New tectonic model for evolution of Australia

A world-first tectonic model for the evolution of eastern Australia recently emerged from work supported by two AuScope programs.

The new model is the result of a remarkable meeting of minds of Ross Cayley, Senior Geologist with Victoria’s Geological Survey and Professor Louis Moresi of The University of Melbourne.

Cayley has been involved since 1990 in detailed mapping of Victoria in order to understand its highly complex geology.

“We had developed quite a crazy model with large fold belts which were twisting back on themselves as a result of a collision by a Tasmanian micro continent about 500 million years ago,” he said.

“We had a lot of confidence in the model, thanks in part to a deep seismic transect funded by AuScope over western Victoria in 2009. That was critical because it gave regional-sized geometries that we could relate our mapping to. But the model had no analogues anywhere in the world. It was so radical that no-one really believed it.”

Without any knowledge of the work being done by Ross Cayley and his team, Louis Moresi had been using the AuScope funded Underworld geodynamic simulation program to explore what happened when a fragment of continental crust collided with a subduction zone.

The modelling showed subduction zones and their associated mountain belts twisted around the continental fragment – exactly as Ross observed.

“From the geophysical data we understood the swirling vortex shape we saw was younger than the rocks that had been folded by it. But we didn’t know how to demonstrate how this could happen. Where else had it happened on Earth? Suddenly Louis had showed how it could happen,” Cayley said.

“It’s really good when you reach the same conclusion from completely directions. It gives you a sense that we really are on to something.”

He said the research by the Geological Survey of Victoria and Professor Moresi had led to a “dramatically different tectonic model for how the Australian continent evolved from about 500 to 400 million years ago.

It is very significant because that’s when all of eastern Australia’s really big mineral deposits formed. The study could help deliver a stronger resources future for Victoria, New South Wales, Queensland and Tasmania in a big way by pointing to where more of these large deposits might be found in the future.”

Caption: The Underworld modelling shows subduction zones and their associated mountain belts twisted around the continental fragment.

Case Study : New tectonic model

Category: Simulation Analysis & Modelling