Project EARTH-17-TM2: The importance and impacts of magmatic volatiles: the behaviour of noble gases and halogens in magmatic systems

Supervisors: Tamsin Mather, Chris Ballentine, David Pyle (all Oxford) and Ray Burgess (Manchester)

Noble gases (He, Ne, Ar, Kr and Xe) and their isotopes form an important suite of tracers of fluid processes, and have the potential to be used to reconstruct magma-source volatile composition, degassing and interaction of the magma with the hydrosphere. These processes underpin our understanding of major scientific questions such as the role of volatiles in eruptive processes (partial melting, crystallisation and gas phase formation), the impact of deep volatiles on the Earth’s surface and the role that such systems play in sustaining a habitable planet. Before the full potential of these new techniques can be realised we need to be able to link these tracers with confidence to major species such as water, CO2 and the halogens (F, Cl, Br, I).

To develop a more complete understanding of the information available through this unique set of trace gases we will exploit recent developments in multi-collector mass spectrometry in noble gas determination (Oxford); and halogen determination by synchrotron micro-XRF (DIAMOND) and irradiation/noble gas techniques (Manchester) to develop analytical solutions to open the way to significant progress in this area.  The focus of the project will be to trace the behaviour of all noble gases together with halogens and other major volatiles as magmas evolve via crystallisation and degassing. The project will have a particular emphasis on volatile behaviour in subduction zones and will operate in the wider context of a major (£8m) UK initiative to investigate the deep geological volatile cycle and its impact on the Earth’s habitability.

Further reading:

Sumino, H., R. Burgess, G. Holland, T. Mizukami, S.R. Wallis and C. J. Ballentine, Seawater-derived noble gases and halogens preserved in exhumed mantle wedge peridotite. Earth and Planet Sci. Lett. 294, 163-172, 2010

Holland, G., Ballentine, C.J., Seawater subduction controls the heavy noble gas composition of the mantle, Nature, 441 (7090), 186-191, 2006.

Pyle, D.M. and T.A. Mather, Halogens in igneous processes and their fluxes to the atmosphere and oceans from volcanic activity: a review, Chemical Geology, 263, 110-121, 2009. (doi:10.1016/j.chemgeo.2008.11.013)

Watt, S.F.L., D.M. Pyle, T.A. Mather and J.A. Naranjo, Arc magma compositions controlled by linked thermal and chemical gradients above the subducting slab, Geophysical Research Letters, 40, 2550-2556, 2013. (doi:10.1002/grl.50513)