Application of stable transition metal isotopes as indicators of ore genesis is becoming more popular, yet the fractionation mechanisms and isotopic distribution in these unconventional systems remain poorly understood. In this study, we present an analysis of sulphide Ni, Cu and Fe isotopes measured from solution using multicollector ICP-MS. The data were collected from the dominant sulphide phases in the Raja prospect within the epigenetic-hydrothermal Rajapalot AuCo deposit, Finnish Lapland. Our main goal was to gain new information on the systematics and behaviour of the isotopes in high-temperature ore-forming environments, with implications for ore genesis. The Raja prospect is hosted by a Paleoproterozoic volcanic-sedimentary sequence and was formed by multi-stage hydrothermal processes during the Svecofennian orogeny. Pyrite shows significant variation in δ56Fe (-2.08 to +3.29 ‰), including the heaviest iron isotopes thus far observed in natural pyrite. The δ56Fe values in pyrrhotite vary less (-0.74 to +0.80 ‰) but are unusually heavy compared to those of magmatic pyrrhotite. δ56Fe in chalcopyrite ranges from +0.10 to +1.45 ‰, δ60Ni in pyrrhotite from -1.03 to +0.18 ‰, and δ65Cu in chalcopyrite from -0.30 to +0.23 ‰. The δ56Fe values in co-existing sulphide phases suggest both equilibrium and kinetic fractionation effects. The extreme Fe fractionation in pyrite implies that kinetic fractionation played a major role in the precipitation of isotopically light pyrite. Moreover, inheritance of low δ56Fe values from a pyrrhotite precursor is likely. The heavy Fe isotopic composition of some of the pyrrhotite and pyrite is probably the result of preferential leaching of light isotopes by late hydrothermal fluids.

中文翻译：

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Ni、Cu 和 Fe 同位素作为成矿指标的应用 - 来自芬兰拉普兰表观遗传-热液 Rajapalot Au[sbnd]Co 远景的新见解


将稳定的过渡金属同位素作为矿石成因的指标的应用越来越受欢迎，但这些非常规系统中的分馏机制和同位素分布仍然知之甚少。在本研究中，我们介绍了使用多接收 ICP-MS 从溶液中测量的硫化物 Ni、Cu 和 Fe 同位素的分析。数据是从芬兰拉普兰表观遗传-热液 Rajapalot AuCo 矿床内的 Raja 远景区的主要硫化物相中收集的。我们的主要目标是获得有关高温成矿环境中同位素的系统学和行为的新信息，这对矿石成因有影响。Raja 勘探区由古元古代火山-沉积序列承载，由 Svecofennian 造山运动期间的多阶段热液过程形成。黄铁矿的 δ56Fe 变化很大（-2.08 至 +3.29 ‰），包括迄今为止在天然黄铁矿中观察到的最重的铁同位素。磁黄铁矿的 δ56Fe 值变化较小（-0.74 至 +0.80 ‰），但与岩浆磁黄铁矿相比异常沉重。黄铜矿中的 δ56Fe 范围为 +0.10 至 +1.45 ‰，磁黄铁矿中的 δ60Ni 范围为 -1.03 至 +0.18 ‰，黄铜矿中的 δ65Cu 范围为 -0.30 至 +0.23 ‰。共存硫化物相中的 δ56Fe 值表明平衡和动力学分馏效应。黄铁矿中的极端 Fe 分馏意味着动力学分馏在同位素轻黄铁矿的沉淀中起了重要作用。此外，磁黄铁矿前驱体可能会继承低 δ56Fe 值。一些磁黄铁矿和黄铁矿的重铁同位素组成可能是晚期热液流体优先浸出轻同位素的结果。