Metal-silicate silicon isotopic fractionation and the composition of the bulk Earth
| Autor: | Zhengbin Deng, Marc Chaussidon, Paul S. Savage, Frédéric Moynier, Ariane Lanteri, Julien Siebert, Rayssa Martins |
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| Přispěvatelé: | Université de Paris (UP), Institut de Physique du Globe de Paris, School of Earth and Environmental Sciences [University St Andrews], University of St Andrews [Scotland], Institut Universitaire de France (IUF), Ministère de l'Education nationale, de l’Enseignement supérieur et de la Recherche (M.E.N.E.S.R.), University of St Andrews. School of Earth & Environmental Sciences, University of St Andrews. St Andrews Centre for Exoplanet Science, University of St Andrews. St Andrews Isotope Geochemistry |
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Accretion
010504 meteorology & atmospheric sciences Itqyi Analytical chemistry engineering.material 010502 geochemistry & geophysics 01 natural sciences Physics::Geophysics chemistry.chemical_compound Geochemistry and Petrology Chondrite Earth and Planetary Sciences (miscellaneous) Chemical composition 0105 earth and related environmental sciences GE DAS Forsterite Silicate Planetary differentiation Geochemistry Geophysics Meteorite chemistry 13. Climate action Space and Planetary Science [SDU]Sciences of the Universe [physics] Core formation Physics::Space Physics Enstatite engineering Astrophysics::Earth and Planetary Astrophysics Geology Earth (classical element) Meteorites GE Environmental Sciences |
| Zdroj: | Earth and Planetary Science Letters Earth and Planetary Science Letters, Elsevier, 2020, 549, pp.116468-. ⟨10.1016/j.epsl.2020.116468⟩ |
| ISSN: | 0012-821X |
| Popis: | The difference in the Si isotopic composition between the Earth and primitive meteorites had been used to constrain the amount of Si in the Earth's core. However, there is presently a debate on the magnitude of the isotopic fractionation between metal and silicates as function of temperature based on experimental data. Here, we use a natural sample, an enstatite meteorite, Itqyi, as a natural experiment to determine an independent Si isotopic fractionation factor between metal and silicate. We determined the temperature of equilibrium between metal and silicate as well as the Si isotopic composition between the phases. We find that the dependence of Si isotopes with temperature to be: Δ 30 Si silicate-metal = 7.6 ( ± 0.7 ) × 10 6 ( 1 S D ) T 2 Using this dependence of the δ30Si with temperature we estimate the bulk Earth δ30Si as a function of Si content of the core for different plausible conditions. Even when using the most extreme parameters, we show that the bulk Earth must be isotopically heavier than any chondrites groups. We therefore confirm that core formation alone cannot account for the isotopic difference between the Earth and primitive meteorites. We show that there is no correlation between δ30Si and the Mg/Si ratio suggesting that forsterite fractionation in the solar nebula may have had only a limited effect, if any. Our new results therefore confirm that volatility should have had a fundamental effect in shaping terrestrial planets chemical composition. |
| Databáze: | OpenAIRE |
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