Heat flow anomaly and lithospheric thinning of the Tuscan extensional back-arc basin (Italy)

摘要

A new thermo-mechanical model for the prediction of the thermal evolution of passive sedimentary basins is presented. The model assumes instantaneous lithospheric stretching and underplate dragging and erosion. Stretching is ascribed to regional stress field related to the plate boundary forces, dragging and erosion to underplate movements of the hotter asthenospheric material. The thinning of the lithosphere causes the subsidence of the basin and the passive upwelling of the asthenospheric material to fill the space left by the lithospheric material. Isostatic equilibrium is maintained throughout the rifting event. The model enables to predict the post-rift thermal and uplift history of passive basins as a function of the stretching factor δ of the crust and the thinning factor β of the lithosphere, where δ ≤ β. The main patterns of the observed regional heat flow anomaly which extends all over the Tuscan back-arc basin of the Northern Apennine subduction area provide a test to validate a three-dimensional (3-D) version of the inferred model. The size of the hot asthenospheric body emplaced into the lithosphere, responsible for the observed thermal anomaly on the earth surface, is estimated by a trial and error procedure.