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Carlson and Colleagues Discover Oldest Known Rocks on Earth |
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Friday, 26 September 2008 |
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Photo: Jonathan O'Neil/ McGill University.
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Rick Carlson and Jonathan O’Neil, a Ph.D. student at McGill University, and colleagues, are featured in this week’s issue of Science for research on Canadian bedrock in the Nuvvuagittuq region of Quebec that may be the world’s oldest. By measuring minute variations in the isotopic composition of rare earth elements neodymium and samarium found in the rocks, the group determined that the rock samples range from 3.8 to 4.28 billion years old. The oldest dates came from rocks termed “faux amphibolite,” which the researchers interpret to be ancient volcanic deposits.
Carlson commented, “There have been older dates from Western Australia for isolated resistant mineral grains called zircons, but these are the oldest whole rocks found so far.” Before this study, the oldest dated rocks were from a body of rock known as the Acasta Gneiss in the Northwest Territories, which are 4.03 billion years old. The Earth itself is 4.6 billion years old, and remnants of its early crust are extremely rare, due to plate tectonics. The rocks are significant not only for their great age but also for their chemical composition, which resembles that of volcanic rocks in geologic settings where tectonic plates are crashing together. Carlson went on to comment, “This gives us an unprecedented glimpse of the processes that formed the early crust.”
For more information, see the full paper or the CIW press release. For the Science “News of the Week” feature, click here.
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