The Paleoproterozoic Flambeau Cu-Zn-Au deposit in northwestern Wisconsin is the only volcanogenic massive sulfide (VMS) deposit to reach production in the Pembine-Wausau terrane of the Penokean orogen, despite the discovery of more than 150 million tonnes of mineralization within 14 deposits since the 1970s. Renewed exploration interest in the region and need for critical minerals has highlighted the importance of the VMS deposits in the region and the need for an improved understanding of their geologic setting. This study examined and sampled 50 drill cores from the Flambeau deposit stored at the Wisconsin state core repository to determine the volcanic, hydrothermal, and tectonic setting of the deposit. The least altered units at the deposit are metadacite and quartz-augen schists that are interpreted to be rapidly emplaced felsic to intermediate crystal-rich tuffs and lapilli tuffs. There are also chlorite ± garnet schists that are interpreted to be mafic sills and/or small flows. The main altered unit is biotite ± andalusite ± white-mica schist that contains porphyroblasts of biotite and/or andalusite that replace the intermediate volcaniclastic units. The ore horizon contains massive sulfide, metachert, and semimassive mineralization within a quartz–white-mica schist. Stratigraphic relationships and chemostratigraphy structurally above and below the ore horizon indicate that the strata are overturned. Despite structural and metamorphic destruction of microtextural evidence, evidence for lateral mineralizing fluid flow in rapidly emplaced, permeable volcanic units, interlayered impermeable to semipermeable units, and macrotextural evidence for lit-par-lit replacement of tuffaceous layers indicate that the Flambeau ores are replacement-style mineralization. Trace element systematics reveal that mafic rock and intermediate rocks are calc-alkalic with low Ti/V values, characteristic of arc environments. Felsic rocks are calc-alkalic, depleted high field strength element (HFSE), FI- to FII-type rhyolites that are also consistent with an arc environment. These lithogeochemical characteristics are similar to those of modern mature oceanic-arc settings. This setting contrasts with other host rocks at nearby deposits (e.g., Lynne, Back Forty) that have petrogenetic evidence for the presence of older Archean basement (i.e., continental crust). Therefore, the geology of the Flambeau deposit highlights the variability of VMS-forming environments within the Penokean orogen and has important local and regional implications for other VMS deposits globally.

中文翻译：

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美国威斯康星州古元古代 Flambeau 铜锌金火山成因块状硫化物矿床的地质和岩石地球化学

尽管在 14 个矿床中发现了超过 1.5 亿吨矿化，但位于威斯康星州西北部的古元古代 Flambeau 铜-锌-金矿床是 Penokean 造山带 Pembine-Wausau 地体中唯一达到生产的火山成因块状硫化物 (VMS) 矿床自 20 世纪 70 年代以来。该地区重新燃起的勘探兴趣和对关键矿物的需求凸显了该地区 VMS 矿床的重要性以及加深对其地质环境了解的必要性。本研究对威斯康星州岩心储存库中储存的 Flambeau 矿床的 50 个钻芯进行了检查和取样，以确定该矿床的火山、热液和构造环境。矿床中改变最小的单元是偏英安岩和石英片岩，它们被解释为快速侵位的长英质到中等富含晶体的凝灰岩和火山灰凝灰岩。还有绿泥石和石榴石片岩，被解释为镁铁质基岩和/或小流量。主要蚀变单元是黑云母±红柱石±白云母片岩，其中含有黑云母和/或红柱石的成斑岩，取代了中间火山碎屑单元。矿层在石英-白云母片岩中含有块状硫化物、变辉石和半块状矿化物。矿层上方和下方的地层关系和化学地层结构表明地层发生了翻转。尽管微观结构证据受到结构和变质破坏，但快速就位的可渗透火山单元、夹层不可渗透到半渗透单元中的横向矿化流体流动的证据，以及凝灰岩层的光亮替换的宏观结构证据表明，Flambeau 矿石是替代性的。风格矿化。微量元素系统学表明，镁铁质岩石和中间岩石是钙碱性的，Ti/V 值较低，是弧环境的特征。长英质岩石是钙碱性、贫化高场强元素 (HFSE)、FI 至 FII 型流纹岩，也符合弧环境。这些岩石地球化学特征与现代成熟洋弧环境的岩石地球化学特征相似。这种环境与附近矿床（例如 Lynne、Back Forty）的其他主岩形成鲜明对比，这些主岩具有古老太古代基底（即大陆地壳）存在的岩石成因证据。因此，Flambeau 矿床的地质特征凸显了 Penokean 造山带内 VMS 形成环境的可变性，并对全球其他 VMS 矿床具有重要的局部和区域影响。