High thermal conductivity of stishovite promotes rapid warming of a sinking slab in Earth's mantle

Abstract

Thermal transport in subducted slabs and mantle critically influences their thermo-chemical evolution and dynamics, where the thermal conductivity controls the magnitude of conductive heat transfer. Here we investigate high-pressure thermal conductivities of stishovite and new-hexagonal-aluminous (NAL) phase, two major slab minerals in the shallow lower mantle, and their impacts on slab dynamics. Pure and Al-bearing stishovite exhibit conductivities of 60–70 and 30–40 Wm−1K−1, respectively, at 25–60 GPa and 300 K, much higher than the Fe-bearing NAL, 10–33 Wm−1K−1, and assemblage of a pyrolitic mantle or subducted basaltic crust. Numerical simulations indicate that subducted crustal materials particularly with local silica-enrichment would have efficient thermal conduction which promotes faster warming of a sinking slab, altering dynamic stability of slab materials and leading to slab stagnation and crust detachment in the shallow lower mantle. Conductive heat transfer in silica-enriched regions along subducted slabs in the shallow lower mantle can be more influential on mantle dynamics than previously thought.