Thermal modelling of arc-trench regions.

The temperature structure of the shallow part of a subduction zone, ie the region between the trench and the volcanic arc, has been calculated with finite difference methods. Published heat flow measurements are used as a constraint for the thermal models. Heat flow in the arc-trench region is low (<40mW m^-2) for subduction zones which have been active for more than about 60 Ma. In the central part of the arc-trench region of these subduction zones average heat flow values range from 30 to 36 mW m^-2. From the thermal modelling it follows that such a heat flow level requires shear stresses of 20-60 MPa near the upper surface of the descending slab at depths between 25 and 75km. In addition, it is shown that the pressure-temperature relations, inferred from mineral assemblages in high-pressure metamorphic belts, can only be reached if significant heat production by friction takes place, with shear stresses similar to those inferred from heat flow data. Subduction related volcanism is caused by high temperatures in the asthenospheric wedge above the slab. It is likely that the volcanic line marks the boundary of the asthenospheric wedge. -Authorstemperature structure a subduction zone finite difference methods heat flow arc trench region volcanism asthenospheric wedge