Siderophile elements magma oceans

In most respects, asteroid 4 Vesta is geochemically similar to the Moon. As judged from howardite-eucrite-diogenite (HED) meteorites (see Chapter 6), Vesta is an ancient, basalt-covered world (Keil, 2002). Its rocks are highly reduced, and its depletions in volatile and siderophile element abundances resemble those of lunar basalts. And like the Moon, Vesta is hypothesized to have had an early magma ocean. The exploration of Vesta is now in progress, and within a few years we may have enough data to discuss it in a similar way that we have considered the Moon. 

Righter K. and Drake M. J. (1999) Effect of water on metal-silicate partitioning of siderophile elements a higji pressure and temperature magma ocean and core formation. Earth Planet Sci. Lett. 171, 383—399. 

Capobianco C. J., Jones J. H., and Drake M. J. (1993) Metal/ silicate thermochemistry at high temperature magma oceans and the excess siderophile element problem of the Earth s Upper Mantle. J. Geophys. Res. 98, 5433-5443. 

Currently, the favored solution to the siderophile element problem, and the most popular model of core formation, is that silicate-metal equilibration took place at high pressures, in a deep magma ocean. Support for this model comes from very high pressure experimental studies of trace element partitioning, which show that metal-silicate partition... 

The accretion of a late veneer. Whether or not a late veneer was added to the Earth towards the end of accretion is not clear. The principal evidence comes from the elevated siderophile element chemistry of the mantle. If there was a late veneer, it had to happen after core formation. At present the evidence from the trace element chemistry is ambiguous, because these data can also be explained by the formation of the core at high pressures and temperatures in a magma ocean, or by continuous core formation with decreasing metal input. Currently, the best evidence for a late veneer comes from Os-isotope evidence, where there is a clear mismatch between the composition of the PUM and chondrite. However, even this is uncertain, as is discussed in the next chapter (Chapter 3, Section 3.2.3.4), for... 

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