Clara Waelkens

PhD student
McGill University

My studies started with a BSc in Geology at the KULeuven in Belgium. I then moved to England for a MSc in Geophysical Hazards at UCL to focus more on volcanology, and finally did a second MSc degree, this time in Geology, back at the KULeuven, from which I graduated in the summer of 2015. Throughout my studies, my focus was always volcanology, especially the study of magmatic processes. My research project during my second MSc focused on the origin of rhyolitic magma on the Isle of Mull, and it allowed me to explore a wide range of geochemical and petrological research niches and further fuelled my passion for magma and magmatic processes.


In September 2015, I started a PhD at McGill University, under the supervision of Professor John Stix. I am studying magmatic processes in large silicic calderas, and am more specifically looking at the cataclysmic Bandelier eruptions that took place in Valles Caldera, New Mexico, between 1.1 and 1.6 million years ago. Shortly before and during these so-called ‘supereruptions’, fresh magma intruded the static Bandelier magma chamber, which probably triggered the eruptions. My first aim will be to characterise this fresh magma and establish its relation with the magma already present in the magma chamber. Does this recharge magma have a similar origin as the Bandelier magma, or is it totally different? And if it is different, has similar magma ever been erupted in earlier eruptions around Valles Caldera? If so, could it be that several magma chambers with different composition existed under Valles? I will attempt to answer these questions based on isotopic analysis.


As the magma started to rise from the magma chamber, first to shallower depth and finally to the surface, H2O and CO2 exsolved from the magma and halogens partly fractionated into the newly-formed free fluid phase. This fractionation of halogens is of major importance, as halogens facilitate transport of metals and can therefore have a part in the formation of hydrothermal ore deposits. In addition, halogens can also severly impact atmospheric chemistry and add to the effect explosive volcanic eruptions have on the climate. The second aim of my PhD will hence be to measure H2O and CO2, and later also halogens (F, Cl, Br, I) in melt inclusions of the entire eruption sequence. This will allow me to determine the total gas budget of the Bandelier eruptions and the role of halogens in the hydrothermal system, and will allow me to quantify the amount of volatiles that were released to the atmsophere during eruption.