Fe-FeH Eutectic Melting Curve and the Estimates of Earth's Core Temperature and Composition

IF 3.9 2区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Journal of Geophysical Research: Solid Earth Pub Date : 2025-01-27 DOI:10.1029/2024jb029283

Shuhei Mita, Shoh Tagawa, Kei Hirose, Nagi Ikuta

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Abstract

Fe and FeH form a binary eutectic system above ∼40 GPa. Here we performed melting experiments in a laser-heated diamond-anvil cell and obtained the Fe-FeH eutectic melting curve between 52 and 175 GPa. Its extrapolation shows the eutectic temperature to be 4,350 K at the inner core boundary (ICB), which is lower than that in Fe-FeSi but is higher than those in the Fe-S, Fe-O, and Fe-C systems. In addition, its dT/dP slope is comparable to those of the melting curves of Fe and FeH endmembers, suggesting that the eutectic liquid composition changes little with increasing pressure and is about FeH_0.6 at the ICB pressure. We also estimated the effect of each light element on depressing the liquidus temperature at 330 GPa based on a combination of binary eutectic temperature and composition and found that the effect is large for C and S and small for H, O, and Si when considering the amount of each element that reduces a certain percentage of a liquid iron density. Furthermore, we searched for a set of possible outer core liquid composition and ICB temperature (the liquidus temperature of the former at 330 GPa should match the latter), which explains the outer core density deficit that depends on core temperature. The results demonstrate that relatively low core temperatures, lower than the solidus temperature of a pyrolitic lowermost mantle at the core-mantle boundary (CMB), are possible.

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来源期刊

Journal of Geophysical Research: Solid Earth Earth and Planetary Sciences-Geophysics

CiteScore

7.50

自引率

15.40%

发文量

559

期刊介绍： The Journal of Geophysical Research: Solid Earth serves as the premier publication for the breadth of solid Earth geophysics including (in alphabetical order): electromagnetic methods; exploration geophysics; geodesy and gravity; geodynamics, rheology, and plate kinematics; geomagnetism and paleomagnetism; hydrogeophysics; Instruments, techniques, and models; solid Earth interactions with the cryosphere, atmosphere, oceans, and climate; marine geology and geophysics; natural and anthropogenic hazards; near surface geophysics; petrology, geochemistry, and mineralogy; planet Earth physics and chemistry; rock mechanics and deformation; seismology; tectonophysics; and volcanology. JGR: Solid Earth has long distinguished itself as the venue for publication of Research Articles backed solidly by data and as well as presenting theoretical and numerical developments with broad applications. Research Articles published in JGR: Solid Earth have had long-term impacts in their fields. JGR: Solid Earth provides a venue for special issues and special themes based on conferences, workshops, and community initiatives. JGR: Solid Earth also publishes Commentaries on research and emerging trends in the field; these are commissioned by the editors, and suggestion are welcome.