WileyActa Medica Okayama1086-93792025The effect of pressure on dihedral angle between liquid Fe]S and orthopyroxene: Implication for percolative core formation in planetesimals and planetary embryosENTakumiMiuraDepartment of Earth and Space Science, Osaka UniversityHidenoriTerasakiDepartment of Earth Sciences, Okayama UniversityHyuTakakiDepartment of Earth Sciences, Okayama UniversityKotaroKobayashiDepartment of Earth Sciences, Okayama UniversityGeoffrey DavidBromileySchool of Geosciences, The University of EdinburghTakashiYoshinoInstitute for Planetary Materials, Okayama UniversityDuring 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.No potential conflict of interest relevant to this article was reported.AIP PublishingActa Medica Okayama0034-67489632025Development of density measurement at high pressure and high temperature using the x-ray absorption method combined with laser-heated diamond anvil cell033907ENHidenoriTerasakiDepartment of Earth Sciences, Okayama UniversityHiroyukiKaminaDepartment of Earth Sciences, Okayama UniversitySaori I.KawaguchiJapan Synchrotron Radiation Research Institute, SPring-8TadashiKondoDepartment of Earth and Space Science, Osaka UniversityKoMoriokaDepartment of Earth Sciences, Okayama UniversityRyoTsuruokaDepartment of Earth and Space Science, Osaka UniversityMoeSakuraiDepartment of Earth Sciences, Okayama UniversityAkiraYonedaDepartment of Earth and Space Science, Osaka UniversitySeijiKamadaAD Science IncorporationNaohisaHiraoJapan Synchrotron Radiation Research Institute, SPring-8The densities of liquid materials at high pressures and high temperatures are important information to understand the elastic behavior of liquids at extreme conditions, which is closely related to the formation and evolution processes of the Earth and planetary interiors. The x-ray absorption method is an effective method to measure the density of non-crystalline materials at high pressures. However, the temperature condition of the x-ray absorption method using a diamond anvil cell (DAC) has been limited to 720 K to date. To significantly expand the measurable temperature condition of this method, in this study, we developed a density measurement technique using the x-ray absorption method in combination with a laser-heated DAC. The density of solid Ni was measured up to 26 GPa and 1800 K using the x-ray absorption method and evaluated by comparison with the density obtained from the x-ray diffraction. The density of solid Ni with a thickness >17 m was determined with an accuracy of 0.01%–2.2% (0.001–0.20 g/cm3) and a precision of 0.8%–1.8% (0.07–0.16 g/cm3) in the x-ray absorption method. The density of liquid Ni was also determined to be 8.70 } 0.15–8.98 } 0.38 g/cm3 at 16–23 GPa and 2230–2480 K. Consequently, the temperature limit of the x-ray absorption method can be expanded from 720 to 2480 K by combining it with a laser-heated DAC in this study.No potential conflict of interest relevant to this article was reported.WileyActa Medica Okayama1086-93795962024Wetting property of Fe]S melt in solid core: Implication for the core crystallization process in planetesimals13141328ENShioriMatsubaraDepartment of Earth Sciences, Graduate School of Science and Technology, Okayama UniversityHidenoriTerasakiDepartment of Earth Sciences, Graduate School of Science and Technology, Okayama UniversityTakashiYoshinoInstitute for Planetary Materials, Okayama UniversitySatoruUrakawaDepartment of Earth Sciences, Graduate School of Science and Technology, Okayama UniversityDaisukeYumitoriDepartment of Earth Sciences, Graduate School of Science and Technology, Okayama UniversityIn differentiated planetesimals, the liquid core starts to crystallize during secular cooling, followed by the separation of liquid–solid phases in the core. The wetting property between liquid and solid iron alloys determines whether the core melts are trapped in the solid core or they can separate from the solid core during core crystallization. In this study, we performed high-pressure experiments under the conditions of the interior of small bodies (0.5–3.0 GPa) to study the wetting property (dihedral angle) between solid Fe and liquid Fe-S as a function of pressure and duration. The measured dihedral angles are approximately constant after 2 h and decrease with increasing pressure. The dihedral angles range from 30 to 48, which are below the percolation threshold