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，发生在大洋内火山弧上。这些地区的火山和海底扩张中心拥有大量的热液系统，这些热液系统将热的、充满矿物的水排放到海洋中，并支持地球上其他地方找不到的独特的微型和大型生物群落。沿大洋间弧发现的热液系统的化学成分与位于大洋中脊的热液系统有很大不同，弧系显示出强烈的岩浆特征。这种独特的化学物质，再加上这些弧形火山中许多火山口所处的浅层深处，导致了高度酸性和富含挥发分的流体，这些流体是经济上富含金属的矿藏的先驱。由于这些系统很难被发现，除非它们是偶然发现的，因此这些系统相对来说没有被研究过，也没有被探索过的微生物群落。这项研究将对收集到的样本进行为期20天的海洋研究考察和岸上实验室研究，以确定其中一座独特火山的特征：西太平洋克尔马德克弧的兄弟火山。这座火山还被选为一个潜在的海洋钻探地点，科学的重点是更好地了解活跃的海底热液系统及其循环路径。本研究计划的目标包括使用远程操作工具对兄弟火山喷口的岩石、喷口流体和微生物进行调查和采样。它还包括一项广泛的热流调查，以确定流体补充和排放的区域。这项研究的更广泛影响包括与新西兰科学家建立合作关系、研究生培训、支持在科学界男女比例不足的两名研究人员，以及通过伍兹霍尔海洋研究所获奖的潜水和发现网站进行公众宣传。当机会出现时，还将向公众介绍情况。还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/或药理作用。这项工作还有助于我们了解与热液喷口有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NSF资助的国际海洋发现计划的科学议程，并提供了一项关键的现场调查，可以作为海底钻探支腿的基础。这项研究的重点是记录和了解西太平洋克尔马德克弧区兄弟火山大楼的地质、热流、热液和微生物特征。为期20天的样品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、地球化学和微生物学工作。该研究项目将检验与兄弟火山热液循环有关的五个假说。工作将包括记录来自火山口的热通量和化学通量；低pH值在这些系统中的作用；以及富含挥发分的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、金属和类金属物质进入海洋的质量转移；金属和相关矿藏的海底下分布；弧形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，因为它的破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色烟雾型流体；(2)中温、充气的酸性硫酸盐水域，那里有自然硫烟囱和广泛的铁氧氢氧化物结壳。在巡航期间，将进行一项测绘、采样和观测计划，包括由遥控飞行器潜入兄弟火山口内四个不同的热液区域。将在热液喷口周围的火山口部署热毯，以测量热流和流体补给区和排泄区。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过去十年由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可能进行海洋钻探的地点，以进一步了解海底弧形火山系统。

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.