Geodynamic models of the formation of large Archean sedimentary basins

Neoarchean and Paleoproterozoic sedimentary basins preserved on cratons contain Earth’s richest deposits of gold, uranium, and iron-ore, but their geodynamic development is poorly understood. Here, two-dimensional numerical models are used to examine how surface topography of large cratonic landmasses evolves under the influence of surface erosion and sedimentation during and after collisional accretion. Models are analyzed using cross-correlation clustering to objectively quantify similarities between model outcomes. Models fall into two main categories, based on the lithosphere deformational style and basin thickness, for which the crustal thermal structure is a first-order control. Models where the initial Moho temperature (T i Moho ) is greater than 850 °C are characterized by lateral crustal flow in the collisional phase creating broad, low-relief surface topography. The uniformly thickened, buoyant crust in the cratonic nucleus inhibits substantial subsidence. Models where T i Moho is <850 °C are highly deformed in the mobile belts, building high-gradient topographic features reflecting localized crustal thickening. The relatively undeformed cratonic nucleus in these cool lower crust models can accommodate up to 10 km of basin subsidence if sediment deposition is at least 10 mm/year for 200–400 million years, comparable to the depositional history of the Witwatersrand Basin on the Kaapvaal Craton, one of Earth’s largest Archean basins. The PTt evolution at the base of the developing sedimentary basin indicates a maximum metamorphic grade of ∼0.3 GPa and 260 °C comparable to estimates from the Hamersley Basin on the Pilbara Craton and the Witwatersrand Basin on the Kaapvaal Craton.