The Birth and Evolution of Plate Tectonics

Abstract

Crustal evolution recommenced after the Late Heavy bombardment caused melting and mixing of the Hadean crust. Upwelling hot mantle spread out carrying the colder brittle crust away from the upwelling current causing rifts and lateral movement of crustal plates. Partial melting due to the reduction of pressure on the mantle generated magma that flowed through the rifts forming new crust while degassing of the magma produced the atmosphere and hydrosphere. New information from the Yilgarn craton in Western Australia indicates that where the lateral movement of converging plates intersected the crust was compressed into multi-kilometre scale folds. Partial melting at the base of the folded crust produced granodiorite and a dense ultramafic restite and the formation of an Archean style craton. The spreading mantle flow loses heat through the crust becoming denser and together with the restite sinks down through the mantle forming a convective cycle. When two cratons approach the intervening mafic crust is folded forming a new craton that joins the cratons into a continent. Mantle plumes rising beneath the continent cause rifts to open and the formation of new ocean crust in the rifts while older ocean crust is subducted beneath the outer margins of the continent.