The system NaAlSi2O6‒CaMgSi2O6−CO2 at 3–6.5 GPa: implications for CO2 stability in the eclogitic suite at depths of 100–200 km

Shatskiy, Anton; Vinogradova, Yulia G.; Arefiev, Anton V.; Litasov, Konstantin D.

doi:10.1007/s00410-023-01999-w

Cited by 1 publication

(3 citation statements)

References 44 publications

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“…A similar effect can be expected in the system we are studying in the current paper, especially for the areas for which the program predicts the coexistence of CO 2 and carbonate melts. This assumption is confirmed by the results of experiments in Di-CO 2 and Di-Jd-CO 2 systems [26,28], which showed a decrease in the melting temperature compared to carbonate-silicate systems without an excess of CO 2 [56]. In addition, the Di-Jd-CO 2 system has a lower melting point compared to that of diopside-CO 2 .…”

Section: Discussionsupporting

confidence: 53%

“…Using thermodynamic calculations, Knoche et al [23] showed that the dilution of the diopside component in clinopyroxene and the pyrope component in garnet shifts the carbonation reaction boundaries to higher pressures. These calculations were verified by experiments with clinopyroxenes of the diopside-jadeite series [28]. The results showed that jadeite does not undergo a carbonation reaction, so clinopyroxene with a high jadeite content coexists with CO 2 to at least 6-6.5 GPa and 1050-1100 • C. In the case of garnet, experimentally identified trends are not so obvious.…”

Section: Introductionmentioning

confidence: 70%

“…The main components of clinopyroxene in eclogites are diopside and jadeite. An experimental study of the reaction of diopside-jadeite solid solutions with CO 2 showed that the jadeite component does not react with CO 2 up to at least 950 • C at 6 GPa [28]. Therefore, the CaCO 3 -MgCO 3 -FeCO 3 ternary solid solution model was employed for calculations of the carbonate portion, while the Na 2 CO 3 component was ignored.…”

Section: Eclogite-comentioning

confidence: 99%

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Stability of CO2 Fluid in Eclogitic Mantle Lithosphere: Thermodynamic Calculations

Vinogradova,

Shatskiy

2024

Minerals

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Findings of solid and liquefied CO2 in diamonds from kimberlites and placers have indicated its presence in the form of a fluid phase in the Earth’s mantle at depths of 150–250 km. However, this is inconsistent with the results of experiments and existing thermodynamic calculations. To clarify this, we carried out thermodynamic modeling of garnet–CO2 and bimineral eclogite–CO2 systems using the Perple_X v. 7.1.3 software package, which establishes the most thermodynamically favorable assemblages for a given bulk composition of the system, unlike previous calculations, for which the phase relationships were simply assumed. The key difference between our results and previously known data is the presence of a region of partial carbonation. In this region, the garnet and clinopyroxene of the new compositions, CO2 fluid, carbonates, kyanite, and coesite are in equilibrium. The calculations revealed that unlike endmember systems (pyrope–CO2 and diopside–CO2) in the eclogite–CO2 system, the carbonation and decarbonation lines do not coincide, and the Grt+Cpx+CO2 and Carb+Ky+Coe+Cpx fields are separated by the Grt+Cpx+CO2+Carb+Ky+Coe region, which extends to pressures exceeding 4.3–6.0 GPa at 1050–1200 °C. This should extend the CO2 stability field in the eclogitic mantle to lower temperatures. Yet, owing to the short CO2 supply in the real mantle, the CO2 fluid should be completely spent on the carbonation of eclogite just below the eclogite + CO2 field. Thus, according to the obtained results, the CO2 fluid is stable in the eclogitic mantle in the diamond stability field at temperatures exceeding 1250 °C and pressures of 5–6 GPa.