Pyrite is ubiquitous in the world-class iron oxide copper-gold (IOCG) deposits of the Candelaria-Punta del Cobre district, documented from early to late stages of mineralization and observed in deep and shallow levels of mineralized bodies. Despite its abundance, the chemical and isotopic signature of pyrite from the Candelaria-Punta del Cobre district, and most IOCG deposits worldwide, remains poorly understood. We evaluated in situ chemical and isotopic variations at the grain scale in a set of pyrite-bearing samples collected throughout the district in order to characterize and further understand the nature of mineralization in this IOCG system. Our multianalytical approach integrated synchrotron micro-X-ray fluorescence (μ-XRF) mapping of pyrite grains with electron probe microanalysis and laser ablation-inductively coupled plasma-mass spectrometry data, and sulfur isotope determinations using secondary ion mass spectrometry (SIMS) complemented with bulk sulfur isotope analyses of coeval pyrite, chalcopyrite, and anhydrite. Synchrotron μ-XRF elemental concentration maps of individual pyrite grains reveal a strong zonation of Co, Ni, As, and Se. The observed relationships between Ni and Se are interpreted to reflect changes in temperature and redox conditions during ore formation and provide constraints on fluid evolution. Co and Ni concentrations and ratios suggest contributions from magmas of mafic-intermediate composition. Pyrite chemical concentrations reflect potential stratigraphic controls, where the sample from the upper part of the stratigraphy diverges from trends formed by the rest of the sample set from lower stratigraphic levels. The SIMS δ³⁴S values of pyrite (and chalcopyrite) range between –2 up to 10‰, and bulk δ³⁴S values of pyrite range between 4 up to 12‰. The majority of the δ³⁴S analyses, falling between –1 and 2‰, indicate a magmatic source for sulfur and, by inference, for the hydrothermal ore fluid(s). Variation in the δ³⁴S signature can be explained by changes in the redox conditions, fluid sources, and/or the temperature of the hydrothermal fluid. The Se/S ratio combined with δ³⁴S values in pyrite is consistent with mixing between a magmatic-hydrothermal fluid and a fluid with a probable basinal signature. The results of this study are consistent with the hydrothermal fluids responsible for mineralization in the Candelaria-Punta del Cobre district being predominantly of magmatic origin, plausibly from mafic-intermediate magmas based on the Ni-Co content in pyrite. External fluid incursion, potentially from a basinal sedimentary source, occurred late in the evolution of the system, adding additional reduced sulfur as pyrite. There is no evidence to suggest that the late fluid added significant Cu-Au mineralization, but this cannot be ruled out. Finally, the data reveal that trace element ratios coupled with spatially resolved sulfur isotope data in pyrite are powerful proxies to track the magmatic-hydrothermal evolution of IOCG systems and help constrain the source of their contained metals.

中文翻译：

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硫铁矿的地球化学和同位素特征，可作为智利坎德拉里亚-蓬塔-科布氧化铁铜-金矿区流体来源和演化的代理

黄铁矿在坎德拉里亚-蓬塔德尔科布雷地区的世界一流的氧化铁铜-金（IOCG）矿床中无处不在，据记载，矿床从成矿的早期到后期，都在深浅的矿化体中发现。尽管其来源丰富，但坎德拉里亚-蓬塔德尔科布雷地区的黄铁矿的化学和同位素特征以及全球大多数IOCG矿床仍然知之甚少。我们在整个地区收集的一组含黄铁矿的样品中评估了晶粒度的原位化学和同位素变化，以表征和进一步了解此IOCG系统中矿化的性质。我们的多分析方法将黄铁矿晶粒的同步加速器微X射线荧光（μ-XRF）测绘与电子探针微分析和激光烧蚀-电感耦合等离子体质谱数据进行了整合，并通过二次离子质谱（SIMS）辅助测定了硫同位素对同时期的黄铁矿，黄铜矿和硬石膏的大量硫同位素分析。单个黄铁矿晶粒的同步加速器μ-XRF元素浓度图揭示了Co，Ni，As和Se的强烈带状分布。镍和硒之间观察到的关系被解释为反映矿石形成过程中温度和氧化还原条件的变化，并为流体演化提供了约束。Co和Ni的浓度和比例表明镁铁质中间成分岩浆的贡献。硫铁矿的化学浓度反映了潜在的地层控制，地层上部的样品与其余样品从较低地层水平形成的趋势不同。SIMSδ^34个黄铁矿（和黄铜矿）范围之间-2向上的价值观至10‰，散装δ ³⁴的黄铁矿范围之间4达12‰的价值观。大多数δ的³⁴论析Zhang，2之间-1和下降沿‰，指示用于硫岩浆源和，通过推断，对于热液流体（多个）。变化在δ ³⁴的签名可以通过在氧化还原条件的变化，流体源，和/或水热液体的温度进行说明。硒/ S比与δ相结合³⁴黄铁矿中的S值与岩浆热液流体和可能具有盆地特征的流体之间的混合相一致。这项研究的结果与导致坎德拉里亚-蓬塔德尔科布雷地区成矿的热液一致，这些热流体主要是岩浆成因，可能是基于黄铁矿中镍-钴含量的镁铁质中间岩浆。外部流体侵入，可能来自盆地沉积源，发生在系统演化的后期，增加了额外的还原硫，如黄铁矿。没有证据表明晚期流体增加了显着的Cu-Au矿化作用，但这不能排除。最后，