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Exploring geological controls on global trends in volcanic gas chemistry


   Department of Earth and Environmental Sciences

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  Dr B Mccormick Kilbride, Dr David Neave, Dr M Hartley, Prof M Burton  No more applications being accepted  Competition Funded PhD Project (UK Students Only)

About the Project

The Earth is home to hundreds of volcanoes, constantly releasing gases into the atmosphere. Through geological time, volcanic emissions have influenced the composition of the atmosphere and driven climatic and environmental change. We study volcanic emissions using satellite observations, field measurements, and laboratory analyses of rocks, minerals and gases. Our data reveal wide spatial variations in volcanic gas chemistry, particularly within and between volcanic arcs, located in Earth’s subduction zones. As yet, we lack a full understanding of the geological processes that govern these spatial trends. Is recycling of slab volatiles to arc volcanoes ubiquitous? Are volatiles incorporated from crustal rocks during magma ascent? Is the arc’s crustal structure or stress state and the depths at which magmas stall and evolve important in controlling volatile exsolution and thus the chemistry of emissions at the surface? How far back in time can we meaningfully extrapolate the spatial trends in gas chemistry we observe today? Without understanding gas emissions in terms of underlying geological processes, our ability to relate changes in volcanic outgassing to environmental or climatic consequences remains limited.

 In this project, we will investigate how magma storage depth relates to arc volcano gas chemistry. Volatile solubility in magmas and therefore magma degassing is strongly pressure controlled. We aim to test the hypothesis that the pressure range over which magmas are stored in different volcanic arcs corresponds to the compositional range in gases emitted at the surface. We will draw on (i) recently expanded data coverage for volcanic emissions, via wider deployments of in situ MultiGAS instruments and comprehensive global observations of SO2 flux from the spaceborne TROPOMI sensor, and (ii) Thermobar, a new open-source Python tool for thermobarometry.

 This project will involve data compilation and manipulation, analysis of satellite data, and use of open-source software packages, i.e. Python. The student will develop statistical methods to compare global compilations of gas chemistry and flux data, with magma storage pressure estimates and derived depth ranges. Our initial focus will be comparing intra-oceanic arcs versus continental arcs, end members in terms of crustal thickness and thus, potentially, also in terms of magma storage depth and volcanic gas chemistry. Substantial effort will be devoted to understanding uncertainty in the various data sets, e.g. assumptions and choices made in calculating pressure and depth from rock and mineral compositions, and time-averaging methods employed in characterising highly variable volcanic emissions. Depending on the student’s interest, there may be opportunities to draw on complementary additional data sets, such as depth estimates derived from global satellite geodesy or estimates of magma volatile content obtained from melt inclusion analyses.

We seek a motivated individual with a strong background (MSc, MSci, BSc) in Earth or physical sciences. This project would suit a numerate student with interest in scientific computing, Python programming, statistical methods and the manipulation of large geological data sets. No specific experience is required, as the selected candidate will be offered training in a range of technical and professional skills. For enquiries please contact Dr Brendan McCormick Kilbride ([Email Address Removed]). 

https://www.research.manchester.ac.uk/portal/brendan.mccormickkilbride.html

https://www.research.manchester.ac.uk/portal/david.neave.html

https://www.research.manchester.ac.uk/portal/margaret.hartley.html

https://www.research.manchester.ac.uk/portal/mike.burton.html


Funding Notes

Fees and stipend provided at the current UKRI rate. Start date of July 2023

References

References for advert:
Aiuppa, A. et al., CO2 flux emissions from the Earth’s most actively degassing volcanoes, 2005-2015, Scientific Reports, 2019.
Wieser, P. et al., Thermobar: an open-source Python3 tool for thermobarometry and hygrometry, EarthArxiv preprint, https://doi.org/10.31223/X5FD0K
Queißer, M., et al., TROPOMI enables high resolution SO2 flux observations from Mt. Etna, Italy, and beyond, Scientific Reports, 2019.
McCormick Kilbride, B., et al., Multi-year satellite observations of sulfur dioxide gas emissions and lava extrusion at Bagana volcano, Papua New Guinea, Frontiers in Earth Science, 2019.
Chaussard, E. & Amelung, F., Regional controls on magma ascent and storage in volcanic arcs, Geochemistry, Geophysics, Geosystems, 2014.

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