Phase relationships in the system K2CO3-CaCO3 at 6 GPa and 900-1450°C

Anton Shatskiy; Yuri M. Borzdov; Konstantin D. Litasov; Igor S. Sharygin; Yuri N. Palyanov; Eiji Ohtani

doi:10.2138/am-2015-5001

Phase relationships in the system K₂CO₃-CaCO₃ at 6 GPa and 900-1450°C

Anton Shatskiy, Yuri M. Borzdov, Konstantin D. Litasov, Igor S. Sharygin, Yuri N. Palyanov, Eiji Ohtani

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Abstract

Phase relations in the system K₂CO₃-CaCO₃ have been studied in the compositional range, X(K₂CO₃), from 100 to 10 mol%, at 6.0 GPa and 900-1450°C. At 900-950°C, the system has three intermediate compounds: K₆Ca₂(CO₃)₅, K₂Ca(CO₃)₂, and K₂Ca₃(CO₃)₄. The K₂Ca(CO₃)₂ compound decomposes to the K₆Ca₂(CO₃)₅ + K₂Ca₃(CO₃)₄ assembly above 950°C. The K₆Ca₂(CO₃)₅ and K₂Ca₃(CO₃)₄ compounds melt congruently slightly above 1200 and 1300°C, respectively. The eutectics were established at 64 and 44 mol% near 1200°C and at 23 mol% near 1300°C. K₂CO₃ remains as a liquidus phase at 1300°C and 75 mol% and melts at 1425 ± 20°C. Aragonite remains as a liquidus phase at 1300°C and 20 mol% and at 1400°C and 10 mol%. CaCO₃ solubility in K₂CO₃ and K₂CO₃ solubility in aragonite are below the detection limit (<0.5 mol%). Infiltration of subduction-derived K-rich Ca-Mg-Fe-carbonatite into the Fe⁰-saturated mantle causes the extraction of (Mg,Fe)CO₃ components from the melt, which shifts its composition toward K-Ca-carbonatite. According to our data this melt can be stable at the P-T conditions of subcratonic lithosphere with geothermal gradient of 40 mW/m² corresponding to temperature of 1200°C at 6 GPa.

Original language	English
Pages (from-to)	223-232
Number of pages	10
Journal	American Mineralogist
Volume	100
Issue number	1
DOIs	https://doi.org/10.2138/am-2015-5001
Publication status	Published - 1 Jan 2015

Keywords

Alkaline carbonates
Buetschliite
Carbonatite
Earth's mantle
Fairchildite
High-pressure experiment

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10.2138/am-2015-5001

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title = "Phase relationships in the system K2CO3-CaCO3 at 6 GPa and 900-1450°C",

abstract = "Phase relations in the system K2CO3-CaCO3 have been studied in the compositional range, X(K2CO3), from 100 to 10 mol%, at 6.0 GPa and 900-1450°C. At 900-950°C, the system has three intermediate compounds: K6Ca2(CO3)5, K2Ca(CO3)2, and K2Ca3(CO3)4. The K2Ca(CO3)2 compound decomposes to the K6Ca2(CO3)5 + K2Ca3(CO3)4 assembly above 950°C. The K6Ca2(CO3)5 and K2Ca3(CO3)4 compounds melt congruently slightly above 1200 and 1300°C, respectively. The eutectics were established at 64 and 44 mol% near 1200°C and at 23 mol% near 1300°C. K2CO3 remains as a liquidus phase at 1300°C and 75 mol% and melts at 1425 ± 20°C. Aragonite remains as a liquidus phase at 1300°C and 20 mol% and at 1400°C and 10 mol%. CaCO3 solubility in K2CO3 and K2CO3 solubility in aragonite are below the detection limit (<0.5 mol%). Infiltration of subduction-derived K-rich Ca-Mg-Fe-carbonatite into the Fe0-saturated mantle causes the extraction of (Mg,Fe)CO3 components from the melt, which shifts its composition toward K-Ca-carbonatite. According to our data this melt can be stable at the P-T conditions of subcratonic lithosphere with geothermal gradient of 40 mW/m2 corresponding to temperature of 1200°C at 6 GPa.",

keywords = "Alkaline carbonates, Buetschliite, Carbonatite, Earth's mantle, Fairchildite, High-pressure experiment",

author = "Anton Shatskiy and Borzdov, {Yuri M.} and Litasov, {Konstantin D.} and Sharygin, {Igor S.} and Palyanov, {Yuri N.} and Eiji Ohtani",

year = "2015",

month = jan,

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doi = "10.2138/am-2015-5001",

language = "English",

volume = "100",

pages = "223--232",

journal = "American Mineralogist",

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TY - JOUR

T1 - Phase relationships in the system K2CO3-CaCO3 at 6 GPa and 900-1450°C

AU - Shatskiy, Anton

AU - Borzdov, Yuri M.

