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

全球近10亿人生活在易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。尽管人们对圣海伦斯火山和胡德山等大型平流层火山的危害已经有了相当的了解，但对一类火山的研究较少，它们是所谓的“单成因”火山中心，即广泛分布在整个地区的较小的火山锥。它们通常由一个小火山锥和相关的熔岩场组成。喷发的物质总量通常小于一立方千米，尽管也有较大的例子。然而，在喀斯喀特火山山脉内，有成千上万的这种类型的火山大厦。它们广泛的地理分布和总体上较短的爆发周期意味着未来爆发的地点和影响与平流层火山不同，并且更难以预测。大多数单基因系统还没有进行详细的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特山脉人口相对较多的俄勒冈中部地区的单成因火山活动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运动的速度和风格。该项目包括培养一名博士后研究员。该项目将重点关注俄勒冈中部地区的一些单基因中心，包括与纽贝里火山（如熔岩丘）和麦肯齐山口地区（科利尔锥体、小贝尔克纳普火山口）有关的一些中心。对选取的火山分带结晶、熔体包裹体和熔体包裹体进行主元素、微量元素的扩散计时和挥发性物质（CO2、H2O）的分析，以限定火山动荡起始到喷发至地表之间的时间。岩浆上升速率也将根据熔体包裹体的深度估计来计算。目标是限制用远程手段（通常是地震研究）探测到新的火山喷发和实际火山喷发之间的时间间隔。对熔体包裹体和晶体组成的研究也将有助于深入了解单源岩浆管道系统的化学和岩石学复杂性和结构。总的来说，这项工作的结果将大大提高对与俯冲有关的单一成因火山作用的认识，以及这些中心所需的危险反应-迄今为止研究较少的火山作用类型。通过挥发性分析评估喷发类型（喷涌型与爆发性）和上升速率，以及计算出的扩散时标，将对一个特征良好的俯冲带系统中的单成因火山作用提供新的认识。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.