The system Na2CO3–CaCO3 at 3 GPa

Podborodnikov, Ivan V.; Shatskiy, Anton; Arefiev, Anton V.; Rashchenko, Sergey V.; Chanyshev, Artem; Litasov, Konstantin D.

doi:10.1007/s00269-018-0961-2

Cited by 23 publications

(28 citation statements)

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“…Room-temperature high-pressure behavior of nyerereite and shortite was recently studied by in situ Raman spectroscopy and X-ray diffraction (Borodina et al, 2018;Rashchenko, Goryainov, et al, 2017;Vennari et al, 2018). The equilibrium high-pressure investigation of the Na 2 CO 3 -CaCO 3 system was initiated by studies of its phase diagram at 3 and 6 GPa (Podborodnikov et al, 2018;Shatskiy et al, 2013Shatskiy et al, , 2015Litasov et al, this volume). The chemistry of intermediate Na-Ca carbonates turned out to be very sensitive to pressure (Figure 13.1): upon pressure increase from 0.1 to 3 GPa, the Na 2 Ca 2 (CO 3 ) 3 phase becomes unstable, while a new high-pressure Na 2 Ca 3 (CO 3 ) 4 phase appears on the phase diagram.…”

Section: Crystal Chemistry Of High-pressure Na-ca Carbonatesmentioning

confidence: 99%

High‐Pressure Na‐Ca Carbonates in the Deep Carbon Cycle

Rashchenko

Shatskiy

Litasov

2020

Geophysical Monograph Series

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Carbonates play a central role in the subduction transport of oxidized carbon from Earth's surface to the deep mantle. The melting of carbonated rocks also leads to the release of carbonate melts, regarded as important oxidizing and metasomatizing agents, from the subducting slab. Although at upper mantle conditions the chemistry of carbonates within the subducting slab is restricted to the thoroughly studied ternary CaCO 3 -MgCO 3 -FeCO 3 system, recent experimental and natural evidences strongly suggest that at conditions of the mantle transition zone, Na-Ca carbonates become the main host of oxidized carbon and define solidus temperatures and chemistry of deep melts. In this chapter, we discuss transport of carbonates to the mantle transition zone within the subducting slab, evidences of sodium migration from silicates into carbonates under high pressure, and crystal chemistry of currently known high-pressure Na-Ca carbonates. 13 13.

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Section: Crystal Chemistry Of High-pressure Na-ca Carbonatesmentioning

confidence: 99%

High‐Pressure Na‐Ca Carbonates in the Deep Carbon Cycle

Rashchenko

Shatskiy

Litasov

2020

Geophysical Monograph Series

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“…This absence might be explained by preferred orientation effects on the intensity of the mode. However, given our results, we believe it is more likely the two mixed sodium-calcium phases (Podborodnikov et al, 2018) are not present, and that the assemblage we observe shortite, nyerereite and aragonite, which may be a consequence of thermal gradients within our samples.…”

Section: A High-pressure/high-temperature Phase In Shortite Above 12 Gpamentioning

confidence: 63%

“…While that interpretation is consistent with the observed spectrum, the decomposition of calcium/sodium carbonates under pressure at elevated temperatures is complex and have not been observed to contain shortite. In heated large volume experiments at 3 and 6 GPa, the observed assemblage of sodium/calcium carbonates consists of CaCO 3 (aragonite and calcite), Na 2 Ca(CO 3 ) 3 , Na 2 Ca 3 (CO 3 ) 4 , and Na 2 Ca 4 (CO 3 ) 5 (Podborodnikov et al, 2018;Shatskiy et al, 2013). Thus, it is possible that the low-pressure, heated assemblage might consist of a more complicated series of sodium/calcium carbonates: for example, Na 2 Ca 3 (CO 3 ) 4 (1,089, 1,085 cm À1 ) and Na 2 Ca(CO 3 ) 2 (1,070, 1,082 cm À1 ) (Podborodnikov et al, 2018).…”

Section: A High-pressure/high-temperature Phase In Shortite Above 12 Gpamentioning

confidence: 99%

“…In heated large volume experiments at 3 and 6 GPa, the observed assemblage of sodium/calcium carbonates consists of CaCO 3 (aragonite and calcite), Na 2 Ca(CO 3 ) 3 , Na 2 Ca 3 (CO 3 ) 4 , and Na 2 Ca 4 (CO 3 ) 5 (Podborodnikov et al, 2018;Shatskiy et al, 2013). Thus, it is possible that the low-pressure, heated assemblage might consist of a more complicated series of sodium/calcium carbonates: for example, Na 2 Ca 3 (CO 3 ) 4 (1,089, 1,085 cm À1 ) and Na 2 Ca(CO 3 ) 2 (1,070, 1,082 cm À1 ) (Podborodnikov et al, 2018). One major expected mode in this scenario is not present in our spectrum: the rather strong peak of Podborodnikov et al (2018) at 1,082 cm À1 that corresponds to the symmetric stretch in Na 2 Ca(CO 3 ) 2 .…”

