Geoscience Australia's geochronology team has identified granite from near Iron Knob in the Middleback Ranges that is 3150 million years old, extending South Ausralia's antiquity back another half a billion years.

Geoscience Australia chief executive officer Dr Neil Williams said rocks older than 3 billion years were uncommon and until now such ancient rocks in Australia were thought to be restricted to areas in the Pilbara and Yilgarn regions of Western Australia.

"The discovery of rocks of similar age to those in the resource rich regions of Western Australia raises the possibility of so far undiscovered mineral resources in South Australia," he said.

The discovery, made during seismic surveys to identify potential energy and mineral resources, had significant implications for establishing how the Australian continent was formed.

Scientists identified the rocks with Geoscience Australia's new Sensitive High Resolution Ion Microprobe (SHRIMP) as part of a collaborative seismic survey with Primary Industries and Resources SA, and the two groups will work together to define the extent of rocks of this age in the area, which should give them clues about the geological history of the region.

Geoscience Australia made the discovery as part of its program under the Australian Government's Energy Security Initiative to predict where new energy and mineral resources may be located deep in the Earth's crust.