Measurement of Thermal Diffusivity for Eclogite and Basalt underHigh Temperature and High Pressure Conditions

Knowledge of the heat-transport properties of eclogite and basalt, which are the most important parts of the oceanic subduction zone, is essential for understanding the thermal regimes and the geodynamics subduction zone.Based on the pulse heating method, we conducted high pressure experiment, and measured thermal diffusivities of eclogite and basalt at 1.0 and 2.0GPa and 373-973K.The results show that the thermal diffusivity of both eclogite and basalt decreases with the increase of temperature, and that, at 1.0 GPa and room temperature (278K), the thermal diffusivity and thermal conductivity of eclogite are about 30% and 50% higher than that of basalt, respectively.In the depth profiles of the subduction plate, the low thermal conductivity of upper basalt hinders the heat exchange between the subduction plate and the surrounding mantle, so that the subduction plate remains cold, hard and brittle, which results in strain accumulation and eventually leads to rupture and earthquake.In the lower half of the subduction plate, the basalt-eclogite phase transition reduces the temperature difference between the subduction plate and surrounding environment, which is favorable for the local dynamic stability.