Collaborative Research: Hydrothermal and Microbiological Investigations of the Active Brothers Volcano in the Kermadec Arc

地球海底火山活动的近三分之一，即22,000公里，发生在海洋内的火山弧上。这些地区的火山和海底扩张中心拥有大量的热液系统，这些热液系统将富含矿物质的热水排放到海洋中，并支持地球上其他地方找不到的独特的微观和宏观生物群落。沿洋间弧发现的热液系统的化学性质与位于洋中脊的热液系统有很大不同，弧系统表现出强烈的岩浆特征。这种独特的化学性质，再加上许多弧状火山的火山口位于较浅的深度，形成了高酸性和富含挥发物的液体，这些液体是富含金属矿床的前兆。因为这些系统很难检测到，除非它们偶然出现，这些系统相对来说没有被研究过，也没有被探索过微生物群落。这项研究将进行为期20天的海洋学研究考察，并对收集的样本进行岸上实验室研究，这些样本是为了描述这些独特的火山之一：西太平洋克马德克弧的兄弟火山。该火山也被选为潜在的海洋钻探地点，科学重点是更好地了解活跃的海底热液系统及其循环途径。目前研究计划的目标包括使用远程操作的车辆对兄弟火山火山口的岩石、喷口流体和微生物进行调查和取样。它还包括广泛的热流调查，以确定流体补给和排放的区域。这项研究的广泛影响包括与新西兰科学家建立合作关系、研究生培训、支持两名在科学领域性别代表性不足的研究人员，以及通过伍兹霍尔海洋研究所屡获殊荣的“潜水与发现”网站进行公众宣传。当机会出现时，还将向公众进行演讲。也有可能发现具有不寻常代谢途径或酶的新微生物物种，这些微生物物种可能具有天然产物和/或药理效用。这项工作也有能力帮助我们了解与热液喷口相关的硫化物矿床的形成，这些矿床通常富含铜、金和钼。这项研究还补充了美国国家科学基金会资助的国际海洋发现计划的科学议程，并提供了海底钻井腿可以基于的关键现场调查。本研究的重点是记录和了解西太平洋克马德克弧兄弟火山大厦的地质、热流、热液和微生物特征。为期20天的样本采集巡航将在兄弟火山的火山口进行，随后将进行陆上实验室的地球化学和微生物工作。该研究项目将测试与兄弟火山热液循环有关的五种假设。工作将包括记录来自火山口的热量和化学通量；低pH值在这些系统中的作用；富挥发物岩浆热液对岩石蚀变的影响。研究还将涉及确定流体-岩石相互作用的机制和程度以及碳、硫、金属和类金属向海洋的质量转移；金属和伴生矿床的海底分布；以及弧火山热液环境中微生物生命的多样性和范围。兄弟火山非常适合进行这类研究，因为它的火山口内有两种不同类型的热液喷口：(1)从富铜金硫化物烟囱中喷出的高温黑烟型液体；(2)温度适中，含气体，酸性硫酸盐水域，天然硫烟囱和广泛的铁-氢氧结壳发生。在巡航期间，将进行测绘、采样和观测计划，包括由远程操作的车辆对兄弟火山口内四个不同的热液场进行一系列潜水。热毯将部署在热液喷口周围的破火山口，以测量热流和流体补给和排放区域。与喷口和周围火山口相关的共存矿物和流体将被收集并进行地球化学分析。这项研究和由此产生的火山口调查补充了NOAA、国家海洋和大气管理局及其与新西兰政府有关的相应机构在过去十年中开展的其他观测和分析工作。调查工作的一个重要目标是确定海洋钻探的潜在地点，以进一步了解海底弧火山系统。

Nearly one third, or 22,000 km of Earth's submarine volcanic activity, occurs along intraoceanic volcanic arcs. The volcanos and seafloor spreading centers in these areas host significant numbers of hydrothermal systems that vent hot, mineral-charged waters into the oceans and support unique micro- and macrobiological communities that are found nowhere else on Earth. The chemistry of hydrothermal systems found along interoceanic arcs differ substantially from those located at mid-ocean ridges, with arc systems exhibiting strong magmatic signatures. This unique chemistry, coupled with the shallow depths at which the calderas of many of these arc volcanoes occur, result in highly acidic and volatile-enriched fluids that are the precursors to economically metal-rich mineral deposits. Because these systems are difficult to detect unless they are come upon by accident, these systems are relatively unstudied and have unexplored microbiological communities. This research will undertake a 20-day oceanographic research expedition and shore-based laboratory studies of the samples that are collected to characterize one of these unique volcanoes: Brothers Volcano in the Kermadec Arc in the Western Pacific Ocean. This volcano has also been selected as a potential ocean drilling site with science focused on the development of a better understanding of active seafloor hydrothermal systems and their circulation pathways. Goals of the present research program include using remotely operated vehicles to survey and sample the rocks, vent fluids, and microbes in the Brothers Volcano caldera. It also includes an extensive heat flow survey to identify areas of fluid recharge and discharge. Broader impacts of the research include establishing collaborations with New Zealand scientists, graduate student training, support of two investigators whose genders are under-represented in the sciences, and public outreach through the Woods Hole Oceanographic Institution's award-winning Dive and Discover website. Presentations will also be made to the public as opportunities present themselves. There is also the potential for the discovery of new microbiological species with unusual metabolic pathways or enzymes which may have natural products and/or pharmacological utility. The work also has the ability to help us understand the formation of hydrothermal vent related sulfide deposits which commonly are rich in copper, gold, and molybdenum. This research also complements the science agenda of the NSF-funded International Ocean Discovery Program and provides a critical site survey upon which seafloor drilling legs can be based. This research is focused on documenting and understanding the geology, heat flow, hydrothermal, and microbial characteristics of the Brothers Volcano edifice in the Kermadec Arc in the Western Pacific Ocean. A 20-day sample collection cruise will take place in the caldera of the Brothers Volcano and will be followed up by onshore laboratory geochemical and microbiological work. The research project will test five hypotheses related to hydrothermal circulation at Brothers volcano. Work will include documenting the heat and chemical fluxes coming from the caldera; the role of low pH in these systems; and the influence of magmatic volatile-rich hydrothermal fluids on rock alteration. Research will also involve determining mechanisms and the extent of fluid-rock interaction and mass transfer of carbon, sulfur, metals and metalloids into the ocean; the subseafloor distribution of metals and associated mineral deposits; and the diversity and extent of microbial life in an arc volcano hydrothermal environment. Brothers volcano is ideally suited for such studies because it harbors two different styles of hydrothermal vents within its caldera: (1) high-temperature black smoker-type fluids discharging from Cu-Au-rich sulfide chimneys; and (2) moderate temperature, gassy, acid-sulfate waters where native sulfur chimneys and extensive Fe-oxyhydroxide crusts occur. During the cruise a mapping, sampling, and observational program will take place, consisting of a series of dives by a remotely operated vehicle to four distinct hydrothermal fields within Brothers caldera. Thermal blankets will be deployed in the caldera around the hydrothermal vents to measure heat flow and fluid recharge and discharge zones. Coexisting minerals and fluids associated with the vents and the surrounding caldera will be collected and geochemically analyzed. This research and the resulting caldera survey complements other observational and analytical work carried out over the past decade by NOAA, the National Ocean and Atmospheric Administration, and its corresponding agency associated with the government of New Zealand. One important goal of the survey work is to identify potential sites for ocean drilling for further understanding of seafloor arc volcanic systems.