Water-Induced Mantle Overturns Leading to the Origins of Archean Continents and Subcontinental Lithospheric Mantle

Abstract

The origins of Archean continents and subcontinental lithospheric mantle (SCLM) were important events in the early Earth. The mechanisms for the origins of Archean continents and the SCLM remain unclear. This study suggests that these events were controlled by the evolution of the hydrous magma ocean (MO). With solidification, the basal MO eventually became gravitationally unstable because of the enrichment of water. The triggered massive mantle overturns resulted in the major pulses of the crust and thick SCLM generations. The model avoids a fatal drawback of the oceanic plateau model for the origin of continents: the source of H2O needed for the formation of tonalite-trondhjemite-granodiorite (TTG). The model can also account for why the TTG and thick SCLM basically occurred in the Archean.