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

马扎间山（火山口湖）深浅岩浆演化的时间尺度

• 批准号: 1144937
• 负责人: Clark Johnson
• 金额: $ 24.92万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-05-01 至 2016-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1144937&HistoricalAwards=false
• 关键词: Timescales; Deep; Shallow; Magmatic; Evolution

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.

火山岩深、浅部岩浆演化的时间尺度。马扎马（火山口湖）智力功绩。弧岩浆作用是大陆形成的主要过程，而形成火山口的喷发可对全球气候产生重大影响。火山口湖是弧型火山口的一个代表性例子，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，这项研究的目的是了解为什么会出现这种情况。该项目旨在增加对弧岩浆活动两个方面的理解：[1]下地壳，特别是年轻的镁铁质地壳，在减缓和减弱岩浆上升方面的作用;[2]大型岩浆体在上地壳中发展的速度。下地壳和上地壳岩浆过程之间的反馈将在山探索。马扎马（火山口湖），目的是了解马扎马岩浆演化的差异，即其他瀑布成层火山。研究将遵循三种途径：[1]利用U-Th和Re-Os同位素，结合Sr-Nd-Pb同位素和微量元素，评价岩浆与镁铁质下地壳的相互作用。这种方法是敏感的石榴石的参与，可以帮助限制下地壳的热和成分特征。[2]利用U-Th和O同位素数据评价近100 kyr喷发的年轻火山矿床U系列数据对热液过程敏感，并将用于限制与前气候岩浆房相关的热液系统的大小。[3]使用U-Th同位素来确定与形成火山爆发的高潮火山口有关的演化喷发单位中晶体货物的停留时间。这些方法将被用来估计岩浆房的整体尺寸，美联储在山的高潮喷发。马扎马和形成山顶破火山口，并更好地了解管道系统和岩浆过程在这座火山运作。更广泛的影响。拟议中的工作将促进UW-Madison，USGS，Boggie-DTM和美国国家公园服务之间的合作，研究可能构成重大地质风险的火山系统。外联活动将包括在火山口湖国家公园举办K-12教师讲习班。