Subduction fluids play a crucial role in regulating long-term chemical cycles. Their characterisation is essential to understand the processes responsible for metasomatism, oxidation and melting of the mantle wedge. Both direct (fluid inclusion studies) and indirect (thermodynamic modelling) approaches to study subduction fluids have reliability issues due to the complexity of the investigated processes. Post-entrapment processes (e.g., solvent loss by diffusion or decrepitation and/or chemical reactions between host mineral and trapped fluid) are likely to modify the chemical fingerprint of ultra-high pressure (UHP) fluid inclusions, while thermodynamic modelling of solute-bearing fluids at UHP conditions is still at the beginning of its application. In this work, we apply and compare data obtained by both approaches for fluid inclusions trapped within UHP clinopyroxene from a chemically simple Ol-Cpx-Dol-Cal marble (Brossasco-Isasca Unit, Dora-Maira Massif, Western Italian Alps). Classical molecular-fluid thermodynamics is adequate to qualitatively describe the post-entrapment reactions between fluid inclusions and host clinopyroxene. However, an electrolytic fluid model is necessary to describe the chemical composition of the solute-bearing aqueous fluids at the peak metamorphic condition (H₂O: 96.30 mol%/88.49 wt%; solutes: 3.61 mol%/11.34 wt%/2.08 mol/kg; other volatiles: 0.09 mol%/0.17 wt%) generated by progressive rock dissolution. Comparison of the model fluid composition with that inferred from the analysis of fluid inclusions clarifies the types and the extent of post-trapping chemical modification of the UHP fluid inclusions. Our data reveal that the fluid-host reactions carry up to 42 mol% of host clinopyroxene component in the fluid inclusion bulk composition, whereas the fluid inclusion decrepitation and the water diffusion in the host clinopyroxene (through dislocations and/or micro-fractures) cause an H₂O loss ranging from 18 mol% to 99 mol%. Applying these approaches, we demonstrate that the most relevant post-entrapment process is H₂O loss. We also demonstrate that some fluid inclusions did not experience post-entrapment fluid-host modification and, thus, preserve the original fluid geochemistry.

俯冲流体在调节长期化学循环中起着至关重要的作用。它们的表征对于理解导致地幔楔交代、氧化和熔化的过程至关重要。由于研究过程的复杂性，研究俯冲流体的直接（流体包裹体研究）和间接（热力学建模）方法都存在可靠性问题。后包封处理（例如，通过扩散或爆裂和/或主机矿物和截留流体之间的化学反应的溶剂损失）可能改变超高压（UH的化学指纹P）流体夹杂物，而热力学模型solute- UH P 的轴承液条件尚处于开始应用阶段。在这项工作中，我们应用并比较了通过两种方法获得的数据，用于捕获来自化学简单的 Ol-Cpx-Dol-Cal 大理石（Brossasco-Isasca Unit，Dora-Maira Massif，意大利西部阿尔卑斯山）的UH P单斜辉石中的流体包裹体。经典的分子流体热力学足以定性地描述流体包裹体和宿主单斜辉石之间的夹带后反应。然而，需要电解液模型来描述在峰值变质条件 (H ₂O：96.30 mol%/88.49 wt%；溶质：3.61 mol%/11.34 wt%/2.08 mol/kg；其他挥发物：0.09 mol%/0.17 wt%）由渐进式岩石溶解产生。与从流体夹杂物澄清的类型和UH的后捕集化学修饰的程度的分析推导出的模型流体组合物的比较P流体夹杂物。我们的数据表明，流体-主体反应在流体包裹体整体成分中携带高达 42 mol% 的主体单斜辉石组分，而主体单斜辉石中的流体包裹体爆裂和水扩散（通过位错和/或微裂缝）导致H ₂ O 损失范围为 18 mol% 至 99 mol%。应用这些方法，我们证明了最相关的诱捕后过程是 H ₂哦损失。我们还证明了一些流体包裹体没有经历捕集后流体-主体改性，因此保留了原始的流体地球化学。