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This project is eligible for support from Cardiff Universtiy through the School of Earth & Ocean Sciences.

To apply, please visit the Cardiff University Postgraduate Research portal: http://www.cardiff.ac.uk/for/prospective/postgraduate/applying.html

 Description

Diffusion and reaction in fluids and solids in metamorphic and metasomatic rocks give rise to complex shapes such as coronas, symplectites and larger scale phenomena that are not well described or even named (Fig. 1).

These shapes are very similar to well-known forms produced by simple models of diffusion and percolation, and they have untapped potential to yield insights into metamorphism/metasomatism. The aim of this project is to investigate processes and temporal and spatial scales of diffusion and reaction in metamorphic and metasomatic rocks through these complex shapes. The quantified geometrical properties will be combined with detailed petrological and geochemical studies, thermodynamic constraints, and numerical modelling to make an important advance in metamorphic and structural geology.

A key question posed by these patterns is the role of fluids in their formation. If a significant fluid role can be demonstrated, then the permeability creating mechanisms in these currently impermeable metamorphic/metasomatic rocks are a critical problem. One hypothesis to be tested will be the possibility of open grain boundaries at the nanometre scale (Kruhl et al. 2013). Fluid sources and fluxes also need to be investigated.

The project will involve fieldwork in the Mount Isa Inlier, Australia. Samples will be analysed through optical and scanning electron microscopy at Cardiff University.  The complex patterns will be described by the techniques of fractal geometry in 2 and 3 dimensions at scales ranging from metres (Fig. 1) to mm. More detailed petrological and microfabric studies will take place at the Technical University of Munich, and electron microprobe studies will be carried out at James Cook University.  Thermodynamic and numerical modelling will be carried out by a combination of existing and newly developed code at Cardiff University.

F1a  F1b

Fig 1. a) Complex intergrowths of garnet and albite in skarn, Mary Kathleen zone, Mount Isa inlier, Australia. Scale of photo is approximately 1 m. b) Symplectite of plagioclase and orthopyroxene, scale 2 mm.

Training

This PhD will combine training in field geology with laboratory analysis and numerical modelling, at three different institutions. The training will directly address four of the most wanted skills in postgraduates (NERC 2012): Modelling, Data Management, Numeracy and Fieldwork. Training will be given in:

1) Field-based structural and metamorphic investigations of metasomatic and metamorphic rocks (Mount Isa inlier, Australia).

2) Techniques of fractal analysis and modelling (Cardiff University, Technical University of Munich).

3) Principal and special tools of microfabric analyses based on polarizing microscopy as well as universal stage (facilities available at TUM).

4) 3D recording of microstructures by X-ray and neutron tomography, in collaboration with colleagues from Ludwig Maximilian University Munich (Dr. Kai-Uwe Hess),

5) Quantification of fabric anisotropy and inhomogeneity, using image analysis (facilities available at TUM).

6) Optical and scanning electron microscopy and microchemistry (facilities at Cardiff University).

7) Electron Microprobe Analysis (Microprobe at James Cook University).

8) Thermodynamic and Numerical Modelling (resources available at Cardiff University).

Background Reading

Kruhl, J., Wirth, R., Morales, L. F. G. 2013. Quartz grain boundaries as fluid pathways in metamorphic rocks. Journal of Geophysical Research: Solid Earth  118, 1957–1967.

Contact Details

Professor Tom Blenkinsop – blenkinsopt@cardiff.ac.uk