scholarly journals Solubilities of O and Si in liquid iron in equilibrium with (Mg,Fe)SiO3perovskite and the light elements in the core

2005 ◽  
Vol 32 (6) ◽  
Author(s):  
Naoto Takafuji
Keyword(s):  
Liquid Iron ◽  
Light Elements ◽  
The Core

Inefficient compaction in small planetary cores -- application to the Moon

2021 ◽  
Author(s):  
Marine Lasbleis
Keyword(s):  
Magnetic Field ◽  
Latent Heat ◽  
Energy Budget ◽  
Inner Core ◽  
Light Elements ◽  
The Moon ◽  
Small Bodies ◽  
Typical Size ◽  
The Core ◽  
Planetary Cores

<div> <p>Growth of the solid inner core is generally considered to power the Earth's present geodynamo. Cristallisation of a solid central inner core has also been proposed to drive the lunar dynamo and to generate a magnetic field in smaller bodies. In a previous work, we estimated the compaction of planetary cores for different scenarios of growth (with or without supercooling) and different sizes of the inner core. Our main results indicated that small inner cores are unlikely to compact efficiently the liquid trapped during the first steps of the growth.</p> <p>This is especially true for small bodies for which the typical size of the core is similar to the compaction length. The light elements are thus trapped during the cristallisation, reducing the release of latent heat and of light elements. We present here a model to include the effect of an inefficient compaction in the energy budget of a planetary core and investigate the implications for the dynamo evolution in small bodies. We apply this model for the evolution of the core of the Moon. </p> </div>

Solubility of carbon and nitrogen in a sulfur-bearing iron melt: Constraints for siderophile behavior at upper mantle conditions

2019 ◽  
Vol 104 (12) ◽  
pp. 1857-1865 ◽  
Author(s):  
Alexander G. Sokol ◽  
Alexander F. Khokhryakov ◽  
Yuri M. Borzdov ◽  
Igor N. Kupriyanov ◽  
Yuri N. Palyanov
Keyword(s):  
Liquid Iron ◽  
Upper Mantle ◽  
Carbon Budget ◽  
Iron Alloy ◽  
Stability Field ◽  
Magma Ocean ◽  
Carbon Solubility ◽  
Carbon And Nitrogen ◽  
Liquid Iron Alloy ◽  
The Core

Abstract Carbon solubility in a liquid iron alloy containing nitrogen and sulfur has been studied experimentally in a carbon-saturated Fe-C-N-S-B system at pressures of 5.5 and 7.8 GPa, temperatures of 1450 to 1800 °C, and oxygen fugacities from the IW buffer to log fO2 ΔIW-6 (ΔIW is the logarithmic difference between experimental fO2 and that imposed by the coexistence of iron and wüstite). Carbon saturation of Fe-rich melts at 5.5 and 7.8 GPa maintains crystallization of flaky graphite and diamond. Diamond containing 2100–2600 ppm N and 130–150 ppm B crystallizes in equilibrium with BN within the diamond stability field at 7.8 GPa and 1600 to 1800 °C, while graphite forms at other conditions. The solubility of carbon in the C-saturated metal melt free from nitrogen and sulfur is 6.2 wt% C at 7.8 GPa and 1600 °C and decreases markedly with increasing nitrogen. A 1450–1600 °C graphite-saturated iron melt with 6.2–8.8 wt% N can dissolve: 3.6–3.9 and 1.4–2.5 wt% C at 5.5 and 7.8 GPa, respectively. However, the melt equilibrated with boron nitride and containing 1–1.7 wt% sulfur and 500–780 ppm boron dissolves twice less nitrogen while the solubility of carbon remains relatively high (3.8–5.2 wt%). According to our estimates, nitrogen partitions between diamond and the iron melt rich in volatiles at DNDm/Met=0.013−0.024. The pressure increase in the Fe-C-N system affects iron affinity of N and C: it increases in nitrogen but decreases in carbon. The reduction of C solubility in a Fe-rich melt containing nitrogen and sulfur may have had important consequences in the case of imperfect equilibration between the core and the mantle during their separation in the early Earth history. The reduction of C solubility allowed C supersaturation of the liquid iron alloy and crystallization of graphite and diamond. The carbon phases could float in the segregated core liquid and contribute to the carbon budget of the overlying silicate magma ocean. Therefore, the process led to the formation of graphite and diamond, which were the oldest carbon phases in silicate mantle.

