We report whole-rock major, trace, and platinum-group element (PGE) geochemistry of volcanic rocks from the Teutonic Bore complex that hosts the Jaguar and Bentley Cu–Zn volcanogenic massive sulfide (VMS) deposits. This study aims to understand their sulfide saturation history and chalcophile element evolution during differentiation of the Jaguar and Bentley magmas, and investigate the role of chalcophile element fertility on the formation of VMS deposits. The fractionated primitive mantle–normalized trace element patterns, with negative Nb and Ti anomalies of basalts, andesites, dacites, and rhyolites from Jaguar and Bentley, are similar to each other. The trace elements and PGE show continuous variations when plotted against fractionation indices such as Yb, which can be explained by a two-stage fractional crystallization model: stage 1 Rayleigh fractionation of plagioclase + clinopyroxene + Cr-spinel, and stage 2 the fractional of plagioclase + clinopyroxene + magnetite + 0.1 wt% sulfide liquid. Dolerites, which postdate the mineralization, differ from the other rock types and require a different magma source. Andesite and basalt are the most PGE-enriched lithologies in Jaguar and Bentley. The PGE behave incompatibly in the early stage of magma differentiation at < 4 ppm Yb, whereas they abruptly decrease at > 4 ppm Yb, indicating sulfide saturation at this point. When Pd/MgO and Pd/Pt are used as chalcophile element fertility indicators, the andesite before sulfide saturation (< 4 ppm Yb) is as fertile as the magmas associated with porphyry Cu-only deposits. In contrast, the andesite after sulfide saturation and other lithologies are characterized by markedly depleted fertility similar to those of barren suites. This suggests that sulfide-undersaturated andesite, and probably basalt, may have been a significant source for Cu in the Jaguar and Bentley Cu–Zn VMS deposits. However, the Au fertility of the Jaguar and Bentley andesite must have been low and not enough to form Au-rich VMS deposits because their Pd/MgO and Pd/Pt values are 5–10 times lower than those of andesite and dacite from the modern Au-rich seafloor massive sulfide deposits. This can be explained if ore formation occurred shortly after sulfide saturation. If the amount of sulfide melt to precipitate was small, Au, with its high partition coefficient into immiscible sulfide melts, would have been largely stripped from the silicate melt, whereas Cu, with its lower partition coefficient, would be little affected. Our study shows that chalcophile element fertility may play an important role in the formation of VMS deposits, especially in controlling the Au contents of the ore, if the magmatic-hydrothermal component is the dominant source for metals in VMS systems.

中文翻译：

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与西澳大利亚 Jaguar 和 Bentley Cu-Zn 火山成因块状硫化物 (VMS) 矿床相关的火山岩的铂族元素地球化学：对亲硫元素肥力对 VMS 矿化作用的影响

我们报告了来自包含 Jaguar 和 Bentley Cu-Zn 火山成因块状硫化物 (VMS) 矿床的 Teutonic Bore 复合体的火山岩的全岩主要、痕量和铂族元素 (PGE) 地球化学。本研究旨在了解 Jaguar 和 Bentley 岩浆分异过程中硫化物饱和历史和亲硫元素演化，并研究亲硫元素肥力对 VMS 矿床形成的作用。Jaguar 和 Bentley 玄武岩、安山岩、英安岩和流纹岩的分馏原始地幔-归一化微量元素模式，具有负的 Nb 和 Ti 异常，彼此相似。当针对 Yb 等分馏指数绘制时，痕量元素和 PGE 显示出连续变化，这可以通过两阶段分馏结晶模型来解释：斜长石 + 斜辉石 + Cr-尖晶石的阶段 1 瑞利分馏，和阶段 2 斜长石 + 斜辉石 + 磁铁矿 + 0.1 wt% 硫化物液体的分馏。晚成矿的辉绿岩不同于其他岩石类型，需要不同的岩浆来源。安山岩和玄武岩是 Jaguar 和 Bentley 中 PGE 含量最高的岩性。PGE 在岩浆分化早期在 < 4 ppm Yb 时表现不相容，而在 > 4 ppm Yb 时它们突然减少，表明此时硫化物饱和。当 Pd/MgO 和 Pd/Pt 用作亲硫元素肥力指标时，硫化物饱和前的安山岩 (< 4 ppm Yb) 与与仅含铜的斑岩矿床相关的岩浆一样肥沃。相比之下，硫化物饱和后的安山岩和其他岩性的特征是与贫瘠套房相似的显着枯竭的肥力。这表明硫化物欠饱和的安山岩，可能还有玄武岩，可能是 Jaguar 和 Bentley Cu-Zn VMS 矿床中铜的重要来源。然而，Jaguar 和 Bentley 安山岩的金肥力一定很低，不足以形成富含 Au 的 VMS 矿床，因为它们的 Pd/MgO 和 Pd/Pt 值比现代安山岩和英安岩的值低 5-10 倍。富含金的海底块状硫化物矿床。如果在硫化物饱和后不久就形成了矿石，这可以解释。如果沉淀的硫化物熔体的量很小，Au 在不混溶的硫化物熔体中具有高分配系数，会从硅酸盐熔体中大量剥离，而 Cu，其分配系数较低，影响不大。我们的研究表明，如果岩浆-热液成分是 VMS 系统中金属的主要来源，那么亲硫元素肥力可能在 VMS 矿床的形成中发挥重要作用，尤其是在控制矿石的 Au 含量方面。