White mica and tourmaline are the dominant hydrothermal alteration minerals at the world-class Panasqueira W–Sn–Cu deposit in Portugal. Thus, understanding the controls on their chemical composition helps to constrain ore formation processes at this deposit and determine their usefulness as pathfinder minerals for mineralization in general. We combine whole-rock geochemistry of altered and unaltered metasedimentary host rocks with in situ LA-ICP-MS measurements of tourmaline and white mica from the alteration halo. Principal component analysis (PCA) is used to better identify geochemical patterns and trends of hydrothermal alteration in the datasets. The hydrothermally altered metasediments are enriched in As, Sn, Cs, Li, W, F, Cu, Rb, Zn, Tl, and Pb relative to unaltered samples. In situ mineral analyses show that most of these elements preferentially partition into white mica over tourmaline (Li, Rb, Cs, Tl, W, and Sn), whereas Zn is enriched in tourmaline. White mica has distinct compositions in different settings within the deposit (greisen, vein selvages, wall rock alteration zone, late fault zone), indicating a compositional evolution with time. In contrast, tourmaline from different settings overlaps in composition, which is ascribed to a stronger dependence on host rock composition and also to the effects of chemical zoning and microinclusions affecting the LA-ICP-MS analyses. Hence, in this deposit, white mica is the better recorder of the fluid composition. The calculated trace-element contents of the Panasqueira mineralizing fluid based on the mica data and estimates of mica-fluid partition coefficients are in good agreement with previous fluid-inclusion analyses. A compilation of mica and tourmaline trace-element compositions from Panasqueira and other W–Sn deposits shows that white mica has good potential as a pathfinder mineral, with characteristically high Li, Cs, Rb, Sn, and W contents. The trace-element contents of hydrothermal tourmaline are more variable. Nevertheless, the compiled data suggest that high Sn and Li contents are distinctive for tourmaline from W–Sn deposits.

中文翻译：

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葡萄牙Panasqueira W-Sn-Cu矿床白云母和电气石中微量元素含量的热液印记

白云母和电气石是葡萄牙世界级Panasqueira W-Sn-Cu 矿床的主要热液蚀变矿物。因此，了解对其化学成分的控制有助于限制该矿床的矿石形成过程，并确定它们作为一般矿化的探路矿物的有用性。我们将蚀变和未蚀变变沉积主岩的全岩地球化学与蚀变晕中电气石和白云母的原位 LA-ICP-MS 测量相结合。主成分分析 (PCA) 用于更好地识别数据集中热液蚀变的地球化学模式和趋势。相对于未变质的样品，热液变质变沉积物富含 As、Sn、Cs、Li、W、F、Cu、Rb、Zn、Tl 和 Pb。原位矿物分析表明，这些元素中的大多数优先分配为白云母而不是电气石（Li、Rb、Cs、Tl、W 和 Sn），而 Zn 富含电气石。白云母在矿床内的不同环境中（灰岩、脉边缘、围岩蚀变带、晚期断裂带）具有不同的成分，表明成分随时间演变。相比之下，来自不同环境的电气石成分重叠，这归因于对主岩成分的更强依赖性以及影响 LA-ICP-MS 分析的化学分区和微包裹体的影响。因此，在该矿床中，白云母是流体成分的更好记录器。根据云母数据和云母-流体分配系数估计值计算出的 Panasqueira 矿化流体的微量元素含量与之前的流体包裹体分析非常一致。来自 Panasqueira 和其他 W-Sn 矿床的云母和电气石微量元素组成的汇编表明，白云母作为探路矿物具有良好的潜力，具有较高的 Li、Cs、Rb、Sn 和 W 含量。热液碧玺的微量元素含量变化较大。尽管如此，汇编的数据表明，高锡和锂含量对于来自 W-Sn 矿床的电气石来说是独一无二的。Li、Cs、Rb、Sn 和 W 含量特别高。热液碧玺的微量元素含量变化较大。尽管如此，汇编的数据表明，高锡和锂含量对于来自 W-Sn 矿床的电气石来说是独一无二的。Li、Cs、Rb、Sn 和 W 含量特别高。热液碧玺的微量元素含量变化较大。尽管如此，汇编的数据表明，高锡和锂含量对于来自 W-Sn 矿床的电气石来说是独一无二的。