World’s oldest rocks found in Canada

The oldest rocks yet found on Earth have been identified on the shore of Hudson’s Bay in Canada: they date back 4.28 billion years, says a McGill University/Université du Québec/Carnegie Institution team in an article published today in Science (short notice here – subscription required for full access).

‘This would make them the oldest rocks ever found on the surface of the Earth’, says McGill’s Jonathan O’Neil, lead author of the report. He has spent the last five summers exploring the Hudson Bay outcropping and hauling chunks of the ancient bedrock back to his Montreal lab.

It’s been known since 2001 that the outcropping was old, but a speckled brown and beige patch O’Neil and his colleagues have pulverized and analyzed has proved to be  much older than other rocks at the site. They believe it originated in a volcano that erupted in a shallow sea not long after the planet’s rocky crust began to form.

The above quoted from the Saskatoon Star Phoenix report. NOVA Geoblog has a picture of this seriously old rock.

UPDATE: Kim at All of My Faults Are Stress-Related has been looking into the mineralogy of this old, old rock and finds that cummingtonite is one of its constituents. Cummingtonite, named after the town of Cummington, Massachusetts, is a metamorphic amphibole that has been making geologists snigger for 4.28 billion years.

News
World’s oldest rocks found in Quebec – Saskatoon Star Phoenix, 25 September 2008
New contender for Earth’s oldest rocks – Science News, 25 September 2008
McGill researchers find oldest rocks on Earth – EurekaAlert, 25 September 2008
New record ancient crust: 4.28 Ga – About.com Geology, 25 September 2008
Old, old rock – NOVA Geoblog, 25 September 2008