High-temperature structural disorders stabilize hydrous aluminosilicates in the mantle transition zone
Baoyun Wang1, Jin Liu2, Yanyao Zhang3
1School of Earth Sciences, Lanzhou University, Lanzhou, 730000, China.
Nature Communications
|January 25, 2025
Summary
Structural disorders enable hydrous aluminosilicates to survive extreme mantle temperatures. This high thermal stability is key to understanding water transport in the deep Earth, impacting the global water cycle.
Area of Science:
- Geochemistry
- Mineral Physics
- Deep Earth processes
Background:
- Hydrous aluminosilicates are crucial for transporting water into the deep mantle.
- Their stability at extreme mantle transition zone temperatures remains poorly understood.
Purpose of the Study:
- Investigate the crystal structures and chemical compositions of hydrous aluminosilicates under deep mantle conditions.
- Determine the mechanisms behind their high thermal stability.
Main Methods:
- Synthesis of single crystals at high pressures (15.5–22.0 GPa) and temperatures (1400–1700 °C).
- Analysis using single-crystal X-ray diffraction, electron probe microanalysis, and nanoscale secondary ion mass spectrometry.
Main Results:
- Observed pervasive structural disorders in synthesized crystals.
- Found extensive occupation of normally vacant Al and Si sites.
- Demonstrated that high temperatures activate these disorders, increasing hydrogen incorporation and local structural variability.
Conclusions:
- The order-to-disorder transition is critical for the high thermal stability of hydrous aluminosilicates.
- This stability significantly influences the deep mantle water cycle.
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