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Laboratory Electrical Conductivity Measurement of Mantle Minerals

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Abstract

Electrical conductivity structures of the Earth’s mantle estimated from the magnetotelluric and geomagnetic deep sounding methods generally show increase of conductivity from 10−4–10−2 to 100 S/m with increasing depth to the top of the lower mantle. Although conductivity does not vary significantly in the lower mantle, the possible existence of a highly conductive layer has been proposed at the base of the lower mantle from geophysical modeling. The electrical properties of mantle rocks are controlled by thermodynamic parameters such as pressure, temperature and chemistry of the main constituent minerals. Laboratory electrical conductivity measurements of mantle minerals have been conducted under high pressure and high temperature conditions using solid medium high-pressure apparatus. To distinguish several charge transport mechanisms in mantle minerals, it is necessary to measure the electrical conductivity in a wider temperature range. Although the correspondence of data has not been yet established between each laboratory, an outline tendency of electrical conductivity of the mantle minerals is almost the same. Most of mineral phases forming the Earth’s mantle exhibit semiconductive behavior. Dominant conduction mechanism is small polaron conduction (electron hole hopping between ferrous and ferric iron), if these minerals contain iron. The phase transition olivine to high-pressure phases enhances the conductivity due to structural changes. As a result, electrical conductivity increases in order of olivine, wadsleyite and ringwoodite along the adiabat geotherm. The phase transition to post-spinel at the 660 km discontinuity further can enhance the conductivity. In the lower mantle, the conductivity once might decrease in the middle of the lower mantle due to the iron spin transition and then abruptly increase at the condition of the D″ layer. The impurities in the mantle minerals strongly control the formation, number and mobility of charge carriers. Hydrogen in nominally anhydrous minerals such as olivine and high-pressure polymorphs can enhance the conductivity by the proton conduction. However, proton conduction has lower activation enthalpy compared with small polaron conduction, a contribution of proton conduction becomes smaller at high temperatures, corresponding to the mantle condition. Rather high iron content in mantle minerals largely enhances the conductivity of the mantle. This review focuses on a compilation of fairly new advances in experimental laboratory work together with their explanation.

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References

  • Badro J et al (2003) Iron partitioning in Earth’s mantle: toward a deep lower mantle discontinuity. Science 300:789–791

    Google Scholar 

  • Bolfan-Cassanova N, Keppler H, Rubie DC (2000) Water partitioning between nominally anhydrous minerals in the MgO–SiO2–H2O system up to 24 GPa: implications for the distribution of water in the Earth’s mantle. Earth Planet Sci Lett 182:209–221

    Google Scholar 

  • Brodholt JP (2000) Pressure-induced changes in the compression mechanism of aluminous perovskite in the earth’s mantle. Nature 407:620–622

    Google Scholar 

  • Bullen KE (1937) Note on the density and pressure inside the Earth. J R Soc NZ 67:122–124

    Google Scholar 

  • Constable S (2006) SEO3: a new model of olivine electrical conductivity. Geophys J Int 166:435–437

    Google Scholar 

  • Constable S, Constable C (2004) Observing geomagnetic induction in magnetic satellite measurements and associated implications for mantle conductivity. Geochem Geophys Geosys 5:Q01006

    Google Scholar 

  • Constable SC, Shankland TJ, Duba AG (1992) The electrical conductivity of an isotropic olivine mantle. J Geophys Res 97:3397–3404

    Google Scholar 

  • Debye PP, Conwell EM (1954) Electrical properties of N-type germanium. Phys Rev 93:693–706

    Google Scholar 

  • Dobson DP (2003) Oxygen ionic conduction in MgSiO3 perovskite. Phys Earth Planet Inter 139:55–64

    Google Scholar 

  • Dobson DP, Brodholt JP (2000) The electrical conductivity of the lower mantle phase magnesiowüstite at high temperatures and pressures. J Geophys Res 105:531–538

    Google Scholar 

  • Dobson DP, Richmond NC, Brodholt JP (1997) A high temperature electrical conduction mechanism in the lower mantle phase (Mg, Fe)1−X O. Science 275:1779–1781

