کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
6428093 1634729 2015 13 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Planetary and meteoritic Mg/Si and δ30Si variations inherited from solar nebula chemistry
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات علوم زمین و سیاره ای (عمومی)
پیش نمایش صفحه اول مقاله
Planetary and meteoritic Mg/Si and δ30Si variations inherited from solar nebula chemistry
چکیده انگلیسی


- Angrites have Si isotopic composition similar to the silicate Earth.
- Gas-forsterite nebular fractionation controlled Mg/Si-δ30Si values of planets.
- The δ30Si value of the silicate Earth is consistent with ∼3.6 wt% Si in the core.
- δ30Si values of planetary mantles are proxies for Mg/Si ratios of bulk planets.

The 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 ∼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 ∼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.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Earth and Planetary Science Letters - Volume 427, 1 October 2015, Pages 236-248
نویسندگان
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