The properties of rocks and minerals at high pressure and temperature control the behaviour and response of the Earth over all time scales.
This covers rapid change during earthquakes (10 seconds) to the slow evolution of the planet over billions of years.
- Tara McElhinney
In order to understand these processes it is necessary to study the physical properties of the rocks and minerals under the conditions that they are under in the Earth.
The pressure and temperature increase strongly with depth in the Earth. So to replicate these conditions in experiments we use a range of high-pressure experimental apparatus (multi-anvil apparatus and diamond cells).
While these devices allow the creation of extreme conditions they also surround the sample, preventing direct measurement of them. Therefore, synchrotron X-rays form a key part of these studies because they can penetrate the high pressure cells enabling measurement of material behaviour. Using synchrotron X-rays we can measure density, phase reactions, rheology, thermal conductivity and anelasticity at pressures above 10 GPa and temperatures up to 1800°C.
Plot from Hunt et al (2019) showing strain-rate in the SiO2 polymorphs quartz coesite and stishovite relative to strain-rate in olivine during deformation experiments. The graph shows that at 800C stishovite is significantly harder than coesite or quartz.
Schematic of high pressure tooling for the 'DT-Cup' from Hunt et al 2014. The figure highlights the changes made to the tooling from a standard multi-anvil module.