chemical composition of the lower mantle: constraints from
TRANSCRIPT
![Page 1: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/1.jpg)
Chemical Composition of the Lower Mantle: Constraints from Elasticity
Motohiko Murakami
Tohoku University
![Page 2: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/2.jpg)
Acknowledgements
Jay D. Bass (University of Illinois)
Stanislav V. Sinogeikin (University of Illinois)
Holger Hellwig (University of Illinois)
Jie Li (University of Illinois)
Zhang Jing (University of Illinois)
Nagayoshi Sata (JAMSTEC)
Yuki Asahara (SPring-8)
Yasuo Ohishi (SPring-8)
Naohisa Hirao (SPring-8)
Kei Hirose (Tokyo Tech)
![Page 3: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/3.jpg)
http://www.lpl.arizona.edu/grad/fieldtrips/2007f-southernnewmexico/
SiO2 46%
MgO 39%
FeO 8%
Al2O3 4%
CaO 3%
wt%
Mineralogical model of upper mantle
“Peridotitic” upper mantle
![Page 4: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/4.jpg)
Is Earth’s mantle chemically homogeneous?
lower mantle
upper mantle
core
lower mantle
upper mantle
core
Homogeneous mantle (Pyrolitic)
Heterogeneous mantle (Si-rich lower mantle?)
? ?
![Page 5: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/5.jpg)
Recent seismological views in Earth’s deep interior
(Garnero & McNamara, 2008)
Large Low-Shear-Velocity Provinces (LLSVPs) Ultra Low Velocity Zones (ULVZs)
![Page 6: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/6.jpg)
1D seismological model in Earth’s interior
Mineralogical modeling of deep mantle
PREM
![Page 7: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/7.jpg)
Challenges for sound velocity measurements
![Page 8: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/8.jpg)
Previous work on MgSiO3 pv
(Li & Zhang, 2005)
up to ~9 GPa by ultrasonic measurement
![Page 9: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/9.jpg)
Previous work on MgSiO3 pv
(Li & Zhang, 2005)
dG/dP (G’0) =2.0 pyrolitic lower mantle
![Page 10: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/10.jpg)
Diamond Anvil Cell (DAC) apparatus Probe laser (514.5 nm, 532 nm) 6-pass tandem Fabry-Perot interferometer
High-pressure Brillouin scattering system
High-Pressure sound velocity
![Page 11: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/11.jpg)
(Murakami et al., 2007)
Shear velocity of MgSiO3 pv
dG/dP (G’0) = 1.56
![Page 12: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/12.jpg)
MgSiO3 perovskite to 100 GPa
(Murakami et al., EPSL, 2007)
MgO to 130 GPa
(Murakami et al., EPSL, 2009)
MgSiO3 ppv to 172 GPa
(Murakami et al., EPSL, 2007b)
High-Pressure sound velocity SiO2 & MgSiO3 glasses to 200 GPa
(Murakami & Bass, PRL, 2010) (Murakami & Bass, PNAS, 2011)
![Page 13: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/13.jpg)
Challenges for sound velocity measurements
![Page 14: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/14.jpg)
Effect of chemistry
High-pressure data are still limited
(Mg,Fe)O fp Al-MgSiO3 pv Crowhurst et al. 2008 Marquardt et al., 2009
Jackson et al. 2005
![Page 15: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/15.jpg)
(Mg0.92Fe0.08)O: 120 GPa, 300 K
Al-MgSiO3 pv: 124 GPa, 300 K (4 wt% Al2O3)
Shear wave velocity measurements for fp and Al-pv
Brillouin System at SP8
![Page 16: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/16.jpg)
Brillouin data (Mg0.94Fe0.08)O
86 GPa
![Page 17: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/17.jpg)
Shear velocity of (Mg,Fe)O
![Page 18: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/18.jpg)
Effect of spin transition on the elasticity
![Page 19: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/19.jpg)
In-situ synthesis of Al-MgSiO3 pv
XRD image at 88 GPa XRD pattern at 88 GPa
![Page 20: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/20.jpg)
Brillouin data of aluminous MgSiO3 pv 95 GPa
![Page 21: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/21.jpg)
Shear velocity of Al-MgSiO3 pv
![Page 22: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/22.jpg)
composition G0 (GPa) G’0 pressure reference
Al-MgSiO3 (4 wt%) 166(1) 1.57(5) 124 GPa This study
Al-MgSiO3 (5 wt %) 165(2) 1.7(2) 45 GPa Jackson et al. 2005
MgSiO3 173(1) 1.56(4) 96 GPa Murakami et al. 2007
Effect of Al on the elasticity of pv
![Page 23: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/23.jpg)
MgSiO3 pv, 96 GPa
MgO, 130 GPa
Al-MgSiO3 pv, 124 GPa
(Mg,Fe)O, 120 GPa
MgO-SiO2 -FeO
(Murakami et al. 2007)
(Murakami et al. 2009)
-Al2O3
(Murakami et al. 2012)
(Murakami et al. 2012.)
