In the current edition of leading science journal
Nature, an international team of researchers publishes proof that the Earth recycles portions of its own crust, driving it deep down into the mantle of the planet and then bringing it back to the surface billions of years later.
ARC Federation Fellow Professor Simon Turner of Macquarie University led a team of US, Italian and Australian geologists and geochemists in the research, published in the paper Boron and oxygen isotope evidence for recycling of subducted components over the past 2.5 Gyr.
"We've known for quite a while that oceanic crust disappears beneath continents in subduction zones like the Andes, and goes somewhere down into the mantle, and we also know that the mantle's convection and heat transfer forces material up at upwelling areas, such as beneath Hawaii, which produces volcanoes and ocean island basalts," Turner explains. "So it's often been speculated that there's a link between those two and there's been a lot of interest in trying to actually demonstrate that material coming up actually once upon a time went down beneath a subduction zone."
Using a range of techniques, the research team analysed material coming up through one of these classic upwelling zones - the Azores archipelago in the Atlantic Ocean. They were able to prove not only that the material was at least 2.5 billion years old - dating it from the Archaean, the earliest stage of Earth's geological evolution - but also that it had once been part of the Earth's crust, due to the presence of a big range of stable isotopes, which demand the low temperature fractionation which only occurs near the planet's surface.
"If you put all of the separate lines of evidence together you have an argument that says oceanic plates were being formed and subducted in the earliest Earth history; that they were undergoing low temperature alteration at the surface then travelling down into the mantle; and that today if we sample basalt coming out of a volcano in the Azores, we're actually sampling that same material," says Turner. "It's a demonstration of how new scientific techniques are giving us a remarkable long-term view of the history of the planet."
Source: Macquarie University
Related stories:
Advance brings low-cost, bright LED lighting closer to reality
Researchers at Purdue University have overcome a major obstacle in reducing the cost of "solid state lighting," a technology that could cut electricity consumption by 10 percent if widely adopted.
Breakthrough in pre-eclampsia test
A team at the University of Leeds has discovered a way of diagnosing pre-eclampsia, a condition which affects almost one in ten pregnant women and accounts for up to 15% of all premature deliveries.
Nanotube forests grown on silicon chips for future computers, electronics
Engineers have shown how to grow forests of tiny cylinders called carbon nanotubes onto the surfaces of computer chips to enhance the flow of heat at a critical point where the chips connect to cooling devices called heat sinks.
Research could lead to treatment for Alzheimer's disease
A molecule designed by a Purdue University researcher could lead to the first drug treatment for Alzheimer's disease.
Ethanol can replace gasoline with big energy savings
Putting ethanol instead of gasoline in your tank saves oil and is probably no worse for the environment than burning gasoline, according to a new analysis by researchers at the University of California, Berkeley. The researchers note, however, that new technologies now in development promise to make ethanol a truly "green" fuel with significantly less environmental impact than gasoline.
Engineers Make Standardized Bulk Synthesis of Nanowires Possible
A team of Yale scientists have demonstrated a method to understand effective synthesis of semiconductor
nanowires (NWs) for both their quality and quantity, according to a report published in the journal
Nanotechnology.
Just How 'Earth-like' Is The Newest Planet?
In the land rush known as extrasolar planet hunting, the most prized real estate is advertised as "Earth-like."
On Monday, June 13, scientists raced to plant their flag on a burning hunk of rock orbiting a red star.
Observation of material circling a supermassive black hole
Astronomers from the University of Oxford and around the world have observed clumps of X-ray-emitting gas whipping around a
black hole at 33,000 kilometres per second, one-tenth the speed of light.
The observation marks the first time scientists have been able to trace individual blobs of gas on a complete journey around a massive black hole, and provides crucial measurements that have long been missing from black hole studies: both an orbital period and an orbital speed. These have allowed the astronomers to calculate a lower limit to the black hole mass of 300,000 times that of our Sun.
