Nature Versus Nurture: Preservation and Destruction of Archean Cratons. Issue 9 (10th September 2021)

• Record Type: Journal Article
• Authors: Bedle, H.; Cooper, C. M.; Frost, C. D.
• Is Part Of: Tectonics. Volume 40:Issue 9(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-09-10
• Subjects: Archean -- craton -- geodynamics -- tomography; Geology, Structural -- Periodicals; 551.8
• DOI: 10.1029/2021TC006714
• Languages: English
• ISSNs: 0278-7407

Abstract

Abstract: 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. Plain Language Summary: Because of Earth's dynamic tectonic processes, much of its continental crust has been eroded and recycled and only a fraction of crust older than 2.5 billion years has survived to the present‐day. These areas of old crust, known as Archean cratons, have not experienced deformation or magmatism for a billion years or more. This study investigates whether craton survival is related to their nature, that is, the conditions of their formation, or to nurture, the subsequent events they experienced. Eight case studies are used to evaluate the properties and processes that promote craton stability. Nature is important: surviving Archean cratons tend to be buoyant, viscous, cold, and thick. Some survive because they have not experienced destabilizing geologic processes that introduce heat, magma, and fluids. Others have been modified to various extents by these processes. Some have been weakened and thinned and other, only marginally stable cratons are susceptible to future deformation and destruction. We conclude that both nature and nurture are essential to the survival of Earth's oldest crust. Key Points: The survival of Archean cratons depends both upon their nature —the initial conditions of formation—and nurture —the subsequent tectonic processes that may modify and destabilize cratonic lithosphere Some cratons have survived by avoiding or being shielded from destabilizing tectonic processes. Metasomatism is particularly destructive because it affects buoyancy, viscosity, and integrated yield strength Stability regime diagrams integrate both time and the magnitude of modification, and indicate that marginally stable cratons today may pass into conditions of marginal instability in the future, when even mild deformational stresses could trigger destruction