    Google Scholar 

  • Du Frane WL, Roberts JJ, Toffelmier DA, Tyburczy JA (2005) Anisotropy of electrical conductivity in dry olivine. Geophys Res Lett 32:L24315

    Google Scholar 

  • Duba AG, von der Gönna (1994) Comment on change of electrical conductivity of olivine associated with the olivine-spinel transition. Phys Earth Planet Int 82:75–77

    Google Scholar 

  • Evans RL, Hirth G, Baba K, Forsyth D, Chave A, Mackie R (2005) Geophysical evidence from the MELT area for compositional controls on oceanic plates. Nature 437:249–252

    Google Scholar 

  • Fei Y, Mao HK (1994) In situ determination of the NiAs phase of FeO at high pressure and high temperature. Science 266:1678–1680

    Google Scholar 

  • Gaillard F, Malki M, Iacono-Marziano G, Pichavant M, Scaillet B (2008) Carbonatite melts and electrical conductivity in the asthenosphere. Science 322:1363–1365

    Google Scholar 

  • Glover PWJ, Vine FJ (1992) Electrical conductivity of carbon bearing granulite at raised temperatures and pressures. Nature: 360:723–726

    Google Scholar 

  • Glover PWJ, Ross RG, Jolly H (1990) The measurement of saturated rock electrical conductivity at lower crustal temperatures and high pressures. High Press Res 5:705–707

    Google Scholar 

  • Goddat A, Peyronneau J, Poirier JP (1999) Dependence on pressure of conduction by hopping of small polarons in minerals mantle. Phys Chem Mineral 27:81–87

    Google Scholar 

  • Hiraga T, Anderson IM, Kohlstedt DL (2004) Grain boundaries as a reservoir of incompatible elements in the Earth’s mantle. Nature 427:699–704

    Google Scholar 

  • Hirose K, Fei Y, Ma Y, Mao H–K (1999) The fate of subducted basaltic crust in the Earth’s lower mantle. Nature 397:53–56

    Google Scholar 

  • Hirsch LM, Shankland TJ (1993) Quantitative olivine-defect chemical model: insights on electrical conduction, diffusion, and the role of Fe content. Geophys J Int 114:21–35

    Google Scholar 

  • Hirsch LM, Shankland TJ, Duba AG (1993) Electrical conduction and polaron mobility in Fe-bearing olivine. Geophys J Int 114:36–44

    Google Scholar 

  • Holme R (1998) Electromagnetic core–mantle coupling, I, explaining decadal changes in the length of day. Geophys J Int 132:167–180

    Google Scholar 

  • Huang X, Xu Y, Karato S (2005) Water content in the transition zone from electrical conductivity of wadsleyite and ringwoodite. Nature 434:746–749

    Google Scholar 

  • Irifune T, Ringwood AE (1993) Phase transformations in subducted oceanic crust and buoyancy relationships at depths of 600–800 km in the mantle. Earth Planet Sci Lett 117:101–110

    Google Scholar 

  • Irifune T, Sekine T, Ringwood AE, Hibberson WO (1986) The eclogite-garnetite transformation at high pressure and some geophysical implications. Earth Planet Sci Lett 77:245–256

    Google Scholar 

  • Ito E, Takahashi E (1989) Post-spinel transformations in the system Mg2SiO4–Fe2SiO4 and some geophysical implications. J Geophys Res 94:10637–10646

    Google Scholar 

  • Karato S (1990) The role of hydrogen in the electrical conductivity of the upper mantle. Nature 347:272–273

    Google Scholar 

  • Karato S, Dai L (2009) Comments on “Electrical conductivity of wadsleyite as a function of temperature and water content” by Manthilake et al. Phys Earth Planet Int 174:19–21

    Google Scholar 

  • Katsura T, Ito E (1996) Determination of Fe–Mg partitioning between perovskite and magnesiowüstite. Geophys Res Lett 23:2005–2008

    Google Scholar 

  • Katsura T, Sato K, Ito E (1998) Electrical conductivity of silicate perovskite at lower-mantle conditions. Nature 395:493–495

