期刊
EARTH AND PLANETARY SCIENCE LETTERS
卷 373, 期 -, 页码 75-82出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.epsl.2013.04.012
关键词
silicon isotopes; eucrites; Vesta; core formation
资金
- NASA [NNX12AD88G, NNX12AH70G]
- McDonnell Center for Space Sciences
- NASA [53369, NNX12AH70G, 19752, NNX12AD88G] Funding Source: Federal RePORTER
Core formation is the main differentiation event in the history of a planet. However, the chemical composition of planetary cores and the physicochemical conditions prevailing during core formation remain poorly understood. The asteroid 4-Vesta is the smallest extant planetary body known to have differentiated a metallic core. Howardite, Eucrite, Diogenite (HED) meteorites, which are thought to sample 4-Vesta, provide us with an opportunity to study core formation in planetary embryos. Partitioning of elements between the core and mantle of a planet fractionates their isotopes according to formation conditions. One such element, silicon, shows large isotopic fractionation between metal and silicate, and its partitioning into a metallic core is only possible under very distinctive conditions of pressure, oxygen fugacity and temperature. Therefore, the silicon isotope system is a powerful tracer with which to study core formation in planetary bodies. Here we show through high-precision measurement of Si stable isotopes that HED meteorites are significantly enriched in the heavier isotopes compared to chondrites. This is consistent with the core of 4-Vesta containing at least 1 wt% of Si, which in turn suggests that 4-Vesta's differentiation occurred under more reducing conditions (Delta IW similar to-4) than those previously suggested from analysis of the distribution of moderately siderophile elements in HEDs. (C) 2013 Elsevier B.V. All rights reserved.
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