Chondrite Models for the Composition of the Earth's Mantle and Core

The terrestrial planets of the inner Solar System are believed to be broadly chondritic in composition. Here I suggest that the lithophile element composition of the terrestrial mantle, as approximated by primitive lherzolites having high Al/Si ratios and low Mg/Si ratios, was established by nebular rather than indigenous processes. The implications of this model include: (i) the Mg/Si ratio of the upper mantle is an instrinsic property of the bulk Earth and does not reflect differentiation of a terrestrial magma ocean; (ii) the Moon probably did not form by a giant impact on to the Earth; (iii) refractory lithophile elements should be 2.5-3.0 chondrites in the bulk silicate Earth; and (iv) silicon is not a major constituent of the Earth's core.