The Troodos ophiolite Cyprus hosts the on-land analogue for actively forming mafic, Cu-rich, or Cyprus-type VMS deposits. In addition to high-temperature (> 350 °C) sulfide mound-related mineralization, other fossil seafloor mineralizing systems are known to operate, including those characterized by an enrichment in Au and abundant silicification. In this study the mineralogy and geochemistry of four Au and silica-rich localities in Troodos are considered, and these include Kokkinovounaros, Mathiatis South, Touronjia, and Alpen Rose. We present whole rock geochemical and mineralogical data characterizing the distribution of Au in the hydrothermal systems of Troodos. Samples from silica-rich localities have two distinct sample mineralogies: supergene samples that contain predominantly goethite, hematite, and jarosite and hypogene samples that contain quartz, amorphous silica and minor hematite. Hypogene samples from Mathiatis South and Kokkinovounaros are enriched in Au with a median concentration of 1.5 ppm relative to supergene samples that contain 0.1 ppm (n = 107). This indicates that Au enrichment occurred on the seafloor and is not solely related to supergene weathering of silica-rich mineralization. We suggest that silica-rich Au mineralization in Troodos formed during the migration of newly formed crust off-axis or as white smokers proximal to known VMS deposits. In silica-rich mineralization that is located distally from known massive sulfide deposits, Au was probably remobilized from shallow crustal reservoirs during the low-temperature fluid flow (100–300 °C) in the lower extrusive sequence as the crust cooled and migrated off-axis. Based on modern seafloor analogues, we propose a revised model for the Troodos hydrothermal system that explains the distribution of Au in silica-rich mineralization that formed off-axis and postdates VMS formation and in zones proximal to VMS deposits that formed simultaneously as white smoker-type vents. We suggest that silica-rich mineralized zones formed an intermediary between high-temperature (> 350 °C) on-axis VMS deposits and the low-temperature silicification of umbers (< 100 °C).

中文翻译：

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镁铁质 VMS 系统中的低温富硅金矿化：来自塞浦路斯 Troodos 蛇绿岩的证据

Troodos蛇绿岩塞浦路斯拥有活跃形成镁铁质、富铜或塞浦路斯型VMS矿床的陆上类似物。除了与高温 (> 350 °C) 硫化物丘相关的矿化外，其他海底化石矿化系统也是已知的，包括以金富集和大量硅化为特征的系统。本研究考虑了特罗多斯四个富含金和二氧化硅的地区的矿物学和地球化学，其中包括 Kokkinovounaros、Mathiatis South、Touronjia 和 Alpen Rose。我们提供了表征金在特罗多斯热液系统中分布的全岩地球化学和矿物学数据。来自富含二氧化硅地区的样品具有两种不同的样品矿物学：表生样品主要包含针铁矿、赤铁矿、以及含有石英、无定形二氧化硅和少量赤铁矿的黄钾铁矾和次质样品。来自 Mathiatis South 和 Kokkinovounaros 的 Hypogene 样品富含 Au，相对于含有 0.1 ppm 的超基因样品（n = 107），Au 的中值浓度为 1.5 ppm。这表明金富集发生在海底，而不仅仅与富硅矿化的表生风化有关。我们认为 Troodos 富含二氧化硅的 Au 矿化形成于新形成的地壳离轴迁移过程中，或作为邻近已知 VMS 矿床的白烟形成。在位于已知块状硫化物矿床远端的富含二氧化硅的矿化中，随着地壳冷却和迁移，金可能在低温流体流动（100-300°C）期间在较低的喷出序列中从浅地壳储层中重新迁移。轴。基于现代海底类似物，我们为 Troodos 热液系统提出了一个修正模型，该模型解释了 Au 在富含二氧化硅的矿化中的分布，这些矿化形成了离轴和后期 VMS 形成，以及在 VMS 沉积物附近的区域中，同时形成了白烟-型通风口。我们认为富含二氧化硅的矿化带在高温 (> 350 °C) 轴上 VMS 沉积物和低温硅化 (< 100 °C) 之间形成了中介​​。