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| Main Authors: | , , , , , |
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| Format: | Artículo Open Access |
| Published: |
Wiley
2025
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| Online Access: | https://onlinelibrary.wiley.com/doi/10.1111/maps.70068 |
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Table of Contents:
- The effect of pressure on dihedral angle between liquid Fe‐S and orthopyroxene: Implication for percolative core formation in planetesimals and planetary embryos Takumi Miura Hidenori Terasaki Hyu Takaki Kotaro Kobayashi Geoffrey David Bromiley Takashi Yoshino Meteoritics & Planetary Science Abstract During precursor stages of planet formation, many planetesimals and planetary embryos are considered to have differentiated, forming an iron‐alloy core and silicate mantle. Percolation of liquid iron‐alloy in solid silicates is one of the major possible differentiation processes in these small bodies. Based on the dihedral angles between Fe‐S melts and olivine, a criterion for determining whether melt can percolate through a solid, it has been reported that Fe‐S melt can percolate through olivine matrices below 3 GPa in an oxidized environment. However, the dihedral angle between Fe‐S melts and orthopyroxene (opx), the second most abundant mineral in the mantles of small bodies, has not yet been determined. In this study, high‐pressure and high‐temperature experiments were conducted under the conditions of planetesimal and planetary embryo interiors, 0.5–5.0 GPa, to determine the effect of pressure on the dihedral angle between Fe‐S melts and opx. Dihedral angles tend to increase with pressure, although the pressure dependence is markedly reduced above 4 GPa. The dihedral angle is below the percolation threshold of 60° at pressures below 1.0–1.5 GPa, indicating that percolative core formation is possible in opx‐rich interiors of bodies where internal pressures are lower than 1.0–1.5 GPa. The oxygen content of Fe‐S melt decreases with increasing pressure. High oxygen contents in Fe‐S melt reduce interfacial tension between Fe‐S melt and opx, resulting in reduced dihedral angles at low pressure. Combined with previous results for dihedral angle variation of the olivine/Fe‐S system, percolative core formation possibly occurs throughout bodies up to a radius of 1340 km for an olivine‐dominated mantle, and up to 770 km for an opx‐dominated mantle, in the case of S‐rich cores segregating under relatively oxidizing conditions. For mantles of small bodies in which abundant olivine and opx coexist, the mineral with the largest volume fraction and/or smallest grain size will allow formation of interconnected mineral channels, and, therefore, the wetting property of this mineral determines the wettability of the melt, that is, controls core formation. 10.1111/maps.70068 http://creativecommons.org/licenses/by-nc-nd/4.0/