research School of Earth Sciences, The Australian National University(Hrvoje.Tkalcic@anu.edu.a)

We have recently obtained new insights on the Earth’s correlation wavefield using the codaof globally recorded large earthquakes, through stacking the cross-correlation of multiple
pairs of waveforms. Our method revealed many of the apparent seismic phases sampling the
Earth’s core that have not previously been observed in either traditional earthquake
seismology or previous cross-correlation studies. Some of these seismic phases resemble
multiple reverberations through the Earth’s core, however we show that they do notcorrespond to Green’s functions, as previously assumed. We propose a principle that explains
both apparent arrivals comparable to those expected in the regular seismic wavefield and thepreviously unobserved and unexplained phases in the correlation wavefield. This insight into
the mechanism producing Earth’s correlation wavefield has far reaching implications forseismology of the Earth’s core since it provides a new view of the seismic wavefield andallows efficient extraction of seismic signals that might lie below the typical noise level inconventional earthquake seismology.
One such signal is the Holy Grail of global observational seismology, the PKJKP waves or
shear waves through the Earth’s inner core. The observation of shear waves would provide
constraints on the rigidity, and more generally, structure and dynamics of the Earth’s innercore. I will present the most recent results on Earth’s correlation wavefield and report on the
search for shear waves in the inner core.

36

S6-2
Ab-initio study of iron diffusion properties in Earth’s inner core
1

1

Sebastian Ritterbex and 1Taku Tsuchiya

Geodynamics Research Center, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577,
Japan (ritterbex.sebastian_arthur_willem.us@ehime-u.ac.jp)
Seismic observations provide evidence that the Earth’s inner core exhibits global anisotropy(Tanaka and Hamaguchi, 1997; Creager, 1999). This anisotropy is thought to result from thecollective alignment of crystals and suggests that the inner core may be subject to plastic
deformation. The plastic properties of the inner core are therefore believed to be of paramountimportance for understanding inner core dynamics and core evolution.
Under high pressure conditions in the deep Earth, plastic deformation is likely to be
governed by diffusion of point defects which may control many mechanisms of plastic
deformation including dislocation creep via climb. Understanding the mechanisms of(anisotropic) atomic diffusion is therefore important to gain insight into the creep processes inEarth’s inner core.
The inner core is expected to be composed of a solid iron-nickel alloy with some unknown
light elements (Mao et al., 1998). Using ab-initio calculations, we study vacancy diffusion in
hcp, bcc and fcc iron at pressure conditions up to the Earth’s inner core. Our results demonstratethat pressure suppresses defect concentration but does not strongly affect defect mobilities. We
found that some light elements, particularly hydrogen, influence metallic bonding and enhanceatomic diffusion. This allows for extrinsic deformation mechanisms in iron at inner core
conditions. Here, we will discuss on the diffusion properties of the inner core iron alloy.

37

S6-3
Local strong slow S-wave anomalies at western edge of Pacific LLSVP in thelowermost mantle
Masayuki Obayashi1, Fenglin Niu2, and Junko Yoshimitsu1
1

JAMSTEC (obayashi@jamstec.go.jp)
2

Rice University

Seismic tomography studies have revealed two broad slow shear-wave speed anomalies
regions beneath the Pacific and Africa called as LLSVPs (Large Low Seismic Velocity
Provinces). There are geographic correlations between the LLSVPs and hotspots, and the
LLSVPs could probably play an important role for convection throughout the mantle andthermal structure and evolution of the earth. The LLSVPs have been considered to beheterogeneous in composition since the boundaries between the normal mantle are sharp. To
investigate the details of the sharp LLSVP edge we measure ScS–S and SKS–S differential
traveltimes in the hypocentral distance of about 60° –90° using Japanese and Chinese seismic
networks. We use
We found anomalously large (more than 5 sec) ScS –S travel times accompanying normal
SKS –S travel times, suggesting local strong slow region in the vicinity of the ScS bounce
points (red circles in Figure 1). Such ScS bounce points locate to the northeast of New Guinea
Island extending over 20 degrees in NE-SW direction. However below New Guinea Island,
both ScS –S and SKS –S travel times are normal (green circles in Figure 1), indicating abrupt
end of the local strong slow anomalies.
We obtained 3750 event-station pairs of ScS –S and 1500 pairs of SKS –S differential travel
times and inverted them for lowermost mantle S-wave speed structure. The result shows verystrong slow anomalies of more than 5% at western edge of Pacific LLSVP that extend
vertically not more than 200 km from the core mantle boundary.

38

S6-4
Mobile broadband seismic observation in Thailand: Its present state andpreliminary results
S. Tanaka1, W. Siripunvaraporn 2, S. Boonchaisuk2, S. Noisagool2, K. Kawai3, Y. Suzuki3, Y.
Ishihara1, T. Kim 1, K. Miyakawa 4, N. Takeuchi4, and H. Kawakatsu4
1
2

JAMSTEC (stan@jamstec.go.jp)

Faculty of Science, Mahidol Univ.
3

4

School of Science, Univ. Tokyo

Earthquake Research Institute, Univ. Tokyo

Thailand is located in an important area to explore deep Earth structure as well as tounderstand tectonics of the Indochina peninsula. However, the number of broadband seismic
stations was not enough to address these issues. Thus, we have conducted a mobile broadband
seismic observation in Thailand, named Thai Seismic Array (TSAR), under the support of
MEXT Kakenhi, Grant-In-Aid for an innovative area “Core-mantle co-evolution”(2015-2019).
In the period from November 2016 to February 2017, we deployed 40 stations thatconsisted of 34 CMG-3Ts, 6 STS-2s for broadband seismometers, 40 RT130s for data loggers,
whose electric powers were supplied by solar panels and batteries. Although, after the
maintenance in February 2018, the number of the station working with full functions are
reduced to be only 22 due to water invasion, machine troubles, damages by creatures andhuman errors, we have succeeded to record valuable seismic records.
Here I show preliminary results on SKS splitting and S-wave velocity structure in thelowermost mantle beneath the southwestern Pacific.

39

S7-3
Melting experiments on Fe–Si–S alloys to core pressures
Shigehiko Tateno1, Kei Hirose1,2, Ryosuke Sinmyo1,2, and Guillaume Morard3
1

Earth-Life Science Institute, Tokyo Institute of Technology (tateno@elsi.jp)
23

Department of Earth and Planetary Science, The University of Tokyo

Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne
Universités

Melting and subsolidus experiments were carried out on Fe–Si–S alloys (2.2–2.7 wt% Si +2.0–2.1 wt% S) up to 146 GPa in a laser-heated diamond-anvil cell (DAC). The melting andsubsolidus phase relations were examined on the basis of in-situ synchrotron X-ray diffraction
measurements and ex-situ textural and chemical characterizations of recovered samples. The
subsolidus phase assemblage changed from Fe-rich hexagonal closed-packed (hcp) phase +Fe3S into a single phase of hcp Fe–Si–S alloy above 80 GPa at ~2500 K. The melting curve
was obtained on the basis of the appearance of diffuse X-ray scattering and/or melting texture
found in the cross section of a recovered sample. Microprobe analyses of quenched molten
samples showed that liquid Fe–Si–S coexisted with Fe-alloy solid being depleted in sulfur but
enriched in silicon compared to the liquid. This indicates that the liquid evolves toward a
Si-poor and S-rich composition upon crystallization. Our data further suggest that the ternary
eutectic liquid composition is Si-deficient and close to the tie line between the eutectic points
in the Fe–Si and Fe–S binary systems at each pressure. The composition of Fe–Si–S liquidthat accounts for the outer core density is outside the liquidus field of solid Fe at the innercore boundary (ICB) pressure. Accordingly, the solid alloy crystallizing from such outer coreliquid must be more enriched in silicon/sulfur than the coexisting liquid and thus cannot form
the denser inner core required from seismic observations. Furthermore, liquid Fe–Si–C nor
Fe–Si–O does not crystallize a denser solid at the ICB.These reinforce the conclusion thatsilicon is not an important light element in the core.

40

S7-1 Invited
Computational models of magnetic field generation in the Earth
Andrew Jackson1, Kuan Li1, Andrey Sheyko1, Philip Livermore2, Chris Finlay3
1

Institute for Geophysics, ETH Zurich (ajackson@ethz.ch)2
3School of Earth & Environment, University of Leeds

National Space Institute, Danish Technical University

Earth's magnetic field is generated by fluid motion in the outer core by a process termed
self-exciting dynamo action. In this process, electrically conducting fluid flows through amagnetic field, inducing electrical currents that reinforce the original magnetic field. The
driving force for this is thought to be thermal convection.
This process can be simulated on the computer in a self-consistent way, albeit in aparameter regime that is somewhat distant from planetary settings. In particular, the values ofviscosity used are too large, and the prospects for reducing these viscosities to more
appropriate values are remote. Despite this, the approach has met with great success and has
demonstrated that magnetic fields can be generated in this way. Many features are quite
Earth-like, most likely because the magnetic Reynolds number (the ratio of magnetic
induction to magnetic diffusion) is in the correct regime. We will contrast conventionalmodels with a different approach in which both inertia and viscosity are omitted from theequations at the outset. This approach, whilst in its infancy, holds the promise of providing
complementary models of planetary magnetic field generation.

41

S7-2
On penetration of compositional convection
into a thermally stable stratified layer in the outer core of the Earth
Youhei Sasaki1, Shin-ichi Takehiro2
1

Department of Mathematics, Kyoto University (uwabami@gfd-dennou.org)
2

Research Institute for Mathematical Sciences, Kyoto University

It is suggested from recent high-pressure experiments and first principle calculations thatthe values of thermal conductivity under conditions of planetary cores are larger than thoseconsidered so far. By using 1-dimensional thermal balance models with the updated values ofthermal conductivity, generation and existence of a stably stratified layer at the upper part of
the Earth's outer core is discussed. However, mixing effect by compositional convection driven
by light element release at the inner core boundary is not considered. It is an importanthydrodynamic issue for determining structure of the outer core, whether compositional
convection erodes and destroy the stable layer or not.
In this study, numerical experiments of two-components Boussinesq fluid system where alight element is injected from the bottom of a thermally stable layer are performed, anddevelopment and penetration height of compositional convection is observed.
We propose distribution of power induced by thermal and compositional buoyancy (rate of
kinetic energy production) as a measure of occurrence of thermal and compositional
convection. The power consists of the terms proportional to heat flux and compositional flux.
The region with positive power is considered that convection is active there because kinetic
energy can be produced by buoyancy force. On the other hand, in the region with negative
power convection is suppressed and stably stratified layer may be produced. Numerical results
show that the heights of developed compositional convection are well explained by positive
kinetic energy production regions on the assumption that the whole layer is mixed up withconvection.

42

S7-4
Melting of iron to 290 gigapascals
Ryosuke Sinmyo1,2, Kei Hirose1,2, and Yasuo Ohishi3
1

Department of Earth and Planetary Science, Graduate School of Science, The University ofTokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan. (sinmyo@eps.s.u-tokyo.ac.jp)
2

Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro,
Tokyo 152-8550, Japan.

3

Japan Synchrotron Radiation Research Institute, 1-1-1 Koto, Sayo, Hyogo 679-5198, Japan.

The Earth’s core is composed mainly of iron. Since liquid core coexists with solid core at the
inner core boundary (ICB), the melting point of iron at 330 gigapascals offers a key constraint
on core temperatures. However, previous results using a laser-heated diamond-anvil cell(DAC) have been largely inconsistent with each other, likely because of an intrinsic large
temperature

gradientandits

temporalfluctuation.

Here

we

employedaninternal-resistance-heated DAC and determined the melting temperature of pure iron up to
290 gigapascals, the highest ever in static compression experiments. A small extrapolation
indicates a melting point of 5500 ± 80 kelvin at the ICB, about 500–1000 degrees lower thanearlier shock-compression data. It suggests the upper bound for the temperature at the core–mantle boundary (CMB) to be 3760 ± 180 K. Such present-day CMB temperature combinedwith the recently-proposed nominal core cooling rate suggests that the lowermost mantle wasno longer globally molten, at least in the early Proterozoic Eon, consistent with the recyclingof subducted crustal materials originally formed more than 1.5 Gyr ago.

