Research plan at Institute for Study of the Earth’s
Interior (ISEI), Okayama University, Japan

Research Theme: Effect of temperature, pressure, Fe content and oxygen
fugacity

ontheelectricalconductivityoforthopyroxene

Collaborative supervisor: Associate Prof. Takashi Yoshino (ISEI)

Applicant: Baohua Zhang (Chinese Academy of Sciences)Affiliation: Institute of Geochemistry, Chinese Academy of Sciences,Guiyang, Guizhou 550081, P. R. China.
E-mail:zhangbaohua@vip.gyig.ac.cn

2016.1.22

1ContentCV------------------------------------------------------------------3Research report---------------------------------------------------5Research plan-----------------------------------------------------72

CURRICULUM VITAE
Baohua Zhang
Gender: Male
Date of birth: Sep. 18, 1978
Place of birth: ShaanXi Province, P. R. China
Position:
Professor
Affiliation: Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, Guizhou
550081, P. R. China.
E-mail: zhangbaohua@vip.gyig.ac.cn
Phone:
86-851-85895786 (O)SpecialityGeophysics

Research Interest
Electrical properties of minerals; Shear deformation; Diffusion

Education
Sep., 2004 – Dec., 2009 : Ph.D., University of Science and Technology of China (USTC).
Sep., 1998 – July, 2002 : B.S., Department of Physics, Northwest University

Professional Record
July, 2002 –Dec., 2007 : Assistant, Hefei University of Technology, China
Jan., 2008 – Mar., 2011: Lecturer, Hefei University of Technology, China
Apr., 2011 – June, 2014: Postdoc, Institute for Study of the Earth’s Interior (ISEI), Okayama
University, Japan
July, 2014 – : Professor, “1000Plan Program for Young Talents” of Chinese government
Institute of Geochemistry, Chinese Academy of Sciences, P. R. ChinaResearch Project
1. Jan., 2015—Dec., 2017: A thermodynamic approach for calculating the diffusion
coefficients in mantle minerals and rocks and its applications in geoscience, NaturalSciences Foundation of China (NSFC), No. 41303048.
( Principal )2. Jan., 2016—Dec., 2018: 1000Plan Program for Young Talents, Department ofOrganization of the People's Republic of China.
( Principal )Honors and Awards
2014
2008

Excellent Doctoral Dissertation Award of Anhui ProvinceZhuLiYueHua Award for Graduate Student of Chinese Academy of Sciences (CAS)3

List of Publications (selected)
1. Zhang B.H., Shan S.M., Wu X.P., 2016. Modeling H, Na, and K diffusion inplagioclase feldspar by relating point defect parameters to bulk properties, Physics
and Chemistry of Minerals, in press, doi: 10.1007/s00269-015-0782-5.
2. Zhang B.H., Shan S.M., 2015. Application of the cBΩ model to the calculation ofdiffusion parameters of Si in silicates, Geochemistry Geophysics Geosystems 16,705-718. doi:10.1002/2014GC005551.
3. Zhang B.H., Shan S.M., 2015. Thermodynamic calculations of Fe–Mg
interdiffusion in (Mg,Fe)2SiO4 polymorphs and perovskite, Journal of Applied
Physics 117(5), 054906.
4. Zhang B.H., Yoshino T., Yamazaki D., Manthilake G., Katsura T., 2014. Electricalconductivity anisotropy of partially molten peridotite under shear deformation,
Earth and Planetary Science Letters 405, 98-109.
5. Zhang B.H., 2014. Calculation of self-diffusion coefficients in iron, AIP Advances
4(1), 017128.
6. Zhang B.H., Wu X.P., 2013. Diffusion of aluminum in MgO: A thermodynamic
approach, Chinese Physics B 22(5), 056601.
7. Zhang B.H., Yoshino T., Wu X.P., Matsuzaki T., Shan S.M., Katsura T., 2012.
Electrical conductivity of enstatite as a function of water content: Implications forthe electrical structure in the upper mantle, Earth and Planetary Science Letters357-358, 11-20.
8. Zhang B.H., Wu X.P., 2012. Calculation of self-diffusion coefficients in diamond,Applied Physics Letters 100(5), 051901.
9. Zhang B.H., Wu X.P., Zhou R.L., 2011. Calculation of oxygen self-diffusion
coefficients in Mg2SiO4 polymorphs and MgSiO3 perovskite based on thecompensation law, Solid State Ionics 186(1), 20-28.
10. Zhang B.H., Wu X.P., 2011. Prediction of self-diffusion and heterodiffusion
coefficients in zircon, Journal of Asian Earth Sciences 42(1-2), 134-141.
11. Zhang B.H., Wu X.P., Xu J.S., Katsura T., Yoshino T., 2010. Electricalconductivity of enstatite up to 20 GPa and 1600 K, Chinese Journal ofGeophysics 53(3), 760-764
12. Zhang B.H., Wu X.P., Xu J.S., Zhou R.L., 2010. Application of the cBΩ modelfor the calculation of oxygen self-diffusion coefficients in minerals, Journal ofApplied Physics 108(5), 053505.

