1. The Core-Mantle Boundary Region Jeanloz & Williams, 1998 Lower mantle Outer core CMB Heat flow

2. Lower mantle mineralogy Classical constraints Bulk composition: observed top-most mantle sample; Peridotitic: 50% olivine + 40% pyroxene + minor phases Acoustic properties match seismological observation; Is similar to chondritic meteorites; Can produce basalt upon partial melting at low pressures (cf. MOR); …Details are uncertain yet

3. Olivine Modified Spinel Spinel Pyroxene Garnet Density D “ layer Volume Fraction (%) Metals (liquids) Pressure (GPa) Depth (km) Lower mantle mineralogy High-pressure experiments Silicates (Solids)

4. Outer core composition Properties are similar to Fe; Among candidates, Fe is most abundant in the universe; Earth’s magnetic field requires electrically conducting fluid; 10% less dense than Fe ‡Fe-rich alloy; (resulting in large uncertainties in the estimated T of CMB)

5. Thermal profile of Earth melting adiabat geotherm Temperature Depth (km) Pressure (Mbar) [Boehler, 1996]

6. Ita & Stixrude,1994 Ito & Katsura, 1989 Chopelas et al., 1994 O. Anderson’s recom. T m of iron 600 K jump? 300 K jump? LM adiabat OC adiabat Thermal bdry layer? Jump? Thermal bdry layer; Jump? Temperature (K) Depth (km) Thermal profile of Earth A suite of free parameters…. [Kuo & Chen, in prep.]

7. Chemical reactions at CMB Ultrahigh pressure & temperature experiments Partial melting [Knittle & Jeanloz, ’86; ‘89] Fe-depleted silicates & Fe alloys: fast and low seismic velocity, respectively; FeO: non-metallic  metal alloy at deep mantle pressure; ( O  metal at > 100 GPa ) High T, melting-point depression in metal-silicate system

8. Lower mantle Outer core Infiltration & reaction zone Liquid metal alloy Igneous & metamorphic processes of CMB

9. Lower Mantle (MgFe)SiO 2 + (MeFe)O perovskite magnesiowiistite D”layer FeO + FeSi metallic alloys Mixed(?) Thermal and Chemical Boundary Layer Reaction Zone Liquid Fe alloy Outer Core [Knittle & Jeanloz, 1991] Thermal-chemical boundary layer