43

S7-5
Core isotopic flavors in OIB, without core entrainment
John Hernlund1, Scott Hull2, Irene Bonati1, Steve Desch3
1

Earth-Life Science Institute, Tokyo Institute of Technology (hernlund@gmail.com)
2
3

School of Earth Sciences, Ohio State University, USA

School of Earth and Space Exploration, Arizona State University, USA

Recent advances in geochemical analysis are better revealing isotopic variations in oceanisland basalt (OIB) sources, including relative depletions in 182W/184W, 4He/3He, and D/H.
While the possibility that these reflect primordial unmixed heterogeneities in the mantle has
generated some excitement in the community, such features might easily be explained by coreisotopic contamination of the mantle at the core-mantle boundary (CMB). However, lacking astrong coupled enhancement in siderophile element abundance, the possibility of coreentrainment directly into the deep mantle has been rejected (e.g., Mundl et al., 2017). On theother hand, several physical processes have been proposed that do not involve entrainment ofexcess metal into upwelling plumes but still permit ample contamination of the basal mantle
by core isotopic flavors. These include: (1) core fluid intrusion via grain-scale decompaction
at CMB topographic lows (Kanda & Stevenson, 2006) followed by compaction and expulsionof fluids, (2) upward sedimentation and viscous compaction of solids crystallized in the outer
core (Buffett et al., 2000), (3) interaction between a liquid basal magma ocean (BMO) and the
top of the core and subsequent accumulation of residues in the CMB region (Labrosse et al.,2007). Mechanism (1) involves ongoing interactions of the lowermost ~1 km of the mantle,
the timing and volume of crystals produced by mechanism (2) is highly uncertain but could beongoing today in the form of SiO2 crystallization (Hirose et al., 2017), while a BMO
mechanism (3) allows for the largest volumes of mantle to be contaminated although theinteraction would have been greatest in the early Earth. In any case, it could be that all 3
mechanisms (and others we do not know about) are responsible for imparting a core isotopic
flavor to the mantle, but without associated entrainment of excess metal into mantle plumes.

44

S8-1 Invited
Shaping mantle volatile concentrations through early heterogeneities andlong-term cycling
Sujoy Mukhopadhyay1, Curtis D. Williams1, Rita Parai2
12

Dept. of Earth and Planetary Sciences, UC Davis, CA 95616, USA (sujoy@ucdavis.edu)

Dept. of Earth and Planetary Sciences, Washington Univ. in St. Louis, St Louis, MO 63105,
USA
The origin and incorporation of volatiles within planetary interiors is of fundamental

importance in understanding the formation and evolution of terrestrial planets. We will showthat high precision neon isotopic measurements in mantle plumes document the presence of
nebular gases in the present day deep mantle. Neon isotopic composition of mantle-derived
basalts, along with ratios of primordial argon to neon and primordial xenon to neon, indicatethat mantle noble gases are a two-component mixture of nebular and chondritic gases. While
mantle neon is dominated by the nebular component, primordial argon and xenon are
dominated by the chondritic component. The nebular component, best preserved in the neon
isotopic ratios, is present in significantly higher proportion in the deep mantle plume sourcecompared to the shallower MORB source. The preservation of distinct reservoirs ofprimordial noble gases in the present day mantle signifies limited interaction between theplume and MORB sources since Earth’s accretion and place constraints on long-term mixingof the mantle.
While some fraction of the chondritic volatiles was introduced into the mantle during
accretion, a substantial fraction of the present day inventory is dominated by subduction ofchondritic surface volatiles. We will show that the evolving xenon isotopic composition of theatmospheric over the Hadean and Archean can be utilized as a constraint on the timing of
initiation of recycling of atmospheric noble gases into the mantle, particularly Xe and water.
Forward modeling mantle processing and crust formation rates with the change inatmospheric xenon isotopic composition suggests significant recycling of atmospheric Xe into
the deep Earth could not have occurred prior to ~2.5 Ga. Since Xe recycling into the mantle isassociated with hydrous phases, water was also not recycled in significant quantities into the
Earth’s interior prior to the Proterozoic.

45

S8-2
Nano-mole sulfur, carbon and oxygen isotope measurement system using
IRMS MAT-253 for high pressure experiment run products
M. Satsh-Kumar1, Shinnosuke Aoyama 1, and Miyako Abe2
1

Faculty of Science, Niigata University (Email: satish@geo.sc.niigata-u.ac.jp)
2

Graduate school of Science and Technology, Niigata University

Geophysical studies and high pressure experimental results have suggested that the Earth’s
core should contain light elements such as hydrogen, carbon, oxygen, sulfur, or silicon. One
potential tool to understand the content of light element in core is the application of massbalance computations on elemental concentration as well as isotopic composition (Wood et al.,2013). Recent studies have suggested the presence of isotope fractionation at high temperatureand high-pressure conditions, especially in magma ocean environment and core segregation(e.g., Satish-Kumar et al., 2011; Shahar et al., 2016; Labidi et al., 2016). In order to understandthe light element isotope fractionation processes in the deep earth, it is necessary to measure
the isotope composition accurately in micro to nano mole scales, because the high pressure
experimental run products are small in volume.
At Niigata University, MAT-253 mass spectrometer (Thermo Fisher Scientific) was
installed through the MEXT Grant-in-Aid for Scientific Research on Innovative Areas. Carbon
and oxygen isotopic composition are measured using CO2 and sulfur isotopic composition aremeasured using SF6 gas. A new micro-volume inlet system was installed and fundamental
parameters such as pressure effect and capillary flow effect were tested. Using the microvolume inlet system the minimum volume required for analysis is 1 micro mole sample gas,
and the precession for carbon, oxygen and sulfur isotopic composition are better than 0.1 ‰.
Multiple sulfur isotope measurement system consists of; 1) curie point pyrolyzer for rapid
conversion of small volume samples to SF6 gas (Ueno et al., 2015), 2) gas chromatograph forpurifying the SF6 gas and 3) micro-volume inlet system for introduction of sample gas toionization chamber. Initial measurements on small volume samples gave precession better that
0.1‰ for both 34S and 33S. However, 36S has large errors due to possible contamination byhydrocarbons. Experiments are now being carried out with better vacuum conditions and higher
purity carrier gas for refining the precision of 36S. Sulfur-bearing samples from experimental
run products as well as natural samples will be measured for multiple sulfur isotopes forunderstanding the presence of mass dependent and independent fractionation in mantle
reservoirs and possible isotope exchange during core-mantle interaction.
References
Labidi, J., Shahar, A., Le Losq, C., Hillgren, V.J., Mysen, B.O., & Farquhar, J. (2016).
Geochimica et Cosmochimica Acta, 175, 181–194.
Satish-Kumar M, So H, Yoshino T, Kato M, Hiroi Y (2011) Earth and Planetary Science Letters,
310, 340-348.
Shahar, A., Schauble, E. A., Caracas, R., Gleason, A. E., Reagan, M. M., Xiao, Y., Shu, J. &Mao, W. (2016) Science 352 (6285), 580-582.
Wood, B.J., Li, J., & Shahar, A., (2013) Reviews in Mineralogy & Geochemistry, 75, 231-250.
Ueno, Y., Aoyama, S., Endo, Y., Matsu’ura, F., Foriel, J., 2015. Chemical Geology, 419, 29–35.
46

S8-3
Determination of the noble gas partition coefficients between metal-silicate
melts
Hirochika Sumino1, Satoshi Kishi1, Ryuichi Nomura2, Kenji Mibe3, Jackson Colin4,
Hideharu Kuwahara2, Shigehiko Tateno5, and Hiroyuki Kagi6
1

Department of Basic Science, Graduate School of Arts and Sciences,
The University of Tokyo (sumino@igcl.c.u-tokyo.ac.jp)
23
4Earthquake Research Institute, The University of Tokyo

National Museum of Natural History, Smithsonian Institution
5

6

Geodynamics Research Center, Ehime University

Earth-Life Science Institute, Tokyo Institute of Technology

Geochemical Research Center, Graduate School of Science, The University of Tokyo

Analyses of ocean island basalts (OIBs) reveal a geochemical reservoir characterized byunradiogenic, “primordial” noble gas signatures (e.g., high 3He/4He and low 40Ar/36Ar ratios),
likely residing in the deep mantle. There has been much debate about the area holding the“primordial” noble gases deep in the Earth [1], including that the “primordial” noble gasses
have been retained in the deepest region of the mantle since 4.4 Ga [2] or in the core since thecore-mantle separation [3]. However, the validity of latter strongly depends on the quantity of
noble gases the core incorporates during accretion and can hold in the present day.
In order to investigate noble gas partitioning behavior between the core and mantle, noble
gases were dissolved into metal-silicate melts under high temperature and pressure
conditions, and then the samples were quenched. After the sample synthesis, the noble gas
concentrations contained in the each phase were analyzed using an ultraviolet laser ablation
apparatus and a noble gas mass spectrometer.
The partition coefficient D, where D = (noble gas in metal phase)/(noble gas in silicate
phase), of argon at 1 GPa varied widely from orders of 10–4 to to 10–1. This resulted fromheterogeneous argon distribution in the metal phase, which seems significantly controlled bycontaminant phases, such as silicate inclusions and micro- or nano-argon bubbles. Therefore
the lowest D so far determined would yield the best estimate, 7  10–5, which is three ordersof magnitude lower than the previous work [4]. On the other hand, D for neon, argon, krypton

47

and xenon at 8 GPa obtained with the samples synthesized with multianvil apparatus were in
the order of 10–3, which is consistent with the previous work [4]. At the present time, we havenot determined helium partition coefficient in the all pressure range as it was difficult to retain
enough amount of helium in high-pressure and temperature apparatus during the experiments.
Further experiments are necessary to obtain the noble gas concentration contained in themetal phase in order to determine the partition coefficients at higher pressure, at least 30 GPa
with which the elemental partition between iron and silicate melt would have occurred duringcore formation [5].
[1] Porcelli & Ballentine, Rev. Mineral. Geochem. 47, 411-480, 2002. [2] Mukhopadhyay,
Nature. 486, 101-104, 2012.

[3] Trieloff & Kunz, Phys. Earth Planet. Inter. 148, 13-38,

2005. [4] Matsuda et al., Science. 259, 788-791, 1993 [5] Righter, Earth Planet. Sci. Lett. 304,
158-167, 2011.

48

S8-4
Silicon’s role in the evolution of the Earth’s core and mantle
Helffrich, G1 (george@elsi.jp), Hirose, K1,4, Ballmer, M D1,2,
and Shahar, A3
1

Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo 152-8551, Japan
2
3

Institute for Geophysics, ETH Zürich, Switzerland

Geophysical Lab, Carnegie Institution for Science, Washington DC, USA
4

Earth and Planetary Science, University of Tokyo, JapanAs the core forms in a planetary embryo or growing planet, the Fe-rich metal that forms thecore dissolves various elements in it. After the core forms and the planetary body cools, thoseelements may become saturated in the metal and exsolve. Hirose et al. (2017) determined
experimentally the saturation limits in liquid Fe of O+Si, two major elements in nebularmaterial. Using a thermodynamic model of the solubility of Si+O, the maximum solubility of
Si+O in metal during accretion of an Earth-sized planet is about 2 wt% SiO2 equivalent in thecore (Helffrich et al. 2018a). When it crystallises from core metal, the SiO2 rises to the top of
the metallic core and power dynamo activity in small bodies until its Si+O inventory drops
below saturation levels. SiO2 can even escape from the core into the lowermost mantle, andmay survive there to the present day in the form of small-scale seismic scatterers (Helffrich etal. 2018a).
Evidence of core-hosted SiO2 might be found as inclusions in diamonds. Diamonds
from the lower mantle are identified through the unusual compositions of the minerals trapped
within the diamond (Kaminsky 2012), and often include SiO2 (stishovite). Though the SiO2
might have exsolved from high-pressure silicate inclusions reverting to low-pressure forms, theisotopic content of 30Si in the SiO2 should have a characteristic signature due to metal-silicate
fractionation when the metal initially dissolved the Si+O (Helffrich et al. 2018b). This should
provide a way to identify core-hosted SiO2 and provide direct proof that core-mantle interaction
occurs.
References. Hirose et al. (2017) Nature 543: 99-102; Helffrich et al. (2018a) J. Geophys. Res.
123: 176-188; Kaminsky, F. (2012) Earth Sci. Rev. 110: 127-147; Helffrich et al. (2018b) Am.
Mineralogist (in press).

49

S9-1 InvitedThorium and uranium power plate tectonics, but not the geodynamo
William F. McDonough1,2, Scott A. Wipperfurth2, Meng Guo2,3, Ondřej Šrámek4
1

Department of Earth Sciences and Research Center for Neutrino Science, Tohoku University,
Sendai 980-8578, Japan (mcdonoug@umd.edu)
2
3

4

Department of Geology, University of Maryland, College Park, MD 20742, USA

Institute of Crustal dynamics, China Earthquake Administration, Beijing 100085, China

Department of Geophysics, Faculty of Mathematics and Physics, Charles University, Prague,
Czech RepublicRadioactive decay of potassium (K), thorium (Th), and uranium (U) power the Earth's

engine, with variations in 232Th/238U recording planetary differentiation, atmospheric oxidation,and biologically mediated processes. We report several thousand 232Th/238U (κ) andtime-integrated Pb isotopic (κPb) values and assess their ratios for the Earth, core, and silicate
Earth. Complementary bulk silicate Earth domains (i.e., continental crust CCκPb = 3.94 +0.20-0.11
and modern mantle MMκPb = 3.87 +0.15-0.07, respectively) tightly bracket the solar system initialSSκPb = 3.890 ± 0.015. These findings reveal the bulk silicate Earth’s BSEκPb is 3.90 +0.13-0.07 (orTh/U = 3.77 for the mass ratio), which resolves a long-standing debate regarding the Earth’s
Th/U value. Experimental studies find marked differences in the partitioning of U and Th
during core formation. We performed a Monte Carlo simulation to calculate the κPb of the BSE
and bulk Earth for a range of U concentrations in the core (from 0 to 10 ng/g). Comparison of
our results with SSκPb constrains the available U and Th budget in the core. Negligible Th/U
fractionation accompanied accretion, core formation, and crust - mantle differentiation, andtrivial amounts of these elements (0.07 ppb by weight, equivalent to 0.014 TW of radiogenic
power) were added to the core and do not power the geodynamo.

