Accessory mineral Eu anomalies (Eu/Eu*) are routinely measured to infer changes in the amount of feldspar over time, allowing accessory mineral U‐Pb dates to be linked to the progressive crystallization of igneous and metamorphic rocks and, by extension, geodynamic processes. However, changes in Eu/Eu* can reflect any process that changes the relative availability of Eu²⁺ and Eu³⁺. We constructed partitioning budgets for Sm, Eu²⁺, Eu³⁺, and Gd in suprasolidus metasedimentary rocks to investigate processes that can influence accessory mineral Eu anomalies. We modeled three scenarios: (1) closed‐system, equilibrium crystallization; (2) fractionation of Eu by feldspar growth during melt crystallization; and (3) removal of Eu by melt extraction. In the closed‐system equilibrium model, accessory mineral Eu/Eu* changes as a function of f O₂ and monazite stability; Eu/Eu* changes up to 0.3 over a pressure‐temperature range of 4–12 kbar and 700–950°C. Fractionation of Eu by feldspar growth is modeled to decrease accessory mineral Eu/Eu* by ~0.05–0.15 per 10 wt% feldspar crystallized. Melt extraction has a smaller effect; removal of 10% melt decreases accessory mineral Eu/Eu* in the residue by ≤0.05. Although these models demonstrate that fractionation of Eu by feldspar growth can be a dominant control on a rocks u budget, they also show that the common interpretation that Eu/Eu* only records feldspar growth and breakdown is an oversimplification that could lead to incorrect interpretation about the duration and rates of tectonic processes. Consideration of other processes that influence Eu anomalies will allow for a broader range of geological processes to be investigated by petrochronology.

中文翻译：

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上固结岩中的辅助矿物Eu异常：长石之外

常规测量辅助矿物Eu异常（Eu / Eu *）以推断长石量随时间的变化，从而使辅助矿物U-Pb日期与火成岩和变质岩的逐步结晶以及扩展的地球动力学过程相关联。但是，Eu / Eu *的变化可以反映出任何改变Eu ²⁺和Eu ³⁺相对可用性的过程。我们为Sm，Eu 2 ⁺，Eu ³⁺构建了分区预算，超固结沉积岩中的Gd，以研究可能影响副矿物Eu异常的过程。我们对三种情况进行了建模：（1）封闭系统，平衡结晶；（2）在熔体结晶过程中通过长石的生长对Eu进行分馏；（3）通过熔融萃取除去Eu。在封闭系统平衡模型中，辅助矿物Eu / Eu *随f O _2的变化而变化独居石的稳定性；在4–12 kbar的压力温度范围和700–950°C的温度范围内，Eu / Eu *的变化最多为0.3。通过长石生长对Eu进行分级分离，可模拟出每10 wt％的长石结晶使辅助矿物Eu / Eu *降低〜0.05–0.15。熔体萃取的作用较小；去除10％的熔体可使残留物中的辅助矿物Eu / Eu *降低≤0.05。尽管这些模型表明，长石生长对Eu的分馏可能是控制岩石u预算的主要控制因素，但它们也表明，Eu / Eu *仅记录长石生长和分解的普遍解释是过分简化，可能导致错误的解释。构造过程的持续时间和速度。