Olivine's high radiative conductivity increases slab temperature by up to 200K

The thermal evolution of slabs governs their subduction dynamics and the transport of water into Earth's interior. However, current slab subduction models often neglect the contribution of radiative thermal conductivity (i.e., heat transport by light) due to the limited constraints on the opacity of minerals at high pressure (P) and temperature (T). Here, using optical experiments at high P, T conditions, we show that the radiative contribution accounts for ~40% of the total heat transport in olivine, the dominant mineral of the upper mantle. Using 2D thermo-kinematic modelling, we quantify the effect of radiative thermal conductivity on slab temperature exploring different ages and subduction velocities. When radiative heating is included, slabs temperatures are ~100-200 K higher than in the models that ignore this contribution. Consequently, water-bearing minerals can reach the Mantle Transition Zone (~410-660 km) only in old slabs (>60 Myrs) and/or at high subduction velocities (≥10 cm/year).