Publication Date:
2019-09-23
Description:
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.
Type:
Article
,
PeerReviewed
Format:
text
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