Helen Thornhill

Profile

I am a PhD researcher in the Institute of Geophysics and Tectonics (IGT), within the School of Earth and Environment. My reserach interests include geochemistry and igneous petrology, with a specific focus on magma dynamics associated with volcanic systems.

My project will apply geochemical, petrological and isotopic methods to investigate the dynamics of magma supply and storage during the post-glacial period at Mocho Choshuenco, a volcano in Chile. I will be specifically focusing on geochemical analysis of olivine-hosted melt inclusions that will be identified from samples that will be collected in the field during this project. 

Research interests

Magma dynamics in the Mocho Choshuenco Volcanic Complex

The majority of subaerial volcanism on our planet occurs at volcanic arcs, regions where the Earth’s crust is subducting below an adjacent tectonic plate. These tectonic settings are also where most of the Earth’s explosive volcanoes can be found. The Mocho Choshuenco volcanic complex is located in Chile’s Southern Volcanic Zone, a region of the Andean Volcanic Arc. This volcano is known to have had a history of frequent explosive eruptions since the last main glaciation of the region (ca. 18ka). Recent research suggests that ice removal may exert a strong control on the composition of magmas erupted from this volcanic system, with compositions ranging from rhyolitic to primitive basaltic melts. Monogenetic cones on the flanks of the volcano have also been found to have unusual melt compositions not sampled by the main vent system. The proximity of the crustal-scale Liquine-Ofqui fault system may facilitate the ascent of these magmas, however this link has not been thoroughly investigated.

Understanding the growth and development of arc volcanoes requires a detailed understanding of the magmatic systems and processes that drive the eruption and formation of volcanic systems such as Mocho Choshuenco. It is clear that the system has some complexity, with links to geodynamic processes such as glaciation and regional fault systems. Detailed geochemical analysis of the products from recent eruptions of Mocho Choshuenco will provide a better insight into the plumbing-system of this system, along with a better understanding of magma storage depths from melt inclusion analysis. Adopting new techniques such as Raman Spectroscopy to determine an accurate carbon content of olivine-hosted melt inclusions, along with the possibility of isotopic analysis, should provide an effective workflow which will contribute to the understanding and study of these magmatic systems. 

Qualifications

• MGeol, First Class, University of Leeds

Research groups and institutes

• Institute of Geophysics and Tectonics