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Abstract We present results from 2D and 3D thermo-mechanical studies of plume-lithosphere interactions in a rifted margin setting and compare inferences of these models with the Northern Atlantic volcanic rifted margin province. We first present a series of 2D models with three different initial locations of the plume: under the oceanic part of the rifted margin system; under the area affected by lithospheric thinning by passive rifting and under continental lithosphere which has not been affected by extension prior to plume emplacement. The style of final plume distribution appears to be controlled by its initial position with respect to different lithospheric segments and rheology of the mantle in the continent-ocean transitional zone rather than by other parameters such as external forcing and rheological structure of the mantle plume. The initial size of the mantle plume controls, to a large extent, the degree of plume head asymmetry. For a strong rheology of the overlaying transitional lithosphere, the effect of plume emplacement is mainly restricted to deep lithospheric levels. In contrast, a weak transitional mantle leads to plume-induced continental break-up when the plume head contributes to the formation of new oceanic lithosphere with asymmetrical propagation of hot plume material towards the continental segment. A common feature of most 2D models is that initially a hot plume weakens the overlying lithosphere, whereas at a later stage frozen mantle plume material is embedded into the lower part of the lithosphere, forming dense and high-velocity bodies. We extend our 2D numerical modelling study to three dimensions and investigate the first-order controls of continental break-up and plume emplacement. We demonstrate that the observed complex Iceland plume geometry with up to 400 km southern propagation can be reproduced numerically in 3D and explained by pre-imposed zones of lithospheric thinning along transform faults. Graphical abstract Image 2 Highlights • Inherited lithospheric structure and initial position of the mantle plume are key factors in plume-induced rifted margin evolution. • The degree of plume head asymmetry is largely controlled by the initial size of the mantle plume anomaly. • Iceland plume propagation can be explained by pre-existing zones of lithospheric thinning along major transform faults. [ABSTRACT FROM AUTHOR]

Abstract: Why some Archean cratons survived for billions of years while the rest of the lithosphere has been reworked, probably for several times, is both enigmatic and fundamental for plate tectonics. Craton longetivity is mainly explained by their buoyancy and analyzed by testing gravitational stability of hardly detectable cratonic mantle “keels” as a function of a hypothesized thermo-rheological structure. Destruction of some cratons suggests that buoyancy is not the only factor of their stability, and many previous studies show that their mechanical strength is equally important. The upper bounds on the integrated strength of cratons are provided by flexural studies demonstrating that T e values (equivalent elastic thickness) in cratons are highest in the world (110–150km). Yet, the lower bounds on the integrated strength of stable cratons are still a matter of debate, as well as the question on how this strength is partitioned between crust and mantle, and which set of rheological parameters is most pertinent. We show that primary observed cratonic features – flat topography and “frozen” heterogeneous crustal structure – represent the missing constraints for understanding of craton longevity. The cratonic crust is characterized by isostatically misbalanced density heterogeneities, suggesting that the lithosphere has to be strong enough to keep them frozen through time without developing major gravitational instabilities and topographic undulations. Hence, to constrain thermo-rheological properties of cratons one should investigate the stability of their topography and internal structure. Our free-surface thermo-mechanical numerical models demonstrate that craton stability cannot be warranted even by very high crustal strength, so that dry olivine mantle and cold thick lithosphere are indispensable conditions. We establish lower-bound limits on the thermo-rheological structure of cratons. In particular, we find that minimal T e needed for long-term stability of continents is approximately 90–110km of which at least 70km should be “contributed” by the lithosphere mantle. [Copyright &y& Elsevier]