Oldest rock lights up earth's age theories
Gympie Times 11/8/2001
PERTH: A 4.4 billion-year-old crystal found in Australia - the oldest rock fragment
discovered on the earth's crust - has cast new light on the planet's origin.
Scientists say the find could suggest oceans existed on earth at that time.
The discovery has excited scientists around the world, including NASA-backed researchers
who want to join the hunt for more old crystals.
Curtin University geology professor Bob Bidgeon said sedimentary rocks known as
"conglomerates" were found at Jack Hills, 800 km north-east of Perth,in l986.
The rocks yielded tiny zircon crystals, and tests showed that about 10 per cent of the
crystals were more than four billion years old.
But new analytical techniques at Curtin allowed researchers to discover recently that one
of the crystals was 4.4 billion years old, sparking renewed excitement about the
significance of the ancient crystals.
Prof Pidgeon said one interpretation of oxygen measurements of the crystals was
that the zircons had come from a rock which itself had come from some melted sediments.
"This implies there was water there to form sediments which, if you extrapolate that
a little bit further, you've got some sort of ocean," Prof Pidgeon said. "It's a
bit of an extrapolation from the measurements, and a lot more measurements are going to
have to be made to confirm these models or interpretations.
"(But) it adds a new dimension to the whole issue of the origin and the
evolution of the earth." Prof Pidgeon said the find was unique to Western Australia.
NASA is interested in the crystals and last month supported five scientists to come to
Australia to study the area where the conglomerates were found.
"By looking at the very early history of the earth they hope to be able to get
various concepts as to what they might find when tbey land on Mars, as to the potential on
Mars for life," Prof Pidgeon saEND OF REPORT
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