Thermal processes under island arcs

Abstract

By numerical experiments on 2-D time dependent heat conduction equations, it is shown that large heat generation along the deep-earthquake fault zone and effective heat transfer in the upper mantle above the deep earthquake zone is required to explain the heat flow pattern across island arcs and marginal seas. It is assumed that the oceanic crust and upper mantle or a 100 km thick lithosphere slides down along the deep-earthquake zone with a velocity of several cm/year. We assume also that the present thermal processes under island arcs started about 100 m.y. (million years) ago and the initial structure was oceanic. The results show that heat generation four times as high as the mean heat flow (1.5 HFU) at the upper surface of the lithosphere and effective heat conduction ten times as large as normal phonon conduction are required to explain the observation. These values can be explained by the viscous dissipative heat generation due to appropriate shear stress and relative movement, and the penetrative convection of upward mass transfer of magma. The upward mass transport under marginal seas may be the cause of the formation of these seas.