Yuhengtang is a representative slate-hosted Au deposit in the Jiangnan orogenic belt, South China, with a reserve of ~55 t Au and an average grade of ~3.9 g/t. Gold mineralization is characterized by veinlet and disseminated ores comprising native gold, auriferous pyrite, and arsenopyrite. Paragenesis of the Yuhengtang deposit can be divided into three stages. Pre-ore stage 1 is composed of bedding-parallel layers of pyrite in slate of the Neoproterozoic Banxi Group. Main ore stage 2 represents the Au mineralization stage, and two distinct types of mineralization can be distinguished: visible Au-arsenopyrite-pyrite in quartz veinlets and auriferous arsenopyrite-pyrite disseminated within altered slate. Post-ore stage 3 consists of quartz-pyrite-calcite-ankerite veins. In this study, we integrate electron microprobe, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and high-resolution ion microprobe (SHRIMP) analyses to document textural, isotopic, and compositional variation among texturally complex pyrite and arsenopyrite assemblages in veinlet and disseminated ores. Additionally, LA-ICP-MS sulfur isotope mapping of pyrite highlights the covariation behavior between trace elements and sulfur isotopes at the grain scale, thus allowing the factors controlling sulfur isotope fractionation in hydrothermal Au deposits to be constrained.Pyrite, of sedimentary origin (stage 1), hosts negligible Au (<1.6 ppm) but is enriched in δ³⁴S (15.6–25.8‰). Pyrite and arsenopyrite from stage 2 veinlet mineralization both display porous and dissolution-reprecipitation textures, have low Au concentrations (<4 and <78 ppm, respectively), and show a large variation in δ³⁴S (–2.7 to 14.7‰ and –10.3 to 12.1‰, respectively). Pyrite and arsenopyrite from disseminated mineralization are, in contrast, characterized by oscillatory zoning textures and homogeneous appearance in backscattered electron (BSE) images, respectively, and are obvious by their relatively high contents of invisible Au (up to 90 and 263 ppm, respectively) and restricted range of δ³⁴S values (0–5.3‰). These data suggest that magmatic-hydrothermal fluids contribute most of the Au and S budget in the Yuhengtang Au deposit. The major differences between veinlet and disseminated mineralization in terms of texture, trace element concentrations, and δ³⁴S signatures of pyrite and arsenopyrite reflect contrasting mechanisms of Au precipitation and an evolution of physicochemical parameters of the ore-forming processes, particularly f_O2 and the intensity of fluid-rock interaction. Pyrite from stage 3 appears homogeneous in BSE images yet displays a wide variation in δ³⁴S values (1.2–31.4‰), further highlighting the controlling role played by physicochemical condition (i.e., pressure) on the δ³⁴S signature of sulfides. Results of the coupled LA-ICP-MS sulfur and trace element mapping reveal that some zoned pyrite grains from stage 2 formed via overgrowth of Au-rich, light δ³⁴S (2.4‰) hydrothermal rims onto Au-poor, heavy δ³⁴S (18.1–18.5‰) sedimentary cores.All results support that multiple depositional mechanisms within a dynamic mineral system were responsible for Au concentration and define the specific textural, compositional, and sulfur isotope signatures of sulfides in coexisting vein/veinlet and disseminated mineralization. The new data highlight the ore-forming processes-based interpretation for ore genesis and underpin the importance of performing complementary in situ mineralogical analyses to elucidate the source and evolution of ore-forming fluids and enable correct interpretation of the architecture of the hydrothermal Au system.

中文翻译：

---

华南板岩玉横塘金矿床硫化物制约成矿过程的互补结构、微量元素和同位素分析

玉横塘是华南江南造山带具有代表性的板岩型金矿床，金储量~55 t，平均品位~3.9 g/t。金矿化的特征是细脉和浸染矿石，包括天然金、含金黄铁矿和毒砂。玉横塘矿床共生作用可分为三个阶段。前矿阶段 1 由新元古代半溪群板岩中的黄铁矿层理平行层组成。主矿阶段 2 代表 Au 矿化阶段，可以区分两种不同类型的矿化：石英细脉中可见的 Au-毒砂-黄铁矿和蚀变板岩中浸染的含金毒砂-黄铁矿。后矿石阶段 3 由石英-黄铁矿-方解石-铁橄榄石脉组成。在这项研究中，我们集成了电子微探针，激光烧蚀电感耦合等离子体质谱 (LA-ICP-MS) 和高分辨率离子微探针 (SHRIMP) 分析，以记录纹理复杂的黄铁矿和毒砂矿脉和浸染矿石中结构复杂的黄铁矿和毒砂组合之间的结构、同位素和成分变化。此外，黄铁矿的 LA-ICP-MS 硫同位素映射突出了微量元素和硫同位素在晶粒尺度上的共变行为，从而限制了控制热液金矿床中硫同位素分馏的因素。 1), 含有可忽略不计的 Au (<1.6 ppm) 但富含 δ 细脉和浸染矿石中结构复杂的黄铁矿和毒砂组合之间的成分变化。此外，黄铁矿的 LA-ICP-MS 硫同位素映射突出了微量元素和硫同位素在晶粒尺度上的共变行为，从而限制了控制热液金矿床中硫同位素分馏的因素。 1), 含有可忽略不计的 Au (<1.6 ppm) 但富含 δ 细脉和浸染矿石中结构复杂的黄铁矿和毒砂组合之间的成分变化。此外，黄铁矿的 LA-ICP-MS 硫同位素映射突出了微量元素和硫同位素在晶粒尺度上的共变行为，从而限制了控制热液金矿床中硫同位素分馏的因素。 1), 含有可忽略不计的 Au (<1.6 ppm) 但富含 δ³⁴秒 (15.6–25.8‰)。来自第 2 阶段细脉矿化的黄铁矿和毒砂均显示多孔和溶解-再沉淀结构，金浓度低（分别<4 和 <78 ppm），δ ³⁴ S变化很大（–2.7 至 14.7‰ 和 –10.3 12.1‰）。相比之下，来自浸染矿化的黄铁矿和毒砂在背散射电子 (BSE) 图像中分别具有振荡分带结构和均匀外观的特征，并且由于它们相对较高的不可见金含量（分别高达 90 和 263 ppm）而显而易见和 δ ^{34 的}限制范围S 值 (0–5.3‰)。这些数据表明，岩浆-热液流体贡献了玉横塘金矿床中的大部分金和硫收支。细脉和浸染矿化在黄铁矿和毒砂的质地、微量元素浓度和 δ ³⁴ S 特征方面的主要差异反映了 Au 沉淀的对比机制和成矿过程物理化学参数的演变，特别是 f _{O 2}和流体-岩石相互作用的强度。来自第 3 阶段的黄铁矿在 BSE 图像中看起来是均匀的，但 δ ³⁴ S 值的变化很大（1.2–31.4‰），进一步突出了物理化学条件（即压力）对 δ ³⁴的控制作用硫化物的 S 特征。耦合 LA-ICP-MS 硫和痕量元素映射的结果表明，通过富金的轻 δ ³⁴ S (2.4‰) 热液边缘过度生长到贫金的重 δ ³⁴上形成了第 2 阶段的一些分区黄铁矿颗粒S (18.1–18.5‰) 沉积岩心。所有结果都支持动态矿物系统内的多种沉积机制是金浓度的原因，并定义了共存的脉/脉和弥散矿化中硫化物的特定结构、成分和硫同位素特征。新数据突出了基于成矿过程的矿石成因解释，并强调了进行补充原位矿物学分析以阐明成矿流体的来源和演化以及正确解释热液金系统结构的重要性。