50

S9-2
Tungsten isotopic heterogeneity in oceanic island basalts produced bycore-mantle interaction
Takashi Yoshino1, Hiroshi Makino2, Toshihiro Suzuki2, and Takafumi Hirata2
1

Institute for Planetary Materials (tyoshino@misasa.okayama-u.ac.jp)
2

Geochemical Research Center, The University of Tokyo

Tungsten isotope composition provide important constraints on the sources of theocean-island basalts (OIB). If the core formation occurred within the first 60 Myr of the solar
system formation, the silicate mantle should be characterized by high Hf/W and positiveµ182W, whereas the metallic core has very low Hf/W and negative µ182W. Recently µ182W
from modern basalts with high 3He/4He originated from the core-mantle boundary region haveshown two distinct features: positive µ182W from Phanerozoic flood basalts indicating apresence of primordial reservoir [1], and negative µ182W from modern OIBs [2]. One
possibility to produce this large variation of µ182W is chemical interaction of the mantle with
the Earth’s outer core.
Here we report tungsten grain boundary diffusion in the lower mantle phases determined bymulti-sink method at 25 GPa and temperatures ranging from 1873-2173 K. Grain boundary
diffusion of tungsten in postspinel is fast and displays strong temperature dependence. Lengthscales over which tungsten isotope can be modified significantly at the base of the lower
mantle through the whole Earth’s history are more than tens of kilometer. Tungsten isotope
exchange between core and mantle by grain boundary diffusion processes can generate a large
variation of µ182W in modern basalts with high 3He/4He as a function of distance of theirsource regions from the core-mantle boundary. Modern oceanic island basalts from Hawaii,
Samoa and Iceland originated from the modified isotope region with negative µ182W justabove the core-mantle boundary, whereas those with the positive µ182W could be derived fromthe thick Large Low Shear Velocity Provinces (LLSVPs) far from the core-mantle boundary.
References[1] H. Rizo et al., 2016. Preservation of Earth-forming events in the tungsten isotopic
composition of modern flood basalts. Science 352, 809–812.
[2] A. Mundl et al., 2017. Tungsten-182 heterogeneity in modern ocean island basalts. Science
356, 66-69.

51

S9-3
Liquid metal-silicate partitioning of carbon in a magma ocean
during the core formation of terrestrial planets
H. Kuwahara1, S. Itoh2, R. Nakada3, T. Irifune1
1
Geodynamics Research Center, Ehime University 2 Department of Earth and Planetary
Science, Kyoto University 3 Kochi Institute for Core Sample Research, Japan Agency
for Marine-Earth Science and Technology
Abstract
Elucidating the distribution of carbon in the Earth during core formation is important forunderstanding mass and composition of the early Earth’s atmosphere, and perhaps thecomposition of the Earth’s core. However, the distribution of carbon in the Earth duringcore-mantle differentiation has not been understood well. Previous studies haveconducted high-pressure experiments on liquid metal-silicate partitioning of carbon andfound that carbon is highly siderophile (iron loving) [e.g., 1, 2]. However, carbon
abundance in the current Earth’s mantle is much more abundant than prediction based on
experiments [e.g., 1, 2]. In order to explain this discrepancy, the late accretion of sulfurrich planetesimals has been proposed because carbon is thought to be expelled to mantle
if planetesimals had sulfur-rich core [3]. However, this hypothesis is based on
experiments for the solubility of carbon in metal and silicate phases using a graphite
capsule. Because the solubility ratio of carbon between metal and silicate may not be
equal to metal-silicate partition coefficient of carbon, it is necessary to perform metalsilicate partitioning experiments on carbon at undersaturated conditions.
In this study, we conducted high-pressure experiments on liquid metal-silicate
partitioning of carbon using a boron nitride capsule and multi-anvil apparatus at 8 GPa
and 1923-2123 K. Carbon in quenched metallic liquid and silicate liquid were analyzed
by electron probe micro-analyzer and secondary ion mass spectrometry, respectively. The
preliminary experimental results show that carbon may not be highly siderophile thanpreviously thought. Although additional experiments are required, preliminary
experimental results suggest that the late accretion of sulfur-rich planetesimals, such as a
Mercury-like impactor, might not be necessary to explain the current abundance of carbon
in the Earth’s mantle.
[1] Dasgupta et al., 2013, Geochim. Cosmochim. Acta 102, 191-212.
[2] Chi et al., 2014, Geochim Cosmochim. Acta 139, 447-471.
[3] Li et al., 2016, Nat. Geosci. 9, 781-785.

52

S10-1 Invited
Chemical Stratification and Magnetic Field Generation
Laneuville M1 (mlaneuville@elsi.jp), Hernlund J1, Labrosse S2,
Lasbleis M1 and Helffrich G1
1

Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo 152-8551, Japan.
2

Université de Lyon, École normale supérieure de Lyon, F-69364 Lyon, France.
The existence of a global magnetic field at any point during planetary evolution is

key information regarding its internal evolution. The motion in a metallic core required tosustain magnetic activity can be generated by thermal and compositional instabilities, or
through mechanical forcing. The first two processes in particular depend strongly on initialstate and subsequent cooling history. Accretion of a terrestrial body may lead to chemically
and/or thermally stratified layers both in the core itself [e.g., Jacobson et al. (2017)] or at thecore-mantle boundary, on the mantle side [e.g., Laneuville et al. (2017)]. In this presentation,
we first show how stratified layers form in planetary interiors and discuss the influence itwould have on magnetic field generation.
In particular, we consider the case of a stably stratified basal magma ocean on the
Earth, and a completely stratified core on Mars. Earth’s ~3.45 billion year old magnetic fieldis thought to be currently sustained by chemical buoyancy due to inner core growth. However,
the existence of an ancient field is inconsistent with the estimated young age of the inner core(~1 Ga) and recent measurements of thermal conductivity of iron at core conditions (about
twice as large as previously thought). In the case of Mars, there is evidence for an ancientmagnetic field within about 500 million years from its formation and no evidence for later
activity. Previous models invoked a change in the planet cooling mode in order to stop athermally driven dynamo [Nimmo and Stevenson, 2000; Roberts et al. (2009)]. In both cases,
the existence of a stratified layer may help reconcile models with observations.
References. [1] Jacobson et al. Earth and Planetary Science Letters 474 (2017): 375-386. [2]Laneuville et al. Physics of the Earth and Planetary Interiors (2017). [3] Nimmo andStevenson. Journal of Geophysical Research: Planets 105.E5 (2000): 11969-11979. [4]Roberts et al. Journal of Geophysical Research: Planets 114.E4 (2009).

53

S10-2
Spatiotemporal variations of core-mantle coupling revealed bygeomagnetic field data (FY2017)
Masaki Matsushima1
1

Department of Earth and Planetary Sciences, Tokyo Institute of Technology(masaki.matsushima@eps.sci.titech.ac.jp)

The dynamo action which generates and maintains the geomagnetic field is driven by
fluid flow in the Earth’s outer core. A combination of downwelling flow at the core-mantle
boundary and upwelling flow at the inner core boundary determines a fluid flow pattern in theouter core. Such a flow pattern is likely to influence generation process of the geomagnetic
field. This implies, inversely, that information of the fluid flow in the core can be provided bygeomagnetic field data, such as spatial and temporal variations of geomagnetic field.
Therefore, spatial and temporal variations of core flow may contain information on
spatiotemporal variations of core-mantle coupling. Accordingly, it is important to derive core
flow near the core-mantle boundary from geomagnetic field data to reveal spatiotemporalvariations of core-mantle coupling. It should be noted that constraint of tangentiallymagnetostrophic flow is imposed in estimating the core flow, since it is more relaxed thanconstraint of tangentially geostrophic constraint as adopted by Matsushima (2015). It was
concluded, in FY2016, that dynamic effects of the geomagnetic field, such as the Lorentz
force, on the modeling of core surface flow are limited. However, core electrical conductivity
was assumed to be 3×105 S/m smaller than some recent estimates (e.g. Ohta et al., 2016).
Hence, effects of core electrical conductivity on core surface flow models are investigated forvarious values of core electrical conductivity. Spatial distribution of the Elsasser number,which is proportional to core electrical conductivity, suggests that core electrical conductivity
can have an effect on the core surface flow through the constraint of tangentiallymagnetostrophic constraint.

54

S10-3Highly precise 182W/184W isotopic compositions of terrestrial samples
Asako Takamasa1, Yusuke Fukami1, Katsuhiro Suzuki1
1

182

JAMSTEC (katz@jamstec.go.jp)

W isotope is a -decay product of derived from 182Hf with the short half life (8.9 m.y),resulting in extinct 182Hf at present. Both Hf and W are highly refractory elements and thus areaccumulated in the early stage of the proto-earth. Hf and W are a lithophile and is a siderophileelements, respectively. This contrast leads to large differentiation of Hf and W during coresegregation in the very early Earth system. 182Hf-182W system could give constraints on metalsilicate (core-mantle).
Though the initial studies cannnot detect the anomalies of 182W/184W in terrestrial rocks
beyond the analytical uncertainties (e.g., Takamasa et al., 2009), improvement of analyticaltechniques of W isotope analyses allows us to obtain highly precise 182W/184W ratios of volcanic
rocks, which leads to findings of W isotope anomalies (mostly positive) in old komatiites (2.4 –3.8 Ga) and young volcanic rocks with positive anomalies of 12 Ma Ontong Java Plateau and 6
Ma Baffin Bay (Rizo et al., 2016) and with negative anamalies of those such as the Loihi basalt.
We developed highly precise W isotope ratio measurement with MC-ICP-MS (Thermo co.
Ltd., NEPTUNE PLUS). We have measured W standard solution (SRM 3163) and obtained theisotopic compositions with a enough high precision of ± 5ppm. However, the standard solution,
which separated by cation or anion exchange resin, has systematical 183W/184W drift of -5ppm.
These phenomena was also reported by Willbold et al. (2011). Therefore, we corrected themeasured W isotope ratios of samples with the standard solution processed by the same method
as that of the samples. This technique leads to the reproducible W isotopic compositions withreproducibility of several ppm. We have obtained the negative 182W/183W for the basalts with thehigh 3He/4He isotopic composition from the Loihi, Hawaii, through the developed analyticalmethod. This result is consitent with that of Mundl et al., (2017). As negative anomaly of
182

W/183W could be created by the early earth core segregation, it is probably a signature of core-mantle interaction.

55

Poster Session

56

P1
The effects of ferromagnetism and interstitial hydrogen on the equation ofstates of hcp and dhcp FeHx
Hitoshi Gomi1, Yingwei Fei2, and Takashi Yoshino1
1

Institute for Planetary Materials, Okayama University, Misasa, Tottori
682-0193, Japan. (hitoshi.gomi@okayama-u.ac.jp)

2Geophysical Laboratory, Carnegie Institution of Washington, Washington,
District of Columbia 20015-1305, USA.

Hydrogen has been considered as an important candidate of light elements in the
Earth’s core. Because iron hydrides are unquenchable, hydrogen content isusually estimated from in-situ X-ray diffraction measurements assuming thefollowing linear relation: x = (VFeHx - VFe) / VH, where x is the hydrogen content,
VH is the volume expansion caused by unit concentration of hydrogen, VFeHx andVFe are volumes of FeHx and pure iron, respectively. To verify the linear
relationship, we computed the equation of states of hexagonal iron withinterstitial hydrogen by using the Korringa-Kohn-Rostoker method with thecoherent

potential

approximation(KKR-CPA).