4

Research report for Zhang Baohua in 2015
In 2015, my research is mainly concentrated on understanding the highly
anisotropic conductivity revealed by magnetotelluric (MT) investigations in the upper
mantle, and predicting the diffusion coefficient of mantle minerals by means of athermodynamic model. Thus the details of these two contents are described asfollowing:

I. Electrical conductivity measurement of partially molten peridotite under shear
deformation
Partial melting hypothesis is considered as the most reasonable interpretation ona high-conductivity layer (HCL) with high anisotropy characterized by higher
conductivity in the direction parallel to plate motion revealed by ocean floor
magnetotelluric (MT) investigations in the oceanic upper mantle (Evans et al., 2005;
Naif et al., 2013). In order to verify this issue, I have conducted electrical conductivity
measurement of partially molten peridotite under shear deformation during the periodof my postdoctoral fellow in Misasa (from April 1st of 2011 to April 1st of 2014). Our
experimental results demonstrated that horizontal electrical conductivity anisotropy
revealed by magnetotelluric surveys in the oceanic asthenosphere can be well
explained by the realignment of partial melt induced by shear stress (Zhang et al.,2014).
Although recent experimental findings are exciting and important, however,some problems in our previous project and others are still needed to be clarified
further. For instance, the effect of melt fraction on the electrical conductivity of partial
molten peridotite is unclear. The minimum volume fraction for melt to produce theanisotropic conductivity in the upper mantle still remains poorly constrained. Inaddition, melt distribution also would vary with melt fraction under shear deformation.
To solve these difficulties, I visited ISEI again (from August 2st of 2015 to September
15st of 2015), and performed in situ 3D electrical conductivity of partially molten
KLB-1 peridotite during deformation in simple shear at 1 GPa in a DIA typeapparatus. The conductivity measurements were performed simultaneously in two
directions of three principal axes: parallel and normal to the shear direction on theshear plane, and perpendicular to the shear plane, by using impedance spectroscopy attemperature ranges of 1483-1548 K in a frequency range from 0.1 Hz to 1 MHz. Our5

results show that the melt fraction, the absolute conductivity values, and the degree ofelectrical anisotropy of partially molten KLB-1 peridotite systematically increases
with temperature. Microstructural observations of the recovered samples suggest thatthe development of conductivity anisotropy was caused by the realignment of partial
melt parallel to the shear direction. Our experiments were very successful and thecorresponding papers are now in preparation or in review:(1)Zhang B.H., Yoshino T., 2016. New constrains on the melt fraction in theoceanic upper mantle inferred from in-situ 3D conductivity measurements,
Manuscript in preparation.
(2)Zhang B.H., Yoshino T., 2016. Effect of graphite on the electricalconductivity of the lithospheric mantle. Physics of the Earth and Planetary Interiors,
in review.
II. Thermodynamic calculation of diffusion coefficient in minerals
On the basis of a thermodynamical model, termed the cBΩ model, we develop anew approach to predict the various elements diffusion coefficients in minerals. Ourresults show that the absolute Si, Fe-Mg, H, Na, K, Cl diffusion rates derived from thecBΩ model are in agreement with experimental data in a variety of rock-forming
minerals including (Mg,Fe)2SiO4 polymorphs, perovskite, feldspar and NaCl.
(1) Zhang B.H., Shan S.M., 2015. Application of the cBΩ model to thecalculation of diffusion parameters of Si in silicates. Geochemistry Geophysics
Geosystems, 16(3), 705-718, doi:10.1002/2014GC005551(2)Zhang B.H., Shan S.M., 2015. Thermodynamic calculations of Fe–Mg
interdiffusion in (Mg,Fe)2SiO4 polymorphs and perovskite. Journal of Applied
Physics, 117(5), 054906, doi: 10.1063/1.4907576(3)Zhang B.H., Shan S.M., Wu X.P., 2016. Modeling H, Na, and K diffusion inplagioclase feldspar by relating point defect parameters to bulk properties. Physics
and Chemistry of Minerals, in press, doi: 10.1007/s00269-015-0782-5(4)Zhang B.H., Li C.B., Shan S.M., 2016. Thermodynamic calculation ofself-diffusion in sodium chloride. Physics and Chemistry of Minerals, accepted

