Abstract Processes active within buoyant hydrothermal plumes are expected to modulate the flux of elements, such as Fe, to the deep ocean; however, they are yet to be described in a comprehensive manner through observations or models. In this study, we compare observed particulate Fe (pFe) speciation with thermodynamic (equilibrium) reaction path modeling for three vent fields in the Eastern Lau Spreading Center (ELSC). At each site, particles were collected from the buoyant rising portion of hydrothermal plumes using in situ filtration with a Remotely Operated Vehicle. Filter bound particles were analyzed by synchrotron micro-probe X-ray fluorescence mapping (XRF), X-ray diffraction (XRD), XRF spectroscopy, and X-ray absorption near edge structure (XANES) spectroscopy at the Fe 1 s edge, as well as XRF-based chemical speciation mapping for Fe. For buoyant plumes of the ELSC, diversity in solid-state chemistry was high, and poorly crystalline, meta-stable phases were common. We demonstrate that to fully describe the crystalline-to-noncrystalline character of plume pFe, a multi-modal XRD-XANES analytical approach is needed. We found that an equilibrium modeling approach worked well for pyrite but performed poorly for important families of meta-stable pFe, namely Fe (oxyhydr)oxides and monosulfides. Based on our findings, we recommend future field expeditions strategically explore sites representing a diversity of site-specific conditions to better capture the full range of processes active in plumes. We also recommend development of kinetic models, as well as expansion of thermodynamic databases to better reflect the solid-state composition of plumes. These steps should allow oceanographers to understand the processes controlling Fe speciation in plumes well enough to create realistic models of hydrothermal fluxes to the ocean.

中文翻译：

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一种测量漂浮热液羽流中颗粒铁形态的多模式方法

摘要 浮力热液羽流中的活动过程预计会调节元素（如 Fe）向深海的通量；然而，它们还有待通过观察或模型以全面的方式进行描述。在这项研究中，我们将观察到的颗粒 Fe (pFe) 形态与东刘扩散中心 (ELSC) 的三个喷口场的热力学（平衡）反应路径模型进行了比较。在每个地点，使用远程操作车辆的原位过滤从热液羽流的浮力上升部分收集颗粒。通过同步加速器微探针 X 射线荧光绘图 (XRF)、X 射线衍射 (XRD)、XRF 光谱和 Fe 1 s 边缘的 X 射线吸收近边结构 (XANES) 光谱分析过滤器结合的颗粒，如以及基于 XRF 的 Fe 化学形态映射。对于 ELSC 的浮力羽流，固态化学的多样性很高，结晶性差的亚稳相很常见。我们证明，为了充分描述羽状 pFe 的结晶到非结晶特性，需要多模式 XRD-XANES 分析方法。我们发现平衡建模方法适用于黄铁矿，但对于亚稳 pFe 的重要家族，即 Fe（羟基）氧化物和单硫化物，表现不佳。根据我们的发现，我们建议未来的实地考察战略性地探索代表各种特定地点条件的地点，以更好地捕捉羽流中活动的全部过程。我们还建议开发动力学模型，以及扩展热力学数据库，以更好地反映羽流的固态成分。