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
N1 - Funding Information:
We are very grateful to Dionysis Foustoukos and Shantanu Keshav for a thorough review and Keith Putirka and Bjorn Mysen for editorial handling and personal attention. Special thanks to Robert Luth for the time he spent reviewing early versions of the manuscript, for his helpful suggestions and comments. This work was supported by the Russian Scientific Fund (proposal no. 14-17-00609) and performed under the project of the Ministry of Education and Science of Russian Federation (no. 14.B25.31.0032).
Publisher Copyright:
© 2015, Walter de Gruyter GmbH. All rights reserved.
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
SN - 0003-004X
VL - 100
SP - 223
EP - 232
JO - American Mineralogist
JF - American Mineralogist
IS - 1
ER -