The

results

indicateadiscontinuous volume change at the magnetic transition and almost nocompositional (x) dependence in the ferromagnetic phase at 20 GPa, whereas thelinearity is confirmed in the non-magnetic phase. In addition to their effects on
density-composition relationship in the Fe-FeHx system, which is important for
estimating the hydrogen incorporation in planetary cores, the magnetism andinterstitial hydrogen also affect the electrical resistivity of FeHx. The thermal
conductivity can be calculated from the electrical resistivity by using the
Wiedemann-Franz law, which is a critical parameter for modeling the thermal
evolution of the Earth. Assuming Fe1-ySiyHx ternary outer core model (0.0  x 0.7), we calculated the thermal conductivity and the age of the inner core. The
resultant thermal conductivity is ~100 W/m/K and the maximum inner core age isranging from 0.49 to 0.86 Gyr.

57

P2
Grain growth kinetics of lower-mantle materials:
Implications for the grain size evolution and the rheology
Masahiro Imamura1, Tomoaki Kubo1,
1

Kyushu Univ. (kubotomo@geo.kyushu-u.ac.jp)

We have conducted grain growth experiments of pyrolitic material at 25-27 GPa and 1600-1950C
using a Kawai-type high-pressure apparatus. Grain growth kinetics data in multi-phase assemblages ofBridgmanite (Brg), ferropericlase (Fp), Ca-perovskite (Capv) and/or majoritic garnet (Mjgt) was
obtained and analyzed on the basis of Zener pining and Ostwald ripening processes. The grain size ratio
between major (Brg) and secondary phases was roughly constant and estimated to be ~1.4 and ~1.8 at 25
GPa (four phases of Brg, Fp, Capv, and Mjgt) and 27 GPa (three phases of Brg, Fp, and Capv),
respectively. The secondary phases are homogeneously distributed at grain boundaries of the major
phase of Brg. These results suggest that the Zener pinning and Ostwald ripening of secondary phases bygrain boundary diffusion control the grain growth of Brg. In this case, the grain size ratio between
primary and secondary phase is described by dI/dII=β/fIIz (dI: grain size of primary phase, dII: grain sizeof secondary phase, fII: volume fraction of secondary phase, β and z: Zener parameters). The
relationship between dI/dII and fII obtained in this study is almost consistent with the previous systematic
study in the olivine-enstatite system (Tasaka and Hiraga, 2013), in which the Zener parameters of β andz were estimated to be 0.7 and 0.5, respectively. Grain growth kinetics is generally described by
dn-d0n=kt (d: grain size, d0: initial grain size, n: grain growth exponent, k: Arrhenius-typetemperature-dependent rate constant, t: time). When assuming the n-value of 4 considering the Ostwald
ripening by grain boundary diffusion, the activation enthalpies for the grain growth in Brg, Fp, and Mjgt
are estimated to be ~400, ~320, ~530 kJ/mol, respectively.
These kinetic data were used to discuss the grain-size evolution and the rheology of the lower
mantle. The grain sizes of Brg in a pyrolitic composition (fII=0.2) were estimated to be ~10-200 µm and~500-3000 µm in 108 years for cold subduciting slabs (800-1400C) and the surrounding lower mantle(1600-2400C), respectively. These grain sizes do not change significantly in different chemicalcompositions of an olivine-like (fII=0.3) and a perovskitic (fII=0.1) lower mantle. These grain sizes arelocated at the boundary condition between diffusion and dislocation creep mechanisms inferred fromdiffusivity data, implying that Brg deforms by dislocation creep in high stress conditions expected in thevicinity of subducting slabs and D” layer. Effects of the weaker and secondary phase of Fp with having
smaller grain size will also be discussed in the presentation.

58

P3
Diffusion mechanisms of creep and grain growthof two-phase polymineralic rocks:
Implications for rheology of the lowermost mantle
Atsuro Okamoto1, Takehiko Hiraga2
1

Earthquake Research Institute, Tokyo University (aokamoto@eri.u-tokyo.ac.jp)
2

Earthquake Research Institute, Tokyo University

The phase (mineral) transition which occurs during downwelling flow to the lower
mantle produces micron-size grains. Such fine grains grow to the size observed in the upper
mantle rocks (i.e., 1~10 mm) during one cycle of the mantle convection (Solomatov andReese, 2008). The grain growth is likely to be most significant at the lowermost mantle where
temperature is the highest and the duration for the grain growth is the longest. When
polycrystalline materials deform by diffusion creep mechanism, their viscosities areproportional to the square or the cube of grain size. Thus, if the lower mantle and D” layer
deform by diffusion creep, viscosities of these regions are highly controlled by the grain
growth.
Grain growth in two-phase rocks, whose microstructure is comparable to that of D” layer,
requires diffusion of atoms with a long-distance, which is almost equivalent to the size of thegrains. Such diffusion is also a necessary process during diffusion creep. In this study, we
examine diffusion mechanisms that control creep and grain growth rates based on
experimental results of creep and grain growth of two-phase aggregates. We estimate the flow
property of D” layer when its deformation is accompanied with grain growth.
We synthesized highly-dense fine-grained (~1 mm) forsterite + periclase (10 vol%)polycrystals by using vacuum sintering technique (Koizumi et al., 2010). The constituent
minerals of the aggregates consist of the similar elements of the D” layer minerals such thatthe mechanisms controlling its creep and grain growth are expected to be identical to that inD” layer. I performed uni-axial compressional creep experiments on the forsterite + periclase
aggregate at atmospheric pressure and high temperature (1150 ~ 1400°C). I also conductedgrain-growth experiments at different temperatures ranging from 1300°C to 1450°C for 500h
to obtain temperature dependency of grain growth. Hanging the samples fixed withtheromocouple at different locations from the central heating zone in the furnace enables to59

obtain the precise grain growth data from various temperatures even by a single experiment. I
observed microstructures of the aggregates after the experiments using scanning electron
microscope.
I calculated grain boundary diffusivities from creep and grain growth rates using theoreticalmodels of grain growth and grain boundary diffusion creep (Coble creep), finding both
diffusivities are essentially identical. Based on this result, I conclude that the creep and grain
growth in forsterite + periclase aggregate is controlled by the common diffusion mechanism.
When creep and grain growth rates are determined by a common diffusivity, viscosity of theaggregate during its diffusion creep accompanied with grain growth should follow η = Ct / dwhere η is viscosity, C is a material constant, t is annealing time under constant temperatureand d is grain size. I applied this time–grain size–viscometer to the lowermost mantle with
substituting 1~10 mm and 100 Myr and obtained 1018 ~ 1019 Pa·s as the maximum viscosityof the lowermost mantle. This value does not contradict with the previous estimate of the very
low viscosity (~1016 Pa·s) of the lowermost mantle, which is based on the decay time of the
Chandler wobble and Earth’s tidal deformation (Nakada and Karato, 2012).

60

P4
Experimental study on transport properties of liquid iron-silicon alloy at
and above the outer core conditions
Kohei Miyanishi1, Toyohito Nishikawa2, Norimasa Ozaki1, 2, 3 , Marion Harmand4, Yuhei
Umeda2, Minoru Hosomi2, Keisuke Shigemori1, Youichi Sakawa1, Takayoshi Sano1, andRyousuke Kodama1, 2, 3
1

Institute of Laser Engineering, Osaka University (miyanishik@ile.osaka-u.ac.jp)
2

Graduate school of engineering, Osaka University
3

Photon Pioneers Center, Osaka University
4

IMPMC, Sorbonne Université

Information on the thermal and electrical transport properties of iron alloys underhigh-pressure and high-temperature conditions corresponding to the earth’s outer core isnecessary to clarify the convection phenomena of the earth and the cooling history. In
particular, the transport properties in the outer core–mantle boundary condition strongly
influence the mantle convection, the outer core convection generating the earth's magnetic
field, the growth and inner flow of the inner core, and so on. However, there are very few
experimental examples concerning high-pressure and high-temperature liquid iron/iron-alloy
which correspond to the outer core conditions, and only a few cases have been reported forpure iron [1]. It is required to investigate transport coefficients of liquid iron alloys containing
light elements to simulate actual outer core, experimentally. Laser shock compression
technique has several advantages to exploring iron-alloys under high-pressure andhigh-temperature condition. As there is no mechanical restriction on pressure generation,
producing the pressure of even TPa is easy, and high heating rate exceeding 1015 K / s ispossible, and it is a closed system that is not affected by surroundings. Therefore thetechnique is effective for generation and observation of high-pressure and high-temperatureliquid iron-alloys. In this research, we report optical reflectivity, pressure and temperature
measurements of laser shock compressed iron and iron-silicon (Fe-Si) alloy at and above theearth's outer core conditions.
Target assemblies containing polypropylene (CH), aluminum, quartz, iron oriron-silicon alloy and magnesium oxide (MgO) window were shock compressed by laser
ablation at the GEKKO XII laser facility, the Institute of Laser Engineering, Osaka

61

University. Iron and iron-silicon alloy were formed by electron beam evaporation on the MgO
window. Laser beams with a wavelength of 527 nm were focused onto the target. A focal spotwas 1 mm in diameter with a flat-top spatial intensity distribution resulting in a planar shock
front. Temporal shape of the laser pulse was approximately a flat-top with a full-width at
half-maximum of 2.5 ns. The velocity interferometer system for any reflector (VISAR)
measure a particle velocity and a reflectivity at the interface between iron or iron-silicon alloy
and MgO. The Ppressure was evaluated using measured particle velocity and a known
equation of state of MgO[2]. The optical pyrometer measures the temperature at the interface
through the MgO window.
The pressures determined from the measurement results were from 200 to 400 GPa,and the temperatures were up to 15000 K. In the pressure range exceeding 200 GPa, in thecase of iron, a decrease in reflectivity was observed as the pressure increased, whereas in thecase of the iron-silicon alloy, a continuous increase following a discontinuous decrease in thereflectivity was observed. The decrease in reflectivity of iron suggests a decrease in electronic
conductivity due to temperature rise with increasing pressure. On the other hand, thecontinuous rise seems to indicate an increase in the density of free electrons derived fromsilicon.
[1] K. Ohta, Y. Kuwayama, K. Hirose, K. Shimizu, Y. Ohisi: Nature, 534, 95-98 (02 June2016).
[2] S. Root, L. Shulenburger, R. W. Lemke et al.: Phys. Rev. Lett, 115, 198501 (2015).

62

P5
Microstructures of experimentally deformed carbon steels
Y. SAKODA1, T. KAWAZOE1, J. ANDO1, N. TOMIOKA2, H. OHFUJI3 and Y. KODAMA4
1

Department of Earth and Planetary Systems Science, Hiroshima University(m171210@hiroshima-u.ac.jp)
2

Kochi Institute for Core Sample Research, JAMSTEC
3

4

Geodynamics Research Center, Ehime University

Department of Marine & Earth Sciences, Marine Works Japan Ltd.

The inner core of the Earth is mainly composed of Fe and Ni, in addition to the small amountsof light elements. O, S, and Si are the important candidates of these light elements, and C isalso deeply thought to be stored in the inner core. The seismic data suggest that the solid innercore is deformed plastically and convected same as the mantle. Therefore, the study of plasticity
of Fe containing the light elements is needed in order to understand the dynamics of the innercore.
Fe-alloy containing C is named “carbon steel”, which is a very useful material for the steel
industry. Therefore, its fundamental deformation behavior at ambient pressure is very wellunderstood. One of the interesting phenomena controlling the plasticity of the carbon steel is C
concentration on the dislocation line as known as Cottrell atmosphere. This phenomenon
contributes to make harder the plastic strength of carbon steel. Meanwhile, the plasticity of the
carbon steel at higher pressure conditions has not been studied well so far. Especially, it is notclear whether the Cottrell atmosphere appears or not at higher pressure conditions. In order tounderstand this point, we conducted the deformation experiments of carbon steels and are
currently working on the microstructural observation of the recovered samples.
For the present research, we used the 6-6 multi-anvil apparatus of BGI for the deformation
experiments, and the cross-section polisher of GRC and FIB of KCC for the sample preparation,
and FE-SEM of GRC and TEM of KCC for the microstructural observation. The used samples
were two types of the carbon streels with different C contents (0.22-0.28 wt%C and 0.90-1.00
wt%C). The experimental conditions were 400 °C, 2-6 GPa, and ca. 1.0 x 10-6/s of strain rate.
In our presentation, we will present the details of deformation experiments and preliminary
results of microstructural observation.

