Discovery of Seafloor Rocks Subducted Deep Within the Earth

A research group including Associate Professor Ryosuke Sinmyo of Meiji University has obtained new evidence suggesting that rocks originating from subducted oceanic plates reach the vicinity of the 'core-mantle boundary' at a depth of approximately 2,900 km, by combining laboratory experiments that recreate deep-Earth conditions, atomic-level theoretical calculations, and seismic wave observations.

As oceanic plates subduct into the Earth's interior, the silicon dioxide (SiO₂) contained in the crust transforms into a high-density structure called 'seifertite' in the deepest mantle. Because this transformation influences the propagation of seismic waves, it serves as a 'marker' for detecting subducted rocks deep within the Earth.

In this study, the phase transition of SiO₂ was precisely determined through high-temperature, high-pressure experiments and quantum beam measurements at SPring-8, and the validity of these results was verified through atomic-level theoretical calculations. Furthermore, by cross-referencing with actual seismic waveform data, the researchers demonstrated that the mineral transformations observed in the laboratory correspond to the seismic velocity anomalies observed in the deep Earth.

The research results were published in the British journal 'Scientific Reports'.