Do Supercontinent-Superplume Cycles Control the Growth and Evolution of Continental Crust?

Abstract

The evolution of continental crust can be directly linked to the first-order supercontinent-superplume cycles. We demonstrate that: (1) a mantle-like oxygen isotopic signature is not a diagnostic feature for distinguishing crustal addition from the reworking of pre-existing continental crust; (2) juvenile continental crust shows a wide range of whole-rock Hf isotopic compositions throughout Earth’s history; and (3) detrital zircon Hf model ages cannot reliably determine the growth of continental crust. Thus, the wide use of zircon Hf model ages, based on zircon grains with mantle-like oxygen isotopes, is inappropriate for estimating the timing of continental crustal generation. Based on an analysis of global Hf and O isotope and zircon age databases, we argue that the actual U-Pb crystallization ages of juvenile zircon grains provide the best opportunity to unravel crustal growth through time and to test its relationship with supercontinent-superplume cycles. Furthermore, when the Hf isotopes of these juvenile grains plot within the field of juvenile continental crust, they correlate well with times of global mantle depletion as recorded by Os and He isotopes, plume activity as recorded by LIP events, and periods of crustal growth and the breakup of supercontinents. In contrast, zircon grains crystallized from magmas that were produced by partial melting of pre-existing continental crust show U-Pb age peaks that correspond mainly to times of supercontinent assembly and crustal reworking. Detailed analysis shows the key role played by recycling of mafic crustal components in the generation of juvenile continental crust.