Collaborative Research: Size, depth and longevity of magma reservoirs under Kilauea's rift zones: Integrating melt inclusion data and thermal modeling

合作研究：基拉韦厄裂谷带下岩浆储层的大小、深度和寿命：整合熔体包裹体数据和热模拟

• 批准号: 2020049
• 负责人: Paul Wallace
• 金额: $ 4.07万
• 依托单位: University of Oregon Eugene
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-07-15 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2020049&HistoricalAwards=false
• 关键词: Collaborative; Research; Size; depth; longevity

Kilauea (Hawai'i) is one of the world’s most active volcanoes. The volcano erupted continuously for 35 years between 1983 and 2018 covering a vast area and burying several communities. The activity that started in May 2018 marked the first time that lava erupted this far east of the summit of Kilauea since 1960, and it led to great anguish for the local population, authorities, and government monitoring agencies. The communities of Leilani Estates, Lanipuna Gardens, Kapoho, and Vacationland (a total of 715 homes) were successively covered by lava flows and tephra, before effusion mostly stopped in August 2018. This eruption stood out in terms of sheer volume, erupting the equivalent of 8 years of prior activity within just a 3-month timeframe. Chemical analyses of the May 2018 lava revealed the anomalous composition of the first lavas: they were not recently supplied to the volcano’s summit magma plumbing system, as normally occurs, but instead had been stored for decades or longer directly underneath those communities located on the eastern flanks of Kilauea. These stored magma pockets slowly cooled and evolved in composition through time, generating no recognizable seismic activity or volcanic gas releases. This collaborative project combines expertise from six different institutions and will investigate the chemical properties of lavas erupted at this site in 2018 and in older nearby eruptions (1790, 1840, 1955, 1960) to determine how long magma pockets can stay in eruptible form within these regions, and at what depths they likely reside. This information will be crucial in the years to come to better understand and inform the local population about hazardous phenomena for the Island of Hawai'i. A 3-day long workshop in Hilo (Hawai'i) involving 8 senior scientists, two graduate students, and a number of undergraduate students from two local universities will seek to communicate new information stemming from this project to academics and the public. Participation in K-12 activities in schools near the 2018 eruption site are proposed not only to offer background information on Kilauea hazards, but also for academics and researchers to gain deeper insight about the effects such eruptive crises have on local populations.In detail, this project proposes to characterize droplets of melt that are trapped within crystals (olivine, pyroxene, plagioclase) during their growth in these older stored pockets of magma. These melt droplets (melt inclusions) preserve key chemical information about the stored magmas before they become modified by mixing with other magmas like in 2018. Chemical fingerprinting of the magma characteristics through different eruptions will help us understand whether these magmas are linked through time, and give first insights on their longevity within the lower east rift zone of Kilauea Volcano. Because melt inclusions also trap volatiles (H2O, CO2, S) whose concentrations depend directly on the depth of magma storage, quantifying these concentrations can be used to reconstruct storage pressure and depth of these magma pockets. Finally, three dimensional numerical models of cooling of magma bodies of different sizes and geometries under the rift zone will be combined with the geochemical information obtained to place tighter constraints on the timescales over which these magma pockets survive in eruptible form. At the time this project is starting, both Mauna Loa and Kilauea volcanoes show signs of magma input in their plumbing systems. Characterizing the complex subsurface magmatic structure of these shield volcanoes is therefore essential.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.

基拉韦厄（夏威夷）是世界上最活跃的火山之一。从1983年到2018年，这座火山连续喷发了35年，覆盖了大片地区，掩埋了几个社区。这场活动始于2018年5月，标志着自1960年以来熔岩首次在基拉韦厄山顶以东的偏远地区喷发，给当地居民、当局和政府监测机构带来了极大的痛苦。Leilani Estates、Lanipuna Gardens、Kapoho和Vacationland（共715所房屋）的社区先后被熔岩流和火山熔岩覆盖，直到2018年8月大部分熔岩流停止。这次火山爆发的规模非常大，在短短3个月的时间内爆发了相当于8年前的火山活动。对2018年5月熔岩的化学分析揭示了第一批熔岩的异常成分：它们不是最近才被供应到火山顶部的岩浆管道系统，而是被储存了几十年或更长时间，直接位于基拉韦厄火山东部侧翼的那些群落的地下。随着时间的推移，这些储存的岩浆袋慢慢冷却并在成分上进化，没有产生可识别的地震活动或火山气体释放。该合作项目结合了来自六个不同机构的专业知识，并将调查2018年在该地点喷发的熔岩和附近更早的喷发（1790年、1840年、1955年、1960年）的化学性质，以确定岩浆穴在这些地区能够以可喷发的形式保持多长时间，以及它们可能存在的深度。在今后的岁月里，这些信息对于更好地了解和告知当地居民夏威夷岛的危险现象将是至关重要的。在夏威夷希洛（Hilo）举行的为期三天的研讨会上，来自当地两所大学的8名资深科学家、两名研究生和一些本科生将寻求与学术界和公众交流来自该项目的新信息。建议在2018年火山喷发地点附近的学校参加K-12活动，不仅可以提供有关基拉韦厄火山危害的背景信息，还可以让学者和研究人员更深入地了解这种喷发危机对当地人口的影响。详细地说，这个项目提出了在这些古老的岩浆储存袋中生长过程中被困在晶体（橄榄石、辉石、斜长石）中的熔体液滴的特征。这些熔融液滴（熔融包裹体）在与其他岩浆混合（如2018年）之前保存了有关储存岩浆的关键化学信息。通过不同喷发的岩浆特征的化学指纹将帮助我们了解这些岩浆是否随时间联系在一起，并首次了解它们在基拉韦厄火山东部下裂谷带的寿命。由于熔融包裹体还会捕获挥发性物质（H2O, CO2， S），这些物质的浓度直接取决于岩浆储存的深度，因此量化这些浓度可以用来重建这些岩浆袋的储存压力和深度。最后，将裂谷带下不同大小和几何形状的岩浆体冷却的三维数值模型与所获得的地球化学信息相结合，对这些岩浆袋以可喷发形式存在的时间尺度进行更严格的约束。在这个项目开始的时候，莫纳罗亚火山和基拉韦厄火山的管道系统都显示出岩浆输入的迹象。因此，表征这些盾状火山复杂的地下岩浆结构是必不可少的。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。