start-ver=1.4 cd-journal=joma no-vol=53 cd-vols= no-issue=14 article-no= start-page=e2026GL121981 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2026 dt-pub=20260710 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Calcium Solubility of Bridgmanite in Subducted Basalt in Earth's Lower Mantle en-subtitle= kn-subtitle= en-abstract= kn-abstract=The calcium solubility in bridgmanite and the resulting abundance of davemaoite under lower-mantle pressure-temperature conditions have been under debate following a recent report of extensive calcium dissolution in bridgmanite. We experimentally investigated the calcium solubility in bridgmanite in a basaltic composition at pressures up to 125 GPa and temperatures up to 3,520 K. Our experimental data are modeled thermodynamically along the bridgmanite-davemaoite solvus to quantify the calcium solubility in bridgmanite and the davemaoite proportion in basaltic and pyrolitic assemblages along lower mantle geotherms. Our results indicate that bridgmanite hosts only 0.001?0.03 Ca cations per formula unit in the lower mantle, while davemaoite remains as an abundant mineral, accounting for 8 and 25 vol% of pyrolitic and basaltic mineralogical models, respectively, along representative lower-mantle geotherms. Our thermoelastic modeling further indicates that the effect of calcium dissolution on the density and bulk sound velocity of lower-mantle assemblages is negligible. en-copyright= kn-copyright= en-aut-name=ZhangChengwei en-aut-sei=Zhang en-aut-mei=Chengwei kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=El GhazaouiElias en-aut-sei=El Ghazaoui en-aut-mei=Elias kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=CharitonStella en-aut-sei=Chariton en-aut-mei=Stella kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=PrakapenkaVitali B. en-aut-sei=Prakapenka en-aut-mei=Vitali B. kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=LiLuo en-aut-sei=Li en-aut-mei=Luo kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=ZhangYanyao en-aut-sei=Zhang en-aut-mei=Yanyao kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=LinJung]Fu en-aut-sei=Lin en-aut-mei=Jung]Fu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= affil-num=1 en-affil=Department of Earth and Planetary Sciences, Jackson School of Geosciences The University of Texas at Austin kn-affil= affil-num=2 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=3 en-affil=School of Earth and Environmental Sciences, Seoul National University kn-affil= affil-num=4 en-affil=Center for Advanced Radiation Sources, The University of Chicago kn-affil= affil-num=5 en-affil=Center for Advanced Radiation Sources, The University of Chicago kn-affil= affil-num=6 en-affil=Department of Earth and Planetary Sciences, Jackson School of Geosciences The University of Texas at Austin kn-affil= affil-num=7 en-affil=Earth and Planetary Sciences, Stanford University kn-affil= affil-num=8 en-affil=Department of Earth and Planetary Sciences, Jackson School of Geosciences The University of Texas at Austin kn-affil= END start-ver=1.4 cd-journal=joma no-vol=16 cd-vols= no-issue=1 article-no= start-page=1866 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2025 dt-pub=20250221 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Grain boundary diffusion cannot explain the W isotope heterogeneities of the deep mantle en-subtitle= kn-subtitle= en-abstract= kn-abstract=The low 182W/184W and high 3He/4He in some ocean island basalts compared to the bulk mantle values may derive from the Earthfs core through long-term core-mantle interactions. It has been proposed that the grain boundary diffusion of siderophile elements is an efficient mechanism for core-mantle interaction and may effectively modify the W isotopic compositions of the plume-source mantle. In this study, we perform large-scale molecular dynamics simulations driven by machine learning potentials of ab initio quality to investigate the diffusion of W along ferropericlase grain boundaries and in (Mg,Fe)O liquid. Here we show that the diffusion of W is sluggish under core-mantle boundary conditions, and thus is unlikely to have observable impacts on the W isotopic compositions of terrestrial igneous rocks. en-copyright= kn-copyright= en-aut-name=PengYihang en-aut-sei=Peng en-aut-mei=Yihang kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=DengJie en-aut-sei=Deng en-aut-mei=Jie kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= affil-num=1 en-affil=Department of Geosciences, Princeton University kn-affil= affil-num=2 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=3 en-affil=Department of Geosciences, Princeton University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=16 cd-vols= no-issue=1 article-no= start-page=3239 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2025 dt-pub=20250404 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Low melt viscosity enables melt doublets above the 410-km discontinuity en-subtitle= kn-subtitle= en-abstract= kn-abstract=Seismic and magnetotelluric studies suggest hydrous silicate melts atop the 410?km discontinuity form 30?100?km thick layers. Importantly, in some regions, two layers are observed. These stagnant layers are related to their comparable density to the surrounding mantle, but their formation mechanisms and detailed structures remain unclear. Here we report a large decrease of silicate melt viscosity at ~14?GPa, from 96(5) to 11.7(6) mPa?s, as water content increases from 15.5 to 31.8?mol% H?O. Such low viscosities facilitate rapid segregation of melt, which would typically prevent thick layer accumulation. Our 1D finite element simulations show that continuous dehydration melting of upwelling mantle material produces a primary melt layer above 410?km and a secondary layer at the depth of equal mantle-melt densities. These layers can merge into a single thick layer under low density contrasts or high upwelling rates, explaining both melt doublets and thick single layers. en-copyright= kn-copyright= en-aut-name=XieLongjian en-aut-sei=Xie en-aut-mei=Longjian kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=AndraultDenis en-aut-sei=Andrault en-aut-mei=Denis kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=HanCunrui en-aut-sei=Han en-aut-mei=Cunrui kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=HammondJames O. S. en-aut-sei=Hammond en-aut-mei=James O. S. kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=XuFang en-aut-sei=Xu en-aut-mei=Fang kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=ZhaoBin en-aut-sei=Zhao en-aut-mei=Bin kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=LordOliver T. en-aut-sei=Lord en-aut-mei=Oliver T. kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= en-aut-name=FeiYingwei en-aut-sei=Fei en-aut-mei=Yingwei kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=9 ORCID= en-aut-name=FalvardSimon en-aut-sei=Falvard en-aut-mei=Simon kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=10 ORCID= en-aut-name=KakizawaSho en-aut-sei=Kakizawa en-aut-mei=Sho kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=11 ORCID= en-aut-name=TsujinoNoriyoshi en-aut-sei=Tsujino en-aut-mei=Noriyoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=12 ORCID= en-aut-name=HigoYuji en-aut-sei=Higo en-aut-mei=Yuji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=13 ORCID= en-aut-name=HenryLaura en-aut-sei=Henry en-aut-mei=Laura kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=14 ORCID= en-aut-name=GuignotNicolas en-aut-sei=Guignot en-aut-mei=Nicolas kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=15 ORCID= en-aut-name=DobsonDavid P. en-aut-sei=Dobson en-aut-mei=David P. kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=16 ORCID= affil-num=1 en-affil=Center for High Pressure Science & Technology Advanced Research kn-affil= affil-num=2 en-affil=Universit? Clermont Auvergne, CNRS, IRD, OPGC, Laboratoire Magmas et Volcans kn-affil= affil-num=3 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=4 en-affil=School of Natural Sciences, Birkbeck, University of London kn-affil= affil-num=5 en-affil=School of Natural Sciences, Birkbeck, University of London kn-affil= affil-num=6 en-affil=School of Earth Sciences, Zhejiang University kn-affil= affil-num=7 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=8 en-affil=School of Earth Sciences, University of Bristol kn-affil= affil-num=9 en-affil=Earth & Planets Laboratory, Carnegie Institution for Science kn-affil= affil-num=10 en-affil=Universit? Clermont Auvergne, CNRS, IRD, OPGC, Laboratoire Magmas et Volcans kn-affil= affil-num=11 en-affil=Japan Synchrotron Radiation Research Institute kn-affil= affil-num=12 en-affil=Japan Synchrotron Radiation Research Institute kn-affil= affil-num=13 en-affil=Japan Synchrotron Radiation Research Institute kn-affil= affil-num=14 en-affil=Synchrotron SOLEIL kn-affil= affil-num=15 en-affil=Synchrotron SOLEIL kn-affil= affil-num=16 en-affil=Department of Earth Sciences, University College London kn-affil= END start-ver=1.4 cd-journal=joma no-vol=78 cd-vols= no-issue=1 article-no= start-page=57 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2026 dt-pub=20260216 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Electrical conductivity measurements of rhyolitic glass at high pressure and high temperature en-subtitle= kn-subtitle= en-abstract= kn-abstract=We performed electrical conductivity measurements of rhyolite glasses across the glass transition temperature at 1 GPa. Our experimental data show that, in the Arrhenius plot, the conductivity of rhyolite with 0.2 wt% H2O has an inflection point between around 760 K, while for rhyolite with 4.9 wt% H2O the gradient changes between 685 and 825 K. These inflection points correlate with the glass transition temperature, and are compared with results of previous experiments. The degree of welding of clastic and hydrous rock can be constrained by estimating glass transition temperatures of volcanic rocks combined with measurements of electrical conductivity structures obtained from electromagnetic soundings beneath volcanic bodies. This, in turn, can be used to aid predictions of volcanic eruption. en-copyright= kn-copyright= en-aut-name=HaraguchiYusuke en-aut-sei=Haraguchi en-aut-mei=Yusuke kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=Fuji-TaKiyoshi en-aut-sei=Fuji-Ta en-aut-mei=Kiyoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=NakamotoMasashi en-aut-sei=Nakamoto en-aut-mei=Masashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=SuzukiMasanori en-aut-sei=Suzuki en-aut-mei=Masanori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=TanakaToshihiro en-aut-sei=Tanaka en-aut-mei=Toshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= affil-num=1 en-affil=Graduate School of Engineering, The University of Osaka kn-affil= affil-num=2 en-affil=Graduate School of Engineering, The University of Osaka kn-affil= affil-num=3 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=4 en-affil=Graduate School of Engineering, The University of Osaka kn-affil= affil-num=5 en-affil=Graduate School of Engineering, The University of Osaka kn-affil= affil-num=6 en-affil=Graduate School of Engineering, The University of Osaka kn-affil= en-keyword=Electrical conductivity kn-keyword=Electrical conductivity en-keyword=Glass transition temperature kn-keyword=Glass transition temperature en-keyword=melt kn-keyword=melt en-keyword=clastics kn-keyword=clastics END start-ver=1.4 cd-journal=joma no-vol=181 cd-vols= no-issue=7 article-no= start-page=55 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2026 dt-pub=20260610 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Electrical conductivity of geikielite (MgTiO3) at lunar mantle conditions: the role of metastable defect states and thermal history en-subtitle= kn-subtitle= en-abstract= kn-abstract=The electrical conductivity of geikielite (MgTiO3), the Mg endmember of the ilmenite group, was investigated at mantle pressures of 2 and 4.3 GPa and temperatures up to 1850 K using a Kawai-type multi-anvil apparatus. Electrical conductivity increases by more than seven orders of magnitude between 800 and 1700 K and exhibits two distinct conduction regimes separated by a transition at ~?1500?1700 K. The high-temperature regime is characterized by large activation enthalpies (ƒ¢H???1.8?2.3 eV), whereas the low-temperature regime shows much lower values (ƒ¢H???0.19?0.31 eV). Stepwise annealing experiments reveal a pronounced thermal-history dependence: repeated heating to progressively higher maximum temperatures (Tmax) produces metastable conductivity states, enhancing low-temperature conductivity by up to six orders of magnitude and systematically reducing activation enthalpy. This behavior indicates activation and freezing-in of defect-related charge carriers. Negative activation volumes further support a hopping-type conduction mechanism. Although Ti?? was not directly detected, the combination of reducing experimental conditions, Al?? impurities (~?0.35 wt% Al?O?), low activation energies, and strong thermal memory is most consistent with small-polaron hopping involving Ti???Ti?? pairs. At lunar core?mantle boundary temperatures, geikielite reaches conductivities of 10??10? S/m, exceeding those of olivine and overlapping estimates for the lunar low-velocity zone. Our results demonstrate that solid-state Ti-rich oxides can produce high electrical conductivity without partial melting, providing new constraints on the thermochemical evolution and electromagnetic structure of the lunar interior. en-copyright= kn-copyright= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YamazakiDaisuke en-aut-sei=Yamazaki en-aut-mei=Daisuke kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=Institute for Planetary Materials, Okayama University kn-affil= en-keyword=Electrical conductivity kn-keyword=Electrical conductivity