EAPSI: Understanding Variations in Thermal Histories in Volcanic Centers Over Time and Space

大型硅质火山中心是地球上最具灾难性的火山爆发的罪魁祸首，包括大规模的“超级火山”爆发。为了潜在地预测超级火山可能爆发的时间，了解岩浆在爆发前产生和储存的时间尺度是很重要的。特别是，目前还不清楚岩浆体在地下以固态（即，作为富含晶体的低温糊状）存在多久，相对于它们以液态（即高温）的可喷发状态存在多久。该项目将研究来自新西兰陶波火山带（TVZ）喷发产物的晶体，陶波火山带是世界上最活跃的火山带。这项工作的目标有两个：1)确定在岩浆储层的高温下晶体存在的比例；2)确定岩浆在火山中心随着时间和空间的变化是如何演化的。这项研究将与新加坡南洋理工大学的菲德尔·科斯塔·罗德里格斯博士合作进行，他是利用扩散剖面确定岩浆温度的专家。为了确定晶体在高温下存在的比例，有必要限制晶体的绝对年龄。通过测量u系列不平衡年龄，可以得到一系列火山喷发斜长石的结晶年龄，结晶年龄与火山喷发年龄的差值可以得到火山喷发时间的长短。为了确定在高温下晶体地下存在的比例，将完成扩散曲线（与温度相关的微量元素分布）的分析。将对一系列火山爆发的结果进行比较，不仅可以确定火山中心如何随时间和空间演变，还可以确定不同震级的火山爆发之间的演变存在什么差异。该奖项由美国国家科学基金会与新加坡国家研究基金会共同资助。

Large silicic volcanic centers are responsible for the most catastrophic volcanic eruptions on earth, including massive 'supervolcanic' eruptions. In order to potentially anticipate when a supervolcano is likely to erupt, it is important to understand the timescales over which magma is generated and stored prior to eruption. In particular, it is not clear for how long magmatic bodies reside in the subsurface in a mostly-solid state (i.e., as low-temperature crystal-rich mushes), relative to how long they spend in a mostly-liquid (i.e., high-temperature), eruptible state. This project will examine crystals from eruptive products from the Taupo Volcanic Zone (TVZ) in New Zealand, the most active volcanic zone in the world. The goals of this work are twofold: 1) to determine what proportion of a crystal's existence was spent at high temperatures within a magma reservoir; 2) to determine how magma evolves differently over both time and space within a volcanic center. This research will be conducted in collaboration with Dr. Fidel Costa Rodriguez, an expert on the use of diffusion profiles to determine magmatic temperatures, at Nanyang Technological University in Singapore.In order to determine what proportion of a crystal's existence was spent at high temperatures, it is necessary to constrain the absolute age of the crystal. Plagioclase crystal ages from a series of TVZ eruptions will be acquired by measuring U-series disequilibrium ages, and the difference between the crystallization age and the eruption age will yield the amount of time spent in the subsurface. Analyses of diffusion profiles (temperature-dependent trace element distributions) will be completed in order to determine what proportion of the crystal's subsurface existence was spent at high temperatures. Results will be compared between a series of eruptions to determine not only how volcanic centers evolve over time and space, but also what differences exist between the evolutions of eruptions of different magnitudes. This NSF EAPSI award is funded in collaboration with the National Research Foundation of Singapore.