WA researchers say that clues from the ancient sedimentary rocks which overlie the massive iron ore deposits in the Pilbara hold the key to solving the puzzle - and probing them may also help mining companies come up with better ways of extracting iron ore by giving new insights into the resource.
The University of Western Australia’s Professor Mark Barley who is a world leader in the evolution of oxygen on Earth, said WA's rich body of iron ore deposits, formed in sedimentary rocks (Banded Iron Formations), may contain evidence in the form of sulphur-isotopes that would describe what the Earth's atmosphere was like between 2.5 and 2.4 billion years ago when oxygen levels started to rise.
"These ancient iron rich sedimentary rocks are not just the world’s major source of iron ore, they are incredibly important rocks in Earth's history, providing clues to help us understand one of the most important periods of environmental change on this planet," he said.
Scientists have known for some time that the Earth's atmospheric chemistry shifted at about this time, but research from around the world has failed to explain exactly why this shift happened, leaving WA the best place to solve the last piece of the puzzle.
In his earlier research published in the prestigious science journal Nature last year, Professor Barley discovered that 3.45 billion years ago the East Pilbara was once a volcanically active area with a shallow sea that may have been home to primitive life.
Professor Barley believes that the subsequent growth of continents and emergence of more volcanoes on land by 2.5 billion years ago might have played a crucial role in establishing an oxygen-rich atmosphere on Earth.
But to prove it, he needs to drill for core samples from about 300 metres beneath the ground on key Pilbara iron ore exploration sites in the south-west Hamersley region.
He hopes some of the large mining companies will get on board by collaborating in a drilling program to allow researches to collect enough samples.
Because 2.45 billion year old Hamersley Banded Iron Formations contain the oldest geochemical evidence for an atmosphere with no oxygen, this drilling would aim to sample the sedimentary rocks that immediately overlie them.
These samples contain the oldest evidence for the permanent increase in Earth's oxygen levels which would be recognised by changes in sulphur isotope-compositions and the abundances of oxygen sensitive metals.
Western Australia's chief scientist, Professor Lyn Beazley, said the international importance of Professor Barley's work, co-authored by Professor Lee Kump from the NASA Astrobiology Institute and Department of Geosciences at Pennsylvania State University, could not be over-estimated.
"Of all the research papers published in Nature, only a handful are chosen by the editors to be discussed further in an editorial," she said.
"The fact that the work of Professors Barley and Kump was chosen not only to be published in Nature, but was also the subject of an editorial by the University of California's Timothy W. Lyons, is a great achievement for WA science and shows just how well-regarded this work is on the international stage."
The paper, entitled “Increased subaerial volcanism and the rise of atmospheric oxygen 2.5 billion years ago”, was published in the 30 August 2007 edition of Nature.
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