AU - Litasov, Konstantin D.

AU - Sharygin, Igor S.

AU - Palyanov, Yuri N.

AU - Ohtani, Eiji

PY - 2015/1/1

Y1 - 2015/1/1

N2 - Phase relations in the system K2CO3-CaCO3 have been studied in the compositional range, X(K2CO3), from 100 to 10 mol%, at 6.0 GPa and 900-1450°C. At 900-950°C, the system has three intermediate compounds: K6Ca2(CO3)5, K2Ca(CO3)2, and K2Ca3(CO3)4. The K2Ca(CO3)2 compound decomposes to the K6Ca2(CO3)5 + K2Ca3(CO3)4 assembly above 950°C. The K6Ca2(CO3)5 and K2Ca3(CO3)4 compounds melt congruently slightly above 1200 and 1300°C, respectively. The eutectics were established at 64 and 44 mol% near 1200°C and at 23 mol% near 1300°C. K2CO3 remains as a liquidus phase at 1300°C and 75 mol% and melts at 1425 ± 20°C. Aragonite remains as a liquidus phase at 1300°C and 20 mol% and at 1400°C and 10 mol%. CaCO3 solubility in K2CO3 and K2CO3 solubility in aragonite are below the detection limit (<0.5 mol%). Infiltration of subduction-derived K-rich Ca-Mg-Fe-carbonatite into the Fe0-saturated mantle causes the extraction of (Mg,Fe)CO3 components from the melt, which shifts its composition toward K-Ca-carbonatite. According to our data this melt can be stable at the P-T conditions of subcratonic lithosphere with geothermal gradient of 40 mW/m2 corresponding to temperature of 1200°C at 6 GPa.

AB - Phase relations in the system K2CO3-CaCO3 have been studied in the compositional range, X(K2CO3), from 100 to 10 mol%, at 6.0 GPa and 900-1450°C. At 900-950°C, the system has three intermediate compounds: K6Ca2(CO3)5, K2Ca(CO3)2, and K2Ca3(CO3)4. The K2Ca(CO3)2 compound decomposes to the K6Ca2(CO3)5 + K2Ca3(CO3)4 assembly above 950°C. The K6Ca2(CO3)5 and K2Ca3(CO3)4 compounds melt congruently slightly above 1200 and 1300°C, respectively. The eutectics were established at 64 and 44 mol% near 1200°C and at 23 mol% near 1300°C. K2CO3 remains as a liquidus phase at 1300°C and 75 mol% and melts at 1425 ± 20°C. Aragonite remains as a liquidus phase at 1300°C and 20 mol% and at 1400°C and 10 mol%. CaCO3 solubility in K2CO3 and K2CO3 solubility in aragonite are below the detection limit (<0.5 mol%). Infiltration of subduction-derived K-rich Ca-Mg-Fe-carbonatite into the Fe0-saturated mantle causes the extraction of (Mg,Fe)CO3 components from the melt, which shifts its composition toward K-Ca-carbonatite. According to our data this melt can be stable at the P-T conditions of subcratonic lithosphere with geothermal gradient of 40 mW/m2 corresponding to temperature of 1200°C at 6 GPa.

KW - Alkaline carbonates

KW - Buetschliite

KW - Carbonatite

KW - Earth's mantle

KW - Fairchildite

KW - High-pressure experiment

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U2 - 10.2138/am-2015-5001

DO - 10.2138/am-2015-5001

M3 - Article

AN - SCOPUS:84921346700

VL - 100

SP - 223

EP - 232

JO - American Mineralogist

JF - American Mineralogist

SN - 0003-004X

IS - 1

ER -

Phase relationships in the system K₂CO₃-CaCO₃ at 6 GPa and 900-1450°C

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