Processes and problems in the continental lithosphere: geological history and physical implications

Abstract

Summary Systematic changes in surface continental patterns of geology, tectonics and magma types reflect the unidirectional non-uniformitarian evolution of the continental lithosphere upon which the dominant constraint has been progressively declining terrestrial heat production. Widespread shallow asthenospheric mantle precluded the early stabilization of continental lithosphere, and the subsequent rapid growth of late Archaean continental crust implies considerable differences in the long-term thermal histories of oceanic and continental lithospheres. Proterozoic continental lithosphere rapidly became thick and refractory, though internally ductile, whilst oceanic lithosphere, the focus of terrestrial heat flow, remained relatively thin and plastic. This physical contrast probably has decreased in more recent times, a trend which may be coupled with the increased evidence for continental fragmentation in the Phanerozoic record. Finally, it is argued from thermal considerations, coupled with freeboard, isotopic and geochemical data, that continental growth has continued at a decreased and decreasing rate throughout post-Archaean time.