The carbon and water cycles in the Earth's interior are linked to key planetary processes, such as mantle melting, degassing, chemical differentiation, and advection. However, the role of water in the carbon exchange between the mantle and core is not well known. Here, we show experimental results of a reaction between Fe₃C and H₂O at pressures and temperatures of the deep mantle and core-mantle boundary (CMB). The reaction produces diamond, FeO, and FeH_x, suggesting that water can liberate carbon from the core in the form of diamond (“core carbon extraction”) while the core gains hydrogen, if subducted water reaches to the CMB. Therefore, Earth's deep water and carbon cycles can be linked. The extracted core carbon can explain a significant amount of the present-day mantle carbon. Also, if diamond can be collected by mantle flow in the region, it can result in unusually high seismic-velocity structures.

中文翻译：

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地球核幔边界的水致钻石形成

地球内部的碳和水循环与关键的行星过程有关，例如地幔融化、脱气、化学分化和平流。然而，水在地幔和地核之间碳交换中的作用尚不清楚。_{在这里，我们展示了 Fe 3} C 和 H ₂ O 在深部地幔和核幔边界 (CMB) 的压力和温度下反应的实验结果。该反应产生金刚石、FeO 和 FeH _x，这表明如果俯冲的水到达 CMB，水可以从核心以金刚石的形式释放碳（“核心碳提取”），而核心获得氢。因此，地球的深水循环和碳循环可以联系起来。提取的核心碳可以解释大量现今的地幔碳。此外，如果可以通过该地区的地幔流收集钻石，它可能会导致异常高的地震速度结构。