On the implications of an olivine dominated upper mantle on the development of a moon of fission origin

In a series of previous papers, a petrological model for the Moon has been developed based on the assumption that the Moon is a globe of differentiated terrestrial mantle material which fissioned from the Earth. One of the major constraints which this model matches is the hypothesis that the lunar upper mantle is dominated by pyroxene. However, it has been recently shown that olivine is most probably the major constituent of the lunar upper mantle and that, at least that part of the Moon has a composition which is very similar to that of pyrolite - the proposed composition of the Earth's mantle. As a result of this new model constraint, the previously proposed differentiation scheme for a Moon of fission origin is reviewed and found to be inadequate, despite modification, for explaining the near pyrolite composition of the lunar upper mantle. As a result, a solidification sequence, which has been proposed to explain the rhythmic banding in terrestrial ultra mafic complexes, is investigated and found to be able to account for the high olivine content of the upper mantle, assuming a pyrolite composition for the Moon.