Metal isotope signatures from lava-seawater interaction during the 2018 eruption of Kīlauea
Metal isotope signatures from lava-seawater interaction during the 2018 eruption of Kīlauea
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DOI：
10.1016/j.gca.2020.05.005
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发表时间：
2020-08
影响因子：
5
通讯作者：
N. Hawco;Shun‐Chung Yang;Rhea K. Foreman;Carolina P. Funkey;Mathilde Dugenne;A. White;Samuel T. Wilson;Rachel L. Kelly;X. Bian;Kuo‐Fang Huang;D. Karl;S. John
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文献类型：
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作者：
N. Hawco;Shun‐Chung Yang;Rhea K. Foreman;Carolina P. Funkey;Mathilde Dugenne;A. White;Samuel T. Wilson;Rachel L. Kelly;X. Bian;Kuo‐Fang Huang;D. Karl;S. John
2018年的克拉维火山喷发与大量熔岩流入沿海海洋有关，这改变了海水化学成分，增加了浮游植物的产量。在海水羽流平流远离熔岩入口的网站，我们观察到十几种金属相对于背景海水和独特的同位素组成的铁，铜，镍，镉和锌的浓度升高。熔岩释放的铁的δ 56 Fe低于夏威夷玄武岩、河流和海岸铁，但与其他高温热液喷口流体的观测结果相似。然而，快速沉淀仅导致溶解铁的适度富集（<10 nM），溶解δ 56 Fe的增加可能是由于与配体介导的颗粒Fe溶解相关的分馏。铜和镍的同位素组成显示背景海水和熔岩源之间的双端元混合的证据。端元δ 65 Cu、δ 66 Zn和δ 114 Cd同位素组成较玄武岩轻，而端元Ni同位素组成反映玄武岩的δ 60 Ni。我们假设，高扩散性和挥发性的亲铜元素导致强烈的动力分馏在快速冷却的熔岩，类似于铜，锌和镉同位素模式中观察到的玻璃陨石。在2018年的Kampillauea火山爆发期间观察到的Cu和Ni的同位素特征远远超过了其正常的海水范围，可能有助于确定在大型火成岩省和其他火山活动形成期间大规模熔岩进入海洋沃茨。
The 2018 eruption of Kīlauea was associated with massive input of molten lava into the coastal ocean, which altered seawater chemistry and increased phytoplankton production. In seawater plumes advected away from the site of lava entry, we observed elevated concentrations of over a dozen metals relative to background seawater and unique isotopic compositions of Fe, Cu, Ni, Cd and Zn. The δ56Fe of iron released from lava was lower than basaltic, riverine and coastal iron from Hawaiʻi, but similar to observations of other high-temperature hydrothermal vent fluids. However, rapid precipitation led to only modest enrichments in dissolved iron (<10 nM), with increasing dissolved δ56Fe likely due to fractionation associated with ligand-mediated dissolution of particulate Fe. The isotopic composition of copper and nickel show evidence for two-endmember mixing between background seawater and a lava source. While the Ni isotopic endmember reflected basaltic δ60Ni, endmember δ65Cu, δ66Zn, and δ114Cd were isotopically lighter than basalt. We hypothesize that high diffusivity and volatility of chalcophile elements leads to strong kinetic fractionation in rapidly cooling lavas, similar to Cu, Zn and Cd isotopic patterns observed in tektites. The isotopic signatures of Cu and Ni observed during the 2018 eruption of Kīlauea far exceed their normal seawater range and may be useful for identifying large-scale lava input into ocean waters during the formation of large igneous provinces and other episodes of volcanism.