GEOPRISMS Postdoctoral Scholar proposal: Unravelling monogenetic volcanism in the Cascades Volcanic Range

在全球范围内，近10亿人生活在受火山灾害影响的地区。在北美，受重大火山灾害影响的人口最多的地区是太平洋西北部。尽管与圣海伦斯火山和胡德山等较大层状火山有关的危害已被很好地了解，但较少研究的一种类型的火山是所谓的“单发生”中心，即广泛分布在整个地区的较小的火山锥。它们通常由一个小的火山锥和相关的熔岩场组成。物质的喷发量通常不到一立方公里的总喷发量，尽管也有更大的例子发生。然而，在喀斯喀特火山山脉内，有数千座这种类型的火山建筑。它们广泛的地理分布和总体较短的喷发寿命意味着未来喷发的位置和影响与层状火山不同，更难预测。大多数单一成因系统还没有被详细地研究来预测未来的喷发行为。该项目旨在更好地了解与喀斯喀德相对人口较多的俄勒冈州中部地区的单生火山作用有关的地下岩浆过程。特别是，该项目将利用一系列岩石学和地球化学技术，重点研究火山喷发期间岩浆在火山大厦中移动的速度和方式。该项目包括一名博士后研究人员的培训。该项目将重点放在俄勒冈州中部地区的一些单基因中心，包括一些与纽伯里火山(如Lava Butte)和麦肯齐山口地区(Collier Cone，小贝尔纳普陨石坑)有关的中心。对于选定的被划分为晶体的火山，将研究熔融包裹体和熔体包裹体，以进行常量元素、微量元素和挥发性物质(CO2、H2O)的扩散测定法，以限制火山动乱开始到喷发到地表的时间。岩浆上升速率也将根据熔体包裹体的深度估计来计算。目标是限制使用远程手段(通常是地震研究)探测到新的喷发的时间和实际喷发可能开始的时间之间的时间。对熔体包裹体和晶体成分的研究还将有助于深入了解单生岩浆管道系统的化学和岩石学复杂性和结构。总体而言，这项工作的结果将大大提高对与俯冲有关的单生火山作用的认识，以及这些中心所需的灾害应对措施--这是一种迄今研究较少的火山作用类型。从挥发性分析中评估喷发类型(热流与爆炸性)和上升率，以及计算的扩散计时表，将为特征良好的俯冲带系统中的单源火山作用提供新的见解。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Globally almost 1 billion people live in areas subject to volcanic hazards. In North America, the most populated region subject to significant volcanic hazards is the Pacific Northwest. Although the hazards associated with larger stratovolcanoes such as Mount St Helens and Mount Hood are reasonably well understood, a less studied type of volcano are the so call "monogenetic" centers, smaller volcanic cones that are widely distributed throughout the region. These typically consist of a small volcanic cone and associated lava fields. The amount of material erupted is typically less than a cubic kilometer total erupted volume, although larger examples also occur. However, within the Cascade Volcanic Range, there are thousands of this type of volcanic edifice. Their wide geographic distribution and overall short eruptive life span mean that the locations and effects of future eruptions are different to stratovolcanoes, and are more difficult to predict. Most monogenetic systems have not been studied in significant detail to predict future eruption behavior. This project seeks to gain greater understanding of the subsurface magmatic processes associated with monogenetic volcanism in the relatively populous Central Oregon region of the Cascades. In particular, the project will focus on the speed and style of magma movement through the volcanic edifice during eruptions, using a range of petrological and geochemical techniques. The project includes the training of a postdoctoral investigator.The project will focus on a number of monogenetic centers in the Central Oregon area, including some related to Newberry Volcano (e.g. Lava Butte) and from the MacKenzie Pass area (Collier Cone, Little Belknap Crater). For the selected volcanoes zoned crystals, melt inclusions and melt embayments will be studied for diffusion chronometry of major elements, trace elements and volatile species analysis (CO2, H2O) to constrain the time between initiation of volcanic unrest and eruption to the surface. Magma ascent rates will also be calculated based on depth estimates from melt inclusions. The goal is to constrain the time between when a new eruption may be detected using remote means (typically seismic studies) and when actual eruptions might commence. Studies of melt inclusion and crystal compositions will also allow insight into the chemical and petrological complexity and structure of monogenetic magma plumbing systems. Overall the results of this work will significantly improve knowledge of subduction-related monogenetic volcanism and the hazard response required for these centers - a hitherto less well studied type of volcanism. Evaluating eruption style (effusive vs explosive) and ascent rates from volatile analysis, together with calculated diffusion chronometry timescales, will give new insight into monogenetic volcanism in a well characterized subduction zone system.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.