Signs of material exchange between Earth’s core and mantle found in China — ScienceAlert
Geoscientists at the University of Science and Technology of China in Hefei concluded that Earth’s core may have transferred materials to the mantle throughout its evolution. ScienceAlert reports, citing a study published in the journal Science Advances.
Hydrogen isotopes as a key to the process
The researchers used path-integral simulations enhanced by machine learning to investigate the quantum behavior of atoms and molecules. They paid particular attention to hydrogen transport in the planet’s interior, as the low mass of this element makes its isotopic composition sensitive to quantum effects.
The team analyzed the deuterium-to-hydrogen ratio, an indicator of the proportion of the heavier hydrogen isotope. A model of the crystallization of the primordial magma ocean showed that isotope separation between minerals and melt should have been weak. Therefore, the ancient mantle should have acquired a relatively uniform hydrogen isotopic composition, despite differences in pressure, temperature, and model assumptions.
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Traces from Earth’s depths
Ocean island basalts, including lavas from Baffin Island in Canada’s Nunavut and from Iceland, form from upwelling flows of material near the core-mantle boundary. According to the study’s authors, these rocks may contain signs of an influx of lighter hydrogen that accumulated in the core from solar nebula material. Such hydrogen may enrich the mantle and lower its deuterium-to-hydrogen ratio.
Scientists also consider helium and tungsten isotope ratios in such basalts to be additional evidence of this process. An elevated ratio of primordial helium-3 to helium-4, as well as the tungsten isotopic signal, are, in their interpretation, consistent with the transfer of materials from deep layers. The authors noted that modern hydrogen isotopic signatures in the lower mantle are more likely to reflect long-term exchange between the core and mantle than unchanged remnants of Earth’s early formation.
