SCIENCE AT THE SHINE DOME canberra 7 - 9 may 2008

New Fellows Seminar

Wednesday, 7 May 2008

Professor Hugh O’Neill
Research School of Earth Sciences, Australian National University

Hugh O'Neill obtained a degree in geology from Oxford University and a PhD from the University of Manchester in the UK, followed by postdoctoral appointments at Arizona State University, the Australian National University and the University of Bayreuth. He is an experimental petrologist whose research focuses on applying physical chemical measurements to understanding the origin and evolution of the Earth and the terrestrial planets. He is especially concerned with studying the accretion and early differentiation of the Earth and how this influences the Earth's composition, and the subsequent mantle processes that lead to partial melting and the production of basaltic magmas. He has spent much of his career measuring the thermodynamic properties of minerals and melts at high temperatures and pressures.

The composition of the Earth – are our assumptions correct?

The chemical composition of the Earth sets the conditions for its geological history. With the help of a few assumptions about how the Earth formed, the average composition of the Earth’s silicate portions can be deduced by studying samples of mantle rocks, which have been brought to the surface by geological processes. But are these assumptions correct? Modern views of terrestrial planet formation have progressed considerably over the last decade, and it is now thought that high-energy impacts between ‘planetary embryos’ play a significant role in the growth of terrestrial planets. There is evidence that such impacts have altered the compositions of planetary embryos, which would lead to the Earth being depleted in key elements, including the heat-producing elements potassium, uranium and thorium. If so, the history of the Earth’s mantle might be simpler than that implied by the current geochemical paradigm.