Long-term thermo-mechanical properties of the continental lithosphere

Abstract

Simple thermo-elastic models successfully explain flexure observations from oceanic lithosphere and are consistent with predictions based on empirical yield stress envelopes for the deformation of olivine. The response of the continental lithosphere, in contrast, has frequently been modelled as a Maxwell viscoelastic solid. By plotting estimates of flexural rigidity against the age of the continental lithosphere at the time of loading, an estimate of which is defined by the radiometric age of the underlying basement, we report here that flexural rigidities for the continental lithosphere are compatible with oceanic flexure results. Analogous to the increase of rigidity with age away from a mid-oceanic ridge, continental rigidities appear to increase with age following a major thermal event. The high rigidities (∼1032 dyn cm) associated with Archaean/Proterozoic terrains and modelling of plate deformation with yield-stress envelopes appropriate for the continents suggest that the long-term thermal behaviour of continental lithosphere is governed by a coolong plate model with a 200–250-km plate thickness.