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E428: Magma rise in basaltic systems (Lead Supervisor: John Maclennan, Earth Sciences)

Supervisors: John Maclennan (Earth Sciences) and John Rudge (Earth Sciences

Importance of the area of research:

The study of pre-eruptive processes has been revolutionised by advances in diffusion-based chronometry. Cutting-edge microanalytical technology and modelling approaches can now be used to quantify the processes that trigger eruptions. This understanding is a key part of building better interpretation of monitoring data from hazardous basaltic volcanoes, such as the Grimsvotn volcanic system in Iceland, the source of the huge AD 1783 Laki eruption. This new approach also provides fundamental constraints upon the processes that drive transport in magmatic systems and build the oceanic crust.

Project summary:

Petrographic and microanalytical study of recent volcanic rocks from Iceland will be used to determine the timescales of magma storage and transport prior to significant and well-studied eruptions. Cutting-edge microanalysis and elemental mapping will be combined with petrography to provide an observational basis for the quantification of crystal zoning patterns. We have recently developed a new finite-element approach that allows for substantial reduction in the uncertainties associated with estimated timescales of crystal residence. This combination of technological and computational advance will allow us to make robust links to geophysical signals of volcanic unrest.

What the student will do:

The student will undertake fieldwork in the active volcanic zones of Iceland and collect suitable samples for diffusion chronometry. They will prepare samples for petrographic quantification and microanalysis, before making use of instrumentation available in Cambridge (QEMSCAN system, EBSD, EPMA) and national facilities (NERC ion-microprobe, Diamond Light Source) image chemical zonation in olivine, plagioclase, clinopyroxene and spinel crystals in the basaltic volcanics. They will use and potentially develop adaptations of a new finite-element approach to robustly constraining diffusion timescales. They will interpret these timescales within a petrographic and petrological framework to understand their significance and link them to magmatic events in space and time.

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:

Rae ASP,  et al., 2016, Time scales of magma transport and mixing at KÄ«lauea Volcano, Hawai'i, Geology, vol. 44, pp 463-466

Shea, T. et al., 2015, Cracking the olivine zoning code: Distinguishing between crystal growth and diffusion, Geology, vol. 43, pp 935-938

Hartley, M.E. et al., 2016, Tracking timescales of short-term precursors to large basaltic fissure eruptions through Fe-Mg diffusion in olivine, Earth and Planetary Science Letters, vol 439, pp 58-70.

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Other projects available from the Lead Supervisor can be viewed here.

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