Isotope and trace element models of crustal evolution

Abstract

Some of the isotopic constraints on the development of continental crust from about 3.8 Ga ago are reviewed. Particularly it is noted that Archaean granitic (sensu lato) rocks have initial $^{143}$Nd/$^{144}$Nd ratios close to predicted values for the bulk Earth at the time before emplacement, whereas those Phanerozoic granites investigated so far diverge considerably from the bulk Earth and betray the existence of later continental crust in their provenance. Geochemical evidence for recycling of some continent-derived elements into the mantle is examined and the important distinction between selected element recycling and bulk return of continental material is emphasized. Various transport models that have been proposed to model the development of continental crust are examined and some of their differences and similarities, particularly with respect to implications for continental recycling, are highlighted.