New data on the system Na2CO3–CaCO3–MgCO3 at 6 GPa with implications to the composition and stability of carbonatite melts at the base of continental lithosphere

Podborodnikov, Ivan V.; Shatskiy, Anton; Arefiev, Anton V.; Bekhtenova, Altyna; Litasov, Konstantin D.

doi:10.1016/j.chemgeo.2019.03.027

Cited by 21 publications

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“…Bütschliite was found in coexistence with dolomite and Na 2 Mg(CO 3 ) 2 eitelite. The present results on KCM (Figure 5a,b) and data on NCM [44,45] indicate that neither bütschliite nor eitelite can coexist with dolomite under the P-T conditions of diamond crystallization in the lithospheric mantle ( Figure 5). This led to the conclusion that at the time of entrapment, the inclusion material was an alkali-bearing dolomitic melt and that bütschliite is a daughter phase [27].…”

Section: Thermal Stability Of Carbonatitic Melts Vs Alkalinitymentioning

confidence: 51%

“…Similar to KCM at 6 GPa, the Na2CO3-CaCO3-MgCO3 system (NCM) forms several intermediate compounds including Dol, Na2Ca4, Na2Ca3, Na4Ca, and Na2Mg [44]. The first melting occurs at 1050 °C, which is close to that in KCM (1090 °C).…”

Section: Comparison With the Na-bearing Systemmentioning

confidence: 93%

“…Figure 8. The diagrams illustrating primary crystallization regions and ternary eutectics in the system K2CO3-CaCO3-MgCO3 at 3 GPa (a) [37] and at 6 GPa (b) (this study) and in the system Na2CO3-CaCO3-MgCO3 at 3 GPa (c) [45] and at 6 GPa (d) [44]. Na2-Na2CO3, Na2Ca2-Na2Ca2(CO3)3, Na2Ca3 -Na2Ca3(CO3)4, Na2Mg-Na2Mg(CO3)2, see the Nomenclature section for other abbreviations.…”

Section: Mutual Solubility Of K 2 Ca(co 3 ) 2 and K 2 Mg(co 3 )mentioning

confidence: 96%

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The K2CO3–CaCO3–MgCO3 System at 6 GPa: Implications for Diamond Forming Carbonatitic Melts

et al. 2019

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Carbonate micro inclusions with abnormally high K2O appear in diamonds worldwide. However, the precise determination of their chemical and phase compositions is complicated due to their sub-micron size. The K2CO3–CaCO3–MgCO3 is the simplest system that can be used as a basis for the reconstruction of the phase composition and P–T conditions of the origin of the K-rich carbonatitic inclusions in diamonds. In this regard, this paper is concerned with the subsolidus and melting phase relations in the K2CO3–CaCO3–MgCO3 system established in Kawai-type multianvil experiments at 6 GPa and 900–1300 °C. At 900 °C, the system has three intermediate compounds K2Ca3(CO3)4 (Ca# ≥ 97), K2Ca(CO3)2 (Ca# ≥ 58), and K2Mg(CO3)2 (Ca# ≤ 10), where Ca# = 100Ca/(Ca + Mg). Miscibility gap between K2Ca(CO3)2 and K2Mg(CO3)2 suggest that their crystal structures differ at 6 GPa. Mg-bearing K2Ca(CO3)2 (Ca# ≤ 28) disappear above 1000 °C to produce K2Ca3(CO3)4 + K8Ca3(CO3)7 + K2Mg(CO3)2. The system has two eutectics between 1000 and 1100 °C controlled by the following melting reactions: K2Ca3(CO3)4 + K8Ca3(CO3)7 + K2Mg(CO3)2 → [40K2CO3∙60(Ca0.70Mg0.30)CO3] (1st eutectic melt) and K8Ca3(CO3)7 + K2CO3 + K2Mg(CO3)2 → [62K2CO3∙38(Ca0.73Mg0.27)CO3] (2nd eutectic melt). The projection of the K2CO3–CaCO3–MgCO3 liquidus surface is divided into the eight primary crystallization fields for magnesite, aragonite, dolomite, Ca-dolomite, K2Ca3(CO3)4, K8Ca3(CO3)7, K2Mg(CO3)2, and K2CO3. The temperature increase is accompanied by the sequential disappearance of crystalline phases in the following sequence: K8Ca3(CO3)7 (1220 °C) → K2Mg(CO3)2 (1250 °C) → K2Ca3(CO3)4 (1350 °C) → K2CO3 (1425 °C) → dolomite (1450 °C) → CaCO3 (1660 °C) → magnesite (1780 °C). The high Ca# of about 40 of the K2(Mg, Ca)(CO3)2 compound found as inclusions in diamond suggest (1) its formation and entrapment by diamond under the P–T conditions of 6 GPa and 1100 °C; (2) its remelting during transport by hot kimberlite magma, and (3) repeated crystallization in inclusion that retained mantle pressure during kimberlite magma emplacement. The obtained results indicate that the K–Ca–Mg carbonate melts containing 20–40 mol% K2CO3 is stable under P–T conditions of 6 GPa and 1100–1200 °C corresponding to the base of the continental lithospheric mantle. It must be emphasized that the high alkali content in the carbonate melt is a necessary condition for its existence under geothermal conditions of the continental lithosphere, otherwise, it will simply freeze.

