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

像托巴火山和黄石火山口这样的火山是地球造成的最大自然灾害的发生地：超级喷发。因此，人们在了解这些喷发的性质、它们的危害以及它们对社会构成的风险方面做出了重大努力也就不足为奇了。然而，虽然现在人们已经很好地了解了超级喷发的形成过程，但在超级喷发之后会发生什么，也就是我们所知的恢复期，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。这个项目试图填补这一知识空白，并通过研究过去200万年来最大的超级火山喷发后的事件：印度尼西亚托巴火山口最年轻的托巴凝灰岩(YTT；约7.4万年前)，来提高我们评估超级火山未来危险和风险的能力。作为NSF EAR博士后研究员，西斯内罗斯·德·莱昂博士将整合记录在TOBA喷发的微观晶体中的时间、化学和温度信息，以建立超级喷发后恢复期间岩浆中物理和化学条件的历史。这种方法还将揭示自超级喷发以来的喷发历史，并能够估计今天在托巴超级火山之下存在的可喷发岩浆的数量，从而能够更好地评估未来的风险。这项提议的目标是将托巴火山口作为一个天然实验室，以解决控制超级火山后火山口复兴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、扩散和使用锆石、尿晶石、独居石、磷灰石、辉长岩和石英的热化学模拟来实现，以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在十年到千年时间尺度上的成分演变有关。其具体目标是：1)开发一种综合的岩石成因方法，根据记录在多种副矿物和主要矿物相中的时间、温度和化学成分，在所有尺度上调查喷发前硅质岩浆储集层；2)利用这些信息推断喷发前岩浆储存的物理化学状态；以及3)确定岩浆作用促进火山口后喷发的速率。为了实现这些目标，本研究将应用稀有气体40Ar/39Ar和(U-Th)/He热年代学来利用Ar-In辉长岩和He-In锆石、独居石和磷灰石的不同闭合温度来解决选定的火山口后喷发的喷发年龄、储存条件和喷发速率。此外，还将利用高空间分辨率二次离子质谱仪(SIMS)和激光烧蚀电感耦合等离子体质谱(LA-ICPMS)分别测定副矿物相和石英的绝对时间尺度和相对时间尺度，并配对测定元素和同位素组成。最后，来自各种晶体尺度记录的数据将被整合到热化学模型中，以评估TOBA岩浆系统的当前状态和重新抬升的驱动力。因此，限制在复苏的储集层中发生岩浆作用的时间尺度、条件和程度将对喷发预测做出根本贡献，特别是当地球物理方法面临挑战，以高分辨率表征含熔体的储集层时。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。

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.