    Google Scholar 

  • Katsura T, Yokoshi S, Kawabe K, Shatskiy A, Okube M, Fukui H, Ito E, Nozawa A, Funakoshi K (2007) Pressure dependence of electrical conductivity of (Mg, Fe)SiO3 ilmenite. Phys Chem Mineral 34:249–255

    Google Scholar 

  • Kawai N (1966) A static high pressure apparatus with tapered multi-piston formed a sphere I. Proc Jpn Acad 42:285–288

    Google Scholar 

  • Kawai N, Endo S (1970) The generation of ultrahigh hydrostatic pressure by a split sphere apparatus. Rev Sci Instrum 41:425–428

    Google Scholar 

  • Keppler H, Kantor I, Dubrovinsky LS (2007) Optical absorption spectra of ferropericlase to 84 GPa. Am Mineral 92:433–436

    Google Scholar 

  • Kittel C (1996) Introduction to solid state physics, 7th edn. Wiley, New York 673 pp

    Google Scholar 

  • Kohlstedt DL, Mackwell SJ (1998) Diffusion of hydrogen and intrinsic point defects in olivine. Z Phys Chem 207:147–162

    Google Scholar 

  • Kohlstedt DL, Keppler H, Rubie DC (1996) Solubility of water in the α, β and γ phases of (Mg, Fe)2SiO4. Contrib Mineral Petrol 123:345–357

    Google Scholar 

  • Kondo T, Sawamoto H, Yoneda A, Kato T, Matsumoto A, Yagi T (1989) Ultrahigh-pressure and high temperature generation by use of the MA8 system with sintered diamond anvils. High Temp High Press 25:105–112

    Google Scholar 

  • Kuvshinov A, Olsen N (2006) A global model of mantle conductivity derived from 5 years of CHAMP, Ørsted, and SAC-C magnetic data. Geophys Res Lett 33:L18301

    Google Scholar 

  • Kuvshinov A, Utada H, Avdeev D, Koyama T (2005) 3-D modelling and analysis of Dst C-responses in the North Pacific Ocean region, revisited. Geophys J Int 160:505–526

    Google Scholar 

  • Lauterbach S, McCammon CA, van Aken P, Langenhorst F, Seifert F (2000) Mössbauer and ELNES spectroscopy of (Mg, Fe)(Si, Al)O3 perovskite: a highly oxidised component of the lower mantle. Contrib Mineral Petrol 138:17–26

    Google Scholar 

  • Lay T, Helmberger DV (1983) A lower mantle S-wave triplication and the shear velocity structure of D”. Geophys J R Astron Soc 75:799–838

    Google Scholar 

  • Lay T, Williams Q, Garnero EJ (1998) The core-mantle boundary layer and deep mantle dynamics. Nature 392:461–468

    Google Scholar 

  • Li X, Jeanloz R (1990a) Laboratory studies of the electrical conductivity of silicate perovskite at high pressures and temperatures. J Geophys Res 95:5067–5078

    Google Scholar 

  • Li X, Jeanloz R (1990b) High pressure–temperature electrical conductivity of magnesiowüstite as a function of iron oxide concentration. J Geophys Res 95:21609–21612

    Google Scholar 

  • Lin J-F et al (2005) Spin transition of iron in magnesiowüstite in Earth’s lower mantle. Nature 436:377–380

    Google Scholar 

  • Lin J-F, Weir ST, Jackson DD, Evans WJ, Vohra YK, Qiu W, Yoo C-S (2007a) Electrical conductivity of the lower-mantle ferropericlase across the electronic spin transition. Geophys Res Lett 34:L16305. doi:10.1029/2007GL030523

    Google Scholar 

  • Lin J-F, Vanko G, Jacobsen SD, Iota V, Strurzhkin VV, Prakapenka VB, Kuznetsov A, Yoo C-S (2007b) Spin transition zone in Earth’s lower mantle. Science 317:1740–1743

    Google Scholar 

  • Lizarralde D, Chave AD, Hirth G, Schultz A (1995) A Northern Pacific mantle conductivity profile from long-period magnetotelluric sounding using Hawaii to California submarine cable data. J Geophys Res 100:17837–17854

