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[SCG47-P08] Evaluation of Enstatite chondrite model based on melting relations in the system MgSiO3-SiO2
Keywords:Enstatite chondrite model, MgSiO3–SiO2 system, High pressure, Magma ocean, Mantle, Silicon content in the core
The available eutectic compositions in the system MgSiO3-SiO2 experimentally determined from 1 to 128 GPa indicate that the XSi of the melts produced from E-chondrite source materials are around 0.6, significantly higher than the current upper mantle, 0.43. To evaluate the E-chondrite model, taking into account the incorporation of Si into the core during core formation in a magma ocean, we estimated the range of Si content in the core assuming an E-chondrite model. Our results showed that Si content in the core would be between 2.7 to 8.6 wt.%, which is within the range of 2 to 9 wt.% Si in the core as predicted by metal-silicate element partitioning [7-9]. On the other hand, through determining the P wave velocity of liquid Fe–Si at the core–mantle boundary conditions based on inelastic X-ray scattering measurements in a laser-heated DAC, the estimated upper limit of silicon concentration in the outer core to be <1.9 wt.% [10]. Considering with the core density deficit and higher Si content in the core predicted by the metal-silicate element partitioning, Nakajima et al. [10] suggested that the present-day liquid outer core was depleted in silicon after crystallizing SiO2 (and MgSiO3) through the history of the Earth. Thus, our results indicate that the E-chondrite model could explain the bulk Earth composition if the Si depletion in the core has operated through Earth’s history.
References
[1] Javoy et al. 2010 Earth Planet. Sci. Lett. 293, 259–268. [2] Bowen and Anderson 1914 Am. J. Sci. 4th ser. 37, 487–500. [3] Dalton and Presnall 1997 Geochim. Cosmochim. Acta 61, 2367–2373. [4] Hudon et al. 2005 J. Petrol. 46, 1859–1880. [5] Moriguti et al. in press Am. Min. [6] Ozawa et al. 2018 Geophys. Res. Lett. DOI: 10.1029/2018GL079313. [7] Wood et al. 2009 Geochim. Cosmochim. Acta, 72, 1415–1426. [8] Rubie et al. 2011 Earth Planet. Sci. Lett. 301, 31–42. [9] Siebert et al. 2013 Science, 339, 1194–1197. [10] Nakajima et al. 2020 J. Geophys. Res. Solid Earth 125(6). DOI: 10.1029/2020JB019399.