Potassium ions (K+) are abundant in ore fluids of lode gold deposits, largely illustrated by pervasive potassic alteration and commonly expressed as K-feldspar and muscovite on both sides of individual gold lodes. However, their potential roles in gold mineralization remain elusive. Here, we present results from ab initio molecular dynamics simulation and geochemical modeling to address this question. Molecular dynamics simulation results show that the ability of K+ pairing with Au(HS)2– complex over a wide temperature–pressure range has a negative linear correlation to fluid density. In high-density liquid-like fluids, little K+ is coordinated with the Au(HS)2– complex. In contrast, this complex can be nearly neutralized by ion association with K+ in low-density, vapor-like fluids, but such a neutral complexation is not very stable, even if under conditions typical of lode gold mineralization. Thus, K+ has a limited role in the complexing and transporting of Au in hydrothermal fluids forming lode gold deposits. We conducted geochemical modeling that integrates geological context and mineral paragenesis. The results reveal that potassic alteration in lode gold deposits, characterized by the transition from K-feldspar to muscovite, occurs alongside decreasing temperature, pH, and oxygen fugacity of the ore-forming fluids. Among these factors, the drop in temperature is the most significant mechanism driving potassic alteration, while also causing the destabilization of Au-bisulfide complex and spatially associated deposition of gold. These results suggest that gold mineralization during potassic alteration is primarily driven by the cooling of ore fluids, which also explains the transition from K-feldspar to muscovite alteration. The combination of molecular simulation and geochemical modeling indicates that the role of potassic alteration in lode gold mineralization reflects the influence of fluid evolution particularly fluid cooling on gold precipitation, rather than a direct control of K+ on Au transport in lode gold deposits. Therefore, potassic alteration can serve as an effective indicator for lode gold exploration and has been widely applied in practical fieldwork.

中文翻译：

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钾在矿脉金矿化中的作用：从头到账分子动力学和地球化学建模的见解


钾离子 （K+） 在矿脉金矿床的矿液中含量丰富，主要表现为普遍的钾蚀变，通常在单个金矿脉的两侧表现为 K-长石和白云母。然而，它们在金矿化中的潜在作用仍然难以捉摸。在这里，我们展示了从头到位分子动力学模拟和地球化学建模的结果来解决这个问题。分子动力学模拟结果表明，K+ 与 Au（HS）2– 配合物在较宽的温度-压力范围内配对的能力与流体密度呈负线性相关。在高密度液体状流体中，少量 K+ 与 Au（HS）2– 配合物配位。相比之下，这种络合物几乎可以被低密度、蒸汽状流体中 K+ 的离子缔合中和，但这种中性络合不是很稳定，即使在典型的矿脉金矿化条件下也是如此。因此，K+ 在形成矿脉金矿床的热液流体中 Au 的络合和运输中的作用有限。我们进行了地球化学建模，将地质背景和矿物共生相结合。结果表明，矿脉金矿床中的钾蚀变，其特征是从钾长石转变为白云母，伴随着成矿液的温度、pH 值和氧逸度的降低而发生的。在这些因素中，温度下降是驱动钾蚀变的最重要机制，同时也导致金-二硫化物络合物不稳定和金的空间相关沉积。这些结果表明，钾蚀变过程中的金矿化主要是由矿液的冷却驱动的，这也解释了从 K-长石到白云母蚀变的转变。 分子模拟和地球化学建模的结合表明，钾蚀变在矿脉金矿化中的作用反映了流体演化的影响，特别是流体冷却对金沉淀的影响，而不是 K+ 对矿脉金矿床中金运移的直接控制。因此，钾蚀变可以作为矿脉金勘探的有效指标，并在实际野外工作中得到广泛应用。