School of Earth and Environment

Amicia Lee Amicia Lee

Teaching Assistant / Postgraduate Researcher

Email address: earall@leeds.ac.uk
Room: 8.152i

Affiliation: Institute of Applied Geoscience

Biography

I am a PhD student working with Dr Taija Torvela, Dr Geoffrey Lloyd and Dr Andrew Walker at the University of Leeds. My work involves field, lab and modelling techniques to assess the seismic and rheological effects or partial melt in orogenic shear zones. My main interests lie in the study of microstructures and how they relate to the regional tectonic scale.

Alongside my PhD I am the teaching assistant for the MSc Structural Geology and Geophysics where I participate in both the teaching and administrative activities for the masters course.

As well as studying mountains I love to run up and down them!

Find me on Twitter: @amicialee

Qualifications

MGeol & BSc, Geological Sciences (International), First Class, University of Leeds
Year abroad at University of California, Santa Barbara

Project details

Project title

Microstructural and seismic properties of mid to lower crustal high temperature shear zones

Supervisors

Dr Taija Torvela
Dr Geoff Lloyd
Dr Andrew Walker

Funding

Fieldwork in Norway and Scotland was kindly funded by the Geological Society of London's Timothy Jefferson
Field Research Fund and the Edinburgh Geological Society Clough and Mykura funds.

Project outline

Partial melting of the middle and lower (M/L) crust within orogenies is known to be a key control on the structural geology of mountain belts. Quantifi cation of melt volume in the lower orogenic crust is important to the understanding of how melt influences the rheology and approximated stability of mountain belts. The location of partial melt in the lower crust can be identifi ed using geophysical methods, but are not reliable in quantifying the melt volume for in situ melting nor the exact shape, location or connectivity of a melt body. Studying the exposed lower crust in palaeo-orogens can help to quantify the melt volume providing it is a closed system. To help tackle this problem I am studying the exposed lower crust from the Caledonian Orogeny in Norway and Scotland in order to quantify the melt volume and melt distribution from outcrop. The samples are used to synthesise seismic data from lower crustal rocks to simulate and compare with seismic responses for melt in active orogenies.

Seismic modelling within my project adapts and critically assesses the reliability of methods used to estimate melt in volcanic regimes and MORs and applies them to orogenies. This incorporates the CPO, chemistry and melt shape in order to evaluate possible signatures and expected uncertainties. EBSD is used to measure CPO in sheared migmatites, from which models varying shape and distribution of melt assess the impact of a melt volume on seismic properties. Thus help improve the understanding of melt in the mid to lower crust.

Results of my study so far indicate that partial melt can greatly a ect the seismic response from the lower crust but that this relationship is not linear with melt volume increase. A comparison with receiver function results from tectonically active regions highlights the simplicity in current models thus emphasising the importance of geological parameters and their eff ect on seismic properties. Mineral composition, melt shape, orientation and wave propagation direction relative to CPO and melt shapes can result in large variations in the same seismic property. Thus, multiple seismic properties as well as lab and modelling experiments should always be considered when predicting melt volume in the middle to lower crust.

Publications