Emergence of continents above sea‐level influences sediment melt composition

Abstract

AbstractThe Archean‐Proterozoic transition heralded a number of fundamental changes on Earth, including the oxygenation of the atmosphere, a marked emergence of continents above sea‐level, and an increase in δ18O of felsic magmas. The potential drivers for the latter are changes in the composition of supracrustal material or increased crustal reworking. Although the onset of subduction‐induced continental collision and associated enhanced crustal recycling could produce high‐δ18O felsic magmas, temporally constrained zircon δ18O reveals an increase in δ18O at ~2.35 Ga that predates the oldest widely recognized supercontinent. In this work, we use the O and Hf isotope ratios of magmatic zircon crystals in Archean and Proterozoic sediment‐derived granitoids of the North China Craton to track the incorporation of supracrustal material into magmas. The results are consistent with a Paleoproterozoic increase of continental freeboard producing sedimentary reservoirs with comparatively elevated δ18O that subsequently partially melted to generate the granitoids.