Professor John Wheeler Ph.D.

Research Overview

I have a varied research interests and expertise involving field and microstructural studies, analysis and modelling of microstructural and chemical data, and collaborating with experimentalists, all to better understand physical and chemical processes in the Earth. In the last ten years my research has focussed on three themes (more information here).

- Electron Backscatter Diffraction
Crystal orientation data allow the investigation of many geoscience problems. We can now gather vast datasets using Electron Backscatter Diffraction, so we need new techniques to automate analysis of them. Liverpool Earth Science began applying EBSD to rocks in the 1990s when the technique was quite new to geoscience, and I have been involved in general technique development and many case studies of deformed and/or metamorphosed rocks since then. I have devised new numerical analysis methods including one to analyse intracrystalline distortion. In 2021 this method was incorporated into Oxford Instruments’ Aztec Crystal software. This will provide further stimulus for use and development of the method, and I will continue to enhance my own code for EBSD analysis.

- Interactions between stress and chemical processes
I am interested in the fundamental interactions between stress and chemical processes in rocks, which influence a vast range of Earth processes. These processes include solid-state reactions under stress, reactive fluid flow in a deforming medium, and diffusion creep. Nature provides countless examples of structures where deformation is linked somehow to metamorphism; my aim is to provide a theoretical foundation to understand those links, and to test that theory in experiments. This is one theme in my NERC grant “Feedbacks between mineral reactions and mantle convection”, started in 2022.

- 4D visualisations of metamorphic reactions
I am working with a team based in Edinburgh on analysis of X-ray tomography data gathered during synchrotron experiments, thus enabling full 4D visualisations of metamorphic reactions (such as dehydration) and deformation. These huge datasets are full of novel insights; I assist with methods to extract relevant aspects of evolution and to model that evolution.