Abstract The current models developed to determine the pore water chemistry of clayrocks consider that Ca, Mg and Fe are controlled by equilibrium reactions with pure carbonates. However, the Ca/Mg ratios measured in pore water are not always in agreement with calculations. Here we investigated the interaction between calcite and dolomite at ambient temperature and at 80 °C. During batch experiments, despite the fast equilibration of the solution composition (within weeks), the gaseous CO2 concentration increased during several months at ambient temperature while it reached a steady state at 80 °C. The observations made at ambient temperature are apparently in conflict (metastable system). However, nanoscale characterizations proved to be useful to evidence a mineralogical evolution during the experiments. Indeed, local equilibria in solution enabled the precipitation of secondary phases despite their undersaturation with respect to the bulk solution and the dissolution of pristine phases. These results suggest that the dissolution/precipitation kinetics are slow and ongoing despite the apparent stability of the system, something usually not considered in the prediction of sedimentary facies over a geological timescale.

中文翻译：

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关于方解石和白云石之间的相互作用：来自气体和水相地球化学和矿物学特征的见解

摘要 当前用于确定粘土岩孔隙水化学的模型认为 Ca、Mg 和 Fe 受与纯碳酸盐的平衡反应控制。然而，在孔隙水中测得的 Ca/Mg 比率并不总是与计算结果一致。在这里，我们研究了环境温度和 80 °C 下方解石和白云石之间的相互作用。在批量实验期间，尽管溶液成分快速平衡（在几周内），但气态 CO2 浓度在环境温度下的几个月内增加，而在 80 °C 时达到稳定状态。在环境温度下进行的观察显然存在冲突（亚稳态系统）。然而，纳米级表征被证明有助于证明实验过程中的矿物演化。确实，溶液中的局部平衡使第二相能够沉淀，尽管它们相对于本体溶液和原始相的溶解不饱和。这些结果表明，尽管系统具有明显的稳定性，但溶解/沉淀动力学缓慢且持续，在地质时间尺度上的沉积相预测中通常不考虑这一点。