6Research plan at Institute for Study of the Earth’s Interior(ISEI), Okayama University, Japan
1. Research Theme:
Effect of temperature, pressure, Fe content and oxygen fugacity on the electricalconductivity of orthopyroxene
2. Background for Research Theme:
Electrical conductivity is a physical parameter that can be characterized, alongwith electromagnetic surveys and seismic wave velocities, from measurements at theEarth’s surface. A comparison of geophysical models with mineral properties would
provide important constraints for mineralogical and compositional models of theEarth’s mantle, as well as that of other planets. Therefore, in situ laboratory
measurements of the electrical conductivity of the major mantle phases under HP-HTand controlled thermodynamic conditions are very important for our construction of
the conductivity-depth profile and interpretation of the recent electrical anisotropy
observations by MT in the upper mantle (Evans et al., 2005; Naif et al., 2013).
Electrical properties of minerals and rocks are highly sensitive to many factors
such as temperature, pressure, oxygen fugacity (fO2), Fe content, water (H2O) content,
electronic spin-state transitions, melting, and so on. To evaluate the influence of thesefactors on the electrical conductivity quantitatively, careful laboratory investigationand novel experimental design are required to distinguish each of them. Althoughtemperature dependence of the electrical conductivity of mantle minerals has been
determined precisely, pressure dependence has not been studied in detail. Due to wide
pressure range for stability of the major silicate minerals, such as olivine, pyroxene,garnet, bridgmanite, knowledge of the pressure dependence of the electricalconductivity of mantle minerals is also important for the construction of a reference
conductivity-depth profile. The electrical conduction mechanisms of the mainiron-bearing mantle minerals are considered to be hopping of small polarons
associated with the charge transfer between Fe2+ and Fe3+. Many workers (Xu et al.,
2000; Yoshino, 2010) have shown that hopping conduction is characterized by a low
activation energy (1–1.8 eV), but their activation volumes have opposite signs. Forexample, Yoshino et al. (2012) observed a negative activation volume (-0.3~-0.7cm3/mol) for olivine, whereas a positive one (+0.6 cm3/mol) was reported by Xu et al.
7(2000) and Dai et al. (2010). Thus, at present we have no reasonable consensus for thepressure dependence of the electrical conductivity of ferromagnesian minerals. In
order to obtain a better understanding of the electrical conductivity of ferromagnesianminerals, we need further studies on the pressure dependence of the electricalconductivity, especially for orthopyroxene.
Iron is the most abundant transition metal in the Earth. The upper mantle, which
is mainly composed of (Fe,Mg)2SiO4 olivine and (Fe,Mg,Al)2(Si,Al)O3 pyroxene,constitutes more than 80% of the Earth upper mantle’s volume and plays an importantrole in the evolution and dynamics of the mantle. Generally, the electricalconductivity is depended on the number of charge carriers and its mobility. In the caseof Fe-bearing silicate minerals, the density of charge carriers is related to Fe content(i.e., Fe3+/∑Fe). As the concentration of Fe3+/∑Fe is controlled by oxygen fugacity,
consequently, the conductivity of iron-bearing silicate minerals should be strongly
controlled by the total Fe content and Fe3+/∑Fe (i.e., oxygen fugacity) (Yoshino et al.,2012).
Oxygen fugacity, fO2, is another important factor affecting the experimental
results of electrical conductivity measurements of minerals and rocks that containvalence variable elements. Oxygen fugacity not only drives redox reactions, element
partitioning, and structural phase transitions, but also controls certain transport
electrical properties and rheological properties, especially in minerals such as silicatesand oxides in which oxygen vacancies play a major role in these processes. Currently,
the ability to adjust the oxygen fugacity in multi-anvil apparatuses has become ahotspot of high pressure research. For most traditional conductivity experiments, it isoften difficult to control fO2 during high-pressure processes due to a number ofprohibitive restrictions, including the selected buffer pairs have a limited adjustment
range of oxygen fugacity and the difficulty of implementing control in an actual
high-pressure apparatus. Nevertheless, little is known about the relationship between
the electrical conductivity of orthopyroxene and oxygen fugacity at high pressure, as
well as Fe content.
Orthopyroxene is the second abundant constituent mineral of the shallow upper
mantle, which constitutes about 20-40% of the minerals in the upper mantle. Thus,
knowledge of how its electrical properties vary as a function of pressure, temperature,oxygen fugacity and chemical composition can be important in interpreting themantle’s electrical conductivity profile. However, electrical conductivities of the8orthopyroxene system have not been studied as thoroughly as the olivine system.
Most previous measurements of the electrical conductivity of orthopyroxene only
considered the effect of chemical composition (Seifert et al., 1982) and water content(Dai and Karato, 2009; Yang et al., 2012, Zhang et al., 2012). Until now, nosystematic data have been reported on the conductivity of orthopyroxene as a functionof temperature, pressure, Fe content and oxygen fugacity. Such precise conductivity
data obtained in the laboratory are essential for interpreting the field results obtainedby geomagnetic depth sounding and magnetotelluric surveys, and also can provide
constraints

