A New Generation of Timescales for Arc Magmatic Processes

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

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.