University:
Widener University
Course:
CHEM-255 | Organic Chemistry I
Academic year:

2023
Views:

376

Pages:

9
Author:

Branden Mccullough

The Core-Mantle Boundary Region Jeanloz & Williams, 1998 H Lower mantle ~ 1 cm/yr T Heat flow BL CMB Outer core ~ 10 km/yr 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 Lower mantle mineralogy High-pressure experiments (Mg, Fe)O-Mw 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) Thermal profile of Earth [Boehler, 1996] [Kuo & Chen, in prep.] Chemical reactions at CMB Ultrahigh pressure & temperature experiments (MgxFe1-x)SiO3 + 3[(1-x)-s]Fe = xMgSiO3 + sSiO2 + [(1-x)-s]FeSi + [3(1-x)-2s]FeO [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 ) Partial melting high T, melting-point depression in metal-silicate system Igneous & metamorphic processes of CMB Lower mantle Infiltration & reaction zone CMB d Liquid metal alloy Outer core Thermal-chemical boundary layer [Knittle & Jeanloz, 1991]