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Abstract The motion of liquid iron (Fe) alloy materials in the outer core drives the dynamo, which generates Mercury's magnetic field. The assessment of core models requires laboratory measurements of the melting temperature of Fe alloys at high pressure. Here, we experimentally determined the melting curve of Fe9wt%Si and Fe17wt%Si up to 17 GPa using in situ and ex situ measurements of intermetallic fast diffusion that serves as the melting criterion in a large‐volume press. Our determined melting slopes are comparable with previous studies up to about 17 GPa. However, when extrapolated, our melting slopes significantly deviate from previous studies at higher pressures. For Mercury's core with a model composition of Fe9wt%Si, the melting temperature‐depth profile determined in our study is lower by ∼150–250 K when compared with theoretical calculations. Using the new melting curve of Fe9wt%Si and the electrical resistivity values from a previous study of Fe8.5wt%Si, we estimate that the electronic thermal conductivity of liquid Fe9wt%Si is 30 Wm−1K−1at the Mercury'sCMBpressure of 5 GPa and 37 Wm−1K−1at an assumedICBof 21 GPa, corresponding to heat flux values of 23 mWm−2and 32 mWm−2, respectively. These values provide new constraints on the core models.
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High Pressure Melting Curve of Fe Determined by Inter‐Metallic Fast Diffusion Technique
Abstract The heat extracted from the core by the overlying mantle across the core‐mantle boundary controls the thermal evolution of the core. This in turn leads to the solidification of the inner core in association with the exsolution of light alloying elements into the liquid outer core. Although the temperature (T) at the inner core boundary (ICB) would be adjusted to account for the effects of the light elements, the melting T of Fe places an upper bound at the ICB and it is a vital point in the thermal profile of the core. Here, we determine the melting T of Fe in the multi‐anvil press by characterizing the interface of Fe‐W interaction. Our data place a tighter constraint on the melting curve of Fe between 8 and 21 GPa, that is directly applicable to small planetary bodies and serves as an anchor for melting curve of Fe at higher pressure.
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- Award ID(s):
- 2022492
- PAR ID:
- 10419167
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 50
- Issue:
- 6
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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