PhD Student,Research School of Earth Sciences,Australian National University
Personal Website: brendanhanger.wordpress.com
Area of Study: Mantle Petrology, Experimental Petrology
Project: Redox Conditions in the Cratonic Lithosphere and Implications for Partial Melting and Metasomatism
What Does That Mean?
I’ll start by defining some of the terms:
- Redox – Reduction/Oxidation: All chemical reactions which lead to the change in oxidation of atoms, in my project I primarily look at the changes in iron (Fe) between Fe2+ (Ferrous) and Fe3+ (Ferric).
- Cratonic Lithosphere – refers to the lithosphere (crust and elastic part of the upper mantle) beneath a craton, which is the old stable parts of the continents, examples include the Kaapvaal (South Africa), Yilgarn (Australia) and the Slave (Canada). I am studying some samples from near the town of Kimberley on the Kaapvaal craton.
- Partial Melting – A process where only part of a solid substance melts; commonly occurs in the Earth when one mineral in a rock will start to melt before other minerals.
- Metasomatism – The process where a rock is chemically altered by a fluid. In the crust these fluids are generally hydrothermal (hot water) whilst in the mantle where I work they can also be carbon-dioxide rich.
Now that I’ve described the terms I can tell you what I actually do. I examine rocks for the cratonic mantle to see how changes in redox state have affected them and how these impacts on the processes that occur, namely partial melting and metasomatism. I examine peridotite xenoliths (pieces of mantle rock) that have been transported to the Earth’s surface by kimberlite volcanic eruptions and obtain detailed chemical analysis of the individual mineral phases. I then use this information to calculate pressure and temperature. I also use synchrotron based techniques to measure Fe3+ in comparison to Fe2+.
The other part of my project involves performing experiments at high pressure and temperature to replicate mantle conditions. I use these to help confirm whether our interpretations of what has happened to mantle rocks is correct and to calibrate the methods we use to determine pressure, temperature and redox state.
How did I get here?
I’ve always been fascinated by science, nature and technology, especially things such as rocks and elements. I started a double degree in Science and Chemical Engineering and had the opportunity to take earth science in first year; from there I became really interested in the chemical processes within the earth and how they affect the rocks. I continued through uni taking a variety of subjects including volcanology, petrology, geology, materials chemistry, thermodynamics and reaction engineering as well as summers spent working in coal mining and copper processing before deciding that I wanted to do Honours in geology. I made the move to ANU for a change and new opportunities and stumbled upon a project using experiments to look at trace elements in magnetite and became hooked on experiments. A change in supervisor and moving deeper into the earth led to my current research.
Where will I go?
Hopefully into a career in research and academia, I love the research I do along with teaching and hope to continue this. Ideally I would also like to spend some time working overseas. In a way I am lucky that not many other places in Australia have the right experimental facilities so going overseas is the best way to get more experience. I also really enjoy the teaching side of things and hope to more over the next few years and into the future.