Discovery of Seafloor Rocks Subducted Deep Within the Earth
A research group including Meiji University and JASRI has announced new evidence suggesting that rocks originating from subducted oceanic plates reach the core-mantle boundary at a depth of approximately 2,900 km, based on experiments, theoretical calculations, and seismic observations.
📋 Article Processing Timeline
- 📰 Published: June 10, 2026 at 23:00
- 🔍 Collected: June 10, 2026 at 14:21
- 🤖 AI Analyzed: June 10, 2026 at 14:48 (27 min after Collected)
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'.
FAQ
What marker did the research team use to identify the subduction point of the oceanic plate?
Silicon dioxide (SiO₂), which is abundant in oceanic crust. SiO₂ transforms into a high-density structure called 'seifertite' at great depths, affecting seismic wave propagation, making it an indicator for tracing subducted rocks.
How did the researchers recreate the deep Earth environment in the laboratory?
They used a laser-heated diamond anvil cell to recreate the extreme conditions near the core-mantle boundary, achieving up to 78 GPa and 6000 K, and conducted high-speed synchrotron X-ray diffraction measurements.
How deep might the rocks derived from the subducted oceanic plate have reached?
Based on the evidence from this study, the rocks may have reached the vicinity of the core-mantle boundary, approximately 2900 km deep within the Earth.
Why were theoretical calculations performed?
To verify the energy differences in phase transitions that could not be explained by experiments alone, and to elucidate the reasons for discrepancies in previous studies, such as the influence of metastable phases due to thermal fluctuations.
What anomalies were detected from seismic wave observations?
A characteristic anomaly was found 100 to 300 km above the core-mantle boundary beneath Central America, where S-waves were slower and P-waves were faster, which was compared with the experimental results.