Geologists say rocks collected from Baffin Island in the Canadian arctic suggest the area can offer clues to the early chemical evolution of Earth.

Researchers from the Carnegie Institution say beneath the island lies a region of Earth's mantle that has escaped the billions of years of melting and reforming that has affected the rest of the planet, an institution release said Wednesday.

This mantle "reservoir" dates from just a few tens of millions of years after the Earth first came together in the collision of smaller bodies in the solar system, scientists say.

It likely represents the composition of the mantle shortly after the formation of the Earth's core, but before 4.5 million years of formation and recycling modified the composition of the rest of the planet's interior.

"This was a key phase in the evolution of the Earth," Richard Carlson of the Carnegie Institution's Department of Terrestrial Magnetism said. "It set the stage for everything that came after. Primitive mantle such as that we have identified would have been the ultimate source of all the magmas and all the different rock types we see on Earth today."