Long-term evolution, stability, and thickness of cratonic lithosphere

Abstract

The thickness of the cratonic lithospheric mantle (CLM) influences the composition of primary mantle melts, the formation and distribution of ore deposits, and the stability of continents. However, it remains debated whether the thickness of the CLM has changed through time. Some studies suggest progressive thinning due to extension, convective removal, mantle plumes, or subduction-driven erosion, while others propose long-term stability due to the intrinsic buoyancy or strength of the CLM. To address this question, we provide new constraints on the evolution of the CLM through time by comparing two recently developed datasets: (1) a global dataset of paleo−lithosphere-asthenosphere boundary (LAB) depth estimates (dating back to 2.1 Ga) produced by fitting geotherms to xenolith- and xenocryst-derived pressure and temperature estimates; and (2) the present-day LAB depth derived from seismic tomography combined with a scaling between wavespeed and temperature. Our results show that the thickness of the CLM beneath most cratons has changed by <50 km since the Paleoproterozoic, that there are no systematic secular trends in CLM thickness changes through time, and that there is no evidence for the previously proposed existence of substantially thicker (>300 km) CLM in the past. These findings suggest that in the majority of places, the cratonic lithosphere has remained largely unchanged for billions of years, reinforcing the idea that cratonic roots represent long-lived, stable features of Earth’s lithosphere. Exceptions are regions with long histories in a supra-subduction setting, followed by the application of extensional stresses (e.g., North China).