Archean dome-and-keel structures indicate local thermal anomalies

Abstract Archean dome-and-keel structures have been interpreted to indicate that vertical tectonics—a style of tectonics different from modern plate tectonics—dominated Earth’s early history. However, others attribute these structures to regional extension and/or compression related to plate tectonics. Here, we use thermomechanical numerical models to test the previously proposed models and explore the mechanisms for forming dome-and-keel structures. Proponents of Archean vertical tectonics have suggested that the dome-and-keel structures formed by folding and sinking the denser greenstone sequences (keels) into a hot, soft, and lighter tonalite-trondhjemite-granodiorite (TTG) crust (domes). Our results reveal that the greenstone volcanic rocks’ rapid cooling and stiffening could impede keel formation. While heating the TTG crust by radioactive decay, magma intrusion, or high mantle heat flux may cause crustal softening and partial convection, these processes cannot effectively heat the overlying greenstone sequences to fold them into the TTG crust. The favorable condition for forming dome-and-keel structures is an eruption of voluminous mafic and/or ultramafic magma with contemporaneous crustal heating by TTG magma intrusion. Such conditions may be found in Archean regions above vigorous mantle plumes, where mantle heat flux was high, mafic–ultramafic magma was voluminous, and TTG magmatism was strong. Therefore, the Archean dome-and-keel structures may reflect local thermal anomalies rather than globally dominant vertical tectonics. We also tested horizontal compression and extension and found that these processes cannot readily reproduce characteristic dome-and-keel structures or the associated rock fabrics. Our findings underscore the importance of plume-driven processes for continental evolution during the Archean eon.