en-keyword=Geikielite kn-keyword=Geikielite en-keyword=High-pressure and high-temperature experiment kn-keyword=High-pressure and high-temperature experiment en-keyword=Ilmenite kn-keyword=Ilmenite en-keyword=Metastable defect states kn-keyword=Metastable defect states END start-ver=1.4 cd-journal=joma no-vol=53 cd-vols= no-issue=2 article-no= start-page=18 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2026 dt-pub=20260524 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=High-pressure spectroscopic investigation of ƒÃ-FeOOH: toward a better understanding of pressure-induced hydrogen-bond symmetrization en-subtitle= kn-subtitle= en-abstract= kn-abstract=High-pressure spectroscopic measurements of ƒÃ-FeOOH were conducted up to ~?65 GPa at room temperature in diamond anvil cells. The pressure evolution of the Raman vibrational modes confirms that a hydrogen-bond-symmetrization-induced phase transition from P21nm to Pnnm occurs at ~?18 GPa. Infrared (IR) spectroscopic measurements suggest that the Pnnm phase has a disordered hydrogen state, and no spectroscopic evidence for fully centered hydrogen bonds is observed within the investigated pressure range. Above ~?45 GPa, Fe3+ in ƒÃ-FeOOH undergoes a high-spin to low-spin transition as indicated by a reduction of the unit cell volume, together with reductions in IR transmitted and Raman signals. These results demonstrate that ƒÃ?FeOOH preserves a disordered hydrogen?bond configuration up to at least 45 GPa, whereas ƒÂ-AlOOH transforms to a centered hydrogen-bond configuration at ~?18 GPa. This compositional contrast suggests that Fe?bearing oxyhydroxides follow a distinct evolution of hydrogen bonding under compression, providing insight into hydrogen behavior in deep Earth materials. en-copyright= kn-copyright= en-aut-name=MashinoIzumi en-aut-sei=Mashino en-aut-mei=Izumi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YamashitaShigeru en-aut-sei=Yamashita en-aut-mei=Shigeru kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= affil-num=1 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=3 en-affil=Institute for Planetary Materials, Okayama University kn-affil= en-keyword=ƒÃ-FeOOH kn-keyword=ƒÃ-FeOOH en-keyword=High pressure kn-keyword=High pressure en-keyword=Spin transition kn-keyword=Spin transition en-keyword=Hydrogen bond symmetrization kn-keyword=Hydrogen bond symmetrization END start-ver=1.4 cd-journal=joma no-vol=687 cd-vols= no-issue= article-no= start-page=120087 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2026 dt-pub=202608 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Phase diagram of Fe-C-S ternary system under planetary core conditions en-subtitle= kn-subtitle= en-abstract= kn-abstract=High-pressure, high-temperature experiments were conducted to investigate melting relations and phase assemblages in the Fe-C-S ternary system at 5 and 15 GPa, covering a temperature range of 1300?1900 K, conditions directly relevant to the Moonfs and Mercuryfs cores. At 1300 K, the system is primarily governed by Fe-S eutectic melting, exhibiting notable complexity in the carbon-rich and sulfur-poor regions. With increasing temperature, the phase diagram simplifies: at 5 GPa and 1700 K, the Fe-Fe?C-FeS system features three regions (Fe+L, C + L, and L). Similar phase assemblages are observed at 15 GPa, with Fe7C3 and diamond replacing Fe3C and graphite, respectively. Extensive Fe+L, C + L, and L regions are observed at 1900 K.
For a Moonfs core composed of a Fe-C-S alloy, nearly pure Fe is the only viable inner core phase above 1700 K. Below this temperature, both Fe and Fe?C are potential solid inner core phases, depending on carbon content; a two-phase solid inner core is also theoretically possible. The inferred compositions of the outer core suggest densities of 6200?7300 kg/m?, with tighter constraints for models featuring an Fe?C core.
At Mercury-relevant pressures, either Fe or Fe?C? may form the solid inner core, again depending on carbon content. If the inner core is nearly pure Fe, the liquid outer core density ranges from 7300 to 7900 kg/m?. In both scenarios, a gsnowh regime is plausible, though with distinct settling times. The ternary phase diagram indicates that Mercury is likely to develop a structurally layered inner core during secular cooling.
en-copyright= kn-copyright= en-aut-name=ZhaoBin en-aut-sei=Zhao en-aut-mei=Bin kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=ZhuJintao en-aut-sei=Zhu en-aut-mei=Jintao kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=AntonangeliDaniele en-aut-sei=Antonangeli en-aut-mei=Daniele kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=MorardGuillaume en-aut-sei=Morard en-aut-mei=Guillaume kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=ChenQi en-aut-sei=Chen en-aut-mei=Qi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= affil-num=1 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=3 en-affil=Mus?um National dfHistoire Naturelle, Sorbonne Universit?, UMR CNRS 7590, Institut de Min?ralogie, de Physique des Mat?riaux et de Cosmochimie, IMPMC kn-affil= affil-num=4 en-affil=Mus?um National dfHistoire Naturelle, Sorbonne Universit?, UMR CNRS 7590, Institut de Min?ralogie, de Physique des Mat?riaux et de Cosmochimie, IMPMC kn-affil= affil-num=5 en-affil=Center for Advanced Radiation Sources, University of Chicago kn-affil= affil-num=6 en-affil=Institute for Planetary Materials, Okayama University kn-affil= en-keyword=planetary core kn-keyword=planetary core en-keyword=phase diagram kn-keyword=phase diagram en-keyword=multi-anvil experiments kn-keyword=multi-anvil experiments en-keyword=iron alloy kn-keyword=iron alloy END start-ver=1.4 cd-journal=joma no-vol=7 cd-vols= no-issue=1 article-no= start-page=265 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2026 dt-pub=20260325 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Stability and distribution of dense hydrous magnesium silicates in the mantle transition zone under low water activity conditions en-subtitle= kn-subtitle= en-abstract= kn-abstract=Water plays a central role in controlling the physical and chemical properties of Earthfs deep interior. It remains uncertain how water is stored in subducting slabs within the mantle transition zone, between depths of about 410 and 660 kilometers, and whether dense hydrous magnesium silicates act as major water carriers to greater depths. Here we report high-pressure and high-temperature laboratory experiments on the Mg-Si-H system at pressures of 16 and 21.5?GPa and a temperature of 1400?K to evaluate hydrous phase stability under transition zone conditions. We find that when bulk water content is below 1.22?wt%, H2O is predominantly incorporated into wadsleyite and ringwoodite rather than forming dense hydrous magnesium silicates. Because estimated water contents in subducted oceanic slabs are typically lower than one weight percent, formation of these silicates is unlikely, suggesting