Anisotropy of thermal diffusivity in the upper mantle

Area of Science:

• Geophysics
• Mineral Physics
• Solid Earth Science

Background:

• Heat transfer in Earth's mantle is crucial for planetary dynamics.
• Olivine exhibits thermal anisotropy, and seismic data reveal large-scale olivine orientations in the upper mantle.
• The thermal anisotropy of mantle minerals at high temperatures and its link to deformation remain poorly understood.

Purpose of the Study:

• To investigate the thermal anisotropy of deformed mantle rocks at high temperatures.
• To understand how deformation influences thermal diffusivity in the uppermost mantle.
• To assess the implications of strain-induced thermal anisotropy for mantle dynamics.

Main Methods:

• Laboratory measurements of thermal diffusivity in deformed mantle rocks (290–1,250 K).
• Petrophysical modeling of heat transfer in the upper mantle.
• Analysis of seismic anisotropy data to infer olivine orientations.

Main Results:

• Deformation induces significant thermal anisotropy in the uppermost mantle.
• Heat transport parallel to the flow direction is up to 30% faster than perpendicular to it.
• Strain-induced thermal anisotropy affects upper-mantle temperature, rheology, and dynamics.

Conclusions:

• Deformation history is a key factor controlling upper-mantle thermal structure and dynamics.
• Oceanic and continental settings exhibit distinct effects of thermal anisotropy on heat transfer and geological processes.
• Anisotropic heating above mantle plumes may influence continental geological activity.