From 1 - 3 / 3
  • Log file and GSAS data files for synchrotron study of NaMnF3. Diffraction patterns from synchrotron experiments on NaMnF3. NERC grant: Understanding the D' zone: novel fluoride analogues to MgSiO3 post perovskite NERC grant abstract: The thermal boundary layers of a convecting system control many aspects of its style of convection and thermo-chemical history. For the silicate Earth these boundary layers are the lithosphere, whose low temperature and high rigidity induces slab-style downwellings, and the D' region on the mantle side of the core-mantle-boundary (CMB). The D' region is the source of plume-style convection and regulates heat exchange from the core to the silicate Earth. The lower thermal boundary is made more complex by the existance of a phase transition in the most common mineral in the lower mantle (magnesium-silicate perovskite) which changes the properties of the D' region at the CMB. Unfortunately, most of these properties cannot be measured at the extreme pressures (120 GPa) of stabilisation of the post-perovskite phase. The best chance of constraining them is through a combination of measurements on low-pressure analogue materials (which have the same crystal structure but a different chemical composition) and ab initio simulations of both the analogue and natural systems. We have recently developed a set of ABF3 analogues whose properties are much more similar to MgSiO3 than are those of the CaBO3 analogues currently in use. We propose, therefore, to use these improved fluoride analogues to determine the properties of post-perovskite which control the dynamics of D' (phase diagram, pressure-temperature-volume relations, viscosity, slip systems and thermal diffusivity). These measurements will allow models to be developed which accurately predict the behaviour of the lower thermal boundary layer of the mantle. This will place coinstraints on (1) the heat budget, dynamo power and start of crystallisation of the inner core, (2)the vigour of plumes, (3) the ratio of underside heating to internal heating in the mantle and, (4) the radioactive element budget of the silicate Earth.

  • High-pressure multi anvil synchrotron data from ID06-LVP at the ESRF. Contains diffraction, radiography, MHz ultrasonic and calibration data from experiments performed to ~ 13 GPa on CaSiO3 perovskite and Ca[Si60Ti40]O3 perovskite samples.

  • This project is aimed at understanding what kind of conditions the Earth's core formed under and how this affected the amount of oxygen present in the rocky interior of the Earth. It uses experiments which simulate the very high pressures and temperatures that would have been present in the Earth's interior when the core formed, combined with very precise chemical analyses of these experiments. From these results I will learn how certain chemical elements distributed themselves between the metal core and the rocky outer part of the Earth, and whether this distribution behaviour changes with different conditions and with the amount of oxygen present. By comparing the results I get from the experiments with the chemical compositions of rocks from the Earth and very primitive meteorites we will be able to understand better how the Earth's core formed, and how this may have affected the chemistry of our planet and the development of its atmosphere and oceans. Four papers are linked to this grant: Stable chromium isotopic composition of meteorites and metal-silicate experiments: Implications for fractionation during core formation Unlocking the zinc isotope systematics of iron meteorites Iron isotope tracing of mantle heterogeneity within the source regions of oceanic basalts Isotopic evidence for internal oxidation of the Earth's mantle during accretion