Lv Mingda, Dorfman Susannah M, Badro James, Borensztajn Stephan, Greenberg Eran, Prakapenka Vitali B
Department of Earth and Environmental Sciences, Michigan State University, East Lansing, MI, USA.
Université de Paris, Institut de physique du globe de Paris, CNRS, Paris, France.
Nat Commun. 2021 Mar 17;12(1):1712. doi: 10.1038/s41467-021-21761-9.
The stable forms of carbon in Earth's deep interior control storage and fluxes of carbon through the planet over geologic time, impacting the surface climate as well as carrying records of geologic processes in the form of diamond inclusions. However, current estimates of the distribution of carbon in Earth's mantle are uncertain, due in part to limited understanding of the fate of carbonates through subduction, the main mechanism that transports carbon from Earth's surface to its interior. Oxidized carbon carried by subduction has been found to reside in MgCO throughout much of the mantle. Experiments in this study demonstrate that at deep mantle conditions MgCO reacts with silicates to form CaCO. In combination with previous work indicating that CaCO is more stable than MgCO under reducing conditions of Earth's lowermost mantle, these observations allow us to predict that the signature of surface carbon reaching Earth's lowermost mantle may include CaCO.
地球深部内部碳的稳定形式控制着地质时期碳在整个行星中的储存和通量，影响着地表气候，并以钻石包裹体的形式承载着地质过程的记录。然而，目前对地球地幔中碳分布的估计并不确定，部分原因是对俯冲作用（将碳从地球表面输送到内部的主要机制）中碳酸盐的归宿了解有限。研究发现，俯冲携带的氧化态碳在大部分地幔中以碳酸镁的形式存在。本研究中的实验表明，在地幔深部条件下，碳酸镁与硅酸盐反应形成碳酸钙。结合之前的研究表明，在地球最下地幔的还原条件下碳酸钙比碳酸镁更稳定，这些观察结果使我们能够预测，到达地球最下地幔的地表碳的特征可能包括碳酸钙。
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