Volatile Clues to the Initial Controls on Large Explosive Volcanic Eruptions

大规模火山喷发初步控制的不稳定线索

• 批准号: 1524824
• 负责人: Paul Wallace
• 金额: $ 31万
• 依托单位: University of Oregon Eugene
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-01 至 2020-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1524824&HistoricalAwards=false
• 关键词: Volatile; Clues; Initial; Controls; Large; Volatile; Clues; Initial; Controls; Large

The goal of this project is to better understand how large explosive volcanic eruptions start and the timescales (days or weeks or more) of precursory activity that might serve as a warning sign of an impending eruption. Enormous explosive eruptions (known as supereruptions) have occurred in the recent geologic past that are many times larger than any eruptions that have taken place in historic times. Some of the best and youngest examples, at Yellowstone, in eastern California, and in New Zealand will be studied in this project. A primary goal is to determine if external factors, like an earthquake and movement along a fault, can cause such eruptions to start, or whether instead, they start when a magma body in the earth?s crust becomes overpressured and bursts, like a ruptured balloon. The project will involve chemical analysis of ash and pumice deposits that were created during the opening stages of the eruptions because these preserve a record of information about how and why the eruptions started and how long it took for magma to move to the Earth's surface. This project will test some fundamental ideas about how large explosive rhyolitic eruptions start and when caldera collapse occurs. Despite many important advances in modeling of these processes, there is a surprising lack of geochemical data on the very earliest deposits from large explosive eruptions that could inform the debate about eruption triggering. A quantitative record of magma decompression and ascent rates shortly before and during the opening stages of these eruptions will be obtained by measuring concentrations and gradients of volatiles (H2O, CO2, Cl, S, F) in melt inclusions and reentrants (unsealed inclusions) in quartz and the OH contents of plagioclase. Because magma ascent rates reflect the extent of overpressure in the underlying magma body, constraining ascent rates for the earliest materials from an eruption using diffusive loss of volatiles can provide insight into whether internal (magma overpressure) or external (little or no overpressure) triggers were involved. Based on preliminary results for the Huckleberry Ridge fall deposit (Yellowstone), such data appear to provide a unique record of the processes and timescales of vent development just prior to and during the opening phases of an eruption, with implications for when and why caldera collapse develops and how magma bodies were configured in the upper crust. The results of this investigation will provide quantitative information about how rapidly supereruptions begin and will contribute data to models of geophysical signals that could precede them. This project involves collaborations with other scientists in the U.S. and New Zealand for some of the specialized chemical analyses that will be done and for computer modeling using the results.

该项目的目的是更好地了解大型爆炸性火山喷发的启动程度以及可能是即将发生爆发的警告信号的前尺度（天或数周或更多）。在最近的地质过去，发生了巨大的爆炸性喷发（称为超级爆发），比在历史时期发生的任何爆发大的次数大。 该项目将研究一些最好和最年轻的例子，在加利福尼亚州东部和新西兰的黄石公园。 一个主要目标是确定外部因素（例如地震和沿断层运动）是否会导致这种喷发开始，或者当地球上的岩浆体中的岩浆体被过压并爆发时，它们是否会开始，例如破裂的气球。该项目将涉及在爆发期间创建的灰分和浮石沉积物的化学分析，因为这些项目保留了有关爆发的方式和原因的记录，以及岩浆移至地球表面所花费的时间。该项目将测试一些基本思想，内容涉及大型爆炸性的节奏爆发以及火山口崩溃的何时发生。尽管在对这些过程进行建模方面取得了许多重要的进步，但令人惊讶的是缺乏对大型爆炸性喷发最早的沉积物的地球化学数据，这些数据可能会为有关喷发触发的辩论提供信息。在这些喷发的开放阶段不久和期间，岩浆解压缩和上升速率的定量记录将通过在石英和Plagioclase的OH含量中测量（H2O，CO2，CL，S，F）的测量（H2O，CO2，CL，S，F）在熔体夹杂物和重新输入剂（未相关的夹杂物）中获得。因为岩浆上升速率反映了潜在岩浆体中过压的程度，所以使用挥发物的扩散损失来限制发射最早材料的上升速率，可以洞悉内部（岩浆过压）还是外部（少量或没有过度压力）触发。基于哈克贝利山脊秋季矿床（黄石）的初步结果，此类数据似乎在喷发的开放阶段和过程中为Caldera崩溃的何时以及为什么在上层croust层中配置了岩浆的身体，在开口阶段的开口阶段和为什么对岩浆造成的含义都提供了独特的记录。这项调查的结果将提供有关超级爆发的开始的量化信息，并将为可以在它们之前的地球物理信号模型中贡献数据。该项目涉及与美国和新西兰的其他科学家合作，以使用结果进行一些专门的化学分析，并用于计算机建模。