The interaction between multi‐component rare earth element (REE) aqueous solutions and carbonate grains (dolomite, aragonite, and calcite) are studied at hydrothermal conditions (21–210 °C). The effect of ionic radii of five REEs (La, Ce, Pr, Nd, Dy) on solid formation are analyzed using two solution types: equal REE concentrations and concentrations normalized to Post Archean Australian Shale Standard (PAAS). The interaction replaces the host Ca–Mg carbonate grains with a series of REE minerals (lanthanite → kozoite → bastnäsite → cerianite). At 165 °C, equal concentration solutions promote kozoite crystallization, maintaining similar REE ratios in solids and solution. PAAS solutions result in zoned REE‐bearing crystals with heterogeneous elemental distributions and discreet REE phases (e.g., cerianite). Chemical signatures indicate metastable REE‐bearing phases transforming into more stable polymorphs, along with symplectite textures formed by adjacent phase reactions. Overall, experiments highlight the dependence of polymorph selection, crystallization pathway, mineral formation kinetics, and chemical texture on REE concentrations, ionic radii, temperature, time, and host grain solubility.

中文翻译：

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稀土碳酸盐的化学结构：模拟氟碳铈矿形成的实验方法


研究了水热条件（21-210°C）下多组分稀土元素（REE）水溶液与碳酸盐颗粒（白云石、霰石和方解石）之间的相互作用。使用两种溶液类型分析五种 REE（La、Ce、Pr、Nd、Dy）的离子半径对固体形成的影响：等 REE 浓度和标准化为太古代澳大利亚页岩标准 (PAAS) 的浓度。这种相互作用用一系列 REE 矿物（镧石 → 钾沸石 → 氟碳铈矿 → 铈长石）取代了主体 Ca-Mg 碳酸盐颗粒。在 165 °C 时，等浓度的溶液促进铜锌矿结晶，保持固体和溶液中相似的 REE 比率。 PAAS 溶液产生具有异质元素分布和离散稀土相（例如，堇长石）的分区含稀土晶体。化学特征表明亚稳态稀土相转变为更稳定的多晶型物，以及由相邻相反应形成的辛晶结构。总体而言，实验强调了多晶型选择、结晶途径、矿物形成动力学和化学结构对稀土元素浓度、离子半径、温度、时间和主体颗粒溶解度的依赖性。