Abstract The Proterozoic Carpentaria Province (McArthur basin and Mount Isa Inlier) in northern Australia comprises a number of world class clastic dominated (CD-type) Zn Pb massive sulphide deposits, formally known as SEDEX deposits. In order to identify the geochemical footprint of any mineralizing system it is necessary to characterize compositional variability of the host-rock to mineralization. In the southern Carpentaria, establishing the baseline composition of the host rock is complicated by varying degrees of tectonic overprint, a lack of metamorphic indicator minerals, and the overall size of the ore forming systems. In this study, samples from drill-holes intersecting the main ore bodies at the world class George Fisher CD-type massive sulphide deposit have been compared to samples from a drill-hole intersecting barren, correlative lithologies of the Urquhart Shale Formation (ca. 1654 Ma). Bulk rock lithogeochemical (X-ray fluorescence, inductively coupled plasma mass spectrometry and LECO) and mineralogical (X-ray diffraction) analyses have been combined with petrographic observations to (1) establish the baseline composition of the Urquhart Shale Formation and (2) determine the geochemical and mineralogical footprint of the CD-type system at George Fisher. The absence of metamorphic indicator minerals, combined with the preservation of illite in un-mineralized Urquhart Shale, suggests that in this part of the Mount Isa area, the host rocks did not reach greenschist facies conditions (>300 °C). Chlorite in the un-mineralized Urquhart Shale is very fine grained (≤ 10 μm) within interstitial pore spaces with other phyllosilicates (e.g., illite), and is interpreted to be diagenetic in origin. Relative to the un-mineralized Urquhart Shale, the first stage of sulphide mineralization (Zn-dominated, stratabound) at George Fisher is associated with decreased abundances of albite, chlorite, and calcite, and higher abundances of dolomite and phyllosilicates (muscovite and phlogopite). These mineralogical transformations are associated with strong minor and trace element depletion (Sr and Na) and enrichment (Tl and Mn). An element index based on this suite of elements (GF index = 10 400 Tl + Mn 10 Sr + Na ) is highly effective in differentiating between the background Urquhart Shale Formation and the alteration footprint at George Fisher and may provide an additional tool for geochemical exploration programmes in the Mount Isa area. This study affirms the benefit of combining lithogeochemical, mineralogical, and petrographic data in order to understand the host rock baseline composition and the alteration footprint of Carpentaria CD-type massive sulphide systems.

中文翻译：

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澳大利亚昆士兰州元古界厄克特页岩组 George Fisher Zn-Pb-Ag 块状硫化物矿床的矿物学和岩石地球化学足迹

摘要 澳大利亚北部的元古代卡奔塔利亚省（麦克阿瑟盆地和伊萨因利尔山）包括许多世界级的以碎屑为主的（CD 型）锌铅块状硫化物矿床，正式名称为 SEDEX 矿床。为了确定任何矿化系统的地球化学足迹，有必要表征主岩对矿化的成分变异性。在 Carpentaria 南部，由于不同程度的构造叠印、变质指示矿物的缺乏以及成矿系统的整体规模，确定主岩的基线组成很复杂。在这项研究中，来自与世界级 George Fisher CD 型块状硫化物矿床主要矿体相交的钻孔样品与来自与贫瘠、Urquhart 页岩组的相关岩性（约 1654 Ma）。大块岩石岩石地球化学（X 射线荧光、电感耦合等离子体质谱和 LECO）和矿物学（X 射线衍射）分析与岩相观察相结合，以 (1) 确定 Urquhart 页岩地层的基线成分和 (2) 确定George Fisher CD 型系统的地球化学和矿物学足迹。变质指示矿物的缺失，加上未矿化厄克特页岩中伊利石的保存，表明在伊萨山地区的这一部分，主岩没有达到绿片岩相条件（>300°C）。未矿化厄克特页岩中的绿泥石在与其他页硅酸盐（例如伊利石）的间隙孔隙中具有非常细的颗粒（≤ 10 μm），并被解释为起源于成岩作用。相对于未矿化的厄克特页岩，George Fisher 硫化物矿化的第一阶段（以锌为主，层状）与钠长石、绿泥石和方解石丰度降低以及白云石和页硅酸盐（白云母和金云母）丰度增加有关. 这些矿物学转变与强烈的微量元素和微量元素消耗（Sr 和 Na）和富集（Tl 和 Mn）有关。基于这组元素的元素指数（GF 指数 = 10 400 Tl + Mn 10 Sr + Na）在区分背景 Urquhart 页岩组和 George Fisher 蚀变足迹方面非常有效，并可能为地球化学勘探提供额外的工具伊萨山地区的项目。本研究肯定了结合石化地球化学、