Crystal-Liquid Dynamics of a Supereruption: The Youngest Toba Tuff and its Aftermath, Sumatra, Indonesia

超级喷发的晶液动力学：最年轻的多巴凝灰岩及其后果，印度尼西亚苏门答腊岛

• 批准号: 1322077
• 负责人: Mary Reid
• 金额: $ 22.93万
• 依托单位: Northern Arizona University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-08-01 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1322077&HistoricalAwards=false
• 关键词: Crystal; Liquid; Dynamics; Supereruption; Youngest

The waxing and waning of eruptive activity at giant volcanic systems like the Toba Caldera Complex of Sumatra, Indonesia or at Yellowstone Caldera, USA, raise fundamental questions about the tempo and physical evolution of these systems, and about the phenomena that could trigger the next eruption. This project targets the highly explosive 75 ka Youngest Toba Tuff (YTT) - at 2800 km3 of magma, the largest eruption experienced by the human race - and the subsequent, more quiescent eruptions that could signal renewal of the sub-volcanic system, or its death throes. Crystals contained within volcanic rocks like the YTT are effective recorders of the origin, assembly, and thermal history of the magmatic systems responsible for them. For the YTT, the crystal record is extraordinarily complicated, and existing results are fragmental and sometimes contradictory. Estimates for the interval of near-eruption crystallization, for example, range from a few hundred years to several tens of thousands of years, with drastically different implications for the magnitude and duration of volcanic unrest. This study aims to reconcile the various disparities in crystal-scale records using samples and analyses strategically selected to complement, extend, and more carefully examine previous work. Investigations will focus on long term changes in crystal growth environments, mineral affinities between the YTT and post-YTT eruptions, and the residence time of crystals at liquid-dominated rather than solid-dominated conditions including the duration of system (re)activation from the conditions and duration of near-eruption mineral growth. This study will test the hypothesis that different portions of the YTT and post-YTT eruptions selectively sample distinct portions of the magmatic system in space and time, including a liquid-dominated cap reservoir, remobilized crystal-rich domains (mush), and the background of magmatic inputs into the system, and examine whether a resident silicic reservoir is developing or dying beneath the Toba Caldera Complex. The PI and Dr. Craig Chesner (EIU), the leading expert on the Toba Caldera Complex system, will collaborate on this project, train graduate students at NAU in conjunction with a new Ph.D. program emphasis in Earth and Planetary Systems, and mentor undergraduates at NAU and EIU.The Toba Caldera Complex is a natural laboratory in which to investigate how highly explosive silicic systems are generated; numerous investigations have also speculated about its impact on major climatic and anthropologic events. The chemical dynamics of magma assembly, the origin of compositional zonation in large volume eruptions, and the timescales of mineral growth, storage, and mush reactivation in high- and low-volume eruptions emitted from the same magmatic system are the main foci of this study. Systematic characterization of representative samples (via serial sectioning of pumices, petrographic studies, and SEM and CL imaging) and strategic in situ chemical and isotopic mineral analyses (via electron and ion microprobe analyses of selected trace elements and 238U-232Th-230Th-207Pb- 206Pb) in the minerals quartz, allanite, and zircon are being undertaken, with complementary analyses of other minerals. A comprehensive approach is needed to distinguish cognate minerals from minerals accidentally incorporated during or before eruption, and to examine the fidelity - to each other and to magmatic conditions - of increasingly-used temperature and chemical proxies. Delimiting the duration of magma remobilization and the frequency of post-caldera magmatism will also contribute to understanding magmatic signals in the lead-up to eruptions, and the potential for future volcanic hazards associated with the Toba Caldera Complex.

印度尼西亚苏门答腊岛的多巴火山口复合体或美国黄石火山口等巨型火山系统喷发活动的盛衰，引发了有关这些系统的速度和物理演化以及可能引发下一次喷发的现象的基本问题。该项目的目标是高度爆炸的 75 ka 最年轻的多巴凝灰岩 (YTT)——岩浆厚达 2800 立方公里，是人类经历过的最大规模的喷发——以及随后的、更静止的喷发，这些喷发可能标志着次火山系统或其系统的更新。死亡的阵痛。 YTT 等火山岩中含有的晶体是岩浆系统起源、聚集和热历史的有效记录者。对于YTT来说，水晶记录异常复杂，现有结果支离破碎，有时甚至相互矛盾。例如，对接近喷发结晶的时间间隔的估计范围从几百年到几万年不等，这对火山动荡的强度和持续时间有着截然不同的影响。这项研究旨在使用战略性选择的样本和分析来协调晶体尺度记录中的各种差异，以补充、扩展和更仔细地检查以前的工作。调查将重点关注晶体生长环境的长期变化、YTT 和后 YTT 喷发之间的矿物亲和力，以及晶体在液体主导而非固体主导条件下的停留时间，包括系统（重新）激活的持续时间。近喷发矿物生长的条件和持续时间。这项研究将检验以下假设：YTT 和 YTT 后喷发的不同部分在空间和时间上选择性地对岩浆系统的不同部分进行采样，包括以液体为主的盖层储层、重新流动的富含晶体的域（糊状）和背景进入系统的岩浆输入量，并检查多巴火山口复合体下方是否存在硅质储层正在发育或死亡。 PI 和多巴火山口综合体系统的首席专家 Craig Chesner 博士（经济学人智库）将在这个项目上进行合作，与新的博士生一起培训 NAU 的研究生。项目重点是地球和行星系统，并指导 NAU 和 EIU 的本科生。 多巴火山口综合体是一个天然实验室，用于研究高爆炸性硅质系统是如何产生的；许多调查还推测了它对主要气候和人类事件的影响。岩浆聚集的化学动力学、大体积喷发中成分分带的起源，以及同一岩浆系统中高、低体积喷发中矿物生长、储存和糊状再活化的时间尺度是本研究的主要焦点。对代表性样品进行系统表征（通过浮石的连续切片、岩相学研究以及 SEM 和 CL 成像）以及战略性原位化学和同位素矿物分析（通过对选定的微量元素和 238U-232Th-230Th-207Pb- 进行电子和离子微探针分析）正在对石英、铜长石和锆石矿物中的 206Pb）进行研究，并对其他矿物进行补充分析。需要一种全面的方法来区分同源矿物和喷发期间或喷发前意外掺入的矿物，并检查日益使用的温度和化学指标的相互之间以及岩浆条件的保真度。确定岩浆再活动的持续时间和火山口后岩浆活动的频率也将有助于了解火山喷发前的岩浆信号，以及与多巴火山口复合体相关的未来火山灾害的可能性。