Search for: All records

The thermal evolution of early cratonic mantle roots is of intense interest from the perspective of craton formation yet few geological constraints are available. Diamonds erupted in Archean times provide invaluable windows into this issue through the thermobarometry of their inclusions and the time- and temperature-dependent aggregation of their nitrogen impurities. The chemistry and pressure–temperature conditions of inclusions in Archean-erupted diamonds lar- gely reflect those of inclusions found within typical lithospheric diamonds erupted in recent times, and indicate that unusually cool thermal conditions pertained in their early evolution. These cool condi- tions are strongly supported by modelling of the nitrogen aggregation systematics in the diamonds as well as in global lithospheric diamonds. Using 1-D thermal models with initial cooling due to latent heat of fusion during peridotite melting, we simulate lithosphere thermal evolution following active plume melting. These models cannot reproduce the cool conditions of silicate inclusions in Archean erupted diamonds and also cannot reproduce the cool mantle diamond-formation temperatures recorded by silicate inclusions in global peridotitic lithospheric diamonds. In contrast, simple thermal models of slab-stacking, produce complex, highly transient ther- mal histories in the first 500 Myr of their evolution, initially characterised by very cool local conditions, matching those seen in Archean erupted diamonds. The thermal evolution of our slab-stacking models involves both cooling and heating intervals depending on depth in the evolving lithospheric root. This complex and varied thermal evolution is much more consistent with the constraints offered by the litho- spheric diamond record. 

Abstract We study the existence and uniqueness of solutions to the vector field Peierls–Nabarro (PN) model for curved dislocations in a transversely isotropic medium. Under suitable assumptions for the misfit potential on the slip plane, we reduce the 3D PN model to a nonlocal scalar Ginzburg–Landau equation. For a particular range of elastic coefficients, the nonlocal scalar equation with explicit nonlocal positive kernel is derived. We prove that any stable steady solution has a one-dimensional profile. As a result, we obtain that solutions to the scalar equation, as well as the original 3D system, are characterized as a one-parameter family of straight dislocations. This paper generalizes results found previously for the full isotropic case to an anisotropic setting.