Rocks from Canadian Arctic Offer New Perspective on Primitive Earth
12.08.2010 - Land & Geology, Arctic
A new discovery made in the Canadian Arctic could offer scientists a fresh perspective on the Earth’s ancient history. According to a paper published in the journal Nature, geochemical evidence from volcanic rocks collected on Baffin Island scientists may have found an untouched part of the Earth's early mantle that could provide better insight into the early chemical evolution of the Earth. The mantle "reservoir", scientists say, could date back to a few tens of millions of years after the Earth’s formation, a key phase before the Earth’s evolution and crust formation modified the composition of most of the rest of its interior.
The scientists focused on the Baffin Island rocks as an extremely early sample of the mantle because a previous study of helium isotopes in these rocks showed them to contain anomalously high ratios of helium-3 to helium-4. High 3He to 4He ratios possibly identify the Baffin Island rocks as parts of a reservoir within the mantle, which might never have expulsed its original helium-3.
While many researchers previously believed that the early Earth’s crust chemistry was similar to that of chondrites before its alteration by the formation of continents, the new study suggests that the Earth's crust was altered before continental formation because of either an earlier Earth differentiation event, or the Earth having originated from already depleted constitutive elements.
