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Thermal expansion of liquid Fe-S alloy at high pressure

Abstract : Local structure and density of liquid Fe-S alloys at high pressure have been determined in situ by combined angle and energy dispersive X-ray diffraction experiments in a multi-anvil apparatus, covering a large temperature and compositional range. Precise density measurements collected for increasing temperature allowed us to directly derive the thermal expansion coefficients for liquid Fe-S alloys as a function of composition. In turn, thermal expansion has been used to refine thermodynamic models and to address the crystallization regime of telluric planetary cores by comparing the adiabatic temperature gradient and the slope of the liquidus in the Fe-FeS system. For Fe-S cores of asteroids and small planetesimals, top-down solidification is the dominant scenario as the compositional domain for which the slope of the liquidus is greater than the adiabatic gradient is limited to a narrow portion on the Fe-rich side. However, bottom-up growth of the inner core is expected for S-poor cases, with this compositional domain expanding to more S-rich compositions with increasing pressure (size of the planetary body). In particular, bottom-up crystallization cannot be excluded for the Moon and Ganymede.
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https://hal.uca.fr/hal-03184365
Contributor : Sylvaine Jouhannel <>
Submitted on : Wednesday, March 31, 2021 - 8:34:02 AM
Last modification on : Friday, April 9, 2021 - 3:19:24 AM

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F. Xu, G. Morard, N. Guignot, A. Rivoldini, Geeth Manthilake, et al.. Thermal expansion of liquid Fe-S alloy at high pressure. Earth and Planetary Science Letters, Elsevier, 2021, 563, pp.116884. ⟨10.1016/j.epsl.2021.116884⟩. ⟨hal-03184365⟩

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