Shock-Induced Chemical Reaction between Iron and Enstatite

2013 ◽  
Vol 703 ◽  
pp. 41-44
Author(s):  
Xiu Fang Chen ◽  
Chao Ping Zhang
Keyword(s):  
Liquid Iron ◽  
Outer Core ◽  
Middle Section ◽  
X Ray Diffraction ◽  
Initial Sample ◽  
X Ray ◽  
Core Mantle Boundary ◽  
The Core ◽  
Gas Gun ◽  
Shock Recovery Experiments

By using a two-stage light gas gun, two experiments of shock recovery experiments with initial sample of Fe+(Mg, Fe)SiO3 (En) were conducted between 78 and 113 GPa shock pressure (the corresponding temperature is estimated as 3000~5000K). The recovered samples were analyzed by X-ray Diffraction (XRD).The XRD observation at the middle section of two recovered samples illustrates the new composition of recovered samples is (Mg, Fe)2SiO4.Comparing with the recovery experiments of MgO+SiO2 ,we can infer that iron and perovskite react to form SiO2 and (Mg, Fe)O. The experiments result indicates that reaction between liquid iron and (Mg, Fe)SiO3 perovskite may occur at the core-mantle boundary in geological history. The reaction creates a very heterogeneous zone at the base of the mantle. Si and O dissolved in liquid iron are rapidly dispersed by the flow of the liquid outer core.

Metal-silicate fractionation in the deep magma ocean and light elements in the core

2006 ◽  
Vol 70 (18) ◽  
pp. A455
Author(s):  
E. Ohtani ◽  
T. Sakai ◽  
T. Kawazoe ◽  
T. Kondo
Keyword(s):  
Light Elements ◽  
Magma Ocean ◽  
The Core ◽  
Metal Silicate

scholarly journals Constraints on Earth’s inner core composition inferred from measurements of the sound velocity of hcp-iron in extreme conditions

2016 ◽  
Vol 2 (2) ◽  
pp. e1500802 ◽  
Author(s):  
Tatsuya Sakamaki ◽  
Eiji Ohtani ◽  
Hiroshi Fukui ◽  
Seiji Kamada ◽  
Suguru Takahashi ◽  
...  
Keyword(s):  
Sound Velocity ◽  
Inner Core ◽  
Earth Model ◽  
Light Elements ◽  
Earth’S Core ◽  
Heated Sample ◽  
Earth's Core ◽  
The Core ◽  
Core Composition ◽  
Earth’S Inner Core

Hexagonal close-packed iron (hcp-Fe) is a main component of Earth’s inner core. The difference in density between hcp-Fe and the inner core in the Preliminary Reference Earth Model (PREM) shows a density deficit, which implies an existence of light elements in the core. Sound velocities then provide an important constraint on the amount and kind of light elements in the core. Although seismological observations provide density–sound velocity data of Earth’s core, there are few measurements in controlled laboratory conditions for comparison. We report the compressional sound velocity (VP) of hcp-Fe up to 163 GPa and 3000 K using inelastic x-ray scattering from a laser-heated sample in a diamond anvil cell. We propose a new high-temperature Birch’s law for hcp-Fe, which gives us the VP of pure hcp-Fe up to core conditions. We find that Earth’s inner core has a 4 to 5% smaller density and a 4 to 10% smaller VP than hcp-Fe. Our results demonstrate that components other than Fe in Earth’s core are required to explain Earth’s core density and velocity deficits compared to hcp-Fe. Assuming that the temperature effects on iron alloys are the same as those on hcp-Fe, we narrow down light elements in the inner core in terms of the velocity deficit. Hydrogen is a good candidate; thus, Earth’s core may be a hidden hydrogen reservoir. Silicon and sulfur are also possible candidates and could show good agreement with PREM if we consider the presence of some melt in the inner core, anelasticity, and/or a premelting effect.

scholarly journals Ab Initio Thermoelasticity of Liquid Iron-Nickel-Light Element Alloys

Minerals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 59 ◽  
Author(s):  
Hiroki Ichikawa ◽  
Taku Tsuchiya
Keyword(s):  
Ab Initio ◽  
Liquid Iron ◽  
Inner Core ◽  
Light Element ◽  
Outer Core ◽  
Light Elements ◽  
Major Element Composition ◽  
Silicon Carbon ◽  
Other Information ◽  
Core Boundary

The earth’s core is thought to be composed of Fe-Ni alloy including substantially large amounts of light elements. Although oxygen, silicon, carbon, nitrogen, sulfur, and hydrogen have been proposed as candidates for the light elements, little is known about the amount and the species so far, primarily because of the difficulties in measurements of liquid properties under the outer core pressure and temperature condition. Here, we carry out massive ab initio computations of liquid Fe-Ni-light element alloys with various compositions under the whole outer core P, T condition in order to quantitatively evaluate their thermoelasticity. Calculated results indicate that Si and S have larger effects on the density of liquid iron than O and H, but the seismological reference values of the outer core can be reproduced simultaneously by any light elements except for C. In order to place further constraints on the outer core chemistry, other information, in particular melting phase relations of iron light elements alloys at the inner core-outer core boundary, are necessary. The optimized best-fit compositions demonstrate that the major element composition of the bulk earth is expected to be CI chondritic for the Si-rich core with the pyrolytic mantle or for the Si-poor core and the (Mg,Fe)SiO3-dominant mantle. But the H-rich core likely causes a distinct Fe depletion for the bulk Earth composition.

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