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

基拉韦厄火山(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。2018年5月开始的活动标志着自1960年以来基拉韦厄山顶的远东地区首次喷发熔岩，给当地民众、当局和政府监测机构带来了巨大的痛苦。莱拉尼庄园、拉尼普纳花园、卡波霍和度假村的社区(共715户)先后被熔岩流和火山灰覆盖，直到2018年8月基本停止渗出。就喷发的规模而言，这次喷发引人注目，在短短3个月的时间内，喷发相当于之前8年的喷发活动。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：它们最近没有像通常发生的那样供应给火山顶端的岩浆管道系统，而是直接在基拉韦厄东侧的那些社区下面储存了几十年或更长时间。这些储存的岩浆袋随着时间的推移慢慢冷却和成分演变，没有产生可识别的地震活动或火山气体释放。这个合作项目结合了六个不同机构的专业知识，将调查2018年在该地点喷发的熔岩以及附近较早的喷发(1790年、1840年、1955年、1960年)的熔岩的化学性质，以确定岩浆袋在这些地区内可以以可喷发的形式保留多长时间，以及它们可能存在的深度。在未来几年里，这些信息对于更好地了解和告知当地民众夏威夷的危险现象将是至关重要的。在希洛(夏威夷)举行的一个为期3天的研讨会，有8名资深科学家、两名研究生和来自当地两所大学的一些本科生参加，将寻求向学术界和公众传达这一项目产生的新信息。参加2018年喷发点附近学校的K-12活动不仅是为了提供基拉韦厄火山灾害的背景信息，也是为了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。具体来说，这个项目提议描述在这些较老的岩浆储存袋中生长时被困在晶体(橄榄石、辉石、斜长石)中的熔滴的特征。这些熔滴(熔体包裹体)保存了有关储存的岩浆的关键化学信息，然后再与其他岩浆混合而改变，就像2018年一样。通过对不同喷发过程中岩浆特征的化学指纹分析，将有助于我们了解这些岩浆是否随着时间的推移而联系在一起，并初步了解它们在基拉韦厄火山东侧裂谷带内的寿命。由于熔体包裹体还捕获挥发分(H2O、CO_2、S)，其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，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将与所获得的地球化学信息相结合，以对这些岩浆袋以喷发形式存在的时间尺度施加更严格的约束。在这个项目开始的时候，莫纳罗亚火山和基拉韦厄火山都有迹象表明它们的管道系统中有岩浆输入。因此，描述这些屏蔽火山复杂的地下岩浆结构是至关重要的。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.