World's oldest rocks spark discussion on origin of life

World's oldest rocks spark discussion on origin of life

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Finding means life could have begun 4.4 billion years ago
boninites (rock)The southwest coast of Guam contains out-croppings of boninites and related rocks dating back 44 million years, much younger than the Canadian rocks. Photo courtesy of Mark Reagan.

In a case of geology impacting biology, an investigation of what are thought to be the world’s oldest rocks has re-opened a discussion of when and where life on Earth began.

An Australian-led team concluded that the 4.4 billion-year-old rock formation—called the Nuvvuagittuq greenstone belt—on the coast of Hudson Bay in Quebec, Canada, likely was formed by subduction, the ongoing tectonic process that recycles the Earth’s crust and is responsible for most of the Earth’s great earthquakes and volcanic eruptions.

Modern subduction produces life-nurturing fluids that flow through life-hosting rocks called serpentinite. A subduction origin for the Nuvvuagittuq greenstone belt suggests that a potential cradle for life existed as much as 900 million years before the oldest direct evidence for life—fossilized bacteria in Western Australia estimated to be 3.5 billion years old.

The team’s findings were published Jan. 6 in Geology, the journal of the Geological Society of America, and are the subject of an article in the Feb. 20 issue of the journal Science.

Mark Reagan, team member and professor and chair of the University of Iowa Department of Earth and Environmental Sciences, says that the Geology paper makes a credible case for pushing subduction and its life-friendly environment as far back 4.4 billion years, but adds that much work remains to determine when, where, and how early life was established.

“Chemical and mineralogical evidence for life and life-friendly environments stretch back to 3.8 billion years at other locations on Earth. Further work in the Nuvvuagittuq area is needed to establish it as an even older site where primitive life or life-like chemistry once existed,” he says.

In 2008, scientists at the Carnegie Institution of Washington and McGill University in Montreal identified the Canadian bedrock along the northeast coast of Hudson Bay as being more than 4 billion years old, a number that was revised to as much as 4.4 billion years old in a paper published in 2012.

Contacts

Mark Reagan, Department of Earth and Environmental Sciences, 319-335-1820

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