Chemical Composition of the Earth

Abstract

Determining the elemental abundances of the Earth is one of the fundamental interests of the Earth and planetary sciences. The elemental abundances of the bulk solar system, chondrites and bulk Earth are reviewed. The elemental abundances of the bulk solar system resemble those of chondrites, with the exception of atmophile elements. CI chondrite may be most resemblant, but significant improvements in solar photosphere spectroscopy are necessary to reject other chondrites. Volatilities of elements control chemical variations among chondrites. These variations may reflect global thermal structures in the proto-solar disk. Alternatively, the variations may correspond to accretion ratios of chondrite-forming components, which are refractory inclusions, chondrules, and matrix, into the parent bodies. The elemental abundances of bulk silicate Earth can be empirically estimated without referring those of the bulk solar system and chondrites if we use chemical variations of mantle rocks. However, the chemical composition of bulk Earth remains largely uncertain because it is difficult to estimate the chemical compositions of the central core and the lower mantle without formation models of the Earth.