Scientists have tracked a particular set of elements that retain the pristine characteristics of the original magma from which the TTG assemblages formed. These data were used to create a model demonstrating that the TTGs, and associated younger rocks, arose from the slow burial, thickening and melting of a precursor crust that probably resembled the crust of an oceanic plateau.
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This discovery refutes the long-standing theory that the Archean TTGs were formed either by meteorite impact or in the Earth’s first subduction zones, when one part of the crust subducted under another and melted, requiring an early onset of plate tectonics. Instead, the main mechanism was internal geological forces that transformed the original Earth’s crust.