    Google Scholar 

  • Mackwell SJ, Kohlstedt DL (1990) Diffusion of hydrogen in olivine: implications for water in mantle. J Geophys Res 95:5079–5088

    Google Scholar 

  • Manthilake G, Matsuzaki T, Yoshino T, Yamashita S, Ito E, Katsura T (2009) Electrical conductivity of wadsleyite as a function of temperature and water content. Phys Earth Planet Int 174:10–18

    Google Scholar 

  • Mao HK (1973) Observation of optical absorption and electrical conductivity in magnesiowüstite at high pressures. Year B Carnegie Inst Wash 72:554–557

    Google Scholar 

  • Mao HK, Shen G, Hemley RJ, Duffy TS (1998) X-ray diffraction with a double hot-plate laser-heated daiamond anvil cell. In: Manghnani MH, Yagi T (eds) Properties of earth and planetary materials at high pressure and temperature. Am Geophys Union, Washington, pp 27–34

    Google Scholar 

  • McCammon C (1997) Perovskite as a possible sink for ferric iron in the lower mantle. Nature 387:694–696

    Google Scholar 

  • McCammon C (2005) The paradox of mantle redox. Science 308:807–808

    Google Scholar 

  • Ming LC, Bassett WA (1974) Laser heating in the diamond anvil press up to 2000°C sustained and 3000°C pulsed at pressures up to 260 kilobars. Rev Sci Instrum 45:1115–1118

    Google Scholar 

  • Murakmi M, Hirose K, Kawamura K, Sata N, Ohishi Y (2004) Post-perovskite phase transition in MgSiO3. Science 304:855–858

    Google Scholar 

  • Neal SL, Mackie RL, Larsen JC et al (2000) Variations in the electrical conductivity of the upper mantle beneath North America and the Pacific Ocean. J Geophys Res 105:2829–2842

    Google Scholar 

  • Ohta K, Hirose K, Onoda S, Shimizu K (2007) The effect of iron spin transition on electrical conductivity of magnesiowüstite. Proc Jpn Acad, Ser B 83:97–100

    Google Scholar 

  • Ohta K, Onoda S, Hirose K, Shinmyo R, Shimizu K, Sata K, Ohishi Y, Yasuhara A (2008) The electrical conductivity of post-perovskite in Earth’s D” layer. Science 320:89–91

    Google Scholar 

  • Ohtani E, Kagawa K, Shimomura O (1989) High-pressure generation by a multiple anvil system with sintered diamond anvils. Rev Sci Instrum 60:922–925

    Google Scholar 

  • Olsen N (1998) The electrical conductivity of the mantle beneath Europe derived from C-responses from 3 to 720 hr. Geophys. J. Int. 133:298–308

    Google Scholar 

  • Olsen N (1999) Induction studies with satellite data. Surv Geophys 20:309–340

    Google Scholar 

  • Omura K (1991) Change of electrical conductivity of olivine associated with the olivine-spinel transition. Phys Earth Planet Int 65:292–307

    Google Scholar 

  • Omura K, Kurita K, Kumazawa M (1989) Experimental study of pressure dependence of electrical conductivity of olivine at high temperatures. Phys Earth Planet Int 57:291–303

    Google Scholar 

  • Ono S, Ito E, Katsura T (2001) Mineralogy of subducted basaltic crust (MORB) from 25 to 37 GPa, and chemical heterogeneity of the lower mantle. Earth Planet Sci Lett 190:57–63

    Google Scholar 

  • Ono S, Oganov AR, Koyama T, Shimizu H (2006) Stability and compressibility of the high pressure phases of Al2O3 up to 200 GPa: implications for the electrical conductivity of the base of the lower mantle. Earth Planet Sci Lett 246:326–335

    Google Scholar 

  • Persson K, Bengtson A, Ceder G, Morgan D (2006) Ab initio study of the composition dependence of the pressure-induced spin transition in the (Mg1−x , Fe x )O system. Geophys Res Lett 33:L16306. doi:10.1029/2006GL026621

