Abstract Time series investigations of hydrothermal fluids from different geological settings at the slow-spreading Mid-Atlantic Ridge (MAR) indicate a surprising medium-term stability of their chemical composition over up to 20 years. This does not only apply to tectonically controlled systems with exposure of mantle rocks where magmatic activity is limited, such as the Logatchev-1 hydrothermal field at 14°45′N. We also found the 407 °C hot and extremely metal-rich fluids at the 5°S site Turtle Pits (2986 m water depth) to discharge at constant composition indicating supercritical phase separation for at least 4 years, which contrasts with rather dynamic volcanically driven hydrothermal systems at the fast-spreading East-Pacific Rise (EPR). Possibly, fluid pathways and pressure-temperature conditions are more stable in tectonically controlled settings at MAR than at the EPR where frequent volcanic activity affects permeability within the hydrothermal systems. Despite some spatial variability, hydrothermal fluids discharging at the shallower (ca. 810–870 m) Menez Gwen hydrothermal field at 37°50′N seem to represent a stable discharge of phase-separated vapor-type fluids over 16 years. This demonstrates that medium-term stability of hydrothermal fluid composition seems to be a general feature at slow-spreading ridges. As a consequence, hydrothermal vent organisms at the MAR may live in a more stable chemical environment compared to vent systems at fast-spreading ridges. Considering the fact that slow-spreading ridges account for more than half of the submarine ridge system, such a constant emanation of hydrothermal fluids makes hydrothermal vent systems on slow spreading ridges a medium-term stable source of Fe and other micronutrients into the ocean.

中文翻译：

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大西洋中脊缓慢扩张的热液地球化学时间序列：中期稳定性的意义

摘要 对缓慢扩张的中大西洋海脊 (MAR) 不同地质环境的热液流体的时间序列研究表明，它们的化学成分在长达 20 年的时间里具有惊人的中期稳定性。这不仅适用于岩浆活动有限的地幔岩暴露的构造控制系统，例如 14°45'N 的 Logatchev-1 热液场。我们还发现 5°S 地点 Turtle Pits（2986 m 水深）的 407 °C 热且富含金属的流体以恒定成分排放，表明超临界相分离至少 4 年，这与相当动态的火山驱动形成对比快速扩张的东太平洋海隆 (EPR) 上的热液系统。可能，在 MAR 的构造控制环境中，流体路径和压力-温度条件比在 EPR 中更稳定，在 EPR 中，频繁的火山活动会影响热液系统内的渗透率。尽管存在一些空间变化，但在 37°50'N 的较浅层（约 810-870 m）Menez Gwen 热液场排放的热液流体似乎代表了相分离蒸汽型流体在 16 年中的稳定排放。这表明热液流体成分的中期稳定性似乎是缓慢扩张脊的普遍特征。因此，与快速扩张山脊的热液喷口系统相比，MAR 的热液喷口生物可能生活在更稳定的化学环境中。考虑到缓慢扩张的海脊占海底海脊系统的一半以上，