Metamorphism and the tectonic evolution of the Archean

The tectonics on the Archean Earth is intricate and contentious, with ongoing debate concerning the dominant surface processes controlled by either a plate tectonics regime or alternative forms of tectonics (stagnant lid, heat pipe, drip tectonics, sluggish plates and other planetary modes of heat loss). In this study, we assess the viability of interpretations of tectonics during the Archean using a newly compiled metamorphic database. We relate Archean cratons and continental history, crustal growth and reworking, and horizontal motion of ancient cratons to infer which tectonic styles and processes operated. Our analysis is synthetized by the highlighting of three distinct Archean periods with different tectonic activity, starting at 3.8 billion years (Ga), from when the first metamorphic data are available. We find that in the interval 3.8-3.5 Ga, tectonics was dominated by short-lived subduction tectonics and non-subduction tectonics, possibly in cohabitation. Between 3.4 and 3.0 Ga, subduction was present and contributed to the lateral growth of the continents. In the 2.8-2.5 Ga period, the assembly of supercontinent/supercratons signals the action of modern-style plate tectonics. In summary Archean metamorphic data allow timing the Earth progression from pre-modern tectonics to modern plate tectonics including the supercontinent cycle.