Storage of noble gases in the core

Jephcoat (1998) observed that Xe forms a high-density solid at deep mantle pressures. Sinking of these solids could transport Xe, and possibly some fraction of other noble gases incorporated into this structure, to the deep mantle or core. However, it has not been demonstrated either that such a scarce element ( 20 fg/g) is sufficiently insoluble in other high pressure phases to form a separate phase, or that it can form separate grains in the mantle sufficiently large to sink. This mechanism for transport to the core therefore cannot be evaluated further. 

Availability of noble gases during core segregation. The light noble gases in the 

Concentrations in the core. If He is partitioned from solid silicates to liquid metal percolating through the deep mantle, initial concentrations must have been provided by irradiated accreting material. The core represents -32% of the bulk mass of the Earth if this was removed from the mantle by a single batch process, then 

If He was provided by equilibration between liquid metal and a magma ocean at lower pressures, the initial mantle concentration was provided by a hot dense atmosphere. In this case, the relevant partition coefficient of D(He)Fe/Ls is lower than that for equilibration with solid silicate, but there may have been greater concentrations of noble gases available from the overlying atmosphere. Then, 

Transport back into the mantle. Various mechanisms can be considered for the transport of noble gases back into the mantle. 

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