Reactions between metal and silicate phases, such as those that may occur at the core/mantle boundary, are charge transfer reactions-involving oxidation and reduction of chemical species. Therefore, the chemical potential driving force can be recast as an electric potential difference. Conversely, the application of an electric field across a metal/silicate interface is capable of driving chemical reactions. To explore the electrochemical behavior of a core/mantle-like boundary, the behavior of a liquid sulfide/silicate boundary in the presence of an externally applied electric potential difference was examined experimentally. The physical and chemical responses of this electrified interface include: (1) reaction zones containing new oxide phases at the similar to 1 V level, (2) unusual partitioning of highly siderophile elements at similar to 100 mV, (3) electrowetting at 10-100 mV, and (4) valence changes, indicating oxygen fugacity perturbations, at a level of similar to 1-10 mu V. An equivalent circuit diagram representing the experimental results is introduced, and extended to processes at the Earth's core/mantle boundary. (c) 2006 Elsevier B.V. All rights reserved.
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