Hot rocks, ice sheets and melted crust:

the local and global impacts of Australia's subterranean heat engine.
 

Tom Raimondo
Associate Professor of Geology and Geochemistry,
 University of South Australia
 
 
Thursday 3rd of October 2019 at 7.45pm 
Mawson Lecture Theatre
Department of Geology 
University of Adelaide
 
Introduction Tom Raimondo
 
Abstract: Australia is not only a sunburnt country but also home to some of the hottest rocks on Earth. Proterozoic rocks that dominate central and southern Australia have heat production values that are roughly twice that of ‘average’ granite. This anomaly is due to an extreme enrichment in the heat-producing elements uranium (U), thorium (Th) and potassium (K), which produce heat via natural radioactive decay. The consequences of such a profound subterranean heat engine are recorded across thousands of kilometres of some of Australia’s best known geological heritage, and span hundreds of millions of years of Earth’s history – a significant yet often overlooked fingerprint of what lies beneath. This talk will explore some key localities where taking the Earth’s temperature has revealed the importance of Australia’s hot rocks at a local and global scale – from the melted crust of Arkaroola and central Australia that has changed our understanding of what drives long-lived metamorphism, to the buried secrets of the Nullarbor Plain that may help explain why the Antarctic ice sheet is melting.
 
Bio: Tom Raimondo is currently Associate Professor of Geology and Geochemistry and Program Director of Environmental and Geospatial Science at the University of South Australia. He completed his PhD at the University of Adelaide in 2011. Tom’s research focuses on the role of fluids in weakening the Earth’s crust and producing earthquakes, improving exploration models for mineral deposits in South Australia, and assessing the impact of hot rocks on ice loss in Antarctica. If you're curious about why central Australia has the world's biggest gravity warp, why rocks are bored until they get splashed with water, or why southern Australia is the geological equivalent of a hot plate cranked to 11, then he may just have some answers for you. At UniSA, Tom is also the leader of Project LIVE (Learning through Immersive Virtual Environments; ProjectLIVE.org.au), an initiative to create interactive virtual field trips that reveal Australia’s best geology to both students and the general public.
 
Members and visitors are warmly invited to attend.  We are obliged for security reasons to keep the front door of the building locked. Please note that latecomers will not be admitted after 8.00 pm, in order not to interrupt the lecture. Everyone is invited to supper following the lecture. For further information visit: www.fieldgeologyclubsa.org.au

Crystal or Cleavage

What is the difference?
If you have a mineral specimen with smooth flat surfaces, it is often difficult to decide whether your specimen is a crystal or a cleavage fragment. The shapes of both are determined by the arrangement of atoms within the mineral.
 
Good crystals can grow when a mineral solidifies slowly from a molten substance or a solution, in a location where there is room for the crystals to grow, and they are able to grow slowly. Such crystals are comparatively rare. Most of the mineral specimens we find are in the form of many very small mineral grains.
 
Cleavage is a breakage characteristic, rather than a growth feature. When a piece of a mineral is dropped or struck, it may tend to break so that the broken pieces are nearly all the same shape, and flat, shiny surfaces are formed.
 
Since both crystal shape and cleavage directions are valuable mineral diagnostic properties, it is important to distinguish between them.