onthemineralogy,chemicalcomposition,

thermalstructure,

thermodynamic state, water distribution, and partial melting of the Earth’s interior.
In this study, we will measure the electrical conductivity of anhydrous
orthopyroxene with various iron contents (XFe=0, 0.1, 0.2, 0.3, 0.5, 0.7, 1.0) over awide range of pressure (P), and temperature (T) and oxygen fugacity (fO2) covering
the stability field of orthopyroxene. Our results are important to understand theconduction mechanism and the origin of the mantle high conductivity layer, and also
to provide some constraints on temperature, oxygen fugacity, chemistry and theconductivity-depth profile in the Earth’s upper mantle.

My research plan is asfollows.
3. Proposed Plan:1) Synthesis of anhydrous orthopyroxene with different Fe content (XFe=0, 0.1,0.2, 0.3, 0.5, 0.7, 1.0)
2) In situ conductivity measurements under high pressure and high temperature(a) Impedance measurements on the orthopyroxene as a function of T and P;(b) Impedance measurements on the orthopyroxene as a function of fO2;
3) Post-experimental analysis
The orthopyroxene samples is analyzed using backscatter electron imaging,
X-ray diffraction, electron microprobe analyzer (EPMA) and FT-IR before andafter the conductivity measurements.
4. Expected Results and Impacts:
In situ laboratory measurements of the electrical conductivity of orthopyroxene
as a function of temperature, pressure, Fe content and oxygen fugacity in conjunction
with conductivity depth profiles of the mantle derived from electromagnetic data canprovide important constraints on mineralogy, chemistry, thermal structure,9thermodynamic state, water distribution, redox state, and partial melting of the Earth’sinterior. Therefore, the present project must not be important only for the electricalconductivity world but must be significant for all the solid geophysics.
5.

A proposed research plan that includes what type of facilities is required:High pressure facilities:
KAWAI-type multi-anvil high-pressure apparatus; Piston cylinder apparatus
Measurement and analysis facilities:
Solartron 1260 impedance/Gain-Phase Analyzer, Solartron 1296 interface;
Optical microscopy; Scanning electron microscopy (SEM); Infrared absorption
spectroscopy (FT-IR); X-ray diffraction; electron microprobe analyses (EPMA); andso on.

6.

Desired stay period

May to June 2016.

Reference:
Dai L.D., Karato S., 2009. Electrical conductivity of orthopyroxene: implications forthe water content of the asthenosphere. Proc. Jpn. Acad. Ser. B 85, 466–475.
Dai L.D., Li H.P., Liu C., Hu H.Y., Shan S.M., 2010. The electrical conductivity ofdry polycrystalline olivine compacts at high temperatures and pressures. Mineral.
Mag. 74, 849–857.
Evans R.L., Hirth G., Baba K., Forsyth D., Chave A., Mackie R., 2005. Geophysicalevidence from the MELT area for compositional controls on oceanic plates.
Nature 437, 249–252.
Naif S., Key K., Constable S., Evans R.L., 2013. Melt-rich channel observed at thelithosphere–asthenosphere boundary. Nature 495, 356–359.
Seifert K.F., Will G., Voigt R., 1982. Electrical conductivity measurements onsynthetic pyroxenes MgSiO3-FeSiO3 at high pressures and temperatures under
defined thermodynamic conditions, in High-pressure Researches in Geoscience,edited by W. Schreyer, pp. 419–432, Schweizerbart’sche, Stuttgart, Germany.
Xu Y.S., Shankland T.J., Duba A.G., 2000. Pressure effect on electrical conductivity ofmantle olivine. Phys. Earth Planet. Int. 118, 149–161.
Yang X.Z., Keppler H., McCammon C., Ni H.W., 2012. Electrical conductivity oforthopyroxene and plagioclase in the lower crust. Contrib. Mineral. Petrol. 163,33–48.
Yoshino T., 2010. Laboratory electrical conductivity measurement of mantle minerals.
Surv. Geophys. 31, 163–206.
Yoshino T., Shimojuku A., Shan S.M., Guo X.Z., Yamazaki D., Ito E., Higo Y.,
Funakoshi K., 2012. Effect of temperature, pressure and iron content on theelectrical conductivity of olivine and its high-pressure polymorphs. J. Geophys.
10Res. 117, B08205.
Zhang B.H., Yoshino T., Wu X.P., Matsuzaki T., Shan S.M., Katsura T., 2012.
Electrical conductivity of enstatite as a function of water content: Implications
for the electrical structure in the upper mantle. Earth Planet. Sci. Lett. 357–358,
11–20.

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