Archean komatiites form an important host rock for Ni-Cu sulfide deposits in the world. In this study, we examined Archean komatiites and komatiitic basalts from four areas in the Vedlozero-Segozero greenstone belt and two areas in the Tikshozero greenstone belt, Russian Karelia, to constrain their Ni-Cu sulfide mineralization potential using chalcophile element geochemistry. The platinum-group element (PGE) concentrations in these Munro-type komatiitic rocks are at a level of other similar S-undersaturated komatiites and komatiitic basalts globally, with Pt and Pd concentrations in the range of 5–20 ppb and Pd/Ir varying from < 10 (komatiites) to > 15 (komatiitic basalts and basalts). Generally, the metals of the iridium-group elements (IPGEs; Ir, Ru, Os) show a compatible behavior, decreasing in abundance with decreasing MgO, whereas the metals of the palladium group (PPGEs; Pt, Pd, Rh) exhibit an incompatible behavior. The poor correlation between Ir and MgO suggests that olivine fractional crystallization is not the main control on the behavior of IPGE. In contrast, Ir, Ru, and Os show positive correlations with Cr, which is consistent with the compatible behavior of IPGEs in chromite or during the co-precipitation of chromite and platinum-group minerals (PGMs). Palladium, Cu, and Au have been variably mobile during alteration and metamorphism whereas Pt appears to have been less mobile. Some samples from the Khizovaara area show low (Pt/Ti) N ratios, low Ni, and high La/Sm and La/Nb, suggesting localized sulfide saturation in response to crustal contamination. However, the potential of the Russian Karelian greenstone belts for Ni-Cu sulfide mineralization is considered relatively low because most samples show neither enrichment nor depletion of chalcophile elements, and the paucity of dynamic lava channel environments, as indicated by the scarcity of olivine-rich adcumulates. In addition, there appears to be a lack of exposed sulfidic sedimentary rocks in the region.

中文翻译：

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俄罗斯卡累利阿太古代绿岩带科马提岩和玄武岩地球化学，重点关注铂族元素

太古宙科马提岩是世界上镍铜硫化物矿床的重要母岩。在这项研究中，我们检查了来自 Vedlozero-Segozero 绿岩带的四个地区和俄罗斯卡累利阿 Tikshozero 绿岩带的两个地区的太古代科马提岩和科马提质玄武岩，以使用亲硫元素地球化学来限制它们的 Ni-Cu 硫化物成矿潜力。这些 Munro 型科马提质岩石中的铂族元素 (PGE) 浓度与全球其他类似的 S 欠饱和科马提岩和科马提质玄武岩处于同一水平，Pt 和 Pd 浓度在 5-20 ppb 范围内，Pd/Ir 各不相同从 < 10（科马提岩）到 > 15（科马提质玄武岩和玄武岩）。通常，铱族元素的金属（IPGEs；Ir、Ru、Os）表现出相容的行为，随着 MgO 的减少，其丰度减少，而钯族金属（PPGEs；Pt、Pd、Rh）则表现出不相容的行为。Ir 和 MgO 之间的相关性较差表明橄榄石分级结晶不是 IPGE 行为的主要控制因素。相比之下，Ir、Ru 和 Os 与 Cr 呈正相关，这与 IPGE 在铬铁矿中或在铬铁矿和铂族矿物 (PGM) 共沉淀过程中的相容行为一致。钯、铜和金在蚀变和变质过程中具有不同的移动性，而铂似乎移动性较小。来自 Khizovaara 地区的一些样品显示出低 (Pt/Ti) N 比、低 Ni 和高 La/Sm 和 La/Nb，表明局部硫化物饱和是对地壳污染的反应。然而，俄罗斯卡累利阿绿岩带的 Ni-Cu 硫化物矿化潜力被认为相对较低，因为大多数样品既没有显示出富集也没有显示出亲硫元素的消耗，并且缺乏动态熔岩通道环境，如富含橄榄石的堆积物的稀缺所示。此外，该地区似乎缺乏暴露的硫化物沉积岩。