Metal-silicate re-equilibration

How well are these assumptions justified Hafiiium-tungsten data for differentiated meteorites indicate that accretion and differentiation of their parent bodies occurred very early (see above). Bodies that formed so early would have melted and differentiated due to accumulation of radiogenic heat produced by decay of abundant Al. Earth therefore most likely accreted from predifferentiated planetesimals. The other assumptions, i.e., constant HfrW ratios and complete metal-silicate re-equilibration, are less well constrained. The effects that changes in these two parameters have on the W isotope evolution of Earth s mantle are shown in Figure 7. 

Figure 7. A. Core formation ages (corresponding to 99% growth) as a function of the assumed degree of metal-silicate re-equilibration during core formation. B. Relation between Hf/W ratio in the mantle of accreting planetesimals and the degree of metal-silicate re-equilibration during core formation.

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