EAR-PF: Timescales and processes of magmatic resurgence at Toba caldera

像多巴火山和黄石火山这样的火山是地球上最严重的自然灾害的发生地：超级火山爆发。因此，毫不奇怪，人们投入了大量精力来了解这些火山喷发的性质、它们的危害以及它们对社会构成的风险。然而，尽管超级火山爆发的形成过程现在已经很清楚了，但超级火山爆发之后会发生什么，即所谓的复苏时期，人们仍然知之甚少。这一点很重要，因为地球上所有活跃的超级火山都处于这种状态，仍然构成重大危险。该项目旨在填补这一知识空白，并通过研究过去200万年来最大的超级火山爆发后的事件来提高我们评估超级火山未来危害和风险的能力：印度尼西亚多巴火山口最年轻的多巴凝灰岩（YTT；大约距今74,000年）。作为NSF EAR博士后研究员，Cisneros de León博士将整合在多巴火山喷发的微观晶体中记录的时间、化学和温度信息，以建立超级喷发后岩浆恢复期间的物理和化学条件的历史。这种方法还将揭示自超级火山爆发以来的喷发历史，并允许估计今天多巴超级火山下面可喷发岩浆的体积，从而更好地评估未来的风险。该提案的目标是将多巴火山口作为一个自然实验室，以解决超级火山火山口后复活的岩浆过程的时间和空间尺度。这将通过整合岩石年代学、热年代学、扩散和热化学建模来实现，使用锆石、allanite、monazite、磷灰石、sanidine和石英来破译这些晶体相的互补记录，因为它们与火山口后管道系统及其成分演化有关，在十年到千年的时间尺度上。具体目标是：1)发展一种综合的岩石成因方法，根据时间、温度和多副相和主要矿物相的化学记录，在所有尺度上研究喷发前的硅质岩浆储层；2)利用这些信息推断喷发前岩浆储存的物理化学状态；3)确定岩浆过程促进火山口后喷发的速率。为了实现这些目标，本研究将采用稀有气体40Ar/39Ar和(U-Th)/He热年代学方法，利用锆英中Ar-和锆石、单氮石和磷灰石中He-的不同闭合温度，来确定火山喷发年龄、储存条件和喷涌火山的挤出速率。此外，高空间分辨率二次离子质谱（SIMS）和激光烧蚀电感耦合等离子体质谱（LA-ICP-MS）将用于辅助矿物相和石英，分别确定与元素和同位素组成配对的绝对和相对时间尺度。最后，将各种晶体尺度记录的数据整合到热化学模型中，以评估多巴岩浆系统的现状和复活隆起的驱动力。因此，限制岩浆过程在复活的储层中发生的时间尺度、条件和范围，将对喷发预测做出根本性的贡献，特别是当地球物理方法面临高分辨率表征含熔体储层的挑战时。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。

Volcanoes like Toba and Yellowstone calderas are the sites of the greatest natural catastrophes produced by the Earth: supereruptions. It is no surprise then that significant effort has been put into understanding the nature of these eruptions, their hazards, and the risk they pose to society. However, whereas the build-up to supereruption is now well understood, what happens after a supereruption, the recovery period known as resurgence, is still poorly understood. This is important because all active supervolcanoes on Earth are in this state and still pose a significant hazard. This project seeks to fill this knowledge gap and improve our ability to assess future hazards and risks at supervolcanoes by studying the events after the largest supereruption in the last 2 million years: the Youngest Toba Tuff (YTT; ca. 74,000 years BP) from the Toba Caldera in Indonesia. As an NSF EAR Postdoctoral Fellow, Dr. Cisneros de León will integrate time, chemistry, and temperature information recorded in microscopic crystals erupted at Toba to build a history of the physical and chemical conditions in the magma during recovery after the supereruption. This approach will also reveal the history of eruptions since the supereruption, and allow estimation of the volume of eruptible magma present today beneath the Toba supervolcano enabling better assessment of future risk. The goal of this proposal is to use Toba caldera as a natural laboratory to resolve time and spatial scales of the magmatic processes governing post-caldera resurgence at supervolcanoes. This will be achieved by integrating petrochronology, thermochronology, diffusion, and thermochemical modeling using zircon, allanite, monazite, apatite, sanidine, and quartz to decipher the complementary records of these crystal phases as they pertain to the post-caldera plumbing system and its compositional evolution over decadal to millennial timescales. The specific aims are to 1) develop an integrated petrogenetic approach for investigating pre-eruptive silicic magma reservoirs at all scales based on time, temperature, and chemistry recorded in multiple accessory and major mineral phases; 2) use this information to infer the physicochemical state of pre-eruptive magma storage; and 3) determine the rates at which magmatic processes promote post-caldera eruptions. To accomplish these goals, this study will apply noble-gas 40Ar/39Ar and (U-Th)/He thermochronology to exploit differing closure temperatures of Ar- in sanidine and He- in zircon, monazite, and apatite to resolve eruption ages, storage conditions, and extrusion rates of effusive volcanism from selected post-caldera eruptions. In addition, high-spatial-resolution secondary ion mass spectrometry (SIMS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) will be employed on accessory mineral phases and quartz to determine absolute and relative timescales, respectively, paired to elemental and isotopic compositions. Finally, data from various crystal-scale records will be integrated into thermochemical models to evaluate the current state of the magma system at Toba and the driving forces for resurgent uplift. Thus, constraining the timescales, conditions, and extent over which magmatic processes are occurring in resurgent reservoirs will make a fundamental contribution to eruption forecasting, especially when geophysical approaches are challenged to characterize melt-containing reservoirs at high resolution.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.