that the mantle transition zone may restrict large scale water transport into the lower mantle. en-copyright= kn-copyright= en-aut-name=SongYunke en-aut-sei=Song en-aut-mei=Yunke kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=GuoXinzhuan en-aut-sei=Guo en-aut-mei=Xinzhuan kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=ZhaiKuan en-aut-sei=Zhai en-aut-mei=Kuan kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=GuoWei en-aut-sei=Guo en-aut-mei=Wei kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= affil-num=1 en-affil=Key Laboratory of High-temperature and High-pressure Study of the Earthfs Interior, Institute of Geochemistry, Chinese Academy of Sciences kn-affil= affil-num=2 en-affil=State Key Laboratory of Critical Mineral Research and Exploration, Institute of Geochemistry, Chinese Academy of Sciences kn-affil= affil-num=3 en-affil=Key Laboratory of High-temperature and High-pressure Study of the Earthfs Interior, Institute of Geochemistry, Chinese Academy of Sciences kn-affil= affil-num=4 en-affil=State Key Laboratory of Geomicrobiology and Environmental Changes, School of Earth Sciences, China University of Geosciences (Wuhan) kn-affil= affil-num=5 en-affil=Institute for Planetary Materials, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=53 cd-vols= no-issue=5 article-no= start-page=e2025GL119568 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2026 dt-pub=20260303 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Electrical Conductivity of Amorphous and Molten CaCO3 at High Pressures and Its Implications for Mantle Conductivity Anomalies en-subtitle= kn-subtitle= en-abstract= kn-abstract=Impedance spectrometry experiments have been conducted on CaCO3 up to 15 GPa and 2,100 K to identify its state under high pressure. The melting temperature of CaCO3 was also determined by the falling of a Re sphere observed via X-ray radiography. The phase transition from aragonite to the amorphous phase does not cause a leap in the Electrical conductivity (EC), while a drastic increase in the EC, by 1.5?2.0 log units, only occurs with the onset of melting. The EC of amorphous CaCO3 is comparable to other hydrous mantle minerals at similar pressure and temperature conditions. The required fraction of amorphous CaCO3 implies that it can be excluded from the potential origins responsible for the observed high EC anomalies in the upper mantle. If the conductivity anomalies are induced by the presence of carbonate, a low-degree melting of carbonate-bearing peridotite is anticipated. en-copyright= kn-copyright= en-aut-name=ZhaoBin en-aut-sei=Zhao en-aut-mei=Bin kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=ChenQi en-aut-sei=Chen en-aut-mei=Qi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=YuTony en-aut-sei=Yu en-aut-mei=Tony kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=ZhangDongzhou en-aut-sei=Zhang en-aut-mei=Dongzhou kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=ChenBin en-aut-sei=Chen en-aut-mei=Bin kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=WangYanbin en-aut-sei=Wang en-aut-mei=Yanbin kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= affil-num=1 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=3 en-affil=Center for Advanced Radiation Sources, The University of Chicago kn-affil= affil-num=4 en-affil=Center for Advanced Radiation Sources, The University of Chicago kn-affil= affil-num=5 en-affil=Center for Advanced Radiation Sources, The University of Chicago kn-affil= affil-num=6 en-affil=School of Ocean and Earth Science and Technology, University of Hawaii at Manoa kn-affil= affil-num=7 en-affil=Center for Advanced Radiation Sources, The University of Chicago kn-affil= END start-ver=1.4 cd-journal=joma no-vol=131 cd-vols= no-issue=1 article-no= start-page=e2025JB033390 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2026 dt-pub=202601 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Electrical Conductivity of Carbonatite Melts to 20?GPa: Constraints on Partial Melting Atop the 410]km Discontinuity and in the Lower Mantle Transition Zone en-subtitle= kn-subtitle= en-abstract= kn-abstract=Deep-origin carbonatite melts are considered to be the products of partial-melting of the oceanic crust in the subduction zones. In this study, we conducted electrical conductivity (EC) measurements on two samples, the composition of which resemble the partial-melting products atop the 410-km discontinuity and in the lower part of the transition zone. The EC of carbonatite melts was investigated using impedance spectroscopy combined with a multi-anvil press up to 20 GPa. Pressure has a great effect on the EC of the carbonatite melts. While the EC dropped overall by 0.6 log unit from 3 to 20 GPa for varying compositions, the pressure effect becomes weaker above 10 GPa. The Hashin-Shtrikman mixing model indicates that melt fraction of 0?0.3 vol% is necessary to account for the EC atop the 410-km discontinuity beneath NE China, north Philippine Sea, north Pacific, and Australian craton. However, this value soars to 1?4.5 vol% for the lower part of the transition zone in the same regions, and further increases to 3.7?7.3 vol% for cold subduction regions if the slab surface temperature is 300 K lower. The difference in the needed melt fraction at different depths implies that the magnitude of partial melting is much larger in the lower part of the mantle transition zone, and it is thus likely to be the main barrier to the recycled carbonates towards the deep interior. en-copyright= kn-copyright= en-aut-name=ZhaoBin en-aut-sei=Zhao en-aut-mei=Bin kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=ZhuJintao en-aut-sei=Zhu en-aut-mei=Jintao kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=ChenQi en-aut-sei=Chen en-aut-mei=Qi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= affil-num=1 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=3 en-affil=Center for Advanced Radiation Sources, University of Chicago kn-affil= affil-num=4 en-affil=Institute for Planetary Materials, Okayama University kn-affil= en-keyword=carbon kn-keyword=carbon en-keyword=carbonatite melts kn-keyword=carbonatite melts en-keyword=electrical conductivity kn-keyword=electrical conductivity en-keyword=impedance spectroscopy kn-keyword=impedance spectroscopy en-keyword=multi-anvil press kn-keyword=multi-anvil press END start-ver=1.4 cd-journal=joma no-vol= cd-vols= no-issue= article-no= start-page= end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2025 dt-pub=20251028 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=The effect of pressure on dihedral angle between liquid Fe]S and orthopyroxene: Implication for percolative core formation in planetesimals and planetary embryos en-subtitle= kn-subtitle= en-abstract= kn-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. en-copyright= kn-copyright= en-aut-name=MiuraTakumi en-aut-sei=Miura