HR: 08:00h
AN: U41A-01 INVITED     [PDF]
TI: Constraints on Chemical Interaction Between Core and Mantle
AU: * Hillgren, V J
EM: hillgren@mpch-mainz.mpg.de
AF: Max Planck Inst., Postfach 3060, Mainz, 55020 Germany
AB: Chemical reactions between the core and mantle have been suggested to explain a variety of phenomena including the D" layer (e.g., Knittle and Jeanloz) and Os isotopic signatures observed in some plume derived magmas (e.g., Walker et al.). However, the chemical nature of a core-mantle interaction depends on several poorly constrained factors such as how close the core and mantle are to chemical equilibrium, the composition of the core (i.e., the identity of the light element(s)), and partitioning of elements between the inner and outer core. The state of equilibrium between the core and mantle is dependant on the mode of core formation: Did the core continually re-equilibrate with the mantle as it formed while the Earth grew, or did core metal equilibrate with mantle silicates at pressures significantly lower than those of the present day core-mantle boundary (for example as in the model of Righter et al.)? In addition any subsequent differentiation of the mantle resulting in the formation of D" (if it is not a direct reaction product between core and mantle) could change the state of equilibrium between the core and mantle especially the development of a zone of partial melt as suggested by the ULVZ. However, experimental studies to date of interactions between the core and mantle have assumed that D" is solid and of similar composition to the rest of the mantle (i.e., Knittle and Jeanloz, Goarant et al., Hillgren and Boehler). All that is known about the composition of the core is that it is Fe alloyed with some lighter element. The identity of the light element is unknown (although there is only a limited number of reasonable candidates) and the amount of that element is dependent upon its identity. The identity of the light element is also critical for determining how elements might partition between the inner and outer core. Recent experimental and theoretical work on core-mantle interaction, light element in the core, and partitioning at very high pressures will be reviewed. Ref: Goarant et al. (1992) JGR 97, 4477. Hillgren and Boehler (2000) AIRRAPT 17, 609. Knittle and Jeanloz (1989) GRL 16, 609. Righter et al. (1997) PEPI 100, 115. Walker et al. (1995) Science 269, 819.
DE: 1010 Chemical evolution
DE: 1015 Composition of the core
SC: U
MN: 2003 Fall Meeting