EAPSI: Probing the Pre-Eruption Magmatic Record of the Youngest Toba Tuff through Titanium and Aluminum Diffusion Timescales in Quartz Crystals

EAPSI：通过石英晶体中的钛和铝扩散时间尺度探测最年轻的多巴凝灰岩的喷发前岩浆记录

• 批准号: 1714053
• 负责人: Casey Tierney
• 金额: $ 0.54万
• 依托单位: Tierney Casey R
• 依托单位国家: 美国
• 项目类别: Fellowship Award
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-06-01 至 2018-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1714053&HistoricalAwards=false
• 关键词: EAPSI; Probing; Pre; Eruption; Magmatic

Constraining how quickly the enormous magma reservoirs that feed volcanic supereruptions can mobilize from a quiescent state to a state capable of eruption is important for overall understanding of large magma systems and the volcanic hazard they may pose. To probe the timescales of magma mobilization, chemical information contained within crystals that were growing in a magma reservoir can be extracted and used to gain insight into the timing of any changes in the conditions and processes that occurred in the magma reservoir before eruption. This project will investigate potential signals of magma mobilization in the pre-eruption growth record of quartz crystals found within the enormous (2800 km3) Youngest Toba Tuff (YTT), which explosively erupted 74,000 years ago from Toba Caldera in Sumatra, Indonesia. The research will be conducted at Nanyang Technological University in Singapore under the mentorship of Dr. Fidel Costa, a noted expert in applying chemical zoning and diffusion in crystals to timescales of magmatic system processes. Striking near-rim zonation present within YTT quartz crystals under cathodoluminescence imaging is indicative of distinct of periods of growth for these crystals, and often with a final stage under different temperature or pressure conditions. The boundary between crystal zones represents a chemical disequilibrium where, through time at magmatic temperatures, elements will diffuse in the crystal to attain equilibrium. For this project, titanium and aluminum concentrations will be measured across crystal zone boundaries to determine the magnitude of diffusional relaxation that has occurred. The yielded diffusion profiles will then be matched to numerically modeled time-dependent profiles to determine the time elapsed between zone growth and eruption. The coupling of titanium diffusional relaxation with that of aluminum in quartz is a novel approach that should yield more robust temporal constraints and interpretations than one element alone. The results will allow the researchers to determine the onset of near-eruption quartz crystallization events, and the potential relation of these events to YTT magma system mobilization and/or alternative processes, such as syn-eruptive decompression. This award, under the East Asia and Pacific Summer Institutes program, supports summer research by a U.S. graduate student and is jointly funded by NSF and the National Research Foundation of Singapore.

限制为火山超级喷发提供动力的巨大岩浆储集层从静止状态转移到能够喷发的状态的速度，对于全面了解大型岩浆系统及其可能构成的火山灾害非常重要。为了探索岩浆流动的时间尺度，可以提取岩浆储藏中生长的晶体中包含的化学信息，并使用这些信息来洞察喷发前岩浆储藏中发生的条件和过程的任何变化的时间。该项目将研究在巨大的(2800千米)最年轻的托巴凝灰岩(YTT)中发现的喷发前石英晶体生长记录中潜在的岩浆动员信号，YTT于74,000年前从印度尼西亚苏门答腊岛的托巴火山口爆炸喷发。这项研究将在新加坡南洋理工大学菲德尔·科斯塔博士的指导下进行，菲德尔·科斯塔博士是一位著名的专家，擅长将晶体中的化学分区和扩散应用于岩浆系统过程的时间尺度。在阴极发光成像下，YTT石英晶体中出现明显的近边缘分带性，表明这些晶体的生长周期明显不同，并且往往在不同的温度或压力条件下处于最后阶段。晶带之间的边界代表着一种化学不平衡，在岩浆温度下，随着时间的推移，元素将在晶体中扩散，达到平衡。对于这个项目，将测量晶区边界上的钛和铝浓度，以确定已经发生的扩散弛豫的大小。然后，将产生的扩散剖面与数值模拟的时间相关剖面进行匹配，以确定区域增长和喷发之间经过的时间。钛和铝在石英中的扩散弛豫耦合是一种新的方法，它应该比单一元素产生更可靠的时间约束和解释。这一结果将使研究人员能够确定近喷发石英结晶事件的开始，以及这些事件与YTT岩浆系统动员和/或替代过程(如同时喷发减压)的潜在关系。该奖项根据东亚和太平洋夏季学院计划，支持一名美国研究生的暑期研究，由NSF和新加坡国家研究基金会联合资助。