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Dauphas N., Poitrasson Franck, Burkhardt C., Kobayashi H., Kurosawa K. (2015). Planetary and meteoritic Mg/Si and delta Si-30 variations inherited from solar nebula chemistry. Earth and Planetary Science Letters, 427, 236-248. ISSN 0012-821X

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Lien direct chez l'éditeur doi:10.1016/j.epsl.2015.07.008

Planetary and meteoritic Mg/Si and delta Si-30 variations inherited from solar nebula chemistry
Année de publication2015
Type de documentArticle référencé dans le Web of Science WOS:000359330800024
AuteursDauphas N., Poitrasson Franck, Burkhardt C., Kobayashi H., Kurosawa K.
SourceEarth and Planetary Science Letters, 2015, 427, p. 236-248. ISSN 0012-821X
RésuméThe bulk chemical compositions of planets are uncertain, even for major elements such as Mg and Si. This is due to the fact that the samples available for study all originate from relatively shallow depths. Comparison of the stable isotope compositions of planets and meteorites can help overcome this limitation. Specifically, the non-chondritic Si isotope composition of the Earth's mantle was interpreted to reflect the presence of Si in the core, which can also explain its low density relative to pure Fe-Ni alloy. However, we have found that angrite meteorites display a heavy Si isotope composition similar to the lunar and terrestrial mantles. Because core formation in the angrite parent-body (APB) occurred under oxidizing conditions at relatively low pressure and temperature, significant incorporation of Si in the core is ruled out as an explanation for this heavy Si isotope signature. Instead, we show that equilibrium isotopic fractionation between gaseous SiO and solid forsterite at similar to 1370 K in the solar nebula could have produced the observed Si isotope variations. Nebular fractionation of forsterite should be accompanied by correlated variations between the Si isotopic composition and Mg/Si ratio following a slope of similar to 1, which is observed in meteorites. Consideration of this nebular process leads to a revised Si concentration in the Earth's core of 3.6 (+6.0/-3.6) wt% and provides estimates of Mg/Si ratios of bulk planetary bodies.
Plan de classementSciences de la Terre : généralités [060]
LocalisationFonds IRD [F B010064911]
Identifiant IRDfdi:010064911
Lien permanenthttp://www.documentation.ird.fr/hor/fdi:010064911

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