期刊
NATURE GEOSCIENCE
卷 14, 期 11, 页码 806-+出版社
NATURE PORTFOLIO
DOI: 10.1038/s41561-021-00838-6
关键词
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资金
- Strategic Priority Research Program (B) of the Chinese Academy of Sciences [XDB41000000]
- Natural Science Foundation of China [41925017, 41721002]
- Fundamental Research Funds for the Central Universities [WK2080000144]
- UCL-Carnegie Postdoctoral Scholarship
- NSF [AST-1910955, EAR1942042]
Earth's volatile element content was largely established by volatile evaporation from molten planetesimals before Earth's formation, as indicated by sulfur isotope fractionation analysis and first-principles calculations.
How and when Earth's volatile content was established is controversial with several mechanisms postulated, including planetesimal evaporation, core formation and the late delivery of undifferentiated chondrite-like materials. The isotopes of volatile elements such as sulfur can be fractionated during planetary accretion and differentiation and thus are potential tracers of these processes. Using first-principles calculations, we examine sulfur isotope fractionation during core formation and planetesimal evaporation. We find no measurable sulfur isotope fractionation between silicate and metallic melts at core-forming conditions, indicating that the observed light sulfur isotope composition of the bulk silicate Earth relative to chondrites cannot be explained by metal-silicate fractionation. Our thermodynamic calculations show that sulfur evaporates mostly as H2S during planetesimal evaporation when nebular H-2 is present. The observed bulk Earth sulfur isotope signature and abundance can be reproduced by evaporative loss of about 90% sulfur mainly as H2S from molten planetesimals before nebular H-2 is dissipated. The heavy sulfur isotope composition of the Moon relative to the Earth is consistent with evaporative sulfur loss under 94-98% saturation condition during the Moon-forming giant impact. In summary, volatile evaporation from molten planetesimals before Earth's formation probably played a key role in establishing Earth's volatile element content. Earth's volatile element content was established largely by volatile evaporation from molten planetesimals before Earth's formation, according to first-principles calculations and examination of sulfur isotope fractionation.
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