Earth's Core Has Been Leaking for 2.5 Billion Years and Geologists Don't Know Why

Live Science | 7/18/2019 | Staff
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Earth's scorching core is not a loner — it has been caught mingling with other, underworldly layers. That's according to a new study that found the innermost part of the planet leaks some of its contents into mantle plumes, some of which eventually reach Earth's surface.

This discovery helps settle a debate that's been raging for decades: whether the core and mantle exchange any material, the researchers said.

Finding - Metal - Tungsten - W - Table

The finding was made possible by the metal tungsten (W), element 74 on the periodic table. If tungsten were to make a dating profile, it would note that it's a siderophile, or "iron lover." So, it's no surprise that a lot of tungsten hangs out in Earth's core, which is made primarily of iron and nickel.

On its profile, tungsten would also list that it has a few isotopes (an element with a different number of neutrons in its nucleus), including W-182 (with 108 neutrons) and W-184 (with 110 neutrons). While devising their study, the researchers realized that these isotopes could help them solve the core-leaking question.

Element - Hafnium - Hf - Lithophile - Rocks

Another element, hafnium (Hf), is a lithophile, meaning it loves rocks and can be found in Earth's silicate-rich mantle. With a half-life of 8.9 million years, hafnium's radioactive isotope Hf-182 decays into W-182. This means that the mantle should have more W-182 than the core does, the scientists reasoned.

"Therefore, chemical exchange between the core and the source of mantle plumes could be detectable in the 182W/184W ratio of ocean island basalts," which come from plumes in the mantle, the researchers wrote in the study.

Difference - Tungsten - Composition - Mantle - Core

But this difference in tungsten would be incredibly small: The tungsten-182 composition in the mantle and core were expected to differ by only about 200 parts per million (ppm). "Fewer than five laboratories in the world can do this type of analysis," the researchers wrote in...
(Excerpt) Read more at: Live Science
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