Abstract This study investigates the partitioning of rare earth elements (REE) from La to Gd between molten metal and silicate to evaluate potential fractionation occurring during core-mantle differentiation. We report molten metal-silicate liquid partition coefficients from 24 multi-anvil experiments, extending the range of pressure, previously ranging from 1 to 8 GPa, up to 14 GPa. Experiments were performed at temperatures of between 2300 and 2560 K, and for oxygen fugacities ranging from the IW (Iron-Wustite buffer) to IW–4. Metal-silicate partition coefficients for the studied REE vary with the oxygen fugacity and S concentration in the metallic phase of the system. These elements were all lithophile during the Earth's accretion. By compiling all existing data on molten metal-silicate liquid partitioning, REE partitioning between the mantle and core during the Earth's accretion can be determined for a wide range of P, T and fo2 conditions representing the early evolution of planetary bodies from planetesimals to planets. REE concentrations of the bulk silicate Earth (BSE) are calculated from accretion scenarios using varying proportions and compositions of chondritic building blocks. The models selected are those that reproduce the Earth's nucleosynthetic isotope signature and the Ni/Co, Th/U and Nb/Ta ratios of the BSE. The BSE refractory element enrichment factor determined from REE data is equal to 2.88 (relative to CI chondrites). This calculation takes into account the depletion in volatile elements in the Earth compared to chondrites. This new estimate is in good agreement with previous determinations based on analysis of the upper mantle rocks, which supports the idea of a chemically homogeneous mantle. We also confirm that the formation of the core, with or without segregation of a sulfide phase, does not fractionate Sm/Nd and cannot be responsible for the 142Nd excess measured in modern terrestrial samples relative to chondrites.

中文翻译：

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从稀土元素的金属硅酸盐实验确定块状硅酸盐地球的耐火富集因子

摘要 本研究调查了熔融金属和硅酸盐之间从 La 到 Gd 的稀土元素 (REE) 的分配，以评估核幔分异过程中发生的潜在分馏。我们报告了来自 24 个多砧实验的熔融金属硅酸盐液体分配系数，扩展了压力范围，以前的范围从 1 到 8 GPa，最高可达 14 GPa。实验在 2300 到 2560 K 之间的温度下进行，氧逸度范围从 IW（铁-维氏体缓冲液）到 IW-4。所研究的 REE 的金属-硅酸盐分配系数随系统金属相中的氧逸度和 S 浓度而变化。这些元素在地球吸积过程中都是亲石的。通过汇编关于熔融金属硅酸盐液体分配的所有现有数据，地球吸积过程中地幔和地核之间的 REE 分配可以确定为范围广泛的 P、T 和 fo2 条件，这些条件代表了行星体从微行星到行星的早期演化。块状硅酸盐地球 (BSE) 的 REE 浓度是根据使用不同比例和球粒陨石构件组成的吸积情景计算得出的。选择的模型是那些重现地球核合成同位素特征和 BSE 的 Ni/Co、Th/U 和 Nb/Ta 比率的模型。根据 REE 数据确定的 BSE 难熔元素富集系数等于 2.88（相对于 CI 球粒陨石）。该计算考虑了与球粒陨石相比地球中挥发性元素的消耗。这一新估计与先前基于上地幔岩石分析的确定结果非常一致，这支持了化学均质地幔的想法。我们还证实，无论有无硫化物相分离，岩心的形成都不会分馏 Sm/Nd，并且不能对现代陆地样品中相对于球粒陨石测量的 142Nd 过量负责。