How mobile are fluids and melts in the lower continental crust?
Hosted by: Open University, School of Environment, Earth and Ecosystem
Primary supervisor: Prof. Clare Warren (Open University)
Country of origin: The Netherlands
Languages: Dutch & English
I am based at the School of Environment, Earth and Ecosystem Sciences of the Open University (OU) in Milton Keynes, the United Kingdom, and I work in close collaboration with the Department of Earth Sciences at the Vrije Universiteit (VU) in the Netherlands. Before starting my position at the OU, I finished my masters in Earth Structure and Dynamics at Utrecht University and partook in a scientific monitoring project of an active volcano in Colima, Mexico. If I’m not fussing over rocks, you will probably find me bouldering, cycling, or exploring British pubs.
About the project
Many people will probably not realize how little we know about fluids in the lower continental crust. I most certainly did not when I started my scientific career. Nevertheless, lower crustal fluids play a dominant role in many important geological processes, such as the the deep carbon cycle, the formation of ore deposits, and large-scale melting of the continental crust. The problem of the lower crust is that we cannot directly access it; our drills are not equipped to withstand extreme crustal conditions and despite our best efforts, we only ever managed to dig a 12.2 km deep hole (about a third of what is necessary to sample the lower crust). Therefore, geologists are restricted to sample lower crustal terrains that have reached the surface through natural processes, such as volcanic activity or mountain building events, even though the chemistry and behaviour of fluids is prone to change during such tectonic ascents. The good news is that despite these challenges, detailed petrological and geochemical work still enable us to learn a lot about deep fluids.
For my PhD project, I will study the mobility of melts and fluids in the lower continental crust. Noble gas geochemistry provides a powerful way to do this; Noble gases are chemically inert and unlikely to participate/fractionate in re-equilibration reactions of exhuming crustal terrains, making them perfect geochemical tracers of fluids and melt transport. As such, my research aims to measure light noble gas concentrations and isotope ratios in rock samples of various lower-crustal Variscan terrains. What makes my research unique is that I will employ multiple analytical techniques – in conjunction with high-resolution petrography – to make these noble gas measurements on samples of different bulk compositions, deformation histories, and melting histories. This approach will help me to identify key locations in which noble gases are stored, and to recognize mechanisms and/or pathways through which noble gases are mobilized during subsequent geological events.
As the mobility of noble gases is intrinsically related to that of fluids, my research will provide valuable data on the length- and time-scales of fluid and melt transport in the lower crust. These data will be paramount for building lower crustal models of fluid reactivity and transport and will ultimately help to understand how mobile fluids and melts are in the lower continental crust.