Hafnium tungsten dating
The authors of the research paper, published April 7 in the journal , studied volcanic rocks that recently erupted from volcanoes in Hawaii and Samoa.
The rocks contain surprising geochemical anomalies—the “fingerprints” of conditions that existed shortly after the planet formed.
Helium-3 is extremely rare on Earth, and tends to show up in samples of rock that have not been melted or otherwise recycled since the planet first formed.
Helium-4, on the other hand, can form from the radioactive decay of uranium and thorium.
Parts of these magma oceans may have crystallized and sunk to the boundary between the mantle and the core, preserving the ancient tungsten and helium signatures.
“Each of these scenarios contain some inconsistencies that we can’t yet explain,” Mundl said.
“We found geochemical signatures that must have been created nearly 4.5 billion years ago,” said Andrea Mundl, a postdoctoral researcher in geology at UMD and the lead author of the study.
“It was especially exciting to find these anomalies in such young rocks.
Earth’s mantle is made of solid rock that nonetheless circulates slowly over millions of years.
On its own, the tungsten isotope ratio is interesting, but not enough to make any convincing conclusions.
But the researchers also observed that the same rocks contain an unusual ratio of helium isotopes.
Tungsten tends to associate with metals, so most of it migrated to Earth’s core, while hafnium, which tends to associate with silicate minerals, stayed in Earth’s mantle and crust.
Most of the rocks on Earth have a similar ratio of tungsten-182 to tungsten-184, and this ratio serves as a global baseline.
Search for hafnium tungsten dating:
Perhaps the volcanoes are drawing material from Earth’s core, where the ratios are expected to favor low tungsten-182 and high helium-3.