Name: Sarlae McAlpine

Position: PhD Student

Earth Materials and Processes

Research School of Earth Sciences

Australian National University

Area of study: Mantle Petrology, Geochemistry

Project: A comparative petrological study of mantle xenolith suites from the West Bismarck Arc, the TLTF Arc and the Solomon Islands.

What does that mean?

Mantle xenoliths are rocks that directly sample the mantle of the earth. My particular focus is on peridotite xenoliths, beautiful green crystalline rocks made up of the minerals olivine, orthopyroxene, clinopyroxene and chromite. These peridotites have been derived from an ‘arc’ tectonic setting formed by the collision of two tectonic plates and the consequent subduction of one below the other. Peridotite xenoliths derived from this tectonic setting are extremely rare even in well-explored sub-aerial arcs and the suite from the West Bismarck Arc is the first global occurrence of peridotites recovered from an active submarine volcanic arc front edifice.

I have studied and analysed the basaltic rock that hosts these xenoliths, obtained detailed chemical analysis of the individual mineral phases and whole rock analyses of the peridotites. I can use this information to calculate parameters such as pressure and temperature, and ultimately unravel the petrological history of these samples and obtain greater understanding of the mantle as a whole.

How did I get here?

I grew up on beautiful sub-tropical Norfolk Island. This little rock in the middle of the ocean gave me a great appreciation for the earth and its environment from a very early age. I was awarded Young Australian of the Year for my outstanding community and environmental involvement on Norfolk Island after my voluntary study of the natural water courses on the Island and campaign against the removal of the wetland system, ultimately saving the lagoon and its ecosystem from increased turbidity and nutrient levels which would have resulted in coral bleaching. With this kind of embarrassing nerdy enthusiasm I was destined for university and academia. I moved to the ‘mainland’ to study Astrophysics at the Australian National University but became quickly seduced by the multidisciplinary science of geology and have never looked back.

Where will I go?

Who knows?! Through geology I have travelled to New Zealand, Chile, the Greek Islands, the UK, the Czech Republic, France and Portugal. This subject opens up some amazing opportunities.

But after seven and a half years of university I am in the classic position of having learnt so much and still realising how much I don’t know…and just how much there is still to explore. Whether this involves travel or different career paths…there are so many exciting things to do.