    Google Scholar 

  • Peyronneau J, Poirier JP (1989) Electrical conductivity of the Earth’s lower mantle. Nature 342:537–539

    Google Scholar 

  • Roberts JJ, Tyburczy JA (1991) Frequency dependent electrical properties of polycrystalline olivine compacts. J Geophys Res 96:16205–16222

    Google Scholar 

  • Roberts JJ, Tyburczy JA (1993) Impedance spectroscopy of single and polyscrystalline olivine: evidence for grain boundary transport. Phys Chem Minerals 20:19–26

    Google Scholar 

  • Roberts JJ, Tyburczy JA (1999) Partial melt electrical conductivity: influence of melt compositon. J Geophys Res 104:737–747

    Google Scholar 

  • Romano C, Poe BT, Kreidie N, McCammon CA (2006) Electrical conductivities of pyrope-almandine garnets up to 19 GPa and 1700°C. Am Mineral 91:1371–1377

    Google Scholar 

  • Schock RN, Duba AG, Shankland TJ (1989) Electrical conduction in olivine. J Geophys Res 94:5829–5839

    Google Scholar 

  • Seifert KF, Will G, Voigt R (1982) Electrical conductivity measurements on synthetic pyroxenes MgSiO3–FeSiO3 at high pressures and temperatures under defined thermodynamic conditions. In: Schreyer W (ed) High-pressure researches in geoscience. Schweizerbart’sche, Stuttgart, pp 419–432

    Google Scholar 

  • Sempolinski DR, Kingery WD, Tuller HL (1980) Electrical conductivity of single crystalline magnesium oxide. J Am Ceram Soc 63:669–675

    Google Scholar 

  • Shankland TJ, Duba AG (1990) Standard electrical conductivity of isotropic, homogeneous olivine in the temperature range 1200–1500°C. Geophys J Int 103:25–31

    Google Scholar 

  • Shankland TJ, Peyronneau J, Poirier J-P (1993) Electrical conductivity of the earth’s lower mantle. Nature 366:453–455

    Google Scholar 

  • Sturhahn W, Jackson JM, Lin J-F (2005) The spin state of iron in minerals of Earth’s lower mantle. Geophys Res Lett 32:L12307. doi:10.1029/2005GL022802

    Google Scholar 

  • Sung C-M, Sung M (1996) Carbon nitrite and other speculative super hard materials. Material Chem Phys 43:1–18

    Google Scholar 

  • Takahashi E, Ito E (1987) Mineralogy of mantle periodotite along a model geotherm up to 700 km depth. In: Manghnani MH, Shono Y (eds) High-pressure research in mineral physics. American Geophysical Union, Washington, pp 427–437

    Google Scholar 

  • Tarits P, Hautot S, Perrier F (2004) Water in the mantle: results from electrical conductivity beneath the French Alps. Geophys Res Lett 31:L06612. doi:10.1029/2003GL019277

    Google Scholar 

  • Ten Grotenhuis SM, Drury MR, Spiers CJ, Peach CJ (2005) Melt distribution in olivine rocks beased on electrical conductivity measurements. J Geophys Res 110:B12201

    Google Scholar 

  • Tsuchiya T, Wentzcovitch RM, da Silva CRS, de Gironcoli S (2006) Spin transition in magnesiowüstite in Earth’s lower mantle. Phys Rev Lett 96:198501. doi:10.1103/PhysRevLett.96.198501

    Google Scholar 

  • Utada H, Koyama T, Shimizu H et al (2003) A semi-global reference model for electrical conductivity in the mid-mantle beneath the north Pacific region. Geophys Res Lett 31:1194. doi:10.1029/2002GL016902

    Google Scholar 

  • Wanamaker BJ, Duba AG (1993) Electrical conductivity of San Carlos olivine along [100] under oxygen- and pyroxene-buffered conditions and implications for defect equilibria. J Geophys Res 98:489–500

    Google Scholar 

  • Wang D, Mookherjee M, Xu Y et al (2006) The effect of water on electrical conductivity of olivine. Nature 443:977–980

