A variety of salt fluids (e.g., aqueous Li₂SO₄, ZnSO₄ and UO₂SO₄ fluid) were observed to separate into a heavy salt-rich fluid (F1) and a light salt-depleted fluid (F2) when heated to appropriate temperatures. The F1–F2 immiscibility (FFI) likely provides an efficient pathway for hydrothermal transport and accumulation of certain ore elements and influences the compositional evolution of hydrothermal fluids, as it considerably concentrates these elements into the F1 phase. However, geological studies to date have paid little attention to the occurrence and influence of this kind of fluid immiscibility. The discrepancy may be explained from two perspectives. First, the complex pressure–temperature–composition (P–T–x) conditions of geological fluids may destabilize the FFI or suppress its occurrence. Alternatively, the FFI in geological fluids may be neglected during geologic investigations due to a lack of knowledge. To bridge the gap between experimental research and geological studies, this study aims to reveal more properties of the FFI and establish some geological constraints for discerning the FFI in geological systems. The partitioning behaviors of sulfate (FFI-relevant component) and perchlorate (FFI-irrelevant component) during the FFI and boiling process in the ZnSO₄–Zn(ClO₄)₂–H₂O system were quantified using Raman spectroscopic analyses integrated with the mass conservation law. Results show inconsistent partitioning behaviors of SO₄²⁻ and ClO₄⁻ during the FFI; SO₄²⁻ is highly concentrated into the F1 phase relative to the light F2 phase, while ClO₄⁻ partitions almost equally between the two phases. On the contrary, SO₄²⁻ and ClO₄⁻ are concentrated proportionally in the residual liquid with boiling. Accordingly, some possible geological constraints, in addition to microthermometry, are postulated for the identification of the FFI in hydrothermal fluids, including (a) the P–T–x trajectory of the fluid intersecting with the FFI's stability region; (b) fluid inclusions showing divergent contents of FFI-relevant components but consistent concentrations of FFI-irrelevant components. This study sheds new light on the research of the salt-rich fluid and salt-depleted fluid immiscibility in geological systems.

各种盐类流体（例如 Li ₂ SO ₄水溶液、ZnSO ₄和 UO ₂ SO ₄流体）被观察到在加热到适当的温度时分离成重盐富盐流体（F1）和轻盐贫化流体（F2）。F1-F2 不混溶性 (FFI) 可能为某些矿石元素的热液输送和积累提供了有效途径，并影响热液流体的成分演化，因为它将这些元素大量集中到 F1 相中。然而，迄今为止的地质研究很少关注这种流体不混溶的发生和影响。这种差异可以从两个方面来解释。首先，复杂的压力-温度-成分（P-T-x) 地质流体的条件可能会破坏 FFI 的稳定性或抑制其发生。或者，由于缺乏知识，地质调查期间可能会忽略地质流体中的 FFI。为了弥合实验研究和地质研究之间的差距，本研究旨在揭示 FFI 的更多特性，并为在地质系统中识别 FFI 建立一些地质约束。在 ZnSO ₄ –Zn(ClO ₄ ) ₂ –H ₂ O 系统中FFI 和沸腾过程中硫酸盐（FFI 相关组分）和高氯酸盐（FFI 无关组分）的分配行为使用拉曼光谱分析与质量守恒定律。结果显示 SO 的分区行为不一致₄ ^2-和 ClO ₄ ^-在 FFI 期间；SO ₄ ^2-相对于轻质F2 相高度集中在F1 相中，而ClO ₄ ^-在两相之间的分配几乎相等。相反，SO ₄ ^2-和ClO ₄ ^-在沸腾的残余液体中成比例地浓缩。因此，除了微量测温法外，还假定了一些可能的地质约束来识别热液中的 FFI，包括 (a) P-T-x流体与 FFI 稳定区域相交的轨迹；(b) 流体包裹体显示 FFI 相关成分的含量不同，但 FFI 无关成分的浓度一致。该研究为地质系统中富盐流体和贫盐流体不混溶性研究提供了新的思路。