Experimental determination of mantle rheology
Lead Research Organisation:
University College London
Department Name: Earth Sciences
Abstract
The most active and destructive phenomena of the Earth's surface, volcanoes and earthquakes, have their origin in dynamic processes that take place in the mantle. These phenomena are a consequence of thermal convection taking place in the mantle. Convection in the Earth's mantle takes place over a billion year time-scale but in essence is similar to the processes taking place in a simmering pan of water, where material is heated at the bottom, rises, reaches the surface and cools. This cool material then sinks and when it reaches the bottom is heated again, in a convective cycle. In order to understand the Earth's convective cycle and its destructive side effects we need to investigate how flow of the minerals present in the mantle changes as a function of temperature, pressure and other parameters. This is done by deforming samples of the minerals under the conditions present in the mantle. Until recently, it was only possible to perform the deformation experiments at pressures found in the top 400km of the mantle. However, with the development of a new piece of experimental apparatus, the Deformation-T-Cup, it is now possible to perform experiments at conditions relevant to the top 700km of the mantle. All the major minerals present in the top 2500km of the Earth are present in the top 700km; therefore this study will be able to characterise the strength and flow properties of almost the entire mantle. In this study I will use the new apparatus to perform experiments measuring the effects of pressure, temperature and other parameters on the strength of mantle minerals. This knowledge will be used to gain a more detailed understanding of the dynamics processes taking place in the Earth's mantle, which in turn will assist in greater understanding of earthquakes and volcanic eruptions.
Organisations
People |
ORCID iD |
Simon Hunt (Principal Investigator) |
Publications
Crichton W
(2016)
High-temperature equation of state of vanadium
in High Pressure Research
Dobson D
(2012)
Slotted carbide anvils: improved X-ray access for synchrotron-based multi-anvil experiments
in High Pressure Research
Dobson D
(2018)
The relative strength of perovskite and post-perovskite NaCoF 3
in Mineralogical Magazine
Dobson D
(2016)
The phase diagram of NiSi under the conditions of small planetary interiors
in Physics of the Earth and Planetary Interiors
Dobson D
(2011)
Towards better analogues for MgSiO3 post-perovskite: NaCoF3 and NaNiF3, two new recoverable fluoride post-perovskites
in Physics of the Earth and Planetary Interiors
Hunt S
(2019)
An Experimental Investigation of the Relative Strength of the Silica Polymorphs Quartz, Coesite, and Stishovite
in Geochemistry, Geophysics, Geosystems
Hunt S
(2012)
The P-V-T equation of state of CaPtO3 post-perovskite
in Physics and Chemistry of Minerals
Hunt S
(2018)
The effect of pressure on thermal diffusivity in pyroxenes
in Mineralogical Magazine
Hunt S
(2016)
In-situ measurement of texture development rate in CaIrO3 post-perovskite
in Physics of the Earth and Planetary Interiors
Hunt S
(2012)
On the increase in thermal diffusivity caused by the perovskite to post-perovskite phase transition and its implications for mantle dynamics
in Earth and Planetary Science Letters
Description | Durng the grant I developed a new apparatus (the DT-Cup) which is canable of performing controlled strain-rate deformation experiments at significantly higher pressures than were possible at the start of the grant. This opens up the capabilites to perform deformation experiments on the minerals present in the Earth at greater depths, specifically those present in the 'transtion-zone' (410-660km depth) and the 'lower-mantle' (>660km). As part of the commissioning experiments I measured the relative strengths of the SiO2 polymorphs. The DT-Cup enables for the first time deformation experiments at pressures equivalent to over 400km deep in the Earth. Opening whole new avenuse of study into the properties and behavious of the deep Earth. |
Exploitation Route | The new apparatus (the DT-Cup) has been showed to work and 2 new NERC grants have been funded with a significant fraction of the work within the grant to be performed on this apparatus. The usefulness and simplicity of my design compared to competing apparatus means that it will become the work horse for very high pressure deformation experiments. 2018: The design has not been replicated by groups in the USA and Japan. |
Sectors | Other |
Description | Rheology of the lower mantle |
Amount | £468,027 (GBP) |
Funding ID | NE/L006898/1 |
Organisation | Natural Environment Research Council |
Sector | Public |
Country | United Kingdom |
Start | 05/2014 |
End | 05/2017 |