Hydrothermal vent fluids from Brothers submarine arc volcano were previously collected in 2004, 2005, and 2017. We present new data from 2018 along with a unique time series of a submarine volcano hosting two distinct types of hydrothermal venting to better understand subsurface processes and how they evolve over time. Samples were collected from known venting locations along the NW Caldera, the Upper and Lower Cone sites, and the newly sampled Upper Caldera site. The NW Caldera wall and Upper Caldera vent fluid compositions are controlled by high-temperature water-rock interactions and phase separation between 2004 and 2018. Fe/Mn molar values suggest that the magmatic impact on all fields has been increasing over time. The Upper Cone has varying influences, including short-term pulses of magmatic degassing, as revealed in K-Mg-SO₄ ternary diagrams, Fe/Mn values, and δD and δ¹⁸O data. The Lower Cone is dominated by low temperatures and CO₂ degassing and shows a pulse in magmatic influence in 2017, followed by a decrease toward earlier conditions in 2018. The 2017 pulse was accompanied by the increase of an enigmatic, soluble MgSO₄ phase, potentially due to the “mining” of a magmatic brine sequestered inside the cone. Stable isotope data across the sites indicate pulses of magmatic waters in 2004 and 2017, immediately followed by episodes of more seawater-dominated fluids in 2005 and 2018. Magmatic degassing, phase separation, permeability, and mineral solubility all strongly influence changes in vent fluid composition. This study highlights the dynamic nature of the Brothers volcano hydrothermal system and the changes in fluid chemistry that may affect resultant mineralization.

中文翻译：

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海底火山热液流体的罕见时间序列：新西兰克马德克弧兄弟火山 14 年的喷口流体成分

兄弟海底弧火山的热液喷口流体之前于 2004 年、2005 年和 2017 年收集。我们提供了 2018 年的新数据以及拥有两种不同类型热液喷口的海底火山的独特时间序列，以更好地了解地下过程及其如何进行。随着时间的推移而发展。样本是从火山口西北沿线的已知通风位置、上锥体和下锥体地点以及新采样的上火山口地点收集的。西北火山口壁和上火山口喷口流体成分受到 2004 年至 2018 年间高温水-岩石相互作用和相分离的控制。Fe/Mn 摩尔值表明，岩浆对所有区域的影响随着时间的推移而增加。上锥体具有不同的影响，包括岩浆脱气的短期脉冲，如 K-Mg-SO ₄三元图、Fe/Mn 值以及 δD 和 δ ¹⁸ O 数据所示。下锥体以低温和 CO ₂脱气为主，并在 2017 年显示出岩浆影响的脉冲，随后在 2018 年向早期条件减少。2017 年的脉冲伴随着神秘的可溶 MgSO 4 相的增加_，可能由于“开采”了锥体内隐藏的岩浆盐水。各个地点的稳定同位素数据表明，2004 年和 2017 年出现了岩浆水脉冲，紧接着在 2005 年和 2018 年出现了更多以海水为主的流体。岩浆脱气、相分离、渗透率和矿物溶解度都强烈影响喷口流体成分的变化。这项研究强调了兄弟火山热液系统的动态性质以及可能影响最终矿化的流体化学变化。