An integrated study of the driving forces and deposits of shallow water eruptions of volatile-rich basalt: Socorro 1993 revisited

富含挥发性玄武岩浅水喷发的驱动力和沉积物的综合研究：Socorro 1993 再访

• 批准号: 1830226
• 负责人: Steven Carey
• 金额: $ 19.65万
• 依托单位: University of Rhode Island
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-07-15 至 2022-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1830226&HistoricalAwards=false
• 关键词: integrated; study; driving; forces; deposits

Shallow water submarine volcanism plays a critical role in the formation of oceanic islands and is associated with hazards to both human populations and marine biological communities. One of the most rarely observed styles of these eruptions is the production of giant floating lava blocks that are filled with gas. When they rise to the sea surface these "lava balloons" often explode and then settle back down to the seafloor. Little is known about this unusual style of submarine volcanism due to the lack of direct observation as only five such eruptions have been documented, all of which occurred at oceanic islands associated with volcanic hotspots such as Hawaii, the Canary Islands, the Azores, and the Revillagigedo archipelago in Mexico. This research develops a better understanding of how these floating gas filled lava blocks are formed during relatively shallow water volcanic eruptions. The project focus on "lava balloon" samples and other associated explosive volcanic products, like ash and other pyroclastic material, erupted from vents off the shores of Mexico's Socorro Island in the eastern Pacific in 1993. During a 2017 oceanographic exploration by the ship, E/V Nautilus, high-resolution video was collected by a submersible, remotely-operated vehicle called Hercules in the area of the eruption at a location where floating gas filled lava blocks were observed while the volcano was active. Other samples of the volcanic material and deposits were also collected and their trace element geochemistry, volatile content, melt inclusions, and the depositional characteristics of the resulting volcanic ash and ejecta layers were targeted for analysis. Objectives of the research include (1) defining the morphology, structure, and nature of the 1993 Socorro vent site based on ultrahigh-resolution bathymetric surveys from the Hercules; (2) carrying out geochemical analyses on the samples to characterize their magmatic composition, volatile content and degassing history, their magma viscosity, and source characteristics; and (3) developing an eruption model for the 1993 event using degassing simulations with inputs from geochemical and textural analyses. Broader impacts of the work include student training at the graduate and undergraduate levels, leveraging unique samples collected at great cost, characterization of a newly designated UNESCO World Heritage Site, and interaction with the Ocean Exploration Trust which is has a major public and K-12 outreach program showcasing the cruise and science coming from the associated research. A video that will have wide dissemination, documenting seagoing research exposing the public to the life of a marine geologist at sea and the wonders of exploring submarine volcanic environments, will be created and there is international collaboration with scientists from Mexico. The work will also contribute to hazard evaluations around the coasts of volcanically-active oceanic islands.Volcanic ejecta of sizes from microns to meters and deposits of these that resulted from the 1993 explosive submarine eruption of Socorro Volcano off the western coast of Mexico will be characterized geochemically and texturally to determine the conditions of eruption and deposition of explosive debris around the vent site. Geochemical analyses will include mineral and glass analyses via electron microprobe, a New Wave 213 nanometer laser ablation system coupled to a Thermo X-Series II inductively coupled mass spectrometer, and a Thermo Nicolet iS50 Fourier Transform Infrared (FTIR) spectrometer. Resulting trace element data will be modeled and new FTIR data will provide minimum values of pre-eruption gas contents for the Socorro magma. CO2/H2O degassing paths, determined from melt inclusion volatile analyses, will provide specific information about whether degassing occurred under closed- or open-system conditions and allow predictions of vesicularities under different degassing scenarios to be made. Magma ascent rates will be modeled using volatile diffusion profiles in glass embayments and phenocrysts in the volcanic ejecta. For very small volcanic particles, a scanning electron microscope (SEM) will be used to examine surface features to evaluate the role of explosive magma/seawater interactions in the eruption process. Another important goal of the research will be development of a well-constrained facies model (scale, morphology, deposit types) for shallow water eruptions of this style, with these samples and this site providing a modern analogue for the paleo-environmental interpretation of ancient, highly vesicular submarine basaltic sequences.This 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.

浅水海底火山活动在海洋岛屿的形成中起着关键作用，并与对人类和海洋生物群落的危害有关。这些喷发中最罕见的一种类型是产生充满气体的巨大漂浮熔岩块。当它们上升到海面时，这些“熔岩气球”经常爆炸，然后沉降到海底。由于缺乏直接观察，人们对这种不寻常的海底火山活动方式知之甚少，因为只有五次这样的火山爆发被记录在案，所有这些都发生在与火山热点有关的海洋岛屿，如夏威夷，加那利群岛，亚速尔群岛和墨西哥的Revillagigedo群岛。 这项研究更好地了解了这些漂浮的充满气体的熔岩块是如何在相对浅水的火山爆发过程中形成的。该项目的重点是1993年从东太平洋墨西哥索科罗岛海岸喷口喷发的“熔岩气球”样品和其他相关的爆炸性火山产物，如灰烬和其他火山碎屑物质。在2017年的海洋学勘探期间，E/V Nautilus在火山喷发区域的一个位置收集了一个名为Hercules的潜水远程操作车辆的高分辨率视频，在火山活动期间观察到漂浮的气体填充熔岩块。还收集了火山物质和沉积物的其他样本，并针对其微量元素地球化学、挥发物含量、熔融包裹体以及所产生的火山灰和喷出物层的沉积特征进行了分析。 研究目标包括：（1）根据大力神号超高分辨率测深测量确定1993年索科罗火山口的形态、结构和性质;（2）对样品进行地球化学分析，以确定其岩浆成分、挥发分含量和脱气历史、岩浆粘度和源区特征;（3）利用地球化学和结构分析的输入，利用脱气模拟建立了1993年火山喷发模型。 这项工作的更广泛的影响包括在研究生和本科生水平的学生培训，利用以高昂的成本收集的独特样本，新指定的联合国教科文组织世界遗产的表征，以及与海洋探索信托基金的互动，该基金有一个主要的公众和K-12推广计划，展示了相关研究的巡航和科学。将制作一个录像，广泛传播，记录海上研究，向公众展示海洋地质学家在海上的生活和探索海底火山环境的奇迹，并与墨西哥科学家进行国际合作。这项工作还将有助于对火山活跃的海洋岛屿海岸周围的危害进行评估，将对1993年墨西哥西海岸外索科罗火山海底爆炸性喷发所产生的从微米到米大小的火山喷出物和沉积物进行地球化学和结构特征分析，以确定喷发条件和喷口周围爆炸性碎片的沉积情况。地球化学分析将包括通过电子显微探针、与Thermo X系列II电感耦合质谱仪耦合的New Wave 213纳米激光烧蚀系统和Thermo尼科莱iS 50傅里叶变换红外光谱仪进行的矿物和玻璃分析。由此产生的微量元素数据将被建模和新的FTIR数据将提供喷发前的索科罗岩浆的气体含量的最低值。CO2/H2O脱气路径，从熔体包裹体挥发性分析确定，将提供有关是否脱气发生在封闭或开放系统条件下的具体信息，并允许在不同的脱气情况下的泡囊预测。岩浆上升率将使用挥发性扩散档案在玻璃海湾和斑晶在火山喷出物。对于非常小的火山颗粒，将使用扫描电子显微镜（SEM）检查表面特征，以评估爆发过程中岩浆/海水相互作用的作用。研究的另一个重要目标将是开发一个良好约束的相模型（规模，形态，存款类型）的浅水喷发的这种风格，与这些样品和这个网站提供了一个现代的模拟古环境的解释古代，该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准。