USAP-DC

Nontechnical project description Globally, 500 million people live near and are threatened by active volcanoes. An important step in mitigating volcanic hazards is understanding the variables that influence the explosivity of eruptions. The rate at which a magma ascends from the reservoir within the Earth to the surface is one such variable. However, magma ascent rates are particularly difficult to determine because of the lack of reliable methods for investigating the process. This research applies a new approach to study magma storage depths and ascent rates at the Erebus volcanic province of Antarctica, one of Earth's largest alkaline volcanic centers. Small pockets of magma that become trapped within growing olivine crystals are called melt inclusions. The concentrations of water and carbon dioxide in these melt inclusions preserve information on the depth of magma reservoirs. Changes to the concentration and isotopic composition of water in the inclusions provide information on how long it took for the host magma to rise to the surface. In combination, these data from samples of olivine-rich volcanic deposits in the Erebus volcanic province will be used to determine the depths at which magmas are stored and their ascent rates. The project results will provide a framework for understanding volcanic hazards associated with alkaline volcanism worldwide. In addition, this project facilitates collaboration among three institutions, and provides an important educational opportunity for a postdoctoral researcher. Technical project description The depths at which magmas are stored, their pre-eruptive volatile contents, and the rates at which they ascend to the Earth's surface are important controls on the dynamics of volcanic eruptions. Basaltic magmas are likely to be vapor undersaturated as they begin their ascent from the mantle through the crust, but volatile solubility drops with decreasing pressure. Once vapor saturation is achieved and the magma begins to degas, its pre-eruptive volatile content is determined largely by the depth at which it resides within the crust. Magma stored in deeper reservoirs tend to experience less pre-eruptive degassing and to be richer in volatiles than magma shallower reservoirs. Eruptive style is influenced by the rate at which a magma ascends from the reservoir to the surface through its effect on the efficiency of vapor bubble nucleation, growth, and coalescence. The proposed work will advance our understanding of pre-eruptive storage conditions and syn-eruptive ascent rates through a combined field and analytical research program. Volatile measurements from olivine-hosted melt inclusions will be used to systematically investigate magma storage depths and ascent rates associated with alkaline volcanism in the Erebus volcanic province. A central goal of the project is to provide a spatial and temporal framework for interpreting results from studies of present-day volcanic processes at Mt Erebus volcano. The Erebus volcanic province of Antarctica is especially well suited to this type of investigation because: (1) there are many exposed mafic scoria cones, fissure vents, and hyaloclastites (exposed in sea cliffs) that produced rapidly quenched, olivine-rich tephra; (2) existing volatile data for Ross Island MIs show that magma storage was relatively deep compared to many mafic volcanic systems; (3) some of the eruptive centers ejected mantle xenoliths, allowing for comparison of ascent rates for xenolith-bearing and xenolith-free eruptions, and comparison of ascent rates for those bearing xenoliths with times estimated from settling velocities; and (4) the cold, dry conditions in Antarctica result in excellent tephra preservation compared to tropical and even many temperate localities. The project provides new tools for assessing volcanic hazards, facilitates collaboration involving researchers from three different institutions (WHOI, U Wyoming, and U Oregon), supports the researchers' involvement in teaching, advising, and outreach, and provides an educational opportunity for a promising young postdoctoral researcher. Understanding the interrelationships among magma volatile contents, reservoir depths, and ascent rates is vital for assessing volcanic hazards associated with alkaline volcanism across the globe.

Person	Role
Gaetani, Glenn	Investigator and contact
Le Roux, Veronique	Co-Investigator
Sims, Kenneth	Investigator
Wallace, Paul	Investigator

Antarctic Earth Sciences	Award # 1644027
Antarctic Earth Sciences	Award # 1644020
Antarctic Earth Sciences	Award # 1644013

USAP-1644013_1

None in the Database

Repository	Title (link)	Format(s)	Status
USAP-DC	Location and Description of Tephra Samples from the Erebus and Discovery Sub-provinces	Excel	exists
USAP-DC	G170 Sample Locations Ross Island & Discovery Province	Excel	exists
USAP-DC	G170 Electron Microprobe Analyses of Melt Inclusions and Host Olivines	Excel	exists
USAP-DC	G170 Secondary Ion Mass Spectrometry Analses of Melt Inclusion Volatiles	Excel	exists
USAP-DC	G170 Secondary Ion Mass Spectrometry Analyses of Melt Inclusion Hydrogen Isotopes	Excel	exists
USAP-DC	G170 Raman Spectroscopy & Tomography Volumes of Melt Inclusions and Vapor Bubbles	Excel	exists

1. Phillips, Erin H. and Sims, Kenneth W.W. and Blichert-Toft, Janne and Aster, Richard C. and Gaetani, Glenn A. and Kyle, Philip R. and Wallace, Paul J. and Rasmussen, Daniel J.. "The nature and evolution of mantle upwelling at Ross Island, Antarctica, with implications for the source of HIMU lavas," Earth and Planetary Science Letters, v.498, 2018. (doi:10.1016/j.epsl.2018.05.049)
2. Sims, K. W. W., Aster, R. C., Gaetani, G., Blichert-Toft, J., Phillips, E. H., Wallace, P. J., … Boyd, E. S. (2021). Chapter 7.2 Mount Erebus. Geological Society, London, Memoirs, 55(1), 695–739. (doi:10.1144/m55-2019-8)
3. Wallace, PJ, Plank, T, Bodnar, RJ, Gaetani, GA, and Shea, T, 2021, Olivine-hosted melt inclusions: A microscopic perspective on a complex magmatic world, Ann Rev Earth Planet Sci., 49: 465-494. (doi:10.1146/annurev-earth-082420-060506)