Geological researchers have located a mantle reservoir based on the atypical ratio of the isotopes helium-3 to helium-4 in rocks found on an island in the canadian arctic. Most helium-3 in Earth rocks has been outgassed over billions of years as the primitive Earth mantle that formed from space rocks got churned through volcanic processes. The fact that this particular rock still contains high levels of helium-3 indicates that it has not gone through this process and represents a reservoir of very primitive material that dates back to a very early time in the Earth’s geologic formation, very shortly after it formed from the accumulation of space rocks or collisions of primitive astrological bodies.
Interestingly, this research calls into question ideas about how the early Earth rocks became differentiated from that of chondrites, which is the material that meteors are comprised of and from which the Earth is believed to have formed. One possible explanation for that differentiation is that it occurred prior to the mantle formation which eventually became the crusts forming continents.
According to this hypothesis, the early rock might have differentiated chemically from chondrites very early on in what would have been a global magma ocean across the entire globe, after which mantle formed and volcanic processes occurred leading to the formation of continents.
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