Mineralized quartz veins within Phanerozoic orogenic belts provide important insights into fluid source and transport, source(s) of S, and genetic implications for ore deposit formation. Here, investigations on mineralized veins hosted by the Hog Mountain tonalite, southernmost Appalachians, were performed using scanned electron microscopy, microprobe analysis, and secondary ion mass spectrometry.The small, reduced Hog Mountain tonalite hosts three different mineralized vein types dominated by Au-bearing quartz veins with a simple base metal sulfide assemblage and spatially associated Au phases (electrum > native gold > maldonite) with Bi phases (native bismuth > unnamed Bi₃Te ≈ hedleyite > bismuthinite). In contrast, barren to low-grade arsenopyrite and sphalerite-pyrite-arsenopyrite-galena-chalcopyrite (Zn-Fe-As-Pb-Cu) veinlets are rare. Base metal sulfides are stoichiometrically homogeneous with the exception of sphalerite and galena that have noticeable enrichments in Fe and Cd, and Bi and Ag, respectively. Trace element concentrations (Au, Ag, Bi, Te, Se, and transition metals) in major and minor base metal sulfides are generally low. In situ sulfur isotope analyses on base metal sulfides from different vein types show two distinct populations: (1) δ³⁴S_sulfide = 12.9 ± 1.4‰ in low-grade arsenopyrite and Zn-Fe-As-Pb-Cu veinlets and (2) δ³⁴S_sulfide = 7.7 ± 0.9‰ in mineralized quartz veins.Based on mineral chemistry, two fluid phases were responsible for metal deposition at Hog Mountain. Fluid phase I with low-soluble Au formed rare, barren to low-grade arsenopyrite and Zn-Fe-As-Pb-Cu veinlets from highly acidic, relatively high temperature fluid with moderate ƒ_S2 and variable ƒ_O2. In contrast, a reduced, near-neutral, low ƒ_S2 fluid phase II had higher soluble Au concentrations and created the dominant Au-bearing quartz veins in which Au was deposited via scavenging by Bi melts syngenetic at lower temperatures. Isotopic modeling shows that both fluid phases sourced their S from the metasedimentary rocks hosting the tonalite and adjacent, coeval gold deposits, with the tonalite contributing some S to fluid phase II, resulting in lower δ³⁴S values. Our results are consistent with mineral assemblage, mineral chemistry, and sulfur source(s) from other intrusion-hosted Phanerozoic orogenic gold deposits and support the syngenetic Au scavenging model by Bi melts as a viable Au deposition process in orogenic gold deposits.

中文翻译：

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西南阿巴拉契亚山脉霍格山含托纳石的含金石英脉的矿物化学和硫同位素地球化学：对金析出机理，硫源和成因的启示

Phanerozoic造山带内的矿化石英脉为流体来源和运输，S来源以及矿床形成的遗传意义提供了重要的见识。在这里，使用扫描电子显微镜，微探针分析和二次离子质谱技术对最南端的阿巴拉契亚山脉Hog Mountain托纳石的矿脉进行了研究，小型，还原的Hog Mountain托纳石具有三种不同的以含金为主的矿化脉类型。石英脉具有简单的贱金属硫化物组合，并且在空间上具有Bi相（本征铋>未命名的Bi ₃）与Au相（电子>天然金>孔雀石）Te≈hedleyite> bismuthinite）。相比之下，贫瘠的低品位毒砂和闪锌矿-黄铁矿-毒砂-方铅矿-黄铜矿（Zn-Fe-As-Pb-Cu）很少见。贱金属硫化物在化学计量上是均质的，除了闪锌矿和方铅矿分别具有明显富集的Fe和Cd以及Bi和Ag之外。主要和次要贱金属硫化物中的痕量元素浓度（Au，Ag，Bi，Te，Se和过渡金属）通常较低。原位硫同位素在基部金属硫化物分析从不同静脉类型显示出两个不同群体：（1）δ ³⁴小号_硫化物= 12.9±1.4‰在低档毒砂和Zn-Fe系作为-铅-铜细脉和（2） δ ³⁴小号_硫化物=矿化石英脉中的7.7±0.9‰。基于矿物化学，霍格山的金属沉积有两个液相。流体相我具有低水溶性的Au形成的罕见，贫瘠到低档毒砂和Zn-Fe系AS-Pb的铜细脉从具有中等ƒ高度酸性的，相对高温流体_{š 2}和可变ƒ _{Ò 2}。相反，减小，近中性，低ƒ _{š 2}液相II具有较高的可溶Au浓度，并形成了主要的含Au石英脉，其中在较低温度下通过Bi熔体的同族清除作用沉积了Au。同位素模拟表明，两个流体相来源它们的S从托管英云和相邻的，同时代金矿床的沉积岩，用英云有助于某些s至流体相II，导致较低的δ ^34个价值观。我们的研究结果与其他侵入体生代造山型金矿中的矿物组合，矿物化学和硫源一致，并支持Bi熔体的同生金清除模型，作为可行的金在造金矿中的沉积过程。