By Sid Perkins
Scientists may have found the world’s oldest intact rocks in a 10-square-kilometer patch of bedrock on the eastern shore of Canada’s Hudson Bay. Geochemical analyses suggest the rocks are around 4.28 billion years old, which would mean they solidified less than 300 million years after Earth formed.
If the dating holds true, the new oldest rocks could be a trove of information about geological processes during Earth’s earliest history, the researchers report in the Sept. 26 Science.
The rocks have the same chemical composition as volcanic deposits, says Jonathan O’Neil, a geochemist at McGillUniversity in Montreal and coauthor of the new study. He and his colleagues measured the ratio of two rare chemical isotopes — neodymium-142 and samarium-146 — to come up with an age estimate for the rocks. The previous oldest known rocks formed about 4.03 billion years ago and were found in what is now Canada’s Northwest Territories.