黄铁矿
地质学
喷气孔
地球化学
矿物学
磁黄铁矿
黄铜矿
热液循环
δ34S
硫化物
火山成因块状硫化物矿床
火山
闪锌矿
流体包裹体
材料科学
冶金
铜
古生物学
作者
Nikolaos N. Zegkinoglou,Ryan Mathur,Stephanos P. Kilias,Linda Godfrey,Vasilios Pletsas,Paraskevi Nomikou,Nina Zaronikola
出处
期刊:Geology
[Geological Society of America]
日期:2023-08-25
卷期号:51 (11): 1072-1076
被引量:1
摘要
Abstract We analyzed the first Cu isotopes in primary cupreous pyrite and orpiment, from modern CO2-degassing, seafloor massive sulfide diffuser vents (“KCO2Ds”), from the Kolumbo submarine volcano, Hellenic volcanic arc. Samples came from six KCO2Ds that are actively boiling. Pyrite comprises colloform pyrite-I and euhedral pyrite-II, which occur erratically distributed within the KCO2Ds and are contemporaneous with barite and spatially concurrent with the chalcopyrite that is lining narrow internal conduits, respectively. Orpiment occurs on the outer walls of the KCO2Ds with barite and stibnite. The δ65Cupyrite-I values show high variability, ranging from +2.93‰ to +6.38‰, whereas the δ65Cupyrite-II and δ65Cuchalcopyrite values vary from −0.94‰ to +0.25‰ and −0.45‰ to –0.09‰, respectively. The range of δ65Cuorpiment between +1.90‰ and +25.73‰ is the most extreme ever reported from any geological setting. Pyrite-I is concentrically layered, with a core comprising random crystallites, whereas the mantle crystallites have grain-size, shape, and orientation variability between layers. Pyrite-II forms aggregates of uniform euhedral pyrite crystals. Pyrite-I has higher concentrations of Cu (≤21,960 ppm) compared to pyrite-II (≤4963 ppm), and both have incompatible and volatile metal(loid)-rich composition and low Sb/Pb (<0.5) and Tl/Pb (<0.03) ratios. When combined with evidence for significant magmatic contributions at Kolumbo and geochemical and micro-textural evidence for recurrent intense boiling and/or flashing or gentle and/or non-boiling, the measured extreme δ65Cu values are consistent with transport of Cu by vapor that is preferentially enriched by heavy 65Cu and controlled by continuous Rayleigh distillation–type Cu fractionation. Boiling-induced Cu vapor transport can generate extreme Cu isotope fractionation.
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