Human activities have led to a considerable increase in trace metal cycling in recent times. The mobilized elements get subjected to a variety of processes leading eventually to their re-concentration. The polluted sites, transformed by Earth's surface processes, become similar to metal accumulations known from geological records. This study examines authigenic metal sulfide mineralization in two peatlands polluted by atmospheric deposition from a nearby Pb-Zn smelter. We use the polluted peatlands as a small-scale model of Zn-Cd-Pb sulfide deposit to determine the role of organic matter in ore genesis and the textural and structural organization of biogenic precipitates.

The study shows that the air-derived metal enrichment (up to 2.3 g Zn kg⁻¹, 1.1 g Pb kg⁻¹, and 62 mg Cd kg⁻¹) is retained in a thin layer (∼30 cm) around 10–15 cm below the peat surface. A combination of focused ion beam (FIB) technology and scanning (SEM) and transmission (TEM) electron microscopy reveals that micrometric spheroids are most characteristic for ZnS and (Zn,Cd)S, although the sulfides readily form pseudomorphs after different plant tissues resulting in much larger aggregates. The aggregates have a complex polycrystalline sphalerite structure much more advanced than typically obtained during low-temperature synthesis or observed in other modern occurrences. Platy highly-disordered radially-aggregated submicrometre crystals develop within the time constraints of several decades in the cold (∼15 °C) and acid (pH 3.4–4.4) peat. The less abundant Pb sulfides occur as small cube-like crystals (<1µm) between ZnS or as flat irregular or square patches on plant root macrofossils. All PbS are crystalline and defect-free. Pb ion complexation with dissolved and solid organic matter is probably responsible for the low number and equilibrium shape of PbS crystals. Iron is absent in the authigenic sulfide mineralization and occurs entirely as organically bound ferric iron (Fe³⁺), as revealed by Mössbauer spectroscopy. The different affinity of metals to organic matter enhances the precipitation of Zn and Cd as sulfides over Pb and Fe. Our findings demonstrate that human activities lead to the formation of near-surface stratiform metal sulfide accumulations in peat, and the polluted sites can be of use to understand and reconstruct ancient ore deposits' genesis and mechanisms of formation.

近年来，人类活动导致痕量金属循环显着增加。被动员的元素会经历各种过程，最终导致它们重新集中。受地球表面过程改造的污染场地变得类似于地质记录中已知的金属堆积物。本研究检查了附近 Pb-Zn 冶炼厂的大气沉积物污染的两个泥炭地中的自生金属硫化物矿化。我们使用受污染的泥炭地作为 Zn-Cd-Pb 硫化物矿床的小规模模型，以确定有机质在矿石成因中的作用以及生物沉淀物的结构和结构组织。

研究表明，空气衍生的金属富集（高达 2.3 g Zn kg ^-1、1.1 g Pb kg ^-1和 62 mg Cd kg ^-1) 保留在泥炭表面下方约 10-15 厘米处的薄层（~30 厘米）中。聚焦离子束 (FIB) 技术与扫描 (SEM) 和透射 (TEM) 电子显微镜的结合表明，微米球体是 ZnS 和 (Zn,Cd)S 的最典型特征，尽管硫化物很容易在不同的植物组织后形成假晶在更大的聚合体中。聚集体具有复杂的多晶闪锌矿结构，比通常在低温合成过程中获得的或在其他现代事件中观察到的要先进得多。在寒冷 (~15 °C) 和酸性 (pH 3.4-4.4) 泥炭中，在几十年的时间限制内，会形成片状高度无序的径向聚集亚微米晶体。含量较低的硫化铅以小的立方体晶体形式出现（< 1µm) 在 ZnS 之间或作为植物根大体化石上的扁平不规则或方形斑块。所有 PbS 都是结晶的且无缺陷。Pb 离子与溶解和固体有机物的络合可能是 PbS 晶体数量少和平衡形状低的原因。铁在自生硫化物矿化中不存在，完全以有机结合的三价铁（Fe³⁺ )，正如穆斯堡尔光谱所揭示的那样。金属对有机物的不同亲和力增强了 Zn 和 Cd 作为硫化物在 Pb 和 Fe 上的沉淀。我们的研究结果表明，人类活动导致泥炭中近地表层状金属硫化物积累的形成，污染地点可用于了解和重建古矿床的成因和形成机制。