To achieve its objectives, BALCONY developed a suite of high-resolution numerical models that simulate the evolution of continental cratons over the past three billion years. The models were implemented using the open-source geodynamic modelling software ASPECT and incorporate geological and geophysical constraints on the properties of cratons, including initial lithospheric thickness, compositional buoyancy, radiogenic heat production and the long-term cooling of Earth’s mantle. Extensive parameter studies were carried out to generate an ensemble of models exploring the sensitivity of craton evolution to these key physical processes.
To reproduce realistic tectonic conditions, the numerical models include velocity boundary conditions representing three episodes of supercontinent assembly and breakup throughout Earth’s history. These models provide a systematic assessment of how mantle cooling, tectonic compression and gravitational instabilities interact over billion-year timescales to control craton thickness. The modelling results establish a simple conceptual framework in which craton thickness reflects the combined effects of thermal thickening during planetary cooling, additional thickening caused by tectonic compression, and lithospheric thinning through gravitational drip removal. The models demonstrate that cooling and compression become increasingly dominant over time. As cratons cool, the viscosity of their lower boundary increases, making gravitational removal of lithospheric material progressively less efficient. Consequently, thickening mechanisms outpace thinning, leading to a gradual increase in craton thickness over geological time.
Numerical results are supported by a comprehensive global database of kimberlite occurrences from cratons worldwide. This database was used to quantify temporal variations in kimberlite eruption frequency and to assemble an additional dataset relating kimberlite size to eruption age. Statistical analyses were then performed to compare the geological observations with the numerical modelling results.
The combined analyses indicate that many cratons were thinner during the early part of Earth’s history and gradually thickened through cooling and tectonic compression. Around 1.5 billion years ago, an increasing proportion of cratons exceeded the critical lithospheric thickness of ~160 km required to host kimberlite melts. Statistical analyses support this interpretation, showing that although individual cratons followed different evolutionary pathways, the probability of developing lithospheric roots deeper than 160 km increased significantly after this time. These results show that craton thickness exerts a first-order control on the temporal and spatial distribution of kimberlite magmatism, providing a quantitative link between the long-term evolution of continental lithosphere and the geological record of kimberlite eruptions.
