The involvement of modified seawater and/or basinal brine in IOCG mineralization was documented by numerous geologic studies. Still, this process remains poorly understood. In this study, we reacted seawater with andesite and basalt, the most common arc volcanic rocks, at 150 and 240 ^oC and water vapor-saturated pressure to assess the Cu leaching capacity and fluid evolution due to the seawater-volcanic rock interactions. The experimental results show that Mg, Fe, Al, and SO₄^2- in the modified seawater decreased significantly, accompanied by an increased Ca concentration. The fluid pH also decreased from 8.3 of the initial seawater to ∼ 7.5 and ∼ 7.0 after 150 and 240 ^oC experiments, respectively. The incongruent calcsilicate (e.g., plagioclase) dissolution and anhydrite precipitation were observed in the reacted rock samples. Thermodynamic modeling confirmed the trends of those concentration changes but predicted several alteration minerals that were not observed in the experiments. Our experiments show that Cu-leaching efficiency is much higher from the andesite than from the basalt, also higher at 240 ^oC than at 150 ^oC. The andesite contains more Cu than the basalt samples, and abundant Cu-rich (average 106 ppm) plagioclase-hosted silicate melt inclusions and Cu-bearing (average 59 ppm) groundmass are identified in the original andesite sample but not in the original basalt sample, which is considered to be the cause of the Cu-leaching differences between the two rock samples. The δ³⁴S value of resultant fluids is dominated by seawater sulfate with a minor contribution of magmatic sulfur from the rock. Thermodynamic modeling combined with recent experimental studies show that deposition of Cu sulfides is the most effective when Cu-bearing fluids react with early-stage pyrite. Our results suggest that the seawater/ (brine)-volcanic rock reactions at 150-250 ^oC can produce Cu-bearing fluids, which in turn can form IOCG deposits, and that Cu mineralization with sulfides zonation can result from replacement reactions between the Cu-bearing fluids and Fe-rich minerals in precursor iron ore bodies.

许多地质研究记录了改性海水和/或盆地盐水在 IOCG 矿化中的作用。尽管如此，这个过程仍然知之甚少。在这项研究中，我们将海水与安山岩和玄武岩（最常见的弧形火山岩）在 150 和 240 ^o C 和水蒸气饱和压力下发生反应，以评估海水-火山岩相互作用引起的铜浸出能力和流体演化。实验结果表明，改性海水中的Mg、Fe、Al和SO ₄ ^2-显着降低，同时Ca浓度升高。^{流体的 pH 值也从初始海水的 8.3 下降到 150 和 240 o}后的 ∼ 7.5 和 ∼ 7.0C实验，分别。在反应的岩石样品中观察到不一致的硅酸钙（例如斜长石）溶解和硬石膏沉淀。热力学模型证实了这些浓度变化的趋势，但预测了实验中未观察到的几种蚀变矿物。我们的实验表明，安山岩的铜浸出效率远高于玄武岩，在 240 ^o C 时也比在 150 ^{o C 时更高。}C. 安山岩比玄武岩样品含有更多的铜，在原始安山岩样品中发现了丰富的富铜（平均 106 ppm）斜长石为主体的硅酸盐熔体包裹体和含铜（平均 59 ppm）地体，但在原始安山岩样品中没有发现玄武岩样品，这被认为是两个岩石样品之间铜浸出差异的原因。所得流体的 δ ³⁴ S 值以海水硫酸盐为主，来自岩石的岩浆硫的贡献较小。热力学模型结合最近的实验研究表明，当含铜流体与早期黄铁矿反应时，硫化铜的沉积是最有效的。我们的研究结果表明，海水/（盐水）-火山岩在 150-250 ^oC 可以产生含铜流体，进而形成 IOCG 矿床，而硫化物带状铜矿化可能是由含铜流体与前体铁矿体中的富铁矿物之间的置换反应引起的。