of 60 at 0.5–3.0 GPa. The oxygen content in the melt decreases with increasing pressure and there are strong positive correlations between the S + O or O content and the dihedral angle. Therefore, the change in the dihedral angle is likely controlled by the O content of the Fe-S melt, and the dihedral angle tends to decrease with decreasing O content in the Fe-S melt. Consequently, the Fe-S melt can form interconnected networks in the solid core. In the obtained range of the dihedral angle, a certain amount of the Fe-S melt can stably coexist with solid Fe, which would correspond to the gtrapped melth in iron meteorites. Excess amounts of the melt would migrate from the solid core over a long period of core crystallization in planetesimals.No potential conflict of interest relevant to this article was reported.Springer Science and Business Media LLCActa Medica Okayama0342-17915032023Sound velocity and elastic properties of Fe–Ni–S–Si liquid: the effects of pressure and multiple light elements19ENIoriYamadaDepartment of Earth and Space Science, Osaka UniversityHidenoriTerasakiDepartment of Earth Sciences, Okayama UniversitySatoruUrakawaDepartment of Earth Sciences, Okayama UniversityTadashiKondoDepartment of Earth and Space Science, Osaka UniversityAkihikoMachidaSynchrotron Radiation Research Center, National Institutes for Quantum Science and Technology (QST)YoshinoriTangeJapan Synchrotron Radiation Research InstituteYujiHigoJapan Synchrotron Radiation Research InstituteFe–Ni–S–Si alloy is considered to be one of the plausible candidates of Mercury core material. Elastic properties of Fe–Ni–S–Si liquid are important to reveal the density profile of the Mercury core. In this study, we measured the P-wave velocity (VP) of Fe–Ni–S–Si (Fe73Ni10S10Si7, Fe72Ni10S5Si13, and Fe67Ni10S10Si13) liquids up to 17 GPa and 2000 K to study the effects of pressure, temperature, and multiple light elements (S and Si) on the VP and elastic properties.<br>
The VP of Fe–Ni–S–Si liquids are less sensitive to temperature. The effect of pressure on the VP are close to that of liquid Fe and smaller than those of Fe–Ni–S and Fe–Ni–Si liquids. Obtained elastic properties are KS0 = 99.1(9.4) GPa, KSf = 3.8(0.1) and 0 =6.48 g/cm3 for S-rich Fe73Ni10S10Si7 liquid and KS0 = 112.1(1.5) GPa, KSf = 4.0(0.1) and 0=6.64 g/cm3 for Si-rich Fe72Ni10S5Si13 liquid. The VP of Fe–Ni–S–Si liquids locate in between those of Fe–Ni–S and Fe–Ni–Si liquids. This suggests that the effect of multiple light element (S and Si) on the VP is suppressed and cancel out the effects of single light elements (S and Si) on the VP. The effect of composition on the EOS in the Fe–Ni–S–Si system is indispensable to estimate the core composition combined with the geodesy data of upcoming Mercury mission.No potential conflict of interest relevant to this article was reported.ElsevierActa Medica Okayama003192013112021Thermocapillary effects in two-phase medium and applications to metal-silicate separation106640ENYanickRicardUniversité de Lyon, ENSL, UCBL, Laboratoire LGLTPEStéphaneLabrosseUniversité de Lyon, ENSL, UCBL, Laboratoire LGLTPEHidenoriTerasakiOkayama University, Department of Earth SciencesDavidBercoviciYale University, Department of Earth & Planetary Sciences The separation of a liquid phase from a solid but deformable matrix made of mineral grains is controlled at small scale by surface tension. The role of interfacial surface tension is twofold as it explains how a small volume of liquid phase can infiltrate the grain boundaries, be distributed and absorbed in the matrix, but after complete wetting of the grains, surface tension favors the self-separation of the liquid and solid phases. Another consequence of surface tension is the existence of Marangoni forces, which are related to the gradients of surface tension that are are usually due to temperature variations. In this paper, using a continuous multi-phase formalism we clarify the role of these different effects and quantify their importances at the scale of laboratory experiments and in planets. We show that Marangoni forces can control the liquid metal-solid silicate phase separation in laboratory experiments. The Marangoni force might help to maintain the presence of metal at the surface of asteroids and planetesimals that have undergone significant melting.No potential conflict of interest relevant to this article was reported.