Veneer of Earth's platinum was from extraterrestrial source say CSIRO scientists

By Rich Bowden.

First printed in The Tech Herald 30/7/09.

Img left: CSIRO headquarters, Canberra, ACT. Credit: CSIRO

Img right:Outcrop of komatiite lava, South Africa. Credit: CSIRO

An Australian study has concluded that a "late veneer" of the Earth's platinum came from extraterrestrial sources.

Scientists at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) have concluded in a report that study of the platinum content of lava flows called komatiites had changed markedly over time. The CSIRO is using the search for platinum as a guide to the availability of nickel.

Their theory is that the Earth's core drained all the available platinum during its formation however later increases can be attributed to "a steady rain" of meteorites which bombarded the planet.

In a CSIRO news release, the organisation's Minerals Down Under Flagship researcher Dr Stephen Barnes said their research had found the amount of platinum had increased between 3.5 billion years to 2.9 billion years ago.

“We found that the oldest komatiites have the lowest platinum content,” Dr Barnes said.

“The platinum content gradually increases from about 3.5 billion years to 2.9 billion years ago."

“This tells us that the deep source where the komatiite came from, down near the boundary between the Earth’s core and mantle, was gradually gaining platinum over time.”

Just how the early platinum vanished is explained by the authors.

“When the Earth’s core formed, it took all the available platinum with it, leaving the mantle and crust with none,” Dr Barnes said.

“Following that, a steady rain of meteorites created the so-called Late Veneer – a thin surface layer of meteorite debris rich in platinum.”

Over time the extraterrestrial platinum was "stirred" in the Earth's interior, says the study.

The authors consider the work to have fundamental benefits for those who study the dynamics of mantle processes and the mechanisms that cause plate tectonics, earthquakes and volcanoes, the release said.


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