en-aut-mei=Takumi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=TerasakiHidenori en-aut-sei=Terasaki en-aut-mei=Hidenori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=TakakiHyu en-aut-sei=Takaki en-aut-mei=Hyu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=KobayashiKotaro en-aut-sei=Kobayashi en-aut-mei=Kotaro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=BromileyGeoffrey David en-aut-sei=Bromiley en-aut-mei=Geoffrey David kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= affil-num=1 en-affil=Department of Earth and Space Science, Osaka University kn-affil= affil-num=2 en-affil=Department of Earth Sciences, Okayama University kn-affil= affil-num=3 en-affil=Department of Earth Sciences, Okayama University kn-affil= affil-num=4 en-affil=Department of Earth Sciences, Okayama University kn-affil= affil-num=5 en-affil=School of Geosciences, The University of Edinburgh kn-affil= affil-num=6 en-affil=Institute for Planetary Materials, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=130 cd-vols= no-issue=10 article-no= start-page=e2025JB032215 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2025 dt-pub=202510 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Electrical Conductivity of Carbonated Hydrous Basaltic Melt: Implications for the Conductivity Anomaly Beneath the Ocean Floors en-subtitle= kn-subtitle= en-abstract= kn-abstract=We measured the electrical conductivity of CO2 and H2O-bearing basaltic melts up to 1750 K at 2 GPa, corresponding to pressure around the lithosphere-asthenosphere boundary. The electrical conductivity of the dry and hydrous samples is comparable to those reported by previous studies on the Fe-free basaltic melt. The substantial CO2 can limit the water solubility in basaltic melt at 2 GPa. Both CO2 and H2O, which cannot completely dissolve in the melt, coexist as fluid phases, resulting in reduced electrical conductivity of the basaltic melt, which has a lower water content relative to the amount of volatile components in the bulk starting system. The activation enthalpy of basaltic melt is markedly higher than those of more evolved silicate melts, especially on the H2O-poor condition, due to the more enriched alkaline earth elements. The present results suggest that an overall melt fraction of 0.1?5.3 vol% is needed to account for the high electrical conductivity anomalies (10?1.3 to 10?0.3 S/m) beneath the oceanic plate near the East Pacific Rise and Cocos plate. However, for those regions where the electrical conductivity is extremely high (?10?0.3 S/m), more than 6 wt% H2O is expected to incorporate to maintain a melt fraction that will not trigger mechanical instability. In turn, it requires a low CO2 budget or degree of carbonation within these regions. en-copyright= kn-copyright= en-aut-name=ZhaoBin en-aut-sei=Zhao en-aut-mei=Bin kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=ZhuJintao en-aut-sei=Zhu en-aut-mei=Jintao kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=HeJinze en-aut-sei=He en-aut-mei=Jinze kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= affil-num=1 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=3 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=4 en-affil=Institute for Planetary Materials, Okayama University kn-affil= en-keyword=electrical conductivity kn-keyword=electrical conductivity en-keyword=basaltic melts kn-keyword=basaltic melts en-keyword=oceanic floors kn-keyword=oceanic floors en-keyword=high pressure kn-keyword=high pressure END start-ver=1.4 cd-journal=joma no-vol=52 cd-vols= no-issue=14 article-no= start-page=e2024GL114146 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2025 dt-pub=20250718 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Unraveling the Complex Features of the Seismic Scatterers in the Mid]Lower Mantle Through Phase Transition of (Al, H)]Bearing Stishovite en-subtitle= kn-subtitle= en-abstract= kn-abstract=Small-scale scatterers observed in the mid-lower mantle beneath the subduction zones are thought to result from the phase transition of stishovite within subducted oceanic crusts. Here we investigate the phase transition of (Al, H)-bearing stishovite with four compositions at simultaneously high P-T conditions combining Raman spectroscopy and X-ray diffraction. These experimental results reveal that the incorporation of 0.01 a.p.f.u Al into stishovite with H/Al ratio of ?1/3 lowers the transition pressure by 6.7(3) GPa. However, the Clapeyron slope of this transition is nearly unaffected by changes in the Al content and has a value of 12.2?12.5(3) MPa/K. According to our results, Al content variation ranging from 0 to 0.07 a.p.f.u in SiO2 can reasonably explain the depth distribution from 800 to 1,900 km of the seismic scatterers observed in the circum-Pacific region. These results deepen our understanding on the complex features of mid-lower mantle seismic scatterers and corresponding dynamic processes. en-copyright= kn-copyright= en-aut-name=YuYingxin en-aut-sei=Yu en-aut-mei=Yingxin kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=ZhangYouyue en-aut-sei=Zhang en-aut-mei=Youyue kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=LiLuo en-aut-sei=Li en-aut-mei=Luo kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=ZhangXinyue en-aut-sei=Zhang en-aut-mei=Xinyue kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=WangDenglei en-aut-sei=Wang en-aut-mei=Denglei kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=MaoZhu en-aut-sei=Mao en-aut-mei=Zhu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=SunNingyu en-aut-sei=Sun en-aut-mei=Ningyu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=ZhangYanyao en-aut-sei=Zhang en-aut-mei=Yanyao kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= en-aut-name=LiXinyang en-aut-sei=Li en-aut-mei=Xinyang kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=9 ORCID= en-aut-name=LiWancai en-aut-sei=Li en-aut-mei=Wancai kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=10 ORCID= en-aut-name=SpezialeSergio en-aut-sei=Speziale en-aut-mei=Sergio kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=11 ORCID= en-aut-name=ZhangDongzhou en-aut-sei=Zhang en-aut-mei=Dongzhou kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=12 ORCID= en-aut-name=LinJung]Fu en-aut-sei=Lin en-aut-mei=Jung]Fu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=13 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=14 ORCID= affil-num=1 en-affil=Deep Space Exploration Laboratory, School of Earth and Space Sciences, University of Science and Technology of China kn-affil= affil-num=2 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=3 en-affil=Deep Space Exploration Laboratory, School of Earth and Space Sciences, University of Science and Technology of China kn-affil= affil-num=4 en-affil=Deep Space Exploration Laboratory, School of Earth and Space Sciences, University of Science and Technology of China kn-affil= affil-num=5 en-affil=Deep Space Exploration