Spin Transition of Iron in Deep‐Mantle Ferromagnesite

Liu, Jiachao; Fu, Suyu; Lin, Jung‐Fu

doi:10.1002/9781119508229.ch12

Cited by 7 publications

(3 citation statements)

References 70 publications

(135 reference statements)

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“…The spin state of iron has important implications for the physical properties of melts and minerals. Spin transitions from high‐spin to low‐spin states in iron‐bearing mantle compositions lead to densification at high pressures (Karki et al., 2018 ; Liu et al., 2020 ; McCammon et al., 2013 ; Speziale et al., 2005 ). Local spin state affects iron coordination and bond length in melts, with high‐spin iron atoms being more highly coordinated with longer bonds (Ghosh & Karki, 2020 ).…”

Section: Resultsmentioning

confidence: 99%

The Speciation and Coordination of a Deep Earth Carbonate‐Silicate‐Metal Melt

et al. 2022

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Ab initio molecular dynamics calculations on a carbonate‐silicate‐metal melt were performed to study speciation and coordination changes as a function of pressure and temperature. We examine in detail the bond abundances of specific element pairs and the distribution of coordination environments over conditions spanning Earth’s present‐day mantle. Average coordination numbers increase continuously from 4 to 8 for Fe and Mg, from 4 to 6 for Si, and from 2 to 4 for C from 1 to 148 GPa (4,000 K). Speciation across all pressure and temperature conditions is complex due to the unusual bonding of carbon. With the increasing pressure, C‐C and C‐Fe bonding increase significantly, resulting in the formation of carbon polymers, C‐Fe clusters, and the loss of carbonate groups. The increased bonding of carbon with elements other than oxygen indicates that carbon begins to replace oxygen as an anion in the melt network. We evaluate our results in the context of diamond formation and of metal‐silicate partitioning behavior of carbon. Our work has implications for properties of carbon and metal‐bearing silicate melts, such as viscosity, electrical conductivity, and reactivity with surrounding phases.

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Section: Resultsmentioning

confidence: 99%

The Speciation and Coordination of a Deep Earth Carbonate‐Silicate‐Metal Melt

et al. 2022

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“…The spin state of iron has important implications for the physical properties of melts and minerals. Spin transitions from high-spin to low-spin states in iron-bearing mantle compositions lead to densification at high pressures (Karki et al, 2018;Liu et al, 2020;McCammon et al, 2013;Speziale et al, 2005). Local spin state affects iron coordination and bond length in melts, with high-spin iron atoms being more highly coordinated with longer bonds .…”

Section: Electronic Structure Of the Meltmentioning

confidence: 99%

The Speciation and Coordination of a Deep Earth Carbonate-Silicate-Metal Melt

Davis¹,

Solomatova²,

Campbell³

et al. 2021

Preprint

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Ab initio molecular dynamics calculations on a carbonate-silicate-metal melt were performed to study speciation and coordination changes as a function of pressure and temperature. We examine in detail the bond abundances of specific element pairs and the distribution of coordination environments over conditions spanning Earth's present-day mantle. Average coordination numbers increase continuously from 4 to 8 for Fe and Mg, from 4 to 6 for Si, and from 2 to 4 for C from 1 to 148 GPa (4,000 K). Speciation across all pressure and temperature conditions is complex due to the unusual bonding of carbon. With the increasing pressure, C-C and C-Fe bonding increase significantly, resulting in the formation of carbon polymers, C-Fe clusters, and the loss of carbonate groups. The increased bonding of carbon with elements other than oxygen indicates that carbon begins to replace oxygen as an anion in the melt network. We evaluate our results in the context of diamond formation and of metal-silicate partitioning behavior of carbon. Our work has implications for properties of carbon and metal-bearing silicate melts, such as viscosity, electrical conductivity, and reactivity with surrounding phases.Plain Language Summary Carbonate melts play an important role in the Earth's upper mantle, but their role in the lower mantle is less well understood. Carbonate melts reacting with lower mantle silicates or metals could yield melts with unusual structural and physical properties. We simulate a carbonate-silicate-metal melt under a host of lower mantle conditions to understand the evolution of speciation and coordination in the melt with pressure and temperature. We find that coordination numbers increase continuously for all cations with pressure. We also find that with the increasing pressure, carbon begins to replace oxygen in the melt network, leading to the formation of unusual chemical species, such as carbon-carbon and carbon-iron clusters. Our work highlights that carbonate-silicate-metal melt compositions in the lower mantle could be parent melts for diamonds or for dense iron-carbon liquids that would carry carbon to the core.

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“…has four unpaired electrons(Liu et al 2020). Therefore, the high-to low-spin transition can result in the decrease of the electrical conductivity of siderite.…”

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confidence: 99%

Electrical conductivity of siderite and the effect of the spin transition of iron

Mashino,

Yoshino,

Mitsui

et al. 2024

Preprint

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We have conducted electrical conductivity measurements of FeCO3 siderite under high pressure up to 62 GPa in order to understand the nature and effect of iron spin transition and its influence on the geophysical properties of siderite, which is an end-member of major carbonate minerals. The results from Raman and Mössbauer spectroscopic measurements show that the high- to low-spin transition of iron occurs at around 50 GPa. A sharp decrease of the electrical conductivity was also observed at around 50 GP, which is associated with the iron spin transition. Although the stability of FeCO3 siderite may be limited under high-temperature conditions along with the mantle geotherm, solid solutions in the MgCO3-FeCO3 system, Mg1-xFexCO3, could be stable up to the pressure-temperature condition of the lowermost mantle. The pressure-temperature range of the iron spin transition of Mg1-xFexCO3 would be narrower than those of the major lower mantle minerals of ferropericlase and bridgmanite, and thus the drop of the electrical conductivity induced by the spin transition could be clearer under the lower mantle conditions. Therefore, the existence of Mg1-xFexCO3 may affect the observed heterogeneity of electrical conductivity in the mid-lower mantle.

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Spin Transition of Iron in Deep‐Mantle Ferromagnesite

Cited by 7 publications

References 70 publications

The Speciation and Coordination of a Deep Earth Carbonate‐Silicate‐Metal Melt

The Speciation and Coordination of a Deep Earth Carbonate‐Silicate‐Metal Melt

The Speciation and Coordination of a Deep Earth Carbonate-Silicate-Metal Melt

Electrical conductivity of siderite and the effect of the spin transition of iron

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