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Mineralogical Model of the Lower Mantle: Constraints from Elasticity

Mineralogical Model of the Lower Mantle: Constraints from Elasticity. Motohiko Murakami. Tohoku University. Acknowledgements Jay D. Bass (University of Illinois) Stanislav V. Sinogeikin ( University of Illinois ) Holger Hellwig ( University of Illinois )

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Mineralogical Model of the Lower Mantle: Constraints from Elasticity

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  1. Mineralogical Model of the Lower Mantle: Constraints from Elasticity Motohiko Murakami Tohoku University

  2. Acknowledgements Jay D. Bass (University of Illinois) Stanislav V. Sinogeikin (University of Illinois) HolgerHellwig (University of Illinois) Jie Li (University of Illinois) Zhang Jing (University of Illinois) NagayoshiSata (JAMSTEC) Yuki Asahara (SPring-8) YasuoOhishi (SPring-8) NaohisaHirao (SPring-8) Kei Hirose (Tokyo Tech)

  3. Mineralogical model of upper mantle “Peridotitic” upper mantle http://www.lpl.arizona.edu/grad/fieldtrips/2007f-southernnewmexico/

  4. Is Earth’s mantle chemically homogeneous? Homogeneous mantle (Peridotitic) Heterogeneous mantle (Si-rich lower mantle?) upper mantle upper mantle lower mantle lower mantle core core ? ?

  5. Recent seismological views in Earth’s deep interior Large Low-Shear-Velocity Provinces (LLSVPs) Ultra Low Velocity Zones (ULVZs) (Garnero & McNamara, 2008)

  6. 1D seismological model in Earth’s interior PREM Mineralogical modeling of deep mantle

  7. Challenges for sound velocity measurements

  8. Previous work on MgSiO3 pv up to ~9 GPaby ultrasonic measurement (Li & Zhang, 2005)

  9. Pressure High-Pressure sound velocity Diamond Anvil Cell (DAC) apparatus Probe laser (514.5 nm, 532 nm) 6-pass tandem Fabry-Perot interferometer Diamond anvil cell Prof. Bass (UIUC) High-pressure Brillouin scattering system

  10. Shear velocity of MgSiO3 pv dG/dP (G’0) =1.56 (Murakami et al., 2007)

  11. Pressure High-Pressure sound velocity MgO to 130 GPa MgSiO3 ppvto 172 GPa MgSiO3 perovskiteto 100 GPa (Murakami et al., EPSL, 2009) (Murakami et al., EPSL, 2007) (Murakami et al., EPSL, 2007b)

  12. Challenges for sound velocity measurements

  13. Effect of chemistry • Composition Al-MgSiO3 pv (Mg,Fe)O fp Crowhurst et al. 2008 Marquardt et al., 2009 Jackson et al. 2005 High-pressure data are still limited

  14. Shear wave velocity measurements for fpand Al-pv (Mg0.92Fe0.08)O: 120 GPa, 300 K Al-MgSiO3 pv: 124 GPa, 300 K (4 wt% Al2O3) Brillouin System at SPring-8

  15. Brillouin data (Mg0.94Fe0.08)O 86 GPa

  16. Shear velocity of (Mg,Fe)O

  17. Effect of spin transition on the elasticity

  18. Brillouin data of aluminous MgSiO3 pv 95 GPa

  19. Shear velocity of Al-MgSiO3 pv

  20. Effect of Al on the elasticity of pv

  21. -Al2O3 MgO-SiO2 -FeO MgSiO3 pv, 96 GPa (Murakami et al. 2007) MgO, 130 GPa (Murakami et al. 2009) (Mg,Fe)O, 120 GPa (Murakami et al. 2012) Al-MgSiO3 pv, 124 GPa (Murakami et al. 2012)

  22. Modeling of lower mantle mineralogy System MgO-SiO2-FeO-Al2O3 (Mg,Fe)O, 120 GPa (Murakami et al. 2012) Al-MgSiO3 pv, 124 GPa (Murakami et al. 2012) Formalism Stixrude & Lithgow-Bertelloni, 2005 Geotherm

  23. Lower mantle geotherms Two extreme models

  24. Modeling of lower mantle mineralogy Whole mantle convection geothermal model

  25. Modeling of lower mantle mineralogy Layered mantle convection geothermal model

  26. Mineralogical Model of Lower Mantle Peridotiticlower mantle Perovskititic lower mantle

  27. Perovskiticlower mantle upper mantle lower mantle core Perovskitite SiO2-enriched lower mantle

  28. Evolution history of the mantle Fractional crystallization Layered mantle convection Chemically stratified mantle upper mantle lower mantle core Early Earth Current Earth

  29. Big question/problem How to maintain such chemical stratification? (Brandenburg et al., 2008)

  30. Challenges for sound velocity measurements

  31. Technical development for sound velocity measurements under H-T

  32. Simultaneous measurement system for Vs,p, V and T Brillouin scattering + XRD + Laser heating (Murakami et al. 2009)

  33. XRD Brillouin spectrum Laser heating Sound velocity under high P-T MgOat 50 GPa, 2500 K

  34. High-T data on (Mg,Fe)SiO3 pv up to 25 GPa and 1200 K Ultrasonic method with large volume press (Chantelet al. 2012) High-T elasticity data support our conclusion

  35. Toward better understanding.. *Effect of spin-transition of iron in Pv on the elasticity *Combined effect of Fe & Al on the elasticity of Pv *Data quality improvement of the high-T data

  36. Summary We have determined the sound velocities of MgSiO3perovskite, MgO, (Mg,Fe)O and Al-MgSiO3 perovsktie under lower mantle pressure conditions Mineralogical modeling using obtained results strongly indicates the perovskiticlower mantle. Development of new Brillouin spectroscopy at high PT enables us to explore the sound velocities under lower mantle condition.

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