synchrotron XRD chemical analysisby TEM

olivine

Discovery of post-perovskite phase transition

Determination of crystal structure by MD simulations

“Si”

CN=6 x 6

8 x 2

“Mg”

CN=6 x 2

8 x 6

exchanged

(1) Compositional effect on post-perovskite phase transition

Post-perovskite phase transition in:

pure MgSiO3

Pyrolite (8% FeO* 4%Al2O3) MORB (10% FeO* 16%Al2O3)

all occur at 110 to 115GPa @ 2500K

based on gold scale

Compositional effect is small!

Mg-Fe partitioning between PPv, Pv & Mw

PPv & CaPv

Mw

110GPa & 2550K

Pv should be more Fe-rich than PP

Murakami, Hirose, Sata, Ohishi, 2005 GRL

Core-mantle chemical reaction

(2) Light elements in the core?

S in the core?

Only 1.2-1.7 wt% S in the core

8 wt% S is necessary to account for the 7% core density deficit

Larger simultaneous solubilities of Si & O at high pressures?

OMg

Si

(3) What is going on at CMB?

Any reaction products?

No reaction products!

in pv

What is the chemical composition of the mantle in contact with the core?

Core liquid should be in equilibrium,at least with the base of the mantle.

(Fe-depleted)

How has chemical reaction at CMB changed the core composition over the geological time?

Core can dissolve more Si & O when the Fe-depleted bottom of the mantle is replaced by the normal mantle

Core is not saturated in Si & O

Si & O contents in the core may have increased with time!

Dissolution of Si & O into the core from partially molten layer in D”?

Thank you.