International Ocean Discovery Program (IODP) Expedition 376 cored the submarine Brothers volcano of the Kermadec arc to provide insights into the third dimension and the evolution of the volcano and its associated ore-forming systems. We present new petrological and geochemical data on dacitic rocks drilled from Brothers as well as mafic rocks collected at two adjacent ridges. These data include major and trace element compositions of whole rocks, including many economically important metals and metalloids such as Cu, Ag, Pt, Au, Mo, As, Sb, Tl, and Bi, plus Sr-Nd-Pb isotope compositions as well as in situ analyses of glasses and minerals. We show that the basalts and basaltic andesites erupted at the volcanic ridges near Brothers represent potential mafic analogues to the dacites that make up Brothers volcano. Mantle melting and ore potential of the associated magmas are locally enhanced by raised mantle potential temperatures and a high flux of subducted components originating from the partially subducted Hikurangi Plateau. As a result, the parental melts at Brothers are enriched in ore metals and metalloids relative to mid-ocean ridge basalts (MORBs), and a high melt oxidation state (Δ log fO2 of +1.5 fayalite-magnetite-quartz [FMQ]) suppresses early sulfide saturation. However, solid sulfide crystallization occurs late during magma differentiation, with the result that the dacitic lavas at Brothers volcano are strongly depleted in Cu but only moderately depleted in Ag and Au. The dacites at Brothers thus have a high fertility for many metals and metalloids (e.g., As, Sb, Bi), and fluids exsolving from the cooling magma have a high ore-forming potential.

中文翻译：

---

新西兰克马德克弧的潜艇兄弟火山的岩浆和金属的起源

国际海洋探索计划 (IODP) 第 376 次探险队对克马德克弧的海底兄弟火山进行了取芯，以深入了解第三维度以及火山及其相关成矿系统的演化。我们提供了从兄弟钻探的英安岩以及在两个相邻山脊收集的镁铁质岩石的新岩石学和地球化学数据。这些数据包括整个岩石的主量和微量元素组成，包括许多经济上重要的金属和准金属，如铜、银、铂、金、钼、砷、锑、铊和铋，以及 Sr-Nd-Pb 同位素组成如玻璃和矿物的原位分析。我们表明，在兄弟附近的火山山脊喷发的玄武岩和玄武质安山岩代表了构成兄弟火山的英安岩的潜在镁铁质类似物。地幔潜在温度升高和源自部分俯冲的希库朗吉高原的俯冲成分的高通量局部增强了地幔熔化和相关岩浆的成矿潜力。因此，相对于洋中脊玄武岩 (MORB)，Brothers 的母体熔体富含矿石金属和类金属，并且高熔体氧化态（+1.5 铁橄榄石-磁铁矿-石英 [FMQ] 的 Δ log fO2）抑制了早期硫化物饱和。然而，固体硫化物结晶发生在岩浆分异过程的后期，导致兄弟火山的英安岩熔岩中铜严重贫乏，而银和金仅中度贫乏。因此，兄弟地区的英安岩对许多金属和类金属（例如砷、锑、铋）具有很高的富集能力，并且从冷却的岩浆中溶出的流体具​​有很高的成矿潜力。