![Page 24: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/24.jpg)
Modeling of lower mantle mineralogy
Al-MgSiO3 pv, 124 GPa
(Mg,Fe)O, 120 GPa (Murakami et al. under review)
(Murakami et al. in prep.)
System
Formalism Stixrude & Lithgow-Bertelloni, 2005
Geotherm
![Page 25: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/25.jpg)
Lower mantle geotherms
Two extreme models
![Page 26: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/26.jpg)
Modeling of lower mantle mineralogy
Whole mantle convection geothermal model
![Page 27: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/27.jpg)
Modeling of lower mantle mineralogy
Layered mantle convection geothermal model
![Page 28: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/28.jpg)
Pv 95%
Fp 5%
0%
0%
Mineral proportion (vol%)
Mineralogical Model of Lower Mantle
Pv 80%
Fp 20%
0%
0%
Mineral proportion (vol%)
Pyrolitic lower mantle Perovskititic lower mantle
![Page 29: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/29.jpg)
lower mantle
upper mantle
core
Perovskitite Pv
95%
Fp 5%
0%
0%
Mineral proportion (vol%)
Perovskititic lower mantle
SiO2-enriched lower mantle
![Page 30: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/30.jpg)
lower mantle
upper mantle
core
Early Earth Current Earth
Layered mantle convection Chemically stratified mantle Fractional crystallization
Evolution history of the mantle
![Page 31: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/31.jpg)
How to maintain such chemical stratification?
Big question/problem
(Brandenburg et al., 2008)
![Page 32: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/32.jpg)
Challenges for sound velocity measurements Effect of temperature
![Page 33: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/33.jpg)
Technical development for sound velocity measurements under H-T
![Page 34: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/34.jpg)
Brillouin scattering + XRD + Laser heating
Simultaneous measurement system for Vs,p, V and T
(Murakami et al. 2009)
![Page 35: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/35.jpg)
XRD Laser heating Brillouin spectrum MgO at 50 GPa, 2500 K
Sound velocity under high P-T
![Page 36: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/36.jpg)
Toward better understanding..
*Combined effect of Fe & Al on the elasticity of Pv
*Data quality improvement of the high-T data
*Effect of spin-transition of iron in Pv on the elasticity
![Page 37: Chemical Composition of the Lower Mantle: Constraints from](https://reader031.vdocuments.us/reader031/viewer/2022012301/61e1d121b29e475ca632abbf/html5/thumbnails/37.jpg)
We have determined the sound velocities of MgSiO3 perovskite, MgO, (Mg,Fe)O and Al-MgSiO3 perovsktie under lower mantle pressure conditions
Mineralogical modeling using obtained results strongly indicates the perovskitic lower mantle.
Development of new Brillouin spectroscopy at high PT enables us to explore the sound velocities under lower mantle condition.
Summary