This study reevaluates the previously proposed hypogene hypothesis and redefines the origin of smithsonite mineralization in the Angouran deposit, Iran (4.7 Mt of sulfide ore at 27.7% Zn; 14.6 Mt of carbonate ore at 22% Zn). Geological mapping and petrological observations reveal a distinct vertical mineralized zoning: a lower primary sulfide zone containing minor amounts of smithsonite, an intermediate transition zone characterized by smithsonite and newly formed sulfides, and an upper oxidation zone comprising smithsonite and Fe–Mn oxides, which is widely recognized as supergene origin under atmospheric oxygen fugacity conditions. This zoning pattern is analogous to classic supergene weathering profiles observed in porphyry Cu deposits. Morphological and sulfur isotopic analyses (³⁴S-depleted signatures) confirm that the newly formed sulfides within the transition zone are of supergene origin, primarily induced by bacterial sulfate reduction processes and partly formed by the direct replacement of primary sphalerite immediately below the paleo-water table. Smithsonite from all three zones exhibits similar C–O isotopic compositions that fall between those of the host marble and travertines, further supporting a consistent supergene origin. Reaction path modeling demonstrates that smithsonite cannot be generated by the direct replacement of sphalerite by CO₂-rich spring water unless under atmospheric oxygen fugacity conditions. The development of the vertical zoning with distinct mineral assemblages is primarily controlled by the position of the paleo-water table. Near it, rapid fluctuations in oxygen fugacity and sulfur fugacity occur, allowing sulfides formed under reducing conditions to coexist with smithsonite precipitated in relatively oxidative environments. The occurrence of supergene sulfides provides valuable insights into the origin of nonsulfide Zn–Pb mineralization and aid in locating deeply buried primary sulfide orebodies.

本研究重新评估了先前提出的次生假说，并重新定义了伊朗 Angouran 矿床中史密森石矿化的起源（4.7 公吨硫化物矿石，锌含量为 27.7%;碳酸盐矿石 14.6 公吨，锌含量为 22%）。地质测绘和岩石学观察揭示了一个独特的垂直矿化带：一个包含少量史密森石的下部原生硫化物区，一个以史密森石和新形成的硫化物为特征的中间过渡区，以及一个由史密森石和 Fe-Mn 氧化物组成的上部氧化区，该氧化区被广泛认为是大气氧逸度条件下的表生起源。这种分区模式类似于在斑岩铜矿床中观察到的经典表生风化剖面。形态学和硫同位素分析（³⁴个 S 耗尽特征）证实，过渡带内新形成的硫化物是表生来源的，主要由细菌硫酸盐还原过程诱导，部分由古水位下方原生闪锌矿的直接替换形成。来自所有三个区域的史密森石都表现出相似的 C-O 同位素组成，介于主大理石和石灰华之间，进一步支持了一致的表生起源。反应路径模型表明，除非在大气氧逸度条件下，否则不能通过富含 CO₂ 的泉水直接替代闪锌矿来生成史密森石。具有独特矿物组合的垂直分区的发展主要由古地下水位的位置控制。 在它附近，氧逸度和硫逸度发生快速波动，使得在还原条件下形成的硫化物与在相对氧化环境中沉淀的史密森石共存。表生硫化物的出现为非硫化物 Zn-Pb 矿化的成因提供了有价值的见解，并有助于定位深埋的原生硫化物矿体。