Carbonates are important carbon-bearing phases in the mantle. While their role in upper mantle petrologic processes has been well studied, their effect on phase relations, melting, and transport properties in the lower mantle is less understood. The stability of carbonates in the mantle depends on a host of factors, including pressure, temperature, oxygen fugacity, and reactions with surrounding mantle phases. To understand the stability of carbonates in the presence of metal in the lower mantle, carbonate-metal reaction experiments on the Fe–Si–Ca–Mg–C–O system were conducted up to 124 GPa and 3200 K. We find that carbonates react with iron alloys to form silicates, iron carbides, and oxides. However, the temperature at which these reactions occur increases with pressure, indicating that along a geotherm in the lowermost mantle carbonates are the stable carbon-bearing phase. Carbon is found to be less siderophilic at high-pressure compared to silicon.

中文翻译：

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下地幔中的碳酸盐-金属反应

碳酸盐是地幔中重要的含碳相。虽然它们在上地幔岩石学过程中的作用已得到充分研究，但它们对下地幔相关系、熔融和输运特性的影响却知之甚少。地幔中碳酸盐的稳定性取决于许多因素，包括压力、温度、氧逸度以及与周围地幔相的反应。为了了解下地幔金属存在下碳酸盐的稳定性，在 Fe-Si-Ca-Mg-C-O 体系上进行了碳酸盐-金属反应实验，实验压力高达 124 GPa、3200 K。我们发现碳酸盐发生反应与铁合金形成硅酸盐、碳化铁和氧化物。然而，这些反应发生的温度随着压力的增加而升高，这表明沿着地温的最下地幔碳酸盐是稳定的含碳相。人们发现，与硅相比，碳在高压下的亲铁性较低。