Timescales of Deep and Shallow Magmatic Evolution of Mt. Mazama (Crater Lake)

马札马山（火山口湖）深、浅岩浆演化的时间尺度。弧岩浆作用是大陆形成的主要过程，而形成火山口的火山喷发对全球气候有重大影响。火山口湖是弧形破火山口的代表，在地质历史和喷发产物的性质方面得到了很好的研究。然而，这种破火山口式的喷发很少发生在其他喀斯喀特火山上，这项研究的目的是了解为什么会出现这种情况。本项目旨在增加对弧岩浆作用的两个方面的认识：b[1]下地壳，特别是年轻的镁质地壳在岩浆上升中的调节和减弱作用；b[2]是上地壳中大型岩浆体发育的速率。将在马扎马火山（火山口湖）探索下地壳岩浆过程和上地壳岩浆过程之间的反馈，目的是了解马扎马火山与其他喀斯喀特层状火山岩浆演化的差异。利用U-Th和Re-Os同位素，结合Sr-Nd-Pb同位素和微量元素，评估岩浆与基性下地壳的相互作用。这种方法对石榴石的介入很敏感，有助于约束下地壳的热特征和成分特征。[2]利用U-Th和O同位素资料评价最近~ 100kyr喷发的年轻火山沉积物。U系列资料对热液过程非常敏感，将用于约束与前高潮岩浆房相关的热液系统的规模。[3]利用U-Th同位素测定与气候型破火山口形成喷发相关的演化喷发单元中结晶货物的停留时间。这些方法将用于估计岩浆室的总体尺寸，这些岩浆室为马扎马火山的高潮喷发提供了动力，并形成了山顶的破火山口，并更好地了解这座火山的管道系统和岩浆过程。更广泛的影响。拟议的工作将促进威斯康星大学麦迪逊分校、美国地质勘探局、卡内基- dtm和美国国家公园管理局之间的合作，研究潜在的重大地质风险的火山系统。拓展活动将包括在火山口湖国家公园举办K-12教师讲习班。

Timescales of deep and shallow magmatic evolution of Mt. Mazama (Crater Lake)Intellectual merit. Arc magmatism is a major process whereby continents form, and caldera-forming eruptions can have substantial impact on global climate. Crater Lake is a representative example of arc-related calderas and is very well studied in terms of the geologic history and nature of eruptive products. However, such caldera-style eruptions seldom occurred at other Cascades volcanoes, and this study aims to understand why this is the case. This project aims to increase understanding of two aspects of arc magmatism: [1] the role of the lower crust, and particularly young mafic crust, in moderating and attenuating the ascent of magmas; and [2] the rate at which large magma bodies develop in the upper crust. Feedbacks between lower and upper crustal magmatic processes will be explored at Mt. Mazama (Crater Lake), with the goal of understanding differences in magmatic evolution at Mazama viz a viz other Cascades stratovolcanoes. Research will follow three approaches: [1] Use of U-Th and Re-Os isotopes, coupled with Sr-Nd-Pb isotopes and trace elements, to evaluate magma interactions with mafic lower crust. This approach is sensitive to involvement of garnet and can help constrain thermal and compositional characteristics of the lower crust. [2] Use of U-Th and O isotopic data to evaluate young volcanic deposits erupted in the last ~100 kyr. U series data are sensitive to hydrothermal processes, and will be used to constrain the size of the hydrothermal system associated with the pre-climactic magma chamber. [3] Use of U-Th isotopes to determine residence times of the crystal cargo in evolved eruptive units associated with the climactic caldera-forming eruption. These approaches will be used to estimate overall dimensions of the magma chamber that fed the climactic eruption at Mt. Mazama and formed the summit caldera, and to better understand the plumbing system and magmatic processes operating at this volcano. Broader impacts. The proposed work will foster collaborations between UW-Madison, USGS, Carnegie-DTM, and US National Park Service on a volcanic system that potentially poses significant geologic risk. Outreach activities will include K-12 teacher workshops at Crater Lake National Park.