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E314: The sulfur burden of large basaltic eruptions (Lead Supervisor: Marie Edmonds, Earth Sciences)

Supervisors: Marie Edmonds (Earth Sciences) and John Maclennan (Earth Sciences)

Importance of the area of research:

Large basaltic eruptions, both in the Earth’s past and in modern times, have been the source of enormous clouds of sulfur dioxide which have been linked to tropospheric cooling, famine and even mass extinctions. Present day measurements of gas emissions have shown that in many cases there is an “excess” of outgassed sulfur over that explained by degassing of melt alone. Syn-eruptive dissolution of sulfides may be an important mechanism for supplying sulfur. Evaluating the controls on such a link is critical for understanding environmental perturbations associated with large basaltic eruptions.

Project summary:

This project will reconstruct the sulfur budget of a young basaltic eruption from the mantle to the atmosphere. Recent work has shown that considerable compositional heterogeneity commonly exists in primary melts, which includes heterogeneity in oxidation state. If a melt is oxidised, considerable fractionation must occur before sulfide saturation. If sulfides form in the shallow crust, they are more likely to be erupted and not segregated by settling. Syn-eruptive breakdown of sulfides will cause enhanced degassing with severe environmental consequences.

What the student will do:

The student will collect samples of basaltic tephra for a recent target eruption where the sulfur emissions were quantified. The samples will be characterised geochemically via microanalysis: melt inclusions and matrix glasses by EMPA and SIMS; sulfides by EMPA and SEM. The detailed timing of sulfide saturation and degassing will be evaluated with reference to the evolution of the melt composition in the glasses. The impact of melt heterogeneity and oxidised primary melts on eruption sulfur output and climate impact will be evaluated.

Please contact the lead supervisor directly for further information relating to what the successful applicant will be expected to do, training to be provided, and any specific educational background requirements.

References:

Jugo, P. J., 2009. Sulfur content at sulfide saturation in oxidized magmas. Geology, v. 37, p. 415-418.

Wallace, .P. J. & M. Edmonds, 2011. The sulfur budget in magmas: evidence from melt inclusions, submarine glasses, and volcanic gas emissions. Reviews in Mineralogy and Geochemistry, vol. 73, no. 1, pp. 215-246.

Nadeau, O., A. E. Williams-Jones & John Stix. Sulphide magma as a source of metals in arc-related magmatic hydrothermal ore fluids. Nature Geoscience 3, no. 7, pp. 501-505.

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