63

P6
Deformation of bridgmanite and post-spinel two-layered sample underlower mantle conditions with DT-Cup apparatus
Fang Xu1
1

Institute for Planetary Materials, Okayama University, Tottori, Japan (fang.xu@upmc.fr)

Viscosity jump at 800- to 1200-kilometers depth was reported by geophysical observation
recently (Rudolph et al., 2015). Due to the absence of phase transition in the main minerals,chemical deviation is one candidate explanation for the viscosity jump. A perovskitic lower
mantle is consist of more than 93 vol.% bridgmanite (Murakami et al., 2012), on the other
hand, subducted harzburgite layer contains ~20 vol.% of ferropericlase (Irifune andRingwood, 1987). Ferropericlase is likely much weaker than bridgmanite may significantly
reduce the bulk viscosity of bridgmanite and ferropericlase aggregate (Yamazaki and Karato,2001). Therefore, the viscosity of bridgmanite and ferropericlase aggregate is critical for us tounderstand the viscosity profile in the lower mantle.
To identify the bulk viscosity of bridgmanite and ferropericlase aggregate, two-layered
sample of bridgmanite and post-spinel (bridgmanite plus ~ 30 vol.% of ferropericlase)
aggregates were deformed simultaneously. We prepared starting material of bridgmanite andpost-spinel aggregates with grain size of 5-10 micron meter at high pressure and hightemperature in a Kawai-type high-pressure apparatus. Then the deformation experiments wereconducted in the DT-Cup apparatus which is a development of the Kawai type multi-anvilpress (Hunt et al., 2014). We deformed bridgmanite and post-spinel two-layered samples up to
strain of ~0.2 at 1500 °C and 25 GPa. As the identical uni-axial stress during deformation, thestrengths of bridgmanite and post-spinel are inversely proportional to their strains.
The recovered bridgmanite and post-spinel samples showed virtually identical strain, whichindicates similar strengths of them. Lattice preferred orientations (LPOs) of bridgmanite
phase in both bridgmanite and post-spinel samples are similar developed, the slip plane of(100) is consistent with the slip system reported by Tsujino et al. (2016). Our result indicateschemical deviation in ferropericlase proportion is unable to be responsible for the viscosity
jump in the lower mantle under current condition. The discordance between this study andGirard et al. (2016), who reported a marked softening of post-spinel aggregate with shear
strain up to 1.0, highlights the possible importance of large shear strain in controlling the bulk
viscosity.

64

P7
Toward development of ultrasonic measurement technique under whole
lower mantle conditions
Yuji Higo1, Tetsuo Irifune 22
1
2

JASRI, SPring-8 (higo@spring8.or.jp)

GRC, Ehime Univ. (irifune@dpc.ehime-u.ac.jp)

Elasticity data on mantle minerals under high pressure and high temperature are critical tointerpret the seismic velocity and density profiles in the Earth’s deep interior. However,ultrasonic measurements of elastic wave velocities under high pressure and high temperature
have been limited to those corresponding to the mantle transition region (<24GPa, <1673K),
because of the technical difficulties. Since only a small sample can be used in the experiment
under the lower mantle conditions, ultrasonic echoes are very weak and cannot perform aprecise elastic measurement. In this study, to overcome this problem, the high-frequency
arbitrary waveform generator, post amplifier and high-speed semiconductor relay were installedin BL04B1 at SPring-8. Since this study has just begun, we will introduce the plan for future
initiatives.

65

P8
Searching for multi light elements in iron-silicate-water system using highpressure and high temperature experiments: Implications for the Earth's
evolution
Riko Iizuka-Oku1*・Hirotada Gotou2・Hiroyuki Kagi1
1

Geochemical Research Center (GCRC), Graduate School of Science, The University ofTokyo (*riizuka@eqchem.s.u-tokyo.ac.jp)
2

The Institute for Solid State Physics (ISSP), The University of Tokyo

The Earth’s outer core is considered to consist of Fe-Ni alloy and some light elements (O,S, Si, H, C). Hydrogen is the most abundant element in the solar system and one of thepromising candidates existing in the Earth’s core. However, the amount of hydrogendissolved in the core and its process are still unknown because hydrogen cannot be detectedby X-ray and it easily escapes from iron by the release of pressure. Recently, hydrogencontent in fcc-Fe at high pressure and temperature has been determined using in-situ neutron
diffraction measurements at J-PARC [1]. It is suggested the possibility that hydrogen had
preferentially dissolved into iron before any other light elements have dissolved in the very
early stage of Earth’s evolution. It is important to further study the partitioning of the otherlight elements between iron hydride and silicates. In this study, we focused on sulfur andinvestigated its effect on hydrogenation.
As a starting material, the powder mixture of iron (#300 mesh), quartz, Mg(OD)2 (or MgO)
and S (or FeS) was used. The mixing ratio was slightly changed. High-pressure andhigh-temperature quench-experiments were carried out using a 500-ton press at ISSP. A
multi-anvil 6-6 type (MA6-6) assembly was used with an improved anvil assembly optimized
for the neutron experiments [1]. The pressure was increased up to 6 GPa and heated up to750-1650°C. The quenched samples were analyzed by XRD and SEM-EDS. In-situ X-ray
diffraction measurements were also conducted at PF-AR, NE7A and NE5C. The products
were identified under high pressure (4-6 GPa) and high temperature (up to 1050°C).
Liquid Fe-FeS was observed in the quenched sample from >1000°C. Liquid iron and solid
FeS coexisted in the recovered sample from 950°C. This was in good agreement with the
Fe-FeS binary system. In the recovered sample from 750°C, solid FeS and solid Fe coexisted
and the iron contained many small vacant holes of a few microns in diameter, indicating the66

evidence of hydrogen dissolved into iron. From in-situ XRD observations, Fe transformed
from bcc into fcc phase at <500°C. At the same time, dehydration of Mg(OD)2 and formationof FeS were observed. At 850°C, fcc-Fe started to melt and FeS and olivine remained in therecovered samples. The results between in-situ and quench experiments were well consistent.
The cell volume of fcc-Fe in the Fe-silicate-water system was several % larger than that ofpure Fe at the same condition, which suggested the obvious hydrogenation. In thepresentation, hydrogen content in fcc-Fe and FeS will be discussed to more clarify theformation process of iron hydride and FeS and the effect of sulfur on hydrogenation.
[1] R. Iizuka-Oku, T. Yagi, H. Gotou, T. Okuchi, T. Hattori, A. Sano-Furukawa, Nature
Commun. 8, 14096 (2017).

67

P9
Melting experiments of hydrous peridotite under the top of the lower
mantle conditions
A. Nakajima1, T. Sakamaki1, T. Kawazoe2, and A. Suzuki1
1
2

Tohoku University (ayano.nakajima.r1@dc.tohoku.ac.jp)

Bayerisches Geoinstitut (at present, Hiroshima University)

There are various igneous activities in the Earth. On the surface of the Earth, for example,
igneous activities occur in island arcs, mid-ocean ridges, hot spots and petit spots. However,
not only on the surface, but also in the interior, melting phenomena are also suggested (e.g., thetop of the asthenosphere [e.g., Barazangi & Isacks, 1971 JGR]; the bottom of the upper mantle[e.g., Bercovici & Karato, 2003 Nature]). In this study, we focused on the melting of hydrous
peridotite at the top of the lower mantle because seismological observation indicates the low
velocity anomaly [e.g., Schmandt et al., 2014 Science]. The low-velocity region is expected tobe caused by mantle melting due to dehydration decomposition of ringwoodite to bridgmanite
and ferro-periclase with a downward flow. Here, we performed melting experiments ofperidotite with 6.98 wt % H2O at 21-26 GPa and 900-1600 °C. As a starting material, a mixtureof several oxide powders was used. In this study, Fe2O3 was used instead of FeO because thelower mantle is expected to be Fe3+-rich [e.g., McCammon, 1997 Nature]. Recovered samples
from 1300-1600 °C showed partial melting texture, and clearly demonstrate that mantle melting
can be occurred under the experimental conditions. The composition of melt was SiO2- andAl2O3-poor and CaO-rich. Mg/(Mg+Fe) in atomic ratio of the melt (= 0.90) is similar to that ofbridgmanite (= 0.89). This result is completely inconsistent with melting experiment under dry
condition [e.g., Ito & Takahashi, 1987 Nature] but consistent with hydrous melting (Fe2+)[Kawamoto, 2004 PEPI]. In addition to decrease in the melting temperature of mantle rock,hydrogen (water) can affect the melt composition such as the partitioning of FeO and MgO
between crystal and melt. The density and compressibility of the magma were calculated basedon the obtained melt composition. Comparing with seismological model, the melt is lighter thanthat of the lower mantle. This implies that the melt can be ponded at the top of lower mantle
and form the seismological low velocity zone.

68

P10
Al substitution mechanism in anhydrous bridgmanite
as a function of Al content
Masamichi Noda1, Sho Kakizawa1, Toru Inoue1,21

Geodynamics Research Center, Ehime University, Matsuyama, Ehime, Japan.
(m_noda@sci.ehime-u.ac.jp)
2

Department of Earth and Planetary System Science & Hiroshima Institute of Plate

Convergence Region Research (HiPeR), Hiroshima University, Higashi-Hiroshima,
Hiroshima, Japan.
It is considered that two substitution mechanisms, Tschermak substitution and oxygen vacancy
substitution, exist in MgSiO3 bridgmanite for the incorporation of Al in anhydrous condition.
Kubo and Akaogi (2000) has conducted the phase equilibrium experiment in the system
MgSiO3-Al2O3, and established the phase diagram up to 28 GPa. However the carefulobservation in the bridgmanite shows that the chemical compositions are slightly deviated from
Tschermak substitution join. The same tendency can be also observed in the run products by
Irifune et al. (1996). This result indicates that pure Tschermak substitution bridgmanite cannot
be stable even in the MgSiO3-Al2O3 join experiment. However, the previous studies used
powder samples as the starting materials, so the absorbed water may affect the results.
Therefore, we tried to conduct the experiment in the join MgSiO3-Al2O3 in extremely
anhydrous condition to clarify whether the pure Tschermak substitution bridgmanite can bestable or not. In addition, we also examined the stability of oxygen vacancy bridgmanite in theextremely anhydrous condition for the comparison.
The high pressure synthesis experiments were conducted at 28 GPa and 1600-1700℃ for
1hour using a Kawai-type multi-anvil apparatus. Four different Al content samples wereprepared as the starting materials along the ideal substitution line of Tschermak (Al=0.025,
0.05, 0.1, 0.15 mol) and oxygen-vacancy (Al=0.025, 0.05, 0.075, 0.1 mol) substitutions,
respectively (when total cation of 2). The glass rods were used as the starting materials toeliminate the absorbed water on the sample surface. The chemical compositions of thesynthesized bridgmanite could not be measured by EPMA because of small grain size less thansubmicron. Therefore the chemical compositions were estimated from the result of the XRD
pattern by subtracting the amount of the other phases. The estimated chemical compositions of69

Tschermak substitution bridgmanites were consistent with the ideal compositions. On the other
hand, oxygen-vacancy substitution bridgmanite was possible to be existed less than Al=0.025
mol on the basis of total cation of 2. These results show that both Tschermak and oxygenvacancy substitution bridgmanites can exist in low Al content in anhydrous condition.
Therefore the deviation from the Tschermak substitution bridgmanite in the previous studies
should be due to the absorbed water, and the hydration of bridgmanite should be easy to occur
to form hydrous bridgmanite.

70

P11
Structures of basaltic glass under high pressure
by in-situ X-ray and neutron diffraction investigations
Tomonori Ohashi1, Tatsuya Sakamaki2, Takanori Hattori3, Asami Sano-Furukawa3,
Ken-ichi Funakoshi4, and Akio Suzuki2
1

Department of Earth and Planetary Materials Science, Tohoku University(tomonori.ohashi.s8@dc.tohoku.ac.jp)
2
Department of Earth Science, Graduate School of Science, Tohoku University
3
Japan Atomic Energy Agency (JAEA)
4
Comprehensive Research Organization for Science and Society (CROSS)
Structure determinations of basaltic glass have been conducted under high pressure using X-ray
diffraction (XRD) and neutron diffraction (ND) techniques. The total structure factor, S(Q) suggeststhat the position of the first sharp diffraction peak (FSDP) shifts to higher-Q region with increasingpressure. This shift indicates the intermediate-range structure of glass becomes compact. The radial
distribution function, G(r) shows the shrinkage of the average T-T length, and no detectable changeof the average T-O length with increasing pressure (T means tetrahedrally coordinated cations, suchas Si4+ and Al3+). This result implies that drastic shrinkage of network structure involving a decreasein the mean T-O-T angle is the dominant structural evolution under experimental pressure conditions.
Moreover, the second sharp diffraction peak, SSDP (Elliot, 1995) was observed in S(Q) from the ND
experiment. The intensity of SSDP enhanced, while that of FSDP weakened with increasing pressure.
These trends indicate the disordering of the intermediate-range order (Salmon, 1994) and the orderingof the extended-range order (Salmon et al., 2005), respectively. G(r) of ND also indicates no extensionof the T-O bond in the present study. Considering the T-O extension reported in basaltic liquid(Sakamaki et al., 2013), this difference seems to be due to thermal effect. Also, G(r) of ND represents
the Mg-O and Fe-O distances show increase two times at about 2.0 and 6.0–6.9 GPa. These changes
is might be caused by the increase in their coordination numbers due to the polymerization of TO4
tetrahedron. On the other hand, Ca-O and Na-O distances are less sensitive to the pressure. Since the
Mg/Fe-O distance is shorter than the Ca/Na-O distance, the Coulomb force between Mg/Fe and O
ions is larger than that of Ca/Na and O ions. Hence, Mg and Fe cations are easier to combine with
non-bridging or isolated O anions than Ca and Na cations.