Laboratory, School of Earth and Space Sciences, University of Science and Technology of China kn-affil= affil-num=6 en-affil=Deep Space Exploration Laboratory, School of Earth and Space Sciences, University of Science and Technology of China kn-affil= affil-num=7 en-affil=Deep Space Exploration Laboratory, School of Earth and Space Sciences, University of Science and Technology of China kn-affil= affil-num=8 en-affil=Earth and Planetary Sciences, Stanford University kn-affil= affil-num=9 en-affil=State Key Laboratory of High Pressure and Superhard Materials, College of Physics, Jilin University kn-affil= affil-num=10 en-affil=CAS Key Laboratory of Crust]Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China kn-affil= affil-num=11 en-affil=GFZ German Research Centre for Geosciences kn-affil= affil-num=12 en-affil=GeoSoilEnviroCARS, University of Chicago kn-affil= affil-num=13 en-affil=Department of Earth and Planetary Sciences, Jackson School of Geosciences, The University of Texas at Austin kn-affil= affil-num=14 en-affil=Institute for Planetary Materials, Okayama University kn-affil= en-keyword=(Al, H)-bearing stishovite kn-keyword=(Al, H)-bearing stishovite en-keyword=phase transition kn-keyword=phase transition en-keyword=mid-lower mantle kn-keyword=mid-lower mantle en-keyword=small-scale seismic scatterers kn-keyword=small-scale seismic scatterers END start-ver=1.4 cd-journal=joma no-vol=59 cd-vols= no-issue=6 article-no= start-page=1314 end-page=1328 dt-received= dt-revised= dt-accepted= dt-pub-year=2024 dt-pub=20240310 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Wetting property of Fe]S melt in solid core: Implication for the core crystallization process in planetesimals en-subtitle= kn-subtitle= en-abstract= kn-abstract=In 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 melth in iron meteorites. Excess amounts of the melt would migrate from the solid core over a long period of core crystallization in planetesimals. en-copyright= kn-copyright= en-aut-name=MatsubaraShiori en-aut-sei=Matsubara en-aut-mei=Shiori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=TerasakiHidenori en-aut-sei=Terasaki en-aut-mei=Hidenori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=UrakawaSatoru en-aut-sei=Urakawa en-aut-mei=Satoru kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=YumitoriDaisuke en-aut-sei=Yumitori en-aut-mei=Daisuke kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= affil-num=1 en-affil=Department of Earth Sciences, Graduate School of Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Department of Earth Sciences, Graduate School of Science and Technology, Okayama University kn-affil= affil-num=3 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=4 en-affil=Department of Earth Sciences, Graduate School of Science and Technology, Okayama University kn-affil= affil-num=5 en-affil=Department of Earth Sciences, Graduate School of Science and Technology, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=8 cd-vols= no-issue=13 article-no= start-page=eabm1821 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2022 dt-pub=20220330 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Viscosity of bridgmanite determined by in situ stress and strain measurements in uniaxial deformation experiments en-subtitle= kn-subtitle= en-abstract= kn-abstract=To understand mantle dynamics, it is important to determine the rheological properties of bridgmanite, the dominant mineral in Earthfs mantle. Nevertheless, experimental data on the viscosity of bridgmanite are quite limited due to experimental difficulties. Here, we report viscosity and deformation mechanism maps of bridgmanite at the uppermost lower mantle conditions obtained through in situ stress-strain measurements of bridgmanite using deformation apparatuses with the Kawai-type cell. Bridgmanite would be the hardest among mantle constituent minerals even under nominally dry conditions in the dislocation creep region, consistent with the observation that the lower mantle is the hardest layer. Deformation mechanism maps of bridgmanite indicate that grain size of bridgmanite and stress conditions at top of the lower mantle would be several millimeters and ~105 Pa to realize viscosity of 1021?22 Pa?s, respectively. This grain size of bridgmanite suggests that the main part of the lower mantle is isolated from the convecting mantle as primordial reservoirs. en-copyright= kn-copyright= en-aut-name=TsujinoNoriyoshi en-aut-sei=Tsujino en-aut-mei=Noriyoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YamazakiDaisuke en-aut-sei=Yamazaki en-aut-mei=Daisuke kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=NishiharaYu en-aut-sei=Nishihara en-aut-mei=Yu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=HigoYuji en-aut-sei=Higo en-aut-mei=Yuji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=TangeYoshinori en-aut-sei=Tange en-aut-mei=Yoshinori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= affil-num=1 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=3 en-affil=Geodynamics Research Center, Ehime University kn-affil= affil-num=4 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=5 en-affil=Japan Synchrotron Radiation Research Institute kn-affil= affil-num=6 en-affil=Japan Synchrotron Radiation Research Institute kn-affil= END start-ver=1.4 cd-journal=joma no-vol=14 cd-vols= no-issue=19 article-no= start-page=5476 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2021 dt-pub=20210922 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Electrical Resistivity of Cu and Au at High Pressure above 5 GPa: Implications for the Constant Electrical Resistivity Theory along the Melting Curve of the Simple Metals en-subtitle= kn-subtitle= en-abstract= kn-abstract=The electrical resistivity of solid and liquid Cu and Au were measured at high pressures from 6 up to 12 GPa and temperatures & SIM;150 K above melting. The resistivity of the metals was also measured as a function of pressure at room temperature. Their resistivity decreased and increased with increasing pressure and temperature, respectively. With increasing pressure at room temperature, we observed a sharp reduction in the magnitude of resistivity at & SIM;4 GPa in both metals. In comparison with 1 atm data and relatively lower pressure data from previous studies, our measured temperature-dependent resistivity in the solid and liquid states show a similar trend. The observed melting temperatures at various fixed pressure are in reasonable agreement with previous experimental and theoretical studies. Along the melting curve, the present study found the resistivity to be constant within the range of our investigated pressure (6-12 GPa) in agreement with the theoretical prediction. Our results indicate that the invariant resistivity theory could apply to the simple metals but at higher pressure above 5 GPa. These results were discussed in terms of the saturation of the dominant nuclear screening