Growth of the Preserved Continental Crust: Integrated U-Pb, O, and Hf isotopic systematics of detrital zircons from Australia and Antarctica

Abstract

When and how the continental crust was generated, and how the volume of the continental crust has changed with time, are fundamental questions in Earth Sciences. Various models for the growth of the continental crust have been proposed, but there is no consensus yet, highlighting the complexity of continental growth. In-situ analyses of U-Pb, O and Lu-Hf isotopes from detrital zircon grains from the world's major rivers can potentially capture the approximate timing of major formation of the felsic continental crust. The U-Pb age of igneous zircon records the time when the source magma crystallized. Lu-Hf isotopes in zircon can be used to calculate a model age of the source magma from which the zircon crystallized: the time when the source material was extracted from the mantle. O isotopes in magmatic rocks are highly sensitive to the incorporation of supracrustal material, which has been subjected to low-temperature processes, especially clays produced by weathering, into a magma source region. O isotopes can be used to indicate the involvement of sediments, which influences the Lu/Hf ratio of the source region, required for model age calculations. In this study, detrital zircons from Antarctica and Australia were analyzed for U-Pb, O and Lu-Hf isotopic compositions to investigate the crustal growth of the two continents and the major tectonic events that have affected these continents. And combined with other datasets from Asia, Africa and North America, using the similar method adopted in this study, the results make it possible for the global growth curve of the present continental crust to be reconstructed.