The Thermodynamic Properties of MgCO3-CaCO3-FeCO3-Na2CO3-K2CO3-Li2CO3 Liquids: New Measurements

该提案的目标是提供MgCO 3-FeCO 3-CaCO 3-Na 2CO 3-K2 CO 3-Li 2CO 3系统中各种液体的各种热力学性质（热容，密度，热膨胀，压缩性）的首次测量。 这些基本的碳酸盐液体，特别是那些含有CaCO 3和MgCO 3的热力学数据，将允许部分熔融的含碳酸盐地幔岩的热力学模型。 需要这样的模型来严格评估复杂的全球碳循环，其中包括碳酸盐洋壳的俯冲，碳酸盐岩熔体的形成，交代不同的地幔岩性，这些碳酸盐岩的部分熔融，以及随后的火山CO2释放到大气中。 多组分碳酸盐液体的热力学性质测量不仅对地球科学家感兴趣，而且对对熔融碳酸盐燃料电池感兴趣的材料科学家也感兴趣，以从氢中获得能量。我们计划将10- 50mol%CaCO3和MgCO 3（和10- 30mol%FeCO3）添加到具有低熔融温度的各种混合碱（Li-Na-K）碳酸盐液体中，并进行热容（通过差示扫描量热法; DSC）、密度（通过双摆锤阿基米德法）和声速（通过声学干涉法）的测量以获得熔体压缩性。 另一个目的是进行一系列相平衡实验以定位各种碳酸盐相（例如，K2 Ca（CO 3）2、Na 2Ca（CO 3）2、Na 2CO 3、CaCO 3、MgCO 3、KLiCO 3等）在P-T空间。 从这两组实验数据中，我们建议使用熔融曲线分析来约束各种碳酸盐相的熔融度以及它们各自的液体值（它们的熔体压缩性的压力依赖性）。

The goal of this proposal is to provide the first measurements of various thermodynamic properties (heat capacity, density, thermal expansion, compressibility) for a wide range of liquids in the MgCO3-FeCO3-CaCO3-Na2CO3-K2CO3-Li2CO3 system. These fundamental thermodynamic data for carbonate liquids, especially those containing CaCO3 and MgCO3, will permit thermodynamic models of partial melting for carbonate-bearing mantle rocks. Such models are needed to rigorously evaluate the complex global carbon cycle, which includes the subduction of carbonated oceanic crust, the formation of carbonatite melts that metasomatize diverse mantle lithologies, the partial melting of these carbonated rocks, and the subsequent volcanic outgassing of CO2 to the atmosphere. Thermodynamic property measurements on multi-component carbonate liquids are of interest not only to earth scientists, but also to material scientists interested in molten carbonate fuel cells to derive energy from hydrogen. We plan to add 10-50 mol % CaCO3 and MgCO3 (and 10-30 mol % FeCO3) to various mixed alkali (Li-Na-K) carbonate liquids with low melting temperatures, and to perform measurements of heat capacity (by differential scanning calorimetry; DSC), density (by the double-bob Archimedean method), and sound speed (by acoustic interferometry) to obtain melt compressibility. An additional objective is to perform a series of phase equilibrium experiments to locate the fusion curves of various carbonate phases (e.g., K2Ca(CO3)2, Na2Ca(CO3)2, Na2CO3, CaCO3, MgCO3, KLiCO3, etc.) in P-T space. From these two sets of experimental data, we propose to use fusion curve analysis to constrain the enthalpies of fusion of the various carbonate phases as well as their respective liquid values (the pressure dependence of their melt compressibility).