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The subduction melange: the interaction of recycled crust with the mantle wedge
Project Description
The cycling of volatiles between Earth’s surface and interior operates over geological time, regulating the composition of our atmosphere, hydrosphere and oceans whilst maintaining our planet’s habitability. Whilst outward volatile fluxes are numerous, the only pathway to recycle material back into the interior is via the subduction of tectonic plates. This PhD project seeks to experimentally investigate the recycling of volatiles and their interplay with the sub-arc environment. These processes influence, amongst other things, volcanic hazards and how economic deposits for the green energy transition are formed.
Whilst previous studies have focussed on the behaviour of individual volatile species, very few have investigated the behaviour and influence of mixed volatile C-O-S-H fluid bearing systems in detail. Understanding these multi-species fluid systems is crucial to understanding the story of crustal recycling. Compared with exclusively water-bearing or carbonate-bearing systems, COSH fluids have a far greater ability to transition between oxidising and reducing species. Such changes in speciation can completely alter fluids’ properties, which in turn control nutrient mobility in the sub-arc.
This project will combine piston cylinder experiments with a range of petrological analytical techniques (e.g. SEM, EPMA, FTIR and Raman) to focus on several aspects of subduction zone recycling, and may also include synchrotron/neutron-source techniques.
Research themes
Project Specific Training
Training in experimental techniques (piston cylinder experiments) will be provided on a one-to-one basis by the supervisory team, but will additionally be supplemented by internationally run schools in experimental techniques for Earth Sciences (e.g. BGI summer school). Training in university-based analytical techniques, including but not limited to, Scanning Electron Microscopy (SEM), Electron Probe Micro Analyses (EPMA), Fourier transform Infrared Spectroscopy (FTIR), Raman spectroscopy will be provided on a one-to-one basis by the supervisory team and/or lab managers of appropriate facilities, but this will also be supplemented by UKRI funded courses delivered by specialist national labs (e.g. annual NERC funded EPMA workshop). Training in synchrotron/neutron source analyses and data reduction, in techniques including, but not limited to, X-ray absorption near-edge spectroscopy (XANES), Synchrotron Mössbauer Spectroscopy (SMS) or Neutron Spectroscopy will be provided by the Beamline scientists acting as experimental local contacts, or via attendance of summer schools provided by Diamond, ISIS, ILL or the ESRF.
Potential Career Trajectory
This project would prepare the PhD student for a career in (i) academia, (ii) research science beyond academic institutions, (iii) science outreach and communication, (iv) any industry scientist position with analytical responsibilities, (v) any quantitative career pathway, where robust data analysis and interpretation is required, (vi) a data science career pathway, (vii) roles within the education sector outside universities, (viii) analytical roles in financial services or insurance. The multi-faceted nature of a PhD, however, also means this project will provide the candidate with skills that are transferable to any future career pathway.
Project supervisor/s
Andrew Thomson
Earth Sciences
UCL
a.r.thomson@ucl.ac.uk
Eleanor Jennings
School of Natural Sciences (Earth Sciences)
Birkbeck
e.jennings@bbk.ac.uk
Supervision balance
50:50