A New Generation of Timescales for Arc Magmatic Processes

该项目旨在提供岩浆库内发生的过程与其表面表现为喷发事件之间的时间联系，从弧火山的长期演变来看。 这个问题从根本上说是地质年代学的问题，因为通过几十年的工作，已经建立了识别分离结晶、岩浆混合和地壳同化等过程的基础。 量化岩浆过程的时间尺度对于了解潜在危险的弧火山是如何形成的，它们的生长速度以及它们最终如何通过灾难性的喷发或部门崩溃而失败至关重要。 由于对弧火山喷发通量的长期变化、岩浆分异的相关时间尺度、分异与岩浆输入与输出事件之间的关系以及地壳厚度在确定特定岩浆需要多长时间才能穿过地壳并喷发方面所起的作用的不完全了解，进展受到阻碍。这些差距将通过详细研究三个火山（Seguam，Puyehue和Parinacota）来弥补，每个火山都位于一个典型的弧形环境（阿留申群岛，南部安第斯山脉和中部安第斯山脉）。 重点是四个目标：（1）测量每座火山在过去20万年中作为时间函数的喷发速率，（2）解决岩浆上升的速率限制步骤是深层分异还是浅层储存，（3）将岩浆系统演化中的重大事件与形成伴随的火山建筑物的重大事件联系起来，（4）量化地壳厚度和成分对上述问题的影响。 测绘和地层学，岩石学，地球化学和实验相平衡运动，以及U-Th地质年代学，以确定岩浆事件的过程和时间尺度和许多关键喷发的精确40 Ar/39 Ar定年，将解决这些目标。该项目的效益将超出其任期，包括：（1）三名博士生的专业培训，（2）智利火山灾害的公共宣传，以及（3）与智利和德国火山学家的国际合作。 我们将利用新的研究性教学与学习整合中心（CIRTL），这是一个由NSF赞助的项目，旨在培养下一代威斯康星大学麦迪逊分校的大学科学教授。 CIRTL的课程和讲习班将促进火山动态数字地图的开发和测试，这些地图可用作各级教育和宣传的工具。 协同增效至关重要，将涉及智利、德国和美国机构之间的数据、想法和学生交流。

This project aims to provide a temporal link between processes occurring within magma reservoirs and their surficial expression as eruptive events, viewed in context of the long-term evolution of arc volcanoes. The problem is fundamentally one of geochronology, since a foundation for identifying processes such as fractional crystallization, magma mixing, and crustal assimilation has already been established through decades of work. Quantifying timescales of magmatic processes is a critical to understanding how potentially dangerous arc volcanoes are built, how fast they grow, and how they eventually fail through catastrophic eruption or sector collapses. Progress is hampered by incomplete knowledge of the long-term variability of eruptive fluxes from arc volcanoes, associated timescales of magma differentiation, relationship between differentiation and magma input vs. output events, and the role that crustal thickness plays in determining how long a particular magma takes to transit the crust and erupt. These gaps will be bridged through detailed study of three volcanoes (Seguam, Puyehue, and Parinacota) each situated in a classic arc setting (Aleutian Islands, Southern Andes, and Central Andes). The focus is on four objectives: (1) Measuring eruptive rates as a function of time for the last 200 thousand years at each volcano, (2) Resolving whether the rate-limiting step in magma ascent is deep differentiation or shallow storage, (3) Tying major events in the evolution of a magmatic system to significant events that shape the accompanying volcanic edifice, and (4) Quantifying the effect of crustal thickness and composition on the above issues. Campaigns of mapping and stratigraphy, petrography, geochemistry, and experimental phase equilibria, alongside U-Th geochronology to identify processes and timescales of magmatic events and precise 40Ar/39Ar dating of many key eruptions, will address these goals. Benefits that will extend beyond the tenure of this project include: (1) Professional training of three PhD students, (2) Public outreach concerning volcanic hazards in Chile, and (3) International collaboration with Chilean and German volcanologists. We will take advantage of the new Center for the Integration of Research Teaching and Learning (CIRTL), an NSF-sponsored program to train the next generation of college science professors based at UW-Madison. CIRTL courses and workshops will foster development and testing of Dynamic Digital Maps of the volcanoes that can be used as tools for education and outreach at different levels. Collaborative synergy is vital and will involve exchanges of data, ideas and students between institutions in Chile, Germany, and the US.