Global electromagnetic induction constraints on transition-zone water content variations.

Area of Science:

• Geophysics
• Mineral Physics
• Seismology

Background:

• Water content profoundly influences mantle material properties like viscosity and seismic velocity.
• Electrical conductivity of mantle minerals, especially wadsleyite and ringwoodite, is highly sensitive to hydrogen (water) content.
• The mantle transition zone's water content has critical implications for Earth's dynamics and geochemistry.

Purpose of the Study:

• To develop a global 3D electrical conductivity model of the Earth's mantle.
• To investigate the relationship between electrical conductivity variations and water content in the mantle transition zone.
• To constrain water distribution in the mantle transition zone using geophysical data.

Main Methods:

• Inversion of long-period geomagnetic response functions.
• Development of a global-scale 3D electrical conductivity model.
• Analysis of conductivity variations in the mantle transition zone.

Main Results:

• Revealed electrical conductivity variations of approximately one order of magnitude in the mantle transition zone.
• Observed higher conductivities in cold, seismically fast regions associated with subducting slabs.
• Identified significant spatial variations in water content throughout the mantle transition zone.

Conclusions:

• Observed electrical conductivity patterns are plausibly explained by significant variations in mantle transition zone water content.
• Subducting cold tectonic plates likely transport water into the mantle transition zone.
• Geophysical constraints on water content improve understanding of mantle dynamics and evolution.