71

P12
Density measurement of metals at high temperatures using newly designed
furnace
Hidenori Terasaki1, Asaka Kamiya1
1

Department of Earth and Space Science, Osaka University(terasaki@ess.sci.osaka-u.ac.jp)

Density and thermo-elastic properties at high temperatures and ambient pressure arefundamental information for describing an equation of state. In order to study thethermo-elastic properties of solid and liquid alloys at high temperatures, we developed a hightemperature furnace designed for density and sound velocity measurements. The furnace iscomposed of a heating element of carbon fiber composite, which enables to heat up to 2173
K, and of two windows for optical observation. A buffer rod can descend down to the sample
during heating. The density and sound velocity are measured based on volume measurement
and pulse-echo overlap method, respectively. Here, we report a set-up of the instrument andresults of density of iron and nickel solids at 1073–1773 K. The effect of temperature on thedensity were measured for -Fe (fcc), -Fe (bcc) and -Ni (fcc). The measured densities of
-Fe and -Ni are consistent with previous results within a difference of ~1.5 % and ~0.5 %,respectively.

72

P13
Silicate melt viscosities at high pressure:
Experimental results and its implications
Longjian Xie1, Akira Yoneda1, Geeth Manthilake3, Daisuke Yamazaki1, Yuji Higo2, Yoshinori
Tange2, Nicolas Guignot 4, Denis Andrault3
1. Institute for Planetary Materials, Okayama University(longjianxie@s.okayama-u.ac.jp)
2. Japan Synchrotron Radiation Research Institute
3. The Laboratoire Magmas et Volcans
4. Synchrotron SOLEIL
It is believed that the early Earth experienced several episodes of magma-ocean, with amajor one just after the giant Moon-forming impact. In this framework, the viscosity of thesilicate melts is a key to understand the dynamics of the magma ocean and the recrystallization
processes.
We succeeded to extend the experimental measurements of silicate-melt viscosity up to
about 30 GPa and more than 2500 K, by devising an in-situ falling sphere method coupled withboron-doped diamond heater and ultra-fast cameral (1000 f/s) in the multi-anvil apparatus. We
determined viscosities of molten forsterite, enstatite and diopside from 5 to 30 GPa and attemperatures just above their liquidus; reproducibility of the measurements is within a few
percents. Experimental uncertainties were estimated by Monte Carlo method based on theuncertainties of pressure, temperature, falling sphere velocities and sphere size.
The viscosity of the melt with forsterite composition increases with increasing pressure
along the liquidus, while those of enstatite and diopside melt compositions decrease withincreasing pressure. Melt viscosities of the three compositions are found very low, in the rangeof 0.01 to 0.1 Pa.s, at mantle pressure conditions. The extremely low viscosity implies a shortlife-time for the magma ocean (1-6 thousand years) and, potentially, a fractional crystallization.

73

P14
Melting of Al-rich phase D up to the uppermost lower mantle andtransportation of H2O to the deep Earth
Chaowen Xu11, Toru Inoue21, 2
1

Geodynamics Research Center, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577,
Japan 1 (416755386@qq.com)
2

Department of Earth and Planetary Systems Science & Hiroshima Institute of Plate

Convergence Region Research (HiPeR), Hiroshima University, 1-3-1 Kagamiyama,
Higashi-Hiroshima 739-8526, Japan 2
We have investigated the stability of the Al-rich dense hydrous magnesium silicate phase
D in MgO-Al2O3-SiO2-H2O (MASH) system between14 and 25 GPa at 900-1500 ºC. Al-rich
PhD has a very wide stability region from 900 ºC and 14 GPa to at least 1500 ºC and 25 GPa.
With pressure increasing, Al-rich PhD decomposes to phase Egg and then to δ at above hot
subduction at transition zone. Al-rich PhD is also determined by X-ray diffraction and Raman
spectroscopy at ambient condition. Compared with Al-free PhD, unit-cell volume of Al-rich
PhD is little larger, but the Raman spectra resemble some of Al-free PhD.
The wide stability region determined in this study makes Al-bearing PhD an important
storage site for water in transition zone, suggesting that it can deliver a certain amount ofwater into the lower mantle along hot subduction and even the normal mantle geotherm P-T
condition. Therefore, dehydration of Al-bearing PhD may be responsible for a series ofobserved seismic discontinuities from transition zone to uppermost lower mantle, and evendeep earthquakes in some typical places.

74

P15
A recent application of NPD anvils to EXAFS spectroscopy:
element-selective elastic properties of Fe-Ni and Fe-Pt Invar alloys
N. Ishimatsu1, M. Kousa2, S. Iwasaki2, H. Maruyama1, N. Kawamura3, M. Mizumaki3,
R. Nomura4, S. Kakizawa4, T. Irifune4 and H. Sumiya5
1

Grad. Sch. Sci., Hiroshima Univ. (ishimatsunaoki@hiroshima-u. ac.jp)
2Fac. Sci., Hiroshima Univ.
3
4

5

JASRI/SPring-8

GRC, Ehime Univ.

Advanced Materials R&D Laboratories, Sumitomo Electric Industries

Nano-polycrystalline diamond (NPD) anvils have been applied recently in high pressure
research using X-ray absorption spectroscopy (XAS) [1,2]. This is because thenanometer-sized polycrystallization in NPD anvils enables to obtain glitch-free X-ray
absorption spectra. NPD anvils drastically improve the experimental conditions of XAS,
which has previously used conventional single-crystal diamond (SCD) anvils. Distorted
spectra due to the glitches from the SCD anvils have been an inevitable problem of XAS.

To

demonstrate how NPD anvils are useful when XAS is measured for high pressure research,
we present our recent study of extended X-ray absorption fine structure (EXAFS) for Fe-Ni
and Fe-Pt Invar alloys.
The zero or negative thermal expansion observed in Fe65Ni35 and Fe72Pt28 alloys is wellknown as Invar effect, however, the microscopic origin of the Invar effect is not fully
understood yet.

In this study, we determined element-selective elastic properties of thesealloys by EXAFS spectra, and examined a possible theory of the Invar effect based on the
non-collinear spin structure model [3].

Our analysis using the glitch-free EXAFS spectra

has revealed differences in the element selective elastic properties: Fe bond is morecompressive than Ni bond, and both bulk moduli become hard in the pressure-induced
paramagnetic phase. We also discuss the comparison between the local bond length probed
by EXAFS and the average interatomic distance determined by XRD measurements.
[1] N. Ishimatsu et al., J. Synchrotron Rad. 19, 768-772 (2012).
[2] T. Irifune et al., Nature (London), 421, 599–600 (2003).
[3] M. Schilfgaarde, I. A. Abrikosov, and B. Johansson, Nature (London) 400, 46-49 (1999).

75

P16
Thermal equations of state of MgSiO4H2 phase H
Masayuki Nishi1,2, Jun Tsuchiya1,2, Takehiro Arimoto1, Sho Kakizawa1, Takehiro Kunimoto1,
Yoshinori Tange3, Yuji Higo3, Tetsuo Irifune1,2
1

Geodynamics Research Center, Ehime University (nishi@sci.ehime-u.ac.jp)
2

Earth and Life Science Institute, Tokyo Institute of Technology
3

Japan Synchrotron Radiation Research Institute

Phase H (MgSiO4H2) is the high-pressure form of dense hydrous silicate, which coulddeliver surface water into the lower mantle. Thus, it plays a significant role in the water cyclein the Earth’s interior. Here we have determined the thermal equations of the state of phase H
using in situ X-ray diffraction measurements in conjunction with a multi-anvil apparatus.
Analysis of the data based on the Mie-Grüneisen-Debye model using third-order BurchMurnaghan equations at a reference pressure of 35 GPa yielded the following results: Vref, =49.610.01 (Å3), Kref = 344.64.1 (GPa), Kref’ = 3.050.32, θref = 974146 (K), γref = 1.80.1,
and q = 1.790.55. The compressibility of phase H observed in this study agrees well with thatderived from theoretical calculations in pressure regions where hydrogen bond symmetrization
is predicted. Furthermore, it was recognized that the volume and compressibility between phase
H and -AlOOH were similar.

76

P17
High pressure generation using double-stage diamond anvil technique:problems and equations of state of rhenium
Takeshi Sakai1, Takehiko Yagi2, Tetsuo Irifune1,3, Hirokazu Kadobayashi1, Naohisa Hirao4,
Takehiro Kunimoto1, Hiroaki Ohfuji1, Saori Kawaguchi-Imada4, Yasuo Ohishi4,
Shigehiko Tateno3 and Kei Hirose3,5
1
2

Geodynamics Research Center, Ehime University (sakai@sci.ehime-u.ac.jp)

Geochemical Research Center, Graduate School of Science, The University of Tokyo
3

Earth-Life Science Institute, Tokyo Institute of Technology
45Japan Synchrotron Radiation Research InstituteDepartment of Earth and Planetary Science, Graduate School of Science, The University ofTokyo
We have developed a double stage diamond anvil cell (ds-DAC) technique forreproducible pressure by precisely fabricating 2nd stage anvils using a focused ion beamsystem [1]. We used 2nd stage micro-anvils made of ultra-fine (< 10 nm) nano-polycrystalline
diamond with various shapes and dimensions synthesized from glassy carbon at high pressure
and temperature. The X-ray diffraction patterns from the rhenium sample always showed verybroad peaks due to large pressure gradients in the culet of the micro-anvils. Deconvolution of
the broad 101 diffraction peak results in compression of rhenium to V/V0 = 0.633 for thesmallest d-spacing. The calculated pressure for this minimum volume varies from 430 to 630
GPa, depending on the choice of the equation of state of rhenium. We conclude that the most
likely pressure achieved for the minimum volume of rhenium is in a range of 430–460 GPa
based on a calibration using the platinum pressure scale to 280 GPa and the latter value of 630
GPa is unreasonably high, suggesting that the pressures in an earlier study for the equation ofstate of rhenium would have been significantly overestimated.
Reference[1] T. Sakai et al., 2018. High pressure generation using double-stage diamond anvil
technique: problems and equations of state of rhenium. High Pressure Research, DOI:
10.1080/08957959.2018.1448082. (in press)

77

P18
Multiple sulfur isotopes of Archean oceanic crust and granitoids:
Implication for the anomalous sulfur budget in the mantle
Shinnosuke Aoyama1, Yuichiro Ueno2,3,4
1

Niigata University (aoyama@geo.sc.niigata-u.ac.jp)
2Tokyo Institute of Technology
3

4

Earth-Life Science InstituteJapan Agency for Marine-Earth Science and Technology

Non-mass dependent sulfur isotopes are found in the Archean rocks, probably owing to thelow oxygen concentration in atmosphere at that time (e.g., Farquhar et al., 2000). While mostof the sulfide minerals in Archean sedimentary rocks show positive 33S (and negative 36S)
anomaly, volume, occurrence and anomaly of Archean sulfate deposits, which exhibit negative
33S (and positive 36S) anomaly, is limited. This suggests that the presence of missing Archeansulfur reservoir somewhere. In general, seawater sulfate is fixed in the oceanic crust in theforms of sulfate minerals (e.g., gypsum) during hydrothermal circulation and sulfide minerals(e.g., pyrite) by microbial and inorganic sulfate reduction processes. Therefore, Archean
greenstone is one of the potential candidates compensating for the missing. Another candidate
is Archean granitoid, because Archean granitoid may be generated by slab melting (Martin etal., 2005). However, multiple sulfur isotopes of those igneous rocks are poorly studied. In orderto evaluate the missing sulfur Archean reservoir, we have measured multiple sulfur isotopes ofArchean greenstone exposed in North Pole Dome and Archean granitoid in Mount Edgar
Complex, Pilbara craton, Western Australia.
We newly introduced Degree of Anomaly Contribution (DAC) value. The DAC value wassimply calculated by multiplication of the total volume, average sulfur concentration andaverage sulfur isotopes anomaly in specific material. DAC value of total Archean sulfate
deposits is three magnitudes lower than that of Archean sedimentary sulfide, clarifying themissing. On the other hand, Archean greenstone and granitoid are two magnitudes lower thanthat of Archean sedimentary sulfide. We concluded that the missing is owing to the Archean
oceanic crust subducted into the mantle, which is comparable DAC value assuming similar
subduction rate to modern and similar sulfur concentration and isotopes anomaly to Archean
greenstone. This suggests approximately 8vol.% of the mantle has sulfur isotopes anomaly,
evidenced by sulfur isotopes anomaly in modern OIB (Cabral et al., 2013; Delavault et al.,2016).

