1. Phase Transitions in the Earth’s Mantle
Dan Shim
54-514, ,

2. PREM

4. Size of Ions in Solids

5. Close Packed Structures

6. Close Packed Structures

7. Inter-atomic Potential

8. Coordination Number

9. Other Crystallographic Considerations

10. Changes in Crystal Structures
Olivine (Siiv, Mgvi)
Pyroxene (Siiv, Mgvi or viii)
hcp to fcc
Wadsleyite (Siiv, Mgvi)
Garnet (Siiv and vi, Mgvi)
Redistribution of Si
Ringwoodite (Siiv, Mgvi)
Akimotoiite (Sivi, Mgvi)
Siiv to Sivi
Perovskite (Sivi, Mgviii-xii)
3D network to 2D layer
Periclase (Mgvi)
Post-Perovskite (Sivi, Mgvi-viii)

11. Comparison of Different Techniques
(GPa)
s(P) T
(K)
s(T)
Sample
(mm3) MA
<30 1
<2500 50
LHDAC
<150 5
10-4

12. Pressure Measurement Methods
Calibration curve
Equation of State
Ito and Takahashi (1989) JGR 94,
Shim et al. (2001) EPSL 203, 729+

13. Temperature Measurement Methods
Thermocouple
Radiometry

14. Phase Diagram of (Mg,Fe)2SiO4
660 km
DZ = 3 km
520 km
DZ = 40 km
410 km
DZ = 13 km
Presnall (1995) in Mineral Physics and Crystallography Handbook

15. Phase Diagram of MgSiO3 660 km w/ Al
Presnall (1995) in Mineral Physics and Crystallography Handbook

16. Clapeyron Slopes of Transition Zone Boundaries
Slope (MPa/K)
a-b
Katsura and Ito (1989) JGR 94,
Morishima et al. (1994) Science 265, 1202+
Katsura et al. (2004) JGR 109,
b-g
Suzuki et al. (2000) GRL 27, 803+
Post-spinel
Ito and Takahashi (1989) JGR 94,
Irifune et al. (1998) Science 297, 1698+
Post-ilmenite
Kuroda et al. (2000) PCM 27, 523+
Post-garnet
+2.4
Hirose et al. (2001) EPSL 184, 567+

17. Implications of the Phase Transitions
Li et al. (1998) Science 281, 675+
Ito and Katsura (1989) GRL 16, 425+

18. Phase Boundary and Mantle Flow
Gu and Dziewonski (2002) JGR 107, 2135

19. Thinner 410-Discontinuity?
Seismic observation
< 5 km
410-km
DZ = 13 km
Presnall (1995) in Mineral Physics and Crystallography Handbook

20. Complex System Effect of Iron Effect of Water Hydrous
Smyth (2002) GRL 29,
Irifune et al. (1998) Nature 392, 702+

21. Post-Spinel Boundary at 600 km?
Irifune et al. (1998) Science 279, 1698+

22. What about Other Boundaries?
Post-Garnet
Post-Ilmenite
580 km
Kuroda et al. (2000) PCM 27, 523+
Hirose et al. (2001) EPSL 184, 567+

23. Problems in P-T Scales?
Shim et al. (2001) Nature 411, 571+

24. 0 or (+) Clapeyron Slope of the Post-Spinel Transition?
Katsura et al. (2003) PEPI 136, 11+

25. Post-Perovskite Transition
MgSiO3 Perovskite (orthorhombic, Pbnm)
MgSiO3 Post-Perovskite (orthorhombic, Cmcm)

26. Pressure of the Post-Perovskite Transition
Existing experimental data do not provide tight constraints.
GPa at K (Murakami et al., 2004)
GPa at K (Shim et al., 2004)
GPa at K (Oganov and Ono, 2004)
Ab-initio calculation
GPa at 2500 K (Oganov and Ono 2004)
GPa at 2500 K (Tsuchiya et al., 2004)
○ Seismic constraint (Sidorin et al, 1999): 127 GPa

27. Clapeyron Slope of the Post-Perovskite Transition
Existing experimental data do not provide constraints.
Ab-initio calculation
MPa/K (Oganov and Ono 2004)
7.5±0.3 MPa/K (Tsuchiya et al., 2004)
○ Seismic constraint (Sidorin et al, 1999): 6 MPa/K

28. Physical Properties of the Post-Perovksite
Density increase
% (Murakami et al., 2004)
1.4 % (Oganov and Ono, 2004)
1.5 % (Tsuchiya et al., 2004)
% (10% Fe, Shieh and Duffy, 2004)
Bulk and shear moduli
K0 = 232 GPa, K0’ = 4.4, DVS = 1.9 %, DVP = 0.3 % (Oganov and Ono, 2004)
K0 = 221 GPa, K0’ = 4.2, DVS = 1.5 % (Tsuchiya et al., 2004)
K0 = 222±9 GPa for K0’ = 4 fixed, DVf = % (10% Fe, Shieh and Duffy, 2004)
Elastic anisotropy
VSH > VSV, Anticorrelation between VS and Vf (Oganov and Ono, 2004)
VSH > VSV due to vertical alignments of [001], but [010] is possible (Tsuchiya et al., 2004)

29. Effect of Iron Shieh and Duffy (MR23A-0182)
10 mol% Fe pyroxene
PPV transition at <105 GPa (600-km above CMB)
Mao et al. (2004, PNAS 101, )
12 mol% Fe olivine, 20 and 40 mol% Fe pyroxene
PPV transition at 100 GPa (700-km above CMB) for 10 %Fe
Fe partitions predominantly into the post-perovskite phase
Murakami et al. (MR22A-01)
Pyrolitic gel starting material
PPV transition at 115 GPa (400-km above CMB)
Fe partitions predominantly into magnesiowüstite

30. Effect of Post-Perovskite Transition for the Mantle Convection
No Post-Pv Transition
Post-Pv with high (+) slope
Post-Pv with low (+) slope
Nakagawa and Tackley (2004) GRL 31, L16611

31. Depth Variations of the Post-Perovskite Boundary
Due to the large Clapeyron slope, T decrease by 500 K may result in elevation of the transition depth by 100 km.
1% Fe increase may result in elevation of the transition depth by km.

32. Temperature Gradient at CMB
Heat from the core?
Experimental constraints?
Melting curve of iron
Melting curve of lower-mantle silicates
~10 K/km
Highly non-linear
Locally (laterally) varied
Clapeyron slope of the post-perovskite transition
→ ~5-7 K/km