发表机构
Michigan State University（密歇根州立大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究通过多阶段地核形成模型模拟地球地幔铁同位素演化，发现多阶段地核形成重新平衡了铁同位素分馏效应，结合随机吸积等因素，表明金属-硅酸盐平衡的同位素分馏并非地球地幔铁同位素组成的主要成因。
AI 中文摘要
一种用于解释行星地幔与球粒陨石之间铁同位素差异的机制是陆地地核形成过程中的金属-硅酸盐平衡。此前对该同位素分馏效应的研究采用单阶段地核形成模型，这类模型无法重现地球地幔的亲铁元素预算。本研究在多阶段地核形成场景下模拟地球地幔的铁同位素演化，该场景符合行星形成的动力学模型，且能重现整体硅酸盐地球的地球化学特征，尤其是难熔的中等亲铁元素。研究发现，多阶段地核形成会重新平衡铁同位素体系中金属-硅酸盐平衡的分馏效应，其幅度与地幔岩石的典型分析不确定性相当或更小。最终，这种重新平衡效应，加之使行星形成过程进一步复杂化的随机吸积与分异历史，使得金属-硅酸盐平衡过程中的同位素分馏不太可能是导致地球地幔铁同位素组成的主要机制。
英文摘要
One proposed mechanism for generating iron isotopic differences between planetary mantles and chondrites is metal-silicate equilibration during terrestrial core formation. Prior studies of this isotopic fractionation effect employ single-stage core formation models that are inconsistent with reproducing the siderophile element budget of the Earth's mantle. Here, we model iron isotopic evolution of the Earth's mantle in a multistage core formation scenario that is consistent with dynamic models of planet formation and reproduces the geochemistry of the bulk silicate Earth, specifically the refractory moderately siderophile elements. We find that multiple stages of core formation rebalance the fractionating effect of metal-silicate equilibration for the iron isotopic system, comparable to or smaller than typical analytical uncertainties in mantle rocks. Ultimately, this rebalancing effect - coupled with stochastic accretion and differentiation histories which further complicate planetary formation processes - makes it unlikely that isotopic fractionation during metal-silicate equilibration is the primary mechanism responsible for the iron isotopic composition of the Earth's mantle.
CommentsAccepted for publication in Geochimica et Cosmochimica Acta, 17 pages, 7 figures