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Section: Thermal Stability Of Carbonatitic Melts Vs Alkalinitymentioning

confidence: 51%

Section: Comparison With the Na-bearing Systemmentioning

confidence: 93%

Section: Mutual Solubility Of K 2 Ca(co 3 ) 2 and K 2 Mg(co 3 )mentioning

confidence: 96%

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The K2CO3–CaCO3–MgCO3 System at 6 GPa: Implications for Diamond Forming Carbonatitic Melts

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“…The results of modeling were also verified experimentally (Shatskiy et al 2013) using a two-pyroxene thermometer (Brey and Kohler, 1990). The maximum temperature gradients within individual samples and across the sample charge vary from 4 to 8 °C/mm as temperature increases from 800 to 1300 °C, respectively (Podborodnikov et al 2019). The modeling reveals that the maximum temperature difference between the thermocouple junction and samples is < 25 °C (Shatskiy et al This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America.…”

Section: Introductionmentioning

confidence: 99%

Revision of the CaMgSi2O6-CO2P-T phase diagram at 3–6 GPa

Shatskiy,

Vinogradova,

Arefiev

et al. 2023

American Mineralogist

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In the present work, we reexamined the phase relationships in the system diopside-CO2 in the range of 3-6 GPa and 850-1500 °C in multianvil experiments including reversal ones lasting up to 169 hours. The reaction CaMgSi2O6 (clinopyroxene) + 2CO2 (fluid) = 2SiO2 (quartz/coesite) + CaMg(CO3)2 (dolomite) passes through 3 GPa/950 °C with a slope of 6 MPa/°C and terminates at an invariant point near 4.5 GPa/1200 °C, where carbonate liquid coexists with clinopyroxene, coesite, dolomite and CO2 fluid. The newly determined boundary has the equation P(GPa) = 0.006×T(°C) -2.7. As temperature increases to 1250 °C at 4.5 GPa, liquid, dolomite, and coesite disappear and clinopyroxene coexists with CO2 fluid. As pressure increases to 6 GPa, the solidus temperature increases to 1300 °C revealing a slope of 15 MPa/°C. At 4.5 and 6 GPa, solidus melts contain about 1 wt% SiO2. As temperature increases to 1400 and 1500 °C at 6 GPa, the silica contents in the carbonate melt increase to 6 and 13 wt%, respectively. Our data combined with that of Luth (2006) This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America.The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.

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“…Alkaline-rich carbonates are relevant as ore minerals, and they might also play an important role in deep carbonatitic environments as their high-pressure phases may fractionate elements from a carbonatitic melt crystallizing in uppermantle conditions (Shatzky et al, 2016a, b;Podbordnikov et al, 2019). The experimental determination of Na 2 CO 3 -K 2 CO 3 -CaCO 3 -MgCO 3 systems at high pressures and temperatures has in fact revealed that above 3 GPa, new classes of Ca-rich alkaline-alkaline earth carbonates are stabilized and are primary liquidus phases, with a possible important role in fractionation of deep carbonatites (Shatzky et al, 2016a, b;Podbordnikov et al, 2019). Burbankite is among these carbonates (Shatzky et al, 2016a, b).…”

Section: Introductionmentioning

confidence: 99%

High-pressure and high-temperature structure and equation of state of Na3Ca2La(CO3)5 burbankite

et al. 2022

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Abstract. In this study we report the synthesis of single crystals of burbankite, Na3Ca2La(CO3)5, at 5 GPa and 1073 K. The structural evolution, bulk modulus and thermal expansion of burbankite were studied and determined by two separate high-pressure (0–7.07(5) GPa) and high-temperature (298–746 K) in situ single-crystal X-ray diffraction experiments. The refined parameters of a second-order Birch–Murnaghan equation of state (EoS) are V0= 593.22(3) Å3 and KT0= 69.8(4) GPa. The thermal expansion coefficients of a Berman-type EoS are α0= 6.0(2) ×10-5 K−1, α1= 5.7(7) ×10-8 K−2 and V0= 591.95(8) Å3. The thermoelastic parameters determined in this study allow us to estimate the larger density of burbankite in the pressure-temperature range of 5.5–6 GPa and 1173–1273 K, with respect to the density of carbonatitic magmas at the same conditions. For this reason, we suggest that burbankite might fractionate from the magma and play a key role as an upper-mantle reservoir of light trivalent rare earth elements (REE3+).

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New data on the system Na2CO3–CaCO3–MgCO3 at 6 GPa with implications to the composition and stability of carbonatite melts at the base of continental lithosphere

Cited by 21 publications

References 47 publications

The K2CO3–CaCO3–MgCO3 System at 6 GPa: Implications for Diamond Forming Carbonatitic Melts

The K2CO3–CaCO3–MgCO3 System at 6 GPa: Implications for Diamond Forming Carbonatitic Melts

Revision of the CaMgSi2O6-CO2P-T phase diagram at 3–6 GPa

High-pressure and high-temperature structure and equation of state of Na<sub>3</sub>Ca<sub>2</sub>La(CO<sub>3</sub>)<sub>5</sub> burbankite

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New data on the system Na2CO3–CaCO3–MgCO3 at 6 GPa with implications to the composition and stability of carbonatite melts at the base of continental lithosphere

Cited by 21 publications

References 47 publications

The K2CO3–CaCO3–MgCO3 System at 6 GPa: Implications for Diamond Forming Carbonatitic Melts

The K2CO3–CaCO3–MgCO3 System at 6 GPa: Implications for Diamond Forming Carbonatitic Melts

Revision of the CaMgSi2O6-CO2P-T phase diagram at 3–6 GPa

High-pressure and high-temperature structure and equation of state of Na&lt;sub&gt;3&lt;/sub&gt;Ca&lt;sub&gt;2&lt;/sub&gt;La(CO&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;5&lt;/sub&gt; burbankite

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New data on the system Na2CO3–CaCO3–MgCO3 at 6 GPa with implications to the composition and stability of carbonatite melts at the base of continental lithosphere

High-pressure and high-temperature structure and equation of state of Na<sub>3</sub>Ca<sub>2</sub>La(CO<sub>3</sub>)<sub>5</sub> burbankite