Academic background

• Senior Lecturer in Earth Sciences, University of Manchester (since 2004)
• Lecturer in Experimental Petrology, University of Manchester (1995-2004)
• Postdoctoral Research Assistant, Department of Geology, University ofBristol (1993-1994)
• Research Specialist, Materials Research Group for High Pressure Synthesis, Department of Chemistry, Arizona State University, USA (1992-1993)
• Postdoctoral Research Assistant, Department of Chemistry, Arizona State University, USA (1990-1992)

Current and recent research projects:

Reactions of sand and dust in jet engines

Every year, millions of tonnes of dust is carried up into the atmosphere, mainly during sand and dust storms. This dust presents a major hazard to modern aircraft engines, which operate at extremely high temperatures that are close to the melting points of many of the minerals in the dust. Particles entrained into the air intake of a turbine engine may be heated to temperatures of well over 1200 °C. If they melt they may clog up the cooling holes in the turbine blades or react with the blade material and cause various degrees of engine damage, leading to a shortened service life of the engine, and potentially engine failure. It is recognised by the aviation industry that this hazard is likely to get worse as future climatic variability and extremes result in an expansion of dusty environments, as well as more frequent and severe sand and dust storms.  At the same time, engine operating temperatures are likely to be higher in the future than they are today. The multidisciplinary DUST research group at the University of Manchester is engaged in a variety of research projects, investigating the impact of airborne dust on aircraft engines at all stages of its passage through the engine, from the characterisation of atmospheric particles entering the engine, their fractionation and fragmentation in the cold section of the engine, through to their deposition and melting in the hot section. We study these using numerical modelling, a variety of experimental approaches, and by analysing real deposits, both from on-wing engines and produced in engine tests.

Halogen partitioning between mantle phases and melts

The halogens are useful tracers of volatile processes in the Earth. We have measured the partitioning of F, Cl and Br between mantle phases and silicate melts at P-T conditions relevant to peridotite melting in the Earth, using a piston-cylinder apparatus for the high-P experiments. Halogen concentrations were determined by TOF-SIMS and noble gas methods in the Isotope Geochemistry Laboratories in Manchester. Within the range of the P-T conditions investigated, halogen partitioning shows a strong temperature dependence but little pressure dependence.

The stability of hydrous minerals and carbonates in subduction zones

A knowledge of the stability of hydrous phases and carbonates at high pressure and low to moderate temperature is necessary to understand the role that H₂O and CO₂ play in subduction zone processes. Some hydrous phases transport H₂O from shallow depths to the source of arc magmatism, e.g. chlorite and antigorite; others only form as the lower-pressure minerals break down, and these may return H₂O deep into the Earth’s mantle, e.g. 10-Å phase. Carbonates are stable over a wide P-T range, with double carbonates stable at shallower depths breaking down to single carbonates during subduction. We have used phase-equilibrium experiments to study the stabilities of these and other subduction zone minerals. Not only do the pure phases show a wide range of stabilities, but the effect of solid solution, e.g. Mg ↔ Fe in 10-Å phase, can be considerable.

Crystal chemistry of high-pressure phases

A knowledge of the crystal chemistry of high-P phases under ambient conditions and at high pressures and temperatures is essential for understanding the mechanisms for their stabilisation in the Earth’s mantle. Detailed characterisation of the 10-Å phase has shown it to have a much more complex composition and structure than previously thought. This has implications for the amount of water it can contain, and the extent of its P-T stability in the Earth. Other phases that we have studied include Ge-pyroxenes and the sodic amphibole eckermannite.

BA Natural Sciences (Cambridge) 1986

PhD Experimental studies of amphiboles (Edinburgh) 1990

• Structural and Petrological Geoscience