Temora rocks tick like clockwork

15 October 2003

Used for dating the ages of rocks, good quality zircons are hard to find. But in the NSW town of Temora, the zircons are among the finest samples in the world. Proven as a reliable benchmark for rock dating, through research published recently by Geoscience Australia scientists, the Temora zircons are increasingly sought after by laboratories all around the world.

Zircon is a common mineral in igneous rocks which can be used to date the ages of rocks. When a rock is formed, tiny traces of radioactive uranium get locked inside its zircon crystals. This uranium then begins to decay in a process that produces small amounts of lead inside the zircon. This process occurs at a fixed rate which allows scientists to measure the amount of lead inside the zircon crystals to calculate the age of the rock.

"Zircon crystals inside rocks act like tiny clocks that have been ticking since the time the rock first formed," Geoscience Australia scientist, Dr Lance Black, said. "But you need crystals of a known age to compare them to, and this is where the Temora zircons come in.

"Zircon "clocks" can be reset if the lead in the rock escapes through geological processes such as weathering. When this happens, they become unreliable for rock dating as they will give an incorrect age. However, the zircons from the Temora rocks are totally undisturbed, which makes them a highly reliable benchmark to use in rock dating.

"We have compared the new benchmark, known simply as TEMORA, with other international zircon dating standards, and it provides the best standard yet."

The Temora zircons are already highly sought after, and are supplied to nearly forty labs around the world. The latest research published by Dr Black and colleagues in the Journal of Chemical Geology, is set to increase international demand for the Australian crystals.

Accurate rock dating is important in mineral exploration and also in the general understanding of processes that operate within the earth.

Dr Black and his colleagues will be in Temora on the 15th and 16th of October 2003, collecting further samples of the Temora zircons for use in the Geoscience Australia geochronology laboratory, and to meet international demand.

Topic contact: media@ga.gov.au Last updated: October 4, 2013