Phase relations in the system Fe–Ni–Si to 200 GPa and 3900 K and implications for Earth's core

Komabayashi, Tetsuya; Pesce, G.; Sinmyo, Ryosuke; Kawazoe, Takaaki; Breton, H.; Shimoyama, Yuta; Glazyrin, Konstantin; Konôpková, Zuzana; Mézouar, M.

doi:10.1016/j.epsl.2019.01.056

Cited by 21 publications

(18 citation statements)

References 43 publications

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“…Phase relations in the Fe-Ni-Si system were experimentally investigated in DAC with in situ synchrotron XRD [58,110,192].…”

Section: Fe-ni-simentioning

confidence: 99%

“…The fcc-hcp Transitions Komabayashi et al [192] examined the P-T locations of the fcc-hcp transitions in Fe-5Ni-4Si in the internally resistive-heated DAC. Their results are compared with existing data for pure Fe [14] and the binary Fe-Ni [57] and Fe-Si [99] systems (Figure 35).…”

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confidence: 99%

“…As such, the simultan addition of Ni and Si has an anomalous effect on the transition pressure and temper which is greatly stabilising the fcc structure under high pressure. [57], Fe-4Si [99], and Fe-5Ni-4Si [192].…”

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confidence: 99%

“…The dP/dT slopes of the fcc-hcp transition boundaries in different systems and related properties, which include the volume change (∆V) and entropy change (∆S) upon transition, were summarized in [192]. The dP/dT slopes and ∆V were directly obtained from the experiments while ∆S were calculated through the Clausius-Clapeyron equation, ∆P/∆T = ∆S/∆V.…”

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confidence: 99%

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Phase Relations of Earth’s Core-Forming Materials

Komabayashi

2021

Crystals

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Recent updates on phase relations of Earth’s core-forming materials, Fe alloys, as a function of pressure (P), temperature (T), and composition (X) are reviewed for the Fe, Fe-Ni, Fe-O, Fe-Si, Fe-S, Fe-C, Fe-H, Fe-Ni-Si, and Fe-Si-O systems. Thermodynamic models for these systems are highlighted where available, starting with 1 bar to high-P-T conditions. For the Fe and binary systems, the longitudinal wave velocity and density of liquid alloys are discussed and compared with the seismological observations on Earth’s outer core. This review may serve as a guide for future research on the planetary cores.

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“…Phase relations in the Fe-Ni-Si system were experimentally investigated in DAC with in situ synchrotron XRD [58,110,192].…”

Section: Fe-ni-simentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Phase Relations of Earth’s Core-Forming Materials

Komabayashi

2021

Crystals

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“…We modeled the solidus and liquidus of the Fe‐Si‐O alloy system at the relevant P ‐ T conditions of the ICB using Matthiessen's additive law based on recent laboratory data in Fe, Fe‐Si, Fe‐O, and Fe‐Si‐O systems (Figure S1 in the supporting information; Anzellini et al, ; Arveson et al, ; Fischer, ; Huang et al, ; Komabayashi, ; Komabayashi et al, ; Morard et al, ; Zhang et al, ). The solidus and liquidus for an Fe‐4Si‐1.5O (wt %) system used in this study are estimated to be ~5,400 and ~5,550 K at the top of the F layer from melting temperatures of an O‐rich Fe alloy (e.g., Fe‐8O‐2S system (Huang et al, )) and Si‐rich Fe alloy (e.g., Fe‐8Ni‐10Si system and Fe‐5Ni‐4Si (Komabayashi et al, ; Zhang et al, )) at ~313 GPa, respectively. Thus, the temperature at top of the F layer is ~5,550 K from the modeled liquidus temperature of Fe‐4Si‐1.5O.…”

Section: Solidification Of Fe‐si‐o System and Geodynamic Modelmentioning

confidence: 99%

Fe Alloy Slurry and a Compacting Cumulate Pile Across Earth's Inner‐Core Boundary

et al. 2019

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Seismic observations show a reduced compressional-wave velocity gradient at the base of the outer core relative to the preliminary reference Earth model and seismic wave asymmetry between the east-west hemispheres at the top of the inner core. Here we propose a model for the inner core boundary (ICB), where a slurry layer forms through fractional crystallization of an Fe alloy at the base of the outer core (F layer) above a compacting cumulate pile at the top of the inner core (F′ layer). Using recent mineral physics data, we show that fractional crystallization of an Fe alloy (e.g., Fe-Si-O) with a solid fraction of~15 ± 5% and preferential light element partitioning into the liquid can explain the observed reduced velocity gradient in the F layer. The compacting cumulate pile in the F′ layer may exhibit lateral variations in thickness between the east-west hemispheres due to lateral variations of large-scale heat flux in the outer core, which may explain the east-west asymmetry observed in the seismic velocity. Our model suggests that the inner core solid has a high shear viscosity >10 22 Pa/s. Plain Language Summary Seismic observations show a reduced P wave velocity gradient layerat the bottom~280 km of the outer core and a hemispherical dichotomy at the top~50-200 km of the inner core compared to the one-dimensional Preliminary reference Earth model (PREM). These seismic features manifest physical and chemical phenomena linked to thermal evolution and formation processes of the inner core. We have developed a physical model to explain these seismic features. At the inner-outer boundary, the crystallization of Fe alloy co-exists with the residue melt producing a "snowing" slurry layer (F layer), consistent with observed seismic velocity gradient. Solid Fe alloy crystals accumulate and eventually compact at the top of the inner core, and may exhibit lateral variations in thickness between the east-west hemispheres. Our model can explain the east-west asymmetry observed in the seismic velocity. Our model uses mineral physics and seismological results to provide a holistic view of the physical and chemical processes for the inner-core growth over geological time.

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