Phase relationships in the system K2CO3-CaCO3 at 6 GPa and 900–1450 °C
Phase relationships in the system K2CO3-CaCO3 at 6 GPa and 900–1450 °C
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K2CO3-CaCO3 系统在 6 GPa 和 900–1450 °C 下的相关系
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
E. Ohtani
中科院分区：
文献类型：
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作者：
A. Shatskiy;Y. Borzdov;K. Litasov;I. Sharygin;Yuri N. Palyanov;E. Ohtani
在6.0GPa和900-1450 °C条件下，研究了K_2CO_3-CaCO_3体系在X（K_2CO_3）= 100 - 10mol%范围内的相关系。在900-950 °C下，该系统有三种中间化合物：K6 Ca 2（CO 3）5，K2 Ca（CO 3）2和K2 Ca 3（CO 3）4。K2 Ca（CO 3）2化合物在950 °C以上分解为K6 Ca 2（CO 3）5 + K2 Ca 3（CO 3）4组合。K6 Ca 2（CO 3）5和K2 Ca 3（CO 3）4化合物分别在略高于1200和1300 °C时熔融。在接近1200 °C时，共晶在64和44摩尔%下建立，在接近1300 °C时，共晶在23摩尔%下建立。K2 CO 3在1300 °C和75 mol%下保持为液相，并在1425 ± 20 °C下熔化。文石在1300 °C和20摩尔%以及在1400 °C和10摩尔%下保持为液相。CaCO_3在K_2CO_3中的溶解度和K_2CO_3在文石中的溶解度低于检测限（<0.5mol%）。俯冲派生的富钾钙镁铁碳酸盐岩渗入Fe 0饱和地幔导致提取（Mg，Fe）CO 3组分从熔体，这将其组合物向K-Ca碳酸盐岩。根据我们的数据，这种熔体可以在亚温岩石圈的P-T条件下稳定，地热梯度为40 mW/m2，对应于6 GPa下1200 °C的温度。
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.