Collaborative Research: Elucidating Brine-Dominated, Segment-Scale Hydrothermal Discharge Along The Cleft Segment, Juan de Fuca Ridge

合作研究：阐明胡安德富卡海岭裂缝段沿线以盐水为主的分段规模热液排放

• 批准号: 2052453
• 负责人: Jeffrey Seewald
• 金额: $ 36.41万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-15 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2052453&HistoricalAwards=false
• 关键词: Collaborative; Research; Elucidating; Brine; Dominated

Hydrothermal Brines on the Juan de Fuca RidgeNew oceanic crust is formed by magma that is injected beneath the seafloor and then cooled by seawater circulation. This hydrothermal circulation exchanges heat and chemicals between hot rocks and seawater, which produces mineral deposits and unique seafloor ecosystems. The injection of magma is irregular as is subseafloor hydrothermal circulation and the composition of the discharging fluid. During and after a magmatic injection event, the heated seawater separates into a low salinity vapor phase lacking many dissolved metals and a high salinity metal-rich brine phase. Seafloor discharge of the vapor is typically short-lived (years) and is followed by a much longer phase (decades to centuries or longer) of brine discharge. Knowledge of brine composition and its temporal and spatial evolution is currently limited. During this investigation hydrothermal fluids along the Cleft Segment of the Juan de Fuca Ridge off the coast of Oregon will be sampled and analyzed for their chemical composition. This portion of young oceanic crust experienced a magmatic event in 1986 and has been discharging brines for more than three decades. Systematic variations in the composition of these fluids will allow us to document the long-term evolution (decades) of brine-dominated submarine hydrothermal systems, characterize the transport of dissolved minerals and gases in brine phases, and contribute to our understanding of element exchange between Earth’s crust and ocean. The intrusion of magma into the oceanic crust results in the thermal and chemical modification of seawater during convective circulation within the oceanic lithosphere before discharging at the seafloor. This hydrothermal discharge impacts biogeochemical cycles in the ocean, the formation of seafloor metal-rich mineral deposits, and seafloor ecosystems. The net effect is dictated by cyclic temporal and spatial evolution of hydrothermal activity. Many systems begin with discharge of a short-lived (years), vapor phase and evolve to a longer-lived (decades to centuries to longer) discharge of brine phase. Relative to vapor-dominated hydrothermal systems, systematic time-series studies of brine-dominated systems are limited. Understanding brine-dominated hydrothermal systems is particularly important because numerical and conceptual models of magma-driven subseafloor hydrothermal circulation indicate that such circulation of brine-dominated fluids can last for centuries or longer, and potentially impact global fluxes of elements from the lithosphere to the ocean. Gas-tight fluid samplers will collect hydrothermal discharge from the Cleft Segment, which has discharge brine-dominated, hydrothermal fluids from the same seafloor features for at least 32 years. In addition, the investigators will measure discharge temperatures, deploy and recover short-term continuous fluid samplers, and deploy temperature recorders for legacy studies. Results from a shore-based fluid characterization program will address the long-term stability, connectivity, and potential changes in subsurface, segment-scale processes within brine-dominated hydrothermal systemsThis award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Juan de Fuca Ridgenew Oceanic Crust上的水热盐水是由岩浆形成的，岩浆被注入海底下方，然后由海水圆圈冷却。这种热液循环在热岩石和海水之间交换了热和化学物质，该海水产生了矿物沉积物和独特的海底生态系统。岩浆的注射是不规则的，亚承热液和排放液的组成也是不规则的。在岩浆注射事件期间和之后，加热的海水分为低盐度蒸气阶段，缺少许多溶解的金属和高盐度金属富含金属的盐水相。蒸气的海底排放通常是短暂的（年），其次是更长的（数十年或更长）的盐水排放。目前，对盐水组成及其暂时和空间进化的知识受到限制。在这项研究期间，将对俄勒冈州海岸的胡安·德福卡山脊的裂口段进行热液液，并分析其化学成分。这部分年轻的海洋壳在1986年经历了一次岩浆事件，并且已经排放了盐水已有三十多年了。这些烟道组成的系统变化将使我们能够记录盐水主导的海底水热系统的长期演变（几十年），这表征了溶解的矿物质和盐水阶段中的气体的运输，并为我们对地球壳和海洋之间元素交换的理解做出了贡献。岩浆侵入海洋壳中，导致海水循环中海水的热和化学修饰，然后在海底排出之前。这种水热排放会影响海洋中的生物地球化学周期，富含海底金属矿物质的矿物质和海底生态系统。净效应取决于水热活性的循环临时和空间演化。许多系统始于排放短暂的（年），蒸气相和盐水阶段寿命更长的（数十年到几个世纪）的变化。相对于蒸汽主导的水热系统，盐水为主导系统的系统时间序列研究受到限制。理解以盐水为主的水热系统尤其重要，因为岩浆驱动的子eaploor水热循环的数值和概念模型表明，这种盐水主导的笛子的循环可以持续数百年或更长的时间，并可能影响从石圈到海洋的元素的全球磁通量。气密流体样品将从裂缝段收集水热排放，该裂隙段至少32年，从相同的海底特征中具有排出盐水为主导的水热钳。此外，研究人员将测量出排气温，部署和恢复短期连续流体样本，并为遗产研究部署温度记录。基于海岸的流体表征计划的结果将解决长期稳定性，连通性和潜在的地下，盐主导水热系统中的节段尺度过程，该奖项反映了NSF的法定任务，并被认为是通过基金会的知识分子和更广泛的影响审查标准来通过评估来通过评估来支持的。