Olivine flotation

Flotation of olivine in the mid-mantle during an early magma ocean would perhaps satisfy the superchondritic Mg/Si ratio (Agee and Walker, 1988). However, McFarlane and Drake (1990) have shown that the Ni/Co ratio of such a layer would be 25% higher than that in the observed upper mantle. In addition, the incompatible nature of platinum, palladium, gold, and rhenium in olivine compared to iridium, ruthenium, and rhodium would undoubtedly lead to nonchondritic HSE ratios such as Pd/Ir, Au/Ru, etc. in the upper mantle, and this is not observed (e.g., Righter et al., 2000). As a result, early olivine flotation seems unlikely. 

The superchondritic Mg/Si ratio of Earth s upper mantle might arise from olivine flotation in an early magma ocean (Agee and Walker, 1988). Such an explanation would have to be consistent with other minor and trace elements, especially those known to be compatible in olivine at low pressure such as nickel, cobalt, and manganese. Olivine is a stable liquidus phase in chondritic and peridotitic compositions to 15 GPa (Agee et aL, 1995 Zhang and Herzberg,... 

A large deposit of perovskite was found recently in the USA (Powderhom). Perovskite deposits are also known to be found in Russia (Cola Pennisula). There is little information available on research into flotation of perovskite conducted on ores from some Russian deposits [6], These ores are relatively complex and contain a variety of gangue minerals including pyroxene, amphibole, olivine, nepheline, biotite and calcite. 

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