78

P19
Crystallization of metasomatic sulfide melt, and recrystallization of
crystalline sulfides constrained by sub-µm-scale investigations for
PGE-bearing sulfide inclusion in Tahitian harzburgite xenolith
Norikatsu Akizawa1, Akira Miyake2, Yohei Igami2, and Tetsu Kogiso3
1

Atmosphere and Ocean Research Institute, The University of Tokyo(akizawa@aori.u-tokyo.ac.jp)
23

Graduate School of Science, Kyoto University

Graduate School of Human and Environmental Studies, Kyoto University

Platinum-group elements (PGEs) in mantle peridotites have been targeted asgeochemical tracers of core–mantle evolution, as they are highly siderophile. Meanwhile,
ascending melts produced by partial melting of the mantle potentially disturb PGE composition
recorded during early Earth’s history. To fully facilitate the PGE as the geochemical tracer ofcore–mantle evolution, mineralogical and geochemical characteristics of metasomatic PGE
host minerals, such as platinum-group minerals (PGMs) and base-metal sulfides (BMSs),
should be properly investigated in metasomatized mantle peridotites.
A sub-micrometer-sized PGE-bearing sulfide inclusion in harzburgite xenolith from
Tahiti island (Society Archipelago) was investigated down to the scale of sub-micrometer,
employing transmission electron microscope with energy dispersive X-ray spectrometer(TEM-EDS). The sulfide inclusion is of metasomatic origin as it is enveloped by carbonaceous
glass (21.2 at% C), and forms inclusion array with other sulfide–carbonaceous glass inclusions
in host clinopyroxene crystal. The Tahitian harzburgite xenolith is, therefore, sufficientappropriate material for elucidating metasomatic behavior of PGEs during carbonatitic
metasomatism in the mantle.
With the mineralogical and geochemical investigations by the TEM-EDS, the sulfide
phases were identified: Fe-rich monosulfide solid solution (MSS), Ni-rich MSS, Fe-richpentlandite, Ni-rich pentlandite, sugakiite, heazlewoodite, chalcopyrite, andCu-Ir-Pt-Rh-thiospinel (cuproiridsite–malanite–cuprorhodsite). Considering empiricalevidence, the first crystallization product from metasomatic sulfide melt was primary MSS
below 1,000 ºC. The primary MSS was recrystallized into the sulfides at low temperatures
down to 500 ºC, below which Ni-rich pentlandite and heazlewoodite can coexist. During the79recrystallization process, most of Cu contained in the primary MSS was absorbed into thesugakiite (6.9 at% Cu). The other Cu-rich sulfides such as chalcopyrite (25.7 at% Cu) andCu-Ir-Pt-Rh-thiospinel (15.1 at% Cu, 26.5 at% Ir, 8.2 at% Pt, and 1.2 at% Rh) were crystallized
directly from evolved Cu-rich sulfide melt after the primary MSS crystallization below 760 ºC.
Hence, the PGE was preferentially partitioned into the evolved Cu-rich sulfide melt. The
preferential partitioning of PGE into the evolved Cu-rich sulfide melt is attributed to highmetal/sulfur ratio (~1.2). The coupling mobility of Ir, Pt, and Rh might function in the case ofmetasomatic activity involving carbonatitic melts in the mantle. Since the primary MSS was
first crystallized at ca. 1,000 ºC through carbonatitic melt involvement, and cooled down to ca.
300–500 ºC before entrainment to the surface via host nephelinite–alkali basalt magmas, thegenesis of the carbonatitic melts were not attributed to magmatism of the host nephelinite–alkali basalt, or rather might be related to plume-derived magmatism.

80

P20
Quantitative isotope imaging methods using secondary ion mass
spectrometry
Shoichi Itoh1
1

Dept. Earth Planet. Sci., Kyoto University (sitoh@kueps.kyoto-u.ac.jp)

Direct ion imaging with secondary ion mass spectrometry (SIMS) has been developed invarious fields, such as Material sciences, Earth and planetary sciences, life sciences. Especially,
quantitative direct ion imaging techniques has recently developed using stigmatic direct ion
imaging methods (e.g., Nittler, 1999; Yurimoto et al., 2003).
In this study, we try to develop the stigmatic secondary ion imaging methods using Cameca
ims-4fE7 SIMS at Kyoto University. The imaging detector system consists of micro-channel
plate (MCP), florescent screen and Cooled 16bit charged-coupled device (CCD) camera (BULN52 Bitrun Co.). This conventional imaging system needs to estimate the calibration
parameter with conversion from ion to electron, and from electron to photon.
In principle, each micro-channel of MCP would be different conversion parameter for electron
converted from secondary ions. Therefore, in order to estimate the qualitative ion imaging using
this system, we need to estimate the error of this conversion parameter in different location ofeach channel.
In this talk, we introduce the estimation of calibration parameter between the light output countrate read by CCD camera and the count rate of secondary ions incident on MCP with different
experimental session. We will estimate the error of each nonlinear exponent parameter for fiveplaces (50 x 50 pixels) and these different parameters cause the error of about 5%. We will
discuss it in detail with quantitative isotope imaging with application of high-pressure
experiments.

81

P21
Behavior of highly siderophile elements in mantle peridotite and its bearing
on the primitive mantle composition
Tetsu Kogiso1 and Norikatsu Akizawa2
1

Graduate School of Human and Environmental Studies, Kyoto University(kogiso@gaia.h.kyoto-u.ac.jp)
2

Atmosphere and Ocean Research Institute, The University of Tokyo

Concentrations of highly siderophile elements (HSE: Ru, Rh, Pd, Re, Os, Ir, Pt and Au) in
the Earth's mantle are controlled by differentiation processes involving metal and sulfide
phases, and therefore give us key insights into the core-mantle differentiation in early Earth's
interior and core-mantle interaction during the Earth's history. The HSE abundances ofhypothetical primitive mantle have been estimated on the basis of HSE concentration data of
fertile lherzolite samples and their covariations with other components like Al2O3 that arethought to indicate the extent of melt extraction. However, primary causes of the covariationsof HSE with other components in mantle peridotites are not well understood yet, indicating
potential large uncertainty in the estimated values of the primitive mantle HSE composition.
Concentrations of HSE in mantle peridotites are controlled by mainly partial melting andmetasomatism, but it is generally difficult to distinguish the effects of these two processes,
because it is not clear how and to what extent HSE are mobilized with silicate melt and aqueouscarbonaceous fluid phases. Recent submicrometer-scale analyses of HSE in natural peridotites
have revealed that HSE are mainly hosted by base-metal sulfides (BMS) and platinum-groupminerals (PGM) in peridotite. High-temperature/high-pressure experimental works have also
revealed that BMS are likely to be molten along a normal mantle geotherm whereas some PGM
phases such as Ir-Os alloy persist in residual solids. These studies anticipate that peridotites thatexperienced large extent of melt extraction would show HSE abundance patterns highly
depleted in "incompatible" HSE like Pt, Pd and Re. However, HSE patterns of natural peridotite
samples do not always show clear correlations with melt extraction indicators. Our
submicrometer-scale petrologic and mineralogical observations of a Tahitian peridotite xenolith
revealed that carbonaceous melt could mobilize incompatible HSE together with some of"compatible" HSE like Ir. It is thus suggested that the behavior of HSE in melting andmetasomatic processes of carbon-bearing peridotite systems should be considered in estimating
the HSE abundances in the primitive mantle.

82

P22
Seismic scatterers in the lower mantle near subduction
Satoshi Kaneshima
Dept. of Earth and Planetary Sciences, Faculty of Science, Kyushu University, Motooka,
Nishi-ku, Fukuoka, JAPANWe investigate the distribution of S-to-P scatterers in the lower mantle beneath subduction
zones, where seismicity extends down to the bottom of the upper mantle and where
downwelling mantle flows probably dominate. We find many strong S-to-P scatterers shallower
than 900 km, at all of the subduction zones around Pacific; Peru to Bolivia, Tonga-Fiji, Vanuatu,
Bismarck, Indonesia, Philippine-Mindanao,Mariana, Izu-Bonin, Japan Sea, Kuril, andOkhotsk. Prominent shallow lower mantle scatterers are found also beneath southern Spain
where the deepest seismicity occurs indicating the subduction of an oceanic lithosphere.
Anomalous later phases in the P coda often arrive along off-great circle paths, and with positive
and nearly zero slowness relative to direct P. Most of them thus cannot be S-to-P conversion at
a globally horizontal discontinuity, but are more adequately interpreted as a scatterer. The delay
times of the S-to-P waves after P waves vary from 20 s to greater than 100 s, and the numberof observations markedly drops above about 50 s. The number of S-to-P scatterers decreases
below about 900 km, although there are certain numbers of deeper S-to-P scatterers. S-to-P
scatterers deeper than 2000 km are not observed. Many of the scatterers are fairy pronounced,
characterized with a much larger amplitudes than the anomalous phases arriving earlier andprobably representing "S660P" waves. This indicates that the elasticity jumps at the scatterer
are larger and occur more abruptly than the post-spinel transformation.

83

P23
Observation of multipathing at the western edge of the Pacific Large LowShear-Velocity Province
Sunil K. Roy1,2, Nozomu Takeuchi1, D. Srinagesh2, M. Ravi Kumar2,3, and Hitoshi
Kawakatsu1
1

Earthquake Research Institute, The University of Tokyo, Tokyo – 1130032, Japan(sunilroy@eri.u-tokyo.ac.jp)
2CSIR-National Geophysical Research Institute, Hyderabad – 500007, India
3
Institute of Seismological Research, Gandhinagar – 382009, India
The waveforms of five deep earthquakes from the Fiji-Tonga subduction zone

recorded by a seismic array in India reveal a secondary pulse just after the Sdiff phase. We
obtained 51 observations for this pulse, in the distance range of 102.0° to 115.1°. The pulse is
sharper on the northern part compared to the southern part of the array, with a azimuthal
variation. The relative arrival time of the second pulse varies from 3.0 to 9.9 s with respect tothe first pulse, with its arrival getting delayed from north to the south along the seismic array,albeit the south array being closer to the earthquake sources. At present, we choose tointerpret the first pulse in terms of the Sdiff phase whose ray path reaches the CMB inside thePacific Large Low-Shear-Velocity Province (LLSVP) and then passes along the vertical sideof the LLSVP. The second pulse is probably the direct S and its diffracted at the top of the
LLSVP. The ray path goes into the LLSVP but bottoms above the CMB. It appears that thesecond wave seems to have stronger amplitudes when the ray bottoms inside the LLSVP and
the sharp vertical boundary lies after the bottoming point. We attempt to model the relative
timing of the first and secondary pulses as well as the absolute arrival times of the first pulse
by incorporating varying thickness and shear wave velocity on either sides of the boundary.
At the time of the presentation, we plan to show our velocity model including azimuthal
variability, to explain the observed data.

84

P24
Examination of local geomagnetic jerks using wavelet analysis
Hisayoshi Shimizu1
1

Earthquake Research Institute, University of Tokyo (shimizu@eri.u-tokyo.ac.jp)

Detection of geomagnetic jerks, sudden variation of secular acceleration of the geomagnetic
field components, has been tried using wavelet analysis by considering that a geomagnetic jerk
is a singularity in time-series. It has been confirmed that geomagnetic jerks occurred globallyaround 1968 and 1978 (Alexandrescu et al., 1995).
Observation of geomagnetic field using satellites allowed identifying local geomagnetic jerksof 2003 and 2007 (e.g. Chulliat et al., 2010), whose signatures are seen strongly in south
Atlantic region in secular acceleration map.

We attempted to analyze the two local

geomagnetic jerks by applying a wavelet analysis on time series of magnetic field at
geomagnetic observatories. The analyzing wavelet is the same as that used by Alexandrescu
et al. (1995).

The two local geomagnetic jerks were successfully identified in wavelet

transform at Mbour (MBO, Senegal), but only the one around 2007 was identified in that at
Chambon la Foret (CLF, France). The global jerks and local jerk around 2003 at MBO showedsimilar regularity. However, the regularity of the local jerk around 2007 at MBO and CLF ishigher than that of the other jerks. These results might imply that the generation mechanism of
the local geomagnetic jerk around 2007 is different from those occurred globally around 1969
and 1978 and locally around 2003.
References:
Alexsandrescu, M. et al., 1995, JGR, 100, 12,557-12,572.
Chulliat, A. et al., 2010, GRL, 37, L0730.

