Abstract The reactive solubility of H2O in CaO-MgO-SiO2-H2O (CMSH) silicate melts at high pressure (P) and temperature (T) is investigated through first principles in the aim of assessing quantitatively the effect of this component on the liquidus. The Forsterite-Diopside-Silica sub-system is taken as case-study for the relevant high-quality petrological data at disposal. It is shown that the bulk molar amount of H2O, due to the stabilizing effect of protons on the liquid aggregation state, coupled with the high chemical potential of the pure component in solution, does not act linearly in depressing the liquidus. Application to the mantle melting at oceanic ridges, while confirming the intrinsic validity of the “melting at the cusp” model of Presnall and coworkers, suggests that it is the melting process that buffers the oceanic geotherm, and not vice-versa, as commonly assumed.

中文翻译：

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质子对岩浆熔融行为的影响：以高压下镁橄榄石-透辉石-二氧化硅系统为例

摘要 通过第一性原理研究了 H2O 在高压 (P) 和高温 (T) 下 CaO-MgO-SiO2-H2O (CMSH) 硅酸盐熔体中的反应溶解度，目的是定量评估该组分对液相线的影响。镁橄榄石-透辉石-二氧化硅子系统被用作相关高质量岩石学数据的案例研究。结果表明，由于质子对液体聚集态的稳定作用，加上溶液中纯组分的高化学势，大量的 H2O 摩尔量不会线性地抑制液相线。应用于洋脊地幔熔融，同时证实了 Presnall 及其同事的“尖端熔融”模型的内在有效性，表明正是熔融过程缓冲了海洋地温，