Michael Allen

Michael Allen

'The interseismic physiochemical character of a major plate boundary; the Alpine Fault, New Zealand'
NERC Doctoral Training Program
Supervisors: Dr. Elisabetta Mariani & Prof. Daniel Faulkner
Description: The Alpine Fault, a transpressional plate boundary between the Australia-Pacific plates, is known to rupture periodically (200-400yr) with large magnitude earthquakes (Mw~8) and is currently nearing the end of its latest interseismic period. Processes taking place during this interseismic period, particularly fluid-rock interaction and mineral growth, alter the physical properties of the fault influencing the timing, nature and style of earthquake rupture. This study aims to determine the physical properties and the microstructural character of fault rocks retrieved during the Deep Fault Drilling Project, which drilled into an active thrust segment of the Alpine Fault at Gaunt Creek, Westland in January 2011. Particular focus will be made on fault sealing behaviour via carbonate precipitation and how this controls fluid flow within fault zones. Techniques used in this investigation include; optical microscopy, cathodeluminesce, scanning electron microscopy, secondary ion microprobe analysis and electron backscatter diffraction as well as laboratory measurements of rock elastic properties and permeability. - Email Michael

Joseph Aslin

Joseph Aslin

'The Deformation and Metamorphism of Micas and their Implications for the Strength of the Earth's Crust: Case Studies in the Italian Alps and New Zealand'
NERC Doctoral Training Program
Supervisors: Dr. Elisabetta Mariani, Prof. John Wheeler & Prof. Daniel Faulkner
Description: Global tectonic stresses deform the Earth’s crust heterogeneously, with large strains localised into fault and shear zones on a variety of scales. Weak phyllosilicate minerals such as micas form a major component of rocks located within fault and shear zones, reducing their strength and focusing deformation. My project seeks to understand the mechanisms by which micas deform and the metamorphic reactions which occur within phyllosilicates during deformation. Samples will be studied using a combination of optical microscopy, scanning electron microscopy, X-ray diffraction and electron backscatter diffraction techniques to observe and quantify the behaviour of micas in these dynamic systems. - Email Joseph

John Bedford

John Bedford

'Phase change and the evolution of porosity during dehydration reactions: examples using calcium sulphate'
NERC
Supervisors: Prof. John Wheeler, Prof. Daniel Faulkner, Dr. Elisabetta Mariani
Description: When hydrous minerals are taken out of equilibrium, due to an increase in temperature or a drop in pressure, they release H2O as a fluid - this is called a dehydration reaction. High pressure fluid released during dehydration can potentially fracture the surrounding crust generating earthquakes. This is thought to a particularly important process in subduction zone settings. A key feature of dehydration reactions is that they are associated with large solid volume reductions which generate porosity. Understanding the interplay of porosity evolution and fluid expulsion is important to help identify scenarios where fluid overpressures might occur. This project uses gypsum (hydrous Ca-sulphate) as an analogue material to experimentally investigate these processes and to try and gain a better understanding of how reaction proceeds. - Email John

Joe Gardner

Joe Gardner

'Deformation in the crust and the role of feldspar: an Alpine study'
NERC Doctoral Training Program
Supervisors: Prof. John Wheeler & Dr. Elisabetta Mariani
Description: At the elevated temperatures and pressures of the middle crust, rocks exposed to tectonic stress deform viscously (i.e. change shape without fracturing). Despite being one of the most common minerals in the Earth’s crust, our understanding of how viscous deformation is accommodated in feldspar remains incomplete due to its low crystal symmetry. We are using electron backscatter diffraction to characterise how neighbour grains have interacted during deformation in feldspar-rich metagabbros from the Italian Alps, and which deformation mechanism dominated strain accommodation. We are also using microstructural observations to investigate how metamorphism and deformation have combined in our samples to produce the strong textural domains we observe. The project aims to better understand how rocks may deform by diffusion creep at natural strain rates in the Earth’s crust. - Email Joe

Aurelio Melia

'Characterization of greywacke basement of TVZ geothermal fields (New Zealand)'
GNS Science - New Zealand
Supervisors: Dr. Elisabetta Mariani
Description: Faults and fractures are a key mechanism for the transport of fluids through the crust, providing a pathway for the emplacement and development of geothermal systems. This project utilizes geomechanics, geophysics and petrology to investigate the dynamics of fluid flow within the greywacke basement at Taupo Volcanic Zone (New Zealand), in relation to the exploitation of the geothermal energy. The experimental work describes the response of this lithology under different conditions of stress and temperature, which are factors influencing the permeability of the reservoir rocks. The results have implications for permeability models of this area, which are fundamental for the planning and development of geothermal fields. - Email Aurelio