    Google Scholar 

  • Wood BJ, Nell J (1991) High-temperature electrical conductivity of the lower-mantle phase (Mg, Fe)O. Nature 351:309–311

    Google Scholar 

  • Wood BJ, Rubie DC (1996) The effect of alumina on phase transformations at the 660 km discontinuity from Fe–Mg partitioning experiments. Science 273:1522–1524

    Google Scholar 

  • Xu Y, McCammon C (2002) Evidence for ionic conductivity in lower mantle (Mg, Fe)(Si, Al)O3 perovskite. J Geophys Res 107:2251. doi:10.1029/2001JB000677

    Google Scholar 

  • Xu Y, Shankland TJ (1999) Electrical conductivity of orthopyroxene and its high pressure phases. Geophys Res Lett 22:2645–2648

    Google Scholar 

  • Xu Y, Poe BT, Shankland TJ et al (1998a) Electrical conductivity of olivine, wadsleyite and ringwoodite under upper-mantle condition. Science 280:1415–1418

    Google Scholar 

  • Xu Y, McCammon C, Poe BT (1998b) Effect of alumina on the electrical conductivity of silicate perovskite. Science 282:922–924

    Google Scholar 

  • Xu Y, Shankland TJ, Duba AG (2000a) Pressure effect on electrical conductivity of olivine. Phys Earth Planet Int 118:149–161

    Google Scholar 

  • Xu Y, Shankland TJ, Poe BT (2000b) Laboratory-based electrical conductivity in the Earth’s mantle. J Geophys Res 105:27865–27875

    Google Scholar 

  • Yoshino T, Katsura T (2009) Effect of iron content on electrical conductivity of ringwoodite, with implications for electrical structure in the mantle transition zone. Phys Earth Planet Int 174:3–9

    Google Scholar 

  • Yoshino T, Walter MJ, Katsura T (2003) Core formation in planetesimals triggered by permeable flow. Nature 422:154–157

    Google Scholar 

  • Yoshino T, Walter MJ, Katsura T (2004) Connectivity of molten Fe alloy in peridotite based on in situ electrical conductivity measurements: implications for core formation in terrestrial planets. Earth Planet Sci Lett 222:625–643

    Google Scholar 

  • Yoshino T, Matsuzaki T, Yamashita S, Katsura T (2006) Hydrous olivine unable to account for conductivity anomaly at the top of the asthenosphere. Nature 443:973–976

    Google Scholar 

  • Yoshino T, Manthilake G, Matsuzaki T, Katsura T (2008a) Dry mantle transition zone inferred from electrical conductivity of wadsleyite and ringwoodite. Nature 451:326–329

    Google Scholar 

  • Yoshino T, Nishi M, Matsuzaki T, Yamazaki D, Katsura T (2008b) Electrical conductivity of majorite garnet and its implications for electrical structure in the mantle transition zone. Phys Earth Planet Int 170:193–200

    Google Scholar 

  • Yoshino T, Yamazaki D, Ito E, Katsura T (2008c) No interconnection of ferro-periclase in post-spinel phase inferred from conductivity measurement. Geophys Res Lett 35:L22303. doi:10.1029/2008GL035932

    Google Scholar 

  • Yoshino T, Matsuzaki T, Shatzkiy A, Katsura T (2009) The effect of water on the electrical conductivity of olivine aggregates and its implications for the electrical structure of the upper mantle. Earth Planet Sci Lett. doi:10.1016/j.epsl.2009.09.032

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Acknowledgments

I wish to express my sincere thanks to the Program Committee and LOC of the Beijing workshop, who offered me a chance to prepare and deliver this review. I am grateful to T. Katsura, E. Ito, D. Yamazaki, K. Baba, T. Koyama, H. Toh and H. Utada for discussion. The comments of two anonymous reviewers aided in improving the manuscript.

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

    Takashi Yoshino

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Yoshino, T. Laboratory Electrical Conductivity Measurement of Mantle Minerals. Surv Geophys 31, 163–206 (2010). https://doi.org/10.1007/s10712-009-9084-0

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