Archean cratons belong to the most remarkable features of our planet
since they represent continental crust that has avoided reworking for
several billions of years. Even more, it has become evident from both
geophysical and petrological studies that cratons exhibit deep
lithospheric keels which equally remained stable ever since the
formation of the cratons in the Archean. Dating of inclusions in
diamonds from kimberlite pipes gives Archean ages, suggesting that the
Archean lithosphere must have been cold soon after its formation in the
Archean (in order to allow for the existence of diamonds) and must have
stayed in that state ever since. Yet, although strong evidence for the
thermal stability of Archean cratonic lithosphere for billions of years
is provided by diamond dating, the long-term thermal stability of
cratonic keels was questioned on the basis of numerical modeling
results. We devised a viscoelastic mantle convection model for exploring
cratonic stability in the stagnant lid regime. Our modeling results
indicate that within the limitations of the stagnant lid approach, the
application of a sufficiently high temperature-dependent viscosity ratio
can provide for thermal craton stability for billions of years. The
comparison between simulations with viscous and viscoelastic rheology
indicates no significant influence of elasticity on craton stability.
Yet, a viscoelastic rheology provides a physical transition from
viscously to elastically dominated regimes within the keel, thus
rendering introduction of arbitrary viscosity cutoffs, as employed in
viscous models, unnecessary.