Hot topics                    

Thursday 23 August 2007 (Updated Wed 29 Aug 07)

RAPID ROUNDUP

Ancient WA diamonds shed light on early Earth - Nature

Embargo lifted at 3am AEST on Thu 23 August 2007

In a report published in Nature on Thursday, researchers describe ancient diamonds found in the Jack Hills region of Western Australia that are over four billion years old, relatively close to the time when the earth was first formed. They are the oldest identified fragments of the Earth’s crust and are unique in preserving information on the earliest evolution of the Earth. Such ancient crystals indicate that the Earth may have cooled much earlier than previously thought.

The paper's authors include Alexander Nemchin, Robert Pidgeon and Simon Wilde from Western Australia's Curtin University of Technology plus Martina Menneken and Thorsten Geisler from Germany's Institut für Mineralogie.

Several experts (including one co-author) comment on the report below. Copies of the paper are available upon request.

Click here for an aerial view of Jack Hills, the location in Western Australia where the diamonds were found.

For further enquiries or for details of other experts available to comment, contact the AusSMC on 08 8207 7415 or email us.


Dr Alexander Nemchin, co-author and senior lecturer in isotope geochemisty at the Department of Applied Geology, Curtin University of Technology, Western Australia

"These zircons were discovered 20 years ago and we've been extracting information ever since. These latest findings indicate that the planet was already cooling and forming a crust much earlier than previously thought.

Jack Hills is the only place on earth that can give us this kind of information about the formation of the earth. We're dealing with the oldest material on the planet."


Dr Martin Van Kranendonk is a senior geologist with the Geological Survey of Western Australia

"Any information about the very early Earth is fantastic, it's like a Christmas present for geoscientists. This work provides a new constraint for geoscientists to consider how the Earth formed into the planet it is today. It's another piece in the early Earth puzzle."

Professor Malcolm Walter is the Director of the Australian Centre for Astrobiology at Macquarie University, NSW.

"It was thought until recently that nearly all knowledge about the history of the Earth from about 4 billion years ago back to its origin at 4.65 billion could only come from inference and models. The oldest rocks are 4.03 billion years old. Then came the discovery of zircon (zirconium silicate) crystals as old as 4.4 billion years old in Western Australia. The detailed chemistry of these crystals revealed an amazing array of information about processes on the early Earth. Now these interpretations have been challenged and extended by the discovery of minute diamonds within some of the zircon crystals.

Contrary to many interpretations, it now seems possible that Earth already had a thick crust as early as 4.25 billion years ago. Not only does this have major implications for the early history of Earth, but it also suggests that life could have originated hundreds of millions of years earlier than previously thought."