[ASC-media] Media Release: Temora rocks tick like clockwork

Leharne.Fountain at ga.gov.au Leharne.Fountain at ga.gov.au
Wed Oct 15 11:24:25 EST 2003

Media Release
Geoscience Australia
15 September 2003

Temora rocks tick like clockwork

For immediate release Wednesday 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

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 & 16th of October
2003, collecting further samples of the Temora zircons for use in the
Geoscience Australia geochronology laboratory, and to meet international

For more information or to arrange an interview call the 
Media Hotline 1800 882 035 (24 hour)

Leharne Fountain | Communications Officer

Geoscience Australia

ph: +61 (0)2 6249 9800 | fx: +61 (0)2 6249 9990
24 hour media hotline: 1800 882 035

email: leharne.fountain at ga.gov.au
web: www.ga.gov.au

Postal: GPO Box 378 Canberra ACT 2601 AUSTRALIA
Physical: Cnr Jerrabomberra Avenue & Hindmarsh Drive Symonston ACT 2609

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