Super-eruptions, Eruptive Centers and Time-volume Behavior of a Continental Hotspot: The Central Snake River Plain

大陆热点的超级喷发、喷发中心和时间体积行为：中央蛇河平原

• 批准号: 0911457
• 负责人: John Wolff
• 金额: $ 21.06万
• 依托单位: Washington State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-15 至 2012-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0911457&HistoricalAwards=false
• 关键词: Super; eruptions; Eruptive; Centers; Time

The largest and potentially most devastating types of volcanic eruptions are known as super-eruptions. Such events are outside human experience, yet it is quite certain that they will occur in the future. Despite some public awareness of these rare but potentially devastating events, there is a shortfall of basic research into their ultimate origins, immediate causes, and environmental impacts. In North America, the most prolific source of super-eruptions for the past 16 million years has been the Snake River Plain-Yellowstone hotspot trace, stretching from SW Idaho and northern Nevada to Yellowstone itself. The most intense episode in this region occurred between ~12 and 9 Ma, with the eruption of the order of 10,000 - 20,000 km3 of rhyolite (for reference, the 1980 eruption of Mount St. Helens involved less than 1 km3 of magma). The magmas erupted during this flare-up were high-temperature rhyolites, an unusual type of magma that has been somewhat neglected in the past and only now is being thoroughly studied with respect to its origin, and behavior during large eruptions. Perhaps the most important aspect of these magmas and the way they erupt is the sheer volume of magma involved in any one event, which largely determines the magnitude of the environmental impact. This and other aspects of the eruptions can only be reconstructed through detailed mapping of volcanic units in the field, a difficult project that requires the full-time attention of an experienced researcher. Therefore, this project will fund a post-doctoral researcher who will be charged with tying together different rock outcrops to establsh unit correlations and volumes, and to use these data to establish the volume and frequency of rhyolitic eruptions from the central Snake River Plain. The work will additionally involve mineral and chemical analysis to fingerprint individual units, and radiometric dating to establish absolute ages. All this information will be used constrain genesis and storage history of the rhyolitic magmas in conjunction with new and existing petrologic data. The results will help inform our understanding of Earth's continental crust during major episodes of volcanism (ultimately driven by unusually high heat flux from the mantle), and provide a basis for assessing the degree of enviromental disruption that might be expected from the next such event.

规模最大、可能最具破坏性的火山爆发类型被称为超级火山爆发。这样的事件是人类经验之外的，但可以肯定的是，它们将在未来发生。尽管公众对这些罕见但具有潜在破坏性的事件有所认识，但对其最终起源、直接原因和环境影响的基础研究仍然不足。在北美，在过去的1600万年里，最多产的超级火山爆发源一直是蛇河平原-黄石公园热点痕迹，从爱达荷州西南部和内华达州北部延伸到黄石公园本身。该地区最强烈的一次喷发发生在~12 ~ 9 Ma之间，流纹岩喷发量为1万~ 2万km3（作为参考，1980年圣海伦火山喷发的岩浆量不到1 km3）。在这次爆发中喷发的岩浆是高温流纹岩，这是一种不同寻常的岩浆，在过去有些被忽视，直到现在才对其起源和大喷发期间的行为进行了彻底的研究。也许这些岩浆及其喷发方式最重要的方面是任何一次事件所涉及的岩浆的绝对数量，这在很大程度上决定了环境影响的程度。火山喷发的这方面和其他方面只能通过实地对火山单元进行详细测绘来重建，这是一个困难的项目，需要有经验的研究人员的全职关注。因此，该项目将资助一名博士后研究员，他将负责将不同的岩石露头联系在一起，以建立单位相关性和体积，并使用这些数据来确定蛇河平原中部流纹岩喷发的体积和频率。这项工作还将包括矿物和化学分析，以确定单个单位的指纹，以及放射性测年，以确定绝对年龄。所有这些信息将结合新的和现有的岩石学资料，用于约束流纹岩岩浆的成因和储存历史。这些结果将有助于我们了解主要火山活动期间（最终由地幔异常高的热通量驱动）地球大陆地壳的情况，并为评估下一次此类事件可能造成的环境破坏程度提供基础。