Project: Deformation and metamorphism in the WOMB, part one

Here is another honours project recently completed, and another example of the projects we may offer.

Can you introduce yourself?

My name is Bradley Williams and I completed a B.Sc. (Hons) at UoN in July 2015. I am 31 years old and live in the Hunter region of NSW, Australia.

Can you tell us about your research project at UoN?

I undertook an Honours research project in structural and metamorphic geology, which focused on an area in southern NSW. I investigated the timing of peak metamorphism relative to deformation in rocks of the study area (southern part of WOMB, Wagga Omeo Metamorphic Belt). I also wanted to resolve the age of metamorphism to determine if granite emplacement was driving metamorphism in the country rock. Achieving this would allow some important geodynamic models for eastern Australia to be tested. The project involved one month in the field to: (i) map metamorphic zonation and structure, and (ii) collect samples for later detailed petrography and monazite geochronology.

What did you find?

My findings indicate metamorphism occurred much earlier in the structural record than what was previously thought, and that large granite bodies in the area were not the source of metamorphic heat. The findings supported one of two competing geodynamic models for eastern Australia, however differed from several geodynamic models previously proposed for rocks specific to the study area. Therefore, a revised geodynamic model was proposed.

What did you particularly enjoy about this project?

I really enjoyed this particular style of research; examining rocks in situ, collecting samples, analyzing thin sections, and dating minerals in colllected samples. Using these data to make interpretations on the geodynamics of eastern Australia was challenging but equally rewarding.

What are your plans for the future?

I am currently trying to secure an earth science career!

 

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Sample showing key metamorphic mineral (retrogressed crd) and 3 deformation fabrics

 

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Project: Elastoplasticity in large strain shear zones

With the year ending, we are looking at prospective honours students. Who’s best to answer questions about honours than current honours students and visitors.

So here we start with Maxime, who came to work with us last winter.

Max

Can you introduce yourself?

My name is Maxime Henriquet. I am 22 years old student From France and I am currently studying in Lyon. During the winter season (2015) I made an internship at UoN to complete my first year for the French Master degree in geosciences.

Can you tell us about your research project at UoN?

The research project I conducted at UoN focused on the elastic energy balance and the strain localization in shear zones with an analogue modeling approach. I realized simple shear experiments using visco-elasto-plastic materials in a 3-D thermomechanical apparatus. I analyzed the influence of the rheological parameters by varying the temperature of the experiments. The quantitative analysis is realized thanks to image correlations of high resolution pictures of the surface model (PIV system). I computed the evolution of velocity and shear strain in the experiments using matlab. Then I could investigate the shear localization and estimate the stored and dissipated elastic energy under different configurations.

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What did you find?

The first results have shown that the deformation localization as well as the amount of stored and dissipated elastic energy are extremely sensitive to the rheology. At high temperature with less strain softening, the plastic strain becomes predominant and the elastic effects are less visible. After rupture of the model an important quantity of stored elastic energy is still conserved in the material. So far, the results are consistent with a new theory which focuses on large strain deformation (Karrech et al., 2011). The acquisition of experimental data could then be used to constrain the numerical model based on this theory.

What did you particularly enjoy about this project?

This project was an opportunity to manipulate thermomechanical apparatus and improved the numerical methods employed to analyze the data. In addition, it was really interesting to interact with the members of the team project as well as the researchers and students of the lab. I also thank David Boutelier for the liberty and the independence he gave to me on that project. I could think by myself about the issues and it was always possible to interact with David for analysis interpretations and to pursue the development of new experiments.

What are your plans for the future?

I am currently preparing a competitive exam to be qualified for teaching geological and biological sciences with an academic level. Next year I would like to finish my Master degree in geology and then pursue with a PhD.

 

After his internship, but before returning to France, Maxime visited Australia and send me these photos

 

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Life and death in the Permian: Swansea heads

Last post I did not include any photos of Swansea head. Here are some good shots of our students trying to study the rocks despite the high tide.

 

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Students measured the orientations of petrified fallen trees and tree stumps.

 

 

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Student made a geological cross-section through the platform and the cliff

 

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Tree stump

 

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Petrified fallen trees

 

 

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Inspecting which way the tree stump lean

 

Thanks Maxime for the photos.



Modelling of sill inception, propagation and growth

We are pleased to inform about a publication from our research group. The paper is published in Earth And Planetary Science Letters and available online at

 http://www.sciencedirect.com/science/article/pii/S0012821X15001879

A model of magma propagation in the crust is presented using a series of analogue experiments, where dyed water is injected at a constant flux into layers of solidified gelatine. Digital image correlation (DIC) is used to calculate incremental strain and finite strain in the deforming host material as it is intruded. This is mapped in 2D for the developing experimental volcanic plumbing system that comprises a feeder dyke and sill. Since the gelatine deforms elastically, strain measurements correlate with stress. Our results indicate that, for constant magma flux, the moment of sill inception is characterised by a significant magmatic pressure decrease of up to ∼60%. This is evidenced by the rapid contraction of the feeder dyke at the moment the sill forms. Sill propagation is then controlled by the fracture properties of the weak interface, with fluid from the feeder dyke extracted to help grow the sill. Pressure drops during sill inception and growth are likely to be important in volcanic systems, where destabilisation of the magmatic plumbing system could trigger an eruption.

 

Model of dyke and sill formation

Model of dyke and sill formation

 

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Welcome to TER

TER is the Tectonics and Earth Resources research group at the University of Newcastle.

In broadest terms, our research examines the geological processes that form the physical environment in which we live. This research is achieved within the plate tectonic framework enabling the formation and dispersal of continents. We aim to identify specific tectonic settings and understand tectonic processes, in order to better understand the growth of the Australian continent and the formation/location of resources undercover.


The material or views expressed on this Blog are those of the author and do not represent those of the University.  Please report any offensive or improper use of this Blog to RPS@newcastle.edu.au.
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