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Iron, copper, and zinc isotopic fractionation in seafloor basalts and hydrothermal sulfides
Marine Geology ( IF 2.6 ) Pub Date : 2021-04-22 , DOI: 10.1016/j.margeo.2021.106491
Zhigang Zeng , Xiaohui Li , Shuai Chen , Jeroen de Jong , Nadine Mattielli , Haiyan Qi , Christopher Pearce , Bramley J. Murton

Studies of the Fe, Cu, and Zn isotopic compositions of volcanic rocks and sulfides provide an important tool for understanding magmatic, hydrothermal, and alteration processes, thereby enabling the determination of both transition metal sources and the quantification of the petrologic environmental impacts of hydrothermal activities. In this study, the δ56Fe and δ57Fe values of the mid-ocean ridge basalts (MORBs) are higher than those of the seafloor hydrothermal fluids, while the reverse is true for the δ66Zn and δ68Zn values, suggesting that basalt-fluid interactions preferentially incorporate isotopically light Fe and heavy Zn into the fluids, resulting in the relative enrichment of heavier Fe and lighter Zn isotopes in altered basaltic rocks. Most of the δ56Fe values (−1.96 to +0.11‰) of the sulfide minerals are within the range of the vent fluids, but they are significantly lower than those of the MORBs and back-arc basin basalts (BABBs), suggesting that the Fe in the sulfides was mainly derived from the fluids. However, the majority of the chalcopyrite δ56Fe and δ57Fe values are higher than those of the sphalerite and pyrite. This suggests that high-temperature sulfide minerals are enriched in 56Fe and 57Fe, whereas medium- and low-temperature sulfides are depleted in 56Fe and 57Fe. Moreover, the δ65Cu (−0.88 to −0.16‰) and δ66Zn (−0.39 to −0.03‰) values of the sulfide minerals are significantly lower than those of the MORBs, BABBs, and fluids, suggesting that 63Cu and 64Zn were preferentially removed from the fluids and incorporated into the chalcopyrite and sphalerite, respectively. Consequently, vent fluid injection and deposition can cause the heavier Cu and Zn isotopic compositions of hydrothermal plumes, seawater, and sediments.



中文翻译:

海底玄武岩和热液硫化物中的铁,铜和锌同位素分馏

对火山岩和​​硫化物的铁,铜和锌同位素组成的研究为理解岩浆,热液和蚀变过程提供了重要的工具,从而可以确定过渡金属来源并量化热液活动对岩石环境的影响。在这项研究中,δ 56 Fe和δ 57大洋中脊玄武岩(MORBs)的铁值比海底热液较高,而当该反转的δ真正66 Zn和δ 68Zn值表明玄武岩-流体相互作用优先将同位素中的轻铁和重锌掺入流体中,从而导致蚀变的玄武岩中较重的铁和较轻的锌同位素相对富集。大部分的δ的56的Fe的值(-1.96至+ 0.11‰)的硫化物矿物的是排气口的流体的范围内,但它们比那些MORBs和弧后盆地玄武岩(BABBs)的显著降低,这表明硫化物中的铁主要来源于流体。然而,大多数的黄铜矿δ的56 Fe和δ 57个的Fe值比所述闪锌矿和黄铁矿的更高。这表明高温硫化物矿物富含56 Fe和57Fe,而中,低温硫化物则贫有56 Fe和57 Fe。此外,δ 65的Cu(-0.88 -0.16至‰)和δ 66的Zn(-0.39 -0.03至‰)的硫化物矿物比那些MORBs,BABBs,和流体都显著降低值,这表明63 Cu和优先从流体中除去64 Zn,并分别掺入黄铜矿和闪锌矿中。因此,排出流体的注入和沉积会导致热液羽流,海水和沉积物中较重的Cu和Zn同位素组成。

更新日期:2021-04-26
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