effect caused by the increasing difference in energy level between the Fermi level and the d-band with increasing pressure. en-copyright= kn-copyright= en-aut-name=EzenwaInnocent C. en-aut-sei=Ezenwa en-aut-mei=Innocent C. kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=Institute for Planetary Materials, Okayama University kn-affil= en-keyword=electrical resistivity kn-keyword=electrical resistivity en-keyword=thermal conductivity kn-keyword=thermal conductivity en-keyword=electrons and phonons interactions kn-keyword=electrons and phonons interactions en-keyword=high pressure and temperature kn-keyword=high pressure and temperature en-keyword=constant resistivity kn-keyword=constant resistivity en-keyword=melting curve kn-keyword=melting curve END start-ver=1.4 cd-journal=joma no-vol=91 cd-vols= no-issue=3 article-no= start-page=035115 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2020 dt-pub=20200319 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Measurement of the Seebeck coefficient under high pressure by dual heating en-subtitle= kn-subtitle= en-abstract= kn-abstract=This study presents a new method for measuring the Seebeck coefficient under high pressure in a multi-anvil apparatus. The application of a dual-heating system enables precise control of the temperature difference between both ends of the sample in a high-pressure environment. Two pairs of W?Re thermocouples were employed at both ends of the sample to monitor and control the temperature difference, and independent probes were arranged to monitor the electromotive force (emf) produced by temperature oscillation at a given target temperature. The temperature difference was controlled within 1 K during the resistivity measurements to eliminate the influence of the emf owing to a sample temperature gradient. The Seebeck measurement was successfully measured from room temperature to 1400 K and was obtained by averaging the two measured values with opposite thermal gradient directions (?20 K). Thermoelectric properties were measured on disk-shaped p-type Si wafers with two different carrier concentrations as a reference for high Seebeck coefficients. This method is effective to determine the thermoelectric power of materials under pressure. en-copyright= kn-copyright= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=WangRan en-aut-sei=Wang en-aut-mei=Ran kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=GomiHitoshi en-aut-sei=Gomi en-aut-mei=Hitoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=MoriYoshihisa en-aut-sei=Mori en-aut-mei=Yoshihisa kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= affil-num=1 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=3 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=4 en-affil=3Department of Applied Science, Okayama University of Science kn-affil= END start-ver=1.4 cd-journal=joma no-vol=530 cd-vols= no-issue= article-no= start-page=115887 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2019 dt-pub=20191023 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Grain boundary diffusion of W in lower mantle phase with implications for isotopic heterogeneity in oceanic island basalts by core-mantle interactions en-subtitle= kn-subtitle= en-abstract= kn-abstract=Tungsten isotopes provide important constraints on the ocean-island basalt (OIB) source regions. Recent analyses of ƒÊ182W in modern basalts with high 3He/4He originating from the core-mantle boundary region reveal two distinct features: positive ƒÊ182W in Phanerozoic flood basalts indicating the presence of primordial reservoir, and negative ƒÊ182W in modern OIBs. One possibility to produce large variations in ƒÊ182W is interaction between the mantle and outer core. Here, we report grain boundary diffusion of W in lower mantle phases. High pressure experimental results show that grain boundary diffusion of W is fast and strongly temperature dependent. Over Earth's history, diffusive transport of W from the core to the lowermost mantle may have led to significant modification of the W isotopic composition of the lower mantle at length scales exceeding one kilometer. Such grain boundary diffusion can lead to large variations in ƒÊ182W in modern basalts as a function of the distance of their source regions from the core mantle boundary. Modern oceanic island basalts from Hawaii, Samoa and Iceland exhibit negative ƒÊ182W and likely originated from the modified isotope region just above the core-mantle boundary, whereas those with positive ƒÊ182W could be derived from the thick Large Low Shear Velocity Provinces (LLSVPs) far from the core-mantle boundary (CMB). When highly-oxidized slabs accumulate at the CMB oxidizing the outer core at the interface, a large W flux with negative ƒÊ182W can be added to the silicate mantle. As a result, the source region of the OIB would be effectively modified to a negative ƒÊ182W. en-copyright= kn-copyright= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=MakinoYoshiki en-aut-sei=Makino en-aut-mei=Yoshiki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=SuzukiToshihiro en-aut-sei=Suzuki en-aut-mei=Toshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=HirataTakafumi en-aut-sei=Hirata en-aut-mei=Takafumi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= affil-num=1 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=Geochemical Research Center, The University of Tokyo kn-affil= affil-num=3 en-affil=Geochemical Research Center, The University of Tokyo kn-affil= affil-num=4 en-affil=Geochemical Research Center, The University of Tokyo kn-affil= en-keyword=core mantle interaction kn-keyword=core mantle interaction en-keyword=grain boundary diffusion kn-keyword=grain boundary diffusion en-keyword=high pressure experiment kn-keyword=high pressure experiment en-keyword=postspinel kn-keyword=postspinel en-keyword=W isotope kn-keyword=W isotope en-keyword=core mantle boundary kn-keyword=core mantle boundary END start-ver=1.4 cd-journal=joma no-vol=100 cd-vols= no-issue=21 article-no= start-page=214302 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2019 dt-pub=20191205 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Resistivity, Seebeck coefficient, and thermal conductivity of platinum at high pressure and temperature en-subtitle= kn-subtitle= en-abstract= kn-abstract= Platinum (Pt) is one of the most widely used functional materials for high-pressure and high-temperature experiments. Despite the crucial importance of its transport properties, both experimental and theoretical studies are very limited. In this study, we conducted density functional theory calculations on the electrical resistivity, the Seebeck coefficient, and the thermal conductivity of solid face-centered cubic Pt at pressures up to 200 GPa and temperatures up to 4800 K by using the Kubo-Greenwood formula. The thermal lattice displacements were treated within the alloy analogy, which is represented by means of