The formation, and evolution of Archean cratons

Models for the formation of Archean cratons range between two mutually exclusive end-members: one involving upwelling of hot mantle and associated melt formation and a second that involves supra-subduction zone related melt production. Petrologic evidence shows that Archean cratons include granitic components in the compositional range of tonalite, trondhjemite and granodiorite (TTG), which are produced by hydrated melting of basalt. In the early Earth, formation of flat continents, lateral expansion and later, vertical thickening has been suggested by geological and geochemical evidence (Cawood et al., 2019). It is crucial to evaluate the dimensional variations of continental crust in the early Earth based on the Geophysical modelling approach.

We develop a numerical geodynamic model of melt production and melt extraction processes applicable to conditions of Archean, focusing on analysing craton formation, and its lateral and vertical dimensional variations. We incorporate the parameters of the water content of the material, water penetration depth, heating modes of the Earth, yield stress of the lithosphere, as well as the ratio of intrusive to extrusive magmatism. Also, we implement melt depletion process to generate sub-continental lithosphere that can preserve the TTG crust for a period of time without being recycled. The geophysical models are compared with the Archean continental crust growth models to verify the hypothesized lateral expansion and thickening of the Archean cratons.

Reference

Cawood P.A. and Hawkesworth C., 2019. Continental crustal volume, thickness and area, and their geodynamic implications Gondwana Res., 66 (2019), pp. 116-125