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Thermal Consequences of Lithospheric Deformation |
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Lithospheric Thinning |
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Thinning produces heat advection as a volume of rock, and the heat attached to it, is displaced vertically resulting in an instantaneous warming of the geotherm (upward compression of the geotherm). It also decreases the thickness of the radiogenic layer therefore decreasing the production of radiogenic heat in the lithosphere. Isostasy produces the subsidence of the lithosphere leading to sedimentation which in turn affects the amount and distribution of the radiogenic heat elements in the crust which also impacts on the geotherm. The interplay between the geometry of the thinning, the thinning rate and the sedimentation rate leads to contrasted thermal history.
The graphs show transient geotherms (0, 20, 50...Ma) following homogeneous thinning (the thicknesses of the crust and the lithospheric mantle are halfed by pure shear deformation). Sedimentation is discarded here. Following the increasing of the geothermal gradient due to deformation, thermal relaxation leads to cooling and therefore the thickening of the lithosphere. |
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