Nature Versus Nurture: Preservation And Destruction Of Archean Cratons

The factors that promote stability of Archean cratons are investigated from a combined geodynamic, geological, and geophysical perspective in order to evaluate the relative importance of nature-the initial conditions of a craton-versus nurture-the subsequent tectonic processes that may modify and destabilize cratonic lithosphere. In this review study, we use stability regime diagrams to understand the factors that contribute to the intrinsic strength of a craton: buoyancy, viscosity, and relative integrated yield strength. Cratons formed early in Earth history when thermal conditions enhanced extraction of large melt fractions and early cratonization (cessation of penetrative deformation, magmatism, and metamorphism) promote formation of stable Archean cratonic lithosphere. Subsequent processes that may modify and weaken cratonic lithosphere include subduction and slab rollback, rifting, and mantle plumes-processes that introduce heat, fluids, and partial melts that warm and metasomatize the lithosphere. We examine tomographic models from eight cratons, including four that are thought to be stable and four that have been proposed to be modified or destroyed. Our review suggests that continental lithosphere formed and cratonized prior to the end of the Archean has the potential to withstand subsequent deformation, heat, and metasomatism. Survivability is enhanced when cratons avoid subsequent tectonic processes, particularly subduction. It also depends on the extent and geometry of modification. However, because craton stability decreases as the Earth cools, marginally stable cratons that undergo even modest modification may be set on a path to destruction. Therefore, preservation of Archean cratons depends both on nature and nurture.