Section: A High-pressure/high-temperature Phase In Shortite Above 12 Gpamentioning

confidence: 99%

“…Thus, it is possible that the low-pressure, heated assemblage might consist of a more complicated series of sodium/calcium carbonates: for example, Na 2 Ca 3 (CO 3 ) 4 (1,089, 1,085 cm À1 ) and Na 2 Ca(CO 3 ) 2 (1,070, 1,082 cm À1 ) (Podborodnikov et al, 2018). One major expected mode in this scenario is not present in our spectrum: the rather strong peak of Podborodnikov et al (2018) at 1,082 cm À1 that corresponds to the symmetric stretch in Na 2 Ca(CO 3 ) 2 . This absence might be explained by preferred orientation effects on the intensity of the mode.…”

Section: A High-pressure/high-temperature Phase In Shortite Above 12 Gpamentioning

confidence: 99%

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High‐Pressure/Temperature Behavior of the Alkali/Calcium Carbonate Shortite (Na₂Ca₂(CO₃)₃): Implications for Carbon Sequestration in Earth's Transition Zone

2018

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The behavior of shortite (Na2Ca2(CO3)3) has been probed using synchrotron‐based single crystal X‐ray diffraction and Raman spectroscopy at high pressures and following laser heating to illuminate carbon retention within the deep earth, and phase equilibria of alkali/calcium carbonate‐rich systems. Above 15 GPa, a transition to the shortite‐II structure occurs at 300 K. This phase is novel as it involves a large distortion of the carbonates, with an onset of 3 + 1 coordination and near‐dimerization of carbonate groups. Above 22 GPa, shortite‐II amorphizes. Samples laser heated at pressures between 12 and 30 GPa crystallize in a new structure, shortite‐III. Below 12 GPa, this phase appears to decompose into a mixture of shortite, nyerereite (Na2Ca(CO3)2), and aragonite (CaCO3) in accord with prior phase equilibria results. The high‐pressure behavior of nyerereite using Raman spectroscopy was also investigated to 25 GPa. The structural response of shortite to pressure is modulated by the sodium cations in the structure; hence, the behavior of alkali‐rich carbonates within kimberlitic systems at depth is likely dependent on the bonding and local geometry of alkali cations. Our results show that complex, dense high‐pressure structures are generated in the shortite system, and phase equilibria of the protoliths of carbonatites and kimberlites at deep upper mantle and transition zone pressures will involve intermediate alkali‐calcium carbonate phases, including the high‐pressure phases of shortite. Moreover, 3 + 1 coordination of carbon is observed at far lower pressures than other systems: this coordination could become important in complex carbonates and possibly liquids at substantially shallower depths than previously anticipated.

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Phase Diagrams of Carbonate Materials at High Pressures, with Implications for Melting and Carbon Cycling in the Deep Earth

Litasov

Shatskiy

Podborodnikov

et al. 2020

Geophysical Monograph Series

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In this chapter, we review phase diagrams of alkali and alkaline earth carbonates at high pressures, particularly simple, binary, and ternary systems, which were recently constrained at pressures of 3 and 6 GPa. These studies revealed a number of new alkali-alkaline earth double carbonates. Major transformations of high-pressure carbonates, including changes in carbon coordination, spin transition, and valence state in Fe-bearing carbonates up to the lower mantle levels, were also discussed. We emphasize the importance of carbonate systems for understanding the low-degree partial melting of carbonated mantle rocks and explaining carbonate inclusions in diamond and other deep-seated minerals. The question of carbonate stability versus the presumably reduced nature of the deep Earth's mantle provides significant impact on the further study of material transport and deep volatile cycle through the history of our planet.

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The system Na2CO3–CaCO3 at 3 GPa

Cited by 23 publications

References 55 publications

High‐Pressure Na‐Ca Carbonates in the Deep Carbon Cycle

High‐Pressure Na‐Ca Carbonates in the Deep Carbon Cycle

High‐Pressure/Temperature Behavior of the Alkali/Calcium Carbonate Shortite (Na₂Ca₂(CO₃)₃): Implications for Carbon Sequestration in Earth's Transition Zone

Phase Diagrams of Carbonate Materials at High Pressures, with Implications for Melting and Carbon Cycling in the Deep Earth

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The system Na2CO3–CaCO3 at 3 GPa

Cited by 23 publications

References 55 publications

High‐Pressure Na‐Ca Carbonates in the Deep Carbon Cycle

High‐Pressure Na‐Ca Carbonates in the Deep Carbon Cycle

High‐Pressure/Temperature Behavior of the Alkali/Calcium Carbonate Shortite (Na2Ca2(CO3)3): Implications for Carbon Sequestration in Earth's Transition Zone

Phase Diagrams of Carbonate Materials at High Pressures, with Implications for Melting and Carbon Cycling in the Deep Earth

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High‐Pressure/Temperature Behavior of the Alkali/Calcium Carbonate Shortite (Na₂Ca₂(CO₃)₃): Implications for Carbon Sequestration in Earth's Transition Zone