Broad variability in craton reworking

Abstract

Cratons are commonly considered as stable parts of continents that can survive a long-term interaction with mantle convective instabilities, basal drag and plate tectonic processes. However, geochemical evidence, geophysical observations and numerical modeling question their long-term stability and suggest heterogeneous modification with possible partial destruction of cratonic lithosphere. Cratonic modification may be identified either from a significant reduction in lithospheric thickness or from densification of cratonic lithospheric mantle e.g. through melt-metasomatism. Both characteristics can be identified through geophysical modeling, such as joint interpretation of thermal and gravity data. The examples from the cratons of Eurasia, South Africa, Greenland and Antarctica demonstrate various degrees of lithosphere reworking by mantle convection and plate tectonics processes. Sharp lithosphere thinning across Greenland possibly marks the Iceland plume passage (10.1016/j.earscirev.2018.10.015) which can hardly be identified from seismic observations (10.1029/2018JB017025). In contrast, the cratonic Siberian LIP region preserves a thick lithosphere, but with a fertile mantle (10.1016/j.epsl.2018.09.034). Similarly thick but fertile lithosphere is present below the southern Africa cratons (10.1016/j.gr.2016.03.002, 10.1016/j.gr.2016.05.002) and in parts of the North China craton (10.1029/2020JB020296), where spatially limited geochemical data have earlier been interpreted as lithosphere destruction by the Mesozoic Pacific plate subduction. Indeed, the lithosphere of West Antarctica has been essentially destroyed by the Mesozoic Phoenix plate subduction, most likely in the back-arc settings (10.1016/j.earscirev.2020.103106). In contrast, the India plate subduction produced heterogeneous pattern in lithosphere thinning below Tibet (10.1029/2022JB026213). Continental regions, typically considered to be stable cratons, may have also essentially lost their cratonic signature, such as cratonic East Antarctica (10.1016/j.earscirev.2022.103954) and the East European craton with strong variations in both lithosphere thickness (10.1016/j.earscirev.2018.11.004) and mantle density (10.1029/2018JB017025). The observed broad variability in the present-day cratonic lithosphere structure precludes unique interpretations of past interactions of the cratons with mantle convection and plate tectonics processes, and indicates the existence of various types and multiple phases of such interactions, controlled by lithosphere rheology.