Better understanding metallogenesis in oceanic crust depends on costly sea-floor drilling projects in areas where metal-bearing deposits, such as sea-floor massive sulfide deposits, are currently forming. In 2018, International Ocean Discovery Program (IODP) Expedition 376 recovered drill cores from an active hydrothermal field at Brothers volcano, in the Kermadec arc. These provide insight into the formation of mineral deposits along arcs, the structure and permeability of hydrothermal sites, and the relationship between the discharge of magmatic fluids and the deep biosphere. We report whole-rock major and trace element compositions and the Re-Os isotope geochemistry of hydrothermally altered volcanic rocks in a core from Hole U1530A, extending 453 m beneath the sea floor, and unaltered volcanic rocks in cores from four other drilling sites and interpret these data to better understand subseafloor mixing of hydrothermal fluids and ambient seawater. The core exhibits more radiogenic ¹⁸⁷Os/¹⁸⁸Os values than typical basal values in four intervals. We propose two causal mechanisms of these radiogenic values: (1) mixing between seawater and hydrothermal fluid, associated with abundant deposition of sulfide or sulfate minerals; and (2) ingress of seawater with radiogenic ¹⁸⁷Os/¹⁸⁸Os values, associated with abundant chlorite and high porosity. Extreme Os enrichments up to 61.5 ppb are interpreted as the result of mobilization of Os as OsO₄ or OsF₆ and transport by volcanic gas, which also affected the Re-Os geochemistry of the rocks from the other Expedition 376 holes. Mobilization and transport of Os by volcanic gas may be an appreciable factor in the influx of unradiogenic Os into the ocean.

中文翻译：

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克马德克弧兄弟火山热液田 U1530A 孔钻芯中铼-锇地球化学深度剖面：火山气体对锇的动员和极度富集

更好地了解洋壳的成矿作用取决于目前正在形成含金属矿床（例如海底块状硫化物矿床）的地区进行昂贵的海底钻探项目。2018 年，国际海洋发现计划 (IODP) 第 376 号探险队从克马德克弧兄弟火山的活跃热液场中回收了钻芯。这些可以深入了解沿弧形矿床的形成、热液地点的结构和渗透性以及岩浆流体的排放与深层生物圈之间的关系。我们报告了 U1530A 孔（延伸至海底 453 m）岩芯中热液蚀变火山岩的全岩主量元素和微量元素组成以及 Re-Os 同位素地球化学，以及来自其他四个钻探地点的岩芯中未蚀变火山岩，并进行了解释这些数据可以更好地了解海底热液和周围海水的混合。核心在四个区间内表现出比典型基础值更多的放射源¹⁸⁷ Os/ ¹⁸⁸ Os 值。我们提出了这些放射性值的两个因果机制：（1）海水和热液之间的混合，与硫化物或硫酸盐矿物的丰富沉积有关；(2) 放射性¹⁸⁷ Os/ ¹⁸⁸ Os 值的海水进入，与丰富的绿泥石和高孔隙度有关。_{高达 61.5 ppb 的 Os 极端富集被解释为 Os 迁移为 OsO 4}或 OsF ₆并通过火山气体传输的结果，这也影响了其他 Expedition 376 孔岩石的 Re-Os 地球化学。火山气体对锇的动员和运输可能是非放射性锇流入海洋的一个重要因素。