How continental lithosphere responds to tec tonic stresses and mantle convective processes is<br/>determined in large part by its mechanical strength and temperature distribution, which depend on crustal<br/>heat production. In order to establish reliable crustal and thermal models for the Superior Craton, Canadian<br/>Shield, new measurements of heat ﬂux and heat production in 28 deep boreholes at 16 sites are combined<br/>with a larger set of older data. The Superior Province was assembled by the docking of volcanic/plutonic<br/>and metasedimentary terranes and continental fragments to the southern margin of an older core around<br/>2.7 Ga. The average heat ﬂux is much lower in the craton core than in the accreted terranes, 31 versus<br/>43 mW m<br/>−2<br/>. The major accreted volcanic/plutonic belts share the same heat production characteristics,<br/>testifying to the remarkable uniformity of crust-building mechanisms. The marked diﬀerence between the<br/>crusts of the core and the accreted belts supports the operation of two diﬀerent crust-forming processes.<br/>The crust of the craton core has an enriched upper layer, in contrast to that of the younger belts which lack<br/>marked internal diﬀerentiation. At the end of amalgamation, the lithosphere of the craton core was colder<br/>and mechanically stronger than the lithosphere beneath newly accreted material. Surrounding the craton<br/>core with weaker belts may have ensured its stability against tectonic and mantle convection perturbations.<br/>This large strength contrast accounts for the lack of lithospheric imbrication at the edge of the craton core<br/>as well as for the diﬀerent characteristics of seismic anisotropy in the lithospheres of the craton core and the<br/>younger terranes.