85

P25
The evaluation of the chemical variation in a single granitic rocksuite revealed by grid sampling toward improving the accuracy ofgeoneutrino flux
Kazuki Minami1, Kenta Ueki2, Tsuyoshi Iizuka3, Sanshiro Enomoto4,
and Hiroyuki K.M. Tanaka1
1

Earthquake Research Institute, University of Tokyo (kminami@eri.u-tokyo.ac.jp)
2Japan Agency for Marine-Earth Science and Technology
3
University of Tokyo
4
University of Washington

Geoneutrino, which is emitted in decay of radioactive elements in the earth, was firstly
observed on the KamLAND (Araki et al., 2005). In the past decade, enough data is observedby KamLAND to estimate the U-Th abundances in the core or mantle (The KamLAND
Collaboration, 2011). Geoneutrino enables us to conduct direct estimation of the U-Th
abundances in the earth. In order to obtain the U-Th abundances with high accuracy based on
the geoneutrino data, it is important to estimate the U-Th distributions in the crust near the
KamLAND (Enomoto et al., 2007). Takeuchi et al. (in review) showed U-Th distributions in
the Japanese crust using the new method, which combined the three-dimensional lithology
model inferred from seismic velocity structure and the rock composition model.
The new compositional model enables us to infer the geoneutrino flux from theJapanese crust. However, calculated geoneutrino flux from the Japanese crust has large
uncertainties. One reason of the uncertainty is derived from wide compositional variations of
the U-Th concentrations in one geological unit. These wide compositional variations make it
difficult to estimate the uncertainty of the typical U-Th concentration values in one geologicalunit, which leads to the large uncertainty of geoneutrino flux. If the U-Th distributions in asingle rock suite are known, the large uncertainties of 70% on geoneutrino flux from theJapanese crust can be reduced to 30% at a maximum.
In order to understand the distributions of element concentrations in a single rock suiteor the relationship between sample size and the U-Th concentrations, we sampled granitic
rocks from Inada granite, Kasama city, Ibaraki prefecture. Inada granite is 60Ma (Arakawa
and Takahashi, 1988) medium-grained granite (Takahashi et al., 2011) in the Ryoke Belt
(Ishihara, 1977). We conducted grid sampling in two stone quarries. Precise locations wereobtained by a high-precision GNSS receiver. Several 2-centimeter cube were cut from one
rock sample and each cube was analyzed by XRF analysis. From obtained data, therelationship between the compositional variation and sample size are discussed.

86

P26
The new database for composition of the basement rocks of Japaneseislands with accurate location information for geo-neutrino modeling
Kenta Ueki1, Satoru Haraguchi1, Mika Mohamed1, Shunsuke Horiuchi1 and Hikaru.

Iwamori1,2.

1Japan Agency for Marine-earth Science and Technology(kenta_ueki@jamstec.go.jp).

2

Department of Earth and Planetary Sciences, Tokyo Institute of Technology

With the aim of determining the amount of radioactive elements contained in the earth's
core and mantle with high precision using the world's highest precision geoneutrino dataobtained with KamLAND, Takeuchi et al. (submitted) constructed the 3D lithological model of
the Japanese crust. Based on the lithological map, Takeuchi et al. (submitted) constructed the
3D U-Th distribution map in the Japanese crust, and evaluated flux of the crustal origin
geoneutrino at KamLAND using the 3D U-Th distribution map. Takeuchi et al. (submitted)
showed that information regarding the spatial correlation of U-Th concentration of a rock typeof interest is necessary to obtain the flux of the crustal origin geoneutrino with the higher
precision. Geochemical data with the precise sample locality is necessary to obtain information
on such spatial correlation.
For the purpose, we construct a new dataset for the chemical composition of the basement
rocks of the Japanese crust with the accurate location information.

The database is called"DODAI” and was presented by Haraguchi et al. (submitted). It consists of 1618 data points
including U-Th concentration, the accurate location coordinates, geological information andsample description at present. Concentrations of multiple elements are included in this dataset.
We present U-Th concentrations and its geographical systematics of various rocks in the
database, as well as its variations among various rock types.
Using the dataset, we can analyze spatial correlations of rock compositions between
various rock suites or rock types in various spatial length. Using the information on spatial
correlations, we can obtain quantitative geoneutrino probability density function (pdf) derived
from Japan arc crust.

87

P27
Effects of iron on the lattice thermal conductivity of lower mantle minerals
evaluated by Ab initio anharmonic lattice dynamics simulations
Haruhiko Dekura1, Taku Tsuchiya1,21

Geodynamics Research Center, Ehime University (dekura.haruhiko.mf@ehime-u.ac.jp)
2

Earth-Life Science Institute, Tokyo Institute of Technology

Determination of lattice thermal conductivity (𝜅lat ) of lower mantle (LM) minerals is a key
to understanding the dynamics and evolution of the earth’s deep interior. Some recent
experimental studies have shown that 𝜅lat of MgO and MgSiO3 are substantially reduced by
Fe incorporation (Manthilake et al., 2012; Goncharov et al., 2015; Ohta et al., 2017; Hsieh etal., 2017); Okuda et al. (2017) reported very weak effects on MgSiO3 at lowermost mantle
pressure. So, experimental results are still largely scattered and effects on Fe in 𝜅lat remains
unclear. We recently established an ab initio technique to compute 𝜅lat of Fe-free systems
based on the density-functional theory (DFT) combined with fully solving the phonon
Boltzmann transport equation, which was successfully applied to MgO (Dekura and Tsuchiya,2017). In this study, the technique is extended further to Fe-bearing systems, (Mg,Fe)SiO3
bridgmanite (Brg) and (Mg,Fe)O ferropericlase (FP), combined with the internally consistent
DFT+U technique (Wang et al., 2015). Calculations demonstrate strong solid solution effects
in both Brg and FP. The effects of Fe are found to be caused mainly by the substantialchanges in harmonic properties.

88

P28
The dependence of mantle convection in super-Earths on the planetarymass
Takehiro Miyagoshi1, Masanori Kameyama2, Masaki Ogawa3
1
2
3

JAMSTEC (miyagoshi@jamstec.go.jp)

Ehime University (kameyama@sci.ehime-u.ac.jp)

University of Tokyo (cmaogawa@mail.ecc.u-tokyo.ac.jp)

A large number of super-Earths, which are terrestrial exoplanets with larger mass thanthe Earth’s, have been discovered in this century.

Physics of mantle convection insuper-Earths is one of the most important keys for understanding the habitability of thembecause it controls the surface tectonics and material circulation such as carbon dioxide in theplanets.

In Miyagoshi et al. (2014, 2015), we show that the strong effect of adiabatic

compression, or the large dissipation number in massive (ten times the Earth’s mass)
super-Earths significantly affects thermal convection in their mantle.
In this paper, following these results, we conduct numerical simulations of thermal
convection in the mantle of super-Earths of various mass.

All of the dissipation number, theRayleigh number, the depth-dependence of the thermal expansivity and the reference densitychange in accordance with the planetary mass.

We found that the effects of adiabatic

compression become conspicuous when the planetary mass exceeds about Mp=4 where Mp isthe planetary mass normalized by the Earth’s. The vigor of hot plumes ascending from thecore-mantle boundary becomes significantly weak when the planetary mass exceeds thethreshold. The thickness of the lithosphere becomes about twice from Mp=1 to 10 while themagnitude of flow velocity of convection is almost independent of Mp although the Rayleighnumber increases as Mp increases. These results give important suggestions to discuss theoperation of plate tectonics in super-Earths.

89

P29
Basic features of the kinematic dynamo action associated with top-down
type convection in a rotating spherical shell
Hinami Taniguchi1, Futoshi Takahashi2
1

Kyushu University (hinami.taniguchi.725@s.kyushu-u.ac.jp)
2

Kyushu University

Terrestrial planets which maintain their intrinsic fields have convection
driven by either thermal or compositional, or both kind of buoyancy in the cores.
In case of the Earth, it is believed that compositional convection, which is fed bylight element ejection from the ICB upon inner core growth, is currently dominant
and powers the geodynamo. On the other hand, the geodynamo would be driven
by thermal convection alone in the past mostly fueled by removal of core heatthrough the CMB by mantle convection: namely “top-down” type convection.
Although it is well known that the velocity field powered by these driving forces
and the resultantly generated magnetic fields are different from each other, thereason why they are distinct is not evident. In this study, the basic feature of the
top-down type of dynamo action is investigated by numerically solving akinematic dynamo problem.
We consider an electrically conducting fluid contained in a rotating sphericalshell, in which a stationary flow given by linear stability analysis for top-down
convection exists. Ekman number 𝐸𝑘 is adopted in the range of 2 × 10−4 to 10−3 .
The induction equation is solved by time-marching with an initial axial dipole
field given as a seed. In this results, the critical magnetic Reynolds number 𝑅𝑚 𝑐 shows apositive correlation with 𝐸𝑘 in a regime of relatively low 𝐸𝑘 . A possible interpretation of therelation arises from the fact that the helicity of convection increases with decreasing 𝐸𝑘 .
Then, the enhanced helicity could make it easier to regenerate the poloidal magnetic field.
The efficient generation of the poloidal field might result in decrease of 𝑅𝑚 𝑐 .

90

P30
Normal mode splitting functions for CMB sensitive modes
Naoki Suda
Hiroshima University (nsuda@hiroshima-u.ac.jp)
Observations of long-period free-oscillation spectra provide constraints on the Earth’s
internal structure on scale lengths of a few thousand kilometers. Lateral heterogeneity in the
Earth’s interior has been obtained as ‘splitting function coefficients’ from analyses of normalmode spectra using least-squares inversion. Splitting function coefficients are linearly
dependent upon the Earth’s internal structure. Although most studies on splitting function
coefficients were done in 1990s (e.g. Resovsky & Ritzwoller 1998), accumulation of highquality seismic records of large earthquakes urged new studies (e.g. Deuss et al. 2013). Even in
those new studies, however, obtained are mostly splitting function coefficients for elastic
structure; those for anelastic structure have not yet been fully obtained.
In this study I obtained splitting function coefficients not only for elastic structure but foranelastic structure. The target modes are 1S8, 1S9 and 1S10, which are sensitive to structurenear the core-mantle boundary. I measured apparent complex frequencies of these modes byapplying the Sompi method to records from broadband seismic stations for large earthquakes.
Then splitting function coefficients were obtained by using a non-linear inversion method.
Although I obtained only ‘self-coupling’ coefficients in this study, the effect of full coupling
between multiplets (Deuss & Woodhouse 2001) was included in computations of theoretical
apparent complex frequencies of the target modes in the inversion process.
From intensive synthetic tests, it was confirmed that spherical harmonic degree-2 ofanelastic lateral heterogeneity could be resolved by using the observed data. I obtained
consistent patterns of lateral heterogeneity with degrees 2, 4 and 6 among the three modes forelastic structure. The degree-2 patterns for anelastic structure are well correlated between 1S8
and 1S9. The patterns for elastic structure are correlated with the recent results of Deuss et al.
(2013) and the pattern derived from S40RTS (Ritsema et al. 2011). The patterns for anelastic
structure showed low attenuations beneath Indonesia and central Atlantic regions, which do notcorrelate with the low-velocity anomalies.

91

P31
Bayesian Inference of 3-D Lithology Distribution Using a Seismic
Tomography Model: Effects of Lithology Mixture
Nozomu Takeuchi1, Kenta Ueki2, Tsuyoshi Iizuka1, and Sanshiro Enomoto1,3
1

University of Toyo (takeuchi@eri.u-tokyo.ac.jp)
2Japan Agency for Marine-Earth Science
3

University of Washington

We present a method to infer 3-D lithology distribution using a seismic
tomography model.

We first assume a prior probability map of lithology, 𝑃(𝒙) (𝑖),the probability that rock at location 𝒙 is type 𝑖.
to take local lithological features into account.

This prior probability allows us

In this study, to apply our method

to calculate the flux at Kamioka, Japan, we use the lithology of the Hidaka
metamorphic belt in Hokkaido, northern Japan, as the prior. The crustal sectionof the Hidaka metamorphic belt is expected to represent a typical example ofcrustal lithology in the Japan arc system.
We then update the probability using Bayes theorem. We refer to a seismic
tomography model to get the P velocity data at 𝒙, 𝑣 𝑜𝑏𝑠 , and compute the posterior
probability map 𝑃(𝒙) (𝑖|𝑣 𝑜𝑏𝑠 ), which constrains 𝑖 to those rock types for which the
P velocity is likely to be around 𝑣 𝑜𝑏𝑠(𝒙) .

Note that, in contrast to previous

studies,models

we

did

not

use

seismologicalwithsomewhatsegmentations of, for example, upper, middle and lower crusts.

ad-hocThe use of thetomography model obtained in a reproducible manner allows us to evaluate theerrors of the seismological data straightforwardly.
probability

map,

𝑃(𝒙) (𝑖|𝑣 𝑜𝑏𝑠 ) ,wedevelop

To compute the posterioranappropriate

Bayesianvelocity-lithology translator. We refer to laboratory experiments by Christensen
and Mooney (1995) for P velocities of various rock types in the crust. We also
develop an appropriate method to take lithology mixture into account and discuss
the differences in the obtained models with and without that effect.

92