the Korringa-Kohn-Rostoker method with the coherent potential approximation. The electrical resistivity decreases with pressure and increases with temperature. These two conflicting effects yield a constant resistivity of similar to 70 mu Omega cm along the melting curve. Both pressure and temperature effects enhance the thermal conductivity at low temperatures, but the temperature effect becomes weaker at high temperatures. Although the pressure dependence of the Seebeck coefficient is negligibly small at temperatures below similar to 1500 K, it becomes larger at higher temperatures. It requires a calibration of a thermocouple such as Pt-Rh in high-pressure and -temperature experiments. en-copyright= kn-copyright= en-aut-name=GomiHitoshi en-aut-sei=Gomi en-aut-mei=Hitoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=Institute for Planetary Materials, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=103 cd-vols= no-issue=8 article-no= start-page=1271 end-page=1281 dt-received= dt-revised= dt-accepted= dt-pub-year=2018 dt-pub=20180801 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=The effects of ferromagnetism and interstitial hydrogen on the equation of states of hcp and dhcp FeHx: Implications for the Earth's inner core age en-subtitle= kn-subtitle= en-abstract= kn-abstract= Hydrogen has been considered as an important candidate of light elements in the Earth's core. Because iron hydrides are unquenchable, hydrogen content is usually estimated from in situ X-ray diffraction measurements that assume the following linear relation: x = (V-FeHx - V-Fe)/Delta V-H, where x is the hydrogen content, Delta V-H is the volume expansion caused by unit concentration of hydrogen, and V-FeHx and V-Fe are volumes of FeHx and pure iron, respectively. To verify the linear relationship, we computed the equation of states of hexagonal iron with interstitial hydrogen by using the Korringa-Kohn-Rostoker method with the coherent potential approximation (KKR-CPA). The results indicate a discontinuous volume change at the magnetic transition and almost no compositional (x) dependence in the ferromagnetic phase at 20 GPa, whereas the linearity is confirmed in the non-magnetic phase. In addition to their effect on the density-composition relationship in the Fe-FeHx system, which is important for estimating the hydrogen incorporation in planetary cores, the magnetism and interstitial hydrogen also affect the electrical resistivity of FeHx. The thermal conductivity can be calculated from the electrical resistivity by using the Wiedemann-Franz law, which is a critical parameter for modeling the thermal evolution of the Earth. Assuming an Fe1-ySiyHx ternary outer core model (0.0 <= x <= 0.7), we calculated the thermal conductivity and the age of the inner core. The resultant thermal conductivity is similar to 100 W/m/K and the maximum inner core age ranges from 0.49 to 0.86 Gyr. en-copyright= kn-copyright= en-aut-name=GomiHitoshi en-aut-sei=Gomi en-aut-mei=Hitoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=FeiYingwei en-aut-sei=Fei en-aut-mei=Yingwei kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= affil-num=1 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=Geophysical Laboratory, Carnegie Institution of Washington kn-affil= affil-num=3 en-affil=Institute for Planetary Materials, Okayama University kn-affil= en-keyword=FeHx kn-keyword=FeHx en-keyword=ferromagnetism kn-keyword=ferromagnetism en-keyword=chemical disorder kn-keyword=chemical disorder en-keyword=equation of states kn-keyword=equation of states en-keyword=KKR-CPA kn-keyword=KKR-CPA END start-ver=1.4 cd-journal=joma no-vol=6 cd-vols= no-issue= article-no= start-page=217 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2018 dt-pub=20181129 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Impurity Resistivity of fcc and hcp Fe-Based Alloys: Thermal Stratification at the Top of the Core of Super-Earths en-subtitle= kn-subtitle= en-abstract= kn-abstract= It is widely known that the Earth's Fe dominant core contains a certain amount of light elements such as H, C, N, O, Si, and S. We report the results of first-principles calculations on the band structure and the impurity resistivity of substitutionally disordered hcp and fcc Fe based alloys. The calculation was conducted by using the AkaiKKR (machikaneyama) package, which employed the Korringa-Kohn-Rostoker (KKR) method with the atomic sphere approximation (ASA). The local density approximation (LDA) was adopted for the exchange-correlation potential. The coherent potential approximation (CPA) was used to treat substitutional disorder effect. The impurity resistivity is calculated from the Kubo-Greenwood formula with the vertex correction. In dilute alloys with 1 at. % impurity concentration, calculated impurity resistivities of C, N, O, S are comparable to that of Si. On the other hand, in concentrated alloys up to 30 at. %, Si impurity resistivity is the highest followed by C impurity resistivity. Ni impurity resistivity is the smallest. N, O, and S impurity resistivities lie between Si and Ni. Impurity resistivities of hcp-based alloys show systematically higher values than fcc alloys. We also calculated the electronic specific heat from the density of states (DOS). For pure Fe, the results show the deviation from the Sommerfeld value at high temperature, which is consistent with previous calculation. However, the degree of deviation becomes smaller with increasing impurity concentration. The violation of the Sommerfeld expansion is one of the possible sources of the violation of the Wiedemann-Franz law, but the present results could not resolve the inconsistency between recent electrical resistivity and thermal conductivity measurements. Based on the present thermal conductivity model, we calculated the conductive heat flux at the top of terrestrial cores, which is comparable to the heat flux across the thermal boundary layer at the bottom of the mantle. This indicates that the thermal stratification may develop at the top of the liquid core of super-Earths, and hence, chemical buoyancies associated with the inner core growth and/or precipitations are required to generate the global magnetic field through the geodynamo. en-copyright= kn-copyright= en-aut-name=GomiHitoshi en-aut-sei=Gomi en-aut-mei=Hitoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YoshinoTakashi en-aut-sei=Yoshino en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil=Institute for Planetary Materials, Okayama University kn-affil= affil-num=2 en-affil=Institute for Planetary Materials, Okayama University kn-affil= en-keyword=band structure kn-keyword=band structure en-keyword=density of states kn-keyword=density of states en-keyword=electrical resistivity kn-keyword=electrical resistivity en-keyword=thermal conductivity kn-keyword=thermal conductivity en-keyword=Linde's rule kn-keyword=Linde's rule en-keyword=KKR-CPA kn-keyword=KKR-CPA END