Mantle controls on magmatic-volcanic cycles at basaltic volcanoes: An isotopic probe of the Pu'u 'O'o, Halema'uma'u, and 2018 Leilani eruptions of Kilauea Volcano

2018年基拉韦厄火山莱拉尼裂谷的壮观喷发吸引了美国和世界各地夜间新闻观察者和互联网冲冲者的注意，并成为夏威夷岛居民的破坏性火山危机。2018年的火山事件包括基拉韦厄火山两次持续熔岩喷发的结束，当地发生了一次大地震（6.9级），火山山顶地区发生了一次巨大的（约0.8平方公里）爆炸性崩塌，破坏了夏威夷火山国家公园的道路和基础设施。在2018年的三个多月里，大量新的熔岩（0.8立方千米）从基拉韦厄火山下东部裂谷区的裂缝中喷发出来，摧毁了约700所房屋。美国地质调查局夏威夷火山观测站的负责人蒂娜·尼尔说，这次喷发的规模（即其高喷发速度和破坏程度）“在现代记录中确实是前所未有的”。人们对控制2018年火山事件的岩浆过程知之甚少。在这项研究中，来自基拉韦厄火山三次喷发的熔岩样本组成的时间变化，每次相隔约20公里，将被用来追踪岩浆在火山管道系统中的运动，作为时间和空间的函数。这些结果将用于验证这样一种假设，即2018年Leilani裂谷爆发是由至少一批大型地幔衍生岩浆向已经储存了异常大量岩浆的火山大厦输送的积极驱动的。这项研究有可能揭示神秘的地幔对基拉韦厄火山活动和危险的控制。将创建一个教育模块，通过角色扮演模拟2018年基拉韦厄火山事件，并将其发布在夏威夷火山和危害教育科学教育资源中心（SERC）网站上，作为本研究的一个组成部分。基拉韦厄经历了数十年至数百年的长期喷发与爆发火山活动的循环，后者通常与峰顶崩塌和/或火山口形成有关。2018年的事件可能标志着基拉韦厄火山周期的高潮。由于其地幔源非均质性和熔融过程，该火山熔岩在年至世纪的时间尺度上显示出系统的化学（如Nb/Y）和同位素（如206Pb/204Pb）变化。这些幔源岩浆组成的变化表明，基拉韦厄火山也经历了独特的岩浆旋回，其中一些与长期的火山旋回相吻合。一个重要的项目目标是验证基拉韦厄长期火山循环最终是由地幔过程驱动的观点，包括(1)在非均质地幔中产生成分不同的岩浆批次和(2)这些岩浆批次从源头到地表的运输。基拉韦厄火山岩浆旋回可能由两种机制引起。一种机制——基本上是被动的——与难熔地幔源有关——部分熔融程度的降低，岩浆供应速率的下降，以及随后的峰顶岩浆管道系统的破坏。这对于之前的岩浆-火山循环非常重要，该循环以1924年的峰顶崩塌和一次爆炸性喷发而结束。另一种机制——主动驱动——与更肥沃的地幔源的高度部分熔融、岩浆供应的高速率以及一个或多个大岩浆批次从地幔的有力输送有关。这一关于2018年事件的假设将通过以下熔岩样本的化学成分和Pb、Sr和Nd同位素比率进行测试：(1)2018年Leilani裂谷喷发，(2)长期存在的Pu ' u ' O ' O裂谷喷发（1983-2018）的最后十年和Halema ' uma ' u火山口内的山顶熔岩湖（2008-2018）。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。

The spectacular 2018 Leilani rift eruption of Kilauea Volcano captivated the attention of nightly news-watchers and internet-surfers around the U.S. and the world, and it became a destructive volcanic crisis for residents of the Island of Hawaii. The volcanic events of 2018 included the end of two sustained lava eruptions at Kilauea, a large (magnitude 6.9) local earthquake, and a voluminous (~0.8 km3) explosive collapse of the volcano’s summit region that damaged roads and infrastructure in Hawaii Volcanoes National Park. Over three months in 2018, a large amount of new lava (0.8 km3) erupted from fissures on Kilauea’s Lower East Rift Zone at Leilani Estates and destroyed ~700 homes. The scale of this eruption (i.e., its high effusion rate and level of destruction) was “truly unprecedented in the modern record” according to Tina Neal, the Scientist-in-Charge at the Hawaiian Volcano Observatory of the U.S. Geological Survey. Very little is yet known about the magmatic processes that controlled the volcanic events of 2018. In this study, the temporal changes in the composition of lava samples from three Kilauea eruptions, each separated by ~20 km, will be used to track the movement of magma batches through the volcano’s plumbing system as a function of time and space. These results will be used to test the hypothesis that the 2018 Leilani rift eruption was actively driven by the delivery of at least one large mantle-derived magma batch to a volcanic edifice that already held an unusually large amount of stored magma. This research has the potential to reveal the enigmatic mantle controls on the behavior and hazards of Kilauea Volcano. An educational module, simulating the volcanic events at Kilauea in 2018 through role playing, will be created and published on the Science Education Resource Center (SERC) website for Hawaiian Volcanoes and Hazards Education as an integral part of this study.Kilauea experiences long-term cycles of dominantly effusive vs. explosive volcanic activity on a time scale of decades to centuries, with the latter often associated with summit collapse and/or caldera formation. The events of 2018 likely mark the culmination of a volcanic cycle at Kilauea. Lavas from this volcano display systematic chemical (e.g., Nb/Y) and isotopic (e.g., 206Pb/204Pb) variations on time scales of years to centuries due to its mantle source heterogeneity and melting processes. These mantle-derived changes in parental magma composition indicate that Kilauea also experiences distinctive magmatic cycles, some of which coincide with the long-term volcanic cycles. An important project goal is to test the idea that the long-term volcanic cycles at Kilauea are ultimately driven by mantle processes, including (1) the generation of compositionally distinct magma batches within the heterogeneous mantle and (2) the transport of these magma batches from the source to the surface. Kilauea’s magmatic-volcanic cycles may be caused by two mechanisms. One mechanism—essentially passive—is related to a refractory mantle source-related decrease in the degree of partial melting, a decline in the magma supply rate, and a subsequent disruption of the summit magmatic plumbing system. This was important for the previous magmatic-volcanic cycle that ended with summit collapse and an explosive eruption in 1924. The other mechanism—actively driven—is related to high degrees of partial melting of a more fertile mantle source, a high rate of magma supply, and the vigorous delivery of one or more large magma batches from the mantle. This hypothesis for the events of 2018 will be tested using the chemistry and Pb, Sr, and Nd isotope ratios of lava samples from (1) the 2018 Leilani rift eruption, and (2) the final decade of the long-lived Pu’u ’O’o rift eruption (1983-2018) and summit lava lake within Halema’uma’u Crater (2008-2018).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.